Adhesive sheet

Abstract

This adhesive sheet (10) contains a base polymer and a metallic complex salt black dye. The base polymer has an acid value of 50 mgKOH / g or less.

Description

adhesive sheet

[0001] The present invention relates to a pressure-sensitive adhesive sheet.

[0002] In the manufacturing process of display panels such as organic EL panels, adhesive sheets are used as a bonding material between components. Known examples of such adhesive sheets include black adhesive sheets containing black pigments for design, light blocking, or anti-reflection properties. Such adhesive sheets are described, for example, in Patent Document 1 listed below.

[0003] JP 2013-32430 A

[0004] The pressure-sensitive adhesive sheet described in Patent Document 1 contains a base polymer and a black pigment. Carbon black is preferably used as the black pigment. However, the black pigment disperses rather than dissolves in the pressure-sensitive adhesive sheet. Therefore, the black pigment increases the haze of the pressure-sensitive adhesive sheet. In order to ensure good design, light-blocking properties, or anti-reflection properties in a black pressure-sensitive adhesive sheet, it is preferable that the haze be low.

[0005] It is conceivable to use a black dye as the black component in the pressure-sensitive adhesive sheet, rather than using a black pigment as in Patent Document 1. However, black dyes have traditionally resulted in reduced weather resistance of the black color.

[0006] The present invention provides a black-based pressure-sensitive adhesive sheet that is suitable for ensuring good black light resistance while suppressing haze.

[0007] The present invention [1] includes a pressure-sensitive adhesive sheet containing a base polymer having an acid value of 50 mg KOH / g or less and a metal complex salt black dye.

[0008] The present invention [2] includes the pressure-sensitive adhesive sheet according to the above [1], wherein the metal complex black dye contains at least one metal selected from the group consisting of chromium and copper.

[0009] The present invention [3] includes the pressure-sensitive adhesive sheet according to the above [1] or [2], wherein the metal complex salt black dye contains an azo dye compound as the dye compound.

[0010] The present invention [4] includes the pressure-sensitive adhesive sheet according to the above [3], wherein the azo dye compound is an aromatic azo dye compound.

[0011] The present invention [5] includes the pressure-sensitive adhesive sheet according to any one of the above [1] to [4], wherein the metal complex salt black dye has a molecular weight of 400 or more.

[0012] The present invention [6] is L ＊ a ＊ b ＊ Transmittance hue b in the color system ＊ The pressure-sensitive adhesive sheet according to any one of [1] to [5] above, wherein the value is 0 or less.

[0013] The present invention [7] includes the pressure-sensitive adhesive sheet according to any one of the above [1] to [6], which has a haze of 3.0% or less.

[0014] As described above, the pressure-sensitive adhesive sheet of the present invention contains a metal complex black dye as a black component. The dye can be dissolved in the pressure-sensitive adhesive composition that forms the pressure-sensitive adhesive sheet during the manufacturing process of the pressure-sensitive adhesive sheet. Therefore, the dye can be more easily dispersed in the pressure-sensitive adhesive sheet than a pigment. Therefore, the pressure-sensitive adhesive sheet containing the dye as a black component is suitable for reducing the haze of the pressure-sensitive adhesive sheet.

[0015] Furthermore, in the pressure-sensitive adhesive sheet of the present invention, as described above, the acid value of the base polymer is 50 mg KOH / g or less. The inclusion of a base polymer with a low acid value of 50 mg KOH / g or less in the pressure-sensitive adhesive sheet is suitable for ensuring the stability of the coordinate bond between the metal and the dye compound in the metal complex black dye (the higher the acid value of the base polymer, the more impaired the coordinate bond). Stabilizing the metal complex black dye helps ensure the lightfastness of the metal complex black dye.

[0016] Therefore, the pressure-sensitive adhesive sheet of the present invention is suitable for ensuring good black light resistance while suppressing haze.

[0017] 2A and 2B are schematic cross-sectional views of an embodiment of a pressure-sensitive adhesive sheet according to the present invention, and show an example of a method for producing the optical pressure-sensitive adhesive sheet shown in Fig. 1. Fig. 2A shows a step of forming a coating film of a pressure-sensitive adhesive composition, Fig. 2B shows a step of forming a base pressure-sensitive adhesive sheet, Fig. 2C shows a step of peeling one of the release liners, Fig. 2D shows a step of supplying a post-added component to the base pressure-sensitive adhesive sheet, and Fig. 2E shows a step of bonding the release liner to the pressure-sensitive adhesive sheet.

[0018] As shown in Figure 1, a pressure-sensitive adhesive sheet 10 according to one embodiment of the present invention has a sheet shape of a predetermined thickness and extends in a direction (plane direction) perpendicular to the thickness direction H. The pressure-sensitive adhesive sheet 10 has an adhesive surface 11 (first adhesive surface) and an adhesive surface 12 (second adhesive surface) opposite to the adhesive surface 11. Figure 1 exemplarily shows a state in which release liners 21, 22 are bonded to the adhesive surfaces 11, 12 of the pressure-sensitive adhesive sheet 10. The release liner 21 is in releasable contact with the adhesive surface 11. The release liner 22 is in releasable contact with the adhesive surface 12. The release liners 21, 22 are each peeled off from the pressure-sensitive adhesive sheet 10 at a predetermined timing when the pressure-sensitive adhesive sheet 10 is in use.

[0019] In this embodiment, the pressure-sensitive adhesive sheet 10 is a sheet-like pressure-sensitive adhesive formed from a pressure-sensitive adhesive composition. The pressure-sensitive adhesive composition contains a base polymer with an acid value of 50 mg KOH / g or less and a metal complex salt black dye. That is, the pressure-sensitive adhesive sheet 10 contains a base polymer with an acid value of 50 mg KOH / g or less and a metal complex salt black dye.

[0020] Examples of base polymers include acrylic polymers, polyurethane polymers, polyamide polymers, and polyvinyl ether polymers. The base polymers may be used alone or in combination of two or more. From the viewpoint of ensuring good adhesiveness and transparency in the pressure-sensitive adhesive sheet 10, acrylic polymers are preferred as the base polymer.

[0021] An acrylic polymer is a copolymer of monomer components containing 50% by mass or more of (meth)acrylic acid ester. "(Meth)acrylic" means acrylic and / or methacrylic.

[0022] The (meth)acrylic acid ester is preferably a (meth)acrylic acid alkyl ester, and more preferably a (meth)acrylic acid alkyl ester having an alkyl group having 1 to 20 carbon atoms. Examples of such (meth)acrylic acid alkyl esters include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, s-butyl (meth)acrylate, t-butyl (meth)acrylate, pentyl (meth)acrylate, isopentyl (meth)acrylate, neopentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, and methyl (meth)acrylate. Examples of the alkyl (meth)acrylate include isooctyl acrylate, nonyl (meth)acrylate, isononyl (meth)acrylate, n-decyl (meth)acrylate, isodecyl (meth)acrylate, undecyl (meth)acrylate, dodecyl (meth)acrylate, n-tridecyl (meth)acrylate, isotridecyl (meth)acrylate, tetradecyl (meth)acrylate, isotetradecyl (meth)acrylate, pentadecyl (meth)acrylate, n-octadecyl (meth)acrylate, isooctadecyl (meth)acrylate, and nonadecyl (meth)acrylate. The alkyl (meth)acrylate esters may be used alone or in combination. The alkyl (meth)acrylate ester is preferably at least one selected from the group consisting of methyl methacrylate (MMA), n-butyl acrylate (BA), and 2-ethylhexyl acrylate (2EHA).

