JPS6177857A - Photosensitive body for forming polychromatic image and polychromatic image forming method - Google Patents

Abstract

PURPOSE:To record a polychromatic image by a single imagewise exposure and to form a polychromatic image with no shear in color at a high speed by forming a layer consisting of plural kinds of distributed color separation filters on an electrically conductive layer to provide a laminated structure. CONSTITUTION:An insulating layer 2 is formed on one side of a photoconductive layer 1, and a light transmitting and electrically conductive layer 3 including a layer 3a consisting of distributed color separation filters is formed on the other side to obtain a photosensitive body 4 having a laminated structure. The photosensitive body 4 is electrostatically charged and imagewise exposed. The resulting primary latent image is uniformly exposed to light LB passed through the blue filter FB, and the electrostatic image is developed to form a yellow toner image. The surface potential VP of the insulating layer 2 is lowered to that of other part, and uniform exposure to light passed through the green filter and development are carried out to form a magenta toner image which overlaps the yellow toner image, forming a dichromatic image. Uniform exposure to red light and development are then carried out to form a cyan toner image which overlaps the dichromatic image, forming a trichromatic full-color image with no turbidity in color.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides a novel multicolor image forming photoreceptor for forming multicolor images using electrophotography, and a multicolor image forming method using the same. Regarding.

[Prior art]

A number of methods and devices used therefor have been proposed for the purpose of obtaining multicolor images using electronic transcription, but they can generally be classified into the following types. One method is to repeatedly form a latent image and develop with color toner according to the number of separated colors using a photoreceptor, or to overlap the colors on the photoreceptor each time, or to transfer the colors to a transfer material each time the development is performed. This is a method of layering. The second method uses a device having a plurality of photoconductors corresponding to the number of separated colors, simultaneously exposes each photoconductor with a light image of each color, and transfers the latent image formed on each photoconductor to color toner. In this method, the image is developed with a 100% polyurethane resin, and then transferred onto a transfer material in order to obtain a multicolor image by overlapping the colors.

The first method has a major drawback in that a plurality of latent image formation and development processes must be repeated M9, and it takes time to record images, making it extremely difficult to increase the speed. In addition, the second method uses multiple photoreceptors in parallel, which is advantageous in terms of high speed, but requires multiple photoreceptors, an optical system, a developing means, etc., making the device complex, large, and expensive. Practicality is low due to the price. Furthermore, both types have a major drawback in that it is difficult to align the image when image formation and transfer are repeated multiple times, and it is impossible to completely prevent color shift of the image.

In order to fundamentally solve these problems, it is sufficient to record a multicolor image on a single photoreceptor with one image exposure, but the reality is that such a system has not yet been developed.

[Purpose of the invention]

The present invention has been made in view of the above circumstances, and -
The first objective is to provide a single photoreceptor that can record a multicolor image by multiple image exposures, and a simple photoreceptor that can be used to form a multicolor image without color shift at high speed. A second object of the present invention is to provide a multicolor image forming method comprising a process.

[Structure of the invention]

The present invention relates to a photoreceptor in which an insulating layer is provided on one side of a photoconductive layer and a transparent conductive layer is provided on the other side, and a plurality of types of color separation filter distribution layers are provided on the side of the conductive layer. A photoconductor for forming a multicolor image, characterized in that it has a laminated structure, and the conductive layer in contact with the photoconductive layer of this photoconductor is grounded to charge the photoconductor from the insulating layer side and transmit light. image exposure from the translucent conductive layer side, and then subjecting the entire surface to specific light from the translucent conductive layer side to form a potential pattern on a specific portion of the insulating layer corresponding to one type of color separation filter. The above object is achieved by this configuration in a multicolor image forming method characterized in that the step of developing the potential pattern with a specific color toner is repeated by changing the color of the toner and the whole surface exposure. .

〔Example〕

The present invention will be described below with reference to the drawings.

In the following explanation, we will discuss a photoreceptor for full color reproduction using red, green, and blue filters that transmit substantially only red, green, and blue light, respectively, as color separation filters, and a photoreceptor using the same. Although a color image forming method will be described, the colors of the color separation filter and the color of the toner used in combination with the color separation filter in the present invention are not limited thereto.

