JP2016193520A - Transparent laminated film and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide means for exhibiting flexibility (bending resistance) which can be practically used, particularly, even when used in the application of a substrate for a flexible display and the like, by a simpler technique than conventional techniques, in a transparent laminated film used in a substrate for an optical member and the like using a heat resistant resin such as polyimide.SOLUTION: There is provided a transparent laminated film which has a pair of transparent substrates having a total light transmittance of 80% or more and a glass transition temperature of 270°C or higher, and a silica-based film which is interposed between the pair of transparent substrates and is formed by a sol-gel method, where any moisture permeability of the pair of transparent substrates on condition of 40°C 90%Rh measured according to JISZ0208 is 10-2,000 g/m24hr.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a transparent laminated film and a method for producing the same.

  In recent years, with the progress of miniaturization and weight reduction of highly functional mobile phones, digital cameras, display devices and other various electronic devices, in particular, transparent and flexible as a substrate material used for these instead of conventional glass substrates. Expectations for display substrates are increasing.

  In order to apply to these, in addition to the heat resistance, transparency, and strength that are the characteristics of conventional glass substrates, toughness, moldability, and the like are required. Currently, as a polymer for forming a substrate for an optical member such as a transparent flexible display substrate, for example, a heat resistant resin such as polyimide is known.

Conventionally, as a technique related to a substrate for an optical member using a heat-resistant resin such as polyimide, for example, in Patent Document 1, a barrier layer made of silicon oxide is formed on at least one surface of a plastic film having a glass transition temperature of 200 ° C. or higher. A technique is disclosed in which the barrier layer surface is hydrophobized while being provided with a wet coating method and then treated with chlorosilanes while the film density of the barrier layer is set to 2.00 g / cm ³ or more.

  Moreover, although it is not a technique related to the substrate for optical members, for example, in Patent Document 2, as a gas barrier laminated film used as a packaging laminated body for electronic parts and the like, at least one surface of a base film made of polyamide has silicon oxide and A laminated film is disclosed after providing a transparent gas barrier layer containing a carbon material and further laminating a gas barrier coating film thereon. In addition, a technique for forming a gas barrier coating film from a composition containing a condensate obtained by polycondensation of alkoxysilane by a sol-gel method in the presence of a catalyst together with a predetermined polymer material, and heating it to form a cured film Is also disclosed.

Japanese Patent No. 5598086 JP 2013-226836 A

  While examining the transparent laminated film used for uses, such as a board | substrate for optical members, the present inventors also examined the technique of the patent document 1 and the patent document 2 mentioned above. In the process, when the techniques described in these patent documents are used, a certain degree of gas barrier property is ensured, but the flexibility (fold resistance) particularly required when used for applications such as flexible display substrates. We found that there is still room for improvement in terms of bendability. Moreover, in the technique described in the above patent document, since it is affected by oxygen and moisture in the manufacturing process, it is necessary to perform the manufacturing in an inert atmosphere. In addition, since it is necessary to perform excimer (vacuum ultraviolet) treatment, there is a problem in that the production equipment is enlarged and the running cost is high.

  The present invention has been made in view of the above circumstances, and in a transparent laminated film used for a substrate for an optical member using a heat-resistant resin such as polyimide, by a simpler method than before, particularly for flexible displays. An object of the present invention is to provide means that can exhibit practical flexibility (bending resistance) even when used in applications such as substrates.

  The present inventors have conducted intensive research to solve the above problems. As a result, it has been found that the above problem can be solved by forming a transparent film by forming a silica-based film by a sol-gel method between transparent substrates made of a heat-resistant resin having a certain degree of moisture permeability, The present invention has been completed.

That is, according to one aspect of the present invention, a pair of transparent substrates having a total light transmittance of 80% or more and a glass transition temperature of 270 ° C. or more are interposed between the pair of transparent substrates. And having a silica-based film formed by a sol-gel method, the moisture permeability of each of the pair of transparent substrates under a condition of 40 ° C. and 90% RH measured by JISZ0208 is 10 to 2000 g / m ^2. A transparent laminated film is provided that is 24 hrs.

  According to the present invention, in a transparent laminated film used for a substrate for an optical member using a heat resistant resin, flexibility (folding resistance) that can be practically used even when used for a substrate for a flexible display, etc. Can be exhibited.

It is a schematic sectional drawing which shows one Embodiment of the laminated constitution of the transparent laminated film which concerns on this invention.

According to one aspect of the present invention, the total light transmittance is 80% or more, and the glass transition temperature is 270 ° C. or more, and the pair of transparent substrates is interposed between the pair of transparent substrates, And a silica-based film formed by a sol-gel method, and the moisture permeability under the condition of 40 ° C. and 90% RH measured by JISZ0208 is 10 to 2000 g / m ² · 24 hr. A transparent laminated film is provided.

  As described above, according to the transparent laminated film according to the present invention, the transparent laminated film used for an optical member substrate using a heat-resistant resin is practical even when used for an application such as a substrate for a flexible display. Possible flexibility (bending resistance) can be exhibited. Here, although the mechanism by which the above-described effects by the configuration of the present invention are exhibited is not completely clear, a silica-based film adjacent to the transparent substrate is subjected to a sol-gel method (with hydrolysis / condensation reaction of alkoxysilane). As a result of joining the silica-based film and the transparent base material through an extremely dense adhesion structure, even if the film is bent, the silica-based film and the transparent base material are It is presumed that the fact that microcracks are less likely to occur contributes to the improvement in flexibility (bending resistance) as described above. In addition, this invention shall not be limitedly interpreted by the said mechanism in any way.

  Embodiments of the present invention will be described below. In addition, this invention is not limited only to the following embodiment. In addition, the dimensional ratios in the drawings are exaggerated for convenience of explanation, and may be different from the actual ratios. In this specification, “X to Y” indicating a range means “X or more and Y or less”. Furthermore, unless otherwise specified, measurements such as operation and physical properties are performed under conditions of room temperature (25 ° C.) / Relative humidity 40 to 50% RH.

<Transparent laminated film>
The layer structure of the transparent laminated film according to one embodiment of the present invention will be described with reference to FIG.

