JPH0461349B2 - - Google Patents

Description

[Detailed description of the invention]

B. Field of Industrial Application The present invention relates to an image forming method, and more particularly to a multicolor image forming method for forming a multicolor image using electrophotography. B. Prior Art Many methods and devices used therefor have been proposed in the past for obtaining multicolor images using electrophotography, but they can generally be classified into the following types. One method is to repeatedly form a latent image using a photoreceptor and develop it with color toner according to the number of separated colors. However, it is a method of layering colors. Another method uses a device that has multiple photoreceptors corresponding to the number of separated colors, and simultaneously exposes each photoreceptor with a light image of each color, and the latent image formed on each photoreceptor is colored. It is developed with toner, sequentially transferred onto a transfer material, and the colors are superimposed to obtain a multicolor image. However, the first method described above has a major drawback in that it takes time to record an image, and it is extremely difficult to speed up the process, since it is necessary to repeat the process of forming and developing a plurality of latent images. In addition, the second method described above is advantageous in terms of high speed because it uses multiple photoreceptors in parallel, but the device is complicated because it requires multiple photoreceptors, an optical system, a developing means, etc. , large size, high price, and poor practicality. Furthermore, both of the above methods have the major drawback that it is difficult to align the image when image formation and transfer are repeated multiple times, and color shift of the image cannot be completely prevented. In order to fundamentally solve these problems, the present inventor has previously proposed a method for recording a multicolor image without color shift on a single photoreceptor through one image exposure. (Patent Application No. 59-83096) This is as follows. In other words, an insulating layer is formed by combining a photosensitive layer that is sensitive to the entire visible light range with multiple color separation filters (filters that substantially transmit only light in a specific wavelength range) in the form of fine lines or a mosaic. Using the arranged photoreceptor, image exposure is first applied to the entire surface of the photoreceptor, and charges are distributed in the photoconductive layer below each filter according to the resolved image density (hereinafter referred to as the primary latent image). By exposing the entire surface to light transmitted through one color separation filter, an electrostatic image corresponding to the first latent image (hereinafter referred to as a second latent image) is formed only on the photoconductive layer under the filter. ) is developed with a color toner of a color corresponding to the type of filter, preferably a complementary color to the color that passes through the filter, and is further uniformly charged. By repeating the operations of exposure, development, and recharging, a multicolor image is formed on the photoreceptor, and the multicolor image is recorded on the transfer material at once by one transfer. However, in multicolor images recorded using this method, (1) it is difficult for the toner images of each color to overlap at the same position; (2) Each toner does not have ideal spectral transmittance characteristics. For these reasons, there were problems in that the image density was insufficient and it was difficult to reproduce ideal black. C. Purpose of the Invention The purpose of the present invention is to provide a method that can add black to a multicolor image without adding complicated steps and form a multicolor image with high image density and good black reproduction. There is a particular thing. D. Structure of the Invention That is, the image forming method according to the present invention includes the steps of imagewise exposing a photoreceptor through a filter layer consisting of a plurality of color separation filter sections that mainly transmit light in different wavelength ranges; A step of repeating the operation of developing with a chromatic toner after the entire surface is exposed to light that passes through at least one kind of the decomposition filter part; After that, the surface of the photoreceptor is uniformly charged and the entire surface is exposed to light, and then developed with a black toner. It consists of a process. E. Examples Hereinafter, examples in which the present invention is applied to a multicolor image forming photoreceptor (hereinafter simply referred to as photoreceptor) and a multicolor image forming process will be described in detail. In the following explanation, red light, green light,
Although only a full-color reproduction photoreceptor using red, green, and blue filters that transmit only blue light will be described, the colors of the color separation filters and the colors of the toners combined therewith are not limited to the above. The process of forming a multicolor image using the above-mentioned photoreceptor will be explained with reference to FIG. The figure schematically shows the image forming process in a portion of a photoreceptor that uses an n-type (that is, high electron mobility) photosemiconductor such as cadmium sulfide as a photoconductive layer. In addition, cross-sectional hatching of each part is omitted. In the figure, 1 and 2 are a conductive substrate and a photoconductive layer, respectively, and 3 is an insulating layer including three color separation filter parts R, G, and B. Further, the graph at the bottom of each figure shows the potential on the surface of each part of the photoreceptor. First, as shown in FIG. 1 [1], when a positive corona discharge is applied to the entire surface by the charger 4, the insulating layer 3
A positive charge is generated on the surface, and a corresponding negative charge is induced at the interface between the photoconductive layer 2 and the insulating layer 3. Next, as shown in FIG. 1 [2], alternating current or negative discharge is applied by a charger 5 equipped with an exposure slit to uniformize the potential on the surface of the insulating layer 3 while exposing it to light. As an example, the figure shows the state of the part irradiated with the red component. This red light passes through the red filter section R of the insulating layer 3 and erases the charge in the photoconductive layer 2 in the same filter section in order to make the photoconductive layer 2 below it conductive. However, the electric charge of the red filter portion R that is not image exposed does not change (in the drawing, the exposed portion and the non-exposed portion of the filter portion R are shown respectively). On the other hand, since the green G and blue filter sections B do not transmit red light, the negative charges on the photoconductive layer 2 remain as they are. Further, due to the action of the charger 5, the charge distribution on the insulating layer 3 changes so that the surface potential of the photoreceptor becomes uniform. The primary latent image is formed in the manner described above. The portions of the document irradiated with the green and blue components also give similar results for each filter section. The primary latent image is a state in which all color components exist as an image-like charge distribution under each filter section. At this stage, not only the portions on the photoconductive layer 2 where the charges have been erased, but also the portions where the charges remain have a uniform potential on the surface of the photoreceptor, and therefore do not function as an electrostatic image. Although FIG. 1 [2] shows a case where the potential after charging is approximately zero, it may be charged to a negative level. Next, as shown in FIG. 1 [3], the light that passes through one of the filters included in the insulating layer 3, for example, the light source 61 and the filter _F1 , passes through the blue filter section B, but the green light passes through it. When the light L ₁ that does not pass through the filter section G and the red filter section R is obtained and the entire surface is exposed with this light L ₁ , the photoconductive layer 2 below the blue filter B becomes conductive, and the photoconductive layer 2 in that part becomes conductive. A part of the negative charge of the filter B and the charge of the conductive substrate 1 are neutralized, and only the charge on the surface of the filter B remains, thereby generating a potential pattern. No change occurs in the G and R portions that do not transmit blue light. This is the second latent image. Then, when the charged image on filter B is developed with a developer containing negatively charged yellow toner TY, the toner adheres only to the surface of the filter B portion, which has a relatively high potential, and development is performed (see Fig. 1). 4)). Further, a charger 81 uniformly charges the surface of the photoreceptor. Next, light L ₂ that passes through the green part G but does not pass through the red part R is obtained from the light source 62 and the filter F ₃ , and when the entire surface is exposed with this light, the part of the green filter part G is exposed as shown in FIG. 1 [6]. A second latent image is formed. If this is developed with magenta toner TM, the magenta toner will adhere only to the portion of filter G as shown in FIG. 1 [7]. Furthermore, the photoreceptor is uniformly charged by the charger 82. Next, Figure 1

As shown in [9], when the entire surface is exposed with the light _L3 that passes through at least the red filter portion R, a second latent image is formed on the red filter portion R. When this is developed with cyan toner TC, the first
A cyan image is formed in the R portion as shown in Figure [10]. Although the multicolor image obtained by the above steps has good color reproduction, the image density is low, so black addition is further performed as follows. (1) The surface of the photoreceptor is uniformly and positively charged (Figure 1 [11]). (2) Expose the entire surface to light (such as weak white light) while applying an alternating current or negative charge (Figure 1 [12]). As a result, in the toner adhesion area on the photoreceptor,
The entire surface exposure does not reach the photoconductive layer sufficiently and it exhibits a different potential than the rest of the photoreceptor. (3) Develop the areas of the photoconductor where the surface potential is relatively low (i.e., the areas to which chromatic toner has already adhered) with the positively charged black toner TK (Figure 1 [13]) . The above steps can be expressed as shown in Table-1. In this table, the symbol "〓" indicates a state in which a charge exists in the photoconductive layer during primary latent image formation, and the symbol "〓" indicates a state in which the charge in the photoconductive layer is lost due to full-surface exposure and the potential increases. The symbol "ⓓ" indicates the state in which development has been performed, and the symbol "↓" indicates that the state in the upper column is maintained as it is. A blank space represents a state in which no charge is present in the photoconductive layer.

