JPH05107862A - Method and apparatus for forming full-color image - Google Patents

Abstract

PURPOSE:To provide the full-color image forming method which prevents the toner of a 1st color on a composite photosensitive body from peeling at the time of developing the latent images on the composite photosensitive body with a toner of a 2nd color. CONSTITUTION: The U layer of the photosensitive body 30 is positively charged and the L layer is negatively charged (a, b); thereafter, the N/P latent image of cyan and the P/P coated latent image of magenta are formed and the main latent image of P/P of the magenta is formed on the L layer by 780nm light (c). After the cyan latent image is subjected to reversal development by using the positively charged cyan toner as the 1st color (d), the cyan latent image and the magenta coated latent image of the U layer are erased by uniform exposing with 680nm light (e). The main latent image of the magenta is subjected to normal development with the positively charged magenta toner as the 2nd color (f). Since the toner of the 2nd color and the toner of the 1st color on the photosensitive body are the same polarity, the toner of the 1st color is not peeled from the surface of the photosensitive body by the developing electric field. After the 2nd color is formed similarly on the other photosensitive body, the images are superposed on transfer paper.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a full-color image forming method adopted in an image forming apparatus such as a copying machine, a facsimile machine, a printer and the like, and an image forming apparatus suitable for carrying out the full-color image forming method. .

[0002]

2. Description of the Related Art Conventionally, as a full-color image forming method of this kind, a first photoconductive layer is provided on a conductive substrate, and a second photoconductive layer is formed directly on the first photoconductive layer or through an intermediate layer. A conductive layer is provided, and the first photoconductor is adjusted such that one photoconductive layer is mainly irradiated with light of A color light, and the other photoconductive layer is mainly converted to light conductor with light of B color light. The second photoconductor is adjusted so that one of the photoconductive layers is mainly made into a conductor by the irradiation of C color light and the other of the photoconductive layers is mainly made into a conductor by the irradiation of D color light.
It is known to use one photoconductor (hereinafter referred to as a composite photoconductor) (for example, Japanese Patent Laid-Open No. 61-163349).

However, in the known full-color image forming method using a composite photoconductor, when two images of different toners having different colors are sequentially formed on one composite photoconductor, the two types of toners are charged. Since the polarities are different from each other, the toner of the first color first adhered to the composite photoconductor by development is removed from the surface of the composite photoconductor during the subsequent development with the second color toner of a different polarity. There was a risk of peeling. That is, when developing with the second color toner, the second color toner is transferred from the developing electrode side to the composite photoconductor surface portion between the developing electrode of the developing device and the composite photoconductor surface portion to which the second color toner should be attached. An electric field for moving is formed. Therefore, if the first color toner having a polarity different from that of the second color toner adheres to the surface portion of the composite photoconductor, the first color toner receives an electrostatic force on the developing electrode side due to the electric field, whereby the composite color It is peeled off from the surface of the photoconductor.

When the composite photoconductor is uniformly irradiated with light of a predetermined color after the development with the toner of the first color to reverse the polarity of the surface potential of the composite photoconductor, red light is used as the light of the predetermined color. However, there is a possibility that the potential of the image latent image to be developed with the second color toner cannot be sufficiently secured. That is, when the cyan toner is used as the toner of the first color, the predetermined photoconductive layer is neutralized by uniformly irradiating with red light while the cyan toner is attached on the composite photoconductor.
However, as shown in FIG. 1 in which the horizontal axis represents the wavelength of the emitted light and the vertical axis represents the ratio of the amount of reflected light, the cyan toner absorbs the red light, and therefore the cyan toner adheres to the composite. The charge removal of the predetermined photoconductive layer on the photoconductor portion becomes insufficient. Therefore, when the potential of the image latent image to be developed by the second color toner on the composite photoconductor portion is insufficient and magenta toner or yellow toner as the second color toner is to be attached to the composite photoconductor portion. However, the adhering amount (developing amount) of the magenta toner or the yellow toner becomes insufficient, and the color reproducibility changes.

It should be noted that, in the above-mentioned Japanese Patent Laid-Open No. 61-163349, as an apparatus for carrying out the above-mentioned full-color image forming method using two composite photoconductors, two composite photoconductors having the same circumference are used. The transfer positions are arranged so as to be separated from each other by the circumferential length of the composite photoconductor on the transfer paper conveyance path, and the image formation is performed on the composite photoconductor on the downstream side in the transfer paper conveyance direction by the other composite photoconductor rotating once. By starting after waiting, the toner images formed on the respective composite photoconductors are aligned on the transfer paper. Therefore, it is necessary to provide an image memory (frame memory) for two images formed on the composite photoconductor on the downstream side in the transfer paper conveyance direction.

In order to align the toner images formed on each of the two composite photoconductors on the transfer paper without using such an image memory, Japanese Patent Application Laid-Open No. 64-91155 discloses a transfer paper conveying method. As the composite photoreceptor on the downstream side, one having a perimeter longer than that of the other composite photoreceptor is used, and the distance from the latent image writing position to the transfer position on the composite photoreceptor on the downstream side is set to the other composite photoreceptor. There is disclosed a full-color image forming apparatus which is set to be equal to the sum of the distance from the latent image writing position to the transfer position and the distance between the transfer positions of both composite photoconductors. However,
In this full-color image forming apparatus, since the composite photoconductors having different peripheral lengths are used, the commonality of the composite photoconductors, which are parts, is lost, leading to an increase in cost.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and a first object thereof is to combine a latent image on a composite photoconductor with a second color toner. To provide a full-color image forming method in which the first color toner adhering on the photoconductor is not peeled off.
The second purpose is to develop a latent image to be developed with the toner of the second color on the compound photoreceptor after the development of the toner of the first color on the photoreceptor by uniform irradiation of red light. In a full-color image forming method that makes the first color toner visible, the third purpose is to provide a full-color image forming method in which the first color toner does not block the uniform irradiation by the red light. Provided is a full-color image forming apparatus that does not require an image memory for aligning a toner image on a transfer paper and can use two composite photoconductors having the same peripheral length as each other. That is.

[0008]

In order to achieve the above-mentioned first object, the full-color image forming method according to claim 1 comprises a first photoconductive layer provided on a conductive substrate, and the first photoconductive layer is provided. Of the two photoconductors in which the second photoconductive layer is provided directly on the conductive layer or via the intermediate layer, the first photoconductor is such that one photoconductive layer is B The other photoconductive layer is adjusted so that the other photoconductive layer is mainly made into a conductor by the irradiation of the colored light, and the second photoconductor has one photoconductive layer irradiated by the light of the C color and the other photoconductive layer by the irradiation of the D color light. Of the first photoconductor and the second photoconductor of each of the first and second photoconductors are charged in opposite directions to each other. When the photoconductor surface potential is set to a predetermined potential and the three primary colors are α, β, γ, the first For the body, one of the α color image and the β color image is A color light and the other image is the A color light and B color light, and one of the α color image and the β color image is A latent image for normal development is written as the latent image for reverse development, the other image is written as a latent image for reversal development, and the one image is developed with toner of a predetermined color, and then uniformly irradiated with light of a predetermined color.
The latent images of the two images written with colored light are erased, and the latent image of the other image written with colored B light is made to appear potential on the surface of the first photoconductor, and the other image is colored with the toner of the predetermined color. Is developed with a toner of a predetermined color having the same polarity as the above, and for the second photoconductor, one of the γ-color image and the black image is C-color light and the other image is C-color light and D-color light, and Either one of the γ-color image and the black image is written as a latent image for regular development and the other image is written as a latent image for reversal development. By uniformly irradiating the latent images of both images written with the C color light and deleting the latent image of the other image written with the D color light to the second image.
Potential surface of the photoreceptor, and develop the other image with a toner of a predetermined color having the same polarity as the toner of the predetermined color,
The visible image formed on each photoconductor is aligned and transferred onto the same transfer medium, and the full-color image forming method according to claim 3 is characterized in that the first image is formed on the conductive substrate. Is provided, and the second photoconductive layer is provided on the first photoconductive layer directly or via an intermediate layer, and one photoconductive layer is irradiated with light of A color, The other photoconductive layer is adjusted so that the other photoconductive layer is mainly made into a conductor by the irradiation of B-color light, and the first and second photoconductive layers of this photoconductor are charged in opposite directions to each other. When the surface potential is a predetermined potential and the three primary colors are α, β, γ,
The first image, which is any one of the α-color image, the β-color image, the γ-image, and the black image, is converted into the α-color image by A-color light.
The second image, which is one of the β-color image, the γ-image, and the black image other than the one image, is A-color light and B-color light, and either one of the first image and the second image Image is written as a latent image for regular development and the other image is written as a latent image for reversal development, one of the images is developed with toner of a predetermined color, and uniform irradiation is performed with light of a predetermined color, and the image is written with A color light. The latent image of the other image, which is erased from the latent image of the image and written with the B color light, is exposed on the surface of the photoconductor in a potential manner,
The other image is developed with a predetermined color toner having the same polarity as the predetermined color toner, the visible images of the first and second images formed on the photoconductor are transferred onto a transfer medium, and the photosensitive material after the transfer is transferred. The body surface is initialized, and then the third image, which is one of the remaining two images of the α color image, the β color image, the γ image, and the black image, is the other image with A color light. The fourth image is written with A-color light and B-color light, and one of the third image and the second image is written as a latent image for regular development, and the other image is written as a latent image for reversal development. One image is developed with toner of a predetermined color, and uniform irradiation is performed with light of a predetermined color to erase the latent image of both images written with the light of A color and B
The latent image of the other image written with colored light is made to appear potential on the surface of the photoconductor, and the other image is developed with a predetermined color toner having the same polarity as the predetermined color toner, and formed on the photoconductor. The visible images of the third and fourth images are aligned with the first and second images on the transfer medium and transferred onto the transfer medium.

