JPH09251229A - Electric charge generator for electrostatic latent image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electric charge generator for an electrostatic latent image forming device capable of forming a control voltage clearance between a finger electrode and the screen electrode without use of a thick insulated film, and improving the durability while reducing the dispersion of an ion pickup amount. SOLUTION: The device is provided with a groove part 2 whose depth is approximately equal to the clearance required between the finger electrode and the screen electrode, formed on the insulating base body 1, and plural line electrodes 3 formed in parallel to each other so as to cross at right angle to the groove part 2. Then, a dielectric layer 4 provided with a uniform thickness is formed on the insulating base body 1 and the line electrodes 3, and the finger electrode 5 is formed along a bottom surface of the groove part 2 on the dielectric layer 4 so as to cross the line electrodes 3. Moreover, the electric charge generator is composed by disposing the planner screen electrode 7 provided with the screen opening 8 on a part corresponding to the crossing part of the line electrode 3 and the finger electrode 5 across the insulating layer 6, on the dielectric layer 4 formed on the insulating base body 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charge generator used in an electrostatic image forming device or a display device used in electrostatic printing.

[0002]

2. Description of the Related Art Conventionally, a charge generator using a corona discharge has been used as a method of forming a latent image by electrostatic charge on a dielectric recording medium based on a principle of transferring and depositing electric charges directly on a dielectric recording medium. Japanese Patent Application Publication No. 2-62862 discloses a technique for forming such a charge generator with high definition using a semiconductor fine processing technique.
68145.

FIG. 23 is a cross-sectional view showing a part of a configuration example of a conventional charge generator for an electrostatic image forming apparatus. In FIG. 23, 100 indicates one charge generation control element, and the charge generator is configured by arranging a large number of charge generation control elements 100 one-dimensionally or two-dimensionally. The charge generation control element 100 is an insulating substrate 101 made of quartz or glass.
, A line electrode 102 made of metal, a dielectric film 103, a finger electrode 104 made of metal, an insulating film 105, and a screen electrode 106, and the finger hole 107 and the screen are formed in the finger electrode 104 and the screen electrode 106. Holes 108 are respectively formed.

The charge generation control device 100 having the above-described configuration
Are formed by forming a resist pattern on a metal film formed by a method such as a sputtering method or a vacuum evaporation method, and then removing portions not covered by the resist pattern by etching. For the dielectric film 103, a material having a high electrostatic withstand voltage such as a silicon oxide film or a silicon nitride film formed by a method such as a CVD (chemical vapor deposition) method or a sputtering method is used. The insulating film 105 is formed by a spin coating method or a screen printing method using a resin that is a high heat-resistant organic film such as polyimide.

Next, the operation of the thus-configured charge generation control device 100 will be described. In FIG.
By applying an AC voltage of a thousand and several hundred volts between the line electrode 102 and the finger electrode 104 disposed with the dielectric film 103 interposed therebetween, a charge group is generated in a region of the finger hole 107 by a corona discharge phenomenon. Negative charges having a large mobility in the charge group are used for latent image formation. When a potential more positive than the potential applied to the finger electrode 104 is applied to the screen electrode 106 formed with the insulating film 105 interposed therebetween, facing the finger electrode 104, the negative charges generated by the corona discharge are applied to the screen electrode 106. It is extracted from the screen hole 108 formed. The negative charges extracted from the screen holes 108 are discharged toward a drum (not shown) which is a dielectric recording material, and are deposited on the drum to form a charge latent image. Conversely, when a negative potential is applied to the screen electrode 106 with respect to the finger electrode 104, extraction of negative charges from the screen hole 108 is blocked, and a latent image is not formed on the drum.

[0006]

By the way, when a conventional charge generator for an electrostatic image forming apparatus is driven, the uniformity of the film thickness of the insulating film disposed between the finger electrodes and the screen electrode is Is an important factor in controlling the extraction amount of. Figure 24 shows the relationship between the variation in the ion current output and the variation in the thickness of the 50-micron insulating film made of polyimide.From this figure, when the thickness of the insulating film is 50 microns, it is within 0.3 microns, namely ± It can be seen that if there is no uniformity of 0.5% or less, the variation in ion current output cannot be suppressed to 2% or less, and uneven density occurs when drawing.

