KR20100081951A - Optical films and liquid crystal display comprising the sames - Google Patents

Abstract

PURPOSE: An optical film and a liquid crystal display including the same are provided, which have low haze and excellent mechanical strength and durability. CONSTITUTION: An optical film comprises an acrylic copolymer resin and a blend resin. The acrylic copolymer resin comprises a comonomer which is selected among acrylic or amid monomer and alpha-methylstyrene. The acrylic or amid monomer includes alkyl methacrylate monomer and acyclic or aromatic ring. The blend resin includes acyclic or aromatic ring on a polymer backbone.

Description

Optical film and liquid crystal display including the same {OPTICAL FILMS AND LIQUID CRYSTAL DISPLAY COMPRISING THE SAMES}

The present invention provides an optical film having excellent heat resistance and optical transparency, low haze, poor breakage, excellent mechanical strength, and excellent durability, a manufacturing method thereof, and a liquid crystal display device including the optical film. This application claims the benefit of the application date of Korean Patent Application No. 10-2009-0000766 filed to the Korea Intellectual Property Office on January 6, 2009, the entire contents of which are incorporated herein.

Recently, display technologies using various methods such as plasma display panels (PDPs) and liquid crystal displays (LCDs), which replace conventional CRTs, have been proposed and marketed based on the development of optical technologies. Polymer materials for such displays are becoming more sophisticated. For example, in the case of liquid crystal displays, as thin film thickness, light weight, and large screen area are promoted, wide viewing angles, high contrast, suppression of image color tone change according to viewing angle, and uniformity of screen display have become particularly important problems.

Accordingly, various polymer films are used for polarizing films, polarizer protective films, retardation films, plastic substrates, light guide plates, and the like. Twisted nematic (TN), super twisted nematic (STN) Various modes of liquid crystal display using vertical alignment (VA), in-plane switching (IPS) liquid crystal cells, and the like have been developed. All of these liquid crystal cells have an inherent liquid crystal array, have inherent optical anisotropy, and in order to compensate for this optical anisotropy, films have been proposed in which various kinds of polymers are drawn to give a retardation function.

The polarizing plate generally has a structure in which a triacetyl cellulose film (hereinafter referred to as a TAC film) is laminated on a polarizer with an aqueous adhesive made of a polyvinyl alcohol-based aqueous solution. By the way, both the polyvinyl alcohol film used as a polarizer and the TAC film used as a protective film for polarizers do not have sufficient heat resistance and moisture resistance. Therefore, when the polarizing plate made of the above films is used for a long time in an atmosphere of high temperature or high humidity, the polarization degree is lowered, the polarizer and the protective film are separated, or the optical properties are deteriorated.

In addition, the TAC film has a great change in the in-plane retardation R _in and the thickness direction retardation R _th , which are existing according to changes in the ambient temperature / humidity environment, and _in particular, the change in retardation with respect to the incident light in the oblique direction is large. When a polarizing plate including a TAC film having such characteristics as a protective film is applied to a liquid crystal display device, there is a problem in that the viewing angle characteristic changes according to a change in the ambient temperature / humidity environment and the image quality is deteriorated. In addition, the TAC film has a large dimensional change rate according to the change of ambient temperature / humidity environment, and the photoelastic coefficient value is also relatively large. Easy to be

Methacrylic (methacryl) resin is well known as a material for compensating for the various disadvantages of the TAC film. However, it is known that methacryl-based resins are brittle or cracked, which is a problem in the carrier property in the production of polarizers and is insufficient in productivity.

In order to solve this problem, a method of blending other resins or toughness modifiers with acrylic resins (Japanese Patent Laid-Open No. 2006-284881, Japanese Patent Laid-Open 2006-284882) or a method of co-extrusion and laminating other resins (Japanese Patent Laid-Open No. 2006-243681, Japanese Patent Laid-Open No. 2006-215463, Japanese Patent Laid-Open 2006-215465, and Japanese Patent Laid-Open No. 2007-017555) have been proposed. However, these methods do not sufficiently reflect the inherent high heat resistance and high transparency of the acrylic resin or have a complicated laminate structure.

An object of the present invention is to provide an optical film having excellent optical properties and excellent optical transparency, and to solve the disadvantages of an acryl-based film that is brittle, to provide excellent workability, and excellent durability such as heat resistance. do.

