JPH1026859A - Multicolor image forming device - Google Patents

Abstract

(57) [Problem] To provide a multicolor image forming apparatus capable of obtaining a good image without color mixture of toner. SOLUTION: A post-recharge exposure device 30 is provided, and the transmittance of the light exposed by the device 30 to the maximum density toner layer already developed on the photoreceptor 1 is changed by the exposure light of the image exposure device. The wavelength of the light to be exposed by the exposure device after recharging is controlled so as to be smaller than the transmittance.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a laser beam printer and an electrostatic recording apparatus, and more particularly to a multicolor image forming apparatus capable of performing multicolor printing.

[0002]

2. Description of the Related Art FIG. 15 shows an example of a conventional two-color image forming apparatus. The photoconductor (photosensitive drum) 1 is provided with a photoconductive layer on a cylindrical conductive substrate, and is rotatably supported in the direction of arrow R1 in the figure. Around the photosensitive drum 1, a first scorotron charger 2 for uniformly charging the surface of the photosensitive drum 1 is read in order along the rotation direction, a document is read, and a color image of one of the two color images is separated. A first exposure device for exposing the photosensitive drum 1 with a laser beam 3 based on a first image signal proportional to the density, forming a first electrostatic latent image, and attaching a toner to the first electrostatic latent image to form a first electrostatic latent image A first developing device 4 for forming a toner image is provided.

Further, a second scorotron charger 5 for charging the photosensitive drum 1 after carrying the first toner image, and a laser beam 6 based on a second image signal proportional to the density of the other color image separated. A second exposure device for exposing to form a second electrostatic latent image;
A second developing device 7 for forming a toner image, a corona transfer charger 8 for transferring a color superimposed image formed on the photosensitive drum 1 onto a transfer paper P as a transfer material, and a transfer paper P on which the color superimposed image is transferred
, A cleaning device 11 for removing residual toner on the photosensitive drum 1 after transferring a color superimposed image, and a pre-exposure (lamp) for removing residual charges on the photosensitive drum 1 12 and the like are arranged.

The transfer paper P on which the color superimposed image has been transferred is
After being separated from the photosensitive drum 1, it is conveyed to the fixing device 10, where the toner image on the surface is fixed, a desired print image is formed, and the print image is discharged outside the image forming apparatus main body.

The image scanner unit 19 converts image information into red, green, and blue electric signals. The electric signals are digitized by the A / D converter 18 and then converted into a signal as a color separation unit. The image signal is sent to the processing unit 17 and is converted into an image signal of 256 gradations proportional to the image density of each of the red and black components.

[0006] The red image signal (first image signal) and the black image signal (second image signal) are sent to laser drivers 16a and 16b as signal generating sections, respectively, and are converted into red and black image signals. Laser 15 according to
a, 15b are modulated. The laser beam 3 modulated according to the red signal writes a first electrostatic latent image on the photosensitive drum 1 via the polygon mirror 14a and the mirror 13e as first image information, and the laser beam 6 modulated according to the black signal. Writes a second electrostatic latent image on the photosensitive drum 1 via the polygon mirror 14b and the mirrors 13f and 13g as second image information.

FIG. 16 is a schematic diagram for explaining an example of a process of a conventional image forming apparatus. (1) to (6) of FIG. 16 schematically show the surface potential of the photoconductor in each step. In (1), the photoconductor is charged to, for example, +400 V by a first scorotron charger. Next, in (2), the photosensitive member is exposed based on the first image signal, and the surface potential of the exposed portion is attenuated to, for example, +50 V at the maximum.

Next, in (3), a bias voltage (for example, DC + 3) is applied to a magnet sleeve of a first developing device having a two-component developer composed of a red toner and an iron powder coated carrier.
(00V: AC may be superimposed, indicated by a broken line), and the exposed portion is subjected to reversal development.

After the first development (4), the photoconductor on which the first toner has been developed is recharged by the second scorotron charger. At this time, for example, the non-developing part adjusts the grid voltage to suppress the potential rise. As a result, the developing section cannot be charged sufficiently, for example, only at 250V.

In (5), a second exposure is performed on the photosensitive member based on the second image signal to form a second electrostatic latent image.
In (6), the bias voltage (for example, +30) is applied to the magnet sleeve of the second developing device having the one-component black toner.
(0 V: AC may be superimposed, indicated by a broken line), and the second exposed portion is reversely developed.