  In FIG. 1, a transparent laminated film 11 according to an embodiment of the present invention includes a polyimide film 12 that is a transparent base material (first transparent base material) made of a heat-resistant resin, and a silica-based film 13 formed by a sol-gel method. And the polyimide film 14 which is a transparent base material (2nd transparent base material) which consists of heat resistant resin similarly to a 1st transparent base material has the structure laminated | stacked in this order.

[Transparent substrate]
If the transparent base material (12, 14) constituting the transparent laminated film 11 according to the present invention has a total light transmittance of 80% or more and a glass transition temperature (Tg) of 270 ° C. or more, There is no restriction | limiting in particular about another structure, A thermoplastic resin may be sufficient and curable resin may be sufficient.

  The glass transition temperature of a transparent base material becomes like this. Preferably it is 270-600 degreeC, More preferably, it is 300-550 degreeC, More preferably, it is 320-500 degreeC. Resins in which the glass transition temperature is not substantially observed (for example, in a measurement range of 400 ° C. or lower) can also be preferably used in the present invention. In addition, as a value of the glass transition temperature of a transparent base material, the value measured by the method as described in the column of the Example mentioned later shall be employ | adopted.

  Examples of resins having a Tg of 270 ° C. or higher include polyimide resins (for example, Kapton (trade name: DuPont: 400 ° C. or higher), Upilex-R (trade name: Ube Industries, Ltd .: 285 ° C.), Upilex-S (trade name: Ube Industries, Ltd .: 400 ° C. or higher)), fluorinated polyimide resin (for example, Flupi-01 (trade name: manufactured by NTT: 335 ° C.)), acryloyl resin (compound of Example-1 of JP-A-2002-80616): (The temperature in parentheses represents Tg).

  Moreover, as resin which comprises a transparent base material, resin which has the spiro structure and resin which have a cardo structure described in Unexamined-Japanese-Patent No. 2005-25495 are mentioned. These resins have high heat resistance, high elastic modulus and high tensile fracture stress, and are also excellent in optical transparency and optical isotropy, require various heating operations in the manufacturing process, and bend. It is suitable as a substrate material for a display such as an organic EL element that is required to have a performance that is difficult to be destroyed.

  If Tg is 270 degreeC or more, the resin which comprises a transparent base material can also use curable resin (crosslinked resin) excellent in solvent resistance, heat resistance, etc. other than a thermoplastic resin. As the curable resin, both a thermosetting resin and a radiation curable resin can be used, and those known in the art can be used without particular limitation. Examples of the thermosetting resin include phenol resin, urea resin, melamine resin, unsaturated polyester resin, epoxy resin, silicon resin, diallyl phthalate resin, furan resin, bismaleimide resin, cyanate resin and the like.

  Radiation curable resins are roughly classified into radical curable resins and cationic curable resins. As the curable component of the radical curable resin, a compound having a plurality of radical polymerizable groups in the molecule is used. As a typical example, a polyfunctional acrylate monomer having 2 to 6 acrylate groups in the molecule And a compound having a plurality of acrylate groups in the molecule called urethane acrylate, polyester arylate, and epoxy acrylate.

  In the transparent substrate, different types of resins may be selected and mixed from the above-mentioned thermosetting resins or radiation curable resins, or a thermosetting resin and a radiation curable resin may be used in combination. Good. Moreover, you may mix and use curable resin (crosslinkable resin) and the polymer which does not have a crosslinkable group.

  In a transparent base material, when the said curable resin (crosslinkable resin) is mixed, since the solvent resistance of a transparent base material, heat resistance, an optical characteristic, and toughness are obtained, it is preferable. Moreover, it is also possible to introduce a crosslinkable group into the resin used for the transparent substrate, and any of the polymer main chain terminal, polymer side chain and polymer main chain may have a crosslinkable group. Good. In this case, the base material may be produced without using a general-purpose crosslinkable resin.

  When the transparent laminated film according to the present invention is used in a liquid crystal display application or the like, the resin used is preferably an amorphous polymer in order to achieve optical uniformity. Furthermore, for the purpose of controlling retardation (Ro) and its wavelength dispersion, it is possible to combine resins having different signs of intrinsic birefringence of the resins, or to combine resins having a large (or small) wavelength dispersion.

  The transparent substrate may be stretched. By stretching, mechanical strength such as folding strength is improved, and there is an advantage that handling property is improved. In particular, those having an orientation release stress (ASTMD1504, hereinafter abbreviated as “ORS”) in the stretching direction of 0.3 to 3 GPa are preferable because the mechanical strength is improved. ORS is an internal stress generated by stretching inherent in a stretched film or stretched sheet.

  As the stretching method, a known method can be used. For example, a roll uniaxial stretching method, a tenter uniaxial stretching method, a simultaneous biaxial stretching method, at a temperature between 10 ° C. and 50 ° C. higher than the Tg of the resin, The film can be stretched by a sequential biaxial stretching method or an inflation method. The draw ratio is preferably 1.1 to 3.5 times.

  Although the film thickness of a transparent base material is not specifically limited, It is preferable that it is 5-200 micrometers, It is more preferable that it is 15-150 micrometers, It is more preferable that it is 25-100 micrometers.

  In the present invention, the total light transmittance of the transparent substrate is essentially 80% or more, preferably 85% or more, more preferably 90% or more. Moreover, the value of the total light transmittance is measured with respect to light of 380 to 780 nm, and the measuring method is described in the column of Examples described later. Here, the haze of the transparent substrate is preferably 3% or less, more preferably 2% or less, and even more preferably 1% or less.

Further, in the present invention, moisture permeability under conditions of 40 ° C. 90% RH transparent substrate are both 10~2000g ^/ m 2 · 24hr, and preferably 50~1000g ^/ m 2 · 24hr. Here, the measurement method of the moisture permeability is described in the column of Examples described later.

