JPS6122298B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a photosensitive screen having a large number of fine apertures used in an electrophotographic apparatus.

Electrophotographic methods using such a photosensitive screen are described, for example, in Japanese Patent Publication No. 44-832 and Japanese Patent Publication No. 45-30320. This electrophotographic method uses a photosensitive screen in which a photoconductive member is adhered to a mesh-like conductive member, but since a primary electrostatic latent image is formed on the photoconductive member, the surface potential cannot be raised and the However, the dark decay is relatively large, and the primary electrostatic latent image cannot be stably maintained for a long time. Therefore, it is actually difficult to form secondary electrostatic latent images many times from a single primary electrostatic latent image.

In addition, as a conventional electrophotographic method, for example,
There is a method described in Publication No.-341. The electrophotographic method disclosed in this publication consists of a primary voltage application process that uniformly charges a photosensitive screen, a subsequent image irradiation process, and a photosensitive exposure process according to the light and dark pattern caused by the image irradiation. A primary electrostatic latent image is formed on the photosensitive screen by a secondary voltage application step that changes the surface potential on the screen. Then, an ion flow from an ion source is applied to the photosensitive screen, the ion flow passing through the photosensitive screen is modulated by the primary electrostatic latent image on the photosensitive screen, and the modulated ions are deposited on the recording member. Next, an electrostatic latent image is formed.

FIG. 1 shows the cross-sectional structure of the photosensitive screen used in the electrophotographic method disclosed in the above-mentioned publication. That is, the photosensitive screen 1 has a photoconductive member 3 coated around a conductive member 2 serving as a base having a large number of openings so that a portion of the conductive member 2 is exposed, and a surface insulating member is further coated on the photoconductive member 3. 4 are laminated to form a structure. In the primary voltage application step for uniformly charging the photosensitive screen 1, as shown in FIG. This is done by connecting a corona power supply 6 between 2 and 2.
That is, if corona discharge is performed from the side of the photosensitive screen 1 where the conductive member 2 is exposed, a corona ion flow will flow into the conductive member 2, making it difficult for the surface insulating member 4 to be sufficiently charged.

Next, as shown in FIG. 3, image irradiation and secondary voltage application are simultaneously performed on the photosensitive screen 1 which has been first charged in this manner. That is, the thin corona wire 7 is placed on the surface insulating member 4 side of the photosensitive screen 1, and the original 8 is placed via the thin corona wire 7. At the same time as the light image of the original 8 is irradiated onto the photosensitive screen 1, an AC voltage 10 on which a DC voltage 9 is superimposed is applied between the conductive member 2 of the photosensitive screen 1 and the thin corona wire 7. In this way, a primary electrostatic latent image corresponding to the original image is formed on the surface insulating member 4 of the photosensitive screen 1.

Thereafter, as shown in FIG. 4, the photosensitive screen 1 is uniformly exposed. In this way, image irradiation and 2
When the entire surface of the photosensitive screen 1 is exposed after the next voltage application process, in the dark part of the light image, the flow of ions for forming the next secondary electrostatic latent image is promoted.
Further, in the light image area, charges that block the flow of the ions are arranged on the surface insulating member 4 of the photosensitive screen 1, respectively. That is, by performing this entire surface exposure, a primary electrostatic latent image with high electrostatic contrast can be formed on the photosensitive screen 1.

FIG. 5 shows a secondary voltage application process for modulating the corona ion flow based on the primary electrostatic latent image formed on the photosensitive screen 1 to form a secondary electrostatic latent image on the recording member. That is, the photosensitive screen 1
A thin corona wire 11 is disposed on the conductive member 2 side, and a conductive support plate 12 which is a counter electrode of the thin corona wire 11 is disposed on the conductive member 2 side.
are placed opposite to each other with the photosensitive screen 1 interposed therebetween. Then, the recording member 13 is placed on this conductive support plate 12. Further, the corona thin wire 11 and the conductive support plate 1
A corona power supply 14 and a conductive support plate bias power supply 15 are connected between the corona wire 11, the screen photoreceptor 1, and the conductive support plate 12, and a voltage is applied so that a potential difference is generated in the direction of the corona thin wire 11, the screen photoreceptor 1, and the conductive support plate 12. In this way, a corona ion flow is applied from the corona thin wire 11 toward the recording member 13. At this time, on the bright side of the photosensitive screen 1, an electric field α is generated in a direction that prevents corona ions (indicated by broken lines) from passing through the screen openings, so the corona ions flow into the exposed conductive member 2. On the other hand, on the dark side of the photosensitive screen 1, an electric field β is generated in a direction that promotes corona ions, so that the corona ions pass through the openings of the photosensitive screen 1 and reach the recording member 13. Therefore, a secondary electrostatic latent image corresponding to the primary electrostatic latent image on the photosensitive screen 1 is formed on the recording member 13.

In the electrophotographic method disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 51-341, the electric charge forming the primary electrostatic latent image is
Since it is electrostatically balanced with opposite polarity charges via the surface insulating member 4, even if the polarity of the modulated corona ion flow is opposite to the charge on the surface insulating member 4, that charge can be canceled. Less is. Therefore, by repeating the secondary electrostatic latent image forming process shown in FIG. It is possible to form a latent image. However, in the primary voltage application process, even if corona charging is performed from the surface insulating member 4 side of the photosensitive screen 1 as shown in FIG. 2, the conductive member 2 is exposed on the opposite side. It is difficult to make the potential of the surface insulating member 4 sufficiently high. Therefore, even if the photosensitive screen 1 shown in FIG. 4 is uniformly exposed, the contrast of the primary electrostatic latent image does not actually become very high. Therefore, even if the primary electrostatic latent image is attenuated little due to the circulation of ions as described above, the copy quality is good from a single primary electrostatic latent image, and therefore, there is no curvature and the contrast is good. The number of copies that can be obtained is also limited.

In addition, as a conventional electrophotographic method, JP-A-48-
There is one described in Publication No. 59840. The photosensitive screen used in this method has a photoconductive member attached to one side of a mesh-like conductive member, and an insulating member and a conductive layer sequentially attached to the other side. Since the primary electrostatic latent image is formed on the photoconductive member, dark decay is large, similar to the electrophotographic method mentioned above.
A good primary electrostatic latent image cannot be maintained for a long time. Furthermore, when a bias voltage is applied between the conductive member and the conductive layer, dielectric breakdown occurs and sparks are generated. Furthermore, such a four-layer structure is complex and difficult to manufacture.

It is an object of the present invention to eliminate the various drawbacks of the conventional electrophotographic photosensitive screens mentioned above, to increase the electrostatic contrast of the primary electrostatic latent image formed on the photosensitive screen, and to have good retention characteristics.
Therefore, from a single primary electrostatic latent image once formed on a photosensitive screen, multiple copies of images with no fog and good contrast can be obtained, and the photosensitive screen is simple in structure and easy to manufacture. We are trying to provide the following.

The photosensitive screen for electrophotography of the present invention has a photoconductive material that is easily charged to a positive polarity, a photoconductive material that is easily charged to a negative polarity, and a photoconductive material that is easily charged to a positive polarity and a photoconductive material that is easily charged to a negative polarity and A first photoconductive member made of a photoconductive material selected from photoconductive substances that are easily charged with a polarity of , and a second photoconductive member made of a photoconductive material other than the selected photoconductive material on the other side. It is characterized in that it includes a photoconductive member and an insulating member formed thereon, and the conductive member is completely covered by these members.

The present invention will be described in detail below with reference to the drawings.

FIG. 6 is a sectional view showing the structure of an example of the electrophotographic photosensitive screen of the present invention. The photosensitive screen 20 shown in FIG.
a first photoconductive member 23c is deposited on one surface of the
On the other surface, a second photoconductive member 24a and an insulating member 22 are sequentially attached so as to completely cover the conductive member 21. In this example, the first photoconductive member 23c has a property of being able to be charged with both positive and negative charges, and the second photoconductive member 24
A has a characteristic that a positive charge is easily charged, but a negative charge is difficult to be charged.

