Mita Industrial Co., Ltd.

Nobuhiro Miyakawa

Teruaki Higashiguchi

Eiichi Inoue

Hiroshi Kokado

Takashi Teshima

Masanori Fujii

Kouzi Maekawa

Koji Yano

Kazuo Yamamoto

Yumiko Sano

Kaname Nakatani

Masatomi Funato

Haruo Koyama

Yoshinobu Kawakami

Takashi Yamaguchi

Kouji Maekawa

Teruaki Higashiguti

Tatsuo Aizawa

Masanori Matsuda

Toshio Watanabe

Kiyoshi Shibata

Yosuke Ohata

Syoji Nakagama

Tomomi Edo

Eiichi Inque

In an electrophotographic developing method using a magnetic brush consisting of a mixture of magnetic carrier and an electroscopic toner, development is carried out at a toner concentration (Ct. %) in the mixture, which satisfies the requirement represented by the following formula: ##EQU1## wherein Sc stands for the specific surface area (cm.sup.2 /g) of the carrier, St stands for the specific surface area (cm.sup.2 /g) of the toner, and k is a number of from 0.90 to 1.14. A toner image having a high quality can be obtained according to this method.

Method for developing electrostatic images using magnetic brush

A two-component electrophotographic developer for use in developing a latent electrostatic image of a low potential. The developer is composed of a mixture of a magnetic carrier of spherical sintered ferrite particles having raised and depressed portions attributed to the primary particles on their surface, a median size of from 30 to 50 micrometers, an apparent density of less than 2.6 g/cc and an electric resistance, measured in the form of a magnetic brush, of from 6.times.10.sup.4 to 2.5.times.10.sup.6 ohms and chargeable toner particles having a volume inherent resistivity of at least 1.times.10.sup.13 ohms-cm and a specific inductive capacity of from 4 to 6. In a preferred embodiment, the chargeable toner particles have a median size of from 10 to 14 micrometers and are substantially free from particles having a particle diameter of not more than 5 micrometers. The developer can give an image of a high density, a high resolution and excellent gradation without brush marks.

Two-component electrophotographic developer with magnetic carrier

Disclosed is an electrophotographic apparatus comprising a photosensitive drum comprising an amorphous silicon type photoconductor layer formed on an electroconductive substrate, a main charging mechanism for charging the surface of the drum with charges having a predetermined polarity, an imagewise exposure mechanism for forming an electrostatic image corresponding to an image of an original on the surface of the drum, a toner development mechanism for forming a toner image corresponding to the electrostatic image, a toner image transfer mechanism for transferring the toner image formed on the surface of the photosensitive drum to a predetermined paper sheet, a toner cleaning mechanism for removing the residual toner adhering to the surface of the photosensitive drum and a fixing mechanism for fixing the transferred toner image to said paper sheet, wherein a heating mechanism is arranged to heat the surface of the photosensitive drum at a temperature of 30.degree. to 40.degree. C. The problem of the flow of an image inherent to the use of an amorphous silicon type photoconductive layer is effectively solved if this electrophotographic apparatus is employed.

Electrophotographic apparatus comprising photosensitive layer of

In a copying machine comprising a photosensitive drum having an amorphous silicon type photoconductive layer, if an image of an original is focussed on the photoconductive layer with a light having a wavelength shorter than 600 nm, the light fatigue of the amorphous silicon photoconductive layer is prevented, and the image memory phenomenon owing to the light fatigue is effectively obviated.

Copying machine having reduced image memory

A toner for electrophotography, comprising an azoic pigment having a silica core as a coloring component, said azoic pigment comprising a core of a fine powder of silica and a coating of a mono- or polyazoic dye chemically bound to the surface of the silica core through an aminosilane coupling agent.

Toner for electrophotography comprising azoic pigment having silica core

An azoic pigment having a silica core comprising a core of a fine powder of silica having a particle diameter of not more than 10 microns and a coating of a mono- or polyazoic dye chemically bound to the surface of the silica core through an aminosilane coupling agent.

Azoic pigments having a silica core

An electrically conductive composition is disclosed, which comprises a protonically conductive compound, a finely divided inorganic solid acid and a binder, especially an aqueous emulsion type carboxyl group-containing polymer. This composition has in combination highly improved electric conductivity, low humidity dependency, reduced tacking tendency and high whiteness and can be manufactured at a low cost. This composition is valuable for production of an electro-sensitive recording material.

Electrically conductive composition for electro-responsive recording

A photosensitive material for electrophotography, which comprises an electroconductive substrate and a photosensitive layer formed on the substrate. The photosensitive layer comprising a charge transfer medium and a charge-generating pigment dispersed in the mediums. The photosensitive layer contains as the matrix resin a thermoplastic polyester consisting essentially of recurring units represented by the following general formula: ##STR1## wherein R.sup.1 stands for a phenylene group or an ethylene group, R.sup.2 stands for a group represented by the formula ##STR2## R.sup.3 stands for a direct bond or a divalent bridging atom or group, and the ring A may have a substituent not participating in the reaction. In another embodiment a photosensitive material for electrophotography includes an electroconductive substrate, a photoconductive organic pigment-containing, charge-generating layer formed on the substrate and a charge transfer layer formed on the charge-generating layer, wherein the charge transfer layer contains as the matrix resin the above-mentioned thermoplastic polyester. These thermoplastic polyesters provide improvements in adhesion to the substrate, surface hardness and abrasion resistance.

Photosensitive material for electrophotography

Disclosed is a photosensitive material for electrophotography containing a pentakisazo pigment of the following formula: ##STR1## wherein the rings A.sub.1 and A.sub.2 may have halogen atoms, alkyl groups or alkoxy groups as substituents at the ortho-positions to the azo groups, the ring B may have a halogen atom, an alkyl group or an alkoxy group as a substituent or may contain the ring Z.sub.1, Z.sub.1 which is an aromatic or hetero ring fused to the benzene ring B, and Y stands for a group of the following formula: ##STR2## in which Z.sub.2 stands for an aromatic ring or a hetero ring, Ar.sub.1 stands for an aromatic ring or a hetero ring, Ar.sub.2 and Ar.sub.3 stand for an aromatic ring, R.sub.0 stands for a hydrogen atom, a lower alkyl group or a phenyl group, R.sub.1 stands for a lower alkyl group, a carboxyl group or an ester thereof, and R.sub.2 and R.sub.3 stand for a hydrogen atom, a lower alkyl group, a phenyl group or a substituted derivative thereof.

Photosensitive material for electrophotography containing photosensitive

Disclosed is a one-component type red color magnetic developer having a self-electroscopic property, which comprises particles prepared from a kneaded composition comprising 100 parts by weight of a magnetic powder composed mainly of ocherous gamma-type diiron trioxide, 2.5 to 30 parts by weight of a red azo pigment and 40 to 200 parts by weight of a binder resin, wherein a fixed image of the particles is measured by a color difference meter, the value x is from 0.51 to 0.73, the value y is from 0.22 to 0.40 and the value Y is from 5 to 65%.

One-component type red color magnetic developer

Electrophotographic photosensitive material comprising an electroconductive substrate and a layer of a photoconductive composition composed of a dispersion of a charge generating pigment in a charge transporting medium, which is formed on the electroconductive substrate, wherein said photoconductive composition contains an N,N-di-substituted-carbamic acid salt in an amount of 20 to 200% by weight based on the charge generating pigment. This electrophotographic electrophotosensitive material has excellent ozone resistance and shows a high initial charge retention ratio and sensitivity retention ratio when the cycle of charging and light exposure is repeated many times.

Electrophotographic photosensitive material with ozone inhibitor

Disclosed is a one-component type magnetic developer consisting essentially of a particulate shaped article of a composition comprising a binder resin medium and a powdery magnetic material dispersed in the binder resin medium, wherein said magnetic material comprising (A) a non-pulverizing agglomerate of cubic particles of magnetite having a particle size of 1 to 10 .mu.m as measured by an electron microscope and (B) magnetite particles having a particle size of 0.2 to 1 .mu.m at an (A)/(B) weight ratio of from 95/5 to 10/90, especially from 95/5 to 30/70.

One-component type magnetic developer comprises particles of cubic

Disclosed is a heat-sensitive recording material capable of forming an image of a hue close to a pure black at a low density, which comprises a dispersion of a leuco dye, a heat-fusible organic acidic substance solid at normal temperature and a sensitizing agent in a binder, wherein the leuco dye comprises a fluoran type leuco dye for forming a black color and a benzofluoran type leuco dye for forming a red dye in an amount of 0.01 to 1% by weight based on said black color-forming leuco dye.

Heat-sensitive black recording material

Disclosed is a heat-sensitive recording element capable of forming an image of a hue close to a pure black at a low density, which comprises a dispersion of a leuco dye, a heat-fusible organic acidic substance solid at normal temperature and a sensitizing agent in a binder, wherein the leuco dye comprises a fluoran type leuco dye for forming a black color and a rhodamine lactam type leuco dye for forming a red dye in an amount of 1.5 to 30% by weight based on said black color-forming leuco dye.

Heat-sensitive black recording element

Disclosed is a transfer-type one-component dry magnetic developer which comprises a binder medium having a high electric resistance and particles of triiron tetroxide of an isometric system having a particle size of 0.25 to 1 micron and a coercive force of 30 to 80 Oe, in which the triiron tetroxide particles are dispersed in the binder medium. This developer provides a transferred image excellent in the density, sharpness and clarity on a plain paper as a transfer sheet in the electrostatic photography.

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Abiko, Japan

Nobuhiro Miyakawa