KR101765372B1 - Protective film for polarizer and polarizing plate comprising the same - Google Patents

Abstract

In this specification, a polarizer protective film comprising a (meth) acrylic resin and having an orientation property of a polymer chain having an anisotropic orientation greater in the TD direction than the MD direction is described, and a polarizing plate comprising the polarizer protective film.

Description

TECHNICAL FIELD [0001] The present invention relates to a polarizing element protective film and a polarizing plate including the polarizing element protective film.

The present application relates to a polarizing element protective film and a polarizing plate including the polarizing element protective film.

The polarizing plate was generally formed by adhering a triacetylcellulose (TAC) film as a protective film to a polarizing element in which iodine or a dichroic dye was adsorbed and oriented on a polyvinyl alcohol (hereinafter referred to as PVA) polymer film with an adhesive.

Recently, an acrylic film having excellent heat resistance and water absorption properties has been adopted as a protective film of a PVA element by substituting triacetyl cellulose film (Fig. 1). However, since the acrylic film has weak toughness characteristic compared with triacetyl cellulose film, Or bending, it is easily broken or broken.

Particularly, when an acrylic protective film is placed at an outermost periphery where a curable hard coating having a high hardness is required to impart scratch resistance and anti-reflection properties to the surface of the film, cracks Is easily transferred to the acrylic protective film to be easily destroyed, and the PVA element is also broken.

In order to improve the low toughness characteristics of such an acrylic film, there has been an effort to improve the toughness of acrylic itself by adding an impact modifier such as rubber elastic particles or by introducing a proportion of a compound having a cyclic structure in an acrylic polymer main chain into a certain amount or more .

However, when an impact modifier such as rubber elastomer particles is added, there arises a problem that the film becomes opaque or the elongation is not uniform due to the added elastomer particles. When a compound having a cyclic structure in an acrylic polymer main chain is contained in a certain amount or more There is a limit in improving the toughness value.

Korean Application Publication No. 2010-0130153

The present application aims to provide a polarizing element protective film in which cracking from an outer layer such as a hard coating layer is not easily performed, and a polarizing plate comprising the polarizing element protective film.

One embodiment of the present invention provides a polarizer protective film comprising a (meth) acrylic resin and having an orientation property of an anisotropic orientation that is larger in the TD direction than in the MD direction in the polymer chain. When addition to that, according to one embodiment, the tensile modulus (E-modulus) value for E _(MD), the tensile elastic modulus value E _(TD) of the TD direction of the polarizer protective film in the MD direction [(E _{(TD )} -E _{( MD )} ) / E _{( MD )} X 100 (%)] is 5% or more.

According to another embodiment, the polarizer protective film has a difference (DELTA E _{( TD- MD)} ) between E _{( TD )} and E _{( MD )} of 100 MPa or more.

Another embodiment of the present disclosure includes a polarizing element; And a polarizing element protective film provided on at least one surface of the polarizing element according to the above-described embodiments.

Another embodiment of the present disclosure provides a method of manufacturing a polarizing element protective film according to the above-described embodiments, including a step of stretching the unstretched precursor of the polarizing element protective film to a greater extent in the TD direction than in the MD direction.

According to some embodiments described herein, when a (meth) acrylic polarizer protective film imparted with anisotropic orientation is laminated with a polarizing element, even if abnormal deformation occurs due to anisotropic orientation, the force is prevented from being dispersed and broken can do. Particularly, when the polymer chain of the polarizing element such as the PVA element and the polymer chain of the protective film of the acrylic polarizing element are oriented orthogonal to each other in the state of the entire polarizing plate structure, even if the film is abnormally deformed, .

The polarizing element protective film described above has the above-described effects. Therefore, in the polarizing plate structure on the viewer's side where hard coating with a large hardness is required on the outermost film surface, when a hard coating layer is provided on the polarizing element protective film , The hard coating layer is not easily broken even when abnormal bending or bending occurs, and cracks generated in the hard coating layer are transferred to the polarizing element protective film or the polarizing element to thereby solve the problem that the polarizing plate cross section is broken.

1 shows an example of a structure in which a protective film is provided on both sides of a PVA element and a surface treatment hard coat layer is provided on one side of the protective film.
2 is a schematic exploded view of the structure of a polarizing plate according to one embodiment of the present invention.

Hereinafter, the present invention will be described in detail.

One embodiment of the present invention provides a polarizer protective film comprising a (meth) acrylic resin and having an orientation property of an anisotropic orientation that is larger in the TD direction than in the MD direction in the polymer chain. Here, the orientation property of anisotropy means that the degree of orientation in the MD direction differs from the degree of orientation in the TD direction of the polarizer protective film, and in this embodiment, it is characterized by having a larger orientation in the TD direction than in the MD direction. Fig. 2 is a schematic exploded view of the structure of the polarizing plate according to one embodiment.

According to the above-described embodiment, the polarizer protective film is oriented in the TD direction larger than in the MD direction. Here, the MD direction corresponds to the alignment direction of the PVA polymer chain of the polarizing element described later. Having a larger anisotropic orientation in the TD direction than in the MD direction means that the modulus in the TD direction is larger than the modulus in the MD direction. The modulus of Young's modulus is obtained by fixing both ends of a sample prepared according to JIS-K6251-1 standard and then applying a force in a direction perpendicular to the thickness direction of the film to calculate a stress per unit area Stress).

