KR20230064611A - variable color adhesive sheet - Google Patents

Abstract

The pressure-sensitive adhesive sheet (S) of the present invention is a variable color pressure-sensitive adhesive sheet provided with a pressure-sensitive adhesive layer (20) capable of color change. The pressure-sensitive adhesive layer 20 contains a colorant capable of developing color by a first external stimulus, and is curable by a second external stimulus different from the first external stimulus. The first shear storage modulus at 25°C of the pressure-sensitive adhesive layer 20 before curing, as shown by dynamic viscoelasticity measurement under conditions of a frequency of 1 Hz and a heating rate of 5°C/min, is 0.1×10 ⁵ Pa or more and 10×10 ⁵ Pa below The ratio of the second shear storage modulus at 25° C. to the first shear storage modulus of the pressure-sensitive adhesive layer 20 after curing as shown in the dynamic viscoelasticity measurement under the above conditions is 2 or more and 300 or less.

Description

variable color adhesive sheet

The present invention relates to a variable color adhesive sheet.

A display panel such as an organic EL panel has a laminated structure including a pixel panel, a cover member, and the like. In the manufacturing process of such a display panel, for example, a transparent adhesive sheet is used for bonding the elements included in the laminated structure.

In addition, as a transparent adhesive sheet disposed on the light output side (image display side) of a pixel panel in a display panel, a colored portion for imparting design, shielding, antireflection, etc. to a predetermined portion of the sheet is formed in advance. It has been proposed to use a pressure-sensitive adhesive sheet. Such an adhesive sheet is described, for example, in Patent Literature 1 below. Patent Literature 1 specifically describes an adhesive sheet having a colored portion containing a carbon black pigment.

Japanese Unexamined Patent Publication No. 2017-203810

However, in the case of using a PSA sheet having pre-formed colored portions in the manufacturing process of the display panel, after bonding the PSA sheet to the adherend, foreign matter and air bubbles between the adherend and the colored portion of the PSA sheet are removed. The presence or absence cannot be properly checked. In bonding of the adhesive sheet in the display panel manufacturing process, it is required to be able to properly inspect the presence or absence of foreign matter and air bubbles between the adherend and the adhesive sheet after the bonding.

On the other hand, from the viewpoint of securing the function of the colored portion provided on the transparent adhesive sheet for display panels, it is required that the deterioration of the colored portion be suppressed.

The present invention provides a color-changing pressure-sensitive adhesive sheet capable of discoloring at least a part of the pressure-sensitive adhesive layer after bonding to an adherend, and suitable for suppressing deterioration of the discolored portion of the pressure-sensitive adhesive layer.

The present invention [1] is a color-changing pressure-sensitive adhesive sheet having a color-changeable pressure-sensitive adhesive layer, wherein the pressure-sensitive adhesive layer contains a colorant capable of developing color in response to a first external stimulus, and a second external stimulus different from the first external stimulus. , and the first shear storage modulus at 25° C. of the pressure-sensitive adhesive layer before curing is 0.1 × 10 5 Pa or more 10 as shown in dynamic viscoelasticity measurement under conditions of a frequency of 1 Hz and a heating rate of ⁵ ° C./min. × 10 ⁵ Pa or less, and the ratio of the second shear storage modulus at 25° C. to the first shear storage modulus of the pressure-sensitive adhesive layer after curing in the dynamic viscoelasticity measurement under the above conditions is 2 or more and 300 or less, variable Colored adhesive sheets are included.

In the present invention [2], the first color change width W1 of the discoloration area formed in the pressure-sensitive adhesive layer and the pressure-sensitive adhesive layer are further reduced by applying the first external stimulus in a linear fashion to the pressure-sensitive adhesive layer after curing at 85°C. The color changeable pressure-sensitive adhesive sheet according to [1] above, wherein the second color change width W2 of the color change region after heat treatment for 120 hours satisfies 0.5≤W2/W1≤2.

In the present invention [3], the first color change width W1 of the discoloration area formed in the pressure-sensitive adhesive layer and the pressure-sensitive adhesive layer are further set at 65° C. and The color-changing pressure-sensitive adhesive sheet according to [1] or [2] above, wherein the third color change width W3 of the color change region after heat treatment at a relative humidity of 90% for 120 hours satisfies 0.5≤W3/W1≤2.4. .

In the present invention [4], the variable color adhesive described in any one of [1] to [3] above, wherein the colorant is a compound that develops color by reaction with an acid, and the pressure-sensitive adhesive layer further contains a photoacid generator. contains a sheet

The present invention [5] includes the variable color pressure-sensitive adhesive sheet according to any one of [1] to [4], wherein the pressure-sensitive adhesive layer has a thickness of 10 to 300 µm.

This invention [6] includes the variable color adhesive sheet according to any one of the above [1] to [5], further comprising a base material disposed on one side of the pressure-sensitive adhesive layer in the thickness direction.

In the variable color pressure sensitive adhesive sheet of the present invention, the pressure sensitive adhesive layer contains a colorant capable of developing color in response to a first external stimulus as described above. Therefore, after the color-changing PSA sheet is bonded to the adherend, the color of the PSA layer can be locally discolored by applying a first external stimulus to the portion to be discolored in the PSA layer. According to such a color-changing pressure-sensitive adhesive sheet, the presence or absence of foreign substances and air bubbles between the sheet and the adherend can be inspected after bonding and before formation of the discolored portion of the pressure-sensitive adhesive layer.

Further, in the variable-color PSA sheet, the pressure-sensitive adhesive layer can be cured by a second external stimulus different from the first external stimulus as described above, and the first shear storage modulus of the pressure-sensitive adhesive layer before curing is 0.1. ×10 ⁵ Pa or more and 10 × 10 ⁵ Pa or less, and the ratio of the second shear storage modulus after curing to the first shear storage modulus is 2 or more and 300 or less. Such a color-changing pressure-sensitive adhesive sheet is suitable for suppressing the diffusion of colorants in the pressure-sensitive adhesive layer after bonding (after curing) while securing the adhesive properties suitable for bonding to the adherend at the time of bonding in the pressure-sensitive adhesive layer (before curing) do. In the pressure-sensitive adhesive layer in which the discolored portion is formed, the deterioration of the discolored portion over time (spreading, discoloration, non-uniformity of color, etc.) of the discolored portion is suppressed by suppressing diffusion of the colorant.

1 is a cross-sectional schematic view of an embodiment of a variable color pressure-sensitive adhesive sheet of the present invention.
Fig. 2 is a schematic cross-sectional view of a modified example of the variable-color PSA sheet of the present invention (where the variable-color PSA sheet is a single-sided PSA sheet with a base material).
3 shows an example of a method of using the variable color pressure-sensitive adhesive sheet of the present invention. Fig. 3A shows a step of preparing a variable color PSA sheet and a member (adhered body), Fig. 3B shows a step of bonding members to each other via the variable color PSA sheet, and Fig. 3C shows a variable color PSA sheet A process of curing the pressure-sensitive adhesive layer is shown, and FIG. 3D shows a process of forming a discolored portion in the pressure-sensitive adhesive layer of the variable color pressure-sensitive adhesive sheet.
4 shows the shear storage modulus (in Examples 1 to 5, the shear storage modulus after curing of the pressure-sensitive adhesive layer) of the pressure-sensitive adhesive layers of the pressure-sensitive adhesive sheets of Examples 1 to 5 and Comparative Example 1, and before the first durability test. It is a graph showing the relationship of the increase rate (W2/W1) of the line width W2 of the linear discoloration part after the same test with respect to the line width W1 of the linear discoloration part.
5 shows the shear storage modulus (in Examples 1 to 5, the shear storage modulus after curing of the pressure-sensitive adhesive layer) of the pressure-sensitive adhesive layers of the pressure-sensitive adhesive sheets of Examples 1 to 5 and Comparative Example 1, and before the second durability test. It is a graph showing the relationship of the increase rate (W3/W1) of the line width W3 of the linear discoloration part after the test with respect to the line width W1 of the linear discoloration part.

The pressure-sensitive adhesive sheet S as an embodiment of the variable-color pressure-sensitive adhesive sheet of the present invention includes a pressure-sensitive adhesive layer 10 as shown in FIG. 1 . The adhesive sheet S has a sheet shape with a predetermined thickness and extends in a direction (surface direction) orthogonal to the thickness direction. The adhesive sheet S is, for example, a transparent adhesive sheet disposed on the image display side of a pixel panel in a display panel such as an organic EL panel (having a laminated structure including a pixel panel and a cover member). used

The pressure-sensitive adhesive layer 10 is a pressure-sensitive adhesive layer formed of a pressure-sensitive adhesive composition and having transparency (visible light transmission). The pressure-sensitive adhesive layer 10 contains a colorant capable of developing color in response to a first external stimulus described later, and a portion subjected to the first external stimulus is capable of discoloration. Specifically, the transparency of the portion of the pressure-sensitive adhesive layer 10 subjected to the first external stimulus can be reduced. In addition, the pressure-sensitive adhesive layer 10 can be cured by a second external stimulus described later different from the first external stimulus.

The shear storage modulus at 25°C (first shear storage modulus) of the pressure-sensitive adhesive layer 10 before curing, as shown in the dynamic viscoelasticity measurement under conditions of a frequency of 1 Hz and a heating rate of 5°C/min, is 0.1×10 ⁵ Pa or more. 10×10 ⁵ Pa or less. In addition, the ratio of the shear storage modulus (second shear storage modulus) at 25° C. to the first shear storage modulus of the pressure-sensitive adhesive layer 10 after curing, as shown in the dynamic viscoelasticity measurement under the above conditions, is 2 or more and 300 below

In the pressure-sensitive adhesive sheet S, the pressure-sensitive adhesive layer 10 contains a colorant capable of developing color in response to a first external stimulus, as described above. Therefore, after bonding the PSA sheet S to the adherend, in the portion to be discolored (at least a part of the PSA layer) in the PSA layer 10, the PSA is applied by applying a first external stimulus to the portion. Layer 10 may be discolored. According to the adhesive sheet S capable of forming a discoloration portion in the adhesive layer 10 after being bonded to an adherend, after bonding and before formation of the discoloration portion of the adhesive layer 10, between the adhesive sheet S and the adherend The presence or absence of foreign matter and air bubbles can be inspected.

