TWI672530B - Polarizers - Google Patents

Abstract

The present invention provides a polarizing plate, which sequentially includes a first protective film, a first adhesive layer, a polarizing film, a second adhesive layer, and a second protective film, wherein the glass transition temperature of the first adhesive layer is Above -15 ° C and below 60 ° C, the glass transition temperature of the second adhesive layer is above 60 ° C.

Description

Polarizer

The present invention relates to a polarizing plate with a protective film bonded on both sides of a polarizing film via an adhesive layer.

A polarizing plate that is widely used in an image display device such as a liquid crystal display device generally has a structure of a double-area layer protective film in a polarizing film. For the bonding of polarizing film and protective film, an adhesive is usually used. Adhesives for protective film bonding include water-based adhesives and active energy ray-curable adhesives.

In Japanese Patent Application Laid-Open No. 2010-286737, it is described that in a polarizing plate with a protective film bonded to a protective film, an adhesive layer formed by curing a radical polymerizable composition on both sides of a polarizing film, one glass of the adhesive layer is reduced. Transfer temperature, and increase the glass transfer temperature of another adhesive layer, which can provide a good punching processability (small stripping of the polarizer end after punching processing), and high temperature and high temperature after punching processing. Polarizer with excellent durability in high temperature and high humidity environment.

Generally, a polarizing plate is manufactured into a long object (polarizing plate reel) by a roll-to-roll method, for example, it is cut to fit The polarizing plate sheet-like body of the size of the image display device used is assembled into the image display device by being attached to the image display element. Therefore, the processability of the polarizing plate when cutting into a sheet-like body is pursued (means that it is difficult to cause peeling between the polarizing film and the protective film even under stress such as when cutting). In addition, after the polarizing plate is cut into a sheet and assembled into an image display device, it is stored or transported for a certain period of time. At this time, the storage / transportation environment may be relatively high temperature. situation. The polarizing plate sheet system exposed to a high temperature environment, for example, has warping (warping), etc., and tends to be deformed compared to the normal temperature environment. The deformed polarizing plate sheet system is not only lacking an adhesive layer. The rationality (easiness of bonding) when bonding to an image display element can also easily lead to a problem that air bubbles are mixed between the adhesive layer and the image display element.

Therefore, an object of the present invention is to provide a polarizing plate which is excellent in workability at the time of cutting and the like, and is less likely to be warped (lifted) even when placed in a high-temperature environment.

The present invention provides the following polarizing plates.

[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 glass transition temperature of the first adhesive layer is -15 ° C or higher and less than 60 ° C, and the glass transition temperature of the second adhesive layer is 60 ° C or higher.

[2] The polarizing plate according to [1], wherein the glass transition temperature of the first adhesive layer is 0 ° C or higher.

[3] The polarizing plate according to [1] or [2], wherein the glass transition temperature of the second adhesive layer is 80 ° C or higher.

[4] The polarizing plate according to any one of [1] to [3], wherein at least one of the first adhesive layer and the second adhesive layer is an active energy ray-curable adhesive. Hardened layer.

[5] The polarizing plate according to the item [4], wherein the active energy ray-curable adhesive agent contains a radical polymerizable compound.

[6] The polarizing plate according to any one of [1] to [5], wherein the first protective film and the second protective film are selected from a polyester resin, a polycarbonate resin, Polyolefin resin, (meth) acrylic resin, and resin in the group which consists of cellulose ester resin.

[7] The polarizing plate according to the item [6], 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.

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

According to the present invention, it is possible to provide a polarizing plate which has good processability at the time of cutting and the like and is less prone to warping (warping) even in a high-temperature environment (good "warpage resistance" in a high-temperature environment). )By.

10‧‧‧The first protective film

15‧‧‧The first adhesive layer

20‧‧‧Second protective film

25‧‧‧The second adhesive layer

30‧‧‧ polarizing film

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

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

(1) Structure of polarizing plate

As shown in FIG. 1, the polarizing plate of the present invention is configured by sequentially including 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. That is, the first protective film 10 is laminated on one surface of the polarizing film 30 via the first adhesive layer 15, and the second protective film 20 is laminated on the other surface of the polarizing film 30 via the second adhesive layer 25. The glass transition temperature Tg1 of the first adhesive layer 15 is -15 ° C or more and not more than 60 ° C, and the glass transition temperature Tg2 of the second adhesive layer 25 is 60 ° C or more. The polarizing plate of the present invention having such a structure exhibits good processability (degree of difficulty in peeling off the film on the end face of the polarizing plate when processing such as cutting and end surface grinding is applied) and warpage resistance. Further, this polarizing plate can be excellent in durability (hereinafter, also referred to as "cold and hot shock resistance") when it is placed under an environment where high temperature conditions and low temperature conditions are repeated.

The polarizing plate of the present invention is not limited to the example shown in FIG. 1 and may contain layers other than the above. If specific examples of other layers are given, for example, an adhesive layer laminated on the outer surface of the first protective film 10 and / or the second protective film 20; a separation film laminated on the outer surface of the adhesive layer (also referred to as "peeling" Film "); 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; laminated on the first protective film via an adhesive layer or an adhesive layer 10 and / or an optical functional film on the outer surface of the second protective film 20.

The polarizing plate of the present invention may be an elongated object of the polarizing plate having the above-mentioned layer structure or a winding roll thereof. The so-called processability at this time refers to the processability when the polarizing plate sheet-like body is cut out from the elongated object and the winding roller; Flexibility refers to the warpage resistance of the polarizer sheet body being cut; the so-called cold and hot shock resistance refers to the cold and hot shock resistance of the elongated object or the winding roller, or from the elongated object or the coil Cold and hot shock resistance of the polarizer sheet-like body cut out by the roll.

Moreover, the polarizing plate of the present invention may be a sheet-like body of the polarizing plate having the above-mentioned layer structure. At this time, the term "workability" refers to the workability when a smaller-size sheet is cut out from the polarizing plate sheet, or the workability when the end surface of the polarizing sheet sheet is ground; the so-called warpage resistance and cold and heat resistance Shock resistance refers to the respective warpage resistance and cold and heat shock resistance of a polarizing plate sheet or a smaller-sized polarizing plate sheet cut from the polarizing plate sheet.

(2) Polarizing film

The polarizing film 30 is a film having a function of selectively penetrating linearly polarized light from a certain direction of natural light. Examples include: an iodine-based polarizing film that adsorbs / orientates iodine on a polyvinyl alcohol-based resin film, a dye-based polarizing film that adsorbs / orientates dichroic dye on a polyvinyl alcohol-based resin film, and coating a lyotropic liquid crystal ( lyotropic liquid crystal), a dichroic dye in a state, and a coating type polarizing film that is oriented / immobilized. These polarizing films are known as absorption-type polarizing films because they selectively penetrate linearly polarized light from one direction of natural light and absorb linearly polarized light from the other direction. The polarizing film 30 is not limited to an absorptive polarizing film, and is a reflective polarizing film that selectively penetrates linearly polarized light from one direction of natural light and reflects linearly polarized light from the other direction, or Any linearly polarized light scattering type polarizing film may be used. However, from the viewpoint of excellent visibility, an absorption type polarizing film is preferred. Of which, partial An iodine-based polarizing film excellent in lightness and transmittance is more preferable.

Polyvinyl alcohol resins are those obtained by saponification using polyvinyl acetate resins. Examples of the polyvinyl acetate-based resin include, in addition to polyvinyl acetate, a homopolymer of vinyl acetate, copolymers of other monomers copolymerizable with vinyl acetate, and the like. Examples of other monomers that can be copolymerized with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, (meth) acrylamidoamines having an ammonium group, and the like.

The saponification degree of polyvinyl alcohol resin is usually about 85 to 100 mole%, and more preferably 98 mole% or more. The polyvinyl alcohol-based resin may be modified, and for example, polyvinyl formaldehyde or polyvinyl acetal modified with aldehydes may be used. The average degree of polymerization of the polyvinyl alcohol resin is usually about 1,000 to 10,000, and preferably about 1500 to 5000. The average degree of polymerization of the polyvinyl alcohol-based resin can be determined in accordance with JIS K 6726.

As the film made of such a polyvinyl alcohol-based resin, an original sheet film that can be used as the polarizing film 30 can be used. The method for forming a polyvinyl alcohol-based resin into a film is not particularly limited, and a known method can be adopted. The thickness of the polyvinyl alcohol-based original sheet film is, for example, 150 μm or less, and preferably 100 μm or less (for example, 50 μm or less).

The polarizing film 30 can be manufactured by a method including the following steps: a step of uniaxially extending the polyvinyl alcohol resin film; and a step of adsorbing the dichroic pigment by dyeing the polyvinyl alcohol resin film with a dichroic dye ; A step of treating (cross-linking treatment) a polyvinyl alcohol-based resin film to which a dichroic pigment is adsorbed, with a boric acid aqueous solution; and performing water treatment with a boric acid aqueous solution Steps of washing.

One axis extension of the polyvinyl alcohol-based resin film can be performed before the dyeing of the dichroic pigment, simultaneously with the dyeing, or after the dyeing. When performing a uniaxial extension after dyeing, this uniaxial extension can be performed before or during a boric acid treatment. Moreover, one-axis extension may be performed in these plural stages.

When one axis is extended, it can be extended to one axis between rollers with different speeds, or it can be extended to one axis by using hot rollers. In addition, the uniaxial stretching may be a dry stretching in the atmosphere, or a wet stretching in which the polyvinyl alcohol-based resin film is stretched in a swelled state using a solvent or water. The stretching ratio is usually about 3 to 8 times.

A method of dyeing a polyvinyl alcohol-based resin film with a dichroic dye is, for example, a method of dipping the film in an aqueous solution containing a dichroic dye. As the dichroic pigment system, iodine and a dichroic organic dye can be used. The polyvinyl alcohol-based resin film is preferably treated by immersion in water before the dyeing treatment.

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

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

Polyvinyl alcohol resin film after boric acid treatment is usually water-washed. The water washing treatment can be performed, for example, by immersing a boric acid-treated polyvinyl alcohol-based resin film in water. The temperature of the water in the water washing treatment is usually about 5 to 40 ° C. The polarizing film 30 can be obtained by performing a drying process after washing with water. The drying process can be performed using a hot-air dryer and a far-infrared heater. The polarizing plate can be obtained by bonding the protective film with the adhesive on both sides of the polarizing film 30.

Moreover, as another example of the manufacturing method of the polarizing film 30, the method described in Unexamined-Japanese-Patent No. 2000-338329, and Unexamined-Japanese Patent No. 2012-159778 is mentioned, for example. In this method, a solution containing a polyvinyl alcohol-based resin is coated on the surface of a substrate film to provide a resin layer, and then a laminated film including the substrate film and the resin layer is extended, and then a dyeing treatment, a crosslinking treatment, and the like are applied, and A polarizing element layer (polarizing film layer) is formed from a resin layer. The polarizing laminated film including the base film and the polarizing element layer can be bonded at the polarizing element level. After the protective film, the base film is peeled and removed, and another protective film is bonded to the polarizing element layer exposed by the peeling of the base film to become a polarizing plate.

The thickness of the polarizing film 30 may be 40 μm or less, and preferably 30 μm or less (for example, 20 μm or less). In addition, according to the method described in Japanese Patent Application Laid-Open No. 2000-338329 or Japanese Patent Application Laid-Open No. 2012-159778, a thin film polarizing film 30 can be more easily manufactured, and the thickness of the polarizing film 30 can be, for example, 20 μm or less, and It can be set to 10 μm or less. The thickness of the polarizing film 30 is usually 2 μm or more. Reducing the thickness of the polarizing film 30 is advantageous for thinning the polarizing plate and even the image display device.

