JP7164558B2 - Adhesive composition, adhesive layer and adhesive sheet - Google Patents

Description

TECHNICAL FIELD The present invention relates to a pressure-sensitive adhesive composition, a pressure-sensitive adhesive layer comprising the pressure-sensitive adhesive composition, and a pressure-sensitive adhesive sheet comprising the pressure-sensitive adhesive layer.

Conventionally, transparent adhesive tapes have been favorably used because the positions of adhesive tapes can be easily grasped in processing steps and operations such as lamination. On the other hand, colored adhesive tapes are also used for the purpose of changing designs, improving designability and visibility, and the like.

For example, Patent Literature 1 describes a colored pressure-sensitive adhesive sheet that has the ability to hide the defects of the adherend by means of the design and decoration of the adherend, or the concealability of the adherend, while reducing the thickness of the pressure-sensitive adhesive sheet.

JP 2013-245298 A

The pressure-sensitive adhesive sheet described in Patent Document 1 is colored by containing a dye in the pressure-sensitive adhesive layer. Therefore, the molded pressure-sensitive adhesive sheet is already colored, and the pressure-sensitive adhesive sheet cannot be colored at an arbitrary timing such as after the process of laminating the sheets.

Accordingly, an object of the present invention is to provide a pressure-sensitive adhesive composition that can be discolored or colored at any time, and a pressure-sensitive adhesive layer and pressure-sensitive adhesive sheet using the pressure-sensitive adhesive composition.

The present inventors have made extensive studies with the aim of providing a pressure-sensitive adhesive composition or the like that can be discolored or colored at any timing. As a result, they came up with the idea of combining a leuco dye that colors by reacting with an acid and a photoacid generator that generates an acid upon irradiation with an active energy ray and using them in a pressure-sensitive adhesive composition. That is, by irradiating an active energy ray to a pressure-sensitive adhesive composition containing a leuco dye and a photoacid generator, the present inventors have found that discoloration or coloring can be achieved at any timing, and have completed the present invention.

One embodiment of the present invention relates to a pressure-sensitive adhesive composition containing a base polymer, a leuco dye, and a photoacid generator.

In one embodiment of the present invention, the leuco dye preferably has an absorption wavelength that changes with pH.

In one embodiment of the present invention, the pressure-sensitive adhesive composition preferably contains 0.1 to 30 parts by mass of the leuco dye per 100 parts by mass of the base polymer.

In one embodiment of the present invention, the leuco dye is preferably at least one dye selected from the group consisting of phthalide dyes and fluorane dyes.

In one embodiment of the present invention, the adhesive composition preferably contains 0.1 to 30 parts by mass of the photoacid generator per 100 parts by mass of the base polymer.

In one embodiment of the present invention, the photoacid generator is preferably at least one compound selected from the group consisting of sulfonium salt compounds, iodonium salt compounds, and aromatic N-oxyimidosulfonates. .

In one embodiment of the invention, it is preferred that the base polymer comprises an acrylic polymer.

In one embodiment of the present invention, the pressure-sensitive adhesive composition may be discolored by active energy ray irradiation.

In one embodiment of the present invention, the pressure-sensitive adhesive composition may be colored by irradiation with active energy rays.

One embodiment of the present invention relates to a pressure-sensitive adhesive layer comprising the above pressure-sensitive adhesive composition.

One embodiment of the present invention relates to a pressure-sensitive adhesive sheet comprising the pressure-sensitive adhesive layer.

In one embodiment of the present invention, the pressure-sensitive adhesive sheet may have a UV absorbing layer on one side of the pressure-sensitive adhesive layer.

In one embodiment of the invention, the UV absorbing layer may be a pressure-sensitive adhesive layer containing a UV absorber.

In one embodiment of the present invention, the adhesive layer in the adhesive sheet may be formed on a substrate.

The pressure-sensitive adhesive composition of one embodiment of the present invention can be discolored or colored by irradiation with active energy rays. Therefore, the pressure-sensitive adhesive layer and the pressure-sensitive adhesive sheet using the pressure-sensitive adhesive composition can be discolored or colored at any timing after lamination.

FIG. 1 is a diagram showing an example of a redox reaction of a leuco dye in an embodiment of the present invention. FIG. 2 is an example of a schematic cross-sectional view of an adhesive layer according to an embodiment of the invention. FIG. 3 is an example of a schematic cross-sectional view of an adhesive sheet according to an embodiment of the present invention. FIG. 4 is an example of a schematic cross-sectional view of an adhesive sheet according to an embodiment of the present invention. FIG. 5 is an example of a schematic cross-sectional view of an adhesive sheet according to an embodiment of the invention. FIG. 6 is an example of a schematic cross-sectional view of an adhesive sheet according to an embodiment of the invention.

Hereinafter, embodiments of the present invention will be described in detail. In addition, this invention is not limited to embodiment described below.

<Adhesive composition>
A pressure-sensitive adhesive composition according to one embodiment of the present invention is characterized by containing a base polymer, a leuco dye, and a photoacid generator.

According to the pressure-sensitive adhesive layer or pressure-sensitive adhesive sheet obtained using the above-described pressure-sensitive adhesive composition, by irradiating with an active energy ray, an acid is generated from the photoacid generator, and the acid reacts with the leuco dye. The pressure-sensitive adhesive layer or pressure-sensitive adhesive sheet can be discolored or colored. That is, since the pressure-sensitive adhesive layer and the pressure-sensitive adhesive sheet obtained using the pressure-sensitive adhesive composition can be discolored or colored by irradiation with active energy rays, discoloration or coloring can be performed at any time after lamination thereof. can be made

In this specification, "A to B" indicating a range means "A or more and B or less". Further, in this specification, "weight" and "mass", "weight %" and "mass %", and "parts by weight" and "parts by mass" are treated as synonyms.

As used herein, the term “discoloration” means that the color changes before and after irradiation with active energy rays, and the color disappears due to irradiation with active energy rays, and the color appears due to irradiation with active energy rays. , and the change of the original color to a different color by irradiation with active energy rays.
In addition, the term "color" as used herein means that a color appears before and after irradiation with an active energy ray. This concept includes changing to a different color, but does not include disappearance of color due to irradiation with active energy rays.

Each component contained in the pressure-sensitive adhesive composition will be described in detail below.

(base polymer)
In the pressure-sensitive adhesive composition of one embodiment of the present invention, the base polymer constituting the pressure-sensitive adhesive composition is not particularly limited, and known polymers used for pressure-sensitive adhesives can be used. Examples thereof include acrylic polymers, rubber polymers, vinyl alkyl ether polymers, silicone polymers, polyester polymers, polyamide polymers, urethane polymers, fluorine polymers, and epoxy polymers. Among them, acrylic polymers and rubber polymers are preferred from the viewpoint of adhesiveness. In addition, acrylic polymers with high transparency are more preferable from the viewpoint that the change in appearance when discolored or colored is remarkable. Such polymers may be used singly or in combination of two or more.

Hereinafter, in the pressure-sensitive adhesive composition of one embodiment of the present invention, an embodiment containing an acrylic polymer as a base polymer will be mainly described, but the present invention is not limited to this embodiment.

The pressure-sensitive adhesive composition of one embodiment of the present invention may contain an acrylic polymer as a base polymer. Typically, the pressure-sensitive adhesive composition may be an acrylic pressure-sensitive adhesive composition containing an acrylic polymer as a main component. The acrylic pressure-sensitive adhesive composition has excellent transparency.

The pressure-sensitive adhesive composition of one embodiment of the present invention includes, for example, 40% by weight or more of (meth)acrylic acid alkyl ester having a linear or branched alkyl group having 1 to 20 carbon atoms at the ester end. As a base polymer, it is preferable to use an acrylic polymer composed of monomer components in a ratio of

Hereinafter, a (meth)acrylic acid alkyl ester having an alkyl group having X or more and Y or less carbon atoms at the ester end may be referred to as "(meth)acrylic acid _CXY alkyl ester". Since it is easy to balance the properties, it is appropriate that the ratio of the (meth)acrylic acid C _1-20 alkyl ester in the total monomer components of the acrylic polymer according to one embodiment is more than 50% by weight. It may be 55% by weight or more, 60% by weight or more, or 70% by weight or more.

For the same reason, the proportion of the (meth)acrylic acid C _1-20 alkyl ester in the monomer component may be, for example, 99.9% by weight or less, 99.5% by weight or less, or 99% by weight or less. good. The ratio of the C _1-20 (meth)acrylic acid alkyl ester to the total monomer components of the acrylic polymer according to another aspect may be, for example, 98% by weight or less, from the viewpoint of improving the cohesiveness of the pressure-sensitive adhesive layer. It may be 95% by weight or less, 85% by weight or less (for example, less than 80% by weight), 70% by weight or less, or 60% by weight or less.

Specific non-limiting examples of (meth)acrylic acid C _1-20 alkyl esters include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, ( meth) n-butyl acrylate, isobutyl (meth) acrylate, s-butyl (meth) acrylate, t-butyl (meth) acrylate, pentyl (meth) acrylate, isopentyl (meth) acrylate, (meth) hexyl acrylate, heptyl (meth) acrylate, octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isooctyl (meth) acrylate, nonyl (meth) acrylate, isononyl (meth) acrylate, (meth) ) Decyl acrylate, isodecyl (meth) acrylate, undecyl (meth) acrylate, dodecyl (meth) acrylate, tridecyl (meth) acrylate, tetradecyl (meth) acrylate, pentadecyl (meth) acrylate, (meth) hexadecyl acrylate, heptadecyl (meth)acrylate, stearyl (meth)acrylate, isostearyl (meth)acrylate, nonadecyl (meth)acrylate, eicosyl (meth)acrylate and the like.

Among these, it is preferable to use at least (meth)acrylic acid C _4-20 alkyl ester, and it is more preferable to use at least (meth)acrylic acid C _4-18 alkyl ester. For example, one or both of n-butyl acrylate (BA) and 2-ethylhexyl acrylate (2EHA) are preferably included as the monomer component, and an acrylic pressure-sensitive adhesive containing at least 2EHA is particularly preferred. Other examples of (meth)acrylic acid C _4-20 alkyl esters that can be preferably used include isononyl acrylate, n-butyl methacrylate (BMA), 2-ethylhexyl methacrylate (2EHMA), isostearyl acrylate (iSTA ) and the like.

In some aspects, the monomer component constituting the acrylic polymer may contain a (meth)acrylic acid C _4-18 alkyl ester in a proportion of 40% by weight or more. The proportion of the (meth)acrylic acid C _4-18 alkyl ester in the monomer component may be, for example, 50% by weight or more, 60% by weight or more, or 65% by weight or more. A monomer component containing a (meth)acrylic acid C _6-18 alkyl ester in a ratio equal to or higher than any of the above lower limits may be used.

In addition, from the viewpoint of increasing the cohesiveness of the pressure-sensitive adhesive layer, the proportion of the (meth)acrylic acid _C4-18 alkyl ester in the monomer component is usually suitably 99.5% by weight or less, and 95% by weight. % or less, 85 wt % or less, or 75 wt % or less. It may be a monomer component containing a (meth)acrylic acid C _6-18 alkyl ester in a proportion not higher than any of the above upper limits.

The monomer component constituting the acrylic polymer contains (meth)acrylic acid alkyl ester and, if necessary, other monomers (copolymerizable monomers) copolymerizable with (meth)acrylic acid alkyl ester. good too. As the copolymerizable monomer, a monomer having a polar group (e.g., carboxy group, hydroxyl group, nitrogen atom-containing ring, etc.) or a homopolymer having a relatively high glass transition temperature (e.g., 10° C. or higher) is preferably used. can do. A monomer having a polar group can be useful for introducing a cross-linking point into the acrylic polymer and increasing the cohesive strength of the pressure-sensitive adhesive. The copolymerizable monomers may be used singly or in combination of two or more.

Specific non-limiting examples of copolymerizable monomers include the following.

Carboxy group-containing monomers: for example acrylic acid, methacrylic acid, carboxyethyl acrylate, carboxypentyl acrylate, itaconic acid, maleic acid, fumaric acid, crotonic acid, isocrotonic acid and the like.

Acid anhydride group-containing monomers: for example maleic anhydride, itaconic anhydride.

Hydroxyl group-containing monomers: for example, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, (meth)acrylic 4-hydroxybutyl acid, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, 12-hydroxylauryl (meth)acrylate, (4-hydroxy hydroxyalkyl (meth)acrylates such as methylcyclohexyl)methyl (meth)acrylate;

Monomers containing sulfonic or phosphoric acid groups: for example, styrenesulfonic acid, allylsulfonic acid, sodium vinylsulfonate, 2-(meth)acrylamido-2-methylpropanesulfonic acid, (meth)acrylamidopropanesulfonic acid, sulfo propyl (meth)acrylate, (meth)acryloyloxynaphthalenesulfonic acid, 2-hydroxyethyl acryloyl phosphate and the like.

Epoxy group-containing monomers: For example, epoxy group-containing acrylates such as glycidyl (meth)acrylate and 2-ethylglycidyl (meth)acrylate, allyl glycidyl ether, glycidyl ether (meth)acrylate, and the like.

Cyano group-containing monomers: for example acrylonitrile, methacrylonitrile and the like.

Isocyanate group-containing monomers: for example, 2-isocyanatoethyl (meth)acrylate and the like.

Amido group-containing monomers: for example, (meth)acrylamide; N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, N,N-dipropyl(meth)acrylamide, N,N-diisopropyl(meth) N,N-dialkyl(meth)acrylamides such as acrylamide, N,N-di(n-butyl)(meth)acrylamide, N,N-di(t-butyl)(meth)acrylamide; N-ethyl(meth)acrylamide , N-isopropyl (meth)acrylamide, N-butyl (meth)acrylamide, N-alkyl (meth)acrylamide such as Nn-butyl (meth)acrylamide; N-vinylcarboxylic acid amides such as N-vinylacetamide; monomers having a hydroxyl group and an amide group, such as 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, N-(4-hydroxybutyl)(meth) N-hydroxyalkyl (meth)acrylamides such as acrylamide; monomers having an alkoxy group and an amide group, such as N-methoxymethyl (meth)acrylamide, N-methoxyethyl (meth)acrylamide, N-butoxymethyl (meth)acrylamide N-alkoxyalkyl(meth)acrylamides such as N-(meth)acrylamide; N,N-dimethylaminopropyl(meth)acrylamide, N-(meth)acryloylmorpholine and the like.

Amino group-containing monomers: for example aminoethyl (meth)acrylate, N,N-dimethylaminoethyl (meth)acrylate, t-butylaminoethyl (meth)acrylate.

Monomers with epoxy groups: eg glycidyl (meth)acrylate, methylglycidyl (meth)acrylate, allyl glycidyl ether.