  The value of the tensile elastic modulus of the transparent substrate is preferably 1.5 to 10 GPa, more preferably 2 to 8 GPa. Here, when the transparent substrate is made of an isotropic film, the same value can be obtained even if the tensile elastic modulus is measured along any direction in the film plane. On the other hand, when the transparent substrate is made of an anisotropic film, the measured value along the slow axis direction of the film is different from the measured value along the fast axis direction. Therefore, in such a case, the arithmetic average value of the measured value along the slow axis direction and the measured value along the fast axis direction of the film is taken as the value of the tensile elastic modulus of the transparent substrate. Here, the value of the in-plane tensile elastic modulus difference (the difference between the measured value along the slow axis direction of the film and the measured value along the fast axis direction) of the transparent substrate is 0 to 2 GPa. It is preferably 0 to 1.7 GPa, more preferably 0 to 1.5 GPa (when this value is 0, it means that the film is isotropic). By setting it as such a structure, generation | occurrence | production of the curl (warp) of a transparent laminated film can be suppressed effectively. In addition, as a value of the tensile elasticity modulus in a transparent base material, the value measured by the method as described in the column of the Example mentioned later shall be employ | adopted.

  Moreover, there is no restriction | limiting in particular also about the value of the hygroscopic expansion coefficient of a transparent base material, Preferably it is 0-50 ppm, More preferably, it is 0-35 ppm. By setting it as such a structure, generation | occurrence | production of the curl (warp) of the transparent laminated film (especially at the time of environmental change) can be suppressed effectively. As the value of the hygroscopic expansion coefficient in the transparent substrate, a value measured by the method described in the column of Examples described later is adopted.

  The transparent base material is a plasticizer, dye / pigment, antistatic agent, ultraviolet absorber, antioxidant, inorganic fine particles, peeling accelerator, leveling agent, inorganic layered silicic acid, as long as the effect of the present invention is not impaired as necessary. Resin modifiers such as salt compounds and lubricants may be included.

  In addition, the transparent laminated film according to the present invention uses a pair of (two) transparent substrates, and the configuration of the pair of transparent substrates may be the same as or different from each other. However, in a preferred embodiment, transparent substrates having the same configuration are used. Here, the difference in tensile elastic modulus between the pair of transparent substrates is preferably 0 to 2 GPa, more preferably 0 to 1.7 GPa, and further preferably 0 to 1.3 GPa. Moreover, the difference in the hygroscopic expansion coefficient between the pair of transparent substrates is preferably 0 to 20 ppm. By setting it as such a structure, when the transparent laminated film is bend | folded, the stress which generate | occur | produces in a film becomes easy to be eased, and the bending resistance of a film improves further.

[Silica film]
In the present invention, the “silica-based film” means a film containing silica (SiO _x ) as a main component. Here, the content of silica in the silica-based film is preferably 50% by mass or more, more preferably 80% by mass or more, still more preferably 90% by mass or more, and particularly preferably 95% by mass or more. Yes, most preferably 98% by mass or more. Examples of components other than silica that can be included in the silica-based film include unreacted alkoxy groups.

  In the present invention, the “silica film” is formed by a sol-gel method. Unlike silica-based films formed by vapor deposition methods such as vapor deposition and sputtering, silica-based films formed by the sol-gel method have a slightly less hydroxyl group or alkoxy group, resulting in a less crystalline structure. There is a perfect part. For this reason, the structure has a high ability to absorb stress due to bending and is less likely to break (crack).

  In order to form a silica-based film by the sol-gel method, a coating film is formed by applying a coating liquid for forming a silica-based film containing alkoxysilane or a hydrolyzate or partial condensate thereof, and the coating film is heated. Good. Here, as a preferable production method of the transparent laminated film according to the present invention, a coating film is formed by applying the coating liquid on the surface of a single transparent substrate (coating film forming step), and the exposed surface of the coating film Another method is to laminate another transparent base material to obtain a laminate (lamination step) and to heat the laminate. Hereinafter, a method for producing a transparent laminated film by such a production method will be described.

(Coating film formation process)
In this step, first, a coating solution for forming a silica-based film containing alkoxysilane or a hydrolyzate or partial condensate thereof is prepared. The coating solution may be a commercially available product or one prepared by itself.

  Although there is no restriction | limiting in particular about alkoxysilane, For example, tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, tetrabutoxysilane etc. are mentioned. Among these, use of an alkoxysilane having a relatively small molecular weight (for example, tetraalkoxysilane having an alkoxy group having 3 or less carbon atoms) is preferable because the silica-based film tends to be dense. An alkoxysilane polymer having an average degree of polymerization of 5 or less is also preferably used.

  The solvent of the coating solution is not particularly limited, but in addition to ketone solvents such as acetone, methyl ethyl ketone, and cyclohexanone, alcohol solvents such as methanol, ethanol, isopropanol, and butanol, ether solvents such as tetrahydrofuran, and esters such as methyl acetate. A system solvent or the like can also be used.

  The coating liquid usually contains a catalyst. The catalyst may be an acid catalyst or a base catalyst, but an acid catalyst is preferably used particularly from the viewpoint of increasing the hardness and density of the membrane.

Examples of the acid catalyst include mineral acids such as hydrochloric acid, nitric acid, boric acid, and borohydrofluoric acid; carbonic acid; organic acids such as acetic acid, formic acid, oxalic acid, trifluoroacetic acid, p-toluenesulfonic acid, and methanesulfonic acid; Preferably, the acid of pKa ≦ 0, perfluorosulfonic acid / PTFE copolymer (H ⁺ type) (for example, Nafion NR50 (registered trademark) manufactured by DuPont), polystyrene sulfonic acid (for example, Amberlyst 15 manufactured by Rohm and Haas) ( Solid acids such as (registered trademark)); and photoacid generators that generate acid upon irradiation with light, specifically, diphenyliodonium hexafluorophosphate, triphenylphosphonium hexafluorophosphate, and the like.

  Examples of the base catalyst include amine compounds and alkali metal hydroxides. Among them, it is preferable to use an amine compound. Examples of such amine compounds include ammonia, methylamine, dimethylamine, trimethylamine, ethylamine, dimethylamine, and trimethylamine.