However, in the conventional charge generator, regardless of the coating method or the printing method, it is necessary to form the insulating film with a uniform thickness of about 50 μm as shown in FIG. The larger the size, the more difficult it becomes. Particularly, in the coating method, the peripheral portion of the substrate tends to have a thicker film than the central portion, and it is difficult to obtain the above uniformity in the process. Therefore, when only the area with good uniformity is used as a charge generator, it is necessary to use a large substrate that exceeds the specifications in order to connect small chips or increase the area with good uniformity. There are drawbacks such as poor productivity and high cost.

Further, the plasma generated by the corona discharge inside the finger holes is confined by the electric field,
Some positive or negative ions leak from there, and the sidewalls of the insulating film 105 and the like are sputtered (shown by arrows) as shown in FIG. Therefore, the insulating film 105 is etched by the ion irradiation, and as shown by the reference numeral 111, the side wall recedes and a change with time occurs, and the control voltage becomes unstable.
As a result, it becomes difficult to extract the charge from the screen hole 108, and the characteristics of the charge generator are significantly deteriorated. Further, due to the receding of the side wall of the insulating film, the eaves of the screen electrode 106 becomes large in the hole for charge extraction, and as shown by reference numeral 112, a crack is generated in the screen electrode 106 and the reliability of the charge generator is deteriorated.

Further, moisture, oxygen, nitrogen, etc. in the atmosphere existing in the screen hole 108 or the finger hole 107 are dissociated by corona discharge to form nitric acid (HNO ₃ ). By attaching this to the insulating film 105,
Corrosion or etching occurs, which causes the side wall of the insulating film to recede, which significantly deteriorates the reliability of the charge generator.

Therefore, in order to avoid these problems, if the insulating film is made of a hard inorganic film that is hard to be etched and has a thickness of several tens of microns, cracks will occur due to the internal stress of the film. In addition, when a thick inorganic hard film is formed by the CVD method or the sputtering method, it takes a long time to form, and it also takes a long time to form a hole.
Productivity is very poor. In order to suppress the generation of nitric acid, it is possible to evacuate the entire charge generator and make the atmosphere inside the screen holes or finger holes a vacuum state, but the size of the device itself becomes large, and it is possible to reduce the size and cost. There is a problem that it is not suitable.

The present invention has been made in order to solve the above problems in the conventional charge generator for an electrostatic image forming apparatus, and does not use a thick insulating film that determines the characteristics of the charge generator, but does not use a finger electrode. It is possible to form the required control voltage interval between the screen electrode and the screen electrode, reduce changes in the amount of individual ions extracted from the charge generation control element, and have excellent resistance to sputtering due to generated ions during corona discharge. Another object of the present invention is to provide a charge generator for an electrostatic image forming apparatus, which has etching resistance against deposits due to products such as nitric acid. Another object of the present invention is to reduce the influence of adjacent charge generation control elements in the charge generator for an electrostatic image forming apparatus. Still another object of the present invention is to increase the amount of extracted ions in the charge generator for the electrostatic image forming apparatus.

[0012]

In order to solve the above problems, the present invention according to claim 1 provides a plurality of line electrodes extending in one direction and in parallel on an insulating substrate, and intersecting the line electrodes. And a finger electrode that extends in a direction that forms a matrix together with the line electrode, and is arranged on the side opposite to the line electrode with respect to the finger electrode, and an opening is formed at a portion corresponding to the intersection of the matrix. A screen electrode, a dielectric film provided between the line electrode and the finger electrode, and an opening formed at a portion corresponding to the intersection of the matrix, provided between the finger electrode and the screen electrode. In the charge generator for an electrostatic image forming apparatus, the insulating substrate is required to be provided between the finger electrodes and the screen electrodes on its surface. A recess having a depth corresponding to the control voltage interval is formed, and the line electrode and the finger electrode are formed in the recess so that the intersection of the matrix is located at the bottom of the recess. The screen electrode is arranged along with the intervening dielectric film, and the screen electrode is arranged along the surface of the insulating substrate through the insulating film.
According to a second aspect of the present invention, in the charge generator for an electrostatic image forming apparatus according to the first aspect, the concave portion of the insulating substrate is formed in a groove shape along the line electrode. According to a third aspect of the present invention, in the charge generator for an electrostatic image forming apparatus according to the first aspect, the concave portion of the insulating substrate is formed in a groove shape along the finger electrodes.

