JPH0943933A - Color image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To supplement a transfer rate of a primary color image and always provide favorable document reproducibility and color reproducibility when the rate is variable within 1 page based on various conditions by making transfer conditions variable within an image plane of the primary color image at the time of transferring to a transfer body. SOLUTION: Conductive wires are bundled to form a brush type transfer charger 41, and the brush type transfer chargers 41 are disposed in a line in a perpendicular direction to a moving direction of a transfer body P. Each brush type transfer charger 41 is connected to a power supply 40 for transfer, and for the power supply 40 for transfer, a current value to energize each brush type transfer charger 41 is controlled by a transfer control means. Even where images of different toner attachment quantity and color component constitution exist in a single image plane, transfer conditions can be controlled for each parted zone corresponding to the transfer charger 41. Transfer by the optimum conditions can thus be performed for each parted zone based on image characteristics on a preliminarily detected image carrier.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color image forming apparatus such as a full-color, multi-color or mono-color electrophotographic or electrostatic recording type copying machine or printer. More specifically, the present invention relates to a transfer device in a color image forming apparatus in which a developing device is arranged on the peripheral surface of an image carrier and a color image is obtained by superimposing monochromatic toner images.

[0002]

2. Description of the Related Art FIG. 1 shows a schematic configuration example of a color image forming apparatus, which has been developed and studied in recent years. An output signal of an image pickup device obtained by scanning an original by an image reading device, a transmission signal from another device such as a facsimile or a computer, data stored in a recording device, etc. are supplied to a computer recording device 1 of a color image forming apparatus. After being converted into a color image signal in the signal processing unit 2, a color image is formed in the image forming unit 3. Here, the color image signal can be decomposed into a plurality of color components having preset spectral characteristics, and the value of each color component can be associated with the image density of each color component in the color image as a gradation value. Therefore, a general color image signal has four kinds of color components of yellow, magenta, cyan and black.

The image forming section 3 is provided with a drum-shaped electrophotographic photosensitive member 310 which is an image carrier, and the photosensitive member 310 rotates in the direction of the drawing. The photoconductor 310 is the first charger 311.
The first color of the color image signal transmitted from the signal processing unit 2 by the exposure optical system 312Y of the first latent image forming means, which is uniformly charged by Y, and is then made of semiconductor laser light or the like. Image exposure is performed based on a component, for example, a yellow component, and a first latent image is formed on the photoconductor 310. This first latent image is developed by a first developing device provided with color toner corresponding to the first color component, for example, a yellow developing device 313Y, and becomes a yellow image which is a first monochromatic image. Subsequent to the formation of the yellow image, the photoconductor 1 is uniformly recharged by the second charger 311M, and then the exposure optical system 312M of the second latent image forming means.
Then, image exposure is performed based on a second color component different from the first color component of the color image signal, for example, a magenta component, and a second latent image is formed on the photoconductor 310. This second latent image is developed by the magenta developing unit 313M which is the second developing unit, and becomes a magenta color image which is the second monochromatic image. Hereinafter, similarly, the third and fourth
Are repeatedly charged in the order of cyan and black to form a primary color image composed of a plurality of single color images on the photoconductor 310, and the primary color image is formed on the transfer material P made of paper or film by the transfer means 314a. Thus, a color image is obtained by carrying out the batch transfer by the action of and passing through the fixing device 317. After the residual toner is removed by the cleaning device 319, the photoconductor 310 is subjected to the next color image forming process.

The color image forming apparatus described above, for example, as disclosed in Japanese Unexamined Patent Publication (Kokai) No. 4-256978, forms a color image by forming a plurality of single-color images on a transfer material P in sequence. Compared to the apparatus, the apparatus can be downsized and the number of constituent parts is small, so that it is easy to maintain the assembling accuracy and it is possible to maintain stable color image formation.

[0005]

In the above-mentioned color image forming apparatus, a plurality of monochromatic images are simultaneously formed on the photosensitive member,
Since the toners are transferred to the transfer material P all at once, the toner adhesion amount on the photoconductor is smaller than that of the halftone image and the solid image in the monochrome image in the monochrome image and the solid image in which the two colors are superposed. There is a wide gap, and the conditions under which optimum transfer is obtained for each image also differ.

Most commonly, the transfer means 314a is a transfer means composed of a so-called transfer charger, which gives the transfer material P an electric charge corresponding to the amount of electric charge of the toner forming the primary color image on the photoconductor. The charge amount applied to the transfer material P by the transfer charger is constant within one page of the image on the photoconductor. That is, when the transfer charger is used in the color image forming apparatus, the conventional transfer means adjusts the current value to be applied to the transfer charger so that a good transferred image can be obtained on average over one page of an image. However, when a single-color halftone image and a solid image in which two colors are overlapped as described above are mixed in one image page, the transfer charger is energized so that optimum transfer can be obtained for one image. Even if the current value is adjusted, the other image has insufficient transfer due to insufficient charge provided by the transfer charger, or the amount of charge provided by the transfer charger becomes excessive, causing the transfer image to be retransferred. Often occurs.

Generally, the primary color image formed on the image carrier is transferred at a certain ratio when it is transferred to the transfer material. If this ratio is called the transfer rate, this transfer rate always fluctuates. In the case of the above-mentioned color image forming apparatus, the transfer rate of the primary color image depends on various conditions such as the transfer voltage (or transfer current when a transfer charger is used), the amount of toner present, the type of toner, and the amount of toner charge. Are different within one page. Therefore, even if a primary color image having the same reproducibility as the original is formed on the image carrier, the original reproducibility and the color reproducibility are deteriorated during transfer.

The present invention has been made in view of the above circumstances. In the color image forming apparatus, when the transfer rate of the primary color image can change within one page due to the various conditions, this is corrected. It is an object of the present invention to provide a full-color compatible image forming apparatus that can always obtain good document reproducibility and color reproducibility.

[0009]

In order to achieve the above object, the first aspect of the present invention is to provide at least an image carrier and a first latent image forming means for forming a first latent image on the image carrier. , A first developing unit that develops the first latent image with a first toner to form a first monochrome image, and a second latent image on the image carrier on which the first monochrome image exists. A second latent image forming unit to be formed, and a primary color image forming unit including a second developing unit that develops the second latent image with a second toner to form a second monochromatic image. What is claimed is: 1. A color image forming apparatus, comprising: a transfer unit that transfers a primary color image formed of at least the first and second monochromatic images on a carrier to a transfer member to form a secondary color image, The means sets the transfer conditions when the primary color image is transferred to the transfer body as the primary color image. Characterized by a variable within the screen of the color image. That is, there are provided a plurality of developing means for each color component, each of which has a developer carrier that carries a developer composed of at least a toner and conveys the developer to a developing area facing the image carrier. A magnetic field and a developing bias electric field are applied between the body and the developer carrying body to develop the latent image on the image carrying body to form a monochromatic image (toner image), and this is repeated for each color component to obtain each color. In a color image forming apparatus of a method of obtaining a secondary color image by transferring a single color image of components onto an image carrier to obtain a primary color image, and then transferring the image from the carrier to a transfer medium such as transfer paper, The transfer condition for transferring the primary color image to the transfer body is variable within the screen of the primary color image.