[0023] The proportion of the (meth)acrylic acid alkyl ester in the monomer component is preferably 55 to 99.9% by mass, more preferably 60 to 99.5% by mass, and even more preferably 62 to 99% by mass. The proportion of the (meth)acrylic acid alkyl ester in the monomer component is preferably 55% by mass or more, more preferably 60% by mass or more, and even more preferably 62% by mass or more. When the proportion of the (meth)acrylic acid alkyl ester is equal to or greater than the above-mentioned lower limit, basic properties such as adhesiveness can be appropriately exhibited in the PSA sheet 10. Furthermore, the proportion of the (meth)acrylic acid alkyl ester in the monomer component is, for example, 99.9% by mass or less, 99.5% by mass or less, or 99% by mass or less.

[0024] The monomer component may include a copolymerizable monomer copolymerizable with the (meth)acrylic acid alkyl ester. Examples of the copolymerizable monomer include a polar group-containing monomer. Examples of the polar group-containing monomer include a hydroxy group-containing monomer, a monomer having a nitrogen atom-containing ring, and a carboxy group-containing monomer. The copolymerizable monomer may be used alone or in combination of two or more types. The polar group-containing monomer is useful for modifying the acrylic polymer, such as ensuring the cohesive strength of the acrylic polymer. The polar group-containing monomer is preferably at least one selected from the group consisting of a hydroxy group-containing monomer and a monomer having a nitrogen atom-containing ring.

[0025] Examples of hydroxy group-containing monomers include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, and 12-hydroxylauryl (meth)acrylate. The hydroxy group-containing monomer is preferably at least one selected from the group consisting of 2-hydroxyethyl acrylate (2HEA), 4-hydroxyethyl acrylate (4HEA), and 4-hydroxybutyl acrylate (4HBA).

[0026] The proportion of the hydroxy group-containing monomer in the monomer components is preferably 0.1 to 30% by mass, more preferably 0.5 to 20% by mass, and even more preferably 1 to 15% by mass. The proportion of the hydroxy group-containing monomer in the monomer components is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, and even more preferably 1% by mass or more. When this proportion of the hydroxy group-containing monomer is equal to or greater than the above-mentioned lower limit, the cohesive strength of the PSA sheet 10 can be ensured, and the adhesive strength of the PSA sheet 10 to the adherend can be ensured. Furthermore, the proportion of the hydroxy group-containing monomer in the monomer components is preferably 30% by mass or less, more preferably 20% by mass or less, and even more preferably 15% by mass or less. When this proportion of the hydroxy group-containing monomer is equal to or less than the above-mentioned upper limit, the polarity of the acrylic polymer (which is related to the compatibility of the acrylic polymer with various additive components in the PSA sheet 10) can be appropriately adjusted.

[0027] Examples of monomers having a nitrogen atom-containing ring include N-vinyl-2-pyrrolidone, N-methylvinylpyrrolidone, N-vinylpyridine, N-vinylpiperidone, N-vinylpyrimidine, N-vinylpiperazine, N-vinylpyrazine, N-vinylpyrrole, N-vinylimidazole, N-vinyloxazole, N-(meth)acryloyl-2-pyrrolidone, N-(meth)acryloylpiperidine, N-(meth)acryloylpyrrolidine, N-vinylmorpholine, N-vinyl-3-morpholinone, N-vinyl-2-caprolactam, N-vinyl-1,3-oxazin-2-one, N-vinyl-3,5-morpholinedione, N-vinylpyrazole, N-vinylisoxazole, N-vinylthiazole, N-vinylisothiazole, and acryloylmorpholine. The monomer having a nitrogen atom-containing ring is preferably N-vinyl-2-pyrrolidone (NVP).

[0028] The proportion of the monomer having a nitrogen atom-containing ring in the monomer components is preferably 1 to 30% by mass, more preferably 5 to 20% by mass, and even more preferably 8 to 17% by mass. The proportion of the monomer having a nitrogen atom-containing ring in the monomer components is preferably 1% by mass or more, more preferably 5% by mass or more, and even more preferably 8% by mass or more. When this proportion of the monomer having a nitrogen atom-containing ring is equal to or greater than the above-mentioned lower limit, the cohesive strength of the PSA sheet 10 can be ensured, and the adhesive strength of the PSA sheet 10 to the adherend can be ensured. Furthermore, the proportion of the monomer having a nitrogen atom-containing ring in the monomer components is preferably 30% by mass or less, more preferably 20% by mass or less, and even more preferably 17% by mass or less. When this proportion of the monomer having a nitrogen atom-containing ring is equal to or less than the above-mentioned upper limit, the glass transition temperature of the acrylic polymer can be appropriately adjusted, and the polarity of the acrylic polymer (which is related to the compatibility of the acrylic polymer with various additive components in the PSA sheet) can be appropriately adjusted.

[0029] Examples of carboxy group-containing monomers include acrylic acid, methacrylic acid, carboxyethyl acrylate, carboxypentyl acrylate, itaconic acid, maleic acid, fumaric acid, crotonic acid, and isocrotonic acid.

[0030] The proportion of the carboxy group-containing monomer in the monomer component is preferably 0.0 to 3 mass%, more preferably 0.0 to 1 mass%, even more preferably 0.0 to 0.5 mass%, and even more preferably 0.0 to 0.1 mass%. The proportion of the carboxy group-containing monomer in the monomer component is preferably 3 mass% or less, more preferably 1 mass% or less, even more preferably 0.5 mass% or less, even more preferably 0.1 mass% or less, and particularly preferably 0.0 mass%. When the proportion of the carboxy group-containing monomer in the monomer component is equal to or less than the above-mentioned upper limit, the acid value of the base polymer can be made equal to or less than 50 mgKOH / g. Furthermore, when the proportion of the carboxy group-containing monomer in the monomer component is equal to or less than the above-mentioned upper limit, acid corrosion of the adherend of the PSA sheet 10 can be suppressed.

[0031] The monomer component may contain other copolymerizable monomers, such as acid anhydride monomers, sulfonic acid group-containing monomers, phosphoric acid group-containing monomers, epoxy group-containing monomers, cyano group-containing monomers, alkoxy group-containing monomers, and aromatic vinyl compounds.

