Mita Industrial Co., Ltd.

Kazuo Fuji

Masahiko Kubo

Noriaki Tsubota

Akihiro Watanabe

Yoshihisa Kuramae

Kazuhisa Edahiro

Akira Nakakuma

Naruo Yabe

Hideki Kita

Toshimitsu Takeuchi

Toshio Nishio

A movable frame member is so mounted on a stationary frame member as to be movable reciprocatingly. A plurality of developing mechanisms are provided on the movable frame member to perform developing in different colors. The same number of toner containers as the number of developing mechanisms are arranged in a fixed manner, and toner feeders for feeding toner into the corresponding developing mechanisms are provided. Each of the toner feders includes a toner conveying device for conveying toner to an upper end portion of a cylindrical member, and a toner dropping passage means for feeding toner conveyed to the upper end portion of the cylindrical member to the developing mechanism. The toner dropping, passage includes an expansion/contraction device so disposed as to extend along the moving direction of the developing mechanism.

Multicolor developing device including expansion/contraction means for

Disclosed is a toner having an excellent transparency for full color development, which comprises a binder resin and a magenta coloring dispersed therein wherein (i) said magenta coloring agent is a quinacridone pigment, (ii) said pigment is dispersed in the binder resin in the form of fine particles and that when the toner is formed into a layer having a thickness of 0.9 .mu.m, the area occupied by the dispersed pigment in 780,000 .mu.m.sup.2 of the area of the formed surface is such that the number of dispersed pigment particles having a size of 10 to 12.5 .mu.m.sup.2 is smaller than 40 and the number of dispersed pigment particles having a size of 12.5 to 15.0 .mu.m.sup.2 is smaller than 20, and (iii) the binder resin has an electroconductivity of 1.0.times.10.sup.-9 to 5.0.times.10.sup.-9 (s/cm). The critical quantities of these dispersed particles having the above sizes differ among magenta, cyan and yellow toners. Each of these color toners has an excellent light-transmitting property, and therefore, these toners can be valuably used for the full color development where these toners are developed in the overlapped state on a transfer material to form a full color image.

Method and toner for full color development

The present invention provides a magnetic brush developing method using a two-component developer, characterized in that the development is carried out under such conditions that at the position where the sliding contact of the magnetic brush with the surface of the photosensitive material drum terminates, the following requirement is satisfied:

Magnetic brush development process

The electrophotographic toner for negative charging according to the present invention is characterized in that a metal compound of an aromatic hydroxycarboxylic acid is used as a charge-controlling agent for negative charging and a quaternary ammonium salt having an oxyacid anion is used as a charge-controlling assistant in combination with the charge-controlling agent. This quaternary ammonium salt used as the assistant is incompatible with a fixing resin but dispersible therein. Therefore, the toner of the present invention provides a sharp distribution of the charge quantity, and formation of a highly charged toner having no contribution to development or a lowly charged toner causing scattering of the toner can be effectively prevented.

Electrophotographic toner for negative charging

The electrophotographic toner for negative charging according to the present invention is characterized in that a polyester resin is used as a fixing resin and a quaternary ammonium salt having an oxyacid anion is used as a charge-controlling assistant in combination with a charge-controlling agent for negative charging. This quaternary ammonium salt used as the assistant is incompatible with a fixing resin but dispersible therein. Therefore, the toner of the present invention provides a sharp distribution of the charge quantity, and formation of a highly charged toner having no contribution to development or a lowly charged toner causing scattering of the toner can be effectively prevented.

The electrophotographic toner for negative charging according to the present invention is characterized in that an acrylamide copolymer-containing sulfonic acid group is used as a charge-controlling agent for negative charging and a quaternary ammonium salt having an oxyacid anion is used as a charge-controlling assistant in combination with the charge-controlling agent. This quaternary ammonium salt used as the assistant is incompatible with a fixing resin but dispersible therein. Therefore, the toner of the present invention provides a sharp distribution of the charge quantity, and formation of a highly charged toner having no contribution to development or a lowly charged toner causing scattering of the toner can be effectively prevented.

The electrophotographic toner for negative charging according to the present invention is characterized in that a quaternary ammonium salt having an oxyacid anion is used as a charge-controlling assistant in combination with a charge-controlling agent for negative charging. This quaternary ammonium salt used as the assistant is incompatible with a fixing resin but dispersible therein. Therefore, the toner of the present invention provides a sharp distribution of the charge quantity, and formation of a highly charged toner having no contribution to development or a lowly charged toner causing scattering of the toner can be effectively prevented.

Electrophotographic tower for negative charging

Disclosed is a developing process using a two-component type magnetic developer, where the main pole of developing magnetic poles in the developing sleeve is arranged upstream of the position, where a photosensitive drum becomes closest to the developing sleeve, in the rotation direction of the developing sleeve, this closest position between the drum and the developing sleeve is included in a region where the flux density in the magnetic force distribution of the main pole decreases toward the downstream side in the rotation direction of the sleeve, an alternating current voltage is applied between the developing sleeve and the drum to form an alternating electric field between the highest voltage and lowest voltage of the electrostatic latent image and in this state the development is carried out. According to this process, the conditions required for the supply of the developer are considerably moderated and an image having a high quality can be advantageously obtained.

Developing process using two-component type magnetic developer

In a developer agitating method, a carrier and a toner are mixed by a spiral in an agitating passage to provide the developer. The developer is conveyed along the axis of the spiral through a high conveying speed section of the passage wherein the developer is agitated in a manner such that a part of the spiral is exposed by extending out of the developer. The developer is conveyed from the high-speed section to a low-speed section wherein the mixture rate of the toner and the carrier is detected. In a preferred embodiment, high-speed and low-speed conveying are controlled according to the pitch of the fans of the spiral. In another preferred embodiment of a developer agitating apparatus, the spiral is arranged with a restricting member which reduces the performance of developer carrying in the vicinity of the toner density sensor, but not at the toner supply mouth.

Developer agitating method and developer agitating apparatus

Disclosed is a developing process using a two-component type developer comprising a magnetic carrier and a toner, in which the developing conditions of the two-component type developer, that is, the composition and density of the developer in a distance between a photosensitive material drum and a developing sleeve (or a distance of a developing zone), are specified based on relations of these conditions to this distance. According to this developing process, the flowability of the developer in the developing zone is improved, and furthermore, the transferability of the toner to the photosensitive material drum is improved.

Developing process

A fixing apparatus detects the surface temperature of a heat roller, detects either the temperature of a press roller which press-contacts the heat roller and incorporates a heater, or the temperature of an external heating apparatus which heats the exterior of the heat roller. The fixing apparatus controls the heater of the above-mentioned press roller or the above-mentioned external heating apparatus based on the results of these detections, and thereby performs a high-quality fixing operation without damaging the heat roller.

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Higashiosaka, Japan

Kazuo Fuji