JP2000242065A - Electrophotographic recording device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrophotographic recording device capable of obtaining a highly accurate image, regardless of the surface shape and the quality of material. SOLUTION: As the method for forming the electrostatic latent image 36 on the insulating image carrier 11, an exposure 13 is carried out by such as laser on a press contact part, in a state of holding the image carrier charged by the charging device 12 in press contact with a photoreceptor 10. Carriers developed on an exposed photosensitive layer 31 forms the electrostatic latent image 36 on the image carrier 11 by erasing the electrostatic charge. Accordingly, the electrostatic latent image with high precision/high contrast, being exactly the same as a razor printer or the LED printer can be formed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic recording apparatus capable of forming a high-definition image on any recording medium using a dry toner or a liquid toner.

[0002]

2. Description of the Related Art An electrophotographic apparatus using a liquid developer has an advantage which cannot be realized by a dry electrophotographic apparatus, and its value is recently being reconsidered. High image quality can be achieved by using a very fine toner of submicron size, sufficient image density can be obtained with a small amount of toner, and it is economical, and it can realize the same texture as printing (for example, offset printing). The main advantage of wet electrophotography over the dry process is that energy can be saved because toner can be fixed on paper at a relatively low temperature.

FIG. 9 shows a wet electrophotographic recording apparatus proposed by the inventors, and a recording method of the wet electrophotographic system will be described. The latent image holder 1 is a photosensitive drum having an organic or amorphous silicon photosensitive layer provided on a conductive substrate. The latent image holding member 1 is uniformly charged by a well-known corona charger or scorotron charger 2-1 and then exposed to an image modulated laser beam 3-1 to form an electrostatic latent image on the surface. You. Thereafter, the electrostatic latent image is visualized by the developing device 4-1 containing the liquid developer. The liquid developer or toner adhering to the electrostatic latent image may be directly transferred to a sheet by the transfer device 5 in the transfer step, but here, the second charger 2-2 and the second laser exposure 3- 2, a second electrostatic latent image is formed, and the second developing device 4-2 stores a second developer of a different color from the liquid developer stored in the first developing device 4-1. Develop this. Therefore, after the second development, a two-color toner image is formed on the latent image holding member 1. Similarly, the third and fourth developments are performed, and a full-color toner image is formed on the latent image holding member 1. This toner image is transferred to a sheet by the transfer device 5, and may be directly transferred to the sheet, or may be transferred to the sheet 9 via the intermediate transfer medium 6 as illustrated in FIG. Is also good. From the latent image carrier 1 to the intermediate transfer medium 6
In the transfer to the sheet 9 and the transfer from the intermediate transfer medium 6 to the paper 9, either of the transfer by electric field or the transfer by pressure (and heat) can be used. In general, many liquid developers can be fixed on paper at room temperature. However, fixing may be performed by heating the pressure roller 7 or the like. Such an image forming process is disclosed in, for example, US Pat. Nos. 5,570,173 and 420,675, and is a conventionally known process.

On the other hand, there are still some problems with transfer of a toner image to a recording medium. As described above, the transfer of the toner image to the recording medium is performed by transferring the toner image directly from the photoreceptor to the recording medium by pressure or electric field, or by temporarily transferring the toner image to the intermediate transfer medium by pressure or electric field as shown in FIG. Then, there is a method of transferring the image by further applying a pressure or an electric field to the recording medium. In order to use an electrophotographic recording apparatus using a liquid toner as an OA device, the recording medium has a wide range of paper qualities and surface properties of the recording medium, from PPC paper with very rough surface to OHP sheet with good surface. It is necessary to record a good image regardless of the image quality. When transferring an image from a photoconductor directly to a recording medium using an electric field,
The image quality of the toner image transferred to the recording medium largely depends on the surface smoothness of the recording medium. In the case of paper having good smoothness, a clear image can be obtained, but in the case of paper having a rough surface such as PPC paper, the toner image is transferred only to the convex portions of the paper.
Further, when transferring from the surface of the photoreceptor to the recording medium by pressure, the toner is hardly peeled off because the surface of the photoreceptor is hard and hardly deformed, and 100% transfer is performed on a recording medium other than the recording medium having a large adhesiveness with the toner. It is quite difficult to get it.
That is, when a toner image is directly transferred from a photoconductor to a recording medium, a recording medium suitable for each method is required to form a clear image.