Preferably, the image forming apparatus further comprises a transfer control means for controlling the transfer conditions, and more preferably, the color image forming apparatus detects at least one of the factors that change the transfer rate of the primary color image. It has an environment detection means and an image characteristic detection means for detecting the characteristics of the primary color image, and the transfer control means controls the amount of electric charge or pressing force applied to the transfer body by the transfer means.

A second aspect of the present invention that achieves the above object is to transfer a color image formed on an image carrier to a moving transfer member.
A color image transfer device for transferring as the transfer body moves, wherein transfer conditions for transferring the color image to the transfer body are changed in a direction intersecting with a moving direction of the moving transfer body. It is characterized by

[0012] It is preferable that the transfer body is contacted with the surface opposite to the surface on which the color image is transferred to give the transfer body an electric charge, and more preferably, a plurality of the transfer bodies are provided with an electric charge. It is composed of an assembly of brush-like transfer chargers.

A third invention for achieving the above object, at least an image carrier, a first latent image forming means for forming a first latent image on the image carrier, and a first latent image for the first latent image. First developing means for developing with a first toner to form a first monochromatic image, second latent image forming means for forming a second latent image on the image carrier on which the first monochromatic image exists , The second latent image to the second
From the first and second single-color images formed on the image carrier, having a primary color image forming unit including a second developing unit that develops with the toner to obtain a second single-color image. A color image forming apparatus for forming a color image on the transfer body in response to an input color image signal by transferring a primary color image to a transfer body to form a color image. When the transfer means transfers the primary color image on the image carrier onto the transfer member,
A transfer environment detection unit that detects at least one of factors that change the transfer rate of the color image transferred onto the transfer body is provided, and based on at least the detection result of the transfer environment detection unit, the first latent image is detected. It is characterized in that it has a latent image forming control means for controlling the image forming means or the second latent image forming means. That is, the color image forming apparatus is provided with a transfer environment detecting means, and means for controlling the writing condition of the latent image forming means based on the detection result of the transfer environment detecting means.

Preferably, the color image forming apparatus further comprises an image characteristic detecting means for detecting an image characteristic based on the input color image signal, and the latent image forming control means comprises the image characteristic detecting means. Based on the detection result,
The first latent image forming unit or the second latent image forming unit is controlled.

More preferably, the color image forming apparatus has a transfer control means for controlling the transfer condition based on the detection result of the transfer environment detection means, and the latent image formation control means has the transfer condition. Based on this, the first latent image forming means or the second latent image forming means is controlled.

[0016]

In the first and second aspects of the present invention, the transfer condition is set for each of the divided areas corresponding to the transfer charger even if there are images with various toner adhesion amounts and color component configurations in one screen. Based on the controllable and previously detected image characteristics on the image carrier and the transfer environment in the case of the second invention, transfer is performed under the most appropriate conditions for each of the divided areas. .

According to the third aspect of the present invention, even if the transfer rate varies under a certain transfer condition when images having various toner abundances exist within one page, the transfer rate which fluctuates in advance. Since the primary color image in consideration of the above is formed on the image carrier, the secondary color image after transfer can be reproduced most faithfully with respect to the input color image signal.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an image forming process and each mechanism of an embodiment of a color image forming apparatus which constitutes each invention of the present application.
This will be described with reference to FIG. FIG. 1 is a sectional configuration diagram showing an example of a color image forming apparatus suitable for carrying out the present invention.

The photosensitive drum 310, which is an image bearing member, is formed by coating a photosensitive layer such as an amorphous silicon layer or an organic photosensitive layer (OPC) on the drum, and is driven and rotated clockwise in a grounded state.

A scorotron charger 311 as a charging means
Y, 311M, 311C, and 311K are used in the image forming process of each color of yellow (Y), magenta (M), cyan (C), and black (K), with respect to the above-described organic photoconductor layer of the photoconductor drum 310. A charging operation is performed by the grid maintained at a predetermined potential and corona discharge by the discharge wire, and a uniform potential is given to the photoconductor drum 310.

An exposure optical system 312Y, which is a latent image forming means,
312M, 312C and 312K are the photosensitive drums 3
An array of 10 light emitting elements arranged in the axial direction is arranged in an array F
LISA with L (phosphor emission), EL (electroluminescence), PL (plasma discharge), LED (light emitting diode), and elements with an optical shutter function arranged.
(Photomagnetic effect optical shutter array), PLZT (transmissive piezoelectric element shutter array), LCS (liquid crystal shutter array), and other exposure elements, and a SELFOC lens as an equal-magnification imaging element.
The output signal of the image pickup device which scans the original by the image reading device, the electric transmission signal from other equipment such as a facsimile and a computer, the data stored in the recording device, etc. are supplied to the color image forming apparatus, and the signal processing unit 2 The converted color image signals are sequentially taken out from the memory and input as electric signals to the exposure optical systems 312Y, 312M, 312C and 312K, respectively. The emission wavelength of the light emitting element used in this embodiment is in the range of 700 to 900 nm, with a long wavelength in consideration of the light advancing property of the toner.

A developing device 313Y, which is a developing means using a non-contact developing method for accommodating one-component or two-component developers of yellow (Y), magenta (M), cyan (C) and black (K), respectively. 313M, 313C and 313
Each K has a developing sleeve that rotates in the same direction with a predetermined gap from the peripheral surface of the photosensitive drum 310.

The developing devices 313Y, 313M, 313 described above.
C and 313K are the scorotron charger 31 described above.
Charging by 1Y, 311M, 311C and 311K,
Exposure optical system 312Y, 312M, 312C and 312
Photosensitive drum 310 formed by image exposure with K
The above electrostatic latent image is reversely developed in a non-contact state by applying a developing bias voltage.

When the image formation is started, the photoconductor drive motor is rotated to rotate the photoconductor drum 310 in the clockwise direction, and at the same time, the charging action of the scorotron charger 311Y starts applying the potential to the photoconductor drum 310. .

After a potential is applied to the photosensitive drum 310, the exposure optical system 312Y starts exposure by an electric signal corresponding to a first color signal, that is, an image signal of yellow (Y), and the drum is rotationally scanned. Thus, an electrostatic latent image corresponding to the yellow (Y) image of the original image is formed on the surface of the photoreceptor layer.

The latent image is reversely developed by the developing device 313Y with the developer on the developing sleeve in a non-contact state to form a yellow (Y) toner image in accordance with the rotation of the photosensitive drum 310.

Next, the photosensitive drum 310 is further provided with a scorotron charger 31 on the yellow (Y) toner image.
A potential is applied by the charging action of 1M, and the exposure optical system 31
The exposure with the electric signal corresponding to the 2M second color signal, that is, the magenta (M) image signal is performed, and the developing device 313
By the non-contact reversal development by M, a magenta (M) toner image is sequentially superimposed on the yellow (Y) toner image.