Usually, the PVA element is stretched only in the MD direction at a high magnification, so that the PVA polymer chain is oriented only in the stretching direction. Due to the morphological characteristics of such a polymer chain, the PVA element film is easily broken when bent in the stretching direction, but is not easily broken in the vertical direction.

By using such a property, anisotropic orientation can be imparted to the polarizing element protective film comprising the (meth) acrylic resin during stretching. For example, if the polymer chain of the polarizing element protective film is further oriented in a direction perpendicular to the alignment direction (MD direction) of the PVA polymer chain of the polarizing element and in the direction perpendicular to the direction (TD direction) and laminated with the PVA element, And the polymer chains of the polarizing element protective film are oriented in directions orthogonal to each other.

In this case, even if the film is deformed abnormally, the force due to deformation is effectively dispersed in the lamination structure of the polarizing plate, so that even if the polarizing protective film is subjected to surface hard coating, it is not easily broken and cracks are generated in the surface hard coating layer, It is difficult to transfer to the element protective film or the polarizing element.

The stretching magnification can be adjusted so that the polymer chain of the (meth) acrylic polarizer protective film has anisotropic orientation. In the case of stretching only in one direction as in the PVA device, since the polymer chains are oriented only in the stretching direction, there may arise a problem that the physical properties of the film in the direction of stretching reverse become weak. Therefore, in order to adjust the orientation properties of the polymer chains while securing the physical properties of a suitable polarizing element protective film, the stretching magnifications in the MD and TD directions can be appropriately adjusted.

When addition to that, according to one embodiment, the tensile modulus (E-modulus) value for E _(MD), the tensile elastic modulus value E _(TD) of the TD direction of the polarizer protective film in the MD direction [(E _{(TD )} -E _{( MD )} ) / E _{( MD )} X 100 (%)] is 5% or more. The stretching magnification of the polarizing element protective film can be adjusted so as to obtain a value according to the above equation.

According to another embodiment, the polarizer protective film has a difference (DELTA E _{( TD- MD)} ) between E _{( TD )} and E _{( MD )} of 100 MPa or more. The stretching magnification of the polarizing element protective film can be adjusted so as to satisfy the difference in tensile modulus value.

The above-described _{[(E (TD) -E (} MD)) / E (MD) X 100 (%)] difference _{(ΔE (TD-MD} of 5% or more than E _(TD) and E _{(MD) value)} ) Of 100 MPa or more means that the polymer chain of the polarizer protective film is more oriented in the TD direction as compared with the MD direction. When the polymer chain is further oriented in the TD direction, the tensile modulus value in the TD direction becomes larger than that in the MD direction. The greater the difference between these values, the more oriented in the TD direction.

The value of [(E _{( TD )} -E _{( MD )} ) / E _{( MD )} X100 (%)] may be selected within a range of 15% or less as necessary. The difference (DELTA E _{( TD - MD )} ) between E _{( TD )} and E _{( MD )} can be selected within a range of, for example, 300 MPa or less.

The film comprising the (meth) acrylic resin as the polarizer protective film can be formed using materials and methods known in the art, except that anisotropic orientation is imparted.

The thickness of the film containing the (meth) acrylic resin may be determined according to purposes, as long as the above-described orientation property of the anisotropy is satisfied. For example, the film containing the (meth) acrylic resin may have a thickness of 0.5 to 200 micrometers, for example, 1 to 100 micrometers. According to one example, the polarizing element protective film according to the above-described embodiments may exhibit a haze of 1% or less, preferably 0.5% or less.

According to one example, the polarizer protective film comprising the (meth) acrylic resin means a film mainly composed of an acrylic resin or a methacrylic resin, and may be expressed as a (meth) acrylic film.

For example, the acrylic resin or the methacrylic resin is not particularly limited, but may be a homo or copolymer of a (meth) acrylic monomer; A copolymer of a (meth) acrylic monomer and an aromatic vinyl monomer; Copolymers of (meth) acrylic monomers, aromatic vinyl monomers and acrylonitrile monomers; Copolymers of (meth) acrylic monomers, aromatic vinyl monomers and acid anhydrides; Copolymers of (meth) acrylic monomers, aromatic vinyl monomers, acrylonitrile monomers and acid anhydrides; Alkyl methacrylate monomers, styrene monomers, phenylmaleimide monomers and copolymers of alkyl acrylate monomers can be used.

As used herein, the term "copolymer" means that an element referred to herein as a monomer is polymerized and contained as a repeating unit in the copolymer resin. In this specification, the copolymer may be a block copolymer or a random copolymer , But is not limited thereto. Also, even when referring to the monomers contained in the copolymer in the present specification, the present invention is not limited to only the monomers mentioned, and other monomers other than the above-mentioned monomers may be used within the scope of the present invention, . ≪ / RTI >

According to one embodiment, the (meth) acrylic film includes a copolymer of an alkyl methacrylate-based monomer, a styrene-based monomer, a phenylmaleimide-based monomer, and an alkyl acrylate-based monomer. When a film is formed using such a copolymer, it is possible to provide a film having excellent heat resistance and optical properties as well as an improvement in production efficiency due to the reduction of the odor generated upon film extrusion and the excellent thermal stability.

 Wherein the copolymer comprises 70 to 98 parts by weight of an alkyl methacrylate monomer, 0.1 to 10 parts by weight of a styrenic monomer, 1 to 15 parts by weight of a phenylmaleimide monomer, based on 100 parts by weight of the copolymer; And 0.1 to 5 parts by weight of an alkyl acrylate monomer.

