TWI868653B - Adhesive sheet - Google Patents

Abstract

An active energy ray peelable adhesive sheet is provided, which can be preferably used in a process under high temperature conditions, and when irradiated with active energy rays after use in the process, the adhesiveness of the adhesive layer is sufficiently reduced, and it can be easily peeled off without leaving adhesive residue on the adherend. The adhesive sheet has an adhesive layer whose adhesive force is reduced by irradiation with active energy rays. The adhesive layer is composed of an active energy ray curing adhesive. The active energy ray curing adhesive is formed by a thermally cured product of an adhesive composition, and contains a thermal reactant of (A) and (C). The adhesive composition comprises at least (A) an adhesive base polymer having an acidic group, (B) an active energy ray reactive oligomer having six or more free radical reactive groups in one molecule, (C) a crosslinking agent, and (D) an α-hydroxyalkylphenone-based photopolymerization initiator, and the mass ratio of (B) to (A):1 is greater than 1.4 and less than 4.0.

Description

Adhesive sheet

The present invention relates to an active energy ray peelable adhesive sheet that can be easily peeled off by irradiating active energy rays from the outside.

In the manufacturing process of substrates (thin electronic circuit substrates, etc.), resin films are bonded and fixed to the substrate using a single-sided adhesive sheet on the base material, so that parts can be mounted and processed on the substrate. After the parts are mounted and processed, the substrate and the adhesive sheet are separated from each other. When the substrate is temporarily fixed by this adhesive sheet, sufficient adhesion is required during the installation and processing process, but if the load applied to the substrate is large when peeling off the adhesive sheet, the substrate will be damaged. Therefore, the adhesion of the adhesive sheet should be as low as possible when peeling off.

In addition, in recent years, electronic parts and semiconductor parts are required to have higher heat resistance than before, mainly for automotive applications. At the same time, the materials that constitute the above parts (such as chip sealing resins in semiconductor packaging) are also required to have higher heat resistance. Resins with high heat resistance usually require higher heating temperatures for curing. Therefore, the adhesive sheet used in the process of curing such high heat-resistant resins also needs to have higher heat resistance.

It is known that there are adhesive sheets for the above-mentioned purposes, such as the adhesive sheet in Patent Document 1, which has sufficient adhesiveness when used, but after use, it is subjected to some external stimulation (such as ultraviolet irradiation, etc.), and the adhesiveness is significantly reduced.

Prior art literature

Patent Literature

Patent document 1: Japanese Patent Application No. 2010-106283

The adhesive sheet disclosed in Patent Document 1 is obtained by placing an adhesive layer composed of an ultraviolet peelable adhesive on a substrate that can transmit ultraviolet rays, wherein the adhesive layer is crosslinked and cured by ultraviolet irradiation, and the adhesive force is reduced. The adhesive sheet maintains sufficient adhesion to the adherend during use, and at the same time, the adhesive is crosslinked and cured by irradiating ultraviolet rays from the substrate side, reducing the adhesive force of the adhesive layer, thereby facilitating the peeling of the adherend.

However, in the adhesive sheet disclosed in Patent Document 1, the adhesive component in the adhesive layer is easily affected by heat. Therefore, if ultraviolet rays are irradiated after a process under high temperature conditions (e.g., 180°C and 20 minutes), the adhesive force of the adhesive layer cannot be sufficiently reduced. Therefore, when the adhesive sheet is peeled off, adhesive residue is generated on the adherend (if high temperature heating is performed before ultraviolet irradiation, the adhesive force reduction after ultraviolet irradiation is not good). In addition, since the adhesive force at the initial stage of bonding is small, there is also a tendency to be difficult to maintain the adherend at room temperature (initial viscosity is small. The adhesive force at the initial stage of bonding at room temperature is poor).

The present invention is proposed in view of the above reasons. The purpose of the present invention is to provide an active energy ray peelable adhesive sheet, which is attached to the adherend and used in various manufacturing processes including the manufacturing process of the above substrate and the manufacturing process of the above electronic parts and semiconductor parts, and the adhesive sheet can be preferably used in a process under high temperature conditions (for example, 180°C and 20 minutes), and if it is irradiated with active energy rays after use in the process, the adhesiveness of the adhesive layer is sufficiently reduced, and it can be easily peeled off without leaving any adhesive residue on the adherend.

As a result of in-depth research, the inventors of the present invention have found that an adhesive sheet having an adhesive layer whose adhesive force is reduced by irradiation with active energy rays can suppress thermal degradation of the adhesive component when used in a process under high temperature conditions when the following conditions are met, and is effective in both easy releasability and adhesive residue when irradiated with active energy rays.

-Use an adhesive base polymer (specific base polymer) having an acidic group and containing a crosslinking agent.

- As the active energy ray-reactive compound, a compound having a prescribed number or more of free radical reactive groups and a small molecular weight (specific active energy ray-reactive oligomer) is used.

-Use α-hydroxyacetophenone-based photopolymerization initiator (specific photopolymerization initiator).

-The mixing amount of the above-mentioned specific active energy ray-reactive oligomer relative to the above-mentioned specific base polymer is within a specific range.

-The adhesive layer is formed by a thermosetting product of the adhesive composition containing the above-mentioned components. That is, the adhesive layer contains a thermoreactive product of a specific base polymer and a crosslinking agent.

Based on these new insights, the inventors of this invention have completed the invention provided below and solved the above problems.

Hereinafter, (A) is an adhesive base polymer having an acidic group, (B) is an active energy ray reactive compound, (B1) is an active energy ray reactive oligomer having 6 or more free radical reactive groups in one molecule, (B2) is an active energy ray reactive monomer, an oligomer or polymer having less than 10 free radical reactive groups in one molecule, (C) is a crosslinking agent, (D) is a photopolymerization initiator, (D1) is an α-hydroxyacetophenone-based photopolymerization initiator, and (D2) is an alkylphenone-based photopolymerization initiator other than (D1). In addition, (A1) is an acrylic resin having an acidic group, (C1) is an isocyanate-based crosslinking agent, and (C2) is an epoxy-based crosslinking agent.

According to the present invention, an adhesive sheet having an adhesive layer whose adhesive force is reduced by irradiation with active energy rays is provided, wherein the adhesive layer is formed by a cured product of an adhesive composition, and is composed of an active energy ray-curable adhesive containing a thermal reaction product of (A) and (C), wherein the adhesive composition contains at least (A), (B), (C) and (D), and the mass ratio of (B) to (A) is greater than 1.4 and less than 4.0.

The above-mentioned adhesive sheet may include the following forms.

-(A) may include (A1).

-(A1) The glass transition temperature can be within the range of -20°C to 40°C.

-(B) may include (B1), but preferably does not include (B2).

-(B1) may include an active energy ray reactive oligomer having 8 or more free radical reactive groups in one molecule.

