TW202041635A - 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 manufacture of electronic components represented by flexible printed circuit boards (FPC: Flexible Printed Circuit), heat-resistant adhesive sheets are used for the purpose of fixing FPC and protecting parts. For the adhesive layer with the heat-resistant adhesive sheet, it is required to suppress the excessive increase in the adhesive force when peeling off after the heat treatment, and to suppress the contamination of the adherend and to suppress the deterioration. In addition, copper foil, polyimide, etc. are widely used for adherends.

Examples of conventional heat-resistant adhesive sheets include those described in JP 2013-032504 A. In Japanese Patent Laid-Open No. 2013-032504, an adhesive is disclosed that includes an acrylic resin with a specific Tg range in which nitrogen-containing monomers are copolymerized as a main component. According to Japanese Patent Laid-Open 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 Laid-Open No. 2013-032504 was obtained under conditions of 180°C for 5 hours using a SUS plate.

[The problem to be solved by the invention]

In recent years, in heat-resistant adhesive sheets, for example, even after heat treatment at a higher temperature than before, such as 200°C, the performance that the adhesive force does not increase is required. In addition, in general, the adherend of the 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 be adhered Body pollution. In addition, when the adherend is copper foil, oxidation of the adherend is likely to occur, that is, degradation of the adherend is likely to occur.

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

The problem to be solved by one embodiment of the present invention is to provide an adhesive composition for a heat-resistant adhesive sheet. For example, even after heat treatment at a high temperature of 200° C. or more, it prevents the adhesive layer from being peeled off from the adherend. Contamination of adherends and suppression of oxidation of adherends are excellent. In addition, the problem to be solved by other embodiments 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]

The means for solving the above-mentioned problems include the following aspects. >1>An adhesive composition for heat-resistant adhesive sheets, containing: (Meth)acrylic copolymer containing a structural unit derived from N-methylol acrylamide, a structural unit derived from hydroxyalkyl methacrylate, and a (meth)acrylic copolymer The constituent units of alkyl acrylate, and Crosslinking agent The ratio of the number of moles of the functional groups of the crosslinking agent to the total number of moles of the crosslinkable functional groups possessed by the (meth)acrylic copolymer is 0.1 or more and 1.0 or less. >2> The adhesive composition for heat-resistant adhesive sheets as in >1>, wherein the glass transition temperature of the (meth)acrylic copolymer is less than -40°C. >3> The adhesive composition for heat-resistant adhesive sheets such as >1> or >2>, in the (meth)acrylic copolymer, the content of the constituent units derived from N-methylolacrylamide is relatively The mass ratio to the content of the structural unit derived from the hydroxyalkyl methacrylate is 0.25 or more and 5.0 or less. >4>For the heat-resistant adhesive sheet adhesive composition of any one of >1>～>3>, the number of moles of the functional group of the crosslinking agent is relative to that of the (meth)acrylic copolymer The ratio of the total mole numbers of the crosslinkable functional groups is 0.2 or more and 1.0 or less. >5> A heat-resistant adhesive sheet, comprising an adhesive layer, and the adhesive layer is a cross-linked product of the adhesive composition for a heat-resistant adhesive sheet as described in any one of >1> to >4>. [Effects of Invention]

According to an embodiment of the present invention, an adhesive composition for a heat-resistant adhesive sheet can be provided. For example, even after heat treatment at a high temperature of 200° C. or higher, the adherend when the adhesive layer is peeled from the adherend is suppressed The pollution and the inhibition of the oxidation of the adherend are excellent. In addition, according to another embodiment of the present invention, there can be provided a heat-resistant adhesive sheet using an adhesive composition for a heat-resistant adhesive sheet.

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 indicated by "～" in this manual refers to the range that includes the numerical values described before and after "～" as the minimum and maximum values. In addition, the amount of each component in the composition in this specification, when several substances corresponding to each component are used in the composition, unless otherwise specified, it means the total amount of several substances corresponding to the component meaning.

In addition, the term "step" in this manual does not only refer to an independent step. Even if it cannot be clearly distinguished from other steps, as long as it achieves the intended purpose of the step, 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 acrylate and methacrylate. The (meth)acrylic copolymer in this specification refers to a polymer formed by polymerizing at least monomers having a (meth)acrylic acid group as the main component of the monomers constituting it The meaning of. The main component in the (meth)acrylic copolymer refers to the content rate (the so-called content rate; the same below.) (mass%) of the monomer components forming the polymer means the most, such as (methyl ) In the case of an acrylic copolymer, it means that the content of the structural unit formed from the monomer having a (meth)acrylic acid group is 50% by mass or more of all the structural units. The adhesive layer is a layer obtained by substantially crosslinking a (meth)acrylic copolymer and a crosslinking agent, for example, it means a solid or gel layer.

(Adhesive composition for heat-resistant adhesive sheets) The adhesive composition for a heat-resistant adhesive sheet of the present invention (hereinafter sometimes referred to as "adhesive composition") contains: (Meth)acrylic copolymer (hereinafter, sometimes referred to as "specific (meth)acrylic copolymer".) This (meth)acrylic copolymer contains a structure derived from N-methylolacrylamide Unit, structural unit derived from hydroxyalkyl methacrylate, and structural unit derived from alkyl (meth)acrylate, and Crosslinking agent The ratio of the number of moles of the functional groups of the crosslinking agent to the total number of moles of the crosslinkable functional groups possessed by the (meth)acrylic copolymer is 0.1 or more and 1.0 or less. As a result of intensive research, the inventors of the present invention have found that the adhesive composition of the present invention can provide an adhesive layer by having the above-mentioned constitution. For example, even after heat treatment at a high temperature of 200°C or higher, the adhesive composition is prevented from being adhered. The contamination of the adherend when the adhesive layer is peeled off and the suppression of oxidation of the adherend are excellent. Although the detailed mechanism for obtaining the above effects is not yet clear, it is presumed to be as follows. In addition, in this specification, the suppression of contamination of the adherend is excellent means that the contamination resistance is excellent. In addition, in this specification, the suppression of the oxidation of the adherend is excellent means that the oxidation resistance is excellent.

