JPS6341876A - Image forming device - Google Patents

Abstract

PURPOSE:To form an image faithful in an original image by increasing the light quantity/energy of a radiation light with a specific wavelength in accordance with a wavelength area in which the effective sensitivity of a photosensitive body is relatively low. CONSTITUTION:The surface of the photosensitive body is charged with uniform potential by an electrostatic charger and the surface potential of the photosensitive body 41 is uniformly applied to the charged surface by the action of a charger 4. When blue light LB obtained from a lamp 6B is projected to the image exposure surface, a potential pattern appears on a B filter part and is developed by a yellow toner developing device 17Y. Then, the surface potential of the photosensitive body 41 is uniformed by the action of a charger 15 for executing corona discharge similarly to the charger 5, green light LG obtained from a lamp 6G is projected to a G filter part to form a potential pattern on the G filter part and the pattern is developed by a Magenta toner developing device 17M. Hereinafter a charger 16 equivalent to the charger 15 is discharged, red light LR obtained by a lamp 6R is uniformly projected and a potential pattern formed an R filter part is developed by cyan toner developing device 17. Consequently, a superposed image of three color toner images consisting of yellow, Magenta and cyan is formed on the photosensitive body 41.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention relates to an image forming apparatus, and particularly to an image forming apparatus that forms images using electrophotography.

BACKGROUND OF THE INVENTION Many methods for forming multicolor images using electrophotography have been proposed in the past. These can generally be divided into the following categories. The first method involves sequentially repeating the formation of a color-separated electrostatic latent image on a single photoreceptor and its development, thereby overlapping colors on the photoreceptor, or transferring the toner image to a transfer material each time it is developed. The colors are superimposed on the transfer material. The above color-separated electrostatic latent image is created by irradiating the original image (original) with white light and passing the reflected or transmitted light through filters sequentially selected from among blue, green, and red filters (the order of selection is (doesn't matter) and is formed by using monochromatic light and performing imagewise exposure for each color. The second method is to perform image exposure through a filter for each color using multiple photoreceptors corresponding to the number of colors, form a toner image of each color on each photoreceptor simultaneously, and transfer them sequentially to a transfer material. It is used to obtain a color image. The latter is advantageous in terms of high speed because the toner images of each color are formed simultaneously on each photoconductor, but it requires multiple photoconductor JPN optical manual projection means, making the device complicated and large.
It is expensive and has little practicality.

Further, all of the above multicolor image forming apparatuses have color overlapping.

In order to fundamentally solve these problems, the present inventors have previously invented an apparatus that can form a multicolor image on a photoreceptor by performing image exposure once.

The apparatus forms a multicolor image as follows using a photoreceptor provided with an electrically conductive member, a photoconductive layer, and an insulating layer including a filter layer consisting of a plurality of different types of filters. That is, by applying a charged straw and imagewise exposure to the surface of the photoreceptor, an image is formed based on the charge density at the interface between the insulating layer and the photoconductive layer, and a filter portion of one of the plurality of types of filters is formed on the image forming surface. A potential pattern is formed on the filter portion of the photoconductor by exposing the entire surface to light that only passes through the filter, and the potential pattern is developed by a developing device containing toner of a specific color to form a monochromatic toner image. be done. After charging to smooth the potential, the entire surface is exposed to light that passes through a different filter part than the previous one, and development is performed using a developing device that stores toner of a different color than the previous one. A second color toner image is formed on the body. Thereafter, charging, full-surface exposure, and development are repeated as many times as necessary. As a result,
Toner of different colors adheres to each filter portion of the photoreceptor to form a multicolor image (Japanese Patent Laid-Open No. 60-2258
Publication No. 55 and Japanese Patent Application No. 59-187044, No. 59-
185440, 60-229524)
. According to this multicolor image forming method, image exposure and transfer only need to be performed once, so there is no risk of color misregistration.

In this multicolor image forming method, color reproduction is performed by a subtractive color method.

As a result of repeated studies, the inventor of the present invention has found that the above-mentioned multicolor image forming method has solved the problems of the conventional methods described above, but the following problems remain. There was found.

Image exposure is performed using white light, and images are formed by charge density for each color using the plurality of types of filters.
Differences in spectral characteristics depending on the type of filter, spectral sensitivity distribution of the photoreceptor, spectral characteristics of the image exposure light source, spectral characteristics of the entire surface exposure light source, differences in reflectance depending on the type of toner, etc., cause the image formed to differ from the original document. Color reproduction is different. It is difficult to make the spectral sensitivity distribution of the photoreceptor uniform in each wavelength range of blue, green, and red components, and in wavelength ranges with low sensitivity, the density of the developed copy is higher than that of the original image. The density tends to increase, making it difficult to reproduce colors faithful to the original image.

Such problems similarly exist in both the above-described method of subjecting a single photoconductor to imagewise exposure for each color and the method of subjecting a plurality of photoconductors to imagewise exposure for each color.

Furthermore, even when a black and white image is formed from a full-color original image, an image with high image density will be reproduced for a specific color of the original image because the spectral sensitivity distribution of the photoreceptor is not flat.

OBJECT OF THE INVENTION An object of the present invention is to solve the above problems and provide an image forming apparatus capable of forming an image faithful to an original image.

20 Structure of the Invention The present invention provides an image forming apparatus that irradiates a photoreceptor with a plurality of lights having different wavelength ranges, at least corresponding to a wavelength range in which the effective sensitivity of the photoreceptor is relatively low. The present invention relates to an image forming apparatus characterized in that it is configured to increase the amount and/or energy of light of a specific wavelength of irradiation light.