-(C) may include (C1) or (C2)

-(C) may contain 0.5 to 5 parts by mass relative to 100 parts by mass of (A).

-(D) may include (D1), but preferably does not include (D2).

-(D1) may include oligo(2-hydroxy-2-methyl-1-(4-(1-methylvinyl)phenyl)acetone).

-(D) may be contained in an amount of 0.1 to 20 parts by mass relative to 100 parts by mass of (B).

-The initial adhesion X1 to glass at 23°C can be above 1.0 (N/25mm).

- After heating at 180°C for 20 minutes and further irradiating with active energy rays, the adhesion to glass at 23°C, i.e. the adhesion after heating and irradiation X3, can be less than 0.5 (N/25mm).

The active energy ray peelable adhesive sheet of the present invention is formed of a heat-cured product of an adhesive composition, has an adhesive layer whose adhesive force is reduced by irradiation with active energy rays, and the mixing amount of a specific active energy ray reactive oligomer relative to a specific base polymer in the adhesive composition is within a specific range, and further includes a crosslinking agent and a specific photopolymerization initiator. Since the adhesive layer is formed of a heat-cured product of the adhesive composition, a heat-reactant of the specific base polymer and the crosslinking agent exists in the adhesive layer. According to the structure of the adhesive layer, even in a process under high temperature conditions (e.g., 180°C and 20 minutes), the reduction in cohesive force caused by thermal degradation of the adhesive component is suppressed. As a result, the adhesiveness of the adhesive layer is sufficiently reduced by irradiating active energy rays after the process, and an active energy ray-peelable adhesive sheet that is not easy to produce adhesive residue on the adherend can be provided.

With the above structure, the adhesive sheet can be suitable for use in a high temperature environment (e.g., above 150°C, preferably above 170°C).

The following describes the best implementation of the present invention, but the present invention is not limited to the following implementation. Without departing from the subject matter of the present invention, appropriate changes and improvements to the following implementation based on the general knowledge of technical personnel in this field are also within the scope of the present invention.

Within the range of values described in this specification, the upper limit or lower limit value described in a certain range of values can be replaced with the value shown in the embodiment.

In this manual, when there are multiple substances corresponding to each component in the composition, unless otherwise specified, the content rate or content of each component in the composition refers to the total content rate or content of the multiple substances in the composition.

In this specification, "(meth)acrylic acid" refers to both acrylic acid and methacrylic acid or either one of them. "(Meth)acrylate" refers to both acrylate and methacrylate or either one of them. The same applies to other similar terms. "Polymer" also includes the concept of "copolymer".

In this specification, the number average molecular weight (Mn) and the mass average molecular weight (Mw) are standard polystyrene conversion values measured by gel permeation chromatography (GPC). The glass transition temperature (Tg) can be measured by differential scanning calorimetry (DSC).

In this manual, unless otherwise specified, "adhesive layer" refers to the adhesive layer before the adhesive force decreases (before irradiation with active energy rays). In addition, "active energy ray-curing adhesive" is a releasable adhesive (re-peelable adhesive), and "adhesive sheet" is a re-peelable adhesive sheet (re-peelable adhesive sheet). "Re-peelability" refers to the ability to reattach to the adherend.

1. <Adhesive sheet>

The adhesive sheet of one embodiment of the present invention has an adhesive layer. The adhesive sheet may be composed of only an adhesive layer (without a substrate), or may be composed of adhesive layers stacked on a substrate (with a substrate). The substrate may be a polymer film, etc. (PET film, etc.). In the absence of the substrate, a peeling sheet may be provided on both surfaces of the adhesive sheet (adhesive layer) (with a double-sided peeling sheet). In the presence of the substrate, a peeling sheet may be provided on a surface opposite to the substrate of the adhesive layer (with a single-sided peeling sheet).

As the above-mentioned peeling sheet, there can be cited: a peeling layer laminate having a peeling sheet substrate and a peeling agent layer provided on one surface of the peeling sheet substrate, or a polyolefin film (such as a polyethylene film, a polypropylene film, etc.) as a polar substrate.

The substrate for the peeling sheet can be paper or polymer film. As the peeling agent constituting the peeling agent layer, for example, a commonly used additive or condensed organic silicon peeling agent or a compound containing a long-chain alkyl group can be used. In particular, an additive organic silicon peeling agent with high reactivity is preferred.

When the adhesive sheet has no substrate, that is, is composed only of an adhesive layer, and has a double-sided peeling sheet, it is preferred that a pair of peeling sheets with different peeling forces are provided on the two surfaces of the adhesive sheet (adhesive layer). That is, in order to facilitate peeling, it is preferred that the peeling sheet on one side and the peeling sheet on the other side have different peeling properties. When the peeling properties on one side and the peeling properties on the other side are different, it is easy to peel only the peeling sheet with higher peeling properties first, thereby improving processability.

2. <Adhesion base layer>

The adhesive layer (the adhesive sheet itself when there is no substrate, the same below) is composed of an active energy ray-curable adhesive. If an active energy ray-curable adhesive is used, an adhesive sheet having an adhesive layer with low elasticity, high flexibility and excellent operability during adhesion can be obtained, and when peeling is required, the adhesive force can be reduced by irradiating active energy rays.

"Active energy ray curing adhesive" is an adhesive that is cured by irradiation with active energy rays, thereby reducing the adhesive force, and is an adhesive that has a specified adhesive force before irradiation with active energy rays. "Adhesion" has the same meaning as peeling force (the force required to peel off the adhesive object). "Active energy rays" refer to electromagnetic waves or charged particle rays with energy quanta. For example, ultraviolet rays, electron rays, visible rays, X-rays, ion rays, etc. can be listed. Among them, from the perspective of versatility, ultraviolet rays or electron rays are preferred, and ultraviolet rays are particularly preferred.

The active energy ray curing adhesive is formed by a thermally cured adhesive composition of a specific composition according to one embodiment of the present invention.

2-1. <Adhesive composition>

An adhesive composition (hereinafter also referred to as "composition") according to one embodiment contains a base polymer, an active energy ray-reactive compound, (C) a crosslinking agent and a photopolymerization initiator. The base polymer, the active energy ray-reactive compound and the photopolymerization initiator respectively contain more than 95% by mass (preferably 100% by mass) of (A) an adhesive base polymer having an acidic group, (B) an active energy ray-reactive oligomer and (D1) an α-hydroxyacetophenone-based photopolymerization initiator. The base polymer, the active energy ray-reactive compound and the photopolymerization initiator may respectively contain components other than (A), (B) and (D). That is, the composition according to one embodiment comprises at least (A), (B), (C) and (D). Below, each ingredient is described in detail.

