JPS6017461A - Electrophotographic color image recording method - Google Patents

Abstract

PURPOSE:To obtain a good-quality image free from any misregister by 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 photoconductive layer and a transparent insulating layer are laminated on a conductive substrate to form a photosensitive drum I. The drum I is electrostatically charged with a corona discharger 1 and then with an AC corona discharger 2. 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, only one part exposed to one luminous flux is selectively exposed to light to form an electrostatic latent image, and developed with a corresponding color toner with each of color developing devices 3-5. The image consisting of color images formed with each toner is transferred onto a transfer paper 7. 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 of 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 Color images are recorded using image signals obtained by separating color originals into multiple colors using terminal color hard copy devices such as color facsimiles, CRTs, and computers. Conventional recording methods include inkjet recording, transfer-type thermal recording, and wire dot recording, in which the recording head is driven line-by-line using signals for each color, but each of these recording methods has the following drawbacks. be.

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, so it is not possible to obtain sufficient reliability and image quality.1. do not have.

Transfer type thermal recording methods include heat-melting ink transfer type and sublimation dye heat transfer type, but because they use a thermal head,
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.

Further, 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 the above-mentioned recording methods, a color image recording device that performs recording by electrophotography by modulating a laser beam with original image signals of each color obtained by separating an original into multiple colors has been proposed, for example, in Japanese Patent Laid-Open No. 55-67275. and JP-A-56-1
This is proposed in Japanese Patent No. 4775.

An example of the image reading section of these devices is shown in FIG. In the figure, 5o is a color original, 51U contact glass, 52 is an original illumination lamp, 531' is a scanning mirror that swings around a fulcrum P, 54 is an imaging lens, 55 is a color separation filter, and 56 is a solid-state image sensor. / are shown respectively. The filter 55 consists of blue, green, and red (7) filters 55B, 55G, and 55R, which have an extra color relation to each other.
In addition, the solid-state image sensor 56 is 56B,
It is composed of three pieces: 56G and 55R.

When reading a document, the light Lr reflected from the document 500 irradiated by the illumination lamp 52 is reflected by the scanning mirror 53, transmitted through the imaging lens 54, and then roughly filtered through each color filter 5.
5B, 55G, and 55Ri and enter solid-state image sensors 56B, 56G, and 56R, respectively. By swinging the scanning mirror 53 around the fulcrum P, the image plane of the original 50 is scanned onto the solid-state image sensor 56, and each solid-state image sensor 56B, 56G,
A color-separated original image signal is detected on 56R.

At this time, the image information detected by the solid-state image sensor 56E, 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 an image signal SMK to be developed in maze/red color, and solid-state image sensor 56RI/il: based on the light transmitted through the detected red filter. The image information is converted and transmitted into an image signal SC to be developed in cyan.

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 NSC 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 the image signals Sy, SM, SC of Tomori et al. The beam diameter of the laser beam is expanded by the beam expander 12.
The focused light and the o-order light Lbo are incident on the acousto-optic modulation element 14 simultaneously driven by multi-frequency waves by the lens 13, and are to be developed with yellow, magenta, and cyan color toners, respectively. 1st-order diffracted light Lby that writes an optical image,
It is divided into LbM and Lbc. This minute ia+san,
The I-order diffracted light is converted into parallel light by the second lens 15, reflected by the rotating polygon mirror 16, and deflected to form an f-θ once 1'
The image is corrected from VC and is focused on the imaging plane at a desired magnification 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 56B, 56G,
The image signal SY r sM , S transmitted from 56R
C is input to modulators 17, 18, and 19 shown in FIG. 2, respectively. High-frequency carrier waves FY, FM, and FC having different frequencies are inputted to the modulators 17, 18, and 9, respectively, and the above image signals are input to the modulators 24, 25, respectively.
, 26, are modulated by each carrier wave, mixed in a mixer 27 to form a single signal, amplified by a power amplifier 28, and inputted to the acousto-optic modulator 14,
Each of the first-order diffracted lights Lby, LbM, and Lbcf is an image signal sy.

In addition to modulating from SM and SCK, the carrier wave FY +
When the light is emitted at different diffraction angles depending on the frequency of FM+Fc and is projected onto the imaging plane for scanning, three parallel scanning lines close to each other will be formed.

