KR20170086961A - Protective optical film for polarizing plate and polarizing plate and liquid crystal display comprising the same - Google Patents

Abstract

The present disclosure relates to optical films; And a coating layer formed on at least one surface of the optical film and including a water dispersible resin, hollow fine particles, and a polyether modified siloxane, and a polarizing plate and a liquid crystal display.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a protective film for a polarizing plate, a polarizing plate including the polarizing plate,

The present invention relates to a protective film for a polarizing plate and a polarizing plate and a liquid crystal display including the same.

The acrylic film generally used as a polarizer protective film is a serious disadvantage in its use as a polarizer protective film which requires a high light transmittance due to a loss of about 4% reflected on one surface. Since it is technically and economically difficult to produce a low reflection film by forming a multilayer thin film after production of an acrylic film, it is necessary to develop an acrylic film in which a low reflection primer layer is practically introduced (in-line coating) during production of an acrylic film. to be.

In order to solve such problems, a method has been devised in which a primer solution containing water-dispersible hollow silica is coated on a water-dispersible resin in order to impart low porosity to the primer layer by lowering the density of the primer layer. However, There is a disadvantage in that the appearance of the coating is deteriorated by a large amount of the hollow silica for the sufficient performance development and the drawing process after the coating. Also, as the haze value increases due to coating defects, there is a problem that brightness enhancement of the display can be reduced.

Japanese Patent Laid-Open No. 2002-258051

The present invention provides a protective film for a polarizing plate, a polarizing plate including the same, and a liquid crystal display.

One embodiment of the present disclosure relates to an optical film; And a coating layer formed on at least one surface of the optical film, the coating layer comprising a polymer resin, hollow fine particles, and a polyether modified siloxane.

Another embodiment of the present disclosure also relates to a polarizer comprising: a polarizer; And a polarizing plate protective film provided on one or both surfaces of the polarizer.

Another embodiment of the present disclosure is

A liquid crystal cell;

A backlight unit provided on one surface of the liquid crystal cell;

An upper polarizer provided on a surface of the liquid crystal cell provided with a backlight unit; And

And a lower polarizer disposed between the liquid crystal cell and the backlight unit,

And the lower polarizer is a polarizer of the above-described embodiment.

The protective film for a polarizing plate according to an embodiment of the present invention may be formed by forming a coating layer on at least one surface of an optical film using a composition comprising a polymer resin and fine hollow particles to improve the brightness of the display by imparting low reflectivity, By adding the polyether-modified siloxane to the coating layer, it is possible to prevent deterioration of the appearance of the coating which can be caused by the composition for imparting low reflectivity or to improve the appearance of the coating.

The polarizing plate according to the embodiments of the present disclosure has a low reflective coating layer having the excellent coating appearance and thus has a low haze value, thereby maximizing the luminance improvement of the display including the polarizing plate.

FIG. 1 illustrates the structure of a protective film for a polarizing plate according to an embodiment of the present invention.
Figures 2 to 4 illustrate the structure of a polarizer according to embodiments of the present disclosure.
5 to 7 illustrate the structure of a liquid crystal display device according to the embodiments of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The respective components in the drawings are intended to indicate relative positions, and the thickness, size, and the like may be changed based on techniques known in the art or common sense of those skilled in the art.

One embodiment of the present disclosure relates to a protective film for a polarizing plate, comprising: an optical film; And a coating layer formed on at least one surface of the optical film, the coating layer comprising a polymer resin, hollow fine particles and a polyether modified siloxane. In this embodiment, the polymer resin and hollow microparticles impart low reflectivity to the protective film for polarizing plate, thereby reducing the reflection of light from the backlight unit, thereby contributing to improvement in brightness of the display.

On the other hand, the coating appearance of the coating layer may affect cohesion and deterioration of the hollow microparticles. Specifically, both the polymer resin and the hollow fine particles in the coating liquid exist in an electric double layer state, and may be well dispersed while maintaining appropriate repulsive force. However, when the coating liquid is dried, the polymer resin may undergo phase inversion, and the dispersibility of the hollow fine particles may be rapidly lowered. In order to improve the appearance of the coating, the hollow fine particles should be uniformly positioned in the coating layer when the coating liquid is dried, so that parallel migration of the hollow fine particles can be performed well when the coating layer is subsequently stretched. If there is a coagulation site of hollow microparticles in the coating layer, the site is relatively hard and does not stretch well. If this is the case, then the other part is stretched more than intended to offset it, and this nonuniformity worsens the appearance of the coating.

Since the polyether-modified siloxane is amphoteric having both hydrophilic and hydrophobic properties, the polyether-modified siloxane is properly positioned between the polymer resin and the hollow fine particles and / or between the hollow fine particles to prevent aggregation of the polymer resin or hollow fine particles have. Further, the presence of the polyether group of the polyether-modified siloxane makes the coating layer somewhat softened and the stretchability can be improved, whereby the appearance of the coating can be improved. This makes it possible to prevent the appearance of the coating layer from becoming poor even when the hollow fine particles are added in an excessive amount or when the coating layer containing hollow fine particles is stretched in the post-treatment process. 1 shows a cross-sectional structure of a protective film 10 for a polarizing plate including an optical film 11 and a coating layer 12. As shown in Fig.

Coating layer

The coating layer provides excellent reflection reducing effect by the polymer resin and fine hollow particles, and has an excellent coating appearance. Therefore, by using a coating layer having an excellent coating appearance, it is possible to prevent light reflected from the backlight unit from being reflected, thereby increasing the amount of light incident on the liquid crystal cell. The coating layer may be formed on a polarizing plate, which will be described later, on the opposite side of the polarizing plate of the backlight unit side protective film of the polarizing plate disposed close to the backlight unit among the polarizing plates provided on both sides of the liquid crystal cell.

The coating layer may be formed by coating a coating composition on an optical film using a coating method well known in the art, for example, a bar coating method, a gravure coating method, a slot die coating method, . At this time, the drying can be performed through a convection oven or the like, but is not limited thereto.

According to one embodiment, the coating layer may be applied and dried as described above, and then stretched if necessary. That is, the coating layer may be stretched. At this time, the stretching method and the stretching conditions can be applied to the description related to stretching of the optical film to be described later.

According to one embodiment, the thickness of the coating layer may be 100 nm to 500 nm, specifically 100 nm to 300 nm. When the thickness of the coating layer is 100 nm or more, it is advantageous to reduce reflection of light. In addition, since the hollow silica can be coated in an appropriate amount within the above-mentioned thickness range, the coating layer becomes hard, so that the tacky property is reduced as compared with the coating layer containing only the conventional polymer, .

When the amount is within the above range, the hollow microparticles and the polyether-modified siloxane are embedded in the coating layer, and the slip property can be properly imparted.

According to an embodiment of the present invention, the refractive index of the coating layer is made lower than the refractive index of the optical film coated with the coating layer, and the refractive index with respect to the air gap is made small, thereby lowering the reflectivity of light passing through the coating layer, . For example, the refractive index of the coating layer is preferably 1.48 or less, more preferably 1.30 to 1.48 or 1.35 to 1.47. When the refractive index of the coating layer is within the above range, since the refractive index is lower than that of an optical film such as a triacetyl cellulose film, a cycloolefin polymer film and an acrylic film, the coating film has an excellent antireflection effect and a high transmittance increasing effect.

According to another embodiment, the coefficient of static friction of the coating layer is preferably 0.8 or less, more preferably 0.6 or less, or 0.5 or less. When the coefficient of static friction of the coating layer is within the above range, it can have excellent anti-blocking property (or slip property).

According to another embodiment, the coating layer preferably has a coefficient of dynamic friction of 0.8 or less, more preferably 0.6 or less, or 0.5 or less. When the coefficient of dynamic friction of the coating layer is within the above range, it can have excellent anti-blocking property (or slip property).

According to another embodiment, the protective film for a polarizing plate coated with the coating layer may have a reflectance of 3.5% or less, for example, 3% or less. The lower the reflectance, the greater the effect of increasing the transmittance.

The coating layer may further include hydrocarbon-based, silicone-based, and fluorine-based dispersing agents, wetting agents, leveling agents, and the like.

If necessary, a surface treatment such as an alkali treatment, a corona treatment or a plasma treatment may be performed on the surface of the optical film in order to improve the adhesion between the optical film and the coating layer.

Polymer resin

In one embodiment of the present invention, the polymer resin is preferably a water-dispersible resin. When a water-dispersible resin is used, it is eco-friendly and advantageous for the safety of the operator, and the above-mentioned polyether-modified siloxane can achieve the above-mentioned effects even when used in combination with a water-dispersible resin.

In one embodiment of the present invention, the water-dispersible resin is used for securing good adhesion between the coating layer and the optical film and for improving the antireflection effect. As the water-dispersible resin, a low refractive polymer resin may be used. Specifically, a resin having a refractive index of 1.55 or less, for example, a refractive index of 1.53 or less, or 1.54 or less may be used. When the low refractive polymer resin satisfying the refractive index is used, the antireflection effect can be realized more effectively.

The water-dispersible resin may be a polyurethane resin, a polyester resin, a polyacrylic resin, or a combination of two or more thereof, but is not limited thereto, and a water-dispersible resin conventionally used in the art can be applied.

The water-dispersible resin has a lower viscosity than the water-soluble resin and is advantageous in coating. Even when a coating layer is formed on a base film which is insufficient in solvent resistance like an acrylic film compared with a solvent type, mechanical properties are reduced due to erosion of the solvent, . In addition, there is an advantage that a uniform coating is possible, and it is environment-friendly, and an explosion-proof equipment is not required, so that it can be coated in an in-line film production.

The polyurethane resin can be produced by reacting a polyol with a polyisocyanate. The polyol is not particularly limited as long as it has two or more hydroxy groups in the molecule. For example, the polyol may be a polyester polyol, a polycarbonate diol, a polyether polyol or a combination thereof.

The polyester polyol is typically obtained by reacting a polybasic acid component with a polyol component. Examples of the polybasic acid component include ortho-phthalic acid, isophthalic acid, terephthalic acid, 1,4-naphthalene dicarboxylic acid, 2,5-naphthalene dicarboxylic acid, 2,6- Aromatic dicarboxylic acids such as phenyl dicarboxylic acid and tetrahydrophthalic acid; Aliphatic dicarboxylic acids such as oxalic acid, succinic acid, malonic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, linoleic acid, maleic acid, fumaric acid, mesaconic acid and itaconic acid; Alicyclic dicarboxylic acids such as hexahydrophthalic acid, tetrahydrophthalic acid, 1,3-cyclohexanedicarboxylic acid and 1,4-cyclohexanedicarboxylic acid; Or reactive derivatives thereof such as acid anhydrides, alkyl esters, acid halides and the like. These may be used alone or in combination of two or more. The polyol may be at least one selected from the group consisting of ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, neopentyl glycol, pentanediol, 1,6- Dihydroxyphenyl propane, 4,4'-dihydroxymethyl methane, diethylene glycol, triethylene glycol, polyethylene glycol, dipropylene glycol, diethylene glycol, Polypropylene glycol, 1,4-cyclohexanedimethanol, 1,4-cyclohexanediol, bisphenol A, bisphenol F, glycerin, 1,1,1-trimethylol propane, 1,2,5- It is preferably at least one selected from the group consisting of erythritol, glucose, sucrose, and sorbitol.