The above is a method called a negative recharging process.
There has been a problem that color mixture of black toner tends to occur in a portion of the exposed portion developed with the red toner. This is because even after the first exposed portion is developed with the red toner and further recharged, the surface potential of that portion is lower than that of the unexposed portion during the second development.
This is because black toner is developed during development.

For example, when the first exposed portion is at +50 V and the unexposed portion is at +400 V, after the first development, the potential of the exposed portion is increased by toner charge, and is further recharged. The portion remains at +400 V by suppressing recharging. That is, the potential difference between the developing section and the non-developing section is 150 V.

After forming the second electrostatic latent image, +30
When the second developing is performed by applying a developing bias of 0 V, the second exposed portion is sufficiently developed, but at the same time, a considerable amount of black toner is also developed in the first exposed portion. At the time of the second development, if the developing bias is set sufficiently low (for example, +200) so that the first exposed portion is not developed, the developing of the second exposed portion becomes insufficient.

As a solution to the above problem, an exposure apparatus 20 (refer to FIG. 15), hereinafter referred to as a post-recharge exposure apparatus, is newly provided between steps (4) and (5) shown in FIG.
An apparatus has been proposed in which uniform exposure of the entire surface of a photoreceptor developed with the first toner is performed with white light or the like to reduce the potential difference between a developing portion and a non-developing portion on the photoreceptor (Japanese Patent Laid-Open No. 58-806).
No. 53).

[0015]

However, the above-mentioned prior art in which the post-recharge exposure device is provided has the following problems.

That is, in this case, the recharging in (4) of FIG.
Set to 600V. Here, FIG. 5 shows a difference in transmittance depending on the wavelength of the red and blue toners and a spectral distribution of cyan light. In the case where the first toner is red, if uniform exposure of the entire surface by the post-recharging exposure device 20 is performed with cyan light, the decrease in the potential of the non-developing portion on the photosensitive drum is about 200 V,
The potentials of the developing section and the non-developing section are approximately equal to about 400 V, and by setting the DC component of the developing bias to +300 V, problems such as color mixing of the second toner with the first toner can be prevented.

However, when the first toner is changed to blue toner, the blue toner transmits cyan light as shown in FIG.
Although the potential is about V, the potential of the developing section is reduced by about 150 V, and the potential difference between the developing section and the non-developing section becomes about 100 V, which is not much different from the case where no exposure is performed after recharging. As a result, a problem such as color mixing of the second toner with the first toner occurs similarly to the case where the second toner is not recharged.

That is, since the post-recharge exposure device does not correspond to the case where the color of the first toner is changed by replacing the developing device, for example, a color other than red (for example, blue, green, When (yellow) is used, a problem occurs in that the black toner of the second toner is mixed with blue, green, and yellow of the first toner.

In addition, when amorphous silicon is used for the photosensitive member, there are advantages such as high durability and a long life,
Since the electrostatic capacity is larger than that of other photoconductors such as OPC, the charging ability is low. In a negative recharge type image forming apparatus, the latent image potential of the developed image of the first color is made substantially the same as the non-developed portion. It is difficult to recharge, and the above problem becomes more pronounced.

Accordingly, it is an object of the present invention to provide a multicolor image forming apparatus capable of obtaining a good image without color mixture of toner.

[0021]

The above object is achieved by a multicolor image forming apparatus according to the present invention. In summary, the present invention provides a multicolor image forming apparatus that repeatedly performs charging, image exposure, and development on an image carrier, forms a multicolor toner image on the image carrier, and collectively transfers the toner image onto a transfer material. And means for uniformly exposing the entire surface of the image bearing member after the second and subsequent charging, and the entire surface exposing means includes a mechanism for controlling a wavelength of light to be exposed. This is a color image forming apparatus.

It is preferable to use amorphous silicon as the image carrier. The entire surface exposure unit is more than a portion where the toner image has already been formed on the image carrier.
It is preferable that the potential of the portion where the toner image is not formed is charged such that the absolute value becomes larger.

It is preferable that the developing device other than the final color has means for judging the color, and based on the judgment result, controls the wavelength of light to be exposed by the entire surface exposing means. It is preferable that the transmittance of the light exposed by the entire surface exposure unit to the maximum density toner layer already developed on the image carrier is smaller than the transmittance of the light exposed by the image exposure device.