【table】

[Table] * Filter on photoreceptor ** Y: Yellow, M: Magenta, C: Cyan, K: Black Indicates the presence of each toner.
The thus obtained multicolor toner image is given a negative charge again and then transferred onto a transfer material such as paper and fixed, thereby forming a multicolor image on the transfer material. In this multicolor image, since black toner is added to the chromatic toner, the image density is high and black reproducibility is good. The transfer/fixing method is not limited to electrostatic transfer, and pressure transfer/fixing or the like may be employed. In addition, in the black addition steps (1) to (3) above, the charging and full-surface exposure in (2) do not necessarily have to be performed at the same time, but can be carried out as in (1) → AC or negative charging → full-scale exposure → (3). It's okay. The entire surface exposure light L ₁ , L ₂ ,
_L3 does not necessarily have to be monochromatic light with a narrow spectral distribution as shown in the embodiment of the previous application (Japanese Patent Application No. 59-83096). In other words, even if light is irradiated onto a portion of the photoconductive layer whose charge has already been erased by full-surface exposure, the potential of that portion will not change.
Toner will not adhere during the subsequent development process. When the spectral transmittance characteristics of the color separation filter included in the insulating layer of the photoreceptor are given as shown in FIG. 2, the spectral distributions of L ₁ , L ₂ , and L ₃ may be as follows. L ₁ ...The longest wavelength is λ ₀ or more and λ ₁ or less. L ₂ ...The longest wavelength is λ ₁ or more and λ ₃ or less. L ₃ ...Those with wavelength components of λ ₃ or more and λ ₅ or less. Therefore, the materials of the light source and filter that form each whole surface exposure light are not strictly limited, and they can be manufactured easily and at low cost. Contrary to the above example, latent image formation and development may be performed in the order of R, G, and B. In this case, each full-surface exposure light (L ₁ ′→L ₂ ′→L ₃ ′) needs to satisfy the following conditions. L ₁ ′...The shortest wavelength is λ ₄ or more and λ ₅ or less. L ₂ ′...The shortest wavelength is λ ₂ or more and λ ₄ or less. L ₃ ′...Has a wavelength component of λ ₀ or more and λ ₂ or less. Furthermore, latent image formation and development may be performed in the order of B, R (or R, B), and G. In this case, the total exposure light (L ₁ ″→L ₂ ″→L ₃ ″) (or L ₂ ″→L ₁ ″→
L ₃ ″) must satisfy the following conditions: L ₁ ″...The longest wavelength is λ ₀ or more and λ ₁ or less. L ₂ ″...The shortest wavelength is λ ₄ or more and λ ₅ or less. L ₃ ″...The wavelength component is λ ₁ or more and λ ₄ or less. Although the above explanation is based on an example using an n-type optical semiconductor layer, it is of course possible to use a p-type (i.e., high hole mobility) optical semiconductor layer such as selenium, and in this case, The basic process is the same, just the signs of the charges are reversed. Note that if it is difficult to inject charge during initial charging, uniform irradiation with light is also used. As is clear from the above explanation, in this example,
A step of applying image exposure while charging a multicolor image forming photoreceptor, and then performing development by applying full-surface exposure with light transmitted through at least one of a plurality of types of filters, depending on the number of types of filters. repeat. Therefore, according to this process, a photoreceptor is used, in which a plurality of color separation filters are arranged in a combination of fine stripes or mosaics on a photosensitive layer that is sensitive to the entire visible light range, and the entire surface of the photoreceptor is first coated. Image exposure is applied to form a primary latent image in the photosensitive layer below each filter according to the resolved image density, and then the entire surface is exposed to light passing through the first color separation filter. A second latent image corresponding to the first latent image is formed on the filter section. and,
A multicolor image is formed on the photoreceptor by developing with a color toner of a color corresponding to the color of the filter, preferably a color complementary to the color transmitted through the filter, and then repeating the same operation for color separation images. A multicolor image can be recorded on the transfer material at once by one transfer. FIG. 3 schematically shows a cross section of a photoreceptor that can be used in the present invention. A photoconductive layer 2 is provided on a conductive member 1 or a substrate, and an insulating layer 3 containing a large number of required color separation filters such as red (R), green (G), and blue (B) filters is laminated thereon. ing. The conductive member 1 is made of aluminum, iron, nickel,
Metals such as copper or their alloys are used to create appropriate shapes such as cylindrical shapes, endless belt shapes, etc. as required.
