JPH06118763A - Multicolor image forming device - Google Patents

Abstract

PURPOSE:To make work efficient by forming the plural units of images on an image forming body in accordance with the size of a unit image when a process for developing a latent image and forming a toner image is repeated and the toner images of respective colors are superimposed. CONSTITUTION:An arithmetic processing part inputted with image data consisting of three primary colors data Yi, Mi, and Ci, and black data BKi calculates desired four colors data, and corrects colors; and a comparing part compares the color-corrected four colors data Ym, Mm, Cm, and BKm with threshold matrix, the binarized four colors data are stored in a memories My, Mn, Mc, MBK, outputted to an exposing system based on command from a control part, so that an electrostatic charge image is formed on the photosensitive body. Plural units of images can be formed on the image forming body in accordance with the size of the formed image of one unit. Thus, the image forming body is effectively utilized and printing speed in the case of performing printing in which image size is smaller than maximum image size is made high, so that the work can be made efficient.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multicolor image forming apparatus, and more particularly to a multicolor image forming apparatus capable of forming images of a plurality of originals on an image forming body.

[0002]

2. Description of the Related Art Conventionally, for example, in order to form a multicolor image by an electrophotographic method, a copying process of charging, exposing, developing and transferring is repeated for each component color, and a toner image of each color is superposed on a copy paper. I am trying to transfer it.

For example, an electrostatic charge image is formed in each of the above steps by using decomposed light of blue, green, red, etc. obtained through a color separation filter, and developed with yellow, magenta, cyan and optionally black toner. To form a toner image, and the toner image for each color is laminated and transferred on a recording paper to form a multicolor image.

However, in such a multi-color image forming method, (1) it is necessary to transfer the image onto the transfer body each time the development of each color is completed. It takes a long time, and (2) it is necessary to guarantee the positional deviation accuracy due to repetitive operations.

Therefore, a plurality of toner images are superposed on the same photoconductor and developed (the toner images are superposed, the toners may or may not overlap), and the image is formed on the image forming body. It is a multicolor image forming apparatus that forms a latent image by writing, and repeats the process of developing the latent image to form a toner image to form toner images of respective colors in a superimposed manner on the image forming body. Although there is a multi-color image forming method that solves the above-mentioned drawbacks, it is possible to disturb the toner image obtained by the development in the former stage, or the toner image obtained in the latter stage can be disturbed in the latter stage development. The toner in the developer at the former stage is mixed in the developer, which causes an adverse effect such as disturbing the color balance of the multicolor image.

In order to avoid such an adverse effect, the photoconductor and the developer layer for developing the electrostatic latent image formed on the photoconductor are made non-contact with each other, and the AC component is superposed on the DC bias applied to the developing device. There has been proposed a method of forming a multicolor image by adopting a system in which toner in a developer is made to fly and development is performed.

In this method, the developer layer does not rub the toner image formed up to the previous stage, so that the image is not disturbed.

The principle of this image forming method will be described below with reference to the flowchart of FIG. FIG. 1 shows changes in the surface potential of the photoconductor, and shows an example in which the charging polarity is positive.

PH is the exposed portion of the photosensitive member, DA is the non-exposed portion of the photosensitive member, DUP is the amount of increase in potential caused by the positively charged toner T adhering to the exposed portion PH in the first development, and CUP is the second portion.
The increase in the potential of the exposed portion PH caused by the second charging is shown.

The photoconductor is uniformly charged by a scorotron charger or the like to give a constant positive surface potential E. The surface potential E is reduced to almost zero potential at the exposed portion PH by the first image exposure by an exposure source such as a laser, a cathode ray tube, a liquid crystal shutter, and an LED.

Here, by applying a positive bias to the developing device in which a direct current component is approximately equal to the surface potential E of the unexposed portion to develop, the positively charged toner T in the developing device has a relative potential. It comes to adhere to the low exposed portion PH, and a first visible image is formed.

In the area where the visible image is formed, the potential increases by DUP due to the adhesion of the positively charged toner T,
Next, the second charging is performed by the charger, and the potential further rises by CUP, and the initial surface potential E is obtained as in the non-exposed area DA.

Then, a second image exposure is performed on the surface of the photoconductor having a uniform surface potential E to form an electrostatic latent image, and a second developing operation is performed through the same developing operation. A visual image is obtained.

By repeating the above process, a multicolor toner image is obtained on the photoconductor, and the multicolor image is obtained by transferring the multicolor toner image onto the recording paper and fixing it by heating or pressing.

The toner and charges remaining on the photoconductor are cleaned to prepare for the next multicolor image formation. In the multicolor image forming method, the second and subsequent charging can be omitted.

If the charging is not repeated and charging is repeated every time, a discharging process by an exposure lamp or corona discharge may be performed before charging. The exposure sources used for each image exposure may be the same or different.

In the multicolor image forming method, toner images of four colors, for example, yellow, magenta, cyan, and black are often formed by superposing on a photoconductor, for the following reason.

A black image should be obtained by superimposing the three primary colors of yellow, magenta, and cyan, but the toner for practical three primary colors does not have an ideal absorption wavelength range, Since it is difficult to precisely align the primary color toner image, it is difficult to reproduce a clear black color required for characters and line drawings with only the three primary colors.

Therefore, as described above, the toner images of four colors in which black is added in addition to the three primary colors are superposed to obtain a multicolor image closer to the original.

In the multicolor image forming method,
A reversal developing method is used as a method for developing an electrostatic latent image. In the reversal development method, it is sufficient to expose only the toner image forming portion of the photoreceptor, and it is not necessary to expose the background portion without a gap as in the case of regular development. Therefore, the photoreceptor on which the toner image has already been formed The latent image can be formed relatively easily on the bottom.

Further, there is an advantage that the fatigue of the photoconductor is small and the life is extended. Further, since the second and subsequent charges are performed with the same polarity as the toner, there is no problem in electrostatic transfer.

