KR102681962B1 - Retardation film and method for manufacturing thereof - Google Patents

Abstract

The retardation film according to an exemplary embodiment of the present application includes an acrylic film; and a coating layer of a negative C-type material provided in direct contact with the acrylic film, wherein the coating layer of the negative C-type material includes a cellulose-based resin and a reactive acrylic binder.

Description

Retardation film and its manufacturing method {RETARDATION FILM AND METHOD FOR MANUFACTURING THEREOF}

This application relates to retardation film and its manufacturing method.

Based on recent developments in optical technology, display technologies using various methods such as plasma display panels (PDP) and liquid crystal displays (LCD), which replace conventional cathode ray tubes, have been proposed and sold. The required characteristics of polymer materials for such displays are becoming more sophisticated.

For example, in the case of liquid crystal displays, as thinner, lighter, and larger screen areas are promoted, wide viewing angles, high contrast, suppression of changes in image color tone depending on the viewing angle, and uniformity of screen display have become particularly important issues.

Accordingly, various polymer films are being used for polarizing films, retardation films, plastic substrates, light guide plates, etc.

In liquid crystal displays, double domain TN (twisted nematic), STN (super twisted nematic), ASM (axially symmetric aligned microcell), OCB (optically compensated blend), VA (vertical alignment), MVA (multidomain VA), SE (surrounding electrode) There are various modes such as patterned VA (PVA), in-plane switching (IPS), and fringe-field switching (FFS) modes, and each of these modes has its own unique liquid crystal arrangement and corresponding It exhibits optical anisotropy, which is the main cause of the narrow viewing angle of liquid crystal displays. Therefore, in order to improve the viewing angle, the optical anisotropy of these liquid crystals must be appropriately compensated, and for this purpose, a retardation film corresponding to each mode is required. Among these, in the case of IPS mode liquid crystal displays, since horizontally oriented liquid crystals are used, the optical anisotropy at the tilt angle in the non-driving state is not large compared to other modes, so it is known that a relatively excellent wide viewing angle can be secured just by using an isotropic protective film. However, in this case, compensation for the absorption axis of the polarizer at the tilt angle is not achieved at all, so contrast reduction and color modulation depending on the viewing angle may still occur. Therefore, in order to secure a perfect wide viewing angle, an IPS mode liquid crystal display must also be used as an appropriate retardation film. must be used.

For compensation for IPS mode, a phase compensation layer that satisfies the condition n _x > n _z > n _y is required. _{Here , n} However, it is known that a retardation compensation layer that satisfies the condition n _x > n _z > n _y is generally difficult to implement using a uniaxially/biaxially stretched film alone. Therefore, in order to form a retardation compensation layer that satisfies the above refractive index conditions, the refractive index is controlled three-dimensionally, such as a method of inducing excessive width shrinkage during stretching using a conventional shrink film, and a method of applying a strong electric field to the stretched film. Several methods have been proposed, but to date, there are limits to continuously producing wide-width films due to various technical/equipment problems.

Therefore, the retardation film for IPS mode is realistically proposed to have a structure composed of two or more multilayer films. For example, A-plate/(+)C-plate, (+)B-plate/(-)C-plate, etc. In terms of material, each layer is a stretched polymer film and a liquid crystalline organic coating layer. , phase difference-generating polymer coating layer, organic-inorganic composite material, etc. Several methods are possible to construct such a multi-layer composite film, such as multi-layer extrusion, adhesion/adhesion, direct coating, thermal lamination, etc., but the multi-layer extrusion method is different from each other. The technical/equipmental difficulty to control the phase difference of the layers is too high, and in the case of lamination using adhesives or adhesives, each layer of film must be manufactured separately, and then various processes such as adhesion and drying must be performed. Therefore, it has the disadvantage of having a high manufacturing cost and a high incidence of defects such as stains, stains, and contamination of foreign substances due to the use of adhesives or adhesives.