FIGS. 1 to 4 are cross-sectional views schematically showing examples of the laminated structure of the photoreceptor of the present invention, and FIGS. 5 to 7 are color separation filters in the transparent conductive layer of the photoreceptor of the present invention, respectively. FIG. 8 is a plan view showing an example of filter distribution of the distribution layer; FIG. 8 is a process diagram showing the image forming process of the multicolor image forming method of the present invention; FIG.
10 are a schematic cross-sectional view and a vertical cross-sectional view showing an example of a recording apparatus that implements the multicolor image forming method of the present invention.

In Figures 1 to 4, 1 is sulfur, sele/.

Photoconductors such as amorphous silicon or alloys containing sulfur, selenium, tellurium, arsenic, antimony, etc., or zinc, aluminum, antimony, bismuth, cadmium,
Oxides of metals such as molybdenum.

Inorganic photoconductors such as iodides, sulfides, selenides, or vinylcarbazole, anthracene7talo7anine, trinitrofluorenone, polyvinylcarbazole,
Organic photoconductive substances such as polyvinylanthracene and polyvinylpyrene are combined with insulating binder resins such as polyethylene, polyester, polypropylene, polystyrene, polyvinyl chloride, polyvinyl acetate, polycarbonate, acrylic resin, silicone resin, fluorinated citrus resin, and epoxy resin. 2 is an insulating layer made of various polymers, resins, etc. or insulating materials such as glass, ceramics, etc., which may be transparent. . 3 is a light-transmitting conductive layer including a distribution layer 3a of color separation filters for red, green (G), and blue (B). The conductivity of the transparent conductive layer 3 in the illustrated example is as follows: aluminum, silver, and lead in contact with the photoconductive layer 1.

A vapor deposited or sputtered layer of metal such as zinc, nickel, gold, chromium, molybdenum, titanium, platinum, etc., formed into a thin film that can transmit light, or indium IIide,
Tin oxide, indium-tin oxide, etc., and the transparent conductive layer 3 in FIG. R is attached in a predetermined pattern by means such as printing.
, G, and B, and the light-transmitting conductive layer 3 shown in FIG. 2 has a structure in which a transparent layer 3G of resin, glass, etc. is further provided on the filter distribution layer 3a of FIG. 1. Regarding the structure, the transparent conductive layer 3 shown in FIG. 3 has a structure in which a transparent layer 3c similar to that shown in FIG. 2 is formed on a conductive layer 3b, and a filter distribution layer 3a is formed thereon. The transparent conductive layer 3 shown in FIG. 4 has a structure in which a transparent layer 3c is further provided on the filter distribution layer 3a shown in FIG. The filter distribution layer 3a in FIGS. 3 and 4 may be formed by depositing a coloring agent in a predetermined pattern on the transparent layer 3c by means such as printing. Furthermore, when a conductive resin is used as the resin forming the filter distribution layer 3a in FIGS. 1 and 2 or the resin forming the transparent layer 3c on the photoconductive layer 1 side in FIGS. 3 and 4, In particular, there is no need to provide the conductive layer 3b.

The laminated structure of the photoreceptor 4 as described above can be made by using the insulating layer 2 as a base and sequentially forming the photoconductive layer 1 and the transparent conductive layer 3 thereon, or by forming the photoconductive layer 1 and the transparent conductive layer 3 on top of the insulating layer 2 as a base. Even if it is made by using the transparent layer 3C as a base and forming a layer on it, in the case of a photoreceptor as shown in Fig. 4, the inner transparent layer 3 is used as an adhesive layer and the layers on both sides are formed. The layers may be made separately and then bonded together at the end. The photoreceptor 4 is formed into a cylindrical shape, a belt shape, or a plate shape.

R, G, in the filter distribution layer 3a of the transparent conductive layer 3,
Although the shape and arrangement of filters such as B are not particularly limited, it is preferable to have a striped distribution as shown in Figure 5 because pattern formation is easy, and delicate multicolor images can be reproduced. A mosaic-like distribution as shown in FIGS. 6 and 7 is preferable in terms of the distribution. The direction in which the R, G, B, etc. filters are arranged may be of course not only in a mosaic distribution but also in a stripe distribution, and may be oriented in any direction in the direction of expansion of the photoreceptor. That is, for example, in the case of a rotating drum-shaped photoreceptor, the length direction of the stripes may be parallel to the axis of the photoreceptor, at right angles, or in a helical shape. However, R.G.