All you have to do is create a structure. The photoconductive layer 2 is a photoconductive material such as sulfur, selenium, amorphous silicon or an alloy containing sulfur, selenium, tellurium, arsenic, antimony, etc.; or oxidation of metal such as zinc, aluminum, antimony, bismuth, cadmium, molybdenum, etc. Inorganic photoconductive substances such as polyvinylcarbazole, anthracenephthalocyanine, trinitrofluorenone, polyvinylcarbazole, polyvinylanthracene, polyvinylpyrene, etc.; It can be made of polystyrene, polyvinyl chloride, polyvinyl acetate, polycarbonate, acrylic resin, silicone resin, fluororesin, epoxy resin, or the like dispersed in an insulating binder resin. The photoconductive layer is
It is preferable to have sensitivity in the ultraviolet and infrared regions. The insulating layer 3 can be made of a transparent insulating material, such as various polymer resins, and its surface,
In some cases, it has a colored portion inside that functions as a color separation filter. The colored portion is as shown in FIG. 3a,
An insulating material colored by adding a coloring agent such as a dye having a desired color is applied onto the photoconductive layer 2 in a predetermined pattern by means such as printing, or as shown in FIG.
It can be formed by depositing a coloring agent in a predetermined pattern on a colorless insulating layer 3a that has been uniformly formed in advance on the photoconductive layer 2 by means of printing, vapor deposition, etc., as shown in FIG. Alternatively, a photoreceptor having the structure shown in FIGS. 3a and 3b can be constructed by attaching a film-like insulating material on which a colored portion has been formed in advance on the photoconductive layer. Furthermore, the surface of the formed colored portion may be further covered with an insulating material 3b to form a structure as shown in FIG. 3c. Alternatively, as shown in FIG. 3d, the coloring agent may be deposited in a predetermined pattern on the photoconductive layer by direct printing, vapor deposition, etc., and the surface thereof may be further covered with an insulating material 3b. . Furthermore, Figures 3a to 3d all show the so-called 3 colors of red, green, and blue.
A case in which a color separation filter is provided is shown. The shape and arrangement of the plurality of types of minute color separation filters constituted by the colored portions are not particularly limited, but may be linear as shown in FIG. , the line is perpendicular to the rotation direction, the line is parallel to the direction of rotation, the line is configured so that multiple types of filters are densely surrounded in a spiral shape around the drum-shaped photoreceptor (each type of filter is one), or It is preferable to configure it in a mosaic shape as shown in FIGS. 4b and 4c. The size of each filter is 30~
The thickness is preferably 300 μm. If the size of the filter is too small, it will be susceptible to the influence of adjacent parts of other colors, and if the width of one unit of the filter is equal to or smaller than the particle size of the toner particles, it will be difficult to manufacture. Furthermore, if the size of the filter becomes too large, the resolution and color mixing properties of the image will decrease, resulting in deterioration of the image quality. Note that the filter portion of the insulating layer is not limited to blue, green, and red, and may be, for example, a neutral density filter or one that includes a portion that transmits ultraviolet light or infrared light. In the above image forming process, the developer used may be either a so-called one-component developer that uses non-magnetic toner or magnetic toner, or a so-called two-component developer that mixes toner and a magnetic carrier such as iron powder. I can do it. For development, direct rubbing with a magnetic brush may be used, but especially after the second development, in order to avoid damage to the formed toner image, it is necessary to It is essential to use a non-contact development method in which the agent layer does not rub against the surface of the photoreceptor. This non-contact method uses a one-component or two-component developer containing non-magnetic toner or magnetic toner that can be freely selected for coloring, forms an alternating electric field in the development area, and connects the electrostatic image support (photoreceptor) and the developer. Development is performed without rubbing the layers. This will be explained in detail below. In repeated development using an alternating electric field as described above, it is possible to repeat the development several times on a photoreceptor on which a toner image has already been formed, but if appropriate development conditions are not set, the toner image may be damaged during subsequent development. , the toner image formed on the photoconductor in the previous stage may be disturbed, or the toner already attached to the photoconductor may return to the developer conveying body, which may contain a developer of a different color from the developer in the previous stage. There is a problem that it may invade the developing device in the subsequent stage, causing color mixing. Basically, to prevent this, the developer layer on the developer transporting member should be operated without rubbing or contacting the photoreceptor. For this purpose, the gap between the image carrier and the developer transporting member is maintained larger than the thickness of the developer layer on the developer transporting member (provided that there is no potential difference between them). Experiments conducted by the present inventors have revealed that desirable development conditions exist in order to more completely avoid the above-mentioned problems and further form each toner image with sufficient image density. These conditions include the gap d (mm) (hereinafter sometimes simply referred to as gap d) between the image carrier and the developer conveying body in the development area, the amplitude V _AC and the frequency of the alternating current component of the developing bias that generates the alternating electric field. It has become clear that it is difficult to obtain an excellent image even if the value of f (Hz) is determined independently, and that these parameters are closely related to each other. The progress will be explained below. The experiment was conducted using the color copying machine shown in FIG. 5, and when forming two-color toner images with the developing devices 17Y and 17M, the influence of parameters such as the voltage and frequency of the AC component of the developing bias of the developing device 17M was investigated. Examined. FIG. 8 shows each developing device 17Y, 1 shown in FIG.
7M, 17C, and 17K, showing the basic configuration of the sleeve 7 and/or magnetic roll 4.
3 rotates, the developer De is conveyed on the circumferential surface of the sleeve 7 in the direction of arrow B, and the developer De
is supplied to the developing area E. As the magnetic roll 43 rotates in the direction of arrow A and the sleeve 7 rotates in the direction of arrow B, the developer D is conveyed in the direction of arrow B. The thickness of the developer De is regulated by a spike regulating blade 40 made of a magnetic material while being transported. A stirring screw 42 is provided in the developer reservoir 47 to sufficiently stir the developer De, and when the toner in the developer reservoir 47 is consumed, the toner supply roller 39 rotates. , toner T is replenished from the toner hopper 38. A DC power source 45 and an AC power source 46 are provided in series between the sleeve 7 and the photosensitive drum 41 to apply a developing bias. R is a protective resistance. First, the developer De stored in the developing device 17M
is a one-component magnetic developer, made of thermoplastic resin 70wt.