(3) Protective film

The first protective film 10 and the second protective film 20 may each include a translucent (preferably optically transparent) thermoplastic resin, such as, for example, a chain polyolefin resin (polypropylene resin, etc.) 、 Polyolefin resins such as cyclic polyolefin resins (norzene resins, etc.); such as triethyl cellulose, cellulose ester resins of diethyl cellulose; such as polyethylene terephthalate Polyester resins of esters, polyethylene naphthalate, polybutylene terephthalate; polycarbonate resins; (meth) acrylic resins; or resin films of these mixtures, copolymers, etc. . In addition, "(meth) acrylic acid" means methacrylic acid and / or acrylic acid, and when it is called "(meth) acrylic acid ester" etc., "(meth)" also has the same meaning. Among them, the first protective film 10 and the second protective film 20 are respectively a group consisting of a polyester resin, a polycarbonate resin, a polyolefin resin, a (meth) acrylic resin, and a cellulose ester resin. The selected resin is preferably constituted.

The first protective film 10 and the second protective film 20 may be either an unstretched film or a film stretched through one axis or two axes. The two-axis extension system may be simultaneous simultaneous two-axis extension in two extension directions, or successive two-axis extension after extending in a predetermined direction and then in other directions. 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. A retardation film is an optically functional film used for the purpose of compensating a retardation caused by a liquid crystal cell of an image display element. For example, a retardation film having an arbitrary retardation value can be provided by extending a film (such as uniaxial extension or biaxial extension) containing the thermoplastic resin, or forming a liquid crystal layer on the film.

Examples of the chain polyolefin resin include copolymers of two or more kinds of chain olefins, in addition to homopolymers of chain olefins such as polyethylene resins and polypropylene resins.

Cyclic polyolefin resins contain cyclic olefins as representative units of norzene, tetracyclododecene (also known as dimethano octahydronaphthalene), or derivatives thereof. Resin collectively. Specific examples of cyclic polyolefin resins are: ring-opened (co) polymers of cyclic olefins and their hydrides, addition polymers of cyclic olefins, and cyclic olefins such as ethylene and propylene. Copolymers of chain olefins or aromatic compounds having vinyl groups, and modified (co) polymers which are modified with unsaturated carboxylic acids or derivatives thereof. Among them, norbornene-based resins using norbornene-based monomers such as norcene and polycyclic norcene-based monomers as cyclic olefins are more suitable.

Cellulose ester resin, based on the hydroxyl groups in cellulose A part of the resin esterified by acetic acid may also be a mixed ester of which a part is esterified with acetic acid and a part is esterified with other acids. The cellulose ester-based resin is preferably an ethyl cellulose-based resin. Specific examples of the ethyl cellulose-based resin include triethyl cellulose, diethyl cellulose, cellulose acetate propionate, cellulose acetate butyrate, and the like.

Polyester resins are resins other than the above-mentioned cellulose ester resins having an ester bond, and are generally those containing a polycondensate of a polycarboxylic 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, and polytrimethylene terephthalate. Diesters, polynaphthalate, polycyclohexane dimethyl terephthalate, cyclohexane dimethyl polynaphthalate. Among them, polyethylene terephthalate is suitable from the viewpoints of mechanical properties, solvent resistance, scratch resistance, cost, and the like. Polyethylene terephthalate refers to a resin composed of more than 80 mol% of repeating units composed of ethylene terephthalate, and may also contain structural units derived from other copolymerization components.

Examples of other copolymerization components include a dicarboxylic acid component and a diol component. Examples of the dicarboxylic acid component system are isophthalic acid, 4,4'-dicarboxydiphenyl, 4,4'-dicarboxybenzophenone, bis (4-carboxyphenyl) ethane, and adipic acid , Sebacic acid, sodium 5-sulfoisophthalate, 1,4-dicarboxycyclohexane, and the like. Examples of the diol component system include propylene glycol, butanediol, neopentyl glycol, diethylene glycol, cyclohexanediol, ethylene oxide adducts of bisphenol A, polyethylene glycol, polypropylene glycol, and polytetramethylene glycol. Methylene glycol and the like. The dicarboxylic acid component and the diol component may be used in combination of two or more kinds, respectively, as necessary. Moreover, the above two The carboxylic acid component and the diol component are used in combination with a hydroxycarboxylic acid such as p-hydroxybenzoic acid and p-β-hydroxyethoxybenzoic acid. It is also possible to use a small amount of a dicarboxylic acid component and / or a diol component having a amine bond, a urethane bond, an ether bond, or a carbonate bond as other copolymerization components.

Polycarbonate resins are polyesters formed from carbonic acid and glycol or bisphenol. Among them, from the viewpoints of heat resistance, weather resistance, and acid resistance, it is preferable to use the aromatic polycarbonate having a diphenylalkane in a molecular chain. Polycarbonate can be exemplified by: 2,2-bis (4-hydroxyphenyl) propane (also known as bisphenol A), 2,2-bis (4-hydroxyphenyl) butane, 1,1-bis ( Polycarbonate derived from bisphenol of 4-hydroxyphenyl) cyclohexane, 1,1-bis (4-hydroxyphenyl) isobutane, and 1,1-bis (4-hydroxyphenyl) ethane.

The (meth) acrylic resin may be a polymer having methacrylate as a main monomer (containing 50% by weight or more), and a copolymer in which the polymer is copolymerized with a small amount of other copolymerization components is preferable. The (meth) acrylic resin is more preferably a copolymer of methyl methacrylate and methyl acrylate, and a third monofunctional monomer may be further copolymerized.

Examples of the third monofunctional single system include, for example, ethyl methacrylate, butyl methacrylate, cyclohexyl methacrylate, phenyl methacrylate, benzyl methacrylate, 2-methacrylic acid 2- Ethylhexyl, 2-hydroxyethyl methacrylate other than methyl methacrylates; such as ethyl acrylate, butyl acrylate, cyclohexyl acrylate, phenyl acrylate, benzyl acrylate, Acrylic esters of 2-ethylhexyl acrylate and 2-hydroxyethyl acrylate; such as methyl 2- (hydroxymethyl) acrylate, methyl 2- (1-hydroxyethyl) acrylate, 2- (hydroxymethyl) ) Ethyl acrylate, 2- (hydroxy Hydroxyalkyl acrylates of butyl (meth) acrylate; such as unsaturated acids of methacrylic acid and acrylic acid; halogenated styrenes such as chlorostyrene and bromostyrene; such as vinyl toluene, α-methylstyrene Substituted styrenes; such as unsaturated nitriles of acrylonitrile and methacrylonitrile; unsaturated anhydrides of maleic anhydride and citraconic anhydride; such as phenylmaleimide and cyclohexylmaleimide Unsaturated hydrazones and the like. The third monofunctional monomer may be used alone or in combination of two or more.

It is also possible to further copolymerize a polyfunctional monomer with a (meth) acrylic resin. Examples of the polyfunctional monosystem include: ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, tetraethylene glycol di (Meth) acrylate, nonethylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, or the oligomers of ethylene glycol at both terminal hydroxyl groups are subjected to (meth) acrylic acid Those esterified; those whose hydroxy groups at both ends of propylene glycol or oligomers are esterified with (meth) acrylic acid; such as neopentyl glycol di (meth) acrylate, hexanediol di (meth) acrylate, The hydroxyl group of a dihydric alcohol of butanediol di (meth) acrylate is esterified with (meth) acrylic acid; bisphenol A, an alkylene oxide adduct of bisphenol A, or a halogen substituted product thereof Both terminal hydroxyl groups are esterified with (meth) acrylic acid; such as trimethylolpropane and neopentyl alcohol are esterified with (meth) acrylic acid, and ring-opening addition of these terminal hydroxyl groups shrinks Glyceryl (meth) acrylate epoxy groups; diacids such as succinic acid, adipic acid, terephthalic acid, phthalic acid, halogenated substitutes of these, and alkylene oxides of these Was ring-opening addition of glycidyl (meth) acrylate of epoxy persons; (meth) acrylic acid aryl esters; such as divinyl benzene, divinyl aromatic compounds and the like. Where It is preferable to use ethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, and neopentyl glycol dimethacrylate.

The (meth) acrylic resin may be one which further undergoes a reaction between functional groups of the copolymer and is modified. The reaction system can be, for example, a methyl alcohol demethylation condensation reaction of a methyl ester group of methyl acrylate and a hydroxyl group of methyl 2- (hydroxymethyl) acrylate, a carboxyl group of acrylic acid, and 2- (hydroxymethyl) acrylic acid. Dehydration condensation reaction in the polymer chain of the hydroxyl group of methyl ester.

The glass transition temperature of the (meth) acrylic resin is preferably 80 to 160 ° C. The glass transition temperature can be adjusted by adjusting the polymerization ratio of methacrylate monomers and acrylate monomers, the carbon chain length of each ester group, the types of functional groups and polyfunctional monomers. Regulated relative to the polymerization ratio of the entire monomer.

In addition, the introduction of a ring structure into the main chain of a polymer can also be effectively used as a means to increase the glass transition temperature of a (meth) acrylic resin. The ring structure is preferably a heterocyclic structure such as a cyclic acid anhydride structure, a cyclic fluorene imine structure, and a lactone structure. Specific examples include cyclic acid anhydride structures such as glutaric anhydride structure and succinic anhydride structure, cyclic fluorene imine structures such as glutarimide structure and succinimide structure, and lactones such as butyrolactone and valerolactone. Ring structure. The larger the content of the ring structure in the main chain, the more the glass transition temperature of the (meth) acrylic resin can be increased. The cyclic anhydride structure and the cyclic fluorene imine structure can be introduced by a method of introducing and copolymerizing a monomer having a cyclic structure such as maleic anhydride and maleimide, and by polymerization. A method for introducing a cyclic acid anhydride structure by post-dehydration / de-methanol condensation reaction, a method for introducing an amine compound into a cyclic amidine imine structure, and the like. Have within The resin (polymer) with an ester ring structure can be prepared by heating a polymer having a hydroxyl group and an ester group in a polymer chain, and then heating the hydroxyl ester group in the obtained polymer as needed. It is obtained by cyclization and condensation in the presence of a catalyst of an organic phosphorus compound to form a lactone ring structure.

The (meth) acrylic resin may contain an additive as needed. Examples of the additive system include a lubricant, an anti-caking agent, a heat stabilizer, an antioxidant, an antistatic agent, a light resistance agent, an impact resistance improver, and a surfactant.

The (meth) acrylic resin may contain acrylic rubber particles containing an impact modifier from the viewpoints of film forming properties and impact resistance of the film. The acrylic rubber particles refer to particles having an elastic polymer mainly composed of acrylate as an essential component, and examples thereof include a single-layer structure including substantially only the elastic polymer, and a multilayer structure including the elastic polymer as a single layer. By. Examples of the elastic polymer include a crosslinked elastic copolymer having an alkyl acrylate as a main component and copolymerizing other vinyl-based monomers and crosslinkable monomers copolymerizable with the main component. The alkyl acrylate which is the main component of the elastic polymer may be, for example, methyl acrylate, ethyl acrylate, butyl acrylate, or 2-ethylhexyl acrylate having a carbon number of about 1 to 8, for use. An alkyl acrylate having an alkyl group having 4 or more carbon atoms is preferred. Other vinyl-based monomers that can be copolymerized with the alkyl acrylate include compounds having one polymerizable carbon-carbon double bond in the molecule, and more specifically, methyl esters such as methyl methacrylate Acrylates, aromatic vinyl compounds such as styrene, vinyl cyanide compounds such as acrylonitrile, and the like. Crosslinkable single systems can be listed in the molecule with at least Crosslinkable compounds having two polymerizable carbon-carbon double bonds. More specifically, the cross-linking compounds include, for example, ethylene glycol di (meth) acrylate, butanediol di (meth) acrylate. (Meth) acrylates of alcohols, such as alkenyl (meth) acrylate of allyl (meth) acrylate, divinylbenzene and the like.

