JPS63172296A - Color electrophotographic device - Google Patents

Abstract

PURPOSE:To prevent toner from being dispersed to the periphery of a photosensitive body and to obtain a clear color print by arranging an electrode for recovering the toner on the downstream side from an electrostatic charging position and on the upstream side from a developing position. CONSTITUTION:The photosensitive body 22 is charged by a charger 23, a latent image is exposed by a light source 24 through a rod lens array 25, the exposed image is developed by developing devices 15-17 and then the whole surface is irradiated with a light emitting diode 26 to erase a latent image. Then the photosensitive body 22 is charged again by a corona charger 23 and then toner to be easily dispersed is recovered from the surface of a toner layer by a metallic toner recovering electrode plate 27. Thereafter, the toner dispersion from the photosensitive body 22 is suppressed, so that contamination on the periphery of the photosensitive body or the generation of color turbidity due to toner mixing into other color developing devices can be removed.

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. In the figure, 1 is 5 rotating in the direction of the arrow.
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 to facilitate electrostatic transfer of the toner image onto plain paper 8, 10 is a corona charger to electrostatically transfer the toner image onto plain paper, and 11 is a heat fixing device. 12 is a cleaning blade for removing toner remaining on the photoreceptor 1 after electrostatically transferring the toner image onto plain paper 8, and 13 is a static elimination lamp for bringing the surface potential of the photoreceptor to an initial state.

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). latent image). Then, negative/positive reversal development is performed using a developing device 4 containing Y toner, which is an electrostatic latent image, 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 a developing condition in which the toner flies, but the other developing devices 5 to 7 are adjusted to a state in which the toner does not fly. 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, the steps of charging, exposing, developing, and optically removing charges are repeated to form Y, M, C, and Bk toner images on the photoreceptor 1 in the same manner as the method used to form the yellow toner image.

After the formation of all toner images is completed, the static elimination lamp 9 is turned on in advance.
The electrostatic latent image is optically neutralized, and the toner image is electrostatically transferred onto plain paper 8 using a corona charger 10. 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, Japanese Patent Laid-Open No. 60-95456).

Problems to be Solved by the Invention When using the conventional apparatus described in the previous section, when printing continuously, toner scatters around the photoreceptor, contaminating the inside of the apparatus, and the developing device becomes dirty with toner of other colors. There has occurred. Such a phenomenon was completely unknown in the past.

When we investigated the cause of this, we found the following. When the toner image formed on the photoreceptor is charged again by a charger, the toner becomes attached to the photoreceptor charged to the same polarity. Therefore, the toner and the photoreceptor are electrostatically repelled. In this state, even the slightest centrifugal force or vibration causes the upper layer toner to scatter from the photoconductor, contaminating the area around the photoconductor or getting into the developing device, causing color turbidity. Ta.

Therefore, it is an object of the present invention to overcome such conventional problems,
To provide a color electrophotographic device capable of producing clear color prints without toner scattering around a photoreceptor.

Means for Solving the Problems The present invention provides a color electrophotographic apparatus in which a cycle of charging, exposure, and development is repeated multiple times to form a plurality of toner images of different colors on a photoreceptor, at a position downstream from the charging position. The color electrophotographic apparatus also has an electrode for collecting toner upstream from the development position.

According to the present invention, after recharging the toner layer adhering to the photoreceptor with a 6-page corona charger, the toner in the top layer, which is most likely to scatter, is immediately electrostatically adsorbed and collected by the collection electrode. After that, it becomes difficult to scatter from the photoreceptor, and it will not contaminate the area around the photoreceptor or mix into developing devices for other colors, causing color turbidity.

Example Toner scattering from the photoreceptor occurs after the toner adhering to the photoreceptor is recharged by a charger. Therefore, for example, if an optical system such as a rod lens array is used in the exposure system,
When installed close to the photoreceptor, the optical system may become contaminated with toner. To prevent this, the position of the collection electrode should be
It is best to install it upstream from the exposure position.

After recharging, the toner is electrostatically repelled by the photoreceptor, so it is sufficient to collect the toner simply by grounding the collection electrode. Furthermore, in order to increase the suction power of the toner,
A voltage having a polarity opposite to that of the toner may be applied.

The material used for the recovery electrode may be any conductive material, but metals such as aluminum and stainless steel are particularly desirable. Further, its shape may be a sheet metal shape or a roller shape.