Monomers having a nitrogen atom-containing ring: for example, 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-vinyl thiazole, N-vinylisothiazole, N-vinylpyridazine and the like (for example, lactams such as N-vinyl-2-caprolactam);

Monomers having a succinimide skeleton: for example, N-(meth)acryloyloxymethylenesuccinimide, N-(meth)acryloyl-6-oxyhexamethylenesuccinimide, N-(meth)acryloyl-8-oxyhexamethylenesuccinimide and the like.

Maleimides: For example, N-cyclohexylmaleimide, N-isopropylmaleimide, N-laurylmaleimide, N-phenylmaleimide and the like.

Itaconimides: for example, N-methylitaconimide, N-ethylitaconimide, N-butylitaconimide, N-octylitaconimide, N-2-ethylhexylitaconimide, N-cyclohexylitaconimide, N-lauryl itaconimide and the like.

Aminoalkyl (meth)acrylates: for example, aminoethyl (meth)acrylate, N,N-dimethylaminoethyl (meth)acrylate, N,N-diethylaminoethyl (meth)acrylate, t (meth)acrylate - butylaminoethyl.

Alkoxy group-containing monomers: for example, 2-methoxyethyl (meth)acrylate, 3-methoxypropyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, propoxyethyl (meth)acrylate, (meth)acrylic acid Alkoxyalkyl (meth)acrylates (alkoxyalkyl (meth)acrylates) such as butoxyethyl and ethoxypropyl (meth)acrylate; methoxyethylene glycol (meth)acrylate, methoxypolyethylene glycol (meth)acrylate, (meth)acrylate alkoxyalkylene glycol (meth)acrylates (for example, alkoxypolyalkylene glycol (meth)acrylates) such as methoxypolypropylene glycol acrylate;

Alkoxysilyl group-containing monomers: such as 3-(meth)acryloxypropyltrimethoxysilane, 3-(meth)acryloxypropyltriethoxysilane, 3-(meth)acryloxypropylmethyldimethoxysilane, 3-(meth)acryloxy alkoxysilyl group-containing (meth)acrylates such as propylmethyldiethoxysilane; alkoxysilyl group-containing vinyl compounds such as vinyltrimethoxysilane and vinyltriethoxysilane;

Vinyl esters: For example, vinyl acetate, vinyl propionate and the like.

Vinyl ethers: For example, vinyl alkyl ethers such as methyl vinyl ether and ethyl vinyl ether.

Aromatic vinyl compounds: for example, styrene, α-methylstyrene, vinyltoluene and the like.

Olefins: For example, ethylene, butadiene, isoprene, isobutylene and the like.

(Meth)acrylic acid esters having an alicyclic hydrocarbon group: for example, cyclopentyl (meth)acrylate, cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, dicyclopentanyl (meth)acrylate, adamantyl (meth)acrylate, etc. alicyclic hydrocarbon group-containing (meth)acrylate.

(Meth)acrylic acid esters having an aromatic hydrocarbon group: For example, aromatic hydrocarbon group-containing (meth)acrylates such as phenyl (meth)acrylate, phenoxyethyl (meth)acrylate and benzyl (meth)acrylate.

In addition, heterocycle-containing (meth)acrylates such as tetrahydrofurfuryl (meth)acrylate, halogen atom-containing (meth)acrylates such as vinyl chloride and fluorine atom-containing (meth)acrylates, silicon atom-containing such as silicone (meth)acrylates (meth)acrylates, (meth)acrylic acid esters obtained from terpene compound derivative alcohols, and the like.

When such a copolymerizable monomer is used, the amount of use is not particularly limited, but it is usually appropriate to use 0.01% by weight or more of the total monomer components. From the viewpoint of better exhibiting the effect of using the copolymerizable monomer, the amount of the copolymerizable monomer used may be 0.1% by weight or more, or 0.5% by weight or more, based on the total monomer components. From the viewpoint of facilitating the balance of adhesive properties, the amount of the copolymerizable monomer to be used is generally 50% by weight or less, preferably 40% by weight or less, of the total monomer components.

In some embodiments, the monomer components that make up the acrylic polymer may include nitrogen atom-containing monomers. Thereby, the cohesive force of the pressure-sensitive adhesive can be increased, and the peeling force after the passage of time can be preferably improved. One suitable example of the nitrogen atom-containing monomer is a monomer having a nitrogen atom-containing ring. As the monomer having a nitrogen atom-containing ring, those exemplified above can be used, and examples thereof include N-vinyl cyclic amides represented by the following general formula (1).

Here, in general formula (1), R ¹ is a divalent organic group, specifically -(CH ₂ ) _n -. n is an integer from 2 to 7 (preferably 2, 3 or 4). Among them, N-vinyl-2-pyrrolidone can be preferably employed. Another suitable example of a monomer having a nitrogen atom is (meth)acrylamide.

The amount of the nitrogen atom-containing monomer (preferably a nitrogen atom-containing ring-containing monomer) is not particularly limited, and is, for example, 1% by weight or more, 3% by weight or more, 5% by weight or more, or 7% by weight or more of the total monomer components. can do. In one embodiment, the amount of the nitrogen atom-containing monomer used may be 10% by weight or more, 15% by weight or more, or 20% by weight or more of the total monomer components. In addition, the amount of the monomer having a nitrogen atom used is, for example, 40% by weight or less of the entire monomer component, and may be 35% by weight or less, 30% by weight or less, or 25% by weight or less. good too. In another aspect, the amount of the nitrogen atom-containing monomer used may be, for example, 20% by weight or less, or 15% by weight or less, of the total monomer components.

In some aspects, the monomer components that make up the acrylic polymer can include hydroxyl group-containing monomers. By using a hydroxyl group-containing monomer, the degree of cohesion and cross-linking (for example, cross-linking with an isocyanate cross-linking agent) of the pressure-sensitive adhesive can be adjusted favorably. The amount used when using a hydroxyl group-containing monomer is not particularly limited, and may be, for example, 0.01% by weight or more, 0.1% by weight or more, or 0.5% by weight or more of the total monomer components. It may be 1% by weight or more, 5% by weight or more, or 10% by weight or more. Further, from the viewpoint of suppressing the water absorption of the pressure-sensitive adhesive layer, in some embodiments, the amount of the hydroxyl group-containing monomer used is, for example, 40% by weight or less of the total monomer components, and 30% by weight or less. may be 25% by weight or less, or 20% by weight or less. In another aspect, the amount of the hydroxyl group-containing monomer used may be, for example, 15% by weight or less, 10% by weight or less, or 5% by weight or less of the total monomer components.

In the adhesive composition of one embodiment of the present invention, the monomer component of the acrylic polymer may or may not contain the alkoxyalkyl (meth)acrylates and alkoxypolyalkyleneglycol (meth)acrylates exemplified above. . In one aspect of the technology according to the present embodiment, the proportion of alkoxyalkyl (meth)acrylate in the monomer components of the acrylic polymer is less than 20% by weight, and the proportion of alkoxypolyalkyleneglycol (meth)acrylate is 20% by weight. is less than As a result, the pressure-sensitive adhesive layer can be easily formed into a sheet without problems such as gelation. By adopting the above monomer composition, the solid content concentration of the monomer mixture can be maintained within a predetermined range to obtain a desired high molecular weight substance (for example, a weight average molecular weight (Mw) of more than 30×10 ⁴ , typically Mw of 40×10 ⁴ ). above) can be preferably polymerized.

The proportion of alkoxyalkyl (meth)acrylate in the monomer component is preferably less than 10% by weight, more preferably less than 3% by weight, and even more preferably less than 1% by weight. In a particularly preferred embodiment, the monomer component is Substantially free of alkoxyalkyl (meth)acrylate (content 0-0.3% by weight). Similarly, the proportion of alkoxypolyalkylene glycol (meth)acrylate in the monomer component is preferably less than 10% by weight, more preferably less than 3% by weight, and even more preferably less than 1% by weight. , the monomer component does not substantially contain alkoxypolyalkylene glycol (meth)acrylate (content 0 to 0.3% by weight).

Further, in the monomer component of the acrylic polymer according to a preferred embodiment, the total ratio of alkoxyalkyl (meth)acrylate and alkoxypolyalkyleneglycol (meth)acrylate is limited to less than 20% by weight from the viewpoint of suppressing gelation. . The total proportion of the alkoxyalkyl (meth)acrylate and alkoxypolyalkylene glycol (meth)acrylate is more preferably less than 10% by weight, still more preferably less than 3% by weight, and particularly preferably less than 1% by weight. , the monomer component substantially does not contain alkoxyalkyl (meth)acrylates and alkoxypolyalkyleneglycol (meth)acrylates (content of 0 to 0.3% by weight).

Similarly, the monomer component of the acrylic polymer according to this embodiment may or may not contain alkoxy group-containing monomers at a rate of less than 20% by weight. The amount of the alkoxy group-containing monomer in the monomer component is preferably less than 10% by weight, more preferably less than 3% by weight, and still more preferably less than 1% by weight. In a particularly preferred embodiment, the monomer component is an alkoxy group Substantially free of contained monomers (content of 0 to 0.3% by weight).

In some embodiments, the proportion of the carboxy group-containing monomer in the monomer component of the acrylic polymer may be, for example, 2% by weight or less, 1% by weight or less, or 0.5% by weight or less (e.g., 0.1% by weight or less). % by weight). It is not necessary to substantially use a carboxy group-containing monomer as a monomer component of the acrylic polymer. Here, "substantially no carboxy group-containing monomer is used" means that no carboxy group-containing monomer is used at least intentionally. An acrylic polymer having such a composition tends to have high water resistance and reliability, and can have metal corrosion prevention properties for adherends containing metal.

Moreover, in a preferred embodiment, the monomer component of the acrylic polymer has a limited proportion of hydrophilic monomers. Here, the "hydrophilic monomer" in the present specification includes a carboxy group-containing monomer, an acid anhydride group-containing monomer, a hydroxyl group-containing monomer, a monomer having a nitrogen atom (typically, an amide group-containing monomer such as (meth)acrylamide). monomers, nitrogen atom-containing ring-containing monomers such as N-vinyl-2-pyrrolidone) and alkoxy group-containing monomers (typically alkoxyalkyl (meth)acrylates and alkoxypolyalkyleneglycol (meth)acrylates) do.

In this embodiment, the proportion of the hydrophilic monomer in the monomer components of the acrylic polymer is preferably 32% by weight or less, and may be, for example, 30% by weight or less, or may be 28% by weight or less. Although not particularly limited, the proportion of the hydrophilic monomer in the monomer component of the acrylic polymer may be 1% by weight or more, 10% by weight or more, or 20% by weight or more. may

In some aspects, the monomer component that constitutes the acrylic polymer may contain an alicyclic hydrocarbon group-containing (meth)acrylate. Thereby, the cohesive force of the pressure-sensitive adhesive can be increased, and the peeling force after the passage of time can be improved. As the alicyclic hydrocarbon group-containing (meth)acrylate, those exemplified above can be used, and for example, cyclohexyl acrylate and isobornyl acrylate can be preferably employed.

The amount of the alicyclic hydrocarbon group-containing (meth)acrylate used is not particularly limited, and can be, for example, 1% by weight or more, 3% by weight or more, or 5% by weight or more of the total monomer components. In one aspect, the amount of the alicyclic hydrocarbon group-containing (meth)acrylate used may be 10% by weight or more, or 15% by weight or more, of the total monomer components. The upper limit of the amount of the alicyclic hydrocarbon group-containing (meth)acrylate used is suitably about 40% by weight or less, and may be, for example, 30% by weight or less, or 25% by weight or less (e.g., 15% by weight). % or less, or even 10% by weight or less).

The composition of the monomer components constituting the acrylic polymer can be set so that the glass transition temperature Tg determined by the Fox equation based on the composition of the monomer components is −75° C. or higher and 10° C. or lower. In some embodiments, the Tg is suitably 0° C. or less, preferably −10° C. or less, or −20° C. or less or −30° C. from the viewpoint of cohesiveness, impact resistance, or the like. It may be below. The above Tg may be, for example, -60°C or higher, -50°C or higher, -45°C or higher, or -40°C or higher.

Here, the Fox equation is a relational expression between the Tg of a copolymer and the glass transition temperature Tgi of a homopolymer obtained by homopolymerizing each of the monomers constituting the copolymer, as shown below. .
1/Tg=Σ(Wi/Tgi)

In the above Fox formula, Tg is the glass transition temperature of the copolymer (unit: K), Wi is the weight fraction of the monomer i in the copolymer (copolymerization ratio based on weight), and Tgi is the content of the monomer i. It represents the glass transition temperature (unit: K) of a homopolymer.

As the glass transition temperature of the homopolymer used for calculating the Tg, the value described in the known materials shall be used. For example, for the monomers listed below, the following values are used as the glass transition temperatures of the homopolymers of the monomers.

2-ethylhexyl acrylate -70°C
n-butyl acrylate -55°C
Isostearyl acrylate -18°C
Methyl methacrylate 105°C
Methyl acrylate 8°C
Cyclohexyl acrylate 15°C
N-vinyl-2-pyrrolidone 54°C
2-hydroxyethyl acrylate -15°C
4-hydroxybutyl acrylate -40°C
Dicyclopentanyl methacrylate 175°C
Isobornyl acrylate 94°C
Acrylic acid 106°C
Methacrylic acid 228°C

For the glass transition temperatures of homopolymers of monomers other than those exemplified above, the values described in "Polymer Handbook" (3rd edition, John Wiley & Sons, Inc., 1989) shall be used. When multiple types of values are described in this document, the highest value is adopted.

For monomers for which glass transition temperatures of homopolymers are not described in the above Polymer Handbook, the values obtained by the following measuring method are used (see Japanese Patent Application Laid-Open No. 2007-51271).

Specifically, 100 parts by weight of a monomer, 0.2 parts by weight of azobisisobutyronitrile and 200 parts by weight of ethyl acetate as a polymerization solvent were added to a reactor equipped with a thermometer, a stirrer, a nitrogen inlet tube and a reflux condenser. It is put in and stirred for 1 hour while nitrogen gas is circulated. After oxygen is removed from the polymerization system in this manner, the temperature is raised to 63° C. and the reaction is allowed to proceed for 10 hours. Then, it is cooled to room temperature to obtain a homopolymer solution having a solid concentration of 33% by weight. Next, this homopolymer solution is cast-coated on a release liner and dried to prepare a test sample (sheet-like homopolymer) having a thickness of about 2 mm. This test sample is punched out into a disk shape with a diameter of 7.9 mm, sandwiched between parallel plates, and subjected to shear strain at a frequency of 1 Hz using a viscoelasticity tester (ARES, manufactured by Rheometrics Co., Ltd.) while applying a temperature range of -70 to 150 ° C. , the viscoelasticity is measured in shear mode at a heating rate of 5° C./min, and the peak top temperature of tan δ is defined as the Tg of the homopolymer.