Inside the above coating solution consisting of a solution containing alkoxysilane, solvent, catalyst, water (for dissolving the catalyst, impurities in the solvent, entering from the humidity of the atmosphere, etc.), during its preparation, during storage and after coating In the above, the hydrolysis reaction shown in the following formula (1) is carried out between the alkoxysilane and water by the action of the catalyst (wherein R is an alkyl group).
_{(-Si-OR) + (H} 2 O) → (-Si-OH) + (ROH) ··· (1)
In addition, hydrolyzed silanol groups (—Si—OH) are subjected to a dehydration condensation reaction as shown in the following formula (2) to form a siloxane bond (—Si—O—Si—).
(—Si—OH) + (— Si—OH) → (—Si—O—Si —) + (H ₂ O) (2)
Whether the alkoxy group of the alkoxysilane undergoes a hydrolysis reaction as shown in the above formula (1) in the coating solution comprising a solution containing an alkoxysilane, etc., and the hydrolyzed silanol groups (—Si—OH) Whether or not to perform a dehydration condensation reaction as shown in the above formula (2) in the coating solution greatly depends on the catalyst concentration in the solution, the concentration of the alkoxysilane or its hydrolyzate, and the amount of water. The lower the concentration of the alkoxysilane and the water content, the less likely the reaction of the above formula (1) occurs, and consequently the less the reaction of the above formula (2) occurs, and the acid concentration of the coating solution is 0-3 in pH. When it is within the range, the reaction of the above formula (1) occurs rapidly, but the reaction of the above formula (2) hardly occurs.

  If a large amount of water is present in the coating solution, the hydrolysis reaction of alkoxysilane is promoted in the solution, and a dehydration condensation reaction is likely to occur, and unevenness in film thickness is likely to occur during drying after coating of the coating solution. Therefore, the concentration of water in the coating solution is preferably as small as possible. Specifically, the concentration of water in the coating solution is preferably 0 to 10% by mass, more preferably 0 to 2% by mass, and still more preferably 0 to 1% by mass.

  When the coating liquid containing the alkoxysilane and the catalyst is stirred, in the coating liquid, the alkoxysilane mainly forms a hydrolyzate by the reaction of the above formula (1), and the hydrolyzate by the reaction of the above formula (2). A part of this undergoes dehydration condensation reaction. In this way, a coating solution is prepared, and in this coating solution, alkoxysilane is present in the form of a monomer (including a hydrolyzate) or a polymer (partial condensate) of less than 20 mer.

  In this step (coating film forming step), the coating solution prepared above is applied to one surface of the transparent substrate described above. There is no restriction | limiting in particular about the specific method for performing application | coating, A conventionally well-known knowledge can be referred suitably.

  Here, the applied coating liquid is heated and converted into a silica-based film in a heating step described later, and the hydrolysis / condensation reaction at this time efficiently proceeds even with the surface of the transparent substrate. Therefore, in order to increase the reaction point on the coated surface of the transparent substrate, the surface of the transparent substrate adjacent to the coating film (surface on which the coating solution is applied) is subjected to a surface hydrophilization treatment, and then the coating solution is applied. It is preferable to do. Here, examples of the surface hydrophilization treatment that can be performed to increase the reaction point include corona discharge treatment, excimer (vacuum ultraviolet) treatment, oxygen plasma treatment, and UV ozone treatment. There is no restriction | limiting in particular about the specific method for performing these surface hydrophilization processes, A conventionally well-known knowledge can be referred suitably. When such surface hydrophilization treatment is performed, the coated surface of the transparent substrate is hydrophilized, and, for example, a large number of hydroxy groups (—OH groups) are generated on the surface of the transparent substrate. When the coating solution is applied in this state and a heating process described later is performed, the hydroxy group becomes involved in the condensation reaction of alkoxysilane. As a result, it is possible to further improve the adhesion between the transparent substrate and the silica-based film.

  After performing the coating film forming step, it is preferable to carry out a step of drying the coating film (drying step) before the laminating step described later. Although there is no restriction | limiting in particular about the specific conditions of a drying process, The other transparent base material (2nd transparent base material) laminated | stacked on the exposed surface of a coating film in the lamination process mentioned later, and the said coating film From the standpoint of ensuring sufficient adhesion, it is better not to dry under very strong conditions. From such a viewpoint, the drying temperature is about 30 to 150 ° C., and the drying time is about 1 to 100 minutes.

(Lamination process)
In this step, another transparent base material (second transparent base material) is laminated on the exposed surface of the coating film formed in the above-described coating film forming step to obtain a laminate.

(Heating process)
In this step, the stacked body obtained in the above-described stacking step is heated. As a result, the hydrolysis / condensation reaction of the alkoxysilane or the hydrolyzate or partial condensate thereof contained in the coating film is advanced to convert the coating film into a silica-based film. As a result, the transparent laminated film according to the present invention is obtained.

  Here, when the coating film as a precursor of the silica-based film is heated in a state of being sandwiched between a pair of transparent substrates having a certain degree of moisture permeability, and the silica-based film is formed by the sol-gel method, the condensation reaction proceeds. Accordingly, water (water vapor) generated by dehydration passes through the transparent base material and is released to the outside of the laminate. For this reason, there exists an advantage that a silica-type film | membrane is easy to be formed.

  There is no restriction | limiting in particular also about the conditions at the time of performing a heating process, Arbitrary conditions may be employ | adopted if it is the conditions which can convert the said coating film into a silica-type film | membrane. However, from the viewpoint of preventing the deterioration of the transparent substrate, the heating temperature is preferably 1 ° C. or more lower than the glass transition temperature (Tg) of the transparent substrate, and more preferably 3 ° C. or more. Preferably, the temperature is lower by 5 ° C. or more. If the material of the transparent substrate changes, its glass transition temperature also changes. Therefore, it is not easy to uniquely define the preferred form of the heating temperature, but as a preferred example, the heating temperature is preferably 250 to 500 ° C. More preferably, it is 280-500 degreeC, More preferably, it is 310-500 degreeC. The heating time is usually about 1 to 100 minutes, and preferably 15 to 40 minutes. Furthermore, although there is no restriction | limiting about the atmospheric conditions at the time of performing heat processing, From a viewpoint that a transparent base material becomes difficult to oxidize, it is preferable to heat-process in an inert atmosphere.

(UV irradiation process)
When manufacturing the transparent laminated film which concerns on this invention, it is preferable to perform the process which performs an ultraviolet irradiation process with respect to the laminated body containing a silica type film | membrane after the heating process mentioned above. By performing such a process, it becomes possible to more surely proceed the hydrolysis / condensation reaction of alkoxysilane inside the silica-based film or at the interface between the silica-based film and the transparent substrate, and the entire transparent laminated film It becomes possible to reduce the water vapor transmission rate. Here, in order to reliably obtain the above effects by performing the ultraviolet irradiation step, it is preferable that the irradiated ultraviolet rays sufficiently reach the silica-based film. From such a viewpoint, when the ultraviolet irradiation process is performed, it is preferable that the transmittance of the transparent substrate disposed at least on the ultraviolet incident side with respect to light having a wavelength of 365 nm is 5% or more. Further, it is more preferable that the pair of transparent base materials satisfy these regulations.