The above "effective sensitivity" refers to light sensitivity, and the color separation function section (
For example, in the case of a photoreceptor provided with a layer consisting of a color separation filter), it refers to the photosensitivity that is the sum of the spectral sensitivity of the photoreceptor and the spectral characteristics of the color separation function section.

E. EXAMPLE Hereinafter, an example in which the present invention is applied to the image forming apparatus described in Japanese Patent Laid-Open No. 60-225855 mentioned above will be described.

Figure 1 is a graph showing the spectral sensitivity distribution of the photoreceptor, Figure 2 is a graph showing the wavelength characteristics of the fluorescent lamp used as the image exposure light source,
Figures 4 (a) and (b), Figure 5, and Figure n are schematic diagrams of the configuration of the multicolor image forming apparatus, and Figure 3 is an enlarged view of the image exposure device in Figures 4, 5, and Figure n. 6 to 11, 14 and 15 are cross-sectional views of the photoreceptor, FIG. 12 is a plan view showing an example of arrangement of multiple types of color separation filters in the insulating layer, and FIG. 13 is a graph showing the spectral transmittance of the color separation filter, FIG. 16 is a cross-sectional view of the developing device, and FIG. 17 is a process diagram showing the state in which image formation is performed in the multicolor image forming device.
Fig. 18 is a graph showing how the surface potential of the photoconductor changes over time according to the process, Fig. 19 is a graph showing the spectral reflectance characteristics of toner, and Fig. 4 is a graph showing the spectral reflectance characteristics of the toner. A graph showing the relationship between the density and the density of a copy. Figure 4 is a diagram schematically showing the state in which toner on a photoreceptor spreads during transfer or fixing. Figure n is a graph showing the relationship between the density and the density of a copy. It is a graph showing spectral characteristics.

In Figures 6 to 11, 1 is aluminum 9m, iron,
A conductive substrate made of metals such as nickel, copper, stainless steel, or alloys thereof, and formed into an appropriate shape and structure as required, such as a cylindrical shape or an endless belt shape, 2 is sulfur, selenium, or amorphous silicon. or photoconductors such as alloys containing sulfur, selenium, tellurium, arsenic, antimony, etc., or oxides, iodides, sulfides of metals such as zinc, aluminum, antimony, bismuth, cadmium, molybdenum, etc.
Inorganic photoconductors such as selenides, azo-, di-azo-, trisazo-, phthalocyanine-based dyes and pigments, vinyl carbazole, trinitrofluorenone, polyvinyl carbazole, oxadiazole, hydrazone compounds,
Charge transport substances such as stilbene derivatives and styryl derivatives are used in polyethylene, polyester, polypropylene, polystyrene, polyvinyl chloride, polyvinyl acetate, polycarbonate, acrylic resin, silicone resin, fluororesin,
A photoconductive layer consisting of a photoconductive layer dispersed in an insulating binder resin such as an epoxy resin or a functionally separated photoconductive layer consisting of a charge generation layer and a charge transfer layer; Red formed by colorant (
This is an insulating layer including a layer 3a made of color separation filters such as R), green (G), and blue (B). The insulating layer 3 in the photoreceptor shown in FIG. 6 is formed by printing, photoresist, vapor deposition, or other means on the photoconductive layer 2 by printing an insulating material such as a resin colored with a coloring agent to form a color separation filter. The insulating layer 3 in the photoreceptor shown in FIG. 7 is formed by forming a filter layer 3a in a predetermined pattern on the surface of a transparent insulating layer 3b formed by conventionally known means. The insulating layer 3 in the photoreceptor shown in FIG. 8 is formed by sandwiching a filter layer 3a between transparent insulating layers 3b, and the insulating layer 3 in the photoreceptor shown in FIG. layer 3a, and a transparent insulating layer 3 on the outside thereof
b. These filter layers 3a are formed by printing, vapor deposition, photoresist, or other means.

The insulating layer 3 may be formed by first forming an insulating film or sheet containing the filter layer 3a, and attaching or adhering it onto the photoconductive layer 2 by appropriate means.

Additionally, the present applicant had previously proposed a photoreceptor (patent application filed in 1983).
-199547).
For example, as shown in FIG. 10, an insulating layer 3c is provided on one surface of the photoconductive layer 2, and a transparent conductive layer 101 and an insulating layer 3a consisting of a color separation filter are sequentially deposited on the other surface. It has a layered structure. The transparent conductive layer 101 is formed by, for example, vapor depositing a metal.

In the photoreceptor having this structure, charging, which will be described later, is performed from the side of the insulating layer 3c, and image exposure and overall exposure are performed from the side of the insulating layer 3a, which is a color separation filter.

Further, as shown in FIG. 11, for example, in the case of a drum-shaped photoreceptor, a transparent insulating layer 3b is provided on the photoconductive layer 2, and R, G, and B filters are formed on the transparent insulating layer 3b with a minute gap md thereon. A layer 103 (similar to the layer 3a) can also be provided coaxially. That is, a cylindrical body 103 consisting of R, G, and B filters is coaxially fitted onto a drum-shaped photoreceptor having no filter, leaving a minute gap md, and the photoreceptor is integrated. By having such a structure, Figs. 12(a) and (b)
Any filter layer having the structure of (C) (details will be described later) can be selected, replaced and used.