FIG. 7 is a sectional view showing the structure of another example of the electrophotographic photosensitive screen of the present invention. In this example, the second photoconductive member 24b has a characteristic that it is easily charged with negative charges but difficult to be charged with positive charges.

As described above, the structure of still another example of the electrophotographic photosensitive screen of the present invention in which the first photoconductive member 23 and the second photoconductive member 24 have different characteristics is shown in FIGS. 8 to 11, respectively.

As mentioned above, there are three types of photoconductive members used in the electrophotographic photosensitive screen of the present invention. These characteristics are shown in FIGS. 12a, b and c, respectively. In other words, Figure 12a shows that positive charges are easy to charge, but negative charges are difficult to charge.
FIG. 12 b shows a characteristic in which negative charges are easily charged, but positive charges are difficult to charge, and FIG. 12 c shows a characteristic in which both positive charges and negative charges are easily charged.

In this specification, for convenience of explanation, photoconductive members having the characteristics shown in FIGS. It corresponds to the characteristics of the photoconductive member.

The above three characteristics are the first and second photoconductive members 23,
At the same time as the bulk properties of the photoconductive member 24, the bonding surface between the first and second photoconductive members 23, 24 and the conductive member 21 is greatly influenced. For example, when Se is vapor-deposited as the first or second photoconductive member 23 or 24, if the temperature of the conductive member 21, which is the vapor deposition substrate, is 60°C or higher, it exhibits the type (a) characteristic, and if it is 60°C or lower, it exhibits ( c) Becomes a type. Also, the first or second photoconductive member 23 or 2
4. When depositing a Se-Te alloy containing several to several percent of Te, if the temperature of the conductive member 21, which is the deposition substrate, is 60°C or higher, type (b) will be formed, and if it is lower than that, type (c) will be formed. . In addition, as a method for obtaining the above-mentioned type (a) characteristics, SeO ₂ ,
As a method of forming a thin film layer of microcrystalline Se, Te, Ge, etc. with a thickness of several μm or less and obtaining the above-mentioned type (c), it is possible to form a thin film layer of microcrystalline Se, Te, Ge, etc. A _S2 at the interface with member 23 or 24
It is known to form a thin film layer of _S3 . Note that CdS generally has the above-mentioned (b) type rectification characteristics.

The conductive member 21 constituting the photosensitive screen 20 as described above has an opening of 50 to 400 meshes, and the first and second
The photoconductive members 23 and 24 are made of Se, PbO, S, Te,
Vacuum-deposited metals and alloys or intermetallic compounds such as Sb, Bi, sputtered ZnO, CdS, _TiO2 , or ZnO, CdS, CdSe,
TiO ₂ or PbO powder dissolved in an insulating organic binder and sprayed or applied, or Se-
Consists of a composite photosensitive material of Te alloy and organic semiconductor.
The insulating member 22 that is adhered onto the second photoconductive member 24 is made of an organic material such as polyethylene, polypropylene, polystine, polyurethane, polyvinyl chloride, acrylic resin, polycarbonate, silicone resin, fluororesin, epoxy resin, etc., which is spray-coated. Formed with etc.

In addition to the above-described photosensitive screen, the photosensitive screen used in the present invention may have a structure as shown in FIGS. 13a and 13b. That is, in the photosensitive screen 20 shown in FIG. 13a, the insulating member 22 is formed only on a part of the second photoconductive member 24 without covering the entirety of the second photoconductive member 24, and the first and second photoconductive members 23, 24 are
It is made by joining. Further, the photosensitive screen 20 shown in FIG. 13b has a mesh-like conductive member 2.
1 has a trapezoidal cross-sectional shape.

As described above, in the electrophotographic photosensitive screen 20 of the present invention, the entire surface of the conductive member 21 is
Since it is completely covered with the photoconductive members 23 and 24 and the insulating member 22 is attached on one side of the photoconductive members 23 and 24, corona ions are not directly adsorbed to the conductive member 21 during the formation of a primary electrostatic latent image, which will be described later. A primary electrostatic latent image with extremely high surface potential can be obtained, resulting in high electrostatic contrast.

Examples of the electrophotographic method using each of the electrophotographic photosensitive screens 20 of the present invention described above will be described below. Incidentally, since the electrophotographic method using the photosensitive screen of the present invention can be roughly classified into the following five methods, the basic steps of each of these methods will be explained first.

Method A Method A sequentially performs the following steps.

1 Process of charging simultaneously with light image irradiation 2 Process of uniform exposure Method B Method B sequentially performs the following steps.

1 Process of performing primary charging simultaneously with light image irradiation 2 Process of performing secondary charging with opposite polarity to primary charging 3 Process of uniform exposure Method C Method C sequentially performs the following steps.

1 Step 2 of performing primary charging Step 3 of performing secondary charging of the opposite polarity to the primary charging simultaneously with light image irradiation Step 3 Process method of uniform exposure D Method D sequentially performs the following steps.

1 Process of performing primary charging at the same time as uniform exposure 2 Simultaneously with light image irradiation, 2
Step 3 of Performing Next Charging Process Method E of Performing Uniform Exposure Method E performs the following steps in sequence.

1 Step of performing primary charging simultaneously with light image irradiation 2 Step of performing uniform exposure 3 Step of performing secondary charging of opposite polarity to the primary charging 4 Step of performing uniform exposure The sequential steps leading to the formation of a primary electrostatic latent image for modulating the corona ion flow are shown.

Example 1 A primary electrostatic latent image is formed on an insulating member 22 according to method A using the photosensitive screen 20 shown in FIG. In this embodiment, the polarity of the charging step performed simultaneously with the light image irradiation is negative. First, as shown in FIG. 14, a thin corona wire 25 is placed on the insulating member 22 side of the photosensitive screen 20, and the thin corona wire 25 is connected to the conductive member 21 of the photosensitive screen 20 so that a negative high voltage is applied to the thin corona wire 25. A DC corona power supply 26 is connected between them. A negative corona ion stream is projected from the thin corona wire 25 toward the photosensitive screen 20, and at the same time, a light image is irradiated from the insulating member 22 side. As a result, the dark part and bright part of the light image are
The amount of charge trapped at the interface between the photoconductive member 24a and the insulating member 22 is different, and therefore the surface potential V _1D of the insulating member 22 in the dark area is different from the surface potential V _1L of the insulating member 22 in the bright area. Becomes a value. In addition, in the dark part of the optical image, the first photoconductive member 2
Some charge is accumulated in 3c. In the photoimage irradiation and simultaneous charging step shown in FIG. 14, a corona thin wire 25 may be placed on the first photoconductive member 23c side to project the corona ion stream.

Next, as shown in FIG.
exposure evenly. When uniform exposure is performed in this manner, the charges accumulated in the first photoconductive member 23c disappear. Therefore, a primary electrostatic latent image is formed only on the insulating member 22, and the electrostatic contrast V _C at this time is V _C =|V _1D −V _1L |. In FIG. 15, uniform exposure can be performed from either or both of the insulating member 22 side and the first photoconductive member 23c side.

