| abstract |
A phosphorus compound represented by the formula (I): n n n n n n n n n n n n wherein R 1 and R 2 are, the same or different, a hydrogen atom, a straight or branched-chain alkyl group having 1 to 6 carbon atoms or an aryl group having 6 to 12 carbon atoms which may be optionally substituted for an alkyl group having 1 to 4 carbon atoms, R 3 , R 4 , R 5 , R 6 and R 7 are, the same or different, a hydrogen atom or an aryl group having 6 to 12 carbon atoms which may be optionally substituted for an alkyl group having 1 to 4 carbon atoms, or R 3 and R 4 , R 4 and R 5 , R 5 and R 6 or R 6 and R 7 may form a 6 membered ring with carbon atoms wherein these groups bond a benzene ring provided that R 3 , R 4 , R 5 , R 6 and R 7 are not hydrogen atoms at the same time. |