JPS62136666A - Color electrophotographic method - Google Patents

Abstract

PURPOSE:To eliminate contamination originating from toner of different kind and to obtain a sharp color print by providing the 1st process in which the 1st electromag netic latent image obtained by charging electrostatically and exposing a photosensitive body is passed through the 1st - the (N-1)th developing device and developed by the (N)th developing device. CONSTITUTION:The photosensitive body 1 is charged electrostatically to form the 1st electrostatic latent image, a developing device 23c is applied with a developing bias to develop the latent image, and then the photosensitive body 1 is charged again electrostatically to form the 2nd electrostatic latent image, which is developed by applying the developing bias to the developing deice 23a. Then the entire surface of the photosensitive body is discharged electrostatically by a discharging lamp 24a. Consequently, the 2nd latent image is never developed with toner of the developing devices 23b and 23c and none of the 1st toner is scattered reversely to developing devices. The developing device 23a is moved back, the 3rd latent image formed on the photosensitive body is developed by the developing deice 23b, and the entire surface is discharged electrostatically by a discharging lamp 24. Therefore, toner on the photosensitive body is prevented from being scattered reversely to a developing device to eliminate contamination originating from toner of different kind and obtain a sharp color print.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a color electrophotographic method 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 this type of color electrophotographic method is shown in FIG. In the figure, 1 is selenium rotating in the direction of the arrow (
Se-To) photoreceptor, 2 is a corona charger that uniformly charges the photoreceptor 1, 3 is a laser beam scanner, 4-7 are yellow (Y), magenta (M), cyan (0), black ( BX) A developing device containing separate toners, 8 a recording paper, 9 a static elimination lamp for facilitating the transfer of the toner image onto the recording paper 8, and 10 a corona charger for transferring the toner image onto the recording paper. 11 is a heat fixing device; 12 is a cleaning blade for removing toner remaining on the photoreceptor 1 after toner transfer; and 13 is a static elimination lamp for erasing the electrostatic latent image on the photoreceptor 1 with light. FIG. 4 shows a specific configuration of the developing device 4-7 used in FIG. 3. In the figure, 14 is a two-component developer (hereinafter referred to as developer) made of a mixture of positively charged toner and a magnetic carrier, 16 is a developing sleeve made of a non-magnetic material such as aluminum, and 16 has a plurality of magnetic poles. A magnet roller, 17 a layer thickness regulating blade for uniformizing the thickness of the developer 140 layer on the developing sleeve 16, and 18 a developing station IJ-
19 is a rotating blade that stirs the developer 14; 20 is a toner for replenishment; 21 is a toner replenishment roller; 22 is a toner removed from the developer 14 on the developing sleeve 15; This is a power source for electrically flying only the photoreceptor 1 towards the photoreceptor 1.

To make the toner fly from the developing sleeve, a voltage that is a combination of a positive DC voltage and an AC voltage is applied to the developing sleeve 16 using a power source 22. Further, in order to stop the toner from flying and make it not contribute to development, the developing sleeve 15 is electrically floated, grounded, or a negative DC voltage is applied.

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 (an electrostatic latent image where the image area is exposed and the interfacial potential of the photoconductor is attenuated). latent image). Then, the electrostatic latent image is reversely developed into a negative/positive state using a developing device 4 containing Y toner, thereby forming a yellow toner image on the photoreceptor 1. At this time, the developing sleeve of the developing device 4 containing the Y toner is connected to the power source 22, but the other developing devices 5-7 are adjusted so that the toner does not fly.

This point will be discussed in detail later. After development with Y toner, the entire surface of the photoconductor 1 is irradiated with a static elimination lamp 13 to erase the yellow electrostatic latent image.

Next, using the same method as that used to form the yellow toner image, the steps of charging, exposing, developing, and optically eliminating charges are repeated to form M, C, and BI toner images on the photoreceptor 1 as well as the Y toner image. Form on top one after another. After the formation of all toner images is completed, the electrostatic latent image is erased using the static eliminating lamp 9, and the toner image is electrostatically transferred onto the recording paper 8 using the corona charger 10. The toner image transferred to the recording paper 8 is fixed by a heat fixing device 11.

On the other hand, after electrostatic transfer, the toner remaining on the photoreceptor 1 is removed by the cleaning blade 12, and the photoreceptor 1 is used again for the next image formation (for example, Japanese Patent Application Laid-Open No. 60-95456). The problem we are trying to solve When we continue to take color prints using the conventional color electrophotographic device explained in Figure 3, the developing device becomes contaminated with different types of toner in proportion to the number of prints, and the color purity of the images gradually decreases. There were some problems.