However, the gap md should not be too large so that the image of the filter cell is not extremely blurred and projected onto the insulating layer and the photoconductive layer. Moreover, the transparent insulating layer 3b
and filter layer 103 may not be completely separated from each other and may be in contact with each other.

The filter layer 3a formed by adhering a coloring agent, colored resin, etc. in the insulating layer 3 is not particularly limited in the shape, arrangement, or size of R%01B minute filters, but may be formed by easily forming a pattern. Figure 12 (a) at the point
6) and (c) in that they reproduce striped distributions as shown in Figure 12, or delicate multicolor images.
It is preferable to use a mosaic distribution as shown in FIG.
The direction in which the R, G, B, etc. filters are arranged may be in any direction in the spreading direction of the photoreceptor, not only in a mosaic distribution but also in a stripe distribution. That is,
For example, in the case of a rotating drum-shaped photoreceptor, the direction of the mosaic or stripes may be parallel to, perpendicular to, or oblique to the axis of the photoreceptor. R,G.

If the size of the filters such as B becomes too large, the resolution and color reproducibility of the image will decrease, resulting in deterioration of the image quality.On the other hand, if the size of the filters such as B becomes too large, the image quality will deteriorate; If it is less than that, it will be easy to be influenced by other adjacent color parts, and it will be difficult to form a filter distribution pattern.

Therefore, each filter part has a length of 10 to 5 as shown in 1 in the figure.
It is preferable that the width or size is 00 μm.

An example of the spectral transmittance of each filter is shown in FIG.

Note that each filter preferably has high resistance. If the resistance is low, they can be electrically insulated from each other by providing a gap or interposing an insulator.

The layer 3a made of the color separation filter as described above is not provided,
A photoreceptor whose photoconductive layer is provided with a color separation function can also be used. FIGS. 14 and 15 show an example of a photoreceptor previously proposed by the present applicant (Japanese Patent Application No. 59-201085). The photoreceptor in FIG. 14 has photoconductive parts 2R12G and 2B having a required spectral sensitivity distribution on a conductive substrate 1, for example, a photoconductive part sensitive to red (R), green (G), and blue (B). A photoconductive layer 102 including a large number of photoconductive layers is provided, and a transparent insulating layer 3b is provided thereon. The photoreceptor in Figure 15 is
A charge transfer layer 202b is provided on a conductive substrate l, a charge generation layer 202a consisting of portions 2B, 2R, and 2G having different spectral sensitivity distributions is provided thereon, and a transparent insulating layer 3 is further provided thereon.
This is a structure in which b is provided. In the photoreceptor shown in Fig. 15,
A photoconductive layer 202 is constituted by the charge generation layer 202a and the charge transfer layer 202b. Photoconductive layer 1 in FIG.
The planar structure of the charge generation layer 202a in FIG. 02 and FIG.
A planar structure similar to that shown in FIGS. (a), (b), or (c) may be used.

First, an original image (original image) is placed on the photoreceptor with the above configuration.
The principle of forming a multicolor image having the same color as the image will be explained with reference to FIG. Note that FIG. 17 shows the photoconductive layer 21 of the photoreceptor.
An example in which a p-type semiconductor photoconductor such as 5 selenium-tellurium is used is shown, and in FIG. 17, the same reference numerals as in FIGS. 6 to 9 indicate the same functional members.

FIG. 17 [1] shows a state in which the photoreceptor 41 is uniformly charged by the negative corona discharge of the charger 4, and the insulating layer 3
A negative charge is generated on the surface of the photoreceptor 410, and a positive charge is correspondingly induced on the interface between the photoconductive layer 2 and the insulating layer 3, and as a result, the surface of the photoreceptor 410 becomes uniform as shown in the graph of the potential E. indicates the potential of

FIG. 17 [2] shows a state in which image exposure is performed on the above-mentioned charged surface by the image exposure device including the charger 5, and as an example, a red image L is shown.
R shows the change in the charged surface of the irradiated part. red image L
Since R passes through the R filter portion of the insulating layer 3 and makes the portion of the photoconductive layer 2 below it conductive, in that portion, direct current or alternating current from the charger 5 of opposite polarity (IE) is superimposed. Due to the discharge, the negative charges on the surface of the insulating layer 3 disappear and further positive charges are accumulated, and the negative charges are accumulated at the interface between the photoconductive layer 2 and the insulating layer 3.

On the other hand, since the G and B filter portions do not transmit the red component LR, the negative charges of the photoconductive layer 2 remain in those portions. The charge on the insulating layer 3 becomes approximately zero due to corona discharge by the charger 5. The same applies to other color components of image exposure. In this way, a latent image is formed on the interface between the insulating layer 3 and the photoconductive layer 2 due to the charge density corresponding to the color component of each filter. However, due to the action of the charger 50 of the image exposure device, the surface potential of the photoreceptor remains unchanged regardless of the amount of charge on the interface between the insulating layer 3 and the photoconductive layer 2, that is, regardless of whether or not image exposure is applied. becomes constant as seen in the graph of potential E. The green component and blue component of image exposure give similar results, and the state in which they are integrated is the state in which image exposure has been performed by the image exposure device, and as it is, it does not function as an electrostatic image.

FIG. 17 [3] shows a state in which the above-mentioned image exposure surface is uniformly exposed to blue light LB from the lamp 6B.

