JP3073126B2 - Image forming method and image forming apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic recording method and an electrophotographic recording apparatus, and more particularly to an image forming method and an image forming method suitable for forming a charge image on a latent image carrier and performing multicolor printing. Related to the device.

[0002]

2. Description of the Related Art A so-called one-pass color image forming apparatus for performing color printing while a photoreceptor makes one rotation includes:
(1) Four sets of image forming means including charging, exposure, and development are arranged around a photoreceptor, and an image forming process is repeated to form a four-color toner image on the photoreceptor. (2) FIGS. As shown in FIG. 8, the charge 2, the exposure 3, the development 4,
5, 7 and 8 are arranged, and after the charging 2, a single exposure 3 causes a 5-level charge image (Vi ₁ <Vi ₂ <Vi in FIG. 8).
₃ <Vi ₄ <V ₀ ), and then the developing units 4, 5, 7,
8, the developing bias is sequentially increased (in FIG. 8, Vb ₁ <
Vb ₂ <Vb ₃ <Vb ₄ ), a reversal developing step is performed, and a toner of the same polarity as the charge image is attached to a portion where the charge has disappeared to form a color image.

[0003]

However, the above-mentioned conventional one-pass color image forming apparatus has the following problems.

[0004] Charge around the photoreceptor shown in the above (1),
The method of arranging four sets of image forming means including exposure and development and repeating the image forming process requires the charging, exposure and development units for the number of colors, so that the color image forming apparatus tends to be large. Was. The one-exposure five-level system shown in FIGS. 7 and 8 in (2) has the advantage that only one charging and exposure unit is required, but the three-time development from the second development to the fourth development is performed. in step, subsequent development bias than the toner image potential formed in the preceding stage is higher (e.g., in the second developing later in FIG. 8, the toner image potential Vt ₁ ~
Vt _4, when representing the developing bias in Vb ₁ ~Vb _4, Vt ₁
<Vb ₂ , Vt ₂ <Vb ₃ , Vt ₃ <Vb ₄ ) in some cases, so that the toner in the subsequent stage is mixed with the toner image formed in the previous stage, and tends to exhibit unintended color mixing. Further, a method of forming a color image using only regular development in the development process is also conceivable, but in the three development processes from the second to the fourth development, an unintended color mixture tends to be similarly exhibited. Further, a method in which the development step is performed by mixing normal development and reversal development is also conceivable. However, in the two subsequent development steps of repeating the reversal development and the regular development, the color development tends to be unintended. .

An object of the present invention is to provide an image forming method and an image forming apparatus capable of eliminating the above-mentioned drawbacks and realizing clear multicolor printing at high speed.

Another object of the present invention is to provide a compact color image forming apparatus capable of performing one-pass color printing.

[0007]

A feature of the present invention is that in an image forming method for forming an image of a plurality of colors through a charging step, an exposing step, a developing step and a transferring step, the exposing step comprises a plurality of exposing steps. After the first exposing step, a developing step of at least one color is performed, and in the subsequent exposing step, the toner image part formed in the at least one color developing step is exposed to reduce the potential of the toner image part. It is characterized in that a charge latent image for forming a toner image of another color is formed while being selectively shifted.

Another feature of the present invention is that the latent image carrier, charging means for the latent image carrier, exposure means for forming a charge latent image on the latent image carrier, In the image forming apparatus including a developing unit that forms a toner image of the following, and a transfer unit that transfers a toner image to be transferred, a plurality of exposure units are provided as the exposure unit, the second exposure unit,
Forming a charge latent image for forming a toner image of another color while selectively shifting a potential of at least one color toner image formed on the charge latent image formed by the first exposure unit; It is characterized by doing.

Another feature of the present invention is that in an image forming method for forming an image of a plurality of colors through a charging step, an exposing step, a developing step, and a transferring step, an exposure method for forming a charge latent image on a latent image carrier is provided. Through the process, latent image dots are formed of a plurality of triangular dots having a latent image shape and the vertices of the one dot adjacent to each other in the exposure main scanning direction are opposite to each other in the exposure sub scanning direction. It is characterized by the following.

[0010]

In the present invention, at a later exposure step, at least one color toner image portion formed up to that time is further exposed to selectively shift the potential of the toner image portion. Color mixing can be prevented. That is, adjustment of the potential of the toner image, the background portion, and the potential of the latent image portion and formation of the latent image are performed as necessary by the subsequent exposure, and the potential of the toner image portion, the background portion, and other latent images is determined during the subsequent normal development. The potential distribution is adjusted so that development can be performed using a high development bias, and during reversal development, development can be performed using a development bias lower than the potentials of the toner image portion, the background portion, and other latent images. Because it can be configured, color mixing is less likely to occur. Therefore, for example, by forming toner images of the first to fourth colors, clear full-color printing can be performed in one pass.

Further, in the present invention, since the shape of the one-dot latent image is triangular, and the positions of the vertices are opposite to each other in the sub-scanning direction between adjacent one-dots in the main scanning direction,
Focusing on one dot of an arbitrary color, the other three colors adjacent in the main scanning direction and the sub-scanning direction can be evenly adjacent to each side of the triangular dot. Therefore, full-color printing with good halftone reproducibility based on the combination of each color can be performed.

[0012]

Embodiments of the present invention will be described below. The present invention is not limited to the following embodiments, and various modifications can be made within the scope of the configuration.

The image forming apparatus of the present invention is, for example, shown in FIG.
This will be described with reference to FIG. A charger 2, a first exposure 3, a first developing unit 4, a second developing unit 5, a second exposing unit 6, a third developing unit 7, a fourth developing unit Device 8, pre-transfer charger 20, transfer device 10, fixing device 11, cleaner 1
2, a discharge corona 13 and a discharge lamp 21 are arranged, and a surface voltmeter 18 and 19 and a second exposure control device for controlling the second exposure.
An exposure control unit 9 is disposed, for example, the first color is yellow, the second color is magenta, the third color is cyan, the fourth color is black, and the light irradiated by the second exposure 6 transmits the first color toner. The color type of the first color toner is selected or the wavelength of the irradiation light is set so that the toner image of four colors is formed on the photoconductor 1 by the method described below.

Reference numerals 14 and 15 denote a first exposure unit and a second exposure unit, respectively, and 16 and 17 denote a first exposure unit and a second exposure unit, respectively.
The second developing bias and the third and fourth developing biases are set to 22
Denotes a paper hopper, 23 denotes a paper stacker, and 24 denotes a color printing condition setting unit.

