JPS63246760A - Color electrophotographic device - Google Patents

Abstract

PURPOSE:To prevent blurring of an image by using an AC corona destatizing device as a destatizing means of a photosensitive body at the time of forming plural color of toner images on the photosensitive body by repeating electric charging, exposing, developing and destatizing cycles repeatedly. CONSTITUTION:The AC corona destatizing device 26 is used as he destatizing means of the photosensitive body 22 in the case of forming the toner images of Y, M and C on the body 22 by repeating the charging, exposing, developing and destatizing cycles repeatedly. Namely, the AC corona destatizing device 26 is used for destaticization of the photosensitive body and, therefore, the attenuation rates of the potential of the bare photosensitive body and the photosensitive body to which the toners adhere are uniformized. Generation of the electric field which induces scattering of the toners to the peripheral part of the image is thus obviated and, therefore the blurring of the image is prevented.

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 color hard copy device such as a color copying machine or a color printer.

Conventional technology Traditionally, charging, exposure, and development are repeated multiple times to form multiple toner images of different colors on an electrophotographic photoreceptor (hereinafter referred to as photoreceptor), and then the toner images are transferred all at once to paper. Various color electrophotographic methods for obtaining color images have been proposed.

A conventional example of an apparatus using such a color electrophotographic method is shown in FIG.
e-Te photoreceptor; 2 is a corona charger that uniformly positively charges the surface of the photoreceptor 1; 3 is a laser beam scanner; 4 to 7 are yellow (Y), magenta (M), cyan (C), respectively; Developing device containing separate black (Bk) developer, 8
is plain paper, 9 is a static elimination lamp for facilitating electrostatic transfer of the toner image onto plain paper 8, 10 is a corona charger for electrostatically transferring the toner image onto plain paper, 11 is a heat fixing device, and 12 is a heat fixing device. A cleaning blade 13 is used to remove toner remaining on the photoreceptor 1 after the toner image is electrostatically transferred onto plain paper 8, and a discharge lamp 13 is used to bring the surface potential of the photoreceptor to an initial level.

Next, a method of forming a color image using the color electrophotographic apparatus described above will be described. First, corona charger 2
After positively charging the photoconductor 1, the laser beam scanner 3 scans and exposes a yellow image signal to form a negative electrostatic latent image (the image area is exposed and the surface potential of the photoconductor is attenuated). Then, the electrostatic latent image is subjected to negative/positive reversal development using a developing device 4 containing Y toner to form a yellow toner image on the photoreceptor 1. At this time, only the developing device 4 containing the Y toner is set to the developing condition that causes the toner to fly away, but the other developing devices 5 to 7 are
is adjusted so that the toner does not fly away. After development with the Y toner, the entire surface of the photoconductor 1 is irradiated with a discharge lamp 13 to optically eliminate the yellow electrostatic latent image.

Next, by repeating the steps of charging, exposing, developing, and optically eliminating charges in the same manner as the method used to form the yellow toner image, Y, M, C, and Bk toner images are formed on the photoreceptor 1. . After the formation of all toner images is completed, the electrostatic latent images are optically neutralized in advance using a static eliminating lamp 9, and the toner images are electrostatically transferred onto plain paper 8 using a corona charger 2. The toner image transferred to the plain paper 8 is heated and fixed by a heating fixing device 11. On the other hand, toner remaining on the photoreceptor 1 after electrostatic transfer is removed by a cleaning blade, completing one cycle of color image formation. (For example, JP-A-60-95458).

Problems to be Solved by the Invention When using the conventional method described in the previous section to eliminate static electricity from the photoreceptor using the static elimination lamp 13, toner was scattered around the Y-color image, resulting in an unclear image.

When we investigated the cause of this, we found the following. This toner scattering phenomenon will be explained in FIG.

When the yellow toner 14 once developed on the photoreceptor is charged again, the positively charged toner adheres to the positively charged photoreceptor as shown in FIG. 3(a). At this time, when the entire surface is irradiated with blue static eliminating light, the potential of the bare photoreceptor portion quickly decreases. On the other hand, since the toner-attached portion is exposed to light through the yellow toner 14, the potential under the toner 14 has a slower light attenuation speed than the bare portion. Therefore, the toner 14 is repelled by the electric field generated between the bare photoconductor part and the toner adhesion part and scatters around the image periphery (third
Figure b).

Therefore, an object of the present invention is to overcome such conventional problems,
To provide a color electrophotographic device capable of obtaining clear color prints without image bleeding.

Means for Solving the Problems The present invention provides a color electrophotographic device that forms a Y-M-C toner image on a photoreceptor by repeating a cycle of charging, exposing, developing, and removing electricity a plurality of times. This is a color electrophotographic apparatus in which the static eliminating means is an AC corona static eliminating device.

According to the present invention, since an AC corona static eliminator is used to eliminate static electricity from the photoreceptor, the rate of potential decay of the bare photoreceptor and the photoreceptor to which toner is adhered becomes uniform. Therefore, an electric field that causes toner scattering is not generated at the periphery of the image, so that the image does not blur.

EXAMPLE Hereinafter, an example of the present invention will be described in detail with reference to FIG.

The developing units 15, 16, and 17 are non-contact non-magnetic one-component developing units that use a DC electric field to remove toner, and a blade 21 forms a thin layer of toner on an aluminum developing roller 18, 19, and 20. It is configured to do this. Yellow (Y) in developer 15, magenta (M) in developer 16
, the developing device 17 contains cyan (C) insulating toner. And the developing roller 18, 19, 29 and the photoreceptor 22
The developing units were disposed facing each other around the photoreceptor 22 with a constant gap between them (developing gap). Each developing device is attached with a separation mechanism that brings it close to the photoreceptor during development and separates it when not developing. The specifications of the developing device used, the developing conditions, and the physical properties of the toner are shown below.

Developing unit specifications and developing conditions Diameter of developing roller: 16 mm Peripheral speed of developing roller: 150 mm/s Thickness of toner layer on developing roller = 30 μm Rotation direction of developing roller: Opposite direction from photoreceptor 22 Developing gap: 150 μm during development , 700 μm when not developed Toner physical properties Toner charge amount: +3 μC/g Average particle size: 10 μm An amorphous 5e-Te photoreceptor drum 22 with a diameter of 100 mm was used as a photoreceptor, and a charger 23 was used while rotating at a circumferential speed of 150 mm/s. (corona voltage: +7 kV) to a surface potential of +800 V, the light emitting diode 24 with an output μW1 wavelength of 670 nm is caused to emit light, and a negative yellow signal is exposed onto the photoreceptor 22 through the rod lens array 25. An electrostatic latent image was formed.

The contrast potential of the latent image was 750V.

After the latent image is reversely developed in a yellow developing device 15 with 8 development states in which +700V is applied to the developing roller 18, the photoreceptor 2
Magenta developer 16 and cyan developer 1 are in a non-developing state.
7 to form a yellow toner image. After development, the latent image was erased with an AC corona static eliminator 26 (corona applied voltage 10 kVPP).

Next, the corona charger 23 (corona voltage: +7.3k
The photoreceptor 22 was charged to +850 V at the 0th order, and then the photoreceptor 22 was exposed to signal light corresponding to magenta from the light emitting diode 24 to form a magenta electrostatic latent image. Here, the surface potential of the image area formed on the Y toner image is +1
At 00V, the contrast potential of the latent image was 750V.

Next, the photoreceptor 22 is passed through a yellow developing device 15 in a non-developing state, a magenta developing device 16 in a developing state in which +800V is applied to the developing roller 19, and a cyan developing device 17 in a non-developing state to form a magenta toner image. Formed. After development, the latent image was erased with an AC corona static eliminator 26 (corona applied voltage 10 kVPP).

The bare photoreceptor and the photoreceptor under the recharged yellow toner were quickly neutralized and no toner splatter occurred.

Next, the corona charger 23 (corona voltage: +7.5k
The photoreceptor 22 was charged to +950V by V). Next, the light emitting diode 24 was used to expose signal light corresponding to cyan to form a cyan electrostatic latent image. Here, the surface potential of the image area formed on the M toner image is +100V.
, the surface potential of the image area formed on the superimposed image of Y toner and M toner was +200V, and the contrast potential of the latent image was 750V.Next, the photoreceptor 22 was placed in an undeveloped state. A cyan toner image was formed by passing through a yellow developing device 15, a magenta developing device 16, and a cyan developing device 17 in a developing state in which +900V was applied to the developing roller 20.

The color toner image thus obtained on the photoreceptor 22 was transferred onto paper 28 by a transfer charger 27 and then thermally fixed.

On the other hand, after the transfer, the fur brush 29 was brought into pressure contact with the photoreceptor 22 for cleaning.

As a result, the color density of the composite color of red, green, and blue is 1°5 or more,
Further, the overlapping density of the three colors Y, M, and C was 1.7 or higher, and the toner did not scatter around the image line, and a clear color image without background fog was obtained.

Effects of the Invention According to the present invention, there is an effect that clear color prints without image bleeding can be obtained.

[Brief explanation of drawings]

FIG. 1 is a principle diagram of a color electrophotographic apparatus according to an embodiment of the present invention, FIG. 2 is a principle diagram of a conventional color electrophotographic apparatus, and FIG. FIG. 2 is a conceptual diagram illustrating a phenomenon in which lines smear when the image is blurred.

Claims (1)

[Claims] A color electrophotographic device that forms toner images of multiple colors on a photoreceptor by repeating a cycle of charging, exposing, developing, and removing static electricity a plurality of times, the color electrophotographic device having an alternating current corona static eliminator as a static eliminating means for the photoreceptor.