JPS6017463A - Electrophotographic color image recording method - Google Patents

Abstract

PURPOSE:To obtain a good-quality image free from any misregister through only one transfer step by writing information on each color image on the same region of a photosensitive body and successively developing the information on each color with each different color toner. CONSTITUTION:A color filter layer, a transparent electrically conductive layer, a photoconductive layer, and a transparent insulating layer are laminated on a transparent substrate to form a photosensitive drum 16. The drum 16 is electrostatically charged with a corona discharger 8 and then with an AC corona discharger 9. At the same time as this action, it is imagewise exposed successively with plural luminous fluxes contg. color-separated image information to write color separated information. Then, it is exposed to light of a color same as that of the color filter to form each electrostatic latent image corresponding to the image information, and developed with a corresponding color toner with each of color developing devices 10-12. The formed toner image is transferred onto a transfer paper with a corona discharger 13. Since only one transfer step is carried out, a good-quality image free from any color misregister can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a method for recording a color image by electrophotography by exposing a photoreceptor to a plurality of light beams containing image information of each color obtained by color-separating a color original.

Conventional technology In a terminal color hard copy device such as a color facsimile, CRT, or computer, the conventional recording method for recording a color image using image signals obtained by separating a color document into multiple colors is to drive the recording head line-sequentially using signals for each color. There are inkjet recording methods, transfer type thermal recording methods, and wire dot recording methods, each of which has the following drawbacks.

Since the inkjet recording method mainly uses water-based ink, it is necessary to control the physical properties of the ink, and plain paper cannot be used due to the relationship between ink clogging and image fixability. or,
There is a limit to the improvement of image resolution due to the relationship between ink clogging and orifice diameter, and it is not possible to obtain sufficient reliability and image quality.

Transfer-type thermal recording methods include heat-melting ink transfer type and sublimation dye heat transfer type, but because they use a thermal bed,
The resolution decreases due to thermal diffusion, the ink ribbon wears out, and in the case of sublimable dyes, the energy required for printing is extremely large, making it difficult to increase the printing speed.

In addition, the wire dot recording method has problems with noise and has limitations in terms of resolution and image quality because it uses a wire head and cloth ink ribbon.

In view of the drawbacks of each of the above-mentioned recording methods, a color image recording device that modulates a laser beam with original image signals of each color obtained by separating an original into multiple colors and performs recording by electrophotography has been proposed, for example, in Japanese Patent Laid-Open No. 55-67275. Official gazette and Japanese Patent Application Laid-open No. 56-14
This is proposed by Publication No. 7.75.

An example of the image reading section of these devices is shown in FIG. In the figure, reference numeral 50 indicates a color original, 51 indicates a contact glass, 52 indicates an original illumination lamp 156, a scanning mirror swings around a fulcrum P, 54 indicates an imaging lens, 55 indicates a color separation filter, and 56 indicates a solid-state image sensor. shown respectively. The filter 55 consists of blue, green, and red filters 55B, 55G, and 55R, which have an extra color relationship with each other, and the solid-state image sensor 56 has filters 56B, 5 (SG, and 56H) corresponding to these.
It is composed of three parts.

When reading a document, reflected light Lr from the document 50 illuminated by the illumination lamp 52 is reflected by the scanning mirror 53, transmitted through the imaging lens 54, and then passed through each color filter 5.
5B, 55G, and 55R, and enter the solid-state image sensors 5 (SB, 56G, and 56R), respectively.

As the scanning mirror 55 swings around the fulcrum P,
The image plane of document 50 is scanned onto solid-state image sensors 56, each solid-state image sensor 5613.56G.

56R, a color-separated original image signal is detected.

At this time, the image information detected by the solid-state image sensor 56B, that is, the image information based on the light transmitted through the blue filter, is to be developed with yellow toner and is output as an image signal Sy. Similarly, image information based on the light transmitted through the green filter detected by the solid-state image sensor 56G is developed as an image signal sM to be developed in magenta color, and image information based on the light transmitted through the red filter detected by the solid-state image sensor 56R is developed in cyan. It is converted into an image signal Sc to be developed in color and transmitted.