The blue light LB does not pass through the R and G filter parts, so it does not change those parts, but it passes through the B filter part and makes the photoconductive layer 2 below it conductive, thereby reducing the light in that part. Charges at the upper and lower interfaces of the conductive layer 2 are neutralized, and as a result, a potential pattern appears on the surface of the insulating layer 30 in the B filter portion, as shown in the graph, which gives a complementary color image of blue in the previous image exposure.

FIG. 17 [4] shows a state in which the potential pattern formed by the entire surface exposure with the blue light Lm is developed by the developing device 8Y containing the positively charged yellow toner TY. The yellow toner TY adheres to the B filter portion where the potential has changed due to the entire surface exposure process, and does not adhere to the R and G filter portions where the potential has not changed. As a result, a color-separated one-color yellow toner image is formed on the surface of the photoreceptor 4. Although the potential of the part of the B filter to which the yellow toner TY is attached increases somewhat due to development, the surface potential is not uniform as shown in the graph.

FIG. 17 [5] shows a state in which corona discharge is performed by the charger 9Y on the surface of the photoreceptor U on which a yellow toner image is formed. This discharge by the charger 9Y increases the potential of the B filter portion to which the yellow toner TY is attached, and makes the surface potential uniform. I shows the surface potential of this photoreceptor 41 in a graph (charges of the B filter section are omitted below).

Similar to that described in FIG. 17 [3], a potential pattern appears in the G filter portion this time. When this potential pattern is developed by a developing device containing magenta toner,
The magenta toner adheres to the G filter part as shown in Figure 17.
4], a magenta toner image is formed. As a result, two-color toner images are formed on the photoreceptor. Further, a corona discharge is applied to this image forming surface using a charger in the same manner as in FIG. 17 [5] to make the surface potential uniform (charges on the G filter section are omitted below). These processes are shown in FIG. 17 [6], [7], and [8].

The entire surface is exposed to the obtained red light LR, but in this case, since it is a red image, no potential pattern is formed, and as shown in FIG. 17 [10], even if development is performed with cyan toner, the cyan toner is Does not stick. In this way, a red image is reproduced from yellow toner and magenta toner.

As a result of completing the above steps, a clear two-color image without color shift or color turbidity is formed on the photoreceptor 41.

Yellow using the three-color separation method performed as described above.
Reproduction of original images using magenta and cyan toners is summarized in Table 1 below. In Table 1, the symbol r1-:>q indicates that an image pattern of charge density is formed at the interface between the insulating layer 3 and the photoconductive layer 2 of the photoconductor, and the symbol "O" indicates that an image-like potential pattern appears on the surface of the photoconductor. The symbol "o" indicates that a toner image is formed, the symbol "↓" indicates that the state in the upper column is maintained as it is, and a blank column indicates that no image exists. Moreover, "-" in the attached toner column means that no toner is attached, YlM.

C indicates that yellow toner, magenta toner, and cyan toner are attached, respectively.

(Margin below, continued on next page) Furthermore, FIG. 18 shows each filter portion B of the photoreceptor.

It shows the situation where the average surface potential of the G and R parts changes according to the image forming process shown in Fig. 1, and the horizontal axis shows 4.5.6B,
7Y, 15.6G, 7M, 16R, 70 are the first
This figure shows a process in which members having the same reference numerals as those in FIG. 4 or FIG. 5, which will be described later, act on the photoreceptor 41&C.

The multicolor image forming apparatus shown in FIG. 4(a) forms an image based on the above principle, and while the drum-shaped photoreceptor 41 rotates once in the direction of the arrow, the multicolor image is formed as follows. form. That is, the charger 4 charges the surface of the photoreceptor 41 to a uniform potential, and the image exposure device m including the charger 5 exposes the image by the reflected light from the document using a light source described later. At the same time, the surface potential of the photoreceptor 41 is made approximately uniform by the action of the charger 50, which performs corona discharge having a direct current or alternating current component having a polarity opposite to that of the charger 4.

Next, the image-exposed surface is uniformly irradiated with blue light Lm obtained by the lamp 6B, thereby causing a potential pattern to appear on the B filter section. This is developed by the developing device 1F Y which stores the ink rotor toner.

Subsequently, the surface potential of the photoreceptor 41 is made uniform by the action of a charger 15 that performs corona discharge similar to the charger 5.

Next, the green light LG obtained by the lamp 6G is uniformly irradiated to form a potential pattern on the G filter portion, and the developing device 17M storing magenta toner develops the image, forming a two-color toner image on the surface of the photoreceptor 41. be done. Thereafter, similarly, discharge of the charger 16 similar to the charger 15, uniform irradiation of the red light LR obtained by the lamp 6R, and development by the developing device 17C containing cyan toner are performed. Through the above steps, a superimposed image of three color toner images of yellow, magenta, and cyan is formed on the photoreceptor 41.

In a process that does not perform normal color conversion, in order to sharpen the image, white light or infrared light is applied from the lamp 6W to the color separation filter portion to which toner has already adhered;
If the developing device 17K performs development with black toner on the potential portion of each color separation filter portion using the slightly generated potential pattern, an even better image is often obtained.

The multicolor toner image formed as described above is given a special charge by the pre-transfer charging logger and is easily transferred, and after being neutralized by the pre-transfer lamp η having white light or infrared light, the multicolor toner image is transferred to the paper feeder 18. The image is transferred by a transfer device 9 onto a recording paper 8 fed from a printer. The recording paper 8, onto which the multicolor toner image has been transferred, is separated from the photoreceptor 41 by a separator 10, sent to a fixing device 13 by a conveyance means 19, where the multicolor toner image is fixed, and then discharged outside the machine. The surface of the photoreceptor 410 to which the multicolor toner image has been transferred is neutralized by a static eliminator 52 that performs exposure and discharge, and residual toner is removed by a group of cleaning devices, and the state returns to the state where the next image formation can be performed again.

Conventionally, a halogen lamp was used to illuminate the document with white light for the image exposure, but in this example, three types of fluorescent lamps that emit blue, green, and red light are used. ing.

Figure 2 shows the relationship between the wavelength of each fluorescent lamp and the relative energy of each party.

The photoconductive layer is made of selenium-tellurium in this example, and has low photosensitivity in the long wavelength region (red light region), as shown in the spectral sensitivity distribution shown in FIG.

In a selenium-tellurium photoconductive layer, it is possible to increase the photosensitivity in the long wavelength range by increasing the concentration of tellurium, but it is impossible to obtain a sufficiently flat spectral sensitivity distribution. The spectral sensitivity distribution of the photoconductive layer made of an arsenic selenium compound is also shown in the figure, and the spectral sensitivity distribution of this photoconductive layer also shows a similar tendency to that of the selenium-tellurium photoconductive layer.

Therefore, in this example, the red fluorescent light is installed closer to the document than the other fluorescent lights, so that the document is irradiated with red light more strongly than other lights, and the long wavelength range of the photoreceptor is This is to compensate for the decrease in photosensitivity.

FIG. 3 shows the image forming apparatus of FIG. 4(a) (a fifth green fluorescent lamp 31 a G and a red fluorescent lamp 31 a H, which will be described later). It is equipped with a curved reflecting mirror 31b that focuses the light emitted from the lamp onto a straight line of the original 51.The reflected light from the original 51 passes through the mirror 31d, the lens group 31e, the mirror 31f, and the mirror 31c.
The surface of the photoreceptor 41 is irradiated via the charger 5 to perform image exposure. Among the three fluorescent lamps, red fluorescent lamp 31
aR is installed at the position closest to the original 51. Note that the distance of each fluorescent lamp to the document is determined according to the spectral sensitivity distribution of the photoconductive layer, but for those whose photoreceptor is equipped with a color separation function, the distance from each fluorescent lamp to the original is determined by the spectral sensitivity distribution of the photoconductive layer alone. In addition, the spectral transmittance of the color separation filter must also be taken into consideration. This step must be determined so that the combined effective spectral sensitivity distribution is flat. However, it is the spectral sensitivity distribution of the photoconductive layer that most influences the effective spectral sensitivity distribution. For a photoreceptor without a color separation function, the spectral sensitivity distribution of the photoconductive layer becomes the effective spectral sensitivity distribution of the photoreceptor.

The multicolor image forming apparatus shown in FIG. 5(a) differs from the image forming apparatus shown in FIG. 4(a) in that a toner image of one color is formed by one rotation of the photoreceptor 410.

The full-surface exposure apparatus of FIG. 5(a) includes a full-surface exposure lamp 6 equipped with a white light source 6 and filters F1, FG, and F+a used by switching the shutter 6S, as shown in FIG. 5(b). The entire surface is exposed to light of a specific color selected by.

The same image forming operation is performed, and it is possible to form a multicolor image without color shift or a monochrome image with excellent image density and resolution. That is, the photoreceptor 41 is charged by the charger 4,
After performing image exposure using the charger 5 and making the surface potential uniform, the entire surface of the photoreceptor 41 is exposed with light from the lamp 6 that has passed through the actual filter FB, thereby forming a potential pattern. The developing device 17Y develops the yellow toner image. This toner image is transferred to the developing devices 17M, 17C, 17, a pre-transfer charger 21, a transfer device 9,
, the separator 10, the cleaning device enclosure, and the charger 4 without being affected. Photoreceptor 4 on which a toner image is formed
When 1 reaches the position of the charger 5, it is not irradiated with light and receives only corona discharge, so that the surface potential becomes uniform, and the entire surface is exposed to light obtained from the lamp 6 and the green filter Fc, so that the potential pattern becomes uniform. It is formed.

Subsequently, this is developed by the developing device 17M to form a magenta toner image. Similarly, red filter F
Formation of potential pattern and development device 1 by light passing through R
Development with 7C is performed to obtain a three-color toner image.

In the next rotation, development is performed using the developing bag ff17K, and this is transferred onto the recording paper 8 to obtain a color image.

On the other hand, the cleaning member 53a, which has been released, comes into pressure contact with the photoreceptor when the superimposed toner images of three colors pass therethrough, and removes the residual toner on the photoreceptor.

A magnetic brush developing device as shown in FIG. 16 is preferably used as the developing devices 17Y to 17K in the multicolor image forming apparatus shown in FIGS. 4(a) and 5(a).

In the developing device shown in FIG. 16, at least one of the developing sleeve 7 and a magnet 43 having N and S magnetic poles on the inner surface of the developing sleeve 7 rotates, and a developer reservoir 47 is rotated by the magnetic force of the magnet 43. The developer adsorbed on the surface of the developing sleeve 70 is conveyed in the direction of the arrow. Then, during the conveyance of the developer, the amount of conveyance is regulated by the layer thickness regulating blade 40 to form a developer layer, and the developer layer is applied to the photoreceptor 41 in the developing area facing the developing sleeve 7, and the potential of the photoreceptor 41 is Develop according to the pattern. During development, a bias power source (DC power source 45, AC power source 46) is applied to the developing sleeve 7.
A developing bias voltage is applied. In addition, even if development is not performed as necessary, the developing sleeve 7 may be used to prevent toner from transferring to the photoreceptor 41 or from the photoreceptor 41 to the developing sleeve 7. A bias voltage may also be applied.

