JPS6177858A - Photosensitive body and image forming method - Google Patents

Abstract

PURPOSE:To improve color reproducibility and to decrease the generation of moire, etc. by forming a filter layer consisting of plural filter parts which have spectral transmittance characteristics different from each other and in which optional hue light transmits at least 2 kinds among the filter parts. CONSTITUTION:A photoconductive layer 2 is provided on a conductive member or substrate 1 and an insulating layer 3 contg. required color separating filters, for example, many filter parts of red (R), green (G) and blue (B) is laminated thereon. The layer 3 is constituted of the filter parts R1, R2, R3, G1, G2, G3, B1, B2, B3 having the spectral transmittance characteristics different from each other. The plural filter parts which allow the transmission of optional hue light, for example, the filter parts having different max. light transmittance, exist in the above-mentioned manner and therefore an edge effect is made properly low and the color reproduction is satisfactorily executed. Since the regularity of the light transmittance in the color separating filter parts is complicated, the generation of moires the interference of the space frequency thereof and the space frequency of an original is decreased.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention relates to a photoreceptor and an image forming method, and more particularly to a photoreceptor and a multicolor image forming method for use in electrophotography for forming multicolor images.

BACKGROUND OF THE INVENTION Many methods and devices used therefor have been proposed in the past for obtaining multicolor images using electrophotography, but they can generally be divided into the following types. Part 1
One method is to repeat latent image formation and development with color toner using a photoreceptor according to the number of separated colors, and then overlap the colors on the photoreceptor, or transfer the colors to a transfer material each time the development is performed. This is a method of layering. 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 recording process, since the process of forming and developing a plurality of latent images must be repeated. In addition, although the second method described above is advantageous in terms of high speed because it uses multiple photoreceptors in parallel, it requires multiple photoreceptors, an optical system, a developing means, etc. is complicated, internalized, expensive, and impractical. In addition, both of the above methods have the major drawback that it is difficult to align the image when reversing the image formation and transfer multiple times, and it is not possible to completely prevent color misalignment of the image. have.

In order to fundamentally solve these problems, the present inventors have previously proposed a method for quickly and easily recording a thousand-color image without color shift on a single photoreceptor with a single image exposure. -This is
It is as follows.

In other words, multiple color separation filters (mainly filtering only light in a specific wavelength range) are applied to a photosensitive layer that is sensitive to the entire visible light range.
Using a photoreceptor, which has an insulating layer made up of fine stripes or a mosaic of filters that transmit light, first image exposure is applied to the entire surface of the photoreceptor, and the photoreceptor layer below each filter is charged according to the decomposed image density. (hereinafter referred to as the primary latent image), and then the photoconductive layer at the bottom of the filter is exposed by exposing the entire surface to light of the same color that passes through the first color separation filter. An electrostatic image corresponding to the first latent image (hereinafter referred to as the second latent image) is formed only in the color corresponding to the type of filter, or more specifically, the complementary color relationship of the color transmitted through the filter. A multicolor image is formed on the photoconductor by developing it with a color toner of a certain color, and then uniformly charging it, and then repeating the same whole-surface exposure, development, and recharging operations for each color separation image. A multicolor image is recorded on the transfer material at once by transferring the images.

However, in this multicolor image forming method, the size, shape, and arrangement of the fine segmented color separation filters are the same for all colors for ease of design and manufacturing. In particular, all of the filter parts for the same color had the same maximum light transmittance. However, (1) Since the color filter is finely divided, the latent image is finely divided, and since this is developed, the edge effect is strong and the gradation reproducibility and color reproducibility tend to be unnatural.

■ Moiré tends to occur due to interference between the spatial frequency of the original and the spatial frequency of the color separation filter.

Problems such as these have been discovered.

C.3 Purpose of the Invention An object of the present invention is to provide a photoreceptor that provides good color reproducibility and less occurrence of moire and the like.

An object of the present invention is to use a photoreceptor that can quickly and easily record a multicolor image without color shift through multiple image exposures, and to form a multicolor image satisfactorily through a fast and simple process. An object of the present invention is to provide an image forming method.