2-1-1.(Base polymer)

In the composition of one embodiment, a composition having an acidic group is used as a base polymer, specifically, (A) an adhesive base polymer having an acidic group is used. (A) used to form the composition is a base of an active energy ray-curable adhesive constituting the adhesive layer. (A) is not particularly limited as long as it has an acidic group. Even in a process under high temperature conditions (e.g., 180°C and 20 minutes), the reduction in cohesive force caused by thermal degradation of the adhesive component is suppressed. As a result, the adhesiveness of the adhesive layer is sufficiently reduced by irradiating active energy rays after the process, so that an active energy ray-peelable adhesive sheet in which adhesive residues are not easily generated on the adherend can be easily obtained. From this point of view, it is preferred that (A) is an acrylic resin containing (A1) having an acidic group.

(A) You can use one type alone or two or more types in combination.

The content (total amount) of (A) in the composition is not particularly limited, but considering the ratio with other ingredients, relative to the total solid amount (100 mass%) of the composition, it is preferably 30 mass% or more, preferably 40 mass% or more, preferably 90 mass% or less, and preferably 80 mass% or less.

(A1) Acrylic resin with acidic group

As component (A1), for example, a material having a mass average molecular weight (Mw) of 50,000 or more, preferably 100,000 or more, and a glass transition temperature (Tg) of -20°C or more, preferably -10°C or more is used. If Mw is less than 50,000, there are problems of increased residual adhesive and peeling force during re-peeling, while if Tg is less than -20°C, peeling force and elastic modulus at high temperature are reduced, so both are not suitable. In addition, if Mw is too high, the problem of abnormal compatibility is likely to occur, and if Tg is too high, the problem of poor adhesion to the adherend is likely to occur. Therefore, as component (A1), in addition to satisfying the above conditions (Mw is 50,000 or more, and Tg is -20°C or more), it is best to also satisfy Mw is 300,000 or less, preferably 200,000 or less, and/or Tg is 40°C or less, preferably 30°C or less.

The dispersion degree (Mw/Mn) of (A1) represented by the ratio of Mw to the number average molecular weight (Mn) is not particularly limited, but from the perspective of adhesion, it is preferably about 3 or more and about 9 or less.

(A1) contains a monomer having an acidic group in the molecule (acidic group-containing monomer) as a monomer unit constituting the resin (polymer). Since the composition of one embodiment contains a crosslinking agent (C), the acidic group of the acidic group-containing monomer reacts with (C), making it easy to control the cohesive force of the resulting adhesive. Therefore, the resulting adhesive layer easily exerts the desired adhesive force.

On the other hand, if (A1) contains only monomers having no acidic group but hydroxyl group in the molecule (monomers having no acidic group but hydroxyl group) as monomer units constituting the resin (polymer), the crosslinking of the adhesive layer is insufficient and the cohesion and adhesive strength are likely to decrease, which is not suitable.

Specific examples of the acidic group of (A1) include carboxyl, sulfonyl, and phosphoric acid groups. From the perspective of the cohesiveness of the adhesive layer, carboxyl groups are preferred.

Examples of monomers having a carboxyl group (carboxyl group-containing monomers) include acrylic acid (AA), methacrylic acid, maleic acid, maleic anhydride, fumaric acid, crotonic acid, itaconic acid, citric acid, 2-(meth)acryloyloxyethyl succinic acid, maleic acid monohydroxyethyl ester (meth)acrylate, fumaric acid monohydroxyethyl ester (meth)acrylate, phthalic acid monohydroxyethyl ester (meth)acrylate, 1,2-dicarboxycyclohexane monohydroxyethyl ester (meth)acrylate, (meth)acrylic acid dimer, ω-carboxy-polycaprolactone mono(meth)acrylate, etc. Among them, carboxyl group-containing monomers are preferably (meth)acrylic acid, and more preferably acrylic acid (AA), from the viewpoint of good compatibility and copolymerizability with other monomers during synthesis and particularly good crosslinking reaction with the crosslinking agent (C). These can be used alone or in combination of two or more.

A monomer containing an acidic group may also have both an acidic group and a hydroxyl group in the molecule. That is, in the molecule of a monomer containing an acidic group, the hydroxyl group is optional.

As a monomer unit constituting the polymer, (A1) contains a monomer containing an acidic group, preferably at least 1 mass %, more preferably at least 3 mass %. By setting the lower limit of the ratio (content) of the monomer containing an acidic group to the above value, high cohesion and heat resistance can be obtained. As a monomer unit constituting the polymer, (A1) contains a monomer containing an acidic group, preferably at least 10 mass %, more preferably at least 7 mass %. By setting the upper limit of the content of the monomer containing an acidic group to the above value, appropriate adhesion can be obtained.

From the perspective of being able to easily exert the desired adhesive force, (A1) is used as a monomer unit constituting the polymer, in addition to a monomer containing an acidic group, preferably a (meth)acrylic acid alkyl ester having an alkyl group with a carbon number of 1 to 20.

Examples of (meth)acrylic acid alkyl esters having an alkyl group with a carbon number of 1 to 20 include: methyl (meth)acrylate (MMA, MA), ethyl (meth)acrylate (EMA, EA), propyl (meth)acrylate, n-butyl (meth)acrylate, n-pentyl (meth)acrylate, n-hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate (EHMA, EHA), isooctyl (meth)acrylate, n-decyl (meth)acrylate, n-dodecyl (meth)acrylate, myristyl (meth)acrylate, palmityl (meth)acrylate, stearyl (meth)acrylate, etc.

Among them, the (meth)acrylic acid alkyl ester having an alkyl group with a carbon number of 1 to 20 is preferably one or more of the (meth)acrylic acid esters having an alkyl group with a carbon number of 1 to 8 from the viewpoint of further improving adhesion. The (meth)acrylic acid ester having an alkyl group with a carbon number of 1 to 8 is preferably one or more of methyl (meth)acrylate (MMA, MA) and 2-ethylhexyl (meth)acrylate (EHMA, EHA) from the viewpoint of adjusting Tg, and methyl acrylate (MA) and 2-ethylhexyl acrylate (EHA) are more preferred. These can be used alone or in combination of two or more.

(A1) As a monomer unit constituting the polymer, the content of alkyl (meth)acrylate having an alkyl group with a carbon number of 1 to 20 is preferably 80% by mass or more, preferably 90% by mass or more, preferably 98% by mass or less, and preferably 95% by mass or less. When the content of alkyl (meth)acrylate is within the above range, Tg can be adjusted to an appropriate range, and appropriate adhesion at room temperature can be obtained.

Within the scope of the effect of the present invention, (A1) is a monomer unit constituting the polymer and may contain monomers other than acidic group-containing monomers and (meth)acrylic acid alkyl esters. In this case, the total ratio (content rate) of the constituent units derived from the acidic group-containing monomers and the constituent units derived from the (meth)acrylic acid alkyl esters is preferably 80% by mass or more, more preferably 85% by mass or more, and even more preferably 90% by mass or more relative to all the constituent monomer units of component (A1) (100% by mass).

