JP7789038B2 - Polarizing plate with adhesive layer - Google Patents

Description

The present invention relates to a polarizing plate with an adhesive layer, which includes a polarizing plate and an adhesive layer laminated thereon.

A polarizing plate, which is obtained by laminating a protective film on one or both sides of a polarizer, is an optical component that is widely used in image display devices such as liquid crystal display devices including mobile televisions and organic electroluminescence (organic EL) display devices, and in particular in various mobile devices in recent years such as mobile phones, smartphones, and tablet terminals.
Polarizing plates are often used by being attached to image display elements (liquid crystal cells, organic EL display elements, etc.) via a pressure-sensitive adhesive layer (see, for example, JP 2010-229321 A (Patent Document 1)). For this reason, polarizing plates are sometimes distributed on the market in the form of pressure-sensitive adhesive layer-attached polarizing plates, in which a pressure-sensitive adhesive layer is previously provided on one surface of the polarizing plate.

JP 2010-229321 A

A laminated optical member obtained by laminating a polarizing plate with a pressure-sensitive adhesive layer onto an optical member such as an image display element may warp due to the influence of heat, etc. during the manufacturing process of incorporating the member into an image display device, or when the member is incorporated into an image display device and used. In recent years, as image display elements and polarizing plates have become thinner, the problem of warping in laminated optical members has become increasingly noticeable.
Warping of the laminated optical element can reduce the workability of the manufacturing process, and when the laminated optical element is stored in a frame and shipped, part of the laminated optical element is pressed against the frame, causing stress and resulting in problems such as damage to the laminated optical element.

Layered optical components are also required to have heat resistance and durability, ensuring good performance even when subjected to heat and other influences during the manufacturing process for incorporating them into image display devices, or when they are incorporated into image display devices and used.

The present invention aims to provide a polarizing plate with a pressure-sensitive adhesive layer that can produce a laminated optical component that has excellent resistance to the above-mentioned warping (hereinafter also referred to as "warping resistance") and heat resistance durability.

The present invention provides a pressure-sensitive adhesive layer-attached polarizing plate and a laminated optical member as described below.
[1] A polarizing plate having a maximum curling force of 500 mN or more at 80°C;
a pressure-sensitive adhesive layer laminated on the polarizing plate;
Including,
The pressure-sensitive adhesive layer has a difference in absolute value between the gel fraction (G80) [%] after heating at 80°C for 24 hours and the gel fraction (G23) [%] at 23°C of greater than 5 points.
[2] The pressure-sensitive adhesive layer-attached polarizing plate according to [1], wherein the pressure-sensitive adhesive layer has a gel fraction (G80) of 60% or more after heating at 80° C. for 24 hours.
[3] The pressure-sensitive adhesive layer-attached polarizing plate according to [1] or [2], wherein the pressure-sensitive adhesive layer has a gel fraction (G80) of 95% or less after heating at 80° C. for 24 hours.
[4] The pressure-sensitive adhesive layer-attached polarizing plate according to any one of [1] to [3], wherein the polarizing plate includes a polarizer having a thickness of 10 μm or more.
[5] The pressure-sensitive adhesive layer-attached polarizing plate according to any one of [1] to [4], wherein the pressure-sensitive adhesive layer is formed from a pressure-sensitive adhesive composition containing a (meth)acrylic resin.
[6] The pressure-sensitive adhesive layer-attached polarizing plate according to [5], wherein the (meth)acrylic resin contains a structural unit derived from a (meth)acrylic monomer having a carboxyl group and a structural unit derived from an alkoxyalkyl(meth)acrylamide monomer.
[7] The pressure-sensitive adhesive layer-attached polarizing plate according to [5] or [6], wherein the pressure-sensitive adhesive composition has a crosslinking agent content of 0 parts by mass or more and 2 parts by mass or less per 100 parts by mass of the (meth)acrylic resin.
[8] A laminated optical member, which is a laminate of the pressure-sensitive adhesive layer-attached polarizing plate according to any one of [1] to [7] and an optical member other than the pressure-sensitive adhesive layer-attached polarizing plate.

It is possible to provide a polarizing plate with a pressure-sensitive adhesive layer that can produce a laminated optical component with excellent warp resistance and heat durability.

1 is a schematic cross-sectional view showing an example of a pressure-sensitive adhesive layer-attached polarizing plate and a laminated optical member according to the present invention. FIG. 2 is a schematic cross-sectional view showing another example of a pressure-sensitive adhesive layer-attached polarizing plate and a laminated optical member according to the present invention. FIG. 2 is a schematic cross-sectional view showing still another example of the pressure-sensitive adhesive layer-attached polarizing plate and laminated optical member according to the present invention. FIG. 2 is a schematic cross-sectional view showing still another example of the pressure-sensitive adhesive layer-attached polarizing plate and laminated optical member according to the present invention.

<Polarizing plate with pressure-sensitive adhesive layer>
[1] Structure of the pressure-sensitive adhesive layer-attached polarizing plate The pressure-sensitive adhesive layer-attached polarizing plate includes a polarizing plate and a pressure-sensitive adhesive layer laminated thereon. Examples of the layer structure of the pressure-sensitive adhesive layer-attached polarizing plate are shown in Figures 1 to 4.

The pressure-sensitive adhesive layer-attached polarizing plate 25 shown in Figure 1 includes a polarizing plate 10 and a first pressure-sensitive adhesive layer 20 laminated thereon. The polarizing plate 10 has a polarizer 1 and a first protective film 3 attached to one side of the polarizer 1. The first protective film 3 is attached to the side of the polarizer 1 opposite the first pressure-sensitive adhesive layer 20. As in the example shown in Figure 1, the first protective film 3 can have a surface treatment layer 2 formed on its outer surface (the side opposite the polarizer 1). The first pressure-sensitive adhesive layer 20 can be used, for example, to attach to an optical member 30. The optical member 30 will be described later.

The pressure-sensitive adhesive layer-attached polarizing plate 25 shown in Fig. 2 is the same as that shown in Fig. 1 except that the polarizing plate 10 further includes a second protective film 4 attached to the other surface of the polarizer 1. The first pressure-sensitive adhesive layer 20 is laminated on the outer surface of the second protective film 4.
The pressure-sensitive adhesive layer-attached polarizing plate 25 shown in Figure 3 is the same as that shown in Figure 1 except that the polarizing plate 10 further includes a retardation film 7 attached to the other surface of the polarizer 1 via a second pressure-sensitive adhesive layer 8.
The pressure-sensitive adhesive layer-attached polarizing plate 25 shown in Fig. 4 is the same as that shown in Fig. 2 except that the polarizing plate 10 further includes a retardation film 7 attached to the outer surface of the second protective film 4 via a second pressure-sensitive adhesive layer 8. In the examples shown in Figs. 3 and 4, the first pressure-sensitive adhesive layer 20 is attached to the retardation film 7.

The adhesive layer-attached polarizing plate 25 may have a separate film laminated on the outer surface of the first adhesive layer 20.

[2] Polarizing Plate The polarizing plate 10 constituting the pressure-sensitive adhesive layer-attached polarizing plate 25 includes at least a polarizer 1, and typically includes the polarizer 1 and a thermoplastic resin film as a protective film or the like laminated to at least one side of the polarizer 1.

[2-1] Polarizer The polarizer 1 is a film that has the function of selectively transmitting linearly polarized light in one direction from natural light. Examples include iodine-based polarizers in which iodine as a dichroic pigment is adsorbed and oriented on a polyvinyl alcohol-based resin film, dye-based polarizers in which a dichroic dye as a dichroic pigment is adsorbed and oriented on a polyvinyl alcohol-based resin film, and coated polarizers in which a dichroic dye in a lyotropic liquid crystal state is coated, oriented, and fixed. These polarizers are called absorption-type polarizers because they selectively transmit linearly polarized light in one direction from natural light and absorb linearly polarized light in the other direction.

Polarizer 1 is not limited to an absorptive polarizer, and may be a reflective polarizer that selectively transmits linearly polarized light in one direction from natural light and reflects linearly polarized light in the other direction, or a scattering polarizer that scatters linearly polarized light in the other direction. However, an absorptive polarizer is preferred due to its excellent visibility. Among these, a polyvinyl alcohol-based polarizer made of a polyvinyl alcohol-based resin is more preferred, a polyvinyl alcohol-based polarizer in which a dichroic pigment such as iodine or a dichroic dye is adsorbed and oriented in a polyvinyl alcohol-based resin film is even more preferred, and a polyvinyl alcohol-based polarizer in which iodine is adsorbed and oriented in a polyvinyl alcohol-based resin film is particularly preferred.

The polyvinyl alcohol resin that constitutes the polyvinyl alcohol polarizer can be a saponified polyvinyl acetate resin. Examples of polyvinyl acetate resins include polyvinyl acetate, which is a homopolymer of vinyl acetate, as well as copolymers of vinyl acetate with other monomers that can be copolymerized with it. Examples of other monomers that can be copolymerized 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 polyvinyl alcohol resins is typically 85 mol% or more and 100 mol% or less, and preferably 98 mol% or more. Polyvinyl alcohol resins may be modified; for example, polyvinyl formal or polyvinyl acetal modified with aldehydes can be used. The average degree of polymerization of polyvinyl alcohol resins is typically 1,000 or more and 10,000 or less, and preferably 1,500 or more and 5,000 or less. The average degree of polymerization of polyvinyl alcohol resins can be determined in accordance with JIS K 6726.

A film formed from such a polyvinyl alcohol-based resin is used as the base film for the polarizer 1. The method for forming the polyvinyl alcohol-based resin film is not particularly limited, and any known method can be used. The thickness of the polyvinyl alcohol-based base film is, for example, 150 μm or less, preferably 100 μm or less (e.g., 50 μm or less), and 5 μm or more.

Polarizer 1 can be produced by a method including the steps of uniaxially stretching a polyvinyl alcohol-based resin film; dyeing the polyvinyl alcohol-based resin film with a dichroic dye to adsorb the dichroic dye; treating the polyvinyl alcohol-based resin film with the adsorbed dichroic dye with an aqueous boric acid solution (crosslinking treatment); and rinsing with water after the treatment with the aqueous boric acid solution.

The polyvinyl alcohol resin film can be uniaxially stretched before, simultaneously with, or after dyeing with a dichroic dye. If uniaxial stretching is performed after dyeing, it may be performed before or during the boric acid treatment. Uniaxial stretching may also be performed in multiple stages.

In uniaxial stretching, the film may be stretched uniaxially between rolls with different peripheral speeds, or may be stretched uniaxially using a heated roll. Uniaxial stretching may be dry stretching, in which stretching is performed in the atmosphere, or wet stretching, in which the polyvinyl alcohol resin film is stretched in a swollen state using a solvent such as water. The stretching ratio is typically 3 to 8 times.

One method for dyeing a polyvinyl alcohol-based resin film with a dichroic dye is to immerse the film in an aqueous solution containing the dichroic dye. Iodine or a dichroic organic dye is used as the dichroic dye. It is preferable to immerse the polyvinyl alcohol-based resin film in water before dyeing.

Examples of dyeing methods using iodine include immersing a polyvinyl alcohol-based resin film in an aqueous solution containing iodine and potassium iodide. The iodine content in this aqueous solution may be 0.01 parts by mass or more and 1 part by mass or less per 100 parts by mass of water. The potassium iodide content may be 0.5 parts by mass or more and 20 parts by mass or less per 100 parts by mass of water. The temperature of this aqueous solution may be 20°C or more and 40°C or less.
On the other hand, examples of dyeing methods using dichroic organic dyes include a method of immersing a polyvinyl alcohol-based resin film in an aqueous solution containing the dichroic organic dye. 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 may be 1 x 10 ^-4 parts by mass or more and 10 parts by mass or less per 100 parts by mass of water. The temperature of this aqueous solution may be 20°C or more and 80°C or less.

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

The polyvinyl alcohol-based resin film after the boric acid treatment is usually washed with water. The washing can be performed, for example, by immersing the boric acid-treated polyvinyl alcohol-based resin film in water. The temperature of the water used in the washing is usually 5° C. or higher and 40° C. or lower. After washing with water, the film is dried to obtain polarizer 1.
The drying treatment can be carried out using a hot air dryer or a far-infrared heater. A thermoplastic resin film as a protective film or the like can be attached to one or both surfaces of the polarizer 1 using an adhesive, thereby obtaining a polarizing plate 10.