FIGS. 2A to 2C are corresponding surface potential distribution diagrams.

First, a charge image of four levels is created by charging and first exposure. These correspond to the first charge image (region R ₁ ), the third charge image (region R ₃ ), the background portion (region of the potential Vw), and the second charge image (region R ₂ ), respectively, from the upper level.

Of the first and third charge images, the first charge image (region R ₁ ) having a large electrostatic contrast (potential level) is subjected to normal development by applying a bias Vb ₁ in the first developing unit 4. The first color toner (for example, yellow toner) is attached. In the second development for forming the second color toner image, the potential V of the first color toner image portion is set to prevent color mixture.
Reversal development is performed by applying a bias lower than t ₁ and the potential of the third latent image portion (FIG. 2A).

Next, in the second exposure 6, the first color toner image portion (region R ₁ ) is irradiated with light having the intensity I ₁ s, and the potential of the first color toner image portion (region R ₁ ) is substantially equal to the background portion potential Vw. At the same time, a fourth image exposure (intensity I ₄ ) is performed to form a fourth charge image in the region R ₄ . The fourth image exposure (intensity I ₄ ) is set so that the potential of the fourth charge image (region R ₄ ) is sufficiently lower than the potential of the second color toner image portion (region R ₂ ). The background potential V is measured by the
w, measuring the potential of the first color toner image portion (region R ₁ ) and the potential of the second color toner image portion (region R ₂ ) after the second exposure,
The exposure intensities I ₁ s and I ₄ may be controlled based on them (FIG. 2B).

The third charge image is subjected to regular development in a third developing section 7 and a third color toner (for example, cyan toner) is attached to form a third color toner image. The third color toner is 1
Regardless of the polarity of the color toner and the second color toner, the third
The charge image and the third developing bias potential Vb ₃ are
Since it is higher than the color toner image potential, 3
No color toner adheres.

The fourth charge image (region I ₄ ) is transferred to a fourth developing device 8
And then apply the fourth color toner (for example, black toner) to form a fourth color toner image. Since the fourth charge image and the fourth developing bias potential Vb ₄ are lower than the first to third color toner image potentials, the fourth color toner does not adhere to the first to third color toner image areas (FIG. 2 ( c)).

From the above, four color toner images are formed on the photoreceptor.

The pre-transfer charger 20 that generates the AC + DC corona unitizes the polarity of the four-color toner image, transfers the same to a transfer target sheet by the transfer unit 10, The color toner image is melted by heat and fixed to the paper.

As described above, in this embodiment, clear full-color printing can be performed in one pass.

A supplementary description will be given of the second exposure step performed before the third development. Immediately before the first developing device 4 and the third developing device 7, surface voltmeters 18 and 19 are disposed, respectively, and the background portion potential Vw and the first color toner image portion after the second exposure are provided.
In order to measure the potential of the (region R ₁ ) and the potential of the second color toner image portion (region R ₂ ) and control the exposure intensities I ₁ s and I ₄ based on these, the detected value signal of the surface potential is The second exposure control condition is stored in the storage unit of the color printing condition setting unit 24, based on the detected value of the surface potential, transmitted to the second exposure control unit 9, and the second exposure unit 15 is controlled.

In the color printing condition setting section 24, the conditions of the first to fourth developing biases are set based on the detected value of the surface potential, and the first to fourth developing biases 1 are set.
6 and 17, the developing bias is controlled, and the initial charging potential is monitored by the surface voltmeter 18, and the charger 2 is controlled to have a predetermined potential.

In the configuration shown in FIG. 1, the third and fourth developing units 7 and 8 are disposed below and tend to accumulate floating scattered toner. Therefore, the color types of the third color toner and the fourth color toner are lightness. It is desirable to use a low color toner (eg, cyan or black).

In such a configuration, the second exposure means for adjusting the surface potential (toner image and latent image potential) of the photoconductor is arranged upstream of the third developing step for performing the second regular development. Since the third developing bias can be set to be equal to or higher than the first color toner image potential by adjusting the surface potential immediately before the third developing, the third developing bias can be set.
No color mixing occurs during development.

In the fourth development, in which the second reversal development is performed, the reversal development is performed using toner of the same polarity as in the second development. However, a development bias lower than the toner image potential formed in the second development is applied. Since the reversal development is performed, no color mixture occurs in the second color toner image, and the fourth development bias is lower than the potentials of the first and third charge images, so that the fourth color toner is contained in the first and third color image areas. There is no mixing. That is, the first to fourth color toner images can express a monochromatic image of yellow, magenta, cyan, and black without color mixture. Therefore, a full-color image can be formed by combining them, and in this embodiment, there is an effect that clear full-color printing can be performed in one pass.

Subsequently, one of the color image forming apparatuses of the present invention will be described.
The dot latent image shape will be described. As shown in FIG.
The one-dot latent image has a triangular shape, and the positions of vertices are opposite to each other in the sub-scanning direction between adjacent one-dots in the main scanning direction. Since the one-dot latent image shape is triangular and the positions of vertices are opposite to each other in the sub-scanning direction between one dot adjacent in the main scanning direction, one dot of an arbitrary color (for example, a bold line in FIG. 4) Or, paying attention to the hatched area Y: yellow, the other three colors (M: magenta, C: cyan, B:
Black) can be evenly adjacent to each side of the triangular dot. Therefore, there is an effect that full-color printing with good halftone reproducibility by combining each color can be performed.

Further, (1) the potential adjustment step is not operated during monochrome printing, (2) the charge amount of the first charger is changed between monochrome printing and multicolor printing, and (3) monochrome charging is performed. If the developing bias at the time of printing is made different from the developing bias at the time of multicolor printing, there is an advantage that the life of the photoconductor can be increased and power can be saved.

When a one-component developer is used as the developer in the first development step, a low potential level second charge image (region R ₂ ) which tends to be generated when a two-component developer is used is removed. There is an effect that carrier adhesion can be avoided.

FIG. 4 shows an example of the second to fourth developing units 5, 7, and 8 used in the color image forming apparatus of the present invention, in which a two-component developing system is used as a developing system. The developer 36 includes a toner 34 and a carrier 35, and a developing bias is applied to the developing sleeve 37. Developer 3
It is desirable to apply the DC component 31 and the AC component 32 when the photoconductor 6 and the photoconductor 1 are not in contact with each other, but may apply only the DC component 31 when the developer 36 and the photoconductor 1 are in contact with each other. . The configuration of the developing roll is such that the developing sleeve 37 rotates in the same direction as the photoconductor 1 at about 1.2 ± 0.4 times the peripheral speed of the photoconductor, and the magnet roll 38 rotates in the opposite direction to the photoconductor 1. Also, the one in which only the developing sleeve 37 rotates in the same direction as the photoconductor 1 is used. The magnet roll 38 is configured by arranging a different pole magnet or a same pole magnet having a magnetic pole pitch of 3 to 10 mm near a portion facing the photoconductor.

