WO2014098333A1

WO2014098333A1 - Optical film and liquid crystal display including same

Info

Publication number: WO2014098333A1
Application number: PCT/KR2013/005191
Authority: WO
Inventors: 유소희; 김란; 이승규; 이범덕
Original assignee: 제일모직 주식회사
Priority date: 2012-12-20
Filing date: 2013-06-12
Publication date: 2014-06-26
Also published as: KR101542621B1; KR20140080362A

Abstract

The present invention relates to an optical film and a liquid crystal display including same. The optical film according to the present invention is a non-liquid crystal thermoplastic resin single film. The film includes first and second surface layers that are positioned on a surface in a thickness direction; and a film inner layer that is positioned between the first and second surface layers. The second surface layer faces a liquid crystal cell. The inner layer is oriented to be inclined in the thickness direction. The inclination orientation angle increases from the first surface layer to the second surface layer to provide a profile which decreases through an inflection point.

Description

【Specification】

[Name of invention]

Optical film and liquid crystal display including the same

The present invention relates to an optical film and a liquid crystal display including the same. More specifically, the present invention relates to an optical film and a liquid crystal display including the same, in which the inclination orientation angle according to the thickness has a specific profile and can significantly improve the viewing angle and the front contrast ratio.

Background Art

Liquid crystal displays (LCDs) are one of the most widely used flat panel displays. In general, a liquid crystal display has a structure in which a liquid crystal cell layer is enclosed between a TFT thin film transistor array substrate and a color filter substrate. When an electric field is applied to the electrodes on the array substrate and the color filter substrate, the arrangement of the liquid crystal molecules of the liquid crystal cell layer enclosed therebetween changes, thereby displaying an image. On the other hand, a polarizing film (polarizing plate) is provided outside the array substrate and the color filter substrate. The polarizer may control polarization by selectively transmitting light in a specific direction among light incident from the backlight and light passing through the liquid crystal cell layer. The polarizing plate generally includes a polarizer, a protective layer, and a compensation film capable of polarizing light in a specific direction.

Due to the refractive anisotropy of the liquid crystal, the liquid crystal display has a fundamental problem of a viewing angle. Wide viewing angle technologies, such as vertical alignment (VA) mode or horizontal alignment mode (IPS, FFS), which improve the viewing angle of the conventional TN twisted nematic mode, are adopted.

Conventionally, a viewing angle compensation film oriented in the thickness direction has been developed, but there is a problem in that the contrast ratio (CR) is lowered.

[Detailed Description of the Invention]

[Technical problem]

One object of the present invention is to provide an optical film and a liquid crystal display including the same that can greatly improve the viewing angle of the liquid crystal display.

Still another object of the present invention is to provide an optical film and a liquid crystal including the same, which can improve light leakage mura and contrast ratio (CR) generated from liquid crystal compensation. To provide a display. Technical Solution

One aspect of the invention relates to an optical film. The optical film is a non-liquid crystalline thermoplastic single film, the film comprising a first and a low 12 surface layer located on the surface in the thickness direction; And a film inner layer positioned between the first and second surface layers, wherein the second surface layer faces the liquid crystal cell, and the film inner layer is oriented obliquely in a thickness direction, from the first surface layer. The inclined orientation angle increases toward the second surface layer, thereby reducing the profile beyond the inflection point.

The inflection point may be closer to the second surface layer than to the first surface layer.

The inflection point may be located between the centerline of the film thickness and the second surface layer. The inflection point may be located about 1 to 49.9% of the thickness from the second surface layer.

The first surface layer may oppose the polarizer;

The first and second surface layers may not be tilted in the thickness direction of the film.

The first and second surface layers may have the following relationship:

[Equation 4]

nx ≠ ny ≠ nz

(Wherein nx, ny and nz are the refractive indices in the _x- axis, _y- axis and _z- axis directions of the film, respectively).

The first and second surface layers may have a thickness from about 1.1 to about 20 from the surface.

The first and second surface worms may be about 1 to about 20% of the total thickness of the film. The film may have a maximum film β angle of about 15 to 35 ^° .

In the film inner layer, the ratio of the maximum β angle (βΐ) and the minimum β angle (β2) (β1 / β2) may be about 1.15-7.0.

As the thermoplastic resin, cycloolefin resin, polycarbonate resin, polyolefin resin, aromatic vinyl resin, polyamide resin, polyimide resin, polyester resin, acrylic resin, etc. may be used. More than one species can be applied.

The optical film may have an in-plane phase retardation value (Ro ′) of about 20 to about 110 nm defined by Equation 1 at 550 nm: [Equation 1]

Ro '= (nx ᅳ ny') xd

(Wherein nx and ny 'are the refractive indexes in the x- and y'-axis directions, respectively, and d is the thickness of the film).

The optical film may have a thickness direction retardation value (Rth ') of about 80 to about 190 nm at 550 nm as defined by Equation 2:

Rth '= [(nx + ny') / 2-nz '] xd

(In the above, nx, ny ', ^η ζ' is the refractive index in the ^χ axis, y 'axis and z' axis direction, respectively, d is the thickness of the film).

Another aspect of the invention relates to a liquid crystal display. The liquid crystal display includes a substrate including a liquid crystal cell; And the optical film laminated on at least one surface of the substrate.

In one embodiment, a polarizing plate is formed on the other surface of the optical film, the second surface layer of the optical film may face the substrate and the first surface layer may face the polarizing plate.

In an embodiment the liquid crystal display can be in TNCTwisted Nematic mode. Advantageous Effects

The optical film of the present invention has an effect of greatly improving the light leakage mura and contrast ratio generated in the viewing angle and liquid crystal compensation of the liquid crystal display. [Brief Description of Drawings]

1 is a profile of an oblique orientation angle of the thickness term of an optical film according to one embodiment of the present invention.

2 is a cross-sectional view schematically showing an optical film according to an embodiment of the present invention.

3 is a conceptual diagram for explaining the film β angle.

Figure 4 schematically shows the image of the polarizing microscope image according to the rotation angle when the optical film of the present invention between the orthogonal Nicole polarizing plate and rotated from 0 to 90 degrees.

5 is a schematic diagram showing a process of manufacturing an optical film according to an embodiment of the present invention.

6 schematically illustrates a liquid crystal display according to one embodiment of the invention It is sectional drawing.

FIG. 7 illustrates a contour map of contrast ratios measured by an EZ contrast spectrometer for an optical film prepared in Example 5. FIG.

8 shows a contour map of contrast ratios measured with an EZ contrast spectrometer for the optical film prepared in Comparative Example 9. FIG.

[Best form for implementation of the invention]

Optical film

1 is a profile of an oblique orientation angle (β angle) of a thickness term of an optical film according to one embodiment of the present invention.

As shown in FIG. 1, the optical film of the present invention is inclined in the thickness direction, and the inclination orientation angle gradually increases from the first surface layer 10a to the second surface layer 10b through the film inner layer 10c. It increases and reaches the inflection point (BP) has a maximum orientation angle, and after the inflection point (BP) is characterized by having a profile that decreases again. That is, the profile has a form of splay profile that forms a decay curve after an increase rather than a profile of progressive increase (WV DLC).

In this case, the position of the inflection point BP having the maximum inclination orientation angle may be closer to the second surface layer 10b than to the first surface layer 10a. Preferably, the inflection point BP may be located between the centerline C of the film thickness and the second surface layer 10b. As such, the inflection point BP having the maximum inclination alignment angle is located closer to the liquid crystal cell, thereby compensating for the alignment liquid crystal in the TN liquid crystal, that is, the lying liquid crystal. More preferably, the inflection point may be located about 1 to 49.9% of the thickness, for example about 5 to 45%, preferably about 10 to 35% of the thickness of the second surface layer. The viewing angle compensation effect is excellent at this position.

2 is a cross-sectional view schematically showing an optical film according to an embodiment of the present invention. As shown in Fig. 2, the optical film 10 of the present invention comprises: first and second surface layers 10a and 10b positioned on the surface in the thickness direction; And a film inner layer 10c positioned between the first and second surface layers. In this case, the second surface layer 10b may face the liquid crystal cell, and the first surface layer 10a may face the polarizer.

The film inner layer 10c is obliquely oriented in the thickness direction. In the embodiment the first and second surface layers 10a, 10b are not obliquely oriented in the thickness direction of the film. At this time, the film inner layer 10c increases the inclination orientation angle toward the second surface layer from the first surface layer to decrease the profile beyond the inflection point BP. Have The optical film 10 is a single liquid crystal thermoplastic resin film.