When recording a color image using signals from a color CRT, Sy can be formed by combining green and red signals, SM can be formed by combining blue and red signals, and SC can be formed by combining blue and green signals.

FIG. 2 is a diagram showing an example of a device for forming a beam for writing an optical image corresponding to these image signals Sy, sM, and SC, and the laser light emitted from the light source (laser oscillator) 1 is a beam The light diameter is expanded by the expander 2, the light is focused by the second lens 5, and is incident on the multi-frequency simultaneous drive acousto-optic light modulation element 4, where it becomes zero-order light LbQ,
First-order diffracted lights r, by, LbM, which write optical images to be developed with yellow, magenta, and cyan color toners, respectively.
It is divided into Lbc and Lbc. This divided first-order diffracted light is
After being converted into parallel light by the second lens 5, it is reflected and deflected by a rotating polygon mirror 6, corrected by an f-theta lens 7, and imaged at a desired magnification on an imaging plane and scanned. Each of the above-mentioned first-order diffraction lights is modulated by the above-mentioned color image signals in the following manner. Each of the solid-state image sensors 5<SB, 56G, 5
The image signals SY+SM+SC transmitted from <SR are input to modulators 17, 18 and 19 shown in FIG. 2, respectively.

High-frequency carrier waves F Yy FM+FC having different frequencies are input to the modulators 17, 18, and 19, respectively, and each image signal is modulated by each carrier wave in each modulator 17, 18, and 19, and mixed. The signal is mixed by the power amplifier 20 to become one signal, which is amplified by the power amplifier 21 and inputted to the acousto-optic light modulation element 4.
'f'TtsuQLby+LbM+Lbc are respectively image signals S
Y+ s; M, SCD modulates the carrier wave F'Y+ FM+ F Six scanning lines will be formed.

Now, as mentioned in the company's article, the laser beam is divided into six image information signals.
When recording a color image using electrophotography by scanning a photoreceptor with five lines modulated and divided by y, SM, and Sc, there are devices that have been proposed in the past, such as yellow 1 magenta, The yC image for each color of cyan is placed in 4 different areas of one photoreceptor drum (G, one photoreceptor drum is rotated 6 times, and the light for each color is 4M, t). A latent image is formed by projecting the image at different timings, and is developed with yellow, magenta, and cyan toner, respectively. A sheet of transfer paper wound around the transfer drum G is rotated six times, and then the latent image is transferred onto the transfer drum G. (Power to overlay and transfer colored toner images)
, ('-G) A laser beam divided into three parts is projected onto each of the six photoreceptor drums to create toner of a different color, and the laser beam is sequentially contacted with these five photoreceptor drums. The images were transferred to the same area of the conveyed transfer paper so as to overlap each other to obtain a full color image (N).

In this method, where three color toner images are superimposed and transferred onto one sheet of transfer paper, misalignment between each color image is likely to occur.
In addition, when forming latent images of each color on different areas of one photoreceptor drum, the diameter of the photoreceptor drum becomes large, and when projecting on six photoreceptor drums, not only the photoreceptor drum but also
Six sets of each process equipment are required, which requires a large space and has the drawback of increasing the size of the equipment. Further, the method of recording by rotating one photosensitive drum six times does not increase the space, but increases the recording time. In addition, in order to project the three divided laser beams at different positions with different timings, mirrors are installed on each YC path of the divided beams to separate the projection positions, and a shift register is installed in the output circuit of the solid-state image sensor. The device is complicated, requires high accuracy (one adjustment), and has the disadvantage of increasing costs.

