JPH0683351B2 - Color image forming apparatus - Google Patents

Description

Detailed Description of the Invention a. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color image forming apparatus, and more particularly to a color image forming apparatus suitable for image formation by electrophotography.

B. 2. Description of the Related Art In recent years, an image forming apparatus for obtaining a full-color copy by using a full-color original image (original) has been developed for image formation by electrophotography. A multicolor image is easy to reproduce from a manuscript of a person, still life, landscape, etc., and it is easy to incorporate a lot of information in one recorded image.
It is convenient for figures and tables.

Under the above circumstances, various methods and apparatuses for forming a multicolor image have been proposed.

For example, a plurality of latent image forming means and a plurality of developing means are arranged around a rotating drum-shaped photoconductor, and latent image formation and development are repeated to form visible images of different colors on the drum-shaped photoconductor. A method in which they are formed in an overlapping manner and transferred onto a recording sheet all at once (Japanese Patent Laid-Open Nos. 52-106743, 56-144452, and 58-7).
9261 and 61-170754).

Further, one latent image forming means and a plurality of developing means are arranged around the rotating drum-shaped photoconductor, and the latent image is formed and developed for one color for each rotation of the photoconductor, and the latent image forming means and the developing means are developed. A method of forming a multicolored visible image on a photoconductor by a plurality of rotations and transferring the multicolored image onto recording paper at once (Japanese Patent Laid-Open No. 60-76766,
No. 60-95456, No. 61-170754).

In the former method, when the colors to be reproduced are yellow, magenta, cyan, and, if necessary, black, which is a full color, the latent image forming means and the developing means are the same in number as the types of the above-mentioned photoreceptors, respectively. Since it has to be arranged in the periphery, the diameter of the photoconductor becomes large and the apparatus becomes large. Also, in order to guarantee the registration (registration) of each color separation latent image when forming a latent image, a control or device that makes the writing accuracy of the latent image forming means such as laser, LED, LCS, etc. extremely high is required. Since the scanning is performed only once, the reading resist is good or a large-capacity image memory is required.

In the latter method, since the latent image forming means is single, the apparatus can be made smaller than in the former method, and the latent image forming means is commonly used, which is advantageous for guaranteeing the latent image resist. However, the photoconductor must be rotated by the same number as the above-mentioned types of colors, and the speed of multicolor image formation becomes slow. On the other hand, in the case of the reading scan, if the image memory is not provided, the reading scan is performed 3 to 4 times, and the resist of the reading means poses a problem, in contrast to the former method.

C. SUMMARY OF THE INVENTION It is an object of the present invention to solve the problems of the conventional image forming method described above and to provide a color image forming apparatus capable of high-speed image formation without increasing the size of the apparatus.

Another object of the present invention is to provide a color image forming apparatus in which a clear color image free from color misregistration is maintained and the memory capacity is greatly reduced.

D. The above-mentioned object is to provide one color image reading device that optically scans an original to form color separation information of blue, green, and red, and processes the color separation information to black, yellow, magenta, and cyan. Processing means for forming a color signal, a selection means for selecting two color signals from the black, yellow, magenta, and cyan color signals, a rotatable image carrier, and a rotation direction of the image carrier in order. First and second latent image forming means arranged to form a latent image on a common area on the image carrier based on the two color signals selected by the selecting means, and the second latent image forming means. One delay means for compensating the latent image formation of the image forming means by the time required for the image carrier to move between the latent image forming positions of the first and second latent image forming means; Of the latent image forming means and the second latent image forming means of And two on the downstream side in the rotation direction of the image carrier of the second latent image forming means, each containing color toners of black, yellow, magenta, and cyan, and the latent image on the image carrier is formed. Develop the image, black, yellow, magenta,
Four developing means for forming a cyan color toner image,
During the first rotation of the image carrier, based on the two color signals selected by the selecting means, in synchronization with the first optical scanning of the color image reading apparatus, the first and second A latent image is formed on the image carrier by the latent image forming means, and one developing means between the first latent image forming means and the second latent image forming means and the second latent image forming means. While developing by one developing means on the downstream side in the rotation direction of the image carrier, while the second rotation of the image carrier is performed, based on the remaining two color signals selected by the selecting means, In synchronization with the second optical scanning of the color image reading device, a latent image is formed on the image carrier by the first and second latent image forming means, and the first latent image forming means and the second latent image forming means form a latent image. Before the second developing means and the second developing means between the second latent image forming means A color image forming apparatus comprising: a control unit that controls to simultaneously transfer the four-color toner images formed by the other developing unit on the downstream side in the rotation direction of the image carrier to the transfer material. To be achieved.

E. Examples Hereinafter, the present invention will be described in detail with reference to the illustrated examples.

First, a preferred embodiment of the present invention will be described.

1 (a) and 1 (b) are schematic configuration diagrams showing an example of a recording apparatus for carrying out the method of the present invention, FIG. 2 is a sectional view of an image reading apparatus, and FIG. 3 is a main part of a one-dimensional image sensor. Sectional views, FIGS. 4 (a), (b) and (c) are schematic configuration diagrams of a laser beam scanner for image exposure, FIG. 5 is a partial sectional view showing an example of a developing device, and FIGS. FIG. 9 is a flowchart for carrying out the method of the present invention, FIGS. 11 and 12 are image forming circuit diagrams, and FIGS. 13 and 14 are image formation time charts. In the recording apparatus shown in FIG. 1 (a), 1 is a drum-shaped image carrier having a photoconductive photosensitive member surface layer such as Se and rotating in the direction of the arrow, and 11 and 12 are the surface of the image carrier 1. Charger for charging, 21 and 22 are image exposure parts for each color of a color image, 31 to 34 are developers for which toners of different colors such as yellow, magenta, cyan and black are used as developers, 13
Reference numerals 41 and 41 are provided in order to facilitate transfer of a color image formed by superimposing a plurality of color toner images on the image carrier 1 to the transfer body P, or to facilitate separation of the transfer body P. A pre-transfer charger and a pre-transfer exposure lamp are provided, 14 is a transfer device, 61 is a fixing device for fixing the toner image transferred to the transfer body P, 42 and 15 are static elimination lamps and static elimination corona dischargers, respectively. Either one or both are used in combination. 16 is a separating electrode for separation, 51 is a surface of the image carrier 1 after the color image is transferred to remove the residual toner on the surface, and by the time the surface after the first development is reached Is a cleaning device having a cleaning blade and a fur brush separated from the surface of the image carrier 1.

