Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – Radiation-sensitive composition or product
Reexamination Certificate
1998-07-06
2003-08-12
Rodee, Christopher (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Electric or magnetic imagery, e.g., xerography,...
Radiation-sensitive composition or product
C430S133000, C430S134000, C430S059600, C430S132000
Reexamination Certificate
active
06605400
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a highly durable electrophotographic photoreceptor which minimizes wear and damage of the surface layer during repeated image-forming processes, and fatigue degradation due to incomplete cleaning, etc.
BACKGROUND OF THE INVENTION
In order to carry out image formation employing an electrophotographic method, the surface of an electrophotographic photoreceptor is charged, exposed imagewise and developed to form a toner image. The toner image is transferred onto a transfer material and fixed to form an image. The photoreceptor which has completed the image transfer is subjected to cleaning and discharging, and is repeatedly employed.
The above-mentioned photoreceptor is required to exhibit excellent electrophotographic properties such as charging potential, sensitivity, residual potential, etc.; in addition to these, physical properties such as long printing life, wear, moisture, etc. during repeated usage, and resistance against ozone, generated by corona discharging and image exposure.
It is commonly assumed that the fatigue-caused degradation of electrophotographic properties of a photoreceptor during the repeated usage is caused by the wear and damage to the surface layer of the photoreceptor during each process such as transfer of toner images formed on the photoreceptor to transfer materials, separation, cleaning of residual toner from the photoreceptor after the transfer, and film formed by hygroscopic substances such as toner, paper dust, etc.
Conventionally, for the above-mentioned photoreceptors, there have been widely employed inorganic photoreceptors, comprising inorganic photoconductive materials, and organic photoreceptors, comprising organic photoconductive materials.
The organic photoreceptors are those prepared by coating, on a conductive support, a photosensitive composition prepared by dissolving or dispersing an organic photoconductive material in a solvent, together with a binder, if desired. Particularly, a function-separated type photoreceptor is practically important in which the charge generating function and the charge transport function are performed by different materials. As the function-separated type photoreceptors, many photoreceptors are employed which specifically comprise a charge generating layer comprising a charge generating material, and a charge transport layer comprising a charge transport material.
The surface of a photoreceptor, prepared by coating an organic or inorganic photoconductive material employing a solvent, is soft compared to a photoreceptor prepared by depositing inorganic photoconductive materials such as selenium, amorphous silicone, etc. employing vaporization, glow discharge, etc., and results in disadvantages such as being susceptible for the increased wear and damage during repeated usage and film formed by hygroscopic materials due to incomplete cleaning. On account of this, improvement in physical properties of the surface layer of the photoreceptor is much in demand.
For example, in Japanese Patent Publication Open to Public Inspection No. 5-113670, a method to prevent the formation of film made by toner, paper dust, etc. is proposed in which siloxane-copolymerized polycarbonate is incorporated into the surface layer of a photoreceptor as a binder resin to make the surface layer of the photoreceptor lubricant and to improve the cleaning properties, and in Japanese Patent Publication Open to Public Inspection No. 4-368953, fine particles of fluoro-resin are incorporated into the surface layer of a photoreceptor in order to obtain the same effects as above.
In Japanese Patent Publication Open to Public Inspection No. 3-155558, a method to improve wear resistance of the surface of a photoreceptor is proposed in which fine inorganic particles such as silica, tin oxide, etc. are incorporated into the surface layer of the photoreceptor.
As a solvent for the inorganic photoreceptor which is prepared by coating a photosensitive composition comprising the above-mentioned inorganic photoconductive material, toluene, tetrahydrofuran, dioxane, methyl ethyl ketone, cyclohexane, etc. have been employed. However, these solvents exhibit poor solubility for binder resins employed for an organic photoreceptor comprising an organic photoconductive material. Instead of these, halogenated solvents such as methylene chloride, ethylene chloride, chloroform, monochlorobenzene, etc. are mainly employed. The halogenated solvents exhibit good solubility and coating properties for binder resins of an organic photoreceptor such as polycarbonate, polyacrylate, etc.
SUMMARY OF THE INVENTION
In the photoreceptor which is prepared by coating a photosensitive composition comprising the above-mentioned inorganic or organic photoconductive material, a part of the solvent inevitably remains in the photosensitive layer during the drying process following coating. This remaining solvent lowers or deletes improvements in wear resistance and degrades cleaning properties of the surface layer of the photoreceptor described, for example, in the above-mentioned references, and when image formation is repeated employing the photoreceptor, it is subjected to fatigue degradation due to wear and damage of the surface layer of the photoreceptor, incomplete cleaning, etc., which result in defective images due to the decrease in image density and formation of background staining.
The above-mentioned halogenated solvents require decreased usage amounts due to environmental pollution and possible carcinogenicity.
By employing dioxolan or a derivative as a solvent for a photosensitive composition, it was found that excellent solubility or dispersing properties is exhibited for photoconductive materials and binder resins and in addition, causes no environmental pollution, carcinogenicity, or ozone depletion. Furthermore, when the optimum amount of dioxolan or the derivative remains in the photosensitive layer, improvements in wear resistance and cleaning properties are further enhanced.
An object of the present invention is to provide a photoreceptor which exhibits improvements in wear resistance and cleaning properties, minimum fatigue degradation during the repeated image-forming process employing the above-mentioned photoreceptor repeatedly, no formation of background staining over an extended period, and stably produces clear images of high density.
MEANS TO SOLVE THE PROBLEMS
The photoreceptor of the present invention and its embodiment are described.
The electrophotographic photoreceptor of the present invention comprises an conductive support having thereon a photosensitive layer, and the surface layer of the photoreceptor comprises binder resin having silicon or fluorine atoms and dioxolan or a derivative thereof at 0.001 to 10 weight percent.
The surface layer may preferably comprise fine organic particles. The fine organic particles are preferably a compound comprising fluorine.
The surface layer may preferably comprise fine inorganic particles. The fine inorganic particles are preferably oxides of silicon or tin.
The surface layer of the photoreceptor may comprise both of fine inorganic and organic particles. The fine organic particles preferably comprise fluorine atoms and fine inorganic particles are preferably oxides of silicon or tin.
The surface layer preferably contains silicone oil.
The electrophotographic photoreceptor comprises an conductive support having thereon a photosensitive layer and the surface layer of the photoreceptor comprises fine organic particles and dioxolan or a derivative thereof at 0.001 to 10 weight percent.
These fine organic particles are preferably a compound comprising fluorine atoms.
The surface layer of this photoreceptor preferably comprises a binder resin having silicon or fluorine atoms.
An electrophotographic photoreceptor comprises an conductive support having thereon a photosensitive layer and the surface layer of the photoreceptor comprises fine inorganic particles and dioxolan or a derivative thereof at 0.001 to 10 weight percent.
The fine inorganic particles are
Asano Masao
Itami Akihiko
Konica Corporation
Muserlian Lucas and Mercanti
Rodee Christopher
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