JPH01201681A - Multicolor image forming device - Google Patents

Abstract

PURPOSE:To form images whose image quality and color reproductivity are excellent by performing the non-linear masking of an input signal by means of a color correcting means. CONSTITUTION:A color separating means by prisms 102-104 alternately inserted into an optical path separates the light source of a color original 82 into three colors; such as blue, green and red. The light sources are formed on three CCD image sensors 104-106, etc., transferred photoelectrically and after that made into digital signals by an A/D converter. The masking and the UCR of those color separating signals are performed so as to obtain image data Y, M, C and Bk of four colors. One of the image data is selected and written on an image forming body 120 through a writing device B using semiconductor laser beams so that electrostatic images are formed. They are developed by a developing device 123, thereby forming color toner images. Thus, the process is performed plural times while changing chrominance signals so that multicolor toner images made up of overlapped toner image in different colors are formed on a forming body. Thus color copies can be easily obtained whose color reproductivity and image quality are excellent.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a multicolor image forming apparatus, and more particularly to a multicolor image forming apparatus that forms multicolor images using a digital method.

[Background of the invention]

In recent years, color image equipment such as computer mm color CRT display devices and Hideotex terminal devices have become popular, and companies,
2. Description of the Related Art As documents and other printed matter in offices and the like are increasingly produced in color, there is an increasing demand for color copies containing a larger amount of information.

Under the above circumstances, various methods and apparatuses for forming multicolor images have been proposed.

2. Description of the Related Art Conventional multicolor image forming apparatuses include one in which toner images of each color formed on an image forming body are sequentially transferred onto recording paper, and the toner images of each color are superimposed on the recording paper. However, such multicolor image forming apparatuses have problems, such as the need for a transfer drum, which increases the size of the apparatus, and the transfer misalignment of each color toner image, making it impossible to obtain a clear multicolor image.

Therefore, for example, a plurality of latent image forming means and a plurality of developing means are arranged around a rotating drum-shaped photoreceptor, and by repeating latent image formation and development, visible images of different colors are formed on the drum-shaped photoreceptor. A method of forming layers in layers and transferring them all at once to recording paper (Japanese Unexamined Patent Publication No. 52-106743), No. 56-1
No. 44452, No. 58-79261, No. 61
-170754) has been proposed.

The resist of the multicolor toner image formed on the image forming body by the above method is significantly improved compared to the above-mentioned color copying method using a transfer drum.

Further, one latent image forming means and a plurality of developing means are arranged around the rotating drum-shaped photoreceptor, and a latent image is formed and developed for one color each time the photoreceptor rotates. Multiple rotations form a multicolor visible image on the photoreceptor, which is then
Method of simultaneously transferring onto recording paper (Japanese Unexamined Patent Publication No. 60-76766), Japanese Patent Application Laid-Open No. 60-95456, No. 61-1707
No. 54) has been proposed.

In this method, since there is only a single latent image forming means, the apparatus can be made more compact than in the former method, and in particular, since the latent image forming means is commonly used, it is advantageous in guaranteeing latent image registration. .

On the other hand, as a color imaging device that reads multicolor image information,
A method of switching filters and light sources is known. Although this method is effective in preventing moiré because it basically does not cause color shift and can utilize a monochrome solid-state imaging device with high resolution, it has the disadvantage that color correction and undercolor removal cannot be performed.

Also known is an imaging means in which three color components of an original are captured simultaneously. With this method, various color corrections can be performed without using a large capacity image memory.

By the way, in the image forming apparatus described above that forms a multicolor toner image on a photoreceptor and then transfers it to a transfer agent to obtain a multicolor image, the following should be taken into consideration when performing color correction from color separation signals. It became clear from the inventor's experiments that this must be done.

(2) To compensate for the influence of the toner image previously formed on the image forming member on subsequent toner image formation.

■It is advantageous in the electrophotographic process to replace part or all of the overlapping portions of yellow, magenta, and cyan toner with black toner to reduce the total toner adhesion amount.

Although an image data imagining method that takes into account the characteristics of the recording method is essential for color reproduction, the prior art did not take this point into consideration.

[Purpose of the invention]

The present invention solves the problems of conventional image forming methods,
It is an object of the present invention to provide a color image forming apparatus capable of forming images with high image quality and good color reproducibility.

[Structure of the Invention] The above object is to provide a reading means for optically scanning a document and outputting color separation signals, a color correction means for color correcting the color separation signals to form image data, and a color correction means for color-correcting the color separation signals to form image data; A multicolor image forming apparatus comprising a recording means for sequentially forming toner images on an image forming body to obtain a multicolor toner image, characterized in that the color correction means performs nonlinear masking of an input signal. This is accomplished by a multicolor image forming device that uses

[Explanation of configuration]

The multicolor image forming apparatus according to the present invention has the following configuration and operation.

(1) The image reading section uses a solid-state image sensor and color separation means. As a result, the image information of the original, for example, B (blue),
A color-separated image of G (green) and R (red) is extracted as an electrical signal.

(2) Perform masking and OCR processing on the color separation image to obtain color image data of yellow, magenta, cyan, and black components.

(3) The output of color image data is performed every - time, and in synchronization with the input, the image forming body is optically scanned and converted into a toner image.

Through the above steps, Y (yellow), 1M (magenta), C (
By superimposing the cyan) and Bk (black) toner images,
After forming a color toner image, it is fixed on transfer paper.

(4) In superimposed image formation, it tends to be difficult to adhere to the previous toner image. This is because the dynamic range of the latent image becomes smaller. Furthermore, the development characteristics differ depending on the toner. Therefore, γ correction and threshold values are selected. Further, sufficient undercolor removal (UCR) is performed to reduce the amount of adhered Y, M, and C toners, and to improve the reproducibility of Bk toner images using Bk1-toner.

(5) There are changes in the spectral distribution of the light source, variations in color separation performance and lens characteristics, and it is necessary to compensate for these for the three colors.

For this purpose, it is effective to correct the input data for each scan by referring to the reference image.

(6) In this method, color corrections such as masking and UCR are performed based on color separation images of three colors, for example, B, G, and R. Therefore, errors in color correction occur due to pixel misalignment in the reading system, resulting in undesirable images such as color ghosts in character areas being output.

When reproducing a color image from Y, M, C, and Bk toners, the M, C, and Bk toners are important in consideration of human vision, and the Y toner is less important than them. Therefore, it is necessary to have a large amount of information in the image data of the G and R systems, which have a strong correlation with the M, C, Bk) color images, and in particular, the resolution of the G and R systems is higher than that of the B system. is desirable.

Originally, it is desirable to set the resolution so that it does not change depending on the lens system or color, but this is difficult.

Therefore, the resolving power of the lens, etc. is set to G compared to B system.

It is desirable to set the R system to a high value. or,
The G, R, and Bk systems may be made higher by MTF correction.

(7) Adding black toner gives the image a tighter appearance. In particular, in this method of overlapping toner images, in order to maintain a high amount of toner adhesion, all Y, M, and C toners are
It is desirable to replace all or part of the areas to which black toner is attached with black toner.

For this purpose, it is preferable to form black data from input decomposed image data through image processing.

If the black data obtained by UCR is output as is, it will become dark, so it is desirable to control the amount of black toner adhesion, such as by setting a certain threshold and making the image data with black toner adhering to the density higher than that. . This corresponds to inking in printing. Of course, in the case of monochrome printing, a different equivalent value is adopted.

Here, masking (2) will be explained in detail.

FIG. 27 shows an example of the spectral transmittance of each color toner measured under specific conditions. FIG. 28 is a model sectional view of the surface of the image forming body, in which (a) shows when the second color image exposure is performed, and (b) and (c) show the time when the second color development is completed.

As shown in FIG. 28(a), when the image forming body 120 to which the toner T1 has adhered and is charged to a uniform potential is irradiated with image exposure (arrow) by a laser beam, the potential at the irradiation position decreases. do. The amount of the drop depends on the actual amount of exposure light that passes through the toner Tt and reaches the surface of the image forming member. For example, toner T1 is the cyan toner in FIG.
When the light source of the exposure light is a semiconductor laser with a wavelength of 780 nm (the position indicated by the dotted line in Figure 27), a considerable portion of the exposure light is absorbed by the toner T, the amount of potential drop is small, and that portion is absorbed by the toner T. When developing at T2, the amount of overlap is the second
8 (b). Also, for example, toner T
1 is the yellow toner in FIG. 27, and when the same exposure light is used, the absorption of the exposure amount by toner T1 is small, so the amount of potential drop is relatively large, and when that part is developed with toner T2, the amount of overlap increases. becomes large as shown in FIG. 28(C).

In addition, factors that determine the overlapping amount of toner T2 include:
There are the amount of adhesion of toner T1, the amount of charge of toner T, etc.

