JPS58168057A - Method and apparatus for forming color image - Google Patents

Abstract

PURPOSE:To enable formation of a high quality copy of an original contg. black characters at high speed, by using an electrophotographic method for the black part of the original and an ink jet method for the colored part. CONSTITUTION:An original is set on an original placing stand, exposed to light, and the reflected light is passed through each of red, green, and red filters, and each color separated image is read with each sensor having sensitivity to each color, respectively, to store each color information except black image information. Then, only the black part of the original is copied, and each color image other than the black image is reproduced on the recording paper on which only the black image is copied, by ejecting each of cyan, magenta, and yellow inks from the corresponding ink jets in accordance with the stored image information.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a color image forming method and apparatus, and more particularly to a color image forming method and apparatus for copying a color original.

Conventionally, electrophotographic methods and inkjet methods have been typically used to form color images.

In the electrophotographic method, a color original is generally color-separated using red, green, and blue color filters, and a latent image is formed in each separated color on a charged photosensitive drum corresponding to the original, and this is developed. After the image is transferred to recording paper, a similar process is performed for each color to reproduce a color image. In this case, the black portion of the document is reproduced by mixing cyan, magenta, and yellow toners, resulting in color shift and other problems, resulting in poor reproducibility. Especially for office manuscripts, etc.
Since most of it is black, it poses a big problem in practical terms.

On the other hand, in a color image forming method using an inkjet method, a document is color-separated using a color filter or the like, and amounts corresponding to the intensities of the colors are stored in a memory. After that, ink is ejected from each color nozzle according to the contents of the memory to reproduce a color image. In this method, the black parts of the document can be calculated by performing logical calculations during the color separation process. For other colors, if ink is not ejected from the nozzle, it is possible to reproduce an image that is easy to see without any color shift in black areas.

However, this method requires a large amount of memory to color separate the original and store the image information, and especially in the case of office manuscripts where most of the parts are written in fine print, bandwidth compression is required. However, it does not significantly reduce the amount of memory required.

Another drawback is that it takes time to form a copied image because each nozzle scans the surface of the paper to be copied.

Therefore, the present invention has been made in order to eliminate such conventional drawbacks, and provides a color image forming method and its method that can reproduce high-quality color images at high speed without requiring a large number of memories. The purpose is to provide equipment.

In order to achieve this objective, the present invention combines an electrophotographic method and an inkjet method, and uses the electrophotographic method for black portions of a document, and ejects ink corresponding to each color for colored portions. It was used in a configuration to reproduce each color and form a color image.

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 shows the principle of the color image forming method according to the present invention as a block diagram. First, in step S1, an original is set on the document table, and then in step S2, it is passed through red, green, and blue color filters. A sensor sensitive to each color reads the color image of the document. A circuit for implementing this is illustrated in FIG. 2, where each red filter 1
, a green filter 2, and a blue filter 3, the light passes through a sensor (for example, composed of a CCD) 1a that senses each color.
+2a and 3a are read, and when the amount of light of each color exceeds a predetermined value, a signal of "0" is generated, which is the Nantes gate 4 and the AND gate 1b.

2b and 3b, respectively, and the cyan color memory 5a.

The data are stored in the magenta color memory 5b and the yellow color memory 5C, respectively. In this case, each memo J5a to J5C stores information obtained by removing black image information from the image information when the image is passed through the red filter 1, green filter 2, and blue filter 3. This corresponds to step S3 in FIG.

Subsequently, as shown in step S4, only the black portion of the original image is copied using a normal electrophotographic method. Subsequently, cyan, magenta, and yellow color inks are ejected by an inkjet according to the signals stored in the respective memories onto the recording paper on which only black has been copied, thereby reproducing an image other than black (step 55-).

The third device embodies this color image forming method.
Illustrated in the figure. In FIG. 3, a color original 10 containing black characters is placed on an original platen 12, this original 10 is illuminated by a light source 13, and the original surface is scanned by an optical system or by moving the original. Also, below the document table is an image sensor 14 equipped with red, green, and blue color filters.
(corresponding to filters and sensors 1-3 and 1a-3a in FIG. 2) are placed and the colored portions of the image are read.

The read image information is a logic circuit (corresponds to the circuit in Figure 2)
After the black information is removed in step 31, the information is separated into cyan, magenta, and yellow color information, and stored in the memory 15 corresponding to each memory ζ2 in FIG.

Further, at the same time, the light irradiated onto the document table 12 passes through the optical system 32 and forms an image on the photoreceptor 17. This photoreceptor 11 is constructed by depositing about 40μWL of Se-Te vapor deposited on a cylindrical aluminum base 16, and the weight ratio of Te is about 20%. It has become a characteristic.

This photoreceptor 17 is charged approximately +500 by the corona charger 18.
It is charged to approximately V, and is then exposed to light by the image of the document passing through the slit 33 as the drum rotates.

At this time, the potential of the portion not irradiated with light, that is, the black portion of the document, is +400V, and the potential of the portion irradiated with the negative end is about +100V or less. The electrostatic latent image thus formed is visualized by a developing roller 19 to which developing toner is attached. Thereafter, the image on the photoreceptor 17 is transferred via the transfer charger 20 onto the recording paper 22 that is fed via the paper feed roller 21, and then fixed by the heat roller 27, and then transferred to the recording paper 22 fed by the paper feed roller 21. After that, it is sent to the inkjet section. After the image corresponding to the black part of the original is reproduced on the recording paper in this way, the photoreceptor 17 is cleaned by the blade 25, and then the entire surface is irradiated by the lamp 26 to remove the residual charge, and the above-mentioned process is repeated. .

