KR20160079707A - Polarizing plate - Google Patents

Abstract

In the present invention, provided is a polarizing plate having excellent cooling and heating resistance properties while having good processability for chopping at the same time. The polarizing plate comprises: a first protective film; a first adhesive layer; a second adhesive layer; and a second protective film in a described order. The first adhesive layer has a storage modulus greater than or equal to 0.1 MPa and less than 800 MPa at 80°C. The second adhesive layer has a storage modulus more than or equal to 800 MPa and less than 10000 MPa.

Description

POLARIZING PLATE

The present invention relates to a polarizing plate in which a protective film is bonded to both surfaces of a polarizing film through an adhesive layer.

Polarizing plates widely used in an image display apparatus typified by a liquid crystal display device generally have a structure in which a protective film is laminated on both sides of a polarizing film. For example, as described in JP-A-2003-139952 and JP-A-2011-017820, an adhesive is usually used for bonding the polarizing film and the protective film. As an adhesive for bonding a protective film, an aqueous adhesive or an active energy ray-curable adhesive is known.

Generally, the polarizing plate is manufactured as a long product (polarizing plate roll) by a roll-to-roll method and then cut into a single sheet of polarizing plate of a size corresponding to the screen size of an applied image display device , And is inserted into the image display device by being bonded to the image display element. Therefore, the polarizing plate is required to have workability (such as when it is cut into wafers (peeling between the polarizing film and the protective film is hardly caused by stress such as cutting).

Further, in an image display apparatus to which a polarizing plate is applied, durability is required under the environment in which it is placed, and thus the durability of the polarizing plate is demanded. Japanese Unexamined Patent Application Publication No. 2003-139952 discloses that an adhesive having a storage elastic modulus at 90 ° C of 0.5 to 5000 MPa is used as an adhesive for bonding a protective film in order to increase the heat resistance of a polarizing plate. Further, Japanese Patent Laid-Open Publication No. 2011-017820 discloses a cured product in which the cured product is heated at a temperature of 80 占 폚 to increase the durability (hereinafter referred to as " resistance to cold and heat shock ") when the product is placed under an environment in which high- An adhesive exhibiting a storage elastic modulus of 600 MPa or more is used. However, these conventional polarizing plates have room for further improvement in terms of both the workability and the resistance to cold and heat shock.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a polarizing plate excellent in workability, such as in cutting, and excellent in cold and heat shock resistance.

The present invention provides the following polarizing plate.

[1] A polarizing plate comprising a first protective film, a first adhesive layer, a polarizing film, a second adhesive layer and a second protective film in this order,

Wherein the first adhesive layer has a storage elastic modulus at 80 캜 of at least 0.1 MPa but less than 800 MPa and a storage elastic modulus at 80 캜 of the second adhesive layer is less than 800 MPa but less than 10,000 MPa.

[2] The polarizer according to [1], wherein the second adhesive layer has a storage elastic modulus at 80 ° C of 1000 MPa or more.

[3] The polarizing plate according to [1] or [2], wherein at least one of the first adhesive layer and the second adhesive layer is a cured layer of an active energy ray curable adhesive.

[4] The polarizer according to [3], wherein the active energy ray-curable adhesive comprises a radical polymerizable compound.

[5] The first protective film and the second protective film may be made of a resin selected from the group consisting of a polyester resin, a polycarbonate resin, a polyolefin resin, a (meth) acrylic resin and a cellulose ester resin The polarizer according to any one of [1] to [4].

[6] The polarizer according to [5], wherein the first protective film is composed of a (meth) acrylic resin, and the second protective film is composed of a polyolefin resin or a cellulose ester resin.

[7] The polarizer according to any one of [1] to [6], wherein at least one of the first protective film and the second protective film is a retardation film.

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to provide a polarizer excellent in workability, such as in cutting, and excellent in cold and heat shock resistance.

1 is a schematic cross-sectional view showing an example of the layer structure of a polarizing plate according to the present invention.

Hereinafter, the polarizing plate according to the present invention will be described in detail.

(1) Configuration of Polarizer

1, a polarizing plate according to the present invention includes a first protective film 10, a first adhesive layer 15, a polarizing film 30, a second adhesive layer 25, and a second protective film 20 ) In this order. That is, the first protective film 10 is laminated on one surface of the polarizing film 30 through the first adhesive layer 15, and the second protective film 20 is polarized through the second adhesive layer 25 Is laminated on the other surface of the film (30). The storage elastic modulus of the first adhesive layer 15 at 80 DEG C is less than or equal to 0.1 MPa and less than 800 MPa and the storage elastic modulus of the second adhesive layer 25 at 80 DEG C is less than 800 MPa and less than 10000 MPa. The polarizing plate of the present invention having such a structure exhibits good workability (the film is difficult to peel off from the end face of the polarizing plate when processing such as cutting or end face polishing is performed) and good cold and heat shock resistance.

1, the polarizing plate according to the present invention may include layers other than those described above. Specific examples of the other layer include, for example, a pressure-sensitive adhesive layer laminated on the outer surface of the first protective film 10 and / or the second protective film 20; A separate film (also referred to as a " release film ") laminated on the outer surface of the pressure-sensitive adhesive layer; A protective film (also referred to as a " surface protective film ") laminated on the outer surface of the first protective film 10 and / or the second protective film 20; Or an optical functional film laminated on the outer surface of the first protective film 10 and / or the second protective film 20 through an adhesive layer or a pressure-sensitive adhesive layer.

The polarizing plate according to the present invention may be a long roll of the polarizing plate having the above-mentioned layer structure or a winding roll thereof. In this case, the workability refers to the workability at the time of cutting a polarizing plate sheet from a long roll or a take-up roll, and the cold and heat shock resistance refers to the resistance to cold and heat with respect to a long sheet or a roll, It says. Thermal shock resistance refers to the durability when the film is placed under an environment in which the high temperature condition and the low temperature condition are repeated as described above. More specifically, it refers to resistance to cracks and cracks of the polarizing film under the above environment.

The polarizing plate according to the present invention may be a sheet-like sheet of a polarizing plate having the layer structure. In this case, the workability refers to workability in cutting each small-sized body smaller in size from the polarizing plate wool, or workability in polishing the end face of each polarizing plate body, and the resistance to cold and heat is defined as a ratio Quot; refers to the resistance to cold and heat with respect to the polarizing plate perforated body of a smaller size.

(2) polarizing film

The polarizing film 30 is a film having a function of selectively transmitting linearly polarized light in any one direction from natural light. For example, an iodine-based polarizing film in which iodine is adsorbed and oriented on a polyvinyl alcohol-based resin film, a dye-based polarizing film in which a dichroic dye is adsorbed and oriented on a polyvinyl alcohol-based resin film, and a dichroic dye in a lyotropic liquid crystal state Coated polarizing films obtained by coating and orientation and immobilization. These polarizing films selectively transmit linearly polarized light in one direction from natural light and absorb linearly polarized light in another direction, and are called absorption type polarizing films. The polarizing film 30 is not limited to the absorption type polarizing film but may be a reflective polarizing film that selectively transmits linearly polarized light in one direction from natural light and reflects linearly polarized light in another direction, A scattering type polarizing film for scattering the polarized light may be used, but an absorbing polarizing film is preferable in view of excellent visibility. Among them, an iodine-based polarizing film excellent in the degree of polarization and transmittance is more preferable.

As the polyvinyl alcohol-based resin, a saponified polyvinyl acetate-based resin can be used. As the polyvinyl acetate resin, a copolymer of vinyl acetate, which is a homopolymer of vinyl acetate, and other monomers copolymerizable with vinyl acetate, and the like can be given. Examples of other monomers copolymerizable with vinyl acetate include (meth) acrylamides having unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids and ammonium groups, and the like.

The saponification degree of the polyvinyl alcohol-based resin is usually about 85 to 100 mol%, preferably 98 mol% or more. The polyvinyl alcohol resin may be modified. For example, polyvinyl formal or polyvinyl acetal modified with aldehydes may be used. The average degree of polymerization of the polyvinyl alcohol-based resin is usually about 1,000 to 10,000, preferably about 1,500 to 5,000. The average polymerization degree of the polyvinyl alcohol-based resin can be obtained according to JIS K 6726.

Such a film of the polyvinyl alcohol-based resin is used as the original film of the polarizing film 30. The method of forming the polyvinyl alcohol-based resin is not particularly limited, and a known method is employed. The thickness of the polyvinyl alcohol type original film is, for example, 150 占 퐉 or less, preferably 100 占 퐉 or less (for example, 50 占 퐉 or less).

The polarizing film (30) comprises a step of uniaxially stretching a polyvinyl alcohol based resin film; A step of adsorbing a dichroic dye by staining a polyvinyl alcohol-based resin film with a dichroic dye; A step of treating (crosslinking) a polyvinyl alcohol-based resin film adsorbed with a dichroic dye with an aqueous solution of boric acid; And a step of washing with water after treatment with an aqueous boric acid solution.

The uniaxial stretching of the polyvinyl alcohol based resin film can be carried out before, simultaneously with, or after dyeing the dichroic dye. When uniaxial stretching is carried out after dyeing, the uniaxial stretching may be carried out before the boric acid treatment or during the boric acid treatment. In addition, uniaxial stretching may be performed in these plural steps.

In uniaxial stretching, the film may be uniaxially stretched between rolls having different circumferential velocities, or may be uniaxially stretched using a heat roll. The uniaxial stretching may be dry stretching in which stretching is performed in the atmosphere, or wet stretching in which stretching is performed in a state in which the polyvinyl alcohol based resin film is swollen with a solvent or water. The stretching magnification is usually about 3 to 8 times.

As a method for dyeing a polyvinyl alcohol-based resin film with a dichroic dye, for example, a method of immersing the film in an aqueous solution containing a dichroic dye is employed. As the dichroic dye, iodine or a dichroic organic dye is used. On the other hand, it is preferable that the polyvinyl alcohol-based resin film is subjected to a treatment for immersion in water before the dyeing treatment.

As a dyeing treatment with iodine, a method of immersing a polyvinyl alcohol-based resin film in an aqueous solution containing iodine and potassium iodide is generally employed. The content of iodine in the aqueous solution may be about 0.01 to 1 part by weight per 100 parts by weight of water. The content of potassium iodide may be about 0.5 to 20 parts by weight per 100 parts by weight of water. The temperature of the aqueous solution may be about 20 to 40 캜. On the other hand, as a dyeing treatment with a dichroic organic dye, a method of immersing a polyvinyl alcohol-based resin film in an aqueous solution containing a dichroic organic dye is usually employed. The aqueous solution containing the dichroic organic dye may contain an inorganic salt such as sodium sulfate as a dyeing aid. The content of the dichroic organic dye in the aqueous solution may be about 1 × 10 ^-4 to 10 parts by weight per 100 parts by weight of water. The temperature of the aqueous solution may be about 20 to 80 캜.

As the boric acid treatment after dyeing with the dichroic dye, a method of immersing the dyed polyvinyl alcohol resin film in an aqueous solution containing boric acid is employed. When iodine is used as the dichroic dye, it is preferable that the aqueous solution containing boric acid contains potassium iodide. The amount of boric acid in the aqueous solution containing boric acid may be about 2 to 15 parts by weight per 100 parts by weight of water. The amount of potassium iodide in the aqueous solution may be about 0.1 to 20 parts by weight per 100 parts by weight of water. The temperature of the aqueous solution may be 50 ° C or higher, for example, 50 to 85 ° C.

The polyvinyl alcohol resin film after boric acid treatment is usually subjected to water washing treatment. The water washing treatment can be carried out, for example, by immersing a boric acid-treated polyvinyl alcohol resin film in water. The temperature of the water in the water washing treatment is usually about 5 to 40 캜. After washing with water, a drying treatment is performed to obtain a polarizing film (30). The drying treatment can be performed using a hot-air dryer or a far-infrared heater. A polarizing plate can be obtained by bonding a protective film to both surfaces of the polarizing film 30 using an adhesive.