Normally, the image density of a recorded image has a one-to-one correspondence with the image data, but in this process, it is necessary to check whether or not toner of another color has already adhered to the position where the toner will adhere, The relationship between image data and image density differs depending on values such as amount, transmittance, and amount of charge.

On the other hand, a linear masking method is widely used as a color correction method. This is blue (B), green (G),
The yellow (Y), magenta (M), and cyan (C) recording data D , t , DM , and D c from the data D8 and D6DR color-separated by red (R) are converted into the following primary sequence, where aiBi , 'j= 1.2.3. ) is a coefficient.

However, as described above, in this process, the overlapping region of toners is strongly influenced by the previously developed color toner, so the above-mentioned linear masking equation does not hold.

Therefore, the inventor created the formula (2) by adding higher-order terms to formula (1).
), the problem was resolved by correcting the color.

D y −a l l D B + a
1 2 DG + a I 3 DR+
a I 4 D a”+ α,, D a”+
α,, D %+ α, 70 G 11 D R+a+
, + DR"D+++a+iDm"Dc+"'D
M= az+D a + a2zD c + a23D
* + a24D a"+ ...D c"' ax+
D B+a32D G+ a33D R+ a34D
a2++++...(2) In equation (2), the higher-order term incorporates the recording characteristics in the overlapping area.

A conversion formula can be constructed by adding the effects of undercolor removal and black addition to such a masking method.

That is, formally, in equation (2), D BK-α, D B+a42D G0aa3D tr
+aa4D i"10-...(3) This is achieved by an equation of the form of adding.

In equation (2) or (3), the error in color reproducibility can be reduced as higher-order terms are added, but this is subject to restrictions such as the amount of work required to obtain coefficients and the scale and time of the circuit that performs the calculation.

The basic configuration of the color image forming apparatus of the present invention will be explained below with reference to FIGS. 1 and 2.

FIG. 1 is a diagram showing a general configuration of a color image forming apparatus and a control system.

FIG. 2 is a block diagram schematically showing an image forming process using the apparatus.

FIG. 1 shows a color image forming apparatus having the following configuration as a representative example. First, for color originals, a light source is separated into three colors of blue, green, and red by color separation means using prisms inserted alternately in the optical path, and images are formed on three CCD image sensors, etc., and the images are photoelectrically converted. , converted into a digital signal by an A/D converter. Masking of these color separation signals, U
CR is performed to obtain four-color image data Y, M, C, and Bk.

One of these image data is selected and written on the image forming body through a writing device using a semiconductor laser to form an electrostatic image, which is developed by a developing device corresponding to the selected color signal. A color toner image is formed. By performing the above process a plurality of times while changing the selected color signal, a multicolor toner image in which toner images of each color are superimposed is formed on the forming body. This multicolor toner image is transferred and fixed onto a transfer agent to obtain a color image.

In FIG. 1, the CPU 1 is controlled by the operation section circuit (304).
By pressing the copy button on the operation panel connected to the main body control CPU, the original reading section A is driven under the control of the optical drive CPIJ2 connected to the main body control CPUI through serial communication.

First, a document 82 on a document table 81 is optically scanned by an optical system. In this optical system, a carriage 8 is provided with a halogen lamp 85, a slit 86, and a reflecting mirror 87.
4. (2) What is the movable mirror unit 38 provided with mirrors 89 and 89'?The carriage 84 and the movable mirror unit 88 are stretched from a pulley 91 attached to a stepping motor 90 via pulleys 93 and 92. The wires run on the slide rail 83 at speeds of V and 1/2V, respectively. Optical information obtained by illuminating the original 82 with the halogen lamp 85 is guided to the optical information conversion unit 100 via the reflecting mirror 87, the mirrors 89 and 89'.

Note that the halogen lamp 85 is subjected to infrared cut treatment. A fluorescent lamp can also be used instead of the halogen lamp 85.

In addition, the platen has a standard white plate 9 on the back side of both ends of the lath 81.
7 and 98 are provided. This is for optically scanning the standard white plate to normalize image signals, which will be described later.

Next, the optical information conversion unit 10 of the image reading section A
0 is a lens 101, an infrared (IR) cut filter 102 made of a multilayer film, and a color separation prism 1 made of a multilayer film.
03, C CD 104 that receives the blue component image, C CD 105 that receives the green component image, C that receives the red component image
Amplify the output from CD 10'6 and each CCD and A/
It is composed of a substrate 107 that performs D conversion. In the optical information conversion unit 100, which is connected to each CCD and the substrate 107 by flexible wiring, the optical information derived from the optical system is focused by the lens 101, and the blue, green,
A color separation means provided with a red color separation prism 103 separates the colors into blue, green, and red optical information, and the CCD
Images are formed on light receiving surfaces 103, 104, and 105, and image signals are output. Note that a correction glass may be inserted to correct the lens 101 and each CCD focal position for each color.

The image signals output from the CCDs 104, 105, and 106 are subjected to calculations such as A/D conversion and shading correction, which will be described later, and then converted into yellow, magenta, cyan, and black image data by masking and UCR. be done.

Thereafter, it is processed by a signal processing device such as binarization, multi-value conversion, dithering, etc. to produce the above-mentioned Y, M, and C.

Bk image data is sequentially output to the writing section B by the selector.

In the writing section B, a laser beam modulated by the selected color image data is first applied to the motor 1 when the power is turned on.
An image forming body 120 is scanned by a polygon mirror 112 which is rotated by a polygon mirror 10 .

When the scanning is started, a laser beam index sensor (198X
(see FIG. 15), and modulation of the beam by image data of the first selected color (for example, cyan data) is started. The modulated beam is directed to the imager 120
Scan above. The image forming body 120 is uniformly charged in advance by a charger 121.

Main scanning is performed by the laser beam, and the image forming body 12
Sub-scanning is performed by the rotation of 0, and an electrostatic image corresponding to the first color image data is formed on the image forming body 120.

This electrostatic image is transferred to a developing device 123 containing cyan toner using a high voltage power source 2. By applying a bias voltage from (241a), development is performed, and a cyan toner image is formed on the image forming body 120. Note that toner replenishment of the developing device 123 is performed at any time by C.
Toner replenishment SD 2 (313) controlled by PUI
will be replenished via. This cyan toner image is formed on the image forming body 1 with the cleaning blade 127 released.
20 rotates, and the pictorial sensitive body 120 is uniformly charged again by the charger 121 while retaining the cyan toner image. Thereafter, an electrostatic image is formed based on the image data of the second color (for example, magenta) in the same manner as in the case of the first color, and the high voltage power supply 2 (241b) is also supplied to the developing device 124 containing magenta toner. By applying a bias voltage, development is performed to form a magenta toner image on the cyan toner image. Note that the electrostatic image must be aligned with the cyan toner image with sufficient accuracy. Similarly, an electrostatic image is formed based on the third color image data (yellow), and a bias voltage is applied from the high-voltage power supply 2 (241c) to the developing device 125 containing yellow toner. A yellow toner image is formed on the cyan toner image and the magenta toner image.

Next, after being charged again, an electrostatic image is formed based on the image data of the fourth color (black), and a black toner image is formed by applying a bias voltage from the voltage power supply 2 (241d) to the developing device 122 containing black toner. is formed on the previous toner image.

A multicolor (four-color) toner image is obtained in the manner described above.

Note that although four-color image formation is described here, color image formation consisting of three colors of Y, M, and C is the same except that UCR is not performed.

The developing units 123, 124, 125, and 122 fly toner toward the image forming body I20 in a non-contact manner while applying AC and DC bias voltages from the high power source 2 (241α, b, c, d). It is preferable that the image be developed using a reversal method. Note that toner replenishment to the developing units 124, 125, and 122 is performed by toner replenishment SD 3 (314) and SD 3 (314) by a signal from the CPU as in the case of the developing unit 123.
4 (315) and S D 1 (312).

The thus obtained multicolor toner image is placed on a transfer material P fed from a paper feeder 141 via a feed roll 142 and a timing roll 143 in synchronization with the rotation of the image forming body 120, and is transferred to a high voltage power source 3 (324). Transferred by the transfer pole 130 to which high pressure is applied from the separation pole 131
It is separated from the image forming body 120 by.

The transfer material P separated by the separation pole 131 is transferred to the microcomputer C.
Fixing device m132 controlled to desired temperature by PUI
The image is conveyed to a printer, fixed, and ejected to obtain a color image. The image forming drum 120 after the transfer is cleaned by a cleaning device 126 and prepared for the next image formation.

In the cleaning device 126, a blade 127
In order to facilitate recovery of the toner cleaned by the blade 127, a metal roll 128 to which a DC voltage is applied from a high voltage power source 4 (325) is arranged without contacting the image forming body. Further, the blade 127 is released from the pressure bond when cleaning is completed, but a cleaning auxiliary roller 129 is further provided to remove toner left behind on the image forming body 120 when the blade 127 is released. The image forming body 120 is sufficiently cleaned by the rotational pressure bonding.