In an embodiment the material that can be used as the optical film 10 of the present invention can be applied to a transparent, extrudable thermoplastic resin surface. In embodiments, the thermoplastic resin may include cycloolefin resin, polycarbonate resin, polyolefin resin, aromatic vinyl resin, polyamide resin, polyimide resin, polyester resin, acrylic resin, and the like. It may be used alone or in combination of two or more.

In the present invention, a single film means that the surface layer and the film inner layer are formed by extrusion without forming a separate coating or adhesive layer. That is, no adhesive layer or coating layer is formed between the first and second surface layers 10a and 10b and the film inner layer 10c, and is the same component and is merely classified for convenience. As described above, the optical film of the present invention is formed to have different orientations according to the surface and the interior thereof, thereby improving the viewing angle and light leakage. In addition, since the manufacturing of the optical film having different inclination orientations according to the surface and the inside can be performed in a single extrusion process, the process can be shortened and manufacturing cost can be reduced.

The system 1 and crab 2 surface layers 10a and 10b may have a thickness (tl, t2) from the surface of about 1 to about 20 μηι, preferably about 3 to about 10 / iii. It is possible to secure an excellent viewing angle in the above range.

In addition, the first and second surface worms may be about 1 to about 20% of the total thickness of the film. It is possible to secure an excellent viewing angle in the above range.

The first and second surface layers may have the following relationship:

[Equation 4]

nx ≠ ny ≠ nz

(Wherein nx, ny and nz are the refractive indices in the _x- axis, y-axis and _z- axis directions of the film, respectively).

The film inner layer 10c thickness t3 may be about 5 to about 100 iffli, preferably about 10 to about 65. 3 is a conceptual diagram for explaining the film β angle. The film inner layer 10c may have a film β angle of about 5 ° to about 35 °, which is defined as an angle at which orthogonal nicotine transmittance is minimum. The film β angle is the same as the intercept alignment angle, and as shown in FIG. 3, an angle formed between the τ axis in the thickness direction and the ζ ′ axis perpendicular to the alignment plane. This film β angle between the polarizer Orthogonal Nicole can be observed to obtain the angle at which orthogonal nicotine transmittance is minimum. The film inner layer 10c has different values of the film β angles along the z axis in the thickness direction, and forms a profile as shown in FIG. 1. In embodiments, the maximum film β angle at the inflection point (BP) may be about 15-35 ^° . It is excellent in the viewing angle improvement effect in the said range. In addition, in the film inner layer 10c, the ratio of the maximum β angle (βΐ) and the minimum β angle (β2) (β1 / β2) is about: 卜 7.0, more preferably about 1.15-7.0, preferably about 1.5-5 More preferably about 2 to 4.5. The viewing angle compensation is excellent in the above range.

The optical film may have an in-plane phase retardation value (Ro) of about 20 to about 110 nm at 550 nm. There is an advantage of viewing angle compensation in this range. Preferably, the in-plane phase retardation value Ro may be about 50 to about 100 nm.

[Equation 1]

Ro '= (nx-ny') xd

The optical film may have a thickness direction retardation value (Rth) of about 80 to about 190 nm, which is defined by Equation 2 at 550 nm. There is an advantage of viewing angle compensation in this range. Preferably, the thickness direction phase retardation value Rth may be about 120 to about 180 nm. ^'

[Equation 2]

Rth '= [(nx + ny') / 2-nz '] xd

(In the above, nx, ny ', ηζ' is the refractive index in the x-axis, y'-axis and z'-axis direction, respectively, d is the thickness of the film).

In embodiments the thickness d of the film may be from about 30 to about 110, preferably from about 50 to about 100 j ^ rn.

Figure 4 schematically shows the image of the polarizing microscope image according to the rotation angle when the optical film of the present invention between the orthogonal Nicole polarizing plate and rotated from 0 to 90 degrees. The black part in the figure means the darkest color (extinction) under orthogonal nicole. As shown, the matte level is formed at any angle on the surface of the film, while the inner layer of the film does not exist, it can be seen that the orientation is in accordance with the thickness. The optical film of the present invention melt-extruded non-liquid crystal thermoplastic resin; And manufacturing the melt-extruded thermoplastic resin in the form of a film by passing the first molding through the second molding and the second molding. The surface temperature of the first and second molding is It is below the glass transition temperature (Tg) of a thermoplastic resin, It is characterized by generating the inclination angle to a film inner layer by generating a different shear force in the film surface and inside according to the run of the said 1st and 2nd forming roll.

