Ink composition

In an ink composition for use in marking pens of the type composed of a dye, a binder and a solvent, the improvement which comprises the solvent being selected from the group consisting of the hexane series and having dissolved therein 5 to 35% by weight of the resinous binder and about 5 to 20% by weight of a modified dye, all % weights being based on the weight of the total composition, said modified dye being at least one species selected from the group consisting of a reaction product obtained by reacting a disazo or anthraquinone dye having at least one group of --CO.sub.2 M and --SO.sub.3 M in the molecule wherein M is an alkali metal with an organic ammonium compound and a reaction product obtained by reacting a basic dye having a positively charged nitrogen, sulfur or oxygen atom in the molecular selected from the group consisting of azo, diphenylmethane, triarylmethane, xanthene, acridiene, methine or polymethine, thiazole, azine, oxazine, thiazine, quinoline and authraquinone dyes with an acid compound:

• said ammonium compound being represented by the formula ##SPC2## ##EQU7## or ##EQU8## wherein R.sub.1, R.sub.2, R.sub.3 and R.sub.4 are respectively a saturated or unsaturated hydrocarbon radical having 1 to 40 carbon atoms, a radical of a saturated or unsaturated hydrocarbon bonded to a saturated or unsaturated hydrocarbon by a divalent group of --O--, --S--, --COO--, --CONH-- or --NH--, the total carbon number of both hydrocarbons bonded being in the range of 2 to 40, or ##EQU9## R' being an alkyl or alkenyl having 1 to 20 carbon atoms, provided that at least one of R.sub.1, R.sub.2, R.sub.3 and R.sub.4 has a carbon number of not lower than 4 and the total carbon number of R.sub.1, R.sub.2, R.sub.3 and R.sub.4 is in the range of 7 to 55;
• R.sub.5 is a saturated or unsaturated hydrocarbon radical having 4 to 40 carbon atoms, a radical of a saturated or unsaturated hydrocarbon bonded to a saturated or unsaturated hydrocarbon by a divalent group of --O--, --S--, --COO--, --CONH-- or --NH--, the total carbon number of both hydrocarbons bonded being in the range of 4 to 40, or ##EQU10## R' being an alkyl or alkenyl having 4 to 20 carbon atoms;
• R.sub.6 is hydrogen atom, methyl or ethyl group;
• R.sub.7 is an aliphatic hydrocarbon radical having 4 to 22 carbon atoms;
• R.sub.8 and R.sub.9 are respectively a hydrocarbon radical having 1 to 10 carbon atoms;
• R.sub.10 is methyl ethyl butyl or propyl group;
• R.sub.11, R.sub.12 and R.sub.13 are respectively a hydrogen atom, a hydrocarbon radical having 1 to 40 carbon atoms, a radical of a hydrocarbon bonded to a hydrocarbon by a divalent group of --O--, --S--, --COO--, --CONH-- or --NH--, the total carbon number of both hydrocarbons bonded being in the range of 2 to 40, or ##EQU11## R' being an alkyl or alkenyl having 1 to 20 carbon atoms, provided that at least one of R.sub.11, R.sub.12 and R.sub.13 is a radical having a carbon number of not lower than 4 and the total carbon number of R.sub.11, R.sub.12 and R.sub.13 is in the range of 4 to 50;
• X is halogen atom and;
• A is an acid residue;
• and said acid compound being represented by the formula
• R.sub.14 Y, ##EQU12## wherein R.sub.14 and R.sub.19 are respectively a saturated or unsaturated aliphatic hydrocarbon radical having 7 to 22 carbon atoms, an aromatic hydrocabon radical having 10 to 28 carbon atoms or a saturated or unsaturated alicyclic hydrocarbon radical having 10 to 28 carbon atoms;
• R.sub.15 is a saturated aliphatic hydrocarbon radical having 2 to 14 carbon atoms;
• R.sub.16, R.sub.17, R.sub.20 and R.sub.21 are respectively a saturated or unsaturated aliphatic hydrocarbon radical having 4 to 22 carbon atoms;
• R.sub.18 is a saturated aliphatic hydrocarbon radical having 4 to 18 carbon atoms;
• M is an alkali metal or ammonium;
• Y is a --CO.sub.2 M, --SO.sub.3 M or --OSO.sub.3 M group wherein M is the same as above.