JPS6348340B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electrophotographic method using a screen photoreceptor having a large number of fine apertures. Using a screen photoreceptor, electrons modulate the corona ion flow based on the primary latent image, which is an electrostatic image, formed on the screen, and form a secondary latent image, which is also an electrostatic image, on the recording member. Various photographic methods are known. In this electrophotographic method, secondary latent images can be formed many times from a single primary latent image formed on a screen photoreceptor, and therefore many copies can be made from one image exposure. There are advantages that can be obtained. However, the number of copies obtained from the primary latent image formed on the screen photoreceptor is only 1 if the screen photoreceptor has poor charge retention.
It is dominated by the attenuation of the next latent image and has a finite value. It also has a large number of fine openings as shown in Japanese Patent Application Laid-open No. 50-19455 and Japanese Patent Application Laid-open No. 51-314.
When using a photoreceptor screen with a cross-sectional shape that basically consists of a photoconductive layer provided on a conductive substrate and a surface insulating layer, a primary latent image is formed on the insulating layer. Since the latent image charge decays very little and there is a conductive member on the modulating corona source side, excessive or unnecessary modulating corona will flow away from the conductive member during modulation, adversely affecting the primary latent image. Although the effect is small, a small amount may go around the screen photoreceptor and cause damage to the 1st layer on the screen photoreceptor.
The subsequent latent image is gradually canceled out, which limits the number of copies that can be repeated. Conventionally, in order to increase the number of copies, research has been conducted on methods to control the amount of modulating corona ion flow in response to the attenuation of the primary latent image potential and the decrease in modulation ability due to the influence of the modulating corona. As the amount of the corona ion flow increases, the modulation ability due to the influence of the modulating corona will decrease significantly, and eventually adjustment will become impossible. Therefore, in the present invention, in addition to forming a secondary latent image, a corona charger and a counter electrode are provided via the screen photoreceptor, and by controlling the distance to the screen photoreceptor and the electric field, the number of copies can be repeatedly made. The main purpose is to provide an electrophotographic method that dramatically increases the In the electrophotographic method according to the present invention, a corona discharger and a counter electrode are provided separately from a corona discharger and a counter electrode for forming a secondary latent image, sandwiching a screen photoreceptor between the counter electrode and a screen for forming a secondary latent image. Keep the distance from the photoconductor to 2 mm or less, and reduce the bias electric field between them.
1.2 KV/mm or less, and the distance between the counter electrode provided separately from the one for forming the secondary latent image and the screen photosensitive member is 2 to 6 mm, and the bias electric field between the two is set to 1.2 KV/mm or less.
It is characterized by being in the range of 1.5 to 2.5 KV/mm. The present invention will be described in detail below with reference to the drawings. FIG. 1 is a sectional view showing the structure of an example of a screen photoreceptor used in the present invention. A screen photoreceptor 1 shown in FIG. 1 has a photoconductive layer 3 provided on a conductive substrate 2 having a large number of openings, and an insulating layer 4 formed on the photoconductive layer. 2 to 5 show an example of the process of forming primary and secondary latent images by electrophotography according to the present invention. Figure 2 shows the primary voltage application process performed on the screen photoreceptor, Figure 3 shows the image irradiation and secondary voltage application process, and Figure 4 shows the entire surface irradiation process. FIG. 5 shows a secondary electrostatic latent image forming step performed by modulating the ion flow using the electrostatic latent image. FIG. 2 shows the primary voltage application step, and shows a state in which the screen photoreceptor 1 is uniformly charged with positive (+) polarity by a corona discharger 5 as a voltage application means.
