JP2020173458A - Polarizing plate - Google Patents

Abstract

To provide a polarizing plate which has good workability in cutting, and prevents curling (warpage) even when being left under high temperature environment.SOLUTION: A polarizing plate includes a first protective film, a first adhesive layer, a polarizing film, a second adhesive layer, and a second protective film in this order, in which a glass transition temperature of the first adhesive layer is -15°C or higher and lower than 60°C, a glass transition temperature of the second adhesive layer is 60°C or higher, a difference between the glass transition temperature of the second adhesive layer and the glass transition temperature of the first adhesive layer is 10°C or higher and 59°C or lower, the first protective film is composed of a (meth)acrylic resin, and the second protective film is composed of a polyolefin-based resin or a cellulose ester-based resin.SELECTED DRAWING: Figure 1

Description

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

A polarizing plate widely used in an image display device represented by a liquid crystal display device usually has a configuration in which protective films are laminated on both sides of a polarizing film. An adhesive is usually used for bonding the polarizing film and the protective film. Water-based adhesives and active energy ray-curable adhesives are known as adhesives for attaching protective films.

According to Japanese Patent Application Laid-Open No. 2010-286737 (Patent Document 1), one of the polarizing plates is adhered to a polarizing plate in which a protective film is bonded via an adhesive layer formed by curing a radically polymerizable composition on both sides of the polarizing film. By lowering the glass transition temperature of the agent layer and increasing the glass transition temperature of the other adhesive layer, the punching workability is good (the peeling at the edge of the polarizing plate after the punching process is small), and after the punching process. It is described that a polarizing plate having excellent durability in a high temperature and high temperature and high humidity environment can be provided.

Japanese Unexamined Patent Publication No. 2010-286737

Generally, a polarizing plate is manufactured as a long object (polarizing plate roll) by a roll-to-roll method, and then cut into a polarizing plate single-wafer having a size corresponding to, for example, the screen size of an applied image display device. It is incorporated into an image display device by being attached to an image display element. Therefore, the polarizing plate is required to have workability such as when cutting into a single frond (it is difficult for peeling between the polarizing film and the protective film to occur even due to stress during cutting). In addition, the polarizing plate may be stored or transported for a certain period of time after being cut into a single frond and before being incorporated into an image display device. At this time, the storage / transportation environment is relatively high. It may become. The polarizing plate fronds exposed to a high temperature environment tend to be more easily deformed than those in a normal temperature environment, such as curling (warping), and the deformed polarizing plate fronds have an adhesive layer. Not only is it lacking in handleability (easiness of bonding) when the image display element is bonded to the image display element, but also problems such as air bubbles being mixed between the adhesive layer and the image display element are likely to occur.

Therefore, an object of the present invention is to provide a polarizing plate which has good processability at the time of cutting and is less likely to cause curl (warp) even when placed in a high temperature environment.

The present invention provides the following polarizing plates.
[1] The first protective film, the first adhesive layer, the polarizing film, the second adhesive layer, and the second protective film are included in this order.
A polarizing plate having a glass transition temperature of the first adhesive layer of −15 ° C. or higher and lower than 60 ° C., and a glass transition temperature of the second adhesive layer of 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 method according to any one of [1] to [3], wherein at least one of the first adhesive layer and the second adhesive layer is a cured product layer of an active energy ray-curable adhesive. Polarizer.

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

[6] The first protective film and the second protective film are composed of a resin selected from the group consisting of polyester resins, polycarbonate resins, polyolefin resins, (meth) acrylic resins and cellulose ester resins. The polarizing plate according to any one of [1] to [5].

[7] The polarizing plate according to [6], wherein the first protective film is made of a (meth) acrylic resin, and the second protective film is made 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, a polarizing plate having good processability such as when cutting and less likely to cause curl (warp) even when placed in a high temperature environment (good "curl resistance" in a high temperature environment). Can be provided.

It is the schematic sectional drawing which shows an example of the layer structure of the polarizing plate which concerns on this invention.

Hereinafter, the polarizing plate according to the present invention will be described in detail.
(1) Configuration of Polarizing Plate As shown in FIG. 1, the polarizing plate according to the present invention includes a first protective film 10, a first adhesive layer 15, a polarizing film 30, a second adhesive layer 25, and a second protective film. The film 20 is included in this order. 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 one surface of the polarizing film 30 via the second adhesive layer 25. It is laminated on. The glass transition temperature Tg1 of the first adhesive layer 15 is −15 ° C. or higher and lower than 60 ° C., and the glass transition temperature Tg2 of the second adhesive layer 25 is 60 ° C. or higher. The polarizing plate of the present invention having such a structure exhibits good processability (difficulty of peeling of the film on the end face of the polarizing plate when processing such as cutting or end face polishing) and curl resistance. Further, this polarizing plate may be excellent in durability (hereinafter, also referred to as "cold thermal impact resistance") when placed in an environment where high temperature conditions and low temperature conditions are repeated.

Not limited to the example of FIG. 1, the polarizing plate according to the present invention may include layers other than the above. Specific examples of other layers include, for example, an adhesive layer laminated on the outer surface of the first protective film 10 and / or the second protective film 20; a separate film laminated on the outer surface of the adhesive layer (“peeling”). Also referred to as "film"); Protective film laminated on the outer surface of the first protective film 10 and / or the second protective film 20 (also referred to as "surface protective film"); first protective film 10 and / or second protective. An optically functional film or the like laminated on the outer surface of the film 20 via an adhesive layer or an adhesive layer.

The polarizing plate according to the present invention can be a long polarizing plate having the above-mentioned layer structure or a winding roll thereof. In this case, the processability refers to the processability when cutting out the polarizing plate fronds from a long object or a winding roll, and the curl resistance refers to the curl resistance of the cut polarizing plate fronds. The term "cold heat impact resistance" refers to the cold heat impact resistance of a long object or a wound roll, or of a polarizing plate frond cut from the same.

Further, the polarizing plate according to the present invention may be a single frond of a polarizing plate having the above-mentioned layer structure. In this case, the processability refers to the processability when cutting out a smaller size frond from the polarizing plate frond or the processability when performing end face polishing of the polarizing plate frond, and is curl resistance and curl resistance. The cold impact resistance refers to the curl resistance and the cold heat impact resistance of the polarizing plate frond or the smaller size polarizing plate frond cut from the polarizing plate frond, respectively.

(2) Polarizing film The polarizing film 30 is a film having a function of selectively transmitting linearly polarized light in a certain direction from natural light. For example, an iodine-based polarizing film in which iodine is adsorbed and oriented on a polyvinyl alcohol-based resin film, a dye-based polarizing film in which a dichroic dye is adsorbed and oriented on a polyvinyl alcohol-based resin film, and a dichroic dye in a Riotrovic liquid crystal state. Examples thereof include a coating type polarizing film coated with, oriented and fixed. These polarizing films are called absorption type polarizing films because they selectively transmit linearly polarized light in one direction from natural light and absorb the linearly polarized light in the other direction. The polarizing film 30 is not limited to the absorption type polarizing film, but is a reflective polarizing film that selectively transmits linearly polarized light in one direction from natural light and reflects the linearly polarized light in the other direction, or linearly polarized light in the other direction. A scattering type polarizing film that scatters the light may be used, but an absorption type polarizing film is preferable from the viewpoint of excellent visibility. Of these, an iodine-based polarizing film having excellent degree of polarization and transmittance is more preferable.

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

The degree of saponification of the polyvinyl alcohol-based resin is usually about 85 to 100 mol%, preferably 98 mol% or more. The polyvinyl alcohol-based resin may be modified, and for example, polyvinyl formal or polyvinyl acetal modified with aldehydes can be used. The average degree of polymerization of the polyvinyl alcohol-based resin is usually about 1000 to 10000, 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.

A film formed of such a polyvinyl alcohol-based resin is used as the raw film of the polarizing film 30. The method for forming a film of the polyvinyl alcohol-based resin is not particularly limited, and a known method is adopted. The thickness of the polyvinyl alcohol-based raw film is, for example, 150 μm or less, preferably 100 μm or less (for example, 50 μm or less).

The polarizing film 30 is a step of uniaxially stretching a polyvinyl alcohol-based resin film; a step of adsorbing a dichroic dye by dyeing the polyvinyl alcohol-based resin film with a dichroic dye; polyvinyl alcohol on which the dichroic dye is adsorbed. It can be produced by a method including a step of treating (cross-linking) the based resin film with an aqueous boric acid solution; and a step of washing with water after the treatment with the aqueous boric acid solution.

The uniaxial stretching of the polyvinyl alcohol-based resin film can be performed before dyeing the dichroic dye, at the same time as dyeing, or after dyeing. If the uniaxial stretching is performed after staining, the uniaxial stretching may be performed before the boric acid treatment or during the boric acid treatment. Moreover, uniaxial stretching may be performed in these a plurality of steps.

In uniaxial stretching, rolls having different peripheral speeds may be uniaxially stretched, or thermal rolls may be used to uniaxially stretch. Further, the uniaxial stretching may be a dry stretching performed in the atmosphere, or a wet stretching performed in a state where the polyvinyl alcohol-based resin film is swollen with a solvent or water. The draw ratio is usually about 3 to 8 times.

As a method of dyeing a polyvinyl alcohol-based resin film with a dichroic dye, for example, a method of immersing the film in an aqueous solution containing a dichroic dye is adopted. As the dichroic dye, iodine or a dichroic organic dye is used. The polyvinyl alcohol-based resin film is preferably immersed in water before the dyeing treatment.

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

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

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

Further, as another example of the method for producing the polarizing film 30, for example, the methods described in JP-A-2000-338329 and JP-A-2012-159778 can be mentioned. In this method, a solution containing a polyvinyl alcohol-based resin is applied to the surface of the base film to provide a resin layer, and then a laminated film composed of the base film and the resin layer is stretched, and then dyeing treatment, cross-linking treatment, etc. To form a polarizer layer (polarizing film layer) from the resin layer. In this polarizing laminated film composed of a base film and a polarizer layer, a protective film is attached to the surface of the polarizer layer, the base film is peeled off, and then the surface of the polarizer film exposed by peeling the base film is covered. A polarizing plate can be obtained by laminating one of the protective films.

The thickness of the polarizing film 30 can be 40 μm or less, preferably 30 μm or less (for example, 20 μm or less). According to the methods described in JP-A-2000-338329 and JP-A-2012-159778, the thin-film polarizing film 30 can be manufactured more easily, and the thickness of the polarizing film 30 is, for example, 20 μm or less. Further, it can be 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 reducing the thickness of the polarizing plate and eventually the image display device.

(3) Protective film The first protective film 10 and the second protective film 20 are each a translucent (preferably optically transparent) thermoplastic resin, for example, a chain polyolefin resin (polypropylene resin or the like). , Polyethylene-based resins such as cyclic polyolefin-based resins (norbornen-based resins, etc.); Cellulosic ester-based resins such as triacetyl cellulose and diacetyl cellulose; Polyester-based resins such as polyethylene terephthalate, polyethylene naphthalate, and polybutylene terephthalate; A resin film composed of a (meth) acrylic resin; or a mixture thereof, a copolymer, or the like can be used. In addition, "(meth) acrylic" means methacrylic and / or acrylic, and "(meth)" in the case of "(meth) acrylate" and the like has the same meaning. Among them, the first protective film 10 and the second protective film 20 are each composed of a resin selected from the group consisting of polyester-based resin, polycarbonate-based resin, polyolefin-based resin, (meth) acrylic-based resin, and cellulose ester-based resin. Is preferable.

