JP7193401B2 - Adhesive composition, adhesive layer, and adhesive sheet - Google Patents

Description

TECHNICAL FIELD The present invention relates to an adhesive composition, an adhesive layer, and an adhesive sheet.

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.

Pigments and dyes are often used to color adhesive tapes. For example, Patent Document 1 discloses an adhesive composition containing an acrylic polymer, a phenolic resin, an epoxy resin, and a colorant, and containing 10 parts by weight or less of the colorant with respect to 100 parts by weight of the acrylic polymer. It is disclosed that pigments and dyes are preferably used as colorants in products.

JP 2015-013946 A

However, when a pigment or dye is used to color the adhesive tape, there is a risk of aggregation occurring in the adhesive composition, and good dispersibility cannot be obtained unless a dispersant is used. There is also a problem that the dye component bleeds out from the pressure-sensitive adhesive composition and remains on the adherend after the pressure-sensitive adhesive tape is peeled off. Furthermore, depending on the type of pigment or dye, it may cause deterioration of adhesive properties. Further, in some cases, a resin having a high acid value is used to improve the dispersibility of the pigment, and in that case, another problem of corrosion of metal adherends such as iron, stainless steel, and ITO may arise.

Therefore, the present invention provides a colored pressure-sensitive adhesive composition that has good adhesive strength, good dispersibility even when a high acid value resin or dispersant is not used, and does not cause bleeding out of the dye component. One object is to provide a composition.

The present inventors have made intensive studies to solve the above problems. As a result, the inventors have found that the above problems can be solved by using an oligomer obtained from a vinyl monomer having at least one kind of dye structure in the side chain, and have completed the invention.

One aspect of the present invention is a pressure-sensitive adhesive composition comprising a base polymer and at least one oligomer, wherein the oligomer comprises a monomer composition comprising at least a vinyl monomer having at least one dye structure in its side chain. The present invention relates to a pressure-sensitive adhesive composition characterized by being an oligomer obtained by polymerization.

In one aspect of the present invention, the pressure-sensitive adhesive composition is preferably such that the base polymer is a (meth)acrylic polymer.

One aspect|mode of this invention WHEREIN: It is preferable that the said oligomer of an adhesive composition is a (meth)acrylic oligomer.

In one aspect of the present invention, in the pressure-sensitive adhesive composition, the (meth)acrylic oligomer may be a homopolymer of a (meth)acrylic monomer having at least one dye structure in a side chain.

In one aspect of the present invention, the pressure-sensitive adhesive composition comprises a (meth)acrylic oligomer in which the (meth)acrylic oligomer is a co-polymer of a (meth)acrylic monomer having at least one dye structure in a side chain and a (meth)acrylic acid alkyl ester. It may be a polymer.

In one aspect of the present invention, the pressure-sensitive adhesive composition preferably contains the oligomer having a weight average molecular weight of 1,000 to 50,000.

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

One aspect of the present invention relates to a pressure-sensitive adhesive sheet including the pressure-sensitive adhesive layer.

In one aspect of the present invention, the pressure-sensitive adhesive sheet may include the pressure-sensitive adhesive layer on a transparent film.

ADVANTAGE OF THE INVENTION According to the present invention, there is provided a colored pressure-sensitive adhesive composition which has good adhesive strength, good dispersibility even when a high acid value resin or dispersant is not used, and does not cause bleeding out of a pigment component. can.

FIG. 1 is an example of a schematic cross-sectional view of an adhesive layer according to an embodiment of the present invention. FIG. 2 is an example of a schematic cross-sectional view of an adhesive sheet according to an embodiment of the present invention. FIG. 3 is an example of a schematic cross-sectional view of an adhesive sheet according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail. In addition, this invention is not limited to embodiment described below.
In this specification, "A to B" indicating a range means "A or more and B or less". Moreover, in this specification, "% by mass" is treated as having the same meaning as "% by weight", and "parts by mass" is treated as having the same meaning as "parts by weight".

[Adhesive composition]
A pressure-sensitive adhesive composition according to one embodiment of the present invention is a pressure-sensitive adhesive composition comprising a base polymer and at least one oligomer, wherein the oligomer is a vinyl polymer having at least one dye structure in its side chain. It is characterized by being obtained by polymerizing a monomer composition containing at least a monomer.
The pressure-sensitive adhesive composition uses, as a dye, an oligomer obtained by polymerizing a vinyl monomer having a dye structure in the side chain, so that dispersibility is good even when a high acid value resin or dispersant is not used. Moreover, bleeding out of the pigment component does not occur.
Each component contained in the pressure-sensitive adhesive composition will be described in detail below.

