WO2012005207A1

WO2012005207A1 - Method for producing dope for optical film, method for producing optical film, optical film, polarizing plate, and liquid crystal display device

Info

Publication number: WO2012005207A1
Application number: PCT/JP2011/065265
Authority: WO
Inventors: 圭宮本
Original assignee: コニカミノルタオプト株式会社
Priority date: 2010-07-06
Filing date: 2011-07-04
Publication date: 2012-01-12
Also published as: JP5614450B2; JPWO2012005207A1; KR101464065B1; KR20130031298A

Abstract

In order to provide a method for producing a dope for an optical film that enables an optical film having excellent transparency, heat resistance, humidity resistance, and processability to be produced, a method for producing a dope for an optical film comprising at least resin particles, and an acrylic resin and cellulose ester resin is disclosed. The method for producing a dope for an optical film comprises: a first mixing step in which a dispersion liquid for the resin particles and a surfactant are mixed to produce a mixture; and a second mixing step in which a resin composition comprising the acrylic resin and the cellulose ester resin at a mass ratio ranging from 95:5 to 30:70, a solvent, and the aforementioned mixture are mixed.

Description

Optical film dope manufacturing method, optical film manufacturing method, optical film, polarizing plate, and liquid crystal display device

The present invention provides a method for producing a dope for an optical film, a method for producing an optical film using the dope for an optical film produced by the method for producing an optical film dope, an optical film obtained by the method for producing the optical film, The present invention relates to a polarizing plate using the optical film as a transparent protective film, and a liquid crystal display device including the polarizing plate.

In the image display area of the liquid crystal display device, various optical films, for example, a transparent protective film for protecting the polarizing element of the polarizing plate, and the like are arranged. As such an optical film, for example, a resin film excellent in transparency such as a cellulose ester film is used.

In addition, the field of use of liquid crystal display devices is diversifying, and not only indoor use but also outdoor use is increasing. Specifically, for example, by displaying video and information on a liquid crystal display device, it works as an advertising medium instead of a poster or the like, that is, when used as a digital signage device, or a large display device on a street or store The case where it installs and uses as is mentioned. In such a case, the liquid crystal display device may be used, for example, under high temperature and high humidity, and the deterioration of the optical film due to moisture absorption may be a problem. Therefore, the optical film used is required to have high moisture resistance that can suppress deterioration due to moisture absorption.

On the other hand, acrylic resins such as polymethyl methacrylate resin (PMMA), which is known as an optical material with low hygroscopicity, have low hygroscopicity and are excellent in transparency and dimensional stability. The use of is being considered. However, an acrylic film containing an acrylic resin has a property of being easily broken and brittle when compared with a cellulose ester film or the like. For this reason, it is difficult to handle, and in particular, it has been difficult to stably manufacture an optical film for a liquid crystal display device having a large screen.

Moreover, as a resin film containing an acrylic resin, the thing of patent documents 1 to 3 is mentioned, for example.

Patent Document 1 describes an acrylic resin film-like material containing a multilayer structure polymer (acrylic particles) of acrylic resin and a thermoplastic polymer (acrylic resin) mainly composed of alkyl methacrylate. .

Patent Document 2 discloses a cellulose ester film containing an acrylic polymer and a cellulose ester.

Patent Document 3 describes an optical film containing an acrylic resin and a cellulose ester resin. Patent Document 3 describes that the optical film may further contain acrylic particles.

Japanese Patent Laid-Open No. 2005-163003 JP 2003-12859 A International Publication No. 2009/47924

According to Patent Document 1, it is disclosed that an acrylic resin film-like material having surface hardness and the like that can be used for vehicle applications can be provided. However, the difficulty of handling as an optical film cannot be solved only by containing resin particles in the acrylic resin. For example, it is difficult to stably produce an optical film, such as cracking when the end of the film is cut.

Further, according to Patent Document 2, by containing a relatively low molecular weight acrylic resin instead of an additive such as a plasticizer, the generation of precipitates or volatiles on the web during production is suppressed, while physical properties are suppressed. It is disclosed that a film having better properties and the like can be produced. As described above, the invention described in Patent Document 2 includes physical properties and the like while suppressing the generation of precipitates or volatiles on the web during production by including an acrylic polymer in the cellulose ester film. Although a better film could be produced, it was not made for the purpose of improving moisture resistance. Specifically, it contains a relatively low molecular weight acrylic resin instead of an additive such as a plasticizer, and does not contain an acrylic polymer in order to improve moisture resistance. Therefore, the invention described in Patent Document 2 has not been made to contain an acrylic polymer to such an extent that the moisture resistance is sufficiently enhanced.

Further, according to Patent Document 3, it is disclosed that an optical film having low hygroscopicity, transparent, high heat resistance, and markedly improved brittleness can be provided. Further, according to Patent Document 3, it is disclosed that the cutting property (cutting) of the film is further improved by containing resin particles.

On the other hand, the optical film as described above is often manufactured using a solution (dope) in which a resin or the like constituting the film is dissolved in a solvent. Specifically, for example, it is produced as a long resin film by a solution casting film forming method or the like. Specifically, the solution casting film forming method is a method in which a resin solution (dope) in which a transparent resin as a raw material resin is dissolved in a solvent is cast on a traveling support and dried to a peelable extent. In this method, a long resin film is produced by peeling the film obtained from the support from the support, and performing drying, stretching and the like while carrying the peeled film with a carrying roller.

When an optical film containing an acrylic resin, a cellulose ester resin, and resin particles is manufactured by a manufacturing method using such a dope, the optical film may not be preferably manufactured. Specifically, the transparency, heat resistance, moisture resistance and the like of the obtained optical film may not be sufficiently improved. Moreover, the workability of the obtained optical film may be lowered. Specifically, this may be the case when the cutting properties such as the film cracking when the end of the film after stretching is cut are reduced.

This invention is made | formed in view of this situation, Comprising: It provides the manufacturing method of dope for optical films which can manufacture the optical film excellent in transparency, heat resistance, moisture resistance, and workability. With the goal. Moreover, the manufacturing method of the optical film using the dope for optical films manufactured by the manufacturing method of such a dope for optical films, the optical film obtained by the manufacturing method of the said optical film, The said optical film as a transparent protective film It is an object to provide a polarizing plate used and a liquid crystal display device including the polarizing plate.

The present inventor considered that the occurrence of the above-described problems was due to the occurrence of aggregation in the dope when the optical film dope was produced. It was speculated that the aggregation generated in the dope was due to the acrylic particles being brought into direct contact with the cellulose ester resin, thereby reducing the dispersibility of the acrylic particles. And when this aggregation generate | occur | produced, it guessed that it was based on the property which each component cannot fully exhibit.

Therefore, as a result of various studies, the present inventor has arrived at the present invention as described below in which a surfactant is used and the timing of adding each component is adjusted.

The method for producing a dope for an optical film according to an aspect of the present invention is a method for producing a dope for an optical film having at least resin particles, an acrylic resin, and a cellulose ester resin, wherein the resin particles and the surfactant are used. A first mixing step for preparing a mixture, a resin composition of the acrylic resin and the cellulose ester resin in a mass ratio of 95: 5 to 30:70, and the mixture And a second mixing step.

According to such a configuration, a method for producing a dope for an optical film capable of producing an optical film excellent in transparency, heat resistance, moisture resistance, and processability can be provided. That is, an optical film dope for an optical film that can produce an optical film excellent in transparency, heat resistance, moisture resistance, and workability is obtained by manufacturing an optical film using a solution casting film forming method or the like. .

This is presumed to be due to the following.

It is considered that the surface of the resin particles is covered with the surfactant by previously mixing the dispersion of the resin particles and the surfactant. It is considered that the resin particles covered with this surfactant are unlikely to deteriorate in dispersibility due to contact with the cellulose ester resin. Therefore, it is considered that a dope having a high dispersibility of resin particles can be obtained even when an acrylic resin, a cellulose ester resin, and resin particles are contained.

By producing a resin film by, for example, a solution casting film forming method using a dope that contains an acrylic resin, a cellulose ester resin, and resin particles, and further has high dispersibility of the resin particles. It is considered that a product that sufficiently exhibits the properties of the acrylic resin, the cellulose ester resin, and the resin particles can be obtained. In addition, it is considered that a resin particle uniformly dispersed is obtained on the entire surface of the obtained film, and from this point, it is considered that a film that sufficiently exhibits the properties of the resin particle is obtained. Specifically, moisture resistance, transparency, heat resistance, etc. possessed by acrylic resins, transparency, flexibility, processability, etc. possessed by cellulose ester resins, processability possessed by resin particles, etc. Is considered to be fully demonstrated. Therefore, the obtained dope for optical films is considered to be because an optical film excellent in transparency, heat resistance, moisture resistance, and workability can be produced.

From the above, according to the manufacturing method of the above configuration, an optical film that can be used for a solution casting film forming method or the like can manufacture an optical film excellent in transparency, heat resistance, moisture resistance, and workability. It is thought that the dope for films is obtained.

Further, in the method for producing a dope for an optical film of the present invention, it is preferable to add the mixture into the mixing container before or during dissolution in the solvent of the resin composition of acrylic resin and cellulose ester resin. According to such a configuration, productivity can be increased. This is considered to be because the resin particles mixed with the surfactant can be dispersed when the resin composition of the acrylic resin and the cellulose ester resin is dissolved in a solvent. In the present invention, the resin particles refer to acrylic resin particles that do not dissolve in the solvent of the resin composition of the acrylic resin and the cellulose ester resin.

In the method for producing a dope for an optical film of the present invention, the surfactant is preferably an ionic surfactant, and more preferably an anionic surfactant. According to such a structure, the manufacturing method of the dope for optical films which can manufacture the optical film excellent in transparency, heat resistance, moisture resistance, and workability can be provided. This is considered to be because the surface of the resin particles can be suitably covered with the surfactant by previously mixing the resin particles and the surfactant.

In the method for producing a dope for an optical film of the present invention, the content of the surfactant is preferably 500 parts by mass or less with respect to 100 parts by mass of the resin particles. According to such a structure, the manufacturing method of the dope for optical films which can manufacture the optical film excellent in transparency, heat resistance, moisture resistance, and workability can be provided. This is considered to be because the surface of the resin particles can be suitably covered with the surfactant by previously mixing the resin particles and the surfactant.

In the method for producing a dope for an optical film of the present invention, the acrylic resin and the cellulose ester resin may be prepared in a mixing container together with a solvent so that the mass ratio is 95: 5 to 50:50. It is preferable to prepare such that the mass ratio is 80:20 to 60:40.

The method for producing an optical film of the present invention comprises a casting step of casting a dope on a traveling support to form a film, and a peeling step of peeling the film from the support. The optical film dope produced by the method for producing an optical film dope of the invention is used. According to such a configuration, an optical film excellent in transparency, heat resistance, moisture resistance, and processability can be produced.

The optical film of the present invention is obtained by the method for producing an optical film of the present invention. According to such a configuration, an optical film excellent in transparency, heat resistance, moisture resistance, and processability can be obtained. And since it is excellent in a hygroscopic property, workability, etc., it can apply easily also to the protective film of the polarizing plate for liquid crystal display devices which enlarged the screen. Further, it can be easily cut into a desired size.