Other examples of methods for manufacturing polarizer 1 include those described in JP 2000-338329 A and JP 2012-159778 A. In this method, a solution containing a polyvinyl alcohol resin is applied to the surface of a substrate film to form a resin layer, and then the laminate film consisting of the substrate film and the resin layer is stretched and then dyed, crosslinked, and other processes are performed to form a polarizer layer (polarizer) from the resin layer. This polarizing laminate film consisting of a substrate film and a polarizer layer can be formed by laminating a thermoplastic resin film as a protective film or the like to the polarizer layer surface, and then peeling and removing the substrate film to form polarizing plate 10 with a thermoplastic resin film on one side of the polarizer. By further laminating a thermoplastic resin film to the polarizer layer surface exposed by peeling off the substrate film, polarizing plate 10 with thermoplastic resin films on both sides of the polarizer can be obtained.

The thickness of the polarizer 1 can be 40 μm or less, preferably 30 μm or less. According to the methods described in JP 2000-338329 A and JP 2012-159778 A, thin-film polarizer 1 can be more easily manufactured, making it easier to set the thickness of polarizer 1 to, for example, 20 μm or less, further 15 μm or less, even 10 μm or less, or 8 μm or less. The thickness of polarizer 1 is typically 2 μm or more, preferably 5 μm or more, and more preferably 10 μm or more. The thickness of polarizer 1 may be 20 μm or more. Reducing the thickness of polarizer 1 is advantageous for reducing the thickness of polarizing plate 10, and therefore of pressure-sensitive adhesive layer-attached polarizing plate 25, laminated optical components, and image display devices. On the other hand, increasing the thickness of polarizer 1 not only increases the degree of polarization of polarizing plate 10, but also works advantageously in terms of the durability of polarizer 1. Therefore, the thickness of polarizer 1 should be appropriately selected depending on the application.

[2-2] Thermoplastic Resin Film The thermoplastic resin film to be attached to one or both surfaces of the polarizer 1 can be a film made of a light-transmitting (preferably optically transparent) thermoplastic resin, for example, a polyolefin resin such as a linear polyolefin resin (e.g., a polypropylene resin) or a cyclic polyolefin resin (e.g., a norbornene resin); a cellulose ester resin such as triacetyl cellulose or diacetyl cellulose; a polyester resin such as polyethylene terephthalate, polyethylene naphthalate, or polybutylene terephthalate; a polycarbonate resin; a (meth)acrylic resin; or a mixture or copolymer thereof.

The thermoplastic resin film attached to one or both surfaces of the polarizer 1 may be either an unstretched film or a uniaxially or biaxially stretched film. The biaxial stretching may be simultaneous biaxial stretching in which the film is stretched simultaneously in two stretching directions, or sequential biaxial stretching in which the film is stretched in a first direction and then stretched in a second direction different from the first direction.
The thermoplastic resin film bonded to one or both sides of the polarizer 1 may be a protective film that plays a role in protecting the polarizer 1, such as the first and second protective films 3 and 4 shown in Figures 1 to 4, or may be a protective film that also has an optical function such as a retardation film.
The retardation film is an optically functional film used for the purpose of compensating for the retardation caused by a liquid crystal cell, which is an image display element, etc. For example, a retardation film having an arbitrary retardation value can be obtained by stretching (uniaxially stretching, biaxially stretching, etc.) a film made of the above-mentioned thermoplastic resin, or by forming a liquid crystal layer or the like on the thermoplastic resin film.

Examples of linear polyolefin resins include homopolymers of linear olefins such as polyethylene resin and polypropylene resin, as well as copolymers made from two or more types of linear olefins.

Cyclic polyolefin resin is a general term for resins containing cyclic olefins, such as norbornene, tetracyclododecene (also known as dimethanooctahydronaphthalene), or their derivatives, as polymerization units. Examples of cyclic polyolefin resins include ring-opening (co)polymers of cyclic olefins and their hydrogenated products, addition polymers of cyclic olefins, copolymers of cyclic olefins with linear olefins such as ethylene and propylene or aromatic compounds having vinyl groups, and modified (co)polymers of these copolymers modified with unsaturated carboxylic acids or their derivatives.
Among these, norbornene-based resins using norbornene-based monomers such as norbornene and polycyclic norbornene-based monomers as cyclic olefins are preferably used.

The cellulose ester resin is a resin in which at least a portion of the hydroxyl groups in cellulose are esterified with acetate, and may be a mixed ester in which a portion is esterified with acetate and a portion is esterified with another acid. The cellulose ester resin is preferably an acetyl cellulose resin.
Examples of the acetyl cellulose resin include triacetyl cellulose, diacetyl cellulose, cellulose acetate propionate, and cellulose acetate butyrate.

The polyester resin is a resin having an ester bond other than the above-mentioned cellulose ester resin, and is generally a polycondensate of a polycarboxylic acid or a derivative thereof with a polyhydric alcohol.
Examples of polyester resins include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polytrimethylene terephthalate, polytrimethylene naphthalate, polycyclohexane dimethyl terephthalate, and polycyclohexane dimethyl naphthalate.
Among these, polyethylene terephthalate is preferably used from the viewpoints of mechanical properties, solvent resistance, scratch resistance, cost, etc. Polyethylene terephthalate refers to a resin in which 80 mol % or more of the repeating units are composed of ethylene terephthalate, and may contain structural units derived from other copolymerization components.

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

Polycarbonate resins are polyesters formed from carbonic acid and glycol or bisphenol. Among them, aromatic polycarbonates having diphenylalkane in the molecular chain are preferably used from the viewpoints of heat resistance, weather resistance, and acid resistance.
Examples of polycarbonates include polycarbonates derived from bisphenols such as 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-bis(4-hydroxyphenyl)isobutane, and 1,1-bis(4-hydroxyphenyl)ethane.

The (meth)acrylic resin may be, for example, a polymer containing a methacrylic acid ester as the main monomer (containing 50% by mass or more), and is preferably a copolymer in which a methacrylic acid ester is copolymerized with another copolymerization component.
In one preferred embodiment, the (meth)acrylic resin contains methyl methacrylate or methyl methacrylate and methyl acrylate as copolymerization components.

Examples of copolymerization components other than methyl acrylate include methacrylic acid esters other than methyl methacrylate, such as ethyl methacrylate, n-, i-, or t-butyl methacrylate, cyclohexyl methacrylate, phenyl methacrylate, benzyl methacrylate, 2-ethylhexyl methacrylate, and 2-hydroxyethyl methacrylate;
acrylic acid esters such as ethyl acrylate, n-, i-, or t-butyl acrylate, cyclohexyl acrylate, phenyl acrylate, benzyl acrylate, 2-ethylhexyl acrylate, and 2-hydroxyethyl acrylate;
hydroxyalkyl acrylates such as methyl 2-(hydroxymethyl)acrylate, methyl 2-(1-hydroxyethyl)acrylate, ethyl 2-(hydroxymethyl)acrylate, and n-, i-, or t-butyl 2-(hydroxymethyl)acrylate;
Unsaturated acids such as methacrylic acid and acrylic acid;
Halogenated styrenes such as chlorostyrene and bromostyrene;
Substituted styrenes such as vinyltoluene and α-methylstyrene;
Unsaturated nitriles such as acrylonitrile and methacrylonitrile;
unsaturated acid anhydrides such as maleic anhydride and citraconic anhydride;
unsaturated imides such as phenylmaleimide and cyclohexylmaleimide;
and the like monofunctional monomers.
The other monofunctional monomers may be used alone or in combination of two or more.

A polyfunctional monomer may be used as the other copolymerization component.
Examples of polyfunctional monomers include ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, nonaethylene glycol di(meth)acrylate, and tetradecaethylene glycol di(meth)acrylate, and other ethylene glycol or oligomers thereof in which both terminal hydroxyl groups are esterified with (meth)acrylic acid;
propylene glycol or an oligomer thereof in which both terminal hydroxyl groups are esterified with (meth)acrylic acid;
dihydric alcohols such as neopentyl glycol di(meth)acrylate, hexanediol di(meth)acrylate, and butanediol di(meth)acrylate, in which the hydroxyl group is esterified with (meth)acrylic acid;
bisphenol A, an alkylene oxide adduct of bisphenol A, or a halogen-substituted product thereof in which both terminal hydroxyl groups have been esterified with (meth)acrylic acid;
Esters of polyhydric alcohols such as trimethylolpropane and pentaerythritol with (meth)acrylic acid, and products obtained by ring-opening addition of epoxy groups of glycidyl (meth)acrylate to the terminal hydroxyl groups of these esters;
ring-opening addition of an epoxy group of glycidyl (meth)acrylate to a dibasic acid such as succinic acid, adipic acid, terephthalic acid, phthalic acid, or a halogen-substituted product thereof, or an alkylene oxide adduct thereof;
Aryl (meth)acrylates; aromatic divinyl compounds such as divinylbenzene;
etc.
Of these, ethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, and neopentyl glycol dimethacrylate are preferably used.

The (meth)acrylic resin may be modified by a reaction between functional groups possessed by the copolymer. Examples of such reactions include an intrapolymer chain methanol condensation reaction between the methyl ester group of methyl (meth)acrylate and the hydroxyl group of methyl 2-(hydroxymethyl)acrylate, and an intrapolymer chain dehydration condensation reaction between the carboxyl group of (meth)acrylic acid and the hydroxyl group of methyl 2-(hydroxymethyl)acrylate.

The glass transition temperature of the (meth)acrylic resin is preferably 80°C or higher and 160°C or lower. The glass transition temperature can be controlled by adjusting the polymerization ratio of the methacrylic acid ester monomer to the acrylic acid ester monomer, the carbon chain length of each ester group and the type of functional group they contain, and the polymerization ratio of the polyfunctional monomer to the total monomers.

As a means for increasing the glass transition temperature of a (meth)acrylic resin, it is also effective to introduce a ring structure into the main chain of the polymer. The ring structure is preferably a heterocyclic structure such as a cyclic acid anhydride structure, a cyclic imide structure, or a lactone structure. Specific examples include cyclic acid anhydride structures such as glutaric anhydride structures and succinic anhydride structures; cyclic imide structures such as glutarimide structures and succinimide structures; and lactone ring structures such as butyrolactone and valerolactone.
The glass transition temperature of the (meth)acrylic resin tends to increase as the content of the ring structure in the main chain increases.
The cyclic acid anhydride structure and the cyclic imide structure can be introduced by a method of introducing a cyclic acid anhydride structure by copolymerizing a monomer having a cyclic structure, such as maleic anhydride or maleimide; a method of introducing a cyclic acid anhydride structure by a dehydration/demethanol condensation reaction after polymerization; or a method of introducing a cyclic imide structure by reacting an amino compound.
A resin (polymer) having a lactone ring structure can be obtained by a method in which a polymer having a hydroxyl group and an ester group in the polymer chain is prepared, and then the hydroxyl group and the ester group in the obtained polymer are subjected to cyclocondensation by heating, if necessary in the presence of a catalyst such as an organic phosphorus compound, to form a lactone ring structure.

The (meth)acrylic resin and the thermoplastic resin film formed therefrom may contain additives as needed, such as lubricants, antiblocking agents, heat stabilizers, antioxidants, antistatic agents, light resistance agents, impact resistance modifiers, surfactants, etc.
These additives can also be used when a thermoplastic resin other than a (meth)acrylic resin is used as the thermoplastic resin constituting the thermoplastic resin film.

The (meth)acrylic resin may contain acrylic rubber particles as an impact modifier from the viewpoint of film formability, impact resistance of the film, etc. The acrylic rubber particles are particles containing an acrylic acid ester-based elastic polymer as an essential component, and examples thereof include those with a single-layer structure essentially consisting of this elastic polymer alone, and those with a multilayer structure having this elastic polymer as one layer.
Examples of the elastic polymer include crosslinked elastic copolymers which contain alkyl acrylate as the main component and are copolymerized with other copolymerizable vinyl monomers and crosslinkable monomers.
Examples of alkyl acrylates that are the main component of the elastic polymer include those in which the alkyl group has 1 to 8 carbon atoms, such as methyl acrylate, ethyl acrylate, butyl acrylate, and 2-ethylhexyl acrylate, and alkyl acrylates having an alkyl group with 4 or more carbon atoms are preferably used.
Examples of other vinyl monomers copolymerizable with the alkyl acrylate include compounds having one polymerizable carbon-carbon double bond in the molecule, and more specific examples include methacrylic acid esters such as methyl methacrylate; aromatic vinyl compounds such as styrene; and vinyl cyanide compounds such as acrylonitrile.
Examples of the crosslinkable monomer include crosslinkable compounds having at least two polymerizable carbon-carbon double bonds in the molecule, and more specific examples include (meth)acrylates of polyhydric alcohols such as ethylene glycol di(meth)acrylate and butanediol di(meth)acrylate; alkenyl esters of (meth)acrylic acid such as allyl (meth)acrylate; and divinylbenzene.

