In one aspect, inks for use with a three-dimensional (3D) printing system are described herein. In some embodiments, an ink described herein comprises up to 80 wt. % oligomeric curable material; up to 80 wt. % monomeric curable material; up to 10 wt. % photoinitiator; up to 1 wt. % non-curable absorber material; and up to 10 wt. % one or more additional components, based on the total weight of the ink, and wherein the total amount of the foregoing components is equal to 100 wt. %. Additionally, the photoinitiator is operable to initiate curing of the oligomeric curable material and/or the monomeric curable material when the photoinitiator is exposed to incident curing radiation having a peak wavelength λ. Moreover, the ink has a penetration depth (D.sub.p), a critical energy (E.sub.c), and a print through depth (D.sub.PT) at the wavelength λ of less than or equal to 2×D.sub.p.

An ink jet ink composition which is a water-based ink, includes a self-dispersible pigment, inorganic oxide particles, and a poly(ethylene glycol) represented by the following general formula (I), and the ink composition contains at least one type of metal ion selected from the group consisting of a potassium ion, a sodium ion, and a lithium ion.

HO—(CH.sub.2—CH.sub.2—O—).sub.n—H  (I)

In the above formula, n represents an integer of 3 to 9.

An ink jet ink composition which is a water-based ink, includes a self-dispersible pigment, inorganic oxide particles, and a poly(ethylene glycol) represented by the following general formula (I), and the ink composition contains at least one type of metal ion selected from the group consisting of a potassium ion, a sodium ion, and a lithium ion.

HO—(CH.sub.2—CH.sub.2—O—).sub.n—H  (I)

In the above formula, n represents an integer of 3 to 9.

An ink set of the present disclosure includes a colored ink jet ink and a decoloring ink. The colored ink jet ink includes a leuco dye, a developer, and a dispersant, and the decoloring ink includes a solvent and water. The solvent includes a specific solvent component that has a Hansen solubility parameter that differs from the Hansen solubility parameter of the developer by an absolute value of less than or equal to 5.3. Preferably, the specific solvent component is a glycol ether or a glycol. Preferably, the leuco dye is a fluoran. Preferably, the developer is a compound containing a phenolic hydroxy group in the molecule.

An ink set of the present disclosure includes a colored ink jet ink and a decoloring ink. The colored ink jet ink includes a leuco dye, a developer, and a dispersant, and the decoloring ink includes a solvent and water. The solvent includes a specific solvent component that has a Hansen solubility parameter that differs from the Hansen solubility parameter of the developer by an absolute value of less than or equal to 5.3. Preferably, the specific solvent component is a glycol ether or a glycol. Preferably, the leuco dye is a fluoran. Preferably, the developer is a compound containing a phenolic hydroxy group in the molecule.

Provided is an aqueous white inkjet ink including: a white pigment; a water-dispersible urethane resin; an amine compound with a molecular weight of 110 to 150; and water, in which an amount of the amine compound with a molecular weight of 110 to 150 relative to a total amount of the ink is 0.2 to 1.3% by mass, and a mass ratio of the amine compound with a molecular weight of 110 to 150 relative to the water-dispersible urethane resin satisfies (a mass of the amine compound with a molecular weight of 110 to 150)/(a mass of the water-dispersible urethane resin)=0.02 to 0.08.

Provided is an aqueous white inkjet ink including: a white pigment; a water-dispersible urethane resin; an amine compound with a molecular weight of 110 to 150; and water, in which an amount of the amine compound with a molecular weight of 110 to 150 relative to a total amount of the ink is 0.2 to 1.3% by mass, and a mass ratio of the amine compound with a molecular weight of 110 to 150 relative to the water-dispersible urethane resin satisfies (a mass of the amine compound with a molecular weight of 110 to 150)/(a mass of the water-dispersible urethane resin)=0.02 to 0.08.

A copper particle mixture ensures suppression of copper oxidation and high dispersibility, and that can be sintered at a low temperature in a short period of time can suitably be used for a conductive copper ink material. The copper particle mixture contains copper fine particle A and copper nanoparticle B, the copper fine particle A having an average particle diameter of 0.1 μm to 5 μm, and being coated with at least one dicarboxylic acid selected from the group consisting of malonic acid and oxalic acid, the copper nanoparticle B comprising a central portion comprising a copper single crystal, and a protective layer surrounding the central portion, and having an average particle diameter of 1 nm to 100 nm, and the protective layer of the copper nanoparticle B containing at least one member selected from the group consisting of C.sub.3-6 primary alcohols, C.sub.3-6 secondary alcohols, and derivatives thereof.

A copper particle mixture ensures suppression of copper oxidation and high dispersibility, and that can be sintered at a low temperature in a short period of time can suitably be used for a conductive copper ink material. The copper particle mixture contains copper fine particle A and copper nanoparticle B, the copper fine particle A having an average particle diameter of 0.1 μm to 5 μm, and being coated with at least one dicarboxylic acid selected from the group consisting of malonic acid and oxalic acid, the copper nanoparticle B comprising a central portion comprising a copper single crystal, and a protective layer surrounding the central portion, and having an average particle diameter of 1 nm to 100 nm, and the protective layer of the copper nanoparticle B containing at least one member selected from the group consisting of C.sub.3-6 primary alcohols, C.sub.3-6 secondary alcohols, and derivatives thereof.

A sprayable and hygroscopic ink for a digital printing process on a fabric includes 3.0 parts by weight to 6.0 parts by weight of a colorant, 0.5 parts by weight to 2.0 parts by weight of a hygroscopic agent, 0.5 parts by weight to 1.0 part by weight of a surfactant, and a balance of a solvent, in which a pH value of the hygroscopic agent is between 6.0 and 8.5 at 25° C., and a particle diameter D90 of the sprayable and hygroscopic ink is between 180 nm and 220 nm.