Color changeable adhesive sheet

Abstract

A variable color adhesive sheet has an adhesive layer (10) that can change color due to an external stimulus. A first color change width W1 and a second color change width W2 satisfy the following equation (1). 0.5 < W2 / W1 < 2 (1).

Description

TECHNICAL FIELD

[0001] The present application relates to a color-changeable adhesive sheet. BACKGROUND

[0002] A display panel such as an organic EL panel has a laminated structure including a pixel panel and a protective member or the like. In the manufacturing process of such a display panel, in order to adhere the elements contained in the laminated structure to each other, for example, a transparent adhesive sheet is used.

[0003] In addition, as a transparent adhesive sheet arranged on the light exit side (image display side) of a pixel panel in a display panel, an adhesive sheet in which a colored portion for imparting design, shielding, anti-reflection, or the like to a prescribed portion of the same sheet is formed in advance is proposed. Such an adhesive sheet is described, for example, in Patent Literature 1 below. In Patent Literature 1, specifically, an adhesive sheet having a colored portion containing carbon black pigment is described.

[0004] PRIOR ART DOCUMENTS

[0005] PATENT LITERATURE

[0006] Patent Literature 1: Japanese Patent Application Publication No. 2017-203810 SUMMARY

[0007] PROBLEMS TO BE SOLVED BY THE INVENTION

[0008] However, in the manufacturing process of a display panel, in the case where an adhesive sheet in which a colored portion is formed in advance is used, after the adhesive sheet is adhered to an adherend, it is not possible to properly check the presence or absence of foreign matter and air bubbles between the adherend and the colored portion of the adhesive sheet. In the adhesion of an adhesive sheet in the manufacturing process of a display panel, it is required that the presence or absence of foreign matter and air bubbles between the adherend and the adhesive sheet after adhesion can be properly checked.

[0009] In addition, from the viewpoint of imparting design, shielding, and anti-reflection, or the like, sometimes the colored component is formed in an arbitrary shape at an arbitrary portion. Also, in this case, depending on the passage of time, sometimes the visibility and the shielding property are reduced.

[0010] The present application provides a color-changeable adhesive sheet in which an adhesive layer can be locally colored after adhesion to an adherend, and which is suitable for imparting design, shielding, and anti-reflection to an arbitrary portion.

[0011] SOLUTION TO THE PROBLEM

[0012] The present application [1] is a color-changeable adhesive sheet having an adhesive layer that can be colored due to an external stimulus, and a first color-changeable width W1 obtained according to Test 1 below and a second color-changeable width W2 obtained according to Test 2 below satisfy the following formula (1).

[0013] 0.5 < W2 / W1 < 2 (1)

[0014] <Experiment 1>

[0015] Step A: Linearly applying an external stimulus to the adhesive layer.

[0016] Step B: After Step A, measuring the width of the color change region formed in the adhesive layer.

[0017] <Experiment 2>

[0018] Step C: After Step A and Step B of the aforementioned Experiment 1, performing a heat treatment at 85°C for 120 hours.

[0019] Step D: After Step C, measuring the width of the color change region formed in the adhesive layer.

[0020] The present application [2] includes the color changeable adhesive sheet described in the aforementioned [1], wherein the aforementioned first color change width W1 and a third color change width W3 obtained according to the following Experiment 3 satisfy the following formula (2).

[0021] 0.5 < W3 / W1 < 2 (2)

[0022] <Experiment 3>

[0023] Step E: After Step A and Step B of the aforementioned <Experiment 1>, performing a heat treatment at 85°C for 240 hours.

[0024] Step F: After Step E, measuring the width of the color change region formed in the adhesive layer.

[0025] The present application [3] includes the color changeable adhesive sheet described in the aforementioned [1] or [2], wherein the aforementioned adhesive layer has a thickness of 10 μm or more and 300 μm or less.

[0026] The present application [4] includes the color changeable adhesive sheet described in any one of the aforementioned [1] to [3], further comprising a substrate disposed on one side in the thickness direction of the aforementioned adhesive layer.

[0027] The present application [5] includes the color changeable adhesive sheet described in any one of the aforementioned [1] to [4], wherein, after the aforementioned adhesive layer is attached to a glass plate, the adhesive force shown with respect to the aforementioned glass plate in a peeling test under peeling conditions of 23°C, a peeling angle of 180°, and a peeling speed of 300 mm / minute is 1.0 N / 25 mm or more and 50 N / 25 mm or less.

[0028] Effects of the Invention

[0029] The color changeable adhesive sheet of the present application has an adhesive layer that can change color due to an external stimulus. Therefore, after the color changeable adhesive sheet is attached to an adherend, an external stimulus is applied to a predetermined portion of the adhesive layer that changes color, and thus the adhesive layer can be partially colored. In such a color changeable adhesive sheet, after attachment and before the formation of the colored portion of the adhesive layer, the presence or absence of foreign matter and air bubbles between the color changeable adhesive sheet and the adherend can be checked.

[0030] In addition, in the color changeable adhesive sheet, the first color change width W1 and the second color change width W2 of the adhesive layer satisfy 0.5 < W2 / W1 < 2. Such a color changeable adhesive sheet is suitable for suppressing the deterioration of the colored portion of the adhesive layer after the formation of the colored portion by an external stimulus, and thus is suitable for imparting design properties, masking properties, and anti-reflection properties to an arbitrary portion. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 A cross-sectional view of an embodiment of the color changeable adhesive sheet of the present application.

[0032] Figure 2 A cross-sectional view of a modification of the color changeable adhesive sheet of the present application (when the adhesive sheet is a single-sided adhesive sheet with a base material).

[0033] Figure 3 A ~ Figure 3 C shows an example of a method of using the color changeable adhesive sheet of the present application. Figure 3 A shows a process of preparing a color changeable adhesive sheet and a member as an adherend. Figure 3 B shows a process of joining members to each other with the color changeable adhesive sheet. Figure 3 C shows a process of forming a colored portion in the adhesive layer of the color changeable adhesive sheet.

[0034] Figure 4 A TEM image of the adhesive layer of Example 7. DETAILED DESCRIPTION

[0035] 1. First color change width W1 and second color change width W2

[0036] The color changeable adhesive sheet of the present application has an adhesive layer that can change color due to an external stimulus, and the first color change width W1 obtained according to Test 1 described below and the second color change width W2 obtained according to Test 2 described below satisfy the following formula (1).

[0037] 0.5 < W2 / W1 < 2 (1)

[0038] The first color change width W1 is obtained according to the following <Test 1>.

[0039] <Test 1>

[0040] Step A: An external stimulus is applied to the adhesive layer in a linear shape. Step B: An external stimulus is applied to the adhesive layer in a circular shape.

[0041] Step B: After Step A, the width of the color change region formed in the adhesive layer is measured.

[0042] The second color change width W2 is found according to the following <Test 2>.

[0043] <Test 2>

[0044] Step C: After Step A and Step B of the above <Test 1>, heat treatment is performed at 85°C for 120 hours.

[0045] Step D: After Step C, the width of the color change region formed in the adhesive layer is measured.

[0046] The color changeable adhesive sheet has an adhesive layer that can change color due to an external stimulus as described above. Therefore, after the color changeable adhesive sheet is attached to an adherend, an external stimulus is imparted to a predetermined portion of the adhesive layer that changes color, and thus the adhesive layer can be locally colored. In such a color changeable adhesive sheet, the presence or absence of foreign matter and air bubbles between the color changeable adhesive sheet and the adherend can be checked before the adhesive layer is colored after attachment.

[0047] In addition, in the color changeable adhesive sheet, the first color change width Wl and the second color change width W2 of the adhesive layer satisfy the above formula (1). Such a color changeable adhesive sheet is suitable for suppressing deterioration of the color change portion of the adhesive layer after the color change portion is formed by imparting an external stimulus, and thus is suitable for imparting design properties, masking properties, and anti-reflection properties to an arbitrary portion.

[0048] As an example of the method of using the color changeable adhesive sheet, the color changeable adhesive sheet is sometimes disposed on the light exit side (image display side) of a pixel panel in a display panel.

[0049] In detail, metal wiring is sometimes provided on a pixel panel provided in a display panel at a fine pitch. Also, from the viewpoint of suppressing reflection of external light in the metal wiring, a colored portion is sometimes provided in a pattern shape corresponding to such metal wiring.

[0050] In the color changeable adhesive sheet, the first color change width Wl and the second color change width W2 satisfy the above formula (1), and thus masking properties and anti-reflection properties can be improved. As a result, reflection of external light in the metal wiring can be suppressed, and the visibility of the display panel provided with the metal wiring can be improved.

[0051] Further, as a method of adjusting in such a manner that the first color change width Wl and the second color change width W2 satisfy the above-described formula (1), for example, there can be mentioned a method using a metal complex (described later) (first method), a method of increasing the elastic modulus of the adhesive layer, a method using a coloring component in the adhesive layer combined with other components, a method of providing the coloring component to the island portion using a sea-island structure of non-solubility or low solubility (second method).

[0052] As the method of increasing the elastic modulus of the adhesive layer, for example, there can be mentioned a method using a multifunctional monomer as a monomer component, a method using a crosslinking agent, and a composite method thereof.

[0053] As the method using a coloring component in the adhesive layer combined with other components, for example, there can be mentioned a method using a colored polymer having a component capable of coloring a polymer in the layer to a prescribed color as a coloring component connected / combined; a method in which the coloring component and the polymer component are different components at first, but the coloring component is combined with the polymer by reaction; and a composite method thereof.

[0054] As the method of providing the coloring component to the island portion using a sea-island structure of non-solubility or low solubility, for example, there can be mentioned a method of providing the coloring component to the island portion as a sea-island structure using a polymer having high solubility with the coloring component and a polymer having low solubility, and the polymer having high solubility becomes the island portion.

