The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Mar. 29, 2005
Filed:
Nov. 01, 2002
Tokuya Ohjimi, Kanagawa, JP;
Fumihiro Sasaki, Shizuoka, JP;
Hiroto Higuchi, Shizuoka, JP;
Maiko Kondo, Shizuoka, JP;
Toshio Koike, Kanagawa, JP;
Atsushi Sampe, Kanagawa, JP;
Masayuki Yamane, Kanagawa, JP;
Kunihiro Ohyama, Kanagawa, JP;
Junichi Sano, Kanagawa, JP;
Takeyoshi Sekine, Tokyo, JP;
Tokuya Ohjimi, Kanagawa, JP;
Fumihiro Sasaki, Shizuoka, JP;
Hiroto Higuchi, Shizuoka, JP;
Maiko Kondo, Shizuoka, JP;
Toshio Koike, Kanagawa, JP;
Atsushi Sampe, Kanagawa, JP;
Masayuki Yamane, Kanagawa, JP;
Kunihiro Ohyama, Kanagawa, JP;
Junichi Sano, Kanagawa, JP;
Takeyoshi Sekine, Tokyo, JP;
Ricoh Company, Ltd., Tokyo, JP;
Abstract
A developing device including a developer containing magnetic toner grains and includes a main pole for development disposed in a sleeve. Flux density generated by the magnetic pole in a direction normal to the surface of the sleeve outside of the surface has an attenuation ratio of 50% or above. The toner grains have a weight mean grain size of 6.0 μm to 8.0 μm while the toner grains having grain sizes of 5 μm and below occupy 40% to 80% of the entire developer. The toner grains have magnetization strength of 10 emu/g to 25 emu/g in a magnetic field of 5 kOe or magnetization strength of 7 emu/g to 20 emu/g in a magnetic field of 1 kOe. The toner grains reduce toner scattering and image defects despite that they are magnetic, thereby implementing ultrahigh resolution.