Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – Post imaging process – finishing – or perfecting composition...
Reexamination Certificate
2000-11-07
2002-09-03
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...
C430S108600, C430S108700, C430S111400, C430S124300, C430S126200
Reexamination Certificate
active
06444389
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a toner for developing an electrostatic latent image (hereinafter, is sometimes referred simply 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.
BACKGROUND OF THE INVENTION
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 of related art, after developing an electrostatic latent image formed on a photoreceptor by an optical method in a developing step, the developed image is transferred to a recording medium such as a recording medium, etc., in a transfer step, and then the transferred image is fixed to the recording medium such as the recording paper, etc., generally by heat and pressure in a fixing step to obtain a black and white image.
However, in the recent electrophotographic technique, the progress of from back and white to full color has been rapidly progressed. In the color image formation by a full color electrophotographic process, the regeneration of 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 color 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 image is held on a recording medium through a development and a transfer steps. Then, the steps are successively repeated plural timers per each color, and while matching the positions of the 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 different point 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 OHP transparency 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 a sharp melting low-molecular weight resin to increase the color mixing property.
In the black toner for the black and white prints of related art, because the toner image is brought into contact with a fixing unit such as a heat roller, etc., in a heat-melt state at fixing, for preventing 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 prints, because 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 structure 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 carrier and the surface of the developing sleeve, and thus the images formed are liable to be deteriorated.
Accordingly, a method has been employed wherein ordinary toners for full color do not contain wax, for the purpose of preventing the occurrence of an 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 a 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 phenomenon of toners but there is a problem that an apparatus for supplying an offset preventing liquid becomes necessary. This is against the direction of small sizing and light weighing 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 strains the insides of apparatus.
Also, between a black and white image and a full color image, the coated area of the toner on a recording medium (image density) and the weight of the toner per unit area in the recording medium are different. That is, in black and white images mainly for letters, it is rare that the image density becomes large or the weight of the toner per unit area in a recording medium becomes large. On the other hand, in full color images mainly for pictorial images such as pictures, photographs, etc., the case of forming images on the whole surface of a recording medium is increased. Also, because in a full color image, the color image is formed by overlapping color toners of yellow, magenta and cyan as described above, the weight of the toners per unit area in the recording medium becomes large. Accordingly, as compared with a black and white image, in a full color image, the image density becomes high and the weight of toners per unit area in a recording medium becomes large.
In general, when an image density is high in a fixing step, the area that the fixing unit is brought into contact with toners in heat-melt state becomes large, whereby an offset phenomenon of toners is liable to occur. Also, when the weight of toners per unit area in a recording medium in a fixing step is large, the height of the unfixed toners formed on the recording medium becomes high. When the height of the unfixed toners becomes high, there occurs a large temperature difference between the toner of the uppermost surface layer and the toner of the lowermost layer. Therefore, when the toners are sufficiently heated and pressed in a fixing step so that the toner of the lowermost layer is completely melted, heat is excessively added to the toner of the uppermost surface layer, whereby the melt viscosity of the toner becomes too small and an offset phenomenon is liable to occur.
As a method of solving the problem, a method of increasing the pressure at fixing to anchor the toner on a transfer material has been employed. In the method, the occurrence of a high-temperature offset phenomenon of the toner of the uppermost surface layer can be prevented. However, in this case, a separated trace of a member of separating the transfer material from a fixing roller appears in the image formed and further, owing to the high pressure, line images are smashed at fixing, whereby image defects of the copy image are liable to occur.
From the reasons described above, as the color toners for full color, the toners have been investigated which use a sharp-melt low molecular weight resin, contain only a small amount of a low-melting wax, and can be fixed without causing image defects even in the case of a high image density and a large weight of toners per unit area in a
Hamano Hirokazu
Ishida Haruhide
Ninomiya Masanobu
Oya Yasuhiro
Yaguchi Hidekazu
LandOfFree
Toner for developing electrostatic latent image,... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Toner for developing electrostatic latent image,..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Toner for developing electrostatic latent image,... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2900399