WO2025220517A1 - Curable resin composition and method for producing same - Google Patents

Abstract

Provided is a method for producing a curable resin composition which comprises: forming a (meth)acrylic copolymer in a reaction solution that contains two or more monomers including a monomer having a (meth)acryloyl group by the copolymerization of the two or more monomers; and forming a curable resin composition that contains the (meth)acrylic copolymer and a curable component. The two or more monomers include a first monomer and a second monomer. During the copolymerization, the ratio of the amount of the second monomer to the amount of the first monomer in the reaction solution is increased continuously or stepwise, thereby forming a (meth)acrylic copolymer which has a main chain containing a terminal moiety that is a random copolymer.

Description

Curable resin composition and method for producing the same

This disclosure relates to a curable resin composition containing a (meth)acrylic copolymer and a method for producing the same.

Adhesive compositions containing (meth)acrylic copolymers are sometimes used to adhere semiconductor chips to circuit boards, etc.

Japanese Patent Application Laid-Open No. 2022-019742

One aspect of the present disclosure relates to a curable resin composition containing a (meth)acrylic copolymer and having excellent adhesive properties.

The present disclosure includes the following:
[1]
forming a (meth)acrylic copolymer by copolymerizing two or more monomers in a reaction solution containing two or more monomers including a monomer having a (meth)acryloyl group;
forming a curable resin composition containing the (meth)acrylic copolymer and a curable component;
A method for producing a curable resin composition, comprising:
the two or more monomers include a first monomer and a second monomer different from the first monomer;
During the copolymerization, the ratio of the amount of the second monomer to the amount of the first monomer in the reaction solution is increased continuously or stepwise, thereby forming the (meth)acrylic copolymer having a main chain including terminal portions that is a random copolymer.
[2]
the mass fraction of the total amount of the second monomer introduced into the reaction liquid is Y ₀ mass% based on the total amount of the two or more monomers introduced into the reaction liquid;
When the mass fraction of the amount of the monomer units derived from the second monomer is Y 1% by mass based on the total amount of the monomer units derived from the two or more monomers in the terminal portion of the formed ( _meth )acrylic copolymer,
The method according to [1], wherein Y ₁ is within ±5% by mass relative to Y ₀ .
[3]
The method according to [1] or [2], wherein the terminal portion is a portion having a molecular weight of 1,000 or more from the end of the main chain of the (meth)acrylic copolymer.
[4]
The method according to any one of [1] to [3], wherein in the (meth)acrylic copolymer formed, a mass fraction of a triplet sequence consisting of three consecutively bonded monomer units derived from the second monomer is 5 mass% or less, based on the total amount of monomer units derived from the two or more monomers.
[5]
The method according to any one of [1] to [4], wherein, among the two or more monomers, the first monomer exhibits the largest Q value and the second monomer exhibits the smallest Q value.
[6]
The method according to any one of [1] to [5], wherein when the Q value of the first monomer is _Q1 and the Q value of the second monomer is _Q2 , |Q ₁ −Q ₂ | is 0.4 or more.
[7]
The method according to any one of [1] to [6], wherein when the e value of the first monomer is _e1 and the e value of the second monomer is _e2 , _e1 × _e2 is a negative value, and | _e1 - _e2 | is 1.0 or more and 2.0 or less.
[8]
The method according to any one of [1] to [7], wherein, when the Q value and the e value of the first monomer are _Q1 and _e1 , respectively, and the Q _value and the e value of the second monomer are Q2 and _e2 , respectively, the reactivity ratio _r1 of the first monomer calculated by the following formula (1) and the reactivity ratio _r2 calculated by the following formula (2) satisfy the following relational formula (3):
r ₁ = (Q ₁ /Q ₂ )×exp(-e ₁ (e ₁ -e ₂ ))...(1)
r ₂ = (Q ₂ /Q ₁ )×exp(-e ₂ (e ₂ -e ₁ ))...(2)
r ₁ <1 < r ₂ ...(3)
[9]
The method according to any one of [1] to [8], wherein the first monomer is an alkyl(meth)acrylate.
[10]
The method according to any one of [1] to [9], wherein the second monomer is an ethylenically unsaturated compound having one or more functional groups selected from a hydroxy group, a carboxy group, an acid anhydride group, a sulfonic acid group, a phosphonic acid group, an amide group, and an aromatic group.
[11]
The method according to any one of [1] to [10], wherein the copolymerization is RAFT polymerization.
[12]
The method according to [11], wherein a reactivity ratio r 1 ' of the first monomer and a reactivity ratio r ₂ ' of the second monomer, which are calculated from a copolymerization ratio of a copolymer produced by RAFT polymerization in a reaction solution for reaction evaluation to which the entire amounts of two types of monomers consisting of the first monomer and the second monomer are introduced all at once in the presence of a _RAFT agent, satisfy the following relational formula (3'):
_r1 '<1< _r2 '...(3')
[13]
a (meth)acrylic copolymer;
A curable component;
A curable resin composition comprising:
the (meth)acrylic copolymer is a copolymer having a main chain containing, as monomer units, two or more types of monomers including a monomer having a (meth)acryloyl group,
the two or more monomers include a first monomer and a second monomer different from the first monomer;
A curable resin composition, wherein the main chain of the (meth)acrylic copolymer has terminal portions that are random copolymers at both ends.
[14]
In the entire (meth)acrylic copolymer, the mass fraction of the amount of the monomer units derived from the second monomer is Y ₀ mass%, based on the total amount of the monomer units derived from the two or more monomers;
In the terminal portion of the (meth)acrylic copolymer, the mass fraction of the amount of the monomer unit derived from the second monomer is Y ₁ % by mass, based on the total amount of the monomer units derived from the two or more monomers;
Y ₁ is within ±5 mass% of Y ₀ ;
The curable resin composition according to [13].
[15]
The curable resin composition according to [13] or [14], wherein the terminal portion is a portion having a molecular weight of 1,000 or more from the terminal of the main chain of the (meth)acrylic copolymer.
[16]
[16] The curable resin composition according to any one of [13] to [15], wherein in the (meth)acrylic copolymer, a mass fraction of a triplet sequence consisting of three consecutively bonded monomer units derived from the second monomer is 5 mass% or less, based on the total amount of monomer units derived from the two or more types of monomers.
[17]
The curable resin composition according to any one of [13] to [16], wherein the molecular weight distribution of the (meth)acrylic copolymer is 1.1 or more and 2.5 or less.
[18]
The curable resin composition according to any one of [13] to [17], wherein the first monomer is an alkyl(meth)acrylate.
[19]
The curable resin composition according to any one of [13] to [18], wherein the second monomer is an ethylenically unsaturated compound having one or more functional groups selected from a hydroxy group, a carboxy group, an acid anhydride group, a sulfonic acid group, a phosphonic acid group, an amide group, and an aromatic group.

A curable resin composition containing a (meth)acrylic copolymer and having excellent adhesive properties can be provided. The curable resin composition according to the present disclosure can also have excellent properties in terms of appropriate melt viscosity, compatibility in varnish, stability of adhesive layer thickness, and void suppression.

FIG. 1 is a perspective view schematically illustrating an example of an adhesive film. FIG. 2 is a cross-sectional view taken along line II-II in FIG.

The present invention is not limited to the following examples. In this specification, "(meth)acryloyl" means acryloyl, methacryloyl, or both.