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-methylol acrylamide. Since N-methylol acrylamide is self-crosslinking under high temperature conditions, the adhesive composition of the present invention containing constituent units derived from N-methylol acrylamide, for example, even at a high temperature of about 200°C Under these conditions, a reasonably high cohesion can 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 a copper foil, the adherend and the adhesive layer are in good adhesion, 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-methylol acrylamide can self-crosslink even under high temperature conditions and can maintain a suitably high cohesive force. Therefore, when the adhesive composition of the present invention is used for the adhesive layer of a heat-resistant adhesive sheet, even if the adherend is polyimide, it can be prevented from being adhered when the adhesive layer is peeled from the adherend. The residue of the adhesive layer on the body (contamination by the adhesive body). In addition, 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 a hydroxyalkyl methacrylate. The above-mentioned structural unit derived from hydroxyalkyl methacrylate has a tendency that a part of the structural unit decomposes (depolymerizes) under high temperature conditions, and the cohesive force is appropriately lowered. Therefore, it is presumed that, for example, it is possible to suppress the increase in adhesion after heat treatment under high temperature conditions of about 200°C. In the adhesive composition of the present invention, it is presumed that the structural unit derived from N-methylol acrylamide and the structural unit derived from hydroxyalkyl methacrylate contained in the specific (meth)acrylic copolymer function 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, the heat treatment can be suppressed The adhesive force of the subsequent adhesive layer increases, and it is excellent to suppress the contamination of the adherend and to suppress the deterioration. Although the detailed mechanism is not clear, in more detail, the decomposition of a part of the structural unit derived from the hydroxyalkyl methacrylate during heat treatment is different from that of N-methylolacrylic acid at an environment above 200°C. The increase in cohesive force caused by the self-crosslinking reaction of amine affects each other to make cohesive force 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 self-crosslinking N-methylolacrylamide Unit, it is excellent for the suppression of the contamination of the adherend which is presumed to be due to the partial decomposition (depolymerization) of one of the structural units derived from the hydroxyalkyl methacrylate. In addition, in the adhesive composition of the present invention, the content of the functional group of the crosslinking agent relative to the total moles of the crosslinkable functional groups possessed by the specific (meth)acrylic copolymer has a molar ratio of 0.1 or more And 1.2 or less, the adhesive composition will be appropriately cross-linked, the cohesive force can be appropriately obtained, and an appropriate adhesive composition for a heat-resistant adhesive sheet can be obtained. Hereinafter, the detailed content of each component contained in the adhesive composition of the present invention will be described.

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

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

>>The constituent unit from N-hydroxymethyl acrylamide >> The specific (meth)acrylic copolymer contains a structural unit derived from N-methylol acrylamide. Commercial products can be used for N-methylol acrylamide, or those obtained by synthesis can also be used.

Regarding the content of the constituent units derived from N-methylol acrylamide, considering contamination resistance and oxidation resistance, it is preferably 0.1 mass relative to all constituent units constituting the specific (meth)acrylic copolymer % To 20% by mass, more preferably 1.0% to 15% by mass, further preferably 1.5% to 11% by mass, particularly preferably 2.0% to 9.0% by mass.

>>Constituted unit from hydroxyalkyl methacrylate>> The specific (meth)acrylic copolymer contains structural units derived from hydroxyalkyl methacrylate. Since the structural unit derived from hydroxyalkyl methacrylate has a tendency to decompose (depolymerize) under high temperature conditions, the cohesive force of the adhesive layer is moderately lowered, so it is estimated that it can be suppressed under high temperature conditions. The increase in adhesive force after heat treatment can further inhibit the contamination and deterioration of the adherend. In addition, the tendency of the cohesive force to decrease due to decomposition (depolymerization) of a part of the structural unit derived from the hydroxyalkyl methacrylate is greater than that of the hydroxyalkyl acrylate. The structural unit derived from hydroxyalkyl methacrylate may be contained individually by 1 type, and may contain 2 or more types.

Examples of the hydroxyalkyl methacrylate monomer forming the structural unit derived from the hydroxyalkyl methacrylate include monomers containing at least one hydroxyl group and methacryloxy group in one molecule.

The hydroxyalkyl methacrylate monomers include, for example, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 3-hydroxypropyl methacrylate, and methacrylic acid- 4-hydroxybutyl ester, 6-hydroxyhexyl methacrylate, 10-hydroxydecyl methacrylate, 12-hydroxylauryl methacrylate, 3-methyl-3-hydroxybutyl methacrylate, methyl methacrylate 1,1-dimethyl-3-hydroxybutyl methacrylate, 1,3-dimethyl-3-hydroxybutyl methacrylate, 2,2,4-trimethyl-3 methacrylate -Hydroxypentyl ester, 2-ethyl-3-hydroxyhexyl methacrylate, etc.

Considering the viewpoints of stain resistance and oxidation resistance, for hydroxyalkyl methacrylate, it is more preferably a hydroxyalkyl methacrylate having 1 to 10 carbon atoms, and more preferably a hydroxyl group having 2 to 8 carbon atoms Alkyl is a hydroxyalkyl methacrylate.

