A pigment dispersion containing a metal pigment, wherein the metal pigment contains plate-like particles, and in the case where the longitudinal diameter on the planar surface of the plate-like particle is X, the lateral diameter is Y, and the thickness is Z, the 50% average particle diameter R50 of a corresponding circle determined from the surface area in the X-Y plane of the plate-like particle is between 0.5 and 3 m, and the condition R50/Z>5 is satisfied.

The present invention relates to an actinic radiation-curable inkjet ink including a photocurable compound, a photopolymerization initiator, and an unsaturated fatty acid ester having no photopolymerizable group. The content of the unsaturated fatty acid ester is 0.3 mass % or more and 4.5 mass % or less based on the total mass of the inkjet ink, and the unsaturated fatty acid ester is a compound having an iodine value of less than 80.

To provide an active energy ray-curable ink composition that increase the content of raw materials derived from biomass and contains a material having superior pigment dispersibility, such as a rosin-modified phenol resin. An active energy ray-curable ink composition containing a compound having one or more ethylenically unsaturated bonds, a specific resin, and a specific liquid ingredient is provided, wherein the specific resin is at least one selected from the group consisting of rosin-modified phenol resins, rosin-modified maleic acid resins, rosin-modified alkyd resins, gilsonite resins, and asphalt resins, and the specific liquid ingredient is fat and oil that is derived from animals or vegetables or a modified product thereof having no ethylenically unsaturated bonds and a solubility parameter value (hereinafter referred to as sp value) of 9.0 (cal/cm.sup.3).sup.1/2 to less than 11.0 (cal/cm.sup.3).sup.1/2 as measured by turbidimetric titration.

To provide an active energy ray-curable ink composition that increase the content of raw materials derived from biomass and contains a material having superior pigment dispersibility, such as a rosin-modified phenol resin. An active energy ray-curable ink composition containing a compound having one or more ethylenically unsaturated bonds, a specific resin, and a specific liquid ingredient is provided, wherein the specific resin is at least one selected from the group consisting of rosin-modified phenol resins, rosin-modified maleic acid resins, rosin-modified alkyd resins, gilsonite resins, and asphalt resins, and the specific liquid ingredient is fat and oil that is derived from animals or vegetables or a modified product thereof having no ethylenically unsaturated bonds and a solubility parameter value (hereinafter referred to as sp value) of 9.0 (cal/cm.sup.3).sup.1/2 to less than 11.0 (cal/cm.sup.3).sup.1/2 as measured by turbidimetric titration.

An object is to provide a printing ink that has high environmental friendliness and is excellent in quick dry-curability of a coating when a plasma is used as a curing system. A solution is to provide an ink composition for plasma curing including a photocatalyst compound and/or a composite of a metal component and a photocatalyst compound and to provide an additive for an ink composition for plasma curing, the additive including a photocatalyst compound and/or a composite of a metal component and a photocatalyst compound.

An object is to provide a printing ink that has high environmental friendliness and is excellent in quick dry-curability of a coating when a plasma is used as a curing system. A solution is to provide an ink composition for plasma curing including a photocatalyst compound and/or a composite of a metal component and a photocatalyst compound and to provide an additive for an ink composition for plasma curing, the additive including a photocatalyst compound and/or a composite of a metal component and a photocatalyst compound.

[Problem] The present invention provides an active energy ray-curable ink composition for offset printing which can maintain excellent drying characteristics with a small dose of UV light.

[Solution] An active energy ray-curable ink composition for offset printing comprising a compound having an ethylenically unsaturated bond, a photopolymerization initiator, and an epoxidized fat or oil is used. Although epoxidized fat or oil is not polymerized through radical polymerization, the present inventors, who have conducted research, have revealed that the reactivity of a radically polymerizable ink composition is increased through addition of epoxidized fat or oil thereto.

A pigment dispersion containing a metal pigment, wherein the metal pigment contains plate-like particles, and in the case where the longitudinal diameter on the planar surface of the plate-like particle is X, the lateral diameter is Y, and the thickness is Z, the 50% average particle diameter R50 of a corresponding circle determined from the surface area in the X-Y plane of the plate-like particle is between 0.5 and 3 m, and the condition R50/Z>5 is satisfied.

A pigment dispersion containing a metal pigment, wherein the metal pigment contains plate-like particles, and in the case where the longitudinal diameter on the planar surface of the plate-like particle is X, the lateral diameter is Y, and the thickness is Z, the 50% average particle diameter R50 of a corresponding circle determined from the surface area in the X-Y plane of the plate-like particle is between 0.5 and 3 m, and the condition R50/Z>5 is satisfied.

An oil-based ink jet recording liquid includes a colorant and an oxidatively polymerizable oil-based medium having at least two unsaturated bonds. The ink jet recording liquid has an iodine value of greater than or equal to 65.