TWI829891B - Adhesive composition for heat-resistant adhesive sheet, and heat-resistant adhesive sheet - Google Patents

Abstract

Provided are an adhesive composition for a heat-resistant adhesive sheet, and a heat-resistant adhesive sheet using the same, the adhesive composition comprising a (meth)acrylic copolymer and a cross-linking agent, the (meth)acrylic copolymer comprising: a structural unit derived from N-methylolacrylamide; a structural unit derived from a hydroxy alkyl methacrylate; and a structural unit derived from an alkyl (meth)acrylate, and a mole ratio of a functional group included in the cross-linking agent with respect to a cross-linking functional group included in the (meth)acrylic copolymer being from 0.1 to 1.0.

Description

Adhesive composition for heat-resistant adhesive sheet, and heat-resistant adhesive sheet

The present invention relates to an adhesive composition for a heat-resistant adhesive sheet and a heat-resistant adhesive sheet.

In the heat treatment step during the manufacturing of electronic components represented by Flexible Printed Circuit (FPC), heat-resistant adhesive sheets are used for the purpose of fixing the FPC and protecting the parts. The adhesive layer of the heat-resistant adhesive sheet is required to suppress an excessive increase in the adhesive force when peeling off after heat treatment, to suppress contamination of the adherend, and to suppress deterioration. In addition, as an adherend, copper foil, polyimide, etc. are widely used.

Examples of conventional heat-resistant adhesive sheets include those described in Japanese Patent Application Laid-Open No. 2013-032504. Japanese Patent Application Laid-Open No. 2013-032504 discloses an adhesive that contains an acrylic resin in a specific Tg range by copolymerizing nitrogen-containing monomers as a main component. According to Japanese Patent Application Publication No. 2013-032504, it still protects the surface of the adherend during the heating step above 170°C and can be peeled off from the surface of the adherend. In addition, the evaluation of the examples in Japanese Patent Application Publication No. 2013-032504 was based on the use of SUS plates and the conditions of 180°C and 5 hours.

[Problem to be solved by the invention]

In recent years, heat-resistant adhesive sheets have been required to have a performance that does not increase the adhesive force even after heat treatment at a higher temperature than before, such as 200°C. In addition, generally speaking, when the adherend of a heat-resistant adhesive sheet is, for example, polyimide, when the heat-resistant adhesive sheet is peeled off, the adhesive is likely to remain on the adherend, that is, it is easy to cause adhesion. body pollution. In addition, when the adherend is copper foil, oxidation of the adherend is likely to occur, that is, deterioration of the adherend is likely to occur.

The adhesive described in Japanese Patent Application Laid-Open No. 2013-032504 has low cohesive force, so it is easy to cause floating and peeling of the adhesive layer under high temperature conditions of 200°C. In addition, when the adherend is copper foil, There will be a problem of oxidation of the adherend.

An object to be solved by one embodiment of the present invention is to provide an adhesive composition for a heat-resistant adhesive sheet that, for example, suppresses peeling of the adhesive layer from the adherend even after heat treatment under high temperature conditions of 200° C. or higher. It is excellent in preventing contamination of adherends and inhibiting oxidation of adherends. In addition, another problem to be solved by another embodiment of the present invention is to provide a heat-resistant adhesive sheet using an adhesive composition for a heat-resistant adhesive sheet. [Means to solve the problem]

Means for solving the above-mentioned problems include the following aspects. >1>An adhesive composition for heat-resistant adhesive sheets, containing: A (meth)acrylic copolymer containing a structural unit derived from N-hydroxymethylacrylamide, a structural unit derived from hydroxyalkyl methacrylate, and a structural unit derived from (methyl) The structural units of alkyl acrylate, and cross-linking agent; The ratio of the molar number of the functional groups of the crosslinking agent to the total molar number of the crosslinkable functional groups of the (meth)acrylic copolymer is 0.1 or more and 1.0 or less. >2> The adhesive composition for a heat-resistant adhesive sheet as in >1>, wherein the glass transition temperature of the (meth)acrylic copolymer is less than -40°C. >3> For example, in the adhesive composition for heat-resistant adhesive sheets of >1> or >2>, in the (meth)acrylic copolymer, the content of the structural unit derived from N-hydroxymethylacrylamide is relatively The mass ratio of the content of the structural unit derived from the hydroxyalkyl methacrylate is 0.25 or more and 5.0 or less. >4> The adhesive composition for heat-resistant adhesive sheets according to any one of >1> to >3>, the molar number of the functional group of the cross-linking agent relative to the molar number of the (meth)acrylic copolymer. The ratio of the total molar number of the crosslinkable functional groups is 0.2 or more and 1.0 or less. >5> A heat-resistant adhesive sheet having an adhesive layer, and the adhesive layer is a cross-linked product of the adhesive composition for a heat-resistant adhesive sheet according to any one of >1> to >4>. [Effects of the invention]

According to one embodiment of the present invention, it is possible to provide an adhesive composition for a heat-resistant adhesive sheet that, for example, suppresses the adhesive composition from being peeled off from the adherend even after heat treatment under high temperature conditions of 200° C. or higher. Excellent in preventing contamination and inhibiting oxidation of adherends. Furthermore, according to another embodiment of the present invention, a heat-resistant adhesive sheet using an adhesive composition for a heat-resistant adhesive sheet can be provided.

The content of the present invention will be described in detail below. The description of the constituent elements described below is based on a representative embodiment of the present invention, but the present invention is not limited to such an embodiment. The numerical range expressed by "～" in this specification means the range including the numerical values written before and after "～" as the minimum value and the maximum value respectively. In addition, the amount of each component in the composition in this specification, when several substances corresponding to each component are used together in the composition, unless otherwise specified, means the total amount of the several substances corresponding to the component. meaning.

In addition, the term "step" in this specification does not only refer to independent steps. Even if it cannot be clearly distinguished from other steps, as long as the expected purpose of the step is achieved, it is included in this term. In addition, in the present invention, "mass %" and "weight %" have the same meaning, and "mass part" and "weight part" have the same meaning. In addition, in the present invention, a combination of two or more ideal aspects is a more preferable aspect.

(Meth)acrylic acid means at least one of acrylic acid and methacrylic acid, and (meth)acrylate means at least one of acrylic acid ester and methacrylic acid ester. The (meth)acrylic copolymer in this specification refers to a polymer formed by polymerizing at least a monomer having a (meth)acrylyl group as the main component among the monomers constituting it. meaning. The main component in a (meth)acrylic copolymer means that the content rate (so-called content ratio; the same applies below) of the monomer components forming the polymer is the largest (mass %), for example, (methyl ) acrylic copolymer means a monomer in which the content of structural units formed from a monomer having a (meth)acrylyl group is 50% by mass or more of the total structural units. The adhesive layer is a layer obtained by substantially cross-linking a (meth)acrylic copolymer and a cross-linking agent, and means, for example, a solid or gel layer.