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

>>Constituted units from alkyl (meth)acrylates>> The specific (meth)acrylic copolymer contains a structural unit derived from an alkyl (meth)acrylate. The specific (meth)acrylic copolymer contains the structural unit derived from the alkyl (meth)acrylate, as far as the adhesive layer formed by the adhesive composition of the present invention is concerned, it can be given the initial and after heat treatment Both are 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 single alkyl (meth)acrylate system that forms the structural unit derived from the alkyl (meth)acrylate is not particularly limited. For example, it may be a substituted or unsubstituted alkyl (meth)acrylate, which is easy to consider From the viewpoint of addition polymerization with the above-mentioned hydroxyalkyl methacrylate monomer and N-methylol acrylamide, a substituted or unsubstituted alkyl acrylate is preferable. The alkyl group in the alkyl (meth)acrylate is not particularly limited, and it may be any of linear, branched, or cyclic. In addition, considering the adhesion of the adhesive layer to the adherend and the adhesion to the substrate, the carbon number of the above-mentioned alkyl group is preferably 1-18, more preferably 1-12.

As far as the alkyl (meth)acrylate is concerned, there are no special restrictions, such as methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, (meth)acrylic acid Isobutyl ester, second butyl (meth)acrylate, third 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 Esters, lauryl (meth)acrylate, cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, etc.

Among these, considering the viewpoint of adhesion, as far as the alkyl (meth)acrylate is concerned, it is preferably an alkyl acrylate, and more preferably selected from methyl acrylate (MA) and tertiary butyl acrylate ( t-BA) and at least one monomer from the group consisting of n-butyl acrylate (n-BA), and more preferably n-butyl acrylate (n-BA).

Regarding the content of the structural unit derived from the alkyl (meth)acrylate in the specific (meth)acrylic copolymer, considering the adhesive force, relative to all the structural units of the specific (meth)acrylic copolymer , Preferably 50% by mass or more and 99.95% by mass, more preferably 60% by mass or more and 99.95% by mass, further preferably 70% by mass or more and 99.95% by mass, especially preferably 80% by mass or more and 99.95% by mass the following.

-The mass ratio of the structural unit derived from N-methylol acrylamide to the structural unit derived from hydroxyalkyl methacrylate- The mass ratio of the content of the constituent units derived from N-methylol acrylamide to the content of the constituent units derived from hydroxyalkyl methacrylate, considering contamination resistance and oxidation resistance, is preferably 0.1 or more and 5.0 Hereinafter, it is more preferably 0.25 or more and 5.0 or less, further preferably 0.3 or more and 4.0 or less, and particularly preferably 0.5 or more and 3.5 or less.

>>Other components>> The specific (meth)acrylic copolymer may contain structural units derived from the above-mentioned N-methylol acrylamide, structural units derived from hydroxyalkyl methacrylate, and structural units derived from Structural units other than the structural units of the 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-methylol acrylamide, hydroxyalkyl methacrylate monomer and alkyl (meth)acrylate. Choose appropriately according to the purpose.

With regard to monomers constituting other structural units, examples include carboxyl groups, alkylene oxide groups, glycidyl groups, amide groups, N-substituted amide groups, tertiary amine groups, and hydroxyl groups (but not corresponding to N -Hydroxymethyl acrylamide and hydroxyalkyl methacrylate and other functional group monomers, or multifunctional (meth)acrylic monomers, aromatic monovinyl monomers, cyanide Vinyl monomers, (meth)acrylic monomers having aromatic rings.

For monomers having a carboxyl group, for example, acrylic acid (AA), methacrylic acid, crotonic acid, maleic anhydride, fumaric acid, itaconic acid, glutaconic acid, citraconic acid, ω-carboxy-poly Caprolactone mono(meth)acrylate (e.g. ω-carboxy-polycaprolactone (n≒2) monoacrylate), succinate (e.g. succinic acid-2-propenyloxyethyl), formic acid Vinyl ester, vinyl acetate, vinyl propionate, vinyl neodecanoate, etc.

As for the monomer having an oxyalkylene group, for example, methoxyethyl (meth)acrylate, 2-(ethoxyethoxy)ethyl acrylate, polyethylene glycol (meth)acrylic acid Ester, polyethylene glycol (meth) methacrylate, polypropylene glycol (meth) methacrylate, polypropylene glycol (meth) acrylate, and methoxy polyethylene glycol (meth) acrylate.

For monomers with glycidyl groups, glycidyl (meth)acrylate, 3,4-epoxycyclohexylmethyl (meth)acrylate, glycidyl vinyl ether, 3 ,4-Epoxycyclohexyl vinyl ether, epoxypropyl (methyl) allyl ether, 3,4-epoxycyclohexyl (methyl) allyl ether, etc.

For monomers having an amide group or N-substituted amide group, acrylamide, methacrylamide, N-methyl(meth)acrylamide, N-ethyl(methyl) Acrylamide, N-methoxymethyl (meth)acrylamide, N-ethoxymethyl (meth)acrylamide, N-propoxymethyl (meth)acrylamide, N -Butoxymethyl (meth)acrylamide, N-tert-butylacrylamide, N-octylacrylamide, diacetone acrylamide, hydroxyethyl acrylamide, etc.

For monomers with tertiary amino groups, dimethylaminoethyl (meth)acrylate, diethylaminoethyl (meth)acrylate, dimethylaminopropyl (methyl) ) Acrylamide, etc.

For monomers having a hydroxyl group other than N-methylol acrylamide and hydroxyalkyl methacrylate, for example, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 4-hydroxypropyl acrylate Hydroxybutyl ester, 6-hydroxyhexyl acrylate, etc.

