Disazo dyes

New disazo dyes used in the preparation of aqueous dye preparations. The dyes have the formula (I); R = H, 1-4 C alkyl, 1-4 C alkoxy, 1-4 C alkylcarbonylamino, ureido or amino; R = H, 1-4 C alkyl, 1-4 C alkoxy, sulfo or carboxy; R = H; unsubstituted alkyl; alkyl substituted by NH2, di-(C1-C4-alkyl)amino, OH or 1-4 C alkoxy; unsubstituted aryl; aryl substituted by 1-4 substituents (same or different) selected from 1-4 C alkyl, 1-4 C alkoxy, NH2, OH, sulfo or carboxy; ureido; formyl; 1-4 C alkylcarbonyl; unsubstituted benzoyl; or benzoyl substituted by 1-4 substituents (same or different) selected from 1-4 C alkyl, 1-4 C alkoxy, sulfo or carboxy; R = H; unsubstituted 1-4 C alkyl; or 1-4 C alkyl substituted by OH or 1-4 C alkoxy; n and n' independently = 0 or 1 provided that (a) in the left-hand naphthyl ring in (I) the OH group is in the 5-, 6- or 8-position, the SO3H group is in the 6-, 7- or 8- position, the (SO3H)n group is in the 1-, 3- or 4-position and the azo group is in the 1- or 2-position and in the right-hand naphthyl ring the NR R group is in the 2- or 3-position and the (SO3H)n group is in the 1- or 2-position and (b) the dye of formula (II) is excluded (known from JP1172907). Independent claims are included covering (a) a process for preparing the dyes (I); (b) use of the dyes (I) for dyeing and printing carbonamide group- and/or cellulose-containing materials; (c) Use of (I) for surface or bulk coloring of paper; (d) Use of (I) for preparing ink jet printer inks; and (e) Aqueous dye preparations containing the (I).