(Adhesive composition for heat-resistant adhesive sheets) The adhesive composition for heat-resistant adhesive sheets of the present invention (hereinafter sometimes referred to as "adhesive composition") contains: (Meth)acrylic copolymer (hereinafter, sometimes referred to as "specific (meth)acrylic copolymer") containing a structure derived from N-methylolacrylamide Units, structural units derived from hydroxyalkyl methacrylate, and structural units derived from alkyl (meth)acrylate, and cross-linking agent; The ratio of the molar number of the functional groups of the crosslinking agent to the total molar number of the crosslinkable functional groups of the (meth)acrylic copolymer is 0.1 or more and 1.0 or less. As a result of in-depth research, the inventors of the present invention have found that the adhesive composition of the present invention, by having the above-mentioned structure, can provide an adhesive layer that, for example, can inhibit the adhesive layer from being adhered even after heat treatment at a high temperature of 200°C or above. It is excellent in preventing contamination of the adherend when the adhesive layer is peeled off and inhibiting oxidation of the adherend. The detailed mechanism for obtaining the above effects is not yet clear, but it is presumed to be as follows. In addition, in this specification, "excellent in inhibiting contamination of the adherend" means excellent in contamination resistance. In addition, in this specification, "excellent in inhibiting oxidation of the adherend" means excellent in oxidation resistance.

The adhesive composition of the present invention contains a specific (meth)acrylic copolymer, and the specific (meth)acrylic copolymer contains a structural unit derived from N-hydroxymethylacrylamide. Because N-methylol acrylamide will self-crosslink under high temperature conditions, the adhesive composition of the present invention containing structural units derived from N-methylol acrylamide can be used even at a high temperature of about 200°C. Under certain conditions, a reasonably high cohesion can still be maintained. Therefore, when the adhesive composition of the present invention is used in the adhesive layer of a heat-resistant adhesive sheet, even if the adherend is, for example, copper foil, the adhesion between the adherend and the adhesive layer is good and the floating of the adhesive layer can be suppressed. Oxidation of the adherend caused by peeling and peeling. In addition, the adhesive composition of the present invention containing structural units derived from N-hydroxymethylacrylamide can self-crosslink even under high temperature conditions and can maintain appropriately high cohesive force. Therefore, when the adhesive composition of the present invention is used in the adhesive layer of a heat-resistant adhesive sheet, even if the adherend is made of polyimide, for example, it can still prevent the adhesive layer from being adhered when peeling off the adherend. Residues of the adhesive layer on the body (contamination by the adhesive body). Furthermore, the adhesive composition of the present invention contains a specific (meth)acrylic copolymer containing a structural unit derived from hydroxyalkyl methacrylate. The above-mentioned structural units derived from hydroxyalkyl methacrylate have a tendency that part of the structural units decomposes (depolymerizes) under high temperature conditions, resulting in a moderate decrease in cohesive force. Therefore, it is presumed that the increase in adhesive force after heat treatment under high temperature conditions of about 200°C, for example, can be suppressed. In the adhesive composition of the present invention, it is presumed that the structural unit derived from N-methylolacrylamide and the structural unit derived from hydroxyalkyl methacrylate contained in the specific (meth)acrylic copolymer play a role. With complementary functions, even after heat treatment under high temperature conditions, the cohesive force will not increase or decrease excessively. Therefore, when the adhesive composition of the present invention is used in the adhesive layer of a heat-resistant adhesive sheet, heat treatment can be suppressed. The adhesive force of the subsequent adhesive layer increases, and it is excellent in suppressing contamination and deterioration of the adherend. Although the detailed mechanism is not yet clear, in more detail, the decomposition of a part of the structural units derived from the hydroxyalkyl methacrylate during heat treatment is related to N-methylol acryl in an environment of 200°C or higher, for example. The increase in cohesion caused by the self-crosslinking reaction of the amine interacts with each other to bring the cohesion into an appropriate range. In addition, the adhesive composition of the present invention contains a specific (meth)acrylic copolymer, and the specific (meth)acrylic copolymer contains a composition derived from N-hydroxymethylacrylamide that undergoes self-crosslinking. unit, it is excellent in suppressing contamination of the adherend that is presumably caused by partial decomposition (depolymerization) of one of the constituent units derived from hydroxyalkyl methacrylate. Furthermore, in the adhesive composition of the present invention, the molar ratio of the functional group content of the crosslinking agent to the total molar number of crosslinkable functional groups of the specific (meth)acrylic copolymer is 0.1 or more. And it is less than 1.2, so the adhesive composition will be properly cross-linked, the cohesion force can be appropriately obtained, and an appropriately heat-resistant adhesive composition for the adhesive sheet can be obtained. Hereinafter, the details of each component contained in the adhesive composition of the present invention will be described.

In addition, in this specification, high-temperature conditions mean temperature conditions of at least 200°C or higher under atmospheric pressure.

>Specific (meth)acrylic copolymer> The adhesive composition of the present invention contains: (meth)acrylic copolymer (specific (meth)acrylic copolymer), and the (meth)acrylic copolymer contains N-hydroxymethylacrylamide. A structural unit, a structural unit derived from hydroxyalkyl methacrylate, and a structural unit derived from alkyl (meth)acrylate.

>>Structural units derived from N-hydroxymethylacrylamide>> The specific (meth)acrylic copolymer contains a structural unit derived from N-methylolacrylamide. N-hydroxymethylacrylamide may be a commercially available product or may be synthesized.

The content of the structural units derived from N-methylolacrylamide is preferably 0.1 mass based on all the structural units constituting the specific (meth)acrylic copolymer from the viewpoint of stain resistance and oxidation resistance. % to 20 mass%, more preferably 1.0 to 15 mass%, further preferably 1.5 to 11 mass%, especially 2.0 to 9.0 mass%.

>>Structural units derived from hydroxyalkyl methacrylate>> The specific (meth)acrylic copolymer contains a structural unit derived from hydroxyalkyl methacrylate. Since some of the structural units derived from hydroxyalkyl methacrylate tend to decompose (depolymerize) under high-temperature conditions and moderately reduce the cohesive force of the adhesive layer, it is presumed that they can suppress the decomposition under high-temperature conditions. The increase in adhesion after heat treatment can further inhibit the contamination and deterioration of the adherend. In addition, the tendency of the cohesion force to decrease due to the decomposition (depolymerization) of a part of the structural units derived from hydroxyalkyl methacrylate is greater than that of hydroxyalkyl acrylate. The structural unit derived from hydroxyalkyl methacrylate may contain one type alone or two or more types.

Examples of the hydroxyalkyl methacrylate monomer that forms a structural unit derived from hydroxyalkyl methacrylate include a monomer containing at least one hydroxyl group and a methacryloxy group per molecule.

Examples of the hydroxyalkyl methacrylate monomer include 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 3-hydroxypropyl methacrylate, and -methacrylate. 4-Hydroxybutyl methacrylate, 6-hydroxyhexyl methacrylate, 10-hydroxydecyl methacrylate, 12-hydroxylauryl methacrylate, 3-methyl-3-hydroxybutyl methacrylate, methacrylate 1,1-dimethyl-3-hydroxybutyl acrylate, 1,3-dimethyl-3-hydroxybutyl methacrylate, 2,2,4-trimethyl-3 methacrylate -Hydroxypentyl ester, 2-ethyl-3-hydroxyhexyl methacrylate, etc.

From the viewpoint of stain resistance and oxidation resistance, the hydroxyalkyl methacrylate is more preferably a hydroxyalkyl methacrylate having 1 to 10 carbon atoms, and further preferably a hydroxyl group having 2 to 8 carbon atoms. Alkyl hydroxyalkyl methacrylate.

The content of the structural units derived from hydroxyalkyl methacrylate is preferably 0.1 mass % to 10 mass %, more preferably 0.5 mass % to all the structural units of the specific (meth)acrylic copolymer. 8% by mass, preferably 1.5% by mass to 6% by mass, and particularly preferably 2.5% by mass to 5% by mass.

>>Structural units derived from alkyl (meth)acrylate>> The specific (meth)acrylic copolymer contains a structural unit derived from an alkyl (meth)acrylate. By containing structural units derived from alkyl (meth)acrylate, the specific (meth)acrylic copolymer can provide the adhesive layer formed from the adhesive composition of the present invention with initial and heat treatment properties. All have excellent adhesion. The specific (meth)acrylic copolymer may contain a single type of structural unit derived from an alkyl (meth)acrylate, or may contain two or more types.

The (meth)acrylic acid alkyl ester monosystem forming the structural unit derived from the (meth)acrylic acid alkyl ester is not particularly limited. For example, it can be a substituted or unsubstituted (meth)acrylic acid alkyl ester, which is easy to consider. From the viewpoint of performing addition polymerization with the above-mentioned hydroxyalkyl methacrylate monomer and N-hydroxymethylacrylamide, a substituted or unsubstituted alkyl acrylate is preferred. The alkyl group in the alkyl (meth)acrylate is not particularly limited and may be linear, branched or cyclic. In addition, considering the adhesive force of the adhesive layer to the adherend and the close contact with the base material, the carbon number of the above-mentioned alkyl group is preferably 1 to 18, and more preferably 1 to 12.

The alkyl (meth)acrylate is not particularly limited, and examples thereof include methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, and (meth)acrylic acid. Isobutyl ester, 2nd butyl (meth)acrylate, 3rd butyl (meth)acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, (meth)acrylic acid-2- Ethylhexyl, n-nonyl (meth)acrylate, isononyl (meth)acrylate, n-decyl (meth)acrylate, n-dodecyl (meth)acrylate, stearyl (meth)acrylate Ester, lauryl (meth)acrylate, cyclohexyl (meth)acrylate, isocamphenyl (meth)acrylate, etc.

Among these, from the viewpoint of adhesion, the alkyl (meth)acrylate is preferably an alkyl acrylate, and more preferably an alkyl acrylate selected from the group consisting of methyl acrylate (MA) and tert-butyl acrylate ( At least one monomer selected from the group consisting of t-BA) and n-butyl acrylate (n-BA) is more preferably n-butyl acrylate (n-BA).

Regarding the content of structural units derived from alkyl (meth)acrylate in a specific (meth)acrylic copolymer, from the viewpoint of adhesion, relative to all structural units of the specific (meth)acrylic copolymer , preferably 50 mass % or more and 99.95 mass % or less, more preferably 60 mass % or more and 99.95 mass % or less, further preferably 70 mass % or more and 99.95 mass % or less, especially 80 mass % or more and 99.95 mass % the following.

-Mass ratio of structural units derived from N-methylolacrylamide to structural units derived from hydroxyalkyl methacrylate- The mass ratio of the content of the structural unit derived from N-hydroxymethylacrylamide to the content of the structural unit derived from hydroxyalkyl methacrylate is preferably 0.1 or more and 5.0 from the viewpoint of contamination resistance and oxidation resistance. below, more preferably 0.25 or more and 5.0 or less, further preferably 0.3 or more and 4.0 or less, especially 0.5 or more and 3.5 or less.

>>Other structural units>> The specific (meth)acrylic copolymer may contain a structural unit derived from the above-mentioned N-hydroxymethylacrylamide, a structural unit derived from a hydroxyalkyl methacrylate, and a structural unit derived from the hydroxyalkyl methacrylate, within the range in which the effects of the present invention are exerted. Structural units other than the structural units of alkyl (meth)acrylate (hereinafter also referred to as "other structural units"). The monomers constituting other structural units are not particularly limited as long as they can be copolymerized with the above-mentioned N-hydroxymethylacrylamide, hydroxyalkyl methacrylate monomer and alkyl (meth)acrylate. Choose appropriately according to the purpose.

Monomers constituting other structural units include carboxyl groups, oxyalkylene groups, glycidyl groups, amide groups, N-substituted amide groups, tertiary amine groups, and hydroxyl groups (but do not correspond to N -Monomers with functional groups such as hydroxymethylacrylamide and hydroxyalkyl methacrylate.), or polyfunctional (meth)acrylic monomers, aromatic monovinyl monomers, cyanide Vinyl monomers and (meth)acrylic monomers with aromatic rings.

Examples of the monomer having a carboxyl group include acrylic acid (AA), methacrylic acid, crotonic acid, maleic anhydride, fumaric acid, itaconic acid, glutaconic acid, citraconic acid, and ω-carboxy-polymer. Caprolactone mono(meth)acrylate (e.g., ω-carboxy-polycaprolactone (n≒2) monoacrylate), succinate (e.g., 2-propenyloxyethyl succinate), formic acid Vinyl ester, vinyl acetate, vinyl propionate, vinyl neodecanoate, etc.

Examples of the monomer having an oxyalkylene group include methoxyethyl (meth)acrylate, 2-(ethoxyethoxy)ethyl acrylate, and polyethylene glycol (meth)acrylic acid. ester, polyethylene glycol methoxy (meth)acrylate, polypropylene glycol methoxy (meth)acrylate, polypropylene glycol (meth)acrylate and methoxypolyethylene glycol (meth)acrylate.

Examples of the monomer having a glycidyl group include glycidyl (meth)acrylate, 3,4-epoxycyclohexylmethyl (meth)acrylate, glycidyl vinyl ether, 3 , 4-epoxycyclohexyl vinyl ether, epoxypropyl (meth) allyl ether, 3,4-epoxy cyclohexyl (meth) allyl ether, etc.

Examples of the monomer having a amide group or an N-substituted amide group include acrylamide, methacrylamide, N-methyl(meth)acrylamide, and N-ethyl(methyl) Acrylamide, N-methoxymethyl(meth)acrylamide, N-ethoxymethyl(meth)acrylamide, N-propoxymethyl(meth)acrylamide, N -Butoxymethyl (meth)acrylamide, N-tert-butylacrylamide, N-octyl acrylamide, diacetone acrylamide, hydroxyethylacrylamide, etc.

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

Examples of the monomer having a hydroxyl group other than N-hydroxymethylacrylamide and hydroxyalkyl methacrylate include 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, and 4-acrylate. Hydroxybutyl ester, 6-hydroxyhexyl acrylate, etc.

Examples of the polyfunctional (meth)acrylic monomer include 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, and neopentyl glycol. Di(meth)acrylate, polyethylene glycol di(meth)acrylate, caprolactone modified dicyclopentenyl di(meth)acrylate, ethylene oxide modified di(meth)acrylic acid Ester, di(meth)acryloyloxyethyl isocyanurate, tricyclodecane dimethanol (meth)acrylate, dimethylol dicyclopentane di(meth)acrylate, epoxy Ethane modified hexahydrophthalate di(meth)acrylate, tricyclopentane dimethanol (meth)acrylate, neopentyl glycol modified trimethylpropane di(meth)acrylate, tricyclopentane dimethanol (meth)acrylate, Hydroxymethylpropane tri(meth)acrylate, dineopenterythritol tri(meth)acrylate, diglyceryl tetra(meth)acrylate, neopentylerythritol tetra(meth)acrylate, dineopenterythritol Tetraol hexa(meth)acrylate, etc.

