CN116529268A

CN116529268A - Copolymer and method for producing the same

Info

Publication number: CN116529268A
Application number: CN202180081988.7A
Authority: CN
Inventors: 井田英理; 木下健宏; 柳正义
Original assignee: Lishennoco Co ltd
Current assignee: Lishennoco Co ltd
Priority date: 2020-12-24
Filing date: 2021-12-08
Publication date: 2023-08-01
Also published as: KR20230096058A; JPWO2022138173A1; WO2022138173A1; TW202237675A

Abstract

A copolymer comprising a structural unit (a) having a blocked isocyanate group blocked with a pyrazole compound, a structural unit (b) having a hydroxyl group, and a structural unit (c) having an acid group, and having a glass transition temperature of 30 ℃ or lower.

Description

Copolymer and method for producing the same

Technical Field

The invention relates to a copolymer, a resin composition, a color filter, an image display element and a method for manufacturing the copolymer.

The present application claims priority based on japanese patent application No. 2020-215474 at 12/24/2020, the contents of which are incorporated herein.

Background

In general, in an organic Electroluminescence (EL) display device (particularly, WRGB system in which white light emitting organic EL is combined with a color filter), an image display element such as a liquid crystal display element, an integrated circuit element, or a solid-state image pickup element, a film such as a color filter, a black matrix, a color filter protective film, a photo spacer, a projection for liquid crystal alignment, a microlens, or an insulating film for a touch panel, and a fine pattern are provided.

In recent years, with the flexibility and wear of displays, the substrate material has been changed from glass to organic materials such as resin. The organic material has lower heat resistance than glass. Therefore, in a member formed by thermally curing a resin composition on a substrate, it is desirable to reduce the temperature at which the resin composition is thermally cured, depending on the heat resistance of the substrate formed of an organic material.

For example, the color filter has been conventionally formed by thermally curing a resin composition on a substrate at a temperature of 210 to 230 ℃. However, in the case of forming a color filter on a flexible substrate formed of a resin, the substrate is required to be formed by thermally curing the resin composition at a temperature of 80 to 150 ℃.

In particular, in a color filter used in an organic EL display device, the content of a colorant contained in a resin composition tends to be large in order to improve color reproducibility. In general, a resin composition containing a large amount of a colorant is not easily photo-curable. Therefore, it is more important for the resin composition used for the color filter of the organic EL display device to be cured by crosslinking by heat. Therefore, the resin composition used for the color filter of the organic EL display device is in particular required to have an improved thermosetting property at low temperatures.

Conventionally, as a resin composition used as a material of a color filter, there are, for example, those described in patent document 1 and patent document 2.

Patent document 1 discloses that (a) methanol has an absorbance at 365nm of 1.0X10 ³ A polymerization initiator having a mL/gcm or more, and (b) an absorbance at 365nm in methanol of 1.0X10 ² Absorption coefficient of 254nm under mL/gcmIs 1.0X10 ³ A polymerization initiator having a ratio of mL/gcm or more, (c) a compound having an unsaturated double bond, (d) an alkali-soluble resin, and (e) a coloring material.

Patent document 2 discloses a photosensitive composition for a color filter, which contains a compound (a) containing a furyl group, a compound (B) containing a photopolymerizable functional group, a photopolymerization initiator (C), and a colorant.

Prior art literature

Patent literature

Patent document 1: japanese patent application laid-open No. 2015-0410258

Patent document 2: japanese patent laid-open No. 2017-194662

Disclosure of Invention

Problems to be solved by the invention

However, the conventional resin composition is not excellent in developability and storage stability when used as a photosensitive material, and is cured at a low temperature to obtain a cured product excellent in solvent resistance.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a resin composition which has good developability when used as a photosensitive material and is excellent in storage stability, and which gives a cured product having excellent solvent resistance even when cured at a low temperature, a copolymer useful for the preparation of the resin composition, and a method for producing the copolymer.

Further, an object of the present invention is to provide a color filter having a colored pattern formed of a cured product of a resin composition which is excellent in solvent resistance even when cured at a low temperature, and an image display element having the color filter.

Means for solving the problems

A first aspect of the present invention provides the following copolymer. [1] A copolymer comprising:

a structural unit (a) having a blocked isocyanate group blocked with a pyrazole compound;

a structural unit (b) having a hydroxyl group; and

a structural unit (c) having an acid group,

and the glass transition temperature is 30 ℃ or lower.

The copolymer of the first aspect of the present invention preferably has the features described in the following [2] to [6 ]. The features described in the following [2] to [6] are also preferably combined in any combination of 2 or more. [2] The copolymer according to [1], wherein the structural unit (b) is a structural unit derived from a hydroxyalkyl (meth) acrylate.

[3] The copolymer according to [1] or [2], wherein the structural unit (c) is a structural unit derived from an unsaturated carboxylic acid.

[4] The copolymer according to any one of [1] to [3], wherein the structural unit (a) is a structural unit derived from a compound having the blocked isocyanate group and a (meth) acryloyloxy group.

[5] The copolymer according to any one of [1] to [4], which contains 1 to 45 mol% of the structural unit (a), 1 to 50 mol% of the structural unit (b), and 1 to 60 mol% of the structural unit (c).

[6] The copolymer according to any one of [1] to [5], which has a weight average molecular weight of 1000 to 50000.

The second aspect of the present invention provides the following resin composition.

[7] A resin composition comprising the copolymer (A) of any one of [1] to [6], and a solvent (B), wherein the solvent (B) contains a hydroxyl group-containing solvent.

The second aspect of the present invention preferably has the following features [8] to [10 ]. These features are also preferably used in combination.

[8] The resin composition according to [7], which further contains a reactive diluent (C) and a photopolymerization initiator (D).

[9] The resin composition according to [8], which further contains a colorant (E).

[10] The resin composition according to [9], which comprises, relative to 100 parts by mass of the total amount of the copolymer (A) and the reactive diluent (C)

10 to 90 parts by mass of the copolymer (A),

30 to 1000 parts by mass of the solvent (B),

10 to 90 parts by mass of the reactive diluent (C),

0.1 to 30 parts by mass of the photopolymerization initiator (D),

3 to 80 parts by mass of the colorant (E).

A third aspect of the present invention provides the following color filter.

[11] A color filter comprising a colored pattern comprising a cured product of the resin composition according to [9] or [10 ].

A fourth aspect of the present invention provides the following image display element.

[12] An image display element comprising the color filter according to [11 ].

A fifth aspect of the present invention provides a method for producing the following copolymer.

[13] A method for producing a copolymer, characterized by comprising the steps of:

a solvent heating step (I) of heating the solvent (B-1) to 60-90 ℃;

a step (II) of dropwise adding a monomer (m-a) having a blocked isocyanate group blocked with a pyrazole compound, a monomer (m-B) having a hydroxyl group, and a monomer (m-c) having an acid group to the solvent (B-1) having been heated, and simultaneously dropwise adding a polymerization initiator solution obtained by dissolving a polymerization initiator in the solvent (B-2) to the solvent (B-1) to prepare a mixed solution; and

a post-polymerization step (III) in which the mixed solution is reacted at 60 to 90 ℃ for 1 to 5 hours while being stirred,

either or both of the solvent (B-1) and the solvent (B-2) contains a hydroxyl group-containing solvent.

The fifth aspect of the present invention preferably also has the following features [14], [15 ].

[14] The method of producing a copolymer according to [13], wherein in the solvent heating step (I), a chain transfer agent is added to the solvent (B-1) and then the temperature is raised.

[15] The method of producing a copolymer according to [13], wherein the post-polymerization step (III) is performed to obtain a copolymer having a glass transition temperature of 30℃or lower, wherein the copolymer contains a structural unit (a) having a blocked isocyanate group blocked with a pyrazole compound, a structural unit (b) having a hydroxyl group, and a structural unit (c) having an acid group.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, there can be provided a resin composition which has good alkali developability when used as a photosensitive material and excellent storage stability, and which can give a cured product having excellent solvent resistance even when cured at a low temperature, a copolymer useful for the preparation of the resin composition, and a method for producing the copolymer.

Further, according to the present invention, a color filter having a colored pattern formed of a cured product of a resin composition which is excellent in alkali developability and which is cured at a low temperature to obtain a cured product excellent in solvent resistance, and an image display element having the color filter can be provided.

Detailed Description

Hereinafter, the copolymer, the method for producing the copolymer, the resin composition, the color filter, and the image display device according to the present invention will be described in detail. However, the present invention is not limited to the embodiments shown below. For example, the present invention is not limited to the following examples, and can be added, omitted, substituted, or altered in number, amount, ratio, composition, kind, position, material, composition, or the like without departing from the scope of the present invention.

In the present specification, the substance expressed as (meth) acrylate means either acrylate or methacrylate. Further, the substance expressed as (meth) acrylic acid means any one of acrylic acid and methacrylic acid.

Copolymer (A) >, copolymer (A)

The copolymer (a) of the present embodiment contains a structural unit (a) (hereinafter, also simply referred to as "structural unit (a)") having a blocked isocyanate group blocked with a pyrazole compound, a structural unit (b) (hereinafter, also simply referred to as "structural unit (b)") having a hydroxyl group, and a structural unit (c) (hereinafter, also simply referred to as "structural unit (c)") having an acid group.

Structure unit (a) >)

The structural unit (a) is a structural unit derived from a monomer (m-a) (hereinafter, also simply referred to as "monomer (m-a)") having a blocked isocyanate group blocked with a pyrazole compound. The blocked isocyanate group of the structural unit (a) included in the copolymer (a) is deblocked by thermally curing the resin composition containing the copolymer (a) to generate an isocyanate group, and the isocyanate group reacts with the hydroxyl group of the structural unit (b) to generate a crosslinked structure. Accordingly, the resin composition containing the copolymer (A) can be cured at a low temperature of 50 to 150℃to obtain a cured film excellent in solvent resistance.

As the pyrazole compound as a blocking agent for blocking isocyanate groups, there can be mentioned pyrazoles; alkylpyrazoles such as 3-methylpyrazole and 5-ethylpyrazole; dialkyl pyrazoles such as 3, 5-dimethylpyrazole and 3, 5-diethylpyrazole; 3-acetamidopyrazole, pyrazole-3, 5-dicarboxylic acid diethyl ester, and the like. Among them, from the viewpoints of low-temperature curability as a resin composition and easiness in obtaining raw materials, dialkylpyrazoles are preferable, and 3, 5-dimethylpyrazole is more preferable.

The monomer (m-a) providing the structural unit (a) is not particularly limited as long as it is a compound copolymerizable with the hydroxyl group-containing monomer (m-b) and the acid group-containing monomer (m-c) described later. As the monomer (m-a), for example, a monomer having a blocked isocyanate group and an ethylenically unsaturated bond can be used from the viewpoint of reactivity in synthesizing the copolymer (a). Examples of the group having an ethylenically unsaturated bond include a vinyl group and a (meth) acryloyloxy group.

Examples of the monomer (m-a) having a blocked isocyanate group and an ethylenically unsaturated bond include an isocyanate compound having an ethylenically unsaturated group and a reactant with a pyrazole compound.

These monomers (m-a) may be used alone or in combination of 2 or more.

The isocyanate compound used for the formation of the monomer (m-a) or the ethylenically unsaturated group-containing isocyanate compound contained in the monomer (m-a) is preferably a compound represented by the following formula (1).

(in formula (1), R ⁴ Represents a hydrogen atom or a methyl group; r is R ⁵ represents-CO-, -COOR ⁶ - (here, R) ⁶ Is an alkylene group having 1 to 6 carbon atoms. ) or-COO-R ⁷ O-CONH-R ⁸ - (here, R) ⁷ Is an alkylene group having 2 to 6 carbon atoms; r is R ⁸ Is an alkylene group having 2 to 12 carbon atoms or an arylene group having 6 to 12 carbon atoms which may have a substituent. ). )

As described above, R in formula (1) ⁴ Represents a hydrogen atom or a methyl group.

R in formula (1) ⁵ represents-CO-, -COOR ⁶ -or-COO-R ⁷ O-CONH-R ⁸ -. Here, R is ⁶ Is an alkylene group having 1 to 6 carbon atoms. For example, the number of carbon atoms may be 2 to 5 or 3 to 4.R is R ⁷ Is an alkylene group having 2 to 6 carbon atoms. For example, the number of carbon atoms may be 2 to 5 or 3 to 4. In addition, R ⁸ Is an alkylene group having 2 to 12 carbon atoms or an arylene group having 6 to 12 carbon atoms which may have a substituent. For example, the number of carbon atoms of the alkylene group may be 3 to 10 or 4 to 8. The number of carbon atoms of the arylene group may be 7 to 10 or 8 to 9. Among them, R in formula (1) ⁵ preferably-COOR ⁶ -. At R ⁵ is-COOR ⁶ In the case of R ⁶ An alkylene group having 1 to 4 carbon atoms is preferable.

Specific examples of the ethylenically unsaturated group-containing isocyanate compound represented by the above formula (1) include 2-isocyanatoethyl (meth) acrylate, 2-isocyanatopropyl (meth) acrylate, 3-isocyanatopropyl (meth) acrylate, 2-isocyanato1-methylethyl (meth) acrylate, 2-isocyanato1, 1-dimethylethyl (meth) acrylate, 4-isocyanatocyclohexyl (meth) acrylate, and (meth) acryloylacrylate.

As the ethylenically unsaturated group-containing isocyanate compound represented by the above formula (1), an equimolar (1 mol: 1 mol) reaction product of a 2-hydroxyalkyl (meth) acrylate and a diisocyanate compound may be used. The alkyl group contained in the 2-hydroxyalkyl (meth) acrylate is preferably an ethyl group or an n-propyl group, and more preferably an ethyl group. Examples of the diisocyanate compound include 1, 6-hexamethylene diisocyanate, 2,4- (or 2, 6-) Toluene Diisocyanate (TDI), 4' -diphenylmethane diisocyanate (MDI), 3, 5-trimethyl-3-isocyanatomethylcyclohexyl isocyanate (IPDI), m- (or p-) xylylene diisocyanate, 1,3- (or 1, 4-) bis (isocyanatomethyl) cyclohexane, and lysine diisocyanate.

Among these ethylenically unsaturated group-containing isocyanate compounds, 2-isocyanatoethyl (meth) acrylate, 2-isocyanatopropyl (meth) acrylate, 3-isocyanatopropyl (meth) acrylate, 2-isocyanato1-methylethyl (meth) acrylate, 2-isocyanato1, 1-dimethylethyl (meth) acrylate, 4-isocyanatocyclohexyl (meth) acrylate and (meth) acryloylacrylate are preferred, and 2-isocyanatoethyl (meth) acrylate and 2-isocyanatopropyl (meth) acrylate are more preferred. These ethylenically unsaturated group-containing isocyanate compounds may be used alone or in combination of 2 or more.

The reaction of the ethylenically unsaturated group-containing isocyanate compound with the pyrazole compound may be carried out regardless of the presence or absence of a solvent. In the case of performing the above reaction using a solvent, a solvent inactive to isocyanate groups is used. In the above reaction, as the catalyst, an organic metal salt of tin, zinc, lead or the like, a tertiary amine or the like can be used.

The above reaction is generally carried out at a temperature of-20 to 150℃and preferably at a temperature of 25 to 130 ℃. If the temperature of the reaction is-20 ℃ or higher, a sufficient reaction rate is obtained. Further, if the temperature of the above reaction is 150 ℃ or less, gelation of the monomer (m-a) providing the structural unit (a) generated after the reaction due to polymerization of the raw material having c=c (double bond) can be prevented.

Examples of the reactant of the ethylenically unsaturated group-containing isocyanate compound and the pyrazole compound include 2- [ (3, 5-dimethylpyrazolyl) carbonylamino ] ethyl methacrylate, 2- [ (3-methylpyrazolyl) carbonylamino ] ethyl methacrylate, and the like. Among them, 2- [ (3, 5-dimethylpyrazolyl) carbonylamino ] ethyl methacrylate is preferred in order that the resin composition containing the copolymer (A) can be easily obtained and cured to obtain a cured product excellent in solvent resistance.

Structural unit (b) having hydroxyl group

The structural unit (b) having a hydroxyl group contained in the copolymer (a) does not have a blocked isocyanate group, but has a hydroxyl group. The structural unit (b) is a structural unit derived from a monomer (m-b) having a hydroxyl group (hereinafter, also simply referred to as "monomer (m-b)") (except for the substances corresponding to the structural unit (a) described above). The hydroxyl group of the structural unit (b) contained in the copolymer (a) reacts with an isocyanate group generated by deblocking the blocked isocyanate group of the structural unit (a) by thermosetting the resin composition containing the copolymer (a), to generate a crosslinked structure.

The monomer (m-b) providing the structural unit (b) is not particularly limited as long as it is a monomer having no blocked isocyanate group but having a polymerizable unsaturated bond and a hydroxyl group. Examples of the monomer (m-b) include (meth) acrylate derivatives having a hydroxyl group. Examples of such a monomer (m-b) include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 2, 3-dihydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, and 2-hydroxy-3-phenoxypropyl (meth) acrylate. These monomers (m-b) may be used alone or in combination of 2 or more.

Among the monomers (m-b), hydroxyalkyl (meth) acrylates are preferable from the viewpoints of reactivity in synthesizing the copolymer (a), low-temperature curability of the resin composition containing the copolymer (a), and easiness of obtaining. As examples of the hydroxyalkyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, and 4-hydroxybutyl (meth) acrylate are preferable, and 2-hydroxyethyl (meth) acrylate, and 4-hydroxybutyl (meth) acrylate are more preferable from the viewpoints of easiness of obtaining and lowering of the glass transition temperature of the copolymer (a).

Structural unit (c) having an acid group

The structural unit (c) having an acid group contained in the copolymer (a) does not have a blocked isocyanate group and a hydroxyl group, but has an acid group. The structural unit (c) is a structural unit derived from a monomer (m-c) having an acid group (hereinafter, also simply referred to as "monomer (m-c)") (except for the substances corresponding to the structural unit (a) and the structural unit (b)). By including the structural unit (c) in the copolymer (a), alkali development is improved in the case of using a resin composition containing the copolymer (a) as a photosensitive material.

Examples of the acid group contained in the structural unit (c) include a carboxyl group, a sulfo group, a phosphono group, and the like. Among these acid groups, a carboxyl group is preferable as the acid group of the structural unit (c) in view of ease of obtaining.

The monomer (m-c) providing the structural unit (c) is not particularly limited as long as it is a monomer having no blocked isocyanate group and hydroxyl group, but having a polymerizable unsaturated bond and an acid group. Examples of the monomer (m-c) include unsaturated carboxylic acids or anhydrides thereof, unsaturated sulfonic acids, unsaturated phosphonic acids, and the like.

Examples of the monomer (m-c) include unsaturated carboxylic acids or anhydrides thereof such as (meth) acrylic acid, α -bromo (meth) acrylic acid, β -furyl (meth) acrylic acid, crotonic acid, propiolic acid, cinnamic acid, α -cyano cinnamic acid, maleic anhydride, monomethyl maleate, monoethyl maleate, monoisopropyl maleate, fumaric acid, itaconic anhydride, citraconic acid, citraconic anhydride, and the like; unsaturated sulfonic acids such as 2-acrylamide-2-methylpropanesulfonic acid, t-butylacrylamide sulfonic acid, and p-styrenesulfonic acid; unsaturated phosphonic acids such as vinylphosphonic acid; etc. These monomers (m-c) may be used alone or in combination of 2 or more.

Among these monomers, in order to be easily available, and the resin composition containing the copolymer (a) has excellent alkali developability, it is preferable to use an unsaturated carboxylic acid, and it is more preferable to use (meth) acrylic acid.

Here, the proportions of the structural unit (a), the structural unit (b), and the structural unit (c) contained in the copolymer (a) will be described.

The proportion of the structural unit (a) contained in the copolymer (a) is not particularly limited, but is preferably 1 to 45 mol%, more preferably 5 to 40 mol%, and most preferably 15 to 35 mol%. If necessary, it may be 18 to 33 mol%, 20 to 30 mol%, 25 to 28 mol%, etc.

The proportion of the structural unit (b) contained in the copolymer (a) is not particularly limited, but is preferably 1 to 50 mol%, more preferably 5 to 45 mol%, and most preferably 10 to 35 mol%. If necessary, it may be 15 to 40 mol%, 18 to 33 mol%, 20 to 30 mol%, 22 to 25 mol%, etc.

The proportion of the structural unit (c) contained in the copolymer (a) is not particularly limited, but is preferably 1 to 60 mol%, more preferably 5 to 50 mol%, and most preferably 10 to 40 mol%. If necessary, it may be 13 to 35 mol%, 15 to 30 mol%, 20 to 28 mol%, 22 to 25 mol%, etc.

Accordingly, the copolymer (A) preferably contains 1 to 45 mol% of the structural unit (a), 1 to 50 mol% of the structural unit (b), and 1 to 60 mol% of the structural unit (c).

In the copolymer (a) of the present embodiment, if the ratio of the structural unit (a) to the structural unit (b) is 1 mol% or more, the hydroxyl group of the structural unit (b) and the isocyanate group generated by deblocking the blocked isocyanate group of the structural unit (a) react sufficiently to generate a crosslinked structure by thermally curing the resin composition containing the copolymer (a). Accordingly, a resin composition containing a copolymer (a) containing 1 mol% or more of the structural unit (a) and the structural unit (b), respectively, gives a cured product having good solvent resistance even when thermally cured at a low temperature.

If the proportion of the structural unit (a) in the copolymer (a) is 45 mol% or less, the storage stability of the resin composition containing the copolymer (a) becomes more excellent. Further, if the proportion of the structural unit (a) is 45 mol% or less, it is easy to ensure the contents of the structural unit (b) and the structural unit (c). Therefore, the effect due to the inclusion of the structural unit (b) and the structural unit (c) is easily obtained.

Further, if the proportion of the structural unit (b) in the copolymer (a) is 50 mol% or less, gelation at the time of polymerization reaction for producing the copolymer (a) can be prevented. In addition, the crosslinked structure obtained by the reaction of the blocked isocyanate group of the structural unit (a) and the structural unit (b) is not excessively formed, and the storage stability of the resin composition containing the copolymer (a) is further improved. Further, if the proportion of the structural unit (b) is 50 mol% or less, it is easy to ensure the contents of the structural unit (a) and the structural unit (c). Therefore, the effect due to the inclusion of the structural unit (a) and the structural unit (c) is easily obtained.

If the proportion of the structural unit (c) in the copolymer (a) is 1 mol% or more, the resin composition containing the copolymer (a) has an alkali development rate of a sufficient rate. If the proportion of the structural unit (c) in the copolymer (a) is 60 mol% or less, the alkali development rate of the resin composition containing the copolymer (a) is moderately suppressed, and thus a fine pattern is easily formed. Further, if the proportion of the structural unit (c) in the copolymer (a) is 60 mol% or less, the content of the structural unit (a) and the structural unit (b) is easily ensured. Therefore, even when the resin composition containing the copolymer (a) is cured at a low temperature, a cured product having more excellent solvent resistance can be easily obtained.

The total amount of the content of the structural unit (a) and the content of the structural unit (b) contained in the copolymer (a) is preferably 10 to 90 mol%, more preferably 20 to 80 mol%, and still more preferably 30 to 70 mol%. If necessary, the amount may be 35 to 65 mol%, 40 to 60 mol%, 45 to 55 mol%, or the like. If the total amount of the content of the structural unit (a) and the content of the structural unit (b) is 10 to 90 mol%, the storage stability of the resin composition containing the copolymer (a) is more excellent, and a cured product excellent in solvent resistance is obtained even when it is cured at a low temperature. Further, since the content of the structural unit (c) is easily ensured, a resin composition having more excellent alkali developability when used as a photosensitive material is easily obtained.

In the case where the resin composition containing the copolymer (a) contains a compound having a hydroxyl group as the reactive diluent (C) in addition to the copolymer (a), the total amount of hydroxyl groups contained in the structural unit (b) contained in the copolymer (a) is preferably reduced according to the amount of hydroxyl groups contained in the reactive diluent (C).

Specifically, the molar ratio of the total amount of blocked isocyanate groups of the structural unit (a) to the total amount of hydroxyl groups contained in the resin composition (the sum of hydroxyl groups of the structural unit (b) and hydroxyl groups of the reactive diluent (C)) is preferably 10: 90-90: 10, more preferably 30: 70-70: 30, more preferably 40: 60-60: 40. when the molar ratio is within the above range, the resin composition containing the copolymer (a) is thermally cured, whereby a crosslinked structure obtained by the reaction of the hydroxyl groups contained in the resin composition and the isocyanate groups generated by deblocking of the blocked isocyanate groups contained in the structural unit (a) is easily generated. Thus, a cured product having more excellent solvent resistance is obtained.

< other structural units (d) >)

The copolymer (a) of the present embodiment may contain other structural units (d) copolymerizable with the structural units (a) to (c) as required (excluding the structural units corresponding to the structural units (a) to (c)).

The monomer (m-d) (hereinafter, also simply referred to as "monomer (m-d)") providing the other structural unit (d) is not particularly limited as long as it is a compound that does not have a blocked isocyanate group, hydroxyl group, or acid group and is copolymerizable with the monomers (m-a) to (m-c).

Specific examples of the monomer (m-d) providing the other structural unit (d) include styrene, alpha-methylstyrene, o-vinyltoluene, p-vinyltolueneAromatic vinyl compounds such as benzene, o-chlorostyrene, m-chlorostyrene, methoxystyrene, p-nitrostyrene, p-cyanostyrene, and p-acetamidostyrene; norbornene (bicyclo [ 2.2.1)]Hept-2-ene), 5-methylbicyclo [2.2.1]Hept-2-ene, tetracyclo [4.4.0.1 ] ^2,5 .1 ^7,10 ]Dodec-3-ene, 8-ethyltetracyclo [4.4.0.1 ] ² ^,5 .1 ^7,10 ]Dodec-3-ene, dicyclopentadiene, tricyclo [5.2.1.0 ^2,6 ]Dec-8-ene, tricyclo [4.4.0.1 ] ^2,5 ]Undec-3-ene, tricyclo [6.2.1.0 ] ^1,8 ]Undec-9-ene, tetracyclo [4.4.0.1 ] ^2,5 .1 ^7,10 .0 ^1,6 ]Dodec-3-ene, 8-ethylenetetracyclo [4.4.0.1 ] ^2,5 .1 ^7,12 ]Dodec-3-ene, pentacyclic [6.5.1.1 ] ^3,6 .0 ^2,7 .0 ^9,13 ]Cyclic olefins having a norbornene structure such as pentadec-4-ene; dienes such as butadiene, isoprene and chloroprene; methyl (meth) acrylate, ethyl (meth) acrylate, isopropyl (meth) acrylate, t-butyl (meth) acrylate, pentyl (meth) acrylate, benzyl (meth) acrylate, isopentyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate, dodecyl (meth) acrylate, cyclohexyl (meth) acrylate, methylcyclohexyl (meth) acrylate, rosin (meth) acrylate, norbornyl (meth) acrylate, 5-ethylnorbornyl (meth) acrylate, dicyclopentenyl (meth) acrylate, dicyclopentadienyloxy ethyl acrylate, isobornyl (meth) acrylate, adamantyl (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, 1-trifluoroethyl (meth) acrylate, perfluoroethyl (meth) acrylate, perfluoro-N-propyl (meth) acrylate, 3- (N), N-dimethylamino) propyl (meth) acrylate, triphenylmethyl (meth) acrylate, phenyl (meth) acrylate, cumyl (meth) acrylate, 4-phenoxyphenyl (meth) acrylate, phenoxyethyl (meth) acrylate, phenoxy polyethylene glycol (meth) acrylate, nonylphenoxy polyethylene glycol mono (meth) acrylate, diphenoxyethyl (meth) acrylate, naphthalene (meth) acrylate, anthracene (meth) ) (meth) acrylates such as acrylic acid esters and ethoxylated phenyl (meth) acrylic acid esters; (meth) acrylic acid amides such as (meth) acrylic acid amide, N-dimethylamide (meth) acrylic acid, N-di-isopropylamide (meth) acrylic acid, and anthrylamide (meth) acrylic acid; vinyl compounds such as anilide (meth) acrylate, acrylonitrile, acrolein, vinyl chloride, 1-dichloroethylene, vinyl fluoride, 1-difluoroethylene, vinyl pyrrolidone, vinyl pyridine, vinyl acetate, and vinyl toluene; unsaturated dicarboxylic acid diesters such as diethyl citraconate, diethyl maleate, diethyl fumarate and diethyl itaconate; mono-maleimides such as N-phenylmaleimide, N-cyclohexylmaleimide, N-laurylmaleimide, and N- (4-hydroxyphenyl) maleimide; glycidyl (meth) acrylate, and the like.

Among them, the (meth) acrylic acid ester is preferably used as the monomer (m-d), and from the viewpoint of adjusting the glass transition temperature of the copolymer (A) to 30℃or lower, it is preferable that the glass transition temperature of the homopolymer is-20℃or lower, and 2-ethylhexyl (meth) acrylate and 4-hydroxybutyl acrylate are particularly preferably used. These monomers (m-d) may be used alone or in combination of 2 or more.

When the copolymer (A) contains other structural units (d), the proportion is not particularly limited, but is preferably 1 to 80 mol%, more preferably 5 to 75 mol%, and most preferably 10 to 50 mol%. If necessary, the amount may be 3 to 45 mol%, 5 to 40 mol%, 10 to 35 mol%, 15 to 30 mol%, or 12 to 25 mol%. The solvent resistance and other properties of the cured product of the resin composition containing the copolymer (a) can be suitably improved by the copolymer (a) containing other structural units (d). If the content of the other structural unit (d) is 80 mol% or less, the content of the structural units (a) to (c) can be easily ensured, and the effect due to the inclusion of the structural units (a) to (c) becomes remarkable.

(weight average molecular weight (Mw))

The polystyrene-equivalent weight average molecular weight of the copolymer (a) is not particularly limited, but is preferably 1,000 to 50,000, more preferably 3,000 to 40,000. If necessary, it may be 5,000 to 20,000, 7,000 to 15,000, 9,000 to 12,000, etc. If the weight average molecular weight of the copolymer (a) is 1,000 or more, alkali development becomes good when the resin composition containing the copolymer (a) is used as a photosensitive material, and pattern deletion after alkali development is less likely to occur. On the other hand, if the weight average molecular weight of the copolymer (a) is 50,000 or less, the development time in the case of using a resin composition containing the copolymer (a) as a photosensitive material becomes appropriate, and the practicality is ensured.

(glass transition temperature (Tg))

The glass transition temperature (Tg) of the copolymer (A) is 30℃or lower, preferably 20℃or lower, and more preferably 0℃or lower. If the glass transition temperature of the copolymer (A) exceeds 30 ℃, the curability at low temperature is adversely affected. Therefore, the glass transition temperature of the copolymer (A) is set to 30℃or lower. The glass transition temperature of the copolymer (A) is preferably-50℃or higher, more preferably-40℃or higher, and still more preferably-30℃or higher. If the glass transition temperature of the copolymer (A) is-50℃or higher, the resin composition containing the copolymer (A) gives a cured film excellent in heat resistance. The glass transition temperature may be-45℃or more and 25℃or less, or may be-35℃or more and 15℃or less, or may be-25℃or more and 10℃or less, or may be-15℃or more and 5℃or less, as required.

(acid value)

The acid value (JIS K6901 5.3) of the copolymer (A) can be appropriately selected. When the resin composition containing the copolymer (A) is used as the photosensitive material, the acid value of the copolymer (A) is preferably 20 to 300KOHmg/g, more preferably 30 to 200KOHmg/g. According to the need, the concentration may be 40 to 150KOHmg/g, 50 to 100KOHmg/g, etc. If the acid value of the copolymer (A) is 20KOHmg/g or more, the alkali development becomes good when the resin composition containing the copolymer (A) is used as a photosensitive material. On the other hand, if the acid value of the copolymer (A) is 300KOHmg/g or less, the pattern shape becomes good because the exposed portion (photo-cured portion) is less likely to be dissolved with respect to the alkaline developer when the resin composition containing the copolymer (A) is used as the photosensitive material.

(equivalent number of blocked isocyanate group)

The copolymer (A) contains a blocked isocyanate group blocked with a pyrazole compound in the molecule. The equivalent number of blocked isocyanate groups is appropriately selected, but is preferably 300 to 6000, more preferably 500 to 3500. And can be 400-2000 and 600-1000 according to the requirement. When the number of equivalents of blocked isocyanate groups is 300 or more, if the hydroxyl groups are sufficiently present in the resin composition containing the copolymer (a), the resin composition is thermally cured to sufficiently form a crosslinked structure obtained by the reaction of the hydroxyl groups in the resin composition with isocyanate groups generated by deblocking of the blocked isocyanate groups of the structural unit (a). Thus, a cured product having more excellent solvent resistance is obtained.

The equivalent number of blocked isocyanate groups in the copolymer (A) is the mass of the copolymer (A) per 1 mol of blocked isocyanate groups contained in the copolymer (A). The equivalent number of the blocked isocyanate groups is determined by dividing the mass of the copolymer (A) by the number of moles of the blocked isocyanate groups contained in the copolymer (A). The equivalent number of the blocked isocyanate groups is a theoretical value calculated from the addition amount of the monomer (m-a).

Process for producing copolymer (A)

The copolymer (a) of the present embodiment can be produced, for example, by a method in which the solvent heating step (I), the dropping polymerization step (II), and the post-polymerization step (III) shown below are sequentially performed.

(solvent heating step (I))

The solvent (B-1) was prepared, and the temperature of the solvent (B-1) was raised to 60 to 90 ℃. In the solvent heating step (I), a chain transfer agent to be described later may be added to the solvent (B-1) and then heated. The polymerization degree of the copolymer (A) synthesized in the dropping polymerization step (II) and the post-polymerization step (III) can be controlled by adding the chain transfer agent to the solvent (B-1) and then raising the temperature.

The concentration of the chain transfer agent in the solvent (B-1) may be, for example, 0.1 to 10% by mass, and is not particularly limited.

(drop polymerization Process (II))

The polymerization initiator solution is added dropwise to the heated solvent (B-1) together with the monomer solution while stirring the heated solvent (B-1), thereby producing a mixed solution.

The monomer solution is obtained by dissolving a monomer (m-a) having a blocked isocyanate group, a monomer (m-B) having a hydroxyl group, a monomer (m-c) having an acid group, and a monomer (m-d) used if necessary in a solvent (B-2). As the solvent (B-2), the solvents exemplified for the solvent (B-1) can be used in the same manner.

The polymerization initiator solution is obtained by dissolving the polymerization initiator in the solvent (B-2).

In the method for producing the copolymer (A) of the present embodiment, either or both of the solvent (B-1) and the solvent (B-2) contains a hydroxyl group-containing solvent.

In the dropwise addition polymerization step (II), a chain transfer agent solution to be described later may be added while being dropwise added instead of the chain transfer agent which may be added in the solvent heating step (I). The chain transfer agent solution is obtained by dissolving the chain transfer agent in the solvent (B-2). In the solvent heating step (I), a part of the chain transfer agent used for producing the copolymer (A) may be added to the solvent (B-1) and then heated, and in the dropwise polymerization step (II), a chain transfer agent solution obtained by dissolving the remaining part of the chain transfer agent used, which is removed from the solvent (B-2), in the solvent (B-1) may be added dropwise to the heated solvent (B-1).

(post polymerization Process (III))

After the completion of the addition of the monomer solution and the polymerization initiator solution, the mixed solution was further reacted at 60 to 90℃for 1 to 5 hours while stirring.

"solvent (B-1)".

The solvent (B-1) used in the solvent heating step (I) may be a hydroxyl group-containing solvent alone, a hydroxyl group-free solvent alone, or both a hydroxyl group-containing solvent and a hydroxyl group-free solvent. The solvent (B-1) preferably contains a hydroxyl group-containing solvent containing a hydroxyl group, more preferably only a hydroxyl group-containing solvent.

Examples of the hydroxyl group-containing solvent include (poly) alkylene glycol monoalkyl ethers such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, diethylene glycol monomethyl ether, diethylene glycol mono-n-butyl ether, triethylene glycol monomethyl ether, propylene glycol monoethyl ether, dipropylene glycol monomethyl ether, tripropylene glycol monoethyl ether, and 3-methoxy-1-butanol; hydroxyl group-containing carboxylic acid esters such as methyl 2-hydroxypropionate, ethyl 2-hydroxypropionate, methyl 2-hydroxy-2-methylpropionate, ethyl glycolate, and methyl 2-hydroxy-3-methylbutyrate; diethylene glycol, and the like.

Among these hydroxyl group-containing solvents, in order to have a high effect of preventing gelation of the reaction solution and controlling the molecular weight of the copolymer (a) to an appropriate range in the dropping polymerization step (II) and/or the post-polymerization step (III), it is preferable to use a primary and/or secondary alcohol solvent or an ether-based solvent, and it is more preferable to use propylene glycol monomethyl ether, ethylene glycol monomethyl ether, and 3-methoxy-1-butanol. These solvents containing hydroxyl groups may be used alone or in combination of 2 or more.

Examples of the solvent not containing a hydroxyl group include (poly) alkylene glycol monoalkyl ether acetates such as ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, propylene glycol monomethyl ether acetate, and propylene glycol monoethyl ether acetate; ethers such as diethylene glycol dimethyl ether, diethylene glycol methyl ethyl ether, diethylene glycol diethyl ether and tetrahydrofuran; ketones such as methyl ethyl ketone, cyclohexanone, 2-heptanone, and 3-heptanone; esters such as methyl 3-methoxypropionate, methyl 3-ethoxypropionate, ethyl ethoxyacetate, 3-methyl-3-methoxybutyl acetate, 3-methyl-3-methoxybutyl propionate, ethyl acetate, n-butyl acetate, isopropyl acetate, isobutyl acetate, n-pentyl acetate, isopentyl acetate, n-butyl propionate, ethyl butyrate, n-propyl butyrate, isopropyl butyrate, ethyl pyruvate, n-propyl pyruvate, methyl acetoacetate, ethyl acetoacetate, and ethyl 2-oxobutyrate; aromatic hydrocarbons such as toluene and xylene; carboxylic acid amides such as N-methylpyrrolidone, N-dimethylformamide and N, N-dimethylacetamide.

Among the solvents containing no hydroxyl group, the ether solvents are preferably used, and propylene glycol monomethyl ether acetate and diethylene glycol methyl ethyl ether are more preferably used, from the viewpoints of easiness of obtaining, cost and quality. These solvents containing no hydroxyl groups may be used alone or in combination of 2 or more.

When the solvent (B-1) used in the solvent heating step (I) contains a hydroxyl group-containing solvent, the content of the hydroxyl group-containing solvent in the solvent (B-1) is preferably 10 to 100% by mass, more preferably 20 to 90% by mass, and even more preferably 40 to 80% by mass. If the content of the hydroxyl group-containing solvent is 10 mass% or more, the effect of inhibiting the reaction of the isocyanate group derived from the monomer (m-a) with the hydroxyl group derived from the monomer (m-b) is sufficiently obtained in the dropping polymerization step (II) and/or the post-polymerization step (III). When the solvent (B-1) contains a solvent containing no hydroxyl group, the effect of improving the amount of crosslinking reaction between the isocyanate group derived from the monomer (m-a) and the hydroxyl group derived from the monomer (m-B) at the time of curing as the resin composition is obtained.

"temperature of solvent and Mixed solution"

In the production method of the present embodiment, in the solvent heating step (I), the solvent (B-1) is added to the reaction vessel, and the temperature is raised to 60 to 90 ℃. In addition, in the dropping polymerization step (II) and the post-polymerization step (III), the mixed solution is reacted at 60 to 90℃for 1 to 5 hours while stirring.

The temperature of the solvent (B-1) in the solvent heating step (I) may be the same as or different from the temperature of the mixed solution in the dropping polymerization step (II) and the post-polymerization step (III).

In this embodiment, since the temperature of the solvent (B-1) in the solvent heating step (I) and the temperature of the mixed solution in the dropping polymerization step (II) and the post-polymerization step (III) are 60℃or higher, the polymerization reaction of the monomers (m-a) to (m-c) and the monomer (m-d) used if necessary in the dropping polymerization step (II) and the post-polymerization step (III) proceeds sufficiently.

Since the temperature of the solvent (B-1) in the solvent heating step (I) and the temperature of the mixed solution in the dropping polymerization step (II) and the post-polymerization step (III) are 90℃or lower, the following effects are obtained when the reactant of the isocyanate compound having an ethylenically unsaturated group and the pyrazole compound is used as the monomer (m-a). That is, in the dropping polymerization step (II) and the post-polymerization step (III), the pyrazole compound can be prevented from dissociating from the blocked isocyanate group to form an isocyanate group. Therefore, the copolymer (A) during production, which is caused by the reaction of the isocyanate group generated by deblocking of the blocked isocyanate group and the hydroxyl group derived from the monomer (m-b) or the acid group derived from the monomer (m-c), can be prevented from gelling. Further, since the above temperature is 90℃or lower, in the dropping polymerization step (II) and the post-polymerization step (III), even if a part of the blocked isocyanate groups of the monomer (m-a) is decomposed to form isocyanate groups, the reaction of the isocyanate groups with the hydroxyl groups derived from the monomer (m-b) can be suppressed. Based on these, a copolymer (a) sufficiently containing a structural unit (a) having a blocked isocyanate group and a structural unit (b) having a hydroxyl group is obtained.

In the dropwise addition polymerization step (II), the polymerization initiator solution and the monomer solution are dropwise added to the solvent (B-1) heated to 60 to 90℃in the solvent heating step (I) to prepare a mixed solution, and polymerization is carried out simultaneously. In the dropping polymerization step (II), the chain transfer agent solution may be further dropped into the solvent (B-1) having been heated to prepare a mixed solution containing the chain transfer agent.

In the dropwise addition polymerization step (II), the polymerization initiator solution and the monomer solution are preferably simultaneously added dropwise to the solvent (B-1) having a temperature increased. In this case, the molecular weight of the copolymer (a) can be controlled with high accuracy, and gelation of the copolymer (a) during production can be prevented.

In the dropping polymerization step (II), in the case of dropping the chain transfer agent solution into the solvent (B-1) whose temperature has been raised, the chain transfer agent solution may be dropped simultaneously with the polymerization initiator solution and the monomer solution, or the chain transfer agent solution may be dropped before or after the dropping of the polymerization initiator solution and the monomer solution.

The dropping rate of the polymerization initiator solution, the monomer solution, the chain transfer agent solution can be appropriately determined according to the capacity of the reaction vessel, the reaction scale of the heated solvent (B-1) and the volumes of the polymerization initiator solution, the monomer solution, the chain transfer agent solution, and the like. For example, in the case of using a 1L reaction vessel, the dropping speed of the polymerization initiator solution, the monomer solution, and the chain transfer agent solution is preferably 0.1 to 5 mL/min.

The time for dropping the polymerization initiator solution, the monomer solution, and the chain transfer agent solution may be, for example, 30 minutes to 1 hour.

The dropping rate and the dropping time of the polymerization initiator solution, the monomer solution, and the chain transfer agent solution may be different from each other or may be partially or completely the same.

In the present embodiment, the polymerization initiator solution, the monomer solution, and the chain transfer agent solution, which is used as needed, are prepared separately.

(polymerization initiator solution)

The polymerization initiator is not particularly limited, and examples thereof include 2,2' -azobis (2, 4-dimethylvaleronitrile), azobisisobutyronitrile, azobisisovaleronitrile, benzoyl peroxide, tert-butyl peroxy-2-ethylhexanoate, and the like. These polymerization initiators may be used alone or in combination of 2 or more.

The concentration of the polymerization initiator in the polymerization initiator solution is preferably a concentration of a mixed solution in which a uniform concentration is easily obtained, and for example, may be 16 to 50 mass%, and is not particularly limited.

The amount of the polymerization initiator solution to be used is preferably an amount of 0.5 to 20 parts by mass, more preferably an amount of 1.0 to 10 parts by mass, based on 100 parts by mass of the total amount of the monomers (i.e., the mass of the monomers (m-a) to (m-d) in the monomer solution) contained in the polymerization initiator solution.

(monomer solution)

The monomer solution is obtained by dissolving a monomer (m-a) having a blocked isocyanate group, a monomer (m-B) having a hydroxyl group, a monomer (m-c) having an acid group, and a monomer (m-d) used if necessary in a solvent (B-2). As the monomers (m-a) to (m-d), those exemplified in the item of the copolymer (A) can be used.

The monomer solution may be produced by a method in which the monomers (m-a) to (m-d) are individually dissolved in the solvent (B-2) and then mixed, or a method in which the monomers (m-a) to (m-d) are mixed and then dissolved in the solvent (B-2).

The total concentration of the monomers (m-a) to (m-d) in the monomer solution is preferably a concentration of a mixed solution in which a uniform concentration is easily obtained, and may be, for example, 50 to 95 mass%, but is not particularly limited.

In the case where 1 or more monomers among the monomers used for producing the copolymer (a) are liquid at ordinary temperature, the monomers that are liquid at ordinary temperature may also serve as solvents in the monomer solution. In this case, the monomer solution may not contain the solvent (B-2).

Examples of the monomer which is liquid at ordinary temperature include 2- [ (3, 5-dimethylpyrazolyl) carbonylamino ] ethyl methacrylate which is a monomer (m-a) having a blocked isocyanate group.

The proportion of each of the monomers (m-a) to (m-c) used in the production of the copolymer (A) is not particularly limited, but is preferably 1 to 45 mol% of the monomer (m-a), 1 to 50 mol% of the monomer (m-b), 1 to 60 mol% of the monomer (m-c), more preferably 5 to 40 mol% of the monomer (m-a), 5 to 45 mol% of the monomer (m-b), 5 to 50 mol% of the monomer (m-c), still more preferably 15 to 35 mol% of the monomer (m-a), 10 to 35 mol% of the monomer (m-b), and 10 to 40 mol% of the monomer (m-c).

When the copolymer (A) contains the structural unit (d), the proportion of each of the monomers (m-a) to (m-d) used in the production of the copolymer (A) is not particularly limited, but is preferably 1 to 45 mol% of the monomer (m-a), 1 to 50 mol% of the monomer (m-b), 1 to 60 mol% of the monomer (m-c), 1 to 80 mol% of the monomer (m-d), more preferably 5 to 40 mol% of the monomer (m-a), 5 to 45 mol% of the monomer (m-b), 5 to 50 mol% of the monomer (m-c), 5 to 75 mol% of the monomer (m-d), still more preferably 15 to 35 mol% of the monomer (m-a), 10 to 35 mol% of the monomer (m-c), and 10 to 50 mol% of the monomer (m-d).

(chain transfer agent solution)

The chain transfer agent solution is obtained by dissolving the chain transfer agent in the solvent (B-2).

In the dropping polymerization step (II), the polymerization degree of the copolymer (a) synthesized in the post-polymerization step (III) can be controlled by dropping a chain transfer agent solution. Accordingly, the copolymer (A) having a desired molecular weight range can be easily produced.

The chain transfer agent is not particularly limited, and for example, a polyfunctional thiol can be preferably used. The polyfunctional thiol is a compound having 2 or more mercapto groups in the molecule.

Examples of the polyfunctional thiol include, but are not particularly limited to, thioglycolic acid, 1, 2-ethanedithiol, 1, 4-bis (3-mercaptobutyryloxy) butane, tetraethyleneglycol bis (3-mercaptopropionate), trimethylolethane tris (3-mercaptobutyrate), trimethylolpropane tris (3-mercaptopropionate), pentaerythritol tetrakis (3-mercaptobutyrate), pentaerythritol tetrakis (3-mercaptopropionate), 1,3, 5-tris (3-mercaptobutyloxyethyl) -1,3, 5-triazine-2, 4,6 (1H, 3H, 5H) -trione, tris- [ (3-mercaptopropionyloxy) -ethyl ] -isocyanurate, dipentaerythritol hexa (3-mercaptopropionate), and the like.

Among the above, pentaerythritol tetrakis (3-mercaptobutyrate) and/or thioglycolic acid, pentaerythritol tetrakis (3-mercaptopropionate) are preferably used as the chain transfer agent from the viewpoints of easiness of obtaining, cost and quality.

The concentration of the chain transfer agent in the polymerization initiator solution is preferably a concentration of a mixed solution in which a uniform concentration is easily obtained, and may be, for example, 0.1 to 10 mass%, without particular limitation.

The amount of the chain transfer agent solution to be used is preferably an amount of, for example, 0.5 to 20 parts by mass, more preferably 1.0 to 10 parts by mass, per 100 parts by mass of the total amount of the monomers (i.e., the mass of the monomers (m-a) to (m-d) in the monomer solution) to be added to the chain transfer agent contained in the mixed solution. By setting the amount of the chain transfer agent solution to be within the above range, the copolymer (A) having a desired molecular weight range can be easily produced in the post-polymerization step (III).

"solvent (B-2)".

As the solvent (B-2) used in the dropping polymerization step (II), the same one as the solvent (B-1) used in the solvent heating step (I) can be used. The solvent (B-2) may be a hydroxyl group-containing solvent alone, a hydroxyl group-free solvent alone, or both a hydroxyl group-containing solvent and a hydroxyl group-free solvent, as in the case of the solvent (B-1). The solvent (B-2) preferably contains a hydroxyl group-containing solvent containing hydroxyl groups, more preferably only a hydroxyl group-containing solvent.

In the method for producing the copolymer (A) of the present embodiment, either or both of the solvent (B-1) and the solvent (B-2) contains a hydroxyl group-containing solvent. Therefore, when the solvent (B-1) used in the solvent heating step (I) does not contain a hydroxyl group-containing solvent, the solvent (B-2) used in the dropwise addition polymerization step (II) contains a hydroxyl group-containing solvent.

The content ratio of the hydroxyl group-containing solvent contained in the total amount of the solvent (B-1) used in the solvent heating step (I) and the solvent (B-2) used in the dropwise addition polymerization step (II) is preferably 10 to 100% by mass, more preferably 20 to 90% by mass, and still more preferably 40 to 80% by mass. If the content of the hydroxyl group-containing solvent is 10 mass% or more, the effect of inhibiting the reaction of the isocyanate group derived from the monomer (m-a) with the hydroxyl group derived from the monomer (m-b) is sufficiently obtained in the dropping polymerization step (II) and/or the post-polymerization step (III). When one or both of the solvent (B-1) and the solvent (B-2) contains a solvent containing no hydroxyl group, if the content of the solvent containing hydroxyl groups is 90 mass% or less, for example, when 2,2' -azobis (2, 4-dimethylvaleronitrile) is used as the polymerization initiator, the polymerization initiator is easily dissolved, and workability is good.

In the production method of the present embodiment, the solvent (B-1) used in the solvent heating step (I) and/or the solvent (B-2) used in the dropwise addition polymerization step (II) contains a hydroxyl group-containing solvent, and therefore the following effects are obtained.

That is, in the dropping polymerization step (II) and/or the post-polymerization step (III), the hydroxyl group of the hydroxyl group-containing solvent reacts with a part of the isocyanate group generated from the blocked isocyanate group of the monomer (m-a).

Thus, in the present embodiment, in the dropping polymerization step (II) and/or the post-polymerization step (III), the reaction of the isocyanate group derived from the monomer (m-a) and the hydroxyl group derived from the monomer (m-b) is moderately inhibited. Therefore, the copolymer (A) can be prevented from gelling during the production in the post-polymerization step (III). Further, the storage stability of the resin composition containing the copolymer (A) is improved.

In addition, according to the present embodiment, the above reaction in the dropping polymerization step (II) and/or the post-polymerization step (III) is appropriately blocked, whereby the isocyanate group derived from the monomer (m-a) and the hydroxyl group derived from the monomer (m-b) can be prevented from decreasing before the resin composition containing the copolymer (a) is thermally cured. Thus, a copolymer (A) in which the isocyanate group derived from the monomer (m-a) and the hydroxyl group derived from the monomer (m-b) remain moderately is obtained. Therefore, the resin composition containing the copolymer (a) is thermally cured to sufficiently form a crosslinked structure, thereby obtaining a cured product having good solvent resistance.

The amounts of the solvent (B-1) used in the solvent heating step (I) and the solvent (B-2) used in the dropwise addition polymerization step (II) are not particularly limited, but are preferably 100 parts by mass, for example, the total amount of the solvent (B-1) and the solvent (B-2) is 30 to 1,000 parts by mass, more preferably 50 to 800 parts by mass, relative to the total amount of the monomers (i.e., the mass of the monomers (m-a) to (m-d) in the monomer solution). If the total amount of the solvent (B-1) and the solvent (B-2) is 1,000 parts by mass or less per 100 parts by mass of the total amount of the monomers to be added, the viscosity of the reaction solution containing the copolymer (A) obtained in the post-polymerization step (III) becomes appropriate. Further, by setting the total amount of the solvent (B-1) and the solvent (B-2) to 1,000 parts by mass or less, it is possible to suppress the decrease in molecular weight of the copolymer (A) caused by the chain transfer effect in the case of dropping the chain transfer agent solution in the dropping polymerization step (II). Further, by setting the total amount of the solvent (B-1) and the solvent (B-2) to 30 parts by mass or more based on 100 parts by mass of the total amount of the monomers to be added, abnormal polymerization in the post-polymerization step (III) can be prevented, and the polymerization can be stably performed. As a result, the copolymer (a) during production can be prevented from gelling, and a copolymer (a) free from coloration can be obtained.

In the production method of the present embodiment, in the post-polymerization step (III), the mixed solution obtained in the dropping polymerization step (II) is reacted at 60 to 90 ℃ for 1 to 5 hours while stirring. The reaction time in the post-polymerization step (III) may be 1 to 5 hours, preferably 1 to 4 hours, and more preferably 2 to 3 hours. When the reaction time is 1 to 5 hours, the copolymer (A) having an appropriate molecular weight can be produced in a good yield.

The copolymer (A) of the present embodiment contains a structural unit (a) having a blocked isocyanate group blocked with a pyrazole compound, a structural unit (b) having a hydroxyl group, and a structural unit (c) having an acid group, and has a glass transition temperature of 30 ℃ or lower. Therefore, the resin composition containing the copolymer (a) of the present embodiment is excellent in alkali developability when used as a photosensitive material, and is excellent in storage stability, and a cured product excellent in solvent resistance is obtained even when cured at a low temperature.

In the method for producing the copolymer (A) of the present embodiment, the solvent (B-1) used in the solvent heating step (I) and/or the solvent (B-2) used in the dropwise addition polymerization step (II) is a solvent containing a hydroxyl group-containing solvent, the solvent (B-1) is heated to 60 to 90℃in the solvent heating step (I), and the mixed solution is reacted at 60 to 90℃in the post-polymerization step (III). Therefore, in the dropping polymerization step (II) and/or the post-polymerization step (III), the reaction of the isocyanate group derived from the monomer (m-a) and the hydroxyl group derived from the monomer (m-b) is moderately hindered. As a result, the copolymer (a) of the present embodiment sufficiently containing the structural unit (a) having a blocked isocyanate group and the structural unit (b) having a hydroxyl group is obtained.

In contrast, conventionally, when a solvent is used for polymerization of a copolymer, a solvent that does not react with a monomer is selected and used. Therefore, in the conventional technique, when the polymerization of the copolymer is performed using a solvent, the monomer does not react with the solvent. Therefore, the conventional technology does not contemplate a method of controlling the properties of the copolymer by the reaction of the monomer and the solvent.

< resin composition >

Next, the resin composition of the present embodiment will be described.

The resin composition of the present embodiment contains the copolymer (a) of the present embodiment and the solvent (B).

The resin composition of the present embodiment may further contain a reactive diluent (C) and a photopolymerization initiator (D) in addition to the copolymer (a) and the solvent (B). Such a resin composition can be preferably used as a photosensitive resin composition.

The resin composition of the present embodiment may further contain a colorant (E) in addition to the copolymers (a) to (D) described above. Such a resin composition can be preferably used as a material for forming a colored pattern of a color filter, a black matrix, a black column spacer, or the like.

(solvent (B))

In the resin composition of the present embodiment, the solvent (B) contains a hydroxyl group-containing solvent. The solvent (B) may be only a hydroxyl group-containing solvent. In the resin composition of the present embodiment, since the solvent (B) contains a hydroxyl group-containing solvent, the storage stability is improved.

The hydroxyl group-containing solvent used as the solvent (B) is not particularly limited as long as it is a hydroxyl group-containing solvent, and the same substances as those used as the solvent (B-1) and the solvent (B-2) in the step of producing the copolymer (A) can be used. Examples of the hydroxyl-free solvent that can be used as the solvent (B) include the same solvents as those that can be used as the solvent (B-1) and the solvent (B-2) in the step of producing the copolymer (A).

The content ratio of the hydroxyl group-containing solvent in the solvent (B) can be set in the same manner as the content ratio of the hydroxyl group-containing solvent in the solvent (B-1) used in the step of producing the copolymer (A).

The solvent (B) may be the same as or different from the solvent (B-1) and/or the solvent (B-2) used in the step of producing the copolymer (A).

The resin composition of the present embodiment can be produced, for example, by a method of appropriately mixing the copolymer (a) separated from the reaction liquid containing the copolymer (a) obtained in the post-polymerization step (III) for producing the copolymer (a) with the solvent (B).

As the resin composition of the present embodiment, a reaction liquid containing the copolymer (a) obtained in the production of the copolymer (a) may be used as it is. In this case, it is not necessary to separate the copolymer (A) from the reaction liquid. In the case where the solvent (B-1) and/or the solvent (B-2) used for producing the copolymer (A) are contained in the reaction solution, the solvent (B-1) and/or the solvent (B-2) in the reaction solution may be used as the solvent (B) as it is. The solvent (B) may be added to the reaction solution as needed.

In the resin composition of the present embodiment, the blending amount of the copolymer (a) and the solvent (B) may be appropriately adjusted according to the purpose of use of the resin composition. The resin composition of the present embodiment preferably contains, for example, 30 to 1,000 parts by mass of the solvent (B), more preferably 50 to 800 parts by mass, per 100 parts by mass of the copolymer (a). If the content of the solvent (B) is 30 parts by mass or more, the viscosity of the resin composition becomes appropriate. If the content of the solvent (B) is 1,000 parts by mass or less, the viscosity of the resin composition can be controlled to an appropriate range, and appropriate film thickness adjustment can be performed.

(reactive diluent (C))

The reactive diluent (C) is contained together with the photopolymerization initiator (D) as required. The reactive diluent (C) is a compound having at least one polymerizable ethylenically unsaturated group in the molecule as a polymerizable functional group. The reactive diluent (C) may be a monofunctional monomer or a polyfunctional monomer, and is preferably a polyfunctional monomer having a plurality of polymerizable functional groups. By using the resin composition containing the reactive diluent (C), the viscosity can be easily adjusted. In addition, by using the resin composition containing the reactive diluent (C), the adhesion of the cured product of the resin composition to the substrate can be improved, or the strength of the cured product of the resin composition can be adjusted.

Examples of the monofunctional monomer used as the reactive diluent (C) include (meth) acrylates such as (meth) acrylamide, hydroxymethyl (meth) acrylamide, methoxymethyl (meth) acrylamide, ethoxymethyl (meth) acrylamide, propoxymethyl (meth) acrylamide, butoxymethoxymethyl (meth) acrylamide, methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 2-phenoxy-2-hydroxypropyl (meth) acrylate, 2- (meth) acryloyloxy-2-hydroxypropyl phthalate, glycerin mono (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, glycidyl (meth) acrylate, 2-trifluoroethyl (meth) acrylate, 2, 3-tetrafluoropropyl (meth) acrylate, and semi (meth) acrylates of phthalic acid derivatives; aromatic vinyl compounds such as styrene, α -methylstyrene, α -chloromethylstyrene, and vinyltoluene; carboxylic acid esters such as vinyl acetate and vinyl propionate. These monofunctional monomers may be used alone or in combination of 2 or more.

Examples of the polyfunctional monomer used as the reactive diluent (C) include ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, butanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, 1, 6-hexanediol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, di (meth) acrylate, pentaerythritol tri (meth) acrylate, dipentaerythritol penta (meth) acrylate, dipentaerythritol hexa (meth) acrylate, 2-bis (4- (meth) acryloxydiethoxyphenyl) propane, 2-bis (4- (meth) acryloxypolyethoxyphenyl) propane, 2-hydroxy-3- (meth) acryloxypropyl (meth) acrylate, ethylene glycol diglycidyl ether di (meth) acrylate, diethylene glycol diglycidyl ether di (meth) acrylate, phthalic acid diglycidyl ester di (meth) acrylate, triacrylate, polyglycidyl ether (meth) acrylate, toluene diisocyanate), reactants of trimethylhexamethylene diisocyanate and 1, 6-hexamethylene diisocyanate with 2-hydroxyethyl (meth) acrylate, and (meth) acrylates such as tri (meth) acrylate of tri (hydroxyethyl) isocyanurate; aromatic vinyl compounds such as divinylbenzene, diallyl phthalate, and diallyl phenylphosphonate; dicarboxylic acid esters such as divinyl adipate; triallyl cyanurate, methylenebis (meth) acrylamide, (meth) acrylamide methylene ether, condensates of polyhydric alcohols with N-methylol (meth) acrylamide, and the like. These polyfunctional monomers may be used alone or in combination of 2 or more.