Here, in the chargers 11 and 12, in particular, those which are superposedly charged on the surface of the image carrier 1 which has already been charged, it is possible to give stable charging with little influence of the previous charging. It is preferable to use a scorotron corona discharger such as Further, in the case where the drum-shaped image carrier 1 is used as in this recording apparatus, the image exposures 21 and 22 are different from each other in the slit exposure as in a normal mono-color electrophotographic copying machine by filters. Although it may be filtered, in order to record a clear color image, a latent image formed by image exposure by a laser beam scanner as shown in FIGS. 4 (a) (b) (c) is formed. Inverse development is preferable. If a laser beam scanner as shown in FIGS. 4 (a) and 4 (b) is used to form the image exposure 104, it is possible to easily form an electrostatic image for each color, as will be described later, and therefore a clear image can be obtained. Color images can be recorded.

The laser beam scanner shown in FIG. 4 (a) is an octahedral rotating polyhedron rotated by a drive motor 130 by turning on / off a laser beam emitted from a laser 121 such as a He-Ne laser by an acousto-optic modulator 122. Mirror scanner consisting of a mirror
It is deflected by 123 and is formed into image exposure 104 in which the surface of the image carrier 1 is scanned at a constant speed through the imaging f-θ lens 124. Incidentally, 125 and 126 are mirrors, and 127 is an image forming f-θ lens 124 for irradiating the image carrier 1 with a beam having an appropriate diameter.
This is a lens for optimizing the diameter of the beam incident on the. Further, as the laser beam scanner, the one having the structure shown in FIG. 4 (b) is also suitable. The laser beam generated by the semiconductor laser 221 is driven by the drive motor 2
It is rotated and scanned by the polygon mirror 223 rotated by 30, and the optical path is bent by the reflecting mirror 237 through the f-θ lens 224 and projected onto the surface of the image carrier 1 to form a bright line 239. Reference numeral 234 is an index sensor for detecting the beam position to control the start of beam scanning, and 235 and 236 are cylindrical lenses for tilt angle correction. 238a, 238
Reference numerals b and 238c denote reflecting mirrors that form a beam scanning optical path and a beam detection optical path. Further, a laser beam scanner and an optical deflector described in the specification of Japanese Patent Application No. 61-239469 filed by the applicant of the present invention, such as an optical deflector obtained by etching a quartz plate, are used.
When 3 is used, reciprocal scanning is possible unlike scanning by a rotating polygon mirror. When such reciprocal scanning is adopted, the optical frame scanning system may have a configuration as shown in FIG. 4 (c).

That is, by arranging the index sensors 234 and 234 ′ in the front-back direction of the scanning direction, the scanning start and the scanning end of the laser beam (because it is the returning of the beam,
Since it can be detected that it is the start of scanning), the corresponding image information can be recorded on the image forming body 1.

In FIG. 4 (c), reference numerals 238c and 238c 'indicate reflection mirrors.

The beam at which scanning is started is detected by the index sensor 234, and the modulation of the beam by the first color signal is started by the modulator (not shown). The modulated beam scans the image carrier 1 which is previously uniformly charged by the charger 11 or 12. By the main scanning by the laser beam 104 and the sub-scanning by the rotation of the image carrier 1, a latent image corresponding to the first color is formed on the drum surface.

Further, the image exposure 104 is not limited to the dot exposure by the laser beam as described above, and may be, for example, an LED or a CRT.
It may be obtained by using a liquid crystal or an optical fiber transmission body. The image carrier may be a belt-shaped recording device.

In the image reading apparatus shown in FIG. 2, 37 is a document holding plate for bringing the document 1 into close contact with the document table, and 38a, 38b, 38c are the document 1
A reflection mirror that reflects the light L when imagewise exposed by the exposure lamp 2, and the light L reflected by the reflection mirror group
Is condensed by the lens 3 and irradiated on the one-dimensional image sensor 4, and is converted into an electric signal. The arrow indicates the light source 2,
The direction in which the mirror groups 38a, 38b, 38c are moved for sub-scanning is shown. The light L ₁ collected by the lens 3 is a reduced image C having a B, G, R mosaic filter layer 42 in FIG.
Drop on the surface of the CD image sensor 4. The light L ₁ is a sensor element 41 densely arranged in the CCD image sensor 4 in one dimension.
And is photoelectrically converted, and the electric signal obtained by the photoelectric conversion is driven by the phase drive pulse 43 of ₁ or ₂ at a speed corresponding to the pulse frequency of the transfer gate pulse 44 to transfer section (CCD shift register). ) 45 is main-scanned in the direction of arrow X and output to output 46. The output signal obtained here is input to the modulator of the laser beam scanner of FIG. 4 via the signal system of the image forming system of FIG. 11 described later. As the color reading device, a method in which each color is separated into three colors by a dichroic mirror and then each is incident on a CCD, or a method in which an original is optically scanned by a color contact image sensor can be used.

Further, as the developing devices 31 to 34, those having a structure as shown in FIG. 5 are preferably used.

In FIG. 5, 131 is a developing sleeve made of a non-magnetic material such as aluminum or stainless steel, 132 is a magnet body provided inside the developing sleeve 131 and having a plurality of magnetic poles in the circumferential direction, and 133 is on the developing sleeve 131. A layer thickness regulating blade that regulates the thickness of the formed developer layer, 134 is a scraper blade that removes the developer layer after development from the developing sleeve 131, and 135 is a stirring rotation that stirs the developer in the developer reservoir 136. Body, 137 is a toner hopper, 138 is a toner replenishing roller having a recess for allowing toner to enter the surface and replenishing toner from the toner hopper 137 to the developer reservoir 136, and 139 is a protective resistance 140
A power supply for applying a bias voltage including an oscillating voltage component to the developing sleeve 131 via the developer to form an electric field for controlling the movement of the toner between the developing sleeve 131 and the image carrier 1. Although the developing sleeve 131 and the magnet body 132 are shown to rotate in the directions of the arrows, respectively, the developing sleeve 131 may be fixed, the magnet body 132 may be fixed, or the developing sleeve 131 and the magnet body 132 may be fixed. The body 132 may rotate in the same direction. When the magnet body 132 is fixed, the image carrier 1 is usually used.
In order to make the magnetic flux density of the magnetic pole opposed to the magnetic pole higher than the magnetic flux density of the other magnetic pole, the magnetization is strengthened, or two magnetic poles of the same or different polarities are provided in close proximity thereto. . In such a developing device, the magnetic poles of the magnet body 132 are usually magnetized to have a magnetic flux density of 500 to 1500 gauss, and the magnetic force causes the developer in the developer reservoir 136 to be attracted to the surface of the developing sleeve 131. The developer is a layer thickness control blade
The developer layer is formed with its thickness regulated by 133, and the developer layer moves in the same direction as the direction of the rotation arrow of the image carrier 1 or in the opposite direction (the same direction in the figure), and the developing sleeve 131
Develops the electrostatic image of the image carrier 1 in the developing area where the surface of the image carrier 1 faces the surface of the image carrier 1, and the rest is the scraper blade.
By 134, it is removed from the surface of the developing sleeve 131 and returned to the developer reservoir 136. Further, the development is repeated so as to superpose the color toner images on each other. At least for the second and subsequent developments, the toner attached to the image carrier 1 in the previous development is not displaced in the subsequent development. In addition, it is preferable to use non-contact development conditions. The non-contact development means that the developer layer on the developing sleeve 131 is separated from the image carrier 1 in the state where the developing bias is not applied, and the superimposing bias of direct current and alternating current is applied to the developing sleeve 131 to alternate. A developing method in which toner is caused to fly under an electric field and adheres onto the image carrier 1.