The polarizing plate of the present invention is a polarizing plate comprising a polarizing element and a transparent protective film disposed on at least one surface of the polarizing element, and the transparent protective film is the optical film of the present invention. It is characterized by. According to such a configuration, since the optical film of the present invention having excellent transparency, heat resistance, moisture resistance, and processability is applied as the transparent protective film of the polarizing plate, for example, a large-screen liquid crystal A polarizing plate that can be suitably used for a display device is obtained. Specifically, even a polarizing plate for a liquid crystal display device having a large screen can suppress deformation due to moisture absorption. Moreover, since the optical film of this invention with favorable workability is used as a transparent protective film, even if it uses a big film, generation | occurrence | production of damage is suppressed.

The liquid crystal display device of the present invention is a liquid crystal display device comprising a liquid crystal cell and two polarizing plates arranged so as to sandwich the liquid crystal cell, and at least one of the two polarizing plates is a polarizing plate. It is a board. According to such a configuration, since the polarizing plate provided with the optical film of the present invention having excellent transparency, heat resistance, moisture resistance, and workability is used, the image display area can be obtained even if the screen is enlarged. It is possible to provide a liquid crystal display device in which the occurrence of defects of the optical film of the present invention disposed in the substrate is suppressed. Specifically, for example, even a liquid crystal display device having a large screen can suppress the occurrence of deformation due to moisture absorption of the optical film of the present invention disposed in the image display region. In addition, since the processability of the optical film of the present invention is good, even when a large film is applied to a large-screen liquid crystal display device, the optical film of the present invention may be damaged during production. Therefore, a liquid crystal display device having a large screen can be provided.

According to the present invention, it is possible to provide a method for producing an optical film dope that can produce an optical film excellent in transparency, heat resistance, moisture resistance, and processability. Moreover, the optical film obtained by the manufacturing method of the optical film using the dope for optical films manufactured by the manufacturing method of such a dope for optical films, the optical film obtained by the manufacturing method of an optical film, and the optical film were used as a transparent protective film. A polarizing plate and a liquid crystal display device including the polarizing plate are provided.

It is the schematic which shows the structure of the manufacturing apparatus of the optical film by a solution casting film forming method.

Hereinafter, although the embodiment concerning the manufacturing method of the dope for optical films of the present invention is described, the present invention is not limited to these.

The method for producing a dope for an optical film according to the present embodiment is a method for producing a dope for an optical film having at least resin particles, an acrylic resin, and a cellulose ester resin, and includes a dispersion of resin particles and a surfactant. A first mixing step for preparing a mixture, a resin composition of an acrylic resin and a cellulose ester resin in a mass ratio of 95: 5 to 30:70, a solvent, and a mixture, And a second mixing step of mixing.

In addition, an optical film is manufactured by, for example, a solution casting film forming method using the optical film dope (hereinafter, also simply referred to as “dope”) manufactured by the optical film dope manufacturing method of the present invention. be able to.

The method for producing a dope by the method for producing an optical film dope of the present invention and producing an optical film using the dope is, for example, that of an optical film by a so-called solution casting film forming method as shown in FIG. Performed by manufacturing equipment. In addition, the dope for optical films obtained by the method for producing a dope for optical films of the present invention is not only used for the solution casting film forming method, but can also be used for other methods for producing an optical film. .

FIG. 1 is a schematic view showing a configuration of an optical film manufacturing apparatus 11 using the method for manufacturing an optical film dope of the present invention. The optical film manufacturing apparatus 11 includes a dope manufacturing apparatus 21, a dope filtering apparatus 22, and a film forming apparatus 23. The dope manufacturing apparatus 21 manufactures a dope. The dope filtering device 22 filters the manufactured dope. The film forming apparatus 23 manufactures an optical film using the filtered dope.

[Dope production equipment]
As shown in FIG. 1, the dope manufacturing apparatus 21 includes a dope charging pot 1, a discharge valve 6, a dope feed pump 2, and the like. The dope charging pot 1 is a container for preparing a dope by mixing a raw material of an optical film such as a resin and an additive and a solvent. In addition, about raw materials, such as resin, a solvent, an additive, it mentions later. In addition, the dope charging pot 1 is connected to a pipe 7 through which a dope is circulated through a discharge valve 6 and sent to another device, for example, a dope filtration device 22. In addition, the piping 7 is connected to the casting die 13 of the film forming apparatus 23 via the dope filtration apparatus 22 etc., for example. The pipe 7 is provided with a dope feed pump 2 for allowing the dope to flow efficiently through the pipe 7 immediately below the discharge valve 6. The dope feed pump 2 may be appropriately disposed not only directly under the discharge valve 6 but also for smooth circulation of the dope in the pipe 7.

The dope charging kettle 1 is not particularly limited, but it is preferable that the material charged in the dope can be heated to a predetermined temperature and stirred in the heated state. Specifically, the thing provided with the stirring blade, the heating apparatus, etc. is mentioned, for example. The heating device for heating the liquid in the dope charging pot 1 is not particularly limited, but is preferably performed from the outside. For example, a jacket type is preferable from the viewpoint of easy temperature control. Moreover, when stirring the material thrown in in dope charging pot 1 in the heated state, in order to suppress the loss of a solvent, it is preferable that dope charging pot 1 is a sealed container. In such a case, the dope charging kettle 1 is preferably a container that can withstand a predetermined pressure, specifically, a pressure equal to or higher than the vapor pressure of the solvent at the temperature at the time of stirring. The pressurization in the dope charging pot 1 may be performed by increasing the vapor pressure of the solvent by heating as described above, or a method of press-fitting an inert gas such as nitrogen gas may be used. The dope charging pot 1 may be appropriately provided with instruments such as a pressure gauge, a thermometer, and a viscometer.

Next, the method for producing the dope for optical films of the present invention will be described. Specifically, for example, a dope manufacturing method using the dope manufacturing apparatus 21 will be described. The dope raw material will be described later.

First, a dispersion of resin particles and a surfactant are mixed in advance. This mixing corresponds to the first mixing step. The mixing method corresponding to the first mixing step is not particularly limited. Specifically, the dispersion of the resin particles and the surfactant may be mixed, and may be mixed in a solvent using a solvent, or may be mixed without using a solvent, that is, powder mixed. . Specific examples of the method include a method of mixing with a stirring blade provided in the dope charging pot 1, a method of separately mixing using a mixer, and the like. Moreover, as a mixer, a well-known thing can be used, For example, a Henschel mixer, a super mixer, a mechano mill, an ang mill, a hybridization system, a Cosmo system etc. are mentioned.

Next, the acrylic resin and the cellulose ester resin are introduced into the dope charging pot 1 together with the solvent so as to have a mass ratio of 95: 5 to 30:70, and stored. Then, the acrylic resin, the cellulose ester resin, and the solvent are mixed in the dope charging pot 1. Although it does not specifically limit as this mixing method, Specifically, the method of mixing by stirring with the stirring blade with which the dope preparation kettle 1 was equipped is mentioned, for example. By doing so, the acrylic resin and the cellulose ester resin are gradually dissolved in the solvent.

At that time, the raw materials of the dope other than the acrylic resin, the cellulose ester resin and the solvent may be added before stirring or may be added during stirring. That is, there is no particular limitation on the timing at which a mixture obtained by previously mixing a dispersion of resin particles and a surfactant (hereinafter simply referred to as a mixture) is added to the dope charging kettle 1. Specifically, for example, the mixture may be added before the acrylic resin and the cellulose ester resin are dissolved in the solvent, or may be added during the dissolution. Alternatively, after the acrylic resin and the cellulose ester resin are dissolved in a solvent, the mixture may be added to the resin solution and further mixed to disperse the mixture in the resin solution. In short, the resin particle dispersion may be added in such a manner that the resin particles are in contact with the acrylic resin and the cellulose ester resin after the resin particles are in contact with the surfactant.

The timing of adding the mixture is not particularly limited as described above, but it is preferable to add the acrylic resin and the cellulose ester resin before or during dissolution of the acrylic resin and cellulose ester resin. This is because the acrylic resin and the cellulose ester resin can be dissolved in the solvent and the mixture can be dispersed in the solvent, so that the productivity is increased.

As described above, the optical film dope for the optical film dope manufacturing method of the present invention is prepared by dispersing the mixture in a resin solution in which an acrylic resin and a cellulose ester resin are dissolved in a solvent. Is done. Further, the viscosity of the dope in the dope charging vessel 1 can be measured using a viscometer disposed in the dope charging vessel 1, for example, FVM-80A-EXHT manufactured by CBC Corporation.

Further, the temperature of the dope in the dope charging vessel 1 is not particularly limited, but also from the viewpoint of enhancing the solubility of the acrylic resin and the cellulose ester resin, it is higher than the boiling point of the main solvent in the solvent, for example, the chlorine solvent. It is preferable that the temperature is 20 to 50 ° C. higher than the boiling point. If the temperature of the liquid at the time of stirring is too low, the time required for dissolving the acrylic resin and the cellulose ester-based resin becomes longer, and the dope productivity tends to decrease. Moreover, when the temperature of the dope at the time of stirring is too high, bubbles generated by boiling of the solvent tend to remain in the obtained dope, and foreign matter due to bubbles tends to be easily generated in the obtained optical film. The dope temperature in the dope charging pot 1 can be measured using a thermometer or the like disposed in the dope charging pot 1. Further, for example, the temperature of the liquid in the dope charging vessel 1 may be measured using FVM-80A-EXHT manufactured by CBC Co., Ltd. given as an example of the above viscometer.

The capacity of the dope charging pot 1 is preferably 2 m ³ to 50 m ³ , and more preferably 5 m ³ to 20 m ³ . If the capacity is too small, it may be necessary to increase the number of dope charging pots or increase the number of treatments depending on the amount of dope produced. On the other hand, if it is too large, the time required for dissolving the acrylic resin and the cellulose ester resin in the solvent becomes longer, and the productivity of the dope tends to decrease.

The dope prepared in the dope charging pot 1 is sent to the dope filtration device 22 through the pipe 7 connected to the dope charging pot 1 by opening the discharge valve 6, and then the film forming device 23, specifically Specifically, the solution is sent to the casting die 13 of the film forming apparatus 23.

The dope raw material used in the method for producing an optical film dope of the present invention will be described.

(Acrylic resin)
Acrylic resin will not be specifically limited if it is resin which can exhibit transparency to the resin film obtained by shape | molding into a film form using the dope obtained by making it contain with a cellulose-ester-type resin. Specifically, for example, it is an acrylic resin that can be contained in the obtained film in a compatible state with a cellulose ester resin, and preferably has high compatibility. By using a combination of an acrylic resin and a cellulose ester resin having high compatibility, the properties of each resin can be supplemented with each other, and physical properties and quality required as an optical film can be achieved. Here, containing acrylic resin and cellulose ester resin in a compatible state means mixing each resin to result in a compatible state.

Whether or not the acrylic resin and the cellulose ester resin are in a compatible state can be specifically determined by, for example, measuring the glass transition temperature Tg. More specifically, for example, it can be determined from the following. Even when the glass transition temperatures of the two resins are different, one glass transition temperature is measured when the compatibility of the two resins is high. That is, the glass transition temperature specific to each resin disappears and is measured as one glass transition temperature. On the other hand, when the compatibility of both resins is low, the glass transition temperature of each resin is present, so two or more glass transition temperatures of the mixture are measured. The glass transition temperature here was measured at a heating rate of 20 ° C./min using a differential scanning calorimeter (DSC-7 model manufactured by Perkin Elmer), and determined according to JIS K7121 (1987). The midpoint glass transition temperature (Tmg) is used.