When we investigated the cause of this, we found that when a photoreceptor carrying a toner image is recharged and image-exposed and passed through a developing device that should not contribute to development, the toner on the photoreceptor flies back to the developing sleeve. There was found. The reason why this reverse flight of toner occurs will be explained next with reference to the drawings.

Figures 5 to 7 show that after the photoconductor carrying the toner image has been recharged and imagewise exposed, a developing device that must not contribute to development (the developing sleeve is grounded or a negative DC voltage is applied) FIG. 2 is a diagram schematically showing the behavior of toner on a photoreceptor and a developing sleeve when the toner passes through a photoreceptor and a developing sleeve.

FIG. 5 shows the situation when the developing sleeve is grounded. A
The photoreceptor 1 in the and C regions has a positive charge.

Further, the toner 24 on the photoreceptor 23 is strongly positively charged by recharging the photoreceptor.

Therefore, the toner 24 in the C area is repelled by the positive charge on the photoreceptor 23 and flies back toward the developing sleeve 26 along the lines of electric force from the photoreceptor 23 toward the developing sleeve 25 . This backward flight of toner increases as the potential difference between the photoreceptor 23 and the developing sleeve 26 increases.

FIG. 6 shows the situation when a negative DC voltage is applied to the developing sleeve 25. In this case, the photoreceptor 2 in the C area
3 and the developing sleeve 25 is larger than that in FIG. Therefore, more toner 24 flies back to the developing sleeve 25 in this region than in the case of FIG. 5, and the developing device becomes more contaminated.

FIG. 7 shows the state when the developing sleeve 25 is electrically floated. As shown in the figure, a mirror image charge of a different polarity with respect to the electrostatic latent image on the photoreceptor 23 is induced in the developing sleeve 26 in opposition to the latent image.

Therefore, the toner 2 on the developing sleeve 26 in area B
The toner 6 flies back toward the photoreceptor 23, and the toner 24 on the photoreceptor 23 in the C region flies back toward the developing sleeve 25 due to the repulsion of the charges.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a color electrophotographic method that can prevent the developing device from being contaminated by different toners and produce clear color prints without complicating the structure of the developing device.

Means for Solving the Problems The present invention is a color electrophotographic method in which charging, exposure, and development are repeated multiple times to form a plurality of toner images of different colors on a photoreceptor. A device, a light source, and N (N is a positive integer, N22) developing devices are arranged in order, and the first electrostatic latent image obtained by first charging and exposing the photoreceptor is transferred from the first to the first. This is a color electrophotographic method that includes a first step of developing in the Nth developing device via the (N-1)th developing device.

The present invention will be described in detail by taking as an example a case where reversal development is performed using a positively chargeable photoreceptor and a positively chargeable toner 20.

Figure 1: A person places the
This shows a state in which an electrostatic latent image is formed. Toner carrier 23
&, 23b is grounded at a distance of 150 μm from the photoreceptor 1. Toner carrier 23 (j is distance 150μ from photoreceptor 1
Open m and apply a developing bias of +700V. The first electrostatic latent image is not developed by the toner carriers 23&, 23b, but is developed only by the toner carrier 230. Next, FIG. 1B shows a state in which the photoreceptor 1 developed with the toner of the toner carrier 230 is recharged to +5 oov to form a second electrostatic latent image. The toner carrier 23 & is spaced apart from the photoreceptor 1 by 150 μm, and development is performed by applying a developing bias of +70°V. Thereafter, the entire surface of the photoconductor 1 is neutralized by the static elimination lamp 24&, and then the toner carrier 23b, which is connected to the photoconductor 1 at a distance of 150 μm, is grounded.
, 230f passes. By doing this, the second electrostatic latent image is developed by the toner on the toner carriers 23b and 23C, and the first toner on the photoreceptor 1 flies back onto the toner carriers 23b and 230. It can also be prevented. Finally, in FIG.
This shows a state in which an electrostatic latent image is formed.

The distance between the toner carrier 23& and the photoreceptor 1 is 700 μm.
Apply a development bias of ground or +700v. Since the toner carrier 232L is separated from the photoconductor 1, it does not develop an electrostatic latent image and does not develop the electrostatic latent image.
The upper toner does not fly back to the toner carrier 23a. This third electrostatic latent image is developed by the toner carrier 23b, which is spaced apart from the photoreceptor 1 by 150 μm and to which a developing bias of +700V is applied. After that, the static elimination lamp 24b
The entire surface of the photoreceptor 1 is neutralized, and then the photoreceptor 1 and the distance 16
0 μm open indicates the grounded toner carrier 23b.

Pass through 23C. By doing so, it is possible to prevent the toner on the photoreceptor 1 from flying back to the toner carrier 230, and it is also possible to prevent the developing device from being contaminated by different types of toner.

