Mita Industrial Co., Ltd.

Ricoh Company, Ltd.

Yoshitake Shimizu

Masahide Inoue

Koichi Tsuyama

Tetsuya Nakano

Naruo Yabe

Seijiro Ishimaru

Kazuya Nagao

Teruaki Teratani

Masatomi Funato

Mitsushi Kuroki

Takayuki Itakura

Toyotsune Inoue

Norio Kubo

Hiroshi Shimoyama

Kenshi Matsui

Takahiro Ishihara

Norio Horikami

Terumichi Asano

Takashi Nishino

Toshikane Nishii

Mizuna Tanaka

Hirofumi Horita

Takafumi Miyazaki

Ikuo Fujii

Nobuhiko Umezawa

Tomoya Tanaka

Masaki Narita

Takashi Fujimoto

Yutaka Aso

Chuanyi Yang

Hongjie Tan

Junlin Cai

Kouichi Tsuyama

Seijirou Ishimaru

Mikiko Tamori

A sheet feeder includes a feeding member to contact a sheet and feed the sheet downstream in a sheet conveyance direction, a friction pad disposed facing the feeding member to contact the feeding member, and a receiving table including a pad mount to hold a side of the friction pad opposite a nip between the friction pad and the feeding member. The friction pad includes a fixed range secured to the pad mount upstream from the nip and a movable range extending downstream the nip in the sheet conveyance direction. A first friction force of the pad mount to act on the movable range of the friction pad is smaller than a second friction force of the sheet to act on the movable range of the friction pad.

Sheet feeder and image forming apparatus

A disclosed remaining amount of developer detection device includes a remaining amount of developer detection section detecting a remaining amount of developer in a development device, an operation amount computation section computing an operation amount of the development device corresponding to a developer consumption amount, and a remaining amount detection control section accumulating the operation amount and detecting the remaining amount of developer based on the accumulated operation amount. In this device, when the remaining amount of developer detection section has detected the remaining amount of developer that has been reduced to a first threshold, the remaining amount detection control section initializes the accumulated operation amount and starts accumulating a new operation amount of the development device corresponding to a developer consumption amount, and determines whether the remaining amount of developer in the development device is in a toner-end status based on the new operation amount.

Remaining amount of developer detection device, development device, process unit, and image forming apparatus

An image forming apparatus including a developer regulating member and sealing members. The developer regulating member regulates an amount of the developer carried by a developer carrying member, and has a center region having a first outer diameter of a first longitudinal cross-sectional region which increases toward an axial center portion of the developer regulating member according to a predetermined calculated amount of deflection of the developer regulating member, side regions located at axial end portions and having a second outer diameter of a second longitudinal cross-sectional region greater than a third outer diameter of a third longitudinal cross-sectional region obtained according to deflection of the developer regulating member. The sealing members have respective inner edges which sandwich boundaries of the center region and each of the side regions.

Method and apparatus for image forming capable of effectively regulating a toner layer, developing mechanism for the apparatus, and a process cartridge provided in the apparatus

Disclosed are a positive charging color toner comprising a coloring agent and a positive charging electric charge controlling material in a fixing resin, wherein the fixing rein is an urethane-modified polyester resin having an acid value of not more than 5 KOHmg/g, a hydroxyl value of not more than 9 KOHmg/g, a weight-average molecular weight of 8,000 to 120,000 and a number-average molecular weight of 2,000 to 70,000, and the positive charging electric charge controlling material is (a) a quaternary ammonium salt having a melting point of not less than 200&deg; C., or (b) a styrene-acrylate copolymer having a trisubstituted amminio group and a glass transition temperature Tg of not less than 55&deg; C.; and a positive charging one-component non-magnetic color toner comprising a polyester resin having an acid value of not more than 5 KOHmg/g, a hydroxyl value of not more than 9 KOHmg/g, a weight-average molecular weight of 7000 to 20,000 and a number-average molecular weight of 1,000 to 6,000, a polyolefine (releasing agent) having an acid value of not more than 10 KOHmg/g and a weight-average molecular weight of 8,000 to 15,000, a proportion of a polyolefine having a particle diameter of not less than 1.5 &mgr;m among polyolefines dispersed in the toner being within 1% in terms of the number, a coloring agent and a positive charging electric charge controlling resin.

Positive charging color toner

Disclosed are a positive charging color toner comprising a coloring agent and a positive charging electric charge controlling material in a fixing resin, wherein the fixing rein is an urethane-modified polyester resin having an acid value of not more than 5 KOHmg/g, a hydroxyl value of not more than 9 KOHmg/g, a weight-average molecular weight of 8,000 to 120,000 and a number-average molecular weight of 2,000 to 70,000, and the positive charging electric charge controlling material is (a) a quaternary ammonium salt having a melting point of not less than 200.degree. C., or (b) a styrene-acrylate copolymer having a trisubstituted amminio group and a glass transition temperature Tg of not less than 55.degree. C.; and a positive charging one-component non-magnetic color toner comprising a polyester resin having an acid value of not more than 5 KOHmg/g, a hydroxyl value of not more than 9 KOHmg/g, a weight-average molecular weight of 7000 to 20,000 and a number-average molecular weight of 1,000 to 6,000, a polyolefine (releasing agent) having an acid value of not more than 10 KOHmg/g and a weight-average molecular weight of 8,000 to 15,000, a proportion of a polyolefine having a particle diameter of not less than 1.5 .mu.m among polyolefines dispersed in the toner being within 1% in terms of the number, a coloring agent and a positive charging electric charge controlling resin.

