JPS597104B2 - electrophotography - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention uses a photosensitive screen (hereinafter referred to as a screen) having a large number of fine apertures and at least a conductive member and a photoconductive member, and uses a photosensitive screen (hereinafter referred to as a screen) to attach an original to a chargeable member. The present invention relates to an electrophotographic device that creates a copy of an image.

Further, the screen used in the present invention uses a conductive member, a photoconductive member, sometimes an insulating member, etc., has a large number of fine openings, and is constructed of several layers of the above-mentioned members.

By imparting photosensitivity to the screen through charging or the like and irradiating it with the optical image of the original, a primary electrostatic latent image is formed in accordance with the image of the original, and the pattern of the primary electrostatic latent image on the screen is Therefore, the passage of the ion stream is controlled by the screen opening, and a secondary electrostatic latent image is formed on the chargeable member.
The above-mentioned electrophotographic technique is known from Japanese Patent Publication No. 15276/1983 and is generally referred to as an electrophotographic method using ion flow control. The secondary electrostatic latent image ι9 formed as described above on the chargeable member is image-fixed and utilized via a conventional developing device or fixing device. In the electrophotographic method described above, the screen used may be formed into a drum shape, for example, in an electrophotographic apparatus aimed at high speed.

When the screen is shaped like a drum as described above, it is necessary to take into account the peculiarities that occur when forming a secondary electrostatic latent image on the chargeable member.

This specificity includes, for example, U.S. Pat.
In the case of electrostatic latent image transfer generally referred to as TES process described in No. 8, the latent image holding member and the chargeable member are in close contact or the maximum gap is about 50 μm, whereas This is due to the fact that in the photographic method, the gap between the screen and the chargeable member is usually about 3 mm. The principle of the present invention will be explained below using the drawings. When the screen is in the form of a drum, the relative shape relationships between the corona discharger, the screen, and the chargeable member during the formation of the secondary latent image are shown in Figures 1a, b,
Shown in c. In the figure, 1 is a portion of a screen that takes the form of a drum, 2 is a chargeable member such as insulating paper or polyethylene terephthalate film on a conductive substrate, and 3 is a chargeable member that is charged through the primary electrostatic latent image on the screen. 1 shows a corona discharger that generates a flow of corona ions that is applied to a charging member. Further, 31 of the corona discharger 3 is a corona wire, and 32 is a shield. In addition, in the figure, the gap between the screen 1 and the chargeable member 2 is enlarged from the actual size in order to facilitate understanding of the following explanation.

In the process of forming a secondary electrostatic latent image, in principle, an ion flow that is precisely controlled in accordance with the primary electrostatic latent image on the screen must reach the chargeable member.

For example, in order to carry out the above process at high speed, it is effective to increase the width of the corona discharger in the circumferential direction of the screen as shown in the figure. However, in this case, it is necessary to pay special attention to the following points. In other words, since the corona ion flow can be considered to flow almost along the lines of electric force, the formation result of the secondary electrostatic latent image Q should be determined by considering the pattern of the lines of electric force between the screen 1 and the chargeable member 2. It will be a good thing if you do. Of course, since the screen 1 and the chargeable member 2 generally move relative to each other, the time required for the corona ion flow to pass through the screen 1 assuming the above-mentioned movement is determined by the relative movement. If it is slow compared to the speed, it becomes a problem.
However, in reality, the mobility of corona ions is 10-47TI.
/V-SeC, and if the electric field between the screen 1 and the chargeable member 2 is 3KV/3mm-106V/m, the flow velocity of corona ions will be about 102m/Sec.

That is, since the relative speed between the screen 1 and the chargeable member 2 and the corona discharger 3 can be considered to be normally 1 m/Sec at the maximum, the relative velocity of the screen 1 and the chargeable member with respect to the speed of the corona ion flow can be ignored. FIG. 1a shows a drum-shaped screen 1 in which the chargeable member 2 is horizontal.