Examples Photoreceptors that can be used in the present invention include amorphous carbon, gas, ZnO, a-8i, and the like. As the developing device, any device can be used as long as it has a counter electrode effect on the electrostatic latent image on the photoreceptor and can develop the electrostatic latent image in a non-contact state between the developer layer and the electrostatic latent image.

For example, a single layer of charged toner is carried on a developing roller.
There are component developers and two-component developers that mix toner and magnetic carrier. Furthermore, although the embodiments of the present invention describe the case of a reversal development method, the present invention can also be applied to a regular development method.

As a specific embodiment of the present invention, a color electrophotographic method having three types of developing devices, cyan, magenta, and yellow, will be described. can also be applied. Further, in the embodiments of the present invention, light irradiation is used as the static eliminating means after development, but good results can also be obtained by using AC corona discharge. Furthermore, in the embodiment of the present invention, a method of increasing the distance between the toner carrier and the photoreceptor is used as a means to disable the developing ability of the developing device, but the toner on the toner carrier is removed and the developing The same effect can be obtained even if the ability is removed.

When using cyan, magenta, and yellow toners, the light source used in the present invention is a light source that has a dominant wavelength within the transmission spectrum of light obtained by overlapping two types of toners selected from three types of toners. Preferably, the order of development is such that the two selected toners are developed first, and then the remaining toner is used last.

At this time, among the three superimposed colors of cyan, magenta, and yellow, red (a mixture of yellow and magenta) has the best transmittance, so it is preferable that the wavelength of the light source is 640 nm or more, and it is developed first. The toner is preferably yellow and magenta.

A light source that transmits red light has a dominant wavelength of 650.
~6801m light emitting diode or semiconductor laser is suitable.

An embodiment of the present invention will be described in more detail with reference to FIG. 2. An amorphous 5s-Te photoreceptor drum 1 with a diameter of 1008 m was rotated at a circumferential speed of 75 wtb/s, and a charger 2 (corona voltage: +7 kV) was connected. It was charged with a surface potential of 500 m. Next, output cuff μW, light emitting diode 2 with a wavelength of 670 nm.
5 was made to emit light, and a yellow signal was exposed through the Selfo lens 26 to form an electrostatic latent image. Next, the electrostatic latent image is deposited on the cyan toner carrier 231L (diameter = 16WIL, peripheral speed near 6/s, traveling direction: same direction as photoreceptor 1, photoreceptor 1
Distance from near 00μm.

Development bias: ○v, toner charge amount: 3μC; #.

Average particle size: 10 μm, toner layer thickness: 39 μm) and magenta toner carrier 23b (diameter: 16 g 1. peripheral speed near 5 m).
/s, traveling direction: same direction as photoreceptor 1.

After passing through the yellow toner carrier 2
3C (Diameter: 16cm 9 peripheral speed near sm/s, traveling direction: same direction as photoconductor 1, distance to photoconductor 1: 150μm, developing bias: +700V,)ner charge amount: 3μQ/g,
When the yellow toner passed through the toner (average particle size: 10 μm, toner layer thickness = 30 μm), the yellow toner flew toward the photoreceptor 1 and adhered thereto. The toner image on the photoreceptor 1 was not transferred to paper, but was once irradiated over the entire surface with a static elimination lamp 13, and then charged again with a corona charger 2. Photoreceptor 1 with or without yellow toner
was charged to +5oov.

Here, among the surface potentials of the photoconductor 1 to which the yellow toner is attached, the potential of the toner is approximately SOV, and the potential of the photoconductor 1 itself is +75.
It was charged to 0V.

Next, the photoreceptor 1 was irradiated with signal light corresponding to magenta by the light emitting diode 26. In areas where yellow toner is not attached, the surface potential of the photoreceptor 1 increases to +30V due to exposure.
It declined to . Approximately aOV in the area where yellow toner is attached
It declined to . Next, the photoreceptor 1 first passes through a yellow toner carrier 23 & with a developing bias QV. At this time, the distance between the yellow toner carrier and the photoreceptor 1 was 700 μm.

Next, the photoreceptor 1 passes through a magenta toner carrier 23b to which a developing bias of +700 V is applied at a distance of 150 μm, and is developed with magenta toner. Thereafter, the entire surface of the photoreceptor 1 is irradiated with the charge eliminating lamp 24b to eliminate the charge, and then the light passes through the yellow toner carrier 230. At this time, the yellow toner carrier 230 was grounded with a distance of 150 μm from the photoreceptor 1.

