Sharp Kabushiki Kaisha Corporation

Sharp Kabushiki Kaishi

Toshihisa Ishida

Tadashi Nakamura

Yasuharu Morinishi

Satoshi Ogawa

Hitoshi Nagahama

Jitsuo Masuda

Takahiro Bito

Hideji Saiko

Katsuaki Sumida

Yoshinori Urata

Tadayuki Sawai

Tatsuo Imafuku

Yoshiaki Akazawa

Toshiaki Ino

Hiroo Naoi

Masayasu Narimatsu

Kanshiro Okamoto

Kouji Kida

Takeaki Ohuchi

Katsuhiro Nagayama

Motoyuki Itoyama

Masato Asanuma

Nobuyasu Honda

Nobuhiko Nakano

Toshihiko Murakami

Yasuo Kitabatake

Tomoko Nishino

Shigeaki Tasaka

Masanori Matsumoto

Kiyoshi Toizumi

Mitsuru Tokuyama

Junichi Saito

Hiroshi Onda

Takafumi Nagai

Masahiko Kubo

Tohru Nishikawa

Naotaka Funayama

Yoshimi Kojima

Mitsuhiro Hasegawa

Satoshi Yamaue

Takeshi Takayama

Tomoko Toizumi

Yuichiro Takesue

Toru Nishikawa

Katsushi Inoue

Takeshi Katoh

Kazuya Maeda

Yuko Takeda

Keizo Kitamura

Masao Suzuki

Yoshiaki Takahashi

Kazuya Korematu

Kazuya Korematsu

Tatuo Imafuku

Akio Matsumoto

Kumiko Nakamura

Takeaki Oouti

Shintaro Hatano

Norio Tateishi

Eisaku Hatanaka

Katuaki Sumida

A two-component developing agent containing a carrier which can maintain a charge-imparting property to a toner at a high level for a long period of time, does not generate flying of the carrier and can correspond to an image forming apparatus of present day having a long operation life and can form a high-quality image having high image density and sharpness, is provided. In the two-component developing agent containing a carrier in which a resin coating layer is formed on a surface of a core material, and a toner, in which an X-ray intensity of an alumina particle by a fluorescent X-ray analysis, the amount of the alumina particle to be used to the resin coating layer is adjusted such that it comes to be smaller than the X-ray intensity by the fluorescent X-ray analysis of a metal contained in a largest amount in the core material.

Carrier and developing agent for electrophotography

Provided is a toner not undergoing the effect of change of temperature and humidity, with high charging stability and having good fixing property and releasability. This is an electrophotographic toner containing at least a binder resin, a colorant, a charge controller and a wax in which the binder resin comprises a polyester resin having an aromatic alcohol ingredient, the charge controller comprises an organic bentonite and the wax comprises a non-polar paraffin wax.

Electrophotographic toner

A non-magnetic mono-component toner of the present invention is composed of a coloring powder at least containing a binder resin, coloring agent and wax and at least one kind of external additive having a mean particle diameter of 0.04 &#x3bc;m or greater, wherein the relationship between the Vickers hardness of the above coloring powder and the mean particle diameter of the external additives satisfies the predetermined expression. Thereby, the present invention is effective in preventing the external additive particles from sinking into the toner surface as well as from falling off from the surface when the toner particles are stressed in the developing unit. As a result, it is possible to provide stable image quality free from degradation of toner charge performance and toner supply performance even for long-term use.

Non-magnetic mono-component toner and developing method with the same

The present invention provides an electrophotographic developer which reduces toner contamination on the surface of a developer carrier even when a development effective range is narrowed and which is stabilized in an image quality in every environmental situation and has a long life and a low cost and an image-forming method using the same. In the present invention, used for the electrostatically charged-image holder described above having a radius of curvature of 18 mm or less in a development effective range is the electrophotographic developer which is a two-component developer comprising a toner comprising at least a binder and a colorant and a carrier which is coated with a resin and has a weight average particle diameter of 40 to 100 &#x3bc;m, wherein the above toner has a volume average particle diameter of 8 to 11.5 &#x3bc;m, and the toner particles having a diameter of 6.35 &#x3bc;m or less account for 20 number % or less.

Electrophotographic developer and image-forming method using the developer

An image forming apparatus having a tandem system configuration, includes: a multiple number of photoreceptors which each form an electrostatic latent image; and a multiple number of developing devices each holding a different color toner from the others for development of the corresponding static latent image, and is constructed so that the plural toners at least include a black toner, and the abrading force of the black toner or its carrier therein acting on the photoreceptor surface is adjusted so as to be smaller than that of the other developing toners or their carrier therein. Since, in a tandem type color image forming apparatus, the developing devices, photoreceptors and toners for all colors will reach the end of their life at the same time, the image forming apparatus can be operated at low cost.

