Abstract: The present invention relates to a dye-containing light-polarizing film wherein a disazo dye represented by the formula (I) is used: ##STR1## wherein Me represents a transition metal, being copper, nickel, zinc or iron, R represents a 1-naphthol or 2-naphthol residue which is bonded to azo group at the position adjacent to its hydroxyl group forming a complex bond together with the transition metal and which may have a substituent such as a sulfonic acid, sulfonamide, amino, acylamino or arylamino group or a hydroxyl group not adjacent to the azo group, X and Y represent a hydrogen atom, a C.sub.1 -C.sub.4 alkyl, lower alkoxy, carboxylic acid, sulfonic acid, sulfonamide, sulfonalkylamide, amino, acrylamino or nitro group or a halogen atom, and Z represents a hydrogen atom or a C.sub.1 -C.sub.4 alkyl or lower alkoxy group, said formula (I) having from 1 to 3 sulfonic acid groups.

Abstract: An azo compound of the formula: ##STR1## wherein R is of the formula: ##STR2## R.sub.1 is hydrogen, methyl or --SO.sub.3 M; R.sub.2 is hydrogen or --SO.sub.3 M; R.sub.2 is hydrogen or --SO.sub.3 M; R.sub.3 is C.sub.4 -C.sub.18 alkyl and M is hydrogen, an alkali metal, ammonium or organic ammonium, provided that when R includes --SO.sub.3 M, R.sub.1 l and R.sub.2 are not --SO.sub.3 M, and when R does not include --SO.sub.3 M, either one of R.sub.1 and R.sub.2 is --SO.sub.3 M, which is useful as a black dyestuff for a solvent type ink composition, particularly for ink jet recording.

Abstract: A dye solution composition containing a black dye obtained by the action of at least one acid or its salt:HO(CH.sub.2).sub.n SO.sub.3 H, Cl(CH.sub.2).sub.n COOH, Br(CH.sub.2).sub.n COOH (n=1 or 2)on one or a mixture of dyes of the formula (I): ##STR1## wherein R is phenylene or naphthylene residue; X and X' are each H, sulfonic acid group or sulfonate group; Y and Y' are each H or alkali metal; R' is one of amino group-containing radicals: ##STR2## (the carboxyl group may be carboxylate group and the sulfonic acid group may be sulfonate group), except that when R' has not sulfonic acid group, X and X' are not the same and when R' has sulfonic acid group, X and X' are H. This is highly stable, preservative and water soluble, and is useful as ink composition for ball-point pen and ink jet recording.