As mentioned above, the multiple steps of positioning and overlapping transfer for each color development and the complexity and size of the equipment are drawbacks of electrophotographic color image recording systems, and these are the main reasons why this system has not developed. Te(・ta)

Purpose of the present invention In view of the above-mentioned drawbacks of the conventional color image recording method using electrophotography, the present invention provides a method for obtaining high-quality images without positional deviation by performing the transfer process only once without performing the transfer process for each color, thereby saving money. The purpose of the present invention is to provide an electrophotographic color image recording method that improves recording speed, reduces the number of component parts and equipment size, and contributes to cost reduction and improved reliability.

Configuration The present invention will be explained in detail below based on the embodiment of the apparatus shown in the drawings.

FIG. 3 shows an embodiment of an electrophotographic color image recording apparatus suitable for implementing the method of the present invention, in which positive polarity electrodes are arranged around the photoreceptor drum 16 in the order of its rotational direction as indicated by the arrow. A primary charging corona discharger 8, a negative polarity corona discharger 9, a yellow developer 10, a magenta developer 11, a cyan developer 12, a transfer corona discharger 16, a static eliminator 14, and a cleaning member 15 are provided. photoreceptor drum 1
6, front, green, and
Light sources 10', 11', 12' with red filters
is provided. The position on the surface of the photoreceptor drum facing the negative polarity corona discharger 9 is the optical image writing position, and the three-divided laser beam ``bY+LbM, r, be'' explained earlier using FIG. Writing is performed by simultaneously scanning light with six spots arranged in close proximity to each other in a direction perpendicular to the scanning direction (the generatrix direction of the photoreceptor drum) by a rotating polygon mirror B. The yellow developing device 10 is normally used. It is a reversal developing device using a magnetic brush.
The magenta and cyan developing devices 11 and 12 are non-contact developing devices in which a gap is provided between the electrostatic latent image holding surface of the photoreceptor 16 and the toner.

The photosensitive drum 16 is partially enlarged in FIG.
As schematically shown in FIG. 5, it has a multilayer structure in which a color filter layer (1), a transparent conductive layer (2), a photoconductive layer (2), and a transparent insulating layer (2) are sequentially laminated on a transparent support I. The order of the transparent support I and the color filter layer ■ may be reversed, but in order to form a clear electrostatic latent image, the filter layer ■ should be placed close to the photoconductive layer ■ as shown in the figure. power (desirable. Color filter layer ■ has 6 colors of blue, green, and red)
It is formed by arranging color stripe-like filters nB, nG, and nR in a repeating line sequential manner in the direction of the generatrix of the photoreceptor drum 16, and the width of the filter stripes is determined by the laser beams Lb, y, Lby, and Lbc to be written. It is determined to match the spot spacing of 25 to 500 .mu.m, preferably about 50 to 500 .mu.m.

A method of recording a color image using the apparatus configured as described above will be described below.

(a) A primary charge of positive polarity is uniformly applied by a corona discharger 8 from the side of the transparent insulating layer 1 on the surface of the multilayer structure photoreceptor drum 16. (b) Next, a corona discharger 9 At the same time as applying secondary charging by performing negative polarity (or alternating current) corona discharge,
Or, just before that, the image writing laser beams Lby, LbM, and LbC divided into three parts are simultaneously exposed and scanned on the positions corresponding to the filter stripes nB, IIG, and IIR to simultaneously write image information of six colors. It's crowded.

(c) (c-1) Next, immediately before development at the yellow developing device 10, the photoreceptor 16 is irradiated with blue light from the side of the transparent support I using a light source 10' having a blue filter. Then, the blue light passes through only the portion of the blue filter stripe IIB, and the yellow image information written in that portion is called out as an electrostatic latent image, and this latent image is developed with yellow toner by the yellow developer 10. .

(c-2) Similarly, at the position of the magenta developing device 11, the photoreceptor 16 is irradiated with green light from the back side by the light source 11' having a green filter, and the green filter stripe [
The magenta image information written in the G portion is made into an electrostatic latent image, and is developed with magenta toner by a magenta developing device 11.

