Resin composition and method for producing the resin composition

Abstract

This copolymer contains a structural unit (a) having a blocked isocyanate group blocked by a pyrazole compound, a structural unit (b) having a hydroxy group, and a structural unit (c) having an acid group, wherein the copolymer has a glass transition temperature of at most 30 °C.

Description

[Technical Field]

[0001] The present invention relates to a copolymer, a resin composition, a color filter, an image display element, and a method for producing the copolymer. This application claims priority based on Japanese Patent Application No. 2020-215474, filed on December 24, 2020, the contents of which are incorporated herein by reference. [Background technology]

[0002] In general, image display elements such as organic electroluminescence (EL) display devices (especially WRGB systems that combine white-emitting organic EL with color filters), liquid crystal display elements, integrated circuit elements, and solid-state imaging elements are provided with films and fine patterns such as color filters, black matrices, color filter protective films, photospacers, protrusions for liquid crystal alignment, or microlenses and insulating films for touch panels.

[0003] In recent years, with the trend toward more flexible and wearable displays, substrate materials have been shifting from glass to organic materials such as resins. Organic materials have inferior heat resistance compared to glass. Therefore, for components formed by thermally curing a resin composition on a substrate, it is desirable to lower the temperature at which the resin composition is thermally cured, depending on the heat resistance of the organic substrate. For example, color filters have conventionally been formed by thermally curing a resin composition on a substrate at a temperature of 210 to 230° C. However, when forming a color filter on a flexible substrate made of resin, the heat resistance of the substrate is poor, so it is required to form the color filter by thermally curing the resin composition at a temperature of 80 to 150° C.

[0004] In particular, in color filters used in organic EL display devices, there is a tendency to increase the content of colorant in the resin composition in order to improve color reproducibility. Generally, resin compositions containing a large amount of colorant are difficult to photocure. Therefore, it is even more important for resin compositions used in color filters of organic EL display devices to be cured by thermal crosslinking. For this reason, there is an increasing need to improve the thermosetting properties, especially at low temperatures, of resin compositions used in color filters of organic EL display devices.

[0005] Conventionally, resin compositions used as materials for color filters include those described in Patent Documents 1 and 2, for example. Patent Document 1 states that (a) the absorption coefficient at 365 nm in methanol is 1.0 × 10 3 mL / gcm or more, (b) a polymerization initiator having an absorption coefficient of 1.0 × 10 at 365 nm in methanol 2 mL / gcm or less, and the extinction coefficient at 254 nm is 1.0 × 10 3 The patent discloses a photosensitive coloring composition containing (a) a polymerization initiator having a viscosity of 1000 kJ / 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 color filters, 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 documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-041058 [Patent Document 2] Japanese Patent Application Publication No. 2017-194662 Summary of the Invention [Problem to be solved by the invention]

[0007] However, conventional resin compositions have not been able to provide a cured product having good developability and storage stability when used as a photosensitive material, and excellent solvent resistance when cured at low temperatures. The present invention has been made in view of the above circumstances, and aims to provide a resin composition that has good developability when used as a photosensitive material, has excellent storage stability, and gives a cured product that has excellent solvent resistance even when cured at low temperatures; a copolymer that is useful for preparing this resin composition; and a method for producing the copolymer. Another object of the present invention is to provide a color filter having a colored pattern made of a cured product of a resin composition that has good developability and that gives a cured product with excellent solvent resistance even when cured at low temperatures, and an image display element equipped with the color filter. [Means for solving the problem]

[0008] A first aspect of the present invention provides the following copolymer: [1] A structural unit (a) having a blocked isocyanato group blocked with a pyrazole compound; a structural unit (b) having a hydroxy group; and a structural unit (c) having an acid group, A copolymer characterized by having a glass transition temperature of 30°C or less.

[0009] The copolymer of the first aspect of the present invention preferably has the characteristics described in the following [2] to [6]. It is also preferable to arbitrarily combine two or more of the characteristics described in the following [2] to [6]. [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 isocyanato group and a (meth)acryloyloxy group.

[0010] [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 1,000 to 50,000.

[0011] A second aspect of the present invention provides the following resin composition. [7] A resin composition comprising the copolymer (A) according to any one of [1] to [6] and a solvent (B), wherein the solvent (B) contains a hydroxy 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], further comprising a reactive diluent (C) and a photopolymerization initiator (D). [9] The resin composition according to [8], further comprising a colorant (E).

[0012]

[10] 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), the solvent (B) is 30 to 1000 parts by mass, the reactive diluent (C) is 10 to 90 parts by mass, the photopolymerization initiator (D) is 0.1 to 30 parts by mass, The resin composition according to [9], wherein the colorant (E) is contained in an amount of 3 to 80 parts by mass.

[0013] A third aspect of the present invention provides the following color filter.

[11] A color filter having a colored pattern made of a cured product of the resin composition according to [9] or

[10] . A fourth aspect of the present invention provides the following image display device.

[12] An image display device comprising the color filter according to

[11] .

[0014] A fifth aspect of the present invention provides the following method for producing a copolymer.

[13] A solvent heating step (I) of heating the solvent (B-1) to 60 to 90 ° C.; A monomer (ma) having a blocked isocyanato group blocked with a pyrazole compound, a hydroxy group-containing monomer (mb), and an acid group-containing monomer (mc) are added dropwise to the heated solvent (B-1), a dropping polymerization step (II) in which a polymerization initiator solution obtained by dissolving a polymerization initiator in a solvent (B-2) is dropped into the solvent (B-1) to form a mixed solution; a post-polymerization step (III) of reacting the mixed solution at 60 to 90°C for 1 to 5 hours while stirring, A method for producing a copolymer, wherein either or both of the solvent (B-1) and the solvent (B-2) contain a hydroxy group-containing solvent.

[0015] The fifth aspect of the present invention preferably has the following features

[14] and

[15] .

[14] The method for producing a copolymer according to

[13] , wherein in the solvent heating step (I), a chain transfer agent is added to the solvent (B-1) before heating.

[15] The method for producing a copolymer according to

[13] , wherein the post-polymerization step (III) produces a copolymer containing a structural unit (a) having a blocked isocyanato group blocked with a pyrazole compound, a structural unit (b) having a hydroxy group, and a structural unit (c) having an acid group, and having a glass transition temperature of 30°C or lower. [Effects of the Invention]

[0016] According to the present invention, it is possible to provide a resin composition that has good alkali developability when used as a photosensitive material, has excellent storage stability, and gives a cured product that has excellent solvent resistance even when cured at low temperatures; a copolymer that is useful for preparing this resin composition; and a method for producing the copolymer. Furthermore, according to the present invention, it is possible to provide a color filter having a colored pattern made of a cured product of a resin composition that has good alkali developability and that gives a cured product with excellent solvent resistance even when cured at a low temperature, and an image display element that includes the color filter. DETAILED DESCRIPTION OF THE INVENTION

[0017] The copolymer, the method for producing the copolymer, the resin composition, the color filter, and the image display element of the present invention will be described in detail below. However, the present invention is not limited to the following embodiments. For example, the present invention is not limited to the following examples, and additions, omissions, substitutions, or changes can be made to the number, amount, ratio, composition, type, position, material, configuration, and the like within the scope of the present invention.

[0018] In this specification, the term "(meth)acrylate" means either acrylate or methacrylate, and the term "(meth)acrylic acid" means either acrylic acid or methacrylic acid.

[0019] <Copolymer (A)> The copolymer (A) of the present embodiment contains a structural unit (a) having a blocked isocyanato group blocked with a pyrazole compound (hereinafter also simply referred to as "structural unit (a)"), a structural unit (b) having a hydroxy group (hereinafter also simply referred to as "structural unit (b)"), and a structural unit (c) having an acid group (hereinafter also simply referred to as "structural unit (c)").

[0020] <Constituent unit (a)> The structural unit (a) is a structural unit derived from a monomer (ma) (hereinafter simply referred to as "monomer (ma)") having a blocked isocyanato group blocked with a pyrazole compound. When a resin composition containing the copolymer (A) is thermally cured, the blocked isocyanato group of the structural unit (a) contained in the copolymer (A) is deblocked to form an isocyanato group, which reacts with a hydroxy group in the structural unit (b) to form a crosslinked structure. Therefore, a resin composition containing the copolymer (A) can produce a cured film with excellent solvent resistance even when cured at a low temperature of 50°C to 150°C.

[0021] Examples of pyrazole compounds that are blocking agents for blocked isocyanato groups include pyrazole; alkylpyrazoles such as 3-methylpyrazole and 5-ethylpyrazole; dialkylpyrazoles such as 3,5-dimethylpyrazole and 3,5-diethylpyrazole; 3-acetylaminopyrazole, pyrazole-3,5-dicarboxylic acid diethyl ester, etc. Among these, from the viewpoints of low-temperature curing properties as a resin composition and easy availability of raw materials, dialkylpyrazoles are preferred, and 3,5-dimethylpyrazole is more preferred.

[0022] The monomer (ma) that provides the structural unit (a) is not particularly limited as long as it is a compound that can be copolymerized with the hydroxy group-containing monomer (mb) and the acid group-containing monomer (mc) described below. For example, from the viewpoint of reactivity during synthesis of the copolymer (A), a monomer having a blocked isocyanato group and an ethylenically unsaturated bond can be used as the monomer (ma). Specific examples of the group having an ethylenically unsaturated bond include a vinyl group and a (meth)acryloyloxy group.

[0023] Examples of the monomer (ma) having a blocked isocyanato group and an ethylenically unsaturated bond include a reaction product of an isocyanate compound containing an ethylenically unsaturated group with a pyrazole compound. These monomers (ma) may be used alone or in combination of two or more.

[0024] The ethylenically unsaturated group-containing isocyanate compound used to form the monomer (ma) or contained in the monomer (ma) is preferably a compound represented by the following formula (1).

[0025] [ka] (In formula (1), R 4 represents a hydrogen atom or a methyl group; R 5 -CO-, -COOR 6 -(where R 6 is an alkylene group having 1 to 6 carbon atoms.) or -COO-R 7 O-CONH-R 8 -(where R 7 is an alkylene group having 2 to 6 carbon atoms; R 8 represents an alkylene group having 2 to 12 carbon atoms or an arylene group having 6 to 12 carbon atoms, which may have a substituent.

[0026] As described above, R in formula (1) 4 represents a hydrogen atom or a methyl group. R in formula (1) 5 -CO-, -COOR 6 -or-COO-R 7 O-CONH-R 8 - where R 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. 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. 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 in the alkylene group may be 3 to 10 or 4 to 8. The number of carbon atoms in the arylene group may be 7 to 10 or 8 to 9. Among these, R in formula (1) 5 -COOR 6- is preferred. 5 Ga-COOR 6 -If R 6 is preferably an alkylene group having 1 to 4 carbon atoms.

[0027] 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-isocyanato-1-methylethyl (meth)acrylate, 2-isocyanato-1,1-dimethylethyl (meth)acrylate, 4-isocyanatocyclohexyl (meth)acrylate, and (meth)acryloyl isocyanate.