The alkyl methacrylate-based monomer can provide the resin composition or the film with high transparency optical properties.

The alkyl moiety of the alkyl methacrylate monomer may be a substituted or unsubstituted alkyl group or a cycloalkyl group, and the alkyl moiety preferably has 1 to 10 carbon atoms, more preferably 1 to 6 carbon atoms , And most preferably a methyl group or an ethyl group. Specific examples include methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, t-butyl methacrylate, hydroxyethyl methacrylate, isobornyl methacrylate, and cyclohexyl methacrylate ≪ / RTI > but is not limited thereto.

The content of the alkyl methacrylate monomer is about 70 to 98 parts by weight, and more preferably about 82 to 97 parts by weight based on 100 parts by weight of the copolymer. When the content satisfies the above range, a film having excellent optical properties can be obtained, and the birefringence generated upon stretching can be minimized.

The styrene-based monomer improves the polymerization efficiency between the respective monomers and can reduce the residual monomers contained in the produced copolymer. Further, the film produced by the resin composition comprising the copolymer containing the styrene-based monomer can control the stretching retardation more easily and can provide a zero-retardation film having excellent birefringence.

The styrene-based monomer may be an unsubstituted styrene monomer or a substituted styrene monomer. The substituted styrene monomer may be an aliphatic hydrocarbon or a styrene substituted with a substituent containing a hetero atom in a benzene ring or a vinyl group. For example, there can be mentioned styrene,? -Methylstyrene, 3-methylstyrene, 4-methylstyrene, 2,4-dimethylstyrene, 2,5-dimethylstyrene, Methyl styrene, 4-chloro-α-methylstyrene, 4-bromo-α-methylstyrene, 4-methyl- -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, 2-bromostyrene, 3- But is not limited to, at least one selected from the group consisting of styrene, 2,4-dibromostyrene,? -Bromostyrene and? -Bromostyrene. More preferably, C _1-4 alkyl or halogen-substituted styrene may be used. More specifically, the styrenic monomer may be at least one member selected from the group consisting of styrene,? -Methylstyrene, p-bromostyrene, p-methylstyrene and p-chlorostyrene, methylstyrene and p-methylstyrene.

The content of the styrene-based monomer is preferably about 0.1 to 10 parts by weight, more preferably about 0.5 to 5 parts by weight, based on 100 parts by weight of the copolymer. When the content of the styrene-based monomer is within the above range, the effect of reducing the residual monomer and the effect of increasing the glass transition temperature of the copolymer can be obtained, and the stretching retardation of the film can be easily controlled, This is because the effect can be obtained.

The above-mentioned phenylmaleimide-based monomer can improve the thermal stability and heat resistance of the resin composition and the film, and improve the compounding compatibility with the polycarbonate resin. Further, unlike the case of using the conventional cyclohexylmaleimide, it is possible to suppress the occurrence of irritating odor when the resin composition is extruded.

Generally, maleimide-based residual monomers generate a stimulant odor during processing and can easily solidify and cause appearance defects when producing optical films. However, unlike the cyclohexylmaleimide monomer, the phenylmaleide monomer has a constant chemical structure of the monomer due to the substitution of the phenyl group, so that it is easy to form a copolymer with the alkylmethacrylate monomer and the styrene monomer, Can be improved, and the polymerization time is relatively short. As a result, the amount of the phenylmaleimide-based monomer remaining in the resin after formation of the copolymer is much lower than that of the cyclohexylmaleimide-based resin, and the generation of odors in the processing due to the residual monomer can be reduced.

Specific examples of the phenylmaleimide-based monomer are selected from the group consisting of phenylmaleimide, nitrophenylmaleimide, monochlorophenylmaleimide, dichlorophenylmaleimide, monomethylphenylmaleimide, dimethylphenylmaleimide, and ethylmethylphenylmaleimide. Is preferable.

The content of the phenylmaleimide-based monomer is preferably about 1 to 15 parts by weight, and more preferably about 2 to 10 parts by weight, based on 100 parts by weight of the copolymer. When the content of the phenylmaleimide monomer is within the above range, the heat resistance of the resin composition or film is enhanced, the film is well mixed with the polycarbonate resin, and the film can be formed without precipitation.

The alkyl acrylate monomer may impart polymerization stability and thermal stability to the resin composition and toughness to the stretched film. By introducing the structural unit into the copolymer, a molding processability such as releasability is improved, and a composition having excellent heat resistance such as preventing weight reduction due to heat during the process is obtained.

The alkyl moiety of the alkyl acrylate monomer may be a substituted or unsubstituted alkyl group or a cycloalkyl group. The alkyl moiety preferably has 1 to 10 carbon atoms, more preferably 1 to 6 carbon atoms, Most preferably a methyl group or an ethyl group. Specifically, it may be methyl acrylate, ethyl acrylate, n-butyl acrylate isopropyl acrylate, t-butyl acrylate, cyclohexyl acrylate, isobornyl acrylate, hydroxymethylacrylate or hydroxyethyl acrylate But is not limited thereto.