In order to achieve the above first and second objects, the full color image forming method according to claim 2 is the full color image forming method according to claim 1,
A color image developed with a toner that is relatively hard to absorb the light of the predetermined color used for the uniform irradiation is written with light that mainly makes the first photoconductive layer a conductor, and the light of the predetermined color is relatively absorbed. Color image developed with toner
Writing is performed with light that mainly turns the photoconductive layer into a conductor and light that turns the second photoconductive layer mainly into a conductor.

In the above claims 1 to 3, B
The color may be different from the color A, the color C may be the same as or different from the color A, and the color D may be the same as or different from the color B as long as it is different from the color C.

In order to achieve the above-mentioned third object, a full-color image forming apparatus according to a fourth aspect of the invention has two photoconductors having the same peripheral surface shape, and one of the two photoconductors. When the three primary colors of the body are α, β, γ, α color image, β
A visible image forming means for forming a visible image of any two images of a color image, a γ image and a black image, and an α color image, β on the other photoconductor of the two photoconductors. Color image, γ
A visible image forming unit for forming a visible image of two images other than the two images out of the image and the black image, and provided for each photoconductor between the photoconductor surface and the transfer material conveying path. An intermediate transfer member is provided, and the intermediate transfer member facing the transfer material transfer path upstream of the other intermediate transfer member in the transfer material transfer direction is intermediate from the image writing position by the visible image forming means of the photosensitive member. The total distance of the distance on the surface of the photoconductor to the position facing the transfer body and the distance on the surface of the intermediate transfer body from the position of the intermediate transfer body facing the photoconductor to the position facing the transfer material transport path is The total distance for the other intermediate transfer member is shorter than the total distance for the other intermediate transfer member by the distance between the facing positions of the both transfer members and the transfer material conveying path. The full-color image forming apparatus of No. 5 has 4. The full-color image forming apparatus according to claim 3, wherein the distances on the surface of the intermediate transfer body from the position where the intermediate transfer body faces the photosensitive body of the intermediate transfer body to the position where the intermediate transfer body faces the transfer material transport path are equal to each other. The position of the intermediate transfer material, which faces the transfer material transport path on the upstream side of the other intermediate transfer material in the transfer material transport direction, facing the photoconductor is changed from the image writing position by the visible image forming means of the photoconductor to the intermediate transfer. The distance on the surface of the photoconductor to the position facing the body is equal to the distance between the positions on the surface of the photoconductor of the other intermediate transfer body facing the transfer material conveying path. The full-color image forming apparatus according to claim 6 is characterized in that the intermediate transfer member for each photoconductor is intermediate from the image writing position by the visible image forming means of the photoconductor. Transcription 4. The full-color image forming apparatus according to claim 3, wherein the distances on the surface of the photoconductor to the position facing each other are equal to each other. The distance on the surface of the intermediate transfer body from the position where the intermediate transfer body faces the photoconductor to the position where the intermediate transfer body faces the transfer material is calculated from the distance on the surface of the intermediate transfer body for the other intermediate transfer body. Also, it is characterized in that it is set so as to be shortened by the distance between the positions of both transfer bodies facing the transfer material transport path.

[0012]

In the full-color image forming method of claim 1, first, in each of the predetermined first and second photoconductors,
The first and second photoconductive layers are charged in opposite directions to set the surface potential of the photoconductor to a predetermined potential. Next, the three primary colors are α,
In the case of β and γ, for the first photoconductor, either one of the α color image and the β color image, for example, the α color image is the A color light and the other image is the β color image is the A color light. And B color light,
Further, one of the α color image and the β color image, for example, the β color image is written as a latent image for regular development, and the other α color image is written as a latent image for reversal development. As a result, a latent image of an α-color image and a cover latent image of a β-color image are formed on the second photoconductive layer which is mainly made into a conductor by the irradiation of the A-color light, and is mainly irradiated by the B-color light. A main latent image of a β-color image is formed on the first photoconductive layer which is the other photoconductive layer to be made into a conductor. Here, the main latent image is a latent image for development, and the coated latent image is a photoconductive layer on which the main latent image is formed until it is erased by uniform irradiation with light of a predetermined color later. A latent image formed on the photoconductive layer charged in the opposite direction so that the main latent image does not appear on the surface of the photoconductor in a potential manner. This also applies to the second photoconductor and the like which will be described later.

Next, after developing the α-color image, which is one of the images appearing electrically on the surface of the second photoconductor, with a toner of a predetermined color, uniform irradiation is performed with light of a predetermined color.
As a result, the latent image and the β of the α-color image written with the A-color light are written.
The cover latent image of the color image is erased and the main latent image of the β-color image written with the B-color light is exposed on the surface of the first photoconductor in a potential manner. Next, the main latent image of the β-color image is developed with a predetermined color toner having the same polarity as the predetermined color toner. This makes the first
A visible image of an α-color image and a β-color image is formed on the surface of the photosensitive member.

For the second photosensitive member, either one of the γ color image and the black image, for example, the black image is the C color light and the other image is the γ color image is the C color light and the D color light, and ,
Either one of the γ-color image and the black image, for example, the γ-color image is written as a latent image for regular development, and the black image that is the other image is written as a latent image for reversal development. As a result, a latent image of a black image and a covered latent image of a γ-color image are formed on the second photoconductive layer, which is mainly made into a conductor by light irradiation of C color light, and is mainly conductive by light irradiation of D color light. A main latent image of a γ-color image is formed on the first photoconductive layer which is the other photoconductive layer to be embodied.

Next, after developing a black image, which is one of the images appearing electrically on the surface of the second photoconductor, with a toner of a predetermined color, uniform irradiation is performed with light of a predetermined color.
As a result, the latent image of the black image written with C color light and γ
The cover latent image of the color image is erased, and the main latent image of the γ-color image written with the D-color light is exposed on the surface of the second photoconductor in a potential manner. Next, the main latent image of the γ-color image is developed with a predetermined color toner having the same polarity as the predetermined color toner. This makes the second
A visible image of a black image and a γ-color image is formed on the surface of the photosensitive member.

Next, the visible images formed on the respective photoconductors are aligned and transferred onto the same transfer medium.
A full color image is formed on the transfer medium.

In a full-color image forming method according to a second aspect, in the full-color image forming method according to the first aspect, each of the photoconductors is developed with a toner which is relatively hard to absorb the light of a predetermined color used for the uniform irradiation. Writing a color image with light that makes the first photoconductive layer mainly a conductor,
A color image developed with a toner that relatively easily absorbs the light of the predetermined color is written with light that makes the first photoconductive layer mainly a conductor and light that makes the second photoconductive layer mainly a conductor. .. As a result, for each photoconductor, the first latent image forming layer on the side of the conductive substrate is provided with a coated latent image of a color image to be developed with toner that relatively easily absorbs the light of the predetermined color and the light of the predetermined color. A latent image of a color image to be developed with a toner that is relatively hard to absorb is formed, and a main latent image of a color image to be developed with a toner that relatively easily absorbs the light of the predetermined color is formed on the second photoconductive layer on the front surface side. Form.

Next, with respect to each photoconductor, the latent image of the color image developed with a toner that is relatively hard to absorb the light of the predetermined color that appears on the surface of the potential is relatively absorbed by the light of the predetermined color. After developing with a difficult toner, uniformly irradiate with the light of the predetermined color, and develop with a toner that relatively easily absorbs the light of the predetermined color. A coated latent image of a color image and the light of the predetermined color are relatively absorbed. The main latent image of the color image to be developed with the toner which is relatively easy to absorb the light of the predetermined color of the second photoconductive layer on the front surface side is erased from the latent image of the color image to be developed with the difficult toner. The potential is exposed on the surface of the body. Next, with respect to each photoconductor, the main latent image is developed with a toner that relatively easily absorbs the light of the predetermined color.

Then, the visible image formed on each photoconductor is aligned and transferred onto the same transfer medium, thereby forming a full-color image on the transfer medium.

In the full-color image forming method according to the third aspect of the present invention, first, the first and second photoconductive layers of a predetermined photoconductor are charged in opposite directions to each other to bring the photoconductor surface potential to a predetermined potential. Next, when the three primary colors are α, β, and γ, a first image that is any one of the α color image, the β color image, the γ image, and the black image, for example, the α image is A color light, α color image, β
A second second image, which is one image other than the one of the color image, the γ image, and the black image, such as a β image with A color light and B color light, and with the first image and the second image One of the images, for example the β image, is written as the latent image for regular development, and the other image, the α image, is written as the latent image for reversal development. As a result, a latent image of an α color image and a β image are formed on the first photoconductive layer, which is mainly made into a conductor by the irradiation of the A color light.
The second photoconductive layer, which is the other photoconductive layer on which a coating latent image of a color image is formed and which is mainly made into a conductor by light irradiation of B color light
A main latent image of a β-color image is formed on the photoconductive layer.