The polyfunctional (meth)acrylic monomers 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)acryloxyethyl isocyanurate, tricyclodecane dimethanol (meth)acrylate, dimethylol dicyclopentane di(meth)acrylate, epoxy Ethane modified hexahydrophthalic acid di(meth)acrylate, tricyclopentane dimethanol (meth)acrylate, neopentyl glycol modified trimethylpropane di(meth)acrylate, three Hydroxymethylpropane tri(meth)acrylate, dineopentyl erythritol tri(meth)acrylate, diglycerol tetra(meth)acrylate, neopentaerythritol tetra(meth)acrylate, dineopentyl Tetraol hexa(meth)acrylate etc.

Examples of aromatic monovinyl monomers include styrene, α-methylstyrene, tertiary butylstyrene, p-chlorostyrene, chloromethylstyrene, vinyl toluene, and vinylpyridine. Examples of vinyl cyanide monomers include acrylonitrile and methacrylonitrile.

For (meth)acrylic monomers having an aromatic ring, for example, phenoxyethyl (meth)acrylate, benzyl (meth)acrylate, phenoxydiethylene glycol (meth) Acrylate, ethylene oxide (EO) modified cresol (meth) acrylate, ethylene oxide (EO) modified nonylphenol (meth) acrylate, hydroxyethylated β-naphthol acrylate , Biphenyl (meth)acrylate.

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

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

>>Weight average molecular weight (Mw) of specific (meth)acrylic copolymers>> The weight average molecular weight (Mw) of the specific (meth)acrylic copolymer is not particularly limited. Considering the viewpoint of improving the adhesion, it is preferably 50,000 to 1 million, more preferably 100,000 to 800,000, and further preferably 20 Ten thousand to six hundred thousand. The weight average molecular weight can be adjusted by the polymerization temperature, time, amount of organic solvent, and the like.

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

(condition) GPC: HLC-8220 GPC [Tosoh Corporation] String: Use 4 TSK-GEL GMHXL [Tosoh Corporation] Mobile phase solvent: tetrahydrofuran Flow rate: 0.8mL/min Column temperature: 40℃

-Glass transition temperature- Considering the viewpoint of increasing the adhesive force of the obtained adhesive layer and suppressing the increase of the adhesive force after heat treatment caused by the excessive increase of cohesive force, the glass transition temperature (Tg) of the specific (meth)acrylic copolymer is preferably -60 ℃～-5℃, more preferably -55℃～-30℃, and further preferably above -50℃ and less than -40℃.

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

式中，Tg₁ 、Tg₂ 、……及Tg_n 係表示單體1、單體2、……及單體n各別之均聚物之以絕對溫度(單位：K；以下亦同。)表示的玻璃轉移溫度。m₁ 、m₂ 、……及m_n 係各別之單體成分的莫耳分率。[Number 1]

In the formula, Tg ₁ , Tg ₂ , ... and Tg _n represent the absolute temperature of the homopolymers of monomer 1, monomer 2, ... and monomer n (unit: K; the same applies below). Indicates the glass transition temperature. m ₁ , m ₂ , ... and m _n are the molar fractions of the individual monomer components.

In addition, "the glass transition temperature of a homopolymer expressed in absolute temperature (K)" refers to the glass transition temperature expressed in absolute temperature (K) of a homopolymer obtained by separately polymerizing the monomer. 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) for the homopolymer to measure 10 mg of the sample in a nitrogen gas stream and raise the temperature The measurement is carried out at a speed of 10°C/min, and the inflection point of the obtained DSC curve is taken as the glass transition temperature of the homopolymer.

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

[Method for manufacturing specific (meth)acrylic copolymer] The method for producing 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 performed in a short time, the specific (meth)acrylic copolymer is preferably manufactured by solution polymerization.

In general, solution polymerization can be used to add predetermined organic solvents, monomers, polymerization initiators, and chain transfer agents according to needs to the polymerization tank, in a nitrogen stream or at the reflux temperature of the organic solvent, while stirring It is heated and reacted for several hours. In addition, the weight average molecular weight of the specific (meth)acrylic copolymer can be adjusted to a desired value by adjusting the reaction temperature, time, amount of solvent, and type and amount of catalyst.

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

Regarding the organic solvent used in the polymerization reaction, for example, benzene, toluene, ethylbenzene, n-propylbenzene, tertiary butylbenzene, o-xylene, meta-xylene, p-xylene, tetralin, ten Hydronaphthalene and aromatic naphtha are represented by aromatic hydrocarbon-based organic solvents; n-hexane, n-heptane, n-octane, isooctane, n-decane, dipentene, petroleum spirit, petroleum naphtha, And turpentine as the representative organic solvent of aliphatic hydrocarbon series or alicyclic hydrocarbon series; ethyl acetate, n-butyl acetate, n-pentyl acetate, 2-hydroxyethyl acetate, 2-butoxyethyl acetate , 3-methoxybutyl acetate, and methyl benzoate as representative organic solvents; acetone, methyl ethyl ketone, methyl-isobutyl ketone, isophorone, cyclohexanone, and methyl cyclic Ketone-based organic solvent represented by hexanone; ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl Ether, and glycol ether-based organic solvents represented by diethylene glycol monobutyl ether; and methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, second butanol, and Alcohol-based organic solvents represented by tributanol.

In addition, examples of the polymerization initiator include organic peroxides and azo compounds that can be used in ordinary polymerization methods.