As long as other monomers can be copolymerized with the monomers containing acidic groups and the (meth) alkyl acrylate, there are no particular restrictions. They can be used alone or in combination of two or more. Examples of other monomers include: (meth) acrylates having cyclic groups such as benzyl (meth) acrylate and phenoxyethyl (meth) acrylate; (meth) alkyl (meth) acrylates such as methoxyethyl (meth) acrylate and ethoxyethyl (meth) acrylate; aromatic monovinyls such as styrene, α-methylstyrene, tert-butylstyrene, p-chlorostyrene, chloromethylstyrene, and vinyltoluene; vinyl cyanides such as acrylonitrile (AN) and methacrylonitrile; vinyl esters such as vinyl formate, vinyl acetate (VA), vinyl propionate, and vinyl versatate; and monomers having functional groups other than acidic groups such as hydroxyl, glycidyl, amide, N-substituted amide, and tertiary amino groups. These can be used alone or in combination of two or more.

Examples of monomers having a hydroxyl group (a monomer containing a hydroxyl group) include hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate (HEMA, HEA), 2-hydroxybutyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, and 3-hydroxypropyl (meth)acrylate.

Examples of monomers having a glycidyl group include: glycidyl (meth)acrylate, 3,4-epoxyhexylmethyl (meth)acrylate, glycidyl vinyl ether, 3,4-epoxyhexyl vinyl ether, (meth)allyl glycidyl ether, and 3,4-epoxyhexyl (meth)allyl ether.

Examples of monomers having an amide group or an N-substituted amide group include acrylamide, methacrylamide, N-methyl(methyl)acrylamide, N-ethyl(methyl)acrylamide, N-methoxymethyl(methyl)acrylamide, N-ethoxymethyl(methyl)acrylamide, N-propoxymethyl(methyl)acrylamide, N-butoxymethyl(methyl)acrylamide, N-tert-butylacrylamide, N-octylacrylamide, and diacetoneacrylamide.

Examples of monomers having a tertiary amino group include dimethylaminoethyl (meth)acrylate, diethylaminoethyl (meth)acrylate, and dimethylaminopropyl (meth)acrylamide.

The acid value (solid content) of (A1) is preferably 10 (mgKOH/g) or more, preferably 20 (mgKOH/g) or more, preferably 100 (mgKOH/g) or less, and preferably 90 (mgKOH/g) or less. By adjusting the acid value of (A1) within the above range, (A1) is crosslinked to a crosslinking density suitable for imparting appropriate adhesion to the adhesive layer, so that sufficient adhesion can be exerted during use and higher heat resistance can be easily obtained.

The acid value refers to the number of milligrams of potassium hydroxide required to neutralize 1 gram of (A1). The acid value of (A1) can be calculated by the following formula. In addition, when multiple monomers containing acidic groups are contained, the acid value of each monomer containing an acidic group is calculated separately by the following formula, and the total value is used as the acid value of component (A1).

(Calculation formula 1) Acid value (mgKOH/g) = (56.1÷X) × (Y/100) × 1000 = (56.1÷X) × Y

In the above formula 1,

‧X is the molecular weight of the monomer containing an acidic group used in (A1).

‧Y is a monomer containing an acidic group used in (A1), and its content (mass %) in all monomers used in (A1).

‧56.1 is the molecular weight of potassium hydroxide (KOH).

The polymerization method of (A1) is not particularly limited. As the polymerization method, known methods such as solution polymerization, emulsion polymerization, suspension polymerization, and block polymerization can be applied. Solution polymerization is preferred. In solution polymerization, a specified organic solvent, monomer, polymerization initiator, and a chain transfer agent used as needed are usually added to a polymerization tank, and the reaction is heated for several hours while stirring in a nitrogen flow or at the reflux temperature of the organic solvent. In this case, at least a portion of the organic solvent, monomer, and polymerization initiator may be added in sequence.

2-1-2. (Active energy ray reaction compounds)

The active energy ray reactive compound (B) used to form the composition is a material that polymerizes and cures by irradiation with active energy rays (described above) in the presence of a photopolymerization initiator. In the composition (B) of one embodiment, as the active energy ray reactive compound, an oligomer form is required. Specifically, (B1) is an active energy ray reactive oligomer having 6 or more free radical reactive groups in one molecule. (B1) may be an ultraviolet curable material that cures by irradiation with ultraviolet rays. Since the adhesive layer contains (B1), after it is attached to an adherend for use, the adhesive layer can be cured by polymerization of (B1) by irradiation with active energy rays, and the adhesive force of the adhesive layer is reduced, thereby making it easy to peel the adhesive sheet from the adherend.

Even if (B) has more than 6 radical reactive groups in one molecule, if it is a (B2) active energy ray reactive monomer with a small molecular weight, there is a problem that the peeling force after heating and active energy ray irradiation is not sufficiently reduced due to the poor heat resistance of the monomer. Even if (B) has more than 6 radical reactive groups in one molecule, if it is a (B2) active energy ray reactive polymer with a large molecular weight, there will be a problem of incompatibility with (A). Even if (B) is an active energy ray reactive oligomer, if the (B2) free radical reactive groups are less than 6, there is a problem that the peeling force is not sufficiently reduced when irradiated with active energy rays.

Since (B1) is an active energy ray reactive oligomer having 6 or more free radical reactive groups, a cross-linking reaction is carried out during the polymerization of (B1), which can effectively cure the adhesive layer and reduce the adhesion. From the perspective of more effectively curing the adhesive layer and reducing the adhesion, the number of reactive groups contained in (B1) is preferably 8 or more. The upper limit of the number of reactive groups is not particularly limited, but even if it exceeds 20, the degree of decrease in adhesion caused by curing of the adhesive layer after active energy ray irradiation is almost not improved.

From the viewpoint of more effectively curing the adhesive layer and thus reducing the adhesive force, the amount of (B1) used is preferably 50% by mass or more, more preferably 70% by mass or more, more preferably 90% by mass or more, particularly preferably 95% by mass or more, and most preferably 100% by mass, relative to the total amount (100% by mass) of the active energy ray-reactive compound (B) used in forming the composition.

The free radical reactive group is a functional group that reacts and cures by free radicals. There is no particular limitation, and examples thereof include: acrylate group, methacrylate group, vinyl group, allyl group, thiol group, etc. From the perspective of the curing speed when irradiated with active energy rays, the free radical reactive group is preferably an acrylate group or a methacrylate group, and more preferably an acrylate group.

Examples of (B1) include epoxy acrylate oligomers and urethane acrylate oligomers. Among them, urethane acrylate oligomers are preferred from the viewpoint of compatibility and adhesion. The polyurethane acrylate oligomer is obtained by reacting a polyol compound such as polyester or polyether with a polyvalent isocyanate compound (e.g., 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 1,3-phenylenediisocyanate, 1,4-phenylenediisocyanate, diphenylmethane 4,4-diisocyanate, etc.), and adding a (meth)acrylate having a hydroxyl group (e.g., 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, polyethylene glycol acrylate, polyethylene glycol methacrylate, or pentaerythritol triacrylate) to the obtained terminal isocyanate prepolymer by a known method.

