JP7587367B2 - Polarizing film with pressure-sensitive adhesive layer, image display panel, method for producing image display panel, and pressure-sensitive adhesive layer - Google Patents

Description

The present invention relates to a polarizing film with an adhesive layer, an image display panel, a method for manufacturing an image display panel, and an adhesive layer.

An image display panel provided in an image display device such as a liquid crystal display device has a structure in which, for example, a polarizing film is attached to a transparent substrate via an adhesive layer. A conductive layer containing a metal oxide such as indium tin oxide (ITO) may be provided on the surface of the transparent substrate to prevent charging of the image display device. When a conductive layer is provided on the surface of the transparent substrate, the adhesive layer is usually in direct contact with the conductive layer in the image display panel.

When manufacturing an image display panel, for example, a polarizing film with an adhesive layer, which includes an adhesive layer and a polarizing film, is attached to a transparent substrate. At this time, problems may occur such as the attachment position of the polarizing film with an adhesive layer being shifted or foreign matter being mixed in between the polarizing film with an adhesive layer and the transparent substrate. In this case, in order to improve the productivity of the image display panel, it is desirable to peel the polarizing film with an adhesive layer from the transparent substrate and reuse the member. Therefore, it is required that the polarizing film with an adhesive layer can be easily peeled off from the transparent substrate. In this specification, the ease of peeling the polarizing film with an adhesive layer from the transparent substrate or the conductive layer is sometimes expressed as the "reworkability of the adhesive layer."

Patent No. 6071459

When the moisture content of the polarizing film is large, the optical properties of the image display device tend to deteriorate when the image display device is used in a high-temperature environment (for example, in an environment with a temperature higher than 95°C) (for example, Patent Document 1). The deterioration of optical properties in a high-temperature environment is particularly noticeable when the polarizer in the polarizing film contains polyvinyl alcohol. Therefore, when it is expected that the image display device will be used in a high-temperature environment, for example, when the image display device is used as an in-vehicle display, it is necessary to heat treat (preheat) the polarizing film with the adhesive layer at a temperature of about 70°C to 95°C at the stage when the polarizing film with the adhesive layer is attached to the transparent substrate, thereby reducing the moisture content of the polarizing film in advance.

However, this preheating can damage the polarizing film or the transparent substrate. Therefore, it is required that the reworkability of the adhesive layer is maintained so that the polarizing film with the adhesive layer can be peeled off from the transparent substrate even after preheating. However, the composition of the adhesive layer in the polarizing film with the adhesive layer is usually adjusted so that the adhesion is improved in a high temperature environment. Therefore, when the above preheating is performed, the adhesion of the adhesive layer tends to improve and the reworkability of the adhesive layer tends to decrease. According to the study by the present inventors, the decrease in reworkability is remarkable when the adhesive layer is in direct contact with a conductive layer, especially an ITO layer.

According to the inventors' investigations, if an excessive amount of a compound that improves the reworkability of the adhesive layer is added to the adhesive layer, it may be possible to suppress the deterioration of the reworkability of the adhesive layer due to preheating. However, in this case, the durability of the adhesive layer in a high-temperature environment tends to decrease significantly.

The present invention aims to provide a polarizing film with an adhesive layer that maintains reworkability after preheating even when attached to a conductive layer and has an adhesive layer that is durable in high-temperature environments.

The present invention relates to
A polarizing film with a pressure-sensitive adhesive layer, comprising a polarizing film and a pressure-sensitive adhesive layer formed from a pressure-sensitive adhesive composition,
The pressure-sensitive adhesive composition contains a compound (C) having an acidic group or an acid anhydride group and a polyether compound (D),
The pressure-sensitive adhesive layer has an adhesive strength P ₈₅ of 10.0 N/25 mm or less as determined by the following Test 1, and an adhesive strength P ₁₀₅ of more than 10.0 N/25 mm as determined by the following Test 2, thereby providing a polarized film with a pressure-sensitive adhesive layer.
Test 1: The adhesive layer attached to the indium tin oxide layer of glass with an indium tin oxide layer is subjected to a heat treatment at 85° C. for 5 hours. The force (adhesive strength P ₈₅ ) required to peel the adhesive layer from the indium tin oxide layer is measured at a peel speed of 300 mm/min and a peel angle of 90°.
Test 2: The adhesive layer attached to the indium tin oxide layer of the indium tin oxide layer-coated glass is subjected to a heat treatment at 105° C. for 24 hours. The force (adhesive strength P ₁₀₅ ) required to peel the adhesive layer from the indium tin oxide layer is measured at a peel speed of 300 mm/min and a peel angle of 90°.

Further, the present invention relates to
The above-mentioned polarizing film with a pressure-sensitive adhesive layer,
A conductive layer including a metal oxide;
A transparent substrate;
Equipped with
The pressure-sensitive adhesive layer is in direct contact with the conductive layer.

Further, the present invention relates to
A method for manufacturing the image display panel, comprising the steps of:
and performing a first heat treatment on the pressure-sensitive adhesive layer at 70° C. to 95° C. in a state in which the pressure-sensitive adhesive layer-attached polarizing film is attached to the conductive layer.

Further, the present invention relates to
A pressure-sensitive adhesive layer formed from a pressure-sensitive adhesive composition,
The pressure-sensitive adhesive composition contains a compound (C) having an acidic group or an acid anhydride group and a polyether compound (D),
A pressure-sensitive adhesive layer is provided which has an adhesive strength P ₈₅ determined by the following Test 1 of 10.0 N/25 mm or less and an adhesive strength P ₁₀₅ determined by the following Test 2 of more than 10.0 N/25 mm.
Test 1: The adhesive layer attached to the indium tin oxide layer of glass with an indium tin oxide layer is subjected to a heat treatment at 85° C. for 5 hours. The force (adhesive strength P ₈₅ ) required to peel the adhesive layer from the indium tin oxide layer is measured at a peel speed of 300 mm/min and a peel angle of 90°.
Test 2: The adhesive layer attached to the indium tin oxide layer of the indium tin oxide layer-coated glass is subjected to a heat treatment at 105° C. for 24 hours. The force (adhesive strength P ₁₀₅ ) required to peel the adhesive layer from the indium tin oxide layer is measured at a peel speed of 300 mm/min and a peel angle of 90°.

According to the present invention, it is possible to provide a polarizing film with an adhesive layer that maintains reworkability after preheating even when attached to a conductive layer, and has an adhesive layer that is durable in high-temperature environments.

1 is a cross-sectional view of a polarizing film with a pressure-sensitive adhesive layer according to one embodiment of the present invention. FIG. 2 is a diagram for explaining the characteristics of a pressure-sensitive adhesive layer included in a pressure-sensitive adhesive layer-attached polarizing film. 1 is a cross-sectional view of an image display panel according to one embodiment of the present invention. FIG. 11 is a cross-sectional view showing a modified example of the image display panel.

The present invention will be described in detail below, but the following description is not intended to limit the present invention to a specific embodiment.

(Embodiment of Polarizing Film with Pressure-Sensitive Adhesive Layer)
As shown in Fig. 1, a pressure-sensitive adhesive layer-attached polarizing film 10 of the present embodiment includes a pressure-sensitive adhesive layer 1 and a polarizing film 2. The pressure-sensitive adhesive layer 1 is in direct contact with the polarizing film 2, for example. The surface of the pressure-sensitive adhesive layer 1 is exposed to the outside of the pressure-sensitive adhesive layer-attached polarizing film 10, for example.

In the pressure-sensitive adhesive layer-attached polarizing film 10, the adhesive strength P ₈₅ determined by test 1 for the pressure-sensitive adhesive layer 1 is 10.0 N/25 mm or less, and the adhesive strength P ₁₀₅ determined by test 2 is greater than 10.0 N/25 mm.

Test 1 is performed by the following method. First, the polarizing film 10 with the adhesive layer is cut into a strip of 150 mm length x 25 mm width to prepare a test piece. Next, a glass with an indium tin oxide (ITO) layer is prepared. The glass with the ITO layer has, for example, an alkali-free glass and an ITO layer in contact with the alkali-free glass. The alkali-free glass is glass that does not substantially contain an alkali component (alkali metal oxide), and in detail, the weight ratio of the alkali component in the glass is, for example, 1000 ppm or less, and further 500 ppm or less. The alkali-free glass is, for example, plate-shaped and has a thickness of 0.5 mm or more. The ITO layer is, for example, composed of only substantially non-crystalline (amorphous) ITO. However, the ITO layer may contain impurities other than ITO. The ITO layer can be formed on the surface of the alkali-free glass by a physical deposition method such as a sputtering method.

Next, the test piece is attached to the surface of the ITO layer of the ITO-layered glass by the adhesive layer 1. The attachment of the test piece to the ITO layer is performed, for example, using a laminator, so as not to allow air bubbles to be mixed between the ITO layer and the adhesive layer 1. After the test piece is attached, it is placed in an autoclave at 50°C and 5 atm (absolute pressure) for 15 minutes to homogenize the bonding between the ITO layer and the adhesive layer 1, and the adhesive layer 1 is adhered to the ITO layer. Next, the test piece (adhesive layer 1) is subjected to a heat treatment for 5 hours under atmospheric pressure at 85°C. Next, the test piece is left in an atmosphere at room temperature (for example, 23°C), and the temperature of the test piece is lowered to room temperature. The test piece is peeled off from the ITO layer at a peeling speed of 300 mm/min and a peeling angle of 90° (measurement length 80 mm). At this time, the force required to peel off the test piece from the ITO layer is measured once at intervals of 0.5 s. The average of the measurements obtained is identified as adhesion _P85 .

Test 2 can be carried out in the same manner as Test 1, except that the heat treatment after homogenizing the bond between the ITO layer and the adhesive layer 1 in the autoclave is carried out in an atmospheric pressure atmosphere at 105°C for 24 hours.

According to the study by the present inventors, when the adhesive strength P ₈₅ is 10.0 N/25 mm or less, the reworkability of the adhesive layer 1 tends to be sufficiently maintained after preheating. The adhesive strength P ₈₅ is preferably 9.0 N/25 mm or less, more preferably 8.0 N/25 mm or less, even more preferably 7.0 N/25 mm or less, and particularly preferably 6.0 N/25 mm or less. From a practical viewpoint, the lower limit of the adhesive strength P ₈₅ is, for example, 3.0 N/25 mm.

According to the study by the present inventors, when the adhesive strength P ₁₀₅ is greater than 10.0 N/25 mm, the adhesive layer 1 tends to have sufficient durability in a high temperature environment. The adhesive strength P ₁₀₅ is preferably 11.0 N/25 mm or more, more preferably 12.0 N/25 mm or more, even more preferably 13.0 N/25 mm or more, and particularly preferably 14.0 N/25 mm or more. The upper limit of the adhesive strength P ₁₀₅ is not particularly limited, and is, for example, 30.0 N/25 mm.

Furthermore, in the polarizing film 10 with the adhesive layer, the adhesive layer 1 may have an adhesive strength P ₀ of 10.0 N/25 mm or less as determined by Test 3. Test 3 may be performed in the same manner as Test 1, except that the heat treatment is not performed after the ITO layer and the adhesive layer 1 are homogenized in an autoclave. The adhesive strength P ₀ is preferably 9.0 N/25 mm or less, more preferably 8.0 N/25 mm or less, even more preferably 7.0 N/25 mm or less, and particularly preferably 6.0 N/25 mm or less. The lower limit of the adhesive strength P ₀ is, for example, 3.0 N/25 mm from a practical viewpoint.

[Adhesive layer]
The pressure-sensitive adhesive layer 1 is formed from a pressure-sensitive adhesive composition. The pressure-sensitive adhesive composition contains a compound (C) having an acidic group or an acid anhydride group and a polyether compound (D), and further contains, for example, a base polymer. The "base polymer" is, for example, a polymer contained in the largest amount by weight in the pressure-sensitive adhesive composition, and functions as a component that contributes to the adhesiveness of the pressure-sensitive adhesive layer 1.

<Compound (C)>
The compound (C) is, for example, a low molecular weight compound or an oligomer. The acidic group of the compound (C) is, for example, a carboxyl group or a mercapto group, and is preferably a carboxyl group. The acidic group of the compound (C) may be a group generated by hydrolysis of an acid anhydride group. Specific examples of the acid anhydride group include carboxylic acid anhydride groups such as succinic anhydride group, phthalic anhydride group, and maleic anhydride group, and is preferably a succinic anhydride group. The total value of the content of the acidic group and the content of the acid anhydride group in the compound (C) is not particularly limited, and is, for example, 5.0 wt% to 50 wt%, and preferably 8.3 wt% to 40 wt%.

Compound (C) may contain a silicon atom, and may further contain a hydrolyzable group (h1) bonded to the silicon atom. The hydrolyzable group (h1) can form a siloxane bond, for example, by hydrolysis and/or condensation. Examples of the hydrolyzable group (h1) include a halogen atom, an alkoxy group, an acyloxy group, an alkenyloxy group, a carbamoyl group, an amino group, an aminooxy group, and a ketoximate group. When the hydrolyzable group (h1) has carbon atoms, the number of carbon atoms is, for example, 10 or less, preferably 6 or less, and more preferably 4 or less. In particular, an alkoxy group or an alkenyloxy group having 4 or less carbon atoms is preferred, and a methoxy group or an ethoxy group is particularly preferred. The content of the hydrolyzable group (h1) in compound (C) is, for example, 10 wt % or more, preferably 13 wt % to 50 wt %, and more preferably 13 wt % to 49 wt %.

Compound (C) may contain functional groups other than the acidic group, the acid anhydride group, and the hydrolyzable group (h1), but it is preferable that it does not contain any other functional groups. As an example, compound (C) does not contain a polyether group.