The acrylic resin is not particularly limited as long as it is an acrylic resin as described above. Specifically, for example, resins obtained by polymerizing monomers containing acrylic monomers such as acrylic acid esters and methacrylic acid esters such as methyl methacrylate are listed. More specifically, for example, a methacrylic resin such as polymethyl methacrylate can be used. Further, the monomer preferably contains 50% by mass to 99% by mass of methyl methacrylate and 1% by mass to 50% by mass of another monomer copolymerizable with methyl methacrylate. Therefore, the acrylic resin is obtained by polymerizing a monomer containing 50% by mass to 99% by mass of methyl methacrylate and 1% by mass to 50% by mass of another monomer copolymerizable with methyl methacrylate. Resins are preferred.

Other monomers that can be copolymerized with methyl methacrylate are not particularly limited. For example, alkyl methacrylate having 2 to 18 carbon atoms in the alkyl group, alkyl acrylate having 1 to 18 carbon atoms in the alkyl group, and acrylic acid. , Α, β-unsaturated acids such as methacrylic acid, unsaturated group-containing dicarboxylic acids such as maleic acid, fumaric acid and itaconic acid, aromatic vinyl compounds such as styrene and α-methylstyrene, acrylonitrile, methacrylonitrile And α, β-unsaturated nitriles such as maleic anhydride, maleimide, N-substituted maleimide, glutaric anhydride and the like. Moreover, these may be used independently and may be used in combination of 2 or more type. Of these, methyl acrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate, s-butyl acrylate, 2-ethylhexyl acrylate, and the like are preferable from the viewpoint of thermal decomposition resistance and fluidity of the copolymer. Particularly preferred are acrylates and n-butyl acrylate.

Also, as the acrylic resin, commercially available resins can be used. Specifically, for example, Delpet 60N manufactured by Asahi Kasei Chemicals Corporation, Delpet 80N manufactured by Asahi Kasei Chemicals Corporation, Dialar BR52 manufactured by Mitsubishi Rayon Co., Ltd., Dialnal BR80 manufactured by Mitsubishi Rayon Co., Ltd., Mitsubishi Rayon Co., Ltd. Examples include company-made Dianar BR83, Mitsubishi Rayon Co., Ltd., Dianar BR85, Mitsubishi Rayon Co., Ltd., Dianar BR88, and Electrochemical Industry Co., Ltd. KT75.

Moreover, acrylic resin may be used by 1 type among the acrylic resins mentioned above, and may be used in combination of 2 or more type.

The acrylic resin has a weight average molecular weight (Mw) of 110,000 to 1, in particular from the viewpoint of improving brittleness as a protective film for a liquid crystal polarizing plate and improving transparency when compatible with a cellulose ester resin. It is preferably 000,000, more preferably 150,000 to 400,000. The weight average molecular weight can be measured by gel permeation chromatography. Examples of the measurement conditions include the following conditions.

Solvent: Methylene chloride Column: Shodex K806 manufactured by Showa Denko KK, Shodex K805 manufactured by Showa Denko KK, and Shodex K803G manufactured by Showa Denko KK are connected and used. Column temperature: 25 ° C.
Sample concentration: 0.1% by mass
Detector: RI Model 504 manufactured by GL Sciences Inc.
Pump: L6000 manufactured by Hitachi, Ltd.
Flow rate: 1.0 ml / min
Calibration curve: A calibration curve created by using 13 samples of standard polystyrene STK standard polystyrene (Mw = 2,800,000 to 500) manufactured by Tosoh Corporation (13 samples: use of materials with different Mw at almost equal intervals) (Preferred)
The method for producing the acrylic resin is not particularly limited as long as the above-mentioned acrylic resin is obtained. Specifically, for example, it can be produced by polymerizing a monomer containing an acrylic monomer such as acrylic acid ester and methacrylic acid ester as described above by a known polymerization method. Although it does not specifically limit as a polymerization method, For example, suspension polymerization, emulsion polymerization, block polymerization, solution polymerization, etc. are mentioned. Here, the polymerization initiator used in the polymerization method is not particularly limited as long as the polymerization reaction can be initiated. For example, a peroxide polymerization initiator, an azo polymerization initiator, a redox polymerization initiator, and the like. Can be mentioned. The polymerization temperature in the polymerization method is not particularly limited as long as it is a temperature at which the polymerization reaction can proceed. Specifically, for example, in the case of suspension polymerization or emulsion polymerization, the temperature is preferably 30 ° C to 100 ° C, and in the case of bulk polymerization or solution polymerization, it is preferably 80 ° C to 160 ° C. Moreover, in order to control the reduced viscosity of the obtained copolymer, you may superpose | polymerize using an alkyl mercaptan etc. as a chain transfer agent.

(Cellulose ester resin)
Cellulose ester-based resin, as well as acrylic resin, is particularly a resin that can exhibit transparency in a resin film obtained by forming into a film using a dope obtained together with an acrylic resin. It is not limited. Specifically, for example, from the viewpoint of improving brittleness and transparency when compatibilized with an acrylic resin, the total substitution degree (T) of the acyl group is 2 to 3, and the carbon number is 3 to 7 A cellulose ester resin having an acyl group substitution degree of 1.2 to 3 is preferred. Further, the substitution degree of the acyl group having 3 to 7 carbon atoms is more preferably 2 to 3. That is, a cellulose ester resin substituted with an acyl group having 3 to 7 carbon atoms and having a substitution degree of 2 to 3 is particularly preferable. Specific examples of the acyl group include a propionyl group and a butyryl group, and a propionyl group is preferably used.

When the total substitution degree (T) of the acyl group of the cellulose ester resin is too low, that is, when the residual amount of the hydroxyl groups at the 2, 3, and 6 positions of the cellulose ester molecule is too high, the compatibility with the acrylic resin is insufficient. Thus, the haze of the obtained optical film tends to increase. Moreover, even if the total substitution degree (T) of the acyl group is high, if the substitution degree of the acyl group having 3 to 7 carbon atoms is too low, the compatibility with the acrylic resin is insufficient or obtained. There exists a tendency for the brittleness of an optical film to fall. Specifically, for example, even when the total substitution degree of the acyl group is 2 or more, the substitution degree of the acyl group having 2 carbon atoms, for example, the acetyl group is high, and the acyl group having 3 to 7 carbon atoms is substituted. When the degree is less than 1.2, the compatibility tends to decrease and the haze tends to increase. In addition, even when the total substitution degree of the acyl group is 2 or more, the substitution degree of the acyl group having 8 or more carbon atoms is high, and the substitution degree of the acyl group having 3 to 7 carbon atoms is less than 1.2. The brittleness tends to deteriorate and the desired characteristics cannot be obtained.

In addition, as described above, the cellulose ester-based resin preferably has a total substitution degree (T) of 2 to 3 and a substitution degree of an acyl group having 3 to 7 carbon atoms of 1.2 to 3. However, it is more preferable that the total degree of substitution of acyl groups having 3 to 7 carbon atoms, that is, acetyl groups or acyl groups having 8 or more carbon atoms is 1.3 or less.

Further, the total substitution degree (T) of the acyl group of the cellulose ester resin is more preferably in the range of 2.5 to 3.

The acyl group is not particularly limited, and may be an aliphatic acyl group or an aromatic acyl group. In the case of an aliphatic acyl group, it may be linear or branched and may further have a substituent. The carbon number of the acyl group includes the carbon number of the substituent of the acyl group.

In addition, when the cellulose ester-based resin has an aromatic acyl group as a substituent, the number of substituents X substituted on the aromatic ring is preferably 0 to 5. Also in this case, the substitution degree of the acyl group having 3 to 7 carbon atoms including the carbon number of the substituent is preferably 1.2 to 3. For example, since the benzoyl group has 7 carbon atoms, when it has a substituent containing carbon, the benzoyl group has 8 or more carbon atoms and is not included in the acyl group having 3 to 7 carbon atoms. It will be.

Furthermore, when the number of substituents substituted on the aromatic ring is 2 or more, they may be the same or different from each other. Further, they may be linked to each other to form a condensed polycyclic compound such as naphthalene, indene, indane, phenanthrene, quinoline, isoquinoline, chromene, chroman, phthalazine, acridine, indole, indoline and the like.

The cellulose ester resin is not particularly limited as long as it is a cellulose ester resin as described above. Specifically, for example, cellulose acetate propionate resin, cellulose acetate butyrate resin, cellulose acetate benzoate resin, cellulose propionate resin, and cellulose butyrate resin are preferably used. That is, a cellulose ester resin having an acyl group having 3 or 4 carbon atoms as a substituent is preferable. Among these, cellulose acetate propionate resin and cellulose propionate resin are particularly preferable. In addition, the portion that is not substituted with an acyl group usually exists as a hydroxyl group.

The cellulose ester resin can be synthesized by a known method. The degree of substitution of the acetyl group and the degree of substitution of other acyl groups are values measured by a method according to ASTM-D817-96.

The weight average molecular weight (Mw) of the cellulose ester resin is preferably 75,000 or more, more preferably 75,000 to 300,000, and more preferably 100000 to 24,000, particularly from the viewpoint of improving compatibility with acrylic resin and brittleness. More preferably, it is particularly preferably from 160000 to 240000. If the weight average molecular weight (Mw) of the cellulose ester resin is too small, the heat resistance and brittleness improvement effects tend to be insufficient. In addition, the cellulose ester resin may be used in combination of two or more cellulose ester resins. In addition, the weight average molecular weight (Mw) of a cellulose ester-type resin can be measured similarly to acrylic resin.

The content ratio of the acrylic resin to the cellulose ester resin is 95: 5 to 30:70 by mass ratio, preferably 95: 5 to 50:50, and 90:10 to 60:40. It is more preferable. If the content of the acrylic resin is too large with respect to the cellulose ester resin, the effect of the cellulose ester resin tends to be insufficient. Further, if the content of the acrylic resin is too small relative to the cellulose ester resin, the effect of the acrylic resin cannot be sufficiently exerted, for example, the moisture resistance of the obtained optical film is insufficient. Tend.

(Resin particles)
Unlike the acrylic resin, the resin particles are not particularly limited as long as they are not soluble in the acrylic resin and the cellulose ester resin solvent. Specifically, for example, acrylic resin particles that are present in a particle state, that is, in an incompatible state, in an optical film containing an acrylic resin and a cellulose ester resin in a compatible state are preferable. More specifically, for example, a predetermined amount of the obtained optical film is collected, stirred in an acrylic resin and a solvent of cellulose ester resin, and a solution in which a component dissolved in the solvent is sufficiently dissolved is acrylic particles. It is preferable that the weight of the insoluble matter filtered and collected using a PTFE membrane filter having a pore size smaller than the volume average particle size is 90% by mass or more of the acrylic resin particles added to the optical film. .

The resin particles are not particularly limited as long as the resin particles are as described above. Specifically, for example, resin particles in which a layer structure of two or more layers is formed are preferable, and a multilayer structure acrylic resin-based granular composite as described below is particularly preferable.