The content of the alkyl acrylate monomer is about 0.1 to 5 parts by weight, more preferably about 0.5 to 3 parts by weight, based on 100 parts by weight of the copolymer. When the content is in the above range, polymerization between the alkyl methacrylate monomer and the phenylmaleimide monomer is facilitated during the formation of the copolymer, thereby reducing the residual phenylmaleimide in the resin composition. Which is capable of overcoming the thermal decomposition phenomenon caused by the phenylmaleimide, and imparting toughness upon stretching the film, thereby facilitating the stretching process.

 According to one embodiment, the weight ratio of the phenylmaleimide-based monomer to the alkyl acrylate-based monomer is preferably about 2: 1 to 10: 1, more preferably about 2: 1 to 7: 1. If the weight ratio of the two monomers satisfies the above range, the residual monomer content in the copolymer can be reduced, and the stability of the retention in the extruder and the polymer filter during film processing can be improved.

According to one embodiment, the (meth) acrylic film includes a copolymer of an alkyl methacrylate monomer, a styrene monomer, a phenylmaleimide monomer and an alkyl acrylate monomer, and the Can be produced using a composition having a content of 30 ppm or less, more preferably 20 ppm or less. At the time of production, an extrusion method described later can be used. It has been found that the cyclohexylmaleimide monomer which is conventionally used as a monomer of a copolymer constituting the heat-resistant resin has a relatively low degree of polymerization because the cyclohexylmaleimide monomer is highly rotatable. Thus, not only is the amount of monomer remaining in the resin after copolymerization large, but also the cyclohexylmaleimide monomer causes irritating and harmful odor, resulting in process problems. However, the phenylmaleimide-based monomer has an advantage in that the polymerization degree is superior to that of the cyclohexylmaleimide-based monomer due to the stable aromatic ring, and the amount of the residual monomer in the copolymer is extremely small, thereby improving the stability of the process.

According to one embodiment, the (meth) acrylic-based film comprises a polycarbonate together with a copolymer of an alkyl methacrylate-based monomer, a styrene-based monomer, a phenylmaleimide-based monomer and an alkyl acrylate-based monomer. The polycarbonate is added for controlling the retardation and may be contained in an amount of about 0.1 to 10 parts by weight based on 100 parts by weight of the total resin composition, and preferably about 1 to 5 parts by weight. When the polycarbonate is contained in an amount of 0.1 part by weight or more, it is possible to prevent the retardation in the thickness direction of the stretched film from increasing in the positive direction. When the content of the polycarbonate is 10 parts by weight or less, Can be prevented, and compatibility with the acrylic resin composition is good, so that whitening can be prevented. Therefore, the absolute value of the retardation (R _in ) of the plane direction defined by the following formula 1 and the absolute value of the thickness retardation R _th defined by the following formula 2 are respectively 5 nm and By weight, preferably 3% by weight, more preferably 0% by weight.

[Equation 1] R _in = (n _x - n _y ) x d,

[Equation 2] R _th = (n _z - n _y ) x d

In the above-mentioned [Formula 1] and [Formula 2]

n _x is the largest refractive index among the refractive indices in the plane direction of the optical film,

n _y is a refractive index in a direction perpendicular to n _{x of the} refractive index in the plane direction of the optical film,

n _z is the refractive index in the thickness direction,

d is the thickness of the film.

The resin composition comprising the copolymer resin and the polycarbonate resin can be produced using a method well known in the art, such as compounding.

According to one embodiment, the glass transition temperature of the copolymer for producing the (meth) acrylic-based film described above or the resin composition containing the same is preferably about 100 ° C to 150 ° C, more preferably 105 ° C to 140 ° C And most preferably 110 to 130 ° C. When the glass transition temperature is 100 占 폚 or higher, the heat resistance is excellent and deformation of the film can be prevented under high temperature and high humidity conditions, thereby preventing deformation of the polarizing plate and preventing unevenness of the liquid crystal panel. When the glass transition temperature is 150 占 폚 or less, the resin processing property is good, and the film is easily formed due to the appropriate viscosity at the time of extrusion processing, and the productivity can be improved.

The copolymer of the alkyl methacrylate monomer, the styrene monomer, the phenylmaleimide monomer and the alkyl acrylate monomer, or the resin composition containing the same, is excellent in thermal stability. In general, zipper decomposition specific to a resin containing alkyl methacrylate occurs at about 260 DEG C at which a resin containing alkyl methacrylate is actually molded by injection molding or extrusion molding. It is known that the double bond at the terminal proceeds as a starting point. On the other hand, the above-mentioned copolymer can reduce the defective molding by suppressing the thermal decomposition at around 260 캜, and can stably manufacture the optical article without deteriorating the color tone. In the present specification, thermal stability can be evaluated using a thermogravimetric analyzer (TGA). For example, it is possible to evaluate the thermal stability by measuring the temperature at which the 2% weight of the resin is reduced in the process of raising the temperature from 30 ° C to 500 ° C at a rate of 10 ° C / min in a nitrogen environment. The 2% weight reduction temperature is preferably 280 DEG C or higher, more preferably 300 DEG C or higher, and most preferably 320 DEG C or higher.

According to one embodiment, a resin having a weight average molecular weight of 1,000 to 2,000,000, specifically 10,000 to 500,000, and 80,000 to 1,500,000 may be used as the (meth) acrylic resin as the material of the (meth) acrylic film have. The glass transition temperature of the (meth) acrylic resin according to an example is 100 to 150 ° C., for example, 120 to 130 ° C., MI (230 ° C., 3.8 kg) 10 or less, preferably 0.5 to 5, . The MI is a measure of the flow of resin, and represents the amount flowing per minute when the load is 230 kg at a load of 3.8 kg.