The first protective film 10 and the second protective film 20 may be either an unstretched film or a uniaxially or biaxially stretched film, respectively. The biaxial stretching may be a simultaneous biaxial stretching that simultaneously stretches in two stretching directions, or may be a sequential biaxial stretching that stretches in a predetermined direction and then in another direction. The first protective film 10 and / or the second protective film 20 can also be a protective film having an optical function such as a retardation film. The retardation film is an optical functional film used for the purpose of compensating for the retardation by a liquid crystal cell which is an image display element. For example, a retardation film to which an arbitrary retardation value is given by stretching a film made of the thermoplastic resin (uniaxial stretching, biaxial stretching, etc.) or forming a liquid crystal layer or the like on the film. Can be.

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

Cyclic polyolefin resin is a general term for resins containing norbornene, tetracyclododecene (also known as dimethanooctahydronaphthalene), or a cyclic olefin typified by a derivative thereof as a polymerization unit. Specific examples of the cyclic polyolefin resin include a ring-opening (co) polymer of a cyclic olefin and a hydrogenated product thereof, an addition polymer of a cyclic olefin, a cyclic olefin and a chain olefin such as ethylene and propylene, or a vinyl group. These include copolymers with aromatic compounds, and modified (co) polymers obtained by modifying these with unsaturated carboxylic acids or derivatives thereof. Of these, a norbornene-based resin using a norbornene-based monomer such as norbornene or a polycyclic norbornene-based monomer is preferably used as the cyclic olefin.

The cellulose ester-based resin is a resin in which at least a part of the hydroxyl groups in cellulose is acetic acid esterified, and even if it is a mixed ester in which a part is acetic acid esterified and a part is esterified with another acid. Good. The cellulosic ester resin is preferably an acetyl cellulosic resin. Specific examples of the acetyl cellulose-based resin include triacetyl cellulose, diacetyl cellulose, cellulose acetate propionate, and cellulose acetate butyrate.

The polyester-based resin is a resin other than the above-mentioned cellulose ester-based resin having an ester bond, and is generally composed of a polyvalent carboxylic acid or a polycondensate of a derivative thereof and a polyhydric alcohol. Specific examples of the polyester-based resin include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polytrimethylene terephthalate, polytrimethylene naphthalate, polycyclohexanedimethylterephthalate, and polycyclohexanedimethylnaphthalate. Of these, polyethylene terephthalate is preferably used from the viewpoints of mechanical properties, solvent resistance, scratch resistance, cost and the like. The polyethylene terephthalate means a resin in which 80 mol% or more of the repeating unit is composed of ethylene terephthalate, and may contain a structural unit derived from other copolymerization components.

Examples of other copolymerization components include a dicarboxylic acid component and a diol component. As the dicarboxylic acid component, isophthalic acid, 4,4'-dicarboxydiphenyl, 4,4'-dicarboxybenzophenone, bis (4-carboxyphenyl) ethane, adipic acid, sebacic acid, 5-sodium sulfoisophthalic acid, 1 , 4-Dicarboxycyclohexane and the like. Examples of the diol component include propylene glycol, butanediol, neopentyl glycol, diethylene glycol, cyclohexanediol, ethylene oxide adduct of bisphenol A, polyethylene glycol, polypropylene glycol, polytetramethylene glycol and the like. The dicarboxylic acid component and the diol component may be used in combination of two or more, if necessary. Further, it is also possible to use a hydroxycarboxylic acid such as p-hydroxybenzoic acid and p-β-hydroxyethoxybenzoic acid in combination with the above dicarboxylic acid component and diol component. As the other copolymerization component, a small amount of a dicarboxylic acid component and / or a diol component having an amide bond, a urethane bond, an ether bond, a carbonate bond and the like may be used.

The polycarbonate resin is a polyester formed from carbonic acid and glycol or bisphenol. Among them, aromatic polycarbonate having a diphenylalkane in the molecular chain is preferably used from the viewpoint of heat resistance, weather resistance and acid resistance. As polycarbonate, 2,2-bis (4-hydroxyphenyl) propane (also known as bisphenol A), 2,2-bis (4-hydroxyphenyl) butane, 1,1-bis (4-hydroxyphenyl) cyclohexane, 1,1 Polycarbonates derived from bisphenols such as −bis (4-hydroxyphenyl) isobutane, 1,1-bis (4-hydroxyphenyl) ethane are exemplified.

The (meth) acrylic resin can be a polymer containing a methacrylic acid ester as a main monomer (containing 50% by weight or more), and a small amount of other copolymerization components are copolymerized therein. It is preferably a polymer. 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 monomer include methacrylic acids such as ethyl methacrylate, butyl methacrylate, cyclohexyl methacrylate, phenyl methacrylate, benzyl methacrylate, 2-ethylhexyl methacrylate, and 2-hydroxyethyl methacrylate. Acrylic acid esters other than methyl; acrylic acid esters such as ethyl acrylate, butyl acrylate, cyclohexyl acrylate, phenyl acrylate, benzyl acrylate, 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate; 2- Hydroxyalkylacrylic acid esters such as methyl (hydroxymethyl) acrylate, methyl 2- (1-hydroxyethyl) acrylate, ethyl 2- (hydroxymethyl) acrylate, butyl 2- (hydroxymethyl) acrylate; methacryl Unsaturated acids such as acids and acrylic acids; halogenated styrenes such as chlorostyrene and bromostyrene; substituted styrenes such as vinyltoluene and α-methylstyrene; unsaturated nitriles such as acrylonitrile and methacrylonitrile Acrylic acid anhydrides such as maleic anhydride and citraconic acid anhydride; unsaturated imides such as phenylmaleimide and cyclohexylmaleimide can be mentioned. As the third monofunctional monomer, only one type may be used alone, or two or more types may be used in combination.

A polyfunctional monomer may be further copolymerized with the (meth) acrylic resin. Examples of the polyfunctional monomer include ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, and nonaethylene glycol di (meth). Acrylate, tetradecaethylene glycol Di (meth) acrylate or other ethylene glycol or oligomer of which both terminal hydroxyl groups are esterified with (meth) acrylic acid; propylene glycol or oligomer of which both terminal hydroxyl groups are (meth) acrylic acid. Esterated with (meth) acrylic acid; the hydroxyl group of a dihydric alcohol such as neopentyl glycol di (meth) acrylate, hexanediol di (meth) acrylate, butanediol di (meth) acrylate; Bisphenol A, an alkylene oxide adduct of bisphenol A, or the hydroxyl groups at both ends of these halogen substituents esterified with (meth) acrylic acid; polyhydric alcohols such as trimethylpropane and pentaerythritol (meth) acrylic. Acid-esterified products and those in which an epoxy group of glycidyl (meth) acrylate is ring-added to these terminal hydroxyl groups; dibasic acids such as succinic acid, adipic acid, terephthalic acid, phthalic acid, and halogen substituents thereof. , And those having an epoxy group of glycidyl (meth) acrylate added by ring opening to these alkylene oxide adducts and the like; aryl (meth) acrylate; aromatic divinyl compounds such as divinylbenzene and the like. Of these, ethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, and neopentyl glycol dimethacrylate are preferably used.

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

The glass transition temperature of the (meth) acrylic resin is preferably 80 to 160 ° C. The glass transition temperature is the polymerization ratio of the methacrylic acid ester-based monomer and the acrylic acid ester-based monomer, the carbon chain length of each ester group, the types of functional groups having them, and the polyfunctional monomer for the entire monomer. It can be controlled by adjusting the polymerization ratio of the mer.

It is also effective to introduce a ring structure into the main chain of the polymer as a means for raising the glass transition temperature of the (meth) acrylic resin. The ring structure is preferably a heterocyclic structure such as a cyclic acid anhydride structure, a cyclic imide structure and a lactone structure. Specific examples thereof include a cyclic acid anhydride structure such as a glutaric anhydride structure and a succinic anhydride structure, a cyclic imide structure such as a glutarimide structure and a succinic anhydride structure, and a lactone ring structure such as butyrolactone and valerolactone. The glass transition temperature of the (meth) acrylic resin can be increased as the content of the ring structure in the main chain is increased. The cyclic acid anhydride structure and the cyclic imide structure are introduced by copolymerizing a monomer having a cyclic structure such as maleic anhydride and maleimide, and a cyclic acid anhydride structure is obtained by a dehydration / demethanol condensation reaction after polymerization. It can be introduced by a method of introduction, a method of reacting an amino compound to introduce a cyclic imide structure, or the like. For a resin (polymer) having a lactone ring structure, after preparing a polymer having a hydroxyl group and an ester group in a polymer chain, the hydroxyl group and the ester group in the obtained polymer are required by heating. Accordingly, it can be obtained by cyclization condensation in the presence of a catalyst such as an organic phosphorus compound to form a lactone ring structure.

The (meth) acrylic resin may contain an additive if necessary. Examples of the additive include a lubricant, an antiblocking agent, a heat stabilizer, an antioxidant, an antistatic agent, a lightproofing agent, an impact resistance improving agent, a surfactant and the like.

The (meth) acrylic resin may contain acrylic rubber particles which are impact improving agents from the viewpoint of film forming property on the film, impact resistance of the film, and the like. Acrylic rubber particles are particles containing an elastic polymer mainly composed of an acrylic acid ester as an essential component, and have a single-layer structure substantially consisting of only this elastic polymer, or one elastic polymer. Examples thereof include a multi-layer structure having layers. Examples of this elastic polymer include a crosslinked elastic copolymer containing alkyl acrylate as a main component and copolymerizing another copolymerizable vinyl-based monomer and a crosslinkable monomer. As the alkyl acrylate which is the main component of the elastic polymer, for example, methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate and the like, which have an alkyl group having about 1 to 8 carbon atoms, are used. Alkyl acrylate having an alkyl group having 4 or more carbon atoms is preferably used. Examples of other vinyl-based monomers copolymerizable with this alkyl acrylate include compounds having one polymerizable carbon-carbon double bond in the molecule, and more specifically, methyl methacrylate. Examples thereof include methacrylic acid esters such as, aromatic vinyl compounds such as styrene, and vinyl cyan compounds such as acrylonitrile. Examples of the crosslinkable monomer include a crosslinkable compound having at least two polymerizable carbon-carbon double bonds in the molecule, and more specifically, ethylene glycol di (meth) acrylate and butanediol. Examples thereof include (meth) acrylates of polyhydric alcohols such as di (meth) acrylates, alkenyl esters of (meth) acrylic acids such as allyl (meth) acrylates, and divinylbenzene.

A laminate of a film made of a (meth) acrylic resin containing no rubber particles and a film made of a (meth) acrylic resin containing rubber particles can also be used as a protective film. Further, it is also possible to use a protective film in which a (meth) acrylic resin layer is formed on one side or both sides of a retardation-developing layer made of a resin different from the (meth) acrylic resin and the retardation is expressed.

The first protective film 10 and / or the second protective film 20 may contain an ultraviolet absorber. When the polarizing plate is applied to an image display device such as a liquid crystal display device, the image display element is deteriorated by ultraviolet rays by arranging a protective film containing an ultraviolet absorber on the visible side of the image display element (for example, a liquid crystal cell). Can be suppressed. Examples of the ultraviolet absorber include salicylic acid ester compounds, benzophenone compounds, benzotriazole compounds, cyanoacrylate compounds, nickel complex salt compounds and the like.

