Mita Industrial Co., Ltd.

Hideki Ota

Nobuhiro Hirano

Hiroshi Shimoyama

Toshiro Tokuno

Tomonori Wada

A toner for developing statically charged images, comprising a binder resin, a colorant and a charge-controlling dye and a process for the preparation of this toner are disclosed. This toner consisting of particles composed of these components have a circularity of from 0.95 to 1.0, and the concentration of the dye on the surfaces of the toner particles is from 1.0.times.10.sup.-3 to 4.times.10.sup.-3 g/g. By dint of these characteristic features, the stability of the frictional chargeability characteristics of the toner is increased, and the contamination of a carrier, a developing device or the like with the dye can be prevented.

Toner for developing statically charged images and process for

Disclosed a process for the preparation of polymer particles, which comprises suspending a polymerizable monomer, a radical initiator and a hardly soluble inorganic dispersant in a dispersion medium and carrying out polymerization in this state, wherein a hardly soluble inorganic dispersant, the solubility of which is changed according to the pH value in the dispersion medium and which is precipitated at a pH value within a certain pH value region of the dispersion medium, is used as the dispersant, suspension of the polymerizable monomer in the dispersion medium is carried out in the state where the dispersant is dissolved in the dispersion medium, an acid or base is then added to adjust the pH value of the dispersion medium to a predetermined level to precipitate the dispersant, and the polymerization is initiated in the state where oil drops having a fine particulate size are formed. The process is effectively utilized for obtaining a toner having good flowability and blocking resistance and excellent developing and fixing properties by using a colorant together with the polymerizable monomer.

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Ikoma, Japan

Hideki Ota