Ricoh Company, Ltd.

Mitsui Petrochemical Industries, Ltd.

Hidefumi Gohhara

Fumihiro Sasaki

Yasuo Asahina

Satoshi Mochizuki

Shinichi Kuramoto

Tomomi Suzuki

Yoshihisa Okamoto

Chiharu Mochizuki

Michio Izumi

Hajime Oyama

Hiroaki Matsuda

Kiyonori Tsuda

Yasushi Akiba

Seiji Oka

Tohru Suganuma

Hideo Nakamura

Susumu Kawakami

Takahisa Kato

Hironori Hata

Yutaka Sakai

Norio Yokoyama

Masaru Wakisaka

Megumi Sakakura

In an image forming apparatus, a developing device has a developing sleeve accommodating a magnet roller therein, and a doctor for regulating the amount of developer to be conveyed to a developing position. When the developing sleeve is rotated, the part of the doctor shaved off by the doctor from the sleeve is moved in a developer storing section to a toner replenishing opening formed in a toner storing section. Then, this part of the developer is returned to the doctor along the surface of the sleeve via the toner replenishing opening. The developer consists of a first developer containing a first carrier and deposited in a layer on the surface of the sleeve, and a second developer containing a second carrier different from the first carrier and stored in the developer storing section in such a manner as to contact the first developer deposited on the sleeve. The first carrier has a higher charging ability than the second carrier. The device does not need a toner replenishing mechanism or a toner concentration sensor and has, therefore, a miniature and inexpensive construction. In addition, the device is applicable even to a high-speed image forming apparatus.

Developing device for an image forming apparatus and toner cartridge

A carrier for a dry two-component developer, includes a core material and a silicone-modified acrylic resin layer coated on the surface of the core material, the silicone-modified acrylic resin layer including a silicone-modified acrylic resin, with the ratio of the percentage transmission of infrared spectrum Si--O stretching vibrations (T.sub.Si) of the silicone-modified acrylic resin layer to the percentage transmission of infrared spectrum C.dbd.O stretching vibrations (T.sub.C) thereof, T.sub.Si /T.sub.C, being at least 1.0. The silicone-modified acrylic resin layer can be made from a water-soluble synthetic resin solution containing a silicone macromonomer (A) with a vinyl group being introduced into one terminal thereof, and a vinyl monomer (B) which is copolymerizable with the silicone macromonomer (A), with the molecular weight of the silicone macromonomer (A) of the silicone-modified acrylic resin being in the range of 1,000 to 10,000. Methods of producing such carriers are provided.

Carrier for dry two-component developer and method of producing the same

A dry toner for use in electrophotography including a coloring agent and a polyol resin serving as a binder resin, which has a main chain portion containing an epoxy resin moiety and an alkylene oxide moiety, and protected terminal portions bonded to the main chain portion.

Electrophotographic dry toner

A developer is composed of toner particles which contain a thermoplastic resin, a coloring agent, one component selected from the group consisting of a fluorine-containing quaternary ammonium salt compound and a fluorine-containing iminium compound, and an aromatic hydroxycarboxylic acid metallic salt. This developer may also contain a carrier.

Developer for developing latent electrostatic images

Growing community of inventors

Numazu, Japan

Hidefumi Gohhara