Sharp Kabushiki Kaisha Corporation

Katsuaki Sumida

Hitoshi Nagahama

Toshihisa Ishida

Toshihiko Murakami

Jitsuo Masuda

Hideji Saiko

Toshiaki Ino

Hiroo Naoi

Masayasu Narimatsu

Tadashi Nakamura

Junichi Saito

Mitsuru Tokuyama

Katsuhiro Nagayama

Motoyuki Itoyama

Toshio Nishino

Masato Asanuma

Takahiro Bito

Yasuharu Morinishi

Tadayuki Sawai

Yasuo Kitabatake

Yuichiro Takesue

Tomoko Nishino

Kanshiro Okamoto

Keizo Kitamura

Eisaku Hatanaka

A toner for developing electrostatic latent images comprises: a colorant; a polyester resin; a negative charge controlling agent comprised of a chromium complex compound; and a positive charge controlling agent, wherein the polyester resin has an acid value Z of 15 to 33 mgKOH/g, a hydroxyl value Y of 4 to 17 mgKOH/g and a number-average molecular weight (Mn) of 5200-7000.

Toner for developing electrostatic latent images, method for forming images and apparatus for forming images

The present invention provides a toner which does not cause problems on generation of an offensive odor and a stain on a surface of a cooling unit and which is excellent in an offset resistance, a low temperature fixability and an environmental dependency. In the toner for developing an electrostatic latent image comprising a polyester resin as a principal component which is formed by reacting dicarboxylic acids of a polybasic acid with diols of a polyhydric alcohol, dimethyl phthalate remaining in the polyester resin described above without reacting has a content of 0.1 % by weight or less.

Toner for developing electrostatic latent image

A magnetic member is arranged at a position on the downstream side with respect to the rotational direction of a developing sleeve, outside the developer conveyance path where the magnetism from the magnetic member has no influence on the magnetic field of the developing magnetic pole. When the magnetic member is arranged with its N pole facing the developing sleeve, the magnetic attractive force from the magnetic member weakens the developer's attraction to the peripheral surface of the developing sleeve. When the magnetic member is arranged with its S pole facing the developing sleeve, the developer being conveyed along the developer conveyance path is magnetized in such a direction as to repel the peripheral surface of the developing sleeve. In either case, the adhering state of the developer to the peripheral surface of the developing sleeve having passed through the developing position is unstable, so that the developer having adhered to the developing sleeve will easily drop off from the developing sleeve after passage of the developing position.

Electrophotographic developing unit

A toner for developing electrostatic latent images comprises a polyester resin and an electric charge controlling agent containing a chromium complex compound, wherein the polyester resin has an acid value Z of 15 to 30 (15<Z&lE;30) mgKOH/g and a hydroxyl value Y of 4 to 17 (4&lE;Y&lE;17) mgKOH/g.

Toner for developing electrostatic latent images and image-forming apparatus

A developing device includes: a multiple number of magnetic poles fixed at predetermined positions; a developer sleeve which rotatably encloses the magnetic poles; a doctor blade for regulating the thickness of the developer layer on the developer sleeve; and an agitating roller arranged adjacent to the developer sleeve and agitating and supplying the developer. In this arrangement, the magnetic poles include a development magnetic pole for developing the static latent image on the photoreceptor drum, and a developer conveyance magnetic pole positioned downstream, with resect to the rotational direction of the developer sleeve, of the development magnetic pole. A magnetic element is arranged opposing the developer sleeve outside the developer flow path where the magnetic field of the developer conveyance pole is not effective.

Developing device having low turbulence developer flow

An image forming apparatus has an arrangement wherein a main charger includes a charger line corresponding to a region within a reference range on a surface of a photoreceptor and second charger lines corresponding to regions outside the reference range, and the first charger line within the reference range and the second charger lines outside the reference range are driven independently. The reference range is set on the surface of the photoreceptor as a width of a transported sheet which is most frequently used. In a processing control, in the case where toner patch density within the reference range becomes higher than toner patch density outside the reference range, an applied voltage with respect to the charger line within the reference range is increased relatively higher than an applied voltage with respect to the charger lines outside the reference range, thus uniformalizing the toner density with respect to the entire surface of the photoreceptor drum.

Image forming apparatus for controlling processing conditions in image

The image forming apparatus of the invention controls the toner density by any one of the following configurations: by correcting the toner density of the developer in association with the agitation total; by controlling a process parameter so that the density of a toner patch formed on the photoreceptor corresponds to a prescribed density value and determining that developing performance of the developer is improved and canceling the toner density correction when the process parameter reaches the prescribed value; by changing the toner density reference value when the variation as to the charger output is equal to or greater than a first predetermined value and maintaining the changed toner density reference value until the variation of the charger output again becomes equal to or greater than the first predetermined value; or by prohibiting toner supply for a constant duration to prevent excessive toner supply if time from the end of the last operation of the developing unit to the start of a next operation, inclusive of the power-activation is equal to or longer the a predetermined period when the developing unit is activated to commence agitation of the developer.

Toner density control for an image forming apparatus

In order to effectively perform image stabilization by control of retaining initial characteristics of a photosensitive body, if correlation between initial and aged values corresponding to bright and dark part signals of the photosensitive body is such that a variation between the initial and aged values of the dark part signal (dark .DELTA.) is greater than a variation between the initial and aged values of the bright part signal (bright .DELTA.), an image stabilizer, first, controls a charging characteristic of the aged values by changing a charging output to the photosensitive body so that the bright .DELTA. and the dark .DELTA. are equal to each other. Next, the image stabilizer makes the aged characteristics of the photosensitive body virtually identical to the initial characteristics by changing an exposure output so that the aged and initial values of the dark part signal become equal to each other.

Image stabilizer

The electrostatic charge image-developing toner contains a colorant, a binder resin, and polyethylene having a melt viscosity of 22000 to 26800 mPa.multidot.s at 140.degree. C. This electrostatic charge image-developing toner prevents an offset phenomenon on the surface of a fixing roller, and does not adhere to and fuse on a photoreceptor drum to cause no stripy and dotwise stain on a reproduced image, that is, preventing a so-called filming phenomenon. The toner also prevents an offset phenomenon on the photoreceptor drum.

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Kashiba, Japan

Katsuaki Sumida