[0032] The acrylic polymer can be formed by polymerizing the above-mentioned monomer components. Polymerization methods include, for example, solution polymerization, emulsion polymerization, bulk polymerization, and photopolymerization. A polymerization initiator is used depending on the polymerization method. Examples of the polymerization initiator include a thermal polymerization initiator and a photopolymerization initiator. The amount of the polymerization initiator used is, for example, 0.05 parts by mass or more and, for example, 1 part by mass or less, per 100 parts by mass of the monomer components.

[0033] Examples of thermal polymerization initiators include azo polymerization initiators and peroxide polymerization initiators. Examples of azo polymerization initiators include 2,2'-azobisisobutyronitrile, 2,2'-azobis-2-methylbutyronitrile, and 2,2'-azobis(2-methylpropionate)dimethyl. Examples of peroxide polymerization initiators include dibenzoyl peroxide, t-butyl permaleate, and lauroyl peroxide.

[0034] Examples of the photopolymerization initiator include a radical photopolymerization initiator, a cationic photopolymerization initiator, and an anionic photopolymerization initiator. Examples of the radical photopolymerization initiator include an acylphosphine oxide photopolymerization initiator, a benzoin ether photopolymerization initiator, an acetophenone photopolymerization initiator, an α-ketol photopolymerization initiator, an aromatic sulfonyl chloride photopolymerization initiator, a photoactive oxime photopolymerization initiator, a benzoin photopolymerization initiator, a benzyl photopolymerization initiator, a benzophenone photopolymerization initiator, a ketal photopolymerization initiator, and a thioxanthone photopolymerization initiator.

[0035] From the viewpoint of ensuring the cohesive strength of the pressure-sensitive adhesive sheet 10, the weight-average molecular weight of the base polymer is preferably 100,000 to 5,000,000, more preferably 300,000 to 3,000,000, and even more preferably 500,000 to 2,000,000. The weight-average molecular weight of the base polymer is preferably 100,000 or more, more preferably 300,000 or more, and even more preferably 500,000 or more. When the weight-average molecular weight of the base polymer is equal to or greater than the above-mentioned lower limit, the cohesive strength of the pressure-sensitive adhesive sheet 10 can be ensured. The weight-average molecular weight of the base polymer is preferably 5,000,000 or less, more preferably 3,000,000 or less, and even more preferably 2,000,000 or less. When the weight-average molecular weight of the base polymer is equal to or less than the above-mentioned upper limit, the flexibility of the pressure-sensitive adhesive sheet 10 can be ensured. The weight-average molecular weight of the acrylic polymer is measured by gel permeation chromatography (GPC) and calculated in terms of polystyrene.

[0036] The glass transition temperature (Tg) of the base polymer is preferably 0°C or lower, more preferably -10°C or lower, and even more preferably -20°C or lower. The glass transition temperature is, for example, -80°C or higher. That is, the glass transition temperature of the base polymer is preferably -80°C to 0°C, more preferably -80°C to -10°C, and even more preferably -80°C to -20°C.

[0037] The base polymer preferably has a crosslinked structure from the viewpoint of ensuring the cohesive strength of the pressure-sensitive adhesive sheet 10. Methods for introducing a crosslinked structure into the base polymer include, for example, the following first and second methods. In the first method, a base polymer having functional groups reactive with the crosslinking agent and a crosslinking agent are blended into a pressure-sensitive adhesive composition, and the base polymer and the crosslinking agent are allowed to react in the pressure-sensitive adhesive sheet. In the second method, a polyfunctional compound (crosslinking agent) such as a polyfunctional monomer is included in the monomer components forming the base polymer, and a base polymer having a branched structure (crosslinked structure) introduced into the polymer chain is formed by polymerization of the monomer components. These methods may be used in combination.

[0038] Examples of the crosslinking agent used in the first method include compounds that react with functional groups (such as hydroxyl groups and carboxyl groups) contained in the base polymer. Examples of such crosslinking agents include isocyanate crosslinking agents, epoxy crosslinking agents, oxazoline crosslinking agents, aziridine crosslinking agents, carbodiimide crosslinking agents, and metal chelate crosslinking agents, and isocyanate crosslinking agents are preferred. The crosslinking agents may be used alone or in combination of two or more.

[0039] Examples of isocyanate crosslinking agents include tolylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, xylylene diisocyanate, hydrogenated xylylene diisocyanate, and diphenylmethane diisocyanate. Derivatives of these isocyanates are also included as isocyanate crosslinking agents. Examples of the isocyanate derivatives include isocyanurate-modified and polyol-modified isocyanates. Commercially available isocyanate crosslinking agents include Coronate L (a trimethylolpropane adduct of tolylene diisocyanate, manufactured by Tosoh Corporation), Coronate HL (a trimethylolpropane adduct of hexamethylene diisocyanate, manufactured by Tosoh Corporation), Coronate HX (an isocyanurate of hexamethylene diisocyanate, manufactured by Tosoh Corporation), and Takenate D110N (a trimethylolpropane adduct of xylylene diisocyanate, manufactured by Mitsui Chemicals).

[0040] The amount of crosslinking agent in the first method is preferably 0.01 parts by mass or more, more preferably 0.05 parts by mass or more, and even more preferably 0.07 parts by mass or more, per 100 parts by mass of base polymer, from the viewpoint of ensuring the cohesive strength of the PSA sheet 10. From the viewpoint of ensuring good tackiness in the PSA sheet 10, the amount of crosslinking agent in the base polymer is preferably 10 parts by mass or less, more preferably 5 parts by mass or less, and even more preferably 3 parts by mass or less. From the viewpoint of achieving both the cohesive strength and good tackiness of the PSA sheet 10, the amount of crosslinking agent in the base polymer is preferably 0.01 to 10 parts by mass, more preferably 0.05 to 5 parts by mass, and even more preferably 0.07 to 3 parts by mass.

[0041] In the second method, the monofunctional monomer and the polyfunctional compound (crosslinking agent) may be polymerized in one step or in multiple steps. In the multi-step polymerization method, the monofunctional monomer is first polymerized (preliminary polymerization), thereby preparing a prepolymer composition containing a partial polymer (a mixture of a low-polymerization polymer and unreacted monomer). Next, the polyfunctional compound (crosslinking agent) is added to the prepolymer composition, and then the partial polymer and the polyfunctional compound are polymerized (main polymerization).

[0042] Examples of polyfunctional compounds include polyfunctional monomers and polyfunctional oligomers containing two or more ethylenically unsaturated double bonds in one molecule, and polyfunctional monomers include polyfunctional (meth)acrylates.

[0043] Examples of the polyfunctional (meth)acrylate include difunctional (meth)acrylate, trifunctional (meth)acrylate, and tetrafunctional or higher polyfunctional (meth)acrylate.

[0044] Examples of bifunctional (meth)acrylates include ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, glycerin di(meth)acrylate, ethoxylated bisphenol A diacrylate (BPAEODE), and neopentyl glycol di(meth)acrylate.

[0045] Examples of trifunctional (meth)acrylates include trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, and tris(acryloyloxyethyl)isocyanurate.

