KR20210094467A - 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 including a (meth)acrylic copolymer and a crosslinking agent, and a heat-resistant adhesive sheet, wherein the (meth)acrylic copolymer includes a structural unit derived from N-methoxymethyl acrylamide, a structural unit derived from a monomer having a hydroxyl group, and a structural unit derived from a (meth)acrylic acid alkylester monomer, and the content of the structural unit derived from N-methoxymethyl acrylamide is in the range of 6 to 30% by mass based on the all structural units.

Description

The adhesive composition for heat-resistant adhesive sheets, and a heat-resistant adhesive sheet TECHNICAL FIELD

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

In the heat treatment process at the time of manufacture of an electronic member represented by a hot press process and a solder reflow process, a heat resistant adhesive sheet is used for the purpose of protecting an electronic member. The pressure-sensitive adhesive layer included in the heat-resistant pressure-sensitive adhesive sheet is required to have properties in which excessive increase and excessive decrease in adhesive strength due to heat treatment are unlikely to occur.

As a method of improving the heat resistance of a conventional adhesive sheet, the method of using the copolymer containing the structural unit derived from a nitrogen-containing monomer as a raw material of an adhesive composition is known.

For example, in Japanese Patent Application Laid-Open No. 2013-177568, an acrylic resin (A) obtained by copolymerizing a copolymer component [I] containing a (meth)acrylic acid ester-based monomer (a1) as a main component is included. A pressure-sensitive adhesive composition for a heat-resistant adhesive film As a copolymerization component [I], the adhesive composition for heat-resistant adhesive films containing the (meth)acrylamide-type monomer (a2) which has a specific structure is disclosed.

In addition, for example, Japanese Patent Application Laid-Open No. 2012-196953 discloses an optical film with an adhesive in which an adhesive layer is formed on at least one surface of an optical film, wherein the adhesive layer has (A) (A-1) a specific structure ( 80 wt% to 96 wt% of meth)acrylic acid ester, (A-2) 1 wt% to 15 wt% of an unsaturated monomer having one olefinic double bond and at least one aromatic ring in the molecule, (A-3) specific structure 0.1 wt% to 5 wt% of N-alkoxyalkyl (meth)acrylamide having a (A-4) acrylic resin, which is a copolymer obtained from a monomer mixture containing 0.5 wt% to 5 wt% Part, (B) 0.3 parts by weight to 12 parts by weight of an ionic compound having an organic cation, and (C) 0.1 parts by weight to 5 parts by weight of a crosslinking agent is disclosed.

In recent years, use at a temperature much higher than the conventional one of 260 degreeC is calculated|required by the heat resistant adhesive sheet. Usually, when an adhesive sheet is used in a high-temperature environment, the adhesive force of an adhesive layer rises and the defect which becomes difficult to peel from a to-be-adhered body is easy to generate|occur|produce. In addition, when the pressure-sensitive adhesive sheet is used in a high-temperature environment, the cohesive force of the pressure-sensitive adhesive layer is lowered, and when the pressure-sensitive adhesive layer is peeled off from the adherend, glue residues are formed on the surface of the adherend to easily contaminate the adherend. Furthermore, when the cohesive force of an adhesive layer falls, when a to-be-adhered body is copper foil, air enters between an adhesive sheet and copper foil, and unintentional peeling may occur or copper foil may discolor by oxidation.

For this reason, in the pressure-sensitive adhesive composition used for the heat-resistant pressure-sensitive adhesive sheet, even when used in a high-temperature environment of, for example, 260° C., good adhesion and releasability to the adherend can be maintained, and it is difficult to contaminate the surface of the adherend at the time of peeling, and It is calculated|required that the adhesive layer which can suppress oxidation of a to-be-adhered body can be formed.

Regarding the above-mentioned points, the pressure-sensitive adhesive composition described in Japanese Patent Application Laid-Open No. 2013-177568 and Japanese Patent Application Laid-Open No. 2012-196953 could not be used at a very high temperature of 260° C. than in the prior art. In addition, according to the examination of the present inventors, when the pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive composition described in Japanese Patent Application Laid-Open No. 2013-177568 and Japanese Patent Application Laid-Open No. 2012-196953 is heat-treated at a high temperature of 260° C., the cohesive force is remarkably reduced and peeling off It turns out that it is easy to generate|occur|produce glue dregs on the surface of a to-be-adhered body at the time of a to-be-adhered body.

The problem to be solved by the present invention is that good adhesion and releasability to the adherend can be maintained even when heat-treated at a high temperature (for example, 260° C.), so that it is difficult to contaminate the surface of the adherend during peeling, and also To provide a pressure-sensitive adhesive composition for a heat-resistant pressure-sensitive adhesive sheet capable of forming a pressure-sensitive adhesive layer capable of suppressing oxidation, and a heat-resistant pressure-sensitive adhesive sheet.

Specific means for solving the problem include the following forms.

<1> a structural unit derived from N-methoxymethyl acrylamide, a structural unit derived from a monomer having a hydroxyl group, and a structural unit derived from a (meth)acrylic acid alkylester monomer, wherein the N-methoxymethyl acrylamide A pressure-sensitive adhesive composition for a heat-resistant pressure-sensitive adhesive sheet comprising a (meth)acrylic copolymer and a crosslinking agent in which the content of the constituent units derived from is in the range of 6% by mass or more to 30% by mass or less with respect to the total constituent units.

<2> The heat-resistant adhesive sheet according to <1>, wherein the content rate of the structural unit derived from the monomer having a hydroxyl group in the (meth)acrylic copolymer is in the range of 1.5% by mass or more and 20% by mass or less with respect to all the structural units. adhesive composition for

<3> The heat-resistant adhesive according to <1> or <2>, wherein the ratio of the number of moles of the crosslinkable functional group in the crosslinking agent to the total mole number of hydroxyl groups and carboxyl groups in the (meth)acrylic copolymer is in the range of 0.1 or more and 1.0 or less. A pressure-sensitive adhesive composition for sheets.

<4> In any one of <1> to <3>, wherein the ratio of the number of moles of the crosslinkable functional group in the crosslinking agent to the total number of moles of hydroxyl groups and carboxyl groups in the (meth)acrylic copolymer is in the range of 0.3 or more and 0.5 or less. The adhesive composition for heat-resistant adhesive sheets as described.

<5> The adhesive composition for heat resistant adhesive sheets in any one of <1>-<4> whose carbon number of the alkyl group in the said (meth)acrylic-acid alkylester monomer is the range of 4 or more and 12 or less.

<6> The heat resistance according to any one of <1> to <5>, wherein the (meth)acrylic acid alkylester monomer contains a (meth)acrylic acid alkylester monomer having a glass transition temperature of -20°C or less when a homopolymer is used. A pressure-sensitive adhesive composition for an adhesive sheet.

<7> The (meth)acrylic copolymer does not contain a structural unit derived from a monomer having a carboxy group, or the content of a structural unit derived from a monomer having a carboxy group is greater than 0% by mass and 10% by mass or less with respect to the total structural units The adhesive composition for heat resistant adhesive sheets in any one of <1>-<6> which is a range.

<8> The pressure-sensitive adhesive composition for heat-resistant adhesive sheets according to any one of <1> to <7>, wherein the weight average molecular weight of the (meth)acrylic copolymer is in the range of 200,000 or more and 1.2 million or less.

<9> The pressure-sensitive adhesive composition for a heat-resistant pressure-sensitive adhesive sheet according to any one of <1> to <8>, wherein the cross-linking agent is an isocyanate-based cross-linking agent.

<10> The heat-resistant adhesive sheet provided with the adhesive layer formed by the adhesive composition for heat-resistant adhesive sheets in any one of <1>-<9>.

According to the present invention, even when heat-treated at a high temperature (for example, 260° C.), good adhesion and peelability to the adherend can be maintained, so that it is difficult to contaminate the surface of the adherend during peeling, and oxidation of the adherend can be suppressed. A pressure-sensitive adhesive composition for a heat-resistant pressure-sensitive adhesive sheet capable of forming a pressure-sensitive adhesive layer and a heat-resistant pressure-sensitive adhesive sheet are provided.

EMBODIMENT OF THE INVENTION Hereinafter, specific embodiment of this invention is described in detail. However, this invention is not limited at all to the following embodiment, A change can be added and implemented suitably within the range of the objective of this invention.

In the present specification, the numerical range indicated using "~" means a range including the numerical values described before and after "~" as the minimum and maximum values, respectively.

In the numerical range described step by step in this specification, the upper limit or lower limit described in a certain numerical range may be substituted with the upper limit or lower limit of the numerical range described in another stepwise manner. In addition, in the numerical range described in this specification, you may substitute the value shown in the Example for the upper limit or lower limit described in a certain numerical range.

In the present specification, a combination of two or more preferred forms is a more preferred form.

In the present specification, the amount of each component means the total amount of the plurality of types of substances unless otherwise specified when there are multiple types of substances corresponding to each component.

In the present specification, "(meth)acrylic copolymer" means that the content of the structural unit derived from the monomer having a (meth)acryloyl group is 50% by mass of the total structural units [that is, the total structural units of the (meth)acrylic copolymer]. It means more than a copolymer.

As used herein, the term “adhesive composition” refers to a liquid or paste-like material before the crosslinking reaction is completed.

As used herein, the term "adhesive layer" refers to a film made of a material after the crosslinking reaction in the pressure-sensitive adhesive composition is completed (so-called crosslinked product of the pressure-sensitive adhesive composition).

In the present specification, “(meth)acryl” is a term including both “acryl” and “methacryl”, and “(meth)acrylate” is a term containing both “acrylate” and “methacrylate”. and "(meth)acryloyl" is a term including both "acryloyl" and "methacryloyl".

In the present specification, "n-" means normal, "i-" means iso, "s-" means secondary, and "t-" means tertiary.

[Adhesive composition for heat-resistant adhesive sheet]

The pressure-sensitive adhesive composition for a heat-resistant pressure-sensitive adhesive sheet of the present invention (hereinafter, simply referred to as “adhesive composition”) is a structural unit derived from N-methoxymethyl acrylamide, a structural unit derived from a monomer having a hydroxyl group, and (meth)acrylic acid alkyl ester A (meth)acrylic copolymer containing a structural unit derived from a monomer, wherein the content of the structural unit derived from N-methoxymethyl acrylamide is in the range of 6% by mass or more and 30% by mass or less with respect to the total structural units [hereinafter , "also referred to as a specific (meth)acrylic copolymer"] and a crosslinking agent.

According to the pressure-sensitive adhesive composition of the present invention, even when heat-treated at a high temperature (eg, 260° C.), good adhesion and releasability to the adherend can be maintained, so that it is difficult to contaminate the surface of the adherend during peeling, and oxidation of the adherend It is possible to form a pressure-sensitive adhesive layer that can suppress the.

Although it is not clear about the reason why the adhesive composition of this invention can show such an effect, the present inventors guess as follows. However, the following guess does not interpret the adhesive composition of this invention limitedly, but demonstrates it as an example.

The pressure-sensitive adhesive composition of the present invention contains a structural unit derived from a monomer having a hydroxyl group and a structural unit derived from a (meth)acrylic acid alkylester monomer, and a structural unit derived from N-methoxymethyl acrylamide, which has relatively high polarity, in a specific range. Since it contains the (meth)acrylic copolymer and the crosslinking agent contained in an amount, it is considered that the pressure-sensitive adhesive layer formed is in close contact with the adherend and exhibits good adhesion and releasability to the adherend in the initial stage (before the so-called heat treatment).