On the other hand, in the case of using an intermediate transfer medium as shown in FIG. 9, if an intermediate transfer medium having a certain degree of elasticity is used according to the knowledge of the present inventors, the use of the intermediate transfer medium may affect the surface properties and material of the recording medium. It is known that a clear toner image can be formed on a recording medium. In other words, the intermediate transfer medium is pressed against the recording medium while heating (the electric field may be further applied), and the intermediate transfer medium is passed between the pressure roller and the intermediate transfer medium. It can be transferred regardless of However, even this method has a problem when the toner image is transferred from the photosensitive member onto the intermediate transfer medium. When transferring from the photoreceptor to the intermediate transfer medium by an electric field, the transfer efficiency changes due to the influence of humidity,
When transferring color images at the same time, there is also a problem that the lower color has lower transfer efficiency and the color is not stable. Also,
When a toner image is transferred from a photoreceptor to an intermediate transfer medium by pressure, very fine characteristics are required for the intermediate transfer medium. That is, the toner image on the photoreceptor is
Transfer from the intermediate transfer medium to the recording medium
A 0% toner image must be transferred. The intermediate transfer medium easily adheres the toner image, but the recording medium has a contradictory property that the toner is easily released. Moreover, it is necessary to maintain such delicate properties for a long time.

[0006]

As described above, in an electrophotographic apparatus using the conventional liquid developing technique, a clear image can be recorded on any recording medium without selecting a recording medium. To From research, it has been found that an image once formed on an elastic body can be clearly transferred by applying pressure regardless of the surface properties of the recording medium. That is, if there is a method capable of directly forming a clear toner image on the elastic body, a clear image can be formed regardless of the recording medium. In addition, in the method of forming an image directly on an elastic body, there is no need for intermediate transfer, and only the property of easily releasing toner from a recording medium is required. It's easy.

As a method of directly forming a toner image on an elastic body, an ion deposition method has been devised.
In this method, air is ionized by discharging the air, and the ions are selectively attached to an insulator to form an electrostatic latent image. By developing the electrostatic latent image thus formed with a liquid toner, a toner image can be directly formed on an insulating surface. But,
In this method, it is very difficult to produce a high-resolution head of 400 dpi or more, it is difficult to form a high-contrast electrostatic latent image, and it is difficult to perform high-speed recording. Can not.

A method has also been considered in which an electrostatic latent image once formed on a photoreceptor is directly transferred to an intermediate transfer member made of an insulator, and the latent image is developed. However, there are problems that it is difficult to form a high-contrast electrostatic latent image even with this method, and that a high-definition electrostatic latent image cannot be formed due to discharge generated when the electrostatic latent image is transferred.

The present invention discloses a method for forming a high-definition electrostatic latent image on an insulating medium. This electrostatic latent image is directly developed with toner, and the insulating recording medium is formed. An object of the present invention is to provide an electrophotographic apparatus that forms a clear image regardless of the surface state or material of a recording medium by transferring a toner image to the recording medium by pressing against the recording medium. I have.

[0010]

According to a first aspect of the present invention, a photoconductor is pressed against an insulator whose surface is charged, and the press-contact portion is selectively exposed in accordance with an image, so that the charge on the insulator is exposed. An electrostatic latent image is formed on an insulator by erasing with electric charges generated in the body, the electrostatic latent image is developed with toner, and the insulator is pressed against the recording medium to form a latent image on the recording medium. This is an electrophotographic recording apparatus that transfers a developed toner image onto an insulator.

According to a second aspect of the present invention, an insulator whose surface is charged is pressed against a photoreceptor via an insulating liquid, and the pressed portion is selectively exposed in accordance with an image, whereby charges on the insulator are reduced. An electrostatic latent image is formed on the insulator by erasing the charge generated by the photoreceptor through the insulating liquid, the electrostatic latent image is developed with toner, and the insulator is pressed against the recording medium. This is an electrophotographic recording apparatus that transfers a toner image developed on an insulating material to a recording medium by doing so. In this manner, electrical contact between the image carrier and the photoconductor is ensured, and it is not necessary to press the image carrier and the photoconductor with a large pressure.