Electric lines of force (indicated by solid lines in the figure) can be drawn at equal intervals on the screen 1, but on the chargeable member 2, the intervals widen as they move away from the screen 1 and the closest part. That is, the spread of the electric lines of force described above is undesirable because it means that the secondary electrostatic latent image becomes blurred. In contrast to the above example, in FIG. 1B, the chargeable member 2 has its center point on the same side as the screen 1 and is arranged at equal intervals from the screen 1.

In this case, the lines of electric force are equally spaced on the screen 1, as shown by the solid lines, and are equally spaced when reaching the chargeable member 2.

That is, the corona ion flow forms a secondary electrostatic latent image on the chargeable member 2, which enlarges the primary electrostatic latent image on the screen 1 by the radius ratio of the screen. Note that the above-mentioned problem of magnification can be solved by correcting the optical system for irradiating the image when forming the primary electrostatic latent image. Further, in the case of the configuration as shown in FIG. 1b, since the width of the corona discharger 3 can be increased in the circumferential direction of the screen 1, the formation speed of the secondary electrostatic latent image can be further increased. It should be noted that transporting the chargeable member 2 as shown in FIG. 1b above has mechanical difficulties. A solution to this difficulty is shown in FIG. 1c.

FIG. 1c shows the center point of the drum-shaped screen 1 and the center point of the arc of the chargeable member 2 conveyed in an arc.
Each has one on the opposite side.

Further, the screen 1 and the chargeable member 2 are illustrated as having the same radius length. In this case, lines of electric force shown by solid lines between the screen 1 and the chargeable member 2 that can be drawn at equal intervals on the screen 1 can also be drawn at equal intervals on the chargeable member 2. That is, in accordance with the primary electrostatic latent image on the screen 1, the image on the chargeable member 2 is not enlarged or reduced.
An electrostatic latent image is then formed. In order to actually convey the sheet-like chargeable member 2 as shown in the figure, a guide plate or a drum-shaped guide body having a predetermined curved surface is placed on the screen 1 in advance as a guide member.
The chargeable member 2 may be provided near the guide member and the chargeable member 2 may be conveyed along the guide member.

Note that when the guide member takes the form of a drum with the same radius as the screen 1, it is sufficient to rotate the drum-shaped screen 1 and the guide member at the same circumferential speed and in opposite directions, and the drive device is also simplified.

As is clear from the above, in the electrophotographic method using a screen, the operating speed of the device is increased by forming the screen into a drum shape, and in this case, the arc directions of both the screen and the charging surface of the chargeable member are opposite to each other. It is preferable to arrange them in a certain manner.

This allows a good secondary electrostatic latent image to be formed on the chargeable member even when the diameter of the drum-shaped screen is reduced, for example, for the purpose of downsizing the device. In particular, if the radius of the drum-shaped screen at the secondary electrostatic latent image forming position is the same as the radius of the surface of the chargeable member, it is possible to obtain a secondary electrostatic latent image in good condition without distortion. Become. Figure 2 is the same as above.
Fig. 3 shows an embodiment of the apparatus of the example of Fig. c;

The device shown in FIG. 2 is applied to an electrophotographic copying device. Before explaining the embodiments, FIG. 3 shows an example of a screen suitable for the device according to the present invention, and FIG. An example process will be described using the screen.

Note that the same numbers and ζ shown in each figure are used for those having the same construction and function. FIG. 3 is an enlarged cross-sectional view of the screen. In the figure, the screen 4 has a photoconductive member and an insulating member on one side so as not to close the openings around the conductive member 5, which has minute openings like a net. The photoconductive layer 6 is a photoconductive layer and the insulating layer 7 is a photoconductive layer. Further, on one side of the screen where the photoconductive member is not thickly coated, the conductive member 5 is constructed so as to be exposed to some extent as shown in the figure. Next, according to FIG. 4 a to d, the screen 4 shown in FIG.
The process of forming a secondary electrostatic latent image will be explained below.