If the individual sizes of filters such as B are too large,
The image resolution and color mixing properties are reduced, the image quality deteriorates, and
Even if the particle size becomes too small and becomes the same as or smaller than the toner particle size, it becomes easier to be influenced by other adjacent color parts and it becomes difficult to form the distribution pattern of the filter. In the case of the distribution of three types of filters as shown in the example, the length l of one cycle of the repeating array is 30 to 3
It is preferable that the width or size is 00 μm.

Of course, the types of filters are not limited to R, G, and B, nor are they limited to three types, and if the number of types changes, the preferable range of the above-mentioned length l will also change.

Next, the multicolor image forming method of the present invention using the following photoreceptor will be explained with reference to FIG. Note that FIG. 8 shows an example in which an n-type semiconductor such as zinc oxide is used for the photoconductive layer 1 of the photoreceptor, and the same reference numerals as in FIGS. 1 to 7 are used in FIG. The same functional components are shown.

First, as shown in FIG. 8 [1]K, the insulating layer 2 of the photoreceptor 4 is
A negative corona discharge is applied to the entire surface from the side by a charger 5. Therefore, negative charges are generated on the surface of the insulating layer 20, and correspondingly positive charges are induced at the interface between the photoconductive layer 1 and the insulating layer 2. As a result, the surface of the insulating layer 20 exhibits a uniform negative potential of K, as seen in the graph of potential vP.

Next, as shown in FIG. 8 [2], alternating current or positive discharge is applied to the charged photoreceptor 4 from the insulating layer 2 side by the charger 6 to erase the charge on the surface of the insulating layer 2. While doing so, imagewise exposure is applied from the transparent conductive layer 3 side as indicated by the arrow. In the image exposure, for convenience of explanation, a portion of the red image where the amount of light is sufficiently strong is indicated as LR.

Since such red image exposure LR passes through the R filter portion of the filter distribution layer 3a and makes the photoconductive layer 1 above it conductive, the negative charge on the surface of the insulating layer 2 is erased by the charger 6. At the same time, the positive charges at the interface between the photoconductive layer l and the insulation N2 also disappear. On the other hand, the G and B filter parts are exposed to red image L.
Since R does not pass through, the positive charges on the boundary between the photoconductive layer 1 and the insulating layer 2 remain without disappearing, and the corresponding negative charges are transferred to the surface of the insulating layer 2, the transparent conductive layer 3, and the photoconductive layer. layer 1
induced by the interface. Of course, the surface potential of the insulating layer 2 in the R filter portion where the charge has disappeared is almost O, but
The surface potential of the insulating layer 2 in the G and B filter parts where charges remain is also almost O due to the balance between positive and negative charges mentioned above.
shows. The red image exposure portion during image exposure has been described above, but the green image exposure portion and the pre-image exposure portion also give similar changes to each filter portion, and their integrated states are the discharge by the charger 6 and the image exposure portion. This is the state of the photoreceptor 4 that has been exposed to light. In this state, the surface potential of the insulating layer 2 is approximately 0 as seen in the graph, and no electrostatic image is shown, but a -order latent image is formed. Note that if a scorotron charger is used as the charger 6 to control the grid voltage, a uniform surface potential of, for example, -200V can be obtained.

As shown in FIG. 8 [3], light of the same color as that of the color separation filter is applied to the photoreceptor 4 on which the -order latent image is formed, that is, from the white light lamp 7. The entire surface is exposed to blue light LB obtained by passing the light through a blue filter FB. This blue light LB does not pass through the G and R filter parts, so it does not change those parts, but it passes through the B filter part and makes the photoconductive layer 1 thereon conductive. As a result, in the B filter part, the negative charge at the interface between the transparent conductive layer 3 and the photoconductive layer 1 and the positive charge at the interface between the photoconductive layer 1 and the insulating layer 2 are partially neutralized, and the insulating layer 2 On the surface of the potential vP
As shown in the graph below, a potential pattern that gives a complementary color image of blue begins to appear.