Now, as mentioned above, the laser beam is converted into three image information signals S.
When recording a color image using electrophotography by scanning a photoreceptor with three beams modulated and divided into Y, SM, and Sc,
In conventionally proposed devices, the optical images for each color of yellow, magenta, and cyan are placed in different areas of one photoreceptor drum, or one photoreceptor drum is rotated three times, and the light images are different each time. Light images for each color are projected at different timings to form latent images, producing yellow, magenta, and
Developed with cyan toner and wrapped around a transfer drum.
Either a sheet of transfer paper is rotated three times and three color toner images are superimposed and transferred onto it, or a laser beam divided into three parts is projected onto each of three photoreceptor drums to create different toner images. A full-color image was obtained by developing with colored toners, sequentially applying the liquid to three photoreceptor drums, and transferring the toner onto the same area of the transferred paper so that they overlapped each other.

In this method, in which three color toner images are superimposed and transferred onto a single sheet of transfer paper, misalignment between each color image is likely to occur, and each color layer image is formed in a different area of the photoreceptor drum. In this case, the diameter of the photoreceptor drum becomes larger, and in order to project onto three photoreceptor drums, not only the photoreceptor drum but also three sets of each process equipment are required, which requires a large space and increases the size of the equipment. It has the disadvantage of being large. Furthermore, the method of recording by rotating one photosensitive drum three times does not increase the space, but increases the recording time. Furthermore, in order to project the three divided laser beams at different positions with different timings, it is necessary to install a mirror in each optical path of the divided beams to separate the projection positions, and to provide a shift register in the output circuit of the solid-state image sensor. Yes, the equipment becomes complicated,
This has the drawback of requiring highly accurate adjustment and 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 the drawbacks of the electrophotographic color image recording system, and these are the main reasons why the 7 SNAMS have not developed. It had become.

Purpose: 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 errors by performing the transfer process only once without performing the transfer process for each color. It is an object of the present invention to provide an electrophotographic color image recording method that improves recording speed due to process saving, reduces the number of component parts and equipment size, and contributes to cost reduction and reliability improvement.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be described in detail based on embodiments of the apparatus shown in the drawings.

FIG. 3 shows an embodiment of an electrophotographic color image recording apparatus suitable for carrying out the method of the present invention, in which positive polarity electrodes are arranged around the photoreceptor drum I in the order of its rotational direction as indicated by the arrow. Primary charging corona discharger 11 Negative polarity corona discharger 2
, a yellow developer 3, a magenta developer 4, a cyan developer 5, a transfer corona discharger 6, a static eliminator consisting of a static eliminator lamp 8 and a corona discharger 9, and a cleaning member 0 are provided. 7 is transfer paper. The position on the surface of the photoreceptor drum facing the negative polarity corona discharger 2 is the optical image writing position, and the three-divided laser beam LILY, LbM, which was previously explained using FIG.

Light scanning and writing are performed at the same time in three spots that are closely aligned with each other in a direction perpendicular to the scanning direction by the rotating polygon mirror 16 of Lbc (the generatrix direction of the photoreceptor drum).

The yellow developing device 3 is a reversal developing device using a normal magnetic brush, while the magenta and cyan developing devices 4 and 5 are non-reversible developing devices that have a gap between the electrostatic a image holding surface of the photoreceptor I and the toner. It is a contact developer.

The photoreceptor drum 1 is partially enlarged in FIG. 4, and as schematically shown in FIG. It has a triple structure consisting of 3 layers stacked one after the other.

As shown in FIG. 4, a mirror 18 is provided on the optical path of the 0th order diffraction source Lb□ emitted from the multi-frequency simultaneously driven acousto-optic light modulator 14, and the reflected light is transmitted to the second lens 1.
5, it is converted into parallel light like the first-order diffracted light f'
After reaching L, the light passes through a rotating polygon mirror 16 and an f-θ lens 17. The optical path of the O-order diffracted light coming out of the f-theta lens 17 is provided with a mirror 19, and the reflected light is reflected by a half mirror 20 arranged as shown in FIGS. 3 and 4.
, a mirror 21, a half mirror 22, and a mirror 23, the light beam is divided into three beams, and images are formed on the photoreceptor l at positions 20', 22', and 23' immediately before the upstream side of each developing device 3, 4.5, respectively. It is supposed to be done. The interval between these imaging positions is determined as follows. From the exposure position P of the laser beam Lby that writes the yellow image, the distance from 20' to 20' is 4.20' to 22' is 4.22' to 23'.
' up to t2, Lby, LJy), LbC(
7) Mirrors 21, 23 and nauf mirrors 20 so that the distance iB between the image formation positions and n is an integer, o-nB tt=(n+1), nt22(n+2)B
゜22 is arranged. Therefore, the entire optical image is written on the photoreceptor by the three 1st-order diffracted lights Lby, LbM, and LbC, and at the same time, the 0th-order diffracted light 20', 22
', zt position, L at position 20'
By vC, the exposed area is irradiated, and at the 22' position, L
The area exposed by bM and the area exposed by Lbc at the position 23' are selectively irradiated with light.

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

(,) First, the transparent insulating layer ■− on the surface of the photoreceptor drum 10
A primary charge of positive polarity is uniformly applied from the side of 3 by a DC corona discharger 1.

(b) Next, perform secondary charging with the negative corona discharger (or AC corona discharger) 2, and at the same time or just before that.
The first-order diffracted laser beam Lby, T, bM.

Light image exposure is performed line-sequentially and simultaneously at Lbc, and color-specific information is written.

(c) (c-'i) When the light irradiation area for yellow comes to the position 20', the 0th order diffracted laser beam reflected by the half mirror 20 selectively After the electrostatic latent image is retrieved, the electrostatic latent image is then developed with yellow toner by a yellow developer '3.

(c-2) When the maze/moonlight irradiation area comes to the position 22', an electrostatic latent image corresponding to magenta information is similarly called out and developed with magenta color toner by the magenta developer 4. .

(c3) When the cyan light irradiation area comes to the position 21, an electrostatic latent image corresponding to the cyan information is similarly called out and developed with cyan color toner by the cyan developing device 5.

(d) The three color toner images obtained in the above steps are simultaneously transferred onto the transfer paper 7 using the transfer corona discharger 6vC.

The transfer paper on which the color image has been transferred is fixed by known means, and the recording of the color image is completed. On the other hand, the photoreceptor drum I is neutralized by static eliminators 8 and 9, and the cleaning section z
When OK is selected, residual toner is removed and preparations are made for the next image recording.

FIG. 6 shows the transition of the surface potential of the photoreceptor I corresponding to the above steps (a) I (b) t (c). In the figure, Vp is the surface potential during primary charging, VL is the surface potential of the exposed area exposed by the first-order diffracted laser beam in step (b), VD is the surface potential of the area not exposed to laser light, and LL is the surface potential of the above 1 The surface potential of the part exposed to the O-order diffracted laser beam in step (e), vDL is the surface potential of the part exposed to only the O-order diffracted laser beam.This V,
LL and VDL are selectively called immediately before development with each color toner, so that each color is developed for each V color information.

In the step (c), the O-order diffraction laser beam that selectively irradiates the light irradiation area for each color is emitted from the same light source (laser oscillator) U as the 1st-order diffraction laser source for writing each color optical information. , is divided by a multi-frequency simultaneous driving acousto-optic light modulator 14, passes through the same deflection means (rotating polygon mirror) 16, and f-0 lens 17, to light irradiation areas 20', 22',
23', so as long as the creepage distance between each color light information writing position and the three irradiation positions 22' and 23' of the 0th-order diffracted light is accurately adjusted in advance, each color light information exposure area can be In the apparatus of this embodiment, which allows selective light irradiation to be reliably synchronized and is very simple to control, the first of the three developing devices 3p4t5 is a reversal developing method using a normal magnetic brush. The latter two completely adopted a non-contact development method in which there is a gap between the electrostatic latent image holding surface and the single layer of toner, so the toner image developed first was disturbed by the subsequent developer and color mixing occurred. It is avoided that

In the above embodiment, the original is divided into blue, green, and
About a color image recording method suitable for reproducing color photographs and paintings in the same color as the original by separating the colors with a red filter and developing the written image information in three colors: yellow, magenta, and cyan. As explained above, the laser beams LbY, LbM, and LbC for recording image 1 have already been color separated f'1. Filter stripes JIB, I[Gr IIR
does not require the color separation function, and has yellow, magenta, and
The 83 cyan filter colors can be distinguished, and Lby, LbM, Lb can be obtained by simply using the same combination as the spectral wavelength band of the colored light irradiated from the transparent support immediately before development.
Each electrostatic latent image corresponding to C can be formed in any filter color area, and in cases where the document is recorded in multiple colors such as three colors, it is not necessary to However, it is not necessary to separate the optical image into three colors that have complementary colors to each other; instead, color separation is performed using a color filter that can distinguish the colors of the original, and the toner also has yellow, magenta, and yellow, which have complementary colors to each other. It is also possible to use toners of other colors instead of cyan.

