WO2024117226A1

WO2024117226A1 - Ultraviolet-curable adhesive composition and method for producing laminate

Info

Publication number: WO2024117226A1
Application number: PCT/JP2023/042957
Authority: WO
Inventors: 晋治河田; 千春奥原; 智基戸田; 涼馬石立; 拓身木田; 雄大緒方
Original assignee: 積水化学工業株式会社
Priority date: 2022-12-01
Filing date: 2023-11-30
Publication date: 2024-06-06
Also published as: WO2024117230A1; TW202432776A; JPWO2024117230A1

Abstract

The present invention is an ultraviolet-curable adhesive composition comprising a maleimide derivative, an ultraviolet-polymerizable compound, a photopolymerization initiator, and an amine compound. When this maleimide derivative contains a maleimide derivative that does not have a structure in which hydrogen is bonded to a heteroatom, the maleimide derivative either does not contain a maleimide derivative that has a structure in which hydrogen is bonded to a heteroatom, or the content in the maleimide derivative of maleimide derivative having a structure in which hydrogen is bonded to a heteroatom is less than 50 mass%. When the maleimide derivative contains only maleimide derivative having a structure in which hydrogen is bonded to a heteroatom, the content of this maleimide derivative having a structure in which hydrogen is bonded to a heteroatom is not more than 9.8 parts by mass per 100 parts by mass of the ultraviolet-polymerizable compound. The ultraviolet-polymerizable compound contains at least 20 mass% of monomer that can be a hydrogen donor. The photopolymerization initiator contains at least one selection from the group consisting of hydrogen-abstracting photopolymerization initiators and polymeric photopolymerization initiators. With regard to the amine compound, the content in this amine compound of amine compound that does not have a structure in which hydrogen is bonded to a heteroatom is at least 50 mass%. The content in the ultraviolet-curable adhesive composition of the amine compound, per 100 parts by mass of the total of the maleimide derivative and ultraviolet-polymerizable compound, is 0.1 parts by mass to 10 parts by mass.

Description

Ultraviolet-curable pressure-sensitive adhesive composition and method for producing laminate

The present invention relates to an ultraviolet-curable adhesive composition. The present invention also relates to a method for producing a laminate using the ultraviolet-curable adhesive composition.

Adhesives are used to bond electronic components inside electronic devices such as smartphones and PCs. In a typical method of bonding using adhesives, an adhesive sheet is first prepared with separators on both sides of the adhesive, and then the adhesive sheet is cut into the desired shape. One separator is then peeled off from the cut adhesive sheet, and one side of the exposed adhesive is bonded to a first adherend, and then the other separator is peeled off, and the other side of the exposed adhesive is bonded to a second adherend. With this method, part of the adhesive sheet is discarded after cutting, generating waste. Also, air bubbles can sometimes get into the bonded surfaces.

In response to this, a method has been developed in which a pressure-sensitive adhesive composition is printed in a desired shape and then bonded to an adherend, without the need to prepare a pressure-sensitive adhesive sheet. This method can reduce waste generation and prevent air bubbles from forming on the bonding surface.

For example, Patent Document 1 discloses an invention for providing a radiation-curable adhesive composition that allows fine patterning and exhibits high adhesion to various adherends such as metals and plastics. Patent Document 1 describes a radiation-curable adhesive composition that contains 10 to 70% by weight of an ethylenically unsaturated monomer that does not contain an aromatic ring, 1 to 10% by weight of a photopolymerization initiator, and 10 to 55% by weight of a crosslinking agent.

Patent Document 2 discloses an invention for providing a photocurable adhesive composition that, even when irradiated with light in the presence of oxygen, gives a laminate having adhesive strength equivalent to that in the absence of oxygen. Patent Document 2 describes a photocurable adhesive composition that contains (A) a (meth)acrylate oligomer, (B) a monofunctional (meth)acrylic monomer, (C) a di- to tetrafunctional (meth)acrylic monomer, (D) a photoinitiator, (E) a tackifier having a softening point of 70 to 150°C, and (F) a liquid plasticizer.

JP 2013-216742 A International Publication No. 2016/163152

As described above, the method of printing the adhesive composition in a desired shape and then laminating it to an adherend without preparing an adhesive sheet can suppress the generation of waste and prevent air bubbles from entering the lamination surface. On the other hand, as a method for curing the adhesive composition, ultraviolet curing is preferable to avoid heating the adherend. However, when an attempt is made to obtain a cured product with high curability by ultraviolet curing in the presence of oxygen, the crosslinking density becomes high, resulting in poor stress relaxation properties, and as a result, the cured product may have poor impact resistance. In addition, if the adhesive composition is not covered with a separator during curing and is exposed to the presence of oxygen, the outermost surface may not be cured, and sufficient adhesion may not be obtained. Furthermore, poor curability of the outermost surface may cause bleeding, and the presence of the bleeding may cause slippage in the shear direction when the adhesive composition is used to laminate the adherend.

The present invention aims to provide an ultraviolet-curable pressure-sensitive adhesive composition that has excellent printability, is unlikely to cause cohesive failure in the cured product, and has excellent impact resistance, and an ultraviolet-curable pressure-sensitive adhesive composition that has excellent adhesion and low bleeding properties. The present invention also aims to provide a method for producing a laminate using the ultraviolet-curable pressure-sensitive adhesive composition.

Disclosure 1 is an ultraviolet-curable pressure-sensitive adhesive composition containing a maleimide derivative, an ultraviolet-polymerizable compound, a photopolymerization initiator, and an amine compound, and when the maleimide derivative contains a maleimide derivative not having a structure in which hydrogen is bonded to a heteroatom, the maleimide derivative does not contain a maleimide derivative having a structure in which hydrogen is bonded to a heteroatom, or the content of the maleimide derivative having a structure in which hydrogen is bonded to the heteroatom in the maleimide derivative is less than 50 mass%, and when the maleimide derivative contains only a maleimide derivative having a structure in which hydrogen is bonded to a heteroatom, the content of the maleimide derivative having a structure in which hydrogen is bonded to the heteroatom relative to 100 parts by mass of the ultraviolet-polymerizable compound is less than 50 mass%. the content of the maleimide derivative having a structure in which hydrogen is bonded to a heteroatom is 9.8 parts by mass or less; the ultraviolet-polymerizable compound contains 20% by mass or more of a monomer capable of acting as a hydrogen donor; the photopolymerization initiator contains at least one selected from the group consisting of hydrogen abstraction type photopolymerization initiators and polymer type photopolymerization initiators; the content of the amine compound not having a structure in which hydrogen is bonded to a heteroatom in the amine compound is 50% by mass or more; and the content of the amine compound is 0.1 parts by mass or more and 10 parts by mass or less relative to a total of 100 parts by mass of the maleimide derivative and the ultraviolet-polymerizable compound.
The present disclosure 2 is the ultraviolet-curable pressure-sensitive adhesive composition of the present disclosure 1, in which the content of the maleimide derivative is 0.1 parts by mass or more and 20 parts by mass or less relative to 100 parts by mass of the ultraviolet-polymerizable compound.
The present disclosure 3 relates to the ultraviolet-curable pressure-sensitive adhesive composition of the present disclosure 1 or 2, wherein the monomer capable of serving as the hydrogen donor is a monomer having at least one structure selected from the group consisting of an ether bond, an acetyl group, a phenoxy group, a benzyl group, and an amide bond.
The present disclosure 4 is an ultraviolet-curable pressure-sensitive adhesive composition according to the present disclosure 1, 2, or ³ , which is obtained by coating the ultraviolet-curable pressure-sensitive adhesive composition on a substrate, and simultaneously irradiating an upper surface of the coating with ultraviolet light having a wavelength of 365 nm and an illuminance of 20 mW/ ^cm2 and light having a wavelength of 405 nm and an illuminance of 40 mW/cm2 in an atmospheric environment so that the total irradiation amount is 900 mJ/ ^cm2 , thereby obtaining a cured product having a thickness of 100 μm, the reaction rate of which is 85% or more.
Disclosure 5 relates to an ultraviolet-curable pressure-sensitive adhesive composition containing a maleimide derivative, an ultraviolet-polymerizable compound, and a photopolymerization initiator, the content of the maleimide derivative being 8 parts by mass or more relative to 100 parts by mass of the ultraviolet-polymerizable compound, and the ultraviolet-curable pressure-sensitive adhesive composition is applied to a substrate, and the substrate is simultaneously irradiated with ultraviolet light having a wavelength of 365 nm and an illuminance of 20 mW/ ^cm2 and light having a wavelength of 405 nm and an illuminance of 40 mW/ ^cm2 in an atmospheric environment without sealing the upper surface of the coating, so that the total irradiation amount is 900 mJ/ ^cm2 , thereby obtaining an ultraviolet-curable pressure-sensitive adhesive composition having a reaction rate of 88% or more of a cured product having a thickness of 100 μm.
The present disclosure 6 is the ultraviolet-curable pressure-sensitive adhesive composition of the present disclosure 5, further comprising an amine compound.
The present disclosure 7 is the ultraviolet-curable pressure-sensitive adhesive composition of the present disclosure 1, 2, 3, 4, 5, or 6, wherein the ultraviolet-polymerizable compound contains 50 mass% or more of a monomer having at least one structure selected from the group consisting of an ether bond, an acetyl group, a phenoxy group, a benzyl group, and an amide bond.
The present disclosure 8 is the ultraviolet-curable pressure-sensitive adhesive composition according to the present disclosure 1, 2, 3, 4, 5, 6, or 7, wherein the ultraviolet-polymerizable compound comprises at least one selected from the group consisting of (meth)acrylic monomers and vinyl monomers.
The present disclosure 9 is the ultraviolet-curable pressure-sensitive adhesive composition according to the present disclosure 8, wherein the ultraviolet-polymerizable compound contains a polyfunctional (meth)acrylic monomer.
Disclosure 10 is the ultraviolet-curable pressure-sensitive adhesive composition of Disclosure 9, wherein the ultraviolet-polymerizable compound contains a polyfunctional (meth)acrylic monomer, and the content of the polyfunctional (meth)acrylic monomer per total 100 parts by mass of the maleimide derivative and the ultraviolet-polymerizable compound excluding the polyfunctional (meth)acrylic monomer is 25 parts by mass or less.
The present disclosure 11 is the ultraviolet-curable pressure-sensitive adhesive composition of the present disclosure 10, in which the content of the polyfunctional (meth)acrylic monomer is 20 parts by mass or less per 100 parts by mass of the total of the maleimide derivative and the ultraviolet-polymerizable compound excluding the polyfunctional (meth)acrylic monomer.
The present disclosure 12 is the ultraviolet-curable pressure-sensitive adhesive composition of the present disclosure 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, or 11, wherein the content of the photopolymerization initiator is 1 part by mass or more and 10 parts by mass or less with respect to a total of 100 parts by mass of the maleimide derivative and the ultraviolet-polymerizable compound.
The present disclosure 13 is the ultraviolet-curable pressure-sensitive adhesive composition of the present disclosure 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, or 12, further comprising a thermoplastic resin.
The present disclosure 14 is the ultraviolet-curable pressure-sensitive adhesive composition of the present disclosure 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, or 13, further comprising a tackifier.
The present disclosure 15 is the ultraviolet-curable pressure-sensitive adhesive composition of the present disclosure 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, or 14, having a viscosity at 25° C. of 10 mPa·s or more and 75,000 mPa·s or less.
The present disclosure 16 is an ultraviolet-curable pressure-sensitive adhesive composition according to the present disclosure 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, ¹³ , 14, or 15, which is obtained by coating the ultraviolet-curable pressure-sensitive adhesive composition on a substrate and simultaneously irradiating the substrate with ultraviolet light having a wavelength of 365 nm and an illuminance of ²⁰ mW/cm2 and light having a wavelength of 405 nm and an illuminance of 40 mW/ ^cm2 so that the total irradiation amount is 900 mJ/cm2, and which has a thickness of 100 μm and a glass transition temperature of −60° C. or higher and 20° C. or lower.
Disclosure 17 is a method for producing a laminate in which the ultraviolet-curable pressure-sensitive adhesive composition of Disclosures 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, or 16 is applied onto a first adherend and exposed to light to form an adhesive layer, and a step of attaching a second adherend onto the adhesive layer, wherein the method for applying the ultraviolet-curable pressure-sensitive adhesive composition is inkjet printing, screen printing, spray coating, spin coating, gravure offset, or reverse offset printing, and the ultraviolet-curable pressure-sensitive adhesive composition is partially applied onto the first adherend.
The present invention will be described in detail below.

Hereinafter, the ultraviolet-curable pressure-sensitive adhesive composition of Disclosure 1 will also be referred to as the "ultraviolet-curable pressure-sensitive adhesive composition of Invention 1," and the ultraviolet-curable pressure-sensitive adhesive composition of Disclosure 5 will also be referred to as the "ultraviolet-curable pressure-sensitive adhesive composition of Invention 2." Furthermore, matters common to the ultraviolet-curable pressure-sensitive adhesive composition of Invention 1 and the ultraviolet-curable pressure-sensitive adhesive composition of Invention 2 will be described as the "ultraviolet-curable pressure-sensitive adhesive composition of the present invention."
The present inventors have studied the use of a combination of a specific maleimide derivative, a specific ultraviolet-polymerizable compound, a specific photopolymerization initiator, and a specific amine compound in a specific content ratio in an ultraviolet-curable adhesive composition. As a result, it has been found that an ultraviolet-curable adhesive composition having excellent printability, a cured product that is unlikely to cause cohesive failure, and excellent impact resistance can be obtained, and the present invention 1 has been completed. In addition, the present inventors have studied the use of a combination of a maleimide derivative, an ultraviolet-polymerizable compound, and a photopolymerization initiator in an ultraviolet-curable adhesive composition, the content of the photopolymerization initiator being within a specific range, and the reaction rate of the cured product of the ultraviolet-curable adhesive composition cured under specific conditions being a specific value or more. As a result, it has been found that an ultraviolet-curable adhesive composition having excellent adhesion and low bleeding can be obtained, and the present invention 2 has been completed.

The ultraviolet-curable pressure-sensitive adhesive composition of the present invention contains a maleimide derivative.
The reaction system of the maleimide derivative basically proceeds by a hydrogen abstraction (Type II) reaction. Photoradical polymerization by hydrogen abstraction reaction is not easily inhibited by oxygen, and therefore can increase the surface curability. In addition, photoradical polymerization by hydrogen abstraction reaction does not give a linear polymer as in cleavage (Type I) reaction, but a branched polymer is obtained, and the cohesive strength is also high. Therefore, the ultraviolet-curable pressure-sensitive adhesive composition of the present invention contains the maleimide derivative in combination with an ultraviolet-polymerizable compound described later, and can obtain a cured product that is less likely to cause bleeding due to a decrease in surface curability and cohesive failure due to a decrease in surface curability and cohesive strength.
In this specification, the "maleimide derivative" refers to a compound having a maleimide group. Although the maleimide derivative has ultraviolet-ray polymerizability, it is not considered to be an ultraviolet-ray polymerizable compound, which will be described later.

