Energy ray crosslinkable adhesive composition, crosslinkable adhesive, and adhesive sheet, and methods for manufacturing the same.

Abstract

The present invention relates to: an energy-ray-crosslinkable adhesive agent composition containing (A) an energy-ray-crosslinkable acrylic polymer, and (B) an acrylic polymer other than component (A) that is substantially free of radically polymerizable unsaturated double bonds and has a weight-average molecular weight (Mw) of 280,000 or less; an adhesive sheet in which the energy-ray-crosslinkable adhesive agent composition is used; a crosslinked adhesive agent obtained by crosslinking the energy-ray-crosslinkable adhesive agent composition using an energy ray; a method for producing the crosslinked adhesive agent; an adhesive sheet in which the crosslinked adhesive agent is used; and a method for producing the adhesive sheet.

Description

Technical Field

[0001] The present invention relates to an energy ray crosslinkable adhesive composition, a crosslinked adhesive and an adhesive sheet, and methods for producing them.

Background Art

[0002] Adhesive sheets are used in a wide range of industrial fields, for example, for label applications for displaying various information, for fixing or temporarily fixing parts in fields such as OA equipment, home appliances, automobiles, and construction, and for masking applications. Hot melt adhesives are widely used as adhesives for adhesive sheets. Since hot melt adhesives can be applied to a base material or the like by heating and melting without using a solvent, they have the advantage of reducing the environmental load when producing adhesive sheets. As hot melt adhesives, for example, synthetic rubber-based hot melt adhesives are widely known. In recent years, with the increasing need for environmental load reduction, the development of acrylic-based hot melt adhesives and the like has also been promoted. For example, Patent Document 1 discloses a radiation-curable hot melt adhesive characterized by containing 100 parts by weight of an acrylic polymer having a radiation-reactive group, 3 to 20 parts by weight of an acrylic monomer, and 0.002 to 0.2 parts by weight of a polymerization inhibitor having a specific structure.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Patent Document 1 describes a radiation-curable hot melt adhesive which contains an acrylic monomer as an essential component to form a crosslinked structure between acrylic polymers having radiation-reactive groups and to improve the cohesive strength of the radiation-curable hot melt adhesive after irradiation. It is also disclosed that a polyfunctional acrylic monomer is preferably used as the acrylic monomer. However, when hot-melt adhesives contain monomers, oligomers, and polymers having these radically reactive unsaturated double bonds, polymerization reactions occur upon heating, causing the viscosity of the hot-melt adhesive to increase over time, leading to a decrease in coatability and gel formation. As a result, the usable time of the hot-melt adhesive, the so-called "pot life," is shortened, which is a problem. Furthermore, since hot-melt adhesives are used as the adhesive layer of adhesive sheets by methods such as coating them onto substrates by heating and melting, good coatability is also required during the coating process.

[0005] The present invention has been made in view of the above problems, and aims to provide an energy ray crosslinkable adhesive composition that can form an adhesive with a long pot life and excellent coating properties, an adhesive sheet using the energy ray crosslinkable adhesive composition and a method for manufacturing the same, a crosslinked adhesive obtained by crosslinking the energy ray crosslinkable adhesive composition with energy rays and a method for manufacturing the same, and an adhesive sheet using the crosslinked adhesive and a method for manufacturing the same. [Means for solving the problem]

[0006] The inventors of the present invention have found that the above problems can be solved by using an acrylic resin having energy ray crosslinking properties and a specific acrylic polymer, and have completed the present invention. In other words, the present invention relates to the following [1] to

[13] . [1] An energy-ray crosslinkable adhesive composition comprising (A) an acrylic polymer having energy-ray crosslinkability, and (B) an acrylic polymer other than component (A) that substantially does not contain radical-reactive unsaturated double bonds and has a weight-average molecular weight (Mw) of 280,000 or less. [2] The energy ray crosslinkable adhesive composition according to [1], wherein component (A) is an acrylic polymer having a benzophenone structure in its side chain. [3] The energy ray crosslinkable adhesive composition according to [1] or [2], wherein the content of component (B) is 50 parts by mass or less per 100 parts by mass of component (A). [4](C) An energy ray crosslinkable adhesive composition according to any one of [1] to [3], comprising a hydrogen abstraction type photoinitiator. [5](D) An energy ray crosslinkable adhesive composition according to any one of [1] to [4] above, comprising a tackifier. [6] The energy ray crosslinkable adhesive composition according to any one of [1] to [5], wherein the content of component (A) is 50 to 98% by mass of 100% by mass of the total amount of the adhesive composition. [7] An adhesive sheet having an energy ray crosslinkable adhesive composition layer on a substrate or release liner, the energy ray crosslinkable adhesive composition being one of the energy ray crosslinkable adhesive compositions described in any one of [1] to [6] above. [8] A method for producing an adhesive sheet having an energy ray crosslinkable adhesive composition layer, comprising the steps 11 and 12 described below. Step 11: A step to obtain an energy-ray crosslinkable adhesive composition by melt-kneading (A) an acrylic polymer having energy-ray crosslinkability and (B) an acrylic polymer other than component (A) that substantially does not contain radical-reactive unsaturated double bonds and whose weight-average molecular weight (Mw) is 280,000 or less. Step 12: A step of forming an energy ray crosslinkable adhesive composition layer by melt-coating the energy ray crosslinkable adhesive composition onto a substrate or release liner. [9] A crosslinking adhesive obtained by irradiating an energy ray with an energy ray from any one of the energy ray crosslinking adhesive compositions described in [1] to [6] above.

[10] A method for producing the crosslinking adhesive described in [9] above, A method for producing a crosslinking adhesive, comprising the step of irradiating the energy ray crosslinkable adhesive composition with energy rays.

[11] An adhesive sheet having an adhesive layer on a substrate or release liner, the adhesive layer being made of the crosslinking adhesive described in [9] or

[10] above.

[12] A method for manufacturing an adhesive sheet, comprising the following steps 22 and 23. Step 22: A step of forming an energy-ray crosslinkable adhesive composition layer on a substrate or release liner, comprising an energy-ray crosslinkable adhesive composition containing (A) an acrylic polymer having energy-ray crosslinkability and (B) an acrylic polymer other than component (A) that substantially does not contain radical-reactive unsaturated double bonds and has a weight-average molecular weight (Mw) of 280,000 or less. Step 23: Step of irradiating the energy ray crosslinkable adhesive composition layer with energy rays to form an adhesive layer made of crosslinkable adhesive.

