JPH0447824B2 - - Google Patents

Description

Detailed Description of the Invention Technical Field The present invention exposes a photoreceptor to a plurality of light beams containing image information of each color obtained by color-separating a color original,
This invention relates to a method of recording color images by electrophotography.

PRIOR TECHNOLOGY In a terminal color hard copy device such as a color facsimile, CRT, or computer, the conventional recording method of recording a color image using image signals obtained by separating a color original into multiple colors is to print a recording head line-sequentially using a signal for each color. There are inkjet recording methods, transfer-type thermosensitive recording methods, and wire dot recording methods that are performed by driving, but each of these recording methods 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. Furthermore, there is a limit to the improvement of image resolution due to the relationship between ink clogging and the orifice diameter, so that sufficient reliability and image quality cannot be obtained.

Transfer-type thermal recording methods include heat-melt ink transfer and sublimation dye heat transfer, but because they use a thermal head, there are problems such as reduced resolution due to thermal diffusion, wear of the ink ribbon, and in the case of sublimation dyes. The energy required for printing is extremely large, making it difficult to increase the speed.

Furthermore, the wire dot recording method has problems with noise and has limitations in terms of resolution and image quality because it uses wire dots and cloth ink ribbons.

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 Japanese Patent Application Laid-Open No. 14775/1983.

An example of the image reading section of these devices is shown in FIG. In the figure, reference numeral 50 denotes a color original, 51 a contact glass, 52 an original illumination lamp, and 53
Reference numeral 54 indicates a scanning mirror that swings about a fulcrum P, 54 an imaging lens, 55 a color separation filter, and 56 a solid-state image sensor. The filters 55 are blue, green, and red filters 55 that have complementary colors to each other.
Correspondingly, the solid-state image sensor 56 consists of 56B, 56G, 55R.
It is composed of three 6Rs.

When reading a document, the reflected light L _r of the document 50 irradiated by the illumination lamp 52 is reflected by the scanning mirror 5
3, transmitted through the imaging lens 54, and further transmitted through each color filter 55B, 55G, 55R, solid-state image sensor 56B, 56G, 5, respectively.
It enters 6R. By swinging the scanning mirror 53 around the fulcrum P, the image surface of the original 50 is scanned onto the solid-state image sensor 56, and color-separated original image signals are transmitted onto each solid-state image sensor 56B, 56G, and 56R. 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 S _Y. Similarly, image information based on the light transmitted through the green filter detected by the solid-state image sensor 56G is converted into an image signal S _M 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 It is converted into an image signal S _C to be developed in cyan and transmitted.

When recording color images from color CRT signals, S _Y is green and red, S _M is blue and red, S _C
can be formed by combining the 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 S _Y , S _M , and S _C , and the laser light emitted from the light source 11 is a beam extractor. The light diameter is expanded by the panda 12, focused by the first lens 13, and incident on the multi-frequency simultaneous drive acousto-optic light modulator ₁₄ . It is divided into first-order diffracted light Lb _Y , Lb _M , and Lb _C that write an optical image to be developed with each color toner.
This divided first-order diffracted light is converted into parallel light by the second lens 15, reflected by the rotating polygon mirror 16 and deflected, corrected by the -θ lens 17, and focused on the imaging plane at a desired magnification. scanned. Each of the above
The next diffraction light is modulated by the above-mentioned color image signals in the following manner. Image signals transmitted from each of the solid-state image sensors 56B, 56G, and 56R
S _Y , S _M , and S _C are the modulators 24 and 25 shown in FIG.
26 respectively. Modulators 24, 25, 26
are high-frequency carrier waves F _Y with different frequencies,
F _M and F _C are input, and each of the above image signals is modulated by each carrier wave in each modulator 24, 25, 26, mixed in a mixer 27 to become one signal, and then outputted by a power amplifier 28. Amplified and input to the acousto-optic modulator 14, the first-order diffracted lights Lb _Y , Lb _M , Lb _C are converted into image signals S _Y , Lb C, respectively.
It is modulated by S _M , S _C and carrier waves F _Y , F _M ,
It is emitted at different diffraction angles depending on the frequency of F _C ,
When scanning is performed by projecting onto the imaging plane, three parallel scanning lines that are close to each other are formed.

As mentioned above, when recording a color image by electrophotography by scanning a photoreceptor with three beams obtained by modulating and dividing a laser beam with three image information signals S _Y , S _M , and S _C , there are conventionally proposed methods. In the device, the optical images for each color of yellow, magenta, and cyan are placed on different areas of one photoreceptor drum, or one photoreceptor drum is rotated three times to create an optical image for a different color each time. , a latent image is formed by projecting the images at different timings, and is developed with yellow, magenta, and cyan toner, respectively, and a sheet of transfer paper wound around a transfer drum is rotated three times to form a latent image.
Either color toner images are superimposed and transferred, or a laser beam divided into three parts is projected onto each of the three photoreceptor drums and each is developed with a different color toner. A full-color image is obtained by overlappingly transferring images onto the same area of transfer paper that is sequentially conveyed in contact with the images.