According to a third aspect of the present invention, an insulator whose surface is charged is pressed against a photoreceptor charged to the same polarity as the insulator, and the pressed portion is selectively exposed in accordance with an image, so that the insulator on the insulator is exposed. An electrostatic latent image is formed on the insulator by erasing the charge with the charge generated on the photoconductor, the electrostatic latent image is developed with toner, and the insulator is pressed against the recording medium by pressing the insulator against the recording medium. This is an electrophotographic recording apparatus that transfers a toner image developed on an insulator to a recording medium. By doing so, the potential on the photoconductor is stabilized, and a large potential difference does not occur between the photoconductor and the image carrier when the photoconductor and the image carrier are in contact with or separated from each other. Disturbance is reduced.

In this manner, a toner image can be directly developed on an arbitrary insulating medium, so that a clear image can be formed on the recording medium regardless of the material and surface condition of the recording medium. It can be formed. In addition, in the method of forming an image directly on an elastic body, there is no need for intermediate transfer, and only the property of easily releasing toner from a recording medium is required. It's easy.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.

FIG. 1 shows a first embodiment of the present invention. FIG.
FIG. 1A is an overall conceptual diagram of the first embodiment of the present application, and FIG.
(B) is a diagram illustrating a main part of the present invention. In the present invention, as shown in FIG. 1, a photoconductor (10) and an image carrier (11)
FIG. 1B is an enlarged view of the press-contact portion. . The image carrier (11) is formed by forming an insulating layer (33) on a conductor drum (32) connected to a metal ground potential or the like. First, the surface of the image carrier is increased to about +800 V by a charger (12). The entire surface is uniformly charged (34). A portion where the image carrier (11) and the photoconductor (10) are pressed against each other is exposed (13) according to an image by a light emitting element such as a laser or an LED. The photoreceptor used at this time is ideally a transparent photoreceptor, and exposes (13) the pressure contact portion between the photoreceptor (10) and the image carrier (11) from the back side of the photoreceptor. As shown in FIG. 1, the optical path may be changed by a mirror (14) or the like. The charge (34) of the image carrier (11) pressed against the photoconductor (10) is erased by the carrier (35) generated in the exposed photoconductive layer (31) of the photoconductor (10). Thus, on the image carrier (11), the electrostatic latent image (3
6) is formed. The electrostatic latent image formed at this time (36)
Has a potential of about +800 V in the non-exposed part and about +200 V in the exposed part. The developing device (15) stores a positively charged toner, and is visualized by developing the electrostatic latent image with the developing device (15) to which a developing bias of about +500 V is applied. Positively charged toner adheres to the portion where the charge has been erased by exposure, and a toner image is formed.
Lastly, after the electric adhesion is reduced by the static elimination charger (18), the image carrier (11) is pressed against the pressure roller (17) via the recording medium (16) to record the image. Transfer of the toner image to the medium (16) is realized. In this transfer, almost 100% of the toner image is transferred, but the toner slightly remaining on the image carrier (11) is removed by the cleaner (1).
9), the image carrier (11) is used again.

By forming an electrostatic latent image using the photoreceptor (10) in this manner, a high contrast that cannot be obtained by an ion deposition or electrostatic image transfer system, which is completely the same as that of a conventional laser printer, is obtained. , A high-definition electrostatic latent image can be obtained. By developing the high-definition electrostatic latent image thus formed, a high-definition toner image can be formed on the insulating image carrier (11). The toner image thus formed is transferred to the recording medium (1) by one pressure transfer.
6), an image without deterioration is formed on the recording medium (16).

The image carrier (11) or the pressure roller (1)
If at least one of 7) is heated, the transfer efficiency to the recording medium (16) increases. In addition, the image carrier (1
Even when an electric field for attracting toner (in the case of positively charged toner, the pressure roller side is made negative with respect to the image carrier) is applied between 1) and the pressure roller (17), the transfer efficiency is improved. Has the effect of increasing.

The developing device used in the electrophotographic recording apparatus of the present invention may be a dry developing device or a wet developing device using a wet toner. However, in the case of a wet developing device, the developing device (15) in FIG. 1 can be realized by applying a voltage to a squeeze roller for squeezing excess toner and a fog removing roller for applying an electric field for removing fog (a squeeze roller). And a set roller for firmly electrically pressing the developed toner against the image carrier.