In the case of direct coating or high-temperature thermal lamination, the range of application is not wide because the phase difference value can easily change depending on the material due to high temperature and erosion of organic solvents, and in the case of direct coating, the problem is that the available base films are limited. There is. In order to directly coat a phase contrast material on a stretched film, the solvent resistance of the substrate film relative to the solvent used is of utmost importance. In the case of cellulose-based or olefin-based retardation films, the solvent resistance is relatively excellent, so a method of directly coating the substrate is preferred. It may be possible, but it cannot be applied for IPS mode because the range of phase difference expression is different. In the case of acrylic/styrene-based retardation films, aromatic hydrocarbons such as toluene and xylene, ketones such as acetone and methyl ethyl ketone, and dichloromethane are used. It is very vulnerable to general-purpose organic solvents such as organic chlorines such as chloroform, and when coated with a coating containing these solvents, it causes poor adhesion, increased brittleness, reduced retardation, and occurrence of stains, which limits the selection of coating agents. There is. Therefore, there is a need for research into the development of a retardation film with excellent organic solvent barrier properties and excellent interfacial adhesion with acrylic films and coating agents.

Republic of Korea Patent Publication No. 10-2015-0009864

Described herein are retardation films and methods for manufacturing them.

One implementation state of this application is,

Acrylic film; and

It includes a coating layer of a negative C type material provided in direct contact with the acrylic film,

The coating layer of the negative C type material provides a retardation film including a cellulose resin and a reactive acrylic binder.

In addition, other embodiments of this application are:

Preparing an acrylic film; and

Forming a coating layer of a negative C type material by coating a composition containing a cellulose resin and a reactive acrylic binder on at least one side of the acrylic film.

It provides a method for manufacturing a retardation film comprising.

In addition, another embodiment of the present application provides a liquid crystal display device including the retardation film.

According to an exemplary embodiment of the present application, it is possible to provide a retardation film in which an acrylic film and a coating layer of a negative C type material are in direct contact with each other.

In addition, according to an exemplary embodiment of the present application, there is excellent adhesion between the acrylic film and the coating layer of the negative C type material.

In addition, according to an exemplary embodiment of the present application, the manufacturing process of the retardation film can be simplified, and thus material and process costs can be reduced.

Below, the present application is described in more detail.

As mentioned above, as the size of liquid crystal displays is promoted, suppressing changes in image color tone depending on the viewing angle and uniformity of screen display are important issues. A retardation compensation layer is needed to compensate for the viewing angle, and the retardation film for IPS mode is usually constructed with two or more multilayer films.

Direct coating or high-temperature thermal lamination are being considered to implement a retardation film with a single layer of film, but there are problems such as changes in phase value or poor adhesion due to high temperature and erosion by organic solvents. Conventionally, a method of implementing this was proposed by introducing a primer layer into the retardation film of a multilayer film of two or more layers. However, since the primer layer is in the middle of the multilayer film, a problem of increased process costs may occur.

Therefore, the present application seeks to provide a retardation film that can exclude the primer layer previously applied and has excellent adhesion between layers, and a method of manufacturing the same.

The retardation film according to an exemplary embodiment of the present application includes an acrylic film; and a coating layer of a negative C-type material provided in direct contact with the acrylic film, wherein the coating layer of the negative C-type material includes a cellulose-based resin and a reactive acrylic binder.

In an exemplary embodiment of the present application, the acrylic film may be manufactured by producing a film using an acrylic polymer by a melt extrusion method or a solution casting method, and then performing a stretching process.

At this time, the acrylic film can be manufactured from an acrylic resin composition, and the acrylic resin only needs to contain an acrylic unit, and its components are not particularly limited. For example, the acrylic resin may be a homogeneous acrylic polymer resin such as polymethyl methacrylate (PMMA), a copolymer resin in which an acrylic unit and another heterogeneous unit are copolymerized, or a blend of an acrylic resin and another resin. It could be Suzy.

At this time, the acrylic unit is sufficient as a compound having a double bond between carbons conjugated with the carbonyl group of the ester group, and its substituent is not particularly limited. The acrylic unit described in this specification is meant to include not only acrylate but also acrylate derivatives, and should be understood as a concept including alkyl acrylate, alkyl methacrylate, alkyl butacrylate, etc. For example, examples of the acrylic unit include a compound represented by the following formula (1).

