Abstract: Provided are a resin composition capable of forming a cured film excellent in elongation properties; a polymer suitable as a component contained in the composition; a cured film formed from the composition; and an electronic part including the cured film. The resin composition includes (A) a polymer containing a structural unit represented by the formula (a1) and a structural unit represented by the formula (a2); and (F) a solvent, wherein in the formula (a1), R1s are each independently a hydrogen atom or hydroxyl group, provided that at least one R1 is hydroxyl group; and R2 is a hydrogen atom or a C1-4 alkyl group; and in the formula (a2), R3s are each independently a group having a cationic polymerizable group, or a hydrogen atom, provided that at least one R3 is a group having a cationic polymerizable group; and R4 is a hydrogen atom or a C1-4 alkyl group.

Abstract: A photosensitive composition capable of forming a cured film having small internal stress; a cured film formed from the composition; and an electronic part including the cured film. The photosensitive composition includes: an alkali soluble resin (A), which includes at least 80% by mass of a novolak resin; a photosensitive compound (B); and a crosslinking agent (C), which includes at least a compound represented by the following formula (C1): wherein R1 is an alkyl group having 1 to 6 carbon atoms or the like; R2 is hydroxyl group or the like; R3 is a (a+1)valent hydrocarbon group or the like; R5 is a (c+1)valent hydrocarbon group or the like; R4 is a single bond or the like; a and c are each independently integers of 1 to 3, wherein the sum a+c is an integer of 3 to 6; and b is an integer of 0 or more.

Abstract: A negative-tone radiation-sensitive resin composition includes an alkali-soluble resin, a radically polymerizable compound, a radiation-sensitive radical initiator, and an organic solvent. The alkali-soluble resin includes a phenolic hydroxyl group. The radically polymerizable compound includes an ethylenically unsaturated double bond. The organic solvent includes an ethylene glycol organic solvent having a saturation vapor pressure of 3 mmHg or less at 20° C. and 1 atmosphere.

Abstract: A negative-tone radiation-sensitive resin composition includes an alkali-soluble resin, a radically polymerizable compound, a radiation-sensitive radical initiator, and an organic solvent. The alkali-soluble resin includes a phenolic hydroxyl group. The radically polymerizable compound includes an ethylenically unsaturated double bond. The organic solvent includes an ethylene glycol organic solvent having a saturation vapor pressure of 3 mmHg or less at 20° C. and 1 atmosphere.