[0055] 2. First color change width Wl and third color change width W3

[0056] The color changeable adhesive sheet preferably satisfies the following formula (2) with respect to the first color change width Wl and the third color change width W3 obtained according to Test 3 described below.

[0057] 0.5 < W3 / Wl < 2 (2)

[0058] The third color change width W3 is obtained according to the following <Test 3>.

[0059] <Test 3>

[0060] Step E: After Step A, Step B of the above-described <Test 1>, heat treatment at 85°C is performed for 240 hours.

[0061] Step F: After Step E, the width of the color change region formed in the adhesive layer is measured.

[0062] The first color change width Wl and the third color change width W3 only need to satisfy the above-described formula (2), and further designability, shielding property, and antireflection property can be imparted to an arbitrary portion.

[0063] Further, as a method of adjustment in a manner that the first color change width Wl and the third color change width W3 satisfy the above-described formula (2), the same as the method of adjustment in a manner that the first color change width Wl and the second color change width W2 satisfy the above-described formula (1) is performed.

[0064] 3. Average transmittance Tl, average transmittance T2, and color difference

[0065] The color changeable adhesive sheet preferably satisfies the following formula (3) with respect to the average transmittance Tl obtained according to the following Test 4 and the average transmittance T2 obtained according to the following Test 5, and preferably satisfies the following formula (4).

[0066] 0.2 < T2 / Tl < 3 (3)

[0067] 0.2 < T2 / Tl < 2 (4)

[0068] The average transmittance Tl is obtained according to the following <Test 4>.

[0069] <Test 4>

[0070] Step G: The adhesive layer is irradiated with light in a wavelength band of 300 nm to 400 nm.

[0071] Step H: The average transmittance of the adhesive layer under a wavelength of 400 nm to 700 nm is measured.

[0072] The average transmittance Tl is, for example, 10% or more, and preferably 15% or more. The average transmittance Tl is, for example, 40% or less, and preferably 30% or less. For the method of measuring the average transmittance Tl, more specifically, it is described in detail in the weather resistance test described later.

[0073] The average transmittance T2 is obtained according to the following <Test 5>.

[0074] <Test 5>

[0075] Step I: After Step G of the above-described <Test 4>, the adhesive layer is irradiated with a xenon lamp having an irradiance of 120 W in a wavelength range of 300 nm to 400 nm for 24 hours using a super xenon weather meter.

[0076] Step J: The average transmittance of the adhesive layer under a wavelength of 400 nm to 700 nm is measured.

[0077] The average transmittance T2 is, for example, 15% or more, and preferably 24% or more. The average transmittance T2 is, for example, 50% or less, and preferably 40% or less. For the method of measuring the average transmittance T2, more specifically, it is described in detail in the weather resistance test described later.

[0078] The variable color adhesive sheet can satisfy the above-described formula (3) or the above-described formula (4), and has excellent weather resistance. As a method of adjusting so that the average transmittance T1 and the average transmittance T2 satisfy the above-described formula (3) or the above-described formula (4), for example, a method of reducing the oxygen permeability of the adhesive layer, a method of adding an antioxidant to the adhesive layer, and a method of laminating a substrate containing an ultraviolet absorber and the adhesive layer can be given.

[0079] In addition, the color difference determined according to 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.

[0080] 4. Variable color adhesive sheet

[0081] An adhesive sheet S, which is an example of the variable color adhesive sheet satisfying the above-described formula (1), preferably the above-described formula (2) to the above-described formula (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-described formula (1), the above-described first method (first embodiment) and the second method (second embodiment) are employed, but are not limited to these.

[0082] As shown in FIG. 1, the adhesive sheet S has an adhesive layer 10. The adhesive sheet S has a sheet shape of a prescribed thickness, and extends in a direction orthogonal to the thickness direction (a surface direction). The adhesive sheet S is used, for example, as a transparent adhesive sheet disposed on the image display side of a pixel panel in a display panel (for example, having a laminated structure including a pixel panel and a protective member). Figure 1 The adhesive layer 10 is a pressure-sensitive adhesive layer having transparency (visible light transmittance) formed of an adhesive composition. The adhesive composition contains a base polymer, a color-developing compound that develops color by reaction with an acid, and an acid generator. In the first embodiment, the adhesive composition further contains a metal complex.

[0083] The base polymer is an adhesive component for realizing adhesiveness in the adhesive layer 10. The base polymer realizes rubber elasticity in the room temperature range. As the base polymer, for example, an acrylic polymer, a rubber polymer, a polyester polymer, a urethane polymer, a polyether polymer, a silicone polymer, a polyamide polymer, and a fluoropolymer can be given. From the viewpoint of securing good transparency and adhesiveness in the adhesive layer 10, as the base polymer, an acrylic polymer is preferably used.

[0084] The content ratio of the base polymer in the adhesive layer 10 is, for example, 50% by mass or more, preferably 60% by mass or more, and more preferably 70% by mass or more, from the viewpoint of appropriately realizing the function of the base polymer in the adhesive layer 10.

[0085] The content ratio of the base polymer in the adhesive layer 10 is, for example, 50% by mass or more, preferably 60% by mass or more, and more preferably 70% by mass or more, from the viewpoint of appropriately realizing the function of the base polymer in the adhesive layer 10.

[0086] The acrylic polymer is, for example, a polymer obtained by polymerizing a monomer component containing an alkyl (meth)acrylate at a proportion of 50% by mass or more. The "(meth)acrylate" means acrylic acid and / or methacrylic acid.

[0087] As the alkyl (meth)acrylate, for example, an alkyl (meth)acrylate having an alkyl group of 1 to 20 carbon atoms in a linear or branched chain can be given. As such an alkyl (meth)acrylate, for example, methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, isopropyl (meth)acrylate, isobutyl (meth)acrylate, sec-butyl (meth)acrylate, t-butyl (meth)acrylate, amyl (meth)acrylate, isoamyl (meth)acrylate, neopentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, isooctyl (meth)acrylate, nonyl (meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, undecyl (meth)acrylate, dodecyl (meth)acrylate, isotridecyl (meth)acrylate, myristyl (meth)acrylate, isotetradecyl (meth)acrylate, pentadecyl (meth)acrylate, hexadecyl (meth)acrylate, heptadecyl (meth)acrylate, octadecyl (meth)acrylate, isooctadecyl (meth)acrylate, nonadecyl (meth)acrylate, and eicosyl (meth)acrylate can be given. The alkyl (meth)acrylate can be used alone or in combination of two or more. As the alkyl (meth)acrylate, it is preferable to use an alkyl acrylate having an alkyl group of 1 to 12 carbon atoms, and it is more preferable to use a combination of methyl acrylate and an alkyl acrylate having an alkyl group of 2 to 12 carbon atoms, and it is further preferable to use a combination of methyl acrylate and 2-ethylhexyl acrylate.

[0088] The proportion of the alkyl (meth)acrylate in the monomer component is, for example, 50% by mass or more, preferably 60% by mass or more, and more preferably 70% by mass or more, from the viewpoint of appropriately exhibiting basic properties such as adhesiveness in the adhesive layer 10. The same proportion is, for example, 99% by mass or less.

[0089] The monomer component can contain a copolymerizable monomer copolymerizable with the alkyl (meth)acrylate. As the copolymerizable monomer, for example, a monomer having a polar group (polar group-containing monomer) can be given. The polar group-containing monomer is advantageous in the introduction of crosslinking points to the acrylic polymer, the modification of the acrylic polymer such as the securing of the aggregation force of the acrylic polymer, and the like.

[0090] As the monomer containing a polar group, for example, a hydroxyl group-containing monomer, a monomer having a ring containing a nitrogen atom, and a carboxyl group-containing monomer can be given. The copolymerizable monomer preferably contains at least one selected from the group consisting of a hydroxyl group-containing monomer, a monomer having a ring containing a nitrogen atom, and a carboxyl group-containing monomer. More preferably, the copolymerizable monomer contains a hydroxyl group-containing monomer and / or a monomer having a ring containing a nitrogen atom.

[0091] As the hydroxyl group-containing monomer, for example, 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 can be given. As the hydroxyl group-containing monomer, 2-hydroxyethyl (meth)acrylate is preferably used, and 2-hydroxyethyl acrylate is more preferably used.

[0092] As for the proportion of the hydroxyl group-containing monomer in the monomer component, for example, 1% by mass or more, preferably 3% by mass or more, and more preferably 5% by mass or more, from the viewpoint of introduction of a crosslinked structure to the acrylic polymer and securing cohesive force in the adhesive layer 10. As for the same proportion, for example, 30% by mass or less, and preferably 20% by mass or less, from the viewpoint of viscosity adjustment of a polymerization reaction solution at the time of polymerization of the acrylic polymer and adjustment of the polarity of the acrylic polymer (concerning the compatibility of various additive components in the adhesive layer 10 with the acrylic polymer).

[0093] As the monomer having a ring containing a nitrogen atom, for example, N-vinyl-2-pyrrolidone, N-methylvinylpyrrolidone, N-vinylpyridine, N-vinylpiperidone, N-vinylimidazole, N-vinylpyrazole, N-vinylpyrrole, N-vinylimidazole, N-vinylthiazole, and N-vinylisothiazole can be given. As the monomer having a ring containing a nitrogen atom, N-vinyl-2-pyrrolidone is preferably used.

[0094] The proportion of the monomer having a ring containing a nitrogen atom in the monomer component is, for example, 1% by mass or more, preferably 3% by mass or more, and more preferably 5% by mass or more, from the viewpoint of ensuring the cohesion in the adhesive layer 10 and ensuring the close contact with the adherend in the adhesive layer 10. The same proportion is, for example, 30% by mass or less, and preferably 20% by mass or less, from the viewpoint of adjusting the glass transition temperature of the acrylic polymer and adjusting the polarity of the acrylic polymer (involving the compatibility of the various additive components in the adhesive layer 10 with the acrylic polymer).

