Patent ID: 8232330

Claim:
A nonaqueous ink, comprising: colorant particles, a dispersant and a radical-polymerization compound; wherein the colorant particles having an average particle diameter of 1 nm or more and less than 50 nm, and having a (D 90 -D 10 ) value of 100 nm or less are obtained by a precipitation process of bringing a colorant dissolved solution into contact with an aqueous medium, at least one of the pigment dissolved solution and the aqueous medium containing the dispersants, to form a dispersion, and further comprising the steps of (i) aggregating the colorant particles into redispersible agglomerates, and separating the agglomerates from the dispersion, (ii) redispersing the agglomerates to form fine particles redispersed in a redispersion medium, and (iii) bringing the agglomerates into contact with an organic solvent for increasing crystallinity of the colorant particles; wherein D 90 -D 10 is a value obtained by subtracting D 10 from D 90 ; D 90 and D 10 represent respectively the particle diameters at cumulative colorant particle numbers of 0.9 (90 number %) and 0.1 (10 number %) in an integral value of the distribution function dG=F(D)dD; and G represents the number of the pigment particles; and D represents the diameter of the particles; wherein the colorant particles comprise quinacridone pigment particles or azo pigment particles; wherein the colorant particles have a crystalline structure as determined by a powder X-ray diffraction analysis, such that the colorant particles do not show a halo specific to an amorphous substance, and wherein the crystallite diameter of the colorant particles is 5 nm or more; and wherein the radical-polymerization compound is a monofunctional radically polymerizable monomer containing only one ethylenic unsaturated group selected from the group consisting of an acrylate group, a methacrylate group, an acrylamide group, a methacrylamide group and a N-vinyl group.