JPS62115477A - Image forming device - Google Patents

Abstract

PURPOSE:To superpose one image on the other on an image carrier with a high precision at a high speed by transferring successively toner images formed on one of at least two image carriers to the other. CONSTITUTION:The first and second exposure light beams B10 and B20 modulated by two-color picture data are taken into the first and second image forming parts 100 and 200 in such relations that color-classified mirror images are formed for one color picture, and the first toner image having the first color is formed on a photosensitive drum 110, and the second toner image having the second color is formed on a photosensitive drum 210. The surface of the first photosensitive drum 110 is irradiated with an LED lamp array 142 of a reverse electric charge inducer 140, and a generated + polarity electric charge is attracted to a transparent electrode 141 having a negative potential and is gathered near the surface of the drum 110. The second toner image consisting of a - polarity electric charge is attracted easily to the drum and is transferred to superpose the second toner image on the first toner image.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention particularly relates to an image forming apparatus such as a color copying machine or a color printer that forms a composite image by superimposing a plurality of images, particularly of a plurality of colors. The present invention relates to the embodiment of an apparatus configuration suitable for overlapping such images on a body and transferring them to a transfer material.

[Technical background of the invention]

FIG. 7 shows an example of a main part of a conventionally used color image forming apparatus of this type.

In other words, in this @ position, the arrow F1 in the figure acts as an image carrier.
A first charger 2 sequentially charges the surface of the photosensitive drum 1, which is rotated in the direction of the photosensitive drum 1, in the direction shown in FIG. A first electrostatic latent image corresponding to a first color of a desired formed image (color image) is first formed by exposure to light mB1. The first electrostatic latent image thus formed is sequentially reversely developed in the first developing device 3 and becomes a first toner image showing a first color image. Next, in the same apparatus, the first toner image forming area on the photoreceptor drum 1 is further uniformly charged by a second charger 4 (usually a scorotron with good charge control properties is used as the charger 4). The toner image is recharged to reduce the potential difference between the image portion and the non-image portion of the first toner image, and then the same portion is re-exposed to the second exposure light 11i1B2 to form a desired image in the second color. A corresponding second electrostatic latent image is formed. The second electrostatic latent image thus formed is also sequentially reversely developed in the second developing device 5 to become a second toner image showing a second color image. Before transferring the first and second toner images, the third charger 6 collects the first toner image, which has a large amount of charge due to the recharging, and the second toner image, which has not been recharged. This is a so-called transfer precharger that maintains the transfer performance of these toner images by pre-adjusting different amounts of charge between the first and second toner images, and the third charger 6 charges the first and second toner images to approximately the same amount. After that, the desired color image is integrally transferred to a transfer material MP such as recording paper based on the corona discharge of the fourth charger 7, which is a transfer charger, and then the same transfer material MP is transferred to the transfer material MP by the fixing device 10. It is settled and fixed. After the transfer, the toner remaining on the photoreceptor drum 1 is cleaned and removed by a cleaning device 8. Further, the surface of the photoreceptor drum 1 is neutralized by a static eliminating lamp 9 in preparation for the next image formation.

[Problems with background technology]

Although in principle it is possible to form a color image (in this example, a two-color image border) with the apparatus shown in FIG. This would cause inconvenience. That is, (1) Although the third charger 6 constituting the transfer precharger adjusts the amount of charge of the first and second toner images, these toner images are placed on the photoreceptor drum 1 in several layers (in this example). In reality, it is difficult to precisely adjust the amount of charge, resulting in poor transfer performance (unbalanced).

■ Exposure light Il on photoreceptor drum 1! B1 and B
Since the exposure positions of the second toner images are different from each other, for example, an image scanner or the like is used to read an image at an arbitrary position on the document and convert it into an electrical signal, and then the first and second toner images are created according to the color configuration of the image. In the case of creating a toner image, at least the second toner image for creating the second toner image is
The contrast time of the exposure light 11B2 is set to 1mB1 of the first exposure light.
The different exposure position and the photosensitive drum 1 are compared to the reference time of
It is necessary to delay by a predetermined time depending on the circumferential speed.

Therefore, the second exposure light 1! The signal for side illuminating the -82 (so-called write signal) must be stored for a predetermined time to be delayed, and for this purpose, an enormous capacity of image memory is also required. These problems become more serious when the number of colors increases further.