By the same process, a cyan (C) toner image corresponding to the third color signal is further obtained by the scorotron charger 311C, the exposure optical system 312C and the developing device 313C, and the scorotron charger 311K, the exposure optical system 312K and Further, a black (M) toner image corresponding to the fourth color signal is sequentially formed by the developing device 313K, and the primary color formed of a plurality of monochromatic images is formed on the peripheral surface of the photosensitive drum 310 within one rotation. An image is formed.

The primary color image thus formed on the peripheral surface of the photosensitive drum 310 is transferred to the transfer means 314a described later.
In the paper feed cassette 315, and is conveyed to the timing roller 316, the timing roller 3
By driving 16, the image is transferred onto a transfer paper P which is a transfer material that is fed in synchronization with the primary color image on the photoconductor drum 310.

Transfer paper P that has received the transfer of the primary color image
In the static eliminator 314b formed of a sawtooth electrode, after being removed from the drum peripheral surface by removing the charge, the conveyor belt 3
The sheet 14e is conveyed to the fixing device 317. Fixing device 3
After the toner is heated and pressure-bonded at 17 to fuse and fix the toner on the transfer paper P, the toner is discharged from the fixing device 317 and conveyed by the paper discharge roller pair 318 a to be discharged to the paper discharge roller 318.
It is discharged onto the tray on the upper part of the device via the.

On the other hand, the photosensitive drum 31 from which the transfer paper is separated
In the cleaning device 319, the surface of the photosensitive drum 310 is rubbed by the cleaning blade 319a in the cleaning device 319, residual toner is removed and cleaned, and the toner image of the original image is continuously formed, or the toner image of a new original image is temporarily stopped. Formation. Cleaning blade 319
The waste toner scraped off by a and the cleaning roller 319b is discharged to a waste toner container (not shown) by the toner conveying screw 319c. After the cleaning is completed, the cleaning blade 319a and the cleaning roller 319b are kept apart from the photosensitive drum 310 in order to prevent damage to the photosensitive drum.

The transfer means of the first invention of the present application makes the transfer conditions variable within the screen of the primary color image formed on the image carrier. The transfer means of the present invention can change the transfer condition in the moving direction of the moving transfer member, and can change the transfer condition in a direction intersecting with the moving direction of the moving transfer member. It is also possible to make the transfer condition variable in a direction intersecting with the moving direction of the moving transfer body and the moving direction of the moving transfer body.

Here, the transfer condition indicates a condition for transferring the primary color image on the image bearing member to the transfer member, and is, for example, the amount of electric charge given to the transfer member by the transfer means. Specifically, the transfer unit continuously drives the transfer charger that applies a charge to the transfer member, the current value that the transfer charger applies to the transfer member, and the transfer charger continues to apply the charge to the transfer member. It can be at least one of the times. Further, as another example of the transfer condition, the transfer means is a pressing force for pressing the transfer body against the image carrier, and specifically, the transfer means is a pressurizing means, At least one of the pressure applied by the means to the image bearing member and the time during which the pressure is continuously applied can be set.

As the transfer means of each invention of the present application, it is possible to employ a means for applying an electric charge to the transfer body by contacting at least the surface of the transfer body opposite to the surface carrying the color image. Specifically, it is composed of an assembly of at least a plurality of brush-shaped transfer chargers, and a current value or a voltage applied to each of the plurality of brush-shaped transfer chargers can be made variable. FIG. 2 shows an example of a brush-shaped transfer charger which is an example of the transfer charger of the present invention. The conductive wires are bundled to form a brush-shaped transfer charger 41, and a plurality of brush-shaped transfer chargers 41 are arranged in a line in a direction orthogonal to the moving direction of the transfer body P. Each brush-shaped transfer charger 41 is connected to the transfer power source 40, and the transfer power source 40 controls the current value to be supplied to each brush-shaped transfer charger by a transfer control means (not shown). Brush resistance is 10 ^-1 to 10 ³ Ω
In cm, the brush-like transfer charger contacts the surface of the transfer member opposite to the surface on which the color image is transferred, and imparts a charge to the transfer member.

The transfer means of each invention of the present application comprises a roller-shaped transfer charger composed of an assembly of a plurality of conductive rollers arranged at least in a direction intersecting with the moving direction of the moving transfer body, It is possible to change the current value or the voltage applied to each of the plurality of conductive rollers. FIG. 3 shows an example of a roller-shaped transfer charger which is another example of the transfer charger of the present invention. A conductive elastic roller 42 made of conductive polyurethane having a diameter of 16 mm, a width of 4.8 mm and a resistance value of 10 ⁷ Ω and an insulating elastic roller 43 having a width of 0.2 mm and a resistance value of 10 ¹² Ω are alternately laminated to each other to form a transfer member. The rollers were arranged in a line in a direction orthogonal to the moving direction of P to form a roller-shaped transfer charger. Each conductive elastic roller 42 is connected to the transfer power supply 40, and the transfer power supply 40 controls the value of the current flowing through each of the conductive rollers by a transfer control means (not shown). The transfer roller contacts the surface of the transfer body opposite to the surface on which the color image is transferred, and imparts an electric charge to the transfer body.

Further, the transfer means of each invention of the present application can apply the electric charge to at least the surface of the transfer body opposite to the surface carrying the color image in a non-contact state. Specifically, it is composed of an assembly of a plurality of corona transfer chargers that give electric charges to the transfer body by corona discharge, and the current value or the applied voltage to each of the plurality of corona transfer chargers is variable. be able to. FIG. 4 shows an example of a corona transfer charger which is another example of the transfer charger of the present invention. The corona discharge wire was used as the corona transfer charger 44, and the corona transfer chargers 44 were arranged in a line in the length direction of the corona discharge wire in a direction orthogonal to the moving direction of the transfer body P. Each corona transfer charger 44 is connected to the transfer power source 40, and the transfer power source 40 controls the current value to be supplied to each corona transfer charger by a transfer control means (not shown). The resistance value of the corona discharge wire is 10 ⁻¹ to 10 ³ Ω · cm. The corona transfer charger applies an electric charge to the transfer body in a non-contact state with the surface of the transfer body opposite to the surface on which the color image is transferred. Alternatively, the transfer means is composed of an electron gun that supplies electrons to at least the surface of the transfer body opposite to the surface that carries the color image, and the electrons supplied by the electron gun. Can also be variable.