FIG. 16 is a diagram showing an example of the process of forming a secondary electrostatic latent image on a recording member based on the primary electrostatic latent image formed as described above. That is, in FIG. 16, a thin corona wire 27 is arranged on the side of the first photoconductive member 23c, and a high voltage of positive polarity is applied to this thin corona wire 27, since the polarity is opposite to that in the charging process shown in FIG. 14. A direct current corona current 28 is connected between the photosensitive screen 20 and the conductive member 21 so that the current is applied. Further, on the insulating member 22 side of the photosensitive screen 20 on which the primary electrostatic latent image is formed, a recording member 30 placed in close contact with the back electrode 29 is disposed to face the back electrode 29.
An accelerating power source 31 is connected between the conductive member 21 of the photosensitive screen 20 so as to generate an electric field that guides the positive corona ion flow projected from the corona thin wire 27 to the back electrode 29. In this way, while performing uniform exposure from the first photoconductive member 23c side, a positive corona ion stream is projected from the corona thin wire 27 toward the recording member 30. At this time, although the electric field strength differs between the bright and dark parts of the opening of the photosensitive screen 20, only the electric field that promotes the positive corona ion flow is generated, so that the corona ion flow projected from the corona thin wire 27 is , the light image of the photosensitive screen 20 reaches the recording member 30 regardless of whether it is a dark area or a bright area, and therefore a secondary electrostatic latent image with a lot of fog is formed. To prevent this, it is necessary to charge the recording member 30 in advance to a constant negative potential (several +V to several 100V).

Example 2 As in Example 1, a primary electrostatic latent image is formed on an insulating member 22 according to method A using the photosensitive screen 20 shown in FIG. In this embodiment, the polarity of the charging process performed simultaneously with the light image irradiation in FIG. 14 is positive. Therefore, in this embodiment, the electrostatic contrast V _C of the primary electrostatic latent image formed on the insulating member 22 is V _C =α _p V _1D −V _1L . However, α _p is expressed as α _p =C _p /C _p +C _i , where α p is the capacitance C _p of the second photoconductive member 24 and Ci is the capacitance of the insulating member 22 . In addition, after the photoimage irradiation and simultaneous charging process,
If the uniform exposure step is not performed, the electrostatic contrast V _C of the primary electrostatic latent image at that time is V _C =|V _1D −V _1L |.

Example 3 A primary electrostatic latent image is formed on an insulating member 22 according to method A using the photosensitive screen 20 shown in FIG. In this embodiment, the polarity of the charging process performed simultaneously with the light image irradiation is positive. The charging polarity in this case is the same as in the second embodiment described above, but the electrostatic contrast V _C of the primary electrostatic latent image formed on the insulating member 22 is V _C =V _1D -V _1L .

Example 4 Similarly to Example 3, a primary electrostatic latent image is formed on an insulating member 22 according to method A using the photosensitive screen 20 shown in FIG. In this embodiment, the polarity of the charging step performed simultaneously with the light image irradiation is negative. The charging polarity in this case is the same as in Example 5 described above, but the electrostatic contrast V _C of the primary electrostatic latent image formed on the insulating member 22 is V _C =-(α _p V _1D − V _1L ) becomes.

Example 5 A primary electrostatic latent image is formed on an insulating member 22 according to method A using the photosensitive screen 20 shown in FIG. Here, the photosensitive screen 20 shown in FIG.
Since the first photoconductive member 23a has rectifying characteristics of the type (a), the polarity in the charging process performed simultaneously with the light image irradiation must be positive. Therefore, in this embodiment, V _C =(α _p
A primary electrostatic latent image having an electrostatic contrast of V _1D −V _1L ) can be formed. Furthermore, in this embodiment, it is necessary to project a negatively polarized corona ion stream onto the photosensitive screen 20 in order to form a secondary electrostatic latent image, but this corona ion stream almost never reaches the first photoconductive member 23a. Not accumulated. Therefore, uniform exposure during formation of a secondary electrostatic latent image can be omitted.

Example 6 A primary electrostatic latent image is formed on an insulating member 22 according to method A using the photosensitive screen 20 shown in FIG. Here, since the first photoconductive member 23b of the photosensitive screen 20 has a characteristic that it is difficult to be charged with a positive charge, the polarity of the charging process performed simultaneously with the irradiation of the light image needs to be negative. Therefore, in this embodiment, V _C =-(α _p V _1D −V ₁
A primary electrostatic latent image having an electrostatic contrast of _L ) can be formed. Further, in this embodiment, in forming a secondary electrostatic latent image, it is necessary to project a positive corona ion stream onto the photosensitive screen 20, but most of this corona ion stream does not reach the first photoconductive member 23b. It is not accumulated. Therefore, as in the case of Example 5, uniform exposure during formation of a secondary electrostatic latent image can be omitted.

Example 7 A primary electrostatic latent image is formed on the insulating member 22 according to method A using the photosensitive screen shown in FIG. Here, the first photoconductive member 23b of the photosensitive screen 20 is of type (b), and the second photoconductive member 24
Since c is of type (c), a primary electrostatic latent image having an electrostatic contrast of V _C =-(V _1D -V _1L ) can be formed in the same manner as in Example 1 described above.
In this embodiment as well, uniform exposure during formation of a secondary electrostatic latent image can be omitted.

Example 8 A primary electrostatic latent image is formed on an insulating member 22 according to method A using the photosensitive screen 20 shown in FIG. In this embodiment, the first photoconductive member 23a of the photosensitive screen 20 is of type (a), and the second photoconductive member 24 is of type (a).
Since b is of type (b), it is possible to form a primary electrostatic latent image having an electrostatic contrast of V _C =(V _1D −V _1L ) in the same manner as in Example 3 described above. In this embodiment as well, uniform exposure during formation of the secondary electrostatic latent image can be omitted.

Example 9 A primary electrostatic latent image is formed on an insulating member 22 according to method B using the photosensitive screen 20 shown in FIG. In this embodiment, the first
Although the photoconductive member 23c can be charged with both positive and negative polarity, the polarity of the primary charging step performed simultaneously with the irradiation of the light image is negative. First, as shown in FIG. 17, a corona thin wire 32 is placed on the insulating member 22 side of the photosensitive screen 20, and the photosensitive screen 2 is placed so that a negative high voltage is applied to the corona thin wire 32.
A DC corona power supply 3 is connected between the conductive member 21 of
Connect 3. Then, a negative corona ion stream is projected from the corona thin wire 32 toward the photosensitive screen 20, and at the same time, a light image is irradiated from the insulating member 22 side. At this time, the first photoconductive member 23 in the light image area
c becomes conductive, whereas the first photoconductive member 23c becomes insulating in the dark part of the optical image. Therefore, when sufficient charging is performed, the surface potential V _1D of the dark portion of the optical image becomes larger in absolute value than the surface potential V _1L of the bright portion of the optical image. In the light image irradiation and simultaneous primary charging step shown in FIG. 17, a corona thin wire 32 may be placed on the first photoconductive member 23c side to project the corona ion stream.

Next, the photosensitive screen 20 is secondarily charged to a polarity opposite to that in the primary charging step, so that the surface potential in bright and dark areas is made to be apparently constant. That is, as shown in FIG. 18, a corona thin wire 34 is arranged on the insulating member 22 side, and in this embodiment, this corona thin wire 3
4, the conductive member 2 of the photosensitive screen 20 is
1, a DC power supply 35 and an AC power supply 36 are connected in series. Note that this secondary reverse charging step
Since it is sufficient to perform charging with a polarity opposite to that in the simultaneous light image irradiation primary charging step shown in FIG. It may be arranged and controlled.

After the secondary reverse charging process is completed, the photosensitive screen 20 is uniformly exposed as shown in FIG. As a result, due to the difference in the amount of charge previously trapped at the interface between the second photoconductive member 24a and the insulating member 22, the surface potentials have different values in the bright and dark areas. Therefore, the electrostatic contrast V _C of the primary electrostatic latent image formed on the insulating member 22 is V _C =-α _i (V _1D −V _1L ) (where α _i =C _i /C _p +C _i ) becomes. That is, in this embodiment, since the absolute value of the surface potential V _1D of the dark part of the optical image can be increased during primary charging, a high electrostatic contrast can be obtained. Although uniform exposure is performed from the insulating member 22 side in FIG. 19, it may be performed from the first photoconductive member 23c side or from both of these sides.

