Patent ID: 8021475

Claim:
A method of producing organic pigment fine particles, including allowing two or more solutions at least one of which is an organic pigment solution in which an organic pigment is dissolved to flow through a microchannel, and depositing organic pigment fine particles from the organic pigment solution in a course of flowing, the method comprising: the step of dividing at least one solution of two or more solutions comprising the organic pigment solution in which an organic pigment is dissolved in an alkaline or acidic aqueous medium and a pH adjustor solution for changing a hydrogen ion exponent of (pH) of the organic pigment solution into a plurality of solutions; the step of combining solutions so that a central axis of at least one divided solution of the plural divided solutions and the central axis of another solution of the two or more solutions different from the one divided solution intersect at one point in a combining region; and the step of depositing the organic pigment fine particles by changing the hydrogen ion exponent (pH) of the organic pigment solution by the pH adjustor solution in the course of allowing the combined solutions to flow through the microchannel; and wherein in the step of combining, an intersection angle of the central axes upon combining the solutions is determined so that S 1 >S 2 is satisfied, wherein a sum of the cross sectional areas of all of the combined solutions in the thickness direction is described as S 1 and the cross sectional area of the microchannel in the radial direction is described as S 2 , and thereby contracting the flow of the solutions at the combining region.