Although the acrylic polymer according to the present embodiment is not particularly limited, it preferably has an SP value of 23.0 (MJ/m ³ ) ^1/2 or less. The above SP value is more preferably 21.0 (MJ/m ³ ) ^1/2 or less (for example, 20.0 (MJ/m ³ ) ^1/2 or less). The ^{lower limit} of the ^{SP value} is not particularly limited. Yes, preferably 18.0 (MJ/m ³ ) ^1/2 or more.

The SP value of the acrylic polymer is calculated according to Fedors' calculation method ["Polymer Engineering and Science (POLYMER ENG. &SCI.)", Vol. 14, No. 2 (1974), pp. 148-154. ] i.e. the expression:
SP value δ=(ΣΔe/ΣΔv) ^1/2
(wherein Δe is the vaporization energy Δe of each atom or atomic group at 25° C., and Δv is the molar volume of each atom or atomic group at the same temperature); An acrylic polymer having the above SP value can be obtained by appropriately determining the monomer composition based on the common technical knowledge of those skilled in the art.

The pressure-sensitive adhesive composition contains the monomer component having the composition described above in the form of a polymer, an unpolymer (that is, a form in which the polymerizable functional group is unreacted), or a mixture thereof. The pressure-sensitive adhesive composition includes a water-dispersed pressure-sensitive adhesive composition in which the pressure-sensitive adhesive (adhesive component) is dispersed in water, a solvent-based pressure-sensitive adhesive composition in which the pressure-sensitive adhesive is contained in an organic solvent, and a An active energy ray-curable adhesive composition prepared to form an adhesive by curing with an active energy ray, a hot-melt adhesive that is coated in a heat-melted state and forms an adhesive when cooled to around room temperature It can be in various forms such as compositions. A preferred embodiment of the pressure-sensitive adhesive composition is a solvent-based pressure-sensitive adhesive composition or a solvent-free pressure-sensitive adhesive composition. The solventless pressure-sensitive adhesive compositions include active energy ray-curable pressure-sensitive adhesive compositions and hot-melt pressure-sensitive adhesive compositions.

In the polymerization, a known or commonly used thermal polymerization initiator or radical photopolymerization initiator can be used depending on the polymerization method, polymerization mode, and the like. Such polymerization initiators can be used singly or in combination of two or more.

Although the thermal polymerization initiator is not particularly limited, for example, an azo polymerization initiator, a peroxide initiator, a redox initiator obtained by combining a peroxide and a reducing agent, and a substituted ethane initiator. etc. can be used.

More specifically, for example, 2,2′-azobisisobutyronitrile (AIBN), 2,2′-azobis(2-methylpropionamidine) disulfate, 2,2′-azobis(2-amidinopropane ) dihydrochloride, 2,2′-azobis[2-(5-methyl-2-imidazolin-2-yl)propane]dihydrochloride, 2,2′-azobis(N,N′-dimethyleneisobutyramidine), 2 , 2′-azobis[N-(2-carboxyethyl)-2-methylpropionamidine]hydrate; azo initiators such as hydrate; persulfates such as potassium persulfate and ammonium persulfate; benzoyl peroxide, t-butyl Peroxide-based initiators such as hydroperoxides, hydrogen peroxide; substituted ethane-based initiators such as phenyl-substituted ethane; e.g. persulfate in combination with sodium bisulfite, peroxide in combination with sodium ascorbate. Redox initiators such as; Thermal polymerization can be preferably carried out at a temperature of, for example, about 20 to 100°C (typically 40 to 80°C).

The photoradical polymerization initiator is not particularly limited, but examples include 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propan-1-one, 1-hydroxy-cyclohexyl-phenyl-ketone, benzophenone, 2,2-dimethoxy-1,2-diphenylethan-1-one, 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide, 2,4,6-trimethyl Benzoyl-phenylethoxy-phosphine oxide, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone-1,2-hydroxy-2-methyl-1-phenyl-propan-1-one, 2 -methyl-1-(4-methylthiophenyl)-2-morpholinopropan-1-one, benzoin methyl ether, benzoin ethyl ether, benzoin isobutyl ether, benzoin isopropyl ether, bis(2,4,6-trimethylbenzoyl)- Phenylphosphine oxide, 2-hydroxy-2-methyl-[4-(1-methylvinyl)phenyl]propanol oligomer, 2-hydroxy-2-methyl-1-phenyl-1-propanone, isopropylthioxanthone, o-benzoyl benzoin methyl acid, [4-(methylphenylthio)phenyl]phenylmethane, 2,4-diethylthioxanthone, 2-chlorothioxanthone, ethylanthraquinone, benzophenone ammonium salt, thioxanthone ammonium salt, bis(2,6-dimethylbenzoyl)-2 ,4,4-trimethyl-pentylphosphine oxide, 2,4,6-trimethylbenzophenone, 4-methylbenzophenone, 4,4'-bisdiethylaminobenzophenone, 1,4-dibenzoylbenzene, 10-butyl-2-chloroacrylate Don, 2,2′-bis(o-chlorophenyl)-4,5,4′,5′-tetrakis(3,4,5-trimethoxyphenyl)-1,2′-biimidazole, 2,2′- Bis(o-chlorophenyl)-4,5,4',5'-tetraphenyl-1,2'-biimidazole, 2-benzoylnaphthalene, 4-benzoylbiphenyl, 4-benzoyldiphenyl ether, acrylated benzophenone, bis(η5 -2,4-cyclopentadien-1-yl)-bis[2,6-difluoro-3-(1H-pyrrol-1-yl)-phenyl]titanium, o-methylben zoyl benzoate, p-dimethylaminobenzoic acid ethyl ester, p-dimethylaminobenzoic acid isoamyl ethyl ester, active tertiary amine, arbazol-phenone photopolymerization initiator, acridine photopolymerization initiator, triazine photopolymerization initiator, Examples include benzoyl-based photopolymerization initiators. These are used alone or in combination of two or more.

The amount of such a thermal polymerization initiator or radical photopolymerization initiator to be used is not particularly limited, and can be a normal amount to be used according to the polymerization method, polymerization mode, and the like. For example, about 0.001 to 5 parts by weight (typically about 0.01 to 2 parts by weight, for example about 0.01 to 1 part by weight) of a polymerization initiator is used with respect to 100 parts by weight of the monomer to be polymerized. be able to.

For the above polymerization, various conventionally known chain transfer agents (which can also be understood as molecular weight modifiers or polymerization degree modifiers) can be used as needed. Mercaptans such as n-dodecylmercaptan, t-dodecylmercaptan, thioglycolic acid and α-thioglycerol can be used as the chain transfer agent. Alternatively, a chain transfer agent containing no sulfur atom (non-sulfur chain transfer agent) may be used.

Specific examples of non-sulfur chain transfer agents include anilines such as N,N-dimethylaniline and N,N-diethylaniline; terpenoids such as α-pinene and terpinolene; α-methylstyrene and α-methylstyrene dimer. styrenes such as dibenzylideneacetone, cinnamyl alcohol, compounds having a benzylidenyl group such as cinnamylaldehyde; hydroquinones such as hydroquinone and naphthohydroquinone; quinones such as benzoquinone and naphthoquinone; 2,3-dimethyl-2-butene , olefins such as 1,5-cyclooctadiene; alcohols such as phenol, benzyl alcohol and allyl alcohol; benzyl hydrogens such as diphenylbenzene and triphenylbenzene;

A chain transfer agent can be used individually by 1 type or in combination of 2 or more types. When a chain transfer agent is used, the amount used can be, for example, about 0.01 to 1 part by mass with respect to 100 parts by mass of the monomer component. The technique according to the present embodiment can also be preferably practiced without using a chain transfer agent.

The molecular weight of the acrylic polymer obtained by appropriately adopting the various polymerization methods described above is not particularly limited, and can be set within an appropriate range according to the required performance. The weight-average molecular weight (Mw) of the acrylic polymer is usually about 10×10 ⁴ or more (for example, 20×10 ⁴ or more), and from the viewpoint of balancing cohesive strength and adhesive strength in a well-balanced manner, more than 30×10 ⁴ It is appropriate to The acrylic polymer according to one aspect is preferably 40×10 ⁴ or more (typically about 50×10 ⁴ or more, for example about 55×10 ⁴ or more) from the viewpoint of obtaining good adhesion reliability even in a high-temperature environment. ). According to a preferred aspect of the technology according to the present embodiment, since gelation can be suppressed by designing the monomer composition, it is possible to obtain a high molecular weight substance within the above range with good productivity by setting an appropriate solid content concentration. The upper limit of Mw of the acrylic polymer can usually be approximately 500×10 ⁴ or less (for example, approximately 150×10 ⁴ or less). The above Mw may be approximately 75×10 ⁴ or less.

Here, Mw refers to a value converted to standard polystyrene obtained by gel permeation chromatography (GPC). As the GPC apparatus, for example, model name "HLC-8320GPC" (column: TSKgelGMH-H(S), manufactured by Tosoh Corporation) may be used. The same applies to the examples described later. The above Mw can be the Mw of the acrylic polymer in either the pressure-sensitive adhesive composition or the pressure-sensitive adhesive layer.

A pressure-sensitive adhesive composition according to some embodiments may be an active energy ray-curable pressure-sensitive adhesive composition. Examples of active energy rays here include light such as ultraviolet rays, visible rays, and infrared rays, and radiation such as α rays, β rays, γ rays, electron beams, neutron rays, and X rays. Energy rays having energy capable of causing chemical reactions such as reactions, cross-linking reactions, decomposition of initiators, etc. can be mentioned.

In the pressure-sensitive adhesive composition of one embodiment of the present invention, the timing of curing the active energy ray-curable pressure-sensitive adhesive composition and the timing of discoloration or coloring are set so that discoloration or coloring is possible at any timing. It is preferable to be able to control them differently. That is, the timing of the chemical reaction such as the polymerization reaction, the crosslinking reaction, or the decomposition of the initiator of the active energy ray-curable pressure-sensitive adhesive composition reacts with the photoacid generator or the photobase generator described later, and the leuco dye is formed. It is preferable to select the type of each component so that the timing of discoloration or coloring does not overlap. In other words, the energy ray that causes chemical reactions such as the polymerization reaction, the cross-linking reaction, and the decomposition of the initiator has a wavelength that causes the reaction with the energy ray that reacts with the photoacid generator and the photobase generator described later. It is preferred to design the compositions to be different.

A suitable example of the active energy ray-curable pressure-sensitive adhesive composition is a photocurable pressure-sensitive adhesive composition. A photocurable pressure-sensitive adhesive composition has the advantage that even a thick pressure-sensitive adhesive layer can be easily formed. Among them, an ultraviolet curable pressure-sensitive adhesive composition is preferred.

Typically, the photocurable pressure-sensitive adhesive composition contains at least part of the monomer components of the composition (may be part of the types of monomers or part of the amount). It is contained in the form of a polymer. The polymerization method for forming the polymer is not particularly limited, and conventionally known various polymerization methods can be appropriately employed. For example, thermal polymerization such as solution polymerization, emulsion polymerization, bulk polymerization (typically performed in the presence of a thermal polymerization initiator); photopolymerization performed by irradiating light such as ultraviolet rays (typically, conducted in the presence of a photoradical polymerization initiator); radiation polymerization conducted by irradiating radiation such as β-rays and γ-rays; Among them, photopolymerization is preferred.

A photocurable pressure-sensitive adhesive composition according to a preferred embodiment contains a partially polymerized monomer component. Such a partial polymer is typically a mixture of a polymer derived from the monomer component and an unreacted monomer, and preferably presents a syrup (viscous liquid). Hereinafter, the partial polymer having such properties is sometimes referred to as "monomer syrup" or simply "syrup". The polymerization method for partially polymerizing the monomer component is not particularly limited, and various polymerization methods as described above can be appropriately selected and used. A photopolymerization method can be preferably employed from the viewpoint of efficiency and convenience. According to photopolymerization, the polymerization conversion rate of the monomer component (monomer conversion) can be easily controlled by the polymerization conditions such as the irradiation amount of light (light amount).

The polymerization conversion rate of the monomer mixture in the partially polymerized product is not particularly limited. The polymerization conversion rate can be, for example, about 70% by weight or less, preferably about 60% by weight or less. From the viewpoint of ease of preparation and coating properties of the pressure-sensitive adhesive composition containing the partially polymerized product, the polymerization conversion rate is usually about 50% by weight or less, and about 40% by weight or less (for example, about 35% by weight). % by weight or less) is preferred. Although the lower limit of the polymerization conversion rate is not particularly limited, it is typically about 1% by weight or more, and usually about 5% by weight or more is suitable.

A pressure-sensitive adhesive composition containing a partially polymerized product of a monomer component can be obtained, for example, by partially polymerizing a monomer mixture containing all of the monomer components used in the preparation of the pressure-sensitive adhesive composition by an appropriate polymerization method (e.g., photopolymerization method). can be obtained by In addition, the pressure-sensitive adhesive composition containing a partial polymer of monomer components is a partial polymer or a complete polymer of a monomer mixture containing a part of the monomer components used in the preparation of the pressure-sensitive adhesive composition, and the remaining monomers. It may be a mixture with a component or a partial polymer thereof. In the present specification, the term "completely polymerized product" means that the polymerization conversion rate is over 95% by weight.

(leuco dye)
The adhesive composition of one embodiment of the present invention contains a leuco dye. As used herein, a leuco dye refers to an organic dye whose color tone reversibly changes with oxidation-reduction. The absorption wavelength may change depending on the pH. More specifically, it refers to a reduced dye having one or more hydrogen atoms that forms a dye and develops color by adding electrons or removing electrons. A leuco dye is colorless or weakly colored in a neutral or alkaline medium, but when reacted with an acidic substance or an electron-withdrawing substance, the lactone ring is opened and colored as shown in FIG. By selecting a leuco dye that is substantially colorless or has a weak color before electrons are removed, it is possible to observe the change in coloration remarkably.

In this embodiment, the leuco dye is colored by an acid generated by irradiating an active energy ray to a photoacid generator, which will be described later.

In the present embodiment, the leuco dye can be colored by opening the lactone ring, and then reacting with a base to close the lactone ring and decolorize the leuco dye. The above base can also be generated by irradiating a photobase generator, which will be described later, with an active energy ray.

Examples of leuco dyes according to the present embodiment include leuco compounds such as phthalide dyes (indolinophthalide-based, triphenylmethanephthalide-based, etc.), fluoran dyes, triphenylmethane dyes, phenothiazine dyes, auramine dyes, and spiropyran dyes. is mentioned.

