JP7764151B2 - Curable resin composition, photosensitive resin composition, cured product, and method for producing curable resin composition - Google Patents

Description

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

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, and this has led to demands for higher performance from the various components used in them. To meet such demands, research has been conducted on curable resin compositions that can be used as materials for various components.
Up to now, curable resin compositions 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.
Furthermore, for example, Patent Document 4 describes a curable resin composition and a photosensitive resin composition having excellent storage stability, which contain a curable resin (A) obtained by reacting an acid group-containing polymer with a compound having a group capable of bonding to an acid group and a polymerizable double bond, and a phosphate ester compound (B).

Japanese Patent Application Publication No. 4-25846 Japanese Patent Application Laid-Open No. 2006-251009 JP 2014-210892 A JP 2013-194189 A

As described above, various studies have been conducted on curable resin compositions, but when conventional curable resin compositions are used together with color materials as raw materials for color filters, for example, there has been a problem that the color materials are eluted from the raw materials into a cleaning solvent during the production of the color filter. Therefore, there has been a demand for further improvement in the solvent resistance of curable resin compositions.
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 compositions described in Patent Documents 1 to 4 have room for improvement in terms of curability and storage stability.
The present invention has been made in view of the above-mentioned current situation, and an object of the present invention is to provide a curable resin composition that can give a cured product having excellent solvent resistance even under low-temperature curing conditions, has good storage stability, and can be suitably used in various applications such as color filters.

The present inventors have conducted extensive research into curable resin compositions and have found that by including a copolymer having an epoxy group-containing group and an acid group in one molecule and having an epoxy equivalent within a specific range, and an acid compound having a specific acid dissociation constant, the crosslinking reaction proceeds well even under low-temperature curing conditions of 160°C or less, a cured product having excellent solvent resistance, and storage stability can be maintained, which has led to the completion of the present invention.
That is, the first aspect of the present invention is
The curable resin composition contains, as essential components, a copolymer having an epoxy group-containing structural unit (A) represented by the following general formula (1) and an acid group-containing structural unit, and having an epoxy equivalent of 10,000 or less, and an acid compound having a pKa of 4.2 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.)
Preferably, the acid group-containing structural unit is an acid group-containing structural unit (B) represented by the following general formula (2).

(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 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.)
The structural unit (B) preferably 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 organic group. b represents 0 or 1.)
The molecular weight of the acid compound having a pKa of 4.2 or less is preferably 400 or less.
The acid compound having a pKa of 4.2 or less is preferably a phosphoric acid derivative.
That is, the present invention also encompasses a copolymer having an epoxy group-containing structural unit (A) represented by the above general formula (1) and an acid group-containing structural unit, and having an epoxy equivalent of 10,000 or less, and a curable resin composition containing a phosphoric acid derivative as essential components.
The curable resin composition preferably further contains a basic compound, and the basic compound is preferably an amine compound.
The content of the acid compound is preferably in the range of 50 to 200 mol % relative to 100 mol % of the basic compound.
The curable resin composition preferably further contains a protic polar solvent.
The copolymer contained in the curable resin composition is preferably a copolymer having a ring structure in the main chain, and further preferably includes a structural unit 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.
Furthermore, a second aspect of the present invention is a photosensitive resin composition comprising the above-mentioned curable resin composition, a polymerizable compound, and a photopolymerization initiator.
The photosensitive resin composition preferably further contains a colorant.
The photosensitive resin composition is preferably a negative photosensitive resin composition.
A third aspect of the present invention is a cured product obtained by curing the above-mentioned curable resin composition or the above-mentioned photosensitive resin composition.
A fourth aspect of the present invention is a method for producing the curable resin composition, comprising:
A step of polymerizing a monomer component including an epoxy group-containing monomer and a hydroxyl group-containing monomer;
The method for producing a curable resin composition includes a step of reacting the polymer obtained in the polymerization step with an acid group-containing compound in the presence of a basic compound, and a step of adding an acid compound having a pKa of 4.2 or less. In the method for producing a curable resin composition, it is preferable to further add a protic polar solvent.

The curable resin composition of the present invention can produce a cured product with excellent solvent resistance even when cured at relatively low temperatures of 160°C or less, and also has good storage stability. The cured product of the present invention is suitable for 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., and 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".
In this specification, the numerical range "Min to Max" means a range equal to or greater than the minimum value Min and equal to or less than the maximum value Max. Furthermore, when preferred numerical values are given in stages for the upper and lower limit values, a numerical range obtained by appropriately combining the separately given upper and lower limit values is also a preferred numerical range.
Each component contained in the curable resin composition according to the first embodiment of the present invention will be described below.
[Copolymer]
The copolymer contained in the curable resin composition 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, and having an epoxy equivalent of 10,000 or less:
Preferably, the copolymer has 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 has an epoxy equivalent of 10,000 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.)
Examples of the acid group of the acid group-containing structural unit 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, and the acid group may have only one of these or two or more of them. Among these, a carboxyl group or a carboxylic anhydride group is preferred, and a carboxyl group is more preferred.
The acid group-containing structural unit is a structural unit derived from an acid group-containing monomer, and a monomer having an acid group and a polymerizable double bond is preferred, for example, unsaturated monocarboxylic acids such as (meth)acrylic acid, crotonic acid, cinnamic acid, vinylbenzoic acid, etc.; unsaturated polycarboxylic acids such as maleic acid, fumaric acid, itaconic acid, citraconic acid, mesaconic acid, etc.; unsaturated monocarboxylic acids in which the unsaturated group and the carboxyl group are chain-extended, such as mono(2-acryloyloxyethyl) succinate and mono(2-methacryloyloxyethyl) succinate; unsaturated acid anhydrides such as maleic anhydride and itaconic anhydride; phosphate group-containing unsaturated compounds such as Light Ester P-1M (manufactured by Kyoeisha Chemical Co., Ltd.); etc. Among these, the acid group-containing structural unit (B) represented by the following general formula (2) is particularly preferred.