By configuring the charge generator in this way, a required control voltage interval is formed between the finger electrodes and the screen electrodes without using a thick insulating film,
Variation in charge output between charge generation control elements due to non-uniformity of the film thickness when forming a thick insulating film is reduced, and the side wall of the insulating film is caused by ion irradiation generated by corona discharge or corrosion caused by product adhesion. Of the electric charge is eliminated, whereby the electric charge can be stably extracted and the change with time can be reduced. Further, by suppressing the receding of the insulating film, it is possible to reduce cracks and the like in the holes of the screen electrode and improve the reliability.

According to a fourth aspect of the present invention, in the charge generator for an electrostatic image forming apparatus according to the first aspect, the recess of the insulating substrate is a box hole or a cylinder at the intersection of the line electrode and the finger electrode. It is formed into a hole shape. This makes it possible to extract charges with good controllability without being affected by the adjacent charge generation control element.

According to a fifth aspect of the present invention, in the charge generator for an electrostatic image forming apparatus according to any one of the first to fourth aspects, the finger electrodes are formed in a plate shape.
In the invention according to claim 6, the finger electrodes are similarly formed in a plate shape with slits.
In the invention described above, the finger electrode is also formed by providing a hole portion for charge generation at the intersection with the line electrode. By forming the finger electrodes in this way, it is possible to increase the amount of charges to be extracted, and it is possible to stably supply charges that contribute to latent image formation for a long period of time.

[0016]

Next, an embodiment will be described. FIG. 1A is a cross-sectional view showing a single charge generation control element constituting the first embodiment of the charge generator for an electrostatic image forming apparatus according to the present invention, and FIG. Is (A) in FIG.
It is a schematic perspective view which abbreviate | omits a part of charge generator of 1st Embodiment which consists of the some charge generation control element shown in FIG. In the figure, 1 is an insulating substrate, and the insulating substrate 1 has a depth substantially equal to the thickness of a conventional thick insulating film, that is, a dimension corresponding to a control voltage interval required between a finger electrode and a screen electrode. The groove portion 2 is formed along the arrangement direction of the finger electrodes described later. Then, on the insulating substrate 1, so as to be orthogonal to the groove portion 2,
In addition, a plurality of line electrodes 3 are formed in parallel with each other along the side wall and the bottom surface of the groove 2, and the insulating substrate 1 and the line electrode 3 have a uniform thickness on the inside of the groove 2. A dielectric film 4 is formed, and a groove 2 is formed on the dielectric film 4.
A plurality of finger electrodes 5 having slits 5a are formed along the bottom surface of the above so as to intersect with the line electrodes 3. Further, a flat plate-shaped screen electrode 7 having a screen hole 8 formed at a portion corresponding to the intersection of the line electrode 3 and the finger electrode 5 is provided on the insulating substrate 1 via an insulating film 6.
The charge generator 10 is formed by disposing the charge generator 10 on the dielectric film 4 formed in the above.

In the charge generator thus constructed, instead of using a conventional thick insulating film made of polyimide, a groove is formed in the insulating substrate so that a desired distance between the finger electrode and the screen electrode can be obtained. Therefore, the variation of the ion output due to the difference in the thickness of the insulating film is reduced, and a dielectric film that is difficult to be etched is formed on the side wall of the groove. The resistance to etching can be imparted to products such as nitric acid without causing receding of the electric field, and thus the electric charge that contributes to latent image formation can be stably supplied between the elements in the initial and long term. The reliability of the charge generator can be improved.