[0095] As the carboxyl group-containing monomer, for example, acrylic acid, methacrylic acid, carboxyethyl acrylate, carboxypentyl acrylate, itaconic acid, maleic acid, fumaric acid, crotonic acid, and isocrotonic acid can be given.

[0096] The proportion of the carboxyl group-containing monomer in the monomer component is, for example, 1% by mass or more, preferably 3% by mass or more, and more preferably 5% by mass or more, from the viewpoint of introducing a crosslinking structure to the acrylic polymer, ensuring the cohesion in the adhesive layer 10, and ensuring the close contact with the adherend in the adhesive layer 10. The same proportion is, for example, 30% by mass or less, and 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 caused by the acid.

[0097] The monomer component can contain other copolymerizable monomers. As the other copolymerizable monomers, for example, 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, alkoxyl group-containing monomers, vinyl esters, vinyl ethers, and aromatic vinyl compounds can be given.

[0098] As the anhydride monomers, for example, maleic anhydride and itaconic anhydride can be given.

[0099] As the sulfonic acid group-containing monomers, for example, styrenesulfonic acid, allylsulfonic acid, sodium vinylsulfonate, 2-(meth)acrylamido-2-methylpropanesulfonic acid, (meth)acrylamidopropylsulfonic acid, (meth)acrylic acid sulfopropyl ester, and (meth)acryloyloxy naphthalenesulfonic acid can be given.

[0100] As the phosphoric acid group-containing monomers, for example, 2-hydroxyethyl acryloyl phosphate can be given.

[0101] As the epoxy group-containing monomers, for example, glycidyl (meth)acrylate and (meth)acrylic acid-2-ethyl glycidyl ether, and the like, which are acrylic esters containing an epoxy group, allyl glycidyl ether, and glycidyl (meth)acrylate can be given.

[0102] As the cyano group-containing monomers, for example, acrylonitrile and methacrylonitrile can be given.

[0103] As the amide group-containing monomer, for example, N-vinyl carboxylic acid amides, N-hydroxyalkyl (meth) acrylamides, N-alkoxyalkyl (meth) acrylamides, N,N-dimethylamino propyl (meth) acrylamides, and N- (meth) acryloyl morpholines can be given.

[0104] As the N-vinyl carboxylic acid amides, for example, (meth) acrylamide, N,N-dialkyl (meth) acrylamides, N-alkyl (meth) acrylamides, and N-vinyl acetamide can be given.

[0105] As the N,N-dialkyl (meth) acrylamides, for example, N,N-dimethyl (meth) acrylamide, N,N-diethyl (meth) acrylamide, N,N-dipropyl (meth) acrylamide, N,N-diisopropyl (meth) acrylamide, N,N-di(n-butyl) (meth) acrylamide, and N,N-di(t-butyl) (meth) acrylamide can be given.

[0106] As the N-alkyl (meth) acrylamides, for example, N-ethyl (meth) acrylamide, N-isopropyl (meth) acrylamide, n-butyl (meth) acrylamide, and N-n-butyl (meth) acrylamide can be given.

[0107] As the N-hydroxyalkyl (meth) acrylamides, 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 can be given. As the N-alkoxyalkyl (meth) acrylamides, for example, N-methoxymethyl (meth) acrylamide, N-methoxyethyl (meth) acrylamide, and N-butoxymethyl (meth) acrylamide can be given.

[0108] As the monomers having a succinimide skeleton, for example, N-(meth) acryloyloxymethylene succinimide, N-(meth) acryloyl-6-oxohexamethylene succinimide, and N-(meth) acryloyl-8-oxohexamethylene succinimide can be given.

[0109] As the maleimides, for example, N-cyclohexyl maleimide, N-isopropyl maleimide, N-lauryl maleimide, and N-phenyl maleimide can be given.

[0110] As the itaconimides, for example, N-methylitaconimide, N-ethylitaconimide, n-butylitaconimide, N-octylitaconimide, N-2-ethylhexylitaconimide, N-cyclohexylitaconimide, and N-laurylitaconimide can be given.

[0111] As the alkoxyl group-containing monomers, for example, alkoxylalkyl (meth) acrylates and alkoxylalkylene glycol (meth) acrylates can be given. As the alkoxylalkyl (meth) acrylates, for example, 2-methoxyethyl (meth) acrylate, 3-methoxypropyl (meth) acrylate, 2-ethoxyethyl (meth) acrylate, propoxyethyl (meth) acrylate, butoxyethyl (meth) acrylate, and ethoxypropyl (meth) acrylate can be given. As the alkoxylalkylene glycol (meth) acrylates, for example, methoxyethylene glycol (meth) acrylate and methoxypolypropylene glycol (meth) acrylate can be given.

[0112] As the vinyl esters, for example, vinyl acetate and vinyl propionate can be given.

[0113] As the vinyl ethers, for example, methyl vinyl ether and ethyl vinyl ether can be given.

[0114] As the aromatic vinyl compounds, for example, styrene, α-methylstyrene, and vinyltoluene can be given. As the olefins, for example, ethylene, butadiene, isoprene, and isobutylene can be given.

[0115] The copolymerizable monomers can be used alone or in combination of two or more.

[0116] The acrylic polymer can be formed by polymerizing the above-mentioned monomer components. As the polymerization method, for example, solution polymerization, bulk polymerization, and emulsion polymerization can be given, and solution polymerization is preferable. In the solution polymerization, for example, a reaction solution is prepared by compounding the monomer components and a polymerization initiator in a solvent, and the reaction solution is heated. Then, the polymerization reaction of the monomer components in the reaction solution is performed, and thus an acrylic polymer solution containing the acrylic polymer can be obtained.

[0117] As the polymerization initiator, for example, a thermal polymerization initiator is used. The amount of the polymerization initiator is, for example, 0.05 parts by mass or more with respect to 100 parts by mass of the monomer components. In addition, the same amount is, for example, 1 part by mass or less.

[0118] As the thermal polymerization initiator, for example, an azo-based polymerization initiator and a peroxide-based polymerization initiator can be given. As the azo-based polymerization initiator, for example, 2,2'-azobisisobutyronitrile, 2,2'-azobis-2-methylbutyronitrile, 2,2'-azobis(2-methylpropionic acid) dimethyl ester, 4,4'-azobis-4-cyanovaleric acid, azobis isovaleronitrile, 2,2'-azobis(2-imidazolin-2-ylpropane) 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 can be given. As the peroxide-based polymerization initiator, for example, dibenzoyl peroxide, t-butylperoxymaleic acid ester, and lauroyl peroxide can be given.

[0119] 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 aggregation force in the adhesive layer 10. The same weight average molecular weight is, for example, 5,000,000 or less, preferably 3,000,000 or less, and more preferably 2,000,000 or less. The weight average molecular weight of the acrylic polymer is measured by gel permeation chromatography (GPC) and calculated based on polystyrene conversion.

[0120] The glass transition temperature (Tg) of the base polymer is, for example, 0°C or lower, preferably -10°C or lower, and more preferably -20°C or lower. The same glass transition temperature is, for example, -80°C or higher.

[0121] The glass transition temperature (Tg) of the polymer can use the glass transition temperature (theoretical value) calculated based on the Fox equation. The Fox equation is a relationship between the glass transition temperature Tg of a polymer and the glass transition temperature Tgi of a homopolymer of a monomer constituting the polymer. In the following Fox equation, Tg represents the glass transition temperature (°C) of the polymer, Wi represents the weight fraction of monomer i constituting the polymer, and Tgi represents the glass transition temperature (°C) of a homopolymer formed from monomer i. As for the glass transition temperature of the homopolymer, a literature value can be used, such as the glass transition temperatures of various homopolymers listed in "Polymer Handbook" (4th edition, John Wiley & Sons, Inc., 1999) and "New Polymer Library 7 Introduction to Synthetic Resins for Coatings" (Kozo Kitayama, Polymer Publishing Association, 1995). On the other hand, as for the glass transition temperature of the homopolymer of the monomer, it can also be calculated by the method specifically described in Japanese Patent Application Publication No. 2007-51271. The same applies to the glass transition temperatures of the hard segment and the soft segment described later.

[0122] Fox formula 1 / (273 + Tg) = ∑[Wi / (273 + Tgi)]

[0123] As the compound which develops color by reaction with an acid (color-developing compound), for example, a leuco dye, a triarylmethane-based colorant, a diphenylmethane-based colorant, a fluoran-based colorant, a spirocyclic pyran-based colorant, and a rhodamine-based colorant can be given. The color-developing compound can be used alone or in combination of two or more.

[0124] As the leuco dye, for example, 2'-anilino-6'-(N-ethyl-N-isopentylamino)-3'-methylspiro[thiophthalene-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-anilinofluoran, 3-diethylamino-6-methyl-7-dimethylaminofluoran, and 3-(4-diethylamino-2-ethoxyphenyl)-3-(1-ethyl-2-methylindol-3-yl)-4-azaphthalene can be given.

[0125] As the triarylmethane-based colorant, for example, p,p',p"-tris(dimethylamino)triphenylmethane can be given. As the diphenylmethane-based colorant, for example, 4,4-bis-dimethylaminophenylbenzhydrylbenzyl ether can be given. As the fluoran-based colorant, for example, 3-diethylamino-6-methyl-7-chlorofluoran can be given. As the spirocyclic pyran-based colorant, for example, 3-methylspirodibenzopyran can be given. As the rhodamine-based colorant, for example, rhodamine-B-anilinolactam can be given.

[0126] In the adhesive layer 10, from the viewpoint of ensuring good black coloring, as the color-developing compound, a leuco dye is preferably used, and 2'-anilino-6'-(N-ethyl-N-isopentylamino)-3'-methylspiro[thiophthalene-3,9'-[9H]xanthene] is more preferably used.

