JPH02275480A - Color electrophotographic device - Google Patents

Abstract

PURPOSE:To preclude fogging after continuous image forming operation by starting destaticization by a transfer charger before a dielectric belt comes into contact with a photosensitive body and finishing the destaticization after the dielectric belt leaves the photosensitive body. CONSTITUTION:A device which composes a toner image on the photosensitive body 39 and brings the dielectric belt 44 into contact with the photosensitive body 39 to transfer a color image from the photosensitive body 39 to paper 45 is so constituted that the transfer charger 48 starts the destaticization before the dielectric belt 44 comes into contact with the photosensitive body 39 and finishes the destaticization after the dielectric belt 44 leaves the photosensitive body 39. Namely, the belt 44 is brought into contact with the photosensitive body 38 while charges are held on the surface of the belt 44. Consequently, the fogging is prevented from being caused after continuous image formation.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a color electrophotographic device that can be used in a hard copy device such as a color copying machine or printer.

Conventional technology In recent years, toner images of different colors are formed on an electrophotographic photoreceptor (hereinafter referred to as photoreceptor) by repeating charging, exposure, and development multiple times, and then the toner images are transferred to paper in bulk. Color electrophotographic devices that obtain color images are being actively studied. This method differs from conventional color electrophotography in that it does not require a transfer drum and has the advantage that the apparatus can be miniaturized.

As this type of color electrophotographic device, for example,
There is a technique disclosed in No. 2-270664.

Hereinafter, an embodiment of the present invention will be described using FIG. 2.

The developing units 1 and 2.3 are non-contact type non-magnetic one-component developing units that use a DC electric field to remove the toner, and the toner is charged by friction with a conductive fur brush 4, 5°6 that is in contact with the developing roller. Aluminum developing rollers 7, 8. 9 on top,
The blades 10, 11, and 12 are configured to form a thin layer of toner.

Yellow (7) is in developer device 1, and magenta (goods) is in developer device 2.

The developing device 3 contains cyan (q) insulating toner.

The developing device 13 is a contact type developing device containing a two-component developer. and developing rollers 7, 8. 9. 14 and photoreceptor 1
The developing devices were disposed facing each other around the photoreceptor 16 with a constant gap (developing gap) between the developing devices and the photoreceptor 16. Each developing device is attached with a separation mechanism that brings it close to the photoreceptor during development and separates it when not developing.

Diameter 1525m with long wavelength sensitization in the infrared region as a photoreceptor
+ amorphous 5e-To photoreceptor drum 16, circumferential speed 1
Rotate at θOnm/m. This photoreceptor 16 is charged to a charging potential of +900 V by a charger 1e (Scorotron charger, corona voltage: +7 KV, grid voltage: 1 KV). Next, the semiconductor laser 17 having a wavelength of 790 nm is caused to emit light for exposure. Using this semiconductor laser 17, a negative black signal is exposed onto the photoreceptor 15 to form an electrostatic latent image.

After the latent image is reversely developed by a black developing device 13 in a developing state with +600 V applied to the developing roller 14 to form a black toner image, the photoreceptor 16 is neutralized by a static eliminating lamp 18 .

Next, use the corona charger 16 again to charge the photoreceptor 15 to +eoov.
is charged with electricity. After that, the semiconductor laser 17 is placed on the photoreceptor 16.
A signal light corresponding to yellow is exposed to form a yellow electrostatic latent image. Next, this photoreceptor is placed on the developing roller 7 by +6
A yellow developer 1 in a developing state with 00V applied and a magenta developer 2 in a non-developing state. The toner toner is passed through a cyan developer 3 and a black developer 13 to form a yellow toner image.

Next, without removing the charge from the photoreceptor 16, the photoreceptor 15 was raised to +81o again by the corona charger 16.
It was charged to v. Thereafter, a semiconductor laser 17 is used to expose a signal light corresponding to magenta to form a magenta electrostatic latent image. Next, the photoreceptor 16 is transferred to the yellow developing device 1 in a non-developing state.
．． A magenta toner image is formed by passing through the magenta developing device 2 in a developing state in which +5 ooV is applied to the developing row 78.

Thereafter, the photoreceptor 15 is passed through the cyan developer 3 and the black developer 14Vc in a non-developing state. Next, this time the photoreceptor 15
AC corona charger 19 (applied voltage: 5 KVrms
), and the photoreceptor 15 is charged to +800V again by the corona charger 16. Thereafter, a semiconductor laser 17 is used to expose the semiconductor laser 17 to signal light corresponding to cyan to form a cyan electrostatic latent image.