%, pigment (carbon black) 10wt%, magnetic material
20Wt%, charge control agent is kneaded and crushed, and the average particle size is
The diameter is 15 μm and a fluidizing agent such as silica is added. The amount of charge is controlled by a charge control agent. As a result of the experiment, results as shown in FIGS. 9 and 10 were obtained. FIG. 9 shows that in the developing device 17M, the gap d between the photosensitive drum 41 and the sleeve 7 is 0.7 mm, the thickness of the developer layer is 0.3 mm, the DC component of the developing bias applied to the sleeve 7 is 50 V, and the AC component of the developing bias is 0.7 mm. This figure shows the relationship between the amplitude of the AC component and the image density of the black toner image when developing an area where the surface potential of the photoreceptor after uniform exposure is 500 V under the condition that the frequency is 1 kHz. Note that, at this time, the two-component developer for yellow is stored in the developing device 17Y. The amplitude E _AC of the AC electric field strength is the value obtained by dividing the amplitude V _AC of the AC voltage of the developing bias by the gap d. Curves A, B, and C shown in FIG. 9 are the results when using magnetic toners with average charge amounts of -5 μc/g, −3 μc/g, and −2 μc/g, respectively. The three curves A, B, and C all indicate that the amplitude of the alternating current component of the electric field is 200 V/mm or more,
Image density is high below 1.5KV/mm, 1.6KV/mm
In this case, it was observed that the toner image previously formed on the photoreceptor drum 44 was partially destroyed. FIG. 10 shows the change in image density when the frequency of the AC component of the developing bias is 2.5 kHz and the AC electric field strength etc. are varied under the same conditions as in the experiment shown in FIG. According to the experimental results, the image density is high when the amplitude E _AC of the AC electric field strength is 500/mm or more and 3.8 KV/mm or less, and when it is 3.2 KV/mm or more (not shown in FIG. 9), the photosensitive drum 4 A portion of the toner image previously formed thereon was destroyed. Note that FIGS. 9 and 10 show that the image density changes to become saturated or to decrease slightly after reaching a certain amplitude. As can be seen from curves A, B, and C, the value of this amplitude does not depend much on the average charge amount of the toner. Now, when we conducted an experiment similar to that shown in Figures 9 and 10 while changing the conditions, we found that the amplitude of the AC electric field strength
E You can organize the relationship between _AC and frequency, and the 11th
The results shown in the figure were obtained. In FIG. 11, the area indicated by is an area where uneven development is likely to occur, the area indicated by is an area where the effect of the AC component does not appear, the area indicated by is an area where destruction of the already formed toner image is likely to occur, , is a preferable range in which the effect of the alternating current component appears, sufficient development density is obtained, and the already formed toner image is not destroyed. As a result, the toner image previously formed on the photoreceptor drum 41 (in the previous stage) is not destroyed.
This shows that in order to develop the next (later stage) toner image with an appropriate density, there is an appropriate range for the amplitude and frequency of the alternating current electric field strength. Based on the above experimental results, the present inventor determined that the amplitude of the AC component of the developing bias was adjusted to V _AC in each developing process.
(v), the frequency is (Hz), and the gap between the photoconductor drum 41 and the sleeve 7 is d (mm).If development is performed under the conditions that satisfy 0.2≦V _AC /(d・)≦1.6, the photoconductor drum 41 is already It was concluded that subsequent development can be performed at an appropriate density without disturbing the toner image formed on the drum 41. In order to obtain sufficient image density and not disturb the toner image formed up to the previous stage, the image density shows an increasing tendency with respect to the AC electric field as shown in FIGS. 9 and 10. It is more desirable to satisfy the condition 0.4≦V _AC /(d・)≦1.2. Furthermore, within this region, it is more desirable that the electric field is slightly lower than that at which the image density is saturated, that is, 0.6≦V _AC /(d·)≦1.0. In addition, in order to prevent uneven development due to the AC component, the frequency of the AC component is set to 200 Hz or more, and when a rotating magnetic roll is used as a means for supplying the developer to the photoreceptor drum 41, the AC component and the magnetic roll are In order to eliminate the influence of beats caused by rotation, it is more desirable that the frequency of the alternating current component be 500 Hz or higher. Next, an experiment was conducted using a color copying machine shown in FIG. 5 in the same manner as above using a two-component developer. The developer De stored in the developing device 17M is a two-component developer consisting of a magnetic carrier and a non-magnetic toner, and the carrier has an average particle size of 20 μm and is magnetized.
A carrier made by dispersing fine iron oxide in a resin to exhibit physical properties of 30 emu/g and a resistivity of 10 ¹⁴ Ω ^- cm. After placing the particles in a container and tapping them, a load of 1Kg/ ^cm2 is applied to the packed particles, and a voltage that generates an electric field of 1000V/cm2 is applied between the load and the bottom electrode, and the current value is read. This is the value obtained. The toner was prepared by adding a small amount of a charge control agent to 90 wt % of a thermoplastic resin and 10 wt % of a pigment (carbon black), kneading and pulverizing the mixture to give an average particle size of 10 μm. A developer D was prepared by mixing 20 wt% of the toner with 80 wt% of the carrier. Note that the toner is negatively charged due to friction with the carrier. The results of this experiment are shown in FIGS. 12 and 13. FIG. 12 shows that the gap d between the photoreceptor drum 41 and the sleeve 7 is 1.0 mm, the developer layer thickness is 0.7 mm, the charging potential of the photoreceptor is 500 V, and the DC component of the developing bias is
It shows the relationship between the amplitude of the AC component and the image density of a colorless toner image when developing an area where the surface potential of the photoreceptor after uniform exposure is 500V under the conditions of 50V and AC component frequency of 1kHz. Note that the developing device 17Y
contains a two-component yellow developer.
The amplitude E _AC of the AC electric field strength is the value obtained by dividing the amplitude V _AC of the AC voltage of the developing bias by the gap d. Curves A, B, and C shown in Fig. 12 indicate that the average charge amount of the toner is -30μc/g, -20μc/g, and -15μc/g, respectively.
These are the results when a charge-controlled g is used. For all three curves A, B, and C, the effect of the AC component appears when the amplitude of the AC component of the electric field is 200V/mm or more, and when the amplitude is 2500V/mm or more, the toner image previously formed on the photoreceptor drum is It was observed that some parts were destroyed. FIG. 13 shows the change in image density when the AC electric field strength E _AC is changed under the same conditions as in the experiment shown in FIG. 12, with the frequency of the AC component of the developing bias being 2.5 kHz. According to this experimental result, when the amplitude E _AC of the alternating current electric field strength exceeds 500 V/mm, the image density becomes large;
Although not shown, when the voltage exceeded 4 KV/mm, part of the toner image previously formed on the photosensitive drum 41 was destroyed. Note that FIGS. 12 and 13 show that the image density changes to become saturated or to decrease slightly after reaching a certain amplitude. As can be seen from curves A, B, and C, the value of this amplitude does not depend much on the average charge amount of the toner. Now, when we conducted the same experiment as shown in Figures 12 and 13 while changing the conditions, we were able to sort out the relationship between the amplitude E _AC of AC electric field strength and the frequency, and obtained the results shown in Figure 14. . In FIG. 14, the area indicated by is an area where uneven development is likely to occur, the area indicated by is an area where the effect of the AC component does not appear, the area indicated by is an area where destruction of the already formed toner image is likely to occur, , is a region in which the effect of the alternating current component appears, a sufficient development density is obtained, and the already formed toner image is not destroyed, and is a particularly preferable region. This result shows that in order to develop the next (later) toner image at an appropriate density without destroying the toner image formed in the previous stage on the photoreceptor drum 41, the amplitude and frequency of the alternating current electric field strength must be adjusted. , indicating that there is an appropriate area. Based on the above experimental results, the inventor determined that the amplitude of the AC component of the developing bias was adjusted to V _AC in each developing process.