A laminate of a film made of a (meth)acrylic resin that does not contain rubber particles and a film made of a (meth)acrylic resin that does contain rubber particles can also be used as the thermoplastic resin film to be attached to the polarizer 1. Alternatively, a (meth)acrylic resin layer can be formed on one or both sides of a retardation-exhibiting layer made of a resin different from a (meth)acrylic resin, thereby exhibiting retardation, and this can also be used as the thermoplastic resin film to be attached to the polarizer 1.

The thermoplastic resin film may contain an ultraviolet absorber. When the polarizing plate 10 is applied to an image display device such as a liquid crystal display device, by disposing a thermoplastic resin film containing an ultraviolet absorber on the viewing side of the image display element (e.g., a liquid crystal cell), deterioration of the image display element due to ultraviolet rays can be suppressed.
Examples of the ultraviolet absorber include salicylic acid ester compounds, benzophenone compounds, benzotriazole compounds, cyanoacrylate compounds, and nickel complex salt compounds.

When thermoplastic resin films are laminated to both sides of the polarizer 1, these thermoplastic resin films may be made of the same thermoplastic resin, or may be made of different thermoplastic resins. Furthermore, these thermoplastic resin films may be the same or different in terms of thickness, the presence or absence and type of additives, retardation properties, etc.

The thermoplastic resin film may have a surface treatment layer 2 (coating layer) such as a hard coat layer, antiglare layer, antireflection layer, light diffusion layer, antistatic layer, antifouling layer, or conductive layer on its outer surface (the surface opposite to the polarizer 1).

The thickness of the thermoplastic resin film is typically 5 μm or more and 200 μm or less, preferably 10 μm or more and 120 μm or less, more preferably 10 μm or more and 85 μm or less, and even more preferably 15 μm or more and 60 μm or less. The thickness of the thermoplastic resin film may be 50 μm or less, or may be 40 μm or less. Reducing the thickness of the thermoplastic resin film is advantageous for reducing the thickness of the polarizing plate 10, and therefore the pressure-sensitive adhesive layer-attached polarizing plate 25, laminated optical components, and image display devices.

The surface of the thermoplastic resin film to which the adhesive is applied may be subjected to a surface modification treatment such as saponification treatment, plasma treatment, corona treatment, or primer treatment in order to improve adhesion, or may not require surface modification treatment in order to simplify the process.
When the thermoplastic resin film is a cellulose acetate resin film, it is preferable to perform a saponification treatment from the viewpoint of improving adhesion. Examples of the saponification treatment include a method of immersing the film in an aqueous alkali solution such as sodium hydroxide or potassium hydroxide.

[2-3] Production of Polarizing Plate Examples of adhesives for bonding the thermoplastic resin film to the polarizer 1 include water-based adhesives and active energy ray-curable adhesives.
Examples of the water-based adhesive include conventionally known adhesive compositions that use a polyvinyl alcohol resin or a urethane resin as the main component.

When a polyvinyl alcohol resin is used as the main component of the adhesive, the polyvinyl alcohol resin may be a polyvinyl alcohol resin such as a partially saponified polyvinyl alcohol or a fully saponified polyvinyl alcohol, or a modified polyvinyl alcohol resin.
The polyvinyl alcohol-based resin may be a vinyl alcohol homopolymer obtained by saponifying polyvinyl acetate, which is a homopolymer of vinyl acetate, or a polyvinyl alcohol-based copolymer obtained by saponifying a copolymer of vinyl acetate and another monomer copolymerizable therewith.

Water-based adhesives containing polyvinyl alcohol resins can contain curing components or crosslinking agents such as polyaldehydes, melamine compounds, zirconia compounds, zinc compounds, glyoxal, glyoxal derivatives, and water-soluble epoxy resins to improve adhesion.

An example of a water-based adhesive containing a urethane resin as the main component is a water-based adhesive containing a polyester ionomer urethane resin and a compound containing a glycidyloxy group. A polyester ionomer urethane resin is a urethane resin with a polyester skeleton into which a small amount of ionic component (hydrophilic component) has been introduced.

An active energy ray-curable adhesive is an adhesive that cures when exposed to active energy rays such as ultraviolet light, visible light, electron beams, or X-rays. When an active energy ray-curable adhesive is used, the adhesive layer on the polarizing plate 10 is a cured layer of the adhesive.

The active energy ray-curable adhesive can be an adhesive containing an epoxy-based compound that cures by cationic polymerization as a curable component, and is preferably an ultraviolet-curable adhesive containing such an epoxy-based compound as a curable component. An epoxy-based compound refers to a compound that has an average of one or more epoxy groups, preferably two or more, per molecule. Only one type of epoxy-based compound may be used, or two or more types may be used in combination.

Examples of epoxy compounds include hydrogenated epoxy compounds (glycidyl ethers of polyols having alicyclic rings) obtained by reacting epichlorohydrin with alicyclic polyols obtained by hydrogenating the aromatic rings of aromatic polyols; aliphatic epoxy compounds such as polyglycidyl ethers of aliphatic polyhydric alcohols or their alkylene oxide adducts; and alicyclic epoxy compounds, which are epoxy compounds having one or more epoxy groups bonded to an alicyclic ring in the molecule.

The active energy ray-curable adhesive can contain a radically polymerizable (meth)acrylic compound as the curable component, instead of or in addition to the above-mentioned epoxy compound. Examples of (meth)acrylic compounds include (meth)acryloyloxy group-containing compounds such as (meth)acrylate monomers having one or more (meth)acryloyloxy groups in the molecule; and (meth)acrylate oligomers obtained by reacting two or more functional group-containing compounds and having at least two (meth)acryloyloxy groups in the molecule.

When the active energy ray-curable adhesive contains an epoxy compound that cures by cationic polymerization as a curable component, it preferably contains a photocationic polymerization initiator. Examples of the photocationic polymerization initiator include aromatic diazonium salts, onium salts such as aromatic iodonium salts and aromatic sulfonium salts, and iron-allene complexes.
When the active energy ray-curable adhesive contains a radically polymerizable component such as a (meth)acrylic compound, it preferably contains a photoradical polymerization initiator. Examples of the photoradical polymerization initiator include acetophenone-based initiators, benzophenone-based initiators, benzoin ether-based initiators, thioxanthone-based initiators, xanthone, fluorenone, camphorquinone, benzaldehyde, and anthraquinone.

The bonding of the polarizer 1 and the thermoplastic resin film can include a process of applying an adhesive to the bonding surface of the polarizer 1 and/or the bonding surface of the thermoplastic resin film, or injecting an adhesive between the polarizer 1 and the thermoplastic resin film, overlapping the two films with the adhesive layer between them, and pressing them together from above and below using, for example, a laminating roll.

A variety of coating methods can be used to form the adhesive layer, including, for example, a doctor blade, wire bar, die coater, comma coater, or gravure coater. Alternatively, the polarizer 1 and the thermoplastic resin film may be continuously fed with their bonding surfaces facing inward, and the adhesive may be cast between them.

Before applying the adhesive, one or both of the bonding surfaces of the polarizer 1 and the thermoplastic resin film may be subjected to an adhesion-enhancing treatment (surface activation treatment) such as saponification treatment, corona discharge treatment, plasma treatment, flame treatment, primer treatment, or anchor coating treatment.

When an active energy ray-curable adhesive is used, the adhesive layer is dried as necessary, and then irradiated with active energy rays to cure the adhesive layer.
The light source used for irradiating the active energy rays may be any light source capable of generating ultraviolet rays, electron beams, X-rays, etc. In particular, light sources having an emission distribution at wavelengths of 400 nm or less, such as low-pressure mercury lamps, medium-pressure mercury lamps, high-pressure mercury lamps, ultra-high-pressure mercury lamps, chemical lamps, black light lamps, microwave-excited mercury lamps, and metal halide lamps, are preferably used.

In the resulting polarizing plate 10, the thickness of the adhesive layer formed from the water-based adhesive is, for example, 10 nm or more and 10 μm or less, preferably 20 nm or more and 5 μm or less, more preferably 30 nm or more and 1 μm or less, and even more preferably 40 nm or more and 500 nm or less.
The thickness of the adhesive layer formed from the active energy ray-curable adhesive is, for example, 10 nm to 20 μm, preferably 100 nm to 10 μm, and more preferably 500 nm to 5 μm.
When thermoplastic resin films are attached to both surfaces of the polarizer 1, the two adhesive layers may have the same thickness or different thicknesses.

[2-4] Other Components of Polarizing Plate The polarizing plate 10 can include an optically functional film other than the polarizer 30 to impart a desired optical function, and a suitable example thereof is a retardation film such as the retardation film 7 shown in FIGS. 3 and 4 .
As described above, the thermoplastic resin film serving as the protective film can also serve as a retardation film, but a retardation film can also be laminated separately from the thermoplastic resin film. In the latter case, the retardation film can be laminated on the outer surface of the thermoplastic resin film via a pressure-sensitive adhesive layer or an adhesive layer.
Alternatively, a retardation film may be laminated instead of the thermoplastic resin film (see FIG. 3). In this case, the retardation film may be laminated on the surface of the polarizer 1 via a pressure-sensitive adhesive layer or an adhesive layer.

Examples of the retardation film include a birefringent film made of a stretched film of a light-transmitting thermoplastic resin; a film in which discotic liquid crystal or nematic liquid crystal is oriented and fixed; and a film in which the above-mentioned liquid crystal layer is formed on a substrate film.
The substrate film is usually a film made of a thermoplastic resin, and an example of the thermoplastic resin is a cellulose ester resin such as triacetyl cellulose.
As the thermoplastic resin for forming the birefringent film, those described for the thermoplastic resin film can be used.

Examples of other optically functional films (optical components) that can be included in polarizing plate 10 include a light collecting plate, a brightness enhancement film, a reflective layer (reflective film), a semi-transmissive reflective layer (semi-transmissive reflective film), a light diffusion layer (light diffusion film), etc. These are generally provided when polarizing plate 10 is a polarizing plate placed on the back side (backlight side) of a liquid crystal cell.

Light-collecting plates are used for purposes such as light path control, and can be prism array sheets, lens array sheets, dot-attached sheets, etc.

Brightness enhancement films are used to improve the brightness of liquid crystal display devices that use polarizing plate 10. Specific examples include reflective polarization separation sheets designed to create anisotropy in reflectance by laminating multiple thin films with different refractive index anisotropies, and circular polarization separation sheets in which an oriented film of cholesteric liquid crystal polymer or a layer of this oriented liquid crystal is supported on a substrate film.

The reflective layer, semi-transmissive reflective layer, and light diffusion layer are provided to make the polarizing plate 10 a reflective, semi-transmissive, or diffuse optical component, respectively. Reflective polarizing plates are used in liquid crystal display devices that display by reflecting incident light from the viewing side, and can eliminate the need for a light source such as a backlight, making it easier to make the liquid crystal display thinner. Semi-transmissive polarizing plates are used in liquid crystal display devices that function as a reflective type in bright places and display using light from a backlight in dark places. Diffusive polarizing plates are used in liquid crystal display devices that are imparted with light diffusion properties to suppress display defects such as moire. The reflective layer, semi-transmissive reflective layer, and light diffusion layer can be formed using known methods.

The polarizing plate 10 may include a protective film for protecting the surface (typically a thermoplastic resin film surface) opposite the side on which the first adhesive layer 20 is laminated. After the adhesive layer-attached polarizing plate 25 is attached to an optical component such as an image display element, the protective film is peeled off and removed along with the adhesive layer it contains.

The protective film is composed of, for example, a base film and an adhesive layer laminated thereon.
The resin constituting the base film may be, for example, a thermoplastic resin such as a polyethylene-based resin such as polyethylene, a polypropylene-based resin such as polypropylene, a polyester-based resin such as polyethylene terephthalate or polyethylene naphthalate, or a polycarbonate-based resin. A polyester-based resin such as polyethylene terephthalate is preferred.