FIG. 2 is a block diagram showing the flow of image signals and control relationships.

Note that, as described later, the masking and UCR sections can be combined into one circuit.

The above is the basic configuration of the color image forming apparatus of the present invention and when forming a color image using the apparatus, and the details thereof will be further explained below.

FIG. 3(a) shows a side view of the optical information exchange unit 100 incorporated into the image reading section A. The unit 100 includes an imaging lens 101, an interference filter 102 that cuts ultraviolet and infrared rays and passes 400 to 700 nm, and a prism 103 that separates the visible light that has passed through the filter into colors.゛C0D104, 105, 106 that receives resolution light and converts it photoelectrically
It has the following elements. Each CCD has panchromatic spectral sensitivity.

For example, each CCD has a sensor size of IOX 50++.
It consists of an element row in which approximately 5,000 minute (approximately 7 μm wide) light-receiving elements are densely arranged within +m.

In this case, if the positional accuracy between pixels of each CCD is not satisfied, color correction for each pixel becomes difficult, and the color reproduction of the resulting color image deteriorates.

In the present invention, each CCD is aligned using a jig and then fixed with an adhesive, so that pixel misalignment can be kept small.

In addition, a CCD with a 5,000-pixel element is used, and pixel misalignment is prevented by high alignment accuracy (Figure 3 (a)). Even in thermal theory and writing systems, it is necessary to maintain positional accuracy during multiple scans.

The imaging lens 101. Filter 102, prism 1
03, CCD 104, 105, 106, etc., must be optically precisely constructed and designed so as not to cause distortion due to changes in the external environment, mechanical vibrations, etc. Furthermore, the optical system must be designed to have no chromatic aberration.

103-(a) of the color separation prism of 103, 103
- A dichroic ivy filter is constructed on the (b) surface. This is an interference filter obtained by alternately vacuum-depositing low refractive index dielectric films and high refractive index dielectric films in multiple layers on a transparent substrate such as glass. ) has spectral transmission characteristics such as For example, Figure 3 (c) (a)
By using CCD 4 for 2 and CCD 4 for 3, CCD 4 for blue information, CCD 5 for red information, and CCD 6 for green information.

The light that has passed through the lens 5 enters the prism surface 103-(c) almost perpendicularly. After that, the light is separated by the tichroic film on the 103-(a) plane (Fig. 3 (c) (a) characteristic example), and the blue component light (400 to 500 nm) is reflected toward the 103-(c) plane. . Blue component light is 103-(c)
It is totally reflected at the boundary between the glass and the air layer.
The light is emitted from the surface almost perpendicularly to the same surface, and is imaged on the CCD 104.

On the other hand, (500
~700nm) light travels straight through the prism, and 103-(
b) reach the surface. Since 103-(b) has a tychroic film (characteristic example in Figure 3(c)(b)), 600-7
The red component of 00 nm is reflected toward the 103-(d) plane.

The red component light is totally reflected at the boundary between the glass surface of the surface 103-(d) and the intake layer, is emitted from the surface 10103-(d) almost perpendicularly to the same surface, and is imaged on the CCD 105.

The green component light of 500 to 600 nm passing through the 103-(b) plane reaches the 103-(e) plane, is totally reflected at the boundary between the air layer and the glass surface of the 103-(e) plane, and is reflected by the 103-( h
) is emitted almost perpendicularly to the same surface and is imaged on the CCD 106.

The color separation prism 103 having the above structure can be easily constructed by researching a large number of prisms having the illustrated surface angles and bonding them together. The prism 103 is 103-(e
) plane, 103-(c) plane, 103-(f), (g),
(h) Configure the external dimensions of the surface so that it forms a large equilateral triangle. With this configuration, the optical path lengths within the glass are all equal, and the lengths are equal to the height of the large equilateral triangle of the prism 21.

It will be understood that by using the prism as described above, the three-color separated optical images are projected onto substantially the same plane B.

Now, when optical images separated into each color are obtained on the same plane as described above, the following advantages arise. Below, the third
A three-color decoding optical system is shown in FIG. 4(d) and will be described.

Three CCDs 104, 105, 106 each have 5
Pixel positions cannot be aligned without adjusting the axes. If each color-separated optical image is obtained on the same plane, the CCD can also be arranged on the same plane.

As a result, we prepared only one S-axis adjustment mechanism and the C of 104
After adjusting the CD first, attach it to the prism 103 by gluing it etc.
I fixed the CD and then used the y-axis adjustment mechanism to
Shift the adjustment mechanism to the position of the CCD 5 and adjust the CCD 105 so that it is based on the prism 104.
3. Fix it with adhesive etc.

Furthermore, use the y-axis adjustment mechanism to shift the adjustment mechanism to the position of 106 CCD, and change the 106 CCD to 105 or 1.
Adjust the prism 103 so that it is based on the CCD of 04.
Fix it with adhesive, etc.

In this way, adjustment can be easily performed by preparing only one adjustment mechanism.

In the present invention, in order to satisfy the above requirements, each of the above elements is configured as follows.

That is, as shown in FIG. 3(A), the C
5.106 is integrally fixed via a fixing member K1 (K2) by a method such as adhesive. For example, in the case of adhesive bonding, as shown in the cross-sectional view of FIG. , the tip surfaces of the fixing members Kl and 2 are COD 104°105.
By adhering to the left and right ends (upper and lower ends in the drawing) of the light receiving surface of 106, it is configured to be integrated with the lens system via the fixing members Kl and 2.

Also, the prism 103 is attached to the support member 10 by screws PL and P5.
It is fixed at 9a.

Further, the lens 101 is integrally fixed by further fixing the lens holder 109b to the support member 109a with screws P4. Note that before each element is fixed by the adhesive and screws, precise optical positioning as described above is required using an adjustment tool.

In this way, the optical information conversion unit 100 installed in the color Ryotsu forming apparatus of the present invention does not suffer from structural distortion due to temperature changes, mechanical vibrations, etc., and as a result, at least three types of color separations are obtained. Information is read by the three CCDs in perfect synchronization.

For reference, FIG. 4(A) shows an example of the spectral characteristics of the document scanning light source 85. The horizontal axis represents wavelength (nm), and the vertical axis represents relative intensity. Further, FIG. 4(b) shows an example of the spectral characteristics of the filter 102 and the color separation prism 103, which are an example of color separation means. The horizontal axis represents wavelength (am), and the vertical axis represents transmittance (%). Sara 1: Also No. 411i1
An example of the spectral characteristics of i11 (c) Niha CCDs 104, 105, and 106 is shown. The horizontal axis represents wavelength (nm), and the vertical axis represents relative sensitivity (%).

In this way, the blue, green, and
After the red image signal is digitized by an A/D converter, it is processed by arithmetic circuits such as masking, UCR, MTF correction, etc., and a multivalue or binarization circuit using dither method, density pattern method, etc. The color signal is output as a color signal to the writing section B, and the semiconductor laser of the writing section B is modulated.

The reading system in the present invention is not limited to one using a reduction optical system, but a contact image sensor or the like may also be used.

Further, a normal imaging system has chromatic aberration. In this embodiment, design and assembly are performed with priority given to ensuring that there is no pixel shift for each color between the solid-state image sensors.

However, the design of the imaging system usually suffers from chromatic aberration and other aberrations (
It is difficult to eliminate both spherical aberration, astigmatism, and coma aberration. In this case, a design that corrects chromatic aberration one summer in advance is preferable.

Other aberrations are compensated for by MTF correction.

At this time, M T by Y, M, C, Bk channels
I will change the correction rate of F correction. For example, to emphasize black characters, the Bk correction rate is set high and edges are emphasized.

The signals photoelectrically converted and A/D converted by the CCD are normalized by a white plate at blue, green, and red levels V B , V
It is normalized by G and VR, and shading correction is performed.

The signals D , , D , , D , obtained in this way are color-corrected in the manner described above to form recording signals DY, DM.

DC and DBK are formed. These signals are subjected to MTF correction and 9-adjustment correction as necessary, and binary or multi-value dot information is formed by a dither method, a density pattern method, or the like.

When performing enlargement/reduction, etc., it is preferable to set up a circuit between after shading correction and before binarization.

Image signals obtained from image scanners are affected by shading effects. The shading correction method adopted in the present invention is performed by multiplying the image signal by a shading correction coefficient stored in a memory, as shown in the block circuit diagram of FIG. This method is performed by changing the reference voltage of the A/D converter for each sample point of the image, and the circuit configuration is simple. It has the advantage that it can be corrected even if First, a reference density plate is scanned to include the maximum brightness, and a digital signal quantized using a sampler and a fixed reference voltage is written into the image memory.