29. The structure of the invention, that is, the photoreceptor according to the invention has a filter layer consisting of a plurality of filter sections having different spectral transmittance characteristics, and light of a given hue is transmitted through at least two types of the filter sections. It is characterized by:

Further, the image forming method according to the present invention includes a filter layer including a plurality of filter sections having mutually different spectral transmittance characteristics, and light of an arbitrary hue passes through at least two types of the filter sections, imagewise exposing the photoreceptor. The process; then,
The method includes a step of repeating an operation of exposing the entire surface of the filter section to light that transmits a small amount (at least a portion) of the filter section, and then performing development.

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, we will discuss a photoreceptor for full color reproduction using red, green, and blue filters that transmit red, green, and blue light as color separation filters, but the color of the filter and the toner to be combined with it will be explained. The colors are not limited to those mentioned above.

The first part shows an example of the shape and arrangement of finely segmented color separation filters. Here, l shown in the figure is desirably set larger than the average particle diameter of the toner used for development. 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 filter is equal to or smaller than the particle size of the toner particles, it will be difficult to create. 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.

FIG. 2 schematically shows a cross section of a photoreceptor that can be used in the present invention. A photoconductive layer 2 on a conductive member or substrate 1
A color separation filter such as red (R) is placed on top of the filter.
, green (G), and blue (B) filter sections are laminated.

The conductive substrate 1 may be made of metals such as aluminum, iron, nickel, copper, or alloys thereof, and may have an appropriate shape and structure as necessary, such as a cylindrical shape or an endless heddle shape.

The photoconductive layer 2 is made of sulfur, selenium, and amorphous silicon.
Photoconductors such as alloys containing t, selenium, tellurium, arsenic, antimony, etc.; or inorganic photoconductors of metal oxides, iodides, sulfides, and selenides such as zinc, aluminum, antimony, bismuth, cadmium, molybdenum, etc. Electrostatically conductive substances; organic photoconductive substances such as vinyl hydroxide, anthracenephthalocyanine, trinitrofluorenone, polyvinyl carbazole, polyvinylanthracene, polyvinylpyrene, polyethylene, polyester, polypropylene, polystyrene, polyvinyl chloride, polyvinyl acetate, It can be composed of something dispersed in an insulating binder resin such as polycarbonate, acrylic resin, silicone resin, fluororesin, or epoxy resin.

The insulating layer 3 is made of a transparent insulating material, such as various polymers,
It can be made of resin or the like, and has a colored portion on its surface or inside that functions as a color separation filter. As shown in FIG. 2(a), the colored portion is formed by attaching an insulating material colored by adding a coloring agent such as a dye having a desired color onto the photoconductive layer 2 in a predetermined pattern by means such as printing. Alternatively, as shown in FIG. 2(b), a colorant is applied to the photoconductive layer 2.
It can be formed by adhering it in a predetermined pattern on a colorless insulating layer 3a that has been uniformly formed thereon by means such as printing or vapor deposition. Furthermore, even if a film-like insulating material on which a colored portion is formed in advance is attached on the photoconductive layer, it is possible to
) and (b). Furthermore, the surface of the formed colored portion may be further covered with an insulating material 3b to form a structure as shown in FIGS. 2(c), 2(d), and 2(e).

Note that FIGS. 2(a) to (C) and FIGS. 3(a) to (e) all show cases in which so-called three-color separation filters of red, green, and blue are provided.

According to the present invention, the above filter layer 3 has filter portions R having mutually different spectral transmittance characteristics as shown in FIG.
1, R2, R3,..., Gl, G2, G1,...,
It is composed of B1, B2, B3, . . .

Specifically, FIG. 3 shows a photoreceptor having a filter layer consisting of a plurality of types of color separation filter sections that mainly transmit light in different wavelength ranges, wherein one of the plurality of color separation filter sections is It is configured as a photoreceptor having a layer consisting of a plurality of types of filter parts having different maximum light transmittances and/or maximum light transmission wavelengths that mainly transmit light of the same hue.

In this way, since there are multiple filter sections that transmit light of arbitrary hues, for example, with different maximum light transmittances, it is possible to moderate the edge effect when developing a fine latent image. This allows for good color reproduction.