[0024] The overall exposure means includes a halogen lamp;
It is preferable to include a filter that changes the wavelength of the halogen lamp and a motor that moves the filter. According to another aspect, it is preferable that the entire-surface exposure means includes a plurality of fluorescent lamps having different wavelengths. According to another aspect, the overall exposure means includes a plurality of LEDs having different wavelengths.
It preferably comprises According to yet another aspect, the charger used for the recharger is preferably a corotron.

[0025]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a multicolor image forming apparatus according to the present invention will be described in more detail with reference to the drawings.

FIG. 1 shows an embodiment of a two-color image forming apparatus according to the present invention. The configuration and operation of the two-color image forming apparatus shown in FIG. 1 are substantially the same as those of the conventional example described with reference to the two-color image forming apparatus shown in FIG. Only the parts different from the above will be described, and the same parts will be omitted. Further, in the following examples, an amorphous silicon drum was used as the photosensitive member 1.

In FIG. 1, the first developing device 4 of the two-color image forming apparatus according to the present invention includes a protrusion 41 for determining the color of the first toner and a means for detecting the position of the protrusion 41. Is provided. Further, in place of the post-recharge exposure apparatus 20 in the conventional example, a post-recharge exposure apparatus 30 having a mechanism for controlling the wavelength of light to be exposed is provided.

The present invention is characterized in that the color of the first toner is determined by the apparatus having the above configuration, and the wavelength of the recharging exposure apparatus is switched based on the determined color.

Hereinafter, a method for determining the color of the first toner will be described with reference to FIG. The first developing device 4 includes:
As shown in FIG. 1, as a means for determining the color of the first toner, a protrusion 41 is provided at a portion corresponding to each color, and a photosensor 42 is provided as a means for detecting the position of the protrusion.

When, for example, the blue toner developing device shown in FIG. 2A is used as the first developing device, the light beam of the first photosensor 42a is blocked by the projection 41a,
An output of signal "1" is obtained. On the other hand, since the light beam of the second photosensor 42b is not blocked, an output of the signal "0" is obtained. The signal “1.0” thus obtained is assigned to blue. Similarly, “0.1” is changed to green (FIG. 2).
(2)), "1.1" is yellow (FIG. 2 (3)), "0.0"
Is assigned as red (FIG. 2 (4)), the color can be determined.

Next, a method of switching the wavelength of the light to be exposed in the recharging exposure device 30 based on the result of the determination of the color of the first developing device by the determination means will be described. The present invention is applied to a two-color image forming apparatus in the following first to third embodiments, and to a three-color image forming apparatus in the fourth embodiment.

Embodiment 1 In Embodiment 1, as shown in FIG. 3, the post-recharge exposure apparatus 30 includes a halogen lamp 31, a filter 32 for switching the wavelength, and a motor 33 for moving the filter 32. .

In accordance with the above-described determination of the color of the first toner, the post-recharging exposure device 30 operates the filter 32 by the motor 33 so that the filter 32 moves to expose light having a wavelength that is difficult for the first toner to transmit. The wavelength of the light from the light source 31 is switched to expose each light.

First, the wavelength of light to be exposed by the post-recharge exposure device 30 will be described. FIG. 4 shows the spectral distribution of the halogen lamp and the spectral distribution when the filters are covered with cyan, yellow, and magenta filters. For example, when the first toner is a red toner, as can be seen from FIG. 5, a cyan light, which is difficult to transmit through the red toner, is exposed on the photosensitive member.
The cyan filter moves over the halogen lamp.

In the same manner, the photosensitive member is exposed to magenta light for the green toner and yellow light for the blue toner.

The cyan light here is light of a so-called complementary color of red, and when exposed to the developed portion of the red toner on the photoconductor, it is ideally blocked by the red toner, Means light of a wavelength that is not irradiated with light. However, in practice, it is difficult to expose light that does not pass through the toner layer at all, due to limitations on the cost of a mechanism for controlling the wavelength of light. Therefore, in the embodiment, light having a wavelength of 20% or less of the exposure amount passes through the toner layer and is irradiated on the photoreceptor in the post-recharge exposure. In addition,
The same applies to magenta light for green toner and yellow light for blue toner.

