WO2022054633A1

WO2022054633A1 - Color-changeable adhesive sheet

Info

Publication number: WO2022054633A1
Application number: PCT/JP2021/031865
Authority: WO
Inventors: 大輔水野; 武史仲野; 真由尾▲崎▼; 雅俊加藤
Original assignee: 日東電工株式会社
Priority date: 2020-09-10
Filing date: 2021-08-31
Publication date: 2022-03-17
Also published as: TW202223026A; KR20230064610A; CN116113674A

Abstract

This color-changeable adhesive sheet comprises an adhesive layer (10) capable of changing colors via an external stimulation. A first color change width W1 and a second color change width W2 satisfy formula (1). (1): 0.5 < W2/W1 < 2

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 and a cover member. In the process of manufacturing such a display panel, for example, a transparent adhesive sheet is used for bonding the elements included in the laminated structure.

Further, as a transparent adhesive sheet arranged on the light emitting side (image display side) of the pixel panel in the display panel, a colored portion for imparting design, shielding, antireflection, etc. to a predetermined portion of the sheet is previously provided. It has been proposed to use the formed pressure-sensitive adhesive sheet. Such an adhesive sheet is described in, for example, Patent Document 1 below. Patent Document 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 process of manufacturing a display panel, when an adhesive sheet having a colored portion formed in advance is used, foreign matter and foreign matter between the adherend and the colored portion of the adhesive sheet are formed after the adhesive sheet is attached to the adherend. The presence or absence of air bubbles cannot be properly inspected. In the bonding of adhesive sheets in the process of manufacturing a display panel, it is required to be able to appropriately inspect the presence or absence of foreign matter and air bubbles between the adherend and the adhesive sheet after bonding.

Further, from the viewpoint of imparting designability, shielding property, antireflection property, etc., a coloring component may be formed in an arbitrary shape at an arbitrary place. In such a case, the visibility and the shielding property may deteriorate with time.

INDUSTRIAL APPLICABILITY According to the present invention, the pressure-sensitive adhesive layer can be locally discolored after being attached to an adherend, and a variable color suitable for imparting designability, shielding property, and antireflection property to an arbitrary portion. Provide an adhesive sheet.

The present invention [1] includes a pressure-sensitive adhesive layer that can be discolored by an external stimulus, and the first discoloration width W1 determined by the following test 1 and the second discoloration width W2 determined by the following test 2 are expressed by the following formula (1). ) Is a variable color adhesive sheet.

0.5 <W2 / W1 <2 (1)

<Test 1>
Step A: External stimulus is linearly applied to the pressure-sensitive adhesive layer.
Step B: After step A, the width of the discolored area formed in the pressure-sensitive adhesive layer is measured.
<Test 2>
Step C: After step A and step B of the test 1, heat treatment is performed at 85 ° C. for 120 hours.
Step D: After step C, the width of the discolored area formed in the pressure-sensitive adhesive layer is measured.

The present invention [2] includes the variable color pressure-sensitive adhesive sheet according to the above [1], wherein the first color change width W1 and the third color change width W3 obtained by the following test 3 satisfy the following formula (2). I'm out.

0.5 <W3 / W1 <2 (2)

<Test 3>
Step E: After step A and step B of <Test 1> above, heat treatment is performed at 85 ° C. for 240 hours.
Step F: After step E, the width of the discolored area formed in the pressure-sensitive adhesive layer is measured.

The present invention [3] includes the variable color pressure-sensitive adhesive sheet according to the above [1] or [2], wherein the pressure-sensitive adhesive layer has a thickness of 10 μm or more and 300 μm or less.

The present invention [4] includes the variable color pressure-sensitive adhesive sheet according to any one of the above [1] to [3], further comprising a base material arranged on one side in the thickness direction of the pressure-sensitive adhesive layer. ..

In the present invention [5], after the pressure-sensitive adhesive layer is attached to a glass plate, the peeling test under the peeling conditions of 23 ° C., a peeling angle of 180 ° and a peeling speed of 300 mm / min is performed on the glass plate. The variable color adhesive sheet according to any one of the above [1] to [4], wherein the adhesive strength shown in the above is 1.0 N / 25 mm or more and 50 N / 25 mm or less.

The variable color adhesive sheet of the present invention includes an adhesive layer that can be discolored by an external stimulus. Therefore, after the variable color pressure-sensitive adhesive sheet is attached to the adherend, the pressure-sensitive adhesive layer can be locally discolored by applying an external stimulus to the portion to be discolored in the pressure-sensitive adhesive layer. With such a variable color pressure-sensitive adhesive sheet, the presence or absence of foreign matter and air bubbles between the variable color pressure-sensitive adhesive sheet and the adherend can be inspected after the bonding and before the formation of the discolored portion of the pressure-sensitive adhesive layer.

Further, in the variable color pressure-sensitive adhesive sheet, the first color change width W1 and the second color change width W2 of the pressure-sensitive adhesive layer satisfy 0.5 <W2 / W1 <2. Such a variable color pressure-sensitive adhesive sheet is suitable for suppressing deterioration of the discolored portion after the discolored portion is formed in the pressure-sensitive adhesive layer by applying an external stimulus. Suitable for imparting antireflection properties.

FIG. 1 is a schematic cross-sectional view of an embodiment of the 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 pressure-sensitive adhesive sheet of the present invention (when the pressure-sensitive adhesive sheet is a single-sided pressure-sensitive adhesive sheet with a base material). 3A to 3C show an example of how to use the variable color adhesive sheet of the present invention. FIG. 3A shows a step of preparing a variable color adhesive sheet and a member as an adherend. FIG. 3B shows a process of joining members to each other via a variable color adhesive sheet. FIG. 3C shows a step of forming a discolored portion in the pressure-sensitive adhesive layer of the variable-color pressure-sensitive adhesive sheet. 3 is a TEM image of the pressure-sensitive adhesive layer of Example 7.

1. 1. First color change width W1 and second color change width W2
The variable color pressure-sensitive adhesive sheet of the present invention includes a pressure-sensitive adhesive layer that can be discolored by an external stimulus, and the first color change width W1 determined by the following test 1 and the second color change width W2 obtained by the following test 2 have the following formulas. Satisfy (1).

0.5 <W2 / W1 <2 (1)

The first discoloration width W1 is obtained by the following <Test 1>.

<Test 1>
Step A: External stimulus is linearly applied to the pressure-sensitive adhesive layer.
Step B: After step A, the width of the discolored area formed in the pressure-sensitive adhesive layer is measured.

The second discoloration width W2 is obtained by the following <Test 2>.

<Test 2>
Step C: After step A and step B of <Test 1> above, heat treatment is performed at 85 ° C. for 120 hours.
Step D: After step C, the width of the discolored area formed in the pressure-sensitive adhesive layer is measured.

As described above, the variable color adhesive sheet includes an adhesive layer that can be discolored by an external stimulus. Therefore, after the variable color pressure-sensitive adhesive sheet is attached to the adherend, the pressure-sensitive adhesive layer can be locally discolored by applying an external stimulus to the portion to be discolored in the pressure-sensitive adhesive layer. With such a variable color pressure-sensitive adhesive sheet, the presence or absence of foreign matter and air bubbles between the variable color pressure-sensitive adhesive sheet and the adherend can be inspected after the bonding and before the formation of the discolored portion of the pressure-sensitive adhesive layer.

Further, in the variable color pressure-sensitive adhesive sheet, the first color change width W1 and the second color change width W2 of the pressure-sensitive adhesive layer satisfy the above formula (1). Such a variable color pressure-sensitive adhesive sheet is suitable for suppressing deterioration of the discolored portion after the discolored portion is formed in the pressure-sensitive adhesive layer by applying an external stimulus. Suitable for imparting antireflection properties.

As an example of how to use this variable color adhesive sheet, the variable color adhesive sheet may be arranged on the light emitting side (image display side) of the pixel panel in the display panel.

Specifically, metal wiring may be provided at a fine pitch on the pixel panel provided in the display panel. Then, from the viewpoint of suppressing external light reflection in the metal wiring, a colored portion may be provided with a pattern shape corresponding to such metal wiring.

In this variable color adhesive sheet, since the first color change width W1 and the second color change width W2 satisfy the above formula (1), the shielding property and the antireflection property can be improved. As a result, it is possible to improve the visibility of the display panel provided with the metal wiring while suppressing the reflection of external light on the metal wiring.

Further, as a method for adjusting the first discoloration width W1 and the second discoloration width W2 so as to satisfy the above formula (1), for example, a method using a metal complex (described later) (first method), adhesion. A method of increasing the elastic modulus of the agent layer, a method of using a color component in the pressure-sensitive adhesive layer bonded to another component, a method of providing a coloring component on an island portion of a sea-island structure utilizing incompatibility or low compatibility. (Second method) can be mentioned.

Examples of the method for increasing the elastic modulus of the pressure-sensitive adhesive layer include a method using a polyfunctional monomer as a monomer component, a method using a cross-linking agent, and a method of combining these.