The multilayer structure acrylic resin-based granular composite is formed by laminating the innermost hard layer polymer, the crosslinked soft layer polymer exhibiting rubber elasticity, and the outermost hard layer polymer from the center to the outer periphery. It is a particulate acrylic resin polymer in which a structure is formed. That is, the multilayer structure acrylic resin-based granular composite is a multilayer structure acrylic resin-based granular composite composed of an innermost hard layer, a crosslinked soft layer, and an outermost hard layer from the center to the outer periphery. A multilayer acrylic resin-based granular composite having such a three-layer core-shell structure is preferably used.

Preferred embodiments of the multilayer structure acrylic resin-based granular composite include the following. That is, the thing provided with what each layer formed as follows is mentioned.

Examples of the innermost hard layer polymer include 80% by mass to 98.9% by mass of methyl methacrylate, 1% by mass to 20% by mass of alkyl acrylate having an alkyl group having 1 to 8 carbon atoms, and a polyfunctional grafting agent 0 And those obtained by polymerizing a mixture of monomers consisting of 0.01 mass% to 0.3 mass%.

Examples of the cross-linked soft layer polymer include, in the presence of the innermost hard layer polymer, 75 to 98.5% by mass of an alkyl acrylate having 4 to 8 carbon atoms in the alkyl group, and a polyfunctional cross-linking agent. Examples thereof include those obtained by polymerizing a mixture of monomers consisting of 0.01% by mass to 5% by mass and a polyfunctional grafting agent 0.5% by mass to 5% by mass.

Further, as the outermost hard layer polymer, for example, in the presence of a polymer composed of the innermost hard layer and the crosslinked soft layer, methyl methacrylate has a mass number of 80 to 99% by mass, and the alkyl group has 1 to 8 carbon atoms. And those obtained by polymerizing a mixture of monomers consisting of 1% by mass to 20% by mass of alkyl acrylate.

And the content ratio of each layer is 5 mass% to 40 mass% for the innermost hard layer polymer, 30 mass% to 60 mass% for the soft layer polymer, and 20 mass% to 50 mass% for the outermost hard layer polymer. A multilayer structure acrylic granular composite is preferably used. Furthermore, a multilayer structure acrylic granular composite having an insoluble part when fractionated with acetone and having a methyl ethyl ketone swelling degree of 1.5 to 4 in the insoluble part is more preferable.

As disclosed in Japanese Patent Publication No. 60-17406 or Japanese Patent Publication No. 3-39095, not only the composition and particle diameter of each layer of the multilayer acrylic granular composite are defined, but also the multilayer acrylic system. By setting the tensile modulus of the granular composite and the degree of swelling of methyl ethyl ketone in the acetone-insoluble portion within a specific range, it is possible to realize a further sufficient balance between impact resistance and stress whitening resistance.

Examples of the innermost hard layer polymer include 80% by mass to 98.9% by mass of methyl methacrylate, 1% by mass to 20% by mass of alkyl acrylate having an alkyl group having 1 to 8 carbon atoms, and a polyfunctional grafting agent 0 What is obtained by polymerizing a monomer mixture comprising 0.01 mass% to 0.3 mass% is more preferred. Here, examples of the alkyl acrylate having 1 to 8 carbon atoms in the alkyl group include methyl acrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate, s-butyl acrylate, 2-ethylhexyl acrylate, and the like. Methyl acrylate and n-butyl acrylate are preferably used.

Further, if the content ratio of the alkyl acrylate in the innermost hard layer polymer is too low, the thermal decomposability of the obtained innermost hard layer polymer tends to increase. On the other hand, if the content ratio of the alkyl acrylate is too high, the glass transition temperature of the innermost hard layer polymer is lowered, and the impact resistance imparting effect of the three-layer structure acrylic granular composite tends to be lowered.

Examples of the polyfunctional grafting agent include polyfunctional monomers having different polymerizable functional groups, such as allyl esters of acrylic acid, methacrylic acid, maleic acid, and fumaric acid, and allyl methacrylate is preferred. Used. The polyfunctional grafting agent is used to chemically bond the innermost hard layer polymer and the soft layer polymer. The blending ratio of the polyfunctional grafting agent used at the time of innermost hard layer polymerization is preferably 0.01% by mass to 0.3% by mass, for example.

Examples of the crosslinked soft layer polymer include, in the presence of the innermost hard layer polymer, 75% to 98.5% by mass of an alkyl acrylate having an alkyl group having 1 to 8 carbon atoms, and a polyfunctional crosslinking agent of 0. What is obtained by polymerizing a mixture of monomers composed of 01% by mass to 5% by mass and a polyfunctional grafting agent 0.5% by mass to 5% by mass is preferable.

Here, as the alkyl acrylate having 4 to 8 carbon atoms in the alkyl group, n-butyl acrylate or 2-ethylhexyl acrylate is preferably used.

In addition to these polymerizable monomers, it is possible to copolymerize 25% by mass or less of other monofunctional monomers capable of copolymerization.

Examples of other monofunctional monomers that can be copolymerized include styrene and substituted styrene derivatives. As the ratio of the alkyl acrylate having 4 to 8 carbon atoms of the alkyl group and styrene increases, the glass transition temperature of the crosslinked soft layer polymer decreases, that is, the ratio can be softened as the former increases.

On the other hand, from the viewpoint of the transparency of the resin assembly, it is advantageous to bring the refractive index at room temperature of the soft layer polymer closer to the innermost hard layer polymer, the outermost hard layer polymer, and the acrylic resin, Considering these factors, the ratio of both is selected.

Examples of the polyfunctional grafting agent here include the same polyfunctional grafting agents used when producing the innermost layer hard polymer. The polyfunctional grafting agent used here is used to chemically bond the soft layer polymer and the outermost hard layer polymer. The blending ratio of the polyfunctional grafting agent used during the innermost hard layer polymerization is preferably 0.5% by mass to 5% by mass from the viewpoint of imparting impact resistance.

As the polyfunctional crosslinking agent, generally known crosslinking agents such as divinyl compounds, diallyl compounds, diacrylic compounds, dimethacrylic compounds and the like can be used, but polyethylene glycol diacrylate (molecular weight 200 to 600) is preferably used.

The polyfunctional cross-linking agent used here is used to generate a cross-linked structure during the polymerization of the cross-linked soft layer polymer and to exhibit the effect of imparting impact resistance. However, if the above polyfunctional grafting agent is used in the polymerization of the cross-linked soft layer polymer, a cross-linked structure of the cross-linked soft layer polymer is generated to some extent, so that the polyfunctional cross-linking agent is not an essential component. When a polyfunctional crosslinking agent is used, the blending ratio of the polyfunctional crosslinking agent used during the polymerization of the crosslinked soft layer polymer may be 0.01% by mass to 5% by mass from the viewpoint of imparting impact resistance. preferable.

In the presence of the innermost hard layer polymer and the soft layer polymer, the outermost hard layer polymer is 80% by weight to 99% by weight of methyl methacrylate and 1% by weight of alkyl acrylate having 1 to 8 carbon atoms in the alkyl group. And those obtained by polymerizing a mixture of monomers consisting of 20 to 20% by weight.

As the acrylic alkylate, those described above are used, and methyl acrylate and ethyl acrylate are preferably used. The proportion of the alkyl acrylate unit in the outermost hard layer polymer is preferably 1% by mass to 20% by mass.

Also, when the outermost hard layer polymer is polymerized, an alkyl mercaptan or the like can be used as a chain transfer agent to adjust the molecular weight for the purpose of improving compatibility with the acrylic resin.

In particular, it is preferable to provide the outermost hard layer with a gradient such that the molecular weight gradually decreases from the inside toward the outside in order to improve the balance between elongation and impact resistance. Specifically, the outermost hard layer is divided into two or more monomer mixtures for forming the outermost hard layer, and the amount of chain transfer agent to be added each time is increased sequentially. It is possible to decrease the molecular weight of the polymer forming the layer from the inside to the outside of the multilayer structure acrylic granular composite.

The molecular weight formed at this time can also be examined by polymerizing a mixture of monomers used each time under the same conditions, and measuring the molecular weight of the resulting polymer.

In the multilayer structure acrylic granular composite, the mass ratio of the core and the shell is not particularly limited. Specifically, for example, when the entire multilayer structure acrylic granular composite is 100 parts by mass, the core layer is preferably 50 parts by mass or more and 90 parts by mass or less, and 60 parts by mass or more and 80 parts by mass or less. More preferably. In addition, the core layer here is an innermost hard layer.

Specific examples of such a commercial product of an acrylic granular composite having a multilayer structure include, for example, Metablene manufactured by Mitsubishi Rayon Co., Ltd., Kane Ace manufactured by Kaneka Co., Ltd., Paraloid manufactured by Kureha Co., Ltd. -Examples include Acryloid manufactured by Hearth, Staphyloid manufactured by Gantz Kasei Co., Ltd., Parapet SA manufactured by Kuraray Co., Ltd. and the like. These may be used alone or in combination of two or more.

Also, as the acrylic resin particles of the resin particles, graft copolymer particles are also preferably used. Specifically, the graft copolymer particles, for example, in the presence of a rubbery polymer, unsaturated carboxylic acid ester monomer, unsaturated carboxylic acid monomer, aromatic vinyl monomer, Examples thereof include graft copolymer particles obtained by copolymerizing a mixture of monomers including other vinyl monomers copolymerizable with these, if necessary.

Specific examples of the rubbery polymer include particles containing diene rubber, acrylic rubber, ethylene rubber, and the like. More specifically, for example, polybutadiene, styrene-butadiene copolymer, block copolymer of styrene-butadiene, acrylonitrile-butadiene copolymer, butyl acrylate-butadiene copolymer, polyisoprene, butadiene-methyl methacrylate copolymer. Polymer, butyl acrylate-methyl methacrylate copolymer, butadiene-ethyl acrylate copolymer, ethylene-propylene copolymer, ethylene-propylene-diene copolymer, ethylene-isoprene copolymer, and ethylene-acrylic Examples thereof include particles containing an acid methyl copolymer. These rubbery polymers may be used alone or in combination of two or more.

Also, commercially available acrylic particles can be used. Specific examples include Metabrene W-341 manufactured by Mitsubishi Rayon Co., Ltd., Chemisnow MR-2G manufactured by Soken Chemical Co., Ltd., and Chemisnow MS-300X manufactured by Soken Chemical Co., Ltd.

Further, the content of the resin particles is not particularly limited. Specifically, for example, it is preferably 0.5% by mass to 30% by mass and more preferably 1% by mass to 15% by mass with respect to the total mass of the resin constituting the optical film.

The particle size of the resin particles is not particularly limited. Specifically, for example, the thickness is preferably 10 nm or more and 1000 nm or less, more preferably 20 nm or more and 500 nm or less, and further preferably 50 nm or more and 400 nm or less.

In addition, it is preferable that the refractive index of the resin particles is close to the refractive index of the acrylic resin or the mixture of the acrylic resin and the cellulose ester resin in order to obtain a highly transparent film. Specifically, for example, the difference in refractive index between the resin particles and the acrylic resin is preferably 0.05 or less, more preferably 0.02 or less, and 0.01 or less. Further preferred.

In order to satisfy the refractive index conditions as described above, a method for adjusting the monomer unit composition ratio of the acrylic resin and a composition ratio of the rubbery polymer or monomer used in the acrylic particles are prepared. And the like. By doing so, a refractive index difference can be made small and the protective film for liquid crystal polarizing plates excellent in transparency can be obtained.