[0127] The compounding amount of the color-developing compound is, for example, 0.5 parts by mass or more, and preferably 1 part by mass or more, with respect to 100 parts by mass of the base polymer. The same compounding amount is, for example, 10 parts by mass or less, and preferably 7 parts by mass or less, and more preferably 5 parts by mass or less.

[0128] As the acid generator, it is preferable to use a photo-acid generator which generates an acid by irradiation of active energy rays. In this case, the part of the adhesive layer 10 which has been irradiated with active energy rays as the external stimulus can undergo color change. Specifically, in the part of the adhesive layer 10 which has been irradiated with active energy rays, an acid is generated from the photo-acid generator, and a color-developing compound is color-developed using the acid. The part of the adhesive layer 10 which has been irradiated with active energy rays is colored, for example, black series color according to the color development of the color-developing compound. The kind of active energy rays as the external stimulus is determined according to the kind of the photo-acid generator (specifically, the wavelength of the active energy rays by which the photo-acid generator generates an acid). As the active energy rays, for example, ultraviolet rays, visible light, infrared rays, X-rays, α-rays, β-rays, and γ-rays can be given. From the viewpoint of versatility of the use equipment and ease of operation, as the active energy rays, it is preferable that ultraviolet rays can be given.

[0129] As the photo-acid generator, for example, an onium compound which generates an acid by ultraviolet irradiation can be given. The onium compound is provided, for example, in the form of an onium salt of an onium cation and an anion. As the onium cation, for example, iodonium and sulfonium can be given. As the anion, for example, CI - , Br - , I - , ZnCl3 - , HSO3 - , BF4 - , PF6 - , AsF6 - , SbF6 - , CH3SO3 - , CF3SO3 - , C4F9HSO3 - , (C6F5)4B - , and (C4H9)4B - may be given. The photo-acid generator can be used alone or in combination of two or more. As the photo-acid generator, it is preferable that an onium salt (onium compound) of sulfonium and C4F9HSO3 - may be given.

[0130] The compounding 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 same compounding 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.

[0131] In addition, the compounding amount of the acid-producing agent 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, relative to 100 parts by mass of the color-developing compound 100. The same compounding 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.

[0132] The metal complex is compounded in order to adjust the first color change width W1 and the second color change width W2 in a manner satisfying the above formula (1). The movement of the coloring component such as the leuco dye is inhibited by coordination bonding with the metal complex. The metal complex is formed by coordination of a ligand to a metal ion.

[0133] As the metal constituting the metal ion, there can be mentioned alkali metals of Group 1, alkaline earth metals of Group 2, and transition metals of Groups 3 to 12 according to the IUPAC Periodic Table of the Elements (version date 19 February 2010. The same hereinafter). As the metal, the alkaline earth metals of Group 2 and the transition metals of Groups 3 to 12 are preferred, and from the viewpoint of strong coordination of the leuco dye to the carboxyl group of the color developer, there can be mentioned Mg (magnesium), and from the viewpoint of contribution of the amphoteric counter ion formed by the metal complex and the leuco dye, there can be mentioned Zn (zinc).

[0134] As the ligand, there can be mentioned, for example, monodentate ligands and bidentate ligands. As the monodentate ligand, there can be mentioned, for example, hydroxyl group (OH - ), halogen (for example, chlorine (Cl - ), and cyano group (CN - ). As the bidentate ligand, there can be mentioned, for example, ethylenediamine, bipyridine, phenanthroline, and salicylic acid. Of such metal complexes, from the viewpoint of contribution of the bidentate ligand and the amphoteric counter ion, zinc salicylate (specifically, zinc salicylate trihydrate) is more preferred. The metal complex can be used alone or in combination of two or more.

[0135] The compounding amount of the metal complex is, for example, 0.1 parts by mass or more, preferably 0.2 parts by mass or more, more preferably 0.5 parts by mass or more, and further preferably 0.8 parts by mass or more, relative to 100 parts by mass of the base polymer 100. The same compounding amount is, for example, 5 parts by mass or less, and preferably 2 parts by mass or less.

[0136] In addition, the compounding amount of the metal complex 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, relative to 100 parts by mass of the color-developing compound 100. The same compounding amount is, for example, 100 parts by mass or less, and preferably 80 parts by mass or less.

[0137] In addition, from the viewpoint of introducing a crosslinking structure to the base polymer, the adhesive composition can contain a crosslinking agent. As the crosslinking agent, for example, isocyanate crosslinking agents, epoxy crosslinking agents, oxazoline crosslinking agents, aziridine crosslinking agents, carbodiimide crosslinking agents, and metal chelate crosslinking agents can be given. The crosslinking agent can be used alone or two or more kinds can be used in combination.

[0138] As the isocyanate crosslinking agent, for example, toluene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, xylene diisocyanate, hydrogenated xylene diisocyanate, diphenylmethane diisocyanate, hydrogenated diphenylmethane diisocyanate, tetramethyl xylene diisocyanate, naphthalene diisocyanate, triphenylmethane triisocyanate, and polymethylene polyphenyl isocyanate can be given. In addition, as the isocyanate crosslinking agent, derivatives of these isocyanates can also be given. As the isocyanate derivative, for example, isocyanurate modified bodies and polyol modified bodies can be given. As the commercially available product of the isocyanate crosslinking agent, for example, CORONATE L (trimethylolpropane adduct of toluene diisocyanate, manufactured by Nippon Polyurethane Industry Co., Ltd.), CORONATE HL (trimethylolpropane adduct of hexamethylene diisocyanate, manufactured by Nippon Polyurethane Industry Co., Ltd.), CORONATE HX (isocyanurate of hexamethylene diisocyanate, manufactured by Nippon Polyurethane Industry Co., Ltd.), and TAKENATE D110N (trimethylolpropane adduct of xylene diisocyanate, manufactured by Mitsui Chemicals, Inc.) can be given.

[0139] As the epoxy crosslinking agent, for example, bisphenol A, an epoxy resin of the epoxy chloropropane type, ethylene glycidyl ether, polyethylene glycol diglycidyl ether, glycerol diglycidyl ether, glycerol triglycidyl ether, 1,6-hexanediol glycidyl ether, 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 given.

[0140] As the crosslinking agent, an isocyanate crosslinking agent can be given, and more preferably a trimethylolpropane adduct of xylene diisocyanate can be given.

[0141] The compounding amount of the crosslinking agent, from the viewpoint of ensuring the cohesion of the adhesive layer 10, is, for example, 0.01 parts by mass or more, preferably 0.05 parts by mass or more, and more preferably 0.07 parts by mass or more, relative to 100 parts by mass of the base polymer. From the viewpoint of ensuring good adhesion in the adhesive layer 10, the compounding amount of the crosslinking agent is, for example, 10 parts by mass or less, preferably 5 parts by mass or less, and more preferably 3 parts by mass or less, relative to 100 parts by mass of the base polymer.

[0142] In the case where a crosslinking structure is introduced in the base polymer, a crosslinking catalyst can be used in order to efficiently perform the crosslinking reaction. As the crosslinking catalyst, for example, a metal-based crosslinking catalyst can be given. As the metal-based crosslinking catalyst, for example, dibutyltin dilaurate, tetra-n-butyl titanate, tetraisopropyl titanate, iron acetylacetonate, and butyltin oxide can be given. As the crosslinking catalyst, dibutyltin dilaurate is preferable. The amount of the crosslinking catalyst is, for example, 0.0001 parts by mass or more with respect to 100 parts by mass of the base polymer. In addition, the amount is, for example, 1 part by mass or less.

[0143] In addition, in the case where an isocyanate crosslinking agent (specifically, a trimethylolpropane adduct of xylene diisocyanate) is compounded as the crosslinking agent, and a metal-based crosslinking catalyst (specifically, dibutyltin dilaurate) is compounded as the crosslinking catalyst, it is preferable that acetylacetone is compounded in the adhesive composition.

[0144] If acetylacetone is compounded, the acetylacetone is coordinated to the dibutyltin dilaurate. Thereby, the progress of the crosslinking reaction can be inhibited before the adhesive composition is applied to the release film (or the base material 20) to form a coating film. In addition, as described in detail later, heating and drying are performed at the time of forming the coating film, and thereby the acetylacetone can be removed and the crosslinking reaction can be performed.

[0145] The amount of the acetylacetone is, for example, 100 parts by mass or more, preferably 10,000 parts by mass or more with respect to 100 parts by mass of the crosslinking catalyst. In addition, the amount is, for example, 50,000 parts by mass or less.

[0146] In addition, the adhesive composition can contain other components as necessary. As the other components, for example, a polymerizable compound and a cured product thereof, a photopolymerization initiator, a silane coupling agent, an adhesion promoter, a plasticizer, a softening agent, an antioxidant, a surfactant, and an antistatic agent can be given.

[0147] As the polymerizable compound, for example, a monomer having one polymerizable functional group (ethylenic unsaturated double bond) (monofunctional monomer) and a monomer having a plurality of polymerizable functional groups (polyfunctional monomer) can be given. As the monofunctional monomer, for example, a monofunctional (meth)acrylate can be given. As the polyfunctional monomer, for example, a polyfunctional (meth)acrylate can be given.

[0148] In the case where the adhesive composition contains the polymerizable compound, it is preferable that the adhesive composition further contains a photopolymerization initiator.

[0149] The adhesive composition is prepared by compounding the base polymer, the compound which develops color by reaction with an acid, the acid generator, the metal complex, the crosslinking agent compounded as necessary, the crosslinking catalyst compounded as necessary, the acetylacetone compounded as necessary, and other components compounded as necessary, in the above-mentioned proportions.

[0150] The adhesive sheet S can be manufactured, for example, by coating the above-mentioned adhesive composition on a release film (first release film) to form a coating film, and then drying the coating film, whereby an adhesive sheet S can be manufactured in which the adhesive surface is covered and protected by a release film. Figure 1 In this case, the adhesive sheet S is arranged on the release film L indicated by the imaginary line.