As a method of using a colored component in the pressure-sensitive adhesive layer bonded to another component, for example, as a colored component, a colored polymer in which a component capable of developing a predetermined color is linked / bonded to a polymer in the layer is used. Examples thereof include a method to be used, a method in which the coloring component and the polymer component are initially separate components, but a method in which the coloring component is bonded to the polymer by a reaction, and a method of combining these.

As a method of providing a coloring component on an island portion of a sea island structure utilizing incompatibility or low compatibility, for example, a polymer having high compatibility with the coloring component and a polymer having low compatibility and having high compatibility are used. As a sea-island structure that becomes an island, a method of providing a coloring component on the island can be mentioned.

2. 2. 1st color change width W1 and 3rd color change width W3
In the variable color adhesive sheet, preferably, the first color change width W1 and the third color change width W3 obtained by the following test 3 satisfy the following formula (2).

0.5 <W3 / W1 <2 (2)

The third color change width W3 is obtained by the following <Test 3>.

If the first discoloration width W1 and the third discoloration width W3 satisfy the above formula (2), further designability, shielding property, and antireflection property can be imparted to any place.

Further, as a method of adjusting the first color change width W1 and the third color change width W3 so as to satisfy the above formula (2), the above-mentioned first color change width W1 and the above-mentioned second color change width W2 are described above. It is the same as the method of adjusting so as to satisfy the equation (1).

3. 3. The average transmittance T1, the average transmittance T2, and the color difference variable color pressure-sensitive adhesive sheet preferably have the average transmittance T1 determined by the following test 4 and the average transmittance T2 determined by the following test 5 according to the following formula (3). ), And preferably the following formula (4).

0.2 <T2 / T1 <3 (3)
0.2 <T2 / T1 <2 (4)

The average transmittance T1 is obtained by the following <Test 4>.

<Test 4>
Step G: The pressure-sensitive adhesive layer is irradiated with light in the wavelength band of 300 nm to 400 nm.
Step H: The average transmittance of the pressure-sensitive adhesive layer at a wavelength of 400 nm to 700 nm is measured.

The average transmittance T1 is, for example, 10% or more, preferably 15% or more. The average transmittance T1 is, for example, 40% or less, preferably 30% or less. The method for measuring the average transmittance T1 will be described in more detail in the weather resistance test described later.

The average transmittance T2 is obtained by the following <Test 5>.

<Test 5>
Step I: After step G of <Test 4> above, the pressure-sensitive adhesive layer is irradiated with a xenon lamp having an illuminance of 120 W in the wavelength range of 300 nm to 400 nm for 24 hours with a super xenon weather meter.
Step J: The average transmittance of the pressure-sensitive adhesive layer at a wavelength of 400 nm to 700 nm is measured.

The average transmittance T2 is, for example, 15% or more, preferably 24% or more. The average transmittance T2 is, for example, 50% or less, preferably 40% or less. The method for measuring the average transmittance T2 will be described in more detail in the weather resistance test described later.

If the variable color adhesive sheet satisfies the above formula (3) or the above formula (4), the weather resistance is excellent. As a method for adjusting the average transmittance T1 and the average permeability T2 so as to satisfy the above formula (3) or the above formula (4), for example, a method for reducing oxygen permeability to the pressure-sensitive adhesive layer and an antioxidant are used. Examples thereof include a method of adding to the pressure-sensitive adhesive layer and a method of laminating a base material or a pressure-sensitive adhesive layer containing an ultraviolet absorber.

Further, the color difference measured by the weather resistance test described later is, for example, 30 or less, preferably 28 or less, more preferably 25 or less, and further preferably 20 or less from the viewpoint of weather resistance.

4. Variable Color Adhesive Sheet The pressure-sensitive adhesive sheet S, which satisfies the above formula (1) and preferably satisfies the above formulas (2) to (4), will be described. In the adhesive sheet S, as a method of adjusting the first color change width W1 and the second color change width W2 so as to satisfy the above formula (1), the above-mentioned first method (first embodiment) and the first method. Although the method 2 (second embodiment) is adopted, the present invention is not limited thereto.

As shown in FIG. 1, the pressure-sensitive adhesive sheet S includes a pressure-sensitive adhesive layer 10. The adhesive sheet S has a sheet shape having a predetermined thickness and extends in a direction (plane direction) orthogonal to the thickness direction. The pressure-sensitive adhesive sheet S is used, for example, as a transparent pressure-sensitive adhesive sheet arranged on the image display side of the pixel panel in a display panel (for example, having a laminated structure including a pixel panel and a cover member).

The pressure-sensitive adhesive layer 10 is a pressure-sensitive adhesive layer having transparency (visible light transmission) formed from the pressure-sensitive adhesive composition. The tacky composition comprises a base polymer, a compound that develops color by reaction with an acid, and an acid generator. In the first embodiment, the tacky composition further comprises a metal complex.

The base polymer is an adhesive component for developing adhesiveness in the adhesive layer 10. The base polymer exhibits rubber elasticity at room temperature. 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 tackiness in the pressure-sensitive adhesive layer 10, an acrylic polymer is preferably used as the base polymer.

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

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

Examples of the (meth) acrylic acid alkyl ester include linear or branched (meth) acrylic acid alkyl esters having an alkyl group having 1 to 20 carbon atoms. Examples of such (meth) acrylic acid alkyl esters include methyl (meth) acrylic acid, ethyl (meth) acrylic acid, propyl (meth) acrylic acid, n-butyl (meth) acrylic acid, and (meth) acrylic acid. Isobutyl (meth) acrylate, s-butyl (meth) acrylate, t-butyl (meth) acrylate, pentyl (meth) acrylate, isopentyl (meth) acrylate, neopentyl (meth) acrylate, (meth) ) Hexyl acrylate, (meth) heptyl acrylate, (meth) 2-ethylhexyl acrylate, (meth) octyl acrylate, (meth) isooctyl acrylate, (meth) nonyl acrylate, (meth) isononyl acrylate, ( Meta) decyl acrylate, (meth) isodecyl acrylate, (meth) undecyl acrylate, (meth) dodecyl acrylate, (meth) isotridecyl acrylate, (meth) tetradecyl acrylate, (meth) isotetradecyl acrylate, Pentadecyl (meth) acrylate, hexadecyl (meth) acrylate, heptadecyl (meth) acrylate, octadecyl (meth) acrylate, isooctadecyl (meth) acrylate, nonadecil (meth) acrylate, and (meth) acrylate. Acrylic acid can be mentioned. The (meth) acrylic acid alkyl ester may be used alone or in combination of two or more. As the (meth) acrylic acid alkyl ester, an acrylic acid alkyl ester having an alkyl group having 1 to 12 carbon atoms is preferably used, and more preferably, it has methyl acrylate and an alkyl group having 2 to 12 carbon atoms. Acrylic acid alkyl ester is used in combination, and more preferably, methyl acrylate and 2-ethylhexyl acrylate are used in combination.

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

The monomer component may contain a copolymerizable monomer copolymerizable with the (meth) acrylic acid alkyl ester. Examples of the copolymerizable monomer include a monomer having a polar group (monomer containing a polar group). The polar group-containing monomer is useful for modifying the acrylic polymer, such as introducing a cross-linking point into the acrylic polymer and ensuring the cohesive force of the acrylic polymer.

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 copolymerizable monomer preferably contains 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 comprises 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, and (meth). ) 4-Hydroxybutyl acrylate, 6-hydroxyhexyl (meth) acrylate, 8-hydroxyoctyl (meth) acrylate, 10-hydroxydecyl (meth) acrylate, 12-hydroxylauryl (meth) acrylate, and (4-Hydroxymethylcyclohexyl) methyl (meth) acrylate can be mentioned. 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, for example, 1% by mass or more, preferably 3% by mass or more, from the viewpoint of introducing a crosslinked structure into the acrylic polymer and ensuring the cohesive force in the pressure-sensitive adhesive layer 10. More preferably, it is 5% by mass or more. The same ratio is, for example, from the viewpoint of adjusting the viscosity of the polymerization reaction solution during the polymerization of the acrylic polymer and adjusting the polarity of the acrylic polymer (related to the compatibility between various additive components in the pressure-sensitive adhesive layer 10 and the acrylic polymer). , 30% by mass or less, 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, N-vinylpiperazine, and N-vinylpyrazine. N-vinylpyrrole, N-vinylimidazole, N-vinyloxazole, N- (meth) acryloyl-2-pyrrolidone, N- (meth) acryloyl piperidine, N- (meth) acryloylpyrrolidin, N-vinylmorpholin, N-vinyl. -3-morpholinone, N-vinyl-2-caprolactam, N-vinyl-1,3-oxadin-2-one, N-vinyl-3,5-morpholindione, N-vinylpyrazole, N-vinylisoxazole, N -Vinylthiazole and N-vinylisothiazole can be mentioned. As the monomer having a nitrogen atom-containing ring, N-vinyl-2-pyrrolidone is preferably used.

The proportion of the monomer having a nitrogen atom-containing ring in the monomer component is, for example, 1% by mass from the viewpoint of ensuring the cohesive force in the pressure-sensitive adhesive layer 10 and the adhesion to the adherend in the pressure-sensitive adhesive layer 10. As mentioned above, it is preferably 3% by mass or more, and more preferably 5% by mass or more. The same ratio is, for example, 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 the compatibility between various additive components in the pressure-sensitive adhesive layer 10 and the acrylic polymer). % Or less, preferably 20% by mass or less.