As another example of the method for producing the polarizing film 30, there may be mentioned, for example, the methods described in JP-A-2000-338329 and JP-A-2012-159778. In this method, a solution containing a polyvinyl alcohol-based resin is applied to the surface of a base film to provide a resin layer, and then a laminated film comprising a base film and a resin layer is stretched, followed by dyeing and crosslinking To form a polarizer layer (polarizing film layer) as a resin layer. The polarizing laminated film comprising a base film and a polarizer layer is obtained by bonding a protective film to a surface of a polarizer layer, then peeling off the base film, and peeling off the base film to expose the surface of the polarizer layer, A polarizing plate can be obtained by bonding a protective film.

The thickness of the polarizing film 30 may be 40 占 퐉 or less, and preferably 30 占 퐉 or less (e.g., 20 占 퐉 or less). On the other hand, according to the methods described in Japanese Patent Application Laid-Open Nos. 2000-338329 and 2012-159778, a polarizing film 30 of a thin film can be more easily manufactured, For example, 20 占 퐉 or less, and further, 10 占 퐉 or less. The thickness of the polarizing film 30 is usually 2 占 퐉 or more. Reducing the thickness of the polarizing film 30 is advantageous for reducing the thickness of the polarizing plate and hence the image display apparatus.

(3) Protective film

The first protective film 10 and the second protective film 20 are each formed of a thermoplastic resin having light transmittance (preferably optically transparent) such as a chain polyolefin resin (polypropylene resin or the like), a cyclic polyolefin resin Norbornene resin and the like); Cellulose ester-based resins such as triacetylcellulose and diacetylcellulose; Polyester resins such as polyethylene terephthalate, polyethylene naphthalate and polybutylene terephthalate; Polycarbonate resin; (Meth) acrylic resins; Or a mixture or copolymer thereof, or the like. On the other hand, "(meth) acryl" means methacryl and / or acryl, and "(meth)" when "(meth) acrylate" Among them, the first protective film 10 and the second protective film 20 are preferably made of a resin selected from the group consisting of a polyester resin, a polycarbonate resin, a polyolefin resin, a (meth) acrylic resin and a cellulose ester resin .

The first protective film 10 and the second protective film 20 may each be a film that is not stretched or a film that is uniaxially or biaxially stretched. Biaxial stretching may be simultaneous biaxial stretching in which two stretching directions are simultaneously performed, or sequential biaxial stretching in which stretching is performed in a predetermined direction and then stretching in another direction. The first protective film 10 and / or the second protective film 20 may be a protective film having an optical function such as a retardation film. The retardation film is an optical functional film used for the purpose of compensating a retardation by a liquid crystal cell serving as an image display element. For example, a retardation film having an arbitrary retardation value can be obtained by stretching (uniaxially stretching or biaxially stretching) a film made of the thermoplastic resin, or forming a liquid crystal layer or the like on the film.

Examples of the chain polyolefin-based resin include a homopolymer of a chain olefin such as a polyethylene resin and a polypropylene resin, and a copolymer composed of two or more chain olefins.

The cyclic polyolefin-based resin is a generic name of a resin containing, as a polymerization unit, a cyclic olefin represented by norbornene or tetracyclododecene (alias: dimethano-octahydronaphthalene) or a derivative thereof. Specific examples of the cyclic polyolefin-based resin include ring-opened (co) polymers of cyclic olefins and hydrogenated products thereof, addition polymers of cyclic olefins, copolymers of cyclic olefins and chain olefins such as ethylene and propylene, or aromatic compounds having vinyl groups, And modified (co) polymers obtained by modifying these with an unsaturated carboxylic acid or a derivative thereof. Among them, a norbornene resin using a norbornene monomer such as norbornene or a polycyclic norbornene monomer as the cyclic olefin is preferably used.

The cellulose ester-based resin may be a mixed ester in which at least a part of the hydroxyl groups in cellulose are converted into acetic ester, and some of them are acetic acid esterified and some of them are esterified with other acid. The cellulose ester-based resin is preferably an acetylcellulose-based resin. Specific examples of the acetylcellulose-based resin include triacetylcellulose, diacetylcellulose, cellulose acetate propionate, and cellulose acetate butyrate.

The polyester-based resin is a resin other than the above-mentioned cellulose ester-based resin having an ester bond, and is generally composed of a polycondensation product of a polyvalent carboxylic acid or a derivative thereof and a polyhydric alcohol. Specific examples of the polyester-based resin include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polytrimethylene terephthalate, polytrimethylene naphthalate, polycyclohexanedimethyl terephthalate, polycyclohexane Dimethyl naphthalate. Among them, polyethylene terephthalate is preferably used from the viewpoints of mechanical properties, solvent resistance, scratch resistance, cost and the like. Polyethylene terephthalate means a resin in which at least 80 mol% of the repeating units are composed of ethylene terephthalate, and may contain constituent units derived from other copolymerizable components.

Other copolymerization components include a dicarboxylic acid component and a diol component. Examples of the dicarboxylic acid component include isophthalic acid, 4,4'-dicarboxydiphenyl, 4,4'-dicarboxybenzophenone, bis (4-carboxyphenyl) ethane, adipic acid, sebacic acid, Phthalic acid, phosgophthalic acid, and 1,4-dicarboxycyclohexane. Examples of the diol component include propylene glycol, butanediol, neopentyl glycol, diethylene glycol, cyclohexanediol, ethylene oxide adduct of bisphenol A, polyethylene glycol, polypropylene glycol, and polytetramethylene glycol. The dicarboxylic acid component and the diol component may be used in combination of two or more kinds, if necessary. In addition to the dicarboxylic acid component and the diol component, a hydroxycarboxylic acid such as p-hydroxybenzoic acid and p-s-hydroxyethoxybenzoic acid may be used in combination. As other copolymerization components, a small amount of a dicarboxylic acid component and / or a diol component having an amide bond, a urethane bond, an ether bond, a carbonate bond or the like may be used.

The polycarbonate resin is a polyester formed from carbonic acid and glycol or bisphenol. Among them, an aromatic polycarbonate having a diphenylalkane in its molecular chain is preferably used from the viewpoints of heat resistance, weather resistance and acid resistance. As the polycarbonate, there may be mentioned 2,2-bis (4-hydroxyphenyl) propane (alicyclic bisphenol A), 2,2-bis (4-hydroxyphenyl) butane, And polycarbonates derived from bisphenols such as hexane, 1,1-bis (4-hydroxyphenyl) isobutane, and 1,1-bis (4-hydroxyphenyl) ethane.

The (meth) acrylic resin may be a polymer containing methacrylic acid ester as a main monomer (containing 50% by weight or more), and is preferably a copolymer in which a small amount of another copolymerizable component is copolymerized. The (meth) acrylic resin is more preferably a copolymer of methyl methacrylate and methyl acrylate, and the third monofunctional monomer may be further copolymerized.

Examples of the third monofunctional monomer include ethyl methacrylate, butyl methacrylate, cyclohexyl methacrylate, phenyl methacrylate, benzyl methacrylate, 2-ethylhexyl methacrylate, 2- Methacrylic acid esters other than methyl methacrylate such as ethyl; Acrylic acid esters such as ethyl acrylate, butyl acrylate, cyclohexyl acrylate, phenyl acrylate, benzyl acrylate, 2-ethylhexyl acrylate, and 2-hydroxyethyl acrylate; Hydroxyalkyl acrylate esters such as methyl 2- (hydroxymethyl) acrylate, methyl 2- (1-hydroxyethyl) acrylate, ethyl 2- (hydroxymethyl) acrylate and butyl 2- (hydroxymethyl) acrylate; Unsaturated acids such as methacrylic acid and acrylic acid; Halogenated styrenes such as chlorostyrene and bromostyrene; Substituted styrenes such as vinyltoluene and? -Methylstyrene; Unsaturated nitriles such as acrylonitrile and methacrylonitrile; Unsaturated acid anhydrides such as maleic anhydride and citraconic anhydride; And unsaturated imides such as phenylmaleimide and cyclohexylmaleimide. The third monofunctional monomer may be used alone, or two or more monofunctional monomers may be used in combination.

A polyfunctional monomer may be further copolymerized with the (meth) acrylic resin. Examples of the polyfunctional monomer include ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, tetraethylene glycol di (meth) (Meth) acrylate, and tetradecaethylene glycol di (meth) acrylate; esterified with (meth) acrylic acid at both terminal hydroxyl groups of the oligomer; Propylene glycol or an oligomer thereof, both terminal hydroxyl groups being esterified with (meth) acrylic acid; (Meth) acrylic acid ester of a hydroxyl group of a dihydric alcohol such as neopentyl glycol di (meth) acrylate, hexanediol di (meth) acrylate and butanediol di (meth) acrylate; Bisphenol A, an alkylene oxide adduct of bisphenol A, or both terminal hydroxyl groups of the halogen substituents thereof esterified with (meth) acrylic acid; Trimethylol propane and pentaerythritol esterified with (meth) acrylic acid, and those in which epoxy groups of glycidyl (meth) acrylate are ring-opening added to these terminal hydroxyl groups; A dibasic acid such as succinic acid, adipic acid, terephthalic acid, phthalic acid, and halogen substituents thereof, and an alkylene oxide adduct thereof, and the like, in which an epoxy group of glycidyl (meth) acrylate is ring- Aryl (meth) acrylate; And aromatic divinyl compounds such as divinylbenzene. Among them, ethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate and neopentyl glycol dimethacrylate are preferably used.

The (meth) acrylic resin may also be modified by a reaction between the functional groups of the copolymer. Examples of the reaction include a condensation reaction in a polymer chain between a methyl ester group of methyl acrylate and a hydroxyl group of 2- (hydroxymethyl) acrylate, a condensation reaction between a carboxyl group of acrylic acid and a hydroxyl group of 2- (hydroxymethyl) A dehydration condensation reaction in a polymer chain, and the like.

The glass transition temperature of the (meth) acrylic resin is preferably 80 to 160 ° C. The glass transition temperature is determined by the polymerization ratio of the methacrylic acid ester monomer and the acrylic ester monomer, the carbon chain length of each ester group, the kind of the functional group contained therein, and the polymerization ratio of the polyfunctional monomer to the whole monomer .

As a means for increasing the glass transition temperature of the (meth) acrylic resin, it is also effective to introduce a ring structure into the main chain of the polymer. The ring structure is preferably a heterocyclic structure such as a cyclic acid anhydride structure, a cyclic imide structure, and a lactone structure. Specifically, a lactone ring structure such as a cyclic imide structure such as an anhydroglutaric acid structure, an anhydrous succinic acid structure and the like, a glutarimide structure and a zwitterimide structure, and a lactone ring structure such as butyrolactone and valerolactone, . The larger the content of the ring structure in the main chain, the higher the glass transition temperature of the (meth) acrylic resin. The cyclic acid anhydride structure and the cyclic imide structure may be introduced by copolymerization of a monomer having a cyclic structure such as maleic anhydride and maleimide, a method of introducing a cyclic acid anhydride structure by a dehydration / A method in which an amino compound is reacted to introduce a cyclic imide structure, or the like. The resin (polymer) having a lactone ring structure can be prepared by preparing a polymer having a hydroxyl group and an ester group in a polymer chain, and then, by heating, the hydroxyl group and the ester group in the obtained polymer are reacted Followed by cyclization and condensation in the presence of a catalyst to form a lactone ring structure.

The (meth) acrylic resin may contain additives as required. Examples of additives include lubricants, antiblocking agents, heat stabilizers, antioxidants, antistatic agents, light stabilizers, impact resistance improvers, surfactants and the like.

The (meth) acrylic resin may contain acrylic rubber particles, which are impact modifiers, from the viewpoints of the film formability to the film and the impact resistance of the film. The acrylic rubber particles are particles composed of an elastomer mainly composed of an acrylate ester as an essential component and substantially of a single layer structure composed of only this elastomer but those having a multilayer structure composed of this elastomer as a single layer have. Examples of the elastomer include a crosslinked elastic copolymer comprising an alkyl acrylate as a main component and another copolymerizable vinyl monomer and a crosslinkable monomer copolymerized with the alkyl acrylate. Examples of the alkyl acrylate which is the main component of the elastomer include alkyl acrylates such as methyl acrylate, ethyl acrylate, butyl acrylate, and 2-ethylhexyl acrylate. The alkyl groups include those having 1 to 8 carbon atoms. Is preferably used. Examples of other vinyl monomers copolymerizable with the alkyl acrylate include compounds having one polymerizable carbon-carbon double bond in the molecule, and more specifically, methacrylic acid esters such as methyl methacrylate, The same aromatic vinyl compounds, and vinyl cyan compounds such as acrylonitrile. Examples of the crosslinking monomer include crosslinkable compounds having at least two polymerizable carbon-carbon double bonds in the molecule, and more specifically, ethylene glycol di (meth) acrylate, butanediol di (meth) acrylate and (Meth) acrylates of the same polyhydric alcohol, alkenyl esters of (meth) acrylic acid such as allyl (meth) acrylate, and divinylbenzene.