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. In 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 smaller glass transition temperature is composed of a (meth) acrylic resin. , The second protective film 20 bonded via the second adhesive layer 25 having a higher glass transition temperature is a combination composed of a polyolefin-based resin or a cellulose ester-based resin. As described above, when the first protective film 10 and the second protective film 20 are compared, the protective film having lower mechanical properties (breaking stress) is passed through the first adhesive layer 15 having a lower glass transition temperature. By laminating on 30, workability can be further improved. Further, the first protective film 10 and the second protective film 20 may be the same or different in terms of thickness, presence / absence of additives, their types, retardation characteristics, and the like.

The first protective film 10 and / or the second protective film 20 has a hard coat layer, an antiglare layer, an antireflection layer, a light diffusion layer, an antistatic layer, and an antistatic layer on the outer surface (the surface opposite to the polarizing film 30). It may have a surface treatment layer (coating layer) such as a dirty layer and a conductive layer.

The thickness of the first protective film 10 and the second protective film 20 is usually 5 to 200 μm, preferably 10 to 120 μm, and more preferably 10 to 85 μm, respectively. 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 the image display device. The thinner the protective film, the easier it is for the cold and thermal impact resistance to decrease. However, according to the present invention, the cold and thermal impact resistance of the polarizing plate is effectively improved even if the thickness of the first protective film 10 and the second protective film 20 is thin. Can be made to.

(4) Adhesive layer The glass transition temperature Tg1 of the first adhesive layer 15 is −15 ° C. or higher and lower than 60 ° C., and the glass transition temperature Tg2 of the second adhesive layer 25 is 60 ° C. or higher. When the glass transition temperatures of the first adhesive layer 15 and the second adhesive layer 25 satisfy such a relationship, the processability and curl resistance of the polarizing plate can be highly compatible with each other. Further, it is possible to improve the cold and thermal impact resistance of the polarizing plate. The glass transition temperature of the adhesive layer is measured by a differential scanning calorimeter (DSC), and an example of the measuring method is the method described in the section of Examples described later.

The glass transition temperature Tg1 of the first adhesive layer 15 is preferably less than 55 ° C, more preferably less than 50 ° C, still more preferably less than 45 ° C, mainly from the viewpoint of processability and also in consideration of curl resistance. Is. On the other hand, if the glass transition temperature Tg1 is too low, even if the glass transition temperature Tg2 of the second adhesive layer 25 is within a predetermined range, the cold thermal impact resistance of the polarizing plate is inferior, and the polarizing film 30 is cracked or cracked. Etc. may occur. From the viewpoint of cold thermal shock resistance and further curl resistance, the glass transition temperature Tg1 is preferably -10 ° C or higher, more preferably -5 ° C or higher, further preferably 0 ° C or higher, and particularly preferably 5 ° C or higher. Is.

The glass transition temperature Tg2 of the second adhesive layer 25 is preferably 70 ° C. or higher, more preferably 80, mainly from the viewpoint of the durability of the polarizing plate, particularly the cold and thermal impact resistance, and further considering the curl resistance. ° C. or higher, more preferably 90 ° C. or higher, particularly preferably 95 ° C. or higher. When the glass transition temperature Tg2 is 60 ° C. or higher, sufficient cold and thermal impact resistance can be obtained, it is possible to suppress the occurrence of defects such as cracks and cracks in the polarizing film 30, and curl resistance. It is also advantageous. On the other hand, if the glass transition temperature Tg2 is too high, the second adhesive layer 25 becomes brittle, and even if the glass transition temperature Tg1 of the first adhesive layer 15 is within a predetermined range, the workability is lowered and the processability is lowered during processing. Problems may occur. Therefore, the glass transition temperature Tg2 is preferably 200 ° C. or lower, more preferably 180 ° C. or lower, and further preferably 160 ° C. or lower.

From the viewpoint of improving curl resistance, the glass transition temperatures Tg1 and Tg2 are each within the above ranges, and the difference between the two (Tg2-Tg1) is preferably 120 ° C. or lower, more preferably 100 ° C. or lower. preferable. Tg2-Tg1 is more preferably 90 ° C. or lower, still more preferably 80 ° C. or lower. Further, setting Tg2-Tg1 to 10 ° C. or higher, further 20 ° C. or higher (for example, 50 ° C. or higher, particularly 55 ° C. or higher) is necessary to obtain good workability, curl resistance and cold thermal impact resistance. It is advantageous.

The adhesive 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 an aqueous adhesive, heating or ultraviolet rays, visible light, etc. Examples thereof include a curable adhesive that is cured by irradiation with active energy rays such as electron beams and X rays. The curable adhesive contains a curable (polymerizable) compound as a main component. Specific examples of the water-based adhesive are polyvinyl alcohol-based resin or urethane resin dissolved in water or dispersed in water as the main component, and are polyvalent aldehyde, melamine-based compound, zirconia compound, zinc compound, glioxal, and the like. It may contain a curable component such as a water-soluble epoxy resin or a cross-linking agent. When a curable adhesive (including the case where the water-based adhesive contains a curable component or a cross-linking agent) is used, the adhesive layer formed from the curable adhesive is a cured product layer of the curable adhesive.

Among the above, a curable adhesive is preferable, and an active energy ray-curable adhesive is more preferable, because the drying step of heating to remove the solvent can be omitted. Water-based adhesives and thermosetting adhesives require a heating step, and this heating may cause curling of the polarizing plate. As a form of the polarizing plate using the active energy ray-curable adhesive, 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. Although it can be mentioned, it is preferable that both the first adhesive layer 15 and the second adhesive layer 25 are cured products 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 according to, for example, the following guidelines. That is, when an adhesive layer is formed from a curable adhesive, the glass transition temperature of the cured product is usually the target glass transition temperature of the adhesive layer as a curable compound contained in the curable adhesive as a main component. A compound close to is selected. The glass transition temperature of the cured product of the curable compound mainly depends on the structure of the curable compound and the combination of the curable compounds. For example, when the curable compound contains an alicyclic epoxy compound or an aromatic epoxy compound, the glass transition temperature of the curable compound tends to be high, and when the curable compound contains an aliphatic epoxy compound, the glass transition temperature tends to be low. is there. The glass transition temperature of the adhesive layer can also be adjusted by the degree of cross-linking of the curable compound. For example, when the amount of the trifunctional or higher functional curable compound used is increased, the glass transition temperature of the adhesive layer tends to increase. is there. It is also possible to adjust the glass transition temperature of the adhesive layer by adding a component other than the main component to the curable adhesive. For example, when a polymer component (thermoplastic resin, etc.) is added, the glass transition of the adhesive layer is performed. The temperature tends to be low.

When classified according to the curing mode, the curable adhesive is a cationically polymerizable adhesive containing a cationically polymerizable compound as the curable compound, a radically polymerizable adhesive containing a radically polymerizable compound as the curable compound, and a cationically polymerizable adhesive. Examples thereof include a hybrid curable adhesive containing both a compound and a radically polymerizable compound. Specific examples of the cationically polymerizable compound include an epoxy compound having one or more epoxy groups in the molecule, an oxetane compound having one or more oxetane rings in the molecule, and a vinyl compound. Specific examples of the radically polymerizable compound include a (meth) acrylic compound and a vinyl compound having one or more (meth) acryloyl groups in the molecule. The curable adhesive may contain one or more cationically polymerizable compounds and / or may contain one or more radically polymerizable compounds.

(4-1) Cationic Polymerization Adhesive The cationically polymerizable compound, which is the main component of the cationically polymerizable adhesive, undergoes a cationic polymerization reaction by irradiation or heating with active energy rays such as ultraviolet rays, visible light, electron beams, and X-rays. It refers to a compound or oligomer that progresses and cures, and examples thereof include epoxy compounds, oxetane compounds, and vinyl compounds. Among them, the preferable cationically polymerizable compound is an epoxy compound. The epoxy compound is a compound having one or more, preferably two or more epoxy groups in the molecule. Only one type of epoxy compound may be used alone, or two or more types may be used in combination. Examples of the epoxy compound include an alicyclic epoxy compound, an aromatic epoxy compound, a hydride epoxy compound, and an aliphatic epoxy compound. Among them, from the viewpoint of weather resistance, curing speed and adhesiveness, the epoxy compound preferably contains an alicyclic epoxy compound or 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 the alicyclic ring in the molecule. The "epoxy group bonded to the alicyclic ring" means a bridging oxygen atom-O-in the structure represented by the following formula (I). In the following formula (I), m is an integer of 2 to 5.

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

Among them, the alicyclic epoxy compound having an epoxycyclopentane structure [m = 3 in the above formula (I)] and an epoxycyclohexane structure [m = 4 in the above formula (I)] is a cured glass. The transition temperature is high, which is advantageous in increasing the glass transition temperature of the adhesive layer, and is also advantageous in terms of the adhesiveness between the polarizing film and the protective film. Specific examples of the alicyclic epoxy compound are given below. Here, the compound names are listed first, and then the chemical formulas corresponding to the respective compounds are shown, and the compound names and the corresponding chemical formulas are given the same reference numerals.

A: 3,4-Epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate,
B: 3,4-Epoxy-6-methylcyclohexylmethyl 3,4-epoxy-6-methylcyclohexanecarboxylate,
C: Ethylene bis (3,4-epoxycyclohexanecarboxylate),
D: Bis (3,4-epoxycyclohexylmethyl) adipate,
E: Bis (3,4-epoxy-6-methylcyclohexylmethyl) adipate,
F: Diethylene glycol bis (3,4-epoxycyclohexylmethyl ether),
G: Ethylene glycol bis (3,4-epoxycyclohexylmethyl ether),
H: 2,3,14,15-Diepoxy-7,11,18,21-Tetraoxatrispyro [5.2.2.5.2.2] Heneicosane,
I: 3- (3,4-epoxycyclohexyl) -8,9-epoxy-1,5-dioxaspiro [5.5] undecane,
J: 4-Vinylcyclohexene dioxide,
K: Limonene Geoxide,
L: Bis (2,3-epoxycyclopentyl) ether,
M: Dicyclopentadiene dioxyside.

An aromatic epoxy compound is a compound having an aromatic ring and an epoxy group in the molecule. Specific examples thereof include bisphenol-type epoxy compounds such as bisphenol A diglycidyl ether, bisphenol F diglycidyl ether, and bisphenol S diglycidyl ether or oligomers thereof; phenol novolac epoxy resin, cresol novolac epoxy resin, and hydroxybenzaldehyde phenol novolac. Novolak type epoxy resin such as epoxy resin; polyfunctional epoxy such as 2,2', 4,4'-tetrahydroxydiphenylmethane glycidyl ether, 2,2', 4,4'-tetrahydroxybenzophenone glycidyl ether Compound: Includes a polyfunctional epoxy resin such as epoxidized polyvinylphenol.

