Radiation imagery chemistry: process – composition – or product th – Including control feature responsive to a test or measurement
Reexamination Certificate
2001-01-12
2003-03-18
Young, Christopher G. (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Including control feature responsive to a test or measurement
Reexamination Certificate
active
06534227
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a photoreceptor which does not produce abnormal images such as images including light and shade stripes, and images including streaks, which are formed by the multiple reflection of coherent light within the photoreceptor.
The present invention also relates to a method of evaluating the photoreceptor.
The present invention also relates to a method of producing the photoreceptor.
The present invention also relates to an image formation apparatus comprising the photoreceptor, which is capable of producing high quality images free of the light and shade stripes and streaks,
2. Discussion of Background
In recent years, there has been a strong demand for image formation with high precision and high resolution in accordance with the request for highly accurate reproduction of image information.
When image formation is carried out with high resolution, using a photoconductor, in addition to an image to be formed based on an original image information, an image based on the information of the photoconductor itself is apt to be formed.
An image formation process by use of coherent light, such as laser light, as writing light, is widely used in the field of electrophotography for the formation of digital images, for instance, as in copying machines, printers and facsimile apparatus. In an electrophotographic process using coherent light as writing light, a problem is apt to be caused that an image including light and shade stripes (hereinafter referred to as the light and shade striped image) is formed due to the interference of the coherent light within a photoconductive layer of the photoconductor.
It is known that such light and shade stripes are generated by the writing light being intensified when the photoconductor satisfies the relationship of 2nd=m&lgr; wherein n is the refractive index of a charge transport layer, d is the thickness of the charge transport layer, &lgr; is the wavelength of the writing light, and m is an integer.
To be more specific, when &lgr;=780 nm and n=2.0, one set of light and shade stripes appears at each change of 0.195 &mgr;m in the thickness of the charge transport layer. In order to remove the light and shade stripes completely, it is necessary to reduce the deviation of the thickness of the charge transport layer to less than 0.195 &mgr;m in the entire image formation area. However, it is economically extremely difficult to produce a photoconductor with such a small deviation of the thickness of the charge transport layer as mentioned above, so that various methods have been proposed to control or reduce the formation of the light and shade stripes in the image.
For instance, in Japanese Laid-Open Patent Application 57-165845, there is proposed a photoconductor comprising a support made of aluminum, a charge transport layer formed on the support, a charge generation layer comprising a-Si formed on the charge transport layer, with the provision of a light absorption layer on the aluminum support to remove the mirror reflection of the aluminum support, thereby preventing the formation of the light and shade stripes in images. The provision of the light absorption layer on the aluminum support is extremely effective for preventing the formation of the light and shade stripes in the image with the photoconductor using the charge generation layer comprising a-Si with the layer structure of the aluminum support/charge transport layer/charge generation layer as mentioned above. However, for an organic photoconductor with a layer structure of aluminum support/charge generation layer layer/charge transport layer in general use, the provision of the light absorption layer on the aluminum support is not so effective for preventing the formation of the light and shade stripes in the image.
In Japanese Laid-Open Patent Application 7-295269, there is disclosed a photoconductor with a layer structure of aluminum support/undercoat layer/charge generation layer/charge transport layer, with the provision of a light absorption layer on the aluminum support for preventing the formation of the light and shade stripes in the image. However, the photoconductor with this layer structure cannot completely prevent the formation of the light and shade stripes in the image.
In Japanese Patent Publication 7-27262, there is disclosed an electrophotographic copying apparatus comprising (1) a photoconductor comprising a cylindrical support which has such a convex cross section that is formed by superimposing a sub-peak on a main peak, when the cylindrical support is cut by a plane which includes the axis of the cylindrical support, and (2) an optical system using a coherent light beam with a beam diameter which is less than one period of the main peak for exposure. The support disclosed in Japanese Patent Publication 7-27262 can be produced relatively easily by machining or like.
In some photoconductors, the formation of the light and shade stripes in the image can be controlled to some extent by use of the above-mentioned support. However, many photoconductors cannot prevent the formation of the light and shade stripes in the image even though the above-mentioned support is used.
There is also known a photoconductor with the parameter of the surface roughness of the support thereof being defined, for example, in Japanese Laid-Open Patent Application 10-301311.
When an electrophotographic copying machine to be used with this photoconductor adopts a low resolution, there is the case where the formation of the light and shade striped image can be prevented. However, when an electrophotographic copying machine with high resolution is used, even if the surface roughness of the substrate is defined by conventionally employed parameters such as maximum height, ten-point mean roughness, and center-line mean roughness, there cannot be determined the conditions under which the formation of the light and shade striped image can be completely prevented.
It is also generally known that the state of the formation of the light and shade striped image can be changed by interposing an undercoat layer comprising a white pigment such as titanium oxide between the support and the photoconductive layer. However, the necessary conditions for the undercoat layer to control the formation of the light and shade striped image, such as the thickness of the undercoat layer, largely differ depending upon the surface state of the support, so that the conditions for completely controlling the formation of the light and shade striped image have not been determined.
Although the conditions for removing the light and shade stripes entirely from the image are not completely known, there are many cases where the formation of the light and shade striped image can be reduced by roughening the surface of the support, so that a photoconductor with the surface of the support being finely roughened, produced by machining or like, is often mounted in an image formation apparatus.
Furthermore, it is also known that the formation of the light and shade striped image can be reduced by changing the thickness of the undercoat layer, but its accurate conditions for reducing the formation of the light and shade striped image are not completely known, so that photoconductors are produced under various conditions, and the conditions under which the light and shade striped image is not formed when the photoconductor is mounted and used in the electrophotographic copying machine are determined experimentally. In order to produce a photoconductor which does not form the light and shade striped image, the above experimentally determined production conditions have to be strictly kept. Even when such production conditions are strictly kept, there are many cases where the light and shade stripes appear in the image when the lot, the material and the shape of the photoconductor are changed, so that it is necessary to check and change the production conditions whenever the lot, the material and the shape of the photoconductor are cha
Fukagai Toshio
Iwata Noriyuki
Kabata Toshiyuki
Katoh Takuji
Miyamoto Yuka
Ricoh & Company, Ltd.
Young Christopher G.
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