FIG. 2 shows a second embodiment of the present invention. Parts having the same functions as those in the first embodiment of the present application are given the same numerals. The image carrier (11) has an insulating layer formed on a drum connected to a metal ground potential or the like. First, the surface is uniformly charged up to about +800 V by a charger (12). . A portion where the image carrier (11) and the photoconductor (10) are pressed against each other is exposed according to an image by a laser (13) or the like. The photoreceptor used at this time is ideally a transparent photoreceptor, and the pressure contact portion between the photoreceptor (10) and the image carrier (11) is subjected to laser exposure (13) from the back of the photoreceptor. Since the solvent applying device (20) containing the insulating solvent applies the insulating solvent thinly to the surface of the image carrier (11), the photoconductor (10) and the image carrier (11) are They are pressed together with the insulating solvent interposed therebetween. It is desirable that the resistance value of the insulating solvent is less than about 10 ¹⁵ Ωcm of the resistance of the photoconductor in the dark. Further, if the resistance value of the insulating solvent is too small, the electrostatic latent image may be erased, so a resistance value of 10 ⁸ Ωcm or more is necessary. The coating layer of the insulating solvent is very thin and is about 1 μm to 5 μm. The carrier generated in the exposed portion of the photoconductor (10) is transferred to the photoconductor (10).
Carrier (11) pressed against the body via an insulating solvent
As a result, an electrostatic latent image is formed on the image carrier (11). This electrostatic latent image is developed (15)
The image carrier (11) is pressed against the pressure roller (17) via the recording medium (16) after the image carrier is visualized by developing the toner and the electric adhesion is reduced by the static elimination charger (18). Thus, transfer of the toner image to the recording medium (16) is realized. Although almost 100% of the toner image is transferred by this transfer, the toner slightly remaining on the image carrier (11) is removed by the cleaner (19), and the image carrier (1) is removed.
1) is used again.

Compared with the first embodiment, the use of the insulating solvent can ensure the contact between the photosensitive member (10) and the image carrier (11). In order for the carrier generated in the photoreceptor (10) to erase the charge of the image carrier (11), it is necessary that the two are surely in contact with each other. Need to be kept. By making the contact through the insulating medium as in the second embodiment, it is not necessary to press the contact with a large force.

By forming an electrostatic latent image using the photoreceptor (10) in this manner, a high contrast that cannot be obtained by the ion deposition or electrostatic image transfer method, which is completely the same as that of a conventional laser printer, is obtained. , A high-definition electrostatic latent image can be obtained. By developing the high-definition electrostatic latent image thus formed, a high-definition toner image can be formed on the insulating image carrier (11). The toner image thus formed is transferred to the recording medium (1) by one pressure transfer.
6), an image without deterioration is formed on the recording medium (16).

When at least one of the image carrier (11) and the pressure roller 17 is heated, the recording medium (1) is heated.
The transfer efficiency to 6) increases. Further, even if an electric field for attracting toner is applied between the image carrier (11) and the pressure roller 17, there is an effect of increasing the transfer efficiency.

When the toner to be used is a liquid developing toner in particular, the solvent coating device (20) is not required. Since the liquid developer is obtained by putting a chargeable coloring agent in an insulating solvent, the image carrier (11) is passed through a developing device (15) once before recording, so that an image is formed. This is because a thin layer of the insulating solvent can be formed on the surface of the carrier (11).

FIG. 3 shows a third embodiment of the present invention. Portions having the same functions as those of the first and second embodiments are denoted by the same numerals. The photoconductor (10) and the image carrier (11) are pressed against each other in the same manner as in the above-described embodiment. The image carrier (11) has an insulating layer formed on a drum connected to a metal ground potential or the like.
The entire surface is uniformly charged up to about 00V. This embodiment is characterized in that the surface of the photoconductor (10) is also charged by the charger (12 '). After the surface of the photoconductor (10) is charged in advance to about +800 V, which is the same as that of the image carrier (11), the photoconductor (10) and the image carrier (11) are pressed against each other. The pressed portion is exposed according to an image by a laser (13) or the like. The photoreceptor used at this time is
A transparent photoreceptor is ideal, and the photoreceptor (10) and the image carrier (1)
The pressure contact portion of 1) is subjected to laser exposure (13) from the back side of the photoreceptor. The carrier generated in the exposed portion of the photoreceptor (10) has a charge on the surface of the photoreceptor (10) and a charge on the image carrier (11) pressed against the photoreceptor (10). By erasing the photoconductor (10) and the image carrier (1).
1) The same electrostatic latent image is formed on it. The electrostatic latent image is visualized by developing it with a developing device (15), and after reducing the electrical adhesion with a static elimination charger (18), the image carrier (11) is removed from the recording medium (16). Pressure roller (1
By pressing against 7), the transfer of the toner image to the recording medium (16) is realized. Although almost 100% of the toner image is transferred by this transfer, the toner slightly remaining on the image carrier (11) is removed by the cleaner (19).
The image carrier (11) is used again.

Since the surface of the photosensitive member (10) is also charged by the charger (12 '), the entire surface of the photosensitive member (10) can always be kept at a constant potential. The variation in the potential of the electrostatic latent image formed on the image carrier (11) is reduced due to the difference between the two. Also, the photoconductor (10) and the image carrier (11) have the same surface potential.
Are pressed against each other, so that it is possible to prevent a discharge that occurs when the distance is reduced during the pressing. Further, even when the photoconductor (10) and the image carrier (11) are separated from each other, since an electrostatic latent image having the same potential is formed on both, no extra discharge occurs here. Such an effect is further enhanced when the press contact portion is wet with an insulating liquid as described in the second embodiment.

By forming an electrostatic latent image using the photoreceptor (10) in this manner, a high contrast that cannot be obtained by the ion deposition or electrostatic image transfer method, which is completely the same as that of a conventional laser printer, is obtained. , A high-definition electrostatic latent image can be obtained. By developing the high-definition electrostatic latent image thus formed, a high-definition toner image can be formed on the insulating image carrier (11). Further, the formed toner image is transferred to the recording medium (16) by one pressure transfer, so that an image without deterioration is formed on the recording medium (16).

FIG. 4 shows a fourth embodiment of the present invention. The embodiments described so far are all examples in which single-color printing is performed. Hereinafter, embodiments in which color printing is performed will be described. In the case of a color recording apparatus, a charger (12-1) for charging the image carrier, a photoconductor (10), a charger (12'-1) for charging the photoconductor, and an exposure unit (13-1) And the single-color unit of the developing device (15-1) is yellow (Y),
This can be realized by arranging three or four colors by the number of colors of magenta (M), cyan (C), and black (Bl). FIG. 4 shows an example of four colors of Y, M, C and Bl.

In this example, a belt-shaped image carrier (21) is used as an insulating image carrier. Of course, there is no problem with the drum-shaped image carrier as described above. The belt-shaped image carrier (21) is driven by a driving device (not shown) as shown by the arrow in the figure. First, the surface of the belt-shaped image carrier (21) is charged by +8 with the charger (12-1).
It is uniformly charged to about 00V. This belt-shaped image carrier (2
In 1), the photoreceptor (10-1) uniformly charged to about +800 V by the charger (12'-1) is pressed against the same. This press-contact portion is exposed by an exposure device (13-1) such as a laser or an LED to form an electrostatic latent image on the surface of the belt-shaped image carrier. Since the electrostatic latent image formed at this time is image data of the first color, for example, Y, the data of, for example, Y is developed by the developing device (15-1) for the first color. The belt-shaped image carrier (21) on which the first color toner image has been formed is then shifted to the second color recording. That is, after the first color toner is developed by the charger (12-2), it is charged again to about + 800V. A photoconductor (10-2) uniformly charged to about +800 V by the charger (12'-2) is pressed against the belt-shaped image carrier (21). A laser or L
Exposure is performed by an exposure device (13-2) such as an ED, and an electrostatic latent image is formed on the surface of the belt-shaped image carrier (21) on which the Y toner image is formed. Since the electrostatic latent image formed at this time is the image data of the second color, for example, M, the developing device (1
In 5-2), for example, M data is developed on the Y toner of the first color. Similarly, the toner images of the third color (for example, M) and the fourth color (for example, Bl) are transferred to the belt-shaped image carrier (2).
A color image is formed on the belt-shaped image carrier (21) by forming the color image on the image carrier 1). The color image formed in this manner is weakened by a static elimination charger, and then pressed against a recording medium (16) by a pressure roller (17, 17 '), transferred under pressure and transferred to a recording medium. A color image is formed on the recording medium. Recording medium (16)
After the image is transferred to the belt-like image carrier (21)
Surface is cleaned with a cleaner (19),
It is used again for recording a color image.

