Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – Radiation-sensitive composition or product
Reexamination Certificate
2001-11-02
2003-06-03
Goodrow, John (Department: 1753)
Radiation imagery chemistry: process, composition, or product th
Electric or magnetic imagery, e.g., xerography,...
Radiation-sensitive composition or product
C430S059100, C430S066000
Reexamination Certificate
active
06573016
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an electrophotographic photoconductor having an inorganic filler-containing photoconductive layer, a method of manufacturing same and to an image forming apparatus using same. More specifically, the present invention is directed to an electrophotographic photoconductor having a long service life, to a method of manufacturing same and to an image forming method, an image forming apparatus and a process cartridge using same. The image forming apparatus and process cartridge are utilized in, for example, electrophotographic copying machines, facsimile apparatuses, laser printers and direct digital printing master making apparatuses.
2. Discussion of the Related Art
The electrophotographic process using an electrophotographic photoconductor includes at least the steps of conducting first charging for uniformly charging the surface of the photoconductor, exposing the charged surface of the photoconductor to light images to form latent electrostatic images thereon, developing the latent electrostatic images with toner to make visible toner images, transferring the toner images to a transfer sheet, fixing the toner images to the transfer sheet, and cleaning the surface of the photoconductor.
Electrophotographic photoconductors used in the above electrophotographic process are desired to have the following properties:
(1) good charging property so as to be charged to an appropriate electric potential in a dark place;
(2) good charge maintaining property such that the decrease of the electric potential is little in a dark place;
(3) good charge dissipating property such that the electric potential is rapidly dissipated by light irradiation;
(4) capability of being produced with relatively low costs;
(5) adaptability to minimize environmental pollution; and
(6) capability of producing good images without image defects such as background fouling for a long time.
Conventional photoconductive layers for use in the photoconductors include selenium photoconductive layers of selenium or a selenium alloy supported on a conductive support; inorganic photoconductive layers containing a binder and an inorganic photoconductive material such as zinc oxide or cadmium sulfide dispersed in the binder; amorphous silicon photoconductive layers of an amorphous silicon material; and organic photoconductive layers containing an organic photoconductive material. In photoconductors for use with the electrophotographic method, organic photoconductive materials are now widely used because such organic photoconductors can be manufactured at low costs by mass production and will not cause environmental pollution.
Many kinds of organic photoconductors are conventionally proposed, for example, a photoconductor employing a photoconductive resin such as polyvinylcarbazole (PVK); a photoconductor comprising a charge transport complex of polyvinylcarbazole (PVK) and 2,4,7-trinitrofluorenone (TNF); a photoconductor of a pigment dispersed type in which a phthalocyanine pigment is dispersed in a binder resin; and a function-separating photoconductor comprising a charge generation material and a charge transport material. In particular, the function-separating photoconductor has now attracted considerable attention.
The mechanism of formation of an electrostatic latent image using the function-separating photoconductor is considered to be as follows:
(1) upon irradiation of a charged organic photoconductor with light, the light passes through a transparent charge transporting layer and is absorbed by a charge generating material contained in a charge generating layer;
(2) the charge generating material which has absorbed the light generates a charge carrier;
(3) the charge carrier, which is injected to the charge transporting layer, moves through the charge transporting layer, which is caused by the electric field formed in the charged photoconductor; and
(4) the charge carrier finally combines with the charge on the surface of the photoconductor, resulting in neutralization of the charge, and thereby an electrostatic latent image is formed.
Functionally separated photoconductors which include a combination of a charge transporting material which has absorbance mainly in an ultraviolet region and a charge generating material which has absorbance mainly in a visible region are well known and preferable. However, even in the functionally separated photoconductors, the durability is not necessarily satisfactory.
Among various image forming machines, electrophotographic apparatuses are now widely distributed for use in offices as well as for domestic, personal use because of their high speed recording. In line with such a trend, there are increasing demands for small-sized machines and running trouble-free machines. In particular, there are increasing demands for machines which can reduce running costs, which permit high-speed printing and which are capable of producing color images. In connection with color printing, production of high grade images of natural and clean figure and landscape are strongly desired.
To respond to such demands, charge rollers are increasingly used in lieu of a scolotron chargers so as to reduce electric power consumption and generation ozone. Further, many attempts are made to use chargers with means for superimposing AC components for the purpose of stabilizing the image quality. Improvement of image quality by using small particle size developer is also proposed in both monochromatic and color printing or copying machines. In view of the fact that a dye or pigment for printing ink has a size of sub-micron order, there still remains an objective problem to develop a toner having a much reduced size. In terms of small-sized and high speed printing and copying machines, electrophotographic photoconductor must be used at high speed. Such machines pose increased hazard to electrophotographic photoconductors. Thus, it is one of the greatest problems to develop an electrophotographic photoconductor having excellent durability.
In order to always obtain stable output images throughout a large number of printing operations, development of techniques for preventing image defects, reduction of image density and reduction of resolution is essential. Such image defects are known to result from scars or scraping of a surface top layer of the photoconductor. Thus, in order to prevent occurrence of image defects during a large number of printing operations, it is necessary that the organic type electrophotographic photoconductors should have high mechanical strengths and excellent abrasion resistance, while ensuring suitable electrostatic characteristics.
Various proposals have been made to improve the abrasion resistance of the surface of the photoconductors are as follows:
(1) Improving Mechanical Strength of Charge Transporting Layer:
For example, Japanese Laid-Open Patent Publications Nos. 10-288846 and 10-239870 disclose photoconductors in which the abrasion resistance thereof is improved by using a polyacrylate resin as a binder resin. Japanese Laid-Open Patent Publications Nos. 9-160264 and 10-239871 disclose photoconductors in which the abrasion resistance thereof is improved by using a polycarbonate resin as a binder resin. Japanese Laid-Open Patent Publications Nos. 10-186688, 10-186687, and 5-040358 disclose photoconductors in which the abrasion resistance thereof is improved by using a polyester resin having a terphenyl skeleton, a polyester resin having a triphenyl methane skeleton, or a polyester resin having a fluorene skeleton as a binder resin. Japanese Laid-Open Patent Publications Nos. 9-12637 and 9-235442 disclose the use of a polymer blend containing a styrene elastomer as a binder for a charge transporting layer.
With the photoconductor mentioned above, however, it is necessary to use a large amount of a charge transporting material having low molecular weight in the photoconductive layer in order to obtain good light decaying property, i.e., good photosensitivity. To use a large amount of a charge transportin
Kami Hidetoshi
Kurimoto Eiji
Matuyama Akihiko
Niimi Tatsuya
Tamoto Nozomu
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