Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – Radiation-sensitive composition or product
Reexamination Certificate
2000-05-04
2002-06-04
Rodee, Christopher (Department: 1753)
Radiation imagery chemistry: process, composition, or product th
Electric or magnetic imagery, e.g., xerography,...
Radiation-sensitive composition or product
C430S065000, C430S069000, C430S131000
Reexamination Certificate
active
06399263
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an electrophotographic photoreceptor having an interlayer, and further to an electrophotographic process and an electrophotographic image forming method in which an electrostatic latent image is formed employing said photoreceptor, and subsequently image formation is carried out employing reversal development.
BACKGROUND OF THE INVENTION
In the transition of electrophotographic receptors, a leading part has been changing from inorganic photoreceptors comprised of arsenic, arsenic/Se alloy, CdS, ZnO, and the like, to organic photoreceptors which are superior to the inorganic photoreceptors with respect to environmental protection, ease of production, and the like. Organic photoreceptors employing various materials have been developed.
In recent years, separate function type photoreceptors, in which a charge generating function and a charge transport function are achieved employing different materials, have played a leading role. Of these, multilayered type photoreceptors are widely employed in which the layer consists of a charge generating layer and a charge transport layer.
When attention is directed to the electrophotographic process, latent image forming methods are mainly divided into analogue image formation employing a halogen lamp as the light source and digital image formation employing LED and laser as the light source. Recently, a latent image forming method employing a digital system has increasingly been employed in hardcopy printers for personal computers as well as common copiers due to ease of image processing as well as ease of expansion to peripheral apparatuses.
As described above, in the image formation employing the digital system, when an electrostatic latent image is formed on a photoreceptor employing image information which is converted to digital electrical signals, employed as light sources are lasers, especially semiconductor laser, and LED. These emit light having a relatively long wavelength and most emit light having a wavelength of at least 650 nm. Charge generating materials, which exhibit viable sensitivity to these light sources, include phthalocyanines, bisimidazoleperylene, squalirium, and the like. Of these, phthalocyanines are most widely employed due to their various crystal forms as well as their general usefulness as pigments.
On the other hand, said phthalocyanines exhibit relatively large variations of the performance due to ambient differences in temperature, humidity, and the like. As a result, required are mechanical controls such as variation of the intensity of exposure light, charged electric current, and the like matching to the ambience, in which said phthalocyanines are employed.
On the other hand, when a latent image is formed employing a laser beam, a peculiar image problem is known in which interference fringes are formed due to reflection from the base body surface. The digital system is mainly employed in combination with reversal development in which an exposed part is developed. Known as peculiar problems of said system are phenomenon in which toner adheres on white background due to a decrease in the electrostatic potential, forming background stain, the formation of white spots and also black spots due to local defects on the photoreceptor.
In order to solve these problems, techniques, in which an interlayer is provided, have been developed. Japanese Patent Publication Open to Public Inspection Nos. 63-231147, 63-234261, and others, disclose similar compositions to minimize interference fringes, or moire, which are formed during writing employing laser beams, upon utilizing irregular reflection due to the refractive index of the white pigment. Further, Japanese Patent Publication Open to Public Inspection No. 10-186703 discloses a countermeasure to minimize differences in the charged amount and the like, between the first rotation and the second rotation of the photoreceptor, which occurs when said phthalocyanine is employed as the charge generating material. Still further, Japanese Patent Publication Open to Public Inspection No. 10-69116 discloses a countermeasure to minimize image defects (such as background stain and minute black spots) as well as a method to minimize variations of the residual potential due to ambient conditions.
Some of these inventions provide methods to overcome any of individual problems. However, when the thickness of an interlayer is increased, with the main aim to overcome the moire problem, the residual potential increases. On the other hand, when minimization of variations of residual potential as well as sensitivity due to ambient conditions is the main goal, only a relatively thin interlayer needs to be provided. Thus, conventional countermeasures have not been capable of producing high quality, nor of providing the optimum charge potential properties, which are required for the photoreceptor.
SUMMARY OF THE INVENTION
In view of the aforementioned conventional technical problems, it is an object of the present invention to provide a photoreceptor which satisfies any of the stated characteristics and is capable of providing electrophotographic images without variation, and an electrophotographic process as well as an electrophotographic image forming method employing-the same.
Specifically, it is an object of the present invention to solve the following problems:
1) To minimize variations of the sensitivity of the photoreceptor due to ambient conditions
2) To minimize differences in the charge amount between the first rotation and the second rotation of said photoreceptor
3) To prevent degradation of chargeability due to ambient conditions as well as repeated use.
(wherein the first rotation means a first rotation of the photoreceptor after an instruction for forming image; and the second rotation means following rotation to the first rotation.)
An outline of the present invention will now be described.
In an electrophotographic photoreceptor comprising an interlayer between the electrically conductive base body and the photosensitive layer, an electrophotographic photoreceptor wherein a contact potential difference of said interlayer with respect to an aluminum-evaporated surface is at least +0.175 V.
Said electrophotographic photoreceptor preferably comprises an interlayer comprised of fine titanium oxide particles and a resin, between the electrically conductive base body and the photosensitive layer.
Said contact potential difference is preferably at least +0.200 V.
When the thickness of said interlayer is set at 5 &mgr;m, the transmittance for light of 780 nm is preferably at least 10 percent.
The thickness of said interlayer is preferably at least 5 &mgr;m.
The charge generating material is preferably phthalocyanine.
The charge generating material, which is contained in a photosensitive layer, is preferably titanyl phthalocyanine having a maximum diffraction peak in the X-ray diffraction spectrum (having a Brag angle 2&thgr;±0.2 degree) of a CuK &agr;-ray at 27.2 degrees.
The charge generating material, which is contained in a photosensitive layer, is titanyl phthalocyanine having a maximum diffraction peak in the X-ray diffraction spectrum (having a Brag angle 2&thgr;±0.2 degree) of a CuK &agr;-ray at 27.2 degrees and peaks at 9.5 degrees as well as 24.1 degrees.
An electrophotographic photoreceptor is preferably employed to form an image employing a reversal development method.
An electrophotographic photoreceptor, after forming an electrostatic latent image on itelf employing a digital system, is preferably employed for an electrophotographic image forming method for image formation.
DETAILED DESCRIPTION OF THE INVENTION
By these inventions, it is possible to achieve following effects from (1) to (4).
(1) Variation of sensitivity is extremely small under various employed ambient conditions from high temperature and high humidity to low temperature and low humidity.
(2) Difference in the charged amount between the first rotation and the second rotation of the photoreceptor is very small.
(3) Variat
Bierman, Muserlian and Lucas
Konica Corporation
Rodee Christopher
LandOfFree
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