JPH07114241A - Color image forming device - Google Patents

Abstract

PURPOSE:To satisfactorily print in terms of reproducibility even on paper in dull color or colored paper by printing white on the entire surface of recording paper by the use of a white-printing means in advance, then, developing image data, outputted from an optical writing unit in order, in respective colors and transferring and fixing the colors to the surface of the recording paper. CONSTITUTION:When the recording paper passes a photosensitive drum 103W for white printing situated uppermost stream side in the carrying direction, white toner is uniformly transferred to the entire surface of the recording paper to obtain a base color. After this, black, magenta, yellow and cyan are transferred in that order by photosensitive drums 103Bk, 103M, 103Y and 103C, respectively, arranged downstream. By uniformly applying the white toner to the entire surface of the recording paper before the transfer of the black, magenta, yellow and cyan toners, inputted image-data colors are satisfactorily printed on the recording paper in terms of reproducibility, regardless of whether the base color of the recording paper is white or not.

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 digital color copying machine or a color printer for forming a color image on a recording sheet based on input image data, and particularly to whether or not the recording sheet is white. The present invention relates to a color image forming apparatus capable of printing an appropriate color regardless of the color and adjusting the amount of toner used to an optimum value according to the color of paper.

[0002]

2. Description of the Related Art In a color image forming apparatus using an electrophotographic process such as a color copying machine and a color printer, yellow (Y), magenta (M), cyan (C) and black which are three primary colors of printing are used. A color printed image is obtained by the colored bodies of four colors to which (Bk) is added. That is, the image data of light is radiated from the optical writing unit for each color on the surface of the photoconductor that has been uniformly charged in advance by the charging device to form an electrostatic latent image. Toner images of different colors are individually applied from the developing devices provided for the respective electro-latent images to form toner images, and then the toner images are transferred and fixed onto recording paper to form images. It is a thing. More specifically, the image data is obtained by, for example, receiving the reflected light of the original obtained by illuminating the surface of the original set on the contact glass with the light source by the color image reading device.
The three color separation lights of lue, green and red are read respectively, and image calculation processing is performed based on the intensity level of each color light to obtain write data for each color of Y, M, C and Bk. . In addition to the image data obtained from the reflected light of the document, other color image processing systems (for example, color facsimile, word processor,
There is image data output from a personal computer or the like). The optical writing unit is, for example, a semiconductor laser or L
It is composed of an ED array, an LCD array, etc. First, optical writing is performed based on Y image data at the first rotation of the photoconductor, and Y toner is applied to the latent image for Y color by the Y developing device. Subsequently, optical writing based on the M image data is performed in the second rotation, and M toner is applied to the latent image for M color by the M developing device. Further, the toner images on the photoconductor are increased one by one for each rotation of C, Bk and the photoconductor. The toner images containing the respective colors of Y, M, C, and Bk thus obtained are transferred onto the recording paper and finally fixed, whereby the recording paper is ejected to the outside of the machine.

In the above description, the case where a developing device dedicated to each color is arranged around one photosensitive member has been described, but there is also a color image forming apparatus having a photosensitive member and a developing device for each color. By the way, in the above-described conventional color image forming apparatus, when four colors of Y, M, C, and Bk are used as color bodies, it is premised that the printing surface of the recording paper as the recording medium is white. ing. Therefore, in the conventional color image forming apparatus, in many cases, a recording paper dedicated to color printing which is optically close to white is used, and the color of the original image cannot be accurately reproduced unless the dedicated recording paper is used. There was a drawback. In addition to this, although the printing quality of the dedicated recording paper is excellent, the cost is high. Also, when a color image is formed on a recording paper other than white, for example, blue recording paper, blue is likely to become darker by the color of the background of the paper, so the gradation of blue in the input image is printed accurately. I couldn't.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above, and prints with good reproducibility even when the recording paper is a color other than white, and the toner usage amount is set to an optimum value according to the color of the paper. It is an object of the present invention to provide a color image forming apparatus capable of performing printing with good reproducibility even on dull colored paper or colored paper by adjusting the above and reducing the printing cost.

[0005]

In the color image forming apparatus according to the present invention, white is printed in advance on the entire recording paper by the white printing means, and subsequently the image data sequentially output from the optical writing unit is developed for each color and finally the image data is developed. Transfer and fix onto recording paper. For this reason, for example, since the blue recording paper is changed to white and then printing is performed, it is possible to print the blue gradation according to the input image. In the color image forming apparatus according to claim 2, when the recording paper is fed, the sensor reads the background color of the recording paper surface, and the image data input based on the data relating to the type and shade of the recording paper color. Is calculated, and the developing device and the like are controlled so as to adjust the print density of each color including white. For example, when printing blue on blue recording paper, if you apply blue toner without considering the density of the background, the printed part of blue becomes darker than the original image, but the density of blue, which is the background color, is reduced. Since the toner adhesion amount is reduced so as to obtain the subtracted density, the color reproducibility can be improved. That is, it is possible to express the gradation as an input image even on a recording paper having a color other than white, and further, the white toner is transferred to the entire surface of the recording paper. The amount of white toner can be significantly reduced. In the apparatus according to claim 3, when the user of the apparatus does not want to print white on the recording paper surface for reasons such as intentionally using a colored recording paper for the purpose of special visual effect, the mode is set. A mode in which white printing is not performed can be selected by the switching means.