A laminate of a film made of a (meth) acrylic resin containing no rubber particles and a film made of a (meth) acrylic resin containing rubber particles may be used as a protective film. The (meth) acrylic resin layer may be formed on one side or both sides of the retardation developing layer made of a resin different from the (meth) acrylic resin so that the retardation is expressed as a protective film.

The first protective film 10 and / or the second protective film 20 may contain an ultraviolet absorber. When a polarizing plate is applied to an image display apparatus such as a liquid crystal display apparatus, a protective film containing an ultraviolet absorber is disposed on the visual side of an image display element (e.g., a liquid crystal cell) to suppress deterioration of the image display element by ultraviolet rays . Examples of the ultraviolet absorber include a salicylic ester compound, a benzophenone compound, a benzotriazole compound, a cyanoacrylate compound, and a nickel complex salt compound.

The first protective film 10 and the second protective film 20 may be a film made of the same resin or a film made of different resins. An example of the combination of the first protective film 10 and the second protective film 20 is a combination of the first protective film 10 bonded through the first adhesive layer 15 having a lower storage elastic modulus at 80 캜 (Meth) acrylic resin, and the second protective film 20 bonded via the second adhesive layer 25 having a larger storage elastic modulus is composed of a polyolefin resin or a cellulose ester resin. As described above, when the first protective film 10 and the second protective film 20 are compared with each other, a protective film having a lower mechanical property (breaking stress) can be polarized through the first adhesive layer 15 having a lower storage elastic modulus By laminating them on the film 30, the workability can be further improved. The first protective film 10 and the second protective film 20 may be the same or different in thickness, presence or absence of additives, kind thereof, retardation characteristics, and the like.

The first protective film 10 and / or the second protective film 20 may have a hard coat layer, an antiglare layer, an antireflection layer, a light diffusion layer, an antistatic layer, (Coating layer) such as an antifouling layer, a conductive layer, or the like.

The thicknesses of the first protective film 10 and the second protective film 20 are generally 5 to 200 μm, preferably 10 to 120 μm, and more preferably 10 to 85 μm. Reducing the thicknesses of the first protective film 10 and the second protective film 20 is advantageous for reducing the thickness of the polarizing plate and the image display apparatus. As the thickness of the first protective film 10 and the thickness of the second protective film 20 are reduced, the cold and heat shock resistance of the polarizing plate can be effectively improved.

(4) Adhesive layer

The storage elastic modulus of the first adhesive layer 15 at 80 DEG C is less than or equal to 0.1 MPa and less than 800 MPa and the storage elastic modulus of the second adhesive layer 25 at 80 DEG C is less than 800 MPa and less than 10000 MPa. When the storage elastic modulus of the first adhesive layer 15 and the second adhesive layer 25 satisfy this relationship, the workability of the polarizing plate and the resistance to cold and heat shock can be highly compatible. The storage elastic modulus of the adhesive layer is measured by the method described in the section of Examples to be described later.

The storage elastic modulus of the first adhesive layer 15 at 80 캜 is preferably 600 MPa or less, more preferably 400 MPa or less, further preferably 200 MPa or less, particularly preferably 20 MPa or less, 100 MPa or less. On the other hand, if the storage elastic modulus of the first adhesive layer 15 is too low, even if the storage elastic modulus of the second adhesive layer 25 is within a predetermined range, the polarizing plate 30 is inferior to the polarizing film 30 Problems such as cracks and cracks may occur. Therefore, the storage elastic modulus of the first adhesive layer 15 at 80 캜 is preferably 0.5 MPa or more, more preferably 1 MPa or more, particularly preferably 5 MPa or more, particularly preferably 10 MPa or more .

The storage elastic modulus of the second adhesive layer 25 at 80 캜 is preferably 900 MPa or more, more preferably 1000 MPa or more, and more preferably 1500 MPa or more, in view of the durability of the polarizing plate, MPa, particularly preferably not less than 2000 MPa. On the other hand, if the storage elastic modulus of the second adhesive layer 25 is too high, the processability may be lowered even if the storage elastic modulus of the first adhesive layer 15 is within a predetermined range. Therefore, the storage elastic modulus of the second adhesive layer 25 at 80 캜 is preferably 8000 MPa or less, more preferably 6000 MPa or less, further preferably 5000 MPa or less.

The difference between the storage elastic modulus at 80 ° C of the second adhesive layer 25 and the storage elastic modulus at 80 ° C of the first adhesive layer 15 is preferably 100 MPa or more, More preferably 500 MPa or more, particularly 900 MPa or more, more preferably 1000 MPa or more, and particularly preferably 2000 MPa or more (2500 MPa or more, for example).

The adhesive for forming the first adhesive layer 15 and the second adhesive layer 25 is not particularly limited as long as the predetermined storage elastic modulus can be obtained and may be an aqueous adhesive, heat or ultraviolet rays, visible light, electron beam, X And a curable adhesive which is cured by irradiation of an active energy ray such as a wire. The curable adhesive includes a curable (polymerizable) compound as a main component. Specific examples of the water-based adhesives include those obtained by dissolving a polyvinyl alcohol resin or a urethane resin as a main component in water or dispersed in water, such as polyaldehyde, a melamine compound, a zirconia compound, a zinc compound, a glyoxal and a water- And may contain a curing component or a crosslinking agent. When a curable adhesive (including a case where the water-based adhesive contains a curable component or a cross-linking agent) is used, the adhesive layer formed therefrom is a cured layer of the curable adhesive.

Of these, a drying step for removing the solvent by heating can be omitted, so that a curable adhesive is preferable, and an active energy ray curable adhesive is more preferable. Water-based adhesives and thermosetting adhesives require a heating process, which may cause curling of the polarizing plate. In the form of a polarizing plate using an active energy ray-curable adhesive, at least one of the first adhesive layer 15 and the second adhesive layer 25 may be a cured layer of an active energy ray-curable adhesive, It is preferable that both the first adhesive layer 15 and the second adhesive layer 25 are cured layers of an active energy ray-curable adhesive.

The storage elastic modulus of the first adhesive layer 15 and the second adhesive layer 25 at 80 캜 can be adjusted, for example, according to the following guidelines. That is, in the case of forming the adhesive layer with the curable adhesive, the storage modulus of the adhesive layer depends on the structure of the curable compound contained as the main component in the curable adhesive and the combination of the curable compounds. For example, when the curable compound contains an alicyclic epoxy compound or an aromatic epoxy compound, the storage elastic modulus tends to be high, and when the aliphatic epoxy compound is included, the storage elastic modulus tends to be low. The storage elastic modulus of the adhesive layer can be adjusted by the degree of crosslinking of the curable compound. For example, when the amount of the curable compound having three or more functional groups is increased, the storage elastic modulus of the adhesive layer tends to be high. The storage elastic modulus of the adhesive layer can be adjusted by adding a component other than the main component to the curable adhesive. For example, when the polymer component (thermoplastic resin or the like) is added, the storage elastic modulus of the adhesive layer tends to be lowered.

The curable adhesive is classified into a cationic polymerizable adhesive containing a cationic polymerizable compound as the curable compound, a radical polymerizable adhesive containing a radically polymerizable compound as the curable compound, a cationic polymerizable compound and a radical And a hybrid type curable adhesive containing both of the polymerizable compound and the like. Specific examples of the cationic polymerizable compound include an epoxy compound having at least one epoxy group in the molecule, an oxetane compound having at least one oxetane ring in the molecule, and a vinyl compound. Specific examples of the radical polymerizable compound include a (meth) acrylic compound and a vinyl compound having at least one (meth) acryloyl group in the molecule. The curable adhesive may contain one kind or two or more kinds of cationic polymerizable compounds and / or may include one kind or two or more kinds of radical polymerizable compounds.

(4-1) Cationic polymerization type adhesive

The cationic polymerizable compound, which is the main component of the cationic polymerization type adhesive, refers to a compound or oligomer that undergoes cationic polymerization reaction and is cured by irradiation or heating of active energy rays such as ultraviolet rays, visible rays, electron rays, and X rays, Cetane compounds, vinyl compounds, and the like. Among them, the preferred cationic polymerizable compound is an epoxy compound. The epoxy compound is a compound having at least one epoxy group, preferably at least two epoxy groups in the molecule. The epoxy compound may be used alone, or two or more epoxy compounds may be used in combination. Examples of the epoxy compound include an alicyclic epoxy compound, an aromatic epoxy compound, a hydrogenated epoxy compound, and an aliphatic epoxy compound. Among them, from the viewpoints of weatherability, curing rate and adhesiveness, the epoxy compound preferably contains an alicyclic epoxy compound or an aliphatic epoxy compound, and more preferably an alicyclic epoxy compound.

The alicyclic epoxy compound is a compound having at least one epoxy group bonded to an alicyclic ring in the molecule. The "epoxy group bonded to the alicyclic ring" means a bridging oxygen atom -O- in the structure represented by the following formula (I). In the following formula (I), m is an integer of 2 to 5.

A compound in which one or more hydrogen atoms of the (CH ₂ ) _m in the formula (I) are removed from other groups in the chemical structure may be an alicyclic epoxy compound. (CH ₂ ) _m may be suitably substituted with a straight chain alkyl group such as methyl group or ethyl group.

Among them, an alicyclic epoxy compound having an epoxy cyclopentane structure (wherein m = 3 in the above formula (I)) and an epoxy cyclohexane structure (wherein m = 4 in the above formula (I) It is advantageous in increasing the storage elastic modulus and is also advantageous in terms of adhesion between the polarizing film and the protective film. Specific examples of the alicyclic epoxy compound are given below. Here, the compound names are given first, and then the corresponding chemical formulas are shown. The compound names and the corresponding chemical formulas are given the same reference numerals.

A: 3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate, 3,4-

B: 3,4-epoxy-6-methylcyclohexylmethyl 3,4-epoxy-6-methylcyclohexanecarboxylate,

C: Ethylene bis (3,4-epoxycyclohexanecarboxylate),

D: bis (3,4-epoxycyclohexylmethyl) adipate,

E: bis (3,4-epoxy-6-methylcyclohexylmethyl) adipate,

F: diethylene glycol bis (3,4-epoxycyclohexylmethyl ether),

G: ethylene glycol bis (3,4-epoxycyclohexylmethyl ether),

H: 2,3,14,15-diepoxy-7,11,18,21-tetraoxatrispyro [5.2.2.5.2.2] henichnoic acid,

I: 3- (3,4-epoxycyclohexyl) -8,9-epoxy-1,5-dioxaspiro [5.5] undecane,

J: 4-vinylcyclohexene dioxide,

K: limonene dioxide,

L: bis (2,3-epoxycyclopentyl) ether,

M: dicyclopentadiene dioxide.

An aromatic epoxy compound is a compound having an aromatic ring and an epoxy group in a molecule. Specific examples thereof include bisphenol-type epoxy compounds such as diglycidyl ether of bisphenol A, diglycidyl ether of bisphenyl F and diglycidyl ether of bisphenol S, or oligomers thereof; Novolak type epoxy resins such as phenol novolak epoxy resin, cresol novolak epoxy resin and hydroxybenzaldehyde phenol novolac epoxy resin; A multifunctional epoxy compound such as glycidyl ether of 2,2 ', 4,4'-tetrahydroxydiphenylmethane and glycidyl ether of 2,2', 4,4'-tetrahydroxybenzophenone; Epoxidized polyvinylphenol, and the like.

The hydrogenated epoxy compound is a glycidyl ether of a polyol having an alicyclic ring and is obtained by subjecting an aromatic polyol to a hydrogenation reaction selectively to an aromatic ring under a pressure in the presence of a catalyst to obtain a glycidyl ether It may have been anger. Specific examples of the aromatic polyol include bisphenol-type compounds such as bisphenol A, bisphenol F, and bisphenol S; Novolak type resins such as phenol novolac resin, cresol novolak resin and hydroxybenzaldehyde phenol novolac resin; Tetrahydroxydiphenylmethane, tetrahydroxybenzophenone, polyvinylphenol, and the like. A glycidyl ether can be obtained by reacting epichlorohydrin with an alicyclic polyol obtained by hydrogenating an aromatic ring of an aromatic polyol. Of the hydrogenated epoxy compounds, diglycidyl ethers of hydrogenated bisphenol A can be mentioned.

The aliphatic epoxy compound is a compound having at least one oxirane ring (3-membered cyclic ether) bonded to an aliphatic carbon atom in the molecule. Monofunctional epoxy compounds such as butyl glycidyl ether and 2-ethylhexyl glycidyl ether; Hexanediol diglycidyl ether, 1,4-butanediol diglycidyl ether, 1,6-hexanediol diglycidyl ether, neopentyl glycol diglycidyl ether and 1,4-cyclohexanedimethanol diglycidyl ether. Epoxy compounds; Trifunctional or higher epoxy compounds such as trimethylolpropane triglycidyl ether and pentaerythritol tetraglycidyl ether; 4-vinylcyclohexene dioxide, limonene dioxide, and the like, and epoxy compounds having an oxirane ring bonded to an aliphatic carbon atom. Among them, a bifunctional epoxy compound (also referred to as an aliphatic diepoxide compound) having two oxirane rings bonded to aliphatic carbon atoms in the molecule is preferable from the viewpoint of adhesion between the polarizing film and the protective film. Such a suitable aliphatic diepoxy compound can be represented, for example, by the following formula (II).

Y in the formula (II) is an alkylene group having 2 to 9 carbon atoms, an alkylene group having 4 to 9 carbon atoms in total having an ether bond, or a divalent hydrocarbon group having 6 to 18 carbon atoms and having an alicyclic structure.

Specific examples of the aliphatic diepoxy compound represented by the formula (II) include diglycidyl ether of an alkanediol, diglycidyl ether of an oligoalkylene glycol having up to about 4 repeating units, or di Glycidyl ether.

Specific examples of the diol (glycol) capable of forming the aliphatic diepoxy compound represented by the formula (II) are shown below. Examples of the alkanediol include ethylene glycol, propylene glycol, 1,3-propanediol, 2-methyl-1,3-propanediol, 2-butyl-2-ethyl-1,3-propanediol, Pentanediol, 3-methyl-2,4-pentanediol, 2,4-pentanediol, 1,5-pentanediol, Pentanediol, 1,6-hexanediol, 1,7-heptanediol, 3,5-heptanediol, 1,8-octanediol, 2-methyl- Octanediol, 1,9-nonanediol, and the like. Examples of the oligoalkyleneglycol include diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol and the like. Examples of the alicyclic diols include cyclohexanediol such as 1,2-cyclohexanediol, 1,3-cyclohexanediol and 1,4-cyclohexanediol, 1,2-cyclohexanedimethanol, 1,3-cyclohexanediol And cyclohexanedimethanol such as methanol and 1,4-cyclohexanedimethanol.

The oxetane compound, which is one of the cationic polymerizable compounds, is a compound containing at least one oxetane ring (oxetanyl group) in the molecule, and specific examples thereof include 3-ethyl-3-hydroxymethyloxetane Ethylxoxymethyl} benzene (also referred to as xylylene bisoxetane), 3-ethyl-2-ethylhexyloxycetane, 3 - [(3-ethyloxetane-3-yl) methoxy} methyl] oxetane, 3-ethyl-3- (phenoxymethyl) oxetane, 3- (cyclohexyloxy) Cetane. The oxetane compound may be used as a main component of the cationic polymerizable compound or may be used in combination with an epoxy compound. When the oxetane compound is used in combination, the curing rate and adhesiveness may be improved.

Examples of the vinyl compound which can be a cationic polymerizable compound include aliphatic or alicyclic vinyl ether compounds. Specific examples thereof include n-amyl vinyl ether, i-amyl vinyl ether, n-hexyl vinyl ether, vinyl ethers of an alkyl or alkenyl alcohol having 5 to 20 carbon atoms such as n-octyl vinyl ether, 2-ethylhexyl vinyl ether, n-dodecyl vinyl ether, stearyl vinyl ether and oleyl vinyl ether; Hydroxyl group-containing vinyl ethers such as 2-hydroxyethyl vinyl ether, 3-hydroxypropyl vinyl ether and 4-hydroxybutyl vinyl ether; Vinyl ethers of aliphatic rings or monoalcohols having aromatic rings such as cyclohexyl vinyl ether, 2-methylcyclohexyl vinyl ether, cyclohexylmethyl vinyl ether and benzyl vinyl ether; Butanediol divinyl ether, 1,4-butanediol divinyl ether, 1,6-hexanediol divinyl ether, neopentyl glycol divinyl ether, pentaerythritol divinyl ether, pentaerythritol tetravinyl Ether, trimethylolpropane divinyl ether, trimethylolpropane trivinyl ether, 1,4-dihydroxycyclohexane monovinyl ether, 1,4-dihydroxycyclohexane divinyl ether, 1,4-dihydroxymethyl Mono-polyvinyl ethers of polyhydric alcohols such as cyclohexane monovinyl ether and 1,4-dihydroxymethylcyclohexane divinyl ether; Polyalkylene glycol mono-divinyl ether such as diethylene glycol divinyl ether, triethylene glycol divinyl ether, and diethylene glycol monobutyl monovinyl ether; Glycidyl vinyl ether, ethylene glycol vinyl ether methacrylate, and other vinyl ethers. The vinyl compound may be used as a main component of a cationic polymerizable compound, or may be used in combination with an epoxy compound, an epoxy compound and an oxetane compound. When the vinyl compound is used in combination, the curing rate and the viscosity of the adhesive can be improved in some cases.

The cationic polymerization type adhesive may further include cationic polymerizable compounds other than those described above such as cyclic lactone compounds, cyclic acetal compounds, cyclic thioether compounds, and spiroorthoester compounds.

From the viewpoint of the adhesion between the polarizing film and the protective film, when the total amount of the curable compound contained in the cationic polymerization type adhesive (including the case of the hybrid type curable adhesive) is 100 wt%, the content of the cationic polymerizable compound (The content of all the cationic polymerizable compounds contained in the cationic polymerization type adhesive, and when two or more cationic polymerizable compounds are included, the total content thereof) is preferably 50% by weight or more, more preferably 60% , More preferably 70 wt% or more. Further, as described above, the cationic polymerization type adhesive may further include a polymer component (such as a thermoplastic resin). This makes it possible to lower the storage modulus of the adhesive layer or improve the adhesion between the polarizing film and the protective film.

The cationic polymerizable adhesive may be active energy ray curable or thermally curable, but it is preferably active energy ray curable because the step of heating can be omitted and curling of the polarizing plate by this heating can be prevented. When a cationic polymerizable adhesive containing a cationic polymerizable compound is imparted with active energy ray curability, it is preferable to add a cationic polymerization initiator to the adhesive. The cationic ionic polymerization initiator generates a cationic species or a Lewis acid by irradiation of an active energy ray such as visible light, ultraviolet ray, X-ray or electron beam to initiate the polymerization reaction of the cationically curable compound. Since the cationic ionic polymerization initiator acts catalytically with light, it is excellent in storage stability and workability even when mixed with a cationic ionic compound. Examples of the compound capable of generating a cationic species or a Lewis acid by irradiation with an active energy ray include an onium salt such as an aromatic iodonium salt and an aromatic sulfonium salt, an aromatic diazonium salt, and an iron-arene complex.

The aromatic iodonium salt is a compound having a diaryliodonium cation, and as the cation, a diphenyliodonium cation is typically exemplified. The aromatic sulfonium salt is a compound having a triarylsulfonium cation. Typical examples of the cation include triphenylsulfonium cation and 4,4'-bis (diphenylsulfonium) diphenylsulfide cation. have. The aromatic diazonium salt is a compound having a diazonium cation, and as the cation, a benzene diazonium cation is typically exemplified. In addition, the iron-arene complex is typically a cyclopentadienyl iron (II) arene cation complex.

The cations described above are paired with anions to form a cationic polymerization initiator. Examples of anions constituting the photocationic polymerization initiator include special phosphorus anion [(Rf) _n PF _6-n ] ^- , hexafluorophosphate anion PF ₆ ^- , hexafluoroantimonate anion SbF ₆ ^- , pentafluoro by hydroxy antimonate anion SbF ₅ (OH) ^-, hexafluoro-acetoxy anion AsF ₆ ^-, anion as tetrafluoroborate BF ₄ ^-, tetrakis (pentafluorophenyl) borate anion B (C ₆ F _{5) 4} ^- and so on. Among them, a special phosphorus anion [(Rf) _n PF _{6 -n} ] ^- and a hexafluorophosphate anion PF ₆ ^- are preferable from the viewpoints of the curability of the cationic polymerizable compound and the safety of the resulting adhesive layer.

The cationic ionic polymerization initiator may be used alone, or two or more of them may be used in combination. Among them, an aromatic sulfonium salt is preferably used because it has an ultraviolet ray-absorbing property even in a wavelength range of around 300 nm and is therefore excellent in curability and can give a cured product having good mechanical strength and adhesive strength.

The blending amount of the photocationic polymerization initiator is usually 0.5 to 10 parts by weight, preferably 6 parts by weight or less, based on 100 parts by weight of the cationic polymerizable compound. By adding not less than 0.5 part by weight of a cationic ion polymerization initiator, the cationic polymerizable compound can be sufficiently cured and high mechanical strength and adhesive strength can be imparted to the obtained polarizing plate. On the other hand, if the amount is excessively large, the amount of the ionic substance in the cured product increases, so that the hygroscopicity of the cured product increases, and the durability of the polarizing plate may decrease.

As described above, a hybrid type curable adhesive can also be obtained by adding a cationic polymerizable compound to a cationic polymerizable adhesive to contain a radical polymerizable compound. By using the radical polymerizable compound in combination, it is possible to expect an effect of increasing the hardness and mechanical strength of the adhesive layer, and furthermore, the viscosity and the curing speed of the curable adhesive can be further easily adjusted.

(4-2) Radical polymerization type adhesive

The radically polymerizable compound as a main component of the radical polymerization type adhesive is a compound or oligomer which undergoes a radical polymerization reaction and is cured by irradiation or heating of an active energy ray such as ultraviolet ray, visible ray, electron ray or X ray, A compound having an unsaturated bond is exemplified. Examples of the compound having an ethylenically unsaturated bond include styrene, styrene sulfonic acid, vinyl acetate, vinyl propionate, N-vinyl-2-pyrrolidone, and the like, in addition to the (meth) acrylic compound having at least one (meth) acryloyl group in the molecule And the like. Among them, the preferred radically polymerizable compound is a (meth) acrylic compound.

The (meth) acrylic compound is a compound obtained by reacting two or more kinds of (meth) acrylate monomers having at least one (meth) acryloyloxy group in the molecule, (meth) acrylamide monomer and functional group- (Meth) acryloyl group-containing compounds such as (meth) acryloyl groups having at least two (meth) acryloyl groups. The (meth) acryl oligomer is preferably a (meth) acrylate oligomer having at least two (meth) acryloyloxy groups in the molecule. The (meth) acrylic compound may be used alone, or two or more kinds thereof may be used in combination.

(Meth) acrylate monomers include monofunctional (meth) acrylate monomers having one (meth) acryloyloxy group in the molecule, bifunctional (meth) acrylate monomers having two (meth) acryloyloxy groups in the molecule (Meth) acrylate monomers having three or more (meth) acryloyloxy groups in the molecule.