(2) In connection with the above (2), when toner images are superimposed upon each other when forming a color image, this cannot be realized in such a @ configuration without using an electrical signal.

Therefore, it is not applicable to ordinary electrophotographic reproduction, and the above-mentioned complicated structure is required to process the electrical signals.

In addition to the configuration shown in FIG. 7, for example, in a color copying machine, a transfer drum having a structure around which the transfer material MP is wound is provided, and this transfer drum is used with the transfer material MP wound around it. A method of realizing the desired color overlap by rotating the color several times has also been put into practice, but this method has problems in terms of image forming speed.

Furthermore, in this case, when the second toner image is transferred in the second rotation of the transfer drum to the first toner image transferred to the transfer material MP on the same day, for example, the second toner image is transferred to the transfer drum. It is necessary to prevent such transfer charges from affecting the amount of charge of the first toner image. This requires complicated control such as reversely charging the first toner image in advance so that the transfer portion of the second toner image also maintains substantially the same amount of charge.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming apparatus that can superimpose images on an image carrier and transfer images to a transfer material with high accuracy and high speed using a relatively simple configuration.

[Essentials of the invention]

In the present invention, at least two image carriers are provided, and the formation of the electrostatic iI image described above on these image carriers and the development thereof are performed separately for each image desired to be synthesized,
Thereafter, the toner images formed on the other image carriers are sequentially transferred to any one of these image carriers, thereby achieving the overlapping of the images. In the transfer portion to the transfer material, these superimposed toner images are transferred to the transfer material all at once. As a result, well-balanced superposition of these toner images can be realized without requiring any complicated adjustment of the charge amount for the toner images. Furthermore, if separate electrostatic latent images are formed on the plurality of image carriers at the same time and the developed images, that is, the toner images are sequentially transferred to any one of the image carriers, the above-mentioned image Superimposition of the same toner images can be easily realized without the need for memory or any processing using electrical signals.

〔Effect of the invention〕

As described above, according to the image forming apparatus according to the present invention,
A high quality composite image can be formed stably and at high speed. Furthermore, although such high performance can be obtained, the other components are simple in structure, and an image forming apparatus which is very preferable in practice can be provided.

[Embodiments of the invention]

FIG. 1 shows an embodiment of an eight-position image forming apparatus according to the present invention.In this embodiment, a two-color color digital copying machine or a color printer is assumed.

First, the general structure of the apparatus of this embodiment will be explained with reference to FIG.

In this device, 11 is a polyhedron, 12 is a scanning lens, 13, 14, and 15 are mirrors, 100 is a first image forming section, and 200 is a second image forming section. The first and second two exposure light beams B10 and 820 are formed by two laser beams that are modulated as required by image data of two colors using a data control product (also not shown). 1
1, and is further scanned as required as it rotates, scanning lens 12 and mirror 13° 14.15
As shown in the figure, one color image is taken into the first and second image forming sections 100 and 200 as mirror images of each color. On the other hand, 21 is a paper feed roller, 22 is an intermediate paper feed roller, 23 is a registration roller, 24 is a paper ejection roller, 30 is a transfer charger, 40 is a fixing device, and 50 is a paper ejection tray. As shown in the figure, the transfer material (recording paper) MP stored in the paper cassette is fed into the machine by the paper feed roller 21 at a predetermined timing accompanying the irradiation of the exposure lights 11B10d5 and B20, and is further fed into the machine by the intermediate paper. feed roller 2
2 to the registration row 523,
After the tips are aligned, they are synchronized with images formed in the first and second image forming sections 100 and 200 in a manner described later based on the taken in exposure light beams 810 and B20. The registration row 523
While proceeding with the rotation of the brass, the formed image is transferred based on the required charging of the brass by the transfer charger 30,
Furthermore, the transferred image is fixed based on the pressure of a heating roller in the fixing device 40, and is discharged and deposited on a paper discharge tray 50 by a paper discharge roller 24.

FIG. 2 shows an enlarged view of the first and second image forming sections 100 and 200, and schematically shows their functions, and FIG. 3 shows the first and second image forming sections 100 and 200. This figure schematically shows the image forming process in the image forming sections 100 and 200, and below, referring to FIGS. The configuration and operation will be explained in detail.

