Patent ID: 7628938

Claim:
A photochromic compound expressed by a following general formula (I): where: each of A 1 , A 2 and A 3 is a five-member ring forming a 6π-electron system, the three rings being identical, partially identical or totally different from each other, and each ring may have a substituent; B 1 and B 2 are functional groups identical to or different from each other, each group having an atomic number of five or larger, including a ring compound, and B 1 is bonded to a 2-carbon of A 2 , and B 2 is bonded to a 2-carbon of A 3 ; and R 1 , R 2 and R 3 are substituents identical to or different from each other, wherein each of R 2 and R 3 in the general formula (I) is selected from phenylethynyl, thiophene, phenylenevinylene and thienylenevinylene.