The leuco dye is particularly preferably at least one leuco dye selected from the group consisting of phthalide dyes and fluoran dyes from the viewpoint of excellent color development.

Specific examples of leuco dyes include the following compounds.

2'-anilino-6'-(N,N-dipentan-1-ylamino)-3'-methyl-3H-spiro[isobenzofuran-1,9'-xanthene]-3-one, 2-anilino-3- methyl-6-dibutylaminofluorane, 2-anilino-3-methyl-6-dipentylaminofluorane, 2-anilino-3-methyl-6-[ethyl(4-methylphenyl)amino]fluorane, 3,3- Bis(p-dimethylaminophenyl)-phthalide, 3,3-bis(p-dimethylaminophenyl)-6-dimethylaminophthalide (alias: crystal violet lactone), 3,3-bis(p-dimethylaminophenyl) -6-diethylaminophthalide, 3,3-bis(p-dimethylaminophenyl)-6-chlorophthalide, 3,3-bis(p-dibutylaminophenyl)phthalide, 3-cyclohexylamino-6-chlorofluorane, 3 -dimethylamino-5,7-dimethylfluorane, 3-(N-methyl-N-isobutyl)-6-methyl-7-anilinofluorane, 3-(N-ethyl-N-isoamyl)-6-methyl -7-anilinofluorane, 3-diethylamino-7-chlorofluorane, 3-diethylamino-7-methylfluorane, 3-diethylamino-7,8-benzfluorane, 3-diethylamino-6-methyl-7- Chlorfluorane, 3-(Np-tolyl-N-ethylamino)-6-methyl-7-anilinofluorane, 3-pyrrolidino-6-methyl-7-anilinofluorane, 2-{N- (3′-trifluoromethylphenyl)amino}-6-diethylaminofluorane, 2-{3,6-bis(diethylamino)-9-(o-chloroanilino)xantylbenzoic acid lactam}3-diethylamino-6-methyl- 7-(m-trichloromethylanilino)fluorane, 3-diethylamino-7-(o-chloroanilino)fluorane, 3-dibutylamino-7-(o-chloroanilino)fluorane, 3-(N-methyl-N-amylamino) -6-methyl-7-anilinofluorane, 3-(N-methyl-N-cyclohexylamino)-6-methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7-anilinofluorane , 3-diethylamino-6-methyl-7-(2′,4′-dimethylanilino)fluorane, 3-(N,N-diethylamino)-5-methyl-7-(N,N-dibenzylamino)fluorane , enzoyl leuco methylene blue, 6′-chloro-8′-methoxy-benzoindolino-spiropyran, 6′-bromo-3′-methoxy-benzoindolino-spiropyran, 3-(2′-hydroxy-4′-dimethylamino Phenyl)-3-(2'-methoxy-5'-chlorophenyl)phthalide, 3-(2'-hydroxy-4'-dimethylaminophenyl)-3-(2'-methoxy-5'-nitrophenyl)phthalide , 3-(2′-hydroxy-4′-diethylaminophenyl)-3-(2′-methoxy-5′-methylphenyl)phthalide, 3-(2′-methoxy-4′-dimethylaminophenyl)-3- (2′-hydroxy-4′-chloro-5′-methylphenyl)phthalide, 3-morpholino-7-(N-propyl-trifluoromethylanilino)fluorane, 3-pyrrolidino-7-trifluoromethylanilinoflu Olan, 3-diethylamino-5-chloro-7-(N-benzyl-trifluoromethylanilino)fluorane, 3-pyrrolidino-7-(di-p-chlorophenyl)methylaminofluorane, 3-diethylamino-5- Chlor-7-(α-phenylethylamino)fluorane, 3-(N-ethyl-p-toluidino)-7-(α-phenylethylamino)fluorane, 3-diethylamino-7-(o-methoxycarbonylphenylamino) Fluorane, 3-diethylamino-5-methyl-7-(α-phenylethylamino)fluorane, 3-diethylamino-7-piperidinofluorane, 2-chloro-3-(N-methyltoluidino)-7-(p- n-butylanilino)fluorane, 3-(N-methyl-N-isopropylamino)-6-methyl-7-anilinofluorane, 3-dibutylamino-6-methyl-7-anilinofluorane, 3,6- Bis(dimethylamino)fluorene spiro(9,3′)-6′-dimethylaminophthalide, 3-(N-benzyl-N-cyclohexylamino)-5,6-benzo-7-α-naphthylamino-4′ -bromofluorane, 3-diethylamino-6-chloro-7-anilinofluorane, 3-{N-ethyl-N-(2-ethoxypropyl)amino}-6-methyl-7-anilinofluorane, 3 -{N-ethyl-N-tetrahydrofurfurylamino}-6-methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7-mesitidino-4',5'-benzofluorane, 3- (p-dimethylaminophenyl)-3-{1,1-bis(p-dimethylaminophenyl)ethylene-2-yl}phthalide, 3-(p-dimethylaminophenyl)-3-{1,1-bis( p-dimethylaminophenyl)ethylene-2-yl}-6-dimethylaminophthalide, 3-(p-dimethylaminophenyl)-3-(1-p-dimethylaminophenyl-1-phenylethylene-2-yl) phthalide, 3-(p-dimethylaminophenyl)-3-(1-p-dimethylaminophenyl-1-p-chlorophenylethylene-2-yl)-6-dimethylaminophthalide, 3-(4'-dimethylamino -2′-methoxy)-3-(1″-p-dimethylaminophenyl-1″-p-chlorophenyl-1″,3″-butadien-4″-yl)benzophthalide, 3-(4′-dimethylamino- 2′-benzyloxy)-3-(1″-p-dimethylaminophenyl-1″-phenyl-1″,3″-butadien-4″-yl)benzophthalide, 3-dimethylamino-6-dimethylamino-fluorene -9-spiro-3'(6'-dimethylamino)phthalide, 6-(diethylamino)-2-[(3-trifluoromethyl)anilino]xanthene-9-spiro-3'-phthalide, 3,3-bis {2-(p-dimethylaminophenyl)-2-(p-methoxyphenyl)ethenyl}-4,5,6,7-tetrachlorophthalide, 3-bis{1,1-bis(4-pyrrolidinophenyl) ) ethylene-2-yl}-5,6-dichloro-4,7-dibromophthalide, bis(p-dimethylaminostyryl)-1-naphthalenesulfonylmethane, bis(p-dimethylaminostyryl)-1-p- Tolylsulfonylmethane.

The leuco dyes according to the present embodiment may be used singly or in combination of two or more.

In an embodiment of the present invention, the leuco dye is preferably 0.01 to 30 parts by mass, more preferably 0.1 to 30 parts by mass, per 100 parts by mass of the base polymer. More preferably 20 parts by mass, more preferably 1 to 10 parts by mass. Within the above range, significant discoloration or coloring due to the leuco dye can be observed.

(Photoacid generator)
The adhesive composition of one embodiment of the present invention contains a photoacid generator. As used herein, the photoacid generator is not limited to light such as ultraviolet light, visible light, and infrared light, and active energy such as radiation such as α-rays, β-rays, γ-rays, electron beams, neutron rays, and X-rays. It is a compound that can generate an acid (cation) when irradiated with radiation. Since the photoacid generator generates acid only after irradiation with the active energy ray, the adhesive layer or adhesive sheet obtained using the adhesive composition can be discolored at any time by using it together with the leuco dye. Or it can be colored.

The photoacid generator is not particularly limited as long as it is a compound capable of generating an acid (cation) by irradiation with an active energy ray. Oximidosulfonates, sulfonic acid ester compounds, halomethyl-substituted S-triazine derivatives, and the like.

From the viewpoint of good compatibility with other components of the pressure-sensitive adhesive composition according to the present invention, the photoacid generator is, in particular, a sulfonium salt compound, an iodonium salt compound, and an aromatic N-oxyimide sulphate. Preferably, it is at least one compound selected from the group consisting of phonates.

Specific examples of sulfonium salt compounds include dimethylphenacylsulfonium, dimethylbenzylsulfonium, dimethyl-4-hydroxyphenylsulfonium, dimethyl-4-hydroxynaphthylsulfonium, dimethyl-4,7-dihydroxynaphthylsulfonium, and dimethyl-4. , 8-dihydroxynaphthylsulfonium, triphenylsulfonium, p-tolyldiphenylsulfonium, p-tert-butylphenyldiphenylsulfonium, diphenyl-4-phenylthiophenylsulfonium and other cations, chloride, bromide, p-toluenesulfonate, trifluoro Salts composed of anions such as romethanesulfonate, tetrafluoroborate, tetrakispentafluorophenylborate, tetrakispentafluorophenylgallate, hexafluorophosphate, hexafluoroarsenate, hexafluoroantimonate, nonafluorobutanesulfonate, etc. .

Examples of iodonium salt compounds include diphenyliodonium, bis(p-chlorophenyl)iodonium, ditolyliodonium, bis(p-tert-butylphenyl)iodonium, p-isopropylphenyl-p-methylphenyliodonium, bis(m-nitro cations such as phenyl)iodonium, p-tert-butylphenylphenyliodonium, p-methoxyphenylphenyliodonium, bis(p-methoxyphenyl)iodonium, p-octyloxyphenylphenyliodonium, p-phenoxyphenylphenyliodonium, chloride, Bromide, p-toluenesulfonate, trifluoromethanesulfonate, tetrafluoroborate, tetrakispentafluorophenylborate, tetrakispentafluorophenylgallate, hexafluorophosphate, hexafluoroarsenate, hexafluoroantimonate, nonafluorobutanesulfonate, etc. and an anion of

Examples of aromatic N-oxyimide sulfonates include N-(trifluoromethylsulfonyloxy)succinimide, N-(trifluoromethylsulfonyloxy)phthalimide, N-(trifluoromethylsulfonyloxy)diphenylmaleimide, N- (trifluoromethylsulfonyloxy)bicyclohept-5-ene-2,3-dicarboximide, N-(trifluoromethylsulfonyloxy)naphthylimide and the like.

Sulfonic acid ester compounds include, for example, benzoin tosylate, α-methylolbenzoin tosylate, o-nitrobenzyl p-toluenesulfonate, p-nitrobenzyl-9,10-diethoxyanthracene-2-sulfonate, and the like. . Specific examples of halomethyl-substituted S-triazine derivatives include 2,4,6-tris(trichloromethyl)-S-triazine, 2-methyl-4,6-bis(trichloromethyl)-S-triazine, 2-phenyl -4,6-bis(trichloromethyl)-S-triazine, 2-methyl-4,6-bis(tribromomethyl)-S-triazine and the like.

In an embodiment of the present invention, the photoacid generator is preferably 0.001 to 30 parts by mass, more preferably 0.01 to 25 parts by mass, per 100 parts by mass of the base polymer. It is more preferably from 0.1 to 20 parts by mass, more preferably from 0.1 to 20 parts by mass. Within the above range, acid can be efficiently generated by active energy ray irradiation, and discoloration or coloring can be observed remarkably.

(Photobase generator)
The adhesive composition of one embodiment of the present invention may contain a photobase generator. The photobase generator is not limited to light such as ultraviolet rays, visible rays, and infrared rays, and is irradiated with active energy rays such as α rays, β rays, γ rays, electron beams, neutron rays, and radiation such as X rays. It is a compound that can generate a base (anion) by Since the photobase generator generates a base only after being irradiated with the active energy ray, the leuco dye can be reduced at any timing after the leuco dye is colored to eliminate the coloration.

When the pressure-sensitive adhesive composition of one embodiment of the present invention contains a photobase generator, the photobase generator generates a base at the same timing as the photoacid generator generates acid by irradiation with active energy rays. It is preferable to set the combination of the photoacid generator and the photobase generator so as not to cause the above-mentioned photoacid generator and photobase generator. That is, it is preferable to design the photobase generator so that a base is generated by a different type of active energy ray than the active energy ray required for the photoacid generator to generate an acid.

The photobase generator is not particularly limited as long as it is a compound capable of generating a base (anion) upon irradiation with an active energy ray. Examples include transition metal complexes, compounds having a benzyl carbamate structure, ortho-substituted nitrobenzene compounds having a structure, oximes, imidazole derivatives, benzoin compounds, compounds having an N-formylated aromatic amino group, compounds having an N-acylated aromatic amino group, compounds having an alkoxybenzylcarbamate group, 1, Including compounds having a 4-dihydropyridine skeleton, oxime esters, quaternary ammonium salts and the like.

The photobase generator according to the present embodiment is preferably 0.001 to 30 parts by mass, more preferably 0.01 to 25 parts by mass, per 100 parts by mass of the base polymer. More preferably, it is 20 parts by mass. Within the above range, a base can be efficiently generated by irradiation with active energy rays, and the colored pressure-sensitive adhesive sheet can be decolored.

(Peel strength increasing agent)
The pressure-sensitive adhesive composition of one embodiment of the present invention may contain a peel strength increasing agent. The release force increasing agent has a function of increasing the release force of the adhesive sheet from the adherend after the surface (adhesive surface) of the adhesive layer formed from the adhesive composition is attached to the adherend. can be appropriately selected and used. For example, a known silane coupling agent can be used as the peel strength increasing agent. The release strength increasing agent is preferably contained in the adhesive composition (and thus the adhesive layer) in free form. Typically, it is preferred that the peel strength increasing agent does not chemically bond with other constituents that may be contained in the pressure-sensitive adhesive composition (and thus the pressure-sensitive adhesive layer). The release force increasing agent contained in the pressure-sensitive adhesive composition in such a form can effectively contribute to the improvement of the release force.

A silane coupling agent is typically a compound containing a functional group X and a functional group Y in one molecule, wherein the functional group X is an alkoxysilyl group. The alkoxysilyl group is a functional group having at least one alkoxy group on the silicon atom. By supplying a silane coupling agent to the surface of the adhesive layer after attachment to the adherend, the silanol groups generated by hydrolysis of the alkoxy groups react with the hydroxyl groups on the adherend surface, thereby It is possible to increase the peel strength of the pressure-sensitive adhesive sheet from the adherend. The alkoxysilyl group is hydrolyzed to form a silanol group that reacts with the hydroxyl group on the surface of the adherend. Therefore, the alkoxysilyl group is a precursor of the group that reacts with the hydroxyl group.

The alkoxy group constituting the alkoxysilyl group is typically a methoxy group or an ethoxy group. Methoxy groups, which are more hydrolyzable, are usually preferred. The alkoxysilyl group may be a trialkoxysilyl group or a dialkoxysilyl group. A silane coupling agent having a trialkoxysilyl group can be preferably employed in some embodiments from the viewpoint of increasing the peel strength increasing effect.