Next, after developing an α-color image, which is one of the images appearing electrically on the surface of the photoconductor, with a toner of a predetermined color, uniform irradiation is performed with light of a predetermined color, and both images are written with A-color light. A latent image of a certain α-color image and a cover latent image of a β-color image are erased, and a main latent image of a β-image, which is a latent image of the other image written with the B-color light, is made to appear potential on the surface of the photoconductor. The main latent image of the β image is developed with a predetermined color toner having the same polarity as the predetermined color toner, the visible images of the α image and the β image formed on the photoconductor are transferred onto a transfer medium, and after transfer. Initialize the photoconductor surface of.

Then, a third image which is one of the remaining two images of the α color image, the β color image, the γ image and the black image, for example, the γ image is converted into the fourth image by the A color light. The black image is the A color light and the B color light, and one of the third image and the second image, for example, the γ image which is the third image is the latent image for regular development, and the other image is A black image is written as a latent image for reversal development. This gives A
A latent image of a γ-color image and a coating latent image of a black image are formed on the first photoconductive layer which is mainly made into a conductor by light irradiation of color light, and a first latent image is made to be a conductor mainly by light irradiation of B-color light. A black latent image is formed on the second photoconductive layer.

Then, the γ image, which is the one of the images that has a potential appearing on the surface of the photoconductor, is developed with toner of a predetermined color, uniformly irradiated with light of a predetermined color, and written with A color light. Main latent image of the black image, which is the other image written with the B color light after erasing the latent image of the black image and the coating latent image of the black image, is potentialized on the surface of the photoconductor, and the black image is colored in the predetermined color. Develop with a predetermined color toner having the same polarity as the toner. As a result, a visible image of a γ image and a black image is formed on the surface of the photoconductor.

Next, the visible images of the γ image and the black image formed on the photoconductor are aligned with the α image and the β image on the transfer medium and transferred onto the transfer medium, whereby the transfer image is transferred. Form a full color image on the medium.

In the full-color image forming apparatus according to claim 4, when one of the two photoconductors having the same peripheral surface shape has three primary colors α, β, γ A visible image of any two of the α color image, the β color image, the γ image and the black image is formed by the visible image forming means. In addition, a visible image of two images other than the two images out of the α color image, the β color image, the γ image, and the black image is formed on the other photoconductor of the two photoconductors as a visible image forming unit. To form. Then, the visible image formed on each photoconductor is transferred to the transfer material transported on the transfer material transport path by an intermediate transfer body provided between the photoconductor surface and the transfer material transport path for each photoconductor. As a result, a full-color image is formed on the transfer material. Here, with respect to the intermediate transfer material that faces the transfer material transport path on the upstream side of the other intermediate transfer body in the transfer material transport direction, the intermediate transfer material faces the intermediate transfer body from the image writing position of the visible image forming means of the photoconductor. The distance on the surface of the intermediate transfer member and the distance on the surface of the intermediate transfer member from the position where the intermediate transfer member faces the photosensitive member to the position where the intermediate transfer member faces the transfer material conveyance path are It is configured to be shorter than the total distance of the transfer members by the distance between the positions of both transfer members facing the transfer material conveying path, so that even if images are simultaneously written on the respective photoconductors. The visible image on each photoreceptor is accurately aligned on the transfer material.

[0026]

EXAMPLE First, a first photoconductive layer and a second photoconductive layer were formed on a conductive substrate.
A specific example of the photoconductor in which the photoconductive layer is laminated will be described. As such a photoreceptor, the above-mentioned JP-A-61 is used.
No. 163349, etc., and Japanese Patent Application No. 2
Those described in No. -100976 can be used. The one described in Japanese Patent Application No. 2-100976 is shown in FIG.
As shown in FIG. 3, a charge transport layer (CTL) and a charge generation layer (CGL) are formed on an aluminum drum, which is a conductive substrate (not shown).
The first photoconductive layer consisting of the L layer, the two-layer structure (lower layer M
I, upper layer MII) intermediate layer M layer, second photoconductive layer U
The layers are constructed by laminating in this order.

The CTL consists of 18 g of an alpha-phenylstilbene compound having the following structural formula (1) and 20 g of a polycarbonate resin having the structural formula (2) below, and dichloromethane (methylene chloride) having the structural formula (3) below. ) Dispersed to 185.5 g, applied on an aluminum drum by a spray method and then dried to have a thickness of 15 ± 1 μm.

CGL was prepared by coating a solution of 1 gram of trisazo pigment having the following structural formula (4) in 99 grams of methylhexanone on the CTL so that the light transmittance at 720 nm was 10 ± 2%. It was formed by. Lower layer MI constituting an intermediate layer provided on the CGL layer
Is a thermosetting phenolic resin 0.8 g having the following structural formula (5), butanol 50 g and methanol 30 g.
A solution dispersed in gram of a mixed solvent was applied on CGL to form a thickness of 0.39 ± 0.03μ. The upper layer MII which constitutes the intermediate layer is composed of 0.8 g of quinacridone having the structural formula (6) below and 0.8 g of thermosetting phenolic resin having the structural formula (5) below, represented by the structural formula (7) below. It is formed by applying a solution dispersed in 80 g of tetrahydrofuran having the above to the lower layer MI so that the transmittance of light of 565 nm is 80 ± 4%.

The U layer is a thiapyrylium salt (4- (p-dimethylaminophenyl) -2) having the following structural formula (8).
-6-diphenylthiabylium perchlorate) 0.
127 grams and 7.51 grams of the polycarbonate resin having the structural formula (2) above and 5.07 grams of the alpha-phenyl stilbene compound having the structural formula above (1) were added to dichloromethane (chlorination) having the structural formula above (3). Methylene) 67.0 g and 1, having the following structural formula (9)
A solution prepared by dispersing 47.5 g of 1,2 trichloroethane in a mixed solvent was applied onto the intermediate layer so that the thickness was 30 ± 3 μm.

In this composite photoreceptor, the U layer and the upper layer MI
The I and the lower layer MI each have a transmittance of 94%, 96%, and 100% with respect to the light of 780 nm, and the L layer is sensitive to this light.
When irradiated with 80 nm light, this light reaches the CGL and makes it conductive. U layer alone is 680 nm
Has a transmittance of 0.3 to 0.4%, and
Since it has sensitivity to this light, when the light of 680 nm is irradiated on the composite photoconductor, this light makes the U layer conductive and is substantially absorbed by this. Therefore, in the laminated state, the L layer becomes a photoconductive layer having sensitivity to 780 nm light and not to 680 nm light, and the U layer has 680 nm.
Is a photoconductive layer having a sensitivity to the light of 780 nm and not to the light of 780 nm. The U layer and the L layer each have sensitivity to the red light of the red LED which is the back lamp of the primary chargers 11 and 12 described later, but this light is absorbed by the U layer, It does not reach the L layer. The intermediate layer (M layer) can be omitted, and U
An overcoat layer may be provided on the surface of the layer.

An example in which the composite photoconductor is used as a first photoconductor and a second photoconductor will be described below. The apparatus shown in FIG. 3 can be used as the embodiment apparatus. In FIG. 3, a first photoconductor drum 30A that is a first photoconductor and a second photoconductor drum 30B that is a second photoconductor are provided side by side above the conveyor belt device 3 that conveys the transfer paper 2. Between the lowermost portions of the photosensitive drums 30A and 30B and the conveyor belt 3a of the conveyor belt device 3, respectively,
Intermediate transfer belts 18 and 28 are provided. As the intermediate transfer belts 18 and 28, for example, JP-A-2-21
The one disclosed in Japanese Patent No. 2870 can be used. A roller structure may be used instead of such a belt structure. Around the photosensitive drums 30, primary chargers 11 and 21 and secondary chargers 12 and 2 equipped with back lamps are provided.
2,780nm laser light source (LD) 13,23 and 680n
Dual wavelength simultaneous writing optical system consisting of m laser light source (LD) 14, 24 and polygon mirror 1, 1, etc., red uniform exposure device 16, 26, AC charging simultaneous white uniform exposure device 19,
29, and a cleaning device 10.20.
In this example, a magenta developing device 17 and a cyan developing device 15 are provided facing the surface of the first photosensitive drum 30A, and a yellow developing device 27 and a black developing device are provided facing the surface of the second photosensitive drum 30B. A container 25 is provided.

First, the charging process using the primary chargers 11 and 21 and the secondary chargers 12 and 22 of the first photosensitive drums 30A and 30B will be described. In this example, since the same charging is applied to each of the photoconductor drums 30A and 30B, only the reference numbers of the photoconductor drum 30A are shown as the members. While rotating the photosensitive drum 30A in a direction of an arrow (counterclockwise) at a predetermined linear velocity, negative corona discharge by the primary charging charger 11 is performed under uniform exposure of the red LED which is the back lamp. At this time, as shown in FIG. 4A, the photosensitive drum 3 is caused by corona discharge.
The negative charge reaching the 0A surface is sensitive to red light U
The positive charges (holes) in the photocarriers generated in the layer are canceled by each other, and the negative charge (electrons) as the other photocarrier is U.
Move through the layer and accumulate evenly on the M layer, which is an insulating layer,
On the other hand, the L layer to which red light does not reach does not lose its electrical insulating property, and a positive charge is induced and uniformly distributed at the boundary surface between the L layer and the aluminum drum. As a result, the L layer is minus 150
It is charged to 0 V (strictly speaking, L layer and M layer together are 1
Although it is 500 V, it is ignored because the M layer is sufficiently thin.
In the following, the negative charges accumulated on the M layer will be referred to as negative charges accumulated on the L layer. ). Primary charging charger 11
To the photosensitive drum 30A rotation direction, a positive corona discharge by the secondary charger 12 is performed in the dark at a position of a predetermined distance along the peripheral surface thereof. At this time, as shown in FIG. 4B, the U layer does not lose its electrical insulating property, so that positive charges are accumulated on the surface of the U layer and are charged to plus 1000V. At this time, some of the lines of electric force (U which were all directed to the aluminum drum side from the negative charges accumulated at the boundary between the U layer and the L layer) (U
(Determined by the ratio of the electrostatic capacities of the layer and the L layer)
Since it is turned to the positive charge side of the 0A surface, the L layer becomes −500V. As a result, the photosensitive drum 30A
The electric potential on the surface is 1000V of the electric charge accumulated in the U layer.
And the electric charge of minus 500V accumulated in the L layer are combined to be approximately plus 500V.