The difference in refractive index referred to here means that the protective film for a liquid crystal polarizing plate according to the present invention is sufficiently dissolved in a solvent in which an acrylic resin is soluble to obtain a cloudy solution, which is subjected to an operation such as centrifugation. By separating the solvent soluble portion and the insoluble portion, the soluble portion (acrylic resin) and the insoluble portion (resin particle) were purified, and the measured refractive index (23 ° C., measurement wavelength: 550 nm) was obtained. Indicates the difference.

(Surfactant)
The surfactant is not particularly limited. Specifically, for example, a cationic surfactant (cationic surfactant), an anionic surfactant (anionic surfactant), and an amphoteric surfactant. Any of ionic surfactants such as (nonionic surfactants) and nonionic surfactants such as fluorine-based surfactants can be used. Among these, an ionic surfactant is preferable, and an anionic surfactant is more preferable.

Specific examples of the cationic surfactant include aliphatic amine salts, aliphatic quaternary ammonium salts, benzalkonium salts, benzethonium chloride, pyridinium salts, imidazolinium salt alkylamine oxides, polyamine derivatives, and the like. Can be mentioned.

Examples of anionic surfactants include higher alcohol (C8 to C22) sulfate esters, aliphatic alcohol phosphate esters, alkylaryl sulfonates, alkylamide sulfonates, dibasic fatty acid ester sulfonates, and the like. Is mentioned.

Specific examples of the higher alcohol (C8 to C22) sulfate ester salts include sodium salt of lauryl alcohol sulfate, sodium salt of octyl alcohol sulfate, ammonium salt of lauryl alcohol sulfate, Teepol-81 manufactured by Shell Chemical Co., Ltd. Secondary sodium alkyl sulfate and the like can be mentioned.

Specific examples of the aliphatic alcohol phosphate salts include sodium salt of cetyl alcohol phosphate.

Specific examples of the alkylaryl sulfonates include sodium salt of dodecylbenzene sulfonic acid, sodium salt of isopropyl naphthalene sulfonic acid, sodium salt of dinaphthalenedisulfonic acid, sodium salt of metanitrobenzene sulfonic acid, and the like. .

Specific examples of alkyl amide sulfonates include C ₁₇ H ₃₃ CON (CH ₃ ) CH ₂ SO ₃ Na.

Specific examples of sulfonates of dibasic fatty acid esters include sodium sulfosuccinic acid dioctyl ester and sodium sulfosuccinic acid dihexyl ester.

Specific examples of amphoteric surfactants include carboxybetaine type amphoteric surfactants, sulfobetaine type amphoteric surfactants, aminocarboxylates, imidazolinium betaines, laurylamidopropylbetaines, laurylaminoacetic acid betaines, and the like. Is mentioned.

Specific examples of the fluorosurfactant include perfluoroalkyl sulfonate, perfluoroalkyl carboxylate, perfluoroalkyl ethylene oxide adduct, perfluoroalkyltrimethylammonium salt, perfluoroalkyl group / hydrophilicity. Group-containing oligomers, perfluoroalkyl / lipophilic group-containing oligomers perfluoroalkyl group-containing urethane, and the like.

Moreover, as the surfactant, a commercially available product can be used. Specifically, examples of the anionic surfactant include Elecut S-412-2 manufactured by Takemoto Yushi Co., Ltd. and Electro Stripper F manufactured by Kao Corporation. Examples of the cationic surfactant include Elegan 264WAX manufactured by NOF Corporation and ELECUT S-531 manufactured by Takemoto Yushi Co., Ltd. Examples of the nonionic surfactant include Riquemar S-100 manufactured by Riken Vitamin Co., Ltd.

The content of the surfactant varies depending on the surfactant and the like, but specifically, for example, it is preferably 500 parts by mass or less with respect to 100 parts by mass of the acrylic particles, and is 1 to 500 parts by mass. More preferably, it is 10 parts by mass to 500 parts by mass. When there are too few surfactants, there exists a tendency for the effect by surfactant not to fully exhibit. Moreover, when there is too much surfactant, surfactant will precipitate from the obtained optical film, or the hygroscopic property of an optical film will become high, and there exists a tendency for the quality which is unpreferable to the quality of an optical film to express.

(Additive)
The optical film dope may be appropriately mixed with various additives in order to adjust the chemical properties, mechanical properties, electrical properties, etc. of the optical film obtained using the optical film dope. . Examples of the additive include a plasticizer, an antioxidant, and an ultraviolet absorber.

The plasticizer is not particularly limited, and examples thereof include those added for imparting appropriate flexibility to the obtained optical film. Specifically, for example, ester plasticizers, phosphate ester plasticizers, phthalate ester plasticizers, trimellitic acid ester plasticizers, pyromellitic acid plasticizers, glycolic acid ester plasticizers, citric acid Examples include ester plasticizers and the glycol plasticizers.

Specifically, the ester plasticizer is formed from a polybasic acid such as an aliphatic dibasic acid, an alicyclic dibasic acid, and an aromatic dibasic acid and a polyhydric alcohol such as glycol. And the like. The aliphatic dibasic acid can be used without any particular limitation, and specific examples include adipic acid, sebacic acid, phthalic acid, terephthalic acid, 1,4-cyclohexyl dicarboxylic acid and the like.

Specific examples of the phosphate plasticizer include triphenyl phosphate, tricresyl phosphate, cresyl diphenyl phosphate, octyl diphenyl phosphate, diphenyl biphenyl phosphate, trioctyl phosphate, tributyl phosphate, and the like.

Specific examples of the phthalate ester plasticizer include diethyl phthalate, dimethoxyethyl phthalate, dimethyl phthalate, dioctyl phthalate, dibutyl phthalate, di-2-ethylhexyl phthalate, and butyl benzyl phthalate.

Specific examples of trimellitic acid plasticizers include tributyl trimellitate, triphenyl trimellitate, triethyl trimellitate, and the like.

Specific examples of pyromellitic acid ester plasticizers include tetrabutyl pyromellitate, tetraphenyl pyromellitate, tetraethyl pyromellitate, and the like.

Specific examples of glycolic acid ester plasticizers include triacetin, tributyrin, ethylphthalylethyl glycolate, methylphthalylethyl glycolate, butylphthalylbutyl glycolate, and the like.

Specific examples of the citrate plasticizer include triethyl citrate, tri-n-butyl citrate, acetyl triethyl citrate, acetyl tri-n-butyl citrate, acetyl tri-n- (2- And ethyl hexyl) citrate.

Examples of the glycol plasticizer include ethylene glycol, diethylene glycol, 1,3-propylene glycol, 1,2-propylene glycol, 1,4-butylene glycol, 1,3-butylene glycol, 1,2-butylene glycol and the like. Can be mentioned.

As the plasticizer, the above plasticizers may be used alone or in combination of two or more.

The antioxidant is not particularly limited, and for example, a hindered phenol compound is preferably used. Specifically, for example, 2,6-di-t-butyl-p-cresol, pentaerythrityl-tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], triethylene Glycol-bis [3- (3-tert-butyl-5-methyl-4-hydroxyphenyl) propionate], 1,6-hexanediol-bis [3- (3,5-di-tert-butyl-4-hydroxy Phenyl) propionate], 2,4-bis- (n-octylthio) -6- (4-hydroxy-3,5-di-t-butylanilino) -1,3,5-triazine, 2,2-thio-diethylene Bis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], octadecyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate Nate, N, N′-hexamethylenebis (3,5-di-t-butyl-4-hydroxy-hydrocinnamamide), 1,3,5-trimethyl-2,4,6-tris (3,5 -Di-t-butyl-4-hydroxybenzyl) benzene, tris- (3,5-di-t-butyl-4-hydroxybenzyl) -isocyanurate and the like. In particular, 2,6-di-t-butyl-p-cresol, pentaerythrityl-tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], triethylene glycol-bis [3 -(3-t-butyl-5-methyl-4-hydroxyphenyl) propionate] and the like. Further, for example, hydrazine-based metal deactivators such as N, N′-bis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionyl] hydrazine and tris (2,4-di- A phosphorus processing stabilizer such as t-butylphenyl) phosphite may be used in combination.

The optical film manufactured using the dope obtained by the method for manufacturing a dope for an optical film of the present invention can be used for a protective film for a polarizing plate, and in this case, deterioration of the polarizing plate or liquid crystal, etc. For prevention, an ultraviolet absorber is preferably used.

As the ultraviolet absorber, those which are excellent in the ability to absorb ultraviolet rays having a wavelength of 370 nm or less and have little absorption of visible light having a wavelength of 400 nm or more are preferably used from the viewpoint of good liquid crystal display properties. Specifically, the transmittance at 380 nm is preferably less than 10%, more preferably less than 5%.

Specific examples of ultraviolet absorbers include oxybenzophenone compounds, benzotriazole compounds (benzotriazole ultraviolet absorbers), salicylic acid ester compounds, benzophenone compounds (benzophenone ultraviolet absorbers), and cyanoacrylates. Examples thereof include compounds, nickel complex salts, and triazine compounds.

Among the above UV absorbers, benzotriazole UV absorbers and benzophenone UV absorbers are preferable. Specific examples of the benzotriazole-based UV absorber and the benzophenone-based UV absorber are given below, but the present invention is not limited thereto.

Specific examples of the benzotriazole ultraviolet absorber include 2- (2′-hydroxy-5′-methylphenyl) benzotriazole, 2- (2′-hydroxy-3 ′, 5′-di-tert). -Butylphenyl) benzotriazole, 2- (2'-hydroxy-3'-tert-butyl-5'-methylphenyl) benzotriazole, 2- (2'-hydroxy-3 ', 5'-di-tert-butyl Phenyl) -5-chlorobenzotriazole, 2- (2′-hydroxy-3 ′-(3 ″, 4 ″, 5 ″, 6 ″ -tetrahydrophthalimidomethyl) -5′-methylphenyl) benzotriazole, 2,2 -Methylenebis (4- (1,1,3,3-tetramethylbutyl) -6- (2H-benzotriazol-2-yl) phenol), 2- (2 -Hydroxy-3'-tert-butyl-5'-methylphenyl) -5-chlorobenzotriazole, 2- (2H-benzotriazol-2-yl) -6- (straight and side chain dodecyl) -4-methyl Phenol (TINUVIN171, manufactured by BASF Japan Ltd.), octyl-3- [3-tert-butyl-4-hydroxy-5- (chloro-2H-benzotriazol-2-yl) phenyl] propionate and 2-ethylhexyl-3 -[3-tert-butyl-4-hydroxy-5- (5-chloro-2H-benzotriazol-2-yl) phenyl] propionate (TINUVIN109, manufactured by BASF Japan Ltd.) and the like.

Specific examples of the benzophenone ultraviolet absorber include 2,4-dihydroxybenzophenone, 2,2′-dihydroxy-4-methoxybenzophenone, 2-hydroxy-4-methoxy-5-sulfobenzophenone, bis (2 -Methoxy-4-hydroxy-5-benzoylphenylmethane) and the like.

