JP7481101B2 - Adhesive layer-attached polarizing film, image display panel, and image display device - Google Patents

Description

The present invention relates to a polarizing film with an adhesive layer having irregularly shaped portions other than rectangular. The present invention also relates to an image display panel and an image display device to which the polarizing film with an adhesive layer is applied.

Image display panels, for example, liquid crystal panels used in liquid crystal display devices, usually have polarizing films laminated on both sides of a liquid crystal cell formed from a liquid crystal layer arranged between a pair of transparent substrates, with a pressure-sensitive adhesive layer interposed between them. On the other hand, when manufacturing an image display panel, when the pressure-sensitive adhesive layer-attached polarizing film is attached to the liquid crystal cell, a release film is peeled off from the pressure-sensitive adhesive layer of the pressure-sensitive adhesive layer-attached polarizing film, and static electricity is generated by the peeling of the release film. The static electricity generated in this way can affect, for example, the orientation of the liquid crystal layer inside the liquid crystal display panel, leading to defects. The generation of static electricity can be suppressed, for example, by forming an antistatic layer (conductive layer) on the outer surface of the polarizing film.

For example, Patent Document 1 proposes arranging a polarizing film having an antistatic layer with a surface resistance value of 1.0×10 ⁹ to 1.0×10 ¹¹ Ω/□ on the viewing side of the liquid crystal layer in order to reduce the occurrence of display defects and malfunctions in a liquid crystal display device with a touch sensing function. It is also known that the generation of static electricity can be suppressed by adding an ionic compound as an antistatic agent to the pressure-sensitive adhesive layer.

On the other hand, in recent years, irregularly shaped in-cell type liquid crystal displays have been increasing in smartphones and car navigation systems, and irregularly shaped polarizing films are also used to match these displays. Patent Document 2 discloses a method for processing a polarizing film to manufacture a polarizing film having an irregular shape other than rectangular. Patent Document 3 proposes that the transparent protective film used for the polarizing film contains inorganic particles having irregular shapes, thereby improving the irregular shape punchability of the polarizing film and the crack durability of the irregularly shaped polarizing film after punching in a heat cycle test.

JP 2013-105154 A JP 2017-151191 A JP 2017-097111 A

According to the polarizing film having an antistatic layer described in Patent Document 1, it is possible to suppress the generation of static electricity. However, even in a polarizing film with an adhesive layer provided with an antistatic layer or an adhesive layer containing an ionic compound, it was not possible to sufficiently suppress static unevenness. In addition, in the case of a polarizing film with an irregular adhesive layer, an antistatic layer or an adhesive layer containing an ionic compound was not able to sufficiently suppress irregular cracks occurring in the irregular portion. In particular, when an adhesive layer-attached polarizing film containing an ionic compound in the adhesive layer and having an irregular portion is applied to an in-cell type liquid crystal panel, it is necessary to add a large amount of an ionic compound to the adhesive layer, and as a result, it was found that the irregular cracks occurring in the irregular portion are worsened.

The present invention aims to provide a polarizing film with an adhesive layer having an irregularly shaped portion, which can suppress the occurrence of irregular cracks even when applied to an in-cell type liquid crystal panel, and which has an antistatic function and can suppress static electricity unevenness.

Another object of the present invention is to provide an image display panel and an image display device to which the pressure-sensitive adhesive layer-attached polarizing film is applied.

As a result of extensive research into solving the above problems, the inventors discovered the following polarizing film with a pressure-sensitive adhesive layer, and completed the present invention.

That is, the present invention is
A polarizing film having a polarizer and a protective film on one or both sides of the polarizer, and a pressure-sensitive adhesive layer-attached polarizing film having a pressure-sensitive adhesive layer,
The pressure-sensitive adhesive layer-attached polarizing film has irregular shapes other than rectangular shapes,
The present invention relates to a pressure-sensitive adhesive layer-attached polarizing film, characterized in that the pressure-sensitive adhesive layer is formed from a pressure-sensitive adhesive composition containing a (meth)acrylic polymer (A) and an ionic compound (B) having a molecular weight of a cationic component of 210 or less.

In the pressure-sensitive adhesive layer-attached polarizing film, the cationic component is preferably a lithium ion.

In the pressure-sensitive adhesive layer-attached polarizing film, the ionic compound (B) is preferably contained in an amount of 0.1 to 13 parts by weight per 100 parts by weight of the (meth)acrylic polymer (A).

In the above-mentioned polarizing film with an adhesive layer, it is preferable that the protective film is any one selected from a cellulose resin film and a (meth)acrylic resin film. In addition, it is preferable that the thickness of the polarizer in the polarizing film is 10 μm or less.

In the polarizing film with an adhesive layer, the polarizing film can be a polarizer and a one-sided protected polarizing film having a protective film only on one side of the polarizer. It is preferable that the one-sided protected polarizing film has the adhesive layer on the other side of the polarizer.

The one-sided protected polarizing film can have the pressure-sensitive adhesive layer via a transparent layer having a thickness of 10 μm or less that is formed directly on the polarizer on the other side of the polarizer. The transparent layer can be a cured product of a forming material that contains a urethane prepolymer, which is a reaction product of an isocyanate compound and a polyhydric alcohol.

In the polarizing film with an adhesive layer, it is preferable that the adhesive layer has a creep value of 120 μm or less at 85°C.

The present invention also relates to an image display panel having the above-mentioned adhesive layer-attached polarizing film. The image display panel can be one in which the adhesive layer of the adhesive layer-attached polarizing film is attached to a liquid crystal cell with a built-in touch sensing function having a liquid crystal layer and a touch sensor section.

The present invention also relates to an image display device having the image display panel.

The polarizing film with adhesive layer of the present invention contains an ionic compound in the adhesive layer, and the adhesive layer can improve the antistatic performance. In addition, since it has been found that the smaller the molecular weight of the cationic component of the ionic compound, the smaller the adverse effect on irregular cracks, the molecular weight of the cationic component used is 210 or less. In particular, it has been found that when a lithium salt is used as the cationic component of the ionic compound, it has an excellent effect of suppressing irregular cracks. It has also been found that the smaller the molecular weight of the cationic component, the more preferable it is in terms of suppressing static unevenness.

The polarizing film with an adhesive layer of the present invention has irregularly shaped parts other than rectangular, but as described above, the polarizing film with an adhesive layer of the present invention contains an ionic compound with a small molecular weight of the cationic component as an ionic compound in the adhesive layer. Therefore, even if the amount of the ionic compound is reduced, the antistatic function of the adhesive layer can suppress static electricity unevenness even when the polarizing film with an adhesive layer is applied to an in-cell type liquid crystal panel. In addition, because the amount of the ionic compound can be reduced, the occurrence of irregular cracks can be suppressed.

Furthermore, it was found that the effect of suppressing irregular cracks is advantageous when a one-sided protected polarizing film, which has a protective film on only one side of the polarizer, is used as the polarizing film. A one-sided protected polarizing film is also advantageous from the standpoint of thinning and reducing costs.

On the other hand, it was also found that when a one-sided protected polarizing film is used as the polarizing film as described above, the antistatic function of the adhesive layer may be reduced in a humid environment due to segregation of the ionic compound contained in the adhesive layer to the polarizer. When a one-sided protected polarizing film is used in this way, discoloration of the edge of the polarizer in a humid environment can be suppressed by providing the adhesive layer on the polarizer via a transparent layer so that the ionic compound in the adhesive layer does not directly affect the polarizer.

As described above, the polarizing film with adhesive layer of the present invention can suppress deterioration of the optical reliability of the polarizer even when a one-sided protected polarizing film is used, and can provide a polarizing film with adhesive layer that is thin, has good optical reliability, and has excellent antistatic properties over a long period of time.

1 is a cross-sectional view showing an example of a pressure-sensitive adhesive layer-attached polarizing film of the present invention. 1 is a cross-sectional view showing an example of a pressure-sensitive adhesive layer-attached polarizing film of the present invention. 1 is a cross-sectional view showing an example of a pressure-sensitive adhesive layer-attached polarizing film of the present invention. FIG. 2 is a top view showing an example of an irregularly shaped portion other than rectangular of the pressure-sensitive adhesive layer-attached polarizing film of the present invention. FIG. 2 is a top view showing a pressure-sensitive adhesive layer-attached polarizing film having an irregularly shaped portion according to an embodiment of the present invention. FIG. 1 is a cross-sectional view showing an example of a liquid crystal panel with a touch sensing function using the pressure-sensitive adhesive layer-attached polarizing film of the present invention. FIG. 1 is a cross-sectional view showing an example of a liquid crystal panel with a touch sensing function using the pressure-sensitive adhesive layer-attached polarizing film of the present invention. FIG. 1 is a cross-sectional view showing an example of a liquid crystal panel with a touch sensing function using the pressure-sensitive adhesive layer-attached polarizing film of the present invention.

The polarizing film with adhesive layer of the present invention is shown in FIG. 1, for example. As shown in FIG. 1, the polarizing film with adhesive layer 1 has a polarizing film 11 and an adhesive layer 21. FIG. 2 shows a case where a single-protected polarizing film 11A having a protective film b only on one side of the polarizer a is used as the polarizing film 11 of FIG. 1, and the single-protected polarizing film 11A has the adhesive layer 21 on the other side of the side that does not have the protective film b with respect to the polarizer a. Although not shown, a laminate in the order of polarizer a/protective film b/adhesive layer 21 can also be used as a single-protected polarizing film A2 having a protective film b only on one side of the polarizer a. FIG. 3 shows a case where the single-protected polarizing film 11A is used and further has a transparent layer d on the other side of the polarizer a. In FIG. 3, the single-protected polarizing film 11A has a transparent layer c and an adhesive layer 21 in this order. It is preferable to provide the transparent layer c directly on the polarizer a, since this can suppress an increase in the moisture content of the polarizer in a high-temperature, high-humidity environment.

<Irregular Shape>
The pressure-sensitive adhesive layer-attached polarizing film of the present invention also has an irregularly shaped portion other than a rectangle. Fig. 4 is a top view of an example of an irregularly shaped portion other than a rectangle. The irregular shape is not particularly limited, and may be any shape depending on the application, function, and design of the pressure-sensitive adhesive layer-attached polarizing film. An example of an irregular shape other than a rectangle is a rectangle having a chipped portion or a through hole.

The notch is provided on the outer edge of the polarizing film with the adhesive layer. When multiple notches are provided, they may have the same shape or different shapes. Two or more notches may be provided on one side, or one or more on each of two sides. The notch may be provided at one of the four corners of the outer edge of the rectangle, or at two or more corners. The corners of the outer edge where the notch is not provided may be angular or rounded. The notch may be a straight line, a curve, or a combination of these. Figure 4 shows an example of an irregularly shaped polarizing film with an adhesive layer 1, in which notches 2 of different shapes are provided on both short sides of the rectangle.

The length of the side W1 of the cutout is adjusted as appropriate depending on the application of the polarizing film. For example, it is preferable to adjust W1 to within a range of about 2 to 100 mm. It is also preferable to adjust the maximum depth D of the cutout 2 from the side W1 to about 2 to 100 mm.

In FIG. 4, the angle θ1 between the two straight lines that define the shape of the chipped portion 2 is shown as 90°, but the angle θ1 is greater than or equal to 90° and less than 180°, and preferably greater than or equal to 90° and less than or equal to 135°. If the angle θ1 is outside the range, stress due to expansion and contraction will concentrate in the portion 4 where the two straight lines intersect in a severe thermal shock environment, making the portion 4 more likely to crack.

In addition, in FIG. 4, a curve constituting the shape of the notch 2 is shown, and the radius of curvature R1 of the curve is 0.2 mm or more, preferably 1 mm or more, more preferably 2 mm or more, even more preferably 3 mm or more, and even more preferably 5 mm or more. If the radius of curvature R1 is less than 0.2 mm, stress due to expansion and contraction will concentrate on the curved portion in a severe environment of thermal shock, and cracks will easily occur in the curved portion.

The through-hole is provided within the plane of the polarizing film with an adhesive layer. When a plurality of through-holes are provided within the plane of the polarizing film with an adhesive layer, they may have the same shape or different shapes. The through-hole is configured with a straight line, a curve, or a combination thereof. Examples of the shape of the through-hole include a circle, an ellipse (one axis of symmetry, two axes of symmetry), a rounded rectangle, a quadrangle (square, rectangle), and a polygon with five or more sides.