The developer 36 is regulated to a predetermined thickness by the doctor plate 33 and is conveyed to a developing section facing the photoreceptor 1.

Reference numeral 39 denotes a stirring member, and reference numeral 40 denotes a scraper. Reference numeral 41 denotes a toner hopper, and reference numeral 42 denotes a supply roller.

When the developer 36 and the photosensitive member 1 are not in contact with each other, the developing gap is set to 800 ± 80 μm and the doctor gap is set to 250 ± 30 μm.
The peripheral speed of the magnet roll 38 is set to 1.1 and 3.1 times the peripheral speed of the photosensitive member 1, respectively, and a frequency of 1.5 KHz is applied as a developing bias to a DC component lower than the surface potential of the background portion of the photosensitive member 1 by about 100V. , About 1 to 2 KVpp, and two-color printing was performed. As a result, even if the second color toner image density of 1.2 (OD) is secured, the first color toner image is disturbed, or 3% (occupied area ratio) or more of the second color toner is contained in the first color toner image. There was no mixing.

When the carrier 35 has a magnetic powder content of 70 to 90 Wt%, the average particle diameter is 80 to 120 μm.
As a result of performing the second development using the resin carrier of m, it was found that there was an effect of preventing the tendency that the carrier adheres to the photoreceptor 1 and the background portion is stained.

FIGS. 5A to 5C show another embodiment of the present invention. The difference from the example of FIG. 2 is that a three-level charge image is formed by the first exposure, first and second developments are performed, and a three-level charge image is formed by the second exposure. The fourth development is performed. As compared with the example of FIG. 2, the second exposure is complicated, but there is an advantage that the first exposure is slightly simplified.

FIGS. 6A to 6C show another embodiment of the present invention. The difference from the example of FIG. 2 is that a 5-level charge image is formed by the first exposure, first and second developments are performed, and a 3-level charge image is formed by the second exposure. The fourth development is performed. As compared with the example of FIG. 2, the first exposure is more complicated, and the second exposure is slightly more complicated. However, in the first exposure, the first to fourth charge image regions (R ₁ , R ₁ ,
Since R ₂ , R ₃ , and R ₄ ) can be set, there is an advantage that positional shift between the charge image areas can be prevented.

The embodiment described so far (potential distribution diagram:
2, 5, and 6) all relate to an apparatus configuration (see FIG. 1) in which the second exposure 6 is performed immediately after the second developing device 5. The present invention is also applicable to a configuration in which the process is performed immediately after the first developing device 4 or immediately after the third developing device 7.

Next, another embodiment will be described.

FIGS. 9 and 10 show an example of an apparatus configuration in which the second exposure 43 is disposed immediately after the first developing device 4. The potential distribution diagrams in this case are shown in FIGS. 11 (a) to (d) and FIGS.
It is shown in (d). FIG. 11 shows that a first latent image of two levels is formed in the region R ₁ by the first exposure 3, developed by the first color developing device 4, the background portion is I _W by the second exposure 43, and the third latent image portion ( R ₃ ) is exposed to I ₃ and the fourth latent image portion (R ₄ ) is exposed to light intensity different from I ₄ to form a four-level image. Thereafter, the second to fourth developments are performed to form toner images of four colors.

In the present embodiment, the fourth color toner is mixed in the second color toner image area and tends to exhibit a mixed color. Therefore, when forming a full color image, it is desirable that the second color is black and the fourth color is yellow. When forming a color image, it is necessary to determine the color arrangement in consideration of the color mixture to the second color toner image portion. Therefore, although there is a restriction in the configuration and arrangement of each color, since the first color toner image is not exposed, the first color toner does not have to have the property of transmitting the light of the second exposure. There are advantages.

[0043] Figure 12, the first exposure 3 to form a 5-level image, after reversal development region R ₁ in the first color toner, the second exposure 43 region other than the first color toner image portion (background And the regions R _{2 to} R ₄ ) with the same light intensity, and the potential level is shifted so that the potential of the first color toner image portion and the potential of the background portion become substantially equal. The development is performed. Also in this example, since the fourth color toner tends to be mixed in the third color toner image portion, it is desirable that the third color be black and the fourth color be yellow when forming a full-color image. Also, as in the example of FIG. 11, the first color toner image area (R ₁ ) is not exposed by the second exposure.
There is an advantage that the first color toner does not have to be light transmissive. Further, in this example, there is an advantage that the first exposure is complicated but the second exposure is relatively simple.

In the examples of FIGS. 11 and 12, the first
If the potential of the color toner image portion is not sufficiently high, as shown in FIG. 10, a recharging device 45 may be arranged before the second exposure 43 to increase the potential.

FIG. 13 shows an example of an apparatus configuration in which the second exposure 46 is disposed immediately after the third developing device 7. FIGS. 14A to 14D show potential distribution diagrams in this case.

FIG. 14 shows that a four-level image is formed by the first exposure, and the high potential portion (R ₁ ) is subjected to regular development in the _first and second developments.
The low potential portion (R ₂ ) is subjected to reversal development, followed by third development. In the second exposure, reversal development can be performed in the fourth development by simply exposing only the fourth latent image portion (R ₄ ). Also in this example, the third color toner tends to be mixed in the first color toner image portion, but there is an advantage that the first color toner does not have to be light transmissive. When forming a full-color image, it is desirable that the first color be black and the third color be yellow.

Another embodiment will be described.

FIGS. 15, 16 and 17 show another embodiment.
This will be described with reference to FIG.

FIGS. 15 and 16 show an embodiment of the image forming apparatus. Charger 2, first exposure 3, first developing device 4, second developing device 5, third developing device 7, fourth developing device 7,
Developing unit 8, light irradiation unit 60 composed of lamp 70 and filter 80, pre-transfer charger 20, transfer unit 10, fixing unit 1
1, a cleaner 12, and a charge removing corona 13 are arranged.
Surface potential meters 18 and 19 and a potential adjusting means 9 for controlling the light irradiating unit are arranged. For example, the first color is cyan, the second color is magenta, the third color is black, and the fourth color is yellow.
The wavelength of the irradiation light is adjusted so that the light irradiated from the light irradiation unit 60 can be absorbed by the first color (cyan) toner, and a four-color toner image is formed on the photoconductor 1 by the method described below. It is.