[0151] As the release film, for example, a plastic film having flexibility can be mentioned. As the plastic film, for example, a polyethylene terephthalate film, a polyethylene film, a polypropylene film, and a polyester film can be mentioned. The thickness of the release film is, for example, 3 μm or more. In addition, the same is, for example, 200 μm or less. The surface of the release film is preferably subjected to a mold release treatment.

[0152] As the coating method of the adhesive composition, for example, roll coating, kiss roll coating, gravure coating, reverse roll coating, roll brush, spray coating, dip roll coating, bar coating, blade coating, air knife coating, curtain coating, lip coating, and die coating can be mentioned. The drying temperature of the coating film is, for example, 50°C or more. In addition, the same is, for example, 200°C or less. The drying time is, for example, 5 seconds or more. In addition, the same is, for example, 20 minutes or less.

[0153] In the case where the adhesive composition contains a crosslinking agent, the crosslinking reaction proceeds simultaneously with the above-mentioned drying, or by subsequent aging. The aging conditions are appropriately set depending on the kind of the crosslinking agent. The aging temperature is, for example, 20°C or more. In addition, the same is, for example, 160°C or less. The aging time is, for example, 1 minute or more. In addition, the same is, for example, 7 days or less.

[0154] In addition, in the case where the adhesive composition contains acetylacetone (in other words, acetylacetone is compounded in dibutyltin dilaurate), acetylacetone compounded in dibutyltin dilaurate is removed at the time of drying. Thereby, the crosslinking reaction can be made to proceed.

[0155] In addition, before or after the aging, a release film (second release film) can be further laminated on the adhesive layer 10 on the first release film. The second release film is, for example, a flexible plastic film on which a surface mold release treatment is performed. As the second release film, the same film as the above-mentioned one with respect to the first release film can be used.

[0156] As mentioned above, an adhesive sheet S in which the adhesive surface is covered and protected by a release film can be manufactured. Each release film is peeled from the adhesive sheet S as necessary when the adhesive sheet S is used.

[0157] The thickness of the adhesive layer 10 is, for example, 10 μm or more, preferably 15 μm or more, from the viewpoint of ensuring sufficient adhesion to the adherend. The thickness of the adhesive layer 10 is, for example, 300 μm or less, preferably 100 μm or less, more preferably 50 μm or less, from the viewpoint of the handling properties of the adhesive sheet S.

[0158] The haze of the adhesive layer 10 is, for example, 3% or less, preferably 2% or less, more preferably 1% or less. Such a configuration is suitable for checking the presence or absence of foreign matter and air bubbles between the adhesive sheet S and the adherend after the adhesive sheet S is attached to the adherend. The haze of the adhesive layer 10 can be measured in accordance with JIS K7136 (2000) using a haze meter. As the haze meter, for example, "NDH2000" manufactured by Nippon Denshoku Industries Co., Ltd. and "HM-150 type" manufactured by Murakami Color Research Laboratory Co., Ltd. can be mentioned.

[0159] The average transmittance of the adhesive layer 10 at a wavelength of 400 nm to 700 nm (average transmittance before application of external stimulus to the adhesive layer 10) is, for example, 80% or more, preferably 85% or more, more preferably 90% or more. Such a configuration is suitable for checking the presence or absence of foreign matter and air bubbles between the adhesive sheet S and the adherend after the adhesive sheet S is attached to the adherend.

[0160] In addition, in the adhesive sheet S, the adhesive force shown with respect to a glass plate after the adhesive layer 10 is attached to the glass plate is, for example, 1.0 N / 25 mm or more, preferably 5.0 N / 25 mm or more, in a peeling test under peeling conditions of 23°C, a peeling angle of 180°, and a peeling speed of 300 mm / minute. The same adhesive force is preferably 50 N / 25 mm or less, more preferably 40 N / 25 mm or less, further preferably 20 N / 25 mm or less.

[0161] The shear storage modulus at 25°C shown in a dynamic viscoelasticity measurement under conditions of a frequency of 1 Hz and a temperature increase rate of 5°C / minute is preferably 0.1 x 10 5 Pa or more, more preferably 0.5 x 10 5 Pa or more, further preferably 1 x 10 5 Pa or more. The shear storage modulus is preferably 10 x 10 5 Pa or less, more preferably 5 x 10 5 Pa or less, further preferably 3 x 10 5 Pa or less.

[0162] In the second embodiment, the polymer component (base polymer) of the adhesive layer 10 has a spherical microphase separation structure. The spherical microphase separation structure specifically has an island-in-sea structure in which spherical dispersed phases (island portions) are dispersed in a matrix (sea portion). In the adhesive layer 10, the dispersed phases have compatibility with the color-developing compound, and the matrix does not have compatibility with the color-developing compound. For such an adhesive sheet S, the color-developing compound is likely to be trapped in the island portions after the color change portion is formed in the adhesive layer 10 (i.e., after the color-developing compound is developed by the external stimulus), and thus, it is suitable to suppress the movement (diffusion, etc.) of the color-developing compound within the adhesive layer 10. By suppressing the movement of the color-developing compound, it is possible to suppress the deterioration (bleeding, discoloration, unevenness of color appearance, etc.) of the color change portion.

[0163] The polymer component contains, for example, a polymer (first polymer) having a soft segment that forms the matrix and a hard segment that forms the dispersed phase in the molecule. As the first polymer, for example, a block polymer having a first polymer block as the soft segment and a second polymer block as the hard segment can be given. The block polymer can have a plurality of first polymer blocks having different monomer compositions, or can have a plurality of second polymer blocks having different monomer compositions (in this case, the block polymer is a multi-block copolymer having three or more block types based on the monomer composition). As the first polymer, a graft polymer having a polymer main chain as the soft segment and a polymer side chain as the hard segment can also be given. The graft polymer can have a plurality of polymer side chains having different monomer compositions, or can have a plurality of polymer blocks having different monomer compositions in the polymer main chain. The polymer component can contain one first polymer, or can contain a plurality of first polymers.

[0164] The polymer component can also contain a polymer other than the first polymer (second polymer). For example, the polymer component can contain a second polymer that forms the matrix together with the soft segment of the first polymer, or can contain a second polymer that forms the dispersed phase together with the hard segment of the first polymer. The polymer component can contain one second polymer, or can contain a plurality of second polymers.

[0165] In the present embodiment, the hard segment that forms the island portion is a segment containing 80% by mass or more of the same monomer composition as the monomer solution (in the case where the monomer solution cannot be prepared at 25°C, a polymer solution) that is determined to have compatibility with the colorant according to the compatibility determination test described later with reference to the embodiments. The color-developing compound has compatibility with the island portion formed of such a hard segment. The glass transition temperature of the hard segment is preferably 0°C or higher, more preferably 30°C or higher, and further preferably 50°C or higher.

[0166] In the present embodiment, the soft segment forming the sea portion is a segment containing 80% by mass or more of the same monomer as the monomer solution (in the case where a monomer solution cannot be prepared at 25°C, a polymer solution) determined to be compatible with the colorant according to the compatibility determination test described later with reference to the embodiment. The color developing compound does not have compatibility with the second phase formed by this soft segment. The glass transition temperature of this soft segment is preferably 0°C or lower, more preferably lower than 0°C, further preferably -30°C or lower, and particularly preferably -50°C or lower. From the viewpoint of ensuring the adhesion of the adhesive layer 10, the mass ratio of the soft segment in the polymer component is preferably greater than the mass ratio of the hard segment.

[0167] 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 easiness of formation of the island-in-sea structure.

[0168] As the rubber polymer, a styrene copolymer is preferably used. As the styrene copolymer, for example, styrene-isoprene-styrene copolymer (SIS), a hydrogenated product of SIS, styrene-ethylene-butylene copolymer (SEB), styrene-butadiene-styrene copolymer (SBS), a hydrogenated product of SBS, styrene-isobutylene-styrene copolymer (SIBS), and styrene-butadiene-styrene-butadiene (SBSB) can be mentioned. Among these styrene copolymers, styrene forms a hard segment, and an unsaturated hydrocarbon copolymerized with styrene forms a soft segment. The rubber polymer can be used alone or in combination of two or more.

[0169] The styrene content ratio 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 ratio in the styrene copolymer is preferably 40% by mass or less, more preferably 30% by mass or less, and further preferably 20% by mass or less.

[0170] As the (meth)alkyl acrylate and the copolymerizable monomer of the acrylic polymer in the second embodiment, the above-mentioned (meth)alkyl acrylate and the copolymerizable monomer of the acrylic polymer described with reference to the first embodiment can be used. As the (meth)alkyl acrylate forming a hard segment, an alkyl acrylate having an alkyl group having a carbon number of 1 to 5 is preferably used, and more preferably at least one selected from the group consisting of methyl acrylate, methyl methacrylate, and n-butyl acrylate is used. As the (meth)alkyl acrylate forming a soft segment, an alkyl acrylate having an alkyl group having a carbon number of 7 to 20 is preferably used, and more preferably at least one selected from the group consisting of 2-ethylhexyl acrylate, dodecyl acrylate, and stearyl acrylate is used. As the copolymerizable monomer forming a hard segment, an aromatic vinyl compound is preferably used, and more preferably styrene is used.

[0171] 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, and 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.

[0172] The adhesive layer 10 of the adhesive sheet S of the second embodiment can contain or can not contain the above-mentioned metal complex relating to the first embodiment.

[0173] Each of the adhesive sheets S of the first and second embodiments can be a single-faced adhesive sheet with a substrate, as shown in Figure 2 In this case, the adhesive sheet S specifically has the adhesive layer 10 and the substrate 20 disposed on one side in the thickness direction D thereof. It is preferable that the substrate 20 be in contact with one face of the adhesive layer 10 in the thickness direction D.

