JP2911511B2 - Multicolor image forming device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multicolor image forming apparatus suitably implemented in, for example, an electrophotographic or thermal transfer printer.

[Conventional technology]

FIG. 8 shows a full-color electrophotographic copying machine which is a multicolor image forming apparatus as a prior art.

The photosensitive drum 1 having a photosensitive layer for electrophotography on its surface is driven to rotate in the direction of the arrow x. A primary charger 2 is disposed on the left side of the photosensitive drum 1, a surface voltmeter 3 for measuring a potential on the surface of the photosensitive drum is disposed diagonally below and to the left of the photosensitive drum 1, and a toner and a carrier are disposed directly below the photosensitive drum 1. Developing units 101M and 10 using a two-component developer mixed with
1C, 101Y, and 101Bk are loaded, and a developing device 100 that can move in the left-right direction is disposed. A transfer device 5 is disposed diagonally above and to the right of the photosensitive drum 1; A front static eliminator 6 for reducing the adhesion of the toner remaining on the surface of the drum 1 to the drum to facilitate cleaning is disposed, and a cleaning device 7 is disposed diagonally above and to the left of the photosensitive drum 1.

An optical system 10 is disposed above the copying machine, and the original image on the platen 28 is scanned by the primary charger 2 and the surface voltmeter 3.
Is configured to project onto the photosensitive drum 1 by the exposure unit 9 located between the two. The optical system 10 includes a first scanning mirror 11,
Second and third scanning mirrors 12 and 13, which move in the same direction at half speed with respect to the first scanning mirror 11, an imaging lens 14, a CCD 15 integrated with B, G, and R filters, and a laser scanner unit 16 , And fixed mirrors 17 and 18.

In the optical system 10, the original illumination light source 20 is configured to move together with the first scanning mirror 11. Therefore,
The reflected light images of the document scanned by the first to third scanning mirrors 11, 12, and 13 pass through a lens 14, are color-separated by a CCD 15 equipped with a BGR4 color separation filter, are converted into electric signals, and are converted into electric signals. After the information signal has undergone information processing such as A / D conversion, it is sent as a video signal to a microprocessor unit (hereinafter, MPU) for controlling the entire copying machine. The MPU oscillates laser light from the laser unit via the laser driver based on this signal, and this laser light
Start the copy sequence while turning on / off.

Further, a fixing device 20 and a paper feeding device 30 are provided on the right side of the copying machine.
Are arranged, and the transfer drum 5, the fixing device 20, and the sheet feeding device
Transfer paper transport systems 25 and 35 are provided between the transfer paper transport systems 25 and 35, respectively.

In the above configuration, the photosensitive drum 1 is charged, exposed, developed, transferred, and cleaned for each color separated by the CCD 15 in the primary charger 2, the optical system 10, and the developing device 10.
0, the transfer is performed by the transfer device 5 and the cleaning device 7.

The developing unit 100 includes developing units 101M (magenta developing unit), 101C (cyan developing unit), 101Y (yellow developing unit),
101Bk (black development unit) is provided, and the color-separated latent images of each color are visualized by the corresponding development units.

The transfer device 5 typically includes a transfer material, that is, a transfer paper P
And a transfer drum 5b provided with a gripper 5a for gripping.
The transfer device 5 grips the leading end of the transfer paper P fed from the transfer paper cassette 31 or 32 of the paper feed device 30 via the transfer paper transport system 35 with the gripper 5a, and sucks the suction paper disposed inside the transfer drum 5b. The transfer paper P is attracted to the transfer drum 5b by the action of the charger 4, and is rotated and transferred so as to transfer a visual image of each color on the photosensitive drum 1. A transfer charger 5c is arranged inside the transfer drum 5 in the transfer area.

The transfer paper P on which the visible image of each color, that is, the toner image is sequentially transferred is released from the gripper 5a, and is separated from the transfer drum 5b by the separation charger 8 and the separation claw 8 '. Next, the transfer paper P is sent to the fixing device 20 by the transfer paper transport system 25. The toner image on the transfer paper P is fixed on the transfer paper by the fixing device 20, and then the transfer paper is discharged onto the tray 23.

[Problems to be solved by the invention]

However, in the above conventional example, in order to reduce the size of the copying machine, the diameter of the transfer drum 5b cannot be increased, so that the transfer paper transport system 35 and the transfer paper transport system 25 after transfer separation are performed.
Are not arranged on the photosensitive drum 1 with sufficient separation in the rotation direction of the transfer drum 5b. That is, since the suction position and the separation position of the transfer paper P are provided at positions that are not sufficiently separated in the rotation direction of the transfer drum 5b from the transfer position of the image, there are the following disadvantages.

1) As shown in FIG. 3A, when the transfer sheet P is a relatively large transfer sheet such as A3 sheet, the transfer sheet constituting the side surface of the transfer drum 5b is pressed by the transfer sheet P. At this time, vibration is applied to the photosensitive drum 1, and the formation of the latent image of the first color is shifted from the latent images of the other colors.

2) As shown in FIG. 3 (b), the transfer image of the first color is
The transfer sheet and the transfer paper P are not sufficiently adhered to each other, so that the transfer sheet P deviates from an image of another color.

3) As shown in FIG. 3 (c), transfer paper P is transferred to transfer sheet 5b.
When the image is separated from the image, vibration is transmitted to the formation of the latent image of the final color, and the transfer position is shifted, so that the transferred image of the final color is also shifted from the latent image of another color.

As shown in FIG. 4A, the image formation pattern of the first color is caused by the image deterioration due to the shift of the transfer position.
The screen angle between the image forming pattern 201 and the image forming pattern 202 of another color slightly shifts, so that a position where the two colors overlap with each other and a position where the two colors do not overlap occur in a long cycle, which is caused by color moiré and color unevenness. Appears.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above technical problems and to provide a multicolor image forming apparatus which does not cause deterioration of image quality even when image formation of each color is misaligned.

[Means for Solving the Problems] For such a purpose, according to the multicolor image forming apparatus of the present invention, a multicolor image forming apparatus that forms a color image composed of at least three color components is provided. Input means for inputting the image data of each color component, and image forming means for forming the color image by forming the image of each color component in a frame-sequential manner in accordance with the image data input by the input means. A first color component formed image of the at least three color components in which image formation is performed at least one of first and last by the image forming unit has a first screen angle; The formed image of the second and third color components of the three color components has a common second screen angle different from the first screen angle.

[Operation] With the above configuration, the overlapping portion and the non-overlapping portion are uniformly formed as shown in FIG. 4B without causing the color shift and the long-period color unevenness as shown in FIG. 4A. Therefore, a uniform image without color unevenness can be obtained even when a position shift occurs for a color for which image formation is performed first or last.

〔Example〕

Hereinafter, a multicolor image forming apparatus according to an embodiment of the present invention will be specifically described with reference to the drawings.

FIG. 1 is a view showing an image forming pattern of each color formed by a full-color copying material according to one embodiment of the present invention. In this embodiment, in order to form a four-color full-color image, a full-color image is formed by superimposing formed images of the respective colors using four-color toners. Then, as shown in FIG. 1, the screen angle (45 °) and the final color (the fourth color) in the magenta (M) image forming pattern of the first color
The screen angle (26.6 °) of the black (Bk) is different from the screen angle (0 °) of the second color cyan (C) and the third color yellow (Y), respectively.

The overall configuration of a full-color copying machine for realizing such an image forming pattern is described in the prior art (8th Edition).
Therefore, the description is omitted here, and only the configuration for forming the above-described image forming pattern will be described.

FIG. 2 is a block diagram of the image forming pattern generator of the present embodiment.

Multicolor image signal A (for example, in this embodiment, M, C,
The four types of digital signals Y and Bk) are converted into an analog signal a by the D / A converter 501 for each color component. On the other hand, a reference signal b (a triangular wave in the embodiment) determined for each color component is generated under the control of the CPU 503 using the clock divided from the high-speed clock by the pulse pattern generator 502. Further, the reference signal b is input to the delay line 506 and is delayed. Day Ray Line 506
Has eight kinds of delay patterns in the present embodiment, and the selector 507 selects one of them. (As shown in FIG. 1, eight types of delay patterns were prepared using 1/4 pixel delay as one unit of delay amount.) The selector 507 uses the CPU 503 to determine the delay pattern information for each line by using the phase change amount. It is being read from the pattern generator 504. In the present embodiment, the pattern generator 504 is a RAM, and stores delay pattern information to be selected for each line of each color. The counter 505 counts the horizontal synchronizing signal, and repeats 1 to 8 to count every line. Each time the counter 505 performs a counting operation, the selector 50 is sequentially operated in accordance with the delay pattern written in the pattern generator 504.
7 selects a delay pattern and outputs it as a reference signal C. As shown in FIG. 1, the unit of the triangular wave is one unit of two pixels (that is, the cycle of the triangular wave corresponds to two pixels), and the delay amount is one unit of 1/4 pixel. The analog signal a is compared with the reference signal c by the comparator 508, becomes the PWM signal d, is amplified by the amplifier 509, and is output as the processed signal B.