Actually, according to the determination of the color of the first toner,
When light of a wavelength such that 20% or less of the exposure amount passes through the toner layer of the developing section and is irradiated on the photoreceptor, the decrease in the potential on the photoreceptor remains at 10 V. On the other hand, in the non-development portion, the exposed light is irradiated on the photoreceptor with the same amount of light, so that the potential drops by several hundred volts. As a result, the potentials of the development portion and the non-development portion on the photoreceptor are made equal. Can be. That is, the developing unit and the non-developing unit can be set to the same potential at a position only several tens of volts lower than the potential of the first developing unit after recharging.

Next, the exposure amount in the post-recharge exposure will be described. FIG. 6 is a graph showing the relationship between the exposure amount of the recharging exposure, the potential (V _d ) of the developing portion on the photoconductor, and the potential (V _nd ) of the non-developing portion. It is known that the amorphous silicon drum used in this embodiment has a substantially linear relationship between the amount of light to be exposed and the surface potential. In order to prevent color mixing of the first toner with the second toner, which is a problem here, it is only necessary that the developing portion and the non-developing portion on the photoconductor have the same potential during the second development. it is sufficient to post-exposure recharged in two points of intersection of the light intensity of the graph of FIG. 6 (i _x).

By performing exposure after recharging as described above, an image forming process as shown in FIG. 7 can be realized. (1) to (7) schematically show the surface potential of the photoconductor in each step. In (1), the photoconductor is charged to, for example, +400 V by a first scorotron charger. Next, in (2), exposure is performed based on the first image signal, and the surface potential of the exposed portion is attenuated to, for example, +50 V at the maximum.

Next, in (3), a bias voltage (for example, DC + 3) is applied to the magnet sleeve of the first developing device having the two-component developer composed of the color toner and the iron powder coated carrier.
(00V: AC may be superimposed, indicated by a broken line), and the exposed portion is subjected to reversal development. After the first development (4), the first non-development part is +6 by the second scorotron charger.
00V and the first developing unit is recharged to + 450V.

In (5), exposure is performed after recharging at the above-described light wavelength and light amount, and the potential of the first non-developing portion and the first developing portion is set to 400V. In (6), the second
The second exposure is performed on the basis of the image signal of (i) to form a second electrostatic latent image. In (7), a bias voltage (for example, +300 V: indicated by a broken line, AC may be superimposed) is applied to the magnet sleeve of the second developing device having the one-component black toner, and the second exposed portion is reversely developed. .

Therefore, as can be seen from the above description, in the present invention, in recharging, it is not necessary to make the first non-developing portion and the first developing portion on the photoreceptor have the same potential. Thus, the potential difference between the first non-image portion and the first image portion is set to 150 V so that the two portions have the same potential.
What is necessary is just to charge to such an extent. Then, after recharging and exposure with light having a wavelength corresponding to the first toner,
The developing bias can be set so that the second toner does not mix with the first toner and the second toner can be sufficiently developed.

In fact, it is difficult to make the first developing section and the first non-developing section have the same potential during recharging (hereinafter referred to as recharging convergence) as described below.

FIG. 8 is a graph of an experimental result showing the current applied to the corotron wire and the photoconductor surface potential of each of the first developing unit and the first non-developing unit after recharging. From this figure, it can be seen that it is difficult for the corotron recharger to converge the potentials of the first developing section and the first non-developing section.

In order to improve the recharge convergence, in the negative recharge system, it is necessary to charge more in the first image developing section than in the non-image first image section, that is, to apply more drum direction current. There is. The corona current discharged from the recharge discharge wire is divided into a drum direction current flowing in the drum direction and a shield direction current flowing in the charger shield. When the corona current is constant, it is considered that the ratio of the current in the drum direction to the current in the shield direction depends on the resistance in each direction. Although the resistance in the shield direction does not usually change, the resistance in the drum direction changes depending on the surface potential and the presence / absence of toner. That is, since the current in the drum direction at the time of recharging changes depending on the state of the first development, the charging potential also becomes the first potential.
It changes depending on the state of development.

FIG. 9 shows experimental results showing the relationship between the first developing state and the current in the drum direction. 400 V and 150 V, respectively, assuming the potential on the toner in the first developed non-image area and the image area.
V and 150 V without toner were compared. First, 4
Comparing 00V and 150V without toner, 150V having a smaller drum surface potential causes more drum current to flow for the same corona current, and the ratio is (40%).
0V) :( 150V) ≒ 4.5: 5.5.

