KR20140086758A - Method for preparing optical film, optical film prepared from the same and liquid crystal display comprising the same - Google Patents

Abstract

The present invention relates to a manufacturing method of an optical film, an optical film manufactured by the same, and a liquid crystal display including an optical film. The manufacturing method of an optical film includes the steps of: melting and extruding a non-liquid crystalline thermoplastic resin; and enabling the melted and extruded non-liquid crystalline thermoplastic resin to pass into the space between a first forming roll and a second forming roll. The surface temperatures of the first and second forming rolls are equal to or less than a glass transition temperature (Tg) of the thermoplastic resin. Different shear forces are generated on the surface of the film and the inside of the film according to the operation of the first and second forming rolls to apply a tilt angle to the film. The non-liquid crystalline thermoplastic resin is extruded to form a multi-layered structure.

Description

TECHNICAL FIELD [0001] The present invention relates to a method of manufacturing an optical film, an optical film produced therefrom, and a liquid crystal display including the optical film and a liquid crystal display including the same. BACKGROUND OF THE INVENTION < RTI ID =

The present invention relates to a method for producing an optical film, an optical film produced therefrom, and a liquid crystal display including the same.

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 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 layer sealed between the array substrate and the color filter substrate 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 polarizing film 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 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 compensating film oriented in the thickness direction has been developed, but it has a structure having an inclined orientation from the surface to the inside. Such a structure has a problem that the contrast ratio (CR) is lowered.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method of manufacturing an optical film capable of increasing the inclination angle in the film thickness direction.

Another object of the present invention is to provide an optical film manufacturing method capable of raising the inclination angle in the thickness direction and widening the application range of process conditions to the stretching conditions such as the stretching ratio.

A method of producing an optical film, which is one aspect of the present invention, comprises melt-extruding a non-liquid crystalline thermoplastic resin; Extruded thermoplastic resin is passed between a first forming roll and a second forming roll to form a film, wherein a surface temperature of the first and second forming rolls is determined by a glass transition temperature Tg ) And generates a different shearing force inside and on the melt-extruded thermoplastic resin surface in accordance with the running of the first and second forming rolls, thereby giving an inclination angle in the thickness direction of the film, and the non-liquid crystalline thermoplastic resin has a multi- To be melt-extruded.

An optical film, which is another aspect of the present invention, can be produced by the above-described production method.

A liquid crystal display, which is another aspect of the present invention, may include the optical film.

According to the present invention, there is provided a manufacturing method of an optical film having an effect of greatly improving a viewing angle of a liquid crystal display and a light source generated in a liquid crystal compensation, without causing any oblique orientation on the surface without a separate coating process, Method. The present invention also provides a method for producing an optical film which can increase the angle of inclination in the film thickness direction and increase the angle of inclination in the thickness direction, thereby widening the application range of process conditions to the stretching conditions such as the stretching ratio.

1 is a schematic view of a method of manufacturing an optical film according to one embodiment of the present invention.
2 is a conceptual view of a film beta angle showing the tilt angle of the optical film.
3 is a cross-sectional view of a thermoplastic resin melt-extruded into two layers.
4 is a cross-sectional view of a thermoplastic resin melt-extruded into three layers.
5 is a schematic cross-sectional view of a first forming roll according to one embodiment of the present invention.
6 is a cross-sectional view of an optical film manufactured according to one embodiment of the present invention.
7 is a cross-sectional view of an optical film made of a thermoplastic resin melt-extruded as a single layer.
8 is a cross-sectional view of a liquid crystal display according to an embodiment of the present invention.

A method of producing an optical film, which is one aspect of the present invention, comprises melt-extruding a non-liquid crystalline thermoplastic resin; And passing the melt-extruded thermoplastic resin between the first forming roll and the second forming roll to produce a film.

Wherein a surface temperature of the first and second forming rolls is equal to or lower than a glass transition temperature (Tg) of the thermoplastic resin and generates different shear forces on the surface and inside of the melt extrudate along the running of the first and second forming rolls, An inclination angle can be given to the inner layer.