[0046] Examples of tetrafunctional or higher polyfunctional (meth)acrylates include ditrimethylolpropane tetra(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol monohydroxypenta(meth)acrylate, alkyl-modified dipentaerythritol penta(meth)acrylate, and dipentaerythritol hexa(meth)acrylate.

[0047] Examples of polyfunctional oligomers include urethane (meth)acrylate oligomers, polyester (meth)acrylate oligomers, polyether (meth)acrylate oligomers, polyol (meth)acrylate oligomers, epoxy (meth)acrylate oligomers, polyethylene glycol di(meth)acrylate, and polypropylene glycol di(meth)acrylate.

[0048] The polyfunctional compound used as the crosslinking agent in the second method may be used alone or in combination of two or more kinds. As the polyfunctional compound, at least one selected from the group consisting of 1,6-hexanediol diacrylate (HDDA) and dipentaerythritol hexaacrylate (DPHA) is preferably used.

[0049] The base polymer content in the pressure-sensitive adhesive sheet 10 is preferably 80 to 99.9% by mass, more preferably 90 to 99.5% by mass, and even more preferably 95 to 99.0% by mass. The base polymer content in the pressure-sensitive adhesive sheet 10 is preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more. When the base polymer content is equal to or greater than the above-mentioned lower limit, the pressure-sensitive adhesive sheet 10 can appropriately exhibit basic properties such as adhesiveness. The base polymer content in the pressure-sensitive adhesive sheet 10 is preferably 99.9% by mass or less, more preferably 99.5% by mass or less, and even more preferably 99.0% by mass or less. When the base polymer content is equal to or less than the above-mentioned upper limit, the content of the metal complex salt black dye can be ensured.

[0050] From the viewpoint of the stability of the coordinate bond in the metal complex black dye, the acid value of the base polymer is preferably 30 mgKOH / g or less, more preferably 10 mgKOH / g or less, even more preferably 5.0 mgKOH / g or less, even more preferably 3.0 mgKOH / g or less, even more preferably 1.0 mgKOH / g or less, and particularly preferably 0.0 mgKOH / g. The acid value of the base polymer is, for example, 0.0 mgKOH / g or more. Methods for adjusting the acid value of the base polymer include, for example, adjusting the composition (monomer composition) of the monomer components that form the base polymer. Adjusting the monomer composition includes, for example, adjusting the proportion of carboxyl group-containing monomers in the monomer components. The acid value of the base polymer is measured in accordance with JIS K0070:1992, as specifically described below in the examples.

[0051] The metal complex black dye is a complex salt of a metal (central metal ion) and a dye compound (ligand). The metal complex black dye may contain a proton. The metal complex black dye can be used as a black component with a different hue from carbon black (yellowish black). However, the black light resistance of pressure-sensitive adhesive sheets containing the metal complex black dye varies depending on the acid value of the base polymer. The present inventors have discovered this finding. The present invention is based on this finding.

[0052] Examples of metals (central metal ions) of the metal complex black dye include chromium, cobalt, nickel, and copper. From the viewpoint of the stability of the metal complex black dye, the metal of the metal complex black dye is preferably chromium or copper. That is, the metal complex black dye of the PSA sheet 10 contains at least one metal (central metal ion of the complex salt) selected from the group consisting of chromium and copper.

[0053] The dye compound (ligand) of the metal complex black dye is preferably an azo dye compound, more preferably an aromatic azo dye compound. Examples of metal complex black dyes include those in which the ratio (numerical ratio) of the dye compound to the metal is 1:1 (1:1 complex salts) and those in which the ratio (numerical ratio) of the dye compound to the metal is 2:1 (2:1 complex salts). From the viewpoint of good color development in the pressure-sensitive adhesive sheet 10, the metal complex black dye is preferably a 2:1 complex salt. A metal complex black dye as a 2:1 complex salt formed from a metal M and an aromatic azo dye compound is shown below as structural formula (1):

[0054]

[0055] In structural formula (1), Ar １ ~Ar ４ Each of Ar represents an aromatic ring which may have a substituent. Examples of the aromatic ring include a benzene ring, a naphthalene ring, an indene ring, and an anthracene ring. １ ~Ar ４ The aromatic rings forming the group may all be the same, some may be the same, or all may be different. Examples of the substituent include a nitro group (—NO ２ ), sulfonic acid group (—SO ３ H), and linear or branched alkyl groups. Examples of the alkyl group include a methyl group, an ethyl group, a propyl group, an n-butyl group, an isobutyl group, an s-butyl group, a t-butyl group, an n-pentyl group, an isopentyl group, a neopentyl group, an n-hexyl group, an n-heptyl group, and a 2-ethylhexyl group. In addition, in the structural formula (1), X １ ~X ４represents —O— or —COO—. １ ~X ４ may be all the same or some of them may be the same.

[0056] Commercially available metal complex salt black dyes include, for example, Valifast Black 3804, 3807, 3808, 3810, 3820, 3830, 3840, 3866, 3870, 3877, and 3878 manufactured by Orient Chemical Industry Co., Ltd. Commercially available metal complex salt black dyes include, for example, Orasol Black X45, X51, and X55 manufactured by BASF Japan Ltd. Commercially available metal complex salt black dyes include, for example, Intraplast Black CN manufactured by Sensient Corporation. Commercially available metal complex salt black dyes include, for example, Aizenspiron Black BH and RLH manufactured by Hodogaya Chemical Co., Ltd.

[0057] The metal complex salt black dye may be used alone or in combination of two or more kinds.

[0058] The metal complex salt black dye has a bluish tinge to the black color, and is therefore preferably at least one selected from the group consisting of the following structural formulas (2) to (4).

[0059]

[0060]

[0061]

[0062] The molecular weight of the metal complex black dye is preferably 400 or more, more preferably 500 or more, and even more preferably 600 or more, from the viewpoint of suppressing bleed-out from the pressure-sensitive adhesive sheet 10. The molecular weight of the metal complex black dye is preferably 50,000 or less, more preferably 40,000 or less, even more preferably 30,000 or less, and even more preferably 10,000 or less, from the viewpoint of ensuring compatibility with the base polymer. The molecular weight of the metal complex black dye is preferably 400 to 50,000, more preferably 500 to 40,000, even more preferably 600 to 30,000, and even more preferably 600 to 10,000, from the viewpoint of achieving both the suppression of bleed-out and the ensuring of compatibility. The molecular weight of the metal complex black dye is determined based on the structural formula of the metal complex black dye.