In the ultraviolet-curable adhesive composition of the present invention 1, when the maleimide derivative contains a maleimide derivative that does not have a structure in which hydrogen is bonded to a heteroatom, the maleimide derivative does not contain a maleimide derivative that has a structure in which hydrogen is bonded to a heteroatom, or the content of the maleimide derivative that has a structure in which hydrogen is bonded to the heteroatom in the maleimide derivative is less than 50 mass%, and when the maleimide derivative contains only a maleimide derivative that has a structure in which hydrogen is bonded to a heteroatom, the content of the maleimide derivative that has a structure in which hydrogen is bonded to the heteroatom relative to 100 mass parts of the ultraviolet-polymerizable compound is 9.8 mass parts or less. As a result, the ultraviolet-curable adhesive composition of the present invention has a cured product that has excellent impact resistance. It is particularly preferable that the maleimide derivative contains only a maleimide derivative that does not have a structure in which hydrogen is bonded to a heteroatom.

Examples of structures in which hydrogen is bonded to the heteroatom include a hydroxyl group, a carboxyl group, a primary amino group, a secondary amino group, etc.

Among the maleimide derivatives not having a structure in which hydrogen is bonded to a heteroatom, examples of monofunctional maleimides include N-cyclohexylmaleimide, N-laurylmaleimide, N-phenylmaleimide, N-(2-methylphenyl)maleimide, N-(4-methylphenyl)maleimide, N-(2,6-diethylphenyl)maleimide, N-methylmaleimide, N-ethylmaleimide, N-isopropylmaleimide, N-butylmaleimide, N-benzylmaleimide, N-phenylmethylmaleimide, N-octadecenylmaleimide, N-dodecenylmaleimide, etc. Among these, at least one selected from the group consisting of N-cyclohexylmaleimide and N-laurylmaleimide is preferred.
Furthermore, examples of polyfunctional maleimides among the maleimide derivatives not having a structure in which hydrogen is bonded to a heteroatom include N,N'-methylene bismaleimide, N,N'-trimethylene bismaleimide, N,N'-dodecamethylene bismaleimide, N,N'-(4,4'-diphenylmethane)bismaleimide, 1,4-dimaleimidecyclohexane, isophorone bisurethane bis(N-ethylmaleimide), N,N'-P-phenylene bismaleimide, N,N'-m-phenylene bismaleimide, N,N'-m-toluylene bismaleimide, N,N N,N'-4,4'-biphenylene bismaleimide, N,N'-4,4'-(3,3'-dimethyl-biphenylene) bismaleimide, N,N'-4,4'-(3,3'-dimethyldiphenylmethane) bismaleimide, N,N'-4,4'-(3,3'-diethyldiphenylmethane) bismaleimide, N,N'-4,4'-diphenylpropane bismaleimide, N,N'-4,4'-diphenylether bismaleimide, N,N'-3,3'-diphenylsulfone bismaleimide, and N,N'-4,4'-diphenylsulfone bismaleimide.
From the viewpoint of increasing the reaction rate, the above-mentioned monofunctional maleimide may be used in combination with these polyfunctional maleimides as the maleimide derivative not having a structure in which hydrogen is bonded to the heteroatom. However, since the gel fraction will increase, it is not preferable to use a large amount of polyfunctional maleimide in combination.

Examples of maleimide derivatives having a structure in which hydrogen is bonded to the heteroatom include N-(4-carboxycyclohexylmethyl)maleimide, 4-hydroxyphenylmaleimide, and N-(4-anilinophenyl)maleimide.

Among the maleimide derivatives in the ultraviolet-curable pressure-sensitive adhesive composition of the second invention, examples of the monofunctional maleimide include N-cyclohexylmaleimide, N-laurylmaleimide, 4-hydroxyphenylmaleimide, N-(4-carboxycyclohexylmethyl)maleimide, N-phenylmaleimide, N-(2-methylphenyl)maleimide, N-(4-methylphenyl)maleimide, N-(2,6-diethylphenyl)maleimide, N-(2-chlorophenyl)maleimide, and N-methylmaleimide. Examples of the monofunctional maleimide include N-ethylmaleimide, N-isopropylmaleimide, N-butylmaleimide, N-benzylmaleimide, N-phenylmethylmaleimide, N-(2,4,6-tribromophenyl)maleimide, N-[3-(triethoxysilyl)propyl]maleimide, N-octadecenylmaleimide, N-dodecenylmaleimide, N-(2-methoxyphenyl)maleimide, N-(2,4,6-trichlorophenyl)maleimide, and N-(1-hydroxyphenyl)maleimide. Among them, it is preferable to select a maleimide derivative that does not have a structure in which hydrogen is bonded to a heteroatom from the viewpoint of increasing the reaction rate. In addition, a maleimide derivative that has a structure in which hydrogen is bonded to a heteroatom from the viewpoint of improving adhesive strength may be used. Specifically, the monofunctional maleimide is preferably at least one selected from the group consisting of N-cyclohexylmaleimide, 4-hydroxyphenylmaleimide, and N-(4-carboxycyclohexylmethyl)maleimide.
Among the maleimide derivatives, examples of polyfunctional maleimides include N,N'-methylene bismaleimide, N,N'-trimethylene bismaleimide, N,N'-dodecamethylene bismaleimide, N,N'-(4,4'-diphenylmethane) bismaleimide, 1,4-dimaleimidecyclohexane, isophorone bisurethane bis(N-ethylmaleimide), N,N'-P-phenylene bismaleimide, N,N'-m-phenylene bismaleimide, N,N'-m-toluylene bismaleimide, and N,N'-4,4'-biphenyl. bismaleimide, N,N'-4,4'-(3,3'-dimethyl-biphenylene)bismaleimide, N,N'-4,4'-(3,3'-dimethyldiphenylmethane)bismaleimide, N,N'-4,4'-(3,3'-diethyldiphenylmethane)bismaleimide, N,N'-4,4'-diphenylpropane bismaleimide, N,N'-4,4'-diphenylether bismaleimide, N,N'-3,3'-diphenylsulfone bismaleimide, and N,N'-4,4'-diphenylsulfone bismaleimide.
From the viewpoint of increasing the reaction rate, the above-mentioned monofunctional maleimide and these polyfunctional maleimides may be used in combination as the maleimide derivative. However, since the gel fraction becomes high, it is not preferable to use a large amount of the polyfunctional maleimide in combination.

In the ultraviolet-curable pressure-sensitive adhesive composition of the first invention, the content of the maleimide derivative is preferably 0.1 parts by mass at the lower limit and 20 parts by mass at the upper limit relative to 100 parts by mass of the ultraviolet-polymerizable compound described below. By setting the content of the maleimide derivative in the ultraviolet-curable pressure-sensitive adhesive composition of the first invention within the above range, the obtained ultraviolet-curable pressure-sensitive adhesive composition has better curability. The more preferred lower limit of the content of the maleimide derivative in the ultraviolet-curable pressure-sensitive adhesive composition of the first invention is 0.5 parts by mass, and the more preferred upper limit is 10 parts by mass.
In the ultraviolet-curable pressure-sensitive adhesive composition of the second invention, the content of the maleimide derivative has a lower limit of 8 parts by mass relative to 100 parts by mass of the ultraviolet-polymerizable compound described below. When the content of the maleimide derivative in the ultraviolet-curable pressure-sensitive adhesive composition of the second invention is 8 parts by mass or more, the obtained ultraviolet-curable pressure-sensitive adhesive composition has excellent surface curing properties. The lower limit of the content of the maleimide derivative in the ultraviolet-curable pressure-sensitive adhesive composition of the second invention is preferably 10 parts by mass, more preferably 12 parts by mass, and even more preferably 14 parts by mass.
From the viewpoint of reaction rate, the upper limit of the content of the maleimide derivative in the ultraviolet-curable pressure-sensitive adhesive composition of the second invention relative to 100 parts by mass of the ultraviolet-polymerizable compound described below is preferably 70 parts by mass, and more preferably 30 parts by mass.

The ultraviolet-curable pressure-sensitive adhesive composition of the present invention contains an ultraviolet-polymerizable compound.
As described above, the ultraviolet-curable pressure-sensitive adhesive composition of the present invention contains the ultraviolet-polymerizable compound in combination with the maleimide derivative, and thereby makes it possible to obtain a cured product that is less susceptible to bleeding due to a decrease in surface curability and cohesive failure due to a decrease in curability and cohesive strength.

In the ultraviolet-curable pressure-sensitive adhesive composition of the first invention, the ultraviolet-polymerizable compound contains a monomer capable of serving as a hydrogen donor. In the ultraviolet-curable pressure-sensitive adhesive composition of the second invention, the ultraviolet-polymerizable compound preferably contains a monomer capable of serving as a hydrogen donor.
In this specification, the above-mentioned "monomer capable of serving as a hydrogen donor" means a monomer having hydrogen capable of being used in a hydrogen abstraction reaction.

The monomer capable of serving as the hydrogen donor is preferably a monomer having at least one structure selected from the group consisting of an ether bond, an acetyl group, a phenoxy group, a benzyl group, and an amide bond. By having the monomer capable of serving as the hydrogen donor be a monomer having at least one structure selected from the group consisting of an ether bond, an acetyl group, a phenoxy group, a benzyl group, and an amide bond, hydrogen can be more easily provided to the hydrogen abstraction reaction. In particular, it is more preferable that the monomer capable of serving as the hydrogen donor be a monomer having at least one structure selected from the group consisting of an ether bond, a phenoxy group, and an amide bond.

In the ultraviolet-curable pressure-sensitive adhesive composition of the present invention 1, the lower limit of the content of the monomer capable of being a hydrogen donor in the ultraviolet-polymerizable compound is 20% by mass. When the content of the monomer capable of being a hydrogen donor in the ultraviolet-polymerizable compound is 20% by mass or more, the ultraviolet-curable pressure-sensitive adhesive composition of the present invention has excellent curability. The preferred lower limit of the content of the monomer capable of being a hydrogen donor in the ultraviolet-polymerizable compound is 35% by mass.
From the viewpoint of impact resistance, the upper limit of the content of the monomer capable of serving as a hydrogen donor in the ultraviolet-polymerizable compound is preferably 90% by mass, and more preferably 70% by mass.
In particular, in the ultraviolet-curable pressure-sensitive adhesive composition of the present invention, the ultraviolet-curable compound preferably contains 50% by mass or more of a monomer having at least one structure selected from the group consisting of an ether bond, an acetyl group, a phenoxy group, a benzyl group, and an amide bond. By containing 50% by mass or more of a monomer having at least one structure selected from the group consisting of an ether bond, an acetyl group, a phenoxy group, a benzyl group, and an amide bond in the ultraviolet-curable pressure-sensitive adhesive composition obtained, the surface curability and the impact resistance of the cured product become more excellent. More preferably, the ultraviolet-curable compound contains 70 parts by mass or more of a monomer having at least one structure selected from the group consisting of an ether bond, an acetyl group, a phenoxy group, a benzyl group, and an amide bond in 100 parts by mass of the (meth)acrylic monomer.
The (meth)acrylic monomer may contain only a monomer having at least one structure selected from the group consisting of an ether bond, an acetyl group, a phenoxy group, a benzyl group, and an amide bond.

The ultraviolet polymerizable compound preferably contains at least one selected from the group consisting of (meth)acrylic monomers and vinyl monomers. When the ultraviolet polymerizable compound contains at least one selected from the group consisting of the (meth)acrylic monomers and the vinyl monomers, the obtained ultraviolet-curable pressure-sensitive adhesive composition has superior curability.
In this specification, the term "(meth)acrylic" means acrylic or methacrylic, the term "(meth)acrylic monomer" means a monomer having a (meth)acryloyl group, and the term "(meth)acryloyl" means acryloyl or methacryloyl.

From the viewpoint of adhesion to various substrates, the (meth)acrylic monomer preferably contains a monofunctional (meth)acrylic monomer.
In this specification, the term "monofunctional (meth)acrylic monomer" refers to a monomer having one (meth)acryloyl group in one molecule.

Examples of the monofunctional (meth)acrylic monomer include monofunctional (meth)acrylic acid ester compounds, monofunctional (meth)acrylamide compounds, etc.

Examples of the monofunctional (meth)acrylic acid ester compound include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, n-heptyl (meth)acrylate, isooctyl (meth)acrylate, isononyl (meth)acrylate, isodecyl (meth)acrylate, lauryl (meth)acrylate, isomyristyl (meth)acrylate, stearyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, and 2-hydroxybutyl (meth)acrylate. 4-hydroxybutyl (meth)acrylate, cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, bicyclopentenyl (meth)acrylate, benzyl (meth)acrylate, 2-methoxyethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, 2-butoxyethyl (meth)acrylate, 2-phenoxyethyl (meth)acrylate, methoxyethylene glycol (meth)acrylate, methoxypolyethylene glycol (meth)acrylate, phenoxydiethylene glycol (meth)acrylate, phenoxypolyethylene glycol (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, tetrahydrofurfuryl alcohol acrylic acid polymer ester, ethyl carbitol (meth)acrylate, 2,2,2-trifluoroethyl (meth)acrylate acrylate, 2,2,3,3-tetrafluoropropyl (meth)acrylate, 1H,1H,5H-octafluoropentyl (meth)acrylate, imido (meth)acrylate, dimethylaminoethyl (meth)acrylate, diethylaminoethyl (meth)acrylate, 2-(meth)acryloyloxyethyl succinate, 2-(meth)acryloyloxyethyl hexahydrophthalate, 2-(meth)acryloyloxyethyl 2-hydroxypropyl phthalate, 2-(meth)acryloyloxyethyl phosphate, (3-ethyloxetan-3-yl)methyl (meth)acrylate, 2-(((butylamino)carbonyl)oxy)ethyl (meth)acrylate, (3-propyloxetan-3-yl)methyl (meth)acrylate, (3-butyloxetan-3-yl)methyl (meth)acrylate, (3-ethyloxetane Examples of the acrylates include (3-ethyloxetan-3-yl)ethyl (meth)acrylate, (3-ethyloxetan-3-yl)propyl (meth)acrylate, (3-ethyloxetan-3-yl)butyl (meth)acrylate, (3-ethyloxetan-3-yl)pentyl (meth)acrylate, (3-ethyloxetan-3-yl)hexyl (meth)acrylate, γ-butyrolactone (meth)acrylate, (2,2-dimethyl-1,3-dioxolan-4-yl)methyl (meth)acrylate, (2-methyl-2-ethyl-1,3-dioxolan-4-yl)methyl (meth)acrylate, (2-methyl-2-isobutyl-1,3-dioxolan-4-yl)methyl (meth)acrylate, (2-cyclohexyl-1,3-dioxolan-4-yl)methyl (meth)acrylate, and cyclic trimethylolpropane formal acrylate.
In this specification, the term "(meth)acrylate" means acrylate or methacrylate.