Thereafter, the entire surface of the photoreceptor 1 was irradiated by the static elimination lamp 13, and then charged to +5 oov by the charger 2, and a signal light corresponding to cyan was irradiated by the light emitting diode 26 to form an electrostatic latent image. This time, the distance between the cyan toner carrier 232L and the photoreceptor 1 is brought closer to 150 μm, and the distance is +7oo
Development was performed by applying a developing bias of v. Thereafter, after the photoreceptor 1 is completely neutralized by the static eliminating lamp 24&, it passes through the magenta toner carrier 23b and the yellow toner carrier 230.

At this time, both toner carriers were grounded at a distance of 150 μm from the photoreceptor 1.

The color toner image thus obtained on the photoreceptor 1 was transferred to the paper 8 by the transfer charger 10, and the paper 8 was peeled off from the photoreceptor 1 by the peeling charger 27, and then thermally fixed. The surface of the photoreceptor 1 is neutralized by the static eliminator 28, and the cleaning device 12
After removing the remaining toner, the resulting color images were of high quality with a maximum density of 1.7 and were of good quality with no color turbidity.This process was continued for 3,000 sheets, and the color images were developed. No foreign toner was mixed into the container.

Effects of the Invention According to the present invention, it is possible to prevent the developing device from being contaminated by different types of toner without complicating the structure of the developing section, and it is possible to stably obtain clear color prints.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a color electrophotographic printer shown to explain the principle of the color electrophotographic method of the present invention, FIG. 2 is a principle diagram of an apparatus implementing the color electrophotographic method of the present invention, and FIG. 3 , Fig. 4, Fig. 6. FIGS. 6 and 7 are diagrams showing the behavior of an apparatus and toner for explaining a conventional color electrophotographic method. 1...Photoreceptor, 2...Charger, 20.
...Toner, 22 ...Bias power supply, 2
3a, 23b, 23c...Developer, 24a
, 24 +... static eliminator, 25...
light source. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure/-m- Photoreceptor Figure 3 Figure 5 Figure 7

Claims (13)

[Claims] (1) A color electrophotographic method in which charging, exposure, and development are repeated multiple times to form multiple toner images of different colors on a photoreceptor, in which a charger, a light source, and , N is a positive integer where N≧2) are arranged in order, and the first electrostatic latent image obtained by first charging and exposing the photoreceptor is the first to (N-1)th developing device. A color electrophotographic method comprising a first step of developing the image using an Nth developing device through the Nth developing device. (2) The color electrophotographic method according to claim 1, wherein the developing device has a toner carrier and means for flying the toner on the toner carrier using an electric field. (3) In the first step, the first to (N-1)
A voltage of approximately the same potential as the latent image potential of the image area of the first electrostatic latent image is applied to the toner carrier of the Nth developing device, and the toner carrier of the Nth developing device is applied with the potential of the latent image of the first electrostatic latent image. 3. The color electrophotographic method according to claim 2, wherein a voltage having substantially the same potential as the potential of the non-image area of the image is applied. (4) Claim 1, wherein a static eliminating means for erasing an electrostatic latent image is disposed between each developing device.
Alternatively, the color electrophotographic method according to item 2 or 3. (5) The color electrophotographic method according to claim 4, wherein the static eliminating means is light irradiation. (6) Claim 4 in which the static eliminating means is corona discharge
Color electrophotographic method described in Section 1. (7) After the first step, the photoreceptor is charged and exposed again to produce the M-th (where M is a positive integer of N≧M≧2) electrostatic latent image, and the developing ability is disabled. the first to (M-1)th developing devices, and the Mth developing device in which a voltage of approximately the same potential as the latent image potential of the non-image area of the latent image was applied to the toner carrier; After passing through the developer, the Mth and (M+
1) The latent image is neutralized by the static eliminating means provided between the developing devices, and then the toner carrier is passed through the grounded (M+1)-th to N-th developing devices to form the M-th developing device. Claim 4 or 5, which has a step of developing with
or the color electrophotographic method according to item 6. (8) The color electrophotographic method according to claim 7, wherein the means for disabling the developing ability is to remove the toner on the toner carrier. (9) The color electrophotographic method according to claim 7, wherein the means for disabling the developing ability is to separate the toner carrier from the photoreceptor. (10) The number of developing devices is three, and each developing device contains yellow, magenta, and cyan toner separately, and two types of toner selected from the three types of toner are superimposed. Using a light source having a dominant wavelength within the transmission spectrum of the light obtained by the method, first development is performed with the two selected toners, and then finally development is performed with the remaining toner. or the color electrophotographic method according to item 9. (11) The color electrophotographic method according to claim 10, wherein the main wavelength of the light source is 640 nm or more, and the toners to be developed first are yellow and magenta. (12) The color electrophotographic method according to claim 11, wherein the light source is a light emitting diode with a dominant wavelength of 650 to 680 nm. (13) Claim 1 in which the light source is a semiconductor laser
The color electrophotographic method according to item 1.