(solvent)
The solvent used in the method for producing a dope for an optical film of the present invention is not particularly limited as long as the solvent can dissolve the acrylic resin and the cellulose ester resin. Specifically, for example, a chlorinated organic solvent such as methylene chloride, and methyl acetate, ethyl acetate, amyl acetate, acetone, tetrahydrofuran, 1,3-dioxolane, 1,4-dioxane, cyclohexanone, ethyl formate, 2,2 , 2-trifluoroethanol, 2,2,3,3-hexafluoro-1-propanol, 1,3-difluoro-2-propanol, 1,1,1,3,3,3-hexafluoro-2-methyl Non-chlorine organic solvents such as -2-propanol, 1,1,1,3,3,3-hexafluoro-2-propanol, 2,2,3,3,3-pentafluoro-1-propanol, nitroethane, etc. Is mentioned. Among these, methylene chloride, methyl acetate, ethyl acetate, acetone and the like are preferable.

Furthermore, it is preferable that the solvent contains a linear or branched aliphatic alcohol having 1 to 4 carbon atoms. The content is preferably 1% by mass to 40% by mass with respect to the entire solvent. When the content ratio of the alcohol in the dope increases, the web gels, and peeling from the metal support becomes easy. When the content ratio of the alcohol is low, the acrylic resin and cellulose in a non-chlorine organic solvent system There is a role of promoting dissolution of the ester resin.

In addition, an acrylic resin, a cellulose ester resin, a dispersion of acrylic particles, and a surfactant are added to a solvent containing methylene chloride and a linear or branched aliphatic alcohol having 1 to 4 carbon atoms. A dope composition in which at least 15% by mass to 45% by mass in total of three kinds of premixed mixtures is dissolved is preferable.

Examples of the linear or branched aliphatic alcohol having 1 to 4 carbon atoms include methanol, ethanol, n-propanol, iso-propanol, n-butanol, sec-butanol, tert-butanol and the like. It is done. Among these, ethanol is preferred for reasons such as high dope stability, relatively low boiling point, and good drying properties.

(Dope filtration device)
As shown in FIG. 1, the dope filtering device 22 includes a dope stationary pot 3, a first filter 4, a second filter 5, a dope feed pump 2, and the like. In the case where almost no undissolved material, precipitates, or the like are generated in the dope manufactured by the dope manufacturing device 21, the dope filtering device 22 may not be installed. However, in order to reduce foreign matter generation in the obtained optical film. In addition, it is preferable to install a dope filtration device 22.

The dope stationary pot 3 is a container for temporarily storing the dope. Moreover, the viscosity of the dope in the dope stationary pot 3, for example, the dope prepared in the dope charging pot 1 and before feeding to the film forming apparatus 23 is a viscometer disposed in the dope stationary pot 3, for example, CBC. It can be measured using FVM-80A-EXHT manufactured by Co., Ltd. Here, the viscosity of the dope indicates a viscosity at 35 ° C. The first filter 4 and the second filter 5 are filters for filtering undissolved substances and precipitates from the dope stored in the dope stationary pot 3. And the filtration apparatus 22 is provided with the 1st filter 4 and the 2nd filter 5, and is each arrange | positioned in series. As shown in FIG. 1, the dope filter 22 has a filter in which a plurality of filters of the first filter 4 and the second filter 5 are connected in series. One or more species may be connected in series, or one species may be used alone. Moreover, there is no restriction | limiting in particular in the material of the filter medium used for the 1st filter 4 and the 2nd filter 5 with which the dope filtration apparatus 22 is equipped, A normal filter medium can be used. For example, a plastic filter material such as polypropylene, a filter paper using cellulose or rayon, or a metal filter material such as stainless steel is preferable because fibers do not fall off. It is preferable from the viewpoint of removing and reducing impurities, particularly bright spot foreign matter, contained in the raw resin solution by filtration. The filtration accuracy is preferably 0.03 mm or less, and more preferably 0.001 mm to 0.015 mm. Moreover, when using a several filter as mentioned above, it is preferable to provide one filter of 0.002 mm to 0.005 mm.

And dope liquid feed pump 2 in order to make dope liquid feed in pipe 7 smooth to pipe 7 etc. which connect dope stationary pot 3, first filter 4 and second filter 5 You may arrange | position suitably. In particular, it is preferable that the dope liquid feed pump 2 is disposed immediately before the first filter 4 and the second filter 5 in order to increase the filtration pressure.

Therefore, the dope prepared by the dope production apparatus 21 is filtered by the dope filtration apparatus 22 and then sent to the film forming apparatus 23, specifically, the casting die 13 of the film forming apparatus 23.

(Film forming equipment)
As shown in FIG. 1, the film forming apparatus 23 includes an endless belt support 12, a casting die 13, a peeling roller 14, a stretching device 15, a drying device 17, a winding device 18, and the like. The casting die 13 casts the dope 19 on the surface of the endless belt support 12. The endless belt support 12 is formed into a film by forming a web made of the dope 19 cast from the casting die 13 and drying it while being conveyed. The peeling roller 14 peels the film from the endless belt support 12. The stretching device 15 stretches the peeled film. The drying device 17 dries the stretched film while being transported by a transport roller. The winding device 18 winds the dried film into a roll shape to obtain a film roll.

Here, as the dope 19, a dope prepared by the dope manufacturing apparatus 21, filtered by the dope filtering apparatus 22 and sent to the film forming apparatus 23 as necessary is used.

As shown in FIG. 1, the casting die 13 is supplied with a dope 19 from a pipe 7 connected to the upper end of the casting die 13. Then, the supplied dope is discharged from the casting die 13 to the endless belt support 12, and a cast film (web) is formed on the endless belt support 12.

As shown in FIG. 1, the endless belt support 12 is a metal endless belt support having a mirror surface and traveling infinitely. As the endless belt support, for example, an endless belt support made of stainless steel or the like is preferably used from the viewpoint of peelability of the film. The width of the casting film (web) cast by the casting die 13 is not particularly limited, but is 80% of the width of the endless belt support 12 from the viewpoint of effectively using the width of the endless belt support 12. To 99% is preferable. In order to finally obtain an optical film having a width of 1000 mm to 4000 mm, the width of the endless belt support 12 is preferably 1500 mm or more. Further, instead of the endless belt support, a rotating metal drum (endless drum support) having a mirror surface may be used.

The endless belt support 12 dries the solvent in the casting film (web) while conveying the casting film (web) formed on the surface thereof. The drying is performed, for example, by heating the endless belt support 12 or by blowing heated air onto the casting membrane (web). At that time, although the temperature of the cast film (web) varies depending on the kind of dope, it is preferably in the range of −5 ° C. to 70 ° C. in consideration of the transport speed and productivity accompanying the evaporation time of the solvent. A range of from 60 ° C to 60 ° C is more preferred. The higher the temperature of the cast film (web), the higher the drying speed of the solvent, which is preferable. However, when the temperature is too high, foaming and flatness tend to deteriorate.

When the endless belt support 12 is heated, for example, a method of heating the cast film (web) on the endless belt support 12 with an infrared heater, a method of heating the back surface of the endless belt support 12 with an infrared heater, endless Examples include a method of heating the back surface of the belt support 12 by blowing a heated air, and the method can be appropriately selected as necessary.

Further, when the heated air is blown, the wind pressure of the heated air is preferably 50 Pa to 5000 Pa in consideration of the uniformity of solvent evaporation and the like. The temperature of the heating air may be dried at a constant temperature, or may be supplied in several steps in the running direction of the endless belt support 12.

After the dope is cast on the endless belt support 12 to form a cast film (web), the solvent is removed from the endless belt support 12 and the formed film is peeled off. The time between them varies depending on the film thickness of the optical film to be produced and the solvent to be used, but is preferably in the range of 0.5 to 5 minutes in consideration of the peelability from the endless belt support 12.

The traveling speed of the endless belt support 12 is not particularly limited, but is preferably about 50 m / min to 200 m / min from the viewpoint of productivity. The ratio of the running speed of the endless belt support 12 to the flow rate of the dope discharged from the casting die 13 (draft ratio) is preferably about 0.8 to 2. When the draft ratio is within this range, a cast film (web) can be stably formed. For example, if the draft ratio is too large, there is a tendency to cause a phenomenon called neck-in in which the cast film (web) is reduced in the width direction, which makes it impossible to form a wide film.

The peeling roller 14 is disposed in the vicinity of the surface of the endless belt support 12 on the side where the dope 19 is cast, and the distance between the endless belt support 12 and the peeling roller 14 is preferably 1 mm to 100 mm. . Using the peeling roller 14 as a fulcrum, the formed film is peeled by pulling the film formed by removing the solvent from the cast film (web) under tension. When the film is peeled from the endless belt support 12, the film is stretched in the film transport direction (machine direction: MD direction) by the peeling tension and the subsequent transport tension. For this reason, it is preferable that the peeling tension and the conveying tension when peeling the film from the endless belt support 12 are, for example, 50 N / m to 400 N / m.

Further, the residual solvent ratio of the film when the film is peeled off from the endless belt support 12 is the peelability from the endless belt support 12, the residual solvent ratio at the time of peeling, the transportability after peeling, and the optical completed after transporting and drying. Considering physical properties of the film, it is preferably 30% by mass to 200% by mass. In addition, the residual solvent rate of a film is defined by following formula (1).

Residual solvent ratio (mass%) = {(M ₁ −M ₂ ) / M ₂ } × 100 (1)
Here, M ₁ is shows the mass at any point in the film, M ₂ shows the mass after drying for 1 hour at 115 ° C. The film was measured M _1.

The stretching device 15 stretches the film peeled from the endless belt support 12 in a direction (Transverse Direction: TD direction) orthogonal to the web conveyance direction. Specifically, both ends in a direction perpendicular to the film transport direction are gripped by clips or the like, and the distance between the opposing clips is increased, thereby stretching in the TD direction. In addition, in 1st Embodiment, although the extending | stretching apparatus 15 was provided, it does not need to be provided. In that case, it is preferable to extend | stretch so that the extending | stretching rate calculated | required by following formula (2) may be 10% to 50%. Further, the stretching ratio is more preferably 12% to 48%, and further preferably 15% to 45%.

Stretch rate (%) = {(length in the width direction after stretching−length in the width direction before stretching) / length in the width direction before stretching} × 100 (2)
When the stretch ratio is too low, there is a tendency that a desired retardation value cannot be obtained, and it is difficult to widen the optical film. On the other hand, if the stretching ratio is too high, the haze of the film increases and the transparency tends to decrease. For this reason, when the obtained optical film is used as a retardation film provided in a liquid crystal display device such as a liquid crystal panel, the contrast tends to decrease, which is not preferable. In some cases, the film may tear and break from the portion gripped by the gripping means (clip).

In addition, when the film is stretched, the film is usually heated. This film may be heated, for example, by blowing heated air on the film, or may be heated by a heating device such as an infrared heater. Further, the temperature (stretching temperature) at the time of stretching is preferably 100 ° C. to 200 ° C., and more preferably 120 ° C. to 180 ° C. If the stretching temperature is too low, excessive stress is applied to the film, so that the haze of the film increases and the transparency tends to decrease. For this reason, when the obtained film is used as a retardation film provided in a liquid crystal display device such as a liquid crystal panel, the contrast tends to decrease, which is not preferable. In some cases, the film may tear and break from the portion gripped by the gripping means (clip). On the other hand, if the stretching temperature is too high, a desired retardation value cannot be obtained or the film is melted, and the surface state and film thickness of the film tend to be non-uniform.