A laminate including a film of a (meth) acrylic resin containing no rubber particles and a film of a (meth) acrylic resin containing rubber particles may be used as the protective film. Further, a (meth) acrylic resin layer may be formed on one or both sides of a phase difference expression layer containing a resin different from the (meth) acrylic resin, and a person expressing the phase difference may be 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 device such as a liquid crystal display device, a protective film containing an ultraviolet absorber is disposed on the visible side of an image display element (for example, a liquid crystal cell), thereby suppressing the image display element from ultraviolet rays While degraded. Examples of the ultraviolet absorber include a salicylate-based compound, a benzophenone-based compound, a benzotriazole-based compound, a cyanoacrylate-based compound, and a nickel salt-based compound.

The first protective film 10 and the second protective film 20 may be films made of the same resin or films made of different resins. As an example of the combination of the first protective film 10 and the second protective film 20, the first protective film 10 bonded via the first adhesive layer 15 having a lower glass transition temperature is made of (meth) acrylic resin, and The second protective film 20 to which the second adhesive layer 25 having a higher glass transition temperature is bonded is a combination 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, the mechanical properties (breaking stress) are low. The protective film is laminated on the polarizing film 30 via the first adhesive layer 15 having a lower glass transition temperature, thereby further improving workability. In addition, the first protective film 10 and the second protective film 20 may be the same or different in thickness, the presence or absence of additives, their types, and retardation characteristics.

The first protective film 10 and / or the second protective film 20 may also have, for example, a hard coat layer, an anti-glare layer, an anti-reflection layer, a light diffusion layer, and an antistatic layer on the outside (the surface opposite to the polarizing film 30). Surface treatment layer (coating layer) of antifouling layer and conductive layer.

The thicknesses of the first protective film 10 and the second protective film 20 are usually 5 to 200 μm, preferably 10 to 120 μm, and more preferably 10 to 85 μm. Reducing the thickness of the first protective film 10 and the second protective film 20 is advantageous for reducing the thickness of the polarizing plate and even the image display device. The thinner the protective film, the easier it is to reduce the cold and hot shock resistance. However, according to the present invention, even if the thicknesses of the first protective film 10 and the second protective film 20 are thin, the cold and hot shock resistance of the polarizing plate can be effectively improved. .

(4) Adhesive layer

The glass transition temperature Tg1 of the first adhesive layer 15 is -15 ° C or more and less than 60 ° C, and the glass transition temperature Tg2 of the second adhesive layer 25 is 60 ° C or more. The glass transition temperature of the first adhesive layer 15 and the second adhesive layer 25 satisfies such a relationship, whereby the workability and the warpage resistance of the polarizing plate can be highly balanced. Furthermore, the cold and hot shock resistance of the polarizing plate can be improved. The glass transition temperature of the subsequent agent layer can be measured by a differential scanning calorimeter (DSC), and an example of the measurement method is the method described in the paragraph of the embodiment described later.

Mainly from the viewpoint of processability, and considering warpage resistance, the glass transition temperature Tg1 of the first adhesive layer 15 is preferably less than 55 ° C, more preferably less than 50 ° C, and even more preferably Less than 45 ° C. On the other hand, if the glass transition temperature Tg1 is too low, even when the glass transition temperature Tg2 of the second adhesive layer 25 is within a predetermined range, the polarizing plate may have poor cold and heat shock resistance, and cracks or cracks may occur in the polarizing film 30 And so bad. From the standpoint of cold and hot shock resistance, and further from the standpoint of warpage resistance, the glass transition temperature Tg1 is preferably -10 ° C or higher, more preferably -5 ° C or higher, even more preferably 0 ° C or higher, and particularly preferably Above 5 ° C.

Mainly from the viewpoint of the durability of the polarizing plate, especially from the viewpoint of resistance to cold and heat, and further considering the warpage resistance, the glass transition temperature Tg2 of the second adhesive layer 25 is preferably 70 ° C or higher, more preferably 80 Above 90 ° C, more preferably above 90 ° C, even more preferably above 95 ° C. When the glass transition temperature Tg2 is 60 ° C. or higher, sufficient cold and hot shock resistance can be obtained, defects such as cracks and cracks in the polarizing film 30 can be suppressed, and warpage resistance is also favorable. On the other hand, if the glass transition temperature Tg2 is too high, the second adhesive layer 25 will become brittle. Even when the glass transition temperature Tg1 of the first adhesive layer 15 is within a predetermined range, the workability will be reduced and the Defects occur during processing. Therefore, the glass transition temperature Tg2 is preferably 200 ° C or lower, more preferably 180 ° C or lower, and even more preferably 160 ° C or lower.

Mainly from the viewpoint of improving the warpage resistance, the glass transition temperatures Tg1 and Tg2 are within the above ranges, respectively, and the difference between the two (Tg2-Tg1) is preferably below 120 ° C, and more preferably below 100 ° C. good. Tg2-Tg1 is more preferably below 90 ° C, and even more preferably below 80 ° C. And, will Tg2-Tg1 is set to 10 ° C or higher, in terms of having good processability, warpage resistance, and resistance to cold and hot shock, it is further set to 20 ° C or higher (for example, 50 ° C or higher, especially 55 ° C or higher). As favorable.

The adhesive for forming the first adhesive layer 15 and the second adhesive layer 25 is not particularly limited as long as the predetermined glass transition temperatures Tg1 and Tg2 can be obtained, and examples thereof include an aqueous adhesive, which can be heated or ultraviolet or visible light. , Hardening adhesive, etc., which are hardened by irradiation with active energy rays such as electron rays and X-rays. The curable adhesive system contains a curable (polymerizable) compound as a main component. Specific examples of the water-based adhesive are those in which a polyvinyl alcohol-based resin or a urethane resin as a main component is dissolved or dispersed in water, and may contain, for example, a polyaldehyde, a melamine-based compound, a zirconia compound, and zinc. Compound, glyoxal, hardening component of water-soluble epoxy resin and crosslinking agent. When a curable adhesive is used (including when the aqueous adhesive contains a curable component and a cross-linking agent), the formed adhesive layer is a cured product layer of the curable adhesive.

Among the above, since the drying step of removing the solvent by heating can be omitted, a hardening adhesive is more preferable, and an active energy ray hardening adhesive is more preferable. The water-based adhesive and the thermosetting adhesive require a heating step, but may cause warping in the polarizing plate due to the heating. The form of the polarizing plate using the active energy ray-curable adhesive is an example in which at least one of the first adhesive layer 15 and the second adhesive layer 25 is a cured product layer of the active energy ray-curable adhesive. It is preferable that both the first adhesive layer 15 and the second adhesive layer 25 are hardened layers of the active energy ray-curable adhesive.

The glass transition temperatures Tg1 and Tg2 of the first adhesive layer 15 and the second adhesive layer 25 can be adjusted, for example, according to the following guidelines. That is, when an adhesive layer is formed from a hardenable adhesive, the hardening compound contained in the hardenable adhesive as a main component is usually selected to have a glass transition temperature close to the target of the adhesive layer. Glass transition temperature compounds. The glass transition temperature of the hardened material of the hardening compound mainly depends on the combination of the structure of the hardening compound and the hardening compound. For example, when the hardening compound contains an alicyclic epoxy compound or an aromatic epoxy compound, the glass transition temperature of the hardening compound tends to increase; when it contains an aliphatic epoxy compound, the glass transition temperature tends to decrease. The tendency. The glass transition temperature of the adhesive layer can also be adjusted by the degree of cross-linking of the curable compound. For example, if the amount of the trifunctional or more functional curable compound is increased, the glass transition temperature of the adhesive layer tends to be higher. The glass transition temperature of the adhesive layer can also be adjusted by adding components other than the main component to the curable adhesive. For example, if a polymer component (thermoplastic resin, etc.) is added, the glass transition temperature of the adhesive layer becomes lower. The tendency.

The sclerosing | hardenable adhesive is classified by the sclerosing form, The cationic polymerization type | mold adhesive containing a cationically polymerizable compound as said sclerosing compound, and the radical polymerization type | mold adhesive containing a radically polymerizable compound as said sclerosing | hardenable compound are mentioned. Agents, mixed-molding curable adhesives containing both cationic polymerizable compounds and radical polymerizable compounds. Specific examples of the cationically polymerizable compound include an epoxy compound having one or more epoxy groups in the molecule, and one or more epoxy compounds in the molecule. An oxetane compound and a vinyl compound. Specific examples of the radical polymerizable compound include a (meth) acrylic compound and a vinyl compound having one or more (meth) acrylfluorenyl groups in a molecule. The curable adhesive may contain one or two or more kinds of cationically polymerizable compounds and / or one or two or more kinds of radically polymerizable compounds.

(4-1) Cationic polymerization type adhesive

A cationically polymerizable compound that is a main component of a cationically polymerizable adhesive refers to a compound or oligomer that undergoes cation polymerization by irradiation and heating with active energy rays such as ultraviolet, visible light, electron rays, and X-rays. Examples include epoxy compounds, oxetane compounds, and vinyl compounds. Among these, a preferable cationic polymerizable compound is an epoxy compound. The epoxy compound refers to a compound having one or more epoxy groups in a molecule, and is preferably a compound having two or more epoxy groups. The epoxy compound may be used alone or in combination of two or more. Examples of the epoxy compound system include an alicyclic epoxy compound, an aromatic epoxy compound, a hydrogenated epoxy compound, and an aliphatic epoxy compound. Among these, from the viewpoints of weather resistance, hardening speed, and adhesiveness, the epoxy compound preferably contains an alicyclic epoxy compound and an aliphatic epoxy compound, and more preferably contains an alicyclic epoxy compound.

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

A compound in which the group in which one or a plurality of hydrogen atoms in (CH ₂ ) _m in the formula (I) is removed is bonded to other chemical structures can be an alicyclic epoxy compound. One or more hydrogen atoms in (CH ₂ ) _m may be appropriately substituted by a linear alkyl group such as a methyl group or an ethyl group.

Among them, an alicyclic epoxy compound having an epoxy-cyclopentane structure [one of m = 3 in the above formula (I)] and an epoxy-cyclohexane structure [one of m = 4 in the above formula (I)], It is advantageous in terms of high glass transition temperature of the hardened material and increasing the glass transition temperature of the adhesive layer, and it is also advantageous in terms of adhesion between the polarizing film and the protective film. Specific examples of the alicyclic epoxy compound will be described below. Here, the compound names are exemplified first, and then the corresponding chemical formulas are shown respectively. The same symbols are attached to the compound names and the corresponding chemical formulas.

A: 3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate, B: 3,4-epoxy-6-methylcyclohexylmethyl 3,4-cyclo Oxy-6-methylcyclohexanecarboxylate, C: vinyl 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-tetraoxa [ 5.2.2.5.2.2] docosane, 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.

Aromatic epoxy compounds are compounds with aromatic rings and epoxy groups in the molecule. Specific examples thereof include bisphenol-type epoxy compounds such as diglycidyl ether of bisphenol A, diglycidyl ether of bisphenol F, and diglycidyl ether of bisphenol S or oligomers thereof; Novolac epoxy resins such as varnish epoxy resin, cresol novolac epoxy resin, hydroxybenzaldehyde novolac epoxy resin, etc .; glycidol of 2,2 ', 4,4'-tetrahydroxydiphenylmethane Polyfunctional epoxy compounds, such as glycidyl ethers of glyceryl ether, 2,2 ', 4,4'-tetrahydroxybenzophenone; polyfunctional epoxy resins, such as epoxidized polyvinyl phenol.