[13] A method for manufacturing an adhesive sheet according to

[12] , comprising the following step 21 prior to step 22, and further comprising forming the energy ray crosslinkable adhesive composition layer in step 22 by melt-coating the energy ray crosslinkable adhesive composition obtained through the following step 21 onto the substrate or the release liner. Step 21: A step to obtain an energy-ray crosslinkable adhesive composition by melt-kneading (A) an acrylic polymer having energy-ray crosslinkability and (B) an acrylic polymer other than component (A) that substantially does not contain radical-reactive unsaturated double bonds and whose weight-average molecular weight (Mw) is 280,000 or less. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide an energy ray crosslinkable adhesive composition that can form an adhesive with a long pot life and excellent coating properties, an adhesive sheet using the energy ray crosslinkable adhesive composition and a method for manufacturing the same, a crosslinked adhesive obtained by crosslinking the energy ray crosslinkable adhesive composition with energy rays and a method for manufacturing the same, and an adhesive sheet using the crosslinked adhesive and a method for manufacturing the same. [Brief explanation of the drawing]

[0008] [Figure 1] This is a schematic cross-sectional view showing an example of the structure of the adhesive sheet of the present invention. [Figure 2] This is a schematic cross-sectional view showing another example of the structure of the adhesive sheet of the present invention. [Figure 3] This is a schematic cross-sectional view showing another example of the structure of the adhesive sheet of the present invention. [Modes for carrying out the invention]

[0009] In this specification, the lower and upper limits described in steps for a preferred numerical range (e.g., a range of content, etc.) can be combined independently. For example, from a description such as "preferably 10 to 90, more preferably 30 to 60," the "preferred lower limit (10)" and the "more preferred upper limit (60)" can be combined to arrive at "10 to 60." Similarly, the same applies to a description such as "preferably 10 or more, more preferably 30 or more, and preferably 90 or less, more preferably 60 or less."

[0010] In this specification, "energy beam" means an electromagnetic wave or charged particle beam that has an energy quantum, and examples include ultraviolet light, radiation, and electron beams. Ultraviolet light can be irradiated, for example, by using an electrodeless lamp, high-pressure mercury lamp, metal halide lamp, UV-LED, etc. as an ultraviolet light source. Electron beams can be irradiated using those generated by an electron beam accelerator, etc. Among the above, ultraviolet light is preferred as the energy beam in one aspect of the present invention. In this specification, "energy ray crosslinkability" means the property of forming a crosslinked structure by irradiating with energy rays. In this specification, "(meth)acryl" is used as a term meaning one or both of "acryl" or "methacryl". Similarly, "(meth)acrylate" is used as a term meaning one or both of "acrylate" or "methacrylate". Similarly, "(meth)acryloyl" is used as a term meaning one or both of "acryloyl" or "methacryloyl". In this specification, the "weight average molecular weight (Mw)" is a value in terms of standard polystyrene measured by gel permeation chromatography (GPC) method, specifically, a value measured based on the method described in the examples. Also, the mechanism of action described in this specification is a speculation and does not limit the mechanism by which the effects of the present invention are achieved.

[0011] [Energy ray crosslinkable adhesive composition] The energy ray crosslinkable adhesive composition which is one aspect of the present invention contains (A) an acrylic polymer having energy ray crosslinkability (hereinafter, also simply referred to as "component (A)"), and (B) an acrylic polymer other than the component (A) which substantially does not contain a radically reactive unsaturated double bond and has a weight average molecular weight (Mw) of 280,000 or less (hereinafter, also simply referred to as "component (B)"), and is an energy ray crosslinkable adhesive composition. The energy ray crosslinkable adhesive composition (hereinafter, also simply referred to as "adhesive composition") forms a crosslinked structure by being irradiated with energy rays to form a crosslinked adhesive. That is, the adhesive composition is a composition which is scheduled to be irradiated with energy rays before or after being attached to an adherend. Energy rays can be irradiated to the adhesive composition at an arbitrary time. Therefore, the adhesive composition has a high degree of freedom in its production method and use method. Specifically, since the adhesive composition does not have an intentionally formed crosslinked structure, it can be heated and melted and is suitable as a hot melt adhesive. Furthermore, since the adhesive composition does not have an intentionally formed crosslinked structure, it also has excellent shape followability. Therefore, the adhesive composition can also be suitably used for applications in which the adhesive composition is attached to an adherend having a step or the like and then a crosslinked adhesive is formed by energy ray irradiation. Next, each component contained in the adhesive composition will be described in detail.

[0012] <(A) Acrylic polymer having energy ray crosslinkability> Component (A) is not particularly limited as long as it is an acrylic polymer having energy ray crosslinkability. Component (A) may be used alone or in combination of two or more.

[0013] Examples of component (A) include acrylic polymers having an energy ray reactive group that reacts upon energy ray irradiation and contributes to the formation of a crosslinked structure. Examples of the energy ray reactive group include those that generate radicals that are excited by energy ray irradiation and trigger a crosslinking reaction. Specific examples of the energy ray reactive group include functional groups having a benzophenone structure, a benzyl structure, an o-benzoylbenzoate structure, a thioxanthone structure, a 3-ketocoumarin structure, a 2-ethylanthraquinone structure, a camphorquinone structure, etc. Among these, the (A) acrylic polymer having energy ray crosslinkability preferably has a benzophenone structure in the side chain. When component (A) has a benzophenone structure, for example, upon energy ray irradiation, the benzophenone structure extracts a hydrogen atom from the hydrocarbon group contained in the side chain of the acrylic polymer, and the radicals recombine to form a crosslinked structure. Furthermore, from the viewpoint of facilitating the formation of crosslinked structures, it is preferable that the energy-ray reactive group is introduced into the side chain of the acrylic polymer. That is, component (A) is preferably an acrylic polymer having a benzophenone structure in its side chain.

[0014] The content of energy-ray reactive groups in component (A) is preferably 0.02 to 5.0% by mass, and more preferably 0.05 to 3.0% by mass, based on the total amount of component (A) (100% by mass).

[0015] As a method for introducing the energy-ray reactive group in component (A), for example, a monomer having a functional group such as a vinyl group that can react with an acrylic monomer, and having the energy-ray reactive group, may be copolymerized with the acrylic monomer. Alternatively, for example, a compound having the energy-ray reactive group may be introduced by reacting it with the side chain of an acrylic polymer using a known method.

[0016] The aforementioned acrylic polymer is a polymer containing acrylic monomers as monomer components and is not particularly limited as long as it has energy ray crosslinking properties, but it is preferable that it contains structural units derived from alkyl (meth)acrylate. Examples of alkyl (meth)acrylates include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, sec-butyl (meth)acrylate, n-hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, n-nonyl (meth)acrylate, isononyl (meth)acrylate, n-decyl (meth)acrylate, and lauryl (meth)acrylate. Among these, alkyl (meth)acrylates with 1 to 8 carbon atoms in the alkyl group are preferred, and 2-ethylhexyl (meth)acrylate, methyl (meth)acrylate, and butyl (meth)acrylate are more preferred. Furthermore, these alkyl (meth)acrylates may be used individually or in combination of two or more types.

[0017] In component (A), the content of constituent units derived from alkyl (meth)acrylate is preferably 80 to 100% by mass, more preferably 90 to 100% by mass, even more preferably 95 to 100% by mass, and even more preferably 98 to 100% by mass, of the total constituent units (100% by mass) of component (A). In this specification, the content of monomer constituent units relative to all constituent units (100% by mass) of component (A) may also be considered as the content of the monomer in 100% by mass of the total amount of monomer blended when synthesizing component (A). Furthermore, unless otherwise specified, the total constituent units (100% by mass) of component (A) do not include, for example, the polymerization initiators, chain transfer agents, and constituent units derived from compounds having energy-ray reactive groups used in the polymerization of the polymer.

[0018] Furthermore, the constituent units derived from monomers that make up the acrylic polymer may, if necessary, include constituent units derived from monomers other than alkyl (meth)acrylate. Examples of other monomers other than alkyl (meth)acrylate that can be used in component (A) include monomers other than monomer (b1) described later in the section on component (B).