Moreover, since the regularity of the light transmittance of each color separation filter section is complicated, the occurrence of moiré due to interference between the spatial frequency of the color separation filter section and the spatial frequency of the document is reduced.

In order to obtain such remarkable effects, the above filter parts R1, R2, R3, . . . , G1, G2, G3, .
, BI, , B2, B3, . . . , the difference in maximum light transmittance between filter parts that transmit light of the same hue, that is, in FIG. 3, for example, B+ (minimum maximum light transmittance) and 83 (
It is desirable that the ratio between the maximum light transmittance and the maximum light transmittance is as follows. In addition to the pattern shown in FIG. 1, various ways of arranging the filters are conceivable (in addition, in the same figure, A is the (all) visible light absorption filter section).

Note that the maximum transmittance and maximum light transmission wavelength of the above-mentioned filter portions R, R, R3, etc. can be determined by changing the type of pigment or dye forming the filter, or by changing the thickness of the filter portion. It can be adjusted by

Next, 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 formation 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. , cross-sectional hatching of each part is omitted. In the figure, 2 and 2 are a conductive substrate and a photoconductive layer, respectively, and 3 is an insulating layer including three color separation filter sections 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. 4 [1], when a positive corona discharge is applied to the entire surface by the charger 4, a positive charge is generated on the surface of the insulating layer 3, and correspondingly, the photoconductive layer 2 and the insulating layer A negative charge is induced at the interface.

Next, as shown in FIG. 4 [2], alternating current or negative discharge is applied by a charger 5 equipped with an exposure slit, and the insulating layer 3 is
While uniformizing the surface potential, a colored image is exposed, for example, a red image of a document is exposed to give Ill.

The red light passes through the red filter section R of the insulating layer 3.

On the other hand, since the green color filter section 3G and the blue color filter section 3B 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, a primary latent image is formed in such a way that the charge distribution on the insulating N3 changes so that the surface potential of the photoreceptor becomes uniform. 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 the same potential on the surface of the photoreceptor, and therefore do not function as an electrostatic image.

Note that although FIG. 4 [2] shows a case where the potential after charging is approximately zero, it may be charged to a negative value.

Next, as shown in FIG. 4 [3], the entire surface is exposed to light of a color that passes through one of the filters included in the insulating layer 3, for example, blue light obtained by the light source 6B and the blue filter FB. , the photoconductive layer 2 below the filter 78 that transmits blue light becomes conductive, and a part of the negative charge of the photoconductive layer 2 in this area and the charge of the conductive substrate 1 are neutralized, and the surface of the filter B becomes conductive. Only the charge remains, which generates a potential pattern. No change occurs in the G and H portions that do not transmit blue light. This is the second latent image. Then, when the charge image on filter B is developed with a developer containing negatively charged yellow toner TY, the toner adheres only to the surface of filter 8, which has a relatively high potential, and development is performed (Fig. 4). (
4)).

Next, after making the surface potential uniform with the charger 15 as shown in FIG. 4 [5] in order to eliminate the potential difference that has occurred, the entire surface is exposed to light with a green light as shown in FIG. 4 [6]. A second latent image is formed in the green filter section G as in the case of full-surface exposure to blue light. If this is developed with magenta toner TM as shown in FIG. 4 [7], magenta toner TM will adhere only to the filter G portion. Subsequently, as shown in FIG. 4 [8], after making the surface potential uniform in the same way, the entire surface is exposed to red light, and the second latent image appearing on the red filter portion R is developed with cyan toner TC. In the illustrated example,
Since there is no charge in the photoconductor N2 in the red filter portion R, no potential difference is generated even when the entire surface is exposed, and no cyan toner is attached even when development is performed with cyan toner.

When the toner image thus obtained is transferred onto a transfer material such as copy paper and fixed, a red image due to a color mixture of yellow toner and magenta toner is reproduced on the transfer material.

As for other colors, color reproduction is performed by combining the three-color separation method and three primary color toners as shown in Table 1 below.

In this table, the symbol "○" indicates the first latent image formation stage, and the symbol "○"
" indicates the second latent image formation stage, the symbol "0" 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.