That is, while only the yellow toner developer is operated and the electrostatic image is developed by the developer 17Y, the other 4th toner developer is operated.
A developing device 17M as shown in FIG. 5(a) and FIG. 5(a),
17C and 17 etc. are kept undeveloped. This can be done by disconnecting the bias power supply 45, 46 of the developing sleeve 7 to put it in a 70-ting state, or by grounding it, or by actively applying a DC bias voltage of the same polarity or opposite polarity to the toner charge to the developing sleeve 7. It is particularly preferable to apply a DC bias voltage of opposite polarity to that of the toner. Since the developing devices 17M and 17C117 are designed to perform development under non-contact developing conditions like the developing device 17Y, the developer layer on the developing sleeve 7 does not need to be particularly removed.

Further, developing devices that are not in use may be stopped.

Thermal theory, separating the developing device from the photoreceptor, and removing the developer from the sleeve are also effective. 44 removes the developer layer that has passed through the development area from the development sleeve 7 and creates a developer reservoir 4.
7, a cleaning blade 42 which stirs and homogenizes the developer in the developer reservoir 47 and frictionally charges the toner; 39 a toner hopper; a toner replenisher which supplies okara toner T to the developer reservoir 47; It's Laura.

The developer used in such a developing device may be a so-called one-component developer consisting only of toner, or a two-component developer consisting of toner and a magnetic carrier. For development, a method may be used in which the developer layer, that is, the surface of the photoreceptor is directly rubbed with a magnetic brush, but especially after the second development, the developer layer is Development methods that do not contact the photoreceptor surface, such as U.S. Pat.
No. 57446, Japanese Patent Application No. 58-238295, Japanese Patent Application No. 1983
No. 8-238296, and Japanese Patent Application Nos. 58-139974 and 59-139 for overlapping on the same latent image.
It is preferable to use the method described in each specification of No. 975. These methods have a large one-component or two-component appearance that includes non-magnetic toner that allows you to freely select the coloring (provided there is no potential difference between the two).
With these settings, development is carried out under the various conditions described above with these gaps and layer thicknesses.

The color toner used for development is made using known techniques and consists of known binding resins, organic and inorganic pigments, various chromatic and achromatic colorants such as dyes, and various magnetic additives that are commonly used in toners. Toner for electrostatic development can be used, and as a carrier, iron powder, ferrite powder, which are usually used for electrostatic images, magnetic materials such as those coated with resin or magnetic materials dispersed in resin can be used. Various known carriers such as carriers are particularly preferred, and high resistance particles of 10 Ωcm or more are preferred, and magnetic carriers with small particle diameters of about 1 μm can be used.

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

Note that FIGS. 17 and 18 show the photoconductive layer 2 of the photoreceptor 41.
has shown an example of a p-type photosemiconductor, but even if an n-type photosemiconductor such as cadmium sulfide is used for the photoconductive layer 2, the basic image will be different because all the signs of the charges will be reversed. The formation process remains unchanged. Furthermore, if it is difficult to inject charges during the first charging of the photoreceptor 41, uniform irradiation with light may also be used.

Next, specific examples will be described.

Example 1 A photoreceptor having the structure shown in FIGS. 9 and 12(c) was used as the photoreceptor 41 of the multicolor image forming apparatus shown in FIG. 4(a).

However, in FIG. 9, the conductive substrate 1 has a thickness of 200 μm.
The photoconductive layer 2 has a thickness of 60 mm.
The photoreceptor was backed with a film made of a 5e-Te alloy (25 wt % Te) of /j m and having a thickness of 5 μm for the insulating layer 3 (the color separation filter layer 3a was 3 μm thick).
In addition, in FIG. 12(e), the period of the mosaic filter in the main scanning direction (direction of the rotation axis of the drum) is 1. is 100μ
m1 period in the sub-scanning direction (rotation direction of the drum) 1. is 10
The value is 0 μm.

The circumferential speed of the photoreceptor 41 is 80 in/36 (closed).

In FIG. 3, the distance between the center of each fluorescent lamp and the irradiation position of the original 51 is 35M for the blue fluorescent lamp 31aB, 35M for the green fluorescent lamp 31aG, and 20m for the red fluorescent lamp 31aR.
The light intensity of each fluorescent lamp can be adjusted.
These light amount adjusting means are shown in FIG. 4('b).
Color balance is performed using fluorescent lamps 31aB and 31a for image exposure.
G, 31aR1 It changes depending on the time series characteristics of 6B, 6G, 6R, and 6W for full-surface exposure.

Therefore, as shown in FIG. 4(b), the original 51 is used for image exposure.
In the optical path from reflection to irradiation on the photoreceptor 41, three 7-photo sensors (not shown) sensitive to each of the blue, green, and red spectra detect the amount of light and send the signal to the CPU. , compared with a preset value and fed back to the power supply of each fluorescent lamp to adjust the power supply. For full exposure,
Photo sensors 70B and 70G are included in the optical path from the light source to the point where the photoreceptor 41 is irradiated.

The 70R170W detects the amount of light, sends the signal to the CPU, compares it with a preset value, and feeds it back to the power supply of each light source to adjust the power supply.

