Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From phenol – phenol ether – or inorganic phenolate
Reexamination Certificate
1999-06-22
2001-01-09
Boykin, Terressa M. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From phenol, phenol ether, or inorganic phenolate
C430S073000, C528S198000
Reexamination Certificate
active
06172176
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an electrophotographic photoconductor comprising an electroconductive support, and a photoconductive layer formed thereon, comprising an aromatic polycarbonate resin. In addition, the present invention also relates to the above-mentioned aromatic polycarbonate resin with charge transporting properties.
2. Discussion of Background
Recently organic photoconductors (OPC) are used in many copying machines and printers. These organic photoconductors have a layered structure comprising a charge generation layer (CGL) and a charge transport layer (CTL) which are successively overlaid on an electroconductive support. The charge transport layer (CTL) is a film-shaped layer comprising a binder resin and a low-molecular-weight charge transport material (CTM) dissolved therein. The addition of such a low-molecular-weight charge transport material (CTM) to the binder resin lowers the intrinsic mechanical strength of the binder resin, so that the CTL film is fragile and has a low tensile strength. Such lowering of the mechanical strength of the CTL causes the wearing of the photoconductor or forms scratches and cracks on the surface of the photoconductor.
Although some vinyl polymers such as polyvinyl anthracene, polyvinyl pyrene and poly-N-vinylcarbazole have been studied as high-molecular-weight photoconductive materials for forming a charge transporting complex for use in the conventional organic photoconductor, such polymers are not satisfactory from the viewpoint of photosensitivity.
In addition, high-molecular-weight materials having charge transporting properties have been also studied to eliminate the shortcomings of the above-mentioned layered photoconductor. For instance, there are proposed an acrylic resin having a triphenylamine structure as reported by M. Stolka et al., in “J. Polym. Sci., vol 21, 969 (1983)”; a vinyl polymer having a hydrazone structure as described in “Japan Hard Copy '89 p. 67”; and polycarbonate resins having a triarylamine structure as disclosed in U.S. Pat. Nos. 4,801,517, 4,806,443, 4,806,444, 4,937,165, 4,959,288, 5,030,532, 5,034,296, and 5,080,989, and Japanese Laid-Open Patent Applications Nos. 64-9964, 3-221522, 2-304456, 4-11627, 4-175337, 4-18371, 4-31404, and 4-133065. However, any materials have not yet been put to practical use.
According to the report of “Physical Review B46 6705 (1992)” by M. A. Abkowitz et al., it is confirmed that the drift mobility of a high-molecular weight charge transport material is lower than that of a low-molecular weight material by one figure. This report is based on the comparison between the photoconductor comprising a low-molecular weight tetraarylbenzidine derivative dispersed in the photoconductive layer and the one comprising a high-molecular polycarbonate having a tetraarylbenzidine structure in its molecule. The reason for this has not been clarified, but it is suggested that the photoconductor employing the high-molecular weight charge transport material produces poor results in terms of the photosensitivity and the residual potential although the mechanical strength of the photoconductor is improved.
Conventionally known representative aromatic polycarbonate resins are obtained by allowing 2,2-bis(4-hydroxyphenyl)propane (hereinafter referred to as bisphenol A) to react with phosgene or diphenylcarbonate. Such polycarbonate resins made from bisphenol A are used in many fields because of their excellent characteristics, such as high transparency, high heat resistance, high dimensional accuracy, and high mechanical strength.
For example, this kind of polycarbonate resin is intensively studied as a binder resin for use in an organic photoconductor in the field of electrophotography. A variety of aromatic polycarbonate resins have been proposed as the binder resins for use in the charge transport layer of the layered photoconductor.
As previously mentioned, however, the mechanical strength of the aforementioned aromatic polycarbonate resin is decreased by the addition of the low-molecular-weight charge transport material in the charge transport layer of the layered electrophotographic photoconductor.
The electrophotographic process is one of the image formation processes, through which the surface of the photoconductor is charged uniformly in the dark to a predetermined polarity, for instance, by corona charge. The uniformly charged photoconductor is exposed to a light image to selectively dissipate the electric charge of the light-exposed area, so that a latent electrostatic image is formed on the photoconductor. The thus formed latent electrostatic image is developed to a visible image by a developer comprising a coloring agent such as a dye or pigment, and a binder agent such as a polymeric material.
Fundamental characteristics required for the photoconductor used in such an electrophotographic process are: (1) chargeability to an appropriate potential in the dark, (2) minimum dissipation of electric charge in the dark, and (3) rapid dissipation of electric charge when exposed to light.
However, the conventional photoconductive materials are not always satisfactory in light of the above-mentioned fundamental characteristics for the photoconductor and the mechanical durability.
SUMMARY OF THE INVENTION
It is therefore a first object of the present invention to provide an electrophotographic photoconductor free from the conventional shortcomings, which can show high photosensitivity and high durability.
A second object of the present invention is to provide an aromatic polycarbonate resin that is remarkably useful as a high-molecular-weight charge transport material for use in an organic electrophotographic photoconductor.
The above-mentioned first object of the present invention can be achieved by an electrophotographic photoconductor comprising an electroconductive support, and a photoconductive layer formed thereon comprising as an effective component an aromatic polycarbonate resin comprising a structural unit of formula (1):
wherein R
1
and R
2
, which may be the same or different, are each a hydrogen atom, an alkyl group which may have a substituent, or an aryl group which may have a substituent; Ar
1
, Ar
2
, Ar
3
, Ar
4
, Ar
6
and Ar
7
, which may be the same or different, are each an arylene group which may have a substituent; Ar
5
and Ar
8
, which may be the same or different, are each an aryl group which may have a substituent; and s is an integer of 0 or 1, and when s=1, X is —O—, —S—, —SO—, —SO
2
—, —CO—, a straight-chain, branched or cyclic alkylene group having 1 to 12 carbon atoms, or an arylene group which may have a substituent.
In the above-mentioned photoconductor, the structural unit of formula (1) may be represented by the following formula (4):
wherein R
1
, R
2
, Ar
5
, Ar
8
and X are the same as those previously defined in formula (1).
Further, the structural unit of formula (4) may be represented by formula (6):
wherein R
1
, R
2
, Ar
5
, Ar
8
and X are the same as those previously defined in formula (1).
To be more specific, the structural unit of formula (6) may be represented by formula (8):
wherein R
1
, R
2
and X are the same as those previously defined in formula (1); and R
18
and R
19
, which may be the same or different, are each a hydrogen atom, an alkyl group which may have a substituent, or an aryl group which may have a substituent.
The first object of the present invention can also be achieved by an electrophotographic photoconductor comprising an electroconductive support, and a photoconductive layer formed thereon comprising as an effective component an aromatic polycarbonate resin having the aforementioned structural unit of formula (1) and a structural unit of the following formula (2), with the composition ratio of the structural unit of formula (1) to the structural unit of formula (2) satisfying a relationship of 0<k/(k+j)≦1, wherein k is the moiety ratio of the structural unit of formula (1), and j is the moiety ratio of the structural unit
Kawamura Shin'ichi
Morooka Katsuhiro
Nagai Katsukiyo
Sasaki Masaomi
Suzuka Susumu
Boykin Terressa M.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Ricoh & Company, Ltd.
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