(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 present invention, the copolymer having the acid group-containing structural unit (B) represented by the above general formula (2), which is particularly preferably used, can give a cured product having excellent solvent resistance even under relatively low curing conditions of 160°C or less (preferably about 90°C). This is presumably because the copolymer has an epoxy group and an acid group, and the acid group is a long-chain acid located relatively far from the main chain, so that the acid group reacts very easily with the epoxy group, allowing the crosslinking reaction to proceed even at relatively low temperatures and forming a strong cured product; and because the acid group-containing structural unit has a longer side chain, the glass transition temperature is lower than that of acrylic acid or methacrylic acid structural units, making the polymer side chain more flexible and allowing the crosslinking reaction to proceed easily at low temperatures.
The copolymer preferably used above has the epoxy group-containing structural unit (A) and the acid group-containing structural unit (B) and has an epoxy equivalent (g/equivalent) of 10,000 or less. If the epoxy equivalent exceeds 10,000, the copolymer may be insufficiently cured, resulting in reduced solvent resistance. The epoxy equivalent of the copolymer of the present invention is preferably 8,000 or less, more preferably 5,000 or less, even more preferably 4,000 or less, even more preferably 3,000 or less, and particularly preferably 2,000 or less. In addition, 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 has an epoxy group-containing structural unit (A) represented by the 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 constituting the hydrocarbon group 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 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).
The divalent organic group preferably has 0 to 10 atoms, more preferably 1 to 5 atoms, and even more preferably 2 to 4 atoms.
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 a structural unit (A-1) represented by the following general formula (1-1), in that it 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 monomers that can introduce the structural unit (A) 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, vinylcyclohexene oxide, etc. Among these, glycidyl (meth)acrylate and (3,4-epoxycyclohexyl)methyl (meth)acrylate are preferred, glycidyl (meth)acrylate is more preferred, and glycidyl methacrylate is even more preferred in that side reactions can be suppressed and improved storage stability can be expected.
The copolymer may have one or more types of the structural unit (A).
In addition, in the copolymer, 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, and more preferably 45% by mass or less, and even more preferably 40% by mass or less.

<Structural Unit (B)>
The copolymer contained in the curable resin composition of the present invention preferably 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 groups described 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.
a represents 0 or 1. In terms of more excellent solvent resistance, a is preferably 1.
The structural unit (B) is preferably a 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 in that solvent resistance can be further improved.
The 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 the monomer into which the structural unit (B) can be introduced include long-chain unsaturated monocarboxylic acids in which the unsaturated group and the carboxyl group are chain-extended, such as β-carboxyethyl (meth)acrylate, mono(2-acryloyloxyethyl) succinate, and mono(2-methacryloyloxyethyl) succinate.
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 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, and succinic anhydride is more preferred, in view of higher addition reactivity.
A specific method for obtaining a copolymer having the structural unit (B) will be described in detail in the section on the method for producing a polymer below.
The copolymer included in the present invention may have one or more types of structural units (B).
In the copolymer, 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, and more preferably 45% by mass or less, and even more preferably 40% by mass or less.

<Structural Unit (C)>
The copolymer contained in the curable resin composition of the present invention is preferably a copolymer 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.
Examples of the monomer capable of introducing a ring structure into the main chain include a monomer having a double bond-containing ring structure in the molecule, a monomer that undergoes cyclopolymerization to form a polymer having a ring structure in the main chain, and a monomer that forms a ring structure after polymerization. From the viewpoint of good 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 because of their even more excellent 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. Among these, dimethyl-2,2'-[oxybis(methylene)]bis-2-propenoate is more preferred from the viewpoints of transparency, dispersibility, ease of industrial availability, and the like.
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 a 2-(hydroxyalkyl)acrylic acid alkyl ester, which can react with (meth)acrylic acid to form a lactone ring structure in the main chain.
Examples of the 2-(hydroxyalkyl)acrylic acid alkyl ester 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 copolymer may have one or more types of structural units (C).
In the 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 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. nyl, 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, 4-(meth)acryloyloxymethyl-2,2-dimethyl-1,3-dioxolane, and the like.
Examples of the monomer having a group that generates an acid group include a compound having a polymerizable double bond and a group that generates an acid group when exposed to heat or an acid. Examples of the group that generates an acid group when exposed to heat or an acid include a tertiary carbon-containing group, a group in which the 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, generating a carboxyl group.
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. A 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 the tertiary carbon-containing monomer 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 such as dihydropyran that can generate a vinyl ether upon ring-opening.
Among the above vinyl ether compounds, dihydropyran is preferred because the protecting group is easily removed at a lower temperature.
The group in which the acid group is blocked with dihydropyran is preferably a group represented by the following formula:

The above-mentioned group in which a phenolic hydroxyl group is protected by a protecting group such as a t-butyl group or an acetyl group is preferably 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 is 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, whereby the protecting group is eliminated and an acid group is generated.
Specific examples of the monomer having a group represented by the above formula include monomers in which the hydroxyl group of an aromatic vinyl compound having a phenolic hydroxyl group, such as p-hydroxystyrene, m-hydroxystyrene, o-hydroxystyrene, p-isopropenylphenol, m-isopropenylphenol, or o-isopropenylphenol, is protected with a t-butyl group or an acetyl group.
Among these, the monomer having a group in which the acid group is blocked with dihydropyran is preferred as the monomer having the group that generates the acid group, since the acid group can 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, 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. Of 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 vinyltoluene, 2-ethylhexyl (meth)acrylate, and dicyclopentanyl (meth)acrylate, in that 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 decreases, thereby improving developability.
The copolymer may have one or more types of structural units (D).
In the 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, and 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. By having a polymerizable double bond in the side chain, the photocurability of the copolymer can be improved. Examples of the polymerizable double bond include those mentioned above, and among them, a (meth)acryloyl group is preferred.
When the copolymer has a polymerizable double bond in a side chain, the double bond equivalent of the copolymer is preferably 200 to 20,000 g/equivalent, 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, in terms of improving curability.
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 determined 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 determined 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 1 g 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 contained in the curable resin composition of the present invention is not particularly limited as long as it is a method that can obtain a copolymer having at least the above-mentioned structural unit (A) and an acid group-containing structural unit (preferably the structural unit (B)) and having an epoxy equivalent within a predetermined range. Examples of the method include a method of polymerizing a monomer component that includes a monomer that can introduce each of the above-mentioned structural units, and a method of polymerizing a monomer component to obtain a base polymer, and then subjecting another compound to an addition reaction with a group that the base polymer has, to obtain 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.
Examples of the polymerization initiator include peroxides and azo compounds that are commonly used as polymerization initiators. Examples of the chain transfer agent include compounds having a mercapto group, such as alkyl mercaptans, mercaptocarboxylic acids, and mercaptocarboxylic acid esters, that are commonly used as chain transfer agents. These may be used alone or in combination of two or more. The amounts of these agents added can be appropriately determined using known methods.
Examples of solvents used in the polymerization include 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.
The polymerization concentration when polymerizing the monomer composition (reaction liquid) containing the above-mentioned monomer components 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 monomers used relative to 100% by mass of the reaction liquid.
Regarding the polymerization conditions, the polymerization temperature may be appropriately set depending on the type and amount of the monomer used, the type and amount of the polymerization initiator, etc., and is, for example, preferably 50 to 130° C., more preferably 60 to 120° C. Similarly, the polymerization time can also be appropriately set and is, for example, preferably 1 to 5 hours, more preferably 2 to 4 hours.
The method for producing the copolymer includes a method of polymerizing a monomer component containing an epoxy group-containing monomer and an acid group-containing monomer. A particularly preferred method for producing a copolymer having an acid group of the structural unit (B) is a method including step (1) of polymerizing a monomer component containing an epoxy group-containing monomer and a hydroxyl group-containing monomer, and step (2) of reacting the polymer obtained in the polymerization step (1) with an acid group-containing compound. By producing the copolymer by such a method, gelation can be suppressed during the production of the copolymer, and a copolymer having the structural unit (A) and the structural unit (B) can be efficiently obtained.
Each step will be explained.
Process (1)
In the method for producing the copolymer, a monomer component containing an epoxy group-containing monomer and a hydroxyl group-containing monomer is polymerized.
Examples of the epoxy group-containing monomer 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 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 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 above-mentioned monomer components.
The method for polymerizing the monomer components is not particularly limited, and the polymerization may be carried out by the above-mentioned known methods. The polymerization temperature and time are also as described above.
In addition, the polymerization may be carried out using a polymerization initiator, a chain transfer agent, a catalyst, a solvent, and the like that are commonly used.
Process (2)
Next, the method includes a step of reacting the polymer obtained in the above step (1) with an acid group-containing compound.
By reacting the polymer (base polymer) obtained in the above step (1) with an acid group-containing compound, the acid group-containing compound is added to the hydroxyl groups of the polymer (base polymer) obtained in 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.
The step of reacting the acid group-containing compound is preferably 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 under lower temperature conditions such as 70° C. Furthermore, since 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, thereby more efficiently producing 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 an acid group-containing compound in the presence of a basic compound at 70° C. or less. In this case, the reaction between the epoxy group and the acid group can be further suppressed, and gelation of the resin can be prevented.
Examples of the acid group-containing compound include the acid group-containing compounds described above.
The basic compound is preferably an amine compound. For example, 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; cycloaliphatic 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 is preferably set appropriately depending on the purpose and application of the copolymer to be obtained so that the content of the structural unit (B) falls within a desired range or so that the acid value of the copolymer falls within a 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, more preferably 50% by mass or more. When the total monomer component concentration is within the above 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. Thus, when the monomer concentration relative to the total amount of polymerization solution of the copolymer is high, the acid group-containing compound can be added without a catalyst, thereby improving the storage stability of the copolymer.
In the above reaction, a catalyst, a solvent, etc. that are commonly used 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 them, the catalyst preferably includes the above-mentioned basic compounds, preferably a secondary amine, a tertiary amine, a heterocyclic amine, or a phosphorus compound, more preferably a tertiary amine or triphenylphosphine.Furthermore, tin compounds such as dibutyltin dichloride, dibutyltin oxide, dibutyltin dibromide, dibutyltin dimaleate, dibutyltin dilaurate, dioctyltin dilaurate, dibutyltin diacetate, dibutyltin sulfide, tributyltin acetate, dioctyltin oxide, or tributyltin chloride, which are generally used as a catalyst for the reaction of an isocyanate monomer with a hydroxyl group, 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 deactivation step of the polymerization initiator or chain transfer agent, a dilution step, a drying step, a concentration step, and a purification step. These steps can be performed by known methods. In the curable resin composition of the present invention, the content of the copolymer is not particularly limited and may be appropriately set depending on the application and the blending of other components. For example, the content of the copolymer 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 solids content of the curable resin composition. Furthermore, the content is preferably 80% by mass or less, more preferably 75% by mass or less, and even more preferably 70% by mass or less. By setting the content within the above range, the crosslinking reaction proceeds well even under low-temperature curing conditions of 160°C or less, and a cured product with excellent solvent resistance can be obtained.
Next, the acid compound having a pKa of 4.2 or less will be described. The curable resin composition of the present invention can be produced by adding a step of adding an acid compound having a pKa of 4.2 or less in addition to the steps of the method for producing the copolymer described above. That is, a method for producing the curable resin composition, which includes the steps of polymerizing a monomer component containing an epoxy group-containing monomer and a hydroxyl group-containing monomer, reacting the polymer obtained in the polymerization step with an acid group-containing compound in the presence of a basic compound, and adding an acid compound having a pKa of 4.2 or less, is also a preferred embodiment of the present invention. The method for producing the curable resin composition preferably further includes the step of adding a protic polar solvent. The protic polar solvent is preferably the solvent described below.

[Acid compounds with pKa of 4.2 or less]
The curable resin composition of the present invention is characterized by containing an acid compound with a pKa of 4.2 or less. The pKa of 4.2 or less is set as a threshold value because the pKa value of the acid group-containing compound that forms the structural unit (B) is used as a threshold value. Specific examples include compounds such as 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 presence of an acid compound with stronger acid strength than the acid compounds that form the copolymer in the resin composition is thought to produce two effects, described below. The first is that the anionicity of the carboxyl groups in the copolymer is reduced, thereby suppressing the reactivity of the acid groups with epoxy groups. The second is that, when a basic compound is present in the resin, the compound with 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 epoxy groups. However, the present invention is not limited to compounds that essentially exhibit these effects. Acid compounds with a pKa of 3 or less are preferred, with those with a pKa of 2 or less being particularly preferred. The lower limit is not particularly limited, but a value of -3 or more is preferred, with a value of 0 or more being particularly preferred. The inclusion of such an acid compound can control the reaction between the acid groups and epoxy groups contained in the copolymer. The acid dissociation constant (pKa) refers to the negative common logarithm (the reciprocal logarithm) of the equilibrium constant Ka in the dissociation reaction in which hydrogen ions are released from an acid, particularly as measured in water at 25°C. For pKa values, see, for example, Chemistry Handbook, Basics II (Revised 5th Edition, Maruzen Co., Ltd.). Values not listed in the literature can be calculated using 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, 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 sulfite, 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, more preferably 350 or less. The lower limit is preferably 150 or more, more preferably 250 or more. Phosphoric acid derivatives are particularly preferred. Phosphoric acid derivatives are preferably phosphate esters or phosphites. When the molecular weight is 400 or less, the resin solid content can be reduced when added, further improving storage stability. Furthermore, the effects of improving the anionicity and reducing the nucleophilic force of the acid groups contained in the copolymer are greater. Furthermore, when the molecular weight is 150 or more, compatibility with the resin composition is further improved.
Preferred examples of the ester group of the phosphate ester include alkyl esters such as methyl, ethyl, octyl, and 2-ethylhexyl, aryl esters such as phenyl, tolyl, and naphthyl, aralkyl esters such as benzyl, and esters having a polymerizable double bond such as 2-acryloyloxyethyl ester and 2-methacryloyloxyethyl ester. These phosphate ester compounds may be used alone or in combination of two or more.
Specific examples of such phosphate esters include 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 triaryl phosphates such as triphenyl phosphate, tricresyl phosphate, tris(nonylphenyl)phosphate, and 2-ethylphenyldiphenyl phosphate.
Among these, when a phosphate ester having a polymerizable double bond is used, it forms a crosslinked structure together with the copolymer, and therefore does not volatilize or elute, and there is a significantly reduced risk of problems such as contamination of a heating furnace or a decrease in the electrical insulation properties of liquid crystals, etc. Therefore, a phosphate ester compound having a polymerizable double bond is preferred as the phosphate ester.