As a method of forming a latent image for forming a multicolor image, in addition to the method of forming an electrostatic latent image by uniformly charging and imagewise exposing the photoconductor, a multi-needle electrode or the like may be used. The inventor has already proposed a method of directly injecting charges onto a support to form an electrostatic latent image, a method of forming a magnetic latent image by a magnetic head, and the like.

Each of the latent image forming methods described above is a method capable of gradation expression. However, since gradation expression by such a method is so-called multi-step gradation, a large amount of image data capacity is required. .

Therefore, an image data forming method has been proposed in which each pixel is binarized or multivalued and recorded, and the gradation thereof is pseudo-expressed by the distribution thereof, and the image data capacity is reduced. .

In order to express the gradation of the image by the above-mentioned image data forming method, for example, multi-planted recording, pulse width modulation, density pattern method, dither method, etc. are used.

The density pattern method shown in FIG. 2 is a method for converting one pixel into a plurality of pixels. 1a is a document, and each pixel has a gradation. Reference numeral 2a denotes a sample for taking out a pixel 5a having a typical density value of the matrix of the original 1a and subjecting it to threshold processing, 3a denotes an M × N threshold density matrix corresponding to the sample, 4a
a is a binarized pattern by comparing the threshold density matrix 3a with the sample 2a.

The dither method shown in FIG. 3 is a method for converting one pixel into one pixel. The original 1b is divided into a density matrix of M × N pixels. 2b is a sample for threshold processing corresponding to the density matrix of the original document 1b, 3b is an M × N threshold density matrix corresponding to the sample 2b,
Reference numeral 4b is a binarized pattern obtained by comparing the threshold density matrix 3b with the sample 2b.

In the conventional gradation expression method, it is said that the arrangement in which the dots are dispersed is preferable so that the spatial frequency becomes high. In this method, as shown in FIG. 2 or 3, the gradation is expressed by the number of dots of a fixed size (dot density). In particular, it was considered that the dither method can minimize the deterioration of resolution.

On the other hand, by adopting an arrangement in which dots are concentrated, a method of giving priority to gradation even with deterioration of resolution has been proposed, and an intermediate arrangement of both methods is also considered.

However, in the above-mentioned multicolor image forming method, since the toner images having different color tones are directly superposed on the image forming body, the influence between the toner dots having different color tones is eliminated when the color image is formed. In addition, it is preferable to form the writing dot positions separately, but this reduces the image density, and if toner dots of different color tones are formed so as to overlap in order to secure the image density, it will be The toner is hard to overlap and the color tone of the image is distorted, and
The gradation cannot be expressed sufficiently.

In order to express the gradation of a multicolor image, there are (1) a method in which different color toner dots are formed in the matrix, and (2) a method in which different color toner dots are formed independently. However, since the dot pattern of a predetermined potential is formed by the light projected to the recording position and the gradation is expressed by developing by controlling the latent image potential and the developing bias, 2 and especially If the diameter of the formed toner dots is large in many cases of 1, the developed toner dots impede the image exposure in the subsequent process, and the latent image formation consisting of the desired dots is not achieved. Dots are not formed, and as a result the color tone of the previous toner image may be overemphasized and the resolution of the multicolor image may impair the color balance.However, the diameter of the toner dots and the interval between different toner dots should be restricted. Can be solved in.

FIG. 15 shows a three-color image forming apparatus. The point is that one rotation of the photoconductor drum 51 can obtain a stack of three color toner images of yellow, magenta, and cyan.

In FIG. 15, the photosensitive member 51 is a drum-shaped photosensitive member and is rotated in the direction of the arrow. This photoconductor 51
As shown in FIG. 15, a scorotron charger 52, an exposure device 53, for forming a yellow toner image on the surface of the
A developing device 54 is arranged, and subsequently, a scorotron charger 56, an exposing device 57, and a developing device 5 for forming a magenta toner image.
8 are arranged, and subsequently, a scorotron charger 60, an exposure device 61, and a developing device 62 for forming a cyan toner image are arranged. Therefore, one cycle of the photoconductor 51 forms three color toner images in a stacked manner.

Incidentally, 55, 59 and 63 are developing rollers and 6
4 is a sheet feeding device, 66 is a transfer electrode, 67 is a separating electrode, 68 is a fixing device, and 70 is a cleaning device. However, although the processing speed is high, this apparatus requires three sets of charging, exposing and developing process units, which increases the size and cost of the apparatus.

Therefore, as shown in FIG. 12, a device is conceivable in which an exposure device is also used for each color and a multicolor toner image is laminated and formed by rotating the image forming body a plurality of times.

This apparatus is an apparatus used in the embodiment of the present invention. FIG. 12 is a sectional view of a multicolor image forming apparatus, FIG. 13 is a laser apparatus applied to the image forming apparatus of FIG.
FIG. 14 shows a developing device applied to the image forming apparatus of FIG.

In FIG. 12, a photosensitive drum 11 is a photosensitive member that rotates in the direction of the arrow, and a uniform charge is applied to the photosensitive member 11 by a scorotron charger 12. This uniform charge is imagewise exposed by the following imagewise exposure means to form an electrostatic charge image.

For example, a laser device 14 shown in FIG. 13 is used as an exposure system, and an image is exposed by a laser beam L from the device 14 to form an electrostatic latent image corresponding to each color on the photoconductor 11. .

Of the electrostatic latent images corresponding to the respective colors, the electrostatic latent image corresponding to yellow is formed by irradiating the laser light modulated by the yellow data.

The electrostatic latent image corresponding to the yellow is the first
And a first toner image (yellow toner image) is formed on the photoconductor 11.

The first toner image is charged by the scorotron charger 12 again on the photoconductor 11 without being transferred to the recording paper P after the charge is removed from the image forming body by the charge eliminating lamp 40.

Next, the laser light is modulated by the magenta data, and the modulated laser light is applied to the photoconductor 11 to form an electrostatic latent image. This electrostatic latent image is developed by the second developing device 16 to form a second toner image (magenta toner image).