One example of a method for producing a curable resin composition includes the steps of: forming a (meth)acrylic copolymer by copolymerizing two or more monomers in a reaction liquid containing two or more monomers, including a monomer having a (meth)acryloyl group; and forming a curable resin composition containing the (meth)acrylic copolymer and a curable component.

The (meth)acrylic copolymer formed has a main chain containing two or more types of monomers as monomer units. The (meth)acrylic copolymer can be, for example, a linear or branched polymer. When the (meth)acrylic copolymer is a branched polymer, the longest polymer chain can be considered the main chain.

The two or more monomers introduced into the reaction solution to form the (meth)acrylic copolymer include a first monomer and a second monomer different from the first monomer. The first monomer, the second monomer, or both may be compounds having a (meth)acryloyl group. During copolymerization of the two or more monomers, the ratio of the amount of the second monomer to the amount of the first monomer may be increased continuously or in stages. Generally, in a copolymer formed by copolymerizing two or more monomers, the polymer formed in the early stages of polymerization corresponds to the terminal portion of the final main chain. Terminal portions formed in the early stages of polymerization tend to form portions (block portions) in which monomers of the same type are bonded consecutively. By using a monomer that has a relatively higher tendency to bond consecutively as the second monomer and initiating copolymerization at a low ratio of the second monomer, and then increasing the ratio of the second monomer, a main chain having terminal portions that are a random copolymer with few block portions is likely to be formed. According to the inventor's findings, the low number of block portions at the terminal portions of the (meth)acrylic copolymer can contribute to the adhesiveness of the curable resin composition and the suppression of voids in the cured product of the curable resin composition.

During copolymerization, the ratio of the amount of the second monomer to the amount of the first monomer can be increased continuously or stepwise by continuously or intermittently introducing the second monomer into the reaction solution. After the entire amount of the second monomer has been introduced into the reaction solution, the copolymerization can be continued. The time from the start of introducing the second monomer into the reaction solution to the time when the entire amount of the second monomer has been introduced into the reaction solution can be, for example, 30 minutes or more and 330 minutes or less.

Whether the terminal portion of the main chain of the (meth)acrylic copolymer is a random copolymer can be evaluated based on the degree to which the mass fraction of the monomer at the terminal portion deviates from the mass fraction of the monomer used in copolymerization. For example, when the mass fraction of the amount of the second monomer introduced into the reaction solution by the end of copolymerization is Y ₀ % by mass, based on the total amount of two or more monomers introduced into the reaction solution by the end of copolymerization, and the mass fraction of the amount of monomer units derived from the second monomer at the terminal portion of the main chain of the (meth)acrylic copolymer formed is Y ₁ % by mass, based on the total amount of monomer units derived from two or more monomers, Y ₁ may be within ±5% by mass of Y _0. In the entire (meth)acrylic copolymer formed, the mass fraction of the amount of monomer units derived from the second monomer at the terminal portion may be Y ₀ % by mass, based on the total amount of monomer units derived from two or more monomers, and the mass fraction Y ₁ of the monomer units derived from the second monomer at the terminal portion may be within ±5% by mass of Y ₀ . In particular, the terminal portion where _Y1 is within ±5% by mass _{of Y0} may be a portion ranging from the end of the main chain of the (meth)acrylic copolymer to a molecular weight of 1,000 or more. The proportion of the portion where _Y1 is within ±5% by mass of _Y0 may be 100% by mass or less, 80% by mass or less, 50% by mass or less, or 40% by mass or less with respect to the molecular weight (or weight average molecular weight) of the (meth)acrylic copolymer. In the entire main chain of the (meth)acrylic copolymer, the mass fraction of the monomer unit derived from the second monomer may be within ±5% by mass of _Y0 , based on the total amount of monomer units derived from two or more monomers. The main chain of the final (meth)acrylic copolymer may have terminal portions that are random copolymers at both ends.

Based on the proportion of sequences in which the second monomer is bonded consecutively, it can be determined that the terminal portion of the main chain of the (meth)acrylic copolymer is a random copolymer. For example, in a (meth)acrylic copolymer, the mass fraction of triple sequences consisting of three monomer units derived from the second monomer and bonded consecutively, based on the total amount of monomer units derived from two or more types of monomers, may be 5% by mass or less, 4% by mass or less, 3% by mass or less, 2% by mass or less, or 1% by mass or less, or may be 0% by mass or more.

The first and second monomers may be selected based on their Q values, which represent their reactivity. For example, among two or more types of monomers, the first monomer may have the largest Q value and the second monomer may have the smallest Q value. By initiating copolymerization with a low ratio of the second monomer, which has a relatively small Q value and high reactivity, a main chain having terminal portions that are random copolymers can be easily formed. However, since the reactivity in actual copolymerization also depends on factors such as the combination of two or more types of monomers, even if the Q value of the first monomer is smaller than the Q value of the second monomer, a main chain having terminal portions that are random copolymers can be formed by continuously or stepwise increasing the ratio of the amount of the second monomer to the amount of the first monomer during copolymerization.

When the Q value of the first monomer is _Q1 and the Q value of the second monomer is _Q2 , | _Q1 - _Q2 | may be 0.4 or greater. For example, when the first monomer or the second monomer is a compound having a functional group that can contribute to adhesiveness, etc., the difference between _Q1 and _Q2 tends to be large. Even in a combination of a first monomer and a second monomer with a large difference between _Q1 and _Q2 , a main chain having a terminal portion that is a random copolymer can be easily formed by initiating copolymerization from a state in which the ratio of the second monomer is low. | _Q1 - _Q2 | may be 0.6 or greater, or 0.8 or greater. | _Q1 - _Q2 | may be 3.0 or less, 2.5 or less, or 2.0 or less.

When the e value of the first monomer is _e1 and the e value of the second monomer is _e2 , _e1 × _e2 may be a negative numerical value, and | _e1 - _e2 | may be 1.0 or more and 2.0 or less. When _e1 and _e2 satisfy these conditions, a main chain having terminal portions that are random copolymers tends to be more easily formed.

The first monomer and the second monomer may be selected so that the reactivity ratio _r1 of the first monomer calculated by the following formula (1) and the reactivity ratio _r2 calculated by the following formula (2) satisfy the following relational formula (3). This makes it possible to more easily form a main chain having a terminal portion that is a random copolymer.
r ₁ = (Q ₁ /Q ₂ )×exp(-e ₁ (e ₁ -e ₂ ))...(1)
r ₂ = (Q ₂ /Q ₁ )×exp(-e ₂ (e ₂ -e ₁ ))...(2)
r ₁ <1 < r ₂ ...(3)

The Q and e values of the first and second monomers are values determined by polymerization tests under conditions that do not include a chain transfer agent such as a RAFT agent, and may be literature values. Table 1 shows examples of literature values for the Q and e values of monomers that can be used as the first or second monomer.

