JP7594712B2 - Ultraviolet-curable pressure-sensitive adhesive composition and method for producing laminate - Google Patents

Description

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 a separator on each side 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.

In response to this, a method has been developed in which the adhesive composition is printed in the desired shape and then attached to the adherend, without the need to prepare an adhesive sheet. This method can reduce the generation of waste.

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 a non-aromatic ring-containing ethylenically unsaturated monomer, 1 to 10% by weight of a photopolymerization initiator, and 10 to 55% by weight of a crosslinking agent.

Furthermore, 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

Tape is used to fix the housing of an electronic device, and the tape must be applied without gaps to prevent liquids and dust from entering the inside of the device. However, when forming a square shape along the periphery of a device with tape, there is a problem that the area of the inner squares becomes waste as it is. In contrast, there is a method of forming a square shape by combining multiple rectangular or L-shaped tapes, but it is difficult to fill the gaps between the tapes when they are applied, and there is a problem that liquids and dust enter through the gaps. As described above, the generation of waste can be suppressed by the method of printing the adhesive composition in a desired shape and then laminating it to the adherend without preparing an adhesive sheet. On the other hand, as a method for curing the adhesive composition, ultraviolet curing is desirable to avoid heating the adherend, but in the conventional adhesive composition, in order to achieve both reactivity to ultraviolet light and adhesive properties, the amount of oxygen on the surface is reduced by placing it in a nitrogen atmosphere or laminating a film, and then the adhesive composition is cured by irradiating it with low-illuminance ultraviolet light so as to obtain a high cumulative light amount. Therefore, there are restrictions on equipment and production speed. In addition, there has been a problem in that the dimensions and shape of the adhesive composition may change after printing due to contact of the film with the uncured adhesive composition or application of heat in the drying process after printing.
On the other hand, when curing is performed by irradiating ultraviolet light in the presence of oxygen, such as in the atmosphere, there is a problem that the holding power decreases due to a difference in reaction rate between the front and back of the cured product. In addition, in recent years, ultraviolet light irradiation devices are being replaced by energy-saving UV-LEDs with a single wavelength from light sources with wide wavelength distributions, such as high-pressure mercury lamps and metal halide lamps. However, with conventional pressure-sensitive adhesive compositions, there are problems in that it is difficult to sufficiently cure when irradiated with high-intensity ultraviolet light using a UV-LED in the presence of oxygen, and sufficient adhesiveness after curing cannot be obtained.

The present invention aims to provide an ultraviolet-curable adhesive composition that has excellent ultraviolet curability in the presence of oxygen, waterproofness and dust resistance, and shape stability after printing, as well as an ultraviolet-curable adhesive composition that has excellent curability when irradiated with high-intensity ultraviolet light in the presence of oxygen, and excellent adhesion and retention performance after curing. The present invention also aims to provide a method for producing a laminate using the ultraviolet-curable adhesive composition.

Disclosure 1 relates to an ultraviolet-curable pressure-sensitive adhesive composition for use in printing, the ultraviolet-curable pressure-sensitive adhesive composition comprising a radical polymerizable monomer, a photopolymerization initiator, and a thickener, the radical polymerizable monomer comprising a compound having a cyclic structure containing a nitrogen atom, and having a viscosity of 3 Pa s or more and 100 Pa s or less as measured using an E-type viscometer at 25°C and 10 rpm.
The present disclosure 2 relates to the ultraviolet-curable pressure-sensitive adhesive composition of the present disclosure 1, which is obtained by coating the ultraviolet-curable pressure-sensitive adhesive composition on a substrate, and irradiating the coated surface with ultraviolet light having a wavelength of 365 nm and an illuminance of 500 mW/ ^cm2 at an irradiation dose of 3000 mJ/ ^cm2 under an atmospheric environment, thereby obtaining a cured product having a thickness of 50 μm, the reaction rate of which is 90% or more.
The present disclosure 3 is the ultraviolet-curable pressure-sensitive adhesive composition according to the present disclosure 1 or 2, wherein the compound having a cyclic structure containing a nitrogen atom includes at least one selected from the group consisting of radical polymerizable monomers having a lactam structure and maleimide derivatives.
Disclosure 4 is the ultraviolet-curable pressure-sensitive adhesive composition of Disclosure 3, wherein the compound having a cyclic structure containing a nitrogen atom comprises the maleimide derivative, and the maleimide derivative has at least a content of a maleimide derivative not having a structure in which hydrogen is bonded to a heteroatom of 50 mass% or more, or a content of a maleimide derivative having a structure in which hydrogen is bonded to a heteroatom of 10 parts by mass or less relative to 100 parts by mass of the radical polymerizable monomer, and the content of the maleimide derivative in 100 parts by mass of the radical polymerizable monomer is 0.1 parts by mass or more and 20 parts by mass or less.
The present disclosure 5 is the ultraviolet-curable pressure-sensitive adhesive composition of the present disclosure 3, wherein the compound having a cyclic structure containing a nitrogen atom comprises the radical polymerizable monomer having the lactam structure, and the content of the radical polymerizable monomer having the lactam structure in 100 parts by mass of the radical polymerizable monomer is 10 parts by mass or more and 60 parts by mass or less.
The present disclosure 6 is the ultraviolet-curable pressure-sensitive adhesive composition according to the present disclosure 1, 2, 3, 4, or 5, wherein the radical polymerizable monomer contains 20 mass% or more of a monomer capable of serving as a hydrogen donor, the photopolymerization initiator contains at least one selected from the group consisting of a hydrogen abstraction type photopolymerization initiator and a polymer type photopolymerization initiator, the ultraviolet-curable pressure-sensitive adhesive composition further contains an amine compound, the amine compound contains an amine compound having no structure in which hydrogen is bonded to a heteroatom in the amine compound in an amount of 50 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 in a total of 100 parts by mass of the ultraviolet-curable pressure-sensitive adhesive composition excluding the photopolymerization initiator.
The present disclosure 7 is the ultraviolet-curable pressure-sensitive adhesive composition according to the present disclosure 1, 2, 3, 4, 5, or 6, wherein the radical polymerizable monomer comprises a polyfunctional (meth)acrylic monomer.
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 thickener comprises at least one selected from the group consisting of a thermoplastic resin, a polymeric thixotropy regulator, and a solid thickener.
The present disclosure 9 is the ultraviolet-curable pressure-sensitive adhesive composition according to the present disclosure 8, wherein the thickener contains the thermoplastic resin, and the thermoplastic resin contains a (meth)acrylic copolymer.
The present disclosure 10 is an ultraviolet-curable pressure-sensitive adhesive composition according to the present disclosure ¹ , 2, 3, 4, 5, 6, 7, 8, or 9, which is obtained by applying the ultraviolet-curable pressure-sensitive adhesive composition to a substrate, and irradiating the applied surface with ultraviolet light having a wavelength of 365 nm and an illuminance of 500 mW/ ^cm2 at an exposure dose of 3000 mJ/cm2 under an atmospheric environment, and which has a thickness of 50 μm and a glass transition temperature of −40° C. or higher and 20° C. or lower.
The present disclosure 11 is an ultraviolet-curable pressure-sensitive adhesive composition according to the present disclosure ¹ , 2, 3, 4, 5, 6, 7, 8, 9, or 10, which is obtained by coating the ultraviolet-curable pressure-sensitive adhesive composition on a substrate, irradiating the coated surface with ultraviolet light having a wavelength of 365 nm and an illuminance of 500 mW/cm2 under an atmospheric environment without sealing the coated surface, so that the irradiation amount is 3000 mJ/ ^cm2, and obtaining a cured product having a thickness of 50 μm, the gel fraction of which is 20 mass% or more and 80 mass% or less.
Disclosure 12 is an ultraviolet-curable pressure-sensitive adhesive composition comprising a monofunctional radical polymerizable monomer, a photopolymerization initiator, and a crosslinking agent having two or more reactive functional groups in one molecule, the monofunctional radical polymerizable monomer comprising a compound having a cyclic structure containing a nitrogen atom, the ultraviolet-curable pressure-sensitive adhesive composition being applied to a substrate, and the coated surface being unsealed and irradiated with ultraviolet light having a wavelength of 365 nm and an illuminance of 500 mW/cm ² in an atmospheric environment at an irradiation dose of 3000 mJ/cm ² to obtain a cured product having a thickness of 50 μm, the cured product having a reaction rate of 90% or more, the cured product having a gel fraction of 20% by mass or more and 80% by mass or less, and the cured product being subjected to dynamic viscoelasticity measurement under conditions of a shear method, a measurement temperature of −70° C. to 200° C., and a frequency of 1 Hz, the temperature at which the loss tangent reaches a maximum value in a temperature range of 50° C. or less is 20° C. or less.
The present disclosure 13 relates to an ultraviolet-curable pressure-sensitive adhesive composition according to the present disclosure 12, wherein the compound having a cyclic structure containing a nitrogen atom includes at least one selected from the group consisting of monofunctional radically polymerizable monomers having a lactam structure and maleimide derivatives.
Disclosure 14 is the ultraviolet-curable pressure-sensitive adhesive composition of Disclosure 13, wherein the compound having a cyclic structure containing a nitrogen atom includes the maleimide derivative, and the maleimide derivative has at least a content of a maleimide derivative not having a structure in which hydrogen is bonded to a heteroatom of 50 mass% or more, or a content of a maleimide derivative having a structure in which hydrogen is bonded to a heteroatom of 10 parts by mass or less relative to 100 parts by mass of the monofunctional radical polymerizable monomer, and the content of the maleimide derivative in 100 parts by mass of the monofunctional radical polymerizable monomer is 0.1 parts by mass or more and 20 parts by mass or less.
Disclosure 15 is the ultraviolet-curable pressure-sensitive adhesive composition of Disclosure 13, wherein the compound having a cyclic structure containing a nitrogen atom comprises a monofunctional radical polymerizable monomer having the lactam structure, and the content of the monofunctional radical polymerizable monomer having the lactam structure in 100 parts by mass of the monofunctional radical polymerizable monomer is 10 parts by mass or more and 60 parts by mass or less.
The present disclosure 16 is an ultraviolet-curable pressure-sensitive adhesive composition according to the present disclosure 12, 13, 14, or 15, wherein the monofunctional radical polymerizable monomer contains 20 mass% or more of a monomer capable of serving as a hydrogen donor, the photopolymerization initiator contains at least one selected from the group consisting of a hydrogen abstraction type photopolymerization initiator and a polymer type photopolymerization initiator, the ultraviolet-curable pressure-sensitive adhesive composition further contains an amine compound, the amine compound has a content of 50 mass% or more of an amine compound not having a structure in which hydrogen is bonded to a heteroatom, and the content of the amine compound is 0.5 parts by mass or more and 8.0 parts by mass or less in a total of 100 parts by mass of the ultraviolet-curable pressure-sensitive adhesive composition excluding the photopolymerization initiator.
Disclosure 17 is the ultraviolet-curable pressure-sensitive adhesive composition of Disclosure 16, 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 18 is the ultraviolet-curable pressure-sensitive adhesive composition of the present disclosure 17, wherein the monofunctional radically polymerizable monomer contains 30 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 19 is the ultraviolet-curable pressure-sensitive adhesive composition according to the present disclosure 12, 13, 14, 15, 16, 17, or 18, wherein the crosslinking agent has, as the reactive functional group, two or more of at least one selected from the group consisting of an isocyanate group, an epoxy group, an aldehyde group, a hydroxyl group, an amino group, a (meth)acryloyl group, and a vinyl group in one molecule.
The present disclosure 20 is the ultraviolet-curable pressure-sensitive adhesive composition of the present disclosure 12, 13, 14, 15, 16, 17, 18, or 19, further comprising a thickener.
The present disclosure 21 is the ultraviolet-curable pressure-sensitive adhesive composition of the present disclosure 20, wherein the thickener is at least one selected from the group consisting of a thermoplastic resin, a polymeric thixotropy regulator, and a solid thickener.
The present disclosure 22 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, 14, 15, 16, 17, 18, 19, 20, or 21, further containing a tackifier.
The present disclosure 23 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, 14, 15, 16, 17, 18, 19, 20, 21, or 22, further containing an antifoaming agent.
Disclosure 24 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, 16, 17, 18, 19, 20, 21, 22, or 23 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 screen printing, stencil printing, or reverse offset printing, and the ultraviolet-curable pressure-sensitive adhesive composition is applied entirely or partially onto the first adherend.
The present disclosure 25 is a method for producing a laminate according to the present disclosure 24, wherein the first adherend and the second adherend are release-treated substrates.
The present disclosure 26 is a method for producing a laminate according to the present disclosure 25, wherein the first adherend and the second adherend are base materials that have been subjected to a release treatment and an antistatic treatment.
The present disclosure 27 is a method for producing a laminate according to the present disclosure 24, 25, or 26, in which the ultraviolet-curable pressure-sensitive adhesive composition is partially coated on 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 12 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 investigated the preparation of an ultraviolet-curable adhesive composition containing a radical polymerizable monomer including a compound having a cyclic structure containing a nitrogen atom, a photopolymerization initiator, and a thickener, and adjusting the viscosity at 25° C. to be within a specific range. As a result, they have found that an ultraviolet-curable adhesive composition having excellent ultraviolet curability in the presence of oxygen, waterproofness and dustproofness, and shape stability after printing can be obtained, leading to the completion of Invention 1. By using the ultraviolet-curable adhesive composition of Invention 1, a square-shaped cured product that maintains its shape without gaps can be formed without generating waste by printing into a predetermined shape and irradiating with ultraviolet light in the atmosphere.
The present inventors have also investigated how to make the reaction rate of a cured product obtained by UV curing an ultraviolet-curable pressure-sensitive adhesive composition containing a monofunctional radical polymerizable monomer containing a compound having a cyclic structure containing a nitrogen atom, a photopolymerization initiator, and a crosslinking agent under specific conditions to a specific value or more, a specific range of gel fraction, and a specific temperature or less. As a result, they have found that it is possible to obtain an ultraviolet-curable pressure-sensitive adhesive composition that is excellent in curability when irradiated with high-intensity ultraviolet light in the presence of oxygen, and in adhesiveness and retention performance after curing, and have completed the present invention 2.