  The thickness of the silica-based film thus formed is preferably 0.05 to 15 μm, more preferably 0.1 to 12 μm, and further preferably 0.5 to 5 μm. If the film thickness of the silica film is 0.05 μm or more, the gas barrier property of the transparent laminated film can be improved even by the presence of the silica film. On the other hand, when the film thickness of the silica film is 15 μm or less, the bending resistance of the transparent laminated film can be further improved.

(Physical properties of transparent laminated film)
According to a preferred embodiment of the present invention, some physical properties of the transparent laminated film provided above are defined.

First, the moisture permeability of the transparent laminated film according to the present invention under the condition of 40 ° C. and 90% RH as measured by JISZ0208 is preferably 0.1 g / m ² · 24 hr or less. Here, the measurement method of the moisture permeability is described in the column of Examples described later.

  Moreover, the total film thickness of the transparent laminated film which concerns on this invention becomes like this. Preferably it is 10-200 micrometers, More preferably, it is 15-150 micrometers, More preferably, it is 15-100 micrometers.

[Use of transparent laminated film]
The transparent laminated film according to the present invention can be used for various applications, but the transparent laminated film according to the present invention as described above has excellent transparency and bending resistance. For this reason, the transparent laminated film which concerns on this invention is a use as a board | substrate (electronic device board | substrate) for electronic devices, such as an organic electroluminescent (EL) element, a photoelectric conversion element (solar cell element), and a liquid crystal display element. It can be preferably used.

  The present invention will be specifically described using the following examples and comparative examples. However, the technical scope of the present invention is not limited only to the following examples. Unless otherwise specified, “%” and “part” mean “% by mass” and “part by mass”, respectively. In the following examples, unless otherwise specified, the operation was performed under conditions of room temperature (25 ° C.) / Relative humidity 40 to 50% RH.

(Production of transparent substrate)
(Preparation of transparent substrates 1, 9 and 10)
Transparent substrates 1, 9, and 10 were produced by the following method using KPI-MX300F manufactured by Kawamura Sangyo Co., Ltd.

First, the dope was prepared by mixing and stirring the following components:
Methylene chloride 100 parts by mass Cyclohexanone 1 part by mass KPI-MX300F 10 parts by mass

  Subsequently, the dope prepared above was cast on a metal drum, and dried by applying hot air to peel off. At this time, the casting speed was adjusted so that the residual solvent amount at the time of peeling the film was 10 to 18% by mass. After peeling off the film, the film was fixed to a metal frame and further dried at 150 ° C. for 20 minutes to produce a transparent substrate 1 (film thickness 25 μm).

  A transparent substrate having a film thickness of 35 μm, which was adjusted only in flow rate in the same manner as the transparent substrate 1, was stretched by 40% at 220 ° C. using a uniaxial stretching machine having a width, and then fixed to a metal frame to 150%. Drying was carried out at 20 ° C. for 20 minutes to produce a transparent substrate 9 (film thickness 25 μm).

  In addition, a transparent base material having a film thickness of 38 μm, in which only the flow rate was adjusted in the same manner as the transparent base material 1, was stretched 55% at 225 ° C. using a uniaxial stretching machine with a width, and subsequently fixed to a metal frame. The substrate was dried at 150 ° C. for 20 minutes to produce a transparent substrate 10 (film thickness 25 μm).

The transparent substrates 1, 9 and 10 obtained above were subjected to corona discharge treatment on one side, and then subjected to excimer (vacuum ultraviolet) irradiation at a wavelength of 172 nm under a nitrogen atmosphere under a condition of 200 mJ / cm ^2. This was used for the production of a transparent laminated film described later. Moreover, about the following transparent base materials, what gave the corona discharge process by the said conditions on the single side | surface was used for preparation of the transparent laminated film mentioned later.

(Preparation of transparent substrates 2 and 7)
Spixeria TP003 (varnish) manufactured by Somar was cast on a SUS304 plate and dried in an oven at 120 ° C. for 25 minutes. Next, the film was peeled off from the SUS304 plate, and then fixed to a metal frame and dried at 150 ° C. for 60 minutes to produce a transparent substrate 2 (film thickness 25 μm).

  Moreover, the transparent base material 7 (film thickness of 18 micrometers) was produced by the method similar to the above except having changed the casting amount.

(Preparation of transparent substrate 3)
Pyromellitic dianhydride 39.7 g (0.180 mol) and N, N-dimethylacetamide 130 g were added to a 300 mL five-necked separable flask equipped with a thermometer, a stirrer, and a nitrogen inlet tube. Stirring to obtain a slurry of pyromellitic dianhydride. On the other hand, a mixed solution of 27.8 g (0.180 mol) of norbornanediamine and 27.8 g of N, N-dimethylacetamide was prepared. This mixed solution was dropped into the slurry over 120 minutes while keeping the temperature constant. Thereafter, the mixed solution was stirred at 50 ° C. for 5 hours to prepare a polyimide precursor-containing solution 1.

  The polyimide precursor containing solution 1 prepared above was applied onto a glass substrate to form a polyimide precursor layer composed of a coating film of the polyimide precursor containing solution 1. And the laminated body with a glass substrate and a polyimide precursor layer was dried at 150 degreeC for 20 minute (s) in oven, and the film was peeled from the glass substrate. Subsequently, the peeled film was fixed to a metal frame and placed in an inert oven. Then, the oxygen concentration in the inert oven is controlled to less than 0.1% by volume, the atmosphere in the oven is heated from 30 ° C. to 300 ° C. over 30 minutes, and further maintained at 300 ° C. for 2 hours, Drying and imidization reactions were advanced to produce a transparent substrate 3 (film thickness 25 μm).