Further, the color image forming apparatus of each invention of the present application preferably further comprises a transfer control means for controlling the transfer condition, and the control means at least in the moving direction of the moving transfer body. Can be controlled to be variable. When the control means controls the current for driving the transfer charger, the current value of the direct current can be continuously variable, but it is a direct current pulse waveform having a constant period and a pulse corresponding to the transfer current. It is also possible to change the pulse width of each of the transfer electrodes and to apply the current to the transfer electrodes so that a current corresponding to the direct current can flow through the transfer electrodes. To give an example, the transfer charger shown in FIG. 2 is energized with a pulsed waveform with a direct current of 100 V and a period of 20 msec, and a pulse corresponding to a desired controlled charge is changed in pulse width for each transfer electrode. Let me give you. Approximate pulse width is 0.5 msec to 5 msec
Becomes

When the transfer control means changes the pressing force of the transfer body against the image carrier, as shown in FIG. 5, when the distance d between the transfer body and the brush fixing portion is shorter than the length of the transfer brush 51, the brush is brushed. Elastically deforms, and a pressing force is generated by the elastic force. This pressing force can be controlled by adjusting the distance d between the transfer body and the brush fixing portion by driving the solenoid motor 52, a hydraulic pump, a pneumatic pump, or the like, and together with the control of the amount of electric charge applied to the transfer body. A better transferred image can be obtained.

In each of the above-mentioned transfer means, when it is a transfer charger, the charge given from the transfer charger tends to diffuse on the surface of the transfer body, and the pressing force of the transfer body against the image carrier is changed. In this case, since the pressing force tends to be dispersed because it is applied through the transfer body, it is extremely difficult to control the electric charge applied to the transfer body in units of dots, which is one tenth of a millimeter. However, in the present invention, there are few images in which the transfer rate is greatly different, for example, a single-color halftone image and a solid image in which two colors are superposed are mixed in a unit of one dot, and several to several hundred dots are grouped together.
The object of the present invention is sufficiently achieved if control can be performed for each divided region of 10 mm square.

In the color image forming apparatus of the first invention of the present application, when the primary color image on the image carrier is transferred onto the transfer body, the transfer rate of the color image transferred onto the transfer body is changed. It is preferable that the image forming apparatus has a transfer environment detecting unit that detects at least one of the factors that cause the transfer condition, and the transfer control unit controls the transfer condition based on at least the detection result of the transfer environment detecting unit.

In the color image forming apparatus according to the second aspect of the present invention, when the transfer means transfers the primary color image on the image carrier onto the transfer body, the color image transferred onto the transfer body. The transfer environment detecting means for detecting at least one of the factors that change the transfer rate of the first transfer means, and based on the detection result of at least the transfer environment detecting means,
The latent image forming means or the latent image forming control means for controlling the second latent image forming means.

The transfer environment detecting means in each invention of the present application is
At the time of transferring the primary color image on the image carrier to the transfer body, at least one of the factors that varies the transfer rate is detected regardless of the characteristics of the primary color image. Here, the transfer rate is the amount of the toner of each color forming the primary color image on the image carrier, and constitutes the secondary color image on the transfer body when the primary color image is transferred to the transfer body. It is obtained by dividing the adhered amount of each color toner. Specific examples of factors that change the transfer rate include the temperature in the color image forming apparatus of the present invention, the relative humidity or the amount of water vapor in the color image forming apparatus, the resistance value of the transfer member, the thickness, the material, and the primary color. There are types of toner of each color forming an image, the charge amount, etc., and a specific example of the transfer environment detecting means is as follows.
There are a temperature sensor, a humidity sensor, a transfer body thickness detection sensor, a transfer body resistance value sensor, a toner charge amount sensor, an image forming number counting device of each developing means, and the like.

It is known that the charge amount of toner changes due to fluctuations in humidity and temperature in the transfer environment.
That is, even if the same toner adhesion amount on the same image carrier is caused by the change in the toner charge amount, the amount of charge imparted to the transfer member and the transfer member relative to the image carrier are required for good transfer. The pressing force fluctuates. It is also known that the resistance value of the transfer member changes due to changes in humidity and temperature. That is, even if the same transfer current is applied to the transfer charger, the charge applied to the transfer body changes, and as a result, the transfer rate changes. And humidity detection is relative humidity,
The amount of water vapor may be any, and it is detected by a known humidity sensor, and the temperature is also detected by a known temperature sensor.

The color image forming apparatus of each invention of the present application further has a transfer body characteristic detecting means for detecting the characteristic of the transfer body, and the transfer control means at least based on the detection result of the transfer body characteristic detecting means. The transfer condition can be controlled, and the latent image formation control unit can control the latent image formation condition based on the detection result of the transfer member characteristic detection unit. That is, even if the same transfer current is applied to the transfer charger by changing the characteristics of the transfer member, the charge applied to the transfer member changes, and as a result, the transfer rate changes. The transfer member characteristic detecting means detects the characteristics of the transfer member by detecting at least the conductivity of the transfer member, or at least by detecting the thickness of the transfer member. Optical detection to detect the transmittance, electrical detection to detect the conductivity of the transfer body, and physical detection to detect the fluctuation of the roller shaft distance when the transfer body passes between the feed rollers are possible. is there. The conductivity of the transfer body can be indirectly detected based on the above-described temperature, the thickness of the transfer body, and the result of detecting the transfer body described below, but it is possible to detect the conductivity of the transfer body before the transfer. The electrodes are provided, and the transfer member is passed between the electrodes,
It is also possible to directly detect by measuring the resistance value. The material of the transfer body can be detected by, for example, a reflected light sensor that detects the smoothness of the surface of the transfer body or a transmitted light sensor that detects the light transmittance of the transfer body. Further, the detection of the characteristics of the transfer body can be replaced with the detection of the characteristics of the various transfer bodies described above based on the result of detecting the mode switching operation of the transfer body by the user.

To detect the characteristics of the transfer body, the screen of the primary color image on the image carrier is divided into a plurality of areas, and the characteristics of the various transfer bodies described above are divided into areas of the transfer body corresponding to the divided areas. By detecting, it is possible to perform excellent transfer even to a transfer body made of a composite material or a transfer body partially subjected to special treatment for the purpose of preventing duplication and forgery.

Further, the color image forming apparatus of the present invention further includes a second toner characteristic for detecting the characteristic of the first toner, a first toner characteristic detecting means and a characteristic of the second toner. The transfer environment detecting means may include a detecting means, and the transfer environment detecting means may detect the transfer environment based on at least the detection result of the first toner characteristic detecting means and the detection result of the second toner characteristic detecting means. The latent image formation control means can control the latent image formation conditions based on the detection results of the toner characteristic detection means. That is, since the transfer rate also changes due to the change in the characteristics of the toner, it is preferable to detect this and control the transfer unit or the latent image forming unit based on the detection result. Toner type detection is
The color components such as yellow, magenta, cyan, and black may be set at the shipping stage of the color image forming apparatus of the present invention, and the setting operation of the toner type performed by the user may be detected every time the toner is replaced. When the toner is exchanged while being stored in the cartridge, the information of the toner stored in the cartridge is recorded electrically, magnetically or optically, and is stored in the color image forming apparatus of the present invention of the cartridge. It is also possible to detect based on the result read by the toner information reading means when the toner is attached. The number of times of image formation of each developing means is detected by the means for counting the number of times of image formation provided in the color image forming apparatus of the present invention, and every time the toner is replaced, the user resets the count of the counting means or the user. It is possible to detect the number of times the image has been formed by detecting the setting operation of the toner type that is performed by or when the toner is replaced while it is stored in the cartridge, by automatically resetting the count when the cartridge is replaced. Becomes The toner charge amount can be detected based on a predetermined toner amount and the result of comparing the potentials of the electrode provided in the developing unit and the reference electrode. When a two-component developer consisting of a magnetic carrier and a non-magnetic toner is used as the developer, the user may reset the count of the counting means each time the carrier is exchanged to count the number of image formations of each developing means. When the carrier is exchanged while it is stored in the cartridge, the count is automatically reset when the cartridge is exchanged, so that the number of times of image formation can be accurately detected. When a two-component developer is used, the toner concentration in the developer can be detected, and the magnetic permeability of the developer housed in the developing means can be detected based on the result of detection by a known means.

The color image forming apparatus of the present invention further has an image characteristic detecting means for detecting the characteristic of the primary color image composed of at least the first and second monochromatic images, and the transfer control means has the image characteristic. The transfer condition can be controlled based on the detection result of the detection unit, and the latent image formation control unit can control the latent image formation condition based on the detection result of the image characteristic detection unit. is there. The image characteristics are the abundance of the toner forming the primary color image existing on the image carrier, the abundance of each color toner forming the primary color image, and the respective colors forming the primary color image. There are types of toner, the shape of the primary color image or each single color image forming the primary color image, and these image characteristics are detected directly or indirectly from a color image signal or the like. Alternatively, the color image forming apparatus of each invention of the present application further detects a characteristic of the first monochromatic image on the image carrier.
It has a first monochromatic image characteristic detecting means and a second monochromatic image characteristic detecting means for detecting the characteristic of the second monochromatic image on the image carrier, and the transfer control means includes at least the first monochromatic image characteristic detecting means. It is possible to control the transfer means based on the detection result of the single-color image characteristic detection means and the detection result of the second single-color image characteristic detection means. It is possible to control the first latent image forming unit and the second latent image forming unit based on the detection result of the detection unit.

The image characteristic detecting means of each invention of the present application is capable of detecting at least the existing amount of toner forming the primary color image on the image carrier, or
At least detecting the abundance of the first toner forming the first monochromatic image and the abundance of the second toner forming the second monochromatic image on the image carrier. Is possible. When the image characteristics are directly detected, for example, in order to detect the existing amount of the toner forming the primary color image, the reflected light of the toner image formed on the photoconductor 310 is detected as the primary color image existing amount. It is detected by a photoelectric sensor (not shown) installed in the vicinity of the photoconductor 310, which is a means, and is sent to the main control unit as a detection signal. Assuming that Vsp and Vsg are the photoelectric sensor output from the toner adhering portion of the reference pattern portion and the output of the background portion, respectively, the amount of toner adhering to the reference pattern per unit area m ₁ (g / cm ² ) is m ₁ = The toner abundance is converted from the relationship of −ln (Vsp / Vsg) /ββ=−6.0×10 ³ (cm ² / g). Here, β is a constant determined by the photoelectric sensor and the toner. In addition,
Here, the value of the black toner is used. Further, yellow, cyan, and magenta can be detected in the same manner.

When one or more pattern latent images are formed on the photoconductor 310 by the latent image forming means,
The amount of toner present after development can be changed by changing the writing width (duty ratio) per dot or by changing the developing electric field during the development of each pattern. When the transfer rate is detected, the reference pattern toner image is transferred to the transfer bias (+8 as an example).
It is transferred to the transfer body P by the transfer roller to which 50 V) is applied. And, it is a transfer image existence amount detection means,
After the transfer, the toner existence amount m ₂ on the transfer body is calculated by a detection signal from a second photoelectric sensor (not shown) installed near the transfer body. From the above results, the transfer rate η is η
= M ₂ / m ₁ × 100 (%).

The color image forming apparatus of each invention of the present application further includes the primary color image abundance detection means and the transfer for detecting the abundance of the toner constituting the secondary color image transferred onto the transfer body. The transfer environment detecting unit has an image existing amount detecting unit, and the transfer environment detecting unit forms a reference pattern primary image on the image carrier in advance before forming the color image and transfers it to the transfer unit, and at least the reference pattern. The transfer rate is detected based on the result of detection of the primary image by the primary color image existence amount detection unit and the result of detection of the reference pattern image transferred on the transfer body by the transfer image existence amount detection unit. Therefore, the transfer environment can be detected.

Further, the color image forming apparatus according to each invention of the present application forms the color image based on the input color image signal, and the image characteristic detecting means at least based on the input color image signal. It is possible to detect image characteristics. When the image characteristics are indirectly detected, most of them are detected based on the input color image signal. The image characteristics of a range corresponding to a certain transfer unit, which is detected from the color image signal, include, for example, the signal occupancy rate of the image signal for each color and the type of a single color image forming the range, a line image, a character image, It is possible to distinguish between halftone images and solid images, etc., by comparing the minimum units (so-called pixels) of the color image signals that make up the range, or by comparing with a template in which various image characteristics are patterned in advance. Detected.

FIG. 6 shows an example of signal processing in each invention of the present application, in which 201 is a shading correction circuit and 202 is an MT.
F correction circuit, 203 is a γ correction circuit, and 204 is color correction-U
A CR processing circuit, 205 is a gradation correction circuit, 206 is a transfer rate correction circuit, 207 is an image memory, and 3 is an image forming unit. An output signal of an image sensor which scans a document by an image reading device, a transmission signal from other devices such as a facsimile and a computer, and data stored in a recording device are generally color-separated into R, G, and B. ing. The shading correction circuit 201 corrects unevenness of the image sensor, uneven illumination of the light source, and the like. In the MTF correction circuit 202,
In particular, the deterioration of the MTF characteristic in a high frequency region is corrected. The γ correction circuit 203 corrects or converts the input data so as to have predetermined desired characteristics such as linear reflectance and linear density. Further, the color correction-UCR processing circuit 204, which can also perform background removal and the like at the same time, corrects the difference between the spectral characteristics of the color separation characteristics of the input system and the color material of the output system, and the color material necessary for faithful color reproduction. , Y, M, and C, and a UCR processing unit for replacing the portion where the three colors Y, M, and C overlap with K. The color correction process can be realized by performing a matrix calculation as shown in the following formula.

[0053]

[Equation 1]

Here, R ', G', and B'indicate the complements of RGB. The matrix coefficients a11 to a33 are determined by the spectral characteristics of the input system and the output system (color material). Here, although the first-order masking equation is taken as an example, B ′ ² ,
G ^{'2, R'} 2 such as quadratic terms or by further using a higher-order terms, it is possible to more accurately color correction. Further, the arithmetic expression may be changed depending on the hue, or the Neugeber equation may be used. In either method, YMC can be obtained from the values of B ', G', R '(or BGR).

On the other hand, UCR processing can be performed by performing arithmetic processing using the following equation.

Y '= Y-αmin (Y, M, C) M' = M-αmin (Y, M, C) C '= C-αmin (Y, M, C) K = αmin (Y, M, C) C) In the above equation, α is a coefficient that determines the amount of UCR, and α = 1
At this time, 100% UCR processing is performed. Note that α may be a constant value. For example, by making α close to 1 in the high density portion and close to 0 in the highlight portion, the image in the highlight portion can be made smooth. The Y, M, C, and K data that has been subjected to color correction and UCR processing is subjected to binary or more multivalued processing in the gradation processing circuit 205. Although the systematic dither method is generally used as the multi-valued processing, the multi-valued processing can be performed by another method such as an error diffusion method.

Next, the gradation-processed image data is sent to the transfer rate correction circuit 206, and the transfer rate is corrected. That is, when the result of gradation processing is the i-th gradation value of 256 gradations, the toner adhesion amount on the photoconductor 310 at that time is ma (mg / cm ² ), and the transfer rate at that time is η. ₁
%, The toner adhesion amount m corresponding to the corrected gradation value
b (mg / cm ² ) is obtained by (ma / η ₁ ) × 100. Then, the jth gradation processing data at the toner adhesion amount mj corresponding to the jth gradation value closest to mb is transmitted to the image forming unit 3 via the image memory 207. The image forming section 3 can output a color image by a known method of forming a gradation image by controlling the latent image forming means based on the signal transmitted from the signal processing section 2. In such a case, the transfer rate correction circuit 206 also functions as the latent image formation control means in the second aspect of the invention. Further, the transfer rate η ₁ varies depending on the temperature, humidity, various characteristics of the transfer member, and various characteristics of the toner, as described above.

An example of control of transfer conditions in the present invention is shown below.

FIG. 7 is a block diagram showing an example of control of transfer conditions in the present invention. The color image signal that has been subjected to the various types of correction processing described above in the signal processing unit 2 is input to the image characteristic detection means 71 for each color component. The color image signal input to the image characteristic detection unit 71 is the image characteristic of the range corresponding to the position of each of the divided transfer units 34. The color components constituting the range, the gradation value of each color component, and each color. Detect the signal occupancy of the component. That is, referring to FIG. 8, at a certain time t ₁ , the color image data for forming the latent image on the photoconductor 310 is divided into n in the width W direction of the transfer material P. The image characteristic of the range A corresponding to a certain transfer unit is detected, and the result is transmitted to the transfer control unit 70. At a time t ₂ when a little longer than that, the image characteristics in the range B in FIG. 8 are detected and similarly transmitted to the transfer control means 70.

On the other hand, the humidity sensor 701 detects the humidity in the color image forming apparatus of the present invention and transmits the result to the transfer control means 70, and the transfer body resistance value sensor 702 detects the resistance value of the transfer body. The result is transmitted to the transfer control means 70, and the transfer body transmitted light sensor 703, the transfer body reflected light sensor 704, and the transfer body thickness sensor 705 are respectively transferred to the transfer body P.
The light transmittance and the optical reflectance of the image are detected, and the results are transmitted to the transfer control means 70.

In the transfer control means 70, based on the detection results transmitted from the image characteristic detection means 71 and the various sensors 701 to 705, a current value optimum for transfer in each divided range is supplied. A control signal is generated to control the transfer power supply 40, and the transfer means 314a at the corresponding position is driven with an electric current most suitable for the transfer in the range.
Then, by repeating this, the transfer means is controlled to the optimum current suitable for each divided range, the optimum transfer rate can always be obtained, and the generation of defective images can be prevented.

It is preferable that the transfer means of each invention of the present application contact at least the surface of the transfer body opposite to the surface on which the color image is transferred, and apply an electric charge to the transfer body. That is, in order to control the transfer current in each of the divided areas, a roller-shaped transfer charger or a brush-shaped transfer charger that transfers in a contact state to the transfer body is more preferable than a corona transfer charger that transfers in a non-contact state to the transfer body. Is easier to control. In the corona transfer charger, ions are generated by the discharge of the electrodes, and the generated ions are applied to the transfer body as charges.Therefore, the response of the amount of charge applied to the transfer body to the fluctuation of the current flowing in the corona transfer charger is slow, Insufficient transfer control is possible. On the other hand, in a roller-type transfer charger or a brush-type transfer charger that transfers in contact with the transfer body, in order to apply an electric charge to the transfer body by Paschen discharge in the area close to the transfer body, The response of the amount of electric charge imparted to the body is sharp and is more preferable in the practice of the present invention.

Further, in the color image forming apparatus of the present invention, when the primary color image is formed, the amount of toner that constitutes the primary color image on the image carrier is irrelevant regardless of the characteristics of the primary color image. A primary color image forming environment detecting means for detecting a primary color image forming environment which is at least one of the factors for changing, and controlling the transfer condition based on the detection result of the primary color image forming environment detecting means. Is possible.

In the primary color image forming environment, the humidity, temperature, characteristics of the developer, and the number of times of image formation are typically detected. Among them, the number of times of image formation is a large factor as a factor of varying the existing amount of toner forming the primary color image on the image carrier. As described above, the transfer rate fluctuates as the charge amount and particle size distribution of the developer change during repeated image formation, but the image changes as the charge amount and particle size distribution of the developer changes. The amount of toner that constitutes the primary color image on the carrier also changes.

Further, the image bearing member is charged, exposed, developed,
While repeating the image formation of transfer, cleaning and charge removal,
The charging potential obtained by the action of the charging means is reduced, and the potential reduction amount of the portion exposed by the latent image forming means is reduced. Further, the latent image forming means reduces the output of the laser or the emission intensity of the LED as the image formation is repeated. That is, while repeating image formation,
Due to such a decrease in the charging potential, a decrease in the potential of the exposed portion, and a decrease in the laser output, the potential difference between the exposed portion and the non-exposed portion, that is, the latent image intensity tends to decrease.
With such a decrease in the latent image intensity, the amount of toner present on the image carrier with respect to the input of the same color image signal tends to decrease. However, by controlling the transfer means to a transfer condition that increases the transfer rate, A good transferred image can be obtained.

In general, with respect to the above-mentioned change in latent image intensity, the bias applied between the developer conveying means and the image carrier in the developing means and the developer conveying amount are changed, The developing unit is controlled so as to secure the existing amount of the toner forming the primary color image on the image carrier, particularly the existing amount of the toner in the high density portion. In such a case,
When the developing device is controlled so that the toner adheres to the latent image having the lowered latent image intensity, the toner amount tends to be excessive in the low density portion. In the image forming apparatus of the present invention, even when the developing unit is controlled in response to the change in the number of times of image formation, the number of times of image formation and the control of the developing unit are detected to detect the amount of toner on the image carrier. The transfer condition is controlled so that the transfer rate becomes low for the portion where the amount is excessive, and conversely the transfer condition is controlled so that the transfer rate becomes high for the portion where the toner amount on the image carrier is insufficient. It is possible to In addition to this, it is also possible to control the transfer condition by controlling the latent image forming unit with respect to the number of image formations and controlling the charging unit with respect to the number of image formations.
The detection of the number of times of image formation is performed by the above-mentioned number of times of image formation detecting means, and every time the image carrier or the latent image forming means is replaced,
When the user resets the count of the counting means, or when the image carrier or the latent image forming means is exchanged while being stored in the cartridge, the count is automatically reset when the cartridge is exchanged, so that the accurate It is possible to detect the number of times of image formation.