5 is a schematic diagram showing a process of manufacturing an optical film according to an embodiment of the present invention. As shown, the thermoplastic resin 44 melt-extruded from the die 43 is passed between the first molding roll 41 and the second molding 42 to be produced in the form of a film.

In another embodiment, the film may be manufactured in a multilayer structure using a main extruder and a coextruder. For example, the main extruder is manufactured by forming a film inner layer and the sub-extruder to form a surface layer, and separately setting the extrusion temperatures of the main extruder and the sub-extruder. In embodiments, the temperature of the surface layer coming out of the auxiliary extruder may be set low, and the temperature of the film inner layer coming out of the main extruder may be set high so as to have a higher value when the inclination angle between the rolls is generated.

As described above, the melt-extruded thermoplastic resin is in contact with a molding roll to form a film, whereas the inside of the film is higher than the Tg temperature, whereas the surface of the film is different from the Tg temperature. When the forming rolls at both ends run in a state where a difference in forming temperature between the film surface and the inside is generated, different shear forces are generated on the surface and inside of the film to have an inclination angle in the thickness direction.

In embodiments, the surface temperature Tr of the first and second moldings (41, 42) may satisfy the following Equation 3:

[Equation 3]

Te X 0.4 <Tr <Te X 0.5

(Te is the thermoplastic resin temperature immediately after melt extrusion, and Tr is the surface temperature of the first and second moldings).

If the surface temperature of the first and second forming rolls 41 and 42 is out of the above range, it is difficult to have a structure in which the surface is not oriented and only the film inner layer is inclined.

In embodiments, the first and second moldings 41 and 42 may form various film β angles by varying the elasticity of each other. For example, the first molding 41 may be larger in elasticity than the second molding roll 42. In a specific embodiment, a combination of rubber roll + FSR, FSR + FSR roll, SFR + FSR roll, metal roll + FSR, SFR roll + SFR, metal + rubber roll can be used. The FSR is a roll in which a water layer and a steel layer are sequentially formed on a metal surface, and the SFR is a roll in which a rubber layer and a steel layer are sequentially formed on a surface of a metal.

Further, the first and second moldings may vary in speed at (41, 42). For example, the speed of the first molding 41 can be faster than the second molding 42. In embodiments, the speed of the first molding can be driven at about 0.9 to about 1.2 times the speed of the second molding roll.

The thermoplastic resin film passed between the first and second moldings 41 and 42 may further include stretching. In the specific example, the stretching may be biaxial stretching, and the stretching may be performed at about 5 to 20% of the traveling direction in the opposite traveling direction (TD). In this range, the front phase difference Ro 'and the side phase difference Rth' can be secured. Preferably, the stretching may be performed at about 8 to 15% of the running direction in the opposite traveling direction (TD).

Preferably, the stretching may be performed at a temperature lower than the glass transition temperature (Tg) of the thermoplastic resin. For example _. , The stretching may be carried out at a temperature of about 1 to 20 ^° C, for example about 5 to 15 ° C lower than the glass transition temperature (Tg) of the thermoplastic resin. There is an advantage that can increase the contrast ratio in the above range.

After the stretching process, the film β angle may be reduced compared to the film β angle immediately after extrusion. In embodiments, the film β angle after stretching may be about 1-20 degrees lower than the film: β angle immediately after extrusion. Liquid crystal display

Another aspect of the invention relates to a liquid crystal display comprising the optical film. The liquid crystal display to which the optical film of the present invention is applied can secure an excellent viewing angle, especially in TN twisted nematic (LC) mode liquid crystals, and can improve light leakage mura and contrast ratios generated in liquid crystal compensation.

In one embodiment the liquid crystal display comprises a substrate comprising a liquid crystal cell; And the optical film laminated on at least one surface of the substrate.