In the above embodiment, the groove formed on the insulating substrate is formed along the portion where the finger electrodes are arranged, but it should be formed along the portion where the line electrodes are arranged. However, the same effect can be obtained.

Next, the first shown in (A) and (B) of FIG.
The method for manufacturing the charge generator according to the embodiment will be described with reference to the manufacturing process diagrams shown in FIGS. First, as shown in FIG. 2, an insulating substrate 11 made of quartz, NA glass, Al ₂ O ₃ or the like is prepared, and as shown in FIG. By the processing method, the elongated groove portion 12 having a depth and a width of about 50 μm is formed. After that, a wet etching process is performed in order to reduce the roughness of the processed surface. Next, a titanium film having a thickness of about 1.0 micron is formed on the entire surface including the groove 12 by a sputtering method or the like, and then a line electrode 13 is formed so as to intersect the groove 12 as shown in FIG. Form a resist pattern on the titanium film,
The portion not covered with the resist pattern is removed by isotropic or anisotropic etching.

Next, after removing the resist pattern, as shown in FIG. 5, a method such as plasma CVD is used.
For example, the dielectric film 14 made of a silicon oxide film is formed on the entire surface by the reaction of monosilane (SiH ₄ ) and nitrous oxide (N ₂ O). The dielectric film 14 made of this silicon oxide film is
A predetermined thickness (5 to 10 μm) capable of withstanding a high voltage applied between the line electrode 13 and a finger electrode described later is required. Next, as shown in FIG. 6, a titanium film 15a having a thickness of about 3.0 μm is formed on the entire surface by a sputtering method or the like, and thereafter, a resist is formed so as to remain only on the finger electrode formation portion at the bottom of the groove 12. The pattern 16 is formed by the photolithography method. Next, as shown in FIG. 7, a portion of the titanium film 15a which is not covered with the resist pattern 16 is removed by isotropic or anisotropic etching to form a finger electrode 15 having a slit. .

Next, as shown in FIG. 8, a thin metal plate 18a made of Ti, TiN, Mo, W, SUS or the like, which serves as a screen electrode, is formed on the lower surface with an insulating film 17 thicker than the dielectric film 14 in advance. Insulating substrate 11 on which dielectric film 14 is formed with an adhesive or the like
Stick on top. Finally, as shown in FIG. 9, the metal thin film 18a for the screen electrode is formed by photolithography.
The insulating film 17 and the insulating film 17 are etched by anisotropic dry etching to form a screen hole 19 to form a screen electrode 18 to complete a charge generator having the same structure as shown in FIGS. 1 (A) and 1 (B). .

The reason why the anisotropic dry etching method is used for the processing of the screen electrode is that the screen electrode is formed of a thin metal plate and has a film thickness of several tens of microns, and a metal film formed by a sputtering method or the like. Much thicker than. Therefore, an etching method that avoids side etching is desirable.

As a method of processing and forming the groove on the insulating substrate, a dry etching method by RIE (Reactive Ion Etching) or a jet method using water pressure may be used. Further, the line electrodes and finger electrodes are shown as those formed using a titanium film by a sputtering method, but these electrode films may be metal films that can withstand high voltage and corona discharge, for example, Materials such as Mo and W are sputtered or CV
You may form using the D method.

Further, although a dielectric film using a silicon oxide film by a plasma CVD method is shown, it is not limited to this, and for example, boron (B), phosphorus (P), aluminum (Al), silicon (Si). ), Titanium (Ti), tantalum (Ta), tungsten (W), zirconium (Zr), calcium (Ca), hafnium (Hf),
Vanadium (V), niobium (Vb), chromium (Cr),
Any of oxides, carbides, nitrides, and fluorides of magnesium (Mg), lead (Pb), tin (Sn), etc. can be used, and a composite film of these compounds may be used.

Next, the second embodiment will be described with reference to FIG.
Description will be made based on (B). 10A is a cross-sectional view showing a single charge generation control element constituting the charge generator according to the second embodiment, and FIG. 10B is shown in FIG. 10A. FIG. 3 is a perspective view of a charge generator that is shown with a part of the charge generator including a plurality of charge generation control elements omitted. In this embodiment, the surface of the insulating substrate 21 is provided with a box hole having a depth substantially equal to the thickness of a conventional thick insulating film, that is, the dimension corresponding to the space required between the finger electrode and the screen electrode. The hole portion 22 having a shape of a circle is formed at a portion corresponding to an intersection of a line electrode and a finger electrode described later. A plurality of line electrodes 23 are formed on the insulating substrate 21 in parallel with each other through the sidewalls and the bottom of the hole 22, and the hole 22 is formed on the insulating substrate 21 and the line electrode 23. A first dielectric film 24-1 having a uniform thickness is formed on the inside of the first dielectric film 24-1, and a hole is formed on the first dielectric film 24-1.
To intersect with the line electrode 23 on the bottom surface of 22,
A plurality of finger electrodes 25 having slits 25a are formed. Then, the finger electrode 25 and the first dielectric film 24
-1 on which the second dielectric film 24-2 is formed except for the slit portion 25a of the finger electrode 25 and its vicinity, and the hole portion 22
A flat plate-shaped screen electrode 27 having a screen hole 28 formed in a portion corresponding to is disposed on the first and second dielectric films 24-1 and 24-2 formed on the insulating substrate 21 via the insulating film 26. Then, the charge generator 30 is configured. The reason why the second dielectric film 24-2 is provided is that it is not preferable in terms of reliability if the screen electrode 27 is directly adhered to the finger electrode 25 via the insulating film 26, and the finger electrode 25 is attached to the second dielectric film 24-2. This is because it is considered that it is better to cover the surface with -2 and then bond the screen electrode 27 through the insulating film 26.

Also in the charge generator of the second embodiment configured as described above, instead of using the conventional thick insulating film made of polyimide, a hole portion is formed in the insulating substrate so that a space between the finger electrode and the screen electrode is formed. Since a desired interval is obtained, holes for charge extraction are formed for each charge generation control element, and the charges generated from the finger electrodes are controlled without being affected by the adjacent charge generation control elements. It can be easily extracted from the screen hole,
The electric charge can be stably output in the initial or long term. Although the hole formed in the insulating substrate has a box hole shape, it may have a cylindrical hole shape, and similar effects can be obtained.

Next, the second shown in FIGS. 10 (A) and 10 (B).
11 to FIG. 11 are views showing a method of manufacturing the charge generator according to the embodiment of FIG.
A description will be given based on the manufacturing process chart shown in FIG. First, as shown in FIG. 11, an insulating substrate 31 made of quartz, NA glass, Al ₂ O ₃ or the like is prepared, and as shown in FIG. 12, a portion where an intersection of a line electrode and a finger electrode, which will be described later, is located is located. The hole portion 32 having a depth and a width of about 50 μm is formed by a mechanical processing method or a laser processing method. After that, a wet etching process is performed in order to reduce the roughness of the processed surface. Next, by the sputtering method, etc. 1.
A titanium film having a thickness of about 0 micron is formed on the entire surface including the hole portion 32, and then, as shown in FIG. 13, a titanium film is formed so that the line electrode 33 is formed over the side wall and the bottom surface of the hole portion 32. Forming a resist pattern on the film,
The portion not covered with the resist pattern is removed by isotropic or anisotropic etching.

Next, as shown in FIG. 14, after removing the resist pattern, a method such as plasma CVD is used.
For example, the first dielectric film 34 made of a silicon oxide film is formed by the reaction of monosilane (SiH ₄ ) and nitrous oxide (N ₂ O). The first dielectric film 34 made of this silicon oxide film
Requires a predetermined thickness (5 to 10 microns) that can withstand the high voltage applied between the line electrode 33 and the finger electrode. Next, as shown in FIG. 15, a titanium film 35a to be a finger electrode film having a thickness of about 3.0 μm is formed on the entire surface by a sputtering method or the like. Next, a resist pattern 36 is formed by a photolithography method so that the charge generation portion of the finger electrode is formed in the hole portion 32 of the insulating substrate 31.

