KR101542621B1 - Optical film and liquid crystal display comprising the same - Google Patents

Abstract

The present invention provides an optical film and a liquid crystal display including the same. The optical film of the present invention is a non-liquid crystalline thermoplastic resin single film, wherein the film comprises first and second surface layers located on the surface in the thickness direction; And a film inner layer positioned between the first and second surface layers, the second surface layer facing the liquid crystal cell, the inner layer being oriented obliquely in the thickness direction, And has a profile in which the angle of inclination is increased toward the surface layer and is decreased beyond the inflection point.

Description

TECHNICAL FIELD [0001] The present invention relates to an optical film and a liquid crystal display including the optical film.

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 optical film, which can significantly improve the viewing angle and front contrast ratio so that the oblique orientation angle according to the thickness has a specific profile.

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 sealed between a TFT (Thin Film Transistor) array substrate and a color filter substrate. When an electric field is applied to the electrodes existing on the array substrate and the color filter substrate, the arrangement of the liquid crystal molecules in the liquid crystal cell layer sealed therebetween is changed, and the image is displayed using the liquid crystal molecules. On the other hand, a polarizing film (polarizing plate) is provided on the outside of the array substrate and the color filter substrate. The polarizer can control the 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 polarizer generally comprises a polarizer capable of polarizing light in a specific direction, a protective layer and a compensation film.

Due to the refractive index anisotropy of the liquid crystal, the liquid crystal display has a fundamental problem of viewing angle. A wide viewing angle technique such as a vertical alignment (VA) mode or a horizontal alignment mode (IPS, FFS) in which a viewing angle of a conventional TN (Twisted Nematic) mode is improved is widely employed.

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

It is an object of the present invention to provide an optical film capable of greatly improving the viewing angle of a liquid crystal display and a liquid crystal display including the optical film.

It is another object of the present invention to provide an optical film capable of improving the contrast ratio and contrast ratio (CR) generated in liquid crystal compensation and a liquid crystal display including the same.

One aspect of the present invention relates to an optical film. Wherein the optical film is a single film of a non-liquid crystalline thermoplastic resin, the film comprising: first and second surface layers positioned on a surface in a thickness direction; And a film inner layer disposed between the first and second surface layers, wherein the second surface layer is opposite to the liquid crystal cell, the inner film layer is obliquely oriented in the thickness direction, And has a profile in which the angle of inclination is increased toward the second surface layer and is decreased after passing through the inflection point.

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

The inflection point may be located between the center line of the film thickness and the second surface layer.

The inflection point may be located at 1 to 49.9% of the thickness from the second surface layer.

The first surface layer may be opposed to the polarizing plate.

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

The first surface layer and the second surface layer may satisfy the following relationship:

[Formula 4]

nx? ny? nz

(Where nx, ny, and nz are refractive indices of the film in the x-, y-, and z-axis directions, respectively).

The first and second surface layers may have a thickness of 1 to 20 mu m from the surface.

The first and second surface layers may be 1 to 20% of the total thickness of the film.

The film may have a maximum film beta angle of 15 to 35 degrees.

The ratio? 1 /? 2 of the maximum? Angle? 1 and the minimum? Angle? 2 in the film inner layer may be 1.15 to 7.0.

The thermoplastic resin may be a cycloolefin resin, a polycarbonate resin, a polyolefin resin, an aromatic vinyl resin, a polyamide resin, a polyimide resin, a polyester resin and an acrylic resin. More than species can be applied.

The optical film may have an in-plane retardation value Ro 'defined by the following equation at 550 nm of 20 to 110 nm:

[Formula 1]

Ro '= (nx - ny') xd

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

The optical film may have a thickness direction phase retardation value (Rth ') defined by the following formula 2 at 550 nm of 80 to 190 nm:

[Formula 2]

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

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

Another aspect of the present 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 side 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 is opposed to the substrate, and the first surface layer is opposed to the polarizing plate.

In an embodiment, the liquid crystal display may be a TN (Twisted Nematic) mode.

The optical film of the present invention has the effect of greatly improving the viewing angle of the liquid crystal display and the contrast of the light generated by the liquid crystal compensation and the contrast ratio.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a profile of the oblique orientation angle of the thickness direction of the optical film according to one embodiment of the present invention. Fig.
2 is a cross-sectional view schematically showing an optical film according to one embodiment of the present invention.
3 is a conceptual diagram for explaining the film beta angle.
Fig. 4 schematically shows an image of a polarizing microscope image according to the rotation angle when the optical film of the present invention is placed between orthogonal Nicol polarizers and rotated 0 to 90 degrees. Fig.
5 is a schematic view showing a process of manufacturing an optical film according to one embodiment of the present invention.
6 is a cross-sectional view schematically showing a liquid crystal display according to one embodiment of the present invention.
FIG. 7 shows a contour map of the contrast ratio measured with an EZ contrast spectrometer for the optical film prepared in Example 5. FIG.
FIG. 8 shows a contour map of the contrast ratio measured with an EZ contrast spectrometer for the optical film produced in Comparative Example 9. FIG.

Optical film

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a profile of the tilt angle (? Angle) of the thickness direction 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 obliquely oriented in the thickness direction, and the inclined orientation angle gradually increases from the first surface layer 10a to the second surface layer 10b through the film inner layer 10c, And reaches the inflection point (BP), has the maximum orientation angle, and has a profile that decreases again after passing the inflection point (BP). That is, the profile has a shape of splay profile that forms a decreasing curve after the incremental profile (WV DLC), not the increment profile.

At this time, the position of the inflection point BP having the maximum oblique orientation angle may be closer to the second surface layer 10b than the first surface layer 10a. Preferably, the inflection point BP may be located between the center line C of the film thickness and the second surface layer 10b. As described above, the inflection point BP having the maximum oblique orientation angle is located closer to the liquid crystal cell, so that the orientation liquid crystal in the TN liquid crystal, that is, the liquid crystal lying down can be compensated. More preferably, the inflection point may be located at a point of 1 to 49.9% of the thickness, for example, 5 to 45%, preferably 10 to 35% of the thickness from the second surface layer. The viewing angle compensation effect at this position is excellent.

2 is a cross-sectional view schematically showing an optical film according to one embodiment of the present invention. As shown in Fig. 2, the optical film 10 of the present invention includes first and second surface layers 10a and 10b, which are located on the surface in the thickness direction; And a film inner layer (10c) located between the first and second surface layers. At this time, the second surface layer 10b is opposed to the liquid crystal cell, and the first surface layer 10a is opposed to the polarizing plate.

The film inner layer 10c is obliquely oriented in the thickness direction. In an embodiment, the first and second surface layers 10a and 10b are not obliquely oriented in the thickness direction of the film. At this time, the film inner layer 10c has a profile in which the angle of inclination is increased from the first surface layer to the second surface layer, and is decreased after the inflection point BP.

The optical film 10 is a non-liquid crystalline thermoplastic resin single film.

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

In the present invention, a single film means that a surface layer and a film inner layer are formed by extrusion without forming a separate coating layer or an adhesive layer. That is, no adhesive layer or coating layer is formed between the first and second surface layers 10a and 10b and the inner film layer 10c, and they are the same components, and are conveniently distinguished according to their orientation.

As described above, the optical film of the present invention has different orientations depending on the surface and the inside, thereby improving viewing angle and light leakage. In addition, since the production of an optical film having different inclined orientations along the surface and inside can be performed in a single extrusion process, the process can be shortened and the manufacturing cost can be reduced.

The first and second surface layers 10a and 10b may have thicknesses t1 and t2 of 1 to 20 mu m, preferably 3 to 10 mu m, from the surface. An excellent viewing angle can be secured in the above range.

Further, the first and second surface layers may be 1 to 20% of the total thickness of the film. An excellent viewing angle can be secured in the above range.

The first surface layer and the second surface layer may satisfy the following relationship:

[Formula 4]

nx? ny? nz

(Where nx, ny, and nz are refractive indices of the film in the x-, y-, and z-axis directions, respectively).

The thickness t3 of the film inner layer 10c may be 5 to 100 mu m, preferably 10 to 65 mu m.

3 is a conceptual diagram for explaining the film beta angle. The inner film layer 10c may have a film angle? Of 5 to 35 degrees, which is defined as an angle at which the perpendicular Nicols penetration is minimized. The film beta angle is the same as the section orientation angle, and is an angle formed between the z axis in the thickness direction and the z 'axis perpendicular to the alignment plane, as shown in Fig. This film? Angle can be obtained at an angle at which the orthogonal Nicole transmissivity is minimized by observing the orthogonal Nicol between the polarizers.

The inner film layer 10c has different values of the film beta angle along the z axis, which is the thickness direction, and forms a profile as shown in Fig. In a specific example, the maximum film beta angle at the inflection point (BP) may be between 15 and 35 degrees. The viewing angle improving effect is excellent in the above range. Further, the ratio (beta 1 / beta 2) of the maximum beta angle (beta 1) to the minimum beta angle beta 2 in the film inner layer 10c is preferably 1 to 7.0, more preferably 1.15 to 7.0, Can be from 2 to 4.5. The viewing angle compensation is excellent in the above range.

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

[Formula 1]

Ro '= (nx - ny') xd

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

The optical film may have a thickness retardation value (Rth) of 80 to 190 nm defined by the following formula (2) at 550 nm. There is an advantage of viewing angle compensation in the above range. Preferably, the retardation value in the thickness direction (Rth) may be 120 to 180 nm.

[Formula 2]

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

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

In an embodiment, the thickness d of the film may be 30 to 110 탆, preferably 50 to 100 탆.

Fig. 4 schematically shows an image of a polarizing microscope image according to the rotation angle when the optical film of the present invention is placed between orthogonal Nicol polarizers and rotated 0 to 90 degrees. Fig. In the figure, the black part means that the darkest part appears on quadrature Nicol (quenching). As shown, it can be seen that the quartz streaks are formed at any angle on the surface of the film, while the inner layer of the film is not quartz-like and is oriented in accordance with the thickness.

The optical film of the present invention is obtained by melt-extruding a non-liquid crystalline thermoplastic resin; And passing the molten extruded thermoplastic resin between the first forming roll and the second forming roll to produce a film form. Wherein a surface temperature of the first and second molding rolls is equal to or lower than a glass transition temperature (Tg) of the thermoplastic resin, and generates a different shearing force inside the film surface in accordance with the running of the first and second molding rolls, And a tilt angle is given to the tilt angle.

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

In other embodiments, the film can be made into a multi-layered structure using a primary extruder and a secondary extruder. For example, the main extruder is manufactured by forming the inner layer of the film and the auxiliary extruder to form a surface layer and separately setting the extrusion temperature of the main extruder and the auxiliary extruder. In the specific example, the temperature of the surface layer coming from the secondary extruder may be set to a low value and the temperature of the film inner layer coming out from the main extruder may be set to a high value so as to have a higher value when the inclination angle in the thickness direction is generated by utilizing the inter-

When the melt-extruded thermoplastic resin is in contact with the molding roll to form a film, the inside of the film is above the Tg temperature, while the surface of the film is below the Tg temperature. When the molding rolls at both ends run in a state in which the molding temperature difference between the film surface and the inside is generated, a different shearing force is generated on the surface and the inside of the film, so that the film has an inclination angle in the thickness direction.

In a specific example, the surface temperature Tr of the first and second forming rolls 41 and 42 may satisfy the following formula 3:

[Formula 3]

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

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

In the embodiment, the first and second forming rolls 41 and 42 may have different degrees of elasticity to form various film beta-angles. For example, the first forming roll 41 may be more resilient than the second forming roll 42. In a specific example, a combination of rubber roll + FSR roll, FSR roll + FSR roll, SFR roll + FSR roll, metal roll + FSR roll, SFR roll + SFR roll, metal roll + rubber roll and the like can be used. The FSR roll is a roll in which a water layer and a steel layer are sequentially formed on the surface of a metal roll, and the SFR roll is a roll in which a rubber layer and a steel layer are sequentially formed on the surface of the metal roll.

Also, the speeds of the first and second forming rolls 41 and 42 may be different. For example, the speed of the first shaping roll 41 may be faster than the speed of the second shaping roll 42. In the specific example, the speed of the first forming roll may be set to be 0.9 to 1.2 times the speed of the second forming roll.

The thermoplastic resin film passed between the first and second forming rolls 41 and 42 may further include a step of stretching. In the specific example, the stretching may be biaxial stretching and stretching may be performed at 5 to 20% relative to the running direction in the opposite direction of travel (TD). The front phase difference Ro 'and the side phase difference Rth' characteristics can be ensured within the above range. Preferably, the elongation can be elongated to 8 to 15% with respect to the running direction in the direction opposite to the running direction (TD).

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

After stretching in this way, the film beta angle can be reduced compared to the film beta angle immediately after extrusion. In the specific example, the film beta angle after stretching may be about 1 to 20 degrees lower than the film beta angle immediately after extrusion.

Liquid crystal display

Another aspect of the present 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 the TN (Twisted Nematic) mode liquid crystal, and can improve the contrast ratio and the light leakage caused by the 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 side of the substrate.