Examples of the monofunctional (meth)acrylamide compounds include N,N-dimethyl(meth)acrylamide, N-(meth)acryloylmorpholine, N-hydroxyethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, N-isopropyl(meth)acrylamide, and N,N-dimethylaminopropyl(meth)acrylamide.

The ultraviolet polymerizable compound may contain a polyfunctional (meth)acrylic monomer as the (meth)acrylic monomer. The polyfunctional (meth)acrylic monomer serves as a cross-linking component.
In this specification, the above-mentioned "polyfunctional (meth)acrylic monomer" means a monomer having two or more (meth)acryloyl groups in one molecule.

Examples of the polyfunctional (meth)acrylic monomer include polyfunctional urethane (meth)acrylates, polyfunctional (meth)acrylic acid ester compounds, and polyfunctional epoxy (meth)acrylates.
In this specification, the above-mentioned "epoxy (meth)acrylate" refers to a compound in which all epoxy groups in an epoxy compound have been reacted with (meth)acrylic acid.

The above-mentioned polyfunctional urethane (meth)acrylate can be obtained, for example, by reacting a (meth)acrylic acid derivative having a hydroxyl group with an isocyanate compound in the presence of a catalytic amount of a tin-based compound.

Examples of isocyanate compounds that are the raw material for the polyfunctional urethane (meth)acrylate include isophorone diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, diphenylmethane-4,4'-diisocyanate (MDI), hydrogenated MDI, polymeric MDI, 1,5-naphthalene diisocyanate, norbornane diisocyanate, tolidine diisocyanate, xylylene diisocyanate (XDI), hydrogenated XDI, lysine diisocyanate, triphenylmethane triisocyanate, tris(isocyanatephenyl)thiophosphate, tetramethylxylylene diisocyanate, and 1,6,11-undecane triisocyanate.

As the isocyanate compound serving as a raw material for the polyfunctional urethane (meth)acrylate, a chain-extended isocyanate compound obtained by reacting a polyol with an excess of an isocyanate compound can also be used.
Examples of the polyol include ethylene glycol, propylene glycol, glycerin, sorbitol, trimethylolpropane, carbonate diol, polyether diol, polyester diol, and polycaprolactone diol.

Examples of the (meth)acrylic acid derivative having a hydroxyl group include hydroxyalkyl mono(meth)acrylates, mono(meth)acrylates of dihydric alcohols, and mono(meth)acrylates or di(meth)acrylates of trihydric alcohols.
Examples of the hydroxyalkyl mono(meth)acrylate include 2-hydroxyethyl(meth)acrylate, 2-hydroxypropyl(meth)acrylate, 2-hydroxybutyl(meth)acrylate, and 4-hydroxybutyl(meth)acrylate.
Examples of the dihydric alcohol include ethylene glycol, propylene glycol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, and polyethylene glycol.
Examples of the trihydric alcohol include trimethylolethane, trimethylolpropane, and glycerin.

Examples of the polyfunctional (meth)acrylic acid ester compounds include 1,3-butanediol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, 1,10-decanediol di(meth)acrylate, ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, 2-n-butyl-2-ethyl-1,3-propanediol di(meth)acrylate, dipropylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, ethylene oxide-added bisphenol A di(meth)acrylate, propylene oxide-added bisphenol A di(meth)acrylate, ethylene oxide-added bisphenol F di(meth)acrylate, dimethylol dicyclopentadienyl di(meth)acrylate, ethylene oxide-modified isocyanuric acid di(meth)acrylate, 2-hydroxy-3-(meth)acryloyloxypropyl (meth)acrylate, carbonate diol di(meth)acryloyloxypropyl (meth)acrylate acrylate, polyether diol di(meth)acrylate, polyester diol di(meth)acrylate, polycaprolactone diol di(meth)acrylate, polybutadiene diol di(meth)acrylate, tricyclodecane dimethanol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, ethylene oxide added trimethylolpropane tri(meth)acrylate, propylene oxide added trimethylolpropane tri(meth)acrylate, caprolactone modified trimethylolpropane tri(meth)acrylate, tetramethylolmethane tetra(meth)acrylate, ethylene oxide added isocyanate Examples of such acrylates include anuric acid tri(meth)acrylate, glycerin tri(meth)acrylate, propylene oxide-added glycerin tri(meth)acrylate, pentaerythritol tri(meth)acrylate, tris(meth)acryloyloxyethyl phosphate, ditrimethylolpropane tetra(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, dipentaerythritol monohydroxypenta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, and caprolactone-modified dipentaerythritol hexa(meth)acrylate.

Examples of the polyfunctional epoxy (meth)acrylate include bisphenol A type epoxy (meth)acrylate, bisphenol F type epoxy (meth)acrylate, bisphenol E type epoxy (meth)acrylate, and caprolactone modified versions of these.

In the ultraviolet-curable adhesive composition of the present invention 1, the preferred upper limit of the content of the polyfunctional (meth)acrylic monomer relative to 100 parts by mass of the total of the maleimide derivative and the ultraviolet-polymerizable compound excluding the polyfunctional (meth)acrylic monomer is 25 parts by mass. By having the content of the polyfunctional (meth)acrylic monomer in the ultraviolet-curable adhesive composition of the present invention 1 be 25 parts by mass or less, the resulting ultraviolet-curable adhesive composition has better printability and impact resistance of the cured product. The more preferred upper limit of the content of the polyfunctional (meth)acrylic monomer in the ultraviolet-curable adhesive composition of the present invention 1 is 20 parts by mass.
From the viewpoints of impact resistance and adhesive strength, in the ultraviolet-curable pressure-sensitive adhesive composition of the first invention, a preferred lower limit of the content of the polyfunctional (meth)acrylic monomer relative to 100 parts by mass of the total of the maleimide derivative and the ultraviolet-polymerizable compound excluding the polyfunctional (meth)acrylic monomer is 5 parts by mass.
In the ultraviolet-curable adhesive composition of the second invention, the content of the polyfunctional (meth)acrylic monomer is preferably 1 part by mass and the content of the polyfunctional (meth)acrylic monomer is preferably 30 parts by mass relative to 100 parts by mass of the total of the maleimide derivative and the ultraviolet-polymerizable compound excluding the polyfunctional (meth)acrylic monomer. By having the content of the polyfunctional (meth)acrylic monomer in the ultraviolet-curable adhesive composition of the second invention within this range, the adhesion of the cured product made of the obtained ultraviolet-curable adhesive composition is more excellent. The content of the polyfunctional (meth)acrylic monomer in the ultraviolet-curable adhesive composition of the second invention is more preferably 3 parts by mass, more preferably 25 parts by mass, even more preferably 20 parts by mass, and particularly preferably 15 parts by mass.

As the vinyl monomer, an amide compound having a vinyl group is preferred, and a cyclic amide compound having a vinyl group is more preferred.

The cyclic amide compound having a vinyl group preferably has a lactam structure, and is more preferably a compound represented by the following formula (1):

In formula (1), n represents an integer from 2 to 6.

Examples of the compound represented by the above formula (1) include N-vinyl-2-pyrrolidone and N-vinyl-ε-caprolactam. Of these, N-vinyl-ε-caprolactam is preferred.

Among the above-mentioned amide compounds having a vinyl group, examples other than the above-mentioned cyclic amide compounds having a vinyl group include N-vinylacetamide, etc.

In the ultraviolet-curable pressure-sensitive adhesive composition of the first invention, when the ultraviolet-polymerizable compound contains the (meth)acrylic monomer and the vinyl monomer, the preferred lower limit of the content of the vinyl monomer relative to 100 parts by mass of the (meth)acrylic monomer is 20 parts by mass, and the preferred upper limit is 80 parts by mass. When the content of the vinyl monomer in the ultraviolet-curable pressure-sensitive adhesive composition of the first invention is 20 parts by mass or more, the obtained ultraviolet-curable pressure-sensitive adhesive composition has better curability. When the content of the vinyl monomer in the ultraviolet-curable pressure-sensitive adhesive composition of the first invention is 80 parts by mass or less, the obtained ultraviolet-curable pressure-sensitive adhesive composition can have excellent properties other than curability. A more preferred lower limit of the content of the vinyl monomer in the ultraviolet-curable pressure-sensitive adhesive composition of the first invention is 40 parts by mass, and a more preferred upper limit is 60 parts by mass.
In addition, in the ultraviolet-curable pressure-sensitive adhesive composition of the second invention, when the ultraviolet-polymerizable compound contains the (meth)acrylic monomer and the vinyl monomer, the preferred lower limit of the content of the vinyl monomer relative to 100 parts by mass of the (meth)acrylic monomer is 8 parts by mass, and the preferred upper limit is 80 parts by mass. When the content of the vinyl monomer in the ultraviolet-curable pressure-sensitive adhesive composition of the second invention is 8 parts by mass or more, the obtained ultraviolet-curable pressure-sensitive adhesive composition has better curability. When the content of the vinyl monomer in the ultraviolet-curable pressure-sensitive adhesive composition of the second invention is 80 parts by mass or less, the obtained ultraviolet-curable pressure-sensitive adhesive composition can have excellent properties other than curability. A more preferred lower limit of the content of the vinyl monomer in the ultraviolet-curable pressure-sensitive adhesive composition of the second invention is 15 parts by mass, and a more preferred upper limit is 60 parts by mass.

The ultraviolet-curable pressure-sensitive adhesive composition of the present invention contains a photopolymerization initiator.
In the ultraviolet-curable pressure-sensitive adhesive composition of the present invention 1, the photopolymerization initiator includes at least one selected from the group consisting of hydrogen abstraction type photopolymerization initiators and polymer type photopolymerization initiators. By using such a photopolymerization initiator in combination with an amine compound described later, the obtained ultraviolet-curable pressure-sensitive adhesive composition can give a cured product that is less susceptible to bleeding due to a decrease in surface curability and cohesive failure due to a decrease in surface curability and cohesive strength.
In the ultraviolet-curable pressure-sensitive adhesive composition of the present invention 2, the photopolymerization initiator preferably contains a hydrogen abstraction type photopolymerization initiator. By using the hydrogen abstraction type photopolymerization initiator in combination with an amine compound described later as the photopolymerization initiator, the obtained ultraviolet-curable pressure-sensitive adhesive composition can provide a cured product that is less susceptible to bleeding due to a decrease in surface curability and cohesive failure due to a decrease in surface curability and cohesive strength.

The hydrogen abstraction type photopolymerization initiator is preferably a benzophenone-based photopolymerization initiator. Examples of the benzophenone-based photopolymerization initiator include benzophenone, 4-chlorobenzophenone, 4,4'-dimethylbenzophenone, 4-methylbenzophenone, 2,4,6-trimethylbenzophenone, o-benzoyl methyl benzoate, 3,3'-dimethyl-4-methoxybenzophenone, 4-phenylbenzophenone, 4-benzoyl-4'-methyl-diphenyl sulfide, 4-morpholinobenzophenone, 4,4'-diphenoxybenzophenone, 4-hydroxybenzophenone, 2-carboxybenzophenone, 2-hydroxy-1-(4-(4-(2-hydroxy-2-methyl-propionyl)-benzyl)-phenyl)-2-methyl-propan-1-one, 1-(4-(4-benzoylphenylthio)phenyl)-2-tosyl-2-methyl-1-propanone, and 3-ketocoumarin.

Commercially available examples of the hydrogen abstraction type photopolymerization initiators include Esacure TZT and Omnirad 4MBZ (both manufactured by IGM Resins).

Examples of the polymeric photopolymerization initiator include polymers of ethyl (2,4,6-trimethylbenzoyl)-phenyl phosphonate, polyethylene glycol di(β-4(4-(2-dimethylamino-2-benzyl)butanoylphenyl)piperazine)propionate, and bis(benzophenone-2-carboxylic acid) polyethylene glycol ester.

Commercially available examples of the above polymer-type photopolymerization initiators include Omnipol TP, Omnipol 910, and Omnipol 2702 (all manufactured by IGM Resins).

In the ultraviolet-curable pressure-sensitive adhesive composition of the second invention, a cleavage-type photopolymerization initiator can also be used as the photopolymerization initiator.
Examples of the cleavage type photopolymerization initiator include 1-hydroxycyclohexyl phenyl ketone, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, and bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide.

In the ultraviolet-curable adhesive composition of the first invention, the content of the photopolymerization initiator is preferably 0.5 parts by mass and 15 parts by mass relative to 100 parts by mass of the total of the maleimide derivative and the ultraviolet-polymerizable compound. When the content of the photopolymerization initiator in the ultraviolet-curable adhesive composition of the first invention is within this range, the obtained ultraviolet-curable adhesive composition is more excellent in storage stability, curability, and adhesion. The more preferred lower limit of the content of the photopolymerization initiator in the ultraviolet-curable adhesive composition of the first invention is 1 part by mass, the more preferred upper limit is 10 parts by mass, the even more preferred lower limit is 3 parts by mass, and the even more preferred upper limit is 9 parts by mass.
In the ultraviolet-curable pressure-sensitive adhesive composition of the present invention 2, the content of the photopolymerization initiator is preferably 1 part by mass at the lower limit and 10 parts by mass at the upper limit, relative to 100 parts by mass of the total of the maleimide derivative and the ultraviolet-polymerizable compound. When the content of the photopolymerization initiator in the ultraviolet-curable pressure-sensitive adhesive composition of the present invention 2 is within this range, the obtained ultraviolet-curable pressure-sensitive adhesive composition is more excellent in storage stability, curability, and adhesion. The more preferred lower limit of the content of the photopolymerization initiator in the ultraviolet-curable pressure-sensitive adhesive composition of the present invention 2 is 3 parts by mass, and the more preferred upper limit is 9 parts by mass.