Next, the captured image signal is read and sampled. When quantizing this sampled image signal, the pixel level of the reference density plate corresponding to each pixel of the image sensor is taken out from the image memory, converted to a reference voltage level by referring to the shading correction memory, and D/ Using the A-converted voltage as a reference voltage, the image signal is digitized, subjected to Qog conversion as a digital signal, and sent to a masking circuit in correspondence with the image density.

When masking, the following points need to be considered.

(1) In order to be able to express halftones, the concept of reflectance (reflection density) of the original 82, which corresponds to the luminance signal of the television signal, is adopted. Therefore, it is desirable to perform the Qog conversion after the aging correction.

(n) Incorporate the concept of matching the color information input from the image reading device with the color (including hue and brightness) reproduced by overlapping toner.

FIG. 6 shows color separation data D, which is the main part of the present invention.

Recorded data of 4 package components from D, , D, D Y, D , ,
Do.

It is an example of the block diagram of the circuit which converts into DB.

This conversion is based on equation (2X3) excluding up to the second-order terms. In the figure, MUL1-42 are multipliers, ADD1-4 are adders, and MEM1-36 are memories for storing each coefficient. These coefficients are determined experimentally in advance. That is, when a recorded material is created based on a color chart original, coefficients are determined by the method of least squares so that both colors are closest.

The circuit of FIG. 6 is a combination of masking and UCR in the block diagram of FIG. 2.

It is also possible to prepare a plurality of sets of coefficients of equation (2×3) and select them appropriately to form the recording data. This switching can be performed by automatically detecting a change in image forming conditions, or by an operator's operation. As a result, color reproducibility can be maintained constant even when the transfer agent or recording conditions change, and it is also compatible with cases such as when trying to form a reversed image or convert colors. It's easy to do.

Output of each image data D Y , D M , D c
, D a selects the image data to be used using the selector circuit 151 and outputs the data serially.

Generally, the causes of MTF deterioration before recording and reproducing images are problems with (1) the optical system, (2) the optical travel system, (3) the processing circuit, and (4) the recording system, as shown below.

Regarding (1), the lens MTF C wavelength range, change in image height, permissible width of imaging position, processing accuracy), prism surface accuracy, CCD mounting accuracy, CCD chip warpage, light source spectrum This is because the performance of the optical system fluctuates due to fluctuations and the like.

In the optical travel system (2), vibrations of optical mirrors and fluctuations in moving speed can be cited.

Regarding the processing circuit (3), there is distortion in the signal waveform due to capacitance components in the analog circuit, especially signal distortion caused by passing through a transmission line.

The following points can be listed as recording-related problems in (4).

・Beam diameter and beam shape of the laser beam ・Toner development characteristics on the photoreceptor drum (toner adhesion amount, toner concentration, toner particle size, toner color, etc.) ・Transfer characteristics (transfer rate, transfer characteristics to transfer paper, etc.) -Fixing characteristics (such as variations in toner diameter before and after toner fixation) Among these factors, the optical system and its running system directly affect resolution deterioration.

FIG. 7 shows MTF values (before correction) in the main scanning direction and the sub-scanning direction when the optical system is driven. This characteristic is 2~16d
These are measured values when scanning a black and white pattern with a spatial frequency up to ots/mm.

The MTF in this case was defined and used as MTF=(W−,BK)/(W×BK) (%). Here, W is a white signal and BK is a black signal.

As is clear from FIG. 7, the deterioration of MTF is significant in the sub-scanning direction. In order to make the correction to the same extent, the correction amount in the sub-scanning direction may be set to 2 to 4f tones relative to the main scanning direction.

In order to improve the reproducibility of fine line portions of images, an MTF value of 30% or more is required.

Therefore, when the resolution correction means is configured by adding weights to the pixel of interest and its surrounding pixels, the above-mentioned main and sub-scanning directions are corrected to the same degree, and the reproducibility of fine line parts is not deteriorated. In this case, a convolution filter using image data of 3×3 pixels may be adopted as the resolution correction means.

If we write the filter elements on the left and the corresponding pixel positions (i, D on the right), we get the following.

For the density ■ij of the pixel (i, j), attention is paid to eight pixels around it. In this case, (i-1, j-1) ~ (
i+1. If the new density value is I ij' for (j+1), then I ij - I ijX Cij where,
Cij is a filter coefficient, C1j=α, b, c,
...i.

An example of filter coefficients for realizing the above-mentioned correction contents is shown below.

When it is desired to increase the amount of correction, the filter coefficients may be appropriately set accordingly.

FIG. 8 is a circuit diagram showing an example of a resolution correction means using a convolution filter.

As shown in the figure, image data is sequentially set in register memory and line memory. Of these, the data required to create the correction data Y (i, D) is X (i
-1,''), X (i, j -1), X (i,
D, X (i+ 1.''), X (i, j+ j+ 1
).

Now, if we take the convolution filter matrix, the correction data is Y (i, D −cX (i, D − [a(X (i,
j+ 1), X (i, j+1)).

+ b(X (i −1, D+ (i+ l, D))]. That is, the central data X (i, j) is multiplied by the coefficient C by the multiplier l, and the data is sent to the subtracter. Also, X (i, j-1) and X (i, j+ 11) are added in adder 2, multiplied by a coefficient S, and the data is sent to adder 3. Adder 3 adds the above two data. The data is added and sent to a subtracter, and the output from this subtracter becomes correction data Y (i, D. Note that Y, M.

If the MTF values are different for each of the C and Bk signals, it is preferable to change the value of the MTF correction convolution filter matrix. After the MTF correction, gradation correction is performed.

FIG. 9 shows the gradation characteristics of a dithered image showing the relationship between the dithered pattern level of yellow, magenta, cyan, and black toners and the reproduced image density.

Image density was measured for yellow, magenta, and cyan toners using complementary color light of blue light, green light, and red light, respectively.

The values of the dither matrix for binarization by the dither method are shown in FIG. 1O. The gradation correction method is the first one, considering the curve that is an inverse function of the gradation characteristic curve shown in Figure 9.
The result is as shown in Figure 1, and gradation correction is performed using this gradation correction curve. However, since the black toner is used to compensate for the lack of density after the cyan, magenta, and yellow toners are developed, it is used when the input image density reaches a certain level. The hardware configuration is shown in FIG.

In the figure, the color signals obtained from each input signal 169
The necessary ROM table is referenced from the corresponding selector output. The output is outputted to the binarization circuit 170 via the buffer circuit 161, and further inputted to the writing unit B via an interface circuit etc. to modulate the semiconductor laser.

In the twelfth illustrated example, a ROM for tone correction
Memory for table group (Y) 164 and memory (M) 16
5, memory (C) 166, and memory (Bk) 167.

FIG. 16 shows the peripheral circuit of the writing section B. A semiconductor laser 191 is provided with a drive circuit 190, and the above-mentioned binary data is supplied to this drive circuit 190 as a modulation signal, and this modulation signal causes the laser to emit light. The beam is internally modulated.

The laser driving circuit 190 is controlled by a control signal from the timing circuit 183 so that it is in a driving state only in the horizontal and vertical effective area sections. Further, the semiconductor laser 191 is provided with a light amount monitor 189, and a signal indicating the amount of light of the laser beam is fed back to the circuit 190, and when the amount of light exceeds a predetermined amount, the driving of the semiconductor laser 191 is controlled to be stopped. Ru.

FIGS. 17(a) and 17(b) are diagrams for explaining how to arrange the layer thickness regulating member 240a. This regulating member 240a is basically an elastic member. Here, the developer is a carrier with a relatively large particle size (5 to 50 μm) and a carrier with a small particle size (1
A two-component developer consisting of a toner (~15 μm) is used. As the material of the layer thickness regulating member 240a, a phosphor bronze plate or a rubber material having a hardness of 55 to 85 degrees is used. For example, a rubber plate having a thickness of 0.1 to 5 mm is bonded to the phosphor bronze plate only or entirely. - As an example, a phosphor bronze plate with a thickness of 0.1 mm is laminated with a polyurethane resin plate with a rubber hardness of 75° and a thickness of 0.5 mm.

The layer thickness regulating member 240a is a rotating sleeve 237.
A developer layer is formed by being elastically pressed against 1a. At this time, a gap is formed between the sleeve surface and the layer thickness regulating member due to the presence of the carrier in the two-component developer, and the amount of developer that moves as the sleeve 2371a rotates is regulated by this gap. .

The amount of developer supplied to the gap is controlled by the layer thickness regulating member 2.
It depends on the size of the wedge-shaped region 242a formed by extending the length Q from the pressure contact point of the regulating member 240a to the sleeve 2371a (or the distance h between the extended tip of the regulating member 240a and the surface of the sleeve 2371a). That is, in order to smoothly supply the developer into the gap, the presence of a wedge-shaped area of an appropriate size is essential. Here, the layer thickness regulating member 240a
The length is usually 0.5 to 2 of the radius r of the sleeve 2371a.
The length of the regulating member for forming the wedge-shaped region is preferably about 0.5 to 2 mm.