The polycarbonate diol is preferably an aliphatic polycarbonate diol. The polyurethane resin synthesized from such an aliphatic polycarbonate diol is advantageous for realizing an antireflection effect because it has excellent water resistance, oil resistance and long-term weatherability as well as excellent mechanical properties and especially has a refractive index lower than that of aromatic. On the other hand, examples of the aliphatic polycarbonate diol include, but are not limited to, poly (hexamethylene carbonate) glycol and poly (cyclohexanecarbonate) glycol. These may be used alone or in combination of two or more.

The polyether polyol is typically obtained by ring-opening polymerization of an alkylene oxide to a polyhydric alcohol. Examples of polyhydric alcohols include ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, glycerin, and trimethylolpropane. These may be used alone or in combination of two or more.

The polyisocyanate is not limited as long as it is a compound having two or more NCO groups and examples thereof include toluene diisocyanate (TDI), 4,4-diphenylmethane diisocyanate (MDI), 1,5-naphthalene diisocyanate (NDI) (XDI), such as tolylene diisocyanate (TODI), hexamethylene diisocyanate (HMDI), isophorone diisocyanate (IPDI), p-phenylenediisocyanate, 1,4-diisocyanate and xylene diisocyanate Can be used in combination.

On the other hand, the method for producing the polyurethane resin may employ any suitable method known in the art. Specifically, a single shot method in which each component is reacted at a time, and a multi-step method in which the components are reacted stepwise. Any suitable urethane reaction catalyst may be used in the production of the polyurethane resin. On the other hand, when the polyurethane resin is water-dispersible, it is more preferable to prepare by a multi-stage method in order to easily introduce a hydrophilic group such as a carboxyl group.

On the other hand, in the production of the polyurethane resin, other polyol and / or other chain extender may be reacted in addition to the above components. Examples of other polyols include polyols having three or more hydroxyl groups such as sorbitol, glycerin, trimethylol ethane, trimethylol propane, and pentaerythritol. Examples of other chain extender include ethylene glycol, diethylene glycol, triethylene glycol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, neopentyl glycol, pentanediol, 1,6 Glycols such as hexanediol and propylene glycol; Aliphatic diamines such as ethylenediamine, propylenediamine, hexamethylenediamine, 1,4-butanediamine and aminoethylenecanolamine; Alicyclic diamines such as isophoronediamine and 4,4'-dicyclohexylmethanediamine; And aromatic diamines such as xylylenediamine and tolylene diamine.

On the other hand, by using a neutralizing agent, the stability of the water-dispersible polyurethane resin in water can be improved. Examples of the neutralizing agent include ammonia, N-methylmorpholine, triethylamine, dimethylethanolamine, methyldiethanolamine, triethanolamine, morpholine, tripropylamine, ethanolamine and triisopropanolamine. These may be used alone or in combination of two or more.

In the production of the water-dispersible polyurethane resin, an organic solvent inert to the polyisocyanate and compatible with water is used. Examples of the organic solvent include ester solvents such as ethyl acetate and ethyl cellosolve acetate; Ketone solvents such as acetone, methyl ethyl ketone and methyl isobutyl ketone; And ether solvents such as dioxane tetrahydrofuran. These may be used alone or in combination of two or more.

The water dispersible polyurethane resin preferably contains a carboxyl group. When a carboxyl group is contained in the water-dispersible polyurethane resin, an anion moiety is formed in the production of a polyurethane resin to disperse it in water, thereby enhancing adhesion. The polyurethane resin containing a carboxyl group can be obtained by, for example, reacting a chain extender having a free carboxyl group in addition to a polyol and a polyisocyanate. Examples of the chain extender having a carboxyl group include dihydroxycarboxylic acid, dihydroxy monoacidic acid, and the like. Examples of the dihydroxycarboxylic acid include dialkylol alkanoic acids including dimethylolacetic acid, dimethylolbutanoic acid, dimethylolpropionic acid, dimethylolbutyric acid and dimethylolalkanoic acid such as dimethylolpentanoic acid, which may be used singly or in combination Can be used.

The water-dispersible acrylic resin may be prepared by polymerizing an acrylic monomer. In this case, an acrylic monomer having a glass transition temperature higher than room temperature is preferably used. Examples thereof include, but are not limited to, methyl methacrylate, ethyl methacrylate, isobutyl methacrylate, and mixtures thereof. For the purpose of improving the adhesive force and physical properties of the coating film, one or more acrylic monomers having a glass transition temperature lower than room temperature such as methoxyethylaminoacrylate, butyl acrylate, hexyl acrylate, ethylhexyl acrylate and the like may be mixed and used.

The water-dispersible acrylic resin may include at least one water-soluble acrylic monomer, for example, hydroxyhexyl acrylate, hydroxyethyl acrylamide, methacrylic acid or a mixture thereof, but is not limited thereto.

The water-dispersible polyester resin can be produced by polymerizing a polyol and a dicarboxylic acid by an esterification method. Alternatively, a polyol and a dicarboxylic acid diester can be prepared by polymerizing the ester by an ester exchange method.