Examples of the carboxy 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 carboxy group-containing monomer in the monomer component is determined from the viewpoint of introducing a crosslinked structure into the acrylic polymer, ensuring the cohesive force in the pressure-sensitive adhesive layer 10, and ensuring the adhesion to the adherend in the pressure-sensitive adhesive layer 10. For example, it is 1% by mass or more, preferably 3% by mass or more, and more preferably 5% by mass or more. The same ratio is, for example, 30% by mass or less, 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, phosphate group-containing monomers, epoxy group-containing monomers, cyano group-containing monomers, amide group-containing monomers, monomers having a succinimide skeleton, and maleimides. Examples include itaconimides, alkoxy group-containing monomers, vinyl esters, vinyl ethers, and aromatic vinyl compounds.

Examples of the acid anhydride monomer include maleic anhydride and itaconic anhydride.

Examples of the sulfonic acid group-containing monomer include styrene sulfonic acid, allyl sulfonic acid, sodium vinyl sulfonic acid, 2- (meth) acrylamide-2-methylpropane sulfonic acid, (meth) acrylamide propane sulfonic acid, and sulfopropyl (meth). Examples include acrylate and (meth) acryloyloxynaphthalene sulfonic acid.

Examples of the phosphate group-containing monomer include 2-hydroxyethylacryloyl phosphate.

Examples of the epoxy group-containing monomer include epoxy group-containing acrylates such as glycidyl (meth) acrylate and -2-ethyl glycidyl ether (meth) acrylate, allyl glycidyl ether, and glycidyl ether (meth) acrylate. ..

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

Examples of the amide group-containing monomer include N-vinylcarboxylic acid amides, N-hydroxyalkyl (meth) acrylamide, N-alkoxyalkyl (meth) acrylamide, N, N-dimethylaminopropyl (meth) acrylamide, and N. -(Meta) Acryloylmorpholine can be mentioned.

Examples of N-vinylcarboxylic acid amides include (meth) acrylamide, N, N-dialkyl (meth) acrylamide, N-alkyl (meth) acrylamide, and N-vinylacetamide.

Examples of N, N-dialkyl (meth) acrylamide include N, N-dimethyl (meth) acrylamide, N, N-diethyl (meth) acrylamide, N, N-dipropyl (meth) acrylamide, and N, N-diisopropyl ( Examples include meth) acrylamide, N, N-di (n-butyl) (meth) acrylamide, and N, N-di (t-butyl) (meth) acrylamide.

Examples of N-alkyl (meth) acrylamide include N-ethyl (meth) acrylamide, N-isopropyl (meth) acrylamide, N-butyl (meth) acrylamide, and Nn-butyl (meth) acrylamide. ..

Examples of N-hydroxyalkyl (meth) acrylamide include N- (2-hydroxyethyl) (meth) acrylamide, N- (2-hydroxypropyl) (meth) acrylamide, and N- (1-hydroxypropyl) (meth). Acrylamide, N- (3-hydroxypropyl) (meth) acrylamide, N- (2-hydroxybutyl) (meth) acrylamide, N- (3-hydroxybutyl) (meth) acrylamide, and N- (4-hydroxybutyl) Examples include (meth) acrylamide. Examples of N-alkoxyalkyl (meth) acrylamide include N-methoxymethyl (meth) acrylamide, N-methoxyethyl (meth) acrylamide, and N-butoxymethyl (meth) acrylamide.

Examples of the monomer having a succinimide skeleton include N- (meth) acryloyloxymethylene succinimide, N- (meth) acryloyl-6-oxyhexamethylene succinimide, and N- (meth) acryloyl-8-oxyhexamethylene succinimide. Can be mentioned.

Examples of maleimides include N-cyclohexylmaleimide, N-isopropylmaleimide, N-laurylmaleimide, and N-phenylmaleimide.

Examples of the itaconimides include N-methylitaconimide, N-ethylitaconimide, N-butylitaconimide, N-octylitaconimide, N-2-ethylhexylitaconimide, N-cyclohexylitaconimide, and , N-laurylitaconimide.

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

Examples of vinyl esters include vinyl acetate and vinyl propionate.

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

Examples of the aromatic vinyl compound include styrene, α-methylstyrene, and vinyltoluene. Examples of olefins include ethylene, butadiene, isoprene, and isobutylene.

The copolymerizable monomer may be used alone or in combination of two or more.

Acrylic polymer can be formed by polymerizing the above monomer components. Examples of the polymerization method include solution polymerization, bulk polymerization, and emulsion polymerization, and solution polymerization is preferable. In solution polymerization, for example, a monomer component and a polymerization initiator are mixed with a solvent to prepare a reaction solution, 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 components in the reaction solution.

As the polymerization initiator, for example, a thermal polymerization initiator is used. The amount of the polymerization initiator used is, for example, 0.05 parts by mass or more with respect to 100 parts by mass of the monomer component. The amount used is, for example, 1 part by mass or less.

Examples of the thermal polymerization initiator include an azo-based polymerization initiator and a peroxide-based polymerization initiator. Examples of the azo-based polymerization initiator include 2,2'-azobisisobutyronitrile, 2,2'-azobis-2-methylbutyronitrile, and 2,2'-azobis (2-methylpropionic acid) dimethyl. 4,4'-Azobis-4-cyanovaleric acid, azobisisobutyvaleronitrile, 2,2'-azobis (2-amidinopropane) dihydrochloride, 2,2'-azobis [2- (5-methyl-2) -Imidazoline-2-yl) propane] dihydrochloride, 2,2'-azobis (2-methylpropionamidine) disulfate, and 2,2'-azobis (N, N'-dimethyleneisobutyramidin) dihydrochloride Can be mentioned. Examples of the peroxide-based polymerization initiator include dibenzoyl peroxide, t-butyl permaleate, and lauroyl peroxide.

The weight average molecular weight of the acrylic polymer is, for example, 100,000 or more, preferably 300,000 or more, and more preferably 500,000 or more, from the viewpoint of ensuring the cohesive force in the pressure-sensitive adhesive layer 10. The weight average molecular weight is, for example, 5,000,000 or less, preferably 3,000,000 or less, and more preferably 2000000 or less. The weight average molecular weight of the acrylic polymer is measured by gel permeation chromatography (GPC) and calculated in terms of polystyrene.

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

For the glass transition temperature (Tg) of the polymer, the glass transition temperature (theoretical value) obtained based on the Fox formula below can be used. The Fox formula is a relational expression between the glass transition temperature Tg of the polymer and the glass transition temperature Tgi of the homopolymer of the monomer constituting the polymer. In the Fox equation below, Tg represents the glass transition temperature (° C.) of the polymer, Wi represents the weight fraction of the monomer i constituting the polymer, and Tgi represents the glass transition temperature of the homopolymer formed from the monomer i. (° C) is indicated. Literature values can be used for the glass transition temperature of homopolymers, for example, "Polymer Handbook" (4th edition, John Willey & Sons, Inc., 1999) and "New Polymer Bunko 7 Introduction to Synthetic Resins for Paints". (Kyozo Kitaoka, Polymer Publishing Association, 1995) lists the glass transition temperatures of various homopolymers. On the other hand, the glass transition temperature of the homopolymer of the monomer can also be obtained by the method specifically described in JP-A-2007-51271. The above is the same for the glass transition temperature of the hard segment and the soft segment described later.

Fox formula 1 / (273 + Tg) = Σ [Wi / (273 + Tgi)]

Examples of the compound (color-developing compound) that develops color by reaction with an acid include leuco-based dye, triarylmethane-based dye, diphenylmethane-based dye, fluorane-based dye, spiropyran-based dye, and rhodamine-based dye. The color-developing compound may be used alone or in combination of two or more.

Examples of leuco-based dyes include 2'-anilino-6'-(N-ethyl-N-isopentylamino) -3'-methylspiro [phthalide-3,9'-[9H] xanthene] and 3-dibutylamino. -6-Methyl-7-anilinofluorane, 3-dipropylamino-6-methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7-anilinofluorane, 3-dimethylamino-6 -Methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7-xylidinofluorane, and 3- (4-diethylamino-2-ethoxyphenyl) -3- (1-ethyl-2-methyl) Indol-3-yl) -4-azaphthalide can be mentioned.

Examples of the triarylmethane dye include p, p', p "-tris-dimethylaminotriphenylmethane. Examples of the diphenylmethane dye include 4,4-bis-dimethylaminophenylbenzhydrylbenzyl. Examples of the fluorin-based dye include 3-diethylamino-6-methyl-7-chlorofluorane. Examples of the spiropyran-based dye include 3-methylspirodinaphthopyrane. Examples of the dye system include rhodamine-B-anilinolactum.

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

The blending amount of the color-developing compound with respect to 100 parts by mass of the base polymer is, for example, 0.5 parts by mass or more, preferably 1 part by mass or more. The blending amount is, for example, 10 parts by mass or less, preferably 7 parts by mass or less, and more preferably 5 parts by mass or less.