The ultraviolet-curable pressure-sensitive adhesive composition of the first invention contains an amine compound.
The ultraviolet-curable pressure-sensitive adhesive composition of the second invention preferably further contains an amine compound.
As described above, by using the amine compound in combination with the hydrogen abstraction type photopolymerization initiator, it becomes possible to obtain an ultraviolet-curable pressure-sensitive adhesive composition that is less susceptible to bleeding due to a decrease in surface curability and cohesive failure due to a decrease in curability and cohesive strength, and a cured product that is less susceptible to bleeding due to a decrease in surface curability and cohesive strength.

In the ultraviolet-curable adhesive composition of the present invention 1, the amine compound has a content of 50% by mass or more of an amine compound that does not have a structure in which hydrogen is bonded to a heteroatom. By using an amine compound having a content of 50% by mass or more of an amine compound that does not have a structure in which hydrogen is bonded to a heteroatom, the obtained ultraviolet-curable adhesive composition can obtain a cured product that is less likely to cause bleeding due to a decrease in surface curability and cohesive failure due to a decrease in surface curability and cohesive strength. In the ultraviolet-curable adhesive composition of the present invention 1, the amine compound has a content of 75% by mass or more of an amine compound that does not have a structure in which hydrogen is bonded to a heteroatom, and most preferably 100% by mass.

Examples of amine compounds that do not have a structure in which hydrogen is bonded to the heteroatom include (bis-N,N-(4-dimethylaminobenzoyl)oxyethylene-1-yl)-methylamine, bis(2-morpholinoethyl)ether, 1-methyl 10-(1,2,2,6,6-pentamethyl-4-piperidinyl) decanedioate, tetrakis(1,2,2,6,6-pentamethyl-4-piperidyl)butane-1,2,3,4-tetracarboxylate, and bis(1,2,2,6,6-pentamethyl-4-piperidyl) sebacate.

Among the amine compounds that do not have a structure in which hydrogen is bonded to the heteroatom, commercially available examples include Esacure A198 (manufactured by IGM Resins), U-cat 660 (manufactured by San-Apro), Eversorb 93 (manufactured by Everlight Chemical), Adeka STAB LA-52, and Adeka STAB LA-72 (all manufactured by ADEKA).

In the ultraviolet-curable adhesive composition of the present invention 2, examples of the amine compound include (bis-N,N-(4-dimethylaminobenzoyl)oxyethylene-1-yl)-methylamine, bis(2-morpholinoethyl)ether, 1-methyl 10-(1,2,2,6,6-pentamethyl-4-piperidinyl) decanedioate, tetrakis(1,2,2,6,6-pentamethyl-4-piperidyl)butane-1,2,3,4-tetracarboxylate, and bis(1,2,2,6,6-pentamethyl-4-piperidyl) sebacate.

In the ultraviolet-curable adhesive composition of the first invention, the lower limit of the content of the amine compound relative to 100 parts by mass of the total of the maleimide derivative and the ultraviolet-polymerizable compound is 0.1 parts by mass, and the upper limit is 10 parts by mass. When the content of the amine compound in the ultraviolet-curable adhesive composition of the first invention is 0.1 parts by mass or more, the curing property of the obtained ultraviolet-curable adhesive composition is excellent. When the content of the amine compound in the ultraviolet-curable adhesive composition of the first invention is 10 parts by mass or less, the cured product of the obtained ultraviolet-curable adhesive composition is unlikely to cause cohesive failure. The preferred lower limit of the content of the amine compound in the ultraviolet-curable adhesive composition of the first invention is 1.5 parts by mass, more preferably 2.5 parts by mass, and the preferred upper limit is 7 parts by mass, more preferably 5 parts by mass.
In the ultraviolet-curable adhesive composition of the second invention, the preferred lower limit of the content of the amine compound in the total of 100 parts by mass of the maleimide derivative and the ultraviolet-polymerizable compound is 1.5 parts by mass, and the preferred upper limit is 8 parts by mass. When the content of the amine compound in the ultraviolet-curable adhesive composition of the second invention is 1.5 parts by mass or more, the obtained ultraviolet-curable adhesive composition has better surface curability. When the content of the amine compound in the ultraviolet-curable adhesive composition of the second invention is 8 parts by mass or less, the cured product of the obtained ultraviolet-curable adhesive composition is less likely to cause cohesive failure. A more preferred lower limit of the content of the amine compound in the ultraviolet-curable adhesive composition of the second invention is 2.5 parts by mass, and a more preferred upper limit is 5 parts by mass.

The ultraviolet-curable pressure-sensitive adhesive composition of the present invention may further contain a thermoplastic resin.
The thermoplastic resin is preferably a compound that does not contain a reactive double bond, or a compound that has a reactive double bond but does not substantially exhibit photoradical polymerization reactivity.

Examples of the thermoplastic resin include a solvent-free acrylic polymer and a polymer obtained by drying a polymer dissolved in a solvent.
Examples of the solvent-free acrylic polymer include a polymer of at least one monomer selected from (meth)acrylic acid alkyl esters having an alkyl group with 1 to 20 carbon atoms, and a copolymer of the monomer and another copolymerizable monomer.
Among the above-mentioned solvent-free acrylic polymers, commercially available ones include, for example, the ARUFON-UP1000 series, UH2000 series, UC3000 series (all manufactured by Toagosei Co., Ltd.), the Clarity LA series, and the Clarity LK series (all manufactured by Kuraray Co., Ltd.).

The content of the thermoplastic resin is preferably 5 parts by mass at the lower limit and 100 parts by mass at the upper limit, relative to 100 parts by mass of the total of the maleimide derivative and the ultraviolet-polymerizable compound. When the content of the thermoplastic resin is within this range, the viscosity of the obtained ultraviolet-curable adhesive composition is improved, a thick coating film can be formed, the printability is superior, and the decrease in adhesion at high temperatures can be suppressed. A more preferable lower limit of the content of the thermoplastic resin is 20 parts by mass, and a more preferable upper limit is 60 parts by mass.

The above-mentioned UV-curable adhesive composition may contain a thermosetting resin or a moisture-curable resin, and thus may exhibit reactivity to triggers such as heat and moisture.

Examples of the thermosetting resin include epoxy resin, phenol resin, urea resin, melamine resin, etc. Among these, epoxy resin is preferable.
Examples of the epoxy resin include bisphenol A type epoxy resins, bisphenol F type epoxy resins, bisphenol S type epoxy resins, phenol novolac type epoxy resins, biphenyl type epoxy resins, biphenyl novolac type epoxy resins, biphenol type epoxy resins, naphthalene type epoxy resins, fluorene type epoxy resins, phenol aralkyl type epoxy resins, naphthol aralkyl type epoxy resins, dicyclopentadiene type epoxy resins, anthracene type epoxy resins, epoxy resins having an adamantane skeleton, epoxy resins having a tricyclodecane skeleton, and epoxy resins having a triazine nucleus in the skeleton.

When the above-mentioned thermosetting resin is used, it is preferable that a thermosetting agent is contained in the ultraviolet-curable pressure-sensitive adhesive composition.
Examples of the heat curing agent include cyanate ester compounds (cyanate ester curing agents), phenol compounds (phenol heat curing agents), amine compounds (amine heat curing agents), thiol compounds (thiol heat curing agents), imidazole compounds, phosphine compounds, acid anhydrides, active ester compounds, and dicyandiamide.
In addition, when an epoxy resin is used as the thermosetting resin, a photocationic polymerization initiator may be contained in the ultraviolet-curable adhesive composition. This allows the curing to proceed gradually even after the first stage of irradiation with active energy rays. As a result, the obtained ultraviolet-curable adhesive composition has a better initial adhesive strength.
Incidentally, even in the case where the epoxy resin and the photocationic polymerization initiator are contained, the epoxy resin is not regarded as the ultraviolet-polymerizable compound.

The photocationic polymerization initiator is not particularly limited as long as it generates a protonic acid or a Lewis acid upon irradiation with light, and may be an ionic photoacid generating type or a non-ionic photoacid generating type.

Examples of the ionic photoacid generating cationic photopolymerization initiator include the following: onium salts whose cationic moiety is an aromatic sulfonium, aromatic iodonium, aromatic diazonium, aromatic ammonium, or (2,4-cyclopentadiene-1-yl)((1-methylethyl)benzene)-Fe cation and whose anionic moiety is BF ₄ ^- , PF ₆ ^- , SbF ₆ ^- , or (BX ₄ ) ^- , where X represents a phenyl group substituted with at least two or more fluorine or trifluoromethyl groups.

The above aromatic sulfonium salts include, for example, bis(4-(diphenylsulfonio)phenyl)sulfide bishexafluorophosphate, bis(4-(diphenylsulfonio)phenyl)sulfide bishexafluoroantimonate, bis(4-(diphenylsulfonio)phenyl)sulfide bistetrafluoroborate, bis(4-(diphenylsulfonio)phenyl)sulfide tetrakis(pentafluorophenyl)borate, diphenyl-4-(phenylthio)phenylsulfonium hexafluorophosphate, diphenyl-4-(phenylthio)phenylsulfonium hexafluoroantimonate, diphenyl-4-(phenylthio)phenylsulfonium tetrafluoroborate, and diphenyl-4-(phenylthio)phenylsulfonium tetrakis(pentafluorophenyl)borate. , triphenylsulfonium hexafluorophosphate, triphenylsulfonium hexafluoroantimonate, triphenylsulfonium tetrafluoroborate, triphenylsulfonium tetrakis(pentafluorophenyl)borate, bis(4-(di(4-(2-hydroxyethoxy))phenylsulfonio)phenyl)sulfide bishexafluorophosphate, bis(4-(di(4-(2-hydroxyethoxy))phenylsulfonio)phenyl)sulfide bishexafluoroantimonate, bis(4-(di(4-(2-hydroxyethoxy))phenylsulfonio)phenyl)sulfide bistetrafluoroborate, bis(4-(di(4-(2-hydroxyethoxy))phenylsulfonio)phenyl)sulfide tetrakis(pentafluorophenyl)borate, etc.

Examples of the aromatic diazonium salt include phenyldiazonium hexafluorophosphate, phenyldiazonium hexafluoroantimonate, phenyldiazonium tetrafluoroborate, and phenyldiazonium tetrakis(pentafluorophenyl)borate.

Examples of the aromatic ammonium salts include 1-benzyl-2-cyanopyridinium hexafluorophosphate, 1-benzyl-2-cyanopyridinium hexafluoroantimonate, 1-benzyl-2-cyanopyridinium tetrafluoroborate, 1-benzyl-2-cyanopyridinium tetrakis(pentafluorophenyl)borate, 1-(naphthylmethyl)-2-cyanopyridinium hexafluorophosphate, 1-(naphthylmethyl)-2-cyanopyridinium hexafluoroantimonate, 1-(naphthylmethyl)-2-cyanopyridinium tetrafluoroborate, and 1-(naphthylmethyl)-2-cyanopyridinium tetrakis(pentafluorophenyl)borate.

Examples of the (2,4-cyclopentadiene-1-yl)((1-methylethyl)benzene)-Fe salt include (2,4-cyclopentadiene-1-yl)((1-methylethyl)benzene)-Fe(II) hexafluorophosphate, (2,4-cyclopentadiene-1-yl)((1-methylethyl)benzene)-Fe(II) hexafluoroantimonate, (2,4-cyclopentadiene-1-yl)((1-methylethyl)benzene)-Fe(II) tetrafluoroborate, and (2,4-cyclopentadiene-1-yl)((1-methylethyl)benzene)-Fe(II) tetrakis(pentafluorophenyl)borate.

Examples of the nonionic photoacid generating cationic photopolymerization initiator include nitrobenzyl esters, sulfonic acid derivatives, phosphate esters, phenolsulfonic acid esters, diazonaphthoquinones, and N-hydroxyimidesulfonates.

The above cationic photopolymerization initiators may be used alone or in combination of two or more kinds.
The content of the photocationic polymerization initiator is preferably such that the lower limit is 0.1 parts by mass and the upper limit is 10 parts by mass relative to 100 parts by mass of the epoxy resin.

Examples of the moisture-curing resin include moisture-curing urethane resin and resin having a crosslinkable silyl group. Among them, moisture-curing urethane resin is preferable. Moisture-curing urethane resin has a urethane bond and an isocyanate group, and the isocyanate group in the molecule reacts with moisture to cure. It is preferable that the isocyanate group is at the end of the molecule.
The moisture-curable urethane resin may have a radical reactive functional group. Even if the moisture-curable urethane resin has a radical reactive functional group, the moisture-curable urethane resin is not treated as the ultraviolet-polymerizable compound.
The moisture-curable urethane resin can be obtained by reacting a polyol compound having two or more hydroxyl groups in one molecule with a polyisocyanate compound having two or more isocyanate groups in one molecule.

When the moisture-curable resin is used, it is preferable to add a moisture curing accelerator to the ultraviolet-curable pressure-sensitive adhesive composition from the viewpoint of improving the curing speed during moisture curing.
Examples of the moisture curing accelerator include a compound having a morpholine skeleton, a compound having a piperidine skeleton, and a compound having a piperazine skeleton.

The ultraviolet-curable pressure-sensitive adhesive composition of the present invention may further contain a tackifier.
Examples of the tackifier include rosin-based resins and terpene-based resins.

The rosin-based resin may, for example, be rosin diol.
The rosin diol is not particularly limited as long as it is a rosin-modified diol having two rosin skeletons and two hydroxyl groups in the molecule. Diols having a rosin component in the molecule are called rosin polyols, and these include polyether types such as polypropylene glycol (PPG) in which the skeleton excluding the rosin component is polyether, and polyester types such as condensation polyester polyols, lactone polyester polyols, and polycarbonate diols.
Examples of the rosin diol include rosin ester obtained by reacting rosin with a polyhydric alcohol, epoxy-modified rosin ester obtained by reacting rosin with an epoxy compound, and modified rosin having a hydroxyl group, such as polyether having a rosin skeleton, etc. These can be produced by conventionally known methods.

The rosin component includes, for example, abietic acid and its derivatives, such as pimaric acid type resin acids as dehydroabietic acid, dihydroabietic acid, tetrahydroabietic acid, diabietic acid, neoabietic acid, and levopimaric acid, hydrogenated rosins obtained by hydrogenating these, and disproportionated rosins obtained by disproportionating these.

Commercially available examples of the above rosin-based resins include Pine Crystal D-6011, Pine Crystal KE-615-3, Pine Crystal KR-614, Pine Crystal KE-100, Pine Crystal KE-311, Pine Crystal KE-359, Pine Crystal KE-604, and Pine Crystal D-6250 (all manufactured by Arakawa Chemical Industries Co., Ltd.).