Among these monomers, from the viewpoint of improving the development form and curability of the resin composition, the reactive diluent (C) is preferably a polyfunctional (meth) acrylate, and more preferably 1 or 2 or more selected from trimethylolpropane tri (meth) acrylate, dipentaerythritol penta (meth) acrylate, and dipentaerythritol hexa (meth) acrylate are used.

When the resin composition contains the reactive diluent (C), the mixing amount of each component is preferably 10 to 90 parts by mass of the copolymer (a), 30 to 1,000 parts by mass of the solvent (B), 10 to 90 parts by mass of the reactive diluent (C), more preferably 20 to 80 parts by mass of the copolymer (a), 50 to 800 parts by mass of the solvent (B), 20 to 80 parts by mass of the reactive diluent (C), still more preferably 30 to 75 parts by mass of the copolymer (a), 100 to 700 parts by mass of the solvent (B), and 25 to 70 parts by mass of the reactive diluent (C) relative to 100 parts by mass of the total amount of the copolymer (a) and the reactive diluent (C). If the mixing amount of each component is within the above range, a resin composition having an appropriate viscosity can be suitably used for various paints, adhesives, binders for printing inks, and the like.

(photopolymerization initiator (D))

The photopolymerization initiator (D) is not particularly limited, and examples thereof include benzoins such as benzoin, benzoin methyl ether, benzoin ethyl ether, and benzoin butyl ether; acetophenones such as acetophenone, 2-dimethoxy-2-phenylacetophenone, 1-dichloroacetophenone, 4- (1-tert-butyldioxy-1-methylethyl) acetophenone, 2-methyl-1- [4- (methylthio) phenyl ] -2-morpholino-propan-1-one, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) butanone-1; anthraquinones such as 2-methylanthraquinone, 2-pentylalnthraquinone, 2-t-butylanthraquinone, and 1-chloroanthraquinone; thioxanthones such as xanthone, thioxanthone, 2, 4-dimethylthioxanthone, 2, 4-diisopropylthioxanthone and 2-chlorothioxanthone; ketals such as acetophenone dimethyl ketal and benzil dimethyl ketal; benzophenone such as benzophenone, 4- (1-t-butyldioxy-1-methylethyl) benzophenone, and 3,3', 4' -tetra (t-butyldioxycarbonyl) benzophenone; acyl phosphine oxides; ethanone 1- [ 9-ethyl-6- (2-methylbenzoyl) -9H-carbazol-3-yl ] -1- (O-acetyl oxime) and the like. These photopolymerization initiators (D) may be used alone or in combination of 2 or more.

When the resin composition contains the photopolymerization initiator (D), the content thereof is preferably 0.1 to 30 parts by mass, more preferably 0.5 to 20 parts by mass, and even more preferably 1 to 15 parts by mass, relative to 100 parts by mass of the total amount of the copolymer (a) and the reactive diluent (C).

(colorant (E))

The colorant (E) is contained as needed. The colorant (E) is not particularly limited as long as it is dissolved or dispersed in the solvent (B), and examples thereof include dyes and pigments. The colorant (E) may be used alone in an amount of 1 or 2 or more in combination depending on the color of the cured product of the target resin composition. As the colorant (E), only a dye may be used, only a pigment may be used, or a dye and a pigment may be used in combination.

As the dye, an acid dye having an acid group such as carboxylic acid or sulfonic acid, a salt of the acid dye with a nitrogen compound, a sulfonamide of the acid dye, or the like is preferably used from the viewpoints of solubility in the solvent (B) and an alkaline developer, interaction with other components in the resin composition, heat resistance, and the like.

Examples of such dyes include acid alizarin violet N; acid black 1, 2, 24, 48; acid blue 1, 7, 9, 25, 29, 40, 45, 62, 70, 74, 80, 83, 90, 92, 112, 113, 120, 129, 147; acid chromium violet K; acid fuchsin; acid green 1, 3, 5, 25, 27, 50; acid orange 6, 7, 8, 10, 12, 50, 51, 52, 56, 63, 74, 95; acid red 1, 4, 8, 14, 17, 18, 26, 27, 29, 31, 34, 35, 37, 42, 44, 50, 51, 52, 57, 69, 73, 80, 87, 88, 91, 92, 94, 97, 103, 111, 114, 129, 133, 134, 138, 143, 145, 150, 151, 158, 176, 183, 198, 211, 215, 216, 217, 249, 252, 257, 260, 266, 274; acid violet 6B, 7, 9, 17, 19; acid yellow 1, 3, 9, 11, 17, 23, 25, 29, 34, 36, 42, 54, 72, 73, 76, 79, 98, 99, 111, 112, 114, 116; food yellow 3 and their derivatives, etc. Among these dyes, azo-based, xanthene-based, anthraquinone-based or phthalocyanine-based acid dyes are preferably used. These dyes may be used alone or in combination of 2 or more kinds depending on the color of the cured product of the aimed resin composition.

Examples of the pigment include yellow pigments such as c.i. pigment yellow 1, 3, 12, 13, 14, 15, 16, 17, 20, 24, 31, 53, 83, 86, 93, 94, 109, 110, 117, 125, 128, 137, 138, 139, 147, 148, 150, 153, 154, 166, 173, 194, 214; orange pigments such as c.i. pigment orange 13, 31, 36, 38, 40, 42, 43, 51, 55, 59, 61, 64, 65, 71, 73; c.i. pigment red 9, 97, 105, 122, 123, 144, 149, 166, 168, 176, 177, 180, 192, 209, 215, 216, 224, 242, 254, 255, 264, 265, etc.; c.i. pigment blue 15, 15: 3. 15: 4. 15: 6. blue pigment such as 60; violet pigments such as c.i. pigment violet 1, 19, 23, 29, 32, 36, 38; green pigments such as c.i. pigment green 7, 36, 58, 59, etc.; brown pigments such as c.i. pigment brown 23, 25; c.i. pigment black 1, 7, carbon black, titanium black, iron oxide and other black pigments. These pigments may be used alone or in combination of 2 or more kinds depending on the color of the cured product of the targeted resin composition.

In the case of using a pigment as the colorant (E), a known dispersant may be contained in the resin composition from the viewpoint of improving the dispersibility of the pigment. As the dispersant, a polymer dispersant excellent in dispersion stability with time is preferably used.

Examples of the polymer dispersant include urethane dispersants, polyethyleneimine dispersants, polyoxyethylene alkyl ether dispersants, polyoxyethylene glycol diester dispersants, sorbitan aliphatic ester dispersants, and aliphatic modified ester dispersants.

As the polymer dispersant, the polymer-based dispersant, substances commercially available under the trade names of EFKA (manufactured by EFKA corporation), disperbyk-161 (manufactured by february corporation), dipyralid (manufactured by february corporation), solserpase (manufactured by february corporation), solserse (manufactured by solserse corporation) and the like can be used.

The type and the mixing amount of the dispersant may be appropriately set according to the type of pigment used and the like.

When the resin composition contains the colorant (E), the content thereof is preferably 3 to 80 parts by mass, more preferably 5 to 70 parts by mass, and even more preferably 10 to 60 parts by mass, based on 100 parts by mass of the total amount of the copolymer (a) and the reactive diluent (C). The resin composition containing the copolymer (a) of the present embodiment is excellent in storage stability, and a cured product excellent in solvent resistance is obtained even when it is cured at a low temperature. Therefore, for example, the content of the colorant (E) may be 20 parts by mass or more relative to 100 parts by mass of the total amount of the copolymer (a) and the reactive diluent (C). The resin composition containing 20 parts by mass or more of the colorant (E) is used as a material for a color filter, whereby the color reproducibility in an image display device provided with the color filter can be improved.

In addition to the above components, the resin composition of the present embodiment may be blended with known additives such as a coupling agent, a leveling agent, and a thermal polymerization inhibitor in order to impart predetermined characteristics. The blending amount of these additives is not particularly limited as long as the effect of the present invention is not impaired.

Since the resin composition of the present embodiment contains the copolymer (a) of the present embodiment, the crosslinking reaction proceeds sufficiently even at low temperature. Therefore, the resin composition of the present embodiment can be cured at a low temperature.

Specifically, the resin composition of the present embodiment is cured at a temperature of preferably 150 ℃ or lower, more preferably 120 ℃ or lower, still more preferably 100 ℃ or lower, and most preferably 80 ℃ or lower. If the temperature at which the resin composition is cured is 150℃or lower, the energy required to cure the resin composition can be reduced. In addition, when the resin composition contains the colorant (E) having poor heat resistance, deterioration of the colorant (E) accompanying heat curing can be suppressed, and a cured product exhibiting the original characteristics of the colorant (E) can be easily obtained. Therefore, as the colorant (E), a substance formed of various materials can be used. In addition, in the case where a cured product is formed by a method of applying a resin composition on a substrate and thermally curing the composition, the cured product can be formed even if the substrate is formed of a material having poor heat resistance. Accordingly, as the substrate, for example, a substrate formed of various materials such as a resin for a flexible display can be used.

The resin composition of the present embodiment is cured at a temperature of preferably 50℃or higher, more preferably 60℃or higher, and still more preferably 70℃or higher. When the temperature at which the resin composition is cured is 50℃or higher, a crosslinked structure is sufficiently formed in a short period of time, and a cured product having good solvent resistance can be efficiently formed.

The heating time (curing time) for curing the resin composition of the present embodiment may be appropriately determined depending on the size, thickness, temperature at which curing is performed, and the like of the cured product, and may be, for example, 10 minutes to 4 hours, preferably 20 minutes to 2 hours.

The resin composition of the present embodiment can be produced by a method of mixing the above components using a known mixing device. The solvent contained in each component used as a raw material in the production of the resin composition of the present embodiment may be used as the solvent (B).

In the case where the resin composition of the present embodiment contains components other than the copolymer (a) and the solvent (B), it can be produced, for example, by a method of adding the reactive diluent (C), the photopolymerization initiator (D), and the colorant (E) to a resin composition containing the copolymer (a) and the solvent (B) which has been produced in advance and mixing them.

Since the resin composition of the present embodiment contains the copolymer (a) of the present embodiment, the resin composition has excellent storage stability, and a cured product having excellent solvent resistance is obtained even when the resin composition is cured at a low temperature. Therefore, the resin composition of the present embodiment can be preferably used as a material such as a color filter, a black matrix, a color filter protective film, a photo spacer, a projection for liquid crystal alignment, a microlens, an insulating film for a touch panel, an adhesive for an electronic material around a flexible printed wiring board, an adhesive sheet, or the like.

When the resin composition of the present embodiment contains the copolymer (a), the solvent (B), the reactive diluent (C), and the photopolymerization initiator (D) of the present embodiment, the resin composition can be preferably used as a photosensitive material having good alkali developability. In particular, a resist used as a color filter incorporated in an organic Electroluminescence (EL) display (for a pixel definition layer (Pixel Defining Layer) (PDL)), a liquid crystal display device, a solid-state imaging device using a Charge Coupled Device (CCD)/Complementary Metal Oxide Semiconductor (CMOS) element, or the like is suitable.

In addition, when the resin composition of the present embodiment contains the copolymer (a), the solvent (B), the reactive diluent (C), the photopolymerization initiator (D), and the colorant (E), a colored pattern composed of a cured product excellent in solvent resistance can be formed at a low temperature. Therefore, deterioration of the colorant (E) accompanying heat curing is suppressed, and a colored pattern exhibiting the original characteristics of the colorant (E) can be formed. Therefore, the resin composition can be preferably used as a photosensitive material for color filters.

< color Filter >)

Next, a color filter according to the present embodiment will be described.

The color filter of the present embodiment has a substrate, a plurality of pixels formed on the substrate and composed of 3 coloring patterns of red (R) pattern, green (G) pattern and blue (B) pattern, a black matrix formed at the boundary of each coloring pattern, and a protective film formed on the pixels and the black matrix.

As the substrate, a known substrate can be used, and for example, a glass substrate, a silicon substrate, a polycarbonate substrate, a polyester substrate, a polyamide substrate, a polyamideimide substrate, a polyimide substrate, an aluminum substrate, a printed wiring substrate, an array substrate, or the like can be used. In the color filter of the present embodiment, an organic substrate having a low heat resistance temperature such as a polycarbonate substrate, a polyester substrate, a polyamide substrate, a polyamideimide substrate, or a polyimide substrate can be used, and the color filter is suitable as a substrate for a flexible substrate.

In the color filter of the present embodiment, the 3 colored patterns forming the black matrix and each pixel are colored patterns composed of a cured product of the resin composition of the present embodiment containing the copolymer (a) of the present embodiment, the solvent (B), the reactive diluent (C), the photopolymerization initiator (D), and the colorant (E).

