JPH09197778A - Color image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the scattering of a superimposed toner image in a pretransfer area and to eliminate image blurring by reducing simultaneous-transfer exposing light to the pretransfer area. SOLUTION: At the time of performing simultaneous-transfer exposure to the superimposed toner image from a simultaneous-transfer exposure device 121 provided inside a photoreceptor drum 10 in the case of transfer, the simultaneous-transfer exposing light L1 is made incident on an image forming body again by the scattering of light by transfer paper P as transfer material. Then, the superimposed toner image in the pretransfer area is discharged, and the toner image is scattered, which is the cause of the image blurring. When it is assumed that the half decay exposure of the image forming body is E0 , transmissivity is T(%), and the exposure at the position of the inner peripheral surface of the transparent base substance of the image forming body by the simultaneous-transfer exposure means is L, in such a case, the minimum exposure L×T necessary to drop the potential by electrification of the image forming body in the transfer area is set to <=2×E0 , thereby, the scattering of light to the pretransfer area becomes considerably smaller than 2×E0 , and the scattering of the superimposed toner image in the pretransfer area is prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile, etc., in which a plurality of sets of charging means, image exposing means and developing means are arranged around the image forming body. The present invention relates to an electrophotographic color image forming apparatus that forms a color image by superimposing toner images during one rotation.

[0002]

2. Description of the Related Art Conventionally, as a method for forming a multicolored image, an image forming body, a charging means, a developing means, etc., which are the same in number as the colors necessary for forming an image, are provided, and a single color formed on each image forming body Image forming apparatus that forms a color image by superimposing the toner image on the transfer material to form a color image, and forms a color image by repeating charging, image exposure and development for each color by rotating the image forming body a plurality of times. There is known an apparatus or a color image forming apparatus which forms a color image by sequentially performing charging, image exposure and development within one rotation of the image forming body.

However, each of the image forming apparatuses described above is provided with the same number of image exposing means, charging means, developing means and the like as the colors required for image formation, and the monochromatic toner images formed on the photoconductors are respectively superposed on the transfer material. A color image forming apparatus for forming a color image has a drawback that the volume of the apparatus is increased because a plurality of image forming bodies and transfer materials need to be conveyed. On the other hand, by rotating the image forming body a plurality of times, each color A color image forming apparatus that forms a color image by repeating charging, image exposure, and development has a smaller volume, but has a limitation that the size of the formed image is limited to the surface area of the photoreceptor or less.

In view of this, a color image forming apparatus which forms a color image by sequentially performing charging, image exposure and development within one rotation of the image forming body has no restriction on the size of the image and is capable of high speed image formation. There are advantages such as Furthermore,
For example, JP-A-5-307307 proposes a device in which a transparent substrate is used as a substrate of an image forming body and an image exposing means is arranged inside the image forming body to downsize the apparatus.

[0005]

However, in a color image forming apparatus in which a transparent substrate is used as a substrate of an image forming body and a color image is formed by sequentially performing charging, image exposure and development within one rotation of the image forming body. During the transfer,
Since the transfer rate is low because the superposed toner images have been recharged or the toner layers have been overlapped and thick, it is necessary to eliminate charge by exposure during transfer in order to improve the transfer rate. As a result of experiments conducted by the inventors, when the simultaneous transfer and exposure were performed from the back surface of the image forming body, there was a problem that the superimposed toner images were scattered and the image was blurred.
That is, the transfer simultaneous exposure light is re-incident on the image forming body due to the light scattering by the transfer paper (especially when a white paper is used) as the transfer material, and the superposed toner image in the area before the transfer is destaticized to remove the toner. The image was scattered, which was a cause of image blur.

The present invention improves and solves the above problems,
An object of the present invention is to provide a color image forming apparatus that prevents the toner image in the area before transfer due to the simultaneous transfer exposure light from scattering during the simultaneous transfer exposure.

[0007]

The object of the present invention is to provide a charger for charging an image forming body around a rotating image forming body,
A plurality of sets of image exposing means for exposing a charged image forming body to form a latent image and a developing device for developing the latent image formed on the image forming body to form a toner image are arranged, and the image forming is performed. A plurality of toner images are formed on the image forming body by sequentially repeating charging of the image forming body by the charging device, image exposure by the image exposing means, and development by the developing device during one rotation of the body. In a color image forming apparatus that superimposes the toner images of, and then collectively transfers the superimposed toner images to a transfer material by a transfer device, the base of the image forming body is a transparent base, and the inside of the image forming body is The image exposure unit and the transfer simultaneous exposure unit that faces the transfer unit and performs exposure when the superimposed toner images are transferred to the transfer material are provided to reduce the half-exposure amount of the image forming body. E _0, the transmittance of the image forming body T When the exposure amount in the transparent substrate in the peripheral surface position of the transfer simultaneous exposure unit and L, L × T ≦
It is achieved by a color image forming apparatus characterized by being 2 × E ₀ .