[0019] The weight-average molecular weight (Mw) of component (A) is not particularly limited as long as the effects of the present invention are achieved, but is preferably 10,000 or more, more preferably 50,000 or more, even more preferably 100,000 or more, and preferably 500,000 or less, more preferably 400,000 or less, and even more preferably 300,000 or less.

[0020] The content of component (A) in the adhesive composition may be 50 to 98% by mass, 60 to 97% by mass, or 70 to 96% by mass, based on 100% by mass of the total amount of the adhesive composition.

[0021] <(B) Acrylic polymers other than component (A) that substantially do not contain radical-reactive unsaturated double bonds and have a weight-average molecular weight (Mw) of 280,000 or less> Component (B) is an acrylic polymer other than component (A), and is not particularly limited as long as it is an acrylic resin that substantially does not contain radical-reactive unsaturated double bonds and has a weight-average molecular weight (Mw) of 280,000 or less. Component (B) may be used alone or in combination of two or more types.

[0022] The adhesive composition can have its adhesive performance improved by including component (B). Since component (B) substantially does not contain radically reactive unsaturated double bonds, when the adhesive composition is heated, the polymerization reaction of component (B) is prevented or suppressed, making it possible to suppress the increase in viscosity of the adhesive composition over time. As a result, it becomes possible to extend the pot life of the adhesive composition.

[0023] The aforementioned "radical-reactive unsaturated double bond" refers to an unsaturated double bond that can participate in radical reactions through heating or energy irradiation. This includes both unsaturated double bonds that generate an active site for a radical reaction by reacting with radicals generated from components other than component (B), such as the initiator, and unsaturated double bonds that are themselves activated by heating or energy irradiation to generate radicals and initiate the reaction.

[0024] An example of the radical-reactive unsaturated double bond is a radical-reactive carbon-carbon double bond. Examples of functional groups containing a radical-reactive carbon-carbon double bond include (meth)acryloyl groups, vinyl groups, and allyl groups.

[0025] Furthermore, the statement that component (B) "substantially does not contain radically reactive unsaturated double bonds" means, for example, that the content of constituent units derived from monomers that still have radically reactive unsaturated double bonds after polymerization is preferably 1.0% by mass or less, more preferably 0.1% by mass or less, and even more preferably 0.05% by mass or less, among the total constituent units (100% by mass) of component (B). In this specification, the content of monomer constituent units relative to all constituent units (100% by mass) of component (B) may also be considered as the content of the monomer in 100% by mass of the total amount of monomer blended when synthesizing component (B). Furthermore, unless otherwise specified, the total constituent units (100% by mass) of component (B) do not include, for example, constituent units derived from polymerization initiators and chain transfer agents used in the polymerization of the polymer.

[0026] Furthermore, if the weight-average molecular weight (Mw) of component (B) exceeds 280,000, the viscosity of the adhesive composition increases, resulting in poor coating properties. Therefore, from the viewpoint of suppressing a decrease in the coating properties of the adhesive composition, the weight-average molecular weight (Mw) of component (B) is preferably 260,000 or less, more preferably 240,000 or less, and even more preferably 220,000 or less. Also, the weight-average molecular weight (Mw) of component (B) is preferably 1,000 or more, more preferably 5,000 or more, and even more preferably 10,000 or more.

[0027] Component (B) is not particularly limited as long as it satisfies the above requirements and is a polymer containing an acrylic monomer as a monomer component, but it is preferable that it contains a structural unit derived from alkyl (meth)acrylate (b1). As for the alkyl (meth)acrylate (b1) (hereinafter also referred to as "monomer (b1)") that can be used in component (B), alkyl (meth)acrylates having 1 to 18 carbon atoms in the alkyl group are preferably used. Specifically, examples include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, sec-butyl (meth)acrylate, tert-butyl (meth)acrylate, n-pentyl (meth)acrylate, n-hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isooctyl (meth)acrylate, n-decyl (meth)acrylate, n-dodecyl (meth)acrylate, n-tridecyl (meth)acrylate, myristyl (meth)acrylate, palmityl (meth)acrylate, stearyl (meth)acrylate, etc. Monomer (b1) may be used alone or in combination of two or more types.

[0028] Among the monomers (b1) mentioned above, alkyl (meth)acrylates with 1 to 8 carbon atoms in the alkyl group are more preferred.

[0029] In component (B), the content of constituent units derived from monomer (b1) is preferably 60 to 100% by mass, more preferably 80 to 100% by mass, even more preferably 90 to 100% by mass, and even more preferably 95 to 100% by mass, of the total constituent units (100% by mass) of component (B), from the viewpoint of achieving better compatibility with component (A).

[0030] Furthermore, component (B) may be an acrylic copolymer that contains, in addition to the constituent units derived from monomer (b1), constituent units derived from monomers other than monomer (b1). Examples of monomers other than monomer (b1) include, for example, functional group-containing monomers that do not have two or more radical-reactive unsaturated double bonds in the molecule; (meth)acrylates having a cyclic structure that does not have two or more radical-reactive unsaturated double bonds in the molecule; vinyl acetate; styrene; and the like. Other monomers may be used individually or in combination of two or more.

[0031] Examples of functional group-containing monomers that do not have two or more radical-reactive unsaturated double bonds in the molecule include monomers having functional groups such as carboxyl groups, hydroxyl groups, epoxy groups, amino groups, cyano groups, nitrogen atom-containing ring groups, and alkoxysilyl groups. Examples of monomers containing a carboxyl group include ethylenically unsaturated carboxylic acids that have only one radical-reactive unsaturated double bond, such as (meth)acrylic acid, crotonic acid, maleic acid, fumaric acid, itaconic acid, and citraconic acid. Examples of monomers containing a hydroxyl group include hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate; and unsaturated alcohols having only one radical-reactive unsaturated double bond, such as vinyl alcohol and allyl alcohol.

[0032] Examples of (meth)acrylates having a cyclic structure that does not contain two or more radical-reactive unsaturated double bonds in the molecule include cyclohexyl (meth)acrylate, benzyl (meth)acrylate, isobornyl (meth)acrylate, and the like.

[0033] If component (B) contains monomer-derived structural units other than monomer (b1), the content of monomer-derived structural units other than monomer (b1) in component (B) is preferably 0.5 to 40% by mass, more preferably 1 to 20% by mass, even more preferably 2 to 10% by mass, and even more preferably 3 to 5% by mass, relative to the total structural units (100% by mass) of component (B).

[0034] If component (B) contains constituent units derived from monomers other than monomer (b1) in addition to constituent units derived from monomer (b1), the total content of constituent units derived from monomer (b1) and constituent units derived from monomers other than monomer (b1) in component (B) may be 100% by mass relative to the total constituent units (100% by mass) of component (B).

[0035] Furthermore, if component (B) is an acrylic copolymer containing constituent units derived from multiple monomers (b1); or an acrylic copolymer containing constituent units derived from one or more monomers (b1) and constituent units derived from one or more monomers other than monomers (b1), the form of copolymerization is not particularly limited and may be a block copolymer or a random copolymer.

[0036] The content of component (B) in the adhesive composition is preferably 50 parts by mass or less per 100 parts by mass of component (A), and more preferably 45 parts by mass or less, and even more preferably 40 parts by mass or less, from the viewpoint of suppressing a reduction in the cohesive force of the adhesive obtained from the adhesive composition and suppressing contamination of the adherend to which the adhesive is applied. Furthermore, the lower limit of the content of component (B) in the adhesive composition is preferably 3 parts by mass or more, more preferably 5 parts by mass or more, and even more preferably 10 parts by mass or more, from the viewpoint of adhesive performance.

[0037] Furthermore, from the viewpoint of making the effects of the present invention easier to achieve, the total content of component (A) and component (B) is preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, and 100% by mass or less, of 100% by mass of the total amount of the adhesive composition.

[0038] <(C) Hydrogen abstraction type photoinitiator> The adhesive composition may further contain (C) a hydrogen abstraction type photoinitiator (hereinafter also simply referred to as "component (C)"). Component (C) has the function of generating radicals. These generated radicals abstract hydrogens bonded to carbons in the main chain skeleton of component (A) and / or component (B), thereby generating radicals in the acrylic polymer and directly crosslinking components (A) with each other, components (B) with each other, or components (A) and components (B).

[0039] Examples of component (C) include aromatic ketones such as acetophenone, benzophenone, P,P'-dimethoxybenzophenone, 4-methylbenzophenone, P,P'-dichlorobenzophenone, P,P'-dimethylbenzophenone, and acetonaphthone. Other examples include aromatic aldehydes such as terephthalaldehyde and quinone-based aromatic compounds such as methylanthraquinone. Among these, it is preferable to use a compound containing benzophenone from the viewpoint of ease of radical generation. Component (C) may be used alone or in combination of two or more types.

[0040] If the adhesive composition contains component (C), the content of component (C) in the adhesive composition is preferably 0.1 parts by mass or more, more preferably 0.2 parts by mass or more, even more preferably 0.3 parts by mass or more, and preferably 3.0 parts by mass or less, more preferably 2.0 parts by mass or less, and even more preferably 1.0 part by mass or less, based on 100 parts by mass of the total of components (A) and (B).

[0041] <(D) Tackifier> The adhesive composition may further contain (D) a tackifier (hereinafter also simply referred to as "component (D)"). Component (D) is a component that can improve the adhesive properties of the resulting crosslinked adhesive, and is not particularly limited as long as the effects of the present invention are achieved.

[0042] Examples of component (D) include rosin resins such as polymerized rosin, polymerized rosin esters, and rosin derivatives, and their hydrides (hydrogenated rosin resins); terpene resins such as polyterpene resins, aromatically modified terpene resins, and terpene phenol resins, and their hydrides (hydrogenated terpene resins); coumarone-indene resins; petroleum resins such as aliphatic petroleum resins, aromatic petroleum resins, and aliphatic / aromatic copolymer petroleum resins, and their hydrides (hydrogenated petroleum resins); styrene or substituted styrene polymers; styrene resins such as α-methylstyrene monopolymer resins, copolymers of α-methylstyrene and styrene, copolymers of styrene monomers and aliphatic hydrocarbon monomers, copolymers of styrene, α-methylstyrene and aliphatic hydrocarbon monomers, homopolymers consisting of styrene monomers, copolymers of styrene monomers and aromatic monomers, and their hydrides (hydrogenated styrene resins); and the like. Component (D) may be used alone or in combination of two or more components.

[0043] The softening point of component (D) is preferably 70 to 140°C, more preferably 80 to 135°C, and even more preferably 85 to 130°C. If the softening point of component (D) is 70°C or higher, it tends to exhibit excellent adhesive strength at high temperatures. Furthermore, if the softening point of component (D) is 140°C or lower, it tends to mix easily with (A) energy-ray crosslinkable acrylic resin. In this specification, the softening point of component (D) refers to the value measured in accordance with JIS K 5601-2-2:1999.

[0044] If the adhesive composition contains component (D), the content of component (D) in the adhesive composition is preferably 5 to 35 parts by mass, more preferably 10 to 30 parts by mass, and even more preferably 15 to 25 parts by mass, per 100 parts by mass of component (A). When the adhesive composition contains component (D), if the content of component (D) is 5 parts by mass or more, it tends to be easier to improve the adhesive strength. Also, if the content of component (D) is 40 parts by mass or less, it tends to be easier to improve the holding power.

[0045] <Other ingredients> The adhesive composition may or may not contain other components besides those described above, as long as the effects of the present invention are achieved. Other components include, for example, softeners; antioxidants; and adhesive additives used in general adhesives. Each of these other components may be used individually or in combination of two or more.

[0046] The antioxidant is not particularly limited, and conventionally known antioxidants can be used, such as hindered phenol antioxidants, sulfur-based antioxidants, and phosphorus-based antioxidants.

[0047] Examples of adhesive additives used in the above-mentioned general adhesives include waxes, fillers, bulking agents, heat stabilizers, light stabilizers, UV absorbers, colorants (pigments, dyes, etc.), flame retardants, antistatic agents, stringing inhibitors, anti-aging agents, inorganic particles, organic particles, and weight-reducing agents. Each of these adhesive additives may be used individually or in combination of two or more types. If these other components are present, the content of each of these other components is preferably 0.0001 to 20 parts by mass, more preferably 0.001 to 10 parts by mass, based on 100 parts by mass of the total of components (A) and (B).

[0048] Furthermore, from the viewpoint of making it easier to achieve the effects of the present invention, it is preferable that the adhesive composition substantially does not contain compounds having radical-reactive unsaturated double bonds, such as polyfunctional acrylates. Here, "substantially does not contain compounds having radical-reactive unsaturated double bonds" means, for example, that the content of compounds having radical-reactive unsaturated double bonds in 100% by mass of the total amount of the adhesive composition is preferably 1.0% by mass or less, more preferably 0.1% by mass or less, and even more preferably 0.05% by mass or less.

[0049] Furthermore, from the viewpoint of reducing environmental impact, it is preferable that the adhesive composition is substantially free of solvents, and more preferably free of solvents. Here, "substantially free of solvents" means, for example, that the solvent content in 100% by mass of the total amount of the adhesive composition is preferably 0.5% by mass or less, and more preferably 0.1% by mass or less.

[0050] Furthermore, if the adhesive composition contains, in addition to component (A) and component (B), one or more components selected from component (C), component (D), and the other components, the total content of component (A) and component (B), and one or more components selected from component (C), component (D), and the other components is preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, and 100% by mass or less, of 100% by mass of the total amount of the adhesive composition.

[0051] <Method for producing an adhesive composition> The adhesive composition can be produced, for example, by a kneading method in which (A) an acrylic resin having energy ray crosslinkability, (B) an acrylic polymer substantially free of radical-reactive unsaturated double bonds and having a weight-average molecular weight (Mw) of component (B) of 280,000 or less, and any other component to be used as needed. In the following explanation, the process of melting and kneading components (A) and (B), etc., may be referred to as the "melt-kneading process."

[0052] The melt-mixing process involves, for example, putting each component into a mixing device equipped with a heating device, such as a heated kneader, and mixing the components while they are in a melted state. Mixing equipment equipped with a heating device includes, for example, single-screw extruders, twin-screw extruders, roll mills, Banbury mixers, intermixers, and pressure kneaders. If a mixing device capable of reducing pressure is used, the inside of the mixing device may be depressurized as needed, and the mixture may be melted and kneaded under reduced pressure.

[0053] The mixing temperature in the melt-mixing process is not particularly limited, and any temperature condition that allows each component to be thoroughly mixed in a molten state should be appropriately selected, but it is preferably 80 to 180°C, more preferably 100 to 170°C, and even more preferably 120 to 150°C.