(The following is a margin, continued on the next page) 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 optical semiconductor layer such as selenium, which has a high hole mobility. In this case, the basic process is the same except that the positive and negative signs of the charges are all reversed. Note that if it is difficult to inject charges during -order charging, uniform irradiation with light is also used.

As is clear from the above description, according to this embodiment, after the multicolor image forming photoreceptor is charged and subjected to imagewise exposure, the entire surface is exposed to light that passes through one of a plurality of types of filters. The steps of applying and developing are repeated depending on the type of filter.

That is, a fine color separation filter is placed on the photoreceptor, and after image exposure (step 2 in FIG. 4), the entire surface is exposed to three-color separated light (steps 3 and 6 in FIG. 4). A second latent image is formed for each color portion of the color separation filter, and developed using toner of the corresponding color (steps [4] and [7] in Fig. 4). This process is repeated to form multiple latent images. Obtain a color image. Therefore, according to this process, a photoreceptor is used, in which a plurality of color separation filters are arranged in a combination of fine lines or mosaics on a photoconductive layer that is sensitive to the entire visible light range. Imagewise 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 to form a first latent image on the filter section. A second latent image is formed in accordance with the first latent image. Then, it is developed 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 the same operation is repeated for each color separation image to form a multicolor image on the photoreceptor. A multicolor image can be recorded on the transfer material at once by forming a multicolor image.

FIG. 5 is a schematic diagram of an image forming section of a color copying machine suitable for carrying out the above process. In the figure, reference numeral 41 denotes a photoreceptor drum having the configuration shown in FIG. 4, the entire surface is charged, and from the electrode 5 equipped with the next exposure slit, an alternating current,
Alternatively, image exposure of the document is applied while receiving a corona discharge of the opposite sign to that of the electrode 4, and the primary latent image forming process is completed.

Next, the light source 6B and the light source blue filter F! The entire surface is exposed to blue light obtained in combination with 1, and a yellow secondary latent image is formed. Next, this is developed by a developing device 17Y loaded with yellow toner. Subsequently, after the surface of the photoreceptor is brought to a uniform potential by the electrode 14, the light source 6G is turned on.
, green light source filter F.

The entire surface is exposed to green light from the image forming apparatus, and the image is developed by a developing device 17M loaded with magenta toner. Furthermore, the potential of the photoreceptor is made uniform by the electrode 15, and the entire surface is exposed to red light from the light source 6R1 and the red light source filter F, and the photoreceptor is developed by the developer 17C loaded with cyan toner. As a result, a multicolor image is formed on the photoreceptor drum. The obtained multicolor toner image is charged by a pre-transfer charging electrode 11 and then transferred by a transfer electrode 9 onto copy paper 8 fed by a paper feeding means. The copy paper carrying the multicolor toner image to be transferred is separated from the photoreceptor drum by a separation electrode 10 and fixed by a fixing device 12 to form a completed multicolor copy and discharged outside the machine.

After the transfer, the photosensitive drum 41 is irradiated with static eliminating light.
The static electricity is eliminated by the static elimination electrode 11, and the toner remaining on the surface is removed by the blade 12' of the cleaning section 13, and the toner is used again.

On the other hand, when forming a monochrome image using this device, the process up to the first latent image formation process is the same as in the case of multicolor image formation.
Thereafter, the toner is uniformly exposed to light [6B, 6G, and 6R, and developed by a developing device 17K containing black toner.

In the above image forming process, the developer used may be either a so-called one-component developer using non-magnetic toner or magnetic toner, or a so-called two-component developer using a mixture of toner and a magnetic carrier such as iron powder. I can do it. Direct rubbing with a magnetic brush may be used for development, but especially after the second development, in order to avoid damage to the formed toner image, the developer layer on the developer transport member should be It is essential to use a non-contact development method that does not rub the photoreceptor surface. 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 development several times on a photoreceptor on which a toner image has already been formed, but if appropriate development conditions are not set, This may disturb the toner image formed on the photoconductor in the previous stage, or the toner already adhered to the photoconductor may return to the developer transport body, which contains developer of a different color from the developer in the previous stage. There is a problem that it invades the subsequent developing device and causes color mixing. Basically, to prevent this, the developer layer on the developer transporting member should be operated without rubbing or contacting the photoreceptor.

