JPH04337771A - Image forming device - Google Patents

Abstract

PURPOSE:To use a high gamma type photosensitive body which is easily abraded in an easy method and to obtain a high-resolution image by digital light input by specifying the surface roughness of a photosensitive body. CONSTITUTION:In a printer using an electrophotographic process, a latent image carrier 1 is obtained by forming a photoconductive photosensitive layer 3 using the high gamma type photosensitive body on a conductive supporting part 2. Toner 8 on the developing roller 9 of a developing device 21 is stuck to the photosensitive layer 3 so that an electrostatic latent image formed on the photosensitive layer 3 is developed. The surface roughness of the photosensitive layer 3 is set equal to or under 50 times, preferably 30 times, as large as the volume average particle size of the additive of the toner 8. Thus, the fixing force of the additive to the photosensitive body is reduced, and the sticking condition of a cleaning blade 17 which press-contacts with the photosensitive body is mitigated, then blade cleaning is accomplished. As a result, the high gamma type photosensitive body is used in an easy cleaning method.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming method using an electrophotographic process, and more particularly to an image forming apparatus that mainly uses a one-component toner.

0002

[Prior Art] A conventional image forming apparatus is
Image formation was carried out by an electrophotographic method using a photoreceptor having a high γ value as disclosed in Japanese Patent No. 2863. For a photoreceptor with an extremely high γ, the charged potential hardly attenuates when the exposure amount is below a certain value, and the charged potential attenuates to almost the residual potential when the exposure amount exceeds a certain value, which makes it clear whether or not it has been exposed. , it is possible to faithfully reproduce minute exposures using laser beams, etc., and form high-resolution electrostatic latent images.

0003

[Problems to be Solved by the Invention] However, although the photoreceptor having a high γ in the prior art described above enables the formation of an electrostatic latent image by inputting digital light, it is difficult to clean the toner adhering to the photoreceptor. Compared to conventional functionally separated organic photoreceptors, the surface of the photosensitive layer is more susceptible to damage and deterioration due to friction caused by the cleaning blade, toner, external additives of toner peeled off from the toner, etc. There is a problem in that scratches on the surface of the photosensitive layer are easily contaminated by toner, resulting in a decrease in image quality and the inability to form high-resolution images. Hydrophobic silica and the like are generally used as external additives for toner, but these external additives adhere to the toner surface in the form of secondary particles, and the size of the secondary particles is about 50 times that of the primary particles. . The external additive is peeled off from the toner surface by agitation in the developing device, an elastic blade on the toner conveyor, or pressure contact with the photoreceptor, and the peeled external additive becomes an abrasive and is rubbed on the photoreceptor. A phenomenon of polishing occurs, which is the biggest cause of damage and deterioration of the photoreceptor. Furthermore, the external additive adhered to the surface of the photoreceptor, and even when the adhered external additive was removed with a blade, the photoreceptor was damaged and deteriorated. Further, there is a problem in that the presence of irregularities on the surface of the photosensitive layer causes non-uniform charging.

The present invention has been made in view of the above-mentioned prior art, and it is an object of the present invention to provide an image forming apparatus that prevents damage and deterioration of a high-γ type photoreceptor and obtains sharp, high-resolution images. I use it as a purpose.

[0005]

[Means for Solving the Problems] The present invention is an image forming apparatus using an electrophotographic process in which an electrostatic latent image is formed on a high γ type photoreceptor and an image is formed by developing this electrostatic latent image. , the surface roughness of the photoreceptor is smaller than 50 times the volume average particle diameter of the external additive of the toner on the toner conveying member of the developing device.

[0006] In the present invention, the above-mentioned "high γ type photoreceptor"
is defined as one that exhibits avalanche-like photosensitivity characteristics and satisfies the following conditions. In other words, a high γ type photoreceptor is a photoreceptor that has light attenuation characteristics as shown in A and C of FIG. The relationship between the exposure amounts E25, E50 and E75 required for is as follows:

[0007]

[Math 1] E25≧0.5・E50

[0008]

[Math 2] E75≦2・E50 More preferably,

[0009]

[Math 3] E25≧0.75・E50

0010

[Math 4] E75≦1.25・E50 shall be defined as something that satisfies the following.