FIG. 20 is a diagram showing an example of the process of forming a secondary electrostatic latent image on the recording member based on the primary electrostatic latent image formed on the insulating member 22 as described above. That is, in FIG. 20, the first photoconductive member 23
A thin corona wire 37 is arranged on the c side, and the conductivity of the photosensitive screen 20 is adjusted so that a high voltage having the same polarity as that in the primary charging step shown in FIG. Sex member 21
A DC corona power supply 38 is connected between the two. Also, a photosensitive screen 2 on which a primary electrostatic latent image is formed
A recording member 40 placed closely on a back electrode 39 is disposed opposite to the insulating member 22 side of 0, and an accelerating power source 41 is connected between the back electrode 39 and the conductive member 21 of the photosensitive screen 20. In this way, a negative polarity corona ion stream is projected toward the recording member 40 from the corona thin wire 37 while performing uniform exposure from the first photoconductive member 23c side. At this time, in FIG. 20, only promoting electric fields with different electric field strengths are generated at the openings of the photosensitive screen 20, so
It is necessary to charge the recording member 40 to a constant low potential of positive polarity in advance. However, if the charging potential in the secondary reverse charging shown in Fig. 20 is appropriately selected, a blocking electric field can be formed in the aperture of the bright part of the optical image, and a promoting electric field can be formed in the aperture of the dark part of the optical image. In this case, it is not necessary to charge the recording member 40 in advance. Also, in Fig. 20, the corona thin line 37
If corona discharge is performed by applying an alternating current voltage superimposed on a direct current voltage, it is not necessary to perform uniform exposure at the same time.

Note that if the primary charging step is of positive polarity, the secondary reverse charging step is of negative polarity, making it impossible to form a primary electrostatic latent image in a steady state. However, since the charging speed and the discharging speed are different between the bright part and the dark part of the optical image, it is possible to form a primary electrostatic latent image by utilizing the transient state.

Example 10 A primary electrostatic latent image is formed on an insulating member 22 according to method B using the photosensitive screen 20 shown in FIG. In this example, the charging polarity in each charging step in Example 9 described above is reversed. Therefore, the electrostatic contrast V _C of the primary electrostatic latent image formed on the insulating member 22 is V _C =α _i (V _1D −V _1L ).

Example 11 A primary electrostatic latent image is formed on an insulating member 22 according to method B using the photosensitive screen 20 shown in FIG. In this embodiment, the polarity of the primary charging step performed simultaneously with the light image irradiation is positive. First, as shown in FIG. 21, a thin corona wire 42 is placed on the insulating member 22 side of the photosensitive screen 20.
A DC corona power source 43 is connected between the photosensitive screen 20 and the conductive member 21 so that a positive high voltage is applied thereto. and the corona thin wire 42
A positive corona ion stream is projected from the photosensitive screen 20 toward the photosensitive screen 20, and at the same time, a light image is irradiated from the insulating member 22 side. At this time, the first photoconductive member 23a
Since it has type (a) rectification characteristics, the first photoconductive member 23a is charged with positive charges in the dark part of the optical image, and no negative charges are trapped at the interface between the second photoconductive member 24c and the insulating member 22. . On the other hand, in the light image area, since the second photoconductive member 24c is irradiated with light, negative ions are injected and trapped at the interface between this and the insulating member 22. Note that the first photoconductive member 23a in the light image area is charged with a slight positive charge.

Next, as shown in FIG.
Then, a secondary reverse charging process is performed. In FIG. 22, the first photoconductive member 23a of the photosensitive screen 20 is
A thin corona wire 44 is arranged on the side, and this thin corona wire 4
1 shown in FIG. 21 between 4 and the conductive member 21.
Secondary reverse charging is performed by connecting the corona power source 45 with a polarity opposite to that in the next charging step. The reason why charging is performed from the first photoconductive member 23a side in this manner is that the first photoconductive member 23a has a property that it is not very negatively charged and thus has the same effect as a control grid. Therefore, the surface potential of the photosensitive screen 20 can be kept apparently constant. Of course, alternating current corona charging or direct current corona charging can be performed by disposing an alternating current corona or a control grid between the corona thin wire and the photosensitive screen 20 from the insulating member 22 side to control the charging potential. In this secondary reverse charging, the second photoconductive member 2 is first charged in the bright part of the light image.
The charges trapped at the interface between the insulating member 4c and the insulating member 22 remain as they are without being able to move. Even if the entire photosensitive screen 20 becomes 0 potential in this secondary reverse charging process, in the bright part of the photoimage, the surface of the insulating member 22 and the interface between this and the second photoconductive member 24c have electrostatically balanced charges.

FIG. 23 shows a uniform exposure process of the photosensitive screen 20 performed after the secondary reverse charging process. In FIG. 23, uniform exposure is performed from the insulating member 22 side, but
It may be carried out from the first photoconductive member 23a side or from both sides. By uniformly exposing the photosensitive screen 20 in this manner, charges trapped at the interface between the second photoconductive member 24c and the insulating member 22 are released in the bright portion of the light image, and the charges that have been trapped at the interface between the second photoconductive member 24c and the insulating member 22 are released, and
A primary electrostatic latent image is formed by being electrostatically balanced with the charges on the surface of 2. The electrostatic contrast V _C in this case is expressed as V _C =-α _i V _1L , but the primary electrostatic latent image in this case has a low potential with respect to the dark part of the optical image, and a high potential with respect to the bright part. Therefore, it is a negative latent image compared to the optical image. However, it is of course possible to form a positive image by appropriately selecting the charging potential in the secondary reverse charging step shown in FIG.

In order to form a secondary electrostatic latent image from the primary electrostatic latent image formed as described above, it may be carried out as shown in FIG. Here, when a negative polarity corona ion stream is projected from the corona thin wire 37 as shown in FIG. 20, a negative secondary electrostatic latent image is formed on the optical image, and when a positive polarity corona ion stream is projected, a positive A secondary electrostatic latent image is formed. Note that when the corona ion flow is of negative polarity, the simultaneous uniform exposure can be omitted. Therefore, depending on the charging potential in the secondary reverse charging shown in FIG. 22 and the polarity of the corona ions forming the secondary electrostatic latent image, positive-positive, positive-negative, negative-positive, negative- Negative primary and secondary electrostatic latent images can be formed.

In addition, in this embodiment, the electrostatic contrast V _C of the primary electrostatic latent image is as shown in FIG.
It is determined by the surface potential V _1L of . Therefore, the 24th
As shown in the figure, if an opaque conductive layer 46 is deposited on the lower side of the first photoconductive member 23a, the first photoconductive member 2
Since no light is incident on the insulating member 3a, the insulating member 22 can be charged to a sufficiently high potential in the primary charging step, and the electrostatic contrast can be further increased.

Example 12 A primary electrostatic latent image is formed on the insulating member 22 by reversing the polarity in each charging step in Example 11 described above. In this case, the electrostatic contrast V _C of the primary electrostatic latent image is expressed by the following equation.

V _C =α _i V _1L Example 13 A primary electrostatic latent image is formed on the insulating member 22 according to method B using the photosensitive screen 20 shown in FIG. In this example, simultaneous light image irradiation 1 is performed first.
The charging polarity in the next charging step is made positive. Therefore, similar to Embodiment 11 described above, the insulating member 2
The electrostatic contrast V _C of the primary electrostatic latent image formed on 2 is V _C =-α _i V _1L .

Example 14 A primary electrostatic latent image is formed on the insulating member 22 by reversing the polarity in each charging step in Example 13 described above. Therefore, this embodiment is similar to the twelfth embodiment described above, and the electrostatic contrast V _C of the primary electrostatic latent image formed on the insulating member 22 is V _C =α _i V _1L .