FIGS. 17A to 17D are corresponding surface potential distribution diagrams, which will be described with reference to FIGS.

First, a five-level charge image is created by charging and exposure. The first charge image (region R ₁ ), the second charge image (region R ₂ ), and the background portion (potential V
w or Vw ′), the fourth charge image (region R ₄ ), the third
This corresponds to the charge image (region R ₃ ).

Of the first and second charge images, the first charge image (region R ₁ ) having a large electrostatic contrast (charge elimination degree) is subjected to reversal development in the first developing unit 4 to perform the first color toner (for example,
(Cyan toner) (FIG. 17A).

In the second development, in order to prevent color mixture with the first color toner image, the potential Vt ₁ of the first color toner image portion is used.
Is desirably kept high. To adjust the potential of the first color toner image portion, the toner has an average particle size of 15 to 25.
μm and a charge amount (absolute value) as large as about 30 to 60 μc / g are desirable. Further, in addition to the above-described method, the relative permittivity of the first toner is reduced (for example, 1.5 to 2.5.
0) Then, as shown in FIG. 16, the light irradiation unit 8 and the recharger 4
5, a method of recharging the toner, or the like can be used.

The light irradiating section 60 containing the lamp 70 and the filter 80, the surface voltmeters 18 and 19, and the potential adjusting means 9 for controlling the light irradiating section apply the light of the lamp 70 to the entire surface of the photosensitive member with the filter 80 interposed therebetween. This attenuates the charged potential of the photoreceptor and irradiates light in a wavelength region that the first color toner absorbs (FIG. 17B).

For example, when the first color toner is cyan, magenta, and yellow, red, green, and blue light are respectively irradiated. When the first color toner is black, light in an arbitrary wavelength region having sensitivity to the photoconductor may be used. When the first color is a color (chromatic color) and the first color toner color is switched, (1) a plurality of lamps 70 having different emission wavelengths
(2) a method of switching a plurality of filters 80 having different transmission wavelength characteristics, (3) a method of adjusting the wavelength of irradiation light performed using a liquid crystal, LED, or gas discharge type color light emitting device. Accordingly, the wavelength of the light emitted from the light irradiation unit 60 can be adjusted so that the light is absorbed by the first color toner image.

As a result, among the potentials of the latent image on the photoreceptor, the potentials of the areas R ₂ , R ₃ , R ₄ , and the background portion W where the toner does not adhere are reduced, but the first color toner image is formed. In the region R ₁ , the potential Vt ₁ of the first color toner image portion after light irradiation
Is retained. Further, by using the recharging device 45 as needed, the potential Vt ₁ of the first color toner image portion is made slightly higher than the second developing bias potential Vb ₂ .

The second charge image is subjected to reversal development in the second developing device 5 to attach a second color toner (for example, magenta),
A color toner image is formed.

The third charge image (region R ₃ ) is subjected to regular development by the third developing device 7 to attach a third color toner (for example, black), thereby forming a third color toner image. Although the third color toner has the opposite polarity to the first and second color toners, the third developing bias potential Vb ₃ is higher than (1) the first and second color toner image potentials Vt ₁ , Vt ₂ , and Since the potential is higher than the potential of the four-charge image (region R ₄ ), the third color toner does not adhere to other image regions (FIG. 17C).

The fourth charge image (region R ₄ ) is subjected to regular development by the fourth developing device 8 and a fourth color toner (for example, yellow) is attached to form a fourth color toner image (FIG. 17D).
The fourth color toner has the opposite polarity to the first and second color toners,
Since the fourth developing bias potential Vb ₄ is higher than the toner image potentials of the first and second colors, 4
No color toner adheres. However, since the fourth developing bias potential Vb ₄ is lower than the third color toner image potential, the fourth color toner also adheres to the third color toner image area (region R ₃ ). Since the fourth color toner is mixed in the third color toner image area, the color type of the third color toner is black or a color toner with low brightness, and the color type of the fourth color toner is yellow or a color toner with high brightness. Is used. In particular, when yellow is used as the fourth color toner, the color type of the third color toner is desirably a toner having a pigment in which cyan and magenta are mixed.

From the above, four color toner images are formed on the photoreceptor.

The pre-transfer charger 20 that generates an AC + DC corona unitizes the polarity of the four-color toner image, transfers the same to a sheet by the transfer unit 10, and forms the four-color toner image by the fixing unit 11. It is melted by heat and fixed on paper.

Further, a supplementary description will be given of the surface potential adjusting step performed before the second development. Immediately before the first developing device 4 and the second developing device 5, surface electrometers 18 and 19 are arranged, respectively, and based on detection signals of the surface electrometers 18 and 19,
The light amount of the lamp 70 and the filter 80 are controlled. The detected value signal of the surface potential is stored in the storage unit of the color printing condition setting unit 24, and based on the detected value of the surface potential, a light irradiation control condition is set and transmitted to the potential adjusting means 9 and the
The second developing bias condition is set and transmitted to the first and second developing biases 25 and 26. The surface potential meter 18 monitors the initial charging potential, and controls the charger 2 to a predetermined potential via the color printing condition setting unit 24. The surface voltmeter 19 monitors the potential Vt ₁ of the first color toner image portion after light irradiation and the potential Vw of the background portion, and monitors the potential Vt and the potential Vw of the background portion via the color printing condition setting portion 24. The potential adjusting means 9 is controlled so that the potential difference becomes a predetermined value.

In such a configuration, a surface potential (toner image and latent image potential) adjusting means for the photosensitive member is arranged upstream of the second developing step in which reversal development is repeated to adjust the surface potential immediately before the second developing. Since the second developing bias can be set slightly lower than the first color toner image potential, no color mixing occurs during the second developing.

In the third development, a toner having a polarity different from that in the first and second developments is used, and a development bias higher than the toner image potential formed in the previous stage is applied to perform the normal development. Since no color mixing occurs in the color toner image and the developing bias is higher than the potential of the fourth charge image,
The third color toner does not enter the fourth color image area.