Next, as shown in FIG. 16, a portion of the titanium film 35a which is not covered with the resist pattern 36 is removed by isotropic or anisotropic etching to obtain a finger having a slit 35-1. The electrode 35 is formed. Next, as shown in FIG. 17, a resist pattern 36
After removing the first dielectric film 34, for example, monosilane (SiH
₄ ) and nitrous oxide (N ₂ O) are reacted to form a second dielectric film 37 made of a silicon oxide film of about 5 μm.

Next, as shown in FIG.
Resist pattern to expose the surface of 35 charge generation parts
By patterning with 38, and then, as shown in FIG. 19, the second dielectric film 37 on the charge generating portion of the finger electrode 35 is removed by isotropic or anisotropic etching to form the slit 35-1. A hole 39 is formed in the second dielectric film 37 so as to expose the surface of the charge generation portion of the finger electrode 35.
Next, as shown in FIG. 20, Ti, TiN, Mo, W, and SU, which are screen electrode materials with an insulating film 41 formed on the lower surface in advance, are formed.
A thin metal plate 42a such as S is attached to the second dielectric film 37 with an adhesive or the like. Finally, as shown in FIG. 21, the metal thin film 42a and the insulating film 41 are etched by a photolithography method to form a screen electrode 42 having a screen hole 43, which is shown in FIGS. A charge generator having the same structure as described above is completed.

In each of the above embodiments, the finger electrodes are provided with slits at the intersections with the line electrodes, but the generated charge amount is slightly reduced, but FIG.
As shown in FIG. 22 (A) showing a modification of the first embodiment, a simple plate-shaped finger electrode 5'may be used. Further, as shown in FIG. 22B, a finger hole 5b may be formed at the center of the intersection with the line electrode to form the finger electrode 5 ″, which is similar to the case where the slit 5a is provided. In addition, a high electric field is generated in the finger holes 5b to generate corona discharge, and the amount of electric charges extracted from the screen holes can be increased.

[0032]

As described in the above embodiments, according to each of the first to third aspects of the present invention, the control voltage interval required between the finger electrode and the screen electrode is eliminated without using a thick insulating film. Is formed, the unevenness of the charge output between elements due to the non-uniformity of the film thickness that occurs during the formation of a thick insulating film is reduced, and the side wall of the insulating film that is caused by the ion irradiation generated by corona discharge or the corrosion due to the adhesion of the product There is no receding, so that the charge can be stably extracted and the change over time can be reduced. Further, by suppressing the receding of the insulating film, it is possible to reduce cracks and the like in the holes of the screen electrode and improve the reliability. Further, according to the invention described in claim 4, the charge can be extracted with good controllability without being influenced by the adjacent element, and according to each invention described in claims 5 to 7, The output characteristics can be increased and stable output characteristics can be obtained over a long period of time.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a first embodiment of a charge generator for an electrostatic image forming apparatus according to the present invention.

FIG. 2 is a diagram showing a manufacturing process for explaining a manufacturing method of the charge generator according to the first exemplary embodiment shown in FIG.

FIG. 3 is a view showing a manufacturing process following the manufacturing process shown in FIG. 2;

FIG. 4 is a view showing a manufacturing process following the manufacturing process shown in FIG. 3;

FIG. 5 is a view showing a manufacturing process subsequent to the manufacturing process shown in FIG. 4;

FIG. 6 is a view showing a manufacturing process subsequent to the manufacturing process shown in FIG. 5;

FIG. 7 is a diagram showing a manufacturing process that follows the manufacturing process shown in FIG. 6;

FIG. 8 is a view showing a manufacturing process subsequent to the manufacturing process shown in FIG. 7;

9 is a diagram showing a manufacturing process that follows the manufacturing process shown in FIG. 8. FIG.

FIG. 10 is a schematic diagram showing a second embodiment of the present invention.