The above-mentioned dicarboxylic acid or dicarboxylic acid diester is not particularly limited, and general polyester resin raw materials can be used. For example, aliphatic dicarboxylic acid, alicyclic dicarboxylic acid, aromatic dicarboxylic acid and diesters thereof may be used singly or in admixture of two or more. Examples thereof include acid anhydrides capable of forming esters, Acid halides can also be used. When the polyester resin is water-dispersible, isophthalic acid substituted with a sulfonic acid salt with a dicarboxylic acid may also be used.

If necessary, the polyester resin may further be copolymerized with an acrylic monomer component to form a polyester acrylic resin containing an acrylic unit together with the ester unit. The acrylic monomer usable in the present invention is, for example, an alkyl (meth) acrylate, an alkyl acrylate, an epoxy (meth) acrylate, a hydroxyalkyl acrylate, And acrylates including sulfonic acid salts.

In one embodiment of the present invention, the water dispersible resin may have a weight average molecular weight of 10,000 to 10. When the weight average molecular weight of the water dispersible resin satisfies the above range, a suitable viscosity is imparted when forming a coating layer, which is advantageous from the viewpoint of processing.

Hollow fine particles

The hollow microparticles are used to reduce the refractive index of the coating layer to maximize the antireflection property. The hollow fine particles may be used without limitation as long as they are mixed with the above-mentioned polymer resin to show the physical properties of the above-mentioned coating layer. For example, the hollow fine particles may be inorganic fine particles such as silica-based, aluminum oxide-based, or titanium oxide-based ones, organic fine particles such as acrylic, silicone, or polystyrene, or mixtures thereof.

According to one embodiment, the hollow microparticles are hollow silica. When the coating layer contains hollow silica, the effect of lowering the refractive index is excellent. The hollow silica may be crystalline particles or amorphous particles, preferably monodisperse particles, but is not limited thereto. The hollow silica is most preferably a spherical particle, but it is also possible to use an indefinite particle.

The hollow silica may be surface treated with a silane coupling agent, but is not limited thereto. However, when the surface treatment is performed with a silane coupling agent, dispersibility with a solvent is improved and durability of the coating layer is improved through network formation with the binder by participating in curing in the curing step. The production method of the hollow silica is not particularly limited and can be produced by a production method generally known in the art.

On the other hand, the refractive index of the hollow fine particles is preferably 1.4 or less, for example, about 1.17 to 1.4, or about 1.17 to 1.35. Here, the refractive index does not mean the refractive index of the fine particles, that is, the refractive index of the outer periphery forming the hollow fine particles, but the refractive index of the whole particles. When the refractive index of the hollow fine particles is within the above range, it is advantageous to realize the desired antireflection property.

The porosity in the hollow microparticles is preferably in the range of 10 to 60%, more preferably in the range of 20 to 60%, and most preferably in the range of 30 to 60%. It is possible to realize an antireflection characteristic superior to the case where the range is satisfied.

The average particle diameter of the hollow fine particles is preferably 10 to 200 nm, more preferably 20 to 100 nm. When the average particle diameter of the hollow microparticles is within the range described above, light scattering in the visible light region does not occur, and thus a transparent film can be produced.

The hollow microparticles are preferably contained in an amount of 10 to 300 parts by weight, more preferably 40 to 200 parts by weight, based on 100 parts by weight of the polymer resin. When the content of the fine hollow particles is within the above range, it is advantageous to control the refractive index of the coating layer and the antireflection characteristic can be excellently exerted.

On the other hand, the hollow fine particles may be water-soluble, water-dispersible, organic solvent-soluble or organic solvent-dispersible. More specifically, when the water-dispersible resin is used, it is preferable to use water-soluble or water-dispersible hollow fine particles, particularly water-dispersible hollow fine particles.

Polyether  denaturalization Siloxane

The polyether-modified siloxane is water-dispersible in water-based coating systems.

The polyether modified siloxane is a compound having a polyether structure introduced into siloxane having Si-O-Si as a siloxane bond. According to one example, a compound having a siloxane bond Si-O-Si, a terminal group being a trimethylsilyl group (Si (CH ₃ ) ₃ ), and at least one of Si constituting the siloxane bond having an ether bond A compound having a substituted polyether structure may be used. The polyether-modified siloxane preferably has a molecular weight or weight average molecular weight of 1,000 to 80,000 actually calculated. The stretching property may not be inhibited within such a molecular weight range.

According to one embodiment, the polyether-modified siloxane may be represented by the following formula (1) or (2).

[Chemical Formula 1]

In Formula 1,

At least one of R ₁ and R ₂ is - (R ₁₁ O) pR ₁₂ , and the remainder is an alkyl group, an alkylaryl group, or an aralkyl group,

R ₁₁ is a direct bond or an alkylene group,

R ₁₂ is an alkyl group, an alkylaryl group, or an aralkyl group,

m and p are each independently an integer of 1 to 10, x and y are each 0 to 10, provided that x + y is 1 or more,

Ra to Rf are the same or different from each other, and each independently is hydrogen, an alkyl group or polyethylene glycol.

(2)

In Formula 2,

R ₃ is - (R ₁₁ O) p R ₁₂ ,

R ₁₁ is a direct bond or an alkylene group,

R ₁₂ is an alkyl group, an alkylaryl group, or an aralkyl group,

m and p are each independently an integer of 1 to 10,

Rg to Rl are the same or different from each other, and each independently hydrogen, an alkyl group or polyethylene glycol.

In the general formulas (1) and (2), the alkyl group may be a linear or branched alkyl group of 1 to 10 carbon atoms, and the aryl group may be a C6 to C20 monocyclic or polycyclic aryl group. Specifically, the alkyl group may be methyl, ethyl, propyl, butyl or the like, and the aryl group may be phenyl, naphthyl, biphenyl, anthryl and the like. The alkylaryl group is an aryl group substituted with an alkyl group, and the above examples can be applied to the alkyl group and the aryl group. The aralkyl group is an alkyl group substituted with an aryl group, and examples of the alkyl group and the aryl group can be applied.