The development was carried out using a non-contact development 1f method using a two-component developer. The carrier is a dispersed carrier made of iron oxide and resin, and has an average particle size of μm, a resistivity of 1d4Ωcm or more, and a magnetization of 40 emu/g. The above resistivity is
After the particles are placed in a container with a cross-sectional area of 0.50 crA and tapped, a load of 19/cTA is applied on the packed particles, and the thickness of the carrier particles at this time becomes about the thickness of IM. This value is obtained by reading the current value when a voltage that generates an electric field of 100 OV/cm is applied between the electrode that also serves as a load and the bottom electrode.
The toner is a color toner with an average particle size of 5 μm (the spectral reflectance is as shown in Figure 19), and the charge amount is 10 μc.
/g, the thickness of the developer layer on the developing sleeve 7 in FIG. 16 is 0.3 mm, and the gap d between the developing sleeve 7 and the photoreceptor 41 is
0.5mm.

The developing bias was a superimposed bias of alternating current and direct current during development.

Under the above conditions, the electrostatic latent image forming conditions were set as shown in Table 2 below, the development conditions were set as shown in Table 3 below, and the process shown in Figures 17 and 18 was carried out. Multicolor image formation was performed according to the following. Scorotron dischargers were used as DC corona dischargers for all chargers.

The obtained multicolor image was of high quality and faithful to the color balance of the original, and no toner color mixing was observed in the developing device.

Note to Table 2) In the table, the white background is the part corresponding to the white background part of the original, and the colored background is the part corresponding to the black background part of the original. The dark decay of the photoreceptor largely contributes to the decrease in the potential contrast obtained.

Table 3 Note) The frequency of each AC component is 2Kflz.

Each developing device is driven only during development, and when the above-mentioned developing bias is not applied, the developing device is stopped, and only a direct current of 500 V is applied as the developing bias.

Figure 4 shows the original density (original density) and image density (
Copy density) is shown for three-color overlapping.

Figure n shows the relationship between the copy density and the original density obtained in the same manner as in this example except that a halogen lamp with white light was used as a conventional light source for image exposure. Therefore, the copy density changes depending on each toner,
In the case of three-color superimposition, the slope of the curve is extremely steep in the original density range of 0.2 to 0.7, and the copy density is extremely high. Ideally, each curve should match the line r = 1 (indicated by a dashed line in the figure) where the original density and copy density are equal, but each drill It's out of place.

Therefore, while the color reproduction of density in highlight areas and solid areas is good, the reproduction of intermediate tones is not so good.
Further, a slight difference in the density of the original image becomes a large difference in the density of the copy, and the density range of the original image in which gradation can be reproduced, the so-called dynamic range, becomes narrow.

On the other hand, in this example, as can be seen from FIG. 4, the curve is closer to the line of γ=1 than in FIG.
It is very close to that of the original statue and is in very good condition. This means that halftones can also be faithfully reproduced.

When forming an image using a photoreceptor having color separation filters, toner is applied to each microfilter as described in FIG. 17. The potential pattern is actually higher at the center of the filter and lower at the periphery, so the amount of toner deposited is also greater at the center and less at the periphery. Therefore, it becomes difficult to obtain a sufficient image density in the solid portion of the original image, and an image with insufficient reproducibility and a density lower than that of the original image is reproduced. Therefore, in this embodiment, as shown in FIG.
M and TC are designed to increase the copy density by spreading the toner and overlapping the toner as shown by the imaginary line during transfer and fixing.

Example 2 A multicolor image was formed using the multicolor image forming apparatus shown in FIG. 5(a), but under the same conditions as in Example 1 above.

Note that, due to the dark decay of the photoreceptor, the potential contrast due to the shift of the black background potential further decreases, so the DC voltage was shifted accordingly and the AC voltage was set to a large value. As a result, the obtained multicolor image was of high quality with excellent color balance, similar to the multicolor image obtained in Example 1.

Example 3 Fluorescent lamp 31 a for the three types of food used in Example 1.2 above
In place of B, 31aG, and 31aR, a three-wavelength type fluorescent lamp having the spectral characteristics shown in Figure n was used.

The spectral characteristics of this fluorescent lamp are particularly strong in energy at a wavelength of 620 nm. The spectral characteristics of this type of fluorescent lamp can be set by selecting the phosphor to be encapsulated. In other respects, there is no difference from the above embodiment 1.2.

This fluorescent lamp was used in the image forming apparatus shown in FIGS. 4 and 5(a), and a multicolor image was formed in the same manner as in Example 1.2. The obtained image was of high quality with good color balance, as in Example 1.2.

Further, the present invention provides a photoreceptor 1410 as shown in Fig.
A multicolor image is formed by 1410 rotations of the photoreceptor according to the type of toner, using charging, image exposure and development for each color in each rotation, and is transferred to the recording paper 8 on the transfer drum in each rotation,
It is also applicable to a Carlson image forming method in which toner is superimposed on the recording paper 8. In this method, the photoreceptor 141
does not require color separation filters, but uses FB, FG,
In the image forming apparatus shown in Fig. 1, which performs image exposure through each FR filter, parts common to those in Figs. 4 and 5(a) are denoted by the same reference numerals.

