(19)
(11) EP 0 306 330 A3

(12) EUROPEAN PATENT APPLICATION

(88) Date of publication A3:
09.08.1989 Bulletin 1989/32

(43) Date of publication A2:
08.03.1989 Bulletin 1989/10

(21) Application number: 88308153.1

(22) Date of filing: 02.09.1988
(51) International Patent Classification (IPC)4G03G 9/08
(84) Designated Contracting States:
DE FR GB

(30) Priority: 02.09.1987 JP 221126/87

(71) Applicant: SOKEN CHEMICAL & ENGINEERING CO. LTD.,
Toshima-ku, Tokyo 171 (JP)

(72) Inventors:
  • Imai, Tatsuhiro c/o Soken Chemical &
    Sayami-shi Saitama (JP)
  • Kawase, Susumu c/o Soken Chemical &
    Sayami-shi Saitama (JP)

(74) Representative: Pett, Christopher Phineas et al
Frank B. Dehn & Co., European Patent Attorneys, 179 Queen Victoria Street
London EC4V 4EL
London EC4V 4EL (GB)


(56) References cited: : 
   
       


    (54) Toner and process for preparation thereof


    (57) Toner particles are described, each particle comprising a spheroidal resin core, a pigment layer on the surface of said core and a layer of a static electrification controlled resin on the surface of said pigment layer. The state of static electrification of the toner is substantially deter­mined by that of the outermost layer of the static electrification con­trolled resin, and thus can be precisely controlled by simply control­ling the amount of static electrification of the resin particles used to form the outermost layer. Since the state of static electrification of the toner can be precisely controlled, the kind and concentration of the pigment used can be freely selected. The presence of the outermost layer 3 prevents the pigment from breaking away from the toner. Further, it is possible to improve the fluidity and anti-block properties of the toner without any adverse effect. In addition, it is not necessary to use an additional static electrification controlling agent such as silica which might adversely affect the color shade of the toner.





    Search report