(Preparation of transparent substrates 4 and 11)
To a 300 mL five-necked separable flask equipped with a thermometer, a stirrer, and a nitrogen inlet tube, 3.15 / 1 of 1,4-cyclohexanediamine (CHDA) (trans ratio 99%) and norbornanediamine (NBDA) A mixture of (mass ratio) (total 0.140 mol) and 168 g of N-methyl-2-pyrrolidone (NMP) as an organic solvent were added and stirred. After the solution became clear, 37.1 g (0.126 mol) of 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride (BPDA) was added in powder form, and the reaction vessel was kept at 120 ° C. And bathed in an oil bath maintained for 5 minutes. At this time, stirring was continued after addition of BPDA, and after removing the oil bath, stirring was further performed at room temperature for 18 hours to prepare a polyimide precursor-containing solution 2.

  The polyimide precursor containing solution 2 prepared above was applied onto a glass substrate to form a polyimide precursor layer composed of a coating film of the polyimide precursor containing solution 2. And the laminated body with a glass substrate and a polyimide precursor layer was dried at 150 degreeC for 20 minute (s) in oven, and the film was peeled from the glass substrate. Subsequently, the peeled film was fixed to a metal frame and placed in an inert oven. Then, the oxygen concentration in the inert oven is controlled to less than 0.1% by volume, the atmosphere in the oven is heated from 30 ° C. to 300 ° C. over 30 minutes, and further maintained at 300 ° C. for 2 hours, Drying and imidization reactions were advanced to produce a transparent substrate 4 (film thickness 25 μm).

  In addition, a film peeled from a glass substrate having a film thickness of 42 μm whose flow rate is adjusted using the same material as described above, is stretched 1.5 times in one direction and 1.1 times in the orthogonal direction by a biaxial stretching machine, and then formed into a metal frame. It fixed, put into inert oven, the process similar to preparation of the said transparent base material 4 was performed, and the transparent base material 11 (film thickness of 25 micrometers) was produced.

(Preparation of transparent substrate 5)
Lucera HF-6301 (transparent resin varnish) manufactured by JSR Co. was added to methanol to precipitate the resin, and the precipitate was further washed and dried to obtain a resin solid.

The dope was then prepared by mixing and stirring the following ingredients:
100 parts by mass of methylene chloride 1 part by mass of cyclohexanone 11 parts by mass of the resin solid content.

  Subsequently, the dope prepared above was cast on a metal drum, and dried by applying hot air to peel off. At this time, the casting speed was adjusted so that the amount of residual solvent at the time of peeling the film was 10% by mass. After peeling off the film, the film was fixed to a metal frame and further dried at 150 ° C. for 20 minutes to produce a transparent substrate 5 (film thickness 25 μm).

(Preparation of transparent substrate 6)
To a 300 mL five-necked separable flask equipped with a Dean-Stark apparatus equipped with a thermometer, a stirrer, a nitrogen introducing tube, and a cooling tube, and a dropping funnel, 4,4′-bis (4-aminophenoxy) biphenyl (BAPB) 26.48 g (0.07187 mol), γ-butyrolactone (GBL) 51.11 g, and triethylamine (TEA) 0.364 g were added and stirred under a nitrogen atmosphere to obtain a solution.

  To this solution, 16.11 g (0.07187 mol) of 1,2,4,5-cyclohexanetetracarboxylic dianhydride (HPMDA) and 12.78 g of dimethylacetamide (DMAC) were added all at once, The reaction system was heated by a bath to raise the temperature inside the reaction system to 180 ° C. And the temperature in reaction system was maintained at 180 degreeC for 3.5 hours, collecting the component distilled off.

  Next, after further adding 96.11 g of DMAC, the reaction system was stirred for about 30 minutes at a temperature in the vicinity of 130 ° C. to obtain a uniform solution, air-cooled to 100 ° C. over about 10 minutes, and a polyimide solution having a solid content concentration of 20% by mass. Got. The obtained polyimide solution was allowed to cool and then poured into methanol to precipitate a polyimide, and the precipitate was further washed and dried to obtain a polyimide resin solid.

The dope was then prepared by mixing and stirring the following ingredients:
100 parts by mass of methylene chloride 1 part by mass of cyclohexanone 10 parts by mass of the above polyimide resin solid content.

  Subsequently, the dope prepared above was cast on a metal drum, and dried by applying hot air to peel off. At this time, the casting speed was adjusted so that the residual solvent amount at the time of peeling the film was 16% by mass. After peeling off the film, the film was fixed to a metal frame and further dried at 150 ° C. for 20 minutes to produce a transparent substrate 6 (film thickness 25 μm).

(Preparation of transparent substrates 8 and 14)
First, the solid content of polyarylate resin was obtained by the following method.

(Synthesis of polyarylate resin solids)
After adding 2514 parts by mass of water to a reaction vessel equipped with a stirrer, 22.7 parts by mass of sodium hydroxide and 9,9-bis (3,5-dimethyl-4-hydroxyphenyl as an aromatic dialcohol component ) Fluorene (BCF) 35.6 parts by mass, 2,2-bis (3,5-dimethyl-4-hydroxyphenyl) propane (TMBPA) 18.5 parts by mass, p-tert-butylphenol (PTBP) as a molecular weight regulator 0.049 part by mass was dissolved, and 0.34 part by mass of a polymerization catalyst (tributylbenzylammonium chloride) was added and stirred.

  On the other hand, 26.8 parts by mass of an equal mixture of terephthalic acid chloride and isophthalic acid chloride as an aromatic dicarboxylic acid component was weighed and dissolved in 945 parts by mass of methylene chloride. This methylene chloride solution was added to the alkaline aqueous solution prepared above with stirring to initiate polymerization. The polymerization reaction temperature was adjusted to be 15 ° C. or higher and 20 ° C. or lower. The polymerization was carried out for 2 hours, and then acetic acid was added to the system to stop the polymerization reaction, and the organic phase and the aqueous phase were separated.

  The obtained organic phase was washed with ion exchange water twice as much as the organic phase for each washing, and then the operation of separating the organic phase and the aqueous phase was repeated. The washing was terminated when the electric conductivity of the washing water became less than 50 μS / cm. The organic phase after washing was put into a hot water tank equipped with a homomixer at 50 ° C., and methylene chloride was evaporated to obtain a powdery polymer. Furthermore, dehydration and drying were performed to obtain a polyarylate resin solid.

The dope was then prepared by mixing and stirring the following ingredients:
100 parts by mass of methylene chloride 1 part by mass of cyclohexanone 10 parts by mass of the polyarylate resin solid content.