Next, the photoconductor 16 is transferred to the yellow developing device 1 and the magenta developing device 2 in a non-developing state. The toner image is passed through the cyan developer 3 in a developing state with +800V applied to the developing roller 9 to form a cyan toner image, thereby completing a color image on the photoreceptor.

The color toner image thus obtained on the photoreceptor 16 is transferred onto paper 21 by a transfer charger 20, and then thermally fixed by a fixing device 22. On the other hand, after the transfer, the surface of the photoreceptor 15 is
Pre-cleaning charger 23 (corona voltage +5.5KV)
After being positively charged, the conductive fur brush 24 to which a voltage of -15 oV has been applied is brought into pressure contact with the photoreceptor 16 for cleaning.

After completing the contact operation between the transfer belt 26 and the photoreceptor 16 in the non-image area on the photoreceptor, the color toner image thus obtained on the photoreceptor 16 is transferred to the nine paper 21 by the corona discharge of the transfer charger 20. Transcribe.

Problems to be Solved by the Invention However, with the above configuration, when transferring a color image formed on a photoreceptor, the paper is brought into close contact with the dielectric belt, and the surface of the paper is pressed against the photoreceptor. Since the toner image is transferred from the back side of the photoreceptor by corona discharge, there is a problem in that capri is generated in a part of the photoreceptor after continuous image formation.

An object of the present invention is to provide a color electrophotographic device that does not cause fogging after continuous image formation in a color electrophotographic device that synthesizes toner images on a photoreceptor and then transfers the toner images onto paper using a dielectric material (V) to obtain a color image. The purpose of the present invention is to provide an electrophotographic device.

Means for Solving the Problems In the present invention, the dielectric belt is connected to the photoreceptor during the process of forming a color image on the photoreceptor by repeating charging, exposure, and reversal development steps using toners of multiple colors. A color electrophotographic apparatus in which the color image on the photoreceptor is transferred to paper by bringing the dielectric belt into contact with the photoreceptor after completing the formation of the color image on the photoreceptor without contacting the photoreceptor, the color electrophotographic apparatus comprising: A color electrophotographic apparatus, wherein the transfer charger starts discharging before the dielectric belt comes into contact with the photoconductor, and the discharging of the transfer charger ends after the dielectric belt is separated from the photoreceptor. It is.

Operation If the transfer charger starts and ends corona discharge while the dielectric belt is in contact with the photoreceptor, after continuous image formation, the area where the DC voltage for transfer corona discharge is not applied will be It was found that the photoreceptor experienced a local charge drop, causing fog. This seems to be related to the amount of charge held on the surface of the plate/& plate when it comes into contact with the photoreceptor, and the polarity.

In order to prevent such fogging from occurring, the belt should be brought into contact with the photoreceptor while the surface of the belt is charged. Therefore, it has been found that fog does not occur if the transfer charger starts corona discharge before the belt comes into contact with the photoreceptor, and ends the corona discharge after the belt separates from the photoreceptor.

Examples The transfer plate/&) used in the present invention has a structure in which a layer of high-resistance material such as hapolytetrafluoroethylene or polyethylene terephthalate is coated on the surface of rubber made conductive by dispersing carbon black or the like. /) is used. Since this paste cannot be transferred if it is completely made into a conductor, it is desirable that its resistance value be in the range of 10' to 10<10 >[Omega]J.

Moreover, the thickness of the transfer belt is preferably in the range of 20 μm to 2 ff.

Hereinafter, embodiments of the present invention will be described in more detail with reference to FIG.

The developing devices 25, 26, and 27 are non-contact type non-magnetic one-component developing devices that use a DC electric field to scatter the toner, and the toner is frictionally charged with a conductive fur brush 28°29.30 in contact with the developing roller. Aluminum developing rollers 31, 3
2, 33, a thin layer of toner is formed by blades 34, 35, 36. The developer 25 is loaded with yellow (7), the developer 26 is loaded with magenta (transfer), and the developer 2 is loaded with magenta (transfer).
7 contains cyan (q) insulating toner. The black developer 37 is a contact type developer containing a two-component developer consisting of an insulating toner and a magnetic carrier, which is widely used in electrophotographic devices. There are developing rollers 31, 32, 33.
Each developing device was placed opposite to the periphery of the photoreceptor 39 with a constant gap (developing gap) between the photoreceptor 38 and the photoreceptor 39 . Each developing device is attached with a separation mechanism that brings it close to the photoreceptor 39 during development and separates it when not developing.

The specifications and developing conditions of the black developing device 37 and the physical properties of the toner are shown below.

・Developer specifications and development conditions Diameter of developing roller 38: 22M Peripheral speed of developing roller 38: 320sn+/sDeveloping roller 3
Thickness of developer layer on top of 8: 4oOμm Direction of rotation of developing roller 38: Opposite direction to photoreceptor 39 (same direction of movement) Development gap (gap between the surface of the developing roller and the 6-mark hole on the surface of the photoreceptor): 300 μm during development.

2ff when not developing ・Developer physical properties Developer type: Two-component developer of toner and carrier Average particle size of carrier: Approximately 50 μm Carrier type: Teflon coated ferrite Toner Charge amount: +15 μC/g Toner average particle size: 12 μm Toner Specification of yellow, magenta, and cyan developing devices, development conditions, and physical properties of toner are shown below.

・Developer specifications and development conditions Development roller diameter: 20ff Development roller circumferential speed: 160 n/ls Development roller rotation direction: Opposite direction to photoreceptor 39 (same traveling direction) Toner layer thickness on development roller = 30μm development gap (
Gap between developing roller surface and photoreceptor surface): 150t1m during development.

2ff when not developed ・Toner physical properties Toner charge amount: +3 μC/11 Average particle size: 12 μm Relative dielectric constant: Approx. 2 As a photoreceptor, a diameter of 1152.
8 m amorphous 5e-To photoreceptor drum 39 (photosensitive layer thickness 63 μm 1 relative permittivity approximately 7, functionally separated selenium photoreceptor sensitized to long wavelengths in the infrared region, half-decreased exposure at wavelength 790 nm 0.6 μI/d) ) and rotated at a circumferential speed of 1 eol/s. This photoreceptor 39 is connected to a charger 40 (scorotron charger, corona voltage: +7KV, grid voltage: 1KV).
) to a charging potential of +900V. Next, the semiconductor laser 41 with a wavelength of 790 nm was emitted to perform exposure. At this time, the light intensity on the photoreceptor surface is 1.5! ! I made it IW. Using this semiconductor laser 41, a negative black signal was exposed onto the photoreceptor 39 to form an electrostatic latent image.

After the latent image is reversely developed by the black developer 37 in the developing state with +600V applied to the developing roller 3B to form a black toner image, the -degree photoreceptor 39 is charged to the AC corona charger 42 (applied AC voltage: 5 , oKV rmll , DC bias component: +200V), and the photoreceptor 39 was further neutralized with a cyan light static elimination lamp 43 .

The thickness of the black toner layer developed on the photoreceptor 39 is from 1 layer to 2 layers.
The toner layer had a thickness of 10 to 20 μm.

Next, the photoreceptor 39 was charged to +600 V again using the corona charger 40 (Scorotron charger, corona voltage: +7 KV, grid voltage: +eoov).

At this time, the charged potential of the photoreceptor 39 to which the black toner was attached became +eooV. Thereafter, the photoreceptor 39 was exposed to signal light corresponding to a yellow color using a semiconductor laser 41 to form a yellow electrostatic latent image. Here, the exposure amount of the semiconductor laser was set to 1.55 mW on the photoreceptor surface. Next, this photoconductor is applied to the developing roller 3 in a yellow developing device 25 in a developing state and a magenta developing device 26 in a non-developing state. The toner was passed through a cyan developer 27 and a black developer 37 to form a yellow toner image. Next, this photoreceptor 39
AC corona charger 42 (applied AC voltage: 6.

KVrms, DC bias component: +200V), and then the corona charger 40 (Scorotron charger, ""f
TK pressure knee 4-7xv, Gu! J)”! Pressure: +94
0V), the photoreceptor 39 was charged to +81ov. At this time, the charged potential of the photoreceptor 39 to which the black and yellow toners were attached became 10 aaoV. After that, the semiconductor laser 4
1, a magenta electrostatic latent image was formed by exposure to signal light corresponding to magenta. Next, the photoreceptor 39 is transferred to the yellow developer 25 in a non-developing state. A magenta toner image was formed by passing through the magenta developing device 26 in a developing state in which +800V was applied to the developing roller 32. At this time, the toner layer in the overlapping portion of yellow and magenta on the photoreceptor 39 is 2 to 4 layers.
layer, and its thickness was 20 to 40 μm.

Thereafter, the photoreceptor 39 was passed through a cyan developer 27 and a black developer 37 in a non-developing state. Next, the photoreceptor 39 is charged with an AC corona charger 42 (applied AC voltage: 5, oKV r
mll, DC bias component: +200V) to remove static electricity,
The photoreceptor 39 is charged with +850V again by the corona charger 40.
It was charged with electricity. At this time, the charged potential of the photoreceptor 39 to which only black, yellow, and magenta toners are attached is +870V.
Became. Further, the charged potential of the photoreceptor 39 at the portion where the yellow and magenta toners overlapped became +780V. Thereafter, a semiconductor laser 41 was used to expose signal light corresponding to cyan to form a cyan electrostatic latent image. Next, the photoreceptor 39
The yellow developing device 26 and the magenta developing device 26 are in a non-developing state. The toner image was passed through a cyan developer 3T in a developing state in which +830V was applied to the developing roller 33 to form a cyan toner image, thereby completing a color image on the photoreceptor 39.

The transfer belt 44 is composed of a conductive rubber belt in which carbon black is dispersed, and the surface thereof is coated with Teflon, and its resistance value is 1oQas and its thickness is 1ff.

The paper 46 is charged in advance by the paper adsorption charger 46 (applied voltage knee 4KV).
) and a grounded conductive brush 47, which is a counter electrode, and was attracted to the transfer belt 44.

The color toner image obtained on the photoreceptor 39 is transferred to the paper 46 by a transfer charger 48 (applied voltage: eKV
), the paper is charged by a paper separation charger 49 (applied voltage knee aKV), the paper is separated from the transfer belt 44, and a positive charger 50 (applied voltage: +4KV) and a negative charger 61 (applied voltage knee aKV) charge the paper. The toner was passed through a pair of chargers (5KV) to be charged, and then heat-fixed by a fixing device 62.

On the other hand, after the transfer, the surface of the photoreceptor 39 was irradiated with an AC corona charger 42 (applied AC voltage: 15, OKV rms, DC bias component: +5 oov), and then the photoreceptor was neutralized with a cyan light static eliminator 43. Then -350
A conductive far plan cleaner 53 (to which a voltage of V is applied)
Specific resistance 1o with carbon black dispersed in rayon fiber
Qas fur wrapped around a stainless steel rod) was pressed against the photoreceptor 39 for cleaning.

As a result, clear images without fogging were obtained after continuous image formation under both environments of 85% relative humidity at 36° C. and 16% relative humidity at 10° C.

Effects of the Invention According to the present invention, it is possible to obtain a color electrophotographic device in which capri does not occur after continuous image formation in a color electrophotographic device that synthesizes toner images on a photoreceptor to obtain a color image.

[Brief explanation of drawings]

FIG. 1 is a side view of a color electrophotographic apparatus according to the present invention, and FIG. 2 is a side view of a conventional color electrophotographic apparatus. 26...Yellow developer, 26...Magenta developer, 27...Cyan developer, 37...
...Black developer, 39...Photoreceptor, 40...
...Corona charger, 41...Semiconductor laser, 44...Transfer be/l/l-149...
・Separation charger, 6o... Charger, 61...
... Charger, 52 ... Heat fixing machine.

Claims (3)

[Claims] (1) During the process of forming a color image on a photoreceptor by repeating charging, exposure, and reversal development steps using toners of multiple colors, the color image is transferred to the photoreceptor without the dielectric belt coming into contact with the photoreceptor. A color electrophotographic apparatus for transferring a color image on the photoreceptor to paper by bringing the dielectric belt into contact with the photoreceptor after completion of forming the image on the photoreceptor, and before the dielectric belt comes into contact with the photoreceptor. 1. A color electrophotographic apparatus, wherein discharging of the transfer charger is started at a certain time, and the discharging of the transfer charger is ended after the dielectric belt is separated from the photoreceptor. (2) The color electrophotographic apparatus according to claim 1, wherein the DC voltage applied to the transfer charger has a polarity opposite to that of the charger that charges the photoreceptor. (3) A color electrophotographic apparatus according to claim 1, wherein the surface of the dielectric belt is charged to a polarity opposite to that of the surface of the photoreceptor before the dielectric belt contacts the photoreceptor.