[0063] The content of the metal complex black dye in the pressure-sensitive adhesive sheet 10 is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, and even more preferably 0.10% by mass or more, from the viewpoint of blackening the pressure-sensitive adhesive sheet 10. The content of the metal complex black dye in the pressure-sensitive adhesive sheet 10 is preferably 10% by mass or less, more preferably 7.0% by mass or less, and even more preferably 5.0% by mass or less, from the viewpoint of ensuring compatibility with the base polymer. The content of the metal complex black dye in the pressure-sensitive adhesive sheet 10 is preferably 0.01 to 10% by mass, more preferably 0.05 to 7.0% by mass, and even more preferably 0.10 to 5.0% by mass, from the viewpoint of achieving both blackening of the pressure-sensitive adhesive sheet 10 and ensuring the compatibility. Furthermore, the content of the metal complex black dye in the pressure-sensitive adhesive sheet 10 is preferably 0.01 parts by mass or more, more preferably 0.05 parts by mass or more, and even more preferably 0.10 parts by mass or more, per 100 parts by mass of the base polymer, from the viewpoint of blackening the pressure-sensitive adhesive sheet 10. In order to ensure compatibility with the base polymer, the content of the metal complex black dye in the adhesive sheet 10 is preferably 10 parts by mass or less, more preferably 7.0 parts by mass or less, and even more preferably 5.0 parts by mass or less per 100 parts by mass of the base polymer.

[0064] The PSA composition may contain other components as needed, such as a silane coupling agent, an ultraviolet absorber, a tackifier, a plasticizer, a softener, an antioxidant, a surfactant, and an antistatic agent.

[0065] Examples of ultraviolet absorbers include benzotriazole ultraviolet absorbers, hydroxyphenyltriazine ultraviolet absorbers, benzophenone ultraviolet absorbers, salicylic acid ester ultraviolet absorbers, cyanoacrylate ultraviolet absorbers, and nickel complex salt ultraviolet absorbers. The ultraviolet absorbers may be used alone or in combination of two or more.

[0066] Examples of the release liner 21 include a release liner having a release treatment layer on the surface of the liner substrate, and a release liner formed from a low-adhesion material. Examples of the liner substrate include resin film and paper. Examples of the resin for the resin film include polyester resin and polycarbonate resin. Examples of polyester resin include polyethylene terephthalate (PET) and polybutylene terephthalate. The release treatment layer can be formed by surface treating the liner substrate with a release treatment agent. Examples of the release treatment agent include silicone release treatment agents, long-chain alkyl release treatment agents, and fluorine release treatment agents. Examples of low-adhesion materials include polyolefin resins and fluorine-based polymers. Examples of polyolefin resins include polyethylene, polypropylene, and cycloolefin polymer (COP). Examples of the fluorine-based polymer include polytetrafluoroethylene.

[0067] Examples of the release liner 22 include a release liner having a release-treated layer on the surface of a liner substrate and a release liner made of a low-adhesion material. Specifically, the release liner 22 is similar to the release liner 21 described above.

[0068] The PSA composition is prepared by blending a base polymer, a metal complex black dye, and other components added as needed. The PSA sheet 10 can then be produced using the PSA composition, for example, as follows (first production method). First, a solvent is blended with the PSA composition to prepare a polymer solution (varnish). Examples of solvents include ethyl acetate and toluene. Next, the polymer solution is applied to a release liner 21 (first release liner) to form a coating film, which is then dried and aged to form the PSA sheet 10. Thereafter, if necessary, a release liner 22 is bonded to the PSA sheet 10 on the release liner 21. In the first production method, the metal complex black dye can be dissolved in a polymer solution containing a solvent. Therefore, the metal complex black dye can be more easily dispersed in the PSA sheet 10 than a pigment (which is not soluble in the solvent).

[0069] The pressure-sensitive adhesive sheet 10 can also be produced, for example, by the following method (second production method).

[0070] First, a prepolymer composition is prepared. Specifically, a mixture (liquid) containing the monofunctional monomer for forming the base polymer and a photopolymerization initiator is prepared (prepolymer composition preparation step). Next, the mixture is irradiated with ultraviolet light to photopolymerize a portion of the monofunctional monomer in the mixture, thereby obtaining a prepolymer composition. Examples of light sources for ultraviolet irradiation include ultraviolet LED lights, black light lamps, high-pressure mercury lamps, and metal halide lamps. In the ultraviolet irradiation, the illuminance is, for example, 5 to 200 mW / cm. ２ m, and the cumulative irradiation light amount is, for example, 100 to 5000 mJ / cm ２ The ultraviolet irradiation is preferably continued until the viscosity of the composition reaches approximately 15 to 25 Pa·s. This viscosity is measured using a Brookfield viscometer with a No. 5 rotor at a rotor rotation speed of 10 rpm and a temperature of 30°C. The prepolymer composition contains a photopolymerized product of a monofunctional monomer and a monofunctional monomer that has not undergone a polymerization reaction (residual monomer). The prepolymer composition does not contain a solvent.

[0071] Next, a multifunctional compound (crosslinking agent), an additional photopolymerization initiator, and other components, if necessary, are added to the prepolymer composition to prepare a pressure-sensitive adhesive composition (pressure-sensitive adhesive composition preparation step). Examples of other components include oligomers, antioxidants, silane coupling agents, and rust inhibitors. This pressure-sensitive adhesive composition does not contain a solvent. In other words, the pressure-sensitive adhesive composition prepared in this step is a solvent-free pressure-sensitive adhesive composition.

[0072] Next, as shown in Figure 2A, a coating film 10A is formed between release liners 21 and 22' (coating film forming step). Specifically, first, a pressure-sensitive adhesive composition is applied to the release surface of release liner 21 to form coating film 10A. Examples of methods for applying the pressure-sensitive adhesive composition include roll coating, kiss roll coating, gravure coating, reverse coating, roll brushing, spray coating, dip roll coating, bar coating, knife coating, air knife coating, curtain coating, lip coating, and die coating. Next, the release surface of release liner 22' is laminated onto coating film 10A on release liner 21. For example, the same release liner as release liner 22 can be used as release liner 22.

[0073] Next, as shown in Figure 2B, ultraviolet light is irradiated onto the coating film 10A between the release liners 21 and 22' to form a base adhesive sheet 10B (base adhesive sheet formation step). Upon exposure to ultraviolet light, a photopolymerization reaction occurs in the coating film in a reaction system containing a monofunctional monomer (residual monomer) and a polyfunctional compound (crosslinking agent), forming a base polymer. Such a base polymer has a crosslinked structure in which linear units derived from the monofunctional monomer are linked by the polyfunctional compound.

[0074] Next, as shown in FIG. 2C, release liner 22' (FIG. 2B) is peeled off from base adhesive sheet 10B (peeling step).

[0075] Next, as shown in FIG. 2D , a later-added component is supplied to the base adhesive sheet 10B (later-added component supplying step). Specifically, a later-added component solution (not shown) containing the later-added component and a solvent is applied to the exposed surface of the base adhesive sheet 10B. Examples of solvents include ethyl acetate and toluene. The later-added component includes a metal complex black dye. The later-added component may also contain other components. Examples of other additives include an ultraviolet absorber and an antioxidant. In this step, for example, the later-added component is allowed to penetrate the base adhesive sheet 10B from the surface thereof, while the solvent is evaporated by heating as necessary. The metal complex black dye can be dissolved in the later-added component solution containing a solvent. Therefore, in this step, the metal complex black dye in the later-added component solution penetrates the base adhesive sheet 10B as a later-added component and can be well dispersed within the adhesive sheet 10. Furthermore, prior to this step, the base polymer already has a crosslinked structure, forming the base adhesive sheet 10B. Therefore, the evaporation of the solvent in this step does not easily (or substantially does not) form an orange peel surface on base adhesive sheet 10B.