Functional group Y is, for example, an epoxy group, an amino group, an isocyanate group (which may constitute an isocyanurate), an acetoacetyl group, a (meth)acryloyl group, a mercapto group, a vinyl group, a halogenated alkyl group, or the like. can be Examples of silane coupling agents having such a functional group Y include, for example, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 2-( Epoxy group-containing silane coupling agents such as 3,4-epoxycyclohexyl)ethyltrimethoxysilane; -aminoethyl) 3-aminopropylmethyldimethoxysilane and other amino group-containing silane coupling agents; for example, 3-isocyanatopropyltriethoxysilane, tris(trimethoxysilylpropyl)isocyanurate and other isocyanate group-containing silane coupling agents; acetoacetyl group-containing silane coupling agents such as acetoacetyl group-containing trimethoxysilane; acryloyl group-containing silane coupling agents; vinyl group-containing silane coupling agents such as vinyltrimethoxysilane and vinyltriethoxysilane; mercapto group-containing silanes such as 3-methacryloxypropylmethyldimethoxysilane and 3-methacryloxypropyltrimethoxysilane coupling agents; halogenated alkyl group-containing silane coupling agents such as 3-chloropropyltrimethoxysilane; Among them, epoxy group-containing silane coupling agents such as glycidoxypropyltrialkoxysilane (eg, 3-glycidoxypropyltrimethoxysilane and 3-glycidoxypropyltriethoxysilane) are preferred.

As the silane coupling agent, one having a functional group Y that reacts with the functional group y contained in the pressure-sensitive adhesive layer can be used. From the viewpoint of reactivity at room temperature, a combination of a carboxyl group as the functional group y and a silane coupling agent having an epoxy group as the functional group Y can be mentioned. Examples of other combinations include a combination of an amino group and an epoxy group, a combination of a hydroxyl group and an epoxy group, a combination of a carboxy group and an amino group, a combination of an isocyanate group and an amino group, and a combination of a sulfo group and an amino group. A combination etc. are mentioned. On the other hand, in some embodiments, the pressure-sensitive adhesive composition contains a silane from the viewpoint of maintaining the release force increasing agent in a free state in the pressure-sensitive adhesive composition, thereby facilitating migration of the release force increasing agent to the surface. It may not have a functional group y (eg, carboxyl group) that reacts with the functional group Y (eg, epoxy group) of the coupling agent.

The molecular weight (chemical formula weight) of the silane coupling agent is not particularly limited, and can be about 120-1000, for example. Generally, a silane coupling agent having a molecular weight of 180 or more, 200 or more, or 220 or more is preferable from the viewpoint of ease of adjustment of the reworkable period and mobility to the adhesive surface. For the same reason, a silane coupling agent having a molecular weight of 800 or less, 600 or less, 400 or less, or 300 or less is preferred. In some aspects, a silane coupling agent having a molecular weight of 200 or more and 300 or less can be preferably used. As the value of the molecular weight of the silane coupling agent, a value calculated based on the structural formula of the silane coupling agent is used. Alternatively, the manufacturer's nominal value may be used.

The amount of the peel strength increasing agent (for example, silane coupling agent) contained in the pressure-sensitive adhesive composition of one embodiment of the present invention can be set so as to obtain desired effects, and is not particularly limited. The amount of the release force increasing agent can be, for example, 0.005 parts by mass or more per 100 parts by mass of the base polymer contained in the pressure-sensitive adhesive composition. The content of the release force increasing agent per 100 parts by mass of the base polymer is usually suitably 0.05 parts by mass or more, 0.10 parts by mass or more, 0.20 parts by mass or more, or 0.30 parts by mass. It can be more than part. By increasing the content of the release force increasing agent, the effect of increasing the release force can be exhibited.

In addition, depending on the mode of use of the release force increasing agent, if the period until the release force increases over time at room temperature is too short, the reworkable period becomes too short, resulting in problems such as complicating process management. It is possible. From this point of view, in some aspects, the content of the release force increasing agent per 100 parts by mass of the base polymer in the pressure-sensitive adhesive composition may be, for example, 5 parts by mass or less, 3 parts by mass or less, or 1 part by mass. parts or less, or 0.7 parts by mass or less (for example, 0.5 parts by mass or less).

(crosslinking agent)
The pressure-sensitive adhesive composition of one embodiment of the present invention can optionally contain a cross-linking agent mainly for the purpose of cross-linking within the pressure-sensitive adhesive layer or cross-linking between the pressure-sensitive adhesive layer and its adjacent surface. The type of the cross-linking agent is not particularly limited, and is selected from conventionally known cross-linking agents so that the cross-linking agent exhibits an appropriate cross-linking function in the pressure-sensitive adhesive layer according to, for example, the composition of the pressure-sensitive adhesive composition. be able to.

Cross-linking agents that can be used include isocyanate cross-linking agents, epoxy cross-linking agents, oxazoline cross-linking agents, aziridine cross-linking agents, carbodiimide cross-linking agents, melamine cross-linking agents, urea cross-linking agents, metal alkoxide cross-linking agents, metal Chelate-based cross-linking agents, metal salt-based cross-linking agents, hydrazine-based cross-linking agents, amine-based cross-linking agents, and the like can be exemplified. These can be used individually by 1 type or in combination of 2 or more types.

As the isocyanate-based cross-linking agent, a polyfunctional isocyanate compound having a functionality of 2 or more can be used. For example, aromatic isocyanates such as tolylene diisocyanate, xylene diisocyanate, polymethylene polyphenyl diisocyanate, tris(p-isocyanatophenyl) thiophosphate, diphenylmethane diisocyanate; alicyclic isocyanates such as isophorone diisocyanate; aliphatic isocyanates such as hexamethylene diisocyanate isocyanate; and the like. Commercially available products include trimethylolpropane/tolylene diisocyanate trimer adduct (manufactured by Tosoh Corporation, trade name "Coronate L"), trimethylolpropane/hexamethylene diisocyanate trimer adduct (manufactured by Tosoh Corporation, trade name " Coronate HL"), an isocyanurate form of hexamethylene diisocyanate (manufactured by Tosoh Corporation, trade name "Coronate HX") and other isocyanate adducts.

As the epoxy-based cross-linking agent, those having two or more epoxy groups in one molecule can be used without particular limitation. An epoxy-based cross-linking agent having 3 to 5 epoxy groups in one molecule is preferred. Specific examples of epoxy-based cross-linking agents include N,N,N',N'-tetraglycidyl-m-xylenediamine, 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane, and 1,6-hexane. Diol diglycidyl ether, polyethylene glycol diglycidyl ether, polyglycerol polyglycidyl ether and the like. Commercially available epoxy-based cross-linking agents include products manufactured by Mitsubishi Gas Chemical Co., Ltd. under the trade names of "TETRAD-X" and "TETRAD-C", DIC under the trade name of "Epiclon CR-5L", and products manufactured by Nagase ChemteX Corporation. name "Denacol EX-512", product name "TEPIC-G" manufactured by Nissan Chemical Industries, Ltd., and the like.

As the oxazoline-based cross-linking agent, those having one or more oxazoline groups in one molecule can be used without particular limitation.

Examples of aziridine-based cross-linking agents include trimethylolpropane tris [3-(1-aziridinyl) propionate], trimethylol propane tris [3-(1-(2-methyl) aziridinyl propionate)], and the like. be done.

A low-molecular-weight compound or a high-molecular-weight compound having two or more carbodiimide groups can be used as the carbodiimide-based cross-linking agent.

In some embodiments, peroxides may be used as cross-linking agents. Peroxides include di(2-ethylhexyl)peroxydicarbonate, di(4-t-butylcyclohexyl)peroxydicarbonate, di-sec-butylperoxydicarbonate, t-butyl peroxyneodecanoate. , t-hexyl peroxypivalate, t-butyl peroxypivalate, dilauroyl peroxide, di-n-octanoyl peroxide, 1,1,3,3-tetramethylbutyl peroxyisobutyrate, di benzoyl peroxide and the like. Among these, di(4-t-butylcyclohexyl)peroxydicarbonate, dilauroyl peroxide, dibenzoyl peroxide and the like are mentioned as peroxides having particularly excellent cross-linking reaction efficiency.

In addition, when a peroxide is used as the polymerization initiator, it is also possible to use the remaining peroxide that has not been used in the polymerization reaction for the cross-linking reaction. In that case, the residual amount of the peroxide is quantified, and if the ratio of the peroxide is less than the predetermined amount, the peroxide may be added as necessary so as to obtain the predetermined amount. Peroxide can be quantified by the method described in Japanese Patent No. 4971517.

The content of the cross-linking agent (the total amount thereof when two or more cross-linking agents are included) is not particularly limited. From the viewpoint of realizing a pressure-sensitive adhesive that exerts adhesive properties such as adhesive strength and cohesive strength in a well-balanced manner, the content of the cross-linking agent is usually about 5 parts by mass with respect to 100 parts by mass of the base polymer contained in the pressure-sensitive adhesive composition. parts or less, preferably about 0.001 to 5 parts by mass, more preferably about 0.001 to 4 parts by mass, and about 0.001 to 3 parts by mass. is more preferred.

Alternatively, it may be a pressure-sensitive adhesive composition that does not contain a cross-linking agent as described above. When a photocurable pressure-sensitive adhesive composition is used as the pressure-sensitive adhesive composition of one embodiment of the present invention, the pressure-sensitive adhesive composition may be substantially free of cross-linking agents such as isocyanate-based cross-linking agents. . Here, the pressure-sensitive adhesive composition substantially does not contain a cross-linking agent (typically an isocyanate-based cross-linking agent) means that the amount of the cross-linking agent is less than 0.05 parts by mass (for example, 0.05 part by mass) relative to 100 parts by mass of the base polymer. 01 parts by mass).

A cross-linking catalyst may be used to promote the cross-linking reaction more effectively. Examples of cross-linking catalysts include metallic cross-linking catalysts such as tetra-n-butyl titanate, tetraisopropyl titanate, Nasem ferric, butyltin oxide, and dioctyltin dilaurate. Of these, tin-based cross-linking catalysts such as dioctyltin dilaurate are preferred.

The amount of cross-linking catalyst used is not particularly limited. The amount of the crosslinking catalyst used relative to 100 parts by mass of the base polymer in the pressure-sensitive adhesive composition may be, for example, about 0.0001 part by mass or more and 1 part by mass or less, or may be 0.001 part by mass or more and 0.1 part by mass or less. , 0.005 parts by mass or more and 0.5 parts by mass or less.

A polyfunctional monomer may be used in the pressure-sensitive adhesive composition (and thus the pressure-sensitive adhesive layer) as necessary. A polyfunctional monomer can be useful for purposes such as adjusting cohesive strength when used in place of the above-described cross-linking agent or in combination with the cross-linking agent. For example, a polyfunctional monomer can be preferably used in a pressure-sensitive adhesive layer formed from a photocurable pressure-sensitive adhesive composition.

Examples of polyfunctional monomers include ethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, Pentaerythritol di(meth)acrylate, pentaerythritol tri(meth)acrylate, dipentaerythritol hexa(meth)acrylate, ethylene glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,12-dodecane Diol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, tetramethylolmethane tri(meth)acrylate, allyl (meth)acrylate, vinyl (meth)acrylate, divinylbenzene, epoxy acrylate, polyester acrylate, urethane acrylate, butyl diol (meth)acrylate, hexyldiol di(meth)acrylate and the like.

Among them, trimethylolpropane tri(meth)acrylate, 1,6-hexanediol di(meth)acrylate, and dipentaerythritol hexa(meth)acrylate can be preferably used. A polyfunctional monomer can be used individually by 1 type or in combination of 2 or more types.

The amount of the polyfunctional monomer used varies depending on its molecular weight, the number of functional groups, etc., but it is usually appropriate to use it in the range of about 0.01 to 3.0 parts by mass with respect to 100 parts by mass of the base polymer. be. In some embodiments, the amount of the polyfunctional monomer used relative to 100 parts by mass of the base polymer may be, for example, 0.02 parts by mass or more, may be 0.1 parts by mass or more, or may be 0.5 parts by mass. parts or more, 1.0 parts by mass or more, or 2.0 parts by mass or more. Higher cohesive strength tends to be obtained by increasing the amount of polyfunctional monomer used.

On the other hand, from the viewpoint of avoiding deterioration of adhesion between the pressure-sensitive adhesive layer and the adjacent layer due to excessive cohesive strength improvement, the amount of the polyfunctional monomer used relative to 100 parts by weight of the base polymer is, for example, 10 parts by weight or less. 5.0 parts by mass or less, or 3.0 parts by mass or less.

(acrylic oligomer)
The pressure-sensitive adhesive composition (and thus the pressure-sensitive adhesive layer) of one embodiment of the present invention has improved cohesive strength and adhesion to a surface adjacent to the pressure-sensitive adhesive layer (for example, it may be the surface of a substrate). From the viewpoint of improvement, etc., an acrylic oligomer can be contained.

As the acrylic oligomer, it is preferable to use a polymer having a Tg higher than that of the acrylic polymer.

The Tg of the acrylic oligomer is not particularly limited, and may be, for example, about 20°C or higher and 300°C or lower. The Tg may be, for example, about 30° C. or higher, about 40° C. or higher, about 60° C. or higher, about 80° C. or higher, or about 100° C. or higher. As the Tg of the acrylic oligomer increases, the effect of improving the cohesive strength tends to generally increase.

In addition, from the viewpoint of anchoring property to the substrate and impact absorption property, the Tg of the acrylic oligomer may be, for example, about 250° C. or less, even about 200° C. or less, about 180° C. or less, or about 150° C. or less. good. The Tg of the acrylic oligomer is a value calculated based on the Fox formula, like the Tg of the acrylic polymer corresponding to the composition of the monomer component.

The Mw of the acrylic oligomer can typically be from about 1000 to less than about 30000, preferably from about 1500 to less than about 10000, more preferably from about 2000 to less than about 5000. When Mw is within the above range, the effect of improving cohesiveness and adhesiveness with adjacent surfaces tends to be favorably exhibited.

The Mw of the acrylic oligomer can be measured by gel permeation chromatography (GPC) and calculated as a value converted to standard polystyrene. Specifically, measurement is performed using HPLC8020 manufactured by Tosoh Corporation, using TSKgelGMH-H(20)×2 columns, and using tetrahydrofuran as a solvent at a flow rate of about 0.5 mL/min.

As the monomer component constituting the acrylic oligomer, various (meth)acrylic acid C _1-20 alkyl esters described above; various alicyclic hydrocarbon group-containing (meth)acrylates described above; Hydrogen group-containing (meth)acrylates; (meth)acrylates obtained from terpene compound derivative alcohols; and other (meth)acrylate monomers can be mentioned. These can be used individually by 1 type or in combination of 2 or more types.

