Method for producing quinacridone solid solution pigment, pigment dispersion, and inkjet ink

A method for producing a pigment dispersion liquid, the method comprising:

• producing a crude quinacridone solid solution;
• drying the crude quinacridone solid;
• producing the quinacridone solid solution pigment by pigmentation comprising heating of the dried crude quinacridone solid solution in a solvent;
• and
• dispersing the quinacridone solid solution pigment in a dispersion medium comprising a pigment dispersant,
• wherein in the producing of the crude quinacridone solid solution, diarylaminoterephthalic acid and dialkylarylaminoterephthalic acid are co-cyclized in polyphosphoric acid so as to obtain the crude quinacridone solid solution, the crude quinacridone solid solution comprising:
• an unsubstituted quinacridone, and
• 2,9-dialkylquinacridone,
• in a solid solution form, and
• further comprising water,
• in the drying, the water-containing crude quinacridone solid solution obtained in the producing the crude quinacridone solid solution is dried so that a water content thereof is reduced to less than 1%, and that the dried crude quinacridone solid solution in a powder form is obtained, and
• in the producing the quinacridone solid solution pigment, the solvent in which the powdery, crude quinacridone solid solution is heated is a liquid medium that does not dissolve the crude quinacridone solid solution, and
• wherein the quinacridone solid solution pigment has peaks at Bragg angles (2θ±0.2°) of 27.3°, 13.9°, and 5.6° in powder X-ray diffraction, and
• a relative intensity ratio of the peak of 27.3° is in a range from about 70 to about 80, and a relative intensity ratio of the peak of 13.9° is in a range from about 60 to about 70, relative to an intensity of the peak of 5.6° as 100.