Examples of the aromatic monovinyl monomer include styrene, α-methylstyrene, tert-butylstyrene, p-chlorostyrene, chloromethylstyrene, vinyltoluene, and vinylpyridine. Examples of the vinyl cyanide-based monomer include acrylonitrile and methacrylonitrile.

Examples of the (meth)acrylic monomer having an aromatic ring include phenoxyethyl (meth)acrylate, benzyl (meth)acrylate, and phenoxydiethylene glycol (methyl) Acrylates, ethylene oxide (EO)-modified cresol (meth)acrylate, ethylene oxide (EO)-modified nonylphenol (meth)acrylate, hydroxyethylated β-naphthol acrylate , diphenyl (meth)acrylate.

The specific (meth)acrylic copolymer may contain other structural units, but from the viewpoint of contamination resistance and oxidation resistance, it is preferable not to contain other structural units. In particular, it is preferable not to contain monomers having hydroxyl groups other than N-hydroxymethylacrylamide and hydroxyalkyl methacrylate. When other structural units are contained, the content of other structural units is preferably 5 mass % or less, more preferably less than 1 mass %, based on all the structural units of the specific (meth)acrylic copolymer. It is further preferably less than 0.1% by mass.

In the adhesive composition of the present invention, the content of the specific (meth)acrylic copolymer can be appropriately adjusted according to the purpose. Considering the adhesive force, it is preferably 80% by mass based on the total solid content of the adhesive composition. % to 99 mass%, more preferably 85 mass% to 99 mass%, further preferably 90 mass% to 98 mass%. In addition, the total mass of solid content means the total mass of the residue after excluding volatile components such as solvents from the adhesive composition.

>>Weight average molecular weight (Mw) of specific (meth)acrylic copolymer>> The weight average molecular weight (Mw) of the specific (meth)acrylic copolymer is not particularly limited, but from the viewpoint of improving adhesion, it is preferably 50,000 to 1,000,000, more preferably 100,000 to 800,000, and further preferably 20 10,000 to 600,000. The weight average molecular weight can be adjusted by polymerization reaction temperature, time, amount of organic solvent, etc.

[Measurement method of weight average molecular weight (Mw)] The weight average molecular weight (Mw) of a specific (meth)acrylic copolymer is determined by the following measurement method. More specifically, the weight average molecular weight (Mw) can be obtained by measuring according to the following (1) to (3). (1) Coat the solution of the specific (meth)acrylic copolymer on release paper and dry it at 100° C. for 1 minute to obtain a film-like specific (meth)acrylic copolymer. (2) The specific (meth)acrylic copolymer in film form obtained in the above (1) is dissolved in tetrahydrofuran to obtain a solid content of 0.2 mass %. (3) Under the following conditions, use gel permeation chromatography (GPC) to measure the weight average molecular weight (Mw) of the specific (meth)acrylic copolymer in the form of a standard polystyrene conversion value.

(condition) GPC: HLC-8220 GPC [Tosoh Co., Ltd.] Column: Use 4 pieces of TSK-GEL GMHXL [manufactured by Tosoh Co., Ltd.] Mobile phase solvent: tetrahydrofuran Flow rate: 0.8mL/minute Tube string temperature: 40℃

-Glass transition temperature- From the viewpoint of improving the adhesion of the obtained adhesive layer and suppressing the increase in adhesion after heat treatment due to excessive increase in cohesion, the glass transition temperature (Tg) of the specific (meth)acrylic copolymer is preferably -60 ℃ ~ -5 ℃, more preferably -55 ℃ ~ -30 ℃, further preferably -50 ℃ or above but not reaching -40 ℃.

The glass transition temperature (Tg) of a specific (meth)acrylic copolymer is the molar average glass transition temperature calculated by the following formula.

[Number 1] In the formula, Tg ₁ , Tg ₂ , ... and Tg _n represent the absolute temperature (unit: K; the same applies below.) represents the glass transition temperature. m ₁ , m ₂ , ... and m _n are the molar fractions of respective monomer components.

In addition, "glass transition temperature expressed as absolute temperature (K) of homopolymer" refers to the glass transition temperature expressed as absolute temperature (K) of a homopolymer obtained by polymerizing the monomer alone. The glass transition temperature of the homopolymer was measured using a differential scanning calorimetry device (DSC) (manufactured by Ta Instruments Japan Inc., product name: DSC2500) in a nitrogen flow, with a sample of 10 mg, and the temperature was raised. The measurement was carried out at a speed of 10°C/min, and the inflection point of the obtained DSC curve was taken as the glass transition temperature of the homopolymer.

The "glass transition temperature of the homopolymer expressed in degrees Celsius (unit: °C; the same applies below)" of the representative monomers is: methyl acrylate is 5 °C, ethyl acrylate is -27 °C, and normal acrylic acid Butyl ester is -57℃, 2-ethylhexyl acrylate is -76℃, N-hydroxymethylacrylamide is 100℃, hydroxyethylacrylamide is 98℃, dimethylaminoethyl acrylate is 18℃, 2-hydroxyethyl methacrylate is 55℃, 2-hydroxybutyl methacrylate is 26℃, 2-hydroxyethyl acrylate is -15℃, and 4-hydroxybutyl acrylate is -39℃, acrylic is 163℃. For example, by using these representative monomers, the above-mentioned glass transition temperature can be appropriately adjusted. Additionally, absolute temperature (K) can be converted to Celsius (°C) by subtracting 273 from absolute temperature (K), and Celsius (°C) can be converted to by adding 273 to Celsius (°C). Absolute temperature (K).

[Production method of specific (meth)acrylic copolymer] The production method of the specific (meth)acrylic copolymer is not particularly limited, and it can be produced by polymerizing monomers by methods such as solution polymerization, emulsion polymerization, and suspension polymerization. In addition, when preparing the adhesive composition of the present invention after manufacturing, considering that the processing steps are relatively simple and can be carried out in a short time, the specific (meth)acrylic copolymer is preferably manufactured by solution polymerization.

Generally speaking, solution polymerization can be performed by adding predetermined organic solvents, monomers, polymerization initiators, and chain transfer agents as required into a polymerization tank in a nitrogen stream or at the reflux temperature of the organic solvent while stirring. A method of heating and reacting for several hours. In addition, by adjusting the reaction temperature, time, solvent amount, and catalyst type and amount, the weight average molecular weight of a specific (meth)acrylic copolymer can be adjusted to a desired value.

The organic solvent used in the polymerization reaction of the specific (meth)acrylic copolymer is not particularly limited, and examples thereof include aromatic hydrocarbon compounds, aliphatic or alicyclic hydrocarbon compounds, ester compounds, ketone compounds, Glycol ether compounds, alcohol compounds, etc. These organic solvents may be used individually by 1 type each, or in mixture of 2 or more types.

Examples of the organic solvent used in the polymerization reaction include benzene, toluene, ethylbenzene, n-propylbenzene, tert-butylbenzene, o-xylene, m-xylene, p-xylene, tetralin, decahydronaphthalene, Aromatic hydrocarbons represented by hydronaphthalene and aromatic naphtha are organic solvents; n-hexane, n-heptane, n-octane, isooctane, n-decane, dipentene, petroleum spirit, petroleum naphtha, Organic solvents of aliphatic hydrocarbons or alicyclic hydrocarbons represented by turpentine; ethyl acetate, n-butyl acetate, n-pentyl acetate, 2-hydroxyethyl acetate, 2-butoxyethyl acetate Esters such as , 3-methoxybutyl acetate, and methyl benzoate are organic solvents; acetone, methyl ethyl ketone, methyl isobutyl ketone, isophorone, cyclohexanone, and methylcyclohexanone Ketones represented by hexanone are organic solvents; ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, and diethylene glycol monoethyl Ethylene glycol ether organic solvents represented by ether and diethylene glycol monobutyl ether; as well as methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, second butanol, and Alcohols such as tributyl alcohol are organic solvents.

