JP7716466B2 - Copolymer, copolymer solution, photosensitive resin composition, cured product, copolymer manufacturing method, and copolymer solution manufacturing method - Google Patents

Description

The present invention relates to a copolymer. More specifically, it relates to a copolymer that can give a cured product with excellent solvent resistance even under low-temperature curing conditions, a copolymer solution, a photosensitive resin composition, a cured product, a method for producing the copolymer, and a method for producing the copolymer solution.

Compositions containing curable resins have been widely studied for their application to various applications, such as various optical components and electric/electronic devices, including color filters, inks, printing plates, printed wiring boards, semiconductor devices, photoresists, organic insulating films, and organic protective films used in liquid crystal displays and solid-state imaging devices, and resins and resin compositions having excellent properties required for each application have been developed.
In recent years, optical components and electrical and electronic devices have become smaller, thinner, and more energy-efficient, which has led to demands for higher performance from the various components used in these devices. To meet these demands, research is being conducted on curable resins, which are used as materials for various components.

Up to now, curable resins have been developed to meet various requirements.
For example, Patent Document 1 describes a photosensitive resin composition containing an oligomer having a carboxyl group and a photoreactive unsaturated group in a side chain and being soluble in an alkaline aqueous solution, a compound having an epoxy group, a sensitizer, and a dicyandiamide-modified product.
Furthermore, for example, Patent Document 2 describes a photosensitive composition containing an alkali-soluble polymer obtained by polymerizing a radical polymerizable monomer having an epoxy group or an oxetanyl group, a radical polymerizable monomer having a carboxyl group, or the like.
Furthermore, for example, Patent Document 3 describes a curable polymer having an acid group, a hydroxy group, and a polymerizable unsaturated bond in a side chain, which is obtained by subjecting an addition copolymer of a (meth)acrylate monomer having a glass transition temperature of 10° C. or less when made into a homopolymer, or a (meth)acrylate monomer having an epoxy group or a carboxyl group, to a specific modification reaction, and a photosensitive polymer composition containing the curable polymer.

Japanese Patent Application Publication No. 4-25846 Japanese Patent Application Laid-Open No. 2006-251009 JP 2014-210892 A

As mentioned above, various studies have been conducted on curable resins. However, when conventional curable resins are used together with colorants as raw materials for color filters, for example, there is a problem in that the colorants leach out of the raw materials into the cleaning solvent during the production of color filters. Therefore, there is a need for further improvements in the solvent resistance of curable resins.

Furthermore, in recent years, particularly in color filter applications, the improvement in quality and expansion of applications of color liquid crystal display devices and the like have led to a strong demand for higher performance, such as higher brightness and contrast, of display panels. However, in the production of color filters, if the baking process (post-curing process) after exposure and development is performed at a high temperature above 200°C, discoloration such as yellowing occurs in the resulting cured product, preventing sufficient high coloration of the desired color. Furthermore, if the baking process is performed at a high temperature, unwanted reactions occur, producing by-products and degrading the properties of the substrate and the cured film. In order to suppress such unwanted reactions and efficiently obtain color filters with desired properties, it is desirable for the curing reaction to proceed sufficiently even under relatively low heating conditions of 200°C or less. Furthermore, if the curable resin composition can be cured at a relatively low temperature, the production efficiency of color filters can also be improved.
The conventional photosensitive resin composition described in Patent Document 1 requires high temperatures for resin synthesis, and there is also room for improvement in the curability of the resin.

The present invention was made in consideration of the above-mentioned current situation, and aims to provide a copolymer that can give a cured product with excellent solvent resistance even under low-temperature curing conditions and can be suitably used as a thermosetting resin for various applications such as color filters.

After extensive research into curable resins, the inventors discovered that by creating a copolymer containing an epoxy group-containing group and a long-chain acid group in one molecule and having an epoxy equivalent weight within a specific range, the crosslinking reaction proceeds smoothly even under low-temperature curing conditions of 160°C or less, resulting in a cured product with excellent solvent resistance, leading to the completion of the present invention.

That is, the present invention relates to a copolymer characterized by having an epoxy group-containing structural unit (A) represented by the following general formula (1) and an acid group-containing structural unit (B) represented by the following general formula (2), and having an epoxy equivalent of 20,000 or less.

(In formula (1), ^R1 represents a hydrogen atom or a methyl group. ^R2 represents a direct bond or a divalent organic group. X represents an epoxy group-containing group.)

(In formula (2), ^R3 represents a hydrogen atom or a methyl group. ^R4 represents a direct bond or an organic group. ^R5 represents a bonding chain having a length of 2 or more atoms. Y represents an acid group. a represents 0 or 1.)

In the above copolymer, the structural unit (A) preferably contains a structural unit represented by the following general formula (1-1):

(In formula (1-1), ^R1 represents a hydrogen atom or a methyl group. ^R6 represents a direct bond or a divalent organic group.)

In the above copolymer, the structural unit (B) preferably includes a structural unit represented by the following general formula (2-1):

(In formula (2-1), ^R3 represents a hydrogen atom or a methyl group. ^R7 and ^R8 are the same or different and represent a direct bond or an organic group. b represents 0 or 1.)

It is further preferable that the above copolymer is a copolymer having a ring structure in the main chain.

It is preferable that the above copolymer further contains structural units derived from a monomer having 5 to 20 atoms in the longest side chain or a monomer having a ring structure in the side chain.

The present invention also relates to a copolymer solution comprising the above-mentioned copolymer and a protic polar solvent.

It is preferable that the copolymer solution further contains an acid compound having a pKa of 4.2 or less.

It is preferable that the above copolymer solution further contains a phosphoric acid derivative.

It is preferable that the copolymer solution further contains a basic compound.

The present invention also relates to a photosensitive resin composition comprising the above-mentioned copolymer or copolymer solution, a polymerizable compound, and a photopolymerization initiator.

It is preferable that the above-mentioned photosensitive resin composition further contains a colorant.

The above photosensitive resin composition is preferably for negative use.

The present invention also relates to a cured product of the above-mentioned copolymer, the above-mentioned copolymer solution, or the above-mentioned photosensitive resin composition.

The present invention also relates to a method for producing a copolymer, comprising the steps of polymerizing a monomer component containing an epoxy group-containing monomer represented by the following formula (a) and a hydroxyl group-containing monomer represented by the following formula (b1), and reacting the polymer obtained in the polymerization step with an acid group-containing compound represented by the following formula (b2) or (b3).

(In formula (a), ^R1 represents a hydrogen atom or a methyl group. ^R2 represents a direct bond or a divalent organic group. X represents an epoxy group-containing group.)

(In formula (b1), ^R3 represents a hydrogen atom or a methyl group, and ^R4 represents a direct bond or an organic group.)

(In formula (b2), ^R5 represents a bonding chain having a length of 2 atoms or more, and Y represents an acid group.)

(In formula (b3), ^R5 represents a bonding chain having a length of 2 atoms or more.)

The present invention also relates to a method for producing a copolymer solution, comprising the steps of: polymerizing a monomer component containing an epoxy group represented by formula (a) below and a hydroxyl group-containing monomer represented by formula (b1) below; reacting the polymer obtained in the polymerization step with an acid group-containing compound represented by formula (b2) or (b3) below in the presence of a basic compound; and adding an acid compound having a pKa of 4.2 or less and a protic polar solvent.

(In formula (a), ^R1 represents a hydrogen atom or a methyl group. ^R2 represents a direct bond or a divalent organic group. X represents an epoxy group-containing group.)

(In formula (b1), ^R3 represents a hydrogen atom or a methyl group, and ^R4 represents a direct bond or an organic group.)

(In formula (b2), ^R5 represents a bonding chain having a length of 2 atoms or more, and Y represents an acid group.)

(In formula (b3), ^R5 represents a bonding chain having a length of 2 atoms or more.)

The copolymer of the present invention can provide a cured product with excellent solvent resistance even under relatively low-temperature curing conditions of 160°C or less. The copolymer of the present invention is suitable for use in a variety of applications, such as various optical components used in liquid crystal, organic EL, quantum dot, and micro LED liquid crystal displays, solid-state imaging devices, touch panel displays, etc., as well as components for electrical and electronic devices, etc.

The present invention will be described in detail below.
It should be noted that a combination of two or more of the individual preferred embodiments of the present invention described below is also a preferred embodiment of the present invention.
In this specification, "(meth)acrylic acid" means "acrylic acid and/or methacrylic acid", and "(meth)acrylate" means "acrylate and/or methacrylate".

1. Copolymer The copolymer of the present invention is characterized by having an epoxy group-containing structural unit (A) represented by the following general formula (1) and an acid group-containing structural unit (B) represented by the following general formula (2), and having an epoxy equivalent of 20,000 or less:

(In formula (1), ^R1 represents a hydrogen atom or a methyl group. ^R2 represents a direct bond or a divalent organic group. X represents an epoxy group-containing group.)

(In formula (2), ^R3 represents a hydrogen atom or a methyl group. ^R4 represents a direct bond or an organic group. ^R5 represents a bonding chain having a length of 2 or more atoms. Y represents an acid group. a represents 0 or 1.)

The copolymer of the present invention can produce a cured product with excellent solvent resistance even when cured at relatively low temperatures of 160°C or below (preferably around 90°C). This is thought to be because the copolymer contains epoxy groups and acid groups, and because the acid groups are long-chain acids located relatively far from the main chain, making the acid groups highly reactive with the epoxy groups, allowing the crosslinking reaction to proceed even at relatively low temperatures and forming a strong cured film. Also, as the side chains of the acid group-containing structural units become longer, the glass transition temperature becomes lower than that of acrylic acid or methacrylic acid structural units, making the polymer side chains more flexible and allowing the above-mentioned crosslinking reaction to proceed more easily at low temperatures.

The copolymer of the present invention has the above-mentioned epoxy group-containing structural unit (A) and acid group-containing structural unit (B), and has an epoxy equivalent (g/equivalent) of 20,000 or less. If the epoxy equivalent exceeds 20,000, curing may be insufficient, and solvent resistance may be reduced. The epoxy equivalent of the copolymer of the present invention is preferably 10,000 or less, more preferably 8,000 or less, even more preferably 5,000 or less, even more preferably 4,000 or less, particularly preferably 3,000 or less, and most preferably 2,000 or less. Furthermore, from the viewpoint of storage stability, the epoxy equivalent is preferably 100 or more, more preferably 150 or more, and even more preferably 200 or more.
The epoxy equivalent can be determined by dividing the solid content of the copolymer by the number of moles of epoxy groups contained in the copolymer. Alternatively, the epoxy equivalent can be determined by a method in accordance with JIS K7236:2001.

<Structural Unit (A)>
The copolymer of the present invention has the epoxy group-containing structural unit (A) represented by the above general formula (1).
In the above general formula (1), R ¹ represents a hydrogen atom or a methyl group.
^R2 represents a direct bond or a divalent organic group. Examples of the organic group include linear or cyclic saturated or unsaturated hydrocarbon groups, -O-, -CO-, -COO-, -NH-, -S-, -SO-, -SO ₂ -, and divalent groups formed from combinations thereof.
Examples of the hydrocarbon group include divalent aliphatic hydrocarbon groups, alicyclic hydrocarbon groups, and aromatic hydrocarbon groups.
The aliphatic hydrocarbon group may be linear or branched, and examples thereof include alkylene groups such as methylene, ethylene, trimethylene, propylene, ethylidene, propylidene, and isopropylidene groups, as well as vinylene, propenylene, and vinylidene groups.
Examples of the alicyclic hydrocarbon group include cycloalkylene groups such as 1,2-cyclopentylene, 1,2-cyclohexylene, cyclopentylidene, and cyclohexylidene.
Examples of the aromatic hydrocarbon group include a 1,2-phenylene group, a 1,2-naphthylene group, a 2,3-naphthylene group, a benzylidene group, a cinnamylidene group, and a biphenylylene group.

The hydrocarbon group may have at least one atom substituted with an oxygen atom, a nitrogen atom, or a sulfur atom. The hydrocarbon group may also have a substituent. Examples of the substituent include a hydroxyl group, an alkoxy group, an alkyl group, an allyl group, an aryl group, and a halogen atom. The substituent may also have a further substituent.

Specific examples of the divalent organic group include -R-, -CO-, -CO-R-, -R-CO-R'-, -COO-, -COO-R-, -R-COO-R'-, -O-R-, and -R-O-R'- (wherein R and R' are the same or different and represent the divalent hydrocarbon group described above).

The number of atoms in the divalent organic group is preferably 0 to 10, more preferably 1 to 5, and even more preferably 2 to 4.

Among these, ^R2 is preferably -R-, -COO-, or -COO-R-, and more preferably -COO- or -COO-R- (R represents a hydrocarbon group having 1 to 4 carbon atoms which may have a substituent, and preferably represents an alkylene group having 1 to 2 carbon atoms).

X represents an epoxy group-containing group. In this specification, the epoxy group-containing group is a group containing an oxirane ring (epoxy group), and includes groups in which an oxirane ring is bonded to a carbon, such as a glycidyl group, groups containing an ether bond or an ester bond, such as a glycidyl ether group and a glycidyl ester group, and alicyclic epoxy groups containing an epoxycyclohexane ring or the like.
Preferred examples of the epoxy group-containing group include groups represented by the following formulae (x1) to (x4).

In the formula, n is an integer of 0 to 10, preferably an integer of 0 to 4, and more preferably an integer of 0 to 2.
m is an integer of 1 to 10, preferably an integer of 2 to 8, and more preferably an integer of 3 to 6.
Among these, (x1) is preferred as X from the viewpoint of reactivity, and (x1) where n=1 is more preferred.

The structural unit (A) is preferably the structural unit (A-1) represented by the following general formula (1-1), as this can further improve solvent resistance.

(In formula (1-1), ^R1 represents a hydrogen atom or a methyl group. ^R6 represents a direct bond or a divalent organic group.)

In the general formula (1-1), R ¹ represents a hydrogen atom or a methyl group, and among these, R ¹ is preferably a methyl group.
Examples of the divalent organic group represented by ^R6 include the same groups as the divalent organic group represented by ^R2 described above.
The divalent organic group represented by ^R6 preferably has 0 to 10 carbon atoms, more preferably 1 to 4 carbon atoms, and even more preferably 1 or 2 carbon atoms.

Among these, the divalent organic group represented by ^R6 is preferably a divalent aliphatic hydrocarbon group, more preferably a divalent aliphatic hydrocarbon group having no substituent, and most preferably a methylene group.

The copolymer having the structural unit (A) can be obtained by polymerizing a monomer component containing a monomer capable of introducing the structural unit (A).
Examples of the monomer into which the structural unit (A) can be introduced include compounds represented by the following formula (a).

(In the formula, R ¹ , R ² , and X are the same as R ¹ , R ² , and X in the general formula (1), respectively.)

Specific examples of monomers into which the structural unit (A) can be introduced include glycidyl (meth)acrylate, β-methyl glycidyl (meth)acrylate, β-ethyl glycidyl (meth)acrylate, vinylbenzyl glycidyl ether, allyl glycidyl ether, (3,4-epoxycyclohexyl)methyl (meth)acrylate, and vinylcyclohexene oxide. Among these, glycidyl (meth)acrylate and (3,4-epoxycyclohexyl)methyl (meth)acrylate are preferred, with glycidyl (meth)acrylate being more preferred, and glycidyl methacrylate being even more preferred because it can suppress side reactions and is expected to improve storage stability.

The copolymer of the present invention may have one or more types of the above structural unit (A).

In the copolymer of the present invention, the content of the structural unit (A) is preferably 0.1 to 50% by mass, more preferably 0.5% by mass or more, and even more preferably 1% by mass or more, relative to 100% by mass of all structural units. It is also more preferably 45% by mass or less, and even more preferably 40% by mass or less.

<Structural Unit (B)>
The copolymer of the present invention further has an acid group-containing structural unit (B) represented by the above general formula (2).

In the above general formula (2), ^R3 represents a hydrogen atom or a methyl group.
^R4 represents a direct bond or an organic group. Examples of the organic group represented by ^R4 include the same groups as the organic group represented by ^R2 described above.
The organic group represented by ^R4 preferably has 1 to 10 atoms, more preferably 1 to 8 atoms, and even more preferably 2 to 5 atoms.
The organic group represented by ^R4 is preferably a divalent organic group which may have a substituent, and is preferably a divalent organic group containing an ester bond; more preferably -CO-O-R- (wherein R represents a divalent aliphatic hydrocarbon group having 1 to 3 carbon atoms) or -CO-O-R(-O-CO-R')- (wherein R represents a linear or branched divalent aliphatic hydrocarbon group having 1 to 3 carbon atoms. R' represents a monovalent aliphatic hydrocarbon group having 1 to 3 carbon atoms), and even more preferably -CO-O-R- (wherein R represents a divalent aliphatic hydrocarbon group having 1 to 3 carbon atoms).

^R5 represents a bonding chain having a length of 2 or more atoms. The length of the bonding chain refers to the number of atoms connected in the main chain of the bonding chain, and does not include the number of atoms constituting the side chain of the bonding chain. Specific examples of bonding chains having a length of 2 atoms include _{-CH2- CH2-} , -C( _CH3 ) _-CH2- , -C( _CH3 )-C( _CH3 )-, _-CH2- O-, -O- _CH2- , -CO-O-, and -CH=CH-. Examples of bonding chains having a length of 3 atoms include -CH2 _-CH2 - _CH2- , -CH2- _O - _CH2- , -CO-O- _CH2- , _{-CH2 -} O-CO-, and -CH=CH- _CH2- . A bonding chain length of 0 is synonymous with a "direct bond."

The length of the bonding chain represented by ^R5 is preferably 10 or less, more preferably 5 or less, and most preferably 2, in terms of superior crosslinkability.

The linking chain is preferably a divalent organic group. Examples of the divalent organic group include the same groups as the divalent organic group represented by ^R2 above.
Among these, the organic group is preferably -R-, -O-R-, -O-R-O-, -CO-R-, or -O-R-O-CO-R'- (R and R' are the same or different and represent divalent hydrocarbon groups which may have a substituent), more preferably -R-, -O-R-, or -O-R-O-CO-R'- (R and R' are the same or different and represent divalent aliphatic hydrocarbon groups which may have a substituent), and even more preferably an ethylene group.

Y represents an acid group. Examples of the acid group include functional groups that undergo a neutralization reaction with alkaline water, such as a carboxyl group, a phenolic hydroxyl group, a carboxylic anhydride group, a phosphoric acid group, and a sulfonic acid group. Only one of these may be present, or two or more of these may be present. Among these, a carboxyl group or a carboxylic anhydride group is preferred, and a carboxyl group is more preferred.
It may also have two or more acid groups.

"a" represents 0 or 1. It is preferable that "a" is 1, as this provides even better solvent resistance.