In general, the heat-treated pressure-sensitive adhesive layer tends to have an increase in adhesive strength and a defect in which it is difficult to peel from the adherend. In general, it is considered that the reason for the increase in the adhesive strength of the pressure-sensitive adhesive layer by heat treatment is that the pressure-sensitive adhesive layer becomes flexible in a high-temperature environment, so that it spreads wet and spreads to the adherend, thereby increasing the adhesive strength with the adherend interface. The pressure-sensitive adhesive composition of the present invention comprises a structural unit derived from a monomer having a hydroxyl group and a structural unit derived from a (meth)acrylic acid alkylester monomer, and a structural unit derived from N-methoxymethyl acrylamide that undergoes a self-crosslinking reaction under a high temperature environment. Since the (meth)acrylic copolymer contained in an amount in a specific range is contained, cure shrinkage resulting from the self-crosslinking reaction of N-methoxymethyl acrylamide occurs during heat treatment in the pressure-sensitive adhesive layer to be formed, and wetness spreads to the adherend It is thought that the excessive increase in adhesive force due to this is suppressed. For this reason, even if it is a case where the adhesive layer formed of the adhesive composition of this invention is heat-processed at high temperature of 260 degreeC, for example, it is thought that the favorable adhesiveness and peelability with respect to a to-be-adhered body can be maintained.

In general, the heat-treated pressure-sensitive adhesive layer has a reduced cohesive force and tends to form glue residue on the surface of the adherend when peeled from the adherend. The pressure-sensitive adhesive composition of the present invention comprises a structural unit derived from a monomer having a hydroxyl group and a structural unit derived from a (meth)acrylic acid alkylester monomer, and a structural unit derived from N-methoxymethyl acrylamide that undergoes a self-crosslinking reaction under a high temperature environment. Since it contains the (meth)acrylic copolymer contained in an amount within a specific range, it is thought that the self-crosslinking reaction of N-methoxymethyl acrylamide proceeds when heat-treated in the pressure-sensitive adhesive layer to be formed, thereby suppressing the decrease in cohesive force. For this reason, it is thought that it is hard to contaminate the surface of a to-be-adhered body at the time of peeling, even if it is a case where the adhesive layer formed of the adhesive composition of this invention is heat-processed at high temperature of 260 degreeC, for example.

In addition, since the pressure-sensitive adhesive composition of the present invention contains a (meth)acrylic copolymer containing a structural unit derived from N-methoxymethyl acrylamide having high polarity in an amount within a specific range, for example, when the adherend is copper It is thought that adhesion becomes more favorable, the float of an adhesive layer from to-be-adhered body is suppressed, and oxidation of copper resulting from the oxygen mixed in the interface of an adhesive layer and to-be-adhered body can be suppressed.

However, when the pressure-sensitive adhesive sheet is adhered to the adherend, oxygen may be mixed between the pressure-sensitive adhesive layer and the adherend. When this mixed oxygen acts on an adherend, the adherend is oxidized, and spots may appear. In particular, in the hot press process, which is one of the manufacturing processes of electronic members, since the adhesive sheet pasted to the adherend is sandwiched between the upper and lower metal plates, the interface between the adherend and the pressure-sensitive adhesive layer is closed and oxygen is released to the outside when oxygen is mixed. It is difficult. For this reason, spot-like traces (also called "bubble traces") resulting from oxygen remaining at the interface between the adherend and the pressure-sensitive adhesive layer are likely to occur. In particular, when a to-be-adhered body is copper foil, there exists a tendency for bubble traces to produce more easily. The pressure-sensitive adhesive composition of the present invention comprises a (meth)acrylic copolymer containing a structural unit derived from N-methoxymethyl acrylamide, which generates methanol that causes a reducing action on copper oxide when thermally cross-linked, in an amount within a specific range. Since it contains, it is thought that the expression of a bubble trace can be suppressed.

[Specific (meth)acrylic copolymer]

The pressure-sensitive adhesive composition of the present invention includes a structural unit derived from N-methoxymethyl acrylamide, a structural unit derived from a monomer having a hydroxyl group, and a structural unit derived from a (meth)acrylic acid alkylester monomer, wherein the N-methoxy Includes (meth)acrylic copolymers [that is, specific (meth)acrylic copolymers] in which the content of the structural units derived from methyl acrylamide is in the range of 6% by mass or more and 30% by mass or less with respect to the total structural units.

<Structural unit derived from N-methoxymethyl acrylamide>

Certain (meth)acrylic copolymers contain structural units derived from N-methoxymethyl acrylamide.

In the present specification, "a structural unit derived from N-methoxymethyl acrylamide" means a structural unit formed by addition polymerization of N-methoxymethyl acrylamide.

The content rate of the structural unit derived from N-methoxymethyl acrylamide in the specific (meth)acrylic copolymer is in the range of 6% by mass or more and 30% by mass or less with respect to the total structural units of the specific (meth)acrylic copolymer, 8 It is preferable that it is the range of mass % or more and 25 mass % or less, and it is more preferable that it is the range of 10 mass % or more and 20 mass % or less.

If the content of the structural unit derived from N-methoxymethyl acrylamide in the specific (meth)acrylic copolymer is 6% by mass or more with respect to the total structural units of the specific (meth)acrylic copolymer, the pressure-sensitive adhesive layer formed is heat-treated at high temperature Even if it is the case where it is peeled, it shows the tendency which it is hard to contaminate the surface of a to-be-adhered body at the time of peeling.

If the content of the constituent units derived from N-methoxymethyl acrylamide in the specific (meth)acrylic copolymer is 30% by mass or less with respect to the total constituent units of the specific (meth)acrylic copolymer, the pressure-sensitive adhesive layer formed is heat-treated at high temperature Even if it is the case where it is oxidized, it shows the tendency which can suppress the oxidation of a to-be-adhered body.

<Structural unit derived from a monomer having a hydroxyl group>

A specific (meth)acrylic copolymer contains the structural unit derived from the monomer which has a hydroxyl group. The hydroxyl group of the structural unit derived from the monomer having a hydroxyl group can form a crosslinked structure by a crosslinking reaction with a crosslinking agent described later.

As used herein, the term "structural unit derived from a monomer having a hydroxyl group" means a structural unit formed by addition polymerization of a monomer having a hydroxyl group.

The kind in particular of the monomer which has a hydroxyl group is not restrict|limited.

As a specific example of the monomer which has a hydroxyl group, 2-hydroxymethyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate , 4-hydroxybutyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, 10-hydroxydecyl (meth) acrylate, 12-hydroxylauryl (meth) acrylate, 3-methyl- 3-hydroxybutyl (meth)acrylate, 1,1-dimethyl-3-hydroxybutyl (meth)acrylate, 1,3-dimethyl-3-hydroxybutyl (meth)acrylate, 2,2,4 -trimethyl-3-hydroxypentyl (meth)acrylate, 2-ethyl-3-hydroxyhexyl (meth)acrylate, N-hydroxyethyl (meth)acrylamide, etc. are mentioned.

As a monomer which has a hydroxyl group, hydroxyalkyl (meth)acrylate is preferable, for example from a viewpoint that copolymerization with a (meth)acrylic-acid alkylester monomer is favorable.

Moreover, as a monomer which has a hydroxyl group, the hydroxyalkyl (meth)acrylate which has a C1-C5 hydroxyalkyl group is preferable, for example from a viewpoint of compatibility with a (meth)acrylic-acid alkylester monomer being favorable, and has a carbon number Hydroxyalkyl (meth)acrylate having a hydroxyalkyl group of 2 to 4 is more preferable, and the group consisting of 2-hydroxyethyl methacrylate, 4-hydroxybutyl acrylate and 2-hydroxyethyl acrylate At least one selected from is more preferable.

The specific (meth)acrylic copolymer may contain only 1 type and may contain 2 or more types of structural units derived from the monomer which has a hydroxyl group.

The content of the structural unit derived from the monomer having a hydroxyl group in the specific (meth)acrylic copolymer is preferably in the range of 1% by mass or more and 25% by mass or less with respect to the total structural units of the specific (meth)acrylic copolymer, 1.5 It is more preferable that it is the range of mass % or more and 20 mass % or less, It is more preferable that it is the range of 5 mass % or more and 15 mass % or less, It is especially preferable that it is the range of 5 mass % or more and 10 mass % or less.

When the content of the structural unit derived from the monomer having a hydroxyl group in the specific (meth)acrylic copolymer is 1% by mass or more with respect to the total structural units of the specific (meth)acrylic copolymer, the formed pressure-sensitive adhesive layer has a more suitable cohesive force. Therefore, even when heat-treated at a high temperature, good adhesion and releasability to the adherend are more easily maintained, and the surface of the adherend is less likely to be contaminated during peeling.

If the content of the structural unit derived from the monomer having a hydroxyl group in the specific (meth)acrylic copolymer is 25% by mass or less with respect to the total structural units of the specific (meth)acrylic copolymer, the pressure-sensitive adhesive layer formed even when heat-treated at high temperature It shows the tendency which can suppress oxidation of a to-be-adhered body more favorably.

<Structural unit derived from (meth)acrylic acid alkyl ester monomer>

A specific (meth)acrylic copolymer contains a structural unit derived from a (meth)acrylic acid alkylester monomer.

The structural unit derived from the (meth)acrylic acid alkylester monomer contributes to adjustment of adhesive force.

In the present specification, "a structural unit derived from a (meth) acrylic acid alkyl ester monomer" means a structural unit formed by addition polymerization of a (meth) acrylic acid alkyl ester monomer.

In addition, the (meth)acrylic acid alkylester monomer which has at least one of a hydroxyl group and a carboxy group is not contained in "(meth)acrylic acid alkylester monomer" in this specification.

The kind in particular of the (meth)acrylic acid alkylester monomer is not restrict|limited.

As a (meth)acrylic-acid alkylester monomer, an unsubstituted (meth)acrylic-acid alkylester monomer is preferable.

Linear, branched or cyclic any may be sufficient as the alkyl group of a (meth)acrylic-acid alkylester monomer.

The number of carbon atoms in the alkyl group is, for example, preferably in the range of 1 or more and 18 or less, more preferably 1 or more and 12 or less, and still more preferably 4 or more and 12 or less from the viewpoint of adhesive strength.

In particular, when the carbon number of the alkyl group is in the range of 4 or more and 12 or less, the cohesive force of the formed pressure-sensitive adhesive layer becomes more suitable, so even when heat-treated at high temperature, good adhesion and peelability to the adherend are more easily maintained, and It shows the tendency which it is hard to contaminate the surface of a complex more.

Specific examples of the (meth)acrylic acid alkyl ester monomer include methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, i-butyl (meth)acrylate, s-butyl (meth)acrylate , t-butyl (meth) acrylate, n-octyl (meth) acrylate, i-octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-nonyl (meth) acrylate, i- nonyl (meth)acrylate, n-decyl (meth)acrylate, stearyl (meth)acrylate, lauryl (meth)acrylate, cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, and the like. there is.

The (meth)acrylic acid alkyl ester monomer preferably contains a (meth)acrylic acid alkyl ester monomer having a glass transition temperature of -20°C or less when, for example, a homopolymer, and the glass transition temperature when a homopolymer is - It is more preferable to include a (meth)acrylic acid alkylester monomer in the range of 80°C or more and -20°C or less, and (meth)acrylic acid having a glass transition temperature in the range of -80°C or more and -50°C or less when a homopolymer is used. It is more preferable that an alkylester monomer is included, and it is especially preferable that the glass transition temperature at the time of setting it as a homopolymer contains the range of -80 degreeC or more -55 degreeC or less (meth)acrylic acid alkylester monomer.

When the (meth) acrylic acid alkyl ester monomer contains a (meth) acrylic acid alkyl ester monomer having a glass transition temperature of -20 ° C. or less when it is used as a homopolymer, the increase in the adhesive force of the pressure-sensitive adhesive layer in the case of heat treatment at high temperature is more suppressed. Even after heat treatment at a high temperature, good adhesion and peelability of the pressure-sensitive adhesive layer to an adherend are more easily maintained.

As a (meth)acrylic acid alkylester monomer having a glass transition temperature of -20°C or less when used as a homopolymer, 2-ethylhexyl acrylate (glass transition temperature as a homopolymer: -76°C), n-butyl acrylate ( Glass transition temperature when it is used as a homopolymer: -57 degreeC), i-octyl acrylate (glass transition temperature when it is set as a homopolymer: -75 degreeC), etc. are mentioned.

The specific (meth)acrylic copolymer may contain only 1 type and may contain 2 or more types of structural units derived from the (meth)acrylic acid alkylester monomer.

Although the content rate of the structural unit derived from the (meth)acrylic acid alkylester monomer in a specific (meth)acrylic-type copolymer is not specifically limited, For example, 50 mass % or more with respect to all the structural units of a specific (meth)acrylic-type copolymer. Preferably, it is more preferably in the range of 50 mass % or more and 93 mass % or less, more preferably 69 mass % or more and 92.5 mass % or less, and particularly preferably in the range of 74 mass % or more and 90 mass % or less. .

Here, the content rate of the structural unit derived from the (meth)acrylic acid alkylester monomer in the specific (meth)acrylic copolymer is 50% by mass or more with respect to the total structural units of the specific (meth)acrylic acid alkylester (meth)acrylic acid alkylester It means that the structural unit derived from the monomer is included as a main component of the structural unit constituting the specific (meth)acrylic copolymer.

<Structural unit derived from a monomer having a carboxyl group>

The specific (meth)acrylic copolymer may contain the structural unit derived from the monomer which has a carboxy group. A carboxyl group of a structural unit derived from a monomer having a carboxyl group can form a crosslinked structure by a crosslinking reaction with a crosslinking agent described later.

As used herein, the term "structural unit derived from a monomer having a carboxyl group" means a structural unit formed by addition polymerization of a monomer having a carboxyl group.

The type of the monomer having a carboxy group is not particularly limited.

Specific examples of the monomer having a carboxyl group include acrylic acid, methacrylic acid, crotonic acid, maleic anhydride, fumaric acid, itaconic acid, glutaconic acid, citraconic acid, ω-carboxy-polycaprolactone mono(meth)acrylate [eg, ω -carboxy-polycaprolactone (n≒2) monoacrylate], succinic acid ester (for example, 2-acryloyloxyethyl- succinic acid), etc. are mentioned.

When the specific (meth)acrylic copolymer includes a structural unit derived from a monomer having a carboxy group, only one type of structural unit derived from a monomer having a carboxy group may be included, or may include two or more types.

The content rate in particular of the structural unit derived from the monomer which has a carboxy group in a specific (meth)acrylic-type copolymer is not restrict|limited.

The specific (meth)acrylic copolymer does not contain a structural unit derived from a monomer having a carboxy group, or the content of a structural unit derived from a monomer having a carboxy group is 0% by mass based on the total structural units of the specific (meth)acrylic copolymer It is preferable that it is in the range of more than 10% by mass, and the content of the structural unit derived from the monomer having a carboxy group is not included or the content of the structural unit derived from the monomer having a carboxy group is in the total structural unit of the specific (meth)acrylic copolymer. It is more preferable that it is in the range of more than 0% by mass to 5% by mass or less, and the content of the structural unit derived from the monomer having a carboxy group is not included or the content of the structural unit derived from the monomer having a carboxy group is a specific (meth)acrylic copolymer. It is more preferable that it is more than 0 mass % and 3 mass % or less with respect to the total structural unit of , and it is especially preferable that the structural unit derived from the monomer which has a carboxy group is not included.

<Other constituent units>

The specific (meth)acrylic copolymer may contain structural units (so-called other structural units) other than the aforementioned structural units within the range in which the effects of the present invention are exhibited.

Examples of the monomer constituting the other structural unit include (meth)acrylate having an aromatic ring represented by benzyl (meth)acrylate and phenoxyethyl (meth)acrylate, methoxyethyl (meth)acrylate, and Aromatic monovinyl, acrylo, represented by alkoxyalkyl (meth)acrylate, styrene, α-methylstyrene, t-butylstyrene, p-chlorostyrene, chloromethylstyrene, and vinyltoluene represented by oxyethyl (meth)acrylate and vinyl cyanide represented by nitrile and methacrylonitrile, and vinyl esters represented by vinyl formate, vinyl acetate, vinyl propionate and vinyl versatate. Moreover, various derivatives of these monomers are mentioned.

When the specific (meth)acrylic copolymer contains other structural units, only 1 type may be included and may contain 2 or more types of other structural units.

When the specific (meth)acrylic copolymer contains other structural units, the content rate of other structural units in the specific (meth)acrylic copolymer is not particularly limited, and may be appropriately set according to the purpose.

<<Glass transition temperature of specific (meth)acrylic copolymer>>

The glass transition temperature (also referred to as “Tg”) of the specific (meth)acrylic copolymer is preferably -20°C or less, more preferably -80°C or more and -20°C or less, and -80°C or more -50°C. It is more preferable that it is the range below, it is especially preferable that it is the range of -75 degreeC or more and -55 degreeC or less, It is most preferable that it is the range of -75 degreeC or more and -60 degreeC or less.

If the glass transition temperature of the specific (meth)acrylic copolymer is -20°C or less, the increase in the adhesive strength of the pressure-sensitive adhesive layer when heat-treated at a high temperature is more suppressed. It shows the tendency which peelability is more easy to maintain.

The glass transition temperature of a specific (meth)acrylic copolymer is a value obtained by converting the absolute temperature (unit: K; hereinafter the same) obtained by calculation from the following formula 1 into Celsius temperature (unit: ℃; hereinafter the same).

1/Tg=m1/Tg1+m2/Tg2+… +m(k-1)/Tg(k-1)+mk/Tgk (Equation 1)

In formula 1, Tg1, Tg2, ... , Tg(k-1) and Tgk respectively represent the glass transition temperatures expressed as absolute temperatures when each monomer constituting the specific (meth)acrylic copolymer is used as a homopolymer. m1, m2, … , m(k-1) and mk represent the mole fraction of each monomer constituting the specific (meth)acrylic copolymer, respectively, m1+m2+... +m(k-1)+mk=1.

In addition, absolute temperature can be converted to degrees Celsius by subtracting 273 from absolute temperature, and Celsius temperature can be converted to absolute temperature by adding 273 to Celsius temperature.

In the present specification, "the glass transition temperature expressed as an absolute temperature when a homopolymer is used" refers to a glass transition temperature expressed as an absolute temperature of a homopolymer prepared by polymerization of the monomer alone.

The glass transition temperature of the homopolymer was measured using a differential scanning calorimetry (DSC) [model number: EXSTAR6000, Seiko Instruments Co., Ltd.] in a nitrogen stream of 10 mg of a measurement sample and a temperature increase rate of 10 ° C./min. DSC curve obtained by measuring The inflection point of was taken as the glass transition temperature of the homopolymer.

The "glass transition temperature expressed in degrees Celsius when a homopolymer is used" of representative monomers is -76 ° C for 2-ethylhexyl acrylate (2EHA), -10 ° C for 2-ethylhexyl methacrylate (2EHMA), n- Butyl acrylate (n-BA) is -57 ° C, n-butyl methacrylate (n-BMA) is 21 ° C, t-butyl acrylate (t-BA) is 41 ° C, t-butyl methacrylate (t -BMA) is 107°C, i-butyl methacrylate (i-BMA) is 48°C, methyl acrylate (MA) is 5°C, methyl methacrylate (MMA) is 103°C, isobornyl methacrylate (IBXMA) ) is 155°C, isobornyl acrylate (IBXA) is 96°C, ethyl acrylate (EA) is -27°C, methacrylic acid (MAA) is 185°C, 4-hydroxybutyl acrylate (4HBA) is -39 ℃, 2-hydroxyethyl acrylate (2HEA) -15 ℃, 2-hydroxyethyl methacrylate (2HEMA) 55 ℃, 2-hydroxypropyl acrylate (2HPA) -7 ℃, acrylic acid (AA) ) is 163°C, i-octyl acrylate (i-OA) is -75°C, dimethylaminoethyl methacrylate (DM) is 18°C, ω-carboxy-polycaprolactone (n≒2) monoacrylate is - 30° C. and -40° C. for 2-acryloyloxyethyl-succinic acid.

The glass transition temperature of a specific (meth)acrylic-type copolymer can be suitably adjusted by using 2 or more types of monomers from which glass transition temperature differs when it is set as a homopolymer, for example.

<<The weight average molecular weight of the specific (meth)acrylic copolymer>>

The weight average molecular weight (also referred to as "Mw") of the specific (meth)acrylic copolymer is preferably in the range of 200,000 or more and 1.2 million or less, more preferably 200,000 or more and 1,000,000 or less, and 200,000 or more and 80 It is more preferable that it is the range of 10,000 or less, and it is especially preferable that it is the range of 200,000 or more and 700,000 or less.

When the weight average molecular weight of the specific (meth)acrylic copolymer is 200,000 or more, the formed pressure-sensitive adhesive layer has more suitable cohesive force, so it is difficult to contaminate the surface of the adherend during peeling even when heat-treated at high temperature.

If the weight average molecular weight of a specific (meth)acrylic-type copolymer is 1.2 million or less, since a viscosity becomes more suitable for an adhesive composition, it shows the tendency which applicability|paintability improves more.

The weight average molecular weight of a specific (meth)acrylic-type copolymer is a value measured by the following method. Specifically, it measures according to the following (1)-(3).

(1) A solution of a specific (meth)acrylic copolymer is applied to a release paper and dried at 100° C. for 1 minute to obtain a specific (meth)acrylic copolymer in the form of a film.

(2) A sample solution having a solid content concentration of 0.2% by mass is obtained using the film-like specific (meth)acrylic copolymer and tetrahydrofuran obtained in the above (1). In addition, the "solid content concentration" here means the mass ratio of the specific (meth)acrylic-type copolymer which occupies for a sample solution.

(3) Using gel permeation chromatography (GPC), the weight average molecular weight of a specific (meth)acrylic copolymer is measured as a standard polystyrene conversion value under the following conditions.

~Condition~

Measuring device: High-speed GPC [Model number: HLC-8220 GPC, Tosoh Corporation]

Detector: Differential Refractometer (RI) [Assembled in HLC-8220, Tosoh Corporation]

Column: 4 TSK-GEL GMHXL [Toso Co., Ltd.] connected in series

Column temperature: 40°C

Eluent: tetrahydrofuran

Injection volume of sample solution: 100 μL

Flow rate: 0.8 mL/min

The weight average molecular weight of a specific (meth)acrylic copolymer can be made into a desired value by adjusting polymerization temperature, polymerization time, the usage-amount of organic solvent, the kind of polymerization initiator, the usage-amount of a polymerization initiator, etc.

<< Content rate of specific (meth)acrylic copolymer >>

Although the content rate in particular of a specific (meth)acrylic-type copolymer in the adhesive composition of this invention is not restrict|limited, For example, it is preferable that it is the range of 65 mass % or more and 99.99 mass % or less with respect to the total solid content in an adhesive composition, 70 mass % or more and 99.99% by mass or less, more preferably 75% by mass or more and 99.95% by mass or less, and particularly preferably 80% by mass or more and 99.95% by mass or less.

In the present specification, "total solid content in the pressure-sensitive adhesive composition" means the total mass of the pressure-sensitive adhesive composition when the pressure-sensitive adhesive composition does not contain a solvent, and when the pressure-sensitive adhesive composition contains a solvent, the mass of the residue excluding the solvent from the pressure-sensitive adhesive composition it means.

As used herein, the term “solvent” refers to water and an organic solvent.

[Method for producing specific (meth)acrylic copolymer]

The manufacturing method in particular of a specific (meth)acrylic-type copolymer is not restrict|limited.

The specific (meth)acrylic copolymer can be produced by polymerizing the above-mentioned monomers by a known polymerization method typified by, for example, a solution polymerization method, an emulsion polymerization method, a suspension polymerization method, and a bulk polymerization method.

As a polymerization method, when preparing the adhesive composition of this invention after manufacture, a solution polymerization method is preferable at the point which a treatment process is comparatively simple and can perform in a short time.

In the solution polymerization method, in general, a predetermined organic solvent, a monomer, a polymerization initiator, and a chain transfer agent used as necessary are put into a polymerization tank, and the reaction is heated for several hours while stirring at the reflux temperature of the organic solvent in a nitrogen stream. In this case, at least one part of an organic solvent, a monomer, a polymerization initiator, and/or a chain transfer agent may be added sequentially.

Examples of the organic solvent used in the polymerization reaction include aromatic hydrocarbon compounds, aliphatic or alicyclic hydrocarbon compounds, ester compounds, ketone compounds, glycol ether compounds, and alcohol compounds.

More specifically, examples of the organic solvent used in the polymerization reaction include benzene, toluene, ethylbenzene, n-propylbenzene, t-butylbenzene, o-xylene, m-xylene, p-xylene, tetralin, decalin. and aromatic hydrocarbon compounds represented by aromatic naphtha, n-hexane, n-heptane, n-octane, i-octane, n-decane, dipentene, petroleum spirit, petroleum naphtha and aliphatic or alicyclic hydrocarbon represented by terepine oil. ester compounds represented by ethyl acetate, n-butyl acetate, n-amyl acetate, 2-hydroxyethyl acetate, 2-butoxyethyl acetate, 3-methoxybutyl acetate and methyl benzoate, acetone, methyl ethyl ketone; Ketone compounds represented by methyl-i-butyl ketone, isophorone, cyclohexanone and methylcyclohexanone, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monomethyl ether Glycol ether compounds represented by ethylene glycol monoethyl ether and diethylene glycol monobutyl ether, methyl alcohol, ethyl alcohol, n-propyl alcohol, i-propyl alcohol, n-butyl alcohol, i-butyl alcohol, s-butyl alcohol and alcohol compounds represented by t-butyl alcohol.

When producing a specific (meth)acrylic copolymer, it is preferable to use an organic solvent that does not easily cause chain transfer during polymerization such as an aromatic hydrocarbon compound, an ester compound, or a ketone compound. In particular, the solubility and polymerization of the specific (meth)acrylic copolymer It is preferable to use at least one selected from the group consisting of ethyl acetate, toluene, and methyl ethyl ketone from the viewpoint of ease of reaction and the like.

In the case of a polymerization reaction, only 1 type may be used and 2 or more types of organic solvents may be used.

As a polymerization initiator, the organic peroxide, azo compound, etc. which are used by the normal solution polymerization method are mentioned.

Examples of the organic peroxide include t-butyl hydroperoxide, cumene hydroperoxide, dicumyl peroxide, benzoyl peroxide, lauroyl peroxide, caproyl peroxide, di-i-propyl peroxydicarbonate, and di-2-ethylhexyl. Peroxydicarbonate, t-butylperoxypivalate, 2,2-bis(4,4-di-t-butylperoxycyclohexyl)propane, 2,2-bis(4,4-di-t-amylper) oxycyclohexyl)propane, 2,2-bis(4,4-di-t-octylperoxycyclohexyl)propane, 2,2-bis(4,4-di-α-cumylperoxycyclohexyl)propane; 2,2-bis(4,4-di-t-butylperoxycyclohexyl)butane and 2,2-bis(4,4-di-t-octylperoxycyclohexyl)butane are mentioned.

Examples of the azo compound include 2,2'-azobisisobutyronitrile [AIBN], 2,2'-azobis(2,4-dimethylvaleronitrile) [ABVN], 2,2'-azobis( 4-methoxy-2,4-dimethylvaleronitrile), 1,1'-azobis(cyclohexane-1-carbonitrile), and 2,2'-azobis(isobutyric acid)dimethyl.

In the production of a specific (meth)acrylic copolymer, it is preferable to use a polymerization initiator that does not cause a graft reaction during the polymerization reaction, and particularly preferably an azo compound.

In the case of a polymerization reaction, only 1 type may be used and 2 or more types may be used for a polymerization initiator.

The usage-amount in particular of a polymerization initiator is not restrict|limited, For example, it can set suitably according to the molecular weight of the specific (meth)acrylic-type copolymer made into the objective.

At the time of manufacture of a specific (meth)acrylic-type copolymer, you may use a chain transfer agent as needed.

Examples of the chain transfer agent include cyanoacetic acid, cyanoacetic acid alkyl ester compounds having 1 to 8 carbon atoms, bromoacetic acid and bromoacetic acid alkyl ester compounds having 1 to 8 carbon atoms, α-methylstyrene, anthracene, phenanthrene, Aromatic compounds represented by fluorene and 9-phenylfluorene, p-nitroaniline, nitrobenzene, dinitrobenzene, p-nitrobenzoic acid, p-nitrophenol and aromatic nitro compounds represented by p-nitrotoluene, benzoquinone and A benzoquinone derivative represented by 2,3,5,6-tetramethyl-p-benzoquinone, a borane derivative represented by tributylborane, carbon tetrabromide, carbon tetrachloride, 1,1,2,2-tetrabromoe Halogenated hydrocarbon compounds represented by tan, tribromoethylene, trichloroethylene, bromotrichloromethane, tribromomethane and 3-chloro-1-propene, aldehyde compounds represented by chloral and furaldehyde, carbon number 1 ~18 alkyl mercaptan compounds, aromatic mercaptan compounds represented by thiophenol and toluene mercaptan, mercaptoacetic acid, mercaptoacetic acid alkyl ester compounds having 1 to 10 carbon atoms, hydroxyalkyl mercaptan compounds having 1 to 12 carbon atoms and terpene compounds represented by pinene and terpinolene.

When a chain transfer agent is used in the production of a specific (meth)acrylic copolymer, the amount of the chain transfer agent used is not particularly limited, and may be appropriately set, for example, according to the molecular weight of the specific (meth)acrylic copolymer intended.

The polymerization temperature is not particularly limited, and can be appropriately set, for example, depending on the molecular weight of the specific (meth)acrylic copolymer intended.

[crosslinking agent]

The pressure-sensitive adhesive composition of the present invention contains a crosslinking agent.

The type of the crosslinking agent is not particularly limited.

As a crosslinking agent, an isocyanate type crosslinking agent, an epoxy type crosslinking agent, and a metal chelate type crosslinking agent are mentioned, for example.

Among these, as a crosslinking agent, an isocyanate type crosslinking agent is preferable.

As used herein, the term "isocyanate-based crosslinking agent" refers to a compound having two or more isocyanate groups in a molecule (so-called polyisocyanate compound). In addition, an "epoxy-type crosslinking agent" refers to the compound (so-called bifunctional or more than bifunctional epoxy compound) which has two or more epoxy groups in a molecule|numerator. In addition, a "metal chelate-type crosslinking agent" refers to a metal chelate compound (hereinafter also referred to simply as a "metal chelate compound") functioning as a crosslinking agent.

Examples of the polyisocyanate compound include aromatic polyisocyanate compounds such as xylylene diisocyanate (XDI), diphenylmethane diisocyanate, triphenylmethane triisocyanate and tolylene diisocyanate (TDI), hexamethylene diisocyanate (HMDI), and pentamethylene diisocyanate. Aliphatic or alicyclic polyisocyanate compounds, such as a hydrogenated substance of isocyanate (PDI), isophorone diisocyanate, and an aromatic polyisocyanate compound, etc. are mentioned.

Moreover, as a polyisocyanate compound, the dimer, trimer, or pentamer of the said polyisocyanate compound, the adduct body of the said polyisocyanate compound and polyol compounds, such as trimethylol propane, the biuret body of the said polyisocyanate compound, etc. are mentioned.

A commercial item can be used as an isocyanate type crosslinking agent.

Examples of commercially available isocyanate crosslinking agents include "Colonate (registered trademark) HX", "Colonate (registered trademark) HL-S", "Colonate (registered trademark) L", "Colonate (registered trademark) L-45E" , "Colonate (registered trademark) 2031", "Colonate (registered trademark) 2030", "Colonate (registered trademark) 2234", "Colonate (registered trademark) 2785", "Aquanate (registered trademark) 200" and "Aquanate (registered trademark)　210" [above, Toso Co., Ltd.], "Smidul (registered trademark)　N3300", "Death module (registered trademark)　N3400" and "Smidul (registered trademark)　N-75" [Above, Sumika Covestro Urethane], "Duranate (registered trademark) 　 E-405-80T", "Duranate (registered trademark) AE700-100", "Duranate (registered trademark) 　 24A-100" and "Duranate (registered trademark) TSE-100" [above, Asahi Kasei Co., Ltd.], "Takenate (registered trademark) D-110N", "Takenate (registered trademark) D-120N", "Takenate ( Registered trademark) M-631N", "MT-Olester (registered trademark) NP1200" and "Stavio (registered trademark) XD-340N" [above, Mitsui Chemicals Co., Ltd.] are mentioned.

Examples of the bifunctional or more functional epoxy compound include ethylene glycol diglycidyl ether, diethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, tripropylene glycol diglycidyl ether, and polypropylene. Glycol diglycidyl ether, neopentyl glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, polytetramethylene glycol diglycidyl ether, glycerol diglycidyl ether, glycerol triglycidyl ether , Diglycerol polyglycidyl ether, polyglycerol polyglycidyl ether, resorcinol diglycidyl ether, 2,2-dibromoneopentyl glycol diglycidyl ether, trimethylolpropane triglycidyl ether, penta Erythritol polyglycidyl ether, sorbitol polyglycidyl ether, adipic acid diglycidyl ester, phthalic acid diglycidyl ester, tris(glycidyl) isocyanurate, tris(glycidoxyethyl) iso cyanurate, 1,3-bis(N,N-glycidylaminomethyl)cyclohexane, N,N,N',N'-tetraglycidyl-1,3-benzene di(methanamine), etc. can be heard

A commercial item can be used as an epoxy-type crosslinking agent.

As an example of the commercial item of an epoxy-type crosslinking agent, "TETRAD (trademark)-X" and "TETRAD (trademark)-C" [above, Mitsubishi Gas Chemical Co., Ltd.] are mentioned.

Examples of the metal chelate compound include aluminum chelate compounds represented by aluminum monoacetylacetonate bis(ethylacetoacetate), aluminum tris(ethylacetoacetate) and aluminum tris(acetylacetonate), titanium chelate compounds, zirconium chelate compounds, cobalt chelate compounds, and the like. can be heard

A commercial item can be used as a metal chelate type crosslinking agent.

As an example of the commercial item of a metal chelate type crosslinking agent, "aluminchelate A", "aluminchelate D", and "ALCH-TR" [above, Kawaken Fine Chemicals Co., Ltd.] are mentioned.

The adhesive composition of this invention may contain 1 type of crosslinking agents, and may contain 2 or more types.

Content in particular of the crosslinking agent in the adhesive composition of this invention is not restrict|limited, For example, it sets suitably according to the kind of crosslinking agent.

For example, when the pressure-sensitive adhesive composition of the present invention contains an isocyanate-based crosslinking agent as a crosslinking agent, the content of the isocyanate-based crosslinking agent in the pressure-sensitive adhesive composition is 0.1 parts by mass or more and 15 parts by mass or less with respect to 100 parts by mass of the specific (meth)acrylic copolymer. It is preferable that it is the range, It is more preferable that it is the range of 0.3 mass part or more and 13 mass parts or less, It is more preferable that it is the range that it is 0.5 mass part or more and 12 mass parts or less.

When the content of the isocyanate-based crosslinking agent in the pressure-sensitive adhesive composition of the present invention is 0.1 parts by mass or more with respect to 100 parts by mass of the specific (meth)acrylic copolymer, the pressure-sensitive adhesive layer formed is the surface of the adherend at the time of peeling, even when heat-treated at a high temperature. It shows a tendency to be difficult to contaminate.

If the content of the isocyanate-based crosslinking agent in the pressure-sensitive adhesive composition of the present invention is 15 parts by mass or less with respect to 100 parts by mass of the specific (meth)acrylic copolymer, the pressure-sensitive adhesive layer formed is good adhesiveness and peelability to the adherend even when heat-treated at a high temperature This shows a tendency to be more easily maintained. Moreover, when a to-be-adhered body is copper, the tendency which can suppress the discoloration by oxidation of copper more favorably is shown.

<<Ratio of the number of moles of the crosslinkable functional group in the crosslinking agent to the total number of moles of hydroxyl groups and carboxyl groups in the (meth)acrylic copolymer>>

Ratio of the number of moles of crosslinkable functional groups in the crosslinking agent to the total moles of hydroxyl groups and carboxyl groups in the (meth)acrylic copolymer [that is, the number of moles of crosslinkable functional groups in the crosslinking agent/sum of hydroxyl groups and carboxyl groups in the (meth)acrylic copolymer number of moles] is not particularly limited, for example, preferably in the range of 0.05 or more and 1.2 or less, more preferably in the range of 0.1 or more and 1.0 or less, still more preferably in the range of 0.1 or more and 0.5 or less, and 0.3 or more and 0.5 It is especially preferable that it is the following range.

When the ratio of the number of moles of crosslinkable functional groups in the crosslinking agent to the total moles of hydroxyl and carboxyl groups in the (meth)acrylic copolymer is 0.05 or more, the formed pressure-sensitive adhesive layer has good adhesion and peelability to the adherend even when heat-treated at a high temperature. It is easy to hold|maintain, and also shows the tendency which it is hard to contaminate the surface of a to-be-adhered body at the time of peeling.

When the ratio of the number of moles of crosslinkable functional groups in the crosslinking agent to the total moles of hydroxyl and carboxyl groups in the (meth)acrylic copolymer is 1.2 or less, the formed pressure-sensitive adhesive layer can better suppress oxidation of the adherend even when heat-treated at high temperatures. indicates a possible trend.

As used herein, the term "crosslinkable functional group in the crosslinking agent" is a functional group possessed by the crosslinking agent, which means a group capable of crosslinking reaction with a hydroxyl group and a carboxyl group in the (meth)acrylic copolymer. For example, when the crosslinking agent is an isocyanate crosslinking agent, it means an isocyanate group, , means an epoxy group when the crosslinking agent is an epoxy crosslinking agent.

In the present specification, the number of moles of the crosslinkable functional group means the total number of moles of all the crosslinkable functional groups when there are a plurality of crosslinkable functional groups.

Ratio of the number of moles of crosslinkable functional groups in the crosslinking agent to the total moles of hydroxyl groups and carboxyl groups in the (meth)acrylic copolymer [that is, the number of moles of crosslinkable functional groups in the crosslinking agent/sum of hydroxyl groups and carboxyl groups in the (meth)acrylic copolymer number of moles] is calculated by the following formulas (1) to (3).

Molar number of crosslinkable functional groups in crosslinking agent [unit: mmol/solid content of crosslinking agent 100g]

= [Content of crosslinkable functional group in crosslinking agent (unit: mass %) / solid content of crosslinking agent (unit: mass %) x crosslinking agent blending amount (unit: g)] / chemical formula weight of crosslinkable functional group (unit: g / mol) x 1000… (One)

Total number of moles of hydroxyl and carboxyl groups in (meth)acrylic copolymer [unit: mmol/solid content of (meth)acrylic copolymer 100g]

= [Content of structural units derived from a monomer having a hydroxyl group in a specific (meth)acrylic copolymer (unit: mass%) / molecular weight of a structural unit derived from a monomer having a hydroxyl group (unit: g/mol) x having a hydroxyl group The number of hydroxyl groups in the structural unit derived from the monomer (valence) x 1000] + [The content of the structural unit derived from the monomer having a carboxyl group in the (meth)acrylic copolymer (unit: mass%) / derived from the monomer having a carboxyl group Molecular weight of the structural unit (unit: g/mol) x the number of carboxyl groups in the structural unit derived from a monomer having a carboxyl group (valence) x 1000]... (2)

Ratio of the number of moles of the crosslinkable functional group in the crosslinking agent to the total number of moles of hydroxyl and carboxyl groups in the (meth)acrylic copolymer

= The value obtained by the formula (1) / The value obtained by the formula (2)... (3)

In addition, when the crosslinking agent is a metal chelate-based crosslinking agent, for example, the hydroxyl group contained in the specific (meth)acrylic copolymer is coordinated with the central metal in the metal chelate compound, which is a metal chelate-based crosslinking agent. By substituting with the number, the number of moles (so-called molar equivalent) of the metal chelate compound used for calculation of the molar equivalent ratio can be obtained.

In the present invention, for example, since the valence of the central metal in the aluminum chelate compound, which is a metal chelate-based crosslinking agent, is 3, the aluminum chelate compound can be calculated by substituting for one having a functional group of 3 moles per 1 mole.

The number of moles of the metal chelate compound is a value calculated by the following formula.

Number of moles of metal chelate compound=(A×B/C)/(D ₁ ×E ₁ /F ₁ +D ₂ ×E ₂ /F ₂ +…+D _n ×E _n ×F _n )

A = valence of the metal of the metal chelate compound

B = 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 = Content ratio (mass %) of each monomer having at least one of a hydroxyl group and a carboxy group in all monomers used in the specific (meth)acrylic copolymer

E ₁ , E ₂ , … , E _n = the total number of hydroxyl groups and carboxyl groups contained in one molecule of each monomer having at least one of a hydroxyl group and a carboxyl group

F ₁ , F ₂ , … , F _n = molecular weight of each monomer having at least one of a hydroxyl group and a carboxy group used in a specific (meth)acrylic copolymer

In addition, n represents the number of the types of the monomer used, for example, when there is one type of monomer used, _{only D 1} is used for calculation, and D ₂ ... D _n is not used in the calculation.

[Organic solvent]

The adhesive composition of this invention may contain the organic solvent from a viewpoint of an applicability|paintability improvement, for example.

As an organic solvent, the thing similar to the organic solvent used at the time of the polymerization reaction of the specific (meth)acrylic-type copolymer mentioned above is mentioned, for example.

When the adhesive composition of this invention contains an organic solvent, only 1 type may be included and may contain 2 or more types of organic solvents.

When the adhesive composition of this invention contains an organic solvent, content in particular of an organic solvent is not restrict|limited, According to the objective, it can set suitably.

[Other ingredients]

The adhesive composition of this invention may contain components (so-called other components) other than the components mentioned above as needed in the range which does not impair the effect of this invention.

As other components, polymers other than a specific (meth)acrylic-type copolymer, a crosslinking catalyst, antioxidant, a coloring agent (for example, dye and a pigment), a light stabilizer (for example, ultraviolet absorber), etc. are mentioned.

When the adhesive composition of this invention contains another component, content of another component can be suitably set in the range in which the effect of this invention is exhibited.

<Use>

The adhesive composition of this invention is suitable as objects for heat resistant adhesive sheets.

The pressure-sensitive adhesive composition of the present invention can maintain good adhesion and releasability to an adherend even when heat-treated at a high temperature (for example, 260° C.), so that it is difficult to contaminate the surface of the adherend during peeling, and also prevents oxidation of the adherend. Since the pressure-sensitive adhesive layer capable of being suppressed can be formed, for example, an adhesive sheet for temporarily fixing a component or protecting an electronic member in a heat treatment step in the production of an electronic member typified by a hot press step and a solder reflow step. Since the effect of the adhesive composition of this invention is exhibited more to use in order to use in order to form the adhesive layer in this, it is preferable.

The pressure-sensitive adhesive composition of the present invention can be applied regardless of the material of the adherend, such as a resin (eg polyimide) or a metal (eg copper).

[Heat-Resistant Adhesive Sheet]

The heat-resistant pressure-sensitive adhesive sheet of the present invention (hereinafter, also simply referred to as "adhesive sheet") is provided with a pressure-sensitive adhesive layer formed of the pressure-sensitive adhesive composition of the present invention.

Since the heat-resistant pressure-sensitive adhesive sheet of the present invention has a pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive composition of the present invention, even when heat-treated at a high temperature (for example, 260° C.), good adhesion and releasability to the adherend can be maintained, and when peeling It is difficult to contaminate the surface of the adherend, and oxidation of the adherend can be suppressed.

The pressure-sensitive adhesive sheet of the present invention may be a base material-type pressure-sensitive adhesive sheet having no base material, or a u-base material type pressure-sensitive adhesive sheet having an pressure-sensitive adhesive layer on at least one surface of the base material.

When the pressure-sensitive adhesive sheet of the present invention is a u-base material type pressure-sensitive adhesive sheet, the base material is not particularly limited as long as the pressure-sensitive adhesive layer can be formed on the base material.

Examples of the base material include polyester-based resins, acetate-based resins, polyethersulfone-based resins, polycarbonate-based resins, polyamide-based resins, polyimide-based resins, polyolefin-based resins, acrylic resins, vinyl chloride-based resins, ABS ( Acrylonitrile Butadiene Styrene) resin, the film containing resin, such as a fluororesin, is mentioned.

The base material may contain various additives, such as a plasticizer, a coloring agent (for example, dye and a pigment), a heat stabilizer, a light stabilizer, an antistatic agent, and a flame retardant.

As for the base material, the pattern may be given to one part or the whole.