(v) When the frequency is (Hz) and the gap between the photosensitive drum 41 and the sleeve 7 is d (mm), 0.2≦V _AC /(d・) {(V _AC /d)−1500}≦1.0 is satisfied. It was concluded that if development is carried out under certain conditions, subsequent development can be carried out at an appropriate density without disturbing the toner image already formed on the photoreceptor drum 41. In order to obtain sufficient image density and not disturb the toner image formed up to the previous stage, among the above conditions, 0.5≦V _AC /(d・) {(V _AC /d)−1500}≦1.0 It is more preferable to satisfy the following. Furthermore, especially when 0.5≦V _AC /(d・) {(V _AC /d)−1500}≦0.8 is satisfied, a clearer multicolor image with no color turbidity can be obtained, and the developing process will continue even after multiple operations. It is possible to prevent toner of a different color from entering the device. In addition, in order to prevent uneven development due to the AC component, the frequency of the AC component is set to 200 Hz or more, as in the case of using a single-component developer, and a rotating magnetic roll is used as a means for supplying the developer to the photoreceptor drum 41. When used, it is more desirable that the frequency of the alternating current component be 500 Hz or more in order to eliminate the influence of beats caused by the alternating current component and the rotation of the magnetic roll. In addition, in the method of the present invention, it is desirable to consider the following characteristic matters. Non-magnetic toners can be used, and vivid color toners can be used. Two-component non-contact development has high reliability as an apparatus in terms of developer transport, charging, etc. Micronization of toner (especially 10μm or less)
Since the size of each mosaic filter (see FIG. 11) is approximately 1/3 to 50 μm, it is desirable to faithfully develop the filter portion. If the toner size is large, it will be about the same as the filter size and will be noisy. However, when the toner is microsized, there arise problems such as a decrease in fluidity and the toner not moving sufficiently under an oscillating electric field unless the toner has a high amount of charge.
In this respect, the two-component non-contact development method can solve the problems of transportation and toner charging using a carrier. This is difficult with one-component development. If color reproduction is performed by additive color mixing, the image density will be low unless a sufficient amount of toner is deposited on each mosaic filter. For this reason, it is desirable to use a developing process that allows a large amount of toner to adhere. This is due to micronization of the carrier (increasing the toner density),
This is possible with a two-component developer that can sufficiently charge and transport the toner (large supply of charged toner). The superimposition of toner images can be performed at a lower AC bias voltage than in the case of one component. In addition, the charge amount distribution of the toner is more stable and narrow than that of a single component, making it easier to set overlapping conditions.
stable. Therefore, it is preferable to use a two-component developer, and the carrier-containing developer used in the method of the present invention is disclosed in Japanese Patent Application No.
No. 183152, No. 58-184381, No. 58-187000,
As stated in Japanese Patent Application No. 58-57446, it is desirable that the carrier and toner meet the appropriate conditions described below. First, regarding the carrier, the fact that the magnetic carrier particles are spherical improves the ability to agitate the toner and carrier and transport the developer, and also improves the ability to control the charge of the toner, making it easier for the toner particles to interact with each other. Prevents agglomeration of toner particles and carrier particles. However, in the present invention, if the average particle size of the magnetic carrier particles is large, the condition of the ears of the magnetic brush formed on the developer transport carrier is rough, so that the electrostatic image cannot be developed while being vibrated by the electric field. However, problems may occur, such as non-uniformity in the toner image, and the toner concentration in the ○ rows being low, such that high-density development cannot be carried out. In order to solve this problem, the average particle size of the carrier particles can be reduced, and as a result of experiments, the effect begins to appear when the average particle size is 50 μm or less, and especially when the particle size is 30 μm or less,
It has been found that the problem of ○B virtually disappears. In addition, the problems of ◯ and ② are also solved by making the magnetic carrier finer particles, which increases the toner concentration in the spikes and enables high-density development. However, if the carrier particles are too fine,
○They become attached to the surface of the image carrier together with the Hutner particles, and ○2 they become easily scattered. These developments are also related to the strength of the magnetic field acting on the carrier particles and the resulting magnetization strength of the carrier particles, but experiments have shown that the average particle size of the carrier particles is
A tendency gradually begins to appear below 15 μm, and becomes noticeable below 5 μm. The carrier particles adhering to the surface of the image bearing member of the present invention are usually dark in color, and some of them migrate onto the recording paper together with the toner, giving a serious adverse effect on color images. From the above, the average particle size of the magnetic carrier is
Appropriate conditions are 50 μm or less, particularly preferably 30 μm or less, 5 μm or more, particularly preferably 15 μm or more,
Preferably, it is spherical. In the present invention, the average particle size refers to the average particle size of Coulter Counter (manufactured by Coulter), Omnicon Alpha (manufactured by Boshilom).
This is the weight average particle diameter determined by Such magnetic carrier particles may contain iron, iron, similar to conventional magnetic carrier particles as magnetic materials.
Metals such as chromium, nickel, and cobalt, or their compounds and alloys, such as triiron tetroxide, γ
- Particles of ferric oxide, chromium dioxide, manganese oxide, ferrite, manganese-copper alloys, and other ferromagnetic or paramagnetic substances are made fine, preferably finely spherical, or preferably these magnetic substances are The surface of the particles is coated spherically with resin such as styrene resin, vinyl resin, ethyl resin, rosin modified resin, acrylic resin, polyamide resin, epoxy resin, polyester resin, or fatty acid wax such as palmitic acid or atearic acid. Alternatively, particles obtained by preferably producing spherical particles by pulverizing or granulating polymerizing resin or fatty acid wax particles containing dispersed magnetic fine particles can be processed using conventionally known methods. It is obtained by particle size selection using an average particle size selection means. In addition to the above-mentioned effects, forming the carrier particles into a spherical shape using resin or the like as described above makes the developer layer formed on the developer transport carrier uniform, and also makes it possible to It also has the effect of making it possible to apply a high bias voltage to the. That is, the carrier particles are made spherical by resin or the like because (1) Generally, carrier particles tend to be magnetized and attracted in the long axis direction, but by sphericalization, this directionality is lost; , the developer layer is formed uniformly, preventing the occurrence of locally low resistance areas and uneven layer thickness; (2) In addition to the high resistance of the carrier particles, the edge portions seen in conventional carrier particles are prevented. As a result, even if a high bias voltage is applied to the developer transport carrier, the electric field will not be concentrated on the edge portion, and as a result, even if a high bias voltage is applied to the developer transport carrier, the electrostatic latent image will be disturbed due to discharge on the image carrier surface. This provides the effect that the bias voltage does not break down. The fact that this high bias voltage can be applied means that when development under an oscillating electric field in a preferred embodiment of the present invention is performed by applying an oscillating bias voltage, the effects described below can be sufficiently achieved. This means that you can make the most of it. As mentioned above, wax can also be used as the carrier particles that produce the above-mentioned effects, but from the viewpoint of the durability of the carrier, it is preferable to use resin as mentioned above. is 10 ⁸ Ω-cm or more, especially 10 ¹³ Ω
It is preferable that insulating magnetic particles are formed so that the diameter is -cm or more. This resistivity makes the particles 0.50cm ²
After placing the particles in a container with a cross-sectional area ^of
This value is obtained by reading the current value when applying a voltage that generates an electric field of 1000 V/cm between the load and the bottom electrode (the thickness of the particles was approximately 1 mm), and this resistivity is If it is low, when a bias voltage is applied to the developer transport carrier, charge is injected into the carrier particles, making it easier for the carrier particles to adhere to the surface of the image carrier, or for bias voltage breakdown to occur more easily. . In summary, the magnetic carrier particles are spherical so that the ratio of the major axis to the minor axis is at least 3 times or less, and there are no protrusions such as needles or edges.
A suitable condition is that the resistivity is 10 ⁸ Ω-cm or more, preferably 10 ¹³ Ω-cm or more. For such magnetic carrier particles, in the case of highly resistive spherical magnetic particles or resin-coated carriers, it is necessary to select spherical magnetic particles as much as possible and coat them with resin, or to use a magnetic fine particle dispersion system. The carrier is manufactured by using fine particles of magnetic material as much as possible, by performing a spheroidization treatment after forming dispersed resin particles, or by obtaining dispersed resin particles by a spray drying method. Next, regarding toner, when the average particle size of toner particles in a two-component developer becomes smaller, the amount of charge qualitatively decreases in proportion to the square of the particle size, and relatively adhesion such as van der Waals force occurs. As the adhesion force increases, it becomes difficult for the toner particles to separate from the carrier particles, and once the toner particles adhere to the non-image area of the image bearing surface, they cannot be easily removed by rubbing with a conventional magnetic brush and become fogged. It begins to give rise to In the conventional magnetic brush development method, when the average particle size of toner particles becomes 10 μm or less,
These problems have become more prominent. In the developing method of the present invention, this problem is solved by performing development using a developer layer, a so-called magnetic brush, under an oscillating electric field. That is, the toner particles attached to the developer layer are easily moved away from the developer layer and transferred to the image area and the non-image area on the image carrier surface by the electrically applied vibrations, and are also easily separated from the developer layer. In addition, toner particles with a low charge amount hardly migrate to image areas or non-image areas, and
Since it does not rub against the surface of the image carrier, it does not adhere to the image carrier due to frictional electrification.
Toner particles with a particle size of about 1 μm have come to be used. Therefore, it is possible to obtain a clear toner image with good reproducibility in which the electrostatic latent image is faithfully developed. Furthermore, since the oscillating electric field weakens the bond between the toner particles and the carrier particles, the adhesion of the carrier particles associated with the toner particles to the image carrier surface is also reduced. In the image area and non-image area, toner particles with a large amount of charge vibrate under an oscillating electric field, and depending on the strength of the electric field, the carrier particles also vibrate, so that the toner particles selectively touch the surface of the image carrier. Since the carrier particles are transferred to the image area, adhesion of the carrier particles to the surface of the image carrier is greatly reduced. On the other hand, as the average particle size of the toner increases, as described above, the roughness of the image becomes noticeable.
Normally, toner with an average particle size of about 20 μm is not a problem in practice for developing fine lines arranged at a pitch of about 10 lines/mm with high resolution.
When the following micronized toner is used, the resolving power is significantly improved, and it becomes possible to provide clear, high-quality images that faithfully reproduce gradation differences, etc. For the above reasons, the appropriate particle size of the toner is an average particle size of 20 μm or less, preferably 10 μm or less. In addition, in order for the toner particles to follow the electric field, the amount of charge of the toner particles should be greater than 1 to 3 μc/g (preferably 3 μc/g).
~100μc/g) is desirable. Particularly when the particle size is small, a high amount of charge is required. Also, the resistivity is
It is preferably at least 10 ⁸ Ω-cm, preferably at least 10 ¹³ Ω-cm. Such toner can be obtained in the same manner as conventional toner. That is, it is possible to use a toner in which spherical or amorphous nonmagnetic or magnetic toner particles in conventional toners are sorted by an average particle size sorting means. Among these, it is preferable that the toner particles are magnetic particles containing magnetic particles, and it is particularly preferable that the amount of magnetic fine particles does not exceed 60 wt%, but in order to obtain color clarity, it is preferable that the amount of magnetic fine particles is 30 wt% or less. A small amount is good. When the toner particles contain magnetic particles, the toner particles are influenced by the magnetic force of the magnet included in the developer transport carrier, so that the uniform formation of the magnetic brush is further improved. The occurrence of fogging is prevented, and furthermore, scattering of toner particles becomes less likely to occur.
However, if the amount of magnetic material contained is too large,
The magnetic force between the toner particles and the carrier particles becomes too large, making it impossible to obtain sufficient developer density, and fine magnetic particles also appear on the surface of the toner particles, making it difficult to control triboelectric charging. In other words, the toner particles tend to be damaged or agglomerate with the carrier particles. To summarize the above, preferred toners in the image forming method of the present invention use fine particles of resin and magnetic material as described for the carrier,
By adding a coloring component such as carbon and a charge control agent as necessary, the particles can be produced by a method similar to a conventionally known toner particle manufacturing method. It consists of particles. In the image forming method of the present invention, a developer in which the above-described spherical carrier particles and toner particles are mixed in the same proportion as in a conventional two-component developer is preferably used;
If necessary, a fluidizing agent to improve the fluidity and sliding of the particles, a cleaning agent to help clean the surface of the image carrier, and the like are mixed. As the fluidizing agent, colloidal silica, silicone varnish, metal soap, or nonionic surfactant can be used, and as the cleaning agent, fatty acid metal salt, organic group-substituted silicone, fluorine, etc. can be used as a surfactant. I can do it. The above are preferable conditions for the developer,
It is possible to prevent color turbidity between the mosaic filters caused by such a developer. Regarding the preferred developing roller used in the present invention, the sleeve 7 and the magnet body 43 can rotate relative to each other, and the figure shows a case where the sleeve 7 rotates in the direction of the arrow. Further, the N and S magnetic poles of the magnet body 43 are normally magnetized to a magnetic flux density of 500 to 1500 Gauss, and the magnetic force causes a layer of the developer D as described above, that is, a magnetic brush, to be formed on the surface of the sleeve 7. form. The speed at which the sleeve 7 rotates in the direction of the arrow and the magnet body 43 rotates in the opposite direction of the arrow is preferably 200 rpm to 2000 rpm. That N,
The magnetic flux densities of the S magnetic poles are approximately equal. However, although the sleeve 7 rotates in the direction of the arrow,
The magnet body 43 is fixed, or the magnet body 43 is fixed.
The magnetic flux densities of the N and S magnetic poles are not the same, and the magnetic flux density of the N magnetic pole facing the image carrier 41 is different from that of the other N and S magnetic poles.
It may be larger than the magnetic flux density of the magnetic pole. In addition,
Of course, as the poles facing the image carrier 41, N magnetic poles may be arranged side by side and opposed to each other, or N and S magnetic poles may be arranged side by side and opposed to each other. By arranging a plurality of magnetic poles to face each other in this manner, it is possible to obtain the effect that development is more stable than when a single pole is posed to face each other. Further, it is preferable that the conveying speed of the developer due to the rotation of the rotating magnet or the rotation of the sleeve is almost the same as or faster than the moving speed of the image carrier. Further, it is preferable that the rotation of the rotating magnet and the rotation of the sleeve are carried in the same direction. Image reproducibility is better in the same direction than in the opposite direction. However, it is not limited to these. In the above, an example is shown in which an oscillating bias voltage is applied to the developer transport carrier, but the developing method of the present invention is not limited thereto. It is also possible to improve the developing effect by setting up several magnetic brushes and applying an oscillating voltage to them to give vibration to the magnetic brushes. In that case, a DC bias voltage is applied to the developer transport carrier, or
Oscillating voltages having different frequencies may be applied. The image forming process according to the present invention is as exemplified above, and subsequent toner images are sequentially developed on the photoreceptor drum 41 at a constant density without destroying the toner image formed on the photoreceptor drum 41. To do this, as development is repeated, toners with higher charge levels are used. The amplitude of the electric field strength of the AC component of the developing bias is gradually decreased. Sequentially increase the frequency of the AC component of the developing bias. It is more preferable to employ these methods individually or in any combination. That is, toner particles with a larger amount of charge are more susceptible to the influence of the electric field. Therefore, if highly charged toner particles adhere to the photoreceptor drum 41 during initial development, these toner particles may return to the sleeve during subsequent development. Therefore, as described above, by using toner particles with a small amount of charge in the initial development, the toner particles are prevented from returning to the sleeve during the subsequent development.
This method prevents the toner particles already attached to the photoreceptor from returning by decreasing the electric field strength sequentially as development is repeated (that is, as development progresses to later stages). Specific methods for reducing the electric field strength include a method in which the voltage of the alternating current component is gradually lowered, and a method in which the gap d between the photoreceptor drum 41 and the sleeve 7 is made wider as the developing stage progresses. Furthermore, the method described above is to prevent toner particles already attached to the photoreceptor drum 9 from returning by increasing the frequency of the alternating current component one after another as development is repeated. Although these are effective when used alone, they are even more effective when used in combination, for example, by sequentially increasing the toner charge amount and sequentially decreasing the alternating current bias as development is repeated. Further, when the above three methods are employed, appropriate image density or color balance can be maintained by adjusting the DC bias respectively. EXAMPLE 1 FIG. 5 is a schematic diagram of a color copying machine suitable for carrying out the method of the invention. In the figure, numeral 41 is a photosensitive drum made of a photosensitive member having the configuration shown in FIG. 3d. The insulating layer is a color separation filter B having the shape and arrangement as shown in Fig. 4b.
Contains G and R. These have spectral transmittance characteristics as shown in FIG. Further, the photoconductive layer is CdS. While rotating, the photosensitive drum 41 is irradiated with light from a light source 65 as needed, and the entire surface of the photosensitive drum 41 is given a positive charge by the charging electrode 4 . Next, exposure L of the document D is applied while receiving alternating current or a corona discharge of the opposite sign to the electrode 4 from the electrode 5 provided with an exposure slit. 6
0 is a light source, and M ₁ to M ₄ are mirrors. With this, the first latent image forming step is completed. Next, the entire surface is exposed to light _L1 obtained by the combination of the light source 61 and the filter _F1 , and a latent image is formed on the blue filter portion B of the photoreceptor. This latent image is developed by a developing device 17Y containing yellow toner. In order to erase the charge on the photoconductive layer in the B section that remains after development and to make the surface potential of the photoreceptor uniform, the entire surface is exposed to light from the light source 62 and filter _F2 .
The photoreceptor is charged with an electrode 81. This entire surface exposure light must be transmitted through the B section and not through the G and R sections. Next, the entire surface of the photoreceptor is exposed to light _L2 obtained by the combination of the same light source 62 and filter _F3 , and G
form a latent image on the area. This latent image is developed by a developing device 17M containing magenta toner. In order to erase the charge remaining on the photoconductive layer in the G section and to equalize the surface potential of the photoreceptor, the entire surface is illuminated with light from the light source 63 and filter _F4 (light that passes through the G section but does not pass through the R section). The photoreceptor is charged with an electrode 82 while being exposed to light. Subsequently, the entire surface of the photoreceptor is exposed to light L ₃ from the light source 63 and filter F ₅ to form a latent image in the R portion. This latent image is developed by a developing device 17C containing cyan toner. Subsequently, the surface of the photoreceptor is uniformly positively charged by the electrode 83, and then transparently charged by the electrode 84, and the light source 6
4 and the entire surface is exposed with light L ₄ from filter F ₆ . As a result, the potential of the portion of the photoreceptor to which the chromatic toner has adhered in the steps up to this point is different from the potential of other portions. The black toner contained in the developing device 17K is attached to this portion. Through the above steps, a multicolor toner image of chromatic colors and black is formed on the photoreceptor. A charge of a specific polarity (negative polarity) is applied to this toner image from the electrode 11, so that electrostatic transfer can be easily performed. Thereafter, the steps of transfer, separation, fixing, and cleaning are performed. That is, the image is transferred by the transfer electrode 9 onto the copy paper 8 fed by the paper feeding means 14. The paper carrying the multicolor toner image to be transferred is separated from the photoreceptor drum by a separation electrode 10, fixed by a fixing device 12 to become a completed multicolor copy, and discharged outside the machine. After the transfer, the photosensitive drum 41 is used again after the toner remaining on the surface is removed by the cleaning device 13. Full-surface exposure light L ₁ to _{L 4} applied to the above process
The spectral distribution of is shown in Fig. 6. Further, λ ₀ to λ ₅ of the spectral transmittance characteristics (FIG. 2) of the filter portions B, G, and R of the photoreceptor have the following values. λ ₀ <350nm, λ ₁ ~460nm λ ₂ ~520nm, λ ₃ ~580nm λ ₄ ~650nm, λ ₅ ~760nm Next, the detailed conditions of the experiment conducted by the inventor in this example are shown in the table below. Shown in 2. When forming a multicolor image under these conditions,
Records with good color reproduction and sufficient image density were obtained.

【table】

[Table] Example 2 Next, it is carried out using the apparatus shown in FIG. The differences from Example 1 are as follows. (1) The positions of developing devices 17M and 17C are exchanged. (2) The order of image formation is TY→TC→TM→TK. (3) The photoreceptor is also sensitive in the ultraviolet and infrared regions. (4) The spectral characteristics of the entire surface exposure light (L ₁ ″→L ₂ ″→L ₃ ″→L ₄ ″) are shown in Figure 7. As a result of image formation, a multicolor image with good color reproduction and sufficient image density was obtained. Other methods of adding black (in the case of CdS) include the following. (1) Charging → Full exposure (2) Charging → AC or simultaneous charging exposure → Exposure In the example shown in Figure 5, after development, the entire surface is exposed through F ₂ and F ₄ filters to form a photoconductive layer. It erases the charges inside, especially the F ₁ of the developer,
If the F ₃ and F ₅ filters have small overlap in transmission wavelength range, such as filters on a photoreceptor,
It is also possible to perform only uniform charging for smoothing the surface potential without performing light irradiation after this development. In addition to the above-described developing method, as a modification of the developing method without rubbing the photoreceptor, only the toner is taken out from the composite developer onto the developer transport carrier, and the toner is used in an alternating electric field. Method of component development (Japanese Patent Application Laid-Open No. 1983-42565, Japanese Patent Application No. 1983-
No. 231434) A method of providing a linear or mesh control electrode and performing development with a one-component developer in an alternating electric field. It goes without saying that the method for performing development (Japanese Patent Application No. 58-97973) is also included in the multicolor image forming method of the present invention. In the above embodiments, corona transfer is used as the toner image transfer method, but other methods may also be used. For example, Tokuko Sho 46-41679
By using the adhesive transfer method described in Japanese Patent Application Publication No. 48-22763, etc., transfer can be performed without considering the polarity of the toner. Further, a method of directly fixing the image onto the photoconductor, such as electrofax, can also be adopted. In addition, the layer structure of the photoreceptor is a transparent insulating layer, a photoconductive layer, a transparent conductive layer, and a filter, and charging is performed from the transparent insulating layer side, image exposure is applied from the back filter side, and full-surface exposure is applied, and development is performed from the transparent insulating layer side. You can also do this. In addition, all of the above explanations have been made regarding examples of color copying machines that use so-called three-color separation filters and three primary color toners, but embodiments of the present invention are not limited to this, and various types of multicolor image recording are possible. Can be widely used in devices, color photo printers, etc. It goes without saying that the color of the separation filter and the combination of the corresponding toner color can be arbitrarily selected depending on the purpose. Furthermore, the filter structure of the photoreceptor is not limited to that described above, and its pattern, arrangement, etc. can be changed in various ways. The characteristics of the light that exposes the entire surface of the developer are not limited to those described above, but the point is that this entire surface exposure increases (decreases) the potential of only a specific type of color separation filter (not limited to one type). ) and has characteristics that allow it to form a potential pattern. F. Effects of the Invention As described above, the present invention, after forming an electrostatic latent image, repeats the steps of whole surface exposure with light transmitted through at least one color separation filter and development with chromatic toner, and then charging, exposure, and black color. Since development is performed using toner, the entire surface is charged and imaged in only one time, which conventionally required multiple times, and there is no need to align various images during transfer, making it easier for the device to operate. It is possible to achieve smaller size, faster speed, and improved reliability. The resulting recorded matter has a high image density with good black reproducibility.

[Brief explanation of the drawing]

The drawings show embodiments of the present invention, and FIG. 1 [1], [2], [3], [4], [5], [6]
，
[7], [8],

[9], [10], [11], [12], [
13] is a process flow diagram showing the image forming process, Figure 2 is a spectrum diagram showing the spectral transmittance characteristics of the color separation filter, Figure 3 a, b, c, and d are cross-sectional views of each photoreceptor, and Figure 4 a, b, and c are plan views showing the arrangement of filters on the surface of the photoreceptor, Fig. 5 is a schematic diagram of a color copying machine, Figs. 6 and 7 are spectral diagrams showing the spectral characteristics of the entire surface exposure light, and Fig. 8 The figure is a cross-sectional view of the developing device, Figures 9 and 10 are graphs of experimental data for development with a one-component developer, Figure 11 is a graph showing preferred conditions for development with a one-component developer, and Figures 12 and 10 are graphs of experimental data for development with a one-component developer. 13
The figure is a graph of experimental data for development using a two-component developer, and FIG. 14 is a graph showing suitable conditions for development using a two-component developer. In addition, in the symbols shown in the drawings, 1... conductive substrate, 2... photoconductive layer, 3... insulating layer including color separation filter, 4, 81, 82, 83, 84...
Charger, 5...Charger with exposure slit, 8
...Copy paper, 17, 17Y, 17M, 17C, 1
7K...Developer, 41...Photosensitive drum, 60,
61, 62, 63, 64...Light source, R...Red filter section, G...Green filter section, B...Blue filter section, _F1 to _F6 ...Filter, L _R ...Image exposure light, L ₁ to L ₄ ...Full exposure light, TY...Yellow toner,
TM...Magenta toner, TC...Cyan toner,
TK...black toner, D...developer, T...toner.

Claims (1)

[Claims] 1. A step of imagewise exposing a photoreceptor having a layer including a plurality of color separation filter sections that mainly transmit light in different wavelength ranges; and then exposing the entire surface with light that passes through at least one of the color separation filter sections. An image forming method for forming a multicolor image by repeating the steps of exposing to light and developing with a chromatic toner; and then uniformly charging the surface of the photoreceptor, exposing the entire surface to light, and then developing with a black toner. .