In the fourth development, the fourth color toner is mixed with the third color toner image.
Since the color type of the third color toner can be set so that the color toner image expresses black, color turbidity can be reduced. In other words, the first, second, and fourth color toner images can express a single color image of yellow, magenta, and cyan without color mixture, and the third color toner image can express black by a mixed color image. Accordingly, a full-color image can be formed by combining them, and in this embodiment, there is an effect that clear full-color printing can be performed with one shot. FIG. 18 shows another embodiment of the present invention.
In the present embodiment, the light irradiation unit 60 is disposed downstream of the third developing device 7, and the second reversal development step is performed by the fourth development.

FIG. 19 is a graph showing the potential distribution on the surface of the photosensitive member according to this embodiment.
(A) to (d). Also in the present embodiment, the first color toner is desirably a color that absorbs the light emitted from the light irradiating unit 60. In the present embodiment, the third color toner is mixed in the second color image portion. Alternatively, it is possible to use a low-brightness toner, or use a yellow or high-brightness color toner as the color type of the third color toner. As an example, the light from the light irradiating unit may be greenish, and the configuration of each color may be magenta for the first color, black for the second color, yellow for the third color, and cyan for the fourth color.

Further, in the present embodiment, the difference between the developing bias of the regular development (the second development 5 and the third development 7 in FIG. 18) and the potential of the reversal development toner image (the first color toner image) is shown in FIG. Therefore, there is an effect that the degree of mixing in the reversal-developed toner image during regular development can be further reduced.

While the photosensitive member 1 makes one rotation, the third developing device 7
Then, instead of the light irradiating section 60, the discharging lamp 21 and the discharging corona 13 are used instead (if recharging is necessary, recharging is performed using the charger 2). If the fourth development is performed in the second rotation by also using the surface voltmeter 18, full-color printing is performed during the two rotations of the photoconductor 1. Also, since the surface voltmeter 19 can be removed, there is an effect that the entire image forming apparatus is reduced in size.

Further, a five-level charge image is formed on the photoreceptor, a plurality of color developing machines using toner of the same polarity are arranged, and the charge image holding device is held upstream of the process after the second reversal development. A potential adjustment step may be provided to adjust the toner image potential and the background portion potential by the reversal development at the previous stage on the body to be substantially equal, and a color image may be formed by reversal development using toner of the same polarity for all developments. Good. In this case, it is necessary to provide the light irradiation unit 60 (the recharger 45 if necessary) immediately before the second to fourth developments, and the color image forming apparatus as a whole tends to be large. Since it can be performed using toners of the same polarity, there is an effect that the pre-transfer charger 20 for unifying the polarity of the toner can be removed.

Further, another embodiment will be described.

FIG. 20 shows an example of a color image forming apparatus.

In FIG. 20, a third exposure control unit 50 for controlling the third exposure is further provided. For example, the first color is yellow, the second color is black, the third color is magenta, and the fourth color is The light emitted by the second exposure 6 and the third exposure 52 is allowed to pass through the first and third color toners, and a four-color toner image is formed on the photoconductor 1 by the method described below. Things.

FIG. 21 is a corresponding surface potential distribution diagram, which will be described with reference to FIG.

First, as shown in FIG.
After uniform charging, four-level charge images are formed by the first exposure. A first charge image (including regions R ₁₃₄ , R ₁₄ , R ₁ , and R ₁₃ ) and a third charge image from the upper level, respectively.
(Regions R ₃ and R ₃₄ ), a background portion (region of potential Vw), and a second charge image (region R ₂ ).

Of the charge images, a first charge image (region R
₁ (including ₁ ), as shown in FIG.
First color toner bias Vb ₁ potential and equal to or more than the third charge image by the developing device 4 (areas R _3, R ₃₄₎ is applied performs normal development (e.g., yellow toner) adhering a. or,
For the second charge image (region R ₂ ), the second developing device 5 applies a bias Vb ₂ lower than the potential Vw of the background portion, performs reverse development, and attaches a second color toner (for example, black toner). Let it.

Next, as shown in FIG. 21B, in the second exposure 6, the first color toner image portion (region R ₁ ) is selectively exposed to adjust the potential. That is,
In the areas R ₁₄ and R ₁ of the first color toner image area, the intensity I ₁₀
And the potentials of the regions R ₁₄ and R ₁ are changed to the background potential V
w, and irradiating the regions R ₁₃₄ and R ₁₃ with light having an intensity I ₁₃ to make the potentials of the regions R ₁₃₄ and R ₁₃ equal to the potentials of the third charge images (regions R ₃ and R ₃₄ ). A third charge image having a first color toner image is formed.

This third charge image (regions R ₃ , R ₃₄ , R
₁₃₄ , R ₁₃ ), as shown in FIG. 21C, the bias V equal to or higher than the potential Vw of the background portion in the third developing device 7.
b ₃ to apply a regular development to the third color toner (for example,
(Magenta toner).

Further, as shown in FIG. 21 (d), in the third exposure 52, the first and second color toner image portions are selectively exposed to adjust the potential, and a new image exposure is performed. (Intensity I ₄ ) to form a fourth charge image. That is, the first color intensity in the region R ₁₄ of the toner image portion I ₁₄
Of the second color toner image portion in the regions R ₃₄ and R
₁₃₄ , the light with the intensity I ₃₄ and the intensity I _134
4 is irradiated with light of intensity I ₄ , and a fourth charge image (regions R ₁₃₄ , R _134)
14 , R ₃₄ , R ₄ ) are sufficiently lower than the potential of the second color toner image area (region R ₂ ).

This fourth charge image (regions R ₁₃₄ , R ₁₄ ,
R ₃₄ , R ₄ ), as shown in FIG. 21 (e), a fourth developing device 8 applies a bias Vb ₄ lower than the potential of the second color toner image area (region R ₂ ) to perform reverse development. Then, a fourth color toner (for example, cyan toner) is attached.

From the above, a four-color toner image is formed on the photoreceptor, and the polarity of the four-color toner image is unified by a pre-transfer charger 29 that generates an AC + DC corona.
This is transferred to a sheet by a transfer unit 10, and a four-color toner image is thermally melted and fixed to the sheet by a fixing unit 11 to perform full-color printing.

Further description of the second exposure and the third exposure will be supplemented. Immediately before the first developing device 4 and the third developing device 7,
Surface voltmeters 18 and 19 are arranged, respectively, and the background portion potential Vw and the potential of the first color toner image portion (region R ₁ ) after the second exposure are measured. Based on these, the second exposure and the third exposure are performed. In order to control the exposure intensity and light quantity, the detected value signal of the surface potential is stored in the storage unit of the color printing condition setting unit 24, and the second exposure and the third exposure are performed based on the detected value of the surface potential.
Exposure control conditions are set and transmitted to the exposure controllers 9 and 50 to control the second exposure unit 15 and the third exposure unit 51.