Examples of the polymerization initiator include organic peroxides and azo compounds that can be used in ordinary polymerization methods.

>Cross-linking agent> The adhesive composition of the present invention contains a cross-linking agent. Examples of the cross-linking agent include isocyanate-based cross-linking agents, epoxy-based cross-linking agents, oxazoline-based cross-linking agents, carbodiimide-based cross-linking agents, metal chelate compounds, etc., considering high temperature conditions. From the following viewpoints of contamination resistance and oxidation resistance after heat treatment, an isocyanate-based cross-linking agent or a metal chelating compound is preferred, and an isocyanate-based cross-linking agent is more preferred. The cross-linking agent may be contained individually by 1 type, or may contain 2 or more types.

Examples of the isocyanate cross-linking agent include compounds having two or more isocyanate groups per molecule (polyisocyanate compounds). Examples of the isocyanate cross-linking agent include aromatic compounds such as xylyl diisocyanate (XDI), diphenylmethane diisocyanate, triphenylmethane triisocyanate, and toluene diisocyanate (TDI). Polyisocyanate compounds; aliphatic or alicyclic compounds such as hexamethylene diisocyanate (HMDI), pentamethylene diisocyanate (PDI), isophorone diisocyanate, hydrogenated products of aromatic polyisocyanate compounds, etc. Polyisocyanate compounds, etc. In addition, examples of the polyisocyanate compound include dimers, trimers, or pentamers of the above-mentioned polyisocyanate compounds, adducts of the above-mentioned polyisocyanate compounds and polyol compounds such as trimethylolpropane, and the above-mentioned polyisocyanate compounds. Biuret form of isocyanate compound, etc.

As the polyisocyanate compound, commercially available products can be used. Examples of commercially available polyisocyanate compounds include "Coronate (registered trademark) HX", "Coronate (registered trademark) HL-S", "Coronate (registered trademark) L", "Coronate (registered trademark) L45E", "Coronate (registered trademark) 2031", "Coronate (registered trademark) 2037", "Coronate (registered trademark) 2234", "Coronate (registered trademark) 2785", "aquanate (registered trademark) 200", and " aquanate (registered trademark) 210" [the above is Tosoh Co., Ltd.]; "Sumidur (registered trademark) N3300", "Desmodur (registered trademark) N3400", and "Sumidur (registered trademark) N-75" [the above is Sumika Covestro Urethane Co., Ltd.]; "DURANATE (registered trademark) E-405-80T", "DURANATE (registered trademark) AE700-100", "DURANATE (registered trademark) 24A-100", and "DURANATE (registered trademark) )TSE-100" [the above is Asahi Kasei Co., Ltd.]; and "TAKENATE (registered trademark) D-110N", "TAKENATE (registered trademark) D-120N", "TAKENATE (registered trademark) M-631N", "MT -OLESTER (registered trademark) NP1200", and "STABiO (registered trademark) XD-340N" [the above are Mitsui Chemicals Co., Ltd.].

Among these, considering the stain resistance and oxidation resistance after heat treatment under high temperature conditions, the cross-linking agent is "Coronate" of the trimethylolpropane adduct of toluene diisocyanate. L45E" is more ideal.

As for metal chelate compounds, aluminum chelates represented by bis(ethyl acetyl acetate)aluminum monoacetylpyruvate, aluminum ginseng(ethyl acetyl acetate), and aluminum ginseng(acetyl acetylpyruvate) can be cited. Compounds, titanium chelate compounds, zirconium chelate compounds, cobalt chelate compounds, etc.

As the metal chelate compound, commercially available products can be used. Examples of commercially available metal chelate compounds include "Aluminum Chelate A", "Aluminum Chelate D", and "ALCH-TR" [Kawaken Fine Chemicals Co., Ltd.].

>>The ratio of the molar number of the functional groups of the cross-linking agent to the total molar number of the cross-linkable functional groups of the (meth)acrylic copolymer>> The ratio (molar ratio) of the molar number of the functional groups of the crosslinking agent to the total molar number of the crosslinkable functional groups of the (meth)acrylic copolymer is 0.1 or more and 1.0 or less. If the above molar ratio is within the above range, decomposition (depolymerization) of a part of the structural units derived from the hydroxyalkyl methacrylate due to heat treatment under high temperature conditions and N-methylol acrylate The complementary effect caused by the self-crosslinking reaction of amines becomes more obvious, the cohesion becomes more appropriate, the increase in adhesive force after heat treatment under high temperature conditions can be suppressed, and the contamination and deterioration of the adherend can be suppressed. Considering the above point of view, the molar ratio is preferably 0.2 or more and 1.0 or less, more preferably 0.25 or more and 0.9 or less, further preferably 0.25 or more and 0.7 or less, especially 0.25 or more and 0.6 or less, most preferably It is 0.3 or more and 0.5 or less.

As for the cross-linking functional group that the (meth)acrylic copolymer has, the cross-linking functional group in the structural unit derived from N-methylol acrylamide is N-hydroxymethyl, which is derived from the hydroxyl group of methacrylic acid. The crosslinking functional group in the structural unit of the alkyl ester is hydroxyl group. The (meth)acrylic copolymer contains, as other structural units, structural units derived from a monomer having a crosslinkable functional group (hereinafter also referred to as “other structural units derived from a monomer having a crosslinkable functional group”). When, in addition to the above-mentioned N-hydroxymethyl and hydroxyl groups, the cross-linking functional groups contained in other structural units also correspond to the cross-linking functional groups of the (meth)acrylic copolymer. As for the cross-linking functional group possessed by other structural units, as long as it is a functional group capable of forming a cross-linked structure through a cross-linking reaction with a cross-linking agent, examples thereof include carboxyl group, ketone group, hydroxyl group, amide group, Functional groups such as N-substituted amide group and epoxy group.

The above molar ratio can be determined by the molar number of the functional groups that the cross-linking agent has (the following formula (1)) and the total molar number of the cross-linkable functional groups that the (meth)acrylic copolymer has (the following formula) (2)) can be obtained by formula (3). In addition, the functional group of the cross-linking agent refers to a group that can carry out a cross-linking reaction with the cross-linking functional group of the above-mentioned (meth)acrylic copolymer. For example, when the cross-linking agent is an isocyanate-based cross-linking agent, the functional group Refers to isocyanate group.