>Crosslinking agent> The adhesive composition of the present invention contains a crosslinking agent. As for the cross-linking agent, for example, isocyanate-based cross-linking agents, epoxy-based cross-linking agents, oxazoline-based cross-linking agents, carbodiimide-based cross-linking agents, metal chelating compounds, etc., are considered. From the following viewpoints of stain resistance and oxidation resistance after heat treatment, isocyanate-based crosslinking agents or metal chelate compounds are preferred, and isocyanate-based crosslinking agents are more preferred. The crosslinking agent may be contained alone or in two or more kinds.

Examples of the isocyanate-based crosslinking agent include compounds (polyisocyanate compounds) having two or more isocyanate groups in one molecule. The isocyanate-based crosslinking agent includes, for example, aromatics such as xylene diisocyanate (XDI), diphenylmethane diisocyanate, triphenylmethane triisocyanate, and toluene diisocyanate (TDI). Polyisocyanate compound; aliphatic or alicyclic such as hexamethylene diisocyanate (HMDI), pentamethylene diisocyanate (PDI), isophorone diisocyanate, hydrogenated aromatic polyisocyanate compound, etc. Group polyisocyanate compounds and so on. In addition, polyisocyanate compounds 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 Biuret 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", and "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 (shares)]; "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" [Above is Asahi Kasei (shares)]; 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" [above is Mitsui Chemicals Co., Ltd.].

Among these, considering the pollution resistance and oxidation resistance after heat treatment under high temperature conditions, the crosslinking agent is the "Coronate" of the trimethylolpropane adduct of toluene diisocyanate. "L45E" is ideal.

As for the metal chelate compound, aluminum chelate represented by bis(ethylacetate) aluminum, ginseng (ethylacetate) aluminum, and ginseng (acetylpyruvate) aluminum Compounds, titanium chelate compounds, zirconium chelate compounds, cobalt chelate compounds, etc.

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

>>The ratio of the mole number of the functional group of the crosslinking agent to the total mole number of the crosslinkable functional group possessed by the (meth)acrylic copolymer>> The ratio (molar ratio) of the number of moles of the functional groups of the crosslinking agent to the total number of moles of the crosslinkable functional groups possessed by the (meth)acrylic copolymer is 0.1 or more and 1.0 or less. If the above-mentioned molar ratio is within the above-mentioned range, the decomposition (depolymerization) of a part of the structural unit derived from a part of the structural unit of hydroxyalkyl methacrylate caused by the heat treatment under high temperature conditions and the N-methylolacrylic acid The complementary effect caused by the self-crosslinking reaction of amine becomes more obvious, the cohesive force becomes more appropriate, the increase in adhesion after heat treatment under high temperature conditions can be suppressed, and the pollution and deterioration of the adherend can be suppressed. Considering the above point of view, the above 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, particularly preferably 0.25 or more and 0.6 or less, and most preferably It is 0.3 or more and 0.5 or less.

Regarding the crosslinkable functional group possessed by the (meth)acrylic copolymer, the crosslinkable functional group in the constituent unit derived from N-methylol acrylamide is N-methylol, derived from methacrylic hydroxyl group The crosslinkable functional group in the structural unit of the alkyl ester is a hydroxyl group. The (meth)acrylic copolymer contains as other structural units a structural unit derived from a monomer having a crosslinkable functional group (hereinafter also referred to as "other structural unit derived from a monomer having a crosslinkable functional group"). In this case, in addition to the above-mentioned N-methylol and hydroxyl groups, the crosslinkable functional groups contained in other structural units also correspond to the crosslinkable functional groups possessed by the (meth)acrylic copolymer. As for the crosslinkable functional groups possessed by other structural units, as long as they are functional groups that can form a crosslinked structure by crosslinking reaction with a crosslinking agent, examples include carboxyl groups, ketone groups, hydroxyl groups, amide groups, Functional groups such as N-substituted amide and epoxy groups.

The above-mentioned molar ratio can be determined by the molar number of functional groups possessed by the crosslinking agent (the following formula (1)) and the total molar number of crosslinkable functional groups possessed by the (meth)acrylic copolymer (the following formula (2)) It can be obtained by formula (3). In addition, the functional group possessed by the crosslinking agent refers to a group capable of undergoing a crosslinking reaction with the crosslinkable functional group possessed by the (meth)acrylic copolymer. For example, when the crosslinking agent is an isocyanate crosslinking agent, the functional group Refers to isocyanate groups.

In addition, when the crosslinking agent is a metal chelate compound, it is considered that the hydroxyl group contained in the above-mentioned (meth)acrylic copolymer is coordinated with the central metal in the metal chelate compound, and the valence of the central metal is replaced Is the number of functional groups, and the equivalent weight (number of moles) of the metal chelate compound used in the calculation of the molar ratio can be obtained. In the present invention, for example, the valence of the central metal in the aluminum chelate compound is 3, and the aluminum chelate compound can be calculated by replacing the functional group with 3 mol per 1 mol. 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 chelate compound Valence B = the number of parts by mass of the metal chelate compound (as a solid content) C = the molecular weight of the metal chelate compound D ₁ , D ₂ , ... D _n = used in the specific (meth)acrylic copolymer The content of each monomer having a cross-linkable functional group in all monomers (mass%) E ₁ , E ₂ ,...E _n = the amount contained in 1 molecule of each monomer having a cross-linkable functional group The number of linkable functional groups F ₁ , F ₂ , ... F _n = the molecular weight of each monomer having a crosslinkable functional group used in the specific (meth)acrylic copolymer. In addition, n represents the monomer used For the number of types, for example, when the (meth)acrylic monomer used is one type, only D ₁ is used in the calculation, and D ₂ ...D _{n is} not used.