Acrylic oligomers include alkyl (meth)acrylates having branched alkyl groups such as isobutyl (meth)acrylate and t-butyl (meth)acrylate; alicyclic hydrocarbon group-containing (meth)acrylates and aromatic hydrocarbons From the viewpoint of improving adhesiveness, it is preferable to contain an acrylic monomer having a relatively bulky structure, such as a group-containing (meth)acrylate, as a monomer unit.

Further, when ultraviolet rays are used in synthesizing an acrylic oligomer or in producing a pressure-sensitive adhesive layer, a monomer having a saturated hydrocarbon group at the ester end is preferable because it is less likely to cause polymerization inhibition. Alkyl (meth)acrylates and saturated alicyclic hydrocarbon group-containing (meth)acrylates in which the group has a branched structure can be preferably used.

The ratio of the (meth)acrylate monomer to the total monomer components constituting the acrylic oligomer is typically more than 50% by weight, preferably 60% by weight or more, more preferably 70% by weight or more (e.g., 80% by weight). or more, and further 90% by weight or more).

In a preferred embodiment, the acrylic oligomer has a monomer composition consisting essentially of one or more (meth)acrylate monomers. When the monomer component contains an alicyclic hydrocarbon group-containing (meth)acrylate and a (meth)acrylic acid C _1-20 alkyl ester, the weight ratio thereof is not particularly limited, for example 10/90 to 90/10. range, 20/80 to 80/20 range, 70/30 to 30/70 range, and the like.

As a constituent monomer component of the acrylic oligomer, in addition to the above (meth)acrylate monomer, a functional group-containing monomer can be used as necessary. Examples of functional group-containing monomers include monomers having a nitrogen atom-containing heterocyclic ring such as N-vinyl-2-pyrrolidone and N-acryloylmorpholine; amino group-containing monomers such as N,N-dimethylaminoethyl (meth)acrylate; amide group-containing monomers such as N-diethyl(meth)acrylamide; carboxy group-containing monomers such as AA and MAA; hydroxyl group-containing monomers such as 2-hydroxyethyl(meth)acrylate; These functional group-containing monomers can be used singly or in combination of two or more.

When a functional group-containing monomer is used, the ratio of the functional group-containing monomer to all monomer components constituting the acrylic oligomer can be, for example, 1% by weight or more, 2% by weight or more, or 3% by weight or more, and For example, it can be 15% by weight or less, 10% by weight or less, or 7% by weight or less.

Suitable acrylic oligomers include, for example, dicyclopentanyl methacrylate (DCPMA), cyclohexyl methacrylate (CHMA), isobornyl methacrylate (IBXMA), isobornyl acrylate (IBXA), dicyclopentanyl acrylate (DCPA), In addition to homopolymers of 1-adamantyl methacrylate (ADMA) and 1-adamantyl acrylate (ADA), copolymers of DCPMA and MMA, copolymers of DCPMA and IBXMA, copolymers of ADA and methyl methacrylate (MMA) copolymers of CHMA and isobutyl methacrylate (IBMA); copolymers of CHMA and IBXMA; copolymers of CHMA and acryloylmorpholine (ACMO); copolymers of CHMA and diethylacrylamide (DEAA); Copolymers of CHMA and AA, and the like can be mentioned.

Acrylic oligomers can be formed by polymerizing their constituent monomer components. The polymerization method and polymerization mode are not particularly limited, and conventionally known various polymerization methods (eg, solution polymerization, emulsion polymerization, bulk polymerization, photopolymerization, radiation polymerization, etc.) can be employed in an appropriate mode. The types of polymerization initiators (e.g., azo polymerization initiators) that can be used as necessary are generally as exemplified for the synthesis of acrylic polymers, and the amount of polymerization initiator and optionally used chain transfer agent ( For example, the amount of mercaptans) is appropriately set based on common technical knowledge so as to achieve a desired molecular weight, so detailed description is omitted.

When the pressure-sensitive adhesive composition contains an acrylic oligomer, the content thereof can be, for example, 0.01 parts by mass or more with respect to 100 parts by mass of the base polymer. 05 parts by mass or more, 0.1 parts by mass or more, or 0.2 parts by mass or more.

From the viewpoint of compatibility with the base polymer, the content of the acrylic oligomer is usually less than 50 parts by mass, preferably less than 30 parts by mass, and more preferably 25 parts by mass or less. and may be 10 parts by mass or less, 5 parts by mass or less, or 1 part by mass or less.

(Other ingredients)
The pressure-sensitive adhesive composition of one embodiment of the present invention may optionally contain a tackifying resin (e.g., rosin-based, petroleum-based, terpene-based, phenol-based, ketone-based, etc.) adhesives as long as the effects of the present invention are not impaired. imparting resin), viscosity modifiers (e.g. thickeners), leveling agents, plasticizers, fillers, colorants such as pigments and dyes, stabilizers, preservatives, antioxidants, etc. General in the field of adhesive compositions Various other additives may be included as other optional ingredients. As for such various additives, conventionally known ones can be used in a conventional manner, and since they do not particularly characterize the present invention, detailed description thereof will be omitted.

In addition, since the technique according to the present embodiment can exhibit good adhesive strength without using the above-described tackifying resin, the content of the above-mentioned tackifying resin in the pressure-sensitive adhesive composition is 100 mass of the base polymer. For example, it can be less than 10 parts by weight, or even less than 5 parts by weight. The content of the tackifying resin may be less than 1 part by mass (for example, less than 0.5 parts by mass) or less than 0.1 parts by mass (0 parts by mass or more and less than 0.1 parts by mass). Alternatively, the pressure-sensitive adhesive composition may be free of tackifying resins.

From the viewpoint of improving transparency, the pressure-sensitive adhesive composition of one embodiment of the present invention preferably has a limited amount of components other than the base polymer in the pressure-sensitive adhesive composition. In the technology according to the present embodiment, the amount of components other than the base polymer in the pressure-sensitive adhesive composition is usually about 30% by weight or less, suitably about 15% by weight or less, preferably about 12% by weight. % or less (for example, approximately 10% by weight or less). The amount of components other than the base polymer in the pressure-sensitive adhesive composition according to one embodiment may be about 5% by weight or less, may be about 3% by weight or less, or may be about 1.5% by weight or less (for example, approximately 1% by weight or less). A composition in which the amounts of components other than the base polymer are thus limited can be preferably employed for the pressure-sensitive adhesive composition of the present embodiment.

<Adhesive layer>
The pressure-sensitive adhesive layer of one embodiment of the present invention is formed from the pressure-sensitive adhesive composition. FIG. 2 shows a schematic cross-sectional view of one structural example of the pressure-sensitive adhesive layer of one embodiment of the present invention.

The pressure-sensitive adhesive layer may be a cured layer of a pressure-sensitive adhesive composition. That is, the pressure-sensitive adhesive layer can be formed by applying (for example, applying) the pressure-sensitive adhesive composition to a suitable surface and then appropriately performing a curing treatment. When two or more curing treatments (drying, cross-linking, polymerization, etc.) are carried out, these can be carried out simultaneously or in multiple stages.

A pressure-sensitive adhesive composition using a partially polymerized monomer component (polymer syrup) typically undergoes a final copolymerization reaction as the curing treatment. That is, the partial polymer is subjected to a further copolymerization reaction to form a complete polymer. For example, in the case of a photocurable pressure-sensitive adhesive composition, light irradiation is carried out. Curing treatments such as cross-linking and drying may be performed as necessary. For example, when it is necessary to dry the photocurable pressure-sensitive adhesive composition (for example, in the case of a photocurable pressure-sensitive adhesive composition in which a partially polymerized monomer component is dissolved in an organic solvent), the composition is dried. It is preferable to perform photocuring after curing.

A pressure-sensitive adhesive composition using a completely polymerized product is typically subjected to drying (drying by heating), cross-linking, or the like as necessary as the curing treatment. In the case of a solvent-based pressure-sensitive adhesive composition to which photocurability (photocrosslinkability) is imparted by the addition of a polyfunctional monomer, photocuring is preferably performed after drying the composition. Here, "after drying the composition" may be after bonding the below-described pressure-sensitive adhesive sheet obtained through the drying to an adherend. The pressure-sensitive adhesive sheet described later can be used in a mode in which it is attached to the adherend by a technique including photocuring after being attached to the adherend.

A pressure-sensitive adhesive layer having a multi-layer structure of two or more layers can be produced by laminating pre-formed pressure-sensitive adhesive layers. Alternatively, the pressure-sensitive adhesive composition may be applied onto a previously formed first pressure-sensitive adhesive layer, and the pressure-sensitive adhesive composition may be cured to form the second pressure-sensitive adhesive layer. When the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet described below used in an application mode in which the adhesive sheet is photo-cured after being laminated to an adherend has a multilayer structure, the photo-curable pressure-sensitive adhesive layer is a part of the multilayer structure. It may be a layer (eg, one layer) or all layers.

Application of the pressure-sensitive adhesive composition can be carried out using conventional coaters such as gravure roll coaters, reverse roll coaters, kiss roll coaters, dip roll coaters, bar coaters, knife coaters, and spray coaters. In a pressure-sensitive adhesive sheet having a form having a substrate, which will be described later, a direct method of forming a pressure-sensitive adhesive layer by directly applying a pressure-sensitive adhesive composition to the substrate may be used as a method of providing the pressure-sensitive adhesive layer on the substrate. Alternatively, a transfer method of transferring the pressure-sensitive adhesive layer formed on the release surface to the substrate may be used.

The thickness of the pressure-sensitive adhesive layer is not particularly limited, and can be, for example, about 3 μm to 2000 μm. From the viewpoint of adhesion to the adherend such as step conformability, in some embodiments, the thickness of the pressure-sensitive adhesive layer may be, for example, 5 μm or more, suitably 10 μm or more, preferably 20 μm or more, or more. It is preferably 30 μm or more. The thickness of the pressure-sensitive adhesive layer may be 50 μm or more, more than 50 μm, 70 μm or more, 100 μm or more, or 120 μm or more.

Further, from the viewpoint of preventing the occurrence of adhesive residue due to cohesive failure of the adhesive layer, in some embodiments, the thickness of the adhesive layer may be, for example, 1000 μm or less, 700 μm or less, or 500 μm or less. , 300 μm or less, 200 μm or less, or 170 μm or less. The technique according to this aspect can also be suitably practiced in the form of a pressure-sensitive adhesive sheet described later, in which the pressure-sensitive adhesive layer has a thickness of 130 μm or less, 90 μm or less, or 60 μm or less (for example, 40 μm or less). In the pressure-sensitive adhesive sheet described later, which has a pressure-sensitive adhesive layer having a multilayer structure of two or more layers, the thickness of the pressure-sensitive adhesive layer refers to the thickness of the pressure-sensitive adhesive layer from the pressure-sensitive adhesive surface that is attached to the adherend to the surface opposite to the pressure-sensitive adhesive surface. refers to the thickness of

<Adhesive sheet>
A pressure-sensitive adhesive sheet of one embodiment of the present invention has the pressure-sensitive adhesive layer. The pressure-sensitive adhesive sheet of the present embodiment may be a pressure-sensitive adhesive sheet with a substrate having a pressure-sensitive adhesive layer on one or both sides of a sheet-shaped substrate (support), and the pressure-sensitive adhesive layer is held by a release sheet. It may be a substrate-less pressure-sensitive adhesive sheet such as The concept of the adhesive sheet as used herein can include what is called an adhesive tape, an adhesive label, an adhesive film, and the like.

The pressure-sensitive adhesive layer is typically formed continuously, but is not limited to such a form. For example, the pressure-sensitive adhesive layer is formed in a regular or random pattern such as dots or stripes. may be Moreover, the pressure-sensitive adhesive sheet of the present embodiment may be roll-shaped or sheet-shaped. Alternatively, it may be a pressure-sensitive adhesive sheet processed into various shapes.

(UV absorption layer)
The pressure-sensitive adhesive sheet of one embodiment of the present invention may have a form in which a UV absorbing layer is provided on one side of the pressure-sensitive adhesive layer. FIG. 3 shows a schematic cross-sectional view of one structural example in which the pressure-sensitive adhesive sheet of one embodiment of the present invention is provided with a UV absorbing layer on one side of the pressure-sensitive adhesive layer. The adhesive sheet 1 shown in FIG. 3 includes an adhesive layer 21 and a UV absorbing layer 31 provided on one side of the adhesive layer. The UV absorbing layer 31 contains a UV absorber such as a UV absorbing polymer.

Depending on the type of photo-oxidizing agent or photo-base generator contained in the adhesive sheet, ultraviolet light contained in sunlight may generate acid or base, which may cause discoloration or coloring of the sheet. In this case, there is a problem that it is difficult to discolor or color the pressure-sensitive adhesive sheet at an arbitrary timing by irradiating the active energy ray. In order to prevent such a problem, it is preferable to provide the UV absorption layer as a countermeasure against external light.

That is, by providing the UV absorbing layer on the side of the pressure-sensitive adhesive layer that is irradiated with sunlight, it is possible to prevent the ultraviolet rays contained in sunlight from reaching the pressure-sensitive adhesive layer. It is possible to prevent the pressure-sensitive adhesive layer from discoloring or coloring due to the irradiation of . Even when the UV absorbing layer is provided, the pressure-sensitive adhesive sheet can be discolored or colored by selecting an active energy ray that is not absorbed by the UV absorbing layer and irradiating it at an appropriate timing.

In addition, when discoloring or coloring by irradiating an active energy ray after laminating the UV absorbing layer on the adhesive layer, the energy that activates the photoacid generator and the photobase generator is absorbed by the UV absorbing layer. In this case, it is preferable to irradiate the active energy ray from the side opposite to the surface of the adhesive sheet on which the UV absorbing layer is provided so that the UV absorbing layer does not absorb the ultraviolet rays as the activation energy.

