Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – Radiation-sensitive composition or product
Reexamination Certificate
2001-03-23
2003-04-15
Rodee, Christopher (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Electric or magnetic imagery, e.g., xerography,...
Radiation-sensitive composition or product
C430S096000
Reexamination Certificate
active
06548216
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an electrophoto-graphic photoconductor comprising an electroconductive support and a photoconductive layer which is formed on the electroconductive support and contains a specific resin. In addition, the present invention relates to an electrophotographic image forming apparatus and method using the above-mentioned photoconductor, and a process cartridge including the photoconductor, which process cartridge is freely attachable to the image forming apparatus and detachable therefrom. The present invention also relates to a long-chain alkyl group containing bisphenol compound and a polymer made from the bisphenol compound, which is useful when used in an electrophoto-graphic photoconductor.
2. Discussion of Background
To achieve image formation by electrophotography, the surface of an electrophotographic photoconductor (hereinafter referred to as a photoconductor) is uniformly charged in the dark, for example, by corona charging, and exposed to light images to selectively dissipate electric charge of a light-exposed portion, thereby forming latent electrostatic images on the surface of the photoconductor. The latent electrostatic images are developed as visible toner images with a toner that is made up of a coloring agent, such as a dye or pigment, and a polymeric material. The toner images formed on the photoconductor are transferred to an image receiving member and fixed thereon. After the toner images are transferred to the image receiving member, residual toner on the surface of the photoconductor is removed therefrom, and the photoconductor is subjected to a quenching step. Image formation can thus be repeated, using the photoconductor, by the so-called Carlson process, for an extended period of time.
Photoconductive material for use in the above-mentioned photoconductor is roughly divided into an inorganic photoconductive material and an organic photoconductive material.
Most of the currently available photoconductors employ organic photoconductive materials. This is because an organic photoconductive material is superior to an inorganic material in terms of the degree of freedom in selection of wavelength of light to which the photoconductive material is sensitive, the filming forming properties, flexibility, transparency of the obtained film, mass productivity, toxicity, and cost.
The photoconductor repeatedly used in the electrophotographic process or the like is required to have basic electrostatic properties such as good sensitivity, sufficient charging potential, charge retention properties, stable charging characteristics, minimal residual potential, and excellent spectral sensitivity. In addition to the above, the photoconductor is also required to have satisfactory physical properties from the viewpoints of printing resistance, wear resistance, and moisture resistance.
In recent years, data processors employing the electrophotographic process have exhibited remarkable development. The image quality and printing reliability have noticeably improved, in particular, in the field of a printer that adapts a digital recording system by which information is converted into a digital signal and recorded by means of light. Such a digital recording system is applied to not only printers, but also to copying machines. Namely, a digital copying machine has been actively developed. Further, there is a tendency for the digital copying machine to be provided with various data processing functions, so that demand for the digital copying machine is expected to rise sharply.
A function-separation layered photoconductor has become the mainstream in the field of electrophotographic photoconductors for the above-mentioned digital copying machine. The function-separation layered photoconductor is constructed in such a manner that a charge generation layer is provided on an electroconductive support directly or via an undercoat layer, and a charge transport layer is further overlaid on the charge generation layer. To improve the durability of the photoconductor from the mechanical and chemical viewpoints, a protective layer may be overlaid on the top surface of the photoconductive layer.
When the surface of the function-separation layered photoconductor is charged and thereafter exposed to light images, the light passes through the charge transport layer and is absorbed by a charge generation material for use in the charge generation layer. Upon absorbing light, the charge generation material produces a charge carrier. The charge carrier is injected into the charge transport layer and travels along an electric field generated by the charging step to neutralize the surface charge of the photoconductor. As a result, latent electrostatic images are formed on the surface of the photoconductor.
In view of the above-mentioned mechanism of the function-separation layered photoconductor, a charge generation material which exhibits absorption peaks within the range from the near infrared region to the visible light region is often used in combination with a charge transport material that does not hinder the charge generation material from absorbing light, in other words, exhibiting absorption within the range from the visible light region (yellow light region) to the ultraviolet region.
As a light source capable of coping with the above-mentioned digital recording system, a semiconductor laser diode (LD) and a light emitting diode (LED), which are compact, inexpensive, and highly reliable, are widely employed. The LD most commonly used these days has an oscillation wavelength range in the near infrared region of around 780 to 800 nm. The emitting wavelength of the typical LED is located at 740 nm.
The beam spot size of the LD or LED is in the range of about 60 to 150 &mgr;m. Therefore, the resolution obtained by currently available electrophotographic image forming apparatus is about 300 to 600 dpi at most, which is not sufficient to produce a high-resolution image equivalent to a photograph. To narrow down the beam spot size to about 30 &mgr;m to increase the resolution to 1200 dpi, or to about 15 &mgr;m to increase the resolution to as high as 2400 dpi, extra optical parts of extremely high precision as well as bulky optical members become necessary. In light of cost and space in the apparatus, such an electrophoto-graphic image forming apparatus has not been put to practical use. Therefore, to produce images with a higher resolution to the extent stated above, shortening of the emitting wavelength of the employed light source has been considered effective. For instance, Japanese Laid-Open Patent Application 5-19598 discloses an electrophoto-graphic image forming apparatus employing a laser beam with a shorter wavelength.
Recently, an LD or LED with oscillation wavelengths of 400 to 450 nm to emit a violet or blue light has been developed and finally put on the market as a light source for writing information so as to cope with the digital recording system. This kind of LD or LED is hereinafter referred to as “shorter wavelength LD or LED.” In the case where a shorter wavelength LD, of which the oscillation wavelength is as short as nearly half the conventional one located in the near infrared light region, is used as the light source for writing, it is theoretically possible to decrease the spot size of a laser beam projected on the surface of a photoconductor, in accordance with the following formula (A):
d∞(
&pgr;/4)(&lgr;
f/D
) (A)
wherein d is the spot size projected on the surface of the photoconductor, &lgr; is the wavelength of the laser beam, f is the focal length of a f&thgr; lens, and D is the lens diameter.
Further, from the use of such a shorter wavelength LD or LED it will be possible to make the electrophoto-graphic image forming apparatus compact as a whole, and to speed up the electrophotographic image forming method. Accordingly, there is an increasing demand for high sensitivity and high stability of the electrophotographic photoconductor so as to cope with the light sou
Kawamura Shin'ichi
Nagai Kazukiyo
Namba Michihiko
Shimada Tomoyuki
Tanaka Chiaki
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Ricoh & Company, Ltd.
Rodee Christopher
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