<Base polymer>
In the pressure-sensitive adhesive composition according to this aspect, 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 (meth)acrylic polymers, rubber polymers, vinyl alkyl ether polymers, silicone polymers, polyester polymers, polyamide polymers, urethane polymers, fluorine polymers, and epoxy polymers. Among them, a (meth)acrylic polymer having high transparency is more preferable from the viewpoint that the coloring by the pigment becomes clear. Such polymers may be used singly or in combination of two or more.

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

A pressure-sensitive adhesive composition according to 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.

As the pressure-sensitive adhesive composition according to one embodiment of the present invention, for example, 40% by mass of (meth)acrylic acid alkyl ester having a linear or branched alkyl group having 1 to 20 carbon atoms at the ester end It is preferable to contain, as a base polymer, an acrylic polymer composed of monomer components contained in the above proportions. 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 mass. It may be 55% by mass or more, 60% by mass or more, or 70% by mass 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 mass or less, 99.5% by mass or less, or 99% by mass 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 mass or less, from the viewpoint of improving the cohesiveness of the pressure-sensitive adhesive layer. It may be 95% by mass or less, 85% by mass or less (for example, less than 80% by mass), 70% by mass or less, or 60% by mass 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 BA 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 mass or more. The proportion of the (meth)acrylic acid C _4-18 alkyl ester in the monomer component may be, for example, 50% by mass or more, 60% by mass or more, or 65% by mass 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 appropriately 99.5% by mass or less, and 95% by mass. % or less, 85 mass % or less, or 75 mass % 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 and the like.

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: such as aminoethyl (meth)acrylate, N,N-dimethylaminoethyl (meth)acrylate, t-butylaminoethyl (meth)acrylate and the like.

Monomers having an epoxy group: such as glycidyl (meth)acrylate, methylglycidyl (meth)acrylate, allyl glycidyl ether, and the like.

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) and the like.

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 and the like.

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 thereof is not particularly limited, but it is usually appropriate to use it in an amount of 0.01% by mass or more based on 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 mass or more, or 0.5% by mass or more based on the total monomer components. In addition, from the viewpoint of facilitating the balance of adhesive properties, the amount of the copolymerizable monomer to be used is generally 50% by mass or less, preferably 40% by mass 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 monomer having a nitrogen atom (preferably a monomer having a nitrogen atom-containing ring) is not particularly limited, and is, for example, 1% by mass or more, 3% by mass or more, 5% by mass or more, or 7% by mass or more of the total monomer components. can do. In one aspect, the amount of the nitrogen atom-containing monomer used may be 10% by mass or more, 15% by mass or more, or 20% by mass or more of the total monomer components. In addition, the amount of the monomer having a nitrogen atom used is, for example, 40% by mass or less of the entire monomer component, and may be 35% by mass or less, 30% by mass or less, or 25% by mass or less. good too. In another aspect, the amount of the nitrogen atom-containing monomer used may be, for example, 20% by mass or less, or 15% by mass 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. It may be 1% by mass or more, 5% by mass or more, or 10% by mass 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 mass or less of the total monomer components, and 30% by mass or less. may be 25% by mass or less, or 20% by mass or less. In another aspect, the amount of the hydroxyl group-containing monomer used may be, for example, 15% by mass or less, 10% by mass or less, or 5% by mass or less of the total monomer components.

In the pressure-sensitive adhesive composition according to 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. good. In one aspect of the technology according to this aspect, the proportion of alkoxyalkyl (meth)acrylate in the monomer components of the acrylic polymer is less than 20% by mass, and the proportion of alkoxypolyalkyleneglycol (meth)acrylate is less than 20% by mass. is. 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 mass, more preferably less than 3% by mass, and even more preferably less than 1% by mass. In a particularly preferred embodiment, the monomer component is Substantially free of alkoxyalkyl (meth)acrylate (content of 0 to 0.3% by mass). Similarly, the proportion of the alkoxypolyalkylene glycol (meth)acrylate in the monomer component is preferably less than 10% by mass, more preferably less than 3% by mass, and even more preferably less than 1% by mass. , the monomer component does not substantially contain alkoxypolyalkylene glycol (meth)acrylate (content 0 to 0.3% by mass).

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

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 mass or less, 1% by mass or less, or 0.5% by mass or less (e.g., 0.1% by mass or less). less than % by mass). 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 aspect, the proportion of the hydrophilic monomer in the monomer components of the acrylic polymer is preferably 32% by mass or less, and may be, for example, 30% by mass or less, or may be 28% by mass or less. Although not particularly limited, the proportion of the hydrophilic monomer in the monomer components of the acrylic polymer may be 1% by mass or more, 10% by mass or more, or 20% by mass 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 mass or more, 3% by mass or more, or 5% by mass 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 mass or more, or 15% by mass 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 mass or less, and may be, for example, 30% by mass or less, or 25% by mass or less (e.g., 15% by mass). % or less, or even 10% by mass 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, a reactor equipped with a thermometer, a stirrer, a nitrogen inlet tube and a reflux condenser was charged with 100 parts by mass of a monomer, 0.2 parts by mass of azobisisobutyronitrile and 200 parts by mass of ethyl acetate as a polymerization solvent. 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 mass. 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 TA Instruments), 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 this aspect 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.);
can be calculated according to 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. The pressure-sensitive adhesive composition according to a preferred embodiment 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 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).

Although the photopolymerization initiator is not particularly limited, for example, ketal photopolymerization initiator, acetophenone photopolymerization initiator, benzoin ether photopolymerization initiator, acylphosphine oxide photopolymerization initiator, α- Ketol photoinitiators, aromatic sulfonyl chloride photoinitiators, photoactive oxime photoinitiators, benzoin photoinitiators, benzyl photoinitiators, benzophenone photoinitiators, thioxanthone photoinitiators A polymerization initiator or the like can be used.

The amount of such a thermal polymerization initiator or 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.

In 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 technology according to this aspect can also be preferably practiced in an aspect that does not use 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 this aspect, gelation can be suppressed by designing the monomer composition, so that a high molecular weight substance within the above range can be obtained 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.

The pressure-sensitive adhesive composition according to some aspects 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.

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 photopolymerization 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 mass or less, preferably about 60% by mass 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 mass or less, and about 40% by mass or less (for example, about 35% by mass). % by mass or less) is preferable. Although the lower limit of the polymerization conversion rate is not particularly limited, it is typically about 1% by mass or more, and usually about 5% by mass or more.

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 this specification, the term "completely polymerized product" means that the polymerization conversion rate is over 95% by mass.

<Oligomer>
An adhesive composition according to one embodiment of the present invention may comprise at least one oligomer. The oligomer in the present invention is obtained by polymerizing a monomer composition containing at least a vinyl monomer having at least one dye structure in its side chain. That is, the oligomer contains at least a vinyl monomer having at least one dye structure in its side chain as a monomer unit.
Since the pressure-sensitive adhesive composition according to one embodiment of the present invention uses, as a dye component, an oligomer containing a vinyl monomer having a dye structure in a side chain as a structural unit, when a pigment or dye is used, dispersibility deteriorates and Avoids dye bleed-out problems.

Examples of vinyl monomers having at least one dye structure in the side chain include (meth)acrylic monomers, aromatic vinyl monomers, and aliphatic hydrocarbon monomers. From the viewpoint of good compatibility with the (meth)acrylic base polymer and maintaining transparency, (meth)acrylic monomers are preferred.
The (meth)acrylic monomer is not particularly limited, but includes, for example, the various (meth)acrylic acid C _1-20 alkyl esters described above; the various alicyclic hydrocarbon group-containing (meth)acrylates described above; (Meth)acrylic monomers such as various aromatic hydrocarbon group-containing (meth)acrylates; (meth)acrylates obtained from terpene compound derivative alcohols; These can be used individually by 1 type or in combination of 2 or more types.

Examples of aromatic vinyl monomers include, but are not particularly limited to, styrene-based monomers such as styrene, chlorostyrene, chloromethylstyrene, and α-methylstyrene. These can be used individually by 1 type or in combination of 2 or more types.

Examples of aliphatic hydrocarbon monomers include, but are not limited to, olefin monomers and diene monomers. These can be used individually by 1 type or in combination of 2 or more types.

The oligomer in the present invention may contain monomers other than the vinyl monomer having at least one dye structure in the side chain. Such monomers are the same as those described above and are not particularly limited, and examples thereof include (meth)acrylic monomers, aromatic vinyl monomers, and aliphatic hydrocarbon monomers.

In the oligomer of the present invention, the vinyl monomer having at least one dye structure in the side chain is preferably 0.1 parts by mass or more, more preferably 1 part by mass or more, per 100 parts by mass of the oligomer. , 5 parts by mass or more. From the viewpoint of compatibility with the base polymer, the amount is preferably 90 parts by mass or less, more preferably 80 parts by mass or less, and even more preferably 70 parts by mass or less.

The oligomer in the present invention is preferably a (meth)acrylic oligomer.
Such a (meth)acrylic oligomer may be a homopolymer of a (meth)acrylic monomer having at least one dye structure in its side chain.
Further, such a (meth)acrylic oligomer is a copolymer of "a vinyl monomer having at least one dye structure in a side chain" and "a monomer other than a vinyl monomer having at least one dye structure in a side chain". may be In this case, of the total amount of "vinyl monomer having at least one dye structure in its side chain" and "monomer other than vinyl monomer having at least one dye structure in its side chain", it corresponds to the (meth)acrylic monomer. It is preferable that the amount of the monomer to be used is 50% by mass or more. More preferably 70% by mass or more, still more preferably 80% by mass or more.
The "monomers other than vinyl monomers having at least one dye structure in the side chain" are preferably "(meth)acrylic monomers having no dye structure in the side chain", more preferably "side (Meth)acrylic acid alkyl ester having no dye structure in the chain”.

When the (meth)acrylic oligomer is a copolymer of "a vinyl monomer having at least one dye structure in a side chain" and "a monomer other than a vinyl monomer having at least one dye structure in a side chain" , A preferred combination is a combination of "(meth)acrylic monomer having at least one dye structure in the side chain" and "(meth)acrylic monomer having no dye structure in the side chain", which is more preferable. The combination is a combination of "a (meth)acrylic monomer having at least one dye structure in its side chain" and "a (meth)acrylic acid alkyl ester having no dye structure in its side chain".
As the (meth)acrylic monomer and the (meth)acrylic acid alkyl ester, those described above can be used.

In addition, the (meth)acrylic oligomer is an alkyl (meth)acrylate having a branched alkyl group structure such as isobutyl (meth)acrylate or t-butyl (meth)acrylate; an alicyclic hydrocarbon group-containing (meth)acrylate; and aromatic hydrocarbon group-containing (meth)acrylate; and the like, as a monomer unit, preferably contains a (meth)acrylic monomer having a relatively bulky structure, from the viewpoint of improving adhesiveness. 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.

In addition to the above-mentioned (meth)acrylic monomers, functional group-containing monomers can also be used as the constituent monomer components of the (meth)acrylic oligomer, if 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 the total monomer components constituting the acrylic oligomer can be, for example, 1% by mass or more, 2% by mass or more, or 3% by mass or more, and For example, it can be 15% by mass or less, 10% by mass or less, or 7% by mass or less.

The dye structures that the oligomer in the present invention has in one molecule may be the same dye structure or different dye structures. In the present invention, different dye structures include not only dye structures having different dye skeletons, but also dye structures having the same dye skeleton and different types of substituents bonded to the dye skeleton. and In the present invention, the dye structure means a structure derived from a dye compound. For example, a structure obtained by removing one or more arbitrary atoms from a dye compound can be mentioned.

The type of the dye structure is not particularly limited, and can be appropriately selected according to the purpose. It may be a structure derived from a compound, or a structure derived from a dye compound having absorption in the infrared region (preferably a compound having a maximum absorption wavelength in the range of 700 to 1200 nm). A structure derived from a dye compound having absorption in the visible region is preferred.

Examples of dye structures include triarylmethane dye structures, xanthene dye structures, anthraquinone dye structures, cyanine dye structures, squarylium dye structures, quinophthalone dye structures, phthalocyanine dye structures, subphthalocyanine dye structures, azo dye structures, and pyrazolotriazole dyes. structure, dipyrromethene dye structure, isoindoline dye structure, thiazole dye structure, benzimidazolone dye structure, perinone dye structure, pyrrolopyrrole dye structure, diketopyrrolopyrrole dye structure, diimmonium dye structure, naphthalocyanine dye structure, rylene dye structure , a dibenzofuranone dye structure, a merocyanine dye structure, a croconium dye structure, an oxonol dye structure, and the like.
Among them, a triarylmethane dye structure, a xanthene dye structure, and a cyanine dye structure are preferred.
The vinyl monomer in the present invention can have at least one of the above dye structures in its side chain.

The oligomer in the present invention can be formed by polymerizing a monomer composition containing at least a vinyl monomer having at least one dye structure in its side chain. 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 such as n-dodecyl mercaptan (NDM)) is appropriately set based on common technical knowledge so as to achieve a desired molecular weight, so detailed description thereof is omitted.

