Dainippon Ink and Chemicals, Incorporated

Dianippon Ink and Chemicals, Inc.

Kenichi Hirabayashi

Takashi Ito

Hitoshi Takayanagi

Kazuo Itoya

Minoru Nomura

Yukiko Soma

Toyomi Hashizume

Masahiro Yoshida

Toshiro Kogawara

Kinji Shinzo

Koichiro Matsuki

Hiroko Sakurai

Hiroyuki Ohminato

A toner for electrostatic image development made of a polyester resin having a spherical or generally spherical shape, which allows the use of a so-called oilless fixation system capable of fixing, without employing an anti-offset solution as a heat roller fixation system, and which also provides a developed image having excellent quality. The toner comprises a binder resin and a colorant. The flow beginning temperature Tfb of the toner is 90&deg; C. or higher and 120&deg; C. or lower, the T1/2 temperature exceeds 120&deg; C. and is 160&deg; C. or lower, and the flow ending temperature T end is 130&deg; C. or higher and 170&deg; C. or lower. The toner has a spherical or generally spherical shape having an average roundness of 0.97 or more. The toner can be produced by phase inversion at a low shear within a range of 0.2-5 m/second employing an added alcohol solvent.

Toner for electrostatic image development and method of producing the same

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

A spherically particulate toner characterized by a volume-average particle diameter of from 1 to 6 &mgr;m, a colorant content of not less than 9.1% by weight, particularly not less than 5% by weight when the colorant is an organic chromatic pigment, based on the total weight of the binder resin and colorant used and an average circularity (average of circularity defined by (perimeter of circle having the same area as the projected area of particle)/(perimeter of the projected image of particle)) of not less than 0.98. The spherically particulate toner according to the present invention gives an excellent image quality and can be consumed in a drastically reduced amount per sheet of printing paper. By predetermining the particle size distribution of spherical toner particles and the added amount of inorganic oxide fine particles to optimum values, the image quality can be further improved.

Spherical toner particle

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.

Electrophotographic toner and process for the preparation thereof

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Kita-adachi-gun, Japan

Kenichi Hirabayashi