[0054] Furthermore, when the adhesive composition is manufactured by melt kneading, the adhesive composition does not need to contain a solvent, and from the viewpoint of reducing the environmental impact, it is preferable that it is substantially solvent-free, and more preferable that it is solvent-free. Here, "substantially solvent-free" means, for example, that the solvent content in 100% by mass of the total amount of the adhesive composition is preferably 0.5% by mass or less, and more preferably 0.1% by mass or less.

[0055] The adhesive composition obtained after melt-kneading may be applied to a substrate or release liner using an extruder or the like while still in its heated and molten state, and used to manufacture an adhesive sheet, which is one embodiment of the present invention described later. Alternatively, if desired, it may be filled into various containers, for example, without going through a molding process.

[0056] [Crosslinking adhesive] A crosslinked adhesive according to one aspect of the present invention is a crosslinked adhesive obtained by irradiating the energy ray crosslinkable adhesive composition according to one aspect of the present invention with energy rays. In other words, the crosslinked adhesive has a crosslinked structure formed by an energy ray crosslinking reaction of (A) an energy ray crosslinkable acrylic resin contained in the energy ray crosslinkable adhesive composition. The crosslinking adhesive itself may also have good adhesive strength and exhibit excellent adhesion to the adherend. For example, from the viewpoint of eliminating the need for an energy ray irradiation step after application to the adherend, the adhesive composition may be irradiated with energy rays before application to the adherend to form the crosslinking adhesive, and then applied to the adherend as a crosslinking adhesive.

[0057] The crosslinking adhesive can be produced by irradiating the energy-ray crosslinkable adhesive composition with energy rays. In other words, the method for producing the crosslinking adhesive comprises the step of irradiating the energy ray crosslinkable adhesive composition with energy rays. In the following description, the step of irradiating the energy ray crosslinkable adhesive composition with energy rays may be referred to as the "energy ray irradiation step."

[0058] [Adhesive sheet] In one aspect of the present invention, the following first adhesive sheet and second adhesive sheet can be provided. The first adhesive sheet is an adhesive sheet having an energy ray crosslinkable adhesive composition layer consisting of the energy ray crosslinkable adhesive composition on a substrate or release liner. The second adhesive sheet is an adhesive sheet having an adhesive layer made of the crosslinking adhesive on a substrate or release liner. In the following description, the "energy ray crosslinkable adhesive composition layer comprising the energy ray crosslinkable adhesive composition" of the first adhesive sheet is also simply referred to as the "adhesive composition layer." Furthermore, the "adhesive layer consisting of the crosslinking adhesive" of the second adhesive sheet is also simply referred to as the "adhesive layer." Furthermore, when simply referred to as "adhesive sheet," it means both the first adhesive sheet and the second adhesive sheet.

[0059] Next, an example of the configuration of an adhesive sheet, which is one aspect of the present invention, will be described with reference to the drawings, but the present invention is not limited to the following example.

[0060] Figure 1(a) shows an example of a first adhesive sheet, an adhesive sheet 10a having a release liner 2 on one side of the adhesive composition layer 1 and a base material 4 on the other side of the adhesive composition layer 1. Furthermore, Figure 1(b) shows an example of a second adhesive sheet, an adhesive sheet 10b having a release liner 2 on one side of the adhesive layer 3 and a base material 4 on the other side of the adhesive layer 3. The adhesive sheets 10a and 10b are suitable for applications such as peeling off the release liner 2 and then attaching the exposed adhesive composition layer 1 or adhesive layer 3 to an object. Examples of such applications include label applications. Furthermore, if the adhesive sheet to be attached to the substrate is the first adhesive sheet, after attaching it to the substrate, an energy ray is irradiated onto the adhesive composition layer to form an adhesive layer consisting of the crosslinked adhesive.

[0061] Figure 2(a) shows a double-sided adhesive sheet 20a as another example of the first adhesive sheet, which has adhesive composition layers 1 on both sides of a substrate 4, with a release liner 2a on the side of one adhesive composition layer 1 opposite to the substrate 4, and a release liner 2b on the side of the other adhesive composition layer 1 opposite to the substrate 4. Furthermore, Figure 2(b) shows a double-sided adhesive sheet 20b as another example of a second adhesive sheet, which has adhesive layers 3 on both sides of a base material 4, with a release liner 2a on the side of one adhesive layer 3 opposite to the base material 4, and a release liner 2b on the side of the other adhesive layer 3 opposite to the base material 4.

[0062] Figure 3(a) shows another example of the first adhesive sheet, a substrate-less adhesive sheet 30a having release liners 2a and 2b on both sides of the adhesive composition layer 1. Furthermore, Figure 3(b) shows another example of a second adhesive sheet, a substrate-less adhesive sheet 30b having release liners 2a and 2b on both sides of the adhesive layer 3.

[0063] The adhesive sheets 20a, 20b, 30a, and 30b are suitable for bonding objects together, for example, by peeling off the release liner 2a on one side, attaching the exposed adhesive composition layer 1 or adhesive layer 3 to an object, and then peeling off the release liner 2b and attaching the exposed adhesive composition layer 1 or adhesive layer 3 to another object. Examples of such applications include fixing or temporarily fixing various parts. Furthermore, in adhesive sheets 30a and 30b, if the peeling force when peeling release liner 2a from the adhesive composition layer 1 or adhesive layer 3 is approximately the same as the peeling force when peeling release liner 2b from the adhesive composition layer 1 or adhesive layer 3, attempting to peel both release liners by pulling them outwards may cause the adhesive composition layer 1 or adhesive layer 3 to be separated and peeled off along with the two release liners. From the viewpoint of suppressing such a phenomenon, it is preferable to use two types of release liners, 2a and 2b, that are designed to have different peeling forces.

[0064] The thickness of the adhesive composition layer in the first adhesive sheet and the thickness of the adhesive layer in the second adhesive sheet are, independently, preferably 5 to 100 μm, more preferably 10 to 60 μm, and even more preferably 15 to 30 μm. When the thickness of the adhesive composition layer and the adhesive layer is 5 μm or more, it tends to be easier to improve the adhesive strength. Also, when the thickness of the adhesive composition layer and the adhesive layer is 100 μm or less, it tends to be easier to handle.

[0065] <Base material> Examples of materials used to form the base material include resin, metal, and paper. Examples of resins include polyolefin resins such as polyethylene and polypropylene; vinyl resins such as polyvinyl chloride, polyvinylidene chloride, polyvinyl alcohol, ethylene-vinyl acetate copolymer, and ethylene-vinyl alcohol copolymer; polyester resins such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate; polystyrene; acrylonitrile-butadiene-styrene copolymer; cellulose triacetate; polycarbonate; urethane resins such as polyurethane and acrylic-modified polyurethane; polymethylpentene; polysulfone; polyetheretherketone; polyethersulfone; polyphenylene sulfide; polyimide resins such as polyetherimide and polyimide; polyamide resins; acrylic resins; and fluorine resins. Examples of metals include aluminum, tin, chromium, and titanium. Examples of paper materials include tissue paper, medium-quality paper, fine-quality paper, impregnated paper, coated paper, art paper, sulfuric acid paper, and glassine paper.

[0066] The forming material of the aforementioned substrate may consist of one type, or two or more types may be used in combination. Examples of substrates using two or more forming materials include paper laminated with a thermoplastic resin such as polyethylene, and resin films or sheets containing resin with a metal film formed on the surface. Methods for forming the metal layer include, for example, depositing the metal by PVD methods such as vacuum deposition, sputtering, or ion plating, or attaching a metal foil made of the metal using a general adhesive.

[0067] Furthermore, from the viewpoint of improving interlayer adhesion between the substrate and other layers to which it is laminated, if the substrate contains resin, the surface of the substrate may be subjected to surface treatment by oxidation, embossing, or other methods, or to primer treatment.

[0068] Depending on the application of the adhesive sheet, the substrate may have, for example, an easy-adhesion layer to facilitate printing; a recording layer to enable recording such as thermal transfer recording or inkjet recording; an overcoat film or overlaminate film to protect these surfaces; an information area for magnetic recording, barcodes, microsemiconductor elements, etc. On the other hand, if the adhesive sheet is a transparent adhesive sheet, then the base material is preferably transparent.

[0069] The base material may contain base material additives as needed. Examples of base material additives include ultraviolet absorbers, light stabilizers, antioxidants, antistatic agents, slip agents, antiblocking agents, and colorants. These base material additives may be used individually or in combination of two or more types.

[0070] The thickness of the substrate is preferably 5 to 1,000 μm, more preferably 15 to 500 μm, and even more preferably 20 to 200 μm. When the substrate thickness is 5 μm or more, it tends to be easier to improve the deformation resistance of the adhesive sheet. On the other hand, when the substrate thickness is 1,000 μm or less, it tends to be easier to improve the handling properties of the adhesive sheet. Note that "base material thickness" refers to the total thickness of the base material. If the base material consists of multiple layers, it refers to the total thickness of all the layers that make up the base material.

[0071] <Removable Liner> Examples of release liners include release liners that have undergone double-sided release treatment, release liners that have undergone single-sided release treatment, etc., and release liners in which a release agent is applied to a substrate for release liners. Examples of substrates for release liners include papers such as fine paper, glassine paper, and kraft paper; plastic films such as polyester resin films such as polyethylene terephthalate resin, polybutylene terephthalate resin, and polyethylene naphthalate resin; and polyolefin resin films such as polypropylene resin and polyethylene resin. Examples of release agents include rubber elastomers such as silicone resins, olefin resins, isoprene resins, and butadiene resins; and long-chain alkyl resins, alkyd resins, and fluororesins. The thickness of the release liner is not particularly limited, but is preferably 10 to 200 μm, more preferably 20 to 180 μm, and even more preferably 30 to 150 μm.

[0072] [Method for manufacturing the first adhesive sheet] One example of the first method for manufacturing an adhesive sheet is a method for manufacturing an adhesive sheet having the following steps 11 and 12. Step 11: A step to obtain an energy-ray crosslinkable adhesive composition by melt-kneading (A) an acrylic resin having energy-ray crosslinkability and (B) an acrylic polymer that substantially does not contain radical-reactive unsaturated double bonds and in which the weight-average molecular weight (Mw) of component (B) is 280,000 or less. Step 12: A step of forming an energy ray crosslinkable adhesive composition layer by melt-coating the energy ray crosslinkable adhesive composition onto a substrate or release liner. In this specification, "on the release liner" means the surface on which the release liner has been peeled if it has been peeled on one side.

[0073] The description of step 11 is the same as the description of the melt-kneading step in the method for producing the energy-ray crosslinkable adhesive composition, which is one aspect of the present invention. Similarly, in step 11, in addition to components (A) and (B), any optional components used as needed, such as the aforementioned components (C), (D), and other components, may be melt-kneaded to obtain the adhesive composition. Components (A), (B), the substrate, the release liner, and the optional components (C), (D), and other components used in the first method for producing the adhesive sheet are the same as those described in the section on the energy-ray crosslinkable adhesive composition, and their preferred embodiments are also the same.

[0074] Step 12 may be a method of forming an adhesive composition layer by applying the energy-ray crosslinkable adhesive composition obtained in Step 11 onto a substrate or release liner using an extruder and a T-die, etc., while the composition is still heated and molten. Subsequently, the process may include a step of cooling the adhesive composition layer as needed.

[0075] By step 12, an adhesive composition layer can be formed on the substrate or release liner. The sheet having the substrate or release liner and the adhesive composition layer may be used as is as a first adhesive sheet, which is one aspect of the present invention, or, if necessary, it may be subjected to other processes to form a desired adhesive sheet. For example, by attaching the release treatment surface of a release liner to the exposed surface of an adhesive composition layer formed on a substrate, an adhesive sheet can be manufactured having a release liner on one side of the adhesive composition layer and a substrate on the other side of the adhesive composition layer, as shown in the adhesive sheet 10a in Figure 1(a). Furthermore, by attaching the substrate surface of the adhesive sheet 10a to the exposed surface of the adhesive composition layer formed on the release liner, a double-sided adhesive sheet can be manufactured, as shown in Figure 2(a), which has adhesive composition layers on both sides of the substrate and a release liner on the side of each adhesive composition layer opposite to the substrate. Furthermore, by attaching the release-treated surface of another release liner to the exposed surface of the adhesive composition layer formed on the release liner, a substrate-less adhesive sheet having release liners on both sides of the adhesive composition layer can be manufactured, as shown in the adhesive sheet 30a in Figure 3(a).

[0076] [Method for manufacturing the second adhesive sheet] As an example of the second method for manufacturing an adhesive sheet, there is a method for manufacturing an adhesive sheet that includes the following steps 22 and 23. Step 22: A step of forming an energy-ray crosslinkable adhesive composition layer on a substrate or release liner, comprising an energy-ray crosslinkable adhesive composition containing (A) an acrylic resin having energy-ray crosslinkability and (B) an acrylic polymer that substantially does not contain radical-reactive unsaturated double bonds and has a weight-average molecular weight (Mw) of 280,000 or less. Step 23: Step of irradiating the energy ray crosslinkable adhesive composition layer with energy rays to form an adhesive layer made of crosslinkable adhesive.

[0077] Step 22 can, for example, be carried out using the same method as step 12 in the method for manufacturing the first adhesive sheet, and it is preferable to use the same method as step 12 in the method for manufacturing the first adhesive sheet. That is, in step 22, it is preferable to form the energy ray crosslinkable adhesive composition layer by melt-coating the energy ray crosslinkable adhesive composition onto a substrate or release liner.

[0078] In step 23, the timing of energy ray irradiation is not particularly limited and can be determined as appropriate considering the manufacturing method of the adhesive sheet, the desired physical properties, etc. For example, when one side of the adhesive composition layer is exposed, energy rays may be irradiated directly onto the adhesive composition layer or through the substrate or release liner, or when the adhesive composition layer has a substrate or release liner on one side and a release liner on the other side, energy rays may be irradiated through the substrate or release liner.

[0079] Furthermore, the energy ray irradiation may be performed in a single step or in multiple steps. When the energy ray irradiation is performed in multiple steps, for example, the first energy ray irradiation may be performed with one side of the adhesive composition layer exposed, and then, after attaching a substrate or release liner to that surface, the second energy ray irradiation may be performed through the substrate or release liner. Furthermore, the first energy ray irradiation may be performed at some point before the adhesive is applied to the substrate, and the second energy ray irradiation may be performed after the adhesive is applied to the substrate.