And the extending | stretching apparatus 15 may be provided with the apparatus which cut | disconnects the area | region which was holding the clip.

The total residual solvent ratio of the film stretched by the stretching apparatus 15 is not particularly limited, but is preferably 1% by mass to 20% by mass from the viewpoint of workability by the drying apparatus 17, for example. When the stretching device 15 is not provided, it is preferable that the total residual solvent ratio of the film is 1% by mass to 20% by mass before the film is supplied to the drying device 17.

The drying device 17 includes a plurality of transport rollers, and dries the film while transporting the film between the rollers. In that case, you may dry using heating air, infrared rays, etc. independently, and you may dry using heating air and infrared rays together. It is preferable to use heated air from the viewpoint of simplicity. The drying temperature varies depending on the amount of residual solvent in the film. However, in consideration of drying time, unevenness of shrinkage, stability of the amount of expansion and contraction, etc. You just have to decide. Moreover, it may be dried at a constant temperature, or may be divided into two to four stages of temperature and divided into several stages of temperature. In addition, the film can be stretched in the MD (Machine Direction) direction while being transported in the drying device 17. The amount of residual solvent in the film after the drying treatment in the drying device 17 is preferably 0.01% by mass to 15% by mass in consideration of the load of the drying process, the dimensional stability expansion / contraction ratio during storage, and the like.

The winding device 18 winds the film having a predetermined residual solvent ratio in the drying device 17 on both ends in the width direction by a hot embossing mechanism, and then winds it on a winding core. The temperature at the time of winding is preferably cooled to room temperature in order to prevent scratches and loosening due to shrinkage after winding. The winder to be used can be used without any particular limitation, and may be a commonly used one, such as a constant tension method, a constant torque method, a taper tension method, or a program tension control method with a constant internal stress. Can be wound up.

Moreover, although the film forming apparatus 23 includes the stretching apparatus 15 and the drying apparatus 17, it may not be provided, and each may be provided at two or more locations.

(Optical film)
Moreover, the optical film manufactured as mentioned above is excellent in transparency, heat resistance, moisture resistance, and workability. Specifically, for example, the haze of the manufactured optical film is preferably 1% or less, more preferably 0.5% or less, although it varies depending on the composition and the like. In addition, variation in haze is small. Specifically, for example, in the width direction of the optical film, three hazes at the end and the center are measured, and the change rate between the maximum value and the minimum value of the measured haze may be less than 10%. preferable. Here, the haze of the optical film can be measured according to JIS K 7136. Specifically, it can be measured using, for example, a haze meter (NDH2000 type manufactured by Nippon Denshoku Industries Co., Ltd.).

The width of the optical film is preferably 1000 mm to 4000 mm from the viewpoint of use in a large liquid crystal display device, use efficiency of the optical film during polarizing plate processing, and production efficiency. The film thickness of the optical film is preferably 30 μm to 90 μm from the viewpoints of thinning the liquid crystal display device and stabilizing the production of the optical film. Here, the film thickness is an average film thickness, and the film thickness is measured from 20 to 200 in the width direction of the optical film with a contact-type film thickness meter manufactured by Mitutoyo Corporation, and the average of the measured values. Values are shown as film thickness.

(Polarizer)
Moreover, the optical film of this invention can be used as a transparent protective film for polarizing plates for protecting the polarizing element of a polarizing plate. Specifically, the polarizing plate includes, for example, a polarizing element and a transparent protective film disposed on the surface of the polarizing element. And the optical film of this invention can be used as the transparent protective film. The polarizing element is an optical element that emits incident light by converting it into polarized light.

As a polarizing plate, for example, an optical film is bonded to at least one surface of a polarizing element produced by immersing and stretching a polyvinyl alcohol film in an iodine solution, using a completely saponified polyvinyl alcohol aqueous solution. Are preferred. Moreover, an optical film may be laminated | stacked also on the other surface of a polarizing element, and the transparent protective film for another polarizing plate may be laminated | stacked. As the transparent protective film for the polarizing plate, for example, as a commercially available cellulose ester film, KC8UX2M, KC4UX, KC5UX, KC4UY, KC8UY, KC12UR, KC8UY-HA, KC8UX-RHA (above, manufactured by Konica Minolta Opto Co., Ltd.), etc. Is preferably used. Or you may use resin films, such as cyclic olefin resin other than a cellulose-ester film, an acrylic resin, polyester, a polycarbonate. In this case, since the saponification suitability is low, it is preferable to perform an adhesive process on the polarizing plate through an appropriate adhesive layer.

As described above, the polarizing plate uses an optical film as a transparent protective film laminated on at least one surface side of the polarizing element. At that time, when the optical film functions as a retardation film, it is preferable that the slow axis of the optical film is arranged so as to be substantially parallel or orthogonal to the absorption axis of the polarizing element.

Further, specific examples of the polarizing element include, for example, a polyvinyl alcohol polarizing film. Polyvinyl alcohol polarizing films include those obtained by dyeing iodine on polyvinyl alcohol films and those obtained by dyeing dichroic dyes. As the polyvinyl alcohol film, a modified polyvinyl alcohol film modified with ethylene is preferably used.

The polarizing element is obtained as follows, for example. First, a film is formed using a polyvinyl alcohol aqueous solution. The obtained polyvinyl alcohol film is uniaxially stretched and then dyed or dyed and then uniaxially stretched. And preferably, a durability treatment is performed with a boron compound.

The film thickness of the polarizing element is preferably 5 μm to 40 μm, more preferably 5 μm to 30 μm, and even more preferably 5 μm to 20 μm.

When laminating a cellulose ester-based optical film on the surface of the polarizing element, it is preferable to bond the cellulose ester-based optical film with a water-based adhesive mainly composed of completely saponified polyvinyl alcohol. Further, in the case of an optical film other than a cellulose ester-based optical film, it is preferably bonded to the polarizing plate through an appropriate adhesive layer.

Since the optical film of the polarizing plate as described above is excellent in transparency, heat resistance, moisture resistance, and workability by using the optical film of the present invention as a transparent protective film, A polarizing plate that can be suitably used for a screened liquid crystal display device is obtained. Specifically, even a polarizing plate for a liquid crystal display device having a large screen can suppress deformation due to moisture absorption. Moreover, since the optical film of this invention with favorable workability is used as a transparent protective film, even if it uses a big optical film, generation | occurrence | production of damage is suppressed.

(Liquid crystal display device)
Moreover, the polarizing plate provided with the optical film of the present invention can be used as a polarizing plate provided in a liquid crystal display device. Specifically, the liquid crystal display device includes, for example, a liquid crystal cell and two polarizing plates arranged so as to sandwich the liquid crystal cell. A polarizing plate can be used as at least one of the two polarizing plates. Note that the liquid crystal cell is a cell in which a liquid crystal substance is filled between a pair of electrodes, and by applying a voltage to the electrodes, the alignment state of the liquid crystal is changed and the amount of transmitted light is controlled. In such a liquid crystal display device, the optical film of the present invention is excellent in transparency, heat resistance, moisture resistance, and workability by using the optical film of the present invention as a transparent protective film for a polarizing plate. Therefore, even if the screen is enlarged, it is possible to provide a liquid crystal display device in which the occurrence of defects in the optical film disposed in the image display area is suppressed. In addition, since the processability of the optical film is good, even in the case of a large optical film that is applied to a large-screen liquid crystal display device, since the occurrence of damage to the optical film is suppressed during manufacturing, A liquid crystal display device having a large screen can be provided.

Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto.

[Example 1]
(Acrylic resin particles)
Acrylic resin particles C1 were prepared as resin particles as follows.

First, 38.2 liters of ion-exchanged water and 111.6 g of sodium dioctylsulfosuccinate were added to a reactor with a reflux condenser having an internal volume of 60 liters, and the temperature was raised to 75 ° C. in a nitrogen atmosphere while stirring at a rotational speed of 250 rpm. Warmed and virtually free of oxygen effects. Then, 0.36 g of ammonium persulfate (APS) was added and stirred for 5 minutes. Thereafter, a monomer mixture consisting of 1657 g of methyl methacrylate (MMA), 21.6 g of n-butyl acrylate (BA), and 1.68 g of allyl methacrylate (ALMA) was added all at once, and after detecting an exothermic peak, an additional 20 Hold for a minute. By doing so, the monomer was polymerized and the innermost hard layer was formed.

Next, 3.48 g of APS was put into a reactor equipped with a reflux condenser while the innermost hard layer was accommodated, and stirred for 5 minutes. Then, a monomer mixture consisting of BA 8105 g, polyethylene glycol diacrylate (PEGDA, molecular weight 200) 31.9 g, and ALMA 264.0 g was continuously added over 120 minutes. After the addition was completed, the mixture was further maintained for 120 minutes. By doing so, the monomer was polymerized and a soft layer was formed on the innermost hard layer.

Next, 1.32 g of APS was put into a reactor equipped with a reflux condenser with the soft layer formed on the innermost hard layer, and stirred for 5 minutes. And the monomer mixture which consists of MMA2106g and BA201.6g was continuously added over 20 minutes, and after completion | finish of addition, it hold | maintained for 20 minutes. By doing so, the monomer was polymerized, and the first outermost hard layer was formed on the soft layer.

Next, 1.32 g of APS was charged into a reactor equipped with a reflux condenser in which the first outermost hard layer was formed, and after 5 minutes, MMA 3148 g, BA 201.6 g, and n-octyl mercaptan A monomer mixture consisting of 10.1 g of (n-OM) was continuously added over 20 minutes, and after completion of the addition, the mixture was kept for another 20 minutes. Thereafter, the temperature was further raised to 95 ° C. and held for 60 minutes. By doing so, the monomer is polymerized, and the multilayer structure acrylic resin granular composite (acrylic resin particle C1) in which the second outermost hard layer is formed on the first outermost hard layer is obtained. A dispersed dispersion was obtained. A small amount of the dispersion thus obtained was collected and the volume average particle diameter was determined by the absorbance method, and the presence of particles having a volume average particle diameter of 0.10 μm was confirmed.

Then, the dispersion was put into a 3% by mass aqueous sodium sulfate solution, salted out and coagulated, and then dehydrated and washed repeatedly. Then, the multilayer structure acrylic resin granular composite (acrylic resin particle C1) was obtained by making it dry.

(Preparation of dispersion containing acrylic resin particles)
First, an acrylic resin particle-containing dispersion was prepared in order to add a surfactant in advance as follows.

In a kettle with a stirrer (not shown) similar to the dope charging kettle (container) 1 shown in FIG. 1, 1 part by mass of the acrylic resin particles C1 prepared as acrylic resin particles and methylene chloride 15 as a solvent. 2 parts by mass of ethanol and 2 parts by mass of ethanol were added, and 0.75 parts by mass of sodium dodecylbenzenesulfonate (ELECUT S-412-2: anionic surfactant manufactured by Takemoto Yushi Co., Ltd.) as a surfactant while stirring. This was added to prepare an acrylic resin particle-containing dispersion (a mixture of a resin particle dispersion and a surfactant).

(Preparation of dope)
Next, a dope containing an acrylic resin particle-containing dispersion was prepared.