[Formula 1]

In Formula 1,

R ₁ , R ₂ and R ₃ each independently represent a hydrogen atom or a monovalent hydrocarbon group having 1 to 30 carbon atoms with or without a hetero atom, and at least one of R ₁ , R ₂ and R ₃ may be an epoxy group. There is,

R ₄ represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms.

Specifically, the acrylic units include methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, and t-butyl. Methacrylate (t-butyl methacrylate), cyclohexyl methacrylate, benzyl methacrylate, methoxyethyl methacrylate, ethoxyethyl methacrylate , butoxymethyl methacrylate, etc., but is not limited thereto.

Meanwhile, the acrylic resin may further include maleic acid-based units, maleimide-based units, lactone ring-based units, aromatic vinyl-based units, aromatic vinyl-based units, and combinations thereof in addition to the acrylic-based units.

In this case, the above components may be added in the polymerization step together with the acrylic monomer and may be included in a copolymerized form with the acrylic monomer, or a polymer or copolymer resin containing one or more of the above components and a polymer or copolymer containing an acrylic unit. It may also be included in the form of blending resins. For example, the acrylic resin of the present invention is not limited thereto, but may be a blend resin of an acrylate-maleimide copolymer resin and a styrene-maleic anhydride copolymer resin.

Meanwhile, specific examples of the maleic acid or maleimide units include maleic anhydride, maleimide, N-methyl maleimide, N-ethyl maleimide, N-propyl maleimide, N-isopropyl maleimide, and cyclohexyl maleimide. These may include, but are not limited to this. When maleic acid-based units, maleimide-based units, lactone ring units, etc. are included, the heat resistance of the acrylic film can be further improved.

In addition, specific examples of the aromatic vinyl unit include styrene, α-methyl styrene, and 4-methyl styrene, but are not limited thereto. When such an aromatic vinyl-based unit is included, the intrinsic birefringence of the resin itself is increased, and as a result, it is possible to more easily implement the retardation value required for the compensation film for IPS mode. At this time, the aromatic vinyl-based unit may be included in the form of copolymerization with an acrylic monomer, or may be included in the form of a blend of acrylic resin and a polymer resin or copolymer resin containing the aromatic vinyl-based unit. Commercially available products can be used as polymers or copolymer resins containing aromatic vinyl units, for example, styrene-maleic anhydride copolymer (SMA), styrene-acrylonitrile copolymer (SAN), α- Examples include, but are not limited to, methyl styrene-acrylonitrile copolymer (AMSAN). For IPS compensation, the content of the aromatic vinyl unit is preferably about 5% by weight to 30% by weight, and more preferably about 10% by weight to 25% by weight, based on the total resin composition.

The acrylic film can be manufactured by forming a film using the above-mentioned components and then stretching it uniaxially or biaxially. The film forming method, uniaxial or biaxial stretching method, etc. is not particularly limited, and methods widely known in the art can be used.

The acrylic film may contain antioxidants, UV absorbers, heat stabilizers, wavelength control agents, etc., as needed.

In an exemplary embodiment of the present application, the plane direction retardation value (R _in ) expressed by Equation 1 below of the acrylic film may be 50 nm to 200 nm, and the thickness direction retardation value (R _th ) may be 50 nm to 250 nm.

[Equation 1]

R _in = (n _x - n _y ) × d

[Equation 2]

R _th = (n _z - n _y ) × d

In Equations 1 and 2 above,

n _x is the refractive index in the direction with the highest refractive index in the plane direction of the film,

n _y is the refractive index in the direction perpendicular to the nx 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 an exemplary embodiment of the present application, the thickness of the acrylic film may be 20㎛ to 80㎛, and 30㎛ to 70㎛. The lower the thickness of the acrylic film, the more desirable it is. However, due to limitations in the process or the need for mechanical strength of the film, a certain thickness or more is required, and it is preferable to satisfy the above-mentioned thickness range in order to have an appropriate retardation value. In addition, when the thickness of the acrylic film exceeds 80㎛, the thickness of the film may become excessively thick, causing turbidity, etc.

In an exemplary embodiment of the present application, the coating layer of the negative C type material may have a plane direction retardation value of -5 nm to 5 nm, expressed by Equation 1 below, and a thickness direction retardation value expressed by Equation 2 below: The value may be -30nm to -200nm.