The oligomer in the present invention preferably has a weight average molecular weight (Mw) of 1,000 to 50,000 from the viewpoint of compatibility with the base polymer. More preferably 2,000 or more, still more preferably 3,000 or more, more preferably 25,000 or less, still more preferably 10,000 or less.
Here, the weight average molecular weight (Mw) refers to a standard polystyrene-equivalent value 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 oligomer in either the pressure-sensitive adhesive composition or the pressure-sensitive adhesive layer.

Moreover, the combination of the base polymer and the oligomer in the present invention is preferably a combination of a (meth)acrylic polymer and a (meth)acrylic oligomer from the viewpoint of good compatibility.

From the viewpoint of colorability, the pressure-sensitive adhesive composition according to the present invention preferably contains 0.01 parts by mass or more of the oligomer, more preferably 1 part by mass or more, relative to 100 parts by mass of the base polymer. Preferably, it is more preferably contained in an amount of 5 parts by mass or more. In addition, from the viewpoint of the influence on physical properties such as adhesive strength, the content of the oligomer is usually 100 parts by mass or less, preferably 90 parts by mass or less, and more preferably 80 parts by mass or less. .

(Other ingredients)
The pressure-sensitive adhesive composition according to one embodiment of the present invention may optionally include a tackifying resin (e.g., rosin-based, petroleum-based, terpene-based, phenol-based, ketone-based, etc.) within a range in which the effects of the present invention are not hindered. Various additives common in the field of adhesive compositions such as tackifying resins), viscosity modifiers (e.g. thickeners), leveling agents, plasticizers, fillers, stabilizers, preservatives, anti-aging agents, etc. It may be included as other optional components. 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 this aspect 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 parts by mass of the base polymer. For example, it can be less than 10 parts by mass, or even less than 5 parts by mass. 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.

The pressure-sensitive adhesive composition according to one embodiment of the present invention is limited in the amount of components other than the base polymer in the pressure-sensitive adhesive composition from the viewpoint of improving transparency and making coloration remarkable with a pigment. is preferred. In the technology according to this aspect, the amount of components other than the base polymer in the pressure-sensitive adhesive composition is usually about 30% by mass or less, suitably about 15% by mass or less, preferably about 12% by mass. or less (for example, about 10% by mass or less). The amount of components other than the base polymer in the pressure-sensitive adhesive composition according to one aspect may be about 5% by mass or less, may be about 3% by mass or less, or may be about 1.5% by mass or less (e.g., about 1% by mass 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 according to this aspect.

<Adhesive layer>
A pressure-sensitive adhesive layer according to one embodiment of the present invention is formed from the pressure-sensitive adhesive composition. FIG. 1 shows a schematic cross-sectional view of one structural example of the pressure-sensitive adhesive layer 11 .

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 steps.

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 according to 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.

(Base material)
The 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. 2 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 a pressure-sensitive adhesive sheet according to one embodiment of the present invention. The adhesive sheet 1 shown in FIG. 2 includes a substrate 21 and an adhesive layer 11 formed on one side of the substrate. As another aspect, FIG. 3 shows a schematic cross-sectional view of a structural example in which pressure-sensitive adhesive layers are formed on both sides of the substrate 21 . The adhesive sheet 2 shown in FIG. 3 comprises a substrate 21, and a first adhesive layer 11 and a second adhesive layer 12 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. A transparent film is preferred. 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 substrate of the pressure-sensitive adhesive sheet according to 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 more than 50% by mass of polyester. Similarly, PPS resin means a resin containing more than 50% by mass of PPS, and polyolefin resin means a resin containing more than 50% by mass of polyolefin.

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 kinds 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, mode of use, etc. 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, workability, 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 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 technique according to this aspect, the haze value of the pressure-sensitive adhesive sheet is suitably about 10% or less, and may be about 5% or less (for example, about 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 for the PSA sheet can also be preferably applied to the haze value of the PSA layer in the technology according to this aspect.

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 this aspect can be preferably used for electronic member applications, optical member applications, construction member applications, and the like.

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

<Preparation of adhesive composition>
[Preparation of adhesive solution]
(Adhesive solution A1)
A reaction vessel equipped with a cooling tube, a nitrogen inlet tube, a thermometer and a stirrer was charged with 97 parts by mass of n-butyl acrylate (BA), 2 parts by mass of acrylic acid (AA), and 4-hydroxybutyl acrylate (4HBA) as monomer components. 1 part by mass and 122 parts by mass of ethyl acetate as a polymerization solvent were charged, and 0.2 parts by mass of 2,2'-azobisisobutyronitrile (AIBN) was added as a thermal polymerization initiator to carry out solution polymerization under a nitrogen atmosphere. By doing so, a pressure-sensitive adhesive solution A1 containing an acrylic polymer having an Mw of 700,000 was obtained.