In the general formulas (1) and ( ₂ ), polyethylene glycol may be represented by - (OCH ₂ CH ₂ ) n R, n is an integer of 1 to 10, and R is hydrogen, an alkyl group or an OH group.

The polyether modified siloxane may be contained in an amount of 0.1 to 20 parts by weight, specifically 1 to 15 parts by weight, based on 100 parts by weight of the polymer resin, but is not limited thereto. When the polyether-modified siloxane is contained in the polymer resin within the above-mentioned range, there is an advantage of realizing the antireflection property.

Optical film

The optical film may be a single layer or a structure in which two or more films are laminated, and in the case of a structure in which two or more films are laminated, the laminated films may be made of the same or different materials. In the present invention, the optical film generally refers to a film that performs an optical function, and not only has a narrow transparent film having a light transmittance of 80% or more, but also has a light transmittance of 50% or less in the case of a film for performing a specific optical function such as a polarizing plate Optical film.

The optical film serves to protect the polarizer of the polarizing plate, and those known in the art can be used. For example, the optical film is preferably a film made of a polymer excellent in transparency, mechanical strength, thermal stability, moisture barrier property, and the like. For example, an acrylic film, a polyethylene terephthalate (PET) film, a triacetylcellulose (TAC) film, a polynorbornene (PNB) film, a cycloolefin polymer (COP) film, a polycarbonate (PC)

Among the above examples, an acrylic film, a polyethylene terephthalate (PET) film or a triacetyl cellulose (TAC) film can be preferably used. Of these, an acrylic film is particularly preferable in consideration of optical characteristics, durability and economical aspects.

In one embodiment of the present invention, the optical film may be an acrylic film. Specifically, the optical film may include a (meth) acrylate resin, and a film containing a (meth) acrylate resin may be obtained by extruding a molding material containing a (meth) acrylate resin as a main component And can be obtained by molding.

The (meth) acrylate-based resin mainly contains a resin containing a (meth) acrylate-based unit. The (meth) acrylate-based resin contains not only a homopolymer resin composed of a (meth) acrylate- A copolymer resin in which a monomer unit is copolymerized, and a blend resin in which another resin is blended with the (meth) acrylate resin as described above.

On the other hand, the (meth) acrylate-based unit may be, for example, an alkyl (meth) acrylate-based unit. Here, the alkyl (meth) acrylate-based unit means both an alkyl acrylate-based unit and an alkyl methacrylate-based unit, and the alkyl (meth) acrylate-based alkyl group preferably has 1 to 10 carbon atoms , More preferably from 1 to 4 carbon atoms.

Examples of the monomer unit copolymerizable with the (meth) acrylate-based unit include a styrene-based unit, a maleic anhydride-based unit, and a maleimide-based unit.

The styrenic unit may include, but is not limited to, styrene,? -Methylstyrene, 3-methylstyrene, 4-methylstyrene, 2,4-dimethylstyrene, 2,5- ? -Methylstyrene, 4-fluoro-? -Methylstyrene, 4-chlorostyrene, 2,4,6-trimethylstyrene, cis-? -Methylstyrene, trans-? methylstyrene, 4-t-butylstyrene, 2-fluorostyrene, 3-fluorostyrene, 4-fluorostyrene, 2,4-difluorostyrene, 2,3 , 4,5,6-pentafluorostyrene, 2-chlorostyrene, 3-chlorostyrene, 4-chlorostyrene, 2,4-dichlorostyrene, 2,6-dichlorostyrene, octachlorostyrene, , 3-bromostyrene, 4-bromostyrene, 2,4-dibromostyrene,? -Bromostyrene,? -Bromostyrene, 2-hydroxystyrene and 4-hydroxystyrene. And styrene,? -Methyl More preferably, it is styrene. These may be used alone or in combination.

Examples of the maleic anhydride monomers include, but are not limited to, maleic anhydride, methylmaleic anhydride, ethylmaleic anhydride, propylmaleic anhydride, isopropylmaleic anhydride, cyclohexylmaleic anhydride, phenylmale Acid anhydrides, and the like, which may be used alone or in combination.

The maleimide-based monomer includes, but is not limited to, maleimide, N-methylmaleimide, N-ethylmaleimide, N-propylmaleimide, N-isopropylmaleimide, N-cyclohexylmaleimide , N-phenylmaleimide, and the like, which may be used alone or in combination.

Examples of the acrylic film include a film comprising a copolymer containing an alkyl (meth) acrylate-based unit and a styrene-based unit and an aromatic resin having a carbonate moiety in the main chain or an alkyl (meth) acrylate- , A 3- to 6-membered heterocyclic unit substituted with at least one carbonyl group, and a vinyl cyanide unit. Further, it may be a film containing an acrylic resin having a lactone structure.

Specific examples of the (meth) acrylate resin having a lactone ring structure include, for example, lactones described in Japanese Unexamined Patent Application Publication No. 2000-230016, Japanese Unexamined Patent Application Publication No. 2001-151814, Japanese Unexamined Patent Application Publication No. 2002-120326, (Meth) acrylate-based resin having a cyclic structure.

Examples of the (meth) acrylate-based resin having an aromatic ring include (a) a (meth) acrylate-based unit containing at least one (meth) acrylate-based derivative described in Korean Patent Laid-open No. 10-2009-0115040; (b) an aromatic-based unit having a chain and an aromatic moiety having a hydroxyl group-containing moiety; And (c) a styrene-based unit containing at least one styrenic derivative. The units (a) to (c) may be included in the resin composition in the form of separate copolymers, and two or more of the units (a) to (c) have.