If the distance between the collection electrode and the photoreceptor is less than 0.5 mm, most of the toner on the photoreceptor will be removed by the collection electrode, resulting in a decrease in image density, which is undesirable. Also, if the distance is wider than 2mm, it will be difficult for the toner to fly off the photoreceptor.
This is not preferable since the toner removal effect is almost lost. Therefore, the distance between the recovery electrode and the photoreceptor should be 0.5 mm or more and 2
It is preferable to make it less than mm.

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

Developing devices 15, 16, and 17 are non-contact non-magnetic one-component developing devices that use a DC electric field to scatter toner, and form a thin layer of toner on aluminum developing rollers 18, 19, 20 with a blade 21. 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. The developing rollers 18, 19, 20 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 and development conditions of the developer 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 give a surface potential of +800V. Next, the output cuff μW,
The light emitting diode 24 was made to emit light at a wavelength of 670 nm, and a negative yellow signal was exposed onto the photoreceptor 22 through the 9-page rod lens array 25 to form an electrostatic latent image.

The contrast potential of the latent image was 750.

After the latent image is reversely developed in the yellow developing device 15 in a developing state with +700V 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 entire surface was irradiated with light emitting diode 26 to erase the latent image.

Next, the corona charger 23 (corona voltage: 17.3k
The photoreceptor 22 was charged to +850V with V). Thereafter, the toner that is more easily scattered on the surface was collected using a metal toner collection electrode plate 27 (made of aluminum, electrode width: 5 mm, distance between the electrode and photoreceptor: 1 mm, and the electrode was grounded).

Next, the photoreceptor 22 was exposed to signal light corresponding to magenta using 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 +100V, and the contrast potential of the latent image is 7.
It was 50v. On the next 10th page, 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 where +800■ is applied to the developing roller 19, and a cyan developing device 17 in a non-developing state. A toner image was formed. After development, the entire surface was irradiated with light emitting diode 26 to erase the latent image.

Next, again the corona charger 23 (corona voltage: 17.5k)
The photoreceptor 22 was charged to +950V by V). Thereafter, the toner that is more easily scattered on the surface of the toner was collected by the metal toner collecting electrode plate 27 .

Next, the light emitting diode 24 was exposed to 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 image where Y toner and M toner are superimposed is +200V, and the potential of the image area formed on the M toner image is +200V. The contrast potential of the image was 750 . next,
A cyan toner image was formed by passing the photoreceptor 22 through a yellow developing device 15 in a non-developing state, a magenta developing device 16, and a cyan developing device 17 in an 11-page developing state in which +900 cm was applied to the developing roller 20.

The color toner image thus obtained on the photoreceptor 22 was transferred onto paper 29 by a transfer charger 28 and then thermally fixed.

On the other hand, after the transfer, the fur brush 30 was pressed against 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,
Moreover, the overlapping density of Y, M, and C colors was 1.7 or more, and a clear color print without color turbidity was obtained. At this time, no toner scattering was observed around the photoreceptor.

Effects of the Invention According to the present invention, there is an effect that clear color prints can be obtained without contaminating the apparatus due to toner developed on the photoreceptor.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a principle diagram of a color electrophotographic apparatus according to an embodiment of the present invention, and FIG. 2 is a principle diagram of a conventional color electrophotographic apparatus. 22... Photoreceptor, 23... Charger, 24... Light source, 15, 16, 17... Developer, 27... Name of toner collection electrode agent Patent attorney Toshio Nakachi Haka 1 first name
Figure 2

Claims (5)

[Claims] (1) In a color electrophotographic device that repeats charging, exposure, and development cycles multiple times to form multiple toner images of different colors on a photoreceptor, toner is placed downstream from the charging position and upstream from the development position. A color electrophotographic device having an electrode for collecting. (2) The color electrophotographic apparatus according to claim 1, wherein the recovery electrode is located upstream from the exposure position. (3) The color electrophotographic apparatus according to claim 1, wherein the recovery electrode is grounded. (4) The color electrophotographic apparatus according to claim 1, wherein a voltage having a polarity opposite to the charging polarity of the toner is applied to the collection electrode. (5) The color electrophotographic apparatus according to claim 1, wherein the distance between the recovery electrode and the photoreceptor is 0.5 mm or more and 2 mm or less.