JPH0675456A - Color electrophotographic recorder - Google Patents

Abstract

(57) [Abstract] [Purpose] In a color electrophotographic recording apparatus of a type in which toner images of color components are once superposed on an intermediate transfer member and then transferred to paper, the toner amount of each color component transferred to paper is constant. The purpose is to do. [Configuration] The pixel information of each color component stored in the memory 3 is read by the CPU 2, and the image information of each color component is sent to the pixel signal generation circuit 9. Pixel signal generation circuit 9
Is the intermediate transfer member 19 so that the toner amount of each color component transferred onto the sheet 26 based on the image information of each color component becomes constant.
The image signal 5 is generated by setting the pulse width so that the light amount of the pixel when the latent image of the toner image to be first transferred is formed is larger than the light amount of the pixel when the latent image of the toner image of the component to be subsequently transferred is formed. It is sent to the exposure control circuit 4. [Effect] A color image with excellent color reproducibility is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color electrophotographic recording apparatus of a type in which a toner image of each color component formed on a photosensitive member is once superposed on an intermediate transfer member and then transferred onto a sheet.

[0002]

2. Description of the Related Art FIG. 3 is a sectional view showing a conventional color electrophotographic recording apparatus, FIG. 4 is a block diagram of a control section of the conventional electrophotographic recording apparatus, and FIG. 5 is a configuration diagram of an exposure section. In FIG. 3, 1 is a device frame. Reference numerals 6 and 7 are a control unit and an exposure unit provided in the apparatus frame 1. As shown in FIG. 4, the controller 6 is composed of a CPU 2, a memory 3 and an exposure device control circuit 4. Reference numeral 5 is an image signal. Reference numeral 8 is a photosensitive belt provided below the exposure unit 7, 10 is a driving roller, and 11 is a driven roller. The photosensitive belt 8 is made of an organic photosensitive member, and is stretched between a driving roller 10 and a driven roller 11.

Reference numeral 12 is a main charger, 13, 14, and 15 are developing devices, 16 is a cleaner, and 17 is a discharge lamp, all of which are provided facing the peripheral portion of the photosensitive belt 8. The developing devices 13 to 15 store developers of yellow, magenta, and cyan, respectively. Reference numeral 18 denotes an intermediate transfer device, which is provided near the drive roller 10. 19 is a transfer belt of the intermediate transfer device 18, 20, 21, 35 are rollers, 22 is an intermediate transfer roller, 23 is a paper transfer roller, 2
Reference numeral 4 is a paper peeling plate, and 25 is a cleaner. The intermediate transfer belt 19 is stretched around the rollers 20, 21, and 35. The intermediate transfer belt 19 stretched over is in contact with the surface of the photosensitive belt 8 between the rollers 20 and 21 in a transferable manner.

Around the intermediate transfer belt 19, an intermediate transfer roller 22, a sheet transfer roller 23, a sheet peeling plate 24, a cleaner 25 and the like are arranged inside the intermediate transfer belt 19 in the order of the transfer process from the contact position with the photosensitive belt 8. It is arranged facing the outside. Reference numeral 26 is a sheet, 27 and 28 are sheet cassettes, 29 and 30 are sheet feeding rollers, and 31 is a timing roller, which are arranged on the sheet feeding side with respect to the intermediate transfer device 18. Further, 32 is a carrying belt, 33 is a fixing device, and 34 is a paper discharge unit, which are provided on the paper discharge side of the intermediate transfer device 18.

In FIG. 5, 36 is a laser oscillator, 37 is a motor, and 38 is a rotary polygon mirror. 39 is a laser beam,
Reference numeral 40 is a scanning line, 41 is an image forming point, and 42 is a lens. The laser projected from the laser oscillator 36 is condensed by the lens 42, and the laser beam 39 is irradiated (image-exposed) onto the photosensitive belt 8 through the rotary polygon mirror 38 to form an image at the image forming point 41. Then, the rotating polygon mirror 38 is rotated by the motor 37.
When is rotated, an electrostatic latent image of a pixel is formed on the scanning line 40 of the photosensitive belt 8. FIG. 6A shows a recording state of pixels on one scanning line recorded on the paper 26. In addition, in FIG.
(b), (c) and (d) show waveform diagrams of the image signal having the pulse width T of one scanning line of yellow, magenta and cyan, respectively.

The operation of the conventional device having such a configuration will be described below. First, the photosensitive belt 8 is once discharged by the discharging lamp 17 and then charged by the main charger 12. Next, the CPU 2 of the control unit 6 of FIG. 4 first reads the yellow pixel information stored in the memory 3, and the image signal 5 is sent to the exposure unit control circuit 4. The exposure device 7 exposes the latent image with the irradiation amount of the laser beam 39 proportional to the pulse width T of the image signal 5 as shown in FIG. 6B, and based on the yellow pixel information on the photosensitive belt 8. A latent image is formed.