Examples of monofunctional (meth) acrylate monomers include alkyl (meth) acrylates. In the alkyl (meth) acrylate, the alkyl group may be straight-chain or branched if it has 3 or more carbon atoms. Specific examples of the alkyl (meth) acrylate include methyl (meth) acrylate, ethyl (meth) acrylate, isopropyl (meth) acrylate, butyl (meth) acrylate, isobutyl Butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate and the like. Also, aralkyl (meth) acrylates such as benzyl (meth) acrylate; (Meth) acrylates of terpene alcohols such as isobornyl (meth) acrylate; (Meth) acrylate having a tetrahydrofurfuryl structure such as tetrahydrofurfuryl (meth) acrylate; Cycloalkyl groups such as cyclohexyl (meth) acrylate, cyclohexylmethyl methacrylate, dicyclopentanyl acrylate, dicyclopentenyl (meth) acrylate, 1,4-cyclohexanedimethanol monoacrylate, (Meth) acrylate; Aminoalkyl (meth) acrylates such as N, N-dimethylaminoethyl (meth) acrylate; (Meth) acrylate having an ether linkage at an alkyl moiety such as 2-phenoxyethyl (meth) acrylate, dicyclopentenyloxyethyl (meth) acrylate, ethylcarbitol (meth) acrylate and phenoxypolyethylene glycol (Meth) acrylate may also be used as the monofunctional (meth) acrylate monomer.

Further, a monofunctional (meth) acrylate having a hydroxyl group at the alkyl moiety or a monofunctional (meth) acrylate having a carboxyl moiety at the alkyl moiety may also be used. Specific examples of the monofunctional (meth) acrylate having a hydroxyl group at the alkyl moiety are 2-hydroxyethyl (meth) acrylate, 2- or 3-hydroxypropyl (meth) acrylate, 4-hydroxybutyl Acrylate, 2-hydroxy-3-phenoxypropyl (meth) acrylate, trimethylolpropane mono (meth) acrylate and pentaerythritol mono (meth) acrylate. Specific examples of the monofunctional (meth) acrylate having a carboxyl group at the alkyl moiety are 2-carboxyethyl (meth) acrylate, omega -carboxy-polycaprolactone (n≈2) mono (meth) (Meth) acryloyloxyethyl] phthalic acid, 1- [2- (meth) acryloyloxyethyl] hexahydrophthalic acid, 1- [2- 2- (meth) acryloyloxyethyl] trimellitic acid, N- (meth) acryloyloxy-N ', N'-dicarboxymethyl-p-phenylenediamine.

(Meth) acrylamide monomer is preferably a (meth) acrylamide having a substituent at the N-position, and a typical example of the substituent at the N- position is an alkyl group, but the ring of the (meth) And the ring may have an oxygen atom as a ring member in addition to the carbon atom and the nitrogen atom of (meth) acrylamide. A substituent such as alkyl or oxo (= O) may be bonded to the carbon atom constituting the ring.

Specific examples of the N-substituted (meth) acryl amide include N-methyl (meth) acrylamide, N-ethyl (meth) acrylamide, N-isopropyl (meth) acrylamide, N-alkyl (meth) acrylamides such as Nt-butyl (meth) acrylamide and N-hexyl (meth) acrylamide; N-dialkyl (meth) acrylamides such as N, N-dimethyl (meth) acrylamide and N, N-diethyl (meth) acrylamide. The N-substituent may be an alkyl group having a hydroxyl group, and examples thereof include N-hydroxymethyl (meth) acrylamide, N- (2-hydroxyethyl) (meth) acrylamide, N- Propyl) (meth) acrylamide. Specific examples of the N-substituted (meth) acrylamides forming the above-mentioned 5-membered ring or 6-membered ring include N-acryloylpyrrolidine, 3-acryloyl-2-oxazolidinone, Pyrroline, N-acryloylpiperidine, N-methacryloylpiperidine, and the like.

Examples of the bifunctional (meth) acrylate monomer include alkylene glycol di (meth) acrylate, polyoxyalkylene glycol di (meth) acrylate, halogen-substituted alkylene glycol di (meth) acrylate, ) Di (meth) acrylates of di (meth) acrylate, hydrogenated dicyclopentadiene or tricyclodecanedialcohol, di (meth) acrylates of dioxane glycol or dioxanedialanol, alkylene oxide adducts of bisphenol A or bisphenol F Di (meth) acrylate, and bisphenol A or bisphenol F epoxy di (meth) acrylate.

More specific examples of the bifunctional (meth) acrylate monomers include ethylene glycol di (meth) acrylate, 1,3-butanediol di (meth) acrylate, 1,4-butanediol di (meth) (Meth) acrylate, neopentyl glycol di (meth) acrylate, trimethylol propane di (meth) acrylate, pentaerythritol di (meth) acrylate, (Meth) acrylate, diethylene glycol di (meth) acrylate, dipropylene glycol di (meth) acrylate, dipropylene glycol di ) Acrylate, polyethylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, polytetramethylene glycol di (meth) acrylate, silicone di (meth) acrylate, (Meth) acryloyloxyethoxyethoxyphenyl] propane, 2,2-bis [4- (meth) acryloyloxy (Meth) acrylate, tricyclodecane dimethanol di (meth) acrylate, 1,3-dioxane-2,5-diyl di (meth) acrylate, (2-hydroxy-1,1-dimethylethyl) -5-ethyl-hexanediol di (meth) acrylate, which is an acetal compound of hydroxypropylaldehyde and trimethylolpropane (trade name: dioxane glycol di Di (meth) acrylate, tris (hydroxyethyl) isocyanurate di (meth) acrylate, 1,4-cyclohexanedimethanol diacrylate and the like of 5-hydroxymethyl-1,3- to be.

Examples of trifunctional or higher polyfunctional (meth) acrylate monomers include glycerin tri (meth) acrylate, alkoxylated glycerin tri (meth) acrylate, trimethylol propane tri (meth) acrylate, ditrimethylol propane tri Acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol tetra (meth) acrylate, dipentaerythritol penta (meth) acrylate, pentaerythritol tetra (Meth) acrylates of trifunctional or higher functional aliphatic polyols such as dipentaerythritol hexa (meth) acrylate, and the like, and also poly (meth) acrylates of trifunctional or higher halogen substituted polyols, alkylene oxides of glycerin Tri (meth) acrylates of adducts, alkylene oxide adducts of trimethylolpropane Tri (meth) acryloyloxyethoxyethoxy] propane, tris (hydroxyethyl) isocyanurate tri (meth) acrylate, and the like. .

On the other hand, (meth) acryl oligomers include urethane (meth) acryl oligomers, polyester (meth) acryl oligomers and epoxy (meth) acryl oligomers.

The urethane (meth) acryl oligomer is a compound having a urethane bond (-NHCOO-) and at least two (meth) acryloyl groups in the molecule. Specifically, the urethanization reaction product of a hydroxyl group-containing (meth) acrylic monomer and a polyisocyanate each having at least one (meth) acryloyl group and at least one hydroxyl group in the molecule, or a polyisocyanate- A urethane reaction product of an isocyanato group-containing urethane compound and (meth) acrylic monomer having at least one (meth) acryloyl group and at least one hydroxyl group in the molecule, and the like.

Examples of the hydroxyl group-containing (meth) acryl monomers used in the urethanization reaction may include hydroxyl group-containing (meth) acrylate monomers. Specific examples thereof include 2-hydroxyethyl (meth) (Meth) acrylate, 2-hydroxybutyl (meth) acrylate, 2-hydroxy-3-phenoxypropyl (meth) acrylate, glycerin di (meth) acrylate, trimethylolpropane di , Pentaerythritol tri (meth) acrylate, and dipentaerythritol penta (meth) acrylate. Specific examples other than the hydroxyl group-containing (meth) acrylate monomer include N-hydroxyalkyl (meth) acrylamide monomers such as N-hydroxyethyl (meth) acrylamide and N-methylol .

Examples of the polyisocyanate used in the urethane formation reaction with the hydroxyl group-containing (meth) acrylic monomer include hexamethylene diisocyanate, lysine diisocyanate, isophorone diisocyanate, dicyclohexylmethane diisocyanate, tolylene diisocyanate, xylylene diisocyanate, Di- or triisocyanates such as diisocyanates obtained by hydrogenating an aromatic isocyanate in a diisocyanate (e.g., hydrogenated tolylene diisocyanate, hydrogenated xylylene diisocyanate, etc.), triphenylmethane triisocyanate and dibenzylbenzene triisocyanate, And polyisocyanates obtained by mass-increasing the above-mentioned diisocyanate.

In addition to the aromatic, aliphatic or alicyclic polyols, polyester polyols, polyether polyols and the like can be used as the polyols used for forming the terminal isocyanato group-containing urethane compound by the reaction with the polyisocyanate. Examples of the aliphatic and alicyclic polyols include 1,4-butanediol, 1,6-hexanediol, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, neopentyl glycol, trimethylolethane, trimethylolpropane, ditrimethylol Propane, pentaerythritol, dipentaerythritol, dimethylolheptane, dimethylolpropionic acid, dimethylolbutanoic acid, glycerin, hydrogenated bisphenol A and the like.

The polyester polyol is obtained by a dehydration condensation reaction between the above-mentioned polyol and a polybasic carboxylic acid or an anhydride thereof. (Anhydrous) succinic acid, adipic acid, (maleic anhydride) maleic acid, (anhydride) itaconic acid, (anhydrous) maleic anhydride, Trimellitic acid, (anhydrous) pyromellitic acid, (anhydrous) phthalic acid, isophthalic acid, terephthalic acid, and hexahydro (phthalic) phthalic acid.

The polyether polyol may be a polyoxyalkylene-modified polyol obtained by reacting the polyol or dihydroxybenzenes with an alkylene oxide in addition to the polyalkylene glycol.

The polyester (meth) acryl oligomer is a compound having an ester bond in the molecule and at least two (meth) acryloyl groups (typically, a (meth) acryloyloxy group). Specifically, it can be obtained by a dehydration condensation reaction using (meth) acrylic acid, a polybasic carboxylic acid or an anhydride thereof, and a polyol. (Anhydrous) succinic acid, adipic acid, (maleic anhydride) maleic acid, (anhydride) maleic acid, and maleic anhydride may be represented by an example of an anhydride carboxylic acid or its anhydride, (Anhydrous) phthalic acid, isophthalic acid, terephthalic acid, and the like can be given as examples of the acid anhydride, itaconic acid, anhydrous trimellitic acid, (anhydrous) pyromellitic acid, hexahydrophthalic anhydride, Examples of the polyol used in the dehydration condensation reaction include 1,4-butanediol, 1,6-hexanediol, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, neopentyl glycol, trimethylolethane, Ditrimethylolpropane, pentaerythritol, dipentaerythritol, dimethylolheptane, dimethylolpropionic acid, dimethylolbutanoic acid, glycerin, hydrogenated bisphenol A, and the like.

The epoxy (meth) acryl oligomer can be obtained, for example, by addition reaction of polyglycidyl ether and (meth) acrylic acid, and has at least two (meth) acryloyloxy groups in the molecule. Examples of the polyglycidyl ether used in the addition reaction include ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, tripropylene glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, bisphenol A diglycidyl ether, and the like.

The radical polymerizable adhesive may be active energy ray curable or thermally curable, but is preferably active energy ray curable. When a radically polymerizable adhesive containing a radically polymerizable compound is imparted with active energy radiation curability, it is preferable to incorporate a photo-radical polymerization initiator into the adhesive. The photo radical polymerization initiator is to initiate the polymerization reaction of the radical-curable compound by irradiation of an active energy ray such as visible light, ultraviolet ray, X-ray or electron beam. The photo radical polymerization initiator may be used alone, or two or more of them may be used in combination.

Specific examples of the photoradical polymerization initiator include acetophenone, 3-methylacetophenone, benzyldimethylketal, 1- (4-isopropylphenyl) -2-hydroxy-2-methylpropan- Acetophenone type initiators such as 1- [4- (methylthio) phenyl-2-morpholinopropane-1-one and 2-hydroxy-2-methyl-1-phenylpropane-1-one; Benzophenone type initiators such as benzophenone, 4-chlorobenzophenone, and 4,4'-diaminobenzophenone; Benzoin ether initiators such as benzoin propyl ether and benzoin ethyl ether; Thioxanthone initiators such as 4-isopropylthioxanthone; In addition, xanthone, fluorenone, camphorquinone, benzaldehyde, and anthraquinone are included.