Moreover, an object of this invention is to provide the manufacturing method of the said optical film, and the liquid crystal display device containing the said optical film.

The present invention comprises 1) (a1) an alkyl methacrylate monomer, and (a2) a (meth) acrylic or imide monomer containing an aliphatic ring or an aromatic ring and at least one comonomer selected from alphamethyl styrene. And an acrylic copolymer resin, and 2) a blend resin of a resin containing an aromatic ring or an aliphatic ring in the polymer main chain, and a plane direction retardation value represented by the following Equation 1 is -5 to 5 nm, and is represented by the following Equation 2 The optical film whose thickness direction retardation value displayed is -5-5 nm is provided.

[Equation 1]

R _in = (n _x -n _y ) × d

[Equation 2]

R _th = (n _z -n _y ) × d

In Equations 1 and 2,

n _x is a refractive index of the direction of the largest refractive index in the plane direction of the film,

n _y is a refractive index in the vertical direction in the n _x direction in the plane direction of the film,

n _z is the refractive index in the thickness direction,

d is the thickness of the film.

In addition, the present invention provides a composition comprising: 1) at least one comonomer selected from (a1) alkyl methacrylate monomers, (a2) (meth) acrylic or imide monomers containing aliphatic rings or aromatic rings, and alphamethyl styrene. (B) preparing a blend resin composition of an acrylic copolymer resin, and (b) a resin including an aromatic ring or an aliphatic ring in a polymer main chain; And 2) provides a method for producing an optical film comprising the step of molding a film using the resin composition. This manufacturing method may further comprise the step of uniaxially or biaxially stretching the film.

In addition, the present invention provides a composition comprising: 1) at least one comonomer selected from (a1) alkyl methacrylate monomers, (a2) (meth) acrylic or imide monomers containing aliphatic rings or aromatic rings, and alphamethyl styrene. It provides an acrylic copolymer resin comprising, and 2) a resin composition comprising a resin containing an aromatic ring or an aliphatic ring in the polymer backbone.

In addition, the present invention provides a liquid crystal display device comprising at least one optical film.

The optical film according to the present invention is excellent in optical properties and also excellent in optical transparency, excellent mechanical properties, excellent workability, heat resistance and phase difference implementation characteristics.

The optical film according to the present invention comprises (1) at least one copolymer selected from (a1) alkyl methacrylate monomers, (a2) (meth) acrylic or imide monomers containing aliphatic rings or aromatic rings, and alphamethyl styrene. 2) a blend resin of an acrylic copolymer resin comprising a monomer, and 2) a blend resin of a resin containing an aromatic ring or an aliphatic ring in the polymer main chain, and having a plane direction retardation value represented by Equation 1 being -5 to 5 nm. The thickness direction retardation value represented by Equation 2 is -5 to 5nm.

In the retardation film according to the present invention, the alkyl group of the alkyl methacrylate monomer of 1) preferably has 1 to 10 carbon atoms, more preferably 1 to 4 carbon atoms, and even more preferably a methyl group or an ethyl group. Specific examples of the alkyl methacrylate monomers include methyl methacrylate, ethyl methacrylate, and the like, and more preferably methyl methacrylate, but are not limited thereto.

The optical film according to the present invention comprises 1) at least one comonomer selected from (meth) acrylic or imide monomers containing an aliphatic ring or an aromatic ring and alphamethyl styrene in the acrylic copolymer resin, thereby obtaining an acrylic copolymer. The heat resistance of resin can be improved.

In the optical film according to the present invention, the (meth) acrylic or imide monomer having the aliphatic ring or the aromatic ring of 1) may be a (meth) acrylic monomer or an imide monomer having heat resistance. More specifically, cyclohexyl methacrylate, benzyl methacrylate, cyclohexyl acrylate, 2-phenoxyethyl acrylate, 3,3,5-trimethylcyclohexyl methacrylate, phenyl methacrylate, naphthyl methacrylate Acrylate, cyclohexyl maleimide, phenyl maleimide, etc. are mentioned, It is more preferable that they are cyclohexyl methacrylate or cyclohexyl maleimide, It is not limited to this.