Example 1 A transfer unit of a digital color copying machine 7728 manufactured by Konica Corporation was modified to use a corotron transfer wire electrode as shown in FIG.
Replaced with the brush-shaped transfer charger shown in. The brush-shaped transfer charger is a transfer brush 62 made by Memowal fiber (Ni-Ti alloy) manufactured by Nippon Tungsten Co., Ltd., in which 100 wires each having a diameter of 30 microns are bundled in a diameter of 5 mm, 100 wires each, and the length to the fixed portion is 10 mm. The books were arranged in a line in a direction orthogonal to the moving direction of the transfer body. The distance from the transfer body to the fixing portion of the transfer brush was set to 7 mm in order to apply the pressing force of the transfer brush. Each transfer brush is connected to a transfer power supply, and the transfer power supply controls the transfer current to be supplied to each transfer brush by the transfer control means. The resistance value of the transfer brush is 10 ^-1 to 10 ³ Ω.
cm. Further, a pointed electrode plate 14b was used as a separating means for separating the photoconductor and the transfer body. The protrusion-type electrode plate is made of a stainless steel plate having a thickness of 0.2 mm, and the height a of the peak is 4 mm and the pitch b is 2 mm in FIG. 9A, and the gap between the photoconductor and the tip of the electrode plate is used. The voltage applied to the electrode plate was set to 1.5 mm, at high temperature and high humidity of -1.2 kV, at room temperature and normal humidity, and at low temperature and low humidity of -1.4 kV (see FIG. 9). Further, a part of the exposure amount control board was modified so that the present invention could be carried out.

On the exposure control board, a color image signal is supplied from 0 to 2 for each color of yellow, magenta, cyan and black.
A signal that has been subjected to gradation processing up to 256 gradation values up to 55 is input, and the exposure amount control board controls the energization to the laser light source. The energization is a direct current and has a pulsed waveform with a period of about 15 μsec, and a pulse according to the controlled light emission time is given to the laser light source by changing its pulse width in 256 steps from 0 to 255. The laser light emitted from the laser light source is deflected by a rotary polygon mirror rotating at about 16000 RPM, and the surface of the photoconductor is scanned with a main scanning diameter of about 63 μ and a sub-scanning diameter of about 85 μm.
Raster scanning is performed with a beam diameter of μm to form a latent image. The minimum unit (hereinafter, pixel) of the input color image signal corresponds to a dot-shaped color image of about 1/16 mm square. For example, a pixel is yellow 255, magenta 2
Approximately 1 if it has a step value of 55, 0 cyan, and 0 black
A dot-shaped red image of 1/6 mm square is formed.

The transfer control means of the present invention controls the transfer current supplied to each transfer brush as follows. First, the input color image signal is divided into blocks corresponding to 5 mm square in the final color image, and the signal occupancy rate in each block is calculated according to the following formula.

[0070]

[Equation 2]

For example, for a color image of 5 mm square, 640
The color image signal of 0 pixel is 25 for each of Y, M, C and K
If there are 6 step values, the following formula is obtained.

[0072]

(Equation 3)

Then, the transfer current applied to each transfer brush corresponding to each block was controlled at a cycle of about 35 milliseconds according to the obtained signal occupancy rate for each block.
The linear velocity of the transfer body was set to 140 mm / sec.

For example, in the case of forming a red image, the transfer current supplied to each transfer brush is controlled as shown in Tables 1 to 8 in Table 1 below with respect to the relative humidity, and yellow is input as shown in Table 2 below. , Tables 1 to 8 in Table 1 are controlled according to the signal occupancy of the magenta color image signal. At this time, the existing amount of each toner corresponding to the signal occupancy rate of 100% on the transfer body is Y: 0.50.
It was mg / cm ² and M: 0.50 mg / cm ² .

[0075]

[Table 1]

[0076]

[Table 2]

When a blue image is formed, the transfer current supplied to each transfer brush is controlled with respect to relative humidity as shown in Tables 1 to 8 in Table 3 below. Control is performed so that table 1 to 8 in Table 3 are selected according to the signal occupancy of the magenta color image signal. At this time, the existing amount of each toner on the transfer body corresponding to the signal occupancy rate of 100% is M: 0.30 mg / c
m ² and C were 0.50 mg / cm ² .

[0078]

[Table 3]

[0079]

[Table 4]

At this time, it should be noted that even if the relative humidity, the transfer member, and the M signal occupancy rate are the same, the transfer current depends on the type and the signal occupancy rate of the monochromatic image of other color components that are simultaneously transferred. Is the difference. That is, the transfer condition is controlled in accordance with the characteristics of all the monochromatic images forming the color image.

Further, the reason why the transfer current for transferring a red image is relatively larger than that for transferring a blue image is that a single-color image is formed on the photosensitive member and then transferred to the transfer member. Up to 8 seconds (Y about 8 seconds, M about 5 seconds, C about 3 seconds, K about 0.5 seconds). The transfer current is also changed with respect to the elapsed time from the formation to the transfer onto the transfer body. In the present invention, by using the result of detecting the abundance of the toner constituting the monochromatic image on the photoconductor or a signal occupancy rate of each monochromatic image as described above for the setting of the transfer condition, A good transfer color image is obtained.

Example 2 The brush-shaped transfer charger in Example 1 was used with a diameter of 16
mm, 4.8 mm width, resistance value 10 ⁷ Ω, hardness 35 (JI
Replace the conductive elastic roller made of foamed conductive polyurethane (S Asker C hardness) and the foamed insulating elastic roller having a width of 0.2 mm and a resistance value of 10 ¹² Ω with a roller-shaped transfer charger laminated as shown in FIG. , As in Example 1,
When the transfer current applied to each conductive elastic roller was controlled, a good transferred image was obtained as in Example 1.

Example 3 The brush-shaped transfer charger used in Example 1 was replaced with Memhoir fiber (Ni-Ti alloy) manufactured by Nippon Tungsten Co., Ltd.
As shown in FIG. 4, corona discharge wires made of 30 μm in diameter and 7 mm in length are arranged in a line in the length direction of the wire and in a corona transfer charger arranged in a direction orthogonal to the moving direction of the transfer body. When exchanged, the transfer current applied to each corona discharge wire was controlled in the same manner as in Example 1. As a result, transfer unevenness was slightly observed compared to Example 1, but a good transferred image was obtained.