The "melt extrudate" includes a melt extruded thermoplastic resin and may be in the form of a film, but is not limited thereto.

That is, when the melt-extruded thermoplastic resin is in contact with the first forming roll and the second forming roll to form a melt extrudate into a film, the interior of the melt extrudate has a thermoplastic resin Tg or more, while the surface of the melt extrudate has a thermoplastic resin Tg Different. When the molding rolls at both ends run in a state in which the molding temperature difference between the surface and the interior of the melt extrudate is generated, a different shearing force is generated on the surface and inside of the melt extrudate, have.

2 is a conceptual view of a film beta angle showing the tilt angle of an optical film having a thickness d.

Referring to FIG. 2, the film beta angle is the same as the section orientation angle, and the angle formed between the z axis in the thickness direction and the z 'axis perpendicular to the orientation plane. 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 non-liquid crystalline thermoplastic resin can be melt-extruded in multiple layers.

When the non-liquid crystalline thermoplastic resin is melted and extruded into a single layer, the molding temperature difference between the surface and inside of the molten extrudate due to the contact with the roll can be generated and the inclined angle can be formed by traveling by both rolls.

The above "melt extrusion with a single layer" means extruding a non-liquid crystalline thermoplastic resin having the same temperature into a single layer without a temperature gradient in the melt extruded thermoplastic resin.

When the melt-extruded material is melt-extruded as described above, a temperature difference occurs between the surface and the interior of the melt-extruded material in the thermoplastic resin having the same temperature. The viewing angle of the display can be improved by increasing the inclination angle of the optical film.

Accordingly, the present invention is characterized in that the temperature difference between the surface and the interior of the melt extrudate is increased compared to the single melt melt extrusion by melt-extruding the non-liquid crystalline thermoplastic resin in multiple layers, thereby increasing the angle of inclination of the film and thereby improving the viewing angle.

Further, it is possible to control the extrusion temperature of each layer by melt-extruding in multiple layers, thereby producing a film having a higher retardation or an inclination angle. Through this, it is possible to produce a film by stretching, It can be wide.

The term "multi-layer melt-extrusion" means that the thermoplastic resin is melt-extruded simultaneously with a plurality of layers composed of the same non-liquid crystalline thermoplastic resin and different only in the melting temperature or the extrusion temperature, .

In an embodiment, the non-liquid crystalline thermoplastic resin may be melt extruded into two or three layers.

In one embodiment, the non-liquid crystalline thermoplastic resin can be melt extruded into two layers.

3 is a partial cross-sectional view of the thermoplastic resin immediately after being melt-extruded in two layers in the direction of the arrow.

Referring to FIG. 3, the extruded thermoplastic resin 44A may be composed of a first layer 441 and a second layer 442.

The first layer and the second layer are made of thermoplastic resin of the same material and differ only in the melt extrusion temperature, and no adhesive layer is included between the first layer and the second layer. That is, the first layer may have a relatively high melt extrusion temperature or may be relatively low compared to the second layer.

In an embodiment, the difference in melt extrusion temperature between the first layer and the second layer may be 5-50 < 0 > C. Within this range, the angle of inclination of the film can be increased and film production possible.

The melt extrusion temperature of the first layer may be 150-300 占 폚, and the melt extrusion temperature of the second layer may be 150-300 占 폚.

The thickness ta1 of the first layer and the thickness ta2 of the second layer may be 1-99% and 1-99%, respectively, of the total thickness ta of the melt extruded thermoplastic resin.

In the above description, it is assumed that the melt extrusion temperature of the first layer is larger, and the first layer may be changed to the second layer and the second layer may be changed to the first layer.

In another embodiment, the non-liquid crystalline thermoplastic resin can be melt extruded into three layers.

4 is a cross-sectional view of the thermoplastic resin immediately after being melt-extruded in three layers in the direction of the arrow.

Referring to FIG. 4, the melt extruded thermoplastic resin 44B may be composed of a first layer 443, a second layer 444, and a third layer 445.