[2-5] Curling Force of Polarizing Plate The present invention is advantageous in improving the curl resistance of the laminated optical member, and is therefore particularly effective when the polarizing plate 10 is prone to curling.
The tendency of the polarizing plate 10 to curl can be evaluated, for example, by the maximum curling force at 80° C. The maximum curling force at 80° C. is measured according to the method described in the section [Examples] below.
The maximum curling force of the polarizing plate 10 of the pressure-sensitive adhesive layer-attached polarizing plate 25 at 80° C. may be 500 mN or more. Even in this case, the present invention can provide a laminated optical member with good warp resistance.
The maximum curling force of polarizing plate 10 of pressure-sensitive adhesive layer-attached polarizing plate 25 at 80°C may be 700 mN or more, 1000 mN or more, 1200 mN or more, or 1500 mN or more. The maximum curling force of polarizing plate 10 of pressure-sensitive adhesive layer-attached polarizing plate 25 at 80°C is usually 10000 mN or less, and may be 5000 mN or less, 3000 mN or less, or 2000 mN or less.
Examples of the configuration of the polarizing plate 10 that is prone to curling include any of the following configurations (a) to (h).
(a) A configuration in which the polarizer 1 is thick;
(b) A configuration in which the thermoplastic resin film is thin;
(c) A configuration in which the adhesive layer interposed between the polarizer 1 and the thermoplastic resin film is a cured layer of an active energy ray-curable adhesive;
(d) A configuration in which a thermoplastic resin film is bonded to only one surface of the polarizer 1;
(e) A configuration in which the thermoplastic resin films bonded to both surfaces of the polarizer 1 have different configurations (such as resin type, thickness, and presence or absence of a surface treatment layer),
(f) A configuration in which adhesive layers for bonding thermoplastic resin films to both surfaces of the polarizer 1 are formed from different types of adhesives.
(g) A configuration in which thermoplastic resin films are bonded to both surfaces of the polarizer 1, and another optically functional film is bonded onto one of the thermoplastic resin films;
(h) Other configurations in which the total number of films and layers on one side of polarizer 1 is different from the total number of films and layers on the other side.

Furthermore, the larger the size of the polarizing plate 10, the more likely it is to curl. From the perspective of the maximum curling force at 80°C mentioned above, the polarizing plate 10 is a rectangular or approximately rectangular polarizing plate sheet, preferably having a size of 100 mm x 40 mm or more, and more preferably having a size of 150 mm x 40 mm or more. The size of the polarizing plate 10 is, for example, 1650 mm x 930 mm or less, and preferably 1430 mm x 810 mm or less.

[3] Pressure-sensitive adhesive layer The pressure-sensitive adhesive layer (first pressure-sensitive adhesive layer 20) constituting the pressure-sensitive adhesive layer-attached polarizing plate 25 is formed from a pressure-sensitive adhesive composition.

[3-1] (Meth)acrylic Resin The pressure-sensitive adhesive composition preferably contains a (meth)acrylic resin from the viewpoints of the optical properties (transparency, polarization properties, etc.) of the pressure-sensitive adhesive layer-attached polarizing plate, the warp resistance and heat resistance durability of the laminated optical member which is a laminate of the pressure-sensitive adhesive layer-attached polarizing plate and other optical members, and the adhesion between the pressure-sensitive adhesive layer (first pressure-sensitive adhesive layer 20) in the laminated optical member and other optical members. The pressure-sensitive adhesive composition may contain one or more (meth)acrylic resins.
In this specification, "(meth)acrylic" means acrylic and/or methacrylic, and the same applies to "(meth)" in (meth)acrylate, etc.
The heat resistance durability means resistance to defects such as lifting or peeling at the interface between the pressure-sensitive adhesive layer and other optical components, and foaming of the pressure-sensitive adhesive layer, which may occur when the laminated optical component is placed at high temperatures or in an environment where high and low temperatures are repeatedly changed.

The (meth)acrylic resin is selected from the group consisting of a (meth)acrylic resin having a structure represented by the following formula (I):

Preferably, the polymer contains, as a main component, a structural unit derived from a (meth)acrylic acid ester represented by the formula: The term "main component" means that the content of the structural unit in the total structural units constituting the (meth)acrylic resin is 50% by mass or more.

In the above formula (I), ^R1 represents a hydrogen atom or a methyl group, and ^R2 represents an alkyl group having from 1 to 14 carbon atoms which may be substituted with an alkoxy group having from 1 to 10 carbon atoms, or an aralkyl group having from 7 to 21 carbon atoms which may be substituted with an alkoxy group having from 1 to 10 carbon atoms. When the aralkyl group is substituted with an alkoxy group, the number of carbon atoms in the aralkyl group is the number of carbon atoms excluding the carbon atoms of the alkoxy group.
^R2 is preferably an alkyl group having 1 to 14 carbon atoms which may be substituted with an alkoxy group having 1 to 10 carbon atoms, and more preferably an alkyl group having 1 to 14 carbon atoms which is not substituted with an alkoxy group.

Examples of the (meth)acrylic acid ester represented by formula (I) include (meth)acrylic acid alkyl esters having a linear alkyl ester moiety, such as methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, n-butyl (meth)acrylate, n-octyl (meth)acrylate, and lauryl (meth)acrylate; and (meth)acrylic acid alkyl esters having a branched alkyl ester moiety, such as isobutyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and isooctyl (meth)acrylate.

When ^R2 is an alkyl group substituted with an alkoxy group, that is, when ^R2 is an alkoxyalkyl group, examples of the (meth)acrylic acid ester represented by formula (I) include 2-methoxyethyl (meth)acrylate and ethoxymethyl (meth)acrylate.
In the case where ^R2 is an aralkyl group having 7 to 21 carbon atoms, examples of the (meth)acrylic acid ester represented by formula (I) include benzyl (meth)acrylate.

The (meth)acrylic acid ester represented by formula (I) may be used alone or in combination of two or more. Among these, the (meth)acrylic acid ester preferably contains n-butyl acrylate.
The (meth)acrylic resin preferably contains 50% by mass or more, more preferably 55% by mass or more, of structural units derived from n-butyl acrylate among all structural units constituting the (meth)acrylic resin. The content of structural units derived from n-butyl acrylate among all structural units constituting the (meth)acrylic resin is usually 90% by mass or less, preferably 85% by mass or less, more preferably 80% by mass or less, and even more preferably 75% by mass or less.
In addition to n-butyl acrylate, other (meth)acrylic acid esters represented by formula (I) can also be used in combination. For example, the (meth)acrylic resin preferably contains structural units derived from n-butyl acrylate and structural units derived from methyl acrylate. When the (meth)acrylic resin contains structural units derived from n-butyl acrylate and structural units derived from methyl acrylate, the content of the structural units derived from n-butyl acrylate is as described above, and the content of the structural units derived from methyl acrylate is typically 1% by mass or more and 50% by mass or less, preferably 5% by mass or more and 45% by mass or less, and more preferably 10% by mass or more and 40% by mass or less, of all structural units constituting the (meth)acrylic resin.

From the viewpoints of the optical properties (transparency, polarization properties, etc.) of the pressure-sensitive adhesive layer-attached polarizing plate, the warp resistance and heat resistance durability of the laminated optical component, and/or the adhesion between the pressure-sensitive adhesive layer and other optical components in the laminated optical component, the content of the (meth)acrylic acid ester-derived structural units is preferably from 60% to less than 100% by mass, more preferably from 70% to 99.9% by mass, and even more preferably from 80% to 99.6% by mass of all structural units constituting the (meth)acrylic resin.

The (meth)acrylic resin may contain a structural unit derived from a (meth)acrylic monomer having a hydroxyl group. The inclusion of this structural unit may be advantageous in improving the warpage resistance and heat resistance of the laminated optical component, and/or the adhesion between the pressure-sensitive adhesive layer in the laminated optical component and other optical components.
Examples of the (meth)acrylic monomer having a hydroxyl group include (meth)acrylic acid esters having a hydroxyl group.
Examples of (meth)acrylic acid esters having a hydroxyl group include 2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 2-(2-hydroxyethoxy)ethyl (meth)acrylate, 2- or 3-chloro-2-hydroxypropyl (meth)acrylate, and diethylene glycol mono(meth)acrylate.

The content of structural units derived from (meth)acrylic monomers having hydroxyl groups is preferably 0.1% by mass or more and 5% by mass or less, and more preferably 0.5% by mass or more and 4% by mass or less, of all structural units constituting the (meth)acrylic resin, from the viewpoints of warp resistance and heat resistance durability of the laminated optical component, and/or processability of the pressure-sensitive adhesive layer in the laminated optical component, and adhesion to other optical components.

The (meth)acrylic resin may contain a structural unit derived from a monomer having a polar functional group other than the (meth)acrylic monomer having a hydroxyl group. The monomer having a polar functional group is preferably a (meth)acrylic monomer having a polar functional group.
Examples of the polar functional group contained in the monomer having another polar functional group include a carboxyl group (free carboxyl group), an amino group, a heterocyclic group (for example, an epoxy group), an amide group, and the like.

Other monomers having polar functional groups include:
Monomers having a carboxyl group ((meth)acrylic monomers having a carboxyl group), such as (meth)acrylic acid and β-carboxyethyl (meth)acrylate;
Monomers having a heterocyclic group, such as (meth)acryloylmorpholine, vinylcaprolactam, N-vinyl-2-pyrrolidone, vinylpyridine, tetrahydrofurfuryl (meth)acrylate, caprolactone-modified tetrahydrofurfuryl (meth)acrylate, 3,4-epoxycyclohexylmethyl (meth)acrylate, glycidyl (meth)acrylate, and 2,5-dihydrofuran;
Examples include monomers having an amino group different from a heterocyclic ring, such as aminoethyl (meth)acrylate, N,N-dimethylaminoethyl (meth)acrylate, and dimethylaminopropyl (meth)acrylate.
The monomer having another polar functional group may be used alone or in combination of two or more kinds.

The content of structural units derived from monomers having other polar functional groups is preferably 0.1% by mass or more and 5% by mass or less, and more preferably 0.5% by mass or more and 3% by mass or less, of all structural units constituting the (meth)acrylic resin, from the viewpoints of warp resistance and heat resistance durability of the laminated optical component, and/or adhesion between the pressure-sensitive adhesive layer in the laminated optical component and other optical components.

The (meth)acrylic resin may further contain a structural unit derived from a monomer having one olefinic double bond and at least one aromatic ring in the molecule (excluding those corresponding to the above formula (I) or the above monomer having a polar functional group).
Inclusion of a structural unit derived from a monomer having one olefinic double bond and at least one aromatic ring in the molecule can be advantageous in terms of effectively suppressing the occurrence of white spots and color unevenness in laminated optical components.

The monomer having one olefinic double bond and at least one aromatic ring in the molecule includes a (meth)acrylic monomer having an aromatic ring.
Examples of the (meth)acrylic monomer having an aromatic ring include neopentyl glycol benzoate (meth)acrylate and the (meth)acrylic monomer represented by the following formula (II):

Examples include (meth)acrylic acid esters having an aryloxyalkyl group, such as (meth)acrylic acid esters containing a phenoxyethyl group represented by the formula: Preferably, these are (meth)acrylic acid esters having an aryloxyalkyl group.

In formula (II), ^R3 represents a hydrogen atom or a methyl group, i represents an integer of 1 to 8, and ^R4 represents a hydrogen atom, an alkyl group, an aralkyl group, or an aryl group. When ^R4 is an alkyl group, it may have about 1 to 9 carbon atoms, when it is an aralkyl group, it may have about 7 to 11 carbon atoms, and when it is an aryl group, it may have about 6 to 10 carbon atoms.

Examples of the alkyl group having 1 to 9 carbon atoms constituting ^R4 in formula (II) include a methyl group, a butyl group, a nonyl group, etc.; examples of the aralkyl group having 7 to 11 carbon atoms include a benzyl group, a phenethyl group, a naphthylmethyl group, etc.; and examples of the aryl group having 6 to 10 carbon atoms include a phenyl group, a tolyl group, a naphthyl group, etc.

Specific examples of the phenoxyethyl group-containing (meth)acrylic acid ester represented by formula (II) include 2-phenoxyethyl (meth)acrylate, 2-(2-phenoxyethoxy)ethyl (meth)acrylate, (meth)acrylic acid ester of ethylene oxide-modified nonylphenol, and 2-(o-phenylphenoxy)ethyl (meth)acrylate.
The phenoxyethyl group-containing (meth)acrylic acid ester may be used alone or in combination of two or more kinds.
Among these, the phenoxyethyl group-containing (meth)acrylic acid ester preferably contains one or more selected from the group consisting of 2-phenoxyethyl (meth)acrylate, 2-(o-phenylphenoxy)ethyl (meth)acrylate, and 2-(2-phenoxyethoxy)ethyl (meth)acrylate, and more preferably contains one or two selected from the group consisting of 2-(o-phenylphenoxy)ethyl (meth)acrylate and 2-(2-phenoxyethoxy)ethyl (meth)acrylate.

From the viewpoint of effectively suppressing the occurrence of white spots and color unevenness in the laminated optical component, the content of structural units derived from monomers having one olefinic double bond and at least one aromatic ring in the molecule is preferably 1% by mass or more and 20% by mass or less, and more preferably 5% by mass or more and 15% by mass or less, of all structural units constituting the (meth)acrylic resin.