The color printing condition setting section 24 sets the conditions of the first to fourth developing biases based on the detected value of the surface potential, and sets the first bias 16 and the second to fourth developing biases. To control the developing bias, and monitor the initial charging potential with the surface voltmeter 18;
The charger 2 is controlled so as to have a predetermined potential.

The color tone of the color superimposed image can be expressed by adjusting the exposure conditions of the first to third exposures and adjusting the first to fourth developing biases.

In such a configuration, the second exposure means for adjusting the surface potential (toner image and latent image potential) of the photosensitive member is disposed upstream of the third developing step for performing the second normal development. (3) Adjust the surface potential immediately before development, and adjust the third development bias V
Since b ₃ to be set to the first color toner image potential (≒ background portion potential Vw) and the second color toner image potential Vt ₂ and equal to or more than three color toner to the other image region is attached is (color mixing occurs at the third development ) Never.

In the fourth development in which the second reversal development is performed, the reversal development is performed using the toner of the same polarity as in the second development, but the fourth reversal development which is lower than the toner image potential Vt ₂ formed in the second development is performed.
Since the reversal development is performed by applying the developing bias Vb ₄ , no color mixing occurs in the second color toner image (region R ₂ ), and the fourth developing bias Vb ₄ is higher than the potential of the first and third charge images. Is low, the fourth color toner does not enter the first and third color image regions (regions R ₁ , R ₁₃ , R ₃ ).

As described above, it is possible not only to superimpose the first to fourth color toner images on the photosensitive member as necessary, but also to form a single color image of yellow, magenta, cyan, and black without color mixture. That is, in the region R ₁₃₄ yellow, magenta, color superimposed images of cyan, in the region R ₁₄ yellow, the color superposition image of cyan, in the region R ₁₃ yellow, the color superposition image of cyan, in the region R ₃₄ magenta, cyan can form a color superposition image, the monochrome superimposed image of yellow in the region R _1, the monochromatic image of black in the region R _2, the single-color image of magenta in the region R _3, may form a single color image of cyan in the region R ₄ .

In each color superimposed image, various color tones can be expressed by controlling each developing bias and each exposure condition.

Therefore, in the present invention, there is an effect that clear full-color printing can be performed in one pass.

FIG. 22 shows another embodiment of the present invention. The difference from the example of FIG. 20 is that the first to fourth exposures 3, 6, 5
2 and 55 are arranged.

FIG. 23 is a surface potential distribution diagram corresponding to the example of FIG. This will be described below.

(A) First exposure / first development (FIG. 23 (a)
Reference :) The first exposure 3 (exposure intensity I ₁ ) lowers the potential of the background part (non-image part) to Vw ₁ , and the first charge image area (areas S ₁ , S ₁₂₃ , S ₁₂₃ ) of the surface potential V _{0 124,} S ₁₃₄₎ by a first developing 4 by applying a developing bias Vb ₁ to deposit the first color toner subjected to normal development.

(B) Second exposure / second development (FIG. 23B)
Reference :) The second exposure 6 (exposure intensity I ₂ , I ₂ s, I ₁₂ s) lowers the potential of the background portion (non-image portion) to Vw ₂ , and the second charge image area (surface potential Vw ₁ ) Regions S ₁₂ , S ₂ , S
₁₂₃ , _S234 ) and the developing bias Vb ₂ by the second developing device 5.
To perform regular development to adhere the second color toner. In the second exposure 6, the exposures I ₂ s and I ₁₂ s with the subscript s
Indicates selective exposure for the first color toner image portion.

(C) Third exposure / third development (FIG. 23C)
Reference: 3rd exposure 52 (exposure intensity I ₁₃ s, I ₃₁ s, I
₃ s, I ₂₃ s, I ₃ , I ₁₂₃ s) for background (non-image)
Is adjusted to V ₀₃ (≒ Vw ₂ ) to lower the surface potential of the third charge image area (areas S ₁₃ , S ₂₃ , S ₃ , S ₂₃₄ , S ₁₃₄ ) to Vr ₃ , and the third developing device 7 by attaching a third color toner perform reversal development by applying a development bias Vb _3. In the third exposure 52, the exposures I ₁₃ s, I ₃₁ s, and
I ₃ s, I ₂₃ s, and I ₁₂₃ s indicate selective exposure to the first or second color toner image portion.

(D) Fourth exposure / fourth development (FIG. 23D)
Reference: 4th exposure 55 (exposure intensity I ₁₄ s, I ₂₄ s, I ₃₄
s, I ₂₃₄ s, I ₄ , I ₁₂₄ s, I ₁₃₄ s)
The potential of the (non-image area) is maintained at V ₀₄ (≒ V ₀₃ ), and the surface potential of the fourth charge image area (areas S ₁₃ , S ₂₃ , S ₃ , S ₂₃₄ , S ₁₃₄ ) is reduced to Vr ₄ . Then, the developing bias Vb ₄ is applied by the fourth developing device 8 to perform reversal development, and the fourth color toner is attached. In the fourth exposure 55, an exposure I with a subscript s
₁₄ s, I ₂₄ s, I ₃₄ s, I ₂₃₄ s, I ₁₂₄ s, I ₁₃₄ s
Indicates selective exposure for the first, second, or third color toner image area.

With such a configuration, a four-color superimposed image and a four-color monochromatic image can be formed by the above-described process. That is, the first color, second color, third color, the fourth color, respectively, yellow, magenta, cyan, if black area S ₁₂ is yellow, magenta, region S ₁₃ is yellow, cyan, yellow in the area S _14, Black, area S
₂₃ , magenta and cyan, area S ₂₄ , magenta, black, area S ₃₄ , cyan, black, area S ₁₂₃ , yellow, magenta, cyan, area S ₁₂₄ , yellow, magenta, black, area S ₁₃₄ , yellow, cyan, black, magenta in region S _234, can be formed cyan, I color superimposition black image, in some areas S ₁ yellow, in some areas S ₂ magenta, in some areas S ₃ cyan, region S ₄ In some cases, a black monochrome image can be formed.

In each color superimposed image, various color tones can be expressed by controlling each developing bias and each exposure condition.

Therefore, the present invention not only has the effect of enabling clear full-color printing in one pass, but also has the advantage that compared to the examples of FIGS. However, there is an advantage that the color superposition of yellow, magenta, cyan, and black can be performed.