Writing by the dual wavelength simultaneous writing optical system will be described below. As is well known, the masking equation is used to convert the R, G, B reflection densities of the original into C, M,
The toner concentration of Y is obtained, the photoconductor surface potential for obtaining the toner concentration is obtained in consideration of the relationship between the toner concentration and the toner adhesion amount per unit area, the photoconductor characteristics, and the like. In order to simplify the explanation, here, for the sake of simplification of description, the adhesion amount of each of C, M, and Y toners is 100 as shown in Table 1 as the development amount. Each original color is reproduced by% or 0%. For example, as shown in Table 1, the cyan color of the original document is reproduced only by attaching 100% of the cyan toner, and the blue-violet color of the original document is reproduced by attaching 100% of the cyan toner and the magenta toner. The areas to which the C, M, and Y toners are attached are the cyan image that is the image component obtained by color-separating the document with the red filter, and the image component obtained by color-separating the document with the green filter. It is determined using image data of each of the magenta image and the yellow image, which is an image component obtained by color-separating the original with a blue filter. Even with such division, almost faithful color reproduction is possible except for blue-violet. Table 1 shows the latent image potential and the image exposure amount (exposure amount) for each original color when a latent image for normal development is formed. % Development amount, and when the exposure amount is 0.5 (the unit is arbitrary), the surface potential of the photosensitive member is 5%.
It is supposed to be attenuated by 00V. (Hereafter, margin)

[Table 1]

On the basis of the above assumptions, in this embodiment, a latent image of a cyan image (hereinafter referred to as a cyan latent image) on the positively charged U layer of the first photoconductor 30A (hereinafter referred to as a cyan latent image) is used for reversal development (hereinafter referred to as a latent image). As an N / P latent image), a latent image of a magenta image (hereinafter referred to as magenta latent image) on the negatively charged L layer as a latent image for normal development (hereinafter referred to as P / P latent image), and Photoconductor 30B
A yellow image latent image (hereinafter referred to as a yellow latent image) is written as a P / P latent image in the negative L layer. Table 2 shows the latent image potential and the exposure amount of the photoconductive layer forming a latent image for each original color in this case.

[Table 2]

Here, in this embodiment, the black portion of the original is registered with the black portion (hereinafter, the original color in this black portion is one black color) in the gradation image having a relatively high registration tolerance. Black areas of characters and diagrams with a relatively small tolerance (hereinafter, the original color in this black area is black 2
It is reproduced by distinguishing it from (color). That is, black 1
Colors are reproduced with four colors of yellow toner (Y), magenta toner (M), cyan toner (C) and black toner, and two colors of black are reproduced with only black toner. To distinguish between the black 1 color and the black 2 colors, a known process such as pictogram separation process can be used. Then, at least black 1 to which black toner is attached
The image areas of two colors and black are treated as black images, and the image area of one black is treated as a part of each of the yellow image, the magenta image, and the cyan image. Then, the latent image of the black image (hereinafter referred to as black latent image) is written as an N / P latent image in the positively charged U layer of the second photoconductor 30B.

Furthermore, in this embodiment, as described later, the positive polarity N / P latent image of the U layer is first subjected to reversal development with the positive polarity toner, so that at this time, the negative polarity P / P latent image of the L layer is obtained. To prevent positive toner from adhering to the image, the negative P / P of this L layer
A positive polarity P / P latent image having the same shape as the latent image and the opposite polarity is formed as a coated latent image. This coating latent image is U layer, L
Although a photoconductive layer different from the layer may be provided and formed on the photoconductive layer, in order to simplify the constitution of the photoconductor in this embodiment, this coating latent image is formed on the L layer. The P / P latent image (corresponding to the main latent image) of the
/ P formed with latent image.

Specifically, for the first photosensitive drum 30A, a cyan image N / P latent image and a magenta image P / P covered latent image are formed on the U layer, and a magenta image P is formed on the L layer. A main latent image of / P is formed. For this purpose, a laser beam of 680 nm having sensitivity to the U layer is modulated with image data for forming an N / P latent image of a cyan image and image data for forming a P / P latent image of a magenta image, and is sensitive to the L layer. 780nm with
The laser beam is modulated with image data for forming a P / P latent image of a magenta image. On the other hand, the second photosensitive drum 30B
In the case of No. 3, a black image N / P latent image and a yellow image P / P coating latent image are formed on the U layer, and a yellow image P / P main latent image is formed on the L layer. For this purpose, a 680 nm laser beam sensitive to the U layer is modulated with image data for forming an N / P latent image of a black image and image data for forming a P / P latent image of a yellow image, and is sensitive to the L layer. A 780 nm laser beam having the above is modulated with image data for forming a P / P latent image of a yellow image.

Table 3 shows the potentials (layer potentials) of the respective layers of the photoconductors 30A and 30B by the latent image formation and the exposure amount at the latent image formation for each original color. In this table, the correspondence between the main latent image and the covering latent image is indicated by arrows.
Further, the photoconductive layer (photosensitive layer), the potential (charge amount) of each photoconductive layer after the charging step, the form of the latent image (writing), and the uniform irradiation performed after the N / P latent image development of the U layer described later. The potential of each layer (after irradiation) is also described.

[Table 3]

At the writing positions 100a and 100b on the respective photosensitive drums 30A and 30B, a laser beam of 780 nm and 680 nm modulated according to the image signal as described above.
A mixed beam of nm laser beams is applied to each photoconductor drum 30.
One-dimensional optical scanning is performed in the axial directions of A and 30B, and a latent image of a cyan image and a magenta image is formed on the first photosensitive drum 30A, and a latent image of two black images and a yellow image is formed on the second photosensitive drum 30B. Each photosensitive drum 30A, 3
Image exposure is performed simultaneously at the same position on 0B. As described above, the 780 nm laser beam passes through the U layer, the upper layer MII, and the lower layer MI, reaches the CGL, is absorbed, generates photocarriers, and accumulates on the L layer minus 100.
Discharge 0V. The 680 nm laser beam is absorbed in the U layer and generates photocarriers in the U layer, discharging the plus 500 V electric charge stored therein.

Here, for example, P of the first photosensitive drum 30A
The magenta latent image, which is a / P latent image, has a minus 500 V of the main latent image of the L layer and a plus 500 V of the covered latent image of the U layer in the portion to which the toner is attached, and the L layer in the portion to which the toner is not attached. The main latent image of 0 V and the portion of the coating latent image of the U layer of plus 500 V cancel each other out, and the contribution to the surface potential of the photoconductor is 0 V, and no potential appears on the surface of the photoconductor. Similarly, the yellow latent image on the second photoconductor drum 30B does not appear on the surface of the photoconductor in a potential manner. As a result, only the N / P latent image of the cyan image on the surface of the first photoconductor drum 30 is 0 V at the portion to which the toner is attached and plus 500 at the portion to which the toner is not attached.
A potential V / N / P latent image appears on the surface of the photoconductor. Similarly, for the second photoconductor drum 30, only the N / P latent image of the two black images is a photoconductor as an N / P latent image in which the toner-adhering portion is 0V and the toner-nonadhering portion is plus 500V. Potentially appears on the surface.

Next, development will be described. First, as the development of the first color, in the first photoconductor drum 30A, the cyan developing device 15 using positively charged cyan toner is used to add a plus 50
A development bias of 0 V is applied to reversely develop the N / P latent image of the cyan image. As a result, as shown in FIG.
One black color of the original that composes the cyan image, cyan color, green color,
Cyan toner is attached to the surface of the photoconductor corresponding to a region such as blue-violet. On the other hand, in the second photoconductor drum 30B, the black developing device 25 using positively charged black toner causes
The developing bias is applied to reversely develop the black 2 image. As a result, as shown in FIG. 5D, black toner is attached to the surface of the photoconductor corresponding to the areas of the black 1 color and the black 2 colors of the original forming the black image.

Next, as shown in FIGS. 4 (e) and 5 (e), uniform exposure is performed by the red uniform exposure devices 16 and 26 with red light, which is light having sensitivity to the U layer, and the U layer is exposed. Almost all accumulated charges are uniformly discharged. This makes the first
The cyan latent image and the covered latent image of the magenta image formed on the U layer of the photoconductor drum 30A are erased, and the main latent image of the magenta image formed on the L layer appears in a potential on the photoconductor. To do. In addition, the black latent image and the covered latent image of the yellow image formed on the U layer of the second photoconductor drum 30B are erased, and the main latent image of the yellow image formed on the L layer is electrically charged on the photoconductor. The state that appears in.