[0028] The ethylenically unsaturated group-containing isocyanate compound represented by the formula (1) can also be an equimolar (1 mol:1 mol) reaction product of a 2-hydroxyalkyl (meth)acrylate and a diisocyanate compound. The alkyl group contained in the 2-hydroxyalkyl (meth)acrylate is preferably an ethyl group or an n-propyl group, more preferably an ethyl group. Examples of the diisocyanate compound include hexamethylene diisocyanate, 2,4- (or 2,6-) tolylene diisocyanate (TDI), 4,4'-diphenylmethane diisocyanate (MDI), 3,5,5-trimethyl-3-isocyanatomethylcyclohexyl isocyanate (IPDI), m- (or p-) xylene diisocyanate, 1,3- (or 1,4-) bis(isocyanatomethyl)cyclohexane, and lysine diisocyanate.

[0029] Among these ethylenically unsaturated group-containing isocyanate compounds, 2-isocyanatoethyl (meth)acrylate, 2-isocyanatopropyl (meth)acrylate, 3-isocyanatopropyl (meth)acrylate, 2-isocyanato-1-methylethyl (meth)acrylate, 2-isocyanato-1,1-dimethylethyl (meth)acrylate, 4-isocyanatocyclohexyl (meth)acrylate, and (meth)acryloyl isocyanate 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 two or more.

[0030] The reaction between an ethylenically unsaturated group-containing isocyanate compound and a pyrazole compound can be carried out regardless of the presence or absence of a solvent. When the reaction is carried out using a solvent, a solvent inactive to the isocyanato group is used. In the reaction, a catalyst such as an organic metal salt of tin, zinc, lead, or the like, or a tertiary amine may be used. The above reaction can generally be carried out at a temperature of -20 to 150°C, preferably 25 to 130°C. When the reaction temperature is -20°C or higher, a sufficient reaction rate can be obtained. Furthermore, when the reaction temperature is 150°C or lower, it is possible to prevent the raw material having a C=C (double bond) from polymerizing, thereby preventing gelation of the monomer (ma) that gives the structural unit (a) produced after the reaction.

[0031] Specific examples of the reaction product of an ethylenically unsaturated group-containing isocyanate compound and a pyrazole compound include 2-[(3,5-dimethylpyrazolyl)carbonylamino]ethyl methacrylate, 2-[(3-methylpyrazolyl)carbonylamino]ethyl methacrylate, etc. Among these, 2-[(3,5-dimethylpyrazolyl)carbonylamino]ethyl methacrylate is preferred because it is easily available, improves the curability of a resin composition containing copolymer (A), and by curing it, a cured product with excellent solvent resistance can be obtained.

[0032] <Structural Unit (b) Having a Hydroxy Group> The structural unit (b) having a hydroxy group contained in copolymer (A) does not have a blocked isocyanato group but has a hydroxy group. The structural unit (b) is a structural unit derived from a monomer (mb) (hereinafter simply referred to as "monomer (mb)") having a hydroxy group (however, this does not include those corresponding to the structural unit (a)). When a resin composition containing copolymer (A) is thermally cured, the hydroxy group of the structural unit (b) contained in copolymer (A) reacts with the isocyanato group generated by deblocking the blocked isocyanato group of the structural unit (a), thereby generating a crosslinked structure.

[0033] The monomer (mb) that provides the structural unit (b) is not particularly limited as long as it does not have a blocked isocyanato group and has a polymerizable unsaturated bond and a hydroxy group. Examples of the monomer (mb) include (meth)acrylic acid ester derivatives having a hydroxy group. Specific examples of such monomers (mb) 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 (mb) may be used alone or in combination of two or more.

[0034] Among the above-mentioned monomers, hydroxyalkyl(meth)acrylate is preferred as the monomer (mb) from the viewpoints of reactivity in synthesizing the copolymer (A), low-temperature curing properties of the resin composition containing the copolymer (A), and ease of availability. Examples of hydroxyalkyl(meth)acrylate include 2-hydroxyethyl(meth)acrylate, 2-hydroxypropyl(meth)acrylate, and 4-hydroxybutyl(meth)acrylate, and from the viewpoints of ease of availability and reducing the glass transition temperature of the copolymer (A), 2-hydroxyethyl(meth)acrylate and 4-hydroxybutyl(meth)acrylate are more preferred.

[0035] <Structural Unit (c) Having an Acid Group> The structural unit (c) having an acid group contained in copolymer (A) does not have a blocked isocyanato group or a hydroxy group, but does have an acid group. The structural unit (c) is a structural unit derived from a monomer (mc) having an acid group (hereinafter simply referred to as "monomer (mc)") (excluding those that fall under structural units (a) and (b)). The inclusion of structural unit (c) in copolymer (A) improves alkaline developability when a resin composition containing copolymer (A) is used as a photosensitive material.

[0036] Examples of the acid group contained in the structural unit (c) include a carboxy group, a sulfo group, a phospho group, etc. Among these acid groups, a carboxy group is preferred as the acid group contained in the structural unit (c) from the viewpoint of ease of availability. The monomer (mc) that gives the structural unit (c) is not particularly limited as long as it does not have a blocked isocyanato group or a hydroxy group and has a polymerizable unsaturated bond and an acid group. Examples of the monomer (mc) include unsaturated carboxylic acids or their anhydrides, unsaturated sulfonic acids, and unsaturated phosphonic acids.

[0037] Specific examples of the monomer (mc) 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-cyanocinnamic acid, maleic acid, maleic anhydride, monomethyl maleate, monoethyl maleate, monoisopropyl maleate, fumaric acid, itaconic acid, itaconic anhydride, citraconic acid, and citraconic anhydride; unsaturated sulfonic acids, such as 2-acrylamido-2-methylpropanesulfonic acid, tert-butylacrylamidosulfonic acid, and p-styrenesulfonic acid; and unsaturated phosphonic acids, such as vinylphosphonic acid. These monomers (mc) may be used alone or in combination of two or more.

[0038] Among these monomers, it is preferable to use an unsaturated carboxylic acid as the monomer (mc), and it is more preferable to use (meth)acrylic acid, because it is easily available and the resin composition containing the copolymer (A) has excellent alkaline developability.

[0039] Here, the proportions of the structural unit (a), the structural unit (b), and the structural unit (c) contained in the copolymer (A) will be explained. 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 %, and may be 18 to 33 mol %, 20 to 30 mol %, or 25 to 28 mol %, as necessary. 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%, and may be 15 to 40 mol%, 18 to 33 mol%, 20 to 30 mol%, or 22 to 25 mol%, as necessary. 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%, and may be 13 to 35 mol%, 15 to 30 mol%, 20 to 28 mol%, or 22 to 25 mol%, as necessary.

[0040] Therefore, it is preferable that the copolymer (A) 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 this embodiment, when the proportion of the structural unit (a) and the structural unit (b) is 1 mol % or more, by thermally curing a resin composition containing the copolymer (A), the hydroxy group of the structural unit (b) reacts with the isocyanato group generated by deblocking the blocked isocyanato group of the structural unit (a), thereby generating a sufficient crosslinked structure. Therefore, a resin composition containing the copolymer (A) containing 1 mol % or more each of the structural unit (a) and the structural unit (b) can produce a cured product with good solvent resistance even when thermally cured at low temperatures.

[0041] When 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) is improved. Furthermore, when the proportion of the structural unit (a) is 45 mol% or less, it is easier to ensure the contents of the structural units (b) and (c). Therefore, it is easier to obtain the effects of including the structural units (b) and (c).

[0042] Furthermore, when the proportion of structural unit (b) in copolymer (A) is 50 mol% or less, gelation during the polymerization reaction to produce copolymer (A) can be prevented. Furthermore, excessive crosslinking structures resulting from the reaction between the isocyanato group formed by deblocking the blocked isocyanato group of structural unit (a) and structural unit (b) are not formed, improving the storage stability of resin compositions containing copolymer (A). Furthermore, when the proportion of structural unit (b) is 50 mol% or less, it becomes easier to ensure the contents of structural unit (a) and structural unit (c). Therefore, the effects of including structural unit (a) and structural unit (c) can be more easily achieved.

[0043] When the proportion of the structural unit (c) in the copolymer (A) is 1 mol % or more, the resin composition containing the copolymer (A) has a sufficiently fast alkaline development rate. When the proportion of the structural unit (c) in the copolymer (A) is 60 mol % or less, the alkaline development rate of the resin composition containing the copolymer (A) is appropriately suppressed, making it easier to form a precise pattern. Furthermore, when the proportion of the structural unit (c) in the copolymer (A) is 60 mol % or less, it is easier to ensure the contents of the structural units (a) and (b). Therefore, the resin composition containing the copolymer (A) is more likely to produce a cured product with excellent solvent resistance, even when cured at low temperatures.

[0044] The total content of the structural unit (a) and the structural unit (b) contained in the copolymer (A) is preferably 10 to 90 mol%, more preferably 20 to 80 mol%, and even more preferably 30 to 70 mol%. If necessary, it may be 35 to 65 mol%, 40 to 60 mol%, or 45 to 55 mol%, for example. When the total content of the structural unit (a) and the structural unit (b) is 10 to 90 mol%, the resin composition containing the copolymer (A) has better storage stability and can produce a cured product with excellent solvent resistance even when cured at low temperatures. Furthermore, since it is easier to ensure the content of the structural unit (c), it is easier to obtain a resin composition with better alkali developability when used as a photosensitive material.

[0045] When a resin composition containing copolymer (A) contains, in addition to copolymer (A), a compound having a hydroxy group as reactive diluent (C), it is preferable that the total amount of hydroxy groups contained in structural unit (b) contained in copolymer (A) is reduced in accordance with the amount of hydroxy groups contained in reactive diluent (C). Specifically, the molar ratio of the total amount of blocked isocyanato groups in the structural unit (a) to the total amount of hydroxy groups contained in the resin composition (the sum of the hydroxy groups in the structural unit (b) and the hydroxy groups contained in the reactive diluent (C)) is preferably 10:90 to 90:10, more preferably 30:70 to 70:30, and even more preferably 40:60 to 60:40. When the molar ratio is within the above range, thermal curing of a resin composition containing copolymer (A) facilitates the formation of a crosslinked structure through the reaction between the hydroxy groups contained in the resin composition and the isocyanato groups formed by deblocking the blocked isocyanato groups in the structural unit (a). This results in a cured product with even better solvent resistance.

[0046] <Other structural units (d)> The copolymer (A) of the present embodiment may, if necessary, contain, in addition to the structural units (a) to (c), another structural unit (d) copolymerizable with these (however, excluding those corresponding to the structural units (a) to (c)).

[0047] The monomer (md) (hereinafter also referred to simply as "monomer (md)") that provides the other structural unit (d) is not particularly limited as long as it is a compound that does not have a blocked isocyanato group, a hydroxy group, or an acid group and is copolymerizable with the monomers (ma) to (mc).

[0048] Specific examples of the monomer (md) that can provide the other structural unit (d) include aromatic vinyl compounds such as styrene, α-methylstyrene, o-vinyltoluene, p-vinyltoluene, o-chlorostyrene, m-chlorostyrene, methoxystyrene, p-nitrostyrene, p-cyanostyrene, and p-acetylaminostyrene; norbornene (bicyclo[2.2.1]hept-2-ene), 5-methylbicyclo[2.2.1]hept-2-ene, tetracyclo[4.4.0.1]hept-2-ene, and methylcyclo[4.4.0.1]hept-2-ene. 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-ethylidenetetracyclo[4.4.0.1 2,5 .1 7,12 ]dodec-3-ene, pentacyclo[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, tert-butyl (meth)acrylate, pentyl (meth)acrylate, benzyl (meth)acrylate, isoamyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, dodecyl (meth)acrylate, cyclohexyl (meth)acrylate, methyl Cyclohexyl (meth)acrylate, rosin (meth)acrylate, norbornyl (meth)acrylate, 5-ethylnorbornyl (meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentanyl (meth)acrylate, dicyclopentenyloxyethyl acrylate, isobornyl (meth)acrylate, adamantyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, 1,1,1-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, phenoxypolyethylene glycol (meth)acrylate, nonylphenoxypolyethylene glycol mono(meth)acrylate, biphenyloxyethyl (meth)acrylate, naphthalene (meth)acrylate, anthracene (meth) (Meth)acrylic acid esters such as acrylates and ethoxylated phenyl (meth)acrylate; (meth)acrylic acid amides such as (meth)acrylic acid N,N-dimethylamide, (meth)acrylic acid N,N-di-isopropylamide, and (meth)acrylic acid anthracenylamide; vinyl compounds such as (meth)acrylic acid anilide, (meth)acrylonitrile, acrolein, vinyl chloride, vinylidene chloride, vinyl fluoride, vinylidene fluoride, N-vinylpyrrolidone, vinylpyridine, vinyl acetate, and vinyltoluene;Examples of unsaturated dicarboxylic acid diesters include diethyl citraconic acid, diethyl maleic acid, diethyl fumaric acid, and diethyl itaconate; monomaleimides such as N-phenylmaleimide, N-cyclohexylmaleimide, N-laurylmaleimide, and N-(4-hydroxyphenyl)maleimide; and glycidyl (meth)acrylate.

[0049] Among these, it is preferable to use a (meth)acrylic acid ester as the monomer (md), and from the viewpoint of adjusting the glass transition temperature of the copolymer (A) to 30° C. or less, it is preferable to use one having a homopolymer glass transition temperature of −20° C. or less, and it is particularly preferable to use 2-ethylhexyl (meth)acrylate or 4-hydroxybutyl acrylate. These monomers (md) may be used alone or in combination of two or more.

[0050] When copolymer (A) contains other structural units (d), the proportion thereof 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, it may be 3 to 45 mol%, 5 to 40 mol%, 10 to 35 mol%, 15 to 30 mol%, or 12 to 25 mol%. By including other structural units (d) in copolymer (A), properties such as solvent resistance of the cured product of a resin composition containing copolymer (A) can be appropriately improved. When the content of other structural units (d) is 80 mol% or less, it becomes easier to ensure the contents of structural units (a) to (c), and the effects of including structural units (a) to (c) become more pronounced.

[0051] (Weight average molecular weight (Mw)) The polystyrene-equivalent weight-average molecular weight of 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, or 9,000 to 12,000. When the weight-average molecular weight of copolymer (A) is 1,000 or more, the alkaline developability is improved when a resin composition containing copolymer (A) is used as a photosensitive material, and chipping of the pattern after alkaline development is less likely to occur. On the other hand, when the weight-average molecular weight of copolymer (A) is 50,000 or less, the development time when a resin composition containing copolymer (A) is used as a photosensitive material is appropriate, ensuring practicality.

[0052] (glass transition temperature (Tg)) The glass transition temperature (Tg) of the copolymer (A) is 30°C or lower, preferably 20°C or lower, and more preferably 0°C or lower. If the glass transition temperature of the copolymer (A) exceeds 30°C, it will adversely affect the curability at low temperatures. For this reason, the glass transition temperature of the copolymer (A) is set to 30°C or lower. The glass transition temperature of the copolymer (A) is preferably -50°C or higher, more preferably -40°C or higher, and even more preferably -30°C or higher. If the glass transition temperature of the copolymer (A) is -50°C or higher, a resin composition containing the copolymer (A) will yield a cured film with excellent heat resistance. If necessary, the glass transition temperature may be -45°C or higher to 25°C or lower, -35°C or higher to 15°C or lower, -25°C or higher to 10°C or lower, or -15°C or higher to 5°C or lower.

[0053] (acid number) The acid value (JIS K6901 5.3) of copolymer (A) can be selected appropriately. When a resin composition containing copolymer (A) is used as a photosensitive material, the acid value of copolymer (A) is preferably 20 to 300 KOHmg / g, more preferably 30 to 200 KOHmg / g. If necessary, it may be 40 to 150 KOHmg / g, or 50 to 100 KOHmg / g, for example. When the acid value of copolymer (A) is 20 KOHmg / g or more, when a resin composition containing copolymer (A) is used as a photosensitive material, alkaline developability is improved. On the other hand, when the acid value of copolymer (A) is 300 KOHmg / g or less, when a resin composition containing copolymer (A) is used as a photosensitive material, the exposed portion (photocured portion) is less likely to dissolve in an alkaline developer, resulting in a good pattern shape.

[0054] (Number of equivalents of blocked isocyanato groups) Copolymer (A) contains blocked isocyanato groups blocked with a pyrazole compound in its molecule. The equivalent weight of the blocked isocyanato groups may be selected as appropriate, but is preferably 300 to 6000, more preferably 500 to 3500. If necessary, it may be 400 to 2000 or 600 to 1000. When the equivalent weight of the blocked isocyanato groups is 300 or more, and if a sufficient number of hydroxy groups are present in a resin composition containing copolymer (A), thermal curing of the resin composition will result in sufficient crosslinking through the reaction between the hydroxy groups in the resin composition and the isocyanato groups generated by deblocking the blocked isocyanato groups of the structural unit (a). This results in a cured product with even better solvent resistance.

[0055] The number of equivalents of the blocked isocyanate group in copolymer (A) is the mass of copolymer (A) per mole of the blocked isocyanate group contained in copolymer (A). The number of equivalents of the blocked isocyanate group is determined by dividing the mass of copolymer (A) by the number of moles of the blocked isocyanate group contained in copolymer (A) (g / mol). The number of equivalents of the blocked isocyanate group is a theoretical value calculated from the amount of monomer (ma) charged.

[0056] <Method for producing copolymer (A)> The copolymer (A) of this embodiment can be produced, for example, by a method in which a solvent heating step (I), a dropwise polymerization step (II), and a post-polymerization step (III) are carried out in this order as shown below. (Solvent heating step (I)) A solvent (B-1) is prepared and heated to 60 to 90°C. In the solvent heating step (I), a chain transfer agent (described later) may be added to the solvent (B-1) before heating. By adding the chain transfer agent to the solvent (B-1) before heating, the degree of polymerization of the copolymer (A) synthesized in the dropping polymerization step (II) and the post-polymerization step (III) can be controlled. The concentration of the chain transfer agent in the solvent (B-1) is not particularly limited and may be, for example, 0.1 to 10% by mass.

[0057] (Drop polymerization step (II)) While stirring the heated solvent (B-1), the polymerization initiator solution is added dropwise to the heated solvent (B-1) together with the monomer solution to form a mixed solution, thereby carrying out dropwise polymerization. The monomer solution is prepared by dissolving a monomer (ma) having a blocked isocyanato group, a hydroxyl group-containing monomer (mb), an acid group-containing monomer (mc), and an optional monomer (md) in a solvent (B-2). As the solvent (B-2), the solvents exemplified for the solvent (B-1) can be used in the same way. The polymerization initiator solution is prepared by dissolving a polymerization initiator in a solvent (B-2). In the method for producing the copolymer (A) of this embodiment, either or both of the solvent (B-1) and the solvent (B-2) contain a hydroxy group-containing solvent.

[0058] In the dropping polymerization step (II), a chain transfer agent solution, which will be described later, may be added dropwise instead of the chain transfer agent that can be added in the solvent heating step (I). The chain transfer agent solution is obtained by dissolving a chain transfer agent in a solvent (B-2). Alternatively, in the solvent heating step (I), a portion of the chain transfer agent used in the production of the copolymer (A) may be added to a solvent (B-1) and then heated. In the dropping polymerization step (II), a portion of the chain transfer agent used may be removed and the remainder may be dissolved in a solvent (B-2), and the resulting chain transfer agent solution may be added dropwise to the heated solvent (B-1).

[0059] (Post-polymerization step (III)) After the dropwise addition of the monomer solution and the polymerization initiator solution is completed, the mixed solution is further reacted at 60 to 90° C. for 1 to 5 hours while being stirred.

[0060] "Solvent (B-1)" The solvent (B-1) used in the solvent heating step (I) may be a hydroxyl group-containing solvent only, a solvent not containing a hydroxyl group only, or a solvent containing both a hydroxyl group-containing solvent and a solvent not containing a hydroxyl group. The solvent (B-1) preferably contains a hydroxyl group-containing solvent that contains a hydroxyl group, and more preferably contains a hydroxyl group-containing solvent only.

[0061] Examples of hydroxy group-containing solvents 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; hydroxy group-containing carboxylic acid esters such as methyl 2-hydroxypropionate, ethyl 2-hydroxypropionate, methyl 2-hydroxy-2-methylpropionate, ethyl 2-hydroxy-2-methylpropionate, ethyl hydroxyacetate, and methyl 2-hydroxy-3-methylbutyrate; and diethylene glycol.

[0062] Among these hydroxyl group-containing solvents, primary and / or secondary alcohol solvents and ether solvents are preferred because they are effective in preventing gelation of the reaction solution and controlling the molecular weight of the copolymer (A) within an appropriate range in the dropping polymerization step (II) and / or post-polymerization step (III), and propylene glycol monomethyl ether, ethylene glycol monomethyl ether, and 3-methoxy-1-butanol are more preferred. These hydroxyl group-containing solvents may be used alone or in combination of two or more.

[0063] Examples of the solvent not containing a hydroxy 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; methyl 3-methoxypropionate, 3-ethyl ether, and methyl ether; Examples of the esters include methyl acetoacetate, ethyl ethoxypropionate, ethyl ethoxyacetate, 3-methyl-3-methoxybutyl acetate, 3-methyl-3-methoxybutylpropionate, ethyl acetate, n-butyl acetate, i-propyl acetate, i-butyl acetate, n-amyl acetate, i-amyl acetate, n-butyl propionate, ethyl butyrate, n-propyl butyrate, i-propyl butyrate, ethyl pyruvate, n-propyl pyruvate, methyl acetoacetate, ethyl acetoacetate, and ethyl 2-oxobutyrate; aromatic hydrocarbons such as toluene and xylene; and carboxylic acid amides such as N-methylpyrrolidone, N,N-dimethylformamide, and N,N-dimethylacetamide.

[0064] Among the solvents not containing a hydroxy group, from the viewpoints of availability, cost, and quality, it is preferable to use an ether solvent, and it is more preferable to use propylene glycol monomethyl ether acetate or diethylene glycol methyl ethyl ether. These solvents not containing a hydroxy group may be used alone or in combination of two or more.

[0065] When the solvent (B-1) used in the solvent heating step (I) contains a hydroxy group-containing solvent, the content of the hydroxy 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. When the content of the hydroxy group-containing solvent is 10% by mass or more, the effect of inhibiting the reaction between the isocyanato group derived from the monomer (ma) and the hydroxy group derived from the monomer (mb) in the dropping polymerization step (II) and / or the post-polymerization step (III) is sufficiently obtained. When the solvent (B-1) contains a solvent that does not contain a hydroxy group, the effect of increasing the amount of crosslinking reaction between the isocyanato group derived from the monomer (ma) and the hydroxy group derived from the monomer (mb) when cured as a resin composition is obtained.

[0066] "Temperature of solvent and mixed solution" In the production method of this embodiment, in the solvent heating step (I), the solvent (B-1) is placed in a reaction vessel and heated to 60 to 90° C. In the dropwise polymerization step (II) and the post-polymerization step (III), the mixed solution is reacted at 60 to 90° C. for 1 to 5 hours while being stirred. 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) may be the same or different.

[0067] In this embodiment, 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°C or higher, so that the polymerization reaction of the monomers (ma) to (mc) and the monomer (md) used as needed proceeds sufficiently in the dropping polymerization step (II) and the post-polymerization step (III).

[0068] Because 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°C or lower, the following effects can be achieved when a reaction product of an ethylenically unsaturated group-containing isocyanate compound and a pyrazole compound is used as the monomer (ma). That is, in the dropping polymerization step (II) and the post-polymerization step (III), dissociation of the pyrazole compound from the blocked isocyanate group to form an isocyanate group can be prevented. Therefore, gelation of the copolymer (A) during production, which would occur if the isocyanate group generated by deblocking the blocked isocyanate group reacted with a hydroxy group derived from the monomer (mb) or an acid group derived from the monomer (mc), can be prevented. Furthermore, because the temperature is 90°C or lower, even if some of the blocked isocyanato groups of the monomer (ma) are deblocked to generate isocyanato groups in the dropping polymerization step (II) and the post-polymerization step (III), the reaction between the isocyanato groups and the hydroxy groups derived from the monomer (mb) can be suppressed. As a result, a copolymer (A) can be obtained that contains a sufficient amount of structural units (a) having blocked isocyanato groups and structural units (b) having hydroxy groups.

[0069] In the dropping polymerization step (II), the polymerization initiator solution and the monomer solution are dropped into the solvent (B-1) heated to 60 to 90°C in the solvent heating step (I) to form a mixed solution, and polymerization is carried out. In the dropping polymerization step (II), a chain transfer agent solution may be further dropped into the heated solvent (B-1) to form a mixed solution containing the chain transfer agent.

[0070] In the dropping polymerization step (II), it is preferable to drop the polymerization initiator solution and the monomer solution simultaneously into the heated solvent (B-1), which allows for accurate control of the molecular weight of the copolymer (A) and prevents gelation of the copolymer (A) during production. In the dropping polymerization step (II), when the chain transfer agent solution is dropped into the heated solvent (B-1), 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 polymerization initiator solution and the monomer solution are dropped.

[0071] The dropwise addition rates of the polymerization initiator solution, the monomer solution, and the chain transfer agent solution can be appropriately determined depending on the reaction scale, such as the capacity of the reaction vessel, the volume of the heated solvent (B-1), the polymerization initiator solution, the monomer solution, and the chain transfer agent solution, etc. When a 1 L reaction vessel is used, for example, the dropwise addition rates of the polymerization initiator solution, the monomer solution, and the chain transfer agent solution are preferably set to a rate of 0.1 to 5 mL / min. The time for dropping the polymerization initiator solution, the monomer solution, and the chain transfer agent solution can be, for example, 30 minutes to 1 hour. The dropwise addition rates and dropwise addition times of the polymerization initiator solution, the monomer solution, and the chain transfer agent solution may be different from one another, or some or all of them may be the same.

[0072] In this embodiment, the polymerization initiator solution, the monomer solution, and the chain transfer agent solution used as needed are each prepared separately. (Polymerization initiator solution) The polymerization initiator solution is prepared by dissolving a polymerization initiator in a solvent (B-2). The polymerization initiator is not particularly limited, but examples thereof include 2,2'-azobis(2,4-dimethylvaleronitrile), azobisisobutyronitrile, azobisisovaleronitrile, benzoyl peroxide, t-butylperoxy-2-ethylhexanoate, etc. These polymerization initiators may be used alone or in combination of two or more.

[0073] The concentration of the polymerization initiator in the polymerization initiator solution is preferably a concentration that makes it easy to obtain a mixed solution of uniform concentration, and can be, for example, 16 to 50 mass %, without any particular limitation. The amount of the polymerization initiator solution used is preferably an amount such that the amount of the polymerization initiator contained in the polymerization initiator solution is 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 monomers charged (i.e., the mass of monomers (ma) to (md) in the monomer solution).

[0074] (monomer solution) The monomer solution is prepared by dissolving a monomer (ma) having a blocked isocyanato group, a hydroxyl group-containing monomer (mb), an acid group-containing monomer (mc), and an optional monomer (md) in a solvent (B-2). The monomers (ma) to (md) may be those exemplified in the section on copolymer (A).

[0075] The monomer solution may be produced by dissolving the monomers (ma) to (md) individually in the solvent (B-2) and then mixing them, or by mixing the monomers (ma) to (md) and then dissolving them in the solvent (B-2). The total concentration of the monomers (ma) to (md) in the monomer solution is preferably a concentration that makes it easy to obtain a mixed solution of uniform concentration, and can be, for example, 50 to 95% by mass, but is not particularly limited.

[0076] When one or more of the monomers used to produce the copolymer (A) are liquid at room temperature, the monomers that are liquid at room temperature may also serve as a solvent in the monomer solution, in which case the monomer solution does not need to contain the solvent (B-2). An example of a monomer that is liquid at room temperature is 2-[(3,5-dimethylpyrazolyl)carbonylamino]ethyl methacrylate, which is a monomer (ma) having a blocked isocyanato group.

[0077] The proportions of the monomers (ma) to (mc) used in producing the copolymer (A) are not particularly limited, but are preferably 1 to 45 mol% of the monomers (ma), 1 to 50 mol% of the monomers (mb), and 1 to 60 mol% of the monomers (mc), more preferably 5 to 40 mol% of the monomers (ma), 5 to 45 mol% of the monomers (mb), and 5 to 50 mol% of the monomers (mc), and even more preferably 15 to 35 mol% of the monomers (ma), 10 to 35 mol% of the monomers (mb), and 10 to 40 mol% of the monomers (mc).

[0078] When copolymer (A) contains structural unit (d), the proportions of the monomers (ma) to (md) used in producing copolymer (A) are not particularly limited, but are preferably 1 to 45 mol% of monomers (ma), 1 to 50 mol% of monomers (mb), 1 to 60 mol% of monomers (mc), and 1 to 80 mol% of monomers (md), more preferably 5 to 40 mol% of monomers (ma), 5 to 45 mol% of monomers (mb), 5 to 50 mol% of monomers (mc), and 5 to 75 mol% of monomers (md), and even more preferably 15 to 35 mol% of monomers (ma), 10 to 35 mol% of monomers (mb), 10 to 40 mol% of monomers (mc), and 10 to 50 mol% of monomers (md).

[0079] (Chain transfer agent solution) The chain transfer agent solution is prepared by dissolving the chain transfer agent in the solvent (B-2). In the dropping polymerization step (II), the degree of polymerization of the copolymer (A) synthesized in the post-polymerization step (III) can be controlled by adding a chain transfer agent solution dropwise, and therefore the copolymer (A) having a desired molecular weight range can be easily produced. The chain transfer agent is not particularly limited, but for example, a polyfunctional thiol can be preferably used. The polyfunctional thiol is a compound having two or more mercapto groups in the molecule.

[0080] The polyfunctional thiol is not particularly limited, but examples thereof include thioglycolic acid, 1,2-ethanedithiol, 1,4-bis(3-mercaptobutyryloxy)butane, tetraethylene glycol bis(3-mercaptopropionate), trimethylolethane tris(3-mercaptobutyrate), trimethylolpropane tris(3-mercaptobutyrate), trimethylolpropane tris(3-mercaptopropionate), pentaerythritol, methylisothiazolinone ... Examples include erythritol 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, and dipentaerythritol hexakis(3-mercaptopropionate).

[0081] Among the above, it is preferable to use pentaerythritol tetrakis(3-mercaptobutyrate) and / or thioglycolic acid, pentaerythritol tetrakis(3-mercaptopropionate) as the chain transfer agent from the viewpoints of availability, cost, and quality. The concentration of the chain transfer agent in the polymerization initiator solution is preferably a concentration that makes it easy to obtain a mixed solution of uniform concentration, and can be, for example, 0.1 to 10% by mass, without any particular limitation.

[0082] The amount of the chain transfer agent solution used is preferably an amount such that the chain transfer agent contained in the mixed solution is, 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 monomers charged (i.e., the mass of monomers (ma) to (md) in the monomer solution). By keeping the amount of the chain transfer agent solution used within the above range, copolymer (A) having a desired molecular weight range can be easily produced in the post-polymerization step (III).

[0083] "Solvent (B-2)" The solvent (B-2) used in the dropping polymerization step (II) can be the same as the solvent (B-1) used in the solvent heating step (I).Similar to the solvent (B-1), the solvent (B-2) may be a hydroxyl group-containing solvent only, a solvent not containing a hydroxyl group only, or a solvent containing both a hydroxyl group-containing solvent and a solvent not containing a hydroxyl group.The solvent (B-2) preferably contains a hydroxyl group-containing solvent containing a hydroxyl group, and more preferably contains only a hydroxyl group-containing solvent.

[0084] In the method for producing the copolymer (A) of this embodiment, either or both of the solvent (B-1) and the solvent (B-2) contain a hydroxy group-containing solvent. Therefore, when the solvent (B-1) used in the solvent heating step (I) does not contain a hydroxy group-containing solvent, the solvent (B-2) used in the dropwise polymerization step (II) contains a hydroxy group-containing solvent.

[0085] The content of the hydroxyl group-containing solvent 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 polymerization step (II) is preferably 10 to 100% by mass, more preferably 20 to 90% by mass, and even more preferably 40 to 80% by mass. When the content of the hydroxyl group-containing solvent is 10% by mass or more, the effect of inhibiting the reaction between the isocyanato group derived from the monomer (ma) and the hydroxyl group derived from the monomer (mb) in the dropwise polymerization step (II) and / or the post-polymerization step (III) is sufficiently obtained. When one or both of the solvents (B-1) and (B-2) contain a solvent that does not contain a hydroxyl group, a content of the hydroxyl group-containing solvent of 90% by mass or less facilitates dissolution of the polymerization initiator, for example, when 2,2'-azobis(2,4-dimethylvaleronitrile) is used as the polymerization initiator, resulting in good workability.