[0006]

In order to achieve the above object, the present invention is a color image forming apparatus for forming an image based on image data from an image data inputting means and printing on a recording paper, in a black printing means and a magenta printing means. In addition to the yellow printing unit and the cyan printing unit, a white printing unit and a control unit for controlling these printing units are provided, and the control unit controls the entire surface of the recording paper by the white printing unit before forming an image on the recording paper. In a color image forming apparatus that controls to print in white, forms an image based on image data from the image data input unit, and prints on a recording paper, a black printing unit, a magenta printing unit, a yellow printing unit,
In addition to the cyan printing unit, a white printing unit, a color detection unit that reads the color of the recording paper, a color correction calculation unit that calculates the optimum toner density based on the relationship between the background color and the density of the recording paper, and these prints. 3. The color image forming apparatus according to claim 2, further comprising a control unit for controlling the means, wherein the color correction calculation unit adjusts the usage amount of the toner of each color to an optimum value according to the color and density of the recording paper. A feature is that a mode for printing white and a mode for not printing white are provided so that both modes can be selected.

The present invention will be described in detail below with reference to the accompanying drawings. FIG. 1 is a schematic structural explanatory view of a color image forming apparatus according to a first embodiment of the present invention.
An image data input unit 101 for inputting image data read by a scanner unit (image reading device) 100 or image data sent from a host computer or the like;
A light emitter control unit (not shown) that generates a control signal based on the image data from the input unit 101 (or a control unit that controls the entire apparatus), and a white W that emits light based on the control signal from the light emitter control unit. , Black Bk, magenta M, yellow Y, cyan C five optical writing units 102W, 1
02Bk, 102M, 102Y, 102C and the photoconductor drums 103W, 103Bk, 103M, 103 arranged corresponding to the respective optical writing units 102W-102C.
Y, 103C and developing units 104W, 104Bk, 10 arranged corresponding to the respective photosensitive drums 103W-103C.
4M, 104Y, 104C and the recording paper fed from the paper feed unit 105 are conveyed to the transfer positions of the respective photoconductor drums, and the toner images of the respective colors on the respective photoconductors are sequentially transferred to the predetermined positions on the recording paper. It has a belt 106, a fixing device 107 that receives the recording papers to which all colors have been transferred from the conveying belt 106, and heats and presses the recording papers to fix the toner image, and a discharge tray 108 that receives the recording papers that have been fixed and discharged. .

The image data input from the image data input unit 101 to the light emitter control unit is image-calculated based on the intensity levels of the blue, green, and red color-separated lights as described in the description of the conventional example. By receiving the processing, the writing data for each color of Y, M, C, and Bk is obtained and is output to each of the optical writing units 102W to 102C. The light emitter control unit controls the light amount of each optical writing unit based on this data to form an electrostatic latent image for each color on each photoconductor drum 103W to 103C. By attaching toner to the electrostatic latent image, toner images of respective colors are formed on the respective photosensitive drums. Toner images are sequentially transferred when the recording paper conveyed on the conveyance belt 106 to the left in the drawing passes the transfer position of each photoconductor. The recording paper on which the toners of all colors have been transferred is fixed and then ejected.

The characteristic construction of the first embodiment of the present invention is that when the recording paper passes through the photosensitive drum (white printing section) 103W for white printing, which is located on the most upstream side in the transport direction, the entire surface of the recording paper is After uniformly transferring the white toner to the background color to form the background color, the photosensitive drums 103Bk sequentially arranged on the downstream side,
Black, magenta, yellow, and cyan are sequentially transferred by 103M, 103Y, and 103C. In this way, by applying the white toner uniformly on the entire surface of the recording paper before transferring the toners of black, magenta, yellow, and cyan, it is possible to input regardless of whether the background color of the recording paper is white or not. The color of the generated image data can be formed on the recording paper with good reproducibility.

Next, FIG. 2 shows an image forming apparatus according to a second embodiment of the present invention. The same parts as those of the embodiment of FIG. 1 are designated by the same reference numerals, and a duplicate description will be omitted. A characteristic is that a color correction calculation unit (density calculation unit) 110 is attached to the data input unit 101, and a color detection unit 111 that detects the color of the recording paper fed to the paper feed unit is provided. The image data read from the scanner unit 100 or the image data from the host machine is input to the image data input unit 101 as in the apparatus shown in FIG. 1, but in this embodiment, the data is once a color correction calculation unit. 110 is input. Further, the data regarding the color of the recording paper obtained by the color detection unit 111 is also input to the color correction calculation unit 110. Color correction calculator 110
Calculates the image data and the data relating to the color of the recording paper on a pixel-by-pixel basis based on the algorithm of FIG. 3 to determine Bk, M, Y, C and white toner densities, respectively. The light emitter control unit controls the light amount of the optical writing unit based on the thus obtained data regarding the toner density for each color, and forms an electrostatic latent image on each of the photoconductor drums 103W to 103C. By sequentially applying toner of each color from each of the developing devices 104W to 104C to these electrostatic latent images, an amount of toner corresponding to the background color of the recording paper is applied. Can be saved.