[0011]

[Operation] According to the above structure of the present invention, in an image forming apparatus using a high γ type photoreceptor, the surface roughness of the photoreceptor is equal to the volume average particle of the external additive of the toner on the toner conveying member of the developing device. By making the diameter smaller than 50 times, the adhesion force of the external additive to the photoconductor is reduced, and the pressure conditions of the cleaning blade that presses against the photoconductor can be relaxed compared to conventional conditions.
Blade cleaning becomes possible. As a result, a high-γ type photoreceptor can be used with a simple cleaning method, and high-resolution images can be formed. If the photoreceptor is subjected to development without specifying the surface roughness on the photoreceptor, external additives peeled off from the toner may stick to the photoreceptor and be peeled off with excessive force by the cleaning blade during cleaning. The high-gamma type photoreceptor, which has inferior printing durability compared to conventional photoreceptors, is easily damaged and deteriorated, making it impossible to perform a large amount of printing. The external additives attached to the toner surface are secondary particles whose size is about 50 times the volume average particle diameter of the primary particles. By making the surface roughness of the photoreceptor 50 times or less the volume average particle diameter of the primary particles of the external additive of the toner,
The adhesion force of the external additive of the toner to the photoreceptor is reduced, and the burden on cleaning is reduced.

Furthermore, by smoothing the surface of the photoreceptor, the charging potential of the photoreceptor by a corona charger or the like becomes uniform. An electrostatic latent image is formed by exposing a charged photoreceptor to light. However, in regular development, in which toner is attached to unexposed areas and visualized, uneven charging potential on the photoreceptor causes uneven image density. will occur. Therefore, by making the surface roughness of the photoreceptor smaller than 50 times the volume average particle diameter of the external additive of the toner, an image with uniform density can be formed.

[0013] The above-mentioned high γ type photoreceptor has its own unique photosensitivity characteristics and is capable of forming high resolution images. This point will be explained below.

FIG. 3 is a diagram showing the distribution of the amount of light on the photoreceptor when exposure is performed, and shows a 600DPI line pair (12
This is a light amount distribution when the photoreceptor is exposed to light at a line pair/mm). As shown in this figure, the exposed portion on the photoreceptor usually exhibits a gentle light intensity distribution. In the figure,
X indicates the center of the line.

On the other hand, FIGS. 4 and 5 are diagrams showing the distribution of absolute values of surface potential when exposure as shown in FIG. 3 is performed. Of these, FIG. 4 shows the surface potential distribution of the conventional photoconductor shown in FIG. It will become blurry.

On the other hand, FIG. 5 shows the surface potential distribution in the case of the high γ type photoreceptor shown in A of FIG. The surface potential distribution is such that the surface potential changes sharply at the boundary with the image area, and a high-contrast, high-resolution image can be formed.

[0017]

Embodiment Embodiment 1 FIG. 1 is a cross-sectional schematic diagram of a printer in an embodiment of the present invention. In this embodiment, the latent image carrier 1 includes a photoconductive photosensitive layer 3 formed on a conductive support 2, and the photosensitive layer 3 is connected to a charger 4 such as a corona charger or a charging roller. After charging using
A potential contrast is obtained by selectively irradiating light from a light source 5 such as a laser or LED through an imaging optical system 6 to the photosensitive layer 3 according to the image, thereby forming an electrostatic latent image on the photosensitive layer 3. .

On the other hand, the developing device 21 conveys and develops the toner 8, and the developing roller 9 that conveys the toner 8 has an elastic layer 11 and a thin film member 12 arranged concentrically around the outer periphery of the shaft 10. The developing roller 9 is rotated with the charged toner held directly on the developing roller and regulated in an appropriate amount by a plate-shaped elastic blade 22 made of non-magnetic or magnetic metal or resin. This conveys a thin layer of toner 8.

A developing roller 9 made of a specific elastic material is pressed against the surface of the photosensitive layer 3 of the latent image carrier 1 with a predetermined pressure, and when the toner 8 on the developing roller 9 is conveyed to the pressed portion, The toner 8 charged according to the potential contrast of the latent image carrier 1 and the developing electric field by the developing bias applying means 14 adheres to the photosensitive layer 3, whereby the electrostatic latent image is visualized. Furthermore, the toner image is transferred onto the recording paper 16 using a transfer device 15 such as a corona transfer device or a transfer roller, and the transferred toner is fixed onto the recording paper by heat or pressure to form a desired image on the recording paper. Can be done. The toner 8 remaining on the latent image carrier 1 after transfer is removed by the cleaning blade 1.
The latent image carrier 1 is removed from the surface of the latent image carrier 1 by step 7 and initialized by the neutralizing light irradiated onto the photosensitive layer 3 from the neutralizing light source 18, and is subjected to the next electrostatic latent image formation.