This electrostatic image is developed by a developing device 8Y using positively charged yellow toner TY, as shown in FIG. 8 [4]. As a result, the yellow toner TY adheres to the surface of the insulating layer 2 in the B filter portion, forming a yellow toner image. Even with the adhesion of this yellow toner TY, the surface potential vP of the insulating layer 2 in the B filter part does not drop to the potential of other parts as shown in the graph below, so next, development is performed with another color toner. Then, toner of other colors tends to adhere on top of the yellow toner, causing color smearing. Therefore, as shown in FIG. 8 [5], the charger 9 is AC or positive discharge is applied to the G and R filter parts, and development is carried out without affecting the charged state of the G and R filter parts.The surface potential vP of the insulating layer 2 of the 9B filter part is compared with other parts as shown in the graph. Lower it to the same level. This prevents color turbidity from occurring.

Next, the surface of the photoreceptor 4 that has been subjected to the above-described potential smoothing is illuminated again from the transparent conductive layer 3 side with light of a different color than before, for example, light that has passed through a green filter, in the same manner as in FIG. 8 [3]. Give a full exposure. As a result, an image potential appears on the surface of the insulating layer 2 in the G filter portion, which provides a complementary color image of green. By developing this electrostatic image with magenta toner in the same manner as in FIG.
A color image is formed. The surface potential of the insulating layer 2 on which this magenta toner image has been formed is also smoothed as in FIG. 8 [5], and the entire surface of the photoreceptor 4 is exposed to red light as in FIG. 8 [3]. , an image potential that provides a red complementary color image appears on the surface of the insulating layer 2 in the R filter portion. According to the explanation of FIG. 8 [2] above, all charges have disappeared in the R filter part, and even if the entire surface is exposed to red light, if red image exposure is performed, all the charges are removed from the R filter part. It is easy to be misunderstood that the image potential does not appear as a high potential to which toner can adhere in the area, but the above explanation refers to the area where the red image exposure LR is sufficiently strong, and in other areas, the intensity of the image exposure The fact that a potential (the weaker is higher) appears in response to the current and forms an image potential is the same as in the case of the B and G filter parts.

By developing this electrostatic image with cyan toner in the same manner as in FIG. A full-color three-color image is formed. It goes without saying that cyan toner does not adhere to areas where red image exposure LR is applied sufficiently strongly.

Although the above description is based on an example in which an n-type semiconductor is used for the photoconductive layer 1 of the photoreceptor 4, it is of course possible to use a p-type semiconductor such as selenium. In that case, the basic process remains unchanged except that the positive and negative signs of the charges in the above explanation are all reversed. In any case, if it is difficult for the charger 5 to inject charges into the photoreceptor 4,
Uniform irradiation with light may also be used. In that case, uniform irradiation from the transparent conductive layer 3 side will be performed with white light,
When the insulating layer 2 is a transparent insulating layer, light other than white light can also be used from the insulating layer 2 side.

The three-color or two-color toner image formed on the insulating layer 2 of the photoreceptor 4 is transferred and fixed onto a recording material by a conventionally known method.

Table 1 shows the relationship between the colors of both K>fa images and image formation using three primary color toners using the above-mentioned three-color separation method.

In Table 1 in the bottom margin of the figure, the color of the original image is shown as giving sufficiently strong light intensity, and the reference numeral 2-1 is the primary latent image, O
indicates an electrostatic latent image, ■ indicates a toner image, ↓ indicates a state in which the state in the upper column is maintained, and a blank indicates a state in which no image exists. Further, in the attached toner column, - indicates that no toner is attached, and Y, M, and G indicate that yellow toner, maze/tattoner, and cyan toner are attached, respectively.

The recording apparatus shown in FIGS. 9 and 10 is a copying machine that forms a multicolor image by the above-described image forming method of the present invention. In this copying machine, a belt-shaped photoreceptor 4 whose photoconductive layer is made of cadmium sulfide rotates in the direction of the arrow in FIG. 10 with the insulating layer side facing outward and the transparent conductive layer side facing inside. On the outside along the rotation path of the light body 40 is a charger 5.6" and a yellow toner, respectively.

Developing device 8Y that develops with magenta toner and cyan toner
, 8M, 80, and between developing devices βY and 8M and between 8M and 8G, chargers 9', 9' and transfer device 10 are provided, respectively.
, a static eliminator 11, and a cleaning device [12], and inside thereof, a mirror 13 for inputting image exposure light to a position corresponding to the discharge position of the charger 6, and a white light lamp 71.7#, respectively. 7171, blue filter FB, and green filter F. , and a red filter FR, and a charge eliminating exposure device 14 is provided at a position corresponding to the charge remover 11. The photoreceptor 4 is charged with a charger 5.
A negative charge is given to the entire surface by the charger 6, and reflected light or transmitted light from the white light of the document 0 is given to the charged part from the inside by the mirror 13 as image exposure as shown in FIG. A positive corona discharge is applied, which causes a primary latent image to be formed as explained in FIG. 8 [2]. This second-layer image forming area is entirely exposed to blue light from the inside by the lamp 7' and the filter FB, thereby forming an electrostatic image giving a complementary color image of blue on the outside surface. This electrostatic image is developed by a developing device 8Y to form a yellow toner layer, and the potential of the toner image forming surface is smoothed by a charger 9'.

A lamp 7' and a filter F are provided in this smoothing part. The combination exposes the entire surface to green light from the inside, the developing device 8M develops the electrostatic image formed thereby into a magenta toner image, the charger 9' smoothes the potential of the developing surface again, and the lamp The combination of 7'' and filter FR exposes the entire surface to red light from the inside, and the developing device 8C develops the electrostatic image formed thereby into a cyan toner image, so there is no color shift or color discoloration. A full-color image is formed by superimposing toner images of three primary colors.In addition, if necessary, in order to make it easier to charge the photoreceptor 4 with the charger 5, the upstream side including the position of the charger 5 may be It is also possible to provide a full-surface exposure device inside or outside the photoreceptor 4 and irradiate it with light.

The multicolor image formed on the photoreceptor 4 is transferred by a transfer device 10 to a recording paper P fed by a recording paper feeding means, and the transferred recording paper P is separated from the photoreceptor 4 and fixed. The toner image is fixed by the device 15 and discharged outside the machine.

The photoconductor 4 to which the toner image has been transferred is exposed to the static eliminator 1 while being irradiated with static eliminating light by the static eliminating exposure device 14 as necessary.
1, the residual toner is removed by the cleaning device 12, and the state returns to the state where a multicolor image is formed again.

In the image forming method IC of the present invention, it is preferable to use a magnetic brush developing device as the developing device, and the developer is a so-called one-component developer consisting only of non-magnetic toner or magnetic toner, or a so-called one-component developer consisting of toner and iron powder, etc. Any two-component developer consisting of a mixture of magnetic carriers can be used. During development, the photoreceptor surface may be rubbed with a magnetic brush, but in order to avoid damage to the formed toner image, especially after the second development, the developer layer should not come into contact with the photoreceptor surface. For example, U.S. Pat.
No. 46, Japanese Patent Application No. 58-238295, Japanese Patent Application No. 58-2
Particularly preferred is the method described in each specification of No. 38296. This method uses a one-component or two-component developer containing non-magnetic toner that can be colored freely, forms an alternating electric field in the development area, and performs development without contact between the photoreceptor and the developer layer. . The fact that the photoconductor and the developer layer are not brought into contact means that the gap between the photoconductor and the developing sleeve that conveys the developer layer of the developing device is the layer thickness of the developer layer that is conveyed to the development area (the thickness of the developer layer that is conveyed to the development area). This means that the layer thickness (with no potential difference between them) is also set wide.

The color toner used for development is made using known techniques and consists of known binding resins, organic and inorganic pigments, various chromatic and achromatic colorants such as dyes, and various magnetic additives that are commonly used in toners. Toner for developing electrostatic images can be used, and carriers such as iron powder, ferrite powder, which are usually used for electrostatic images, those coated with resin, or those with magnetic material dispersed in resin can be used. Various known carriers such as magnetic carriers can be used.

In addition, the applicant filed the patent application No. 58-24966 earlier.
The developing methods described in the specifications of No. 9 and No. 240066 may be used.

All of the above explanations have been made regarding examples of color copying machines that use so-called three-color separation filters and subtractive three-primary-color toner, but the present invention is not limited to the illustrated example, and the number and color of separation filters and It goes without saying that the combination of toner colors corresponding thereto can also be arbitrarily selected depending on the purpose. For example, processes for obtaining two-color copies are also conceivable.