The above operation is performed for each color component, and the M component is not delayed for odd-numbered lines, and is delayed for 4/4 pixels for even-numbered lines, so that an image is formed at a screen angle of 45 ° (FIG. 1 (a) )), The C and Y components are imaged without delay for all runs, that is, at a screen angle of 0 ° (first image).
(B) and FIG. 1 (C)), the Bk component has no delay for the (i + 1) th line (i = 0, 1, 2,...), A delay of 2/4 pixel for the (i + 2) th line, and a delay for the (i + 3) th line. Is 4/4
With respect to the (i + 4) th line with a pixel delay, image formation is performed at a screen angle of 26.6 ° with a 6/4 pixel delay (FIG. 1 (d)). In this way, each color is output as a multiplex image by the above-described full-color copying machine.

In this way, by setting the screen angles for forming the first and fourth colors to be different from the screen angles of the second and third colors, it is possible to eliminate color unevenness and the like as shown in FIG. 4 (b). Can be.

[Other Embodiments] The present invention is not limited to a four-color full-color image as in the first embodiment, but is effective in all cases of outputting a multicolor image of two or more colors.

FIG. 5 shows an example of an image forming pattern at the time of forming a full-color image of three colors of M, C, and Y. FIGS. 6 and 7 show M + C (B), C
An example of an image forming pattern in a two-color multiplex image such as + Y (G) or Y + M (R) is shown.

These images can be output using the configuration of the image forming apparatus in the first embodiment as it is.

Further, the present invention is not limited to the electrophotographic system as in the embodiment, but is effective for all apparatuses that form a multiplex image of two or more colors, such as a thermal transfer printer, an LED printer, and an ink jet printer. .

〔The invention's effect〕

As described above, in the case where image formation of at least three color components is performed in a frame-sequential manner, at least the second and third color components of the first color component in which the image formation is performed at least at the first or last time. Since the image formation is performed at a screen angle different from the common screen angle in the image formation of the color components of the color components, color shift, occurrence of color unevenness, and printing are performed for at least one of the first and last colors. It is possible to suppress a change in color every time the image is reproduced, and to stabilize the image quality at all times.

[Brief description of the drawings]

FIG. 1 is a diagram showing an image forming pattern of each color according to an embodiment of the present invention, FIG. 2 is a block diagram showing a structure for creating the image forming pattern shown in FIG. 1, and FIG. Transfer paper P in full color copier
FIG. 4 is a diagram for explaining a state in which paper is fed to the copying drum 5b, FIG. 4 is a diagram for explaining the problems of the prior art and the effects of the present invention, and FIG. 5 to FIG. FIG. 8 is a diagram showing an image forming pattern of each color in the embodiment. FIG. 8 is a cross-sectional view showing the overall configuration of a full-color copying machine which is a multi-color image forming apparatus. 501 ... D / A converter 502 ... Pulse pattern generator 503 ... CPU 504 ... Phase change amount pattern generator 505 ... Counter 506 ... Delay line 507 ... Selector 508 ... Comparator 509 ... Amplifier

Continued on the front page (72) Inventor Masataka Yamada 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (72) Inventor Hajime Suzuki 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (72) Inventor Katsuhito Kato 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (56) References JP-A-61-189774 (JP, A) JP-A-61-213820 (JP, A JP-A-62-42693 (JP, A) JP-A-3-177885 (JP, A) JP-A-2-244047 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) B41J 2/525 B41J 5/30 H04N 1/23 H04N 1/40

Claims (1)

(57) [Claims] 1. A multicolor image forming apparatus for forming a color image composed of at least three color components, comprising: input means for inputting image data of each color component; and the image input by the input means. An image forming means for forming the color component image in a plane-sequential manner in accordance with data, and forming the color image, wherein the image formation is performed at least one of first and last by the image forming means. The formed image of the first color component of the at least three color components has a first screen angle, and the formed images of the second and third color components of the at least three color components are the same as the first screen angle. A multi-color image forming apparatus having a different common second screen angle.