The blending amount of the photo radical polymerization initiator is usually 0.5 to 20 parts by weight, preferably 1 to 6 parts by weight, based on 100 parts by weight of the radical polymerizable compound. By compounding at least 0.5 part by weight of the photo radical polymerization initiator, the radical polymerizable compound can be sufficiently cured and high mechanical strength and adhesive strength can be imparted to the resulting polarizing plate. On the other hand, if the amount is excessively large, the durability of the polarizing plate may deteriorate.

(4-3) Additive

The adhesive forming the first adhesive layer 15 and / or the second adhesive layer 25 may contain other additives as required. Specific examples of the additives include ion trapping agents, antioxidants, chain transfer agents, polymerization accelerators (polyols and the like), sensitizers, sensitizer aids, light stabilizers, tackifiers, thermoplastic resins, fillers, flow regulators, plasticizers, , A silane coupling agent, a dye, an antistatic agent, an ultraviolet absorber, and a thermal polymerization initiator. On the other hand, the thermal polymerization initiator is used instead of the photopolymerization initiator in the case of preparing a thermosetting adhesive. A photopolymerization initiator and a thermal polymerization initiator may be used in combination. Examples of the ion trap agent include inorganic compounds such as powdery bismuth, antimony, magnesium, aluminum, calcium, titanium and mixtures thereof. Examples of the antioxidant include hindered phenol antioxidants .

(4-4) Glass transition temperature of adhesive

The glass transition temperature of the first adhesive layer 15 is preferably from -15 DEG C to less than 60 DEG C, more preferably from -10 DEG C to less than 55 DEG C, more preferably from -5 DEG C to less than 50 DEG C, Lt; 0 > C to less than 45 < 0 > C. The glass transition temperature of the second adhesive layer 25 is preferably 60 占 폚 or higher, more preferably 70 to 200 占 폚, still more preferably 80 to 180 占 폚, particularly preferably 90 to 160 占 폚. The glass transition temperature of the first adhesive layer 15 and the second adhesive layer 25 within this range is advantageous for improving the inner curl of the polarizing plate under the high temperature environment as well as the workability and resistance to cold and heat shock. The inner curl means that curling (warping) of the polarizing plate is difficult to occur.

The difference between the glass transition temperature of the second adhesive layer 25 and the glass transition temperature of the first adhesive layer 15 is preferably 10 to 100 占 폚 in view of satisfactory workability, More preferably 20 to 90 占 폚 (e.g., 50 to 80 占 폚).

The Tg of the adhesive layer is measured by a differential scanning calorimeter (DSC), and can be measured, for example, by the following method. For example, in the case of the active energy ray-curable adhesive, two thermoplastic resin films were prepared, and the adhesive prepared on the surface of one thermoplastic resin film was coated so as to have a film thickness after curing of 2 m without corona treatment, And another thermoplastic resin film is superimposed on the coated surface. The active energy ray is irradiated on the thermoplastic resin film side of one of the bonded products to cure the adhesive. Subsequently, a thermoplastic resin film sandwiched by the cured product is peeled off, 5 mg of the cured product is taken out, placed in an aluminum push cover type container, and pressed tightly to seal the sample to prepare a measurement sample. Subsequently, a vessel containing the measurement sample described above was set in a differential scanning calorimeter (DSC) (for example, "EXSTAR-6000 DSC6220" marketed by SII Eye Nanotechnology Co., Ltd.) The temperature is lowered from -60 ° C to -60 ° C, the temperature is raised to -60 ° C, the temperature is raised from -60 ° C to 150 ° C at a rate of 10 ° C / minute, . Then, the midpoint glass transition temperature defined in JIS K 7121-1987 " Method of measuring transition temperature of plastic " is determined from the DSC curve when the temperature is raised from -60 ° C to 150 ° C, The glass transition temperature of the adhesive layer.

(4-5) Coating of adhesive and adhesion between polarizing film and protective film

The first protective film 10 is laminated and adhered to one surface of the polarizing film 30 through the first adhesive layer 15 and the second adhesive layer 25 is applied to the other surface of the polarizing film 30 The second protective film 20 is laminated and bonded to obtain a polarizing plate according to the present invention. The first protective film 10 and the second protective film 20 (hereinafter collectively referred to simply as " protective film ") may be laminated one by one in a stepwise manner, Or may be laminated and bonded.

Concretely, the polarizing film 30 and the protective film are adhered by applying an adhesive to the bonding surface of the polarizing film 30 and / or the bonding surface of the protective film, (For example, in the case of a water-based adhesive), or by irradiating with an active energy ray (in the case of an active energy ray-curable adhesive), or by pressing the adhesive layer on the adhesive layer And then cured by heating (in the case of a thermosetting adhesive). In the case of using the active energy ray-curable adhesive, the heat treatment may be performed simultaneously with the irradiation of the active energy ray or after the active energy ray irradiation. Prior to the formation of the coating layer of the adhesive, one or both of the bonding surfaces of the polarizing film 30 and the protective film are subjected to a bonding treatment such as saponification treatment, corona discharge treatment, plasma treatment, flame treatment, primer treatment, May be carried out.

For forming the coating layer of the adhesive, various coating methods such as a doctor blade, a wire bar, a die coater, a comma coater, and a gravure coater can be used. It is also possible to employ a method in which the polarizing film 30 and the protective film are continuously supplied so that the joint surfaces of the polarizing film 30 and the protective film are inwardly and the adhesive is cast therebetween.

From the viewpoint of coating properties, the adhesive forming the first adhesive layer 15 and the second adhesive layer 25 preferably has a low viscosity. Specifically, the viscosity at 25 ° C is preferably 1000 mPa · s or less, more preferably 500 mPa · s or less, and furthermore preferably 100 mPa · s or less. The adhesive may be a solvent-free type, but may contain an organic solvent for adjusting the viscosity to a suitable coating method.

At least one of the protective film and the adhesive may be heated in the step of forming the coating layer of the adhesive or in the step of bonding the polarizing film 30 and the protective film. This improves the adhesion between the polarizing film 30 and the protective film, particularly the adhesion between the protective film and the adhesive layer. Specific examples of the heating include heating of the protective film, heating of the adhesive, heating of the laminated body in which the polarizing film 30 and the protective film are laminated through the uncured or undried adhesive layer, and the like. Examples of the method for heating the protective film or the laminate include a method in which a long protective film or a laminate is sequentially passed through a device for emitting radiant heat such as an infrared heater or a method in which a long protective film or laminate is heated And a method of spraying a gas. Examples of the method for heating the adhesive include a method in which the adhesive is heated and maintained in advance in a storage tank and the heated adhesive is supplied to the coating apparatus. The temperature for heating the protective film, adhesive or laminate is preferably 30 to 80 ° C, more preferably 40 to 60 ° C. If the heating temperature exceeds 80 캜, the protective film, adhesive or laminate may be deteriorated by heat. If the heating temperature is less than 30 占 폚, the effect of improving the adhesion between the protective film and the polarizing film 30 tends to be insufficient.

When the coating layer of the adhesive is formed on the protective film, the moisture content of the protective film according to the dry weight method is preferably 0.2 to 5% by weight. When the moisture content is in the above range, the reactivity of the adhesive is improved particularly when the adhesive is a cationic polymerization type adhesive, and the adhesion between the protective film and the polarizing film 30 tends to be improved.

The light source of the active energy ray may be, for example, one that generates ultraviolet rays, electron rays, and X rays. The active energy ray is preferably ultraviolet radiation. As the ultraviolet light source, a light source having a light emission distribution at a wavelength of 400 nm or less is preferable. Examples of the ultraviolet light source include a low pressure mercury lamp, a medium pressure mercury lamp, a high pressure mercury lamp, an ultra high pressure mercury lamp, a chemical lamp, a black light lamp, a microwave excited mercury lamp, .

The strength for irradiating the adhesive layer with the active energy ray is determined for each adhesive composition, and it is preferable that the light irradiation intensity in the wavelength range effective for activating the photopolymerization initiator is 0.1 to 1000 mW / cm2. If the light irradiation intensity is too small, the reaction time becomes long. On the other hand, if the light irradiation intensity is too high, the heat radiated from the lamp and the heat generated during polymerization of the adhesive deteriorate the yellowing of the adhesive layer, , Or the skin of the protective film. The light irradiation time to the adhesive is also controlled for each adhesive composition, and it is preferable that the accumulated light amount, which is expressed as a product of the light irradiation intensity and the light irradiation time, is set to 10 to 5000 mJ / cm 2. If the amount of accumulated light is too small, the generation of active species derived from the photopolymerization initiator is not sufficient and the curing of the resulting adhesive layer may be insufficient. On the other hand, if the accumulated amount of light is too large, It is easy to be disadvantageous.

The timing of laminating the protective film on the polarizing film 30 through the coating layer of the adhesive and the timing of curing or drying the coating layer are not particularly limited. For example, the protective layer may be cured or dried after laminating one protective film, and then the other protective film may be laminated to cure or dry the coated layer. Alternatively, the protective films on both sides may be simultaneously cured or dried after laminating protective films on both sides or simultaneously. The active energy ray may be applied to either of the protective films. For example, when one protective film contains an ultraviolet absorber and the other protective film does not contain an ultraviolet absorber, it is preferable to irradiate an active energy ray on the protective film side not containing the ultraviolet absorber. By such irradiation, the active energy ray to be irradiated can be effectively utilized, and the curing rate can be increased.

The thickness of the first and second adhesive layers 15, 25 after curing or after drying is usually 20 占 퐉 or less, preferably 10 占 퐉 or less, more preferably 5 占 퐉 or less, particularly preferably 3 占 퐉 or less. If the thickness of the first and second adhesive layers (15, 25) is excessively large, the reactivity of the adhesive decreases, and the humidity resistance of the polarizing plate tends to deteriorate. The thickness of the first and second adhesive layers 15 and 25 is usually 0.01 μm or more, preferably 0.1 μm or more. The first adhesive layer 15 and the second adhesive layer 25 may have the same thickness or different thicknesses.

(5) Other components of the polarizer

(5-1) Optical functional film

The polarizing plate may be provided with an optical functional film other than the polarizing film 30 for imparting a desired optical function, and a suitable example thereof is a retardation film. As described above, the first protective film 10 and / or the second protective film 20 may also serve as a retardation film, but the retardation film may be laminated separately from the protective film. In the latter case, the retardation film can be laminated on the outer surface of the first protective film 10 and / or the second protective film 20 through the adhesive layer or the adhesive layer.

Specific examples of the retardation film include a birefringent film composed of a stretched film of a thermoplastic resin having light transmittance, a film on which a discotic liquid crystal or a nematic liquid crystal is aligned and fixed, and a substrate film on which the liquid crystal layer is formed. The base film is usually a thermoplastic resin film, and as the thermoplastic resin, a cellulose ester-based resin such as triacetyl cellulose is preferably used.

As the thermoplastic resin for forming the birefringent film, those described in connection with the protective film can be used. For example, in the case of using a cellulose ester resin, a method of forming a film by adding a compound having a retardation adjusting function to a cellulose ester resin, a method of forming a film having a retardation adjusting function on the surface of the cellulose ester resin film A birefringent film can be obtained by a method of applying a cellulose ester resin or a method of uniaxially or biaxially stretching a cellulose ester resin. As the thermoplastic resin forming the birefringent film, other thermoplastic resins such as a polyvinyl alcohol-based resin, a polystyrene-based resin, a polyarylate-based resin, and a polyamide-based resin may be used.

Two or more retardation films may be used in combination for the purpose of controlling optical characteristics such as broadening. Further, a retardation film which is substantially optically isotropic as the retardation film can be used instead of the film having optical anisotropy. The zero retardation film refers to a film having an in-plane retardation value R _e and a thickness direction retardation value R _th together of -15 to 15 nm. Herein, the in-plane retardation value R _e and the thickness direction retardation value R _th are values at a wavelength of 590 nm.