The UV-absorbing polymer used as UV-absorber can preferably be selected from a class of polymers containing structural units with UV-absorbing capability. Examples include 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-octoxybenzophenone, 2-hydroxy-4-dodecyloxybenzophenone, 2-hydroxy-4-methoxy-5-sulfobenzophenone, 2,4- Dihydroxybenzophenone, 2,2'-dihydroxy-4,4'-dimethoxybenzophenone, bis(2-methoxy-4-hydroxy-5-benzoylphenyl)methane, 2-hydroxy-4-acryloyloxybenzophenone, 2-hydroxy-4 -methacryloyloxybenzophenone, 2-hydroxy-4-(2-acryloyloxy)ethoxybenzophenone, 2-hydroxy-4-(2-methacryloyloxy)ethoxybenzophenone, 2-hydroxy-4-(2-methyl-2-acryloyloxy) ) 2-hydroxybenzophenone derivatives including ethoxybenzophenone; 2-(2′-hydroxy-5′-methylphenyl)benzotriazole, 2-(2′-hydroxy-5′-t-butylphenyl)benzotriazole, 2- (2'-hydroxy-5'-3',5'-di-t-butylphenyl)benzotriazole, 2-(2'-hydroxy-3'-t-butyl-5'-methylphenyl)-5-chloro Benzotriazole, 2-(2′-hydroxy-3′-5′-di-t-amylphenyl)benzotriazole, 2-{2′-hydroxy-3′-(3″,4″,5″,6″ -tetrahydrophthalimidomethyl-5′-methylphenyl}benzotriazole, 2,2-methylenebis{4-(1,1,3,3-tetramethylbutyl)-6-(2H-benzotriazol-2-yl)phenol} , 2-{2′-hydroxy-5′-(methacryloyloxy)phenyl}benzotriazole, 2-[2′-hydroxy-5′-(acryloyloxy)phenyl]benzotriazole, 2-[2′-hydroxy-3 '-t-butyl-5'-(methacryloyloxy)phenyl]benzotriazole, 2-[2'-hydroxy-3'-methyl-5'-(acryloyloxy)phenyl]benzotriazole, 2-{2'-hydroxy -5'-(methacryloyloxypropyl)phenyl}-5-chlorobenzotriazole, 2-[2'-hydroxy-5'-(methacryloyloxyethyl)phenyl]benzotriazole, 2-[2'-hydroxy-5'- (Akrylo yloxyethyl)phenyl]benzotriazole, 2-[2′-hydroxy-3′-t-butyl-5′-(methacryloyloxyethyl)phenyl]benzotriazole, 2-[2′-hydroxy-3′-methyl- 5′-(Acryloyloxyethyl)phenyl]benzotriazole, 2-[2′-hydroxy-5′-(methacryloyloxypropyl)phenyl]-5-chlorobenzotriazole, 2-[2′-hydroxy-5′-( 2-hydroxybenzotriazole derivatives including acryloyloxybutyl)phenyl]-5-methylbenzotriazole, [2-hydroxy-3-t-butyl-5-(acryloyloxyethoxycarbonylethyl)phenyl]benzotriazole and the like; Examples include, but are not limited to, salicylic acid derivatives such as phenyl salicylate, pt-butylphenyl salicylate, and p-octylphenyl salicylate.

Preferably, the UV absorbing polymer has a maximum absorption wavelength in the range of 300-400 nm.

The UV absorbing polymer is preferably a copolymer that is the reaction product of a mixture of a UV absorbing vinyl monomer and one or more copolymerizable compatible vinyl monomers, wherein the UV absorbing vinyl monomer is It contains structural units that have UV absorbing capabilities such as

Examples of copolymerizable vinyl monomers include acrylic acid, alkylacrylic acid (methacrylic acid, etc.), esters or amides derived from acrylic acid (e.g., acrylamide, methacrylamide, n-butylacrylamide, t-butylacrylamide, di Acetone acrylamide, methyl acrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate, t-butyl acrylate, isobutyl acrylate, 2-ethylhexyl acrylate, n-octyl acrylate, lauryl acrylate, 2-ethoxyethyl acrylate, 2-methoxyethyl acrylate, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, b-hydroxyl methacrylate, etc.), vinyl esters (e.g., vinyl acetate, vinyl propionate, vinyl laurate, etc.), acrylonitrile, methacryloyl nitrile, aromatic vinyl compounds (e.g., Styrene and its derivatives such as vinyl toluene, divinylbenzene, vinylacetophenone, sulfostyrene, etc.), iraconic acid, citraconic acid, crotonic acid, vinylidene chloride, vinyl alkyl ethers (such as vinyl ethyl ether), maleic acid, N- Esters such as vinyl-2-pyrrolidone, N-vinylpyridine, 2- or 4-vinylpyridine, sulfonic acids containing monomers (e.g. acrylamido-2,2′-dimethylpropanesulfonic acid, 2-sulfoethyl methacrylate, 3- sulfopropyl methacrylate, etc.).

Among these monomers, esters of acrylic acid, esters of methacrylic acid and aromatic vinyl compounds are preferred.

Specific examples of preferred comonomers include butyl acrylate; 2-ethylhexyl acrylate; 2-ethoxyethyl acrylate; 2-methoxyethyl acrylate; acrylic acid; -2-pyrrolidone; 2-sulfoethyl methacrylate and its metal salts; 2-acrylamido-2-methylpropanesulfonic acid and its metal salts.

(Adhesive layer containing UV absorber)
The pressure-sensitive adhesive sheet of one embodiment of the present invention includes a pressure-sensitive adhesive layer containing a UV absorber on one side of the pressure-sensitive adhesive layer (hereinafter also referred to as a "UV absorber-containing pressure-sensitive adhesive layer" or a "UV-absorbing pressure-sensitive adhesive layer"). It can be a form provided with FIG. 4 shows a schematic cross-sectional view of one configuration example in which the pressure-sensitive adhesive sheet of one embodiment of the present invention is provided with a UV absorber-containing pressure-sensitive adhesive layer on one side of the pressure-sensitive adhesive layer. The adhesive sheet 2 shown in FIG. 4 includes an adhesive layer 21 and a UV absorber-containing adhesive layer 41 provided on one side of the adhesive layer 21 . This makes it possible to take measures against external light in the same manner as the UV absorption layer.

As the UV absorber contained in the adhesive layer 41, the same UV absorber as described above can be used. Moreover, the adhesive layer 41 containing the UV absorber can contain the same components as the adhesive layer of one embodiment of the present invention described above.

(Base material)
A pressure-sensitive adhesive sheet according to some embodiments may be in the form of a substrate-attached pressure-sensitive adhesive sheet that includes a substrate bonded to the other back surface of the pressure-sensitive adhesive layer. FIG. 5 shows a schematic cross-sectional view of a configuration example in which a pressure-sensitive adhesive layer is formed on one side of a substrate in the pressure-sensitive adhesive sheet of one embodiment of the present invention. The adhesive sheet 3 shown in FIG. 5 includes a substrate 51 and an adhesive layer 21 formed on one side of the substrate.

As an adhesive sheet according to another embodiment, FIG. 6 shows a schematic cross-sectional view of a configuration example in which adhesive layers are formed on both sides of a substrate 51 . The adhesive sheet 4 shown in FIG. 6 includes a substrate 51, and a first adhesive layer 21 and a second adhesive layer 22 formed on both sides of the substrate.

The material of the base material is not particularly limited, and can be appropriately selected according to the intended use and mode of use of the pressure-sensitive adhesive sheet. Non-limiting examples of substrates that can be used include polyolefin films based on polyolefins such as polypropylene and ethylene-propylene copolymers, polyester films based on polyesters such as polyethylene terephthalate and polybutylene terephthalate, Plastic films such as polyvinyl chloride films containing polyvinyl chloride as the main component; Foam sheets made of foams such as polyurethane foam, polyethylene foam, polychloroprene foam; Synthetic fibers such as polyester and vinylon, semi-synthetic fibers such as acetate, etc.) Woven fabric and non-woven fabric by single or blended spinning; Paper such as Japanese paper, fine paper, kraft paper, crepe paper; Aluminum foil, copper metal foil such as foil; A base material having a structure in which these are combined may be used. Examples of such a substrate having a composite structure include a substrate having a structure in which a metal foil and the plastic film are laminated, and a plastic sheet reinforced with inorganic fibers such as glass cloth.

Various films (hereinafter also referred to as support films) can be preferably used as the base material of the pressure-sensitive adhesive sheet of one embodiment of the present invention. The support film may be a porous film such as a foam film or a non-woven fabric sheet, or may be a non-porous film, in which a porous layer and a non-porous layer are laminated. It may be a structured film.

In some embodiments, as the support film, a film containing a resin film that can independently maintain its shape (self-supporting or independent) as a base film can be preferably used. As used herein, "resin film" means a non-porous structure, typically a substantially voidless resin film. Therefore, the resin film is a concept distinguished from foam films and non-woven fabrics. The resin film may have a single-layer structure or a multilayer structure of two or more layers (for example, a three-layer structure).

Examples of the resin material constituting the resin film include polyester, polyolefin, polycycloolefin derived from a monomer having an alicyclic structure such as norbornene structure, nylon 6, nylon 66, and polyamide (PA) such as partially aromatic polyamide. , polyimide (PI), polyamideimide (PAI), polyetheretherketone (PEEK), polyethersulfone (PES), polyphenylene sulfide (PPS), polycarbonate (PC), polyurethane (PU), ethylene-vinyl acetate copolymer (EVA), polystyrene, polyvinyl chloride, polyvinylidene chloride, fluororesins such as polytetrafluoroethylene (PTFE), acrylic resins such as polymethyl methacrylate, cellulose polymers such as diacetyl cellulose and triacetyl cellulose, vinyl butyral polymers , an arylate-based polymer, a polyoxymethylene-based polymer, an epoxy-based polymer, and the like can be used.

The resin film may be formed using a resin material containing only one of such resins, or may be formed using a resin material in which two or more of these resins are blended. good too. The resin film may be unstretched or may be stretched (for example, uniaxially stretched or biaxially stretched).

Preferable examples of the resin material constituting the resin film include polyester resins, PPS resins and polyolefin resins. Here, the polyester-based resin refers to a resin containing polyester in a proportion exceeding 50% by weight. Similarly, PPS resin refers to a resin containing PPS in a proportion exceeding 50% by weight, and polyolefin resin refers to a resin containing polyolefin in a proportion exceeding 50% by weight.

As the polyester-based resin, typically, a polyester-based resin containing a polyester obtained by polycondensation of a dicarboxylic acid and a diol as a main component is used. Specific examples of polyester resins include polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), polybutylene naphthalate, and the like.

As the polyolefin resin, one kind of polyolefin can be used alone, or two or more kinds of polyolefins can be used in combination. The polyolefin may be, for example, an α-olefin homopolymer, a copolymer of two or more α-olefins, a copolymer of one or more α-olefins and other vinyl monomers, and the like.

Specific examples include polyethylene (PE), polypropylene (PP), poly-1-butene, poly-4-methyl-1-pentene, ethylene-propylene copolymers such as ethylene-propylene rubber (EPR), ethylene-propylene- Examples include butene copolymers, ethylene-butene copolymers, ethylene-vinyl alcohol copolymers, ethylene-ethyl acrylate copolymers, and the like. Both low density (LD) and high density (HD) polyolefins can be used.

Examples of polyolefin resin films include unstretched polypropylene (CPP) film, biaxially stretched polypropylene (OPP) film, low density polyethylene (LDPE) film, linear low density polyethylene (LLDPE) film, medium density polyethylene (MDPE) films, high-density polyethylene (HDPE) films, polyethylene (PE) films obtained by blending two or more types of polyethylene (PE), PP/PE blend films obtained by blending polypropylene (PP) and polyethylene (PE), and the like.

Specific examples of resin films that can be preferably used as substrates include PET films, PEN films, PPS films, PEEK films, CPP films and OPP films. PET films, PEN films, PPS films and PEEK films are preferred from the viewpoint of strength. A preferred example is a PET film from the viewpoint of availability, dimensional stability, optical properties, and the like.

If necessary, known additives such as light stabilizers, antioxidants, antistatic agents, colorants (dyes, pigments, etc.), fillers, slip agents, antiblocking agents, etc., may be added to the resin film. can be done. The blending amount of the additive is not particularly limited, and can be appropriately set according to the use of the pressure-sensitive adhesive sheet.

The method for producing the resin film is not particularly limited. For example, conventionally known general resin film forming methods such as extrusion molding, inflation molding, T-die casting, and calendar roll molding can be appropriately employed.

The substrate may be substantially composed of such a resin film. Alternatively, the substrate may contain an auxiliary layer in addition to the resin film. Examples of the auxiliary layers include optical property adjusting layers (e.g., antireflection layers), printed layers and laminate layers for imparting desired appearance to substrates or pressure-sensitive adhesive sheets, antistatic layers, undercoat layers, and release layers. and other surface treatment layers. Further, the substrate may be an optical member described later.

The thickness of the base material is not particularly limited, and can be selected according to the intended use and mode of use of the pressure-sensitive adhesive sheet. The thickness of the substrate may be, for example, 1000 μm or less, 500 μm or less, 100 μm or less, 70 μm or less, 50 μm or less, 25 μm or less, 10 μm or less, or 5 μm or less. When the thickness of the substrate is reduced, the flexibility of the pressure-sensitive adhesive sheet and the followability to the surface shape of the adherend tend to be improved.

Moreover, from the viewpoint of handleability, processability, etc., the thickness of the substrate may be, for example, 2 μm or more, and may be more than 5 μm or more than 10 μm. In some aspects, the thickness of the substrate can be, for example, 20 μm or greater, 35 μm or greater, or 55 μm or greater.

The surface of the substrate that is to be bonded to the adhesive layer may be subjected to corona discharge treatment, plasma treatment, ultraviolet irradiation treatment, acid treatment, alkali treatment, primer application, and antistatic treatment, if necessary. A conventionally known surface treatment such as the above may be applied. Such a surface treatment can be a treatment for improving the adhesion between the substrate and the adhesive layer, in other words, the anchoring property of the adhesive layer to the substrate. The composition of the primer is not particularly limited, and can be appropriately selected from known ones. Although the thickness of the undercoat layer is not particularly limited, it is usually suitably about 0.01 μm to 1 μm, preferably about 0.1 μm to 1 μm.

The surface of the substrate opposite to the side to be bonded to the pressure-sensitive adhesive layer (hereinafter also referred to as the back surface) may be subjected to peeling treatment, adhesion or stickiness improvement treatment, antistatic treatment, etc. as necessary. A conventionally known surface treatment may be applied. For example, the unwinding force of the pressure-sensitive adhesive sheet wound into a roll can be reduced by surface-treating the back surface of the substrate with a release agent. Examples of release agents that can be used include silicone-based release agents, long-chain alkyl-based release agents, olefin-based release agents, fluorine-based release agents, fatty acid amide-based release agents, molybdenum sulfide, and silica powder. .

(Release liner)
In the pressure-sensitive adhesive sheet of this embodiment, the pressure-sensitive adhesive layer and the UV absorber-containing pressure-sensitive adhesive layer may be protected by a release liner (separator, release film) until use.

As the release liner, a conventional release paper or the like can be used, and is not particularly limited. etc. can be used.

Substrates having a release treatment layer include, for example, plastic films and papers surface-treated with release agents such as silicone, long-chain alkyl, fluorine, and molybdenum sulfide.

Examples of fluorine-based polymers for low-adhesive substrates made of fluorine-based polymers include polytetrafluoroethylene, polychlorotrifluoroethylene, polyvinyl fluoride, polyvinylidene fluoride, tetrafluoroethylene-hexafluoropropylene copolymer, chloro A fluoroethylene/vinylidene fluoride copolymer and the like can be mentioned.