Another embodiment of the present invention is a polarizing element protective film according to the above-described embodiment, which is provided on one side of the (meth) acrylic film of the polarizing element protective film, and the resin film having a greater toughness than the (meth) And a polarizing element protective film. In this case, when an ultraviolet flaw material is added to a resin film having a higher toughness than the (meth) acrylic film without adding an ultraviolet absorber to the (meth) acrylic film, the melted material from the T-DIE in the co- The surface of the polarizing element protective film which is in contact with the roll is on the side of the (meth) acrylic film, thereby preventing the ultraviolet absorber from flowing out during the manufacturing process.

In the above-described embodiment, the ultraviolet absorber may be used singly or in combination of two or more of those known in the art. For example, a (benzo) triazole-based ultraviolet absorber, a triazine-based ultraviolet absorber and the like may be used.

In addition, the (meth) acrylic film or resin film may further include other additives such as an antioxidant, if necessary.

In another embodiment of the present invention, a surface-treated hard coating layer is provided on one side of the above-described polarizer protective film.

The surface-treated hard coating layer may be formed by materials and methods known in the art. If necessary, a primer layer may be formed between the surface-treated hard coating layer and the polarizing element protective film.

According to one embodiment, the hard coating layer may be formed by a composition comprising a binder resin, fine particles, a solvent and the like. For example, the composition for forming the hard coat layer may use a binder resin well known in the art such as an acrylic binder resin or the like as the binder resin. The type of the acrylic binder resin is not particularly limited, and any resin known in the art can be used without any particular limitation. Examples of the acrylic binder resin include an acrylate monomer, an acrylate oligomer, a mixture thereof, and the like. At this time, the acrylate monomer or the acrylate oligomer preferably contains at least one acrylate functional group capable of participating in the curing reaction.

The types of the acrylate monomers and the acrylate oligomers are not particularly limited, and those commonly used in the technical field of the present invention can be selected and used without limitation. As the acrylate oligomer, urethane acrylate oligomer, epoxy acrylate oligomer, polyester acrylate, polyether acrylate or a mixture thereof may be used. Examples of the acrylate monomers include dipentaerythritol hexaacrylate, dipentaerythritol hydroxypentaacrylate, pentaerythritol tetraacrylate, pentaerythritol triacrylate, trimethylene propyl triacrylate, propoxylated glycerol triacrylate , Trimethylolpropane ethoxy triacrylate, 1,6-hexane diol diacrylate, propoxylated glycerol triacrylate, tripropylene glycol diacrylate, ethylene glycol diacrylate, or a mixture thereof But the present invention is not limited to these examples.

On the other hand, the fine particles are not necessarily included in the hard coat layer, and may or may not be included as needed. The fine particles may be organic fine particles, inorganic fine particles, or a mixture thereof. The content of the fine particles is not limited thereto, but may be about 0.1 to 100 parts by weight based on 100 parts by weight of the binder resin. When the content of the fine particles satisfies the above-described numerical value range, sufficient unevenness is formed in the coating film and the coatability is improved.

The inorganic fine particles may be selected from the group consisting of silica, silicon particles, aluminum hydroxide, magnesium hydroxide, alumina, zirconia and titania, or two or more thereof.

The organic fine particles may be selected from the group consisting of polystyrene, polymethyl methacrylate, polymethyl acrylate, polyacrylate, polyacrylate-co-styrene, polymethyl acrylate-co-styrene, polymethyl methacrylate- , Polyvinyl chloride, polybutylene terephthalate, polyethylene terephthalate, polyamide, polyimide, polysulfone, polyphenylene oxide, polyacetal, epoxy resin, phenol resin, silicone resin, melamine resin, benzoguanamine, At least one selected from the group consisting of polydivinylbenzene, polydivinylbenzene-co-styrene, polydivinylbenzene-co-acrylate, polydiallyl phthalate and triallyl isocyanurate polymers, or copolymers of two or more thereof copolymer may be used.

The solvent may be included in an amount of about 50 parts by weight to about 1000 parts by weight based on 100 parts by weight of the binder resin. When the content of the solvent satisfies the above-described numerical value range, the coatability of the hard coating layer is excellent, the film strength of the coating film is excellent, and it is easy to manufacture the thick film.

The kind of the solvent usable in the present invention is not particularly limited, and an organic solvent can usually be used. For example, at least one member selected from the group consisting of C1 to C6 lower alcohols, acetates, ketones, cellosolve, dimethylformamide, tetrahydrofuran, propylene glycol monomethyl ether, toluene, Can be used. The lower alcohol may be one selected from the group consisting of methanol, ethanol, isopropyl alcohol, butyl alcohol, isobutyl alcohol and diacetone alcohol. The acetate may be selected from the group consisting of methyl acetate, ethyl acetate, isopropyl acetate, butyl acetate And cellosolve acetate, and the ketone may be one selected from the group consisting of methyl ethyl ketone, methyl isobutyl ketone, acetyl acetone, and acetone, but is not limited thereto.

On the other hand, the above-mentioned composition for forming a hard coat layer may further include a UV curing initiator added for the purpose of curing by UV irradiation, if necessary. The UV curing initiator may be selected from the group consisting of 1-hydroxycyclohexyl phenyl ketone, benzyl dimethyl ketal, hydroxy dimethyl acetophenone, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, and benzoin butyl ether And may be a single selected material or a mixture of two or more materials.