The hydrogenated epoxy compound is a glycidyl ether of a polyhydric alcohol having an alicyclic ring. The hydrogenated epoxy compound can be a selective hydrogenation reaction of an aromatic polyol on an aromatic ring under the presence of a catalyst under pressure, and The obtained nuclear hydrogenated polyhydroxy compound is subjected to glycidyl etherification. Specific examples of the aromatic polyol include bisphenols such as bisphenol A, bisphenol F, and bisphenol S. Type compounds; novolac resins such as phenol novolac resin, cresol novolac resin, hydroxybenzaldehyde phenol novolac resin; polyfunctional compounds such as tetrahydroxydiphenylmethane, tetrahydroxybenzophenone, and polyvinylphenol . The alicyclic polyol obtained by hydrogenating the aromatic ring of the aromatic polyol with epichlorohydrin can be reacted to form a glycidyl ether. Preferred among the hydrogenated epoxy compounds are diglycidyl ethers of hydrogenated bisphenol A.

An aliphatic epoxy compound is a compound having at least one oxetane ring (a three-membered cyclic ether) bonded to an aliphatic carbon atom in the molecule. For example: monofunctional epoxy compounds such as butyl glycidyl ether, 2-ethylhexyl glycidyl ether; 1,4-butanediol diglycidyl ether, 1,6-hexanediol diglycidyl Ether, neopentyl glycol diglycidyl ether, 1,4-cyclohexane dimethanol diglycidyl ether and other bifunctional epoxy compounds; trimethylolpropane triglycidyl ether, neopentyl tetraol shrink Glyceryl ether and more than three functional epoxy compounds; 4-vinylcyclohexene dioxide, limonene dioxide, etc. have an epoxy group directly bonded to an alicyclic ring and an aliphatic carbon atom. Epoxy compounds of oxenes and the like. Among them, from the viewpoint of the adhesiveness between the polarizing film and the protective film, it is a bifunctional epoxy compound (also referred to as a fat) having an oxetane ring bonded to an aliphatic carbon atom in the molecule. Group diepoxy compounds) are preferred. Such a suitable aliphatic diepoxide can be represented by the following formula (II), for example.

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

The aliphatic diepoxy compound represented by the above formula (II) is specifically a diglycidyl ether of an alkanediol, a diglycidyl ether of an oligomeric alkylene glycol having a repeating number of about 4 or an alicyclic type Glycidyl ether of glycol.

Specific examples of glycols which can form the aliphatic diepoxide compound represented by the formula (II) are described below. Alkanes are: ethylene glycol, propylene glycol, 1,3-propanediol, 2-methyl-1,3-propanediol, 2-butyl-2-ethyl-1,3-propanediol, 1,4-butanediol Glycol, neopentyl glycol, 3-methyl-2,4-pentanediol, 2,4-pentanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 2-methyl-2,4-pentanediol, 2,4-diethyl-1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 3,5-heptanediol Diol, 1,8-octanediol, 2-methyl-1,8-octanediol, 1,9-nonanediol and the like. Oligoalkylene glycols include diethylene glycol, triethylene glycol, tetraethylene glycol, and dipropylene glycol. The alicyclic diols include: cyclohexanediol such as 1,2-cyclohexanediol, 1,3-cyclohexanediol, 1,4-cyclohexanediol, 1,2-cyclohexanedimethanol, Cyclohexanedimethanol, such as 1,3-cyclohexanedimethanol and 1,4-cyclohexanedimethanol.

An oxetane compound, which is one of the cationically polymerizable compounds, is a compound containing one or more oxetane rings (oxetane) in the molecule. Specific examples include: 3-ethyl 3-Hydroxymethyloxa Cyclobutane (also known as oxetanol), 2-ethylhexyloxetane, 1,4-bis [((3-ethyloxetane-3-yl) methoxy Methyl} methyl] benzene (also known as stubyl dioxetane), 3-ethyl-3 [{(3-ethyloxetane-3-yl) methoxy} methyl ] Oxetane, 3-ethyl-3- (phenoxymethyl) oxetane, 3- (cyclohexyloxy) methyl-3-ethyloxetane. An oxetane compound can be used as a main component of a cationically polymerizable compound, and can also be used together with an epoxy compound. By using an oxetane compound in combination, there is a case where the curing speed and adhesion can be improved.

Examples of the vinyl compound that can be a cationically polymerizable compound include aliphatic or alicyclic vinyl ether compounds. Specific examples include n-pentyl vinyl ether, iso-pentyl vinyl ether, and n-hexyl. Vinyl ether, n-octyl vinyl ether, 2-ethylhexyl vinyl ether, n-dodecyl vinyl ether, stearyl vinyl ether, oleyl vinyl ether, etc. Vinyl ethers based on alkenyl or alkenyl alcohols; vinyl ethers containing hydroxyl groups such as 2-hydroxyethyl vinyl ether, 3-hydroxypropyl vinyl ether, 4-hydroxybutyl vinyl ether; cyclohexyl vinyl ether, 2-methylcyclohexyl vinyl ether, cyclohexyl methyl vinyl ether, benzyl vinyl ether and other vinyl ethers of monoalcohols having aliphatic or aromatic rings; glycerol monovinyl ether, 1,4 -Butanediol monovinyl ether, 1,4-butanediol divinyl ether, 1,6-hexanediol divinyl ether, neopentyl glycol divinyl ether, neopentyl tetraol divinyl ether , Neopentaerythritol tetravinyl ether, trimethylolpropane divinyl ether, trimethylolpropane trivinyl ether, 1,4-dihydroxycyclohexane monovinyl ether , 1,4-dihydroxycyclohexane divinyl ether, 1,4-dihydroxymethyl cyclohexane divinyl ether, 1,4-dihydroxymethyl cyclohexane divinyl ether, etc. Single to polyethylene Polyether; diethylene glycol divinyl ether, triethylene glycol divinyl ether, diethylene glycol monobutyl monovinyl ether, and other polyalkylene glycol mono to divinyl ether; glycidyl vinyl Ethers, other vinyl ethers such as ethylene glycol vinyl ether methacrylate. The vinyl compound may be used as a main component of the cationically polymerizable compound, or may be used in combination with an epoxy compound, or an epoxy compound and an oxetane compound. When a vinyl compound is used in combination, the curing speed and the viscosity of the adhesive may be reduced.

The cationically polymerizable adhesive system may further contain a cationically polymerizable compound other than the above, such as a cyclic lactone compound, a cyclic acetal compound, a cyclic thioether compound, and a spiro orthoester compound.

From the viewpoint of the adhesiveness between the polarizing film and the protective film, when the total amount of the curable compound contained in the cationically polymerizable adhesive (when the curable adhesive is mixed) is 100% by weight, the cation The content of the polymerizable compound (the content of all the cationic polymerizable compounds contained in the cationic polymerizable adhesive, and the total content of these when the polymer contains two or more kinds of cationic polymerizable compounds) is preferably 50% by weight or more. It is more preferably 60% by weight or more, and more preferably 70% by weight or more. As described above, the cationically polymerizable adhesive system may further contain a polymer component (such as a thermoplastic resin). Thereby, it is possible to lower the glass transition temperature of the adhesive layer and improve the adhesion between the polarizing film and the protective film.

The cation polymerization type adhesive agent can be active energy ray-hardenable or thermally hardenable. However, since the heating step can be omitted, and warping of the polarizing plate caused by the heating can be prevented, active energy radiation is preferred. Line hardening. When a cationic polymerizable adhesive containing a cationic polymerizable compound is applied with active energy ray hardening properties, it is preferred that a photocationic polymerization initiator is formulated in the adhesive. The photo-cationic polymerization initiator is an active energy ray such as visible light, ultraviolet rays, X-rays, or electron rays, which generates a cationic species or a Lewis acid, and starts a polymerization reaction of a cation-hardening compound. Since the photocationic polymerization initiator performs photocatalytic action with light, even when mixed with a photocationic hardening compound, it has excellent storage stability and handling properties. Compounds that produce cationic species or Lewis acids by irradiation with active energy rays include, for example, aromatic iodonium salts, onium salts of aromatic sulfonium salts, aromatic diazonium salts, iron-aromatic complexes, etc. .

The aromatic iodonium salt is a compound having a diaryl iodonium cation. Typical examples of the cation include a diphenyl iodonium cation. The aromatic sulfonium salt is a compound having a triarylsulfonium cation. Typical examples of the cation include triphenylsulfonium cation and 4,4'-bis (diphenylsulfonyl) diphenylsulfide cation. The aromatic diazonium salt is a compound having a diazonium cation. Typical examples of the cation include a benzenediazonium cation. The iron-arene complex is typically a cyclopentadienyl iron (II) arene cation complex salt.

The cations shown above are paired with anions (negative ions) to constitute a photocationic polymerization initiator. Example constituting the optical cationic polymerization initiator of the anionic, include: phosphorus-based special anion _{[(Rf) n PF 6-} n] -, hexafluorophosphate anion PF ₆ ^-, a hexafluoroantimonate anion ester SbF ₆ ^- , antimony-pentafluoro-hydroxy ester anion SbF ₅ (OH) ^-, hexafluoro arsenate anions AsF ₆ ^-, tetrafluoroborate anion BF ₄ ^-, tetrakis (pentafluorophenyl) borate anion B (C ₆ F ₅ ) ₄ ^- etc. Wherein the curable compound and the resulting polymeric cation of the next layer of security viewpoint perspective, phosphorus-based special anion _{[(Rf) n PF 6-} n] -, hexafluorophosphate anion PF ₆ ^- Is better.

The photocationic polymerization initiator may be used alone or in combination of two or more. Among them, the aromatic sulfonium salt has ultraviolet absorption characteristics even in a wavelength region around 300 nm, so it can be used as a hardened product which is excellent in hardenability and has good mechanical strength and adhesion strength.

The blending amount of the photocationic polymerization initiator is usually 0.5 to 10 parts by weight, and preferably 6 parts by weight or less, based on 100 parts by weight of the cationically polymerizable compound. By blending the photocationic polymerization initiator in an amount of 0.5 parts by weight or more, the cationic polymerizable compound can be sufficiently hardened, and high mechanical strength and adhesion strength can be imparted to the obtained polarizing plate. On the other hand, when the amount of the photocationic polymerization initiator becomes excessive, there may be a case where the hygroscopicity of the hardened material becomes high due to the increase of the ionic substance in the hardened material, and the durability of the polarizing plate may decrease.

As described above, the cationically polymerizable adhesive may include a radically polymerizable compound in addition to the cationically polymerizable compound, thereby forming a hardenable adhesive with a mixed shape. By using a radically polymerizable compound in combination, it is possible to improve the effect of the hardness and mechanical strength of the adhesive layer, and it is easier to adjust the viscosity and curing speed of the curable adhesive.

(4-2) Radical polymerization type adhesive

The radically polymerizable compound as a main component of the radically polymerizable adhesive refers to ultraviolet rays, visible light, electron rays, and X-rays. Specific examples of compounds or oligomers that undergo radical polymerization such as irradiation and heating with active energy rays and harden, include compounds having ethylenically unsaturated bonds. Examples of the compound having an ethylenically unsaturated bond include a styrene, a styrene sulfonic acid, and a vinyl acetate, in addition to the (meth) acrylic compound having one or more (meth) acrylfluorenyl groups in the molecule. , Vinyl propionate, vinyl compounds of N-vinyl-2-pyrrolidone and the like. Among them, preferred are radical polymerizable compounds (meth) acrylic compounds.

Examples of the (meth) acrylic compound include compounds containing a (meth) acrylfluorenyl group, such as a (meth) acrylfluorene oligomer having at least two (meth) acrylfluorenyl groups in the molecule. A (meth) acrylic acid ester monomer having at least one (meth) acrylfluorenyloxy group in the molecule, a (meth) acrylamide monomer, and a functional group-containing compound are reacted in two or more types. The (meth) acrylic acid oligomer is preferably a (meth) acrylic acid ester oligomer having at least two (meth) acryloxy groups in the molecule. The (meth) acrylic compound may be used alone or in combination of two or more.

Examples of the (meth) acrylic acid ester monomer include a monofunctional (meth) acrylic acid ester monomer having one (meth) acryloxy group in the molecule, and two (meth) acrylic acid fluorene in the molecule. A bifunctional (meth) acrylate monomer having an oxy group, and a polyfunctional (meth) acrylate monomer having three or more (meth) acryloxy groups in the molecule.