Examples of the non-polar polymer of the low-adhesive substrate made of non-polar polymer include olefin-based resins (eg, polyethylene, polypropylene, etc.). The release liner can be formed by a known or commonly used method. Also, the thickness of the release liner is not particularly limited.

In the technology according to the present embodiment, the haze value of the adhesive sheet is suitably approximately 10% or less, and may be approximately 5% or less (for example, approximately 3% or less). The haze value is preferably 1.0% or less. Such highly transparent pressure-sensitive adhesive sheets are preferable in the present invention from the viewpoint that the change in appearance is remarkable when the sheet is discolored or colored. The haze value of the adhesive sheet may be less than 1.0%, less than 0.7%, or 0.5% or less (eg, 0 to 0.5%). These haze values relating to the adhesive sheet can also be preferably applied to the haze value of the adhesive layer in the technology according to this embodiment.

Here, the term "haze value" refers to the ratio of diffuse transmitted light to the total transmitted light when the object to be measured is irradiated with visible light. Also called cloudiness value. A haze value can be represented by the following formula.
Th[%]=Td/Tt×100

In the above formula, Th is the haze value [%], Td is the scattered light transmittance, and Tt is the total light transmittance. The haze value can be measured according to the method described in Examples below. The haze value can be adjusted, for example, by selecting the composition, thickness, etc. of the pressure-sensitive adhesive layer.

The technology according to the present embodiment can be preferably used, for example, in electronic member applications, optical member applications, building member applications, and the like.

Hereinafter, embodiments of the present invention will be described in more detail using examples.

[Preparation of adhesive composition]
(Adhesive composition A1)
A reaction vessel equipped with a cooling tube, a nitrogen inlet tube, a thermometer and a stirrer was charged with 95 parts by weight of n-butyl acrylate (BA) as a monomer component, 5 parts by weight of acrylic acid (AA), and 122 parts by weight of ethyl acetate as a polymerization solvent. was charged, and 0.2 parts by weight of 2,2′-azobisisobutyronitrile (AIBN) was added as a thermal polymerization initiator, and solution polymerization was performed under a nitrogen atmosphere to obtain an acrylic polymer having an Mw of 600,000. A solution containing 1 was obtained.

1 weight of 6-(diethylamino)-2-[(3-trifluoromethyl)anilino]xanthene-9-spiro-3′-phthalide as a leuco dye per 100 parts by weight of the polymer component was added to the solution obtained above. part, 0.1 part by weight of propylene carbonate solution (trade name: CPI-100P, manufactured by San-Apro Co., Ltd.) containing 50% active ingredient containing triarylsulfonium hexafluorophosphate as the main component as a photoacid generator, epoxy-based cross-linking agent (1 , 3-bis(N,N-diglycidylaminomethyl)cyclohexane, trade name: Tetrad C, manufactured by Mitsubishi Gas Chemical Co., Ltd.) was added in an amount of 0.05 part by weight based on the solid content and uniformly mixed to form an adhesive composition. A1 was prepared.

(Adhesive composition A2)
A pressure-sensitive adhesive composition A2 was prepared in the same manner as the pressure-sensitive adhesive composition A1, except that the amount of the photoacid generator used was 1 part by weight per 100 parts by weight of the polymer component.

(Adhesive composition A3)
A pressure-sensitive adhesive composition A3 was prepared in the same manner as the pressure-sensitive adhesive composition A1, except that the amount of the photoacid generator used was 5 parts by weight per 100 parts by weight of the polymer component.

(Adhesive composition A4)
A pressure-sensitive adhesive composition A4 was prepared in the same manner as the pressure-sensitive adhesive composition A1, except that the amount of the photoacid generator used was 10 parts by weight per 100 parts by weight of the polymer component.

(Adhesive composition A5)
PSA composition A5 was prepared in the same manner as PSA composition A1, except that the amount of leuco dye used was 10 parts by weight per 100 parts by weight of the polymer component, and the amount of photoacid generator was 20 parts by weight. prepared.

(Adhesive composition A6)
The type of photoacid generator is triphenylsulfonium/nonafluorobutane-1-sulfonic acid (trade name: ADEKA Arkles SP-056, manufactured by ADEKA), and the amount used is 1 part by weight. Adhesive composition A6 was prepared in the same manner as for product A1.

(Adhesive composition A7)
A pressure-sensitive adhesive composition A7 was prepared in the same manner as the pressure-sensitive adhesive composition A6, except that the amount of the photoacid generator used was 5 parts by weight.

(Adhesive composition A8)
A pressure-sensitive adhesive composition A8 was prepared in the same manner as the pressure-sensitive adhesive composition A1, except that no photoacid generator was used.

(Adhesive composition A9)
A pressure-sensitive adhesive composition A9 was prepared in the same manner as the pressure-sensitive adhesive composition A2, except that no leuco dye was used.

<Production of adhesive sheet>
(Example 1)
The adhesive composition A1 is applied to a 38 μm thick release film R1 (Mitsubishi Plastics Co., Ltd., MRF #38) in which one side of the polyester film is a release surface, and dried at 135 ° C. for 2 minutes to obtain a thickness of 50 μm. to form an adhesive layer B1. A 38 μm thick release film R2 (Mitsubishi Plastics Co., Ltd., MRE #38) having a polyester film with a release surface on one side is attached to the adhesive layer B1, whereby the film R2 and the adhesive layer B1 are separated. A pressure-sensitive adhesive sheet of Example 1 was obtained in which the film R1 was laminated in this order.

(Example 2)
A pressure-sensitive adhesive sheet of Example 2 was produced in the same manner as in Example 1, except that the pressure-sensitive adhesive composition A2 was used instead of the pressure-sensitive adhesive composition A1.

(Example 3)
A pressure-sensitive adhesive sheet of Example 3 was produced in the same manner as in Example 1, except that the pressure-sensitive adhesive composition A3 was used instead of the pressure-sensitive adhesive composition A1.

(Example 4)
A pressure-sensitive adhesive sheet of Example 4 was produced in the same manner as in Example 1, except that the pressure-sensitive adhesive composition A4 was used instead of the pressure-sensitive adhesive composition A1.

(Example 5)
A pressure-sensitive adhesive sheet of Example 5 was produced in the same manner as in Example 1, except that the pressure-sensitive adhesive composition A5 was used instead of the pressure-sensitive adhesive composition A1.

(Example 6)
A pressure-sensitive adhesive sheet of Example 6 was produced in the same manner as in Example 1, except that the pressure-sensitive adhesive composition A6 was used instead of the pressure-sensitive adhesive composition A1.
(Example 7)
A pressure-sensitive adhesive sheet of Example 7 was produced in the same manner as in Example 1, except that the pressure-sensitive adhesive composition A7 was used instead of the pressure-sensitive adhesive composition A1.

(Example 8)
The release film R2 of the adhesive sheet prepared in Example 2 was peeled off, and an adhesive tape (Nitto Denko Co., Ltd., product name: CS9934U) 100 μm with a UV absorption function was pasted together to obtain the adhesive of Example 8 having a UV absorption layer. A sheet was produced.

(Comparative example 1)
A pressure-sensitive adhesive sheet of Comparative Example 1 was produced in the same manner as in Example 1, except that the pressure-sensitive adhesive composition A8 was used instead of the pressure-sensitive adhesive composition A1.

(Comparative example 2)
A pressure-sensitive adhesive sheet of Comparative Example 2 was produced in the same manner as in Example 1, except that the pressure-sensitive adhesive composition A9 was used instead of the pressure-sensitive adhesive composition A1.

<Measurement of adhesive strength>
(Adhesive strength before UV irradiation)
The adhesive strength (initial) before UV irradiation was measured for each of the adhesive sheets of Examples 1 to 7 and Comparative Examples 1 and 2 produced above. The adhesive strength was measured according to the following procedure.
First, each pressure-sensitive adhesive sheet was cut to a width of 20 mm and a length of 10 cm, and the release film was peeled off. Subsequently, the pressure-sensitive adhesive sheet of each example was attached to a soda plate glass having a thickness of 1.2 mm by reciprocating twice with a 2-kg roller. Using a tensile tester (AUTOGRAPH AGS-X, manufactured by Shimadzu Corporation), the adhesive force (N/20 mm) was measured as the peeling force at a peeling angle of 180 degrees and a peeling speed of 300 mm/min. Table 1 shows the results.

(Adhesive strength after UV irradiation)
The adhesive strength after UV irradiation (after triggering) was measured for each of the adhesive sheets of Examples 1 to 7 and Comparative Examples 1 and 2. The adhesive strength after UV irradiation was measured in the same manner as described above, except that UV (wavelength range: 200 to 400 nm) was irradiated after the pressure-sensitive adhesive sheet was pressure-bonded to soda lime glass having a plate thickness of 1.2 mm.
UV irradiation was carried out through the alkali glass plate under an environment of 23° C. and 50% RH. More specifically, the 6- ⁽ diethylamino) ^-2 -[(3 -trifluoromethyl)anilino]xanthene-9-spiro-3′-phthalide and triarylsulfonium·PF6 salt were reacted. Table 1 shows the results.

<Optical property test>
In this test, the coloration of the pressure-sensitive adhesive sheet by UV irradiation was evaluated by the change in transmittance before and after coloration.
Using a spectrophotometer U4100 manufactured by Hitachi High Technologies, the adhesive sheets of Examples 1 to 7 and Comparative Examples 1 and 2 were laminated to a blue plate glass with a plate thickness of 1.2 mm, and the total light transmittance at 380 to 780 nm. was measured at a pitch of 5 nm. Such measurements were performed before and after UV treatment (UV wavelength range: 200 to 400 nm), and the "change in transmittance (%)", which is the maximum change in transmittance before and after UV treatment, was obtained. Table 1 shows the results.
<Weather resistance test>
In this test, the weather resistance against light equivalent to ultraviolet rays in the outside light was evaluated depending on the presence or absence of the UV absorption layer.
Using a super xenon weather meter SX75 manufactured by Suga Test Instruments Co., Ltd., the pressure-sensitive adhesive sheets obtained in Examples 2 and 8 were attached to a soda plate glass having a thickness of 1.2 mm, and an output of 120 W and a wavelength band of 300 to 400 nm were obtained. Light (corresponding to ultraviolet light in outside light) was irradiated for 1 hour with a super xenon lamp. In addition, in Example 8 provided with a UV absorption layer, light was irradiated from the UV absorption layer side. After that, the "transmittance change (%)" was measured in the same manner as above, and the results are shown in Table 2.

The adhesive sheets of Examples 1 to 7 containing a leuco dye and a photo-oxidation generator changed their transmittance upon UV irradiation. Therefore, the pressure-sensitive adhesive sheet of the present invention containing a leuco dye and a photo-oxidation generator could be discolored or colored at any timing by irradiation with active energy rays.
On the other hand, the pressure-sensitive adhesive sheets of Comparative Examples 1 and 2, which did not contain a leuco dye or a photo-oxidation generator, showed almost no change in transmittance due to UV irradiation.
The adhesive sheets of Examples 1 to 7 and Comparative Examples 1 and 2 did not change in adhesive strength due to UV irradiation.

In addition, the pressure-sensitive adhesive sheet of Example 8, which has a UV-absorbing layer on the pressure-sensitive adhesive layer containing a leuco dye and a photo-oxidation generator, has a change in transmittance compared to the pressure-sensitive adhesive sheet of Example 2, which does not have a UV-absorbing layer. is suppressed and the weather resistance is improved.

1, 2, 3, 4 Adhesive sheets 21, 22 Adhesive layer 31 UV absorption layer 41 UV absorber-containing adhesive layer 51 Base material

Claims (15)

A pressure-sensitive adhesive composition containing a base polymer, a leuco dye, a photoacid generator, and a cross-linking agent ,
The photoacid generator is at least one selected from the group consisting of sulfonium salt compounds, iodonium salt compounds, aromatic N-oxyimide sulfonates, sulfonic acid ester compounds, and halomethyl-substituted S-triazine derivatives. A pressure-sensitive adhesive composition, which is a compound. The pressure-sensitive adhesive composition according to claim 1, wherein the leuco dye has an absorption wavelength that changes depending on pH. 3. The pressure-sensitive adhesive composition according to claim 1, containing 0.1 to 30 parts by mass of the leuco dye per 100 parts by mass of the base polymer. The adhesive composition according to any one of claims 1 to 3, wherein the leuco dye is at least one dye selected from the group consisting of phthalide dyes and fluoran dyes. The pressure-sensitive adhesive composition according to any one of claims 1 to 4, which contains 0.1 to 30 parts by mass of the photoacid generator per 100 parts by mass of the base polymer. The pressure-sensitive adhesive composition according to any one of claims 1 to 5, wherein the base polymer comprises an acrylic polymer. The pressure-sensitive adhesive composition according to any one of claims 1 to 6, which changes color when exposed to active energy rays. The pressure-sensitive adhesive composition according to any one of claims 1 to 6, which is colored by irradiation with active energy rays. A pressure-sensitive adhesive layer comprising the pressure-sensitive adhesive composition according to any one of claims 1 to 8 . At least one selected from the group consisting of a base polymer, a leuco dye, a sulfonium salt compound, an iodonium salt compound, an aromatic N-oxyimide sulfonate, a sulfonic acid ester compound, and a halomethyl-substituted S-triazine derivative A pressure-sensitive adhesive layer comprising a pressure-sensitive adhesive composition containing two compounds, a photoacid generator and a pressure-sensitive adhesive layer whose adhesive strength does not change upon exposure to active energy rays. A pressure-sensitive adhesive sheet comprising the pressure-sensitive adhesive layer according to claim 9 or 10 . The pressure-sensitive adhesive sheet according to claim 11 , comprising a UV absorbing layer on one side of the pressure-sensitive adhesive layer. The pressure-sensitive adhesive sheet according to claim 12 , wherein the UV absorbing layer is a pressure-sensitive adhesive layer containing a UV absorber. At least one selected from the group consisting of a base polymer, a leuco dye, a sulfonium salt compound, an iodonium salt compound, an aromatic N-oxyimide sulfonate, a sulfonic acid ester compound, and a halomethyl-substituted S-triazine derivative A pressure-sensitive adhesive layer made of a pressure-sensitive adhesive composition containing a photoacid generator that is one compound, and a pressure-sensitive adhesive sheet comprising a UV-absorbing layer on one side of the pressure-sensitive adhesive layer, wherein the UV-absorbing layer contains a UV-absorbing agent. A pressure-sensitive adhesive sheet, which is a pressure-sensitive adhesive layer to be contained. The pressure-sensitive adhesive sheet according to any one of claims 11 to 14, wherein the pressure-sensitive adhesive layer is formed on a substrate.

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