In the example of FIG. 22, the normal development method is used for the first and third developments, and the reversal development method is used for the second and fourth developments. May be used, and the regular development method may be used for the second and third developments, and the reversal development method may be used for the first and fourth developments. Further, (b) all of the first to fourth developments may be performed by a reversal development method, (c) all of the first to fourth developments may be performed by a regular development method, and (d) first to fourth developments. Three of the development may be performed by the regular development method and one may be performed by the reversal development method. (E) Three of the first to fourth developments are performed by the reversal development method and one is performed by the normal development method. You may go in.

In the above-described example, the present invention has been described by taking as an example a method of forming a color image while the photoconductor rotates once (one-pass full-color printing system). Needless to say, the present invention can be similarly applied to a method of forming a color image (multi-pass full color printing method). Hereinafter, another embodiment (of a two-pass color printing method) for forming a color image while the photoconductor rotates twice will be described with reference to FIG. The surface potential distribution and the image forming process are the same as those described above with reference to FIG. This embodiment differs from the example of FIG. 20 in the following items (1) to (3).

(1) One exposure 6 is used for both the second exposure and the third exposure.

(2) During the first rotation of the photoconductor 1, the charging unit 2, the first exposure unit 3, the first developing unit 4, the second developing unit 5, and the second exposure unit 6
And the third developing unit 7 are operated, and the third color is placed on the photoreceptor 1 from the first color.
A color toner image is formed. At this time, the fourth developing device 8, the pre-transfer charging device 20, the transfer device 10, the charge removing lamp 21, the charge removing corona 13 and the cleaner 12 are in a non-operating state so as not to scrape or disturb the toner image on the photoreceptor 1. And kept out of contact with the photoreceptor 1. Also, the paper is kept in a non-contact state with the photoreceptor 1 without being transported to the transfer section.

(3) When the photosensitive member 1 is rotated for the second time, the exposure 6 and the fourth developing device 8 which also serve as the third exposure are operated, and
A fourth color toner image is formed on the photoconductor 1 holding the third color toner image. After that, the pre-transfer charger 2
At 0, the polarities of the toner images of the four colors are unified, and the toner images of the four colors are heat-fused by the transfer device 10 and fixed to the paper by the fixing device 11. The surface potential distribution and the untransferred toner remaining on the photoreceptor 1 after the transfer are removed by the charge removing lamp 21, the charge removing corona 13 and the cleaner 12, respectively. Also, the first developing unit 4, the second developing unit 5, and the third developing unit 7 use a bias power source such as reducing the developing bias so that the photosensitive member 1 does not adhere the first to third color toners during the second rotation. It was controlled.

In such a configuration, the printing speed is halved as compared with the example shown in FIG. 20, but one exposure 6 is used for both the second exposure and the third exposure. Is 2
There is an advantage that the number of printing units can be reduced and the whole apparatus can be downsized.

Further, one exposure 3 may be used for the first to third exposures, and the photoreceptor 1 may form a color image at the third rotation. In this case, the printing speed is 1/3
However, since one exposure 6 also serves as the first to third exposures, only one (for example, three) exposure means may be used, and the number of printing units is further reduced to reduce the size of the entire apparatus. There are advantages that can be done.

In the embodiments described above, the apparatus using the photosensitive drum as the latent image carrier has been described. However, even if the latent image carrier is a photosensitive belt or another substitute, the object of the present invention is not limited. Clearly what can be achieved. Further, in the above-described embodiment, the configuration in which the image is directly transferred from the photosensitive drum to the sheet has been described as an example. However, an intermediate transfer member such as a transfer drum may be used.

In the above embodiment, the printing condition setting unit 24, the exposure control unit 9 and the like are described as being integrated with the device for charging, exposing and developing the latent image carrier. The printing condition setting unit 24, the exposure control unit 9, and the like may be separately provided and separated from the device portion that forms the toner image.

The present invention can be applied to various products such as a printer, a copying machine, and an image forming system connected to an electronic computer.

[0108]

According to the present invention, unintended color mixing can be prevented in an image of a plurality of colors, particularly, four colors of yellow, magenta, cyan, and black, so that an image can be formed which can be printed at high speed and clearly. .

Also, color printing can be performed with one pass.
A high-speed color image forming apparatus can be provided.

In the present invention, a compact color image forming apparatus can be constructed.

Further, according to the present invention, since dots of different colors can be made adjacent to each side of the triangular dots, there is an effect that full-color printing with a good halftone reproducibility by a combination of each color is possible. .

[Brief description of the drawings]

FIG. 1 is a diagram illustrating an image forming apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram showing a distribution of a surface potential in an image forming method according to an embodiment of the present invention.

FIG. 3 is a diagram showing a dot shape and an arrangement of dots of each color used in an image forming method according to an embodiment of the present invention.

FIG. 4 is a sectional view of a developing machine used in the image forming apparatus according to one embodiment of the present invention.

FIG. 5 is a diagram showing a distribution of surface potential in an image forming method according to an embodiment of the present invention.

FIG. 6 is a diagram showing a distribution of a surface potential in an image forming method according to an embodiment of the present invention.

FIG. 7 is a diagram illustrating a conventional image forming apparatus.

FIG. 8 is a diagram showing a distribution of a surface potential in a conventional image forming method.

FIG. 9 is a diagram illustrating an image forming apparatus according to an embodiment of the present invention.

FIG. 10 is a diagram illustrating a part of an image forming apparatus according to an embodiment of the invention.

FIG. 11 is a diagram showing a distribution of a surface potential in an image forming method according to an embodiment of the present invention.

FIG. 12 is a diagram showing a distribution of a surface potential in an image forming method according to an embodiment of the present invention.

FIG. 13 is a diagram illustrating an image forming apparatus according to an embodiment of the present invention.

FIG. 14 is a diagram showing a distribution of surface potential in an image forming method according to an embodiment of the present invention.

FIG. 15 is a diagram illustrating an image forming apparatus according to an embodiment of the present invention.

FIG. 16 is a diagram illustrating a part of an image forming apparatus according to an embodiment of the invention.

FIG. 17 is a diagram showing a distribution of surface potential in an image forming method according to an embodiment of the present invention.

FIG. 18 is a diagram illustrating an image forming apparatus according to an embodiment of the present invention.

FIG. 19 is a diagram showing a distribution of surface potential in an image forming method according to an embodiment of the present invention.

FIG. 20 is a diagram illustrating an image forming apparatus according to an embodiment of the present invention.

FIG. 21 is a diagram showing a distribution of a surface potential in an image forming method according to an embodiment of the present invention.