In the same manner as described above, the third developing device 17, the fourth
The toner is sequentially developed by the developing device 18 to form a third toner image (cyan toner image) and a fourth toner image (black toner image), and a four-color toner image sequentially laminated on the photoconductor 11 is formed. It

The four-color toner images are similarly discharged from the image forming body by the discharging lamp 40, recharged by the charging device 19, and supplied from the paper feeding device 20 to the recording paper P.
It is transferred by the action of the transfer pole 24. It is desirable that the charging here has the same chargeability as the charging by the scorotron charger 12. By doing so, the conditions of the previously recharged toner can be made the same and the transferability is improved. The scorotron charger 12 is preferable as the charger 19. Here, 23 is a paper feed roller, and 22 is a guide plate.

Then, the recording paper P carrying the transferred toner image
Is separated from the photoconductor 11 by the separation electrode 25, is conveyed by the guide 26 and the conveyance belt 27, is carried into the fixing roller 28, is heat-fixed, and is discharged to the discharge tray 29.

On the other hand, the photoconductor 11 which has completed the transfer is discharged by the static eliminator 31 that was not used during the toner image formation, and then the toner remaining on the surface is released during the toner image formation by the cleaning device. It is removed by the blade 32 of 30 and the fur brush so as not to interfere with the formation of the next multicolor image.

However, in any of the image forming apparatuses controlled as described above, the same printing speed will be obtained regardless of whether the size of the image formed is large or small in the step of forming an image on the image forming body. .

That is, the peripheral length of the image forming body (possibly forming a drum or a belt) is determined so as to be compatible with the maximum image size, and when forming a small image size, a wasteful portion occurs. It had the drawback of being lost.

[0049]

SUMMARY OF THE INVENTION The present invention eliminates the above-mentioned drawbacks of the prior art, and increases the printing speed when printing an image size smaller than the maximum image size by effectively utilizing the image forming body. An object of the present invention is to provide a multicolor image forming apparatus that can improve work efficiency.

[0050]

SUMMARY OF THE INVENTION The present invention is a multicolor image forming apparatus capable of changing the number of images formed on an image forming body according to the size of an image of one unit, and the usefulness of the present invention will be described. Generally, as the size of an image, for example, the size of a document used to form a unit of image used in an office is A-3, A-4, B-4, B in the size of a normal paper size.
Therefore, when used as a printer or a copying machine, the peripheral length and width of the image forming body must be at least the size including the maximum paper size. That is, the perimeter needs to be longer than the length of the paper size.

However, for example, the length of A-3 is 4
Although it is 20 mm, which is twice as large as that of A-4, the printing speeds of A-3 and A-4 are exactly the same in the above-described multicolor image forming apparatus. This is A-
This is because when printing a 4 size image, half of the image forming body is not used at all (in the case of 1: 1 size).

Therefore, in the present invention, when the image size can accommodate a plurality of sheets on the image forming body, the printing speed is improved by forming a plurality of toner images.

For example, in the drum-shaped image forming body capable of printing the maximum A-3, when the developed state is shown in FIG. 11, it is slightly larger than the perimeter around which the paper A-3 is wound. It is possible to put two A-4s vertically within this size. Of course, in the case of B-5, it is possible to add two sheets.

Therefore, when the image size is A-4,
Image size information (set by the user, included in the image data, determined by the size of the paper to be used, or if an image reading device is used, in addition to the above examples, it is determined from the detection of the document size. And the like), two images are formed in parallel on the image forming body.

That is, after charging the image forming body, image exposure of the first image is performed, then image exposure of the second image is performed, and then a development process with a yellow toner is performed, and the toner used. Repeat 3 to 4 times with changing to magenta toner and cyan toner (the fourth time is black toner). The plurality of multicolor toner images formed in this manner are transferred to the paper conveyed in synchronization with each image and then discharged.

Further, according to the present invention, for example, the circumference of the image forming body is set to a length capable of accommodating a plurality of maximum image sizes,
A small image size may be configured to accommodate a larger number.

Then, the first by writing the image data
After forming the image of, if, for example, the first image can be repeated, fast multiplex printing can be performed,
In this case, the same image is formed on the image forming body a plurality of times, and if different images can be written, fast page printing can be performed. In this case, a plurality of different images are formed on the image forming body. It will be done.

[0058]

Embodiments of the present invention will be described below, but the embodiments of the present invention are not limited thereto.

[0059]

[Embodiment 1] First, an example of a method of forming image data will be described.

In the multicolor image forming method of the present invention, for example, an output signal of an image pickup device obtained by scanning a multicolor original, a transmission signal from another device such as a facsimile, or data stored in a storage device is used as image data. To be done.

The image data is typically composed of yellow, magenta, and cyan three primary color data Yi, Mi, Ci, and black data BKi. When performing such a multicolor image formation, the image data is input to the arithmetic processing unit of the color correction section of FIG. 4, and the data of the desired four colors is calculated by the following arithmetic expression [1], for example.

Formula [1] Ym = α1 Yi-β1 min [Yi, Mi, Ci] Mm = α2 Mi-β2 min [Yi, Mi, Ci] Cm = α3 Ci-β3 min [Yi, Mi, Ci] BKm = α4 BKi−β4 min [Yi, Mi, Ci] where Ym, Mm and Cm are data after calculation and Yi and M
i and Ci are input image data, α1, α2, α3,
α4, β1, β2, β3, β4 are color correction coefficients based on external factors such as phenomenon conditions, and min [Yi, Mi, Ci] is the color tone having the minimum density value among the three primary colors of yellow, magenta, and cyan. ing.

Next, in order to understand the arithmetic expression [1], α 1 to α
The case will be described below by taking as an example the case where 4 and β1 to β4 are all 1.

Now, if the color tone of the minimum density value is cyan (Ci) as shown in FIG. 5, if the density corresponding to this cyan is subtracted from each of the three primary colors, they are gathered together. Is obtained.