The outline of this process is the pre-charging process [Figure a], the discharging process carried out simultaneously or sequentially with image irradiation [Figure B], the entire surface irradiation process carried out as necessary [Figure C], and the secondary electrostatic latent process carried out on the chargeable member. This method includes a step of forming an image [Fig. d], and will be explained in more detail below. FIG. 4a shows a pre-charging process, and shows an eyelid in which a semiconductor made of Se or an alloy thereof, which uses holes as the main carrier, is used as the material for forming the photoconductive layer 6. Therefore, in the pre-charging, the insulating material 7 is uniformly charged with negative polarity by a charging means such as a corona discharger. Note that the side on which the conductive member is exposed is referred to as the A side, and the side opposite to the A side is referred to as the B side. Due to the above-mentioned charging, a layer of positive charges is formed at the interface between the photoconductive layer 6 and the insulating layer 7 via the conductive member 5. FIG. 4b shows an AC current in which a positive bias voltage is superimposed on the pre-charged screen 1 at the same time or sequentially as the image is irradiated using light rays, radiation, etc. that react according to the characteristics of the photoconductive material. The results are shown in which a discharge was performed using a corona discharger or the like so that the surface potential of the insulating layer 7 became approximately positive.

Through the above steps, an electrostatic latent image is formed on the surface of the screen, although the contrast is low, but it follows the brightness and darkness of the original.

Note that arrows in the figure indicate reflected light from bright areas of the original. Next figure 4c
shows the result of uniformly exposing the entire surface of the screen 4 having the latent image.

Due to the exposure, the potential of the dark portion of the screen 4 changes to a potential proportional to the amount of charge on the surface of the insulating layer 7. In other words, if we take the dark side of the opening of the screen 4 as an example, the A
The surface potential is 0 potential, and as you go from approximately the side surface of the opening toward the B surface side, the surface potential gradually changes to a higher negative potential. Based on the change in potential, an electric field is generated in the aperture that accelerates or blocks ion flow, which will be described later. Figure 4d shows that a secondary electrostatic latent image is formed on a chargeable member such as electrostatic recording paper or a resin layer on a dried paper metal substrate by the primary electrostatic latent image formed on the screen 4 as described above. Indicates the state in which In the figure, reference numeral 9 denotes an electrode opposite the corona wire 8, and an electrostatic recording paper 10 is placed on the electrode 9. When a positive ion flow is applied to the recording paper 10 from the corona wire 8 through the screen 4, an electric field indicated by a solid line α is generated in the bright portion of the screen due to the potential changing from the B side to the A side.

The electric field prevents the ion stream from passing through the opening, and the ion stream flows into the conductive member 5. On the other hand, in the dark part of the screen, the solid line β is caused by the potential changing from the A side to the B side.
An electric field shown by is generated. Due to the electric field, the ion flow reaches the recording paper 10 in a state where the charges in the opening are hardly canceled out.

The secondary electrostatic latent image formed on the recording paper 10 is developed using a conventional developer. As mentioned above, conductive members, photoconductive layers,
A similar process can be applied to a screen having an insulating layer, and other types of screens can also be applied to the embodiment apparatus described below. In the figure, E1 indicates a power source for the corona wire 8, and E2 indicates a power source for bias potential applied to the screen and the opposing viewing electrode 9. In the electrophotographic copying apparatus shown in FIG.
2, and the original image of the original 11 is reflected by the reflectors 13, 1.
4. An image is formed via a lens system 15 and a reflector 16 on a drum-shaped screen 17 that rotates in the direction of the arrow.

In the figure, 29 is a pre-exposure lamp for giving a uniform light history to the photosensitive screen; 18 is a corona discharger for pre-charging; 19
AC voltage is applied by a corona discharger for static elimination, and the back of the shield plate is optically opened for image irradiation.

20 is a lamp for further increasing the contrast of the electrostatic latent image on the screen 17, 25 is a corona discharger for forming a secondary electrostatic latent image, and 31 is a lamp for scattering the light from the lamp 20 to the image irradiation position. It is a light absorbing plate that prevents

Here, an electrostatic latent image according to the image of the document 11 is formed on the screen 17 by the primary electrostatic latent image process, and the screen 17 having the primary electrostatic latent image forms a secondary electrostatic latent image. Suppose that it rotates to this position. By this time, the recording paper 30 has been conveyed from the storage capacity set 21 of the recording paper 30 via the static eliminator 23 by the feed roller 22 to the drum-shaped recording paper holder 24 which is a guiding member for the electrostatic recording paper. . Note that the static eliminator 23 has a cylindrical conductive mesh 231 and a corona discharge wire 232, and also serves as a conveyor. Further, the holding body 24 applies a suction effect using atmospheric pressure or electrostatic force, and if necessary, a corona discharger 25 or a screen 17 may be used.
A bias voltage can be applied from the potential relationship.