This optical image writing method uses multi-frequency simultaneous drive sound and acousto-optic light modulators to simultaneously write each color signal, but the conventional method of writing each color signal line-by-line line by line is also possible. A combination of reverse development with negative light image writing (image area laser irradiation, non-image area non-irradiation) or positive image writing with normal positive/positive development 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 image can be developed sequentially with different color toners and transferred at once, so only one photoreceptor drum is required, and the same information for each color can be transferred. There is no need to repeat the process planning, there is no generation of color stains, the image recording speed is improved, and the equipment is simplified, downsized, and costs are reduced. .

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an example of the configuration of a known color image reading section, and FIG. 2 is a sectional view of a device for forming a light beam for writing a plurality of optical images corresponding to the n1 image signal read by the above-mentioned 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 photoreceptor, and FIG. 6 is a curve diagram showing an example of the transition of the surface potential of each part of the surface of the photoreceptor according to the method KJ of the present invention. l...Corona discharger for primary charging 2...Corona discharger for secondary charging 3.4.5...Developer for each color 6...Corona discharger for transfer 7...Transfer paper 1. ... Photosensitive drum 1-t... Conductive support 1-2... Photoconductive layer j-3... Transparent insulating layer Lby
, LbM, Lbc='Writing luminous flux Lb□...
・0th order diffraction - laser beam Figure 1 Figure 2 i, , Figure 53 E 1:1. ' 4 i, ', 4 Procedural amendment July 4, 1980 Manabu Shiga, Commissioner of the Patent Office 1 Indication of the case 1981 Patent Application No. 124857 2 Name of the invention Electrophotographic color image recording method 3 Make amendments Relationship with the patent case Patent Applicant address and name (674) Ryo Co., Ltd. 4 Agent address Kaji Kogyo Building 6, 2-32-4 Nishi-Shinbashi, Minato-ku, Tokyo, subject of amendment Column 7 of the detailed explanation of the invention in the specification, contents of amendment (11) "17, 18, 19" used in the 11th line and 12th line of page 7 of the specification, respectively, are changed to "24., 25, 26J"
I am corrected. (2) Delete ``Laser beam for image writing...can be formed, and also'' from line 14 on page 16 of the same book to line 3 on page 17.

Claims (4)

[Claims] (1) A plurality of light beams containing image information of each color obtained by color-separating the original are projected and exposed onto an electrophotographic photoreceptor, and each electrostatic latent image formed is developed with toner of a different color. In an electrophotographic color image recording method for obtaining a color image by transferring to the same transfer paper, the electrophotographic photoreceptor described above is constructed by laminating a photoconductive layer and a transparent insulating layer in this order on a conductive support. , (a) uniformly charging the photoreceptor from the transparent insulating layer side by direct current corona discharge; (b) charging the photoconductor uniformly from the transparent insulating layer side at the same time as, or just before, direct current corona or alternating current corona discharge of opposite polarity to the previous step; A step of performing line-sequential light image exposure with a plurality of light beams containing decomposed image information and writing color-specific information; (c) selectively exposing only the light image-exposed area with the above-mentioned one light beam from the transparent insulating layer side; A step of sequentially performing a step for each color of irradiation with light to form an electrostatic image corresponding to the color-specific information written and edited by the light flux, and developing this with toner of that color, (d) Pre-process An electrophotographic color image forming method comprising steps of transferring a stray toner image formed on a photoreceptor in the preceding steps onto the surface of a transfer paper in this order. (2) The plurality of light beams used for optical image writing in the step (b) above are modulated with carrier waves of different frequencies for each color and input to an acousto-optic light modulation element driven simultaneously at multiple frequencies. 2. The method according to claim 1, wherein a plurality of first-order diffracted laser beams are emitted from a single laser beam at different diffraction angles for each color. (3) The development of the second and subsequent colors in the step (C) above is carried out by a non-contact development method in which a gap is provided between the electrostatic latent image holding surface of the photoreceptor and the surface of the toner layer. A method according to claim 1, characterized in: (4) The light beam used for selectively irradiating the first optical image exposure part with each light beam in the step (C) above is emitted from the multi-frequency simultaneous drive acousto-optic light modulation element. 0
3. The method according to claim 2, wherein the second-order diffracted laser beam is a beam that has passed through the same deflection means and the same f-θ characteristic correction means as the first-order diffracted laser beam.