That is, the gap between the photoreceptor and the developer transport member is maintained larger than the thickness of the developer layer on the developer transport 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 problems and further form each toner image with sufficient image density. To satisfy this condition, the gap d (mm) C or less (sometimes simply referred to as gap d) between the image carrier and the developer conveying body in the development area, the amplitude VAC of the alternating current component of the developing bias that generates the alternating electric field. It has become clear that it is difficult to determine and obtain the values of frequency i (Hz) and frequency i (Hz) independently, and that these parameters are closely related to each other.

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. 6 shows each developing device 17Y, 17M, 17 shown in FIG.
This shows the basic configuration of C117, and by rotating the sleeve 7 and/or the magnetic roll 43, 1,
The developer De is conveyed on the circumferential surface of the sleeve 42 in the direction of arrow B, and is supplied across the development area. 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 is conveyed in the direction of arrow B.

The thickness of the developer De is regulated by an accumulation regulating blade 40 made of a magnetic material during transportation. Developer reservoir 47
A stirring screw 42 is provided inside the developer reservoir 47 to sufficiently agitate the developer De. When the toner in the developer reservoir 47 is consumed, the toner supply roller 39 rotates and the toner hopper 38 Kara Toner T
will be replenished.

A developing bias is applied between the sleeve 7 and the photosensitive drum 41 (a DC power supply 45 and an AC power supply 46 are provided in series. R is a protection resistor).

The developer De initially stored in the developing device 17M is a one-component magnetic developer, containing 7Qwt% of thermoplastic resin and pigment (
Carbon blank) 1Qwt%, magnetic material 20wj%, and a charge control agent are kneaded and pulverized to have an average particle size of 15 μm, and a fluidizing agent such as silica is further added. The amount of charge is controlled by a charge control agent.

As a result of the experiment, the results shown in FIGS. 7 and 8 were obtained.

FIG. 7 shows that in the developing device 17M, the gap d between the photoreceptor drum 41 and the sleeve 7 is 0.7f11, and the developer layer thickness is 0.
．． 31. The DC component of the developing bias applied to the sleeve 7 is 50 V, and the frequency of the AC component of the developing bias is 1 kHz.
, shows the relationship between the amplitude of the AC component and the image density of the black toner image when developing a region where the surface potential of the photoreceptor is 500 V after uniform exposure. Note that at this time, the developing device 1i
A two-component developer for yellow is stored in 17Y.

The amplitude EAC of the AC electric field strength is the value obtained by dividing the amplitude VaC of the AC voltage of the developing bias by the gap d. Curves A, B, and C shown in FIG. 7 each indicate an average charge amount of magnetic toner of 15
These are the results when μc/g, −3 μc/g, and −2 μc/g were used. The three curves A, B, and C are all
The amplitude of the AC component of the electric field is 200V/w or more, 1.5kV
Image density is high below /w, 1.6kV / 璽-
In this case, it was observed that the toner image previously formed on the photoreceptor drum 41 was partially destroyed.

Figure 8 shows the frequency of the AC component of the developing bias at 2.5k.
Hz, and shows changes in image density when alternating current electric field strength, etc. are changed under the same conditions as in the experiment shown in FIG.

According to this experimental result, the amplitude EAC of the alternating current electric field strength
When the voltage is 500 V/m or more and 3.8 kV/u+ or less, the image density becomes large, and when it exceeds 3.2 kV/m (shown in the lower part of FIG. Part of the statue was destroyed.

As can be seen from the results in Figures 7 and 8, the image density changes to saturate or slightly decrease after a certain amplitude; As you can see, it does not depend much on the average charge amount of the toner.

Now, when we conducted experiments similar to those shown in Figures 7 and 8 while changing the conditions, we were able to sort out the relationship between the amplitude E^C of AC electric field strength and frequency, and obtained the results shown in Figure 9. .