Image forming apparatus

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 binder resin as the main component of the toner has a low molecular weight polypropylene as a separating agent, encapsulated therein. Using this binder a toner with the wax having a diameter of 0.3 .mu.m or less dispersed therein is produced. The wax is included 0.5 part to 5 parts by weight for 100 parts by weight of the binder resin. This limitation of the toner prevents the setoff phenomenon during the fixing process and at the same time prevents the filming phenomenon over the photoreceptor and achieves an improved fixing performance.

Toner for electrophotography and a production method thereof

In toner 1 containing a binder resin 2, wax particles 3 and a coloring agent, the wax particles 3 are designed so that the ratio of major axis/minor axis is set in the range of 1.4 to 4.0 and so that the major axis L is not more than 6.0 .mu.m. Moreover, the melt index of the binder resin ranges from 5.0 to 11.0, and the dielectric loss tangent (tan .delta.) is not more than 5.0. This arrangement prevents the wax particles 3 inside the toner 1 or at the toner 1 surface layer from exposing to or sticking out of the toner 1 surface, thereby making it possible to provide a superior offset-reducing property during the fixing process and electrophotographing toner that can reduce wax contamination on the surface of the toner-bearing body.

Toner used for electrophotography

A toner for electrophotography includes a binder resin as the main component and a coloring agent, wherein the binder resin contains a low molecular weight polypropylene as a separating agent, encapsulated therein; the acid value of the binder resin is adjusted equal to 1.0 (mgKOH/g) or below; and the coloring agent has a surface which is not oxidation treated and presents a pH of 7.0 or higher. Limiting the added amount and the diameter of encapsulated and dispersed polypropylene wax provides prevention against both the setoff and filming phenomena.

Toner for electrophotography

A process for preparing a toner includes forming a melt-kneaded mixture by mixing a raw material mixture containing a quaternary ammonium salt compound at a temperature ranging from (M-7).degree. C. to (M+7).degree. C., where M is a melting point of the quaternary ammonium salt compound, with a kneading device having a discharge port whose temperature is set lower than a temperature at which a melt viscosity of the melt-kneaded mixture at the discharge port is not higher than 10,000 Pa.a, removing the melt-kneaded mixture from the kneading device, rolling out the melt-kneaded mixture to a thickness ranging from 1.2 mm to 3.0 mm, and cooling down the melt-kneaded mixture. With the use of the toner produced by this process, the amount of charge during copying is retained in an appropriate range irrespectively of the working atmosphere and conditions of use, thereby maintaining a good image density.

Toner, Developer, and process for producing the same

An electrophotographic toner is made up of toner particles composed of irregularly-shaped core particles made chiefly of binder resin, and surface-modifying fine particles which are first dispersed over and attached to the surface of the core particles, and then affixed or formed into a film thereon. The BET specific surface area, based on N.sub.2 adsorption, of the toner particles is less than 0.64 times the BET specific surface area of the core particles and surface-modifying fine particles combined together. Further, this value is 1.07 times the BET specific surface area of hypothetical toner particles which are perfect spheres. Consequently, the toner is not prone to problems such as filming, toner scattering, and fogging which are caused by peeling, separation, etc. of the surface-modifying fine particles, nor to poor cleaning due to spherical toner particles. Further, since the toner is manufactured with a quantitative grasp of the state of modification of the surface of the core particles by the surface-modifying fine particles, it is a toner in a stable state.

Electrophotographic toner and method of manufacturing same

The present invention provides electrophotographic printing-use toner capable of producing a quality image, without depending on excessive addition of a fluidizing agent, even after maintained at high temperature which causes toner to aggregate. The electrophotographic printing-use toner constituting two-component developer with magnetic powder carrier, made of a toner mother particle including binding agent synthetic resin and a coloring agent, whose surface is added with a fluidizing agent is manufactured so that a ratio of .DELTA.Q.sub.h /.DELTA.Q.sub.s is not less than 0.37, more preferably not less than 0.45, where .DELTA.Q.sub.s is a charging rate of the toner mother particle, at a start of mixing with respect to the magnetic powder carrier, maintained at normal temperature, and .DELTA.Q.sub.h is a charging rate of the toner mother particle, at the start of mixing, maintained under a condition of temperature and time which causes the electrophotographic printing-use toner to aggregate.

Electrophotographic printing-use toner

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

An image forming apparatus has a developer container, a development device for developing a latent image formed on a surface of a photoreceptor drum by supplying toner to the latent image, and an agitation roller for supplying toner to the development device and agitating the toner in the developer container. The development device and the agitation roller are installed in the developer container. Moreover, the image forming apparatus includes a flying toner detecting device for detecting an amount of toner flying from the development device, and a control unit for controlling various developer operations such as the toner related agitating operation of the agitation roller, toner supply amount, etc. in response to a result of a detection performed by the flying toner detecting device. This structure prevents the toner from flying from the development device.

Image forming apparatus with flying toner detecting device

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

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Kashiba, Japan

Toshihisa Ishida