Examples of the terpene resin include terpene phenol resins.
The terpene phenol resin is a copolymer of phenol and a terpene resin, which is an essential oil component obtained from natural products such as rosin and orange peel, and also includes partially hydrogenated terpene phenol resins in which at least a portion of the copolymer is hydrogenated, and fully hydrogenated terpene phenol resins in which the copolymer is completely hydrogenated.
Here, the fully hydrogenated terpene phenolic resin is a terpene resin obtained by substantially completely hydrogenating a terpene phenolic resin, and the partially hydrogenated terpene phenolic resin is a terpene resin obtained by partially hydrogenating a terpene phenolic resin. The terpene phenolic resin has a double bond derived from a terpene and an aromatic ring double bond derived from a phenol. Therefore, the fully hydrogenated terpene phenolic resin means a resin in which both the terpene portion and the phenol portion are completely or almost hydrogenated, and the partially hydrogenated terpene phenolic resin means a resin in which the degree of hydrogenation of these portions is not complete but partial. The hydrogenation method and reaction form are not particularly limited.
Among the above terpene phenol-based resins, examples of commercially available ones include YS Polystar NH (fully hydrogenated terpene phenol-based resin) manufactured by Yasuhara Chemical Co., Ltd.

The content of the tackifier is preferably 5 parts by mass at the lower limit and 50 parts by mass at the upper limit, relative to 100 parts by mass of the total UV-curable adhesive composition not including the tackifier. When the content of the tackifier is within this range, the resulting UV-curable adhesive composition has better adhesion to various substrates. A more preferred lower limit of the content of the tackifier is 10 parts by mass, and a more preferred upper limit is 35 parts by mass.

The ultraviolet-curable pressure-sensitive adhesive composition of the present invention may contain a plasticizer.
Examples of the plasticizer include organic acid esters, organic phosphates, and organic phosphites.

Examples of the organic acid ester include monobasic organic acid esters and polybasic organic acid esters.
Examples of the monobasic organic acid ester include glycol esters obtained by reacting a monobasic organic acid such as butyric acid, isobutyric acid, caproic acid, 2-ethylbutyric acid, heptyl acid, n-octylic acid, 2-ethylhexyl acid, pelargonic acid (n-nonylic acid), or decylic acid with a glycol such as triethylene glycol, tetraethylene glycol, or tripropylene glycol.
Examples of the polybasic organic acid ester include ester compounds obtained by reacting a polybasic organic acid such as adipic acid, sebacic acid, or azelaic acid with an alcohol having a linear or branched structure having 4 to 8 carbon atoms.

Specific examples of the organic acid esters include triethylene glycol di-2-ethylbutyrate (3GH), triethylene glycol di-2-ethylhexanoate (3GO), triethylene glycol dicaprylate, triethylene glycol di-n-octanoate, and triethylene glycol di-n-heptanoate (3G7). In addition, tetraethylene glycol di-n-heptanoate (4G7), tetraethylene glycol di-2-ethylhexanoate, dibutyl sebacate, dioctyl azelate, dibutyl carbitol adipate, ethylene glycol di-2-ethylbutyrate, and 1,3-propylene glycol di-2-ethylbutyrate. In addition, 1,4-butylene glycol di-2-ethylbutyrate, diethylene glycol di-2-ethylbutyrate, diethylene glycol di-2-ethylhexanoate, and dipropylene glycol di-2-ethylbutyrate are also included. Other examples include triethylene glycol di-2-ethylpentanoate, tetraethylene glycol di-2-ethylbutyrate (4GH), diethylene glycol dicapryate, dihexyl adipate (DHA), dioctyl adipate, hexylcyclohexyl adipate, diisononyl adipate, heptylnonyl adipate, etc. Other examples include oil-modified sebacic acid alkyd, a mixture of a phosphate ester and an adipate ester, and a mixed adipate ester made from an alkyl alcohol having 4 to 9 carbon atoms and a cyclic alcohol having 4 to 9 carbon atoms.

The organic phosphate or organic phosphite may be a compound obtained by a condensation reaction between phosphoric acid or phosphorous acid and an alcohol. Among them, a compound obtained by a condensation reaction between an alcohol having 1 to 12 carbon atoms and phosphoric acid or phosphorous acid is preferable.
Examples of the alcohol having 1 to 12 carbon atoms include methanol, ethanol, butanol, hexanol, 2-ethylbutanol, heptanol, octanol, 2-ethylhexanol, decanol, dodecanol, butoxyethanol, butoxyethoxyethanol, and benzyl alcohol.
Examples of the organic phosphate ester or organic phosphite ester include trimethyl phosphate, triethyl phosphate, tripropyl phosphate, tributyl phosphate, tri(2-ethylhexyl) phosphate, tri(butoxyethyl) phosphate, tri(2-ethylhexyl) phosphite, isodecylphenyl phosphate, and triisopropyl phosphate.

The ultraviolet-curable pressure-sensitive adhesive composition of the present invention may contain a defoaming agent.
Examples of the defoaming agent include silicone-based defoaming agents, acrylic polymer-based defoaming agents, vinyl ether polymer-based defoaming agents, and olefin polymer-based defoaming agents.

The ultraviolet-curable pressure-sensitive adhesive composition of the present invention may further contain various known additives such as a crosslinking agent, a viscosity modifier, a silane coupling agent, a sensitizer, a heat curing agent, a curing retarder, an antioxidant, a storage stabilizer, a dispersant, and a filler, within the scope of not impairing the object of the present invention.
In addition, from the viewpoint of preventing a decrease in ultraviolet reactivity, it is preferable that the ultraviolet-curable pressure-sensitive adhesive composition of the present invention is substantially free of organic solvents. Specifically, it is preferable that the content of the organic solvent is 1.5 mass% or less relative to 100 mass% of the ultraviolet-curable pressure-sensitive adhesive composition.

The method for preparing the ultraviolet-curable adhesive composition of the present invention 1 can be, for example, a method of mixing the maleimide derivative, the ultraviolet-polymerizable compound, the photopolymerization initiator, the amine compound, and additives added as necessary using a mixer. The method for preparing the ultraviolet-curable adhesive composition of the present invention 2 can be, for example, a method of mixing the maleimide derivative, the ultraviolet-polymerizable compound, the photopolymerization initiator, and additives added as necessary using a mixer. The mixer can be, for example, a homodisper, a homomixer, a universal mixer, a planetary mixer, a kneader, a three-roll mixer, etc.

The ultraviolet-curable adhesive composition of the present invention 2 is obtained by coating the ultraviolet-curable adhesive composition on a substrate, and simultaneously irradiating the coated surface with ultraviolet light having a wavelength of 365 nm and an illuminance of 20 mW/cm ² and light having a wavelength of 405 nm and an illuminance of 40 mW/cm ² in an atmospheric environment without sealing the coated surface, to a total irradiation amount of 900 mJ/cm ² , and the cured product has a reaction rate of 88% or more. The ultraviolet-curable adhesive composition of the present invention 1 is obtained by coating the ultraviolet-curable adhesive composition on a substrate, and simultaneously irradiating the coated surface with ultraviolet light having a wavelength of 365 nm and an illuminance of 20 mW/cm ² and light having a wavelength of 405 nm and an illuminance of 40 mW/cm ² in an atmospheric environment without sealing the coated surface, to a total irradiation amount of 900 mJ/cm ² , and the cured product has a reaction rate of 85% or more. Since the reaction rate of the cured product in the ultraviolet-curable pressure-sensitive adhesive composition of the present invention 1 is 85% or more, the ultraviolet reactivity in the presence of oxygen can be said to be sufficiently high, and it becomes possible to apply a method in which the ultraviolet-curable pressure-sensitive adhesive composition is printed in a desired shape and then laminated to an adherend. A more preferable lower limit of the reaction rate of the cured product in the ultraviolet-curable pressure-sensitive adhesive composition of the present invention 1 is 88%.
As the substrate, a PET film (release PET film) with a release treatment on the surface is preferably used. The above conditions are that after the ultraviolet-curable adhesive composition is coated on the substrate, ultraviolet irradiation is performed in the presence of oxygen without covering the coated surface with a separator. Therefore, the reaction rate of the cured product reflects the ultraviolet reactivity in the presence of oxygen. That is, the high reaction rate of the cured product makes the ultraviolet-curable adhesive composition of the present invention excellent in adhesion in the presence of oxygen and low bleeding. The preferable lower limit of the reaction rate of the cured product is 90%, and the more preferable lower limit is 92%.
In addition, the higher the reaction rate of the cured product, the more preferable it is, but the practical upper limit is 99%.

Specifically, the reaction rate of the cured product can be measured, for example, according to the following procedure.
That is, first, the ultraviolet-curable pressure-sensitive adhesive composition is applied onto a release PET film as a substrate, and then, using an ultraviolet irradiation device, ultraviolet light having a wavelength of 365 nm and an illuminance of 20 mW/ ^cm2 and light having a wavelength of 405 nm and an illuminance of 40 mW/ ^cm2 are simultaneously irradiated to a total irradiation amount of 900 mJ/ ^cm2 , thereby curing the ultraviolet-curable pressure-sensitive adhesive composition to obtain a cured product having a thickness of 100 μm.
Approximately 0.3 g of the obtained cured product is placed on an aluminum pan, and a mixed solvent containing THF: acetone: ethanol in a mass ratio of 8: 1: 1 is gently added so that the cured sample does not scatter, and the sample is allowed to swell for about 2 hours. After that, the sample is dried at 110°C for 30 minutes, at 170°C for 1 hour, and at 190°C for 30 minutes. The mass of the aluminum pan and the dried sample after drying are then weighed, and the reaction rate of the cured product is calculated using the following formula.
Reaction rate [%] = (total mass of aluminum pan and sample after drying - mass of aluminum pan before drying) / (mass of sample before swelling) x 100

The ultraviolet-curable adhesive composition of the present invention is preferably obtained by coating the ultraviolet-curable adhesive composition on a substrate and simultaneously irradiating ultraviolet light having a wavelength of 365 nm and an illuminance of 20 mW/ ^cm2 and light having a wavelength of 405 nm and an illuminance of 40 mW/ ^cm2 so that the total irradiation amount is 900 mJ/ ^cm2 , and the glass transition temperature of the cured product having a thickness of 100 μm is preferably −60° C. or more and 20° C. or less. By having the glass transition temperature of the cured product in this range, it is possible to obtain an excellent adhesion to various substrates. It is more preferable that the glass transition temperature is 10° C. or less.

Specifically, the glass transition temperature of the cured product can be measured, for example, according to the following procedure.
That is, the ultraviolet-curable pressure-sensitive adhesive composition is first applied onto a release PET film as a substrate, and then simultaneously irradiated with ultraviolet light having a wavelength of 365 nm and an illuminance of 20 mW/ ^cm2 and light having a wavelength of 405 nm and an illuminance of 40 mW/ ^cm2 so that the total irradiation amount is 900 mJ/ ^cm2 , thereby curing the ultraviolet-curable pressure-sensitive adhesive composition to obtain a cured product having a thickness of 100 μm.
The glass transition temperature of the resulting cured product can be determined by measuring the tan δ peak temperature under the following conditions using a dynamic viscoelasticity measuring device, such as MCR-702e (manufactured by Anton Paar).
<Conditions>
Shear method: Measured with twin drive using 8 mm parallel plate Measurement temperature: -70 to 200°C
Heating rate: 7°C/min Frequency: 1Hz
While cooling from 50°C to -70°C at a rate of 10°C/min, pre-pressure was applied at 8N, and measurements were taken from the low temperature as described below in (1) to (6).
(1) The temperature was raised with a normal force of 20 N and a strain of 0.005%, and measurements were taken under these conditions until the torque value became less than 1,500 μN·m.
(2) After (1), the temperature is increased with a normal force of 8 N and a strain of 0.05%, and measurements are taken under these conditions until the torque value becomes less than 200 μN·m.
(3) After (2), raise the temperature with a normal force of 3 N and a strain of 0.5%, and measure under these conditions until the torque value is less than 150 μN·m. If the torque in (3) is 150 μN·m or more up to 120°C, proceed to (4).
(4) After (3), raise the temperature with a normal force of 1.5 N and a strain of 2%, and measure under these conditions until the torque value is less than 100 μN·m. If the torque in (4) is 100 μN·m or more up to 170°C, proceed to (5).
(5) After (4), raise the temperature with a normal force of 1N and a strain of 5%, and measure under these conditions until the torque value is less than 80 μN·m. If the torque in (5) is 80 μN·m or more up to 190°C or if the thickness is less than 30 μm, proceed to (6).
(6) After (5), the temperature is raised with a normal force of 1 N and a strain of 10%, and measurements are taken under these conditions until the temperature reaches 200° C. When the thickness becomes less than 20 μm before the temperature of (6) reaches 200° C., the measurement is terminated.

The ultraviolet-curable adhesive composition of the present invention is suitable for printing. If an adhesive layer is formed by applying a desired pattern on an adherend (substrate) by printing, there is an advantage that the cutting process can be omitted compared to the case where an adhesive of a desired shape is obtained by cutting a sheet-like adhesive just before lamination. As a result, it is possible to suppress the generation of waste and reduce the environmental load.
Examples of methods for printing the ultraviolet-curable pressure-sensitive adhesive composition of the present invention include screen printing, inkjet printing, gravure printing, etc. Among these, screen printing is preferably used.

The ultraviolet-curable pressure-sensitive adhesive composition of the present invention has a viscosity at 25° C. of preferably 5 mPa·s at its lower limit and 100,000 mPa·s at its upper limit. By setting the viscosity within this range, the ultraviolet-curable pressure-sensitive adhesive composition of the present invention is more suitable for printing. The more preferred lower limit of the viscosity is 10 mPa·s at its upper limit and 75,000 mPa·s at its upper limit.
The viscosity can be measured, for example, using a VISCOMETER TV-22 (manufactured by Toki Sangyo Co., Ltd.) as an E-type viscometer, using an appropriate cone plate for each viscosity, under conditions of 25° C. and 10 rpm.

The ultraviolet-curable adhesive composition of the present invention forms an adhesive layer by curing it through irradiation with ultraviolet light, and its method of use may involve forming an adhesive layer on a substrate (separator) to produce an adhesive sheet that can be transferred to an adherend, or forming an adhesive layer directly on an adherend. In the method of forming an adhesive layer directly on an adherend, the number of times of lamination can be minimized and air bubbles can be prevented from entering the interface during lamination. On the other hand, in the method of forming an adhesive layer on a substrate (separator), the adhesive layer is placed on the adherend by transfer, which has the advantage of fewer constraints on construction.