FIG. 11 is a diagram showing a manufacturing process for explaining the manufacturing method of the charge generator according to the second exemplary embodiment shown in FIG. 10.

FIG. 12 is a diagram showing a manufacturing process that follows the manufacturing process shown in FIG. 11.

FIG. 13 is a diagram showing a manufacturing process that follows the manufacturing process shown in FIG. 12.

14 is a diagram showing a manufacturing process that follows the manufacturing process shown in FIG. 13.

15 is a diagram showing a manufacturing process that follows the manufacturing process shown in FIG. 14.

16 is a diagram showing a manufacturing process that follows the manufacturing process shown in FIG. 15.

FIG. 17 is a diagram showing a manufacturing process that follows the manufacturing process shown in FIG. 16.

18 is a diagram showing a manufacturing process that follows the manufacturing process shown in FIG. 17.

FIG. 19 is a diagram showing a manufacturing process that follows the manufacturing process shown in FIG. 18.

20 is a diagram showing a manufacturing process that follows the manufacturing process shown in FIG. 19.

FIG. 21 is a diagram showing a manufacturing process that follows the manufacturing process shown in FIG. 20.

22 is a schematic diagram showing a modification of the first embodiment shown in FIG. 1.

FIG. 23 is a cross-sectional view showing a part of a configuration example of a conventional charge generator for an electrostatic image forming apparatus.

FIG. 24 is a diagram showing a relationship of variations in ion current output with variations in thickness of an insulating film.

FIG. 25 is an explanatory diagram for explaining a problem of the conventional charge generator.

FIG. 26 is an explanatory diagram for explaining another problem of the conventional charge generator.

[Explanation of symbols]

 1,11,21,31 Insulation substrate 2,12 Groove part 3,13,23,33 Line electrode 4,14 Dielectric film 5,15,25,35 Finger electrode 6,17,26,41 Insulation film 7,18,27 , 42 Screen electrode 8, 19, 28, 43 Screen hole 10, 30 Charge generator 16, 36, 38 Resist pattern 22, 32 Hole part 24-1, 34 First dielectric film 24-2, 37 Second dielectric film

Claims (7)

[Claims] 1. A plurality of line electrodes extending in one direction and in parallel on an insulating substrate, finger electrodes extending in a direction intersecting with the line electrodes and forming a matrix with the line electrodes, A screen electrode, which is arranged on the side opposite to the line electrode with respect to the finger electrode and has an opening formed in a portion corresponding to the intersection of the matrix, and a dielectric provided between the line electrode and the finger electrode. In a charge generator for an electrostatic image forming device, which comprises a film and an insulating film provided between the finger electrodes and the screen electrodes and having an opening formed in a portion corresponding to an intersection of the matrix, The insulating substrate is
A recess having a depth corresponding to a control voltage interval required between the finger electrode and the screen electrode is formed on the surface, and the line electrode and the finger electrode in the recess have an intersection of the matrix. A static electrode, which is arranged with a dielectric film interposed between both electrodes so as to be located at the bottom of the concave portion, and the screen electrode is arranged along the surface of the insulating substrate through the insulating film. A charge generator for an image forming device. 2. The charge generator for an electrostatic image forming apparatus according to claim 1, wherein the concave portion of the insulating substrate is formed in a groove shape along the line electrode. 3. The charge generator for an electrostatic image forming apparatus according to claim 1, wherein the concave portion of the insulating substrate is formed in a groove shape along the finger electrodes. 4. The electrostatic image forming apparatus according to claim 1, wherein the concave portion of the insulating substrate is formed in a box hole shape or a cylindrical hole shape at an intersection of the line electrode and the finger electrode. Charge generator. 5. The charge generator for an electrostatic image forming apparatus according to claim 1, wherein the finger electrodes are formed in a plate shape. 6. The charge generator for an electrostatic image forming apparatus according to claim 1, wherein the finger electrodes are formed in a plate shape with slits. 7. The electrostatic image according to any one of claims 1 to 4, wherein the finger electrode has a hole for charge generation at an intersection with the line electrode. Charge generator for forming device.