Examples of the monofunctional (meth) acrylate monomer are alkyl (meth) acrylates. In the alkyl (meth) acrylate, as long as the alkyl group has 3 or more carbon atoms, it may be linear or branched. Specific examples of alkyl (meth) acrylates include methyl (meth) acrylate and (meth) acrylic acid. Ethyl ester, isopropyl (meth) acrylate, butyl (meth) acrylate, isobutyl (meth) acrylate, third butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate Wait. Also, an aralkyl (meth) acrylate such as benzyl (meth) acrylate; a (meth) acrylate of a terpene alcohol such as isobornyl (meth) acrylate; such as (meth) Tetrahydrofuran methyl acrylate (meth) acrylate with tetrahydrofuran methyl structure; such as cyclohexyl (meth) acrylate, cyclohexyl methyl (meth) acrylate, dicyclopentyl acrylate, (meth) acrylic acid Dicyclopentenyl esters, 1,4-cyclohexanedimethanol monoacrylate, (meth) acrylates having a cycloalkyl group at the alkyl portion; such as (meth) acrylic acid N, N-dimethylamino Aminoalkyl (meth) acrylates of ethyl esters; such as 2-phenoxyethyl (meth) acrylate, dicyclopentenyloxyethyl (meth) acrylate, ethylcarbitol (methyl ) As a monofunctional (meth) acrylate monomer, a (meth) acrylate having an ether bond at the alkyl portion of an acrylate or a phenoxy polyethylene glycol (meth) acrylate is used.

Further, a monofunctional (meth) acrylate having a hydroxyl group at an alkyl moiety and a monofunctional (meth) acrylate having a carboxyl group at an alkyl moiety can also be used. Specific examples of the monofunctional (meth) acrylate having a hydroxyl group at the alkyl portion include 2-hydroxyethyl (meth) acrylate, 2- or 3-hydroxypropyl (meth) acrylate, and (meth) 4-hydroxybutyl acrylate, 2-hydroxy-3-phenoxypropyl (meth) acrylate, trimethylolpropane mono (meth) acrylate, neopentyltetraol mono (meth) acrylate. Specific examples of the monofunctional (meth) acrylate having a carboxyl group at an alkyl group include 2-carboxyethyl (meth) acrylate, ω-carboxy-polycaprolactone (n ≒ 2) mono (methyl) Acrylate, 1- [2- (meth) acrylic acid oxyethyl] phthalate, 1- [2- (meth) acrylic acid Oxyethyl] hexahydrophthalate, 1- [2- (meth) acrylic acid oxyethyl] succinate, 4- [2- (meth) acrylic acid oxyethyl] trimellitic acid Ester, N- (meth) acryloxy-N ', N'-dicarboxymethyl-p-phenylene diamine.

The (meth) acrylamide monomer is preferably a (meth) acrylamide having a substituent at the N-position. A typical example of the N-position substituent is an alkyl group, but it can also be used with (meth) The nitrogen atoms of acrylamide form a ring together. In addition to the carbon atom and the nitrogen atom of (meth) acrylamide, the ring system may also have an oxygen atom as a ring member. Further, a substituent such as an alkyl group or a pendant oxygen group (= O) may be bonded to a carbon atom constituting the ring.

Specific examples of N-substituted (meth) acrylamide include: N-methyl (meth) acrylamide, N-ethyl (meth) acrylamide, N-isopropyl (methyl) Acrylamide, N-n-butyl (meth) acrylamide, N-third-butyl (meth) acrylamide, N-alkyl (methyl) of N-hexyl (meth) acrylamide ) Acrylamide; such as N, N-dimethyl (meth) acrylamide, N, N-diethyl (meth) acrylamide, N, N-dialkyl (meth) acrylamine amine. 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 -(2-hydroxypropyl) (meth) acrylamide and the like. In addition, specific examples of the N-substituted (meth) acrylamide forming the 5-membered ring or the 6-membered ring described above are: N-acrylfluorenyl pyrrolidine, 3-acrylfluorenyl-2- Azolidone, 4-propenylmethylmorpholine, N-propenylmethylpiperidine, N-methacrylmethylpiperidine and the like.

Examples of the bifunctional (meth) acrylate monosystem include: alkylene glycol di (meth) acrylate, polyoxyalkylene glycol di (meth) acrylate, and halogen-substituted alkylene glycol di (meth) acrylate. ) Acrylate, di (meth) acrylate of aliphatic polyhydric alcohol, di (meth) acrylate of hydrogenated dicyclopentadiene or tricyclodecanedialkanol, di Alkanol or di Di (meth) acrylates of alkanediols, di (meth) acrylates of alkylene oxide adducts of bisphenol A or bisphenol F, bis (meth) acrylic acid of bisphenol A or bisphenol F Epoxy esters, etc.

More specific examples of bifunctional (meth) acrylate monomers include ethylene glycol di (meth) acrylate, 1,3-butanediol di (meth) acrylate, 1 1,4-butanediol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, 1,9-nonanediol di (meth) acrylate, neopentyl glycol di ( (Meth) acrylates, trimethylolpropane di (meth) acrylate, neopentaerythritol di (meth) acrylate, bis (trimethylolpropane) di (meth) acrylate, diethylene glycol Alcohol di (meth) acrylate, triethylene glycol di (meth) acrylate, dipropylene glycol di (meth) acrylate, tripropylene glycol di (meth) acrylate, polyethylene glycol di (meth) Acrylate, polypropylene glycol di (meth) acrylate, polytetramethylene glycol di (meth) acrylate, polysiloxane di (meth) acrylate, hydroxytrimethylacetic acid neopentyl glycol two (Meth) acrylate, 2,2-bis [4- (meth) propenyloxyethoxyethoxyphenyl] propane, 2,2-bis [4- (meth) propenyloxy Ethoxyethoxycyclohexyl] propane, hydrogenated dicyclopentadienyl di (meth) acrylate, tricyclic Decane dimethanol di (meth) acrylate, 1,3-di Alkane-2,5-diyldi (meth) acrylate [aka: di Alkanol di (meth) acrylate], acetal compound of hydroxytrimethylacetaldehyde and trimethylolpropane [chemical name: 2- (2-hydroxy-1,1-dimethylethyl) -5 -Ethyl-5-hydroxymethyl-1,3-di Alkane] bis (meth) acrylate, gins (hydroxyethyl) trimeric isocyanate di (meth) acrylate, 1,4-cyclohexanedimethanol diacrylate, and the like.

Polyfunctional (meth) acrylate monomers with tri- or higher functionality, representative examples are glycerol tri (meth) acrylate, alkoxylated glycerol tri (meth) acrylate, trimethylolpropane tri (methyl) Base) acrylate, bis (trimethylolpropane) tri (meth) acrylate, bis (trimethylolpropane) tetra (meth) acrylate, neopentaerythritol tri (meth) acrylate, new Pentaerythritol tetra (meth) acrylate, dinepentaerythritol tetra (meth) acrylate, dinepentaerythritol penta (meth) acrylate, dinepentaerythritol hexa (meth) acrylate, etc. Poly (meth) acrylates of trifunctional or higher aliphatic polyhydric alcohols, others include: poly (meth) acrylates of trifunctional or higher halogen-substituted polyols, and tertiary alkylene oxide adducts of glycerol ( (Meth) acrylate, trimethylolpropane alkylene oxide adduct, tri (meth) acrylate, 1,1,1-ginseng ((meth) acrylic acid ethoxyethoxyethoxy) Propane, ginseng (hydroxyethyl) trimer isocyanate tri (meth) acrylate, and the like.

On the other hand, (meth) acrylic acid oligomers include urethane (meth) acrylic acid oligomers, polyester (meth) acrylic acid oligomers, and epoxy (meth) acrylic acid oligomers. Things.

The urethane (meth) acrylic acid oligomer is a compound having a urethane bond (-NHCOO-) and at least two (meth) acrylfluorene groups in the molecule. Specifically, it can be a urethane reaction product of a hydroxyl-containing (meth) acrylic monomer having at least one (meth) acrylfluorenyl group and at least one hydroxyl group in a molecule, and a polyisocyanate. , And, the urethane compound containing an isocyanate group at the end obtained by reacting a polyol with a polyisocyanate, and a (methyl group having at least one (meth) acrylfluorenyl group and at least one hydroxyl group in the molecule, respectively) Urethanes of acrylic monomers Reaction products.

The hydroxyl group-containing (meth) acrylic monomer used in the aforementioned urethanization reaction may be, for example, a hydroxyl group-containing (meth) acrylate monomer, and specific examples thereof include (meth) acrylic acid 2 -Hydroxyethyl ester, 2-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 2-hydroxy-3-phenoxypropyl (meth) acrylate, di (meth) acrylic acid Glyceryl ester, trimethylolpropane di (meth) acrylate, neopentaerythritol tri (meth) acrylate, dinepentaerythritol penta (meth) acrylate. Specific examples other than the hydroxyl-containing (meth) acrylate monomer include N-hydroxyalkyl groups such as N-hydroxyethyl (meth) acrylamidonium, N-hydroxymethyl (meth) acrylamidoamine ( Methacrylamide monomer.

Polyisocyanates that can be supplied to the urethanization reaction of (meth) acrylic monomers containing hydroxyl groups include hexamethylene diisocyanate, lysine diisocyanate, isophorone diisocyanate, Cyclohexylmethane diisocyanate, toluene diisocyanate, xylene diisocyanate, diisocyanates obtained by hydrogenating aromatic isocyanates in these diisocyanates (e.g., hydrogenated toluene diisocyanate, hydrogenated xylene diisocyanate, etc.), triphenyl Di- or tri-isocyanates such as methane triisocyanate and benzylbenzene triisocyanate; and polyisocyanates obtained by polymerizing the above-mentioned diisocyanates.

In addition, as a polyol to be used as a urethane compound containing an isocyanate group at its terminal by reaction with a polyisocyanate, a polyhydric alcohol other than an aromatic, aliphatic, or alicyclic polyol can be used. Ester polyol, polyether polyol, etc. Aliphatic and alicyclic polyols are available Examples: 1,4-butanediol, 1,6-hexanediol, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, neopentyl glycol, trimethylolethane, trimethylol Propane, bis (trimethylolpropane), neopentaerythritol, dinepentaerythritol, dimethylol heptane, dimethylol propionic acid, dimethylol butyric acid, glycerol, hydrogenated bisphenol A, etc. .

The polyester polyol is obtained by the dehydration condensation reaction of the above-mentioned polyol and a polycarboxylic acid or its anhydride. Examples of polybasic carboxylic acids or their anhydrides are those with an "(anhydride)" if they can be acid anhydrides: succinic acid (anhydride), adipic acid, maleic acid (anhydride), and itaconic acid (anhydride ), Trimellitic acid (anhydride), pyromellitic acid (anhydride), phthalic acid (anhydride), isophthalic acid, terephthalic acid, hexahydrophthalic acid (anhydride) and the like.

The polyether polyols may be polyoxyalkylene-modified polyols obtained by the reaction of the above-mentioned polyols or dihydroxybenzenes with alkylene oxides, in addition to polyalkylene glycols.

The so-called polyester (meth) acrylic oligomer is a compound having an ester bond in the molecule and at least two (meth) acrylfluorenyl groups (typically (meth) acrylfluorenyloxy). Specifically, it can be prepared by carrying out a dehydration condensation reaction using (meth) acrylic acid, a polycarboxylic acid or an anhydride thereof, and a polyhydric alcohol. Examples of polycarboxylic acids or their anhydrides that can be used in the dehydration condensation reaction. If "(anhydride)" is attached to those that can be acid anhydrides, there are: succinic acid (anhydride), adipic acid, and maleic acid (anhydride ), Iconic acid (anhydride), trimellitic acid (anhydride), pyromellitic acid (anhydride), hexahydrophthalic acid (anhydride), phthalic acid (anhydride), isophthalic acid, terephthalic acid Wait. In addition, the polyhydric alcohols that can be used in the dehydration condensation reaction include 1,4-butanediol, 1,6-hexanediol, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, neopentyl Diol, trimethylolethane, trimethylolpropane, di (tri (Methylolpropane), neopentaerythritol, dipentaerythritol, dimethylolheptane, dimethylolpropanoic acid, dimethylolbutanoic acid, glycerol, hydrogenated bisphenol A, and the like.