In the PSA sheet S, as described above, the PSA layer 10 can be cured by a second external stimulus different from the first external stimulus, and in the PSA layer 10, before curing, The first shear storage modulus is 0.1 × 10 ⁵ Pa or more and 10 × 10 ⁵ Pa or less, and the ratio of the second shear storage modulus after curing to the first shear storage modulus is 2 or more and 300 or less. Such an adhesive sheet S secures the adhesive properties suitable for bonding to the adherend at the time of bonding in the adhesive layer 10 (before curing), while maintaining the colorant in the adhesive layer 10 after bonding (after curing). suitable for suppressing the spread of In the pressure-sensitive adhesive layer 10 in which the discolored portion is formed, the deterioration of the discolored portion over time (spreading, discoloration, non-uniformity of color, etc.) of the discolored portion is suppressed by suppressing the diffusion of the coloring agent.

As described above, the pressure-sensitive adhesive sheet S is capable of discoloring at least a part of the pressure-sensitive adhesive layer 10 after bonding to an adherend, and is suitable for suppressing deterioration of the discolored portion of the pressure-sensitive adhesive layer 10. Suppression of deterioration of the discolored portion in the pressure-sensitive adhesive layer 10 is useful for maintenance of functional characteristics of the discolored portion, such as design, shielding, and antireflection.

The aforementioned first shear storage modulus of the pressure-sensitive adhesive layer 10 is preferably 0.2×10 ⁵ Pa or more, more preferably 0.3×10 ⁵ Pa or more. The first shear storage modulus is preferably 5×10 ⁵ Pa or less, more preferably 3×10 ⁵ Pa or less. These configurations are suitable for securing adhesive properties (adhesive strength, tackiness, etc.) suitable for bonding to an adherend in the pressure-sensitive adhesive layer 10 (before curing).

In the pressure-sensitive adhesive layer 10, the ratio of the second shear storage modulus to the first shear storage modulus is preferably 5 or more, more preferably 10 or more. The ratio is preferably 250 or less, more preferably 100 or less, still more preferably 50 or less, and particularly preferably 30 or less. These configurations are suitable for attaining coexistence of the above-described adhesive properties in the pressure-sensitive adhesive layer 10 before curing and the above-described colorant diffusion suppression in the pressure-sensitive adhesive layer 10 after curing.

Adjustment of the first shear storage modulus of the pressure-sensitive adhesive layer 10 is, for example, adjustment of the constituent monomer composition in the polymer component such as the base polymer contained in the pressure-sensitive adhesive layer 10, molecular weight of the polymer component (for example, weight average molecular weight), use of a crosslinking agent for crosslinking polymer components, and adjustment of the content ratio of polymer components in the pressure-sensitive adhesive layer 10. Adjustment of the first shear storage modulus of the pressure-sensitive adhesive layer 10 is, for example, selection of the kind of monomer component contained as a curing component in the pressure-sensitive adhesive layer 10, and the amount of the monomer component in the pressure-sensitive adhesive layer 10. It may be realized by adjusting the content ratio.

Adjustment of the second shear storage modulus of the pressure-sensitive adhesive layer 10 is, for example, selection of the kind of monomer component contained as a curing component in the pressure-sensitive adhesive layer 10, the amount of the monomer component in the pressure-sensitive adhesive layer 10 This can be realized by adjusting the content ratio and using a crosslinking agent that crosslinks polymer components such as the base polymer contained in the pressure-sensitive adhesive layer 10 . Adjustment of the second shear storage modulus is, for example, adjustment of the constituent monomer composition of the polymer component in the pressure-sensitive adhesive layer 10, adjustment of the molecular weight of the polymer component, and inclusion of the polymer component in the pressure-sensitive adhesive layer 10. It may be realized by adjusting the ratio.

Adjustment of the ratio of the second shear storage modulus to the first shear storage modulus is, for example, adjustment of the constituent monomer composition in the polymer component such as the base polymer contained in the pressure-sensitive adhesive layer 10, the molecular weight of the polymer component Adjustment, adjustment of the content ratio of the polymer component in the pressure-sensitive adhesive layer 10, use of a crosslinking agent for crosslinking the polymer component, selection of the kind of monomer component contained as a curing component in the pressure-sensitive adhesive layer 10, and pressure-sensitive adhesive layer ( It can be realized by adjusting the content ratio of the monomer component in 10).

In the pressure-sensitive adhesive sheet S, a first color change width W1 of a discoloration area formed in the pressure-sensitive adhesive layer 10 by applying a first external stimulus in a linear form to the pressure-sensitive adhesive layer 10 after curing, and the pressure-sensitive adhesive layer ( 10) is further heat-treated at 85°C for 120 hours, and the second discoloration width W2 of the discolored area satisfies the following formula (1).

0.5≤W2/W1≤2 ... (1)

Such a configuration is suitable for suppressing deterioration (spreading, discoloration, non-uniformity of color, etc.) of the discolored portion formed on the pressure-sensitive adhesive layer 10, and thus, it is helpful to maintain the functional characteristics of the discolored portion. .

By applying the first external stimulus linearly to the pressure-sensitive adhesive layer 10 after curing, the first color change width W1 of the discoloration area formed in the pressure-sensitive adhesive layer 10 and the pressure-sensitive adhesive layer 10 are further increased at 65°C and The third discoloration width W3 of the discoloration area after heat treatment at 90% relative humidity for 120 hours satisfies the following formula (2).

0.5≤W3/W1≤2.4 ... (2)

Such a configuration is suitable for suppressing deterioration (spreading, discoloration, non-uniformity of color, etc.) of the discolored portion formed on the pressure-sensitive adhesive layer 10, and thus, it is helpful to maintain the functional characteristics of the discolored portion. .

The aforementioned second shear storage modulus of the pressure-sensitive adhesive layer 10 is preferably 0.2×10 ⁵ Pa or more, more preferably 2×10 ⁵ Pa or more, and even more preferably 5×10 ⁵ Pa or more. In the pressure-sensitive adhesive layer 10 in which the discolored portion is formed by the first external stimulus, such a configuration is suitable for suppressing the diffusion of the colorant in the discolored portion, and therefore suitable for suppressing deterioration of the discolored portion.

Further, the second shear storage modulus is preferably 100×10 ⁵ Pa or less, more preferably 50×10 ⁵ Pa or less, and still more preferably 25×10 ⁵ Pa or less. Such a configuration is suitable for securing the adhesive force to the adherend in the pressure-sensitive adhesive layer 10 after curing. In addition, these configurations regarding the second shear storage modulus are preferable for adjusting the pressure-sensitive adhesive layer 10 so as to satisfy the above formula (1), and also to satisfy the above formula (1), the pressure-sensitive adhesive layer ( 10) is preferred. By adjusting the second shear storage modulus of the pressure-sensitive adhesive layer 10, the pressure-sensitive adhesive layer 10 can be adjusted so as to satisfy the above formula (1) and/or formula (2).

In addition, as a method of adjusting the pressure-sensitive adhesive layer 10 so as to satisfy the above equations (1) and/or (2), the ratio of the first shear storage modulus and the second shear storage modulus to the first shear storage modulus It is also possible to apply, for example, the following method in a state where the ratio is maintained within the above range. A method of blending a metal complex in an adhesive layer (adhesive composition) (first method), a method using a component bonded to another component as a coloring component in the adhesive layer (second method), and incompatible with each other Alternatively, it is a method (third method) of providing a coloring component to islands in a sea-island structure formed by at least two components for bottom phase use.

The metal complex in the first method will be described later.

As the second method, for example, a method of using a polymer to which a component capable of developing color in a predetermined color is bonded as a component that serves both as a coloring component and a polymer component such as a base polymer in the pressure-sensitive adhesive layer; A method in which a component and a polymer component are bonded through reaction in the pressure-sensitive adhesive layer, and a method in which these are combined are exemplified.

As a third method, for example, a first polymer component having high compatibility with the coloring component and a second polymer component having low compatibility with the coloring component are used as polymer components in the pressure-sensitive adhesive layer, and furthermore, the pressure-sensitive adhesive layer. In this method, the coloring component is provided on the coating portion by forming a sea-island structure in which the first polymer component constitutes the coating portion.

The pressure-sensitive adhesive layer 10 contains, for example, a base polymer, a polymerizable compound, and a photopolymerization initiator in addition to a colorant capable of developing color in response to a first external stimulus.

The base polymer is an adhesive component for expressing adhesiveness in the adhesive layer 10 . The base polymer exhibits rubber elasticity in the room temperature region. Examples of the base polymer include acrylic polymers, rubber polymers, polyester polymers, urethane polymers, polyether polymers, silicone polymers, polyamide polymers, and fluoropolymers. From the viewpoint of ensuring good transparency and adhesiveness of the pressure-sensitive adhesive layer 10, an acrylic polymer is preferably used as the base polymer.

The content of the base polymer in the pressure-sensitive adhesive layer 10 is preferably 50% by mass or more, more preferably 60% by mass or more, from the viewpoint of appropriately expressing the function of the base polymer in the pressure-sensitive adhesive layer 10. More preferably, it is 70 mass % or more.

An acrylic polymer is, for example, a polymer obtained by polymerizing a monomer component containing an alkyl (meth)acrylate in a proportion of 50% by mass or more. "(meth)acrylic acid" means acrylic acid and/or methacrylic acid.

As an alkyl (meth)acrylate, the (meth)acrylic acid alkylester which has a linear or branched C1-C20 alkyl group is mentioned, for example. Examples of such alkyl (meth)acrylates include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, isopropyl (meth)acrylate, and (meth)acrylate. ) Isobutyl acrylate, s-butyl (meth)acrylate, t-butyl (meth)acrylate, pentyl (meth)acrylate, isopentyl (meth)acrylate, neopentyl (meth)acrylate, hexyl (meth)acrylate, (meth) Heptyl acrylate, 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, isooctyl (meth)acrylate, nonyl (meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, (meth)acrylic acid Isodecyl, (meth)acrylate undecyl, (meth)acrylate dodecyl, (meth)acrylate isotridecyl, (meth)acrylate tetradecyl, (meth)acrylate isotetradecyl, (meth)acrylate pentadecyl, (meth)acrylate hexadecyl acrylate, heptadecyl (meth)acrylate, octadecyl (meth)acrylate, isooctadecyl (meth)acrylate, nonadecyl (meth)acrylate, and eicosyl (meth)acrylate. (meth)acrylic-acid alkyl ester may be used independently, and 2 or more types may be used together. As the (meth)acrylic acid alkyl ester, preferably, an alkyl acrylate ester having an alkyl group of 1 to 12 carbon atoms is used, more preferably, methyl acrylate and an alkyl acrylate ester having an alkyl group of 2 to 12 carbon atoms are used together , More preferably, methyl acrylate and 2-ethylhexyl acrylate are used together.