The hydrogenated epoxy compound is a glycidyl ether of a polyol having an alicyclic ring, and is a nuclear hydrogenated poly obtained by selectively hydrogenating an aromatic polyol into an aromatic ring under pressure in the presence of a catalyst. The hydroxy compound can be glycidyl etherified. Specific examples of aromatic polyols include bisphenol-type compounds such as bisphenol A, bisphenol F, and bisphenol S; novolak-type resins such as phenol novolac resin, cresol novolac resin, and hydroxybenzaldehyde phenol novolac resin; tetrahydroxydiphenylmethane and tetrahydroxy. Contains polyfunctional compounds such as benzophenone and polyvinylphenol. A glycidyl ether can be obtained by reacting epichlorohydrin with an alicyclic polyol obtained by hydrogenating the aromatic ring of an aromatic polyol. Among the hydrogenated epoxy compounds, the diglycidyl ether of hydrogenated bisphenol A can be mentioned.

The aliphatic epoxy compound is a compound having at least one oxylan ring (three-membered cyclic ether) bonded to an aliphatic carbon atom in the molecule. For example, monofunctional epoxy compounds such as butyl glycidyl ether and 2-ethylhexyl glycidyl ether; 1,4-butanediol diglycidyl ether, 1,6-hexanediol diglycidyl ether, neopentyl glycol diglycidyl ether, 1,4- Bifunctional epoxy compounds such as cyclohexanedimethanol diglycidyl ether; trifunctional or higher functional epoxy compounds such as trimethylolpropan triglycidyl ether and pentaerythritol tetraglycidyl ether; alicyclic such as 4-vinylcyclohexene dioxide and limonendioxide. There are epoxy compounds having one epoxy group directly bonded to the formula ring and an oxylane ring bonded to an aliphatic carbon atom. Of these, a bifunctional epoxy compound (also referred to as an aliphatic diepoxy compound) having two oxylan rings bonded to an aliphatic carbon atom in the molecule is preferable from the viewpoint of adhesiveness between the polarizing film and the protective film. Such a suitable aliphatic diepoxy compound can be represented by, for example, the following formula (II).

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 intervening an ether bond, or a divalent group having 6 to 18 carbon atoms having an alicyclic structure. It is a hydrocarbon group of.

Specifically, the aliphatic diepoxy compound represented by the above formula (II) is a diglycidyl ether of an alkanediol, a diglycidyl ether of an oligoalkylene glycol up to about 4 repetitions, or a diglycidyl ether of an alicyclic diol. Is.

Specific examples of the diol (glycol) capable of forming the aliphatic diepoxy compound represented by the above formula (II) are listed below. Alcandiols include ethylene glycol, propylene glycol, 1,3-propanediol, 2-methyl-1,3-propanediol, 2-butyl-2-ethyl-1,3-propanediol, and 1,4-butanediol. , Neopentyl glycol, 3-methyl-2,4-pentanediol, 2,4-pentanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 2-methyl-2,4-pentane Diol, 2,4-diethyl-1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 3,5-heptandiol, 1,8-octanediol, 2-methyl-1,8 There are −octanediol, 1,9-nonanediol and the like. Examples of the oligoalkylene glycol include diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol and the like. Examples of the alicyclic diol include cyclohexanediols such as 1,2-cyclohexanediol, 1,3-cyclohexanediol, and 1,4-cyclohexanediol, 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, and 1, There are cyclohexanedimethanol and the like such as 4-cyclohexanedimethanol.

An oxetane compound, which is one of the cationically polymerizable compounds, is a compound containing one or more oxetane rings (oxetanyl groups) in the molecule, and specific examples thereof are 3-ethyl-3-hydroxymethyloxetane (oxetane alcohol). Also called), 2-ethylhexyloxetane, 1,4-bis [{(3-ethyloxetane-3-yl) methoxy} methyl] benzene (also called xylylenebis oxetane), 3-ethyl-3 [{( 3-Ethyloxetane-3-yl) methoxy} methyl] oxetane, 3-ethyl-3- (phenoxymethyl) oxetane, 3- (cyclohexyloxy) methyl-3-ethyloxetane. The oxetane compound may be used as the main component of the cationically polymerizable compound, or may be used in combination with the epoxy compound. The combined use of an oxetane compound may improve the curing speed and adhesiveness.

Examples of vinyl compounds that can be cationically polymerizable compounds include aliphatic or alicyclic vinyl ether compounds, and specific examples thereof include n-amyl vinyl ether, i-amyl vinyl ether, n-hexyl vinyl ether, and n-octyl vinyl ether. , 2-Ethylhexyl vinyl ether, n-dodecyl vinyl ether, stearyl vinyl ether, oleyl vinyl ether and other alkyl or alkenyl alcohol vinyl ethers having 5 to 20 carbon atoms; 2-hydroxyethyl vinyl ether, 3-hydroxypropyl vinyl ether, 4-hydroxybutyl vinyl ether and the like. Hydroxyl group-containing vinyl ether; monoalcohol vinyl ether having an aliphatic ring or aromatic ring such as cyclohexyl vinyl ether, 2-methylcyclohexylvinyl ether, cyclohexylmethylvinyl ether, benzylvinyl ether; glycerol monovinyl ether, 1,4-butanediol monovinyl ether, 1, 4-Butanediol divinyl ether, 1,6-hexanediol divinyl ether, neopentyl glycol divinyl ether, pentaerythritol divinyl ether, pentaerythritol tetravinyl ether, trimethylolpropane divinyl ether, trimethylolpropanetrivinyl ether, 1,4-dihydroxycyclohexane Mono-polyvinyl ethers of polyhydric alcohols such as monovinyl ether, 1,4-dihydroxycyclohexanedivinyl ether, 1,4-dihydroxymethylcyclohexanemonovinyl ether, 1,4-dihydroxymethylcyclohexanedivinyl ether; diethylene glycol divinyl ether, triethylene glycol di Polyalkylene glycol mono to divinyl ethers such as vinyl ethers and diethylene glycol monobutyl monovinyl ethers; other vinyl ethers such as glycidyl vinyl ethers and ethylene glycol vinyl ether methacrylates. 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. By using a vinyl compound in combination, it may be possible to improve the curing speed and the viscosity reduction of the adhesive.

The cationically polymerizable adhesive can further contain other cationically polymerizable compounds other than the above, such as a cyclic lactone compound, a cyclic acetal compound, a cyclic thioether compound, and a spirolthoester compound.

When the total amount of the curable compound contained in the cationically polymerized adhesive (including the case where it is a hybrid curable adhesive) is 100% by weight from the viewpoint of the adhesiveness between the polarizing film and the protective film. , The content of the cationically polymerizable compound (the content of all the cationically polymerizable compounds contained in the cationically polymerizable adhesive, and the total content of two or more kinds of cationically polymerizable compounds when they are contained) , 50% by weight or more, more preferably 60% by weight or more, and even more preferably 70% by weight or more. Further, as described above, the cationically polymerizable adhesive may further contain a polymer component (thermoplastic resin or the like). This makes it possible to lower the glass transition temperature of the adhesive layer and improve the adhesiveness between the polarizing film and the protective film.

The cationically polymerized adhesive may be active energy ray-curable or thermosetting, but it is preferable because the heating step can be omitted and the polarizing plate can be prevented from curling due to this heating. Is active energy ray curable. When imparting active energy ray curability to a cationically polymerizable adhesive containing a cationically polymerizable compound, it is preferable to add a photocationic polymerization initiator to the adhesive. The photocationic polymerization initiator generates a cationic species or Lewis acid by irradiation with active energy rays such as visible light, ultraviolet rays, X-rays, or electron beams, and initiates a polymerization reaction of a cationically curable compound. .. Since the photocationic polymerization initiator acts catalytically with light, it is excellent in storage stability and workability even when mixed with a photocationic curable compound. Examples of the compound that produces a cationic species or Lewis acid by irradiation with active energy rays include onium salts such as aromatic iodonium salts and aromatic sulfonium salts, aromatic diazonium salts, and iron-alene complexes.

The aromatic iodonium salt is a compound having a diaryliodonium cation, and examples of the cation include a diphenyliodonium cation. The aromatic sulfonium salt is a compound having a triarylsulfonium cation, and examples of the cation include a triphenylsulfonium cation and a 4,4'-bis (diphenylsulfonio) diphenylsulfide cation. The aromatic diazonium salt is a compound having a diazonium cation, and typical examples of the cation include a benzenediazonium cation. Also, the iron-alene complex is typically a cyclopentadienyl iron (II) allene cation complex salt.

The cations shown above are paired with anions (anions) to form a photocationic polymerization initiator. Examples of anions which constitute the photo-cationic polymerization initiator, a special phosphorus based anions _{[(Rf) n PF 6-} n] -, hexafluorophosphate anion PF ₆ ^-, hexafluoroantimonate anion SbF ₆ ^-, pentafluorophenyl hydroxy antimonate anion _SbF 5 (OH) ^-, hexafluoro ah cell anions AsF ₆ ^-, tetrafluoroborate anion BF ₄ ^-, tetrakis (pentafluorophenyl) borate anion _{B (C 6 F 5) 4} - and the like. Among them, the special phosphorus anion [(Rf) _n PF _6-n ] ⁻ and the hexafluorophosphate anion PF ₆ ⁻ are preferable from the viewpoint of curability of the cationically polymerizable compound and the safety of the obtained adhesive layer. ..

Only one type of photocationic polymerization initiator may be used alone, or two or more types may be used in combination. Among them, the aromatic sulfonium salt is preferably used because it has an ultraviolet absorbing property even in a wavelength region near 300 nm, and therefore has excellent curability and can give a cured product having good mechanical strength and adhesive strength.

The blending amount of the photocationic polymerization initiator is usually 0.5 to 10 parts by weight, preferably 6 parts by weight or less, based on 100 parts by weight of the cationically polymerizable compound. By blending 0.5 parts by weight or more of the photocationic polymerization initiator, the cationically polymerizable compound can be sufficiently cured, and high mechanical strength and adhesive strength can be imparted to the obtained polarizing plate. On the other hand, if the amount is excessively large, the amount of ionic substances in the cured product increases, so that the hygroscopicity of the cured product increases, and the durability of the polarizing plate may decrease.

As described above, a hybrid type curable adhesive can also be obtained by containing a radically polymerizable compound in addition to the cationically polymerizable compound in the cationically polymerizable adhesive. By using the radically polymerizable compound in combination, the effect of increasing the hardness and mechanical strength of the adhesive layer can be expected, and further, the viscosity and curing rate of the curable adhesive can be adjusted more easily.

(4-2) Radical Polymerization Adhesive The radical polymerizable compound, which is the main component of the radical polymerization type adhesive, undergoes a radical polymerization reaction by irradiation or heating with active energy rays such as ultraviolet rays, visible light, electron beams, and X-rays. A compound or oligomer that progresses and cures, and specific examples thereof include a compound having an ethylenically unsaturated bond. Compounds having an ethylenically unsaturated bond include (meth) acrylic compounds having one or more (meth) acryloyl groups in the molecule, styrene, styrene sulfonic acid, vinyl acetate, vinyl propionate, and N-vinyl. Examples thereof include vinyl compounds such as -2-pyrrolidone. Among them, the preferred radically polymerizable compound is a (meth) acrylic compound.

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

The (meth) acrylate monomer includes a monofunctional (meth) acrylate monomer having one (meth) acryloyloxy group in the molecule and a bifunctional (meth) acrylate having two (meth) acryloyloxy groups in the molecule. Examples thereof include monomers and polyfunctional (meth) acrylate monomers having three or more (meth) acryloyloxy groups in the molecule.

