Patent ID: 8378120

Claim:
A compound selected from dyes of formula: wherein: X and Y are the same or different and are selected from oxygen, sulphur, and the group: one of groups R 1 and R 2 is the group: remaining R 1 or R 2 is selected from methyl, ethyl and the group —(CH 2 ) n —COOR 7 ; where R 7 is selected from H, C 1 -C 4 alkyl and CH 2 OC(O)R 8 , where R 8 is methyl, or t-butyl and n is an integer from 1 to 10; groups R 3 and R 4 are independently selected from hydrogen, NO 2 , halogen, SO 3 − , C 1 -C 4 alkoxy and —(CH 2 ) m —COOR 7 ; where R 7 is selected from H, C 1 -C 4 alkyl and CH 2 OC(O)R 8 , where R 8 is methyl, or t-butyl, and m is 0 or an integer from 1 to 5; R 5 is C 1 -C 6 alkyl optionally substituted with COOR 7 , SO 3 − , or OH; where R 7 is selected from H, C 1 -C 4 alkyl and CH 2 OC(O)R 8 , where R 8 is methyl, or t-butyl, and m is 0 or an integer from 1 to 5.