Next, comparing the surface potential and the presence or absence of toner, a comparison is made between the presence of toner and the presence of toner, the smaller the current in the drum direction relative to the same corona current, and the ratio is (no toner): (no toner) ) ≒ 6: 4. That is, in the negative recharge system, a larger amount of current flows in the drum direction from the point of surface potential to the first developed image portion (eg, 150 V on the toner) than the first developed non-image portion (eg, 400 V), and This is a direction that is advantageous for convergence, but is a direction that is disadvantageous for recharge convergence from the viewpoint of the presence or absence of toner.

The total recharging convergence is determined by both of these factors, and in this experimental system, the graph shows (first developed non-image portion) :( first developed image portion) ≒ 5.5:
It is 4.5 and it can be seen that it does not converge. From the graph, it is assumed that when more corona current is applied, this relationship is reversed and eventually converges.However, a larger charger is required, which is very disadvantageous in terms of cost and body space. It is considered to be.

Although these relations are slightly different depending on the kind, amount or potential setting of the toner, it can be said that these are fundamental problems in the negative recharge system.

As a means for solving this problem, there is a method using a recharger having a high charging ability. However, they are not only expensive but also require more space and a large power supply. Not efficient.

Next, it is conceivable to use a scorotron charger as the recharger, reduce the drum direction current flowing in the first developed non-image area, and secure the drum direction current flowing in the first developed image area. FIG. 10 is a graph of an experimental result showing the voltage applied to the grid and the drum surface potential of the first developed non-image area and the first developed image area after recharging. As can be seen from this figure, when the voltage applied to the grid is substantially equal to that of the first developed non-image area, the first developed image area is most charged while the potential of the first developed non-image area after recharging is suppressed. It can be seen that the convergence is improved.
However, with such a grid voltage, a large amount of current in the drum direction is required to sufficiently increase the potential of the first developed image area after recharging. It is considered very disadvantageous.

The above is the result of the recharging, and the first developing unit and the first developing unit
This is the reason why it is difficult to make the non-developing portions the same potential.

In the two-color image forming apparatus of the present embodiment, the transmittance of the light exposed by the exposure device after recharging to the maximum density toner layer already developed on the photosensitive member is determined by the exposure of the image exposure device. By controlling the wavelength of the light to be exposed by the post-recharging exposure device so as to make the transmittance smaller than the light transmittance, it is possible to obtain a good image with less color mixture of each toner.

Second Embodiment Next, in the second embodiment, as shown in FIG. 11, the post-recharge exposure device 30 'includes three fluorescent lamps 31' and 32 'having different wavelengths covered with cyan, yellow and magenta filters. ,
33 '. Here, according to the determination of the color of the first toner, light having a wavelength that is difficult to transmit through the toner of that color is transmitted to the first toner.
One of the fluorescent lamps is turned on so that the photosensitive member is exposed with a light amount at which the potentials of the toner developing portion and the non-developing portion become substantially equal. For example, when the first toner is red toner, a fluorescent lamp covered with a cyan filter is turned on to expose the photosensitive member with cyan light. In the same manner, magenta light is exposed for the green toner, and yellow light is exposed for the blue toner.

Here, the cyan light is a light having a wavelength at which 20% or less of the exposed light amount is blocked by the red toner when exposed on the photoconductor on which the red toner has been developed. Means The same applies to magenta light for green toner and yellow light for blue toner.

In this embodiment, there is an advantage that the mechanism can be simplified because there is no need to move the filter and the like, and the power consumption can be reduced by using a fluorescent lamp as compared with a halogen lamp.

Third Embodiment Next, in a third embodiment, as shown in FIG. 12, the post-recharge exposure device 30 "includes three LEDs for outputting red, green, and blue.
31 ", 32", and 33 ". Here, in accordance with the determination of the color of the first toner, light having a wavelength that is difficult to transmit through the toner of that color is made substantially equal in potential between the developing portion and the non-developing portion of the first toner. Exposure is performed on the photoreceptor with an appropriate light amount.

Table 1 below shows how the LEDs corresponding to the respective color toners are turned on. For example, when the first toner is the red toner, the green and blue LEDs are turned on. Then, the photoconductor is exposed by the additive color mixture. Similarly, red and blue LEDs are lit for green toner and red and green for blue toner.

Here, the cyan light is a light having a wavelength at which 20% or less of the exposed light amount is blocked by the red toner when exposed on the photoconductor on which the red toner has been developed. Means The same applies to magenta light for green toner and yellow light for blue toner.