Each of the developing devices (123, 124, 125,) is provided with a scraping plate made of an elastic plate such as Mylar and a support for scraping off the developer layer after development. The developer layer after development is a developer layer after the toner has been consumed and cannot be used for the next development, so a flexible elastic plate is used to prevent the developer from damaging the sleeve surface. By completely scraping off the layer and supplying new developer, the developer is refreshed to ensure continuous good development.

The image forming body is rotated four times, and the first .
Second. The cyan, magenta, yellow, and black multicolor toner images obtained by the third and fourth developing devices are transferred to the transfer material P fed at the same timing from the paper feeding means by the transfer device 130. Electrostatically transferred, separated pole 1
31 and separation claws 250 in FIG.

After the transfer material P has been separated, the image forming body 120 is cleaned by a cleaning device [1126] shown in FIG. 281 is a cleaning blade device, 282 is a blade plate 127
A holding member 283 that holds the holding member 282 is a screw that rotatably supports the holding member 282 on the support member 284 (up and down in the drawing). After the multicolor toner image is transferred, the blade plate 127 is pressed against the image forming body 120 to perform a cleaning operation.The blade plate 127 is pressed against the image forming body 120 to perform a cleaning operation. This is achieved by rotating the

Reference numeral 128 denotes a rotatable metal roller to which a DC voltage is applied, which discharges the toner scraped off by the blade 281 to a discharge screw conveyor 289. This roller rotates in the direction of the arrow, and a voltage of about 100 V is applied with a bias polarity opposite to that of the toner to remove residual toner. The material is preferably stainless steel or the like.

Further, reference numeral 129 denotes an auxiliary cleaning roller made of sponge, which removes the image forming body 1 after the blade 281 finishes its cleaning operation.
Immediately after being separated from the blade 20, it is rotated about the shaft 291 and pressed against the image forming body 120 to clean the toner left behind by the blade 127, and the cleaned toner flows down the guide plate 292 and is struck. By vibrating the guide plate with the roll 293, it is discharged to the discharge screw conveyor 289.

By configuring the cleaning device 126 as described above,
Even when a developer containing the above-mentioned fine particle toner is used for the purpose of high image quality, it can exhibit a very effective cleaning effect.

The image forming body 120 thus sufficiently cleaned is ready for the next image formation.

The above is a detailed explanation of the color image forming apparatus of the present invention.
The overall control mechanism of the device will be explained below with reference to FIG. 19 and circuit diagrams of other parts. In FIG. 19, as described above, the optical information from the color original 82 is transmitted through the color separation prism 103 by B,
Separated into G and R color separation information, CCD 104,1
05 and 106, and the respective image signals are output.

Section 20 shows the relationship between the image signal and various timing signals, and the horizontal effective area signal (H-VALID) (C in the same figure) corresponds to the maximum document reading width W of CCD 104, 105, 106, and The image signal shown in F is read out in synchronization with the synchronous clock CLK (E in the figure) from the counter clock circuit 299 in FIG.

These image signals are supplied to the A/D converter 145 in FIG. 19 via a normalizing amplifier (not shown), thereby converting them into digital signals of a predetermined number of bits.

Shading correction is performed during A/D conversion.

Therefore, a memory 146 for shading correction is prepared, and one line of self-portrait data is extracted from outside the image reading area, stored in memory, and used as data for shading correction.

For this reason, the memory 146 is read out in synchronization with the clock of the CCD drive pulse generation circuit 147. A clock circuit 299 is provided in the generation circuit 147. The timing of the memory 146 is regulated by an index signal for starting scanning from an index sensor 199 shown in FIG.

As already explained based on FIGS. 6 and 7, masking, OCR, etc. are performed. Further, MTF correction and gradation correction are performed as explained based on FIGS. 8 and 12.

Here, as shown in Figure m21, the main scanning direction for the original 82 is the line direction (horizontal scanning direction) of C0D106 with respect to the scanning surface 82A, and the sub-scanning direction is C0D106 line direction (horizontal scanning direction) with respect to the scanning surface 82A.
The direction is perpendicular to the lines of CD 106 (vertical scanning direction).

The color signals C, M, Y, and Bk after gradation correction are converted into binary color signals in the binary conversion circuit 160 in FIG. 19.

A selection signal G (see FIG. 6.7.12) for the color signal is sent from the CPU 2 (second microcomputer).

The selection signal G is 3-color recording by Y, M, C1-ner, Y,
The output state changes depending on either a four-color recording color conversion mode using M, C, or Bk toners or a color designated recording mode such as monochrome recording.

Note that the conversion of three or four color color signals from a color original is performed every rotation of the image forming body 120.

In this way, the extremely specific and clear circuit configuration enables faithful color reproduction and the formation of clear color images.

FIGS. 22(a) and 22(b) are time charts showing the relationship between the image forming process and the gate signal (G) in three-color or four-color mode, and FIG. 23 in monochrome (red) mode. .

In the three-color mode as shown in FIG. 22(a), the gate signals G supplied to the AND gates 165 to 168 in FIGS. Eight types of 3-bit gate signals G synchronized with the rotation of the body 120 are formed (FIG. 22).

Among these, color signals corresponding to B, G, and R are used. At the same time, the developing bias shown in FIG. 22C to 125 is supplied to the developing units 123 to 125 in synchronization with the rotation of the image forming member 120.

As a result, the exposure process 1 to ■ for each color (G in the same figure)
After that, exposure and development steps are sequentially performed.

In the four-color mode as shown in FIG. 22(b), the first
The gate signals G supplied to the AND gates 165 to 168 in FIG. (Figure 22).

At the same time, the developing bias shown in FIG. 22C to 125 is supplied to the developing units 122 to 125 in synchronization with the rotation of the image forming member 120.

As a result, the exposure process I~■ for each color (G in the same figure)
Then, exposure and development processes are sequentially performed. Exposure is in the order of R, G, B, and Bk, and development is in the order of cyan, magenta, yellow, and black.The four colors shown in Figure 22 (a) are cyan, magenta, yellow, and black added. You can also get images.

On the other hand, in the case of a monochromatic color mode as shown in FIG. 23, for example, the OCR component and the signal 157 in FIG. 7 are selected as image data, while the gradation correction in FIG. Selecting the threshold shown in the figure results in a single specified image forming process. Therefore, the color code signal 1
51 and selection signal G ROM 157.16 for thermal correction
Select 7. At this time, the single color threshold ROM 17 is also selected.

The example shown in FIG. 23 is a case where red is specified.

At the same time, a developing bias is supplied to the corresponding developing devices 124 and 125 (D in the figure), and these become in operation. Therefore, since the developing devices 124 and 125 containing magenta toner and yellow toner (developer) are driven together, the specific color information of the color original l is recorded as an image in red. .

Other colors (black or yellow, magenta, cyan, green,
Since the image forming process is the same when specifying red, blue), detailed explanation thereof will be omitted.

Next, the color signal outputted through the gradation correction circuit 150 in FIG. 19 is inputted to the binarization circuit previously explained in FIG. 13 and, if necessary, the enlargement/reduction circuit explained in FIG. 14. ,
After being binarized, it is output to the interface circuit.

The interface circuit 295 in FIG. 19 is composed of a first interface 2951 that receives binary data, and a second interface 2952 that receives the binary data sent therefrom.

The first interface 2951 receives horizontal and vertical valid area signals (H-VALID) from the timing circuit 296.
.

(v-vALID) is supplied, and a predetermined frequency (6 MHz in this example) is supplied from the counter clock circuit 299.
0 glue is supplied.

Furthermore, a CCD drive clock is supplied. As a result, C
Binary data is sent to the second interface 2952 in synchronization with the CD drive clock.

The counter clock circuit 299 is designed to be synchronized with an index signal (described later) that indicates the start position of the laser beam scan, but this is achieved by synchronizing the timing of sending out binary data with the rotation of the polygon motor. This is the second step to get an image without.

The second interface 1952 is an interface for selecting the binary data sent from the first interface 1951 and other image data and sending it to the writing section B side.

Other image data refers to the following image data.

The first is the test pattern image data obtained from the test pattern circuit 297, the second is the patch image data obtained from the toner density control patch circuit 298, and the third is the image and image data obtained from the printer control circuit 294. It is character data.

The test pattern image data is used for checking image processing, and the punch image data for detecting toner density is used for batch output.

Both the test pattern circuit 297 and the batch circuit 298 are driven based on the clock of the counter clock circuit 299, and thereby the first interface 295
The timing is adjusted with the binary data sent from 1.

The binary data output from the second interface 2952 will be used by the writing section B as a modulation signal for the laser beam.