[Equation 1]

R _in = (n _x - n _y ) × d

[Equation 2]

R _th = (n _z - n _y ) × d

In Equations 1 and 2 above,

n _x is the refractive index in the direction with the highest refractive index in the plane direction of the film,

n _y is the refractive index in the direction perpendicular to the nx 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 an exemplary embodiment of the present application, the thickness of the coating layer of the negative C type material may be 3㎛ to 20㎛. The lower the thickness of the coating layer of the negative C type material, the more desirable it is, but it is preferable that it satisfies the above-mentioned thickness range for the desired retardation value. In addition, if the thickness of the coating layer of the negative C type material exceeds 20㎛, the thickness may become excessively thick and exceed the desired retardation value, and shrinkage during coating drying may cause bending of the film and cause damage due to drying. Process productivity may decrease.

In an exemplary embodiment of the present application, the coating layer of the negative type C material includes a cellulose-based resin and a reactive acrylic binder.

In an exemplary embodiment of the present application, the weight average molecular weight of the cellulose-based resin may be 50,000 g/mol to 350,000 g/mol. If the weight average molecular weight of the cellulose resin is less than 50,000 g/mol, the phase difference expression characteristics by coating may rapidly deteriorate, and if it exceeds 350,000 g/mol, the phase difference expression characteristics are excellent, but the viscosity is too high to be suitable for coating. It can be difficult.

In an exemplary embodiment of the present application, the cellulose resins include methyl cellulose (MC), hydroxy propyl methyl cellulose (HPMC), and hydroxy ethyl methyl cellulose (HEMC). ), ethyl cellulose (EC), etc., but is not limited thereto.

In an exemplary embodiment of the present application, based on the total weight of the coating layer of the negative type C material, the content of the reactive acrylic binder may be 5% by weight to 30% by weight, and may be 7% by weight to 20% by weight. The higher the content of the reactive acrylic binder, the more the phase development is inhibited, so a lower content is more appropriate. However, if the content of the reactive acrylic binder is less than 5% by weight based on the total weight of the coating layer of the negative type C material, the negative type C material The adhesion of the coating layer of the material may not be secured.

The reactive acrylic binder may include the acrylic resin described above. Since most of the acrylic monomers constituting the reactive acrylic binder have good adhesion to acrylic films, most monomers that can be used in acrylic films can be used. However, acrylic binders have good adhesion to acrylic films but have poor compatibility with cellulose resins. Therefore, in this application, a monomer that can be mixed with a cellulose resin was introduced into the acrylic binder and used. In this application, a monomer containing carboxylic acid was used, but there is no problem in introducing a monomer that can be mixed with other cellulose-based resins, such as hydroxyl-based resins. In addition, when introducing monomers that can be mixed with cellulose-based resins, such as carboxylic acid or hydroxyl-based, a reaction is induced with the cellulose-based resin using an appropriate cross-linking agent as an acrylic binder with a reactive functional group, thereby improving mechanical strength and chemical resistance. It can be raised. Therefore, in an exemplary embodiment of the present application, the reactive acrylic binder is suitably an acrylic binder containing 5 to 50 wt% of carboxylic acid-based monomer or hydroxyl-based monomer.

In an exemplary embodiment of the present application, the coating layer of the negative C type material may further include an organic metal crosslinking agent.

The organometallic crosslinking agent includes tetraisopropyl titanate, tetranol malbutyl titanate, butyl titanate dimer, tetraoctyl titanate, titanium acetylacetonate, titanium tetraacetylacetate, titanium ethyl acetate, titanium octylene glycolate, Titanium ethyl acetate, titanium lactate, titanium triethanolamitate, titanium triethanolamitate, tetramethylamyl titanate, tetrastearyl titanate, tetrastearyl titanate, titanium acetylacetate, titanium-1,3-propane dioxy beads ( Ethyl acetoacetate), titanium diethanol aminate, titanium aminoethylaminoethanoate, normal propyl zirconate, normal butyl zirconate, zirconium tetraacetyl acetate, zirconium monoacetyl acetate, zirconium stearate, zirconium lactate, etc. There is.