The UV curing initiator is preferably added in an amount of 0.1 to 10 parts by weight based on 100 parts by weight of the binder resin. When the content of the UV curing initiator satisfies the above-described numerical range, sufficient curing may occur and the film strength of the film may be improved.

The above-mentioned composition for forming a hard coat layer may further comprise at least one additive selected from a leveling agent, a wetting agent, and a defoaming agent, if necessary. The additive may be added in an amount of 0.01 to 10 parts by weight based on 100 parts by weight of the binder resin.

The thickness of the hard coat layer is not limited to this, but may be about 1 탆 to 30 탆, preferably about 1 탆 to 20 탆.

The hard coat layer may be formed by applying a composition for forming a hard coat layer on the second primer layer, followed by drying and / or curing, wherein the application is performed by application methods well known in the art, for example, , A roll coating method, a bar coating method, a spray coating method, a dip coating method and a spin coating method. However, the application method is not limited thereto, and various other application methods used in the art may be used.

The drying and / or curing may be performed by forming a primer layer on the polarizing element protective film as required, applying a composition for forming a hard coating layer, and irradiating heat and / or light. The step and the curing step may be performed sequentially or simultaneously. However, considering the convenience of the process, it is more preferable that the curing step is performed by a method of irradiating light such as UV.

On the other hand, the curing conditions can be appropriately adjusted according to the compounding ratio and the composition of the composition for forming a hard coat layer. For example, in the case of electron beam or ultraviolet curing, the irradiation amount is set to 0.01 J / cm 2 to 2 J / To about 10 minutes. In the electron beam or ultraviolet ray curing, when the curing time satisfies the above numerical range, the binder resin can be sufficiently cured, so that mechanical properties such as abrasion resistance are excellent, and the durability of the acrylic film can be improved.

The hard coating layer may have a single layer structure or a multi-layer structure of two or more layers.

Another embodiment of the present disclosure includes a polarizing element; And a polarizing element protective film provided on at least one surface of the polarizing element according to the above-described embodiments.

A polarizing plate according to an example includes a polarizing element; And a polarizing element protective film provided on at least one surface of the polarizing element. In the case where the protective film according to the embodiment of the present invention is provided on only one side of the polarizing element, the protective film according to the embodiment of the present invention or a known protective film may be provided on the other side.

In this specification, the polarizing element is not limited to those known in the art. For example, a film made of polyvinyl alcohol (PVA) containing iodine or a dichroic dye can be used. In the present specification, a film made of PVA may also be referred to as a PVA element. The polarizing element can be produced by saponifying iodine or a dichroic dye to a PVA film, but the production method thereof is not particularly limited. In the present specification, the polarizing element means a state not including a protective film, and the polarizing plate means a state including a polarizing element and a protective film.

Adhesion between the polarizing element and the protective film can be performed using an adhesive layer. The adhesive that can be used when the protection film and the polarizing plate are combined is not particularly limited as long as it is known in the art. For example, a one-component or two-component polyvinyl alcohol (PVA) adhesive, a polyurethane adhesive, an epoxy adhesive, a styrene butadiene rubber adhesive (SBR adhesive), or a hot melt adhesive.

Among these adhesives, a polyvinyl alcohol-based adhesive is preferable, and it is particularly preferable to use an adhesive comprising a polyvinyl alcohol-based resin containing an acetacetyl group and an amine-based metal compound crosslinking agent. The adhesive for the polarizing plate may include 100 parts by weight of the polyvinyl alcohol resin containing the acetacetyl group and 1 to 50 parts by weight of the amine metal compound crosslinking agent.

The polyvinyl alcohol resin is not particularly limited as long as it can sufficiently adhere the polarizing element and the protective film, is excellent in optical transparency and does not change with time, such as yellowing. In consideration of a smooth crosslinking reaction with a crosslinking agent It is preferable to use a polyvinyl alcohol-based resin containing an acetacetyl group.

Here, the degree of polymerization and degree of saponification of the polyvinyl alcohol-based resin is not particularly limited as long as it contains an acetacetyl group, but it is preferably in the range of 200 to 4,000 and a degree of saponification of 70 to 99.9 mol% Range. It is more preferable that the polymerization degree is within the range of 1,500 to 2,500 and the degree of saponification is within the range of 90 to 99.9 mol% in consideration of the flexible mixing with the contained material due to the freedom of molecular motion. At this time, the polyvinyl alcohol-based resin preferably contains the acetacetyl group in an amount of 0.1 to 30 mol%. The reaction with the crosslinking agent can be performed smoothly in the range of the acetacetyl group, and the water resistance and the adhesive strength of the desired adhesive are sufficiently taken into consideration.

The amine-based metal compound crosslinking agent is preferably a water-soluble crosslinking agent having a functional group having reactivity with the polyvinyl alcohol-based resin, in the form of a metal complex containing an amine-based ligand. Possible metals include zirconium (Zr), titanium (Ti), hafnium (Hf), tungsten (W), iron (Fe), cobalt (Co), nickel (Ni), ruthenium (Ru), osmium A transition metal such as rhodium (Rh), iridium (Ir), palladium (Pd) or platinum (Pt) can be used as the ligand. The ligand bound to the center metal includes primary amine, secondary amine (diamine), tertiary amine, And at least one amine group such as a carboxyl group and a carboxyl group. The amount of the polyvinyl alcohol resin to be used is preferably adjusted to 1 to 50 parts by weight based on 100 parts by weight of the polyvinyl alcohol resin. It is possible to impart a sufficiently significant adhesive force to the desired adhesive in the above-mentioned range and to improve the storage stability (pot life) of the adhesive.