(B1) One type can be used alone, or two or more types can be used in combination.

The mass average molecular weight of (B) is preferably 500 or more, preferably 800 or more, and more preferably 1000 or more; preferably 10000 or less, preferably 7000 or less, and more preferably 5000 or less. The viscosity of (B) is about 300 to 10000 mPa. s at 25°C, preferably 5000 to 8000 mPa. s.

The mass ratio of (B) in the composition relative to (A) is preferably greater than 1.4, more preferably greater than 1.5, more preferably greater than 1.8, and particularly preferably greater than 2.0. By setting the lower limit of the mass ratio of (B) to the above value, the advantage of reducing the peeling force when irradiated with active energy rays can be obtained. The mass ratio of (B) relative to (A) is preferably less than 4.0, more preferably less than 3.6, more preferably less than 3.2, and particularly preferably less than 3.0. By setting the upper limit of the mass ratio of (B) to the above value, the advantage of sufficient film-forming performance can be obtained.

2-1-3. (Crosslinking agent)

The (C) crosslinking agent used to form the composition is a substance that can crosslink (A) to form a crosslinked polymer. By forming a crosslinked polymer, the thermal degradation of the adhesive component can be suppressed when used in a process under high temperature conditions, and the adhesive can be easily peeled off when irradiated with active energy rays.

As (C), for example, isocyanate crosslinking agents, epoxy crosslinking agents, melamine crosslinking agents, peroxide crosslinking agents, urea crosslinking agents, metal alkoxide crosslinking agents, metal chelate crosslinking agents and metal salt crosslinking agents, carbodiimide crosslinking agents, oxazoline crosslinking agents, aziridine crosslinking agents and amine crosslinking agents can be listed. (C) can be used alone or in combination of two or more. Among them, from the perspective of the cohesive force of the adhesive layer, it is preferred to use isocyanate crosslinking agents and epoxy crosslinking agents.

Examples of isocyanate crosslinking agents include: low-order aliphatic polyisocyanates such as butanediisocyanate (BDI) and hexamethylene diisocyanate (also known as HDI); alicyclic isocyanates such as cyclopentanediisocyanate, cyclohexanediisocyanate, and isophorone diisocyanate (also known as IPDI); aromatic isocyanates such as 2,4-toluene diisocyanate (also known as 2,4-TDI), 4,4'-diphenylmethane diisocyanate, and xylylene diisocyanate; trihydroxymethylpropane/toluene diisocyanate trimer adduct (manufactured by TOSOH, product name "Coronate L”), trihydroxymethylpropane/hexamethylene diisocyanate trimer adduct (manufactured by TOSOH, product name “Coronate HL”), isocyanurate of hexamethylene diisocyanate (manufactured by TOSOH, product name “Coronate HX”), and isocyanurate of isophorone diisocyanate (manufactured by Evonik Japan, product name “VESTANAT T1890E”) and other isocyanate adducts. Isocyanate crosslinking agents may be used alone or in combination of two or more.

Examples of epoxy crosslinking agents include aliphatic epoxy such as ethylene glycol diglycidyl ether, trihydroxymethylpropane diglycidyl ether, and diglycidylamine; 1,3-bis(N,N'-diglycidylaminomethyl)cyclohexane (manufactured by Mitsubishi Gas Chemical Co., Ltd., trade name "TETRAD-C"), 1,6-hexanediol diglycidyl ether, N,N,N'-diglycidylaminomethyl)cyclohexane (manufactured by Mitsubishi Gas Chemical Co., Ltd., trade name "TETRAD-C"), , N'-tetraglycidyl-m-phenylenediamine and other aliphatic epoxides; diglycidylaniline and other aromatic epoxides; 1,3,5-tri-(2,3-epoxybutyl)-isocyanurate, 1,3,5-tri-(3,4-epoxybutyl)-isocyanurate, 1,3,5-tri-(4,5-epoxypentyl)-isocyanurate and other heterocyclic epoxides, etc. Epoxide crosslinking agents can be used alone or in combination of two or more.

The content (total amount) of (C) in the composition varies depending on the type of crosslinking agent, the number of functional groups, etc., and is therefore not particularly limited, but is preferably 0.5 parts by mass or more, preferably 1.0 parts by mass or more, preferably 5 parts by mass or less, and preferably 3 parts by mass or less, relative to 100 parts by mass of (A). By setting the content of (C) within the above range, it is suitable in terms of preventing adhesive residues and facilitating the adjustment of adhesion.

2-1-4. (Photopolymerization initiator)

The (D) photopolymerization initiator used to form the composition is one that initiates the polymerization of (B) by irradiating active energy rays (described above). In the composition of one embodiment, as the (D) photopolymerization initiator, a specific (D1) α-hydroxyacetophenone type photopolymerization initiator needs to be used. Because, if an alkyl phenone type photopolymerization initiator other than (D1) is used, such as (D2) benzyl methyl ketal type photopolymerization initiator (such as 2,2-dimethoxy-1,2-diphenylethane-1-one, etc.), although the mechanism is not clear, the inventors of the present invention have found that when used in a process under high temperature conditions, adverse conditions such as thermal degradation of the adhesive component are likely to occur.

As (D1), for example, there can be listed: 2-hydroxy-2-methyl-1-phenyl-propane-1-one, 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propane-1-one, 2-hydroxy-1-{4-[4-(2-hydroxy-2-methyl-propionyl)-benzyl]-phenyl}-2-methyl-propane-1-one, oligo(2-hydroxy-2-methyl-1-(4-(1-methylvinyl)phenyl)acetone), etc. Among them, oligo(2-hydroxy-2-methyl-1-(4-(1-methylvinyl)phenyl)acetone) is preferred.

(D1) One type can be used alone, or two or more types can be used in combination.

As (D1), a properly synthesized product or a commercially available product may be used. Examples of commercially available products include: 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propane-1-one, "OMNIRAD659" from IGM RESINS; oligo(2-hydroxy-2-methyl-1-(4-(1-methylvinyl)phenyl)acetone), "ESACURE ONE" or "ESACURE KIP150" from IGM RESINS, etc.

The content (total amount) of (D) in the composition is preferably 0.1 parts by mass or more, more preferably 1 part by mass or more, preferably 20 parts by mass or less, and more preferably 15 parts by mass or less, relative to 100 parts by mass of (B). By making the content of (D) within the above range, the thermal degradation of the adhesive component when used in a process under high temperature conditions can be suppressed, and the curing by active energy rays is fully carried out, so that it is easy to obtain an adhesive layer with appropriately reduced adhesion.

2-1-5. (Optional ingredients)

The composition of one embodiment may contain any component (E) other than the above-mentioned components (A), (B), (C), and (D) within the scope that does not impair the effect of the present invention. As (E), for example, components known as additives for adhesives can be listed. For example, plasticizers, antioxidants, antistatic agents, leveling agents, metal retarders, silane coupling agents, ultraviolet absorbers, hindered amine compounds and other light stabilizers can be selected as needed. In addition, dyes and pigments can also be added for the purpose of coloring.

As a plasticizer, for example, a non-functional acrylic polymer can be used. Examples of the non-functional acrylic polymer include a polymer composed only of an acrylic monomer unit having no functional group other than an acrylate group, and a polymer composed of an acrylic monomer unit having no functional group other than an acrylate group and a non-acrylic monomer unit having no functional group. Since the non-functional acrylic polymer is not cross-linked, it does not affect adhesion.

As antioxidants, there can be listed: phenolic antioxidants (preferably hindered phenolic antioxidants), amine antioxidants, lactone antioxidants, phosphorus antioxidants, sulfur antioxidants, etc. When mixing antioxidants, it is preferred to use phenolic antioxidants from the perspective of durability such as heat resistance and weather resistance of the cured film. Such antioxidants may be used alone or in combination of two or more.

As a metal corrosion inhibitor, from the perspective of compatibility and effectiveness with adhesives, benzotriazole resins can be cited as a better example.

Examples of silane coupling agents include alkyl alkoxysilane compounds such as alkyl substituted alkoxy oligomers, (meth)acryloxypropyl methoxysilane, etc. Examples of ultraviolet light absorbers include benzotriazole compounds, benzophenone compounds, triazine compounds, etc.

Examples of thickening resins include rosin resins, terpene resins, styrene resins, benzofuran resins, xylene resins (preferably alkylphenol-modified xylene resins), etc. When mixing thickening resins, it is preferred to use xylene resins from the perspective of heat resistance. These thickening resins may be used alone or in combination of two or more.

When (E) is contained in the composition, its mixed content (total amount) is preferably 0.1 parts by mass or more, preferably 1 part by mass or more, preferably 15 parts by mass or less, and preferably 10 parts by mass or less, relative to 100 parts by mass of (A) and (B).

The composition of one embodiment can be prepared or manufactured by mixing the above-mentioned components (A), (B), (C), and (D), and, if necessary, adding (E). There is no particular restriction on the mixing order of the components, as long as the components are mixed uniformly.

2-2. <Thermosetting materials>

The above-mentioned active energy ray-curing adhesive is formed by the heat-cured product of the above-mentioned composition (coating liquid). Since the adhesive layer is composed of the above-mentioned active energy ray-curing adhesive, the production of the adhesive layer includes a heating process.

By forming an adhesive layer composed of the above-mentioned active energy ray-curing adhesive from the heat-cured product of the above-mentioned composition, in addition to (B) and (D), the heat-cured products of (A) and (C) also exist in the adhesive layer. According to this structure, even through a process under high temperature conditions such as 180°C for 20 minutes, the reduction of cohesive force caused by thermal degradation of the adhesive component can be suppressed. As a result, by irradiating active energy rays after the process under high temperature conditions, the adhesion of the adhesive layer can be sufficiently reduced, making it difficult to produce adhesive residues on the adherend. This knowledge is the first discovery of the inventors.

The above composition may contain a solvent. In this case, the solvent is used to improve the spreadability of the above composition. Examples of the solvent include: hydrocarbons such as toluene; halogenated hydrocarbons; alcohols; ethers; ketones such as methyl isobutyl ketone; esters; polyols such as ethylene glycol monomethyl ether and their derivatives, etc.

When the above composition contains a solvent, an adhesive layer composed of an active energy ray-curable adhesive is formed while the solvent is removed by heating the composition.

3.<Manufacturing example of adhesive sheet>

An example of manufacturing an adhesive sheet according to an embodiment is as follows. First, the composition according to an embodiment is applied to one surface of a peeling sheet (in the case of no substrate) or a substrate (in the case of a substrate) to form a coating layer having the composition. The coating method may be a known method, such as a roller coating method, a double roller coating (comma coater) method, a slit coating (die coater) method, a reverse coating method, a screen printing method, a gravure coating method, etc.

Next, the coating is dried and cured by heating to form an adhesive layer of an active energy ray-curing adhesive formed by the thermally cured product of the composition. The heating and drying conditions can be appropriately adjusted according to the thickness of the coating, the heat resistance of the coated object (peeling sheet or substrate), etc. For example, it is between 100°C and 200°C and between 0.5 minutes and 10 minutes, preferably between 120°C and 180°C and between 1 minute and 5 minutes.

In one embodiment, the heat-cured product of the composition obtained after heat drying and curing can be stored (left standing) for a specified time. That is, the production of the adhesive layer can include a maintenance process in addition to the heating process. By performing maintenance after heat drying, even if the uncrosslinked parts of (A) and (C) remain, the crosslinking reaction can be completed, which helps to stabilize the performance of the adhesive layer. The maintenance conditions are, for example, 20°C (room temperature) or more and 60°C or less and 3 days or more and 2 weeks or less.

The thickness of the adhesive layer (thickness after heat drying) can be appropriately set according to the purpose, without special limitation, preferably 5μm to 200μm. By making the thickness of the adhesive layer within the above range, the extrusion and stickiness of the adhesive can be suppressed while maintaining the adhesive performance, and the processability can be improved. After the adhesive layer is formed, the peeling sheet can be attached to the exposed surface of the adhesive layer by a known method as needed.

4.<Examples of using adhesive sheets>

An example of using an adhesive sheet according to one embodiment is as follows. First, the adhesive sheet is adhered to the surface of an adherend with the exposed surface of the adhesive layer facing each other. Then, the adhesive sheet adhered to the surface of the adherend is irradiated with active energy rays to reduce the adhesive force of the adhesive layer. The various conditions of the irradiated active energy rays (irradiation intensity (mJ/ ^cm2 ), irradiation time (seconds), etc.) are not particularly limited and can be set as needed. Finally, the adhesive sheet with reduced adhesive force is removed from the adherend.

As described above, the composition of one embodiment contains a specific (B) active energy ray reactive compound (the above (B1)) and a specific (D) photopolymerization initiator (the above (D1)). Therefore, the adhesive layer of the active energy ray curing adhesive formed by the thermosetting product of the composition is polymerized and cured by irradiation with active energy rays, and as a result, the adhesive force after irradiation is effectively reduced compared to before irradiation with active energy rays.

The adhesive layer in the adhesive sheet of one embodiment has appropriate adhesion to the adherend before being irradiated with active energy rays, and can be adhered to the adherend with an adhesive force that is not easy to peel off in various manufacturing processes, wherein the various manufacturing processes include: the manufacturing process of substrates (thin electronic circuit substrates, etc.), including the installation of parts and the processing of components; the manufacturing process of electronic parts and semiconductor parts. On the other hand, after irradiation with active energy rays, the adhesive layer has an effective reduction in adhesion due to the polymerization of (B1) and can be easily peeled off from the adherend.