(c-3) Similarly, at the position of the cyan developing device 12,
A light source 12' having a red filter irradiates the photoreceptor 16 with red light from the back side, and a red filter stripe [H
The cyan image information written in the portion corresponding to the image is made into an electrostatic latent image, and is developed with cyan toner by a cyan developer 12.

(d) The six color toner images obtained in the above steps are simultaneously transferred onto transfer paper using the transfer corona discharger 13. The transferred toner image is fixed by known means to record a color image, while the photosensitive drum is neutralized by a static eliminator 14 and residual toner is cleaned by a cleaning member 15 in preparation for the next image recording.

Through the above steps (a), (b), and (C), the photoreceptor 16
Figure 6(a) shows the process by which an electrostatic latent image is formed on l(b).
) l (e) is schematically shown. Figures (a) and (b)
(C) corresponds to steps (a), (b), and (C).
Ru. Note that in Figures (b) and (C), the laser beam [, by is the part corresponding to the blue filter and tribe IIB for writing yellow image information, and the blue light L is exposed from the back side.
13 is representatively shown, but the same applies to the green and red filter stripes.

Further, FIG. 7 is a curve diagram showing the transition of the surface potential of the photoreceptor 16 corresponding to each of the above steps (a), (b), and (C), where Vp is the surface potential during primary charging. , VL is the surface potential of the laser beam irradiated area, and vD is the surface potential of the laser beam non-irradiated area.
vDB, VDG, and vDB are the surface potentials of the so-called skin areas of the blue, green, and red filter light irradiated areas in the non-laser beam irradiation area, and ■LB, VLG, and vLR are the surface potentials of the so-called skin areas in the laser beam irradiation area, respectively. It shows the surface potential of the so-called image area of the red filter light irradiation area.

In the apparatus of this embodiment, the first of the three developing units 10, 11 and 12 uses a reversal developing method using a normal magnetic brush, while the other two develop using an electrostatic latent image holding surface and a single layer of toner. Since a non-contact development method with a gap between the toner images is adopted, it is possible to prevent the first developed toner image from being disturbed by a subsequent developing device and from causing color mixing.

In addition, in each step of '(C-1), (C-2), and (CI), the blue, green, and red filter stripe portions of the photoreceptor 16 are illuminated by the blue, green, and red light rays irradiated from the back surface of the photoreceptor 16. In order to reduce the influence on the filter parts adjacent to each of the filter stripes, it is desirable to use a spectral wavelength band of the irradiation light that is narrower than that of the filter stripes. In this case, it is desirable to use a color filter with a narrower wavelength band than the color filter used for the photoreceptor.

In the above embodiment, the original is divided into blue, green, and
Explains a color image recording method suitable for reproducing color photographs and paintings in the same colors as the original by separating the colors with a red filter and developing the written image information in six colors: yellow, magenta, and cyan. However, in cases where the original is recorded in multiple colors, such as six colors, it is not necessarily necessary to separate the optical image into six colors that are complementary to each other; It is also possible to perform color separation using a color filter that allows colors to be distinguished, and use toners of other colors instead of yellow, magenta, and cyan, which are complementary colors to each other.

This pre-image writing method uses a multi-frequency simultaneous drive acousto-optic light modulator to simultaneously write each color signal, but it is also possible to use the conventional method of writing each color signal line-by-line line by line. A combination of reversal development with image writing (laser irradiation on the image area, non-irradiation on the non-image area) or normal positive/positive development with positive image writing can be selected as appropriate.

