Ricoh Company, Ltd.

Other

Nobuhiro Nakayama

Mitsuo Aoki

Yasuo Asahina

Hiroyuki Fushimi

Tetsuo Isoda

Kayo Makita

Yasuaki Iwamoto

Yoichiro Watanabe

Kazunori Bannai

Noboru Sawayama

Takashi Bisaiji

Takayuki Maruta

Takeyoshi Sekine

Kouji Hayashi

Tetsuro Miura

Kazunari Yamada

Fumihiro Sasaki

Nobuyuki Koinuma

Shunichi Chiba

Karumi Kakigawa

Norimitu Kikuchi

Norimitsu Kikuchi

Yosihisa Okamoto

Youichirou Watanabe

A multi-color electrophotographic image formation method of a digital type for forming multi-color images is disclosed, in which latent electrostatic images corresponding to yellow, magenta, cyan and black images separated from an original image are developed with a yellow developer, a magenta developer, a cyan developer and a black developer, respectively to form visible yellow, magenta, cyan and black images, and the visible yellow, magenta, cyan and black images are fixed to an image receiving member, with the reflection image density (ID.sub.ref) and the transmission image density (ID.sub.tr) of the fixed black images formed by the black developer being in the relationship of ID.sub.ref .gtoreq.1.8.times.ID.sub.tr when the deposition of the black developer is in the range of 1.0 mg/cm.sup.2 or less.

Multi-color electrophotographic image formation method

Image forming equipment having an image carrier and a developer carrier located face-to-face and forming an AC-superposed DC electric field between them to develop a latent image electrostatically formed on the image carrier. Sensors responsive to image forming conditions are provided and protected from noise ascribable to an AC component included in the electric field in the event when the sensors operate.

Image forming equipment having improved toner sensing

An image forming apparatus having a developing device of the type using a two-component type developer and developing an electrostatic latent image by a bias electric field having an alternating electric field. A predetermined reference latent image is electrostatically formed on an image carrier by a reference latent image forming device and then developed by the developing device to become a reference toner image. An irregularity detecting circuit determines the degree of difference between the density of the edge and the density of the central portion of the reference toner image. A bias electric field control circuit controls the bias electric field in matching relation to the output of the irregularity detecting circuit, thereby preventing the image quality from being degraded by a change in the resistance of the carrier.

Electrophotographic image forming apparatus which controls developer

A dry type toner for electrophotography is disclosed which comprises as the main components (a) a coloring agent; and (b) a polyol resin serving as a binder agent in an effective amount, the polyol resin being prepared by subjecting a bisphenol-type epoxy resin containing epoxy groups, which may contain secondary hydroxyl groups, to reaction steps (1), (2) and (3), or steps (2) and (3), in any sequential combination, until substantially no epoxy groups remain in the polyol resin, wherein the reaction step (1) comprises a step of causing the epoxy groups in the bisphenol-type epoxy resin to react with a primary amine; the reaction step (2) comprising a step of causing the epoxy groups to react with a compound containing one active hydrogen capable of reacting with the epoxy groups; and the reaction step (3) comprising a step of esterifying at least part of the secondary hydroxyl groups or hydroxyl groups produced in the bisphenol-type epoxy resin by reaction step (1) and/or reaction step (2) by use of an esterifying agent.

Dry type toner for electrophotography

The present invention relates to the positively chargeable black toner particles which comprise binder resins, carbonblack as a main colorant, quaternary anmonium salt of the following formula (I) as a charge control agent and .beta.-form Cu-phthalocyanine as a stabilizing agent for chargeability of toner particles without being affected by the change of environmental conditions. ##STR1## Wherein R.sub.1 is C.sub.1 -C.sub.8 alkyl or benzyl, R.sub.2 and R.sub.3 are each C.sub.1 -C.sub.18 alkyl, R is C.sub.1 -C.sub.118 alkyl or benzyl, X is hydroxy or amino, and Y is hydoroxy or hydrogen; (c) .beta.-form Cu-phthalocyanine; and (d) carbonblack. The present invention further relates to the two component dry-type developer composed by the improved above said positively chargeable toner particles and the carrier particles coated with silicone polylmers which have the strong durability without being changed to a supent carrier particles for a use of long time period.

Dry type developer for electrophotography

A triboelectric charge application member for imparting or applying electrostatic charge to a toner through the triboelectric charging thereof for developing electrostatic images with the charge toner to visible toner images. The triboelectric charge application member includes an overcoat layer comprising as the main component a polymer which comprises a fluoro-olefin compound and an unsaturated silicon compound as the monomer units of the polymer. The triboelectric charge application member may be carrier particles having the above overcoat layer and a toner transportation member having the overcoat layer, depending upon its application.

Triboelectric charge application member for toner comprising copolymer

A magenta toner is disclosed, which comprises a coloring composition comprising a thioindigo pigment, and a xanthene dye having general formula (I) or a laked xanthene dye thereof, and a binder resin: ##STR1## wherein R.sup.1, R.sup.2, R.sup.5, R.sup.6, and R.sup.7 each represent hydrogen or a lower alkyl group; R.sup.3 and R.sup.4 each represent a lower alkyl group; and A.sup.- represents halogen.

Magenta color toner for developing latent electrostatic images in color

The disclosure describes carrier particles for use in a two-component dry-type developer, consisting of core particles which are coated with a silicone resin hardened by an organic tin catalyst.

Carrier particles for use in a two-component dry-type developer

A toner for developing latent electrostatic images is disclosed, which comprises a colorant, and a binder agent comprising (i) polyester resin or epoxy resin, and (ii) styrene - methyl acrylate copolymer.

Toner for developing latent electrostatic images

A triboelectric charge application member for imparting or applying electrostatic charge to a toner through the triboelectric charging thereof for developing electrostatic images with the charged toner to visible toner images. The triboelectric charge application member includes an overcoat layer comprising as the main component a polymer which comprises a fluoro-olefin compound and an unsaturated silicon compound as the monomer units of the polymer. The triboelectric charge application member may be carrier particles having the above overcoat layer and a toner transportation member having the overcoat layer, depending upon its application.

Triboelectric charge application member for toner

Carrier particles for use in a two-component dry-type developer for developing latent electrostatic images comprising a core particle and a silicone resin layer coated on the core particle, the silicone resin layer comprising a silicone resin, an organic tin compound and finely-divided electroconductive particles.

Carrier particles for use in a developer for developing latent

Carrier particles for use in a two-component dry-type developer for developing latent electrostatic images are disclosed, which core particle comprises a core particle and a silicone resin layer coated on the core particles, and the silicone resin layer contains an organic tin compound, which serves as a catalyst for hardening the silicone resin layer in the course of the formation of the silicone resin layer on the core particle under application of heat thereto, with a concentration gradient in the direction of the thickness of the silicone resin layer towards the outer surface of the carrier particles.

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Susono, Japan

Nobuhiro Nakayama