The compound (C) includes, for example, at least one selected from the group consisting of an alkoxysilane compound (S1) having an acidic group or an acid anhydride group, an organopolysiloxane compound (S2) having an acidic group or an acid anhydride group, and a hydrolysis condensate thereof, and preferably includes an organopolysiloxane compound (S2).

The alkoxysilane compound (S1) is represented, for example, by the following formula (1).
R ¹ R ² _a Si(OR ³ ) _3-a (1)

In formula (1), R ¹ is an organic group having 1 to 20 carbon atoms and having an acidic group or an acid anhydride group. This organic group may be linear, branched, or cyclic. R ² 's are each independently a hydrogen atom or a monovalent hydrocarbon group having 1 to 20 carbon atoms which may be substituted with a halogen atom. R ³ 's are each independently an alkyl group having 1 to 10 carbon atoms, preferably a methyl group or an ethyl group. a is 0 or 1.

From the viewpoint of availability of the alkoxysilane compound (S1), R ¹ is preferably an organic group represented by the following formula (2).

In formula (2), A is a linear or branched alkylene or alkenylene group having 2 to 10 carbon atoms, and is preferably a linear or branched alkylene group having 2 to 6 carbon atoms. Specific examples of A include an ethylene group and a propane-1,3-diyl group.

Examples of alkoxysilane compounds (S1) include 2-trimethoxysilylethylsuccinic anhydride, 3-trimethoxysilylpropylsuccinic anhydride (manufactured by Shin-Etsu Chemical Co., Ltd., product name "X-12-967C"), 3-triethoxysilylpropylsuccinic anhydride, 3-methyldiethoxysilylpropylsuccinic anhydride, and 1-carboxy-3-triethoxysilylpropylsuccinic anhydride.

The organopolysiloxane compound (S2) is a compound having a siloxane bond, and contains, for example, a siloxane unit (U1) represented by the following formula (3). The organopolysiloxane compound (S2) may further contain a siloxane unit (U2) represented by the following formula (4).

In formula (3), X is an organic group having an acidic group or an acid anhydride group, and is preferably an organic group represented by formula (2). In formulas (3) and (4), R ⁴ is each independently a hydrogen atom, an alkoxy group having 1 to 10 carbon atoms, or a monovalent hydrocarbon group having 1 to 20 carbon atoms which may be substituted with a halogen atom. The alkoxy group of R ⁴ is preferably a methoxy group or an ethoxy group. The hydrocarbon group of R ⁴ is, for example, a methyl group.

The number of siloxane units (U1) contained in the organopolysiloxane compound (S2) is not particularly limited and may be, for example, 1 to 100, preferably 1 to 50, and more preferably 1 to 20. The number of siloxane units (U2) contained in the organopolysiloxane compound (S2) is not particularly limited and may be, for example, 0 to 100, preferably 0 to 50, and more preferably 0 to 20. It is preferable that the organopolysiloxane compound (S2) contains at least one siloxane unit (U2).

The organopolysiloxane compound (S2) may have a structure in which at least one siloxane unit (U1) is inserted between O-Si bonds contained in an alkoxysilane represented by the following formula (5) or a partial hydrolysis condensate thereof. Both the siloxane unit (U1) and the siloxane unit (U2) may be inserted between the O-Si bonds. Of the multiple O-Si bonds, the siloxane unit (U1) may be inserted between some of the O-Si bonds, and the siloxane unit (U2) may be inserted between the other O-Si bonds.
R ⁵ _n Si (OR ⁶ ) _3-n (5)

In formula (5), ^R5 's are each independently a hydrogen atom or a monovalent hydrocarbon group having 1 to 20 carbon atoms which may be substituted with a halogen atom. ^R6 's are each independently an alkyl group having 1 to 10 carbon atoms. n is 0 or 1.

Examples of alkoxysilanes or their partial hydrolysis condensates represented by formula (5) include tetramethoxysilane, methyltrimethoxysilane, tetraethoxysilane, methyltriethoxysilane, and compounds obtained by partial hydrolysis condensation of one or more of these alkoxysilanes.

The organopolysiloxane compound (S2) can be produced by known production methods, for example, those described in JP-A-2013-129809 and JP-A-2013-129691.

The compound (C) is not limited to the above alkoxysilane compound (S1) and organopolysiloxane compound (S2) as long as it has an acidic group or an acid anhydride group. The compound (C) may contain a (meth)acrylic oligomer (B) having an acidic group or an acid anhydride group. The (meth)acrylic oligomer (B) contains, for example, a structural unit derived from an alkyl (meth)acrylate as the main component, and also contains a structural unit derived from a (meth)acrylate having an acidic group or an acid anhydride group. In this specification, "(meth)acrylate" means acrylate and/or methacrylate. "Main component" means the structural unit contained most abundantly in the polymer by weight.

Examples of the alkyl (meth)acrylate constituting the (meth)acrylic oligomer (B) include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, butyl (meth)acrylate, isobutyl (meth)acrylate, s-butyl (meth)acrylate, t-butyl (meth)acrylate, pentyl (meth)acrylate, isopentyl (meth)acrylate, hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate, isooctyl (meth)acrylate, nonyl (meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, undecyl (meth)acrylate, and dodecyl (meth)acrylate. Examples of (meth)acrylates having an acidic group include (meth)acrylic acid, carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, and other carboxyl group-containing (meth)acrylates.

Examples of other monomers constituting the (meth)acrylic oligomer (B) include esters of (meth)acrylic acid and alicyclic alcohols such as cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, and dicyclopentanyl (meth)acrylate; aryl (meth)acrylates such as phenyl (meth)acrylate and benzyl (meth)acrylate; (meth)acrylates obtained from terpene compound derivative alcohols; and alkyl (meth)acrylates containing ether bonds such as methoxyethyl (meth)acrylate and phenoxyethyl (meth)acrylate. Such (meth)acrylates can be used alone or in combination of two or more kinds. As a monomer constituting the (meth)acrylic oligomer (B), a monomer constituting the (meth)acrylic polymer (A) described later can also be used.

As with the (meth)acrylic polymer (A) described later, the polymerization method for the (meth)acrylic oligomer (B) may be solution polymerization, emulsion polymerization, bulk polymerization, emulsion polymerization, polymerization by heat or active energy ray irradiation (thermal polymerization, active energy ray polymerization), etc. Among these, solution polymerization and active energy ray polymerization are preferred in terms of transparency, water resistance, cost, etc. The resulting (meth)acrylic oligomer (B) may be any of a random copolymer, a block copolymer, a graft copolymer, etc.

From the viewpoint of improving the durability, corrosion resistance and reworkability of the adhesive layer 1, the content of compound (C) in the adhesive composition is preferably 0.05 to 10 parts by weight, more preferably 3 parts by weight or less, even more preferably 2 parts by weight or less, particularly preferably 1 part by weight or less, and most preferably 0.6 parts by weight or less, relative to 100 parts by weight of the base polymer described below. The content of compound (C) is more preferably 0.1 parts by weight or more, even more preferably 0.2 parts by weight or more, and particularly preferably 0.4 parts by weight or more, relative to 100 parts by weight of the base polymer.

The weight average molecular weight of compound (C) is not particularly limited and is, for example, 10,000 or less, preferably 8,000 or less, more preferably 5,000 or less, even more preferably 3,000 or less, and particularly preferably 1,500 or less. The lower limit of the weight average molecular weight of compound (C) is not particularly limited and is, for example, 100.

Compound (C) may have a low acid dissociation constant pKa due to the acidic group. The pKa (particularly the first acid dissociation constant) of compound (C) is, for example, 12 or less, preferably 11 or less, more preferably 8 or less, even more preferably 6 or less, and particularly preferably 5 or less. The lower limit of the pKa of compound (C) is not particularly limited, and is, for example, 1. In this specification, pKa is the value in water at 25°C.

<Polyether compound (D)>
The polyether compound (D) is a compound having a polyether skeleton. The polyether skeleton may be linear or branched. The polyether skeleton of the polyether compound (D) contains, for example, an oxyalkylene unit (U3) represented by the following formula (6).

In formula (6), R ⁷ is a linear or branched alkylene group having 1 to 10 carbon atoms. The carbon number of R ⁷ is preferably 2 to 6, and more preferably 3. The polyether compound (D) may contain one or more types of oxyalkylene units (U3). The polyether compound (D) may be a random copolymer or a block copolymer. Specific examples of the oxyalkylene unit (U3) include an oxyethylene group, an oxypropylene group, and an oxybutylene group. The oxyalkylene unit (U3) is preferably an oxypropylene group (particularly -CH ₂ CH(CH ₃ )O-) in terms of ease of production of the material and stability of the material.

The polyether compound (D) may contain a silicon atom, and may further contain a hydrolyzable group (h2) bonded to the silicon atom. The hydrolyzable group (h2) can form a siloxane bond, for example, by hydrolysis and/or condensation. Examples of the hydrolyzable group (h2) include halogen atoms, alkoxy groups, acyloxy groups, alkenyloxy groups, carbamoyl groups, amino groups, aminooxy groups, and ketoximate groups. When the hydrolyzable group (h2) has carbon atoms, the number of carbon atoms is, for example, 10 or less, preferably 6 or less, and more preferably 4 or less. In particular, an alkoxy group or alkenyloxy group having 4 or less carbon atoms is preferred, and a methoxy group or an ethoxy group is particularly preferred. The content of the hydrolyzable group (h2) in the polyether compound (D) is, for example, 14 wt% or less, preferably less than 13 wt%, and more preferably less than 10 wt%. The lower limit of the content of the hydrolyzable group (h2) is not particularly limited, and may be, for example, 2.0 wt%, 2.5 wt%, or 3.0 wt%. In some cases, the content of the hydrolyzable group (h2) may be 2.0 wt% or less.

The hydrolyzable group (h2) bonded to a silicon atom is located, for example, at an end of the polyether compound (D). As an example, the polyether compound (D) has a reactive silyl group (b) represented by the following formula (7) at at least one end.
-SiR ⁸ _a M _3-a (7)

In formula (7), R ⁸ is, independently of each other, a monovalent organic group having 1 to 20 carbon atoms, which may have a substituent. R ⁸ is preferably a linear or branched alkyl group having 1 to 8 carbon atoms, a fluoroalkyl group having 1 to 8 carbon atoms, or a phenyl group, more preferably an alkyl group having 1 to 6 carbon atoms, and particularly preferably a methyl group. When multiple R ^8s are present in the polyether compound (D), the multiple R ^8s may be the same as or different from each other. M is, independently of each other, a hydroxyl group or a hydrolyzable group (h2). When multiple Ms are present in the polyether compound (D), the multiple Ms may be the same as or different from each other. a is an integer of 0 to 2.

The polyether compound (D) has, for example, at least one reactive silyl group (b) per molecule at its end. When the polyether compound (D) is linear, the polyether compound (D) may have one or two reactive silyl groups (b) at its end, and preferably has two reactive silyl groups (b). When the polyether compound (D) is branched, the polyether compound (D) has at least one reactive silyl group (b) at the main chain end or the side chain end. The number of reactive silyl groups (b) can be appropriately adjusted according to the number of ends of the polyether compound (D), and is preferably 2 or more, and may be 3 or more.

It is preferable that the polyether compound (D) has a reactive silyl group (b) at least in part of its molecular terminals, and has at least one reactive silyl group (b) in the molecule, preferably 1.1 to 5 reactive silyl groups (b), and more preferably 1.1 to 3 reactive silyl groups (b).

The reactive silyl group (b) is preferably an alkoxysilyl group (b1) represented by the following formula (8) or an alkoxysilyl group (b2) represented by the following formula (9).

In formula (8) and formula (9), R ⁹ , R ¹⁰ and R ¹¹ are each independently a monovalent hydrocarbon group having 1 to 6 carbon atoms, such as a linear or branched alkyl group having 1 to 6 carbon atoms, a linear or branched alkenyl group having 2 to 6 carbon atoms, a cycloalkyl group having 5 to 6 carbon atoms, a phenyl group, etc. Specific examples of -OR ⁹ , -OR ¹⁰ and -OR ¹¹ in formula (8) and formula (9) include a methoxy group, an ethoxy group, a propoxy group, a propenyloxy group, a phenoxy group, etc., with a methoxy group and an ethoxy group being preferred, and a methoxy group being particularly preferred.

The main chain of the polyether compound (D) is preferably substantially composed of a polyether skeleton, except for the reactive silyl group (b). However, the main chain of the polyether compound (D) may contain a small amount of other chemical structures. Examples of other chemical structures include a chemical structure derived from an initiator for forming the oxyalkylene unit (U3) and a linking group between the polyether skeleton and the reactive silyl group (b). The content of the oxyalkylene unit (U3) in the polyether compound (D) is preferably 50% by weight or more, and more preferably 80% by weight or more.

The polyether compound (D) is represented, for example, by the following formula (10).
R ¹² _a M _3-a Si-X-Y-(AO) _n -Z (10)

In formula (10), R ¹² are each independently a monovalent organic group having 1 to 20 carbon atoms which may have a substituent. M are each independently a hydroxyl group or a hydrolyzable group (h2). a is an integer of 0 to 2. AO is a linear or branched oxyalkylene group having 1 to 10 carbon atoms. n represents the average number of moles added of the oxyalkylene group and is 1 to 1700. X is a linear or branched alkylene group having 1 to 20 carbon atoms. Y is an ether bond, an ester bond, a urethane bond, or a carbonate bond. Z is a hydrogen atom, a monovalent hydrocarbon group having 1 to 10 carbon atoms, a group represented by the following formula (11), or a group represented by the following formula (12).
-Y ¹ -X-SiR ¹² _a M _3-a (11)
-Q{-(OA) _n -Y-X-SiR ¹² _a M _3-a } _m (12)

In formula (11), R ¹² , M, and X are the same as in formula (10). Y ¹ is a single bond, a —CO- bond, a —CONH- bond, or a —COO- bond. In formula (12), R ¹² , M, X, Y, and n are the same as in formula (10). OA is the same as AO in formula (10). Q is a divalent or higher hydrocarbon group having 1 to 10 carbon atoms. m is a value obtained by subtracting 1 from the valence of the hydrocarbon group of Q.