As described above, when a color image is continuously formed by superimposing a color image on an image carrier, a liquid developer is ideal as a developer. The photoreceptor is pressed against the toner image of the previous color in order to form an electrostatic latent image of the next color. This is because the image of the previous color formed with the normal dry toner is disturbed by the pressing. When a liquid toner is used, the thickness of the toner layer of the previous color is as thin as about 1 μm to 5 μm, and as described in the second embodiment, when a liquid toner is used, This is because the charge is erased and an electrostatic latent image is formed, so that it is not necessary to apply a large pressure to make contact.

In the embodiment shown in FIG. 4, the transfer efficiency can be increased by heating the press-contact portion between the belt-shaped image carrier (21) and the recording medium (16) at the image transfer section. It is. For example, it can be realized by heating at least one of the pressure rollers (17, 17 '). Although the formation order of the four colors has been described in the order of Y, M, C, and B1, the order is not limited to this order.

FIG. 5 shows an embodiment relating to still another color image forming method. In the embodiment of FIG. 4, a method is shown in which, after the color images are superimposed on the image carrier, the color images are collectively transferred to the recording medium. In the method shown in FIG. 5, a tandem method in which an image for each color formed on an image carrier is continuously transferred onto a recording medium will be described. First, an image carrier that forms an image of the first color (11-1)
Is charged to +800 V by the charger (12-1). At the same time, the entire surface of the photoconductor (10-1) is uniformly charged by the charger (12'-1).
The photoconductor (10-1) and the image carrier (11-1) are pressed against each other. At the same time, based on the image data of the first color, the press-contact portion is exposed to light (13
-1) is performed. The charge generated on the surface of the photoconductor (10-1) and the surface of the image carrier (11-1) is erased by the carrier generated in the exposed portion of the photoconductor (10-1), and the image carrier (11-
An electrostatic latent image of the first color is formed on 1). This electrostatic latent image is developed by the developing device (15-1) containing the first color toner, and the image carrier (11-) is discharged by the static eliminator (18-1).
After the adhesive force to 1) is reduced, the recording medium (16)
To the recording medium (1-1) from the image carrier (11-1).
It is transferred to 6). Image carrier after transfer (11-
After the residual toner is cleaned by the cleaner (19-1), the surface of 1) is charged again by the charger (12-1) and used for the next recording cycle.

While transferring the first color to the recording medium (16), the recording medium (16) is driven by the conveyor belt (22) in the direction of the arrow, and is conveyed to the second color transfer position. The second color toner image formed in the same manner as the first color is formed by the second pressure roller (17-2) by a signal delayed by the time required to move from the first color transfer position to the second color transfer position. The image is pressed and transferred onto the recording medium (16) on which the first color image has been formed. Similarly, four color toner images are successively superimposed on the recording medium (16) to form a color image.

FIG. 6 shows a modification of the tandem type color recording system shown in FIG. The difference from FIG. 5 is that
This means that one belt-shaped photoconductor (23) is used without using individual photoconductors corresponding to each color. By driving such a belt-shaped photoconductor (23) in the direction shown by the arrow in the figure, the same operation as using an individual photoconductor is performed. First color charger (12'-
By 1), the portion of the photoreceptor belt (23) used for the first color exposure (13-1) is charged over the entire surface. After the first color exposure (13-1) is completed, the image carrier (11-
When the electrostatic latent image is formed on 1), the photosensitive belt (23)
The portion used for the first color exposure is conveyed as indicated by the arrow, and then used for the fourth color exposure. Even if the belt-shaped photoconductor (23) is driven endlessly in this manner, the chargers (12'-1, 12'-2, 12'-) are exposed before the exposure of each color.
By performing uniform charging in (3, 12'-4), the same operation as in the embodiment of FIG. 5 using individual photoconductors is achieved. Other operations are the same as in the example of FIG.

FIG. 7 shows an embodiment of still another color recording system. Each of the methods shown in FIGS. 4, 5, and 6 is a method that requires a stage for four colors. This is an effective method for increasing the recording speed, but tends to increase the size and cost of the apparatus. A color recording method which is designed to reduce the size and cost even if the speed is sacrificed to some extent is the method shown in FIG. In this method, first, the surface of the image carrier (11) and the surface of the photoreceptor (10) are respectively charged by the respective chargers (1).
(2, 12 '). A portion where the image carrier (11) and the photoconductor (10) are pressed against each other is exposed (13) with a laser beam or the like, and a first-color electrostatic latent image is formed on the image carrier (11). . This electrostatic latent image is stored in a developing device (1
5-1) is moved to a predetermined position and developed to form a first color toner image on the image carrier (11). The toner image is pressed and transferred to the recording medium (16) by the pressure roller (17) in a state where the electrostatic adhesion is reduced by the charge removing charger (18). Image carrier after transfer (11)
Is used in the next recording cycle after the residual toner is cleaned by the cleaner (19).

The first color image is placed on the recording medium (16).
When the recording for the page is completed, the recording medium (16) can reciprocate as indicated by an arrow, so that the recording medium (16) returns to the original position. Next, the printing operation of the second color starts. Similarly to the first color, first, the surface of the image carrier (11) and the photoconductor (1)
The surface of 0) is uniformly charged by each charger (12, 12 ′). The portion where the image carrier (11) and the photoreceptor (10) are pressed against each other is exposed (13) to the second color data using a laser beam or the like, and the second color electrostatic latent image is placed on the image carrier (11). An image is formed. This electrostatic latent image is developed by moving the second color developing unit (15-2) to a predetermined position, and a second color toner image is formed on the image carrier (11). The second color toner image is pressed against the recording medium (16) by the pressure roller (17) in a state where the electrostatic adhesion is reduced by the charge removing charger (18), and the first color image is formed. And the second color toner image is transferred. The transferred image carrier (11) is used in the next recording cycle after the residual toner is cleaned by the cleaner (19). By repeating such an operation four times, a full-color image can be formed on the recording medium. However, in this case, it is necessary to perform one color printing operation four times serially in order to print one page of color image, so that the printing speed is almost 1/4 that of the tandem type. But,
Since the device configuration is simplified, it is characterized by miniaturization and reduction in size.

Although the example shown in FIG. 7 shows an example in which the recording medium is reciprocated four times to overlap the color image, the recording medium is adhered to the roller using a large pressure roller or the like. There is also a method of performing color superposition by rotating.

When a liquid toner is used for the developer, a color image can be recorded by a method as shown in FIG. In this method, first, the surface of the image carrier (11) and the surface of the photoreceptor (10) are respectively charged by the chargers (12,
At 12 '), it is uniformly charged. The portion where the image carrier (11) and the photoconductor (10) are pressed against each other is exposed to laser light or the like (1).
3) Then, a first-color electrostatic latent image is formed on the image carrier (11). This electrostatic latent image is stored in the first color developing unit (15-
1) is moved to a predetermined position and developed, and a first color toner image is formed on the image carrier (11).

When one page of the first color image is recorded on the image carrier (11), the printing operation of the second color starts.
As in the case of the first color, first, the surface of the image carrier (11) and the surface of the photoconductor (10) are connected to the respective chargers (12, 12 ').
Is charged uniformly. Image carrier (11) and photoreceptor (10)
Is exposed to the second color data with laser light or the like (13), and a second color electrostatic latent image is formed on the image carrier (11) on which the first color toner image is developed. You. This electrostatic latent image is developed by moving the developing device (15-2) for the second color to a predetermined position and forming the toner image of the second color on the image carrier (11). Formed on top. The same operation is repeated four times to form four color images on the image carrier (11). When a four-color superimposed color image is formed, the charge eliminator (18) is operated to reduce the electrostatic adhesive force, and the recording medium (16) is pressed against the recording medium (16) by a pressure roller (17). Is done.
The four color images are collectively transferred to the recording medium (16). The image carrier (11) after the transfer is used in the next recording cycle after the cleaner (19) comes into contact with the image carrier (11) as shown by an arrow and cleans the residual toner. In this case, since a four-color image is formed on the image carrier (11) by Image on Image, there is an advantage that the transfer to the recording medium (16) is performed only once. When liquid toner is used, the reason why such an image-on-image on the image carrier is possible is that, as described in the second embodiment, the photoconductor and the image carrier are interposed via the solvent. When in contact, the solvent carries the carrier to erase the electrostatic charge on the image carrier.
In this case, there is no need to press the image carrier with the photoconductor with a large force, so that the toner image previously formed on the image carrier is not destroyed by the subsequent operation.

[0039]

As described above, according to the present invention,
Since it is possible to form a high-definition, high-contrast electrostatic latent image directly on an insulating image carrier, the use of an insulating elastic body for the image carrier allows the It is possible to provide an electrophotographic recording apparatus capable of forming a high-definition image regardless of the surface shape and the material. As a method of forming an electrostatic latent image on an insulative image carrier, the pressed portion is exposed with a laser or the like in a state where the image carrier charged by a charger and the photoreceptor are pressed. Carriers generated in the exposed photosensitive layer erase charges on the image carrier to form an electrostatic latent image. Therefore, it is possible to form a high-definition and high-contrast electrostatic latent image, just like a laser printer or an LED printer. Also, in the method of forming an image directly on an elastic body, there is no need for intermediate transfer, so that only the property of easily releasing toner from the recording medium is sufficient.
Maintaining material selectivity and performance is much easier.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating an outline and main parts of an electrophotographic recording apparatus according to a first invention of the present application.

FIG. 2 is an explanatory diagram of an electrophotographic recording apparatus according to a second invention of the present application.

FIG. 3 is an explanatory diagram of an electrophotographic recording apparatus according to a third invention of the present application.

FIG. 4 is an explanatory view of a color electrophotographic recording apparatus according to a fourth invention of the present application.

FIG. 5 is an explanatory view of another color electrophotographic recording apparatus according to the fifth invention of the present application.

FIG. 6 is a diagram illustrating a modification of the color electrophotographic recording apparatus according to the fifth invention of the present application.

FIG. 7 is an explanatory diagram of a simplified color electrophotographic recording apparatus according to a sixth invention of the present application.

FIG. 8 is a diagram illustrating a modification of the color electrophotographic recording apparatus according to the sixth invention of the present application.

FIG. 9 is a diagram illustrating a conventional example.

DESCRIPTION OF SYMBOLS 10 Photoconductor 11 Image carrier 12, 12 ′ Charger 13 Exposure 14 Mirror 15 Developing device 16 Recording medium 17 Pressure roller 18 Static elimination charger 19 Cleaner 20 Solvent coating device 21 Belt-shaped image carrier 22 Conveyor belt 23 Belt-shaped photoconductor

Claims (5)

[Claims] 1. An insulating substrate, comprising: an insulating substrate; means for charging the insulating substrate; and a photosensitive member in contact with the insulating substrate, and means for exposing a contact position between the insulating substrate and the photosensitive member. An electrophotographic recording apparatus, comprising: means for forming an electrostatic latent image on a recording medium; means for developing the latent image; and means for transferring the developed image to a recording medium. 2. The press-contact portion between the image carrier and the photoconductor is 10 ⁸
2. The electrophotographic recording apparatus according to claim 1, wherein the electrophotographic recording apparatus is filled with an insulating solvent having a resistance of from ¹⁰ Ωcm to 10 ¹⁵ Ωcm. 3. The electrophotographic recording device according to claim 1, wherein the photosensitive member is uniformly charged to the same polarity as the uniformly charged image carrier. apparatus. 4. The method according to claim 1, wherein the insulative substrate is made of an elastic insulator, and the transfer means is of a type to which at least pressure or heat is applied together with the pressure. An electrophotographic recording apparatus according to claim 3. 5. The method according to claim 1, wherein the insulating substrate is made of an elastic insulator, and the photoreceptor is in the form of a roller or a belt which can be used repeatedly. An electrophotographic recording apparatus according to claim 3 or 4.