FIG. 5 shows a state of developing under non-contact developing conditions.

Further, the developing devices 31 to 34 do not need to include a black or brown magnetic substance in the toner, so that a toner having a clear color can be obtained, and the toner charge control can be easily performed. It is preferred to use so-called two-component developers, which consist of a mixture with a magnetic carrier. In particular, magnetic carriers include resins such as styrene resin, vinyl resin, ethylene resin, rosin-modified resin, acrylic resin, polyamide resin, epoxy resin, and polyester resin, and ferric tetroxide, γ-ferric oxide, and dioxide. Chromium, manganese oxide, ferrite,
It is made of a material in which fine particles of a ferromagnetic material or paramagnetic material such as a manganese-copper alloy are dispersedly contained, or the surface of the particles of the magnetic material is covered with the resin as described above. It is preferable that the insulating carrier has a resistivity of 10 ⁸ Ωcm or more, preferably 10 ¹³ Ωcm or more. If this resistivity is low,
When a bias voltage is applied to the developing sleeve 131, electric charges are injected into the carrier particles, and the carrier particles tend to adhere to the surface of the image carrier 1, and the bias voltage is not sufficiently applied. In particular, when the carrier adheres to the image carrier 1, the color tone of the color image is adversely affected.

Incidentally, after resistivity was tapping putting particles in a container having a sectional area of 0.50 cm ^2, on packed particles 1 kg / cm ²
It is a value obtained by applying a load of, and reading the current value when a voltage that generates an electric field of 1000 V / cm is applied between the load and the bottom electrode.

If the average particle size of the carrier is less than 5 μm, the magnetization becomes too weak, and if it exceeds 50 μm, the image is not improved, and breakdown or discharge is likely to occur, which tends to make it impossible to apply a high voltage. The diameter is preferably 5 μm or more and 40 μm or less, and if necessary, a fluidizing agent such as hydrophobic silica is appropriately added as an additive.

The toner preferably has an average particle size of 1 to 20 μm, which is obtained by adding various pigments and a charge control agent, if necessary, to a resin, and has an average charge amount of 3 to 300 μc / g, particularly 10 to 100 μc / g. Those are preferable. When the average particle diameter of the toner is less than 1 μm, it becomes difficult to separate from the carrier, and when it exceeds 20 μm, the resolution of the image is deteriorated.

When the developer composed of the mixture of the insulating carrier and the toner as described above is used, the bias voltage applied to the developing sleeve 131 of FIG. 3 causes the toner to sufficiently adhere to the electrostatic image,
Moreover, the setting can be easily performed without fear of causing a leak so that the fogging does not occur. In order to more effectively control the development movement of the toner by applying such a bias voltage, the toner contains a magnetic material used for a magnetic carrier within a range in which the vividness of color is not impaired. Good.

The above is the constitution of the developing device and the developer which are preferably used in the method of the present invention, but the present invention is not limited thereto, and JP-A Nos. 50-30537, 55-18656 to 18659, and 5 are the same.
You may use the developing device and developer as described in 6-144452 and 58-116553 to 116554. More preferably, JP-A-58-57446 previously filed by the applicant of the present application,
58-96900-96903, 58-97973, 60-192710-11
No. 60-14537, No. 60-14539, No. 60-176069, and non-contact development conditions with a two-component developer as described in each specification. Particularly, in the developing device disclosed in Japanese Patent Laid-Open No. 60-176069, the magnet body in the developing sleeve is fixed, and the developing is performed in the thin developer layer portion between the magnetic poles. It is preferable because the developing electric field can be formed sufficiently large to obtain high developing performance. Not rotating the magnet body is also advantageous for deviceization, especially for a developing and forming apparatus having a plurality of developing devices.

It should be noted that each image exposure must be carried out at a position on the image carrier that exactly coincides with each other.
A registration index marker (one, if necessary, a plurality, not shown) provided at a fixed position of the image carrier, a pulse of an encoder rotating together with the image carrier, or the like is detected every time the image carrier rotates. This can be easily and accurately performed by position detection and image exposure timing control by a usual photo sensor, and color shift does not occur in the obtained image.

Further, in the case of a laser optical system, as a light scanning means which also serves as a polygon, a position control method according to JP-A-56-161566, 57-64718 and 59-53866, and a method for forming a plurality of laser beams by polygons are disclosed. Image misalignment can be prevented particularly accurately by using Japanese Laid-Open Patent Publication No. 60-150066 and a plurality of laser beam forming methods using an optical modulator.

Further, as described above, in the above recording method, the toner image formed on the image carrier 1 is directly transferred from the image carrier 1 to the transfer member P by the transfer device 14 without using the transfer drum. Therefore, the size of the device can be reduced without causing color misregistration.

With the recording apparatus as described above, the method of the present invention as shown in FIGS. 6 to 9 can be carried out. 6 to 9 all show up to the stage where the second development is performed.

In FIG. 6, an electrostatic image is formed by the electrostatic image forming method in which the image-exposed portion serves as the background portion and the non-exposed portion serves as the electrostatic image, and the toner to which the electrostatic charge is applied is attached to the electrostatic image during development. 3 shows an embodiment of the present invention carried out thereby. this is,
According to the recording apparatus of FIG. 1 (a), the surface of the image carrier 1 in the initial state in which the electric charge is eliminated by the static eliminators 15 and 42 and the potential is 0 by the cleaning device 51 is rotated once. The first charge is uniformly applied to the eyes by the charger 11, and the charged surface is subjected to the first image exposure by which the potential except the electrostatic image portion becomes substantially 0 by the image exposure 21 for each color. An electrostatic image whose developed potential is substantially equal to the potential of the first charging is applied to the developing device 31-
Of the 32, the first development is performed by the developing device using the developer of the color toner corresponding to the image exposure 21, and the toner T having the opposite polarity is attached.

The charging device 12 again uniformly performs the second charging, and the charged surface is subjected to the second image exposure in which the potentials other than the electrostatic image portion become substantially 0 by the image exposure 22 for a color different from the previous one. Then, the obtained electrostatic image is developed a second time by the toner T'by any of the other developing units 33 to 34 using the developers of the corresponding color toners.