(Adhesive solution A2)
An adhesive solution A2 having an Mw of 650,000 was prepared in the same manner as the adhesive solution A1, except that the monomer components were 95 parts by mass of n-butyl acrylate (BA) and 5 parts by mass of acrylic acid (AA).

(Adhesive solution A3)
Adhesive solution A3 having an Mw of 600,000 was prepared in the same manner as the adhesive solution A1 except that the monomer components were 95 parts by mass of n-butyl acrylate (BA) and 5 parts by mass of 4-hydroxybutyl acrylate (4HBA). prepared.

Table 1 summarizes the formulation of the adhesive solution.

[Preparation of dye oligomer solution]
(Dye oligomer solution B1)
A reaction vessel equipped with a cooling tube, a nitrogen inlet tube, a thermometer and a stirring device was charged with 90 parts by mass of n-butyl acrylate (BA) as a monomer component, and a blue polymerizable dye that is a vinyl monomer having a dye structure in a side chain. 10 parts by mass of RDW-B01 (manufactured by Fujifilm Wako Pure Chemical Industries), 5 parts by mass of n-dodecyl mercaptan (NDM) as a chain transfer agent, 122 parts by mass of ethyl acetate as a polymerization solvent, and 2 parts by mass as a thermal polymerization initiator. 2′-Azobisisobutyronitrile (AIBN) is added to 0.2 parts by mass and solution polymerization is performed in a nitrogen atmosphere to obtain a dye containing a (meth)acrylic blue dye oligomer having Mw of 5,000. An oligomer solution B1 was obtained.

(Dye oligomer solution B2)
A dye oligomer solution B2 having an Mw of 5,000 was obtained in the same manner as the dye oligomer B1 except that 10 parts by mass of yellow RDW-Y02 (manufactured by Fuji Film Wako Pure Chemical Industries) was used as the polymerizable dye.

(Dye oligomer solution B3)
A dye oligomer solution B3 having an Mw of 1,300 was obtained in the same manner as the dye oligomer B1, except that the amount of n-dodecyl mercaptan (NDM) used was 20 parts by weight per 100 parts by weight of the monomer component.

(Dye oligomer solution B4)
A dye oligomer solution B4 having an Mw of 48,000 was obtained in the same manner as the dye oligomer B1 except that the amount of n-dodecyl mercaptan (NDM) used was 0.1 parts by mass per 100 parts by mass of the above monomer component. .

(Dye oligomer solution B5)
A dye oligomer solution B4 having an Mw of 600 was obtained in the same manner as the dye oligomer B1, except that the amount of n-dodecyl mercaptan (NDM) used was 30 parts by weight per 100 parts by weight of the monomer component.

(Dye oligomer solution B6)
A dye oligomer solution B6 having an Mw of 120,000 was obtained in the same manner as the dye oligomer B1 except that the amount of n-dodecyl mercaptan (NDM) used was 0.02 parts by mass per 100 parts by mass of the monomer component. .

Table 2 summarizes the formulation of the above dye oligomer solution.

[Preparation of adhesive composition]
(Adhesive composition C1)
To the pressure-sensitive adhesive solution A1 obtained above, 1 part by mass of the dye oligomer solution B1 and 0.8 parts by mass of the isocyanate-based cross-linking agent Coronate L (manufactured by Tosoh) are added per 100 parts by mass of the polymer component used to prepare the solution. was added and uniformly mixed to prepare a pressure-sensitive adhesive composition C1.

(Adhesive composition C2)
A pressure-sensitive adhesive composition C2 was prepared in the same manner as the pressure-sensitive adhesive composition C1, except that the amount of the dye oligomer solution B1 used was 5 parts by mass.

(Adhesive composition C3)
Adhesive solution A2 was used, and 0.08 parts by mass of Tetrad C (Mitsubishi Gas Chemical Co., Ltd.) was used instead of 0.8 parts by mass of Coronate L in the same manner as in the preparation of adhesive composition C2. , to prepare an adhesive composition C3.

(Adhesive composition C4)
A pressure-sensitive adhesive composition C4 was prepared in the same manner as the pressure-sensitive adhesive composition C2, except that the pressure-sensitive adhesive solution used was the pressure-sensitive adhesive solution A3.

(Adhesive composition C5)
A pressure-sensitive adhesive composition C5 was prepared in the same manner as the pressure-sensitive adhesive composition C2, except that the dye oligomer solution used was 2.5 parts by mass of the dye oligomer solution B1 and 2.5 parts by mass of B2.