In FIG. 9, the areas marked with ■ are areas where uneven development is likely to occur, the areas marked with ■ are areas where the effect of the alternating current component does not appear, and the areas marked with ■ are likely to cause destruction of the already formed toner image. The area ◎■ is an area where the effect of the alternating current component appears, a sufficient developing density is obtained, and the already formed toner image is not destroyed, and the area ■ is a particularly preferable area.

This result shows that in order to develop the toner image formed on the photoreceptor drum 41 in the previous stage (in the previous stage) at an appropriate density without destroying the toner image formed in the previous stage (in the previous stage), the amplitude of the alternating current electric field strength must be This shows that there is an appropriate range for that frequency.

Based on the above experimental results, the present inventor has determined that in each development step,
When the amplitude of the AC component of the developing bias is VaC (V), the frequency is j (Hz), and the gap between the photosensitive drum 41 and the sleeve 7 is d (mm), 0.2≦VAc/(d-f)≦
It was concluded that if development is performed under the conditions satisfying 1.6, subsequent development can be performed 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, the image density should be 0.4, which is the region in which the image density tends to increase with respect to the alternating current electric field, as shown in FIGS. 7 and 8. It is more desirable to satisfy the condition of ≦VAc/(d·B)≦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, satisfying 0.6≦Vac/(d−f)≦1.0.

In addition, in order to prevent uneven development due to the AC component, the frequency A 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 effect of beat caused by the rotation of the AC component, the frequency of the AC component is set to 5.
It is more desirable to set it to 00H2 or more.

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.
It is a carrier made by dispersing fine iron oxide in a resin so that it has physical properties of 30 emu/g, magnetization 30 emu/g, and resistivity 10'4 Ω-cm, and the resistivity is 0.50
After tapping in a container with a cross-sectional area of CD,
This value is obtained by applying a load of 1 kg/cra on the packed particles and 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 toner was prepared by adding a small amount of a charge control agent to 9Qwt% of a thermoplastic resin and 10wt% of a pigment (carbon blank), kneading and pulverizing the mixture to give an average particle size of 10 μm.

A developer was prepared by mixing 3Qwt% of cough carrier with 20wt% of 8y toner. Note that the toner is negatively charged due to friction with the carrier.

The experimental results are shown in FIGS. 10 and 11.

FIG. 10 shows the gap d between the photosensitive drum 41 and the sleeve 7.
An area where the surface potential of the photoreceptor after uniform exposure was 500 V was developed under the following conditions: 1.0 fl, developer layer thickness 0.7 m, DC component of the developing bias was 50 V, and AC component frequency was 1 kHz. 3 shows the relationship between the amplitude of the AC component and the image density of the black toner image. Note that the developing device 17Y stores a two-component developer for yellow. The amplitude EAC of the AC electric field strength is the amplitude vAc of the AC voltage of the developing bias.
is divided by the gap d.

Curves A, B, and C shown in FIG. 10 indicate that the average charge amount of the toner is -30 μc/g, −20 μc/g, and −15 μC, respectively.
These are the results when using a device whose charge was controlled.

The three curves A, B, and C all show that the amplitude of the alternating current component of the electric field is 200V≠, and that when the amplitude exceeds 2500V/mm, the toner image previously formed on the photoreceptor drum is partially destroyed. was observed.

Figure 11 shows that the frequency of the AC component of the developing bias is 2.5.
kHz, and shows changes in image density when alternating current electric field intensity EAC is changed under the same conditions as in the experiment shown in FIG.

According to this experimental result, the amplitude EAC of the alternating current electric field strength
When the voltage exceeds 500 V/■■, the image density becomes high, and although not shown, when the voltage exceeds 4 kV/N, a part of the toner image previously formed on the photoreceptor drum 41 is destroyed.

As can be seen from the results in Figures 10 and 11, the image density changes to become saturated or to decrease slightly after a certain amplitude, but the value of this amplitude is different from the song &? IA,B
, C, it does not depend much on the average charge amount of the toner.

Now, when experiments similar to those shown in FIGS. 10 and 11 were conducted while changing the conditions, the relationship between the amplitude EAc of the alternating current electric field strength and the frequency f could be sorted out, and the results shown in FIG. 12 were obtained.