A corona ion flow is applied from the corona discharger 25 to the recording paper 30 conveyed as described above via the primary electrostatic latent image of the lean 17, thereby forming a secondary electrostatic latent image. The recording paper on which the secondary electrostatic latent image has been formed follows the path shown by the dashed line, and is first separated from the holder 24 by the separation claw 31, and the electrostatic latent image is developed into an image by the developer 26 using toner. Let's do it.

Afterwards, the recording paper is heated and fixed by the heat roller 27, and then transported to the outside of the apparatus by the transport bell port 6.

The above series of devices is operated by an electrically and mechanically controlled drive source, drive transmission means, etc. (not shown). Furthermore, when the screen 17 adopts the illustrated configuration, since the surface is covered with an insulating material, attenuation of the primary electrostatic latent image is small, so that the same latent image can be used multiple times.
An electrostatic latent image may then be formed. The primary electrostatic latent image that is no longer needed is erased by the next latent image forming process, and the screen 17 is used repeatedly. Of course, screens 17 having other configurations can also be used.Furthermore, the secondary electrostatic latent image is formed on a drum-shaped insulating member that is used repeatedly, and this is developed with toner or the like, and later a visible image is formed by the development. It may also be configured such that it is transferred onto plain paper. As explained above, if the chargeable member is flat with respect to the drum-shaped screen as shown in FIG. 1A, it is inevitable that the secondary electrostatic latent image will be blurred.

In addition, when there is a chargeable member on one circumference having the same center as the screen as shown in Fig. 1b, the secondary electrostatic latent image becomes larger than the primary one, and on the other hand, the transport of the chargeable member becomes difficult. In contrast to the above example, when the screen and the chargeable member face each other in an arc with their centers on opposite sides, as shown in Figure 1c, a highly accurate secondary electrostatic latent image is formed without blur. Furthermore, the shape of the corona discharger allows for faster secondary electrostatic latent image formation, and by reducing the diameter of the drum-shaped screen, the device can be made smaller.

[Brief explanation of drawings]

Figures 1A and b are explanatory diagrams showing the state of ion flow passage control when changing the radius of the screen and the chargeable member, Figure 1c
is an explanatory diagram showing the passage control state of the ion flow according to the present invention,
FIG. 2 is a cross-sectional view of the main part of the device showing an embodiment of the device having a secondary electrostatic latent image forming mechanism according to the present invention, and FIG.
FIG. 4 is an explanatory diagram of the structure of the screen used in the apparatus shown in FIG. 4, and FIG. 4 is an explanatory diagram of an exemplary process of forming an electrostatic latent image using the screen of FIG. 3. In the figure, 1... Screen, 2...
・Chargeable member, 3...Corona discharger, 4...
... Screen, 5 ... Conductive member, 6 ...
...Photoconductive layer, 7...Insulating layer, 10...
...word? Kanto, 11...Manuscript, 17...
・Drum-shaped screen 18, 19... Corona discharger, 20... Lamp, 24...
Recording paper holder, 26...Developer, 30...
··Recording paper.

Claims (1)

[Claims] 1. In an electrophotographic device that forms a secondary electrostatic latent image on a chargeable member by controlling the passage of an ion flow according to a primary electrostatic latent image formed on a photosensitive screen having a large number of fine apertures. , a photosensitive screen that moves in an arc at a position where the passage of the ion flow is controlled, and a chargeable member holder that holds and conveys a chargeable member that has the same radius as the screen at the ion flow control position; and a corona discharger for generating a controlled ion flow, located relative to the screen at the ion flow control position.