Additionally, the organometallic crosslinking agent may be represented by the following formula (2), but is not limited thereto.

[Formula 2]

Based on the total weight of the coating layer of the negative type C material, the content of the organic metal crosslinking agent may be 0.1% by weight to 20% by weight, and may be 0.5% by weight to 10% by weight. Based on the total weight of the coating layer of the negative type C material, if the content of the organic metal crosslinking agent is less than 0.1% by weight, it may be insufficient to induce crosslinking of the cellulose resin or reactive acrylic binder, and if it exceeds 20% by weight, it may be insufficient to induce crosslinking of the cellulose resin or reactive acrylic binder. Phase contrast expression may be inhibited, the color of the coating layer may be discolored, and the stability of the coating mixture may be impaired.

In an exemplary embodiment of the present application, the coating layer of the negative C type material may be provided on only one side of the acrylic film or on both sides.

The retardation film according to an exemplary embodiment of the present application adjusts the retardation of each of the acrylic film and the coating layer of the negative C type material to provide a retardation that satisfies the condition n _x > n _z > n _y for compensation for IPS mode. You can. The in-plane retardation value (R _in ) of the entire retardation film may be 50 nm to 200 nm, 70 nm to 150 nm, and the thickness direction retardation value (R _th ) is greater than the in-plane retardation value (R _in ) in the range of 10 nm to 200 nm. It must have a small value. That is, the ratio of R _th to R _in (R _th /R _in ) may be 0.2 to 0.8, and may be 0.3 to 0.7.

The thickness of the entire retardation film is not particularly limited, but may be 30㎛ to 120㎛.

A method of manufacturing a retardation film according to an exemplary embodiment of the present application includes preparing an acrylic film; and forming a coating layer of a negative C type material by coating at least one side of the acrylic film with a composition containing a cellulose resin and a reactive acrylic binder.

In the method of manufacturing a retardation film according to an exemplary embodiment of the present application, the contents of the acrylic film, cellulose resin, reactive acrylic binder, coating layer of negative type C material, etc. are the same as the above, so detailed description will be omitted. Do this.

In an exemplary embodiment of the present application, the composition including the cellulose resin and the reactive acrylic binder may further include a solvent. The solvent is not particularly limited, but considering solubility, coating properties, drying ability, storage stability, etc., aromatic hydrocarbons such as toluene and xylene; Alcohols such as ethanol, propanol, and butanol; Acetates; Cycloalkanes such as cyclohexane can be used by mixing them in a certain ratio. When the solvent includes cycloalkanes, the content of the cycloalkanes may range from 5% by weight to 50% by weight based on the total weight of the solvent.

In an exemplary embodiment of the present application, the coating method for forming the coating layer of the negative type C material is not particularly limited, but considering continuous process and coating thickness, it is preferable to use slot die coating, comma coating, etc. After coating, drying conditions are not particularly limited, but it is preferable to dry with hot air for 1 to 10 minutes at a temperature of 50°C to 100°C where the phase difference of the acrylic film does not change.

Additionally, an exemplary embodiment of the present application provides a liquid crystal display device including the retardation film.

In an exemplary embodiment of the present application, the liquid crystal display device may be an in-plane switching (IPS) mode liquid crystal display device.

A more detailed look at the liquid crystal display device including the retardation film is as follows.

In a liquid crystal display device including a liquid crystal cell and a first polarizer and a second polarizer respectively provided on both sides of the liquid crystal cell, a retardation film may be provided between the liquid crystal cell and the first polarizer and/or the second polarizer. there is. That is, a retardation film may be provided between the first polarizer and the liquid crystal cell, and a retardation film may be provided between the second polarizer and the liquid crystal cell, or between the first polarizer and the liquid crystal cell and between the second polarizer and the liquid crystal cell. Two or more may be provided.

The first and second polarizers may include a protective film on one or both sides. The internal protective film includes a triacetate cellulose (TAC) film, a polynorbornene-based film prepared by ring opening metathesis polymerization (ROMP), and HROMP (HROMP) obtained by hydrogenating the ring-opening polymerized cyclic olefin-based polymer again. It may be a polymer film (ring opening metathesis polymerization followed by hydrogenation), a polyester film, or a polynorbornene-based film manufactured by addition polymerization. In addition, films made of transparent polymer materials may be used as protective films, but are not limited to these.

