Copolymer, resin composition, spacer for display panel, planarization film, thermosetting protective film, microlens, and process for producing copolymer

A resin composition, comprising a copolymer [A] and an organic solvent [B], the copolymer [A] comprising an epoxy group and a carboxyl group, and having a constitutional component derived from (a1) and a constitutional component derived from (a2) below:

• (a1) a reaction mixture between at least one of an ethylenically unsaturated carboxylic acid and an ethylenically unsaturated carboxylic acid anhydride and at least one reactive compound selected from the group consisting of the compounds represented by general formulae (I), (II) and (III) below,
• R1—O—R3—O—R2 (I)
• wherein, R1 and R2 each independently represent an alkyl group having 1 to 4 carbon atoms, and R3 represents a linear hydrocarbon group having 2 to 4 carbon atoms which does not contain an oxygen atom, or a linear or branched hydrocarbon group having 2 to 4 carbon atoms which contains an oxygen atom,
• wherein, R4 and R5 each independently represent an alkyl group having 1 to 4 carbon atoms,
• wherein, R6 and R7 each independently represent an alkyl group having 1 to 4 carbon atoms, and R8 represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms;
• and
• (a2) at least one epoxidized ethylenically-unsaturated compound selected from the group consisting of glycidyl acrylate, 2-methyl glycidyl acrylate, 3,4-epoxy butyl acrylate, 6,7-epoxy heptyl acrylate, glycidyl methacrylate, 2-methyl glycidyl methacrylate, 3,4-epoxy butyl methacrylate, 6,7-epoxy heptyl methacrylate, α-glycidyl ethyl acrylate, α-n-glycidyl propyl acrylate, α-n-butyl acryl glycidyl, α-ethyl acrylate 6,7-epoxyheptyl, o-vinyl benzyl glycidyl ether, m-vinyl benzyl glycidyl ether and p-vinyl benzyl glycidyl ether.