(Adhesive composition C6)
The dye oligomer solution used was 2.5 parts by mass of the dye oligomer solution B1, 2.5 parts by mass of the organic pigment Pigment Blue 15 (manufactured by Tokyo Kasei Kogyo), and 0.5 parts of the dispersant Ajisper PB821 (manufactured by Ajinomoto Fine-Techno). A pressure-sensitive adhesive composition C6 was prepared in the same manner as the pressure-sensitive adhesive composition C2, except that parts by mass were added.

(Adhesive composition C7)
A pressure-sensitive adhesive composition C7 was prepared in the same manner as the pressure-sensitive adhesive composition C2, except that the dye oligomer solution used was the dye oligomer solution B3.

(Adhesive composition C8)
A pressure-sensitive adhesive composition C8 was prepared in the same manner as the pressure-sensitive adhesive composition C2, except that the dye oligomer solution used was the dye oligomer solution B4.

(Adhesive composition C9)
A pressure-sensitive adhesive composition C9 was prepared in the same manner as the pressure-sensitive adhesive composition C2, except that the dye oligomer solution used was the dye oligomer solution B5.

(Adhesive composition C10)
A pressure-sensitive adhesive composition C10 was prepared in the same manner as the pressure-sensitive adhesive composition C2, except that the dye oligomer solution used was the dye oligomer solution B6.

(Adhesive composition C11)
A pressure-sensitive adhesive composition C11 was prepared in the same manner as the pressure-sensitive adhesive composition C1, except that 1 part by mass of the organic pigment Pigment Blue 15 was used instead of the dye oligomer solution B1.

(Adhesive composition C12)
The pressure-sensitive adhesive composition was prepared in the same manner as the pressure-sensitive adhesive composition C11 except that 2.5 parts by mass of Pigment Blue 15 and 2.5 parts by mass of Pigment Yellow 74 (manufactured by Oakwood Products, Inc.) were used as organic pigments. C12 was prepared.

(Adhesive composition C13)
A pressure-sensitive adhesive composition C13 was prepared in the same manner as the pressure-sensitive adhesive composition C1, except that the dye oligomer solution B1 was not used.

(Adhesive composition C14)
A pressure-sensitive adhesive composition C14 was prepared in the same manner as the pressure-sensitive adhesive composition C11, except that 0.5 parts by mass of a dispersant Ajisper PB821 (manufactured by Ajinomoto Fine-Techno Co., Ltd.) was added.

(Adhesive composition C15)
A pressure-sensitive adhesive composition C15 was prepared in the same manner as the pressure-sensitive adhesive composition C14, except that the amount of the organic pigment Pigment Blue 15 used was 5 parts by mass.

(Adhesive composition C16)
The adhesive solution used was adhesive solution A2, 0.08 parts of Tetrad C (manufactured by Mitsubishi Gas Chemical Co., Ltd.) was used instead of 0.8 parts by mass of Coronate L, and no dispersant was used. Adhesive composition C16 was prepared in the same manner as in the preparation.

<Production of adhesive sheet>
(Example 1)
The pressure-sensitive adhesive composition C1 is applied to a release film R1 (Mitsubishi Plastics Co., Ltd., MRF #38) having a thickness of 38 μm 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 30 μm. to form an adhesive layer. A 75-μm-thick polyethylene terephthalate (PET) film that has been subjected to corona treatment is attached to this adhesive layer, thereby forming an adhesive sheet 1 in which a PET film (support), an adhesive layer, and a release film R1 are laminated in this order. Obtained.

(Examples 2 to 10)
PSA sheets 2 to 10 were produced in the same manner as in Example 1, except that PSA compositions C2 to C10 were used instead of PSA composition C1.

(Comparative Examples 1 and 2)
PSA sheets 11 and 12 were produced in the same manner as in Example 1, except that PSA compositions C11 and C12 were used instead of the PSA compositions.

(Reference examples 1 to 4)
PSA sheets 13 to 16 according to each example were produced in the same manner as in Example 1, except that PSA compositions C13 to C16 were used instead of the PSA compositions.

<Evaluation of dispersibility>
The dispersibility of the dye oligomer or known organic pigment in the pressure-sensitive adhesive sheets 1 to 16 produced above was evaluated according to the degree of presence of aggregates as follows.
○ (Good dispersibility): No visible aggregates were observed in the 10 cm × 10 cm test piece △ (Slightly good dispersibility): Less than 10 visible aggregates were observed in the 10 cm × 10 cm test piece x (poor dispersibility): 10 or more visible aggregates were observed in a test piece of 10 cm x 10 cm. Table 3 shows the results. In Table 3, "-" means that this evaluation was not performed.