By adding this black component to the black data BKi,
As black image data. Also, the remainder obtained by subtracting the cyan density equivalent from each of the three primary colors is shown in FIG.
Use primary color image data.

Thus, improvement of color balance at the time of phenomenon,
Toner consumption can be saved and development operation efficiency can be improved.

The four-color data Ym, Mm, Cm, and BKm that have been color-corrected by the arithmetic processing unit of FIG. 4 are compared with a threshold matrix to be described later and binarized four-color data Yo, Co, and
Co and BKo are obtained.

This data is stored in the memories My, Mm, Mc,
Although it is stocked in MBK, it is output to the exposure system in response to a command from the control unit, and an electrostatic charge image is formed on the photoconductor. The electrostatic charge image is preferably developed in a non-contact manner by four types of developing devices that respectively store yellow, magenta, cyan, and black toners driven by a command from the control unit.

Thus, toner images of four colors are laminated on the photoconductor and transferred and fixed on the recording paper fed at the same timing as the photoconductor to form a multicolor image.

As the threshold matrix used in the present invention, for example, spiral type matrices YP, MP, CP and BKP which are distributed by separating each color as shown in FIG. 7 are used.

The toner image obtained by using such a threshold matrix is composed of concentrated dots as shown by YD, MD, CD and BKD, and the gradation is expressed by the size of the dots. Moreover, since the dots of each color do not overlap each other, a clear multicolor image having an extremely excellent color balance can be obtained.

In this case, when expressing the gradation of a multicolor image, there are a method of forming different color toner dots in the matrix and a method of forming different color toner dots in a group in the matrix. Conceivable.

In the case of the former method, FIGS. 8A and 8B show an example of the matrix in this case. FIG. 8A is an 8 × 8 matrix, and each color is a 4 × 4 sub-matrix. Alternately. M. C. It consists of BK and side by side. For example, where the symbol Y is attached, when yellow data is input, it is compared with the threshold value to determine printing (black circle in FIG. 10) or non-printing (white circle in FIG. 10). No data is entered.

FIG. 8B shows a 6 × 6 matrix,
Each color is regularly arranged, but the BK corresponding to FIG. 8A is not formed in the matrix. The arrangement of threshold values of the sub-matrix forming the toner image of each color is used in a distributed type, a concentrated type, or a mixture thereof.

In the case of the latter method, toner dots of different colors are formed in groups in a matrix,
The arrangement of the toner dots of each color is used in a dispersed type, a concentrated type, or a mixture thereof.

9 (a) and 9 (b) show an example of the matrix in this case. FIG. 9 (a) is an 8 × 8 matrix, and each color is composed of 4 × 4 organized sub-matrices. Has become. FIG. 9B is a 6 × 6 matrix, and each color is composed of three 2 × 2 sub-matrices, and this configuration has the matrix of FIGS. 8A and 8B and the matrix of FIG. 9A. It can also be called an intermediate arrangement.

In addition to the gradation expression method as described above, a gradation expression method in which toner dots of each color are distributed in a matrix pattern so that at least some of the dots overlap may be used.

In this case, there is a problem in that the desired latent image is not formed because the overlapping portion is different from the non-overlapping portion, or the image exposure is blocked by the previous toner dot and does not reach the image forming body sufficiently. .

In the present invention, even when the dots of different colors overlap each other, the toners having high light-transmitting properties are superposed in this order, or a concentrated type dot structure is used instead of the conventional dispersion type. In addition to reducing the adverse effects, the angle of the different color toner dots is changed to prevent moire,
It is even better to reduce the overlap between toner dots of different colors and to be able to visually exhibit each color tone.

Next, the case where a plurality of identical prints (continuous copying) is obtained will be specifically described below with reference to the above-mentioned drawings.

FIG. 12 is a sectional view of a multicolor image forming apparatus for explaining the present embodiment, FIG. 13 is a laser device applied to the image forming apparatus of FIG. 14, and FIG. 14 is applied to the image forming apparatus of FIG. 1 shows a developing device. The details of the drawings are omitted because they have been described above.

In FIG. 12, a photosensitive drum 11 is a selenium photosensitive member having a diameter of 180 mm which rotates in a direction of an arrow at a linear velocity of 180 mm / sec. A uniform charge of +600 V is applied on the photosensitive member 11 by a scorotron charger 12. Is given. This uniform charge is imagewise exposed by the following imagewise exposing means,
An electrostatic charge image is formed.

That is, the A-4 size data Yi, Mi, Ci, BKi stored in the storage device in advance are input as image data to the arithmetic processing unit of the color correction section in FIG. 1] to obtain color-corrected data Ym, Mm, Cm, and BKm, which are shown in FIG.
And the binarized data Yo, Mo, Co, BKo are obtained.

These data are stored in the memories My, Mm, M
Although it is stocked in c and MB K, it is output to the exposure system according to a command from the control unit.

In this embodiment, the laser device 14 of FIG. 13 is used as the exposure system, and the laser beam L from the device 14 is imagewise exposed to form a first A-4 size electrostatic latent image. Then, by exposing the data from the memory imagewise, the same two A-4s corresponding to the respective colors are formed on the photoconductor 11.
An electrostatic latent image of size is formed.

The details of the laser device 14 are shown in FIG. 13, and the helium-neon laser output from the oscillation source 33 is passed through the reflecting mirrors 37 and 38, and the acoustic light modulator (AO).
M) 34, where it is modulated by the binarized image data. The modulated laser light is polarized by a mirror scanner 35 composed of a rotating octahedron, and the surface of the photoconductor 11 is scanned at a constant speed through an imaging f-θ lens 36 to perform image exposure. Reference numeral 39 is an inspector for determining the writing position of the laser light L.

Of the electrostatic latent images corresponding to the respective colors, the electrostatic latent image corresponding to yellow is formed by irradiating the laser light modulated by the yellow data.

The yellow data is binarized using the YP matrix of FIG.

Threshold matrices YP and M for each color
In P, CP, and BKP, where no numeral is shown, black data is not output even when data corresponding thereto is input, that is, it is not applied in the same manner as the white circle in FIG.