Next, the pre-transfer processing 13,41, the transfer electrode 14, the static eliminators 15,42, and the cleaning device 51 are disabled, and the electrostatic image formation and development of FIGS. 3 and 4 are repeated in the second rotation. When the fourth development is performed and a color image in which the color toner images are superimposed is formed, the pre-transfer charger 13 and the pre-transfer exposure lamp 41 are operated until the color image passes, and then the transfer device 14 is used. The color image is transferred to the transfer body P that is sent in synchronization with the rotation of the image carrier 1, and the transferred color image is fixed to the transfer body P by the fixing device 11, and the surface of the image carrier 1 onto which the color image is transferred. Is an embodiment of the present invention in which one cycle of color image recording is completed by removing the charge by the charge removers 15 and 42 and returning to the initial state by being cleaned by the cleaning device 14. That is, the charging for forming the electrostatic image is performed twice by the chargers 11 and 12 each time, and the image exposure is also performed twice by the two exposure devices formed by the second laser beam scanner, for example. , To make the recording device compact and inexpensive, and
High-speed recording is possible.

In the embodiment shown in FIG. 6, since the development is carried out by the developing method in which the electrostatic image is developed with the toner which is charged in the opposite polarity, it is easy to increase the development density of each color, and therefore the clear color is easily obtained. Images can be recorded.
Since the potentials of the previous toner images remain and color mixing is likely to occur, in order to avoid color mixing, it is advisable to set the DC bias in the development to be sequentially higher in the subsequent cycles. Correspondingly, it is preferable to set the charging potential sequentially higher. Further, at the time of transfer, means for aligning the polarities of the toner is required.

7 to 9 show that an electrostatic image is formed by the electrostatic image forming method in which the image exposed portion becomes an electrostatic image having a lower potential than that of the background portion, and the development becomes an electrostatic image with the same polarity as the background portion potential. 4 shows an example of the reversal development of the present invention performed by depositing charged toner.

The embodiment of FIG. 7 by the recording apparatus of FIG.
The surface of the image carrier 1 in the same initial state as in the figure is uniformly charged by the charger 11 in the first rotation, and the charged surface is subjected to color-wise image exposure by the laser beam scanner of FIG.
21 is projected to perform the first image exposure in which the potential of the electrostatic image portion becomes substantially 0, and the obtained electrostatic image is exposed to the image in the developing devices 31 to 32.
21 color toner developer (However, in this case,
Unlike the example in the figure, the toner is first developed by a developing device using a developer whose toner is charged to the same polarity as the charging of the image carrier 1, and the charging devices 11 and 12 are used for subsequent latent image formation. Without using the laser beam scanner, the second image exposure is performed by projecting the image exposure 22 of a different color at a position deviated from the projection position of the previous image exposure 21 or at the same position as the projection position of the previous image exposure 21, and the potential obtained by that is obtained. Is developed by one of the other developing units 33 to 34 using the developers of the corresponding color toners, and the third and fourth electrostatic image formation is performed in the second rotation. And the development are repeated, and thereafter, one cycle of color image recording is completed in the same manner as described with reference to FIG. In this example, the electrostatic image with a potential of about 0 is
Even if the toner T that has been developed and charged to the same polarity as that of the image carrier 1 is attached, the potential does not become substantially equal to the background portion potential as shown in the figure, so that the electrostatic image formed later has a different color. At the time of development to which the toner T'is attached, the toner T'is accumulated and attached to the electrostatic image portion to which the toner T has been attached, although it is not exposed, that is, written. Therefore, it is possible to obtain a single-color image or a multi-color image excellent in sharpness by utilizing the fact that the toners of different colors are easily overlapped.

In the example of FIG. 8, the example of FIG. 7 positively forms an electrostatic image at the position where the electrostatic image was previously formed, while the electrostatic image portion previously developed is formed. This is an example in which recharging is performed and smoothed in order to prevent color mixture that adheres even if a small amount of different color toner is used in development. The example in FIG. 8 is the same from the initial stage to the first development as in the first development in FIG. 7, but next, the charger 12 uniformly charges the second time again, and the charged surface The second example is different from the example in FIG. 7 in that the second image exposure is performed, the second development is performed, and then the third and fourth electrostatic image formations and developments are similarly repeated. Thus, in the example of FIG. 8 in which the surface of the image bearing member 1 is uniformly charged again after the previous development to perform the subsequent electrostatic image formation and development, in the example of FIG. Similarly, it is possible to form an electrostatic image by superimposing it on the position where the electrostatic image was previously formed.
It is possible to obtain the effect that the toner of the subsequent color difference hardly adheres unless it is exposed to the image position where the previous toner adheres.

The example of FIG. 9 is an example in which it is particularly prevented that the toners of different colors later are attached to the image position where the previous toner is attached. This example is the same as the first development of FIG. 8 up to the first development, but after the first development, as shown in FIG. 1B, the image bearing is performed by using the exposure lamp 71. The surface of the body 1 is uniformly exposed and then secondly charged by the charger 12, or first secondly uniformly charged by the charger 12 and then weakly by the exposure lamp 71 indicated by a virtual line. Or even exposure, then the second
The image exposure and the second development are performed, and then the third and fourth electrostatic image formation and development are similarly repeated. Here, after the development, if the uniform exposure is performed first, the photosensitive member including the portion where the toner is adhered after the development is subjected to the uniform exposure to almost 0 potential, and the toner is adhered by performing the second charging there. The difference between the potential of the portion and the potential of the portion other than that where the electrostatic image is formed next becomes smaller, and the surface of the image carrier 1 can be uniformly charged. It also gives favorable results to a photoreceptor having an optical memory. Also, after development, the second
When the surface of the image carrier 1 is uniformly charged by performing a double charge and the light is uniformly weakly exposed there, the charged state of the toner on the surface of the image carrier 1 is when the toner is not adhered. Higher potential.

Therefore, when developing the next formed electrostatic image,
Since the potential is smoothed or high at the portion where the toner is attached, it is possible to effectively prevent the different color toner from being attached thereto.

In any of the above examples, it is preferable that the developing device 31 to 34 be developed by using a developer composed of a mixture of toner and an insulating carrier under non-contact developing conditions. Thereby,
As described above, mixing of different color toners is prevented, and it becomes easy to apply an appropriate bias voltage for toner control to the developing sleeve 131 of the developing device, which is similar to a laser beam scanner. Even in the case of the electrostatic image forming method or the developing method as in the example of FIG. 7 to FIG. 9 in which the image exposure apparatus is advantageously used, it is possible to record a color image having a high developing density and excellent sharpness.

Next, an outline of the color image forming system according to the present invention will be described.
It will be described with reference to the drawings. This image forming method uses the process shown in FIG. Recording device by control signal from CPU,
The dot pattern memory and the image forming process are manufactured and driven. For example, the exposure system (lamp 2, mirrors 38a, 38b,
Along with the movement of 38c), the CCD image sensor 4, which is a kind of color scanner, reads the color information of B, G, and R in the horizontal direction of the document 1 and outputs an analog video signal. This signal is A /
After the D conversion, the shading correction is performed to remove the color information and the distortion due to the optical system, and is temporarily input to the buffer memory so that each B, G, and R corresponds to the same image position.