Methods for forming the irregularly shaped portion include, for example, punching, end mill processing, and laser processing. The irregularly shaped portion is usually formed by the above processing after each layer is laminated.

<Polarizing film with adhesive layer>
First, each member constituting the pressure-sensitive adhesive layer-attached polarizing film of the present invention will be described. The polarizing film used has a polarizer and a protective film on one or both sides of the polarizer.

The polarizer is not particularly limited, and various types can be used. Examples of polarizers include hydrophilic polymer films such as polyvinyl alcohol films, partially formalized polyvinyl alcohol films, and partially saponified ethylene-vinyl acetate copolymer films, which are uniaxially stretched after adsorbing a dichroic substance such as iodine or a dichroic dye, and polyene-based oriented films such as dehydrated polyvinyl alcohol and dehydrochlorinated polyvinyl chloride. Among these, polarizers made of a polyvinyl alcohol film and a dichroic substance such as iodine are preferable. The thickness of these polarizers is not particularly limited, but is generally about 80 μm or less.

As the polarizer, a thin polarizer having a thickness of 10 μm or less can be used. From the viewpoint of thinning, the thickness is preferably 1 to 7 μm. Such thin polarizers have little thickness unevenness, excellent visibility, and excellent durability due to little dimensional change, and are also preferable in that the thickness as a polarizing film can be made thin.

As a material for forming the protective film, for example, a thermoplastic resin excellent in transparency, mechanical strength, thermal stability, moisture blocking properties, isotropy, etc. is used. Specific examples of such thermoplastic resins include cellulose resins such as triacetyl cellulose, polyester resins, polyethersulfone resins, polysulfone resins, polycarbonate resins, polyamide resins, polyimide resins, polyolefin resins, (meth)acrylic resins, cyclic polyolefin resins (norbornene-based resins), polyarylate resins, polystyrene resins, polyvinyl alcohol resins, and mixtures thereof. Note that the protective film is usually attached to one side of the polarizer by an adhesive layer, but the protective film on the other side can be made of a thermosetting resin or an ultraviolet-curing resin such as a (meth)acrylic, urethane, acrylic urethane, epoxy, or silicone-based resin.

As the material for the protective film (transparent protective film), cellulose resin and (meth)acrylic resin are preferred because they can control the fluctuation of the surface resistance value of the adhesive layer to a small value. As the (meth)acrylic resin, it is preferred to use a (meth)acrylic resin having a lactone ring structure. Examples of the (meth)acrylic resin having a lactone ring structure include (meth)acrylic resins having a lactone ring structure described in JP-A-2000-230016, JP-A-2001-151814, JP-A-2002-120326, JP-A-2002-254544, JP-A-2005-146084, etc. In particular, cellulose resin is preferred because it is more effective than (meth)acrylic resin in suppressing irregular cracks and polarizer cracks, which are problems with one-sided protected polarizing films.

As the protective film, a retardation film, a brightness enhancement film, a diffusion film, etc. can also be used. As the retardation film, there can be mentioned one having a front retardation of 40 nm or more and/or a thickness direction retardation of 80 nm or more. The front retardation is usually controlled in the range of 40 to 200 nm, and the thickness direction retardation is usually controlled in the range of 80 to 300 nm. When a retardation film is used as the protective film, the retardation film also functions as a polarizer protective film, so that a thinner film can be achieved.

The surface of the protective film to which the polarizer is not attached can be provided with a functional layer such as a hard coat layer, an anti-reflection layer, an anti-sticking layer, a diffusion layer, or an anti-glare layer.

The protective film and the polarizer are laminated via an intervening layer such as an adhesive layer, a pressure-sensitive adhesive layer, or an undercoat layer (primer layer). In this case, it is desirable to laminate the two without any air gaps by using the intervening layer. It is preferable to laminate the protective film and the polarizer via an adhesive layer. There are no particular limitations on the adhesive used to bond the polarizer and the protective film, as long as it is optically transparent, and various types of adhesives such as water-based, solvent-based, hot-melt, radical curing, and cationic curing types can be used, but water-based adhesives or radical curing adhesives are preferred.

<Adhesive Layer>
The pressure-sensitive adhesive layer is formed from a pressure-sensitive adhesive composition containing a (meth)acrylic polymer (A) and an ionic compound (B).

The (meth)acrylic polymer (A) contains alkyl (meth)acrylate as a monomer unit as a main component. Note that (meth)acrylate refers to acrylate and/or methacrylate, and (meth) in the present invention has the same meaning.

As the alkyl (meth)acrylate constituting the main skeleton of the (meth)acrylic polymer (A), a linear or branched alkyl group having 1 to 18 carbon atoms can be exemplified. For example, the alkyl group can be methyl, ethyl, propyl, isopropyl, butyl, isobutyl, amyl, hexyl, cyclohexyl, heptyl, 2-ethylhexyl, isooctyl, nonyl, decyl, isodecyl, dodecyl, isomyristyl, lauryl, tridecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl, etc. These can be used alone or in combination. The average carbon number of these alkyl groups is preferably 3 to 9.

The weight ratio of the alkyl (meth)acrylate, as a monomer unit, is preferably 70% by weight or more in the weight ratio of all constituent monomers (100% by weight) constituting the (meth)acrylic polymer (A). The weight ratio of the alkyl (meth)acrylate can be considered as the remainder of other copolymerization monomers. Setting the weight ratio of the alkyl (meth)acrylate within the above range is preferable in terms of ensuring adhesion.

In addition to the alkyl (meth)acrylate monomer unit, one or more types of copolymerizable monomers having a polymerizable functional group with an unsaturated double bond, such as a (meth)acryloyl group or a vinyl group, can be introduced by copolymerization into the (meth)acrylic polymer (A) in order to improve adhesion and heat resistance.

Examples of the copolymerizable monomer include functional group-containing monomers such as carboxyl group-containing monomers, hydroxyl group-containing monomers, and amide group-containing monomers.

A carboxyl group-containing monomer is a compound that contains a carboxyl group in its structure and also contains a polymerizable unsaturated double bond such as a (meth)acryloyl group or a vinyl group. Specific examples of carboxyl group-containing monomers include (meth)acrylic acid, carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, itaconic acid, maleic acid, fumaric acid, and crotonic acid. Among the above carboxyl group-containing monomers, acrylic acid is preferred from the viewpoints of copolymerizability, cost, and adhesive properties.

Hydroxyl group-containing monomers are compounds that contain a hydroxyl group in their structure and a polymerizable unsaturated double bond such as a (meth)acryloyl group or a vinyl group. Specific examples of hydroxyl group-containing monomers include hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, and 12-hydroxylauryl (meth)acrylate, and (4-hydroxymethylcyclohexyl)-methyl acrylate. Among the hydroxyl group-containing monomers, 2-hydroxyethyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate are preferred from the viewpoint of durability, with 4-hydroxybutyl (meth)acrylate being particularly preferred.

When the adhesive composition contains a crosslinking agent, the carboxyl group-containing monomer and the hydroxyl group-containing monomer become reaction sites with the crosslinking agent. Carboxyl group-containing monomers and hydroxyl group-containing monomers are highly reactive with intermolecular crosslinking agents, and are therefore preferably used to improve the cohesiveness and heat resistance of the resulting adhesive layer. In addition, the carboxyl group-containing monomer is preferred in terms of achieving both durability and reworkability, and the hydroxyl group-containing monomer is preferred in terms of reworkability.

The weight ratio of the carboxyl group-containing monomer is preferably 10% by weight or less, more preferably 0.01 to 8% by weight, even more preferably 0.05 to 6% by weight, and even more preferably 0.1 to 5% by weight. A weight ratio of the carboxyl group-containing monomer of 0.01% by weight or more is preferable from the standpoint of durability. On the other hand, if it exceeds 10% by weight, it is not preferable from the standpoint of reworkability.

The weight ratio of the hydroxyl group-containing monomer is preferably 3% by weight or less, more preferably 0.01 to 3% by weight, even more preferably 0.1 to 2% by weight, and even more preferably 0.2 to 2% by weight. A weight ratio of the hydroxyl group-containing monomer of 0.01% by weight or more is preferable from the viewpoint of crosslinking the adhesive layer, durability, and adhesive properties. On the other hand, if it exceeds 3% by weight, it is not preferable from the viewpoint of durability.

An amide group-containing monomer is a compound that contains an amide group in its structure and a polymerizable unsaturated double bond such as a (meth)acryloyl group or a vinyl group. Specific examples of the amide group-containing monomer include acrylamide-based monomers such as (meth)acrylamide, N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, N-isopropylacrylamide, N-methyl(meth)acrylamide, N-butyl(meth)acrylamide, N-hexyl(meth)acrylamide, N-methylol(meth)acrylamide, N-methylol-N-propane(meth)acrylamide, aminomethyl(meth)acrylamide, aminoethyl(meth)acrylamide, mercaptomethyl(meth)acrylamide, and mercaptoethyl(meth)acrylamide; N-acryloyl heterocyclic monomers such as N-(meth)acryloylmorpholine, N-(meth)acryloylpiperidine, and N-(meth)acryloylpyrrolidine; and N-vinyl group-containing lactam monomers such as N-vinylpyrrolidone and N-vinyl-ε-caprolactam. Amide group-containing monomers are preferred for suppressing the increase in surface resistance over time (especially in a humid environment), for satisfying durability, and for suppressing irregular cracks. Among amide group-containing monomers, N-vinyl group-containing lactam monomers are particularly preferred for suppressing the increase in surface resistance over time (especially in a humid environment), for satisfying durability for the transparent conductive layer (touch sensor layer), and for suppressing irregular cracks.

When the weight ratio of the amide group-containing monomer increases, the anchoring property for the optical film tends to decrease, so the weight ratio is preferably 10% by weight or less, and more preferably 5% by weight or less. From the viewpoint of suppressing an increase in the surface resistance value over time (especially in a humid environment), the weight ratio of the amide group-containing monomer is preferably 0.1% by weight or more. The weight ratio is preferably 0.3% by weight or more, and more preferably 0.5% by weight or more. The amide group-containing monomer is suitable in relation to the ionic compound (B) contained in the pressure-sensitive adhesive layer of the present invention.

In the adhesive composition used to form the adhesive layer, when an amide group is present in the side chain of the base polymer (meth)acrylic polymer (A), the presence of the amide group prevents the surface resistance of the adhesive layer adjusted by blending the ionic compound (B) from fluctuating and increasing even in a humid environment, which is preferable for maintaining the surface resistance within the desired range. It is believed that the presence of the amide group introduced as a functional group of the copolymerization monomer in the side chain of the (meth)acrylic polymer (A) increases the compatibility between the (meth)acrylic polymer (A) and the ionic compound (B).

In addition, when an amide group is introduced into the side chain of the (meth)acrylic polymer (A) that is the base polymer, the pressure-sensitive adhesive layer has good durability against both glass and transparent conductive layers (such as an ITO layer), and can suppress peeling, lifting, and the like when attached to a liquid crystal panel. In addition, the pressure-sensitive adhesive layer can also satisfy durability in a humid environment (after a humid reliability test).

As the copolymerizable monomer, for example, an aromatic ring-containing (meth)acrylate can be used. An aromatic ring-containing (meth)acrylate is a compound that contains an aromatic ring structure in its structure and also contains a (meth)acryloyl group. Examples of the aromatic ring include a benzene ring, a naphthalene ring, and a biphenyl ring.

Specific examples of aromatic ring-containing (meth)acrylates include, for example, benzyl (meth)acrylate, phenyl (meth)acrylate, o-phenylphenol (meth)acrylate, phenoxy (meth)acrylate, phenoxyethyl (meth)acrylate, phenoxypropyl (meth)acrylate, phenoxydiethylene glycol (meth)acrylate, ethylene oxide modified nonylphenol (meth)acrylate, ethylene oxide modified cresol (meth)acrylate, phenol ethylene oxide modified (meth)acrylate, 2-hydroxyphenyl (meth)acrylate, phenyl ethylene oxide modified ... Examples of such acrylates include those having a benzene ring, such as methoxy-3-phenoxypropyl (meth)acrylate, methoxybenzyl (meth)acrylate, chlorobenzyl (meth)acrylate, cresyl (meth)acrylate, and polystyryl (meth)acrylate; those having a naphthalene ring, such as hydroxyethylated β-naphthol acrylate, 2-naphthoethyl (meth)acrylate, 2-naphthoxyethyl acrylate, and 2-(4-methoxy-1-naphthoxy)ethyl (meth)acrylate; and those having a biphenyl ring, such as biphenyl (meth)acrylate.

As the aromatic ring-containing (meth)acrylate, benzyl (meth)acrylate and phenoxyethyl (meth)acrylate are preferred from the viewpoint of adhesive properties and durability, with phenoxyethyl (meth)acrylate being particularly preferred.

The weight ratio of the aromatic ring-containing (meth)acrylate is preferably 25% by weight or less, more preferably 3 to 25% by weight, even more preferably 10 to 22% by weight, and even more preferably 14 to 20% by weight. If the weight ratio of the aromatic ring-containing (meth)acrylate is 3% by weight or more, this is preferable in terms of suppressing display unevenness. On the other hand, if it exceeds 25% by weight, the suppression of display unevenness is not sufficient and durability tends to decrease.

Specific examples of copolymerizable monomers other than those mentioned above include: acid anhydride group-containing monomers such as maleic anhydride and itaconic anhydride; caprolactone adducts of acrylic acid; sulfonic acid group-containing monomers such as allylsulfonic acid, 2-(meth)acrylamido-2-methylpropanesulfonic acid, (meth)acrylamidopropanesulfonic acid, and sulfopropyl (meth)acrylate; and phosphoric acid group-containing monomers such as 2-hydroxyethyl acryloyl phosphate.

In addition, alkylaminoalkyl (meth)acrylates such as aminoethyl (meth)acrylate, N,N-dimethylaminoethyl (meth)acrylate, and t-butylaminoethyl (meth)acrylate; alkoxyalkyl (meth)acrylates such as methoxyethyl (meth)acrylate and ethoxyethyl (meth)acrylate; N-(meth)acryloyloxymethylene succinimide, N-(meth)acryloyl-6-oxyhexamethylene succinimide, N-(meth)acryloyl-8-oxyoctamethyl succinimide, and N-(meth)acryloyloxymethylene succinimide; Examples of monomers for modification purposes include succinimide monomers such as ethylene succinimide; maleimide monomers such as N-cyclohexylmaleimide, N-isopropylmaleimide, N-laurylmaleimide, and N-phenylmaleimide; itaconimide monomers such as N-methylitaconimide, N-ethylitaconimide, N-butylitaconimide, N-octylitaconimide, N-2-ethylhexylitaconimide, N-cyclohexylitaconimide, and N-laurylitaconimide.

As further modifying monomers, vinyl monomers such as vinyl acetate and vinyl propionate; cyanoacrylate monomers such as acrylonitrile and methacrylonitrile; epoxy group-containing (meth)acrylates such as glycidyl (meth)acrylate; glycol (meth)acrylates such as polyethylene glycol (meth)acrylate, polypropylene glycol (meth)acrylate, methoxyethylene glycol (meth)acrylate, and methoxypolypropylene glycol (meth)acrylate; (meth)acrylate monomers such as tetrahydrofurfuryl (meth)acrylate, fluorine (meth)acrylate, silicone (meth)acrylate, and 2-methoxyethyl acrylate can also be used. Further examples include isoprene, butadiene, isobutylene, and vinyl ether.

Furthermore, copolymerizable monomers other than those mentioned above include silane-based monomers containing silicon atoms. Examples of silane-based monomers include 3-acryloxypropyltriethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, 4-vinylbutyltrimethoxysilane, 4-vinylbutyltriethoxysilane, 8-vinyloctyltrimethoxysilane, 8-vinyloctyltriethoxysilane, 10-methacryloyloxydecyltrimethoxysilane, 10-acryloyloxydecyltrimethoxysilane, 10-methacryloyloxydecyltriethoxysilane, 10-acryloyloxydecyltriethoxysilane, and 10-acryloyloxydecyltriethoxysilane.

In addition, examples of copolymerizable monomers include tripropylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, bisphenol A diglycidyl ether di(meth)acrylate, neopentyl glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, and dipentaerythritol helix. Polyfunctional monomers having two or more unsaturated double bonds such as (meth)acryloyl groups or vinyl groups, such as esters of (meth)acrylic acid and polyhydric alcohols, such as hexa(meth)acrylate and caprolactone-modified dipentaerythritol hexa(meth)acrylate, and polyester (meth)acrylates, epoxy (meth)acrylates, urethane (meth)acrylates, etc., in which two or more unsaturated double bonds such as (meth)acryloyl groups or vinyl groups are added as functional groups similar to those of the monomer components to the backbone of polyester, epoxy, urethane, etc., can also be used.

The proportion of the other copolymerizable monomer in the (meth)acrylic polymer (A) is preferably about 0 to 10% by weight, more preferably about 0 to 7% by weight, and even more preferably about 0 to 5% by weight, based on the weight ratio of all constituent monomers (100% by weight) of the (meth)acrylic polymer (A).

The (meth)acrylic polymer (A) of the present invention usually has a weight average molecular weight of 1 million to 2.5 million. Considering durability, particularly heat resistance, the weight average molecular weight is preferably 1.2 million to 2 million. A weight average molecular weight of 1 million or more is preferable in terms of heat resistance. Furthermore, if the weight average molecular weight is greater than 2.5 million, the adhesive tends to become hard and peeling is likely to occur. Furthermore, the weight average molecular weight (Mw)/number average molecular weight (Mn), which indicates the molecular weight distribution, is preferably 1.8 to 10, more preferably 1.8 to 7, and even more preferably 1.8 to 5. If the molecular weight distribution (Mw/Mn) exceeds 10, it is not preferable in terms of durability. The weight average molecular weight and the molecular weight distribution (Mw/Mn) are measured by GPC (gel permeation chromatography) and calculated in terms of polystyrene.

The (meth)acrylic polymer (A) can be produced by appropriately selecting a known production method such as solution polymerization, bulk polymerization, emulsion polymerization, or various radical polymerizations. The resulting (meth)acrylic polymer (A) may be any of a random copolymer, a block copolymer, a graft copolymer, etc.

In solution polymerization, for example, ethyl acetate, toluene, etc. are used as the polymerization solvent. In a specific example of solution polymerization, the reaction is carried out under a stream of inert gas such as nitrogen, with the addition of a polymerization initiator, usually at about 50 to 70°C, for about 5 to 30 hours.

The polymerization initiator, chain transfer agent, emulsifier, etc. used in the radical polymerization are not particularly limited and can be appropriately selected and used. The weight average molecular weight of the (meth)acrylic polymer (A) can be controlled by the amount of polymerization initiator and chain transfer agent used and the reaction conditions, and the amount used is appropriately adjusted depending on the type of these.

<Ionic Compound (B)>
The ionic compound (B) contained in the pressure-sensitive adhesive composition forming the pressure-sensitive adhesive layer of the present invention is one having a molecular weight of 210 or less. The molecular weight of the cationic component is preferably 150 or less, more preferably 110 or less, more preferably 50 or less, and even more preferably 10 or less, from the viewpoint of suppressing the occurrence of irregular cracks. The larger the molecular weight of the cationic component, the more likely it is that the (meth)acrylic polymers in the pressure-sensitive adhesive layer will be entangled, and the physical properties of the pressure-sensitive adhesive layer will tend to become softer. Therefore, the smaller the molecular weight, the less likely the physical properties of the pressure-sensitive adhesive layer will become soft, and the occurrence of irregular cracks can be suppressed. In addition, the smaller the molecular weight of the cationic component, the more likely it is that the surface resistance value of the pressure-sensitive adhesive layer will decrease, and static electricity unevenness will be suppressed.

The ionic compound (B) is preferably an alkali metal salt and/or an organic cation-anion salt. The alkali metal salt may be an organic salt or an inorganic salt of an alkali metal. In the present invention, the term "organic cation-anion salt" refers to an organic salt whose cation component is composed of an organic substance, and whose anion component may be either an organic substance or an inorganic substance. The "organic cation-anion salt" is also called an ionic liquid or an ionic solid. By incorporating the ionic compound (B) in the adhesive layer, the surface resistance value of the adhesive layer can be reduced to suppress the generation of static electricity, and the orientation of the liquid crystal layer caused by charging can be disturbed, which can suppress the occurrence of light leakage (uneven charging).

<Alkali metal salt>
Examples of the alkali metal ions constituting the cationic component of the alkali metal salt include lithium, sodium and potassium ions, with the lithium ion being preferred among these alkali metal ions.

The anion component of the alkali metal salt may be composed of an organic substance or an inorganic substance. Examples of the anion components constituting the organic salt include CH ₃ COO ⁻ , CF ₃ COO ⁻ , CH ₃ SO ₃ ⁻ , CF ₃ SO ₃ ⁻ , (CF ₃ SO ₂ ) ₃ C ⁻ , C ₄ F ₉ SO ₃ ⁻ , C ₃ F ₇ COO ⁻ , (CF ₃ SO ₂ ) (CF ₃ CO) N ⁻ , ^−O ₃ S (CF ₂ ) ₃ SO ₃ ⁻ , PF ₆ ⁻ , CO ₃ ² − , and the anion components of the following general formulae (1) to (4):
(1): (C _n F _2n+1 SO ₂ ) ₂ N ⁻ (wherein n is an integer from 0 to 10);
(2): CF ₂ (C _m F _{2 m} SO ₂ ) ₂ N ⁻ (wherein m is an integer of 1 to 10);
(3): ^-O3S ( _CF2 ) _{lSO3- (} wherein l is _an integer from 1 to ¹⁰ );
(4): (C _p F _2p+1 SO ₂ )N ^- (C _q F _2q+1 SO ₂ ), (where p and q are integers from 1 to 10), and the like are used. In particular, an anion component containing a fluorine atom is preferably used because it gives an ionic compound with good ionic dissociation properties. Examples of an anion component constituting an inorganic salt include Cl ^- , Br ^- , I ^- , AlCl ₄ ^- , Al ₂ Cl ₇ ^- , BF ₄ ^- , PF ₆ ^- , ClO ₄ ^- , NO ₃ ^- , AsF ₆ ^- , SbF ₆ ^- , NbF ₆ ^- , TaF ₆ ^- , (CN) ₂ N ^- , and the like. As the anion component, (perfluoroalkylsulfonyl)imides represented by the above general formula (1), such as (CF ₃ SO ₂ ) ₂ N ⁻ or (C ₂ F ₅ SO ₂ ) ₂ N ⁻ , are preferred, with (trifluoromethanesulfonyl)imide represented by (CF ₃ SO ₂ ) ₂ N ⁻ being particularly preferred.

Specific examples of organic salts of alkali metals include sodium acetate, sodium alginate, sodium ligninsulfonate, sodium _{toluenesulfonate} , _LiCF3SO3 , _Li ( _{CF3SO2 )2N, Li(CF3SO2)2N, Li(C2F5SO2)2N , Li ( C4F9SO2 ) 2N , Li ( CF3SO2} ) _3C , _KO3S ( _CF2 ) _3SO3K , _LiO3S ( _CF2 ) _{3SO3K ,} and _the like _. Of _{these, LiCF3SO3, Li(CF3SO2 ) 2N , Li ( C2F5SO2 ) 2N ,} Li _{( C4F Preferred} are fluorine- _containing lithium imide salts, which _{are bis} ( _{fluorosulfonyl)imide lithium salts such as Li(CF3SO2 ) 2N ,} Li( _C2F5SO2 ) _2N , and Li( _C4F9SO2 ) _2N , and particularly preferred are ( _{perfluoroalkylsulfonyl} )imide lithium salts. Other examples include 4,4,5,5- _tetrafluoro - _{1,3,2 -} dithiazolidine-1,1,3,3- _tetraoxide lithium salt.

Also, examples of inorganic salts of alkali metals include lithium perchlorate and lithium iodide.