The (meth)acrylic resin may contain a constituent unit derived from a monomer (hereinafter also referred to as "other monomer") other than the (meth)acrylic acid ester of formula (I) described above, the monomer having a polar functional group, and the monomer having one olefinic double bond and at least one aromatic ring in the molecule.
Examples of other monomers include structural units derived from (meth)acrylic acid esters having an alicyclic structure in the molecule, structural units derived from styrene-based monomers, structural units derived from vinyl-based monomers, structural units derived from monomers having multiple (meth)acryloyl groups in the molecule, and structural units derived from (meth)acrylamide monomers.
The other monomers may be used alone or in combination of two or more.
The inclusion of structural units derived from other monomers, particularly structural units derived from (meth)acrylamide monomers, can be advantageous in improving the warpage resistance and heat resistance durability of the laminated optical component, and/or the adhesion between the pressure-sensitive adhesive layer in the laminated optical component and other optical components.

The alicyclic structure in the (meth)acrylic acid ester having an alicyclic structure in the molecule is a cycloparaffin structure having usually 5 or more, preferably 5 to 7 carbon atoms.
Examples of (meth)acrylic acid esters having an alicyclic structure include isobornyl (meth)acrylate, cyclohexyl (meth)acrylate, dicyclopentanyl (meth)acrylate, cyclododecyl (meth)acrylate, methylcyclohexyl (meth)acrylate, trimethylcyclohexyl (meth)acrylate, t-butylcyclohexyl (meth)acrylate, cyclohexylphenyl (meth)acrylate, and cyclohexyl α-ethoxyacrylate.

Examples of styrene-based monomers include styrene; alkyl styrenes such as methylstyrene, dimethylstyrene, trimethylstyrene, ethylstyrene, diethylstyrene, triethylstyrene, propylstyrene, butylstyrene, hexylstyrene, heptylstyrene, and octylstyrene; halogenated styrenes such as fluorostyrene, chlorostyrene, bromostyrene, dibromostyrene, and iodostyrene; nitrostyrene, acetylstyrene, methoxystyrene, and divinylbenzene.

Vinyl monomers include fatty acid vinyl esters such as vinyl acetate, vinyl propionate, vinyl butyrate, vinyl 2-ethylhexanoate, and vinyl laurate; vinyl halides such as vinyl chloride and vinyl bromide; vinylidene halides such as vinylidene chloride; nitrogen-containing aromatic vinyls such as vinylpyridine, vinylpyrrolidone, and vinylcarbazole; conjugated diene monomers such as butadiene, isoprene, and chloroprene; acrylonitrile, methacrylonitrile, and the like.

Examples of monomers having multiple (meth)acryloyl groups in the molecule include monomers having two (meth)acryloyl groups in the molecule, such as 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, and tripropylene glycol di(meth)acrylate; and monomers having three (meth)acryloyl groups in the molecule, such as trimethylolpropane tri(meth)acrylate.

(Meth)acrylamide monomers include N-methylol (meth)acrylamide, N-(2-hydroxyethyl) (meth)acrylamide, N-(3-hydroxypropyl) (meth)acrylamide, N-(4-hydroxybutyl) (meth)acrylamide, N-(5-hydroxypentyl) (meth)acrylamide, N-(6-hydroxyhexyl) (meth)acrylamide, N,N-dimethyl (meth)acrylamide, N,N-diethyl (meth)acrylamide, and N-isopropyl N-propyl(meth)acrylamide, N-(3-dimethylaminopropyl)(meth)acrylamide, N-(1,1-dimethyl-3-oxobutyl)(meth)acrylamide, N-[2-(2-oxo-1-imidazolidinyl)ethyl](meth)acrylamide, 2-acryloylamino-2-methyl-1-propanesulfonic acid, N-(methoxymethyl)acrylamide, N-(ethoxymethyl)(meth)acrylamide, N-(propoxymethyl)(meth)acrylamide, N-(1- N-(methylethoxymethyl)(meth)acrylamide, N-(1-methylpropoxymethyl)(meth)acrylamide, N-(2-methylpropoxymethyl)(meth)acrylamide [alias: N-(isobutoxymethyl)(meth)acrylamide], N-(butoxymethyl)(meth)acrylamide, N-(1,1-dimethylethoxymethyl)(meth)acrylamide, N-(2-methoxyethyl)(meth)acrylamide, N-(2-ethoxyethyl)(meth)acrylamide, N- These include (2-propoxyethyl)(meth)acrylamide, N-[2-(1-methylethoxy)ethyl](meth)acrylamide, N-[2-(1-methylpropoxy)ethyl](meth)acrylamide, N-[2-(2-methylpropoxy)ethyl](meth)acrylamide (also known as N-(2-isobutoxyethyl)(meth)acrylamide), N-(2-butoxyethyl)(meth)acrylamide, and N-[2-(1,1-dimethylethoxy)ethyl](meth)acrylamide. Of these, N-(methoxymethyl)acrylamide, N-(ethoxymethyl)acrylamide, N-(propoxymethyl)acrylamide, N-(butoxymethyl)acrylamide, and N-(2-methylpropoxymethyl)acrylamide are preferred.

The (meth)acrylamide monomer is preferably an alkyl(meth)acrylamide monomer which may be substituted with an alkoxy group, from the viewpoints of warp resistance and heat resistance durability of the laminated optical component, and adhesion between the pressure-sensitive adhesive layer in the laminated optical component and other optical components.
In the alkyl(meth)acrylamide monomer which may be substituted with an alkoxy group, the number of carbon atoms in the alkoxy group is preferably 1 or more and 10 or less, and the number of carbon atoms in the alkyl group is preferably 1 or more and 14 or less. When an alkyl group is substituted with an alkoxy group, the number of carbon atoms in the alkyl group is the number of carbon atoms excluding the carbon atoms in the alkoxy group.
The alkyl(meth)acrylamide monomer which may be substituted with an alkoxy group includes a compound represented by the following formula (III):

Examples of suitable alkoxyalkyl (meth)acrylamide monomers include those represented by the following formula:
In formula (III), ^R5 represents a hydrogen atom or a methyl group, ^R6 represents an alkyl group having 1 to 14 carbon atoms, and n represents an integer of 1 to 8.
Examples of the alkyl group include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a tert-butyl group, an n-hexyl group, an n-heptyl group, and an n-octyl group.
n is preferably 1 or more and 6 or less.

From the viewpoint of the warp resistance and heat resistance durability of the laminated optical component, and/or the adhesion between the pressure-sensitive adhesive layer and other optical components in the laminated optical component, the content of structural units derived from other monomers (especially (meth)acrylamide monomers) is preferably from 0.1% to 20% by mass, more preferably from 0.2% to 10% by mass, and even more preferably from 0.3% to 5% by mass, of all structural units constituting the (meth)acrylic resin.

From the viewpoint of warp resistance and heat resistance durability of the laminated optical component, and/or adhesion between the pressure-sensitive adhesive layer in the laminated optical component and other optical components, the (meth)acrylic resin preferably contains a structural unit derived from a (meth)acrylic monomer having a carboxyl group and a structural unit derived from an alkoxyalkyl(meth)acrylamide monomer.
From the viewpoint of the warp resistance and heat resistance durability of the laminated optical component, and/or the adhesion between the pressure-sensitive adhesive layer and other optical components in the laminated optical component, the total content of the structural units derived from the (meth)acrylic monomer having a carboxyl group and the structural units derived from the alkoxyalkyl (meth)acrylamide monomer is preferably 0.1 mass % or more and 15 mass % or less, more preferably 0.2 mass % or more and 10 mass % or less, and even more preferably 0.3 mass % or more and 4 mass % or less, of all structural units constituting the (meth)acrylic resin.

The (meth)acrylic resin preferably has a weight average molecular weight (Mw) of 500,000 to 2,000,000, and more preferably 600,000 to 1,800,000, as determined by gel permeation chromatography (GPC) in terms of standard polystyrene. A pressure-sensitive adhesive composition containing a (meth)acrylic resin having an Mw within the above range can be advantageous from the viewpoint of ensuring the warp resistance and heat resistance durability of the laminated optical member, and/or the ease of handling of the (meth)acrylic resin during preparation of the pressure-sensitive adhesive composition.
The molecular weight distribution, expressed as the ratio (Mw/Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn), is usually about 2 or more and 10 or less, and preferably 3 or more and 8 or less.

(Meth)acrylic resins can be produced by known methods such as solution polymerization, bulk polymerization, suspension polymerization, and emulsion polymerization. A polymerization initiator is typically used in the production of (meth)acrylic resins. The polymerization initiator can be used in an amount of approximately 0.001 to 5 parts by mass per 100 parts by mass of the total of all monomers used in the production of the (meth)acrylic resin. (Meth)acrylic resins may also be produced by a method in which polymerization is promoted by active energy rays such as ultraviolet light.

As the polymerization initiator, a thermal polymerization initiator, a photopolymerization initiator, or the like is used.
Examples of the photopolymerization initiator include 4-(2-hydroxyethoxy)phenyl(2-hydroxy-2-propyl)ketone.
Examples of the thermal polymerization initiator include azo compounds such as 2,2'-azobisisobutyronitrile, 2,2'-azobis(2-methylbutyronitrile), 1,1'-azobis(cyclohexane-1-carbonitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), 2,2'-azobis(2,4-dimethyl-4-methoxyvaleronitrile), dimethyl-2,2'-azobis(2-methylpropionate), and 2,2'-azobis(2-hydroxymethylpropionitrile); lauryl peroxide; Examples of the peroxide include organic peroxides such as benzoyl peroxide, tert-butyl hydroperoxide, benzoyl peroxide, tert-butyl peroxybenzoate, cumene hydroperoxide, diisopropyl peroxydicarbonate, dipropyl peroxydicarbonate, tert-butyl peroxyneodecanoate, tert-butyl peroxypivalate, and (3,5,5-trimethylhexanoyl) peroxide; and inorganic peroxides such as potassium persulfate, ammonium persulfate, and hydrogen peroxide.
Furthermore, a redox initiator using a peroxide and a reducing agent in combination can also be used as the polymerization initiator.

Among the methods listed above, solution polymerization is preferred as a method for producing a (meth)acrylic resin. One example of the solution polymerization method is to mix the monomers and organic solvent to be used, add a thermal polymerization initiator under a nitrogen atmosphere, and stir the mixture at about 40°C to 90°C, preferably about 50°C to 80°C, for about 3 hours to 15 hours. To control the reaction, the monomers and the thermal polymerization initiator may be added continuously or intermittently during polymerization, or may be added in a dissolved state in an organic solvent.
Examples of organic solvents include aromatic hydrocarbons such as toluene and xylene; esters such as ethyl acetate and butyl acetate; aliphatic alcohols such as propyl alcohol and isopropyl alcohol; and ketones such as acetone, methyl ethyl ketone, and methyl isobutyl ketone.

[3-2] Crosslinking Agent The PSA composition may further contain a crosslinking agent. The crosslinking agent is a compound that reacts with polar functional groups in the (meth)acrylic resin to crosslink the (meth)acrylic resin.
The crosslinking agent may be selected from an isocyanate-based compound, an epoxy-based compound, an aziridine-based compound, a metal chelate-based compound, and the like.
Of these, the isocyanate-based compounds, epoxy-based compounds and aziridine-based compounds have at least two functional groups in the molecule that can react with polar functional groups in the (meth)acrylic resin.
The crosslinking agent may be used alone or in combination of two or more kinds.

An isocyanate compound is a compound having at least two isocyanato groups (--NCO) in the molecule.
Examples of isocyanate compounds include tolylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, xylylene diisocyanate, hydrogenated xylylene diisocyanate, diphenylmethane diisocyanate, hydrogenated diphenylmethane diisocyanate, naphthalene diisocyanate, triphenylmethane triisocyanate, etc. In addition, adducts obtained by reacting these isocyanate compounds with polyols such as glycerol and trimethylolpropane, and dimers, trimers, etc. of isocyanate compounds can also serve as crosslinking agents.
Two or more isocyanate compounds may be used in combination.

An epoxy compound is a compound having at least two epoxy groups in the molecule.
Examples of epoxy compounds include bisphenol A epoxy resins, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerin diglycidyl ether, glycerin triglycidyl ether, 1,6-hexanediol diglycidyl ether, trimethylolpropane triglycidyl ether, N,N-diglycidylaniline, N,N,N',N'-tetraglycidyl-m-xylylenediamine, and 1,3-bis(N,N'-diglycidylaminomethyl)cyclohexane.
Two or more epoxy compounds may be used in combination.

Aziridine compounds are compounds that have at least two three-membered ring skeletons, each consisting of one nitrogen atom and two carbon atoms, within the molecule, and are also called ethyleneimines.
Examples of aziridine compounds include diphenylmethane-4,4'-bis(1-aziridinecarboxamide), toluene-2,4-bis(1-aziridinecarboxamide), triethylenemelamine, isophthaloylbis-1-(2-methylaziridine), tris-1-aziridinylphosphine oxide, hexamethylene-1,6-bis(1-aziridinecarboxamide), trimethylolpropane-tris-β-aziridinylpropionate, and tetramethylolmethane-tris-β-aziridinylpropionate.
Two or more aziridine compounds may be used in combination.

Examples of metal chelate compounds include compounds in which acetylacetone or ethyl acetoacetate is coordinated with a polyvalent metal such as aluminum, iron, copper, zinc, tin, titanium, nickel, antimony, magnesium, vanadium, chromium, or zirconium.
Two or more metal chelate compounds may be used in combination.

Among these, isocyanate compounds can be advantageous in improving the warp resistance and heat resistance durability of the laminated optical member, and/or the adhesion between the pressure-sensitive adhesive layer in the laminated optical member and other optical members.
Among the isocyanate compounds, xylylene diisocyanate, tolylene diisocyanate, or hexamethylene diisocyanate; adducts obtained by reacting these isocyanate compounds with polyols such as glycerol or trimethylolpropane; dimers, trimers, etc. of these isocyanate compounds, or mixtures thereof; and mixtures of two or more of the above-mentioned isocyanate compounds are preferably used.
Suitable isocyanate compounds include tolylene diisocyanate, an adduct obtained by reacting tolylene diisocyanate with a polyol, a dimer of tolylene diisocyanate, and a trimer of tolylene diisocyanate, as well as hexamethylene diisocyanate, an adduct obtained by reacting hexamethylene diisocyanate with a polyol, a dimer of hexamethylene diisocyanate, and a trimer of hexamethylene diisocyanate.

The content of the crosslinking agent in the pressure-sensitive adhesive composition is typically 0 to 5 parts by mass, and preferably 0 to 2 parts by mass, per 100 parts by mass of the (meth)acrylic resin. When the pressure-sensitive adhesive composition contains a crosslinking agent, the lower limit of the content is, for example, 0.05 parts by mass per 100 parts by mass of the (meth)acrylic resin.

[3-3] Ionic Compound The PSA composition may further contain an ionic compound as an antistatic agent for imparting antistatic properties to the PSA layer (first PSA layer 20). The ionic compound is a compound having an inorganic cation or an organic cation and an inorganic anion or an organic anion.
Two or more ionic compounds may be used.

Examples of inorganic cations include alkali metal ions such as lithium cation [Li ⁺ ], sodium cation [Na ⁺ ], and potassium cation [K ⁺ ], and alkaline earth metal ions such as beryllium cation [Be ²⁺ ], magnesium cation [Mg ²⁺ ], and calcium cation [Ca ²⁺ ].

Examples of organic cations include imidazolium cations, pyridinium cations, pyrrolidinium cations, ammonium cations, sulfonium cations, and phosphonium cations.

Of the cationic components listed above, organic cationic components are preferably used because they have excellent compatibility with the adhesive composition. Among organic cationic components, pyridinium cations and imidazolium cations are particularly preferred because they are less likely to become charged when the separation film provided on the adhesive layer (first adhesive layer 20) is peeled off.

Examples of inorganic anions include chloride anion [Cl ⁻ ], bromide anion [Br ⁻ ], iodide anion [I ⁻ ], tetrachloroaluminate anion [AlCl ₄ ⁻ ], heptachlorodialuminate anion [Al ₂ Cl ₇ ⁻ ], tetrafluoroborate anion [BF ₄ ⁻ ], hexafluorophosphate anion [PF ₆ ⁻ ], perchlorate anion [ClO ₄ ⁻ ], nitrate anion [NO ₃ ⁻ ], hexafluoroarsenate anion [AsF ₆ ⁻ ], hexafluoroantimonate anion [SbF ₆ ⁻ ], hexafluoroniobate anion [NbF ₆ ⁻ ], hexafluorotantalate anion [TaF ₆ ⁻ ], dicyanamide anion [(CN) ₂ N ^- ］ and the like.

Examples of organic anions include acetate anion [CH ₃ COO ⁻ ], trifluoroacetate anion [CF ₃ COO ⁻ ], methanesulfonate anion [CH ₃ SO ₃ ⁻ ], trifluoromethanesulfonate anion [CF ₃ SO ₃ ⁻ ], p-toluenesulfonate anion [p-CH ₃ C ₆ H ₄ SO ₃ ⁻ ], bis(fluorosulfonyl)imide anion [(FSO ₂ ) ₂ N ⁻ ], bis(trifluoromethanesulfonyl)imide anion [(CF ₃ SO ₂ ) 2 N − ], tris(trifluoromethanesulfonyl)methanide anion [(CF ₃ SO ₂ ) ₃ C ⁻ ], dimethylphosphinate anion [(CH 3 ) ₂ POO ⁻ ], and dimethylphosphinate anion [(CH ₃ ) ₂ POO ^{− ].} ], (poly)hydrofluorofluoride anion [F(HF) _n ⁻ ] (n is approximately 1 or more and 3 or less), thiocyan anion [SCN ⁻ ], perfluorobutanesulfonate anion [C ₄ F ₉ SO ₃ ⁻ ], bis(pentafluoroethanesulfonyl)imide anion [(C ₂ F ₅ SO ₂ ) ₂ N ⁻ ], perfluorobutanoate anion [C ₃ F ₇ COO ⁻ ], (trifluoromethanesulfonyl)(trifluoromethanecarbonyl)imide anion [(CF ₃ SO ₂ )(CF ₃ CO)N ⁻ ], perfluoropropane-1,3-disulfonate anion [ ⁻ O ₃ S(CF ₂ ) ₃ SO ₃ ⁻ ], carbonate anion [CO ₃ ²⁻ ], and the like.

Among the above-mentioned anionic components, anionic components containing fluorine atoms are particularly preferred because they provide ionic compounds with excellent antistatic properties. Examples of anionic components containing fluorine atoms include bis(fluorosulfonyl)imide anion, hexafluorophosphate anion, and bis(trifluoromethanesulfonyl)imide anion.

Specific examples of ionic compounds can be selected from the combinations of the cation and anion components listed above. Examples of ionic compounds having organic cations are listed below, categorized by the structure of the organic cation.

Pyridinium salts:
N-hexylpyridinium hexafluorophosphate,
N-octylpyridinium hexafluorophosphate,
N-octyl-4-methylpyridinium hexafluorophosphate,
N-butyl-4-methylpyridinium hexafluorophosphate,
N-decylpyridinium bis(fluorosulfonyl)imide,
N-dodecylpyridinium bis(fluorosulfonyl)imide,
N-tetradecylpyridinium bis(fluorosulfonyl)imide,
N-hexadecylpyridinium bis(fluorosulfonyl)imide,
N-dodecyl-4-methylpyridinium bis(fluorosulfonyl)imide,
N-tetradecyl-4-methylpyridinium bis(fluorosulfonyl)imide,
N-hexadecyl-4-methylpyridinium bis(fluorosulfonyl)imide,
N-benzyl-2-methylpyridinium bis(fluorosulfonyl)imide,
N-benzyl-4-methylpyridinium bis(fluorosulfonyl)imide,
N-hexylpyridinium bis(trifluoromethanesulfonyl)imide,
N-octylpyridinium bis(trifluoromethanesulfonyl)imide,
N-octyl-4-methylpyridinium bis(trifluoromethanesulfonyl)imide,
N-butyl-4-methylpyridinium bis(trifluoromethanesulfonyl)imide.

Imidazolium salts:
1-ethyl-3-methylimidazolium hexafluorophosphate,
1-ethyl-3-methylimidazolium p-toluenesulfonate,
1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide,
1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide,
1-butyl-3-methylimidazolium methanesulfonate,
1-butyl-3-methylimidazolium bis(fluorosulfonyl)imide.

Pyrrolidinium salts:
N-butyl-N-methylpyrrolidinium hexafluorophosphate,
N-butyl-N-methylpyrrolidinium bis(fluorosulfonyl)imide,
N-butyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide.

Quaternary ammonium salts:
tetrabutylammonium hexafluorophosphate,
tetrabutylammonium p-toluenesulfonate,
(2-hydroxyethyl)trimethylammonium bis(trifluoromethanesulfonyl)imide,
(2-hydroxyethyl)trimethylammonium dimethylphosphinate.

Examples of ionic compounds with inorganic cations are shown below.

lithium bromide,
lithium iodide,
lithium tetrafluoroborate,
lithium hexafluorophosphate,
lithium thiocyanate,
lithium perchlorate,
lithium trifluoromethanesulfonate,
lithium bis(fluorosulfonyl)imide,
lithium bis(trifluoromethanesulfonyl)imide,
lithium bis(pentafluoroethanesulfonyl)imide,
lithium tris(trifluoromethanesulfonyl)methanide,
lithium p-toluenesulfonate,
sodium hexafluorophosphate,
sodium bis(fluorosulfonyl)imide,
sodium bis(trifluoromethanesulfonyl)imide,
sodium p-toluenesulfonate,
potassium hexafluorophosphate,
potassium bis(fluorosulfonyl)imide,
potassium bis(trifluoromethanesulfonyl)imide,
Potassium p-toluenesulfonate.

The ionic compound is preferably a solid at room temperature. An ionic compound that is a solid at room temperature can maintain antistatic performance for a longer period of time than an ionic compound that is a liquid at room temperature. From the perspective of long-term stability of antistatic properties, the ionic compound preferably has a melting point of 30°C or higher, and even more preferably 35°C or higher. On the other hand, if the melting point is too high, compatibility with the (meth)acrylic resin will be poor, so the melting point of the ionic compound is preferably 90°C or lower, more preferably 70°C or lower, and even more preferably below 50°C.

The content of the ionic compound in the pressure-sensitive adhesive composition is preferably 0.2 parts by mass or more and 8 parts by mass or less, more preferably 0.2 parts by mass or more and 6 parts by mass or less, even more preferably 0.5 parts by mass or more and 5 parts by mass or less, and particularly preferably 1 part by mass or more and 5 parts by mass or less, relative to 100 parts by mass of the (meth)acrylic resin. An ionic compound content of 0.2 parts by mass or more is advantageous for improving antistatic performance, while an ionic compound content of 8 parts by mass or less is advantageous for maintaining the heat resistance durability of the pressure-sensitive adhesive layer (first pressure-sensitive adhesive layer 20).

[3-4] Silane Compound The pressure-sensitive adhesive composition may further contain a silane compound, which can enhance the adhesion between the pressure-sensitive adhesive layer (first pressure-sensitive adhesive layer 20) and an optical member such as a glass substrate.

Examples of the silane compound include vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris(2-methoxyethoxy)silane, N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-chloropropylmethyldimethoxysilane, 3-chloropropyltrimethoxysilane, 3-methacryloyloxypropyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropyldimethoxymethylsilane, and 3-glycidoxypropylethoxydimethylsilane.
Two or more silane compounds may be used.

The silane compound may be a silicone oligomer type. Examples of silicone oligomers expressed in the form of (monomer) oligomers include the following:

3-mercaptopropyltrimethoxysilane-tetramethoxysilane copolymer,
3-mercaptopropyltrimethoxysilane-tetraethoxysilane copolymer,
3-mercaptopropyltriethoxysilane-tetramethoxysilane copolymer,
mercaptopropyl group-containing copolymers such as 3-mercaptopropyltriethoxysilane-tetraethoxysilane copolymer;
mercaptomethyltrimethoxysilane-tetramethoxysilane copolymer,
mercaptomethyltrimethoxysilane-tetraethoxysilane copolymer,
mercaptomethyltriethoxysilane-tetramethoxysilane copolymer,
mercaptomethyl group-containing copolymers such as mercaptomethyltriethoxysilane-tetraethoxysilane copolymer;
3-glycidoxypropyltrimethoxysilane-tetramethoxysilane copolymer,
3-glycidoxypropyltrimethoxysilane-tetraethoxysilane copolymer,
3-glycidoxypropyltriethoxysilane-tetramethoxysilane copolymer,
3-glycidoxypropyltriethoxysilane-tetraethoxysilane copolymer,
3-glycidoxypropylmethyldimethoxysilane-tetramethoxysilane copolymer,
3-glycidoxypropylmethyldimethoxysilane-tetraethoxysilane copolymer,
3-glycidoxypropylmethyldiethoxysilane-tetramethoxysilane copolymer,
Copolymers containing 3-glycidoxypropyl groups, such as 3-glycidoxypropylmethyldiethoxysilane-tetraethoxysilane copolymer;
3-methacryloyloxypropyltrimethoxysilane-tetramethoxysilane copolymer,
3-methacryloyloxypropyltrimethoxysilane-tetraethoxysilane copolymer,
3-methacryloyloxypropyltriethoxysilane-tetramethoxysilane copolymer,
3-methacryloyloxypropyltriethoxysilane-tetraethoxysilane copolymer,
3-methacryloyloxypropylmethyldimethoxysilane-tetramethoxysilane copolymer,
3-methacryloyloxypropylmethyldimethoxysilane-tetraethoxysilane copolymer,
3-methacryloyloxypropylmethyldiethoxysilane-tetramethoxysilane copolymer,
Methacryloyloxypropyl group-containing copolymers such as 3-methacryloyloxypropylmethyldiethoxysilane-tetraethoxysilane copolymer;
3-acryloyloxypropyltrimethoxysilane-tetramethoxysilane copolymer,
3-acryloyloxypropyltrimethoxysilane-tetraethoxysilane copolymer,
3-acryloyloxypropyltriethoxysilane-tetramethoxysilane copolymer,
3-acryloyloxypropyltriethoxysilane-tetraethoxysilane copolymer,
3-acryloyloxypropylmethyldimethoxysilane-tetramethoxysilane copolymer,
3-acryloyloxypropylmethyldimethoxysilane-tetraethoxysilane copolymer,
3-acryloyloxypropylmethyldiethoxysilane-tetramethoxysilane copolymer,
Copolymers containing acryloyloxypropyl groups, such as 3-acryloyloxypropylmethyldiethoxysilane-tetraethoxysilane copolymer;
vinyltrimethoxysilane-tetramethoxysilane copolymer,
vinyltrimethoxysilane-tetraethoxysilane copolymer,
vinyltriethoxysilane-tetramethoxysilane copolymer,
vinyltriethoxysilane-tetraethoxysilane copolymer,
vinylmethyldimethoxysilane-tetramethoxysilane copolymer,
vinylmethyldimethoxysilane-tetraethoxysilane copolymer,
vinylmethyldiethoxysilane-tetramethoxysilane copolymer,
vinyl group-containing copolymers such as vinylmethyldiethoxysilane-tetraethoxysilane copolymer;
3-aminopropyltrimethoxysilane-tetramethoxysilane copolymer,
3-aminopropyltrimethoxysilane-tetraethoxysilane copolymer,
3-aminopropyltriethoxysilane-tetramethoxysilane copolymer,
3-aminopropyltriethoxysilane-tetraethoxysilane copolymer,
3-aminopropylmethyldimethoxysilane-tetramethoxysilane copolymer,
3-aminopropylmethyldimethoxysilane-tetraethoxysilane copolymer,
3-aminopropylmethyldiethoxysilane-tetramethoxysilane copolymer,
Amino group-containing copolymers such as 3-aminopropylmethyldiethoxysilane-tetraethoxysilane copolymer.

Many of the silane compounds exemplified above are liquid. The content of the silane compound in the pressure-sensitive adhesive composition is typically 0.01 to 10 parts by mass, preferably 0.05 to 5 parts by mass, and more preferably 0.2 to 0.4 parts by mass, per 100 parts by mass of the (meth)acrylic resin. When the content of the silane compound is 0.01 parts by mass or more, it is easy to achieve an improved effect in adhesion between the pressure-sensitive adhesive layer (first pressure-sensitive adhesive layer 20) and an optical member such as a glass substrate. Furthermore, when the content of the silane compound is 10 parts by mass or less, bleeding out of the silane compound from the pressure-sensitive adhesive layer can be suppressed.

[3-5] Other Components The pressure-sensitive adhesive composition may contain additives such as a crosslinking catalyst, a weather stabilizer, a tackifier, a plasticizer, a softener, a dye, a pigment, an inorganic filler, light-scattering fine particles, a resin other than a (meth)acrylic resin, etc. In addition, a harder pressure-sensitive adhesive layer may be obtained by blending an ultraviolet-curable compound into the pressure-sensitive adhesive composition, forming a pressure-sensitive adhesive layer, and then curing the resulting composition by irradiating the pressure-sensitive adhesive layer with ultraviolet light.
Examples of the crosslinking catalyst include amine compounds such as hexamethylenediamine, ethylenediamine, polyethyleneimine, hexamethylenetetramine, diethylenetriamine, triethylenetetramine, isophoronediamine, trimethylenediamine, polyamino resins, and melamine resins.

[3-6] Gel fraction of adhesive layer In the adhesive layer-attached polarizing plate according to the present invention, from the viewpoint of achieving both good warp resistance and good heat resistance durability of the laminated optical component, the adhesive layer (first adhesive layer 20) has an absolute value of the difference between the gel fraction (hereinafter sometimes referred to as "G80") [%] after heating at 80°C for 24 hours and the gel fraction (hereinafter sometimes referred to as "G23") [%] at 23°C, of which the absolute value is greater than 5 points.
The absolute value of the difference between G80 [%] and G23 [%] is preferably 10 points or more, more preferably 15 points or more, even more preferably 20 points or more, and particularly preferably 50 points or more, particularly from the viewpoint of improving warp resistance.

In order to improve the warp resistance of the laminated optical component, the heat resistance durability of the laminated optical component, and the adhesion between the pressure-sensitive adhesive layer (first pressure-sensitive adhesive layer 20) in the laminated optical component and other optical components, it is preferable that the pressure-sensitive adhesive layer satisfy one or more of the above (A) and (B).
(A) G23 is 80% or less.
(B) G80 is 60% or more.

From the viewpoint of the warpage resistance of the laminated optical component, G80 is preferably 60% or more, more preferably 65% or more, and even more preferably 70% or more, and is preferably 95% or less, more preferably 90% or less, and even more preferably 88% or less.
From the viewpoint of warpage resistance of the laminated optical member, G23 is preferably 80% or less. There is no particular lower limit for G23, but it is preferably 5% or more.
Generally, G80 is greater than G23. G23 and G80 are measured according to the method described in the Examples section below.

For example, G23 tends to be reduced by not including a crosslinking agent in the pressure-sensitive adhesive composition that forms the pressure-sensitive adhesive layer, or by reducing the content of the crosslinking agent in the pressure-sensitive adhesive composition. Also, G23 tends to be reduced by reducing the content of polar functional groups that can react with the crosslinking agent in the (meth)acrylic resin contained in the pressure-sensitive adhesive composition.
Furthermore, it is advantageous in terms of increasing G80 for the PSA composition to contain a (meth)acrylic resin that contains a structural unit derived from a (meth)acrylic monomer having a carboxyl group and a structural unit derived from an alkoxyalkyl (meth)acrylamide monomer such as the alkoxyalkyl (meth)acrylamide monomer represented by the above formula (III).
From the viewpoint of increasing G80, the (meth)acrylic resin preferably contains a structural unit derived from a (meth)acrylic acid ester represented by the above formula (I), a structural unit derived from a (meth)acrylic monomer having a hydroxyl group, a structural unit derived from a (meth)acrylic monomer having a carboxyl group, a structural unit derived from a phenoxyethyl group-containing (meth)acrylic acid ester represented by the above formula (II), and a structural unit derived from an alkoxyalkyl (meth)acrylamide monomer such as the alkoxyalkyl (meth)acrylamide monomer represented by the above formula (III).

[3-7] Formation of Pressure-Sensitive Adhesive Layer The pressure-sensitive adhesive layer (first pressure-sensitive adhesive layer 20) can be obtained by dissolving or dispersing each component constituting the pressure-sensitive adhesive composition in a solvent to form a solvent-containing pressure-sensitive adhesive composition, then applying the composition onto a substrate film or a polarizing plate 10, and drying the composition.

The base film is generally a thermoplastic resin film, a typical example of which is a release-treated separate film. The separate film may be, for example, a film made of a resin such as polyethylene terephthalate, polybutylene terephthalate, polycarbonate, or polyacrylate, the surface of which is formed with the pressure-sensitive adhesive layer being subjected to a release treatment such as silicone treatment.
For example, a pressure-sensitive adhesive composition can be directly applied to the release-treated surface of a separate film to form a pressure-sensitive adhesive layer, and this pressure-sensitive adhesive layer with separate film can be laminated on polarizing plate 10 to obtain a polarizing plate with a pressure-sensitive adhesive layer.
The pressure-sensitive adhesive composition may be directly applied to the surface of the polarizing plate 10 to form a pressure-sensitive adhesive layer, and if necessary, a separate film may be laminated on the outer surface of the pressure-sensitive adhesive layer to form a pressure-sensitive adhesive layer-attached polarizing plate.
When providing the adhesive layer on the surface of the polarizing plate 10, it is preferable to subject the bonding surface of the polarizing plate 10 and/or the bonding surface of the adhesive layer to a surface activation treatment such as plasma treatment or corona treatment, and it is more preferable to subject the layer to corona treatment.

The thickness of the pressure-sensitive adhesive layer (first pressure-sensitive adhesive layer 20) is preferably 10 μm or more and 45 μm or less, more preferably 10 μm or more and 30 μm or less, and even more preferably 10 μm or more and 25 μm or less. Having a pressure-sensitive adhesive layer thickness within this range can be advantageous in improving the warp resistance and heat resistance durability of the laminated optical component, and/or the adhesion between the pressure-sensitive adhesive layer and other optical components in the laminated optical component.

<Laminated optical member>
1 to 4, the laminated optical member is a laminate of a pressure-sensitive adhesive layer-attached polarizing plate 25 and an optical member 30 other than the pressure-sensitive adhesive layer-attached polarizing plate 25. Typically, the laminated optical member includes the optical member 30 and the pressure-sensitive adhesive layer-attached polarizing plate 25 laminated thereon with a first pressure-sensitive adhesive layer 20 interposed therebetween.
The pressure-sensitive adhesive layer-attached polarizing plate 25 according to the present invention can provide a laminated optical member having good warp resistance and heat resistance durability.

The optical member 30 may be an image display element such as a liquid crystal cell or an organic EL display element.
The optical member 30 may be a member that constitutes the image display element, such as a substrate.
Examples of the substrate include a thermoplastic resin film and a glass substrate.

The present invention will be explained in more detail below using examples, but the present invention is not limited to these examples. Below, parts and percentages representing amounts used or contents are by weight unless otherwise specified.

<Production Examples 1 to 9: Production of (meth)acrylic resin for pressure-sensitive adhesive layer>
A reaction vessel equipped with a condenser, a nitrogen inlet tube, a thermometer, and a stirrer was charged with a monomer mixture diluted with ethyl acetate having the monomer composition shown in Table 1 (% by mass when the total amount of monomers is 100% by mass). The air in the vessel was purged with nitrogen gas to remove oxygen, and the internal temperature was raised to 55°C. Thereafter, the entire amount of a solution of azobisisobutyronitrile (polymerization initiator) dissolved in ethyl acetate was added. After the addition of the polymerization initiator, the temperature was maintained for 1 hour. Ethyl acetate was then continuously added to the reaction vessel while maintaining the internal temperature at 54-56°C. When the concentration of the (meth)acrylic resin reached 35% by mass, the addition of ethyl acetate was stopped, and the vessel was further maintained at this temperature for 12 hours from the start of the ethyl acetate addition. Finally, ethyl acetate was added to adjust the concentration of the (meth)acrylic resin to 20% by mass, thereby preparing a solution of the (meth)acrylic resin in ethyl acetate.

The weight average molecular weight (Mw) and number average molecular weight (Mn) of the resulting (meth)acrylic resin were measured.
Mw and Mn were measured in terms of standard polystyrene using a GPC apparatus with a total of five columns connected in series: four "TSKgel XL" columns manufactured by Tosoh Corporation and one "Shodex GPC KF-802" column manufactured by Showa Denko K.K. and sold by Shoko Tsusho Co., Ltd.; tetrahydrofuran as the eluent; a sample concentration of 5 mg/mL; a sample introduction amount of 100 μL; a temperature of 40° C.; and a flow rate of 1 mL/min.
Table 1 shows the monomer composition (mass %) of the monomer mixture used, as well as the Mw and molecular weight distribution (Mw/Mn) of the resulting (meth)acrylic resin.

The abbreviations in the "Monomer composition" column of Table 1 represent the following monomers.
BA: Butyl acrylate MA: Methyl acrylate PEA: 2-phenoxyethyl acrylate PEA2: 2-(2-phenoxyethoxy)ethyl acrylate HEA: 2-hydroxyethyl acrylate BMAA: N-butoxymethylacrylamide MEA: Methoxyethyl acrylate AA: Acrylic acid

<Examples 1 to 9, Comparative Examples 1 and 2>
(1) Preparation of Pressure-Sensitive Adhesive Compositions Solutions of pressure-sensitive adhesive compositions were prepared by mixing 100 parts by mass of the solid content of the (meth)acrylic resin obtained in the above Production Examples with the crosslinker and silane compound in the amounts (parts by mass) shown in Table 2 (some examples did not include the crosslinker), and then adding ethyl acetate to give a solid content concentration of 28% by mass. In Table 2, the blending amounts (parts by mass) of the crosslinker and silane compound are calculated as solid content amounts.

