JP2002357943A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve unevenness in an image of a full color print in an a-Si type photoreceptor. SOLUTION: In the apparatus, the processing time for electrifying, exposing and developing processes are made the same by making developing positions for each color the same for the a-Si type photoreceptor.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device used for an electrophotographic or electrostatic recording device.

[0002]

2. Description of the Related Art In an image forming apparatus for electrostatically transferring a toner image electrostatically formed on the surface of an image carrier to a sheet-like recording member such as paper adhered thereto, a conductive member is used as a transfer member. The one using a transfer roller or a corona charger is well known. In this image forming apparatus, the transfer member is pressed against or brought close to the image carrier, a transfer nip is formed between the image carrier and the transfer member, and the recording material is passed through the transfer nip portion. The toner image on the image carrier is transferred to the recording member surface by applying a bias voltage having a polarity opposite to that of the toner image to the recording member.

The photosensitive member used for the electrophotographic image forming apparatus on which an image is formed as described above is an organic photosensitive member or an amorphous silicon photosensitive member (hereinafter referred to as “a-S”).
System photoreceptor ". ) Is often used, but the a-Si-based photoreceptor has a high surface hardness, exhibits high sensitivity to semiconductor lasers and the like, and is hardly deteriorated by repeated use. And a photoreceptor for electrophotography such as a laser beam printer (LBP).

FIG. 4 is a schematic configuration diagram for explaining still another layer configuration of the photosensitive member for an image forming apparatus according to the present invention. The photoconductor 700 for an image forming apparatus shown in FIG.
A photosensitive layer 702 is provided on a support 701 for a photosensitive member. The photosensitive layer 702 is composed of a photoconductive layer 703 made of a-Si: H, X and having photoconductivity.

The photosensitive member 700 for an image forming apparatus shown in FIG. 4B has a photosensitive layer 702 provided on a support 701 for the photosensitive member. The photosensitive layer 702 is a-S
i: Photoconductive layer 703 made of H and X and having photoconductivity
And an a-Si-based surface layer 704.

Further, as shown in FIGS. 4C to 4F, a-S
An i-type charge injection blocking layer 705 is provided,
May be composed of a charge generation layer 707 and a charge transport layer 708 made of a-Si: H, X, and an a-Si-based surface layer 704. The support may be a conductive or electrically insulating support subjected to a conductive treatment.

The photoconductive layer 7 constituting a part of the photosensitive layer 702
03 is formed on the support 701 and, if necessary, on an undercoat layer (not shown), and is formed by plasma CVD (hereinafter, p-CV).
It can be formed by a known thin film deposition method such as D) method, sputtering method, vacuum evaporation method, ion plating method, photo CVD method, thermal CVD method and the like. As the p-CVD method, p-CVD using an RF band, a VHF band, and a μW band is used, and each of the above layers is manufactured by a known apparatus and a film forming method. In the present invention, the layer thickness of the photoconductive layer 703 is appropriately determined as desired from the viewpoint that desired electrophotographic characteristics are obtained, the electric capacity in a use state falls within the above-described range, economic effects, and the like. , Preferably 20 to 50 μm.

[0008]

However, the above a-S
The i-type photoreceptor has a problem that dark decay is large as compared with an organic photoreceptor usually used in a full-color electrophotographic apparatus.

For this reason, when an a-Si photosensitive member is used in a conventional color copying machine as shown in FIG. 5, the potential after charging and exposure at the developing position of each color differs, and a difference occurs in the developing contrast of each color. In addition, there is a problem that color unevenness occurs due to a difference in gradation reproducibility of each color, and that a sufficient developing contrast cannot be obtained at a developing position far from the exposure position.

[0010]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has a photoconductive image carrier, a charging device for charging the surface of the image carrier, and a charged image carrier. Exposure means for exposing the surface of the carrier to form an electrostatic latent image, a developing device for developing the electrostatic latent image to form a toner image, and transferring the toner image formed on the image carrier to a transfer material In a full-color digital electrophotographic apparatus having a unit for transferring and fixing, a configuration is adopted in which developing devices for each color perform development at the same position on the photoconductor.

As described above, the development is always performed at the same position on the photoconductor, so that the developing device for each color performs development at the same position on the photoconductor. It is possible to obtain between the developing sleeve and the photoconductor, and it is possible to obtain a good image without color unevenness even when using the a-Si photoconductor.

[0012]

FIG. 4 is a schematic sectional view showing the structure of an a-Si photosensitive member used in this embodiment.
In the photoconductor 700 for an image forming apparatus shown in FIG. 4A, a photosensitive layer 702 is provided on a support 701 for the photoconductor. The photosensitive layer 702 is composed of a photoconductive layer 703 made of a-Si: H, X and having photoconductivity.

The photosensitive member 700 for an image forming apparatus shown in FIG. 4B has a photosensitive layer 702 provided on a conductive support 701 made of Al or the like for the photosensitive member.
The photosensitive layer 702 includes a photoconductive layer 703 made of a-Si: H, X and having photoconductivity, and an a-Si based surface layer 704.

Further, as shown in FIGS. 4C to 4F, a-S
i-system charge injection blocking layer 705 (here, charge injection blocking layer 7
Reference numeral 05 denotes a block for preventing charge injection from the conductive support 701 to the photoconductive layer 703, and is provided as necessary. ), Or the photoconductive layer 703 is made of a-Si:
H, X charge generation layer 707 and charge transport layer 7
08 and an a-Si-based surface layer 704. Here, the problems solved in the present invention will be described.

The method of manufacturing an aS-based photoreceptor is as follows. Since the gas is solidified by turning the gas into plasma with high frequency or microwave, and deposited on an aluminum cylinder to form a film, if the plasma is not uniform, it is formed on an aluminum cylinder. The characteristics of the film to be formed are non-uniform.

As a result, potential unevenness of about 20 V has occurred in the developing section. This is due to the phenomenon that the difference in electrostatic capacity due to the unevenness of the film thickness causes the difference in the charging ability, and the potential decay between the charging and the development due to the pre-exposure used for erasing the optical memory in the front circumference is caused by A difference occurs due to the difference in the potential attenuation characteristics of the entire surface, and the difference is caused by further increasing the potential unevenness in the developing unit.

The above optical memory will be described.
When the photoreceptor is charged and subjected to image exposure, photo carriers are generated and the potential is attenuated. However, at this time, the a-Si photoreceptor has many tangling bonds (unbonded bonds), which become localized levels and capture a part of the optical carrier to lower its traveling property. Alternatively, the recombination probability of the photogenerated carrier is reduced. Therefore, in the image forming process, a part of the photocarriers generated by exposure is released from the localized level at the same time when an electric field is applied to the a-Si photoconductor at the time of charging in the next step, and is released from the exposed portion and the unexposed portion. This causes a difference in the surface potential of the a-Si photosensitive member, and this finally becomes an optical memory.

Therefore, it is general to erase the optical memory by performing uniform exposure in the pre-exposure step so that the number of photo carriers latent in the a-Si photosensitive member becomes excessive and uniform over the entire surface. . At this time, the amount of pre-exposure emitted from the pre-exposure source is increased or the wavelength of pre-exposure is set to a
-The spectral sensitivity peak of the Si photoreceptor 7 (about 680 to 700
nm), the optical memory (ghost) can be erased more effectively.

However, if the a-Si photoreceptor has a film thickness unevenness or a difference in potential attenuation characteristics due to a difference in film quality as described above, the electric field applied between the photoconductive layers is different.
There is a difference in the release of the photocarrier from the above-mentioned localized level, and even if the charging unit can charge uniformly, the potential unevenness occurs in the developing unit. Also, the charging ability is disadvantageous because the smaller the film thickness, the greater the capacitance, and the lower the charging ability, the more uneven the charging in the developing section becomes.

The present invention employs the following configuration in order to eliminate the difference in development characteristics due to the dark decay characteristics of the a-Si photosensitive member. FIG. 1 is a schematic sectional view of the image forming apparatus used in the first embodiment of the present invention.

In this embodiment, in order to eliminate the image defect due to the difference in the potential attenuation characteristics of the a-Si photosensitive member, a-S
To develop each color at the same position on the i-type photoconductor,
A magenta developing unit 1M, a cyan developing unit 1C, and a developing unit 1 are rotatably arranged near the a-Si photosensitive member 7.
Developing devices of a yellow developing device 1Y and a black developing device 1Bk are arranged.

FIG. 2 is a view showing the relationship between the developing unit 1 and the a-Si photosensitive member 7. In the magenta developing device 1M, the developing unit 1 and the a-Si photoreceptor 7 are arranged on a straight line connecting the center.
It is disposed so as to face the -Si photoconductor 7 and to have a distance between the developing sleeve and the surface of the a-Si photoconductor of 200 µm to 1 mm (500 µm in this embodiment).

The developing unit 1 is rotatable in the direction of the arrow, and the developing units (1) for each color other than the magenta developing unit 1M are provided.
C, 1Y1, and Bk) are arranged at predetermined positions (the position of the magenta developing device 1M in FIG. 2) by rotating the developing unit 1 when developing each color. An actual full-color image is formed in the following procedure.

The a-Si type photoreceptor 7 is uniformly charged by the primary charger 2 and then subjected to image exposure with a laser beam E modulated by a magenta image signal to form an electrostatic latent image, which is developed in advance. The development is performed by the magenta developing device 1M fixed at the position.

The developed magenta toner image is transferred onto the transfer material adsorbed on the transfer drum 5, and the a-Si photoreceptor 7 is cleaned by the cleaning means, charged again by the primary charger 2, and charged to the next charger. Image exposure is performed by a cyan image signal.

During this time, the developing unit 1
After performing rotation, the next cyan developing unit 1C is fixed at a predetermined developing position to perform cyan developing.