The proportion of (meth)acrylic acid alkyl ester in the monomer component is preferably 50% by mass or more, more preferably 60% by mass or more, from the viewpoint of appropriately expressing basic properties such as adhesiveness in the pressure-sensitive adhesive layer 10 , More preferably, it is 70 mass % or more. The ratio is, for example, 99% by mass or less.

The monomer component may also contain a copolymerizable monomer copolymerizable with (meth)acrylic acid alkyl ester. As a copolymerizable monomer, the monomer which has a polar group is mentioned, for example. Examples of the polar group-containing monomer include a hydroxyl group-containing monomer, a monomer having a nitrogen atom-containing ring, and a carboxy group-containing monomer. The polar group-containing monomer is useful for modifying the acrylic polymer, such as introducing a crosslinking point into the acrylic polymer and securing cohesive force of the acrylic polymer.

The copolymerizable monomer preferably includes at least one selected from the group consisting of a hydroxyl group-containing monomer, a monomer having a nitrogen atom-containing ring, and a carboxy group-containing monomer. More preferably, the copolymerizable monomer includes a hydroxyl group-containing monomer and/or a monomer having a nitrogen atom-containing ring.

Examples of the hydroxyl group-containing monomer include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, ( 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, 12-hydroxylauryl (meth)acrylate, and (4-hydroxymethylcyclohexyl)methyl (meth)acrylate. As the hydroxyl group-containing monomer, 2-hydroxyethyl (meth)acrylate is preferably used, and 2-hydroxyethyl acrylate is more preferably used.

The ratio of the hydroxyl group-containing monomer in the monomer component is preferably 1% by mass or more, more preferably 3% by mass or more, from the viewpoint of introduction of a crosslinked structure into the acrylic polymer and securing of cohesive force in the pressure-sensitive adhesive layer 10. It is mass % or more, More preferably, it is 5 mass % or more. The ratio is preferably from the viewpoint of adjusting the viscosity of the polymerization reaction solution during polymerization of the acrylic polymer and adjusting the polarity of the acrylic polymer (related to compatibility between various additive components in the pressure-sensitive adhesive layer 10 and the acrylic polymer). is 30% by mass or less, more preferably 20% by mass or less.

Examples of the monomer having a nitrogen atom-containing ring include N-vinyl-2-pyrrolidone, N-methylvinylpyrrolidone, N-vinylpyridine, N-vinylpiperidone, N-vinylpyrimidine, and N- Vinylpiperazine, N-vinylpyrazine, N-vinylpyrrole, N-vinylimidazole, N-vinyloxazole, N-(meth)acryloyl-2-pyrrolidone, N-(meth)acryloylphy Peridine, N-(meth)acryloylpyrrolidine, N-vinylmorpholine, N-vinyl-3-morpholinone, N-vinyl-2-caprolactam, N-vinyl-1,3-oxazine- 2-one, N-vinyl-3,5-morpholinedione, N-vinylpyrazole, N-vinylisoxazole, N-vinylthiazole, and N-vinylisothiazole. As a monomer having a nitrogen atom-containing ring, N-vinyl-2-pyrrolidone is preferably used.

The ratio of the monomer having a nitrogen atom-containing ring in the monomer component is determined from the viewpoints of securing the cohesive force in the pressure-sensitive adhesive layer 10 and securing the adhesion to the adherend in the pressure-sensitive adhesive layer 10. , Preferably it is 1 mass % or more, More preferably, it is 3 mass % or more, More preferably, it is 5 mass % or more. The ratio is preferably 30 mass from the viewpoint of adjusting the glass transition temperature of the acrylic polymer and adjusting the polarity of the acrylic polymer (related to compatibility between various additive components in the pressure-sensitive adhesive layer 10 and the acrylic polymer). % or less, more preferably 20% by mass or less.

Examples of the carboxyl group-containing monomer include acrylic acid, methacrylic acid, carboxyethyl acrylate, carboxypentyl acrylate, itaconic acid, maleic acid, fumaric acid, crotonic acid, and isocrotonic acid.

The ratio of the carboxyl group-containing monomer in the monomer component is determined from the viewpoints of introducing a crosslinked structure into the acrylic polymer, securing cohesive force in the pressure-sensitive adhesive layer 10, and securing adherence to the adherend in the pressure-sensitive adhesive layer 10. In , it is preferably 1% by mass or more, more preferably 3% by mass or more, and still more preferably 5% by mass or more. The ratio is preferably 30% by mass or less, more preferably 20% by mass or less, from the viewpoint of adjusting the glass transition temperature of the acrylic polymer and avoiding the risk of corrosion of the adherend by acid.

The monomer component may contain other copolymerizable monomers. Examples of other copolymerizable monomers include acid anhydride monomers, sulfonic acid group-containing monomers, phosphoric acid group-containing monomers, epoxy group-containing monomers, cyano group-containing monomers, amide group-containing monomers, monomers having a succinimide skeleton, maleimides, Itaconimides, alkoxy group-containing monomers, vinyl esters, vinyl ethers, and aromatic vinyl compounds.

As an acid anhydride monomer, maleic acid anhydride and itaconic acid anhydride are mentioned, for example.

Examples of the sulfonic acid group-containing monomer include styrenesulfonic acid, allylsulfonic acid, sodium vinylsulfonate, 2-(meth)acrylamide-2-methylpropanesulfonic acid, (meth)acrylamidepropanesulfonic acid, and sulfonic acid. propyl (meth)acrylate, and (meth)acryloyloxynaphthalenesulfonic acid.

As a phosphoric acid group containing monomer, 2-hydroxyethyl acryloyl phosphate is mentioned, for example.

As the epoxy group-containing monomer, for example, epoxy group-containing acrylates such as glycidyl (meth)acrylate and 2-ethyl glycidyl (meth)acrylate, allyl glycidyl ether, and glycidyl (meth)acrylate ether.

Examples of the cyano group-containing monomer include acrylonitrile and methacrylonitrile.

Examples of the amide group-containing monomer include N-vinylcarboxylic acid amides such as (meth)acrylamide, N,N-dialkyl (meth)acrylamide, N-alkyl (meth)acrylamide, and N-vinylacetamide. , N-hydroxyalkyl (meth)acrylamide, N-alkoxyalkyl (meth)acrylamide, N,N-dimethylaminopropyl (meth)acrylamide, and N-(meth)acryloylmorpholine. . Examples of N,N-dialkyl (meth)acrylamide include N,N-dimethyl (meth)acrylamide, N,N-diethyl (meth)acrylamide, and N,N-dipropyl (meth)acrylamide. acrylamide, N,N-diisopropyl (meth)acrylamide, N,N-di(n-butyl) (meth)acrylamide, and N,N-di(t-butyl) (meth)acrylamide. can Examples of N-alkyl (meth)acrylamides include N-ethyl (meth)acrylamide, N-isopropyl (meth)acrylamide, N-butyl (meth)acrylamide, and N-n-butyl (meth)acrylamide. amides. As N-hydroxyalkyl (meth)acrylamide, for example, N-(2-hydroxyethyl) (meth)acrylamide, N-(2-hydroxypropyl) (meth)acrylamide, N-(1 -Hydroxypropyl) (meth)acrylamide, N-(3-hydroxypropyl) (meth)acrylamide, N-(2-hydroxybutyl) (meth)acrylamide, N-(3-hydroxybutyl) (meth)acrylamide, and N-(4-hydroxybutyl) (meth)acrylamide. Examples of N-alkoxyalkyl (meth)acrylamide include N-methoxymethyl (meth)acrylamide, N-methoxyethyl (meth)acrylamide, and N-butoxymethyl (meth)acrylamide. can

Examples of the monomer having a succinimide skeleton include N-(meth)acryloyloxymethylenesuccinimide, N-(meth)acryloyl-6-oxyhexamethylenesuccinimide, and N-(meth)acryloyloxymethylenesuccinimide. ) acryloyl-8-oxyhexamethylene succinimide.

As maleimides, N-cyclohexyl maleimide, N-isopropyl maleimide, N-lauryl maleimide, and N-phenyl maleimide are mentioned, for example.

Examples of itaconimides include N-methyl itaconimide, N-ethyl itaconimide, N-butyl itaconimide, N-octyl itaconimide, and N-2-ethylhexyl itaconimide. imide, N-cyclohexylitaconimide, and N-laurylitaconimide.

Examples of the alkoxy group-containing monomer include alkoxyalkyl (meth)acrylates and alkoxyalkylene glycols (meth)acrylates. Examples of alkoxyalkyl (meth)acrylates include 2-methoxyethyl (meth)acrylate, 3-methoxypropyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, and propoxyethyl (meth)acrylate. , butoxyethyl (meth)acrylate, and ethoxypropyl (meth)acrylate. Examples of the alkoxyalkylene glycols (meth)acrylates include methoxyethylene glycol (meth)acrylates and methoxypolypropylene glycol (meth)acrylates.

Examples of vinyl esters include vinyl acetate and vinyl propionate.

Examples of vinyl ethers include methyl vinyl ether and ethyl vinyl ether.

As an aromatic vinyl compound, styrene, (alpha)-methylstyrene, and vinyltoluene are mentioned, for example. As olefins, ethylene, butadiene, isoprene, and isobutylene are mentioned, for example.

A copolymerizable monomer may be used independently and two or more types may be used together.

An acrylic polymer can be formed by polymerizing the above-mentioned monomer components. Examples of the polymerization method include solution polymerization, bulk polymerization, and emulsion polymerization, preferably solution polymerization. In solution polymerization, a reaction solution is prepared by blending a monomer component and a polymerization initiator in a solvent, for example, and then the reaction solution is heated. Then, an acrylic polymer solution containing an acrylic polymer can be obtained by undergoing a polymerization reaction of the monomer component in the reaction solution. As a polymerization initiator, a thermal polymerization initiator is used, for example. The usage amount of the polymerization initiator is, for example, 0.05 part by mass or more, and, for example, 1 part by mass or less, based on 100 parts by mass of the monomer component.