The formed latent image is developed by the developing device 13 to form a yellow toner image. The yellow toner image is the voltage applied between the intermediate transfer roller 22 and the driving roller 10,
The image is transferred from the photosensitive belt 8 to the intermediate transfer member 19. The transfer portion on the photosensitive belt 8 is sent to the cleaner 16, and the residual toner after the transfer is cleaned. Similarly, (c) of FIG.
And (d) the latent image is formed on the photosensitive belt 8 with the irradiation amount of the image signal 5 having the same pulse width T, and the developing devices 14, 15
Then, the magenta and cyan toner images are sequentially developed and then transferred onto the intermediate transfer member 19 in an overlapping manner.

When the transfer of the intermediate transfer member 19 for each color component is completed, the paper 26 delivered from the paper cassette 27 or 28 is carried to the intermediate transfer device 18. When the conveyed paper 26 passes between the paper transfer roller 23 and the roller 35, a voltage is applied between the two rollers 23 and 35, and the toner image in which the respective color components are mixed is transferred again to the paper 26 side. . The paper 26 is peeled from the intermediate transfer body 19 by the paper peeling plate 24 and sent to the fixing device 33 to fix the mixed color toner image. Further, the transfer portion of the intermediate transfer body 19 is sent to the cleaner 25, and the residual toner is cleaned.

[0009]

[Problems to be Solved by the Invention] This type of intermediate transfer member 1
In a color photographic recording apparatus that retransfers multiple toner images of respective color components onto the paper 26 via the intermediate transfer member 19,
Adhesive forces such as van der Waals force act strongly between the molecules of the toner transferred to.
On the other hand, the conventional color electrophotographic recording apparatus, as described above,
The toner image of the latent image exposed with the same irradiation amount is developed by using the image signal 5 having the same pulse width regardless of the transfer order of the paper 26. Therefore, residual toner is generated when transferring from the intermediate transfer member 19 to the paper 26. Therefore, there is a problem in that the toner amounts of the color components of the mixed colors transferred to the paper 26 side are different and the reproducibility of the hue transferred on the paper 26 is reduced.

It is an object of the present invention to obtain a color electrophotographic recording apparatus which has a constant toner amount of each color component transferred onto a sheet and has excellent hue reproducibility.

[0011]

SUMMARY OF THE INVENTION The present invention attaches color toner to a latent image formed on a photoconductor by irradiating a light beam modulated into an image signal for each color component, thereby forming a toner for each normal color component. In a color electrophotographic recording apparatus that develops an image and transfers the developed toner images for each color component onto the intermediate transfer member in sequence, retransfer to the paper and fix it to record a color photograph. The amount of light emitted by the light beam during the latent image formation of the toner image that first transfers the toner image for each color component to the intermediate transfer member, and the light beam during the latent image formation of the toner image of the color component that is subsequently transferred. The color electrophotographic recording apparatus is provided with a light amount increasing means for increasing the irradiation light amount.

[0012]

In the color electrophotographic recording apparatus according to the present invention, the irradiation light amount at the time of forming the latent image of the toner image first transferred to the intermediate transfer member is the irradiation amount of the pixels at the time of forming the latent image of the toner image of the color component transferred thereafter. A large amount of light is selected. Therefore, the first toner amount that adheres to the photoconductor and develops the latent image increases almost in proportion to the irradiation light amount of the pixel when the latent image is formed, and the first toner amount that remains on the intermediate transfer member after being transferred to the sheet. The amount corresponding to the toner amount is compensated. As a result, the toner amount of each color component transferred to the paper becomes constant, and the reproducibility of the hue of the primary color becomes good.

[0013]

【Example】

Example 1. An embodiment of the present invention will be described below with reference to FIG. FIG. 1 is a block diagram of a control unit of an electrophotographic recording apparatus according to an embodiment of the present invention, and FIG. 2A is an explanatory diagram showing an array state of pixels of each color component of an image on one scanning line recorded on a sheet, 2B to 2D are waveform diagrams of yellow, magenta, and cyan image signals corresponding to FIG. 2A.

In FIG. 1, 2 is a CPU, 3 is a memory,
Reference numeral 5 is an image signal, and 4 is an exposure device control circuit. The respective parts such as the CPU 2 and the configurations of FIGS. In particular, in the present invention, the image signal generation circuit 9 is provided in the output circuit of the CPU 2, and the control unit 6 is configured by the above-mentioned respective units such as the CPU 2 including the image signal generation circuit 9.

