Dainippon Ink and Chemicals, Incorporated

Yukiko Soma

Takashi Ito

Hitoshi Takayanagi

Minoru Nomura

Kazuo Itoya

Kenichi Hirabayashi

Toyomi Hashizume

Hiroyuki Ohminato

Toshiro Kogawara

Kinji Shinzo

Koichiro Matsuki

Hiroko Sakurai

Shoji Okuno

The present invention provides a polyester resin toner which has good fixing properties and is superior in image quality in a heat roller fixation system without employing an anti-offset solution, and which has a spherical or generally spherical shape and has a small particle diameter, and a method of producing the same. In a toner for electrostatic image development comprising a binder resin and a colorant, said binder resin is made of a polyester resin. Furthermore, the weight-average molecular weight as measured by gel permeation chromatography of a tetrahydrofuran-soluble fraction of said polyester resin contained in the toner is 30,000 or more and the weight-average molecular weight/number-average molecular weight is 12 or more and, moreover, the area ratio of a molecular weight of 600,000 or more is 0.5% or more and the area ratio of a molecular weight of 10,000 or less is within a range of 20-80%. The toner for electrostatic image development has a spherical or generally spherical shape having the average circularity (average value of circularity defined by (perimeter of a circle having the same area as that of a projected area of particles)/(perimeter of a projected image of particles)) of 0.97 or more.

Toner for electrostatic image development

An electrophotographic toner having a volume-average particle diameter of from 3 to 15 .mu.m. The toner comprises a spherical particulate material having an average circularity of not less than 0.97 having a colorant encapsulated in a binder resin. The binder resin is a styrene-acrylic resin having an acid value of from 30 to 150 which is at least partly crosslinked. The tetrahydrofuran insoluble content in the whole of the binder resin including crosslinkd portions in the particulate material is from 0.5 to 70% by weight.

Electrophotographic toner and process for the preparation thereof

Disclosed are an electrophotographic toner which is a spherical particle comprising a binder resin having encapsulated therein a colorant and has a volume average particle size of from 3 to 12 .mu.m, the binder resin being a non-crosslinked styrene-acrylic resin having an acid value of from 30 to 120, containing from 5 to 60% by weight of the components having a molecular weight in terms of polystyrene by gel permeation chromatography of 200,000 or more and having a ratio (Mw/Mn) of the weight-average molecular weight Mw to the number-average molecular weight Mn of from 4 to 30; and a process for preparing an electrophotographic toner comprising spherical particles having a volume average grain size of from 3 to 12 .mu.m, the process comprising mixing a mixture comprising the above-described resin, a colorant, a wax and an organic solvent as essential components with an aqueous medium in the presence of a neutralizer in an amount sufficiently large to render the resin self-emulsifiable to effect phase inversion emulsification, thereby producing particles each comprising a binder resin having encapsulated therein a colorant and a wax in the liquid medium, and separating and drying the particles. The toner obtained by the present invention is improved in the thermal fixing characteristics and the environmental stability of charging, exhibits a wide fixing temperature width at the heated roll fixing and has excellent triboelectricity.

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Tokyo, Japan

Yukiko Soma