The ultraviolet-curable pressure-sensitive adhesive composition of the present invention 1 has a viscosity measured using an E-type viscometer at 25° C. and 10 rpm, with a lower limit of 3 Pa·s and an upper limit of 100 Pa·s. When the viscosity is within this range, the ultraviolet-curable pressure-sensitive adhesive composition of the present invention 1 has excellent printability and shape stability after printing. The ultraviolet-curable pressure-sensitive adhesive composition of the present invention 1 has a preferred lower limit of 5 Pa·s, a more preferred lower limit of 10 Pa·s, a preferred upper limit of 70 Pa·s, and a more preferred upper limit of 40 Pa·s.
The viscosity of the ultraviolet-curable pressure-sensitive adhesive composition of the first invention can be measured, for example, using a VISCOMETER TV-22 (manufactured by Toki Sangyo Co., Ltd.) as an E-type viscometer with an appropriate cone plate under conditions of 25° C. and 10 rpm.
The ultraviolet-curable pressure-sensitive adhesive composition of the second invention has a viscosity at 25° C. of preferably 5 mPa·s at lower limit and 250,000 mPa·s at upper limit. When the viscosity is within this range, the ultraviolet-curable pressure-sensitive adhesive composition of the second invention is suitable for printing. The ultraviolet-curable pressure-sensitive adhesive composition of the second invention has a more preferable viscosity lower limit and 150,000 mPa·s at upper limit.
The viscosity of the ultraviolet-curable pressure-sensitive adhesive composition of the second invention can be measured, for example, using a VISCOMETER TV-22 (manufactured by Toki Sangyo Co., Ltd.) as an E-type viscometer with an appropriate cone plate under conditions of 25° C. and 10 rpm.

The ultraviolet-curable pressure-sensitive adhesive composition of the present invention 1 has a thixotropic index at 25° C. of preferably 1.05 at the lower limit and 2.5 at the upper limit. When the thixotropic index is in this range, the ultraviolet-curable pressure-sensitive adhesive composition has better printability and shape stability after printing. The more preferred lower limit of the thixotropic index is 1.1, and the more preferred upper limit is 2.0.
In this specification, the "thixotropic index" refers to the value obtained by dividing the viscosity measured using an E-type viscometer at 1 rpm by the viscosity measured at 10 rpm.

The ultraviolet-curable adhesive composition of the present invention 1 contains a radically polymerizable monomer. By containing the above-mentioned radically polymerizable monomer, the ultraviolet-curable adhesive composition of the present invention 1 has excellent curability and adhesion after curing.

The radical polymerizable monomer includes a compound having a cyclic structure containing a nitrogen atom. By including the compound having a cyclic structure containing a nitrogen atom, the ultraviolet-curable adhesive composition of the present invention 1 has excellent ultraviolet curing properties in the presence of oxygen.

The compound having a cyclic structure containing a nitrogen atom preferably includes at least one selected from the group consisting of radical polymerizable monomers having a lactam structure and maleimide derivatives, and more preferably includes a maleimide derivative.
The reaction system of the radical polymerizable monomer having the lactam structure and 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 can increase the surface curability. In addition, photoradical polymerization by hydrogen abstraction reaction does not produce a linear polymer like cleavage (Type I) reaction, but produces a branched polymer, and the cohesive strength is also high. Therefore, the ultraviolet-curable pressure-sensitive adhesive composition contains at least one selected from the group consisting of the radical polymerizable monomer having the lactam structure and the maleimide derivative, 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 above "maleimide derivative" means a compound having a maleimide group.

The maleimide derivative preferably has a content of at least 50 mass% of maleimide derivatives not having a structure in which hydrogen is bonded to a heteroatom, or a content of maleimide derivatives having a structure in which hydrogen is bonded to a heteroatom relative to 100 mass parts of the radical polymerizable monomer is 10 mass parts or less. This allows the cured product of the obtained ultraviolet-curable pressure-sensitive adhesive composition to have excellent impact resistance. More preferably, the content of maleimide derivatives having a structure in which hydrogen is bonded to a heteroatom relative to 100 mass parts of the radical polymerizable monomer is 5 mass parts or less.
It is particularly preferable that the maleimide derivative contains only maleimide derivatives that do not have a structure in which hydrogen is bonded to a heteroatom.

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

Examples of maleimide derivatives that do not have a structure in which hydrogen is bonded to the heteroatom 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, and N-dodecenylmaleimide. Of these, N-cyclohexylmaleimide is preferred.

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

In the ultraviolet-curable adhesive composition of the present invention 1, the preferred lower limit of the content of the maleimide derivative in 100 parts by mass of the radical polymerizable monomer is 0.1 parts by mass, and the preferred upper limit is 20 parts by mass. When the content of the maleimide derivative is within this range, the obtained ultraviolet-curable adhesive composition has better surface curing properties and adhesion. A more preferred lower limit of the content of the maleimide derivative is 0.5 parts by mass, and a more preferred upper limit is 10 parts by mass.

It is preferable that the above-mentioned radical polymerizable monomer having a lactam structure is 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, N-vinyl-ε-caprolactam, etc. Among these, N-vinyl-ε-caprolactam is preferred.

In the ultraviolet-curable adhesive composition of the present invention 1, the preferred lower limit of the content of the radical polymerizable monomer having the lactam structure in 100 parts by mass of the radical polymerizable monomer is 10 parts by mass, and the preferred upper limit is 60 parts by mass. When the content of the radical polymerizable monomer having the lactam structure is within this range, the obtained ultraviolet-curable adhesive composition has better surface curing properties and adhesion. A more preferred lower limit of the content of the radical polymerizable monomer having the lactam structure is 15 parts by mass, and a more preferred upper limit is 50 parts by mass.

The radical polymerizable monomer preferably contains a monomer capable of serving as a hydrogen donor. By containing the radical polymerizable monomer in combination with at least one selected from the group consisting of the radical polymerizable monomer having a lactam structure and a maleimide derivative, it is 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 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 the monomer capable of serving as the hydrogen donor being 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, it becomes possible to more easily provide hydrogen to the hydrogen abstraction reaction. In particular, it is more preferable that 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, a phenoxy group, and an amide bond.

In the ultraviolet-curable pressure-sensitive adhesive composition of the present invention 1, the preferred lower limit of the content of the monomer capable of being a hydrogen donor in the radical polymerizable monomer is 20% by mass. When the content of the monomer capable of being a hydrogen donor in the radical polymerizable monomer is 20% by mass or more, the obtained ultraviolet-curable pressure-sensitive adhesive composition has better surface curability. The more preferred lower limit of the content of the monomer capable of being a hydrogen donor in the radical polymerizable monomer 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 radical polymerizable monomer is preferably 90% by mass, and more preferably 70% by mass.
In particular, the radical polymerizable monomer 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. When the radical polymerizable monomer 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 obtained ultraviolet-curable pressure-sensitive adhesive composition has better curability and impact resistance of the cured product. More preferably, the radical polymerizable monomer contains 70% 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 radical polymerizable monomer preferably contains a monofunctional (meth)acrylic monomer. When the radical polymerizable monomer contains the monofunctional (meth)acrylic monomer, the resulting ultraviolet-curable pressure-sensitive adhesive composition has better adhesion.
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. In addition, in this specification, the term "monofunctional (meth)acrylic monomer" means 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 (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-dioxene (meth)acrylate, (2-methyl-2-ethyl-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, cyclic trimethylolpropane formal acrylate, and the like.
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, N,N-dimethylaminopropyl(meth)acrylamide, etc.