In this multicolor image forming apparatus, three types of monochromatic fluorescent lamps 31a B, 31a G, 31 shown in FIG. 3 are used as image exposure light sources.
Either arrange the aR in the same manner as shown in Figure 3, or use a three-wavelength type fluorescent lamp having the spectral characteristics shown in Figure 22. Conventionally, this multicolor image forming apparatus uses a white light source and a blue light source. , green, and red filters were switched each time the photoreceptor rotated to perform image exposure for each color. Therefore, as described above, it was not possible to obtain good color balance, but by applying the present invention, it is possible to obtain good color balance.

In the embodiment described above, a monochromatic light source that emits image exposure light in a wavelength range in which the photoreceptor has low photosensitivity is positioned close to the original. However, a photoreceptor with a color separation function uses a multi-wavelength light source that increases the energy in the wavelength range with low effective sensitivity, taking into account the spectral transmittance characteristics of the color separation filter and the spectral sensitivity characteristics of the photoreceptor. In this way, imperfections in the spectral sensitivity distribution of the photoreceptor (including the spectral characteristics of the color separation filter) are compensated for.

In addition to forming multicolor images, the present invention is also suitable for making black and white copies from full-color originals.

For example, when a photoreceptor with low photosensitivity in a long wavelength range is used and image exposure is performed with white light, the red portion of the document is reproduced with a higher image density than the original image. By using the image forming apparatus according to the present invention, it is possible to obtain a black and white copy having the same tone as a full-color original.

Note that the light amount and/or energy of the irradiation light in a specific wavelength range is increased in response to the wavelength range in which the effective sensitivity of the photoreceptor is relatively low, not only for the image exposure light but also in Example 1. It is also effective when applied to the light source for full-surface exposure using specific light in 2.3. That is, in FIG. 17, L
By using the light source for full-surface exposure using SI, LG, and LR as described above, it is possible to make the potential pattern formed in each filter part more uniform and to obtain good color balance.

As described in detail in Section 6 of the invention, the present invention provides a method for increasing the light amount and/or energy of a specific wavelength of irradiation light, at least corresponding to a wavelength range in which the effective sensitivity distribution of a photoreceptor is relatively low. Therefore, it is possible to flatten the spectral sensitivity distribution that combines the photoreceptor and the exposure light source (if it has a color separation filter, it is taken into account). As a result, a high-quality image with a tone that is faithful to the original image is formed.

[Brief explanation of the drawing]

Figures 1 to 4 show examples of the present invention; Figure 1 is a graph showing an example of the spectral sensitivity distribution of a photoreceptor that does not have a color separation function; Figure 2 (a); (b) and (e) are graphs showing the spectral characteristics of a monochromatic fluorescent lamp. Figure 3 is a partially enlarged sectional view of the area around the image exposure device of the image forming apparatus. Figure 4 shows the configuration of the image forming apparatus. Figure 5(a) is a schematic diagram of the configuration, Figure Cb) is a schematic diagram showing the configuration and control of exposure amount, Figure 5(a) is a schematic diagram of the configuration of another image forming apparatus, Figure 5(b)
) is a schematic sectional view of the entire surface exposure lamp; FIGS. 6, 7, 8, 9, 10, and 11 are sectional views of the photoreceptor, respectively; 13 is a graph showing the spectral transmittance of the color separation filter, and FIGS. 14 and 15 are cross-sectional views of other photoreceptors, respectively.
FIG. 6 is a cross-sectional view of the developing device, FIG. 17 is a process flow diagram for explaining the multicolor image formation process, and FIG. 18 is a graph showing changes in the average surface potential of the photoreceptor during the multicolor image formation process. Figure 19 is a graph showing the spectral reflectance characteristics of toner, No. 1 is a graph showing the relationship between original density and copy density, and Figure 21 is a schematic diagram showing the state in which toner on a photoreceptor spreads during transfer or fixing. , FIG. 22 is a graph showing the spectral characteristics of a three-wavelength type fluorescent lamp, and FIG. 4 is a schematic diagram of the configuration of another image forming apparatus. Figure 1 is a graph showing the relationship between the density of a copy and the density of an original image obtained by a conventional image forming apparatus. In addition, in the symbols shown in the drawings, 1.101...... Conductive substrate 2.102.
202...Photoconductive layer 3...
・Insulating layer whistle 1 3a... Color separation filter layer 3b, 3C・
・・・・・・Transparent insulation layer 4.5.15.16, Ri・
...Charger 6.6B, 6G, SR...
...Full exposure lamp 8...Recording paper 17.17Y, 17M, 17C, 17K...
...Developing device 31... Image exposure device 31aB... Blue fluorescent lamp 31aG...
...Green fluorescent light 31 a R...
・Red fluorescent lamp 41...Photoreceptor 53...Cleaning device Fn, FC,
FR・・・・・・Filter L・・・・・・・・・
Image exposure light LR... Red component of image exposure light a, Lc
, Ln...Full exposure light R, G, B...
...It is a color separation filter. Agent: Hiroshi Aisaka, Patent Attorney Figure 4 (b) Figure 5 Figure 12 Figure 13 Figure 5 skin & (nm) Figure 17 [9] [10] Figure □ Figure 21 Reflection fF-<%)ノ36 Units 吃1-Ir Otsu No. 22 Liquid Keeper + nm) Original * degree

Claims (1)

[Claims] 1. In an image forming apparatus that irradiates a photoconductor with a plurality of lights having different wavelength ranges, at least a specific wavelength light of the irradiation light corresponds to a wavelength range in which the effective sensitivity of the photoconductor is relatively low. An image forming apparatus characterized in that the image forming apparatus is configured to increase the amount of light and/or energy of the image forming apparatus.