In formula (10), X is a linear or branched alkylene group having 1 to 20 carbon atoms. The alkylene group preferably has 2 to 10 carbon atoms, and more preferably has 3 carbon atoms.

Y in formula (10) is a bond formed by reaction with the hydroxyl group of the oxyalkylene group at the end of the polyether skeleton, and is preferably an ether bond or a urethane bond, and more preferably a urethane bond.

Z is derived from a hydroxy compound that is an initiator used in synthesizing an oxyalkylene polymer used in preparing the polyether compound (D) represented by formula (10). Z is, for example, a hydrogen atom or a monovalent hydrocarbon group having 1 to 10 carbon atoms. In this case, the polyether compound (D) represented by formula (10) has one reactive silyl group (b) at its end. When Z is a hydrogen atom, this corresponds to the use of a structural unit similar to that of the oxyalkylene polymer as the hydroxy compound. When Z is a monovalent hydrocarbon group having 1 to 10 carbon atoms, this corresponds to the use of a hydroxy compound having one hydroxyl group.

On the other hand, when Z is represented by formula (11) or formula (12), the polyether compound (D) has a plurality of reactive silyl groups (b) at its terminal. When Z is represented by formula (11), it corresponds to the case where a structural unit similar to that of the oxyalkylene polymer is used as the hydroxy compound. When Z is represented by formula (12), it corresponds to the case where a hydroxy compound having two hydroxyl groups and different from the structural unit of the oxyalkylene polymer is used. Note that, like Y in formula (10), Y ¹ in formula (11) is a bond formed by reacting with the hydroxyl group of the oxyalkylene group at the terminal of the polyether skeleton.

From the viewpoint of reworkability, the polyether compound (D) is preferably represented by the following formula (13), formula (14) or formula (15).
Z ⁰ -A ² -O-(A ¹ O) _n -Z ¹ (13)
Z ⁰ -A ² -NHCOO-(A ¹ O) _n -Z ² (14)
Z ³ -O-(A ¹ O) _n -CH{-CH ₂ -(A ¹ O) _n -Z ³ } ₂ (15)

In formulas (13) to (15), Z ⁰ is an alkoxysilyl group represented by formula (8) or formula (9). ^{A 1} O is an oxyalkylene group having 2 to 6 carbon atoms, preferably an oxypropylene group. The oxyalkylene group of A ¹ O may be linear or branched. n indicates the average number of moles added of A ¹ O, and is 1 to 1700. A ² in formulas (13) and (14) is an alkylene group having 2 to 6 carbon atoms, preferably a propylene group. The alkylene group of A ² may be linear or branched. Z ¹ in formula (13) is a hydrogen atom or -A ² -Z ^0. Z ² in formula (14) is a hydrogen atom or -CONH-A ² -Z ⁰ . Z ³ in the formula (15) is a hydrogen atom or -A ² -Z ⁰ , and at least one Z ³ is -A ² -Z ⁰ .

As the compound represented by formula (14), for example, a compound represented by the following formula (16) is preferable.

In formula (16), R ⁹ , R ¹⁰ and R ¹¹ are each independently a monovalent hydrocarbon group having 1 to 6 carbon atoms. n represents the average number of moles of oxypropylene groups added and is 1 to 1700. Z ²¹ is a hydrogen atom or a trialkoxysilyl group represented by the following formula (17).

In formula (17), R ⁹ , R ¹⁰ and R ¹¹ are the same as in formula (16).

From the viewpoint of reworkability, the number average molecular weight of the polyether compound (D) is preferably 300 to 100,000. The number average molecular weight is preferably 500 or more, more preferably 1,000 or more, more preferably 2,000 or more, more preferably 3,000 or more, more preferably 4,000 or more, and even more preferably 5,000 or more, and is preferably 50,000 or less, more preferably 40,000 or less, more preferably 30,000 or less, more preferably 20,000 or less, and even more preferably 10,000 or less. n (average number of moles of oxyalkylene groups added in the polyether skeleton) in the above formulas (10) to (16) is appropriately adjusted, for example, so that the number average molecular weight of the polyether compound (D) is in the above range. When the number average molecular weight of the polyether compound (D) is 1,000 or more, the above n is usually 10 to 1,700.

The Mw (weight average molecular weight)/Mn (number average molecular weight) of the polyether compound (D) is preferably 3.0 or less, more preferably 1.6 or less, and particularly preferably 1.5 or less. In order to obtain a polyether compound (D) with a small Mw/Mn, it is preferable to use a method in which a reactive silyl group is introduced by modifying the terminals of an oxyalkylene polymer obtained by polymerizing a cyclic ether in the presence of an initiator using the composite metal cyanide complex shown below as a catalyst.

The polyether compound (D) can be produced, for example, by using an oxyalkylene polymer having a functional group at the molecular end as a raw material and bonding a reactive silyl group to the molecular end via an organic group such as an alkylene group. The oxyalkylene polymer used as the raw material is preferably a polymer having a hydroxyl group at the end obtained by ring-opening polymerization of a cyclic ether in the presence of a catalyst and an initiator.

As the initiator, a compound having one or more active hydrogen atoms per molecule, for example, a hydroxy compound having one or more hydroxyl groups per molecule, can be used. Examples of initiators include hydroxy compounds such as ethylene glycol, propylene glycol, dipropylene glycol, butanediol, hexamethylene glycol, hydrogenated bisphenol A, neopentyl glycol, polybutadiene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, allyl alcohol, methallyl alcohol, glycerin, trimethylolmethane, trimethylolpropane, pentaerythritol, and alkylene oxide adducts thereof. The initiator may be one or more types.

When a cyclic ether is subjected to ring-opening polymerization in the presence of an initiator, a polymerization catalyst can be used. Examples of polymerization catalysts include alkali metal compounds such as potassium hydroxide, potassium methoxide, and other potassium compounds, and cesium compounds such as cesium hydroxide; composite metal cyanide complexes; metal porphyrin complexes; and compounds having a P=N bond.

The polyether skeleton (polyoxyalkylene chain) in the polyether compound (D) is preferably composed of oxyalkylene units formed by ring-opening polymerization of an alkylene oxide having 2 to 6 carbon atoms, more preferably composed of oxyalkylene units formed by ring-opening polymerization of at least one alkylene oxide selected from the group consisting of ethylene oxide, propylene oxide, and butylene oxide, and particularly preferably composed of oxyalkylene units formed by ring-opening polymerization of propylene oxide. When the polyoxyalkylene chain is composed of two or more types of oxyalkylene units, the arrangement of the two or more types of oxyalkylene units may be in a block form or a random form.

The polyether compound (D) represented by the above formula (14) can be obtained, for example, by subjecting a polymer having a polyoxyalkylene chain and a hydroxyl group to a urethane reaction using a compound having a reactive silyl group (b) and an isocyanate group. The polyether compound (D) represented by formula (14) can also be obtained by adding hydrosilane or mercaptosilane to the unsaturated group of an oxyalkylene polymer having an unsaturated group, for example, an allyl-terminated polyoxypropylene monol obtained by polymerizing an alkylene oxide using allyl alcohol as an initiator, to introduce a reactive silyl group (b) into the molecular end.

The method for introducing reactive silyl group (b) to the end group of the hydroxyl-terminated oxyalkylene polymer obtained by ring-opening polymerization of a cyclic ether in the presence of an initiator is not particularly limited, and the following methods (a) to (c) in which a reactive silyl group is further linked to the end group via an organic group are usually preferred.

(a) A method in which an unsaturated group is introduced at the end of an oxyalkylene polymer having a hydroxyl group, and then a reactive silyl group (b) is bonded to this unsaturated group.
As this method, the following two methods (a-1) and (a-2) can be further exemplified: (a-1) A method using a so-called hydrosilylation reaction in which a hydrosilyl compound is reacted with the unsaturated group in the presence of a catalyst such as a platinum compound.
(a-2) A method of reacting an unsaturated group with a mercaptosilane compound.

Examples of the mercaptosilane compound (a-2) include 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 3-mercaptopropyltriisopropenyloxysilane, 3-mercaptopropylmethyldimethoxysilane, 3-mercaptopropyldimethylmonomethoxysilane, and 3-mercaptopropylmethyldiethoxysilane.

When reacting an unsaturated group with a mercapto group, a compound such as a radical generator used as a radical polymerization initiator may be used, or if desired, the reaction may be carried out by radiation or heat without using a radical polymerization initiator. Examples of radical polymerization initiators include peroxide-based, azo-based, and redox-based polymerization initiators, as well as metal compound catalysts, and specific examples include 2,2'-azobisisobutyronitrile, 2,2'-azobis-2-methylbutyronitrile, benzoyl peroxide, tert-alkyl peroxy ester, acetyl peroxide, and diisopropyl peroxycarbonate. The reaction conditions when reacting an unsaturated group with a mercapto group using a radical polymerization initiator vary depending on the decomposition temperature (half-life temperature) of the polymerization initiator, but it is preferable to carry out the reaction for several hours to several tens of hours at a reaction temperature of 20 to 200°C, preferably 50 to 150°C.

Methods for introducing unsaturated groups into the terminals of an oxyalkylene polymer include reacting an oxyalkylene polymer with a functional group that can be linked to the terminal hydroxyl group of the oxyalkylene polymer by an ether bond, ester bond, urethane bond, carbonate bond, or the like, and a reactant having an unsaturated group. A method for introducing unsaturated groups into at least a portion of the terminals of an oxyalkylene polymer by copolymerizing an unsaturated group-containing epoxy compound such as allyl glycidyl ether when polymerizing a cyclic ether in the presence of an initiator can also be used.

The hydrosilylation reaction is preferably carried out at a temperature of 60 to 120°C. In general, the hydrosilylation reaction proceeds sufficiently within a reaction time of a few hours.

(b) A method of reacting an oxyalkylene polymer having a hydroxyl group at its terminal with an isocyanate silane compound having a reactive silyl group (b).
Examples of the isocyanate silane compound include isocyanate silane compounds such as 1-isocyanate methyl trimethoxysilane, 1-isocyanate methyl triethoxysilane, 1-isocyanate propyl trimethoxysilane, 1-isocyanate propyl triethoxysilane, 3-isocyanate propyl trimethoxysilane, 3-isocyanate propyl triethoxysilane, 1-isocyanate methyl methyl dimethoxysilane, 1-isocyanate methyl dimethyl monomethoxysilane, 1-isocyanate methyl methyl diethoxysilane, 1-isocyanate propyl methyl dimethoxysilane, 1-isocyanate propyl dimethyl monomethoxysilane, 1-isocyanate propyl methyl diethoxysilane, 3-isocyanate propyl methyl dimethoxysilane, 3-isocyanate propyl dimethyl monomethoxysilane, and 3-isocyanate propyl methyl diethoxysilane. Of these, 3-isocyanatepropyltrimethoxysilane and 1-isocyanatemethylmethyldimethoxysilane are more preferred, and 3-isocyanatepropyltrimethoxysilane is particularly preferred.

The reaction between the oxyalkylene polymer and the isocyanate silane compound is preferably carried out so that the molar ratio of the isocyanate group (NCO) of the isocyanate silane compound to the hydroxyl group (OH) of the oxyalkylene polymer is NCO/OH = 0.80 to 1.05. This method can significantly reduce the process time because of the small number of manufacturing steps, and does not require complicated operations such as purification because there are few impurities produced as by-products during the manufacturing process. A more preferable molar ratio of NCO groups to OH groups is NCO/OH = 0.85 to 1.00. If the NCO ratio is low, the remaining OH groups may react with reactive silyl groups, resulting in a decrease in storage stability. In this case, it is preferable to adjust the silylation rate to a predetermined level by newly reacting with an isocyanate silane compound or a monoisocyanate compound and consuming the excess OH groups.

When reacting the hydroxyl group of the oxyalkylene polymer with the above-mentioned isocyanate silane compound, a known urethane reaction catalyst may be used. The reaction temperature and the reaction time required to complete the reaction vary depending on whether or not a urethane reaction catalyst is used and the amount used, but it is preferable to carry out the reaction between the oxyalkylene polymer and the isocyanate silane compound at a temperature of, for example, 20 to 200°C, preferably 50 to 150°C, for several hours.

(c) A method in which an oxyalkylene polymer having a hydroxyl group at the molecular terminal is reacted with a polyisocyanate compound under conditions of an excess of isocyanate groups to produce an oxyalkylene polymer having an isocyanate group at at least a portion of the terminals, and then the isocyanate group is reacted with a silicon compound having a functional group.
The functional group of the silicon compound is at least one active hydrogen-containing group selected from the group consisting of a hydroxyl group, a carboxyl group, a mercapto group, a primary amino group, and a secondary amino group. Examples of silicon compounds include aminosilane-based compounds such as N-phenyl-3-aminopropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-phenyl-3-aminopropylmethyldimethoxysilane, 3-aminopropylmethyldimethoxysilane, and 3-aminopropylmethyldiethoxysilane; and mercaptosilane-based compounds such as 3-mercaptopropyltrimethoxysilane and 3-mercaptopropylmethyldimethoxysilane. When reacting the oxyalkylene polymer with the silicon compound, a known urethanization reaction catalyst may be used. The reaction temperature and the reaction time required for the reaction to be completed vary depending on the presence or absence of the urethanization reaction catalyst and the amount of the catalyst used, but the reaction is preferably carried out for several hours at a temperature of, for example, 20 to 200° C., preferably 50 to 150° C.