Example 15 A primary electrostatic latent image is formed on an insulating member 22 according to method B using the photosensitive screen 20 shown in FIG. First, as shown in FIG. 25, a thin corona wire 47 is placed on the insulating member 22 side of the photosensitive screen 20, and a corona power source 48 is connected between the thin corona wire 47 and the conductive member 21.
A corona ion stream of negative polarity is projected from the photosensitive screen 20 toward the photosensitive screen 20, and a light image is irradiated from the same insulating member 22 side. Photosensitive screen 20 here
Since the first photoconductive member 23b can be sufficiently charged with (b) type negative polarity charge, the first photoconductive member 23b and the insulating member 22 on the surface of the photosensitive screen 20 in the dark part of the optical image have a potential of V _1D . becomes. At this time, positive charges are injected into the second photoconductive member 24a, and these positive charges are trapped at the interface between the insulating member 22 and the second photoconductive member 24a. On the other hand, in the light image area, the first photoconductive member 23b partially becomes conductive due to the action of the light transmitted through the insulating member 22, and the interface between the second photoconductive member 24a and the insulating member 22 becomes conductive. The amount of trapped charge is also smaller than in the dark area, and the surface potential V _1L of the photosensitive screen 20 is smaller than the surface potential V _1D in the dark area.
The potential is lower than that of

Next, as shown in FIG.
Then, a secondary reverse charging process is performed. In FIG. 26, the first photoconductive member 23b of the photosensitive screen 20
A thin corona wire 49 is arranged on the side, and this thin corona wire 4
A corona power source 50 is connected between the conductive member 9 and the conductive member 21 with a polarity opposite to that in the primary charging step to perform secondary reverse charging. The reason why reverse charging is performed from the side of the first photoconductive member 23b is that the first photoconductive member 23b has rectifying characteristics of the type (b), so it is hardly charged with positive polarity. . That is, the entire surface potential of the photosensitive screen 20 can be controlled by the surface potential (positive saturation potential) of the first photoconductive member 23b, and therefore, in this example, the entire surface of the photosensitive screen 20 exhibits zero voltage. . Of course, it is also possible to control the charging level by placing an AC corona or a control grid between the thin corona wire and the photosensitive screen 20 from the insulating member 22 side. In addition,
In this secondary reverse charging step, the charges trapped at the interface between the second photoconductive member 24a and the insulating member 22 in the previous light irradiation simultaneous primary charging step hardly move, and the charges are superficially The entire photosensitive screen 20 is at a certain potential.

FIG. 27 shows a uniform exposure process of the photosensitive screen 20 performed after the secondary reverse charging process. Although uniform exposure is performed from the insulating member 22 side in FIG. 27, it may be performed from the first photoconductive member 23b side or both. This uniform exposure step is a step for releasing charges trapped at the interface between the second photoconductive member 24a and the insulating member 22. The charge trapped on the boundary surface is released by exposure to light, but on the surface of the insulating member 22, there are negative charges in the dark areas and positive charges in the bright areas, and the opposite charges corresponding to these charges are added to the surface of the insulating member 22. It remains on the interface and is electrostatically balanced. Therefore, a primary electrostatic latent image consisting of positive and negative charges is formed on the insulating member 22.
Also, the electrostatic contrast of this primary electrostatic latent image V _C
becomes V _C =−α _i (V _1D −V _1L ).

FIG. 28 is a diagram showing an example of the process of forming a secondary electrostatic latent image on the recording member based on the primary electrostatic latent image formed on the insulating member 22 as described above. That is, in FIG. 28, the first photoconductive member 23
A thin corona wire 51 is arranged on the b side, a DC corona power source 52 is connected between the thin corona wire 51 and the conductive member 21 of the photosensitive screen 20, and a positive voltage (6 to 10 KV) is applied to the thin corona wire 51. Apply.
Further, a recording member 54 placed in close contact with a back electrode 53 is disposed opposite to the insulating member 22 side of the photosensitive screen 20 on which the primary electrostatic latent image is formed.
An acceleration power source 55 is connected between the back electrode 53 and the conductive member 21, and a negative voltage (-3.5 to -4 KV) is applied to the back electrode 53. Note that the distance between the photosensitive screen 20 and the back electrode 53 is approximately 4 mm. In this way, a positive corona ion stream is projected from the corona thin wire 51 toward the recording member 54. At this time, a promoting electric field is formed in the aperture in the dark part of the light image of the photosensitive screen 20, which allows the corona ion flow of positive polarity to pass through the aperture, so that the corona ion flow passes through the aperture and is recorded. It is attached onto the member 54. On the other hand, in the light image area, the surface potential of the insulating member 22 is a positive voltage (50~
(appropriately 130V), and a blocking electric field is formed in the opening that prevents the flow of positive corona ions from passing through. Therefore, a positive secondary electrostatic latent image is formed on the recording member 54.

In addition, in FIG. 28, the photosensitive screen 20
uniform exposure is not necessary. Furthermore, in order to obtain a negative secondary electrostatic latent image, the polarities of the corona power source 52 and the acceleration power source 55 may be reversed. In this case, it is necessary to expose the photosensitive screen 20 uniformly.

Example 16 A primary electrostatic latent image is formed on an insulating member 22 according to method B using the photosensitive screen 20 shown in FIG. In this example, the charging polarity of each charging step in Example 15 described above may be reversed, and the electrostatic contrast V _C of the primary electrostatic latent image formed in this case is V _C = α _i (V _1D −V _1L ).

In this embodiment, the first photoconductive member 23a is (a)
Since it is a mold, uniform exposure is required when forming a secondary electrostatic latent image by direct current corona discharge.

Example 17 A primary electrostatic latent image is formed on an insulating member 22 according to method C using the photosensitive screen 20 shown in FIG. FIG. 29 is a diagram showing an example of the primary charging process, and in this example, the insulating member 22 of the photosensitive screen 20
A DC corona power source 57 is connected between the corona thin wire 56 disposed on the side and the conductive member 21, and a negative corona ion flow is projected from the corona thin wire 56,
The photosensitive screen 20 is uniformly charged. Note that this primary charging can also be performed from the first photoconductive member 23c side. In this primary charging step, since the second photoconductive member 24a is of type (a), a positive charge is generated at the interface between it and the insulating member 22 corresponding to the negative charge charged on the insulating member 22. Trapped.

FIG. 30 is a diagram showing an example of a light image irradiation simultaneous secondary reverse charging process performed after the primary charging process. In this example, a corona thin wire 58 is arranged on the insulating member 22 side, and a positive electrode is attached to this corona thin wire 58. A DC power supply 59 is connected between the photosensitive screen 20 and the conductive member 21 so that an AC voltage with a superimposed DC voltage is applied.
and AC power supply 60 are connected in series. Note that this secondary reverse charging may be performed from the first photoconductive member 23c side. When the secondary reverse charging is performed in this manner, a light image is irradiated from the insulating member 22 side at the same time, and the surface potential of the entire photosensitive screen 20 is made to be apparently constant. At this time, in the dark part of the optical image, the positive charges that were previously trapped at the interface between the second photoconductive member 24a and the insulating member 22 are not released, and therefore negative charges are retained on the insulating member 22. become. Note that positive charges are accumulated on the first photoconductive member 23c on the opposite side of the insulating member 22. On the other hand, in the bright portion of the optical image, the previously trapped positive charges disappear, and negative charges are injected and trapped, and correspondingly, positive charges are held in the insulating member 22.

FIG. 31 is a diagram showing an example of a uniform exposure process performed after the simultaneous secondary reverse charging process of light image irradiation. In this example, the photosensitive screen 20 is uniformly exposed from the insulating member 22 side, but the first light It can also be performed from the conductive member 23c side or from both sides. When the photosensitive screen 20 is uniformly exposed in this way, charges of opposite polarity corresponding to the negative charges and positive charges respectively charged in the dark and bright parts of the optical image of the insulating member 22 are transferred to the second photoconductive member 24a. It is trapped at the interface with the insulating member 22 and is electrostatically balanced. Therefore, a primary electrostatic latent image consisting of positive and negative charges is formed on the insulating member 22.