[0008]

Embodiments of the present invention will be described below. Note that the description in this column does not limit the technical scope of the claims and the meaning of terms. Also, the following assertive description in the embodiment of the present invention indicates the best mode, and does not limit the meaning of the terms of the present invention or the technical scope.

An image forming process and each mechanism of an embodiment of a color image forming apparatus of the present invention will be described with reference to FIGS.
This will be described with reference to FIG. 1 is a cross-sectional configuration diagram of a color image forming apparatus showing one embodiment of the present invention, and FIG.
FIG. 3 is an enlarged view of a main part of a transfer area according to the present invention.
FIG. 4 is an enlarged view of an essential part of FIG. 2, showing light scattering due to transfer simultaneous exposure, and FIG. 4 is a view showing a light attenuation characteristic curve of the image forming body.

As shown in FIG. 1, the image forming apparatus of the present invention uses an image forming body in which the base of the image forming body is made of a transparent material and a photosensitive layer is provided on the outer peripheral surface of the transparent base. Further, as shown in FIG. 1, an image exposure means and a transfer simultaneous exposure means are provided inside the image forming body, and an image forming process means such as a charger, a developing device, a transfer device, a static eliminator and a cleaning device is provided outside. Is the structure where is arranged.

The photosensitive drum 10, which is an image forming body, is provided with a cylindrical substrate formed of a transparent member of transparent acrylic resin inside, and a transparent conductive layer, an a-Si layer or an organic photosensitive layer (OPC). ) Is formed on the outer circumference of the substrate, and is rotated clockwise in the state of being grounded as shown by the arrow in FIG.

In the present embodiment, it is sufficient that the photoconductive layer of the photosensitive drum has an exposure light amount capable of giving an appropriate contrast. Therefore, the light transmittance of the transparent substrate of the photosensitive drum in the present embodiment does not need to be 100%, and may have a characteristic that some light is absorbed when the exposure beam is transmitted. As the material of the translucent substrate, an acrylic resin, particularly one polymerized using methyl methacrylate monomer, has transparency, strength, accuracy,
Acrylic, fluorine used for other general optical members, etc.
Various translucent resins such as polyester, polycarbonate, and polyethylene terephthalate can be used. The light-transmitting conductive layer was made of indium tin oxide (ITO), tin oxide, lead oxide, indium oxide, copper iodide, Au, Ag, Ni, Al, etc. A metal thin film is used, and as a film forming method, a vacuum vapor deposition method, an active reaction vapor deposition method, various sputtering methods, various CVs.
D method, dip coating method, spray coating method and the like are used.
Further, as the photoconductor layer, amorphous silicon (a
-Si) alloy photosensitive layer, amorphous selenium alloy photosensitive layer, and various organic photosensitive layers (OPC) can be used.

The scorotron charger 11 as a charger is used in the image forming process of each color of yellow (Y), magenta (M), cyan (C) and black (K), and is the photosensitive drum 10 as an image forming body. As a control grid and a discharge electrode, which are attached to face the photoconductor drum 10 in a direction orthogonal to the moving direction of the photoconductor, and are held at a predetermined potential with respect to the above-mentioned organic photoconductor layer of the photoconductor drum 10. The charging action is performed by corona discharge using the electrode 11a, and a uniform potential is applied to the photoconductor drum 10. Other wire electrodes may be used as the discharge electrodes.

As shown in FIG. 1, the exposure unit 12 as the image exposure means for each color determines the exposure position on the photosensitive drum 10 by the sharp electrode 11a of the scorotron charger 11.
And the leading end of the development control electrode 139 provided in the developing device 13, it is arranged in a state of being provided on the upstream side in the rotation direction of the photosensitive drum with respect to the developing sleeve 131.

The exposure unit 12 is an L-shaped light emitting element arranged in the main scanning direction in parallel with the axis of the photosensitive drum 10.
A linear exposure element 12a in which a plurality of EDs (light emitting diodes) are arranged in an array and a SELFOC lens 12b as an equal-magnification imaging element are configured as an exposure unit attached to a holder (not shown). . The exposure unit 12 is
Exposure unit 1 included in the photosensitive drum 10
The image data of each color stored in the memory is sequentially read out from the memory and is input to the exposure unit 12 for each color as an electric signal.