  Subsequently, the dope prepared above was cast on a metal drum, and dried by applying hot air to peel off. At this time, the casting speed was adjusted so that the residual solvent amount at the time of peeling the film was 22% by mass. After peeling off the film, the film was fixed to a metal frame and further dried at 150 ° C. for 20 minutes to produce a transparent substrate 8 (film thickness 25 μm).

  Further, the transparent substrate 8 obtained above was stretched 20% at 255 ° C. using a width-maintaining uniaxial stretching machine, then fixed to a metal frame and dried at 150 ° C. for 20 minutes, A transparent substrate 14 (film thickness 20 μm) was produced.

(Preparation of transparent substrate 12)
Spixeria TP001 (varnish) manufactured by Somar was cast on a SUS304 plate, and dried in an oven at 120 ° C. for 25 minutes. Next, the film was peeled off from the SUS304 plate, and then fixed to a metal frame and dried at 150 ° C. for 60 minutes to produce a transparent substrate 12 (film thickness 30 μm).

(Preparation of transparent substrate 13)
In a 300 mL five-necked separable flask equipped with a thermometer, a stirrer, a nitrogen inlet tube, and a dropping funnel, 15.7 g (0.110 mol) of 1,4-bis (aminomethyl) cyclohexane and N, N- 192 g of dimethylacetamide was added and stirred. To this mixed solution, 32.4 g (0.110 mol) of powdery 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride was added. After the addition of 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, the reaction vessel was bathed in an oil bath maintained at 120 ° C. for 5 minutes. Here, although the salt precipitated about 3 minutes after the addition of 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, it quickly dissolved. This mixed solution was further stirred at room temperature for 18 hours to obtain a polyimide precursor-containing solution 3.

  The polyimide precursor containing solution 3 prepared above was applied onto a glass substrate to form a polyimide precursor layer composed of a coating film of the polyimide precursor containing solution 3. And the laminated body of a glass substrate and a polyimide precursor layer was dried at 150 degreeC for 30 minute (s) in oven, and the film was peeled from the glass substrate. During peeling, the film was stretched 1.3 times in the peeling direction due to peeling tension. Subsequently, the peeled film was fixed to a metal frame and placed in an inert oven. Then, the oxygen concentration in the inert oven is controlled to less than 0.1% by volume, the atmosphere in the oven is heated from 30 ° C. to 270 ° C. over 40 minutes, and further maintained at 270 ° C. for 2 hours, Drying and imidization reaction was advanced to produce a transparent substrate 13 (film thickness 25 μm).

[Measurement of physical properties of transparent substrate]
About the transparent base materials 1-14 produced above, various physical properties were measured with the following methods. The results are shown in Table 1 below.

(Measurement of total light transmittance and haze)
Based on JISK7361, total light transmittance and haze were measured using a haze meter (manufactured by Murakami Color Research Laboratory Co., Ltd., HM-150).

(Measurement of glass transition temperature (Tg))
Based on JISK7121 (1987), the glass transition temperature of the transparent substrate was measured. As a measuring apparatus, DSC 6220 manufactured by Seiko Instruments Inc. was used, and a sample of 10 mg of a transparent substrate was used, and the measurement was performed under a temperature rising rate of 10 ° C./min.

(Measurement of moisture permeability)
Based on JISZ0208, the moisture content permeating through the transparent substrate was measured from the mass change of calcium chloride by the cup method under the condition of 40 ° C. and 90% RH, and the moisture permeability (unit: g / m ² · 24 hr) was obtained. .

(Measurement of tensile modulus)
The value of the tensile modulus was measured by the following method according to JISK7127.

  First, the film was cut into a size of 100 mm (MD direction) × 10 mm (TD direction) to prepare a sample. This sample was pulled in the longitudinal direction (MD direction) of the sample using Tensilon RTC-1225A manufactured by Orientec Co., Ltd., and the distance between chucks was 50 mm, and the tensile elastic modulus in the MD direction was measured. Similarly, the tensile elastic modulus in the width direction (TD direction) of the sample was also measured. The measurement was performed at 23 ° C. and 55% RH. Here, from the evaluation using an automatic birefringence meter (manufactured by Oji Scientific Instruments, KOBRA31PR), the direction in which the refractive index is maximum (the slow axis direction) is the direction in which the tensile modulus is maximum in the plane of the film. The direction perpendicular to it (the fast axis direction) was the direction in which the tensile elastic modulus was minimized. Table 1 below also shows the average value of the tensile modulus in each of the slow axis direction and the fast axis direction, and the absolute value of the difference in the tensile modulus in each of the slow axis direction and the fast axis direction. It is described.

(Measurement of hygroscopic expansion coefficient)
The hygroscopic expansion coefficient was measured using TMA7100 manufactured by Seiko Instruments Inc. and a circulation type humidity control unit. Specifically, the sample is such that the slow axis direction calculated using an automatic birefringence meter (manufactured by Oji Scientific Instruments Co., Ltd., KOBRA31PR) is 3 mm in width so that the long axis direction is the long axis direction, and the length of the measurement portion is 10 mm. , Set the device tension to the minimum tension, change the humidity at 23 ° C, measure the dimensions 60 minutes after the environment stabilizes, and calculate the hygroscopic expansion coefficient in the slow axis direction did. The relative humidity in the dimension measurement environment was set at three points of 15%, 50%, and 90%. The results are shown in Table 1 below.

[Production of transparent laminated film]
(Preparation of transparent laminated film 1)
After mixing materials with the following composition and stirring at room temperature for 45 minutes, the solid catalyst was separated by filtration to prepare a coating solution for forming a silica-based film containing a condensate of reactive alkoxysilane.

Acetone 100 parts by mass Tetraethoxysilane (TEOS) 10 parts by mass Amberlyst 15 (solid catalyst) 2 parts by mass.

  Subsequently, the silica-based film-forming coating solution prepared above was applied to the surface of the transparent substrate 1 prepared above subjected to the corona discharge treatment using a wire bar, and warm air of 60 ° C. to 80 ° C. And dried for 10 minutes to form a coating film. Subsequently, another transparent base material 1 was laminated | stacked on the formed coating film using a roll so that the surface which gave the corona discharge process might contact, and the laminated body was obtained.