5. <Adhesion of adhesive layer>

The adhesive force of the adhesive layer in the adhesive sheet of one embodiment before and after the active energy ray irradiation, and the rate of decrease of the adhesive force after the irradiation relative to before the active energy ray irradiation, can be appropriately designed according to the purpose and the conditions of use. In particular, in order to withstand the process under high temperature conditions when used in various manufacturing processes (mentioned above), it is preferable to design as follows.

The adhesion 1 (initial adhesion X1) of the adhesive layer to glass at 23°C is preferably 1.0 (N/25mm) or more, preferably 3.0 (N/25mm) or more, and even more preferably 7.0 (N/25mm) or more. If X1 is less than 1.0 (N/25mm), the adhesion is insufficient, the adhesion to the adherend deteriorates, and it may lead to undesirable conditions such as reduced processability.

After irradiation with active energy rays, the adhesive layer's adhesion to glass at 23°C (adhesion after irradiation X2) is preferably less than 0.2 (N/25mm), and more preferably less than 0.05 (N/25mm). If X2 exceeds 0.2 (N/25mm), it will be difficult to peel off from the adherend, which may lead to adverse conditions such as reduced workability.

The reduction rate of the adhesive force of the adhesive layer (adhesion 2/adhesion 1) is not particularly limited, but is preferably below 0.5, and more preferably below 0.2.

After heating at 180°C for 20 minutes and irradiating with active energy rays, the adhesive layer's adhesion to glass at 23°C (adhesion after heating and irradiation X3) is preferably less than 0.5 (N/25mm), and more preferably less than 0.1 (N/25mm). If X3 exceeds 0.5 (N/25mm), it will be difficult to peel off from the adherend, which may lead to adverse conditions such as reduced workability.

In addition, "adhesion to glass" refers to the adhesion measured by adhering the adhesive layer of the adhesive sheet (25mm wide × 100mm long) to a blue plate glass (3mm thick) (adhesion conditions: 2kg roller back and forth once) and placing it in an environment of temperature 23℃ and humidity 65% for 20 minutes, and then conducting a tensile test on the blue plate glass (peeling speed: 300mm/min, peeling angle 180°).

6.<Purpose of adhesive sheet>

As described above, the adhesive sheet according to one embodiment of the present invention can be used in a wide range of manufacturing processes including substrate (thin electronic circuit substrate, etc.) manufacturing processes (including parts installation and component processing), as well as various manufacturing processes of electronic parts and semiconductor parts, including processes under high temperature conditions (e.g., 180°C, 20 minutes).

Implementation example

The present invention is described in detail below based on experimental examples (including embodiments and comparative examples), but the present invention is not limited to such experimental examples. In the following description, "parts" refers to "parts by mass" and "%" refers to "% by mass".

[Composition of the composition]

The following base polymers were prepared.

‧A1a: Acrylic resin with acidic groups

(Glass transition temperature: -7°C, mass average molecular weight 150,000)

‧A2: Acrylic resin without acidic groups

(Glass transition temperature: -42°C, mass average molecular weight 390,000)

In addition, the above "A1a" is a copolymer of 2-ethylhexyl acrylate (EHA), methyl acrylate (MA) and acrylic acid (AA), and the mass ratio is EHA:MA:AA=25:70:5. The above "A2" is a copolymer of 2-ethylhexyl acrylate (EHA), vinyl acetate (VA) and 2-hydroxyethyl methacrylate (HEMA), and the mass ratio is EHA:VA:HEMA=63.7:35:1.3.

The following active energy ray-reactive compounds were prepared.

‧B1a: Active energy ray-responsive oligomer

(urethane acrylate, 15 acrylate groups, mass average molecular weight 3000)

‧B1b: Active energy ray-responsive oligomer

(urethane acrylate, 10 acrylate groups, mass average molecular weight 6000)

‧B2: Active energy ray reactive monomer

(Dipentaerythritol hexaacrylate, 6 acrylate groups, mass average molecular weight 600)

The following crosslinking agents were prepared.

‧C1a: Crosslinking agent 1 (IPDI series, isophorone diisocyanate trimer)

‧C1b: Crosslinking agent 2 (HDI series, hexamethylene diisocyanate trimer)

The following photopolymerization initiators were prepared.

‧D1: α-Hydroxyacetophenone-based photopolymerization initiator

(Oligosuccinic acid [2-hydroxy-2-methyl-1-[4-(1-methylvinyl)phenyl]propanone])

‧D2: Benzyl methyl ketal-based photopolymerization initiator

(2,2-dimethoxy-1,2-diphenylethane-1-one)

The following were prepared as optional ingredients.

‧E1: Antioxidant (hindered phenols)

(Pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate])

‧E2: Thickener resin

‧E3: Solvent (mixed solvent of toluene and methyl isobutyl ketone)

[Experimental Examples 1 to 19]

1. Preparation of composition

The above-mentioned components are uniformly mixed and dissolved at the solid content ratio (mass conversion) shown in Table 1 to prepare an adhesive composition (coating liquid). In addition, the total solid content of each coating liquid is adjusted to 30% by mass.

2. Preparation of adhesive sheet

The coating liquid obtained in each experimental example was applied to one side of the substrate (PET film with a thickness of 12 μm) using a Baker-type applicator, so that the thickness of the formed adhesive layer was about 10 μm, and then heat-treated at 160°C for 2 minutes to generate a cured product by crosslinking, thereby forming an adhesive layer on one side of the substrate film. Then, a separator (PET film with a thickness of 25 μm and a mold release treatment applied on one side) was attached to the surface of the adhesive layer, so that the mold release treatment surface was in contact with the surface. Then, it was stored in an environment of 40°C and 50% RH for 5 days, that is, it was cured to terminate the crosslinking reaction, thereby preparing the adhesive sheet (substrate/adhesive layer/separator) of each experimental example.

3. Evaluation

For the adhesive sheets obtained in each experimental example, the physical properties of the adhesive layer were evaluated or measured by the following method. The results are shown in Table 1.

(3-1) Initial adhesion (X1)

The adhesive sheet obtained in each experimental example was cut into a size of 25 mm wide × 100 mm long, and the diaphragm was peeled off from the obtained thin sheet as a test piece (substrate/adhesive layer). A blue plate glass (AGC, thickness 3 mm, width 70 mm) was attached to the entire surface of the adhesive layer of the test piece (temperature 23°C, humidity 65%, 2 kg roller back and forth once). A tensile test was performed on the evaluation sample obtained as above. After the evaluation sample was installed in the tensile testing machine, it was placed in an environment with a temperature of 23°C and a humidity of 65% for 20 minutes, and then the tensile test was started. The conditions of the tensile test were a peeling angle of 180° and a peeling speed (pulling speed): 300 mm/min. The load when peeling the adhesive sheet from the blue plate glass was measured, and the maximum load at this time was taken as the initial adhesion X1 of the adhesive sheet, and evaluated according to the following criteria.

