Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – Post imaging process – finishing – or perfecting composition...
Reexamination Certificate
2000-05-24
2002-10-22
Rodee, Christopher (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Electric or magnetic imagery, e.g., xerography,...
Post imaging process, finishing, or perfecting composition...
C430S108700, C430S047300, C430S124300, C399S252000
Reexamination Certificate
active
06468707
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an image-forming apparatus, such as a copying machine, printer, etc., of an electrophotographic system of forming monochromatic or multi-color images, particularly capable of omitting a cleaning apparatus, to an image-forming process using it, and to a toner used for these apparatus.
BACKGROUND OF THE INVENTION
Recently, with the rapid propagation of the employment of a computer system, a network system, etc., in offices, the market of copying machines, printers, etc., wherein a monochromatic system has hitherto been the mainstream, is changing to the market wherein a full color system is the mainstream. With the tendency, the requirement for a copying machine, a printer, etc., of an electrophotographic system, which have hitherto been advantageous in the points of the image quality, the speed, etc., has been more and more increased. Particularly, in addition to the increase of the image quality, the increase of the reliability, etc., as well as to small-sizing, light-weighing, the reduction of cost, and the increase of the speed, the ecological counterplans such as energy saving, resource saving, recycling, etc., have been strongly required. Also, to cope with the requirements, the improvements and the new developments of an image-forming process, an image-forming apparatus, and toners used for the system have been carried out.
An image-forming process by an electrophotographic system is generally consisted of an electrostatically charging step of uniformly charging an electrostatic latent image holder surface, a light-exposure step of light-exposing the electrostatic latent image holder surface to form an electrostatic latent image on the surface, a developing step of developing the latent image formed on the electrostatic latent image holder surface using a developer layer formed at a developer holder surface to obtain a toner image, a transfer step of transferring the toner image onto the surface of a transfer material, a fixing step of fixing the toner image on the transfer material, and a cleaning step of removing toners remaining on the electrostatic latent image holder surface in the transfer step.
The toner used for the image-forming process described above is required to have following many fundamental characteristics.
First, in the above-described development step, an appropriate toner charged amount, a charge-retaining property, an environmental stability, etc., are required. Also, in the above-described transfer step, a good transferring property, etc., are required. In the above-described fixing step, a low-temperature fixing property, an offset resistance, etc., are required. Also, in the above-described cleaning step, a good cleaning performance, a stain resistance, etc., are required. In particular, by the recent acceleration of the increase of the image quality, the increase of speed, the formation of color images, etc., the toners have been required to have more and more complicated characteristics.
For example, the image-forming process which recently becomes the mainstream as a full-color copying machine, printer, etc., capable of realizing the formation of images having a high image quality at high speed is an indirect transfer type image-forming process wherein an intermediate transfer material is used for more facilitating matching of the registration at forming color images in the above-described transfer step, and after transferring the toner image on the electrostatic latent image holder surface onto the intermediate transfer material, the toner image is transferred onto a transfer material.
However, in the indirect transfer-type image-forming process, because the transferring times of toners are increased, to realize a high image-quality, an excellent transfer performance is required. Accordingly, for the toners used, a more stabilized charging performance, additives for improving the transfer efficiency, the techniques of controlling the forms and surface structures of the toners, etc., are required.
Also, in the above-described cleaning step, not only from the view points of small-sizing and cost-reducing of the apparatus, and prolonging the life by the abrasion resistance of the electrostatic latent image holder but also from the ecological view points of energy saving, resource saving, the reduction of waste materials, etc., it becomes problems to reduce the amount of the toner remained at transferring and omit the cleaning apparatus.
Particularly, in a full-color image-forming apparatus using four-color developers of yellow, magenta, cyan, and black, the reduction of the amount of toners remained at transferring, omitting the cleaning apparatus, etc., are important problems to be improved.
For the above-described problems, from the view point of generating no waste toners, a cleaner-less system of recovering the toner remained at transferring simultaneously with development without forming a cleaning step is proposed in Japanese Patent Laid-Open Nos. 133573/1984 and 157661/1984.
However, in the above-described cleaner-less system, waste toner is not generated but because foreign matters such as paper powders, etc., are recovered in a developing apparatus together with the remaining toner, there is a problem that the life of the developer is shortened.
On the other hand, a cleaner-less system of not recovering a remained toner is proposed but in the system, there are problems of causing a positive ghost that the toner remained on an electrostatic latent image holder surface is printed and a negative ghost by the light-shielding effect of the toner remained on the electrostatic latent image holder surface.
To avoid the occurrence of the problems of these ghosts, for example, in Japanese Patent Laid-Open No. 114063/1991, a technique of reducing the amount of the toner remained at transferring to 0.35 mg/cm
2
or less is proposed and also in Japanese Patent Laid-Open No. 172880/1991, a technique of increasing the transfer efficiency of the toner at transfer step to at least 80% is proposed. In these cleaner-less apparatus, it is required to keep the transfer efficiency of toner at a high level.
As the method of keeping the transfer efficiency of toner at a high level, there are a method of increasing the area of a bias applying portion of a transfer roller proposed in Japanese Patent Laid-Open No. 126872/1981, a method of applying an AC transferring electric field proposed in Japanese Patent Laid-Open Nos. 88770/1983 and 140769/1983, etc.
According to these methods, the transfer efficiency of toner is improved but it is difficult to completely transfer the toner particles directly attached to the electrostatic latent image holder surface and thus these methods are insufficient as a cleaner-less apparatus.
To increase the transfer efficiency of toner, it is important to completely transfer the toner particles directly attached to the electrostatic latent image holder surface and for the purpose, it is effective to lower the adhesive force between the toner particles and the electrostatic latent image holder surface. As such a method, there is a method wherein releasing fine particles such as silica, etc., are incorporated in a developer and the fine particles are placed between toners and the electrostatic latent image holder surface to lower the adhesive force between the toner and the electrostatic latent image holder surface, whereby the transfer efficiency of the toner is increased as proposed by Japanese Patent Laid-Open Nos. 1870/1990, 81053/1990, 18671/1990, 118672/1990, and 157766/1990.
However, in these methods, because to increase the transfer efficiency, it is necessary to highly establish the covering ratio of the toner surfaces by the fine particles, it is required to add a large amount of the fine particles. Thereby, there occur the problems that the charging property of the toner is deteriorated and the liberated fine particles are liable to attach to the electrostatic latent image holder to cause problems of filming, the hindrance of the fixing property, etc.
Also, because by a
Kubo Tsutomu
Matsumoto Akira
Mukoyama Naotaka
Okita Masahiro
Okuno Hiroyoshi
Fuji 'Xerox Co., Ltd.
Oliff & Berridg,e PLC
Rodee Christopher
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