The crosslinking agent used in the examples and comparative examples was "Coronate L" (an ethyl acetate solution of a trimethylolpropane adduct of tolylene diisocyanate: solids concentration 75% by mass) obtained from Tosoh Corporation. The silane compound used in the examples and comparative examples was "KBM-403" (3-glycidoxypropyltrimethoxysilane) obtained from Shin-Etsu Chemical Co., Ltd.

(2) Preparation of Pressure-Sensitive Adhesive Layer and Measurement of Gel Fraction The pressure-sensitive adhesive composition prepared in (1) above was applied to the release-treated surface of a separate film made of a release-treated polyethylene terephthalate film ("PLR-382190" available from Lintec Corporation) using an applicator so as to give a thickness after drying of 20 μm, and the applied film was dried at 100° C. for 1 minute to prepare a pressure-sensitive adhesive layer (pressure-sensitive adhesive sheet).

The pressure-sensitive adhesive layer (pressure-sensitive adhesive sheet) was left at 23°C for 5 days immediately after preparation, and the gel fraction [gel fraction at 23°C (G23)] was measured. The gel fraction was measured according to the following [a] to [d]. The results are shown in Table 3.
[a] An adhesive layer having an area of about 8 cm x about 8 cm is bonded to a metal mesh (whose mass is Wm) made of SUS304 having an area of about 10 cm x about 10 cm.
[b] The adhesive sheet obtained in [a] above is weighed, and its mass is designated as Ws. Next, the adhesive sheet is folded four times so as to enclose the adhesive layer, and stapled. The adhesive sheet is then weighed, and its mass is designated as Wb.
[c] The mesh stapled in [b] above is placed in a glass container, and 60 mL of ethyl acetate is added to soak it, and then the glass container is stored at room temperature for 3 days.
[d] The mesh is removed from the glass container, dried at 120°C for 4 hours, and then weighed. The mass is designated as Wa, and the weight is calculated by the following formula:
The gel fraction is calculated based on the following formula: Gel fraction (mass%) = [{Wa - (Wb - Ws) - Wm} / (Ws - Wm)] x 100.

The gel fraction [gel fraction after heating at 80°C for 24 hours (G80)] was measured in the same manner as above, except that the pressure-sensitive adhesive layer (pressure-sensitive adhesive sheet) was left at 23°C for 5 days immediately after preparation, and then left in a dry atmosphere at 80°C for 24 hours. The results are shown in Table 3. The difference between G80 and G23 (G80 - G23) is also shown in Table 3.

(3) Preparation of Polarizing Plate and Measurement of Maximum Curl Force at 80°C A polarizing plate was prepared by laminating a 75 μm thick protective film made of a (meth)acrylic resin on one side of a 23 μm thick polarizer in which iodine was adsorbed and oriented on a uniaxially stretched polyvinyl alcohol film, and a 50 μm thick retardation film made of a cyclic polyolefin resin on the other side thereof via an active energy ray-curable adhesive.
The maximum curling force of the obtained polarizing plate at 80° C. was measured according to the following procedure.
A sample measuring 40 mm × 40 mm was cut out from the polarizing plate so that a pair of opposing sides were parallel to the absorption axis of the polarizer. The sample was placed on the main plate of a viscoelasticity measuring device ("Physica MCR301" manufactured by Anton Paar) with each side not fixed, with the retardation film side facing up, and a measuring jig (PP25) was placed in the center. The gap of the measuring jig was adjusted so that the stress applied to the measuring jig was approximately 3 N, and the position raised 0.02 mm from this point was used as the reference height.
Next, while monitoring the stress on the measuring jig, the main body plate was heated from 23°C to 80°C at 2°C/min, held at 80°C for 240 minutes, and then cooled to 23°C at 2°C/min. The maximum value of the stress recorded during this process that was applied to the measuring jig due to the thermal shrinkage of the sample was taken as the maximum curl force [mN] at 80°C. The maximum curl force at 80°C was 1716 mN.

(4) Preparation of a polarizing plate with an adhesive layer The surface of the adhesive layer prepared in (2) above opposite to the separate film (adhesive layer surface) was bonded to the outer surface of the retardation film of the polarizing plate using a laminator, and then the resulting film was cured for 5 days under conditions of a temperature of 23°C and a relative humidity of 65% to obtain a polarizing plate with an adhesive layer.

(5) Evaluation of Warpage Resistance of Laminated Optical Members The adhesive-backed polarizing plate obtained in (4) above was cut to a size of 150 mm x 40 mm so that the absorption axis of the polarizer was the long side. The separate film was peeled off from the cut adhesive-backed polarizing plate, and the exposed adhesive layer was attached to the center of an alkali-free glass substrate (Corning Incorporated's "Eagle XG") measuring 160 mm in length, 50 mm in width, and 0.5 mm in thickness. This was used as a sample. This sample was left in a dry atmosphere at 80°C for 24 hours. Thereafter, it was removed from the sample to an environment at a temperature of 23°C and a relative humidity of 55%. Within 30 minutes after removal, the difference in height from the base of the center of the polarizing plate and each corner of the polarizing plate (four points) was measured using a two-dimensional dimension measuring device (Nikon Corporation's "NEXIV Model: VMZ-R4540"). The average of the four values obtained was taken as the warpage amount [mm] of the sample. The results are shown in Table 3. If the amount of warping is 2.0 mm or less, the warping resistance can be evaluated as good.

(6) Evaluation of Heat Resistance and Durability of Laminated Optical Members (6-1) Presence or Absence of Lifting/Peeling and Foaming at the Interface After peeling off the separator from the pressure-sensitive adhesive layer-attached polarizing plate prepared in (4) above, the pressure-sensitive adhesive layer surface was attached to both sides of an alkali-free glass substrate ("Eagle XG" manufactured by Corning Inc.) in a crossed Nicol configuration to prepare an evaluation sample. Using this sample, the following two types of heat resistance and durability tests were carried out.
[Heat resistance durability test]
- Heat resistance test in which the sample is kept at a temperature of 80°C under dry conditions for 500 hours. - Heat shock resistance test in which the sample is kept at a temperature of 70°C under dry conditions for 30 minutes, followed by a temperature of -40°C under dry conditions for 30 minutes, and this cycle is repeated 200 times.

After each test, the samples were visually inspected for lifting or peeling at the interface between the pressure-sensitive adhesive layer and the glass substrate, and for foaming in the pressure-sensitive adhesive layer, and the heat resistance durability was evaluated according to the following evaluation criteria. The results are shown in Table 3 (heat resistance durability X in Table 3).
A: No changes in appearance such as lifting, peeling, or foaming are observed. B: Slight changes in appearance such as lifting, peeling, or foaming are observed. C: Significant changes in appearance such as lifting, peeling, or foaming are observed.

(6-2) Presence or absence of bubbles at the interface edge After peeling off the separator from the pressure-sensitive adhesive layer-attached polarizing plate prepared in (4) above, the pressure-sensitive adhesive layer surface was attached to both sides of an alkali-free glass substrate ("Eagle XG" manufactured by Corning Inc.) in a crossed Nicol configuration to prepare an evaluation sample. Using this sample, the following two types of heat resistance and durability tests were carried out.
[Heat resistance durability test]
- Heat resistance test in which the sample is kept at a temperature of 80°C under dry conditions for 500 hours. - Heat shock resistance test in which the sample is kept at a temperature of 70°C under dry conditions for 30 minutes, followed by a temperature of -40°C under dry conditions for 30 minutes, and this cycle is repeated 200 times.

After each test, the samples were visually inspected for the presence or absence of streaky bubbles at the interface between the adhesive layer and the glass substrate at the edge of the evaluation sample, and the heat resistance durability was evaluated according to the following evaluation criteria. The results are shown in Table 3 (heat resistance durability Y in Table 3).
A: No streaky foaming is observed. B: A small amount of streaky foaming is observed. C: A large amount of streaky foaming is observed.

(7) Evaluation of Adhesion in Laminated Optical Members The adhesive polarizing plate obtained in (4) above was cut to a size of 150 mm x 25 mm so that the absorption axis of the polarizer was the long side. The separate film was peeled off from the cut adhesive polarizing plate, and the exposed adhesive layer was attached to the center of an alkali-free glass substrate (Corning's "Eagle XG") with a length of 160 mm, a width of 50 mm, and a thickness of 0.7 mm. The obtained test piece with the glass substrate attached (adhesive polarizing plate with glass substrate attached) was then pressed in an autoclave at a temperature of 50 ° C. and a pressure of 5 kgf / cm ² (490.3 kPa) for 20 minutes to obtain a sample. Thereafter, it was stored in an environment of 23 ° C. and a relative humidity of 55% for 24 hours.
Next, a cutter blade was inserted between the glass substrate and the adhesive layer, and the adhesive layer was peeled 30 mm from the end in the longitudinal direction. The peeled portion was gripped with the grip of a universal tensile tester (manufactured by Shimadzu Corporation under the trade name "AGS-50NX"). The test piece in this state was subjected to a 180-degree peel test at a gripping speed of 300 mm/min in an atmosphere of 23°C and 55% relative humidity, in accordance with JIS K 6854-2:1999 "Adhesives - Peel Adhesion Strength Test Method - Part 2: 180° Peel." The average peel force over a length of 120 mm, excluding the 30 mm gripped portion, was determined, and this was taken as the adhesion strength at a temperature of 23°C. The results are shown in Table 3.
The adhesion strength was measured in the same manner as above, except that the sample was left in a dry atmosphere at 50°C for 48 hours and that the measurement was carried out on this sample in an atmosphere at a temperature of 23°C and a relative humidity of 55%, and this was taken as the adhesion strength at 50°C. The results are shown in Table 3.

1 Polarizer, 2 Surface treatment layer, 3 First protective film, 4 Second protective film, 7 Retardation film, 8 Second adhesive layer, 10 Polarizing plate, 20 First adhesive layer, 25 Adhesive layer-attached polarizing plate, 30 Optical member.

Claims (7)

a polarizing plate having a maximum curling force of 500 mN or more at 80°C;
a pressure-sensitive adhesive layer (excluding a pressure-sensitive adhesive layer containing an antistatic agent) laminated on the polarizing plate;
Including,
the polarizing plate and the pressure-sensitive adhesive layer are in direct contact with each other,
the polarizing plate comprises a polarizer and two thermoplastic resin films bonded to both sides of the polarizer via an adhesive layer , the two thermoplastic resin films each being a single-layer film, and each optionally having a surface-treated layer selected from the group consisting of a hard coat layer, an antiglare layer, an antireflection layer, a light-diffusing layer, an antistatic layer, an antifouling layer, and a conductive layer, and the two thermoplastic resin films differ from each other in the type of thermoplastic resin constituting the thermoplastic resin film, thickness, or presence or absence of surface treatment;
the pressure-sensitive adhesive layer has an absolute value of the difference between a gel fraction (G80) [%] after heating at 80°C for 24 hours and a gel fraction (G23) [%] at 23°C that is greater than 5 points;
the pressure-sensitive adhesive layer has a gel fraction (G23) at 23°C of 75% or less,
The gel fraction at 23° C. (G23) is the gel fraction of the pressure-sensitive adhesive layer after it has been left at 23° C. for 5 days immediately after production of the pressure- sensitive adhesive layer-attached polarizing plate. The polarizing plate with a pressure-sensitive adhesive layer according to claim 1, wherein the pressure-sensitive adhesive layer has a gel fraction (G80) of 60% or more after heating at 80°C for 24 hours. The polarizing plate with a pressure-sensitive adhesive layer according to claim 1 or 2, wherein the pressure-sensitive adhesive layer has a gel fraction (G80) of 95% or less after heating at 80°C for 24 hours. The pressure-sensitive adhesive layer-attached polarizing plate according to any one of claims 1 to 3, wherein the polarizer has a thickness of 10 μm or more. The polarizing plate with a pressure-sensitive adhesive layer according to any one of claims 1 to 4, wherein the pressure-sensitive adhesive layer is formed from a pressure-sensitive adhesive composition containing a (meth)acrylic resin. The pressure-sensitive adhesive layer-attached polarizing plate according to claim 5, wherein the (meth)acrylic resin contains a structural unit derived from a (meth)acrylic monomer having a carboxyl group and a structural unit derived from an alkoxyalkyl(meth)acrylamide monomer. The pressure-sensitive adhesive layer-attached polarizing plate according to claim 5 or 6, wherein the pressure-sensitive adhesive composition contains a crosslinking agent in an amount of 0 parts by mass or more and 2 parts by mass or less per 100 parts by mass of the (meth)acrylic resin.