Acid dyes

A compound of formula (I)

• wherein
• R1 and R2 are independently selected from the group consisting of unsubstituted unbranched C1-6alkyl, unsubstituted branched C3-6alkyl, substituted unbranched C1-6alkyl, and substituted branched C3-6alkyl,
• R3 is selected from the group consisting of hydrogen, unsubstituted unbranched C1-6alkyl, unsubstituted branched C3-6alkyl, substituted unbranched C1-6alkyl, and substituted branched C3-6alkyl,
• R4 and R5 are independently selected from the group consisting of hydrogen, unsubstituted unbranched C1-6alkyl, unsubstituted branched C3-6alkyl, substituted unbranched C1-6alkyl, substituted branched C3-6alkyl, and halogen,
• R6 is selected from the group consisting of hydrogen, unsubstituted unbranched C1-6alkyl, unsubstituted branched C3-6alkyl, substituted unbranched C1-6alkyl, substituted branched C3-6alkyl, unsubstituted unbranched C1-6alkoxy, unsubstituted branched C3-6alkoxy, substituted unbranched C1-6alkoxy, substituted branched C3-6alkoxy, halogen, —NHCO—(C1-6alkyl) with an unbranched C1-6alkyl group, which is substituted or unsubstituted, —NHCO—(C3-6alkyl) with a branched C3-6alkyl group, which is substituted or unsubstituted, and —NHCONH2,
• R7 and R8 are independently selected from the group consisting of unsubstituted unbranched C1-6alkyl, unsubstituted branched C3-6alkyl, substituted unbranched C1-6alkyl, substituted branched C3-6alkyl, aryl, and —(CH2)n-aryl where n=1, 2, 3 or 4.