The other surface of the optical film may further include a polarizing plate. 6 is a schematic cross-sectional view of a liquid crystal display according to one embodiment of the present invention. As shown, the liquid crystal panel includes a liquid crystal cell layer 40 encapsulated between the U-substrate 30a and the second substrate 30b, and the present invention is provided on one surface of the first and second substrates 30a. Optical films 10 may be laminated respectively. In one embodiment, the first substrate 30a may be a color filter (CF) substrate (upper substrate), and the second substrate 30b may be a TFT (Thin Film Transistor) substrate (lower substrate). In the present invention, the upper (surface) and the lower (surface) are given names for convenience based on the upper and lower sides of the drawings and are not necessarily used as names meaning upper and lower parts.

The first substrate 30a and the second substrate 30b may be a glass substrate or a plastic substrate. The plastic substrate can be used for a flexible display Polyethylene terephthalate (PET), polycarbonate (PC), polyimide (Pl),

Polyethylene naphthalate (PEN), polyether sulfone (PES), PARC polyary late)

It may be a plastic substrate such as a cycloolefin copolymer (COC), but the present invention is not limited thereto.

The optical film 10 of the present invention may be stacked on the first substrate 30a. In addition, the optical film 10 of the present invention may be stacked below the second substrate 30b.

The polarizing plate 20 including a polarizer and a protective film may be formed on the optical film 10. In this case, the second surface layer 10b of the optical film may face the substrates 30a and 30b, and the first surface layer 10a may face the polarizer 20.

In addition, although not shown in the drawings, a conventional pressure-sensitive adhesive layer, a reflective ring layer, a hard coating layer may be further formed.

The liquid crystal cell layer ₄₀ may be a liquid crystal cell layer including a twisted nematic (TN) mode liquid crystal. In general, TN liquid crystal displays have liquid crystals standing vertically in a liquid crystal cell when a voltage is applied, while liquid crystals are laid on the surface of the alignment agent due to anchoring force with the alignment agent. At this time, the viewing angle of the TN liquid crystal display is narrowed by the lying liquid crystal, and the optical film of the present invention can compensate for the lying liquid crystal in the TN liquid crystal by having a maximum inclination orientation angle on the plane attached to the liquid crystal-display. Hereinafter, the configuration and operation of the present invention will be described in more detail with reference to preferred embodiments of the present invention. However, the following examples are provided to aid the understanding of the present invention, and the scope of the present invention is not limited to the following examples. Do not. The information that is not described here will be omitted in the technical field can be inferred by those skilled in the art. Example

Examples 1-8

The RX4500 thermoplastic resin manufactured by JSR was melt-extruded with a T die at 230-280 ° C., and was produced in a film form by passing an FSR between and a metal roll. At this time, the FSR was set so that the ratio of speed / metal roll speed was 1.01 to 1.03. The extruded film was stretched 8 to 15% of the traveling direction in the opposite traveling direction (TD) to prepare an optical film having a thickness of 90 Ά. The maximum β angle (β 3) from the first surface layer to the film thickness center (C) and the maximum β angle (βΐ) and β β position between the film thickness center (C) and the second surface layer were changed as shown in Table 1 below. Β angle maximum is 2nd of total thickness The distance from the surface layer is calculated in%.

After the epoxy molding of the prepared optical film, the film thickness was 90 ^ m, microtome using GLASS KNIFE so that the section thickness 10. The film slices were placed on glass, sandwiched between orthogonal nicotine polarizing plates, and observed with a polarizing microscope to confirm the orientation according to the angle. Table 1]

Comparative Example 1-9

The maximum β angle (βΐ) and the maximum β angle position between the maximum surface angle (β3) from the first surface layer to the film thickness center (C) and the second surface layer at the film thickness center (C) were changed as shown in Table 2 below. . Comparative Example 1 is a case where the inclination orientation is parallel in the entire thickness direction. Table 2]

Property evaluation method

Nx, ny 'and nz' were calculated using Axo scan for the prepared film, and Ro 'and Rth 'value was calculated | required by following formula (1) and (2).

[Equation 1]

Ro '= (nx-ny') ^χ d

[Equation 2]

Rth '= [(nx + ny') / 2-nz '] xd

(In the above, nx'ny 'and nz' are the refractive indices in the x-axis, y'-axis, and z'-axis directions, respectively, and d is the thickness of the film).

(2) β angle: It measured using Axo scan. In order to see the detailed thickness profile in the thickness direction, an image analysis program was used to analyze the luminance distribution of the polarizing microscope image by angle.