The writing section B is as described above with reference to FIGS. 15 and 16, and has the advantage that the semiconductor laser 191 rises quickly and enables high-speed recording, especially when it has a light amount control system.

Next, all of the above-mentioned units and circuits in the color image forming apparatus of the present invention are controlled by the CPUI and CPU2.

Therefore, first, the CPU 2 will be explained below.

CPU2 is a microcomputer for optical drive control, and a first microcomputer CPUI for controlling the main body.
The exchange of various information signals between the two is serial communication.

Further, the optical scanning start signal sent from the first microcomputer cpui is sent to the second microcomputer C.
It is directly supplied to the interrupt terminal of PU2.

The second microcomputer CPU2 generates various command signals in synchronization with a clock of a predetermined frequency (12 MHz) obtained from the reference clock circuit 332.

The second microcomputer CPU2 detects data for shading correction, and sends a command signal for storing the data to the memory 146 for shading correction, and also sends a selection signal for density selection to the threshold table 174. A color selection signal 151 for color recording is also supplied.

The second microcomputer CPU2 further outputs the following control signals.

First, a control signal for turning on and off the drive power of the CCDs 104, 105, and 106 is supplied to the power supply control circuit S thereof.

Second, a predetermined control signal is supplied to a lighting control circuit 301 for a light source (such as a halogen or fluorescent lamp) 85 for irradiating the document 82 with necessary light.

Thirdly, a control signal is also supplied to a control circuit 303 for a light amount stabilizing heater (not shown) when a fluorescent lamp 85 is used. Note that data indicating the light amount information of the optical unit, the halogen lamp 85, and the home position are input to the second microcomputer CPU2.

The first microcomputer CPUI is mainly for controlling the main body of the color image forming apparatus;
The input/output system of the apparatus main body will be explained below based on the drawings.

The operation section circuit 304 allows magnification specification through the operation panel.
Various input data such as recording position designation and recording color designation are input, and their contents are displayed.

As the display means, an element such as an LED or a liquid crystal display is used.

The paper size detection circuit 305 is used to detect and display the size of the cassette paper loaded in the tray, or to automatically select the paper size according to the size of the document.

A drum index sensor 306 detects the rotational position of the drum 120, which is an image forming member, and the timing of various processes is controlled using the index signal.

A zero-sheet detection sensor 307 detects whether the number of sheets in the cassette is zero. Manual feed zero detection sensor 3
Similarly, in step 08, the presence or absence of paper for manual feeding in the manual feeding mode is detected.

The toner density detection sensor 309 detects the reflected density of the drum 120 or the toner adhered area after fixing, and if the reflected density is lower than the reference value, the toner replenishment solenoids 313α, 313b, 313c, and 313d are activated as necessary. The toner is replenished into the developing device.

In addition, four toner remaining amount detection sensors 310α, 310b
.

310c and 310d, each of the developing devices 122 to 125
The amount of toner remaining in each toner storage chamber is individually detected, and when the toner runs out, a display element (not shown) provided on the operating section is controlled to light up.

The temporary stop sensor 316 detects whether paper is correctly fed from the cassette to the second paper feed roller (not shown) during use of the color copying machine, and temporarily stops paper feeding by the first paper feed roller. It is for.

Contrary to the above, the paper ejection sensor 317 is used to determine whether or not the fixed paper is correctly ejected to the outside.

Manual feed sensor 318 is used to detect whether manual feed mode is selected.

The sensor output obtained from each sensor as described above is taken into the first microcomputer CPU 1, and necessary data is displayed on the operation/display unit 304, and the driving state of the color image forming apparatus is adjusted as desired. controlled.

In the case of a color copying machine, in addition to motors for developing cyan, magenta, and yellow, a motor 320 exclusively for black is provided, and these motors are all controlled by the first microcomputer CPU.
Controlled by command signals from I. Similarly, the main motor (drum motor) 321 is driven by a PLL-controlled drive circuit 32.
2, the drive state is controlled by this drive circuit 322.
Also, its driving state is controlled by a control signal from the first microcomputer CPUI.

During color development, it is necessary to apply a predetermined high voltage to a developing device or the like during development. Therefore, a high voltage power source 323 for charging and a high voltage power source 241 for developing (α, b.

c, d) A high-voltage power source 324 for transfer and separation, and a high-voltage power source 325 for the metal roller 128 for the toner receiver are provided, and a predetermined high voltage is applied to them when necessary. .

In addition, 326 is the pressure contact of the cleaning auxiliary roller 129.
327 is a solenoid for driving the first paper feed, 328 is a solenoid for driving the second paper feed roller, and 330 is a cleaning blade plate 127.
and a motor for releasing the pressure bonding of the cleaning auxiliary roller 129. Furthermore, 329 is a driving solenoid that controls turning on and off of the separating claw.

The second paper feed roller is used to send out the paper conveyed by the first paper feed roller at an appropriate timing.

The fusing heater is controlled by a fusing heater on/off circuit 331. Further, the surface temperature of the fixing heat roll is monitored by a thermistor. 300 is a clock circuit (approximately 12 MHz).

A non-volatile memory 333 provided along with the first microcomputer CPUI stores initial setting values such as a copy number count and a total count during the image forming process, and stores information such as a copy number count and a total count during the image forming process of initial setting values. When copying is resumed after copying has been interrupted due to an accident, the copying operation can continue from the count before the accident.

In this way, the first and second microcomputers CP
U1. The CPU 2 executes various controls necessary for color image processing according to a predetermined sequence.

The above is the overall control mechanism of the color image forming apparatus of the present invention, and based on this control mechanism, the entire process from reading to final color image formation is controlled in real time, so that image formation can be performed with high efficiency.

In the color image forming apparatus having the above structure, a multicolor toner image formed by a digital method is transferred and fixed onto an image forming body to form a color image. For this reason, toner of another color is selectively deposited on top of the toner image on the image forming body, and the formed toner image is sometimes destroyed, or the developing device that accommodates the toner of the other color The process is required not to enter Moreover, each color toner image has 50
It is composed of fine dot images of ~80 μm, and each dot image is required to have sufficient resolution. Therefore, in the present invention, the developer and developing method used to meet the above requirements are configured as follows.

[Developer] The developer used in the present invention is composed of a toner and a carrier because it has advantages such as easy control of triboelectric charging of the toner, excellent developability, and the ability to impart any color to the toner. A two-component developer is used.

(Toner) Toner, which is a component of the two-component developer, is usually prepared by mixing an appropriate amount of a coloring agent, a charge control agent, and, if necessary, a release agent, etc. in a binder resin, melting it, kneading it, cooling it, and then pulverizing it. ,
It is obtained by classifying the particles to a desired particle size. Examples of the binder resin include polyester resin and styrene/acrylic resin.

(Carrier) The carrier, which is another component of the two-component developer, is a core material made of magnetic particles, preferably spherical magnetic particles, and a resin solution is dip-coated or sprayed onto the core material. A thin resin film is formed by coating and drying or by spray drying or the like to form a coach carrier.

Next, the developer of the present invention is obtained by mixing appropriate amounts of the carrier and toner, but the mixing ratio varies depending on the particle size, that is, the surface area ratio, of Kimaria and toner. In particular, the larger the carrier, the more the toner mixing ratio will be made to reduce the amount of

For example, the ratio of the total area SC of the carrier to the total area ST of the toner in a unit volume of the phenomenon agent ST/SC=0
．． It is best to set it as 5 to 2, and the weight ratio is carrier 100.
The range is 5 to 20 parts by weight per part by weight of toner.

In addition, the particle size or average particle size of toner and carrier as used in the present invention means a weight average particle size, and the weight average particle size is a value measured with a Coulter Counter (trade name) (manufactured by Coulter Inc.). . In addition, the specific resistance of the particles is 0.50 cm
After tamping in a container with a cross-sectional area of
It is determined from the current value that flows when an electric field of /am is generated.

[Developing method] In the present invention, as described above, a two-component developer is used, and the image forming body and the developer layer are not in contact with each other when no developing bias is applied. The phenomenon occurs by causing toner to fly under an electric field and selectively adhere to the electrostatic image of the image forming body.

When such a non-contact developing method is used, development is performed multiple times on the image forming body to form a multicolor toner image consisting of a yellow toner image, magenta toner image, cyan toner image, black toner image, etc. This method has the advantage that the previous toner image will not be damaged during subsequent development.

In the developing method of the present invention, preferably the developer is configured as described above, the developing area (the image forming body and the sleeve face each other, and the transported toner applies electrostatic force to the image forming body). The thickness is 2000 μm in the area where it can be transferred
Hereinafter, development is performed with a thin developer layer, preferably 1000 Pra or less, more preferably 10 to 500 pm, and even more preferably 10 to 4002 m, and a small gap between the image forming body and the sleeve. Even if the bonding force between the developer used in the case and the toner and the carrier and the sleeve is weak, since the developer layer is extremely thin, it will not adhere sufficiently to the sleeve. There is no chance of toner scattering or the like.