Next, as the second color development, in the first photoconductor drum 30A, a magenta developing device 17 using positively charged magenta toner is applied with a developing bias of 0 V to form a magenta image P / P latent image. Regular development. As a result, as shown in FIG. 4 (f), the magenta toner is attached to the surface of the photoconductor corresponding to the areas of one black color, magenta color, red color, blue violet color, etc. of the original forming the magenta image. Meanwhile, the second
On the photosensitive drum 30B, a yellow developing device 27 using positively charged yellow toner applies a developing bias of 0 V to normally develop the yellow latent image. As a result,
As shown in (f), yellow toner is adhered to the surface of the photoconductor corresponding to the areas of one black color, yellow color, red color, green color, etc. of the original forming the yellow image.

Next, the transfer onto the transfer paper 2 will be described. The toner images formed on the photosensitive drums 30A and 30B as described above are transferred to the intermediate transfer belts 18 and 28, respectively.
Are collectively transferred to the surfaces of the intermediate transfer belts 18 and 28 at the intermediate transfer positions 101a and 101b which are contact points with the transfer positions 102a and 102a which are contact points with the transfer paper by the movement of the intermediate transfer belts 18 and 28. It is conveyed to 102b. Then, the conveyor belt 3a conveyed by the conveyor belt device 3
First, as shown in FIG. 4 (g), the toner image from the first photosensitive drum 30A is transferred onto the upper transfer paper 2 at a transfer position 102a which is set relatively upstream in the transport direction of the transfer paper 2. The toner image from the second photoconductor drum 30B is transferred in alignment with the toner image from the first photoconductor drum 30A at the time point when the toner image is conveyed to the transfer positions 102b on the relatively downstream side.

In the present embodiment, the transfer positions of the toner images from the respective photosensitive drums 30A and 30B on the transfer paper 2 are adjusted by the first photosensitive member on which the toner image transferred first on the transfer paper 2 is formed. The sum of the length of the path from the writing position 100a of the drum 30A to the transfer position 102a via the intermediate transfer position 101a and the length between the transfer positions 102a and 102b is the writing position 100 of the second photosensitive drum 30B.
b to the transfer position 102b via the intermediate transfer position 101b.
It is done by configuring the length of the route up to.

For example, as shown in FIG. 6, the path length from the writing position 100a to the intermediate transfer position 101a on the first photosensitive drum 30A is from the writing position 100b on the second photosensitive drum 30B to the intermediate transfer position. The transfer positions 102a, 102a,
It can be set so as to be shortened by the length of 102b. Further, as shown in FIG. 7, the first photosensitive drum 30
The peripheral length of the intermediate transfer belt 108 for A is such that the path length from the intermediate transfer position 101a to the transfer position 102a is greater than the path length of the intermediate transfer belt 28 for the second photoconductor drum 30B at both transfer positions 102, 102b. It may be set to be shorter by the length of the route between them. According to this, each of the photoconductor drums 30A and 30B can share the image forming unit disposed around them.

As described above, the transfer paper 2 on which the toner image has been transferred is discharged to the outside of the machine after the toner image is fixed by a fixing device (not shown). On the other hand, each photosensitive drum 30A,
The surface of 30B is charged by the simultaneous white uniform exposure devices 19 and 29 for charging, and then cleaned by the cleaning devices 10 and 20 to prepare for the next image formation.

In this embodiment, the toner images from the two photoconductor drums are aligned and transferred onto the transfer paper 2 by using the intermediate transfer belts 18 and 28. This is also effective in an image forming apparatus such as that shown in FIG. 8 in which an ordinary photoconductor is used instead of the body. In the image forming apparatus of FIG. 8, the toner images of two colors respectively from the two photoconductor drums 30A and 30B are transferred onto the transfer paper 2 on the conveyor belt 3a conveyed by the conveyor belt device 3 as in the above-described embodiment. The images are aligned and transferred to form a full-color image on the transfer. The basic structure of this device is the same as that of the device of the above embodiment, and the corresponding members are designated by the same reference numerals. The difference from the above-described embodiment apparatus is that each photosensitive drum 30
A and 30B are provided with a normal photoconductor instead of the composite photoconductor, and a single charging without a back lamp is used instead of the primary chargers 11 and 21 and the secondary chargers 12 and 22 for the charging process. Using the devices 11a and 21a, two writing positions 100a, 103a, 100b, 10 on the respective photosensitive drums 30A, 30B instead of the dual wavelength simultaneous writing optical system.
4b simultaneous writing optical system in which 3b is set (laser light sources 13, 14, 23, 24 are all 780 nm
Laser irradiation) and that the second chargers 12 and 22 are provided instead of the red light uniform exposure devices 16 and 26.

Also in the above configuration, the first photosensitive drum 30A on which the toner image to be transferred first onto the transfer paper 2 is formed
Of the path from the writing position 100a to the transfer position 102a via the intermediate transfer position 101a and each transfer position 1
The sum of the length between 02a and 102b is from the writing position 100b of the second photoconductor drum 30B to the intermediate transfer position 101.
This is done by configuring the length of the path to reach the transfer position 102b via b, and for this purpose, a configuration such as the example shown in FIGS. 6 and 7 can be adopted. Incidentally. In this device, each photosensitive drum 3
Two writing positions 100a, 1 for 0A and 30B
Since 03a, 100b, and 103b are set, an image memory is required for image alignment in writing based on the distance between the writing positions, but as described above, the toner images from the photoconductor drums 30A and 30B are used. An image memory is not required for the registration of the image on the transfer paper 2.

In the above embodiment, since the cyan toner or the black toner, which is relatively easy to absorb the red light used for uniform irradiation after the first color development, is used for the first color development, this uniform irradiation light is used. These toners may be absorbed and the potential of the latent image of the second color may not be sufficiently secured.
In addition, these toners form a cyan latent image or a black latent image to be developed by these toners on the L layer provided on the side of the aluminum drum, which is a conductive substrate, even though the toner sharply affects the sharpness of the image. Therefore, sharpness may decrease.
As a countermeasure against this, cyan toner or black toner is used for the second color development, and a cyan latent image or a black latent image is formed on the U layer of each photoconductor drum 30A, 30B. FIG. 9 is a schematic configuration diagram of such an image forming apparatus, FIG. 10 is a process diagram for the first photoconductor drum 30A of the image forming device, and FIG. 11 is a process for the second photoconductor drum 30B of the image forming device. It is a figure.

In FIG. 9, the basic structure of the apparatus of this embodiment is the same as that of the above-described apparatus (see FIG. 3), and the corresponding members are designated by the same reference numerals. The difference from the apparatus of the above embodiment is that each of the photosensitive drums 30A and 30B is
Color developing devices 15, 25 and second color developing devices 17, 2
7 is changed so that the developing devices 15 and 25 using the cyan toner and the black toner described above can be used for the development of the second color, and the exposure for performing uniform irradiation after the development of the first color. As a container, for example, 750-850
This is that the latent image to be developed as the second color can be formed on the U layer by using the near-infrared light uniform exposure devices 16a and 26a that irradiate the near-infrared light having the sensitivity of the L layer of nm. .

Then, a color image is formed in the next step. First, in the step of charging the photosensitive drums 30A and 30B, as shown in FIGS. 10 (a) and 11 (a),
A negative corona discharge is performed by the primary charging charger 11 to charge the L layer to minus 1500V. And
As shown in FIGS. 10 (b) and 11 (b), the secondary charger 12 performs a weaker positive corona discharge than that in the above-described embodiment to charge the U layer to plus 1000V. As a result, the L layer becomes −1000 V, and the potential of the surface of the photoconductor drum 30A becomes +500 V of the charge accumulated in the U layer and −1000 V of the charge accumulated in the L layer.
Together with V, it becomes approximately minus 500V.

Then, as shown in FIGS. 10 (c) and 11 (c), writing is performed by the dual wavelength simultaneous writing optical system. In this embodiment, with respect to the first photoconductor drum 30A, a main latent image of N / P of a cyan image is formed on the U layer, and a P / P latent image of a magenta image and an N / P of a cyan image are formed on the L layer. Form a coated latent image. For this reason, the sensitivity of the U layer is 6
The 80 nm laser beam is modulated with the image data for forming the N / P latent image of the cyan image, and the 780 nm laser beam having sensitivity to the L layer is used to form the image data for forming the P / P latent image of the magenta image and the cyan image. Modulate with image data for N / P latent image formation. On the other hand, for the second photoconductor drum 30B, a black image N / P main latent image is formed on the U layer, and a yellow image P / P latent image and a black image N / P covered latent image are formed on the L layer. To form. For this reason, a 680 nm laser beam sensitive to the U layer is modulated with image data for forming an N / P latent image of a black image, and a 780 nm laser beam sensitive to the L layer is modulated to a P / P latent image of a yellow image. The image data for image formation and the image data for N / P latent image formation of a black image are modulated.

Table 4 shows the potential (layer potential) of each layer of the photoconductors 30A and 30B due to latent image formation for each document color, and the exposure amount at the time of latent image formation. Also in this table, the correspondence between the main latent image and the coated latent image is indicated by arrows as in Table 3 in the above-mentioned examples, and the photoconductive layer (photosensitive layer) and the potentials of the photoconductive layers after the charging step ( The charge amount), the form of the latent image (writing), and the layer potentials (after irradiation) after the uniform irradiation performed after the N / P latent image development of the U layer described later are also described.

[Table 4]

As a result, the potential of each layer of the photoconductor drums 30A and 30B is lowered according to the amount of exposure, and the main latent image of the cyan image formed in the U layer is formed on the surface of the first photoconductor drum 30A. Only the P / P latent image of the magenta image does not appear to be covered by the coating latent image of the cyan image formed on the layer, but appears on the surface, and the U layer is formed on the surface of the second photoconductor drum 30B. The main latent image of the black image is not covered by the covered latent image of the black image formed on the L layer and does not appear, and only the P / P latent image of the yellow image appears in a potential manner.

Next, as the first color development, in the first photosensitive drum 30A, a magenta developing device 17 using positively charged magenta toner applies a developing bias of 0 V to a P / P latent image of a magenta image. Reverse development,
As shown in (d), magenta toner is adhered to the surface of the photosensitive member corresponding to the areas of one color of black, magenta, red, blue-violet, etc. of the original forming the magenta image. On the other hand, on the second photoconductor drum 30B, a yellow developing device 27 using positively charged yellow toner applies a developing bias of 0 V to normally develop a yellow image. As a result, FIG. 5 (d)
As shown in FIG.
Yellow toner is adhered to the surface of the photoconductor corresponding to areas such as yellow, red, and green.

Then, as shown in FIGS. 10 (e) and 11 (e), uniform exposure by near-infrared light, which is light sensitive to the L layer, is performed by the near-infrared light uniform exposure devices 16a and 26a. By doing so, the magenta latent image formed on the L layer and the covering latent image of the cyan image are erased, and the main latent image of the cyan image formed on the U layer is made to appear on the photoconductor in a potential manner. Further, the yellow latent image and the covered latent image of the black image formed on the L layer of the second photoconductor drum 30B are erased, and the main latent image of the black image formed on the U layer has a potential on the photoconductor. The state that appears in.

Next, as the second color development, in the first photoconductor drum 30A, a cyan developing device 15 using positively charged cyan toner is applied with a developing bias of plus 500 V to obtain the main N / P ratio of the cyan image. Reverse development of the latent image. As a result, as shown in FIG. 10F, the cyan toner is attached to the surface of the photoconductor corresponding to the areas of one color of black, cyan, green, blue-violet, etc. of the original forming the cyan image. on the other hand,
On the second photoconductor drum 30B, a black developing device 25 using positively charged black toner applies a developing bias of plus 500 V to reverse develop the main latent image of the black image. As a result,
As shown in 1 (f), the black 1 of the original forming the black image
Black toner is attached to the surface of the photoconductor corresponding to the areas of two colors, black.

Thereafter, as in the above embodiment, the toner images formed on the photoconductor drums 30A and 30B are conveyed by the conveyor belt device 3 via the intermediate transfer belts 18 and 28. The toner image is transferred onto the upper transfer paper 2 in alignment with the toner image. Then, the transfer paper 2 on which the toner image is transferred is discharged to the outside of the machine after the toner image is fixed by a fixing device (not shown). On the other hand, each photosensitive drum 30
The surfaces of A and 30B are white uniform exposure devices for simultaneous simultaneous charging 19 and 29
After being charged by (1), it is cleaned by the cleaning devices 10 and 20 and is prepared for the next image formation.

In each of the above embodiments, a full-color image is formed by using two photoconductor drums 30A and 30B. Instead of this, one photoconductor drum composed of a composite photoconductor is used. Will be described. FIG. 12 is a schematic configuration diagram of such an image forming apparatus. In FIG. 12, the photoconductor drum 30 is a composite photoconductor provided with a U layer and an L layer as in each of the above-described embodiments. Around the photosensitive drum 30, a primary charger 11, a secondary charger 12, a cyan developing device 15, a yellow developing device 27, a near-infrared light uniform exposing device 16a, and a magenta developing device equipped with a back lamp. 17, black developing device 25, AC charging simultaneous white uniform exposure device 1
9 and the cleaning device 10 are sequentially arranged along the movement path of the surface of the photosensitive drum 30. And 7
A two-wavelength simultaneous writing optical system including an 80 nm laser light source (LD) 13, a 680 nm laser light source (LD) 14, a polygon mirror 1 and the like is provided, and the writing position on the photoconductor drum by this is the secondary charger 12 and It is set between the cyan developing device 15 and the cyan developing device 15. In addition, the black developing device 2
5 and the AC charging simultaneous white uniform exposure device 19 so that the surface of the photoconductor drum 30 is brought into contact with the intermediate transfer belt 18
A backup roller 18 is provided at the lowermost part of the intermediate transfer belt 18 so as to face the intermediate transfer belt 18.
b oppose each other to form a transfer portion to the transfer paper 2. A cleaner 18a is provided so as to face the surface of the intermediate transfer belt 18. Further, a conveyor belt device 3 for conveying the transfer paper 2 that has passed through the transfer section is also provided.

In the above-described structure, the first developing drum 30 is rotated over the photosensitive drum 30 by using the yellow developing device 27 and the magenta developing device 17, which are arranged with the near-infrared light uniform exposure device 16a interposed therebetween. Two-color toner images of a yellow image and a magenta image are formed, and the near-infrared light uniform exposure device 16a is also sandwiched between the second rotation while the two-color toner images are carried on the photosensitive drum 30. Cyan developing device 15
And a black developing device 25 and the like are used to form two color toner images of a cyan image and a black image on the photoconductor drum 30, whereby four color toner images are superposed on the photoconductor drum 30. , On the transfer paper 2 via the intermediate transfer belt 18
A color toner image is transferred to form a full-color image.

The process of forming a full-color image will be specifically described below with reference to FIGS. 14 and 15. FIG. 14 is a process drawing of the first rotation of the photosensitive drum 30, and FIG. 15 is a process drawing of the second rotation of the photosensitive drum 30.
First, in the charging step of the photosensitive drum 30 of the first rotation, as shown in FIG.
Charge to 00V. Then, as shown in FIG. 14B, positive corona discharge is performed by the secondary charger 12,
The U layer is charged to plus 500V. As a result, the L layer becomes minus 1000V, and the potential of the surface of the photosensitive drum 30A becomes approximately minus 500V when the charge accumulated in the U layer plus 500V and the charge accumulated in the L layer minus 1000V.

Then, as shown in FIG. 14C, writing of the yellow latent image and the magenta latent image is performed by the dual wavelength simultaneous writing optical system. An N / P main latent image of a magenta image is formed on the U layer, and a P / P latent image of a yellow image and an N / P covered latent image of a magenta image are formed on the L layer. For this purpose, a 680 nm laser beam sensitive to the U layer is modulated with image data for forming a magenta image N / P latent image, and L
A layer-sensitive 780 nm laser beam is modulated with image data for forming a P / P latent image of a yellow image and image data for forming an N / P latent image of a magenta image.

Table 5 shows the photosensitive drum 3 by latent image formation in the first rotation (1) and the second rotation (2) for each original color.
It shows the potential of each layer of 0 (potential of each layer) and the exposure amount at the time of latent image formation. Also in this table, the correspondence between the main latent image and the coated latent image is indicated by arrows, as in Tables 3 and 4 for each of the above-mentioned examples, and the photoconductive layer (photosensitive layer) and each photoconductive layer after the charging step are shown. Potential (charge amount), latent image form (writing), U described later
The potential of each layer (after irradiation) after the uniform irradiation performed after the N / P latent image development of the layer is also described. (Hereafter, margin)

[Table 5]

As a result, the potential of each layer of the photosensitive drum 30 is lowered according to the exposure amount, and the main latent image of the magenta image formed in the U layer is formed on the surface of the photosensitive drum 30 in the magenta layer formed in the L layer. The P / P latent image of the yellow image is not exposed by being covered with the coating latent image of the image, but appears in a potential manner.

Next, as the development of the first color, a developing bias of 0 V is applied by the yellow developing device 27 using the positively charged yellow toner to normally develop the yellow latent image as shown in FIG. 14 (d). , Yellow toner is adhered to the surface of the photoconductor corresponding to areas such as one black color, a yellow color, a red color, and a green color of a document forming a yellow image.

Next, as shown in FIG. 14E, the near-infrared light uniform exposure device 16a performs uniform exposure by the near-infrared light, which is light having sensitivity to the L layer, and is formed on the L layer. The yellow latent image and the covered latent image of the magenta image are erased, and the main latent image of the magenta image formed in the U layer is brought into a state in which it appears in a potential on the photoconductor.

Next, as the second color development, on the photosensitive drum 30, the magenta developing device 17 using positively charged magenta toner applies a developing bias of plus 500 V to the main latent image of N / P of the magenta image. Figure 4
As shown in (f), magenta toner is adhered to the surface of the photosensitive member corresponding to the areas of one color of black, magenta, red, blue-violet, etc. of the original forming the magenta image.

While the toner images of the yellow image and the magenta image are passing through the portion facing the intermediate transfer belt 18 and the cleaning device 10, the intermediate transfer belt 18 and the cleaning device 10 are in contact with the surface of the photosensitive drum 30. Evacuate so that it does not happen. The cyan developing device 15 and the black developing device 25 which are not used during the first rotation are also retracted from the photosensitive drum 30.

Next, the second rotation is carried out while carrying the toner images of the first color and the second color as shown in FIG.
As shown in (b), the photosensitive drum 30 is charged in the same manner as in the first rotation, and the potential on the surface of the photosensitive drum 30A is set to plus 500 V of the charge accumulated in the U layer and the charge accumulated in the L layer. Approximately minus 500V by adding the minus 1000V.