The pH of the adhesive aqueous solution containing the acetacetyl group-containing polyvinyl alcohol-based resin and the amine-based metal compound crosslinking agent is preferably adjusted to 9 or less by using a pH adjusting agent. More preferably, the pH can be adjusted in the range of more than 2 to 9, and more preferably the pH can be adjusted in the range of 4 to 8.5.

The adhesive of the polarizing element and the protective film is first coated on the surface of the polarizing element protective film or the polarizing element PVA film using a roll coater, a gravure coater, a bar coater, a knife coater, a capillary coater or the like , Or by a method in which the protective film and the polarizing element are thermally pressed or pressed at room temperature by a joint roll before the adhesive is completely dried. When a hot-melt type adhesive is used, a hot press roll is used.

When a polyurethane adhesive is used, it is preferable to use a polyurethane adhesive produced by using an aliphatic isocyanate compound which is not yellowed by light. When a single-component or two-component adhesive for dry lamination or an adhesive having relatively low reactivity with an isocyanate and a hydroxy group is used, a solution type adhesive agent diluted with an acetate type solvent, a ketone type solvent, an ether type solvent or an aromatic type solvent May be used. At this time, it is preferable that the adhesive viscosity is a low viscosity type of 5000 cps or less. The adhesives are preferably excellent in storage stability and have a light transmittance of 90% or more at 400 to 800 nm.

A pressure-sensitive adhesive can also be used if it can exhibit sufficient adhesion. It is preferable that the adhesive is sufficiently cured by heat or ultraviolet rays after laminating and the mechanical strength is improved to the level of the adhesive. Also, the adhesive strength of the adhesive is so high that the adhesive force is such that the adhesive is not peeled off without destruction of either one of the two films .

Specific examples of usable pressure-sensitive adhesives include natural rubber, synthetic rubber or elastomer excellent in optical transparency, vinyl chloride / vinyl acetate copolymer, polyvinyl alkyl ether, polyacrylate, modified polyolefin-based pressure sensitive adhesive, etc. and a curing type And a pressure-sensitive adhesive.

In this specification, when a polarizing element protective film according to an embodiment of the present invention is provided only on one side of a polarizing element, a known protective film may be used on the other side of the polarizing element, and a retardation film may be provided instead of the protective film . Known protective films include triacetyl cellulose (TAC) films, cyclic olefin based resin films, and the like, but are not limited thereto.

The polarizer prepared as described above can be used for various purposes. Specifically, it can be preferably used for an image display apparatus including a polarizing plate for a liquid crystal display (LCD), an antireflection polarizing plate for an organic EL display, and the like. Further, the polarizing plate according to the present invention may be combined with various optical layers such as various functional films, for example, a retardation plate such as a? / 4 plate, a? / 2 plate, a light diffusion plate, a viewing angle enlargement plate, And can be applied to one complex polarizing plate.

The polarizing plate may have a pressure-sensitive adhesive layer on at least one surface thereof so that the polarizing plate can be easily applied to an image display device or the like thereafter. In addition, a release film may be further provided on the pressure-sensitive adhesive layer to protect the pressure-sensitive adhesive layer until the polarizing plate is applied to an image display device or the like.

In addition, another embodiment of the present disclosure provides an electronic device including a polarizing plate according to the above-described embodiments. The electronic device may be an image display device such as an LCD.

According to an example, the light source, the first polarizing plate, the liquid crystal cell, and the second polarizing plate are sequentially stacked, and at least one of the first polarizing plate and the second polarizing plate includes the polarizing element protective film An image display device is provided.

The liquid crystal cell includes a liquid crystal layer; A substrate capable of supporting the substrate; And an electrode layer for applying a voltage to the liquid crystal. In this case, the optical film or the retardation film according to the present invention can be applied to various types of optical devices such as an in-plane switching mode (IPS mode), a vertically aligned mode (VA mode), an OCB (Optically Compensated Birefringence mode) A twisted nematic mode (TN mode), and a FFS mode (Fringe Field Switching mode). [0030] In another embodiment of the present invention, the unstretched precursor of the polarizing element protective film is moved in the MD direction Of the polarizing element protective film according to the above-described embodiments, wherein the polarizing element protective film is further stretched in the TD direction. In the present specification, the term "unstretched precursor" means a precursor that becomes a polarizing element protective film by performing stretching.

According to one example, the polarizing element protective film may be formed into a film form by a method well known in the art, such as a solution casting method or an extrusion method, using a resin composition containing a (meth) acrylic resin, . It is more preferable to use the extrusion method in view of the economical aspect.

The stretching process includes both longitudinal (MD) stretching and transverse (TD) stretching, which may be performed individually or simultaneously. The stretching may be performed in one step or in multiple steps. In the case of longitudinal stretching, stretching can be performed by the speed difference between the rolls, and in the case of transverse stretching, TENTER can be used.

On the other hand, when the glass transition temperature of the resin contained in the resin composition is Tg, the stretching is preferably performed at a temperature of Tg or higher, more preferably 5 to 30 ° C or higher than Tg More preferable. When the stretching temperature is lowered, the breaking rate of the film becomes higher. On the other hand, when the stretching temperature is too high, the polymer chain is not sufficiently oriented in accordance with the stretching, and the physical properties of the film are deteriorated.