The invention provides toner for a two-component type developer containing toner particles including a binder resin and magnetic powder dispersed in the binder resin. The binder resin in the toner is prepared from a composition including at least one of (1) a polymer having an anionic group and a wax grafted portion and (2) a mixture of a polymer having an anionic group and a polymer having a wax grafted portion. The magnetic powder is contained in the toner particles at a proportion ranging between 0.1 and 5 parts by weight per 100 parts by weight of the binder resin.

Toner for a two-component type developer

The invention provides toner for a two-component type developer containing toner particles including a binder resin and magnetic powder dispersed in the binder resin. The binder resin in the toner is made of a composition including a low molecular weight polymer and a high molecular weight polymer both having an anionic group. The magnetic powder is contained in the toner particles in the range of 0.1 to 5 parts by weight per 100 parts by weight of the binder resin.

A toner in which a small amount of magnetic powder is disposed in a resin medium for fixing which comprises a cationic polar group-containing copolymer resin or a resin composition. A distinguished feature resides in that the toner does not contain a charge control agent. The toner is positively charged and exhibits very good spent resistance. The toner further exhibits favorable electrophotographic properties such as transfer efficiency despite there is contained no charge control agent.

Toner for a two-component-type magnetic developing agent having

A negatively charged toner for a two-component-type magnetic developing agent, wherein a resin medium for fixing is a copolymer resin or a resin composition having anionic polar groups and contains a magnetic powder in an amount of from 0.1 to 5 parts by weight per 100 parts by weight of the resin medium, but contains no charge control agent. The toner without containing the charge control agent exhibits very excellent spent resistance.

The developer in accordance with the present invention includes toner, and a carrier having a core material the surface of which is coated with a coating layer made of a polymer, the coating layer having a resistance value sufficient to minimize the counter electric charge remaining in the coating layer, and the toner having any of characteristic values required for preventing a counter electric charge remaining in the coating layer from being increased. The use of the developer of the present invention not only prevents the occurrence of so-called carrier scattering, to thereby prevent blanking, but also produces an image of high quality having a high initial image density.

Two-component developer

A two-component developer comprising a magnetic carrier having a carbon black-containing resin-coating layer and a toner composed of a carbon black-containing resin composition is disclosed. A styrene resin, an acrylic resin or a styrene-acrylic copolymer resin is selected as each of the carrier-coating resin and the toner-forming resin, and the carbon black content A in the carrier-coating layer and the carbon black content B in the toner-forming layer satisfy requirements represented by the following formulae: ##STR1## Namely, by adjusting the carbon black contents A and B within specific ranges relatively to each other, a two-component developer which is well-balanced between the frictional chargeability characteristic and the electric resistance is provided.

A toner composition comprising a binder resin having dispersed therein additives including a colorant and a charge control agent, wherein said additives are present as agglomerates having an average sectional area of from 1.4 to 1.7 .mu.m.sup.2 in a section of toner particles, the total sectional area of the agglomerates in the section of toner particles ranging from 1.5 to 1.8%, or wherein said colorant and charge control agent are present as agglomerates having an average sectional area of from 1.4 to 1.7 .mu.m.sup.2 in a section of toner particles, and said composition has such rheological characteristics that a dissipation factor (tan .delta.) is from 0.95 to 1.25 when a storage elastic modulus (G') is 10.sup.4 dyne/cm.sup.2.

Toner composition

The present invention provides a start developer wherein an output voltage of a sensor in the start developer having a particular toner density is not less than 0.9 times an output voltage of the sensor in a developer having the same toner density in a time period during which image characteristics are stabilized after repeating image formation by an image forming apparatus and is less than a threshold value at which the supply of toner is started and a method of controlling the toner density using the start developer. According to the present invention, good images can be always formed irrespective of the variation in characteristics between sensors in image forming apparatuses and from the early stage of image formation to the stable time period.

Start developer and method of controlling toner density

In an electrophotographic toner, by using as the binder resin a styrene/acrylic resin in which in the gel permeation chromatogram, a high molecular weight peak value appears in a molecular weight region higher than 1.times.10.sup.5, a low molecular weight peak value appears in a molecular weight region of from 2.times.10.sup.4 to 500, a minimum value appears halfways between the two peaks and the ratio (V/P) of the area of the valley to the peak area is lower than 0.3, the internal cohesive force of the binder resin for the toner can be prominently improved while maintaining the low-temperature fixing property and offset resistance at high levels, and pulverization of the toner and formation of the spent toner can be prevented during the developing operation and the durability of the toner can be improved.

Electrophotographic toner

The present invention provides an electrophotographic developer comprising (i) a toner containing a fixing resin in which the content of an acrylic component is limited to a predetermined range, or a toner of which surface dye density is limited to a predetermined range, and (ii) a carrier coated with a coating resin containing, as an acrylic component, dodecyl methacrylate or 2-hydroxyethyl acrylate. In the electrophotographic developer of the present invention, the electric charging characteristics are always stable.

Growing community of inventors

Kyoto, Japan

Yoshitake Shimizu