Although FIG. 3 shows a CCD color image sensor, a contact color image sensor can also be used.

Further, in order to improve the color separation characteristics of the color separation filter, a notch filter for cutting light between B and G and between G and R may be provided. An interference filter is preferably used as the notch filter, and for example, a notch filter having a spectral characteristic as shown in FIG. 15 is used. As shown in FIG. 16, the notch filter 171 is set before and after the lens system in the lens system 170 and between the lenses, and is used before and after the light converging element in the contact color image sensor. FIG. 17 shows an image reading apparatus using the light converging element 181.
In the figure, 182 is an exposure lamp for exposing an image, 183 is a reflecting mirror, 184 is a slit, and 185 is a contact image sensor. Next, the BGR signal from the buffer memory is subjected to complementary color change to YMC and gradation correction is performed, and then black component extraction (UCR) is performed from each YMC data to separate it into a chromatic color component and an achromatic color component. . Where Y is the chromatic component.
The MC is color-corrected and the gradation is corrected together with the black component (BK), and then input to the pattern generator (PG). Here, it is changed into a digital dot pattern signal based on the dither method, for example, and stored in the page memory for each color. These image data are output to the recording device via a line memory required as a buffer in synchronization with the rotation of the image forming body to perform writing and image formation. In FIG. 11, M is passed through a selector that selects color information at the first rotation of the image forming body.
The Y dot patterns are output from the first latent image forming means and the second latent image forming means, respectively, through the delay circuit for ensuring the space between the dot pattern and the two image forming means, and the image forming body for the next second rotation is the same. When it comes to the position, the BK dot pattern is delayed from the C dot pattern and is output from the first latent image forming means and the second latent image forming means from the page memory at the write timing.

FIG. 12 shows a case where the image memory is greatly reduced. First
Similar to FIG. 11, the image data is input to the pattern generator (PG) by the first scanning by the color scanner. Here, for example, the M dot pattern signal which is changed into a digital dot pattern signal based on the dither method and which is first written is subjected to writing and image formation almost in synchronization with reading through a line memory required as a buffer. On the other hand, the second writing Y
The dot pattern signal is output to the recording device via a delay circuit that ensures a space between the two image forming means. At the next rotation of the image forming body, the C dot pattern is scanned again by the color scanner in accordance with the writing timing, while BK
The dot patterns are sequentially taken out via the delay circuit.
The color scanner scans in synchronization with the rotation of the image forming body.

The delay circuit in FIGS. 11 and 12 is an image memory having a role as a shift register. This image memory is for compensating for the difference in writing timing between the two image forming means.

In the normal color mode, the developing device having the color toner corresponding to the image data operates. In the image forming apparatus of FIGS. 1A and 1B, the developing devices 31 and 32 having magenta toner and cyan toner correspond to the case of developing the image data output without passing through the delay circuit, and yellow and black. This corresponds to the case where the developing device having toner develops the image data output through the delay circuit. The image forming means 21 corresponds to the first image forming means, and the image forming means 22 corresponds to the second image forming means. The first and second latent image forming means have different recording positions on the photosensitive drum. Therefore, it is necessary to accurately shift the timing of sending data from the delay circuit. The timing shift is determined by counting the first horizontal synchronizing signal, and the second image signal (color information) is transmitted when the specified number of times is reached. In addition to such means, it is also possible to set from the drum rotation state and time by a drum encoder or the like.

In the system described in FIG. 12, the reading system needs to be returned to the next writing time, and further, the alignment of the image on the image forming body is required. Since it is extremely difficult to do this mechanically, it is preferable to prepare a necessary line memory as a buffer for each screen. That is, as the positioning of the document, when the light source is moved (at the time of reading the document), the document table, or the moving position of the light source or the document end is stored as a reference position in the reading buffer memory, while the writing timing is formed on the drum. If the signal corresponding to the M reference toner image position is detected and the writing is performed after the second rotation, the position of the image can be accurately adjusted. This superimposed toner image is transferred to the pre-transfer charger 13 and the exposure lamp.
After being easily transferred by the action of 41, it is transferred by the action of the transfer electrode 14 onto the transfer sheet P supplied from the cassette, and the transfer sheet P is separated by the action of the separating electrode 16 and is heated and fixed in the fixing device 61. . After the transfer, the surface of the image forming body 1 is cleaned of the residual toner by a charge removing device 15 and a cleaning device 51 having a cleaning blade to prepare for the next image formation.

As described above, in the present embodiment, since the dot pattern of each color is written in synchronization with the read image signal, a buffer memory is sufficient and a large-capacity frame memory is not required, which reduces costs. It is great to contribute.

The reference signals Ey ₁ , Em ₁ , Ec ₁ , and Ek ₁ are reference density patterns for feedback of toner density control, charging potential, exposure intensity, and development bias, and reproducibility of color images is greatly improved. It

13 is a timing chart of the system described with reference to FIG. 13, FIG. 14, FIG. 11 and FIG.

This color image forming apparatus can print an arbitrary single-color image or two-color image
It can be obtained by rotating the image forming body once.

As described in the process shown in FIG. 7, a single color image can be obtained by developing the same latent image a plurality of times without recharging. In this case, a specific color separation component or sum obtained by one-time scanner scanning is used as image data to be written by the image forming means 21 in FIG. It is used to develop and transfer. For example, to produce a green monochromatic image, Y toner and C
Develop with toner. At this time, the charger 12 and the image forming means 22 are not operated. Of course, when operating the developing devices 33, 34, the charger 12 and the image forming means 22 may be operated.

In the image reading apparatus, there are cases where it is desired to represent a specific area by M or C in a two-color mode, for example, a black original. At this time, by trimming, a specific color area is designated, image formation of the specific area by the image forming device 21, development recharging (12) by the developing device 31 or 32 by the specific color, and image formation of the specific area by the image forming device 22. By developing with the developing devices 33 and 34 for a specific color, a two-color image can be obtained by one reading scan and one rotation of the image forming body. The output data from the selector is output to the first latent image and the second latent image forming means by dividing the same black data according to the trimmed area. M
In case of black and black, M after charging and image exposure by image forming device 21
After developing with toner and recharging, the image forming device 22
Image exposure is performed to develop in black.

By alternately arranging the two image forming means and the plurality of developing devices in this manner, not only the color image formation but also various modes can be effectively used.

Although the image forming body is configured to rotate, it is necessary to have a size equal to or larger than the size of the image in order to superimpose the images by a plurality of rotations.

When the image size includes A-3, even small images such as A-4 and B-5 have the same print speed, resulting in extremely poor efficiency. In such a case, it is advisable to form a plurality of images on the image forming body. (Japanese Patent Application No. 60-66321 and No. 60-66322) In response to this, the scanning for reading is repeated according to the original document and then returning to the start position after scanning. In the time chart shown in FIG. 14, two writing scans are included in the first reading scan. This changes the timing of charging, image exposure, and development, but the delay time between the two image forming means is the same.

As can be seen from the processes of FIGS. 6 to 9, the electrostatic image (latent image) forming means is constituted by the charger and the image exposure device.

Next, the examples of FIGS. 6 to 9 will be described more specifically as Examples 1 to 3, respectively.

Example 1 (Example of FIG. 6) The color image forming apparatus as shown in FIGS. 1 (a) and 2 was used. Color image formation was performed by the method shown in FIGS. The image carrier 1 has an OPC (organic photoconductive layer) surface layer, and its peripheral speed was 90 mm / sec. The surface of the image carrier 1 is charged to -600 V by a charger 11 using a scorotron corona discharger, and a magenta image information is recorded on the charged surface by a semiconductor laser beam scanner.
The first image exposure was carried out with 21 at a density of 16 dots / mm.
As a result, an electrostatic image in which the potential of the non-exposed portion was -600 V was formed on the image carrier 1 with respect to the background portion potential of -50 V of the exposed portion.
This electrostatic image is first transferred by the developing device 31 as shown in FIG.
Developed twice.

The developing device 31 has a spherical ferrite resin coated with an average particle size of 30 μm, a magnetization of 30 emu / g, and a resistivity of 10 ¹⁴ Ωcm.
The average particle size of the above carrier, 10 parts by weight of magenta pigment and other load control agent in styrene-acrylic resin is
A developer consisting of 10 μm non-magnetic toner was used under the condition that the ratio of toner to carrier was 25 wt%. The outer diameter of the developing sleeve 131 is 20 mm, the rotation speed is 100 rpm, and the magnetic flux density of the developing sleeve surface of the N and S magnetic poles of the magnet body 32 is 1000.
Gauss, rotation speed 1000 rpm, thickness of developer layer in the developing area
0.4 mm, the gap between the developing sleeve 131 and the image carrier 1 is 0.6 mm,
The developing sleeve 131 has a DC voltage of -100V and 3kHz, 1000V.
It was based on the non-contact development condition of applying a superimposed voltage of (effective value) AC voltage.

While developing the electrostatic image with the developing device 31, the other fifth
The developing devices 32 to 34 shown in the figure were kept in a non-developed state. That is, the developing sleeve 131 is separated from the power source 139 to be in a floating state, or a DC bias voltage having the same polarity as the charging of the image carrier 1 but the polarity opposite to the charging of the toner is positively applied to the developing sleeve 131. To be achieved. Since the developing devices 32 to 34 are also developed under the non-contact developing condition like the developing device 31, the developer layer on the developing sleeve 131 does not have to be particularly removed. The developing device 33 uses a developer in which the toner of the developer of the developing device 31 is changed to a toner containing a yellow pigment instead of the magenta pigment, and the developing device 32 also uses copper phthalocyanine as a cyan pigment. A developer having a composition changed to a toner containing was used, and a developer having a composition changed to a toner containing carbon black as a black pigment was also used for the developing device 34. Of course, color toners made of other pigments or dyes may be used, and the order of developing colors and the order of developing devices may be appropriately selected.

The surface of the image carrier 1 subjected to the first development was recharged to -650V by operating the scorotron corona charger 12. A non-contact developing condition in which yellow image information is subjected to the second image exposure on the charged surface by the laser beam scanner 22 and then a superimposed voltage of −150 V DC voltage and 3 kHz, 1000 V AC voltage is applied to the developing sleeve 131. Then, the second development of magenta toner was performed by the developing device 33. Next, in the second rotation, the laser beam scanner 21 is used for charging and cyan image information.
The image exposure by the developer and the third development of the cyan toner by the developing device 32, the image exposure by the laser beam scanner 22 for the charging and the black image information and the fourth development of the black toner by the developing device 34 were repeated. In the second and subsequent developments, the amplitude of the DC bias component or the AC component of the voltage applied to the developing sleeve 131 is appropriately adjusted according to the change in the surface potential of the image carrier 1, the development characteristics, and the color reproducibility. The selection time of frequency and time selection conversion is changed. In particular, increasing the absolute value of the charging potential sequentially while increasing the absolute value of the DC bias has the effect of preventing toner mixing.

When the fourth development is performed and a color image of four colors is formed on the image carrier 1, the pre-transfer charger 13 and the pre-transfer exposure lamp 41 facilitate the transfer, and the transfer device 14 transfers the transferred image. It was transferred to P and fixed by the fixing device 12. The proper exposure by the pre-transfer exposure lamp 41 also has an effect that the transfer body P is easily separated from the image carrier 1. The image carrier 1 on which a color image is transferred is
The charge is removed by the static eliminator 15 and the static elimination lamp 42, and the residual toner is removed from the surface by the contact of the cleaning blade and the sponge roller of the cleaning device 51, and when the surface on which the color image is formed passes the cleaning device 51. One cycle process of color image recording was completed completely.

The color image recorded by the above was clear with each color showing sufficient density, but a slight color mixture of toner was observed in the area where the color toners were closely attached to each other. .

The timing of the image forming process is shown in the timing chart of FIG. The screen signals read by the CCD image sensor 4 are not stocked in the dot pattern memory, and the M pattern and Y pattern signals are output to the recording device without passing through the page memory or through the line memory, if necessary. Each of the C and BK pattern signals is delayed by a shift register (delay circuit) having a capacity that corresponds to the space between the image forming apparatuses, and sequentially taken out at the timing of image formation. Therefore, the first M toner image and Y toner image are formed almost in synchronization with the image reading. In this image forming process, since image formation is performed by two reading scans and two rotations of the image forming body 21 and reading and writing are performed in synchronization, high-speed recording is possible and a page memory corresponding to a plurality of sheets. The capacity is being saved.

Example 2 (example of combined use of FIG. 7 and FIG. 8) A color image forming apparatus as shown in FIG. 1 (a) and FIG. 2 was used.

A two color image is obtained from a single color image. The case is shown where the original is a black monochromatic image and the specific area is green by trimming and the others are red.

The image carrier 1 has a long-wavelength-sensitized Se photoconductor surface layer, and its peripheral speed is 120 mm / sec. The surface of this image carrier 1 is charged to +800 V by a charger 11 using a scorotron corona discharger, and 12 dots / m 2 by a laser beam scanner 21 of FIG. 2 using a semiconductor laser on the charged surface.
The first image exposure was performed at a density of m. As a result, the potential of the exposed portion of the image carrier 1 is + 50V with respect to the background potential of + 800V.
Electrostatic image was formed. This electrostatic image was subjected to the first reversal development by the developing device 31 as shown in FIG.