Specific examples of polyether compounds (D) include MS Polymer S203, S303, S810; SILYL EST250, EST280; SAT10, SAT200, SAT220, SAT350, SAT400 manufactured by Kaneka Corporation, and EXCESTAR S2410, S2420, S3430 manufactured by Asahi Glass Co., Ltd.

The content of the polyether compound (D) in the adhesive composition is preferably 0.001 to 20 parts by weight per 100 parts by weight of the base polymer. When the content is 0.001 parts by weight or more, the reworkability of the adhesive layer 1 tends to be sufficiently improved. The content of the polyether compound (D) is preferably 0.01 parts by weight or more, more preferably 0.02 parts by weight or more, even more preferably 0.1 parts by weight or more, and even more preferably 0.5 parts by weight or more. When the content of the polyether compound (D) is 20 parts by weight or less, the adhesive layer 1 has sufficient moisture resistance and is less likely to peel off in a reliability test or the like. The content of the polyether compound (D) is preferably 10 parts by weight or less, more preferably 5 parts by weight or less, and even more preferably 3 parts by weight or less. The content of the polyether compound (D) may be 1 part by weight or less, or even 0.5 parts by weight or less.

<Adhesive>
Examples of the adhesive contained in the adhesive composition include rubber-based adhesives, acrylic-based adhesives, silicone-based adhesives, urethane-based adhesives, vinyl alkyl ether-based adhesives, polyvinylpyrrolidone-based adhesives, polyacrylamide-based adhesives, cellulose-based adhesives, etc. As the adhesive, acrylic-based adhesives are preferred because they have excellent optical transparency, appropriate adhesive properties such as wettability, cohesiveness, and adhesion, and excellent weather resistance, heat resistance, etc.

The adhesive composition containing an acrylic adhesive contains a (meth)acrylic polymer (A) as a base polymer. The (meth)acrylic polymer (A) contains, for example, a structural unit derived from an alkyl (meth)acrylate as a main component.

<(Meth)acrylic polymer (A)>
The number of carbon atoms of the alkyl group contained in the alkyl (meth)acrylate for forming the main skeleton of the (meth)acrylic polymer (A) is not particularly limited, and is, for example, 1 to 18. The alkyl group may be linear, branched, or cyclic. Examples of the alkyl group include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, an amyl group, a hexyl group, a cyclohexyl group, a heptyl group, a 2-ethylhexyl group, an isooctyl group, a nonyl group, a decyl group, an isodecyl group, a dodecyl group, an isomyristyl group, a lauryl group, a tridecyl group, a pentadecyl group, a hexadecyl group, a heptadecyl group, and an octadecyl group. The alkyl (meth)acrylates may be used alone or in combination. The average number of carbon atoms of the alkyl group is preferably 3 to 9.

The monomers constituting the (meth)acrylic polymer (A) include, in addition to alkyl (meth)acrylates, one or more copolymerizable monomers selected from the group consisting of aromatic ring-containing (meth)acrylates, amide group-containing monomers, carboxyl group-containing monomers, and hydroxyl group-containing monomers. The copolymerizable monomers can be used alone or in combination. The (meth)acrylic polymer (A) preferably has an acidic group resulting from a copolymerizable monomer such as a carboxyl group-containing monomer. The (meth)acrylic polymer (A) having an acidic group is suitable for maintaining the reworkability of the pressure-sensitive adhesive layer 1 after preheating.

Aromatic ring-containing (meth)acrylates are compounds that contain an aromatic ring structure and a (meth)acryloyl group in their structure. Examples of aromatic rings include benzene rings, naphthalene rings, and biphenyl rings. Aromatic ring-containing (meth)acrylates have the effect of adjusting the phase difference that occurs when stress is applied to the pressure-sensitive adhesive layer 1 due to the shrinkage of an optical film such as the polarizing film 2, and can suppress light leakage that occurs due to the shrinkage of the optical film.

Examples of aromatic ring-containing (meth)acrylates include 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-hydroxy- Examples of such acrylates include those having a benzene ring, such as 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. Among these, benzyl (meth)acrylate and phenoxyethyl (meth)acrylate are preferred from the viewpoint of improving the adhesive properties and durability of the adhesive layer 1.

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. 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. Among these, N-vinyl group-containing lactam monomers are preferred from the viewpoint of improving the durability of the adhesive layer 1 relative to the conductive layer.

The carboxyl group-containing monomer is a compound that contains a carboxyl group in its structure and a polymerizable unsaturated double bond such as a (meth)acryloyl group or a vinyl group. Examples of the carboxyl group-containing monomer include (meth)acrylic acid, carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, itaconic acid, maleic acid, fumaric acid, and crotonic acid. Among these, acrylic acid is preferred from the viewpoints of copolymerizability, cost, and improving the adhesive properties of the adhesive layer 1.

The hydroxyl group-containing monomer is a compound that contains a hydroxyl group in its structure and a polymerizable unsaturated double bond such as a (meth)acryloyl group or a vinyl group. Examples of the hydroxyl group-containing monomer 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 these, from the viewpoint of improving the durability of the adhesive layer 1, 2-hydroxyethyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate are preferred, and 4-hydroxybutyl (meth)acrylate is more preferred.

The copolymerization monomer serves as a reaction point 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 adhesive layer 1. Carboxyl group-containing monomers are preferred in that they provide both durability and reworkability, and hydroxyl group-containing monomers are preferred in that they improve reworkability.

From the viewpoint of improving the adhesiveness of the pressure-sensitive adhesive layer 1, the ratio of alkyl (meth)acrylate to all monomer components forming the (meth)acrylic polymer (A) is preferably 50% by weight or more.

When an aromatic ring-containing (meth)acrylate is used as a monomer component, the ratio of the aromatic ring-containing (meth)acrylate to all monomer components forming the (meth)acrylic polymer (A) is preferably 3 to 25% by weight, more preferably 22% by weight or less, and even more preferably 20% by weight or less, from the viewpoint of improving the durability of the pressure-sensitive adhesive layer 1. This ratio is more preferably 8% by weight or more, and even more preferably 12% by weight or more. By adjusting the copolymerization rate of the aromatic ring-containing (meth)acrylate within the above range, light leakage due to shrinkage of the optical film can be suppressed, and the reworkability of the pressure-sensitive adhesive layer 1 tends to be improved.

When a hydroxyl group-containing monomer is used as a monomer component, the ratio of the hydroxyl group-containing monomer to the total monomer components forming the (meth)acrylic polymer (A) is preferably 0.01 to 10% by weight, more preferably 5% by weight or less, even more preferably 2% by weight or less, and particularly preferably 1% by weight or less, from the viewpoint of improving the adhesive properties and durability of the adhesive layer 1. This ratio is more preferably 0.03% by weight or more, and even more preferably 0.05% by weight or more. By adjusting the copolymerization rate of the hydroxyl group-containing monomer within the above range, the adhesive in the adhesive layer 1 can be sufficiently crosslinked while preventing the adhesive from hardening, which tends to improve the durability of the adhesive layer 1.

As the monomer component, in addition to the alkyl (meth)acrylate and the above-mentioned copolymerizable monomers, other copolymerizable monomers having a polymerizable functional group containing an unsaturated double bond, such as a (meth)acryloyl group or a vinyl group, can be used for the purpose of improving the adhesive property and heat resistance of the pressure-sensitive adhesive layer 1. The other copolymerizable monomers can be used alone or in combination.

Other copolymerizable monomers include, for example, 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; phosphoric acid group-containing monomers such as 2-hydroxyethyl acryloyl phosphate; alkylaminoalkyl (meth)acrylates such as aminoethyl (meth)acrylate, N,N-dimethylaminoethyl (meth)acrylate, and t-butylaminoethyl (meth)acrylate; methoxyethyl (meth)acrylate. alkoxyalkyl (meth)acrylates such as N-(meth)acryloyloxymethylene succinimide, N-(meth)acryloyl-6-oxyhexamethylene succinimide, and N-(meth)acryloyl-8-oxyoctamethylene succinimide; succinimide monomers such as N-cyclohexylmaleimide, N-isopropylmaleimide, N-laurylmaleimide, and N-phenylmaleimide; maleimide monomers such as N-methylitaconimide, N-ethylitaconimide, N-butylitaconimide, N-octylitaconimide, N-2-ethylhexylitaconimide, N-cyclohexyl Itaconimide monomers such as silitaconimide and N-laurylitaconimide; 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; tetrahydrofurfuryl (meth)acrylate, fluorine (meth)acrylate, silicone (meth)acrylate, etc. (meth)acrylate monomers such as acrylate and 2-methoxyethyl acrylate; silane-based monomers containing silicon atoms such as 3-acryloxypropyltriethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, 4-vinylbutyltrimethoxysilane, 4-vinylbutyltriethoxysilane, 8-vinyloctyltrimethoxysilane, 8-vinyloctyltriethoxysilane, 10-methacryloyloxydecyltrimethoxysilane, 10-acryloyloxydecyltrimethoxysilane, 10-methacryloyloxydecyltriethoxysilane, and 10-acryloyloxydecyltriethoxysilane.

Furthermore, other copolymerizable monomers include, for example, polyfunctional monomers having two or more unsaturated double bonds, such as 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, dipentaerythritol hexa(meth)acrylate, and caprolactone-modified dipentaerythritol hexa(meth)acrylate.

When other copolymerizable monomers are used as monomer components, the ratio of the other copolymerizable monomers to the total monomer components forming the (meth)acrylic polymer (A) is preferably 10% by weight or less, more preferably 7% by weight or less, and even more preferably 5% by weight or less.

<Method for producing (meth)acrylic polymer (A)>
The (meth)acrylic polymer (A) can be prepared by a known polymerization method such as solution polymerization, radiation polymerization using electron beams or UV rays, or various radical polymerizations such as bulk polymerization and emulsion polymerization. The obtained (meth)acrylic polymer (A) may be any of a random copolymer, a block copolymer, a graft copolymer, and the like.

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

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 the polymerization initiator and chain transfer agent used, the reaction conditions, etc. Therefore, the amount of the polymerization initiator and chain transfer agent used is appropriately adjusted depending on the composition.

Examples of polymerization initiators include azo initiators such as 2,2'-azobisisobutyronitrile, 2,2'-azobis(2-amidinopropane)dihydrochloride, 2,2'-azobis[2-(5-methyl-2-imidazolin-2-yl)propane]dihydrochloride, 2,2'-azobis(2-methylpropionamidine)disulfate, 2,2'-azobis(N,N'-dimethyleneisobutylamidine), and 2,2'-azobis[N-(2-carboxyethyl)-2-methylpropionamidine]hydrate (VA-057, manufactured by Wako Pure Chemical Industries, Ltd.); persulfates such as potassium persulfate and ammonium persulfate; di(2-ethylhexyl)peroxydicarbonate, di(4-t-butylcyclohexyl)peroxydicarbonate, di-sec-butyl ... Examples of initiators include, but are not limited to, peroxide initiators such as carbonate, t-butyl peroxyneodecanoate, t-hexyl peroxypivalate, t-butyl peroxypivalate, dilauroyl peroxide, di-n-octanoyl peroxide, 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate, di(4-methylbenzoyl)peroxide, dibenzoyl peroxide, t-butyl peroxyisobutyrate, 1,1-di(t-hexylperoxy)cyclohexane, t-butyl hydroperoxide, and hydrogen peroxide; and redox initiators that combine a peroxide and a reducing agent, such as a combination of a persulfate and sodium hydrogen sulfite, or a combination of a peroxide and sodium ascorbate.

The polymerization initiators can be used alone or in combination, but the total amount used is preferably about 0.005 to 1 part by weight, and more preferably about 0.01 to 0.5 parts by weight, per 100 parts by weight of the monomer components.

Examples of chain transfer agents include lauryl mercaptan, glycidyl mercaptan, mercaptoacetic acid, 2-mercaptoethanol, thioglycolic acid, 2-ethylhexyl thioglycolate, and 2,3-dimercapto-1-propanol. Chain transfer agents may be used alone or in combination of two or more, but the total amount used is about 0.1 parts by weight or less per 100 parts by weight of the monomer component.

Examples of emulsifiers used in emulsion polymerization include anionic emulsifiers such as sodium lauryl sulfate, ammonium lauryl sulfate, sodium dodecylbenzenesulfonate, ammonium polyoxyethylene alkyl ether sulfate, and sodium polyoxyethylene alkyl phenyl ether sulfate; and nonionic emulsifiers such as polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, polyoxyethylene fatty acid ester, and polyoxyethylene-polyoxypropylene block polymer. Emulsifiers can be used alone or in combination.

Examples of reactive emulsifiers include emulsifiers into which radically polymerizable functional groups such as propenyl groups and allyl ether groups have been introduced. Specific examples of such emulsifiers include Aqualon HS-10, HS-20, KH-10, BC-05, BC-10, and BC-20 (all manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), and Adeka Reasoap SE10N (manufactured by ADEKA Corporation). Reactive emulsifiers are preferred because they are incorporated into the polymer chain after polymerization and improve water resistance. The amount of emulsifier used is preferably 0.3 to 5 parts by weight per 100 parts by weight of the total amount of monomer components, and more preferably 0.5 to 1 part by weight in terms of polymerization stability and mechanical stability.

In radiation polymerization, the monomer components are polymerized by irradiating them with radiation such as electron beams or UV light to produce the (meth)acrylic polymer (A). When radiation polymerization is performed with electron beams, it is not necessary to include a photopolymerization initiator in the monomer components. When radiation polymerization is performed with UV light, a photopolymerization initiator may be included in the monomer components due to the advantage of being able to shorten the polymerization time. Photopolymerization initiators can be used alone or in combination.

The photopolymerization initiator is not particularly limited as long as it initiates photopolymerization, and any commonly used photopolymerization initiator can be used. Examples of photopolymerization initiators that can be used include benzoin ethers, acetophenones, α-ketols, photoactive oximes, benzoins, benzils, benzophenones, ketals, and thioxanthones. The amount of photopolymerization initiator used is 0.05 to 1.5 parts by weight, and preferably 0.1 to 1 part by weight, per 100 parts by weight of the monomer component. The photopolymerization initiators can be used alone or in combination.

The weight average molecular weight of the (meth)acrylic polymer (A) is usually 1 million to 2.5 million. Considering durability, particularly heat resistance, the weight average molecular weight of the (meth)acrylic polymer (A) 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. If the weight average molecular weight is 2.5 million or less, the adhesive tends not to harden and peeling is unlikely to occur. The weight average molecular weight (Mw)/number average molecular weight (Mn), which means the molecular weight distribution, is preferably 1.8 to 10, more preferably 1.8 to 7, and even more preferably 1.8 to 5. A molecular weight distribution (Mw/Mn) of 10 or less is preferable in terms of durability. The weight average molecular weight and molecular weight distribution (Mw/Mn) are measured by GPC (gel permeation chromatography) and calculated in terms of polystyrene.

<Silane coupling agent>
The pressure-sensitive adhesive composition may further contain a silane coupling agent (E) in addition to the compound (C) and the polyether compound (D). The silane coupling agent (E) may have a reactive functional group other than an acidic group and an acid anhydride group. The reactive functional group is preferably at least one selected from the group consisting of an epoxy group, an amino group, an isocyanate group, an isocyanurate group, a vinyl group, a styryl group, an acetoacetyl group, a ureido group, a thiourea group, a (meth)acrylic group, and a heterocyclic group. The silane coupling agent (E) may be used alone or in combination.

Examples of the silane coupling agent (E) include epoxy group-containing silane coupling agents such as 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, and 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane; 3-aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, 3-triethoxysilyl-N-(1,3-dimethylbutylidene)propylamine, and N-phenyl-γ -amino group-containing silane coupling agents such as aminopropyltrimethoxysilane; isocyanate group-containing silane coupling agents such as 3-isocyanatepropyltriethoxysilane; vinyl group-containing silane coupling agents such as vinyltrimethoxysilane and vinyltriethoxysilane; styryl group-containing silane coupling agents such as p-styryltrimethoxysilane; (meth)acrylic group-containing silane coupling agents such as 3-acryloxypropyltrimethoxysilane and 3-methacryloxypropyltriethoxysilane. Among these, epoxy group-containing silane coupling agents are preferred.

As the silane coupling agent (E), one having multiple alkoxysilyl groups in the molecule (oligomeric silane coupling agent) can also be used. Specific examples of oligomeric silane coupling agents include epoxy group-containing oligomeric silane coupling agents manufactured by Shin-Etsu Chemical Co., Ltd., trade names "X-41-1053", "X-41-1059A", "X-41-1056", "X-40-2651", etc. Oligomeric silane coupling agents are preferred because they are less likely to volatilize and have multiple alkoxysilyl groups, which can effectively improve the durability of the adhesive layer 1.

When the pressure-sensitive adhesive composition contains a silane coupling agent (E), the content of the silane coupling agent (E) in the pressure-sensitive adhesive composition is preferably 0.001 to 5 parts by weight, more preferably 1 part by weight or less, and even more preferably 0.6 parts by weight or less, relative to 100 parts by weight of the base polymer. The content of the silane coupling agent (E) is more preferably 0.01 part by weight or more, more preferably 0.05 parts by weight or more, and particularly preferably 0.1 part by weight or more, relative to 100 parts by weight of the base polymer. By appropriately adjusting the content of the silane coupling agent (E), the durability of the pressure-sensitive adhesive layer 1 tends to be improved.

When the pressure-sensitive adhesive composition contains a silane coupling agent (E), the weight ratio of compound (C) to silane coupling agent (E) (compound (C)/silane coupling agent (E)) is preferably 0.1 or more, more preferably 0.5 or more, and even more preferably 1 or more, from the viewpoint of improving the durability of the pressure-sensitive adhesive layer 1, and is preferably 50 or less, more preferably 15 or less, and even more preferably 5 or less.

<Crosslinking Agent>
The pressure-sensitive adhesive composition may further contain a crosslinking agent. As the crosslinking agent, an organic crosslinking agent, a polyfunctional metal chelate, etc. can be used. As the organic crosslinking agent, for example, an isocyanate crosslinking agent, a peroxide crosslinking agent, an epoxy crosslinking agent, an imine crosslinking agent, etc. can be mentioned. In the polyfunctional metal chelate, a polyvalent metal atom is covalently bonded or coordinately bonded to an organic compound. As the polyvalent metal atom, Al, Cr, Zr, Co, Cu, Fe, Ni, V, Zn, In, Ca, Mg, Mn, Y, Ce, Sr, Ba, Mo, La, Sn, Ti, etc. can be mentioned. The organic compound that is covalently bonded or coordinately bonded contains, for example, an oxygen atom, etc., and preferably includes an alkyl ester, an alcohol compound, a carboxylic acid compound, an ether compound, a ketone compound, etc. The crosslinking agent can be used alone or in combination.

As the crosslinking agent, an isocyanate-based crosslinking agent and/or a peroxide-based crosslinking agent is preferred, and it is more preferred to use an isocyanate-based crosslinking agent and a peroxide-based crosslinking agent in combination.

As the isocyanate-based crosslinking agent, a compound having at least two isocyanate groups (including isocyanate regenerating functional groups in which the isocyanate groups are temporarily protected by a blocking agent or oligomerization) can be used. For example, known aliphatic polyisocyanates, alicyclic polyisocyanates, aromatic polyisocyanates, etc., which are generally used in urethanization reactions, can be used.

Examples of aliphatic polyisocyanates 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 alicyclic isocyanates include 1,3-cyclopentene diisocyanate, 1,3-cyclohexane diisocyanate, 1,4-cyclohexane diisocyanate, isophorone diisocyanate, hydrogenated diphenylmethane diisocyanate, hydrogenated xylylene diisocyanate, hydrogenated tolylene diisocyanate, and hydrogenated tetramethylxylylene diisocyanate.

Examples of aromatic diisocyanates 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, and xylylene diisocyanate.

Examples of isocyanate-based crosslinking agents include polymers (dimers, trimers, pentamers, etc.) of the above diisocyanates, urethane modified products reacted with polyhydric alcohols such as trimethylolpropane, urea modified products, biuret modified products, alphanate modified products, isocyanurate modified products, carbodiimide modified products, etc.

Examples of commercially available isocyanate crosslinking agents include products manufactured by Tosoh Corporation under the trade names "Millionate MT," "Millionate MTL," "Millionate MR-200," "Millionate MR-400," "Coronate L," "Coronate HL," and "Coronate HX," and products manufactured by Mitsui Chemicals under the trade names "Takenate D-110N," "Takenate D-120N," "Takenate D-140N," "Takenate D-160N," "Takenate D-165N," "Takenate D-170HN," "Takenate D-178N," "Takenate 500," and "Takenate 600."

As the isocyanate-based crosslinking agent, aromatic polyisocyanates and their modified products, which are aromatic polyisocyanate-based compounds, and aliphatic polyisocyanates and their modified products, which are aliphatic polyisocyanates, are preferred. Aromatic polyisocyanate-based compounds have a good balance between crosslinking speed and pot life, and are preferably used. As the aromatic polyisocyanate-based compound, tolylene diisocyanate and its modified products are particularly preferred.

Any peroxide can be used as long as it generates radical active species when heated or irradiated with light to promote crosslinking of the base polymer of the adhesive composition (e.g., (meth)acrylic polymer (A)). Taking into consideration workability and stability, it is preferable to use a peroxide with a 1-minute half-life temperature of 80°C to 160°C, and more preferably a peroxide with a 1-minute half-life temperature of 90°C to 140°C.

Examples of peroxides 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-butyl peroxydicarbonate (1-minute half-life temperature: 92.4°C), t-butyl peroxyneodecanoate (1-minute half-life temperature: 103.5°C), t-hexyl peroxypivalate (1-minute half-life temperature: 109.1°C), t-butyl peroxypivalate (1-minute half-life temperature: 110.3°C), dilauroyl peroxide (1 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 particularly preferred because of their excellent crosslinking reaction efficiency.

The half-life of a peroxide is an index showing the decomposition rate of the peroxide, and refers to the time it takes for the remaining amount of peroxide to be reduced to half. The decomposition temperature required to obtain the half-life at any given time, and the half-life time at any given temperature are listed in manufacturer catalogs, for example, NOF Corporation's "Organic Peroxide Catalog 9th Edition (May 2003)."

When a crosslinking agent is blended into the adhesive composition, the amount of crosslinking agent is preferably 0.01 to 3 parts by weight, more preferably 0.02 to 2 parts by weight, and even more preferably 0.03 to 1 part by weight, relative to 100 parts by weight of the base polymer. When the amount of crosslinking agent is 0.01 parts by weight or more, the adhesive layer 1 is sufficiently crosslinked, and durability and adhesive properties tend to improve. On the other hand, when the amount of crosslinking agent is 3 parts by weight or less, the adhesive layer 1 tends to become hard, and a decrease in durability tends to be suppressed.

When an isocyanate-based crosslinking agent is blended into the adhesive composition, the blending amount of the isocyanate-based crosslinking agent is preferably 0.01 to 2 parts by weight, more preferably 0.02 to 2 parts by weight, and even more preferably 0.05 to 1.5 parts by weight, per 100 parts by weight of the base polymer. When the blending amount of the isocyanate-based crosslinking agent is within the above range, the cohesive strength of the adhesive layer 1 is improved, and peeling during durability tests tends to be suppressed.

When peroxide is blended into the adhesive composition, the blending amount of peroxide is preferably 0.01 to 2 parts by weight, more preferably 0.04 to 1.5 parts by weight, and even more preferably 0.05 to 1 part by weight, per 100 parts by weight of the base polymer. When the blending amount of peroxide is within the above range, the processability, crosslinking stability, etc. of the adhesive layer 1 can be easily adjusted.

<Other Ingredients>
The adhesive composition may further contain an ionic compound. The ionic compound is not particularly limited, and those used in this field can be suitably used. Examples of the ionic compound include those described in JP-A-2015-4861, and among them, (perfluoroalkylsulfonyl)imide lithium salt is preferred, and bis(trifluoromethanesulfonylimide)lithium is more preferred. The amount of the ionic compound is not particularly limited, and can be within a range that does not impair the effects of the present invention, but for example, it is preferably 10 parts by weight or less, more preferably 5 parts by weight or less, even more preferably 3 parts by weight or less, and particularly preferably 1 part by weight or less, relative to 100 parts by weight of the base polymer.

The adhesive composition may contain other known additives, such as 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, and foil-like materials, which can be added as appropriate depending on the application. Furthermore, a redox system containing a reducing agent may be used 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 base polymer.

<Method of manufacturing pressure-sensitive adhesive layer>
When forming the pressure-sensitive adhesive layer 1 from the pressure-sensitive adhesive composition, it is preferable to adjust the total amount of crosslinking agent added to the pressure-sensitive adhesive composition and to fully consider the effects of the crosslinking temperature and crosslinking time.

Depending on the crosslinking agent used, the crosslinking temperature and crosslinking time can be adjusted as appropriate. The crosslinking temperature is preferably 170°C or less. Such crosslinking may be performed at the temperature during the drying process of the pressure-sensitive adhesive layer 1, or may be performed by providing a separate crosslinking process after the drying process. The crosslinking time can be set taking into consideration productivity and workability, but is usually about 0.2 to 20 minutes, and preferably about 0.5 to 10 minutes.

The method for forming the adhesive layer 1 is not particularly limited, and may be a method in which the adhesive composition is applied to various substrates, dried in a dryer such as a heat oven to volatilize the solvent, and crosslinked as necessary to form the adhesive layer 1, and the adhesive layer 1 is transferred onto the polarizing film 2, or a method in which the adhesive composition is applied directly onto the polarizing film 2 to form the adhesive layer 1.

The substrate is not particularly limited, and examples include various substrates such as release films and transparent resin film substrates.

Various methods can be used to apply the adhesive composition to the substrate or polarizing film 2. Specific examples include extrusion coating using a fountain coater, roll coating, kiss roll coating, gravure coating, reverse coating, roll brushing, spray coating, dip roll coating, bar coating, knife coating, air knife coating, curtain coating, lip coating, and a die coater.

The above drying conditions (temperature, time) are not particularly limited and can be set appropriately depending on the composition and concentration of the adhesive composition, but for example, are about 80 to 170°C, preferably 90 to 200°C, and 1 to 60 minutes, preferably 2 to 30 minutes. After drying, a crosslinking treatment can be performed as necessary, and the conditions are as described above.

The thickness of the adhesive layer 1 (after drying) is, for example, preferably 5 to 100 μm, more preferably 7 to 70 μm, and even more preferably 10 to 50 μm. If the thickness of the adhesive layer 1 is 5 μm or more, the adhesive layer 1 tends to have improved adhesion to the adherend and sufficient durability under humid conditions. On the other hand, if the thickness of the adhesive layer is 100 μm or less, the adhesive composition can be sufficiently dried when drying to form the adhesive layer 1, and residual air bubbles and uneven thickness of the adhesive layer 1 can be suppressed, so that problems with appearance tend not to occur.

Examples of materials that can be used for the release film include resin films such as polyethylene, polypropylene, polyethylene terephthalate, and polyester films; porous materials such as paper, cloth, and nonwoven fabric; nets, foam sheets, metal foils, and laminates of these. Resin films are preferably used as the release film because of their excellent surface smoothness. Examples of resin films include polyethylene films, polypropylene films, polybutene films, polybutadiene films, polymethylpentene films, polyvinyl chloride films, vinyl chloride copolymer films, polyethylene terephthalate films, polybutylene terephthalate films, polyurethane films, and ethylene-vinyl acetate copolymer films.

