Photosensitive resin composition, process for producing patterned hardened film with use thereof and electronic part

A photosensitive resin composition, comprising:

• (a) a copolymer of a polybenzoxazole precursor having an A structure unit and a B structure unit represented by a general formula (III),
• wherein each of U, V, W, and X represents a divalent organic group, at least one of U and V is a group containing an aliphatic chain structure having 1 to 30 carbon atoms, j and k represent molar fractions of the A structure unit and the B structure unit, respectively, and the sum of j and k is 100 mol %;
• (b) a photosensitizer;
• (c) a solvent;
• and
• (d) a crosslinking agent capable of causing crosslinking or polymerization by heating,
• wherein the component (a) is represented by a general formula (IV),
• wherein each of R1 and R2 independently represents hydrogen, fluorine, or an alkyl group having 1 to 6 carbon atoms, each of U, W, and X represents a divalent organic group, j and k represent molar fractions of the A structure unit and the B structure unit, respectively, the sum of j and k is 100 mol %, and a′ represents an integer of 1 to 30.