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

Examples of the photoacid generator include an onium compound that generates an acid by irradiation with ultraviolet rays. Onium compounds are provided, for example, in the form of onium salts of onium cations and anions. Examples of onium cations include iodonium and sulfonium. 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-. The photoacid generator may be used alone or in combination of two or more. The photoacid generator preferably includes an onium salt (onium compound) composed of sulfonium ^and _C4 F ₉ HSO _3- .

The blending amount of the acid generator with respect to 100 parts by mass of the base polymer is, for example, 1 part by mass or more, preferably 2 parts by mass or more, more preferably 5 parts by mass or more, and further preferably 6 parts by mass or more. The blending amount is, for example, 20 parts by mass or less, preferably 15 parts by mass or less, and more preferably 10 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, and further preferably 330 parts by mass or more. be. The blending amount is, for example, 1000 parts by mass or less, preferably 700 parts by mass or less, and more preferably 500 parts by mass or less.

The metal complex is blended in order to adjust the first discoloration width W1 and the second discoloration width W2 so as to satisfy the above formula (1). The movement of coloring components such as leuco-based dyes is suppressed by the coordination bond with the metal complex. A metal complex is one in which a ligand is coordinated with a metal ion.
The metals that make up the metal ions are according to the IUPAC Periodic Table of the Elements (version date 19 February 2010). The same shall apply hereinafter. Group 1 alkali metals, Group 2 alkaline earth metals, Group 3 ~ Group 12 transition metals can be mentioned. The metal is preferably Mg from the viewpoint of the strong coordination of the group 2 alkaline earth metal, the group 3 to group 12 transition metal, and the leuco dye to the carboxyl group of the chromogen. From the viewpoint of the contribution of (magnesium) and the amphoteric counterion formed with the leuco-based dye by the metal complex, Zn (zinc) can be mentioned.

Examples of the ligand include a monodentate ligand and a bidentate ligand. Examples of the monodentate ligand include hydroxo (OH ⁻ ), halogen (eg, chloro (Cl ⁻ )), and cyano (CN ⁻ ). Bidentate ligands include, for example, ethylenediamine, bipyridine, phenanthroline, and salicylic acid. Among such metal complexes, zinc salicylate (specifically, zinc salicylate trihydrate) is more preferable from the viewpoint of contribution of bidentate ligand and amphoteric counterion. The metal complex may be used alone or in combination of two or more.

The blending 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 parts by mass or more, more preferably 0.5 parts by mass or more, still more preferably 0.8. It is more than a mass part. The blending amount is, for example, 5 parts by mass or less, preferably 2 parts by mass or less.

The blending 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.

Further, the adhesive composition may contain a cross-linking agent from the viewpoint of introducing a cross-linked structure into the base polymer. Examples of the cross-linking agent include an isocyanate cross-linking agent, an epoxy cross-linking agent, an oxazoline cross-linking agent, an aziridine cross-linking agent, a carbodiimide cross-linking agent, and a metal chelate cross-linking agent. The cross-linking agent may be used alone or in combination of two or more.

Examples of the isocyanate cross-linking agent include tolylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, xylylene diisocyanate, hydrogenated xylylene diisocyanate, diphenylmethane diisocyanate, hydrogenated diphenylmethane diisocyanate, tetramethylxylylene diisocyanate, naphthalin diisocyanate, and triphenylmethane tri. Examples thereof include isocyanate and polymethylene polyphenyl isocyanate. Further, examples of the isocyanate cross-linking agent include derivatives of these isocyanates. Examples of isocyanate derivatives include isocyanurate-modified products and polyol-modified products. Examples of commercially available isocyanate cross-linking agents include coronate L (trimethylolpropane adduct of tolylene diisocyanate, manufactured by Tosoh), coronate HL (trimethylolpropane adduct of hexamethylene diisocyanate, manufactured by Tosoh), and coronate HX (hexa). Examples thereof include isocyanurate form of methylene diisocyanate (manufactured by Toso) and Takenate D110N (trimethylolpropane adduct form of xylylene diisocyanate, manufactured by Mitsui Kagaku).

Examples of the epoxy cross-linking 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, and trimethylolpropane. Triglycidyl ether, diglycidyl aniline, diamine glycidyl amine, N, N, N', N'-tetraglycidyl-m-xylylenediamine, and 1,3-bis (N, N-diglycidylaminomethyl) cyclohexane Can be mentioned.

Examples of the cross-linking agent include an isocyanate cross-linking agent, and more preferably a trimethylolpropane adduct body of xylylene diisocyanate.

From the viewpoint of ensuring the cohesive force of the pressure-sensitive adhesive layer 10, the blending amount of the cross-linking agent is, for example, 0.01 part by mass or more, preferably 0.05 part by mass or more, more preferably, with respect to 100 parts by mass of the base polymer. Is 0.07 parts by mass or more. From the viewpoint of ensuring good tackiness in the pressure-sensitive adhesive layer 10, the blending amount of the cross-linking agent with respect 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. It is 3 parts by mass or less.

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

Further, an isocyanate cross-linking agent (specifically, a trimethylolpropane adduct of xylylene diisocyanate) is blended as a cross-linking agent, and a metal-based cross-linking catalyst (specifically, dibutyltin dilaurate) is used as a cross-linking catalyst. When blending, preferably, acetylacetone is blended in the adhesive composition.

When acetylacetone is added, acetylacetone coordinates with dibutyltin dilaurate. Thereby, the progress of the crosslinking reaction can be suppressed before the adhesive composition is applied onto the release film (or the base material 20) to form a coating film. Further, as will be described in detail later, acetylacetone can be removed and the crosslinking reaction can proceed by heating and drying at the time of forming the coating film.

The amount of acetylacetone used is, for example, 100 parts by mass or more, preferably 10,000 parts by mass or more, based on 100 parts by mass of the cross-linking catalyst. The amount used is, for example, 50,000 parts by mass or less.

Further, the adhesive composition may contain other components, if necessary. Other components include, for example, polymerizable compounds and cured products thereof, photopolymerization initiators, silane coupling agents, tackifiers, plasticizers, softeners, antioxidants, surfactants, and antistatic agents. Can be mentioned.

Examples of the polymerizable compound include a monomer having one polymerizable functional group (ethylenically unsaturated double bond) (monofunctional monomer) and a monomer having a plurality of polymerizable functional groups (polyfunctional monomer). Be done. Examples of the monofunctional monomer include monofunctional (meth) acrylate. Examples of the polyfunctional monomer include polyfunctional (meth) acrylate.

When the adhesive composition contains a polymerizable compound, the adhesive composition preferably further contains a photopolymerization initiator.

The tacky composition comprises a base polymer, a compound that develops color by reaction with an acid, an acid generator, a metal complex, a cross-linking agent to be blended if necessary, a cross-linking catalyst to be blended if necessary, and a cross-linking catalyst to be blended if necessary. It is obtained by blending the acetylacetone to be added and other components to be blended as necessary in the above-mentioned ratios.

The pressure-sensitive adhesive sheet S can be produced, for example, by applying the above-mentioned adhesive composition on a release film (first release film) to form a coating film, and then drying the coating film (in FIG. 1, virtual). The adhesive sheet S is arranged on the release film L indicated by the line).

Examples of the release film include a flexible plastic film. Examples of the plastic film include polyethylene terephthalate film, polyethylene film, polypropylene film, and polyester film. The thickness of the release film is, for example, 3 μm or more. The same thickness is, for example, 200 μm or less. The surface of the release film is preferably mold-released.

Examples of the method of applying the adhesive composition include roll coat, kiss roll coat, gravure coat, reverse coat, roll brush, spray coat, dip roll coat, bar coat, knife coat, air knife coat, curtain coat, and lip coat. , And die coat. The drying temperature of the coating film is, for example, 50 ° C. or higher. The impression temperature is, for example, 200 ° C. or lower. The drying time is, for example, 5 seconds or more. The drying time is, for example, 20 minutes or less.

When the adhesive composition contains a cross-linking agent, the cross-linking reaction proceeds at the same time as the above drying or by subsequent aging. The aging conditions are appropriately set depending on the type of the cross-linking agent. The aging temperature is, for example, 20 ° C. or higher. The aging temperature is, for example, 160 ° C. or lower. The aging time is, for example, 1 minute or more. The aging time is, for example, 7 days or less.

Further, when the adhesive composition contains acetylacetone (in other words, when acetylacetone is coordinated to dibutyltin dilaurate), the acetylacetone coordinated to dibutyltin dilaurate is removed at the time of drying. This allows the cross-linking reaction to proceed.

Further, before or after aging, a release film (second release film) may be further laminated on the pressure-sensitive adhesive layer 10 on the first release film. The second release film is, for example, a flexible plastic film that has been subjected to a surface release treatment. As the second release film, the same film as described above for the first release film can be used.

As described above, the pressure-sensitive adhesive sheet S whose adhesive surface is covered and protected by the release film can be manufactured. Each release film is peeled off from the pressure-sensitive adhesive sheet S as needed when using the pressure-sensitive adhesive sheet S.