Here, if the potentials of the bright and dark areas of the primary electrostatic latent image are V _L and V _D , the following relational expression holds between V _L and V _D.

V _D =α _p V _L −α _i |V _1D |, −|V _1D |V _L |V _2L | The relationship between V _D and V _L and the electrostatic contrast in this case V _C = | V _D − V _L | is shown in FIGS. 32 and 33, respectively. As is clear from FIG. 33, theoretically, the electrostatic contrast V _C of the primary electrostatic latent image is maximum, V _C = α _i (V _2L + | V _1D |)
However, since V _1D = -V _2D is generally set, the maximum contrast V _Cnax is V _Cnax = -2
α ₁ V _2D . Then V _1D = V _1L , V _2D = V _2L =
Let it be _VL . Note that V _2D and V _2L represent the surface potentials of the dark and bright areas, respectively, caused by charges applied to the photosensitive screen 20 by secondary reverse charging.

FIG. 34 is a diagram showing an example of the process of forming a secondary electrostatic latent image from the primary electrostatic latent image formed as described above. In FIG. 34, a corona thin wire 61 is placed on the first photoconductive member 23c side of the photosensitive screen 20.
A DC corona power source 62 is connected between the thin corona wire 61 and the conductive member 21 of the photosensitive screen 20 to project a positive corona ion stream onto the photosensitive screen 20. Further, on the insulating member 22 side of the photosensitive screen 20, a recording member 64 placed in close contact with the back electrode 63 is arranged to face the photosensitive screen 20.
An acceleration power source 65 is connected between the back electrode 63 and the conductive member 21 so that an electric field is generated to accelerate the positive corona ion flow projected from the corona thin wire 61. In this way, the corona thin wire 61 is exposed while uniformly exposing the photosensitive screen 20.
A positive corona ion stream is projected from the recording member 64 toward the recording member 64 . At this time, in the bright part of the photosensitive screen 20, a blocking electric field is formed in the openings to prevent the passage of the positive corona ion flow, and in the dark part, a promoting electric field is formed in the openings to promote the passage of the corona ion flow. As a result, a fog-free secondary electrostatic latent image with high contrast is formed on the recording member 64. In addition, in FIG. 34, if the corona power source 62 and the accelerating power source 65 are reversed, a negative secondary electrostatic latent image can also be formed.

Example 18 A primary electrostatic latent image is formed according to method C using the photosensitive screen 20 shown in FIG. In this embodiment, the second photoconductive member 24b of the photosensitive screen 20 is
Since it is of type (b), it differs from Example 17 in that the primary charging shown in FIG. 29 is performed with positive polarity. Therefore, the electrostatic contrast V _C of the primary electrostatic latent image according to this embodiment is V _C =α _i V _2D .

Example 19 A primary electrostatic latent image is formed according to method C using the photosensitive screen 20 shown in FIG. Here, the first photoconductive member 23b of the photosensitive screen 20 is (b)
Since the second photoconductive member 24a is of type (a), 1
The charging polarity in the next charging step must be negative. Therefore, this embodiment is similar to the 17th embodiment described above, and the electrostatic contrast V _C of the primary electrostatic latent image formed on the insulating member 22 is V _C =-α _i V ₂ . However, V ₂ represents the surface potential generated by the charge applied to the photosensitive screen 20 by secondary reverse charging.

Example 20 A primary electrostatic latent image is formed according to method C using the photosensitive screen 20 shown in FIG. In this embodiment, the second photoconductive member 24 of the photosensitive screen 20
Since b is of the (b) type, the charging polarity in the primary charging step must be positive. Therefore, in this embodiment, the polarity of each charging step in the above-mentioned embodiment 25 is reversed, and the electrostatic contrast V _C of the primary electrostatic latent image formed on the insulating member 22 is V _C = α _i It becomes V ₂ .

Example 21 A primary electrostatic latent image is formed on an insulating member 22 according to method D using the photosensitive screen 20 shown in FIG. Since the second photoconductive member 24a of the photosensitive screen 20 has rectifying characteristics of the type (a), it is necessary that the polarity of the primary charging performed simultaneously with the uniform exposure be negative. First, as shown in FIG. 35, a corona thin wire 66 is placed on the insulating member 22 side of the photosensitive screen 20, and this corona thin wire 66 and the photosensitive screen 2
A DC corona power supply 6 is connected between the conductive member 21 of
7 to perform negative corona charging while uniformly exposing the photosensitive screen 20 to light. Here, positive charges are injected into the interface between the second conductive member 24a and the insulating member 22 of the photosensitive screen 20, and the photosensitive screen 20, which is trapped, is uniformly charged to a negative polarity. Note that this uniform exposure and simultaneous primary charging step is performed on the first photoconductive member 23 of the photosensitive screen 20.
It can also be done from the c side.

Next, the photosensitive screen 20 is subjected to a secondary reverse charging process simultaneously with the light image irradiation. For this reason, in this embodiment, as shown in FIG. 36, a thin corona wire 68 is disposed on the insulating member 22 side, and in order to perform AC corona discharge with a positive DC voltage superimposed by this thin corona wire 68, the photosensitive screen 20 conductive members 21
DC power supplies 69 and 70 were connected in series between the two. In this way, secondary reverse charging is performed from the insulating member 22 side, and at the same time, a light image is irradiated from the same side. As a result, in the bright part of the optical image, the positive charge previously trapped at the interface between the second photoconductive member 24a and the insulating member 22 is released, and the negative charge is injected and trapped, and in the dark part, the insulating member The negative charge held on the surface of 22 is canceled out to some extent, and the surface potentials of the bright and dark areas become apparently equal to the voltage value of the DC power supply 69. Note that the secondary reverse charging can also be performed from the first photoconductive member 23c side.

FIG. 37 shows a uniform exposure process, in which charges trapped at the interface between the second photoconductive member 24a and the insulating member 22 due to primary charging are released in the dark areas of the optical image. , electrostatically balances the charge held on the insulating member 22 after secondary reverse charging. Therefore, by appropriately selecting the charging voltage in the secondary reverse charging, the insulating member 22
A primary electrostatic latent image consisting of positive and negative charges can be formed thereon.

Here, the relationship between the potential V _L of the bright part and the potential V _D of the dark part of the primary electrostatic latent image finally formed on the insulating member 22 is as follows: V _D = α _p V _L − α _i |V _1L | −|V _1L |V _L |V _2L | |V _1L |=|V _2L |. Similar to FIGS. 32 and 33, V _D ,
The relationship between V _L and the relationships between V _C and V _L are shown in FIGS. 38 and 39, respectively. As is clear from these figures, the potential V _L of the bright part of the light image is 0V _L |L _1L
By selecting the secondary reverse voltage so that α _p > α _i , the electrostatic contrast V _C
is V _C = α _i (V _2L + |V _1L |), and the maximum contrast V _Cnax is when |V _2L |= |V _1L |
V _Cnax =2α _i |V _1L |.