As shown in FIG. 2, these first and second image forming sections 100 and 200 are arranged in close proximity to each other, which rotate at the same circumferential speed in the direction of arrows FIO and F20 in the figure, respectively, as image carriers. photosensitive drums 110 and 21 of
0, and the first and second exposure light beams B10 and B20 taken in as mirror images are adapted to expose each of the photoreceptor drums 110 and 210, respectively. In addition, these first and second 2
The two photoreceptor drums 110 and 210 are both positive and
It is assumed that the OPC photoreceptor is constructed of an OPC photoreceptor having substantially the same charging ability for both negative polarities.

Now, in these image forming sections 100 and 200, the first image forming section 100 first positions the first photoreceptor drum 110 at a position before it is exposed by the first exposure light beam 810. For example, here the surface is
a charger 120 for uniformly charging the battery to a negative potential;
The photoreceptor drum 1 is exposed by the exposure light beam B10 of
A developing device (first developing device) 130 inverts the electrostatic latent image formed on the electrostatic latent image formed on the developing device 10, and a toner image is formed by this development. @ A reverse charge inducer 140 that induces charges of opposite polarity (in this example, charges of ■ polarity) near the surface of the photo drum 110, and the transfer charger 30 (in this example, a "positive" corona). Each photoreceptor drum 110 is provided with a cleaning device 150 for removing toner remaining on the photoreceptor drum 110 after the transfer is performed (by performing electric discharge). Note that the developing device 130 is supplied with a developer D1 having a first color, and this (more precisely, this toner) has a "negative" potential (
(1) The image is attached to the @ image on the photosensitive drum 110 based on the rotation of the developing row 5131 biased in the direction of arrow F11 in the figure. Further, the reverse charge inducer 140 is at a position rnJWEr (V2) with respect to the photoreceptor drum 110.
A transparent electrode 141 is biased to induce e-polar charges, and the photoreceptor drum 11 is
It is composed of an LED lamp (red) row 142 that exposes the surface of the photoreceptor drum 142, and a reflecting mirror 143 that concentrates the light emitted from the LED lamp row 142 toward the photoreceptor drum 110 side.

On the other hand, the second image forming section 200 performs an image forming process on the surface of the second photoreceptor drum 210 at a position before being exposed to the second exposure light beam B20.
a charger 220 for uniformly charging the battery to a negative potential;
The photoreceptor drum 2 is exposed by the exposure light beam B20.
For example, here, the electrostatic latent image formed on 10 is
A developing device (second developing device) 230, in which the developed toner image is transferred to the first photosensitive drum 110 in a manner described later in part 1 of the figure, and then the photosensitive drum 2 of the cylinder 2 is transferred to the photosensitive drum 230.
cleaning device 25 for removing toner remaining on 10;
0, and a static elimination lamp 24o (which can also be composed of a red LED lamp array) that eliminates the surface charge of the second photosensitive drum 210 to an initial state. Note that a developer D2 having a second color different from the first color is supplied to the second developing device 230, and this (more precisely, this toner) is supplied to the second photoreceptor drum 210. The latent image is attached to the second photosensitive drum 210 based on the rotation of the developing roller 231, which is biased to a "negative" potential (3), in the direction of arrow F21 in the figure. Further, this second photoreceptor drum 210 is biased to a "negative" potential (V4) with respect to the first photoreceptor 110, thereby forming a second toner image (the second photoreceptor drum The toner image formed on the first photoreceptor drum 110) is transferred onto the first photoreceptor drum 110, and the toner image formed on the second photoreceptor drum 110 is
This makes it possible to superimpose the toner image on the first toner image (the toner image formed on the first photoreceptor drum 110). Incidentally, the circumferential distance L1 on the photoreceptor drum 110 from the point where the second toner image is transferred to the irradiation position P of the first exposure light and the gland B10, and the second exposure light from the same position The circumferential distance L2 on the photosensitive drum 210 to the mB2O irradiation position Q is set equal to
During the transfer of the second toner acid, the second toner image is accurately superimposed on the first toner image.

Next, the color image forming operation by the first and second image forming sections 100 and 200 will be described in detail with reference to FIG. 3 as well.