[0174] The substrate 20 is an element that functions as a transparent support. The substrate 20 is, for example, a plastic film having flexibility. As a constituent material of the plastic film, for example, polyolefin, polyester, polyamide, polyimide, polyvinyl chloride, polyvinylidene chloride, cellulose, polystyrene, and polycarbonate can be mentioned. As the polyolefin, for example, polyethylene, polypropylene, poly-1-butene, poly-4-methyl-1-pentene, ethylene / propylene copolymer, ethylene / 1-butene copolymer, ethylene / vinyl acetate copolymer, ethylene / ethyl acrylate copolymer, and ethylene / vinyl alcohol copolymer can be mentioned. As the polyester, for example, polyethylene terephthalate, polyethylene naphthalate, and polybutylene terephthalate can be mentioned. As the polyamide, for example, polyamide 6, polyamide 6,6, and partially aromatic polyamide can be mentioned. In the substrate 20, the plastic material of the substrate 20 is preferably polyester, and more preferably polyethylene terephthalate, from the viewpoint of balancing the transparency and mechanical strength thereof.

[0175] The substrate 20 has transparency. The haze of the substrate 20 is, for example, 3% or less, preferably 2% or less, and more preferably 1% or less. The haze of the substrate 20 can be measured in accordance with JIS K7136 (2000) using a haze meter.

[0176] The surface of the substrate 20 on the side of the adhesive layer 10 can be subjected to physical treatment, chemical treatment, or primer treatment for improving adhesion to the adhesive layer 10. As the physical treatment, for example, corona treatment and plasma treatment can be mentioned. As the chemical treatment, for example, acid treatment and alkali treatment can be mentioned.

[0177] From the viewpoint of ensuring the strength of the substrate 20 functioning as a support, the thickness of the substrate 20 is, for example, 5 μm or more, preferably 10 μm or more, and more preferably 20 μm or more. In addition, from the viewpoint of achieving a moderate flexibility in the adhesive sheet S, the thickness of the substrate 20 is, for example, 200 μm or less, preferably 150 μm or less, and more preferably 100 μm or less.

[0178] Figure 2 The adhesive sheet S shown can be manufactured in the same manner as the above-described manufacturing method, except that the substrate 20 is used instead of the first release film.

[0179] Figure 3 A~B Figure 3 C shows an example of a method of using each of the adhesive sheets S of the first and second embodiments. The method includes a preparation step, a bonding step, and a color change portion forming step.

[0180] First, in the preparation step, as shown in Figure 3 A, 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 can be other electronic devices and optical devices. The second member 32 is, for example, a transparent substrate. As the transparent substrate, a transparent plastic substrate and a transparent glass substrate can be given.

[0181] Next, in the bonding step, as shown in Figure 3 B, the first member 31 and the second member 32 are bonded with the adhesive sheet S. Thus, the laminate W is obtained. In the laminate W, the adhesive sheet S is disposed so as to contact one face in the thickness direction of the first member 31, and the second member 32 is disposed so as to contact one face in the thickness direction of the adhesive sheet S.

[0182] After the bonding step, the presence or absence of foreign matter and air bubbles between the members 31, 32 and the adhesive sheet S is checked as needed.

[0183] Next, in the color change step, as shown in Figure 3 C, an external stimulus is applied to the adhesive layer 10 in the laminate W, and the color change portion 11 is formed in the adhesive layer 10. Specifically, from the side of the transparent second member 32, the adhesive layer 10 is irradiated with active energy rays as the external stimulus, through a mask pattern (not shown) for masking a prescribed region in the adhesive layer 10. Thus, the portion of the adhesive layer 10 not masked by the mask pattern is colored.

[0184] In this step, in the portion of the adhesive layer 10 that has been irradiated with the active energy rays, an acid is generated from the photoacid generator, and a color-developing compound is color-developed by a reaction with the acid. Thus, the color change portion 11 is formed in the adhesive layer 10.

[0185] The adhesive layer 10 of the adhesive sheet S contains the color-developing compound as described above. Therefore, after the adhesive sheet S is attached to an adherend (the members 31 and 32 in the present embodiment), the adhesive layer 10 can be partially colored by applying an external stimulus to a predetermined portion of the adhesive layer 10. In the adhesive sheet S in which the colored portion 11 can be formed in the adhesive layer 10 after attachment to the adherend, the presence or absence of foreign matter and air bubbles between the adhesive sheet S and the adherend can be checked before the colored portion 11 of the adhesive layer 10 is formed after attachment.

[0186] In addition, in the adhesive sheet S, the first color change width Wl and the second color change width W2 of the adhesive layer 10 satisfy the above-described formula (1). Such an adhesive sheet S is suitable for suppressing deterioration of the colored portion of the adhesive layer 10 after the colored portion is formed by applying an external stimulus, and thus is suitable for imparting design, shielding, and anti-reflection properties to an arbitrary portion.

[0187] In addition, as an example of the use method of the adhesive sheet S, the adhesive sheet S is sometimes arranged on the light exit side (image display side) of a pixel panel in a display panel. In detail, in the case where the first member 31 is a display panel, the colored portion 11 is provided in a pattern shape corresponding to (i.e., opposite to) a conductor layer that is a metal wiring formed on a pixel panel included in the display panel. Thereby, external light reflection in the conductor layer can be suppressed.

[0188] The width of the conductor layer is, for example, 10 μm or more. In addition, the width of the conductor layer is, for example, 300 μm or less. In addition, the conductor layer is preferably formed at a fine pitch. The interval between the respective conductor layers is, for example, 10 μm or more. In addition, the same interval is, for example, 100,000 μm or less.

[0189] The line width of the colored portion 11 corresponds to the width of the above-described conductor layer. Specifically, the line width of the colored portion 11 is, for example, 10 μm or more. In addition, the same line width is, for example, 300 μm or less. In addition, the interval between the respective colored portions 11 is, for example, 10 μm or more. In addition, the same interval is, for example, 100,000 μm or less.

[0190] In this adhesive sheet S, the first color change width Wl and the second color change width W2 satisfy the above-described formula (1), and thus the shielding and anti-reflection properties can be improved. As a result, external light reflection in the metal wiring can be suppressed, and the visibility of the display panel provided with the metal wiring can be improved.

[0191] Note that the present application is characterized in that W2 / W1 is adjusted, preferably W3 / W1 is adjusted. That is, as a utilization form of the variable color film of the present application, it is not limited to a colored portion (a developed portion) in a linear shape, and various shapes of colored portions can be formed. More specifically, as the colored portion that can be formed, a linear shape, a dot shape, a rectangular shape, a circular shape, an elliptical shape, an indefinite shape, and the like can be exemplified.

[0192] Example

[0193] With regard to the present application, the following examples are specifically described, but the present application is not limited to the examples. In addition, the compounding amount (content), the physical property value, the parameter, and the like described below can be replaced with the upper limit (a value defined as "from" or "less than") or the lower limit (a value defined as "from" or "more than") of the compounding amount (content), the physical property value, the parameter, and the like corresponding thereto described in the above "DETAILED DESCRIPTION".

[0194] Production Example 1 (Preparation of base polymer)

[0195] In a reaction vessel provided with a stirrer, a thermometer, a reflux condenser, and a nitrogen introduction tube, a mixture containing 2-ethylhexyl acrylate (2EHA) 63 parts by mass, methyl methacrylate (MMA) 9 parts by mass, 2-hydroxyethyl acrylate (HEA) 13 parts by mass, N-vinyl-2-pyrrolidone (NVP) 15 parts by mass, 2,2'-azobisisobutyronitrile (AIBN) 0.2 parts by mass as a polymerization initiator, and ethyl acetate 233 parts by mass as a solvent was stirred at 60°C for 7 hours under a nitrogen atmosphere (polymerization reaction). Thus, a polymer solution containing an acrylic polymer was obtained. The weight average molecular weight (Mw) of the acrylic polymer in the polymer solution was 1.2 million.

[0196] [Example 1]

[0197] Preparation of Adhesive Composition

[0198] In the above polymer solution containing the acrylic polymer of Production Example 1, with respect to 100 parts by mass of the acrylic polymer (base polymer), the following ingredients were uniformly mixed to prepare an adhesive composition.

[0199] A color-developing compound that develops color by reaction with an acid: a leuco dye (trade name "S-205", 2'-anilino-6'-(N-ethyl-N-isopentylamino)-3'-methyl spiro[ tetrachlorophthalide-3,9'-[9H]xanthene], manufactured by Yamada Chemical Industry Co., Ltd.) 2.00 parts by mass

[0200] An acid generator: a photogenerator (trade name "CPI-310B", sulfonium and (C6F5)4B -Phenyltrimethylammonium chloride (manufactured by San-Apro Ltd.) 7.00 parts by mass

[0201] Metal complex: zinc salicylate trihydrate (manufactured by FUJIFILM Wako Pure Chemical Corporation) 0.38 parts by mass

[0202] Crosslinking agent: "TAKENATE D110N" (75% ethyl acetate solution of trimethylolpropane adduct of xylene diisocyanate, manufactured by Mitsui Chemicals, Inc.) 0.25 parts by mass (solid content conversion amount)

[0203] Acetylacetone: 3.00 parts by mass

[0204] <Formation of adhesive layer>

[0205] An adhesive composition was applied to a release film (trade name "MRF #38", polyester film, thickness 38 μm, manufactured by Mitsubishi Plastics, Inc.) on which one surface was made a release surface, to form a coating film. Next, the coating film was dried at 132°C for 3 minutes to form an adhesive layer having a thickness of 25 μm. A release film (trade name "MRF #38", polyester film, thickness 38 μm, manufactured by Mitsubishi Plastics, Inc.) on which one surface was made a release surface was attached to the adhesive layer. Thereafter, aging treatment was performed at 60°C for 24 hours, and a crosslinking reaction was performed in the adhesive layer.