The electrostatic latent image corresponding to the yellow is the first
The developing device 15 develops the toner to form two first toner images (yellow toner images) on the photoconductor 11.

The first toner image is not transferred to the recording paper P, and is again transferred onto the photoconductor 11 by the scorotron charger 2
Is charged by + 600V.

Then, the laser light is modulated by the magenta data binarized using the threshold matrix MP of FIG. 7, and the modulated laser light is irradiated on the photoconductor 11 to form an electrostatic latent image. .

This electrostatic latent image is developed by the second developing device 16 to form two second toner images (magenta toner images), and the threshold matrix C is formed in the same manner as described above.
P and BKP are sequentially used, and the third developing device 17 and the fourth developing device 18 sequentially perform reversal development to obtain two third toner images (cyan toner images) and two fourth toner images (black toner images). ) Is formed, and two four-color toner images sequentially formed on the photoconductor 11 are formed.

A developing device which is not used for development does not damage the toner image formed on the image forming body and does not supply unnecessary toner to the latent image when the development is OFF and during the development (ON).
There is a method of cutting the AC bias component of (time) to leave only the DC bias component, making it in a floating state, grounding, or applying a DC bias having a polarity opposite to that of the toner. Further, a method of separating the developing device from the image forming body and further removing the developer from the developing sleeve can be mentioned. Alternatively, it may be used in combination with the change of the bias.

The four color toner images are charged by the charger 19 and transferred onto the two recording papers P continuously supplied from the paper feeding device 20 by the action of the transfer electrodes 24. Here, 23 is a paper feed roller, and 22 is a guide plate.

The recording paper P carrying the transferred toner image is separated from the photoconductor 11 by the separation electrode 25, is conveyed by the guide 26 and the conveying belt 27, is carried into the fixing roller 28, is heat-fixed, and is discharged onto the sheet discharge tray 29. Is discharged.

On the other hand, after the transfer, the photoconductor 11 is discharged by the static eliminator 31 which was not used during the toner image formation, and the toner remaining on the surface of the photoconductor 11 is released during the toner image formation. It is removed by the blade 32 of 30 and the fur brush so as not to interfere with the formation of the next multicolor image.

Next, a developing device suitable for use in the multicolor image forming apparatus of FIG. 12 will be described.

The development in carrying out the present invention may be either regular development or reversal development, and the developing method, conditions, apparatus, etc. are not particularly limited, but they are already formed during development. The developing layer containing toner does not directly contact the surface of the image forming body so as not to disturb the toner image present, that is, there is no steady potential difference between the developing medium carrier such as a sleeve and the image forming body. At this time, the developing layer thickness in the developing zone of the developer layer with the developer transporting body (hereinafter simply referred to as the developing zone developer layer thickness) is smaller than the gap between the developer transporting body and the image forming body. It is preferable to employ a developing method set as above, which is so-called non-contact developing. An oscillating electric field may be applied to the developing area, but Japanese Patent Application No. 238295/1983 and Japanese Patent Application No.
It is preferable to apply under the conditions described in Japanese Patent No. 8296.

Although four devices are used as the developing device, they may have the same or similar structure, and a cross-sectional view of the first developing device 15 is shown in FIG. 14 as a representative.

The developer D is 1000 r.p.m. for the magnetic roll 41 having 16 poles. p. direction of arrow F at speed of m,
The sleeve 42 having a diameter of 30 mm is conveyed in the direction of arrow G by rotating in the direction of arrow G at a linear velocity of 120 mm / sec.

This developer D is a two-component developer,
The thickness of the blade is regulated by the standing blade 43 during the conveyance, and a developer layer having a developing layer thickness of 0.5 mm is formed.

A stirring screw 45 is provided in the developer reservoir 44 so that the developer D is sufficiently agitated, and when the developer D in the developer reservoir 44 is consumed, a toner supply roller 46 is provided. The toner T is replenished from the toner hopper 47 by rotating.

Next, the gap between the sleeve 42 and the photosensitive drum 11 is set to 0.8 mm, and a DC power source 48 is provided between the sleeve 42 and the photosensitive drum 11 to apply a developing bias for reversal development, and the developer D is supplied between them. The developer D is vibrated in the developing area E, and the developer D
AC power supply 49 is provided in series with the DC power supply 48 so that the power is sufficiently supplied to the photosensitive drum 11. In addition,
R is a protective resistance.

Here, the developing bias has a DC component of, for example, +50 when the charged potential of the image forming body is + 600V.
0 V, the AC component is 2 KHz, and the effective value is 1.5 KV. In the developing device 15, the toner T contained in the developer carried by the sleeve 42 reaches the developing area E by 2
A charge amount of 0 μC / g is provided.

On the other hand, as a developer used in such a machine, a two-component developer composed of a toner and a carrier and a one-component developer composed of only a toner can be used.

The two-component developer requires control of the amount of toner with respect to the carrier, but has the advantage that the triboelectric charge control of toner particles can be easily performed. Further, especially in a two-component developer composed of a magnetic carrier and a non-magnetic toner, it is not necessary to include a large amount of a black magnetic substance in the toner particles, and thus it is possible to use a color toner that does not cause color turbidity due to the magnetic substance. It is possible to form a clear color image.

The two-component developer used in the present invention is particularly preferably composed of a magnetic carrier as a carrier and a non-magnetic toner as a toner.

The toner has the following structure.

(1) Thermoplastic resin: Binder 80 to 90
wt% Example: Polystyrene, styrene acrylic polymer polyester, polyvinyl butyral epoxy resin, polyamide resin, polyethylene, ethylene vinyl acetate copolymer are mixed and used.

(2) Pigment: Coloring agent 0 to 15 wt% Example: Black: Carbon black Cyan: Copper phthalocyanine, sulfonamide dielectric dye Yellow: Benzidine derivative Magenta: Rhodamine B lake, Carmine 6B, etc.