As described above, the acid compound is particularly preferably one having a radically polymerizable unsaturated bond and a phosphate ester group in the molecule (a radically polymerizable unsaturated monomer having a phosphate ester group), and most preferably the monomer has two or more polymerizable unsaturated bonds. Examples of radically polymerizable unsaturated monomers having a phosphate ester group in the molecule include 2-methacryloyloxyethyl acid phosphate.
Other examples include 2-acryloyloxyethyl acid phosphate, 3-methacryloyloxypropyl acid phosphate, methacryloxypolyoxyethylene glycol acid phosphate, methacryloxypolyoxypropylene glycol acid phosphate, etc. These may be used alone or in combination of two or more.
The above-mentioned acid compounds are commercially available under the following trade names. For example, Light Ester P-1M and Light Ester P-2M (both manufactured by Kyoeisha Chemical Co., Ltd.) and Hosmer M (both manufactured by Unichemical Co., Ltd.) are listed. Among them, P-2M is the most preferable.
The content of the acid compound (preferably a phosphate ester compound) having a pKa of 4.2 or less is not particularly limited and may be appropriately set depending on the application, the blending of other components, etc., but is typically preferably 0.01% to 5% by mass, more preferably 0.01% to 3% by mass, and most preferably 0.02% to 2% by mass, relative to 100% by mass of the total solids content excluding the solvent of the curable resin composition. Furthermore, relative to 100 parts by mass of the copolymer, the content of the acid compound having a pKa of 4.2 or less is preferably 0.01 to 10 parts by mass, more preferably 0.05 to 5 parts by mass, and most preferably 0.1 to 3 parts by mass. Furthermore, when a basic compound, as described below, is contained, the content of the acid compound is preferably 50 mol% to 200 mol%, more preferably 70 mol% to 150 mol%, and particularly preferably 80 mol% to 120 mol%, relative to 100 mol% of the basic compound used. That is, by setting the content of the acid compound in the range of 0.5 to 2.0 molar equivalents relative to the basic compound, the effect of improving storage stability is greatly exhibited and coloration is further suppressed.

[Basic Compounds]
The curable resin composition of the present invention preferably further contains a basic compound. The basic compound can further promote the reaction between the epoxy group and the acid group in the copolymer having the epoxy group-containing structural unit (A) represented by the above general formula (1) and the acid group-containing structural unit and having an epoxy equivalent of 10,000 or less. Therefore, even under low-temperature curing conditions of 160°C or less, the crosslinking reaction can proceed well, and a cured product with excellent solvent resistance can be obtained.
The basic compound is preferably an amine compound. For example, 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; cycloaliphatic 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 content of the basic compound (preferably an amine compound) is not particularly limited and may be appropriately set depending on the application, the blending of other components, etc., but is usually preferably 0.01% by mass to 10% by mass, more preferably 0.01% by mass to 6% by mass, and most preferably 0.02% by mass to 4% by mass, relative to 100 parts by mass of the total solids content excluding the solvent of the curable resin composition. 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 most preferably 0.1 to 6 parts by mass, relative to 100 parts by mass of the copolymer.
In addition, when the above-mentioned basic compound used as a catalyst during the synthesis of the above-mentioned copolymer (during the addition reaction) remains in the copolymer solution after the synthesis of the copolymer, the content in the curable resin composition may be adjusted by adding the basic compound according to the remaining amount.

[Protic polar solvents]
The curable resin composition of the present invention preferably further contains a protic polar solvent. That is, the present invention also relates to a curable resin composition (also referred to as a copolymer solution) characterized by containing the above-mentioned copolymer, an acid compound having a pKa of 4.2 or less, a basic compound, and/or a protic polar solvent. The inclusion of a protic polar solvent results in a copolymer solution with superior 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 addition of a protic polar solvent improves the storage stability of the copolymer is not clear, but it is speculated that, particularly in copolymers having long-chain acids, the presence of acid groups such as carboxyl groups at positions distant from the main chain allows the protic polar solvent to relatively easily form 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.
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-based solvent is preferably a secondary alcohol or a tertiary alcohol, in that it can suppress reactivity with epoxy groups and reduce the viscosity of the copolymer solution (curable resin composition).
The number of carbon atoms in the alcohol solvent is preferably 1 to 10, more preferably 2 to 8, and even more preferably 3 to 6, in that the boiling point is relatively low and the solvent can be easily removed by heating.
As the alcohol solvent, propylene glycol monomethyl ether is particularly preferred.
Examples of the amine solvent include diethyleneamine, dimethylamine, and oleylamine.
Examples of the phenolic solvent include phenol, cresol, o-cresol, m-cresol, p-cresol, and xylenol.
The protic polar solvents may be used alone or in combination of two or more.
The boiling point of the protic polar solvent is preferably 70 to 170°C, more preferably 100 to 160°C, and even more preferably 120 to 150°C, in that it is easy to remove by heating, has a certain boiling point, and is easy to form a flat film.
The content of the protic polar solvent in the copolymer solution (curable resin composition) is preferably 10% by mass or more, more preferably 30% by mass, and even more preferably 40% by mass or more, relative to 100% by mass of the total solid content of the curable resin composition. 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 total solid content of the curable resin composition.
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% 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 a polymerization solution containing the copolymer obtained during polymerization with the protic polar solvent, or by adding the protic polar solvent to a polymerization solution containing the copolymer. When the copolymer solution is prepared by adding the protic polar solvent to a polymerization solution containing the copolymer, the copolymer solution may contain the polymerization solvent.

[Photosensitive resin composition]
The above-mentioned curable resin composition, a polymerizable compound, and a photopolymerization initiator can be combined to form a photosensitive resin composition, preferably a negative-tone photosensitive resin composition.
Since the photosensitive resin composition contains the curable resin composition of the present invention, it has good storage stability and can provide a cured product with excellent solvent resistance even under low-temperature curing conditions. Furthermore, when the photosensitive resin composition contains the protic polar solvent, it also has excellent storage stability. Such a photosensitive resin composition is also one of the preferred embodiments of the present invention.
In the photosensitive 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 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.
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 photosensitive resin composition preferably contains the above-mentioned protic polar solvent in order to improve the stability of the composition.
In order to ensure the stability of the photosensitive resin composition, the content of the protic polar solvent in the photosensitive 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 photosensitive resin composition, the content of the protic polar solvent in the photosensitive 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 solid content of the photosensitive 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.
Since the photosensitive resin composition contains the curable resin composition described above, it has good storage stability and 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. Other components are described below.

<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 compound 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 the carboxyl group are chain-extended; unsaturated acid anhydrides; aromatic vinyls; conjugated dienes; vinyl esters; vinyl ethers; N-vinyl compounds; unsaturated isocyanates; and the like. Examples of these include the same compounds as those listed as the monomer components of the copolymer. Furthermore, 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,

a tri- or higher functional (meth)acrylate compound such as a modified product of dipentaerythritol hexaacrylate represented by the formula:
polyfunctional 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;
vinyl ether group-containing (meth)acrylic acid esters 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.
As the polyfunctional polymerizable compound, from the viewpoints of reactivity, economy, availability, etc., preferred are 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 are polyfunctional (meth)acrylate compounds. By including a compound having a (meth)acryloyl group, the photosensitive resin composition has better photosensitivity and curability, and a cured product with even higher hardness and transparency can be obtained. It is even more preferred to use a trifunctional or higher polyfunctional (meth)acrylate compound as the polyfunctional polymerizable compound.
The 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 appropriately set as long as it is within a range in which the effects of the present invention are exhibited. However, in order to allow the photosensitive resin composition to have an appropriate viscosity, the content is preferably 5 to 60 mass %, and more preferably 10 to 50 mass %, relative to 100 mass % of the total solid 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), [1-hydroxy-cyclohexyl-phenyl-ketone + benzophenone] ("IRGACURE 500", manufactured by BASF), and the like; as well as other alkylphenone compounds exemplified in paragraphs [0084] to [0086] of JP 2013-227485 A; 1,2-octabenzophenone; 1,2-Octanedione, 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 as appropriate. For example, the content is preferably 0.3 to 20 mass%, more preferably 0.5 to 10 mass%, and even more preferably 1 to 8 mass%, relative to 100 mass% of the total solid 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 solid 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.
As the coloring material, a pigment or a dye is preferably used. The preferred form and content of the coloring material are as described in [0077] to [0087] of JP-A-2013-61599.
Specifically, the content of the colorant is preferably 3 to 70% by mass, more preferably 5 to 60% by mass, and even more preferably 10 to 50% by mass, relative to 100% by mass of the total solid content of the photosensitive resin composition of the present invention.
The preferred forms and content ratios of the dispersant, heat resistance improver, leveling agent, and development aid are also as described in [0088] to [0097] of the same publication.

<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]
The cured product obtained by curing the curable resin composition or the photosensitive resin composition of the present invention has excellent solvent resistance. Such a cured product also constitutes the present invention.
When the cured product is a cured film, its film thickness is preferably 0.1 μm or more. When the film thickness is 0.1 μm or more, even better solvent resistance can be exhibited. 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 may be set appropriately depending on the purpose and use of the cured film, but is, for example, 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 cured product may be obtained by applying or molding the curable resin composition or photosensitive resin composition described above onto a substrate, and then curing the resulting composition by drying, heating, or irradiating it with energy rays such as ultraviolet rays, or by a combination of these.
The curable resin composition or photosensitive resin composition of the present invention can provide a cured product having excellent solvent resistance even under low-temperature curing conditions. A preferred method for producing such a cured product includes, for example, a step of applying the photosensitive resin composition to a substrate to form a coating film, a step of irradiating the formed coating film with light, and a step of heating the irradiated coating film at 160°C or less.
The substrate is not particularly limited and may be appropriately selected 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 the coating film is irradiated with light, the light irradiation may be carried out through a photomask. As the photomask, a mask having a light-shielding portion formed thereon according to the desired pattern may be used. When the light irradiation is carried out through a photomask, it is preferable to carry out a development step thereafter. 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 a known method, and specifically, 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, more preferably 150° C. or lower. The lower limit of the heating temperature is preferably 70° C. or higher, 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 curable resin composition or photosensitive resin composition of the present invention can provide a cured product with excellent solvent resistance by undergoing a curing reaction sufficiently even under low-temperature curing conditions of 160° C. or less, for example, about 90° C. Therefore, the composition can be suitably used in applications requiring sufficient curing under low-temperature conditions or applications requiring solvent resistance.
The curable resin composition or photosensitive resin composition of the present invention, and cured products obtained therefrom, can be suitably used for, for example, color filters used in liquid crystal, organic EL, quantum dot, and micro LED liquid crystal displays, solid-state imaging devices, touch panel display devices, etc., 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 electrical and electronic devices, etc. Among these, they are preferably used for color filters.
The curable resin composition or photosensitive resin composition of the present invention is suitably used as an optical material, and is also suitably used as a negative type.
[Color filter]
A color filter having a cured product of the above-mentioned photosensitive resin composition on a 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 developing step is not particularly limited as long as it dissolves the photosensitive resin composition, but typically an organic solvent or an alkaline aqueous solution is used, or a mixture thereof 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. The heating temperature is more preferably 80°C or higher, and even more preferably 90°C or higher. The heating time in the heating step is not particularly limited, but is preferably, for example, 5 to 60 minutes. The heating method is also not particularly limited, but can be performed using a heating device such as a hot plate, a convection oven, or a 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, more preferably 0.5 to 15 μm, and even more preferably 1 to 10 μm.

[Display device]
A display device including 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 curable resin composition and photosensitive resin composition of the present invention have good storage stability and can provide a cured product with excellent solvent resistance even under low-temperature curing conditions. The curable resin composition and photosensitive resin composition of the present invention can be suitably used in various applications such as electrical and electronic devices, as various optical members and components used in liquid crystal, organic EL, quantum dot, and micro LED liquid crystal displays, solid-state imaging devices, touch panel display devices, etc.

The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. Unless otherwise specified, "parts" means "parts by mass" and "%" means "% by mass."
[Evaluation method]
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 Resistance 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 listed in Table 5 at 30°C for 5 minutes and then removed. The absorbance of the immersion solvent 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.
(7) 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 (6). 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.
(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.).

The following copolymers were prepared:
(Production Example 1)
Copolymer solution A-1
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 replacing with nitrogen, it was heated 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-1 was obtained. The physical properties of the obtained copolymer are shown in Table 1.
(Production Example 2)
Copolymer solution A-2
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 replacing with nitrogen, it was heated 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 acetate was added so that the solids content became 27%, and copolymer solution A-2 was obtained. The physical properties of the obtained copolymer are shown in Table 1.

The descriptions in Table 1 are as follows:
BzMI: N-benzylmaleimide CHMA: cyclohexyl methacrylate HEMA: 2-hydroxyethyl methacrylate GMA: glycidyl methacrylate SAH: succinic anhydride TEA: triethylamine

The components of the obtained copolymer solution were mixed by the following method to prepare a photosensitive resin composition having the composition shown in Table 2, and the solvent resistance was evaluated by the method described above. The results are shown in Table 2.
(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
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) as a radical polymerizable photopolymerization initiator, 30.0 parts of pigment dispersion 1, 1.0 part of P-2M, and further a dilution solvent (propylene glycol monomethyl ether acetate) were added to a solids concentration of 20%, and the mixture was stirred to obtain photosensitive resin composition 1.
(Example 2, Comparative Examples 1 and 2)
Photosensitive resin compositions 2 to 4 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 4 was evaluated, and the results are shown in Table 2.

Table 2 shows that a photosensitive resin composition containing a copolymer having an epoxy group-containing structural unit and an acid group-containing structural unit and an epoxy equivalent of 10,000 or less and an acid compound having a pKa of 4.2 or less exhibits good curability and gives a cured product with excellent solvent resistance, even when cured at a low temperature of 90°C. The product with P-2M added exhibited solvent resistance that was equal to or better than the product without P-2M. These data show that P-2M functions as a crosslinking agent, resulting in good solvent resistance.
Examples 3 to 13, Comparative Examples 3 to 8
(Storage stability confirmation)
The following procedure was performed to investigate the effects of acid compounds and diluent solvents on storage stability. A copolymer solution was prepared by adding 35 parts of diluent solvent (corresponding to 129.6% by mass relative to 100% by mass of copolymer solids) to 100 parts of copolymer solution A (as is). Further copolymer solutions were prepared by adding P-1M, P-2M, MSA, and ACA in the amounts shown in Tables 3 and 4. The changes in physical properties (viscosity) of the copolymer solutions (Curable Resin Compositions 1 to 17) before and after storage at 40°C for 1 to 2 weeks were examined. The changes in the physical properties of the resulting copolymer solutions are shown in Tables 3 and 4.
The change in viscosity (thickening rate) was expressed as the ratio (%) of the difference in viscosity before and after storage to the viscosity before storage.

P-1M: Light Ester P-1M (Kyoeisha Chemical Co., Ltd.) 2-methacryloyloxyethyl acid phosphate, pKa 1.78, Fw 210.12
P-2M: Light Ester P-2M (Kyoeisha Chemical Co., Ltd.) 2-methacryloyloxyethyl acid phosphate, pKa 1.29, Fw 322.25
MSA: methanesulfonic acid, pKa -2.6 Fw 96.1
ACA: Acetic acid, pKa 4.76 Fw 60.05

Tables 3 and 4 show that when an acid compound with a pKa of 4.2 or less was added, the viscosity change after storage was smaller than when no acid compound was added, and the storage stability of the curable resin composition was superior. Furthermore, copolymer solutions containing added alcohol (protic polar solvents) exhibited superior effects. Furthermore, it was confirmed that when 50 to 200 mol% of the acid compound was added relative to 100 mol% of the basic compound, which is the preferred amount of acid compound, the viscosity change was smaller and the storage stability was superior. On the other hand, even when a compound with a pKa of 4.2 or more (ACA) was added, the viscosity change after storage did not decrease compared to when no acid compound was added. This demonstrates that adding an acid compound with a pKa of 4.2 or less is effective in improving storage stability.

Claims (18)

A curable resin composition comprising, as essential components, a copolymer 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 100 to 4000 , and an acid compound having a pKa of 4.2 or less , wherein the acid compound is a phosphoric acid ester, and the content of the acid compound is 0.01 to 10 parts by mass per 100 parts by mass of the content of the copolymer :
(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 curable resin composition according to claim 1, wherein the molecular weight of the acid compound is 400 or less. The curable resin composition according to claim 1 or 2, wherein the acid compound is a phosphate ester compound having a polymerizable double bond . The curable resin composition according to any one of claims 1 to 3, further comprising a basic compound. The curable resin composition according to claim 4, wherein the basic compound is an amine compound. The curable resin composition according to claim 4 or 5, wherein the content of the acid compound is in the range of 50 to 200 mol % relative to 100 mol % of the basic compound. The curable resin composition according to any one of claims 1 to 6, further comprising a protic polar solvent. The curable resin composition according to any one of claims 1 to 7, wherein the acid group-containing structural unit (B) is represented by the following general formula (2-1):
(In formula (2-1), R ³ represents a hydrogen atom or a methyl group. ⁷ represents a divalent aliphatic hydrocarbon group which may have a substituent. ⁸ represents a divalent hydrocarbon group which may have a substituent; and b represents 0 or 1. 9. The curable resin composition according to claim 1, wherein the copolymer further comprises a structural unit (C) having a ring structure in the main chain. 10. The curable resin composition according to claim 1, wherein the copolymer contains the structural unit (A) in an amount of 1 to 45 % by mass relative to 100% by mass of all structural units, and the structural unit (B) in an amount of 1 to 45% by mass relative to 100% by mass of all structural units. 11. The curable resin composition according to claim 9 , wherein the content of the structural unit (C) in the copolymer is 0.1 to 40% by mass relative to 100% by mass of all structural units. The curable resin composition according to any one of claims 9 to 11 , wherein the copolymer has another structural unit (D), and the content of the structural unit (D) is 0.1 to 40 mass% relative to 100 mass% of all structural units. A photosensitive resin composition comprising the curable resin composition according to any one of claims 1 to 12 , a polymerizable compound, and a photopolymerization initiator. The photosensitive resin composition according to claim 13 , further comprising a colorant. The photosensitive resin composition according to claim 13 or 14, which is for negative use. A cured product obtained by curing the curable resin composition according to any one of claims 1 to 12 or the photosensitive resin composition according to any one of claims 13 to 15 . A method for producing the curable resin composition according to any one of claims 1 to 12 , comprising:
A step of polymerizing a monomer component including an epoxy group-containing monomer and a hydroxyl group-containing monomer;
A method for producing a curable resin composition, comprising the steps of: reacting the polymer obtained in the polymerization step with an acid group-containing compound in the presence of a basic compound; and adding an acid compound having a pKa of 4.2 or less. The method for producing a curable resin composition according to claim 17 , further comprising the step of adding a protic polar solvent.