The method for producing the (meth) acrylate based resin film is not particularly limited, and for example, the (meth) acrylate based resin and other polymers, additives, and the like are thoroughly mixed by any appropriate mixing method to prepare the thermoplastic resin composition (Meth) acrylate resin, other polymers, additives, and the like may be prepared as separate solutions and then mixed to form a homogeneous mixture solution, followed by film formation.

The thermoplastic resin composition is prepared by pre-blending the film raw material with any suitable mixer such as an omni mixer, and then extruding and kneading the resulting mixture. In this case, the mixer used for the extrusion kneading is not particularly limited, and any suitable mixer such as an extruder such as a single screw extruder, a twin screw extruder, or a press kneader can be used.

The film forming method may be any suitable film forming method such as a solution casting method (solution casting method), a melt extrusion method, a calendering method, a compression molding method, and the like. , Melt extrusion method is preferable.

Examples of the solvent used in the solution casting method (solution casting method) include aromatic hydrocarbons such as benzene, toluene and xylene; Aliphatic hydrocarbons such as cyclohexane and decalin; Esters such as ethyl acetate and butyl acetate; Ketones such as acetone, methyl ethyl ketone and methyl isobutyl ketone; Alcohols such as methanol, ethanol, isopropanol, butanol, isobutanol, methyl cellosolve, ethyl cellosolve and butyl cellosolve; Ethers such as tetrahydrofuran and dioxane; Halogenated hydrocarbons such as dichloromethane, chloroform and carbon tetrachloride; Dimethylformamide; Dimethylsulfoxide, etc. These solvents may be used alone or in combination of two or more.

Examples of the apparatus for carrying out the solution casting method (solution casting method) include a drum casting machine, a band casting machine and a spin coater. Examples of the melt extrusion method include a T-die method and an inflation method. The molding temperature is specifically 150 to 350 占 폚, more specifically 200 to 300 占 폚, but is not limited thereto.

When a film is formed by the T-die method, a T-die is attached to the tip of a known single-screw extruder or a twin-screw extruder, and a rolled film is obtained by winding a film extruded in a film form. At this time, uniaxial stretching can also be performed by stretching in the extrusion direction by appropriately adjusting the temperature of the winding roll. Further, simultaneous biaxial stretching, sequential biaxial stretching, and the like can also be carried out by stretching the film in a direction perpendicular to the extrusion direction. In particular, in the case of biaxially stretching, the mechanical strength is improved and the film performance is improved. On the other hand, the stretching can be performed by a stretching method well known in the art.

The acrylic film may be either an unoriented film or a stretched film. In the case of a stretched film, it may be a uniaxially stretched film or a biaxially stretched film, and in the case of a biaxially stretched film, it may be a simultaneous biaxially stretched film or a sequential biaxially stretched film. When biaxially stretched, the mechanical strength is improved and the film performance is improved. By mixing other thermoplastic resins, the acrylic film can suppress an increase in retardation even when stretching, and can maintain optical isotropy.

The stretching temperature is preferably in the vicinity of the glass transition temperature of the thermoplastic resin composition as the raw material of the film and is preferably (glass transition temperature-30 占 폚) to (glass transition temperature + 100 占 폚) Temperature -20 占 폚) to (glass transition temperature + 80 占 폚). If the stretching temperature is lower than (glass transition temperature -30 占 폚), there is a possibility that a sufficient stretching ratio may not be obtained. On the other hand, if the stretching temperature exceeds (glass transition temperature + 100 deg. C), the resin composition may flow (flow), and stable drawing may not be performed.

The stretching ratio defined by the area ratio is preferably 1.1 to 25 times, more preferably 1.3 to 10 times. If the draw ratio is less than 1.1 times, there is a possibility that the toughness accompanying the draw may not be improved. If the stretching magnification exceeds 25 times, there is a possibility that the effect of increasing the stretching magnification may not be recognized.

The stretching speed is preferably 10 to 20,000% / min, more preferably 100 to 10.000% / min in one direction. When the drawing speed is less than 10% / min, it takes a long time to obtain a sufficient drawing magnification, which may increase the manufacturing cost. If the stretching speed is higher than 20,000% / min, the stretched film may be broken.

The acrylic film may be subjected to a heat treatment (annealing) after the stretching treatment so as to stabilize its optical isotropy or mechanical properties. The heat treatment conditions are not particularly limited and any suitable conditions known in the art can be employed.

On the other hand, if necessary, the optical film may be subjected to a surface treatment for improving the adhesive strength. For example, at least one surface of the optical film may be subjected to at least one surface treatment selected from the group consisting of alkali treatment, corona treatment and plasma treatment Can be performed.

According to another embodiment, the polarizing plate protective film coated with the coating layer preferably has a visible light transmittance of 93% or more, more preferably 93.5% or more. By coating the above-mentioned coating layer on the optical film, the transmittance is increased, and thereby the luminance enhancement effect can be further improved.

Another embodiment of the present disclosure relates to a polarizer, comprising: a polarizer; And a protective film for a polarizing plate provided on one side or both sides of the polarizer. 2 illustrates a cross-sectional structure of a polarizing plate including a protective film 10 for a polarizing plate and a polarizer 21 including an optical film 11 and a coating layer 12. As shown in FIG.

When the polarizing plate protective film 10 is provided on one side of the polarizer 21, an additional optical film may be provided on the opposite side. The structure in which the additional optical film 13 is provided is illustrated in Fig. The above-mentioned additional optical film 13 may be those exemplified as the optical film 11 described above.

The attachment of the polarizer 21 to the polarizing plate protective film 10 or the optical film 13 may be carried out by using a polarizer 21 or an optical film (for example, a polarizing plate) using a roll coater, a gravure coater, a bar coater, a knife coater or a capillary coater 11, and 13 may be coated with an adhesive, followed by heat-joining them with a pile roll, or by laminating them at room temperature, or by UV irradiation after laminating. On the other hand, as the adhesive, adhesives used in the related art, for example, a polyvinyl alcohol adhesive, a polyurethane adhesive, an acrylic adhesive, a cationic or radical UV adhesive, and the like can be used without limitation. Structures in which the adhesive layers 31 and 32 are provided between the polarizer 21 and the optical films 11 and 13 are illustrated in Figs. 3 and 4. Fig.

When the modified PVA containing an acetoacetyl group or the like is used as the adhesive, the adhesiveness can be further improved. More specifically, Z-100, Z-200, Z-200H and Z- -210, Z-229, Z-320, and the like can be used, but the present invention is not limited thereto.

In one embodiment of the present invention, the average of the haze value of the polarizing plate may be 0.5% or less.

Polarizer

Another embodiment of the present disclosure relates to a liquid crystal display, comprising: a liquid crystal cell; A backlight unit provided on one surface of the liquid crystal cell; An upper polarizer provided on a surface of the liquid crystal cell provided with a backlight unit; And a lower polarizer plate provided between the liquid crystal cell and the backlight unit, wherein the lower polarizer plate is the polarizer of the above-described embodiment. Figs. 5 to 7 show an example in which the polarizing plate shown in Figs. 2 to 4 is provided between the liquid crystal cell 41 and the backlight unit 51. Fig. In this specification, a polarizing plate disposed close to the backlight unit is referred to as a lower polarizing plate 61, and a polarizing plate disposed close to a user of the liquid crystal display device is referred to as an upper polarizing plate 62 for convenience.

The upper polarizer 62 may be any type of polarizer, optical film / polarizer, polarizer / optical film, optical film / polarizer / optical film, and the like, as long as it is generally used in a liquid crystal display device.

The polarizer 22 used in the upper polarizer 62 may be any film known in the art such as a film made of polyvinyl alcohol containing iodine or a dichroic dye, It is not limited.

The optical films 14 and 15 used in the upper polarizer 62 may be formed of an acrylic film, a polyethylene terephthalate (PET) film, a triacetylcellulose (TAC) film, a polynorbornene (PNB) film, a cycloolefin polymer COP) film, a polycarbonate (PC) film, and the like. Of these, an acrylic film is particularly preferable. The details of the acrylic film are as described above.

On the other hand, the attachment of the polarizer and the optical film may be carried out by coating the surface of the polarizer or optical film with an adhesive using a roll coater, a gravure coater, a bar coater, a knife coater or a capillary coater, Followed by laminating at room temperature, and the like. On the other hand, as the adhesive, adhesives used in the related art, for example, a polyvinyl alcohol adhesive, a polyurethane adhesive, an acrylic adhesive, a cationic or radical UV adhesive, and the like can be used without limitation. Reference numerals 33 and 34 in Figs. 5 to 7 denote an adhesive layer.

The upper polarizer 62 of the present invention may include a retardation film for compensating for the optical retardation generated in the liquid crystal cell 20. In this case, the structure may be, for example, an optical film / polarizer / optical film / retardation film. Here, the retardation film usable in the present invention is not particularly limited, and a retardation film generally used in the related art may be used according to various liquid crystal modes of a liquid crystal display device.

The liquid crystal cell 41 may be of any type as long as it is generally used in a liquid crystal display device. The structure of the liquid crystal cell 41 may be, for example, an upper transparent substrate / color filter / protective film / transparent conductive film electrode / orientation film / liquid crystal / A transparent substrate or the like. Various types of liquid crystal may be used for the liquid crystal cell 41. For example, a double domain TN (twisted nematic), an axially symmetric aligned microcell (ASM), an optically compensated blend (OCB) MVA (multidomain VA), surrounding electrode (SE), patterned VA (PVA), in-plane switching (IPS), and fringe-field switching (FFS) modes.

On the other hand, in the liquid crystal display of the present invention, the attachment of the liquid crystal cell 41 and the polarizing plates 61 and 62 is not particularly limited, and can be attached by a method commonly used in the related art.

The backlight unit 51 can be used without limitation as long as it is commonly used in a liquid crystal display, and may include, for example, a light source and a plurality of optical films. The light source used for the backlight unit 51 may include various types of light sources such as cold cathode fluorescent lamps (CCFLs), external electrode fluorescent lamps (EEFLs), light emitting diodes (LEDs), surface light source lamps Can be used. As the optical film, there can be used an optical film for a backlight unit well known in the art such as a prism sheet, a diffusion film, a light guide plate, a diffusion plate, a reflection film, etc. without limitation.

Hereinafter, the present invention will be described in detail by way of examples with reference to the drawings. However, the embodiments according to the present disclosure can be modified in various other forms, and the scope of the present specification is not construed as being limited to the embodiments described below. Embodiments of the present disclosure are provided to more fully describe the present disclosure to those of ordinary skill in the art.

[ Example ]

A non-stretched film having a width of 800 mm was prepared using a poly (cyclohexylmaleimide-co-methylmethacrylate) (LGMMA PMMA830HR) resin at 250 rpm and 250 rpm using a T- And stretched 1.8 times in the MD direction to prepare a longitudinally stretched acrylic film.