[0086] In the production method of this embodiment, the solvent (B-1) used in the solvent heating step (I) and / or the solvent (B-2) used in the dropwise polymerization step (II) contain a hydroxy 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 hydroxy group of the hydroxy group-containing solvent reacts with a part of the isocyanato group generated from the blocked isocyanato group of the monomer (ma).

[0087] As a result, in this embodiment, the reaction between the isocyanato group derived from the monomer (ma) and the hydroxy group derived from the monomer (mb) is moderately inhibited in the dropping polymerization step (II) and / or the post-polymerization step (III). Therefore, gelation of the copolymer (A) during production in the post-polymerization step (III) can be prevented. Furthermore, the storage stability of the resin composition containing the copolymer (A) is improved.

[0088] Furthermore, in this embodiment, by appropriately inhibiting the above-mentioned reactions in the dropping polymerization step (II) and / or the post-polymerization step (III), it is possible to prevent the isocyanato groups derived from the monomer (ma) and the hydroxyl groups derived from the monomer (mb) from decreasing before the resin composition containing the copolymer (A) is thermally cured. As a result, the copolymer (A) is obtained in which the isocyanato groups derived from the monomer (ma) and the hydroxyl groups derived from the monomer (mb) remain in an appropriate amount. Therefore, by thermally curing the resin composition containing the copolymer (A), a crosslinked structure is sufficiently formed, and a cured product with good solvent resistance is obtained.

[0089] The amounts of solvent (B-1) used in the solvent heating step (I) and solvent (B-2) used in the dropping polymerization step (II) are not particularly limited. However, for example, the total amount of solvent (B-1) and solvent (B-2) is preferably 30 to 1,000 parts by mass, more preferably 50 to 800 parts by mass, per 100 parts by mass of the total monomer charge (i.e., the mass of monomers (ma) to (md) in the monomer solution). When the total amount of solvent (B-1) and solvent (B-2) is 1,000 parts by mass or less per 100 parts by mass of the total monomer charge, the viscosity of the reaction solution containing copolymer (A) obtained in the post-polymerization step (III) is appropriate. Furthermore, by keeping the total amount of solvent (B-1) and solvent (B-2) at 1,000 parts by mass or less, a decrease in the molecular weight of copolymer (A) due to chain transfer can be suppressed when a chain transfer agent solution is dropped in the dropping polymerization step (II). Furthermore, by setting the total amount of solvent (B-1) and solvent (B-2) to 30 parts by mass or more per 100 parts by mass of the total amount of monomers charged, abnormal polymerization reactions in the post-polymerization step (III) can be prevented and the polymerization reaction can be carried out stably. As a result, gelation of copolymer (A) during production can be prevented and a colorless copolymer (A) can be obtained.

[0090] In the production method of this embodiment, in the post-polymerization step (III), the mixed solution obtained in the dropwise polymerization step (II) is reacted at 60 to 90°C for 1 to 5 hours while being stirred. The reaction time in the post-polymerization step (III) can 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 with good yield.

[0091] The copolymer (A) of this embodiment contains a structural unit (a) having a blocked isocyanato group blocked with a pyrazole compound, a structural unit (b) having a hydroxy group, and a structural unit (c) having an acid group, and has a glass transition temperature of 30° C. or lower. Therefore, a resin composition containing the copolymer (A) of this embodiment has good alkali developability when used as a photosensitive material, has excellent storage stability, and can give a cured product with excellent solvent resistance even when cured at low temperatures.

[0092] In the method for producing copolymer (A) of this embodiment, the solvent (B-1) used in the solvent heating step (I) and / or the solvent (B-2) used in the dropping polymerization step (II) are solvents containing a hydroxyl group-containing solvent. In the solvent heating step (I), the solvent (B-1) is heated to 60 to 90°C, and in the post-polymerization step (III), the mixed solution is reacted at 60 to 90°C. Therefore, in the dropping polymerization step (II) and / or the post-polymerization step (III), the reaction between the isocyanato group derived from monomer (ma) and the hydroxyl group derived from monomer (mb) is moderately inhibited. As a result, copolymer (A) of this embodiment is obtained that contains a sufficient amount of structural unit (a) having a blocked isocyanato group and structural unit (b) having a hydroxyl group.

[0093] In contrast, in the past, when a solvent was used in copolymerization, a solvent that did not react with the monomer was selected and used. Therefore, in the conventional technology, when copolymerization was performed using a solvent, the monomer did not react with the solvent. For this reason, the conventional technology did not anticipate utilizing the reaction between the monomer and the solvent, and there was no method for controlling the properties of the copolymer by utilizing the reaction between the monomer and the solvent.

[0094] <Resin composition> Next, the resin composition of this embodiment will be described. The resin composition of this embodiment contains the copolymer (A) of this embodiment and a solvent (B). The resin composition of the present embodiment may further contain not only the copolymer (A) and the solvent (B), but also a reactive diluent (C) and a photopolymerization initiator (D). Such a resin composition can be preferably used as a photosensitive resin composition. The resin composition of this embodiment may further contain a colorant (E) in addition to the above-mentioned copolymer (A) to photopolymerization initiator (D). Such a resin composition is preferably used as a material for forming colored patterns such as color filters, black matrices, and black column spacers.

[0095] (Solvent (B)) In the resin composition of this embodiment, the solvent (B) contains a hydroxy group-containing solvent. The solvent (B) may consist solely of a hydroxy group-containing solvent. In the resin composition of this embodiment, since the solvent (B) contains a hydroxy group-containing solvent, storage stability is improved.

[0096] The hydroxyl group-containing solvent used as solvent (B) is not particularly limited as long as it contains a hydroxyl group, and the same solvents as those usable as solvents (B-1) and (B-2) in the process for producing copolymer (A) can be used. Examples of solvents that do not contain a hydroxyl group that can be used as solvent (B) include the same solvents as those usable as solvents (B-1) and (B-2) in the process for producing copolymer (A).

[0097] The content of the hydroxy group-containing solvent in the solvent (B) can be set in the same manner as the content of the hydroxy 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).

[0098] The resin composition of this embodiment can be produced, for example, by a method of appropriately mixing the copolymer (A) isolated from a reaction liquid containing the copolymer (A) obtained in the post-polymerization step (III) for producing the copolymer (A) with a solvent (B). As the resin composition of this embodiment, the reaction solution containing copolymer (A) obtained during the production of copolymer (A) may be used as is. In this case, it is not necessary to isolate copolymer (A) from the reaction solution. Furthermore, when solvent (B-1) and / or solvent (B-2) used in the production of copolymer (A) are contained in the reaction solution, solvent (B-1) and / or solvent (B-2) in the reaction solution can be used as solvent (B) as is. If necessary, solvent (B) may be added to the reaction solution.

[0099] In the resin composition of this embodiment, the blending amounts of copolymer (A) and solvent (B) may be adjusted appropriately depending on the intended use of the resin composition. For example, the resin composition of this embodiment preferably contains 30 to 1,000 parts by mass, and more preferably 50 to 800 parts by mass, of solvent (B) per 100 parts by mass of copolymer (A). When the content of solvent (B) is 30 parts by mass or more, the viscosity of the resin composition becomes appropriate. When the content of solvent (B) is 1,000 parts by mass or less, the viscosity of the resin composition can be controlled within an appropriate range, allowing for appropriate film thickness adjustment.

[0100] (Reactive diluent (C)) The reactive diluent (C) is optionally contained together with the photopolymerization initiator (D). The reactive diluent (C) is a compound having at least one polymerizable ethylenically unsaturated group as a polymerizable functional group in the molecule. The reactive diluent (C) may be a monofunctional monomer or a polyfunctional monomer, preferably a polyfunctional monomer having multiple polymerizable functional groups. By preparing a resin composition containing the reactive diluent (C), it becomes easy to adjust the viscosity. Furthermore, by preparing a resin composition containing the reactive diluent (C), it is possible to improve the adhesion of the cured product of the resin composition to a substrate and adjust the strength of the cured product of the resin composition.

[0101] Examples of monofunctional monomers that can be used as the reactive diluent (C) include (meth)acrylamide, methylol (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-hydroxypropyl methyl ... Examples of the monofunctional monomer include (meth)acrylates such as propyl (meth)acrylate, 2-(meth)acryloyloxy-2-hydroxypropyl phthalate, glycerin mono(meth)acrylate, tetrahydrofurfuryl (meth)acrylate, glycidyl (meth)acrylate, 2,2,2-trifluoroethyl (meth)acrylate, 2,2,3,3-tetrafluoropropyl (meth)acrylate, and half (meth)acrylates of phthalic acid derivatives; aromatic vinyl compounds such as styrene, α-methylstyrene, α-chloromethylstyrene, and vinyltoluene; and carboxylic acid esters such as vinyl acetate and vinyl propionate. These monofunctional monomers may be used alone or in combination of two or more.

[0102] Examples of polyfunctional monomers 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, butylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, 1,6-hexane glycol di(meth)acrylate, and trimethylol propane. Di(meth)acrylate, glycerin di(meth)acrylate, pentaerythritol di(meth)acrylate, pentaerythritol tri(meth)acrylate, dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, 2,2-bis(4-(meth)acryloxydiethoxyphenyl)propane, 2,2-bis(4-(meth)acryloxypolyethoxyphenyl)propane, 2-hydroxy-3-(meth)acryloyloxypropyl(meth)acrylate Examples of the (meth)acrylates include acrylate, ethylene glycol diglycidyl ether di(meth)acrylate, diethylene glycol diglycidyl ether di(meth)acrylate, phthalic acid diglycidyl ester di(meth)acrylate, glycerin triacrylate, glycerin polyglycidyl ether poly(meth)acrylate, urethane (meth)acrylate (i.e., tolylene diisocyanate), reaction products of trimethylhexamethylene diisocyanate, hexamethylene diisocyanate, or the like with 2-hydroxyethyl (meth)acrylate, and tris(hydroxyethyl)isocyanurate tri(meth)acrylate; aromatic vinyl compounds such as divinylbenzene, diallyl phthalate, and diallylbenzene phosphonate; dicarboxylic acid esters such as divinyl adipate; triallyl cyanurate, methylene bis(meth)acrylamide, (meth)acrylamide methylene ether, and condensates of polyhydric alcohols and N-methylol (meth)acrylamide. These polyfunctional monomers may be used alone or in combination of two or more.

[0103] Among these monomers, from the viewpoint of improving the development form and curability of the resin composition, it is preferable to use a polyfunctional (meth)acrylate as the reactive diluent (C), and it is more preferable to use one or more selected from trimethylolpropane tri(meth)acrylate, dipentaerythritol penta(meth)acrylate, and dipentaerythritol hexa(meth)acrylate.

[0104] When the resin composition contains a reactive diluent (C), the blending amounts of each component are preferably 10 to 90 parts by weight of copolymer (A), 30 to 1,000 parts by weight of solvent (B), and 10 to 90 parts by weight of reactive diluent (C) per 100 parts by weight of the total amount of copolymer (A) and reactive diluent (C), more preferably 20 to 80 parts by weight of copolymer (A), 50 to 800 parts by weight of solvent (B), and 20 to 80 parts by weight of reactive diluent (C), and even more preferably 30 to 75 parts by weight of copolymer (A), 100 to 700 parts by weight of solvent (B), and 25 to 70 parts by weight of reactive diluent (C). When the blending amounts of each component are within the above ranges, the resin composition has an appropriate viscosity and can be suitably used for various coatings, adhesives, printing ink binders, etc.

[0105] (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, 2,2-dimethoxy-2-phenylacetophenone, 1,1-dichloroacetophenone, 4-(1-t-butyldioxy-1-methylethyl)acetophenone, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholino-propan-1-one, and 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)butanone-1; 2-methylanthraquinone, 2-amylanthraquinone, 2-t-butylanthraquinone, and 1-chloroanthraquinone; Examples of the photopolymerization initiator (D) include anthraquinones such as anthraquinone; thioxanthones such as xanthone, thioxanthone, 2,4-dimethylthioxanthone, 2,4-diisopropylthioxanthone, and 2-chlorothioxanthone; ketals such as acetophenone dimethyl ketal and benzil dimethyl ketal; benzophenones such as benzophenone, 4-(1-t-butyldioxy-1-methylethyl)benzophenone, and 3,3',4,4'-tetrakis(t-butyldioxycarbonyl)benzophenone; acylphosphine oxides; and ethanone 1-[9-ethyl-6-(2-methylbenzoyl)-9H-carbazol-3-yl]-1-(O-acetyloxime). These photopolymerization initiators (D) may be used alone or in combination of two or more.

[0106] When the resin composition contains a 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, per 100 parts by mass of the total amount of the copolymer (A) and the reactive diluent (C).

[0107] (Colorant (E)) A colorant (E) is contained as needed. The colorant (E) is not particularly limited as long as it is soluble or dispersible in the solvent (B), and examples thereof include dyes and pigments. The colorant (E) may be used alone or in combination of two or more types depending on the desired color of the cured product of the resin composition. As the colorant (E), only a dye may be used, only a pigment may be used, or a combination of a dye and a pigment may be used.

[0108] As the dye, it is preferable to use an acid dye having an acidic group such as a carboxylic acid or sulfonic acid, a salt of an acid dye with a nitrogen compound, or a sulfonamide of an acid dye, from the viewpoints of solubility in the solvent (B) and the alkaline developer, interaction with other components in the resin composition, heat resistance, etc.

[0109] 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 chrome 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 red1, 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, 11 4,129,133,134,138,143,145,150,151,158,176,183,198,211,215,216,217,249,252,257,260,266,274;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 derivatives thereof. 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 two or more types depending on the desired color of the cured product of the resin composition.

[0110] Examples of pigments include yellow pigments such as CI 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, and 214; orange pigments such as CI Pigment Orange 13, 31, 36, 38, 40, 42, 43, 51, 55, 59, 61, 64, 65, 71, and 73; and CI Pigment Red 9, 97, 105, 122, 123, 144, 149, 166, and 168. , 176, 177, 180, 192, 209, 215, 216, 224, 242, 254, 255, 264, 265, and other red pigments; blue pigments such as CI Pigment Blue 15, 15:3, 15:4, 15:6, 60, and other blue pigments; violet pigments such as CI Pigment Violet 1, 19, 23, 29, 32, 36, 38, and other violet pigments; green pigments such as CI Pigment Green 7, 36, 58, 59, and other brown pigments; and black pigments such as CI Pigment Black 1, 7, carbon black, titanium black, and iron oxide. These pigments may be used alone or in combination depending on the desired color of the cured product of the resin composition.

[0111] When a pigment is used as the colorant (E), a known dispersant may be contained in the resin composition in order to improve the dispersibility of the pigment. As the dispersant, it is preferable to use a polymer dispersant which has excellent dispersion stability over time. Examples of polymer dispersants include urethane-based dispersants, polyethyleneimine-based dispersants, polyoxyethylene alkyl ether-based dispersants, polyoxyethylene glycol diester-based dispersants, sorbitan aliphatic ester-based dispersants, and aliphatic modified ester-based dispersants.

[0112] As the polymer dispersant, commercially available products such as EFKA (manufactured by EFKA Chemicals BV), Disperbyk-161 (manufactured by BYK-Chemie), Disparlon (manufactured by Kusumoto Chemicals Co., Ltd.), and SOLSPERSE (manufactured by Zeneca) may be used. The type and amount of dispersant to be used may be determined appropriately depending on the type of pigment to be used.

[0113] When the resin composition contains a 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, per 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 this embodiment has excellent storage stability, and even when cured at low temperatures, it can produce a cured product with excellent solvent resistance. Therefore, for example, the content of the colorant (E) can be set to 20 parts by mass or more per 100 parts by mass of the total amount of the copolymer (A) and the reactive diluent (C). When a resin composition containing 20 parts by mass or more of the colorant (E) is used as a material for a color filter, it can improve the color reproducibility of an image display device equipped with the color filter.

[0114] In addition to the above components, the resin composition of the present embodiment may contain known additives such as coupling agents, leveling agents, thermal polymerization inhibitors, etc. The amounts of these additives added are not particularly limited as long as they do not impair the effects of the present invention.

[0115] Since the resin composition of this embodiment contains the copolymer (A) of this embodiment, the crosslinking reaction proceeds sufficiently even at low temperatures, and therefore the resin composition of this embodiment can be cured at low temperatures. Specifically, the resin composition of this embodiment is preferably cured at a temperature of 150°C or less, more preferably 120°C or less, even more preferably 100°C or less, and most preferably 80°C or less. Curing the resin composition at a temperature of 150°C or less reduces the amount of energy required to cure the resin composition. Furthermore, when the resin composition contains a colorant (E) with poor heat resistance, deterioration of the colorant (E) due to thermal curing can be suppressed, making it easier to obtain a cured product that exhibits the inherent properties of the colorant (E). Therefore, various materials can be used as the colorant (E). Furthermore, when a cured product is formed by applying a resin composition to a substrate and thermally curing it, a cured product can be formed even if the substrate is made of a material with poor heat resistance. Therefore, various materials, such as resins for flexible displays, can be used as the substrate.

[0116] The resin composition of this embodiment is preferably cured at a temperature of 50° C. or higher, more preferably 60° C. or higher, and even more preferably 70° C. or higher. When the resin composition is cured at a temperature of 50° C. or higher, a crosslinked structure is sufficiently generated in a short time, and a cured product with good solvent resistance can be efficiently formed. The heating time (curing time) for curing the resin composition of this embodiment can be appropriately determined depending on the size and thickness of the cured product, the curing temperature, etc., and can be, for example, 10 minutes to 4 hours, and preferably 20 minutes to 2 hours.

[0117] The resin composition of this embodiment can be produced by mixing the above components using a known mixing device. The solvent contained in each component used as a raw material when producing the resin composition of this embodiment can be used as solvent (B). When the resin composition of the present embodiment contains components other than the copolymer (A) and the solvent (B), it may be produced, for example, by a method in which a reactive diluent (C), a photopolymerization initiator (D), and a colorant (E) are added to a resin composition containing the copolymer (A) and the solvent (B) that has been produced in advance, and then mixed.

[0118] The resin composition of this embodiment contains the copolymer (A) of this embodiment, and therefore has excellent storage stability, and a cured product having excellent solvent resistance can be obtained even when cured at low temperatures. Therefore, the resin composition of this embodiment can be preferably used as a material for, for example, color filters, black matrices, protective films for color filters, photospacers, protrusions for liquid crystal alignment, microlenses, insulating films for touch panels, adhesives for electronic materials around flexible printed wiring boards, adhesive sheets, etc.

[0119] The resin composition of this embodiment, which contains the copolymer (A), the solvent (B), the reactive diluent (C), and the photopolymerization initiator (D), is suitable as a photosensitive material with good alkaline developability, particularly as a resist for use in color filters incorporated in organic electroluminescence (EL) displays (for black pixel defining layers (PDLs)), liquid crystal displays, and solid-state imaging devices using charge-coupled devices (CCDs) and complementary metal-oxide semiconductor (CMOS) elements.

[0120] Furthermore, when the resin composition of this embodiment contains the copolymer (A) of this embodiment, a solvent (B), a reactive diluent (C), a photopolymerization initiator (D), and a colorant (E), a colored pattern can be formed from a cured product with excellent solvent resistance at low temperatures. Therefore, deterioration of the colorant (E) due to thermal curing is suppressed, and a colored pattern can be formed in which the inherent properties of the colorant (E) are exhibited. Therefore, the above-mentioned resin composition can be preferably used as a photosensitive material for color filters.

[0121] <Color filter> Next, the color filter of this embodiment will be described. The color filter of this embodiment has a substrate, a plurality of pixels formed on the substrate, each consisting of three colored patterns: a red (R) pattern, a green (G) pattern, and a blue (B) pattern, a black matrix formed at the boundaries of each colored pattern, and a protective film formed on the pixels and the black matrix.

[0122] As the substrate, a known substrate can be used, 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 board, an array substrate, etc. In the color filter of this embodiment, an organic substrate having a relatively low heat resistance temperature and suitable as a flexible substrate, such as a polycarbonate substrate, a polyester substrate, a polyamide substrate, a polyamideimide substrate, or a polyimide substrate, can be used.

[0123] In the color filter of this embodiment, the black matrix and the three colored patterns forming each pixel are colored patterns made of a cured product of the resin composition of this embodiment, which contains the copolymer (A) of this embodiment, a solvent (B), a reactive diluent (C), a photopolymerization initiator (D), and a colorant (E). The protective film is not particularly limited, and any known film can be used.

[0124] Next, an example of the method for producing the color filter of this embodiment will be described. To manufacture the color filter of this embodiment, first, a colored pattern that will become a black matrix and three colored patterns that will form each pixel are formed on a substrate. First, a colored pattern that will become a black matrix is ​​formed on the substrate, and then a red pattern, a green pattern, and a blue pattern that will form each pixel are formed within the area defined by the black matrix. The order in which the red pattern, green pattern, and blue pattern are formed is not particularly limited.

[0125] Each colored pattern can be formed by photolithography using the resin composition of this embodiment. Specifically, the resin composition of this embodiment is applied to a substrate to form a coating film. Next, the coating film is exposed to light through a photomask having a predetermined pattern shape, and the exposed portions are photocured. The unexposed portions of the coating film are then removed by alkaline development using an alkaline aqueous solution. Thereafter, the exposed portions of the coating film are heated and cured by baking. Through these steps, a colored pattern having a predetermined shape and made of a cured product of the resin composition of this embodiment is obtained.

[0126] The method for applying the resin composition to form a colored pattern is not particularly limited, and for example, screen printing, roll coating, curtain coating, spray coating, spin coating, etc. can be used. After the resin composition is applied, if necessary, the coating film may be heated using a heating means such as a circulation oven, an infrared heater, or a hot plate to volatilize and remove the solvent (B) contained in the coating film. Heating to remove the solvent (B) from the coating film can be carried out at a temperature of, for example, 50° C. to 120° C. Heating to remove the solvent (B) from the coating film can be carried out for, for example, 30 seconds to 30 minutes. The heating temperature and heating time to remove the solvent (B) from the coating film can be appropriately set depending on the composition of the resin composition, the thickness of the coating film, etc.

[0127] When exposing the coating film, for example, a known negative mask can be used as the photomask. When exposing the coating film, it is preferable to use active energy rays such as ultraviolet rays and excimer laser light. 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, etc. can be used. The energy dose irradiated onto the coating film can be appropriately selected depending on the thickness of the coating film, the composition of the resin composition, etc., and can be, for example, 30 to 2000 mJ / cm. 2 It can be said that:

[0128] The alkaline aqueous solution used in alkaline development is not particularly limited, and examples thereof include aqueous solutions of sodium carbonate, potassium carbonate, calcium carbonate, sodium hydroxide, potassium hydroxide, or the like; aqueous solutions of amine compounds such as ethylamine, diethylamine, and dimethylethanolamine; and aqueous solutions 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-methanesulfonamidoethylaniline, 3-methyl-4-amino-N-ethyl-N-β-methoxyethylaniline, and sulfates, hydrochlorides, or p-toluenesulfonates thereof. These aqueous solutions can be selected appropriately depending on the composition of the resin composition, etc. If necessary, additives such as antifoaming agents and surfactants may be added to these alkaline aqueous solutions. In this embodiment, after alkaline development using an alkaline aqueous solution, the substrate is preferably washed with water to remove the alkaline aqueous solution and then dried before baking.

[0129] In this embodiment, the temperature at which the exposed portion of the coating film is heated and cured by baking can be appropriately selected depending on the thickness of the coating film, the composition of the resin composition, etc. In this embodiment, the coating film is formed using a resin composition containing the copolymer (A) of this embodiment, so that the exposed portion of the coating film can be cured even at a low temperature.

[0130] The temperature to which the exposed portion of the coating film is heated can be, for example, 210°C or lower, and may be 150°C or lower as needed, 120°C or lower, 100°C or lower, or even 80°C or lower. When the temperature to which the exposed portion of the coating film is heated is 210°C or lower, a material with low heat resistance, such as a substrate with low heat resistance, can be used as the material for the color filter. When the temperature to which the exposed portion of the coating film is heated is 150°C or lower, the amount of energy required to cure the coating film is reduced, which is preferable. Furthermore, when the temperature to which the exposed portion of the coating film is heated is 150°C or lower, a colored pattern containing a colorant (E) with poor heat resistance, which has traditionally been difficult to use as a material for colored patterns, can be formed while suppressing deterioration of the colorant (E). Furthermore, when the temperature to which the exposed portion of the coating film is heated is 150°C or lower, a colored pattern can be formed on a substrate with poor heat resistance, which has traditionally been difficult to use as a substrate for color filters.

[0131] The temperature to which the exposed portion of the coating film is heated is preferably 50°C or higher, more preferably 60°C or higher, and even more preferably 70°C or higher. When the temperature to which the exposed portion of the coating film is heated is 50°C or higher, the copolymer (A) and the reactive diluent (C) are sufficiently crosslinked, resulting in good solvent resistance of the colored pattern and a good pattern shape. Furthermore, when the temperature to which the exposed portion of the coating film is heated is 50°C or higher, the exposed portion of the coating film can be heated in a short time, allowing for efficient production of a colored pattern. The time for heating the exposed portion of the coating film can be appropriately selected depending on the temperature to which the exposed portion of the coating film is heated, the thickness of the coating film, the composition of the resin composition, etc., and can be, for example, 10 minutes to 4 hours, and preferably 20 minutes to 2 hours.

[0132] Next, a protective film is formed by a known method on the colored pattern that will become the black matrix and the three colored patterns that will form the pixels. Through the above steps, the color filter of this embodiment is obtained.

[0133] In the color filter of this embodiment, the three colored patterns forming each pixel and the black matrix are colored patterns made of a cured product of the resin composition of this embodiment, which contains the copolymer (A) of this embodiment, a solvent (B), a reactive diluent (C), a photopolymerization initiator (D), and a colorant (E). The resin composition of this embodiment has good alkaline developability, and even when cured at low temperatures, a cured product with excellent solvent resistance can be obtained. Therefore, in the color filter of this embodiment, the pixels and black matrix can be formed using a method of curing the resin composition at low temperatures, which increases the selection of materials that can be used for color filters.

[0134] Therefore, the color filter of this embodiment can have pixels and / or a black matrix that contain a colorant (E) having poor heat resistance and have a good pattern shape. Also, by forming the pixels and black matrix using a method of curing a resin composition at low temperature, a color filter can be obtained that has a substrate made of a material having poor heat resistance.

[0135] In contrast, when a colored pattern is formed using a conventional resin composition instead of the resin composition of the present embodiment, if the temperature at which the exposed portion of the coating film is heated and cured is less than 210°C, the solvent resistance of the cured colored pattern is insufficient. Therefore, when a colored pattern is formed using a conventional resin composition, it is not possible to set the temperature at which the exposed portion of the coating film is heated to 210°C or less. For this reason, in conventional techniques, it has been difficult to use a colorant (E) with poor heat resistance as a material for the colored pattern. Furthermore, it has also been difficult to use a substrate with poor heat resistance as a substrate for a color filter.

[0136] In the color filter of the present embodiment, an example has been described in which the colored pattern has pixels and a black matrix made 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). However, instead of the photopolymerization initiator (D), a resin composition containing a curing accelerator and a known epoxy resin may be used.

[0137] In this case, a colored pattern can be formed, for example, by the following method. First, a resin composition is applied to a substrate by an inkjet method to form a coating film having a predetermined pattern shape. Next, the coating film is heated and cured. By the above method, a colored pattern having a desired shape and made of a cured product of the resin composition can be formed. A resin composition containing a curing accelerator and a known epoxy resin instead of the photopolymerization initiator (D) can also produce a cured product with excellent solvent resistance even when cured at low temperature. Therefore, even in this case, pixels and a black matrix can be formed using a method of curing a resin composition at low temperature, thereby increasing the options for materials that can be used for color filters.

[0138] <Image display element> Next, the image display element of this embodiment will be described. An example of a liquid crystal display element as an image display element of this embodiment is one in which a first substrate having a color filter and a first electrode formed on its surface and a second substrate having a second electrode formed on its surface are arranged so that the first electrode and the second electrode face each other via a spacer, and a liquid crystal composition is sandwiched between the first substrate and the second substrate. The liquid crystal display element of this embodiment includes the color filter of this embodiment as a color filter. In the liquid crystal display element of this embodiment, known materials can be used for the members other than the color filter.

[0139] The liquid crystal display element of this embodiment can be manufactured, for example, by the manufacturing method described below. First, a color filter and a first electrode are formed in this order on a first substrate. The color filter can be formed using the manufacturing method described above. The first electrode can be formed using a known method. Next, a second electrode and spacers are formed on the second substrate by a known method. Thereafter, the first substrate and the second substrate are bonded together with the first electrode and the second electrode facing each other, and a liquid crystal composition is injected between the first substrate and the second substrate, and the space is sealed. Through the above steps, the liquid crystal display element of this embodiment is obtained.

[0140] The liquid crystal display element of this embodiment includes the color filter of this embodiment, and therefore the pixels and black matrix of the color filter can be formed by a method of curing a resin composition at a low temperature. Therefore, materials with poor heat resistance can be used as materials for the liquid crystal display element, and the range of usable materials can be increased.

[0141] In the above-described embodiment, a liquid crystal display element has been described as an example of the image display element of the present embodiment, but the image display element of the present embodiment is not limited to a liquid crystal display element as long as it is equipped with the color filter of the present embodiment. The image display element of the present embodiment may be, for example, an organic EL display element or a solid-state imaging device using a CCD element or a CMOS element. [Example]

[0142] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[0143] [Synthesis Example 1] Into a flask equipped with a stirrer, a dropping funnel, a condenser, a thermometer, and a gas inlet tube, 207.7 g of propylene glycol monomethyl ether (manufactured by Sankyo Chemical Co., Ltd.) as solvent (B-1) was placed, and the mixture was stirred while replacing with nitrogen gas and heated to 78°C (solvent heating step (I)).

[0144] Next, 20.6 g of 2,2'-azobis(2,4-dimethylvaleronitrile) (polymerization initiator) was dissolved in 79.1 g of propylene glycol monomethyl ether as a solvent (B-2) to prepare a polymerization initiator solution. In addition, 50.2 g (20 mol%) of MOI-BP, 26.0 g (20 mol%) of 2-hydroxyethyl methacrylate, 12.9 g (15 mol%) of methacrylic acid, and 82.8 g (45 mol%) of 2-ethylhexyl acrylate (2EHA) were dissolved in 61.8 g of propylene glycol monomethyl ether as a solvent (B-2) and then mixed to prepare a monomer solution. Thereafter, the polymerization initiator solution and the monomer solution were simultaneously dropped into the flask containing the solvent heated to 78°C using a dropping funnel while stirring the solvent (B-1) in the flask to form a mixed solution, thereby carrying out dropping polymerization (dropping polymerization step (II)). The dropping rate was 1.7 ml / min for both the polymerization initiator solution and the monomer solution.

[0145] After the dropwise addition was completed, the mixed solution was stirred and reacted at 78° C. for 3 hours to produce a copolymer (A) (post-polymerization step (III)). To the reaction liquid containing the copolymer (A) thus obtained, propylene glycol monomethyl ether was added as the solvent (B) so that the components other than the solvent were 35% by mass, thereby obtaining a polymer composition of Synthesis Example 1.

[0146] [Synthesis Examples 2 to 6, 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 Tables 1 and 2 were used in the proportions shown in Tables 1 and 2.

[0147] [Table 1]

[0148] [Table 2]

[0149] In Tables 1 and 2, (ma) indicates a monomer having a blocked isocyanato group, (mb) indicates a hydroxyl group-containing monomer, (mc) indicates an acid group-containing monomer, and (d) indicates other monomers that do not fall under (ma), (mb), or (mc). In Tables 1 and 2, (equivalent number of blocked isocyanato group) indicates the equivalent number of blocked isocyanato group contained in the molecule of copolymer (A).

[0150] The materials used in Tables 1 and 2 are as follows: MOI-BP: Karenz (registered trademark) MOI-BP (2-[(3,5-dimethylpyrazolyl)carbonylamino]ethyl methacrylate, manufactured by Showa Denko K.K.) MOI-BM: Karenz (registered trademark) MOI-BM (2-[0-(1'-methylpropylideneamino)carboxyamino]ethyl methacrylate, manufactured by Showa Denko K.K.) 4-Hydroxybutyl acrylate (Mitsubishi Chemical Corporation) 2-Hydroxyethyl methacrylate (Kyoeisha Chemical Co., Ltd.) Methacrylic acid (Kuraray Co., Ltd.) Acrylic acid (manufactured by Toagosei Co., Ltd.)