As shown in FIG. 3, for black, magenta, yellow, and cyan, it is judged whether or not the value obtained by subtracting the density of the recording paper from the density value of the input image (color) is smaller than "0", and it is small. In this case, the white density is maximized and the print density is the input density. For example, in the case of printing a cyan color that is lighter than the cyan background color, the white toner is once attached to the printed portion, and then the cyan toner having the density according to the primary color is applied. If it is larger than "0", the print density is calculated by the formula "input density-paper density".
In other words, for example, when printing a cyan color that is darker than the ground color on a recording paper having a cyan ground color, the cyan toner is applied so as to compensate for the darker color than the ground color.

Next, in each of the above-mentioned embodiments, the case where the white toner is uniformly applied is shown. However, when the recording paper is white or the user of the apparatus intentionally aims for a special visual effect. When there is a circumstance such as when a colored recording paper is used, it is not desired to print white on the recording paper surface. Therefore, in such a case, the mode switching unit may be configured to realize a mode in which white printing is not performed. In this case, a control program stored in a storage unit such as a ROM of a control unit (not shown) may be created so as to enable mode switching as described above. That is, the device of the embodiment of FIG.
The apparatus of the second embodiment is provided with a selection switch as to whether or not to print white, respectively, and the operator can arbitrarily switch between the white printing mode and the other printing modes by operating this switch. To configure. In the claims, the printing means is a concept including an optical writing unit, a photoconductor, and a developing device. Further, it goes without saying that each component of the image forming apparatus is controlled by a control unit (not shown).

[0013]

As described above, according to the present invention, white printing means (optical writing unit 102W, photoconductor 103W, developing unit 104W) prints white on the entire recording paper in advance, and then the optical writing unit Since the image data that is sequentially output is developed for each color and finally transferred and fixed on the recording paper, it is possible to print the blue gradation according to the input image even on the blue recording paper. Further, it is not necessary to use a recording paper dedicated to color printing, which is expensive and has a color close to white. Further, in the color image forming apparatus according to claim 2,
When the recording paper is fed, the background color of the recording paper is read by the sensor, the input image data is calculated on the basis of the data relating to the type and shade of the recording paper, and the color of each color including white is calculated. The developing device and the like are controlled so as to adjust the print density. For example, when blue is printed on blue recording paper, if the blue toner is applied without considering the density of the background, the printed part of blue becomes darker than the original image, but the density of blue, which is the background color, is reduced. Since the amount of toner is reduced so as to obtain the subtracted density, color reproducibility can be improved. That is, it is possible to express the gradation according to the input image even on the recording paper having a color other than white, and the white toner is transferred to the entire surface of the recording paper. The amount of white toner can be significantly reduced. In the apparatus according to claim 3, when the user of the apparatus does not want to print white on the recording paper surface for reasons such as intentionally using the recording paper with a color intended for a special visual effect, the mode is set. A mode in which white printing is not performed can be selected by the switching means.

[Brief description of drawings]

FIG. 1 is a schematic configuration explanatory diagram of a color image forming apparatus according to a first embodiment of the present invention.

FIG. 2 is a schematic configuration explanatory diagram of a color image forming apparatus according to a second embodiment of the present invention.

FIG. 3 is a flowchart showing an algorithm in control of the second embodiment.

[Explanation of symbols]

100 scanner unit (image reading device), 101 image data input unit, 102 (102W, 102Bk, 102)
M, 102Y, 102C) Optical writing unit, 103
(103W, 103Bk, 103M, 103Y, 103
C) photoconductor drum, 104 (104W, 104Bk,
104M, 104Y, 104C) developing device, 105 paper feed unit, 106 transport belt,

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI Technical display location H04N 1/407 1/46 4226-5C H04N 1/40 101 B 4226-5C 1/46 Z

Claims (3)

[Claims] 1. A color image forming apparatus for printing an image formed on the basis of image data from image data inputting means on a recording paper, in addition to black printing means, magenta printing means, yellow printing means, cyan printing means, and white A printing unit and a control unit for controlling these printing units;
The color image forming apparatus, wherein the control unit controls the white printing means to print the entire surface of the recording paper in white before forming an image on the recording paper. 2. A color image forming apparatus for printing an image formed on the recording paper based on image data from an image data inputting means, in addition to black printing means, magenta printing means, yellow printing means, cyan printing means, white A printing unit, a color detection unit that reads the color of the recording paper, a color correction calculation unit that calculates the optimum toner density based on the relationship between the background color and the density of the recording paper, and a control unit that controls these printing units. A color image forming apparatus, characterized in that the color correction calculation unit adjusts the amount of toner used for each color to an optimum value according to the color and density of the recording paper. 3. The color image forming apparatus according to claim 2, further comprising a switching unit for switching between a mode for printing white and a mode for not printing white so that both modes can be selected. apparatus.