When the developer layer becomes thin as described above, the gap between the image forming body and the sleeve can be reduced, so the voltage of the developing bias required to form the oscillating electric field for causing the toner to fly can be lowered. Can be done. Therefore, there is an advantage that not only the toner scattering is reduced from this point of view, but also leakage discharge due to the developing bias from the sleeve surface is suppressed. Furthermore, when the gap between the image forming body and the sleeve is made smaller, the electric field strength formed by the latent image in the developing area becomes larger, and as a result, subtle changes in gradation and fine patterns can be developed well. It becomes like this.

If the developer layer is made thinner, the amount of toner transported to the development area will generally be reduced, and the amount of development will be reduced. In order to increase the conveyance amount, it is effective to rotate the sleeve at high speed. However, if the linear velocity ratio between the image forming body and the sleeve is 1+
When the value is 10, the velocity component of the toner to be developed parallel to the latent image surface increases, directionality appears in the development, and the image quality deteriorates.

Therefore, as the lower limit of the amount of developer layer conveyed, it is necessary that the toner adheres to the sleeve surface at a density of at least 0.4 mg/cm.In general, the linear velocity of the sleeve is When the linear velocity of the image forming body is Vd, and the amount of toner in the thin layer on the sleeve is Mt, it is necessary to satisfy the following conditions. Considering the development efficiency, it is preferable that From the experimental facts, it was found that it is more preferable.

The ratio of toner to carrier in the developer at this time is preferably such that the ratio of the total surface area of toner to carrier in a unit volume is 0.5 to 2, as described above.

By setting the above conditions, the toner in the developer layer can be efficiently developed, and the developability is stable.
Good image quality can be obtained.

As mentioned above, as a means for forming the developer layer, an elastic material is used for the sleeve, which is effective in eliminating impurities such as dust, fibers, paper powder, or aggregates of toner or carrier contained in the developer. A layer forming member consisting of a pressure contact plate lightly pressed against the surface is preferably used.

This layer forming member forms a thin layer by allowing the developer to pass between the sleeve and the elastic plate using an elastic plate that is pressed against the sleeve so that its tip faces upstream of rotation of the sleeve.

The structure of the elastic plate is as described above in FIGS. 17(a) and 17(b), but with further reference to FIG. The gap h (mm) between the sleeve 237 and
The relationship with the amount of developer attached to 1a will be explained with reference to the graph in FIG. 24.

It can be seen from the figure that when the gap exceeds a certain value, the amount of developer on the sleeve is stable against these changes.

In this stable state, the toner necessary for the above-mentioned development can be sufficiently transported.

Other experiments have shown that the layer thickness changes little and that other parameters have little effect on the appearance of this steady state.

Therefore, when the gap at the tip is set to Q, Q3+nm or more, a certain amount of toner can be stably conveyed despite variations in mounting precision and mechanical precision. Furthermore, the gap at the tip is O
, 1 mm or more is preferable because stability increases.

Of course, it is not desirable to make the gap between the tips unnecessarily large, and it has been observed that when the gap is increased to 5 mm or more, the uniformity of the developer layer is disrupted.

Next, the developer layer made into a thin layer as described above is transported to a development area and the electrostatic image on the image forming body is developed without contact. It is based on the following formulas (a) and (b).

Here, Vsff is the linear velocity of the sleeve mm/sec,
n represents the number of magnetic poles of the magnetic roll, ωm represents the rotational angular velocity of the magnetic roll, h' represents the height of the magnetic brush, Vd represents the linear velocity of the image forming member, and it represents the amount of toner deposited per unit area of the sleeve. V sQ, ωm is positive when it is in the same direction as the movement of the image forming body.

Further, the height of the magnetic brush refers to the average height of the magnetic brush on the sleeve, which stands on top of the magnetic pole in the sleeve. Specifically, the linear velocity ■sQ of the sleeve is 50~
500mm/seα, magnetic roll number n of magnetic poles is 4 to 2
0, the rotational angular velocity ωm of the magnetic roll is 30 to 200 rad
ian/see, the height h' of the magnetic brush is 50~50
Linear velocity V dmm/sec of 0 μm1 image forming body is 30
~500, toner adhesion amount per unit area of sleeve mt
is 0.2 to 1.0 mg/cm2. These relationships serve as a guideline for achieving desirable development, but they vary depending on the gap d between the image forming body and the sleeve, the magnitude of the bias voltage, etc.

Preferred development conditions taking such factors into consideration are shown by the following formula.

Here, Vp-p is the AC bias peak-to-peak voltage (KV)
, d is the distance between the image forming body and the sleeve (μm), and h" is the maximum height of the magnetic brush (μm). Represents the maximum height of the brush.

Next, in the developing method of the present invention, since image formation is performed digitally, an electrostatic image is formed by a dot-shaped optical signal, and a so-called inversion is performed in which toner is attached to the portion where the electric charge has been erased by the optical signal. It is desirable to use a developing method. The principle of multicolor image formation by the process of the present invention using reversal development is illustrated in FIG.

FIG. 25 shows changes in the surface potential of the image forming body, where PH is the exposed area of the image forming body, DA is the unexposed area of the image forming body, and DUP is the toner applied to the exposed area PH during the first development. It shows the increase in potential caused by the attachment of T1. For the sake of explanation, the polarity of the electrostatic image is assumed to be negative.

(2) The image forming body is uniformly charged by a charger and has a constant negative surface potential E.

(2) First image exposure is applied using a laser, cathode ray tube, or LED as an exposure source, and the potential of the exposed portion PH decreases in accordance with the amount of light.

(2) The electrostatic image thus formed is developed by a developing device to which a negative bias approximately equal to the surface potential E of the unexposed area is applied. As a result, the negatively charged toner T adheres to the exposed portion PH, which has a relatively low potential, and a first toner image is formed. The potential of the area where this toner image is formed increases by DUP due to the adhesion of the negatively charged toner T1, but normally it does not have the same potential as the unexposed area DA.

■ Next, the surface of the image forming body on which the first toner image has been formed is charged a second time by a charger, and as a result, the toner T
Regardless of the presence or absence of , a uniform surface potential E is obtained.

(2) A second image exposure is performed on the surface of this image forming body to form an electrostatic image.

(2) Similarly to (2) above, charged toner T2 of a different color from toner T1 is developed to obtain a second toner image.

As described above, when forming a multicolor toner image consisting of toner images of each color on an image forming body, development can be performed using fine particle toner without causing damage to the toner image, and high quality color can be obtained. The above-mentioned non-contact reversal development is advantageous in that images can be obtained. In order to obtain a better color image, it is preferable to carry out development while paying attention to the following points.

In other words, repeat the development and follow the pattern. ■ Use toners with larger charge amounts in order.

■ Gradually reduce the amplitude of the electric field strength of the AC component of the developing bias.

(2) It is preferable to employ methods such as sequentially increasing the frequency of the alternating current component of the developing bias, either alone or in any combination.

That is, toner particles having a large amount of charge are easily affected by the electric field. Therefore, if highly charged toner particles adhere to the image forming member during initial development, these toner particles may return to the sleeve during subsequent development.

The above method (2) uses toner particles with a small amount of charge in the initial development to prevent the toner particles used in the previous stage from returning to the sleeve during the subsequent development. Method (2) is a method in which the electric field strength is successively reduced as development is repeated (that is, as development progresses to later stages), thereby preventing the toner particles already attached to the image forming body 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 image forming member and the sleeve is made wider as the developing stage progresses. Further, (2) is a method in which the frequency of the alternating current component is sequentially increased as development is repeated to prevent the toner particles already attached to the image forming body from returning.

These ■■■ methods are effective even when used alone, but
For example, it is more effective to use a combination such as increasing the toner charge amount and decreasing the alternating current bias sequentially as development is repeated. Further, when the above three methods are adopted, appropriate image density or color balance can be maintained by adjusting the DC bias respectively.

Next, as the image forming body used in the color image forming apparatus of the present invention, since a semiconductor laser is used in the writing section C, a photoreceptor having a wavelength range that absorbs the laser beam is preferably used.

Such image forming bodies include functionally separated organic photoreceptors or amorphous silicon germanium-based inorganic photoreceptors having a carrier generation layer containing a carrier generation substance and a carrier transport layer containing a carrier transport substance. An example of an organic photoreceptor with the above-mentioned functional separation is shown in Fig. 26 (a).
, (b) is preferable. In this layer configuration, an intermediate layer 40 is provided on the conductive support 400 if necessary.
A carrier generation layer 401 is provided through the carrier layer 3, and a carrier transport layer 402 is provided on the carrier generation layer 401.