FIG. 40 is a diagram showing an example of the process of modulating the corona ion flow based on the primary electrostatic latent image formed as described above to form a secondary electrostatic latent image on the recording member. In this embodiment, the corona thin wire 7 disposed on the first photoconductive member 23c side of the photosensitive screen 20
A DC corona power supply 7 is connected between the conductive member 1 and the conductive member 21.
2 are connected, and a positive corona ion stream is projected toward the photosensitive screen 20 while uniformly exposing the photosensitive screen 20. In addition, the photosensitive screen 20
A recording member 74 placed in close contact with the back electrode 73 is disposed facing the insulating member 22 side of the back electrode 73 and the conductive member 2 of the photosensitive screen 20.
An accelerating power source 75 is connected between the photosensitive screen 20 and the photosensitive screen 20 so that the positive corona ion flow passing through the openings of the photosensitive screen 20 can be guided to the recording member 74. An electric field that promotes the passage of positive corona ions is formed in the openings in the dark part of the photosensitive screen 20, and an electric field that blocks the positive corona ions is formed in the openings in the bright part, so that on the recording member 74, Positive charges are attached only to areas corresponding to dark areas, forming a fog-free, high-contrast secondary electrostatic latent image. In addition,
If the polarities of the corona power source 72 and the acceleration power source 75 are reversed, corona ions will pass through in the bright area, making it possible to form a negative secondary electrostatic latent image due to negative charges. If it is uniformly charged to a predetermined potential with one polarity in advance, a secondary electrostatic latent image consisting of positive and negative charges can also be formed.

Example 22 A primary electrostatic latent image is formed according to method D using the photosensitive screen 20 shown in FIG. In this embodiment, the second photoconductive member 24b of the photosensitive screen 20 is
(b) type, the charging polarity of the uniform exposure simultaneous primary charging step shown in FIG. 35 is positive in Example 21.
It differs from Therefore, the electrostatic contrast V _C of the primary electrostatic latent image according to this embodiment is V _C =α _i V _2D .

Example 23 A primary electrostatic latent image is formed according to method D using the photosensitive screen 20 shown in FIG. Here, the second photoconductive member 24c of the photosensitive screen 20 can be charged with both positive and negative charges.
The charging polarity of the uniform exposure simultaneous primary charging step shown in FIG. 5 can also be arbitrarily selected. In this embodiment, the polarity of this primary charging is positive. Therefore, Example 22
However, the electrostatic contrast V _C of the primary electrostatic latent image formed on the insulating member 22 is V _C =α _i V ₂ .

Example 24 In this example, in the above-mentioned Example 23, the charging polarity in the uniform exposure simultaneous primary charging step is made negative. Therefore, finally the insulation member 2
The primary electrostatic latent image contrast V _C formed on 2
becomes V _C =-α _i V _2D .

Example 25 A primary electrostatic latent image is formed according to method D using the photosensitive screen 20 shown in FIG. In this embodiment, the first photoconductive member 23b of the photosensitive screen 20
It differs from Example 23 described above in that it is of type (b).
Therefore, the static band contrast V _C of the primary electrostatic latent image formed on the insulating member 22 is V _C =α _i V _2D as in Example 24.

Example 26 This example differs from Example 25 described above in that the charging polarity in the uniform simultaneous primary charging process is made negative. Therefore, the electrostatic contrast V _C of the primary electrostatic latent image finally formed on the insulating member 22 is V _C =-α _i V ₂ as in Example 23 described above.

Example 27 A primary electrostatic latent image is formed according to method D using the photosensitive screen 20 shown in FIG. Since the second photoconductive member 24a of the photosensitive screen 20 has rectifying characteristics of the type (a), it is necessary to make the charging polarity negative in the first uniform exposure and simultaneous primary charging step. Therefore, this embodiment is similar to the above-described embodiment 21, and the electrostatic contrast V _C of the primary electrostatic latent image formed on the insulating member 22 is V _C =-α _i V ₂ . That is, it is determined by the surface potential generated by the charge applied to the photosensitive screen 20 by secondary reverse charging upon irradiation of the light image.

Example 28 A primary electrostatic latent image is formed according to method D using the photosensitive screen 20 shown in FIG. In this embodiment, the second photoconductive member 24 of the photosensitive screen 20
Since b has rectification characteristics of type (b), it is necessary to make the charging polarity positive in the uniform exposure simultaneous primary charging step. Therefore, this example is similar to Example 27 described above.
The polarity of each charging process in is reversed,
The electrostatic contrast V _C of the primary electrostatic latent image formed on the insulating member 22 is V _C =α _i V ₂ .

Example 29 A primary photoelectrostatic latent image is formed on an insulating member 22 according to method E using the photosensitive screen 20 shown in FIG. First, as shown in FIG. 41, a corona thin wire 76 of a corona charger is placed on the insulating member 22 side of the photosensitive screen 20, and a corona power source 77 is connected between the corona thin wire 76 and the conductive member 27. A light image is irradiated from the insulating member 22 side while the screen 20 is negatively charged. At this time, the first photoconductive member 23c in the bright part of the optical image is equivalent to a conductor, but in the dark part, the first photoconductive member 23c has a high resistance, so if sufficient charging is performed, the surface potential of the dark part V _1D has a larger absolute value than the surface potential V _1L in the bright area. In addition, in FIG. 41, primary charging may be performed from the first photoconductive member 23c side.

Next, as shown in FIG.
exposure evenly. Through this step, the charge previously charged on the first photoconductive member 23c in the dark part of the optical image disappears, and a potential difference V _1D is created between the dark part and the bright part of the optical image.
_- V _1L occurs. Note that this uniform exposure can be performed from either or both of the insulating member 22 and the first photoconductive member 23c.

Thereafter, the photosensitive screen 20 is charged to a polarity opposite to that in the simultaneous primary charging step shown in FIG. 41. For this reason, in this embodiment, as shown in FIG.
and an AC power supply 80 are connected in series to perform an AC corona discharge with a positive DC voltage superimposed thereon. Therefore, the photosensitive screen 20 is charged uniformly by the apparent DC voltage in both the bright and dark areas of the photoimage. Note that this secondary reverse charging can also be performed from the first photoconductive member 23c side.

FIG. 44 is a diagram showing an example of the uniform exposure step performed after the above-mentioned secondary reverse charging. Through this step, charges of opposite polarity corresponding to charges held on the insulating member 22 after secondary reverse charging are trapped at the interface between the second photoconductive member 24a and the insulating member 22, and are electrostatically charged. _{A primary electrostatic latent image is formed on the insulating member 22 with an electrostatic contrast V c =} α _i (V _1D −V _1L ). In addition, in FIG. 44, negative charges are held on the insulating member 22 in both the bright and dark areas, but if the charging voltage in the secondary reverse charging process shown in FIG. It is possible to form a primary electrostatic latent image with different charge polarities. Further, this uniform exposure can be performed from either one or both sides of the insulating member 22 or the first photoconductive member 23c.

FIG. 45 is a diagram showing an example of the process of modulating the corona ion flow based on the primary electrostatic latent image formed as described above to form a secondary electrostatic latent image on the recording member. In this embodiment, the corona thin wire 8 is arranged on the first photoconductive member 23c side of the photosensitive screen 20.
A DC corona power supply 8 is connected between the conductive member 1 and the conductive member 21.
2 are connected, and a positive corona ion stream is projected toward the photosensitive screen 20 while uniformly exposing the photosensitive screen 20. Further, a recording member 84 placed closely on a back electrode 83 is disposed facing the insulating member 22 side of the photosensitive screen 20, and the back electrode 83 and the conductive member 22 of the photosensitive screen 20
An accelerating power source 85 is connected between the photosensitive screen 20 and the photosensitive screen 20 so that the positive corona ion flow passing through the openings of the photosensitive screen 20 can be guided to the recording member 84. Here, in the openings of the photosensitive screen 20, a promoting electric field is formed that promotes the passage of positive corona ions, although the electric field strength is different in both the bright and dark areas. Therefore, the secondary electrostatic latent image formed on the recording member 84 will have a lot of fog, so it is necessary to uniformly charge the recording member 84 to a negative low potential in advance. be.

Example 30 A primary electrostatic latent image is formed according to method E using the photosensitive screen 20 shown in FIG. This example differs from Example 29 in that the charging polarity in the light image irradiation simultaneous primary charging step shown in FIG. 41 is positive. Therefore, the electrostatic contrast V _c of the primary electrostatic latent image finally formed on the insulating member 22 of the photosensitive screen 20 is V _c =α _i (V _1D −V _1L ).

