Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – Post imaging process – finishing – or perfecting composition...
Reexamination Certificate
2001-09-14
2003-06-17
Goodrow, John (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Electric or magnetic imagery, e.g., xerography,...
Post imaging process, finishing, or perfecting composition...
C430S109300, C430S109500, C430S111400
Reexamination Certificate
active
06579653
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a toner used for copying machines, laser printers, plain paper facsimiles, color PPCs, color laser printers and color facsimiles, and also to an electrophotographic apparatus.
BACKGROUND OF THE INVENTION
In recent years, the objective of electrophotographic apparatuses has been changing from office-use to personal-use, and there have been increasing demands for techniques for achieving small-size and maintenance-free apparatuses. For this reason, conditions, such as a superior maintenance property for recycling a waste toner and reduced ozone generation, need to be satisfied.
The following description will discuss a printing process carried out by a copying machine and a printer of an electrophotographic system. First, an image-bearing member (hereinafter, referred to as a photosensitive member) is charged so as to form an image. As to the charging method for evenly charging a surface of a photosensitive member, a corona charger may be used as has been conventionally used, or in recent years, a contact-type charging method in which a conductive roller is directly pressed onto a photosensitive member has been adopted in an attempt to cut generation of ozone. In the case of a copying machine, after a photosensitive member has been charged, light is directed to an original material to be copied and the reflected light is directed to a photosensitive member through a lens system. Alternatively, in the case of a printer, an image signal is sent to a light-emitting diode or a laser diode serving as an exposing light source so that a latent image is formed on a photosensitive member based on ON-OFF operations of light. When the latent image (resulting from high and low portions of the surface potential) has been formed, the latent image on a photosensitive member is converted into a visible image by toner that is preliminarily charged color powder (having a diameter of approximately 5 &mgr;m to 15 &mgr;m). The toner is allowed to adhere to a surface of a photosensitive member in accordance with the high and low portions of the surface electric potential of a photosensitive member, and electrically transferred onto a sheet of transfer paper. In other words, the toner, which has been preliminarily charged positively or negatively, is electrically absorbed by applying a charge having an opposite polarity to the toner polarity from behind the transfer paper. As to a transferring method, the conventional method using a corona charger may be used, or a recently-developed contact-type transfer method in which a conductive roller is directly pressed onto a photosensitive member has been put to practical use in an attempt to cut generation of ozone. At the time of the transferring process, all the toner on a photosensitive member is not necessarily transferred onto a sheet of transfer paper, and one portion thereof remains on a photosensitive member. This residual toner is scraped by a cleaning blade, etc., in a cleaning section to form a waste toner. Then, the toner that has been transferred onto the transfer paper is fixed onto a sheet of paper by heat and pressure applied in a fixing process.
As to the fixing method, there are proposed a pressure fixing system in which a sheet of paper is allowed to pass through not less than two metal rolls, an oven fixing system in which the paper is allowed to pass through an atmosphere heated by an electric heater and a heat roll fixing system in which the paper is allowed to pass through heated rollers. In the case of the heat roll fixing system, a preferable thermal efficiency is obtained at the time when the toner image is fused onto the sheet of transfer paper because the surface of the heating roller and the toner surface on the sheet of transfer paper are made in press-contact with each other, thereby making it possible to carry out the fixing process quickly. However, in the case of the heat roll fixing system, the toner in a heated and melted state is made in press-contact with the surface of the heating roller, with the result that one portion of the toner tends to adhere to the roller surface to again adhere to the sheet of transfer paper, resulting in a stained image, which phenomenon is referred to as an offset phenomenon. As to a method for preventing the offset phenomenon, a method has been proposed in which the surface of the heating roller is formed by fluorine resin or silicone rubber that has a heat resisting property and a superior mold-releasing property to toner, and an anti-offset liquid such as silicone oil is supplied onto the surface so as to coat the roller surface with a thin-film of the liquid. In this method, however, when the liquid such as silicone oil is heated, an offensive odor is generated, and additional devices are required so as to supply the liquid, making the mechanism of the copying machine complex. Moreover, in order to prevent the offset in a stable manner, it is necessary to control the supply of the liquid with high precision, and this causes high costs of the copying machine. Therefore, there have been demands for a toner which provides a superior fixed image and is free from an offset, without the necessity of supplying such a liquid.
As has been generally known, an electrostatic charge developing toner, used for an electrophotographic method, is generally composed of a resin component, a coloring component formed by a pigment or dye, a plasticizer, a charge control agent and an additive component such as a mold-releasing agent to be added, if necessary. As to the resin component, a natural or synthetic resin is used alone or in combination as the resin component.
Then, the additive agents are preliminarily mixed at an appropriate ratio, and heated and kneaded in a thermally molten state, and this is finely ground through an air-flow collision plate system, and then finely classified to form a toner base material. Then, an external additive agent is externally added to this toner base material, thereby forming a toner.
In mono-component developing system, only the toner is used, and in the case of a two-component developing agent, the toner and a carrier composed of magnetic particles are mixed.
In a color copying machine, a photosensitive member is charged by a corona discharge using a static charger, and latent images of respective colors are applied to a photosensitive member as light signals to form electrostatic latent images, and this is developed by, for example, a yellow toner serving as a first color, so as to visualize the latent image. Thereafter, a transfer member, which has been charged to a polarity opposite to the charge of the yellow toner, is made in contact with a photosensitive member so that the yellow toner image, formed on a photosensitive member, is transferred thereon. After residual toner from the transferring process has been cleaned therefrom, a photosensitive member is subjected to a static charge eliminating process, thereby completing the developing and transferring processes of the first color toner.
Thereafter, the same processes as the yellow toner are repeated as to toners of magenta and cyan so that the toner images of the respective colors are superimposed on a transfer member to form a color image. These superimposed toner images are transferred onto a sheet of transfer paper that has been charged to a polarity opposite to the toner, and then fixed, thereby completing the copying process.
As to the color-image forming method, generally-used systems are: a transfer drum system in which toner images of the respective colors are successively formed on a single photosensitive member, and a transfer member wrapped on the transferring drum is rotated and allowed to face a photosensitive member repeatedly so as to successively superimpose the toner images of respective colors thereon, and a continuous superimposing system in which a plurality of image-forming units are placed side by side, and a transfer member, transported by a belt, is allowed to pass through the respective image-forming units so as to successively transfer t
Hirota Noriaki
Maeda Masahisa
Yuasa Yasuhito
Goodrow John
Matsushita Electric - Industrial Co., Ltd.
Wenderoth , Lind & Ponack, L.L.P.
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