The operation of the embodiment of the present invention having such a configuration will be described below.
It will be described next. The CPU 2 reads the pixel information of each color component stored in the memory 3, and outputs the pixel information of each color component to the image signal generation circuit 9. The image signal generation circuit 9 sets the pulse width based on the input pixel information of each color component including the transfer order of the paper 26, generates the image signal 5 and sends it to the exposure device control circuit 4. The exposure device control circuit 4 controls the exposure device 7 according to the input image signal 5 to perform the following color recording operation.

When recording red of the first pixel on the scanning line of FIG. 2A, a yellow image signal 5 and a magenta image signal 5 are output. In the present invention, when the pulse widths T1 and T2 have a relationship of T1> T2, the image signal generating circuit 9
A yellow image signal 5 having a pulse width T1 shown in FIG.
And a magenta image signal 5 having a pulse width T2 shown in FIG.

Here, the yellow toner transferred first on the paper 26 and the magenta toner transferred next on the paper 26 have the same amount of N, and
The amounts of yellow and magenta toner remaining on the intermediate transfer body 19 after the transfer onto the paper 26 are N1 and N2. Since the adhesive force such as the Van der Waals force described above acts on the toner image first transferred to the paper, the following 2 are added to N1 and N2.
There is a relationship like two expressions. N1 >> N2 (1) N2 → 0 (2)

The amount of toner adhering to the latent image on the photosensitive belt 8 and the amount of toner transferred to the intermediate transfer member 19 are the irradiation light amount of the light beam when the latent image is formed on the photosensitive belt 8, that is, the pulse of the image signal 5. Increase or decrease corresponding to the widths T1 and T2. In addition, the transfer efficiency of the toner image transferred from the photosensitive belt 8 to the intermediate transfer member 19 can be regarded as substantially the same for each color component.
Therefore, the following equation (3) is established. T1 / T2 = (N + N1) / N (3)

From the equation (3), if the pulse width of the yellow image signal to be transferred first is T1, then T1 = [(N + N1) / N] × T2 (4) is selected and retransferred to the paper 26. It is possible to set the amount of yellow toner which is the same as N to the amount of magenta toner.
The same operation is performed after "blue" of the second pixel in FIG. 2 and the toner amounts of the two color components retransferred to the paper 26 become constant. Therefore, according to the present invention having such a configuration, it is possible to obtain an image quality with excellent color reproducibility of the original color image.

In the above-described embodiment of the present invention, the case where two color toners are superposed and transferred on the intermediate transfer member has been described as an example, but the present invention is also applicable to the case where three or more color toners are superposed one after another. The invention can be applied. Although the laser oscillator is used as the light source for exposure, a light beam from a light source such as an LED array may be used.

[0021]

The electrophotographic recording apparatus according to the present invention is
A configuration is such that the irradiation light amount at the time of forming a latent image of the toner image that first transfers the toner image of each color component from the photoconductor to the intermediate transfer member is larger than the irradiation light amount at the time of forming the latent image of the toner image of the component that is transferred subsequently. did. As a result, the amount of toner of each color component transferred to the paper becomes equal, and an image quality with excellent color reproducibility of the original color image can be obtained.

[Brief description of drawings]

FIG. 1 is a block diagram of a control unit of an electrophotographic recording apparatus according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram of a recording operation of the electrophotographic recording apparatus according to the embodiment of the present invention.

FIG. 3 is a diagram illustrating a configuration of a conventional electrophotographic recording device.

FIG. 4 is a block diagram of a control unit of a conventional electrophotographic recording apparatus.

FIG. 5 is a configuration explanatory view of an exposure device of a conventional electrophotographic recording apparatus.

FIG. 6 is an explanatory diagram of a recording operation of a conventional electrophotographic recording device.

[Explanation of symbols]

 1 Device Frame 5 Image Signal 7 Exposure Device 8 Photosensitive Belt 9 Image Signal Generation Circuit (Light Quantity Increasing Means) 18 Intermediate Transfer Body

Claims (1)

[Claims] 1. A color toner is adhered to a latent image formed on a photoconductor by an image signal for each color component to sequentially develop a toner image for each color component, and the developed toner image for each color component is formed. In a color electrophotographic recording apparatus that sequentially superimposes on an intermediate transfer member, retransfers to a sheet, fixes and records the image, when forming an electrostatic latent image of a toner image transferred first from the photosensitive member to the intermediate transfer member. A color electrophotographic recording apparatus comprising a light amount increasing means for increasing an image exposure amount over an image exposure amount of a toner image of a color component to be subsequently transferred.