Preferably, the structural unit (B) is the structural unit (B-1) represented by the following general formula (2-1):

(In formula (2-1), ^R3 represents a hydrogen atom or a methyl group. ^R7 and ^R8 are the same or different and represent a direct bond or an organic group. b represents 0 or 1.)

In the general formula (2-1), ^R3 represents a hydrogen atom or a methyl group, and is preferably a ^methyl group in that the heat resistance and developability of the polymer are improved.
Preferred examples of the organic group represented by ^R7 and ^R8 include the divalent organic groups described above. Among these, ^R7 is preferably a divalent hydrocarbon group which may have a substituent, more preferably a divalent aliphatic hydrocarbon group which may have a substituent, and even more preferably an alkylene group.
R ⁸ is preferably a divalent hydrocarbon group which may have a substituent, more preferably a divalent aliphatic hydrocarbon group which may have a substituent, and even more preferably an alkylene group.

The organic group represented by R ⁷ and R ⁸ preferably has 1 to 10 carbon atoms, more preferably 1 to 5 carbon atoms, and even more preferably 1 to 3 carbon atoms.

b represents 0 or 1, but is preferably 1, as this can further improve solvent resistance.

A copolymer having the structural unit (B) can be obtained by polymerizing a monomer component containing a monomer capable of introducing the structural unit (B), or by reacting an acid group-containing compound with a base polymer obtained by polymerizing a monomer component containing a hydroxyl group-containing monomer.

Examples of monomers that can introduce the structural unit (B) include long-chain unsaturated monocarboxylic acids in which the unsaturated group and carboxyl group are chain-extended, such as β-carboxyethyl (meth)acrylate, mono(2-acryloyloxyethyl) succinate, and mono(2-methacryloyloxyethyl) succinate.

An example of the hydroxyl group-containing monomer is a compound represented by the following formula (b1):

(In the formula, ^R3 and ^R4 are the same as ^R3 and ^R4 in the general formula (2) above.)

Specific examples of the hydroxyl group-containing monomer include hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, and 2,3-hydroxypropyl (meth)acrylate; polyol mono(meth)acrylates such as glycerin mono(meth)acrylate, trimethylolpropane mono(meth)acrylate, pentaerythritol mono(meth)acrylate, ditrimethylolpropane mono(meth)acrylate, and dipentaerythritol mono(meth)acrylate; and hydroxyalkyl acrylamides such as N-hydroxyethyl acrylamide.

Examples of the acid group-containing compound include compounds represented by the following formula (b2) or formula (b3):

(In the formula, ^R5 and Y are the same as ^R5 and Y in the general formula (2), respectively.)

(In the formula, ^R5 is the same as ^R5 in the general formula (2) above.)

Specific examples of the acid group-containing compound include carboxylic acids such as succinic acid, maleic acid, phthalic acid, tetrahydrophthalic acid, and trimellitic acid; and carboxylic acid anhydrides such as succinic anhydride, maleic anhydride, phthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, methyltetrahydrophthalic anhydride, itaconic anhydride, and trimellitic anhydride. Among these, carboxylic acid anhydrides are preferred due to their higher addition reactivity, and succinic anhydride is even more preferred.

Specific methods for obtaining a copolymer having the above structural unit (B) will be described in detail in the polymer production method described below.

The copolymer of the present invention may have one or more types of structural unit (B).

In the copolymer of the present invention, the content of the structural unit (B) is preferably 0.1 to 50% by mass, more preferably 0.2% by mass or more, and even more preferably 1% by mass or more, relative to 100% by mass of all structural units. It is also more preferably 45% by mass or less, and even more preferably 40% by mass or less.

<Structural Unit (C)>
The copolymer of the present invention is preferably a copolymer further having a ring structure in the main chain. That is, the copolymer preferably further has a structural unit (C) having a ring structure in the main chain. When the copolymer is a polymer having a ring structure in the main chain, a cured product having excellent heat resistance can be obtained.
Examples of the ring structure include an imide ring, a tetrahydropyran ring, a tetrahydrofuran ring, and a lactone ring.
A copolymer having the structural unit (C) can be obtained by polymerizing a monomer component containing a monomer capable of introducing a ring structure into the main chain.

Monomers capable of introducing a ring structure into the main chain include, for example, monomers having a double bond-containing ring structure within the molecule, monomers that undergo cyclopolymerization to form a polymer having a ring structure in the main chain, and monomers that form a ring structure after polymerization. From the standpoint of excellent heat resistance, hardness, colorant dispersibility, etc., specific examples include at least one monomer selected from the group consisting of N-substituted maleimide monomers, dialkyl-2,2'-(oxydimethylene)diacrylate monomers, and α-(unsaturated alkoxyalkyl)acrylate monomers. Among these, N-substituted maleimide monomers are preferred due to their even superior solvent resistance.

Examples of the N-substituted maleimide monomer include N-cyclohexylmaleimide, N-phenylmaleimide, N-methylmaleimide, N-ethylmaleimide, N-isopropylmaleimide, N-t-butylmaleimide, N-dodecylmaleimide, N-benzylmaleimide, and N-naphthylmaleimide, and one or more of these can be used. Among these, from the viewpoint of heat resistance, N-phenylmaleimide, N-benzylmaleimide, and N-cyclohexylmaleimide are preferred, and N-benzylmaleimide is more preferred.

Examples of the N-benzylmaleimide include benzylmaleimide; alkyl-substituted benzylmaleimides such as p-methylbenzylmaleimide and p-butylbenzylmaleimide; phenolic hydroxyl group-substituted benzylmaleimides such as p-hydroxybenzylmaleimide; and halogen-substituted benzylmaleimides such as o-chlorobenzylmaleimide, o-dichlorobenzylmaleimide, and p-dichlorobenzylmaleimide.

Examples of the dialkyl-2,2'-(oxydimethylene) diacrylate monomer include dimethyl-2,2'-[oxybis(methylene)]bis-2-propenoate, diethyl-2,2'-[oxybis(methylene)]bis-2-propenoate, di(n-propyl)-2,2'-[oxybis(methylene)]bis-2-propenoate, di(isopropyl)-2,2'-[oxybis(methylene)]bis-2-propenoate, di(n-butyl)-2,2'-[oxybis(methylene)]bis-2-propenoate, and di(isobutyl)-2,2'-[oxybis(methylene)]bis-2-propenoate. Examples of suitable hydroxybis(methylene)-2,2'-diol include di(t-butyl)-2,2'-[oxybis(methylene)]bis-2-propenoate, di(t-amyl)-2,2'-[oxybis(methylene)]bis-2-propenoate, di(stearyl)-2,2'-[oxybis(methylene)]bis-2-propenoate, di(lauryl)-2,2'-[oxybis(methylene)]bis-2-propenoate, and di(2-ethylhexyl)-2,2'-[oxybis(methylene)]bis-2-propenoate. Of these, dimethyl-2,2'-[oxybis(methylene)]bis-2-propenoate is more preferred from the standpoints of transparency, dispersibility, and ease of industrial availability.

Examples of the α-(unsaturated alkoxyalkyl)acrylate monomer include α-(allyloxymethyl)acrylate monomers.
Specific examples of the α-(allyloxymethyl)acrylate monomer include α-allyloxymethylacrylic acid; methyl α-allyloxymethylacrylate, ethyl α-allyloxymethylacrylate, n-propyl α-allyloxymethylacrylate, i-propyl α-allyloxymethylacrylate, n-butyl α-allyloxymethylacrylate, s-butyl α-allyloxymethylacrylate, t-butyl α-allyloxymethylacrylate, n-amyl α-allyloxymethylacrylate, and α-allyloxymethylacrylate. s-amyl α-allyloxymethyl acrylate, t-amyl α-allyloxymethyl acrylate, n-hexyl α-allyloxymethyl acrylate, s-hexyl α-allyloxymethyl acrylate, n-heptyl α-allyloxymethyl acrylate, n-octyl α-allyloxymethyl acrylate, s-octyl α-allyloxymethyl acrylate, t-octyl α-allyloxymethyl acrylate, 2-ethylhexyl α-allyloxymethyl acrylate, capryl α-allyloxymethyl acrylate, α-allyloxymethyl acrylate Nonyl methylacrylate, decyl α-allyloxymethylacrylate, undecyl α-allyloxymethylacrylate, lauryl α-allyloxymethylacrylate, tridecyl α-allyloxymethylacrylate, myristyl α-allyloxymethylacrylate, pentadecyl α-allyloxymethylacrylate, cetyl α-allyloxymethylacrylate, heptadecyl α-allyloxymethylacrylate, stearyl α-allyloxymethylacrylate, nonadecyl α-allyloxymethylacrylate, α-allyloxymethylacrylate, alkyl-(α-allyloxymethyl)acrylate monomers such as eicosyl α-allyloxymethylacrylate, ceryl α-allyloxymethylacrylate, and melissyl α-allyloxymethylacrylate; methoxyethyl α-allyloxymethylacrylate, methoxyethoxyethyl α-allyloxymethylacrylate, methoxyethoxyethoxyethyl α-allyloxymethylacrylate, 3-methoxybutyl α-allyloxymethylacrylate, ethoxyethyl α-allyloxymethylacrylate, and α-allyloxymethylacrylate; alkoxyalkyl-(α-allyloxymethyl)acrylate monomers such as ethoxyethoxyethyl α-allyloxymethylacrylate, phenoxyethyl α-allyloxymethylacrylate, and phenoxyethoxyethyl α-allyloxymethylacrylate; hydroxyethyl α-allyloxymethylacrylate, hydroxypropyl α-allyloxymethylacrylate, hydroxybutyl α-allyloxymethylacrylate, fluoroethyl α-allyloxymethylacrylate, difluoroethyl α-allyloxymethylacrylate, chloroethyl α-allyloxymethylacrylate, dichloroethyl α-allyloxymethylacrylate, bromoethyl α-allyloxymethylacrylate, dibromoethyl α-allyloxymethylacrylate, vinyl α-allyloxymethylacrylate, allyl α-allyloxymethylacrylate, methallyl α-allyloxymethylacrylate, crotyl α-allyloxymethylacrylate, propargyl α-allyloxymethylacrylate, cyclopentyl α-allyloxymethylacrylate, and α-allyloxymethylacrylate. cyclohexyl acrylate, 4-methylcyclohexyl α-allyloxymethylacrylate, 4-t-butylcyclohexyl α-allyloxymethylacrylate, tricyclodecanyl α-allyloxymethylacrylate, isobornyl α-allyloxymethylacrylate, adamantyl α-allyloxymethylacrylate, dicyclopentadienyl α-allyloxymethylacrylate, phenyl α-allyloxymethylacrylate, methylphenyl α-allyloxymethylacrylate, dimethylphenyl α-allyloxymethylacrylate, trimethylphenyl α-allyloxymethylacrylate, 4-t-butylphenyl α-allyloxymethylacrylate, benzyl α-allyloxymethylacrylate, diphenylmethyl α-allyloxymethylacrylate, diphenylethyl α-allyloxymethylacrylate, triphenylmethyl α-allyloxymethylacrylate, cinnamyl α-allyloxymethylacrylate, naphthyl α-allyloxymethylacrylate, anthranyl α-allyloxymethylacrylate; and the like. Among these, alkyl-(α-allyloxymethyl)acrylate monomers are preferred, and as the alkyl-(α-allyloxymethyl)acrylate monomer, methyl α-allyloxymethylacrylate (also referred to as methyl-(α-allyloxymethyl)acrylate) is particularly preferred from the viewpoints of transparency, dispersibility, ease of industrial availability, etc.

The above-mentioned α-(unsaturated alkoxyalkyl)acrylate can be produced, for example, by the production method disclosed in WO 2010/114077.

Another preferred example of a monomer capable of introducing a ring structure into the main chain is 2-(hydroxyalkyl)acrylic acid alkyl ester. 2-(hydroxyalkyl)acrylic acid alkyl ester can react with (meth)acrylic acid to form a lactone ring structure in the main chain.

The above-mentioned 2-(hydroxyalkyl)acrylic acid alkyl esters include 2-(1-hydroxyalkyl)acrylic acid alkyl esters and 2-(2-hydroxyalkyl)acrylic acid alkyl esters. Specific examples include methyl 2-(1-hydroxymethyl)acrylate, ethyl 2-(1-hydroxymethyl)acrylate, isopropyl 2-(1-hydroxymethyl)acrylate, n-butyl 2-(1-hydroxymethyl)acrylate, t-butyl 2-(1-hydroxymethyl)acrylate, and 2-ethylhexyl 2-(1-hydroxymethyl)acrylate. Of these, methyl 2-(1-hydroxymethyl)acrylate and ethyl 2-(1-hydroxymethyl)acrylate are preferred. These may be used alone or in combination of two or more.

The above copolymer may have one or more types of structural unit (C).

In the above copolymer, the content of the structural unit (C) is preferably 0.1 to 50% by mass, more preferably 0.2% by mass or more, and even more preferably 1% by mass or more, relative to 100% by mass of all structural units, and is more preferably 45% by mass or less, and even more preferably 40% by mass or less.

<Structural Unit (D)>
The copolymer may further have another structural unit (D) in addition to the structural units (A), (B), and (C) described above. Examples of the structural unit (D) include structural units derived from the hydroxyl group-containing monomers described above, as well as acid group-containing monomers other than the long-chain unsaturated monocarboxylic acids described above, (meth)acrylic acid ester monomers, monomers having a group capable of generating an acid group, other copolymerizable monomers, and the like.

Examples of the acid group-containing monomer include unsaturated monocarboxylic acids such as (meth)acrylic acid, crotonic acid, cinnamic acid, and vinylbenzoic acid; unsaturated polycarboxylic acids such as maleic acid, fumaric acid, itaconic acid, citraconic acid, and mesaconic acid; unsaturated acid anhydrides such as maleic anhydride and itaconic anhydride; and phosphate group-containing unsaturated compounds such as Light Ester P-1M (manufactured by Kyoeisha Chemical Co., Ltd.).

Examples of the (meth)acrylic acid ester monomers include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, i-propyl (meth)acrylate, n-butyl (meth)acrylate, s-butyl (meth)acrylate, n-amyl (meth)acrylate, s-amyl (meth)acrylate, n-hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isodecyl (meth)acrylate, tridecyl (meth)acrylate, octyl (meth)acrylate, isooctyl (meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate, cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, 1-adamantyl (meth)acrylate, (3,4-epoxycyclohexyl)methyl (meth)acrylate, and dicyclopentaerythritol (meth)acrylate. Examples include methyl acrylate, dicyclopentenyl (meth)acrylate, benzyl (meth)acrylate, 2-methoxyethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, N,N-dimethylaminoethyl (meth)acrylate, N,N-diethylaminoethyl (meth)acrylate, 1,4-dioxaspiro[4,5]dec-2-yl methacrylic acid, (meth)acryloylmorpholine, 4-(meth)acryloyloxymethyl-2-methyl-2-ethyl-1,3-dioxolane, 4-(meth)acryloyloxymethyl-2-methyl-2-isobutyl-1,3-dioxolane, 4-(meth)acryloyloxymethyl-2-methyl-2-cyclohexyl-1,3-dioxolane, and 4-(meth)acryloyloxymethyl-2,2-dimethyl-1,3-dioxolane.

The monomer having a group that generates an acid group includes a compound having a group that generates an acid group by heat or acid and a polymerizable double bond, such as a (meth)acryloyl group, a vinyl group, an allyl group, or a methallyl group.
Examples of the group that generates an acid group by heat or acid include a tertiary carbon-containing group, a group in which an acid group is blocked with a vinyl ether compound, and a group in which a phenolic hydroxyl group is protected with a protecting group such as a t-butyl group or an acetyl group.

The tertiary carbon-containing group is preferably a group represented by -COO ^* R ^a (R ^a represents a monovalent organic group, and the carbon atom bonded to O ^* is a tertiary carbon atom). By heating, the O-C bond between -COO ^* and R ^a is cleaved, and a carboxyl group is generated.

R ^a in the above -COO ^* R ^a represents a monovalent organic group, and the carbon atom bonded to O ^* is a tertiary carbon atom. The tertiary carbon atom means a carbon atom bonded to three other carbon atoms.

The monovalent organic group is preferably a monovalent linear, branched or cyclic saturated or unsaturated hydrocarbon group having a carbon number of 1 to 91. The organic group may have a substituent.
The number of carbon atoms in R ^a is more preferably 1 to 50, even more preferably 1 to 35, still more preferably 1 to 20, particularly preferably 1 to 12, and most preferably 1 to 9.

R ^a can preferably be represented by -C(R ^b )(R ^c )(R ^d ). In this case, R ^b , R ^c , and R ^d are preferably the same or different and are hydrocarbon groups having 1 to 30 carbon atoms. The hydrocarbon group may be a saturated hydrocarbon group or an unsaturated hydrocarbon group, may have a cyclic structure, or may have a substituent. Furthermore, R ^b , R ^c , and R ^d may be linked to each other at their terminal positions to form a cyclic structure.

In the tertiary carbon-containing group, it is preferable that at least one of the adjacent carbon atoms of the tertiary carbon atom is bonded to a hydrogen atom. For example, when R ^a is a group represented by -C(R ^b )(R ^c )(R ^d ), it is preferable that at least one of R ^b , R ^c , and R ^d contains a carbon atom having one or more hydrogen atoms, and that the carbon atom is bonded to the tertiary carbon atom.
The above R ^b , R ^c and R ^d may be the same or different and are preferably saturated hydrocarbon groups having 1 to 15 carbon atoms, more preferably saturated hydrocarbon groups having 1 to 10 carbon atoms, even more preferably saturated hydrocarbon groups having 1 to 5 carbon atoms, and particularly preferably saturated hydrocarbon groups having 1 to 3 carbon atoms.
The above R ^a is preferably a t-butyl group or a t-amyl group.

Preferred examples of tertiary carbon-containing monomers include t-butyl (meth)acrylate and t-amyl (meth)acrylate.

Examples of the group in which the acid group is blocked with a vinyl ether compound include groups in which a vinyl ether compound is bonded to the above-mentioned acid group such as a carboxyl group.
Examples of the vinyl ether compound include aliphatic vinyl ether compounds such as methyl vinyl ether, ethyl vinyl ether, i-propyl vinyl ether, n-propyl vinyl ether, n-butyl vinyl ether, i-butyl vinyl ether, t-butyl vinyl ether, 2-ethylhexyl vinyl ether, and cyclohexyl vinyl ether; and cyclic ether compounds capable of generating vinyl ethers by ring-opening, such as dihydropyran.
Among the above vinyl ether compounds, dihydropyran is preferred because the protecting group is easily removed at a lower temperature.

Preferably, the group in which the acid group is blocked with dihydropyran is a group represented by the following formula:

Preferably, the group in which a phenolic hydroxyl group is protected by a protecting group such as a t-butyl group or an acetyl group is a group represented by the following formula:

(In the formula, n represents the number of substituents and is an integer of 1 to 5.)