Now, the first and second photosensitive drums 110 and 21
The circumferential speed of 0 is 60s+/sec, and the charging voltage Vs is Vs=-600 (Vl) Furthermore, each of the bias voltages 1 to V4 mentioned above is V, =-300 (V) V2 = -2000 (V) V3 = -300 (V) V4 - -250 (V) Below, the arrows FIO and F20 of the first and second photoreceptor drums 110 and 210 are selected.
The operations are sequentially listed for each step accompanying the rotation in the direction.

1) The above voltage V3 (-600V) is applied by the charger 120.
The first photosensitive drum 11 is assumed to be uniformly charged.
0 is exposed to the first exposure light 11B10 in the manner described above. As a result, a negatively charged electrostatic latent image as shown by, for example, FLl in FIG. 3(a) is formed in the exposed portion according to the modulation mode of the first exposure light beam B10 by the above-described image data. .

In parallel with this, exposure with the second exposure light beam 820 is also performed in the second image forming section 200, and second image data of the second color is also formed on the second photoreceptor drum 210. Corresponding to the above first photoreceptor drum 110
A second electrostatic latent image is formed which is a mirror image of the electrostatic latent image EL1 formed above.

2) The above negative voltage V with respect to the first photoreceptor drum 110
Developing roller 1 biased to 1 (-300V)
31, reversal development using the developer D1 having the first color is performed. As a result, the first photoreceptor drum 1
A first toner image of e polarity, for example, as shown by TNl in FIG. 3(a), is formed on a portion of the image forming apparatus 10 where there is no negative voltage (a portion where the electrostatic latent image ELI is not formed).

In the 29th image forming section 200, the second
The second toner by color! g! (TN2> to be described later) is similarly formed. Of course, this second toner image also has the mirror image relationship with respect to the first toner image TN1.

3) The above negative voltage V with respect to the first photoreceptor drum 110
2 (-2000■) of the transparent electrode 141 of the reverse charge inducer 140 (the gap between the first photoreceptor drum 110 and the transparent electrode 141 is set to, for example, 0.2 rm). , the surface of the first photoreceptor drum 110 is connected to the LE of the opposite charge inducer 140.
It is irradiated with a light beam B142 emitted by a D lamp array 142.

As shown in FIG. 3(b), this light ray B passes through the carrier transport layer 111 of the first photoreceptor drum 110 and reaches the carrier teacher @112, so that the carrier generation layer 112 generates a pair of charges (holes and electrons). In addition, the polar charges (holes) generated in this way are attracted to the transparent electrode 141 at the negative potential and slowly pass through the charge transport layer, which has a thickness of, for example, about 20 μm over a period of 0.2 to 0.4 seconds. The particles gather near the surface of the first photoreceptor drum 110.

Such development similarly occurs on the back surface of the first toner film TN1. That is, the light beam B142 reaches the carrier generation layer 112 even through the toner fl+TN1, although the light beam B142 is smaller than the portion where the toner image TN1 is not formed, and thereby the toner image TN1 In the same way as above, polar charges are induced on the back surface of the . Due to the action of the reverse charge inducer 140, the first toner image TN1 formed on the first photoreceptor drum 110 converts the above-mentioned (1) polar charge into a mirror image charge of its own charge. It will be held securely on top.

Note that this photosensitive drum 110 has a bipolar charging ability as described above. Since it is composed of a p c photoreceptor, even if the toner image TN1 moves away from the transparent electrode 141 of the reverse charge inducer 140 due to its rotation, the induced will not be discharged. This ■ polar charge is at least 0.2~0
．． It takes 4 seconds to discharge slowly. This means that the induced (1) polar charge is not discharged and is held until the next transfer position T of the second toner image, which is located at a position sufficiently close to the position where the (1) polar charge is induced. means.

In other words, these induced positions and transcription positions are set under these conditions.

4) On the first photoreceptor drum 110,
The first toner image TNI having the e-polar charge held by the polar charge and the second toner image TN2 formed on the photoreceptor drum 210 of ':A2 and also having the e-polar charge are at the position T( (closest or contact position)
reach. The second photoconductor drum 210 has the above-mentioned negative potential v4 <-250V) with respect to the first photoconductor drum 110.
As a result, the transfer is performed at the position T as shown in FIG. 3(C). That is,
The second photosensitive drum 110 has a negative voltage applied to the first photosensitive drum 110.
The second toner image TN2 consisting of e-polar charges on the photosensitive drum 210 is at this positive potential, and the first toner image TN2 has e-polar charges induced near its surface as described above.
It is easily attracted to the photosensitive drum 110, and the transfer is successfully achieved as shown in FIG. 3(C). Furthermore, as a result of this transfer, the first and second toner images TN1 and TN2 are superimposed on each other when they are mirror images of one color image with respect to each other, as described above, so that they accurately correspond to the desired color image. Color toner image (T
N1+TN2) is formed on the first photosensitive drum 110 (see FIG. 3(d)).