In this method, in which toner images of three colors are superimposed and transferred onto one sheet of transfer paper, misalignment between the images of each color tends to occur, and latent images of each color are formed in different areas of one photoreceptor drum. In this case, the diameter of the photoreceptor drum becomes larger, and when projecting 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 the size of the equipment is also large. There are drawbacks to becoming 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. However, the device is complicated, requires highly accurate adjustment, and has the disadvantage of increasing costs.

As mentioned above, the drawbacks of the electrophotographic color image recording system are the multiple steps of positioning and overlapping transfer for each color development, and the complexity and size of the equipment, and these were the main reasons why this system did not develop. .

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

Configuration The present invention will be described in detail below 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. A charger consisting of a corona discharger 1 for subsequent charging, a negative polarity corona discharger 2, a yellow developer 3, a magenta developer 4, a cyan developer 5, a transfer corona discharger 6, a static elimination lamp 8, and a corona discharger 9. Electric appliances and a cleaning member 10 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 laser beam divided into three parts as previously explained using FIG.
Writing is performed by simultaneously optically scanning three spots Lb _Y , Lb _M , and Lb _C that are closely aligned with each other in a direction perpendicular to the scanning direction of the rotating polygon mirror 16 (the generatrix direction of the photoreceptor drum). The yellow developer 3 is a reversal developer using a normal magnetic brush.
The magenta and cyan developing units 4 and 5 are non-contact developing units in which a gap is provided between the electrostatic latent image holding surface of the photoreceptor and the toner.

The photosensitive drum has a photoconductive layer 2 and a transparent insulating layer 3 laminated in this order on a transparent support 1, as shown partially enlarged in FIG. 4 and schematically shown in FIG. It has a triple structure consisting of

The above multi-frequency simultaneous drive acousto-optic light modulator 1
As shown in FIG. 4, a mirror 18 is provided on the optical path of the O-order diffracted light Lb _O emitted from the optical system 4, and the reflected light is guided to the second lens 15 and converted into parallel light in the same way as the first-order diffracted light. After the rotating polygon mirror 16
and -θ lens 17. A mirror 19 is provided in the optical path of the O-th order diffracted light coming out of the -θ lens 17, and the reflected light is reflected by a half mirror 2 disposed as shown in FIGS. 3 and 4.
0, mirror 21, half mirror 22, mirror 23
The light beams are divided into three beams, and are distributed at positions 20', 22', and 22' immediately before the upstream side of each developing device 3, 4, and 5, respectively.
The image is formed on the photoreceptor at 23'.
The interval between these imaging positions is determined as follows. The creepage distance from the exposure position P of the laser beam Lb _Y that writes the yellow image to 20' is l ₀ , 2
From 0' to 22' is l ₁ , from 22' to 23' is l ₂ ,
When the interval between the imaging positions of Lb _Y , Lb _M , and Lb _C is B and n is an integer, the mirrors 21 and 23 are arranged so that l ₀ = nB l ₁ = (n+1) B l ₂ = (n+2) B. and half mirrors 20, 22 are arranged. Therefore, the three first-order diffracted laser beams Lb _Y , Lb _M , and Lb _C write an optical image on the photoreceptor, and at the same time, the O-th diffracted beam writes a 20',
When irradiating the positions 22' and 23', the area exposed by Lb _Y is irradiated at the 20' position, the area exposed by Lb _M is irradiated at the 22' position, and the area exposed by Lb _C is irradiated at the 23' position.
The exposed areas are selectively irradiated with light.

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

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

(b) Next, a negative corona discharger (or AC corona discharger) 2 performs secondary charging, and at the same time or just before that, the first-order diffracted laser beams Lb _Y , Lb _M ,
Light image exposure is performed line-by-line at the same time using Lb _C , and color information is written.

(c) (c-1) When the yellow light irradiation part comes to the position 20', it is selectively irradiated with light by the O-order diffracted laser beam reflected by the half mirror 20, and the electrostatic latent corresponding to yellow information is selectively irradiated with light. The image is recalled and this electrostatic latent image is then developed with yellow toner by yellow developer 3.

(c-2) When the magenta light 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 developing device 4.

(c-3) When the cyan light irradiation area comes to the position 23', an electrostatic latent image corresponding to cyan information is similarly called out and developed with cyan toner by the cyan developer 5.

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

The transfer paper onto which the toner image has been transferred is fixed by known means, and recording of the color image is completed. on the other hand,
The photosensitive drum is neutralized by static eliminators 8 and 9,
The remaining toner is removed by the cleaning member 10 to prepare for the next image recording.

FIG. 6 shows the changes in surface potential of the photoreceptor corresponding to the above steps (a), (b), and (c). In the figure, V _P is the surface potential during primary charging, V _L is the surface potential of the exposed area exposed by the first-order diffracted laser beam in step (b), V _D is the surface potential of the area not exposed to laser light, and V _LL is 1 above
The surface potential of the area exposed to the O-order diffracted laser beam in step (c), V _DL
is the surface potential of the area exposed only to the O-order diffracted laser beam. By selectively calling these V _LL and V _DL immediately before development with each color toner, development is performed for each color for each color information.

The O-order diffracted laser beam that selectively irradiates the light irradiation area for each color in the step (c) is emitted from the same light source (laser oscillator) 11 as the first-order diffracted laser beam for writing each color optical information, and is It is divided by a frequency-simultaneously driven acousto-optic light modulation element 14, and guided to the light irradiation parts 20', 22' and 23' through the same deflection means (rotating polygon mirror) 16 and -θ lens 17, so that each color light information As long as the creepage distance between the writing position and the three irradiation positions 20', 22' and 23' of the O-order diffracted light is adjusted accurately in advance, each color light information exposure area can be reliably irradiated with selective light in synchronization. This makes control very easy.

In the apparatus of this embodiment, there are three developing units 3, 4, 5.
The first one is a reversal development method using a normal magnetic brush, but the other two are non-contact development methods that have a gap between the electrostatic latent image holding surface and the toner layer. This prevents the initially developed toner image from being disturbed by subsequent developers and from causing color mixing.

In the above embodiment, the original is color-separated using blue, green, and red filters that have an extra color relationship with each other, and the written image information is developed in three colors, yellow, magenta, and cyan, so that color photographs and paintings can be created. We have described a color image recording method suitable for reproducing images in the same colors as the original, but in cases where the original is recorded in multiple colors, such as three colors, it is not always possible to reproduce the optical image. There is no need to separate the colors into three colors that are complementary colors to each other; instead, color separation is performed using a color filter that can distinguish the colors of the original, and toners can also be used instead of using yellow, magenta, and cyan, which are complementary colors to each other. It is also possible to use toners of different colors.

This optical image writing method uses a multi-frequency simultaneous drive acousto-optic light modulator to simultaneously write each color signal, but the conventional method of writing each color signal one line at a time is also possible. 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 of each color is written in the same area on the photoreceptor at once, and each image is sequentially developed with a different color toner and transferred at once. As a result, only one drum is required for the photoreceptor, there is no need to repeat the same process for each color, there is no color shift, image recording speed is improved, and the device is simpler and more compact. , 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 sectional view of a device for forming light beams for writing a plurality of optical images corresponding to image signals 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 an enlarged sectional view of a part of the photoreceptor, and FIG. 5 is a sectional view showing an example. FIG. 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 of the present invention. 1...Corona discharger for primary charging, 2...Corona discharger for secondary charging, 3, 4, 5...Developer for each color,
6...Corona discharger for transcription, 7...Transfer paper,...
... Photoreceptor drum, -1 ... Conductive support, -
2...Photoconductive layer, -3...Transparent insulating layer, _LbY ,
Lb _M , Lb _C ... Light beam for writing, Lb _O ... O-th order diffracted laser beam.

Claims (1)

[Claims] 1. A plurality of light beams containing image information of each color obtained by color-separating an original are projected onto an electrophotographic photoreceptor for exposure, and each electrostatic latent image formed is transferred to toner of a different color. In an electrophotographic color image recording method in which a color image is obtained by developing the electrophotographic photoreceptor and transferring it to the same transfer paper, the above electrophotographic photoreceptor is laminated on a conductive support with a photoconductive layer and a transparent insulating layer in this order. (a) uniformly charging the photoreceptor from the transparent insulating layer side by direct current corona discharge; (b) simultaneously charging the photoreceptor from the transparent insulating layer side with direct current corona or alternating current corona discharge of opposite polarity to the previous process. or immediately before that, a step of line-sequentially performing light image exposure with a plurality of light beams containing color-separated image information and writing color-specific information; (c) selectively only the light image-exposed area with the above one light beam; A step of irradiating light from the transparent insulating layer side, forming an electrostatic latent image corresponding to the color information written by the above-mentioned luminous flux, and developing this with a toner of that color, for each color, (d ) An electrophotographic color image forming method comprising, in this order, the steps of transferring the toner image formed on the photoreceptor in the steps up to the previous step onto the surface of a transfer paper. 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 into an acousto-optic light modulation element that is 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 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. 4 The light beam used for selective light irradiation of the optical image exposure area with each light beam in the step (c) above is a 0th-order diffracted laser beam emitted from the multi-frequency simultaneous drive acousto-optic light modulator. 3. The method according to claim 2, wherein the beam passes through the same deflection means and the same −θ characteristic correction means as the first-order diffracted laser beam.