[0151] 2EHA: 2-ethylhexyl acrylate (manufactured by Toagosei Co., Ltd.) TCDMA: Tricyclo[5.2.1.0 2,6 ]Decanyl-8-methacrylate (Hitachi Chemical Co., Ltd.) GMA: Glycidyl methacrylate (NOF Corporation)

[0152] The weight-average molecular weight (Mw), glass transition temperature (Tg), storage stability, and acid value of the polymer compositions of Synthesis Examples 1 to 6 and Comparative Synthesis Examples 1 to 3 shown in Tables 1 and 2 were measured and evaluated by the methods described below. The results are shown in Tables 1 and 2, respectively.

[0153] <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 converted into standard polystyrene, measured using gel permeation chromatography (GPC) under the following conditions. Column: Showdex (registered trademark) LF-804 + LF-804 (manufactured by Showa Denko K.K.) Column temperature: 40℃ Sample: 0.2% by mass solution of copolymer in tetrahydrofuran Developing solvent: tetrahydrofuran Detector: Differential refractometer (Shodex (registered trademark) RI-71S) (manufactured by Showa Denko K.K.) Flow rate: 1mL / min

[0154] <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°C under reduced pressure for 24 hours. They were then redissolved in acetone and dried again at 50°C under reduced pressure for 24 hours. The solid content of the copolymer solution from which the volatile components had been removed was measured using a DSC (differential scanning calorimeter, measuring device: Seiko DSC6200) in a nitrogen stream at a heating rate of 10°C / min in accordance with JIS-K7121 (midpoint glass transition temperature). The result was taken as the glass transition temperature (Tg) of the copolymer (A).

[0155] <Storage stability> After the preparation, equal amounts of the polymer compositions of Synthesis Examples 1 to 6 and Comparative Synthesis Examples 1 to 3, each containing 35% by mass of components other than the solvent, were weighed into glass containers, and the containers were covered with lids to prevent dust and other contaminants from entering, to prepare samples. After measuring the viscosity of each sample, the samples were left to stand for three months in an incubator maintained at 12°C. The viscosity of each sample that had been left to stand for three months was then measured. The viscosity measurements were performed at 25°C and 10 rpm using an E-type viscometer (RE-80L, manufactured by Toki Sangyo Co., Ltd., cone No. 3).

[0156] For each sample, the viscosity increase rate after leaving it undisturbed for 3 months relative to the viscosity before leaving it undisturbed in the incubator {(1-(viscosity after leaving it undisturbed for 3 months / viscosity before leaving it undisturbed)) x 100(%)} was calculated and evaluated according to the following criteria. ◎ (Excellent): Viscosity increase rate 10% or less Good: Viscosity increase rate 10.1% to 20% △(poor): Thickening rate 20.1% or more

[0157] As shown in Tables 1 and 2, the storage stability of the polymer compositions of Synthesis Examples 1 to 6 and Comparative Synthesis Example 3 was evaluated as ⊚ (excellent) or ○ (good), confirming that they have excellent storage stability. In contrast, as shown in Table 2, the polymer compositions of Comparative Synthesis Examples 1 and 2 were evaluated as having poor storage stability. Although they did not harden upon storage, their viscosity increased compared to the results of the Examples, indicating that their storage stability was insufficient.

[0158] <Acid value> The acid values ​​of the polymer compositions of Synthesis Examples 1 to 6 and Comparative Synthesis Examples 1 to 3 were measured and used as the acid values ​​of the copolymers (A). The acid value of the curable polymer is measured in accordance with JIS K6901 5.3. That is, the acid value means the number of milligrams of potassium hydroxide required to neutralize the acidic components contained in 1 g of copolymer.

[0159] [Examples 1 to 6, 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, (B) propylene glycol monomethyl ether acetate as a solvent, (C) a mixture of dipentaerythritol pentaacrylate and dipentaerythritol hexaacrylate (Kayarad DPHA, manufactured by Nippon Kayaku Co., Ltd.) as a reactive diluent, (D) ethanone, 1-[9-ethyl-6-(2-methylbenzoyl)-9H-carbazol-3-yl]-, 1-(o-acetyloxime) (manufactured by BASF Japan Ltd.) as a photopolymerization initiator, and (E) a dye (VALIFAST BLUE 2620) as a colorant were mixed in the proportions shown in Table 3 to prepare the resin compositions of Examples 1 to 6 and Comparative Examples 1 to 3.

[0160] [Table 3]

[0161] The amount of copolymer (A) shown in Table 3 does not include the amount of solvent contained in the reaction liquid used in producing copolymer (A). The amount of solvent (B) shown in Table 3 is the sum of the solvent (propylene glycol monomethyl ether) contained in the polymer composition and the solvent (propylene glycol monomethyl ether acetate) added during production of the resin composition. The content of the hydroxy group-containing solvent in solvent (B) shown in Table 3 is 79.1 mass%.

[0162] The resin compositions of Examples 1 to 6 and Comparative Examples 1 to 3 were evaluated for alkaline developability and solvent resistance by the methods described below. (1) Alkaline developability Each of the resin compositions of the Examples and Comparative Examples was spin-coated onto a square glass substrate (alkali-free glass substrate) measuring 5 cm in length and 5 cm in width in plan view to form a coating film with a thickness of 2.5 μm after exposure. The coating film was then heated at 100°C for 3 minutes to volatilize and remove the solvent in the coating film.

[0163] Next, a photomask with a predetermined pattern was placed at a distance of 100 μm from the coating film, and ultraviolet light with a wavelength of 365 nm was irradiated onto the coating film through this photomask at an energy dose of 40 mJ / cm. 2 The exposed portion was photocured. Next, an aqueous solution containing 0.1% by mass of sodium carbonate was sprayed at a temperature of 23°C and a pressure of 0.3 MPa to dissolve and develop the unexposed areas, followed by baking at 100°C for 20 minutes to form a predetermined pattern.

[0164] The pattern after alkali development was then observed using an electron microscope S-3400 manufactured by Hitachi High-Technologies Corporation to confirm residues after alkali development and evaluate them according to the following criteria. The results are shown in Table 4. ○ (Good): No residue in unexposed areas × (Not acceptable): Residue remains in unexposed areas

[0165] (2) Solvent resistance Each of the resin compositions of the Examples and Comparative Examples was spin-coated onto a square glass substrate (alkali-free glass substrate) measuring 5 cm in length and 5 cm in width in plan view to form a coating film with a thickness of 2.5 μm after exposure. The coating film was then heated at 100°C for 3 minutes to volatilize and remove the solvent in the coating film.

[0166] Next, the coating film was irradiated with ultraviolet light of 365 nm wavelength at an energy dose of 40 mJ / cm 2 The coated film was then cured by baking at 80°C for 30 minutes or at 100°C for 20 minutes to form a cured film. The cured film was immersed in 20 g of propylene glycol monomethyl ether at 23°C for 15 minutes. The color change (ΔEab) of the cured film before and after immersion was measured using a UV-1650PC spectrophotometer (Shimadzu Corporation), and the solvent resistance was evaluated based on the results. The results are shown in Table 4. Note that the smaller the color change before and after immersion, the better.

[0167] [Table 4]

[0168] As shown in Table 4, the cured films obtained by curing the resin compositions of Examples 1 to 6 were evaluated as having good alkaline developability. Furthermore, the cured films obtained by curing the resin compositions of Examples 1 to 6 had a ΔEab of less than 2 and good solvent resistance, both when the coating films were cured at a temperature of 80°C for 30 minutes and at a temperature of 100°C for 20 minutes.

[0169] The cured films obtained by curing the resin compositions of Comparative Examples 1 to 3 were evaluated as having good alkaline developability. However, the cured films obtained by curing the resin compositions of Comparative Examples 1 and 2 had ΔEab of 2 or more when the coating film was cured at 80°C for 30 minutes, indicating insufficient solvent resistance. Furthermore, the cured film obtained by curing the resin composition of Comparative Example 3 had ΔEab of 2 or more when the coating film was cured at 80°C for 30 minutes and at 100°C for 20 minutes, indicating insufficient solvent resistance. [Industrial Applicability]

[0170] According to the present invention, there are provided a resin composition that has good alkaline developability when used as a photosensitive material, has excellent storage stability, and gives a cured product that has excellent solvent resistance even when cured at low temperatures, a copolymer useful for preparing this resin composition, and a method for producing the copolymer. Furthermore, according to the present invention, there are provided a colored pattern made of a cured product of a resin composition that has good alkaline developability and gives a cured product that has excellent solvent resistance even when cured at low temperatures, a color filter having the same, 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 for transparent films, protective films, insulating films, overcoats, photospacers, black matrices, black column spacers, resists for color filters, and the like.

Claims

1. a structural unit (a) having a blocked isocyanato group blocked with a pyrazole compound; a structural unit (b) having a hydroxy group; and a structural unit (c) having an acid group, a copolymer (A) having a glass transition temperature of 30°C or lower; a solvent (B) containing a hydroxy group-containing solvent; A resin composition comprising a reactive diluent (C) and a photopolymerization initiator (D).

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

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

4. The resin composition 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 isocyanato group and a (meth)acryloyloxy group.

5. The resin composition according to any one of claims 1 to 4, comprising 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 resin composition according to any one of claims 1 to 5, having a weight average molecular weight of 1,000 to 50,000.

7. The resin composition according to claim 1 , further comprising a colorant (E).

8. 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), the solvent (B) is 30 to 1000 parts by mass, 10 to 90 parts by mass of the reactive diluent (C), the photopolymerization initiator (D) is 0.1 to 30 parts by mass, The resin composition according to claim 7, wherein the colorant (E) is contained in an amount of 3 to 80 parts by mass.

9. A color filter characterized by having a colored pattern made of a cured product of the resin composition described in claim 7 or claim 8.

10. An image display element comprising the color filter according to claim 9.

11. a solvent heating step (I) of heating the solvent (B-1) to 60 to 90°C; A monomer (ma) having a blocked isocyanato group blocked with a pyrazole compound, a hydroxy group-containing monomer (mb), and an acid group-containing monomer (mc) are added dropwise to the heated solvent (B-1), a dropping polymerization step (II) in which a polymerization initiator solution obtained by dissolving a polymerization initiator in a solvent (B-2) is dropped into the solvent (B-1) to form a mixed solution; a post-polymerization step (III) of reacting the mixed solution at 60 to 90°C for 1 to 5 hours while stirring to obtain copolymer (A) containing a structural unit (a) having a blocked isocyanato group blocked with a pyrazole compound, a structural unit (b) having a hydroxy group, and a structural unit (c) having an acid group, and having a glass transition temperature of 30°C or lower, a step of producing a copolymer, wherein either or both of the solvent (B-1) and the solvent (B-2) contain a hydroxy group-containing solvent; and a step of producing a resin composition by mixing the copolymer (A), a solvent (B) containing a hydroxy group-containing solvent, a reactive diluent (C), and a photopolymerization initiator (D).

12. The method for producing a resin composition according to claim 11, wherein in the solvent heating step (I), a chain transfer agent is added to the solvent (B-1) and then the temperature is raised.

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