[0080] Furthermore, the method for manufacturing the second adhesive sheet preferably includes the following step 21 prior to step 22, and further, in step 22, the energy ray crosslinkable adhesive composition obtained through the following step 21 is melt-coated onto the substrate or the release liner to form the energy ray crosslinkable adhesive composition layer. Step 21: A step to obtain an energy-ray crosslinkable adhesive composition by melt-kneading (A) an acrylic resin having energy-ray crosslinkability and (B) an acrylic polymer that substantially does not contain radical-reactive unsaturated double bonds and in which the weight-average molecular weight (Mw) of component (B) is 280,000 or less.

[0081] Step 21 is the same as step 11 in the method for manufacturing the first adhesive sheet, and is as described in step 11.

[0082] [Applications of energy ray crosslinkable adhesive compositions, crosslinkable adhesives, and adhesive sheets] The aforementioned energy ray crosslinkable adhesive composition, crosslinkable adhesive, and adhesive sheet, which are one aspect of the present invention, can be used for a variety of applications. Specifically, examples include label applications; fixing or temporary fixing of various parts; surface protection applications; sealing material applications; decorative and display applications; and so on. Among these, label applications and applications for fixing or temporarily fixing various components are preferred.

[0083] Adhesive sheets for labeling may be directly attached to various products, or they may be attached to packaging films, packaging containers, etc., of various products. Examples of constituent materials for packaging films and packaging containers include olefin resins such as polypropylene and polyethylene; polyester resins such as polyethylene terephthalate (PET) and polylactic acid; glass, paper, metal; and the like. As an adhesive sheet for fixing or temporary fixing purposes, it is suitable for fixing or temporarily fixing, for example, electronic components, optical components, automobile parts, mechanical components, building components, decorative components, etc. [Examples]

[0084] The present invention will be specifically described by the following examples, but the present invention is not limited to these examples. The physical properties in each example were measured by the following methods.

[0085] [Weight average molecular weight (Mw)] The weight-average molecular weight (Mw) was measured using a gel permeation chromatograph under the following conditions and determined on a standard polystyrene basis. (Measuring equipment) • Measuring device: Product name "HLC-8320GPC", manufactured by Tosoh Corporation • Detector: Differential refractometer • Columns: One "TSK guard column super HH", two "TSK gel super HM-H" in series, and one "TSK gel super H2000" (all manufactured by Tosoh Corporation) are connected in this order from the sample inlet side. (Measurement conditions) Column temperature: 40°C • Developing solvent: tetrahydrofuran ·Flow rate: 1.0mL / min

[0086] [Thickness of each layer] The measurement was taken at 23°C using a constant-pressure thickness gauge manufactured by Teclock Corporation (model number: "PG-02J", compliant with standards: JIS K 6783, Z 1702, Z 1709).

[0087] Details of the materials used in the following examples and comparative examples are as follows.

[0088] <Component (A): Energy-ray crosslinkable acrylic polymer> • A260UV: Acrylic polymer having a benzophenone structure in its side chain, trade name "acResin(registered trademark) A260UV" (manufactured by BASF): Weight-average molecular weight (Mw) 185,000

[0089] <Component (B): An acrylic polymer other than component (A) that substantially does not contain radical-reactive unsaturated double bonds and has a weight-average molecular weight (Mw) of 280,000 or less> P(BA)-1: "Poly(n-butyl acrylate)": Weight-average molecular weight (Mw) 200,000 P(BA)-2: "Poly(n-butyl acrylate)": Weight-average molecular weight (Mw) 100,000

[0090] <Component (C): Hydrogen abstraction type photoinitiator> • MBP: 4-methylbenzophenone, trade name "SpeedCure® MBP" (manufactured by Lambson).

[0091] <Component (D): Tackifier> • D-125: Rosin-based resin (polymerized rosin ester), product name "Pensel (registered trademark) D-125" (manufactured by Arakawa Chemical Industries, Ltd.)

[0092] <Other ingredients> • P(BA)-3: "Polybutyl acrylate": Weight-average molecular weight (Mw) 300,000 • SR399E: Dipentaerythritol pentaacrylate, product name "Sartomer (registered trademark) SR399E" (manufactured by Sartomer Corporation) • CN104NS: Epoxy acrylate, product name "Sertomer (registered trademark) CN104NS" (manufactured by Sertomer Corporation)

[0093] Examples 1-7, Comparative Examples 1-3 (Manufacturing of energy ray crosslinkable adhesive compositions) Each component was blended in the composition shown in Table 1 (unit: parts by mass), and kneaded at 130°C for 20 minutes under nitrogen purging using a heated kneader to obtain an energy-ray crosslinkable adhesive composition.

[0094] (Manufacturing of the first adhesive sheet) The energy-ray crosslinkable adhesive composition obtained above was coated onto a transparent polyethylene terephthalate film (thickness: 50 μm), which was a substrate, using a die coater while it was still in a heated and molten state. This resulted in obtaining a first adhesive sheet having an energy-ray crosslinkable adhesive composition layer (thickness: 20 μm) made of the energy-ray crosslinkable adhesive composition on the substrate.

[0095] (Manufacturing of the second adhesive sheet) For the energy-crosslinkable adhesive composition layer of the first adhesive sheet obtained above, a high-pressure mercury lamp (manufactured by iGraphics Co., Ltd.) was used to apply a UV-C integrated light intensity of 60 mJ / cm² from the exposed side. 2 The material was irradiated with ultraviolet light under the specified conditions. This formed an adhesive layer (thickness: 20 μm) by crosslinking the energy-ray crosslinkable adhesive composition layer of the first adhesive sheet with energy rays. Subsequently, the release-treated surface of a release liner (thickness: 38 μm) was bonded to the side of the adhesive layer opposite to the substrate to obtain a second adhesive sheet having the substrate, adhesive layer, and release liner in this order.

[0096] [Melting viscosity] The viscosity of the energy-ray crosslinkable adhesive compositions prepared in each example and comparative example was measured at 160°C using a viscometer (BROOKFIELD, product name "DV-III ULTRA") and a heater (BROOKFIELD, product name "THERMOSEL") at 1 hour and 10 hours after the start of heating. The results are shown in Table 1 below.

[0097] [Assessment of contamination of the object] The second adhesive sheets produced in each example and comparative example were cut to 25 mm x 50 mm in an environment of 23°C and 50% RH (relative humidity), and two test pieces were prepared for each example. The release liner was removed from the test pieces, and the exposed adhesive layer was attached to the substrate (stainless steel plate) in each example. Then, the test specimens attached to the substrate were left to stand for 7 days at 70°C, followed by 1 day at 23°C and 50%RH. At 23°C and 50%RH, one of the test specimens was peeled off by hand in a 180° direction at a speed of approximately 300 mm / min (low-speed peeling), and the other specimen was peeled off by hand in a 180° direction at a speed of approximately 30 m / min (high-speed peeling). Furthermore, the condition of each layer of the test specimen after peeling was visually observed, and contamination of the adherend was confirmed according to the following criteria. The results obtained are shown in Table 1 below. No contamination: The adhesive layer peels off at the interface with the substrate, leaving no adhesive residue on the substrate and exhibiting excellent peelability. Cohesive failure: The adhesive layer broke down, and residue of the adhesive layer was confirmed on the adherend.