[0076] Next, as shown in FIG. 2E, another release liner 22 is attached to the pressure-sensitive adhesive sheet 10 (attaching step).

[0077] In this manner, adhesive sheet 10 having its adhesive surface covered and protected by release liners 21, 22 can be manufactured.

[0078] The PSA sheet 10 can also be produced by a manufacturing method similar to the above-mentioned second manufacturing method (third manufacturing method), except for the following: In the PSA composition preparation step, a metal complex black dye is added to a solventless PSA composition. In the step shown in Figure 2B, the PSA sheet 10 is formed from the PSA composition (containing a base polymer and a metal complex black dye). The steps shown in Figures 2C to 2E are not performed. This third manufacturing method also makes it possible to produce a PSA sheet 10 whose adhesive surface is covered and protected by release liners 21, 22.

[0079] In the second and third production methods, the pressure-sensitive adhesive sheet 10 can be produced from a solvent-free pressure-sensitive adhesive composition. Such a pressure-sensitive adhesive sheet 10 is suitable for reducing the environmental load. That is, a pressure-sensitive adhesive sheet 10 formed from a solvent-free pressure-sensitive adhesive composition is environmentally friendly and is preferable from the perspective of sustainable development.

[0080] The thickness of the pressure-sensitive adhesive sheet 10 is preferably 10 μm or more, more preferably 15 μm or more, and even more preferably 20 μm or more, from the viewpoint of ensuring sufficient adhesiveness to the adherend. The thickness of the pressure-sensitive adhesive sheet 10 is preferably 300 μm or less, more preferably 200 μm or less, even more preferably 100 μm or less, and even more preferably 50 μm or less, from the viewpoint of ease of handling and thinning of the pressure-sensitive adhesive sheet 10. The thickness of the pressure-sensitive adhesive sheet 10 is preferably 10 to 300 μm, more preferably 15 to 200 μm, even more preferably 20 to 100 μm, and even more preferably 20 to 50 μm, from the viewpoint of achieving both the above-mentioned adhesiveness and the above-mentioned ease of handling and thinning.

[0081] L of the adhesive sheet 10 ＊ a ＊ b ＊ Transmittance hue b in the color system ＊ From the viewpoint of ensuring a bluish tint in the black color of the pressure-sensitive adhesive sheet 10, the value is preferably 0 or less, more preferably −1 or less, and even more preferably −2 or less.

[0082] From the viewpoint of ensuring the transparency required for a pressure-sensitive adhesive sheet 10 for use in a display panel, the haze of the pressure-sensitive adhesive sheet 10 is preferably 3.0% or less, more preferably 1.0% or less, and even more preferably 0.8% or less. The haze of the pressure-sensitive adhesive sheet 10 is, for example, 0.0% or more, 0.2% or more, or 0.4% or more. The method for measuring the haze is as described below in the examples.

[0083] As described above, the pressure-sensitive adhesive sheet 10 contains a metal complex black dye as a black component. The dye can be dissolved in a solution for forming the pressure-sensitive adhesive sheet 10 during the manufacturing process of the pressure-sensitive adhesive sheet 10. Therefore, the dye can be dispersed more easily in the pressure-sensitive adhesive sheet 10 than a pigment. Therefore, the pressure-sensitive adhesive sheet 10 containing a dye as a black component is suitable for reducing the haze of the pressure-sensitive adhesive sheet 10.

[0084] Furthermore, as described above, the base polymer in the pressure-sensitive adhesive sheet 10 has an acid value of 50 mg KOH / g or less. The acid value is the amount (mg) of potassium hydroxide required to neutralize the acidic components contained in 1 g of the target object. The lower the acid value of the target object, the fewer acidic components there are in the target object. The pressure-sensitive adhesive sheet 10 contains a base polymer with a low acid value of 50 mg KOH / g or less, which is suitable for ensuring the stability of the coordinate bond between the metal and the dye compound in the metal complex black dye (the higher the acid value of the base polymer, the more impaired the coordinate bond). Stabilizing the metal complex black dye helps ensure the light resistance of the metal complex black dye.

[0085] Therefore, the pressure-sensitive adhesive sheet 10 is suitable for ensuring good black light resistance while suppressing haze.

[0086] The pressure-sensitive adhesive sheet 10 is, for example, an optical pressure-sensitive adhesive sheet that is disposed at a light-transmitting portion of a display panel. Examples of display panels include liquid crystal display panels and organic EL display panels. Display panels have a laminated structure that includes elements such as a pixel panel, a polarizing film, a touch panel, and a cover glass. The pressure-sensitive adhesive sheet 10 is used, for example, to bond elements included in the laminated structure during the manufacturing process of the display panel.

[0087] The present invention will be described in detail below with reference to examples, but is not limited to these examples. The specific numerical values ​​of the blending amounts (contents), physical property values, parameters, etc. described below can be substituted for the upper limits (numerical values ​​defined as "not more than" or "less than") or lower limits (numerical values ​​defined as "not less than" or "exceeding") of the corresponding blending amounts (contents), physical property values, parameters, etc. described in the above-mentioned "Description of the Invention."

[0088] Preparation of Acrylic Polymer P1: In a reaction vessel equipped with a reflux condenser, a nitrogen inlet tube, a thermometer, and a stirrer, a mixture containing 63 parts by mass of 2-ethylhexyl acrylate (2EHA), 9 parts by mass of methyl methacrylate (MMA), 13 parts by mass of 2-hydroxyethyl acrylate (2HEA), 15 parts by mass of N-vinyl-2-pyrrolidone (NVP), 0.2 parts by mass of 2,2'-azobisisobutyronitrile (AIBN) as a polymerization initiator, and 233 parts by mass of ethyl acetate as a solvent was stirred at 60°C for 7 hours under a nitrogen atmosphere (polymerization reaction). This produced a polymer solution S1 containing the acrylic polymer P1.

[0089] <Preparation of Acrylic Polymer P2> In a reaction vessel equipped with a reflux condenser, a nitrogen inlet tube, a thermometer, and a stirrer, a mixture containing 99 parts by mass of butyl acrylate (BA), 1 part by mass of 4-hydroxybutyl acrylate (4HBA), 0.2 parts by mass of AIBN as a polymerization initiator, and 155 parts by mass of ethyl acetate as a solvent was stirred under a nitrogen atmosphere at 60°C for 7 hours (polymerization reaction), thereby obtaining a polymer solution S2 containing the acrylic polymer P2.

[0090] Preparation of Acrylic Polymer P3: In a reaction vessel equipped with a reflux condenser, a nitrogen inlet tube, a thermometer, and a stirrer, a mixture containing 90 parts by mass of BA, 10 parts by mass of 4HBA, 0.2 parts by mass of AIBN as a polymerization initiator, and 233 parts by mass of ethyl acetate as a solvent was stirred at 60° C. for 7 hours under a nitrogen atmosphere (polymerization reaction), thereby obtaining a polymer solution S3 containing the acrylic polymer P3.