When the copolymerization is RAFT polymerization in the presence of a RAFT agent, the reactivity ratio r1' of the first monomer and the reactivity ratio r2' of the second monomer, which are calculated from the copolymerization ratio of a copolymer produced by RAFT polymerization in a reaction solution for reactivity evaluation into which the entire amounts of two types of monomers, the first monomer and the second _{monomer, are introduced at once in} the presence of the RAFT agent, may satisfy the following relational formula (3'). This makes it possible to more easily form a main chain having a terminal portion that is a random copolymer. The reactivity ratios _r1 ' and _r2 ' are calculated from the copolymerization ratio of a copolymer produced by RAFT polymerization of only two types of monomers, the first monomer and the second monomer.
_r1 '<1< _r2 '...(3')

The first monomer may be an alkyl (meth)acrylate having an unsubstituted alkyl group. Examples of alkyl (meth)acrylates include methyl (meth)acrylate, ethyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl acrylate, tert-butyl (meth)acrylate, pentyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, dodecyl (meth)acrylate, cyclohexyl (meth)acrylate, methylcyclohexyl (meth)acrylate, rosin (meth)acrylate, norbornyl (meth)acrylate, 5-ethylnorbornyl (meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentanyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, isobornyl (meth)acrylate, and adamantyl (meth)acrylate.

The second monomer may be an ethylenically unsaturated compound having one or more functional groups selected from a hydroxy group, a carboxy group, an acid anhydride group, a sulfonic acid group, a phosphonic acid group, an amide group, and an aromatic group. The second monomer may be a compound having a (meth)acryloyl group and one or more functional groups selected from a hydroxy group, a carboxy group, an acid anhydride group, a sulfonic acid group, a phosphonic acid group, an amide group, and an aromatic group.

Examples of ethylenically unsaturated compounds having a hydroxy group include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 2,3-dihydroxypropyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate.

The ethylenically unsaturated compound having a carboxy group or an acid anhydride group may be an unsaturated carboxylic acid or an anhydride thereof, examples of which include (meth)acrylic acid, α-bromo(meth)acrylic acid, β-furyl(meth)acrylic acid, crotonic acid, propiolic acid, cinnamic acid, α-cyanocinnamic acid, maleic acid, maleic acid, monomethyl maleate, monoethyl maleate, monoisopropyl maleate, fumaric acid, itaconic acid, citraconic acid, citraconic acid, and anhydrides thereof.

The ethylenically unsaturated compound having a sulfonic acid group may be an unsaturated sulfonic acid, examples of which include 2-acrylamido-2-methylpropanesulfonic acid, tert-butylacrylamidosulfonic acid, and p-styrenesulfonic acid.

The ethylenically unsaturated compound having a phosphonic acid group may be an unsaturated phosphonic acid, examples of which include vinylphosphonic acid.

Examples of ethylenically unsaturated compounds having an amide group include (meth)acrylic acid amide, (meth)acrylic acid N,N-dimethylamide, (meth)acrylic acid N,N-diisopropylamide, and (meth)acrylic acid anthracenylamide.

Examples of ethylenically unsaturated compounds having an aromatic group include styrene, α-methylstyrene, α-chloromethylstyrene, vinyltoluene, divinylbenzene, diallyl phthalate, diallylbenzene phosphonate, 4-phenoxyphenyl (meth)acrylate, phenoxyethyl (meth)acrylate, phenoxypolyethylene glycol (meth)acrylate, nonylphenoxypolyethylene glycol mono(meth)acrylate, and benzyl (meth)acrylate.

The first monomer may be an alkyl (meth)acrylate (e.g., n-butyl acrylate), acrylamide, or styrene, and the second monomer may be 2-hydroxyethyl acrylate, acrylic acid, benzyl methacrylate, 2-hydroxyethyl acrylate, acrylic acid, or benzyl methacrylate.

The step of forming the (meth)acrylic copolymer may include, for example, forming a first monomer liquid containing a first monomer, adding a polymerization initiator to the first monomer liquid to form a reaction liquid, and continuously or intermittently adding a second monomer liquid containing a second monomer to the reaction liquid while heating the reaction liquid. Alternatively, the step of forming the (meth)acrylic copolymer may include forming a first monomer liquid containing a first monomer in a raw material tank, introducing a reaction liquid containing the first monomer and the second monomer from the raw material tank into a reaction tank while continuously or intermittently adding a second monomer liquid containing a second monomer to the first monomer liquid in the raw material tank, and heating the reaction liquid in the reaction tank. In this case, a polymerization initiator may be supplied to the raw material tank or the reaction tank.

Based on the total amount of two or more monomers introduced into the reaction solution and subjected to copolymerization, the proportion of the amount of the first monomer may be 40 mol% or more and 99 mol% or less, and the proportion of the amount of the second monomer may be 1 mol% or more and 60 mol% or less. The proportion of the amount of the first monomer may be 60 mol% or more and 99 mol% or less, and the proportion of the amount of the second monomer may be 1 mol% or more and 40 mol% or less. The proportion of the amount of the first monomer may be 75 mol% or more and 99 mol% or less, and the proportion of the amount of the second monomer may be 1 mol% or more and 25 mol% or less. Based on the total amount of monomer units derived from two or more monomers constituting the (meth)acrylic copolymer, the proportion of monomer units derived from the first monomer may be 40 mol% or more and 99 mol% or less, and the proportion of monomer units derived from the second monomer may be 1 mol% or more and 60 mol% or less.

The first monomer liquid and the second monomer liquid may each further contain an additional monomer that is a compound other than the first monomer and the second monomer. Of the two or more monomers used in copolymerization, the total proportion of the first monomer and the second monomer may be 50% by mass or more, 60% by mass or more, 70% by mass or more, 80% by mass or more, 90% by mass or more, or 95% by mass or more, or may be 100% by mass or less.

The first monomer liquid, the second monomer liquid, or both may further contain a solvent. Examples of solvents include esters such as ethyl acetate, propyl acetate, and butyl acetate; aromatic hydrocarbons such as toluene, xylene, and benzene; aliphatic hydrocarbons such as hexane and heptane; alicyclic hydrocarbons such as cyclohexane and methylcyclohexane; ketones such as methyl ethyl ketone and methyl isobutyl ketone; glycols such as ethylene glycol, propylene glycol, and dipropylene glycol; glycol ethers such as methyl cellosolve, propylene glycol monomethyl ether, and dipropylene glycol monomethyl ether; and glycol esters such as ethylene glycol diacetate and propylene glycol monomethyl ether acetate. The solvents may be used alone or in combination of two or more.

The copolymerization may be RAFT polymerization. In that case, for example, the first monomer liquid may further contain a RAFT agent (chain transfer agent). The RAFT agent can be selected from those commonly used in RAFT polymerization. Examples of RAFT agents include 2-cyano-2-[(dodecylsulfanylthiocarbonyl)sulfanyl]propane, S-cyanomethyl-S-dodecyltrithiocarbonate, 2-[(dodecylsulfanylthiocarbonyl)sulfanyl]propanoic acid, 2-{[(2-carboxyethyl)sulfanylthiocarbonyl]sulfanyl}propanoic acid, bis{4-[ethyl-(2-hydroxyethyl)carbamoyl]benzyl}trithiocarbonate, 4-[(2-carboxyethylsulfanylthiocarbonyl)sulfanyl]-4-cyanopentanoic acid, 4-cyano-4- [(Dodecylsulfanylthiocarbonyl)sulfanyl]pentanoic acid, S,S-dibenzyl trithiocarbonate, methyl 4-cyano-4-[(dodecylsulfanylthiocarbonyl)sulfanyl]pentanoate, 2-cyano-2-propyldodecyltrithiocarbonate, bis[4-(allyloxycarbonyl)benzyl]trithiocarbonate, bis[4-(2,3-dihydroxypropoxycarbonyl)benzyl]trithiocarbonate, bis{4-[ethyl-(2-acetyloxyethyl)carbamoyl]benzyl}trithiocarbonate, bis[ trithiocarbonates such as 4-(2-hydroxyethoxycarbonyl)benzyl]trithiocarbonate; dithioesters such as cyanoethyl dithiopropionate, benzyl dithiopropionate, benzyl dithiobenzoate, acetoxyethyl dithiobenzoate, 2-phenyl-2-propyldithiobenzoic acid, 2-cyano-2-propyldithiobenzoic acid, 4-cyano-4-(phenylcarbonothioylthio)pentanoic acid, and S-(thiobenzoyl)thioglycolic acid; ethyl 2-[(ethoxycarbonothioyl)thio]propionate, O-ethyl-S-(2-propoxyethoxy) Dithiocarbonates such as O-ethyl-S-(1-cyano-1-methylethyl)dithiocarbonate; and dithiocarbamates such as 2-cyano-2-propyldiethyldithiocarbamate, 2'-cyanobutan-2'-yl 4-chloro-3,5-dimethylpyrazole-1-dithiocarbamate, 2'-cyanobutan-2'-yl 3,5-dimethylpyrazole-1-dithiocarbamate, cyanomethyl 3,5-dimethylpyrazole-1-dithiocarbamate, and cyanomethyl N-methyl-N-phenyldithiocarbamate. RAFT polymerization can easily produce (meth)acrylic copolymers with narrow molecular weight distributions. The amount of RAFT agent may be 0.05 to 5% by mass based on the total amount of two or more monomers used in the copolymerization.

The polymerization initiator can be, for example, any thermal radical polymerization initiator. Examples of polymerization initiators include azo compounds such as 2'-azobis(2,4-dimethylvaleronitrile). The amount of polymerization initiator may be 0.01 to 2% by mass based on the total amount of two or more monomers to be copolymerized.

The reaction liquid is heated to a temperature at which the copolymerization proceeds appropriately. The heating temperature may be, for example, 50 to 150°C. The copolymerization reaction time may be, for example, 2 to 24 hours. The reaction liquid may be stirred during the copolymerization.

After copolymerization, the reaction liquid containing the (meth)acrylic copolymer can be mixed directly with the curing agent component and other components added as needed to form a curable resin composition. The (meth)acrylic copolymer recovered from the reaction liquid may also be mixed with the curing agent component, etc.

The weight average molecular weight (Mw) of the (meth)acrylic copolymer may be 10,000 or more and 1,000,000 or less, 20,000 or more and 600,000 or less, or 30,000 or more and 400,000 or less. The molecular weight distribution (Mw/Mn) of the (meth)acrylic copolymer may be 1.1 or more and 2.5 or less. A narrow molecular weight distribution of the (meth)acrylic copolymer can contribute to improving the adhesiveness of the curable resin composition, etc.

The curable resin composition may further contain an additional thermoplastic resin different from the (meth)acrylic copolymer exemplified above. The additional thermoplastic resin may be, for example, an acrylic rubber. The acrylic rubber may be a copolymer containing a (meth)acrylic acid ester and acrylonitrile as monomer units. The acrylic rubber may have a reactive group selected from an epoxy group, a carboxy group, an acryloyl group, a methacryloyl group, a hydroxyl group, and an episulfide group. When the curable resin composition contains an additional thermoplastic resin, with regard to the amount of each component exemplified below, "100 parts by mass of the (meth)acrylic copolymer" can be read as "100 parts by mass of the total of the (meth)acrylic copolymer and the additional thermoplastic resin."

The curable resin composition may be a varnish containing a solvent. The solvent may be the solvent contained in the reaction liquid used to synthesize the (meth)acrylic copolymer. The amount of solvent in the curable resin composition may be 1 to 50 mass % based on the amount of the curable resin composition.

The curable component can be a compound having a reactive group. A curing reaction involving the reactive group forms a cured product of the curable resin composition. The curable component may be a curable resin, examples of which include epoxy resins, acrylic resins, silicone resins, phenolic resins, thermosetting polyimide resins, polyurethane resins, melamine resins, and urea resins. These can be used alone or in combination of two or more.

Epoxy resins are compounds containing epoxy groups, and examples include diglycidyl ethers of bisphenols such as bisphenol A epoxy resins, novolac epoxy resins such as phenol novolac epoxy resins and cresol novolac epoxy resins, glycidylamine epoxy resins, epoxy resins containing heterocycles, and alicyclic epoxy resins. These can be used alone or in combination of two or more.

The curable component may include an epoxy resin and its curing agent. Examples of curing agents for epoxy resins include amines, polyamides, acid anhydrides, polysulfides, boron trifluoride, bisphenols, phenol novolac resins, bisphenol A novolac resins, and cresol novolac resins. These can be used alone or in combination of two or more.

The content of the curable component in the curable resin composition may be 70 to 240 parts by mass, 70 to 180 parts by mass, or 70 to 120 parts by mass per 100 parts by mass of the (meth)acrylic copolymer.

The curable resin composition may contain a curing accelerator for the curable component. Examples of curing accelerators include imidazole compounds, dicyandiamide, dicarboxylic acid dihydrazide, triphenylphosphine, tetraphenylphosphonium tetraphenylborate, 2-ethyl-4-methylimidazole-tetraphenylborate, and 1,8-diazabicyclo[5.4.0]undecene-7-tetraphenylborate. These may be used alone or in combination of two or more. In particular, when the (meth)acrylic copolymer has a reactive group (e.g., a hydroxy group, a carboxy group, or an acid anhydride group), the curable resin composition may contain a curing accelerator (e.g., an imidazole compound) that can promote the reaction between the reactive group and the curable component.

The content of the curing accelerator in the curable resin composition may be 0.01 to 2.0 parts by mass, 0.02 to 1.5 parts by mass, or 0.03 to 1.0 part by mass per 100 parts by mass of the (meth)acrylic copolymer.

The curable resin composition may further contain a filler. The filler may be an inorganic filler, an organic filler, or both. The inorganic filler may be a metal filler (silver powder, gold powder, copper powder, etc.), a non-metallic inorganic filler (silica, alumina, boron nitride, titania, glass, iron oxide, ceramic, etc.), or a combination thereof. The inorganic filler may be particles having a surface modified with an organic group. Examples of organic fillers include carbon, rubber-based fillers, silicone-based microparticles, polyamide microparticles, and polyimide microparticles.

The filler content in the curable resin composition may be 450 parts by mass or less, 400 parts by mass or less, or 350 parts by mass or less, or 10 parts by mass or more, or 50 parts by mass or more, per 100 parts by mass of the (meth)acrylic copolymer. The filler content in the curable resin composition may be 10 parts by mass or more and 450 parts by mass or less, per 100 parts by mass of the (meth)acrylic copolymer.

The curable resin composition may further contain a silane coupling agent. Examples of silane coupling agents include trimethoxyphenylsilane, dimethyldimethoxyphenylsilane, triethoxyphenylsilane, dimethoxymethylphenylsilane, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris(2-methoxyethoxy)silane, N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, and 3-glycidoxypropyltrimethoxysilane. These include propylmethyldimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-isocyanatopropyltriethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-ureidopropyltriethoxysilane, N-(1,3-dimethylbutylidene)-3-(triethoxysilyl)-1-propanamine, N,N'-bis(3-(trimethoxysilyl)propyl)ethylenediamine, polyoxyethylenepropyltrialkoxysilane, and polyethoxydimethylsiloxane.

The content of the silane coupling agent may be 0 to 10 parts by mass, 0 to 5 parts by mass, or 0 to 3 parts by mass per 100 parts by mass of the (meth)acrylic copolymer.

The curable resin composition can be used, for example, as an adhesive or a thermally conductive material. The curable resin composition may be used to form a resin layer that is an adhesive layer and/or a thermally conductive layer. If the curable resin composition is a varnish containing a solvent, the resin layer may be formed by a method that includes forming a varnish film and removing the solvent from the varnish film.

The melt viscosity of the resin layer containing the curable resin composition at 130°C may be 3,500 Pa·s to 20,000 Pa·s. When the melt viscosity of the resin layer at 130°C is within this range, the resin layer can achieve both excellent adhesion and thickness stability at a high level. From a similar perspective, the melt viscosity of the resin layer containing the curable resin composition at 130°C may be 4,000 to 19,000 Pa·s, 4,000 to 15,000 Pa·s, or 4,000 to 13,000 Pa·s.

The melt viscosity at 130°C of a resin layer containing a curable resin composition can be measured by a method that includes laminating multiple resin layers to form a sample approximately 200 μm thick, measuring the melt viscosity of the sample using parallel plates with a diameter of 25 mm at a temperature rise rate of 10°C/min and a frequency of 1 Hz over a temperature range of 20 to 200°C to obtain a viscosity curve showing the relationship between melt viscosity and temperature, and determining the melt viscosity at 130°C from the viscosity curve. To measure the melt viscosity, a viscoelasticity measuring device such as the ARES (trade name) manufactured by Rheometrics Scientific F.E., Inc. can be used.

FIG. 1 is a perspective view schematically illustrating an example of an adhesive film having an adhesive layer containing a curable resin composition. FIG. 2 is a cross-sectional view taken along line II-II in FIG. 1. The adhesive film 10 shown in FIGS. 1 and 2 comprises a strip-shaped carrier film 1, a plurality of adhesive layers 3p disposed on the carrier film 1 and arranged to form a row 3A along the longitudinal direction X of the carrier film 1, and a protective film 5p covering the main surface F2 of the adhesive layer 3p opposite the carrier film 1. As shown in FIG. 2, one main surface F1 of the adhesive layer 3p contacts the carrier film 1, and the main surface F2 opposite the main surface F1 contacts the protective film 5p. The adhesive film 10 can be used, for example, to bond a semiconductor chip to a flexible wiring board. If the thickness of the adhesive layer 3p is stable after the bonding process, processes such as wire bonding can be performed more easily.

The area of the main surfaces F1, F2 of one adhesive layer 3p can be, for example, 10 to 200 ^mm2 . The proportion of the area on the surface of the carrier film 1 covered by the multiple adhesive layers 3p (adhesive layer area ratio) may be, for example, 10 to 60% or 10 to 35% based on the area of the carrier film 1. This area ratio may be a value calculated using the following formula from the area A of the main surfaces F1, F2 of one adhesive layer 3p, the pitch P between the multiple adhesive layers 3p provided on the carrier film 1, and the width W of the carrier film 1. The pitch P is the total length of one adhesive layer 3p and the distance from that adhesive layer 3p to the adjacent adhesive layer 3p in the direction along the longitudinal direction X of the carrier film 1.
Area ratio R (%) = {A/(P×W)}×100

The thickness of the adhesive layer 3p may be, for example, 1 to 200 μm, 3 to 150 μm, or 5 to 150 μm.

The width W of the carrier film 1 may be 100 mm or less, or may be 10 to 50 mm, 10 to 30 mm, or 10 to 20 mm. The carrier film 1 may be transparent. The carrier film 1 may be a plastic film, examples of which include polyester films (e.g., polyethylene terephthalate films, etc.), polyolefin films, polyvinyl chloride films, and polyimide films. The polyolefin film may be polytetrafluoroethylene, polyethylene film, polypropylene film, polymethylpentene film, polyvinyl acetate film, poly-4-methylpentene-1 film, ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer, or a film containing two or more resins selected from these. The carrier film 1 may have a single-layer structure or a multi-layer structure. The thickness of the carrier film 1 may be, for example, 10 to 200 μm, 20 to 100 μm, or 25 to 80 μm.

In order to increase the adhesion of the adhesive layer 3p to the carrier film 1, the surface of the carrier film 1 may be subjected to a chemical or physical surface treatment such as corona treatment, chromic acid treatment, ozone exposure, flame exposure, high-voltage shock exposure, or ionizing radiation treatment. A release layer containing a release agent such as a silicone-based release agent, a fluorine-based release agent, or a long-chain alkyl acrylate-based release agent may be provided on the surface of the carrier film 1.

The protective film 5p has substantially the same shape as the main surfaces F1 and F2 of the adhesive layer 3p. The protective film 5p may be easily peelable from the adhesive layer 3p. The protective film 5p may be a plastic film, examples of which include polyester films (e.g., polyethylene terephthalate films, etc.), polyolefin films, polyvinyl chloride films, and polyimide films. The polyolefin film may be polytetrafluoroethylene, polyethylene film, polypropylene film, polymethylpentene film, polyvinyl acetate film, poly-4-methylpentene-1 film, ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer, or a film containing two or more resins selected from these. The carrier film 1 may have a single-layer structure or a multi-layer structure. The thickness of the protective film 5p may be, for example, 10 to 200 μm, 20 to 100 μm, or 25 to 80 μm. The protective film 5p may be colored.

The adhesive film 10 can be obtained, for example, by a method including forming an adhesive layer containing a curable resin composition on a carrier film 1, laminating a protective film to the adhesive layer to form a laminate having the carrier film 1, the adhesive layer, and the protective film, and removing a portion of the adhesive layer and the protective film. The adhesive layer and a portion of the protective film may also be removed by die-cutting using a cutting means such as a blade.

The present invention is not limited to the following examples.

1. Synthesis of (meth)acrylic copolymers Monomers of the types and charged amounts (parts by mass) shown in Table 2, Table 3, Table 4, Table 5, or Table 6 were copolymerized by the following procedure to synthesize (meth)acrylic copolymers.

(1) Random copolymer (second monomer dropwise addition/RAFT polymerization)
Example 1
A flask equipped with a stirrer, dropping funnel, condenser, thermometer, and gas inlet tube was charged with 1.0 g of 2-cyano-2-[(dodecylsulfanylthiocarbonyl)sulfanyl]propane (RAFT agent), 230.1 g of ethyl acetate, and 269.1 g of n-butyl acrylate as the first monomer. The resulting mixture was then stirred, and the flask was heated to 60°C while the atmosphere inside the flask was purged with nitrogen gas. Subsequently, a mixture of 0.2 g of 2,2'-azobis(2,4-dimethylvaleronitrile) and 24.5 g of ethyl acetate was added to the mixture in the flask. Next, a mixture of 29.9 g of ethyl acetate and 29.9 g of 2-hydroxyethyl acrylate as the second monomer was added dropwise from the dropping funnel to the flask over 2 hours. After completion of the dropwise addition, the resulting reaction solution was stirred at 60°C for 5 hours to allow copolymerization of n-butyl acrylate and 2-hydroxyethyl acrylate to proceed. A resin varnish containing a (meth)acrylic copolymer formed by copolymerization and ethyl acetate was obtained.

The weight average molecular weight (Mw) and number average molecular weight (Mn) of the (meth)acrylic copolymer contained in the resin varnish were measured by gel permeation chromatography (GPC). The determined weight average molecular weight (Mw) and number average molecular weight (Mn) were values converted from a calibration curve using standard polystyrene. The GPC measurement conditions were as follows. The Mw and Mn of the (meth)acrylic copolymers obtained in other examples or comparative examples were measured using the same method.
Apparatus: LC-20AD (Shimadzu Corporation)
Detector: SHODEX RI-501 (manufactured by Resonac Co., Ltd.)
Column: SHODEX LF-804 (manufactured by Resonac Co., Ltd.)
Eluent: tetrahydrofuran Sample concentration: 0.5% by mass
Flow rate: 1.0ml/min

Examples 2 to 8
A resin varnish containing a (meth)acrylic copolymer and ethyl acetate was obtained in the same manner as in Example 1, except that the types and amounts of monomers charged were changed as shown in the table.

(2) Random copolymer (second monomer dropwise addition/non-RAFT polymerization)
Example 9
A flask equipped with a stirrer, dropping funnel, condenser, thermometer, and gas inlet tube was charged with 244.6 g of ethyl acetate and 269.1 g of n-butyl acrylate as the first monomer. The resulting mixture was then stirred, and the flask was heated to 60°C while the atmosphere inside the flask was purged with nitrogen gas. Subsequently, a mixture of 0.2 g of 2,2'-azobis(2,4-dimethylvaleronitrile) and 24.5 g of ethyl acetate was added to the mixture in the flask. Next, a mixture of 29.9 g of ethyl acetate and 29.9 g of 2-hydroxyethyl acrylate as the second monomer was added dropwise from the dropping funnel to the flask over 2 hours. After the addition was completed, the resulting reaction solution was stirred at 60°C for 5 hours to allow the copolymerization of n-butyl acrylate and 2-hydroxyethyl acrylate to proceed. A resin varnish containing a (meth)acrylic copolymer formed by copolymerization and ethyl acetate was obtained.

Examples 10 to 12
A resin varnish containing a (meth)acrylic copolymer and ethyl acetate was obtained in the same manner as in Example 9, except that the types and amounts of monomers charged were changed as shown in the table.

(3) Copolymer containing a block portion (second monomer dropwise addition/RAFT polymerization)
Comparative Example 1
A flask equipped with a stirrer, dropping funnel, condenser, thermometer, and gas inlet tube was charged with 1.0 g of 2-cyano-2-[(dodecylsulfanylthiocarbonyl)sulfanyl]propane (RAFT agent), 230.1 g of ethyl acetate, and 269.1 g of n-butyl acrylate as the first monomer. The resulting mixture was then stirred, and the flask was heated to 60°C while the atmosphere inside the flask was purged with nitrogen gas. Subsequently, a mixture of 0.2 g of 2,2'-azobis(2,4-dimethylvaleronitrile) and 24.5 g of ethyl acetate was added to the mixture in the flask. Next, a mixture of 29.9 g of ethyl acetate and 29.9 g of acrylamide as the second monomer was added dropwise from the dropping funnel to the flask over 2 hours. After completion of the dropwise addition, the resulting reaction solution was stirred at 60°C for 5 hours to allow copolymerization of n-butyl acrylate and acrylamide to proceed. A resin varnish containing a (meth)acrylic copolymer formed by copolymerization and ethyl acetate was obtained.

Comparative Examples 2 to 7
A resin varnish containing a (meth)acrylic copolymer and ethyl acetate was obtained in the same manner as in Comparative Example 1, except that the types and amounts of monomers charged were changed as shown in the table.

(4) Copolymer containing block moieties (monomer simultaneous introduction/RAFT polymerization)
Comparative Example 8
A flask equipped with a stirrer, condenser, thermometer, and gas inlet tube was charged with 1.0 g of 2-cyano-2-[(dodecylsulfanylthiocarbonyl)sulfanyl]propane (RAFT agent), 245.6 g of ethyl acetate, 269.1 g of n-butyl acrylate, and 29.9 g of 2-hydroxyethyl acrylate. The resulting mixture was then stirred, and the flask was heated to 60°C while the atmosphere inside was purged with nitrogen gas. Subsequently, a mixture of 0.2 g of 2,2'-azobis(2,4-dimethylvaleronitrile) and 24.5 g of ethyl acetate was added to the mixture in the flask. The resulting reaction solution was then stirred at 60°C for 7 hours to allow copolymerization of n-butyl acrylate and 2-hydroxyethyl acrylate to proceed. A resin varnish containing a (meth)acrylic copolymer formed by copolymerization and ethyl acetate was obtained.

Comparative Examples 10, 12 to 15, 17, 19 to 21
A resin varnish containing a (meth)acrylic copolymer and ethyl acetate was obtained in the same manner as in Comparative Example 8, except that the types and amounts of monomers charged were changed as shown in the table.

(5) Copolymer containing block portion (monomer simultaneous introduction/non-RAFT polymerization)
Comparative Example 9
A flask equipped with a stirrer, condenser, thermometer, and gas inlet tube was charged with 244.6 g of ethyl acetate, 269.1 g of n-butyl acrylate, and 29.9 g of 2-hydroxyethyl acrylate. The resulting mixture was then stirred, and the flask was heated to 60°C while the atmosphere inside the flask was purged with nitrogen gas. Subsequently, a mixture of 0.2 g of 2,2'-azobis(2,4-dimethylvaleronitrile) and 24.5 g of ethyl acetate was added to the mixture inside the flask. The resulting reaction solution was then stirred at 60°C for 7 hours to allow copolymerization of n-butyl acrylate and 2-hydroxyethyl acrylate to proceed. A resin varnish containing a (meth)acrylic copolymer formed by copolymerization and ethyl acetate was obtained.

Comparative Examples 11, 16, and 18
A resin varnish containing a (meth)acrylic copolymer and ethyl acetate was obtained in the same manner as in Comparative Example 9, except that the types and amounts of monomers charged were changed as shown in the table.

The reactivity ratio of each monomer used in Examples or Comparative Examples 1 to 7 was determined from the Q value and e value in Table 1.
In the combinations of n-butyl acrylate (first monomer) and 2-hydroxyethyl acrylate (second monomer) (Examples 1, 2, 9, and 10), the reactivity ratio _r1 of n-butyl acrylate was 0.37, and the reactivity ratio _r2 of 2-hydroxyethyl acrylate was 2.56.
In the combinations of n-butyl acrylate (first monomer) and acrylic acid (second monomer) (Examples 3, 4, 11 and 12), the reactivity ratio _r1 of n-butyl acrylate was 0.47, and the reactivity ratio _r2 of acrylic acid was 2.12.
In the combination of n-butyl acrylate (first monomer) and benzyl methacrylate (second monomer) (Examples 5 and 6), the reactivity ratio _r1 of n-butyl acrylate was 0.28, and the reactivity ratio _r2 of acrylic acid was 2.76.
In the combination of acrylamide (first monomer) and n-butyl acrylate (second monomer) (Example 7), the reactivity ratio _r1 of acrylamide was 0.72, and the reactivity ratio _r2 of n-butyl acrylate was 1.27.
In the combination of styrene (first monomer) and n-butyl acrylate (second monomer) (Example 8), the reactivity ratio _r1 of styrene was 0.70, and the reactivity ratio _r2 of n-butyl acrylate was 0.09.
In the combination of n-butyl acrylate (first monomer) and acrylamide (second monomer) (Comparative Examples 1 and 2), the reactivity ratio _r1 of n-butyl acrylate was 1.27, and the reactivity ratio _r2 of acrylamide was 0.72.
In the combination of n-butyl acrylate (first monomer) and styrene (second monomer) (Comparative Examples 3 and 4), the reactivity ratio _r1 of n-butyl acrylate was 0.09, and the reactivity ratio _r2 of styrene was 0.70.
In the case of copolymerization of styrene and n-butyl acrylate (Example 8), the reactivity ratio r ₁ ' of styrene and the reactivity ratio r ₂ ' of n-butyl acrylate calculated from the copolymerization ratio of the copolymer produced by RAFT polymerization in the presence of a RAFT agent are considered to satisfy r ₁ '<1<r ₂ '.

2. Polymer (1) Sequence at the Initial Stage of Polymerization When the second monomer was added dropwise after the introduction of the polymerization initiator, 10 mg of the reaction solution in the flask was sampled one hour after the start of the dropwise addition of the second monomer. When the first and second monomers were introduced all at once, 10 mg of the reaction solution in the flask was sampled one hour after the completion of the addition of 2,2'-azobis(2,4-dimethylvaleronitrile). The polymer contained in the sampled reaction solution corresponds to the terminal portion of the main chain of the final (meth)acrylic copolymer. The ¹ H-NMR spectrum of a sample prepared by dissolving the sampled reaction solution in 1.0 g of deuterated chloroform was measured. The mass fraction of each monomer was calculated from the integrated values derived from each of the two monomers in the obtained ¹ H-NMR spectrum, based on the total amount of monomer units constituting the polymer. The polymer sequence was determined according to the following criteria by comparing the mass fraction calculated from the ¹ H-NMR spectrum with the theoretical value of the mass fraction calculated from the charged amounts (the mass fraction of the charged amount of each monomer based on the total amount of the two monomers).
Block: The mass fraction of any of the monomers calculated from the ¹ H-NMR spectrum deviates from the theoretical value by 5% by mass or more.
Random: The mass fraction calculated from the ¹ H-NMR spectrum of each monomer is within ±5% by mass of the theoretical value.

(2) Molecular Weight The Mw and Mn of the polymer in the early stage of polymerization contained in the reaction solution sampled for sequence evaluation were measured in the same manner as in the measurement of Mw and Mn of the (meth)acrylic copolymer.

3. Preparation of Adhesive Varnish The resin varnish obtained in the Examples or Comparative Examples was mixed with the following materials, and the mixture was subjected to vacuum degassing to obtain an adhesive varnish. The amount of the (meth)acrylic copolymer (50 parts by mass) is the amount excluding the solvent (ethyl acetate).
(1) Thermoplastic resin (meth)acrylic copolymer (Example or Comparative Example): 50 parts by mass; Acrylic rubber having a glycidyl group (HTR-860P-3 (trade name), manufactured by Nagase ChemteX Corporation, molecular weight 1,000,000, Tg -7 ° C): 50 parts by mass; (2) Thermosetting resin; o-cresol novolac epoxy resin (YDCN-700-10 (trade name), manufactured by Nippon Steel & Sumikin Chemical Co., Ltd., epoxy equivalent 210): 30 parts by mass; Phenolic resin (PSM-4326 (trade name), manufactured by Gunei Chemical Industry Co., Ltd., functional group equivalent 105): 95 parts by mass; Bisphenol F epoxy resin (2) Curing accelerator: Imidazole compound (2PZ-CN (trade name), manufactured by Shikoku Chemical Industry Co., Ltd.): 0.3 parts by mass; Surface-treated filler: SC-2050-HLG (trade name, manufactured by Admatechs Co., Ltd.): 330 parts by mass; (3) Curing accelerator: Imidazole compound (2PZ-CN (trade name), manufactured by Shikoku Chemical Industry Co., Ltd.): 0.3 parts by mass; Surface-treated filler: SC-2050-HLG (trade name, manufactured by Admatechs Co., Ltd.): 330 parts by mass; (4) Silane coupling agent: γ-mercaptopropyltrimethoxysilane (A-189 (trade name), manufactured by NUC Co., Ltd.): 0.9 parts by mass; γ-ureidopropyltriethoxysilane (A-1160 (trade name), manufactured by NUC Co., Ltd.): 2 parts by mass.

4. Evaluation of Compatibility The state of each adhesive varnish was visually observed, and compatibility was evaluated according to the following criteria.
A: The adhesive varnish is transparent. B: The adhesive varnish is cloudy. C: Both cloudiness and sediment are observed in the adhesive varnish.

5. Preparation of Adhesive Film The adhesive varnish was applied to a polyethylene terephthalate film (50 μm thick, manufactured by Teijin DuPont Films Co., Ltd., product name: Teijin Tetron Film A-63) having a release-treated surface. The coating was dried to form an adhesive layer with a thickness of 25 μm. A colored polyethylene film (50 μm thick, manufactured by Tamapoly Co., Ltd., TDM-1) was bonded to the adhesive layer to form a laminate having an adhesive layer. Portions of the adhesive layer and polyethylene film of the laminate were removed by die-cutting to form an adhesive layer and polyethylene film having a rectangular shape with one side forming a convex portion, as exemplified in FIG. 1 .

6. Melt Viscosity An adhesive sample approximately 200 μm thick was formed by laminating multiple adhesive layers. The melt viscosity of the adhesive sample was measured using parallel plates 25 mm in diameter at a temperature rise rate of 10°C/min and a frequency of 1 Hz in the temperature range of 20 to 200°C. The melt viscosity at 130°C was determined from the viscosity curve obtained by the measurement. The measuring device used was an ARES (trade name) manufactured by Rheometrics Scientific F.E. Co., Ltd. The melt viscosity was evaluated according to the following criteria:
A: 10,000 Pa·s or more and 20,000 Pa·s or less B: 3,000 Pa·s or more and less than 10,000 Pa·s, or more than 20,000 Pa·s and 24,000 Pa·s or less C: Less than 3,000 Pa·s, or more than 24,000 Pa·s

7. Evaluation of Adhesives (1) Module Fabrication A semiconductor chip (approximately 15 mm long x 15 mm wide x 0.4 mm thick) was prepared. A 3.2 mm x 3.2 mm adhesive layer was placed on the top surface of the semiconductor chip, and a polyethylene film covering the adhesive layer was placed on it. In this state, a pressure of 10 N was applied to the adhesive layer from the polyethylene film side for 0.5 seconds at a temperature of 90°C, temporarily bonding the adhesive layer to the semiconductor chip. The polyethylene film was peeled off, and the tip of the FPC substrate was pressed against the exposed adhesive layer. For bonding, the adhesive layer was heated to 130°C, and a pressure of 15 N was applied to the FPC substrate and adhesive layer for 1 second. After bonding, the FPC substrate was held in place while applying tension to the adhesive layer by pulling the FPC substrate with a force of 250 g in the direction away from the semiconductor chip, and the adhesive layer was cured by heating at 130°C for 1 hour. This resulted in a module consisting of a connection structure consisting of an FPC substrate, adhesive layer, and semiconductor chip. These steps were repeated to fabricate 10 modules.

(2) Elongation of Adhesive Layer The thickness of the adhesive layer of each of the four modules where tension was applied during curing was measured using an optical microscope image. Based on the average value of the measured adhesive layer thickness, the elongation of the adhesive layer was evaluated according to the following criteria. Small elongation of the adhesive layer corresponds to small variation in the adhesive layer thickness after curing.
A: Less than 30 μm B: 30 μm or more and 250 μm or less C: More than 250 μm D: In three or more of the four modules, the FPC board peeled off from the adhesive layer during curing.

(3) Adhesion The semiconductor chip of the module was fixed by attaching it to the surface of a table. In this state, a gradually increasing stress was applied to the FPC board in a direction away from the semiconductor chip. Adhesion was evaluated according to the following criteria based on the number of modules out of 10 modules in which the FPC board peeled off from the semiconductor chip by the time a force of 0.5 N was applied to the FPC board.
A: 2 or less B: 3 to 8 C: 9 or more D: In 5 or more of the 10 modules, the FPC board peeled off from the adhesive layer during curing.

(4) Voids in the adhesive layer Two modules were inspected using an ultrasonic imaging system (SAT, manufactured by Hitachi Power Solutions, FS200II) to determine the percentage of voids in the adhesive layer. Based on the percentage of voids, the state of voids was evaluated according to the following criteria.
A: Less than 10% B: 10% or more

(5) Results The evaluation results are shown in Tables 2 to 5. Each table also shows the mass fraction of each monomer introduced into the reaction solution. In the examples, the polymer at the initial stage of polymerization was a random copolymer containing each monomer unit in a copolymerization ratio close to the theoretical value, and its weight-average molecular weight was significantly greater than 1,000. Therefore, in the obtained (meth)acrylic copolymer, the terminal portion, which is the portion from the end of the main chain with a molecular weight of 1,000 or more, can be said to be a random copolymer. The adhesive layer containing the curable resin composition of the examples containing the (meth)acrylic copolymer exhibited excellent adhesive properties. The curable resin composition of the examples was also excellent in terms of suppressing voids in the adhesive layer after curing.

Claims (19)

forming a (meth)acrylic copolymer by copolymerizing two or more monomers in a reaction solution containing two or more monomers including a monomer having a (meth)acryloyl group;
forming a curable resin composition containing the (meth)acrylic copolymer and a curable component;
A method for producing a curable resin composition, comprising:
the two or more monomers include a first monomer and a second monomer different from the first monomer;
During the copolymerization, the ratio of the amount of the second monomer to the amount of the first monomer in the reaction solution is increased continuously or stepwise, thereby forming the (meth)acrylic copolymer having a main chain including terminal portions that is a random copolymer. the mass fraction of the total amount of the second monomer introduced into the reaction liquid is Y ₀ mass% based on the total amount of the two or more monomers introduced into the reaction liquid;
When the mass fraction of the amount of the monomer units derived from the second monomer is Y 1% by mass based on the total amount of the monomer units derived from the two or more monomers in the terminal portion of the formed ( _meth )acrylic copolymer,
The method according to claim 1 , wherein Y ₁ is within ±5% by weight of Y ₀ . The method of claim 1, wherein the terminal portion is a portion of the (meth)acrylic copolymer having a molecular weight of 1,000 or more from the end of the main chain. The method of claim 1, wherein in the (meth)acrylic copolymer formed, the mass fraction of triad sequences consisting of three consecutively bonded monomer units derived from the second monomer is 5 mass% or less, based on the total amount of monomer units derived from the two or more monomers. The method of claim 1, wherein, of the two or more monomers, the first monomer exhibits the largest Q value and the second monomer exhibits the smallest Q value. 2. The method of claim 1, wherein when the Q value of the first monomer is _Q1 and the Q value of the second monomer is _Q2 , | _Q1 - _Q2 | is 0.4 or greater. 2. The method of claim 1, wherein when the e value of the first monomer is _e1 and the e value of the second monomer is _e2 , _e1 x _e2 is a negative value and | _e1 - _e2 | is 1.0 or more and 2.0 or less. The method according to claim 1, wherein, when the Q value and e value of the first monomer are _Q1 and _e1 , respectively, and the Q value and e value of the second monomer are _Q2 and _e2 , respectively, the reactivity ratio _r1 of the first monomer calculated by the following formula (1) and the reactivity ratio _r2 of the second monomer calculated by the following formula (2) satisfy the following relationship (3).
r ₁ = (Q ₁ /Q ₂ )×exp(-e ₁ (e ₁ -e ₂ ))...(1)
r ₂ = (Q ₂ /Q ₁ )×exp(-e ₂ (e ₂ -e ₁ ))...(2)
r ₁ <1 < r ₂ ...(3) The method of claim 1, wherein the first monomer is an alkyl (meth)acrylate. The method of claim 1, wherein the second monomer is an ethylenically unsaturated compound having one or more functional groups selected from a hydroxy group, a carboxy group, an acid anhydride group, a sulfonic acid group, a phosphonic acid group, an amide group, and an aromatic group. The method of claim 1, wherein the copolymerization is RAFT polymerization. The method according to claim 11, wherein the reactivity ratio r 1 ' of the first monomer and the reactivity ratio r ₂ ' of the second monomer, which are determined from the copolymerization ratio of a copolymer produced by RAFT polymerization in a reaction solution for reactivity evaluation into which the entire amounts of two types of monomers consisting of the first monomer and the second monomer are introduced all at once in the presence of a _RAFT agent, satisfy the following relational formula (3'):
_r1 '<1< _r2 '...(3') a (meth)acrylic copolymer;
A curable component;
A curable resin composition comprising:
the (meth)acrylic copolymer is a copolymer having a main chain containing, as monomer units, two or more types of monomers including a monomer having a (meth)acryloyl group,
the two or more monomers include a first monomer and a second monomer different from the first monomer;
A curable resin composition, wherein the main chain of the (meth)acrylic copolymer has terminal portions that are random copolymers at both ends. In the entire (meth)acrylic copolymer, the mass fraction of the amount of the monomer units derived from the second monomer is Y ₀ mass%, based on the total amount of the monomer units derived from the two or more monomers;
In the terminal portion of the (meth)acrylic copolymer, the mass fraction of the amount of the monomer unit derived from the second monomer is Y ₁ % by mass, based on the total amount of the monomer units derived from the two or more monomers;
Y ₁ is within ±5 mass% of Y ₀ ;
The curable resin composition according to claim 13. The curable resin composition according to claim 13, wherein the terminal portion is a portion of the (meth)acrylic copolymer having a molecular weight of 1,000 or more from the end of the main chain. The curable resin composition according to claim 13, wherein in the (meth)acrylic copolymer, the mass fraction of a triplet sequence consisting of three consecutively bonded monomer units derived from the second monomer is 5 mass% or less, based on the total amount of monomer units derived from the two or more monomers. The curable resin composition according to claim 13, wherein the molecular weight distribution of the (meth)acrylic copolymer is 1.1 or more and 2.5 or less. The curable resin composition according to claim 13, wherein the first monomer is an alkyl (meth)acrylate. The curable resin composition according to claim 13, wherein the second monomer is an ethylenically unsaturated compound having one or more functional groups selected from a hydroxy group, a carboxy group, an acid anhydride group, a sulfonic acid group, a phosphonic acid group, an amide group, and an aromatic group.