<Organic cation-anion salt>
The organic cation-anion salt used in the present invention is composed of a cation component and an anion component, and the cation component is an organic substance. Specific examples of the cation component include pyridinium cation, piperidinium cation, pyrrolidinium cation, cation having a pyrroline skeleton, cation having a pyrrole skeleton, imidazolium cation, tetrahydropyrimidinium cation, dihydropyrimidinium cation, pyrazolium cation, pyrazolinium cation, tetraalkylammonium cation, trialkylsulfonium cation, and tetraalkylphosphonium cation.

Examples of the anion components include Cl ^- , Br ^- , I ^- , AlCl ₄ ^- , Al ₂ Cl ₇ ^- , BF ₄ ^- , PF ₆ ^- , ClO ₄ ^- , NO ₃ ^- , CH ₃ COO ^- , CF ₃ COO ^- , CH ₃ SO ₃ ^- , CF ₃ SO ₃ ^- , (CF ₃ SO ₂ ) ₃ C ^- , AsF ₆ ^- , SbF ₆ ^- , NbF ₆ ^- , TaF ₆ ^- , (CN) ₂ N ^- , C ₄ F ₉ SO ₃ ^- , C ₃ F ₇ COO ^- , ((CF ₃ SO ₂ )(CF ₃ CO)N ^- , ^-O ₃ S(CF ₂ ) _{3SO3- ,} or ^the following general formulas (1) to (4):
(1): (C _n F _2n+1 SO ₂ ) ₂ N ⁻ (wherein n is an integer from 0 to 10);
(2): CF ₂ (C _m F _{2 m} SO ₂ ) ₂ N ⁻ (wherein m is an integer of 1 to 10);
(3): ^-O3S ( _CF2 ) _{lSO3- (} wherein l is _an integer from 1 to ¹⁰ );
(4): (C _p F _2p+1 SO ₂ )N ⁻ (C _q F _2q+1 SO ₂ ), (wherein p and q are integers of 1 to 10), and the like are used. Among these, an anion component containing a fluorine atom is preferably used because it gives an ionic compound with good ionic dissociation properties.

The organic cation-anion salt is an appropriately selected compound consisting of a combination of the above-mentioned cation component and anion component. Specific preferred examples of the organic cation-anion salt include methyltrioctylammonium bis(trifluoromethanesulfonyl)imide, 1-methyl-1-propylpyrrolidinium bis(trifluoromethanesulfonyl)imide, and ethylmethylimidazolium bis(fluorosulfonylimide). Of these, 1-methyl-1-propylpyrrolidinium bis(trifluoromethanesulfonyl)imide and ethylmethylimidazolium bis(fluorosulfonylimide) are more preferred.

In addition to the above-mentioned alkali metal salts and organic cation-anion salts, examples of the ionic compound (B) include inorganic salts such as ammonium chloride, aluminum chloride, copper chloride, ferrous chloride, ferric chloride, and ammonium sulfate.

When the ionic compound (B) is an alkali metal salt, alkali metal ions such as lithium, sodium, and potassium are cationic components with a molecular weight of 210 or less, so that alkali metal salts containing these alkali metal ions as cationic components can be preferably used. In particular, from the viewpoint of compatibility with the adhesive layer, an organic salt of an alkali metal in which the anionic component of the alkali metal salt is composed of an organic substance is preferred. In addition, as the alkali metal ion, lithium ions, which have the smallest molecular weight, are preferred. As the ionic compound (B), lithium salts are preferred, and organic salts of lithium are particularly preferred. On the other hand, when the ionic compound (B) is an organic cation-anion salt, a molecular weight of 210 or less can be selected from the above-mentioned exemplified cationic components and used. In particular, from the viewpoint of compatibility with the adhesive layer, an organic cation-anion salt in which the anionic component is composed of an organic substance is preferred.

The ratio of the ionic compound (B) in the adhesive composition of the present invention can be appropriately adjusted so as to satisfy the antistatic properties of the adhesive layer and the sensitivity of the touch panel. For example, it is preferable to adjust the ratio of the ionic compound ^{( B} ) according to the type of liquid crystal panel with built-in touch sensing function while considering the type of protective film of the polarizing film, etc., so that the surface resistance value of the adhesive layer is in the range of 1.0×10 8 to 1.0×10 12 Ω/□. For example, in the in-cell type liquid crystal panel with built-in touch sensing function shown in FIG. 6, the adhesive layer is preferably controlled to have an initial surface resistance value in the range of 1×10 ⁸ to 6×10 ¹⁰ Ω/□. In addition, in the semi-in-cell type liquid crystal panel with built-in touch sensing function shown in FIG. 7 or the on-cell type liquid crystal panel with built-in touch sensing function shown in FIG. 8, the adhesive layer is preferably controlled to have an initial surface resistance value in the range of 1×10 ¹⁰ to 1×10 ¹² Ω/□.

If the amount of the ionic compound (B) is too large, the ionic compound (B) may precipitate, and furthermore, peeling due to humidity may easily occur. Also, if the amount of the ionic compound (B) is too large, the surface resistance value may become too low, and the sensitivity of the touch panel may decrease due to baseline fluctuation (malfunction at the time of touch caused by too low surface resistance value). The ratio of the ionic compound (B) is, for example, usually preferably 40 parts by weight or less, more preferably 20 parts by weight or less, and even more preferably 13 parts by weight or less, relative to 100 parts by weight of the (meth)acrylic polymer (A). If the amount is too small, the antistatic property may be poor, and if the amount is too large, there is a risk of a decrease in touch sensitivity, precipitation of the ionic compound, and deterioration of peeling due to humidity of the adhesive. On the other hand, in order to improve the antistatic performance, it is preferable to use 0.1 parts by weight or more of the ionic compound (B). From this viewpoint, the amount of the ionic compound (B) is preferably 1 part by weight or more, and even more preferably 5 parts by weight or more.

The adhesive composition of the present invention may contain a crosslinking agent (C). As the crosslinking agent (C), an organic crosslinking agent or a polyfunctional metal chelate may be used. Examples of organic crosslinking agents include isocyanate crosslinking agents, peroxide crosslinking agents, epoxy crosslinking agents, and imine crosslinking agents. The polyfunctional metal chelate is a compound in which a polyvalent metal is covalently or coordinately bonded to an organic compound. Examples of polyvalent metal atoms include Al, Cr, Zr, Co, Cu, Fe, Ni, V, Zn, In, Ca, Mg, Mn, Y, Ce, Sr, Ba, Mo, La, Sn, and Ti. Examples of atoms in the organic compound that are covalently or coordinately bonded include oxygen atoms, and examples of the organic compound include alkyl esters, alcohol compounds, carboxylic acid compounds, ether compounds, and ketone compounds.

As the crosslinking agent (C), an isocyanate-based crosslinking agent and/or a peroxide-based crosslinking agent is preferred.

As the isocyanate-based crosslinking agent (C), a compound having at least two isocyanate groups can be used. For example, known aliphatic polyisocyanates, alicyclic polyisocyanates, aromatic polyisocyanates, etc., which are generally used in urethane reactions, can be used.

Any peroxide can be used as long as it generates radical active species when heated or irradiated with light and promotes crosslinking of the base polymer of the adhesive composition. Taking into consideration workability and stability, it is preferable to use a peroxide with a one-minute half-life temperature of 80°C to 160°C, and more preferably a peroxide with a one-minute half-life temperature of 90°C to 140°C.

Examples of peroxides that can be used include di(2-ethylhexyl)peroxydicarbonate (1-minute half-life temperature: 90.6°C), di(4-t-butylcyclohexyl)peroxydicarbonate (1-minute half-life temperature: 92.1°C), di-sec-butylperoxydicarbonate (1-minute half-life temperature: 92.4°C), t-butylperoxyneodecanoate (1-minute half-life temperature: 103.5°C), t-hexylperoxypivalate (1-minute half-life temperature: 109.1°C), t-butylperoxypivalate (1-minute half-life temperature: 110.3°C), dilauroylperoxypivalate (1-minute half-life temperature: 111.1°C), dilauroylperoxypivalate (1-minute half-life temperature: 112.1°C), dilauroylperoxypivalate (1-minute half-life temperature: 113.1°C), dilauroylperoxypivalate (1-minute half-life temperature: 114.1°C), dilauroylperoxypivalate (1-minute half-life temperature: 115.1°C), dilauroylperoxypivalate (1-minute half-life temperature: 116.1°C), dilauroylperoxypivalate (1-minute half-life temperature: 117.1°C), dilauroylperoxypivalate (1-minute half-life temperature: 118.1°C), dilauroylperoxypivalate (1-minute half-life temperature: 119.1°C), dilauroylperoxypivalate (1-minute half-life temperature: 120.1°C), dilauroylperoxypivalate (1-minute half-life temperature: 122.1°C), dilauroylperoxypivalate (1-minute half-life temperature: 123.1°C), dilauro peroxide (1-minute half-life temperature: 116.4° C.), di-n-octanoyl peroxide (1-minute half-life temperature: 117.4° C.), 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate (1-minute half-life temperature: 124.3° C.), di(4-methylbenzoyl)peroxide (1-minute half-life temperature: 128.2° C.), dibenzoyl peroxide (1-minute half-life temperature: 130.0° C.), t-butylperoxyisobutyrate (1-minute half-life temperature: 136.1° C.), 1,1-di(t-hexylperoxy)cyclohexane (1-minute half-life temperature: 149.2° C.), and the like. Among these, di(4-t-butylcyclohexyl) peroxydicarbonate (1-minute half-life temperature: 92.1°C), dilauroyl peroxide (1-minute half-life temperature: 116.4°C), dibenzoyl peroxide (1-minute half-life temperature: 130.0°C), etc. are preferably used because they have particularly excellent crosslinking reaction efficiency.

The amount of crosslinking agent (C) used is preferably 3 parts by weight or less, more preferably 0.01 to 3 parts by weight, even more preferably 0.02 to 2 parts by weight, and even more preferably 0.03 to 1 part by weight, per 100 parts by weight of (meth)acrylic polymer (A). If the amount of crosslinking agent (C) is less than 0.01 part by weight, the adhesive layer may be insufficiently crosslinked, and durability and adhesive properties may not be satisfactory. On the other hand, if the amount is more than 3 parts by weight, the adhesive layer may become too hard, tending to reduce durability.

The pressure-sensitive adhesive composition of the present invention may contain a silane coupling agent (D). By using the silane coupling agent (D), durability can be improved. Specific examples of silane coupling agents include epoxy group-containing silane coupling agents such as 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, and 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane; amino group-containing silane coupling agents such as 3-aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, 3-triethoxysilyl-N-(1,3-dimethylbutylidene)propylamine, and N-phenyl-γ-aminopropyltrimethoxysilane; (meth)acrylic group-containing silane coupling agents such as 3-acryloxypropyltrimethoxysilane and 3-methacryloxypropyltriethoxysilane; and isocyanate group-containing silane coupling agents such as 3-isocyanatepropyltriethoxysilane. Of the silane coupling agents exemplified above, epoxy group-containing silane coupling agents are preferred.

In addition, as the silane coupling agent (D), one having multiple alkoxysilyl groups in the molecule can also be used. Specific examples include X-41-1053, X-41-1059A, X-41-1056, X-41-1805, X-41-1818, X-41-1810, and X-40-2651 manufactured by Shin-Etsu Chemical Co., Ltd. These silane coupling agents having multiple alkoxysilyl groups in the molecule are less likely to volatilize, and since they have multiple alkoxysilyl groups, they are effective in improving durability and are preferable. In particular, durability is suitable even when the adherend of the optical film with the adhesive layer is a transparent conductive layer (e.g., ITO, etc.) to which alkoxysilyl groups are less likely to react than glass. In addition, silane coupling agents having multiple alkoxysilyl groups in the molecule are preferably those having epoxy groups in the molecule, and more preferably those having multiple epoxy groups in the molecule. Silane coupling agents that have multiple alkoxysilyl groups in the molecule and epoxy groups tend to have good durability even when the adherend is a transparent conductive layer (e.g., ITO, etc.). Specific examples of silane coupling agents that have multiple alkoxysilyl groups in the molecule and epoxy groups include X-41-1053, X-41-1059A, and X-41-1056 manufactured by Shin-Etsu Chemical Co., Ltd., and X-41-1056 manufactured by Shin-Etsu Chemical Co., Ltd., which has a high epoxy group content, is particularly preferred.