Example 31 A primary electrostatic latent image is formed according to method E using the photosensitive screen 20 shown in FIG. In this example, the charging polarity in the light image irradiation simultaneous primary charging step shown in FIG. The electric contrast V _c is V _c =α _i (α _p V _1D −V _1L ).

Example 32 A primary electrostatic latent image is formed according to method E using the photosensitive screen 20 shown in FIG. This example differs from Example 31 in that the charging polarity in the light image irradiation simultaneous primary charging step shown in FIG. 41 is negative. Therefore, the electrostatic contrast V _c of the primary electrostatic latent formed on the insulating member 22 is V _c = α _i ² V ₁ . Note that V ₁ represents the surface potential generated by the charge applied to the photosensitive screen by primary charging.

Example 33 A primary electrostatic latent image is formed according to method E using the photosensitive screen 20 shown in FIG. In this example, the charging polarity in the simultaneous primary charging step performed initially with light image irradiation is assumed to be positive, and the electrostatic contrast V _c of the primary electrostatic latent image formed on the insulating member 22 is similar to Example 31 described above. As in Example 32, V _c =-α _i ² V ₁ .

Example 34 A primary electrostatic latent image is formed according to method E using the photosensitive screen 20 shown in FIG. This example differs from Example 33 in that the charging polarity in the light image irradiation simultaneous primary charging step shown in FIG. 41 is negative. Therefore, the electrostatic contrast V _c of the primary electrostatic latent image formed on the insulating member 22 is that of Example 31.
Similarly, V _c =-α _i (α _p V _1D −V _1L ).

Example 35 A primary electrostatic latent image is formed according to method E using the photosensitive screen 20 shown in FIG. In this embodiment, as shown in FIG. 41, the charging polarity in the first light image irradiation simultaneous primary charging step is positive. Therefore, the electrostatic contrast V _c of the primary electrostatic latent image formed on the insulating member 22 is V _c =-α _i (V _1D - V _1L ), as in Example 29.

Example 36 A primary electrostatic latent image is formed according to method E using the photosensitive screen 20 shown in FIG. In this example, the charging polarity in the light image irradiation simultaneous primary charging step shown in FIG. 41 is negative, and is similar to Example 30 described above. Therefore, the electrostatic contrast V _c of the primary electrostatic latent image formed on the insulating member 22 is V _c =α _i (V _1D −V _1L ).

As described above, in the electrophotographic photosensitive screen of the present invention, the first photoconductive member is deposited on one surface of the mesh-like conductive member so as to completely cover the mesh-like conductive member,
A second photoconductive member and an insulating member having different characteristics from those of the first photoconductive member are sequentially deposited on the other surface to form a primary electrostatic latent image for modulating the ion flow. Since it can be formed on an insulating member,
It has the following advantages:

A primary electrostatic latent image with high electrostatic contrast can be formed.

Since the photosensitive screen has good charge retention characteristics, secondary electrostatic latent images can be formed many times based on a single primary electrostatic latent image once formed on the photosensitive screen.

Since no bias voltage is applied to the photosensitive screen, problems such as sparks do not occur.

It has a simpler structure and is easier to manufacture than a four-layer photosensitive screen.

Good moisture resistance and charge retention properties.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing the structure of a conventional electrophotographic photosensitive screen, and FIGS. 2, 3, and 4 show each step of forming a primary electrostatic latent image using the photosensitive screen shown in FIG. 5 is a diagram showing the process of forming a secondary electrostatic latent image using the photosensitive screen shown in FIG. 1, and FIGS. 6 to 11 are diagrams showing the electrophotographic photosensitive screen of the present invention, respectively. 12 is a diagram showing the characteristics of the photoconductive member of the electrophotographic photosensitive screen of the present invention; FIG. 13 is a sectional view showing still another structure of the electrophotographic photosensitive screen of the present invention; 14 to 16 are diagrams for explaining an electrophotographic method according to method A using the electrophotographic photosensitive screen of the present invention shown in FIG. 6, and FIG. 14 shows a light image irradiation simultaneous charging step. Diagram, Fig. 15 is a diagram showing the uniform exposure process, Fig. 1
Figure 6 is a diagram showing the process of forming a secondary electrostatic latent image;
17 to 20 are diagrams for explaining the electrophotographic method according to method B using the photosensitive screen for electrophotography of the present invention shown in FIG. The line diagram shown in Fig. 18 is 2
Figure 19 is a diagram showing the secondary reverse charging process, Figure 19 is a diagram showing the uniform exposure process, Figure 20 is a diagram showing the secondary electrostatic latent image formation process, Figures 21 to 23 are Figure 8. FIG. 21 is a diagram showing the sequential steps of forming a primary electrostatic latent image according to the electrophotographic method according to method B using the photosensitive screen for electrophotography of the present invention shown in FIG. 22 is a diagram showing the secondary reverse charging step, FIG. 23 is a diagram showing the uniform exposure step, and FIG. 24 is a sectional view showing still another structure of the electrophotographic photosensitive screen of the present invention. 25 to 28 are diagrams for explaining the electrophotographic method according to method B using the photosensitive screen for electrophotography of the present invention shown in FIG.
A diagram showing the next charging process, Figure 26 is a diagram showing the secondary reverse charging process, Figure 27 is a diagram showing the uniform exposure process, and Figure 28 is a diagram showing the secondary electrostatic latent image forming process. , FIGS. 29 to 34 are diagrams for explaining the electrophotographic method according to method C using the electrophotographic photosensitive screen of the present invention shown in FIG. 6, and FIG. 29 is a diagram showing the primary charging process. Figure 30 is a diagram showing the secondary reverse charging process at the same time of light image irradiation, Figure 31 is a diagram showing the uniform exposure process, and Figures 32 and 33 are the diagrams showing the primary electrostatic charge formed on the photosensitive screen, respectively. A diagram showing the surface potential and electrostatic contrast of the latent image,
FIG. 34 is a diagram showing the process of forming a secondary electrostatic latent image, and FIGS. 35 to 40 illustrate an electrophotographic method according to method D using the photosensitive screen for band photography of the present invention shown in FIG. 6. Figure 35 is a diagram showing the uniform exposure simultaneous primary charging process, Figure 36 is a diagram showing the light image irradiation simultaneous secondary charging process, and Figure 37 is a diagram showing the uniform exposure process. , FIG. 38 and FIG. 39 are diagrams showing the surface potential and electrostatic contrast of the primary electrostatic latent image formed on the photosensitive screen, respectively, and FIG. 40 is a diagram showing the process of forming the secondary electrostatic latent image. , FIGS. 41 to 45 are diagrams for explaining the electrophotographic method according to method E using the electrophotographic photosensitive screen of the present invention shown in FIG. A diagram showing the process, Figure 42 is a diagram showing the uniform exposure process performed after the primary charging process at the same time as light image irradiation, Figure 43 is a diagram showing the secondary reverse charging process, and Figure 44 is the secondary reverse charging process. FIG. 45 is a diagram showing a uniform exposure process performed after the process, and FIG. 45 is a diagram showing a secondary electrostatic latent image forming process. 20... Photosensitive screen, 21... Conductive member, 22... Insulating member, 23... First photoconductive member, 24... Second photoconductive member, 46... Opaque conductive layer.

Claims (1)

[Claims] 1. A photoconductive material that is easily charged to a positive polarity, a photoconductive material that is easy to be charged to a negative polarity, and a light that is easily charged to either a positive or a negative polarity are placed on one side of a mesh-like conductive member having many fine openings. A first photoconductive member made of one photoconductive substance selected from conductive substances, and a second photoconductive member made of a photoconductive substance other than the selected one photoconductive substance on the other side;
1. A photosensitive screen for electrophotography, comprising: an insulating member formed thereon, and the conductive member is completely covered by these members.