Effects As described above, according to the present invention, using one photoreceptor,
Image information for each color can be written in the same area on the photoreceptor at once and each can be sequentially developed with a different color toner and transferred at once, so only one photoreceptor drum is required, and the process is the same for each color. There is no need to repeat the process, and there is no color shift.
Improving image recording speed, and simplifying and downsizing equipment.
Excellent effects such as cost reduction can be achieved.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an example of the configuration of a known color image reading section, and FIG. 2 is a diagram showing a device for forming light beams for writing a plurality of optical images corresponding to image signals read by the above reading section. 3 is a sectional view showing an embodiment of an apparatus for carrying out the method of the present invention, FIG. 4 is a sectional view showing an enlarged part of the photoreceptor, and FIG. 5 is a sectional view showing one example. 6 is a schematic diagram showing the structure of the photoconductor, FIG. 6 is a schematic diagram showing the step-by-step process of forming an electrostatic latent image on the photoconductor by the method of the present invention, and FIG. 7 is a schematic diagram showing various parts of the surface of the photoconductor by the method of the present invention. FIG. 3 is a curve diagram showing an example of the transition of the surface potential of FIG. 8...Corona discharger for primary charging 9...Corona discharger for secondary charging 10.11.12...Developers for each color 10', 11', 12'...Color light source 13...
・Transfer corona discharger 16... Electrophotographic photoreceptor ■... Transparent support ■... Color filter layer [I
B, IIG, IIR... Color filter stripe ■... Transparent conductor ■... Photoconductive layer ■... Transparent insulating layer bby, LbM, Lbc... Light flux for writing Figure 1 Figure 2:ㅅ I Figure 3 Ikkoku'1 Figure 5 July 4, 1980 Manabu Shiga, Commissioner of the Patent Office 1 Indication of the case 1981 Patent Application No. 124859 2 Name of the invention Electrophotographic color image recording method 3 Amendment Relationship with the case of a person who makes a patent Applicant's name (name) (674) Ricoh Co., Ltd. 4 Agent 6 Column 7 for detailed explanation of the invention in the specification subject to amendment, Contents of amendment (1) ) Insert the following sentence between "I explained it to you" and "For example, the manuscript" on page 16, line 16 of the specification box. [Laser beam for image writing LbY, LbM: Lbo
filter stripes IIB and JIG because they already have pure color information that has been separated into colors. ■R does not require a color separation function, and is a color that can be distinguished from three colors such as yellow, magenta, and cyan filters, and it is only necessary to use the same combination as the spectral wavelength band of the colored light irradiated from the transparent support immediately before development. LbY, LbM, Lbc
Each electrostatic latent image corresponding to Vc can be formed at any filter color site, and

Claims (1)

[Scope of Claims] (1) A plurality of light beams containing image information of each color obtained by color-separating the original are projected onto an electrophotographic photoreceptor for exposure, and each electrostatic latent image formed is divided into different colors. In an electrophotographic color image recording method in which a color image is obtained by developing with a toner of A color filter layer, a transparent conductive layer, a photoconductive layer, and a transparent insulating layer are laminated in this order. Polar DC corona or AC corona charging is performed, and at the same time or immediately before this, each color filter portion of the photoreceptor adjacent to each other is simultaneously exposed with a light beam containing color-separated image information of each color to obtain color-specific information. (c) irradiating light of the same color as the color filter with the photoreceptor filter layer from the transparent support side to form an electrostatic latent image corresponding to the image information written on the filter portion on the transparent insulating layer side; , a step of developing this with a toner of a predetermined color corresponding to this information is sequentially repeated for each color of the filter in the filter layer, (d) a step of developing the toner image formed on the photoreceptor in the previous step onto the surface of the transfer paper. An electrophotographic color image forming method, comprising the steps of transferring, in this order. (2) The plurality of light beams used for optical image writing in the step (b) above include one laser beam and image information of each color obtained by color-separating the document, and the plurality of light beams include image information of each color obtained by color-separating the original, and 2. The method according to claim 1, wherein the laser beam is divided into a plurality of laser beams forming spots at the same intervals as the intervals between the filter stripes of each color. (6) The development of the second and subsequent colors in the steps (,) above is performed by a non-contact development method in which a gap is provided between the electrostatic latent image holding surface and the toner. The method described in Section 1. (4) In step (c) above, the spectral wavelength band of each color light beam irradiated from the transparent support side of the photoreceptor is the same as or narrower than the spectral wavelength band of each color filter in the photoreceptor filter layer. A method according to claim 1, characterized in that: