Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – Post imaging process – finishing – or perfecting composition...
Reexamination Certificate
2002-03-26
2004-06-08
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...
C430S111100, C399S358000
Reexamination Certificate
active
06746810
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an image formation method comprising developing an electrostatic latent image to form an image by a method such as an electrophotography method, electrostatic recording method and the like, a replenishing toner used in this method and a method of producing the same, and a carrier-containing toner cartridge.
2. Description of the Related Art
In an electrophotography method, an electrostatic latent image formed on the surface of an electrostatic latent image holding member (photorecepter) is developed with a toner containing a colorant, the resulting toner image is transferred onto an image-receiving member such as paper and the like, and this is fixed by a heat roll and the like, to give an image. On the other hand, the surface of an electrostatic latent image holding member after transfer of a toner image is generally cleaned for forming an electrostatic latent image again.
Dry developers used in such an electrophotography method are roughly classified into one-component developers which provide single use of a toner produced by compounding a colorant and the like with a bonding resin, and two-component developers obtained by mixing the above-mentioned toner with a carrier. One-component developers can be classified into magnetic one-component developers which use a magnetic powder and convey an image with a developer holding member by magnetic force and cause development, and non-magnetic one-component developers which convey an image with a developer holding member by electric charge and cause development, without using a magnetic powder.
From the later period of the nineteen eighties, the market of electrophotography has received requirements for size reduction and increase in functions using a key word, digitization, and particularly with respect to full color image quality, high grade printing, and high image quality near silver halide photography are desired. As the means for attaining high image quality, digitization treatment is essential, and as the effect of such digitization regarding image quality, an ability of carrying out complicated image processing at high speed is mentioned. By this, letters and photography images can be controlled separately, and reproducibility of both qualities is improved as compared with analogy technologies. Particularly regarding photography images, that gradation correction and color correction have become possible is a great merit, and advantages exist in the points of gradation property, definition, sharpness, color reproduction and graininess as compared with an analog method.
For output of an image, a latent image made by an optical system is required to be correctly converted into an image, the particle size of a toner is further decreasing, and there is an accelerated action intending correct reproduction. Only by decrease in the particle size of a toner, however, it is difficult to stably obtain an image of high image quality, improvements of basic properties in development, transfer and fixing properties are further important.
In the case of obtaining color images, three-color or four-color toners are piled to form images, generally. Therefore, when any of these color toners exhibits different properties from the initial properties from the standpoints of development, transfer and fixing, or a different ability from those of other colors, decrease in color reproduction, deterioration in graininess, uneven color and the like would be caused. For maintaining an image of stable high quality like the initial state even with the lapse of time, the way to stably control properties of color toners is important.
Recently, from the standpoint of increase in speed in obtaining color images (may simply be referred to as “color speed up”), there is adopted a so-called tandem development system using a plurality of xerography units composed of a developer apparatus containing a developer holding member, and of an electrostatic latent image holding member and the like, and from the standpoint of trying to reduce the size of an apparatus due to need for space saving, the sizes of the electrostatic latent image holding members are intended to be reduced. Further, there are a lot of patent applications regarding the tandem development system (Japanese Patent Application Laid-Open (JP-A) Nos. 6-35287, 6-100195, and the like).
When such a tandem development system is adopted, increase in speed of color image formation becomes easier as compared with a rotary development system, however, also in trying to obtain an image of single color such as black and the like, it is general that developer holding members of other colors also come into contact with the electrostatic latent image holding member and, simultaneously, forced to rotate toward the process direction. In such as case, a developer receives large stress, decrease in the charging ability of a developer is induced, and decrease in a developing ability and decrease in a transferring ability are easily caused, finally, leading to lowering of image quality. Further, in the tandem development system, due to restriction of space around an electrostatic latent image holding member and the size of an apparatus, the size of one developer apparatus is limited, and sufficient developer amount cannot be secured in each developer apparatus from the standpoint of space. Therefore, a developer tends to receive larger stress from apparatus-structural point of view. Consequently, deterioration of a developer occurs and the developer would be changed, this leads to remarkable increase in service cost.
As means for suppressing deterioration of a developer, JP-A No. 8-234550 discloses a technology using several kinds of replenishing toners containing carriers having different physical properties. In this technology, toner flowability and toner inter-color property and the like are influenced by change of physical properties of carriers, leading to a complicated control system, increase in the size of an apparatus, or increase in cost. JP-A No. 11-202630 discloses a technology of replenishing a replenishing toner containing a carrier having a charge amount higher than that of a carrier used in the start developer. These technologies are very effective in that the developer life is elongated, however, when image stability is taken into consideration, it is important that developer physical properties are not changed by environments and lapse of time, and it is difficult to control this change into micro level.
On the other hand, also a toner has a problem that irregularity of the form and particle size of a toner causes irregularity of the charging property of a toner, toners having excellent charging property are selectively consumed and toners having low charging property remain in a developer apparatus, to cause lowering of developing property as the whole developer, indicating selective development. When deterioration of a developer progresses due to the selective development, necessity to change a developer occurs, leading to remarkable increase in service cost. Particularly in the tandem development system, since sufficient developer amount cannot be secured in each developer apparatus from the standpoint of space, deterioration of a developer because of irregularity of the charging property of a toner progresses easily, and it is desired to improve a property to maintain a developer also from the standpoint of a toner.
Further, it is reported that toners are stirred in a developer apparatus and fine structural change on the surface of a toner occurs easily, to significantly change transferring property (JP-A No. 10-312089). Because of fine structural change of the surface of a toner, irregularity of the charging property of a toner tends to increase, resulting in promotion of the above-mentioned selective development, and the problem of decrease in developer maintaining property becomes further remarkable.
SUMMARY OF THE INVENTION
Therefore, the present invention is intended to solve the above-mentioned conventional
Eguchi Atsuhiko
Fukuda Hiroyuki
Inoue Satoshi
Iwasaki Eiji
Kataoka Rieko
Fuji 'Xerox Co., Ltd.
Goodrow John
Oliff & Berridg,e PLC
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