Due to the above-mentioned charging, the surface of the insulating layer 4 is charged with positive polarity, and due to this charging, a negative-polarity charge layer having the opposite polarity to the above-mentioned charging is formed in the vicinity of the insulating layer 4 of the photoconductive layer 3. . Note that if the interface between the photoconductive layer 3 and the conductive substrate 2 and the photoconductive layer have rectifying properties such that majority carriers are injected but minority carriers are not injected, even in dark areas,
By injection, it is possible to form a charge layer in the vicinity of the insulating layer 4 in the photoconductive layer 3 as described above. For those that do not have the above-mentioned rectifying properties or that do not form a charge layer as described above by applying a primary voltage, charging is performed such as charging the insulating layer in a bright area as described in U.S. Pat. No. 2,955,938. sell. FIG. 3 shows the results of simultaneously performing image irradiation and a secondary voltage application process on the screen photoreceptor 1 that has undergone the above-mentioned primary voltage application process. Note that 6 in the figure is an original image, the D side shows a dark part, the L side shows a bright part, and an arrow 7 shows light from a light source (not shown). and 8
is a corona discharger for applying a secondary voltage, and in the figure, corona discharge from a corona wire to which a DC voltage of negative (-) polarity is applied reverses the polarity so that the surface potential of the insulating layer 4 becomes negative. It is electrically charged. When the surface potential of the insulating layer 4 is made negative as described above, the substance of the photoconductive layer 3 becomes conductive on the bright side L due to image irradiation, and as a result, the surface potential of the insulating layer 4 becomes negative. However, on the dark side D, because of the negative charge layer existing on the insulating layer 4 side of the photoconductive layer 3, the charge on the surface of the insulating layer 4 remains positive. Considering the rate of change in polarity of the potential on the insulating layer 4 of the screen 1 in the above process, the part of the insulating layer facing the corona discharger 8 (front side) changes fastest, and the part facing the corona discharger 8 changes fastest. The substantially side surface forming the opening changes later. Therefore,
In the image irradiation section, the potential on the side surface where the conductive substrate 2 is exposed is the potential of the conductive substrate 2, and the potential gradually increases from the back side to the front side. Figure 4 shows the results of uniform exposure as a whole-surface irradiation process on the entire surface of the screen 1 that has undergone the image irradiation and secondary voltage application processes. shows. Due to this entire surface irradiation, the potential on the dark side D of the screen photoreceptor changes to a potential proportional to the amount of charge on the surface of the insulating layer 4. FIG. 5 shows a state in which the ion flow is modulated by the primary latent image to form a secondary latent image on the image receptor. In the figure, 10 is the corona wire of the discharger, 1
1 is a counter electrode member, and 12 is an image receptor such as a paper film which is a chargeable surface, and a secondary latent image is formed on the surface thereof. Reference numerals 13 and 14 denote power supply units that form an electric field between the corona wire and the image receptor 12 in the direction in which corona ions flow. The image receptor 12 is placed close to the side of the screen photoreceptor facing the insulating layer 4, and an ion current is applied to the image receptor 12 from a corona wire 10 placed through the screen photoreceptor. At this time, an electric field due to the primary latent image of the screen photoreceptor acts, that is, an electric field that blocks the negative ion flow shown by the solid line α acts on the bright side of the image, and an electric field that accelerates the ion flow shown as the solid line β acts on the dark side. acts. As a result, a secondary latent image is formed on the image receptor 12 in the state of a positive image of the original image. Furthermore, in addition to the secondary latent image formation described above, a corona discharger and a counter electrode member are provided via the screen photoreceptor, and the distance between the screen photoreceptor and the counter electrode member is set to 2 mm to 6 mm. The electric field between the body and the counter electrode member is 1.5KV/mm ~
By adjusting the value to a value in the range of 2.5 KV/mm and passing a corona ion stream through the screen, the number of repeated copies can be dramatically increased. To explain the present invention in more detail, it is known that when charged particles flow between two electrodes, the charged particles ionize the air, generating ionized ions. The present invention utilizes the above-mentioned development to compensate for the reduced charge due to the attenuation of the primary latent image on the screen photoreceptor or the reduced charge of the primary latent image on the screen due to the modulation corona, thereby modulating the corona of the screen. It is about how to keep the ability constant. That is,
In the dark part of the original image of the screen photoreceptor shown in FIG. 5, the corona ion flow from the corona wire 10 passes through the screen photoreceptor, ionizes the air between the screen photoreceptor and the counter electrode 11, and generates Among the ionized ions, negative ions arrive at the counter electrode 11 along with the corona ion flow from the corona wire. Further, among the generated ionized ions, positive ions move toward the screen photoreceptor side due to the electric field, and compensate for the positive charge canceled by the corona for attenuation or modulation of the primary latent image on the screen photoreceptor. On the other hand, in the portion of the screen photoreceptor corresponding to the bright area of the original image, the corona ion flow from the corona wire 10 flows into the conductive substrate 2 of the screen photoreceptor, does not pass through the screen 1, and no ionized ions are generated. Therefore, when making repeated copies, changes in the corona ion flow passing through the screen photoreceptor will occur if the attenuation of the potential is small.
The amount of positive charge A that is canceled out and reduced by the corona for attenuation or modulation of the next latent image, and the amount of positive charge B that adheres to the screen photoreceptor among the ionized cations generated between the screen photoreceptor and the counter electrode. It is determined by the difference between the two amounts of charge. That is, when the amount of charge on A exceeds the amount of charge on B, the current passing through the screen photoreceptor gradually decreases as the number of copies is increased. Also, the amount of charge of B is A
If the amount of charge exceeds the amount of charge, the current passing through the screen photoreceptor gradually increases as the number of copies is increased. In addition, the ionized ions generated in case B are the amount of corona ions passing through the screen photoreceptor and the amount of corona ions passing through the screen photoreceptor and the counter electrode 1.