The group represented by the above formula can be reacted, for example, in a solvent in the presence of an acid catalyst such as hydrochloric acid or sulfuric acid at a temperature of 50 to 150°C for 1 to 30 hours, to remove the protecting group and generate an acid group.

Specific examples of monomers having a group represented by the above formula include monomers in which the hydroxyl groups of aromatic vinyl compounds having phenolic hydroxyl groups, such as p-hydroxystyrene, m-hydroxystyrene, o-hydroxystyrene, p-isopropenylphenol, m-isopropenylphenol, and o-isopropenylphenol, are protected with t-butyl or acetyl groups.

Among these, the monomer having a group in which the acid group is blocked with the above-mentioned dihydropyran is preferred as the monomer having the above-mentioned group that generates an acid group, as this allows the acid group to be generated at a lower temperature.

Examples of the other copolymerizable monomer include one or more of the following compounds:
(Meth)acrylamides such as N,N-dimethyl(meth)acrylamide, N-methylol(meth)acrylamide, and N-isopropylacrylamide; macromonomers having a (meth)acryloyl group at one end of the polymer molecular chain, such as polystyrene, polymethyl(meth)acrylate, polyethylene oxide, polypropylene oxide, polysiloxane, polycaprolactone, and polycaprolactam; conjugated dienes such as 1,3-butadiene, isoprene, and chloroprene; vinyl esters such as vinyl acetate, vinyl propionate, vinyl butyrate, and vinyl benzoate; aromatic vinyls such as styrene, vinyl toluene, α-methylstyrene, xylene, methoxystyrene, and ethoxystyrene; methyl vinyl ether, ethyl vinyl ether, and the like. vinyl ethers such as propyl vinyl ether, butyl vinyl ether, 2-ethylhexyl vinyl ether, n-nonyl vinyl ether, lauryl vinyl ether, cyclohexyl vinyl ether, methoxyethyl vinyl ether, ethoxyethyl vinyl ether, methoxyethoxyethyl vinyl ether, methoxypolyethylene glycol vinyl ether, 2-hydroxyethyl vinyl ether, and 4-hydroxybutyl vinyl ether; N-vinyl compounds such as N-vinylpyrrolidone, N-vinylcaprolactam, N-vinylimidazole, N-vinylmorpholine, and N-vinylacetamide; unsaturated isocyanates such as isocyanatoethyl (meth)acrylate and allyl isocyanate; and the like.

In particular, by copolymerizing a monomer having an amide group, such as the above-mentioned (meth)acrylamides, as a monomer that provides the structural unit (D), an addition reaction can be carried out without using a basic catalyst such as an amine, and the storage stability of the copolymer can be improved.
Furthermore, even when a monomer having an amine group, such as N,N-dimethylaminoethyl (meth)acrylate or N,N-diethylaminoethyl (meth)acrylate, is used, the addition reaction can be carried out without using a catalyst, and the storage stability of the copolymer can be improved.

In addition, as the monomer that gives the structural unit (D), it is preferable to use a monomer having a long side chain or a monomer having a large steric hindrance, in that gelation is suppressed and storage stability is improved.
The monomer having a long side chain preferably has the longest side chain having 5 to 20 atoms, more preferably 6 to 20 atoms, and even more preferably 7 to 10 atoms. The side chain may be linear or branched. A specific example of the monomer having a long side chain is 2-ethylhexyl (meth)acrylate.

Preferred examples of the monomer with large steric hindrance include those having a ring structure in the side chain, such as cyclohexyl, bicyclo, phenyl, biphenyl, dicyclopentanyl, furan, pyran, and piperidine. Specific examples of the monomer with large steric hindrance include vinyltoluene, benzyl (meth)acrylate, cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, 1-adamantyl (meth)acrylate, phenoxyethyl (meth)acrylate (meth)acrylate, (meth)acrylic acid, dicyclopentanyl (meth)acrylate, dicyclopentenyl (meth)acrylate, tricyclodecanyl (meth)acrylate, isobornyl (meth)acrylate, and pentamethylpiperidinyl (meth)acrylate. Among these, dicyclopentanyl (meth)acrylate, vinyltoluene, benzyl (meth)acrylate, and cyclohexyl (meth)acrylate are preferred.

In particular, the copolymer preferably contains structural units derived from at least one monomer selected from the group consisting of vinyl toluene, 2-ethylhexyl (meth)acrylate, and dicyclopentanyl (meth)acrylate, as this can further improve storage stability. Furthermore, when the copolymer contains structural units derived from 2-ethylhexyl (meth)acrylate, the glass transition temperature of the copolymer is lowered, thereby improving developability.

The above copolymer may have one or more types of structural unit (D).

In the above copolymer, the content of the structural unit (D) is preferably 0.1 to 50% by mass, more preferably 0.2% by mass or more, and even more preferably 1% by mass or more, relative to 100% by mass of all structural units. Also, it is more preferably 45% by mass or less, and even more preferably 40% by mass or less.

The acid value of the copolymer is preferably 10 mgKOH/g or more, more preferably 20 mgKOH/g or more, and even more preferably 30 mgKOH/g or more, and is preferably 300 mgKOH/g or less, more preferably 250 mgKOH/g or less, even more preferably 200 mgKOH/g or less, and even more preferably 100 mgKOH/g or less.
The acid value is a value obtained by measurement by neutralization titration using a potassium hydroxide (KOH) solution, and is an acid value per 1 g of polymer solid content.

The weight average molecular weight of the copolymer is preferably 2,000 or more, more preferably 3,000 or more, and even more preferably 4,000 or more, and is preferably 250,000 or less, more preferably 100,000 or less, even more preferably 50,000 or less, and even more preferably 20,000 or less.
The weight average molecular weight of the copolymer can be measured by gel permeation chromatography (GPC), specifically by the method described in the examples.

The copolymer may have a polymerizable double bond (carbon-carbon double bond) in the side chain. Having a polymerizable double bond in the side chain can improve the photocurability of the copolymer. Examples of the polymerizable double bond include those listed above, with a (meth)acryloyl group being preferred.

When the copolymer has a polymerizable double bond in the side chain, the double bond equivalent of the copolymer is preferably 200 to 20,000 g/equivalent. In terms of improving curability, the double bond equivalent is more preferably 250 to 15,000 g/equivalent, even more preferably 300 to 10,000 g/equivalent, and even more preferably 300 to 4,000 g/equivalent.

The double bond equivalent is the mass of the solid content of the polymer solution per 1 mol of double bonds in the copolymer. The mass of the solid content of the polymer solution is the sum of the mass of the monomer components constituting the copolymer and the mass of the polymerization inhibitor. The double bond equivalent can be calculated by dividing the mass (g) of the polymer solid content of the polymer solution by the amount of double bonds (mol) in the copolymer. The amount of double bonds in the copolymer can be calculated from the amounts of the acid group-containing monomer and the compound having a polymerizable double bond used in the polymerization. It can also be measured using various analyses such as titration, elemental analysis, NMR, and IR, or differential scanning calorimetry. For example, it can be calculated by measuring the number of ethylenic double bonds contained per gram of copolymer in accordance with the iodine value test method described in JIS K 0070:1992.

<Method of producing copolymer>
The method for producing the copolymer of the present invention is not particularly limited as long as it is a method that can give a copolymer having at least the above-mentioned structural unit (A) and structural unit (B) and having an epoxy equivalent within a predetermined range. Examples of such a method include a method of polymerizing a monomer component containing a monomer that can introduce each of the above-mentioned structural units, and a method of polymerizing a monomer component to give a base polymer, and then subjecting another compound to an addition reaction with a group in the base polymer to give a polymer having a predetermined structural unit.

The method for polymerizing the monomer components is not particularly limited, and commonly used techniques such as bulk polymerization, solution polymerization, and emulsion polymerization can be used. Among these, solution polymerization is preferred because it is industrially advantageous and allows for easy structural adjustment such as molecular weight. Furthermore, the polymerization mechanism of the monomer components can be based on a polymerization method based on a mechanism such as radical polymerization, anionic polymerization, cationic polymerization, and coordination polymerization, but a polymerization method based on a radical polymerization mechanism is preferred because of its industrial advantages.
The molecular weight of the polymer obtained by polymerizing the above-mentioned monomer components can be controlled by appropriately adjusting the amount and type of polymerization initiator, the polymerization temperature, and the type and amount of chain transfer agent.

The polymerization initiator may be a peroxide or azo compound, which is typically used as a polymerization initiator. The chain transfer agent may be a compound having a mercapto group, such as alkyl mercaptans, mercaptocarboxylic acids, or mercaptocarboxylic acid esters, which are typically used as chain transfer agents. These may be used alone or in combination of two or more. The amounts of these added may be appropriately determined using known methods.

Solvents used in the polymerization include, for example, ethers such as tetrahydrofuran, dioxane, ethylene glycol dimethyl ether, and diethylene glycol dimethyl ether; ketones such as acetone and methyl ethyl ketone; esters such as ethyl acetate, butyl acetate, propylene glycol monomethyl ether acetate, and 3-methoxybutyl acetate; aromatic hydrocarbons such as toluene, xylene, and ethylbenzene; chloroform; dimethyl sulfoxide; and dimethyl carbonate. These solvents may be used alone or in combination of two or more.

When polymerizing a monomer composition (reaction liquid) containing the above-mentioned monomer components, the polymerization concentration is preferably 5 to 90% by mass, more preferably 5 to 70% by mass, and even more preferably 10 to 60% by mass. The polymerization concentration is the mass % of the monomer used relative to 100% by mass of the reaction liquid.

Regarding the polymerization conditions, the polymerization temperature can be set appropriately depending on the type and amount of monomer used, the type and amount of polymerization initiator, etc., but is preferably 50 to 130°C, and more preferably 60 to 120°C. Similarly, the polymerization time can also be set appropriately, and is preferably 1 to 5 hours, and more preferably 2 to 4 hours.

A preferred example of a method for producing the copolymer includes a step (1) of polymerizing a monomer component containing an epoxy group-containing monomer represented by the formula (a) above and a hydroxyl group-containing monomer represented by the formula (b1) above, and a step (2) of reacting the polymer obtained in the polymerization step (1) with an acid group-containing compound represented by the formula (b2) or (b3) above.
By producing the copolymer by such a method, gelation can be suppressed during the production of the copolymer, and the copolymer having the structural unit (A) and the structural unit (B) can be efficiently obtained.
That is, the present invention also provides a method for producing a copolymer, comprising: a step (1) of polymerizing a monomer component containing an epoxy group-containing monomer represented by formula (a) and a hydroxyl group-containing monomer represented by formula (b1); and a step (2) of reacting the polymer obtained in the polymerization step (1) with an acid group-containing compound represented by formula (b2) or formula (b3).

Each step in the above manufacturing method will now be described.
Process (1)
In the method for producing the copolymer of the present invention, a monomer component containing an epoxy group-containing monomer represented by the above formula (a) and a hydroxyl group-containing monomer represented by the above formula (b1) is polymerized.
Examples of the epoxy group-containing monomer represented by the formula (a) include the monomers described above as the monomers capable of introducing the structural unit (A) of the copolymer. Examples of the hydroxyl group-containing monomer represented by the formula (b1) include those described above.

The content ratio of the epoxy group-containing monomer and the hydroxyl group-containing monomer is not particularly limited, and may be appropriately set so that the content ratio of the structural unit (A) and the structural unit (B) described above is achieved in the resulting copolymer.

The above-mentioned monomer component may contain other monomer components in addition to the acid group-containing compound used in step (2) described below. Examples of the other monomer components include the monomer components described above.

The method for polymerizing the above-mentioned monomer components is not particularly limited, and the polymerization may be carried out using the known methods described above. The polymerization temperature and time are also as described above.

The above polymerization may also use commonly used polymerization initiators, chain transfer agents, catalysts, solvents, etc.

Process (2)
Next, the method includes a step of reacting the polymer obtained in the step (1) with an acid group-containing compound represented by the formula (b2) or (b3).
By reacting the polymer (base polymer) obtained in the step (1) with the acid group-containing compound represented by the formula (b2) or (b3), the acid group-containing compound is added to the hydroxyl groups of the polymer (base polymer) obtained in the step (1), thereby forming long-chain acid groups.

The reaction method is not particularly limited, and can be carried out by a known method.
The reaction temperature is, for example, preferably 25 to 100°C, more preferably 30 to 90°C.
The reaction time is not particularly limited, but may be, for example, 1 to 20 hours.

Furthermore, the step of reacting the acid group-containing compound may be carried out in the presence of a basic compound. By carrying out the reaction in the presence of a basic compound, the reaction between the hydroxyl group and the acid group can be carried out at a lower temperature of 70°C or less. Furthermore, because the reaction is carried out under such low temperature conditions, the reaction between the epoxy group and the acid group can be suppressed, and only the reaction between the hydroxyl group and the acid group can proceed, allowing for more efficient production of a copolymer having the structural unit (A) and the structural unit (B).

For example, in step (2), the polymer (base polymer) obtained in step (1) may be reacted with the acid group-containing compound in the presence of a basic compound at 70°C or less. In this case, if the temperature exceeds 70°C, the reaction between the epoxy groups and the acid groups may proceed more easily, which may result in gelation of the resin.

Examples of the acid group-containing compound represented by the formula (b2) or (b3) include the acid group-containing compounds described above.
Examples of the basic compound include ammonia; primary amines such as methylamine; secondary amines such as dimethylamine; tertiary amines such as triethylamine and diethylmethylamine; aliphatic amines such as dimethylethanolamine, n-butylamine and diethylamine; cyclic aliphatic amines such as cyclohexylamine; heterocyclic amines such as piperidine, morpholine, N-ethylpiperidine, N-ethylmorpholine and pyridine; aromatic amines such as benzylamine, N-methylaniline and N,N-dimethylaniline; tetraalkylammonium halides such as tetramethylammonium chloride and tetraethylammonium chloride; organic acid salts of tetraalkylammonium such as tetramethylammonium acetate; inorganic acid salts of tetraalkylammonium such as tetramethylammonium hydrogen sulfate and tetraethylammonium hydrogen sulfate; (hydroxy)alkylammonium hydroxides such as tetramethylammonium hydroxide, tetraethylammonium hydroxide and monohydroxyethyltrimethylammonium hydroxide; hydroxides of alkali metals such as sodium and potassium; hydroxides of transition metals such as barium, strontium, calcium and lanthanum; [Pt(NH ₃ ) ₆ ](OH) and phosphorus compounds such as _{triphenylphosphine} , tricyclohexylphosphine, trimethylphosphine, etc. Among these, secondary amines, tertiary amines, heterocyclic amines, and phosphorus compounds are preferred in terms of ease of evaporation and ease of handling, and tertiary amines and triphenylphosphine are more preferred in terms of being able to suppress side reactions and to suppress an increase in the molecular weight of the polymer after addition.

The amount of the basic compound used is not particularly limited, but from the viewpoint of reaction efficiency, it is preferably 0 to 5 mol%, more preferably 0 to 4 mol%, and even more preferably 0 to 3 mol%, relative to 100 mol% of the amount of the acid group-containing compound used.

The amount of the acid group-containing compound used can be appropriately set depending on the purpose and application of the copolymer to be obtained so that the content of the structural unit (B) falls within the desired range, or so that the acid value of the copolymer falls within the desired range.

The total monomer component concentration in the total amount of polymerization solution during the addition reaction of the acid group-containing compound is preferably 40% by mass or more, and more preferably 50% by mass or more. When the total monomer component concentration is within this range, the acid group-containing compound can be added to the base polymer without using the basic compound as a catalyst, thereby improving the storage stability of the resulting copolymer. In this way, when the monomer concentration relative to the total amount of copolymer polymerization solution is high, the acid group-containing compound can be added without a catalyst, improving the storage stability of the copolymer.

In the above reaction, commonly used catalysts, solvents, etc. may be used.

Furthermore, to produce a copolymer having a polymerizable double bond in the side chain, after the above step (1), an acid group-containing monomer or an isocyanate group-containing polymerizable monomer can be subjected to an addition reaction with the hydroxyl group, or after the above step (1) or (2), an acid group-containing monomer can be subjected to an addition reaction with the epoxy group, thereby introducing a polymerizable double bond into the side chain of the copolymer.
Examples of the acid group-containing monomer include those mentioned above, and (meth)acrylic acid is preferred.
Examples of the isocyanate group-containing polymerizable monomer include the unsaturated isocyanates described above, and isocyanatoethyl (meth)acrylate is preferred because it can undergo an addition reaction at low temperatures and can provide a copolymer with good storage stability.
The addition reaction is not particularly limited and can be carried out by a known method.
In the above addition reaction, compounds, catalysts, solvents, etc. that are usually used may be used.

Among these, the above-mentioned basic compounds are preferred as catalysts, with secondary amines, tertiary amines, heterocyclic amines, and phosphorus compounds being preferred, and tertiary amines and triphenylphosphine being more preferred. Additionally, tin-based compounds such as dibutyltin dichloride, dibutyltin oxide, dibutyltin dibromide, dibutyltin dimaleate, dibutyltin dilaurate, dioctyltin dilaurate, dibutyltin diacetate, dibutyltin sulfide, tributyltin acetate, dioctyltin oxide, and tributyltin chloride, which are commonly used as reaction catalysts for isocyanate monomers and hydroxyl groups, can also be suitably used.

The method for producing the copolymer may include other steps in addition to the reaction step described above. Examples include an aging step, a neutralization step, a step for deactivating the polymerization initiator or chain transfer agent, a dilution step, a drying step, a concentration step, and a purification step. These steps can be carried out by known methods.

2. Copolymer Solution The present invention also provides a copolymer solution comprising the above-described copolymer and a protic polar solvent. The copolymer solution of the present invention has excellent storage stability.
As described above, the copolymer has an acid group and an epoxy group, and since these groups are highly reactive, the copolymer can be easily cured at low temperatures, but it is difficult to ensure storage stability. The present inventors have found that the storage stability of the copolymer can be improved by adding a protic polar solvent, and that both high solvent resistance and storage stability can be achieved.
The reason why the storage stability of the copolymer is improved by adding a protic polar solvent is not clear, but it is presumed that this is because, in the copolymer, acid groups such as carboxyl groups are present at positions away from the main chain, and the protic polar solvent relatively easily forms hydrogen bonds with the acid groups, reducing the anionic nature of the acid groups and suppressing the reactivity of the acid groups with epoxy groups.

<Protic polar solvent>
Examples of the protic polar solvent include water, alcohol-based solvents, amine-based solvents, and phenol-based solvents. Of these, the protic polar solvent is preferably an alcohol-based solvent.