A method for producing a laminate in which the ultraviolet-curable adhesive composition of the present invention is applied to a first adherend and exposed to light to form an adhesive layer, and a second adherend is attached to the adhesive layer, the method for applying the ultraviolet-curable adhesive composition being inkjet printing, screen printing, spray coating, spin coating, gravure offset, or reverse offset printing, and the ultraviolet-curable adhesive composition is partially applied to the first adherend, is also one aspect of the present invention.

Examples of the material for the first adherend and the second adherend include metals such as stainless steel and aluminum, resins, etc.

The thickness of the adhesive layer is preferably 30 μm or more, and more preferably 50 μm or more. By having a thickness of the adhesive layer of 30 μm or more, sufficient adhesion can be obtained. Furthermore, from the viewpoint of responding to the trend toward thinner electronic devices, the thickness of the adhesive layer is preferably 1000 μm or less, and more preferably 500 μm or less.

According to the present invention, it is possible to provide an ultraviolet-curable pressure-sensitive adhesive composition that has excellent printability, is unlikely to cause cohesive failure in the cured product, and has excellent impact resistance, and an ultraviolet-curable pressure-sensitive adhesive composition that has excellent adhesion and low bleeding properties. In addition, according to the present invention, it is possible to provide a method for producing a laminate using the ultraviolet-curable pressure-sensitive adhesive composition.

The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to these examples.

(Examples 1-1 to 1-40, Comparative Examples 1-1 to 1-17)
According to the compounding ratios shown in Tables 1 to 6, each material was mixed with a planetary mixer (Thinky Corporation, "Awatori Rentaro") to obtain each of the pressure-sensitive adhesive compositions of Examples 1-1 to 1-40 and Comparative Examples 1-1 to 1-17.
Details of the materials indicated by abbreviations in the table are as follows.
(Maleimide derivatives)
CHMI: N-cyclohexylmaleimide (manufactured by Nippon Shokubai Co., Ltd., no structure with hydrogen bonded to a heteroatom)
LMI: N-laurylmaleimide (Seiko Chemical Industry Co., Ltd., no structure with hydrogen bonded to a heteroatom)
HPM: 4-hydroxyphenylmaleimide (Seiko Chemical Industry Co., Ltd., has a structure in which hydrogen is bonded to a heteroatom)
(UV-polymerizable compound)
CBA: Ethyl carbitol acrylate (manufactured by Osaka Organic Chemical Industry Co., Ltd., "Viscoat #190", containing ether bonds)
MEDOL-10: (2-methyl-2-ethyl-1,3-dioxolan-4-yl)methyl acrylate (manufactured by Osaka Organic Chemical Industry Co., Ltd., containing an ether bond)
Viscoat #192: Phenoxyethyl acrylate (Osaka Organic Chemical Industry Co., Ltd., containing phenoxy group)
Viscoat #216: acrylic acid-2-butylcarbamoyloxyethyl ester (Osaka Organic Chemical Industry, Inc., containing amide bond)
NOAA: n-octyl acrylate (Osaka Organic Chemical Industry Co., Ltd.)
4-HBA: 4-hydroxybutyl acrylate (manufactured by Mitsubishi Chemical Corporation)
UA-160TM: Polyether-based multifunctional urethane acrylate (manufactured by Shin-Nakamura Chemical Co., Ltd.)
NVC: N-vinyl-ε-caprolactam (manufactured by Tokyo Chemical Industry Co., Ltd.)
(Photopolymerization initiator)
Esacure TZT: a mixture of 2,4,6-trimethylbenzophenone and 4-methylbenzophenone (manufactured by IGM Resins, a hydrogen abstraction type photopolymerization initiator)
Omnirad 4MBZ: 4-methylbenzophenone (manufactured by IGM Resins, hydrogen abstraction type photopolymerization initiator)
Omnipol TP: Ethyl (2,4,6-trimethylbenzoyl)-phenyl phosphinate polymer (manufactured by IGM Resins, polymeric photopolymerization initiator)
Omnipol 910: polyethylene glycol di(β-4(4-(2-dimethylamino-2-benzyl)butanoylphenyl)piperazine)propionate (manufactured by IGM Resins, polymer type photopolymerization initiator)
Omnipol 2702: bis(benzophenone-2-carboxylic acid) polyethylene glycol ester (manufactured by IGM Resins, polymeric photopolymerization initiator)
Omnirad 184: 1-hydroxycyclohexyl phenyl ketone (IGM Resins, cleavage-type photopolymerization initiator)
Omnirad TPO: 2,4,6-trimethylbenzoyldiphenylphosphine oxide (manufactured by IGM Resins, cleavage-type photopolymerization initiator)
Omnirad 819: bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (manufactured by IGM Resins, cleavage-type photopolymerization initiator)
(Amine Compound)
Esacure A198: (bis-N,N-(4-dimethylaminobenzoyl)oxyethylene-1-yl)-methylamine, bis(2-morpholinoethyl)ether (manufactured by IGM Resins, no structure in which hydrogen is bonded to a heteroatom)
U-cat 660M: bis(2-morpholinoethyl)ether (manufactured by San-Apro Co., Ltd., no structure in which hydrogen is bonded to a heteroatom)
Eversorb 93: 1-methyl 10-(1,2,2,6,6-pentamethyl-4-piperidinyl) decanedioate (manufactured by Everlight Chemical Co., no structure in which hydrogen is bonded to a heteroatom)
Adekastab LA-72: bis(1,2,2,6,6-pentamethyl-4-piperidyl) sebacate (manufactured by ADEKA Corporation, no structure with hydrogen bonded to a heteroatom)
Adekastab LA-52: Tetrakis(1,2,2,6,6-pentamethyl-4-piperidyl)butane-1,2,3,4-tetracarboxylate (manufactured by ADEKA Corporation, no structure in which hydrogen is bonded to a heteroatom)
Adekastab LA-77Y: bis(2,2,6,6-tetramethyl-4-piperidyl) sebacate (manufactured by ADEKA Corporation, has a structure in which hydrogen is bonded to a heteroatom)
Adekastab LA-57: Tetrakis(2,2,6,6-tetramethyl-4-piperidyl)butane-1,2,3,4-tetracarboxylate (manufactured by ADEKA Corporation, has a structure in which hydrogen is bonded to a heteroatom)
(Tackifier)
KE-359: Rosin resin (manufactured by Arakawa Chemical Industries, Ltd.)
(Thermoplastic resin)
LA2140: Acrylic block copolymer (manufactured by Kuraray)
LA4285: Acrylic block copolymer (manufactured by Kuraray)
(Crosslinking Agent)
・Coronate L: Toluene diisocyanate (manufactured by Tosoh Corporation)

(Reaction rate of cured product)
The obtained pressure-sensitive adhesive composition was applied onto a release PET film (manufactured by Nippa Corporation, "1-E", thickness 50 μm) by the method described below to obtain a cured product having a thickness of 100 μm.
For each of the adhesive compositions obtained in Examples 1-1 to 1-35, 1-40, and Comparative Examples 1-1 to 1-12, 0.5 mL of each adhesive composition was dropped onto a release PET film, and a thin layer was prepared by applying the composition at 5000 rpm for 10 seconds using a spin coater (manufactured by Mikasa, "MSB-150"). Next, in an atmospheric environment without sealing the upper surface of the coating, ultraviolet light having a wavelength of 365 nm and an illuminance of 20 mW/cm ² and light having a wavelength of 405 nm and an illuminance of 40 mW/cm ² were simultaneously irradiated so that the total irradiation amount was 900 mJ/cm ² using a batch-type UV LED curing device (manufactured by ITEC, "M UVBA"). This was repeated until the thickness of the cured product reached 100 μm.
For each of the adhesive compositions obtained in Examples 1-36 to 1-39 and Comparative Examples 1-13 and 1-14, the adhesive composition was coated on a release PET film to a thickness of 100 μm using a screen printer (manufactured by SERIA, "SSA-PC560E"). Thereafter, without sealing the coated surface, the adhesive composition was cured in an atmospheric environment by simultaneously irradiating ultraviolet light having a wavelength of 365 nm and an illuminance of 20 mW/cm ² and light having a wavelength of 405 nm and an illuminance of 40 mW/cm ² to a total irradiation amount of 900 mJ/cm ² using a batch-type UV LED curing device to obtain a cured product having a thickness of 100 μm. As the batch-type UV LED curing device, M UVBA (manufactured by ITEC Co., Ltd.) was used.
The pressure-sensitive adhesive composition obtained in Comparative Example 1-15 was applied to a release-treated PET film using a coater so that the thickness after drying would be 100 μm, and then dried at 80° C. for 1 hour and at 110° C. for 20 minutes to obtain a cured product.
For each of the adhesive compositions obtained in Comparative Examples 1-16 and 1-17, the adhesive composition was applied onto a release PET film using an applicator, and the upper surface of the applied film was sealed with a release PET film (manufactured by Nippa Corporation, "1-E", thickness 50 μm) to form a UVWet laminate coating. The obtained UVWet laminate coating was simultaneously irradiated with ultraviolet light having a wavelength of 365 nm and an illuminance of 20 mW/cm ² and light having a wavelength of 405 nm and an illuminance of 40 mW/cm ² using a batch-type UV LED curing device so that the total irradiation amount was 900 mJ/cm ² , thereby curing the adhesive composition and obtaining a cured product having a thickness of 100 μm. As the batch-type UV LED curing device, M UVBA (manufactured by ITEC Co., Ltd.) was used.
Approximately 0.3 g of the obtained cured product was placed on an aluminum pan, and a mixed solvent containing THF:acetone:ethanol in a mass ratio of 8:1:1 was gently added so that the cured sample would not scatter, and the sample was allowed to swell for about 2 hours. After that, the sample was dried at 110°C for 30 minutes, at 170°C for 1 hour, and at 190°C for 30 minutes. The masses of the aluminum pan and the dried sample after drying were weighed, and the reaction rate of the cured product was calculated using the following formula.
Reaction rate [%] = (total mass of aluminum pan and sample after drying - mass of aluminum pan before drying) / (mass of sample before swelling) x 100
The reaction rate of the cured product of each of the pressure-sensitive adhesive compositions obtained in Examples 1-1 to 1-35, and 1-40, and Comparative Examples 1-1 to 1-12 corresponds to the reaction rate of the cured product of the pressure-sensitive adhesive composition applied by inkjet printing.

(Glass transition temperature of the cured product)
For the cured product obtained in the same manner as in "(Reaction rate of the cured product)" above, dynamic viscoelasticity measurement was carried out under the following conditions using a dynamic viscoelasticity measuring device ("MCR-702e" manufactured by Anton Paar), and the tan δ peak temperature was determined as the glass transition temperature.
<Conditions>
Shear method: Measured with twin drive using 8 mm parallel plate Measurement temperature: -70 to 200°C
Heating rate: 7°C/min Frequency: 1Hz
While cooling from 50°C to -70°C at a rate of 10°C/min, pre-pressure was applied at 8N, and measurements were taken from the low temperature as described below in (1) to (6).
(1) The temperature was raised with a normal force of 20 N and a strain of 0.005%, and measurements were taken under these conditions until the torque value became less than 1,500 μN·m.
(2) After (1), the temperature is increased with a normal force of 8 N and a strain of 0.05%, and measurements are taken under these conditions until the torque value becomes less than 200 μN·m.
(3) After (2), raise the temperature with a normal force of 3 N and a strain of 0.5%, and measure under these conditions until the torque value is less than 150 μN·m. If the torque in (3) is 150 μN·m or more up to 120°C, proceed to (4).
(4) After (3), raise the temperature with a normal force of 1.5 N and a strain of 2%, and measure under these conditions until the torque value is less than 100 μN·m. If the torque in (4) is 100 μN·m or more up to 170°C, proceed to (5).
(5) After (4), raise the temperature with a normal force of 1N and a strain of 5%, and measure under these conditions until the torque value is less than 80 μN·m. If the torque in (5) is 80 μN·m or more up to 190°C or if the thickness is less than 30 μm, proceed to (6).
(6) After (5), the temperature is raised with a normal force of 1 N and a strain of 10%, and measurements are taken under these conditions until the temperature reaches 200° C. When the thickness becomes less than 20 μm before the temperature of (6) reaches 200° C., the measurement is terminated.

<Evaluation>
The pressure-sensitive adhesive compositions obtained in Examples 1-1 to 1-40 and Comparative Examples 1-1 to 1-17 were evaluated as follows. The results are shown in Tables 1 to 6.

(Printability)
On a 50 mm x 50 mm aluminum substrate, 0.5 mL of each of the adhesive compositions obtained in Examples 1-1 to 1-35, 1-40, and Comparative Examples 1-1 to 1-12 was dropped, and a thin layer was prepared by applying for 10 seconds at 5000 rpm using a spin coater (manufactured by Mikasa, "MSB-150"). Next, using a batch-type UV LED curing device (manufactured by ITEC, "M UVBA"), ultraviolet light with a wavelength of 365 nm and an illuminance of 20 mW/cm ² and light with a wavelength of 405 nm and an illuminance of 40 mW/cm ² were irradiated simultaneously so that the total irradiation amount was 900 mJ/cm ^2. This was repeated until the thickness of the cured product reached 100 μm.
In addition, 1 part by mass of KS-66 (manufactured by Shin-Etsu Chemical Co., Ltd.) was added as a defoamer to 100 parts by mass of each of the pressure-sensitive adhesive compositions obtained in Examples 1-36 to 1-39 and Comparative Examples 1-13 and 1-14 to obtain a screen-printable composition. The obtained screen-printable composition was screen-printed by applying a pattern to a release PET film (manufactured by Nippa Corporation, "1-E", thickness 50 μm) using a screen printer (manufactured by SERIA Corporation, "SSA-PC560E"). A pattern-treated 70-mesh printing plate was used as the screen-printing plate. Next, a batch-type UV LED curing device (manufactured by ITEC Corporation, "M UVBA") was used to simultaneously irradiate ultraviolet light with a wavelength of 365 nm and an illuminance of 20 mW/cm ² and light with a wavelength of 405 nm and an illuminance of 40 mW/cm ² so that the total irradiation amount was 900 mJ/cm ² , thereby obtaining a cured product.
The obtained cured products were visually inspected, and the printability was evaluated according to the following criteria. Note that, in Examples 1-1 to 1-35, and 1-40, and Comparative Examples 1-1 to 1-12, application was performed by spin coating as an alternative to inkjet printing, and the printability of each pressure-sensitive adhesive composition obtained in Examples 1-1 to 1-35, and 1-40, and Comparative Examples 1-1 to 1-12 corresponds to the printability in inkjet printing.
○: No uncured areas and no bleeding was observed. ×: There were uncured areas, or there were no uncured areas, but bleeding was observed.

(Adhesion and Peel Mode)
(1) Preparation of Test Pieces (1-1) Examples 1-1 to 1-35, 1-40, and Comparative Examples 1-1 to 1-12
For each of the adhesive compositions obtained in Examples 1-1 to 1-35, 1-40, and Comparative Examples 1-1 to 1-12, 0.5 mL of each adhesive composition was dropped onto a release PET film (manufactured by Nippa, "1-E", thickness 50 μm), and a thin layer with a width of 50 mm and a length of 50 mm was prepared by coating for 10 s at 5000 rpm using a spin coater. MSB-150 (manufactured by Mikasa) was used as the spin coater. Thereafter, using a batch-type UV LED curing device (manufactured by ITEC, "M UVBA"), ultraviolet light with a wavelength of 365 nm and an illuminance of 20 mW/cm ² and light with a wavelength of 405 nm and an illuminance of 40 mW/cm ² were simultaneously irradiated so that the total irradiation amount was 900 mJ/cm ² , thereby curing the composition. This was repeated to obtain a cured product with a thickness of 100 μm.
Next, the air side of the cured product was sealed with an easily adhesive polyester film (manufactured by Toyobo Co., Ltd., "Cosmoshine A4100") having a width of 50 mm and a length of 200 mm, and the film was cut to a width of 25 mm and a length of 200 mm (adhesion surface 20 mm x 50 mm) to prepare a laminated film. Thereafter, the release PET film was peeled off from the laminated film, and the exposed surface was attached to a SUS substrate and pressure-bonded by moving it back and forth once with a 2 kg roller to obtain a test specimen.
(1-2) Examples 1-36 to 1-39 and Comparative Examples 1-13 and 1-14
For each of the adhesive compositions obtained in Examples 1-36 to 1-39 and Comparative Examples 1-13 and 1-14, the adhesive composition was applied to a thickness of 100 μm on an easily adhesive polyester film (Toyobo Co., Ltd., "Cosmoshine A4100") using a screen printer (SERIA Co., Ltd., "SSA-PC560E"). Thereafter, the adhesive composition was cured by simultaneously irradiating ultraviolet light having a wavelength of 365 nm and an illuminance of 20 mW/cm ² and light having a wavelength of 405 nm and an illuminance of 40 mW/cm ² to a total irradiation amount of 900 mJ/cm ² using a batch-type UV LED curing device (ITEC Co., Ltd., "M UVBA") to obtain a cured product having a thickness of 100 μm.
Next, the air surface of the cured product was sealed with a release PET film (Nippa Corporation, "1-E", thickness 50 μm) and cut to a width of 25 mm and a length of 200 mm (adhesion surface 25 mm × 80 mm) to prepare a laminated film. Thereafter, the release PET film was peeled off from the laminated film, and the exposed surface was attached to a SUS substrate and pressure-bonded by moving it back and forth once with a 2 kg roller to obtain a test specimen.
(1-3) Comparative Example 1-15
For the pressure-sensitive adhesive composition obtained in Comparative Example 1-15, the pressure-sensitive adhesive composition was applied to an easily adhesive polyester film (manufactured by Toyobo Co., Ltd., "Cosmoshine A4100") using a coater so that the thickness after drying would be 100 μm, and the composition was dried at 80° C. for 1 hour and at 110° C. for 20 minutes to obtain a cured product.
Next, the air surface of the cured product was sealed with a release PET film (Nippa Corporation, "1-E", thickness 50 μm) and cut to a width of 25 mm and a length of 200 mm (adhesion surface 25 mm × 80 mm) to prepare a laminated film. Thereafter, the release PET film was peeled off from the laminated film, and the exposed surface was attached to a SUS substrate and pressure-bonded by moving it back and forth once with a 2 kg roller to obtain a test specimen.
(1-4) Comparative Examples 1-16 and 1-17
For each of the adhesive compositions obtained in Comparative Examples 1-16 and 1-17, the adhesive composition was applied to an easily adhesive polyester film (manufactured by Toyobo Co., Ltd., "Cosmoshine A4100") using an applicator, and the upper surface of the applied film was sealed with a release PET film (manufactured by Nippa Corporation, "1-E", thickness 50 μm) to form a UVWet laminate coating. The obtained UVWet laminate coating was simultaneously irradiated with ultraviolet light having a wavelength of 365 nm and an illuminance of 20 mW/cm ² and light having a wavelength of 405 nm and an illuminance of 40 mW/cm ² using a batch-type UV LED curing device so that the total irradiation amount was 900 mJ/cm ² , thereby curing the adhesive composition to obtain a cured product having a thickness of 100 μm. As the batch-type UV LED curing device, M UVBA (manufactured by ITEC Co., Ltd.) was used.
Next, a laminated film was prepared by cutting it to a width of 25 mm and a length of 200 mm (adhesion surface 25 mm × 80 mm). After that, the release PET film was peeled off from the laminated film, and the exposed surface was attached to a SUS substrate and pressed by moving it back and forth with a 2 kg roller to obtain a test specimen.

(2) Measurement of adhesive strength and confirmation of peeling mode The obtained test pieces were aged for one day in an environment of 25°C and 50% RH, and then the adhesive strength was measured by performing a 180° peel at a speed of 300 mm/min using a universal testing machine (manufactured by A&D Co., Ltd., "Tensilon RTI-1310").
The peeling mode at 180° peel was evaluated according to the following criteria.
AF: interfacial peeling WLB: cohesive peeling near the interface Zip: zipping peeling CF: cohesive failure Note that AF and WLB are favorable results, Zip is an inferior result, and CF is an even worse result.

(Impact resistance)
The cured products obtained in the same manner as in the above "(Reaction rate of the cured product)" were subjected to an impact resistance test by the following method.
A SUS substrate of 40 mm x 40 mm x 3 mmt with a hole of 20 mm x 20 mm x 3 mmt in the center was bonded to a SUS substrate of 25 mm x 25 mm x 3 mmt via a cured product cut to 25 mm x 25 mm to obtain a laminate. The obtained laminate was pressure-bonded at 62 N using a universal testing machine (manufactured by A & D Co., Ltd., "Tensilon RTI-1310") to prepare a test piece. Using a drop weight impact tester (manufactured by IMATEK Co., Ltd., "IM1C-15 type"), a drop weight of 16 Φ and a total mass of 5 kg was dropped naturally from a height of 51 mm to impact the center of the test piece. From the spectrum of ms v.s.N, the area (amount of energy) of the first peak was taken as the impact absorption rate ΔE [J], and the peak force (impact resistance test force [N]) was calculated. Impact resistance was evaluated according to the following criteria.
◎: When ΔE exceeds 0.3 J or when the peak force exceeds 1.4 N ○: When ΔE is 0.15 J or more and 0.3 J or less, and when the peak force is 0.8 N or more and 1.4 N or less ×: When ΔE is less than 0.15 J, and when the peak force is 0.8 N or more and 1.4 N or less XX: When ΔE is less than 0.15 J, and when the peak force is less than 0.8 N

(Examples 2-1 to 2-20, Comparative Examples 2-1 to 2-3)
According to the compounding ratios shown in Tables 7 to 9, each material was mixed with a planetary mixer (Thinky Corporation, "Awatori Rentaro") to obtain each of the pressure-sensitive adhesive compositions of Examples 2-1 to 2-20 and Comparative Examples 2-1 to 2-3.
Details of the materials indicated by abbreviations in the table are as follows.
(Maleimide derivatives)
CHMI: N-cyclohexylmaleimide (manufactured by Nippon Shokubai Co., Ltd.)
HPM: 4-hydroxyphenylmaleimide (Seiko Chemical Co., Ltd.)
NCCHMI: N-(4-carboxycyclohexylmethyl)maleimide (Seiko Chemical Co., Ltd.)
(UV-polymerizable compound)
CBA: Ethyl carbitol acrylate (manufactured by Osaka Organic Chemical Industry Co., Ltd., "Viscoat #190", containing ether bonds)
MEDOL-10: (2-methyl-2-ethyl-1,3-dioxolan-4-yl)methyl acrylate (manufactured by Osaka Organic Chemical Industry Co., Ltd., containing an ether bond)
Viscoat #192: Phenoxyethyl acrylate (Osaka Organic Chemical Industry Co., Ltd., containing phenoxy group)
Viscoat #216: acrylic acid-2-butylcarbamoyloxyethyl ester (Osaka Organic Chemical Industry, Inc., containing amide bond)
NOAA: n-octyl acrylate (Osaka Organic Chemical Industry Co., Ltd.)
4-HBA: 4-hydroxybutyl acrylate (manufactured by Mitsubishi Chemical Corporation)
UA-160TM: Polyether-based multifunctional urethane acrylate (manufactured by Shin-Nakamura Chemical Co., Ltd.)
NVC: N-vinyl-ε-caprolactam (manufactured by Tokyo Chemical Industry Co., Ltd.)
(Photopolymerization initiator)
Omnirad 184: 1-hydroxycyclohexyl phenyl ketone (IGM Resins, cleavage-type photopolymerization initiator)
Omnirad TPO: 2,4,6-trimethylbenzoyldiphenylphosphine oxide (manufactured by IGM Resins, cleavage-type photopolymerization initiator)
Omnirad 819: bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (manufactured by IGM Resins, cleavage-type photopolymerization initiator)
Esacure 1001M: 1-(4-(4-benzoylphenylthio)phenyl)-2-tosyl-2-methyl-1-propanone (manufactured by IGM Resins, hydrogen abstraction type photopolymerization initiator)
Esacure 3644: 3-ketocoumarin (manufactured by IGM Resins, hydrogen abstraction type photopolymerization initiator)
(Amine Compound)
Esacure A198: (bis-N,N-(4-dimethylaminobenzoyl)oxyethylene-1-yl)-methylamine, bis(2-morpholinoethyl)ether (manufactured by IGM Resins)
U-cat 660M: bis(2-morpholinoethyl)ether (manufactured by San-Apro Co., Ltd.)
(Tackifier)
KE-359: Rosin resin (manufactured by Arakawa Chemical Industries, Ltd.)
(Thermoplastic resin)
LA2140: Acrylic block copolymer (manufactured by Kuraray)

The acrylic polymer used as the thermoplastic resin in Examples 2-1 to 2-20 and Comparative Examples 2-1 to 2-3 was prepared by the following method.
100 parts by mass of 2-ethylhexyl acrylate, 3 parts by mass of acrylic acid, 0.1 parts by mass of 2-hydroxyethyl acrylate, and 300 parts by mass of ethyl acetate as a polymerization solvent were added to a 2L separable flask equipped with a thermometer, a stirrer, a nitrogen inlet tube, and a cooling tube. Next, nitrogen gas was blown into the reaction vessel for 30 minutes to replace the atmosphere inside the reaction vessel with nitrogen, and the reaction vessel was heated to 80°C while stirring. After 30 minutes, 0.5 parts by mass of t-butylperoxy-2-ethylhexanoate (1-hour half-life temperature: 92.1°C, 10-hour half-life temperature: 72.1°C) as a polymerization initiator was diluted with 5 parts by mass of ethyl acetate, and the obtained polymerization initiator solution was added dropwise to the reaction vessel over 6 hours. After that, the mixture was further reacted at 80°C for 6 hours, and then the reaction liquid was cooled to obtain an acrylic polymer solution.
The obtained acrylic polymer solution was diluted with a dilution solvent (a mixed solvent of methanol and toluene, the mass ratio of methanol to toluene was 1:2) to obtain a solution with a solid content of 20 mass %. This solution was then applied to a release-treated PET film using a coater so that the thickness after drying would be 100 μm, and dried at 80° C. for 1 hour and at 110° C. for 20 minutes to obtain an acrylic polymer.

(viscosity)
0.4 mL of the obtained pressure-sensitive adhesive composition was sampled, and the viscosity was measured at 25° C. and 10 rpm using a VISCOMETER TV-22 (manufactured by Toki Sangyo Co., Ltd.) as an E-type viscometer with an appropriate cone plate for each viscosity.

(Reaction rate of cured product)
The obtained pressure-sensitive adhesive composition was applied onto a release PET film (manufactured by Nippa Corporation, "1-E", thickness 50 μm) by the method described below to obtain a cured product having a thickness of 100 μm.
For each of the adhesive compositions obtained in Examples 2-1 to 2-14, 2-16 to 2-20, and Comparative Examples 2-1 to 2-3, the adhesive composition was coated on a release PET film to a thickness of 100 μm using a screen printer (manufactured by SERIA, "SSA-PC560E"). Thereafter, in an atmospheric environment without sealing the coated surface, a batch-type UV LED curing device was used to simultaneously irradiate ultraviolet light having a wavelength of 365 nm and an illuminance of 20 mW/cm ² and light having a wavelength of 405 nm and an illuminance of 40 mW/cm ² so that the total irradiation amount was 900 mJ/cm ² , thereby curing the adhesive composition to obtain a cured product having a thickness of 100 μm. As the batch-type UV LED curing device, M UVBA (manufactured by ITEC Co., Ltd.) was used.
For the adhesive composition obtained in Example 2-15, 0.5 mL of the adhesive composition was dropped onto a release PET film, and a thin layer was prepared by coating for 10 seconds at 5000 rpm using a spin coater (manufactured by Mikasa, "MSB-150"). Next, in an atmospheric environment without sealing the upper surface of the coating, ultraviolet light having a wavelength of 365 nm and an illuminance of 20 mW/cm ² and light having a wavelength of 405 nm and an illuminance of 40 mW/cm ² were simultaneously irradiated so that the total irradiation amount was 900 mJ/cm ² using a batch-type UV LED curing device (manufactured by ITEC, "M UVBA"). This was repeated until the thickness of the cured product reached 100 μm.
Approximately 0.3 g of the obtained cured product was placed on an aluminum pan, and a mixed solvent containing THF:acetone:ethanol in a mass ratio of 8:1:1 was gently added so that the cured sample would not scatter, and the sample was allowed to swell for about 2 hours. After that, the sample was dried at 110°C for 30 minutes, at 170°C for 1 hour, and at 190°C for 30 minutes. The masses of the aluminum pan and the dried sample after drying were weighed, and the reaction rate of the cured product was calculated using the following formula.
Reaction rate [%] = (total mass of aluminum pan and sample after drying - mass of aluminum pan before drying) / (mass of sample before swelling) x 100
In Example 2-15, application was performed by spin coating instead of inkjet printing, and the reaction rate of the cured product of the pressure-sensitive adhesive composition obtained in Example 2-15 corresponds to the reaction rate of the cured product of the pressure-sensitive adhesive composition applied by inkjet printing.