(3) Charge control agent 0 to 5 wt% plus toner: Many nigrosine electron-donating dyes,
In addition, alkoxylated amines, alkylamides, chelates, pigments, quaternary ammonium salts, etc. Minus Toner: Electron-accepting organic complexes are effective, and in addition, chlorinated paraffin, chlorinated polyester, polyester with excess acid groups, chlorinated copper phthalocyanine, etc.

(4) Fluidizing agent Example: Colloidal silica and hydrophobic silica are typical.
Others include silicon varnish, metal soap, and nonionic surfactant.

(5) Cleaning Agent To prevent toner filming on the photosensitive member. Example: fatty acid metal salt, silicon oxide having organic groups on the surface,
Fluorine-based surfactants may be mentioned.

(6) Filler The purpose is to improve the gloss of the surface of the image and reduce the cost of raw materials. Examples: Calcium carbonate, clay, talc, pigments, etc.

In addition to these materials, a magnetic material may be contained in order to prevent fogging and toner scattering.

As the magnetic material, 0.1 to 1 μm triiron tetraoxide, r-ferric oxide, chromium dioxide, nickel ferrite, iron alloy powder and the like have been proposed.
A large amount of ferrosoferric oxide is used, and 5 to 70 wt.
% Contained. The resistance of the toner changes considerably depending on the type and amount of magnetic powder, but in order to obtain sufficient resistance, it is preferable that the amount of magnetic material be 55 wt% or less.

Further, in order to maintain a vivid color as the color toner, it is desirable that the amount of the magnetic material be 30 wt% or less.

In addition, as the resin suitable for the toner for pressure fixing, wax, polyolefins, ethylene vinyl acetate copolymer, polyurethane, rubber may be used so that it may be plastically deformed by a force of about 20 kg / cm to adhere to paper. Adhesive resin, etc. are selected, and capsule toner can also be used. By using the above materials, a toner can be manufactured by a conventionally known manufacturing method.

In the constitution of the present invention, in order to obtain a more preferable image, it is desirable that the weight average particle diameter of these toner particles is usually about 50 μm or less in consideration of the resolution. The particle size of the toner is preferably 1 to 50 μm, particularly 5 to 20 μm, in view of the resolving power, toner scattering and conveyance.
m is preferable, and the average charge amount is 3 to 300 μC.
/ G, especially 10 to 100 μC / g is preferable.

When the weight 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 lowered. In this embodiment, toner having a weight average particle diameter of 10 μm is used for all four colors.

Further, in order to improve delicate points or lines or gradation, magnetic carrier particles are particles composed of magnetic particles and resin, for example, resin dispersion system of magnetic powder and resin or resin-coated magnetic particles. Even more preferably, it is spherical.

In this embodiment, the weight average particle diameter is 50 μm for all four colors.
m carrier particles were used. The weight average particle diameters of the toner and carrier were measured with a Coulter counter (manufactured by Coulter Co.).

In addition, there is a problem that the bias voltage of carrier particles, particularly the oscillating voltage, is likely to inject charges to easily attach the carrier to the surface of the image forming body, which hinders good image formation, and a sufficient bias voltage is applied. In order to prevent the problem that the carrier is not generated, the carrier has a resistivity of 10 8 Ωcm or more, preferably 10 13 Ωcm or more, and more preferably 10 14 Ωcm or more, and preferably has an insulating property.
Further, it is preferable that the particle diameters of the above-mentioned resistivities are as described above.
In this embodiment, a resin dispersion type carrier having a magnetization of 50 e · m · u and a specific resistance of 10 14 Ωcm or more was used.

The specific resistance of the carrier is measured by the following measuring method. That is, the particles are placed in a container having a cross-sectional area of 0.50 cm2 and tapped, and then a load of 1 kg / cm2 is applied to the packed particles to generate a voltage of 1000 V / cm between the load and the bottom electrode. Apply,
It is obtained by reading the current value flowing at that time and performing a predetermined calculation. At this time, the thickness of the carrier particles is about 1 mm.

In the method for producing such finely divided carrier, the surface of the magnetic material is coated with resin by using the magnetic material and the thermoplastic resin described in the toner, or the magnetic material particles are dispersed and contained. The particles can be obtained by making particles with a resin and selecting the particles obtained by a conventionally known average particle size selecting means.

Further, it is desirable to improve the stirring property of the toner and the carrier and the transport property of the developer, and to improve the charge controllability of the toner so that the toner particles and the toner particles and the carrier are spherical. As the magnetic carrier particles of the resin-coated carrier particles, the spherical particles of the magnetic substance particles should be selected as much as possible, and the resin should be subjected to the coating treatment. It is manufactured by subjecting the dispersed resin particles to spheroidizing treatment with hot air or hot water, or directly forming spherical dispersed resin particles by a spray dry method.

When a four-color image with gradation was formed under the above conditions, a clear image with high image power, excellent gradation, and good color balance was obtained. Also, clear recording was obtained for characters and line drawings.

[0129]

Embodiment 2 Next, an outline of a color image forming system having an input system will be described with reference to FIG. The image reading device and the printer can handle up to A3 size, and the printer is the one used in the first embodiment.

The recording device, the dot pattern memory and the image forming process are controlled and driven by a control signal from the CPU, and for example, the exposure system (lamp 2, mirrors 6a, 6) shown in FIG.
b, 6c), which is a kind of color scanner C
CD image sensor 4 is B (blue) in the horizontal direction of the original,
The color information of G (green) and R (red) is read and an analog video signal is output.

This signal is subjected to shading correction to remove color information after A / D conversion and distortion due to an optical system and the like, and is temporarily input to a buffer memory to be supplied to each B,
G and R are made to correspond to the same image position. Next, B, G and R signals from the buffer memory are Y (yellow) and M
After complementary color conversion to (magenta) and C (cyan) and gradation correction are performed, black component extraction (UCR) is performed from each of Y, M, and C data to obtain a chromatic color component and an achromatic color component. To separate.