The developing conditions of the developing device 31 having magenta toner are as follows: the average particle diameter of the carrier of the developer is 30 μm, the ratio of the toner to the carrier is 20 wt%, and the developing sleeve 131 has +600
Example 1 was the same as Example 1 except that a superimposed voltage of a DC voltage of V and a DC voltage of 1.5 kHz, 700V (effective value) was applied. The conditions of the other developing devices 32 to 34 were the same as those in Example 1 except for the bias voltage. However, in this case, the bias voltage for holding the developing device that is not involved in the development in the non-development state has the opposite polarity to the charging of the toner and also to the charging of the image carrier 1. First
The second image exposure by the laser beam scanner 22 is not performed on the surface of the image carrier 1 that has been developed by the magenta toner a second time without the charging device 12 acting, and then the yellow toner is generated by the developing device 33. Second development was carried out. As a result, a red toner image was formed on the same latent image.
After recharging to +800 V by the charger 12 at the second rotation, the laser beam scanner 21 performs the second image exposure, and similarly, the developing device 32 performs the third development of cyan toner and the developing device 33 performs the fourth yellow toner. The development was repeated to form a green toner image on the same latent image. In the second and subsequent developments, the amplitude of the DC bias component or the AC component of the voltage applied to the developing sleeve 131 is appropriately adjusted according to the change in the surface potential of the image carrier 1, the development characteristics, and the color reproducibility. The frequency and the selection time of time selection conversion are changed. Particularly in this example, increasing the DC bias sequentially every time is effective in improving the color reproduction of the toner.

After the fourth development is performed and a two-color image is formed on the image carrier 1, after that, the image is transferred to the transfer body P and fixed as in Example 1, and the image carrier 1 is discharged and cleaned. Then, one cycle process of color image recording was completed.

The timing of the image forming process is partially different from the timing chart of FIG. As the image signal read by the CCD image sensor 4, only the BK pattern signal is used. The BK pattern signal converted into a red image is output to the recording device through the first image forming means without passing through the page memory or through the line memory if necessary. In this image forming process, the first red toner image is formed almost in synchronization with the first image reading. Since the green toner image formation is performed in the same manner as the first time by the two reading scans and the second rotation of the image forming body 21 and the reading and the writing are performed in synchronization, the delay circuit is not used.

Example 3 (Example in which FIGS. 7 and 8 are used in combination) A color image forming apparatus as shown in FIGS. 1 (a) and 2 was used.

A two color image is obtained from a single color image. The case where the original is a black monochromatic image and the specific region is magenta and the others are black by trimming is shown. The image carrier 1 has an Se photoconductor surface layer, and its peripheral speed is 120 mm / sec. The surface of the image carrier 1 is charged to +800 V by a charger 11 using a scorotron corona discharger, and 12 dots / m 2 is charged by a laser beam scanner 21 shown in FIG. 4 using a semiconductor laser.
The first image exposure was performed at a density of m. As a result, the potential of the exposed portion of the image carrier 1 is + 50V with respect to the background potential of + 800V.
Electrostatic image was formed. This electrostatic image was first developed by the developing device 31 as shown in FIG.

The developing conditions of the developing device 31 having magenta toner are as follows: the average particle diameter of the carrier of the developer is 30 μm, the ratio of the toner to the carrier is 20 wt%, and the developing sleeve 131 has +600
Example 1 was the same as Example 1 except that a superimposed voltage of a DC voltage of V and an AC voltage of 1.5 kHz and 700 V (effective value) was applied. Also,
The conditions of the other developing devices 32-34 are the same as those of the first embodiment except the bias voltage.
Same as However, in this case, the bias voltage for holding the developing device that is not involved in the development in the non-development state has the opposite polarity to the charging of the toner and also to the charging of the image carrier 1.

The charging device 12 is caused to act on the surface of the image carrier 1 which has been developed with the magenta toner for the first time, and then the second image exposure is performed by the laser beam scanner 22, and then the black toner is developed by the developing device 34. Second development was carried out. As a result, a two-color toner image composed of magenta and black was formed. In the second and subsequent developments, the amplitude and frequency of the DC bias component and AC component of the voltage applied to the developing sleeve 131 are appropriately adjusted according to the change in the surface potential of the image carrier 1, the development characteristics, and the color reproducibility. , The selection time of time selection conversion is changed. Particularly in this example, increasing the DC bias sequentially every time is effective in improving the color reproduction of the toner.

After development is performed to form a two-color image on the image bearing member 1, the image is transferred to the transfer member P and fixed in the same manner as in Example 1, and the image bearing member 1 is discharged and cleaned to obtain a color image. One cycle process of recording was completed. In this case, the image carrier forms a two-color image with one rotation. The timing of the image forming process uses only the first half shown in the timing chart of FIG. As the image signal read by the CCD image sensor 4, only the BK pattern signal is used. The BK pattern signal converted into the M image is output to the recording device without passing through the page memory or through the line memory as necessary, but each BK pattern signal output as a black image corresponds to the image forming device. It is delayed by a shift register having a certain capacity, and is sequentially taken out at the timing of image formation. Therefore, the first M toner image is formed almost in synchronization with the image reading. In this image forming process, high-speed recording is possible because image formation is performed by one reading scan and one rotation of the image forming body 21 and reading and writing are performed in synchronization.

The color image recorded as described above was as clear as in Example 1.

Example 4 (Example of FIG. 8) Using the same apparatus as in Example 1 and using the Se photoconductor used in Example 2, the voltage applied to the developing sleeve 131 of the developing device is +600 V DC voltage and 1000 Hz, Color image recording was carried out under the same conditions as in Example 1 except that a superposed voltage of an AC voltage of 500 V (effective value) was used, and the surface potential of the image carrier 1 was charged to 700 V by the charger 12 and reverse image formation was used. It was

The recorded color image is more than that according to Example 1.
The color mixture of the toner in the portion where the color toners are closely adhered to each other was reduced, and the image was clearer.

According to this embodiment, as mentioned above, Y,
In order to superimpose toner images composed of M, C, and BK toners, it is desirable to superimpose the previous image exposure position and the subsequent image exposure position.
In this case, in order to form an electric latent image by image exposure, it is desirable that the previously formed toner image has translucency with respect to image exposure light. Further, since the order of colors to be developed has a considerable influence on the sharpness of a color image, it is necessary to carefully determine the order of colors to be developed.

Fifth Embodiment (Example of FIG. 9) A recording apparatus having an exposure lamp 71 (shown by a phantom line) provided between the charger 12 and the laser beam scanner 22 as shown in FIG. 1B. used. The voltage applied to the developing sleeve 131 of the developing device is + 600V DC voltage and 2kHz, 500V
The surface potential of the image carrier 1 is +700 V before each image exposure after the second image exposure, with the superimposed voltage of (effective value) AC voltage.
The charging by the charger 11 or 12 and the surface potential are
Color image recording was performed under the same conditions as in Example 4 except that uniform weak exposure was performed by the exposure lamp 71 (shown by phantom lines) that lowers the voltage to 0V. If the uniform exposure is too strong, the light fatigue of the photoconductor increases.

The recorded color image was extremely clear with no color mixing of the toner even in the areas where the color toners were closely attached to each other.

In this embodiment, it is effective for a photoreceptor having light fatigue.

According to the above-described embodiment, the recording apparatus is configured to be small in size and low in cost by using four sets of electrostatic image forming apparatus which repeats four times, the recording speed is relatively fast, and the synchronous control of each image exposure is performed. It is also possible to obtain an excellent effect that it is easily and accurately performed, and each time development is performed by a developing method in which a toner charged to the opposite polarity is attached to an electrostatic image for which development density control is relatively easy. Alternatively, a laser beam scanner can be used in the image exposure device, and a developing method in which toner having the same polarity as that of the electrostatic image is attached to the electrostatic image can be used. Further, in any developing method, the development is not performed. It is possible to obtain an excellent effect that a color image having a sufficient development density and excellent in sharpness can be recorded under the contact development condition.

In addition to the above embodiments, various modifications can be made based on the idea of the present invention.

For example, when it is not necessary to form a color image, for example, when forming an image of one black color, a latent image can be formed by an arbitrary combination of either the charger 11 or 12 and the laser beam scanner 21 or 22. Is. When the dark decay of the photosensitive layer of the image carrier 1 is large, the charger 12
It is preferable that a latent image is formed by a combination of the laser beam scanner 22 and the laser beam scanner 22, and the latent image is developed by the developing device 34. This is because it is possible to utilize the fact that the time between each step of charging, image exposure and developing is short (small distance). In the case of forming a monocolor image using another one color, yellow, magenta, and cyan toner, the combination may be selected in the same way.

Needless to say, in the case of two colors or three colors, any combination can be selected according to the necessity or performance.

Further, it is possible to form various color images by appropriately selecting the combination of the image exposure and the developing device.

In addition, it is possible to perform image composition on the image carrier 1 by performing image exposure with different image information from the laser beam scanners 21 and 22.

As described above, the present invention is not limited to one in which a recording device having a drum-shaped image carrier is used, and is not limited to one in which a color image is transferred to a transfer member. . That is, the present invention can be applied to the one in which the image forming body is mounted on the substrate like the electrofax paper, and the color image formed on the image forming body is fixed without being transferred. In this case, the pre-transfer charging device, the pre-transfer exposure lamp, the transfer device, and the cleaning device are unnecessary. However, the pre-transfer charger, the pre-transfer exposure lamp or the static eliminator may be omitted when transferring, the transfer may be direct pressure transfer or transfer mediated by an intermediate transfer member, and fixing may be performed by heat roller fixing. Of course, it is not limited to.

F. Effects of the Invention As described above, the present invention has the following effects.

(1) Since a plurality of latent image forming means are used and at least one of these means is repeatedly used, it is possible to use one of the image bearing members.
As compared with image formation by rotating or moving once, or image forming by rotating 3 to 4 times or moving 3 to 4 times, a color image forming apparatus with a smaller image forming speed can be provided.

(2) By synchronizing with the image reading means, a color image can be formed efficiently with a small capacity memory.

(3) For many multicolor modes such as single color, two colors, color,
Can be dealt with efficiently. Single-color or two-color printing can be performed by one reading scan and one rotation or one movement of the image carrier.

[Brief description of drawings]

Each of the drawings shows an embodiment of the present invention, and FIGS. 1 (a) and (b) and FIG. 10 are schematic configuration diagrams of an image forming apparatus, and FIG. 2 is a schematic configuration diagram of an image reading apparatus. FIG. 3 is a diagram showing a CCD line image sensor for reading an image, FIGS. 4 (a), (b) and (c) are schematic diagrams of a laser beam scanner for image exposure, and FIG. FIG. 6, FIG. 7, FIG. 8 and FIG. 9 are flow charts showing the process of image formation, FIG. 11 and FIG. 12 are circuit configuration diagrams of image formation, FIG. FIG. 14 is a time chart of image formation, FIG. 15 is a graph showing spectral characteristics of a notch filter, FIG. 16 is a configuration diagram in which a notch filter is provided in a lens system, and FIG. 17 is an image using a light converging element. FIG. 3 is a schematic configuration diagram of a reading device. In the reference numerals shown in the drawings, 1 ... image carrier 11, 12 ... charger 14 ... transfer device 15 ... static eliminator 42 ... static elimination lamp 31, 32, 33, 34 ... development Device 41 …… Pre-transfer exposure lamp 51 …… Cleaning device 61 …… Fixer 71 …… Uniform exposure lamp 121,221 …… Laser 122 …… Acousto-optic modulator 123,223 …… Mirror scanner 124,224 …… F-θ for imaging Lens 125,126,237,238a, 238b …… Mirror 127,235,236 …… Lens 131 …… Developing sleeve 132 …… Magnetic body 133 …… Developer layer thickness regulating blade 134 …… Scraper blade 135 …… Stirring rotor 136 …… Developer pool 137… Toner hopper 138 Toner replenishing roller 139 Power supply 140 Protective resistance P ...... Transfer T, T '... Toner PH ...... Exposed area DA ...... Unexposed area

Claims (1)

[Claims] 1. A color image reading device for optically scanning a document to form blue, green, and red color separation information; and processing the color separation information for black, yellow, magenta, and
A processing unit for forming a cyan color signal, a selection unit for selecting two color signals from the black, yellow, magenta, and cyan color signals, a rotatable image carrier, and a rotation direction of the image carrier. First and second latent image forming means which are arranged in order and form a latent image in a common area on the image carrier based on the two color signals selected by the selecting means; One delay means for compensating the latent image formation of the latent image forming means by the time required for the image carrier to move between the latent image forming positions of the first and second latent image forming means; Two of them are arranged between the one latent image forming means and the second latent image forming means and on the downstream side of the second latent image forming means in the rotation direction of the image carrier, and each of them is black, yellow and magenta. And an image carrier containing a cyan color toner. Developing means for developing the latent image of 4 to form color toner images of black, yellow, magenta and cyan, and two color signals selected by the selecting means during the first rotation of the image carrier. On the basis of the above, the first and second latent image forming means form a latent image on the image carrier in synchronization with the first optical scanning of the color image reading apparatus, and the first latent image is formed. The image bearing is performed by the developing means between the forming means and the second latent image forming means and the developing means on the downstream side of the second latent image forming means in the rotation direction of the image carrier. During the second rotation of the body, based on the remaining two color signals selected by the selection means, in synchronization with the second optical scanning of the color image reading device, the first and second latent images are scanned. A latent image is formed on the image carrier by the image forming means, Development is performed by the other developing means between the first latent image forming means and the second latent image forming means and the other developing means downstream of the second latent image forming means in the rotation direction of the image carrier. And a control means for controlling the four color toner images thus formed to be simultaneously transferred to a transfer material.