Ink nozzles 28, 29, 28, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 32, 29, 32, 29, 29, 29, 29, 28, 29, 29, 29, 29, 29, 29, 29, 28, 29, 29, 28, 29, 2s and 3ssssssss. ink years, injecting cyan, magenta, and yellow ink onto the recording paper 22, which has reproduced the black characters of the original. 30 is driven by a signal from the memory 15 storing image information, images other than black characters are reproduced.

The inkjet nozzle used in this example is
For example, the one described in Japanese Patent Application Laid-Open No. 54-59936 is used, in which a 5i02 oxide film 41 is formed by thermal oxidation on the surface of a silicon wafer 40, as shown in an enlarged view in FIG. 42 is used. For example, a vapor deposited film of HfB is used as the heating element,
Both ends are connected by a vapor-deposited film of Al, and when a voltage of about +400 V, for example, HfB2, is applied in response to a signal, heat is generated, and the supplied ink is turned into a mist state, as will be described later. Note that a 5i02 film 43 made by CVD is formed on the surface of this HfB to protect the heating element 4z. Further, a silicon wafer 44 having an oxide film 45 formed on its surface is placed on top of this to form an inkjet nozzle. In this case, two silicon wafers 40. 44) Holes each having a diameter of 40 μm are formed at a density of 16 holes, and the heating element 42 is installed in each hole.

Such an inkjet nozzle is connected to an ink reservoir 50 via a cock 52 and a pump 51 as shown in FIG.
The ink I is supplied to the nozzle.

In such a configuration, when the drive circuit 49 is driven by a signal from the memory 15, the heating element 42 is heated;
As a result, the ink (2) supplied from the ink pump 51 forms a bubble 46 on the surface of the heating element, becomes a mist 47 due to the pressure thereof, and is discharged from the nozzle.

At this time, if the recording paper 22 is placed near the nozzles, ink mist will adhere to the recording paper 22.

By using such an inkjet device, the third
As shown in the figure, three colors of cyan, magenta, and yellow are successively reproduced on a recording paper 22 on which a black image has been formed by electrophotography, thereby reproducing a color image.

The ink used in the present invention had the structure shown in Table 1.

Table 1 Ink prescription Recording paper can be used, for example, high-quality paper commercially available as Chain Ring and Seven Star (both trade names), medium-quality paper commercially available as Hakupeony (trade name), and Toyo Although non-size paper commercially available as Jigami-ya 4 (trade name) was used, good results were obtained with any of the recording papers.

Further, in this example, an inkjet that generates ink mist using thermal energy is used, but the invention is not limited to this.
It goes without saying that an inkjet method such as the Steynme method described in No. 120 can be used.

In addition, in the above embodiment, an image including black text was explained, but for example, when a color is specified, ink of colors such as red and blue is ejected instead of overlapping each color. By doing so, an image of that color can be reproduced. In this case, since the image is not reproduced by superimposing colors, an image with good resolution can be obtained.

In addition, in each of the embodiments, after a color image is formed by synchronizing the reproduction of an image by electrophotography and the reproduction of a color image by an inkjet method, the next image is copied. When making multiple copies of an original,
As shown in FIG. 4, high-speed recording becomes possible by storing the recording paper that reproduces black characters once in the storage box 34 and sending it out to the inkjet recording surface by the paper feed roller 35.

In addition, by storing the number of copies of the black part in memory together with the image information and preparing multiple storage boxes, after the black part has been copied, the next document can be copied in parallel with the inkjet recording of the previous image. High-speed image formation becomes possible.

As explained above, according to the present invention, the black parts of the document are reproduced using electrophotography, and the colored parts are reproduced by ejecting ink corresponding to each color to form a color image. Therefore, it is possible to copy originals containing black characters at extremely high speed and with high quality, and also to reproduce clear color images for other color images.

[Brief explanation of the drawing]

Each figure shows an embodiment of the present invention; FIG. 1 is a block diagram showing the principle of the method of the present invention, FIG. 2 is a circuit diagram showing an image processing logic circuit, and FIG. FIG. 4 is a configuration diagram of an apparatus of the present invention showing different embodiments, FIG. 5 is a sectional view showing the configuration of an inkjet nozzle, and FIG. 6 is an explanatory diagram illustrating driving of the inkjet nozzle of the present invention. . 1... Red filter 2... Green filter 3.
...Blue filter 10...Original 12...Original table 14...Sensor 15...Memory
17... Photoreceptor 1B... Charger
19...Developing roller 20...Transfer charger
28-30... Inkjet nozzle ・□
50... Ink tank Figure 1 Figure 3

Claims (1)

[Claims] (+) A color image in which a document is read, black parts of the document are reproduced using electrophotography, and colored parts are reproduced by discharging ink corresponding to each color to form a color image. Image forming method. (2) means for forming a latent image of the original on a photoreceptor and developing it;
means for separating and reading the original document, ejecting ink corresponding to each color, transferring the developed image onto recording paper, ejecting the ink of each color corresponding to the transferred image, and producing a color image. A color image forming apparatus characterized by forming a color image.