The protective film is not particularly limited, and a known one can be used.

Next, a method for manufacturing the color filter according to the present embodiment will be described by way of example.

In manufacturing the color filter of the present embodiment, first, a coloring pattern to be a black matrix and 3 coloring patterns to be formed for each pixel are formed on a substrate, respectively. First, a coloring pattern to be a black matrix is formed on a substrate, and then, a red pattern, a green pattern, and a blue pattern to be formed for each pixel are formed in a range divided by the black matrix. The order of forming the red, green, and blue patterns is not particularly limited.

Each colored pattern can be formed by photolithography using the resin composition of the present embodiment.

Specifically, the resin composition of the present embodiment is coated on a substrate to form a coating film. Then, the coating film is exposed to light through a photomask having a predetermined pattern shape, and the exposed portion is photo-cured. The unexposed portion of the coating film was then removed by alkali development with an aqueous alkali solution. Then, the exposed portion of the coating film is heated to cure by baking. Through the above steps, a colored pattern having a predetermined shape and composed of a cured product of the resin composition of the present embodiment is obtained.

The method of applying the resin composition to form the colored pattern is not particularly limited, and for example, a screen printing method, a roll coating method, a curtain coating method, a spray coating method, a spin coating method, or the like can be used.

After the resin composition is applied, the coating film is heated by a heating means such as a circulating oven, an infrared heater, or a hot plate, if necessary, so that the solvent (B) contained in the coating film can be volatilized and removed.

The heating for removing the solvent (B) in the coating film may be performed at a temperature of 50 to 120 ℃. The heating for removing the solvent (B) in the coating film may be performed for 30 seconds to 30 minutes, for example. The heating temperature and heating time for removing the solvent (B) in the coating film may be appropriately set according to the composition of the resin composition, the thickness of the coating film, and the like.

In exposing the coating film, a known negative mask can be used as a photomask, for example.

When exposing the coating film, active energy rays such as ultraviolet rays and excimer lasers are preferably used. The light source used for exposure is not particularly limited, and for example, a low-pressure mercury lamp, a medium-pressure mercury lamp, a high-pressure mercury lamp, a xenon lamp, a metal halide lamp, or the like can be used. The amount of the energy ray to be irradiated to the coating film may be appropriately selected depending on the thickness of the coating film, the composition of the resin composition, etc., and may be, for example, 30 to 2000mJ/cm ² 。

The aqueous alkali solution used for the alkali development is not particularly limited, and for example, aqueous solutions of sodium carbonate, potassium carbonate, calcium carbonate, sodium hydroxide, potassium hydroxide and the like can be used; aqueous solutions of amine compounds such as ethylamine, diethylamine, and dimethylethanolamine; the aqueous solution of p-phenylenediamine compounds such as tetramethylammonium, 3-methyl-4-amino-N, N-diethylaniline, 3-methyl-4-amino-N-ethyl-N- β -hydroxyethylaniline, 3-methyl-4-amino-N-ethyl-N- β -methanesulfonamide ethylaniline, 3-methyl-4-amino-N-ethyl-N- β -methoxyethylaniline, and their sulfate, hydrochloride, p-toluenesulfonate and the like can be appropriately selected depending on the composition of the resin composition and the like.

To these aqueous alkali solutions, an antifoaming agent and a surfactant may be added, if necessary.

In the present embodiment, it is preferable that the substrate is washed with water after alkali development with an aqueous alkali solution and before baking, and the aqueous alkali solution is removed and dried.

In the present embodiment, the temperature at which the exposed portion of the coating film is heated to be cured by baking may be appropriately selected depending on the thickness of the coating film, the composition of the resin composition, and the like. In the present embodiment, since the coating film is formed using the resin composition containing the copolymer (a) of the present embodiment, the exposed portion of the coating film can be cured even at a low temperature.

The temperature at which the exposed portion of the coating film is heated may be, for example, 210 ℃ or lower, 150 ℃ or lower, 120 ℃ or lower, 100 ℃ or lower, or 80 ℃ or lower, as required. If the temperature at which the exposed portion of the coating film is heated is 210 ℃ or lower, a material having low heat resistance such as a substrate having low heat resistance can be used as a material of the color filter. When the temperature at which the exposed portion of the coating film is heated is 150 ℃ or lower, the energy required for curing the coating film is preferably small. Further, if the temperature at which the exposed portion of the coating film is heated is 150 ℃ or lower, it is possible to form a colored pattern containing a colorant (E) having poor heat resistance, which has been difficult to use as a material for a colored pattern in the past, while suppressing degradation of the colorant (E). In addition, when the temperature at which the exposed portion of the coating film is heated is 150 ℃ or lower, a colored pattern can be formed on a substrate having poor heat resistance, which has been difficult to use as a substrate for a color filter in the past.

The temperature at which the exposed portion of the coating film is heated is preferably 50 ℃ or higher, more preferably 60 ℃ or higher, and still more preferably 70 ℃ or higher. If the temperature at which the exposed portion of the coating film is heated is 50℃or higher, the copolymer (A) and the reactive diluent (C) are sufficiently crosslinked, so that the solvent resistance of the colored pattern becomes good, and a good pattern shape is obtained. Further, if the temperature at which the exposed portion of the coating film is heated is 50 ℃ or higher, the exposed portion of the coating film can be heated in a short time, and a colored pattern can be efficiently produced.

The time for heating the exposed portion of the coating film may be appropriately selected depending on the temperature at which the exposed portion of the coating film is heated, the thickness of the coating film, the composition of the resin composition, and the like, and may be, for example, 10 minutes to 4 hours, preferably 20 minutes to 2 hours.

Next, a protective film was formed on the colored pattern to be the black matrix and the 3 colored patterns to be formed for each pixel by a known method.

Through the above steps, the color filter of the present embodiment is obtained.

The color filter of the present embodiment is a color pattern formed by a cured product of the resin composition of the present embodiment containing the copolymer (a) of the present embodiment, the solvent (B), the reactive diluent (C), the photopolymerization initiator (D), and the colorant (E), and the black matrix and 3 color patterns forming each pixel. The resin composition of the present embodiment has good alkali developability, and a cured product having excellent solvent resistance is obtained even when cured at a low temperature. Therefore, with the color filter of the present embodiment, pixels and black matrices can be formed by using a method of curing the resin composition at a low temperature, and the choice of materials that can be used for the color filter can be made to be large.

Therefore, in the color filter of the present embodiment, for example, a colorant (E) having poor heat resistance may be contained, and a color filter having pixels and/or a black matrix with good pattern shape may be manufactured. Further, by forming pixels and a black matrix by using a method of curing the resin composition at a low temperature, a color filter having a substrate formed of a material having poor heat resistance can be manufactured.

In contrast, in the case of forming a colored pattern using a conventional resin composition instead of the resin composition of the present embodiment, if the exposed portion of the coating film is heated to a temperature of less than 210 ℃, the solvent resistance of the colored pattern as a cured product is insufficient. Therefore, when a colored pattern is formed using a conventional resin composition, the temperature at which the exposed portion of the coating film is heated cannot be 210 ℃ or lower. Therefore, it is difficult to use a colorant (E) having poor heat resistance as a material for coloring a pattern in the conventional technique. In addition, as a substrate of the color filter, it is also difficult to use a substrate having poor heat resistance.

In the color filter of the present embodiment, the case where the colored pattern has pixels and a black matrix formed of a cured product of a resin composition containing the copolymer (a) of the present embodiment, the solvent (B), the reactive diluent (C), the photopolymerization initiator (D), and the colorant (E) has been described as an example, but a resin composition in which a curing accelerator and a known epoxy resin are mixed instead of the photopolymerization initiator (D) may be used.

In this case, for example, a coloring pattern can be formed by the method shown below. First, a resin composition is applied onto a substrate by an inkjet method to form a coating film having a predetermined pattern shape. Next, the coating film is heated to be cured. By the above method, a colored pattern having a desired shape and composed of a cured product of the resin composition can be formed. In place of the photopolymerization initiator (D), a resin composition in which a curing accelerator and a known epoxy resin are blended, gives a cured product excellent in solvent resistance even when cured at a low temperature. Therefore, in this case, pixels and black matrices can be formed by curing the resin composition at a low temperature, and the choice of materials that can be used for the color filter can be made large.

< image display element >)

Next, an image display element of the present embodiment will be described.

As a liquid crystal display element of the image display element of the present embodiment, for example, a 1 st substrate having a color filter and a 1 st electrode formed on the surface thereof and a 2 nd substrate having a 2 nd electrode formed on the surface thereof are disposed so that the 1 st electrode and the 2 nd electrode face each other via a spacer, and the liquid crystal composition is sandwiched between the 1 st substrate and the 2 nd substrate.

The liquid crystal display element of the present embodiment includes the color filter of the present embodiment as a color filter. In the liquid crystal display element of the present embodiment, a known material may be used for members other than the color filter.

The liquid crystal display element of the present embodiment can be manufactured by, for example, the following manufacturing method.

First, a color filter and a 1 st electrode are sequentially formed on a 1 st substrate. The color filter may be formed using the above-described manufacturing method. The 1 st electrode can be formed by a known method.

Next, the 2 nd electrode and the spacer are formed on the 2 nd substrate by a known method.

Then, the 1 st substrate and the 2 nd substrate are arranged so that the 1 st electrode and the 2 nd electrode face each other, and the liquid crystal composition is injected between the 1 st substrate and the 2 nd substrate, and the substrates are sealed.

Through the above steps, the liquid crystal display element of the present embodiment is obtained.

Since the liquid crystal display element of the present embodiment includes the color filter of the present embodiment, pixels and a black matrix of the color filter can be formed by using a method of curing the resin composition at a low temperature. Therefore, as a material that can be used for the liquid crystal display element, a material having poor heat resistance can be used, and a large number of options can be made for the material that can be used.

The above-described embodiment has been described as an example of the image display device according to the present embodiment by taking a liquid crystal display device as an example, but the image display device according to the present embodiment is not limited to the liquid crystal display device as long as the image display device is provided with the color filter according to the present embodiment. The image display element of the present embodiment may be, for example, a solid-state imaging device using an organic EL display element or a CCD element/CMOS element.

Examples

The present invention will be described in more detail below with reference to examples and comparative examples. The present invention is not limited to the following examples.

Synthesis example 1

207.7g of propylene glycol monomethyl ether (manufactured by Sanyo chemical Co., ltd.) as the solvent (B-1) was added to a flask equipped with a stirring device, a dropping funnel, a condenser, a thermometer and a gas introduction tube, and the mixture was stirred while being replaced with nitrogen gas, and the temperature was raised to 78 ℃ (solvent heating step (I)).

Next, 20.6g of 2,2' -azobis (2, 4-dimethylvaleronitrile) (polymerization initiator) was dissolved in 79.1g of propylene glycol monomethyl ether as solvent (B-2) to prepare a polymerization initiator solution.

Further, 50.2g (20 mol%) of MOI-BP, 26.0g (20 mol%) of 2-hydroxyethyl methacrylate, 12.9g (15 mol%) of methacrylic acid, and 82.8g (45 mol%) of 2-ethylhexyl acrylate (2 EHA) were dissolved in 61.8g of propylene glycol monomethyl ether as the solvent (B-2) and mixed to prepare a monomer solution.

Then, in the above-mentioned flask in which the solvent having been heated to 78℃was added, the solvent (B-1) in the flask was stirred, and the polymerization initiator solution and the monomer solution were simultaneously added dropwise using a dropping funnel to prepare a mixed solution, and the polymerization was carried out dropwise (dropwise polymerization step (II)). With respect to the dropping rate, the polymerization initiator solution and the monomer solution were both 1.7 ml/min.

After completion of the dropwise addition, the mixed solution was allowed to react at 78℃for 3 hours while stirring to give a copolymer (A) (post-polymerization step (III)).

To the reaction solution containing the copolymer (a) thus obtained, propylene glycol monomethyl ether as the solvent (B) was added so that the content of the components other than the solvent became 35 mass%, thereby obtaining a polymer composition of synthesis example 1.

Synthesis examples 2 to 6 and comparative Synthesis examples 1 to 3

Polymer compositions of Synthesis examples 2 to 6 and comparative Synthesis examples 1 to 3 were obtained in the same manner as in Synthesis example 1 except that the materials shown in Table 1 and Table 2 were used in the proportions shown in Table 1 and Table 2.

