The dispersion ink patent was filed July 28, 1998. The patent was issued Aug. 8, 2000, with anticipated expiration in 2018. The listed inventors are Shoji Saibara, Shigeo Aoyama and Tetsuya Taki.
The U.S. Patent 6099627 details dispersion ink as being used for ink-jet recording. Dispersion ink is used for high-definition print quality, and re-dispersibility can be obtained by using ultrafine particles of a pigment or a disperse dye that have an average particle diameter of 75 nanometers or less.
Dispersion ink, or fine particles of a pigment, possesses a large specific surface area and can be present in a greatly increased number per a unit volume, making dispersed particles of the pigment easily coagulated. When fine particles of the disperse dye are used, the molecular weight of the amphiphilic compound must increase to assure the re-dispersibility. When a combination of a disperse dye and an amphiphilic compound is employed, the pigment or dye provides improved dispersibility and can be made into ink with high-definition qualities.