Patent ID: 8039532

Claim:
A compound represented by formula (I-1): wherein R 21 , R 22 , R 23 and R 24 each independently represent a hydrogen atom or a monovalent substituent, with the proviso that compounds, in which R 21 , R 22 , R 23 and R 24 each are an alkylthio group, are excluded; R 21 and R 22 and/or R 23 and R 24 may bond to each other to form a ring, with the proviso that compounds, in which the formed ring is a dithiol ring or a dithiolane ring, are excluded; at least one of R 21 , R 22 , R 23 and R 24 represents —CN, —COOR 28 , —CONR 29 R 30 , —COR 31 or —SO 2 R 32 (in which R 28 , R 29 , R 30 , R 31 and R 32 each represent a hydrogen atom or a monovalent substituent); R 25 and R 26 each independently represent a hydrogen atom or a monovalent substituent; X 21 , X 22 , X 23 and X 24 each independently represent a nitrogen atom, an oxygen atom or a sulfur atom; compounds, wherein R 21 , R 22 , R 23 and R 24 each represent a cyan group; X 21 , X 22 , X 23 and X 24 each represent a sulfur atom; and R 25 and R 26 each represent a hydroxyl group or a hydrogen atom, are excluded; and compounds, wherein R 21 and R 23 each represent a hydrogen atom; R 22 and R 24 each represent an arylcarbonyl group; X 21 , X 22 , X 23 and X 24 each represent a sulfur atom; and R 25 and R 26 each represent a hydroxyl group, are excluded.