[0206] An adhesive sheet of Example 1 was produced as above. The composition of the adhesive layer in the adhesive sheet of Example 1 is shown in Table 1 (the same applies to Examples 1 to 3 and Comparative Example 1 described later).

[0207] [Examples 2, 3 and Comparative Example 1]

[0208] Each of the adhesive sheets of Examples 2, 3 and Comparative Example 1 was produced in the same manner as the adhesive sheet of Example 1. Among them, the composition of the adhesive composition was changed to the amounts shown in Table 1.

[0209] [Example 4]

[0210] <Preparation of adhesive composition>

[0211] An adhesive composition was prepared by uniformly mixing the following components with respect to 100 parts by mass of a styrene-isoprene-styrene block copolymer (trade name "Quintac 3520", styrene content ratio 15% by mass, manufactured by ZEON CORPORATION) as a first polymer (base polymer).

[0212] 2nd polymer: styrene-acrylic block copolymer (trade name "FBP-001", manufactured by Toray Fine Chemicals Co., Ltd.) 5 parts by mass

[0213] Color-developing compound (color-developing compound) which develops color by reaction with an acid: leuco dye, 2'-anilino-6'-(N-ethyl-N-isopentylamino)-3'-methylspiro[ tetrachlorophthalan-3,9'-[9H]oxanthrene] (trade name "S-205", manufactured by Yamada Chemical Industry Co., Ltd.) 2.00 parts by mass

[0214] Acid generator: photo-acid generator (trade name "CPI-310B", sulfonium and (C6F5)4B - of onium salt, manufactured by San-Apro Ltd.) 7.00 parts by mass

[0215] Crosslinking agent: 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane (trade name "TETRAD-C", manufactured by Mitsubishi Gas Chemical Co., Inc.) 0.25 parts by mass

[0216] <Formation of adhesive layer>

[0217] An adhesive composition was applied to a release-treated surface of a base film (trade name "MRF#38", polyester film, manufactured by Mitsubishi Plastics, Inc.) having a thickness of 38 μm, and a coating film was formed. Subsequently, the coating film was dried by heating at 132°C for 3 minutes. Thus, an adhesive layer having a thickness of 25 μm was formed on the base film. Subsequently, a release film (trade name "MRE#38", polyester film, manufactured by Mitsubishi Plastics, Inc.) having a thickness of 38 μm was attached to the adhesive layer on the base film with the release-treated surface of the release film facing the adhesive layer. Thereafter, the adhesive layer was subjected to a curing treatment at 60°C for 24 hours to allow a crosslinking reaction to proceed. In this manner, an adhesive sheet of Example 4 was produced. The composition of the adhesive layer in the adhesive sheet of Example 4 is shown in Table 2 (the same applies to Examples 5 to 7 described later) with the unit being parts by mass.

[0218] [Examples 5 to 7]

[0219] Each of the adhesive sheets of Examples 5 to 7 was produced in the same manner as the adhesive sheet of Example 4. In this case, the compounding amount of the 2nd polymer was changed to the amount shown in Table 2.

[0220] <Assessment>

[0221] 1. Weather resistance test

[0222] (Production of sample for weather resistance test)

[0223] For one face in the thickness direction of Eagle glass (thickness 0.55 mm, manufactured by Nippon Sheet Glass Co., Ltd.), an adhesive layer 25 μm, UVA-TAC 32 μm, UVA-OCA 100 μm, and UVA-TAC 32 μm of each of the examples and comparative examples were sequentially laminated in this order. In each of the laminates of the examples and comparative examples, ultraviolet rays were irradiated to the sample. Specifically, for the adhesive sheet (adhesive layer) in the sample, ultraviolet rays were irradiated from the Eagle glass side through the same glass in an environment of 23°C and a relative humidity of 50% (by the UV irradiation, a leuco dye in the adhesive layer was allowed to react with a photoacid generator). In the UV irradiation, a UV-LED lamp of wavelength 365 nm in a UV-LED irradiation device (model "QEL-350-RU6W-CW-MY") manufactured by Quarktec Technology Co., Ltd. was used as a light source, and the cumulative light amount of irradiation was made 8000 mJ / cm2(wavelength 320 nm to 390 nm). As above, a sample for the weather resistance test was prepared. 2 (accumulative light amount of irradiation in the range of wavelength 320 nm to 390 nm). As above, a sample for the weather resistance test was prepared.

[0224] A film sequentially having a UVA-TAC: TAC film (KC2UA, manufactured by KONICA MINOLTA, INC.) and a hard coat layer (a hard coat layer (thickness: 7 μm) was formed on one face of KC2UA (thickness: 25 μm) by a hard coat treatment, and thus a film (thickness: 32 μm) was obtained

[0225] UVA-OCA: adhesive tape having an ultraviolet absorbing function, trade name "CS9934U", thickness 100 μm, manufactured by Nittobo Co., Ltd.

[0226] (Weather resistance test)

[0227] In the samples for the weather resistance test of Examples 1 to 3 and Comparative Example 1, the values of the average transmittance, L*, a*, and b* were measured.

[0228] Specifically, in the sample for the weather resistance test, a light irradiation from the Eagle glass side was performed using a transmittance measuring device (U4150-type spectrophotometer, manufactured by Hitachi High-Tech Corporation). Then, the values of the average transmittance, L*, a*, and b* under wavelength 400 nm to 700 nm were measured, respectively.

[0229] In detail, the average transmittance (T1) under wavelength 400 nm to 700 nm of the sample for the weather resistance test, L* (L1*) of the sample for the weather resistance test, a* (a1*) of the sample for the weather resistance test, and b* (b1*) of the sample for the weather resistance test were measured, respectively.

[0230] Next, the weather resistance test sample was irradiated with a super xenon weather tester SX75 manufactured by Suga Test Instruments Co., Ltd. for 24 hours with a super xenon lamp having an irradiance of 120 W in a range of 300 nm to 400 nm. Thus, the weather resistance test sample after 24 hours of irradiation was obtained.

[0231] Next, the average transmittance, L*, a*, and b* of the weather resistance test sample after 24 hours of irradiation were measured according to the same procedure as described above.

[0232] In detail, the average transmittance (T2) of the weather resistance test sample after 24 hours of irradiation at a wavelength of 400 nm to 700 nm, L* of the weather resistance test sample after 24 hours of irradiation (L2*), a* of the weather resistance test sample after 24 hours of irradiation (a2*), and b* of the weather resistance test sample after 24 hours of irradiation (b2*) were measured, respectively.

[0233] Then, the color difference (ΔE) was calculated based on the following formula (7).

[0234] ΔE = ((L2* - L1*) 2 +(a 2 *-a1*) 2 +(b2*-b1*) 2 ) 1 / 2 (7)

[0235] The results of T1, T2, and the color difference (ΔE) are shown in Table 1.

[0236] 2. Durability Test

[0237] A linear discoloration portion was formed in the adhesive layer of the adhesive sheet by irradiating ultraviolet rays through a photomask having a linear opening portion. The photomask was formed of a dry film photoresist disposed on the side surface of the base film in the adhesive sheet, and the line width of the opening portion of the photomask was 200 μm. In the ultraviolet irradiation, a UV-LED lamp having a wavelength of 365 nm in a UV-LED irradiation device (model "QEL-350-RU6W-CW-MY") manufactured by Quarktec Technology Co., Ltd. was used as a light source, and the adhesive layer was irradiated with ultraviolet rays through the photomask and the base film so that the cumulative light amount of the irradiation was 2000 mJ / cm 2 (wavelength: 320 nm to 390 nm).

[0238] Next, the line width of the line-shaped color change portion formed in the adhesive layer was measured (measurement of the 1st color change width W1). Specifically, first, the line-shaped color change portion formed in the adhesive layer was observed using a digital microscope (trade name "VHX-900", manufactured by KEYENCE Corporation) at a magnification of 50x to take an image of a region including a part of the color change portion and its vicinity. Next, the taken image was subjected to a binaryzation process using an image analysis software. Next, the line width of the line-shaped color change portion (1st color change width W1) was measured in the binaryzation-processed image.

[0239] Next, the adhesive sheet in which the line-shaped color change portion was formed in the adhesive layer was subjected to a heat treatment at 85°C for 120 hours (1st durability test).

[0240] Next, the line width of the line-shaped color change portion in the adhesive layer of the adhesive sheet was measured (measurement of the 2nd color change width W2). The measurement method was the same as the above measurement method relating to the measurement of the 1st color change width W1. The 1st color change width W1 of the line-shaped color change portion before the 1st durability test, the 2nd color change width W2 of the line-shaped color change portion after the 1st durability test, and the change rate of the 2nd color change width W2 with respect to the 1st color change width W1 (W2 / W1) are shown in Tables 1 and 2.

[0241] In addition, for the adhesive layer of each of the adhesive sheets of Examples 1 to 7 and Comparative Example 1, a 2nd durability test was conducted instead of the 1st durability test, and otherwise, the line width of the formed line-shaped color change portion was investigated in the same manner as the above method. In the 2nd durability test, the adhesive sheet in which the line-shaped color change portion was formed in the adhesive layer was subjected to a heat treatment at 85°C for 240 hours. The 1st color change width W1 of the line-shaped color change portion before the 2nd durability test, the 3rd color change width W3 of the line-shaped color change portion after the 2nd durability test, and the change rate of the 3rd color change width W3 with respect to the 1st color change width W1 (3rd color change width W3 / 1st color change width W1) are shown in Tables 1 and 2.

[0242] 3. Peeling Test

[0243] The adhesive layer of each of the examples and comparative examples was attached to a glass plate. Thereafter, the adhesive force to the glass plate was measured based on the following conditions. The results are shown in Table 1.