TABLE 1

TABLE 2

In tables 1 and 2, (m-a) represents a monomer having a blocked isocyanate group. (m-b) represents a hydroxyl group-containing monomer. (m-c) represents a monomer containing an acid group. (d) Represents other monomers not corresponding to (m-a), (m-b) and (m-c).

In tables 1 and 2, (equivalent number of blocked isocyanate groups) represents equivalent number of blocked isocyanate groups contained in the molecule of the copolymer (a).

The materials used in tables 1 and 2 are as follows.

MOI-BP: 2- [ (3, 5-dimethylpyrazolyl) carbonylamino ] ethyl methacrylate, MOI-BP (registered trademark), manufactured by Zhaoshi electric Co., ltd.

MOI-BM: moi-BM (2-methylpropionate-0- (1' -methylpropionamino) carboxyamino) ethyl ester (manufactured by Zhaohe electric Co., ltd.)

4-hydroxybutyl acrylate (Mitsubishi chemical Co., ltd.)

2-hydroxyethyl methacrylate (Co., ltd.)

Methacrylic acid (made by kura corporation)

Acrylic acid (manufactured by Toyama Synthesis Co., ltd.)

2EHA: 2-ethylhexyl acrylate (manufactured by Toyama Synthesis Co., ltd.)

TCDMA: tricyclo [5.2.1.0 ^2,6 ]Decyl-8-methacrylate (manufactured by Hitachi chemical Co., ltd.)

GMA: glycidyl methacrylate (manufactured by Nipple Co., ltd.)

The polymer compositions of synthesis examples 1 to 6 and comparative synthesis examples 1 to 3 shown in tables 1 and 2 were evaluated by measuring the respective physical properties of weight average molecular weight (Mw), glass transition temperature (Tg), storage stability and acid value by the methods shown below. The results are shown in tables 1 and 2.

Weight average molecular weight (Mw) >

The weight average molecular weight (Mw) of each of the copolymers (A) contained in the polymer compositions of Synthesis examples 1 to 6 and comparative Synthesis examples 1 to 3 was measured.

The weight average molecular weight is a weight average molecular weight in terms of standard polystyrene measured using Gel Permeation Chromatography (GPC) under the following conditions.

Column: mono and Udio, UK, LF-804+LF-804 (manufactured by Zhaohe electric Co., ltd.)

Column temperature: 40 DEG C

Sample: 0.2% by mass of a tetrahydrofuran solution of the copolymer

Developing solvent: tetrahydrofuran (THF)

A detector: differential refractometer (Pop-Du brand) RI-71S (manufactured by Zhaowa electric Co., ltd.)

Flow rate: 1 mL/min

< glass transition temperature (Tg) >)

The polymer compositions of Synthesis examples 1 to 6 and comparative Synthesis examples 1 to 3 were applied to a glass substrate, and dried at 50℃under reduced pressure for 24 hours. Then, the mixture was redissolved in acetone, and dried again at 50℃under reduced pressure for 24 hours. The solid content of the copolymer solution from which the volatile components were removed in this manner was measured by DSC (differential scanning calorimeter, measuring apparatus: seti コ DSC 6200) under a nitrogen gas stream at a heating rate of 10 ℃/min in accordance with JIS-K7121 (intermediate glass transition temperature). The obtained result was defined as the glass transition temperature (Tg) of the copolymer (A).

< preservation stability >

After the preparation, the polymer compositions of Synthesis examples 1 to 6 and comparative Synthesis examples 1 to 3, each having a component other than the solvent of 35 mass%, were weighed into glass containers in equal amounts, and capped to prevent the entry of dust and the like, thereby preparing samples. After the viscosity of each sample was measured, it was left to stand in a thermostat maintained at 12℃for 3 months, respectively. Further, the viscosity of each sample was measured after standing for 3 months. The viscosity was measured using an E-type viscometer (RE-80L, manufactured by DONGCHINESE INDUSTRIAL APPLICABILITY, cone. No. 3) at 25℃and a rotation speed of 10 rpm.

For each sample, the thickening ratio { (1- (viscosity after 3 months of standing/viscosity before standing)) ×100 (%) } was calculated with respect to the viscosity before standing in a thermostat, and evaluated by the following criteria.

Excellent (excellent): the tackifying rate is below 10 percent

((good): the tackifying rate is 10.1 to 20 percent

Delta (difference): the tackifying rate is more than 20.1 percent

As shown in tables 1 and 2, the polymer compositions of synthesis examples 1 to 6 and comparative synthesis example 3 were evaluated for storage stability as excellent or good, and were confirmed to have excellent storage stability.

In contrast, as shown in table 2, the polymer compositions of comparative synthesis examples 1 and 2 were evaluated for storage stability as Δ (poor), and although they were not cured by storage, the viscosity was higher than the results of examples, and the storage stability was insufficient.

< acid value >

The acid values of the polymer compositions of Synthesis examples 1 to 6 and comparative Synthesis examples 1 to 3 were measured, respectively, and were used as the acid value of the copolymer (A).

The acid value of the curable polymer was measured in accordance with JIS K6901.5.3. That is, the acid value is the mg of potassium hydroxide required for neutralizing the acidic component contained in 1g of the copolymer.

Examples 1 to 6 and comparative examples 1 to 3

The polymer compositions of synthesis examples 1 to 6 and comparative synthesis examples 1 to 3 shown in tables 1 and 2, propylene glycol monomethyl ether acetate as the solvent (B), a mixture of dipentaerythritol pentaacrylate and dipentaerythritol hexaacrylate as the reactive diluent (C) (manufactured by japan chemical company, DPHA), 1- [ 9-ethyl-6- (2-methylbenzoyl) -9H-carbazol-3-yl ] ethanone 1- (o-acetoxime) (manufactured by BASF corporation) as the photopolymerization initiator (D), and dye (VALIFAST BLUE 2620) as the colorant (E) were mixed in the proportions shown in table 3, respectively, to prepare resin compositions of examples 1 to 6 and comparative examples 1 to 3.

TABLE 3

The amount of the solvent contained in the reaction liquid used in producing the copolymer (a) was not contained in the copolymer (a) shown in table 3.

The amount of the solvent (B) shown in table 3 is an amount obtained by adding the solvent (propylene glycol monomethyl ether) contained in the polymer composition and the solvent (propylene glycol monomethyl ether acetate) added at the time of production of the resin composition. The content of the hydroxyl group-containing solvent in the solvent (B) shown in table 3 was 79.1 mass%.

The resin compositions of examples 1 to 6 and comparative examples 1 to 3 were evaluated for alkali developability and solvent resistance by the methods shown below.

(1) Alkali developability

The resin compositions of examples and comparative examples were spin-coated on a glass substrate (alkali-free glass substrate) having a square shape in plan view and having a longitudinal direction of 5cm and a transverse direction of 5cm so that the thickness after exposure became 2.5. Mu.m, respectively, to form a coating film. Then, the solvent in the coating film was volatilized and removed by heating at 100℃for 3 minutes.

Next, a photomask having a predetermined pattern was placed at a distance of 100 μm from the coating film, and the energy beam was applied to the coating film via the photomask at an energy beam of 40mJ/cm ² Ultraviolet rays with a wavelength of 365nm were irradiated to expose the exposed portions to light, thereby curing the exposed portions.

Then, an aqueous solution containing 0.1 mass% sodium carbonate was sprayed at a temperature of 23℃and a pressure of 0.3MPa, and the unexposed portion was dissolved and developed. Then, baking was performed at 100℃for 20 minutes to form a prescribed pattern.

Further, the pattern after alkali development was observed by using a Hitachi-Tech high-level electron microscope S-3400, and the residue after alkali development was confirmed and evaluated by the following criteria. The results are shown in Table 4.

O (good): without residues of unexposed parts

X (not): residues with unexposed portions

(2) Solvent resistance

Next, the energy ray was applied to the film at an energy of 40mJ/cm ² Ultraviolet rays with a wavelength of 365nm were irradiated to expose the exposed portions to light, thereby curing the exposed portions. Then, the coated film was cured by baking at 80℃for 30 minutes or at 100℃for 20 minutes to prepare a cured film.

The cured film thus produced was immersed in 20g of propylene glycol monomethyl ether at 23℃for 15 minutes. The color change (. DELTA.Eab) of the cured film before and after dipping was measured by a spectrophotometer UV-1650PC (manufactured by Shimadzu corporation), and the solvent resistance was evaluated based on the result. The results are shown in Table 4. The color change values before and after dipping were good for a few hours.

TABLE 4

As shown in table 4, the cured films obtained by curing the resin compositions of examples 1 to 6 were evaluated to be good in alkali developability.

The cured films obtained by curing the resin compositions of examples 1 to 6 were excellent in solvent resistance, and had a Δeab of less than 2 at a temperature of 80 ℃ for 30 minutes and a temperature of 100 ℃ for 20 minutes.

The cured films obtained by curing the resin compositions of comparative examples 1 to 3 were evaluated for their alkali developability well. However, the cured films obtained by curing the resin compositions of comparative examples 1 and 2 had insufficient solvent resistance, and Δeab was 2 or more when the temperature of curing the coating film was 80 ℃ and the time was 30 minutes. Further, the cured film obtained by curing the resin composition of comparative example 3 had Δeab of 2 or more at a temperature of 80 ℃ for 30 minutes and at a temperature of 100 ℃ for 20 minutes, respectively, and the solvent resistance was insufficient.

Industrial applicability

According to the present invention, there are provided a resin composition which has good alkali developability when used as a photosensitive material and is excellent in storage stability, and which gives a cured product having excellent solvent resistance even when cured at a low temperature, a copolymer useful for the preparation of the resin composition, and a method for producing the copolymer. Further, according to the present invention, there are provided a colored pattern composed of a cured product of a resin composition which is excellent in solvent resistance even when cured at a low temperature and which is excellent in alkali developability, a color filter having the colored pattern, and an image display element having the color filter.

The resin composition of the present invention can be preferably used in a wide range of applications as a material such as a transparent film, a protective film, an insulating film, an overcoat film, a photo spacer, a black matrix, a black column spacer, a resist for a color filter, and the like.

Claims

1. A copolymer comprising:

a structural unit (b) having a hydroxyl group; and

a structural unit (c) having an acid group,

and the glass transition temperature is 30 ℃ or lower.

2. The copolymer according to claim 1, wherein the structural unit (b) is a structural unit derived from a hydroxyalkyl (meth) acrylate.

3. The copolymer according to claim 1 or 2, wherein the structural unit (c) is a structural unit derived from an unsaturated carboxylic acid.

4. The copolymer according to any one of claims 1 to 3, wherein the structural unit (a) is a structural unit derived from a compound having the blocked isocyanate group and a (meth) acryloyloxy group.

5. The copolymer according to any one of claims 1 to 4, which contains 1 to 45 mol% of the structural unit (a), 1 to 50 mol% of the structural unit (b), and 1 to 60 mol% of the structural unit (c).

6. The copolymer according to any one of claims 1 to 5, having a weight average molecular weight of 1000 to 50000.

7. A resin composition comprising the copolymer (A) according to any one of claims 1 to 6, and a solvent (B),

the solvent (B) comprises a hydroxyl group-containing solvent.

8. The resin composition according to claim 7, further comprising a reactive diluent (C) and a photopolymerization initiator (D).

9. The resin composition according to claim 8, further comprising a colorant (E).

10. The resin composition according to claim 9, which comprises, relative to 100 parts by mass of the total amount of the copolymer (A) and the reactive diluent (C)

10 to 90 parts by mass of the copolymer (A),

30 to 1000 parts by mass of the solvent (B),

10 to 90 parts by mass of the reactive diluent (C),

0.1 to 30 parts by mass of a photopolymerization initiator (D),

3-80 parts by mass of the colorant (E).

11. A color filter comprising a colored pattern comprising a cured product of the resin composition according to claim 9 or 10.

12. An image display element comprising the color filter according to claim 11.

13. A method for producing a copolymer, characterized by comprising the steps of:

A solvent heating step (I) of heating the solvent (B-1) to 60-90 ℃;

14. The method for producing a copolymer according to claim 13, wherein in the solvent heating step (I), a chain transfer agent is added to the solvent (B-1) and then the temperature is raised.

15. The method for producing a copolymer according to claim 13, wherein the post-polymerization step (III) is performed to obtain a copolymer having a glass transition temperature of 30 ℃ or lower, wherein the copolymer contains a structural unit (a) having a blocked isocyanate group blocked with a pyrazole compound, a structural unit (b) having a hydroxyl group, and a structural unit (c) having an acid group.