The alcohol solvent is preferably a saturated alcohol, and examples thereof include monofunctional alcohols (monoalcohols), polyhydric alcohols, and glycol monoethers.
Specific examples of the alcohol solvent include primary alcohols such as methanol, ethanol, 1-propanol, 1-butanol, 1-pentanol, 1-hexanol, ethylene glycol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol mono-n-propyl ether, ethylene glycol mono-n-butyl ether, ethylene glycol monophenyl ether, diethylene glycol, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol mono-n-propyl ether, diethylene glycol mono-n-butyl ether, triethylene glycol, triethylene glycol monomethyl ether, triethylene glycol mono-n-butyl ether, tripropylene glycol, and tripropylene glycol mono-n-butyl ether;
secondary alcohols such as isopropanol, 2-butanol, 2-pentanol, 3-pentanol, 2-hexanol, cyclohexanol, 2-heptanol, 3-heptanol, propylene glycol, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol mono-n-propyl ether, propylene glycol mono-n-butyl ether, propylene glycol monophenyl ether, dipropylene glycol, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol mono-n-propyl ether, dipropylene glycol mono-n-butyl ether, or tripropylene glycol monomethyl ether;
Examples include tertiary alcohols such as tert-butanol, tert-pentanol, and tert-hexanol.
Among these, the alcohol solvent is preferably a secondary alcohol or a tertiary alcohol, since it can suppress reactivity with epoxy groups and reduce the viscosity of the copolymer solution.

The carbon number of the alcohol solvent is preferably 1 to 10, more preferably 2 to 8, and even more preferably 3 to 6, as these have a relatively low boiling point and are easily removed by heating.

Propylene glycol monomethyl ether is particularly preferred as the alcohol solvent.

Examples of the amine solvent include diethyleneamine, dimethylamine, and oleylamine.

Examples of the phenol-based solvent include phenol, cresol, o-cresol, m-cresol, p-cresol, and xylenol.

The above protic polar solvents may be used alone or in combination of two or more.

The boiling point of the above-mentioned protic polar solvent is preferably 70 to 170°C, more preferably 100 to 160°C, and even more preferably 120 to 150°C, as these solvents are easily removed by heating, have a certain boiling point, and are likely to form a flat film.

The content of the protic polar solvent in the copolymer solution is preferably 10% by mass or more, more preferably 30% by mass or more, and even more preferably 40% by mass or more, relative to 100% by mass of the copolymer solids. Furthermore, in order to facilitate concentration adjustment in the curable resin composition, the content of the protic polar solvent is preferably 1000% by mass or less, more preferably 300% by mass or less, and even more preferably 200% by mass or less, relative to 100% by mass of the copolymer solids.

From the viewpoint of stability, the copolymer solution preferably contains, in addition to the protic polar solvent, another solvent capable of forming hydrogen bonds, such as N,N-dimethylformamide.
In addition, the solvent for adjusting the concentration may include, for example, ethers such as tetrahydrofuran, dioxane, ethylene glycol dimethyl ether, and diethylene glycol dimethyl ether; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; esters such as ethyl acetate, butyl acetate, propylene glycol monomethyl ether acetate, and 3-methoxybutyl acetate; aromatic hydrocarbons such as toluene, xylene, and ethylbenzene; chloroform; and dimethyl sulfoxide.

When the copolymer solution contains a solvent other than the protic polar solvent, the content of the protic polar solvent is preferably 5 parts by mass or more, more preferably 10% by mass or more, and even more preferably 20% by mass or more, relative to 100% by mass of the total amount of the protic polar solvent and the other solvent; and is preferably 99% by mass or less, more preferably 90% by mass or less, and even more preferably 80% by mass or less.

The copolymer solution may be prepared by mixing the copolymer purified from the copolymer-containing polymerization solution obtained during polymerization with the protic polar solvent, or by adding the protic polar solvent to the copolymer-containing polymerization solution. When the copolymer solution is prepared by adding the protic polar solvent to the copolymer-containing polymerization solution, the copolymer solution may contain the polymerization solvent.

The copolymer solution may further contain other components. Examples of other components include components that improve the storage stability of the copolymer and components that improve the curing properties. Examples of components that improve the storage stability of the copolymer include acid compounds and phosphoric acid derivatives. Examples of components that improve the curing properties of the copolymer include basic compounds. These components may be used appropriately depending on the purpose, and may also be used in combination.

<Acid compound>
The copolymer solution may further contain an acid compound having a pKa of 4.2 or less.
By including an acid compound having a pKa of 4.2 or less in the copolymer solution, the reaction between the acid groups and the epoxy groups in the copolymer is suppressed, thereby further improving the storage stability of the copolymer. The reason why the storage stability of the copolymer can be improved by including an acid compound having a pKa of 4.2 or less is thought to be that the presence of an acid compound with a stronger acid strength than the acid groups capable of forming the acid group-containing structural unit (B) in the copolymer reduces the anionicity of the acid groups in the copolymer, thereby suppressing the reactivity of the acid groups with the epoxy groups. Furthermore, when a basic compound is present in the copolymer solution, the acid compound having a pKa of 4.2 or less captures the basic compound that formed a salt with the carboxyl groups, thereby reducing the nucleophilic force of the carboxyl groups in the copolymer and suppressing the reactivity of the acid groups with the epoxy groups.

The reason for setting the pKa to 4.2 or less is that the pKa values of the monomers into which the structural unit (B) can be introduced and the acid group-containing monomers are set as the threshold values. Examples of the pKa values of the monomers include acrylic acid (pKa 4.35), methacrylic acid (pKa 4.26), mono(2-acroyloxyethyl) succinate (pKa 4.35), and mono(2-methacryloyloxyethyl) succinate (pKa 4.35).
The pKa of the acid compound is preferably 3 or less, and more preferably 2 or less. There is no particular limitation on the lower limit of the pKa of the acid compound, but it is preferably −3 or more, and more preferably 0 or more.

pKa (acid dissociation constant) means the negative common logarithm (reciprocal logarithm) of the equilibrium constant Ka in the dissociation reaction in which hydrogen ions are released from an acid, and particularly means the value in water at 25°C.
For the pKa value, reference can be made to literature such as Chemistry Handbook, Basics II (revised 5th edition, Maruzen Co., Ltd.), and values not published in the literature can be calculated by the method described in the literature.

Specific examples of acid compounds having a pKa of 4.2 or less include hydrochloric acid, hydrobromic acid, hydroiodic acid, phosphoric acid, phosphorous acid, hypophosphorous acid, phosphonic acid, phosphinic acid, pyrophosphoric acid, polyphosphoric acid, sulfuric acid, sulfurous acid, thiosulfuric acid, dimethyl sulfite, diethyl sulfite, dipropyl sulfite, dibutyl sulfite, diphenyl sulfite, dimethyl sulfate, diethyl sulfate, dipropyl sulfate, dibutyl sulfate, diphenyl sulfate, aromatic sulfonic acids such as benzenesulfinic acid, toluenesulfinic acid, naphthalenesulfinic acid, benzenesulfonic acid, toluenesulfonic acid, trifluoromethanesulfonic acid, dodecylbenzenesulfonic acid, naphthalenesulfonic acid, diisopropylnaphthalenesulfonic acid, and diisobutylnaphthalenesulfonic acid; alkyl sulfonic acids such as methylsulfonic acid, ethylsulfonic acid, and propylsulfonic acid; α-olefin sulfonic acids; sulfonated polystyrenes; methyl acrylate-sulfonated styrene copolymers; and derivatives thereof.

The molecular weight of the acid compound is preferably 400 or less, and more preferably 350 or less. The molecular weight of the acid compound is preferably 150 or more, and more preferably 250 or more.

<Phosphate derivatives>
The copolymer solution may further contain a phosphoric acid derivative, which can improve the storage stability of the copolymer.

Preferred examples of the phosphoric acid derivative include phosphate ester, phosphite ester, phosphorous acid, hypophosphorous acid, phosphonic acid, and phosphinic acid, and more preferred examples include phosphate ester, phosphonic acid, and phosphinic acid.
Examples of the ester group of the phosphate ester or phosphite ester include alkyl ester groups, aryl ester groups, aralkyl ester groups, and ester groups having a polymerizable double bond. Examples of the alkyl of the alkyl ester group include methyl, ethyl, octyl, and 2-ethylhexyl. Examples of the aryl of the aryl ester group include phenyl, tolyl, and naphthyl. Examples of the aralkyl of the aralkyl ester group include benzyl. Examples of the ester group having a polymerizable double bond include a 2-acryloyloxyethyl ester group and a 2-methacryloyloxyethyl ester group.

Specific examples of the phosphoric acid ester include monoalkyl phosphates such as methyl phosphate; dialkyl phosphates such as dibutyl phosphate; trialkyl phosphates such as trimethyl phosphate, triethyl phosphate, tributyl phosphate, trioctyl phosphate, tridecyl phosphate, trioctadecyl phosphate, distearyl pentaerythrityl diphosphate, tris(2-chloroethyl)phosphate, and tris(2,3-dichloropropyl)phosphate; tricycloalkyl phosphates such as tricyclohexyl phosphate; and monoaryl phosphates. diaryl phosphates; triaryl phosphates such as triphenyl phosphate, tricresyl phosphate, tris(nonylphenyl)phosphate, and 2-ethylphenyldiphenyl phosphate; and phosphate esters containing an ester group having a polymerizable double bond, such as 2-methacryloyloxyethyl acid phosphate, 2-acryloyloxyethyl acid phosphate, 3-methacryloyloxypropyl acid phosphate, methacryloyloxypolyoxyethylene glycol acid phosphate, and methacryloyloxypolyoxypropylene glycol acid phosphate.
Specific examples of the phosphonic acid include alkylphosphonic acids such as methylphosphonic acid, and arylphosphonic acids such as phenylphosphonic acid.
Specific examples of the phosphinic acid include alkylphosphinic acids such as methylphosphinic acid, and arylphosphinic acids such as phenylphosphinic acid.

Among these, the phosphate ester is preferably a phosphate ester containing an ester group having a polymerizable double bond. When the phosphate ester containing an ester group having a polymerizable double bond is used, a crosslinked structure is formed together with the copolymer and the polymerizable compound during curing of the curable resin composition containing the copolymer solution, and volatilization and elution of the components contained therein are suppressed, thereby significantly suppressing problems such as contamination of the reaction system and deterioration of electrical insulation.
The above phosphate ester preferably contains two or three or more polymerizable double bonds.

In the present invention, commercially available products can be used as the phosphate ester containing an ester group with a polymerizable double bond. For example, Light Ester P-1M, Light Ester P-2M (both manufactured by Kyoeisha Chemical Co., Ltd.), and Phosmer M (manufactured by Unichemical Co., Ltd.) can be used. Of these, Light Ester P-2M is preferred.

The molecular weight of the phosphoric acid derivative is preferably 400 or less, and more preferably 350 or less. When the molecular weight of the phosphoric acid derivative is 400 or less, the resin solids content can be reduced when added, further improving storage stability. In addition, the effects of improving the anionicity of the acid group and reducing the nucleophilic force are greater. The molecular weight of the phosphoric acid derivative is preferably 150 or more, and more preferably 250 or more. When the molecular weight of the phosphoric acid derivative is 150 or more, compatibility with the resin composition can be further improved.

The phosphoric acid derivative may be the acid compound having a pKa of 4.2 or less. In other words, from the viewpoints of storage stability and compatibility, the copolymer solution of the present invention preferably contains an acid compound or phosphoric acid derivative having a pKa of 4.2 or less, and more preferably contains a phosphoric acid derivative having a pKa of 4.2 or less.

The contents of the acid compound and phosphoric acid derivative are not particularly limited and can be set appropriately depending on the application, the blending of other components, etc., but are typically 0.01 to 5 mass% relative to 100 mass% of the total solids content of the copolymer solution, more preferably 0.01 to 3 mass%, and even more preferably 0.02 to 2 mass%. Note that when the acid compound and phosphoric acid derivative are used in combination, the above contents refer to the combined amounts of the acid compound and phosphoric acid derivative. Furthermore, in this specification, "total solids content" refers to the total amount of components that form the cured product (excluding solvents and the like that volatilize during the formation of the cured product).

The content of the acid compound and phosphoric acid derivative is preferably 0.01 to 10 parts by mass, more preferably 0.05 to 5 parts by mass, and even more preferably 0.1 to 3 parts by mass, per 100 parts by mass of copolymer in the copolymer solution. Note that when the acid compound and phosphoric acid derivative are used in combination, the above content refers to the total amount of the acid compound and phosphoric acid derivative.

When the copolymer solution further contains a basic compound (described below), the content of the acid compound and phosphoric acid derivative is preferably 50 to 200 mol %, more preferably 70 to 150 mol %, and even more preferably 80 to 120 mol %, relative to 100 mol % of the basic compound. By setting the content of the acid compound and phosphoric acid derivative to a range of 0.5 to 2.0 molar equivalents relative to the basic compound, the storage stability of the copolymer can be further improved and discoloration of the cured product can be further suppressed. Note that when the acid compound and phosphoric acid derivative are used in combination, the above content is the combined amount of the acid compound and phosphoric acid derivative.

<Basic Compounds>
The copolymer solution may further contain a basic compound, which allows the crosslinking reaction to proceed smoothly even at low temperatures of 160°C or less during curing of the copolymer, thereby providing a cured product with even better solvent resistance.

Examples of the basic compound include the basic compounds described above. Among these, amine compounds are preferred. Furthermore, secondary amines, tertiary amines, heterocyclic amines, and phosphorus compounds are more preferred as the basic compound in terms of ease of evaporation and ease of handling, and tertiary amines and triphenylphosphine are more preferred in terms of their ability to suppress side reactions and the increase in molecular weight of the polymer after addition.

The content of the basic compound is not particularly limited and may be set appropriately depending on the application and the blending of other components, but is preferably 0.01 to 10% by mass, more preferably 0.01 to 6% by mass, and even more preferably 0.02 to 4% by mass, relative to 100% by mass of the total solids content of the copolymer solution.

Furthermore, the content of the basic compound is preferably 0.01 to 20 parts by mass, more preferably 0.1 to 10 parts by mass, and even more preferably 0.1 to 6 parts by mass, per 100 parts by mass of the copolymer.

If the basic compound used as a catalyst during the synthesis of the copolymer (during the addition reaction) remains in the copolymer solution after copolymer synthesis, the content in the copolymer solution can be adjusted by adding basic compound according to the remaining amount.

<Method of producing copolymer solution>
A preferred example of a method for producing the copolymer solution includes a step of polymerizing a monomer component containing an epoxy group-containing monomer represented by the above formula (a) and a hydroxyl group-containing monomer represented by the above formula (b1) (polymerization step), a step of reacting the polymer obtained in the polymerization step with an acid group-containing compound represented by the above formula (b2) or (b3) in the presence of a basic compound (reaction step), and a step of adding an acid compound having a pKa of 4.2 or less and a protic polar solvent (addition step).
That is, the present invention also includes a method for producing a copolymer solution, which comprises the steps of: polymerizing a monomer component containing an epoxy group-containing monomer represented by formula (a) and a hydroxyl group-containing monomer represented by formula (b1); reacting the polymer obtained in the polymerization step with an acid group-containing compound represented by formula (b2) or formula (b3) in the presence of a basic compound; and adding an acid compound having a pKa of 4.2 or less and a protic polar solvent.

The polymerization step may be the same as step (1) in the above-mentioned method for producing the copolymer.

The reaction step can be the same as step (2) in the above-mentioned copolymer production method, in which the step is carried out in the presence of a basic compound. Specific examples of the acid group-containing compound represented by formula (b2) or formula (b3) and the basic compound include the same acid group-containing compounds and basic compounds as those described above.

The acid compound with a pKa of 4.2 or less and the protic polar solvent used in the above addition step are as described above.

3. Curable Resin Composition The copolymer of the present invention and the copolymer solution can be combined with other components to form a curable resin composition. Since the curable resin composition contains the copolymer of the present invention, it can provide a cured product with excellent solvent resistance even under low-temperature curing conditions. Furthermore, when the curable resin composition contains the copolymer solution, it also has excellent storage stability. Such a curable resin composition containing the copolymer or copolymer solution is also a preferred embodiment of the present invention.

In the curable resin composition, the content of the copolymer is not particularly limited and may be set appropriately depending on the application, the blending of other components, and the like. For example, the content is preferably 5% by mass or more, more preferably 10% by mass or more, and even more preferably 15% by mass or more, relative to 100% by mass of the total solid content of the curable resin composition, and is preferably 80% by mass or less, more preferably 75% by mass or less, and even more preferably 70% by mass or less.
In this specification, the term "total amount of solids" refers to the total amount of components that form the cured product (excluding solvents and the like that volatilize during the formation of the cured product).

The curable resin composition preferably contains the above-mentioned protic polar solvent, in that the stability of the composition is improved.
In order to ensure the stability of the curable resin composition, the content of the protic polar solvent in the curable resin composition is preferably 10% by mass or more, more preferably 30% by mass or more, and even more preferably 40% by mass or more, relative to 100% by mass of the solid content of the copolymer, and is preferably 3000% by mass or less, and more preferably 1000% by mass or less.

In order to ensure the stability of the curable resin composition, the content of the protic polar solvent in the curable resin composition is preferably 1% by mass or more, more preferably 5% by mass or more, and even more preferably 10% by mass or more, relative to 100% by mass of the solids content of the curable resin composition, and is preferably 400% by mass or less, more preferably 300% by mass or less, and even more preferably 200% by mass or less.

The curable resin composition may further contain various components such as a polymerizable compound, a polymerization initiator, etc. Examples of the various components such as the polymerizable compound and the polymerization initiator include the same components as those of the photosensitive resin composition described below.
As an example of a preferred embodiment of the curable resin composition, a photosensitive resin composition will be described.

3-1. Photosensitive Resin Composition The copolymer or copolymer solution of the present invention can be further combined with a polymerizable compound and a photopolymerization initiator to form a photosensitive resin composition.
Since the photosensitive resin composition contains the copolymer described above, it can provide a cured product with excellent solvent resistance even under low-temperature curing conditions of 160°C or less, for example, about 90°C. Furthermore, since it further contains a polymerizable compound, it can provide a cured product with excellent physical properties such as curability, adhesion to substrates, surface hardness, and heat resistance. Such a photosensitive resin composition containing the copolymer or copolymer solution described above, a polymerizable compound, and a photopolymerization initiator also constitutes one aspect of the present invention.

In the photosensitive resin composition of the present invention, the content of the copolymer is not particularly limited and may be set appropriately depending on the intended use, the blending of other components, etc. However, for example, it is preferably 5% by mass or more, more preferably 10% by mass or more, and even more preferably 15% by mass or more, relative to 100% by mass of the total solid content of the photosensitive resin composition, and is preferably 80% by mass or less, more preferably 75% by mass or less, and even more preferably 70% by mass or less.

<Polymerizable compound>
The polymerizable compound is a low molecular weight compound having a polymerizable unsaturated bond (also referred to as a polymerizable unsaturated group) that can be polymerized by irradiation with active energy rays such as free radicals, electromagnetic waves (e.g., infrared rays, ultraviolet rays, X-rays, etc.), and electron beams. Examples of the polymerizable compound include monofunctional compounds having one polymerizable unsaturated group in the molecule and polyfunctional compounds having two or more polymerizable unsaturated groups.

Examples of the monofunctional compounds include N-substituted maleimide monomers; (meth)acrylic acid esters; (meth)acrylamides; unsaturated monocarboxylic acids; unsaturated polycarboxylic acids; unsaturated monocarboxylic acids in which the unsaturated group and carboxyl group are chain-extended; unsaturated acid anhydrides; aromatic vinyls; conjugated dienes; vinyl esters; vinyl ethers; N-vinyl compounds; unsaturated isocyanates; and the like. These include, for example, the same compounds as those listed as monomer components of the copolymer above. Monomers having an active methylene group or an active methine group can also be used.

Examples of the polyfunctional compound include the following compounds.
bifunctional (meth)acrylate compounds such as ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, butylene glycol di(meth)acrylate, hexanediol di(meth)acrylate, cyclohexanedimethanol di(meth)acrylate, bisphenol A alkylene oxide di(meth)acrylate, and bisphenol F alkylene oxide di(meth)acrylate;

Trimethylolpropane tri(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, glycerin tri(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, tripentaerythritol hepta(meth)acrylate, tripentaerythritol octa(meth)acrylate, ethylene oxide-added trimethylolpropane tri(meth)acrylate, ethylene oxide-added ditrimethylolpropane tetra(meth)acrylate, ethylene oxide-added pentaerythritol tetra(meth)acrylate, ethylene oxide-added dipentaerythritol hexa(meth)acrylate, propylene oxide-added trimethylolpropane Tri(meth)acrylate, propylene oxide-added ditrimethylolpropane tetra(meth)acrylate, propylene oxide-added pentaerythritol tetra(meth)acrylate, propylene oxide-added dipentaerythritol hexa(meth)acrylate, ε-caprolactone-added trimethylolpropane tri(meth)acrylate, ε-caprolactone-added ditrimethylolpropane tetra(meth)acrylate, ε-caprolactone-added pentaerythritol tetra(meth)acrylate, ε-caprolactone-added dipentaerythritol hexa(meth)acrylate, dipentaerythritol pentaacrylate succinic acid-modified product, pentaerythritol triacrylate succinic acid-modified product, dipentaerythritol pentaacrylate phthalic acid-modified product, pentaerythritol triacrylate phthalic acid-modified product, the following formula:

A trifunctional or higher polyfunctional (meth)acrylate compound, such as a modified product of dipentaerythritol hexaacrylate represented by the formula:

Multifunctional vinyl ethers such as ethylene glycol divinyl ether, diethylene glycol divinyl ether, polyethylene glycol divinyl ether, propylene glycol divinyl ether, butylene glycol divinyl ether, hexanediol divinyl ether, bisphenol A alkylene oxide divinyl ether, bisphenol F alkylene oxide divinyl ether, trimethylolpropane trivinyl ether, ditrimethylolpropane tetravinyl ether, glycerin trivinyl ether, pentaerythritol tetravinyl ether, dipentaerythritol pentavinyl ether, dipentaerythritol hexavinyl ether, ethylene oxide-added trimethylolpropane trivinyl ether, ethylene oxide-added ditrimethylolpropane tetravinyl ether, ethylene oxide-added pentaerythritol tetravinyl ether, and ethylene oxide-added dipentaerythritol hexavinyl ether;

(meth)acrylic acid esters containing a vinyl ether group, such as 2-vinyloxyethyl (meth)acrylate, 3-vinyloxypropyl (meth)acrylate, 1-methyl-2-vinyloxyethyl (meth)acrylate, 2-vinyloxypropyl (meth)acrylate, 4-vinyloxybutyl (meth)acrylate, 4-vinyloxycyclohexyl (meth)acrylate, 5-vinyloxypentyl (meth)acrylate, 6-vinyloxyhexyl (meth)acrylate, 4-vinyloxymethylcyclohexylmethyl (meth)acrylate, p-vinyloxymethylphenylmethyl (meth)acrylate, 2-(vinyloxyethoxy)ethyl (meth)acrylate, and 2-(vinyloxyethoxyethoxyethoxy)ethyl (meth)acrylate;

Polyfunctional allyl ethers such as ethylene glycol diallyl ether, diethylene glycol diallyl ether, polyethylene glycol diallyl ether, propylene glycol diallyl ether, butylene glycol diallyl ether, hexanediol diallyl ether, bisphenol A alkylene oxide diallyl ether, bisphenol F alkylene oxide diallyl ether, trimethylolpropane triallyl ether, ditrimethylolpropane tetraallyl ether, glycerin triallyl ether, pentaerythritol tetraallyl ether, dipentaerythritol pentaallyl ether, dipentaerythritol hexaallyl ether, ethylene oxide-added trimethylolpropane triallyl ether, ethylene oxide-added ditrimethylolpropane tetraallyl ether, ethylene oxide-added pentaerythritol tetraallyl ether, and ethylene oxide-added dipentaerythritol hexaallyl ether;

Allyl group-containing (meth)acrylic acid esters such as allyl (meth)acrylate; polyfunctional (meth)acryloyl group-containing isocyanurates such as tri(acryloyloxyethyl)isocyanurate, tri(methacryloyloxyethyl)isocyanurate, alkylene oxide-added tri(acryloyloxyethyl)isocyanurate, and alkylene oxide-added tri(methacryloyloxyethyl)isocyanurate; polyfunctional allyl group-containing isocyanurates such as triallyl isocyanurate; polyfunctional urethane (meth)acrylates obtained by reacting polyfunctional isocyanates such as tolylene diisocyanate, isophorone diisocyanate, and xylylene diisocyanate with hydroxyl group-containing (meth)acrylic acid esters such as 2-hydroxyethyl (meth)acrylate and 2-hydroxypropyl (meth)acrylate; polyfunctional aromatic vinyls such as divinylbenzene; etc. These polymerizable compounds may be used alone or in combination of two or more.
However, although a polymer having a vinyl ether group on the side chain improves the curability of the resin composition, it may reduce the storage stability. Therefore, from the viewpoint of storage stability, it is preferable that the photosensitive resin composition does not contain a polymer having a vinyl ether group on the side chain.

Among the above polymerizable compounds, it is preferable to use a polyfunctional polymerizable compound from the viewpoint of further enhancing the curability of the photosensitive resin composition. The number of functionalities of the above polyfunctional polymerizable compound is preferably 3 or more, more preferably 4 or more. Moreover, the number of functionalities is preferably 10 or less, more preferably 8 or less.
The molecular weight of the polymerizable compound is not particularly limited, but is preferably 2,000 or less from the viewpoint of handling.

From the viewpoints of reactivity, economy, availability, etc., preferred examples of the polyfunctional polymerizable compound include compounds having a (meth)acryloyl group, such as polyfunctional (meth)acrylate compounds, polyfunctional urethane (meth)acrylate compounds, and (meth)acryloyl group-containing isocyanurate compounds, and more preferred examples include polyfunctional (meth)acrylate compounds. By including a compound having a (meth)acryloyl group, the photosensitive resin composition has superior photosensitivity and curability, and a cured product with even greater hardness and transparency can be obtained. It is even more preferred to use a tri- or higher functional polyfunctional (meth)acrylate compound as the polyfunctional polymerizable compound.

The above polymerizable compounds may be used alone or in combination of two or more.

In the photosensitive resin composition of the present invention, the content of the polymerizable compound is not particularly limited and may be set appropriately as long as the effects of the present invention are achieved. However, in order to achieve an appropriate viscosity for the photosensitive resin composition, the content is preferably 5 to 60% by mass, and more preferably 10 to 50% by mass, relative to 100% by mass of the total solids content of the photosensitive resin composition.

<Photopolymerization initiator>
The photopolymerization initiator is preferably a radically polymerizable photopolymerization initiator, which generates polymerization-initiating radicals when irradiated with active energy rays such as electromagnetic waves or electron beams.

Specific examples of the photopolymerization initiator include aminoketone compounds such as 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one ("IRGACURE907", manufactured by BASF), 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone-1-one ("IRGACURE369", manufactured by BASF), and 2-dimethylamino-2-(4-methyl-benzyl)-1-(4-morpholin-4-yl-phenyl)-butan-1-one ("IRGACURE379", manufactured by BASF); 2,2-dimethoxy-1,2-diphenylethan-1-one ("IRGACURE651", manufactured by BASF), and phenylglyoxylic acid methyl ester ("DAROCURE benzyl ketal compounds such as 1-hydroxy-cyclohexyl-phenyl-ketone ("IRGACURE184", manufactured by BASF), 2-hydroxy-2-methyl-1-phenyl-propan-1-one ("DAROCUR1173", manufactured by BASF), 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propan-1-one ("IRGACURE2959", manufactured by BASF), 2-hydroxy-1- Hydroketone compounds such as {4-[4-(2-hydroxy-2-methyl-propionyl)-benzyl]-phenyl}-2-methyl-propan-1-one ("IRGACURE 127", manufactured by BASF) and [1-hydroxy-cyclohexyl-phenyl-ketone + benzophenone] ("IRGACURE 500", manufactured by BASF); other alkylphenone compounds exemplified in paragraphs [0084] to [0086] of JP 2013-227485 A; 1,2-octyl benzophenone; Tanedione, 1-[4-(phenylthio)phenyl]-, 2-(O-benzoyloxime) ("OXE01", manufactured by BASF), ethanone, 1-[9-ethyl-6-(2-methylbenzoyl)-9H-carbazol-3-yl]-, 1-(O-acetyloxime) ("OXE02", manufactured by BASF), 1,2-octanedione, 1-[4-(phenylthio)-, 2-, (O-benzoyloxime)], ethanone ("OXE03", manufactured by BASF), 1-[9-ethyl-6- Examples of such compounds include oxime ester compounds such as [(2-methylbenzoyl)-9H-carbazol-3-yl]-,1-(O-acetyloxime) ("OXE04", manufactured by BASF), benzophenone compounds, benzoin compounds, thioxanthone compounds, halomethylated triazine compounds, halomethylated oxadiazole compounds, biimidazole compounds, titanocene compounds, benzoic acid ester compounds, acridine compounds, and phosphine oxide compounds. Of these, aminoketone compounds and oxime ester compounds are preferred.
The photopolymerization initiators may be used alone or in combination of two or more.

The content of the photopolymerization initiator is not particularly limited as long as it is within a range in which the effects of the present invention are exhibited, and may be set appropriately. For example, it is preferably 0.3 to 20% by mass, more preferably 0.5 to 10% by mass, and even more preferably 1 to 8% by mass, relative to 100% by mass of the total solids content of the photosensitive resin composition of the present invention.

<Photoacid generator>
The photosensitive resin composition of the present invention preferably further contains a photoacid generator. By further containing a photoacid generator, the curability of the photosensitive resin composition can be further improved.
The photoacid generator is a compound that generates an acid when exposed to active energy rays such as radiation, and examples thereof include strong acids such as toluenesulfonic acid or boron tetrafluoride; onium salts such as sulfonium salts, ammonium salts, phosphonium salts, iodonium salts, and selenium salts; iron-allene complexes; silanol-metal chelate complexes; sulfonic acid derivatives such as disulfones, disulfonyldiazomethanes, disulfonylmethanes, sulfonylbenzoylmethanes, imidosulfonates, and benzoinsulfonates; and organic halogen compounds.

The content of the photoacid generator is preferably 0.3 to 20% by mass, more preferably 0.5 to 10% by mass, and even more preferably 1 to 8% by mass, relative to 100% by mass of the total solids content of the photosensitive resin composition.

<Other ingredients>
In addition to the above-mentioned components, the photosensitive resin composition of the present invention may contain other components as needed. Examples of such other components include solvents; colorants (pigments, dyes); dispersants; heat resistance improvers; leveling agents; development aids; inorganic fine particles such as silica fine particles; silane-based, aluminum-based, and titanium-based coupling agents; fillers; thermosetting resins such as epoxy resins, phenolic resins, and polyvinylphenols; curing aids such as polyfunctional thiol compounds; plasticizers; polymerization inhibitors; UV absorbers; antioxidants; matting agents; defoaming agents; antistatic agents; slip agents; surface modifiers; thixotropic agents; thixotropic aids; quinone diazide compounds; polyhydric phenol compounds; cationically polymerizable compounds; and acid generators. These may be used alone or in combination of two or more. These other components may be appropriately selected from known compounds, and the amounts used may be appropriately determined.
For example, when the photosensitive resin composition is used for a color filter, the photosensitive resin composition preferably contains a coloring material.

<Preparation of Photosensitive Resin Composition>
The method for preparing the photosensitive resin composition of the present invention is not particularly limited and may be a known method, for example, a method in which the above-mentioned components are mixed and dispersed using various mixers or dispersers. The mixing and dispersion step is not particularly limited and may be performed by a known method. In addition, other commonly performed steps may be further included. When the photosensitive resin composition contains a colorant, it is preferable to prepare it through a known step such as a colorant dispersion step.

<Cured product>
A cured product obtained by curing the copolymer, copolymer solution, or photosensitive resin composition (curable resin composition) of the present invention has excellent solvent resistance. The cured product of such a copolymer, copolymer solution, or photosensitive resin composition also constitutes one aspect of the present invention.

When the cured product is a cured film, its film thickness is preferably 0.1 μm or more. A film thickness of 0.1 μm or more can exhibit even better solvent resistance. The film thickness is more preferably 0.5 μm or more, and even more preferably 1 μm or more. The upper limit of the film thickness is not particularly limited and can be set appropriately depending on the purpose and application of the cured film; for example, it is preferably 20 μm or less, more preferably 15 μm or less, and even more preferably 10 μm or less.

The method for obtaining the cured product is not particularly limited, and any known method may be used. For example, the above-mentioned copolymer, copolymer solution, or photosensitive resin composition may be applied to or molded onto a substrate, and then cured by drying, heating, or irradiation with energy rays such as ultraviolet rays, or a combination of these, to obtain a cured product.

By using the copolymer, copolymer solution, or photosensitive resin composition of the present invention, it is possible to obtain a cured product that has excellent solvent resistance even under low-temperature curing conditions. A preferred example of a method for producing such a cured product includes the steps of applying the photosensitive resin composition to a substrate to form a coating film, irradiating the formed coating film with light, and heating the irradiated coating film at 160°C or less.

The substrate is not particularly limited and may be selected appropriately depending on the purpose and application. Examples include substrates made of various materials such as glass plates and plastic plates.

The method for forming a coating film by applying the photosensitive resin composition is not particularly limited, and can be any known method such as spin coating, slit coating, roll coating, or cast coating.
In the above-mentioned production method, it is preferable to coat the photosensitive resin composition on a substrate and then dry the coated product to form a coating film. The drying can be carried out by a known method, and specifically, it can be carried out by a method similar to the drying method described in the "Arrangement step" in "<Color filter production method>" described later.

The manufacturing method includes a step of forming a coating film and then irradiating the coating film with light.
The method for irradiating the formed coating film with light is not particularly limited and can be performed by a known method. Specifically, it can be performed by a method similar to the method described in the "Light irradiation step" in "<Method for producing a color filter>" described below.

When irradiating the coating film with light, the light irradiation may be carried out through a photomask. It is preferable to use a mask having light-shielding portions formed according to the desired pattern as the photomask. When light irradiation is carried out through a photomask, it is preferable to carry out a development step afterwards. By carrying out the development step, the desired pattern can be formed in the coating film. The development method is not particularly limited and can be carried out by any known method. Specifically, it can be carried out by a method similar to the method described in the "Development Step" section of "<Color Filter Manufacturing Method>" below.

The above-mentioned production method also includes a step of heating the light-irradiated coating film at 160° C. or less. Since the above-mentioned production method uses the above-mentioned photosensitive resin composition, the heating step (post-curing step) after light irradiation can be carried out under relatively low temperature conditions of 160° C. or less.
The heating temperature is preferably 155° C. or lower, and more preferably 150° C. or lower. The lower limit of the heating temperature is preferably 70° C. or higher, and more preferably 90° C. or higher, in order to maintain curability.
The heating method other than the temperature is not particularly limited and can be performed by a known method, for example, a method similar to the method described in the "Heating step" section of "<Color filter manufacturing method>" below.

<Application>
The copolymer, copolymer solution, and photosensitive resin composition (curable resin composition) containing the copolymer of the present invention undergo a curing reaction sufficiently and can give a cured product with excellent solvent resistance even under low-temperature curing conditions of 160° C. or less, for example, about 90° C. Therefore, the copolymer, copolymer solution, and photosensitive resin composition (curable resin composition) containing the copolymer of the present invention can be suitably used in applications requiring sufficient curing under low-temperature conditions or applications requiring solvent resistance.

Specifically, the copolymer, copolymer solution, and photosensitive resin composition of the present invention can be suitably used for applications such as color filters, black matrices, photospacers, black column spacers, inks, printing plates, printed wiring boards, semiconductor elements, photoresists, insulating films, films, organic protective films, and other components of various optical members and electric/electronic devices, etc., used in liquid crystal, organic EL, quantum dot, and micro LED liquid crystal displays, solid-state imaging devices, touch panel display devices, etc. Among these, they are preferably used for color filters.
The photosensitive resin composition of the present invention is suitably used as an optical material, and is also suitably used as a negative type.

3. A color filter having a cured product of the above-mentioned photosensitive resin composition on a color filter substrate is also one of the preferred embodiments of the present invention.
In the color filter, the cured product formed from the photosensitive resin composition is particularly suitable as a segment that requires coloring, such as a black matrix or each pixel of red, green, blue, yellow, etc., but is also suitable as a segment that does not necessarily require coloring, such as a photospacer, a protective layer, or an alignment control rib.

Substrates used in the color filters include, for example, glass substrates such as white plate glass, blue plate glass, alkali-strengthened glass, and silica-coated blue plate glass; sheets, films, or substrates made of thermoplastic resins such as polyester, polycarbonate, polyolefin, polysulfone, ring-opening polymers of cyclic olefins, and hydrogenated products thereof; sheets, films, or substrates made of thermosetting resins such as epoxy resins and unsaturated polyester resins; metal substrates such as aluminum plates, copper plates, nickel plates, and stainless steel plates; ceramic substrates; semiconductor substrates having photoelectric conversion elements; and components made of various materials such as glass substrates having a colorant layer on the surface (e.g., color filters for LCDs). Among these, glass substrates and sheets, films, or substrates made of heat-resistant resins are preferred from the standpoint of heat resistance. It is also preferred that the substrates be transparent.
If necessary, the substrate may be subjected to corona discharge treatment, ozone treatment, or chemical treatment using a silane coupling agent or the like.