The thickness of the release film is usually 5 to 200 μm, and preferably about 5 to 100 μm. If necessary, the release film can be subjected to a release treatment and an antifouling treatment using a release agent such as a silicone-based, fluorine-based, long-chain alkyl-based, or fatty acid amide-based agent, or silica powder, or an antistatic treatment such as a coating type, kneading type, or deposition type. In particular, by appropriately performing a release treatment such as a silicone treatment, a long-chain alkyl treatment, or a fluorine treatment on the surface of the release film, the releasability from the adhesive layer 1 can be further improved.

As the transparent resin film substrate, although there is no particular limitation, various resin films having transparency are used. The resin film is formed of a single layer of film. For example, the material may be polyester-based resins such as polyethylene terephthalate and polyethylene naphthalate, acetate-based resins, polyethersulfone-based resins, polycarbonate-based resins, polyamide-based resins, polyimide-based resins, polyolefin-based resins, (meth)acrylic-based resins, polyvinyl chloride-based resins, polyvinylidene chloride-based resins, polystyrene-based resins, polyvinyl alcohol-based resins, polyarylate-based resins, polyphenylene sulfide-based resins, etc. Among these, polyester-based resins, polyimide-based resins, and polyethersulfone-based resins are particularly preferred. The thickness of the film substrate is preferably 15 to 200 μm.

[Polarizing film]
The polarizing film 2 is a laminate including a polarizer and a transparent protective film. The transparent protective film is disposed, for example, in contact with a main surface (the surface having the largest area) of the layered polarizer. The polarizer may be disposed between two transparent protective films.

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 preferred, and iodine-based polarizers containing iodine and/or iodine ions are more preferred. The thickness of the polarizer is not particularly limited, but is generally about 5 to 80 μm.

In polyvinyl alcohol-based films, the optical properties of the film may deteriorate when the polyvinyl alcohol undergoes a dehydration reaction to become polyenated in a high-temperature environment. Polyenation tends to occur more significantly when the polarizing film 2 has a high moisture content. Therefore, when using a polyvinyl alcohol-based film as a polarizer, it is particularly important to preheat the polarizing film 2 to reduce the moisture content in advance.

A polarizer obtained by dyeing a polyvinyl alcohol-based film with iodine and stretching it uniaxially can be produced, for example, by dyeing the polyvinyl alcohol by immersing it in an aqueous solution of iodine and stretching it to 3 to 7 times its original length. If necessary, the polyvinyl alcohol can also be immersed in an aqueous solution of potassium iodide containing boric acid, zinc sulfate, zinc chloride, etc. Furthermore, if necessary, the polyvinyl alcohol-based film may be immersed in water and washed before dyeing. Washing the polyvinyl alcohol-based film with water not only makes it possible to wash off dirt and blocking inhibitors on the surface of the polyvinyl alcohol-based film, but also has the effect of suppressing the occurrence of uneven dyeing by swelling the polyvinyl alcohol-based film. The stretching of the polyvinyl alcohol-based film may be performed after dyeing with iodine, may be performed while dyeing, or may be performed before dyeing with iodine. The stretching may be performed in an aqueous solution of boric acid, potassium iodide, etc., or in a water bath.

As the polarizer, a thin polarizer having a thickness of 10 μm or less can also be used. From the viewpoint of thinning, the thickness of the polarizer is preferably 1 to 7 μm. Such a thin polarizer has little thickness unevenness, excellent visibility, and excellent durability due to little dimensional change, and is also preferable in that it allows the polarizing film 2 to be thinned.

Representative examples of thin polarizers include the thin polarizing films described in JP-A-51-069644, JP-A-2000-338329, WO 2010/100917, Japanese Patent No. 4751481, and JP-A-2012-073563. These thin polarizing films can be obtained by a manufacturing method including a step of stretching a polyvinyl alcohol-based resin (hereinafter also referred to as PVA-based resin) layer and a resin substrate for stretching in a laminated state, and a step of dyeing. With this manufacturing method, since the PVA-based resin layer is supported by the resin substrate for stretching, defects such as breakage due to stretching can be suppressed even if the PVA-based resin layer is thin.

Among the manufacturing methods including the steps of stretching and dyeing the laminate, the manufacturing methods including the step of stretching in an aqueous boric acid solution described in International Publication No. 2010/100917, Japanese Patent No. 4751481, and Japanese Patent Publication No. 2012-073563 are preferred because they allow high stretching ratios and improve polarization performance, and in particular, the manufacturing methods including the step of supplementary air-stretching before stretching in an aqueous boric acid solution described in Japanese Patent No. 4751481 and Japanese Patent Publication No. 2012-073563 are preferred.

As a material for forming the transparent protective film provided on one or both sides of the polarizer, for example, a thermoplastic resin excellent in transparency, mechanical strength, thermal stability, moisture blocking property, 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. The material of the transparent protective film may be a thermosetting resin or an ultraviolet-curing resin such as a (meth)acrylic, urethane, acrylic urethane, epoxy, or silicone-based resin. When the polarizing film 2 has two transparent protective films, the materials of the two transparent protective films may be the same or different from each other. For example, a transparent protective film made of a thermoplastic resin may be attached to one main surface of the polarizer via an adhesive, and a transparent protective film made of a thermosetting resin or an ultraviolet-curable resin may be attached to the other main surface of the polarizer. The transparent protective film may contain one or more types of optional additives. Examples of additives include ultraviolet absorbers, antioxidants, lubricants, plasticizers, release agents, coloring inhibitors, flame retardants, nucleating agents, antistatic agents, pigments, and colorants. The content of the thermoplastic resin in the transparent protective film is preferably 50 to 100% by weight, more preferably 50 to 99% by weight, even more preferably 60 to 98% by weight, and particularly preferably 70 to 97% by weight. When the content of the thermoplastic resin in the transparent protective film is 50% by weight or more, the inherent high transparency of the thermoplastic resin tends to be fully exhibited.

The thickness of the transparent protective film can be determined as appropriate, but is generally about 10 to 200 μm, taking into consideration strength, ease of handling, thinness, and other factors.

The moisture permeability of at least one transparent protective film included in the polarizing film 2 is preferably 300 g/m ² ·24 h or more, more preferably 500 g/m ² ·24 h or more, and even more preferably 800 g/m ² ·24 h or more. When the moisture permeability of the transparent protective film is high, the moisture content of the polarizing film 2 can be easily reduced by preheating. On the other hand, when the moisture permeability of the transparent protective film is excessively high, the humidification durability of the polarizing film 2 may be reduced. Therefore, the moisture permeability of the transparent protective film is preferably 1600 g/m ² ·24 h or less, and more preferably 1300 g/m ² ·24 h or less. The moisture permeability is a value measured in accordance with the moisture permeability test (cup method) of JIS Z0208, and is the weight of water vapor that permeates a sample with an area of 1 m ² in 24 hours at 40°C and a relative humidity difference of 90%.

The polarizer and the transparent protective film are usually adhered to each other via a water-based adhesive. Examples of water-based adhesives include isocyanate-based adhesives, polyvinyl alcohol-based adhesives, gelatin-based adhesives, vinyl latex-based adhesives, water-based polyurethanes, and water-based polyesters. Examples of adhesives other than the above-mentioned adhesives include ultraviolet-curing adhesives and electron beam-curing adhesives. Electron beam-curing adhesives for polarizing films exhibit suitable adhesion to various transparent protective films. The adhesive may contain a metal compound filler.

In the polarizing film 2, a phase difference film or the like can be formed on the polarizer instead of the transparent protective film. Another transparent protective film can be further provided on the transparent protective film, or a phase difference film or the like can be provided.

For the transparent protective film, a hard coat layer may be provided on the surface opposite to the surface adhered to the polarizer, and treatments may also be applied for the purposes of anti-reflection, anti-sticking, diffusion, anti-glare, etc.

[Other components]
The pressure-sensitive adhesive layer-attached polarizing film 10 may further include other optical films other than the polarizing film 2. Examples of the other optical films include films used in liquid crystal display devices, such as a reflector, a translucent plate, a retardation film, a viewing angle compensation film, and a brightness enhancement film. Retardation films include, for example, a half-wave plate and a quarter-wave plate. The pressure-sensitive adhesive layer-attached polarizing film 10 may include one or more of these other optical films.

The polarizing film 10 with the adhesive layer may further include an anchor layer located between the polarizing film 2 and the adhesive layer 1. The material forming the anchor layer is not particularly limited, and examples thereof include various polymers, metal oxide sols, silica sols, and the like. Among these, polymers are particularly preferably used. The polymers may be used in any of the following forms: solvent-soluble, water-dispersible, and water-soluble.

Examples of the above polymers include polyurethane resins, polyester resins, acrylic resins, polyether resins, cellulose resins, polyvinyl alcohol resins, polyvinylpyrrolidone, and polystyrene resins.

When the adhesive layer 1 of the polarizing film 10 with an adhesive layer is exposed, the adhesive layer 1 may be protected with a release film (separator) until it is put to practical use. Examples of the release film include those mentioned above. When a release film is used as the substrate in producing the adhesive layer 1, the release film can be used as the release film for the adhesive layer 1 of the polarizing film 10 with an adhesive layer by bonding the adhesive layer 1 on the release film to the polarizing film 2, which allows for simplification in terms of the process.

[Characteristics of adhesive layer]
Next, the reason why the adhesive layer 1 of the adhesive layer-attached polarizing film 10 can maintain reworkability after preheating and has durability in high-temperature environments even when attached to a conductive layer will be explained together with a possible mechanism.

After forming the adhesive layer 1 from the adhesive composition, the acid anhydride group of the compound (C) in the adhesive layer 1 is hydrolyzed by moisture in the air and converted into an acidic group. On the other hand, on the surface of the conductive layer containing a metal oxide such as ITO, not only hydroxyl groups but also metal cations generated by the hydroxyl groups being detached as hydroxide ions are present. As shown in FIG. 2, when the polarizing film 10 with the adhesive layer is attached to the conductive layer 3 by the adhesive layer 1, the acidic group of the compound (C) is deprotonated by a neutralization reaction with the hydroxide ion present near the surface of the conductive layer 3. The anion thus generated forms an ionic bond with the metal cation on the surface of the conductive layer 3. That is, an acid-base reaction occurs between the acidic group of the compound (C) and the conductive layer 3. As a result, the compound (C) is segregated on the surface of the conductive layer 3, and it is presumed that a first layer 11 containing the compound (C) is formed in the adhesive layer 1.

After the first layer 11 is formed, the polyether compound (D) tends to segregate on the surface of the first layer 11. Therefore, in the adhesive layer 1, a second layer 12 containing the polyether compound (D) is formed on the first layer 11. Note that when the adhesive layer 1 does not contain the compound (C), the polyether compound (D) hardly segregates on the surface of the conductive layer 3. Therefore, the first layer 11 can be regarded as a surface modification layer that modifies the surface of the conductive layer 3 so that the polyether compound (D) easily segregates.

In this way, it is presumed that by attaching the polarizing film 10 with the adhesive layer to the conductive layer 3 with the adhesive layer 1, a first layer 11 and a second layer 12 are formed in the adhesive layer 1. By forming the first layer 11 and the second layer 12, for example, a third layer 13 mainly containing an adhesive is further formed in the adhesive layer 1. The first layer 11, the second layer 12, and the third layer 13 are arranged in this order in the stacking direction.

Before preheating, the first layer 11 and the second layer 12 have a smaller cohesive strength than the third layer 13. Therefore, before preheating, the polarizing film 10 with the adhesive layer can be easily peeled off from the conductive layer 3 due to cohesive failure in the first layer 11 or the second layer 12.

For example, when preheating is performed at a temperature of about 70°C to 95°C, the cohesive strength of the first layer 11 tends to increase significantly due to the reaction of the compound (C). The increase in the cohesive strength of the first layer 11 is particularly noticeable when the compound (C) contains a hydrolyzable group (h1). On the other hand, the cohesive strength of the second layer 12 is less likely to increase than that of the first layer 11. Therefore, after preheating, the polarizing film 10 with the adhesive layer can be easily peeled off from the conductive layer 3 due to cohesive failure at the second layer 12 or at the interface between the first layer 11 and the second layer 12. In other words, the second layer 12 functions as a layer that ensures the reworkability of the adhesive layer 1 after preheating.

Furthermore, when the adhesive layer 1 is placed in an environment with a temperature higher than 95°C, the cohesive strength of the second layer 12 tends to increase significantly due to the reaction of the polyether compound (D) and the like. The increase in the cohesive strength of the second layer 12 is particularly noticeable when the polyether compound (D) contains a hydrolyzable group (h2). This tends to significantly increase the adhesive strength between the adhesive layer 1 and the conductive layer 3, and improve the durability of the adhesive layer 1.

From another aspect, the present invention provides
A pressure-sensitive adhesive layer 1 formed from a pressure-sensitive adhesive composition,
The pressure-sensitive adhesive composition contains a compound (C) having an acidic group or an acid anhydride group and a polyether compound (D),
A pressure-sensitive adhesive layer 1 is provided, which has an adhesive strength P ₈₅ determined by test 1 of 10.0 N/25 mm or less and an adhesive strength P ₁₀₅ determined by test 2 of more than 10.0 N/25 mm.

(Embodiments of Image Display Panel)
3, the image display panel 100 of the present embodiment includes a polarizing film 10 with an adhesive layer, a conductive layer 3, and a transparent substrate 4. The conductive layer 3 and the transparent substrate 4 are, for example, members that constitute a liquid crystal cell 20. That is, the image display panel 100 is a liquid crystal display panel that includes the polarizing film 10 with an adhesive layer and the liquid crystal cell 20. However, the image display panel 100 may include an organic EL cell instead of the liquid crystal cell 20. In the image display panel 100, the polarizing film 10 with an adhesive layer is, for example, located closer to the viewing side than the liquid crystal cell 20.

The polarizing film 10 with an adhesive layer, the conductive layer 3, and the transparent substrate 4 are arranged, for example, in this order in the stacking direction, and the adhesive layer 1 of the polarizing film 10 with an adhesive layer is in direct contact with the conductive layer 3. In other words, the polarizing film 10 with an adhesive layer is attached to the conductive layer 3 by the adhesive layer 1. The conductive layer 3 is in direct contact with, for example, the transparent substrate 4. If necessary, other layers such as an undercoat layer or an oligomer prevention layer may be disposed between the conductive layer 3 and the transparent substrate 4.

[Adhesive layer]
As described above, when the pressure-sensitive adhesive layer-attached polarizing film 10 is attached to the conductive layer 3 by the pressure-sensitive adhesive layer 1, a first layer 11, a second layer 12, and a third layer 13 are formed in the pressure-sensitive adhesive layer 1. The conductive layer 3, the first layer 11, the second layer 12, and the third layer 13 are arranged in this order in the stacking direction, and the third layer 13 is located between the second layer 12 and the polarizing film 2.

The first layer 11 contains, for example, a compound (C) or a reactant (R1) thereof. When the compound (C) contains a hydrolyzable group (h1), the reactant (R1) is, for example, a hydrolysis condensate of a plurality of compounds (C), or a reaction product of the compound (C) and a hydroxyl group on the surface of the conductive layer 3. The first layer 11 may contain the compound (C) or the reactant (R1) thereof as a main component.

The second layer 12 contains, for example, a polyether compound (D) or a reactant thereof (R2). When the polyether compound (D) contains a hydrolyzable group (h2), the reactant (R2) is, for example, a hydrolysis condensate of multiple polyether compounds (D). The second layer 12 may contain the polyether compound (D) or a reactant thereof (R2) as a main component.

The third layer 13 contains a base polymer such as a (meth)acrylic polymer (A) or a reactant thereof (R3). When the adhesive composition forming the adhesive layer 1 contains a crosslinking agent, the reactant (R3) is, for example, a crosslinked product of the (meth)acrylic polymer (A). The third layer 13 may contain the (meth)acrylic polymer (A) or the reactant thereof (R3) as a main component.

The presence of the first layer 11, the second layer 12, and the third layer 13 in the adhesive layer 1 may be confirmed by a method such as time-of-flight secondary ion mass spectrometry (TOF-SIMS). For example, an adhesive composition for forming the adhesive layer 1 is prepared. This adhesive composition is applied to the conductive layer 3 to produce a coating film that has a thickness of about 1 μm after drying. The film obtained by drying the coating film is analyzed by TOF-SIMS from its surface through the thickness direction of the film. This makes it possible to confirm that the adhesive layer 1 has the first layer 11, the second layer 12, and the third layer 13.

[Conductive layer]
The conductive layer 3 is not particularly limited as long as it contains a metal oxide. Examples of the metal oxide include oxides containing at least one metal selected from the group consisting of indium, tin, zinc, gallium, antimony, titanium, silicon, zirconium, magnesium, aluminum, gold, silver, copper, palladium, and tungsten. The conductive layer 3 may contain not only a metal oxide but also a metal shown in the above group, as necessary. The material of the conductive layer 3 is preferably indium tin oxide, tin oxide containing antimony, or the like. Indium tin oxide means indium oxide containing tin oxide, and is called indium-tin composite oxide or ITO. The conductive layer 3 preferably contains ITO, and more preferably is substantially made of ITO.

In the ITO contained in the conductive layer 3, the indium oxide content is preferably 80 to 99% by weight. The tin oxide content in the ITO is preferably 1 to 20% by weight. The ITO may be crystalline or non-crystalline (amorphous).

The thickness of the conductive layer 3 is not particularly limited, but is preferably 10 nm or more, more preferably 15 to 40 nm, and even more preferably 20 to 30 nm.

The method for forming the conductive layer 3 is not particularly limited, and any conventionally known method can be used. Specifically, the conductive layer 3 can be produced by a vacuum deposition method, a sputtering method, an ion plating method, or the like. These methods can be appropriately selected depending on the required film thickness of the conductive layer 3.

[Transparent substrate]
The transparent substrate 4 may be made of any material as long as it is transparent. Examples of the transparent substrate 4 include glass and transparent resin film substrates. Examples of the transparent resin film substrate include those described above.

[Liquid crystal cell]
The liquid crystal cell 20 further includes, for example, a liquid crystal layer 5 and a transparent substrate 6 in addition to the conductive layer 3 and the transparent substrate 4. In the liquid crystal cell 20, the conductive layer 3, the transparent substrate 4, the liquid crystal layer 5 and the transparent substrate 6 are arranged in this order in the stacking direction.

The liquid crystal layer 5 is not particularly limited, and any type such as TN type, STN type, π type, VA type, IPS type, etc. can be used. The transparent substrate 6 is not particularly limited in material as long as it is a transparent substrate. Examples of the transparent substrate 6 include glass and transparent resin film substrates. Examples of the transparent resin film substrates include those mentioned above.

[Other components]
In addition to the pressure-sensitive adhesive layer-attached polarizing film 10 and the liquid crystal cell 20, the image display panel 100 may further include optical films such as a retardation film, a viewing angle compensation film, and a brightness enhancement film.

[Method of Manufacturing Image Display Panel]
The method for manufacturing the image display panel 100 is not particularly limited, and includes, for example, performing a first heat treatment on the adhesive layer 1 at 70°C to 95°C in a state in which the polarizing film 10 with the adhesive layer is attached to the conductive layer 3.

The first heat treatment corresponds to preheating to reduce the moisture content of the polarizing film 2. The temperature of the first heat treatment is preferably 80°C to 95°C. The time of the first heat treatment is not particularly limited, and is, for example, 1 hour to 5 hours, and preferably 3 hours to 5 hours.

The moisture content of the polarizing film 2 after the first heat treatment is not particularly limited, and is, for example, 7 g/m ² or less. The moisture content of the polarizing film 2 can be measured by the method described in Patent Document 1.

The method for manufacturing the image display panel 100 may further include performing a second heat treatment on the adhesive layer 1 at a temperature higher than 95°C after the first heat treatment. The second heat treatment tends to significantly increase the adhesive strength of the adhesive layer 1 and improve the durability of the adhesive layer 1. The temperature of the second heat treatment may be 100°C to 150°C. The time of the second heat treatment is not particularly limited and is, for example, 1 hour to 1000 hours, and is preferably 24 hours or more.

(Modifications of Image Display Panel)
The image display panel 100 may include two adhesive layer-attached polarizing films 10. As shown in Fig. 4, the image display panel 110 according to this modified example includes two adhesive layer-attached polarizing films 10a and 10b. Except for the adhesive layer-attached polarizing film 10b, the structure of the image display panel 110 is the same as the structure of the image display panel 100. Therefore, elements common to the image display panel 100 and the image display panel 110 of the modified example are given the same reference symbols, and their descriptions may be omitted.

The polarizing film 10b with the adhesive layer is attached to the transparent substrate 6 of the liquid crystal cell 20 by the adhesive layer 1b. In the image display panel 110, the liquid crystal cell 20 is located between the polarizing films 10a and 10b with the adhesive layer, and is located on the viewing side of the polarizing film 10b with the adhesive layer.

The adhesive layer 1b and the polarizing film 2b of the polarizing film with an adhesive layer 10b may be the same as or different from the adhesive layer 1a and the polarizing film 2a of the polarizing film with an adhesive layer 10a. The adhesive layer 1b and the polarizing film 2b may be those conventionally used in this field.

(Embodiment of Image Display Device)
The image display device of this embodiment includes, for example, an image display panel 100 and an illumination system. In the image display device, an image display panel 110 can be used instead of the image display panel 100. In the image display device, the image display panel 100 is disposed, for example, on the viewing side of the illumination system. The illumination system includes, for example, a backlight or a reflector, and irradiates light onto the image display panel 100.

Examples of image display devices include liquid crystal display devices, electroluminescence (EL) displays, plasma displays (PDs), and field emission displays (FEDs). These image display devices can be used for home appliance applications, in-vehicle applications, and public information displays (PIDs), with in-vehicle applications being particularly preferred.

The present invention will be described in more detail below with reference to the following examples. The present invention is not limited to the following examples. In the following, unless otherwise specified, "%" indicates "weight %", "parts" indicates "parts by weight", and "thickness" indicates "physical film thickness". Unless otherwise specified, the indoor temperature and humidity are 23°C and 65% RH.

(Acrylic Polymer (A1))
A monomer mixture containing 100 parts by weight of butyl acrylate (BA), 0.075 parts by weight of 4-hydroxybutyl acrylate (HBA), and 5 parts by weight of acrylic acid (AA) 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 by weight of 2,2'-azobisisobutyronitrile (AIBN) was charged as a polymerization initiator together with 100 parts of ethyl acetate for 100 parts by weight of the monomer mixture, and nitrogen gas was introduced while gently stirring to replace the atmosphere with nitrogen. The liquid temperature in the flask was kept at around 55°C and the polymerization reaction was carried out for 6 hours. As a result, a solution of an acrylic polymer (A1) having a weight average molecular weight of 2.4 million and Mw/Mn=4.5 was prepared.

(Acrylic polymer (A2))
A solution of the acrylic polymer (A2) was prepared in the same manner as for the acrylic polymer (A1), except that the monomers used were changed as shown in Table 1.

(Acrylic Oligomer (B1))
Into a four-neck flask equipped with a stirring blade, a thermometer, a nitrogen gas inlet tube, and a cooler, 85 parts by weight of butyl acrylate (BA), 15 parts by weight of acrylic acid (AA), 0.1 parts by weight of 2,2'-azobisisobutyronitrile as a polymerization initiator, 100 parts by weight of toluene, and 3.5 parts by weight of α-thioglycerol were charged, and nitrogen gas was introduced while gently stirring to sufficiently replace the atmosphere with nitrogen, and then a polymerization reaction was carried out for 4 hours while maintaining the liquid temperature in the flask at around 60°C, to prepare a solution of acrylic oligomer (B1). The weight average molecular weight of the acrylic oligomer (B1) was 6700.

(Acrylic Oligomer (B2))
Acrylic oligomer (B2) was prepared in the same manner as acrylic oligomer (B1), except that the monomers used were changed as shown in Table 1.

The abbreviations in Table 1 are as follows.
BA: n-butyl acrylate HBA: 4-hydroxybutyl acrylate AA: acrylic acid PEA: phenoxyethyl acrylate NVP: N-vinyl-2-pyrrolidone MEA: 2-methoxyethyl acrylate

(Compound (C1))
Compound (C1) was prepared according to the method described in Example 1 of JP 2013-129809 A. Compound (C1) was an organopolysiloxane compound and contained the above-mentioned siloxane units (U1) and (U2). In the siloxane unit (U1), X was a propylsuccinic anhydride group, and R ⁴ was a methyl group. In the siloxane unit (U2), both of the two R ⁴ were methoxy groups. The content of the siloxane unit (U1) in compound (C1) was 27 mol%. The content of the siloxane unit (U2) in compound (C1) was 73 mol%. The weight average molecular weight of compound (C1) was about 1000.

(Polarizing film)
[HC-added TAC film]
First, a resin solution in which a UV-curable resin monomer or oligomer mainly composed of urethane acrylate was dissolved in butyl acetate (manufactured by DIC Corporation, product name: Unidic 17-806, solid content concentration: 80%) was prepared. Next, 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) were added to the resin solution per 100 parts of solid content of the resin solution. Next, a material for forming a hard coat layer was prepared by adding cyclopentanone and propylene glycol monomethyl ether in a ratio of 45:55 to the solution so that the solid content concentration of the obtained solution was 36%. Next, this material was applied onto a TAC film (TJ40UL manufactured by Fuji Film 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. Next, 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, thereby forming a hard coat layer (HC). Thus, a TAC film with HC was produced.

[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, and the temperature was raised to 105° C. while nitrogen was passed through the reactor. When reflux started, 5.0 g of t-butylperoxyisopropyl carbonate (Kayacarvon BIC-7, manufactured by Kayaku Akzo Co., Ltd.) was added as a polymerization initiator, and 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 at about 105 to 120° C. under reflux, and maturation was carried out over a further 4 hours.

30 g of a stearyl phosphate/distearyl phosphate mixture (Phoslex A-18, Sakai Chemical Industry Co., Ltd.) was added to the resulting polymer solution, and a cyclization condensation reaction was carried out under reflux at approximately 90 to 120°C for 5 hours. The resulting polymer solution was then introduced into a vent-type twin-screw extruder (φ=29.75 mm, L/D=30) with a barrel temperature of 260°C, a rotation speed of 100 rpm, a vacuum degree 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. In this extruder, further cyclization condensation reaction and devolatilization proceeded. As a result, transparent pellets of lactone ring-containing polymer were obtained.

Dynamic TG measurement of the obtained lactone ring-containing polymer detected a mass loss of 0.17% by mass. This 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 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 film thus produced 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 (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.

Next, a polarizing film was prepared by the following method. First, a 45 μm thick polyvinyl alcohol film was dyed in a 0.3% iodine solution (temperature 30° C.) for 1 minute between multiple rolls with different speed ratios, while being stretched to a stretch ratio of 3 times. Next, the obtained stretched film was stretched to a total stretch ratio of 6 times while being immersed in an aqueous solution (temperature 60° C.) containing 4% boric acid and 10% potassium iodide for 0.5 minutes. Next, the stretched film was washed by immersing it in an aqueous solution (temperature 30° C.) containing 1.5% potassium iodide for 10 seconds. Next, the stretched film was dried at 50° C. for 4 minutes to obtain a polarizer with a thickness of 18 μm. The above saponified HC-attached TAC film was attached to one main surface of the obtained polarizer via a polyvinyl alcohol-based adhesive. At this time, the triacetyl cellulose film was located closer to the polarizer than the hard coat layer. The above-mentioned acrylic film was attached to the other main surface of the polarizer via a polyvinyl alcohol adhesive. This resulted in a polarizing film.

