Hitachi, Ltd.

Hitachi Koki Co., Ltd.

Susumu Akimaru

Nobuyoshi Hoshi

Masayasu Anzai

Isamu Komatsu

Yasuro Hori

Kunio Sato

An electronic blackboard having a copy function, and an edit function or communication function. A single reading unit is used in common for both reading an image on a flat board and reading an image or an original document. Reflected light from the flat board and from the original document is converged and projected onto a light receiving surface of a single photoelectric conversion element. An image of the flat board of the original document can be selectively read, or the composite image of both the flat board and original document can be read. Further, the electrical signal corresponding to the image can be modulated and transmitted, and a received electrical signal can be demodulated to reproduce a corresponding image. Furthermore, in accordance with the electrical signal obtained by photoelectrically converting an image, the layout of the image on the flat board can be determined and edited to change the shape of the image.

Electronic blackboard

A toner of a first color incorporated into a development appartaus for second color is charged to a polarity opposite to a polarity of a charge of an electrostatic latent image for the second color by a frictional action with a toner in the development apparatus for the second color. The toner of the first color incorporated into the second development apparatus is caused to adhere to a charge-non-released region of a drum, whereby accumulation of the first toner in the second color development apparatus is prevented. The first and second toners are electrostatically transferred onto a paper by a bias electric field having a polarity opposite to that of the toner images, whereby at reversal development of the second color, the toner of the first color adhering to the charge-non-released region is prevented from being transferred onto the paper. Further, the toner of the first color, incorporated in the second development apparatus, changed reversly in its polarity, or reduced to about zero in the charge quantity can be removed by electrical and mechanical removal means provided in the second development apparatus.

Method for forming multi-color toner image

Disclosed is a second toner developing apparatus for use in a two color electro-photographic recording apparatus in which a photosensitive drum is uniformly charged, subject to a first exposure, developed with a first toner, subject to a second exposure, and then developed with a second toner. The second developing apparatus is provided with a rotary sleeve for performing magnetic brush development and a fixed magnet disposed within the rotary sleeve. The fixed magnet includes a plurality of magnetic poles of the same polarity provided close to each other, so as to temporarily separate the second developer from the surface of the rotary sleeve at the position of these same polarity magnetic poles. An electrostatic attraction electrode attracts the first toner mixed in the thus separated second developer to thereby remove the first toner from the second developer.

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Hitachi, Japan

Susumu Akimaru