FIG. 22 is a diagram illustrating an image forming apparatus according to an embodiment of the present invention.

FIG. 23 is a diagram showing a distribution of surface potential in the image forming method according to one embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Photoreceptor, 2 ... Charging device, 3 ... 1st exposure, 4 ... 1st developing device, 5 ... 2nd developing device, 6, 43, 46 ... 2nd exposing device, 7
... 3rd developing device, 8 ... 4th developing device, 9 ... 2nd exposure control part,
10 transfer device, 11 fixing device, 12 cleaner, 13
Static elimination corona, 14: First exposure unit, 15: Second exposure unit, 16, 25, 26: First and second developing bias, 17, 27, 28: Third and fourth developing bias, 1
8, 19: surface electrometer, 20: pre-transfer charger, 21: static elimination lamp, 22: paper hopper, 23: paper stutter, 2
4. Color printing condition setting unit, 31: DC component of developing bias, 32: AC component of developing bias, 33: Doctor plate, 34: Toner, 35: Carrier, 36: Developer, 3
7 developing sleeve, 38 magnet roll, 39 stirring member, 40 scraper, 41 toner hopper, 42
... supply roller, 44 ... potential adjusting means, 45 ... recharger,
Reference numeral 60 denotes a light irradiation unit, 70 denotes a lamp, and 80 denotes a filter.

Continued on the front page (72) Inventor Noboru Tokuyasu 7-1-1, Omika-cho, Hitachi City, Ibaraki Prefecture Within Hitachi Research Laboratory, Hitachi, Ltd. (72) Inventor Susumu Tateyama 2-6-2 Otemachi, Chiyoda-ku, Tokyo Hitachi Koki Co., Ltd. (56) References JP-A-4-352183 (JP, A) JP JP-A-1-304471 (JP, A) JP-A-63-273883 (JP, A) JP-A-3-253873 (JP, A) JP-A-4-86847 (JP, A) JP-A-63-146057 (JP, A) A) JP-A-63-68865 (JP, A) JP-A-3-209276 (JP, A) JP-A-5-265295 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) ) G03G 13/01 G03G 15/01-15/01 117 B41J 2/44

Claims (7)

(57) [Claims] A latent image carrier; a charging unit configured to charge a surface of the latent image carrier to a predetermined potential; an exposure unit configured to form a charge latent image on the latent image carrier by exposure; An image forming apparatus comprising: a plurality of developing units that form a plurality of color toner images; and a transfer unit that transfers the plurality of color toner images to a transfer target body. Wherein the first exposing unit forms a charge latent image for forming a toner image of at least one color, and the second exposing unit is formed by the first exposing unit. And selectively shifting a potential of at least one color toner image portion formed on the formed charge latent image portion , wherein the first and second exposure means are configured such that the charge latent image shape is a plurality of triangular dots. Between the adjacent dots in the exposure main scanning direction. An image forming apparatus comprising the position of the point to form a latent image dots as the opposite direction to each other in the exposure sub-scanning direction. 2. A latent image carrier having a latent image carrier, 1) charging means for charging the latent image carrier, and 2) a first means for forming a charge latent image on the latent image carrier by exposure. 3) one or more developing means for forming at least one color toner image on the charge latent image formed by the first exposure means; and 4) a charge latent image on the latent image carrier by exposure. 5) one or more developing means for forming at least one color toner image on the charge latent image formed by the second exposing means; and 6) Transfer means for collectively transferring a plurality of color toner images formed on the latent image carrier, and a transfer means for sequentially transferring the latent image carrier in a rotational direction of the latent image carrier. Forming a charge latent image to be formed, wherein the second exposure means At least one color potential of the toner image portion of the formed latent image portion formed by the exposure means to potential substantially equal to the background portion potential selectively shifted, for forming a toner image of the remaining colors An image forming apparatus which forms a charge latent image and sequentially performs a series of steps from charging to transfer while the latent image carrier makes one rotation. 3. An image forming apparatus according to claim 2 , wherein said first exposure means forms at least three levels of charge latent images. 4. An image forming apparatus according to claim 2, before has a potential detection means for detecting the potential of Kisenzo carrier, said second exposing means, said at least one color by the potential detection means Based on the detected value of the potential of the toner image portion of
An image forming apparatus, wherein exposure is performed by controlling the amount of exposure. 5. A latent image carrier having a latent image carrier, 1) charging means for charging the latent image carrier, and 2) a first means for forming a charge latent image on the latent image carrier by exposure. of
An exposure unit; and 3) a charge latent image formed by the first exposure unit.
One or more current toners forming at least one color toner image
And 4) a second means for forming a charge latent image on the latent image carrier by exposure
Exposure means; and 5) the charge latent image formed by the second exposure means.
One or more current toners forming at least one color toner image
Image means, 6) a plurality of color images formed on the latent image carrier
Transfer means for collectively transferring the toner images are sequentially arranged in the rotation direction of the latent image carrier , and the first exposure means forms a toner image of at least one color.
Forming a charge latent image to be formed, and the second exposure means
Is other than the potential of the toner image portion where the toner image is formed.
The potential formed by the first exposure means of
The potential of the remaining color is shifted to a potential
Forming a charge latent image for forming a toner image;
A series of steps from charging to transfer during one rotation of the carrier
Are sequentially performed. 6. A latent image carrier, comprising: 1) a charging means for charging the latent image carrier around the latent image carrier; and 2) a first means for forming a charge latent image on the latent image carrier by exposure. of
An exposure unit; and 3) a charge latent image formed by the first exposure unit.
One or more current toners forming at least one color toner image
And 4) a second means for forming a charge latent image on the latent image carrier by exposure
Exposure means; and 5) the charge latent image formed by the second exposure means.
One or more current toners forming at least one color toner image
Image means, 6) a plurality of color images formed on the latent image carrier
Transfer means for collectively transferring the toner images are sequentially arranged in the rotation direction of the latent image carrier , and the first exposure means forms a toner image of at least one color.
Forming a charge latent image to be formed, and the second exposure means
Sets the potential of the at least one color toner image to at least
Selectively shifts to two levels to remove the remaining color toner image
Forming a charge latent image for forming the latent image carrier;
Perform a series of steps from charging to transfer while rotating
An image forming apparatus comprising: 7. An image forming apparatus according to claim 6, wherein said second exposing means comprises a toner image of at least one color.
Exposure intensity of some areas is stronger than other areas
Forming a two-level latent charge image.
Image forming device.