In the optical film according to the present invention, 1) the content of the (meth) acrylic or imide monomer and the alpha methyl styrene containing an alkyl methacrylate monomer, an aliphatic ring or an aromatic ring in the acrylic copolymer resin is 0.1 to It may be selected within the range of 99.9% by weight. In particular, the alkyl methacrylate monomer is preferably 60 to 99.9% by weight, the (meth) acrylic or imide monomer containing the aliphatic ring or aromatic ring, or alphamethyl styrene is 0.1 to 40% by weight Preferred but not limited thereto.

In the optical film according to the present invention, the 1) acrylic copolymer resin is a copolymer resin of methyl methacrylate and cyclohexyl methacrylate; Copolymer resins of methyl methacrylate and cyclohexyl maleimide; Copolymer resins of methyl methacrylate, cyclohexyl methacrylate and alphamethyl styrene; Or a copolymer resin of methyl methacrylate, cyclohexyl maleimide, and alphamethyl styrene, but is not limited thereto.

In the optical film according to the present invention, the resin containing an aromatic ring or an aliphatic ring in the polymer main chain is polycarbonate resin, polyarylate resin, polynaphthalene resin, polynorbornene resin, polyphenoxy resin, or the like. And it can be used, It is more preferable that it is polycarbonate resin or polyethoxy resin, It is not limited only to this.

In the optical film according to the present invention, 1) the content of the acrylic copolymer resin in the blend resin is 90% or more and less than 100% by weight, 2) the content of the resin containing an aromatic ring or aliphatic ring in the polymer backbone is greater than zero It is preferable that it is 10 weight% or less.

In the optical film according to the present invention, the glass transition temperature of the blend resin is preferably 110 ° C or higher, and more preferably 120 ° C or higher. In addition, the weight average molecular weight of the blend resin is preferably 50,000 to 200,000 in terms of heat resistance, sufficient processability, productivity and the like.

The optical film according to the present invention can be used as a polarizer protective film.

When the optical film according to the present invention is used as a polarizer protective film, it is excellent in transparency, optical properties, mechanical strength, and the like, and particularly has excellent heat resistance.

In addition, the method for producing an optical film according to the present invention is selected from 1) (a1) alkyl methacrylate monomers, (a2) (meth) acrylic or imide monomers containing aliphatic rings or aromatic rings, and alphamethyl styrene. (B) preparing a blend resin composition of an acrylic copolymer resin comprising one or more comonomers, and (b) a resin containing an aromatic ring or an aliphatic ring in the polymer backbone; And 2) molding the film using the resin composition. The method of manufacturing the optical film may further include uniaxially or biaxially stretching the film.

Specific details of the acrylic copolymer resin, a resin including an aromatic ring or an aliphatic ring in the polymer backbone are the same as described above, and thus the description thereof will be omitted.

In the method of manufacturing an optical film according to the present invention, the resin composition of step 1) may be prepared by melt-blending and blending the aforementioned components. Melt mixing of the components can be carried out using a solution cast method, extrusion method and the like.

In the method for producing a retardation film according to the present invention, it is more preferable to prepare a film by using a solution casting method and to perform a stretching step.

In addition, in some cases, it is also possible to proceed with the extrusion method by adding a modifier.

The resin composition may further include antioxidants, UV stabilizers, heat stabilizers, and the like commonly used in the art.

The method for producing an optical film according to the present invention may further include the step of uniaxially or biaxially stretching the film. The stretching step may be performed in the longitudinal direction (MD) stretching or in the transverse direction (TD) stretching, or both. When extending | stretching both a longitudinal direction and a lateral direction, after extending | stretching either one, you can extend in another direction and you may extend | stretch both directions simultaneously. Stretching can be done in one step or stretched in multiple steps. When extending | stretching in a longitudinal direction, extending | stretching by the speed difference between rolls can be performed, and when extending | stretching in a lateral direction, a tenter can be used. The starting angle of the tenter is 10 degrees or less in total, suppressing the bowing phenomenon which arises at the time of a lateral stretch, and controls the angle of an optical axis regularly. The same boeing suppression effect can also be obtained by making transverse stretching into multiple stages.

The stretching may be performed at a temperature of (Tg-20 ° C) to (Tg + 30 ° C) when the glass transition temperature of the resin composition is Tg. The glass transition temperature refers to a region from the temperature at which the storage modulus of the resin composition begins to decrease, and thus the loss modulus becomes larger than the storage modulus, at which the orientation of the polymer chain is relaxed and lost. Glass transition temperatures can be measured by differential scanning calorimetry (DSC). The temperature at the time of the stretching step is more preferably the glass transition temperature of the film.

The drawing speed is preferably in the range of 1 to 100 mm / min in the case of a universal drawing machine (Zwick Z010) and in the range of 0.1 to 2 m / min in the case of a pilot drawing machine. It is preferable to stretch the film by applying an elongation of 5 to 300%.

The optical film according to the present invention can be uniaxially or biaxially stretched by the above-described method, thereby adjusting the phase difference characteristics.

In addition, the present invention provides a composition comprising: 1) at least one comonomer selected from (a1) alkyl methacrylate monomers, (a2) (meth) acrylic or imide monomers containing aliphatic rings or aromatic rings, and alphamethyl styrene. It provides an acrylic copolymer resin comprising, and 2) a resin composition comprising a resin containing an aromatic ring or an aliphatic ring in the polymer backbone.

In the resin composition according to the present invention, specific details of the acrylic copolymer resin, a resin including an aromatic ring or an aliphatic ring in the polymer main chain are the same as described above, and thus the description thereof will be omitted.

In the resin composition according to the present invention, 1) the content of the (meth) acrylic or imide monomer and the alpha methyl styrene containing an alkyl methacrylate monomer, an aliphatic ring or an aromatic ring in the acrylic copolymer resin is 0.1 to It may be selected within the range of 99.9% by weight. In particular, the alkyl methacrylate monomer is preferably 60 to 99.9% by weight, the (meth) acrylic or imide monomer containing the aliphatic ring or aromatic ring, or alphamethyl styrene is 0.1 to 40% by weight Preferred but not limited thereto.

In the resin composition according to the present invention, the content of the 1) acrylic copolymer resin is 90% or more and less than 100% by weight, and 2) the content of the resin containing an aromatic ring or an aliphatic ring in the polymer backbone is greater than 0 10 It is preferable that it is weight% or less.

The resin composition according to the present invention can be prepared by melt blending the aforementioned components. Melt mixing of the components can be carried out using a solution cast method, extrusion method and the like.

The resin composition according to the present invention has a very excellent miscibility between the 1) acrylic copolymer resin and 2) a resin containing an aromatic ring or an aliphatic ring in the polymer main chain. In addition, the resin composition according to the present invention is excellent in heat resistance, processability, productivity and the like, and can be applied to the production of various optical films.

In addition, the present invention provides a liquid crystal display device comprising one or two or more optical films.

For example, the present invention includes a light source, a first polarizing plate, a liquid crystal cell, and a second polarizing plate sequentially stacked, and includes the optical film according to the present invention as a protective film of at least one of the first and second polarizing plates. A liquid crystal display device is provided.

The liquid crystal cell is a liquid crystal layer; A substrate capable of supporting this; And an electrode layer for applying a voltage to the liquid crystal. At this time, the polarizing plate according to the present invention is an in-plane switching mode (IPS mode), vertically aligned (VA mode), OCB (Optically Compensated Birefringence mode), twisted nematic mode (Twisted Nematic mode) TN mode) and FFS (Fringe Field Switching mode; FFS mode).

The optical film according to the present invention may be provided on both sides of the polarizer. In addition, the optical film is provided on one side of the polarizer, the other side is provided with a polarizer protective film known in the art, such as TAC film, PET film, COP film, PC film, polynorbornene-based film, etc. It may be.

Adhesion of the polarizer and the optical film may be performed using an adhesive layer. The adhesive which can be used when laminating the optical film and the polarizing plate is not particularly limited as long as it is known in the art. For example, there are one- or two-component polyvinyl alcohol (PVA) adhesives, polyurethane adhesives, epoxy adhesives, styrene butadiene rubber (SBR) adhesives, hot melt adhesives, and the like, but are not limited thereto. Polyvinyl alcohol adhesive is more preferable among the said adhesive agents.

The adhesion of the polarizer and the optical film is first coated with an adhesive using a roll coater, a gravure coater, a bar coater, a knife coater, or a capillary coater on the surface of a polarizer protective film or a PVA film that is a polarizer. Before drying completely, the protective film and the polarizing film may be carried out by a method of laminating by heating or pressing at room temperature with a lamination roll. In the case of using a hot melt adhesive, a heat press roll should be used.

When using a polyurethane adhesive, it is preferable to use the polyurethane adhesive manufactured using the aliphatic isocyanate compound which is not yellowed by light. When using one-component or two-component dry laminate adhesives or adhesives with relatively low reactivity between isocyanates and hydroxyl groups, a solution-type adhesive diluted with an acetate solvent, a ketone solvent, an ether solvent, or an aromatic solvent, etc. You can also use At this time, the adhesive viscosity is preferably low viscosity of 5,000 cps or less. The adhesives are excellent in storage stability and preferably have a light transmittance of 90% or more at 400 to 800 nm.

A tackifier can also be used if it can exert sufficient adhesive force. It is preferable that the adhesive is sufficiently cured by heat or ultraviolet rays after lamination, and thus the mechanical strength is improved to the level of the adhesive. The adhesive strength is also large so that the adhesive does not peel off without breaking of either film to which the adhesive is attached. It is preferable.

Specific examples of the pressure-sensitive adhesive that can be used include natural rubber, synthetic rubber or elastomer having excellent optical transparency, vinyl chloride / vinyl acetate copolymer, polyvinyl alkyl ether, polyacrylate, modified polyolefin-based pressure-sensitive adhesive, and the like, and a curing agent having a curing agent such as isocyanate added thereto. An adhesive is mentioned.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the following Examples are only for illustrating the present invention and are not intended to limit the scope of the present invention.

< Example >

< Example  1>

The resin was prepared from 98.5 parts by weight of copolymer of methyl methacrylate (80 parts by weight) and cyclohexyl methacrylate (20 parts by weight) and 1.5 parts by weight of polycarbonate. As a result of measuring the glass transition temperature and the weight average molecular weight of manufactured resin, the resin with a glass transition temperature of 123 degreeC and a weight average molecular weight 100,000 was obtained. After this resin was produced the film using the solution casting method, it extended | stretched at the glass transition temperature, and measured the phase difference value of the film. As a result, the surface retardation value / thickness retardation value was 4.6 nm / 2 nm.

< Example  2>

Resin was prepared from 99 parts by weight of copolymer of methyl methacrylate (80 parts by weight) and cyclohexyl methacrylate (20 parts by weight) and 1 part by weight of polycarbonate. As a result of measuring the glass transition temperature and the weight average molecular weight of manufactured resin, the resin with a glass transition temperature of 123 degreeC and a weight average molecular weight 100,000 was obtained. After this resin was produced the film using the solution casting method, it extended | stretched at the glass transition temperature, and measured the phase difference value of the film. As a result, the plane retardation value / thickness retardation value was 3.6 nm / -1.8 nm.

< Example  3>

Resin was prepared from 99 parts by weight of copolymer of methyl methacrylate (80 parts by weight) and cyclohexyl maleimide (20 parts by weight) and 1 part by weight of polycarbonate. As a result of measuring the glass transition temperature and the weight average molecular weight of manufactured resin, the resin of glass transition temperature 124 degreeC and a weight average molecular weight 100,000 was obtained. After this resin was produced the film using the solution casting method, it extended | stretched at the glass transition temperature, and measured the phase difference value of the film. As a result, the plane retardation value / thickness retardation value was 2.3 nm / -1.5 nm.

< Example  4>

Resin was prepared from 98.5 parts by weight of copolymer of methyl methacrylate (80 parts by weight), cyclohexyl methacrylate (17 parts by weight), alphamethylstyrene (3 parts by weight) and polycarbonate. As a result of measuring the glass transition temperature and the weight average molecular weight of manufactured resin, the resin with a glass transition temperature of 123 degreeC and a weight average molecular weight 100,000 was obtained. After this resin was produced the film using the solution casting method, it extended | stretched at the glass transition temperature, and measured the phase difference value of the film. As a result, the surface direction retardation value / thickness direction retardation value obtained 2.7 nm / -0.6 nm.

< Example  5>

The resin was prepared from 98.5 parts by weight of copolymer of methyl methacrylate (80 parts by weight) and cyclohexyl methacrylate (20 parts by weight) and 1.5 parts by weight of phenoxy resin. As a result of measuring the glass transition temperature and the weight average molecular weight of manufactured resin, the resin of glass transition temperature 124 degreeC and a weight average molecular weight 100,000 was obtained. After this resin was produced the film using the solution casting method, it extended | stretched at the glass transition temperature, and measured the phase difference value of the film. As a result, surface direction retardation value / thickness direction retardation value obtained 1.8 nm / 1.3 nm.

< Example  6>

The resin was prepared from 98.5 parts by weight of a copolymer of methyl methacrylate (80 parts by weight), cyclohexyl maleimide (17 parts by weight), alphamethylstyrene (3 parts by weight) and phenoxy resin. As a result of measuring the glass transition temperature and the weight average molecular weight of manufactured resin, the resin of glass transition temperature 124 degreeC and a weight average molecular weight 100,000 was obtained. After this resin was produced the film using the solution casting method, it extended | stretched at the glass transition temperature, and measured the phase difference value of the film. As a result, the surface direction retardation value / thickness direction retardation value obtained 1.7 nm / 1.5 nm.

< Comparative example  1>

Except that the resin was prepared from 90 parts by weight of the copolymer of methyl methacrylate (80 parts by weight) and cyclohexyl methacrylate (20 parts by weight) and 10 parts by weight of polycarbonate, the rest was the same as in Example 1 above. The experiment was conducted. As a result, a resin having a glass transition temperature of 124 ° C and a weight average molecular weight of 110,000 was obtained. After this resin was produced the film using the solution casting method, it extended | stretched at the glass transition temperature, and measured the phase difference value of the film. As a result, the surface direction retardation value / thickness direction retardation value obtained 150 nm / -80 nm.

< Comparative example  2>

Except that the resin was prepared from 85 parts by weight of the copolymer of methyl methacrylate (80 parts by weight) and cyclohexyl acrylate (20 parts by weight) and 15 parts by weight of polycarbonate, the remainder was experimented in the same manner as in Example 1. Proceeded. As a result, a resin having a glass transition temperature of 124 ° C and a weight average molecular weight of 110,000 was obtained. After this resin was produced the film using the solution casting method, it extended | stretched at the glass transition temperature, and measured the phase difference value of the film. As a result, the surface retardation value / thickness direction retardation value obtained 262 nm / -137 nm.

< Comparative example  3>

Except that the resin was prepared from 80 parts by weight of the copolymer of methyl methacrylate (80 parts by weight) and cyclohexyl methacrylate (20 parts by weight) and 20 parts by weight of polycarbonate, the rest was the same as in Example 1 above. The experiment was conducted. As a result, a resin having a glass transition temperature of 125 ° C. and a weight average molecular weight of 110,000 was obtained. After this resin was produced the film using the solution casting method, it extended | stretched at the glass transition temperature, and measured the phase difference value of the film. As a result, the plane retardation value / thickness retardation value obtained 170 nm / -200 nm.

The results of Examples 1 to 6 and Comparative Examples 1 to 3 are shown in Tables 1 and 2 below.

TABLE 1

A resin: A resin containing an aromatic ring or an aliphatic ring in the polymer main chain

MMA: Methyl Methacrylate

CHMA: cyclohexyl methacrylate

CHMI: Cyclohexyl Maleimide

PC: Polycarbonate

TABLE 2

(1) Weight average molecular weight (Mw): The prepared resin was dissolved in tetrahydrofuran and measured by gel osmosis chromatography (GPC).

(2) Glass transition temperature (Tg): Measured using a DSC (Differential Scanning Calorimeter) from TA Instrument.

(3) Retardation value (R _in / R _th ): After stretching at the glass transition temperature of the film was measured using AxoScan from Axometrics.

From the results of Examples 1 to 6 and Comparative Examples 1 to 3, the optical film according to the present invention is excellent in optical properties and also excellent in optical transparency, excellent mechanical properties, excellent workability, heat resistance and phase difference implementation characteristics Able to know.

