JPH04337735A - Image forming device - Google Patents

Abstract

PURPOSE:To provide a printer which forms an image with high resolution by digital light input. CONSTITUTION:In a printer using an electrophotographic process that an electrostatic latent image is formed on a high gamma type photosensitive body and developed so as to form the image, the dark surface resistance of the photosensitive body is set to >=10<15>OMEGA/cm<2>. Thus, the electrostatic latent image on the photosensitive body by the digital light output is held without being spoiled until developing.

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 value in the prior art described above is capable of forming an electrostatic latent image by inputting digital light, it is not possible to form an electrostatic latent image at high temperatures or high humidity or when continuously forming an image. When printing is performed, there is a problem in that image deletion occurs and the quality of the image deteriorates, making it impossible to form a high-resolution image.

The present invention has been made in view of the above-mentioned prior art, and is capable of producing sharp, high-resolution images without deteriorating the photosensitive characteristics of the high-γ type photoreceptor even at high temperatures and high humidity or when printing continuous images. The purpose is to provide an image forming apparatus for obtaining images.

[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 dark surface resistance of the photoreceptor is 1015Ω/cm.
It is characterized by being 2 or more.

[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 dark surface resistance of the photoreceptor can be reduced to 10
By setting the resistance to 15 Ω/cm2 or more, there will be no deterioration in image quality even when images are formed at high temperatures and high humidity or continuously.
It becomes possible to use a high-γ type photoreceptor, and high-resolution image formation becomes possible. When images are formed continuously, chloride ions, sulfide ions, etc. contained in the paper are adsorbed onto the photoreceptor, reducing the surface resistance of the photoreceptor. When the surface resistance decreases, charge leaks in the surface direction, and the surface potential difference forming the electrostatic latent image cannot be maintained, resulting in image deletion. Therefore, in order to prevent image deletion, it is effective to set the surface resistance of the photoreceptor to 1015 Ω/cm2 or more.

[0012] The above-mentioned high-gamma type photoreceptor has its own unique photosensitivity characteristics, but 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 show 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.

[0016]

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 positively charging the photosensitive layer 3 using a light source 5 such as a laser or LED, a potential contrast is obtained by selectively irradiating light from a light source 5 such as a laser or an LED to the photosensitive layer 3 according to the image through an imaging optical system 6. 3, an electrostatic latent image is formed.

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 negatively charged in accordance with 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, thereby making the electrostatic latent image visible. 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 the transfer is removed from the latent image carrier 1 by the cleaning blade 17, and the latent image carrier is initialized by the neutralizing light irradiated onto the photosensitive layer 3 from the neutralizing light source 18. 1 is used for 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 the high-γ type photoreceptor, a phthalocyanine-based single-layer positively charged organic photoreceptor shown in A of FIG. 2 was used.

Photosensitive layer 3 in an atmosphere of 20° C. temperature and 50% humidity.
When a latent image carrier with a surface resistance of 1 x 1015 Ω/cm2 was used in a printer as shown in Fig. 1 to continuously form line images, character images, and solid images on 10,000 sheets, the line images became thicker. A high-density solid image with an OD value of 1.4 or more, which is stably formed without any trailing at the edge of the character image (toner scattering at the trailing edge) or background fog (toner adhesion to non-image areas). could be formed stably.

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

Photosensitive layer 3 in an atmosphere of temperature 33° C. and humidity 90%.
When the surface resistance was measured, it was 3×1013Ω/cm2
Met. When line images, character images, and solid images were continuously formed under this atmosphere using a printer as shown in FIG. 1, image deletion occurred and good images could not be obtained.

(Example 2) A high γ type photoreceptor was used as the material constituting the photosensitive layer 3 described above. As the high-γ type photoreceptor, a phthalocyanine-based single-layer positively charged organic photoreceptor shown in A of FIG. 2 was used. A coating solution containing a mixture of urethane and silicone and diluted with n-BuoH was dip coated onto the photosensitive layer 3, and dried at 120°C to form a surface protective layer. The surface resistance of this latent image carrier with a surface protective layer was measured at a temperature of 33°C.
When measured in an atmosphere with 90% humidity, it was 1.5 x 1015
It was Ω/cm2. When line images, character images, and solid images were continuously formed on 10,000 sheets using a latent image carrier with a surface protective layer in the printer shown in Figure 1 in this atmosphere, the line images did not become thick. It was possible to stably form a high-density solid image with an OD value of 1.4 or more without trailing or background fog at the edges of character images.

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

Photosensitive layer 3 in an atmosphere of temperature 30° C. and humidity 50%
When a latent image carrier with a surface resistance of 1 x 1015 Ω/cm2 was used in a printer as shown in Fig. 1 to continuously form line images, character images, and solid images on 10,000 sheets, the line images became thicker. A high-density solid image with an OD value of 1.4 or more, which is stably formed without any trailing at the edge of the character image (toner scattering at the trailing edge) or background fog (toner adhesion to non-image areas). could be formed stably.

[0026] As the surface protective layer, acrylic resin, epoxy resin, polyvinyl butyral, cellulose derivative, etc. can be used. Materials other than those listed can be used as long as they can be held.

[0027]

[Effects of the Invention] In the image forming apparatus according to the present invention,
By using a high γ type photoreceptor as the photoreceptor that forms the electrostatic latent image and setting the dark surface resistance of the photoreceptor to 1015 Ω/cm2 or more, the electrostatic latent image is maintained without deterioration until the time of development. The high γ value allows digital light to be input to the photoreceptor, which has the effect of enabling high-resolution image formation.

[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 Charger 5 Light source 8 Toner 9 Developing roller 10 Shaft 11 Elastic layer 12 Thin film member 14 Development bias application means 15　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 the electrostatic latent image, the image forming apparatus comprising: An image forming apparatus characterized by having a surface resistance of 1015 Ω/cm2 or more.