In the ultraviolet-curable adhesive composition of the present invention 1, the preferred lower limit of the content of the monofunctional (meth)acrylic monomer in 100 parts by mass of the radical polymerizable monomer is 10 parts by mass, and the preferred upper limit is 99 parts by mass. When the content of the monofunctional (meth)acrylic monomer is within this range, the obtained ultraviolet-curable adhesive composition has better printability and adhesion to various substrates. A more preferred lower limit of the content of the monofunctional (meth)acrylic monomer is 20 parts by mass, and a more preferred upper limit is 95 parts by mass.

The radical polymerizable monomer preferably contains a polyfunctional (meth)acrylic monomer. By containing the polyfunctional (meth)acrylic monomer, the ultraviolet-curable pressure-sensitive adhesive composition of the first invention has better adhesion and retention performance after curing.
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 term "(meth)acrylate" means acrylate or methacrylate, and the term "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 serve as raw materials for the above-mentioned polyfunctional urethane (meth)acrylates 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, 1,6,11-undecane triisocyanate, etc.

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, 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 di(meth)acrylate, carbonate diol di(meth)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 acrylate, ethylene oxide-added isocyanuric 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 hexa(meth)acrylate, and caprolactone-modified dipentaerythritol hexa(meth)acrylate.

Examples of the above-mentioned polyfunctional epoxy (meth)acrylates 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 lower limit of the content of the polyfunctional (meth)acrylic monomer in 100 parts by mass of the radical polymerizable monomer is 0.5 parts by mass, and the preferred upper limit is 20 parts by mass. When the content of the polyfunctional (meth)acrylic monomer is within this range, the obtained ultraviolet-curable adhesive composition has better adhesion and retention performance after curing. A more preferred lower limit of the content of the polyfunctional (meth)acrylic monomer is 1 part by mass, and a more preferred upper limit is 10 parts by mass.

The ultraviolet-curable pressure-sensitive adhesive composition of the present invention 2 contains a monofunctional radically polymerizable monomer. By containing the monofunctional radically polymerizable monomer, the ultraviolet-curable pressure-sensitive adhesive composition of the present invention 2 has excellent adhesiveness after curing.
In this specification, the above-mentioned "monofunctional radically polymerizable monomer" means a monomer having one radically polymerizable group in one molecule.

The monofunctional radically polymerizable monomer includes a compound having a cyclic structure containing a nitrogen atom. By including the compound having a cyclic structure containing a nitrogen atom, the ultraviolet-curable adhesive composition of the present invention 2 has excellent ultraviolet curing properties in the presence of oxygen.

The compound having a cyclic structure containing a nitrogen atom preferably contains at least one selected from the group consisting of monofunctional radically polymerizable monomers having a lactam structure and maleimide derivatives, and more preferably contains a maleimide derivative.
The reaction system of the monofunctional radical polymerizable monomer having a lactam structure and 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 can increase the surface curability. In addition, photoradical polymerization by hydrogen abstraction reaction does not produce a linear polymer like cleavage (Type I) reaction, but produces a branched polymer, and the cohesive strength is also high. Therefore, the ultraviolet-curable pressure-sensitive adhesive composition contains at least one selected from the group consisting of the monofunctional radical polymerizable monomer having a lactam structure and the maleimide derivative, 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 the ultraviolet-curable pressure-sensitive adhesive composition of the present invention 2, the maleimide derivative preferably has a content of at least 50 mass% of maleimide derivatives not having a structure in which hydrogen is bonded to a heteroatom, or a content of maleimide derivatives having a structure in which hydrogen is bonded to a heteroatom relative to 100 mass parts of the monofunctional radical polymerizable monomer is 10 mass parts or less. This allows the cured product of the obtained ultraviolet-curable pressure-sensitive adhesive composition to have excellent adhesive strength and holding power. More preferably, the content of maleimide derivatives having a structure in which hydrogen is bonded to a heteroatom relative to 100 mass parts of the monofunctional radical polymerizable monomer is 5 mass parts or less.
It is particularly preferable that the maleimide derivative contains only maleimide derivatives that do not have a structure in which hydrogen is bonded to a heteroatom.

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

Examples of maleimide derivatives that do not have a structure in which hydrogen is bonded to the heteroatom 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, and N-dodecenylmaleimide. Of these, N-cyclohexylmaleimide is preferred.

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

In the ultraviolet-curable adhesive composition of the present invention 2, the preferred lower limit of the content of the maleimide derivative in 100 parts by mass of the monofunctional radical polymerizable monomer is 0.1 parts by mass, and the preferred upper limit is 20 parts by mass. When the content of the maleimide derivative is within this range, the obtained ultraviolet-curable adhesive composition has better surface curing properties and adhesion. A more preferred lower limit of the content of the maleimide derivative is 0.5 parts by mass, and a more preferred upper limit is 10 parts by mass.

It is preferable that the above-mentioned monofunctional radically polymerizable monomer having a lactam structure is 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, N-vinyl-ε-caprolactam, etc. Among these, N-vinyl-ε-caprolactam is preferred.

In the ultraviolet-curable adhesive composition of the present invention 2, the preferred lower limit of the content of the monofunctional radical polymerizable monomer having a lactam structure in 100 parts by mass of the monofunctional radical polymerizable monomer is 10 parts by mass, and the preferred upper limit is 60 parts by mass. When the content of the monofunctional radical polymerizable monomer having a lactam structure is within this range, the obtained ultraviolet-curable adhesive composition has superior surface curing properties and adhesion. A more preferred lower limit of the content of the monofunctional radical polymerizable monomer having a lactam structure is 15 parts by mass, and a more preferred upper limit is 50 parts by mass.

The monofunctional radical polymerizable monomer preferably contains a monomer capable of acting as a hydrogen donor. By including the monofunctional radical polymerizable monomer in combination with at least one selected from the group consisting of the monofunctional radical polymerizable monomer having a lactam structure and a maleimide derivative, it is 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.

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 the monomer capable of serving as the hydrogen donor being 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, it becomes possible to more easily provide hydrogen to the hydrogen abstraction reaction. In particular, it is more preferable that 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, a phenoxy group, and an amide bond.

In the ultraviolet-curable pressure-sensitive adhesive composition of the present invention 2, the preferred lower limit of the content of the monomer capable of being the hydrogen donor in the monofunctional radical polymerizable monomer is 20% by mass. When the content of the monomer capable of being the hydrogen donor in the monofunctional radical polymerizable monomer is 20% by mass or more, the obtained ultraviolet-curable pressure-sensitive adhesive composition has better surface curing properties. The more preferred lower limit of the content of the monomer capable of being the hydrogen donor in the monofunctional radical polymerizable monomer is 35% by mass.
From the viewpoint of adhesion and retention performance, the upper limit of the content of the monomer capable of serving as a hydrogen donor in the monofunctional radically polymerizable monomer is preferably 90% by mass, and more preferably 70% by mass.
In particular, the monofunctional radical polymerizable monomer preferably contains 30% 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. When the monofunctional radical polymerizable monomer contains 30% 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 obtained ultraviolet-curable pressure-sensitive adhesive composition has better curability and adhesiveness and retention performance of the cured product. The monofunctional radical polymerizable monomer more preferably contains 50% by mass or more, and even more preferably contains 70% 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.

It is preferable that the monofunctional radical polymerizable monomer contains a monofunctional (meth)acrylic monomer. When the monofunctional radical polymerizable monomer contains the monofunctional (meth)acrylic monomer, the resulting ultraviolet-curable pressure-sensitive adhesive composition has superior adhesion.

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 compounds 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 (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-dioxene (meth)acrylate, (2-methyl-2-ethyl-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, cyclic trimethylolpropane formal acrylate, and the like.

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, N,N-dimethylaminopropyl(meth)acrylamide, etc.

The ultraviolet-curable pressure-sensitive adhesive composition of the present invention contains a photopolymerization initiator.
The photopolymerization initiator preferably includes at least one selected from the group consisting of hydrogen abstraction type photopolymerization initiators and polymer type photopolymerization initiators. By using at least one selected from the group consisting of hydrogen abstraction type photopolymerization initiators and polymer type photopolymerization initiators as the photopolymerization initiator, it becomes possible to obtain a cured product in which bleeding due to a decrease in surface curability and cohesive failure due to a decrease in surface curability and cohesive strength are less likely to occur in the obtained ultraviolet-curable pressure-sensitive adhesive composition.

As the hydrogen abstraction type photopolymerization initiator, a benzophenone-based photopolymerization initiator is preferred. 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 above hydrogen abstraction type photopolymerization initiators include Esacure TZT and Omnirad 4MBZ (both manufactured by IGM Resins).

Examples of the above-mentioned polymeric photopolymerization initiators 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).

As the photopolymerization initiator, a cleavage type photopolymerization initiator can also be used.
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 pressure-sensitive adhesive composition of the present invention 1, the content of the photopolymerization initiator is preferably 0.5 parts by mass at the lower limit and 15 parts by mass at the upper limit with respect to 100 parts by mass of the radical polymerizable monomer. By the content of the photopolymerization initiator being within this range, the obtained ultraviolet-curable pressure-sensitive adhesive composition is more excellent in storage stability, curability, and adhesiveness after curing. The more preferred lower limit of the content of the photopolymerization initiator is 3 parts by mass, and the 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 0.5 parts by mass at the lower limit and 15 parts by mass at the upper limit relative to 100 parts by mass of the monofunctional radical polymerizable monomer. By having the content of the photopolymerization initiator in this range, the obtained ultraviolet-curable pressure-sensitive adhesive composition is more excellent in storage stability, curability, and adhesiveness after curing. The more preferred lower limit of the content of the photopolymerization initiator is 1 part by mass, and the more preferred upper limit is 9 parts by mass.

The ultraviolet-curable pressure-sensitive adhesive composition of the present invention preferably 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 surface curability and cohesive strength, and thus a cured product that is less susceptible to bleeding due to a decrease in surface curability and cohesive strength.

The above amine compound preferably has a content of 50% by mass or more of amine compounds that do 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 amine compounds that do 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. The above amine compound more preferably has a content of 75% by mass or more of amine compounds that do not have a structure in which hydrogen is bonded to a heteroatom, and most preferably has a content of 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 above 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 Corporation).

In the ultraviolet-curable adhesive composition of the present invention 1, the preferred lower limit of the content of the amine compound in the total of 100 parts by mass of the ultraviolet-curable adhesive composition excluding the photopolymerization initiator is 0.1 parts by mass, and the preferred upper limit is 10 parts by mass. When the content of the amine compound is 0.1 parts by mass or more, the obtained ultraviolet-curable adhesive composition has better surface curing properties. When the content of the amine compound is 10 parts by mass or less, the obtained adhesive sheet is less likely to cause cohesive failure. The more preferred lower limit of the content of the amine compound is 0.5 parts by mass, and the more preferred upper limit is 8.0 parts by mass.
In the ultraviolet-curable adhesive composition of the present invention 2, the preferred lower limit of the content of the amine compound in the total of 100 parts by mass of the ultraviolet-curable adhesive composition excluding the photopolymerization initiator is 0.5 parts by mass, and the preferred upper limit is 8.0 parts by mass. When the content of the amine compound is 0.5 parts by mass or more, the obtained ultraviolet-curable adhesive composition has better surface curing properties. When the content of the amine compound is 8.0 parts by mass or less, the obtained adhesive sheet is less likely to cause cohesive failure. The more preferred lower limit of the content of the amine compound is 1.0 parts by mass, and the more preferred upper limit is 5.0 parts by mass.