An example of a monofunctional (meth) acrylate monomer is an alkyl (meth) acrylate. In an alkyl (meth) acrylate, the alkyl group may be linear or branched as long as it has 3 or more carbon atoms. Specific examples of alkyl (meth) acrylates include methyl (meth) acrylate, ethyl (meth) acrylate, isopropyl (meth) acrylate, butyl (meth) acrylate, isobutyl (meth) acrylate, t-butyl (meth) acrylate, and the like. Examples thereof include 2-ethylhexyl (meth) acrylate. Also, aralkyl (meth) acrylates such as benzyl (meth) acrylates; (meth) acrylates of terpenal alcohols such as isobornyl (meth) acrylates; and tetrahydrofurfuryl structures such as tetrahydrofurfuryl (meth) acrylates (meth). ) Acrylate; has a cycloalkyl group at the alkyl group moiety such as cyclohexyl (meth) acrylate, cyclohexylmethyl methacrylate, dicyclopentanyl acrylate, dicyclopentenyl (meth) acrylate, 1,4-cyclohexanedimethanol monoacrylate (meth). ) Acrylate; Aminoalkyl (meth) acrylate such as N, N-dimethylaminoethyl (meth) acrylate; 2-phenoxyethyl (meth) acrylate, dicyclopentenyloxyethyl (meth) acrylate, ethyl carbitol (meth) acrylate , (Meta) acrylate having an ether bond at the alkyl moiety such as phenoxypolyethylene glycol (meth) acrylate can also be used as the monofunctional (meth) acrylate monomer.

Further, a monofunctional (meth) acrylate having a hydroxyl group at the alkyl moiety and a monofunctional (meth) acrylate having a carboxyl group at the alkyl moiety can also be used. Specific examples of the monofunctional (meth) acrylate having a hydroxyl group at the alkyl moiety include 2-hydroxyethyl (meth) acrylate, 2- or 3-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, and 2-hydroxy. -3-Phenoxypropyl (meth) acrylate, trimethylolpropane mono (meth) acrylate, pentaerythritol mono (meth) acrylate are included. Specific examples of monofunctional (meth) acrylates having a carboxyl group at the alkyl moiety include 2-carboxyethyl (meth) acrylate, ω-carboxy-polycaprolactone (n≈2) mono (meth) acrylate, 1- [2- ( Meta) acryloyloxyethyl] phthalic acid, 1- [2- (meth) acryloyloxyethyl] hexahydrophthalic acid, 1- [2- (meth) acryloyloxyethyl] succinic acid, 4- [2- (meth) acryloyl Oxyethyl] Contains trimellitic acid, N- (meth) acryloyloxy-N', N'-dicarboxymethyl-p-phenylenediamine.

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

Specific examples of N-substituted (meth) acrylamide are N-methyl (meth) acrylamide, N-ethyl (meth) acrylamide, N-isopropyl (meth) acrylamide, Nn-butyl (meth) acrylamide, and Nt-. N-alkyl (meth) acrylamide such as butyl (meth) acrylamide, N-hexyl (meth) acrylamide; N, N- such as N, N-dimethyl (meth) acrylamide, N, N-diethyl (meth) acrylamide. Contains dialkyl (meth) acrylamide. Further, the N-substituted group may be an alkyl group having a hydroxyl group, and examples thereof include N-hydroxymethyl (meth) acrylamide, N- (2-hydroxyethyl) (meth) acrylamide, and N- (2-hydroxy). There are propyl) (meth) acrylamide and the like. Further, specific examples of the N-substituted (meth) acrylamide forming the above-mentioned 5-membered ring or 6-membered ring include N-acryloylpyrrolidine, 3-acryloyl-2-oxazolidinone, 4-acryloylmorpholine, and N-acryloyl. There are piperidine, N-methacryloyl piperidine and the like.

Examples of the bifunctional (meth) acrylate monomer include alkylene glycol di (meth) acrylate, polyoxyalkylene glycol di (meth) acrylate, halogen-substituted alkylene glycol di (meth) acrylate, aliphatic polyol di (meth) acrylate, and hydrogenation. Di (meth) acrylate of dicyclopentadiene or tricyclodecanediakanol, di (meth) acrylate of dioxane glycol or dioxandialkanol, di (meth) acrylate of alkylene oxide adduct of bisphenol A or bisphenol F, bisphenol A or bisphenol Examples thereof include the epoxy di (meth) acrylate of F.

To give a more specific example of the bifunctional (meth) acrylate monomer, ethylene glycol di (meth) acrylate, 1,3-butanediol di (meth) acrylate, 1,4-butanediol di (meth) acrylate, 1 , 6-Hexanediol di (meth) acrylate, 1,9-nonanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, trimethylpropandi (meth) acrylate, pentaerythritol di (meth) acrylate, ditri Methylolpropandi (meth) acrylate, diethylene glycol 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, silicone di (meth) acrylate, hydroxypivalate neopentyl glycol ester di (meth) acrylate, 2,2-bis [4- (meth) Acryloyloxyethoxyethoxyphenyl] propane, 2,2-bis [4- (meth) acryloyloxyethoxyethoxycyclohexyl] propane, hydrogenated dicyclopentadienyldi (meth) acrylate, tricyclodecanedimethanol di (meth) acrylate , 1,3-Dioxane-2,5-diyldi (meth) acrylate [also known as dioxane glycol di (meth) acrylate], acetal compound of hydroxypivalaldehyde and trimethylpropane [chemical name: 2- (2-hydroxy) -1,1-dimethylethyl) -5-ethyl-5-hydroxymethyl-1,3-dioxane] di (meth) acrylate, tris (hydroxyethyl) isocyanurate di (meth) acrylate, 1,4-cyclohexanedi Methanol diacrylate and the like.

Examples of the trifunctional or higher functional polyfunctional (meth) acrylate monomer include glycerin tri (meth) acrylate, alkoxylated glycerin tri (meth) acrylate, trimethyl propantri (meth) acrylate, ditrimethylol propanthry (meth) acrylate, and ditrimethylol. Propanetetra (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol tetra (meth) acrylate, dipentaerythritol penta (meth) acrylate, dipentaerythritol hexa (meth) acrylate, etc. Poly (meth) acrylates of trifunctional or higher functional aliphatic polyols are typical, and in addition, poly (meth) acrylates of trifunctional or higher functional halogen-substituted polyols and tri (meth) alkylene oxide adducts of glycerin are used. Acrylate, tri (meth) acrylate of alkylene oxide adduct of trimethylolpropane, 1,1,1-tris [(meth) acryloyloxyethoxyethoxy] propane, tris (hydroxyethyl) isocyanurate tri (meth) acrylate and the like. Be done.

On the other hand, the (meth) acrylic oligomer includes urethane (meth) acrylic oligomer, polyester (meth) acrylic oligomer, epoxy (meth) acrylic oligomer and the like.

The urethane (meth) acrylic oligomer is a compound having a urethane bond (-NHCOO-) and at least two (meth) acryloyl groups in the molecule. Specifically, a urethanization reaction product of a hydroxyl group-containing (meth) acrylic monomer having at least one (meth) acryloyl group and at least one hydroxyl group in the molecule and polyisocyanate, and a polyol as polyisocyanate. It can be a urethanization reaction product of a terminal isocyanato group-containing urethane compound obtained by reaction and a (meth) acrylic monomer having at least one (meth) acryloyl group and at least one hydroxyl group in the molecule. ..

The hydroxyl group-containing (meth) acrylic monomer used in the urethanization reaction can be, for example, a hydroxyl group-containing (meth) acrylate monomer, and specific examples thereof include 2-hydroxyethyl (meth) acrylate and 2-hydroxypropyl (meth). ) Acrylate, 2-Hydroxybutyl (meth) acrylate, 2-hydroxy-3-phenoxypropyl (meth) acrylate, glycerindi (meth) acrylate, trimethylpropandi (meth) acrylate, pentaerythritol tri (meth) acrylate, di Contains pentaerythritol penta (meth) acrylate. Specific examples other than the hydroxyl group-containing (meth) acrylate monomer include N-hydroxyalkyl (meth) acrylamide monomers such as N-hydroxyethyl (meth) acrylamide and N-methylol (meth) acrylamide.

Examples of the polyisocyanate used for the urethanization reaction with the hydroxyl group-containing (meth) acrylic monomer include hexamethylene diisocyanate, lysine diisocyanate, isophorone diisocyanate, dicyclohexylmethane diisocyanate, tolylene diisocyanate, xylylene diisocyanate, and among these diisocyanates, aromatic ones. Diisocyanates obtained by hydrogenating isocyanates (for example, hydrogenated tolylene diisocyanates, hydrogenated xylylene diisocyanates, etc.), di- or tri-isocyanates such as triphenylmethane triisocyanates, dibenzylbenzene triisocyanates, and the above. Examples thereof include polyisocyanate obtained by increasing the amount of diisocyanate.

Further, as the polyol used to obtain the terminal isocyanato group-containing urethane compound by the reaction with the polyisocyanate, a polyester polyol, a polyether polyol, or the like can be used in addition to an aromatic, aliphatic or alicyclic polyol. it can. Aliphatic and alicyclic polyols include 1,4-butanediol, 1,6-hexanediol, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, neopentyl glycol, trimethylolethane, trimethylolpropane, and ditri. Examples thereof include methylolpropane, pentaerythritol, dipentaerythritol, dimethylolheptan, dimethylolpropionic acid, dimethylolbutanoic acid, glycerin, and hydrogenated bisphenol A.

The polyester polyol is obtained by a dehydration condensation reaction between the above-mentioned polyol and a polybasic carboxylic acid or an anhydride thereof. Examples of polybasic carboxylic acids or their anhydrides, which may be anhydrous, are represented by adding "(anhydride)" to (anhydrous) succinic acid, adipic acid, (anhydrous) maleic anhydride, (anhydrous). There are itaconic acid, (anhydrous) trimellitic acid, (anhydrous) pyromellitic acid, (anhydrous) phthalic acid, isophthalic acid, terephthalic acid, hexahydro (anhydrous) phthalic acid and the like.

In addition to the polyalkylene glycol, the polyether polyol may be the above-mentioned polyol or a polyoxyalkylene-modified polyol obtained by reacting dihydroxybenzenes with an alkylene oxide.

A polyester (meth) acrylic oligomer is a compound having an ester bond and at least two (meth) acryloyl groups (typically (meth) acryloyloxy groups) in the molecule. Specifically, it can be obtained by a dehydration condensation reaction using (meth) acrylic acid, a polybasic carboxylic acid or an anhydride thereof, and a polyol. Examples of polybasic carboxylic acids or their anhydrides used in the dehydration condensation reaction, which can be anhydrous, are represented by adding "(anhydride)" to (anhydrous) succinic anhydride, adipic acid, (anhydride). There are maleic acid, (anhydrous) itaconic acid, (anhydrous) trimellitic acid, (anhydrous) pyromellitic acid, hexahydro (anhydrous) phthalic acid, (anhydrous) phthalic acid, isophthalic acid, terephthalic acid and the like. Examples of the polyol used in the dehydration condensation reaction include 1,4-butanediol, 1,6-hexanediol, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, neopentyl glycol, trimethylolethane, and trimethylolpropane. Examples thereof include ditrimethylolpropane, pentaerythritol, dipentaerythritol, dimethylolheptan, dimethylolpropionic acid, dimethylolbutanoic acid, glycerin, and hydrogenated bisphenol A.