<Evaluation of bleed-out property>
The bleed-out properties of the pressure-sensitive adhesive sheets 1 to 16 produced above were evaluated according to the extent of the dye component remaining on the adherend after peeling, as described below. The region where the dye component remained in the following evaluation was determined by measuring the change in weight of the adhesive sheet before and after peeling, with the specific gravity of the adhesive layer being 1.17 g/cm ³ .
○ (good bleed-out property): No residual dye component was observed on the 2.5 cm × 7 cm peeled surface △ (slightly good bleed-out property): less than 10% of the area on the 2.5 cm × 7 cm peeled surface Remaining dye component was observed × (poor bleeding out property): Residual dye component was observed in 10% or more of the peeled surface of 2.5 cm × 7 cm. Table 3 shows the results. In Table 3, "-" means that this evaluation was not performed.

<Measurement of adhesive strength>
The adhesive force was measured for the adhesive sheets 1 to 16 produced above.
The adhesive force was measured by cutting each of the adhesive sheets 1 to 16 into pieces having a width of 25 mm and a length of 10 cm, and peeling off the release liner.
Subsequently, each pressure-sensitive adhesive sheet was attached to an alkali glass by reciprocating once with a 2-kg roller under pressure.
Using a tensile tester (AUTOGRAPH AGS-X, manufactured by Shimadzu Corporation), the adhesive strength (N/25 mm) was measured by peeling at a peeling angle of 180 degrees and a peeling speed of 300 mm/min.
Table 3 shows the results. In Table 3, "-" means that this measurement was not performed.

The pressure-sensitive adhesive sheets of Examples 1 to 10 containing dye oligomers had good dispersibility and bleed-out properties. Among them, in Examples 1 to 8 in which the weight average molecular weight (Mw) of the dye oligomer was 1,000 to 50,000, both dispersibility and bleed-out properties were particularly good. In addition, although the pressure-sensitive adhesive sheet of Example 6 contains a pigment, it also contains a dispersant, and thus good results were obtained.
On the other hand, the pressure-sensitive adhesive sheets of Comparative Examples 1 and 2 contained pigments instead of dye oligomers, and thus were poor in both dispersibility and bleeding-out properties.
In the pressure-sensitive adhesive sheets of Reference Examples 2 and 3, a dispersant was added to the pressure-sensitive adhesive composition of Comparative Example 1. Therefore, the pressure-sensitive adhesive sheet of Comparative Example 1 was poor in both dispersibility and bleed-out properties, while the pressure-sensitive adhesive sheets of Reference Examples 2 and 3 were good in both dispersibility and bleed-out properties. In addition, the pressure-sensitive adhesive sheet of Reference Example 4 used a pressure-sensitive adhesive solution containing a polymer with a high acid value, and therefore had good dispersibility and bleed-out properties.

1, 2 adhesive sheets 11, 12 adhesive layer 21 substrate

Claims (9)

A pressure-sensitive adhesive composition comprising a base polymer and at least one oligomer,
The oligomer is an oligomer obtained by polymerizing a monomer composition containing at least a vinyl monomer having at least one dye structure in a side chain,
Adhesive composition. The pressure-sensitive adhesive composition according to claim 1, wherein the base polymer is a (meth)acrylic polymer. The pressure-sensitive adhesive composition according to claim 1 or 2, wherein the oligomer is a (meth)acrylic oligomer. 4. The pressure-sensitive adhesive composition according to claim 3, wherein the (meth)acrylic oligomer is a homopolymer of a (meth)acrylic monomer having at least one dye structure in a side chain. The pressure-sensitive adhesive according to claim 3, wherein the (meth)acrylic oligomer is a copolymer of a (meth)acrylic monomer having at least one dye structure in a side chain and a (meth)acrylic acid alkyl ester. Composition. The pressure-sensitive adhesive composition according to any one of claims 1 to 5, wherein the oligomer has a weight average molecular weight of 1,000 to 50,000. A pressure-sensitive adhesive layer comprising the pressure-sensitive adhesive composition according to any one of claims 1 to 6. A pressure-sensitive adhesive sheet comprising the pressure-sensitive adhesive layer according to claim 7. The pressure-sensitive adhesive sheet according to claim 8, comprising the pressure-sensitive adhesive layer on a transparent film.

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