Claims (15)

1) an acrylic copolymer comprising (a1) an alkyl methacrylate monomer, (a2) an (meth) acrylic or imide monomer containing an aliphatic ring or an aromatic ring and at least one comonomer selected from alphamethyl styrene Resin, and
2) a blend resin of a resin containing an aromatic ring or an aliphatic ring in the polymer backbone,
An optical film having a plane direction retardation value represented by Equation 1 below −5 to 5 nm and a thickness direction retardation value represented by Equation 2 below −5 to 5 nm:
[Equation 1]
R _in = (n _x -n _y ) × d
[Equation 2]
R _th = (n _z -n _y ) × d
In Equations 1 and 2,
n _x is a refractive index of the direction of the largest refractive index in the plane direction of the film,
n _y is a refractive index in the vertical direction in the n _x direction in the plane direction of the film,
n _z is the refractive index in the thickness direction,
d is the thickness of the film. The optical film of claim 1, wherein the alkyl methacrylate monomer of 1) is methyl methacrylate or ethyl methacrylate. The method according to claim 1, wherein the (meth) acrylic or imide monomer containing the aliphatic ring or aromatic ring of 1) is cyclohexyl methacrylate, benzyl methacrylate, cyclohexyl acrylate, 2-phenoxyethyl acrylate, 3,3,5-trimethylcyclohexyl methacrylate, phenyl methacrylate, naphthyl methacrylate, cyclohexyl maleimide, and an optical film comprising at least one member selected from the group consisting of phenyl maleimide . The method according to claim 1, wherein 1) the content of the alkyl methacrylate monomer in the acrylic copolymer resin is 60 to 99.9% by weight, and in the (meth) acrylic or imide monomers and aliphatic styrene containing an aliphatic ring or an aromatic ring The content of at least one comonomer to be selected is an optical film, characterized in that 0.1 to 40% by weight. The method according to claim 1, wherein 1) the acrylic copolymer resin is a copolymer resin of methyl methacrylate and cyclohexyl methacrylate; Copolymer resins of methyl methacrylate and cyclohexyl maleimide; Copolymer resins of methyl methacrylate, cyclohexyl methacrylate and alphamethyl styrene; Or a copolymer resin of methyl methacrylate, cyclohexyl maleimide, and alphamethyl styrene. The method of claim 1, wherein the resin containing an aromatic ring or an aliphatic ring in the polymer main chain is selected from the group consisting of polycarbonate resin, polyarylate resin, polynaphthalene resin, polynorbornene resin and polyphenoxy resin. An optical film characterized by including at least one. The method according to claim 1, wherein 1) the content of the acrylic copolymer resin in the blend resin is 90% or more and less than 100% by weight, 2) the content of the resin containing an aromatic ring or aliphatic ring in the polymer backbone is greater than 0 to 10% by weight An optical film, characterized in that. The optical film of claim 1, wherein the blend resin has a glass transition temperature of 110 ° C. or higher and a weight average molecular weight of 50,000 to 200,000. The optical film according to claim 1, wherein the optical film is for a polarizer protective film. 1) an acrylic copolymer comprising (a1) an alkyl methacrylate monomer, (a2) an (meth) acrylic or imide monomer containing an aliphatic ring or an aromatic ring and at least one comonomer selected from alphamethyl styrene (B) preparing a blend resin composition of a resin comprising an aromatic ring or an aliphatic ring in a polymer backbone; And
2) molding the film using the resin composition
Method for producing an optical film comprising a. The method of claim 10, further comprising, after the step 2), uniaxially or biaxially stretching the film. 1) an acrylic copolymer comprising (a1) an alkyl methacrylate monomer, (a2) an (meth) acrylic or imide monomer containing an aliphatic ring or an aromatic ring and at least one comonomer selected from alphamethyl styrene Resin, and
2) resins containing aromatic rings or aliphatic rings in the polymer backbone
Resin composition comprising a. The method according to claim 12, wherein 1) the content of the alkyl methacrylate monomer in the acrylic copolymer resin is 60 to 99.9% by weight, and in the (meth) acrylic or imide monomers and aliphatic styrene containing an aliphatic ring or an aromatic ring The content of at least one comonomer selected is a resin composition, characterized in that 0.1 to 40% by weight. The method according to claim 12, wherein 1) the content of the acrylic copolymer resin is more than 90% by weight less than 100% by weight, 2) the content of the resin containing an aromatic ring or aliphatic ring in the polymer backbone is greater than 0 to 10% by weight or less Resin composition made into. The liquid crystal display device containing the optical film of any one of Claims 1-9.