The silane coupling agent (D) may be used alone or in a mixture of two or more kinds, but the total content is preferably 5 parts by weight or less, more preferably 0.001 to 5 parts by weight, even more preferably 0.01 to 1 part by weight, even more preferably 0.02 to 1 part by weight, and even more preferably 0.05 to 0.6 parts by weight, relative to 100 parts by weight of the (meth)acrylic polymer (A). This is an amount that improves durability.

The adhesive composition of the present invention may further contain other known additives, such as polyether compounds having reactive silyl groups, polyether compounds of polyalkylene glycols such as polypropylene glycol, colorants, powders such as pigments, dyes, surfactants, plasticizers, tackifiers, surface lubricants, leveling agents, softeners, antioxidants, anti-aging agents, light stabilizers, UV absorbers, polymerization inhibitors, inorganic or organic fillers, metal powders, particles, foils, etc., which can be added appropriately depending on the application. In addition, a redox system may be used by adding a reducing agent within a controllable range. These additives are preferably used in an amount of 5 parts by weight or less, more preferably 3 parts by weight or less, and even more preferably 1 part by weight or less, per 100 parts by weight of the (meth)acrylic polymer (A).

The adhesive layer can be formed, for example, by applying the adhesive composition to a peel-treated separator or the like, drying and removing the polymerization solvent, etc. to form an adhesive layer, which is then transferred to an optical film (polarized film), or by applying the adhesive composition to an optical film (polarized film), drying and removing the polymerization solvent, etc. to form an adhesive layer on the optical film. When applying the adhesive, one or more solvents other than the polymerization solvent may be added as appropriate.

The thickness of the adhesive layer is not particularly limited and is, for example, about 1 to 100 μm. It is preferably 2 to 50 μm, more preferably 2 to 40 μm, and even more preferably 5 to 35 μm.

The adhesive layer applied to the adhesive layer-attached polarizing film of the present invention preferably has a creep value at 85°C of 120 μm or less, more preferably 100 μm or less, even more preferably 85 μm or less, and particularly preferably 60 μm or less, from the viewpoint of application to an irregular polarizing film. The lower limit of the creep value is preferably 15 μm or more, more preferably 30 μm or more. If the creep value exceeds 120 μm, as described in the examples, cracks that occur in the irregular polarizing film may worsen. If the creep value is below 15 μm, the stress relaxation property of the adhesive layer is reduced, and peeling of the adhesive layer may easily occur in a durability test.

<Transparent layer>
The transparent layer is described in more detail below.

From the viewpoint of thinning and optical reliability, the thickness of the transparent layer is preferably 10 μm or less, more preferably 5 μm or less, more preferably 3 μm or less, more preferably 1.5 μm or less, and even more preferably 1 μm or less. If the transparent layer is too thick, the thickness of the polarizing film may become thick, and the optical reliability of the polarizer may be reduced. On the other hand, from the viewpoint of keeping the variation ratio of the surface resistance value of the pressure-sensitive adhesive layer small, the thickness of the transparent layer is preferably 0.1 μm or more, more preferably 0.2 μm or more, and even more preferably 0.3 μm or more.

The material for forming the transparent layer can be one that is transparent and can suppress the influence of the adhesive layer on the polarizer. One example of such a material is a forming material containing urethane prepolymer (a), which is a reaction product of an isocyanate compound and a polyhydric alcohol.

As the isocyanate compound, for example, a polyfunctional isocyanate compound is preferable, and specific examples thereof include polyfunctional aromatic isocyanate compounds, alicyclic isocyanates, aliphatic isocyanate compounds, and dimers thereof.

Examples of polyfunctional aromatic isocyanate compounds include phenylene diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 2,2'-diphenylmethane diisocyanate, 4,4'-diphenylmethane diisocyanate, 4,4'-toluidine diisocyanate, 4,4'-diphenylether diisocyanate, 4,4'-diphenyl diisocyanate, 1,5-naphthalene diisocyanate, xylylene diisocyanate, methylene bis 4-phenylisocyanate, p-phenylene diisocyanate, and the like.

Examples of polyfunctional alicyclic isocyanate compounds include 1,3-cyclopentene diisocyanate, 1,3-cyclohexane diisocyanate, 1,4-cyclohexane diisocyanate, 1,3-bisisocyanatomethylcyclohexane, isophorone diisocyanate, hydrogenated diphenylmethane diisocyanate, hydrogenated xylylene diisocyanate, hydrogenated tolylene diisocyanate, and hydrogenated tetramethylxylylene diisocyanate.

Examples of polyfunctional aliphatic isocyanate compounds include trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, pentamethylene diisocyanate, 1,2-propylene diisocyanate, 1,3-butylene diisocyanate, dodecamethylene diisocyanate, and 2,4,4-trimethylhexamethylene diisocyanate.

Examples of polyfunctional isocyanate compounds include those having three or more isocyanate groups, such as tris(6-isocyanatehexyl) isocyanurate.

Examples of polyhydric alcohols include ethylene glycol, diethylene glycol, 1,3-butanediol, 1,4-butanediol, neopentyl glycol, 3-methyl-1,5-pentanediol, 2-butyl-2-ethyl-1,3-propanediol, 2,4-diethyl-1,5-pentanediol, 1,2-hexanediol, 1,6-hexanediol, 1,8-octanediol, 1,9-nonanediol, 2-methyl-1,8-octanediol, 1,8-decanediol, octadecanediol, glycerin, trimethylolpropane, pentaerythritol, hexanetriol, and polypropylene glycol.

In the present invention, it is preferable to use, as the urethane prepolymer (a), a molecular structure having a rigid structure in which the proportion of cyclic structures (benzene rings, cyanurate rings, isocyanurate rings, etc.) in the structure is large. For example, the polyfunctional isocyanate compound can be used alone or in combination of two or more types, but aromatic isocyanate compounds are preferred from the viewpoint of suppressing moisture contamination of the polarizer. Other polyfunctional isocyanate compounds can be used in combination with aromatic isocyanate compounds. In particular, it is preferable to use at least one of tolylene diisocyanate and diphenylmethane diisocyanate as the isocyanate compound among aromatic isocyanate compounds.

As the urethane prepolymer (a), trimethylolpropane-tri-tolylene isocyanate and trimethylolpropane-tri-diphenylmethane diisocyanate are preferably used. The urethane prepolymer (a) is a compound having a terminal isocyanate group, and is obtained, for example, by mixing an isocyanate compound with a polyhydric alcohol, stirring and reacting the mixture. In general, it is preferable to mix the isocyanate compound with the polyhydric alcohol so that there is an excess of isocyanate groups relative to the hydroxyl groups of the polyhydric alcohol.

The urethane prepolymer (a) may also be one in which a protecting group has been added to the terminal isocyanate group. Examples of the protecting group include oxime and lactam. When the isocyanate group is protected, the protecting group is dissociated from the isocyanate group by heating, and the isocyanate group becomes reactive.

The material for forming the transparent layer may contain, in addition to the urethane prepolymer (a), a compound (b) having at least two functional groups having active hydrogen that are reactive with isocyanate groups. Examples of functional groups having active hydrogen that are reactive with isocyanate groups include hydroxyl groups and amino groups. The more functional groups having active hydrogen that the compound (b) has, the more reaction points there are with the isocyanate groups of the urethane prepolymer (a), making it easier to form a cured product, so the number of functional groups is preferably 3 or more.

It is also preferable that the molecular weight of compound (b) divided by the number of functional groups is 350 or less. By defining the relationship between the molecular weight and the number of functional groups in this way, the reactivity of compound (b) with the isocyanate groups of urethane prepolymer (a) can be ensured.

The molecular weight of the compound (b) is preferably 1000 or less. Compound (b) having a molecular weight of 1000 or less is preferred in terms of compatibility when preparing a forming material as a solution together with the urethane prepolymer (a).

Examples of the compound (b) include polyhydric alcohols, polyamines, and compounds having a hydroxyl group and an amino group in the molecule.

Examples of polyhydric alcohols include bifunctional alcohols such as ethylene glycol, diethylene glycol, 1,3-butanediol, 1,4-butanediol, neopentyl glycol, 3-methyl-1,5-pentanediol, 2-butyl-2-ethyl-1,3-propanediol, 2,4-diethyl-1,5-pentanediol, 1,2-hexanediol, 1,6-hexanediol, 1,8-octanediol, 1,9-nonanediol, 2-methyl-1,8-octanediol, 1,8-decanediol, octadecanediol, and polypropylene glycol; trifunctional alcohols such as glycerin and trimethylolpropane; tetrafunctional alcohols such as pentaerythritol, hexanetriol, and sorbitol; and alkylene oxide (e.g., propylene oxide) adducts to the polyhydric alcohols such as polyoxypropylene glyceryl ether, polyoxypropylene trimethylolpropane ether, and polyoxypropylene sorbitol ether.

Examples of polyamines include ethylenediamine, propylenediamine, hexamethylenediamine, diethylenetriamine, triethylenetetramine, isophoronediamine, dicyclohexylmethane-4,4'-diamine, and dimer diamine.

Examples of compounds having a hydroxyl group and an amino group in the molecule include diamines having a hydroxyl group in the molecule, such as 2-hydroxyethylethylenediamine, 2-hydroxyethylpropylenediamine, di-2-hydroxyethylethylenediamine, di-2-hydroxyethylpropylenediamine, 2-hydroxypropylethylenediamine, and di-2-hydroxypropylethylenediamine;
Examples of the alkanolamines include ethanolamine, diethanolamine, and triethanolamine.

As the compound (b), it is preferable to use a polyhydric alcohol in order to prevent deterioration of the optical reliability of the polarizer, and in particular, trimethylolpropane is preferable in terms of reactivity with the urethane prepolymer (a).

The forming material contains the urethane prepolymer (a) as a main component. It is preferable that the urethane prepolymer (a) contains 50% by weight or more of the solid content of the forming material.

The blending ratio of the compound (b) to the urethane prepolymer (a) is preferably 5% by weight or more relative to the total weight (solid content ratio) of the urethane prepolymer (a) and the compound (b) being 100% by weight. The blending ratio of the compound (b) is preferably 10% by weight or more from the viewpoint of improving the film strength. On the other hand, if the blending ratio of the compound (b) is high, the optical reliability of the polarizer may deteriorate, so the blending ratio of the compound (b) is preferably 80% by weight or less, and more preferably 50% by weight or less.

The forming material may further use a reaction catalyst to increase the reactivity of the isocyanate group. There is no particular restriction on the reaction catalyst, but a tin-based catalyst or an amine-based catalyst is preferred. One or more reaction catalysts may be used. The amount of reaction catalyst used is usually 5 parts by weight or less per 100 parts by weight of the urethane prepolymer (a). If the amount of reaction catalyst is large, the crosslinking reaction speed increases and foaming of the forming material occurs. Even if the foamed forming material is used, sufficient adhesion cannot be obtained. Usually, when a reaction catalyst is used, 0.01 to 5 parts by weight, and more preferably 0.05 to 4 parts by weight, is preferred.

A reaction catalyst can be used to further increase the reactivity of the isocyanate group. There are no particular restrictions on the reaction catalyst, but tin-based catalysts or amine-based catalysts are preferred. One or more types of reaction catalyst can be used. The amount of reaction catalyst used is usually 5 parts by weight or less per 100 parts by weight of urethane prepolymer. If the amount of reaction catalyst is too large, the crosslinking reaction speed increases and foaming of the forming material occurs. Even if the foamed forming material is used, sufficient adhesion cannot be obtained. Usually, when a reaction catalyst is used, 0.01 to 5 parts by weight, and more preferably 0.05 to 4 parts by weight, are preferred.

As the tin catalyst, either inorganic or organic can be used, but organic catalysts are preferred. Examples of inorganic tin catalysts include stannous chloride and stannic chloride. As the organic tin catalyst, those having at least one organic group such as an aliphatic group or an alicyclic group having a skeleton such as a methyl group, an ethyl group, an ether group, or an ester group are preferred. Examples include tetra-n-butyltin, tri-n-butyltin acetate, n-butyltin trichloride, trimethyltin hydroxide, dimethyltin dichloride, and dibutyltin dilaurate.

There are no particular limitations on the amine catalyst. For example, those having at least one organic group such as an alicyclic group, such as quinoclidine, amidine, or diazabicycloundecene, are preferred. Other examples of amine catalysts include triethylamine. Other examples of reaction catalysts include cobalt naphthenate and benzyltrimethylammonium hydroxide.

The forming material is usually used as a solution containing the urethane prepolymer (a) and the compound (b). The solution may be a solvent-based solution or a water-based solution such as an emulsion, colloidal dispersion, or aqueous solution.

There are no particular limitations on the organic solvent, so long as it does not have a functional group having an active hydrogen reactive with an isocyanate group and dissolves the urethane prepolymer (a) and the compound (b) constituting the forming material uniformly. One or more organic solvents can be used in combination. Separate organic solvents can be used for the urethane prepolymer (a) and the compound (b). In this case, the forming material can be prepared by mixing the solutions after preparing each solution. The viscosity of the forming material can be adjusted by further adding an organic solvent to the prepared forming material. Furthermore, in the case of a solvent-based solution dissolved in an organic solvent, the following alcohols, water, etc. can be included as a solvent.

Organic solvents include aromatic hydrocarbons such as toluene and xylene; esters such as ethyl acetate and butyl acetate; aliphatic or alicyclic hydrocarbons such as hexane, cyclohexane and methylcyclohexane; halogenated alkanes such as 1,2-dichloroethane; ethers such as tert-butyl methyl ether; ketones such as methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, cyclopentanone and acetylacetone; etc.

When making it a water-based system, for example, alcohols such as n-butyl alcohol and isopropyl alcohol, and ketones such as acetone can be blended. When making it a water-based system, a dispersant can be used, or functional groups that are less reactive with isocyanate groups, such as carboxylates, sulfonates, and quaternary ammonium salts, or water-dispersible components such as polyethylene glycol can be introduced into the urethane prepolymer.

Examples of materials for forming the transparent layer other than the urethane prepolymer include cyanoacrylate-based forming materials, epoxy-based forming materials, and urethane acrylate-based forming materials.

The formation of the transparent layer can be appropriately selected depending on the type of the forming material, but for example, the forming material can be applied to a polarizer or the like and then cured, and the transparent layer can be obtained as a coating layer. Usually, after the application, the cured layer is formed by drying at about 30 to 100°C, preferably 50 to 80°C, for about 0.5 to 15 minutes. Furthermore, if the forming material contains an isocyanate component, an annealing treatment can be performed at about 30 to 100°C, preferably 50 to 80°C, for about 0.5 to 24 hours to promote the reaction.

<Image display panel, image display device>
The pressure-sensitive adhesive layer-attached polarizing film of the present invention can be applied to various image display panels, and the image display panel can be applied to conventional image display devices. The other configurations of the image display device are the same as those of conventional image display devices. Specific examples of image display devices to which the image display panel can be applied include liquid crystal display devices, electroluminescence (EL) displays, plasma displays (PDs), field emission displays (FEDs), and the like.

The polarizing film with adhesive layer of the present invention has a small variation ratio of surface resistance value, making it suitable for use in liquid crystal panels with built-in touch sensing function.

In addition to the above configuration, the liquid crystal panel can be provided with optical films such as retardation films, viewing angle compensation films, and brightness enhancement films as appropriate.

The liquid crystal layer is not particularly limited, and any type may be used, such as TN type, STN type, π type, VA type, IPS type, etc. The transparent substrate 9 (light source side) may be a transparent substrate, and the material is not particularly limited, but examples thereof include glass and transparent resin film substrates. Examples of transparent resin film substrates include those mentioned above.

The polarizing film with an adhesive layer that is conventionally used in this field can be used on the light source side of the liquid crystal layer, and the one described in this specification can also be suitably used.

Specific examples of the above-mentioned liquid crystal panel with built-in touch sensing function are shown, for example, in Figs. 6 to 8. Figs. 6 to 8 show an example in which the adhesive layer-attached polarizing film 1 shown in Fig. 1 is used on the viewing side of a liquid crystal cell as the adhesive layer-attached polarizing film of the present invention. That is, the one-sided protected polarizing film 11 and adhesive layer 21 in Fig. 1 are shown as the first polarizing film 11 and first adhesive layer 21 in Figs. 6 to 8.

Figure 6 shows a so-called in-cell type liquid crystal panel with built-in touch sensing function, which has a configuration from the viewing side of a first polarizing film 11/first adhesive layer 21/first transparent substrate 41/touch sensor section 5/liquid crystal layer 3/drive electrode/sensor section 6/second transparent substrate 42/second adhesive layer 22/second polarizing film 12. In the in-cell type liquid crystal panel with built-in touch sensing function of Figure 6, for example, the liquid crystal cell C has a touch sensor section 5 and a drive electrode/sensor section 6 within the first and second glass substrates 41 and 42 (within the liquid crystal cell) that sandwich the liquid crystal layer 3.

Also, FIG. 7 shows a modified example of a so-called in-cell type (semi-in-cell type) liquid crystal panel with built-in touch sensing function, which has a configuration from the viewing side of the first polarizing film 11/first adhesive layer 21/touch sensor section 5/first transparent substrate 41/liquid crystal layer 3/drive electrode and sensor section 6/second transparent substrate 42/second adhesive layer 22/second polarizing film 12. In the in-cell type liquid crystal panel with built-in touch sensing function of FIG. 7, for example, the liquid crystal cell C is on the outside of the first transparent substrate 41, and the touch sensor section 5 is in direct contact with the first adhesive layer 21, and the drive electrode and sensor section 6 is on the side of the second transparent substrate 42 within the first and second glass substrates 41 and 42 (within the liquid crystal cell) that sandwich the liquid crystal layer 3.

Also, FIG. 8 shows a so-called on-cell type liquid crystal panel with built-in touch sensing function, which has a configuration of, from the viewing side, first polarizing film 11/first adhesive layer 21/touch sensor section 5/driving electrode/sensor section 6/first transparent substrate 41/liquid crystal layer 3/driving electrode 7/second transparent substrate 42/second adhesive layer 22/second polarizing film 12. In the on-cell type liquid crystal panel with built-in touch sensing function of FIG. 8, for example, the liquid crystal cell C has a touch sensor section 5 and a driving electrode/sensor section 6 on the outside of the first transparent substrate 41, the touch sensor section 5 is in direct contact with the first adhesive layer 21, and has a driving electrode 7 on the side of the second transparent substrate 42 within the first and second glass substrates 41 and 42 (inside the liquid crystal cell) that sandwich the liquid crystal layer 3.

In a liquid crystal panel with built-in touch sensing function, when the touch sensor portion 5 of the liquid crystal cell C and the first adhesive layer 21 are in direct contact with each other, the antistatic function of the first adhesive layer 21 (containing an ionic compound) is likely to deteriorate, particularly in a humid environment. Therefore, the liquid crystal panel with built-in touch sensing function of the present invention is preferably applied to an in-cell type (modified example) liquid crystal panel with built-in touch sensing function shown in FIG. 7 or an on-cell type liquid crystal panel with built-in touch sensing function shown in FIG. 8, among the above examples.

The first polarizing film 11 arranged on the viewing side of the liquid crystal cell C and the second polarizing film 12 arranged on the opposite side to the viewing side can be used by laminating other optical films depending on the suitability of their respective locations. Examples of the other optical films include optical layers that may be used in the formation of liquid crystal displays, such as reflectors, anti-transmitting films, retardation films (including 1/2 and 1/4 wavelength plates), visual compensation films, and brightness enhancement films. These films can be used in one layer or two or more layers. Even when using these other optical films, it is preferable that the adhesive layer closest to the liquid crystal layer 3 is the first adhesive layer 21.

The liquid crystal layer 3 of the liquid crystal cell C is a liquid crystal layer containing liquid crystal molecules that are homogeneously oriented in the absence of an electric field, which is applicable to liquid crystal panels with built-in touch sensing functions. For example, an IPS type liquid crystal layer is preferably used as the liquid crystal layer 3. In addition, any type of liquid crystal layer can be used as the liquid crystal layer 3, such as TN type, STN type, π type, VA type, etc. The thickness of the liquid crystal layer is, for example, about 1.5 μm to 4 μm.

In the liquid crystal cell C, the first transparent substrate 41 and the second transparent substrate 42 can sandwich the liquid crystal layer 3 to form a liquid crystal cell. Depending on the form of the liquid crystal panel with built-in touch sensing function, a touch sensor section 5, a driving electrode/sensor section 6, a driving electrode 7, etc. are formed inside or outside the liquid crystal cell. In addition, a color filter substrate can be provided on the liquid crystal cell (first transparent substrate 41).

Examples of the material forming the transparent substrate include glass and polymer film. Examples of the polymer film include polyethylene terephthalate, polycycloolefin, polycarbonate, and the like. When the transparent substrate is formed of glass, the thickness is, for example, about 0.3 mm to 1 mm. When the transparent substrate is formed of a polymer film, the thickness is, for example, about 10 μm to 200 μm. The transparent substrate may have an easy-adhesion layer or a hard coat layer on its surface.

The touch sensor section 5 (capacitive sensor), the driving electrode/sensor section 6, and the driving electrode 7 are formed as a transparent conductive layer. The material of the transparent conductive layer is not particularly limited, and examples thereof include metals such as gold, silver, copper, platinum, palladium, aluminum, nickel, chromium, titanium, iron, cobalt, tin, magnesium, and tungsten, and alloys of these metals. The material of the transparent conductive layer includes metal oxides of indium, tin, zinc, gallium, antimony, zirconium, and cadmium, and specifically includes metal oxides consisting of indium oxide, tin oxide, titanium oxide, cadmium oxide, and mixtures thereof. In addition, other metal compounds consisting of copper iodide and the like are used. The metal oxide may further include oxides of metal atoms shown in the above group as necessary. For example, indium oxide (ITO) containing tin oxide, tin oxide containing antimony, and the like are preferably used, and ITO is particularly preferably used. It is preferable that ITO contains 80 to 99% by weight of indium oxide and 1 to 20% by weight of tin oxide.

There is no restriction on the location where the touch sensor layer 5 is formed in the liquid crystal cell C, and the touch sensor layer 5 is formed according to the form of the liquid crystal panel with built-in touch sensing function. For example, in Figs. 6 to 8, the touch sensor layer 5 is disposed between the first polarizing film 11 and the liquid crystal layer 3. The touch sensor layer 5 can be formed, for example, as a transparent electrode pattern on the first transparent substrate 41. For the driving electrode/sensor unit 6 and the driving electrode 7, transparent electrode patterns can be formed according to a conventional method according to the form of the liquid crystal panel with built-in touch sensing function. The transparent electrode pattern is usually electrically connected to a wiring line (not shown) formed at the end of the transparent substrate, and the wiring line is connected to a controller IC (not shown). The transparent electrode pattern can be any shape depending on the application, such as a comb shape, a stripe shape, or a diamond shape. The height of the transparent electrode pattern is, for example, 10 nm to 100 nm, and the width is 0.1 mm to 5 mm.

In addition, the LCD panel with built-in touch sensing function can use materials that form an LCD display device, such as a backlight or reflector in the lighting system, as appropriate.

The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. Note that all parts and percentages in each example are by weight. Unless otherwise specified below, all room temperature storage conditions are 23°C and 65% RH.

<Measurement of weight average molecular weight of (meth)acrylic polymer (A)>
The weight average molecular weight (Mw) of the (meth)acrylic polymer (A) was measured by gel permeation chromatography (GPC). The Mw/Mn ratio was also measured in the same manner.
Analytical equipment: Tosoh Corporation, HLC-8120GPC
Column: Tosoh Corporation, G7000H _XL + GMH _XL + GMH _XL
Column size: 7.8 mm diameter x 30 cm, total 90 cm
Column temperature: 40°C
Flow rate: 0.8 mL / min
Injection volume: 100 μL
Eluent: Tetrahydrofuran Detector: Differential refractometer (RI)
・Standard sample: polystyrene

<Production Example 1>
(Preparation of 40 μm TAC film with HC and 25 μm TAC film with HC)
A resin solution in which an ultraviolet-curable resin monomer or oligomer mainly composed of urethane acrylate is dissolved in butyl acetate (manufactured by DIC Corporation, product name: Unidic 17-806, solid content concentration: 80%) was added with 5 parts of a photopolymerization initiator (manufactured by BASF Corporation, product name: IRGACURE 907) and 0.1 parts of a leveling agent (manufactured by DIC Corporation, product name: GRANDIC PC4100) per 100 parts of solid content in the solution. Then, cyclopentanone and propylene glycol monomethyl ether were added to the solution in a ratio of 45:55 so that the solid content concentration in the solution was 36%, to prepare a hard coat layer forming material. The prepared hard coat layer forming material was applied onto TJ40UL (manufactured by Fujifilm Corporation, raw material: triacetyl cellulose polymer, thickness: 40 μm) so that the thickness of the hard coat layer after curing was 7 μm to form a coating film. Thereafter, the coating film was dried at 90° C. for 1 minute, and then irradiated with ultraviolet light from a high-pressure mercury lamp at an integrated light quantity of 300 mJ/cm ² to harden the coating film to form a hard coat layer (HC), thereby producing a 40 μm TAC film with HC.
Similarly, a hard coat layer (HC) having a thickness of 7 μm was formed on TJ25UL (manufactured by Fuji Film, raw material: triacetyl cellulose polymer, thickness: 25 μm) to prepare a 25 μm TAC film with HC.

<Production Example 2>
(Preparation of 30 μm acrylic film)
A 30 L kettle reactor equipped with a stirrer, a temperature sensor, a cooling tube, and a nitrogen inlet tube was charged with 8,000 g of methyl methacrylate (MMA), 2,000 g of methyl 2-(hydroxymethyl)acrylate (MHMA), 10,000 g of 4-methyl-2-pentanone (methyl isobutyl ketone, MIBK), and 5 g of n-dodecyl mercaptan. The mixture was heated to 105° C. while passing nitrogen through it, and when it was refluxed, 5.0 g of t-butylperoxyisopropyl carbonate (Kayacarvon BIC-7, manufactured by Kayaku Akzo Co., Ltd.) was added as a polymerization initiator. At the same time, a solution consisting of 10.0 g of t-butylperoxyisopropyl carbonate and 230 g of MIBK was added dropwise over 4 hours, while solution polymerization was carried out under reflux at about 105 to 120° C., and the mixture was further aged over 4 hours.
To the obtained polymer solution, 30 g of a stearyl phosphate/distearyl phosphate mixture (Phoslex A-18, Sakai Chemical Industry Co., Ltd.) was added, and a cyclization condensation reaction was carried out under reflux at about 90 to 120° C. for 5 hours. The obtained polymer solution was then introduced into a vent-type screw twin-screw extruder (φ=29.75 mm, L/D=30) with a barrel temperature of 260° C., a rotation speed of 100 rpm, a reduced pressure of 13.3 to 400 hPa (10 to 300 mmHg), one rear vent, and four fore vents at a processing rate of 2.0 kg/h in terms of resin amount, and further cyclization condensation reaction and devolatilization were carried out in this extruder, and transparent pellets of a lactone ring-containing polymer were obtained by extrusion.
The lactone ring-containing polymer thus obtained was subjected to dynamic TG measurement, and a mass loss of 0.17% by mass was detected. The lactone ring-containing polymer had a weight average molecular weight of 133,000, a melt flow rate of 6.5 g/10 min, and a glass transition temperature of 131° C.
The pellets obtained were mixed and extruded in a mass ratio of 90/10 with an acrylonitrile-styrene (AS) resin (TOYO ASAS20, manufactured by Toyo Styrene Co., Ltd.) using a single-screw extruder (screw diameter: 30 mm) to obtain transparent pellets. The glass transition temperature of the pellets obtained was 127° C.
The pellets were melt-extruded from a 400 mm wide coat hanger type T die using a 50 mmφ single screw extruder to produce a film with a thickness of 120 μm. The produced film was stretched 2.0 times in the vertical direction and 2.0 times in the horizontal direction at a temperature of 150 ° C. using a biaxial stretching device to obtain a stretched film (30 μm acrylic film) with a thickness of 30 μm. The optical properties of this stretched film were measured to find that the total light transmittance was 93%, the in-plane retardation Δnd was 0.8 nm, and the thickness direction retardation Rth was 1.5 nm.

<Preparation of Polarizing Film (1)>
A polyvinyl alcohol film having a thickness of 45 μm was stretched to 3 times between rolls having different speed ratios while being dyed in a 0.3% concentration iodine solution at 30° C. for 1 minute. Thereafter, the film was stretched to 6 times the total stretch ratio while being immersed in an aqueous solution containing 4% concentration boric acid and 10% concentration potassium iodide at 60° C. for 0.5 minutes. Next, the film was washed by immersing in an aqueous solution containing 1.5% concentration potassium iodide at 30° C. for 10 seconds, and then dried at 50° C. for 4 minutes to obtain a polarizer having a thickness of 18 μm. A saponified HC-attached 40 μm TAC film (triacetyl cellulose film side) obtained in Production Example 1 was attached to one side of the polarizer, and a 30 μm acrylic film obtained in Production Example 2 was attached to the other side with a polyvinyl alcohol-based adhesive to produce a polarizing film (1).

<Preparation of Polarizing Film (2)>
(Preparation of Thin Polarizer A)
One side of an amorphous isophthalic acid copolymerized polyethylene terephthalate (IPA copolymerized PET) film (thickness: 100 μm) substrate having a water absorption rate of 0.75% and a Tg of 75° C. was subjected to a corona treatment, and an aqueous solution containing polyvinyl alcohol (degree of polymerization 4200, degree of saponification 99.2 mol%) and acetoacetyl-modified PVA (degree of polymerization 1200, degree of acetoacetyl modification 4.6%, degree of saponification 99.0 mol% or more, manufactured by Nippon Synthetic Chemical Industry Co., Ltd., product name "GOHSEFYMER Z200") in a ratio of 9:1 was applied to the corona-treated surface and dried at 25° C. to form a PVA-based resin layer having a thickness of 11 μm, and a laminate was produced.
The obtained laminate was uniaxially stretched at its free end by 2.0 times in the longitudinal direction (machine direction) between rolls having different peripheral speeds in an oven at 120° C. (auxiliary air stretching treatment).
Next, the laminate was immersed in an insolubilizing bath (a boric acid aqueous solution obtained by mixing 4 parts by weight of boric acid with 100 parts by weight of water) at a liquid temperature of 30° C. for 30 seconds (insolubilizing treatment).
Next, the polarizing plate was immersed in a dye bath at a liquid temperature of 30° C. while adjusting the iodine concentration and immersion time so that the polarizing plate had a predetermined transmittance. In this example, the polarizing plate was immersed for 60 seconds in an iodine aqueous solution obtained by mixing 0.2 parts by weight of iodine and 1.0 part by weight of potassium iodide with respect to 100 parts by weight of water (dyeing treatment).
Next, the piece was immersed in a crosslinking bath (a boric acid aqueous solution obtained by mixing 3 parts by weight of potassium iodide and 3 parts by weight of boric acid with 100 parts by weight of water) at a liquid temperature of 30° C. for 30 seconds (crosslinking treatment).
Thereafter, the laminate was immersed in an aqueous boric acid solution (an aqueous solution obtained by blending 4 parts by weight of boric acid and 5 parts by weight of potassium iodide with respect to 100 parts by weight of water) at a liquid temperature of 70° C., and uniaxially stretched in the longitudinal direction (longitudinal direction) between rolls having different peripheral speeds so that the total stretch ratio was 5.5 times (underwater stretching treatment).
Thereafter, the laminate was immersed in a cleaning bath (an aqueous solution obtained by mixing 4 parts by weight of potassium iodide with 100 parts by weight of water) at a liquid temperature of 30° C. (cleaning treatment).
In this manner, an optical film laminate including a polarizer having a thickness of 5 μm was obtained.

(Preparation of adhesive to be applied to transparent protective film)
An ultraviolet-curing adhesive was prepared by mixing 45 parts by weight of acryloylmorpholine, 45 parts of 1,9-nonanediol diacrylate, 10 parts of an acrylic oligomer obtained by polymerizing a (meth)acrylic monomer (ARUFONUP1190, manufactured by Toagosei Co., Ltd.), 3 parts of a photopolymerization initiator (IRGACURE 907, manufactured by BASF Corporation), and 1.5 parts of a polymerization initiator (KAYACURE DETX-S, manufactured by Nippon Kayaku Co., Ltd.).

<Preparation of Polarizing Film (2)>
The ultraviolet-curable adhesive was applied to the surface of the polarizer A of the optical film laminate so that the thickness of the adhesive layer after curing was 1 μm, and the HC-attached 25 μm TAC film (triacetyl cellulose film side) obtained in the above Production Example 1 was laminated thereon, and then ultraviolet rays were irradiated as active energy rays to cure the adhesive. The ultraviolet irradiation was performed using a gallium-encapsulated metal halide lamp, an irradiation device: Light HAMMER10 manufactured by Fusion UV Systems, Inc., a bulb: V bulb, a peak illuminance: 1600 mW/cm ² , and an integrated irradiation amount of 1000/mJ/cm ² (wavelength 380 to 440 nm), and the illuminance of the ultraviolet rays was measured using a Sola-Check system manufactured by Solatell. Next, the amorphous PET substrate was peeled off to produce a polarizing film (2) using a thin polarizer. The optical properties of the resulting polarizing film were a single transmittance of 42.8% and a polarization degree of 99.99%.

<Preparation of Transparent Layer-Attached Polarizing Film (2)>
The transparent layer forming material described below was applied to the polarizer surface of the above polarizing film (2) (the polarizer surface on which the HC-attached 25 μm TAC film was not provided) using a bar coater, and then heat treatment was performed at 60° C. for 12 hours to form a urethane resin layer having a thickness of 3 μm, thereby producing a polarizing film with a transparent layer (2).

<Transparent layer forming material>
As the solution of urethane prepolymer (a), a 75% ethyl acetate solution of a urethane prepolymer made of tolylene diisocyanate (TDI) and trimethylolpropane (TMP) (manufactured by Tosoh Corporation, product name "Coronate L") was used.
Separately, trimethylolpropane was dissolved in cyclopentanone to a solid content concentration of 10% to prepare a trimethylolpropane solution.
To 100 parts of a 75% ethyl acetate solution of the above urethane prepolymer (manufactured by Tosoh Corporation, product name "Coronate L"), the above trimethylolpropane solution was added so that the solids ratio of urethane prepolymer:trimethylolpropane was 90:10, and 0.1 parts of a dioctyltin dilaurate catalyst (manufactured by Tokyo Fine Chemical Co., Ltd., product name "Envirizer OL-1") was added, and a forming material (coating liquid) was prepared by adjusting the solids concentration to 10% using methyl isobutyl ketone as a solvent.

Example 1
(Preparation of Acrylic Polymer (A))
A monomer mixture containing 78.9 parts of butyl acrylate, 16 parts of phenoxyethyl acrylate, 5 parts of acrylic acid, and 0.1 parts of 4-hydroxybutyl acrylate was charged into a four-neck flask equipped with a stirring blade, a thermometer, a nitrogen gas inlet tube, and a cooler. Furthermore, 0.1 parts of 2,2'-azobisisobutyronitrile as a polymerization initiator was charged together with 100 parts of ethyl acetate per 100 parts of the monomer mixture (solid content), and nitrogen gas was introduced while gently stirring to replace the atmosphere with nitrogen. The liquid temperature in the flask was kept at about 55°C, and a polymerization reaction was carried out for 8 hours to prepare a solution of an acrylic polymer having a weight average molecular weight (Mw) of 2.2 million and Mw/Mn = 4.0.

(Preparation of Pressure-Sensitive Adhesive Composition)
A solution of an acrylic pressure-sensitive adhesive composition was prepared by blending 10 parts of lithium bis(trifluoromethanesulfonyl)imide, 0.6 parts of an isocyanate crosslinking agent (Tosoh's Coronate L, trimethylolpropane tolylene diisocyanate), 0.1 parts of benzoyl peroxide (NOF Corporation's Niper BMT), and 0.3 parts of an epoxy group-containing silane coupling agent (Shin-Etsu Chemical Co., Ltd.: X-41-1056) with respect to 100 parts of the solid content of the acrylic polymer solution obtained above.

(Preparation of Polarizing Film with Pressure-Sensitive Adhesive Layer)
Next, the solution of the acrylic pressure-sensitive adhesive composition was applied to one side of a polyethylene terephthalate film (separator film: MRF38, manufactured by Mitsubishi Chemical Polyester Film Co., Ltd.) treated with a silicone-based release agent so that the thickness of the pressure-sensitive adhesive layer after drying would be 20 μm, and the film was dried at 155° C. for 1 minute to form a pressure-sensitive adhesive layer on the surface of the separator film. Next, the pressure-sensitive adhesive layer formed on the separator film was transferred to the acrylic film side of the polarizing film (1) prepared above to prepare a pressure-sensitive adhesive layer-attached polarizing film.

Examples 2 to 10, Comparative Examples 1 and 2
In Example 1, as shown in Table 1, the types and the ratios of the monomers used in the preparation of the acrylic polymer (A) were changed, and the production conditions were controlled to prepare solutions of the acrylic polymer (A) shown in Table 1.

Also, as shown in Table 1, a polarizing film with an adhesive layer was produced in the same manner as in Example 1, except that the type of polarizing film and the type or blending ratio of the ionic compound (B) used in the preparation of the adhesive composition were changed as shown in Table 1. When the polarizing film (2) was used as the polarizing film, the adhesive layer shown in Table 1 was formed on the polarizer surface of the polarizing film (2) (the polarizer surface on which the 25 μm TAC film with HC was not provided), and when the polarizing film with a transparent layer (2) was used, the adhesive layer shown in Table 1 was formed on the transparent layer of the polarizing film with a transparent layer.

The following evaluations were carried out on the polarizing films with adhesive layers obtained in the above examples, comparative examples, and reference examples. The evaluation results are shown in Table 1.

<Surface resistance value (Ω/□): Conductive>
After peeling off the separator film from the pressure-sensitive adhesive layer-attached polarizing film, the surface resistance of the pressure-sensitive adhesive layer surface was measured, and this was taken as the surface resistance of the pressure-sensitive adhesive layer-attached polarizing film. The measurement was performed using MCP-HT450 manufactured by Mitsubishi Chemical Analytech Co., Ltd.

<Creep value measurement>
The upper end 10 mm x 10 mm of the adhesive layer-attached polarizing film (adhesive layer thickness: 20 μm) cut to a size of 10 mm x 30 mm was attached to a SUS plate via the adhesive layer, and autoclaved for 15 minutes under conditions of 50 ° C. and 5 atm. A precision hot plate installed so that the heating surface was vertical was heated to 85 ° C., and the SUS plate to which the adhesive layer-attached polarizing film was attached was installed so that the surface to which the adhesive layer was not attached was in contact with the heating surface of the hot plate. Five minutes after the SUS plate started to be heated at 85 ° C., a load of 500 g was applied to the lower end of the adhesive layer-attached polarizing film and left for 1 hour. The deviation between the adhesive layer-attached polarizing film and the SUS plate before and after the load was applied was measured, and the deviation was taken as the creep value (μm) at 85 ° C.

<Durability test>
The prepared polarizing film with adhesive layer was cut to a size of 300 x 220 mm so that the absorption axis of the polarizing film was parallel to the long side. The polarizing film with adhesive layer was attached to an alkali-free glass (manufactured by Corning, product name "EG-XG") of 350 x 250 mm x 0.7 mm thickness using a laminator. Then, the adhesive layer was attached to the glass by autoclaving at 50°C and 0.5 MPa for 15 minutes. The sample thus treated was treated in an atmosphere of 85°C for 500 hours, and then treated in an atmosphere of 60°C/95% RH for 500 hours, and the appearance of the sample was visually evaluated according to the following criteria.
(Evaluation criteria)
A: No change in appearance such as foaming or peeling was observed.
B: There is slight peeling or foaming at the edges, but no practical problems.
C: Peeling or bubbling at the edge, but no practical problem unless for special purposes.
D: There is significant peeling at the edge, which is problematic for practical use.

<ESD Test>
After peeling off the separator film from the adhesive layer-attached polarizing film, it was attached to the viewing side of an in-cell type liquid crystal cell to prepare a liquid crystal panel with a built-in touch sensing function. That is, the obtained adhesive layer-attached polarizing film was attached to the first transparent substrate of the in-cell type liquid crystal cell shown in Figure 6 to form a first adhesive layer and a first polarizing film. An ESD (electrostatic discharge) gun (10 kV) was fired at the polarizing film surface of the liquid crystal panel, and the time until the white spots caused by electricity disappeared was measured and judged according to the following criteria.
(Evaluation criteria)
A: Within 1 second.
B: More than 1 second to less than 10 seconds.
C: More than 10 seconds.

<Evaluation of irregular cracks>
The pressure-sensitive adhesive layer-attached polarizing film thus produced was processed into the shape shown in FIG. 5 using a _CO2 laser processing machine Spirit (manufactured by GCC, 30 W) under conditions of speed 10, laser output 35, and 400 ppi.
The pressure-sensitive adhesive layer-attached polarizing film that had been subjected to the irregular shape processing was attached to a non-alkali glass (manufactured by Corning Incorporated, product name "EG-XG") of 350 mm x 250 mm x 0.7 mm thickness, and then autoclaved at 50°C and 0.5 MPa for 15 minutes to adhere the pressure-sensitive adhesive layer to the glass. The thus-treated sample was placed in a heat cycle test tank, and the presence or absence of cracks occurring in the irregular shape portion at the 100th and 200th cycles was visually confirmed. Five identical samples were placed for each condition, and the number of samples that had cracks is shown in Table 1.
(Test condition)
Temperature conditions: -40°C (held for 30 minutes) ⇒ 85°C (held for 30 minutes) is repeated as one cycle. Temperature increase/decrease rate: 10°C/min.

<Evaluation of color loss at edges>
The polarizing film with one side protected (or both sides protected) with the adhesive layer obtained in the examples and comparative examples was cut to 50 mm x 50 mm, and after peeling off the separator film, the film was attached to an alkali glass (microslide glass, manufactured by Matsunami Glass Co., Ltd.) with a thickness of 1.2 to 1.5 mm via the adhesive layer to prepare a sample. The sample was kept in a high-temperature and high-humidity environment of 60°C and 90% RH for 500 hours, and the edge color loss was measured under the following conditions using a differential interference microscope (manufactured by Olympus, product name "MX-61L"). The edge color loss was determined by the distance between the corner and the closest point to the center of the diagonal line of the four corners of the sample, and the average value of the four corners was determined as the edge color loss of the sample.
Apparatus: Olympus MX-61L
Measurement conditions Lens magnification: 5x ISO: 200
Shutter speed: 1/100
Reflected light amount: Scale 0
White balance: Auto Transmitted light controller: LG-PS2
Amount of transmitted light: 5
Transmitted light polarization direction: Crossed Nicol direction with respect to the transmission axis of the polarizing film

In Table 1,
BA is butyl acrylate,
PEA is phenoxyethyl acrylate;
AA is acrylic acid,
NVP is N-vinyl-2-pyrrolidone;
HBA is 4-hydroxybutyl acrylate;
The isocyanate-based agent is an isocyanate crosslinking agent (Coronate L, trimethylolpropane tolylene diisocyanate, manufactured by Tosoh Corporation);
BPO is benzoyl peroxide (Niper BMT manufactured by Nippon Oil & Fats Co., Ltd.);
Li-TFSI is lithium bis(trifluoromethanesulfonyl)imide;
K-bis(trifluoromethanesulfonyl)imide potassium TMPA-TFSI is trimethylpropylammonium bis(trifluorosulfonylimide),
EMP-TFSI is ethylmethylpyrrolidinium bis(trifluorosulfonylimide);
TBMA-TFSI is tributylmethylammonium bis(fluorosulfonylimide);
MTOA-TFSI stands for methyltrioctylammonium bis(trifluorosulfonylimide).

Reference Signs List 1: Polarizing film with adhesive layer 11: One-sided protected polarizing film a: Polarizer b: Protective film c: Transparent layer 21: Adhesive layer 2: Chipped portion (irregularly shaped portion)
W1 Length of the chipped portion D Maximum depth of the chipped portion from W1 θ1 Angle between two straight lines R1 Radius of curvature of curve 11, 12 First and second polarizing films 21, 22 First and second adhesive layers 3 Liquid crystal layer 41, 42 First and second transparent substrates 5 Touch sensor section 6 Driving electrode/sensor section 7 Driving electrode C Liquid crystal cell

Claims (13)

A polarizing film having a polarizer and a protective film on one or both sides of the polarizer, and a pressure-sensitive adhesive layer-attached polarizing film having a pressure-sensitive adhesive layer (excluding the case where the pressure-sensitive adhesive layer-attached polarizing film has a heat insulating layer having a thermal conductivity of 0.20 W/(m K) or less),
The pressure-sensitive adhesive layer-attached polarizing film has an irregularly shaped portion other than a rectangular shape when viewed from above,
The pressure-sensitive adhesive layer comprises a (meth)acrylic polymer (A) {provided that the (meth)acrylic polymer (A) excludes the following acrylic triblock copolymer (I) satisfying requirements (E1), (E2), (E3) and (E4).
Acrylic triblock copolymer (I):
(E1) A compound represented by the following general formula (1):
A1-B-A2 (1)
(wherein A1 and A2 each independently represent a methacrylic acid alkyl ester polymer block having no functional group reactive with an isocyanate compound and having a glass transition temperature of 100° C. or higher, and B represents an acrylic acid alkyl ester polymer block having no functional group reactive with an isocyanate compound and having a glass transition temperature of −20° C. or lower);
(E2) the content of polymer block B is 40 to 95 mass%;
(E3) the weight average molecular weight (Mw) is 50,000 to 300,000; and
( E4) the molecular weight distribution (Mw/Mn) is 1.0 to 1.5.} and an ionic compound (B) having a molecular weight of a cationic component of 210 or less. The polarizing film with a pressure-sensitive adhesive layer according to claim 1, characterized in that the cationic component is a lithium ion. The polarizing film with a pressure-sensitive adhesive layer according to claim 1 or 2, characterized in that it contains 0.1 to 13 parts by weight of the ionic compound (B) per 100 parts by weight of the (meth)acrylic polymer (A). The polarizing film with a pressure-sensitive adhesive layer according to any one of claims 1 to 3, characterized in that the protective film is any one selected from a cellulose resin film and a (meth)acrylic resin film. The pressure-sensitive adhesive layer-attached polarizing film according to any one of claims 1 to 4, characterized in that the thickness of the polarizer is 10 μm or less. The polarizing film with a pressure-sensitive adhesive layer according to any one of claims 1 to 5, characterized in that the polarizing film is a one-sided protected polarizing film having a polarizer and a protective film on only one side of the polarizer. The polarizing film with adhesive layer according to claim 6, characterized in that the one-sided protective polarizing film has the adhesive layer on the other side of the polarizer. The polarizing film with adhesive layer according to any one of claims 7 to 9, characterized in that the adhesive layer is provided on the other side of the polarizer in the one-sided protective polarizing film via a transparent layer having a thickness of 10 μm or less that is formed directly on the polarizer. The polarizing film with a pressure-sensitive adhesive layer according to claim 8, characterized in that the transparent layer is a cured product of a forming material containing a urethane prepolymer, which is a reaction product of an isocyanate compound and a polyhydric alcohol. The polarizing film with an adhesive layer according to any one of claims 1 to 9, characterized in that the adhesive layer has a creep value of 120 μm or less at 85°C. An image display panel comprising a polarizing film with a pressure-sensitive adhesive layer according to any one of claims 1 to 10. The image display panel according to claim 11, characterized in that the adhesive layer of the adhesive layer-attached polarizing film is attached to a liquid crystal cell with a built-in touch sensing function having a liquid crystal layer and a touch sensor section. An image display device having the image display panel according to claim 11 or 12.

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