In a charging vessel (container) of an optical film manufacturing apparatus as shown in FIG. 1, 40 parts by mass of methyl methacrylate resin (Dianar BR88 manufactured by Mitsubishi Rayon Co., Ltd.) as an acrylic resin, cellulose as a cellulose ester resin Acrylic particle-containing dispersion prepared by 59 parts by mass of acetate propionate resin (acyl group total substitution degree: 2.75, acetyl group substitution degree: 0.19, propionyl group substitution degree: 2.56, Mw: 200000) 18.75 parts by mass were added together with 285 parts by mass of methylene chloride and 38 parts by mass of ethanol. At that time, the mixing ratio (mass ratio) of the acrylic resin, the cellulose ester resin, and the acrylic resin particles is the mixing ratio shown in Table 1. And since the methylene chloride and ethanol contained in the dope contained the methylene chloride and ethanol contained in the acrylic particle-containing dispersion, they were 300 parts by mass and 40 parts by mass, respectively.

Then, the mixture in the container was heated with stirring. Then, the dope was prepared by stirring until the acrylic resin and the cellulose ester resin were dissolved. Thereafter, the obtained dope was cooled to 35 ° C. and filtered using a filter equipped with a filter paper having a filtration accuracy of 0.005 mm.

Using this filtered dope, an optical film was produced as follows.

(Manufacture of optical film)
First, the temperature of the endless belt support having a width of 2 m was adjusted to 22 ° C. The prepared dope is adjusted to 35 ° C., sent to a casting die (coat hanger die) through a pipe, and from the casting die (coat hanger die), a traveling speed of 60 m / min, made of stainless steel and super The prepared dope was cast on an endless belt support polished to a mirror surface. By doing so, a cast film (web) was formed on the endless belt support, and it was conveyed while being dried. Then, the film formed by evaporation of the solvent from the endless belt support was peeled off at a peeling tension of 100 N / m. At that time, the film was dried so that the residual solvent ratio of the film when peeled was 100%.

The peeled film was dried while being conveyed in a roll at 35 ° C. Thereafter, when the residual solvent ratio was 10%, the film was stretched 1.1 times in the width direction using a stretching device (tenter) while holding both ends of the film with clips in an atmosphere of 135 ° C. And after extending | stretching the stretched film at 130 degreeC for 5 minute (s), it was dried, carrying out roll conveyance in 120 degreeC or 140 degreeC atmosphere. In addition, the residual solvent ratio shows the value calculated | required by Formula (1) as described in a specification text.

Thereafter, using a cutting device, the area held by the clip was cut to obtain a film having a width of 1.5 m. And after giving a knurling process which forms the convex part of width 10mm and height 5micrometer on the both ends of the obtained film, it wound up with the winding device, and manufactured the roll-shaped optical film.

[Examples 2 to 22]
An optical film was produced in the same manner as in Example 1 except that the components to be contained and the content thereof were changed to the conditions shown in Table 1.

Specifically, for example, the acrylic resin particles, the type of surfactant, and the addition amount of the surfactant used when producing the acrylic resin particle-containing dispersion are changed to those shown in Table 1, or dope Optical films were produced by replacing the types of acrylic resins and cellulose ester resins used in production and the contents thereof with those shown in Table 1.

In Table 1, BR-85, which is used as an acrylic resin, indicates Dianal BR85 manufactured by Mitsubishi Rayon Co., Ltd. 80N indicates Delpet 80N manufactured by Asahi Kasei Chemicals Corporation.

In Table 1, the acrylic resin particles C2 and the acrylic resin particles C3 used as the acrylic resin particles are respectively Metabrene W-341 manufactured by Mitsubishi Rayon Co., Ltd. and Chemisnow MR-2G manufactured by Soken Chemical Co., Ltd. Indicates.

In Table 1, electro stripper F used as a surfactant indicates polyoxyethylene alkyl ether phosphate (electro stripper F manufactured by Kao Corporation: anionic surfactant). Elegan 264WAX indicates a modified fatty acid dimethylethylammonium etosulphate (Elegan 264WAX: a cationic surfactant manufactured by NOF Corporation). S-100 indicates glycerin monostearate (Riquemar S-100 manufactured by Riken Vitamin Co., Ltd .: nonionic surfactant). Elecut S-531 is a quaternary ammonium salt (Elecut S-531: a cationic surfactant manufactured by Takemoto Yushi Co., Ltd.).

(Comparative Examples 1 to 4, 6)
The components to be contained and the content thereof are replaced with the conditions shown in Table 1, and the acrylic resin particle-containing dispersion is not adjusted in advance, but the dope is prepared using all the components, as in Example 1. Similarly, an optical film was produced. That is, the acrylic resin-containing dispersion is not adjusted in advance, so-called pre-addition, but is added at the same time (direct addition) into the container with the components and contents shown in Table 1 to prepare a dope. In the same manner as in Example 1, an optical film was produced.

(Comparative Example 5)
An optical film was produced in the same manner as in Example 1 except that the dope was prepared in place of the components to be contained and the content thereof shown in Table 1. That is, an optical film was produced in the same manner as in Example 1 except that a dope was prepared without using a surfactant.

(Comparative Example 7)
An optical film was produced in the same manner as in Example 1 except that the components to be contained and the content thereof were changed to the conditions shown in Table 1.

The following evaluation was performed for Examples 1 to 22 and Comparative Examples 1 to 7.

(Haze)
First, the haze of the manufactured optical film was measured according to JIS K7136. Specifically, in the width direction of the manufactured optical film, three hazes at the end portion and the central portion were measured using a haze meter (NDH2000 type manufactured by Nippon Denshoku Industries Co., Ltd.). And the rate of change between the minimum value and the maximum value of the measured haze was calculated. Note that the rate of change is a value obtained by dividing the difference between the maximum value and the minimum value by the maximum value. If the rate of change is less than 10%, it is evaluated as “◯”, if it exceeds 10% and less than 30%, it is evaluated as “Δ”, and if it exceeds 30%, it is evaluated as “x”. did.

(Processability: Ductile fracture)
First, a test body having a size of 100 mm × 10 mm was cut from the manufactured optical film. The cut specimen was subjected to a valley fold and a mountain fold once each so that a crease was formed in the central portion in the longitudinal direction, and it was confirmed whether or not the folded specimen was broken. And the same operation was performed 3 times. In addition, cracking here refers to a test body being divided | segmented into two parts.

As a result, if it was not broken even once, it was evaluated as “◯”, and if it was broken even once, it was evaluated as “x”. From this evaluation, the brittleness of the optical film can be evaluated.

(Processability: Cutting property)
Using a light load tear tester manufactured by Toyo Seiki Seisakusho Co., Ltd., the produced optical film was torn and the tear surface and the like were visually confirmed. At that time, if the tear surface is very smooth and straight, it is evaluated as `` ○ '', and some burrs can be confirmed on the tear surface, but if it is straight, it is evaluated as `` △ '' and straight If it was not torn, it was evaluated as “×”.

(Heat-resistant)
First, the manufactured optical film was cut to a size of 10 cm × 10 cm. The cut optical film was used as a test piece. The test piece was left in an atmosphere of 90 ° C. in a dry state (relative humidity of 5% RH or less) for 1000 hours. Thereafter, the deformation of the optical film was visually confirmed. If the deformation of the optical film cannot be confirmed, it is evaluated as “◯”, and if one deformation of the film is confirmed, it is evaluated as “Δ”, and if two or more deformations of the optical film are confirmed, Evaluated as “x”.

(Moisture resistance)
A cross mark was added as two marks in the casting direction (longitudinal direction) of the manufactured optical film. The distance between the two marks was measured using an optical microscope.

The optical film with this mark was heat-treated by leaving it in an atmosphere of 60 ° C. and 90% relative humidity for 1000 hours. Thereafter, the distance between the two marks was again measured using an optical microscope.

Using the distance between the marks measured as described above, the change rate (dimensional change rate) of the distance was calculated from the following formula (3).

Dimensional change rate (%) = [(L1-L2) / L1] × 100 (3)
In the formula, L1 represents a distance before the heat treatment, and L2 represents a distance after the heat treatment.

If the dimensional change rate is less than 0.3%, it is evaluated as “◯”, and if it is 0.3% or more and less than 0.5%, it is evaluated as “Δ”, and 0.5% or more. If so, it was evaluated as “×”.

The evaluation results are shown in Table 2 below.

As can be seen from Tables 1 and 2, the dope containing an acrylic resin, a cellulose ester resin, and acrylic resin particles, in which a dispersion of acrylic particles is premixed with a surfactant, When a dope obtained by adding an acrylic resin and a cellulose ester resin to a liquid mixed with a solvent so as to have a mass ratio of 95: 5 to 30:70 (Examples 1 to 22) ) When a dispersion of acrylic resin particles is not mixed with a surfactant in advance (Comparative Examples 1 to 4, 6), when a surfactant is not used (Comparative Example 5), and when there is too little acrylic resin. It was found that an optical film excellent in transparency, heat resistance, moisture resistance, and processability can be produced as compared with (Comparative Example 7).

1 Dope charging pot (container)
DESCRIPTION OF SYMBOLS 2 Dope liquid feed pump 3 Dope

stationary pot

4,5 Filter 6 Discharge valve 7 Piping 11 Optical film manufacturing apparatus 12 Endless belt support 13 Casting die 14 Peeling roller 15 Stretching apparatus 17 Drying apparatus 18 Winding apparatus 19 Dope 20 Heat exchanger 21 Dope production device 22 Filtration device 23 Film forming device

Claims

At least a method for producing a dope for an optical film having resin particles, an acrylic resin, and a cellulose ester resin,
A first mixing step of mixing a dispersion of the resin particles and a surfactant to produce a mixture;
And a second mixing step of mixing the resin composition of the acrylic resin and the cellulose ester resin in a mass ratio of 95: 5 to 30:70, a solvent, and the mixture. A method for producing a dope for an optical film.
The method for producing a dope for an optical film according to claim 1, wherein the resin particles are acrylic resin particles.
The method for producing a dope for an optical film according to claim 1 or 2, wherein the surfactant is an ionic surfactant.
The method for producing a dope for an optical film according to claim 3, wherein the ionic surfactant is an anionic surfactant.
The method for producing a dope for an optical film according to any one of claims 1 to 4, wherein the content of the surfactant is 500 parts by mass or less with respect to 100 parts by mass of the resin particles. .
The method for producing a dope for an optical film according to any one of claims 1 to 5, wherein a mass ratio of the acrylic resin to the cellulose ester resin is 95: 5 to 50:50. .
The method for producing a dope for an optical film according to any one of claims 1 to 5, wherein a mass ratio of the acrylic resin to the cellulose ester resin is 80:20 to 60:40. .
A casting process in which a dope is cast on a traveling support to form a film;
In the method for producing an optical film having a peeling step of peeling the film from the support,
The said dope is dope for optical films manufactured by the manufacturing method of the dope for optical films of any one of Claim 1 to 7, The manufacturing method of the optical film characterized by the above-mentioned.
An optical film obtained by the method for producing an optical film according to claim 8.
A polarizing plate comprising a polarizing element and a transparent protective film disposed on at least one surface of the polarizing element,
The said transparent protective film is an optical film of Claim 9, The polarizing plate characterized by the above-mentioned.
A liquid crystal display device comprising a liquid crystal cell and two polarizing plates arranged so as to sandwich the liquid crystal cell,
A liquid crystal display device, wherein at least one of the two polarizing plates is the polarizing plate according to claim 10.