Hereinafter, the embodiments described in this specification will be illustrated through examples. However, it is not intended that the scope of the above embodiments is limited by the following examples.

< Example >

< Manufacturing example 1> Preparation of reactive acrylic binder

After preparing a cooling pipe, a stopper, and a reactor capable of introducing nitrogen, the solvent, propylene glycol methyl ether, was added, and the monomer was added. The monomers were 30% by weight of methyl methacrylate, 20% by weight of ethyl acrylate, 20% by weight of methacrylic acid, and 30% by weight of styrene. At this time, the solid content was set to 40%. Stirring was performed at 250 rpm, the cooler temperature was fixed at 25°C, and nitrogen purging was performed before raising the reactor temperature. After raising the temperature to 60°C, the initiator was added. At this time, the initiator used was tert-butyl perbenzoate, and the content was added at 15% compared to the monomer. After adding the initiator, the reaction proceeded for more than 6 hours, and the reaction was terminated when the viscosity reached 2,000 cps or more. At this time, the acid value of the prepared composite was 51.51 mmgKOH/g.

< Manufacturing example 2> Preparation of reactive acrylic binder

Preparation Example 1 was performed in the same manner as Preparation Example 1, except that benzyl methacrylate was used instead of the styrene.

< Example 1>

Poly(cyclohexylmaleimide-co-methyl methacrylate) (LGMMA Co., Ltd., PMMA830HR) and styrene-acrylonitrile copolymer (LG Chemical Co., Ltd., SAN80HF, acrylonitrile content 24% by weight) at a weight ratio of 80:20, respectively. A resin composition was prepared by compounding at 250°C and 200rpm using a twin extruder. An unstretched film with a width of 800 mm was manufactured using the above resin composition using a T-die film forming machine under conditions of 250°C and 250 rpm. The unstretched film was stretched 1.5 times in the MD direction in a roll-to-roll manner at a temperature of 125°C, and then stretched 3.0 times in the TD direction using a tenter stretching machine at the same temperature to prepare an acrylic +B-plate. The thickness of the final stretched film obtained was about 55㎛, and the in-plane retardation value (R _in ) and thickness direction retardation value (R _th ) were 126 nm and 188 nm, respectively.

The negative C coating solution was prepared by dissolving ethyl cellulose (Dow EC100, Mw 210,000, Ethoxyl content: 49%) and the reactive acrylic binder of Preparation Example 1 in a toluene/ethanol (2/8) mixed solvent with gradual stirring at room temperature. I ordered it. The solid content at this time was set to 10%. The completely dissolved coating solution was coated on an acrylic film with an applicator to a final coating thickness of 14.2㎛ and then dried in an oven at 90°C for 5 minutes.

< Example 2 to 7>

The same procedure as Example 1 was performed, except that the components and contents listed in Table 1 below were applied.

When preparing the negative C coating solution, in Examples 2 to 6, a toluene/ethanol (2/8) mixed solvent was applied in the same manner as in Example 1, and in Example 7, a toluene/ethanol/cyclohexane (2/6/2) mixed solvent was used. Solvent was applied.

< Comparative example 1 to 3>

The same procedure as Example 1 was performed, except that the components and contents listed in Table 1 below were applied.

[Table 1]

BUTVAR B98: butyral resin from Eastman

Cross-linking agent: Organometallic cross-linking agent represented by Chemical Formula 2

A: Ethylcellulose DOW EC STD 100 (Mw 210,000 g/mol)

B: Ethylcellulose DOW EC STD 10 (Mw 80,000 g/mol)

C: Ethylcellulose DOW EC STD 200 (Mw 260,000 g/mol)

D: Ethylcellulose DOW EC STD 300 (Mw 300,000 g/mol)

< Experiment example >

The retardation values and adhesion of the retardation films of Examples 1 to 7 and Comparative Examples 1 to 3 were evaluated and are shown in Table 2 below.

The phase difference value, adhesion, etc. were measured in the following manner.

