Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – Radiation-sensitive composition or product
Reexamination Certificate
1999-07-30
2001-02-20
Goodrow, John L (Department: 1753)
Radiation imagery chemistry: process, composition, or product th
Electric or magnetic imagery, e.g., xerography,...
Radiation-sensitive composition or product
C399S159000
Reexamination Certificate
active
06190811
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an electrophotographic photosensitive member, a process cartridge and an electrophotographic apparatus, and more particularly to an electrophotographic photosensitive member, a process cartridge and an electrophotographic apparatus which are suited for short-wavelength semiconductor lasers capable of making images have higher resolution.
2. Related Background Art
Lasers used in electrophotographic apparatus making use of lasers as light sources as typified by laser printers are prevailingly semiconductor lasers having oscillation wavelength around 800 nm or around 680 nm. In recent years, various approaches to higher resolution are made with an increase in demand for reproducing images having a higher image quality. Wavelengths of lasers also deeply concern the higher resolution. As disclosed in Japanese Patent Application Laid-Open No. 9-240051, the shorter oscillation wavelength a laser has, the smaller spot diameter the laser can have. This enables formation of latent images having a high resolution.
Some methods are available for making laser oscillation wavelength shorter.
One is a method in which a non-linear optical material is utilized so that the wavelength of laser light is shortened to half by using secondary higher harmonic generation (SHG) (e.g., Japanese Patent Application Laid-Open Nos. 9-275242, 9-189930 and 5-313033). This system can achieve a long life and a large output, since it can use GaAs semiconductor lasers or YAG lasers as primary light sources, which have already established their technique and can achieve a high output.
Another is a method in which a wide-gap semiconductor is used, and can make apparatus smaller in size than devices utilizing the SHG. ZnSe semiconductor lasers (e.g., Japanese Patent Application Laid-Open Nos. 7-321409 and 6-334272) and GaN semiconductor lasers (e.g., Japanese Patent Application Laid-Open Nos. 8-088441 and 7-335975) have long been studied in great deal because of their high emission efficiency.
It, however, has been difficult for these semiconductor lasers to be optimized in their device structure, crystal growth conditions and electrodes, and, because of defects in crystals, has been difficult to make long-time oscillation at room temperature, which is essential for putting them into practical use.
However, with progress of technological innovations on substrates and so forth, Nichia Kagaku Kogyo K.K. reported, in October, 1997, GaN semiconductor laser's continuous oscillation for 1,150 hours (condition: 50° C.), and materialization for its practical use stands close at hand.
Japanese Patent Application Laid-Open No. 9-240051 discloses as a photosensitive member suited for 400 nm to 500 nm lasers a multi-layer photosensitive member in which a single layer or charge generation layer making use of &agr;-type titanyl phthalocyanine is formed as the outermost layer. Studies made by the present inventors, however, have revealed that the use of such a material brings about a problem that, because of a poor sensitivity and besides a very great memory especially for light of about 400 nm, photosensitive members may undergo great potential variations when used repeatedly.
SUMMARY OF THE INVENTION
An object of the present invention is to provide an electrophotographic photosensitive member having high sensitivity characteristics even in wavelength region of 380 nm to 500 nm and also having small photomemory and undergoing small potential variations when used repeatedly, and a process cartridge having such a photosensitive member, and also provides an electrophotographic apparatus that is practical and can stably reproduce images with a high image quality by using such a photosensitive member and a short wavelength laser.
The present invention provides an electrophotographic photosensitive member comprising a support and a photosensitive layer provided thereon, and being exposed to semiconductor laser light having a wavelength of from 380 nm to 500 nm;
the photosensitive layer containing a gallium phthalocyanine compound or an oxytitanium phthalocyanine compound having a strong peak at 27.2° plus-minus 0.2° of the diffraction angle in CuK&agr; characteristic X-ray diffraction.
The present invention also provides a process cartridge having the electrophotographic photosensitive member described above.
The present invention still also provides an electrophotographic apparatus comprising the electrophotographic photosensitive member described above and a short-wavelength semiconductor laser as an exposure light source.
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Chen, et al. “Segmentation . . . Algorithm,” Comp. Graphics and Image Processing, vol. 10, pp. 172-182 (1979).
Kass, et al. “Snakes : Active Contour Models”; Int. J. Comp. Vision, vol. 1, No. 4, (1987) pp. 321-331.
Takai Hideyuki
Tanaka Masato
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Goodrow John L
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