The above is an outline of the image forming apparatus. In the method of the present invention, a high γ type photoreceptor was used as the material constituting the photosensitive layer 3. As a high γ photoreceptor,
As shown in FIG. 2A, a phthalocyanine-based single-layer positively charged organic photoreceptor was used.

In a printer as shown in FIG. 1, the surface roughness of the photosensitive layer 3 is determined by the volume average particle diameter (
When line images, character images, and solid images were continuously formed on 10,000 sheets using the latent image carrier 1 whose particle diameter was 50 times or less, preferably about 30 times the volume average particle diameter (approximately 10 nm), the line images became line thick. The dots are formed stably without any distortion, and the dots are formed with good reproducibility and a good gray scale is obtained, resulting in trailing at the edge of the character image (toner scattering at the trailing edge) and background fog (toner adhesion to non-image areas).
It was possible to stably form a high-density, even solid image with an OD value of 1.4 or higher.

(Comparative Example 1) A high γ type photoreceptor was used as the material constituting the photosensitive layer 3 described above. As the high-γ photoreceptor, a phthalocyanine-based single-layer positively charged organic photoreceptor shown in FIG. 2A was used.

Using a printer as shown in FIG. 1, the surface roughness of the photosensitive layer 3 was set to 1 μm, and the volume average particle diameter of the external additive of the toner 8 was set to about 10 nm, and 10,000 line images, character images, and solid images were printed on 10,000 sheets. When continuously formed, line widths were not constant in line images, and image outputs with unstable OD values were obtained even in solid images. Furthermore, toner adhesion to non-image areas also occurred.

(Example 2) A high γ type photoreceptor was used as the material constituting the photosensitive layer 3 described above. As the high-γ photoreceptor, a functionally separated two-layer organic photoreceptor shown in FIG. 2C was used.

In a printer as shown in FIG. 1, the surface roughness of the photosensitive layer 3 is determined by the volume average particle diameter (1
Using a latent image carrier 1 whose size is about 20 times that of (around 0 nm),
10,000 line images, character images, and solid images
When continuously formed over multiple sheets, line images were formed stably without line thickening, dots were formed with good reproducibility, and a good gray scale was obtained, and there was no tailing at the edge of the character image (toner scattering at the trailing edge). It was possible to stably form a solid image with no background fog (adhesion of toner to non-image areas) and a high density with an OD value of 1.4 or more and no unevenness.

[0026]

[Effects of the Invention] In the image forming apparatus according to the present invention,
A high γ type photoreceptor is used as the photoreceptor that forms the electrostatic latent image, and the surface roughness of the photoreceptor is made smaller than 50 times the volume average particle diameter of the external additive of the toner on the toner conveying member of the developing device. This improves the cleaning characteristics of the photoconductor, reduces damage and deterioration to the photoconductor caused by cleaning blades and toner, and enables the use of high-γ type photoconductors, which reduces digital light input to the photoconductor due to high γ. This has the effect of enabling high-resolution image formation.

Furthermore, since the charging potential is stabilized, it is possible to form an image without density unevenness.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional schematic diagram of a printer in an embodiment of the present invention.

FIG. 2 is a diagram showing light attenuation characteristics of a photoreceptor.

FIG. 3 is a distribution diagram of the amount of light on a photoreceptor.

FIG. 4 is a distribution diagram of absolute values of surface potential when a conventional photoreceptor is exposed to light.

FIG. 5 is a distribution state diagram of absolute values of surface potential when a high γ type photoreceptor is exposed to light.

[Explanation of symbols]

1 Latent image carrier 2 Conductive support part 3 Photosensitive layer 4 Corona charger 5 Light source 8 Toner 9 Developing roller 10 Shaft 11 Elastic layer 12 Thin film member 14 Development bias application means 15 Corona transfer device 16 Recording paper 17 Cleaning blade 18 Static elimination light source 21 Developing device 22 Elastic blade

Claims (1)

[Claims] 1. An image forming apparatus using an electrophotographic process that forms an image by forming an electrostatic latent image on a high γ type photoreceptor and developing this electrostatic latent image, wherein the surface roughness of the photoreceptor is An image forming apparatus characterized in that the diameter is smaller than 50 times the volume average particle diameter of an external additive of toner on a toner conveying member of a developing device.