Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – Radiation-sensitive composition or product
Reexamination Certificate
2000-05-30
2003-02-04
Rodee, Christopher (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Electric or magnetic imagery, e.g., xerography,...
Radiation-sensitive composition or product
C430S078000, C430S135000, C540S139000, C540S140000, C540S141000
Reexamination Certificate
active
06514651
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to metal phthalocyanine crystal particles, a production method thereof, and an electrophotographic photoreceptor as well as an electrophotographic process using the same.
BACKGROUND OF THE INVENTION
Since electrophotographic photoreceptors employing charge transfer complexes, comprised of 2,4,6-trinitro-9-fluorenone and poly-N-vinylcarbazole, were discovered, development of organic electrophotographic photoreceptors has been progressed, and improvement of sensitivity, durability, and the like of the photoreceptors have increasingly been reported. Further, separate-function type organic photoreceptors have been developed, and heretofore, various compounds have been developed and reported. When referred to charge generating materials related to the present invention, in order to meet requirements for high speed as well as high sensitivity without variations, various azo pigments, condensed polycyclic pigments, various types of phthalocyanine pigments, and the like, have been studied and a number of results have been reported. Developed in each compound group have been those which exhibit relatively high sensitivity. However, apart from the enhancement of the simple charge generating efficiency, all demands for the charge generating material are not satisfied, and still, the problems described below remain unsolved. It is difficult to enhance the purity of the azo pigments. As a result, it is difficult to obtain high level performance without variation.
Condensed polycyclic pigments exhibit excellent stability of electric potential and the like, while due to the short wavelength absorption, they do not exhibit sufficient practical sensitivity for a semiconductor laser beam of 780 nm, which is commonly utilized as a light source for digitization.
Phthalocyanine based pigments exhibit high sensitivity as well as sufficient sensitivity for a 780 nm light source. However, variation of performance due to the difference in ambient conditions such as temperature, humidity, and the like, is relatively large. Further, they have serious problems in which when they are suspended after repeated use for an extended period of time, the electrostatic potential after the first rotation markedly decreases compared to that after the second rotation, and as a result, readily noticed stain due to toner on white background causes an image defects. Said phenomenon, though there is difference in magnitude, has been pointed out as a problem, which are common to phthalocyanines. For example, Japanese Patent Publication Open to Public Inspection No. 10-186703 describes said problem.
Said phenomenon becomes a cause of the problem in which specifically, during reversal development, a copy formed by the first rotation of a photoreceptor is clearly inferior to those formed by the second and subsequent rotations. In order to overcome said problem, a process has inevitably been employed in which the electrostatic potential is stabilized by rotating the photoreceptor one to several times without image formation, and only after the second rotation or several rotations, are images formed. Accordingly, electric power is squandered during the idle rotation of the photoreceptor. Further, time is also wasted until the first image is outputted. Thus, it has been desired to overcome said problems for protection of environment and resources, as well as for achievement of higher speed.
Described in the following is an electrophotographic photoreceptor which comprises a plurality of pigment particles as the embodiment analogous to the present invention. When a plurality of pigment particles, and the like, are mixed and employed, different types of particles which are separately prepared during preparation of particles are blended and a visually uniform state is obtained by employing a means, such as dispersion. Alternatively, different fine particles which are initially obtained by dispersion and the like are blended to obtain a visually uniform state. In Japanese Patent Publication Open to Public Inspection No. 7-128889, by employing said method, gallium phthalocynanine is blended with perylene or anthanthrone to a charge generating layer.
On the other hand, a method is known in which during particle preparation stage, a plurality of materials are blended at the molecular level and thereafter, particles which simultaneously comprise these materials are prepared. The means to blend materials at the molecular level include co-evaporation, acid paste treatment, melt blending, and the like. Examples, in which charge generating materials are prepared employing such methods, are described in Japanese Patent Publication Open to Public Inspection No. 7-114196 (titanyl phthalocyanine/perylenebisimide mixing), Japanese Patent Publication Open to Public Inspection No. 9-157540 (mixing of different types of phthalocyanines), Japanese Patent Publication Open to Public Inspection No. 3-50553 (mixing of different types of phthalocyanines and naphthalocyanines), Japanese Patent Publication Open to Public Inspection No. 7-5715 (mixing of metal-free phthalocyanine/perylenecarboxylic acid diimide, and dimidazole), Japanese Patent Publication Open to Public Inspection No. 8-110649 (mixing of titanyl phthalocyanine/metal-free phthalocyanine), and other methods.
However, the main purpose of these inventions is the formation of novel crystal forms, an increase in the spectral sensitivity region as well as an increase in sensitivity, and said inventions do not disclose any specific means to overcome the aforementioned problems which are common to phthalocyanine based charge generating materials.
Registered Japanese Patent No. 2754739 discloses phthalocyanine particles. The patent teaches the formation of crystal form of phthalocyanines, employing the formation of mixed crystal. The inventor has found that, when mixed crystal particles were employed, problems occurred in which an extreme decrease in chargeability was caused in the registered mixed amount range (between 0.1 and 50 weight parts). There is no suggestion of aforementioned problem corresponding to the rotation time of the photoreceptor.
As described above, when the electrophotographic photoreceptor for digital copiers, employing a semiconductor laser, is prepared, charge generating materials have been desired in which ideal electrophotographic characteristics as well as stability may be compatible with each other.
SUMMARY OF THE INVENTION
An object of the present invention is to provide metal phthalocyanine crystal particles which achieve the performance described below, an electrophotographic photoreceptor employing said crystal particles, and a electrophotographic process which makes it possible to form an acceptable image from the first rotation, employing said photoreceptor.
Even after repeated use, the difference in electrostatic potential between the first rotation and the second and subsequent rotations of the photoreceptor is minimal, forming excellent images after the first rotation.
Variation of characteristics of a photoreceptor during repeated use is minimal and images exhibit minimal variation.
The present invention and the embodiments thereof will now be described.
Metal phthalocyanine crystal particles wherein metal phthalocyanine compound A in an amount of at least 0.001 to less than 0.1 weight part is uniformly dispersed at the molecular level in 100 weight parts of metal phthalocyanine compound B which has a different chemical structure from said metal phthalocyanine compound A.
Metal phthalocyanine compound A preferably has an electron attractive group.
The preferred electron attractive group is a nitro group.
One example of a central metal of metal phthalocyanine compound A is titanium.
Metal phthalocyanine crystal particles preferably have a maximum diffraction peak in the X-ray diffraction spectrum (having a Brag angle of 2&thgr;±0.2 degree) of a CuK &agr;-ray at 27.2 degrees.
Metal phthalocyanine crystal particles preferably have a maximum diffraction peak in the X-ray diffraction spectrum (having a Br
Bierman, Muserlian and Lucas
Konica Corporation
Rodee Christopher
LandOfFree
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