The in-plane phase difference value R _e and the thickness direction phase difference value R _th satisfy the following equations:

R _e = (n _x -n _y ) x d

R _th = _{[(n x + n y) /} 2-n z × d]

. Expression, n _x is a refractive index in a slow axis direction (x axis direction) in the film plane, n _y is a refractive index in the fast axis direction (y-axis direction perpendicular to the x-axis in-plane) in the film plane, n _z is the thickness of the film (Z-axis direction perpendicular to the film plane), and d is the thickness of the film.

As the zero retardation film, a thermoplastic resin described in relation to a protective film or a birefringent film can be used. Examples of the retardation film include a polyolefin resin such as a cellulose ester resin, a chain polyolefin resin and a cyclic polyolefin resin, a polyolefin resin such as polyethylene terephthalate A resin film made of a polyester-based resin can be used. Of these, cellulose ester-based resins and polyolefin-based resins are preferably used since the control of phase difference is easy and easy to obtain.

Examples of other optical functional films (optical members) that can be included in the polarizing plate include a light-collecting plate, a luminance enhancement film, a reflection layer (reflection film), a transflective layer (transflective film), a light diffusion layer (light diffusion film) These are generally provided when the polarizing plate is a polarizing plate disposed on the back side (backlight side) of the liquid crystal cell.

The light collecting plate is used for the purpose of optical path control or the like and may be a prism array sheet, a lens array sheet, a dot laying sheet, or the like.

The brightness enhancement film is used for the purpose of improving the brightness in a liquid crystal display device to which a polarizing plate is applied. Specifically, a reflection type polarizing separation sheet designed to produce anisotropy in reflectance by stacking a plurality of thin films having different anisotropy of refractive index, an orientation film of a cholesteric liquid crystal polymer, and an orientation film of the cholesteric liquid crystal polymer supported on the base film A circularly polarized light separation sheet and the like.

The reflection layer, the transflective layer, and the light diffusion layer are provided to make the polarizing plate an optical member of a reflection type, a semi-transmission type, and a diffusion type, respectively. The polarizing plate of the reflection type is used in a liquid crystal display device of the type in which incident light from the viewer side is reflected and displayed, and since a light source such as a backlight can be omitted, the liquid crystal display device can be easily thinned. The transflective type polarizing plate is used for a liquid crystal display device of the type that is reflected in a spot (bright spot) and displayed in light from a backlight in a dark place (dark place). In addition, the diffusion type polarizing plate is used in a liquid crystal display device in which display defects such as moire patterns are suppressed by imparting light diffusibility. The reflection layer, the transflective layer and the light diffusion layer can be formed by a known method.

(5-2) Pressure-sensitive adhesive layer

The polarizing plate according to the present invention may include a pressure-sensitive adhesive layer for bonding the polarizing plate to an image display element such as a liquid crystal cell or another optical member. The pressure-sensitive adhesive layer can be laminated on the outer surface of the protective film. The pressure-sensitive adhesive layer may be laminated on the outer surface of the first protective film or may be laminated on the outer surface of the second protective film.

As a pressure-sensitive adhesive for use in the pressure-sensitive adhesive layer, a (meth) acrylic resin, a silicone resin, a polyester resin, a polyurethane resin, a polyether resin or the like may be used as the base polymer. Among them, a (meth) acrylic pressure-sensitive adhesive is preferably used from the viewpoints of transparency, adhesive strength, reliability, weather resistance, heat resistance, reworkability and the like. (Meth) acrylic pressure-sensitive adhesives include (meth) acrylic acid alkyl esters having an alkyl group having 20 or less carbon atoms such as methyl group, ethyl group or butyl group and (meth) acrylic acid alkyl esters having a functional group such as (meth) acrylic acid or (meth) (Meth) acrylic resin having a weight average molecular weight of 100,000 or more, which is blended such that the monomer has a glass transition temperature of preferably 25 占 폚 or lower, more preferably 0 占 폚 or lower, is useful as the base polymer.

The pressure-sensitive adhesive layer may be formed on the polarizing plate by, for example, dissolving or dispersing the pressure-sensitive adhesive composition in an organic solvent such as toluene or ethyl acetate to prepare a solution of 10 to 40% by weight and directly coating the pressure- Or a method in which a pressure-sensitive adhesive layer is formed in a sheet form on a release film subjected to a release treatment and is then transferred to a target surface of a polarizing plate. The thickness of the pressure-sensitive adhesive layer is determined depending on the adhesive strength and the like, but is suitably in the range of about 1 to 50 mu m, preferably 2 to 40 mu m.

The polarizing plate may include the above separate film. The separator film may be a film made of a polyethylene-based resin such as polyethylene, a polypropylene-based resin such as polypropylene, or a polyester-based resin such as polyethylene terephthalate. Among them, a stretched film of polyethylene terephthalate is preferable.

A filler, pigment, colorant, antioxidant, ultraviolet absorber, antistatic agent and the like may be blended in the pressure-sensitive adhesive layer, if necessary, with glass fiber, glass bead, resin bead, metal powder or other inorganic powder.

Examples of the antistatic agent include ionic compounds, conductive fine particles, and conductive polymers, and ionic compounds are preferably used. The cation component constituting the ionic compound may be an inorganic anion or an organic anion, but it is preferably an organic cation from the viewpoint of compatibility with the (meth) acrylic resin. Examples of the organic cations include pyridinium cations, imidazolium cations, ammonium cations, sulfonium cations and phosphonium cations. On the other hand, the anion component constituting the ionic compound may be an inorganic anion or an organic anion, but an anionic component containing a fluorine atom is preferable because it gives an ionic compound excellent in antistatic property. As the anionic component containing a fluorine atom, a phosphate anion hexafluorophosphate ^{_{[(PF 6 -)],}} ( methanesulfonyl-trifluoromethyl) bis imide anion _{[(CF 3 SO 2) 2} N -] anion, a bis (fluoroalkyl (FSO ₂ ) ₂ N ^- ] anion, and the like.

(5-3) Protect film

The polarizing plate according to the present invention may include a protective film for temporarily adhering and protecting its surface (protective film surface). After the polarizing plate is bonded to, for example, an image display element or another optical member, the protective film is peeled off from the pressure-sensitive adhesive layer.

The protective film is composed of a base film and a pressure-sensitive adhesive layer laminated on the base film. As for the pressure-sensitive adhesive layer, the above-mentioned contents are cited. Examples of the resin constituting the base film include polyethylene resins such as polyethylene, polypropylene resins such as polypropylene, polyester resins such as polyethylene terephthalate and polyethylene naphthalate, and thermoplastic resins such as polycarbonate resins have. Preferably, it is a polyester resin such as polyethylene terephthalate.

The plate of the present invention can be bonded to an image display device such as a liquid crystal cell through a pressure-sensitive adhesive layer. Examples of the liquid crystal cell include IPS type and VA type.

[Example]

Hereinafter, the present invention will be described in more detail with reference to examples and comparative examples, but the present invention is not limited to these examples. In the following examples, the following were used as the radical polymerizing compound, the photo radical polymerization initiator and the additive constituting the adhesive.

(Radical Polymerizable Compound)

[1] Curable compound 1: dicyclopentanyl acrylate (trade name "FA-513AS", available from Hitachi Chemical Co., Ltd.)

[2] Curable compound 2: 4-hydroxybutyl acrylate (trade name "4HBA", available from Osaka Yuki Kogyo Co., Ltd.)

[3] Curable compound 3: N, N-dimethylacrylamide (trade name "DMAA" available from KJ Chemical Co., Ltd.)

[4] Curable compound 4: N- (2-hydroxyethyl) acrylamide (trade name "HEAA" available from KJ Chemical Co., Ltd.)

[5] Curable compound 5: trimethylol propane triacrylate (trade name "A-TMPT", obtained from Shin Nakamura Kagaku Kogyo Co., Ltd.)

[6] Curing compound 6: Polyethylene glycol # 600 diacrylate (trade name "A-600" available from Shin Nakamura Kagaku Kogyo Co., Ltd.)

[7] Curing compound 7: dipentaerythritol hexaacrylate (trade name "A-DPH", available from Shin Nakamura Kagaku Kogyo Co., Ltd.)

[8] Curable compound 8: UV-curable urethane acrylate resin (trade name "UV-3700B", available from Nippon Gohsei Kagaku Kogyo Co., Ltd.)

[9] Curable compound 9: UV-curable urethane acrylate resin (trade name "UV-3000B", available from Nippon Ko Seikagaku Kogyo Co., Ltd.)

[10] Curable compound 10: 1,4-Cyclohexanedimethanol monoacrylate (trade name "CHDMMA", available from Nippon Paper Industries Co., Ltd.).

On the other hand, the ultraviolet curing type urethane acrylate resin (trade name: UV-3700B) is an ultraviolet curing type resin having a main constitution of urethane acrylate and has a viscosity of 30000 to 60000 mPa s / 60 캜, a molecular weight 38000, and the number of oligomer functional groups is 2.

The ultraviolet curing type urethane acrylate resin (trade name: UV-3000B) is an ultraviolet curable resin having a main constitution of urethane acrylate, and has a viscosity of 45,000 to 65,000 mPa · s / 60 ° C and a molecular weight (Mw) of 18000, and the number of oligomer functional groups is 2.

(Photo radical polymerization initiator)

[11] Initiator 1: 2-Methyl-1- [4- (methylthio) phenyl] -2-methylpolinopropane-1-one (trade name "Irgacure 907" obtained from BASF).

(additive)

[12] Additive 1: silicone leveling agent (trade name "SH710", available from Dow Corning).

≪ Preparation Examples 1 to 5: Preparation of ultraviolet ray curable adhesive >

The radically polymerizable compound, the photo-radical polymerization initiator, and the additive described above were put into a 20-mL screw tube with the mixing ratio shown in Table 1 (the numerical value in Table 1 indicates parts by weight), mixed and defoamed to obtain a liquid UV-curable adhesives A to E were respectively prepared.

≪ Preparation Examples 6 to 9: Preparation of ultraviolet ray-curable adhesive >

The radically polymerizable compound, the photo-radical polymerization initiator, and the additive described above were put into a 20-mL screw tube with the mixing ratio shown in Table 2 (the numerical value in Table 2 indicates parts by weight), mixed and defoamed to obtain a liquid UV-curable adhesives F to I were prepared.

Production Example 10: Production of (meth) acrylic resin film [

(Meth) acrylic resin which is a copolymer obtained by copolymerizing methyl methacrylate and methyl acrylate in a weight ratio of 96: 4. The innermost layer is composed of a hard polymer polymerized by using methyl methacrylate with a small amount of allyl methacrylate and the intermediate layer is composed of butyl acrylate as a main component and styrene and a small amount of allyl methacrylate Layer structure composed of a soft polymer composed of a soft elastic material and an outermost layer made of a hard polymer polymerized by using a small amount of ethyl acrylate with methyl methacrylate and having an average particle diameter of 240 nm to an elastic material as an intermediate layer Rubber particles were prepared.

The above-mentioned (meth) acrylic resin and the above acrylic rubber particles were blended at a weight ratio of 70:30, and a pallet containing a benzotriazole-based ultraviolet absorber was added and melt-kneaded with a twin-screw extruder. And 0.05 parts by weight of stearic acid as a lubricant were added and mixed to obtain a pallet of a (meth) acrylic resin composition. This pellet was fed into a single screw extruder having a diameter of 65 mm and extruded through a T-die having a set temperature of 275 DEG C. The both surfaces of the extruded film-like molten resin were cooled by being sandwiched between two polish rolls To prepare a (meth) acrylic resin film having a thickness of 80 mu m. The transmittance of the obtained (meth) acrylic resin film at a wavelength of 380 nm was 25% or less.