5) The color toner image (TN1+TN2>) thus formed on the first photosensitive drum 110 is then transferred to the third transfer position until it reaches the transfer position on the transfer material MP where the transfer charger 30 is located.
It is transported in a stable state as shown in Figure (d). That is, in this case, the first 1Hener 6TNI and the second toner image TN2 have already been reliably held on the first photoreceptor 110 as the Sll electric image of the induced charges of the polarity opposite to their own charges. This process does not cause image disturbance or the like. In addition, the first photoreceptor 1
The (1) polarity induced charges in the portions 10 where no toner image is present slowly move toward the base electrode and are discharged, as shown in FIG. 3(d).

In the state shown in FIG. 3(d), the color toner image is transferred onto the transfer material MP based on the positive corona discharge of the transfer charger 30 (see FIG. 2).

As explained above, according to the device of this embodiment, ■ 1
Since images corresponding to two different colors constituting one color image are formed by exposure on the two photoreceptor drums 110 and 210 in a mirror image relationship, substantially one exposure is required. It becomes possible to synthesize images of the same color. This also makes it possible to form color image copies at high speed by direct exposure using reflected light from the original. Note that a more suitable configuration for this purpose will be described in detail later.

■ In connection with the above ■, the two photoreceptor drums 110
Since the distance from the position where each exposure is performed to the position where each toner image is superimposed on 210 is set to be the same distance (L1 = L2), this can be calculated for the two images having the above-mentioned mirror-other relationship. The electrostatic latent images can be formed simultaneously by simultaneous exposure. Therefore, the same image can be easily and accurately formed without using any means such as the above-mentioned drawing pad memory or the like for temporarily storing image data electrically or reading out the stored data at a predetermined timing. be able to.

(2) In relation to (2) above, the phase alignment of the toner images involved in superimposing the images can be achieved by adjusting the exposure position, which is relatively easy to adjust. Therefore, it is easy to design and maintain.

(yA) of the electrostatic image is performed separately on the two photoreceptor drums 110 and 210, and then the second toner image (TN2) on the photoreceptor drum 210 of cylinder 2 is transferred to the first
by transferring the first image onto the photoreceptor drum 110 of
Since this toner is superimposed on the first toner image (TN1) on the photosensitive drum 110 of It can also be completely avoided. Incidentally, in conventional apparatuses, the two images are developed in sequence on one photoreceptor drum, so for example, some of the toner of the toner image developed first may be transferred to the subsequent developing device. Another problem has been that the toner mixes with other types of toner, causing the toner color to gradually change.

(2) When transferring the second toner image, the first photoreceptor drum 110 is only charged with a reverse charge (reverse admiration charge), and no charge is applied to the first photoreceptor drum 110. It is possible to realize well-balanced superposition of toner images without changing the electric power of the first lunium formed on the photoreceptor drum 110, and as a result, clear and high-quality color images can be produced. Obtainable. In other words, by providing the above-mentioned reverse charge inducing means, there is no need for any complicated charge control process such as charging for adjusting the amount of charge, and moreover, the color image formed through such a charge control process is Much higher quality images can be blued.

■ Since a photoconductor having bipolar charging ability is used as the first photoconductor constituting at least the first photoconductor drum 110, the induced reverse charge does not discharge immediately and lasts a relatively long time. time is retained. Further, this held opposite charge acts as a mI and an electric current for the superimposed first and second toner images, and effectively and stably holds and conveys these toner images to their transfer position.

(2) Similarly, when transferring the second toner image, this can be avoided by applying a bias to the second photoreceptor drum 210 that holds the second toner image so as to have a negative potential ((4)) with respect to the first photoreceptor drum 110. Since this is realized, the toner charge role of the first and second toner images does not change unnecessarily, and a well-balanced superposition of the toner images can be achieved.