As the exposure element, there is a linear element in which a plurality of light emitting elements such as FL (fluorescent substance emission), EL (electroluminescence), PL (plasma discharge), LED (light emitting diode) are arranged in an array. Used. The emission wavelength of the light emitting element used in this embodiment is usually Y,
A range of 680 to 900 nm, which has a high transmittance of the M and C toners, is preferable, but a shorter wavelength which does not have sufficient transparency for the color toner since image exposure is performed from the back surface may be used.

In the present embodiment, the developing device provided in accordance with the color order in which images are formed and the rotating photosensitive drum is arranged in the rotational direction of the photosensitive drum 10 in the present embodiment. On the other hand, the Y and M developing devices 13 are arranged on the left side of the photoconductor drum 10, and the C and K developing devices 13 are arranged on the right side of the photoconductor drum 10. The Y and M scorotron chargers 11 are arranged below, and the C and K scorotron chargers 11 are arranged above the developing casing 138 of the C and K developing units 13.

The developing device 13, which is a developing means for each color, contains one-component or two-component developers of yellow (Y), magenta (M), cyan (C), and black (K), respectively. A developing sleeve 131 is provided which rotates in the same direction as the rotation direction of the photoconductor drum 10 at the developing position while maintaining a predetermined gap with respect to the peripheral surface of the body drum 10.

The developing device 13 for each color applies the electrostatic latent image on the photosensitive drum 10 formed by the charging by the scorotron charger 11 and the image exposure by the exposure unit 12 to the developing bias voltage and the developing control electrode. Reverse development is performed in a non-contact state by a non-contact developing method by applying a voltage.

As the original image, an image read by an image pickup device of an image reading apparatus separate from this apparatus or an image edited by a computer is temporarily stored as image data for each color of Y, M, C and K in a memory. Store and store in.

At the start of image recording, a photoconductor drive motor (not shown) is rotated to rotate the photoconductor drum 10 in the clockwise direction shown by the arrow in FIG. 1, and at the same time, the left side of the photoconductor drum 10 is colored yellow (Y). Development casing 138 of the developing device 13
The application of a potential to the photosensitive drum 10 is started by the charging action of the Y scorotron charger 11 arranged below the photosensitive drum 10.

After a potential is applied to the photosensitive drum 10, exposure is started by a first color signal, that is, an electric signal corresponding to the Y image data in the Y exposure unit 12, and the surface of the photosensitive drum 10 is exposed by rotational scanning of the drum. An electrostatic latent image corresponding to the Y image of the original image is formed on the layer.

The latent image is reversal-developed by the Y developing device 13 in a state where the developer on the developing sleeve is not in contact with the developer, and a yellow (Y) toner image is formed in accordance with the rotation of the photosensitive drum 10.

Next, the photosensitive drum 10 is placed on the magenta (M) developing unit 1 on the yellow (Y) toner image and further on the left of the photosensitive drum 10 and above the yellow (Y).
3 is provided with a potential by the charging action of the magenta (M) scorotron charger 11 disposed below the developing casing 138, and an electric signal corresponding to the second color signal of the M exposure unit 12, that is, the image data of M. Exposure is performed by non-contact reversal development by the developing device 13 of M, and magenta (M) is formed on the yellow (Y) toner image.
Are sequentially superimposed and formed.

By the same process, the developing casing 13 of the cyan (C) developing device 13 is provided on the right side of the photosensitive drum 10.
8, a cyan (C) scorotron charger 11, an exposure unit 12 of C, and a developing device 13 of C are provided on the cyan toner image of cyan (C) corresponding to the third color signal. The black (K) scorotron charger 11, the exposure unit 12, and the developing unit 13, which are arranged on the right side of the drum 10 and below the C, above the developing casing 138 of the black (K) developing unit 13, make the fourth color. A black (K) toner image corresponding to the signal is sequentially superimposed and formed, and a color toner image is formed on the peripheral surface of the photosensitive drum 10 within one rotation.

Exposure unit 1 for Y, M, C and K
Exposure of the organic photosensitive layer of the photosensitive drum 10 by 2 is performed from the inside of the drum through the transparent substrate described above. Therefore, the exposure of the images corresponding to the second, third, and fourth color signals is performed without any influence from the previously formed toner image, and the same exposure as the image corresponding to the first color signal is performed. It is possible to form an electrostatic latent image.