The optical film may further include a polarizing plate on the other side. 6 is a cross-sectional view schematically showing a liquid crystal display according to one embodiment of the present invention. As shown in the figure, the liquid crystal display device includes a liquid crystal panel including a liquid crystal cell layer 40 sealed between a first substrate 30a and a second substrate 30b. The optical film 10 of the present invention can 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 side (face) and the lower side (face) are names attached for convenience in reference to the upper and lower sides in the drawing, and the names are not necessarily used for the upper and lower sides.

The first substrate 30a and the second substrate 30b may be a glass substrate or a plastic substrate. The plastic substrate may be made of a material selected from the group consisting of polyethylene terephthalate (PET), polycarbonate (PC), polyimide (PI), polyethylene naphthalate (PEN), polyether sulfone (PES), polyarylate ), But the present invention is not limited thereto.

The optical film 10 of the present invention may be laminated on the first substrate 30a. Also, the optical film 10 of the present invention may be laminated on the lower part of the second substrate 30b.

On the optical film 10, a polarizing plate 20 including a polarizer and a protective film may be formed. The second surface layer 10b of the optical film may be opposed to the substrates 30a and 30b and the first surface layer 10a may be opposed to the polarizing plate 20. [

In addition, although not shown in the drawing, a normal pressure-sensitive adhesive layer, a reflection ring layer, a hard coating layer, and the like can be further formed.

The liquid crystal cell layer 40 may be a liquid crystal cell layer including a TN (Twisted Nematic) mode liquid crystal. Typically, a TN liquid crystal display has a liquid crystal lying vertically in a liquid crystal cell when a voltage is applied, while a liquid crystal lies on an oriented surface due to an anchoring force with an alignment agent. The viewing angle of the TN liquid crystal display is narrowed by the liquid crystal lying at this time. The optical film of the present invention has a maximum oblique orientation angle to the surface attached to the liquid crystal display to compensate the liquid crystal lying in the TN liquid crystal.

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 understanding of the present invention, and the scope of the present invention is not limited to the following examples. The contents not described here are sufficiently technically inferior to those skilled in the art, and a description thereof will be omitted.

Example

Examples 1 to 8

RX4500 thermoplastic resin manufactured by JSR was melt extruded at 230 ~ 280 ° C in a T die and passed between FSR roll and metal roll to produce a film. At this time, the ratio of the FSR roll speed / metal roll speed was set to be 1.01 to 1.03. The extruded film was stretched by 8 to 15% in the running direction (TD) with respect to the running direction to produce an optical film having a thickness of 90 탆. The maximum beta angle (? 3) from the first surface layer to the film thickness center (C) and the maximum beta angle (? 1) and beta 1 position between the second surface layer at the film thickness center (C) were changed as shown in Table 1 below. The maximum beta angle position is calculated as a percentage of the total thickness from the second surface layer.

The prepared optical film was subjected to epoxy molding and then microtome was made using GLASS KNIFE so that the film thickness was 90 μm and the slice thickness was 10 μm. The film slice was placed on a glass plate, the plate was sandwiched between orthogonal Nicol polarizers, and observed with a polarizing microscope to confirm the orientation according to the angle.

? 3 (max)
First surface layer ~ center () beta 1 (max)
Center to second surface layer () Maximum beta angle position (%) Viewing angle
Up Down Left Right Front contrast ratio Example One 17 20 20 10/11/15/15 1100 2 17 22 25 11/11/14/15 1200 3 17 23 26 12/13/16/16 900 4 18 22 25 11/12/14/15 1000 5 18 24 30 15/13/18/17 1150 6 19 22 20 12/13/17/17 1250 7 19 23 28 10/11/15/15 1030 8 19 24 25 11/11/15/15 1010

Comparative Examples 1 to 9

The maximum beta angle (? 3) between the first surface layer and the film thickness center (C) and the maximum beta angle (? 1) and the maximum beta angle between the second surface layer at the film thickness center (C) were changed as shown in Table 2 . Comparative Example 1 is a case in which the oblique orientation is parallel to the entire thickness direction.

? 3 (max)
First surface layer ~ center () beta 1 (max)
Center to second surface layer () Maximum β angle position
(%) Viewing angle
Up Down Left Right Front contrast ratio Comparative Example One 20 20 - 8/9/13/13 800 2 20 17 51 4/5/13/13 500 3 22 17 51 6/7/13/13 530 4 23 17 51 4/5/12/12 480 5 22 18 51 4/6/10/11 570 6 24 18 51 4/7/10/10 600 7 22 19 51 3/5/13/13 630 8 23 19 51 3/5/12/13 650 9 24 19 51 4/5/13/11 590

Property evaluation method

Nx, ny 'and nz' were obtained by using Axo scan for the manufactured film, and values of Ro 'and Rth' were obtained by the following equations (1) and (2).

[Formula 1]

Ro '= (nx - ny') xd

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

[Formula 2]

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

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

(2) β angle: Axo scan. To observe 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: At polar angle 80 °, CR was measured up / down / left / right through EZ contrast.

(4) Contrast Ratio (CR): The luminance ratio of the screen to the white and black in a state where the polarizing plate is attached to the liquid crystal panel, was measured through EZ contrast.

Contrast ratios (contrast ratio) of the optical films prepared in Example 5 and Comparative Example 9 measured with an EZ contrast spectrometer are shown in FIGS. 7 and 8, respectively.

As shown in Tables 1 and 2, it can be seen that the optical films of Examples 1 to 8 are superior in viewing angle to the optical films prepared in Comparative Examples 1 to 10. 7 and 8, the front contrast ratio and the viewing angle of FIG. 7 are superior to those of FIG. 8.

10: Optical film 20: Polarizing plate
30a, 30b: first and second substrates 40: liquid crystal cell layer
41: first forming roll 42: second forming roll
43: T die 44: thermoplastic resin

Claims (17)

Non-liquid crystalline thermoplastic resin single film,
The film comprising: first and second surface layers located on a surface in a thickness direction; And a film inner layer positioned between the first and second surface layers,
The second surface layer is opposed to the liquid crystal cell,
Wherein the film inner layer is obliquely oriented in the thickness direction and has a profile in which the tilt orientation angle increases from the first surface layer to the second surface layer and decreases beyond an inflection point.
The optical film according to claim 1, wherein the inflection point is closer to the second surface layer than the first surface layer.
The optical film according to claim 2, wherein the inflection point is located between the center line of the film thickness and the second surface layer.
The optical film according to claim 3, wherein the inflection point is located at 1 to 49.9% of the thickness from the second surface layer.
The optical film according to claim 1, wherein the first surface layer is opposed to the polarizing plate.
The optical film according to claim 1, wherein the first and second surface layers are not obliquely oriented in the thickness direction of the film.
The optical film according to claim 1, wherein the first and second surface layers satisfy the following relationship:
[Formula 4]
nx? ny? nz
(Where nx, ny, and nz are refractive indices of the film in the x-, y-, and z-axis directions, respectively).
The optical film according to claim 1, wherein the first and second surface layers have a thickness of 1 to 20 탆 from the surface.
The optical film according to claim 1, wherein the first and second surface layers are 1 to 20% of the total film thickness.
The optical film according to claim 1, wherein the film has a maximum film beta angle of 20 to 35 degrees.
The optical film according to claim 1, wherein a ratio (? 1 /? 2) of a maximum? Angle (? 1) to a minimum? Angle (? 2) in the film inner layer is 1.15 to 7.0.
The thermoplastic resin composition according to claim 1, wherein the thermoplastic resin is selected from the group consisting of a cycloolefin resin, a polycarbonate resin, a polyolefin resin, an aromatic vinyl resin, a polyamide resin, a polyimide resin, An optical film comprising at least one selected resin.
The optical film according to claim 1, wherein the optical film has an in-plane retardation value (Ro ') of 20 to 110 nm defined by the following formula at 550 nm:
[Formula 1]
Ro '= (nx - ny') xd
(Where nx and ny 'are the refractive index in the x and y'-axis directions, respectively, and d is the thickness of the film).
The optical film according to claim 1, wherein the optical film has a thickness retardation value (Rth ') of 80 to 190 nm defined by the following formula (2) at 550 nm:

[Formula 2]
Rth '= [(nx + ny') / 2 - nz '] xd
(Where nx, ny 'and nz' are the refractive indices in the x-, y- and z'-axis directions, respectively, and d is the thickness of the film).
1. A liquid crystal display comprising: a substrate comprising a liquid crystal cell; And
An optical film according to any one of claims 1 to 14 laminated on at least one side of the substrate;
≪ / RTI >

16. The method 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 is opposed to the substrate, and the first surface layer is opposed to the polarizing plate.
16. The liquid crystal display of claim 15, wherein the liquid crystal display is a TN (Twisted Nematic) mode.

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