1) Phase difference value: The phase difference value of the film was measured with Axoscan from Axometrics.

2) Adhesion: Adhesion was evaluated based on astm d3359. Measurements were made on a grid of 100 with 11 cuts spaced at 1 mm intervals. The judgment criteria were: poor adhesion when more than 20% of the separated surface, good adhesion when 5% to 20%, and excellent adhesion when it was 1% to 5%.

X: Bad

○: Good

◎: Excellent

[Table 2]

In Table 2, R _th /㎛ is expressed as (total retardation film R _th - acrylic film R _th )/negative coating layer thickness, which is a value to see how efficiently the phase of the negative C coating layer was developed, and is expressed as R _th per thickness. It means how much has been expressed.

In addition, according to the above experimental results, if the molecular weight of the cellulose resin, which is a phase material, is low, the adhesion is good, but the phase development is also low. Therefore, when the molecular weight is appropriately combined, the phase development (R _th /㎛) can be increased, and the solvent, If cyclohexane is included, it may help in arranging the polymer for phase development during volatilization, thereby increasing phase development.

As shown in the above results, according to an exemplary embodiment of the present application, it is possible to provide a retardation film in which an acrylic film and a coating layer of a negative C type material are in direct contact with each other.

In addition, according to an exemplary embodiment of the present application, there is excellent adhesion between the acrylic film and the coating layer of the negative C type material.

In addition, according to an exemplary embodiment of the present application, the manufacturing process of the retardation film can be simplified, and thus material and process costs can be reduced.

Claims (13)

Acrylic film; and
It includes a coating layer provided in direct contact with the acrylic film,
The coating layer is a retardation film comprising a cellulose-based resin and a reactive acrylic binder. The method according to claim 1, wherein the in-plane retardation value (R _in ) of the acrylic film expressed by Equation 1 below is 50 nm to 200 nm,
A retardation film in which the thickness direction retardation value (R _th ) expressed by Equation 2 below is 50 nm to 250 nm:
[Equation 1]
R _in = (n _x - n _y ) × d
[Equation 2]
R _th = (n _z - n _y ) × d
In Equations 1 and 2 above,
n _x is the refractive index in the direction with the highest refractive index in the plane direction of the film,
n _y is the refractive index in the direction perpendicular to the nx 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 retardation film according to claim 1, wherein the acrylic film has a thickness of 20㎛ to 80㎛. The method according to claim 1, wherein the coating layer has a plane direction retardation value expressed by Equation 1 below of -5 nm to 5 nm,
A retardation film having a thickness direction retardation value of -30 nm to -200 nm expressed by Equation 2 below:
[Equation 1]
R _in = (n _x - n _y ) × d
[Equation 2]
R _th = (n _z - n _y ) × d
In Equations 1 and 2 above,
n _x is the refractive index in the direction with the highest refractive index in the plane direction of the film,
n _y is the refractive index in the direction perpendicular to the nx 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 retardation film according to claim 1, wherein the coating layer has a thickness of 3㎛ to 20㎛. The retardation film according to claim 1, wherein the cellulose-based resin has a weight average molecular weight of 50,000 g/mol to 350,000 g/mol. The method of claim 1, wherein the cellulose resin is methyl cellulose (MC), hydroxy propyl methyl cellulose (HPMC), hydroxy ethyl methyl cellulose (HEMC), and ethyl cellulose ( A retardation film selected from ethyl cellulose (EC). The retardation film according to claim 1, wherein the content of the reactive acrylic binder is 5% by weight to 30% by weight, based on the total weight of the coating layer. The retardation film according to claim 1, wherein the reactive acrylic binder contains 5% by weight to 50% by weight of carboxylic acid-based monomer or hydroxyl-based monomer. The retardation film according to claim 1, wherein the coating layer further includes an organic metal crosslinking agent. Preparing an acrylic film; and
Forming a coating layer by coating a composition containing a cellulose resin and a reactive acrylic binder on at least one side of the acrylic film.
Method for manufacturing a retardation film comprising. A liquid crystal display device comprising the retardation film of any one of claims 1 to 10. The liquid crystal display device of claim 12, wherein the liquid crystal display device is an in-plane switching (IPS) mode liquid crystal display device.