The ultraviolet-curable adhesive composition of the first invention contains a thickener. By containing the above-mentioned thickener, it becomes easy to adjust the viscosity and thixotropic index of the ultraviolet-curable adhesive composition of the first invention to the above-mentioned range. In addition, the ultraviolet-curable adhesive composition of the second invention may further contain a thickener.

It is preferable that the thickener contains at least one selected from the group consisting of thermoplastic resins, polymeric thixotropy regulators, and solid thickeners.

As the above-mentioned thermoplastic resin, it is preferable that the compound does not contain a reactive double bond, or even if it has a reactive double bond, it does not substantially exhibit photoradical polymerization reactivity.

Examples of the thermoplastic resin include (meth)acrylic copolymers, polyolefins, polyesters, polyamides, polyurethanes, etc. Among these, it is preferable that the thermoplastic resin contains a (meth)acrylic copolymer.

The (meth)acrylic copolymer may, for example, be a solvent-free acrylic polymer.
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 preferred lower limit of the weight average molecular weight of the thermoplastic resin is 5,000, and the preferred upper limit is 800,000. When the weight average molecular weight of the thermoplastic resin is within this range, it becomes easier to adjust the viscosity and thixotropic index of the obtained ultraviolet-curable pressure-sensitive adhesive composition to the above-mentioned range. The more preferred lower limit of the weight average molecular weight of the thermoplastic resin is 10,000, and the more preferred upper limit is 500,000.
In this specification, the weight average molecular weight is a value obtained by measuring by gel permeation chromatography (GPC) using tetrahydrofuran as a solvent and converting the weight average molecular weight into polystyrene equivalent. Examples of columns used for measuring the weight average molecular weight converted into polystyrene equivalent by GPC include Shodex LF-804 (manufactured by Showa Denko KK).

In the ultraviolet-curable adhesive composition of the present invention 1, when the thermoplastic resin is contained as the thickener, the content of the thermoplastic resin is preferably 5 parts by mass at the lower limit and 85 parts by mass at the upper limit with respect to 100 parts by mass of the radical polymerizable monomer. By the content of the thermoplastic resin being within this range, it becomes easier to adjust the viscosity and thixotropic index of the obtained ultraviolet-curable adhesive composition to the above-mentioned range, and the decrease in adhesion at high temperatures can also be suppressed. The more preferred lower limit of the content of the thermoplastic resin is 15 parts by mass, and the more preferred upper limit is 65 parts by mass.
In addition, in the ultraviolet-curable adhesive composition of the present invention 2, when the thermoplastic resin is contained as the thickener, the content of the thermoplastic resin is preferably 1.0 parts by mass and 70 parts by mass relative to 100 parts by mass of the monofunctional radical polymerizable monomer. By the content of the thermoplastic resin being 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. The more preferable lower limit of the content of the thermoplastic resin is 5.0 parts by mass, and the more preferable upper limit is 60 parts by mass.

Examples of the above-mentioned polymeric thixotropy adjusters include amides, castor oil, polyether phosphate esters, etc.

The solid thickener may be inorganic particles or organic particles.
Examples of the inorganic particles include insulating and heat-dissipating fillers, conductive fillers, and high dielectric constant fillers.
Examples of the insulating and heat-dissipating filler include talc, silica, alumina, aluminum nitride, magnesium oxide, and diamond.
Examples of the conductive filler include carbon filler, metal filler, metal oxide filler, and metal-coated filler.
An example of the high dielectric constant filler is barium titanate.
Examples of the organic particles include (meth)acrylic copolymer particles, melamine resin particles, (meth)acrylic-styrene copolymer particles, and organic-inorganic composite particles.
The organic-inorganic composite particles include, for example, particles made of silicone-acrylic resin.
The organic particles may be hollow particles or thermally expanded particles.

The solid thickener has a preferred lower limit of 5 nm and a preferred upper limit of 20 μm. When the solid thickener has an average particle size in this range, the resulting ultraviolet-curable adhesive composition has better printability. The solid thickener has a more preferred lower limit of 10 nm and a more preferred upper limit of 10 μm.
The average particle size of the solid thickener can be measured by dispersing the solid thickener in a solvent (water, organic solvent, etc.) using a particle size distribution measuring device such as NICOMP 380ZLS (manufactured by PARTICLE SIZING SYSTEMS).

In the ultraviolet-curable pressure-sensitive adhesive composition of the present invention 1, when the solid thickener is contained as the thickener, the content of the solid thickener is preferably 1.0 parts by mass and 70 parts by mass relative to 100 parts by mass of the radical polymerizable monomer. When the content of the solid thickener in the ultraviolet-curable pressure-sensitive adhesive composition of the present invention 1 is within this range, it becomes easier to adjust the viscosity and thixotropic index of the obtained ultraviolet-curable pressure-sensitive adhesive composition to the above-mentioned range. The more preferred lower limit of the content of the solid thickener in the ultraviolet-curable pressure-sensitive adhesive composition of the present invention 1 is 2.0 parts by mass, and the more preferred upper limit is 50 parts by mass.
In the ultraviolet-curable adhesive composition of the present invention 2, when the solid thickener is contained as the thickener, the content of the solid thickener is preferably 1.0 parts by mass and 70 parts by mass relative to 100 parts by mass of the monofunctional radical polymerizable monomer. When the content of the solid thickener in the ultraviolet-curable adhesive composition of the present invention 2 is within this range, the obtained ultraviolet-curable adhesive composition has better printability. The more preferred lower limit of the content of the solid thickener in the ultraviolet-curable adhesive composition of the present invention 2 is 2.0 parts by mass and the more preferred upper limit is 50 parts by mass.

The ultraviolet-curable adhesive composition of the present invention 2 contains a crosslinking agent having two or more reactive functional groups in one molecule. In addition, the ultraviolet-curable adhesive composition of the present invention 1 preferably contains a crosslinking agent having two or more reactive functional groups in one molecule. By containing the above-mentioned crosslinking agent, the ultraviolet-curable adhesive composition of the present invention can easily adjust the gel fraction of the cured product to the range described below, and has excellent adhesion and retention performance after curing.

In the ultraviolet-curable pressure-sensitive adhesive composition of the second invention, the crosslinking agent preferably has, as the reactive functional group, at least one type selected from the group consisting of an isocyanate group, an epoxy group, an aldehyde group, a hydroxyl group, an amino group, a (meth)acryloyl group, and a vinyl group, in one molecule, in a number of two or more, and more preferably has at least one type selected from the group consisting of an isocyanate group, an epoxy group, and a (meth)acryloyl group, in one molecule, in a number of two or more.
In the ultraviolet-curable pressure-sensitive adhesive composition of the first invention, the crosslinking agent preferably has, as the reactive functional group, at least one type selected from the group consisting of an isocyanate group, an epoxy group, an aldehyde group, a hydroxyl group, and an amino group, in one molecule, in a quantity of two or more, and more preferably has at least one type selected from the group consisting of an isocyanate group and an epoxy group, in one molecule.

Examples of crosslinking agents having two or more (meth)acryloyl groups in one molecule in the ultraviolet-curable adhesive composition of present invention 2 include polyfunctional urethane (meth)acrylates, polyfunctional (meth)acrylic acid ester compounds, polyfunctional epoxy (meth)acrylates, etc.

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 serve as raw materials for the above-mentioned polyfunctional urethane (meth)acrylates 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, 1,6,11-undecane triisocyanate, etc.

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 the suitable 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 above-mentioned polyfunctional epoxy (meth)acrylates 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.

Examples of crosslinking agents having the above-mentioned isocyanate groups include polyisocyanates, polymeric MDI, blocked isocyanates, etc.

Examples of crosslinking agents having the above-mentioned epoxy groups include N,N,N',N'-tetraglycidyl-m-xylylenediamine, etc.

In the ultraviolet-curable pressure-sensitive adhesive composition of the present invention 2, the preferred lower limit of the content of the crosslinking agent relative to 100 parts by mass of the monofunctional radical polymerizable monomer is 0.5 parts by mass. When the content of the crosslinking agent in the ultraviolet-curable pressure-sensitive adhesive composition of the present invention 2 is 0.5 parts by mass or more, the obtained ultraviolet-curable pressure-sensitive adhesive composition has better retention performance after curing. The more preferred lower limit of the content of the crosslinking agent is 1.0 parts by mass.
From the viewpoint of adhesive strength, the upper limit of the content of the crosslinking agent in the ultraviolet-curable pressure-sensitive adhesive composition of invention 2 is preferably 10 parts by mass, and more preferably 5.0 parts by mass.
In the ultraviolet-curable pressure-sensitive adhesive composition of the present invention 1, the preferred lower limit of the content of the crosslinking agent relative to 100 parts by mass of the radical polymerizable monomer is 0.5 parts by mass. When the content of the crosslinking agent in the ultraviolet-curable pressure-sensitive adhesive composition of the present invention 1 is 0.5 parts by mass or more, the resulting ultraviolet-curable pressure-sensitive adhesive composition has better adhesion and retention performance after curing. The more preferred lower limit of the content of the crosslinking agent in the ultraviolet-curable pressure-sensitive adhesive composition of the present invention 1 is 1.0 parts by mass.
From the viewpoints of printability and impact resistance of the cured product, the upper limit of the content of the crosslinking agent in the ultraviolet-curable pressure-sensitive adhesive composition of invention 1 is preferably 10 parts by mass, and more preferably 5.0 parts by mass.

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.

Examples of the rosin component include pimaric acid-type resin acids such as abietic acid and its derivatives, such 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, or 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 obtained 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 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.

In the ultraviolet-curable pressure-sensitive adhesive composition of the first invention, the preferred lower limit of the content of the defoaming agent relative to 100 parts by mass of the radical polymerizable monomer is 0.1 parts by mass, and the preferred upper limit is 5 parts by mass. When the content of the defoaming agent in the ultraviolet-curable pressure-sensitive adhesive composition of the first invention is within this range, the resulting ultraviolet-curable pressure-sensitive adhesive composition has better printability. The more preferred lower limit of the content of the defoaming agent 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 3 parts by mass.
In the ultraviolet-curable pressure-sensitive adhesive composition of the second invention, the preferred lower limit of the content of the defoaming agent relative to 100 parts by mass of the monofunctional radical polymerizable monomer is 0.1 parts by mass, and the preferred upper limit is 5 parts by mass. When the content of the defoaming agent in the ultraviolet-curable pressure-sensitive adhesive composition of the second invention is within this range, the resulting ultraviolet-curable pressure-sensitive adhesive composition has better printability. The more preferred lower limit of the content of the defoaming agent in the ultraviolet-curable pressure-sensitive adhesive composition of the second invention is 0.5 parts by mass, and the more preferred upper limit is 3 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, triethylene glycol di-n-heptanoate (3G7), etc. In addition, examples of the organic acid esters include tetraethylene glycol di-n-heptanoate (4G7), tetraethylene glycol di-2-ethylhexanoate, dibutyl sebacate, dioctyl azelate, dibutyl carbitol adipate, ethylene glycol di-2-ethylbutyrate, 1,3-propylene glycol di-2-ethylbutyrate, etc. Further examples include 1,4-butylene glycol di-2-ethylbutyrate, diethylene glycol di-2-ethylbutyrate, diethylene glycol di-2-ethylhexanoate, dipropylene glycol di-2-ethylbutyrate, etc. Further 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 phosphoric acid ester and an adipic acid ester, a mixed type adipic acid ester prepared from an alkyl alcohol having 4 to 9 carbon atoms and a cyclic alcohol having 4 to 9 carbon atoms, etc.

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 further contain various known additives, such as a silane coupling agent, a sensitizer, a heat curing agent, a cure retarder, an antioxidant, a storage stabilizer, a dispersant, an ultraviolet absorber, a radical polymerization inhibitor, a light stabilizer, a heat stabilizer, a dehydrating agent, a colorant, an antibacterial/antifungal agent, a flame retardant, a leveling agent, a wetting/dispersing agent, an anti-settling agent, an anti-sagging agent, an emulsifier, an anti-fogging agent, a lubricant, an antifouling agent, an antistatic agent, and a conductive agent, within a range that does not impair 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.

Examples of the method for preparing the ultraviolet-curable pressure-sensitive adhesive composition of the first invention include a method in which the radical polymerizable monomer, the photopolymerization initiator, the thickener, the amine compound, and additives added as necessary are mixed using a mixer. Examples of the mixer include a homodisper, a homomixer, a universal mixer, a planetary mixer, a kneader, and a three-roll mixer.
Examples of the method for preparing the ultraviolet-curable pressure-sensitive adhesive composition of the second invention include a method in which the monofunctional radical polymerizable monomer, the photopolymerization initiator, the crosslinking agent, the amine compound, and additives added as necessary are mixed using a mixer. Examples of the mixer include a homodisper, a homomixer, a universal mixer, a planetary mixer, a kneader, and a three-roll mixer.

The ultraviolet-curable pressure-sensitive adhesive composition of the present invention 2 is obtained by applying the ultraviolet-curable pressure-sensitive adhesive composition to a substrate, and irradiating the coated surface with ultraviolet light having a wavelength of 365 nm and an illuminance of 500 mW/cm ² at an irradiation dose of 3000 mJ/cm ² under an atmospheric environment, and the lower limit of the reaction rate of the cured product having a thickness of 50 μm is 90%. The ultraviolet-curable pressure-sensitive adhesive composition of the present invention 1 is obtained by applying the ultraviolet-curable pressure-sensitive adhesive composition to a substrate, and irradiating the coated surface with ultraviolet light having a wavelength of 365 nm and an illuminance of 500 mW/cm ² at an irradiation dose of 3000 mJ/cm ² under an atmospheric environment, and the lower limit of the reaction rate of the cured product having a thickness of 50 μm is 90%.
As the substrate, a PET film with a release treatment on the surface (release PET film) is preferably used. The above conditions are that after the ultraviolet-curable pressure-sensitive adhesive composition is coated on the substrate, ultraviolet light is irradiated in the presence of oxygen without covering the coated surface with a separator. Therefore, the reaction rate of the cured product reflects the ultraviolet light reactivity in the presence of oxygen.
Since the reaction rate of the cured product is 90% or more, it can be said that the ultraviolet reactivity in the presence of oxygen is 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 bonded to an adherend.
The lower limit of the reaction rate of the cured product in the ultraviolet-curable pressure-sensitive adhesive composition of the present invention 2 is preferably 92%, more preferably 94%. The lower limit of the reaction rate of the cured product in the ultraviolet-curable pressure-sensitive adhesive composition of the present invention 1 is more preferably 91%, still more preferably 93%.
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, the ultraviolet-curable pressure-sensitive adhesive composition is first coated on a release PET film as a substrate, and then, without sealing the coated surface, the coated surface is simultaneously irradiated with ultraviolet light having a wavelength of 365 nm and an illuminance of 500 mW/ ^cm2 at an irradiation dose of 3000 mJ/ ^cm2 using an ultraviolet irradiation device in an atmospheric environment to cure the ultraviolet-curable pressure-sensitive adhesive composition and obtain a cured product having a thickness of 50 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)×100

In the ultraviolet-curable pressure-sensitive adhesive composition of the second invention, the upper limit of the temperature at which the loss tangent is maximized in a temperature range of 50° C. or less (hereinafter also referred to as the "glass transition temperature of the cured product") in a viscoelasticity chart obtained by performing dynamic viscoelasticity measurement on the cured product under the conditions of a shear method, a measurement temperature of -70° C. to 200° C., and a frequency of 1 Hz is 20° C. Since the glass transition temperature of the cured product is 20° C. or less, the ultraviolet-curable pressure-sensitive adhesive composition of the second invention has excellent adhesion and retention performance after curing. The upper limit of the glass transition temperature of the cured product in the ultraviolet-curable pressure-sensitive adhesive composition of the second invention is preferably 15° C., more preferably 10° C.
In addition, the ultraviolet-curable pressure-sensitive adhesive composition of the present invention 1 is coated on a substrate, and the coated surface is not sealed, and in an atmospheric environment, ultraviolet light having a wavelength of 365 nm and an illuminance of 500 mW/cm ² is irradiated at an irradiation dose of 3000 mJ/cm ² to obtain a cured product having a thickness of 50 μm. The glass transition temperature of the cured product is preferably −40° C. at the lower limit and 20° C. at the upper limit. When the glass transition temperature of the cured product is in this range, the ultraviolet-curable pressure-sensitive adhesive composition of the present invention 1 has better adhesion and retention performance after curing. The glass transition temperature of the cured product in the ultraviolet-curable pressure-sensitive adhesive composition of the present invention 1 is more preferably −20° C. at the lower limit and 15° C. at the upper limit.

Specifically, the glass transition temperature of the cured product can be measured, for example, according to the following procedure.
That is, first, for a cured product obtained in the same manner as in the reaction rate measurement, dynamic viscoelasticity measurement is performed under the following conditions using a dynamic viscoelasticity measuring device to obtain a viscoelasticity chart. In the obtained viscoelasticity chart, the tan δ peak temperature in a temperature range of 50° C. or less can be determined as the glass transition temperature. As the dynamic viscoelasticity measuring device, for example, DVA-200 (manufactured by IT Measurement & Control Co., Ltd.) can be used.
<Conditions>
Shear method Measurement temperature: -70℃ to 200℃
Heating rate: 1° C./min Distortion: 0.1%
Frequency: 1Hz

In the ultraviolet-curable pressure-sensitive adhesive composition of the present invention 2, the lower limit of the gel fraction of the cured product is 20% by mass, and the upper limit is 80% by mass. When the gel fraction of the cured product is within the above range, the ultraviolet-curable pressure-sensitive adhesive composition of the present invention 2 has excellent adhesion and retention performance after curing. In the ultraviolet-curable pressure-sensitive adhesive composition of the present invention 2, the lower limit of the gel fraction of the cured product is preferably 30% by mass, more preferably 40% by mass, and the upper limit is preferably 75% by mass, more preferably 70% by mass.
The ultraviolet-curable adhesive composition of the present invention 1 is coated on a substrate, and the coated surface is not sealed, and the cured product having a thickness of 50 μm is obtained by irradiating the substrate with ultraviolet light having a wavelength of 365 nm and an illuminance of 500 mW/cm ² at an irradiation dose of 3000 mJ/cm ² under an atmospheric environment. The gel fraction of the cured product is preferably 20% by mass at the lower limit and 80% by mass at the upper limit. When the gel fraction of the cured product is within the above range, the ultraviolet-curable adhesive composition of the present invention 1 has better adhesion and retention performance after curing. The more preferred lower limit of the gel fraction of the cured product in the ultraviolet-curable adhesive composition of the present invention 1 is 30% by mass, and the more preferred upper limit is 70% by mass.

Specifically, the gel fraction of the cured product can be measured, for example, according to the following procedure.
That is, first, 0.15 g of the cured product obtained in the same manner as in the reaction rate measurement above is weighed into a glass bottle, and then immersed in 30 g of tetrahydrofuran and shaken and immersed for 36 hours at 23° C. Next, the cured product is removed through a 200 mesh filter and dried by heating at 110° C. for 1 hour. The mass of the cured product is then measured, and the gel fraction can be calculated by the following formula.
Gel fraction (mass%)=( _W2 / _W1 )×100
_W1 : Mass of the cured product before immersion in tetrahydrofuran at 23°C. _W2 : Mass of the cured product after immersion in tetrahydrofuran at 23°C, removal and drying

The ultraviolet-curable adhesive composition of the present invention 1 is used for printing. The ultraviolet-curable adhesive composition of the present invention 2 is preferably used 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. In addition, since lamination without gaps is possible by printing, the composition has excellent waterproof and dustproof properties.

Examples of the method for printing the ultraviolet-curable pressure-sensitive adhesive composition of the first invention include screen printing, stencil printing, reverse offset printing, etc. Among these, screen printing is preferably used.
Examples of the method for applying the ultraviolet-curable pressure-sensitive adhesive composition of the second invention include gravure printing, flexographic printing, slot die coating, knife coating, inkjet printing, spray coating, spin coating, screen printing, stencil printing, reverse offset printing, etc. Among these, screen printing, stencil printing, and reverse offset printing are preferably used, and screen printing is more preferably used.

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.

The 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 screen printing, stencil printing, or reverse offset printing, and the ultraviolet-curable adhesive composition is applied entirely or partially to the first adherend, is also one aspect of the present invention.

Examples of the material of the first adherend and the second adherend include metals such as stainless steel and aluminum, resins, etc. In particular, the first adherend and the second adherend are preferably substrates that have been subjected to a release treatment, and more preferably substrates that have been subjected to a release treatment and an antistatic treatment.

From the viewpoint of suppressing waste generation and reducing the environmental burden, in the manufacturing method of the laminate of the present invention, it is preferable that the ultraviolet-curable adhesive composition of the present invention is partially coated on the first adherend.

The thickness of the adhesive layer is preferably 30 μm or more. By having a thickness of the adhesive layer of 30 μm or more, sufficient adhesion can be obtained. The thickness of the adhesive layer is more preferably 50 μm or more.
In addition, 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 ultraviolet curability in the presence of oxygen, waterproofness and dust resistance, and shape stability after printing, as well as an ultraviolet-curable pressure-sensitive adhesive composition that has excellent curability when irradiated with high-intensity ultraviolet light in the presence of oxygen, and excellent adhesion and retention performance after curing. Furthermore, 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 described in more detail below with reference to examples, but the present invention is not limited to these examples.