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

The haze of the pressure-sensitive adhesive layer 10 is, for example, 3% or less, preferably 2% or less, and more preferably 1% or less. Such a configuration is suitable for inspecting the presence or absence of foreign matter and air bubbles between the pressure-sensitive adhesive sheet S and the adherend after the pressure-sensitive adhesive sheet S is attached to the adherend. The haze of the pressure-sensitive adhesive layer 10 can be measured using a haze meter in accordance with JIS K7136 (2000). Examples of the haze meter include "NDH2000" manufactured by Nippon Denshoku Kogyo Co., Ltd. and "HM-150 type" manufactured by Murakami Color Technology Research Institute.

The average transmittance of the pressure-sensitive adhesive layer 10 at a wavelength of 400 nm to 700 nm (the average transmittance before applying an external stimulus to the pressure-sensitive adhesive layer 10) is, for example, 80% or more, preferably 85% or more, and more preferably 90%. That is all. Such a configuration is suitable for inspecting the presence or absence of foreign matter and air bubbles between the pressure-sensitive adhesive sheet S and the adherend after the pressure-sensitive adhesive sheet S is attached to the adherend.

Further, in the pressure-sensitive adhesive sheet S, after the pressure-sensitive adhesive layer 10 is attached to the glass plate, in a peeling test under the peeling conditions of 23 ° C., a peeling angle of 180 ° and a peeling speed of 300 mm / min, the pressure-sensitive adhesive layer 10 is applied to the glass plate. The adhesive strength shown is, for example, 1.0 N / 25 mm or more, preferably 5.0 N / 25 mm or more. The adhesive strength is preferably 50 N / 25 mm or less, more preferably 40 N / 25 mm or less, and further preferably 20 N / 25 mm or less.

The shear storage elastic modulus at 25 ° C., which is shown by the dynamic viscoelasticity measurement of the pressure-sensitive adhesive layer 10 under the conditions of a frequency of 1 Hz and a heating rate of ⁵ ° C./min, is preferably 0.1 × 105 Pa or more. More preferably, it is 0.5 × 10 ⁵ Pa or more, and even more preferably 1 × 10 ⁵ Pa or more. The shear storage elastic modulus is preferably 10 × 10 ⁵ Pa or less, more preferably 5 × 10 ⁵ Pa or less, and further preferably 3 × 10 ⁵ Pa or less.

In the second embodiment, the polymer component (base polymer) of the pressure-sensitive adhesive layer 10 has a sphere-type microphase-separated structure. The sphere-type microphase-separated structure specifically has a sea-island structure, in which spherical dispersed phases (islands) are dispersed in a matrix (sea). In the pressure-sensitive adhesive layer 10, the dispersed phase is compatible with the color-developing compound, and the matrix is not compatible with the color-developing compound. In such a pressure-sensitive adhesive sheet S, the color-developing compound tends to stay on the islands after the discolored portion is formed on the pressure-sensitive adhesive layer 10 (that is, after the color-developing compound is developed by an external stimulus). Suitable for suppressing the movement (diffusion, etc.) of color-developing compounds within. By suppressing the movement of the color-developing compound, deterioration of the discolored portion (bleeding, fading, non-uniformity of color, etc.) is suppressed.

The polymer component includes, for example, a polymer (first polymer) having a soft segment forming a matrix and a hard segment forming a dispersed phase in the molecule. Examples of the first polymer include a block polymer having a first polymer block as a soft segment and a second polymer block as a hard segment. The block polymer may have a plurality of first polymer blocks having different monomer compositions, or may have a plurality of second polymer blocks having different monomer compositions (in this case, the block polymer may have a plurality of second polymer blocks having different monomer compositions. It is a multi-block copolymer in which the number of block types based on the above is 3 or more). Examples of the first polymer include a graft polymer having a polymer main chain as a soft segment and a polymer side chain as a hard segment. The graft polymer may have a plurality of polymer side chains having different monomer compositions, or may have a plurality of polymer blocks having different monomer compositions in the polymer main chain. The polymer component may contain one kind of first polymer or may contain a plurality of kinds of first polymers.

The polymer component may contain a polymer other than the first polymer (second polymer). For example, the polymer component may include a second polymer that forms a matrix with the soft segments of the first polymer, or may include a second polymer that forms a dispersed phase with the hard segments of the first polymer. The polymer component may contain one kind of second polymer or a plurality of kinds of second polymers.

In the present embodiment, the hard segment forming the island portion is a monomer solution (when a monomer solution cannot be prepared at 25 ° C., a polymer solution) in which the colorant is determined to have compatibility by the compatibility determination test described later with respect to Examples. ), Which is a segment containing 80% by mass or more of the same monomer composition. The color-developing compound has compatibility with the islands formed from such hard segments. The glass transition temperature of this hard segment is preferably 0 ° C. or higher, more preferably 30 ° C. or higher, still more preferably 50 ° C. or higher.

In the present embodiment, the soft segment forming the sea portion is a monomer solution in which the colorant is determined to be incompatible by the compatibility determination test described later with respect to the examples (when the monomer solution cannot be prepared at 25 ° C., m). It is a segment containing 80% by mass or more of the same monomer composition as the polymer solution). The color-developing compound has no compatibility with the second phase formed from such soft segments. The glass transition temperature of this soft segment is preferably 0 ° C. or lower, more preferably less than 0 ° C., still more preferably −30 ° C. or lower, and particularly preferably −50 ° C. or lower. From the viewpoint of ensuring the adhesive strength of the pressure-sensitive adhesive layer 10, the mass ratio of the soft segment in the polymer component is preferably larger than the mass ratio of the hard segment.

As the polymer contained in the base polymer in the present embodiment, a rubber polymer and / or an acrylic polymer is preferably used from the viewpoint of ease of forming a sea-island structure.

As the rubber polymer, a styrene copolymer is preferably used. Examples of the styrene copolymer include styrene-isoprene-styrene copolymer (SIS), SIS hydrogenated additive, styrene-ethylene-butylene copolymer (SEB), and styrene-butadiene-styrene copolymer (SBS). , SBS hydrogenated additives, styrene-isobutylene-styrene copolymer (SIBS), and styrene-butadiene-styrene-butadiene (SBSB). In these styrene copolymers, styrene forms a hard segment and unsaturated hydrocarbons copolymerizing with styrene form a soft segment. The rubber polymer may be used alone or in combination of two or more.

The styrene content in the styrene copolymer is preferably 5% by mass or more, more preferably 7% by mass or more, and further preferably 10% by mass or more. The styrene content in the styrene copolymer is preferably 40% by mass or less, more preferably 30% by mass or less, still more preferably 20% by mass or less.

As the (meth) acrylic acid alkyl ester and the copolymerizable monomer of the acrylic polymer in the second embodiment, the above-mentioned (meth) acrylic acid alkyl ester and the copolymerizable monomer for the acrylic polymer in the first embodiment are used. Can be done. As the (meth) acrylic acid alkyl ester forming a hard segment, an acrylic acid alkyl ester having an alkyl group having 1 to 5 carbon atoms is preferably used, and more preferably, methyl acrylate, methyl methacrylate, and acrylic. At least one selected from the group consisting of n-butyl acid acid is used. As the (meth) acrylic acid alkyl ester forming a soft segment, an acrylic acid alkyl ester having an alkyl group having 7 to 20 carbon atoms is preferably used, and more preferably 2-ethylhexyl acrylate, dodecyl acrylate, and the like. And at least one selected from the group consisting of octadecyl acrylate is used. As the copolymerizable monomer forming the hard segment, an aromatic vinyl compound is preferably used, and styrene is more preferably used.

The polymer component preferably contains a styrene-isoprene-styrene copolymer as the first polymer and a styrene-n-butyl acrylate copolymer as the second polymer. The amount of the styrene-n-butyl acrylate copolymer with respect to 100 parts by mass of the styrene-isoprene-styrene copolymer is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and further preferably 5 parts by mass or more. Further, it is preferably 50 parts by mass or less, more preferably 40 parts by mass or less, and further preferably 30 parts by mass or less.

The pressure-sensitive adhesive layer 10 of the pressure-sensitive adhesive sheet S of the second embodiment may or may not contain the metal complex described above with respect to the first embodiment.

As shown in FIG. 2, each of the pressure-sensitive adhesive sheets S of the first and second embodiments may be a single-sided pressure-sensitive adhesive sheet with a base material provided with a base material 20 in addition to the pressure-sensitive adhesive layer 10. In this case, the pressure-sensitive adhesive sheet S specifically includes a pressure-sensitive adhesive layer 10 and a base material 20 arranged on one side in the thickness direction D thereof. Preferably, the base material 20 comes into contact with one surface of the pressure-sensitive adhesive layer 10 in the thickness direction D.

The base material 20 is an element that functions as a transparent support. The base material 20 is, for example, a flexible plastic film. 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 the like. Examples thereof include an ethylene / ethyl acrylate copolymer and an ethylene / vinyl alcohol copolymer. Examples of the polyester include polyethylene terephthalate, polyethylene naphthalate, and polybutylene terephthalate. Examples of the polyamide include polyamide 6, polyamide 6, 6 and partially aromatic polyamide. From the viewpoint of achieving both transparency and mechanical strength of the base material 20, the plastic material of the base material 20 is preferably polyester, more preferably polyethylene terephthalate.

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

The surface of the base material 20 on the pressure-sensitive adhesive layer 10 side may be subjected to a physical treatment, a chemical treatment, or an undercoat treatment for enhancing the adhesion to the pressure-sensitive adhesive layer 10. Physical treatments include, for example, corona treatment and plasma treatment. Examples of the chemical treatment include acid treatment and alkali treatment.

The thickness of the base material 20 is, for example, 5 μm or more, preferably 10 μm or more, more preferably 20 μm or more, from the viewpoint of ensuring the strength for the base material 20 to function as a support. Further, from the viewpoint of realizing appropriate flexibility in the pressure-sensitive adhesive sheet S, the thickness of the base material 20 is, for example, 200 μm or less, preferably 150 μm or less, and more preferably 100 μm or less.

The pressure-sensitive adhesive sheet S shown in FIG. 2 can be manufactured in the same manner as the above-mentioned manufacturing method except that the base material 20 is used instead of the first release film, for example.

3A to 3C show an example of how to use each of the adhesive sheets S according to the first and second embodiments. This method includes a preparation step, a joining step, and a discolored portion forming step.

First, in the preparation process, 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. The first member 31 may be another electronic device or an optical device. The second member 32 is, for example, a transparent base material. Examples of the transparent base material include a transparent plastic base material and a transparent glass base material.

Next, in the joining step, as shown in FIG. 3B, the first member 31 and the second member 32 are joined via the adhesive sheet S. As a result, the laminated body W is obtained. In the laminated body W, the adhesive sheet S is arranged so as to be in contact with one surface in the thickness direction of the first member 31, and the second member 32 is arranged so as to be in contact with one surface in the thickness direction of the adhesive sheet S. ..

After the joining step, if necessary, inspect for foreign matter and air bubbles between the

members

31, 32 and the pressure-sensitive adhesive sheet S.

Next, in the discoloration step, as shown in FIG. 3C, an external stimulus is applied to the pressure-sensitive adhesive layer 10 in the laminated body W to form the discolored portion 11 in the pressure-sensitive adhesive layer 10. Specifically, the active energy as an external stimulus to the pressure-sensitive adhesive layer 10 from the side of the transparent second member 32 via a mask pattern (not shown) for masking a predetermined region in the pressure-sensitive adhesive layer 10. Irradiate the line. As a result, the portion of the pressure-sensitive adhesive layer 10 that is not masked by the mask pattern is discolored.

In this step, an acid is generated from the photoacid generator at the portion of the pressure-sensitive adhesive layer 10 that has been irradiated with the active energy rays, and the color-developing compound is developed by the reaction with this acid. As a result, the discolored portion 11 is formed on the pressure-sensitive adhesive layer 10.

In the pressure-sensitive adhesive sheet S, the pressure-sensitive adhesive layer 10 contains a color-developing compound as described above. Therefore, after the pressure-sensitive adhesive sheet S is attached to the adherend (

members

31, 32 in the present embodiment), the pressure-sensitive adhesive layer 10 is locally discolored by applying an external stimulus to the portion to be discolored in the pressure-sensitive adhesive layer 10. be able to. In the pressure-sensitive adhesive sheet S capable of forming the discolored portion 11 on the pressure-sensitive adhesive layer 10 after being bonded to the adherend, the pressure-sensitive adhesive sheet S and the adherend are formed after the bonding and before the discolored portion 11 of the pressure-sensitive adhesive layer 10 is formed. The presence or absence of foreign matter and air bubbles can be inspected between.

Further, in the pressure-sensitive adhesive sheet S, the first color change width W1 and the second color change width W2 of the pressure-sensitive adhesive layer 10 satisfy the above formula (1). Such a pressure-sensitive adhesive sheet S is suitable for suppressing deterioration of the discolored portion after the discolored portion is formed on the pressure-sensitive adhesive layer 10 by applying an external stimulus. Suitable for imparting antireflection properties.

Further, as an example of how to use the adhesive sheet S, the adhesive sheet S may be arranged on the light emitting side (image display side) of the pixel panel in the display panel. Specifically, when the first member 31 is a display panel, the discolored portion 11 is provided with a pattern shape corresponding to (that is, facing) the conductor layer as the metal wiring formed on the pixel panel included in the display panel. Thereby, the reflection of external light in the conductor layer can be suppressed.

The width of the conductor layer is, for example, 10 μm or more. The width of the conductor layer is, for example, 300 μm or less. Further, the conductor layer is preferably formed at a fine pitch. The distance between the conductor layers is, for example, 10 μm or more. The same interval is, for example, 100,000 μm or less.

The line width of the discolored portion 11 corresponds to the width of the conductor layer described above. Specifically, the line width of the discolored portion 11 is, for example, 10 μm or more. The line width is, for example, 300 μm or less. Further, the interval between the discolored portions 11 is, for example, 10 μm or more. The same interval is, for example, 100,000 μm or less.

In this adhesive sheet S, since the first discoloration width W1 and the second discoloration width W2 satisfy the above formula (1), the shielding property and the antireflection property can be improved. As a result, it is possible to improve the visibility of the display panel provided with the metal wiring while suppressing the reflection of external light on the metal wiring.

The feature of the present invention is to adjust W2 / W1 described above, preferably to adjust W3 / W1. That is, the mode of use of the variable color film of the present invention is not limited to forming a linear colored portion (color-developing portion), and various colored portions can be formed. More specifically, examples of the colored portion that can be formed include a linear shape, a point shape, a rectangular shape, a circular shape, an elliptical shape, and an indefinite shape.

The present invention will be specifically described below with reference to examples, but the present invention is not limited to the examples. In addition, the specific numerical values such as the blending amount (content), the physical property value, the parameter, etc. described below are the blending amounts corresponding to them described in the above-mentioned "form for carrying out the invention" (forms for carrying out the invention). It can be replaced with an upper limit (numerical value defined as "less than or equal to" or "less than") or a lower limit (numerical value defined as "greater than or equal to" or "greater than or equal to") such as content), physical property value, and parameter.

Production Example 1 (Preparation of base polymer)
In a reaction vessel equipped with a stirrer, a thermometer, a reflux cooler, and a nitrogen gas introduction tube, 63 parts by mass of 2-ethylhexyl acrylate (2EHA), 9 parts by mass of methyl methacrylate (MMA), and 2-acrylic acid. 13 parts by mass of hydroxyethyl (HEA), 15 parts by mass of N-vinyl-2-pyrrolidone (NVP), and 0.2 parts by mass of 2,2'-azobisisobutyronitrile (AIBN) as a polymerization initiator. The mixture containing 233 parts by mass of ethyl acetate as a solvent was stirred at 60 ° C. for 7 hours under a nitrogen atmosphere (polymerization reaction). As a result, 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.

[Example 1]
<Preparation of adhesive composition>
The following components were uniformly mixed with the above polymer solution containing the acrylic polymer of Production Example 1 per 100 parts by mass of the acrylic polymer (base polymer) to prepare an adhesive composition.

Compound that develops color by reaction with acid: Leuco dye (trade name "S-205", 2'-anilino-6'-(N-ethyl-N-isopentylamino) -3'-methylspiro [phthalide-3, 9'-[9H] xanthene], manufactured by Yamada Chemical Industry Co., Ltd.) 2.00 parts by mass Acid generator: Photoacid generator (trade name "CPI-310B", sulfonium ^and ₍ C6 F ₅ ) ₄ B- Onium salt, manufactured by San-Apro Co., Ltd.) 7.00 parts by mass Metal complex: Zinc salicylate trihydrate (manufactured by Fujifilm Wako Junyaku Co., Ltd.) 0.38 parts by mass Cross-linking agent: "Takenate D110N" (Trimethylol propane of xylylene diisocyanate) Adduct 75% ethyl acetate solution, manufactured by Mitsui Kagaku) 0.25 parts by mass (solid content equivalent) Cross-linking catalyst: dibutyltin dilaurate (1 mass% ethyl acetate solution) 0.01 parts by mass (solid content equivalent)
Acetylacetone: 3.00 parts by mass

<Formation of adhesive layer>
The adhesive composition was applied to a release film (trade name "MRF # 38", polyester film, thickness 38 μm, manufactured by Mitsubishi Plastics Co., Ltd.) having one side as a release surface to form a coating film. Next, this coating film was dried at 132 ° C. for 3 minutes to form a pressure-sensitive adhesive layer having a thickness of 25 μm. A release film (trade name "MRF # 38", polyester film, thickness 38 μm, manufactured by Mitsubishi Plastics Co., Ltd.) having a release surface on one side was attached to this pressure-sensitive adhesive layer. Then, it was aged at 60 ° C. for 24 hours, and the crosslinking reaction was allowed to proceed in the pressure-sensitive adhesive layer.

As described above, the 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 units of mass (the same applies to Examples 1 to 3 and Comparative Example 1 described later).

[Examples 2 and 3 and Comparative Example 1]
Each of the pressure-sensitive adhesive sheets of Examples 2 and 3 and Comparative Example 1 was prepared in the same manner as the pressure-sensitive adhesive sheet of Example 1. However, the composition of the adhesive composition was changed to the amount shown in Table 1.

[Example 4]
<Preparation of adhesive composition>
The following components are uniformly mixed per 100 parts by mass of a styrene-isoprene-styrene block copolymer (trade name "Quintac 3520", styrene content ratio 15% by mass, manufactured by Nippon Zeon Corporation) as the first polymer (base polymer). The adhesive composition was prepared.

Second polymer: styrene-acrylic block copolymer (trade name "FBP-001", manufactured by Fujikura Kasei Co., Ltd.) 5 parts by mass A compound that develops color by reaction with an acid (color-developing compound): Leuco-based dye, 2'-anilino -6'-(N-ethyl-N-isopentylamino) -3'-methylspiro [phthalide-3,9'-[9H] xanthene] (trade name "S-205", manufactured by Yamada Chemical Industry Co., Ltd.) 2. 00 parts by mass acid generator: Photoacid generator (trade name "CPI-310B", onium salt of sulfonium ^and (C ₆ F ₅ ) ₄ B-, manufactured by San-Apro) 7.00 parts by mass cross-linking agent: 1, 3-Bis (N, N-diglycidylaminomethyl) cyclohexane (trade name "Tetrad-C", manufactured by Mitsubishi Gas Chemicals, Inc.) 0.25 parts by mass

<Formation of adhesive layer>
A coating film is coated with an adhesive composition on the release-treated surface of a 38 μm-thick base film (trade name “MRF # 38”, polyester film, manufactured by Mitsubishi Plastics) whose one side is mold-released. Formed. The coating was then dried by heating at 132 ° C. for 3 minutes. As a result, a pressure-sensitive adhesive layer having a thickness of 25 μm was formed on the base film. Next, on the pressure-sensitive adhesive layer on the base film, a release-treated surface of a 38 μm-thick release film (trade name “MRE # 38”, polyester film, manufactured by Mitsubishi Resin Co., Ltd.) whose one side is mold-released is applied. I pasted them together. Then, it was aged at 60 ° C. for 24 hours to allow the cross-linking reaction in the pressure-sensitive adhesive layer to proceed. As described above, the pressure-sensitive adhesive sheet of Example 4 was produced. The composition of the pressure-sensitive adhesive layer in the pressure-sensitive adhesive sheet of Example 4 is shown in Table 2 in units of mass (the same applies to Examples 5 to 7 described later).

[Examples 5 to 7]
Each of the pressure-sensitive adhesive sheets of Examples 5 to 7 was prepared in the same manner as the pressure-sensitive adhesive sheet of Example 4. However, the blending amount of the second polymer was changed to the amount shown in Table 2.

<Evaluation>
1. 1. Weather resistance test (manufacturing of sample for weather resistance test)
Adhesive layer 25 μm, UVA-TAC 32 μm, UVA-OCA 100 μm, and UVA-TAC 32 μm of each Example and each comparative example with respect to one side in the thickness direction of eagle glass (thickness 0.55 mm, manufactured by Matsunami Glass Co., Ltd.). They were laminated in the order of. In the laminated body of each Example and each Comparative Example, the sample was irradiated with ultraviolet rays. Specifically, the adhesive sheet (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 a relative humidity of 50% (adhesive by the UV irradiation). The leuco-based dye in the layer was reacted with the photoacid generator). In this UV irradiation, a UV-LED lamp having a wavelength of 365 nm in a UV-LED irradiation device (model number "QEL-350-RU6W-CW-MY") manufactured by Quark Technology Co., Ltd. is used as a light source, and the integrated irradiation amount is 8000 mJ / cm. It was set to ² (integrated irradiation light amount in the wavelength range of 320 nm to 390 nm). As described above, a sample for weather resistance test was prepared.

UVA-TAC: A film having a TAC film (KC2UA, manufactured by Konica Minolta) and a hard coat layer in order (a hard coat layer (thickness: 7 μm) is formed on one surface of KC2UA (thickness: 25 μm) by a hard coat treatment). (Thickness: 32 μm)
UVA-OCA: Adhesive tape with UV absorption function, product name "CS9934U", thickness 100 μm, manufactured by Nitto Denko Corporation

(Weather resistance test)
The average transmittance, L ^* , a ^* , and b ^* values were measured in the weather resistance test samples of Examples 1 to 3 and Comparative Example 1.

Specifically, in the weather resistance test sample, it was installed in a transmittance measuring device (U4150 type spectrophotometer, manufactured by Hitachi High-Tech Science Co., Ltd.) so that light was applied from the eagle glass side. Then, the average transmittance and the values of L ^* , a ^* , and b ^* at wavelengths of 400 nm to 700 nm were measured.

Specifically, the average transmittance (T1) of the weathering test sample at a wavelength of 400 nm to 700 nm, L ^* (L ₁ ^* ) for the weathering test sample, and a ^* (a ₁ ^* ) for the weathering test sample. And b ^* (b ₁ ^* ) for the weather resistance test sample were measured, respectively.

Next, the weather resistance test sample was irradiated with a super xenon lamp having an illuminance of 120 W in the wavelength range of 300 nm to 400 nm for 24 hours using a super xenon weather meter SX75 manufactured by Suga Test Instruments Co., Ltd. As a result, a sample for weather resistance test after irradiation for 24 hours was obtained.

Then, by the same procedure as above, the average transmittance, L ^* , a ^* , and b ^* values of the weather resistance test sample after irradiation for 24 hours were measured.

Specifically, the average transmittance (T2) of the weather resistance test sample after 24-hour irradiation at a wavelength of 400 nm to 700 nm, L ^* (L ₂ ^* ) for the weather resistance test sample after 24-hour irradiation, and 24-hour irradiation. A * (a _{2 *) for the later weather resistance test sample and b * (b 2} ^* ⁾ _for ^the ^weather resistance test sample after 24-hour irradiation were measured, respectively.

Then, the color difference (ΔE) was calculated based on the following formula (7).

ΔE = ((L ₂ ^* -L ₁ ^* ) ² + (a ₂ ^* -a ₁ ^* ) ² + (b ₂ ^* -b ₁ ^* ) ² ) ^1/2
(7)

Table 1 shows the results of T1, T2, and the color difference (ΔE).

2. 2. Durability test A linear discolored portion was formed on the pressure-sensitive adhesive layer by irradiating the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet with ultraviolet rays through a photomask having a linear opening. The photomask was formed from a dry film photoresist placed on the surface of the pressure-sensitive adhesive sheet on the base film side, and the line width of the opening of the photomask was 200 μm. For ultraviolet irradiation, a UV-LED lamp with a wavelength of 365 nm in a UV-LED irradiation device (model number "QEL-350-RU6W-CW-MY") manufactured by Quark Technology Co., Ltd. is used as a light source through a photo mask and a base film. The pressure-sensitive adhesive layer was irradiated with ultraviolet rays, and the integrated irradiation light amount was set to 2000 mJ / cm ² (the integrated irradiation light amount in the wavelength range of 320 nm to 390 nm).

Next, the line width of the linear discolored portion formed on the pressure-sensitive adhesive layer was measured (measurement of the first discolored width W1). Specifically, first, the linear discolored portion formed on the adhesive layer is observed with a digital microscope (trade name "VHX-900", manufactured by KEYENCE), and a part of the discolored portion and its vicinity are included. The area to be used was photographed at a magnification of 50 times. Next, the captured image was binarized by image analysis software. Next, in the image after the binarization process, the line width (first color change width W1) of the linear color change portion was measured.

Next, the pressure-sensitive adhesive sheet having the linear discolored portion formed on the pressure-sensitive adhesive layer was heat-treated at 85 ° C. for 120 hours (first durability test).

Next, the line width of the linear discolored portion in the adhesive layer of the adhesive sheet was measured (measurement of the second discolored width W2). The specific measurement method is the same as the measurement method described above for the measurement of the first color change width W1. The first discoloration width W1 of the linear discoloration portion before the first durability test, the second discoloration width W2 of the linear discoloration portion after the first durability test, and the second discoloration width W2 with respect to the first discoloration width W1. The rate of change (W2 / W1) is shown in Tables 1 and 2.

Further, the pressure-sensitive adhesive layers of the pressure-sensitive adhesive sheets of Examples 1 to 7 and Comparative Example 1 were formed in the same manner as in the above method except that the second durability test was performed instead of the first durability test. The line width of the linear discolored part was examined. In the second durability test, the pressure-sensitive adhesive sheet having the linear discolored portion formed on the pressure-sensitive adhesive layer was heat-treated at 85 ° C. for 240 hours. The first discoloration width W1 of the linear discoloration portion before the second durability test, the third discoloration width W3 of the linear discoloration portion after the second durability test, and the third discoloration width W3 with respect to the first discoloration width W1. The rate of change (third color change width W3 / first color change width W1) is shown in Tables 1 and 2.

3. 3. Peeling test The pressure-sensitive adhesive layers of each example and each comparative example were attached to a glass plate. Then, the adhesive strength to the glass plate was measured based on the following conditions. The results are shown in Table 1.

(Measurement condition)
Temperature: 23 ° C
Peeling angle: 180 °
Peeling speed: 300 mm / min

4. Confirmation of Micro-Phase Separation Structure The micro-phase separation structure was confirmed for the pressure-sensitive adhesive layer of each of the pressure-sensitive adhesive sheets of Examples 4 to 7 as follows. First, a sample for observation with a transmission electron microscope (TEM) was prepared. Specifically, the pressure-sensitive adhesive layer was stained and then rapidly frozen, and flakes were cut out from the pressure-sensitive adhesive layer using an ultramicrotome (manufactured by Leica). Then, the flakes were observed and photographed using a transmission electron microscope (trade name "HT7820", manufactured by Hitachi High-Technologies Corporation). Next, the obtained TEM image was analyzed by image analysis software and binarized. The microphase separation of the pressure-sensitive adhesive layer in Example 7 is typically shown in FIG.

In the pressure-sensitive adhesive layer of each of the pressure-sensitive adhesive sheets of Examples 4 to 7, a sphere-type microphase-separated structure could be confirmed. In each pressure-sensitive adhesive layer, the matrix (sea part) formed by the isoprene block (soft segment) of the first polymer is filled with the styrene (hard segment) of the first polymer and the second polymer (styrene-n-butyl acrylate copolymer). The spherical dispersed phase (island) formed by and was dispersed.

5. Compatibility determination test The compatibility of each of the color-developing compound and the acid generator used in Examples 4 to 7 with various monomer or polymer solutions was examined.

Specifically, first, as a monomer solution, styrene, n-butyl acrylate, methyl methacrylate (MMA), acrylic acid, N-vinyl-2-pyrrolidone (NVP), 2-methoxyethyl acrylate (2MEA), Solutions of methyl acrylate, 2-ethylhexyl acrylate (2EHA), lauryl acrylate (dodecyl acrylate), and stearyl acrylate (octadecyl acrylate) were prepared.

Next, a mixture containing 7.8 g of the monomer solution and 0.2 g of compound C (color-developing compound or photoacid generator) was stirred in a 50 mL screw tube (the ratio of compound C was 2.5% by mass). (First stirring). A magnetic stirrer was used for stirring. In stirring, the temperature was 25 ° C., the rotation speed of the stirrer was 500 rpm, and the stirring time was 5 minutes. After stirring, it was visually confirmed whether the compound C was dissolved in the monomer solution without causing turbidity or precipitation by such stirring. The color-developing compound and the photoacid generator were dissolved in each solution of styrene, n-butyl acrylate, MMA, acrylic acid, NVP, 2MEA, and methyl acrylate without causing turbidity or precipitation (compound). C showed compatibility). On the other hand, the color-developing compound and the photoacid generator caused turbidity or precipitation with respect to each solution of 2EHA, lauryl acrylate, and stearyl acrylate, respectively (Compound C did not show compatibility).

On the other hand, a polyisoprene solution was prepared as the polymer solution (the isoprene monomer solution could not be prepared because the isoprene is too volatile). Next, a mixture containing 7.8 g of the polymer solution and 0.2 g of compound C (color-developing compound or photoacid generator) was stirred in a 50 mL screw tube (the ratio of compound C was 2.5% by mass). (Second stirring). The conditions for the second stirring are the same as the conditions for the first stirring described above. It was confirmed by observation after the second stirring that the color-developing compound and the photoacid generator each produced turbidity or precipitation with respect to the polymer solution (Compound C did not show compatibility).

Then, with respect to the phase in which the segment containing 80% by mass or more of the same monomer composition as the monomer solution in which the compound C exhibits the above-mentioned compatibility is formed in the microphase separation structure by the polymer component having the segment, the compound C is added. It was determined to have compatibility. Further, with respect to a phase in which a segment containing 80% by mass or more of the same monomer composition as the above-mentioned monomer solution in which compound C does not exhibit compatibility is formed in a microphase separation structure by a polymer component having the segment, compound C is used. Was determined to be incompatible. That is, the color-developing compound and the photoacid generator used in Examples 4 to 7 each have an island portion formed by a hard segment (HS) containing styrene and n-butyl acrylate in a microphase-separated structure. (In HS in Examples 4 to 7, the proportion of the monomer (styrene, n-butyl acrylate) in which compound C is compatible is 80% by mass or more). The color-developing compound and the photoacid generator used in Examples 4 to 7 are not compatible with the sea portion formed by the soft segment (SS) containing isoprene in the microphase-separated structure, respectively (Example). In SS in 4 to 7, the proportion of isoprene in which compound C is incompatible is 80% by mass or more).

6. Light Transmittance For the pressure-sensitive adhesive layer of each of the pressure-sensitive adhesive sheets of Examples 4 to 7, the average transmittance at a wavelength of 400 nm to 700 nm was examined as follows.

First, the adhesive sheet was attached to eagle glass (thickness 0.55 mm, manufactured by Matsunami Glass Co., Ltd.) to prepare a measurement sample (first measurement sample). Next, with respect to the measurement sample, the average transmittance at a wavelength of 400 nm to 700 nm was measured using a spectrophotometer U4150 manufactured by Hitachi High-Technologies Corporation (first transmittance measurement). In this measurement, the total light transmittance of the measurement sample at a wavelength of 400 nm to 700 nm is measured at a pitch of 1 nm with the measurement sample installed in the device so that the measurement sample is exposed to light from the eagle glass side. did. In this measurement, the transmittance spectrum obtained by measuring only the eagle glass under the same conditions was used as the baseline. The above-mentioned average transmittance measurements in Examples 1 to 3 and Comparative Example 1 were also specifically carried out in the same manner as in this measurement. Table 2 shows the measured average transmittance T1 (average transmittance at a wavelength of 400 nm to 700 nm before UV irradiation) of the pressure-sensitive adhesive layer.

On the other hand, for each of the pressure-sensitive adhesive sheets of Examples 4 to 7, the average transmittance at a wavelength of 400 nm to 700 nm after UV irradiation was examined as follows.

First, a sample similar to the above-mentioned first measurement sample was prepared. Next, the sample was irradiated with ultraviolet rays. Specifically, the adhesive sheet (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 a relative humidity of 50% (adhesive by the UV irradiation). The leuco-based dye in the layer was reacted with the photoacid generator). In this UV irradiation, a UV-LED lamp having a wavelength of 365 nm in a UV-LED irradiation device (model number "QEL-350-RU6W-CW-MY") manufactured by Quark Technology Co., Ltd. is used as a light source, and the integrated irradiation amount is 8000 mJ / cm. It was set to ² (integrated irradiation light amount in the wavelength range of 320 nm to 390 nm). As described above, a measurement sample (second measurement sample) was prepared.

Next, for the second measurement sample, the average transmittance at a wavelength of 400 nm to 700 nm was measured 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 2 shows the measured average transmittance T2 (average transmittance at a wavelength of 400 nm to 700 nm after UV irradiation) of the pressure-sensitive adhesive layer. Table 2 also shows the ratio of the average transmittance T2 to the above-mentioned average transmittance T1.

The above-described embodiment is an example of the present invention, and the present invention should not be construed in a limited manner by the embodiment. Modifications of the invention that are apparent to those skilled in the art are included in the claims below.

The variable color adhesive sheet of the present invention is used, for example, in the process of manufacturing 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 Discolored part 20 Base material 31 First member 32 Second member

Claims

Equipped with an adhesive layer that can be discolored by external stimuli
A variable color adhesive sheet in which the first discoloration width W1 determined by the following test 1 and the second discoloration width W2 determined by the following test 2 satisfy the following formula (1).
0.5 <W2 / W1 <2 (1)
<Test 1>
Step A: External stimulus is linearly applied to the pressure-sensitive adhesive layer.
Step B: After step A, the width of the discolored area formed in the pressure-sensitive adhesive layer is measured.
<Test 2>
Step C: After step A and step B of the test 1, heat treatment is performed at 85 ° C. for 120 hours.
Step D: After step C, the width of the discolored area formed in the pressure-sensitive adhesive layer is measured.
The variable color adhesive sheet according to claim 1, wherein the first color change width W1 and the third color change width W3 obtained by the following test 3 satisfy the following formula (2).
0.5 <W3 / W1 <2 (2)
<Test 3>
Step E: After step A and step B of <Test 1> above, heat treatment is performed at 85 ° C. for 240 hours.
Step F: After step E, the width of the discolored area formed in the pressure-sensitive adhesive layer is measured.
The variable color pressure-sensitive adhesive sheet according to claim 1, wherein the pressure-sensitive adhesive layer has a thickness of 10 μm or more and 300 μm or less.
The variable color pressure-sensitive adhesive sheet according to claim 1, further comprising a base material arranged on one side in the thickness direction of the pressure-sensitive adhesive layer.
After the pressure-sensitive adhesive layer is attached to the glass plate, in a peeling test under the peeling conditions of 23 ° C., a peeling angle of 180 ° and a peeling speed of 300 mm / min, the adhesive strength shown to the glass plate is 1. The variable color adhesive sheet according to claim 1, which is 0.0N / 25 mm or more and 50N / 25 mm or less.