■ In relation to the above ■ and ■, the charging of the first and second photoreceptors due to actual charging such as corona discharge has been kept to a minimum, so even if used for a long time, the surface of the first and second photoconductors will remain low. The possibility that a resistive film etc. will be formed is extremely low.
The life of these photoreceptors will also be extended.

■ Particularly in relation to the above ■, the induction of the opposite charge is
Since this is performed based on the light irradiation of the first photoreceptor by the ED lamp array 142, the generation of the reverse charge is limited to the irradiation section of the light and does not have any adverse effect on other electrophotographic processes. This can be done quickly without giving up.

With many excellent effects such as, high quality color images can be formed efficiently and quickly.

Moreover, such a preferable state can be maintained for a long period of time.

Note that ff11 and the second
The circumferential speed values of the photoreceptor drums 110 and 210 or the values of each bias voltage V~4 are merely examples as a rough guide, and in practical use, they should each be within a range that satisfies the above-mentioned predetermined conditions. Of course, any value can be selected depending on the actual situation.

Further, in the same embodiment, as shown in FIG. 3(C), the first
and second photoreceptor drums 110 and 210,
Carrier generation layers (112 and 2
12) and on which the carrier transport layers (111 and 211) are arranged. As shown in FIG. 4 as 210', it is also possible to use a photoreceptor having a structure in which a carrier transport layer 211' is located near the base electrode and a single layer 212' of carrier plates is disposed on the surface. In other words, in this case, the second image forming section 200 forms an electrostatic latent image EL2' with charges of the polarity (1), and during this development, the toner f! TN2
', and furthermore, by applying a negative voltage 5 to the first photoreceptor drum 110 as the bias voltage, transfer and superposition of toner images as described above can be achieved. can be realized.

In addition, as shown in FIG.
It is also possible to have a structure in which a carrier generating layer (112' and 212') is located near each base electrode and a carrier generation layer (112' and 212') is disposed on the surface.

That is, in this case, 1) the charger 120 charges the first photoreceptor drum 1;
After the surface of 10' is uniformly charged to a "positive" voltage, an electrostatic latent image EL1' of polar charge is formed by exposure as shown in FIG. 5(a).

2) The formed electrostatic latent image EL1' is regularly developed with a developer having the first color as described above, and the image is developed as shown in FIG.
A first toner image TN1' as shown in a) is formed.

3) The above-mentioned light (B'I irradiation) is applied to the first toner image TN1' forming portion by the reverse charge inducer 140.

As a result, as shown in FIG. 5(b), carriers consisting of hole-electron pairs are generated in the carrier generation layer 112' of the first photoreceptor drum 110', and a negative voltage applied to the transparent electrode 141 is V6 (e.g. -2000
Due to the electric field generated by the bias voltage V), the electrons among them escape to the base electrode side of the photoreceptor. Therefore, in this case as well, the first
A polar charge is induced on the surface of the photoreceptor drum 110', and the induced charge continues to be slowly discharged thereafter.

4) Similarly to the example shown in FIG. 4, the second toner image TN
2' is formed between the second photoreceptor drum 210' and the first photoreceptor drum 110' as shown in FIG. 5(C).
The second toner @TN2' is transferred onto the first photosensitive drum 110' while applying a bias voltage V7 (for example, -250 V) shown in FIG. At this transfer position T, the above-mentioned induced charge is also sufficiently retained as described above,
Good transfer and superposition of toner images are achieved.

5) Color toner image (TN1') thus formed
+TN2') is securely held on the first photoreceptor drum 110' as a mirror image charge of the induced charge of the polarity (1), which is opposite in polarity to its own charge, as shown in FIG. 5(C). Thereafter, the transfer material is transported to a transfer position to the transfer material MP where the transfer charger 30 is located.

Through these steps, a color image can be successfully formed as in the previous embodiment. Incidentally, the embodiment shown in FIG. 5 is suitable for use in color copying, etc., in which a color image is formed by direct exposure with the above-mentioned original reflected light.

Further, the reverse charge inducer 140 attracts the second toner f21 (TN2 or TN2') with its induced electric hook, and furthermore, causes the induced charge to act as a mirror image charge of the superimposed toner image, thereby As mentioned above, the reverse charge inducer 140 is very effective in stably holding and transporting the device, but the reverse charge inducer 140 can also be used alone for devices other than the device of this embodiment. As long as the above-mentioned photoconductor having bipolar charging ability is used as a photoconductor in a copying machine or printer, it can be used in an appropriate manner to achieve the same effects as described above.

