A monoazo dye of the following formula (I): ##STR1## wherein R is phenyl, phenoxy or benzyl, and D is a group of the formula (D1), (D2), (D3) or (D4): ##STR2## wherein each of X.sup.1, X.sup.2 and X.sup.3, which are independent of one another, is hydrogen or chlorine, X.sup.4 is hydrogen, chlorine, methyl or --NHCOR.sup.1, wherein R.sup.1 is C.sub.1-4 alkyl or phenyl; ##STR3## wherein X.sup.4 is as defined above, Y.sup.1 is hydrogen, chlorine or C.sub.1-4 alkoxy; ##STR4## wherein X.sup.5 is hydrogen, halogen, methyl or --NHZ, wherein Z is C.sub.1-4 alkylsurfonyl, C.sub.1-4 alkylcarbonyl, phenylsulfonyl, phenylcarbonyl, C.sub.1-2 alkoxy C.sub.1-2 alkylcarbonyl or aminocarbonyl, Y.sup.2 is hydrogen, methyl or C.sub.1-2 alkoxy, and Q.sup.1 is cyano or C.sub.1-4 alkylcarbonyl; ##STR5## wherein P is formyl, nitro or cyano, Q.sup.2 is cyano or nitro, T is halogen, methyl, phenyl or methylsulfonyl, X.sup.5 is as defined above, and Y.sup.3 is hydrogen or C.sub.1-2 alkoxy.