In this embodiment, since each LED is small, there is an advantage that the size of the exposure device 30 after recharging can be reduced.

[0061]

[Table 1]

Embodiment 4 Next, the configuration of the three-color image forming apparatus in Embodiment 4 is different from that of the two-color image forming apparatus described so far (FIG. 1) in that the downstream of the second developing device 5 in the photoconductor rotating direction. Beside the third
Scorotron charger, second post-recharge exposure device, and third
A developing device is added. The operation of each part is the same as that of the two-color image forming apparatus except that a process of forming the third toner image is added.

Here, for example, a case where the first toner is red, the second toner is blue, and the third toner is black will be described. FIG. 5 shows the difference in transmittance depending on the wavelength of red and blue toner light and the spectral distribution of cyan light and green light.

First, the red toner of the first toner is developed, and in accordance with the determination of the color, the post-recharge exposure device exposes light having a wavelength that is difficult to transmit through the first toner, for example, cyan light.
As a result, the potentials of the first developing section and the non-developing section become substantially equal. Next, after developing the blue toner of the second toner, according to the determination of the first and second colors, light of a wavelength that hardly transmits red and blue, for example, green light is exposed. Then, the potentials of the first, second developing section and non-developing section become substantially equal.

Here, the cyan light refers to a light having a wavelength at which 20% or less of the exposed light amount is blocked by the red toner when exposed on the photoconductor on which the red toner is developed. Means Also, the green light means that when the red and blue toners are exposed on the developed photoreceptor, 20% or less of the amount of light exposed in the red toner developing unit and the blue toner developing unit is irradiated on the photoreceptor. It refers to light of a wavelength.

The exposure amount refers to an exposure amount such that the potential of the developed portion and the potential of the non-developed portion become substantially equal after exposure in both of the two exposures after recharging.

In the present invention, the transmittance of the light to be exposed by the exposure device after recharging to the developing portion on the photoreceptor is made smaller than the transmittance of the second image exposure.
This has the advantage that the second latent image can be easily formed on the first toner image.

Further, in the above embodiment, the case where the positively charged amorphous silicon drum is used as the photoreceptor 1 for the reversal development of the positive polarity toner has been described. However, the present invention is also applicable to the case of the OPC drum. Since the OPC drum is normally used with negative charging, in this case, the toner may be reversely developed using a negative toner.

Also, it is not appropriate to use a corotron charger as the second scorotron charger 5 because the charged amount is largely different between the developing portion and the non-developing portion on the photosensitive member. However, as can be seen from the relationship between the drum surface potential and the wire applied current of the corotron charger and scorotron charger under the same conditions shown in FIG. 13, and the relationship between the drum surface potential and the wire applied voltage shown in FIG. It can be seen that the charging efficiency is better when the container is used. In the present invention, it is possible to replace the second scorotron charger with a corotron charger having good charging efficiency by the operation of the above-described post-recharge exposure device.

Further, in the embodiments, the case where the first toner is red, green, and blue has been described. However, the present invention can be applied to other colors (for example, yellow, magenta, and cyan).

Although the pre-transfer charger for adjusting the charge amounts of the two-color toner images on the drum before the transfer has not been described in detail, the charge amount is controlled by AC or DC using a corotron or scorotron. It is known.

Of course, it is also known that it is effective to transfer and separate a two-color image, which is a step of attenuating the photoconductor potential by using a pre-transfer exposure (not shown) in combination with this.

In the pre-exposure, in which the photosensitive member is neutralized at the end of the process, it is necessary to appropriately set the wavelength, intensity, and the like so that the ghost of the previous image does not occur.

In the above-described embodiment, the case of an image forming apparatus in which two or three colors are developed by one rotation of the photosensitive member has been described. However, an image forming apparatus in which four or more colors are developed by one rotation of the photosensitive member is described. Or multiple rotations of the photoconductor,
The present invention is also applied to an image forming apparatus that develops a plurality of colors.

In any case, it will be easily understood by those skilled in the art that these can be used in combination with the present invention.

[0076]

As described above, according to the present invention,
A means for performing uniform full-surface exposure on the image carrier after the second and subsequent charging, and a mechanism for controlling the wavelength of light to be exposed by the entire-surface exposure means, so that color mixing of each toner is reduced. A multicolor image forming apparatus capable of obtaining a good image was obtained.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of a two-color image forming apparatus according to the present invention.