◎: 7.0 (N/25mm) or more (excellent adhesion)

○: Less than 7.0 (N/25mm) and above 1.0 (N/25mm) (good adhesion)

×: Less than 1.0 (N/25mm) (insufficient adhesion)

(3-2) Adhesion after irradiation (X2)

Under the same environment (temperature 23°C, humidity 65%), the evaluation sample obtained by the same process as above (3-1) was irradiated with ultraviolet light from the substrate side (irradiation intensity: 220mW/ ^cm2 , integrated light quantity: 190mJ/ ^cm2 ), and then the tensile test was performed in the same manner as above (3-1). Then, the load when the adhesive sheet was peeled off from the blue plate glass was measured, and the maximum load at this time was taken as the adhesive force X2 of the adhesive sheet after irradiation, and the evaluation was performed according to the following criteria.

◎: 0.05 (N/25mm) or less (excellent peeling properties)

○: Greater than 0.05 (N/25mm) and less than 0.2 (N/25mm) (good peeling properties)

X: greater than 0.2 (N/25mm) (insufficient peeling properties)

(3-3) Adhesion after heating and irradiation (X3)

The evaluation sample obtained by the same process as above (3-1) was heated at 180℃ for 20 minutes and then cooled in the same environment (temperature 23℃, humidity 65%). Then, as in above (3-2), after irradiating with ultraviolet rays from the substrate side, a tensile test was performed. Then, the load when the above adhesive sheet was peeled off from the blue plate glass was measured, and the maximum load at this time was taken as the adhesion force X3 after heating and irradiation of the adhesive sheet, and evaluated according to the following criteria.

◎: 0.1 (N/25mm) or less (excellent peeling properties)

○: Greater than 0.1 (N/25mm) and less than 0.5 (N/25mm) (good peeling properties)

X: greater than 0.5 (N/25mm) (insufficient peeling properties)

(3-4) Residual Rubber (X4)

Observe the adhesive surface of the blue glass from which the adhesive sheet was peeled off in (3-3) above using a microscope (magnification 150x) to check whether there are adhesive layer components (residues X4) still attached to the blue glass. Specifically, count the number of attached objects with a particle size (the length of the longest side in the case of irregular shapes) of 1000μm or more and evaluate according to the following criteria.

○: The number of attachments is less than 5 (no residual glue)

×: The number of attachments is more than 5 (there is residual glue)

(3-5) Film-forming properties (adhesion to substrate)

For the test piece obtained by the same process as above (3-1), the adhesion between the adhesive layer and the substrate was visually observed and evaluated according to the following criteria.

○: There is peeling (good adhesion)

×: No peeling (insufficient adhesion)

Table 1

4. Inspection

As shown in Table 1, when (A) in the liquid does not contain a substance with an acidic group (Experimental Example 9), it cannot satisfy one or more of the adhesion (X1, X2, X3), residual glue (X4) and film-forming properties.

Even if (A) is a substance containing an acidic group, if (B) is not contained (Experimental Example 11), or even if (B) is contained, but the mass ratio of (B) to (A) is less than 1.4 (Experimental Example 1) or greater than 4.0 (Experimental Example 8), it is not possible to satisfy at least one of the following conditions: adhesion (X1, X2, X3), residual adhesive (X4), and film-forming property.

Even if (A) contains a substance with an acidic group and the mass ratio of (B) to (A) is within an appropriate range (greater than 1.4 and less than 4.0), if the contained hexafunctional or higher (B) is not an oligomer (Experimental Example 12), or does not contain (C) (Experimental Example 19), or does not contain (D) (Experimental Example 13), or even if (D) is contained but it is not an α-hydroxyacetophenone (Experimental Example 14), then at least one of the adhesion (X1, X2, X3), residual glue (X4) and film-forming properties cannot be satisfied.

In contrast, when (A) contains a substance having an acidic group, the mass ratio of (B) to (A) is within an appropriate range (greater than 1.4 and less than 4.0), (B) contains an oligomer with more than 6 functions, (C) contains, and (D) contains α-hydroxyacetophenones (Experimental Examples 2-7, 10, 15-18), adhesion (X1, X2, X3), residual glue (X4) and film-forming properties can all be satisfied.

Claims (8)

An adhesive sheet having an adhesive layer whose adhesive force is reduced by irradiation with active energy rays, wherein the adhesive layer is formed of a heat-cured adhesive composition, and is composed of an active energy ray-curing adhesive containing a thermal reactant of (A) and (C), and has a thickness of 10 μm to 200 μm, the adhesive composition at least comprises (A), (B), (C) and (D), (A) includes (A1), (B) includes (B1) but does not include (B2), (D) includes (D1) but does not include (D2), and the mass ratio of (B) to (A) is greater than 1.4 and less than 4.0, (A) is an adhesive base polymer having an acidic group, (A1) is an acrylic acid having an acidic group, Acrylic resin having a glass transition temperature in the range of -10°C to 40°C, (B) is an active energy ray reactive compound, (B1) is an active energy ray reactive oligomer having 10 or more free radical reactive groups in one molecule and a mass average molecular weight of 10,000 or less, (B2) is an active energy ray reactive monomer, an oligomer or polymer having less than 10 free radical reactive groups in one molecule, (C) is a crosslinking agent, (D) is a photopolymerization initiator, (D1) is an α-hydroxyacetophenone-based photopolymerization initiator, and (D2) is an alkylphenone-based photopolymerization initiator other than (D1). As in the adhesive sheet of claim 1, wherein (A1) has a mass average molecular weight in the range of 100,000 to 300,000, and further has a dispersion degree (mass average molecular weight/number average molecular weight) in the range of 3 to 9. The adhesive sheet of claim 1, wherein (A1) has an acid value in the range of 10 (mgKOH/g) to 100 (mgKOH/g). An adhesive sheet as claimed in any one of claims 1 to 3, wherein (B1) contains an acrylate group or a methacrylate group as a free radical reactive group. An adhesive sheet as claimed in any one of claims 1 to 3, wherein (D1) comprises oligo(2-hydroxy-2-methyl-1-(4-(1-methylvinyl)phenyl)acetone). The adhesive sheet of any one of claims 1 to 3, wherein (D) is contained in a range of 0.1 to 20 parts by mass relative to 100 parts by mass of (B). An adhesive sheet as claimed in any one of claims 1 to 3, wherein the initial adhesion X1 of the adhesive layer to the glass at 23°C is 1.0 (N/25mm) or more, and after heating at 180°C for 20 minutes and further irradiating with active energy rays, the adhesion X3 after heating and irradiation to the glass at 23°C is 0.5 (N/25mm) or less. The adhesive sheet of any one of claim items 1 to 3 is used in a high temperature environment above 150°C.