In addition, when the cross-linking agent is a metal chelate compound, considering that the hydroxyl group contained in the above (meth)acrylic copolymer is coordinately bonded with the central metal in the metal chelate compound, by replacing the valence of the central metal is the number of functional groups, the equivalent weight (molar number) of the metal chelate compound used in the above calculation of the molar ratio can be obtained. In the present invention, for example, if the valence of the central metal in the aluminum chelate compound is 3, then the aluminum chelate compound can be calculated as having 3 moles of functional groups per 1 mole. The equivalent weight of the metal chelate compound is a value calculated by the following formula. Equivalent=(A×B/C)/(D ₁ ×E ₁ /F ₁ +D ₂ ×E ₂ /F ₂ +……+D _n ×E _n ×F _n ) A=metal of metal chelate compound Valence B = number of parts by mass of the metal chelate compound (amount as solid content) C = molecular weight of the metal chelate compound D ₁ , D ₂ ,...D _n = used in specific (meth)acrylic copolymers Content rate of each monomer with a cross-linkable functional group in all monomers (mass %) E ₁ , E ₂ ,...E _n = content of each monomer with a cross-linkable functional group in 1 molecule The number of linking functional groups F ₁ , F ₂ , ... F _n = the molecular weight of each monomer having a cross-linking functional group used in the specific (meth)acrylic copolymer. In addition, n represents the monomer used. The number of types, for example, when one type of (meth)acrylic monomer is used, only D ₁ is used in the calculation, and D ₂ ...D _n is not used.

The molar number of the functional group of the cross-linking agent used in the calculation of the molar ratio can be calculated by using the content rate of the functional group in the cross-linking agent, the solid content of the cross-linking agent, and the blending amount (added mass parts ), obtained by the following equation (1).

The mole number of the functional group in the cross-linking agent (unit: mmol/100g of solid content of the specific (meth)acrylic copolymer) =[(Content rate of functional groups in the cross-linking agent (unit: mass %) × blending amount of the cross-linking agent (unit: g))/solid content of the cross-linking agent (unit: mass %)]/functional group Molecular weight (unit: g/mol) × 1000... Formula (1)

The total number of moles of the cross-linkable functional groups of the specific (meth)acrylic copolymer (unit: mmol/100g of solid content of the specific (meth)acrylic copolymer) =[Content rate of structural units derived from N-methylolacrylamide in the specific (meth)acrylic copolymer (unit: mass %)/molecular weight of N-methylolacrylamide (unit: g/ mol) × the number (valence) of N-hydroxymethyl groups in the structural units derived from N-hydroxymethylacrylamide × 1000] + [hydroxyl groups derived from methacrylic acid in the specific (meth)acrylic copolymer Content rate of the structural units of the alkyl ester (unit: mass %) / molecular weight of hydroxyalkyl methacrylate (unit: g/mol) × number of hydroxyl groups derived from the structural units of hydroxyalkyl methacrylate (Valence) × 1000] + [Content of other structural units derived from the monomer having a cross-linkable functional group in the specific (meth)acrylic copolymer (unit: mass %) / having a cross-linkable functional group The molecular weight of the monomer (unit: g/mol) × the number (valency) of cross-linking functional groups in other structural units × 1000]]... Formula (2)

The ratio of the molar number of the functional groups in the cross-linking agent to the total molar number of the cross-linkable functional groups of the specific (meth)acrylic copolymer = the above formula (1)/the above formula (2)... Formula (3)

There is no particular restriction on the content of the cross-linking agent, but from the viewpoint of contamination resistance and oxidation resistance, the content is calculated as an active ingredient conversion value based on 100 parts by mass of the total structural units of the specific (meth)acrylic copolymer. In total, it is preferably 0.1 part by mass or more and 20 parts by mass or less, and more preferably 1 part by mass or more and 10 parts by mass or less.

-Cross-linking catalyst- The adhesive composition of the present invention may also contain a cross-linking catalyst. When the adhesive composition of the present invention contains a cross-linking catalyst, even when it contains a monomer with a large molecular structure, the cross-linking reaction will still proceed easily, and an adhesive layer with a high cross-linking density can be formed. The durability and reworkability under high temperature conditions are more likely to be excellent. When the adhesive composition of the present invention contains a cross-linking catalyst, the cross-linking catalyst may contain only one type or two or more types.

As the cross-linking catalyst, a known cross-linking catalyst that can be used in adhesive compositions can be appropriately used. The cross-linking catalyst is not particularly limited, and examples include 1,2-dimethylimidazole, 1-benzyl-2-methylimidazole, 1-benzyl-2-phenylimidazole, and 2, Imidazole compounds are represented by 3-dihydro-1H-pyrrolo[1,2-a]benzimidazole; dioctyltin dilaurate and 1,3-diethyloxytetrabutylstannoxane are represented by Organometallic compounds; and tertiary amine compounds represented by triethylenediamine and N-methylphenidate.

Commercially available cross-linking catalysts can be used. Examples of commercially available cross-linking catalysts include "Curezol (registered trademark) 1B2MZ" and "Curezol (registered trademark) 1B2PZ" of Shikoku Chemical Industry Co., Ltd. , "Curezol (registered trademark) TBZ", and "Curezol (registered trademark) 1,2DMZ" (all are trade names).

When the adhesive composition of the present invention contains a cross-linking catalyst, from the viewpoint of further shortening the curing time, the content rate of the cross-linking catalyst is preferably 100 parts by mass of the specific (meth)acrylic copolymer. It is 0.01-1.5 parts by mass, more preferably 0.05-1.0 parts by mass, further more preferably 0.05-0.5 parts by mass.

[Other ingredients] In addition to the above-mentioned specific (meth)acrylic copolymer, cross-linking agent, and cross-linking catalyst, the adhesive composition of the present invention may also appropriately contain a silane coupling agent, an organic solvent, and a weather-resistant stabilizer according to the needs. Agents, plasticizers, softeners, stripping aids, dyes, pigments, inorganic fillers, surfactants, antioxidants, metal anti-corrosion agents, adhesion-imparting resins, antistatic agents, ultraviolet absorbers, and hindered amine compounds etc. are represented by light stabilizers, etc.

[Use of adhesive composition] There are no particular restrictions on the uses of the adhesive composition of the present invention. Examples thereof include heat-resistant adhesive sheets suitable for use in adhering to an adherend through an adhesive layer and embodiments of the present invention described below. For example, it is suitable for laminating transparent conductive films and glass substrates in the manufacturing process of electrostatic capacitive touch panels. In addition, it is suitable for temporary fixation or surface protection of parts during hot pressing, reflow soldering, or back grinding steps in FPC manufacturing steps.

[Heat-resistant adhesive sheet] The heat-resistant adhesive sheet of the present invention is provided with an adhesive layer, and the adhesive layer is a cross-linked product of the adhesive composition for the heat-resistant adhesive sheet. Since the heat-resistant adhesive sheet of the present invention has an adhesive layer that is a cross-linked product of the adhesive composition of the present invention, it has excellent contamination resistance and oxidation resistance after heat treatment under high temperature conditions. In addition, the outermost surface of the heat-resistant adhesive sheet can also be protected by a release film.

For the release film protecting the surface on the adhesive layer side, in order to easily peel the release film from the adhesive layer, for example, a release agent such as fluororesin, palm wax, or polysiloxane can be applied to the surface. Synthetic resin films such as polyester that have been mold-released are ideal. When the surface on the adhesive layer side and the opposite side are protected by a release film, examples of the release film include surface protection films such as hard-coated polyethylene terephthalate (PET) films.

The thickness of the adhesive layer in the heat-resistant adhesive sheet of the present invention can be appropriately set according to the types of the base material and the adherend, the surface roughness of the base material and the adherend, etc. Generally speaking, the thickness of the adhesive layer is 1 μm to 100 μm, preferably 5 μm to 50 μm, and more preferably 10 μm to 30 μm.

The heat-resistant adhesive sheet of the present invention is produced by a known method. There is no particular restriction on the method for producing the heat-resistant adhesive sheet. For example, the adhesive composition of the present invention is applied to a release film and dried to form a coating layer of the adhesive composition on the release film. Then, it is a method of making a heat-resistant adhesive sheet by curing it. In addition, as another example of the method for producing a heat-resistant adhesive sheet, the adhesive composition of the present invention is coated on a release film, dried, and a coating layer of the adhesive composition is formed on the release film. , set a peeling film on the exposed surface of the coating layer to make it tightly connected, and produce a double-sided adhesive tape without a support. Then, the coating layer is cured to form an adhesive layer. In addition, drying conditions may include, for example, drying at 70° C. to 120° C. for 1 minute to 3 minutes using a hot air dryer.

For the heat-resistant adhesive sheet of the present invention, from the viewpoint of contamination resistance and oxidation resistance after heat treatment under high temperature conditions, it is ideal that the difference between the adhesive force before heat treatment and the adhesive force after heat treatment under high temperature conditions is small. Considering the same point of view, the difference between the adhesive force before heat treatment and the adhesive force after heat treatment under high temperature conditions should be 2.0N/mm, and more preferably less than 0.5N/mm. In addition, the above-mentioned initial adhesive force and the adhesive force after heat treatment under high temperature conditions represent the adhesive force when the heat-resistant adhesive sheet is peeled off from the adherend in the 180° direction at 0.3m/min. [Example]

Hereinafter, the present invention will be described in more detail using examples, but the present invention is not limited to these examples. The glass transition temperature (Tg), weight average molecular weight (Mw), and molar ratio of the examples were measured and calculated by the above methods.

>Manufacture of (meth)acrylic copolymer> (Manufacture example 1) In a reactor equipped with a thermometer, a mixer, a reflux condenser, and a sequential dropping device, add acetone: 117 parts by mass, toluene: 51 parts by mass, and azobisisobutyronitrile (AIBN): 0.048 parts by mass. Then, (meth)acrylic acid containing 186.6 parts by mass of n-butyl acrylate (BA) (86 mass % with respect to the total mass of the structural units in the (meth)acrylic copolymer) and having a nitrogen atom and a hydroxyl group was prepared. 26.0 parts by mass of N-hydroxymethylacrylamide (N-MAM) as a monomer (12.0% by mass relative to the total mass of the structural units in the (meth)acrylic copolymer), and derived from methacrylic acid 4.3 parts by mass of 2-hydroxyethyl methacrylate (2-HEMA) as a constituent unit of the hydroxyalkyl ester (2.0 mass % relative to the total mass of the constituent units in the (meth)acrylic copolymer) 385 parts by mass of the monomer mixed solution, 97 parts by mass (25% by mass) thereof, were added to the reaction device, heated, and refluxed at the reflux temperature for 20 minutes. Then, under reflux temperature conditions, the remaining 288 parts by mass (75% by mass) of the above-mentioned monomer mixed solution, acetone: 124 parts by mass, toluene: 96 parts by mass, and AIBN: 0.48 parts by mass were gradually added dropwise over 90 minutes. The polymerization reaction was carried out for another 75 minutes. Thereafter, a mixture of 96 parts by mass of toluene and 1.92 parts by mass of AIBN was gradually added dropwise over 50 minutes, and the polymerization reaction was further performed for 120 minutes. After the reaction was completed, the solid content concentration was diluted with toluene to 41% by mass, and a solution of the (meth)acrylic copolymer of Production Example 1 was obtained. In addition, the "solid content" means the amount of the residue after removing volatile components such as solvent from the solution of the (meth)acrylic copolymer.

(Manufacture Examples 2 to 20) The (meth)acrylic copolymer 1 was synthesized in the same manner as the (meth)acrylic copolymer 1, except that the monomer composition was set to the monomer composition shown in Table 1 and the amounts of the organic solvent and polymerization initiator were changed to adjust the weight average molecular weight. ) Acrylic copolymer 2 to 20. Table 1 shows the monomer composition and weight average molecular weight (Mw) of (meth)acrylic copolymers 2 to 20.

[Table 1]

"-" in Table 1 means it does not contain this ingredient. In Table 1, the hydroxyl composition ratio represents the content (mass %) of the N-hydroxymethylacrylamide monomer in the (meth)acrylic copolymer relative to the content (mass %) of the hydroxyalkyl methacrylate monomer. %)The ratio. The abbreviations in Table 1 are as follows. ・2EHA: 2-ethylhexyl acrylate ・BA: n-butyl acrylate ・EA: Ethyl acrylate ・MA: Methyl acrylate ・DMAEA: Dimethylaminoethyl acrylate ・N-MAM: N-hydroxymethylacrylamide ・HEAA: Hydroxyethylacrylamide ・2HEMA: 2-hydroxyethyl methacrylate ・2HBMA: 2-hydroxybutyl methacrylate ・2HEA: 2-hydroxyethyl acrylate ・AA: Acrylic

(Example 1) >>Preparation of adhesive composition>> 243.9 parts by mass (solid content converted to 100 parts by mass) of the solution of (meth)acrylic copolymer 1 prepared in Production Example 1 (solid content concentration: 41 mass %), "Coronate (registered trademark)" as a cross-linking agent ) L-45E (manufactured by Tosoh Co., Ltd., adduct of toluyl diisocyanate (TDI) and trimethylolpropane (TMP), solid content concentration: 45 mass%) 6.67 parts by mass (solid content conversion 3.0 parts by mass) and stir thoroughly to obtain an adhesive composition. Using the obtained adhesive composition, follow the following method for producing a heat-resistant adhesive sheet for testing to prepare an adhesive sheet for testing and conduct various tests. The ratio of the molar number of the functional group (isocyanate group) of the cross-linking agent to the total molar number of the hydroxyl group and N-hydroxymethyl group (crosslinkable functional group) of the (meth)acrylic copolymer is 0.4 .

>>Preparation of heat-resistant adhesive sheet for test>>Use the adhesive composition obtained above to prepare an adhesive sheet for test in the following manner. On the polyimide (PI) sheet (product name: kapton (registered trademark), manufactured by DU PONT-TORAY CO., LTD.), apply the adhesive composition so that the coating amount after drying becomes 10 g/m ² , use a hot air circulation dryer to dry at 100°C for 60 seconds to form an adhesive layer. After that, a PET (polyethylene terephthalate) film is placed on the release film whose surface is protected by a polysiloxy release agent so as to contact the adhesive layer, and is pressed with a pressure roller. Connect to make it fit. After that, it was cured for 1 week in an environment of 23°C and 50% RH to obtain an adhesive sheet for testing.

>Evaluation> >>Adhesion>> Cut the adhesive sheet for testing into a size of 25mm x 150mm and prepare 4 adhesive sheets for testing. Peel off the release film on one side of the prepared adhesive sheet for testing, and laminate it to electrolytic copper foil (thickness: 10 μm, product name: NC-WC, manufactured by Furukawa Electric Co., Ltd.) and polyacrylic foil. Amine (PI) tablets [Product name: kapton (registered trademark), manufactured by DU PONT-TORAY CO., LTD.].

[Initial adhesion (adherent: copper foil)] The first test adhesive sheet was attached to the copper foil and placed in an environment of 23°C and 50% RH for 24 hours. Then, the test adhesive sheet was peeled off from the copper foil at a speed of 0.3m/min to measure the initial adhesion. force.

[Adhesion after heat resistance test (adherent: copper foil)] The adhesive sheet for the second test was attached to the copper foil and placed in an environment of 23°C and 50%RH for 24 hours, then placed in an environment of 200°C for 60 minutes, and then placed in an environment of 23°C and 50%RH again. Place it for 3 hours, peel the test adhesive sheet from the copper foil at 0.3m/min, and measure the adhesive force after the heat resistance test.

[Initial adhesion (adherent: polyimide)] The third adhesive sheet for testing was attached to polyimide and placed in an environment of 23°C and 50% RH for 24 hours. Then, the adhesive sheet for testing was peeled off from polyimide at a speed of 0.3m/min. Determine the initial adhesion.

[Adhesion after heat resistance test (adherent: polyimide)] The adhesive sheet for the fourth test was bonded to polyimide and placed in an environment of 23°C and 50%RH for 24 hours, then placed in an environment of 200°C for 60 minutes, and then placed in an environment of 23°C and 50%RH again. Place it in the same environment for 3 hours, peel the test adhesive sheet from the polyimide at 0.3m/min, and measure the adhesive force after the heat resistance test.

The initial adhesion and the adhesion after the heat resistance test are evaluated according to the following standards. When the evaluation of the initial adhesive strength is A to C, unintentional lifting and peeling from the adherend are suppressed, and the peeling workability from the adherend can be appropriately performed, so it is within the allowable range. In addition, when the adhesive force evaluation after the heat resistance test is A to C, unintentional lifting and peeling from the adherend are suppressed, and excessive rise after heat treatment is suppressed, which is within the allowable range. -Initial adhesion, and adhesion after heat resistance test- A: 1.5N/mm or more and less than 2.0N/mm. B: 0.9N/mm or more but less than 1.5N/mm, or 2.0N/mm or more but less than 2.5N/mm. C: 0.5N/mm or more but less than 0.9N/mm, or 2.5N/mm or more but less than 3.0N/mm. D: Less than 0.5N/mm or 3.0N/mm or more.

>>Contamination resistance>> For the polyimide or copper foil after measuring the adhesion after the heat resistance test, visually observe the surface of the polyimide or copper foil, and evaluate the contamination resistance according to the following evaluation criteria. If it is A to C, it is the allowable range. A: Confirm that there is no residual glue on the surface of polyimide or copper foil. B: A little residual glue can be seen on the edge of the polyimide or copper foil surface. C: Residual glue is observed at the edge of the surface of polyimide or copper foil, but no residual glue is observed within the usage range of 5mm to 145mm inward from the edge without residual glue. D: There is residual glue on the surface of polyimide or copper foil within the usage range of 0mm to 150mm from the periphery to the inside.

>>Antioxidation>> For the copper foil after measuring the adhesive force after the heat resistance test, the surface of the copper foil was visually observed, and the oxidation resistance was evaluated in accordance with the following evaluation standards. If it is A to C, it is the allowable range. A: It was confirmed that there was no discoloration (oxidation) on the copper foil. B: Slight discoloration (oxidation) was observed at the edge of the copper foil. C: There is discoloration (oxidation) at the edge of the copper foil, but no discoloration (oxidation) is observed in the usage range of 5 mm to 145 mm inward from the peripheral portion that is not discolored (oxidized). D: There is discoloration (oxidation) within the usage range of 0 mm to 150 mm from the peripheral part of the copper foil to the inside. -: There is obvious glue residue and it is difficult to confirm the discoloration.

(Examples 2 to 20 and Comparative Examples 1 to 10) Except for changing the (meth)acrylic copolymer and/or cross-linking agent of the production examples shown in Table 2 and Table 3, an adhesive composition was prepared in the same manner as in Example 1, and the adhesive composition was used Heat-resistant adhesive sheets are made for each object. Using the obtained heat-resistant adhesive sheet, a test adhesive sheet was produced in the same manner as in Example 1, and each evaluation was performed on the test adhesive sheet in the same manner as in Example 1. The results are shown in Table 2 and Table 3.

[Table 2]

[table 3]

The abbreviations in Table 2 and Table 3 are as follows. In addition, the mass fractions in Table 2 and Table 3 are conversion values of solid content concentration or active ingredients. In addition, the "mol ratio" in Table 2 and Table 3 represents the mol ratio of the functional group of the cross-linking agent relative to the total mol number of N-methylol and hydroxyl groups in the (meth)acrylic copolymer. , the ratio of the Mohr number is obtained by the above formula (3). The "Dry parts" in Table 2 and Table 3 represent the converted value of the active ingredient.

・Coronate L45E: Trade name ("Coronate" is a registered trademark), adduct of toluyl diisocyanate (TDI) and trimethylolpropane, solid content: 45 mass%, isocyanate group content: 7.9 mass %, isocyanate cross-linking agent, Tosoh Co., Ltd. ・Aluminum Chelate A: Trade name, refer to aluminum acetate acetonate, metal chelate compound, Kawaken Fine Chemicals Co., Ltd.)・TAKENATE D-110N: Trimethylolpropane and xylyl diisocyanate adduct , isocyanate cross-linking agent, manufactured by Mitsui Chemicals Co., Ltd. ・Coronate HX: Hexamethylene diisocyanate terpolymer, isocyanate cross-linking agent, manufactured by Tosoh Co., Ltd.

As shown in the results of Table 2 and Table 3, it can be seen that the heat-resistant adhesive sheets formed by the adhesive compositions of Examples 1 to 20 are better than the heat-resistant adhesive sheets formed by the adhesive compositions of Comparative Examples 1 to 10. Even after heat treatment under high-temperature conditions, the adhesive sheet is superior in suppressing contamination of the adherend when it is peeled off from the adherend. In addition, it can be seen that the heat-resistant adhesive sheets formed from the adhesive compositions of Examples 1 to 20 are more effective in protecting the adherend than the heat-resistant adhesive sheets formed from the adhesive compositions of Comparative Examples 1 to 10. The inhibition of oxidation is also better.

Claims (4)

An adhesive composition for heat-resistant adhesive sheets, containing: (meth)acrylic copolymer, the (meth)acrylic copolymer containing structural units derived from N-methylolacrylamide, derived from methacrylic acid hydroxyl groups A structural unit of an alkyl ester, a structural unit derived from an alkyl (meth)acrylate, and a cross-linking agent; the molar number of the functional group of the cross-linking agent is relative to the molar number of the (meth)acrylic copolymer. The ratio of the total molar number of the crosslinkable functional groups is 0.1 or more and 1.0 or less, and in the (meth)acrylic copolymer, the structural unit derived from N-methylol acrylamide is larger than the structural unit derived from methyl group. The mass ratio of the structural units of the hydroxyalkyl acrylate is 0.30 or more and 5.0 or less. The adhesive composition for a heat-resistant adhesive sheet according to claim 1, wherein the glass transition temperature of the (meth)acrylic copolymer is less than -40°C. For example, in the adhesive composition for a heat-resistant adhesive sheet according to claim 1 or 2, the number of moles of the functional groups of the cross-linking agent is relative to the total moles of the cross-linking functional groups of the (meth)acrylic copolymer. The ratio of numbers is 0.2 or more and 1.0 or less. A heat-resistant adhesive sheet is provided with an adhesive layer, and the adhesive layer is a cross-linked product of the adhesive composition for a heat-resistant adhesive sheet according to any one of claims 1 to 3.