As a thermal polymerization initiator, an azo polymerization initiator and a peroxide polymerization initiator are mentioned, for example. Examples of the azo polymerization initiator include 2,2'-azobisisobutyronitrile, 2,2'-azobis-2-methylbutyronitrile, and 2,2'-azobis(2-methylpropionic acid). ) dimethyl, 4,4'-azobis-4-cyanovalerian acid, azobisisovaleronitrile, 2,2'-azobis (2-amidinopropane) dihydrochloride, 2,2' -azobis[2-(5-methyl-2-imidazolin-2-yl)propane] dihydrochloride, 2,2'-azobis(2-methylpropionamidine) disulfate, and 2,2 '-azobis(N,N'-dimethyleneisobutylamidine) dihydrochloride. As a peroxide polymerization initiator, dibenzoyl peroxide, t-butyl permaleate, and lauroyl peroxide are mentioned, for example.

The weight average molecular weight of the acrylic polymer is preferably 100000 or more, more preferably 300000 or more, still more preferably 500000 or more, from the viewpoint of securing the cohesive force in the pressure-sensitive adhesive layer 10. The same weight average molecular weight is preferably 5000000 or less, more preferably 3000000 or less, still more preferably 2000000 or less. The weight average molecular weight of the acrylic polymer is measured by a gel permeation chromatograph (GPC) and calculated in terms of polystyrene.

The glass transition temperature (Tg) of the base polymer is preferably 0°C or lower, more preferably -10°C or lower, still more preferably -20°C or lower. The copper glass transition temperature is, for example, -80°C or higher.

Regarding the glass transition temperature (Tg) of the polymer, a glass transition temperature (theoretical value) obtained based on the following formula of Fox can be used. Fox's formula is a relational expression between the glass transition temperature Tg of a polymer and the glass transition temperature Tgi of a homopolymer of monomers constituting the polymer. In Fox's formula below, Tg represents the glass transition temperature (°C) of a polymer, Wi represents the weight fraction of monomer i constituting the polymer, and Tgi represents the glass transition temperature of a homopolymer formed from monomer i. (°C) is shown. For the glass transition temperature of the homopolymer, literature values can be used, for example, "Polymer Handbook" (4th edition, John Wiley & Sons, Inc., 1999) and "New Polymer Library 7 Synthesis for Paints" Introduction to resins” (Kyojo Kitaoka, Polymer Publishing Society, 1995) lists the glass transition temperatures of various homopolymers. On the other hand, about the glass transition temperature of the homopolymer of a monomer, it is also possible to obtain|require by the method specifically described in Unexamined-Japanese-Patent No. 2007-51271.

Fox's equation 1/(273+Tg)=Σ[Wi/(273+Tgi)]

The adhesive composition may contain a crosslinking agent from the viewpoint of introducing a crosslinked structure into the base polymer. Examples of the crosslinking agent include isocyanate crosslinking agents, epoxy crosslinking agents, oxazoline crosslinking agents, aziridine crosslinking agents, carbodiimide crosslinking agents, and metal chelate crosslinking agents. A crosslinking agent may be used independently and two or more types may be used together.

Examples of the isocyanate crosslinking agent include tolylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, xylylene diisocyanate, and hydrogenated xylylene diisocyanate. nate, diphenylmethane diisocyanate, hydrogenated diphenylmethane diisocyanate, tetramethylxylylene diisocyanate, naphthaline diisocyanate, triphenylmethane triisocyanate , and polymethylene polyphenyl isocyanate. Moreover, derivatives of these isocyanates are also mentioned as an isocyanate crosslinking agent. As the said isocyanate derivative, an isocyanurate modified body and a polyol modified body are mentioned, for example. As a commercially available isocyanate crosslinking agent, for example, Coronate L (trimethylolpropane adduct of tolylene diisocyanate, manufactured by Tosoh), Coronate HL (of hexamethylene diisocyanate) Trimethylolpropane adduct, manufactured by Tosoh), Coronate HX (isocyanurate of hexamethylene diisocyanate, manufactured by Tosoh), and Takenate D110N (trimethyl of xylylene diisocyanate) All-propane adducts, manufactured by Mitsui Chemicals) are exemplified.

Examples of the epoxy crosslinking agent include bisphenol A, epichlorohydrin type epoxy resin, ethylene glycidyl ether, polyethylene glycol diglycidyl ether, glycerin diglycidyl ether, glycerin triglycidyl ether, 1,6- Hexanediol glycidyl ether, trimethylolpropane triglycidyl ether, diglycidylaniline, diamineglycidylamine, N,N,N',N'-tetraglycidyl-m-xyl relendiamine, and 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane.

The blending amount of the crosslinking agent is, for example, 0.01 part by mass or more, preferably 0.05 part by mass or more, and more preferably 0.07 part by mass with respect to 100 parts by mass of the base polymer, from the viewpoint of securing the cohesive force of the pressure-sensitive adhesive layer 10. More than that. From the viewpoint of ensuring good tackiness in the pressure-sensitive adhesive layer 10, the compounding amount of the crosslinking agent relative to 100 parts by mass of the base polymer is, for example, 10 parts by mass or less, preferably 5 parts by mass or less, and more preferably 3 parts by mass. is less than

When a crosslinking structure is introduced into the base polymer, a crosslinking catalyst may be used to effectively advance the crosslinking reaction. Examples of the crosslinking catalyst include dibutyltin dilaurate, tetra-n-butyl titanate, tetraisopropyl titanate, ferric nasem, and butyltin oxide, and preferably both Dibutyltin iraurate is used. The amount of the crosslinking catalyst used is, for example, 0.0001 part by mass or more and 1 part by mass or less with respect to 100 parts by mass of the base polymer.

When a crosslinking catalyst is used, a crosslinking inhibitor that can be removed posthumously from the adhesive composition may be incorporated into the adhesive composition. When dibutyltin dilaurate is used as a crosslinking catalyst, acetylacetone is preferably used as a crosslinking inhibitor. In this case, in the adhesive composition, acetylacetone is coordinated with dibutyltin dilaurate, and the crosslinking reaction of the crosslinking agent with respect to the base polymer is suppressed. In the manufacturing process of the adhesive sheet S described later, after the adhesive composition is applied on the peeling film to form a coating film, acetylacetone can be volatilized and removed from the coating film by heating at a desired timing. Thereby, the crosslinking reaction of the crosslinking agent can be advanced.

The blending amount of the crosslinking inhibitor is, for example, 100 parts by mass or more, preferably 1000 parts by mass or more, based on 100 parts by mass of the crosslinking catalyst. The blending amount of copper is, for example, 5000 parts by mass or less.

A polymerizable compound is a compound having a polymerizable functional group. The polymerizable functional group has an ethylenically unsaturated double bond. As a polymerizable functional group, a vinyl group, a propenyl group, and a (meth)acryloyl group are mentioned, for example. A (meth)acryloyl group means an acryloyl group and/or a methacryloyl group. From the viewpoint of reactivity, a compound having a (meth)acryloyl group as a polymerizable functional group is preferably used as the polymerizable compound.

A polymeric compound may be used independently, and 2 or more types may be used together.

Moreover, as a polymeric compound, the monomer (monofunctional monomer) which has one polymerizable functional group, and the monomer (polyfunctional monomer) which has several polymerizable functional groups are mentioned, for example.

Examples of the monofunctional monomer include ethyl (meth)acrylate, n-butyl (meth)acrylate, ter-butyl (meth)acrylate, isobutyl methacrylate, 2-ethylhexyl (meth)acrylate, Isodecyl (meth)acrylate, butoxydiethylene glycol (meth)acrylate, methoxypolyethylene glycol (meth)acrylate, glycidyl (meth)acrylate, lauryl (meth)acrylate, Stearyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, caprolactone-modified tetrahydrofurfuryl (meth)acrylate, cyclohexyl (meth)acrylate, dicyclopentanyl (meth)acrylate, Cyclopentenyl (meth)acrylate, dicyclopentenyloxy (meth)acrylate, isobornyl (meth)acrylate, adamantyl (meth)acrylate, benzyl (meth)acrylate, phenyl (meth)acrylate Latex, phenoxyethyl (meth)acrylate, phenoxydiethylene glycol (meth)acrylate, phenoxytetraethylene glycol (meth)acrylate, nonylphenoxyethyl (meth)acrylate, butoxyethyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, glycerol (meth)acrylate, trifluoroethyl (meth)acrylate, methacryloxyoxyethyl acid phosphate, 2-hydroxyethyl methacrylic acid phosphate, γ-methacryloxypropyltrimethoxysilane, γ-acryloxypropyltrimethoxysilane, acryloylmo polyne, morpholinoethyl (meth)acrylate, dimethylaminoethyl (meth)acrylate, diethylaminoethyl (meth)acrylate, and N,N-dimethylaminoethyl (meth)acrylate. .

Examples of the polyfunctional monomer include bifunctional monomers, trifunctional monomers, and tetrafunctional or higher functional monomers.

Examples of the difunctional monomer include ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, and tetraethylene glycol di(meth)acrylate. Methacrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, glycerin di(meth)acrylate, neopentyl glycol di(meth)acrylate ) acrylate, stearic acid-modified pentaerythritol di(meth)acrylate, dicyclopentenyl diacrylate, di(meth)acryloyl isocyanurate, and alkylene oxide-modified bisphenol di(meth)acrylate can be heard

As a trifunctional monomer, trimethylolpropane tri (meth)acrylate, pentaerythritol tri (meth)acrylate, and tris (acryloyloxyethyl) isocyanurate are mentioned, for example.

Examples of the tetrafunctional or higher functional monomer include ditrimethylolpropane tetra(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol monohydroxypenta(meth)acrylate, and alkyl modified dipentaerythritol pentaacrylate, and dipentaerythritol hexa(meth)acrylate.

From the viewpoint of the rapid curability of the pressure-sensitive adhesive layer 10, as the polymerizable compound, preferably a polyfunctional monomer is used, more preferably a trifunctional monomer or a tetrafunctional or higher functional monomer is used. As the trifunctional monomer for the polymerizable compound, trimethylolpropane tri(meth)acrylate is preferably used, and trimethylolpropane triacrylate is more preferably used. As the tetrafunctional or higher functional monomer for the polymerizable compound, dipentaerythritol hexa(meth)acrylate is preferably used, and dipentaerythritol hexaacrylate is more preferably used.

The blending amount of the polymerizable compound is preferably 5 parts by mass or more, more preferably 7 parts by mass or more, with respect to 100 parts by mass of the base polymer, from the viewpoint of ensuring sufficient hardness in the pressure-sensitive adhesive layer 10 after curing. Preferably it is 9 parts by mass or more, particularly preferably 10 parts by mass or more. From the viewpoint of ensuring sufficient adhesive strength in the pressure-sensitive adhesive layer 10 after curing, the blending amount of the polymerizable compound relative to 100 parts by mass of the base polymer is preferably 50 parts by mass or less, more preferably 45 parts by mass or less, still more preferably It is 43 parts by mass or less.

The photopolymerization initiator initiates a polymerization reaction of a polymerizable compound by receiving active energy ray irradiation as a second external stimulus. Examples of the photopolymerization initiator include benzoin ether photopolymerization initiator, acetophenone photopolymerization initiator, α-ketol photopolymerization initiator, aromatic sulfonyl chloride photopolymerization initiator, photoactive oxime photopolymerization initiator, benzoin photopolymerization initiator, benzyl photopolymerization initiator, and benzophenone photopolymerization initiator. , ketal photopolymerization initiators, thioxanthone photopolymerization initiators, and acylphosphine oxide photopolymerization initiators.

The colorant is preferably a compound that develops color by reaction with an acid (color-developing compound). When the colorant is a color-developing compound, the adhesive composition further contains an acid generator.

As a color developing compound, a leuco dye, a triarylmethane dye, a diphenylmethane dye, a fluoran dye, a spiropyran dye, and a rhodamine dye are mentioned, for example. A color developing compound may be used independently, and 2 or more types may be used together.

Examples of the leuco dye include 2'-anilino-6'-(N-ethyl-N-isopentylamino)-3'-methylspiro[phthalide-3,9'-[9H]xanthene]; 3-Dibutylamino-6-methyl-7-anilinofluoran, 3-dipropylamino-6-methyl-7-anilinofluoran, 3-diethylamino-6-methyl-7-anilinofluoran , 3-dimethylamino-6-methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7-xylidinofluorane, and 3-(4-diethylamino-2-ethoxyphenyl )-3-(1-ethyl-2-methylindol-3-yl)-4-azaphthalide.

Examples of the triarylmethane dye include p,p',p"-tris-dimethylaminotriphenylmethane. Examples of the diphenylmethane dye include 4,4-bis- Dimethylaminophenylbenzhydrylbenzyl ether.Examples of the fluoran dye include 3-diethylamino-6-methyl-7-chlorofluorane.As the spiropyran dye, Examples of the rhodamine pigment include 3-methylspirodinaphthopyran, and rhodamine-B-anilinolactam.

From the viewpoint of ensuring good colorability in the pressure-sensitive adhesive layer 10, the color-developing compound is preferably a leuco dye, more preferably 2'-anilino-6'-(N-ethyl-N-isopentylamino)- 3'-methylspiro[phthalide-3,9'-[9H]xanthene] is used.

The compounding amount of the color developing compound relative to 100 parts by mass of the base polymer is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more. The blending amount is preferably 10 parts by mass or less, more preferably 7 parts by mass or less.

As the acid generator, a photoacid generator that generates an acid when irradiated with active energy rays is preferably used. In this case, the portion of the pressure-sensitive adhesive layer 10 that has been irradiated with active energy rays as the first external stimulus can be discolored. Specifically, in a portion of the pressure-sensitive adhesive layer 10 irradiated with active energy rays, an acid is generated from a photoacid generator, and the color-developing compound develops color with the acid. That is, the color-developing compound as a colorant can develop color in response to a first external stimulus. The portion of the pressure-sensitive adhesive layer 10 that has been irradiated with active energy rays is colored dark, for example, according to the color development of the color-developing compound. The type of active energy ray as the first external stimulus is determined by the type of photoacid generator (specifically, the wavelength of the active energy ray at which the photoacid generator generates acid). Examples of active energy rays include ultraviolet rays, visible light, infrared rays, X-rays, α-rays, β-rays, and γ-rays. From the viewpoint of diversity of use equipment and ease of handling, ultraviolet rays are preferably used as the active energy ray.

As the photoacid generator, for example, an onium compound that generates an acid by ultraviolet irradiation (first external stimulus) is exemplified. The onium compound is provided in the form of, for example, an onium salt of an onium cation and an anion. As an onium cation, iodonium and sulfonium are mentioned, for example. Examples of anions include Cl ^- , Br ^- , I ^- , ZnCl ₃ ^- , HSO ₃ ^- , BF ₄ ^- , PF ₆ ^- , AsF ₆ ^- , SbF ₆ ^- , CH ₃ SO ₃ ^- , CF ₃ SO ₃ ^- , C ₄ F ₉ HSO ₃ ^- , (C ₆ F ₅ ) ₄ B ^- , and (C ₄ H ₉ ) ₄ B ^- . A photoacid generator may be used independently, or two or more types may be used together. The adhesive composition preferably contains an onium salt (onium compound) composed of sulfonium and C ₄ F ₉ HSO ₃ ^- as a photoacid generator.

When the pressure-sensitive adhesive layer 10 contains both the photoacid generator and the photopolymerization initiator described above, the pressure-sensitive adhesive layer 10 preferably has a ratio of the absorbance Y of the photopolymerization initiator to the absorbance X of the photoacid generator of 2 or more. It has a wavelength range within the range of 300 nm or more and 500 nm or less. The ratio is preferably 3 or more, more preferably 10 or more, still more preferably 50 or more, and particularly preferably 100 or more. The same ratio is, for example, 1 million or less.

The blending amount of the acid generator with respect to 100 parts by mass of the base polymer is preferably 1 part by mass or more, more preferably 2 parts by mass or more, even more preferably 5 parts by mass or more, and particularly preferably 7 parts by mass or more. The blending amount is preferably 20 parts by mass or less, more preferably 15 parts by mass or less, still more preferably 12 parts by mass or less.

The blending amount of the acid generator with respect to 100 parts by mass of the color developing compound is, for example, 100 parts by mass or more, preferably 200 parts by mass or more, more preferably 300 parts by mass or more, still more preferably 330 parts by mass or more. . The blending amount is preferably 1000 parts by mass or less, more preferably 700 parts by mass or less, still more preferably 500 parts by mass or less.

The adhesive composition may contain other components as needed. Examples of other components include silane coupling agents, tackifiers, plasticizers, softeners, antioxidants, surfactants, and antistatic agents.

The adhesive composition may contain a metal complex capable of coordinate bonding with a coloring component such as a leuco dye. As a means for adjusting the pressure-sensitive adhesive layer 10 so as to satisfy the above formula (1) and/or formula (2), such a metal complex can be used.

As the metal constituting the metal ion of the metal complex, alkali metals of group 1, alkaline earth metals of group 2, in the periodic table (according to IUPAC Periodic Table of the Elements (version date 19 February 2010). and transition metals of Groups 3 to 12, preferably alkaline earth metals of Group 2 and transition metals of Groups 3 to 12 are used. When a leuco dye is used as a coloring component, magnesium (Mg) is preferable as the metal from the viewpoint of the strong coordination bond between the carboxyl group and the metal of the leuco dye in the form of a chromogen. Zinc (Zn) is preferable as the metal from the viewpoint of stabilizing an amphoteric counter ion formed by the leuco dye and metal complex when the leuco dye is used as the coloring component.

As a ligand of a metal complex, a monodentate ligand and a bidentate ligand are mentioned, for example. Examples of monodentate ligands include hydroxo (OH-), halogen (eg, chloro (Cl-)), and cyano (CN-). Examples of the bidentate ligand include ethylenediamine, bipyridine, phenanthroline, and salicylic acid.

As the metal complex, a metal complex having a bidentate ligand is preferably used, and from the viewpoint of stabilizing the positive counter ion described above, zinc salicylate (specifically, zinc salicylate trihydrate) is more preferably used. A metal complex may be used independently and two or more types may be used together.

The compounding amount of the metal complex with respect to 100 parts by mass of the base polymer is, for example, 0.1 part by mass or more, preferably 0.2 part by mass or more, more preferably 0.5 part by mass or more, still more preferably 0.8 part by mass or more. The blending amount is, for example, 5 parts by mass or less, preferably 2 parts by mass or less.

The compounding amount of the metal complex with respect to 100 parts by mass of the color developing compound is, for example, 10 parts by mass or more, preferably 20 parts by mass or more, and more preferably 40 parts by mass or more. The blending amount is, for example, 100 parts by mass or less, preferably 80 parts by mass or less.

The adhesive sheet S can be produced, for example, by applying the above-described adhesive composition onto a release film (first release film) to form a coating film, and then drying the coating film (in FIG. 1, The adhesive sheet S is arrange|positioned on the peeling film L shown by a phantom line).

As a peeling film, the plastic film which has flexibility is mentioned, for example. As the said plastic film, a polyethylene terephthalate film, a polyethylene film, a polypropylene film, and a polyester film are mentioned, for example. The thickness of the peeling film is, for example, 3 μm or more, and is, for example, 200 μm or less. The surface of the release film is preferably subjected to release treatment.

As a method of applying the adhesive composition, for example, roll coating, kiss roll coating, gravure coating, reverse coating, roll brush, spray coating, dip roll coating, bar coating, knife coating, air knife coating, curtain coating, lip coating, and die coating. The drying temperature of the coating film is, for example, 50°C to 200°C. Drying time is 5 seconds - 20 minutes, for example.

When the adhesive composition contains a crosslinking agent, a crosslinking reaction proceeds simultaneously with the drying described above or by aging thereafter. Aging conditions are appropriately set depending on the type of crosslinking agent. The aging temperature is, for example, 20°C to 160°C. The aging time is, for example, 1 minute to 7 days.

Moreover, you may laminate|stack a peeling film (2nd peeling film) further on the adhesive layer 10 on the 1st peeling film before or after aging. The second release film is a flexible plastic film subjected to surface release treatment, and the same one as described above for the first release film can be used.

As described above, the adhesive sheet S in which the adhesive face is covered and protected by the release film can be manufactured. Each peeling film is peeled off from the adhesive sheet S as needed when using the adhesive sheet S.

The thickness of the pressure-sensitive adhesive layer 10 is preferably 10 μm or more, more preferably 15 μm or more, from the viewpoint of ensuring sufficient adhesiveness to the adherend. From the standpoint of the handleability of the PSA sheet S, the thickness of the PSA layer 10 is preferably 300 μm or less, more preferably 200 μm or less, even more preferably 100 μm or less, and particularly preferably 50 μm or less.

After the pressure-sensitive adhesive sheet S is bonded to the glass plate, the adhesive strength to the stainless plate in a peeling test under peeling conditions of 23°C, a peeling angle of 180°, and a peeling speed of 300 mm/min is, for example, 1 N/min. It is 25 mm or more and, for example, 50 N/25 mm or less.

The haze of the pressure-sensitive adhesive layer 10 is preferably 3% or less, more preferably 2% or less, and still more preferably 1% or less. Such a structure is suitable for inspecting the presence or absence of foreign matter and air bubbles between the adhesive sheet S and the adherend after bonding the adhesive sheet S to the adherend. The haze of the adhesive layer 10 can be measured using a haze meter based on JIS K7136 (2000). As a haze meter, "NDH2000" by Nippon Denshoku Kogyo Co., Ltd. and "HM-150 type|mold" by Murakami Color Technology Laboratory Co., Ltd. are mentioned, for example.

The average transmittance T1 (average transmittance before UV irradiation) of the pressure-sensitive adhesive layer 10 at a wavelength of 400 to 700 nm is preferably 80% or more, more preferably 85% or more, still more preferably 90% or more. The average transmittance T1 is, for example, 100% or less. Such a structure is suitable for inspecting the presence or absence of foreign matter and air bubbles between the adhesive sheet S and the adherend after bonding the adhesive sheet S to the adherend. The average transmittance T1 is obtained by a method described later in the Examples.

The average transmittance T2 at a wavelength of 400 to 700 nm of the pressure-sensitive adhesive layer 10 subjected to UV irradiation (specifically, UV irradiation under the conditions described later regarding the second transmittance measurement in the later example) is preferably 50% or less, more preferably 40% or less, even more preferably 30% or less, particularly preferably 25% or less. Average transmittance T2 is 0% or more, for example. Such a configuration is preferable from the viewpoint of securing the function of the discolored portion in the pressure-sensitive adhesive layer 10 in which the discolored portion is formed. Average transmittance T2 is obtained by a method described later in relation to Examples.

The ratio of the average transmittance T2 to the average transmittance T1 (T2/T1) is preferably 0.4 or less, more preferably 0.3 or less, still more preferably 0.2 or less. Moreover, the ratio (T2/T1) is 0.001 or more, for example. These configurations are preferable from the viewpoint of ensuring the function of the discolored portion in the pressure-sensitive adhesive layer 10 in which the discolored portion is formed.

As shown in FIG. 2 , the PSA sheet S may be a single-sided PSA sheet with a base material including a base material 20 in addition to the PSA layer 10 . In this case, the pressure-sensitive adhesive sheet S specifically includes the pressure-sensitive adhesive layer 10 and the base material 20 disposed on one side in the thickness direction. Preferably, the substrate 20 contacts one side of the pressure-sensitive adhesive layer 10 in the thickness direction.

The substrate 20 is an element that functions as a transparent support. The substrate 20 is, for example, a plastic film having flexibility. Examples of the constituent material of the plastic film include polyolefin, polyester, polyamide, polyimide, polyvinyl chloride, polyvinylidene chloride, cellulose, polystyrene, and polycarbonate. Examples of the polyolefin include polyethylene, polypropylene, poly-1-butene, poly-4-methyl-1-pentene, ethylene/propylene copolymer, ethylene/1-butene copolymer, ethylene/vinyl acetate copolymer, and ethylene. • Ethyl acrylate copolymer, and ethylene/vinyl alcohol copolymer. As polyester, polyethylene terephthalate, polyethylene naphthalate, and polybutylene terephthalate are mentioned, for example. Examples of the polyamide include polyamide 6, polyamide 6 and 6, and partially aromatic polyamide. In the base material 20, from the viewpoint of achieving both transparency and mechanical strength, the plastic material of the base material 20 is preferably polyester, more preferably polyethylene terephthalate.

The substrate 20 has transparency. The haze of the substrate 20 is preferably 3% or less, more preferably 2% or less, still more preferably 1% or less. The haze of the substrate 20 can be measured using a haze meter in accordance with JIS K7136 (2000).

The surface of the base material 20 on the side of the pressure-sensitive adhesive layer 10 may be subjected to physical treatment, chemical treatment, or undercoating treatment for enhancing adhesion to the pressure-sensitive adhesive layer 10 . As a physical treatment, a corona treatment and a plasma treatment are mentioned, for example. As a chemical treatment, acid treatment and alkali treatment are mentioned, for example.

The thickness of the substrate 20 is preferably 5 μm or more, more preferably 10 μm or more, and still more preferably 20 μm or more, from the viewpoint of securing strength for the substrate 20 to function as a support. Further, from the viewpoint of realizing appropriate flexibility in the adhesive sheet S, the thickness of the substrate 20 is preferably 200 μm or less, more preferably 150 μm or less, still more preferably 100 μm or less.

The PSA sheet S shown in FIG. 2 can be manufactured, for example, by the same method as the PSA sheet manufacturing method described above, except that the substrate 20 is used instead of the first peeling film.

3A to 3D show an example of a method of using the pressure-sensitive adhesive sheet S. This method includes a preparation process, a bonding process, a curing process, and a discoloration portion forming process.

First, in the preparation step, as shown in Fig. 3A, the adhesive sheet S, the first member 31, and the second member 32 are prepared. The first member 31 is, for example, a display panel such as an organic EL panel. The first member 31 may be another electronic device or an optical device. The second member 32 is, for example, a transparent substrate. As a transparent base material, a transparent plastic base material and a transparent glass base material are mentioned.

Next, in the joining step, as shown in Fig. 3B, the first member 31 and the second member 32 are joined with the adhesive sheet S interposed therebetween. In this way, the layered product Z is obtained. In the layered body Z, the adhesive sheet S is disposed so as to contact one surface of the first member 31 in the thickness direction, and the second member 32 is disposed on one side of the adhesive sheet S in the thickness direction. It is placed so as to contact the surface.

After the bonding step, the presence or absence of foreign substances and air bubbles between the members 31 and 32 and the adhesive sheet S is inspected as necessary.

Next, in the curing step, as shown in FIG. 3C , a second external stimulus is applied to the pressure-sensitive adhesive layer 10 in the layered product Z (when the above test is performed, the layered product Z that has passed the test) to cure the pressure-sensitive adhesive layer 10. In this embodiment, the second external stimulus is active energy ray irradiation. This active energy ray is irradiated to the pressure-sensitive adhesive layer 10 from the side of the transparent second member 32 . As a light source for active energy ray irradiation in this process, an ultraviolet LED light, a high pressure mercury lamp, and a metal halide lamp are mentioned, for example. In the active energy ray irradiation in this step, a wavelength cut filter for cutting a part of the wavelength region in the active energy ray emitted from the light source may be used as needed.

The active energy ray as the second external stimulus has a different wavelength range from the active energy ray as the first external stimulus. In the present embodiment, the active energy ray as the second external stimulus has a wavelength that does not substantially generate acid in the acid generator. The lower limit of the wavelength range of the active energy ray is preferably 365 nm, more preferably 370 nm, still more preferably 375 nm, still more preferably 380 nm, still more preferably 385 nm, still more preferably 390 nm, particularly preferably It is 395 nm. In the present embodiment, preferably, a photopolymerization initiator that initiates a polymerization reaction of a polymerizable compound by receiving active energy ray irradiation of such a wavelength is incorporated into the pressure-sensitive adhesive layer 10 .

In this step, in the pressure-sensitive adhesive layer 10 subjected to active energy ray irradiation, the polymerization reaction of the polymerizable compound is started by the photopolymerization initiator, and the polymerization reaction proceeds. As a result, the modulus of elasticity of the pressure-sensitive adhesive layer 10 increases.

As described above, the pressure-sensitive adhesive layer 10 preferably has a wavelength range (wavelength range R) in which the ratio of the absorbance Y of the photopolymerization initiator to the absorbance X of the photoacid generator is 2 or more within a wavelength range of 300 nm or more and 500 nm or less. do. The ratio (Y/X) in the wavelength range R is preferably 3 or more, more preferably 10 or more, still more preferably 100 or more. Preferably, at least a part of the wavelength of the active energy ray irradiated as the second external stimulus is within the wavelength range R. More preferably, all of the wavelengths of the active energy ray irradiated as the second external stimulus are within the wavelength range R. A configuration in which an active energy ray having a wavelength within such a wavelength range is applied to the pressure-sensitive adhesive layer 10 as a second external stimulus causes the pressure-sensitive adhesive layer 10 to be cured while suppressing discoloration in the pressure-sensitive adhesive layer 10. suitable for curing In the curing step, from the viewpoint of curing the pressure-sensitive adhesive layer 10 while suppressing discoloration in the pressure-sensitive adhesive layer 10, the ratio of the absorbance Y of the photopolymerization initiator to the absorbance X of the photoacid generator is preferably larger. .

Next, in the discoloration portion forming step, as shown in FIG. 3D, a first external stimulus is applied to the adhesive layer 10 in the layered product Z to form the discoloration portion 11 in the adhesive layer 10. form Specifically, from the side of the transparent second member 32, a mask pattern (not shown) for masking a predetermined area in the pressure-sensitive adhesive layer 10 is interposed, and the pressure-sensitive adhesive layer 10 acts as a first external stimulus. An active energy ray (first active energy ray) is irradiated. As a result, the portion of the pressure-sensitive adhesive layer 10 not masked by the mask pattern is discolored. As the shape of the discoloration part 11 formed in this way, a linear shape, a dotted shape, a rectangular shape, a circular shape, an elliptical shape, and an irregular shape are mentioned, for example.

As a light source for active energy ray irradiation in this process, an ultraviolet LED light, a high pressure mercury lamp, and a metal halide lamp are mentioned, for example. In the active energy ray irradiation in this step, a wavelength cut filter for cutting a part of the wavelength region in the active energy ray emitted from the light source may be used as needed.

The first active energy ray has a different wavelength range from the above-described active energy ray (second active energy ray) serving as the second external stimulus. The wavelength range of the first active energy ray preferably includes at least a range smaller than the wavelength range of the second active energy ray (wavelength range on the shorter wavelength side) (the wavelength range of the first active energy ray is equal to the wavelength of the second active energy ray). ranges and overlapping ranges may be included). When the first active energy ray has a lower limit in the wavelength range or, for example, when a lower limit is provided in the wavelength range of the first active energy ray using a wavelength cut filter, the lower limit of the wavelength range of the first active energy ray is, It is preferably 300 nm, more preferably 305 nm, even more preferably 310 nm, even more preferably 315 nm, still more preferably 320 nm, still more preferably 325 nm, and particularly preferably 330 nm. Alternatively, light with a wavelength of less than 300 nm may be contained in the first active energy ray. As a light source of such light, a high pressure mercury lamp and a metal halide lamp are mentioned, for example. When the first active energy ray has an upper limit on the wavelength range, or when an upper limit is provided on the wavelength range of the first active energy ray using, for example, a wavelength cut filter, the upper limit of the wavelength range of the first active energy ray is, It is preferably 400 nm, more preferably 395 nm, even more preferably 390 nm, even more preferably 385 nm, still more preferably 380 nm, still more preferably 375 nm, and particularly preferably 370 nm. In the present embodiment, preferably, a photoacid generator that generates an acid by being irradiated with an active energy ray of such a wavelength is blended into the pressure-sensitive adhesive layer 10 .

In this step, acid is generated from the photoacid generator in the portion of the pressure-sensitive adhesive layer 10 that has been irradiated with the first active energy ray, and the color-developing compound develops color by reaction with the acid. As a result, the discoloration portion 11 is formed in the pressure-sensitive adhesive layer 10 .

For example, as described above, the adhesive sheet S can be used for bonding between members. When the first member 31 is a display panel such as an organic EL panel, by providing the discoloration portion 11 in a pattern shape corresponding to (that is, facing) the metal wiring formed on the pixel panel included in the panel, External light reflection in the said metal wiring can be suppressed.

In the above usage method, since the adhesive layer 10 of the adhesive sheet S contains a colorant capable of developing color in response to a first external stimulus, the adhesive sheet S is attached to an adherend (a member in this embodiment). 31, 32)), the pressure-sensitive adhesive layer 10 can be locally discolored by applying a first external stimulus to the discoloration scheduled portion in the pressure-sensitive adhesive layer 10. In the PSA sheet S capable of forming the discoloration portion 11 on the PSA layer 10 after bonding to an adherend, after bonding and before formation of the discoloration portion 11 of the PSA layer 10, the PSA sheet S ) and the adherend, the presence or absence of foreign matter and air bubbles can be inspected.

Further, in the pressure-sensitive adhesive sheet S, the pressure-sensitive adhesive layer 10 can be cured by a second external stimulus different from the first external stimulus, and in the pressure-sensitive adhesive layer 10, the first shear before curing. The storage modulus is 0.1×10 ⁵ Pa or more and 10×10 ⁵ Pa or less, and the ratio of the second shear storage modulus after curing to the first shear storage modulus is 2 or more and 300 or less. Such an adhesive sheet S secures the adhesive properties suitable for bonding to the adherend at the time of bonding in the adhesive layer 10 (before curing), while maintaining the colorant in the adhesive layer 10 after bonding (after curing). suitable for suppressing the spread of In the pressure-sensitive adhesive layer 10 in which the discolored portion 11 is formed, diffusion of the colorant is suppressed, thereby suppressing deterioration of the discolored portion 11 over time (smearing, discoloration, non-uniformity of color, etc.). Suppression of deterioration of the color-changing portion 11 in the pressure-sensitive adhesive layer 10 is useful for maintaining functional characteristics of the color-changing portion 11, such as design, shielding, and antireflection.

Example

The present invention will be described in detail by showing examples below, but the present invention is not limited to the examples. In addition, the specific numerical values such as the compounding amount (content), physical property values, and parameters described below are the compounding amounts (content), physical property values, and parameters corresponding to them described in the above-mentioned “Specific Content for Carrying Out the Invention”. It can be substituted with the upper limit (numerical value defined as "below" or "less than") or the lower limit (numerical value defined as "greater than" or "exceeding") of the same.

[Example 1]

<Preparation of base polymer>

In a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen gas inlet pipe, 63 parts by mass of 2-ethylhexyl acrylate (2EHA), 9 parts by mass of methyl methacrylate (MMA), and 2-hydroxy acrylate 13 parts by mass of ethyl (HEA), 15 parts by mass of N-vinyl-2-pyrrolidone (NVP), 0.2 part by mass of 2,2'-azobisisobutyronitrile (AIBN) as a polymerization initiator, and a solvent A mixture containing 233 parts by mass of ethyl acetate as the mixture was stirred at 60°C for 7 hours in a nitrogen atmosphere (polymerization reaction). In this way, a polymer solution containing an acrylic polymer was obtained. The weight average molecular weight (Mw) of the acrylic polymer in this polymer solution was 1.2 million.

<Preparation of adhesive composition>

To the above-described polymer solution containing an acrylic polymer, 11.1 parts by mass of dipentaerythritol hexaacrylate (DPHA) (manufactured by Daicel Allnex) as a polymerizable compound per 100 parts by mass of the acrylic polymer (base polymer), and a photopolymerization initiator ( Trade name "Omnirad 819", bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, manufactured by IGM Resins BV) 0.1 parts by mass, and a leuco dye as a chromogenic compound (trade name "S-205", 2'-anyl 2.2 parts by mass of rhino-6'-(N-ethyl-N-isopentylamino)-3'-methylspiro[phthalide-3,9'-[9H]xanthen], manufactured by Yamada Chemical Industry Co., Ltd., and photoacid generation agent (trade name "Sp-056", an onium salt of sulfonium and C ₄ F ₉ HSO ₃ ^- manufactured by ADEKA) 7.8 parts by mass and an isocyanate crosslinking agent as a crosslinking agent (trade name "Takenate D110N", xylylene diiso 75% ethyl acetate solution of trimethylolpropane adduct of cyanate, manufactured by Mitsui Chemicals) 0.25 parts by mass (solid content equivalent) and dibutyltin dilaurate (trade name "OL-1") as a crosslinking catalyst , 1% by mass ethyl acetate solution, manufactured by Tokyo Fine Chemical Co., Ltd.) 0.01 parts by mass (in terms of solid content) and 3 parts by mass of acetylacetone as a crosslinking inhibitor (ligand for crosslinking catalyst) were added and mixed to prepare an adhesive composition.

<Formation of pressure-sensitive adhesive layer>

On a polyethylene terephthalate film (base film) having a thickness of 38 μm, the surface of which was subjected to release treatment, the adhesive composition was applied with a fountain roll to form a coating film. Next, this coating film was dried by heating at 132°C for 3 minutes. In this way, an adhesive layer having a thickness of 25 μm was formed on the base film. Next, the release-treated surface of the separator (a polyethylene terephthalate film having a thickness of 38 µm and subjected to release treatment on one side) was bonded to the pressure-sensitive adhesive layer on the base film. Thereafter, aging treatment was performed at 60°C for 24 hours to promote crosslinking reaction in the pressure-sensitive adhesive layer.

In the above manner, the pressure-sensitive adhesive sheet of Example 1 was produced. The composition of the pressure-sensitive adhesive layer in the pressure-sensitive adhesive sheet of Example 1 is shown in Table 1 in parts by mass (the same applies to Examples and Comparative Examples later).

[Examples 2 to 5 and Comparative Example 1]

Except for the following, each PSA sheet of Examples 2 to 5 and Comparative Example 1 was produced in the same manner as the PSA sheet of Example 1.

In the production process of each PSA sheet of Examples 2 to 5, in preparing the PSA composition, each component was blended in the compounding amount shown in Table 1. In the preparation of the adhesive composition in the production process of the adhesive sheet in Examples 4 and 5, trimethylolpropane triacrylate (TMPTA) (manufactured by Osaka Organic Chemical Industry Co., Ltd.) was used as the polymerizable compound instead of DPHA. In addition, in the production process of the PSA sheet of Comparative Example 1, in preparing the PSA composition, each component was blended in the blending amount shown in Table 1 (a polymerizable compound and a photopolymerization initiator were not blended).

<Light transmittance>

The average transmittance at a wavelength of 400 to 700 nm was investigated as follows for the pressure-sensitive adhesive layer of each pressure-sensitive adhesive sheet in Examples 1 to 5 and Comparative Example 1.

First, the adhesive sheet was bonded to eagle glass (thickness: 0.55 mm, manufactured by Matsunami Glass Co., Ltd.) to prepare a measurement sample (first measurement sample). Next, the average transmittance at a wavelength of 400 to 700 nm was measured for the sample for measurement using a spectrophotometer U4150 manufactured by Hitachi High-Technologies Co., Ltd. (first transmittance measurement). In this measurement, the total light transmittance of the sample for measurement at a wavelength of 400 to 700 nm was measured at a pitch of 1 nm. In addition, in this measurement, the transmittance spectrum obtained by measuring only the eagle glass under the same conditions was used as a baseline. Table 1 shows the measured average transmittance T1 (average transmittance at a wavelength of 400 to 700 nm before UV irradiation) of the pressure-sensitive adhesive layer.

On the other hand, the average transmittance at a wavelength of 400 to 700 nm after UV irradiation was investigated for each of the PSA sheets of Examples 1 to 5 and Comparative Example 1 as follows.

First, a sample similar to the first measurement sample described above was produced. Next, the sample was irradiated with ultraviolet rays. Specifically, the pressure-sensitive adhesive sheet (pressure-sensitive adhesive layer) in the sample was irradiated with ultraviolet rays from the eagle glass side through the glass in an environment of 23°C and 50% relative humidity (by the UV irradiation, the pressure-sensitive adhesive layer The leuco dye and the photoacid generator in the reaction were reacted). In this UV irradiation, a UV-LED lamp with a wavelength of 365 nm in a UV-LED irradiation device manufactured by Quark Technology (model number "QEL-350-RU6W-CW-MY") was used as a light source, and the cumulative irradiation light amount was 8000 mJ/ It was set as cm ² (the cumulative amount of irradiation light in the range of wavelength 320 to 390 nm). As described above, a measurement sample (second measurement sample) was produced.

Next, the average transmittance at a wavelength of 400 to 700 nm was measured for the second measurement sample using a spectrophotometer U4150 manufactured by Hitachi High-Technologies Corporation (second transmittance measurement). Regarding the specific measurement method and conditions, the second transmittance measurement is the same as the first transmittance measurement described above. Table 1 shows the measured average transmittance T2 (average transmittance at a wavelength of 400 to 700 nm after UV irradiation) of the pressure-sensitive adhesive layer. Table 1 also shows the ratio of average transmittance T2 to average transmittance T1 described above.

<Shear storage modulus of pressure-sensitive adhesive layer (before curing treatment)>

The shear storage modulus of the pressure-sensitive adhesive layer of each pressure-sensitive adhesive sheet of Examples 1 to 5 and Comparative Example 1 was investigated by dynamic viscoelasticity measurement (first measurement).

The sample for the 1st measurement was produced as follows. First, for each pressure-sensitive adhesive layer to be measured, 60 pressure-sensitive adhesive layers (thickness: 25 µm) were laminated to obtain laminated pressure-sensitive adhesive layers (thickness: 1.5 mm). Next, the laminated pressure-sensitive adhesive layer was punched to obtain a cylindrical pellet (thickness: 1.5 mm, diameter: 7.9 mm) as a first measurement sample.

For the dynamic viscoelasticity measurement, a dynamic viscoelasticity measuring device (trade name "ARES", manufactured by Rheometrics) was used. Specifically, after fixing a sample for measurement to a jig of a parallel plate having a diameter of 7.9 mm, measurement of dynamic viscoelasticity was performed with the device described above. In this measurement, the measurement mode was the shear mode, the measurement temperature range was -70°C to 250°C, the temperature increase rate was 5°C/min, and the frequency was 1 Hz. Table 1 shows the shear storage modulus (E1) of the pressure-sensitive adhesive layer (before curing treatment) at 25°C.

<Shear storage modulus of pressure-sensitive adhesive layer (after curing treatment)>

The shear storage modulus of the pressure-sensitive adhesive layers of the pressure-sensitive adhesive sheets of Examples 1 to 5 and Comparative Example 1 after the curing treatment was measured by dynamic viscoelasticity measurement (second measurement).

The sample for the second measurement (cylindrical pellets obtained by punching the laminated pressure-sensitive adhesive layer having a thickness of 1.5 mm) was subjected to ultraviolet irradiation (curing treatment) for each of the 60 pressure-sensitive adhesive layers before lamination, and the first It was produced in the same way as the sample for measurement. In the curing treatment, specifically, ultraviolet irradiation was performed on each pressure-sensitive adhesive layer before lamination in an environment of 23°C and a relative humidity of 50%. In this ultraviolet irradiation, a UV-LED lamp with a wavelength of 405 nm in a UV-LED irradiation device manufactured by Quark Technology (model number "QEL-350-RU6W-CW-MY") was used as a light source, and the cumulative irradiation light amount was 2000 mJ/ It was set as cm ² (the cumulative amount of irradiated light in a wavelength range of 395 to 445 nm).

The second measurement was performed under the same apparatus and conditions as the first measurement. Table 1 shows the shear storage modulus (E2) of the pressure-sensitive adhesive layer (after curing) at 25°C, 65°C, and 85°C.

<Durability test>

With respect to the pressure-sensitive adhesive layer of each pressure-sensitive adhesive sheet in Examples 1 to 5 and Comparative Example 1, the degree of blurring suppression of the formed discolored portion was investigated as follows.

First, a plurality of PSA sheets were prepared for each PSA sheet in Examples 1 to 5 and Comparative Example 1.

Next, the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet was irradiated with ultraviolet light in an environment at 23° C. and a relative humidity of 50% (the pressure-sensitive adhesive layer of each pressure-sensitive adhesive sheet in Examples 1 to 5 was cured by the ultraviolet light irradiation). In this ultraviolet irradiation, a UV-LED lamp with a wavelength of 405 nm in a UV-LED irradiation device manufactured by Quark Technologies (model number "QEL-350-RU6W-CW-MY") was used as a light source, and the pressure-sensitive adhesive layer was applied over the base film. Ultraviolet rays were irradiated, and the cumulative irradiation light amount was set to 2000 mJ/cm ² (the irradiation integrated amount in the range of 395 to 445 nm) (this ultraviolet irradiation condition is the curing treatment in the sample preparation process of the second measurement are the same as the UV irradiation conditions of).

Next, the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet was irradiated with ultraviolet light through a photomask having linear openings to form linear discolored portions in the pressure-sensitive adhesive layer. The photomask is formed of a dry film photoresist disposed on the base film-side surface of the adhesive sheet, and the line width of the opening of the photomask is about 250 to 280 μm (the line width of the opening differs for each photomask). In the ultraviolet irradiation, a UV-LED lamp with a wavelength of 365 nm in a UV-LED irradiation device manufactured by Quark Technology (model number "QEL-350-RU6W-CW-MY") was used as a light source, and an adhesive was applied over a photomask and base film. The layer was irradiated with ultraviolet rays, and the cumulative amount of irradiation light was 2000 mJ/cm ² (the integrated amount of irradiation light in the range of wavelength 320 to 390 nm).

Next, the line width of the linear discoloration portion formed on the pressure-sensitive adhesive layer was measured (measurement of initial line width). Specifically, first, the linear discoloration portion formed on the pressure-sensitive adhesive layer was observed with a digital microscope (trade name "VHX-900", manufactured by KEYENCE), and the area including a part of the discoloration portion and its vicinity was magnified 50 times. was filmed with Next, the captured image was binarized by image analysis software. Next, in the image after the binarization process, the line width (W1) of the linear discoloration portion was measured.

Next, the pressure-sensitive adhesive sheet in which linear discoloration portions were formed in the pressure-sensitive adhesive layer was subjected to heat treatment at 85°C for 120 hours (first durability test).

Next, the line width of the linearly discolored portion in the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet was measured. The specific measuring method is the same as the measuring method described above regarding the measurement of the initial line width. Table 1 shows the line width W1 of the linear discoloration portion before the first durability test, the line width W2 of the linear discoloration portion after the first durability test, and the increase rate (W2/W1) of the line width W2 relative to the line width W1. 4 shows a graph showing the relationship between the shear storage modulus of the pressure-sensitive adhesive layer at 85°C (the shear storage modulus of the cured pressure-sensitive adhesive layer in Examples 1 to 5) and the rate of increase in line width (W2/W1). .

On the other hand, with respect to the pressure-sensitive adhesive layer of each pressure-sensitive adhesive sheet of Examples 1 to 5 and Comparative Example 1, except that the second durability test was performed instead of the first durability test, the same method as described above was performed to suppress the spread of the formed linear discoloration portion investigated the extent of In the second durability test, the pressure-sensitive adhesive sheet in which linear discoloration portions were formed in the pressure-sensitive adhesive layer was subjected to heat treatment at 65°C and 90% relative humidity for 120 hours. Table 1 shows the line width W1 of the linear discoloration portion before the second durability test, the line width W3 of the linear discoloration portion after the second durability test, and the increase rate (W3/W1) of the line width W3 relative to the line width W1. 5 shows a graph showing the relationship between the shear storage modulus of the pressure-sensitive adhesive layer at 65°C (the shear storage modulus of the cured pressure-sensitive adhesive layer in Examples 1 to 5) and the rate of increase in line width (W3/W1). .

The rate of increase (W2/W1) in the line width of the linearly discolored portion after the first durability test is the shear storage modulus (E2 ) ratio (E2/E1) of 2 or more and 300 or less) was smaller than that of the adhesive sheet of Comparative Example 1. The rate of increase in line width (W3/W1) of the linear discoloration portion after the second durability test was also smaller in the PSA sheets of Examples 1 to 5 than in the PSA sheet in Comparative Example 1. That is, in each of the PSA sheets of Examples 1 to 5, the bleeding of the discolored portion of the PSA layer was suppressed more than the PSA sheet in Comparative Example 1.

The embodiment described above is an illustration of the present invention, and the present invention should not be interpreted limitedly by the embodiment. Modifications of the present invention obvious to those skilled in the art in the art are included in the scope of the later claims.

The variable-color adhesive sheet of the present invention is used, for example, in the manufacturing process of a display panel for bonding elements included in a laminated structure of a display panel.

S Adhesive Sheet (Variable Color Adhesive Sheet)
10 adhesive layer
11 discoloration part
20 entries
31 first member
32 Second member

Claims (6)

A color changeable pressure-sensitive adhesive sheet having a color-changeable pressure-sensitive adhesive layer,
The pressure-sensitive adhesive layer,
Contains a colorant capable of developing color by a first external stimulus;
Curable by a second external stimulus different from the first external stimulus,
The first shear storage modulus of the pressure-sensitive adhesive layer before curing at 25°C, as shown in dynamic viscoelasticity measurement under conditions of a frequency of 1 Hz and a heating rate of 5°C/min, is 0.1×10 ⁵ Pa or more and 10×10 ⁵ Pa or less, ,
The ratio of the second shear storage modulus at 25 ° C. to the first shear storage modulus of the pressure-sensitive adhesive layer after curing is 2 or more and 300 or less. According to claim 1,
The first color change width W1 of the discoloration region formed in the pressure-sensitive adhesive layer by applying the first external stimulus in a linear form to the pressure-sensitive adhesive layer after curing, and the above after further heating the pressure-sensitive adhesive layer at 85°C for 120 hours. The color changeable pressure-sensitive adhesive sheet, wherein the second color change width W2 of the color change area satisfies 0.5≤W2/W1≤2. According to claim 1,
The 1st color change width W1 of the discoloration area formed in the said adhesive layer by giving the said 1st external stimulus linearly with respect to the said adhesive layer after hardening, and the said adhesive layer was further maintained at 65 degreeC and 90% of a relative humidity for 120 hours. The color changeable pressure-sensitive adhesive sheet, wherein a third color change width W3 of the color change region after heat treatment satisfies 0.5≤W3/W1≤2.4. According to claim 1,
The coloring agent is a compound that develops color by reaction with an acid,
The variable color pressure-sensitive adhesive sheet, wherein the pressure-sensitive adhesive layer further contains a photo-acid generator. According to claim 1,
The pressure-sensitive adhesive layer has a thickness of 10 to 300 μm. According to claim 1,
The variable color pressure-sensitive adhesive sheet further comprising a base material disposed on one side of the pressure-sensitive adhesive layer in the thickness direction.

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