A [1]benzothieno[3,2-b][1]benzothiophene compound expressed by General Formula (I): General Formula (I) where X and Y are each independently a hydrogen atom； a halogen atom； or a functional group having a straight or branched aliphatic alkyl group optionally having a halogen atom, a functional group having an alicyclic alkyl group optionally having a halogen atom, a functional group having a straight or branched aliphatic alkenyl group optionally having a halogen atom, a functional group having an alicyclic alkenyl group optionally having a halogen atom, a functional group having a carboxyl group, or a functional group having a thiol group, as a partial structure； and X and Y are the same or each independently different, provided that at least one of X and Y has a straight or branched aliphatic alkenyl group, an alicyclic alkenyl group, a carboxyl group or a thiol group, as a partial structure.
