Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – Post imaging process – finishing – or perfecting composition...
Reexamination Certificate
2000-11-28
2004-05-11
Dote, Janis L. (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Electric or magnetic imagery, e.g., xerography,...
Post imaging process, finishing, or perfecting composition...
C430S111400, C430S124300
Reexamination Certificate
active
06733938
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a toner for developing an electrostatic latent image (hereinafter, is sometimes simply referred to as “toner”) utilizing an electrophotographic process or an electrostatic recording process, a two-component developer containing the toner, and an image-forming process using the toner.
2. Related Art
Hitherto, in the case of forming images in a copying machine, a laser beam printer, etc., a Carlson process is generally used. In an image-forming process by a black and white electrophotographic process in a conventional art, an electrostatic latent image formed on a photoreceptor by an optical method is developed with a developing step, thereafter, the developed image is transferred to a recording medium such as a recording paper, etc., in a transfer step, and then the transferred image is fixed to the recording medium such as the recording paper, etc., generally by a heat and pressure in a fixing step to obtain a black and white image.
However, in the recent electrophotographic technique, the progress of from black and white to full color has been rapidly progressed. In the color image formation by a full color electrophotographic process, the regeneration of all colors is generally carried out using four-color toners composed of three-color toners of yellow, magenta, and cyan which are the three primary colors added with a black toner. In a general full color electrophotographic process, first, an original is color-separated in yellow, magenta, cyan, and black and per each color, an electrostatic latent image is formed on a photoconductive layer. Then, a toner is held on a recording medium through a development and a transfer step. Then, the above-described steps are successively carried out plural times per each color, and while matching the positions of toner images each having each different color, the toner images each having each different color are overlapped on a same recording medium. Also, by applying one fixing process, a full color image is obtained. The point of overlapping several kinds of toner images each having a different color as described above is a large difference between the black and white electrophotographic process and the full color electrophotographic process. In the color toners used for the full color electrophotographic process, it is necessary that the toners of many colors are sufficiently mixed in the fixing process and by sufficiently mixing these multicolor toners, the color reproducibility and the transparency of an OHP image are improved, and a full color image having a high image quality can be obtained. Thus, as compared with a black toner for black and white print, it is desired that the color toners are generally formed by sharp melting low-molecular weight resin to increase the color mixing property.
In the black toner for the black and white prints of prior art, because the toner image is brought into contact with a fixing unit such as a heat roller, etc., in a heat-melt state, to prevent the occurrence of a so-called offset phenomenon that a part of the toner image attaches and transfers to the surface of the heat roller, the black toner contains therein a wax having a high crystalline property and a relatively high melting point, such as polyethylene, polypropylene, etc. In general, in the case of a high viscous toner such as the black toner for the black and white print, since the intermolecular cohesive force at heat-melting of the toner is strong, the occurrence of the offset phenomenon can be prevented by oozing out a small amount of the wax. However, when it is necessary to color by overlapping toners of two or more colors such as full color toners and to form a flat fixed image surface for giving a transparency of an OHP image, it is required to lower the viscosity of the toners and increase the heat-melting property of the toners. In this case, for obtaining a sufficient effect for the anti-offset property, it is necessary to add a large amount of wax to the toners. However, because in the case of the toners prepared by a melt-kneading/grinding method, the toners become the structures of exposing the wax onto the surfaces of the toners, whereby a large amount of the wax exposed on the surfaces of the toners causes filming to a photoreceptor and is liable to stain the carriers and the surfaces of the developing sleeve, and thus the images formed are liable to be deteriorated.
Accordingly, a method has been employed wherein usually color toners for full color do not contain wax, for the purpose of preventing the occurrence of offset phenomenon, the surface of heat-fixing roller is formed with a silicone rubber or a fluorine resin excellent in the releasing property to the toners and further a releasing liquid such as s silicone oil, etc., is supplied to the surface of the roller. The method is very effective in the point of preventing the occurrence of the offset phenomenons of toners, but there is a problem that an apparatus for supplying an offset preventing liquid becomes necessary. This is not directed to the small sizing and the light weighing of the image-forming apparatus, and also there sometimes occur the problems that the offset preventing liquid is evaporated by heating to give an unpleasant smell and the vapor of the liquid stains the inside of the apparatus.
Therefore, for the color toners for full color, a sharp melting low-molecular resin is used, and the toners contain only a small amount of a low-melting wax and can be fixed without supplying a releasing liquid to the surface of the heat-fixing roller has been investigated.
As one of the investigations, various reports have been made for controlling the molecular weight distribution of binder resins. In general, a resin having a low molecular weight has a low viscosity and is sharp melting and is useful for a low-temperature fixing and the formation of a flat fixed image, but is inferior in the anti-offset property. Also, a resin having a high molecular weight has a high viscosity and is useful for the anti-offset property but is disadvantageous for low-temperature fixing and the formation of a flat fixed image.
Thus, there are many attempts of satisfying both the low-temperature fixing property and the anti-offset property by combining a resin having a low-molecular weight if and a resin having a high-molecular weight, or by defining the molecular weight distribution. For example, as the toner defining the molecular weight distribution, there are a toner defining the value of Mw/Mn as described in Japanese Patent Laid-Open Nos. 284863/1989 and 207126/1998, a toner having the two maximum values as described in Japanese Patent Laid-Open No. 294866/1991, a toner having the three maximum values as described in Japanese Patent Laid-Open Nos. 221758/1989 and 63035/1998, a toner finely defining the ratio of a low molecular weight component and a high molecular weight component as described in Japanese Patent Laid-Open Nos. 44110/1996, 228131/1998, and 278067/1991, and the like.
Because these toners have a low fixing temperature and can improve the anti-offset property, they are sufficient for obtaining monochromatic images. However, because the toners containing a crosslinking component or a high molecular weight component of at least 1×10
6
as described in Japanese Patent Laid-Open Nos. 294866/1991 and 221758/1998 do not have a low melt viscosity and cannot form a flat fixed image, the transparency is bad and these toners are insufficient as full color toners.
Also, by the molecular weight distributions having a wide distribution as defined in Japanese Patent Laid-Open Nos. 284863/1989, 44110/1996, 207126/1998, and 228131/1998, the balance of the low molecular weight component and the high molecular weight component is bad and all of the low-temperature fixing property, the OHP transparency, and the flat fixed image forming performance cannot be simultaneously satisfied in sufficiently levels. That is, because the molecular weight distribution having a wide distribution cont
Hamano Hirokazu
Ishida Haruhide
Ninomiya Masanobu
Oya Yasuhiro
Yaguchi Hidekazu
Dote Janis L.
Fuji 'Xerox Co., Ltd.
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