The thickness of the base material is generally 500 µm or less, preferably 300 µm or less, and more preferably 200 µm or less.

Although the lower limit in particular of the thickness of a base material is not restrict|limited, For example, it is preferable that it is 30 micrometers or more.

The adhesive layer exposed in the adhesive sheet of this invention may be protected by the peeling film.

The release film is not particularly limited as long as it can be easily peeled off the pressure-sensitive adhesive layer, and for example, a resin film to which one or both surfaces have been subjected to surface treatment with a release treatment agent (so-called easy peeling treatment).

As a resin film, the polyester film typified by a polyethylene terephthalate (PET) film is mentioned, for example.

As a peeling agent, a fluororesin, paraffin wax, silicone, a long-chain alkyl group compound, etc. are mentioned.

The release film protects the surface of the pressure-sensitive adhesive layer until the pressure-sensitive adhesive sheet is put into practical use and is peeled off in use.

The thickness in particular of an adhesive layer is not restrict|limited, For example, it can set suitably according to the kind of base material. Generally, the thickness of an adhesive layer is the range of 1 micrometer or more and 100 micrometers or less, It is preferable that it is the range of 5 micrometers or more and 50 micrometers or less, It is more preferable that it is the range of 10 micrometers or more and 30 micrometers or less.

The adherend in particular of the adhesive sheet of this invention is not restrict|limited.

Examples of the material of the adherend include various metals represented by copper, aluminum, and SUS (stainless steel), polyimide-based resins, acrylic resins, ABS resins, and various resins represented by polyester-based resins (eg, PET); Various inorganic materials represented by glass are mentioned.

The adhesive sheet of this invention can be used suitably especially for sticking to the to-be-adhered body which uses copper as a material. The pressure-sensitive adhesive composition of the present invention is a specific (meth)acrylic type comprising a structural unit derived from N-methoxymethyl acrylamide, which generates methanol that causes a reducing action on copper oxide by self-crosslinking under a high-temperature environment, in an amount within a specific range. Since it contains a copolymer, in the adhesive sheet of this invention, even if it is a case where oxygen mixed in the interface of an adhesive layer and to-be-adhered body remains, the tendency which a bubble trace is hard to produce is shown. In addition, since the pressure-sensitive adhesive layer provided in the pressure-sensitive adhesive sheet of the present invention has excellent adhesion to the adherend, oxygen hardly mixes at the interface between the pressure-sensitive adhesive layer and the adherend, and copper discoloration due to oxidation hardly occurs.

The manufacturing method in particular of the adhesive sheet of this invention is not restrict|limited.

The adhesive sheet of this invention can be manufactured by the following method, for example.

In the case of a baseless type pressure-sensitive adhesive sheet, first, the pressure-sensitive adhesive composition of the present invention is applied on the surface of the release film to form a coating film. Next, the formed coating film is dried. A base material type adhesive sheet having a laminated structure of release film/adhesive layer/release film by overlapping the exposed side of the coating film after drying so that the side of the other release film is in contact with the exposed side that does not come in contact with the release film. can

In the case of the u-base material type pressure-sensitive adhesive sheet, the pressure-sensitive adhesive layer is formed by applying the pressure-sensitive adhesive composition of the present invention on the surface of the base material, drying and curing. Thereby, the u-base material-type adhesive sheet which has a laminated structure of a base material/adhesive layer layer can be manufactured.

As another method, the following method is also mentioned, for example.

A pressure-sensitive adhesive layer is formed by applying the pressure-sensitive adhesive composition of the present invention on the surface of the release film, drying and curing. Next, the formed pressure-sensitive adhesive layer is transferred to the base material.

That is, the surface of the release film on the side on which the pressure-sensitive adhesive layer is formed is pressed against the base material to prepare a laminate having a laminate structure of the base material/adhesive layer/release film, and then the release film is peeled off of the base material/adhesive layer. It is possible to manufacture a u-base material type pressure-sensitive adhesive sheet having a laminated structure.

Moreover, as another method, the following method is also mentioned, for example.

After apply|coating the adhesive composition of this invention on the surface of a peeling film, it dries, and produces a film with an adhesive. Next, it is possible to manufacture a u-base material-type pressure-sensitive adhesive sheet having a laminated structure of the base material/adhesive layer/peelable film by bonding the base material to the pressure-sensitive adhesive surface of the pressure-sensitive adhesive film and curing it.

There is no restriction|limiting in particular as a method of apply|coating the adhesive composition on the surface of a base material or peeling film, For example, a gravure roll coater, a reverse roll coater, a kiss roll coater, a dip roll coater, a knife coater, a spray coater, a bar coater, an applicator A well-known method using etc. is mentioned.

The application amount of the pressure-sensitive adhesive composition on the surface of the base material or release film is appropriately set according to the thickness of the pressure-sensitive adhesive layer to be formed.

There is no restriction|limiting in particular as a method of drying the adhesive composition apply|coated on the surface of a base material or a peeling film, Natural drying, heat drying, hot air drying, vacuum drying, etc. are mentioned.

The drying temperature and drying time of the pressure-sensitive adhesive composition applied on the surface of the base material or the release film are not particularly limited, and are appropriately set depending on the thickness of the applied pressure-sensitive adhesive composition, the amount of the organic solvent in the pressure-sensitive adhesive composition, and the like.

As an example of drying conditions, the conditions of drying for 1 minute - 3 minutes at 70 degreeC - 120 degreeC using a hot air dryer are mentioned.

Curing is performed for 4 days - 7 days in an environment of 20 degreeC - 35 degreeC, for example.

By curing, the crosslinking reaction of the pressure-sensitive adhesive composition is terminated to form a pressure-sensitive adhesive layer.

Example

Hereinafter, the present invention will be described in more detail by way of Examples. The present invention is not limited to the following examples unless the gist thereof is exceeded.

[Production of (meth)acrylic copolymer]

[Production Example 1]

190.0 parts by mass of ethyl acetate [organic solvent] and 2,2'-azobisisobutyronitrile [AIBN; polymerization initiator] 0.05 mass part was put. Next, 2-ethylhexyl acrylate [2EHA; Tg of acrylic acid alkylester monomer and homopolymer: -76°C] 260.0 parts by mass, 120.0 parts by mass of N-methoxymethyl acrylamide (NMMA), and 2-hydroxyethyl methacrylate [2HEMA; Monomer having a hydroxyl group] 385.0 parts by mass of a monomer mixture containing 20.0 parts by mass is prepared, of which 100.9 parts by mass (equivalent to 25.2 mass % of the monomer mixture) is put into the reactor and heated to reflux at 85° C. (reflux temperature) for 20 minutes. was done. Next, while maintaining the temperature in the reactor at the reflux temperature, the remaining 299.1 parts by mass of the monomer mixture (equivalent to 74.8% by mass of the monomer mixture), 50.0 parts by mass of ethyl acetate, and 2,2'-azobisisobutyronitrile (AIBN) ) 0.5 mass parts was dripped sequentially over 90 minutes, and polymerization reaction was performed for 75 minutes after completion|finish of dripping.

Next, a mixture of 27.0 parts by mass of ethyl acetate and 1.99 parts by mass of 2,2'-azobis(isobutyric acid) dimethyl [polymerization initiator] was added dropwise sequentially over 50 minutes, followed by polymerization reaction for 120 minutes after completion of the dropping.

After completion of the reaction, the obtained polymerization product was diluted with ethyl acetate so that the solid content concentration was 45% by mass to obtain a solution of the (meth)acrylic copolymer of Production Example 1.

"Solid content concentration" here means the mass ratio of the (meth)acrylic-type copolymer to the solution of a (meth)acrylic-type copolymer.

It is the same also about each solution of the (meth)acrylic-type copolymer of the following manufacture examples 2 - manufacture example 27.

[Production Example 2 - Production Example 14]

In Production Examples 2 to 14, by adjusting at least one of the monomer composition of the (meth)acrylic copolymer is changed to the monomer composition shown in Table 1, the amount of the organic solvent used and the amount of the polymerization initiator used in the (meth)acrylic copolymer. Except having adjusted the weight average molecular weight (Mw) to the weight average molecular weight (Mw) shown in Table 1, the same operation as in Production Example 1 was performed, and the solid content concentration was 45% by mass of Production Examples 2 to 14 (meth)acrylic system. Each solution of the copolymer was obtained.

[Production Example 15 - Production Example 27]

In Production Examples 15 to 27, the monomer composition of the (meth)acrylic copolymer was changed to the monomer composition shown in Table 2, and by adjusting at least one of the amount of the organic solvent used and the amount of the polymerization initiator used, the (meth)acrylic copolymer was Except having adjusted the weight average molecular weight (Mw) to the weight average molecular weight (Mw) shown in Table 2, the same operation as in Production Example 1 was performed, and the solid content concentration was 45% by mass of Production Examples 15 to 27 (meth)acrylic system. Each solution of the copolymer was obtained.

The monomer composition (unit: mass %) and weight average molecular weight (Mw) of the (meth)acrylic copolymer of Preparation Examples 1 to 27 of Preparation Example 27 [unit: 10,000 (indicated as “×10 ⁴ ” in the table)] is shown in Table 1 and Table 2.

The weight average molecular weight (Mw) of the (meth)acrylic copolymer of Preparation Examples 1 to 27 was measured by the same method as the above-described method for measuring the weight average molecular weight (Mw) of the specific (meth)acrylic copolymer.

Among the (meth)acrylic copolymers obtained above, the (meth)acrylic copolymers of Production Examples 1 to 17 correspond to the specific (meth)acrylic copolymer in the present invention.

The detail of each monomer of Table 1 and Table 2 is as showing below.

"2EHA": 2-ethylhexyl acrylate [Tg as a homopolymer: -76°C, acrylic acid alkyl ester monomer]

“n-BA”: n-butyl acrylate [Tg as a homopolymer: -57°C, acrylic acid alkyl ester monomer]

"MA": methyl acrylate [Tg when used as a homopolymer: 5 degreeC, acrylic acid alkylester monomer]

"MMA": methyl methacrylate [Tg when used as a homopolymer: 103 ° C., methacrylic acid alkyl ester monomer]

"NMMA": N-methoxymethyl acrylamide

"NEMA": N-ethoxymethyl acrylamide

"NBMA": N-butoxymethyl acrylamide

"2HEMA": 2-hydroxyethyl methacrylate [monomer having a hydroxyl group]

"4HBA": 4-hydroxybutyl acrylate [monomer having a hydroxyl group]

"2HEA": 2-hydroxyethyl acrylate [monomer having a hydroxyl group]

"DMAEA": dimethylaminoethyl acrylate

"AA": acrylic acid [monomer having a carboxyl group]

In Tables 1 and 2, "-" described in the column of the monomer composition means that the monomer corresponding to the column is not included.

In Tables 1 and 2, "weight average molecular weight" was expressed as "Mw".

[Preparation of adhesive composition]

[Example 1]

100 parts by mass (in terms of solid content) of the solution of the (meth)acrylic copolymer of Production Example 1, and Colonate (registered trademark) L-45E [trade name, isocyanate-based crosslinking agent, tolylene diisocyanate (TDI) and trimethylol as a crosslinking agent) The adduct body of propane (TMP), solid content: 45 mass %, content rate of an isocyanate group: 7.9 mass %, Tosoh Corporation] 3.0 mass parts (solid content conversion value) was fully mixed, and the adhesive composition of Example 1 was obtained.

In the obtained pressure-sensitive adhesive composition, the ratio of the number of moles of the crosslinkable functional group in the crosslinking agent to the total number of moles of hydroxyl groups and carboxyl groups in the (meth)acrylic copolymer [that is, the number of moles of the crosslinkable functional group in the crosslinking agent / (meth)acrylic copolymer The total number of moles of hydroxyl groups and carboxyl groups] was 0.3.

The ratio of the number of moles of the crosslinkable functional group in the crosslinking agent to the total number of moles of the hydroxyl group and the carboxyl group in the (meth)acrylic copolymer was calculated using the aforementioned formulas (1) to (3). Specifically, it was calculated as follows. Moreover, the solid content of Colonate (trademark) L-45E which is an isocyanate type crosslinking agent is 45 mass %, and the content rate of an isocyanate group is 7.9 mass %. In addition, the formula weight of the isocyanate group is 42. In addition, the molecular weight of the structural unit derived from 2-hydroxyethyl methacrylate which is a monomer which has a hydroxyl group is 130.

Calculation formula (1)

Molar number of crosslinkable functional groups in crosslinking agent [unit: mmol/solid content of crosslinking agent 100g]

= content of crosslinkable functional group in crosslinking agent (unit: mass %) / solid content of crosslinking agent (unit: mass %) x crosslinking agent blending amount (unit: g) / chemical formula weight of crosslinkable functional group (unit: g / mol) x 1000

=7.9 (mass %)/45 (mass %) x 3 (g)/42 (g/mol) x 1000 = 12.53... ≒12.5

Calculation formula (2)

Total number of moles of hydroxyl and carboxyl groups in (meth)acrylic copolymer [unit: mmol/solid content of (meth)acrylic copolymer 100g]

= [(meth)acryl-based copolymer content rate (unit: mass %) of structural units derived from a monomer having a hydroxyl group / molecular weight of a structural unit derived from a monomer having a hydroxyl group (unit: g/mol) × a monomer having a hydroxyl group The number of hydroxyl groups in the structural unit derived from (number) x 1000] + [The content of the structural unit derived from the monomer having a carboxyl group in the (meth)acrylic copolymer (unit: mass %) / Composition derived from the monomer having a carboxyl group The molecular weight of the unit (unit: g/mol) x the number of carboxyl groups in the structural unit derived from a monomer having a carboxyl group (valence) x 1000]

=[5.0 (parts by mass)/100 (parts by mass) x 100 (%)/130 (g/mol) x 1 x 1000] = 38.46... ≒38.5

Calculation formula (3)

Ratio of the number of moles of crosslinkable functional groups in the crosslinking agent to the total moles of hydroxyl groups and carboxyl groups in the (meth)acrylic copolymer [that is, the number of moles of crosslinkable functional groups in the crosslinking agent/sum of hydroxyl groups and carboxyl groups in the (meth)acrylic copolymer number of moles]

=Value obtained by formula (1)/Value obtained by formula (2)

=12.5/38.5=0.32… ≒0.3

[Examples 2-26]

Except having changed the composition of the adhesive composition into the composition shown in Table 3 in Example 1, operation similar to Example 1 was performed, and each adhesive composition of Examples 2-26 was obtained.

[Comparative Examples 1 to 10]

Except having changed the composition of the adhesive composition into the composition shown in Table 4 in Example 1, operation similar to Example 1 was performed, and each adhesive composition of Comparative Examples 1-10 was obtained.

The ratio of the number of moles of the crosslinkable functional group in the crosslinking agent to the total number of moles of hydroxyl and carboxyl groups in the composition of the pressure-sensitive adhesive composition of Examples 1 to 26 and Comparative Examples 1 to 10 and the (meth)acrylic copolymer [that is, The number of moles of the crosslinkable functional group in the crosslinking agent/the total number of moles of the hydroxyl group and the carboxyl group in the (meth)acrylic copolymer] are shown in Tables 3 and 4.

The detail of each crosslinking agent of Table 3 and Table 4 is as showing below.

"Colonate L-45E" [isocyanate type crosslinking agent, adduct of tolylene diisocyanate (TDI) and trimethylolpropane (TMP), solid content: 45 mass %, content rate of isocyanate group: 7.9 mass %, Tosoh Corporation ]

"Takenate D-110N" [isocyanate type crosslinking agent, xylylene diisocyanate (XDI), solid content: 75 mass %, content rate of isocyanate group: 11.5 mass %, Mitsui Takeda Chemical Co., Ltd.]

"TETRAD-X" [epoxy crosslinking agent, solid content: 100 mass %, epoxy group content: 90 mass %, Mitsubishi Gas Chemical Co., Ltd.]

"Colonate HX" [isocyanate type crosslinking agent, isocyanurate body of hexamethylene diisocyanate (HMDI), solid content: 100 mass %, content rate of isocyanate group: 21.3 mass %, Tosoh Corporation]

"Colonate", "Takenate" and "TETRAD" are all registered trademarks.

<Production of adhesive sheet for evaluation test>

The adhesive sheet for evaluation tests was produced as follows using the adhesive composition obtained above. An adhesive composition was applied to the surface of the polyimide film [product name: Kapton (registered trademark), Toray-DuPont Co., Ltd.] so that the coating amount after drying was 10 g/m 2 , thereby forming a coating film. Next, the formed coating film was dried using a hot air circulation dryer under drying conditions of a drying temperature of 100° C. and a drying time of 60 seconds to form an adhesive film on the polyimide film. Next, the exposed side of the adhesive film was overlaid on the surface-treated side of the release film [trade name: Film Viner (registered trademark) 100E-0010 No.23, Fujimori Kogyo Co., Ltd.] surface-treated with a silicone-based release treatment agent, followed by a pressure nip roll It was pressed and glued together. Next, the obtained laminate is allowed to stand for 1 week in an environment of an atmospheric temperature of 23 ° C. and 50% RH and cured to advance a crosslinking reaction to obtain an evaluation test adhesive sheet having the configuration of a polyimide film / adhesive layer / peeling film got it

[evaluation]

1. Adhesion

The adhesive sheet for evaluation tests was cut|disconnected to the size of 25 mm x 150 mm, and seven adhesive sheet pieces for evaluation tests were prepared. Hereinafter, the six pressure-sensitive adhesive sheet pieces for evaluation tests are the first pressure-sensitive adhesive sheet piece for evaluation test, the second pressure-sensitive adhesive sheet piece for the evaluation test, the third pressure-sensitive adhesive sheet piece for the evaluation test, the fourth pressure-sensitive adhesive sheet piece for the evaluation test, and the fifth pressure-sensitive adhesive sheet piece for the evaluation test. , the 6th adhesive sheet piece for evaluation tests, and the 7th adhesive sheet piece for evaluation tests are called.

Among the seven adhesive sheet pieces for evaluation tests, for the first to third pressure-sensitive adhesive sheet pieces for evaluation tests, the release film of the pressure-sensitive adhesive sheet piece for evaluation test (composition: polyimide film/adhesive layer/peelable film) was peeled, and the adhesive exposed by peeling The side of the layer was overlaid on the side of a polyimide (PI) film [trade name: Kapton (registered trademark) 100H, Toray-DuPont Co., Ltd.], and then pressed using a pressure nip roll to fit together.

For the adhesive sheet piece for the 4th to 6th evaluation test, the peeling film of the adhesive sheet piece for evaluation test (composition: polyimide film / adhesive layer / peeling film) was peeled, and the surface of the adhesive layer exposed by peeling was copper foil [brand name : NC-WC, thickness: 10 μm, Furukawa Electric Co., Ltd.], and then pressed using a pressure nip roll to fit together.

As for the 7th adhesive sheet piece for evaluation test, the peeling film of the adhesive sheet piece for evaluation test (composition: polyimide film / adhesive layer / peeling film) was peeled, and the surface of the adhesive layer exposed by peeling was copper foil [brand name: NC- WC, thickness: 10 µm, Furukawa Electric Industry Co., Ltd.], it was laminated and pasted without pressurization.

(1) Initial (adherent: polyimide film)

The 1st adhesive sheet piece for evaluation tests was made to stand still in the environment of 23 degreeC of atmospheric temperature, and 50 %RH, after sticking together with the polyimide film for 24 hours. Then, with respect to the first adhesive sheet piece for evaluation test after standing, as a measuring device, a single column type material testing machine (model number: STA-1225) manufactured by A&D Co., Ltd. was used, and the peeling rate was 0.3 in an environment of 23°C and 50% RH at an atmospheric temperature. The adhesive force (unit: N/25mm) when the adhesive sheet piece for the 1st evaluation test (composition: polyimide film/adhesive layer) was peeled 180 degrees in the long side (150mm) direction from a polyimide film under the conditions of m/min (unit: N/25mm) was measured Thus, the initial adhesive force (adherent: polyimide film) was obtained.

(2) After heat treatment (adherent: polyimide film)

The 2nd adhesive sheet piece for evaluation tests was made to stand still in the environment of 23 degreeC of atmospheric temperature, and 50 %RH, after affixing to a polyimide film for 24 hours. Next, after standing for 30 minutes in a hot air circulation dryer [model: PHH-200, SPEC Co., Ltd.] in which the second adhesive sheet piece for evaluation test after standing still was set to 260 ° C., an atmosphere of 23 ° C. and 50% RH. It was allowed to stand for 3 hours under Next, for the second pressure-sensitive adhesive sheet piece for evaluation test after standing, the adhesive force is measured by the same method as in the measurement of the adhesive force in the above "(1) initial stage (adhesive: polyimide film)", and the adhesive force after heat treatment (adherent: polyimide) film).

(3) After heat press (adherent: polyimide film)

The 3rd adhesive sheet piece for evaluation tests was made to stand still in the environment of 23 degreeC of atmospheric temperature, and 50%RH, after sticking together with the polyimide film for 24 hours. Next, the pressure-sensitive adhesive sheet piece for the third evaluation test after standing was hot-pressed for 30 minutes under the conditions of a pressure of 20 kg/cm 2 using a hot press machine set at 260 ° C. . Next, for the adhesive sheet piece for the third evaluation test after standing, the adhesive force is measured by the same method as in the measurement of the adhesive force in "(1) initial stage (adherent: polyimide film)", and the adhesive force after hot pressing (adherent: polyimide film) mid film).

(4) Initial (substrate: copper foil)

After affixing the adhesive sheet piece for a 4th evaluation test to copper foil, it was made to stand still in the environment of 23 degreeC of atmospheric temperatures, and 50 %RH for 24 hours. Then, the adhesive sheet piece for the fourth evaluation test after standing was measured by the same method as the adhesive force measurement in the above "(1) initial stage (adhesive: polyimide film)", and the initial (adherent: copper foil) of It was set as adhesive force.

(5) After heat treatment (adherent: copper foil)

After the adhesive sheet piece for a 5th evaluation test was put together with copper foil, it was made to stand still in the environment of 23 degreeC of atmospheric temperatures, and 50 %RH for 24 hours. Next, after standing for 30 minutes in a hot-air circulation dryer [model: PHH-200, SPEC Co., Ltd.] in which the adhesive sheet piece for the fifth evaluation test after standing still was set at 260 ° C., an atmosphere of 23 ° C. and 50% RH. It was allowed to stand for 3 hours under Next, with respect to the 5th evaluation test adhesive sheet piece after standing, the adhesive force is measured by the same method as the adhesive force measurement in "(1) initial stage (adherent: polyimide film)", and the adhesive force after heat treatment (adherent: copper foil) ) was set.

(6) After heat press (substrate: copper foil)

The adhesive sheet piece for a 6th evaluation test was made to stand still in the environment of 23 degreeC of atmospheric temperature, and 50 %RH after affixing together with copper foil for 24 hours. Next, the pressure-sensitive adhesive sheet piece for the sixth evaluation test after standing was hot-pressed for 30 minutes at a pressure of 20 kg/cm 2 using a hot press machine set at 260 ° C. . Next, for the 6th evaluation test adhesive sheet piece after stationary, the adhesive force is measured by the same method as the adhesive force measurement in "(1) initial stage (adherent: polyimide film)", and the adhesive force after hot pressing (adherent: copper) Park).

The adhesive force after the initial stage, after heat treatment and after hot pressing was evaluated according to the following evaluation criteria.

The results are shown in Tables 5 and 6.

If the evaluation result was "A", "B" or "C", it was judged that there was no problem practically.

An adhesive having an evaluation result of "A", "B" or "C" does not cause unintentional peeling from an adherend, and can be easily peeled off from an adherend, thereby exhibiting good adhesion and releasability to the adherend. It means layer.

-Evaluation standard-

A: The initial adhesive force is 1.0N/25mm or more and less than 2.0N/25mm.

B: The initial adhesive force is 0.7N/25mm or more and less than 1.0N/25mm, or 2.0N/25mm or more and less than 5.0N/25mm.

C: Initial adhesive force is 0.4N/25mm or more and less than 0.7N/25mm, or 5.0N/25mm or more and less than 10.0N/25mm.

D: The initial adhesive force is less than 0.4N/25mm or 10.0N/25mm or more.

2. Contamination resistance

(1) polyimide film

The surface of the polyimide film after measuring the initial adhesive force, the polyimide film after measuring the adhesive force after heat treatment, and the polyimide film after measuring the adhesive force after hot pressing was visually observed, and stain resistance according to the following evaluation criteria (Adhesive: polyimide film) was evaluated.

The results are shown in Tables 5 and 6.

If the evaluation result was "A", "B" or "C", it was judged that there was no problem practically.

-Evaluation standard-

A: No glue residue was observed at all in the initial stage, after heat treatment, and after hot pressing.

B: At least one of the initial stage, after heat treatment, and after heat press, some glue residue is confirmed on the rim portion of the pasting.

C: In at least one of the initial stage, after heat treatment, and after heat press, glue residues are confirmed on the rim portion of the alignment, but residues of glue are not confirmed on the surface of the alignment and pasting.

D: At least one of the initial stage, after heat treatment, and after heat press, glue residue is confirmed on the bonding surface.

(2) copper foil

The surface of the copper foil after measuring the initial adhesive force, the copper foil after measuring the adhesive force after heat treatment, and the copper foil after measuring the adhesive force after hot pressing was visually observed, and the inside of the "(1) polyimide film" The stain resistance (adherent: copper foil) was evaluated according to the same evaluation criteria as staining property.

The results are shown in Tables 5 and 6.

If the evaluation result was "A", "B" or "C", it was judged that there was no problem practically.

3. Oxidation resistance

(1) the presence or absence of discoloration

The surface was visually observed for the copper foil after measuring the adhesive force after heat treatment and the copper foil after measuring the adhesive force after hot pressing, and the oxidation resistance based on the presence or absence of discoloration was evaluated according to the following evaluation criteria.

The results are shown in Tables 5 and 6.

If the evaluation result was "A", "B" or "C", it was judged that there was no problem practically.

-Evaluation standard-

A: No discoloration is observed either after heat treatment or after hot pressing.

B: A slight discoloration is observed at the edge portion of the pasting at least either after heat treatment or after heat press.

C: After heat treatment and after heat press, discoloration was confirmed on the edge portion of the pasting, but no discoloration was confirmed on the side of the pasting.

D: Discoloration is confirmed on the bonding surface in at least one of after heat treatment and after heat press.

-: It is difficult to discriminate discoloration because there is significant glue residue on the bonding surface at least either after heat treatment or after heat press.

(2) the presence or absence of traces of air bubbles

The 7th adhesive sheet piece for evaluation tests was made to stand still in the environment of 23 degreeC of atmospheric temperature, and 50 %RH, after sticking together with copper foil for 24 hours. Next, after standing still for 30 minutes in a hot-air circulation dryer [model: PHH-200, SPEC Co., Ltd.] in which the 7th evaluation test adhesive sheet piece after standing was set at 260 ° C., an atmosphere of 23 ° C., 50% RH. It was allowed to stand for 3 hours under Next, with respect to the 7th adhesive sheet piece for evaluation test after standing still, as a measuring device, a single column type material tester (model number: STA-1225) manufactured by A&D Co., Ltd. was used, and the peeling rate was 0.3 in an environment of 23°C and 50% RH at an atmospheric temperature. On the conditions of m/min, 180 degrees of the adhesive sheet piece for 7th evaluation tests (composition: polyimide film/adhesive layer) was peeled in the long side (150 mm) direction from copper foil. The surface of the copper foil after peeling was visually observed, and the oxidation resistance based on the presence or absence of the discoloration of a spot type (so-called bubble trace) was evaluated according to the following evaluation criteria.

The results are shown in Tables 5 and 6.

If the evaluation result was "A", "B" or "C", it was judged that there was no problem practically.

-Evaluation standard-

A: No bubble traces are observed.

B: The area ratio occupied by the bubble trace is more than 0% and less than 20% of the area of the pasting.

C: The area ratio occupied by bubble traces is 20% or more and less than 50% of the area of the pasting.

D: The area ratio occupied by the bubble trace is 50% or more of the area of the pasting.

-: It is difficult to identify traces of air bubbles because there is significant glue residue on the bonding surface.

From the results shown in Table 5, according to the pressure-sensitive adhesive compositions of Examples 1 to 26, even when heat-treated at a high temperature of 260 ° C., good adhesion and releasability to the adherend can be maintained, so that the surface of the adherend is contaminated during peeling. It became clear that it is difficult and can form the adhesive layer which can suppress the oxidation of a to-be-adhered body.

On the other hand, as shown in Table 6, the pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive composition of Comparative Example 1 in which the (meth)acrylic copolymer does not contain a structural unit derived from a monomer having a hydroxyl group is heat-treated at a high temperature of 260 ° C. It was confirmed that the surface of the adherend was markedly contaminated.

The pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive composition of Comparative Example 2 in which the content rate of the constituent units derived from N-methoxymethyl acrylamide in the (meth)acrylic copolymer exceeds 30% by mass based on the total constituent units is a high temperature of 260 ° C. It was confirmed that the adhesive force to the adherend was remarkably reduced when heat-treated. In addition, when the pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive composition of Comparative Example 2 is heat-treated at a high temperature of 260 ° C., the copper foil as an adherend is significantly discolored, and traces of air bubbles are remarkably generated in the copper foil, so that oxidation of the adherend cannot be suppressed. that has been confirmed

A pressure-sensitive adhesive formed by the pressure-sensitive adhesive composition of Comparative Examples 3, 4 and 9 in which the content rate of the constituent units derived from N-methoxymethyl acrylamide in the (meth)acrylic copolymer is less than 6% by mass based on the total constituent units. It was confirmed that when all of the layers were heat-treated at a high temperature of 260 DEG C, the surface of the adherend was markedly contaminated during peeling.

The pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive composition of Comparative Example 5 in which the (meth)acrylic copolymer contains a constituent unit derived from N-ethoxymethyl acrylamide instead of a constituent unit derived from N-methoxymethyl acrylamide is 260° C. It was confirmed that the surface of the adherend was markedly contaminated during peeling when heat treatment was performed at a high temperature.

A pressure-sensitive adhesive formed by the pressure-sensitive adhesive composition of Comparative Examples 6 and 10 in which the (meth)acrylic copolymer contains a constituent unit derived from N-butoxymethyl acrylamide instead of a constituent unit derived from N-methoxymethyl acrylamide It was confirmed that when all of the layers were heat-treated at a high temperature of 260 DEG C, the surface of the adherend was markedly contaminated during peeling.

The pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive composition of Comparative Example 7 in which the (meth)acrylic copolymer does not contain a structural unit derived from N-methoxymethyl acrylamide is heat-treated at a high temperature of 260° C. Significant contamination was confirmed.

The pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive composition of Comparative Example 8, in which the (meth)acrylic copolymer does not contain both a structural unit derived from a monomer having a hydroxyl group and a structural unit derived from N-methoxymethyl acrylamide, prevents discoloration of copper foil. It was confirmed that it could not be suppressed.

Claims (10)

A structural unit derived from N-methoxymethyl acrylamide, a structural unit derived from a monomer having a hydroxyl group, and a structural unit derived from a (meth)acrylic acid alkyl ester monomer, and a structural unit derived from the N-methoxymethyl acrylamide A pressure-sensitive adhesive composition for a heat-resistant pressure-sensitive adhesive sheet comprising a (meth)acrylic copolymer having a content rate of constituent units in the range of 6% by mass to 30% by mass based on all constituent units, and a crosslinking agent. The method according to claim 1,
The content rate of the structural unit derived from the monomer which has the said hydroxyl group in the said (meth)acrylic-type copolymer is the range of 1.5 mass % or more and 20 mass % or less with respect to all the structural units, The adhesive composition for heat-resistant adhesive sheets. The method according to claim 1 or 2,
The ratio of the number of moles of the crosslinkable functional group in the crosslinking agent to the total number of moles of hydroxyl groups and carboxyl groups in the (meth)acrylic copolymer is in the range of 0.1 or more and 1.0 or less. The method according to claim 1 or 2,
The ratio of the number of moles of the crosslinkable functional group in the crosslinking agent to the total number of moles of hydroxyl groups and carboxyl groups in the (meth)acrylic copolymer is in the range of 0.3 or more and 0.5 or less. The method according to claim 1 or 2,
The pressure-sensitive adhesive composition for a heat-resistant pressure-sensitive adhesive sheet, wherein the alkyl group in the (meth)acrylic acid alkylester monomer has 4 or more and 12 or less carbon atoms. The method according to claim 1 or 2,
The (meth) acrylic acid alkyl ester monomer is a heat-resistant pressure-sensitive adhesive composition for a pressure-sensitive adhesive sheet containing a (meth) acrylic acid alkyl ester monomer having a glass transition temperature of -20 ° C. or less when a homopolymer. The method according to claim 1 or 2,
The (meth)acrylic copolymer does not contain a structural unit derived from a monomer having a carboxy group, or the content of a structural unit derived from a monomer having a carboxy group is in the range of more than 0% by mass to 10% by mass or less with respect to the total structural units A pressure-sensitive adhesive composition for a heat-resistant pressure-sensitive adhesive sheet. The method according to claim 1 or 2,
The weight average molecular weight of the (meth)acrylic copolymer is in the range of 200,000 or more and 1.2 million or less, the pressure-sensitive adhesive composition for a heat-resistant adhesive sheet. The method according to claim 1 or 2,
The pressure-sensitive adhesive composition for a heat-resistant pressure-sensitive adhesive sheet, wherein the cross-linking agent is an isocyanate-based cross-linking agent. A heat resistant adhesive sheet provided with the adhesive layer formed with the adhesive composition for heat resistant adhesive sheets of Claim 1 or 2.