Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – Post imaging process – finishing – or perfecting composition...
Reexamination Certificate
2000-06-01
2002-06-11
Goodrow, John (Department: 1753)
Radiation imagery chemistry: process, composition, or product th
Electric or magnetic imagery, e.g., xerography,...
Post imaging process, finishing, or perfecting composition...
C430S108700, C430S110300
Reexamination Certificate
active
06403271
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a toner for developing an electrostatic latent image, a process for producing the same, a developer for developing an electrostatic latent image, and a process for forming an image in an electrophotographic process and an electrostatic recording method.
BACKGROUND OF THE INVENTION
In the electrophotographic process, an electrostatic latent image formed on a latent image holding member (photoreceptor) is developed with a toner containing a coloring agent, and a resulting toner image is transferred to a transferring material and then fixed with a heat roll, so as to obtain an image. The latent image holding member is separately subjected to cleaning for forming another electrostatic image.
A dry developer used in the electrophotographic process is roughly classified to a one-component developer solely using a toner containing a binder resin and a coloring agent and a two-component developer containing the toner mixed with a carrier. The one-component toner can be further classified to a magnetic one-component type, in which magnetic powder is used and the developer is transported by a developing roll with a magnetic force, and a non-magnetic one-component type, in which magnetic powder is not used and the developer is transported by a developing roll with application of charge by a charging roll.
Since a second half of the 1980s, an apparatus of a compact size and sophisticated performance is demanded in the market of electrophotography based on a trend of digitization, and particularly with respect to quality of a full color image, high class printing and high image quality equivalent to a silver halide photography. A digitized process is indispensable as means for attaining high image quality, and an effect of the digitization in image quality includes the complicated image processing that can be conducted at a high speed. By employing such a digitized process, text information and photographic image information can be controlled separately, and thus the reproducibility of the quality of both of them is greatly improved in comparison to the analog technology. Particularly, with respect to a photographic image, it is notable that gray level correction and color correction can be conducted, and the digitized process is advantageous over the analog technology in gray level characteristics, fineness, sharpness, color reproducibility and graininess. However, a latent image formed by an optical system must be faithfully reproduced as an image output, and therefore an attempt of realizing faithful reproduction is increasingly conducted with the decrease in particle diameter of a toner. However, it is difficult to stably obtain high image quality only by decreasing the particle diameter of the toner, and there is increasing importance in improvement of basic characteristics of development, transferring and fixing characteristics.
In particular, a color image is formed by superimposing color toners of three colors or four colors. Therefore, when at least one of the toners exhibits different performance from the initial stage or different performance from the toners of the other colors from the standpoint of development, transferring or fixing, deterioration in image quality occurs, such as deteriorated color reproducibility, low graininess and color unevenness. It is an important demand to maintain an image having stable high image quality equivalent to the initial stage even after the lapse of time that the characteristics of the toners are stably controlled. It has been reported that a toner is agitated in a developing device, and the fine structure on the surface of the toner is easily changed, to cause great change in transferring property (JP-A-10-312089).
In recent years, a cleaning system without cleaner has been proposed from the standpoints of miniaturization of an apparatus for space saving, decrease of the waste toner for environmental protection, and prolongation of the service life of the latent image holding member. In the cleaning system without cleaner, without using a cleaning system, the toner remaining on a photoreceptor drum after transferring is dispersed by a brush in contact with the photoreceptor drum, and the dispersed toner is recovered by the developing device simultaneously with development (JP-A-5-94113). In general, when the remaining toner is recovered simultaneously with development, because the recovered toner has different charging characteristics from the other toners to cause problems in that the recovered toner is not developed but is accumulated in the developing device, it is necessary that the transferring efficiency is further improved to control the amount of the recovered toner to the minimum value.
It is proposed to make the shape of the toner approaching a sphere shape to improve the flowability, the charging property and the transferring property (JP-A-62-184469). However, the following problems occur when the toner has a sphere shape. A developing device is equipped with a transporting amount controlling plate for controlling the transporting amount of the developer constant, and it can be controlled by changing the distance between a magnet roll and the transporting amount controlling plate. However, when a toner having a sphere shape is used, the flowability of the developer is increased, and at the same time, the tapped bulk density thereof is increased. As a result, a phenomenon occurs in that the developer piles up at a part where the transportation thereof is controlled, and the transporting amount becomes unstable. While the transporting amount can be somewhat improved by controlling the surface roughness of the magnet roll and making the distance between the controlling plate and the magnet roll small, the packing phenomenon due to piling up of the developer is becomes remarkable to increase the stress applied to the toner. A problem has been confirmed in that, owing to the phenomenon, the change of the micro structure of the surface of the toner, particularly burying and peeling of an external additive, readily occurs, and thus the developing property and the transferring property are greatly changed from those in the initial stage.
In order to solve the problems, it has been reported that the packing phenomenon is suppressed by using a spherical toner and a non-spherical toner in combination to attain high image quality (JP-A-6-308759). However, although the packing phenomenon is effectively suppressed, the non-spherical toner is liable to remain as a transferring residue, and a high transferring efficiency cannot be attained. Furthermore, in the case where the simultaneous recovering of the developer is conducted, there is a problem in that the non-spherical toner as the transferring residue is recovered to increase the proportion of the non-spherical toner, and the transferring efficiency is further decreased.
There has been disclosed that in order to improve the developing property, the transferring property and cleaning property of a spherical toner, two kinds of inorganic fine particles, one of which has an average particle diameter of 5 m&mgr; or more and less than 20 m&mgr;, and the other of which has an average particle diameter of from 20 to 40 m&mgr;, are used in combination, which are added in specific amounts (JP-A-3-100661). While this method provides excellent developing property, transferring property and cleaning property in the initial stage, because the stress applied to the toner cannot be reduced after the lapse of time, burying and peeling of an external additive readily occurs to greatly change the developing property and the transferring property from those in the initial stage.
It has been disclosed that the use of inorganic fine particles is effective to suppress the burying of the external additive on the toner (colored particles) due to the stress (JP-A-7-28276, JP-A-9-319134 and JP-A-10-312089). However, since the true specific gravity of the inorganic particles is large, the peeling of the external additive becomes unavoidable due to the stress
Eguchi Atsuhiko
Inoue Satoshi
Nakajima Tomohito
Ota Kozo
Suzuki Chiaki
Fuji 'Xerox Co., Ltd.
Goodrow John
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