Regarding this reverse charge inducer 140, in the above embodiment, it is disposed near the surface of the first photoreceptor drum 110 and is biased to a negative potential with respect to the first photoreceptor drum 110. body drum 110
Although the transparent electrode 142 is used as an electrode that transmits the irradiated light, a slit electrode having a plurality of openings for transmitting the irradiated light can also be used as the electrode. By using such a slit electrode, the transmission efficiency of the irradiated light can be maintained for a long time even if the electrode surface becomes dirty with toner.

Further, in the above-described embodiments, for convenience, the case where a two-color image is obtained by overlapping toner images of two different colors with each other has been described, but the second image forming unit 200
By providing at least two systems of components such as a photoreceptor drum, an exposure means for the same, and a developing device, it is easy to form a full-color image based on any three or more colors or the three basic colors. You will be able to do this. Particularly in this case, the three photoreceptor drums corresponding to the three primary colors are arranged in the manner shown in FIG. The exposure positions of the exposure light beams B10, 820 and B2O of 3FJ to these photoconductor drums are determined as indicated by the arrows FIO1F20 and F2O, and the exposure positions of the 3FJ exposure beams B10, 820 and B2O are determined as 0 [1] at the P position, Q position and R position shown in the figure. The circumferential distance between the drum 110 and the second photosensitive drum 210 is the closest position or contact position (second toner image transfer position @) T1 to the P position and the Q position, and 2 and 2 are equal, and the first The closest approach or contact position between the photoreceptor drum 110 and the third photoreceptor 310 (the transfer position of the third toner image, which is assumed to be formed on the third photoreceptor drum 310 in the same manner as described above)
) Circumferential distance L from T2 to these P and R positions
Assuming that 3 and L4 are equal, for example, in a case where the image color at an arbitrary position of a multicolor original is separated into three primary colors, the combination ratio of these is read with an image scanner, and these are recombined to generate a full color image. 3 to synthesize
Immediately write the result of calculating the mixing ratio of the primary colors (
Exposure with the above exposure light beam 810°820 and B2O)
In this case as well, the full-color image can be easily and quickly generated without the need for the above-mentioned image memory or the like. Moreover, the above exposure light lB10.820
As mentioned above, since B2O can directly utilize the light reflected from the original, when applied to full-color visual copying, the copying speed is amazingly improved (3 times that of conventional equipment based on simple calculations). You can force it. In addition,
The first photoreceptor drum 110 at the reverse charge inducer 140
If there is a concern that charges having a polarity opposite to the toner charges induced in the toner image may be discharged before the transfer of the third toner image, the reverse charge inducer 140b is set as shown by the broken line in FIG.
may be additionally provided.

Furthermore, although the above description is based on the premise of forming color images, the application of these embodiment devices is not necessarily limited to color image forming devices, but is applicable to well-known photo compositing and other image compositing techniques. can also be widely applied. In other words, in this case, the toner (developer) supplied to each developing device does not necessarily have to be of a different color, and the relationships among the circumferential distances, drum diameters, and circumferential speeds mentioned above can be arbitrary. .

Furthermore, in all of the embodiments described above, a photoreceptor is used as an image carrier, but when this is particularly applied to a printer, other carriers, such as needle electrode discharge, may be used. An image carrier on which an image is formed can also be used.