[0244] (Measurement Conditions)

[0245] Temperature: 23°C

[0246] Peeling angle: 180°

[0247] Peeling speed: 300 mm / minute

[0248] 4. Confirmation of Microscopic Phase Separation Structure

[0249] The microphase separation structure was confirmed for the adhesive layer of each of the adhesive sheets of Examples 4 to 7 as follows. First, a sample for observation based on a transmission electron microscope (TEM) was prepared. Specifically, the adhesive layer was dyed and then rapidly frozen, and a thin slice was cut from the adhesive layer using an ultramicrotome (manufactured by Leica). Then, observation and photographing were performed for the thin slice using a transmission-type electron microscope (trade name "HT7820", manufactured by Hitachi High-Technologies Corp.). Next, the obtained TEM image was analyzed and binarized using image analysis software. The microphase separation structure of the adhesive layer in Example 7 is shown in FIG. 9. Figure 4 .

[0250] In the adhesive layer of each of the adhesive sheets of Examples 4 to 7, a spherical microphase separation structure could be confirmed. In each of the adhesive layers, the matrix (sea portion) formed of the isoprene block (soft segment) of the first polymer had dispersed therein the spherical dispersed phase (island portion) formed of the styrene (hard segment) of the first polymer and the second polymer (styrene / n-butyl acrylate copolymer).

[0251] 5. Solubility judgment test

[0252] The solubility with respect to each of the monomer or polymer solutions was investigated for the color-developing compound and the acid generator used in Examples 4 to 7.

[0253] Specifically, first, as the monomer solution, each of a solution of styrene, n-butyl acrylate, methyl methacrylate (MMA), acrylic acid, N-vinyl-2-pyrrolidone (NVP), 2-methoxyethyl acrylate (2MEA), methyl acrylate, 2-ethylhexyl acrylate (2EHA), lauryl acrylate (dodecyl acrylate), and stearyl acrylate (octadecyl acrylate) was prepared.

[0254] Next, a mixture (the proportion of the compound C was 2.5 mass%) containing the monomer solution 7.8 g and the compound C (color-developing compound or photo-acid generator) 0.2 g was stirred (first stirring) in a screw tube of 50 mL. A magnetic stirrer was used in the stirring. In the stirring, the temperature was set to 25°C, the rotation speed of the stirrer was set to 500 rpm, and the stirring time was set to 5 minutes. After the stirring, it was visually confirmed whether the compound C was dissolved in the monomer solution without generating turbidity or precipitation by this stirring. The color-developing compound and the photo-acid generator were dissolved in each of the solutions of styrene, n-butyl acrylate, MMA, acrylic acid, NVP, 2MEA, and methyl acrylate without generating turbidity or precipitation (the compound C showed solubility). On the other hand, the color-developing compound and the photo-acid generator generated turbidity or precipitation in each of the solutions of 2EHA, lauryl acrylate, and stearyl acrylate (the compound C did not show solubility).

[0255] On the other hand, as a polymer solution, a polyisoprene solution (a monomer solution of isoprene cannot be prepared because of too high volatility of isoprene) was prepared. Next, a mixture (the proportion of compound C was 2.5 mass%) containing the polymer solution 7.8 g and compound C (a color-developing compound or a photo-acid generator) 0.2 g was stirred in a 50 mL screw tube (second stirring). The conditions of the second stirring were the same as those of the first stirring described above. It was confirmed by observation after the second stirring that the color-developing compound and the photo-acid generator respectively caused turbidity or precipitation in the polymer solution (compound C did not show phase compatibility).

[0256] Further, it was determined that compound C had phase compatibility with respect to a phase in which a segment having a monomer composition of 80 mass% or more of the same monomer as the monomer solution in which compound C showed phase compatibility was formed in a microphase-separated structure of a polymer component having the segment. It was also determined that compound C did not have phase compatibility with respect to a phase in which a segment having a monomer composition of 80 mass% or more of the same monomer as the monomer solution in which compound C did not show phase compatibility was formed in a microphase-separated structure of a polymer component having the segment. That is, the color-developing compound and the photo-acid generator used in Examples 4 to 7 respectively had phase compatibility with respect to island portions of a hard segment (HS) containing styrene and n-butyl acrylate formed in a microphase-separated structure (in the HS in Examples 4 to 7, the proportion of the monomers (styrene, n-butyl acrylate) in which compound C showed phase compatibility was 80 mass% or more). The color-developing compound and the photo-acid generator used in Examples 4 to 7 respectively did not have phase compatibility with respect to sea portions of a soft segment (SS) containing isoprene formed in a microphase-separated structure (in the SS in Examples 4 to 7, the proportion of isoprene in which compound C did not show phase compatibility was 80 mass% or more).

[0257] 6. Light transmittance

[0258] The average transmittance at a wavelength of 400 nm to 700 nm was investigated for the adhesive layers of each of the adhesive sheets of Examples 4 to 7.

[0259] First, an adhesive sheet was attached to Eagle glass (thickness 0.55 mm, manufactured by Nippon Sheet Glass Co., Ltd.) to produce a sample for measurement (a first sample for measurement). Next, for the sample for measurement, the average transmittance at wavelengths of 400 nm to 700 nm was measured using a spectrophotometer U4150 manufactured by Hitachi High-Technologies Corp. (first transmittance measurement). In this measurement, for the sample for measurement, the total light transmittance at wavelengths of 400 nm to 700 nm was measured at an interval of 1 nm with the sample for measurement set in the device in a manner such that light was irradiated from the side of the Eagle glass. In addition, in this measurement, the transmittance spectrum obtained by measuring only the Eagle glass under the same conditions was used as a baseline. The above-described measurement of the average transmittance in Examples 1 to 3 and Comparative Example 1 was also specifically performed in the same manner as in this measurement. The measured average transmittance T1 of the adhesive layer (average transmittance at wavelengths of 400 nm to 700 nm before UV irradiation) is shown in Table 2.

[0260] On the other hand, for each of the adhesive sheets of Examples 4 to 7, the average transmittance at wavelengths of 400 nm to 700 nm after UV irradiation was investigated as follows.

[0261] First, a sample identical to the above-described first sample for measurement was produced. Next, ultraviolet rays were irradiated onto the sample. Specifically, for the adhesive sheet (adhesive layer) in the sample, ultraviolet rays were irradiated from the side of the Eagle glass through the same glass in an environment at 23°C and a relative humidity of 50% (by this UV irradiation, the leuco dye in the adhesive layer was allowed to react 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 "QEL-350-RU6W-CW-MY") manufactured by Quarktec Technology Co., Ltd. was used as a light source, and the cumulative light amount of irradiation was set to 8000 mJ / cm2(wavelength range of 320 nm to 390 nm). As described above, a sample for measurement (a second sample for measurement) was produced. 2 (wavelength range of 320 nm to 390 nm). As described above, a sample for measurement (a second sample for measurement) was produced.

[0262] Next, for the second sample for measurement, the average transmittance at wavelengths of 400 nm to 700 nm was measured using a spectrophotometer U4150 manufactured by Hitachi High-Technologies Corp. (second transmittance measurement). The specific measurement method and conditions were the same as in the above-described first transmittance measurement. The measured average transmittance T2 of the adhesive layer (average transmittance at wavelengths of 400 nm to 700 nm after UV irradiation) is shown in Table 2. In addition, the ratio of the average transmittance T2 to the above-described average transmittance T1 is also shown in Table 2.

[0263] [Table 1]

[0264] Table 1

[0265]

[0266] The adhesive layer is discolored to red.

[0267] [Table 2]

[0268] Table 2

[0269]

[0270] The above-described embodiments are examples of the present application, and the present application should not be construed limitatively by the embodiments. Modificatons of the present application that are obvious to a person skilled in the art are included in the appended claims.

[0271] Industrial applicability

[0272] The color-changeable adhesive sheet of the present application is used, for example, for bonding elements contained in a layered structure of a display panel to each other in a manufacturing process of the display panel.

[0273] Explanation of reference numerals

[0274] S adhesive sheet (color-changeable adhesive sheet)

[0275] 10 adhesive layer

[0276] 11 color-changeable portion

[0277] 20 substrate

[0278] 31 first member

[0279] 32 second member

Claims

1. A color changeable adhesive sheet comprising an adhesive layer capable of changing color due to an external stimulus, the adhesive layer comprises a polymer component, a color developing compound which develops color by reaction with an acid, an acid generator, and a metal complex, or the adhesive layer comprises a polymer component, a color developing compound which develops color by reaction with an acid, and an acid generator, the polymer component forms a microphase separation structure comprising a matrix and a dispersed phase dispersed in the matrix, and the dispersed phase has a phase compatibility with the compound, the matrix does not have a phase compatibility with the compound, a first color change width Wl calculated according to Test 1 below and a second color change width W2 calculated according to Test 2 below satisfy the following formula (1), 0.5 < W2 / Wl < 2 (1) < Test 1 > Step A: an external stimulus is applied to the adhesive layer in a linear form, Step B: after Step A, the width of a color change region formed in the adhesive layer is measured, < Test 2 > Step C: after Step A and Step B of the Test 1, a heat treatment at 85°C is performed for 120 hours, Step D: after Step C, the width of a color change region formed in the adhesive layer is measured.

2. The color-variable adhesive sheet according to claim 1, wherein the first color change width Wl and a third color change width W3 calculated according to Test 3 below satisfy the following formula (2), 0.5 < W3 / Wl < 2 (2) < Test 3 > Step E: after Step A and Step B of the < Test 1 >, a heat treatment at 85°C is performed for 240 hours, Step F: after Step E, the width of a color change region formed in the adhesive layer is measured.

3. The color-variable adhesive sheet according to claim 1, wherein the adhesive layer has a thickness of 10 μm or more and 300 μm or less.

4. The color changeable adhesive sheet according to claim 1, further comprising a substrate disposed on one side of the adhesive layer in the thickness direction.

5. The color-variable adhesive sheet according to claim 1, wherein when the adhesive layer is attached to a glass plate, the adhesive force shown to the glass 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 1.0 N / 25 mm or more and 50 N / 25 mm or less.

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