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

The radical polymerization type adhesive may be active energy ray-curable or thermosetting, but is preferably active energy ray-curable. When imparting active energy ray curability to a radical polymerization type adhesive containing a radically polymerizable compound, it is preferable to add a photoradical polymerization initiator to the adhesive. The photoradical polymerization initiator initiates the polymerization reaction of a radical curable compound by irradiation with active energy rays such as visible light, ultraviolet rays, X-rays, or electron beams. As the photoradical polymerization initiator, only one type may be used alone, or two or more types may be used in combination.

Specific examples of the photoradical polymerization initiator are acetophenone, 3-methylacetophenone, benzyldimethylketal, 1- (4-isopropylphenyl) -2-hydroxy-2-methylpropan-1-one, 2-methyl-1-[ Acetphenone-based initiators such as 4- (methylthio) phenyl-2-morpholinopropane-1-one, 2-hydroxy-2-methyl-1-phenylpropan-1-one; benzophenone, 4-chlorobenzophenone, 4,4'. -Benzophenone-based initiators such as diaminobenzophenone; benzoin ether-based initiators such as benzoin propyl ether and benzoin ethyl ether; thioxanthone-based initiators such as 4-isopropylthioxanthone; and other benzophenone-based initiators; ..

The blending amount of the photoradical polymerization initiator is usually 0.5 to 20 parts by weight, preferably 1 to 6 parts by weight, based on 100 parts by weight of the radically polymerizable compound. By blending 0.5 parts by weight or more of the photoradical polymerization initiator, the radically polymerizable compound can be sufficiently cured, and high mechanical strength and adhesive strength can be imparted to the obtained polarizing plate. On the other hand, if the amount is excessively large, the durability of the polarizing plate may decrease.

(4-3) Additives The adhesive forming the first adhesive layer 15 and / or the second adhesive layer 25 may contain other additives, if necessary. Specific examples of additives include ion trapping agents, antioxidants, chain transfer agents, polymerization promoters (polyols, etc.), sensitizers, sensitizing aids, light stabilizers, tackifiers, thermoplastic resins, fillers. , Flow conditioner, plasticizer, antifoaming agent, leveling agent, silane coupling agent, dye, antistatic agent, ultraviolet absorber, thermal polymerization initiator. The thermal polymerization initiator is used in place of the photopolymerization initiator when preparing a thermosetting adhesive. A photopolymerization initiator and a thermal polymerization initiator can also be used in combination. Examples of the ion trap agent include powdered bismuth-based, antimony-based, magnesium-based, aluminum-based, calcium-based, titanium-based, and inorganic compounds such as a mixture thereof, and examples of the antioxidant include a hindered phenol-based antioxidant. And so on.

(4-4) Coating of Adhesive and Adhesion between Polarizing Film and Protective Film The first protective film 10 is laminated and adhered to one surface of the polarizing film 30 via the first adhesive layer 15, and the polarizing film 30 is laminated. The polarizing plate according to the present invention can be obtained by laminating and adhering the second protective film 20 to the other surface of the film via the second adhesive layer 25. The first protective film 10 and the second protective film 20 (hereinafter, collectively referred to as simply "protective film") may be laminated and bonded one side at a time, or the protective films on both sides may be laminated and adhered step by step. May be laminated and bonded with.

To bond the polarizing film 30 and the protective film, specifically, an adhesive is applied to the bonding surface of the polarizing film 30 and / or the bonding surface of the protective film, and both are coated via the coating layer of the adhesive. The films are laminated and pressed from above and below using, for example, a bonding roll, and then the adhesive layer is dried (for example, in the case of a water-based adhesive) or cured by irradiating with active energy rays (active). This can be done by (in the case of an energy ray-curable adhesive) or by heating and curing (in the case of a thermosetting adhesive). Even when the active energy ray-curable adhesive is used, the heat treatment may be performed at the same time as the irradiation with the active energy ray or 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 are subjected to saponification treatment, corona discharge treatment, plasma treatment, flame treatment, primer treatment, and anchor coating treatment. The easy-adhesion treatment such as

For forming the coating layer of the adhesive, for example, various coating methods such as a doctor blade, a wire bar, a die coater, a comma coater, and a gravure coater can be used. Further, it is also possible to adopt a method in which the polarizing film 30 and the protective film are continuously supplied so that the bonding surface of both is on the inside, and the adhesive is spread between them.

From the viewpoint of coatability, the adhesive forming the first adhesive layer 15 and the second adhesive layer 25 preferably has a low viscosity. Specifically, the viscosity at 25 ° C. is preferably 1000 mPa · s or less, more preferably 500 mPa · s or less, still more preferably 100 mPa · s or less. The adhesive can be solvent-free, but may contain an organic solvent to adjust the viscosity to suit 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 laminating the polarizing film 30 and the protective film. As a result, the adhesion between the polarizing film 30 and the protective film, particularly the adhesion between the protective film and the adhesive layer is improved. Specific embodiments of heating include heating of a protective film, heating of an adhesive, heating of a laminate in which a polarizing film 30 and a protective film are laminated via an uncured or undried adhesive layer, and the like. Examples of the method of heating the protective film or laminate include a method of sequentially passing a long protective film or laminate through a device that emits radiant heat such as an infrared heater, a method of passing a long protective film or laminate through a blower, or the like. A method of spraying a heated gas using the above can be mentioned. Further, as a method of heating the adhesive, for example, a method of heating and keeping the adhesive in advance in a storage tank and supplying the heated adhesive to the coating apparatus can be mentioned. The temperature for heating the protective film, the adhesive or the laminate is preferably 30 to 80 ° C, more preferably 40 to 60 ° C. If the heating temperature exceeds 80 ° C., the protective film, adhesive or laminate may be deteriorated by heat. Further, if the heating temperature is less than 30 ° C., the effect of improving the adhesion between the protective film and the polarizing film 30 tends to be insufficient.

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

The light source of the active energy ray may be, for example, one that generates ultraviolet rays, electron beams, X-rays, or the like. The active energy ray is preferably ultraviolet light. As the ultraviolet light source, a light source having an emission distribution having a wavelength of 400 nm or less is preferable, and examples thereof include a low pressure mercury lamp, a medium pressure mercury lamp, a high pressure mercury lamp, an ultrahigh pressure mercury lamp, a chemical lamp, a black light lamp, a microwave pumped mercury lamp, and a metal halide lamp. be able to.

The intensity of irradiation with active energy rays on the adhesive layer is determined for each adhesive composition, and the intensity of light irradiation in the wavelength region effective for activating the photopolymerization initiator is 0.1 to 1000 mW / cm ^2. It is preferable to do so. If the light irradiation intensity is too low, the reaction time will be too long, while if the light irradiation intensity is too high, the adhesive layer will yellow or be polarized due to the heat radiated from the lamp and the heat generated during the polymerization of the adhesive. There is a possibility that the film 30 may deteriorate or the protective film may have poor skin. The light irradiation time of the adhesive is also controlled for each adhesive composition, but the integrated light amount expressed as the product of the light irradiation intensity and the light irradiation time is set to be 10 to 5000 mJ / cm ^2. Is preferable. If the integrated light intensity is too small, the active species derived from the photopolymerization initiator may not be sufficiently generated, and the resulting adhesive layer may be insufficiently cured. On the other hand, if the integrated light intensity is too large, the light intensity may be insufficient. The irradiation time becomes very long, which tends to be disadvantageous for improving productivity.

The timing of laminating the protective film on the polarizing film 30 via the coating layer of the adhesive and the timing of curing or drying the coating layer are not particularly limited. For example, after laminating one protective film, the coating layer can be subsequently cured or dried, and then the other protective film can be laminated to cure or dry the coating layer. Alternatively, after laminating both protective films sequentially or simultaneously, the coating layers on both sides may be cured or dried at the same time. Further, the irradiation of the active energy rays may be performed from either protective film side. For example, when one protective film contains an ultraviolet absorber and the other protective film does not contain an ultraviolet absorber, it is preferable to irradiate the active energy ray from the protective film side that does not contain the ultraviolet absorber. By irradiating in this way, the irradiated active energy rays can be effectively used and the curing rate 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, more preferably 5 μm or less, and particularly preferably 3 μm or less. If the thicknesses of the first and second adhesive layers 15 and 25 are excessively large, the reaction rate of the adhesive tends to decrease, 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, preferably 0.1 μm or more. The first adhesive layer 15 and the second adhesive layer 25 may have the same thickness or different thicknesses.

(5) Other Components of the Polarizing Plate (5-1) Optical Functional Film The polarizing plate may include an optical functional film other than the polarizing film 30 for imparting a desired optical function. A preferred example thereof is a retardation film. As described above, the first protective film 10 and / or the second protective film 20 can also serve as the retardation film, but the retardation film can also be laminated separately from the protective film. In the latter case, the retardation film can be laminated on the outer surface of the first protective film 10 and / or the second protective film 20 via an adhesive layer or an adhesive layer.

Specific examples of the retardation film include a birefringent film composed of a stretched film of a translucent thermoplastic resin, a film in which a discotic liquid crystal or a nematic liquid crystal is oriented and fixed, and the above liquid crystal layer on a base film. Includes those formed. The base film is usually a thermoplastic resin film, and a cellulose ester resin such as triacetyl cellulose is preferably used as the thermoplastic resin.

As the thermoplastic resin for forming the birefringent film, the one described for the protective film can be used. For example, in the case of using a cellulose ester resin, a method of forming a film from a cellulose ester resin containing a compound having a phase difference adjusting function, a phase difference on the surface of the cellulose ester resin film. A birefractive film can be obtained by a method of applying a compound having an adjusting function or a method of stretching a cellulose ester resin uniaxially or biaxially. As the thermoplastic resin for forming the birefractive film, other thermoplastic resins such as polyvinyl alcohol-based resin, polystyrene-based resin, polyarylate-based resin, and polyamide-based resin can also be used.

Two or more retardation films may be used in combination for the purpose of controlling optical characteristics such as widening the bandwidth. Further, the film is not limited to a film having optical anisotropy, and a substantially optically isotropic zero retardation film can be used as the retardation film. The zero Letters retardation film in-plane retardation value _{R e} and the thickness direction retardation _{R th} means a film are both -15～15Nm. The in-plane retardation value _Re and the thickness direction retardation value R _th referred to here are values at a wavelength of 590 nm.

The in-plane retardation value _Re and the thickness direction retardation value R _th are expressed by the following equations, respectively:
_Re = (n _{x −} n _y ) × d
R _th = [(n _x + n _y ) /2- _nz ] × d
Defined in. Wherein, n _x is a refractive index in a slow axis direction (x-axis direction) in the film plane, n _y is the fast axis direction in the film plane of the (y-axis direction orthogonal to the x-axis in a plane) The refractive index, _nz is the refractive index in the film thickness direction (the z-axis direction perpendicular to the film surface), and d is the film thickness.

As the zero retardation film, a thermoplastic resin described for a protective film or a birefractive film can be used, and for example, a polyolefin resin such as a cellulose ester resin, a chain polyolefin resin and a cyclic polyolefin resin, A resin film made of a polyester resin such as polyethylene terephthalate can be used. Among them, cellulose ester-based resins and polyolefin-based resins are preferably used because the retardation value can be easily controlled and easily obtained.