Epoxy (meth) acrylic acid oligomer can be prepared, for example, by addition reaction of polyglycidyl ether and (meth) acrylic acid, and has at least two (meth) acrylic acid in the molecule base. Examples of polyglycidyl ethers that can be used in the addition reaction include ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, tripropylene glycol diglycidyl ether, and 1,6-hexanediol diglycidyl ether. Ether, bisphenol A diglycidyl ether, and the like.

The radical polymerization type adhesive may be active energy ray-curable or heat-curable, but is preferably active energy ray-curable. When imparting active energy ray-hardenability to a radically polymerizable adhesive containing a radically polymerizable compound, a photoradical polymerization initiator is preferably blended in the adhesive. Photo radical polymerization initiators are those who initiate polymerization reactions of radically curable compounds by irradiation with active energy rays such as visible light, ultraviolet rays, X-rays, or electron rays. The photo radical polymerization initiator may be used alone or in combination of two or more.

Specific examples of the photo-radical polymerization initiator include acetophenone, 3-methylacetophenone, benzyldimethylketal, and 1- (4-isopropylphenyl) -2-hydroxy- 2-methylpropane-1-one, 2-methyl-1- [4- (methylthio) phenyl-2-morpholinylpropane-1-one, 2-hydroxy-2-methyl-1- Acetophenone-based initiators such as phenylpropane-1-one; benzophenone-based initiators such as benzophenone, 4-chlorobenzophenone, 4,4'-diaminobenzophenone ; Benzoin ether-based initiators, such as benzoin propyl ether, ethyl ether; Benzoin ether-based initiators, such as 4-isopropyloxanthanone; Others, oxygen Heteroanthrone, fluorenone, camphorquinone, benzaldehyde, Anthraquinone.

The blending amount of the photo radical polymerization initiator is usually 0.5 to 20 parts by weight, and preferably 1 to 6 parts by weight, with respect to 100 parts by weight of the radical polymerizable compound. By blending the photoradical polymerization initiator in an amount of 0.5 parts by weight or more, the radical polymerizable compound can be sufficiently hardened, and the obtained polarizing plate can be given high mechanical strength and adhesive strength. On the other hand, if the blending amount is too large, the durability of the polarizing plate may be reduced.

(4-3) Additives

The adhesive forming the first adhesive layer 15 and / or the second adhesive layer 25 may contain other additives as necessary. Specific examples of the additives include ion trapping agents, antioxidants, chain transfer agents, polymerization accelerators (polyols, etc.), sensitizers, sensitizers, light stabilizers, tackifiers, thermoplastic resins, fillers, Flow regulator, plasticizer, defoamer, leveling agent, silane coupling agent, pigment, antistatic agent, ultraviolet absorber, thermal polymerization initiator. When preparing a thermosetting adhesive, a thermal polymerization initiator may be used instead of the photopolymerization initiator. A photopolymerization initiator and a thermal polymerization initiator may be used in combination. Examples of the ion trapping agent include powdery inorganic compounds such as bismuth-based, antimony-based, magnesium-based, aluminum-based, calcium-based, titanium-based and mixed systems thereof, and antioxidants include hindered phenol-based antioxidants.

(4-4) Adhesive coating, and polarizing film and protective film

The first protective film 10 is laminated on one surface of the polarizing film 30 via the first adhesive layer 15, and the second protective layer is passed on the other surface of the polarizing film 30. 25 is laminated, followed by the second protective film 20, thereby obtaining the polarizing plate of the present invention. The first protective film 10 and the second protective film 20 (hereinafter, also simply referred to as "protective films" hereinafter) can be laminated on one side in a stepwise manner, and can also be formed on both sides in one step. Laminate then.

Adhesion between the polarizing film 30 and the protective film can be specifically performed by applying an adhesive to the adhesive surface of the polarizing film 30 and / or the adhesive surface of the protective film, and applying the adhesive through the coating layer of the adhesive. The two films are overlapped, and for example, the adhesive layer is dried by pressing from above with a bonding roller, and the adhesive layer is dried (for example, in the case of an aqueous adhesive), and the active agent ray is irradiated to harden the adhesive layer (for active energy ray hardening). (In the case of an adhesive) or heating to harden the layer of the adhesive (in the case of a thermosetting adhesive). Even when an active energy ray-curable adhesive is used, heat treatment may be performed while the active energy ray is irradiated, or heat treatment may be performed after the irradiation with the active energy ray. Before forming the coating layer of the adhesive, one or both of the bonding surfaces of the polarizing film 30 and the protective film may be subjected to, for example, saponification treatment, corona discharge treatment, plasma treatment, flame treatment, and primer treatment. 2, the easy treatment of anchor coating.

For the formation of the coating layer of the adhesive, various coating methods such as a doctor blade, a wire rod, a die coater, a dot coater, and a gravure coater can be used. Further, a method may be adopted in which the adhesive is continuously supplied while the bonding surfaces of both the polarizing film 30 and the protective film are inside, while the adhesive is spread therebetween.

From the viewpoint of coatability, the adhesive for 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, and more preferably Below 500mPa‧s, more preferably below 100mPa‧s. The adhesive may be a solvent-free type, but it may contain an organic solvent in order to adjust the viscosity to the coating method used.

Further, 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 the step of laminating and polarizing the polarizing film 30 and the protective film. Thereby, the adhesion between the polarizing film 30 and the protective film is improved, especially the adhesion between the protective film and the adhesive layer is improved. Specific examples of heating include heating of a protective film, heating of an adhesive, heating of a laminated body in which a polarizing film 30 and a protective film are laminated through an uncured or undried adhesive layer. The method for heating the protective film or the laminated body can be, for example, a method of causing the elongated protective film and the laminated body to sequentially emit radiant heat through an infrared heater or the like, and using a blower or the like to blow the heated gas to the elongated protection. Film, laminate, etc. The method of heating the adhesive agent may be, for example, a method of heating and holding the adhesive agent in a storage tank in advance, and supplying the heated adhesive agent to the coating device. The temperature for heating the protective film, the adhesive or the laminate is preferably 30 to 80 ° C, and more preferably 40 to 60 ° C. If the heating temperature exceeds 80 ° C., there is a concern that the protective film, the adhesive, or the laminate is deteriorated by heat. In addition, if the heating temperature does not reach 30 ° C., there is a tendency that the effect of improving the adhesion between the protective film and the polarizing film 30 is 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. With the moisture content in the above range, especially when the adhesive is a cationic polymerization type adhesive, the reactivity of the adhesive is improved, and the protective film and the polarizing film 30 Adhesion tends to improve.

The source of the active energy ray may be any material that generates, for example, ultraviolet rays, electron rays, X-rays, and the like. The active energy rays are preferably ultraviolet rays. The ultraviolet light source is preferably a light source with a luminous distribution below a wavelength of 400 nm. Examples include low-pressure mercury lamps, medium-pressure mercury lamps, high-pressure mercury lamps, ultra-high-pressure mercury lamps, fluorescent lamps, black light lamps, microwave-excited mercury lamps, and metal halogen lamps.

The intensity of the active energy ray irradiation to the adhesive layer depends on the composition of each adhesive, but the light irradiation intensity in the wavelength region effective for activation of the photopolymerization initiator is 0.1 to 1000 mW / cm ² Is better. If the light irradiation intensity is too small, the reaction time becomes too long. On the other hand, if the light irradiation intensity is too large, the adhesive layer may be generated due to the heat radiated by the lamp and the heat generated during the polymerization of the adhesive. Yellowing, deterioration of the polarizing film 30, or defective surface of the protective film. In addition, the light irradiation time to the adhesive is also limited by each adhesive composition, but it is preferable to set the cumulative light amount expressed by the product of the light irradiation intensity and the light irradiation time 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 may be insufficient, and the hardening of the resulting adhesive layer may be insufficient; on the other hand, if the amount of accumulated light is too large, the light The irradiation time becomes very long and easily becomes unfavorable for improving productivity.

There are no particular restrictions on the timing of laminating the protective film on the polarizing film 30 through the coating layer of the adhesive and the timing of hardening or drying the coating layer. For example, a protective film can be laminated, and then the coating layer can be hardened or dried, and then another protective film can be laminated to harden or dry the coating layer. or, It is also possible to laminate the protective films on both sides sequentially or simultaneously, and then harden or dry the coated layers on both sides at the same time. In addition, irradiation of active energy rays can be performed from any protective film side. For example, when one protective film contains an ultraviolet absorbent and the other protective film does not contain an ultraviolet absorbent, it is preferable to irradiate active energy rays from the side of the protective film that does not contain an ultraviolet absorbent. By irradiating in this way, the active energy rays irradiated can be effectively used, and the curing speed can be increased.

The thickness of the first and second adhesive layers 15 and 25 after curing or drying is usually 20 μm or less, preferably 10 μm or less, even more preferably 5 μm or less, and even more preferably 3 μm or less. When the thicknesses of the first and second adhesive layers 15, 25 are too large, the reaction rate of the adhesive decreases, and the moisture and heat resistance of the polarizing plate tends to deteriorate. The thicknesses of the first and second adhesive layers 15 and 25 are usually 0.01 μm or more, and 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 polarizing plate (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 a retardation film different from the protective film may be separately laminated. 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 an adhesive layer and an adhesive layer.

Specific examples of the retardation film include a birefringent film composed of a stretched film of a thermoplastic resin having translucency, and a disk fixed in orientation. Films of discotic liquid crystals or nematic liquid crystals, and those having the above-mentioned liquid crystal layer formed on a substrate film. The base film is usually a thermoplastic resin film, and a cellulose ester resin such as triethylfluorenyl cellulose is preferably used for the thermoplastic resin.

The thermoplastic resin that forms a birefringent film can be used as described in the protective film. For example, if a cellulose ester resin is used as an example, a birefringent film can be obtained by a method in which a cellulose ester resin contains a compound having a phase difference adjustment function to form a film. A method, a method of coating a compound having a retardation adjustment function on the surface of a cellulose ester resin film, and a method of extending the cellulose ester resin toward one or two axes. As the thermoplastic resin forming the birefringent film, other thermoplastic resins such as polyvinyl alcohol-based resin, polystyrene-based resin, polyarylate-based resin, and polyamide-based resin can also be used.

For the purpose of controlling the optical characteristics such as wideband, the retardation film can be used in combination of two or more. Further, it is not limited to a film having optical anisotropy, and a zero retardation film that is substantially optically in the same direction may be used as the retardation film. The zero retardation film refers to a film in which the in-plane retardation value R _e and the thickness direction retardation value R _th are both -15 to 15 nm. The so-called 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 are respectively defined by the following formulas: R _e = (n _x -n _y ) × d

R _th = [(n _x + n _y ) / 2-n _z ] × d. In the formula, n _x is the refractive index in the slow axis direction (x-axis direction) in the film plane, and n _y is the refractive index in the fast axis direction (y-axis direction perpendicular to the x-axis in the plane), n _z is the refractive index of the film thickness direction (the z-axis direction perpendicular to the film surface), and d is the thickness of the film.

As the zero-retardation film system, a thermoplastic resin described in a protective film and a birefringent film can be used. For example, a polyolefin resin such as a cellulose ester resin, such as a chain polyolefin resin, and a cyclic polyolefin resin, such as a polymer, can be used. Resin film of polyester resin of ethylene terephthalate. Among these, since it is easy to control a phase difference value and it is also easy to obtain, it is preferable to use a cellulose ester resin and a polyolefin resin.

Examples of other optically functional films (optical members) that can be included in polarizing plates are light collecting plates, brightness enhancement films, reflective layers (reflective films), transflective reflective layers (transflective reflective films), and light diffusion layers ( Light diffusing film), etc. These are generally provided when the polarizing plate is a polarizing plate arranged on the back side (backlight side) of the liquid crystal cell.

The light-concentrating plate is used for the purpose of controlling the light path, and can be a prismatic array sheet, a lens array sheet, a dot attached sheet, or the like.

Brightening film is used to improve the brightness of liquid crystal display devices suitable for polarizing plates. Specific examples include: laminated thin film films having mutually different anisotropies of refractive index, and reflective polarized separation films designed in such a way as to produce anisotropy in reflectance; an orientation film of a cholesteric liquid crystal polymer The circularly polarized light separation sheet supported by the alignment liquid crystal layer of the alignment film on the substrate film.

The reflection layer, transflective reflection layer, and light diffusion layer are The polarizing plates are respectively provided as reflective, transflective, and diffused optical members. A reflective polarizing plate is a type of liquid crystal display device that can reflect incident light from the viewing side and display it. The light source such as a backlight can be omitted, so the liquid crystal display device can be made thinner. The semi-transmissive polarizing plate is a liquid crystal display device that can be used in a reflective type in bright places and displays light from a backlight in dark places. Further, the diffusion-type polarizing plate is a liquid crystal display device that can be used to impart light diffusivity and suppress display defects such as moire. The reflection layer, the transflective reflection layer, and the light diffusion layer can be formed by a known method.

(5-2) Adhesive layer

The polarizing plate of the present invention may include an adhesive layer for bonding the polarizing plate to an image display element such as a liquid crystal cell or other optical components. The adhesive layer can be laminated on the outer surface of the protective film. The 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.

Adhesives that can be used in the adhesive layer. (Meth) acrylic resins and silicone resins, polyester resins, polyurethane resins, polyether resins, etc. can be used as the matrix polymer. By. Among them, from the viewpoints of transparency, adhesion, reliability, weather resistance, heat resistance, reworkability, etc., it is preferable to use a (meth) acrylic adhesive. In the (meth) acrylic adhesive, an alkyl group having a carbon number of 20 or less such as methyl, ethyl, or butyl is prepared so that the glass transition temperature is preferably 25 ° C or lower, more preferably 0 ° C or lower. (Meth) acrylic acid alkyl esters and (meth) acrylic monomers containing functional groups such as (meth) acrylic acid and hydroxyethyl (meth) acrylate, and the weight average molecular weight of the (meth) acrylic acid is 100,000 or more Resin, useful As a matrix polymer.

Forming an adhesive layer on a polarizing plate can be prepared by, for example, dissolving or dispersing the adhesive composition in an organic solvent such as toluene or ethyl acetate to prepare a solution of 10 to 40% by weight, and directly applying this solution to the polarizing plate. A method of forming an adhesive layer on the target surface of the object; a method of forming the adhesive layer into a thin sheet on the release film subjected to the release treatment and moving it to the target surface of the polarizing plate. The thickness of the adhesive layer is determined depending on its adhesive force and the like, but a range of about 1 to 50 μm is appropriate, and it is preferably 2 to 40 μm.

The polarizing plate may contain the above-mentioned separation film. The separation membrane may be a membrane containing a polyethylene resin such as polyethylene, a polypropylene resin such as polypropylene, or a polyester resin such as polyethylene terephthalate. Among them, a stretched film of polyethylene terephthalate is preferred.

In the adhesive layer, it can also be blended as required: fillers containing glass fiber, glass beads, resin particles, metal powder and other inorganic powders, pigments, colorants, antioxidants, ultraviolet absorbers, antistatic agents, etc.

Examples of the antistatic agent include ionic compounds, conductive fine particles, and conductive polymers. The use of ionic compounds is preferred. The cation component constituting the ionic compound may be an inorganic cation or an organic cation, but an organic cation is preferred from the viewpoint of compatibility with a (meth) acrylic resin. Examples of the organic cation system include pyridinium cation, imidazolium cation, ammonium cation, sulfonium cation, and sulfonium cation. On the other hand, the anionic component constituting the ionic compound may be an inorganic anion or an organic anion. However, in order to impart excellent antistatic properties to the ionic compound, the anionic component containing a fluorine atom good. An anionic component containing a fluorine-based atoms include: hexafluorophosphate anion [(PF ₆ ^-)], bis (trifluoromethane sulfonic acyl) acyl imide anion _{[(CF 3 SO 2) 2} N -], bis- ( sulfo acyl-fluoro) acyl imide anion ^{_{[(FSO 2) 2 N -}} ] and the like.

(5-3) Protective film

The polarizing plate of the present invention may contain a protective film for temporarily protecting the surface (protective film surface) thereof. The protective film is, for example, after the polarizing plate is attached to the image display element and other optical members, the adhesive layer is peeled off and removed one by one.

The protective film is composed of a base film and an adhesive layer laminated on the base film. The adhesive layer refers to the above description. The resin constituting the substrate film may be, for example, a polyethylene-based resin such as polyethylene, a polypropylene-based resin such as polypropylene, or a polyester-based resin such as polyethylene terephthalate and polyethylene naphthalate. Resin, thermoplastic resin such as polycarbonate resin. Polyester resins such as polyethylene terephthalate are preferred.

The polarizing plate of the present invention can be bonded to an image display element such as a liquid crystal cell via an adhesive layer. Examples of the liquid crystal cell system include an IPS type and a VA type.

[Example]

Hereinafter, the present invention will be described more specifically by showing examples and comparative examples, but the present invention is not limited to these examples. In the following examples, a radical polymerizable compound constituting an adhesive, a photoradical polymerization initiator, and The following additives were used as the additives.

(Radical Polymerizable Compound)

[1] hardenable compound 1: dicyclopentenyl acrylate (trade name "FA-513AS" obtained from Hitachi Chemical Co., Ltd., glass transition temperature 120 ° C), [2] hardenable compound 2: 1, 4-cyclohexanedimethanol monoacrylate (trade name "CHDMMA", glass transition temperature 18 ° C obtained from Nippon Kasei Co., Ltd.), [3] hardenable compound 3: hydroxyethyl acrylate (from Osaka Organic Industrial (Co., Ltd.) trade name "HEA", glass transition temperature -15 ° C), [4] hardenable compound 4: 4-hydroxybutyl acrylate (trade name obtained from Osaka Organic Industry Co., Ltd.) "4HBA", glass transition temperature -32 ° C), [5] hardenable compound 5: N, N-dimethylacrylamide (trade name "DMAA" obtained from KJ Chemicals Co., Ltd., glass transition temperature 119 ° C), [6] hardenable compound 6: N- (2-hydroxyethyl) acrylamide (trade name "HEAA", glass transition temperature: 98 ° C, obtained from KJ Chemical Co., Ltd.), [7 ] Hardening Compound 7: Polyethylene Glycol # 600 Diacrylate (obtained from Shin Nakamura Chemical Industry Co., Ltd.) Name "A-600", a glass transition temperature of -23 ℃), [8] hardening compound 8: ethoxylated glycerol triacrylate (trade name "A-GLY-20E" obtained from Shin Nakamura Chemical Industry Co., Ltd.), [9] hardening compound 9: ω-carboxyl- Polycaprolactone (n ≒ 2) monoacrylate (trade name "M-5300", glass transition temperature -41 ° C, obtained from East Asia Synthesis ((Company))), [10] hardenable compound 10: ultraviolet light Hardened urethane acrylate resin (trade name "UV-3000B", glass transition temperature -39 ° C, obtained from Nippon Synthetic Chemical Industry Co., Ltd.), [11] hardenable compound 11: dioxin Tetraol hexaacrylate (trade name "A-DPH" obtained from Shin Nakamura Chemical Industry Co., Ltd.), [12] hardenable compound 12: UV-curable urethane acrylate resin (synthesized from Japan) Trade name "UV-3700B" obtained by Chemical Industry Co., Ltd.).

The ethoxylated glycerol triacrylate (trade name "A-GLY-20E") has the following structural formula.

In addition, the above-mentioned UV-curable urethane acrylate resin (trade name "UV-3000B") is a UV-curable resin mainly composed of urethane acrylate, and has a viscosity of 45,000 to 65000mPa‧s / 60 ℃, molecular weight (Mw) is 18000, and the number of functional groups of the oligomer is 2.

In addition, the above-mentioned ultraviolet-curable urethane acrylate resin (trade name "UV-3700B") is an ultraviolet-curable resin mainly composed of urethane acrylate, and the viscosity is 30,000 to 60,000 mPa / 60 ° C, molecular weight (Mw) is 38000, and oligomer functional group is 2.

(Photo radical polymerization initiator)

[13] Starter 1: 2-methyl-1- [4- (methylthio) phenyl] -2-morpholinylpropane-1-one (trade name "Irgacure 907" obtained from BASF) .

(additive)

[14] Additive 1: Polysiloxane based leveling agent (trade name "SH710" obtained from Toray‧Dow Corning (Co., Ltd.)).

<Manufacturing Examples 1 to 6: Preparation of UV-curable adhesive>

The above-mentioned radically polymerizable compound, photo-radical polymerization initiator, and additives were mixed into a 20-mL spiral sample tube at a mixing ratio (the numerical values in Table 1 represent parts by weight) described in Table 1 and mixed / desorbed. Foam, and prepare liquid ultraviolet curing adhesives A to F, respectively.

<Manufacturing Examples 7 to 8: Preparation of UV-curable Adhesive>

The above-mentioned radically polymerizable compound, photo-radical polymerization initiator, and additives were mixed into a 20-mL spiral sample tube at the mixing ratio (the numerical value in Table 2 represents parts by weight) described in Table 2 and mixed / desorbed. Foam, and prepare liquid ultraviolet curing adhesives G and H, respectively.

<Manufacturing Example 9: Production of (meth) acrylic resin film>

A (meth) acrylic resin was prepared by copolymerizing methyl methacrylate and methyl acrylate at a weight ratio of 96: 4. In addition, acrylic rubber particles are prepared, which are elastomer particles having a three-layer structure, in which the innermost layer contains a hard polymer, which is used less because of methyl methacrylate. The amount of allyl methacrylate polymerized; the intermediate layer contains a soft elastomer, which is based on butyl acrylate, and further polymerized by using styrene and a small amount of allyl methacrylate; most The outer layer contains a hard polymer, which is polymerized from methyl methacrylate using a small amount of ethyl acrylate; the average particle size up to the elastomer of the middle layer is 240 nm.

The above-mentioned (meth) acrylic resin and the above-mentioned acrylic rubber particles were prepared at a weight ratio of 70:30, and the particles were added with a benzotriazole-based ultraviolet absorber and melted in a biaxial extruder. While kneading, 0.05 parts by weight of stearic acid as a lubricant was added to 100 parts by weight of the particles, and the mixture was mixed to obtain particles of a (meth) acrylic resin composition. Put this particle in 65mm A one-shaft extruder is extruded through a T-die set at a temperature of 275 ° C, and the two sides of the extruded film-shaped molten resin are sandwiched and cooled by two polishing rollers set at 45 ° C and having a mirror surface to produce A (meth) acrylic resin film having a thickness of 80 μm. 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 5> (1) Production of polarizing plate

Corona discharge treatment was applied to one side of the (meth) acrylic resin film (first protective film) produced in Production Example 9, and a bar coater was used on the corona discharge treated surface so that the thickness after hardening became The adhesive described in Table 3 as a first adhesive (adhesive for forming a first adhesive layer) was applied so as to be about 2.5 μm. Then, a polyvinyl alcohol (PVA) -iodine-based polarizing film having a thickness of 25 μm was laminated on the coated surface. Next, an in-plane retardation value at a wavelength of 590 nm for a retardation film having a thickness of 50 μm including a cyclic polyolefin resin (norzene resin) [trade name “ZEONOR” manufactured by Zeon (Japan) Co., Ltd.] R _e: 52nm] (second protective film) is administered sided corona discharge treatment, a corona discharge treatment to its surface using a bar coater so that the thickness becomes 2.5μm after hardening of the coating as a second embodiment from about The adhesives (adhesives forming the second adhesive layer) are also described in Table 3 for the adhesives. On the coating surface, the polarizing film with the (meth) acrylic resin film produced as described above was laminated on the polarizing film side, and the laminated body was obtained by pressing and bonding with a bonding roller. For this laminated body, an ultraviolet irradiation device using an attached conveyor from the side of the cyclic polyolefin resin film [the lamp system uses "D Bulb" manufactured by Fusion UV systems] is used to accumulate a light amount of 250 mJ / cm ² (UVB) method to irradiate ultraviolet rays to harden the adhesive layer on both sides to produce a polarizing plate.

