JPH0352866B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION 1. Field of Industrial Application The present invention uses a photoreceptor in which an electrically insulating layer and a photoconductive layer are sequentially laminated on a conductive substrate.
This invention relates to a copying method, in particular an electrophotographic copying method, in which images corresponding to each image part are obtained from a document having an image part (for example, a color image part such as red) and a second image part (for example, a black image part). be.

2. Prior Art Conventionally, in order to reproduce originals in which black and multiple chromatic colors coexist using electrophotography or electrostatic printing, an electrostatic charge image corresponding only to an image area of a certain color is formed, and this is The image was developed using a developer of that color, and this process was performed for each color. By such a method, it is possible to reproduce an image of a document consisting of various color combinations. In this case, an electrostatic charge image corresponding to the light from each image area is formed on an image support such as a photoreceptor drum, and this is developed with a developer mixed with toner and, if necessary, carrier. An image is formed based on a process in which the toner image is electrostatically transferred onto a transfer sheet and further fixed.

As such a multicolor copying method, a method using an NP photoreceptor is known. For example,
According to Publication No. 34770, the photoreceptor is imagewise exposed through a red light filter and at the same time positively charged, and then imaged through a cyan filter and at the same time negatively or AC charged to form an electrostatic latent image for red only. After red color development and transfer, an electrostatic latent image for black color is formed in a conventional manner, and this is developed and transferred to black color. In addition, special public service 1973-
According to Publication No. 33066, the entire surface is exposed to a positive charge, and then the image is exposed through a cyan filter, and the electrostatic latent images are charged negatively or AC at the same time, and then the red and black electrostatic latent images are made to have opposite polarities by exposing the image through a red filter. Each latent image is developed with toner of opposite polarity and transferred to obtain a two-color image.

However, in the method using the NP photoreceptor described above, it is necessary to carry out image exposure at the same time as charging due to the process. It is not easy to control the charging to occur under these conditions. Moreover, since image exposure and charging are performed at the same time, it is relatively difficult to maintain a sufficient charging potential, and when using a photoreceptor with a long carrier transit time (for example, an organic photosemiconductor), the sensitivity is low. tends to decline.

On the other hand, as another multicolor copying method,
As seen in Japanese Patent No. 3537, etc., there is a method of using a composite photoreceptor in which a photosensitive layer insensitive to red light and a photosensitive layer sensitive to at least red light are laminated. According to this, primary charging is performed while exposing uniformly so that only the upper photosensitive layer exhibits photoconductivity, then secondary charging with opposite polarity is performed in a dark place, and further image exposure is performed. Therefore, the charge in the area corresponding to the white image area is erased, and the charge of the photosensitive layer insensitive to red light is left only in the area corresponding to the red image area, and the polarity of the surface potential is reversed to that of the black area. .

However, with this known method, the layer structure of the photoreceptor is complicated and it is difficult to prepare, and the potential stability is poor due to the influence of the residual potential of each photoreceptor layer. Put it away.

3. Purpose of the Invention The purpose of the present invention is to enable the use of a photoreceptor with a relatively simple layer structure, eliminate the need for image exposure and charging at the same time by applying the normal Carlson process, and further reduce residual charge and potential. The goal is to provide a method that requires less change.

4. Structure of the Invention That is, the present invention provides the copying method described at the beginning, (a) a step of first charging the photoreceptor, (b) simultaneously with this first charging, or before and/or (c) a first image exposure step of exposing an area corresponding to the first image area (for example, using light of the same color as the first image area); (c) a step of exposing the area corresponding to the first image area; a second charging step of charging the photoreceptor; (d) performing a second image exposure using light other than the light used during the first image exposure; forming a first electrostatic latent image having a polarity opposite to that of the first charging only in the corresponding region; (e) developing and transferring the first electrostatic latent image; (f) forming the first electrostatic latent image; a third charging step in which the photoreceptor is charged to a polarity opposite to that in step 1; a full-surface exposure step in which the entire surface of the photoreceptor is exposed to light simultaneously with the third charging, or before and/or after the third charging; (h ) a fourth charging step of charging the photoreceptor to the same polarity as the first charging; (i) exposing an area corresponding to the first image area;
forming a second electrostatic latent image having a polarity opposite to that of the first electrostatic latent image only in an area corresponding to the second image area; (j) developing and transferring the second electrostatic latent image; The present invention relates to a copying method characterized by comprising steps.

5 Examples Hereinafter, the present invention will be described in detail with reference to the drawings. In the following, to simplify the explanation, image reproduction of a two-color original having a black image area and a red image area on a white background will be described.

FIG. 1 shows an example of an electrophotographic reproduction apparatus for forming two-color reproduction images according to the present invention. At the top of this device body is a document table 1 that moves back and forth.
A document 5 placed on the document table 11 is illuminated by an illumination lamp 12 .
13 and 14 are mirrors, 15 is a fixed lens, 16 is a movable red filter configured to be able to enter and exit the optical path, and 17 is a circuit that reflects red light and passes cyan, which is complementary to red. It is a movable dichroic filter that can be moved in and out of the optical path. In FIG. 1, the red filter 16 is shown out of the optical path, and the dichroic filter 17 is placed in the optical path. A photosensitive layer 2 is provided on the surface of a drum-shaped photosensitive member 3, and when the photosensitive member 3 rotates clockwise, the photosensitive layer 2 is uniformly charged by a corona charger 4. The photosensitive layer 2 is made of selenium, an organic semiconductor, or the like.

Around the photoreceptor 3, there are a charger 4 that uniformly charges the photoreceptor layer 2, a black developer 18 with positively charged black toner, and a red developer 19 with negatively charged red toner. , and a cleaning device 20 for removing toner and charges remaining on the photosensitive layer 2. Reference numeral 21 denotes a transfer drum which has the same diameter as the photoreceptor 3 and is driven in contact with the photosensitive layer 2 or rotates counterclockwise. 33 is a transfer electrode consisting of a corona discharger, 22 is a copy paper feed tray, 2
3 is a paper feed roller that feeds the copy paper 32 stored in the copy paper feed tray 22 one by one; 24 is a first conveyance roller that transports the copy paper to the transfer drum 21; and 25 is a drum that transports the copy paper after transfer. An electrostatic separator 26 removes static electricity to make it easier to separate the copy paper from the drum 21. A separating claw 26 forcibly separates the copy paper from the drum 21.
Further, 27 is a fixing device with a built-in heater.
However, although a guide plate is actually provided to guide the copy paper 32, this illustration is omitted.

The configuration of the photoreceptor used will be explained.

As shown in FIGS. 2 and 3, the photoreceptor 3 has a structure in which an electrically insulating layer 41 and a photoconductive layer (photosensitive layer) 2 are sequentially laminated on a conductive substrate 40. As shown in FIGS. The photoconductive layer 2 can be formed of a single photoreceptor layer that has hole or electron mobility and is sensitive to at least the entire visible light range. Alternatively, as shown in FIG. 2, a photoreceptor may be used in which the photoconductive layer 2 is composed of a laminated structure of a carrier generation layer 42 and a photosensitive layer 43 (for example, selenium), and the carrier generation layer 42 is sensitive to chromatic light. On the other hand, the photosensitive layer 43 may be configured to transmit chromatic light and be sensitive to light other than chromatic light. Furthermore, as shown in FIG. 3, a photoreceptor may be used in which the photoconductive layer 2 is formed by a laminated structure of a first carrier generation layer 42, a carrier transport layer 44, and a second carrier generation layer 45. I can do it. In this case, the first carrier generation layer 4
2 has sensitivity to chromatic light, the second carrier generation layer 45 has sensitivity to light other than chromatic light, and the second carrier generation layer 45 and carrier transport layer 44 transmit chromatic light. None, and the polarity of the first charge is negative if the carrier transport layer 44 has good hole mobility, and positive if the electron mobility is good. Conversely, the second carrier generation layer 45 is sensitive to chromatic light, and the first carrier generation layer 42 is sensitive to light other than chromatic light,
Second carrier generation layer 45 and carrier transport layer 44
is made to transmit light other than chromatic light, and the polarity of the first charge is positive when the mobility of holes in the carrier transport layer 44 is good, and negative when the mobility of electrons is good. may be used as

The photoreceptor shown in FIG. 3 includes, for example, an insulating layer 41 made of acrylic-melamine-epoxy resin with a thickness of 7 μm on an Al substrate 40, a first carrier generation layer 42 made of copper phthalocyanine with a thickness of 0.5 μm, and a first carrier generation layer 42 made of copper phthalocyanine with a thickness of 12 μm.
styryl compound and polycarbonate (3:4)
carrier transport layer 44 consisting of a mixture of
A layer in which a second carrier generation layer 45 made of an anthurone pigment of 0.5 μm is laminated can be used. It is considered desirable that the insulating layer 44 has a thickness of 1 to 20 μm, the carrier generation layers 42 and 45 have a thickness of 0.1 to 2 μm, and the carrier transport layer 44 has a thickness of 5 to 20 μm. Furthermore, the carrier transport layer 44 may be made of a triphenylmethane compound or the like.

Among the layer configurations exemplified above, for example, the third
The process of obtaining a two-color image using the photoreceptor 3 having the structure shown in the figure will be described (however, the photoconductive layer 2 is shown in a simplified manner). First, as shown in FIG. 4a, the entire surface of the photoreceptor is uniformly primary negatively charged by, for example, -6 KV DC corona discharge. Through this charging process,
Negative charges are induced on the surface of the photoreceptor, and positive charges are induced on the back surface of the insulating layer 41.

Next, as shown in FIG. 4b, the red filter 1
6, reflected light 46 from the image of the original 5 (consisting of a red image portion 5R, a black image portion 5B, and a white portion 5W) is irradiated. However, since the black image area 5B absorbs light, no reflected light can be obtained from it. The light 46 reaches the regions corresponding to the white part 5W and the red image part 5R, passes through the second carrier generation layer and the carrier transport layer, and generates carriers in the first carrier generation layer. Among the generated carriers, holes move through the carrier transport layer and neutralize the surface charge. Therefore, it appears that negative charges have been injected from the surface to the surface of the insulating layer.

The above-mentioned primary charging and the above-mentioned exposure may be performed at the same time, or the same effect as above can be obtained even if the exposure is performed not only after the primary charging but also before, before, and after the primary charging. .

Next, when the photoreceptor is neutralized by alternating current or secondary charged with opposite polarity (positive polarity), no charge is injected into the area corresponding to the black part 5B, as shown in FIG. 4c. Therefore, the surface charge is erased, but a portion of the positive charge on the back side of the insulating layer is released while the charge remains inside in the regions corresponding to the red part 5R and the white part 5W.

Next, as shown in FIG. 4d, when the original image is irradiated through the cyan filter 17, the white portion 5
The light reaches the area corresponding to W, but the red area 5W
Since the reflected light (red) is complementary to the cyan filter 17, it does not pass through the filter, and the light does not return from the black portion 5B either.
As a result, in the region corresponding to the white part 5W, carriers are generated in the second carrier generation layer to neutralize the surface charge, and holes move to the surface of the insulating layer to neutralize a part of the internal charge. .

By the above process, an electrostatic latent image with a positive potential (for example, 300 V) is formed only in the region corresponding to the red part 5R, and the potential is near zero or negative (for example, -100 V) in other regions.

Next, development is performed using a magnetic brush method using, for example, a two-component red toner that is negatively charged, and the image is further transferred onto copy paper. Then, the photoreceptor is neutralized (by light or alternating current) and cleaned.

Next, the photoreceptor is uniformly positively tertiary charged as shown in FIG. 5a. This charge is
This can be done with a 6KV DC corona discharge.

Next, as shown in FIG. 5B, the entire surface of the second carrier generation layer is exposed to sensitive light 47, so that charges are injected to the surface of the insulating layer in the same manner as described above. In this case as well, the exposure is not limited to after the tertiary charging, but may be performed before or before and after the tertiary charging.

Next, as shown in Fig. 5c, when negative charging (fourth order charging) is performed uniformly by DC corona discharge of, for example, -4KV, the surface of the photoreceptor is charged while positive charges remain on the surface of the internal insulating layer. is charged with a negative charge.

Next, as shown in Figure 5d, the red filter 16
When the reflected light 46 from the original is irradiated through the filter 16, the light in the red portion 5R and the white portion 5W reaches the photoreceptor, but the light does not reach the black portion 5W. As a result, in the regions corresponding to the white and red parts, carriers are generated in the first carrier generation layer, apparently negative charges are injected in the same way as described above, and some of the positive charges on the surface of the insulating layer are neutralized. , the negative charge on the surface of the photoconductive layer disappears.

In this way, negative charges are left only in the area corresponding to the black portion 5B, forming a second electrostatic latent image with a negative potential (for example, -300V). The potential of the white and red parts is +70V.

Thereafter, this latent image is developed with a positively charged two-component black toner, for example, using a magnetic brush method, and is transferred onto copy paper while being aligned with the above-mentioned red transferred image.

As a result, a two-color image of red and black can be accurately transferred onto a sheet of copy paper, and the two-color image can be further fixed by the next hot roll type fixing device. Note that the steps of forming the first and second electrostatic latent images (and further developing and transferring) may be performed in the reverse order to that described above. Of course, the present invention is also applicable to the formation of two-color images made of other color combinations, or images of three or more colors.

6 Effects of the Invention As described above, the present invention can form a multicolor image of two or more colors using a photoreceptor with a relatively simple structure (i.e., a laminated structure of a photoconductive layer and an electrically insulating layer). It is possible to easily create a photoreceptor to be used. In particular, insulating layers can be easily formed under less stringent conditions than photoconductive layers.

In addition, since the copying process itself can be performed by repeating the Carlson process, it is not necessary to perform charging at the same time as image exposure, making it easy to obtain a predetermined potential, and reducing sensitivity even with photoreceptors with long carrier transit times. Does not occur.

Furthermore, since only one photoconductive layer is required, the effects of residual potential and potential changes due to fatigue of the photoreceptor are reduced, and furthermore, known processes can be applied and used, increasing practicality.

[Brief explanation of drawings]

The drawings show embodiments of the present invention, in which FIG. 1 is a schematic sectional view of an electrophotographic copying machine for forming two-color images, and FIGS. Cross-sectional views, Fig. 4 a, b, c, d and Fig. 5 a,
b, c, and d are schematic cross-sectional views sequentially showing the copying process (however, cross-sectional hatching is omitted for ease of understanding). In addition, in the symbols used in the drawings, 2
... Photoconductive layer, 3 ... Photoreceptor, 4 ... Corona charger, 5 ... Original, 16 ... Red filter, 17
...Cyan filter, 18...Black developer,
19...Red developing device, 21...Transfer drum, 27
... Fixing device, 32 ... Copying paper, 33 ... Transfer electrode, 40 ... Substrate, 41 ... Electrical insulating layer, 42,
45...Carrier generation layer, 43...Photosensitive layer, 44
...This is the carrier transport layer.

Claims (1)

[Claims] 1. Using a photoreceptor in which an electrically insulating layer and a photoconductive layer are sequentially laminated on a conductive substrate, a document having a first image area and a second image area can be converted to each image area. In a copying method for obtaining corresponding images, the steps include: (a) first charging the photoreceptor; (b) simultaneously with, or before and/or after the first charging, the first image; (c) a second charging step of charging the photoreceptor to a polarity opposite to that of the first charging; (d) during the first image exposure; By performing second image exposure using light other than the used light, a first electrostatic latent image having a polarity opposite to that of the first charging is formed only in the area corresponding to the first image area. (e) a step of developing and transferring this first electrostatic latent image; (f) a third charging step of charging the photoreceptor to a polarity opposite to that of the first charging; g) At the same time as this third charging, or before and/or after this, an entire surface exposure step of exposing the entire surface of the photoreceptor; (h) a fourth step of charging the photoreceptor to the same polarity as the first charging; (i) exposing an area corresponding to the first image area to light;
forming a second electrostatic latent image having a polarity opposite to that of the first electrostatic latent image only in an area corresponding to the second image area; (j) developing and transferring the second electrostatic latent image; A copying method comprising the steps of: 2. The method according to claim 1, wherein the transferred image of the first electrostatic latent image and the transferred image of the second electrostatic latent image are aligned with each other and formed on the recording material. 3. The method according to claim 1 or 2, wherein the first image portion consists of a chromatic image and the second image portion consists of a black image. 4. The method according to claim 3, wherein a photoreceptor is used in which the photoconductive layer has hole or electron mobility and is sensitive in at least the entire visible light range. 5 A photoreceptor is used in which a photoconductive layer is formed by a laminated structure of a carrier generation layer and a photosensitive layer, and the carrier generation layer is sensitive to chromatic light, while the photosensitive layer is sensitive to chromatic light and transmits the chromatic light. The method according to claim 3, wherein the method is sensitive to light other than the chromatic light. 6. The method described in claim 3, which uses a photoreceptor in which a photoconductive layer is formed by a laminated structure of a first carrier generation layer, a carrier transport layer, and a second carrier generation layer. . 7 The first carrier generation layer is sensitive to chromatic light, the second carrier generation layer is sensitive to light other than the chromatic light, and the second carrier generation layer and the carrier transport layer are sensitive to chromatic light. The claim is that the carrier transport layer is made to transmit light, and the polarity of the first charge is negative when the carrier transport layer has good hole mobility, and positive when the electron mobility is good. The method described in Section 6. 8 The second carrier generation layer is sensitive to chromatic light, the first carrier generation layer is sensitive to light other than the chromatic light, and the second carrier generation layer and the carrier transport layer are sensitive to chromatic light. A patent that allows light other than light to pass through, and the polarity of the first charge is positive when the carrier transport layer has good hole mobility, and negative when the electron mobility is good. A method according to claim 6.