[0098] [Table 1]

[0099] Table 1 shows that the adhesive compositions obtained in Examples 1-7 exhibited low melt viscosity at 160°C and excellent coating properties. Furthermore, there was no significant increase in viscosity after 10 hours of continuous heating at 160°C, confirming that these adhesive compositions have a long pot life and can be used sufficiently even after 10 hours of heating. Furthermore, it was confirmed that the second adhesive sheets obtained in Examples 1-3 and 5-7 did not contaminate the adherend even when peeled off at a low speed or at a high speed after being applied to the adherend. In Example 4, although cohesive failure occurred when peeled off at a high speed, it was confirmed that the adherend was not contaminated when peeled off at a low speed. On the other hand, the adhesive compositions obtained in Comparative Examples 1 and 2 both contained a compound having a radical-reactive unsaturated double bond instead of component (B). As a result, the melt viscosity after continuous heating at 160°C for 10 hours exceeded 45,000 cP in both cases, and the coating properties were significantly reduced, confirming that these adhesive compositions had short pot lives. Furthermore, the adhesive composition obtained in Comparative Example 3 had a weight-average molecular weight (Mw) of component (B) exceeding 280,000, resulting in a high melt viscosity of 42,000 cP after 1 hour at 160°C, confirming that its coating properties were inferior to those of each example. [Explanation of symbols]

[0100] 1. Energy ray crosslinkable adhesive composition layer 2, 2a, 2b Release Liner 3. Adhesive layer 4 Base material 10a, 20a, 30a First adhesive sheet 10b, 20b, 30b Second adhesive sheet

Claims

1. An energy-ray crosslinkable hot melt adhesive composition comprising (A) an acrylic polymer having energy-ray crosslinkability, and (B) an acrylic polymer other than component (A) that substantially does not contain radical-reactive unsaturated double bonds and has a weight-average molecular weight (Mw) of 280,000 or less, The above component (A) is an acrylic polymer having a benzophenone structure in its side chain, The acrylic polymer contains structural units derived from alkyl (meth)acrylate, The content of the constituent units derived from the alkyl (meth)acrylate is 80 to 100% by mass of the total constituent units of component (A). The above component (B) contains a constituent unit derived from alkyl (meth)acrylate (b1), The content of the constituent units derived from the alkyl (meth)acrylate (b1) is 60 to 100% by mass of the total constituent units of component (B). The content of component (B) is 5 parts by mass or more and 50 parts by mass or less per 100 parts by mass of component (A). The total content of component (A) and component (B) is 60% by mass or more of the total amount of the energy-ray crosslinkable hot melt adhesive composition, The content of radical-reactive compounds having unsaturated double bonds other than component (A) is 1.0% by mass or less of the total amount of the energy-crosslinkable hot melt adhesive composition (100% by mass). Energy ray crosslinkable hot melt adhesive composition.

2. (C) The energy ray crosslinkable hot melt adhesive composition according to claim 1, comprising a hydrogen abstraction type photoinitiator.

3. (D) The energy ray crosslinkable hot melt adhesive composition according to claim 1 or 2, comprising a tackifier.

4. The energy ray crosslinkable hot melt adhesive composition according to any one of claims 1 to 3, wherein the content of component (A) is 50 to 98% by mass of 100% by mass of the total amount of the energy ray crosslinkable hot melt adhesive composition.

5. An adhesive sheet having an energy ray crosslinkable adhesive composition layer on a substrate or release liner, the energy ray crosslinkable adhesive composition being the energy ray crosslinkable hot melt adhesive composition according to any one of claims 1 to 4.

6. A method for manufacturing an adhesive sheet having an energy ray crosslinkable adhesive composition layer, comprising the following steps 11 and 12, Step 11: A step to obtain an energy-ray crosslinkable hot melt adhesive composition by melt-kneading (A) an acrylic polymer having energy-ray crosslinkability and (B) an acrylic polymer other than component (A) that substantially does not contain radical-reactive unsaturated double bonds and has a weight-average molecular weight (Mw) of 280,000 or less. Step 12: A step of forming an energy-ray crosslinkable hot melt adhesive composition layer by melt-coating the energy-ray crosslinkable hot melt adhesive composition onto a substrate or release liner. The above component (A) is an acrylic polymer having a benzophenone structure in its side chain, The acrylic polymer contains structural units derived from alkyl (meth)acrylate, The content of the constituent units derived from the alkyl (meth)acrylate is 80 to 100% by mass of the total constituent units of component (A). The above component (B) contains a constituent unit derived from alkyl (meth)acrylate (b1), The content of the constituent units derived from the alkyl (meth)acrylate (b1) is 60 to 100% by mass of the total constituent units of component (B). The content of component (B) is 5 parts by mass or more and 50 parts by mass or less per 100 parts by mass of component (A). The total content of component (A) and component (B) is 60% by mass or more of the total amount of the energy-ray crosslinkable hot melt adhesive composition, The content of radical-reactive compounds having unsaturated double bonds other than component (A) is 1.0% by mass or less of the total amount of the energy-crosslinkable hot melt adhesive composition (100% by mass). A method for manufacturing adhesive sheets.

7. A crosslinked adhesive obtained by irradiating an energy ray with an energy ray from an energy ray crosslinkable hot melt adhesive composition according to any one of claims 1 to 4.

8. A method for producing the crosslinking adhesive described in claim 7, A method for producing a crosslinked adhesive, comprising the step of irradiating the energy ray crosslinkable hot melt adhesive composition with energy rays.

9. An adhesive sheet having an adhesive layer made of the crosslinking adhesive described in claim 7 on a substrate or release liner.

10. A method for manufacturing an adhesive sheet, comprising the following steps 22 and 23, Step 22: A step of forming an energy-ray crosslinkable adhesive composition layer on a substrate or release liner, comprising an energy-ray crosslinkable hot melt adhesive composition containing (A) an acrylic polymer having energy-ray crosslinkability and (B) an acrylic polymer other than component (A) that substantially does not contain radical-reactive unsaturated double bonds and has a weight-average molecular weight (Mw) of 280,000 or less. Step 23: Step of irradiating the energy ray crosslinkable adhesive composition layer with energy rays to form an adhesive layer made of crosslinkable adhesive. The above component (A) is an acrylic polymer having a benzophenone structure in its side chain, The acrylic polymer contains structural units derived from alkyl (meth)acrylate, The content of the constituent units derived from the alkyl (meth)acrylate is 80 to 100% by mass of the total constituent units of component (A). The above component (B) contains a constituent unit derived from alkyl (meth)acrylate (b1), The content of the constituent units derived from the alkyl (meth)acrylate (b1) is 60 to 100% by mass of the total constituent units of component (B). The content of component (B) is 5 parts by mass or more and 50 parts by mass or less per 100 parts by mass of component (A). The total content of component (A) and component (B) is 60% by mass or more of the total amount of the energy-ray crosslinkable hot melt adhesive composition, The content of radical-reactive compounds having unsaturated double bonds other than component (A) is 1.0% by mass or less of the total amount of the energy-crosslinkable hot melt adhesive composition (100% by mass). A method for manufacturing adhesive sheets.

11. A method for manufacturing an adhesive sheet according to claim 10, comprising the following step 21 prior to step 22, and further comprising forming the energy ray crosslinkable adhesive composition layer in step 22 by melt-coating the energy ray crosslinkable hot melt adhesive composition obtained through step 21 onto the substrate or the release liner. Step 21: A step to obtain an energy ray crosslinkable hot melt adhesive composition by melt-kneading component (A) and component (B).

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