(3) Viewing angle: CR was measured by EZ contrast up / down / left / right at a polar angle of 80 ^° .

(4) Contrast Ratio (CR): The ratio of luminance to the back and white bumps of the screen when the polarizer was attached to the liquid crystal panel was measured by EZ contrast. Contrast ratio (contrast ratio) contour maps measured with an EZ contrast spectrometer for the optical films prepared in Example 5 and Comparative Example 9 are shown in FIGS. 7 and 8, respectively.

As shown in Tables 1 and 2, it can be seen that the optical film of Examples 1 to 8 has an excellent viewing angle compared to the optical film prepared in Comparative Examples 1 to 10. In addition, as shown in FIGS. 7 and 8, it is confirmed that the front contrast ratio and the viewing angle of FIG. 7 are superior to those of FIG. 8.

Claims

[Range of request]

[Claim 1]

Non-liquid-crystalline thermoplastic single film,

The film includes first and second surface layers positioned on the surface in the thickness direction; And a film inner layer positioned between the first and second surface layers;

The second surface layer is opposite to the liquid crystal cell,

The film inner layer is oriented obliquely in the thickness direction, the inclined orientation angle increases from the first surface layer to the second surface layer has a profile that decreases past the inflection point.

[Claim 2]

The optical film of claim 1, wherein the inflection point is closer to the second surface layer than to the first surface layer.

[Claim 3]

3. The optical film of claim 2, wherein the inflection point is located between the centerline of the film thickness and the two surface layers of the crab.

[Claim 4]

The optical film of claim 3, wherein the inflection point is located about 1 to 49.9% of the total thickness from the second surface layer.

[Claim 5]

The optical film of claim 1, wherein the first surface layer opposes the polarizing plate.

[Claim 6]

The optical film of claim U wherein the first and second surface layers are not obliquely oriented in the thickness direction of the film.

[Claim 7]

The optical film according to claim U, wherein the first and second surface layers have a relationship of Equation 4 below:

[Equation 4] nx ≠ ny ≠ nz

Where nx, ny and nz are the refractive indices in the _x- , _y- and _z- axis directions of the film, respectively.

[Claim 8]

The optical film of claim 1, wherein the first and second surface layers have a thickness from about 1 to about 20 from the surface.

[Claim 9]

The optical film of claim 1, wherein the first and second surface layers are from about 1 to about 20 ^< ¾ of the overall thickness of the film.

[Claim 10]

The optical film of claim 1, wherein the film has a maximum film β angle of about 15 to 35 degrees.

[Claim 11]

The optical film of claim 1, wherein a ratio (β1 / β2) of maximum β angle (βΐ) and minimum β angle (β2) in the film inner layer is about 1.15-7.0.

[Claim 12]

The method of claim 1, wherein the thermoplastic resin is a group consisting of cycloulphine resin, polycarbonate resin, polyolefin resin, aromatic vinyl resin, polyamide resin, polyimide resin, polyester resin and acrylic resin. Optical film comprising at least one resin selected from.

[Claim 13]

The optical film of claim 1, wherein the optical film has an in-plane retardation value (Ro ′) of about 20 to about 110 nm at 550 nm:

Equation 1

Ro '= (nx-ny') xd

(Wherein nx and ny 'are refractive indexes in the χ and y' axis directions, respectively, and d is the thickness of the film).

[Claim 14] The optical film of claim 1, wherein the optical film has a thickness direction phase retardation value (Rth ′) of about 80 to about 190 nm at 550 nm.

[Equation 2]

Rth '= [(nx + ny') / 2-nz '] xd

(In the above, nx, ny 'and nz' are the refractive indices in the x-axis, y'-axis and z'-axis directions, respectively, and d is the thickness of the film).

[Claim 15]

A substrate including a liquid crystal cell; And

Claim 1 to claim 14 of any one of the optical film laminated on at least one surface of the substrate;

Liquid crystal display comprising a. [Claim 16]

The liquid crystal display of claim 15, wherein a polarizing plate is formed on the other surface of the optical film, the second surface layer of the optical film faces the substrate, and the first surface layer faces the polarizing plate. [Claim 17]

The liquid crystal display of claim 15, wherein the liquid crystal display is in TN Twisted Nematic mode.