Then, as shown in FIG. 15C, the cyan latent image and the black latent image are written by the dual wavelength simultaneous writing optical system. Form the main latent image of N / P of the black image on the U layer,
A P / P latent image of a cyan image and an N / P covered latent image of a black image are formed on the L layer. For this reason, the sensitivity of the U layer is 68
A 0 nm laser beam is modulated with N / P latent image forming image data for a black image, and a 780 nm laser beam having a sensitivity in the L layer is used for forming a cyan image P / P latent image forming image and a black image. Modulation is performed with image data for N / P latent image formation.

As a result, as shown in Table 5 above, the potential of each layer of the photosensitive drum 30 is lowered according to the exposure amount,
On the surface of the photosensitive drum 30, the main latent image of the black image formed on the U layer is not covered with the covered latent image of the black image formed on the L layer and does not appear, and only the P / P latent image of the cyan image is formed. Make it appear as a potential.

Next, for developing the third color, the cyan developing device 15 using positively charged cyan toner applies a developing bias of 0 V to normally develop the N / P latent image of the cyan image. ), Cyan toner is attached to the surface of the photoconductor corresponding to the areas of one black color, cyan color, green color, bluish purple, etc. of the original forming the cyan image.

Next, as shown in FIG. 15 (e), the near-infrared light uniform exposure device 16a performs uniform exposure by the near-infrared light, which is light having sensitivity to the L layer, and is formed on the L layer. The cyan latent image and the covered latent image of the black image are erased so that the main latent image of the black image formed in the U layer appears in a potential on the photoconductor.

Next, as the development of the fourth color, a black developing device 25 using positively charged black toner applies a developing bias of plus 500 V to reverse develop the N / P main latent image of the black image. As shown in FIG. 15 (d), black toner is adhered to the surface of the photoconductor corresponding to the black 1 color and black 2 color regions of the original forming the black image.

As described above, while the four color toner images formed on the photosensitive drum 30 are passing through the portion facing the intermediate transfer belt 18, the intermediate transfer belt 18 is moved to the photosensitive drum 30.
The toner images are collectively transferred to the transfer paper 2 through the intermediate transfer belt 18 by contacting the surface of the transfer paper 2 with each other, thereby forming a full-color image on the transfer paper 2. The yellow developing device 27 and the magenta developing device 17 which are not used during the second rotation are retracted from the photosensitive drum 30.

Then, the transfer paper 2 on which the toner image is transferred is discharged to the outside of the machine after the toner image is fixed by a fixing device (not shown). On the other hand, the surface of the photoconductor drum 30 is charged by the simultaneous white uniform exposure devices 19 and 29 for charging, and then cleaned by the cleaning device 10 to prepare for the next image formation.

In the above embodiment, for example, when a full-color image is formed in synchronization with the development reading by the image input device (scanner), the development reading is performed at the first rotation and the second rotation of the photosensitive drum 30, respectively. By
Image memory requirements can be reduced while using a single photoreceptor drum.

In the above embodiment, the four color toner images formed on the photosensitive drum 30 are transferred to the intermediate transfer belt 1.
Although the image is transferred to the transfer paper 2 via 8, the intermediate transfer belt 18 may not be used, and the transfer may be made directly from the photosensitive drum 30 to the transfer paper.

Further, in the above embodiment, since the toner images of the yellow image and the magenta image are formed in the first rotation, the toner images of the third and fourth colors are formed in the second rotation while carrying the toner images. Even if the above is performed, the color reproducibility is excellent as compared with the case where a toner image such as cyan toner or black toner that is relatively easy to absorb the light used for writing is used for the toner image formation in the first rotation. . However, if a toner that is relatively hard to absorb the light used for writing can be used due to improvements in the toner, etc., the first color
The order of the toners used for the fourth color is arbitrary, latent image formation is selected according to the order of use, and the arrangement of the developing device is determined.

Further, instead of forming four color toner images on the photosensitive drum and then collectively transferring them to a transfer paper or the like, 1
The two color toner images formed by the second rotation are transferred to the intermediate transfer belt 1.
8. Transfer onto a transfer paper held on a transfer drum or a transfer paper conveyed by a conveyor belt device capable of switchback conveyance, and charge the surface of the photoconductor drum 30 by the simultaneous white uniform exposure devices 19 and 29. Cleaning may be performed by the cleaning device 10 to form the remaining two color toner images at the second rotation, and the color image transferred and aligned on the transfer paper may be formed. In this case, when the above-mentioned intermediate transfer belt or transfer drum is used, the peripheral length of the intermediate transfer belt or transfer drum is set longer than the maximum copy length, for example, 420 mm of A-3 size. The order of the toners used for the first to fourth colors is arbitrary, and for example, for the first photosensitive drum 30A in the full-color image forming process shown in FIGS. 4 and 5 or 10 and 11 described above. The two-color toner image forming step is the two-color toner image forming step for the first rotation of the photosensitive drum 30 in the above-described embodiment, and the two-color toner image forming step for the second photosensitive drum 30B is the photosensitive member in the above-described embodiment. It can be adopted in the two-color toner image forming step of the second rotation of the drum 30.

It is possible to form a full-color image by using one photoconductor drum as in the above embodiment even when the photoconductor is not a composite photoconductor but a normal photoconductor. FIG. 13 is a schematic configuration diagram of such an image forming apparatus. The image forming apparatus of FIG. 13 has a primary charger 11, a secondary charger 12, a cyan developing device 15, which are provided with a back lamp, around the photoconductor drum 30, as in the above-described embodiment.
Yellow developing device 27, magenta developing device 17, black developing device 2
5, AC charger 19, cleaning device 10, etc.
They are sequentially arranged along the movement path on the surface of the photoconductor drum 30. Further, the intermediate transfer belt 18, the backup roller 18b, the cleaner 18a, and the conveyor belt device 3 are also provided. The difference from the apparatus of the above embodiment is that the photoconductor drum 30 is provided with an ordinary photoconductor instead of the composite photoconductor, and the primary charger 11 and the secondary charger 1 for the charging process.
In place of 2, a single charger 11a having no back lamp is used, and two-beam writing in which two writing positions 100 and 103 are set on the photosensitive drum 30 in place of the two-wavelength simultaneous writing optical system. An optical system is used (both two laser light sources 13a and 13b are 780 nm laser irradiation), and a second charger 12a is provided instead of the near-infrared light uniform exposure device 16a. .

This image forming apparatus forms a toner image of a cyan image and a magenta image at the first rotation of the photosensitive drum 30 as in the above-described embodiment, and the toner images of the two colors are formed on the photosensitive drum 30. At the second rotation while carrying the toner image, two color toner images of a cyan image and a black image are formed on the photoconductor drum 30, whereby four color toner images are superposed on the photoconductor drum 30. Four color toner images are transferred onto the transfer paper 2 via the intermediate transfer belt 18 to form a full-color image.

Also in this apparatus, for example, when a full-color image is formed in synchronism with the development and reading by the image input device (scanner), the development and reading should be performed at the first rotation and the second rotation of the photosensitive drum 30, respectively. This reduces the required amount of image memory while using a single photoconductor drum. Further, the modifications described with respect to the apparatus of the above-described embodiment can be similarly applied to this apparatus.

In each of the above embodiments and the like, the photosensitive member is formed on the surface of the drum-shaped substrate, but instead of this, it may be formed on the surface of the belt-shaped substrate.

[0086]

According to the invention of claim 1, 2 or 3, since the toner of the same polarity as the toner already adhered on the photoreceptor by development is used as the second color toner for each photoreceptor. When developing with the second color toner, the electric field for moving the second color toner formed between the developing electrode and the photoconductor surface from the developing electrode side to the photoconductor surface causes the first color toner to move to the developing electrode side. It is possible to prevent peeling of the toner of the first color from the surface of the photoconductor without receiving an electrostatic force to the surface of the photoconductor.

In particular, according to the invention of claim 2, after developing the latent image of the color image to be developed with the toner which is relatively hard to absorb the light of the predetermined color used for uniform irradiation for each photoconductor, The main latent image of the color image is uniformly irradiated with the light of the predetermined color, and then, the main latent image of the color image is developed with the toner that relatively easily absorbs the light of the predetermined color. The toner, which is relatively easy to absorb the above light, does not block the uniform irradiation, and good color reproducibility can be obtained. Further, the toner that relatively easily absorbs the light of the predetermined color affects the sharpness of the image relatively greatly,
Since the main latent image of the color image developed with the toner is formed on the first photoconductive layer on the front surface side, good image sharpness can also be obtained.

According to the third aspect of the invention, it is possible to form a full-color image at a relatively high speed with a relatively simple structure. That is, as a method for forming a full-color image, one photosensitive member is rotated four times, as described in the above-mentioned JP-A-61-161.
A method in which two composite photoconductors are used to superpose two-color toner images formed on the composite photoconductors on a transfer material as in the method disclosed in Japanese Patent No. 163349, etc. There is also a method in which a toner image is simultaneously formed on the above, and these are superposed in the form of a transfer material. However, it is difficult to increase the speed by the method of rotating one photoconductor 4 times, and in the case of using two composite photoconductors or the one using four photoconductors, one photoconductor is used because a plurality of composite photoconductors are used. The cost will be higher than that using. In particular, in the case where four photoconductors are used, as long as a power source of 100 V and 15 amperes is used in view of the relationship with the electric power required by the fixing device to obtain a glossy image, for example, about 15 to 20 sheets / min. Speeding is the limit. However, according to the third aspect of the invention, since one composite photoconductor is used, it is relatively easy to reduce the cost to the same extent as one photoconductor rotates four times, and it is possible to rotate the composite photoconductor twice. Since a full-color image can be formed, as long as a power source of 100 V and 15 amperes is used, the speed can be increased to the same extent as that using four photosensitive drums.