The first layer, the second layer, and the third layer may be made of thermoplastic resin of the same material and may differ only in the melt extrusion temperature, and may be formed between the first layer and the second layer, and between the second layer and the third layer No adhesive layer is included.

In embodiments, the difference between the highest temperature and the lowest temperature in the first, second, and third layers may be 5-50 ° C. Within this range, it is possible to increase the tilting angle of the film and make it possible to produce a film.

The temperatures of the first layer, the second layer and the third layer are all different, but the two types may have the same temperature and the other one may have different temperatures.

In one embodiment, the second layer is an inner layer, the first and third layers are a first surface layer and a second surface layer, respectively, and the temperatures of the first and third layers may be the same.

In one embodiment, the inner layer may have a higher temperature than the surface layer.

The temperature difference between the inner layer and the surface layer may be 5-50 ° C, the inner layer 150-300 ° C, and the surface layer 150-300 ° C. The thickness tb2 of the second layer of the total thickness tb of the extruded thermoplastic resin may be 50-99%, and the sum tb1 + tb3 of the thicknesses of the first layer and the third layer may be 1-50%.

In other embodiments, the inner layer may have a lower temperature than the surface layer.

The temperature difference between the inner layer and the surface layer may be 5-50 ° C, the inner layer 150-300 ° C, and the surface layer 150-300 ° C. The thickness tb2 of the second layer of the total thickness tb of the extruded thermoplastic resin may be 50-99%, and the sum tb1 + tb3 of the thicknesses of the first layer and the third layer may be 1-50%.

In the above description, the first layer, the second layer, and the third layer are described in order based on the drawings, and the order may be changed.

The non-liquid crystalline thermoplastic resin is transparent and can be applied to an extrudable thermoplastic resin.

In a 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 and an acrylic resin. These may be used alone or in combination of two or more.

1 is a schematic view of a method of manufacturing an optical film according to one embodiment of the present invention. 1 shows a state in which a non-liquid crystalline thermoplastic resin is melt-extruded into three layers.

The above-mentioned "three-layer" is composed of the first surface layer-inner layer-second surface layer as described above, which are made of the thermoplastic resin of the same material and differ only in the melt extrusion temperature, It means that the adhesive layer is not included.

Referring to FIG. 1, the thermoplastic resin 44 melt-extruded in the die 43 can be passed between the first forming roll 41 and the second forming roll 42 to be produced in the form of a film.

The thermoplastic resin can be melt-extruded into a multi-layer structure using a main extruder and a secondary extruder. For example, the inner layer (B) is formed as the main extruder and the surface layer (A) is formed as the auxiliary extruder. By separately setting the extrusion temperature of the main extruder and the auxiliary extruder, the thermoplastic resin can be melt-extruded into a multilayer structure.

In the specific example, the temperature of the surface layer coming out of the secondary extruder can be set to a low value, and the temperature of the inner layer coming out of the main extruder can be set to a high value, so that a higher value can be obtained when the inclination angle in the thickness direction is generated utilizing the inter-

In another embodiment, the temperature of the surface layer coming out of the secondary extruder is made higher and the temperature of the inner layer coming out of the main extruder is set to a lower value so that a higher value can be obtained when the inclination angle in the thickness direction is generated utilizing the inter-

It is preferable that the roll on which the molten extruded thermoplastic resin 44 is wound is the second forming roll 42.

The melt extruded thermoplastic resin is in contact with the first forming roll and the second forming roll so that the inside of the melt extrudate during film forming is at least Tg of the thermoplastic resin while the surface of the melt extrudate becomes less than Tg. When the molding rolls at both ends run in a state where the molding temperature difference is generated between the surface of the melt extrudate and the inside thereof, a different shearing force is generated on the surface and inside of the melt extrudate, and thus the finally produced film may have 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 1:

[Formula 1]

Te x 0.3 < Tr < Te x 0.6

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

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

In the specific example, the surface temperature Tr of the first shaping roll 41 is 20 to 200 占 폚, preferably 50 to 150 占 폚, and most preferably 80 to 130 占 폚. It is possible to secure the phase difference value and the tilt angle through the phase expression in the above range.

The surface temperature of the second forming roll 42 is 20 to 200 캜, preferably 80 to 130 캜. It is possible to secure the phase difference value and the tilt angle through the phase expression in the above range.

The temperature difference between the first forming roll 41 and the second forming roll 42 is 2 to 50 캜, preferably 5 to 30 캜, more preferably 5 to 20 캜. It is possible to secure the phase difference value and the tilt angle through the phase expression in the above range.

In the embodiment, the first and second forming rolls 41 and 42 may have different degrees of elasticity to form various film beta-angles. Preferably, the first forming roll is more elastic than the second forming roll.

5 is a schematic cross-sectional view of a first forming roll according to one embodiment of the present invention.

Referring to FIG. 5, the first forming roll 41 includes a rotatable cylindrical inner member 411; A surface member 413 formed at an interval from the outer circumference of the cylindrical inner member; And a liquid phase layer (412) filled between the cylindrical inner member and the surface member.

As the material of the cylindrical inner member 411, metal, glass, ceramics, plastic, rubber, or the like can be applied, preferably a metal, more preferably steel. The diameter of the cylindrical inner member 411 may be 200 to 500 mm.

The surface member 413 surrounds the outer periphery of the first forming roll 41 and is spaced apart from the cylindrical inner member 411. The surface member 413 may be made of metal. The metal may be a single metal, a metal plated with a second metal, or an alloy of two or more metals. Preferably, a steel metal may be applied. The average distance between the cylindrical inner member 411 and the surface member 413 may be 0.1 to 10 mm.

A liquid-phase layer 412 is filled between the cylindrical inner member 411 and the surface member 413. The liquid phase layer 412 may be water, oil, or the like. The double water is preferable because the temperature can be easily controlled.

The second forming roll 42 applies a metal roll, preferably a steel roll.

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 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. For example, the speed of the first forming roll 41 may be 1 to 60 m / min, and the speed of the second forming roll 42 may be 1 to 50 m / min.

Preferably, the difference in speed between the first forming roll 41 and the second forming roll 42 may be within 30%. In a preferred embodiment, the peripheral speed difference may be 0 to 10%, more preferably 0.1 to 5%. It is advantageous to secure a phase difference value and a tilt angle through phase expression in the above range.

The 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 stretching can be performed in a direction opposite to the running direction (TD) to 8 to 25%, more preferably 10 to 20%, with respect to the running direction.

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. The phase difference value and the inclination angle can be ensured through the phase expression 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.

An optical film, which is another aspect of the present invention, can be produced by the above-described production method.

6 is a cross-sectional view of an optical film manufactured according to one embodiment of the present invention.

Referring to Fig. 6, the optical film of the present invention is a single film.

The 'single film' means that the surface layer and the inner layer are formed by extrusion without forming any additional coating layer 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 inner layer 10c, and they are the same components, and they are conveniently distinguished according to their orientation.

Referring to FIG. 6, the optical film 10 includes first and second surface layers 10a and 10b located on the surface in the film thickness direction; And a film inner layer (10c) positioned between the first and second surface layers, wherein the first and second surface layers (10a, 10b) are not obliquely oriented in the thickness direction of the film, (10c) is oriented obliquely in the thickness direction of the film.

In Fig. 6, the absolute value of the difference between the inclination angles of the film inner layer and the first and second surface layers may be 1-15 [deg.].

The present invention will be described in more detail with reference to Fig.

The inner film layer 10c may have different values of the film beta angle along the z axis which is the thickness direction. For example, at a position of 1-50 μm from the film surface, the film β angle is 0-30 °, whereas at a position 10-100 μm from the film surface, the film β angle may be 10-45 °. Thus, the angle of inclination depends on the thickness of the film, and the angle of the film beta is different.

Preferably, the ratio β1 / β2 of the maximum β angle (β1) to the minimum β angle (β2) in the film inner layer may be 1.5-1.0, more preferably 1.3-1.0. 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 2 at a wavelength of 550 nm of 10-200 nm. There is an advantage of viewing angle compensation in the above range. Preferably, the in-plane phase retardation value Ro may be 10-100 nm.

[Formula 2]

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 (unit: nm) of the optical film).

The optical film may have a retardation value in the thickness direction (Rth) defined by the following formula 3 at a wavelength of 550 nm of 50-300 nm. There is an advantage of viewing angle compensation in the above range. Preferably, the thickness retardation value (Rth) may be 100-200 nm.

[Formula 3]

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

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

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

On the other hand, an optical film produced by extruding a thermoplastic resin into a single layer is shown in Fig. Referring to FIG. 7, it can be seen that the angle of inclination with respect to FIG. 6 is low.

6, the surface of the optical film may not be obliquely oriented in the thickness direction of the film but may be obliquely oriented in the thickness direction of the film. 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 optical film may have a film angle? Of 5 to 40 degrees, which is defined as an angle at which the orthogonal Nicole transparency becomes minimum.

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.

Also, the first and second surface layers may be 1 to 30% of the total thickness of the film. An excellent viewing angle can be secured in the above range.

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

Another aspect of the present invention relates to a liquid crystal display comprising the optical film.

In an embodiment, the liquid crystal display comprises a polarizing film; And the optical film laminated on the polarizing film.

The polarizing film may further include a liquid crystal layer on the other surface thereof.

8 is a schematic cross-sectional view of a liquid crystal display according to one embodiment of the present invention.

A liquid crystal panel 40 including a liquid crystal layer 40 sealed between a first substrate 30a and a second substrate 30b as shown in FIG. The optical film 10 of the present invention may be laminated. 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. 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).

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, although not shown in the drawing, the optical film 10 of the present invention may also be laminated on the lower part of the second substrate 30b.

On the optical film 10, a polarizing film 20 including a polarizer and a protective film may be formed.

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 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.

Example  1-2

RX4500 thermoplastic resin manufactured by JSR company was melt-extruded at 230 ~ 280 ° C in T-die and passed between FSR roll and metal roll to produce film form.

At this time, the thermoplastic resin was melt-extruded into three layers composed of the first surface layer-inner layer-second surface layer using the main extruder and the auxiliary extruder, and the extrusion temperature was as shown in Table 1 below.

The surface temperature of the FSR roll was 100 占 폚, the surface temperature of the metal roll was 120 占 폚, and the ratio of the FSR roll speed / metal roll speed was set to 1.01 to 1.03.

The extruded film was stretched by 12% in the running direction (TD) with respect to the running direction to produce an optical film having a thickness of 80 to 90 탆.

Comparative Example  1-2

In the above examples, an optical film was produced in the same manner as in Example 1, except that the thermoplastic resin was melt-extruded into a single layer and the melt extrusion temperature was changed as shown in Table 1.

The following optical properties of the produced optical film were evaluated.

(1) Ro 'and Rth' values: nx, ny 'and nz' were obtained using Axo scan and OPMF-2 series manufactured by Axometrics Inc, and Ro 'and Rth' .

[Formula 2]

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 (unit: nm) of the optical film).

[Formula 3]

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

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

(2) Mean β angle: Axo scan was used. This is calculated as an average value of the angle of beta distributed in the thickness direction of the entire film.

To observe the detailed thickness profile in the thickness direction, the luminance distribution of the polarized light microscope image was analyzed by an image analysis program, and the average luminance was calculated by dividing the polarized light microscope image into nine equal parts at intervals of about 10 탆 in the thickness direction of the film. Next, an angle and an average luminance were plotted (PLOT), and a film beta angle was obtained. The β-angular distribution was plotted for each thickness and the mean value was obtained.

Process conditions Properties Structure of thermoplastic resin immediately after melt extrusion Extrusion temperature by layer (℃) R0 (nm) Rth (nm) Average beta angle
(°) The first surface layer Inner layer The second surface layer Example 1 3rd Floor 230 250 230 47 78 34 Example 2 3rd Floor 230 270 230 43 75 32 Comparative Example 1 fault 250 40 70 28 Comparative Example 2 fault 270 25 50 25

As shown in Table 1, it can be seen that the optical film produced by melt extrusion of a thermoplastic resin in multiple layers according to the present invention is significantly higher than the comparative example in which the average beta angle is melt-extruded as a single layer.

On the other hand, it can be confirmed that the average average beta angle of the comparative example melt-extruded as a single layer is relatively low compared to the present invention.

It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

Claims (15)

Melt-extruding a non-liquid crystalline thermoplastic resin; And passing the molten extruded thermoplastic resin between a first forming roll and a second forming roll to produce a film form,
Wherein the surface temperature of the first and second forming rolls is not higher than the glass transition temperature (Tg) of the thermoplastic resin,
A different shearing force is generated on the surface and inside of the melt-extruded thermoplastic resin in accordance with the running of the first and second forming rolls, thereby giving an inclination angle in the thickness direction of the film,
Wherein the non-liquid crystalline thermoplastic resin is melt-extruded in multiple layers.
The method of producing an optical film according to claim 1, wherein the non-liquid crystalline thermoplastic resin is melt-extruded into two or three layers.
The non-liquid-crystalline thermoplastic resin according to claim 1, wherein the non-liquid crystalline thermoplastic resin is melt-extruded into three layers of a first surface layer-an inner layer-a second surface layer,
Wherein the temperature difference between the first surface layer or the second surface layer and the inner layer is 5-50 ° C.
4. The method of claim 3 wherein the temperature of the inner layer is 150-300 &lt; 0 &gt; C,
Wherein a temperature of the first surface layer and a surface temperature of the second surface layer are respectively 150-300 캜,
Wherein the inner layer has a lower temperature than the first surface layer and the second surface layer.
5. The method of producing an optical film according to claim 4, wherein the thickness of the inner layer is 50-99% of the total thickness of the three layers, and the sum of the thicknesses of the first surface layer and the second surface layer is 1-50%.
4. The method of claim 3 wherein the temperature of the inner layer is 150-300 &lt; 0 &gt; C,
Wherein a temperature of the first surface layer and a surface temperature of the second surface layer are respectively 150-300 캜,
Wherein the inner layer has a higher temperature than the first surface layer and the second surface layer.
The optical film according to claim 6, wherein the thickness of the inner layer is 50-99% of the total thickness of the three layers, and the sum of the thicknesses of the first surface layer and the second surface layer is 1-50%.
The method for producing an optical film according to claim 1, wherein the surface temperature (Tr) of the first and second shaping rolls has the following formula (1):
[Formula 1]
Te x 0.3 < Tr < Te x 0.6
(Where Te is the temperature of the thermoplastic inner layer immediately after melt extrusion,
And Tr is the surface temperature of the first and second forming rolls).
The method of manufacturing an optical film according to claim 1, wherein the first and second forming rolls have different degrees of elasticity from each other.
The thermoplastic resin composition according to claim 1, wherein the thermoplastic resin is at least one of a cycloolefin resin, a polycarbonate resin, a polyolefin resin, an aromatic vinyl resin, a polyamide resin, a polyimide resin, a polyester resin, &Lt; / RTI &gt;
The method of claim 1, further comprising stretching the film passed between the first and second forming rolls.
12. The method of producing an optical film according to claim 11, wherein the stretching is performed in a direction opposite to the running direction (TD) by 5 to 20% relative to the running direction.
The method for producing an optical film according to claim 11, wherein the stretching is performed at a temperature lower than a glass transition temperature (Tg) of the thermoplastic resin.
An optical film produced by the manufacturing method according to any one of claims 1-13.
Polarizing film; And
A liquid crystal display comprising the optical film of claim 14 laminated on the polarizing film.

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