(Examples 1-1 to 1-7 , 1-11 to 1-14, 1-17 to 1-35, Reference Examples 1-8 to 1-10 , 1-15, 1-16, Comparative Examples 1-1 to 1-4)
According to the compounding ratios shown in Tables 1 to 4, each material was mixed in a planetary mixer (Thinky Corporation, "Awatori Rentaro") to obtain each of the ultraviolet-curable pressure-sensitive adhesive compositions of Examples 1-1 to 1-7 , 1-11 to 1-14, 1-17 to 1-35, Reference Examples 1-8 to 1-10 , 1-15, and 1-16, and Comparative Examples 1-1 to 1-4.
Details of the materials indicated by abbreviations in Tables 1 to 4 are as follows.
(Radical polymerizable monomer)
CHMI: N-cyclohexylmaleimide (manufactured by Nippon Shokubai Co., Ltd., no structure with hydrogen bonded to a heteroatom)
CHCMA: N-(4-carboxycyclohexylmethyl)maleimide (Seiko Chemical Industry Co., Ltd., has a structure in which hydrogen is bonded to a heteroatom)
HPM: 4-hydroxyphenylmaleimide (Seiko Chemical Industry Co., Ltd., has a structure in which hydrogen is bonded to a heteroatom)
NVC: N-vinyl-ε-caprolactam (manufactured by Tokyo Chemical Industry Co., Ltd.)
M-140: N-acryloyloxyethylhexahydrophthalimide (manufactured by Toagosei Co., Ltd.)
NOAA: n-octyl acrylate (Osaka Organic Chemical Industry Co., Ltd.)
CBA: Ethyl carbitol acrylate (manufactured by Osaka Organic Chemical Industry Co., Ltd., "Viscoat #190", containing ether bonds)
4-HBA: 4-hydroxybutyl acrylate (manufactured by Mitsubishi Chemical Corporation)
Viscoat #200: Cyclic trimethylolpropane formal acrylate (manufactured by Osaka Organic Chemical Industry Co., Ltd.)
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 #216: acrylic acid-2-butylcarbamoyloxyethyl ester (Osaka Organic Chemical Industry, Ltd., containing amide bond)
UA-160TM: Polyether-based multifunctional urethane acrylate (manufactured by Shin-Nakamura Chemical 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 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)
(Amine Compound)
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)
(Tackifier)
KE-359: Rosin resin (manufactured by Arakawa Chemical Industries, Ltd.)
D-6011: Rosin resin (manufactured by Arakawa Chemical Industries, Ltd.)
(Thickener)
LA2140: Acrylic block copolymer (Kuraray, thermoplastic resin)
FBP-009: Styrene-acrylic block copolymer (manufactured by Fujikura Chemical Industries, thermoplastic resin)
Acrylic polymer A: Synthesized by the method described below (thermoplastic resin)
Disparlon 3500: Polyether phosphate ester (manufactured by Kusumoto Chemicals, polymeric thixotropy regulator)
Aerosil R805: Fumed silica (manufactured by Nippon Aerosil Co., Ltd., solid thickener)
(Crosslinking Agent)
・Coronate L: Toluene diisocyanate (manufactured by Tosoh Corporation)

(Acrylic Polymer A)
In a 2L separable flask equipped with a thermometer, a stirrer, a nitrogen inlet tube, and a cooling tube, 75 parts by mass of butyl acrylate, 25 parts by mass of 2-ethylhexyl acrylate, 3 parts by mass of acrylic acid, 0.1 parts by mass of 4-hydroxybutyl acrylate, and 300 parts by mass of ethyl acetate as a polymerization solvent were added. Next, nitrogen gas was blown in for 30 minutes to replace the atmosphere in 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 ethyl acetate to obtain a solution with a solid content of 20% by mass. The obtained solution was then applied onto a release 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 1 hour to obtain an acrylic polymer A.

(Comparative Example 1-5)
100 parts by mass of the obtained acrylic polymer A was dissolved in 50 parts by mass of toluene. 20 parts by mass of a rosin-based resin (manufactured by Arakawa Chemical Industries, Ltd., "KE-359") as a tackifier was added to the obtained solution, and the mixture was stirred to dissolve. Thereafter, 2 parts by mass of toluene diisocyanate (manufactured by Tosoh Corporation, "Coronate L") as a crosslinking agent was added and stirred to obtain an ultraviolet-curable pressure-sensitive adhesive composition.

(Viscosity and thixotropic index at 25° C.)
The viscosity of the obtained ultraviolet-curable pressure-sensitive adhesive composition was measured at 25°C and 10 rpm using an E-type viscometer (manufactured by Toki Sangyo Co., Ltd., "TV-22") with an appropriate cone plate according to the composition. The viscosity of the obtained ultraviolet-curable pressure-sensitive adhesive composition was also measured at 25°C and 1 rpm, and the viscosity measured at 1 rpm was divided by the viscosity measured at 10 rpm to obtain the thixotropic index (Ti value). The results are shown in Tables 1 to 4.

(Reaction rate of cured product)
The obtained ultraviolet-curable pressure-sensitive adhesive composition was applied onto a release PET film (manufactured by Nippa Corporation, "1-E", thickness 50 μm) using an applicator. Next, without sealing the upper surface of the coating, the film was irradiated with ultraviolet light having a wavelength of 365 nm and an illuminance of 500 mW/cm ² in an atmospheric environment using a batch-type UV LED curing device (manufactured by CSS Corporation, "UV-LED PROCESSOR LSS-61") so that the irradiation amount was 3000 mJ/cm ² , thereby obtaining a cured product having a thickness of 50 μm. Thereafter, the atmospheric surface was sealed with a release PET film (manufactured by Nippa Corporation, "1-C", thickness 38 μm) to obtain a laminate.
After that, both release films were peeled off from the laminate, and about 0.3 g of the cured product of the ultraviolet-curable adhesive composition was placed on an aluminum pan with a diameter of 10 cm and a height of 1 cm, 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. Then, the sample was 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 after drying and the dried sample were weighed, and the reaction rate of the cured product was calculated using the following formula. The results are shown in Tables 1 to 4.
Reaction rate (%)=(total mass of aluminum pan and sample after drying−mass of aluminum pan before drying)/(mass of sample before swelling)×100

(Gel fraction of cured product)
Both release films were peeled off from the laminate obtained in the same manner as in "(Reaction rate of cured product)" above, and 0.15 g of the cured product of the ultraviolet-curable pressure-sensitive adhesive composition was weighed into a glass bottle, which was then immersed in 30 g of tetrahydrofuran and immersed with shaking at 23°C for 36 hours. The cured product was then removed through a 200-mesh filter and dried by heating at 110°C for 1 hour. The mass of the cured product was then measured, and the gel fraction was calculated using the following formula. The results are shown in Tables 1 to 4.
Gel fraction (mass%)=( _W2 / _W1 )×100
_W1 : Mass of the cured product before immersion in tetrahydrofuran at 23°C. _W2 : Mass of the cured product after immersion in tetrahydrofuran at 23°C, removal and drying

(Glass transition temperature of the cured product)
Both release films were peeled off from the laminate obtained in the same manner as in "(Reaction rate of cured product)" above, and the cured product of the ultraviolet-curable pressure-sensitive adhesive composition was laminated to a thickness of 1 mm, which was then attached to a jig and subjected to dynamic viscoelasticity measurement under the following conditions using a dynamic viscoelasticity measuring device (manufactured by IT Measurement & Control Co., Ltd., "DVA-200") to obtain a viscoelasticity chart. The tan δ peak temperature in the obtained viscoelasticity chart was determined as the glass transition temperature. The results are shown in Tables 1 to 4.
<Conditions>
Shear method Measurement temperature: -70 to 200°C
Heating rate: 1° C./min Distortion: 0.1%
Frequency: 1Hz

<Evaluation>
The ultraviolet-curable pressure-sensitive adhesive compositions obtained in Examples 1-1 to 1-7 , 1-11 to 1-14, 1-17 to 1-35, Reference Examples 1-8 to 1-10 , 1-15, and 1-16, and Comparative Examples 1-1 to 1-5 were evaluated as follows. The results are shown in Tables 1 to 4.

(180° peel adhesive strength)
Each of the obtained ultraviolet-curable pressure-sensitive adhesive compositions was applied to the inner treated surface of an easily adhesive polyester film (manufactured by Toyobo Co., Ltd., "Cosmoshine A4100") with an applicator. Thereafter, without sealing the coated surface, the film was irradiated with ultraviolet light having a wavelength of 365 nm and an illuminance of 500 mW/ ^cm2 in an atmospheric environment using a batch-type UV LED curing device (manufactured by CSS, "UV-LED PROCESSOR LSS-61") so that the irradiation amount was 3000 mJ/ ^cm2 , thereby obtaining a cured product having a thickness of 50 μm. The illuminance and integrated light amount were measured using an ultraviolet irradiation meter UVR-T2 and a light receiving unit UD-T36T2 (manufactured by TOPCON Corporation). Next, the air surface was sealed with a release PET film (manufactured by Nippa, "1-C", thickness 38 μm), and cut to a width of 25 mm and a length of 200 mm (adhering surface 20 mm × 125 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 pressed by moving it back and forth with a 2 kg roller to obtain a test piece. The test piece was stored in a 25 ° C. environment for 24 hours, and the 180 ° peel 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, "Tensilon RTI-1310").

(Printability (shape stability after printing))
(Screen printing)
To 100 parts by mass of the obtained ultraviolet-curable adhesive composition, 1 part by mass of KS-66 (manufactured by Shin-Etsu Chemical Co., Ltd.) was added as an antifoaming agent to obtain a screen printable composition. The ultraviolet-curable adhesive composition obtained in Example 1-34 was used as a screen printable composition without adding an antifoaming agent. The obtained screen printable composition was screen-printed by applying a pattern to the inner treated surface of an easy-adhesive polyester film (manufactured by Toyobo Co., Ltd., "Cosmoshine A4100") using a screen printer (manufactured by SERIA Co., Ltd., "SSA-PC560E"). A pattern-treated 80-mesh printing plate was used as the screen printing plate. The shape of the opening of the screen printing plate was a square with a line width of 1.5 mm, and the dimensions inside the line were a square with one side of 21.5 mm.
One minute after printing, the upper surface of the coating was not sealed and was irradiated with ultraviolet light having a wavelength of 365 nm and an illuminance of 500 mW/ ^cm2 at an exposure dose of 3000 mJ/ ^cm2 in an atmospheric environment using a batch-type UV LED curing device (manufactured by CSS, "UV-LED PROCESSOR LSS-61") to obtain a cured product having a thickness of 50 μm.
The line widths of the four sides of the obtained cured product were measured using a microscope (manufactured by KEYENCE Corporation) and the average value was calculated. The rate of change of the average measured line width relative to the design line width (1.5 mm) was calculated using the following formula.
Line width change rate (%)=(1-average line width/design line width)×100
The printability (shape stability after printing) was evaluated according to the following criteria.
◎: When the absolute value of the line width change rate is less than 5%. ◯: When the absolute value of the line width change rate is 5% or more and less than 15%. △: When the absolute value of the line width change rate is 15% or more. ×: When mesh transmission is impossible or when there is a hole that divides the line.

(Water resistance test)
The center of a SUS304 plate having a square shape with sides of 40 mm was laser-cut to a square shape with sides of 20 mm, and the surface of the resulting frame-shaped SUS plate was mirror-polished. The polished surface was then washed with ethanol and dried to prepare a SUS adherend.
The cured product prepared in the same manner as in the evaluation of "(printability)" above was bonded to the polished surface of the SUS adherend, and then a PET film having a thickness of 0.05 mm was bonded to the surface of the cured product opposite the SUS adherend to obtain a laminate. The obtained laminate was pressed at 45 N using a universal testing machine (manufactured by A&D Co., Ltd., "Tensilon RTI-1310") and allowed to stand for 48 hours in a 25°C environment. Then, a cylinder with an inner diameter of 30 mm and a height of 20 mm with packing on both sides was placed on the opposite side of the surface of the SUS adherend to which the cured product was attached. The laminate with the cylinder placed was sandwiched between an acrylic plate A with an air inlet and an acrylic plate B with a square hole with a side of 28 mm, and fixed with screws. At this time, the PET film with the cured product attached was made to fit inside the hole of the acrylic plate B. 10 mL of water was poured from the air inlet of the acrylic plate A, and an air inlet tube was connected. Air was introduced by applying pressure at a rate of 7 kPa/min, and the maximum pressure (breaking pressure) immediately before the cured product peeled off and water began to leak was measured.

(Evaluation of printability (shape stability after printing) when changing printing substrate)
For the ultraviolet-curable pressure-sensitive adhesive compositions obtained in Examples 1-20, 1-26, 1-29 to 1-33 and Comparative Examples 1-2 and 1-5, screen printing similar to the evaluation of "(Printability (shape stability after printing))" above and stencil printing described below were performed on each printing substrate shown in Table 5. For screen printing, printability (shape stability after printing) was evaluated according to the same evaluation criteria as for the evaluation of "(Printability (shape stability after printing))" above, and for stencil printing, printability (shape stability after printing) was evaluated according to the following evaluation criteria. The results are shown in Table 5.
The details of each printing substrate listed in Table 5 are as follows.
PET film: Highly adhesive polyester film (Toyobo Co., Ltd., "Cosmoshine A4100")
Release PET film: PET film with one side release treatment (manufactured by Nippa Corporation, "1-E", thickness 50 μm)
・SUS-BA board: SUS304-BA board

(Stencil printing)
The obtained ultraviolet-curable pressure-sensitive adhesive composition was stencil-printed onto each printing substrate shown in Table 5 using a screen printer (Microtec Corporation, "LABTOP-38"). The stencil plate was a 55 μm-thick SUS plate, the shape of the opening was a square with a line width of 1.5 mm, and the dimensions inside the line were a square with one side of 21.5 mm. In addition, a 0.3 mm-wide bridge was left by half etching to support the SUS plate part inside the pattern.
One minute after printing, the upper surface of the coating was not sealed and was irradiated with ultraviolet light having a wavelength of 365 nm and an illuminance of 500 mW/ ^cm2 at an exposure dose of 3000 mJ/ ^cm2 in an atmospheric environment using a batch-type UV LED curing device (manufactured by CSS, "UV-LED PROCESSOR LSS-61") to obtain a cured product having a thickness of 50 μm.
The line widths of the four sides of the obtained cured product were measured using a microscope (manufactured by KEYENCE Corporation) and the average value was calculated. The rate of change of the average measured line width relative to the design line width (1.5 mm) was calculated using the following formula.
Line width change rate=(1-average line width/design line width)×100
The printability (shape stability after printing) was evaluated according to the following criteria.
◎: When the absolute value of the line width change rate was less than 5%. ◯: When the absolute value of the line width change rate was 5% or more and less than 15%. △: When the absolute value of the line width change rate was 15% or more. ×: When it was impossible to discharge liquid from the opening.

( Reference Examples 2-1 to 2-28, Comparative Examples 2-1 to 2-4)
According to the compounding ratios shown in Tables 6 to 8, each material was mixed with a planetary mixer (Thinky Corporation, "Awatori Rentaro") to obtain each of the ultraviolet-curable pressure-sensitive adhesive compositions of Reference Examples 2-1 to 2-28 and Comparative Examples 2-1 to 2-4.
Details of the materials indicated by abbreviations in the table are as follows.
(Monofunctional radically polymerizable monomer)
CHMI: N-cyclohexylmaleimide (manufactured by Nippon Shokubai Co., Ltd., no structure with hydrogen bonded to a heteroatom)
CHCMA: N-(4-carboxycyclohexylmethyl)maleimide (Seiko Chemical Industry Co., Ltd., has a structure in which hydrogen is bonded to a heteroatom)
HPM: 4-hydroxyphenylmaleimide (Seiko Chemical Industry Co., Ltd., has a structure in which hydrogen is bonded to a heteroatom)
NVC: N-vinyl-ε-caprolactam (manufactured by Tokyo Chemical Industry Co., Ltd.)
M-140: N-acryloyloxyethylhexahydrophthalimide (manufactured by Toagosei Co., Ltd.)
NOAA: n-octyl acrylate (Osaka Organic Chemical Industry Co., Ltd.)
CBA: Ethyl carbitol acrylate (manufactured by Osaka Organic Chemical Industry Co., Ltd., "Viscoat #190", containing ether bonds)
4-HBA: 4-hydroxybutyl acrylate (manufactured by Mitsubishi Chemical Corporation)
Viscoat #200: Cyclic trimethylolpropane formal acrylate (manufactured by Osaka Organic Chemical Industry Co., Ltd.)
Viscoat #216: acrylic acid-2-butylcarbamoyloxyethyl ester (Osaka Organic Chemical Industry, Ltd., containing amide bond)
IBOA: Isobornyl acrylate (manufactured by Nippon Shokubai Co., Ltd.)
M-5300: ω-carboxy-polycaprolactone monoacrylate (manufactured by Toagosei 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 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)
(Crosslinking Agent)
UA-160TM: Polyether-based multifunctional urethane acrylate (manufactured by Shin-Nakamura Chemical Co., Ltd.)
Millionate MR200: Polymeric MDI (manufactured by Tosoh Corporation)
TETRAD-X: N,N,N',N'-tetraglycidyl-m-xylylenediamine (manufactured by Mitsubishi Chemical Corporation)
(Amine Compound)
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)
(Tackifier)
KE-359: Rosin resin (manufactured by Arakawa Chemical Industries, Ltd.)
D-6011: Rosin resin (manufactured by Arakawa Chemical Industries, Ltd.)
(Thickener)
LA2140: Acrylic block copolymer (Kuraray, thermoplastic resin)
FBP-009: Styrene-acrylic block copolymer (manufactured by Fujikura Chemical Industries, thermoplastic resin)
Acrylic polymer A: Synthesized by the method described below (thermoplastic resin)
Disparlon 3500: Polyether phosphate ester (manufactured by Kusumoto Chemicals, polymeric thixotropy regulator)
Aerosil R805: Fumed silica (manufactured by Nippon Aerosil Co., Ltd., solid thickener)

(Acrylic Polymer A)
In a 2L separable flask equipped with a thermometer, a stirrer, a nitrogen inlet tube, and a cooling tube, 75 parts by mass of butyl acrylate, 25 parts by mass of 2-ethylhexyl acrylate, 3 parts by mass of acrylic acid, 0.1 parts by mass of 4-hydroxybutyl acrylate, and 300 parts by mass of ethyl acetate as a polymerization solvent were added. Next, nitrogen gas was blown in for 30 minutes to replace the atmosphere in 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 ethyl acetate to obtain a solution with a solid content of 20% by mass. The obtained solution was then applied onto a release 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 1 hour to obtain an acrylic polymer A.

(Reaction rate of cured product)
The obtained ultraviolet-curable adhesive composition was applied onto a release PET film (manufactured by Nippa, "1-E", thickness 50 μm) using an applicator. Next, a batch-type UV LED curing device (manufactured by CSS, "UV-LED PROCESSOR LSS-61") was used to irradiate ultraviolet rays having a wavelength of 365 nm and an illuminance of 500 mW/cm ² so that the irradiation amount was 3000 mJ/cm ² , thereby obtaining a cured product having a thickness of 50 μm. Thereafter, the air surface was sealed with a release PET film (manufactured by Nippa, "1-C", thickness 38 μm) to obtain a laminate. For the ultraviolet-curable adhesive composition obtained in Reference Example 2-16, after obtaining the laminate, it was aged at 40 ° C. for 48 hours. For the ultraviolet-curable adhesive composition obtained in Reference Example 2-17, after obtaining the laminate, it was aged at 40 ° C. for 48 hours.
After that, both release films were peeled off from the laminate, and about 0.3 g of the cured product of the ultraviolet-curable adhesive composition was placed on an aluminum pan with a diameter of 10 cm and a height of 1 cm, 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. Then, the sample was 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 after drying and the dried sample were weighed, and the reaction rate of the cured product was calculated using the following formula. The results are shown in Tables 6 to 8.
Reaction rate (%)=(total mass of aluminum pan and sample after drying−mass of aluminum pan before drying)/(mass of sample before swelling)×100

(Gel fraction of cured product)
Both release films were peeled off from the laminate obtained in the same manner as in "(Reaction rate of cured product)" above, and 0.15 g of the cured product of the ultraviolet-curable pressure-sensitive adhesive composition was weighed into a glass bottle, which was then immersed in 30 g of tetrahydrofuran and immersed with shaking at 23°C for 36 hours. The cured product was then removed through a 200-mesh filter and heated and dried at 110°C for 1 hour. The mass of the cured product was then measured, and the gel fraction was calculated using the following formula. The results are shown in Tables 6 to 8.
Gel fraction (mass%)=( _W2 / _W1 )×100
_W1 : Mass of the cured product before immersion in tetrahydrofuran at 23°C. _W2 : Mass of the cured product after immersion in tetrahydrofuran at 23°C, removal and drying

(Glass transition temperature of the cured product)
Both release films were peeled off from the laminate obtained in the same manner as in "(Reaction rate of cured product)" above, and the cured product of the ultraviolet-curable pressure-sensitive adhesive composition was laminated to a thickness of 1 mm, which was then attached to a jig and subjected to dynamic viscoelasticity measurement under the following conditions using a dynamic viscoelasticity measuring device (manufactured by IT Measurement & Control Co., Ltd., "DVA-200") to obtain a viscoelasticity chart. In the obtained viscoelasticity chart, the tan δ peak temperature in the temperature range of 50°C or less was determined as the glass transition temperature. The results are shown in Tables 6 to 8.
<Conditions>
Shear method Measurement temperature: -70 to 200°C
Heating rate: 1° C./min Distortion: 0.1%
Frequency: 1Hz

<Evaluation>
The ultraviolet-curable pressure-sensitive adhesive compositions obtained in Reference Examples 2-1 to 2-28 and Comparative Examples 2-1 to 2-4 were evaluated as follows. The results are shown in Tables 6 to 8.

