Naphtol derivative and process for producing the same

A naphthol compound represented by the formula (I):

• ##STR11## wherein Y is --(CONH).sub.n --X or --COR, and Y' is --(CONH).sub.n --X' or --COR';
• X and X' may be the same or different and represent a pyridyl group, a thiazolyl group, a benzothiazolyl group or an imidazolyl group, and each group may be optionally substituted;
• R and R' may be the same or different and represent a hydroxyl group, an optionally branched alkoxy group having 1 to 6 carbon atoms, a halogen atom, a benzyloxy group, a phenyloxy group or a phenacyloxy group;
• R.sub.2 is a hydrogen atom, an alkali metal, an optionally branched alkyl group having 1 to 6 carbon atoms, an acyl group having 1 to 6 carbon atoms or a phenylalkylene group,
• Z, which may be substituted on any ring of the naphthalene ring, is at least one moiety selected from the group consisting of a hydrogen atom, a halogen atom, a nitro group, a nitroso group and an amino group, and
• n is an integer of 1 or 2;
• provided that Y and Y' are not simultaneously --COR and --COR', respectively.