Here, after the chromatic color components Y, M, and C are color-corrected and the tone is corrected together with the black component (BK),
Input to the pattern generator (PG). Here, the dither processing based on the dither method as described above is performed to change into a digital dot pattern signal, which is stored in the page memory for each color. Next, the Y dot pattern is output to the recording device through a line memory required as a buffer, and the same two first toner images are written and the image is formed. Similarly, the M dot pattern, C dot pattern, BK dot pattern, etc., stored in the page memory are sequentially taken out in accordance with the write timing, and are written, an electrostatic image is formed and developed, and two color toners are formed. An image is formed.

The outline of the system is configured as described above. According to the method described above, the image forming body can be effectively used, and the image forming body can be effectively used as compared with the printing speed of A-3.
The print speed of 4 is doubled.

When a page print is obtained, image exposure is performed using the first A-4 size yellow data and then the second A-4 size yellow data is transferred. Then, image exposure is performed. It should be noted that the data transfer may be carried out in advance by transferring two sheets in advance and stocking them in the memory.

In this way, an electrostatic latent image consisting of two types of images is formed on the image forming body, and then this is developed with yellow toner. By repeating this process for magenta data, cyan data and black data, two multicolor toner images are formed on the image forming body, and then the toner images are transferred and fixed. In this way, it is possible to print the third and fourth sheets, the fifth and sixth sheets, and so on.

[0136]

[Embodiment 3] Next, a case where toner images are sequentially formed on an image forming body in synchronization with an image reading apparatus without using the frame memory 11 will be described.

First, the image reading apparatus and printer can handle up to A3 size.

In this case, when the document A-3 is placed on the image reading device, the image reading and the writing to the image forming body are performed in synchronization, and by repeating this, many images are formed on the image forming body. A color toner image can be formed.

When the original is A-4, two originals A and B are arranged side by side, and the same operation as that for the original A-3 is performed, so that the two originals corresponding to the two originals are formed on the image forming body. A color toner image is formed.

The two multicolor toner images thus formed are transferred to the paper conveyed in synchronism with the images of the originals A and B, and are sequentially ejected. Such two originals are used. The image forming apparatus in this case is shown in FIGS.
Also, the time chart is shown in FIG.
EM1, EC1, and EB1 correspond to so-called patches written for forming the reference toner image, and these are developed by each developing device (development timing is DY1, DM
1, DC1, DB1) and the toner density is controlled from the developed state. There is also a mode in which this information (patch information) is used by being fed back to the charging potential, exposure intensity, and developing bias. In the figure, high level indicates that each means is being driven.

Further, RA1, RB1, RA2 and R in FIG.
B2, RA3, RB3, RA4, and RB4 indicate the timing of reading the A and B originals by the scanner, and FIG.
Y, VM, VC, and VB are yellow, magenta, and
Charging timing EY for developing cyan and black toner
2A, EY2B, EM2A, EM2B, EC2A, EC2B, EB2
A and EB2B are timings RA1, RB1 and RA2, respectively.
, RB2, RA3, RB3, RA4, and RB4 respectively read the information of yellow, magenta, cyan, and black at the timing of writing, and this written information depends on timing DY2, DM2, DC2, and DB2 of yellow, magenta, cyan, and black. Development of the developing device 15, 16,
It is performed by 17, 18.

FIG. 16 is a timing chart for reading the original A first, corresponding to FIG. 15, or in FIG. 14, the original B is read first.

When the image reading apparatus has a device for automatically feeding and printing a large number of documents (automatic document feeder) as shown in FIGS. 18 and 19, A is detected by the paper size detection or the paper size designation. -4 size is 2
One original is fed and read, and a multicolor toner image corresponding to the two originals is formed on the image forming body.

Further, when a large number of originals are to be copied, the originals are mixed with each other when they are ejected to the paper ejection device. Therefore, two prints are ejected as a set and multiple copies are made.

FIG. 18 is a schematic view of an example of an image forming apparatus using a document feeding device which sets the document surface downward, and FIG. 19 shows a document feeding which sets the document surface upward. 13A and 13B are schematic views of other examples of the image forming apparatus using the apparatus, respectively.
17, the same members as those shown in FIG. 17 are designated by the same reference numerals, and the description thereof will be omitted. In the case shown in FIG. Set them so that the front side (the side with the image to be recorded) is facing down, and then copy start to copy two originals B and A.
Are fed and set on the platen. Then, the optical system including the exposure lamp 2, the mirrors 6a, 6b and 6c, and the lens 3 starts scanning from the left side in the drawing, causes the CCD image sensor 4 to read information, and exposes the image on the photoconductor 11, which is an image forming body. Is done.

After the predetermined operation is performed, the originals A and B are printed on the discharge tray of the discharge device 8 (using a sorter in the embodiment) with the tables B and A in this order. Pages are aligned as they are ejected.

In the apparatus shown in FIG. 19, a large number of documents A-4 are set on the automatic document feeder 7 with the front side facing up, and then two documents B,
A is fed and set on the document table 1. Then, the optical system including the exposure lamp 2, the mirrors 6a, 6b and 6c, and the lens 3 starts scanning from the right side in the figure, and the information is transferred to the CCD.
While being read by the image sensor 4, image exposure is performed on the photoconductor 11 which is an image forming body.

After the predetermined operation is performed, the prints of the originals A and B are discharged on the discharge tray of the discharge device 8 in the order of A and B in the state that the front side is in the downward state, so that the pages are aligned. Done.

Further, in the case of the original A-4, the scanning process for image reading is limited to the position A-4, the reading process is performed again by quickly returning the image to the original position and performing the image reading again during one rotation of the photosensitive member. You may do it. By doing so, the same two toner images can be formed on the photoconductor and the printing speed can be increased. Also in this case, the frame memory may not be provided.

[0150]

[Embodiment 4] In the third embodiment, the case where the image reading and the image formation are performed in synchronization and the frame memory is not used is shown. However, when the frame memory is used, it is the same as the second embodiment. However, it is too expensive to prepare multiple sheets because the frame memory is expensive, so the image reading data at that time can be framed while synchronizing the image reading and image formation. It can be stored in memory and used for later imaging.