(2) Measurement of the glass transition temperature Tg of the adhesive layer

Two stretched films of a cyclic polyolefin resin with a thickness of 25 μm [“ZeonorFilm” sold by Zeon (Japan) Co., Ltd.] were prepared and used without corona treatment. Next, the prepared ultraviolet curable adhesive was applied on the surface of one stretched film with a bar coater so that the film thickness after curing became 2 μm, and another stretched film was superposed on the coating surface. From the side of the cyclic polyolefin-based resin film, which is one of the bonded products, the ultraviolet light irradiation device of the attached conveyor [the lamp system uses "D lamp" manufactured by Fusion UV systems] so that the accumulated light amount becomes 250 mJ / cm ² The ultraviolet-ray curing agent is cured by irradiating ultraviolet rays. Next, the stretched film sandwiching the cured product was peeled off, and 5 mg of the cured product was collected, placed in an aluminum gland-type container, pressed and sealed, and a sample for measurement was produced.

The container into which the above-mentioned measurement sample was placed was mounted in a differential scanning calorimeter (DSC) ["EXSTAR-6000 DSC6220" sold by SII · Nano Technology (Co., Ltd.). The temperature was lowered to -60 ° C, and the temperature was maintained at -60 ° C for 1 minute, and then the temperature was increased from -60 ° C to 150 ° C at a rate of 10 ° C / min. When the temperature reached 150 ° C, the temperature was immediately reduced to 20 ° C. The DSC curve when the temperature was raised from -60 ° C to 150 ° C, the intermediate point glass transition temperature specified in JIS K 7121-1987 "Method for Measuring the Transition Temperature of Plastics" was determined, and this was set as the UV curability of the measurement target The glass transition temperature of the adhesive layer (cured material) formed by the adhesive. The glass transition temperature of the first adhesive layer formed by the first adhesive is set to Tg1, and the glass transition temperature of the second adhesive layer formed by the second adhesive is set to Tg2.

(3) Evaluation of warpage resistance of polarizing plate in high temperature environment

From the polarizing plate produced in the above (1), a sheet-shaped body having a size of 80 mm × 80 mm was cut. After placing the sheet in an environment at a temperature of 23 ° C and a relative humidity of 60% for one night, the sheet was placed in a dry condition at a temperature of 80 ° C for 10 minutes, and then in an environment of a temperature of 23 ° C and a relative humidity of 60% for 3 hours , Measure the amount of warpage of the sheet. The amount of warpage is placed on a horizontal platform with the curved sheet body facing downward to become a convex shape. The height of the four corners from the platform to the sheet body is measured with a ruler, and the 4 points obtained are obtained. The average of the values. according to Based on the obtained warpage amount, warpage resistance was evaluated on the following basis. The evaluation results are shown in Table 3.

A: The amount of warpage is less than 5 mm, B: The amount of warpage is 5 mm or more and less than 10 mm, and C: The amount of warpage is 10 mm or more.

(4) Evaluation of processability of polarizing plate

A 800mm × 800mm blade made by Dumbbell was used to punch holes from the first protective film side of the polarizing plate, and visually observe the state of floating and peeling of the end of the polarizing plate, and evaluate the processability on the following basis. The evaluation results are shown in Table 3.

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

(5) Formation of adhesive layer

(Meth) acrylic acid obtained by adding an isocyanate-based crosslinking agent, a silane coupling agent, and an antistatic agent to a (meth) acrylic resin of a copolymer of butyl acrylate, methyl acrylate, acrylic acid, and hydroxyethyl acrylate. The organic solvent solution of the adhesive is applied to a 38 μm-thick separation membrane containing polyethylene terephthalate subjected to release treatment by a die coater so that the thickness after drying is 20 μm [from Lintec ( Co., Ltd.) obtained the release treatment surface under the trade name "SP-PLR 382052"] and made a thin film with a separation membrane Sheet adhesive. Then, the surface (adhesive surface) opposite to the separation film of the sheet-shaped adhesive obtained as described above is bonded to the surface of the cyclic polyolefin resin film of the polarizing plate produced in (1) above by a laminator. Then, it was aged for 7 days under the conditions of a temperature of 23 ° C. and a relative humidity of 65% to obtain a polarizing plate having an adhesive layer.

(6) Evaluation of cold and hot shock resistance of polarizing plate

A sheet having a size of 200 mm × 150 mm was cut out from the polarizing plate having an adhesive layer prepared in the above (5), and an alkali-free glass was bonded to the side of the adhesive layer [trade name “EAGLE XG” manufactured by Corning Corporation] As a measurement sample for the hot and cold shock test (Heat Shock test). For each of the polarizing plate sheet systems, four measurement samples were prepared. The cold and hot shock test is performed with one cycle of maintaining at -40 ° C for 30 minutes, and then raising the temperature to 70 ° C for 30 minutes. This cycle is repeated for a total of 100 cycles. The above-mentioned cold and hot shock test was performed on four measurement samples, and the cold and hot shock resistance was evaluated from the ratio of cracks or cracks observed from the polarizing film after the test with respect to the total number of samples (4). The evaluation results are shown in Table 3.

<Examples 4 to 6> (1-1) Production of polarizing plate (Example 4)

Corona discharge treatment was performed on one side of the (meth) acrylic resin film (first protective film) produced in Production Example 9. On the corona discharge treated surface, a bar coater was used so that the thickness after curing became The adhesive described in Table 4 was applied as a first adhesive (adhesive for forming the first adhesive layer) to a thickness of about 2.5 μm. Then, a polyvinyl alcohol (PVA) -iodine-based polarizing film having a thickness of 25 μm was laminated on the coated surface. Next, a corona discharge treatment was applied to one side of a retardation film (trade name "KC4CR" made by Konica Minolta (Co., Ltd.)) (second protective film) containing an ethyl cellulose resin with a thickness of 40 μm. The corona discharge treated surface was coated with a bar coater so that the thickness after curing was about 2.5 μm. As the second adhesive (adhesive for forming the second adhesive layer), the adhesives described in Table 4 were also applied. Agent. On the coating surface, the polarizing film with the (meth) acrylic resin film produced as described above was laminated on the polarizing film side, and pressed and bonded using a bonding roller to obtain a laminated body. For this laminated body, an ultraviolet irradiation device using an attached conveyor from the side of the ethyl cellulose resin film side [the lamp system uses a "D lamp" manufactured by Fusion UV Systems], and the accumulated light amount becomes 250 mJ / cm ² (UVB) method to irradiate ultraviolet rays to harden the adhesive layer on both sides to produce a polarizing plate.

(1-2) Fabrication of Polarizer (Examples 5 to 6)

Corona discharge treatment was applied to one side of the (meth) acrylic resin film (the first protective film) produced in Production Example 9, and the corona discharge treated surface was treated with a bar coater so that the thickness after curing became The adhesive described in Table 4 was applied as a first adhesive (adhesive for forming a first adhesive layer) to a thickness of about 2.5 μm. Then, a polyvinyl alcohol (PVA) -iodine-based polarizing film having a thickness of 25 μm was laminated on the coated surface. Next, an in-plane retardation value Re at a wavelength of 590 nm in a retardation film having a thickness of 50 μm including a cyclic polyolefin resin (norzene resin) [trade name “ZEONOR” manufactured by Zeon (Japan) Co., Ltd.] and a wavelength of 590 nm : 52nm] (second protective film) is subjected to a corona discharge treatment on one side, and a bar coater is applied to the corona discharge treated surface so that the thickness after curing becomes about 2.5 μm as a second adhesive. (Adhesive for forming the second adhesive layer) The adhesives described in Table 4 are also described. On the coating surface, the polarizing film with the (meth) acrylic resin film produced as described above was laminated on the polarizing film side, and pressed and bonded using a bonding roller to obtain a laminated body. For this laminated body, an ultraviolet irradiation device using an attached conveyor was used from the cyclic polyolefin resin film side [the lamp system uses a "D lamp" manufactured by Fusion UV Systems], and the cumulative light amount was 250 mJ / cm ² (UVB ) Method to irradiate ultraviolet rays to harden the adhesive layer on both sides to produce a polarizing plate.

(2) Measurement of the glass transition temperature Tg of the adhesive layer

In the same manner as in Examples 1 to 3 and Comparative Examples 1 to 5 (2), the glass transition temperature Tg1 of the first adhesive layer formed from the first adhesive was measured, and the first adhesive layer formed from the second adhesive was measured. 2 The glass transition temperature Tg2 of the adhesive layer.

(3) Evaluation of warpage resistance of polarizing plate in high temperature environment

The polarizing plates obtained in Examples 4 to 6 were evaluated for warpage resistance in the same manner as (3) of <Examples 1 to 3 and Comparative Examples 1 to 5>. The evaluation results are shown in Table 4.

(4) Evaluation of processability of polarizing plate

The polarizing plates obtained in Examples 4 to 6 were evaluated for workability in the same manner as (4) of <Examples 1 to 3 and Comparative Examples 1 to 5>. The evaluation results are shown in Table 4.

(5) Formation of adhesive layer

In the same manner as in (5) of <Examples 1 to 3 and Comparative Examples 1 to 5>, the polarizing plate obtained in Examples 4 to 6 was used to obtain a polarizing plate having an adhesive layer. The sheet-like adhesive is adhered to the surface of the cyclic polyolefin-based resin film or the surface of the ethyl acetate resin film of the polarizing plate.

(6) Evaluation of cold and hot shock resistance of polarizing plate

The polarizing plates obtained in Examples 4 to 6 were evaluated for cold and hot shock resistance in the same manner as in (6) of <Examples 1 to 3 and Comparative Examples 1 to 5>. The evaluation results are shown in Table 4.

Claims (8)

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 sequence, wherein the glass transition temperature of the first adhesive layer is -5°C The above temperature does not reach 60°C, and the glass transition temperature of the second adhesive layer is 60°C or higher. The polarizing plate as described in item 1 of the patent application, wherein the glass transition temperature of the first adhesive layer is 0°C or higher. The polarizing plate as described in item 1 of the patent application, wherein the glass transition temperature of the second adhesive layer is 80° C. or higher. The polarizing plate according to item 1 of the patent application range, wherein at least any one of the first adhesive layer and the second adhesive layer is a cured product layer of an active energy ray-curable adhesive. The polarizing plate as described in item 4 of the patent application range, wherein the active energy ray-curable adhesive contains a radical polymerizable compound. The polarizing plate as described in item 1 of the patent application range, wherein the first protective film and the second protective film are selected from polyester-based resins, polycarbonate-based resins, polyolefin-based resins, (meth) It is composed of resins in the group consisting of acrylic resins and cellulose ester resins. The polarizing plate according to item 6 of the patent application range, wherein the first protective film is composed of (meth)acrylic resin, and the second protective film is composed of polyolefin resin or cellulose ester resin . The polarizing plate according to item 1 of the patent application range, wherein at least one of the first protective film and the second protective film is a retardation film.