Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – Radiation-sensitive composition or product
Reexamination Certificate
2001-08-31
2003-07-15
Goodrow, John (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Electric or magnetic imagery, e.g., xerography,...
Radiation-sensitive composition or product
C430S056000, C430S073000
Reexamination Certificate
active
06593047
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a single-layer type electrophotosensitive material, which is used in image forming apparatuses such as electrostatic copying machine, facsimile and laser beam printer. More particularly, the present invention relates to a single-layer type electrophotosensitive material, which is less likely to cause wear even when used in image forming apparatuses equipped with a blade cleaning means, and is also superior in durability.
In the image forming apparatuses described above, various photosensitive materials having the sensitivity within a wavelength range of a light source used in said apparatuses have been used. One of them is an inorganic photosensitive material using an inorganic material such as selenium in a photosensitive layer, while the other one is an organic photosensitive material (OPC) using an organic material in a photosensitive layer. Among these photosensitive materials, the organic photosensitive material has widely been studied because it is easily produced as compared with the inorganic photosensitive material and has a wide range of choice of photosensitive materials such as electric charge transferring material, electric charge generating material and binder resin as well as high functional design freedom.
The organic photosensitive materials are classified roughly into a so-called multi-layer type electrophotosensitive material having a structure of an electric charge generating layer containing an electric charge generating material and an electric charge transferring layer containing an electric charge transferring material, which are mutually laminated, and a single-layer type photosensitive material wherein an electric charge generating material and an electric charge transferring material are dispersed in the same photosensitive layer. Among these organic photosensitive materials, it is a multi-layer type photosensitive material, which has a monopoly position in the wide market.
The single-layer type photosensitive material has become of major interest recently because of its advantages described below. That is, the single-layer type photosensitive material is superior in productivity because of its simple layer construction and can inhibit the occurrence of layer defects of the photosensitive layer, and can also improve optical characteristics because of less interface between layers. Furthermore, one photosensitive material can be used as both of positive and negative charge type photosensitive materials by using, as the electric charge transferring material, an electron transferring material and a hole transferring material in combination.
The electrophotosensitive material is used in the repeated steps of charging, exposing, developing, transferring, cleaning and charge neutralizing in the image formation process. An electrostatic latent image formed by charging/exposure is developed with a toner as a powder in the form of microparticles. Furthermore, the developed toner is transferred to a transfer material such as paper in the transfer process. However, the toner is not transferred completely (100%) and is partially remained on the photosensitive material. If the remained toner is not removed, it is made impossible to obtain a high-quality image, which is free from contamination in the repeated processes. Therefore, it is required to clean the remained toner.
In the cleaning process, a fur brush, a magnetic brush or a blade is typically used. In view of the cleaning accuracy and rationalization of apparatus construction, it is general to select a blade cleaning wherein cleaning is performed by contacting a blade-shaped resin plate directly with a photosensitive material.
As described above, according to the blade cleaning, the remained toner on the surface of the photosensitive material is removed by contacting the blade-shaped resin plate with the surface of the photosensitive material. Although the blade cleaning has high accuracy, it increases a mechanical load on the photosensitive material, thereby causing problems such as increase in wear quantity of the photosensitive layer, reduction in surface potential, lowering of the sensitivity and the like, thus making it difficult to obtain a high-quality image.
It is possible to reduce the wear quantity of the photosensitive layer by decreasing a pressing force (blade linear pressure) exerted on the surface of the photosensitive material by the cleaning blade. However, the remained toner passes through a microspace between the blade and the surface of the photosensitive material in the pressed state and adheres firmly to the surface of the photosensitive material in the state where toner particles are crushed and thus the remained toner is not removed by the blade, that is, a so-called “dash mark” or “toner filming” phenomenon occurs to drastically reduce the potential of the surface of the photosensitive material at the portion where the toner is fused. Also no optical attenuation occurs because of light screening, thus causing defects of images.
To the contrary, when the blade linear pressure is increased to prevent dash mark or toner filming, a mechanical load on the surface of the photosensitive material increases and the wear quantity of the photosensitive layer increases, thereby deteriorating electric characteristics, thus making it difficult to obtain a high-quality image. A resonance sound is created when the blade slides over the surface of the photosensitive material, that is, a so-called “blade squeaking” phenomenon occurs.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a single-layer type electrophotosensitive material, which exhibits good wear resistance with respect to the photosensitive layer even when used in image forming apparatuses equipped with a blade cleaning means, and is also superior in durability. Another object of the present invention is to provide a highly sensitive single-layer type electrophotosensitive material, which causes none of blade squeaking, dash mark and toner filming.
The present inventors have intensively studied and found that a single-layer type electrophotosensitive material comprising a conductive substrate and a photosensitive layer made of a binder resin containing at least an electric charge generating material and a hole transferring material and an electron transferring material as an electric charge transferring material, which is formed on the conductive substrate, wherein the binder resin contains a polycarbonate resin having a repeating structural unit represented by the general formula [1]:
wherein R
10
and R
11
are the same or different and each represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and the solid content of the electric charge transferring material (hole transferring material and electron transferring material) is not less than 30% by weight and not more than 50% by weight based on the entire solid content, exhibits good wear resistance with respect to the photosensitive layer even when used in an image forming apparatus equipped with a blade cleaning means, and is also superior in durability.
Also, the present inventors have found that the single-layer type electrophotosensitive material, which further contains as the binder resin the following polycarbonate resin having a repeating structural unit represented by the general formula [2] and/or the following copolymer polycarbonate resin having a repeating structural unit represented by the general formula [3], exhibits good wear resistance with resect to the photosensitive layer even when used in an image forming apparatus equipped with a blade cleaning means, is excellent in durability, and causes none of blade squeaking, dash mark and toner filming.
A polycarbonate resin having a repeating structural unit represented by the general formula [2]:
wherein X
20
, X
21
and X
22
are the same or different and each represents —(CH
2
)
n
—, n represents an integer of 1 to 6; R
20
, R
21
, R
22
and R
23
are the same or different a
Azuma Jun
Honma Hisakazu
Nakamura Kyoichi
Uchida Maki
Watanabe Yukimasa
Kyocera Mita Corporation
Smith , Gambrell & Russell, LLP
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