2, and does not depend on the type or material of the counter electrode 11. Therefore, the screen photoreceptor and the counter electrode 11
By appropriately controlling the bias electric field applied between , it is possible to balance A and B and keep the current passing through the screen photoreceptor constant. In order to make effective use of the above phenomenon, it is necessary to keep the distance between the screen photoreceptor and the counter electrode at 6 mm or less; if the distance is greater than that, the electric field will be distorted by the generated ionized ions, causing spark discharge. This may cause dielectric breakdown on the surface of the screen photoreceptor. In addition, the primary latent image is most effectively attenuated when the electric field between the screen photoreceptor and the counter electrode is used within the range of 1.5 to 2.5 KV/mm, preferably 1.5 KV/mm to 2.0 KV/mm. Alternatively, it has been confirmed that ionized positive ions can be supplied to balance the positive charge decreased due to the influence of the modulating corona. However, the smaller the distance between the screen photoreceptor and the image receptor when forming the secondary latent image, the better the reproduction of the cost image, especially when the screen photoreceptor and image receptor are made cylindrical in shape. If the distance between the two is large, such as when the curvatures of the two are different,
If the length of the formed secondary latent image in the circumferential direction does not match that of the primary latent image, a phenomenon occurs, which is undesirable. Furthermore, when forming a secondary latent image pole, the screen photoconductor is drawn toward the counter electrode (or secondary latent image forming member) due to the electric field caused by applying a bias voltage between the screen photoconductor and the counter electrode, and the screen photoconductor is The distance between the body and the opposing electrode is changed (=displacement), and the amount of displacement increases as the electric field becomes stronger. Furthermore, since the displacement due to the bias electric field differs depending on each part of the screen photoreceptor, the actual bias electric field increases by the amount of this displacement, creating a difference between each part of the screen. Therefore, the smaller the distance between the screen photoreceptor and the counter electrode, the larger the difference or increase in each part becomes, the bias electric field becomes non-uniform, and spark discharge is more likely to occur in parts with large displacements. Therefore, when considering the uniformity of the bias electric field, it is preferable that the distance between the screen photoreceptor and the counter electrode be large. Therefore, in order to faithfully reproduce the original image when forming a secondary latent image, the distance between the screen photoreceptor and the image receptor is kept small, and the effective bias electric field does not become non-uniform due to deformation due to bias voltage application. In addition, apart from the formation of the secondary latent image, a corona discharger and a counter electrode are provided via the screen photoreceptor, and the distance between the screen photoreceptor and the counter electrode is increased to increase the secondary latent image formation. The amount of positive charge A that is reduced by attenuation of the primary latent image of the screen photoreceptor or canceled by the modulating corona while the influence on the image of the displacement of the screen photoreceptor due to the application of a bias electric field of the same polarity as that for image formation is reduced. By balancing the amount of positive charge B attached to the screen photoreceptor among the ionized cations generated between the screen photoreceptor and the counter electrode, and keeping the current passing through the screen photoreceptor constant, 2
This prevents attenuation of the primary latent image when forming the next latent image. In other words, for secondary latent image formation, the screen and
The distance from the next latent image forming member is set to 2 mm or less, and the bias electric field between the two is set to 1.2 KV/mm or less, especially
Set to 1.0KV/mm or less. In the corona discharger provided separately from the one for forming the secondary latent image, the distance between the screen photoreceptor and the counter electrode is 2 mm or more and 6 mm or less, preferably 4 mm.
mm to 6 mm, and the bias electric field for both is 1.5 mm.
This is possible by adjusting within the range of ~2.5KV/mm. If the bias electric field is smaller than 1.5 KV/mm, corona ions are not generated or are difficult to generate, and the effect of preventing attenuation cannot be obtained. Moreover, if it is larger than 2.5 KV/mm, spark discharge is likely to occur due to contact with the counter electrode due to deformation of the screen photoreceptor due to the electric field, etc. Furthermore, the bias electric field is 1.5~
Even within the range of 2.5 KV/mm, if the distance between the counter electrode and the screen photoreceptor is smaller than 2 mm, spark discharge is likely to occur, and if it is larger than 6 mm, an effective attenuation prevention effect cannot be obtained. In addition to the cases shown in FIGS. 1 to 5, the charging polarity is reversed depending on the type of screen photoreceptor. FIG. 6 shows an example of an electrophotographic apparatus used in the present invention. The original image is placed on a document table 15, and a light source 16,
The screen photoreceptor 31 is an optical system consisting of a mirror 17, a prism 18, a lens 20, and a mirror 19.