<Color filter manufacturing method>
To obtain the color filter, it is preferable to employ a manufacturing method that includes, for each pixel color (i.e., for each pixel color), a step of disposing the photosensitive resin composition on a substrate (also referred to as a disposing step), a step of irradiating the photosensitive resin composition disposed on the substrate with light (also referred to as a light irradiation step), a step of developing with a developer (also referred to as a developing step), and a step of heat treatment (also referred to as a heating step), and that repeats this same procedure for each color. Note that the order in which the pixels of each color are formed is not particularly limited.

(1) Arrangement step (preferably application step)
The disposing step is preferably carried out by coating. Examples of a method for coating the photosensitive resin composition on a substrate include spin coating, slit coating, roll coating, and cast coating, and any of these methods can be preferably used.
In the disposing step, it is also preferable to dry the coating film after applying the photosensitive resin composition to the substrate. The coating film can be dried using, for example, a hot plate, an IR oven, a convection oven, etc. The drying conditions are appropriately selected depending on the boiling point of the solvent components contained, the type of curable component, the film thickness, the performance of the dryer, etc., but it is usually preferable to dry at a temperature of 50 to 160°C for 10 to 300 seconds.

(2) Light Irradiation Step In the light irradiation step, examples of the light source for the actinic ray used include lamp light sources such as xenon lamps, halogen lamps, tungsten lamps, high-pressure mercury lamps, ultra-high-pressure mercury lamps, metal halide lamps, medium-pressure mercury lamps, low-pressure mercury lamps, carbon arcs, and fluorescent lamps, and laser light sources such as argon ion lasers, YAG lasers, excimer lasers, nitrogen lasers, helium cadmium lasers, and semiconductor lasers. Examples of the exposure system include the proximity system, mirror projection system, and stepper system, with the proximity system being preferred.
In the step of irradiating with active energy rays, depending on the application, the active energy rays may be irradiated through a predetermined mask pattern. In this case, the exposed area is cured, and the cured area is made insoluble or hardly soluble in a developer.

(3) Development Step: The development step is a step in which, after the light irradiation step described above, development is performed using a developer to remove unexposed areas and form a pattern. This allows a patterned cured film to be obtained. The development step can usually be performed at a development temperature of 10 to 50°C by a method such as immersion development, spray development, brush development, or ultrasonic development.

The developer used in the development step is not particularly limited as long as it dissolves the photosensitive resin composition. Typically, an organic solvent or an alkaline aqueous solution is used, and a mixture of these may also be used. When an alkaline aqueous solution is used as the developer, it is preferable to wash with water after development. Examples of organic solvents and alkaline aqueous solutions include those similar to those described in JP 2015-157909 A.

(4) Heating Step The heating step is a step (also referred to as a "post-curing step") in which the exposed portion (cured portion) is further cured by baking after the above-mentioned development step. Examples include a step of post-exposing the film using a light source such as a high-pressure mercury lamp at a light intensity of 0.5 to 5 J/ ^cm2 , and a step of post-heating the film at a temperature of 60 to 200°C for 10 seconds to 120 minutes. By performing such a post-curing step, it is possible to further increase the hardness and adhesion of the patterned cured film.
The heating step is generally carried out at a temperature of about 200 to 260° C., but if the photosensitive resin composition is used, sufficient curing can be achieved under relatively low temperatures of 200° C. or less, preferably 160° C. or less. Therefore, it is possible to obtain a product with excellent solvent resistance without impairing the properties retained by the substrate or the cured product.

In the heating step, the heating temperature is preferably 160°C or lower, more preferably 155°C or lower, and even more preferably 150°C or lower. Furthermore, the heating temperature is preferably 70°C or higher, more preferably 90°C or higher, and even more preferably 95°C or higher.

The heating time in the heating step is not particularly limited, but is preferably 5 to 60 minutes, for example. The heating method is also not particularly limited, but can be performed using a heating device such as a hot plate, convection oven, or high-frequency heater.

The thickness of the cured film obtained by the heating step (i.e., the cured coating film obtained by thermally curing the photosensitive resin composition) is preferably 0.1 to 20 μm. The thickness is more preferably 0.5 to 15 μm, and even more preferably 1 to 10 μm.

4. Display Device A display device equipped with the above-described color filter is also one of the preferred embodiments of the present invention.
A display device member and a display device having a cured product of the photosensitive resin composition are also included in preferred embodiments of the present invention. The cured product (cured film) formed from the photosensitive resin composition is stable, has excellent adhesion to substrates, etc., has high hardness, exhibits high smoothness, and has high transmittance, so is particularly suitable as a transparent member and is also useful as a protective film or insulating film in various display devices.

As the display device, for example, a liquid crystal display device, a solid-state image pickup device, a touch panel display device, etc. are suitable.
When the cured product (cured film) is used as a member for a display device, the member may be a film-like single-layer or multi-layer member constituted by the cured film, or may be a member in which another layer is further combined with the single-layer or multi-layer member, or may be a member containing the cured film in its configuration.

As described above, the copolymer, copolymer solution, and photosensitive resin composition (curable resin composition) of the present invention can provide a cured product with excellent solvent resistance even under low-temperature curing conditions. The copolymer, copolymer solution, and photosensitive resin composition of the present invention can be suitably used in a variety of applications in electrical and electronic devices, such as various optical components and components used in liquid crystal, organic EL, quantum dot, and micro LED liquid crystal displays, solid-state imaging devices, and touch panel display devices.

The present invention will be explained in more detail below with reference to the following examples, but the present invention is not limited to these examples. Unless otherwise specified, "parts" means "parts by mass" and "%" means "% by mass."

In the examples, various physical properties were measured by the following methods.
(1) Weight average molecular weight (Mw)
The weight average molecular weight was measured by GPC (gel permeation chromatography) using polystyrene as a standard substance and tetrahydrofuran as an eluent, with an HLC-8220GPC (manufactured by Tosoh Corporation) and a column: TSKgel Super HZM-M (manufactured by Tosoh Corporation).

(2) Approximately 1 g of the solid copolymer solution was weighed into an aluminum cup, dissolved in approximately 3 g of acetone, and then air-dried at room temperature. The solution was then dried under vacuum at 140°C for 1.5 hours using a hot air dryer (product name: PHH-101, manufactured by Espec Corporation), cooled in a desiccator, and its mass was measured. The solid content (% by mass) of the polymer solution was calculated from the mass loss.

(3) Acid Value: 3 g of the copolymer solution was precisely weighed and dissolved in a mixed solvent of 90 g of acetone and 10 g of water, and titrated using a 0.1 N aqueous solution of KOH as a titrant. The titration was carried out using an automatic titrator (product name: COM-555, manufactured by Hiranuma Sangyo Co., Ltd.), and the acid value per 1 g of solid content (mg KOH/g) was calculated from the acid value of the solution and the solid content of the solution.

(4) Epoxy equivalent (g/equivalent)
It was determined by dividing the mass (g) of the copolymer solid content by the number of moles (mol) of epoxy groups contained in the copolymer.

(5) Double bond equivalent (g/equivalent)
It was determined by dividing the mass (g) of the copolymer solid content by the amount of double bonds (mol) of the copolymer.

(6) Solvent-resistant: The photosensitive resin composition was spin-coated onto a 5 cm square glass substrate, dried at 100°C for 3 minutes, exposed to 200 mJ using a high-pressure mercury lamp, and heat-treated (post-cured) at 90°C or 110°C for 40 minutes, yielding a cured film with a thickness of 2 μm. The cured film was then immersed in 20 g of 1-methyl-2-pyrrolidone (NMP) at 40°C for 10 minutes and then removed. The absorbance of the immersion liquid (NMP) after removal of the cured film was measured using a UV3100 spectrophotometer (manufactured by Shimadzu Corporation) and evaluated according to the following criteria. A higher absorbance value indicates that more colorant was eluted into the immersion liquid, and the solvent resistance of the photosensitive resin composition is evaluated as being lower.
(Evaluation criteria)
◎: absorbance value is less than 0.2 ◯: absorbance value is 0.2 or more and less than 0.3 △: absorbance value is 0.3 or more and less than 0.4 ×: absorbance value is 0.4 or more XX: film peeling

(7) Solvent resistance (Examples 20 to 23)
The photosensitive resin composition was spin-coated onto a 5 cm square glass substrate, dried at 90° C. for 2 minutes, exposed to 100 mJ using a high-pressure mercury lamp, and heat-treated (post-cured) at 90° C. for 30 minutes to obtain a cured film with a thickness of 2 μm. The cured film was then immersed in 20 g of the immersion solvent shown in Table 5 at 30° C. for 5 minutes and then removed. The absorbance of the immersion solvent after removing the cured film was measured using a UV3100 spectrophotometer (manufactured by Shimadzu Corporation).

(8) Viscosity The viscosity of the copolymer solution was measured at 25° C. using a viscometer (VISCOMETER TV-22, manufactured by Toki Sangyo Co., Ltd.).

(9) Film Remaining Rate The film remaining rate was calculated by measuring the weight of the film before and after the evaluation of the solvent resistance in (7) above. Specifically, the glass substrate was used as the tare weight to calculate the film weight before the solvent resistance evaluation. Then, the film remaining rate was calculated by dividing the film weight after the solvent resistance evaluation by the film weight before the evaluation.

(Production Example 1)
Preparation of copolymer solution A-1 (SAH adduct solution of HEMA-GMA copolymer): A reaction vessel equipped with a thermometer, a stirrer, a gas inlet, a cooling tube, and a dropping vessel inlet was charged with 185.3 parts of propylene glycol monomethyl ether acetate, and after nitrogen substitution, heated to 90 ° C. On the other hand, as the dropping vessel (A), a beaker was prepared by stirring and mixing 30.0 parts of 2-hydroxyethyl methacrylate, 70.0 parts of glycidyl methacrylate, 30 parts of propylene glycol monomethyl ether acetate, and 2.0 parts of t-butylperoxy-2-ethylhexanoate (manufactured by NOF Corporation, "Perbutyl (registered trademark) O"), and a dropping vessel (B) was prepared by stirring and mixing 2.0 parts of n-dodecyl mercaptan and 18.0 parts of propylene glycol monomethyl ether acetate. After the temperature of the reaction vessel reached 90°C, dropwise addition from the dropping vessel was initiated over 3 hours while maintaining the same temperature, and polymerization was carried out. After the dropwise addition was completed, the mixture was maintained at 90°C for 30 minutes, then heated to 115°C and aged for 90 minutes. After cooling to room temperature, 11.5 parts of succinic anhydride, 0.33 parts of triethylamine as a catalyst, 189 parts of dimethyl carbonate, and 29.6 parts of propylene glycol monomethyl ether acetate were added and reacted at 40°C for 10 hours, yielding copolymer solution A-1. The physical properties of the obtained copolymer are shown in Table 1.

(Production Example 2)
Preparation of Copolymer Solution A-2 (SAH Adduct Solution of BzMI-CHMA-HEMA-GMA Copolymer) A reaction vessel equipped with a thermometer, a stirrer, a gas inlet tube, a condenser, and a dropping vessel inlet was charged with 172.0 parts of propylene glycol monomethyl ether acetate, and the atmosphere was replaced with nitrogen, followed by heating to 90°C. On the other hand, a dropping tank (A) was prepared by stirring and mixing 10.0 parts of N-benzylmaleimide, 43.6 parts of cyclohexyl methacrylate, 30.0 parts of 2-hydroxyethyl methacrylate, 16.4 parts of glycidyl methacrylate, 30 parts of propylene glycol monomethyl ether acetate, and 2.0 parts of t-butylperoxy-2-ethylhexanoate (manufactured by NOF Corporation, "Perbutyl (registered trademark) O") in a beaker, and a dropping tank (B) was prepared by stirring and mixing 2.0 parts of n-dodecyl mercaptan and 31.33 parts of propylene glycol monomethyl ether acetate. After the temperature of the reaction tank reached 90 ° C, dropwise addition from the dropping tank was initiated over 3 hours while maintaining the same temperature, and polymerization was carried out. After completion of the dropwise addition, the temperature was maintained at 90 ° C for 30 minutes, and then the temperature was increased to 115 ° C, and aging was carried out for 90 minutes. After cooling to room temperature, the mixture was reacted with 11.5 parts of succinic anhydride, 0.33 parts of triethylamine as a catalyst, and 29.0 parts of propylene glycol monomethyl ether acetate at 60°C for 10 hours to obtain a copolymer solution A-2. The physical properties of the obtained copolymer are shown in Table 1.

(Production Example 3)
Preparation of Copolymer Solution A-3 (SAH Adduct Solution of BzMI-VT-HEMA-GMA Copolymer) A reaction vessel equipped with a thermometer, a stirrer, a gas inlet pipe, a condenser, and a dropping vessel inlet was charged with 172.0 parts of propylene glycol monomethyl ether acetate, and the atmosphere was replaced with nitrogen, followed by heating to 90°C. On the other hand, a dropping tank (A) was prepared by stirring and mixing 10.0 parts of N-benzylmaleimide, 43.6 parts of vinyltoluene, 30.0 parts of 2-hydroxyethyl methacrylate, 16.4 parts of glycidyl methacrylate, 30 parts of propylene glycol monomethyl ether acetate, and 2.0 parts of t-butylperoxy-2-ethylhexanoate (manufactured by NOF Corporation, "Perbutyl (registered trademark) O") in a beaker, and a dropping tank (B) was prepared by stirring and mixing 2.0 parts of n-dodecyl mercaptan and 31.33 parts of propylene glycol monomethyl ether acetate. After the temperature of the reaction tank reached 90°C, dropwise addition from the dropping tank was initiated over 3 hours while maintaining the same temperature, and polymerization was carried out. After completion of the dropwise addition, the temperature was maintained at 90°C for 30 minutes, and then the temperature was increased to 115°C and aged for 90 minutes. After cooling to room temperature, 11.5 parts of succinic anhydride, 0.33 parts of triethylamine as a catalyst, and 29.0 parts of propylene glycol monomethyl ether acetate were added and reacted at 60°C for 10 hours to obtain copolymer solution A-3. The physical properties of the obtained copolymer are shown in Table 1.

(Production Example 4)
Preparation of Copolymer Solution A-4 (SAH Adduct Solution of BzMI-2EHA-HEMA-GMA Copolymer) A reaction vessel equipped with a thermometer, a stirrer, a gas inlet pipe, a condenser, and a dropping vessel inlet was charged with 172.0 parts of propylene glycol monomethyl ether acetate, and the atmosphere was replaced with nitrogen, followed by heating to 90°C. On the other hand, a dropping tank (A) was prepared by stirring and mixing 10.0 parts of N-benzylmaleimide, 43.6 parts of 2-ethylhexyl acrylate, 30.0 parts of 2-hydroxyethyl methacrylate, 16.4 parts of glycidyl methacrylate, 30 parts of propylene glycol monomethyl ether acetate, and 2.0 parts of t-butylperoxy-2-ethylhexanoate (manufactured by NOF Corporation, "Perbutyl (registered trademark) O") in a beaker, and a dropping tank (B) was prepared by stirring and mixing 2.0 parts of n-dodecyl mercaptan and 31.33 parts of propylene glycol monomethyl ether acetate. After the temperature of the reaction tank reached 90°C, dropwise addition from the dropping tank was initiated over 3 hours while maintaining the same temperature, and polymerization was carried out. After completion of the dropwise addition, the temperature was maintained at 90°C for 30 minutes, and then the temperature was increased to 115°C and aged for 90 minutes. After cooling to room temperature, 11.5 parts of succinic anhydride, 0.33 parts of triethylamine as a catalyst, and 29.0 parts of propylene glycol monomethyl ether acetate were added and reacted at 60°C for 10 hours to obtain a copolymer solution A-4. The physical properties of the obtained copolymer are shown in Table 1.

(Production Example 5)
Preparation of copolymer solution A-5 (SAH adduct solution of BzMI-CHMA-HEAA-GMA copolymer) A reaction vessel equipped with a thermometer, a stirrer, a gas inlet, a cooling tube, and a dropping vessel inlet was charged with 85.6 parts of diethylene glycol ethyl methyl ether, and after nitrogen substitution, it was heated to 90 ° C. On the other hand, as the dropping vessel (A), 10.0 parts of N-benzylmaleimide in a beaker, 46.65 parts of cyclohexyl methacrylate, 26.8 parts of N-hydroxyethyl acrylamide, 16.55 parts of glycidyl methacrylate, 49.8 parts of diethylene glycol ethyl methyl ether, t-butylperoxy-2-ethylhexanoate (manufactured by NOF Corporation "Perbutyl (registered trademark) O") 2.0 parts were stirred and mixed to prepare a dropping vessel (B), 2.0 parts of n-dodecyl mercaptan, and 98.0 parts of diethylene glycol ethyl methyl ether were stirred and mixed to prepare a dropping vessel. After the temperature of the reaction vessel reached 90°C, dropwise addition from the dropping vessel was initiated over 3 hours while maintaining the same temperature, and polymerization was carried out. After the dropwise addition was completed, the mixture was maintained at 90°C for 30 minutes, then heated to 115°C, and aged for 90 minutes. After cooling to room temperature, 13.0 parts of succinic anhydride and 32.5 parts of diethylene glycol ethyl methyl ether were reacted at 60°C for 10 hours, yielding copolymer solution A-5. The physical properties of the obtained copolymer are shown in Table 1.

(Production Example 6)
Preparation of Copolymer Solution A-6 (SAH Adduct Solution of BzMI-CHMA-GLMA-GMA Copolymer) A reaction vessel equipped with a thermometer, a stirrer, a gas inlet tube, a condenser, and a dropping vessel inlet was charged with 50.1 parts of propylene glycol monomethyl ether acetate and 50.1 parts of diethylene glycol ethyl methyl ether, and the atmosphere was replaced with nitrogen, followed by heating to 90°C. On the other hand, a dropping tank (A) was prepared by stirring and mixing 10.0 parts of N-benzylmaleimide, 46.65 parts of cyclohexyl methacrylate, 30.0 parts of glycerin monomethacrylate ("Blemmer GL" manufactured by NOF Corporation), 13.35 parts of glycidyl methacrylate, 24.1 parts of propylene glycol monomethyl ether acetate, 24.1 parts of diethylene glycol ethyl methyl ether, and 2.0 parts of t-butylperoxy-2-ethylhexanoate ("Perbutyl (registered trademark) O" manufactured by NOF Corporation) in a beaker, and a dropping tank (B) was prepared by stirring and mixing 2.0 parts of n-dodecyl mercaptan, 42.5 parts of propylene glycol monomethyl ether acetate, and 42.5 parts of diethylene glycol ethyl methyl ether. After the temperature of the reaction tank reached 90°C, dropwise addition from the dropping tank was initiated over 3 hours while maintaining the same temperature, and polymerization was carried out. After the dropwise addition, the mixture was maintained at 90°C for 30 minutes, then heated to 115°C and aged for 90 minutes. After cooling to room temperature, 9.4 parts of succinic anhydride, 12.0 parts of propylene glycol monomethyl ether acetate, and 12.0 parts of diethylene glycol ethyl methyl ether were added and reacted at 60°C for 10 hours to obtain copolymer solution A-6. The physical properties of the obtained copolymer are shown in Table 1.

(Production Example 7)
Preparation of Copolymer Solution A-7 (SAH Adduct Solution of BzMI-CHMA-HEMA-GMA-NIPAM Copolymer) A reaction vessel equipped with a thermometer, a stirrer, a gas inlet tube, a condenser, and a dropping vessel inlet was charged with 30.9 parts of propylene glycol monomethyl ether acetate, and the atmosphere was replaced with nitrogen, followed by heating to 90°C. On the other hand, a dropping tank (A) was prepared by stirring and mixing 10.0 parts of N-benzylmaleimide, 23.6 parts of cyclohexyl methacrylate, 30.0 parts of 2-hydroxyethyl methacrylate, 16.4 parts of glycidyl methacrylate, 20.0 parts of N-isopropylacrylamide, 10.0 parts of propylene glycol monomethyl ether acetate, and 2.0 parts of t-butylperoxy-2-ethylhexanoate (manufactured by NOF Corporation, "Perbutyl (registered trademark) O") in a beaker, and a dropping tank (B) was prepared by stirring and mixing 4.0 parts of n-dodecyl mercaptan and 67.4 parts of propylene glycol monomethyl ether acetate. After the temperature of the reaction tank reached 90 ° C, dropwise addition from the dropping tank was initiated over 3 hours while maintaining the same temperature, and polymerization was carried out. After completion of the dropwise addition, the temperature was maintained at 90 ° C for 30 minutes, and then the temperature was increased to 115 ° C, and the mixture was aged for 90 minutes. After cooling to room temperature, 11.5 parts of succinic anhydride and 4.7 parts of propylene glycol monomethyl ether acetate were added and reacted at 60°C for 10 hours to obtain copolymer solution A-7. The physical properties of the obtained copolymer are shown in Table 1.

(Production Example 8)
Preparation of Copolymer Solution A-8 (SAH Adduct Solution of MAA Adduct of BzMI-CHMA-HEMA-GMA Copolymer) A reaction vessel equipped with a thermometer, a stirrer, a gas inlet tube, a condenser, and a dropping vessel inlet was charged with 64.0 parts of propylene glycol monomethyl ether acetate, purged with nitrogen, and then heated to 90°C. On the other hand, a dropping tank (A) was prepared by stirring and mixing 10.0 parts of N-benzylmaleimide, 19.0 parts of cyclohexyl methacrylate, 30.0 parts of 2-hydroxyethyl methacrylate, 41.0 parts of glycidyl methacrylate, 10.0 parts of propylene glycol monomethyl ether acetate, and 2.0 parts of t-butylperoxy-2-ethylhexanoate (manufactured by NOF Corporation, "Perbutyl (registered trademark) O") in a beaker, and a dropping tank (B) was prepared by stirring and mixing 4.0 parts of n-dodecyl mercaptan and 54.82 parts of propylene glycol monomethyl ether acetate. After the temperature of the reaction tank reached 90 ° C, dropwise addition from the dropping tank was initiated over 3 hours while maintaining the same temperature, and polymerization was carried out. After completion of the dropwise addition, the temperature was maintained at 90 ° C for 30 minutes, and then the temperature was increased to 115 ° C, and aging was carried out for 90 minutes. After cooling to room temperature, 13.5 parts of methacrylic acid, 0.34 parts of triphenylphosphine as a catalyst, and 0.17 parts of Antage W-400 were added and reacted at 85°C for 12 hours. After cooling to room temperature, 13.1 parts of succinic anhydride were added and reacted at 60°C for 5 hours to obtain copolymer solution A-8. The physical properties of the obtained copolymer are shown in Table 1.

(Production Example 9)
Preparation of Copolymer Solution A-9 (SAH Adduct Solution of Karenz MOI Adduct of BzMI-CHMA-HEMA-GMA Copolymer) A reaction vessel equipped with a thermometer, a stirrer, a gas inlet tube, a condenser, and a dropping vessel inlet was charged with 208.7 parts of propylene glycol monomethyl ether acetate, purged with nitrogen, and then heated to 90°C. On the other hand, a dropping tank (A) was prepared by stirring and mixing 10.0 parts of N-benzylmaleimide, 14.3 parts of cyclohexyl methacrylate, 55.0 parts of 2-hydroxyethyl methacrylate, 20.7 parts of glycidyl methacrylate, 10.0 parts of propylene glycol monomethyl ether acetate, and 2.0 parts of t-butylperoxy-2-ethylhexanoate (manufactured by NOF Corporation, "Perbutyl (registered trademark) O") in a beaker, and a dropping tank (B) was prepared by stirring and mixing 2.0 parts of n-dodecyl mercaptan and 98.00 parts of propylene glycol monomethyl ether acetate. After the temperature of the reaction tank reached 90 ° C, dropwise addition from the dropping tank was initiated over 3 hours while maintaining the same temperature, and polymerization was carried out. After completion of the dropwise addition, the temperature was maintained at 90 ° C for 30 minutes, and then the temperature was increased to 115 ° C, and aging was carried out for 90 minutes. After cooling to room temperature, 26.2 parts of 2-isocyanatoethyl methacrylate ("Karenz MOI (registered trademark)" manufactured by Showa Denko KK), 0.13 parts of triethylamine, and 0.19 parts of Antage W-400 were reacted at 90°C for 4 hours. After cooling to room temperature, 14.7 parts of succinic anhydride and 0.28 parts of triethylamine as a catalyst were reacted at 60°C for 7 hours, and then 69 parts of propylene glycol monomethyl ether was added and the reaction was continued at 60°C for 1 hour to eliminate the remaining succinic anhydride, thereby obtaining copolymer solution A-9. Various physical properties of the obtained copolymer are shown in Table 1.

(Production Example 10)
Preparation of Copolymer Solution A-10 (SAH Adduct Solution of AMA-TBMA-HEMA-GMA Copolymer) A reaction vessel equipped with a thermometer, a stirrer, a gas inlet pipe, a condenser, and a dropping vessel inlet was charged with 172 parts of propylene glycol monomethyl ether acetate, and the atmosphere was replaced with nitrogen, followed by heating to 90°C. On the other hand, a dropping tank (A) was prepared by stirring and mixing 10.0 parts of methyl α-(allyloxymethyl)acrylate, 43.6 parts of tertiary butyl methacrylate, 30.0 parts of 2-hydroxyethyl methacrylate, 16.4 parts of glycidyl methacrylate, 30.0 parts of propylene glycol monomethyl ether acetate, and 2.0 parts of t-butylperoxy-2-ethylhexanoate (manufactured by NOF Corporation, "Perbutyl (registered trademark) O") in a beaker, and a dropping tank (B) was prepared by stirring and mixing 2.0 parts of n-dodecyl mercaptan and 31.3 parts of propylene glycol monomethyl ether acetate. After the temperature of the reaction tank reached 90°C, dropwise addition from the dropping tank was initiated over 3 hours while maintaining the same temperature, and polymerization was carried out. After completion of the dropwise addition, the temperature was maintained at 90°C for 30 minutes, and then the temperature was increased to 115°C and aged for 90 minutes. After cooling to room temperature, 11.5 parts of succinic anhydride, 0.33 parts of triethylamine as a catalyst, and 29.04 parts of propylene glycol monomethyl ether acetate were added and reacted at 60°C for 10 hours to obtain a copolymer solution A-10. The physical properties of the obtained copolymer are shown in Table 1.

(Production Example 11)
Preparation of Copolymer Solution A-11 (SAH Adduct Solution of AA Adduct of MD-CHMA-HEMA-GMA Copolymer) A reaction vessel equipped with a thermometer, a stirrer, a gas inlet tube, a condenser, and a dropping vessel inlet was charged with 86.5 parts of propylene glycol monomethyl ether acetate, and the atmosphere was replaced with nitrogen, followed by heating to 90°C. On the other hand, a dropping tank (A) was prepared by stirring and mixing 10.0 parts of dimethyl-2,2'-[oxybis(methylene)]bis-2-propenoate, 43.6 parts of cyclohexyl methacrylate, 30.0 parts of 2-hydroxyethyl methacrylate, 16.4 parts of glycidyl methacrylate, 48.8 parts of propylene glycol monomethyl ether acetate, and 2.0 parts of t-butylperoxy-2-ethylhexanoate ("Perbutyl (registered trademark) O" manufactured by NOF Corporation) in a beaker, and a dropping tank (B) was prepared by stirring and mixing 2.0 parts of n-dodecyl mercaptan and 98 parts of propylene glycol monomethyl ether acetate. After the temperature of the reaction tank reached 90°C, dropwise addition from the dropping tank was initiated over 3 hours while maintaining the same temperature, and polymerization was carried out. After completion of the dropwise addition, the temperature was maintained at 90°C for 30 minutes, and then the temperature was increased to 115°C and aged for 90 minutes. After cooling to room temperature, 5.0 parts of acrylic acid, 0.32 parts of triethylamine as a catalyst, 0.16 parts of Antage W-400, and 20 parts of propylene glycol monomethyl ether acetate were reacted at 115°C for 7 hours. After cooling to room temperature, 12.6 parts of succinic anhydride and 20 parts of propylene glycol monomethyl ether acetate were reacted at 60°C for 10 hours to obtain copolymer solution A-11. Various physical properties of the obtained copolymer are shown in Table 1.

(Production Example 12)
Preparation of Copolymer Solution A-12 (SAH Adduct Solution of CHMI-CHMA-HEMA-GMA Copolymer) A reaction vessel equipped with a thermometer, a stirrer, a gas inlet tube, a condenser, and a dropping vessel inlet was charged with 172 parts of propylene glycol monomethyl ether acetate, and the atmosphere was replaced with nitrogen, followed by heating to 90°C. On the other hand, a dropping tank (A) was prepared by stirring and mixing 10.0 parts of N-cyclohexylmaleimide, 43.6 parts of cyclohexyl methacrylate, 30.0 parts of 2-hydroxyethyl methacrylate, 16.4 parts of glycidyl methacrylate, 30.0 parts of propylene glycol monomethyl ether acetate, and 2.0 parts of t-butylperoxy-2-ethylhexanoate (manufactured by NOF Corporation, "Perbutyl (registered trademark) O") in a beaker, and a dropping tank (B) was prepared by stirring and mixing 2.0 parts of n-dodecyl mercaptan and 31.3 parts of propylene glycol monomethyl ether acetate. After the temperature of the reaction tank reached 90°C, dropwise addition from the dropping tank was initiated over 3 hours while maintaining the same temperature, and polymerization was carried out. After completion of the dropwise addition, the temperature was maintained at 90°C for 30 minutes, and then the temperature was increased to 115°C and aged for 90 minutes. After cooling to room temperature, 11.5 parts of succinic anhydride, 0.33 parts of triethylamine as a catalyst, and 29.0 parts of propylene glycol monomethyl ether acetate were added and reacted at 60°C for 10 hours to obtain a copolymer solution A-12. The physical properties of the obtained copolymer are shown in Table 1.

(Production Example 13)
Preparation of Copolymer Solution A-13 (SAH Adduct Solution of BzMI-DCPMA-HEMA-GMA Copolymer) A reaction vessel equipped with a thermometer, a stirrer, a gas inlet tube, a condenser, and a dropping vessel inlet was charged with 53.4 parts of propylene glycol monomethyl ether acetate, and the atmosphere was replaced with nitrogen, followed by heating to 90°C. On the other hand, a dropping tank (A) was prepared by stirring and mixing 5.0 parts of N-benzylmaleimide, 25.0 parts of dicyclopentanyl methacrylate, 40.0 parts of 2-hydroxyethyl methacrylate, 30.0 parts of glycidyl methacrylate, 10 parts of propylene glycol monomethyl ether acetate, and 2.0 parts of t-butylperoxy-2-ethylhexanoate ("Perbutyl (registered trademark) O" manufactured by NOF Corporation) in a beaker, and a dropping tank (B) was prepared by stirring and mixing 6.0 parts of n-dodecyl mercaptan and 54.0 parts of propylene glycol monomethyl ether acetate. After the temperature of the reaction tank reached 90°C, dropwise addition from the dropping tank was initiated over 3 hours while maintaining the same temperature, and polymerization was carried out. After completion of the dropwise addition, the temperature was maintained at 90°C for 30 minutes, and then the temperature was increased to 115°C and aged for 90 minutes. After cooling to room temperature, the mixture was reacted with 23.1 parts of succinic anhydride and 9.13 parts of propylene glycol monomethyl ether acetate at 60°C for 12 hours, and then diluted with 172 parts of propylene glycol monomethyl ether to obtain copolymer solution A-13. The physical properties of the obtained copolymer are shown in Table 1.

(Production Example 14)
Preparation of Copolymer Solution A-14 (SAH Adduct Solution of BzMI-CHMA-HEMA-GMA Copolymer) A reaction vessel equipped with a thermometer, a stirrer, a gas inlet tube, a condenser, and a dropping vessel inlet was charged with 165.3 parts of propylene glycol monomethyl ether acetate, and the atmosphere was replaced with nitrogen, followed by heating to 90°C. On the other hand, a dropping tank (A) was prepared by stirring and mixing 10.0 parts of N-benzylmaleimide, 27.5 parts of cyclohexyl methacrylate, 30.0 parts of 2-hydroxyethyl methacrylate, 32.5 parts of glycidyl methacrylate, 30 parts of propylene glycol monomethyl ether acetate, and 2.0 parts of t-butylperoxy-2-ethylhexanoate (manufactured by NOF Corporation, "Perbutyl (registered trademark) O") in a beaker, and a dropping tank (B) was prepared by stirring and mixing 2.0 parts of n-dodecyl mercaptan and 38.0 parts of propylene glycol monomethyl ether acetate. After the temperature of the reaction tank reached 90°C, dropwise addition from the dropping tank was initiated over 3 hours while maintaining the same temperature, and polymerization was carried out. After completion of the dropwise addition, the temperature was maintained at 90°C for 30 minutes, and then the temperature was increased to 115°C and aged for 90 minutes. After cooling to room temperature, the mixture was reacted with 11.5 parts of succinic anhydride, 0.33 parts of triethylamine as a catalyst, and 29.0 parts of propylene glycol monomethyl ether acetate at 60°C for 10 hours, and then diluted with 76 parts of propylene glycol monomethyl ether. Copolymer solution A-14 was obtained. The physical properties of the obtained copolymer are shown in Table 1.

(Production Example 15)
Preparation of Copolymer Solution A-15 (SAH Adduct Solution of BzMI-2EHA-HEMA-GMA Copolymer) A reaction vessel equipped with a thermometer, a stirrer, a gas inlet tube, a condenser, and a dropping vessel inlet was charged with 172.0 parts of propylene glycol monomethyl ether acetate, and the atmosphere was replaced with nitrogen, followed by heating to 90°C. On the other hand, a dropping tank (A) was prepared by stirring and mixing 10.0 parts of N-benzylmaleimide, 29.0 parts of 2-ethylhexyl acrylate, 30.0 parts of 2-hydroxyethyl methacrylate, 31.0 parts of glycidyl methacrylate, 30 parts of propylene glycol monomethyl ether acetate, and 2.0 parts of t-butylperoxy-2-ethylhexanoate (manufactured by NOF Corporation, "Perbutyl (registered trademark) O") in a beaker, and a dropping tank (B) was prepared by stirring and mixing 2.0 parts of n-dodecyl mercaptan and 31.33 parts of propylene glycol monomethyl ether acetate. After the temperature of the reaction tank reached 90°C, dropwise addition from the dropping tank was initiated over 3 hours while maintaining the same temperature, and polymerization was carried out. After completion of the dropwise addition, the temperature was maintained at 90°C for 30 minutes, and then the temperature was increased to 115°C and aged for 90 minutes. After cooling to room temperature, the mixture was reacted with 6.2 parts of succinic anhydride, 0.33 parts of triethylamine as a catalyst, and 16.5 parts of propylene glycol monomethyl ether acetate at 60°C for 10 hours, and then diluted with 40 parts of propylene glycol monomethyl ether to obtain copolymer solution A-15. The physical properties of the obtained copolymer are shown in Table 1.

(Production Example 16)
Preparation of Copolymer Solution A-16 (SAH Adduct Solution of BzMI-CHMA-HEMA-GMA Copolymer) A reaction vessel equipped with a thermometer, a stirrer, a gas inlet tube, a condenser, and a dropping vessel inlet was charged with 83.6 parts of propylene glycol monomethyl ether acetate, and the atmosphere was replaced with nitrogen, followed by heating to 90°C. On the other hand, a dropping tank (A) was prepared by stirring and mixing 20.0 parts of N-benzylmaleimide, 25.0 parts of cyclohexyl methacrylate, 50.0 parts of 2-hydroxyethyl methacrylate, 5.0 parts of glycidyl methacrylate, 50 parts of propylene glycol monomethyl ether acetate, and 2.0 parts of t-butylperoxy-2-ethylhexanoate ("Perbutyl (registered trademark) O" manufactured by NOF Corporation) in a beaker, and a dropping tank (B) was prepared by stirring and mixing 0.3 parts of n-dodecyl mercaptan and 99.70 parts of propylene glycol monomethyl ether acetate. After the temperature of the reaction tank reached 90°C, dropwise addition from the dropping tank was initiated over 3 hours while maintaining the same temperature, and polymerization was carried out. After completion of the dropwise addition, the temperature was maintained at 90°C for 30 minutes, and then the temperature was increased to 115°C and aged for 90 minutes. After cooling to room temperature, the mixture was reacted with 34.6 parts of succinic anhydride, 0.40 parts of triethylamine as a catalyst, and 78.9 parts of propylene glycol monomethyl ether acetate at 60°C for 10 hours to obtain a copolymer solution A-16. The physical properties of the obtained copolymer are shown in Table 1.

(Production Example 17)
Preparation of Copolymer Solution A-17 (SAH Adduct Solution of AA Adduct of BzMI-CHMA-HEMA-GMA Copolymer) A reaction vessel equipped with a thermometer, a stirrer, a gas inlet tube, a condenser, and a dropping vessel inlet was charged with 16.6 parts of propylene glycol monomethyl ether acetate, purged with nitrogen, and then heated to 90°C. On the other hand, a dropping tank (A) was prepared by stirring and mixing 30.0 parts of N-benzylmaleimide, 10.0 parts of cyclohexyl methacrylate, 10.0 parts of 2-hydroxyethyl methacrylate, 50.0 parts of glycidyl methacrylate, 30.0 parts of propylene glycol monomethyl ether acetate, and 2.0 parts of t-butylperoxy-2-ethylhexanoate (manufactured by NOF Corporation, "Perbutyl (registered trademark) O") in a beaker, and a dropping tank (B) was prepared by stirring and mixing 6.0 parts of n-dodecyl mercaptan and 82.24 parts of propylene glycol monomethyl ether acetate. After the temperature of the reaction tank reached 90°C, dropwise addition from the dropping tank was initiated over 3 hours while maintaining the same temperature, and polymerization was carried out. After the dropwise addition was completed, the temperature was maintained at 90°C for 30 minutes, and then the temperature was increased to 115°C and aged for 90 minutes. After cooling to room temperature, 22.8 parts of acrylic acid, 0.37 parts of triphenylphosphine as a catalyst, and 0.18 parts of Antage W-400 were added and reacted at 85°C for 12 hours. After cooling to room temperature, 4.6 parts of succinic anhydride were added and reacted at 60°C for 8 hours, followed by dilution with 118 parts of propylene glycol monomethyl ether to obtain copolymer solution A-17. The physical properties of the obtained copolymer are shown in Table 1.

(Production Example 18)
Preparation of Copolymer Solution A-18 (SAH Adduct Solution of KarenzMOI Adduct of BzMI-CHMA-HEMA-GMA Copolymer) A reaction vessel equipped with a thermometer, a stirrer, a gas inlet tube, a condenser, and a dropping vessel inlet was charged with 78.6 parts of propylene glycol monomethyl ether acetate, purged with nitrogen, and then heated to 90°C. On the other hand, a dropping tank (A) was prepared by stirring and mixing 10.0 parts of N-benzylmaleimide, 29.3 parts of cyclohexyl methacrylate, 40.0 parts of 2-hydroxyethyl methacrylate, 20.7 parts of glycidyl methacrylate, 10.0 parts of propylene glycol monomethyl ether acetate, and 6.0 parts of t-butylperoxy-2-ethylhexanoate ("Perbutyl (registered trademark) O" manufactured by NOF Corporation) in a beaker, and a dropping tank (B) was prepared by stirring and mixing 2.0 parts of n-dodecyl mercaptan and 48.00 parts of propylene glycol monomethyl ether acetate. After the temperature of the reaction tank reached 90°C, dropwise addition from the dropping tank was initiated over 3 hours while maintaining the same temperature, and polymerization was carried out. After completion of the dropwise addition, the temperature was maintained at 90°C for 30 minutes, and then the temperature was increased to 115°C and aged for 90 minutes. After cooling to room temperature, 4.8 parts of 2-isocyanatoethyl methacrylate ("Karenz MOI (registered trademark)" manufactured by Showa Denko) and 0.16 parts of Antage W-400 were added and reacted at 90°C for 8 hours. After cooling to room temperature, 14.6 parts of succinic anhydride and 0.36 parts of triethylamine as a catalyst were added and reacted at 60°C for 10 hours to obtain copolymer solution A-18. Various physical properties of the obtained copolymer are shown in Table 1.

(Production Example 19)
Preparation of Copolymer Solution B-1 (BzMI-CHMA-HEMA-Cyclomer M100-MAA Copolymer) A reaction vessel equipped with a thermometer, a stirrer, a gas inlet tube, a condenser, and a dropping vessel inlet was charged with 145.3 parts of propylene glycol monomethyl ether acetate, and the atmosphere was replaced with nitrogen, followed by heating to 90°C. On the other hand, as a dropping tank (A), 10.0 parts of N-benzylmaleimide, 47.4 parts of cyclohexyl methacrylate, 13.45 parts of 2-hydroxyethyl methacrylate, 20.25 parts of 3,4-epoxycyclohexylmethyl methacrylate (manufactured by Daicel Corporation "Cyclomer M100 (registered trademark)"), 8.9 parts of methacrylic acid, 10.0 parts of propylene glycol monomethyl ether acetate, 2.7 parts of t-butyl peroxypivalate (manufactured by Arkema Yoshitomi Co., Ltd. "Luperox 11 (registered trademark)") were prepared in a beaker, and a dropping tank (B) was prepared by stirring and mixing 2.0 parts of n-dodecyl mercaptan and 78 parts of propylene glycol monomethyl ether acetate. After the temperature of the reaction tank reached 70 ° C., dropping was started from the dropping tank over 3 hours while maintaining the same temperature, and polymerization was carried out. After the dropwise addition, the temperature was maintained at 70°C for 30 minutes, then the temperature was raised to 80°C and aged for 180 minutes to obtain copolymer solution B-1. The physical properties of the obtained copolymer are shown in Table 1.

(Production Example 20)
Preparation of Copolymer Solution B-2 (BzMI-CHMA-HEMA-GMA-MAA Copolymer) A reaction vessel equipped with a thermometer, a stirrer, a gas inlet pipe, a condenser, and a dropping vessel inlet was charged with 145.3 parts of propylene glycol monomethyl ether acetate, and the atmosphere was replaced with nitrogen, followed by heating to 70°C. On the other hand, as the dropping tank (A), 10.0 parts of N-benzylmaleimide, 52.95 parts of cyclohexyl methacrylate, 13.45 parts of 2-hydroxyethyl methacrylate, 14.7 parts of glycidyl methacrylate, 8.9 parts of methacrylic acid, 10.0 parts of propylene glycol monomethyl ether acetate, and 2.7 parts of t-butyl peroxypivalate ("Luperox 11 (registered trademark)" manufactured by Arkema Yoshitomi Co., Ltd.) were prepared in a beaker, and in the dropping tank (B), 2.0 parts of n-dodecyl mercaptan and 78 parts of propylene glycol monomethyl ether acetate were prepared in a stirred mixture. After the temperature of the reaction tank reached 70 ° C, the same temperature was maintained, and dropwise addition from the dropping tank was started over 3 hours, and polymerization was carried out. After the dropwise addition was completed, the temperature was maintained at 70 ° C for 30 minutes, and then the temperature was raised to 80 ° C. and aged for 180 minutes to obtain copolymer solution B-2. The physical properties of the copolymer obtained are shown in Table 1.

The descriptions in Table 1 are as follows:
BzMI: N-benzylmaleimide AMA: α-(allyloxymethyl)methyl acrylate MD: dimethyl-2,2'-[oxybis(methylene)]bis-2-propenoate CHMI: N-cyclohexylmaleimide CHMA: cyclohexyl methacrylate VT: vinyl toluene 2EHA: 2-ethylhexyl acrylate DCPMA: dicyclopentanyl methacrylate TBMA: tert-butyl methacrylate HEMA: 2-hydroxyethyl methacrylate HEAA: N-hydroxyethylacrylamide GLMA: glycerin monomethacrylate M100: 3,4-epoxycyclohexylmethyl methacrylate GMA: glycidyl methacrylate NIPAM: N-isopropylacrylamide MAA: methacrylic acid AA: Karenz acrylate MOI: 2-methacryloyloxyethyl isocyanate SAH: succinic anhydride

(Preparation of Pigment Dispersion 1)
12.9 parts of propylene glycol monomethyl ether acetate, 0.4 parts of Disparlon DA-7301 as a dispersant, 2.25 parts of C.I. Pigment Green 58 as a colorant, and 1.5 parts of C.I. Pigment Yellow 138 were mixed and dispersed for 3 hours using a paint shaker to obtain pigment dispersion 1 (solid content 22% by mass).

Example 1
In terms of solid content, 35.0 parts of Copolymer Solution A-1, 30.0 parts of dipentaerythritol hexaacrylate as a radical polymerizable compound, 5.0 parts of Irgacure OXE-02 (manufactured by BASF Japan Ltd.) as a radical polymerizable photopolymerization initiator, 30.0 parts of Pigment Dispersion 1, and further a dilution solvent (propylene glycol monomethyl ether acetate) were added to a solid content concentration of 20%, and the mixture was stirred to obtain Photosensitive Resin Composition 1.

(Examples 2 to 18, Comparative Examples 1 and 2)
Photosensitive resin compositions 2 to 20 were obtained in the same manner as in Example 1 except that the formulations shown in Table 2 were used.
The solvent resistance of the obtained photosensitive resin compositions 1 to 20 was evaluated, and the results are shown in Table 2.

Table 2 shows that photosensitive resin compositions containing copolymers having epoxy group-containing structural units and long-chain acid group-containing structural units and having an epoxy equivalent of 20,000 or less exhibit good curability and give cured products with excellent solvent resistance, even when cured at low temperatures of 90°C or 110°C.

Example 19, Comparative Example 3
(Storage stability confirmation)
The following procedure was carried out to examine the effect of the dilution solvent on storage stability. A copolymer solution was prepared by adding 20 parts of dilution solvent (corresponding to 66.7% by mass relative to 100% by mass of copolymer solids) to 100 parts (as is) of Copolymer Solution A-2, and the changes in the physical properties (weight average molecular weight and viscosity) of the copolymer were confirmed before and after two weeks of storage at 40°C. Two types of dilution solvents were used: propylene glycol monomethyl ether acetate and propylene glycol monomethyl ether. The changes in the physical properties of the resulting copolymer solution are shown in Table 3.
The change in weight average molecular weight was expressed as a percentage (%) of the difference in weight average molecular weight before and after storage relative to the weight average molecular weight before storage, and the change in viscosity was expressed as a percentage (%) of the difference in viscosity before and after storage relative to the viscosity before storage.

Table 3 shows that when propylene glycol monomethyl ether, an alcohol-based solvent, was added, the changes in weight-average molecular weight and viscosity after storage were smaller than when propylene glycol monomethyl ether acetate was added, indicating that the storage stability of the copolymer was superior.

(Production Example 21)
Preparation of copolymer solution A-19: A reaction vessel equipped with a thermometer, a stirrer, a gas inlet, a cooling tube, and a dropping vessel inlet was charged with 105.3 parts of propylene glycol monomethyl ether acetate, and after nitrogen substitution, the temperature was raised to 90 ° C. On the other hand, as the dropping vessel (A), a beaker was prepared in which 10.0 parts of N-benzylmaleimide, 27.5 parts of cyclohexyl methacrylate, 30.0 parts of 2-hydroxyethyl methacrylate, 32.5 parts of glycidyl methacrylate, 30 parts of propylene glycol monomethyl ether acetate, and 2.0 parts of t-butylperoxy-2-ethylhexanoate (manufactured by NOF Corporation, "Perbutyl (registered trademark) O") were stirred and mixed, and a dropping vessel (B) was prepared in which 2.0 parts of n-dodecyl mercaptan and 98.0 parts of propylene glycol monomethyl ether acetate were stirred and mixed. After the temperature of the reaction vessel reached 90°C, dropwise addition from the dropping vessel was initiated over 3 hours while maintaining the same temperature, and polymerization was carried out. After the dropwise addition was completed, the mixture was maintained at 90°C for 30 minutes, then heated to 115°C and aged for 90 minutes. After cooling to room temperature, 11.5 parts of succinic anhydride, 0.33 parts of triethylamine as a catalyst, and 29.0 parts of propylene glycol monomethyl ether acetate were added and reacted at 60°C for 7 hours. Thereafter, 42.0 parts of propylene glycol monomethyl ether was added so that the solids content became 27%, and copolymer solution A-19 was obtained. The physical properties of the obtained copolymer are shown in Table 4.

(Production Example 22)
Preparation of Copolymer Solution A-20: Copolymer solution A-20 was obtained in the same manner as in Copolymer Solution A-19, except that propylene glycol monomethyl ether acetate was added instead of propylene glycol monomethyl ether. The physical properties of the obtained copolymer are shown in Table 4.

The descriptions in Table 4 are as follows:
BzMI: N-benzylmaleimide CHMA: cyclohexyl methacrylate HEMA: 2-hydroxyethyl methacrylate GMA: glycidyl methacrylate SAH: succinic anhydride TEA: triethylamine

(Example 20)
In terms of solid content, 35.0 parts of copolymer solution A-19, 30.0 parts of dipentaerythritol hexaacrylate as a radical polymerizable compound, 5.0 parts of Irgacure OXE-02 (manufactured by BASF Japan) as a radical polymerizable photopolymerization initiator, 30.0 parts of pigment dispersion 1, 1.0 part of P-2M (Light Ester P-2M, pKa: 1.29, manufactured by Kyoeisha Chemical Co., Ltd.), and further a dilution solvent (propylene glycol monomethyl ether acetate) were added to a solid content concentration of 20%, and the mixture was stirred to obtain photosensitive resin composition 21.

(Examples 21 to 23)
Photosensitive resin compositions 22 to 24 were obtained in the same manner as in Example 20 except that the formulations shown in Table 5 were used.
The solvent resistance of the obtained photosensitive resin compositions 21 to 24 was evaluated, and the results are shown in Table 5.

Table 5 shows that photosensitive resin compositions containing copolymers having epoxy group-containing structural units and acid group-containing structural units and having an epoxy equivalent of 20,000 or less have good curability and excellent solvent resistance, even when cured at a low temperature of 90°C.

Examples 24 to 40
(Storage stability confirmation)
Copolymer solutions were prepared by adding a diluent solvent (propylene glycol monomethyl ether) and P-1M, P-2M, MSA, or ACA to 100 parts of the copolymer solution (as is) in the amounts shown in Table 6 or Table 7. The amount of diluent solvent in Table 6 (35 parts) corresponds to 129.6% by mass relative to 100% by mass of the copolymer solids, and in Table 7 (8 parts) corresponds to 29.6% by mass relative to 100% by mass of the copolymer solids. Using the resulting copolymer solution, changes in the physical properties (viscosity) of the copolymer solution were confirmed before and after storage at 40°C for 1 to 2 weeks. The changes in the physical properties of the resulting copolymer solution are shown in Tables 6 and 7. The change in viscosity (thickening rate) is expressed as the percentage (%) of the difference in viscosity before and after storage relative to the viscosity before storage. The contents of the acid compounds (P-1M, P-2M, MSA, ACA) relative to 100 mol% of the basic compound (TEA) in the copolymer solution are also shown in the tables.

The descriptions in Tables 6 and 7 are as follows:
P-1M: Light Ester P-1M (Kyoeisha Chemical Co., Ltd.) 2-methacryloyloxyethyl acid phosphate, pKa: 1.78, molecular weight: 210.12
P-2M: Light Ester P-2M (Kyoeisha Chemical Co., Ltd.) 2-methacryloyloxyethyl acid phosphate, pKa: 1.29, molecular weight: 322.25
MSA: methanesulfonic acid, pKa: -2.6, molecular weight: 96.1
ACA: acetic acid, pKa: 4.76, molecular weight: 60.05

Tables 6 and 7 confirm that in a copolymer solution containing a copolymer having an epoxy group-containing structural unit and an acid group-containing structural unit and an epoxy equivalent of 20,000 or less, and a protic polar solvent, by further containing an oxidation complex having a pKa of 4.2 or less, the viscosity increase rate after storage is low and storage stability is excellent.

Claims (13)

an epoxy group-containing structural unit (A) represented by the following general formula (1);
an acid group-containing structural unit (B) represented by the following general formula (2);
and a structural unit (D) derived from a hydroxyl group-containing monomer,
the content of the structural unit (D) is 1 to 50% by mass relative to 100% by mass of all structural units;
Epoxy equivalent is 100 or more and 20,000 or less
A copolymer characterized by:

(In formula (1), ^R1 represents a hydrogen atom or a methyl group. ^R2 represents a direct bond or a divalent organic group. X represents an epoxy group-containing group.)

(In formula (2), ^R3 represents a hydrogen atom or a methyl group. ^R4 represents a direct bond or an organic group. ^R5 represents a bonding chain having a length of two or more atoms and represents -R-, -O-R-, -O-R-O-, -CO-R-, or -O-R-O-CO-R'-. R and R' may be the same or different and represent a divalent aliphatic hydrocarbon group which may have a substituent. Y represents a carboxyl group, a phenolic hydroxyl group, a carboxylic anhydride group, a phosphate group, or a sulfonic acid group. a represents 0 or 1.) The copolymer described in claim 1, characterized in that the content of the structural unit (A) is 0.1 to 50 mass% relative to 100 mass% of all structural units, and the content of the structural unit (B) is 0.1 to 50 mass% relative to 100 mass% of all structural units. The copolymer described in claim 1 or 2, characterized in that the weight average molecular weight of the copolymer is 4,000 or more and 20,000 or less. The copolymer according to any one of claims 1 to 3, wherein the structural unit (A) contains a structural unit represented by the following general formula (1-1):

(In formula (1-1), ^R1 represents a hydrogen atom or a methyl group. ^R6 represents a direct bond or a divalent organic group.) The copolymer according to any one of claims 1 to 4, wherein the structural unit (B) contains a structural unit represented by the following general formula (2-1):

(In formula (2-1), ^R3 represents a hydrogen atom or a methyl group. ^R7 and ^R8 are the same or different and represent a direct bond or an optionally substituted divalent aliphatic hydrocarbon group . b represents 0 or 1.) 6. The copolymer according to claim 1, wherein the acid value is 30 mg KOH/g or more and 300 mg KOH/g or less. The copolymer according to any one of claims 1 to 6 , further comprising a structural unit (C) having a ring structure in the main chain. 8. The copolymer according to claim 7 , wherein the content of the structural unit (C) is 0.1 to 50% by mass relative to 100% by mass of all structural units. A curable resin composition comprising the copolymer according to any one of claims 1 to 8 and a polymerizable compound. The curable resin composition according to claim 9 , further comprising a colorant. A cured product of the curable resin composition according to claim 10 . A member for a display device, comprising the cured product according to claim 11 . A method for producing a copolymer having an epoxy equivalent of 100 or more and 20,000 or less, comprising:
A step of polymerizing a monomer component including an epoxy group-containing monomer represented by the following formula (a) and a hydroxyl group-containing monomer represented by the following formula (b1);
The method includes a step of reacting the polymer obtained in the polymerization step with an acid group-containing compound represented by the following formula (b3) in the presence of a basic compound,
The copolymer has structural units derived from the hydroxyl group-containing monomer.
A method for producing a copolymer comprising the steps of:

(In formula (a), ^R1 represents a hydrogen atom or a methyl group. ^R2 represents a direct bond or a divalent organic group. X represents an epoxy group-containing group.)

(In formula (b1), ^R3 represents a hydrogen atom or a methyl group, and ^R4 represents a direct bond or an organic group.)

(In formula (b3), ^R5 represents a bonding chain having a length of 2 atoms or more, and represents -R-, -O-R-, -O-R-O-, -CO-R-, or -O-R-O-CO-R'-. R and R' may be the same or different and represent a divalent aliphatic hydrocarbon group which may have a substituent. )