(Glass transition temperature of the cured product)
For the cured product obtained in the same manner as in "(Reaction rate of the cured product)" above, dynamic viscoelasticity measurement was carried out under the following conditions using a dynamic viscoelasticity measuring device ("MCR-702e" manufactured by Anton Paar), and the tan δ peak temperature was determined as the glass transition temperature.
<Conditions>
Shear method: Measured with twin drive using 8 mm parallel plates Measurement temperature: -70 to 200°C
Heating rate: 7°C/min Frequency: 1Hz
While cooling from 50°C to -70°C at a rate of 10°C/min, pre-pressure was applied at 8N, and measurements were taken from the low temperature as described below in (1) to (6).
(1) The temperature was raised with a normal force of 20 N and a strain of 0.005%, and measurements were taken under these conditions until the torque value became less than 1,500 μN·m.
(2) After (1), the temperature is increased with a normal force of 8 N and a strain of 0.05%, and measurements are taken under these conditions until the torque value becomes less than 200 μN·m.
(3) After (2), raise the temperature with a normal force of 3 N and a strain of 0.5%, and measure under these conditions until the torque value is less than 150 μN·m. If the torque value in (3) is 150 μN·m or more up to 120°C, proceed to (4).
(4) After (3), raise the temperature with a normal force of 1.5 N and a strain of 2%, and measure under these conditions until the torque value is less than 100 μN·m. If the torque value in (4) is 100 μN·m or more up to 170°C, proceed to (5).
(5) After (4), raise the temperature with a normal force of 1N and a strain of 5%, and measure under these conditions until the torque value is less than 80 μN·m. If the torque value in (5) is 80 μN·m or more up to 190°C or if the thickness is less than 30 μm, proceed to (6).
(6) After (5), the temperature is raised with a normal force of 1 N and a strain of 10%, and measurements are taken under these conditions until the temperature reaches 200° C. When the thickness becomes less than 20 μm before the temperature of (6) reaches 200° C., the measurement is terminated.

<Evaluation>
The pressure-sensitive adhesive compositions obtained in Examples 2-1 to 2-20 and Comparative Examples 2-1 to 2-3 were evaluated as follows. The results are shown in Tables 7 to 9.

(Open Adhesion and Peel Mode)
(1) Preparation of test pieces (1-1) Examples 2-1 to 2-14, 2-16 to 2-20, and Comparative Examples 2-1 to 2-3
For each of the adhesive compositions obtained in Examples 2-1 to 2-14, 2-16 to 2-20, and Comparative Examples 2-1 to 2-3, the adhesive composition was coated on an easily adhesive polyester film (manufactured by Toyobo Co., Ltd., "Cosmoshine A4100") using a screen printer to a thickness of 100 μm, width of 25 mm, and length of 80 mm. As the screen printer, SSA-PC560E (manufactured by SERIA Co., Ltd.) was used. Thereafter, without sealing the upper surface of the coating, the adhesive composition was cured by simultaneously irradiating ultraviolet light having a wavelength of 365 nm and an illuminance of 20 mW/cm ² and light having a wavelength of 405 nm and an illuminance of 40 mW/cm ² in an atmospheric environment to a total irradiation amount of 900 mJ/cm ² using a batch-type UV LED curing device to obtain a cured product having a thickness of 100 μm. As the batch-type UV LED curing device, M UVBA (manufactured by ITEC Co., Ltd.) was used.
Next, the air surface of the cured product was sealed with a release PET film (Nippa Corporation, "1-E", thickness 50 μm) and cut to a width of 25 mm and a length of 200 mm to prepare a laminated film. Thereafter, the release PET film was peeled off from the laminated film, and the exposed surface was attached to a SUS substrate and pressure-bonded by moving it back and forth once with a 2 kg roller to obtain a test specimen.
(1-2) Example 2-15
For each adhesive composition obtained in Example 2-15, 0.5 mL of each adhesive composition was dropped onto a release PET film (manufactured by Nippa, "1-E", thickness 50 μm) and coated for 10 s at 5000 rpm using a spin coater (manufactured by Mikasa, "MSB-150") to prepare a thin layer with a width of 50 mm and a length of 50 mm. Then, using a batch-type UV LED curing device (manufactured by ITEC, "M UVBA"), ultraviolet light with a wavelength of 365 nm and an illuminance of 20 mW/cm ² and light with a wavelength of 405 nm and an illuminance of 40 mW/cm ² were simultaneously irradiated so that the total irradiation amount was 900 mJ/cm ² to cure the composition. This was repeated to obtain a cured product with a thickness of 100 μm.
Next, the air side of the cured product was sealed with an easily adhesive polyester film (manufactured by Toyobo Co., Ltd., "Cosmoshine A4100") having a width of 50 mm and a length of 200 mm, and the film was cut to a width of 25 mm and a length of 200 mm (adhesion surface 20 mm x 50 mm) to prepare a laminated film. Thereafter, the release PET film was peeled off from the laminated film, and the exposed surface was attached to a SUS substrate and pressure-bonded by moving it back and forth once with a 2 kg roller to obtain a test specimen.

(2) Measurement of adhesive strength and confirmation of peeling mode The obtained test pieces were aged for one day under an environment of 25°C and 50% RH, and then the adhesive strength (Open) was measured by performing a 180° peel at a speed of 300 mm/min using a universal testing machine (manufactured by A&D Co., Ltd., "Tensilon RTI-1310").
The peeling mode at 180° peel was evaluated according to the following criteria.
AF: interfacial peeling WLB: cohesive peeling near the interface Zip: zipping peeling CF: cohesive failure Note that AF and WLB are favorable results, Zip is an inferior result, and CF is an even worse result.

(Adhesion (Close) and Adhesion Ratio)
The adhesive strength (Close) was measured as a reference for comparison with the above adhesive strength (Open).
For compositions in which the components other than the photopolymerization initiator were the same as those in Examples 2-1 to 2-20 and Comparative Examples 2-1 to 2-3, 0.5 parts by mass each of Omnirad 184, Omnirad TPO, and Omnirad 819 were added to 100 parts by mass of the maleimide derivative and the ultraviolet-polymerizable compound, and mixed with a planetary mixer to obtain a pressure-sensitive adhesive composition. Awatori Rentaro (manufactured by Thinky Corporation) was used as the planetary mixer.
For each of the obtained adhesive compositions, the adhesive composition was coated on an easily adhesive polyester film (Toyobo Co., Ltd., "Cosmoshine A4100") to a thickness of 100 μm using a screen printer (SERIA Co., Ltd., "SSA-PC560E"). Thereafter, the coated upper surface (air surface) was sealed with a release PET film (Nippa Co., Ltd., "1-E", thickness 50 μm). Next, using a batch-type UV LED curing device, ultraviolet light with a wavelength of 365 nm and an illuminance of 20 mW/cm ² and light with a wavelength of 405 nm and an illuminance of 40 mW/cm ² were simultaneously irradiated so that the total irradiation amount was 900 mJ/cm ² , thereby curing the adhesive composition to obtain a cured product with a thickness of 100 μm. As the batch-type UV LED curing device, M UVBA (ITEC Co., Ltd.) was used.
Next, the obtained laminate of the highly adhesive polyester film, the cured product, and the release PET film was cut to a width of 25 mm and a length of 200 mm (adhesion surface 25 mm x 80 mm) to prepare a laminate film. Thereafter, the release PET film was peeled off from the laminate film, and the exposed surface was attached to a SUS substrate and pressure-bonded by moving it back and forth once with a 2 kg roller to obtain a test specimen.
The obtained test piece was aged for one day under an environment of 25°C and 50% RH, and then a universal testing machine (manufactured by A&D Co., Ltd., "Tensilon RTI-1310") was used to perform a 180° peel at a speed of 300 mm/min to measure the adhesive strength (Close). The adhesive strength ratio was calculated as (adhesive strength (Open)/adhesive strength (Close)) x 100.

(Low bleeding)
For the cured product obtained in the same manner as in "(Reaction rate of the cured product)" above, five lines of about 1 cm length were drawn on the surface at intervals of about 2 mm using an oil-based marker (Zebra's "Mackie"), and the condition of each line was visually observed. The anti-bleeding property was evaluated according to the following criteria.
○: All five lines were drawn without fading. △: All five lines were drawn, but fading was confirmed in one or more lines. ×: One or more lines could not be drawn.

Claims

The ultraviolet-curable pressure-sensitive adhesive composition contains a maleimide derivative, an ultraviolet-polymerizable compound, a photopolymerization initiator, and an amine compound,
When the maleimide derivative contains a maleimide derivative not having a structure in which hydrogen is bonded to a heteroatom, the maleimide derivative does not contain a maleimide derivative having a structure in which hydrogen is bonded to a heteroatom, or the content of the maleimide derivative having a structure in which hydrogen is bonded to the heteroatom in the maleimide derivative is less than 50 mass%;
when the maleimide derivative contains only a maleimide derivative having a structure in which hydrogen is bonded to a heteroatom, the content of the maleimide derivative having a structure in which hydrogen is bonded to a heteroatom is 9.8 parts by mass or less per 100 parts by mass of the ultraviolet polymerizable compound,
The ultraviolet-polymerizable compound contains 20% by mass or more of a monomer capable of serving as a hydrogen donor,
The photopolymerization initiator includes at least one selected from the group consisting of a hydrogen abstraction type photopolymerization initiator and a polymer type photopolymerization initiator,
The amine compound has a content of 50 mass% or more of an amine compound that does not have a structure in which hydrogen is bonded to a heteroatom,
an ultraviolet-curable pressure-sensitive adhesive composition, characterized in that the content of the amine compound is 0.1 parts by mass or more and 10 parts by mass or less relative to a total of 100 parts by mass of the maleimide derivative and the ultraviolet-polymerizable compound.
The ultraviolet-curable adhesive composition according to claim 1, wherein the content of the maleimide derivative relative to 100 parts by mass of the ultraviolet-polymerizable compound is 0.1 parts by mass or more and 20 parts by mass or less.
The ultraviolet-curable adhesive composition according to claim 1 or 2, wherein the monomer capable of serving as a hydrogen donor is a monomer having at least one structure selected from the group consisting of an ether bond, an acetyl group, a phenoxy group, a benzyl group, and an amide bond.
The ultraviolet-curable pressure-sensitive adhesive composition according to claim 1, 2 or 3, wherein the ultraviolet-curable pressure-sensitive adhesive composition is applied onto a substrate, and the coated surface is not sealed, and is simultaneously irradiated with ultraviolet light having a wavelength of 365 nm and an illuminance of 20 mW/ cm2 and light having a wavelength of 405 nm and an illuminance of 40 mW/cm2 in an atmospheric environment so that the total irradiation amount is 900 mJ/ cm2 , to obtain a cured product having a thickness of 100 μm, which has a reaction rate of 85% or more.
a UV-curable pressure-sensitive adhesive composition comprising a maleimide derivative, a UV-polymerizable compound, and a photopolymerization initiator;
the content of the maleimide derivative relative to 100 parts by mass of the ultraviolet polymerizable compound is 8 parts by mass or more,
The ultraviolet-curable pressure-sensitive adhesive composition is applied onto a substrate, and then simultaneously irradiated with ultraviolet light having a wavelength of 365 nm and an illuminance of 20 mW/ cm2 and light having a wavelength of 405 nm and an illuminance of 40 mW/ cm2 in an atmospheric environment without sealing the coated surface, so that the total irradiation amount is 900 mJ/ cm2 , thereby obtaining a cured product having a thickness of 100 μm, which has a reaction rate of 88% or more.
The ultraviolet-curable adhesive composition according to claim 5, further comprising an amine compound.
The ultraviolet-curable adhesive composition according to claim 1, 2, 3, 4, 5 or 6, wherein the ultraviolet-polymerizable compound contains 50% by mass or more of a monomer having at least one structure selected from the group consisting of an ether bond, an acetyl group, a phenoxy group, a benzyl group, and an amide bond.
The ultraviolet-curable adhesive composition according to claim 1, 2, 3, 4, 5, 6 or 7, wherein the ultraviolet-polymerizable compound includes at least one selected from the group consisting of (meth)acrylic monomers and vinyl monomers.
The ultraviolet-curable adhesive composition according to claim 8, wherein the ultraviolet-polymerizable compound contains a polyfunctional (meth)acrylic monomer.
The ultraviolet-polymerizable compound contains a polyfunctional (meth)acrylic monomer,
10. The ultraviolet-curable pressure-sensitive adhesive composition according to claim 9, wherein the content of the polyfunctional (meth)acrylic monomer is 25 parts by mass or less relative to a total of 100 parts by mass of the maleimide derivative and the ultraviolet-polymerizable compound excluding the polyfunctional (meth)acrylic monomer.
The ultraviolet-curable adhesive composition according to claim 10, wherein the content of the polyfunctional (meth)acrylic monomer is 20 parts by mass or less per 100 parts by mass of the total of the maleimide derivative and the ultraviolet-polymerizable compound excluding the polyfunctional (meth)acrylic monomer.
The ultraviolet-curable adhesive composition according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 or 11, wherein the content of the photopolymerization initiator is 1 part by mass or more and 10 parts by mass or less per 100 parts by mass of the total of the maleimide derivative and the ultraviolet-polymerizable compound.
The ultraviolet-curable adhesive composition according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 or 12, further comprising a thermoplastic resin.
The ultraviolet-curable adhesive composition according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 or 13, further comprising a tackifier.
The ultraviolet-curable adhesive composition according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13 or 14, having a viscosity of 10 mPa·s or more and 75,000 mPa·s or less at 25°C.
The ultraviolet-curable pressure-sensitive adhesive composition according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 , 13, 14, or 15, wherein the ultraviolet-curable pressure-sensitive adhesive composition is applied onto a substrate, and then simultaneously irradiated with ultraviolet light having a wavelength of 365 nm and an illuminance of 20 mW/ cm2 and light having a wavelength of 405 nm and an illuminance of 40 mW/ cm2 so that the total irradiation amount is 900 mJ/cm2, to obtain a cured product having a thickness of 100 μm, the glass transition temperature of which is −60° C. or higher and 20° C. or lower.
The method includes a step of applying the ultraviolet-curable pressure-sensitive adhesive composition according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, or 16 onto a first adherend, followed by exposing the composition to light to form a pressure-sensitive adhesive layer, and a step of attaching a second adherend onto the pressure-sensitive adhesive layer,
The method for applying the ultraviolet-curable pressure-sensitive adhesive composition is inkjet printing, screen printing, spray coating, spin coating, gravure offset, or reverse offset printing, and the ultraviolet-curable pressure-sensitive adhesive composition is partially applied onto the first adherend.