The number of moles of functional groups of the cross-linking agent used in the calculation of the molar ratio can be used as the content of the functional groups in the cross-linking agent, the solid content of the cross-linking agent, and the blending amount (added mass parts ), obtained by the following formula (1).

The number of moles of functional groups in the crosslinking agent (unit: mmol/solid content of the specific (meth)acrylic copolymer 100g) =[(The content rate of the functional group in the crosslinking agent (unit: mass%) × the blending amount of the crosslinking agent (unit: g))/the solid content of the crosslinking agent (unit: mass%)]/functional group The molecular weight (unit: g/mol)×1000……Formula (1)

The total number of moles of crosslinkable functional groups of the specific (meth)acrylic copolymer (unit: mmol/solid content of the specific (meth)acrylic copolymer 100g) =[The content of the constituent units derived from N-methylol acrylamide in the specific (meth)acrylic copolymer (unit: mass %)/the molecular weight of the N-methylol acrylamide (unit: g/ mol)×The number of N-methylol groups in the structural unit derived from N-methylol acrylamide (valence)×1000]+[The methacrylic hydroxyl group in the specific (meth)acrylic copolymer The content of the structural unit of the alkyl ester (unit: mass %) / the molecular weight of the hydroxyalkyl methacrylate (unit: g/mol) × the number of hydroxyl groups in the structural unit derived from the hydroxyalkyl methacrylate (Valency)×1000]+[The content of other constituent units derived from the monomer having a crosslinkable functional group in the specific (meth)acrylic copolymer (unit: mass %) / having a crosslinkable functional group The molecular weight of the monomer (unit: g/mol) × the number of cross-linkable functional groups in the other constituent units (valence) × 1000]]……Formula (2)

The ratio of the number of moles of functional groups in the crosslinking agent to the total number of moles of crosslinkable functional groups possessed by 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 crosslinking agent. Considering stain resistance and oxidation resistance, the value is calculated as the effective ingredient relative to the total of 100 parts by mass of the 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.

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

As the crosslinking catalyst, a known crosslinking catalyst that can be used for the adhesive composition can be suitably used. As for the crosslinking catalyst, there is no particular limitation, and examples include 1,2-dimethylimidazole, 1-benzyl-2-methylimidazole, 1-benzyl-2-phenylimidazole, and 2, 3-Dihydro-1H-pyrrolo[1,2-a]benzimidazole is a representative imidazole compound; dioctyltin dilaurate, and 1,3-diethoxytetrabutylstannoxane are representative Organometallic compounds; and tertiary amine compounds represented by triethylenediamine and N-methyl 𠰌line.

Commercial products can be used as cross-linking catalysts. For commercial products of cross-linking catalysts, for example, "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" (both are product names).

When the adhesive composition of the present invention contains a cross-linking catalyst, considering that the curing time can be shortened, the content of the cross-linking catalyst is preferably relative to 100 parts by mass of the specific (meth)acrylic copolymer It is 0.01 parts by mass to 1.5 parts by mass, more preferably 0.05 parts by mass to 1.0 parts by mass, and further preferably 0.05 parts by mass to 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 contain a silane coupling agent, organic solvent, and weather resistance as required. Agents, plasticizers, softeners, peeling aids, dyes, pigments, inorganic fillers, surfactants, antioxidants, metal corrosion inhibitors, and adhesion imparting resins, antistatic agents, UV absorbers, and hindered amine compounds Etc. as the representative light stabilizer etc.

[Use of adhesive composition] The use of the adhesive composition of the present invention is not particularly limited, and examples include heat-resistant adhesive sheets suitable for use in pasting to an adherend through an adhesive layer. The heat-resistant adhesive sheet of the embodiment of the present invention described later, For example, it is suitable for the application of bonding a transparent conductive film to a glass substrate in the manufacturing process of a capacitive touch panel. In addition, it is suitable for temporary fixation or surface protection of parts during hot pressing, reflow soldering, or Back Grinding in the FPC manufacturing process.

[Heat resistant adhesive sheet] The heat-resistant adhesive sheet of the present invention includes an adhesive layer, which is a cross-linked product of the adhesive composition for a 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 stain 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 the release film.

Regarding the release film for protecting the side of the adhesive layer, in order to easily peel the release film from the adhesive layer, for example, using a release agent such as fluorine-based resin, palm wax, and silicone on the surface Synthetic resin films such as polyester that have been demolded are ideal. When the surface on the side of the adhesive layer and the surface on the opposite side are protected with a release film, the release film includes surface protection films such as a polyethylene terephthalate (PET) film that has been hard-coated.

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 substrate and the adherend, the surface roughness of the substrate and the adherend, and the like. 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 are no particular restrictions on the method of making 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, other examples of the method for producing a heat-resistant adhesive sheet include coating the adhesive composition of the present invention on a release film, and then drying, and forming a coating layer of the adhesive composition on the release film , Set a release film on the exposed surface of the coating layer to make it close to each other to make an adhesive tape on both sides without a support. Then, curing the coating layer to make the adhesive layer. In addition, the drying conditions include, for example, using a hot air dryer and drying at 70°C to 120°C for 1 minute to 3 minutes.

In the heat-resistant adhesive sheet of the present invention, considering the pollution resistance and oxidation resistance after heat treatment under high temperature conditions, the difference between the adhesive force before heat treatment and the adhesive force after heat treatment under high temperature conditions is preferably 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, more preferably less than 0.5N/mm. In addition, the above-mentioned initial adhesive force and adhesive force after heat treatment under high temperature conditions represent the adhesive force when the heat-resistant adhesive sheet is peeled from the adherend in the 180° direction under the condition of 0.3 m/min. [Example]

Hereinafter, the present invention will be explained in more detail through 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 are measured and calculated by the above methods.

>Manufacturing of (meth)acrylic copolymers> (Manufacturing Example 1) In a reactor equipped with a thermometer, a stirrer, a reflux condenser, and a dropwise addition device, acetone: 117 parts by mass, toluene: 51 parts by mass, and azobisisobutyronitrile (AIBN): 0.048 parts by mass were added. Then, prepare 186.6 parts by mass of n-butyl acrylate (BA) (86% by mass relative to the total mass of the constituent units in the (meth)acrylic copolymer), and (meth)acrylic acid having a nitrogen atom and a hydroxyl group 26.0 parts by mass of N-methylol acrylamide (N-MAM) as a monomer (12.0% by mass relative to the total mass of the constituent units in the (meth)acrylic copolymer), and is derived from methacrylic acid 4.3 parts by mass of 2-hydroxyethyl methacrylate (2-HEMA) as the constituent unit of hydroxyalkyl ester (2.0% by mass relative to the total mass of the constituent units in the (meth)acrylic copolymer) The monomer mixed solution was 385 parts by mass, 97 parts by mass (25% by mass) of the monomer mixture solution was 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 monomer mixture 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. After that, a mixture of toluene: 96 parts by mass and AIBN: 1.92 parts by mass was added dropwise gradually over 50 minutes, and the polymerization reaction was performed for another 120 minutes. After the reaction was completed, the solid content concentration was 41% by mass by diluting with toluene to obtain a solution of the (meth)acrylic copolymer of Production Example 1. In addition, "solid content" means the amount of residue after removing volatile components such as a solvent from a solution of a (meth)acrylic copolymer.

(Manufacturing examples 2-20) The monomer composition shown in Table 1 was set, and the amount of organic solvent and polymerization initiator was changed to adjust the weight average molecular weight. Other than that, the (meth)acrylic copolymer 1 was synthesized in the same manner as the (meth)acrylic copolymer 1. ) Acrylic copolymer 2-20. The monomer composition and weight average molecular weight (Mw) of (meth)acrylic copolymers 2-20 are shown in Table 1.

[Table 1]

"-" in Table 1 means that the ingredient is not contained. In Table 1, the hydroxyl composition ratio represents the content (mass %) of the N-methylol acrylamide 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-methylol acrylamide ・HEAA: Hydroxyethyl acrylamide ・2HEMA: 2-hydroxyethyl methacrylate ・2HBMA: 2-hydroxybutyl methacrylate ・2HEA: 2-hydroxyethyl acrylate ・AA: Acrylic

(Example 1) >>Preparation of adhesive composition>> The solution (solid content concentration: 41% by mass) of the (meth)acrylic copolymer 1 prepared in Production Example 1 was 243.9 parts by mass (100 parts by mass in terms of solid content), and "Coronate (registered trademark) as a crosslinking agent ) L-45E (manufactured by Tosoh Co., Ltd., adduct of toluene diisocyanate (TDI) and trimethylolpropane (TMP), solid content: 45% by mass) 6.67 parts by mass (calculated as solid content) (3.0 parts by mass)), mix and stir thoroughly to obtain an adhesive composition. Using the obtained adhesive composition, follow the following method of making heat-resistant adhesive sheets for testing to make test adhesive sheets and perform various tests. The ratio of the molar number of the functional group (isocyanate group) of the crosslinking agent to the total molar number of the hydroxyl group and the N-methylol group (crosslinkable functional group) possessed by the (meth)acrylic copolymer is 0.4 .

>>Production of heat-resistant adhesive sheet for test>> Using the adhesive composition obtained above, the adhesive sheet for test is made as follows. Coat the adhesive composition on a polyimide (PI) sheet (product name: kapton (registered trademark), manufactured by DU PONT-TORAY CO., LTD.) so that the coating amount after drying becomes 10 g/m ² , The adhesive layer is formed by drying at 100°C for 60 seconds with a hot-air circulating dryer. After that, a PET (polyethylene terephthalate) film is placed on the release film whose surface is protected by a silicone-based release agent in contact with the adhesive layer, and pressed by 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 a test adhesive sheet.

>Evaluation> >>Adhesion>> Cut the test adhesive sheet into a size of 25mm×150mm, and prepare 4 test adhesive sheets. Separate the release film on one side of the produced test adhesive sheet, and paste it on the electrolytic copper foil (thickness: 10μm, product name: NC-WC, manufactured by Furukawa Electric Co., Ltd.), and Polya Amine (PI) tablets [product name: kapton (registered trademark), manufactured by DU PONT-TORAY CO., LTD.].

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

[Adhesion after heat resistance test (Adherent body: copper foil)] The second test adhesive sheet is attached to 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 Leave it for 3 hours, peel off the adhesive sheet for the test from the copper foil at 0.3 m/min, and measure the adhesive force after the heat resistance test.

[Initial adhesion (adhesive body: polyimide)] The third test adhesive sheet is attached to polyimide and left in an environment of 23°C and 50%RH for 24 hours, and then the test adhesive sheet is peeled from the polyimide at a condition of 0.3m/min. Determine the initial adhesion.

[Adhesion after heat resistance test (Adhesive body: Polyimide)] The fourth test adhesive sheet is attached 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 again at 23°C and 50%RH Leave it for 3 hours in the same environment, peel off 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 benchmarks. When the initial adhesive strength is evaluated as A to C, unintentional floating and peeling from the adherend are suppressed, and the peeling workability from the adherend can be performed appropriately, so it is within the allowable range. In addition, when the evaluation of the adhesive force after the heat resistance test is A to C, it is within the allowable range to suppress unintentional floating and peeling from the adherend, and to suppress excessive rise after heat treatment. -Initial adhesion and adhesion after heat resistance test- A: 1.5N/mm or more and less than 2.0N/mm. B: 0.9 N/mm or more and less than 1.5 N/mm, or 2.0 N/mm or more and less than 2.5 N/mm. C: 0.5 N/mm or more and less than 0.9 N/mm, or 2.5 N/mm or more and less than 3.0 N/mm. D: Less than 0.5 N/mm, or 3.0 N/mm or more.