Subsequently, the above steps are performed for yellow and black, respectively, and toner images of four colors are transferred to the transfer material adsorbed on the transfer drum. The transfer material after the transfer is peeled off from the transfer drum and sent to a fixing device (hot-press roller fixing device) 6, where a full-color print image is formed.

During the image formation, the developing units for each color and a
-Si-based photoreceptor 7 is always developed at the same position, so that the time required for the process from charging to exposure to development is always the same. As a result, a stable developing contrast can be obtained between the developing sleeve and the photoconductor, and a good image without color unevenness can be obtained even when an a-Si photoconductor is used.

(Embodiment 2) FIG. 2 is a schematic sectional view of an image forming apparatus used in a second embodiment of the present invention. In this embodiment, in order to eliminate image defects due to the difference in the potential attenuation characteristics of the a-Si photosensitive member, development of each color is performed at the same position on the a-Si photosensitive member 7. In the developing unit 1 arranged in the vicinity of the photoconductor 7 so as to be movable in the horizontal direction, magenta developing units 1M, cyan developing units 1C, yellow developing units 1Y, and black developing units 1Bk are arranged.

In the magenta developing device 1M, the developing unit 1 and the a-Si photosensitive member 7 are opposed to the a-Si photosensitive member 7 on a straight line connecting the center, and the developing sleeve and the surface of the a-Si photosensitive member 7 Is 200 μm to 1 mm (500 mm in this embodiment).
μm).

The developing unit 1 is rotatable in the direction of the arrow, and the developing units (1) for each color other than the magenta developing unit 1M are provided.
C, 1Y1, and Bk) are arranged at predetermined positions (the position of the magenta developing device 1M in FIG. 2) by rotating the developing unit 1 when developing each color. The formation of a full-color image is performed in the following procedure.

The a-Si type photoreceptor 7 is uniformly charged by the primary charger 2, and then subjected to image exposure by a laser beam E modulated by a magenta image signal, thereby forming an electrostatic latent image and developing in advance. The development is performed by the magenta developing device 1M fixed at the position.

The developed magenta toner image is transferred onto the transfer material adsorbed on the transfer drum 5, the a-Si based photoreceptor 7 is cleaned by the cleaning means, charged again by the primary charger 2, and then charged to the next. Image exposure is performed by a cyan image signal.

During this time, the developing unit 1 moves horizontally in the direction of arrow B, and the next cyan developing unit 1C is fixed at a predetermined developing position to perform cyan developing.

Subsequently, the above steps are performed for yellow and black, respectively, and the toner images of four colors are transferred to the transfer material adsorbed on the transfer drum.

The transfer material after the transfer is peeled off from the transfer drum and sent to a fixing device (heat-pressure roller fixing device) 6, where a full-color print image is formed.

During the image formation, the developing units for each color and a
-Si-based photoreceptor 7 is always developed at the same position, so that the time required for the process from charging to exposure to development is always the same.

As a result, a stable developing contrast can be obtained between the developing sleeve and the photosensitive member, and a-S
Even when an i-type photoreceptor is used, a good image without color unevenness can be obtained.

[0039]

According to the present invention, by making the processing time such as charging, exposure and development the same for each color developing device, a stable contrast can be obtained when developing each color, and each color is stable. It is now possible to obtain improved gradation.

As a result, even when an a-Si photosensitive member is used, a good image without unevenness can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an image forming apparatus according to a first embodiment of the present invention.

FIG. 2 is a configuration diagram of a developing unit used in a first embodiment of the present invention.

FIG. 3 is a schematic configuration diagram of an image forming apparatus according to a second embodiment of the present invention.

FIG. 4 is an explanatory view of a photosensitive member used in the present invention.

FIG. 5 is a schematic configuration diagram of a conventional color copying machine. 1 Developing unit 2 Primary charger 3 Exposure system 4 Cleaner 5 Transfer drum 6 Fixing device 7 Photoreceptor 8 Original plate 700 Photoreceptor 701 Support 702 Photosensitive layer 703 Photoconductive layer 704 surface layer 705 charge injection blocking layer 706 free surface 707 charge generation layer 708 charge transport layer

Claims (4)

[Claims] 1. A photoconductive image carrier, a charging device for charging a surface of the image carrier, an exposing means for exposing a charged image carrier surface to form an electrostatic latent image, and In a digital full-color electrophotographic apparatus having a developing device that develops an electrostatic latent image to form a toner image and a unit that transfers and fixes the toner image formed on the image carrier to a transfer material, the developing device for each color is And an image forming apparatus for performing development at the same position on a photosensitive member. 2. The image forming apparatus according to claim 1, wherein said image carrier has a photoconductive layer made of a non-single-crystal material containing hydrogen atoms and / or halogen atoms having silicon atoms as a base. apparatus. 3. The image forming apparatus according to claim 1, wherein each of the developing devices to be used is rotatably disposed near the photosensitive member. 4. The image forming apparatus according to claim 1, wherein each of the developing devices to be used is slidably disposed near the photosensitive member.