[0091] Preparation of Acrylic Polymer P4: In a reaction vessel equipped with a reflux condenser, a nitrogen inlet pipe, a thermometer, and a stirrer, a mixture containing 95 parts by mass of BA, 5 parts by mass of acrylic acid (AA), 0.2 parts by mass of AIBN as a polymerization initiator, and 233 parts by mass of ethyl acetate as a solvent was stirred under a nitrogen atmosphere at 60° C. for 7 hours (polymerization reaction), thereby obtaining a polymer solution S4 containing the acrylic polymer P4.

[0092] Example 1 Preparation of Pressure-Sensitive Adhesive Composition 0.25 parts by mass (solids equivalent) of an isocyanate crosslinker (Takenate D110N, manufactured by Mitsui Chemicals, Inc.) and 0.16 parts by mass (solids equivalent) of a first black dye (Valifast Black 3810, 1% by mass ethyl acetate solution, manufactured by Orient Chemical Industry Co., Ltd.) were added to and mixed with the polymer solution S1 per 100 parts by mass of acrylic polymer P1 to prepare a pressure-sensitive adhesive composition. The first black dye contained a metal complex salt black dye represented by the above structural formula (2), a metal complex salt black dye represented by the above structural formula (3), and a metal complex salt black dye represented by the above structural formula (4).

[0093] <Preparation of Pressure-Sensitive Adhesive Sheet> First, a pressure-sensitive adhesive composition was applied to the release-treated surface of a 38 μm-thick first release liner (trade name "MRF#38", polyester film, manufactured by Mitsubishi Chemical Corporation) with one release-treated surface to form a coating film. Next, this coating film was dried by heating at 132°C for 3 minutes. This formed a 25 μm-thick pressure-sensitive adhesive layer on the first release liner. Next, the release-treated surface of a 38 μm-thick second release liner (trade name "MRE#38", polyester film, manufactured by Mitsubishi Chemical Corporation) with one release-treated surface was bonded to the pressure-sensitive adhesive layer on the first release liner. This was then subjected to an aging treatment at 60°C for 24 hours to promote the crosslinking reaction in the pressure-sensitive adhesive layer. In this manner, a black pressure-sensitive adhesive sheet (25 μm thick) with a release liner was prepared as the pressure-sensitive adhesive sheet of Example 1.

[0094] [Example 2] A release-liner-attached PSA sheet of Example 2 was produced in the same manner as the PSA sheet of Example 1, except for the following: In preparing the PSA composition, polymer solution S2 (containing acrylic polymer P2) was used in place of polymer solution S1.

[0095] [Example 3] A release-liner-attached PSA sheet of Example 3 was produced in the same manner as the PSA sheet of Example 1, except for the following: In preparing the PSA composition, polymer solution S3 (containing acrylic polymer P3) was used in place of polymer solution S1.

[0096] Example 4 A release-liner-equipped PSA sheet of Example 4 was prepared in the same manner as the PSA sheet of Example 1, except for the following: In preparing the PSA composition, 0.16 parts by mass (solids equivalent) of a second black dye (trade name "Valifast Black 3820", 1 mass% MEK solution, manufactured by Orient Chemical Co., Ltd.) was blended as the black component in place of the first black dye. The second black dye is a metal complex salt black dye represented by the above structural formula (2).

[0097] Example 5 A release-liner-equipped PSA sheet of Example 5 was produced in the same manner as the PSA sheet of Example 1, except for the following: In preparing the PSA composition, polymer solution S2 (containing acrylic polymer P2) was used instead of polymer solution S1, and 0.16 parts by mass (solids equivalent) of a second black dye (Valifast Black 3820) was blended in place of the first black dye as the black component.

[0098] Example 6 A release-liner-equipped PSA sheet of Example 6 was produced in the same manner as the PSA sheet of Example 1, except for the following: In preparing the PSA composition, polymer solution S3 (containing acrylic polymer P3) was used instead of polymer solution S1, and 0.16 parts by mass (solids equivalent) of a second black dye (Valifast Black 3820) was blended in place of the first black dye as the black component.

[0099] Comparative Example 1 First, 0.25 parts by mass (solids equivalent) of an epoxy crosslinker (trade name "Tetrad-c", manufactured by Mitsui Chemicals, Inc.) and 0.16 parts by mass (solids equivalent) of a first black dye (Valifast Black 3810) as a black component were added to and mixed with polymer solution S4 per 100 parts by mass of acrylic polymer P4 to prepare a pressure-sensitive adhesive composition. Thereafter, in the same manner as described above for Example 1, a coating film of the pressure-sensitive adhesive composition was formed on a first release liner, the coating film was dried to form a pressure-sensitive adhesive layer, a second release liner (MRE #38) was bonded to the pressure-sensitive adhesive layer, and the pressure-sensitive adhesive layer was subjected to an aging treatment. In this manner, a black pressure-sensitive adhesive sheet (thickness 25 μm) with a release liner was produced as the pressure-sensitive adhesive sheet of Comparative Example 1.

[0100] [Comparative Example 2] A release-liner-equipped PSA sheet of Comparative Example 2 was prepared in the same manner as the PSA sheet of Comparative Example 1, except for the following: In preparing the PSA composition, 0.16 parts by mass (solids equivalent) of a second black dye (Valifast Black 3820) was blended as the black component in place of the first black dye.

[0101] Comparative Example 3 A release-liner-equipped PSA sheet of Comparative Example 3 was prepared in the same manner as the PSA sheet of Example 1, except for the following: In preparing the PSA composition, 0.16 parts by mass (solids equivalent) of a third black dye (trade name "OIL BLACK HBB", 1 mass% methyl ethyl ketone solution, manufactured by Orient Chemical Co., Ltd.) was blended as the black component in place of the first black dye. The third black dye is not a metal complex salt black dye.

[0102] Comparative Example 4 A release-liner-equipped PSA sheet of Comparative Example 4 was prepared in the same manner as the PSA sheet of Example 1, except for the following: In preparing the PSA composition, 0.16 parts by mass (solids equivalent) of a fourth black dye (trade name "Solvent Violet 13", 1 mass% methyl ethyl ketone solution, manufactured by Taiyo Fine Chemical Co., Ltd.) was blended as the black component in place of the first black dye. The fourth black dye is not a metal complex salt black dye.

[0103] Comparative Example 5 A release-liner-attached PSA sheet of Comparative Example 5 was prepared in the same manner as the PSA sheet of Example 1, except for the following: In preparing the PSA composition, a carbon black (CB) pigment (trade name "ATDN101 Black", manufactured by Dainichiseika Color & Chemicals Mfg. Co., Ltd.) was blended as the black component in place of the first black dye at a ratio of 0.25% by mass in the PSA layer.

[0104] <Haze, Luminous Transmittance, and Hue> The haze, luminous transmittance (Y value), and hue of each of the pressure-sensitive adhesive sheets of the Examples and Comparative Examples were examined as follows.