, 2.12 g of a water-dispersed polyurethane resin (CK-PUD Coating paint, 30% aqueous solution of solid content), 0.21 g of hollow silica (average particle size: 50 nm, solid content of 8.8% aqueous solution) 5 parts by weight based on parts by weight, and 4.06 g of pure water were mixed to prepare a coating solution. The prepared coating solution was coated on the above longitudinally stretched acrylic film to a dry thickness of 100-200 nm with a Meyer bar, dried at 95 for 20 seconds, and then drawn at 2.5 times in the TD direction at 135. [

[ Experimental Example ]

The coating appearance (pre-drying and stretching), transmittance and haze of the final film obtained through the above Examples were evaluated and are shown in Table 1 below. The transmittance and haze were measured with a haze meter at three points on the surface of the protective film prepared above, and the average value of the transmittance and haze was calculated. In this case, the transmittance is the total transmittance (Tt), the standard is JIS K7361, and the haze is JIS K7136.

additive coating
Exterior Properties Remarks
(Additive classification) Permeability
(%) Hayes
(%) Additive classification Comparative Example 1 No coating layer formed O 92.4 0.2 - Comparative Example 2 No additive added. X 93.8 1.4 - Example 1 BYK-348 O 94.0 0.4 Polyether-modified siloxane Example 2 BYK-349 O 94.0 0.4 Polyether-modified siloxane Comparative Example 3 DISPERBYK-190 X 93.8 1.9 High molecular weight block copolymer Comparative Example 4 BYK-315 X 93.8 2.0 Polyester-based silicone Comparative Example 5 BYK-322 △ 93.9 1.1 Polyester-based silicone Comparative Example 6 BYK-340 X 93.8 2.0 Fluorine Comparative Example 7 EFKA3570 X 93.8 1.8 Fluorine Comparative Example 8 EFKA3772N X 93.9 1.5 Fluorine Comparative Example 9 PEG (Mw = 4,000) △ 93.9 0.6 Polyether Comparative Example 10 PEG (Mw = 20,000) X 93.8 2.0 Polyether

As shown in Table 1, in Examples 1 and 2, compared to Comparative Example 1 in which no coating layer was used, Comparative Example 2 in which no additive was added to the coating layer, or Comparative Examples 3 to 10 in which other additives were used, We can confirm that the haze is greatly improved.

10 Protective Film for Polarizer
11, 13, 14, 15 Optical film
12 coating layer
21, 22 Polarizer
31, 32, 33, 34 Adhesive layer
41 liquid crystal cell
51 Backlight Unit
61 lower polarizer plate
62 upper polarizer plate

Claims (14)

Optical film; And a coating layer formed on at least one surface of the optical film, the coating layer comprising a polymer resin, hollow fine particles, and a polyether modified siloxane. The protective film for a polarizing plate according to claim 1, wherein the thickness of the coating layer is 10 nm to 500 nm. The protective film for a polarizing plate according to claim 1, wherein the polymer resin is a water-dispersible resin. The protective film for a polarizing plate according to claim 3, wherein the water dispersible resin comprises a polyurethane resin, a polyester resin, a polyacrylic resin, or a combination of two or more thereof. The protective film for a polarizing plate according to claim 1, wherein the hollow fine particles are hollow silica. The protective film for a polarizing plate according to claim 1, wherein the hollow fine particles have a refractive index of 1.17 to 1.4. The protective film for a polarizing plate according to claim 1, wherein the hollow fine particles are contained in an amount of 10 to 300 parts by weight based on 100 parts by weight of the polymer resin. The protective film for a polarizing plate according to claim 1, wherein the polyether-modified siloxane is water-dispersible. The polyether-modified siloxane according to claim 1, wherein the polyether-modified siloxane is represented by the following formula (1) or (2)
[Chemical Formula 1]

In Formula 1,
At least one of R ₁ and R ₂ is - (R ₁₁ O) pR ₁₂ , and the remainder is an alkyl group, an alkylaryl group, or an aralkyl group,
R ₁₁ is a direct bond or an alkylene group,
R ₁₂ is an alkyl group, an alkylaryl group, or an aralkyl group,
m and p are each independently an integer of 1 to 10, x and y are each 0 to 10, provided that x + y is 1 or more,
Ra to Rf are the same or different from each other, and each independently is hydrogen, an alkyl group or polyethylene glycol.
(2)

In Formula 2,
R ₃ is - (R ₁₁ O) p R ₁₂ ,
R ₁₁ is a direct bond or an alkylene group,
R ₁₂ is an alkyl group, an alkylaryl group, or an aralkyl group,
m and p are each independently an integer of 1 to 10,
Rg to Rl are the same or different from each other, and each independently hydrogen, an alkyl group or polyethylene glycol. The protective film for a polarizing plate according to claim 1, wherein the polyether modified siloxane is contained in an amount of 0.1 to 20 parts by weight based on 100 parts by weight of the water dispersible resin. The protective film for a polarizing plate according to claim 1, wherein the optical film is an acrylic film. A polarizer; And a protective film for a polarizing plate according to any one of claims 1 to 11, provided on one surface or both surfaces of the polarizer. The polarizing plate according to claim 12, wherein the polarizing plate has an average haze value of 0.5% or less. A liquid crystal cell;
A backlight unit provided on one surface of the liquid crystal cell;
An upper polarizer provided on a surface of the liquid crystal cell provided with a backlight unit; And
And a lower polarizer disposed between the liquid crystal cell and the backlight unit,
Wherein the lower polarizer plate is the polarizer plate according to claim 12.

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