In a full-color image forming apparatus according to claim 4, 5 or 6, two photoconductors having the same peripheral surface shape are used, and a visible image formed on each photoconductor is printed on the photoconductor surface for each photoconductor. With an intermediate transfer member provided in a predetermined configuration between the transfer material and the transfer material transporting path, the transfer material is transferred onto the transfer material transported on the transfer material transporting path. Since the visible image on each photoconductor is accurately aligned on the transfer material, no image memory is required for aligning the toner image on the transfer paper, and the peripheral lengths of two composite photoconductors are increased. Can be the same.

[Brief description of drawings]

FIG. 1 is a characteristic diagram of light reflectance characteristics of toner.

FIG. 2 is a cross-sectional view of a photoconductor according to an example.

FIG. 3 is a schematic configuration diagram of an image forming apparatus according to an embodiment.

FIG. 4 is a process diagram of image formation on a first photosensitive drum of the image forming apparatus.

FIG. 5 is a process diagram of image formation on the first photosensitive drum of the image forming apparatus.

FIG. 6 is a schematic configuration diagram of an image forming apparatus according to another embodiment.

FIG. 7 is a schematic configuration diagram of an image forming apparatus according to still another embodiment.

FIG. 8 is a schematic configuration diagram of an image forming apparatus according to still another embodiment.

FIG. 9 is a schematic configuration diagram of an image forming apparatus according to still another embodiment.

FIG. 10 is a process diagram of image formation on the first photosensitive drum of the image forming apparatus.

FIG. 11 is a process diagram of image formation on the second photosensitive drum of the image forming apparatus.

FIG. 12 is a schematic configuration diagram of an image forming apparatus according to still another embodiment.

FIG. 13 is a schematic configuration diagram of an image forming apparatus according to a modification.

FIG. 14 is a process diagram of image formation for the first rotation of the photosensitive drum in the image forming apparatus of FIG.

FIG. 15 is a process diagram of image formation for the second rotation of the photosensitive drum in the image forming apparatus.

[Explanation of symbols]

2 transfer paper, 3 conveying belt device 10 cleaning device, 11 primary charger 12 secondary charger, 13 laser light source (780 nm) 14 laser light source (680 nm), 15 cyan developing device 17 magenta developing device, 18 intermediate transfer belt 23 laser Light source (780 nm), 24 Laser light source (680 nm) 25 Black developing device, 26 Yellow developing device 27 Uniform exposure device, 28 Intermediate transfer belt

Claims (6)

[Claims] 1. A first photoconductive layer is provided on a conductive substrate, and a second photoconductive layer is formed on the first photoconductive layer directly or through an intermediate layer.
Of the two photoconductors having the photoconductive layer of No. 1, the first photoconductor has one photoconductive layer of B
The other photoconductive layer is adjusted so that the other photoconductive layer is mainly made into a conductor by the irradiation of the colored light, and the second photoconductor has one photoconductive layer irradiated by the light of the C color and the other photoconductive layer by the irradiation of the D color light. Of the first photoconductive layer and the photoconductive layer of each of the first and second photoconductors are charged in opposite directions to each other. When the surface potential of the photoconductor is set to a predetermined potential and the three primary colors are α, β, γ, for the first photoconductor, one of the α-color image and the β-color image is irradiated with the A-color light to the other. Image of A color light and B color light, and α color image and β color image
One of the color images is written as a latent image for regular development and the other image is written as a latent image for reversal development, and the one image is developed with toner of a predetermined color, and then uniformly irradiated with light of a predetermined color. The latent image of the two images written with the A color light is erased and the latent image of the other image written with the B color light is erased first.
Potential on the surface of the photoconductor, and the other image is developed with a predetermined color toner having the same polarity as the predetermined color toner. For the second photoconductor, a γ color image and a black image are formed. One of the images is C-color light, the other image is C-color light and D-color light, and one of the γ-color image and the black image is a latent image for regular development, and the other image is for reverse development. After writing one image as a latent image and developing the one image with toner of a predetermined color, uniform irradiation with light of a predetermined color is performed and the latent image of both images written with C color light is erased and the other image written with D color light Latent image of the latent image on the surface of the second photoconductor, and the other image is developed with a predetermined color toner having the same polarity as the predetermined color toner, and a visible image formed on each photoconductor. Full-color, which aligns and transfers images on the same transfer medium Image forming method. 2. The full-color image forming method according to claim 1, wherein a color image developed by a toner that is relatively hard to absorb the light of a predetermined color used for the uniform irradiation is applied to each of the photoconductors. A color image in which the layer is mainly made into a conductor to be written, and a color image which is developed with a toner which easily absorbs the light of the predetermined color is converted into a light in which the first photoconductive layer is mainly made into a conductor and the second light. 2. The full-color image forming method according to claim 1, wherein the conductive layer is mainly written by light that becomes a conductor. 3. A first photoconductive layer is provided on a conductive substrate, and a second photoconductive layer is provided directly on the first photoconductive layer or via an intermediate layer.
And the photoconductive layer is adjusted so that one of the photoconductive layers is irradiated with light of A color and the other of the photoconductive layers is irradiated with light of B color. When the first and second photoconductive layers of the photoconductor are charged in opposite directions to set the photoconductor surface potential to a predetermined potential, and the three primary colors are α, β, γ, an α color image, β Color image,
The first image, which is any one of the γ image and the black image, is A-color light, and is the one image other than the one image of the α-color image, the β-color image, the γ-image, and the black image. A certain second image is written as A color light and B color light, and one of the first image and the second image is written as a latent image for regular development and the other image is written as a latent image for reversal development. , One of the images is developed with toner of a predetermined color, uniform irradiation is performed with light of a predetermined color, the latent images of both images written with A color light are erased, and the latent image of the other image written with B color light is exposed. A potential image is made visible on the body surface, the other image is developed with a toner of a predetermined color having the same polarity as the toner of the predetermined color, and the visible images of the first and second images formed on the photoconductor are transferred. Transfer to a medium, initialize the surface of the photoconductor after transfer, then α color image, β color image, γ The third image, which is one of the remaining two images of the image and the black image, is A-color light and the fourth image, which is the other image, is A-color light and B-color light, and the third image Either one of the image and the second image is written as a latent image for regular development and the other image is written as a latent image for reversal development, and one of the images is developed with a toner of a predetermined color, and uniformized by light of a predetermined color. Irradiation is performed to erase the latent images of both images written with the A-color light, and the latent image of the other image written with the B-color light is exposed on the surface of the photosensitive member in a potential manner, and the other image is colored with the toner of the predetermined color. The transfer medium is developed by developing with a toner of a predetermined color having the same polarity as that of the transfer medium, and the visible images of the third and fourth images formed on the photoconductor are aligned with the first and second images on the transfer medium. A full-color image forming method, characterized in that the image is transferred on top. 4. Two photoconductors having the same peripheral surface shape, and when one of the two photoconductors has three primary colors α, β, γ, an α color image, a β color image Visible image forming means for forming a visible image of any two images of an image, a γ image and a black image, and an α color image and a β color image on the other photoconductor of the two photoconductors. Between a visible image forming means for forming a visible image of two images other than the two images among the image, the γ image and the black image, and between the photosensitive member surface and the transfer material conveying path for each photosensitive member. And an intermediate transfer member provided on the intermediate transfer member, and an image is written by the visible image forming unit of the photosensitive member on the intermediate transfer material that faces the transfer material transport path on the upstream side of the other intermediate transfer body in the transfer material transport direction. The distance on the surface of the photoconductor from the position to the position facing the intermediate transfer body, and the facing of the intermediate transfer body to the photoconductor The total distance from the position on the surface of the intermediate transfer body to the position facing the transfer material transport path is larger than the total distance of the other intermediate transfer body, A full-color image forming apparatus, wherein the full-color image forming apparatus is configured to be shortened by the distance between the facing positions. 5. The distances on the surface of the intermediate transfer body from the position where the intermediate transfer body of each of the photosensitive bodies faces the photosensitive body of the intermediate transfer body to the position where the intermediate transfer body faces the transfer material conveying path are equal to each other. In the full-color image forming apparatus of item 3, the position of the intermediate transfer material facing the transfer material upstream of the other intermediate transfer material in the transfer material transfer direction facing the photosensitive material is set to the visible image of the photosensitive material. The distance on the surface of the photoconductor from the position where the image is written by the forming means to the position facing the intermediate transfer body is larger than the distance on the surface of the photoconductor for the other intermediate transfer body, and the transfer material conveying path for both transfer bodies is provided. 4. The full-color image forming apparatus according to claim 3, wherein the distance is set to be shorter by the distance between the facing positions. 6. The distance on the surface of the photosensitive member from the image writing position of the intermediate transfer member of each photosensitive member by the visible image forming means of the photosensitive member to the position facing the intermediate transfer member is equal to each other. In the full-color image forming apparatus of No. 3, in the transfer material conveyance direction, the transfer material conveyance path from the position of the intermediate transfer material facing the photoconductor on the upstream side of the other intermediate transfer material to the transfer material conveyance path The distance on the surface of the intermediate transfer body to the position facing the intermediate transfer body is equal to the distance on the surface of the intermediate transfer body of the other intermediate transfer body from the position facing the transfer material conveying path. 4. The full-color image forming apparatus according to claim 3, wherein the full-color image forming apparatus is set to be shorter.