[0105] First, a measurement sample was prepared. Specifically, the second release liner was peeled off from the adhesive sheet of a release-liner-attached adhesive sheet (first release liner / adhesive sheet / second release liner), and the adhesive sheet exposed by this peeling was then bonded to an alkali-free glass plate (0.55 mm thick, Eagle Glass, manufactured by Matsunami Glass Co., Ltd.). Next, the first release liner was peeled off from the adhesive sheet on the alkali-free glass, and a polyethylene terephthalate (PET) film (product name "G981 E75", thickness 75 μm, manufactured by Mitsubishi Chemical Corporation) was then bonded to the adhesive sheet exposed by this peeling. This resulted in a laminate (alkali-free glass / adhesive sheet / PET film) containing the adhesive sheet. Next, the laminate was autoclaved at 50°C, 0.5 MPa, and for 15 minutes. This resulted in a measurement sample.

[0106] The measurement sample was then measured using a spectrometer (product name "HSP-150Vis", manufactured by Murakami Color Research Laboratory Co., Ltd.) to determine the haze, luminous transmittance, and hue. ＊ value and b ＊The luminous transmittance was measured (first measurement). In this measurement, the measurement sample was placed in the device so that light was incident on the non-alkali glass side of the measurement sample. In this measurement, the measurement results (transmittance spectrum) obtained by measuring the laminate film of the above-mentioned non-alkali glass plate (Eagle Glass) and PET film (G981 E75) under the same conditions were used as a baseline. Specifically, the luminous transmittance is the transmittance (Y value) in the CIE-XYZ color system of light transmitted through the measurement sample at wavelengths of 380 nm to 780 nm. a ＊ value and b ＊ The value is L ＊ a ＊ b ＊ Hue a in the color system ＊ ,b ＊ The measurement results are shown in Table 1. The luminous transmittance is shown in Table 1 as a Y value (%) before the light resistance test described later.

[0107] <Acid Value of Acrylic Polymer> The acid value of each of the acrylic polymers P1 to P4 was measured in accordance with JIS K 0070:1992. Specifically, approximately 2 g of acrylic polymer (sample) was precisely weighed into a 100 mL container (Erlenmeyer flask) using a precision balance. Next, 10 mL of solvent was added to the container, and the acrylic polymer was dissolved in the solvent to prepare a first solution. A mixed solvent containing ethanol and diethyl ether in a mass ratio of 1:1 was used as the solvent. Next, 1 to 3 drops of a phenolphthalein ethanol solution as an indicator were added to the first solution, and the solution was stirred. This yielded a second solution (measurement solution). The second solution was then titrated with a 0.1 N potassium hydroxide-ethanol solution. In this titration, the neutralization endpoint was determined when the indicator color (light red) persisted for 30 seconds or more. Based on the results of the neutralization titration, the acid value of the acrylic polymer was calculated using the following formula: In the calculation formula, B is the amount (mL) of 0.1N potassium hydroxide-ethanol solution used, f is the factor of 0.1N potassium hydroxide-ethanol solution, and 5.611 is the formula weight of potassium hydroxide, 56.11 x 10 －１ and S is the amount (g) of sample (acrylic polymer) collected.

[0108] Acid value (mgKOH / g) = (B x f x 5.611) / S

[0109] <Light Resistance Test> A light resistance test was carried out on each of the pressure-sensitive adhesive sheets of the Examples and Comparative Examples as follows.

[0110] First, the measurement sample (alkali-free glass / adhesive sheet / PET film) used in the first measurement was placed in the chamber of a light resistance test device (product name "Super Xenon Weather Meter SX75", manufactured by Suga Test Instruments Co., Ltd.). Specifically, the test sample was placed in the chamber so that the PET film of the test sample was positioned on the light source (super xenon lamp) side. Next, in an environment of 55°C and relative humidity 55%, the adhesive sheet of the test sample was irradiated with light from a super xenon lamp (wavelength 300 nm to 400 nm) for 168 hours (light resistance test).

[0111] Then, the luminous transmittance of the measurement sample after the lightfastness test was measured using a spectrometer (product name "HSP-150Vis", manufactured by Murakami Color Research Laboratory Co., Ltd.) (second measurement). The method and conditions for this measurement were the same as those for the first measurement. The measured luminous transmittance is shown in Table 1 as the Y value (%) after the lightfastness test. The difference in Y value before and after the lightfastness test, ΔY value (Y value after test - Y value before test), is also shown in Table 1.

[0112] [Evaluation] The PSA sheet of Comparative Example 5 contained carbon black (CB) as the black component and had a high haze of 4.5%. The PSA sheets of Comparative Examples 3 and 4 contained a black dye compound (not a metal complex salt black dye) as the black component and had a large ΔY value (Comparative Example 3: 16.7%, Comparative Example 4: 16.9%). The PSA sheets of Comparative Examples 1 and 2 contained a metal complex salt black dye as the black component, but the acid value of the base polymer exceeded 50 mg KOH / g, resulting in a large ΔY value (Comparative Example 1: 15.2%, Comparative Example 2: 14.4%). In other words, the PSA sheets of Comparative Examples 1 to 4 had low black light resistance.

[0113] In contrast, each PSA sheet of the Examples contained a metal complex black dye as the black component, and the acid value of the base polymer was 50 mg KOH / g or less. Each of these PSA sheets of the Examples had a low haze of 1 or less. Furthermore, each PSA sheet of the Examples had a small ΔY value of 6.5% or less (Example 5). That is, the PSA sheets of each Example had higher black light resistance than the PSA sheets of Comparative Examples 1 to 4.

[0114]

[0115] The above invention is provided as an exemplary embodiment of the present invention, but it is merely an example and should not be interpreted as being limiting. Modifications of the present invention that are obvious to those skilled in the art are intended to be included in the scope of the following claims.

[0116] The pressure-sensitive adhesive sheet of the present invention can be suitably used in the production of display panels such as organic EL panels, for example.

[0117] 10 Pressure-sensitive adhesive sheet H Thickness direction 11 First surface 12 Second surface 21, 22 Release liner

Claims

1. An adhesive sheet containing a base polymer with an acid value of 50 mg KOH / g or less and a metal complex black dye.

2. The pressure-sensitive adhesive sheet according to claim 1, wherein the metal complex black dye contains at least one metal selected from the group consisting of chromium and copper.

3. The adhesive sheet according to claim 1, wherein the metal complex black dye contains an azo dye compound as a dye compound.

4. The adhesive sheet according to claim 3, wherein the azo dye compound is an aromatic azo dye compound.

5. The adhesive sheet according to claim 1, wherein the metal complex black dye has a molecular weight of 400 or more.

6. L ＊ a ＊ b ＊ Transmittance hue in the color system b ＊ The pressure-sensitive adhesive sheet according to claim 1 , wherein the value is 0 or less.

7. The pressure-sensitive adhesive sheet according to any one of claims 1 to 6, having a haze of 3.0% or less.

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