Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – Radiation-sensitive composition or product
Reexamination Certificate
2000-08-31
2002-09-10
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
Reexamination Certificate
active
06447965
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an electrophotographic photoreceptor using oxotitanyl phthalocyanine (TiOPc) as a charge generating material, and also relates to a coating liquid for a charge generating layer for producing the same and a method for manufacturing the same.
2. Description of the Related Art
In image forming apparatuses such as a printer, a laser light source, in particular a small-sized semiconductor laser light source of high reliability, is used instead of a white light source, to realize image formation of high speed, high image quality and non impact.
Electrophotographic photoreceptors installed in image forming apparatuses are classified into inorganic photoreceptors and organic photoreceptors. Typical inorganic materials used as the inorganic photoreceptor include selenium (Se) containing materials such as amorphous selenium (a-Se) and, amorphous arsenic selenium (a-AsSe), zinc oxide (ZnO), cadmium sulfide (CdS) and amorphous silicon (a-Si), which have been subjected to dye sensitization and dispersed in a binder resin, but they are substantially not applied to practical use due to various problems. Specifically, a photoreceptor using Se containing material or CdS is inferior in heat resistance and storage stability, and involves a problem in disposal. A photoreceptor using ZnO is low sensitive and poorly durable. A photoreceptor using a-Si is low in causing environmental pollution and is highly sensitive and highly durable, but it brings about image defects caused by a production process, i.e., a plasma CVD (chemical vapor deposition) method, and has low productivity, which causes an increase in production cost.
On the other hand, since the organic materials used for the organic photoreceptor include many kinds of materials, a photoreceptor having high storage stability and low toxicity can be obtained by selecting an appropriate one from among the materials, and formation of a thin film can be easily conducted by coating at a low production cost. Thus, improvements in sensitivity and durability have been rapidly realized in recent years. Such materials include bisazo type compounds, squaric acid methine type dyes, indoline type dyes, cyanine type dyes, pyrylium type dyes and phthalocyanine type compounds.
It is firstly desirable in a photoreceptor installed in an image forming apparatus using a laser light source to exhibit high sensitivity to light of a long wavelength band of about 800 nm, which is the wavelength band of the laser light source. A photoreceptor using a bisazo type compound has low sensitivity to light of a long wavelength band. A photoreceptor using a squaric acid methine type dye, indoline type dye, cyanine type dye or pyrylium type dye has relatively high sensitivity to light of a long wavelength band, but is inferior in stability of reiteration characteristics. Therefore, these organic materials cannot be subjected to practical use. A photoreceptor using a phthalocyanine type compound has high sensitivity to light of a long wavelength band and higher stability than the other materials. In particular, a photoreceptor using TiOPc has high sensitivity.
The phthalocyanine type compounds have different sensitivity peaks and physical properties depending on whether a central metallic atom is present or not and on the species thereof, and the physical properties vary depending on the crystal forms thereof. Accordingly, it is necessary to include the crystal form in criteria for judging whether the compounds can be used for a photoreceptor. The crystal forms of TiOPc are classified by difference in diffraction angle of an X-ray diffraction spectrum in Denshi Shashin Gakkai-shi (The Society Journal, Society of Electrophotography of Japan), (Vol.32, No. 3, 1993): 282-289) Japanese Unexamined Patent Publication JP-A 61-239248 (1986) discloses a type, Japanese Unexamined Patent Publication JP-A 62-67094 (1987) discloses A type, Japanese Unexamined Patent Publication JP-A 64-17066 (1989) discloses Y type, Japanese Unexamined Patent Publication JP-A 3-54264 (1991) discloses M-&agr; type, and furthermore C type, M type and I type are present. The crystal types of TiOFc, the lattice constants of which have been known, are C type, Phase I type and Phase II type. Phase II type is of the triclinic system, and Phase I type and C type are of the monoclinic system. Prom the crystal lattice constants, A type and I type belong to Phase I type, &agr; type and &bgr; type belong to II type, and M type belongs to C type. Furthermore, Japanese Unexamined Patent Publication JP-A 10-237347 (1998) discloses a photoreceptor using crystalline TiOPc exhibiting a specific X-ray diffraction spectrum.
Secondly, the photoreceptor is desired to form an image without generation of interference fringes. Because laser light has a single wavelength, incident light on a photosensitive layer and reflected light on a support interfere at an interface of the photosensitive layer with the support to form an interference fringe. As precautionary measures against generation of interference fringes, the following measures are disclosed in Denshi Shashin Gakkai-shi (The Society Journal, Society of Electrophotography of Japan), (Vol.32, No. 3, 1993): 282-289), i.e., (1) a surface of the support is roughened by cutting, spiral cutting, blast processing or anodic oxidation, (2) the surface of the support is appropriately roughened by coating an electroconductive layer using slectroconductive particles, (3) particles scattering light are incorporated into an adhesive layer between the support and the photosensitive layer, and (4) a photoreceptor is made transparent. The measures (1) to (3) are related to irregularly reflecting light, and the measure (4) is related to transmitting incident light. As a specific example of the measure (4), Japanese Unexamined Patent Publication JP-A 8-194322 (1996) discloses a technique in that an organic photoelectroconductive transparent sheet formed by accumulating an organic photoelectroconductive layer on a transparent electroconductive base sheet is wound on a support having a surface made black.
In the measure (1), however, the support must be separately processed. In the measure (2), another layer must be provided. In the measure (3), particles must be newly introduced. There is a possibility that these bring about deterioration in coating properties of a coating liquid and deterioration in electric characteristics. In the measure (4), the material for the electroconductive support itself must be changed, resulting in an increase in production costs.
SUMMARY
An object of the invention is to provide an electrophotographic photoreceptor which exhibits high sensitivity to laser light and can form an image without forming an interference fringe, to provide a coating liquid for a charge generating layer for forming the photoreceptor, and to provide a method for manufacturing an electrophotographic photoreceptor, by which the photoreceptor can be produced with excellent coating properties and high electric characteristics at a low cost.
The invention relates to an electrophotographic photoreceptor comprising:
an electroconductive support; and
a photosensitive layer on the electroconductive support, including at least a charge generating layer and a charge transporting layer accumulated thereon,
the charge generating layer containing oxotitanyl phthalocyanine as a charge generating material,
the charge generating layer having a Y value of 37 or less, which Y value is one element of three excitation values in XYZ color system showing an object color.
According to the invention, the photoreceptor exhibits high sensitivity to laser light since TiOPc is contained, and an image can be formed without generation of an interference fringe due to laser light since the Y value is 37 or less. In the invention, the Y value is used as an index showing the darkness or lightness of the charge generating layer. The Y value is one element of the three excitation values in the XYZ color system showing an object color, an
Miyauchi Masato
Nakamura Tomomi
Rodee Christopher
Sharp Kabushiki Kaisha
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