As for such a process, if a photoreceptor with G filters scattered thereon is used, and the original is made up of two colors, red and black, the process is basically the same as above. (However, full exposure is G, R or F.
When using iG and B), for the black part of the original, a nearly black copy made of black toner and red toner is obtained, and for the red part of the original, a black copy part that is almost black is obtained from red toner. There is a process that yields the red part.

Therefore, the photoreceptor having a distribution layer of multiple types of filters in the above explanation is a photoreceptor having a layer consisting of a single type of color separation filter and a portion (C) without a filter (which may be transparent resin, air, etc.). In this case, the portion without a filter is regarded as a transparent filter and included in the plural types of filters.

In addition, in the above explanation, the spectral characteristics of light for full-surface exposure are
Green (G), blue (B), and red (m) can be obtained using a filter, but they can also be obtained by means other than filters, and their spectral characteristics are also G, B, H.
The spectral characteristics are not limited to the above, but in short, any spectral characteristic is sufficient as long as the latent image is formed only on a specific filter portion (not limited to one type) corresponding to the specific light on the photoreceptor by full exposure to the specific light. .

Furthermore, although the photoconductive layer and the conductive layer may be directly liquefied, a thin intermediate layer such as a resin may be interposed between the photoconductive layer and the conductive layer in order to improve the adhesion between the two. Further, in order to improve the charge retention properties of the photoconductive layer, a semiconductor layer having rectifying properties may be provided, or an insulating layer may be provided.

The present invention is applicable not only to copying machines but also to various multicolor image recording devices,
Can be widely used in color photo printers, etc.

〔Effect of the invention〕

According to the present invention, the entire surface charging and image exposure, which conventionally required multiple times, can be performed only once, eliminating the need for alignment of various images during transfer, making multicolor electrophotographic devices more compact and faster, and Reliability can be improved. The resulting recorded matter will also be of high quality with no color shift. That is, since the toner-attached portion and the exposure side are on opposite sides with respect to the photoconductive layer, image information is not prevented from reaching the photoconductive layer by the toner, and an image with high reproducibility can be obtained.

[Brief explanation of the drawing]

FIGS. 1 to 4 are cross-sectional views schematically showing examples of the laminated structure of the photoreceptor of the present invention, and FIGS. 5 to 7 are color separation filters in the transparent conductive layer of the photoreceptor of the present invention, respectively. FIG. 8 is a plan view showing an example of filter distribution of the distribution layer; FIG. 8 is a process diagram showing the image forming process of the multicolor image forming method of the present invention; FIG.
10 are a schematic cross-sectional view and a vertical cross-sectional view showing an example of a recording apparatus that implements the multicolor image forming method of the present invention. 1... Photoconductive layer, 2... Insulating layer, 3...
- Transparent conductive layer, 3a... Color separation filter distribution layer, 3b... Conductive layer, 3C... Transparent layer, 4... Photoreceptor, 5... Charger, 6... charger,
LR...Red image exposure, 7, 7', 7',
7”...white light lamp, FB...blue filter,
Fo...Jil filter, FR...red filter,
8Y, 8M, 8C...Developing device, 9, 9', 9
'... Charger, 10... Transfer device, 11... Static eliminator, 12... Cleaning device, 13... Mirror, 1
4... Exposure device for static elimination, 0 original, 15... Fixing device. Patent applicant Konishiroku Photo Industry Co., Ltd. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7

Claims (2)

[Claims] (1) A photoreceptor in which an insulating layer is provided on one side of a photoconductive layer and a transparent conductive layer is provided on the other side, and a laminated layer in which a plurality of types of color separation filter distribution layers are provided on the side of the conductive layer. A photoreceptor for forming multicolor images characterized by comprising a structure. (2) A photoreceptor in which an insulating layer is provided on one side of the photoconductive layer and a transparent conductive layer is provided on the other side, and a laminated layer in which a plurality of types of color separation filter distribution layers are provided on the side of the conductive layer. A multicolor image forming photoreceptor is used, and the conductive layer of the photoreceptor in contact with the photoconductive layer is grounded to charge the photoreceptor from the insulating layer side and from the translucent conductive layer side. image exposure, and then applying specific light to the entire surface from the light-transmitting conductive layer side to form a potential pattern on a specific portion of the insulating layer corresponding to one type of color separation filter, and forming the potential pattern. A method for forming a multicolor image, characterized in that the step of developing with a specific color toner is repeated with the entire surface exposure and the color of the toner being changed.