Example 4 When forming a red image in the modified digital color copying machine, the transfer of the second monochromatic image on the transfer paper corresponding to the gradation value of the magenta color image signal before the transfer rate correction While the amount fluctuates in each case, the gradation value of the signal sent to the exposure means was corrected according to each condition. For reference, Table 5 extracts the step value of the pulse width of the laser emitted when the control is performed so as to obtain the ideal magenta toner transfer amount under each condition. In addition,
At this time, the temperature of the transfer brush is 20 ° C, the relative humidity is 50%,
A current of 0.60 μA was applied to the transfer brush corresponding to the transfer of a red image having a signal occupancy of 90% onto plain paper. Further, FIG. 10 shows the relationship between the gradation value of the magenta color image signal before the transfer rate correction and the magenta toner transfer amount in the second monochrome image on the transfer paper in the fourth embodiment.

[0085]

[Table 5]

As described above, the exposure amount in the magenta image formation is controlled in consideration of the result of detecting the existing amount of the other monochromatic image forming the color image, so that the input color image signal can be obtained. A color image faithfully reproduced on the transfer body was obtained.

Embodiment 5 When forming a blue image in the color image forming apparatus of Embodiment 4, the magenta toner transfer amount on the transfer paper corresponding to the gradation value of the magenta color image signal before transfer rate correction is The gradation value of the signal sent to the exposure means was corrected according to each condition, although it varied depending on the case. For reference, Table 6 extracts the step value of the pulse width emitted by the laser when controlled to obtain the ideal amount of magenta toner present under each condition. At this time, the transfer brush had an air temperature of 20 ° C., a relative humidity of 50%, and a signal occupancy rate of 9%.
A current of 0.60 μA was applied to the transfer brush corresponding to the transfer of a 0% blue image to plain paper. Further, FIG. 11 shows the relationship between the gradation value of the magenta color image signal before the transfer rate correction and the magenta toner transfer amount in the second monochromatic image on the transfer paper in the fifth embodiment.

[0088]

[Table 6]

At this time, the point to be noted is that the degree of transfer correction depends on the types and gradation values of other single-color images that are transferred at the same time, even if the gradation values are the same relative humidity, transfer member, and magenta. It is a different point. That is, the transfer correction is performed according to the characteristics of all the monochromatic images forming the color image.

Further, the gradation value after transfer correction in the blue image is relatively larger than the gradation value after transfer correction in the red image because in the red image, the yellow value existing on the photoconductor is large. Since a magenta single-color image is formed overlaid on a single-color image, it is less susceptible to the adhesive force with the photoconductor during transfer, and is easy to transfer, whereas a magenta single-color image is a photoconductor on a blue image. Since a cyan single-color image is formed after being directly formed on the upper surface, the transfer rate tends to decrease due to the influence of the adhesive force with the photoconductor.
Such a tendency was also seen in the yellow single color image and the green image in the red image and the green image, and the cyan single color image in the blue image.

For reference, in the case of plain paper, the transfer current values in Examples 4 and 5 were controlled as shown in Table 7 below.

[0092]

[Table 7]

[0093]

According to the present invention, it is possible to obtain a color image having a stable image quality in spite of a change in the transfer environment, even though it is a small color image forming apparatus.

[Brief description of drawings]

FIG. 1 is a sectional view showing an example of a color image forming apparatus suitable for an embodiment of the present invention.

FIG. 2 is an embodiment of the color image transfer device of the present invention.

FIG. 3 is a different embodiment of the color image transfer device of the present invention.

FIG. 4 is a different embodiment of the color image transfer device of the present invention.

FIG. 5 is a positional relationship between a color image transfer device of the present invention and an image carrier.

FIG. 6 is a specific example of the signal processing unit 2 according to the present invention.

FIG. 7 is an example of control of transfer conditions in the present invention.

FIG. 8 is an explanatory diagram of signal occupancy detection.

FIG. 9 is a pointed electrode plate.

FIG. 10 is a graph showing a relationship between a gradation value of a magenta color image signal before transfer rate correction and a magenta toner transfer amount in a second monochromatic image on a transfer sheet in the fourth embodiment.

FIG. 11 is a graph showing a relationship between a gradation value of a magenta color image signal before transfer rate correction and a magenta toner transfer amount in a second monochromatic image on a transfer sheet in the fifth embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Computer and storage device 2 Signal processing unit 3 Image forming unit 40 Transfer power source 41 Brush-like transfer charger 42 Conductive elastic roller 43 Insulating elastic roller 44 Corona transfer charger 51 Transfer brush 52 Solenoid motor 70 Transfer control means 71 Image characteristic detection Means 310 Photoreceptor Drum (Photoreceptor) 311Y, 311M, 311C, 311K Scorotron Charger (Charger) 312Y, 312M, 312C, 312K Exposure Optical System 313Y, 313M, 313C, 313K Developer 314a Transfer Means 314b Separation Means Electric appliance) 319 Cleaning device 201 Shading correction circuit 202 MTF correction circuit 203 γ correction circuit 204 Color correction-UCR correction circuit 205 Gradation processing circuit 206 Transfer rate correction circuit 207 Image memory 701 Humidity correction Sensor 702 transfer body resistance value sensor 703 transfer body transmitted light sensor 704 transfer body reflected light sensor 705 transfer body thickness sensor P transfer body (transfer material, transfer paper)

Claims (2)

[Claims] 1. At least an image carrier, a first latent image forming means for forming a first latent image on the image carrier, the first latent image is developed with a first toner, and a first latent image is developed. First developing means for forming a monochromatic image, second latent image forming means for forming a second latent image on the image carrier on which the first monochromatic image exists, and second latent image for forming the second latent image. At least the first and second monochromatic images formed on the image carrier, having a primary color image forming unit including a second developing unit that develops with a second toner to form a second monochromatic image. A color image forming apparatus having a transfer means for transferring a primary color image to a transfer body to form a secondary color image, wherein the transfer means is a transfer condition for transferring the primary color image to the transfer body. Is a color image forming apparatus in which the primary color image is variable within the screen. 2. An image carrier, at least a first latent image forming means for forming a first latent image on the image carrier, the first latent image is developed with a first toner, and the first latent image is developed. First developing means for forming a monochromatic image, second latent image forming means for forming a second latent image on the image carrier on which the first monochromatic image exists, and second latent image for forming the second latent image. At least the first and second monochromatic images formed on the image carrier, having a primary color image forming unit including a second developing unit that develops with a second toner to form a second monochromatic image. A color image forming apparatus for forming a color image on the transfer body in response to an input color image signal by transferring a primary color image consisting of , The transfer means transfers the primary color image on the image bearing member onto the transfer member. A transfer environment detecting means for detecting at least one of the factors that change the transfer rate of the color image transferred on the transfer body, and based on at least the detection result of the transfer environment detecting means, the first Color image forming apparatus having latent image forming control means for controlling the latent image forming means or the second latent image forming means.