A salt-forming compound represented by the following general formula (3): ##STR00001##
where X.sup.1 and X.sup.2 each independently represent an aromatic ring group optionally containing a substituent; Y represents a divalent hydrocarbon group that the carbon atom directly bound to X.sup.1 or X.sup.2 does not have a π bond; Z.sup.+ represents an organic cation group; e represents an integer of from 1 to 4; and when e is 2 or more, a plurality of Ys and a plurality of Z.sup.+ s may be each the same or different; A.sup.c- represents a heteropolyoxometalate anion which is a c-valent anion and which has an oxidation-reduction potential larger than −0.3 V relative to the silver/silver chloride electrode; f and c are each an integer of 2 or more; g is an integer of 1 or more; and the salt-forming compound is a normal salt that f×e=c×g.

Provided herein are hybrid pigments and methods of making the same. The hybrid pigments include a natural polyamide substrate and an acid dye disposed on the natural polyamide substrate. The hybrid pigments are biodegradable, compostable, or both, and provide an environmentally friendly alternative to synthetic polymer particle-based pigments.

Provided herein are hybrid pigments and methods of making the same. The hybrid pigments include a natural polyamide substrate and an acid dye disposed on the natural polyamide substrate. The hybrid pigments are biodegradable, compostable, or both, and provide an environmentally friendly alternative to synthetic polymer particle-based pigments.

A color material dispersion liquid including a color material, which is a salt-forming compound of an organic dye with a heteropolyoxometalate, a dispersant and a solvent, wherein the organic dye is at least one organic dye selected from the group consisting of a porphyrin dye, a tetraazaporphyrin dye, a phthalocyanine dye and a squarylium dye, and wherein the heteropolyoxometalate is a heteropolyoxometalate which has an oxidation-reduction potential larger than −0.3 V relative to the silver/silver chloride electrode.

A salt-forming compound represented by the following general formula (3):

##STR00001##

where X.sup.1 and X.sup.2 each independently represent an aromatic ring group optionally containing a substituent; Y represents a divalent hydrocarbon group that the carbon atom directly bound to X.sup.1 or X.sup.2 does not have a π bond; Z.sup.+ represents an organic cation group; e represents an integer of from 1 to 4; and when e is 2 or more, a plurality of Ys and a plurality of Z.sup.+ s may be each the same or different; A.sup.c− represents a heteropolyoxometalate anion which is a c-valent anion and which has an oxidation-reduction potential larger than −0.3 V relative to the silver/silver chloride electrode; f and c are each an integer of 2 or more; g is an integer of 1 or more; and the salt-forming compound is a normal salt that f×e=c×g.

Provided is an aqueous ink composition using colored resin particles with excellent color development suitable for writing instruments such as felt-tip pens, marking pens, and ballpoint pens. The aqueous ink composition for writing instruments of the present invention includes colored resin particles colored by a salt-forming dye, which is a salt-forming body of an acid dye and a basic dye.

A color material dispersion liquid including a color material, which is a salt-forming compound of an organic dye with a heteropolyoxometalate, a dispersant and a solvent, wherein the organic dye is at least one organic dye selected from the group consisting of a porphyrin dye, a tetraazaporphyrin dye, a phthalocyanine dye and a squarylium dye, and wherein the heteropolyoxometalate is a heteropolyoxometalate which has an oxidation-reduction potential larger than −0.3 V relative to the silver/silver chloride electrode.

The present disclosure concerns the design, formulations, preparations and optical properties of compounds of Formulas (I) and (VI):

(charged dye.sup.m+).sub.x.Math.(counterion.sup.n).sub.y.Math.(counterion receptor).sub.z(I) and

(charged dye.sup.m).sub.x.Math.(counterion.sup.n+).sub.y.Math.(counterion receptor).sub.z(VI).

The charged dye.sup.m+ is a cationic dye, counterion.sup.n is an anion, and counterion receptor is a binding ligand for the counterion.sup.n, wherein m, n, x and y are integers greater than or equal to 1, and products of x.Math.n and m.Math.y are identical for formula (I).

The charged dye.sup.m is a anionic dye, counterion.sup.n+ is a cation, and counterion receptor is a binding ligand for the counterion.sup.n+, wherein m, n, x and y are integers greater than or equal to 1, and products of x.Math.n and m.Math.y are identical for formula (VI).

A compound represented by the following general formula (I): ##STR00001##
(the symbols in the general formula (I) are as described in the Description), wherein the compound contains one or more structures selected from the following (i) and (ii): (i) A is an aliphatic hydrocarbon group containing two or more alicyclic hydrocarbon groups, containing a saturated aliphatic hydrocarbon group at a terminal position directly bound to N, and optionally containing O, S, N in a carbon chain (ii) at least one of R.sup.2, R.sup.3, R.sup.4 and R.sup.5 is a cycloalkyl group optionally containing a substituent group or an aryl group optionally containing a substituent group.

A compound represented by the following general formula (I): ##STR00001##
(the symbols in the general formula (I) are as described in the Description), wherein the compound contains one or more structures selected from the following (i) and (ii): (i) A is an aliphatic hydrocarbon group containing two or more alicyclic hydrocarbon groups, containing a saturated aliphatic hydrocarbon group at a terminal position directly bound to N, and optionally containing O, S, N in a carbon chain (ii) at least one of R.sup.2, R.sup.3, R.sup.4 and R.sup.5 is a cycloalkyl group optionally containing a substituent group or an aryl group optionally containing a substituent group.