In addition, if the photoreceptor can stably hold and transport a toner image by 1 m by another method that does not rely on reverse charge induction as described above, it is not necessarily necessary to use the above-mentioned OPC photoreceptor.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing a schematic configuration of an embodiment of an image forming apparatus according to the present invention, and FIG. 2 is a schematic enlarged view of the main parts of the embodiment, including its functions. FIG. 3 is a schematic diagram schematically showing an image forming process using the same embodiment of the apparatus, and FIG. 4 schematically shows a part of the image forming process of another embodiment of the image forming apparatus according to this embodiment. 5 is a schematic diagram schematically showing the image forming process of further embodiments of the image forming apparatus according to the present invention, and FIG. 6 is a schematic diagram showing the photoreceptor when these embodiments are used for full-color image formation. FIG. 7 is a schematic diagram showing an example of a drum configuration and an exposure method. FIG. 7 is a schematic diagram schematically showing the main part configuration of a conventional color image forming apparatus. 1. 110, 210, 310...[Hepatic drum, 2
．． 4.6, 7.30, 120.220... Charger, 3
．． 5,130.230...Developer, 8,150°25
0... Cleaning device, 9,240... Static elimination lamp, 10.40... Fixing device, 11... Polyhedral technique, 1
2...Scanning lens, 13.14.15...Mirror,
21.22, 23.24...Roller, 5o... Paper discharge tray, 131,231. ...Developing roller, 140.
...Reverse charge inducer, 141...Transparent electrode, 142...
- LED lamp row, 143...Reflector, MP...Transfer material. One-1211 Figure 3 (Q) Figure 3 (d) +i2 Figure 4 Figure 7 Figure 5 (a) Figure 5 (d)

Claims (10)

[Claims] (1) A first image carrier consisting of a photoconductor having a cylindrical shape and having a bipolar charging ability that rotates around its axis, and an opposing circumferential surface parallel to the first image carrier. one or more second image carriers that are arranged close to or in contact with each other and that also have a cylindrical shape and rotate about their axes, and for each of the first and second image carriers, an electrostatic latent image forming means for forming an electrostatic latent image corresponding to each composite desired image; and an electrostatic latent image forming means disposed separately corresponding to the first and second image carriers to form the electrostatic latent image, respectively. a developing means for separately developing each image with toner; and a toner image developed on the second image bearing member is transferred to the first image bearing member at a position close to or in contact with the first image bearing member. a bias means for applying a required bias voltage between the first and second image carriers, and a bias means for applying a required bias voltage between the first and second image carriers; a reverse charge inducing means disposed facing the first image bearing member and inducing a charge having a polarity opposite to that of the toner near the surface of the first image bearing member; The toner image developed on the first image carrier and the first image carrier are transferred to a transfer material that is disposed facing the first image carrier on the downstream side in the rotating direction of the carrier and moves therebetween. An image forming apparatus comprising a transfer means for collectively transferring the toner image transferred to an image carrier, and a fixing means for fixing the collectively transferred toner image to the transfer material. (2) The image forming apparatus according to claim (1), wherein the first and second image carriers are photoreceptors that rotate in opposite directions at the same speed. (3) The electrostatic latent image forming means includes an optical system that simultaneously irradiates each of the photoreceptors with a laser beam modulated by color-separated image data, and the developing means The image forming apparatus according to claim 2, wherein the electrostatic latent image is reversely developed using toner of a color corresponding to the image data. (4) The electrostatic latent image forming means includes an optical system that simultaneously irradiates color-separated original reflected light onto each of the photoreceptors, and the developing means corresponds to each of these original reflected lights. The image forming apparatus according to claim (2), which regularly develops the electrostatic latent image with colored toner. (5) The light irradiation position on each image carrier by the optical system is as follows:
The distance from these light irradiation positions to the proximity or contact portion of each image carrier is set at a position that is equal between the first image carrier and the second image carrier, and the optical system is , configured such that electrostatic latent images having a mirror image relationship are formed by the light irradiated on the first image carrier and the light irradiated on the second image carrier for one color image, respectively. An image forming apparatus according to claim (3) or (4). (6) The reverse charge inducing means includes a light transmitting electrode disposed near the surface of the first image carrier, and a light irradiating means for irradiating light onto the surface of the first image carrier through the light transmitting electrode. The first image carriers are arranged so that among the carriers generated on the first image carriers by the light irradiation, carriers having a polarity opposite to the charge of the toner gather near the surface of the first image carriers. The image forming apparatus according to claim 1, further comprising bias means for applying a required bias voltage between the image forming apparatus and the light-transmitting electrode. (7) The image forming apparatus according to claim (6), wherein the light-transmitting electrode is a transparent electrode. (8) The image forming apparatus according to claim (6), wherein the light-transmitting electrode is a slit electrode. (9) The image forming apparatus according to claim (3), wherein the first image carrier has a structure in which a carrier generation layer and a carrier transport layer are sequentially deposited on a base electrode thereof. (10) The image forming apparatus according to claim (4), wherein the first image carrier has a structure in which a carrier transport layer and a carrier generation layer are sequentially deposited on a base electrode thereof.