In FIG. 12, the areas marked with ■ are areas where uneven development is likely to occur, the areas marked with ■ are areas where the effect of the AC component does not appear, and the areas marked with ■ are where destruction of the already formed toner image occurs. The easy areas, (1) and (2) are areas where the effect of the alternating current component appears, a sufficient development density is obtained, and the already formed toner image is not destroyed, and (2) is a particularly preferable area.

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, as in the case of -component developer, This shows that there is an appropriate range for the amplitude of the alternating current electric field strength and its frequency.

Based on the above experimental results, the present inventor has determined that in each development step,
When the amplitude of the AC component of the developing bias is vAc (V), the frequency is j (Hz), and the gap between the photosensitive drum 41 and the sleeve 7 is d (+n), 0.2 ≦■Ac/(d・su). It was concluded that if development is performed under the conditions that are satisfied, subsequent development can be performed at an appropriate density without disturbing the toner image already formed on the photoreceptor drum 41. Among the above conditions, it is more preferable to satisfy 0.5≦Vac/(d'f) in order to obtain sufficient image density and not disturb the toner image formed up to the previous stage. Furthermore, especially among these, if 0.5≦VAc/(d-f) (()envy/d)-1500)/su≦0.8,
A clearer multicolor image with no color turbidity can be obtained, and it is possible to prevent toners of different colors from getting mixed into the developing device even if the developing device is operated many times.

In addition, in order to prevent uneven development due to the AC component, the frequency of the AC component is set at 200
Hz or higher, and when a rotating magnetic roll is used as a means for supplying the developer to the photoreceptor drum 41, the frequency of the AC component is set to 500 Hz or higher in order to eliminate the influence of the beat caused by the AC component and the rotation of the magnetic roll. It is even more desirable to do so.

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 achieve this, as development is repeated, (1) Use toners with a larger charge amount.

■Sequentially reduce the amplitude of the AC component of the developing bias.

■ 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 large amount of charge are easily affected by 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, the above-mentioned point (2) is to prevent the toner particles from returning to the sleeve during the subsequent development by using toner particles with a small amount of charge in the initial development.

(2) The electric field strength is gradually decreased as the development process is repeated (that is, as the development progresses to a later stage). This method prevents toner particles already attached to the surface from returning. 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. Also,
The above method (2) is to prevent the toner particles from returning during development. These ■■■ are effective when used alone, but when used in combination, for example, by sequentially increasing the toner charge amount and gradually decreasing the AC bias as development is repeated, appropriate image density can be achieved. Alternatively, color balance can be maintained.

Based on the above results, the present inventors used a photoreceptor in which a color separation filter having the shape shown in FIG. 1(b) was printed on an insulating layer as shown in FIG. 2(b), and A multicolor image was formed under the conditions shown in Table 2.

As a result, the recorded image had good color reproducibility and almost no moiré occurred.

(The following is a margin, continued on the next page) Table 2 In addition to the developing method described above, as a variation of the developing method that is performed without rubbing the photoreceptor, only the toner from the composite developer is transferred onto the developer transport carrier. A method in which one-component development is performed using toner in an alternating electric field (Japanese Patent Laid-Open No. 59-42)
565, Japanese Patent Application No. 58-231434), a method of providing a linear or mesh control electrode and performing development with a monocomponent developer in an alternating electric field (Japanese Patent Application Laid-Open No. 56-125753)
It goes without saying that the multicolor image forming method according to the present invention also includes a method (Japanese Patent Application No. 58-97973) in which a similar control electrode is provided and development is carried out using a two-component developer in an alternating electric field.

In the above embodiments, corona transfer is used as the toner image transfer method, but other methods may also be used. For example, Japanese Patent Publication No. 46-41679, No. 48-
When the adhesive transfer method described in Japanese Patent No. 22763 is used, transfer can be performed without considering the polarity of the toner. Furthermore, a method of directly fixing the image on the photoconductor, such as electrofax, can also be adopted.

In addition, the layer structure of the photoreceptor is provided with a transparent insulating layer, an irradiation layer, an electromagnetic layer, and a filter to provide primary and secondary charging from the transparent insulating layer side, image exposure from the filter side, and overall exposure from the back side. Alternatively, a configuration may be adopted in which development is performed from the transparent insulating layer side. Furthermore, 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 multi-color images can be produced. It can be widely used in recording 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 also be arbitrarily selected depending on the purpose.

In the multicolor image forming process described above, each uniform exposure light does not necessarily have to be B, G', and 'R light.

That is, in the filter portion of the photoreceptor through which uniform exposure has already passed, the charge at the interface between the insulating layer and the photoconductive layer has already disappeared, so even if light passes through it again, no change in surface potential occurs. Therefore, for example, uniform exposure can be changed to red light, yellow light,
Even if the development is performed in the order of white light and the cyan toner, magenta toner, and yellow toner are developed in that order, a multicolor image with good color reproduction of the document can be obtained.

Of course, the exposure is not limited to this, and uniform exposure may be performed using light with other spectral distributions. In short, it is only necessary to form a potential pattern on a specific type of filter. As mentioned above, when the exposure light uniformly passes through a part of the filter on the photoreceptor twice or more, in order to completely erase the charge on the interface between the insulating layer and the photoconductive layer after development, Irradiation with light is desirable. Further, the filter structure of the photoreceptor is not limited to the one described above, and its pattern, arrangement, etc. can be changed in various ways.

F. Effects of the Invention As described above, the present invention allows light of any hue to pass through two or more types of filter sections having different spectral transmittance characteristics, so that a fine latent image can be developed. In this case, it is possible to moderate the edge effect and achieve good color reproduction. Furthermore, since the regularity of the spectral transmittance of each color separation filter section is complicated, it is possible to reduce the occurrence of moiré due to interference of the spatial frequency with the spatial frequency of an original image such as a document.

In addition, using this photoreceptor, after forming an electrostatic latent image by imagewise exposure, the entire surface is exposed to light that passes through at least one type of color separation filter, and the development process is repeated, which previously required multiple steps. Full-surface charging and image exposure can be performed only once, and there is no need to align various images during transfer (this allows the device to be smaller, faster, and more reliable. Objects will also be of high quality with no color shift.

[Brief explanation of drawings]

1 to 12 show examples of the present invention, and FIG. Figures 2 (a), (b), (C), and (d) are plan views showing the arrangement of filters on the surface of the photoreceptor; Figure 3 is a spectrum diagram showing the spectral transmittance characteristics of the filter; Figure 4 [1] ], [2], [3], [4], [5], [6
], [7], and [8] are process flow diagrams showing the image forming process, Figure 5 is a schematic diagram of a color copying machine, Figure 6 is a cross-sectional view of a developing device, and Figures 7 and 8 are one-component Graph of experimental data for development with a developer; Figure 9 is a graph showing preferred conditions for development with a one-component developer; Figures 1O and 11 are graphs of experimental data of development with a two-component developer; Figure 12. 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 a color separation filter 4.14.15... Charger 5... Exposure slit Charger 8, copy paper 17, 17Y, 17M, 17C, developer 41, etc.
Photoreceptor drum R,, R,, R,...Red filter section Cz, Gz
, G:l...Green filter section B"+, B2, B
3...Blue filter section Fw...Blue filter Fc...Green filters F, l...Red filter LII...Red image exposure,...Blue image exposure G...Green image exposure TY...Yellow toner TM---? Zea yhf-(b De... Developer T... Toner. Agent: Patent attorney Hiroshi Aisaka, a Figure 1 Figure 2 Figure 3 Figure 5 Figure 8 Figure 9 ul' 1 [kHzl 110Figure 11Figure 012 εACrkv/ml

Claims (1)

[Scope of Claims] 1. In a photoreceptor having a filter layer made up of a plurality of types of filter sections having mutually different spectral transmittance characteristics, light of any hue substantially passes through at least two types of the filter sections. A photoreceptor characterized by: 2. imagewise exposing the photoreceptor, which has a filter layer made up of a plurality of types of filter sections having different spectral transmittance characteristics, and allows light of a given hue to substantially pass through at least two of the filter sections; After that, the image forming method comprises repeating the steps of performing whole-surface exposure with light that passes through at least one of the filter parts and then developing.