Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – Radiation-sensitive composition or product
Reexamination Certificate
2002-07-17
2004-11-30
Rodee, Christopher (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Electric or magnetic imagery, e.g., xerography,...
Radiation-sensitive composition or product
C430S131000, C399S159000
Reexamination Certificate
active
06824938
ABSTRACT:
The present invention relates to an electrophotographic photoreceptor. Particularly, it relates to an electrophotographic photoreceptor which is capable of controlling the infrared reflectance of the photoreceptor by preventing interference fringes without impairing the electrophotographic properties.
Heretofore, for electrophotographic photoreceptors, an inorganic photoconductive material such as selenium, a selenium-tellurium alloy, arsenic selenide or cadmium sulfide, has been widely employed. On the other hand, in recent years, there have been active researches on photosensitive layers employing organic photoconductive materials which can easily be produced. Particularly, function-separated laminated photoreceptors comprising a charge generation layer having a function to generate electric charge upon absorption of light and a charge transport layer having a function to transport the generated electric charge, have become most common. Such photoreceptors are widely used in the fields of copying machines, laser printers, etc.
Electrophotographic photoreceptors have a basic structure such that a photosensitive layer is formed on an electroconductive substrate. It is common to provide an undercoat layer between the photosensitive layer and the substrate in order to solve a problem of image defects due to defects of the substrate or due to injection of electric charge from the substrate, or to improve the electrification properties or the adhesion with the photosensitive layer. Heretofore, it has been known to use, for the undercoat layer, a resin material such as a polyamide resin, a polyester resin, a polyurethane resin, a polycarbonate resin, an epoxy resin, a polyurethane resin, a vinyl chloride resin, an acrylic resin, a phenol resin, a urea resin, a melamine resin, a guanamine resin, a polyvinyl alcohol, casein or gelatin. Among these resin materials, a solvent-soluble polyamide resin is particularly preferred (JP-A-52-25638, JP-A-56-21129, and JP-A-4-31870).
In recent years, along with the trend of digitization, electrophotographic apparatus have become mainly of digital system. Among electrophotographic apparatus of digital system, those employing semiconductor lasers to form images, are required to suppress image defects by interference patterns. As one of methods to avoid interference fringes, it is known to roughen the surface of a substrate (electroconductive substrate) by rough cutting, sand blasting or the like (e.g. JP-A-60-225854, JP-A-3-62039). However, such a method has a problem that the degree of roughening of the substrate can hardly be precisely reproduced, and there will be a variation in the effect for reducing interference fringes, among production lots. Further, along with the progress in high resolution of the apparatus in recent years, at a resolution of 1,200 dpi (dots per inch), there will be a case where no adequate effect for reducing interference fringes is obtainable only by roughening of the substrate. Further, as described hereinafter, in a case where the obtained photoreceptor is used for an electrophotographic apparatus employing an optical toner density sensor, there may be a case where the surface roughness of the substrate adversely affects the detection of the toner density.
On the other hand, a method is also proposed wherein a near infrared absorbing dye is incorporated in the photosensitive layer or in the undercoat layer (e.g. JP-A-63-165864, JP-A-2-82263, JP-A-3-33858, JP-A-7-160028 (U.S. Pat. No. 5,403,686, EP 0645680), JP-A-2000-105480, JP-A-2000-199977). However, there has been an adverse effect to the electrical properties of the photoreceptor, particularly it has been difficult to obtain a photoreceptor having a high sensitivity, and no adequate effect has been obtained due to deterioration by light, etc.
Further, a method has been proposed in which coarse particles are incorporated to the undercoat layer to increase scattered light in the undercoat layer thereby to reduce interference fringes. However, in order to obtain an adequate effect to prevent interference fringes solely by this method, the thickness of the undercoat layer is required to be thick, a step of curing such an undercoat layer will accordingly be required, whereby there will be a problem that the production process will be complex, and the production cost increases.
Further, in recent years, many image-forming apparatus of electrophotographic system are designed to obtain a constant image by carrying out an image density control in such a manner that in order to correct deviations of various conditions due to a change of environment of their use, deterioration of the photoreceptor or developing material, etc., toner patches for detecting densities are formed on the photoreceptor, and their densities are detected by an optical density sensor, so that from the detected results, feedback is applied to the light exposure, the development bias, etc. to control the image density (JP-A-7-36230 (U.S. Pat. No. 5,477,312), etc.). Further, especially with a color image-forming apparatus, it is known that the measuring precision can be improved by measuring the diffuse reflection component of the toner patches (JP-A-2000-105480).
Under these circumstances, with the above-mentioned photoreceptor having the substrate surface of the photoreceptor roughened to reduce interference fringes, it is difficult to obtain such a photoreceptor having constant reflection properties, since the diffuse reflection of the substrate roughness is substantial, and due to variation in the process of roughening the photoreceptor substrate, for example, due to variation in the cutting tool state during the rough cutting or in the reproducibility of the cutting feed pitch, the reflection characteristics of the resulting substrate will vary. Further, the diffuse reflection of the substrate surface of the photoreceptor is high, and when the image density control is carried out by a diffuse reflection density sensor, no adequate S/N ratio to the diffuse reflection of the toner patches can be obtained, whereby accurate control of the image density tends to be hardly possible.
Further, with a photoreceptor wherein coarse particles are incorporated to the undercoat layer to increase scattered light in the undercoat layer thereby to prevent interference fringes, the irradiated light from the toner density sensor transmitted through and scattered by the toner patches, will be further scattered by the undercoat layer and will thereby adversely affect the detection of the toner density. Thus, no adequate effect to prevent interference fringes can be obtained in electrophotography of a high resolution of a level of 1,200 dpi, solely by surface roughening of the substrate of the photoreceptor. In the above-mentioned toner density sensor measuring only the diffuse reflection component, the above-mentioned surface roughness of the substrate influences substantially over the infrared light reflectance of the photoreceptor. In a case where the substrate surface is roughened to prevent interference fringes, the infrared reflectance of the photoreceptor varies depending upon the individual difference in the surface roughness, whereby accurate control of the image density can hardly be carried out. Further, the diffuse reflection of the substrate surface of the photoreceptor is essentially high, whereby an adequate S/N (signal to noise) ratio can hardly be secured for detecting the toner density.
Further, especially when scattering in the undercoat layer is utilized to prevent interference fringes, the irradiated light from the sensor transmitted through and scattered by the toner patches will be detected as further scattered by the undercoat layer, whereby there will be problem that the detected level is higher than the actual toner density.
Under these circumstances, it is an object of the present invention to provide an electrophotographic photoreceptor which is capable of preventing interference fringes without impairing electrophotographic properties and which is capable of controlling the infrared reflect
Ishio Kozo
Kizaki Hiroe
Nozomi Mamoru
Ozawa Tetsuo
Mitsubishi Chemical Corporation
Rodee Christopher
LandOfFree
Electrophotographic photoreceptor does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Electrophotographic photoreceptor, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Electrophotographic photoreceptor will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3292320