Examples of other optical functional films (optical members) that can be included in the polarizing plate are a condenser plate, a brightness improving film, a reflective layer (reflective film), a semitransmissive reflective layer (semi-transmissive reflective film), and a light diffusing layer (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 condensing plate is used for the purpose of controlling the optical path, and may be a prism array sheet, a lens array sheet, a sheet with dots, or the like.

The brightness improving film is used for the purpose of improving the brightness in a liquid crystal display device to which a polarizing plate is applied. Specifically, a reflective polarizing separation sheet designed to generate anisotropy in reflectance by laminating a plurality of thin films having different refractive index anisotropy, an alignment film of cholesteric liquid crystal polymer, and its orientation. Examples thereof include a circularly polarized light separation sheet in which a liquid crystal layer is supported on a base film.

The reflective layer, the semitransmissive reflective layer, and the light diffusing layer are provided to make the polarizing plate a reflective type, a semitransparent type, and a diffusing type optical member, respectively. The reflective polarizing plate is used in a liquid crystal display device of a type that reflects and displays incident light from the viewing side, and since a light source such as a backlight can be omitted, the liquid crystal display device can be easily made thinner. The transflective polarizing plate is used in a liquid crystal display device of a type that displays light from a backlight in a dark place as a reflective type in a bright place. Further, the diffusion type polarizing plate is used for a liquid crystal display device that imparts light diffusivity and suppresses display defects such as moire. The reflective layer, the transflective reflective layer and the light diffusing layer can be formed by a known method.

(5-2) Adhesive Layer The polarizing plate according to 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 another optical member. The pressure-sensitive adhesive layer can be laminated on the outer surface of the protective film. The pressure-sensitive adhesive layer may be laminated on the outer surface of the first protective film, or may be laminated on the outer surface of the second protective film.

As the pressure-sensitive adhesive used for the pressure-sensitive adhesive layer, a (meth) acrylic resin, a silicone-based resin, a polyester-based resin, a polyurethane-based resin, a polyether-based resin, or the like as a base polymer can be used. Among them, a (meth) acrylic pressure-sensitive adhesive is preferably used from the viewpoints of transparency, adhesive strength, reliability, weather resistance, heat resistance, reworkability and the like. The (meth) acrylic pressure-sensitive adhesive includes a (meth) acrylic acid alkyl ester having an alkyl group having 20 or less carbon atoms such as a methyl group, an ethyl group, and a butyl group, and (meth) acrylic acid and (meth) acrylic acid. A functional group-containing (meth) acrylic monomer such as hydroxyethyl is blended so that the glass transition temperature is preferably 25 ° C. or lower, more preferably 0 ° C. or lower, and the weight average molecular weight is 100,000 or more (meth). Acrylic resins are useful as base polymers.

To form the pressure-sensitive adhesive layer on the polarizing plate, for example, a pressure-sensitive adhesive composition is dissolved or dispersed in an organic solvent such as toluene or ethyl acetate to prepare a solution of 10 to 40% by weight, and this is used as the target surface of the polarizing plate. A method of forming an adhesive layer by directly coating the film, or a method of forming an adhesive layer in a sheet shape on a separate film that has been subjected to a mold release treatment and transferring it to the target surface of the polarizing plate. It can be done by such as. The thickness of the pressure-sensitive adhesive layer is determined according to the adhesive strength and the like, but the range of about 1 to 50 μm is appropriate, and it is preferably 2 to 40 μm.

The polarizing plate may include the above-mentioned separate film. The separate film can be a film made of a polyethylene resin such as polyethylene, a polypropylene resin such as polypropylene, a polyester resin such as polyethylene terephthalate, or the like. Of these, a polyethylene terephthalate stretched film is preferable.

The pressure-sensitive adhesive layer contains, if necessary, a filler made of glass fiber, glass beads, resin beads, metal powder or other inorganic powder, a pigment, a colorant, an antioxidant, an ultraviolet absorber, an antistatic agent, etc. It may have been.

Examples of the antistatic agent include ionic compounds, conductive fine particles, conductive polymers, and the like, and ionic compounds are preferably used. The cation component constituting the ionic compound may be an inorganic anion or an organic anion, but is preferably an organic cation from the viewpoint of compatibility with the (meth) acrylic resin. Examples of the organic cation include pyridinium cation, imidazolium cation, ammonium cation, sulfonium cation, phosphonium cation and the like. On the other hand, the anion component constituting the ionic compound may be an inorganic anion or an organic anion, but an anion component containing a fluorine atom is preferable because it provides an ionic compound having excellent antistatic performance. As anion components containing a fluorine atom, hexafluorophosphate anion [(PF ₆ ⁻ )], bis (trifluoromethanesulfonyl) imide anion [(CF ₃ SO ₂ ) ₂ N ⁻ ] anion, bis (fluorosulfonyl) imide anion [ (FSO ₂ ) ₂ N ⁻ ] anions and the like can be mentioned.

(5-3) Protective film The polarizing plate according to the present invention may include a protective film for temporarily adhering and protecting the surface (protective film surface). After the polarizing plate is attached to, for example, an image display element or another optical member, the protective film is peeled off and removed together with the adhesive layer contained therein.

The protective film is composed of a base film and an adhesive layer laminated on the base film. The above description is cited for the pressure-sensitive adhesive layer. The resin constituting the base film is, for example, a polyethylene resin such as polyethylene, a polypropylene resin such as polypropylene, a polyester resin such as polyethylene terephthalate or polyethylene naphthalate, or a thermoplastic resin such as a polycarbonate resin. be able to. A polyester resin such as polyethylene terephthalate is preferable.

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

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these examples. In the following examples, the following radically polymerizable compounds, photoradical polymerization initiators, and additives constituting the adhesive were used.

(Radical polymerizable compound)
[1] Curable compound 1: Dicyclopentanyl acrylate (trade name "FA-513AS" obtained from Hitachi Chemical Co., Ltd., glass transition temperature 120 ° C.),
[2] Curable compound 2: 1,4-cyclohexanedimethanol monoacrylate (trade name "CHDMMA" obtained from Nihon Kasei Corporation, glass transition temperature 18 ° C.),
[3] Curable compound 3: Hydroxyethyl acrylate (trade name "HEA" obtained from Osaka Organic Industry Co., Ltd., glass transition temperature -15 ° C),
[4] Curable compound 4: 4-hydroxybutyl acrylate (trade name "4HBA" obtained from Osaka Organic Industry Co., Ltd., glass transition temperature -32 ° C),
[5] Curable compound 5: N, N-dimethylacrylamide (trade name "DMAA" obtained from KJ Chemicals Co., Ltd., glass transition temperature 119 ° C.),
[6] Curable compound 6: N- (2-hydroxyethyl) acrylamide (trade name "HEAA" obtained from KJ Chemicals Co., Ltd., glass transition temperature 98 ° C.),
[7] Curable compound 7: Polyethylene glycol # 600 diacrylate (trade name "A-600" obtained from Shin-Nakamura Chemical Industry Co., Ltd., glass transition temperature -23 ° C),
[8] Curable compound 8: Ethoxylated glycerin triacrylate (trade name "A-GLY-20E" obtained from Shin Nakamura Chemical Industry Co., Ltd.),
[9] Curable compound 9: ω-carboxy-polycaprolactone (n≈2) monoacrylate (trade name "M-5300" obtained from Toa Synthesis Co., Ltd., glass transition temperature −41 ° C.),
[10] Curable compound 10: Ultraviolet curable urethane acrylate resin (trade name "UV-3000B" obtained from Nippon Synthetic Chemical Industry Co., Ltd., glass transition temperature -39 ° C),
[11] Curable compound 11: Dipentaerythritol hexaacrylate (trade name "A-DPH" obtained from Shin-Nakamura Chemical Industry Co., Ltd.),
[12] Curable compound 12: Ultraviolet curable urethane acrylate resin (trade name "UV-3700B" obtained from Nippon Synthetic Chemical Industry Co., Ltd.).

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

The ultraviolet curable urethane acrylate resin (trade name "UV-3000B") is an ultraviolet curable resin mainly composed of urethane acrylate, has a viscosity of 45,000 to 65,000 mPa · s / 60 ° C., and has a molecular weight (Mw). ) Is 18,000, and the number of oligomer functional groups is 2.

The ultraviolet curable urethane acrylate resin (trade name "UV-3700B") is an ultraviolet curable resin mainly composed of urethane acrylate, has a viscosity of 30,000 to 60,000 mPa · s / 60 ° C., and has a molecular weight (Mw). ) Is 38,000, and the number of oligomer functional groups is 2.

(Photoradical polymerization initiator)
[13] Initiator 1: 2-Methyl-1- [4- (methylthio) phenyl] -2-moriphorinopropane-1-one (trade name "Irgacure 907" obtained from BASF).

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

<Production Examples 1 to 6: Preparation of UV Curable Adhesive>
The above radical polymerizable compound, photoradical polymerization initiator, and additive are weighed into a 20 mL screw tube at the blending ratio shown in Table 1 (the numerical values in Table 1 indicate parts by weight), mixed, and defoamed. Then, liquid ultraviolet curable adhesives A to F were prepared respectively.

<Production Examples 7 to 8: Preparation of UV Curable Adhesive>
The above radical polymerizable compound, photoradical polymerization initiator, and additive are weighed into a 20 mL screw tube at the blending ratio shown in Table 2 (the numerical values in Table 2 indicate parts by weight), mixed, and defoamed. The liquid UV-curable adhesives G and H were prepared, respectively.

<Manufacturing Example 9: Preparation of (Meta) Acrylic Resin Film>
A (meth) acrylic resin, which is a copolymer obtained by copolymerizing methyl methacrylate and methyl acrylate at a weight ratio of 96: 4, was prepared. The innermost layer is composed of a hard polymer polymerized with methyl methacrylate and a small amount of allyl methacrylate, and the intermediate layer is mainly composed of butyl acrylate, and is further polymerized with styrene and a small amount of allyl methacrylate. The outermost layer is an elastic body having a three-layer structure composed of a hard polymer polymerized with methyl methacrylate and a small amount of ethyl acrylate, and is an intermediate layer. Acrylic rubber particles having an average particle size of 240 nm were prepared.

A pellet in which the above (meth) acrylic resin and the above acrylic rubber particles are blended in a weight ratio of 70:30 and a benzotriazole ultraviolet absorber is added is prepared, and this is biaxially extruded. While melt-kneading with a machine, 0.05 parts by weight of stearic acid as a lubricant was added to 100 parts by weight of the pellets and mixed to obtain pellets of a (meth) acrylic resin composition. These pellets are put into a 65 mmφ uniaxial extruder and extruded through a T-type die having a set temperature of 275 ° C., and both sides of the extruded film-like molten resin are polished with two mirror surfaces whose temperature is set to 45 ° C. It was sandwiched between rolls and cooled to prepare 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 and Comparative Examples 1 to 5>
(1) Preparation of Plate Plate A corona discharge treatment is applied to one side of the (meth) acrylic resin film (first protective film) prepared in Production Example 9, and a first adhesive (first adhesive) is applied to the corona discharge treatment surface. As the adhesive for forming the agent layer), the adhesive shown in Table 3 was applied using a bar coater so that the thickness after curing was about 2.5 μm. Next, a polyvinyl alcohol (PVA) -iodine-based polarizing film having a thickness of 25 μm was attached to the coated surface. Next, a retardation film having a thickness of 50μm consisting of cyclic polyolefin resin (norbornene resin) [Nippon Zeon Co., Ltd. under the trade name "ZEONOR" in-plane retardation value at a wavelength of 590 nm _R e: 52 nm] (second One side of the protective film) is subjected to corona discharge treatment, and the thickness of the adhesive shown in Table 3 as a second adhesive (adhesive forming the second adhesive layer) after curing is applied to the corona discharge treatment surface. The coating was applied using a bar coater so as to have a thickness of about 2.5 μm. A polarizing film with the (meth) acrylic resin film prepared above was laminated on the coated surface on the polarizing film side, and pressed and bonded using a bonding roll to obtain a laminate. From the cyclic polyolefin resin film side of this laminate, the integrated light amount is 250 mJ / cm ² (UVB) using an ultraviolet irradiation device with a belt conveyor [the lamp uses a "D valve" manufactured by Fusion UV Systems). ) Was irradiated with ultraviolet rays, and the adhesive layers on both sides were cured to prepare a polarizing plate.

(2) Measurement of glass transition temperature Tg of adhesive layer Prepare two stretched films of cyclic polyolefin resin with a thickness of 25 μm [“Zeonoa film” sold by Nippon Zeon Corporation] without corona treatment. It was used as it was. Then, using a bar coater, the surface of one of the stretched films is coated with the prepared ultraviolet curable adhesive so that the film thickness after curing is 2 μm, and another stretched film is laminated on the coated surface. It was. From one of the bonded products, the cyclic polyolefin resin film side, the integrated light amount is 250 mJ / cm ² by the ultraviolet irradiation device with a belt conveyor [the lamp uses "D valve" manufactured by Fusion UV Systems). Was irradiated with ultraviolet rays to cure the ultraviolet curable adhesive. Next, the stretched film sandwiching the cured product was peeled off, 5 mg of the cured product was collected, placed in an aluminum presser lid type container, pressed and sealed to prepare a sample for measurement.

Differential scanning calorimetry (DSC) [Set the container containing the above measurement sample in "EXSTAR-6000 DSC6220" sold by SII Nanotechnology Co., Ltd., and purge nitrogen gas at 20 ° C. After lowering the temperature from -60 ° C to -60 ° C and holding for 1 minute after reaching -60 ° C, the temperature is raised from -60 ° C to 150 ° C at a heating rate of 10 ° C / min, and when it reaches 150 ° C, it immediately reaches 20 ° C. The temperature has dropped. Then, from the DSC curve when the temperature is raised from -60 ° C to 150 ° C, the intermediate point glass transition temperature specified in JIS K 7121-1987 "Method for measuring transition temperature of plastic" is obtained, and this is UV-cured to be measured. The glass transition temperature of the adhesive layer (cured product) formed by the sex adhesive was used. The glass transition temperature of the first adhesive layer formed from the first adhesive is Tg1, and the glass transition temperature of the second adhesive layer formed from the second adhesive is Tg2.

(3) Evaluation of Curl Resistance of Polarizing Plate in High Temperature Environment A single-wafer having a size of 80 mm × 80 mm was cut out from the polarizing plate produced in (1) above. The fronds are left overnight at a temperature of 23 ° C. and a relative humidity of 60%, then placed under dry conditions at a temperature of 80 ° C. for 10 minutes, and then left at a temperature of 23 ° C. and a relative humidity of 60% for 3 hours. After that, the amount of curl of the frond was measured. The amount of curl was obtained by placing a curved singlet on a horizontal table so that it was convex downward, and measuring the height from the table to the four corners of the singlet with a ruler. It was calculated as the average value of the point values. Based on the obtained curl amount, the curl resistance was evaluated according to the following criteria. The evaluation results are shown in Table 3.

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

(4) Evaluation of Workability of Polarizing Plate Using a blade of 800 mm × 800 mm manufactured by Dumbbell Co., Ltd., punch out from the first protective film side of the polarizing plate, and visually observe the floating and peeling state of the end of the polarizing plate. Workability was evaluated according to the following criteria. The evaluation results are shown in Table 3.

A: There is no floating or peeling at the end of the polarizing plate.
B: There is floating or peeling at the end of the polarizing plate.

(5) Formation of Adhesive Layer An isocyanate-based cross-linking agent, a silane coupling agent, and an antistatic agent are added to a (meth) acrylic resin which is a copolymer of butyl acrylate, methyl acrylate, acrylic acid, and hydroxyethyl acrylate. Separate film [trade name "SP-PLR382052" obtained from Lintec Co., Ltd.] made of polyethylene terephthalate that has been subjected to a mold release treatment with an organic solvent solution of a (meth) acrylic adhesive. The mold-treated surface was coated with a die coater so that the thickness after drying was 20 μm to prepare a sheet-like adhesive with a separate film. Next, the surface (adhesive surface) opposite to the sheet-like adhesive separate film obtained above is bonded to the cyclic polyolefin resin film surface of the polarizing plate produced in (1) above with a laminator, and then the temperature is increased. The film was cured at 23 ° C. and a relative humidity of 65% for 7 days to obtain a polarizing plate having an adhesive layer.

(6) Evaluation of Cold Thermal Impact Resistance of Polarizing Plate A 200 mm × 150 mm size single-wafer is cut out from the polarizing plate having the pressure-sensitive adhesive layer prepared in (5) above, and non-alkali glass [Corning] is used on the pressure-sensitive adhesive layer side. It was attached to the trade name "EAGLE XG"] manufactured by the company to prepare a measurement sample for a cold shock test (heat shock test). Four measurement samples were prepared for each polarizing plate frond. The thermal shock test was carried out by holding at −40 ° C. for 30 minutes, then raising the temperature to 70 ° C. and holding for 30 minutes as one cycle, and repeating this for a total of 100 cycles. The above-mentioned thermal shock test was performed on four measurement samples, and the cold impact resistance was evaluated from the ratio of the total number of samples (4) to which cracks or cracks were observed in the polarizing film after the test. The evaluation results are shown in Table 3.

<Examples 4 to 6>
(1-1) Fabrication of Polarizing Plate (Example 4)
An adhesive that applies a corona discharge treatment to one side of the (meth) acrylic resin film (first protective film) produced in Production Example 9 and forms a first adhesive (first adhesive layer) on the corona discharge treated surface. ), The adhesive shown in Table 4 was applied using a bar coater so that the thickness after curing was about 2.5 μm. Next, a polyvinyl alcohol (PVA) -iodine-based polarizing film having a thickness of 25 μm was attached to the coated surface. Next, one side of a 40 μm-thick retardation film (trade name “KC4CR” manufactured by Konica Minolta Co., Ltd.) (second protective film) made of an acetyl cellulose resin is subjected to corona discharge treatment, and the corona discharge treated surface is subjected to corona discharge treatment. As the second adhesive (adhesive forming the second adhesive layer), the adhesive also shown in Table 4 was applied using a bar coater so that the thickness after curing was about 2.5 μm. A polarizing film with the (meth) acrylic resin film prepared above was laminated on the coated surface on the polarizing film side, and pressed and bonded using a bonding roll to obtain a laminate. From the acetyl cellulose resin film side of this laminate, the integrated light amount is 250 mJ / cm ² (UVB) using an ultraviolet irradiation device with a belt conveyor [the lamp uses a "D valve" manufactured by Fusion UV Systems). ) Was irradiated with ultraviolet rays, and the adhesive layers on both sides were cured to prepare a polarizing plate.

(1-2) Preparation of Polarizing Plate (Examples 5 to 6)
An adhesive that applies a corona discharge treatment to one side of the (meth) acrylic resin film (first protective film) produced in Production Example 9 and forms a first adhesive (first adhesive layer) on the corona discharge treated surface. ), The adhesive shown in Table 4 was applied using a bar coater so that the thickness after curing was about 2.5 μm. Next, a polyvinyl alcohol (PVA) -iodine-based polarizing film having a thickness of 25 μm was attached to the coated surface. Next, a retardation film having a thickness of 50μm consisting of cyclic polyolefin resin (norbornene resin) [Nippon Zeon Co., Ltd. under the trade name "ZEONOR" in-plane retardation value at a wavelength of 590 nm _R e: 52 nm] (second One side of the protective film) is subjected to corona discharge treatment, and the thickness of the adhesive shown in Table 4 as a second adhesive (adhesive forming the second adhesive layer) after curing is applied to the corona discharge treatment surface. The coating was applied using a bar coater so as to have a thickness of about 2.5 μm. A polarizing film with the (meth) acrylic resin film prepared above was laminated on the coated surface on the polarizing film side, and pressed and bonded using a bonding roll to obtain a laminate. From the cyclic polyolefin resin film side of this laminate, the integrated light amount is 250 mJ / cm ² (UVB) using an ultraviolet irradiation device with a belt conveyor [the lamp uses a "D valve" manufactured by Fusion UV Systems). ) Was irradiated with ultraviolet rays, and the adhesive layers on both sides were cured to prepare a polarizing plate.

(2) Measurement of Glass Transition Temperature Tg of Adhesive Layer The glass of the first adhesive layer formed from the first adhesive in the same manner as in (2) of <Examples 1 to 3 and Comparative Examples 1 to 5>. The transition temperature Tg1 and the glass transition temperature Tg2 of the second adhesive layer formed from the second adhesive were measured.

(3) Evaluation of Curl Resistance of Polarizing Plates in High Temperature Environment The polarizing plates obtained in Examples 4 to 6 have resistance to curl in the same manner as in (3) of <Examples 1 to 3 and Comparative Examples 1 to 5>. The curl property was evaluated. The evaluation results are shown in Table 4.

(4) Evaluation of Workability of Polarizing Plates The workability of the polarizing plates obtained in Examples 4 to 6 was evaluated in the same manner as in (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 is used to have an adhesive layer. A polarizing plate was obtained. The sheet-shaped pressure-sensitive adhesive was attached to the cyclic polyolefin-based resin film surface or the acetyl-cellulose-based resin film surface of the polarizing plate.

(6) Evaluation of Cold Thermal Impact Resistance of Polarizing Plates The cold thermal shock resistance of the polarizing plates obtained in Examples 4 to 6 is the same as in (6) of <Examples 1 to 3 and Comparative Examples 1 to 5>. Was evaluated. The evaluation results are shown in Table 4.

10 1st protective film, 15 1st adhesive layer, 20 2nd protective film, 25 2nd adhesive layer, 30 polarizing film.

Claims (6)

The first protective film, the first adhesive layer, the polarizing film, the second adhesive layer, and the second protective film are included in this order.
The glass transition temperature of the first adhesive layer is −15 ° C. or higher and lower than 60 ° C., and the glass transition temperature of the second adhesive layer is 60 ° C. or higher.
The difference between the glass transition temperature of the second adhesive layer and the glass transition temperature of the first adhesive layer is 10 ° C. or higher and 59 ° C. or lower.
A polarizing plate in which the first protective film is made of a (meth) acrylic resin and the second protective film is made of a polyolefin resin or a cellulose ester resin. The polarizing plate according to claim 1, wherein the glass transition temperature of the first adhesive layer is 0 ° C. or higher. The polarizing plate according to claim 1 or 2, wherein the glass transition temperature of the second adhesive layer is 80 ° C. or higher. The polarizing plate according to any one of claims 1 to 3, wherein at least 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 according to claim 4, wherein the active energy ray-curable adhesive contains a radically polymerizable compound. The polarizing plate according to any one of claims 1 to 5, wherein at least one of the first protective film and the second protective film is a retardation film.

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