FIG. 2 is an explanatory diagram for explaining a technique for determining the color of toner in a first developing device of the two-color image forming apparatus of FIG. 1;

FIG. 3 is a schematic view showing the entire surface exposure apparatus after recharging according to the first embodiment of the present invention.

FIG. 4 is a graph showing a spectral distribution when a halogen lamp and a cyan, yellow, and magenta filter are put on the halogen lamp.

FIG. 5 shows a difference in transmittance depending on the wavelength of light of red and blue toners;
6 is a graph showing the spectral distribution of cyan light and green light.

FIG. 6 is a graph showing the relationship between the amount of light exposed by the exposure device after recharging and the potential of a developing portion and a non-developing portion on a photoconductor.

FIG. 7 is a graph showing an example of an image forming process of the two-color image forming apparatus according to the present invention.

FIG. 8 is a graph of an experimental result showing a drum surface potential with respect to a current applied to a corotron recharger wire in a two-color image forming process.

FIG. 9 is a graph of an experimental result showing a relationship between a first developing state and a current in a drum direction.

FIG. 10 is a graph of an experimental result showing a drum surface potential with respect to a current applied to a corotron recharger wire in a two-color image forming process.

FIG. 11 illustrates a second example of the two-color image forming apparatus according to the present invention.
FIG. 1 is a schematic configuration diagram of a post-recharge exposure apparatus of an embodiment.

FIG. 12 illustrates a third example of the two-color image forming apparatus according to the present invention.
FIG. 1 is a schematic configuration diagram of a post-recharge exposure apparatus of an embodiment.

FIG. 13 is a graph showing a relationship between a drum surface potential and a wire applied current of a corotron charger and a scorotron charger.

FIG. 14 is a graph showing a relationship between a drum surface potential and a wire applied voltage of a corotron charger and a scorotron charger.

FIG. 15 is a schematic configuration diagram illustrating an example of a conventional two-color image forming apparatus.

FIG. 16 is a graph showing an example of an image forming process of a conventional two-color image forming apparatus.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Image carrier 2 1st charging device 4 1st developing device 5 2nd charging device 30, 30 ', 30 "Recharge exposure apparatus (overall exposure means) 41 Color discrimination projection part 42 Color discrimination photo sensor

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Takao Honda 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (72) Inventor Yoshihiro Murasawa 3-30-2 Shimomaruko, Ota-ku, Tokyo Non Corporation

Claims (9)

[Claims] 1. A multicolor image forming apparatus which repeatedly performs charging, image exposure, and development on an image carrier to form a multicolor toner image on the image carrier and collectively transfer the toner images onto a transfer material. Multicolor image formation, comprising: means for uniformly exposing the entire surface of the image carrier after the second or subsequent charging, wherein the entire surface exposing means comprises a mechanism for controlling a wavelength of light to be exposed. apparatus. 2. The multicolor image forming apparatus according to claim 1, wherein amorphous silicon is used as said image carrier. 3. The image forming apparatus according to claim 1, wherein the entire surface exposing unit has a larger absolute value of a potential of a portion where the toner image is not formed than a portion where the toner image is already formed on the image carrier. 3. The multicolor image forming apparatus according to claim 1, wherein the multicolor image forming apparatus is charged. 4. The developing device for a color other than the final color has means for judging the color, and controls the wavelength of light to be exposed by the entire surface exposing means based on the judgment result. And 2 or 3 multicolor image forming apparatuses. 5. The transmittance of the light exposed by the full-surface exposure means to the maximum density toner layer already developed on the image carrier is smaller than the transmittance of the light exposed by the image exposure device. The multicolor image forming apparatus according to any one of claims 1 to 4, wherein: 6. A halogen lamp, a filter for changing a wavelength of the halogen lamp, and
The multi-color image forming apparatus according to any one of claims 1 to 5, further comprising a motor that moves the filter. 7. The multicolor image forming apparatus according to claim 1, wherein said overall exposure means comprises a plurality of fluorescent lamps having different wavelengths. 8. The multicolor image forming apparatus according to claim 1, wherein said overall exposure means comprises a plurality of LEDs having different wavelengths. 9. The multicolor image forming apparatus according to claim 1, wherein the charger used for the recharger is a corotron.