image is exposed. Prior to image exposure, the screen photoreceptor is charged by a corona discharger 21,
Simultaneously with image exposure, it is charged to the opposite polarity by a corona discharger 22. Next, the entire surface is exposed by the light source 23 to form a primary latent image. Next, a secondary latent image is formed on the transfer paper fed from the paper feed section 24 at a portion where the corona discharger 25 and the counter electrode 26 are arranged by modulating the corona ion flow. The secondary latent image formed on the transfer paper is developed and fixed by a developing device 27 and a fixing device 28 to form a copy. After the secondary latent image is formed, the screen photoreceptor is processed by a separately provided corona discharger 29 and counter electrode 30 to prevent the primary latent image from attenuating according to the present invention. <Example> In the production of the screen photoreceptor according to the present invention, the conductive member was made of a nickel alloy with a line width of 30μ formed by electroforming method.
Using a 250 mesh substrate, the openings of the conductive member were filled with a solution containing 30% by weight of room-temperature curing silicone resin as a binder mixed with CdS (cadmium sulfide) powder, which is used in general electrophotographic photoreceptors. A photoconductive layer is formed by spraying the photoconductive layer from one side of the conductive member.
At this time, the photoconductive layer is deposited so that its maximum thickness is approximately 25 μm. After that, it was dried and cured, and then the same resin as the binder was sprayed in the same manner as above to make a surface insulating layer so that the maximum thickness was about 3μ without blocking the openings, and then dried and cured. . The screen photoreceptor produced as described above is charged to +300V by the primary voltage application process. Next, an image is irradiated with an exposure amount of 8 lux·sec, and at about the same time, a negative corona discharge is applied to charge the screen photoreceptor to the opposite polarity, and then the entire surface is irradiated. As a result, a primary electrostatic latent image is obtained on the surface insulating layer of the screen photoreceptor. Electrostatic recording paper, which is a chargeable surface, is placed opposite to the primary latent image surface formed in this manner at a distance of 1 mm. While keeping the potential of this recording paper at +0.75 KV with respect to the conductive member of the screen photoreceptor, negative corona discharge is performed toward the recording paper via the primary latent image on the screen photoreceptor. At this time, the corona wire applies about -4 KV to the conductive member, and the screen photoreceptor is operated at a speed of about 40 cm/sec. As a result, the corona ion flow is modulated by the primary latent image, and a secondary electrostatic latent image is formed on the recording paper. In addition to the electrode for forming the secondary latent image, a counter electrode is placed oppositely at a distance of 4 mm from the surface of the screen photoreceptor. While maintaining the potential of this counter electrode at +6.80 KV with respect to the conductive substrate of the screen photoreceptor, negative corona discharge is applied to the counter electrode via the screen photoreceptor to prevent attenuation of the primary latent image.
At this time, the corona wire is -
Approximately 4KV is applied. A comparison will be made below between a case where only a corona charger for forming a secondary latent image is used and a case where a process for preventing attenuation of a primary latent image is separately performed. 【table】

[Brief explanation of the drawing]

Figure 1 shows one of the screen photoreceptors used in the present invention.
Indicates the mode. 2 to 5 show one embodiment of the electrophotographic method according to the present invention, in which FIG. 2 shows the primary voltage application step, FIG. 3 shows the image exposure simultaneous secondary voltage application step, and FIG. 4 shows the entire surface irradiation step. and FIG. 5 shows the secondary latent image forming step. FIG. 6 shows one embodiment of an electrophotographic apparatus used in the present invention. 1... Screen photoreceptor, 2... Conductive substrate, 3...
Photoconductive layer, 4... Insulating layer, 5... Corona discharger, 6...
Original image, 25 and 29...corona discharger, 26 and 30...counter electrode, 31...screen photoreceptor.

Claims (1)

[Claims] 1 In electrophotography, in which a secondary latent image corresponding to the primary latent image is formed on an image receptor by modulating the ion flow using a primary latent image formed on a screen photoreceptor, corona radiation for forming the secondary latent image is used. Separately from the electric device and the counter electrode, a corona discharger and a counter electrode are provided sandwiching the screen photoreceptor, and the distance between the counter electrode for forming a secondary latent image and the screen photoreceptor is 2 mm or less, and the bias electric field between the two is reduced. 1.2 KV/mm or less, and the distance between the counter electrode provided separately from that for secondary latent image formation and the screen photoreceptor is 2 to 6 mm, and the bias electric field between the two is in the range of 1.5 to 2.5 KV/mm. An electrophotographic method characterized by: