NOVELTY - A polyimide precursor resin composition comprises polyimide precursor comprising structural unit (I) and having weight average molecular weight of 15000-200000 or polyimide precursor comprising structural unit derived from 1,4-cyclohexanediamine and structural unit derived from s-biphenyl tetracarboxylic dianhydride, and organic solvent. A resin coating film is formed on carrier board, using the polyimide precursor resin composition, a circuit is formed on resultant resin coating film and the resin film is peeled, to obtain flexible device substrate.    USE - Polyimide precursor resin composition is used for forming substrate in manufacture of flexible device e.g. display device e.g. liquid crystal display, organic electroluminescent display and electronic paper (all claimed), and thin-film solar cell.    ADVANTAGE - The substrate formed using the polyimide precursor resin composition has excellent strength, reduced thickness and suppressed defect. The lightweight flexible device provided using the substrate has excellent heat resistance and toughness, low thermal-expansion coefficient and suppressed peeling of carrier board layer.    DETAILED DESCRIPTION - A polyimide precursor resin composition comprises polyimide precursor comprising structural unit of formula (I) and having weight average molecular weight of 15000-200000 or polyimide precursor comprising structural unit derived from 1,4-cyclohexanediamine and structural unit derived from s-biphenyl tetracarboxylic dianhydride, and organic solvent. A resin coating film is formed on carrier board, using the polyimide precursor resin composition, a circuit is formed on resultant resin coating film and the resin film is peeled, to obtain flexible device substrate.    R=H or monovalent organic group;    R1=group chosen from group of formulae (i)-(iv);    R'=alkyl optionally substituted by halo;    R2=group chosen from group of formulae (v)-(viii);and    n=positive integer.    When R1 is structural unit based on p-phenylenediamine, R2 is not a structural unit based on pyromellitic acid anhydride. An INDEPENDENT CLAIM is included for manufacture of flexible device, which involves coating polyimide precursor resin composition on a carrier board, forming polyimide resin film, forming a circuit on the resin film, and peeling the resin film.