Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – Post imaging process – finishing – or perfecting composition...
Reexamination Certificate
2001-12-04
2003-02-11
Goodrow, John (Department: 2852)
Radiation imagery chemistry: process, composition, or product th
Electric or magnetic imagery, e.g., xerography,...
Post imaging process, finishing, or perfecting composition...
C430S045320, C430S111410, C430S125320
Reexamination Certificate
active
06517985
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a developer for using development of an electrostatic latent image in an electrophotographic process and an electrostatic recording process, and a process for forming an image.
2. Description of the Related Art
In the electrophotographic process, an electrostatic latent image formed on a latent image holding member (photoreceptor) is developed with a toner containing a colorant, and the resulting toner image is transferred to a transfer material and then fixed with a heat roll to obtain an image. The latent image holding member is separately subjected to cleaning for the formation of another electrostatic latent image. A dry developer used in the electrophotographic process is roughly classified to a one-component developer employing solely a toner formed by mixing a binder resin and a colorant, and a two-component developer formed by mixing a toner and a carrier. The one-component developer can is classified to a magnetic one-component developer using magnetic powder, which is transported by magnetic power for development, and a non-magnetic one-component developer using no magnetic powder, which is transported by application of charge with a charging roll for development. In the market of electrophotography in the last half of eighties, miniaturization and high performance are strongly demanded for digitalization, and particularly for a full color image, high image quality equivalent to sophisticated printing and silver halide photography is demanded.
Digital processing is essential for realizing high image quality, and the effect of the digital processing includes complicated image processing that can be carried out at high speed. According to the effect, characters and photographic images can be separately controlled, and reproducibility of qualities of them is greatly improved in comparison to the analog technology. In particular, it is important for photographic images that gradation correction and color correction become possible, it is advantageous in gradation characteristics, fineness, sharpness, color reproducibility and graininess in comparison to the analog technology. It is necessary that an image as an image output must be produced strictly reflecting a latent image produced by an optical system, and reduction in the particle diameter of toners is accelerated to aim for highly faithful reproducibility. However, it is difficult only by the reduction of the particle diameter of the toner that high image quality is stably obtained, and improvements of the basic characteristics in development, transferring, fixing and cleaning characteristics are becoming important. In particular, the reduction of the particle diameter of the toner increases the adhesion force thereof to be liable to cause deterioration of transferring performance, and therefore various techniques to handle a toner of a small particle diameter have been reported.
For example, the transfer property is improved by approaching the toner to a spherical shape (Japanese Patent Laid-Open No. 184469/1987). Although the transfer property is improved by making the toner spherical, cleaning failure occurs due to the non-transferred remaining toner that is slightly formed. As an inverted idea, a cleanerless system is proposed, in which a toner remaining on a photoreceptor drum (photoreceptor) is recovered by a developing device simultaneously with development to omit a cleaning system (Japanese Patent Laid-Open No. 302772/1990 and No. 94113/1993). In general, when the remaining toner is recovered simultaneously with development, the recovered toner has charging property that is different from the other toners, and problems occur in that the recovered toner is not developed but is accumulated in the developing device. Therefore, it becomes necessary that the transfer efficiency be further improved to control the toner amount to be recovered to a minimum value. Furthermore, even when the amount of the remaining toner can be minimum, the photoreceptor drum is contaminated with various substances, such as an external additive, paper powder and an ozonide product, and the toner may remain in a large amount on the photoreceptor drum when an accident, such as paper jam, occurs. Therefore, a cleaning system cannot be completely omitted because the substances and the toners cannot be completely recovered by the developing device, but some kinds of a cleaning system is necessary.
Various methods for cleaning a spherical toner have been proposed. In particular, a technique of cleaning by using a blade has been earnestly investigated. For example, it has been proposed that a spherical toner and an irregular-shaped toner be mixed under a predetermined condition, so as to compensate the poor cleaning property of the spherical toner by the irregular-shaped toner (Japanese Patent Publication No. 22979/1991). However, it is necessary in this method that at least 10% of the irregular-shaped toner is mixed with the spherical toner, and the excellent transfer performance and the high image quality of the spherical toner cannot be fully enjoyed.
It has also been proposed to add irregular-shaped particles containing magnetic powder to a developer (Japanese Patent Laid-Open No. 122347/2000). Although the cleaning performance is improved by the method, the image quality is deteriorated when the irregular-shaped particles are transferred, and the photoreceptor is damaged by the irregular-shaped particles containing magnetic powder. It is then proposed to add an aliphatic acid metallic salt to a toner (Japanese Patent Laid-Open No. 89502/2000). Although it is effective to reduce the frictional force at the nip part of the cleaning blade, the addition of the aliphatic acid metallic salt greatly decrease the charge amount of the toner, and as a result, fogging and scattering of the toner occurs on development to deteriorate the image quality.
It has been also proposed that after developing and transferring a spherical toner, the surface of a photoreceptor be developed with irregular-shaped particles, followed by cleaning the photoreceptor (Japanese Patent Laid-Open No. 126670/1989). However, this method requires a complicated system, and additional processes and additional members are necessary for supplying the irregular-shaped particles, so as to cause a problem from the standpoint of space saving of the machine.
Furthermore, it has been proposed that in a full color electrophotographic process, an irregular-shaped toner is used in one developing device of yellow, magenta, cyan and black, and spherical toners are used in the other developing devices, so as to improve the blade cleaning property (Japanese Patent Laid-Open No. 254873/1996). However, in the case where the same image is repeatedly output for a long period of time in this method, the irregular-shaped toner is non-uniformly supplied to the blade to cause a problem of cleaning failure in the part where the small amount of the irregular-shaped toner is developed.
It is also proposed that lubricating agent particles are added to the surface of a blade, so as to suppress the friction force at the nip part of the blade on the photoreceptor drum under the condition of intervening the non-transferred remaining toner to prevent the toner from scraping through (Japanese Patent Laid-Open No. 212190/1992). This method improves the cleaning property in the initial stage, but the lubricating agent particles on the surface of the blade is depleted for a long period to cause cleaning failure.
It is proposed to apply a direct current or alternating current bias voltage to a cleaning blade (Japanese Patent Laid-Open No. 265360/1993). However, because the charge amount of the non-transferred remaining toner varies depending on the charge amount of the developed toner, the transferring conditions, the environment of the case, and the sort of the image, cleaning cannot be completely carried out only by the application of the cleaning bias voltage. Furthermore, the cleaning bias voltage accelerates deteriorati
Inoue Satoshi
Kataoka Rieko
Kiyono Fusako
Ohishi Kaori
Suzuki Chiaki
Fuji 'Xerox Co., Ltd.
Goodrow John
Oliff & Berridg,e PLC
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