(180° peel adhesive strength)
Each of the obtained ultraviolet-curable pressure-sensitive adhesive compositions was applied to the inner treated surface of an easily adhesive polyester film (manufactured by Toyobo Co., Ltd., "Cosmoshine A4100") with an applicator. Thereafter, without sealing the coated surface, the film was irradiated with ultraviolet light having a wavelength of 365 nm and an illuminance of 500 mW/ ^cm2 in an atmospheric environment using a batch-type UV LED curing device (manufactured by CSS, "UV-LED PROCESSOR LSS-61") so that the irradiation amount was 3000 mJ/ ^cm2 , thereby obtaining a cured product having a thickness of 50 μm. The illuminance and integrated light amount were measured using an ultraviolet irradiation meter UVR-T2 and a light receiving unit UD-T36T2 (manufactured by TOPCON Corporation). Next, the air surface was sealed with a release PET film (manufactured by Nippa, "1-C", thickness 38 μm), and cut to a width of 25 mm and a length of 200 mm (adhering surface 25 mm × 125 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 pressed by moving it back and forth with a 2 kg roller to obtain a test piece. The test piece was stored in a 25 ° C. environment for 24 hours, and the 180 ° peel 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, "Tensilon RTI-1310").

(Retention performance)
The laminate obtained in the same manner as in "(Reaction rate of cured product)" above was cut to 25 mm x 25 mm, one release PET film (1-C) was peeled off, and the cured product was attached to a mirror-polished SUS substrate with a width of 25 mm, a length of 100 mm, a thickness of 2 mm, and a 5 mm hole at the long edge. Next, the other release PET film (1-E) was peeled off, and the mirror-polished surface of a similar SUS substrate was attached to the exposed cured product surface, and then the specimen was pressed at 215 N using a universal testing machine (manufactured by A&D Co., Ltd., "Tensilon RTI-1310") and allowed to stand for 48 hours in an environment of 25°C to obtain a test specimen.
The obtained test piece was hung using an S-hook, and further, a weight of 500 g was hung from the lower SUS substrate.
This was left at 25° C., and the time until the weight fell was measured, and the retention performance was evaluated according to the following criteria.
◎: The weight did not fall even after 24 hours. ○: It took 12 hours or more but less than 24 hours for the weight to fall. △: It took 1 hour or more but less than 12 hours for the weight to fall. ×: It took less than 1 hour for the weight to fall.

(Printability)
(1) Coating Method (1-1) Spin Coating ( Reference Examples 2-1 to 2-19 and Comparative Examples 2-1 to 2-4)
On a 50 mm x 50 mm aluminum substrate, 0.5 mL of each of the obtained ultraviolet-curable adhesive compositions was dropped and applied for 10 seconds at 5000 rpm using a spin coater ("MSB-150" manufactured by Mikasa Co., Ltd.) to prepare a thin layer. Next, using a batch-type UV LED curing device ("UV-LED PROCESSOR LSS-61" manufactured by CSS Co., Ltd.), ultraviolet rays with a wavelength of 365 nm and an illuminance of 500 mW/cm ² were irradiated so that the irradiation amount was 3000 mJ/cm ^2. This was repeated until the thickness of the cured product was 50 μm.
(1-2) Applicator ( Reference Examples 2-20 to 2-26, 2-28)
The obtained ultraviolet-curable pressure-sensitive adhesive composition was applied onto a release PET film (Nippa Corporation's "1-E", thickness 50 μm) with an applicator. Next, using a batch-type UV LED curing device (CSS Corporation's "UV-LED PROCESSOR LSS-61"), ultraviolet light with a wavelength of 365 nm and an illuminance of 500 mW/ ^cm2 was irradiated to an irradiation amount of 3000 mJ/ ^cm2 to obtain a cured product with a thickness of 50 μm.
(1-3) Screen printing ( Reference Example 2-27)
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 the obtained ultraviolet-curable pressure-sensitive adhesive composition to obtain a screen-printable composition. The obtained screen-printable composition was screen-printed by applying a pattern to the inner treated surface of an easily adhesive polyester film (manufactured by Toyobo Co., Ltd., "Cosmoshine A4100") using a screen printer (manufactured by SERIA Co., Ltd., "SSA-PC560E"). A pattern-treated 80-mesh printing plate was used as the screen printing plate. Next, a batch-type UV LED curing device (manufactured by CSS Co., Ltd., "UV-LED PROCESSOR LSS-61") was used to irradiate ultraviolet light with a wavelength of 365 nm and an illuminance of 500 mW/cm ² so that the irradiation amount was 3000 mJ/cm ² , thereby obtaining a cured product with a thickness of 50 μm.

(2) Evaluation of printability Each of the obtained cured products was visually inspected, and the printability was evaluated according to the following criteria.
○: A cured product with uniform thickness and surface smoothness was obtained. ×: The thickness was not uniform, and surface irregularities or cissing occurred.

According to the present invention, it is possible to provide an ultraviolet-curable pressure-sensitive adhesive composition that has excellent ultraviolet curability in the presence of oxygen, waterproofness and dust resistance, and shape stability after printing, as well as an ultraviolet-curable pressure-sensitive adhesive composition that has excellent curability when irradiated with high-intensity ultraviolet light in the presence of oxygen, and excellent adhesion and retention performance after curing. Furthermore, according to the present invention, it is possible to provide a method for producing a laminate using the ultraviolet-curable pressure-sensitive adhesive composition.

Claims (15)

An ultraviolet-curable pressure-sensitive adhesive composition for use in printing, comprising:
Contains a radical polymerizable monomer, a photopolymerization initiator, and a thickener,
The radical polymerizable monomer includes a compound having a cyclic structure containing a nitrogen atom,
the compound having a cyclic structure containing a nitrogen atom includes at least one selected from the group consisting of radical polymerizable monomers having a lactam structure and maleimide derivatives,
The radical polymerizable monomer contains 20% by mass or more of a monomer capable of serving as a hydrogen donor,
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, and is other than the radical polymerizable monomer having a lactam structure and the maleimide derivative;
The photopolymerization initiator includes a hydrogen abstraction type photopolymerization initiator ,
The ultraviolet-curable pressure-sensitive adhesive composition further contains an amine compound,
the amine compound is other than the radical polymerizable monomer, and the content of the amine compound not having a structure in which hydrogen is bonded to a heteroatom in the amine compound is 50 mass% or more;
the content of the amine compound is 0.1 parts by mass or more and 10 parts by mass or less in 100 parts by mass of the ultraviolet-curable pressure-sensitive adhesive composition excluding the photopolymerization initiator;
The ultraviolet-curable pressure-sensitive adhesive composition is characterized in that the viscosity of the ultraviolet-curable pressure-sensitive adhesive composition measured using an E-type viscometer at 25° C. and 10 rpm is 3 Pa·s or more and 100 Pa·s or less. The ultraviolet-curable pressure-sensitive adhesive composition according to claim 1, wherein the ultraviolet-curable pressure-sensitive adhesive composition is applied onto a substrate, and the applied surface is irradiated with ultraviolet light having a wavelength of 365 nm and an illuminance of 500 mW/ ^cm2 under an atmospheric environment without being sealed, so that the irradiation amount is 3000 mJ/ ^cm2 , to obtain a cured product having a thickness of 50 μm, which has a reaction rate of 90% or more. The compound having a cyclic structure containing a nitrogen atom includes the maleimide derivative.
the maleimide derivative has a content of at least 50 mass% of a maleimide derivative not having a structure in which hydrogen is bonded to a heteroatom, or a content of a maleimide derivative having a structure in which hydrogen is bonded to a heteroatom, relative to 100 mass parts of the radical polymerizable monomer, of 10 parts by mass or less;
3. The ultraviolet-curable pressure-sensitive adhesive composition according to claim 1 , wherein the content of the maleimide derivative is from 0.1 parts by mass to 20 parts by mass in 100 parts by mass of the radical polymerizable monomer. the compound having a cyclic structure containing a nitrogen atom includes the radical polymerizable monomer having a lactam structure,
3. The ultraviolet-curable pressure-sensitive adhesive composition according to claim 1 , wherein the content of the radical polymerizable monomer having a lactam structure is 10 parts by mass or more and 60 parts by mass or less in 100 parts by mass of the radical polymerizable monomer. The ultraviolet-curable adhesive composition according to claim 1 or 2, wherein the radically polymerizable monomer includes a polyfunctional (meth)acrylic monomer. The ultraviolet-curable adhesive composition according to claim 1 or 2, wherein the thickener comprises at least one selected from the group consisting of a thermoplastic resin, a polymeric thixotropy regulator, and a solid thickener. The ultraviolet-curable pressure-sensitive adhesive composition according to claim 6 , wherein the thickener contains the thermoplastic resin, and the thermoplastic resin contains a (meth)acrylic copolymer. The ultraviolet-curable pressure-sensitive adhesive composition according to claim 1 or ² , wherein the ultraviolet-curable pressure-sensitive adhesive composition is applied onto a substrate, and the applied surface is irradiated with ultraviolet light having a wavelength of 365 nm and an illuminance of 500 mW/cm2 under an atmospheric environment without being sealed, so that the exposure dose is 3000 mJ/ ^cm2 , to obtain a cured product having a thickness of 50 μm, the glass transition temperature of which is −40° C. or higher and 20° C. or lower. 3. The ultraviolet-curable pressure-sensitive adhesive composition according to claim 1 or 2, wherein the ultraviolet-curable pressure-sensitive adhesive composition is applied onto a substrate, and the coated surface is irradiated with ultraviolet light having a wavelength of 365 nm and ^an illuminance of 500 mW/cm2 under an atmospheric environment without sealing, so that the irradiation amount is 3000 mJ/ ^cm2 , to obtain a cured product having a thickness of 50 μm, the gel fraction of which is 20% by mass or more and 80% by mass or less. The ultraviolet-curable adhesive composition according to claim 1 or 2, further comprising a tackifier. The ultraviolet-curable adhesive composition according to claim 1 or 2, further comprising an antifoaming agent. The method includes a step of applying the ultraviolet-curable pressure-sensitive adhesive composition according to claim 1 or 2 onto a first adherend, and exposing the applied 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 screen printing, stencil printing, or reverse offset printing, and the ultraviolet-curable pressure-sensitive adhesive composition is applied entirely or partially onto the first adherend. The method for producing a laminate according to claim 12 , wherein the first adherend and the second adherend are release-treated substrates. The method for producing a laminate according to claim 13 , wherein the first adherend and the second adherend are base materials which have been subjected to a release treatment and an antistatic treatment. The method for producing a laminate according to claim 12 , wherein the ultraviolet-curable pressure-sensitive adhesive composition is applied partially onto the first adherend.