>>Fouling resistance>> For the polyimide or copper foil after the heat resistance test is measured, the surface of the polyimide or copper foil is visually observed, and the contamination resistance is evaluated 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 confirmed on the edge of the surface of polyimide or copper foil. C: Glue residue is observed at the edge of the surface of polyimide or copper foil, but no glue residue is observed within the use range of 5mm to 145mm from the edge without glue residue to the inner side. D: There is residual glue on the surface of polyimide or copper foil in the range of 0mm～150mm from the periphery to the inside.

>>Antioxidant>> With respect to 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 according to the following evaluation criteria. If it is A to C, it is the allowable range. A: It is confirmed that there is no discoloration (oxidation) at all on the copper foil. B: A slight discoloration (oxidation) was confirmed at the edge of the copper foil. C: There is discoloration (oxidation) at the edge of the copper foil, but no discoloration (oxidation) is confirmed in the use range of 5mm to 145mm inward from the undiscolored (oxidized) peripheral part. D: There is discoloration (oxidation) in the range of 0mm～150mm from the periphery of the copper foil to the inside. -: There is obvious residual glue and it is difficult to confirm the discoloration.

(Examples 2-20 and Comparative Examples 1-10) Except for changing to the (meth)acrylic copolymer and/or crosslinking 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 Make heat-resistant adhesive sheets individually. Using the obtained heat-resistant adhesive sheet, an adhesive sheet for a test was produced in the same manner as in Example 1, and the adhesive sheet for a test was evaluated 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 parts in Table 2 and Table 3 are the conversion values of the solid content concentration or the effective ingredient. In addition, the "mole ratio" in Tables 2 and 3 means the mol ratio of the functional group of the crosslinking agent to the total number of moles of the N-methylol and hydroxyl groups in the (meth)acrylic copolymer , The ratio of the number of moles 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 toluene diisocyanate (TDI) and trimethylolpropane, solid content: 45% by mass, isocyanate group content: 7.9 mass %, isocyanate-based crosslinking agent, Tosoh (shares) ・Aluminum Chelate A: Trade name, aluminum acetone, metal chelate compound, Kawaken Fine Chemicals Co., Ltd.) ・TAKENATE D-110N: Trimethylolpropane and xylene diisocyanate adduct , Isocyanate-based crosslinking agent, manufactured by Mitsui Chemicals Co., Ltd. ・Coronate HX: Trimer of hexamethylene diisocyanate, isocyanate-based crosslinking agent, manufactured by Tosoh Corporation

As shown in the results of Table 2 and Table 3, it can be seen that the heat-resistant adhesive sheet formed from the adhesive composition of Examples 1 to 20 is compared with the heat-resistant adhesive sheet formed from the adhesive composition of Comparative Examples 1 to 10 The adhesive sheet, even after heat treatment under high temperature conditions, peels off from the adherend, it is more excellent in terms of suppression of contamination of the adherend. In addition, it can be seen that the heat-resistant adhesive sheet formed from the adhesive composition of Examples 1 to 20 is more effective than the heat-resistant adhesive sheet formed from the adhesive composition of Comparative Examples 1-10. The suppression of oxidation is also more excellent.

Claims (6)

An adhesive composition for heat-resistant adhesive sheets, containing: (Meth)acrylic copolymer containing a structural unit derived from N-methylol acrylamide, a structural unit derived from hydroxyalkyl methacrylate, and a (meth)acrylic copolymer The constituent units of alkyl acrylate, and Crosslinking agent The ratio of the number of moles of the functional groups of the crosslinking agent to the total number of moles of the crosslinkable functional groups possessed by the (meth)acrylic copolymer is 0.1 or more and 1.0 or less. The adhesive composition for a heat-resistant adhesive sheet of claim 1, wherein the glass transition temperature of the (meth)acrylic copolymer is less than -40°C. According to the adhesive composition for a heat-resistant adhesive sheet of claim 1 or 2, in the (meth)acrylic copolymer, the content of the N-methylol acrylamide-derived structural unit is relative to the methyl-derived adhesive composition The mass ratio of the content of the structural unit of the hydroxyalkyl acrylate is 0.25 or more and 5.0 or less. According to the adhesive composition for heat-resistant adhesive sheets of claim 1 or 2, the number of moles of the functional groups of the crosslinking agent is relative to the total number of moles of the crosslinkable functional groups of the (meth)acrylic copolymer The ratio of the numbers is 0.2 or more and 1.0 or less. According to the adhesive composition for a heat-resistant adhesive sheet of claim 1 or 2, in the (meth)acrylic copolymer, the content of the N-methylol acrylamide-derived structural unit is relative to the methyl-derived adhesive composition The mass ratio of the structural units of the hydroxyalkyl acrylate is 0.25 or more and 5.0 or less, The ratio of the number of moles of the functional groups of the crosslinking agent to the total number of moles of the crosslinkable functional groups of the (meth)acrylic copolymer is 0.2 or more and 1.0 or less. A heat-resistant adhesive sheet is provided with an adhesive layer which is a cross-linked product of the adhesive composition for a heat-resistant adhesive sheet according to any one of claims 1 to 5.