The developing unit 13 is set in a gap of a predetermined value from the photosensitive drum 10 by an abutting roller (not shown), for example, 100 μm.
.About.1000 .mu.m and kept in a non-contact state, and when developing by the developing device 13 for each color, the developing sleeve 131
To the developing control electrode 139, a developing bias applied with a DC voltage or an AC voltage is applied to the developing control electrode 139. Non-contact reversal development is performed by applying a DC bias of the same polarity as the toner to the photoconductor drum 10 whose ground is the conductive layer to attach the toner to the exposed portion.

A transfer sheet P, which is a transfer material, is sent out from a sheet feeding cassette 15 which is a transfer material storing means, and is conveyed to a timing roller 16. In the transfer section, the photosensitive drum 1
The color superposed toner image formed on the peripheral surface of No. 0 has a function of removing static electricity so that good transfer is performed. Therefore, the fixing member 20 provided inside the photosensitive drum 10 is used.
The transfer paper P, which is a transfer material that is fed in synchronization with the toner image on the photosensitive drum 10 by being driven by the timing roller 16 by being exposed by the transfer simultaneous exposure device 121 as the transfer simultaneous exposure means supported by The image is transferred by the transfer roller 14a as a transfer device.

In the transfer section (transfer area) provided with the transfer roller 14a and the separation section (separated charge removing area) provided with the static eliminator 14b, a light source having a width corresponding to the axial length of the photosensitive drum 10 is provided. Transfer simultaneous exposure device 121 as a transfer simultaneous exposure means, such as an exposure lamp or L
Light is removed from the inside of the photoconductor drum 10 by the transfer simultaneous exposure light from the ED, so that the transfer efficiency of the transfer device 14a and the separation performance of the charge remover 14b are improved.

The transfer roller 14a is synchronized with the transfer paper P fed to the transfer portion by the timing roller 16, and the transfer paper P is transferred by the length of the photosensitive drum 10 in the circumferential direction. The control unit provided in the image forming apparatus (not shown) and the transfer unit are provided so that the photosensitive drum 10 is pressed against the photosensitive drum 10 only while the transfer process is not performed, and is separated from the photosensitive drum 10 when the transfer process is not performed. It is operated by the pressure contact release mechanism of the roller. A transfer belt or a corona discharger may be used instead of the transfer roller 14a.

The transfer paper P on which the toner image has been transferred is removed from the drum peripheral surface by removing the charge of the transfer paper P charged at the time of transfer by the static eliminator 14b, and then separated from the drum peripheral surface.
It is conveyed to the fixing device 17 by e. After the toner is welded and fixed on the transfer paper P by being heated and pressure-bonded in the fixing device 17, the toner is discharged from the fixing device 17 and is conveyed by the pair of paper discharging / conveying rollers 18 a, and is discharged onto the tray on the upper part of the device through the paper discharging rollers 18. Then, the transfer paper P is discharged with the toner image on the lower surface.

On the other hand, the photosensitive drum 10 from which the transfer paper is separated
Is rubbed against the surface of the photoconductor drum 10 by the cleaning blade 19a in the cleaning device 19 to remove and clean the residual toner and continue to form the toner image of the original image, or temporarily stop the toner image of a new original image. Formation. The waste toner scraped off by the cleaning blade 19a and the cleaning roller 19b is discharged to a waste toner container (not shown) by the toner conveying screw 19c. After the cleaning is completed, the cleaning blade 19a and the cleaning roller 19b are kept apart from the photoconductor drum 10 in order to prevent damage to the photoconductor drum 10.

The photoconductor drum 10 charged by the scorotron charger 11 when the light is irradiated from the surface of the image forming body.
A light attenuation characteristics curve of the charging potential is shown in FIG. 4, the half decay exposure to the maximum charging potential decayed to V _0/2 of the potential V ₀ which showing the light sensitivity of the image forming member is E ₀ (Lux · sec) of is there.