The stretching magnification may be adjusted to 1.2 to 5 times, preferably 1.5 to 3.5 times, for each stretching axis. The higher the stretching magnification, the higher the chain orientation ratio in the polymer, and as a result, the properties such as the strength and / or elongation of the final film are improved. In the case of the (meth) acrylic resin, since the resin itself has a very brittle characteristic, if the draw ratio is too high, breakage may occur, and therefore the draw ratio can be determined in consideration of the physical properties of such a resin .

Hereinafter, the technique according to the above-described embodiment will be described in detail through the embodiments. However, the following examples are intended to illustrate the invention and are not intended to limit the scope of the invention.

The acrylic resin was melted at 250 占 폚, passed through a T-die, and a base film was produced through a chrome casting roll and a drying roll. The base film thus prepared was stretched by a biaxial stretching method. The MD / TD direction modulus of the film prepared by varying the draw ratio and the difference therebetween are shown in Table 1 below.

division Example 1 Example 2 Comparative Example 1 Comparative Example 2 Example 3 E _{( MD )} , MPa 1,992 1,960 2,076 2,068 1,549 E _{( TD )} , MPa 2,104 2,038 2,087 1,460 2,003 ΔE _{( TD - MD )} , MPa 112 78 11 -122 454 [(E _{( TD )} -E _{( MD )} ) / E _(MD) X100 (%)] 5.6% 4% 0.5% -29.4% 29.3%

Table 2 shows the results of a mandrel test for a polarizing plate comprising a film containing the (meth) acrylic resin of the above Examples and Comparative Examples.

division Mandrel Test Ф10 mm Ф12 mm Ф14 mm Ф16 mm Ф18 mm Ф20 mm Example 1 fracture crack
(~ 3.5 mm) crack
(~ 1.0 mm) crack
(~ 1.0 mm) No crack No crack Example 2 - - fracture crack
(~ 3.5 mm) crack
(~ 1.5 mm) No crack Comparative Example 1 - - fracture fracture crack
(~ 3.0 mm) Comparative Example 2 - - - - fracture fracture Example 3 crack
(~ 3.5 mm) crack
(~ 2.0 mm) crack
(~ 1.0 mm) crack
(~ 1.0 mm) No crack No crack

[Evaluation method of mandrel]

A method of evaluating whether a surface hard coating layer is fractured (cracked or broken) by wrapping a polarizing plate on a cylindrical metal rod (outside of the surface treatment hard coating layer) and applying a constant load, Ф 4 mm, Ф 6 mm, Ф 8 mm, Ф10 mm, and Ф12 mm), cracks and polarizer breaks were observed. A load of 300 g is applied to the polarizer plate in the state of being applied to the mandrel.

As in the examples and the comparative examples, in the case of Example 1 in which the value of DELTA E (TD-MD) was as large as 112 MPa, the crack and cracking properties by the mandrel test were relatively excellent and cracking and cracking . Compared with Examples 1 and 2, Comparative Example 1 in which the value of DELTA E (TD-MD) was low showed cracking and cracking at a relatively large mandrel diameter, and a comparative example in which DELTA E (TD-MD) 2, the absolute value is large, but since the orientation is in the MD direction since it is a minus sign, the result of the mandrel test is the worst. In the case of Example 3, the modulus E (MD) value in the MD direction was very large at 454 because the MD stretching was made small, meaning that the polymer chain was oriented in the TD direction, It was not broken even with a diameter of 10 mm. However, in the case of Example 3, since the stretching magnification in the MD direction is lowered to increase the value of DELTA E (TD-MD), it may be necessary to compensate the physical properties of the MD in the MD direction.

Claims (8)

(Meth) acrylic resin, and the orientation of the polymer chain has an orientation greater than that of the MD direction in the TD direction,
Tensile modulus (E-modulus) values _{E (MD), E (MD} ) to that the tensile modulus values in the TD direction E _(TD) to the MD direction is less than 1,960MPa 1,992MPa, E _(TD) is A polarizer protective film having a refractive index of 2,038 MPa or more and 2,104 MPa or less. (E _(TD) -E _(MD) ) / _{(TD), where} E _(MD) is the tensile modulus value in the _MD direction and E _(TD) is the tensile modulus value in the TD direction. E _(MD) X 100 (%)] is 5% or more and 15% or less. The method according to claim 1, the difference between E _(TD) and E _(MD) when said tensile modulus of elasticity (E-modulus) value for E _(MD), TD tensile modulus value of E _(TD) in the direction of the MD direction (ΔE _(TD-MD) ) of 100 MPa or more and 300 MPa or less. The polarizing element protecting film according to claim 1, further comprising an ultraviolet absorber. The polarizing element protecting film according to claim 1, wherein a surface hard coating layer is provided on one surface. A polarizing element; And a polarizing element protective film according to any one of claims 1 to 5 provided on at least one surface of the polarizing element. 7. The polarizing plate according to claim 6, wherein the polarizing element is a film made of PVA, and the MD direction is the alignment direction of the PVA polymer chains of the polarizing element. A method for producing a polarizing element protective film according to any one of claims 1 to 5, comprising the step of stretching the unstretched precursor of the polarizing element protective film to a larger extent in the TD direction than in the MD direction.

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