As the carrier generating substance contained in the carrier generating layer 401, a phthalocyanine pigment, a polycyclic quinone pigment, or a hisazo pigment is used.

Any of the various photoreceptors described above can be suitably incorporated as a drum-shaped image forming member in the color image forming apparatus of the present invention.

〔Example〕

EXAMPLES The present invention will be specifically explained below with reference to Examples, but the embodiments of the present invention are not limited thereto.

The optical information conversion unit shown in FIG. 3, the color separation system shown in FIGS. 5 to 12, the semiconductor laser writing device shown in FIG. 15, the developing device shown in FIG. 17, the cleaning device and fixing device shown in FIG. The color image forming apparatus shown in FIG. 1, which incorporates a control mechanism for the entire apparatus shown in the figure, is used to form cyan, magenta, yellow, and black toners according to the image forming conditions shown in Tables 1 to 3 below, according to the image forming process. A four-color image was formed.

The apparatus used an image forming drum having the following configuration and a two-component developer consisting of toner and carrier.

Imaging body: 0.2 mm on a surface-cleaned 180 mm AQ drum.
A μm-thick poly-p-hydroxystyrene resin intermediate layer is provided, and a compound example (
V-15) 0.8 parts by weight and 0.06 parts by weight of dihexylammonium chloride as a substance that improves repeatability.
Weight parts and polycarbonate resin (Panrai) L-1
250; trade name, manufactured by Konjin Kasei Co., Ltd.) and 1.6 parts by weight.
A dispersion prepared by mixing and dispersing in 100 parts by weight of 2-dichloroethane was coated and dried to form a carrier generation layer having a thickness of 0.2 μm.

Next, a solution of 10.0 parts by weight of Compound Example (Vl-30) as a carrier transport substance and 13.2 parts by weight of the polycarbonate resin dissolved in 100 parts by weight of 1,2-dichloroethane was placed on the carrier generation layer. 25μ after coating and drying
A carrier transport layer having a thickness of m was formed to obtain the photoreceptor of this example.

Color toner (cyan toner, magenta toner, yellow toner, black toner): Polyester resin (U
0P: Trade name, manufactured by Kako Soup Co., Ltd.) 100 parts by weight, and phthalocyanine blue (C, 1, Pigmen) as a coloring agent.
t Blue 15:3), 5 parts by weight, 4 parts by weight of low molecular weight polypropylene (660P, trade name, manufactured by Sanyo Chemical Co., Ltd.) as a mold release agent, and oxynaphthoic acid derivative (Bontron E-82; trade name, Orient) as a charge control agent. 2 parts (manufactured by Kagaku Co., Ltd.) were thoroughly mixed in a ball mill for 5 hours, and then kneaded with two rolls at 150°C. After cooling naturally, the mixture was coarsely pulverized using a cutter mill, further finely pulverized using a pulverizer using a jet stream, and further classified using an air classifier to obtain a cyan toner having a weight average particle size of 10.5 μm.

Brilliant Carmine 6 is also used as a coloring agent for magenta.
B (C, 1, Pigment Red57:l) was mixed with Disazo Yellow AAA (C, 1, Pigment Red 57:l) for yellow.
Each color toner was obtained in the same manner as the cyan toner except that ment Yellow 12) was used.

Furthermore, carbon black (
A yellow toner was obtained in the same manner as the cyan toner except that 10 parts by weight of Mogul L (trade name, manufactured by Capot Co., Ltd.) was used and no charge control agent was added.

Carrier: Cu − with an average particle size of 40 μm and a particle size range of 10 to 80 μm
Zn-based ferrite particles are used as the core, and 1.2
A coated carrier was obtained by forming a resin coating layer of methyl methacrylate styrene copolymer having a thickness of μm.

Developer: 10 parts by weight of toner was mixed with 90 parts by weight of the carrier, and 0.4 parts by weight of colloidal silica (Aerosil R-812; trade name, manufactured by Nippon Aerosil Co., Ltd.) was externally added as a fluidizing agent for development. obtained the drug.

Table 1 Table 2 Also, masking was performed by incorporating up to the second order term in equation (2X3). The block diagram is shown in FIG.

Under the above conditions, the masking coefficients were optimized and determined, and then a copy of the color original was created. As a result, the color difference △E
ab"l was always 20 or less, and the color reproducibility was extremely good.

〔Effect of the invention〕

As is clear from the above description, according to the color image forming apparatus of the present invention, the apparatus is compact and therefore low in cost, and has excellent operability since all process steps are controlled in real time. As a result, effects such as the ability to easily obtain high-quality color copies with good brown color reproducibility can be achieved.

[Brief explanation of the drawing]

Figure 1 is a sectional view explaining the basic configuration of a color image forming apparatus, Figure 2 is a schematic diagram showing an outline of the image forming process, and Figures 3 (A) and (B) are of the optical information exchange unit. 3(C) is a cross-sectional view, FIG. 3(C) is a filter spectral transmittance, FIG. 3(D) is a perspective view of the color separation optical path, and FIG. 4 is a graph showing the spectral characteristics of the light source, color separation dichroic mirror, and CCD image sensor. , FIG. 5 is a block circuit diagram of shading correction, FIG. 6 is a masking and UCR circuit diagram, FIG. 7 is a graph showing MTF values depending on the scanning direction of the optical system, and FIG. 8 is a circuit configuration showing an example of resolution correction means. 9 shows the gradation characteristics of the dithered image, FIG. 1θ shows the dither matrix, FIG. 11 shows the inverse function curve of the gradation characteristics, and FIG. 12 shows the gradation correction circuit diagram. . Fig. 13 is a binarization circuit diagram, Fig. 14 is a graph for obtaining interpolated data during enlargement, Fig. 15 is a sectional view of the writing device,
FIG. 16 is a writing peripheral circuit diagram, FIG. 17 is a sectional view illustrating the arrangement of the developer layer regulating member on the developing roll, and FIG.
The figure is a sectional view illustrating separation and cleaning of the separation claw. Also, Fig. 19 is a circuit diagram explaining the overall control mechanism of the entire device, Fig. 20 is a time chart explaining the relationship between image signals and various timing signals, and Fig. 21 is a diagram showing the horizontal and vertical scanning areas and effective Perspective view showing the scanning area, second
2 and 23 are time charts illustrating the relationship between exposure/development and gate signals in the four-color mode and the single-color mode. Further, FIG. 24 is a graph showing the relationship between the gap between the tip of the developer regulating member and the sleeve and the amount of developer, and FIG. 25 is a process diagram showing changes in the surface potential of the image forming body in the reversal development method.
FIG. 26 is a cross-sectional view showing the layer structure of the organic photoreceptor, and FIG. 27 is an example of the spectral transmittance of each color toner.
FIG. 28 is a model sectional view of the surface of the image forming body. 82... Original 84... Carriage 85.86... Light source 87.89.89', 117... Reflection mirror 90.
...Stepping motor 97.98...Standard white plate 100...Optical information conversion unit 102, 103, 104, 105...Color separation filter 106...CCD image sensor A...Reading section B... -Writing unit 110...Motor 112...Polygon mirror 121...Charger 122, 123, 124, 125. ...Developer 126
... Cleaning device 127 ... Blade plate 128 ... Metal roller 129 ... Cleaning auxiliary roller 130 ... Transfer device 131 ... Separator 132 ... Fixing device

Claims (4)

[Claims] (1) A reading unit that optically scans a document and outputs color separation signals; a color correction unit that performs color correction on the color separation signals to form image data; A multicolor image forming apparatus comprising a recording means for sequentially forming toner images to obtain a multicolor toner image, wherein the color correction means performs nonlinear masking of an input signal. Forming device. (2) Blue, green, and red color separation data are D_B, D_G, and D_R, and yellow, magenta, cyan, and black recording data are D_Y, D_M, and D_, respectively.
2. The multicolor image forming apparatus according to claim 1, wherein when C, D_B_K, the color correction is performed based on the following equation. D_Y=ΣkαβγD_B^α・D_G^β・D_R^
γ D_M=ΣlαβγD_B^α・D_G^β・D_R^
γ D_C=ΣmαβγD_B^α・D_G^β・D_R^
γ D_B_K=ΣnαβγD_B^α・D_G^β・D_
R^γ [Here, α, β, γ are integers greater than or equal to 0, kαβγ, lαβ
γ, mαβγ, nαβγ are coefficients given in advance,
Σ means that it is a series with respect to α, β, and γ. ] (3) The multicolor image forming apparatus according to claim 2, wherein when the integers α, β, and γ are α+β+γ≧3, kαβγ=lαβγ=mαβγ=nαβγ=0. (4) The coefficients are αβγ, lαβγ, mαβγ, nαβ
Claim 2, characterized in that a plurality of sets of γ are prepared, and the set can be selected and used at the time of color correction.
The multicolor image forming apparatus according to item 1 or 3.