  Then, the laminate obtained above is put into an inert oven set at 345 ° C., subjected to a heat treatment with warm air for 30 minutes, and further subjected to a heat treatment for 5 minutes using an infrared furnace to obtain a transparent laminated film 1. Produced. In addition, the film thickness of the silica type film in the obtained transparent laminated film 1 was 6 micrometers.

(Preparation of transparent laminated films 2 to 22)
As two transparent base materials (referred to as transparent base material A and transparent base material B), except that the materials shown in the following Table 2 were used, Laminated films 2 to 22 were produced. The temperature of the inert oven was set to a value obtained by subtracting 5 ° C. from the lesser value of the Tg values of the transparent substrate A and the transparent substrate B, and the heat treatment was performed.

  Here, in Table 2 below, in addition to the numbers of the two transparent substrates used (transparent substrate A and transparent substrate B), the Tg value of each transparent substrate, the set temperature of the inert oven, each Value of moisture permeability of transparent substrate, film thickness of silica-based film, difference of average value of tensile elastic modulus between transparent substrates (AB), slow axis direction and advance in each transparent substrate The value of the larger difference in tensile elastic modulus in the phase axis direction and the value of the difference in hygroscopic expansion coefficient between the transparent substrates are also described.

[Measurement of physical properties of transparent laminated film]
About the transparent laminated films 1-22 produced above, various physical properties were measured with the following methods. The results are shown in Table 3 below.

(Measurement of moisture permeability)
First, the water vapor transmission rate was measured by the same method as the measurement of the water vapor transmission rate in the transparent base material mentioned above. Next, the moisture permeability of the sample whose measured value was less than 0.1 g / m ² · 24 hr was further measured by the following method.

  That is, a calcium layer and an aluminum layer were sequentially deposited on one side of the transparent laminated film, and allowed to stand for 4 hours at 40 ° C. and 90% RH. Thereafter, the moisture permeability was measured using FMB1000 manufactured by Mitsuwa Frontec Co., Ltd., and the obtained measured value was multiplied by 6 to obtain the moisture permeability when left standing at 40 ° C. and 90% RH for 24 hours.

Moreover, after performing the bending test (bending test A) by the following method, the water vapor transmission rate was evaluated by the method similar to the above. Table 3 below shows the value of the moisture permeability obtained and the change in moisture permeability before and after the bending test (absolute value of the increase in moisture permeability). In practice, it is acceptable if the change in moisture permeability before and after the bending test is 1 g / m ² · 24 hours.

(Bending test A)
The film was cut into a size having a width of 10 mm and a length of 50 mm to obtain a sample. This sample was bent twice at ± 90 ° along a cylinder having a radius of 10 mm under a condition of a load of 0.25 kgf and a period of 5 seconds.

(Bending test B)
As a bending resistance test (bending test B), according to the method of JIS P8115, using MIT D-2 manufactured by Toyo Seiki Co., Ltd., under the conditions of a load of 0.25 kgf, R = 0.8 mm, 90 °, until breakage Was measured (rounded to one decimal place). The results are shown in Table 3 below.

(Measure curl after heat treatment)
About the transparent laminated | multilayer film 1, 15, 16, and 17 produced above, the film was cut into the size of width 10mm and length 50mm, and it was set as the sample. Table 3 below shows the results obtained by measuring the lifting height of the four corners for this sample a plurality of times (4 to 5 times) and calculating the average value.

  From the results of Table 3 above, the transparent laminated film No. 1 according to the present invention was obtained. 1-11 and 15-22 are film No. of a comparative example. It turns out that it is excellent in bending resistance compared with 12-14.

11 Transparent laminated film,
12 1st transparent base material,
13 Silica-based membrane,
14 Second transparent substrate.

Claims (12)

A pair of transparent substrates having a total light transmittance of 80% or more and a glass transition temperature of 270 ° C. or more;
A silica-based film formed by a sol-gel method interposed between the pair of transparent substrates;
Have
A transparent laminated film in which the moisture permeability of each of the pair of transparent base materials is 10 to 2000 g / m ² · 24 hr under a condition of 40 ° C. and 90% RH as measured by JISZ0208.   The transparent laminated film according to claim 1, wherein a difference in tensile elastic modulus between the pair of transparent base materials is 0 to 2 GPa.   The transparent laminated film of Claim 1 or 2 whose difference of the in-plane tensile elasticity modulus in each of a pair of said transparent base material is 0-2GPa.   The transparent laminated film of any one of Claims 1-3 whose film thickness of the said silica-type film | membrane is 0.05-15 micrometers.   The transparent laminated film of any one of Claims 1-4 whose difference of the hygroscopic expansion coefficient between said pair of transparent base materials is 0-20 ppm. The transparent laminated film of any one of Claims 1-5 whose moisture permeability in 40 degreeC90% RH conditions measured by JISZ0208 is 0.1 g / m < ² > * 24hr or less. A coating film forming step of forming a coating film by applying a coating solution for forming a silica-based film containing alkoxysilane or a hydrolyzate or partial condensate thereof on the surface of the first transparent substrate;
A laminating step of laminating a second transparent substrate on the exposed surface of the coating film to obtain a laminate;
A heating step of heating the laminate;
Including
The manufacturing method of the transparent laminated | multilayer film whose total light transmittance of a said 1st transparent base material and a said 2nd transparent base material is 80% or more, and whose glass transition temperature is 270 degreeC or more.   The manufacturing method of the transparent laminated film of Claim 7 whose heating temperature in the case of the said heating is 250-500 degreeC.   The transparent laminated film according to claim 7 or 8, wherein the first transparent substrate and the second transparent substrate are subjected to a hydrophilic treatment on the surface adjacent to the coating film. Production method.   The manufacturing method of the transparent laminated film of any one of Claims 7-9 which further includes the ultraviolet irradiation process which performs an ultraviolet irradiation process with respect to the said laminated body after the said heating process.   The manufacturing method of the transparent laminated | multilayer film of Claim 10 whose transmittance | permeability with respect to the light of wavelength 365nm of a said 1st transparent base material and a said 2nd transparent base material is 5% or more.   The substrate for electronic devices which consists of a transparent laminated film of any one of Claims 1-6, or the transparent laminated film manufactured by the manufacturing method of any one of Claims 7-11.