The present invention relates to a metal fine particle-containing ink containing metal fine particles (a) dispersed therein with a polymer B, in which the ink contains an ink solvent S; a difference ΔSP (|SP(S)−SP(B)|) between solubility parameters of the solvent S and the polymer B is not more than 1.5 (cal/cm.sup.3).sup.0.5 wherein SP(S) and SP(B) are a solubility parameter of the ink solvent S and a solubility parameter of the polymer B, respectively, as measured by a Fedors method; and the SP(B) is not less than 9.5 (cal/cm.sup.3).sup.0.5 and not more than 10.5 (cal/cm.sup.3).sup.0.5, as well as a method for producing a printed material, which includes the step of applying the metal fine particle-containing ink to a printing substrate to form a metal coating film of the ink on the printing substrate under ordinary-temperature environments, thereby obtaining the printed material.

An ink jet ink composition containing a metal pigment, and a liquid medium component, in which the metal pigment is made of a metal particle, the metal particle is surface-modified with a surface treatment agent, the surface treatment agent is at least one selected from the group consisting of a compound represented by formula (1) below and a compound represented by formula (2) below, and the ink jet ink composition is a water-based ink or a solvent-based ink:

(R—O).sub.aP(O)(OH).sub.3-a   (1)

(R)P(O)(OH).sub.2   (2) where R is independently a hydrocarbon group having a carbon skeleton having 13 or more carbon atoms, and a is 1 or 2.

An ink jet ink composition containing a metal pigment, and a liquid medium component, in which the metal pigment is made of a metal particle, the metal particle is surface-modified with a surface treatment agent, the surface treatment agent is at least one selected from the group consisting of a compound represented by formula (1) below and a compound represented by formula (2) below, and the ink jet ink composition is a water-based ink or a solvent-based ink:

(R—O).sub.aP(O)(OH).sub.3-a   (1)

(R)P(O)(OH).sub.2   (2) where R is independently a hydrocarbon group having a carbon skeleton having 13 or more carbon atoms, and a is 1 or 2.

An aqueous ink jet ink composition of the present disclosure contains a color material represented by Formula (1) below, a water-soluble organic solvent, and water. The color material represented by Formula (1) below contains two or more alkali metal ions as counterions, and the counterions include at least a sodium ion.

##STR00001##

(In Formula (1), M represents a counterion.)

An aqueous ink jet ink composition of the present disclosure contains a color material represented by Formula (1) below, a water-soluble organic solvent, and water. The color material represented by Formula (1) below contains two or more alkali metal ions as counterions, and the counterions include at least a sodium ion.

##STR00001##

(In Formula (1), M represents a counterion.)

A nano composite, a nanoparticle ink composition including a solvent and the nanocomposite, and a light-emitting device including a first electrode, a second electrode facing the first electrode, and an interlayer between the first electrode and the second electrode, wherein the interlayer includes an emission layer, and at least one layer included in the interlayer is made from the nanoparticle ink composition. The nano composite includes: a metal oxide nanoparticle; and a chelating ligand bonded to a surface of the nanoparticle and including a cyclic moiety.

A nano composite, a nanoparticle ink composition including a solvent and the nanocomposite, and a light-emitting device including a first electrode, a second electrode facing the first electrode, and an interlayer between the first electrode and the second electrode, wherein the interlayer includes an emission layer, and at least one layer included in the interlayer is made from the nanoparticle ink composition. The nano composite includes: a metal oxide nanoparticle; and a chelating ligand bonded to a surface of the nanoparticle and including a cyclic moiety.

An ink set including at least one first ink composition and at least one second ink composition, wherein the first ink composition contains a pigment, an inorganic oxide colloid, and water, the second ink composition contains a dye and water, and in the ink set, an arithmetic mean of a conductivity of the at least one first ink composition at 25° C. and a conductivity of the at least one second ink composition at 25° C. is 2.5 mS/cm or less.

An ink set including at least one first ink composition and at least one second ink composition, wherein the first ink composition contains a pigment, an inorganic oxide colloid, and water, the second ink composition contains a dye and water, and in the ink set, an arithmetic mean of a conductivity of the at least one first ink composition at 25° C. and a conductivity of the at least one second ink composition at 25° C. is 2.5 mS/cm or less.

An ink jet ink composition contains at least one disperse dye, a silicone surfactant, and water. The disperse dye content is 1.0% by mass or more and 3.0% by mass or less. When 1.0 part by mass of the silicone surfactant and 99.0 parts by mass of a 10% by mass aqueous solution of propylene glycol are mixed to give a mixture, the mixture has a cloud point of 60° C. or above.