As shown in FIG. 3, at the time of transfer, when the superimposed toner images are subjected to the transfer simultaneous exposure by the transfer simultaneous exposure device 121 provided inside the photosensitive drum 10, the transfer simultaneous exposure light L1 is generated. Light is re-incident on the image forming body due to light scattering by the transfer paper P as a transfer material (especially light scattering is large when white paper is used), the superimposed toner image in the area before transfer is neutralized, and the toner image is scattered. However, the half-exposure amount of the image forming body was reduced to E ₀ (Lux · s
ec), the transmittance is T (%), and the exposure amount at the position of the inner peripheral surface of the transparent base of the image forming body of the transfer simultaneous exposure means is L (Lux.se).
c), by setting the minimum exposure amount L × T required to reduce the charging potential of the image forming body in the transfer area to 2 × E ₀ or less, the light scattering to the area before transfer is 2 It was confirmed to be much smaller than × E ₀ , and scattering of the superimposed toner image in the area before transfer was prevented. Here, the reason why 2 × E ₀ is set is that the transfer simultaneous exposure light is divided into the upstream and the downstream of the transfer region. Here, E ₀ is a half-exposure amount when the transfer simultaneous exposure light is irradiated from the surface of the image forming body.

Under the above conditions, even if the transfer simultaneous exposure light is scattered by the transfer material during the transfer simultaneous exposure and re-enters the image forming body, the transfer simultaneous exposure light to the area before the transfer is small. It is possible to prevent the superimposed toner images from scattering in the area (3) and form a good color image without image blur. Further, reduction potential of the image forming body at most fit with V _0/2, toner scattering does not occur.

Here, the exposure amount L of the transfer simultaneous exposure means is preferably 2E ₀ or more and 8E ₀ or less. 8
When it is E ₀ or more, the toner image is disturbed and the image forming body is fatigued. Further, by doing so, the photosensitive drum 1
The transfer simultaneous exposure light L2 that is re-reflected on the inner surface of the transparent substrate of 0 is prevented. On the other hand, if it is 2E ₀ or less, the charging potential of the image forming body does not drop, the transfer rate becomes low, and separation failure occurs.

Further, it has been confirmed that it is preferable to reduce the transmittance T of the photoreceptor layer of the image forming body so that the transmittance T is 20% or less to prevent the leakage of the simultaneous exposure light for transfer.

[0038]

According to the first aspect of the present invention, even when the transfer simultaneous exposure light is scattered by the transfer material and is incident on the image forming body again during the transfer simultaneous exposure, the transfer simultaneous exposure light to the area before the transfer is small. The scattering of the superimposed toner image in the area before transfer is prevented, and a good color image without image blur is formed.

According to the second aspect, fatigue of the image forming body is prevented. In addition, the transfer rate does not decrease and the separation failure does not occur without the charging potential of the image forming body decreasing.

According to the third aspect, the light leakage from the image forming body is eliminated and reduced, and the scattering of the superimposed toner image in the area before the transfer is better prevented.

[Brief description of drawings]

FIG. 1 is a cross-sectional configuration diagram of a color image forming apparatus according to an embodiment of the present invention.

FIG. 2 is an enlarged view of a main part of a transfer region according to the present invention in FIG.

FIG. 3 is an enlarged view of a main part of FIG. 2, showing light scattering due to transfer and simultaneous exposure.

FIG. 4 is a diagram showing a light attenuation characteristic curve of an image forming body.

[Explanation of symbols]

 10 Photoreceptor Drum 11 Scorotron Charger 12 Exposure Unit 13 Developer 14a Transfer Roller 121 Transfer Simultaneous Exposure Device P Transfer Paper

Claims (3)

[Claims] 1. A charging device for charging the image forming body around the rotating image forming body, an image exposing means for exposing the charged image forming body to form a latent image, and an image forming means formed on the image forming body. A plurality of sets of developing devices for developing the formed latent image to form a toner image are arranged, and during one rotation of the image forming body, the image forming body is charged by the charger and the image is formed by the image exposing means. After a plurality of toner images are superposed on the image forming body by sequentially repeating the formation of the toner image by the exposure and the development by the developing device, the superposed toner images are collectively transferred to the transfer material by the transfer device. In the color image forming apparatus, the base of the image forming body is a transparent base, and the image exposing means is provided inside the image forming body, and the superimposed toner images are formed on the transfer material so as to face the transfer device. Simultaneous transfer exposure hand that performs exposure during transfer And a half exposure amount of the image forming body is E ₀ , a transmittance of the image forming body is T, and an exposure amount of the transfer simultaneous exposing means at the position of the inner peripheral surface of the transparent substrate is L.
And L × T ≦ 2 × E ₀ . 2. The color image forming apparatus according to claim 1, wherein L = (2 to 8) × E ₀ . 3. The color image forming apparatus according to claim 1, wherein T ≦ 20%.