Example 1
A solution of an acrylic adhesive composition was prepared by mixing 0.4 parts of compound (C1), 0.4 parts of polyether compound (D) (Silyl SAT10 manufactured by Kaneka Corporation), 0.5 parts of lithium bis(trifluoromethanesulfonyl)imide, 1 part of an isocyanate crosslinking agent (Coronate L manufactured by Tosoh Corporation, trimethylolpropane tolylene diisocyanate), and 0.2 parts of benzoyl peroxide (Niper BMT manufactured by NOF Corporation) per 100 parts of the solid content of the solution of acrylic polymer (A1). Silyl SAT10 is a compound represented by the above formula (13), in which A ¹ is -CH ₂ CH(CH ₃ )-, A ² is -C ₃ H ₆ -, Z ¹ is -C ₃ H ₆ -Z ⁰ , and the reactive silyl group (Z ⁰ -) is a dimethoxymethylsilyl group. The number average molecular weight of Silyl SAT10 is 5,000.

Next, the obtained solution of the acrylic 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 adhesive layer would have a thickness of 20 μm after drying. The applied film was dried at 155°C for 1 minute to form an adhesive layer on the surface of the separator film. Next, the adhesive layer formed on the separator film was transferred to the acrylic film side of the polarizing film to produce the polarizing film with the adhesive layer of Example 1.

(Examples 2 to 12, Comparative Examples 1 to 3)
The pressure-sensitive adhesive layer-attached polarizing films of Examples 2 to 12 and Comparative Examples 1 to 3 were produced in the same manner as in Example 1, except that the composition of the acrylic pressure-sensitive adhesive composition was changed as shown in Table 2.

[evaluation]
<Weight average molecular weight (Mw) of acrylic polymer and acrylic oligomer>
The weight average molecular weight (Mw) of the resulting acrylic polymer and acrylic oligomer was measured by GPC (gel permeation chromatography).
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: 0.8ml/min
Injection volume: 100 μl
Eluent: Tetrahydrofuran Detector: Differential refractometer (RI)
・Standard sample: polystyrene

<Adhesive strength>
The adhesive strengths P ₀ , P ₈₅ and P ₁₀₅ of the pressure-sensitive adhesive layer were measured by the above-mentioned tests 1 to 3. The ITO-layered glass was prepared by forming an ITO layer on an alkali-free glass (manufactured by Corning, product name "EG-XG") having a thickness of 7 mm. The ITO layer was prepared by a sputtering method. In the ITO layer, the ratio of the weight of Sn atoms to the total value of the weight of Sn atoms and the weight of In atoms (Sn ratio) was 3 wt%. The surface of the ITO layer was analyzed under the following measurement conditions using an atomic force microscope (AFM, manufactured by Bruker, Dimension3100+NanoscopeV). As a result, the average surface roughness Ra of the ITO layer was 0.2 nm, the root-mean-square roughness Rq was 0.3 nm, and the maximum height Rmax was 2.6 nm. The test piece was peeled off from the ITO layer using a tensile tester (Autograph Shimazu AG-1 1OKN).
(AFM measurement conditions)
Measurement mode: tapping mode Cantilever: Si single crystal Measurement area: 10 μm square

<Initial reworkability>
The ITO-layered glass used for measuring the adhesive strength was used to carry out a rework test by the following method. First, the polarizing film with the adhesive layer was cut into a strip of 230 mm long x 120 mm wide to prepare a test piece. Next, the test piece was attached to the surface of the ITO layer of the ITO-layered glass by the adhesive layer. The test piece was attached to the ITO layer using a laminator. After the test piece was attached, it was placed in an autoclave at 50°C and 5 atm (absolute pressure) for 15 minutes to homogenize the bonding between the ITO layer and the adhesive layer, and the adhesive layer was adhered to the ITO layer. Next, the test piece was peeled off from the ITO-layered glass by hand. The rework test was carried out three times using the above procedure, and the initial reworkability of the adhesive layer was evaluated according to the following criteria.
(Evaluation Criteria)
A: All three sheets were able to be peeled off smoothly without any adhesive residue or film breakage.
B: The film was broken in some of the three sheets when peeled off, but could be peeled off by peeling again.
C: All three films were broken when peeled off, but could be peeled off by peeling again.
D: All three sheets had adhesive residue, or the film broke and could not be peeled off no matter how many times attempts were made to peel it off.

<Reworkability after preheating>
In the rework test, the reworkability after preheating of the adhesive layer was evaluated in the same manner as in the evaluation of reworkability described above, except that after the bonding between the ITO layer and the adhesive layer was homogenized in an autoclave, heat treatment was performed for 5 hours under atmospheric pressure at 85°C, and after the heat treatment, the test piece was left in an atmosphere at room temperature to reduce the temperature of the test piece to room temperature.

<Durability>
The durability test was carried out by the following method using the glass with the ITO layer used for measuring the adhesive force. First, the polarizing film with the adhesive layer was cut into a strip of 300 mm length x 220 mm width to prepare a test piece. Next, the test piece was attached to the surface of the ITO layer of the glass with the ITO layer by the adhesive layer. The test piece was attached to the ITO layer using a laminator. After the test piece was attached, it was placed in an autoclave at 50 ° C and 0.5 MPa for 15 minutes to homogenize the bonding between the ITO layer and the adhesive layer, and the adhesive layer was adhered to the ITO layer. Next, the test piece was subjected to a heat treatment for 500 hours under an atmospheric pressure atmosphere at 105 ° C. The appearance of the adhesive layer between the polarizing film and the ITO layer was visually observed, and the durability of the adhesive layer was evaluated according to the following criteria.
(Evaluation Criteria)
A: No change in appearance such as foaming or peeling was observed.
B: Peeling or bubbling is observed at the edge, but this does not pose a problem in practical use unless it is for a special purpose.
C: There is significant peeling at the edge, which is problematic for practical use.

The abbreviations in Table 2 are as follows.
A1: Acrylic polymer (A1)
A2: Acrylic polymer (A2)
B1: Acrylic oligomer (B1)
B2: Acrylic oligomer (B2)
C1: Compound (C1)
X- 12-967C : 3-trimethoxysilylpropylsuccinic anhydride (manufactured by Shin-Etsu Chemical Co., Ltd.)
SAT10: Silyl SAT10 (manufactured by Kaneka Corporation)
X-41-1056: Epoxy group-containing oligomer type silane coupling agent (manufactured by Shin-Etsu Chemical Co., Ltd.)

As can be seen from Table 2, the adhesive layer of the polarizing film with the adhesive layer of this embodiment maintained reworkability after preheating even when attached to a conductive layer, and had durability in a high-temperature environment. In Comparative Examples 2 and 3 in which the compound (C) was not present, the polyether compound (D) Silyl SAT10 was hardly segregated on the surface of the ITO layer under the conditions for measuring the adhesive strengths P ₀ and P ₈₅ , while it is presumed that the Silyl SAT10 segregated on the surface of the ITO layer under the conditions for measuring the adhesive strength P _105. This is considered to have resulted in the adhesive strength P ₁₀₅ being lower than the adhesive strength P ₈₅ in Comparative Examples 2 and 3, and the durability after heat treatment at 105 ° C. being low.

The polarizing film with the adhesive layer of the present invention can be suitably used in image display devices such as liquid crystal displays, electroluminescence (EL) displays, plasma displays (PD), and field emission displays (FED).

REFERENCE SIGNS LIST 1 adhesive layer 2 polarizing film 3 conductive layer 4 transparent substrate 10 polarizing film with adhesive layer 11 first layer 12 second layer 13 third layer 20 liquid crystal cell 100, 110 image display panel

Claims (18)

A polarizing film with a pressure-sensitive adhesive layer, comprising a polarizing film and a pressure-sensitive adhesive layer formed from a pressure-sensitive adhesive composition,
The pressure-sensitive adhesive composition includes a base polymer, a compound (C) having an acidic group or an acid anhydride group , and a polyether compound (D),
the content of the compound (C) in the pressure-sensitive adhesive composition is 0.4 parts by weight or more based on 100 parts by weight of the base polymer,
A polarizing film with a pressure-sensitive adhesive layer, wherein the pressure-sensitive adhesive layer has an adhesive strength P ₈₅ determined by the following Test 1 of 10.0 N/25 mm or less and an adhesive strength P ₁₀₅ determined by the following Test 2 of more than 10.0 N/25 mm.
Test 1: The adhesive layer attached to the indium tin oxide layer of glass with an indium tin oxide layer is subjected to a heat treatment at 85° C. for 5 hours. The force (adhesive strength P ₈₅ ) required to peel the adhesive layer from the indium tin oxide layer is measured at a peel speed of 300 mm/min and a peel angle of 90°.
Test 2: The adhesive layer attached to the indium tin oxide layer of the indium tin oxide layer-coated glass is subjected to a heat treatment at 105° C. for 24 hours. The force (adhesive strength P ₁₀₅ ) required to peel the adhesive layer from the indium tin oxide layer is measured at a peel speed of 300 mm/min and a peel angle of 90°. The polarizing film with a pressure-sensitive adhesive layer according to claim 1 , wherein the pressure-sensitive adhesive layer has an adhesive strength P ₀ of 10.0 N/25 mm or less as determined by the following Test 3.
Test 3: The adhesive layer attached to the indium tin oxide layer of the indium tin oxide layer-coated glass is peeled off from the indium tin oxide layer at a peeling speed of 300 mm/min and a peeling angle of 90°. The force required for this (adhesive strength P ₀ ) is measured. The polarizing film with a pressure-sensitive adhesive layer according to claim 1 or 2, wherein the weight average molecular weight of the compound (C) and the number average molecular weight of the polyether compound (D) are each 10,000 or less. The polarizing film with a pressure-sensitive adhesive layer according to any one of claims 1 to 3, wherein the acid anhydride group is a carboxylic acid anhydride group. The polarizing film with a pressure-sensitive adhesive layer according to any one of claims 1 to 4, wherein the compound (C) further has a silicon atom and a hydrolyzable group bonded to the silicon atom. The polarizing film with a pressure-sensitive adhesive layer according to claim 5, wherein the content of the hydrolyzable group in the compound (C) is 10 wt % or more. The polarizing film with a pressure-sensitive adhesive layer according to any one of claims 1 to 6, wherein the compound (C) has a siloxane bond. The polarizing film with a pressure-sensitive adhesive layer according to any one of claims 1 to 7, wherein the polyether compound (D) further has a silicon atom and a hydrolyzable group bonded to the silicon atom. The polarizing film with a pressure-sensitive adhesive layer according to claim 8, wherein the content of the hydrolyzable group in the polyether compound (D) is 14 wt % or less. The pressure-sensitive adhesive layer-attached polarizing film according to any one of claims 1 to 9, wherein the pressure -sensitive adhesive composition comprises a (meth)acrylic polymer (A) as the base polymer. The polarizing film with a pressure-sensitive adhesive layer according to claim 10, wherein the (meth)acrylic polymer (A) has an acidic group. A polarizing film with a pressure-sensitive adhesive layer according to any one of claims 1 to 11,
A conductive layer including a metal oxide;
A transparent substrate;
Equipped with
The pressure-sensitive adhesive layer is in direct contact with the conductive layer. The image display panel of claim 12, wherein the metal oxide includes indium tin oxide. the pressure-sensitive adhesive layer has a first layer containing the compound (C) or a reactant thereof, and a second layer containing the polyether compound (D) or a reactant thereof,
14. The image display panel according to claim 12, wherein the conductive layer, the first layer, and the second layer are arranged in this order in a stacking direction. the pressure-sensitive adhesive layer further has a third layer containing a (meth)acrylic polymer (A) or a reaction product thereof,
The image display panel according to claim 14 , wherein the third layer is located between the second layer and the polarizing film. A method for manufacturing the image display panel according to any one of claims 12 to 15, comprising the steps of:
and performing a first heat treatment on the pressure-sensitive adhesive layer at 70° C. to 95° C. in a state in which the pressure-sensitive adhesive layer-attached polarizing film is attached to the conductive layer. The method for manufacturing an image display panel according to claim 16, further comprising performing a second heat treatment on the adhesive layer at a temperature higher than 95°C after the first heat treatment. A pressure-sensitive adhesive layer formed from a pressure-sensitive adhesive composition,
The pressure-sensitive adhesive composition includes a base polymer, a compound (C) having an acidic group or an acid anhydride group , and a polyether compound (D),
the content of the compound (C) in the pressure-sensitive adhesive composition is 0.4 parts by weight or more based on 100 parts by weight of the base polymer,
A pressure-sensitive adhesive layer having an adhesive strength P ₈₅ determined by the following Test 1 of 10.0 N/25 mm or less and an adhesive strength P ₁₀₅ determined by the following Test 2 of more than 10.0 N/25 mm.
Test 1: The adhesive layer attached to the indium tin oxide layer of glass with an indium tin oxide layer is subjected to a heat treatment at 85° C. for 5 hours. The force (adhesive strength P ₈₅ ) required to peel the adhesive layer from the indium tin oxide layer is measured at a peel speed of 300 mm/min and a peel angle of 90°.
Test 2: The adhesive layer attached to the indium tin oxide layer of the indium tin oxide layer-coated glass is subjected to a heat treatment at 105° C. for 24 hours. The force (adhesive strength P ₁₀₅ ) required to peel the adhesive layer from the indium tin oxide layer is measured at a peel speed of 300 mm/min and a peel angle of 90°.

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