Dainippon Ink and Chemicals, Incorporated

Dianippon Ink and Chemicals, Inc.

Minoru Nomura

Takashi Ito

Hitoshi Takayanagi

Kazuo Itoya

Kenichi Hirabayashi

Yukiko Soma

Kinji Shinzo

Toyomi Hashizume

Hiroyuki Ohminato

Masahiro Yoshida

Hideki Watanabe

Toshiro Kogawara

Seiichi Uno

Nansei Tashiro

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

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

The present invention provides a novel developer comprising a spherically particulate toner having a volume-average particle diameter of from about 1 to 6 &mgr;m for use in the development of electrostatic image in electrophotographic copying machines or printers having a colorant content of from 8 to 20% by weight, if the colorant is carbon black, or from 3 to 20% by weight, if the colorant is an organic pigment, based on the sum of the weight of binder resin and colorant and a resin-coated carrier having a volume-average particle diameter of from 20 to 150 &mgr;m. The present invention also provides a suitable polymerization or emulsification process for the preparation of a particulate toner to be incorporated in the developer. The use of the electrostatic image developer makes it possible to not only improve the quality of images provided by copying machines or printers but also realize drastic reduction of the amount of toner to be consumed per sheet of printing paper.

Electrostatic image developer

A non-magnetic one-component development process is provided which comprises supplying a developer onto a photoreceptor using a non-magnetic one-component developing machine comprising at least a developer-supporting roll and a layer-forming blade so that an electrostatic latent image on said photoreceptor is developed, characterized in that as said developer there is used a spherically particulate toner having a volume-average particle diameter of from 1 to 6 .mu.m and the amount of said toner to be attached to said developer-supporting roll is from 0.1 mg/cm.sup.2 to 0.45 mg/cm.sup.2. In accordance with the process of the present invention, the image quality can be drastically improved while drastically reducing the consumed amount of the toner. In particular, by predetermining the colorant content in the spherically particulate toner to be used in the development process of the present invention to not less than 8% by weight, if the colorant is carbon black, or not less than 3% by weight, if the colorant is an organic pigment, the image quality can be further improved. Further, by optimizing the circularity, particle size distribution, added amount of inorganic material fine particles and other conditions of the spherically particulate toner, the image quality can be even further improved.

Image forming method using spherical toner particle

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.

A toner containing at least a colorant and a resin, in which the resin is a polyester resin having a total acid radical content of 2 to 50 mg equivalents per 100 g and having a weight-average molecular weight of 2,000 to 100,000, and the toner particles are spherical and have an average particle diameter of 3 to 13 .mu.m. The toner is produced by a process comprising adding an aqueous medium to a dispersion of at least a colorant and an anionic self-emulsifiable resin in a water-miscible organic solvent to cause phase inversion to obtain an emulsion, and separating the produced particles from the aqueous medium, followed by drying, in which the anion self-emulsifiable resin is a polyester resin having a neutral salt structure, having a total acid radical content of 2 to 50 mg equivalents per 100 g and having a weight-average molecular weight of 2,000 to 100,000.

Growing community of inventors

Saitama, Japan

Minoru Nomura