That is, in this embodiment, A-3 or A
All you have to do is to prepare the frame memory for 4 screens of 1 color.

When one sheet of A-4 original is prepared, the image reading and the image formation of this one original are performed in synchronization with each other, and the signal from the image reading is temporarily stored in the frame memory, To write the second sheet to form an image. As a result, two same toner images are formed on the image forming body.

This process is repeated 3 to 4 times for each color to form two multicolor toner images, which are then transferred to the paper conveyed in synchronization with each image and discharged.

The time chart in this case is shown in FIG. 21, and shows that each means is driven at a high level in FIG.

RA1, RA2, RA3, RA4 indicate the timing of reading the original by the scanner, and VY1
, VM1, VC1, and VB1 are yellow, magenta, cyan, and black read at timings RA1, RA2, RA3, and RA4, respectively, for charging timings EY2, EM2, EC2, and EB2 for yellow, magenta, cyan, and black development, respectively. Is the timing of writing the information, and the contents of RA1, RA2, RA3, and RA4 stored in the frame memory at the same time of reading are EY2 ', EM2', EC2 ', and EB2', respectively.
The information written at the timing of # 2, DM2, DC2, and DB2 is used for the development of the yellow, magenta, cyan, and black developing devices 15 and 1 by the timings DY2, DM2, DC2, and DB2.
6, 17, 18 are performed.

Unlike the third embodiment, the image reading apparatus may scan the A-4 document and return to the initial position. In FIG. 21, the first sheet to be recorded first is recorded without passing through the memory, and the second sheet is recorded from the data in the memory. However, document scanning is performed quickly and image data is stored in the memory. It may be recorded using data.

Incidentally, EY1, EM1, EC1 and EB1 correspond to so-called patches written for forming the reference toner image as described above, and these are developed by the respective developing devices, and the developed state thereof. It is used by being fed back from the toner density control, charging potential, exposure intensity, and developing bias.

If the image reading apparatus has a device for automatically feeding a large number of originals (automatic original feeder), the next original may be sent out after printing and the above operation may be repeated. The device may be used by changing the discharge tray for each copy of a document.

Although the contents of the frame memories used in the second and fourth embodiments change depending on the color signal from the image reading apparatus, when the original or print is of a single color (normal monochrome copying). If you take a number of copies like a machine) If you read the image once and store it in the frame memory, you can use this frame memory to print any number of sheets.

Further, in the above-mentioned embodiment, the case of equal magnification has been described as an example, but the idea of the present invention can be applied to the case of magnification change.

For example, a document of A-3 size is reduced to A-4 size or B-5 size, or A-4, B-
When cutting out in 5 sizes, the sequence is changed to form a plurality of images on the photoconductor.

On the contrary, when the A-4 size is enlarged to the A-3 size, the sequence is changed to form one image on the photoconductor. In this way, the image forming body can be effectively used.

[0163]

As described above, according to the present invention, as long as the image can be stored in the maximum image size, a plurality of originals can be printed, or a plurality of prints can be printed in the maximum image size. Since it can be performed in the time required for printing, it has an excellent effect that it can be performed in a very short time.

[Brief description of drawings]

FIG. 1 is a diagram showing a principle of an image forming method.

FIG. 2 is a diagram showing a relationship between a density distribution, a threshold group, and a pattern.

FIG. 3 is a diagram showing a relationship between a density distribution, a threshold group, and a pattern.

FIG. 4 is a diagram illustrating a calculation processing unit of a color correction section.

FIG. 5 is a diagram showing density values.

FIG. 6 is a diagram showing density values.

FIG. 7 is a diagram showing a matrix.

FIG. 8 (a) is a diagram showing a matrix. (B) It is a figure which shows a matrix.

FIG. 9 (a) is a diagram showing a matrix. (B) It is a figure which shows a matrix.

FIG. 10 is a diagram showing a pattern.

FIG. 11 is a diagram showing a developed state of the image forming body.

FIG. 12 is a schematic view showing a multicolor image forming apparatus.

FIG. 13 is a schematic view showing a laser device.

FIG. 14 is a schematic view showing a developing device.

FIG. 15 is a schematic view showing a multicolor image forming apparatus.

FIG. 16 is a diagram showing an outline of a color image system.

FIG. 17 is a diagram showing an exposure system.

FIG. 18 is a schematic view showing a multicolor image forming apparatus.

FIG. 19 is a schematic view showing a multicolor image forming apparatus.

FIG. 20 is a time chart showing the operation of each unit of the multicolor image forming apparatus.

FIG. 21 is a time chart showing the operation of each unit of the multicolor image forming apparatus.

[Explanation of symbols]

1 ... Original platen 2 ... Exposure lamp 3 ... Lens 4 ... CCD image sensor 6a, 6b, 6c ... Mirror 7 ... Automatic document feeder 8 ... Paper ejection device 11, 51 ... Image forming body 12 , 52 ... Scorotron charging device 14, 53, 57, 61 ... Exposure device 15, 16, 17, 18, 54, 58, 62 ... Developing device 24, 66 ... Transfer electrode 25, 67 ... Separation electrode 48 ...... DC bias power source 49 …… AC bias power source T …… Toner D …… Developer P …… Recording paper Yi, Mi, Ci, BKi …… Image data from external memory Ym, Mm, Cm, BKm …… Calculation Data after color correction in the processing unit Yo, Mo, Co, BKo ... Binarized data My, Mm, Mc, Mbk ... Image data of each color data memory

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location B41J 2/525 2/385 G03G 15/00 302

Claims (1)

[Claims] 1. A process of writing an image on an image forming body to form a latent image and developing the latent image to form a toner image is repeated to superimpose each color toner image on the image forming body. In the multicolor image forming apparatus for forming,
A multicolor image forming apparatus characterized in that a plurality of unit images can be formed on the image forming body according to the size of the unit image.