Patent ID: 7297415

Claim:
A method for producing a polymeric fluorescent substance characterized by comprising the step of treating with an acid a polymeric fluorescent substance that is fluorescent in a solid state and has a polystyrene equivalent number average molecular weight of 1×10 4 to 1×10 8 and contains at least one repeating unit represented by the following formula (1): —Ar 1 —(CR 1 ═CR 2 ) k — (1) wherein Ar 1 represents a divalent group that forms carbon-carbon bonds with the adjacent two groups, respectively, which is an arylene group with 6 to 60 carbon atoms in the main chain moiety, or a heterocyclic compound group with 4 to 60 carbon atoms in the main chain moiety wherein said arylene group and said heterocyclic compound group may have a substituent; R 1 and R 2 each independently represent a group selected from a group consisting of a hydrogen atom, an alkyl group with 1 to 20 carbon atoms, an aryl group with 6 to 60 carbon atoms, and a heterocyclic compound group with 4 to 60 carbon atoms and a cyano group wherein said aryl group and said heterocyclic compound group may have a substituent; and k is 0 or 1.