≪ Examples 1 to 3, Comparative Examples 1 to 3 >

(1) Production of Polarizer

Corona discharge treatment was applied to one side of the (meth) acrylic resin film (first protective film) produced in Production Example 10, and a corona discharge treatment was performed on the corona discharge treated surface as a first adhesive (an adhesive for forming the first adhesive layer) The adhesive described in Table 3 was coated by a bar coater to a thickness of about 2.5 占 퐉 after curing. Then, a polyvinyl alcohol (PVA) -iodine-based polarizing film having a thickness of 25 mu m was bonded to the coated surface. Then, a retardation film (trade name: "ZEONOR" manufactured by Nippon Zeon Co., Ltd.) having a thickness of 50 μm and made of a cyclic polyolefin resin (norbornene resin) has an in-plane retardation value R _{e of} 52 nm at a wavelength of 590 nm (A protective film) was subjected to a corona discharge treatment, and the adhesive described in Table 3 was applied to the corona discharge treated surface in the same manner as the second adhesive (adhesive forming the second adhesive layer) to a thickness of about 2.5 占 퐉 By using a bar coater. On the coated surface, a polarizing film provided with the (meth) acrylic resin film prepared above was laminated on the side of the polarizing film and pressed using a bonding roll and bonded to obtain a laminate. The stacked body was irradiated with ultraviolet light having an accumulated light quantity of 1500 mJ / cm 2 (UVB) using an ultraviolet irradiation device equipped with a belt conveyor (lamp: "D bulb" manufactured by Fusion UV Systems Co., Ltd.) was used on the side of the annular polyolefin- , And the adhesive layers on both sides were cured to prepare a polarizing plate.

(2) Measurement of the storage elastic modulus of the adhesive layer at 80 DEG C (in the case of the adhesive A)

(Manufactured by Barcoater, Dai-ichi Kikaku K.K.) on the surface of a polarizing film of a polarizing plate obtained by laminating a triacetylcellulose film having a thickness of 25 占 퐉 on one side of a polarizing film having a thickness of 25 占 퐉, (Adhesive A) was coated so as to have a thickness of about 2.5 占 퐉 after curing, and then a ring-shaped polyolefin-based resin film having a thickness of 50 占 퐉 was laminated on the coated surface. Subsequently, the adhesive layer was cured by irradiating ultraviolet light on the side of the cyclic polyolefin resin film so that the accumulated light quantity became 1500 mJ / cm 2 (UVB) by "D bulb" manufactured by Fusion UV Systems. Subsequently, the cyclic polyolefin-based resin film was peeled off, and a laminate having a cured adhesive layer laminated on the polarizing plate was prepared and used as a sample for measurement.

The storage elastic modulus of the adhesive layer was measured by a torsional shear method using a rotary viscoelasticity measuring device "Physica MCR 301" sold by Anton Paar Co., Ltd. Specifically, the sample for measurement is set in the apparatus so as to be a stage / polarizer / adhesive layer / meshing system, and after a load of 1 N is applied, the sample is heated at a frequency of 1 Hz and a distortion of 1% The temperature was raised at a rate of temperature rise of < RTI ID = 0.0 > C / min, < / RTI > The results are shown in Table 3.

(3) Measurement of the storage elastic modulus of the adhesive layer at 80 DEG C (in the case of adhesives B to E)

(Adhesive B to E) prepared in Production Examples 2 to 5 were coated on one surface of a 50 占 퐉 -thick ring-shaped polyolefin resin film using a coating machine (Barcoater, Daiichi Rika K.K.) And a ring-shaped polyolefin-based resin film having a thickness of 50 占 퐉 was further laminated on the coated surface. Subsequently, the adhesive layer was cured by irradiating ultraviolet light with "D bulb" manufactured by Fusion UV Systems Co., Ltd. so that the accumulated light quantity became 1500 mJ / cm 2 (UVB). This was cut to a size of 5 mm x 30 mm, and the annular polyolefin resin film was peeled off to obtain a cured film of an adhesive. This cured film was gripped at a gap of 2 cm between grippers using a dynamic viscoelasticity measuring device " DVA-220 " manufactured by Haitai Sosukei Kagaku Co., Hz, and the rate of temperature rise was set at 10 ° C / min to obtain a storage elastic modulus at a temperature of 80 ° C. The results are shown in Table 3.

(4) Evaluation of processability of polarizer

Using a 800 mm x 800 mm blade manufactured by Dumbbell Company, punching was performed on the side of the first protective film of the polarizing plate, and the state of lifting and peeling of the edge of the polarizing plate was visually observed and observed. The evaluation results are shown in Table 3.

A: No peeling or peeling at the end of the polarizing plate,

B: There is peeling or peeling at the end of the polarizing plate.

(5) Formation of pressure-sensitive adhesive layer

An organic solvent solution of a (meth) acrylic pressure-sensitive adhesive obtained by adding an isocyanate crosslinking agent, a silane coupling agent and an antistatic agent to a (meth) acrylic resin which is a copolymer of butyl acrylate, methyl acrylate, acrylic acid and hydroxyethyl acrylate, , A release film of a 38 占 퐉 -thick separate film (trade name "SP-PLR382052" obtained from LINTEC CO., LTD.) Made of polyethylene terephthalate subjected to releasing treatment was applied to the release treated surface with a die coater so as to have a thickness of 20 μm Thus, a sheet-type pressure-sensitive adhesive with a separate film was produced. Subsequently, the surface of the annular polyolefin-based resin film of the polarizing plate prepared in (1) above was bonded to the surface (pressure-sensitive adhesive side) opposite to the separator film of the sheet-type pressure-sensitive adhesive obtained above with a laminator, C for 7 days to obtain a polarizing plate having a pressure-sensitive adhesive layer.

(6) Evaluation of heat and shock resistance of polarizer

Each sheet having a size of 200 mm x 150 mm was cut out from the polarizing plate having the pressure-sensitive adhesive layer prepared in the above (5), bonded to a non-alkali glass (trade name "EAGLEXG" manufactured by Corning Incorporated) (Heat shock test). Four measurement samples were prepared for each polarizer plate. The cold / heat impact test was carried out by maintaining one cycle at -40 占 폚 for 30 minutes, then increasing the temperature to 70 占 폚 for 30 minutes, and repeating this operation for a total of 100 cycles. The four measurement samples were subjected to the above-described cold / heat impact test, and the cold / heat shock resistance was evaluated from the ratio of the number of cracks or cracks observed in the polarizing film after the test to the total number of samples (4). The evaluation results are shown in Table 3.

≪ Examples 4 to 6 >

(1) Production of Polarizing Plate (Example 4)

Corona discharge treatment was applied to one side of the (meth) acrylic resin film (first protective film) produced in Production Example 10, and a corona discharge treatment was performed on the corona discharge treated surface as a first adhesive (an adhesive for forming the first adhesive layer) The adhesive described in Table 4 was applied by a bar coater to a thickness of about 2.5 占 퐉 after curing. Then, a polyvinyl alcohol (PVA) -iodine-based polarizing film having a thickness of 25 mu m was bonded to the coated surface. Then, a corona discharge treatment was carried out on one side of a retardation film (trade name: "KC4CR", manufactured by Konica Minolta Co., Ltd.) (second protective film) made of acetylcellulose resin with a thickness of 40 μm and subjected to corona discharge treatment , And the adhesive described in Table 4 was similarly applied as a second adhesive (adhesive forming the second adhesive layer) using a bar coater so that the thickness after curing was about 2.5 占 퐉. On the coated surface, a polarizing film provided with the (meth) acrylic resin film prepared above was laminated on the side of the polarizing film and pressed using a bonding roll and bonded to obtain a laminate. The stacked body was irradiated with ultraviolet light having an accumulated light quantity of 1500 mJ / cm 2 (UVB) using an ultraviolet irradiator equipped with a belt conveyor ("D bulb" manufactured by Fusion UV Systems Co., Ltd.) on the acetylcellulose- , And the adhesive layers on both sides were cured to prepare a polarizing plate.

(2) Production of polarizing plate (Examples 5 to 6)

Corona discharge treatment was applied to one side of the (meth) acrylic resin film (first protective film) produced in Production Example 10, and a corona discharge treatment was performed on the corona discharge treated surface as a first adhesive (an adhesive for forming the first adhesive layer) The adhesive described in Table 4 was applied by a bar coater to a thickness of about 2.5 占 퐉 after curing. Then, a polyvinyl alcohol (PVA) -iodine-based polarizing film having a thickness of 25 mu m was bonded to the coated surface. Then, a retardation film (trade name: "ZEONOR" manufactured by Nippon Zeon Co., Ltd.) having a thickness of 50 μm and made of a cyclic polyolefin resin (norbornene resin) has an in-plane retardation value R _{e of} 52 nm at a wavelength of 590 nm (A protective film) was subjected to a corona discharge treatment, and the adhesive described in Table 4 was similarly applied to the corona discharge treated surface as a second adhesive (an adhesive for forming the second adhesive layer) to a thickness of about 2.5 占 퐉 By using a bar coater. On the coated surface, a polarizing film provided with the (meth) acrylic resin film prepared above was laminated on the side of the polarizing film and pressed using a bonding roll and bonded to obtain a laminate. The stacked body was irradiated with ultraviolet light having an accumulated light quantity of 1500 mJ / cm 2 (UVB) using an ultraviolet irradiation device equipped with a belt conveyor (lamp: "D bulb" manufactured by Fusion UV Systems Co., Ltd.) was used on the side of the annular polyolefin- , And the adhesive layers on both sides were cured to prepare a polarizing plate.

(3) Measurement of the storage elastic modulus of the adhesive layer at 80 DEG C (in the case of adhesives F to I)

(Adhesive F to I) prepared in Production Examples 6 to 9 was coated on one surface of a cyclic polyolefin-based resin film having a thickness of 50 占 퐉 using a coating machine (manufactured by Barcoater, Daicelica Co., Ltd.) And a ring-shaped polyolefin-based resin film having a thickness of 50 mu m was further laminated on the coated surface. Subsequently, the adhesive layer was cured by irradiating ultraviolet light with "D bulb" manufactured by Fusion UV Systems Co., Ltd. so that the accumulated light quantity became 1500 mJ / cm 2 (UVB). This was cut to a size of 5 mm x 30 mm, and the annular polyolefin resin film was peeled off to obtain a cured film of an adhesive. This cured film was gripped at a gap of 2 cm between grippers using a dynamic viscoelasticity measuring device " DVA-220 " manufactured by Haitai Sosukei Kagaku Co., Ltd., Hz, and the rate of temperature rise was set at 10 ° C / min to obtain the storage elastic modulus at a temperature of 80 ° C. The results are shown in Table 4.

(4) Evaluation of processability of polarizer

The polarizers obtained in Examples 4 to 6 were evaluated for processability in the same manner as in (4) of Examples 1 to 3 and Comparative Examples 1 to 3. The evaluation results are shown in Table 4.

(5) Formation of pressure-sensitive adhesive layer

A polarizing plate having a pressure-sensitive adhesive layer was obtained using the polarizing plates obtained in Examples 4 to 6 in the same manner as in (5) of Examples 1 to 3 and Comparative Examples 1 to 3. On the other hand, the sheet-type pressure-sensitive adhesive was bonded to the surface of the annular polyolefin-based resin film of the polarizing plate or the surface of the acetylcellulose-based resin film.

(6) Evaluation of heat and shock resistance of polarizer

The polarizing plates obtained in Examples 4 to 6 were evaluated in terms of heat and cold shock resistance in the same manner as in (6) of Examples 1 to 3 and Comparative Examples 1 to 3. The evaluation results are shown in Table 4.

Claims (7)

A first protective film, a first adhesive layer, a polarizing film, a second adhesive layer and a second protective film in this order,
Wherein the first adhesive layer has a storage elastic modulus at 80 DEG C of at least 0.1 MPa but less than 800 MPa and a storage elastic modulus at 80 DEG C of the second adhesive layer is less than 800 MPa but less than 10,000 MPa. The polarizing plate according to claim 1, wherein the second adhesive layer has a storage elastic modulus at 80 캜 of 1000 MPa or more. The polarizing plate according to claim 1, wherein at least one of the first adhesive layer and the second adhesive layer is a cured layer of an active energy ray curable adhesive. The polarizing plate according to claim 3, wherein the active energy ray-curable adhesive comprises a radically polymerizable compound. The method according to claim 1, wherein the first protective film and the second protective film are made of a resin selected from the group consisting of a polyester resin, a polycarbonate resin, a polyolefin resin, a (meth) acrylic resin and a cellulose ester resin . ≪ / RTI > The polarizing plate according to claim 5, wherein the first protective film is composed of a (meth) acrylic resin, and the second protective film is composed of a polyolefin resin or a cellulose ester resin. The polarizing plate according to claim 1, wherein at least one of the first protective film and the second protective film is a retardation film.

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