JPH09174915A - Charge generation controlling element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a charge generation controlling element, in which stable output is obtained, by a method wherein the retreat of the side wall of an insulating film due to the ion irradiation by corona discharge or the adhesion of product is suppressed. SOLUTION: In a charge generation controlling element 100 consisting of a line electrode 102 formed on the surface of an insulating board 101, a dielectric film 103 formed on the surface of the line electrode 102, a finger electrode 104, which is formed on the upper part of the dielectric film 103 and at the center of which a finger hole 107 for producing charge is formed, and a screen electrode 106 having a charge efflux screen hole 108 formed on the surface of the finger electrode 104 through an insulating film 105 having a hole, through which charge is passed, at its center, the side wall, through the hole of which charge is passed, of the insulating film 105 is so constituted as to be covered with an inorganic insulating film 121.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charge generation control element that constitutes an electrostatic image forming apparatus used in electrostatic printing.

[0002]

2. Description of the Related Art Conventionally, a charge generation control element utilizing corona discharge has been used as a method for forming a latent image by electrostatic charges on a dielectric recording body by the principle of transferring charges directly onto the dielectric recording body and depositing them. Is disclosed in Japanese Patent Publication No. 2-62862, and such a charge generation control element is
The method of forming high definition using semiconductor fine processing technology,
It is proposed in Japanese Patent Application No. 6-268145 filed by the applicant.

FIG. 25 is a sectional view showing a structural example of a charge generation control element for a conventional electrostatic image forming apparatus. In FIG. 25, 100 indicates one charge generation control element, and a large number of charge generation control elements 100 are arranged one-dimensionally or two-dimensionally to form a charge generator. 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. The finger electrode 104 and the screen electrode 106 have finger holes 107 and Each screen hole 108 is formed.

The charge generation control device 100 having the above-described configuration
Each of the electrodes constituting the is formed by forming a resist pattern on the metal film formed by a method such as a sputtering method or a vacuum deposition method, and then removing the portion not covered by the resist pattern by etching. Has become. For the dielectric film 103, a material having a high electrostatic breakdown 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 an organic film having high heat resistance such as polyimide.

Next, the operation of the thus-configured charge generation control device 100 will be described. In FIG. 25,
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 facing the finger electrode 104 with the insulating film 105 interposed, the negative charge generated by the corona discharge is generated. It is extracted from the screen hole 108 formed in the. Screen hole 108
The negative charges thus extracted are accelerated toward a drum (not shown) which is a dielectric recording body, and are deposited on the drum to form a latent charge image. Conversely, on the screen electrode 106,
When a negative potential is applied to the finger electrodes 104, the extraction of negative charges from the screen holes 108 is blocked,
No latent image is formed on the drum.

[0006]

However, the conventional charge generation control element for an electrostatic image forming apparatus has the following problems. That is, when driving the charge generation control element, the plasma due to the corona discharge generated inside the finger holes is confined by the electric field, but some positive or negative ions leak from the electric field, and the holes of the insulating film The sidewalls are sputtered as indicated by the arrow in FIG.
As a result, the insulating film is etched, the side wall recedes as indicated by reference numeral 111, and the control voltage becomes unstable. As a result, it becomes difficult to extract the charge from the screen hole, and the characteristics of the charge generation control element are significantly deteriorated. Further, due to the receding of the side wall of the insulating film, the projecting eaves of the screen electrode in the hole for extracting electric charges becomes large, and the reference numeral
As shown by, a crack is generated in the screen electrode, which deteriorates the reliability of the charge generation control element.

Further, moisture, oxygen, nitrogen, etc. in the atmosphere existing in the screen holes or finger holes are dissociated by corona discharge to form nitric acid (HNO ₃ ). When this adheres to the insulating film, corrosion or etching of the insulating film occurs, which causes the side wall of the insulating film to recede, which significantly deteriorates the reliability of the charge generation control element.

Further, in order to avoid these problems, if the insulating film is formed of a hard inorganic film which is hard to be etched and has a thickness of several tens of microns, internal stress causes cracks. Further, when the inorganic insulating film is formed by the CVD method or the sputtering method, it takes a long time to form the insulating film.
Since it takes time to process the hole formation, the productivity is very poor.

Further, in order to suppress the generation of nitric acid, the entire charge generator including a large number of charge generation control elements is evacuated,
It is considered that the atmosphere in the screen or the finger holes is in a vacuum state, but the size of the device itself becomes large, which is not suitable for downsizing and cost reduction.

The present invention has been made in order to solve the above-mentioned problems in the conventional charge generation control element, and the charge generation control capable of stably outputting the negative charge generated by the corona discharge for a long period of time. The purpose is to provide a device. The purpose of each claim is as follows. That is, it is an object of the invention according to claim 1 to provide a charge generation control element having excellent sputtering resistance due to ions during corona discharge and etching resistance against deposits due to products such as nitric acid. . Further, the invention according to claim 2 can further enhance the sputtering resistance even to a portion where the irradiation of ions during corona discharge is relatively large, and the etching resistance against the deposits due to products such as nitric acid. An object of the present invention is to provide a charge generation control element having Further, the invention according to claim 3 can increase the sputtering resistance even to a portion where the irradiation of ions during corona discharge is relatively large, and further the heat or impact due to the irradiation of ions causes the insulating film and the screen. It is an object of the present invention to provide a charge generation control element that prevents the problem of deteriorating the adhesion with electrodes and improves reliability. A fourth aspect of the invention is to provide a suitable material for the inorganic insulating film in each of the first to third aspects of the invention.

[0011]

In order to solve the above problems, the invention according to claim 1 provides a line electrode 102 formed on the surface of an insulating substrate 101 as shown in the conceptual diagram of FIG.
And the dielectric film 103 formed on the surface of the line electrode 102.
And a finger electrode 104 formed on the dielectric film 103 and having a finger hole 107 for charge generation in the center,
A charge generation control element 100 consisting of a screen electrode 106 having a screen hole 108 for discharging charges in the center, which is formed on the surface of the finger electrode 104 through an insulating film 105 having a hole for allowing the charges to pass through in the center. In, the side wall of the hole that allows the charge of the insulating film 105 to pass through is an inorganic insulating film.
It is configured to be covered with 121. With this structure, the side wall of the hole of the insulating film 105 is prevented from receding, stable output characteristics are obtained, and the side wall of the hole of the insulating film 105 is suppressed from receding.
The occurrence of cracks and the like in the screen holes 108 of 106 is also reduced, and the reliability can be improved.

According to a second aspect of the invention, as shown in the conceptual diagram of FIG. 2, the line electrode formed on the surface of the insulating substrate 101.
102 and the dielectric film 10 formed on the surface of the line electrode 102.
3 and a finger electrode 104 formed on the dielectric film 103 and having a finger hole 107 for charge generation in the center.
And formed on the surface of the finger electrode 104 via an insulating film 105 having a hole for allowing charges to pass through in the center,
In the charge generation control element 100 consisting of the screen electrode 106 having the screen hole 108 for discharging charges in the center,
The lower layer portion 105-1 of the insulating film 105 is formed of an inorganic insulating film,
The upper layer 105-2 is formed of an organic insulating film, and the lower layer 10-2 is formed.
The side wall of the hole of the insulating film 105 composed of 5-1 and the upper layer 105-2 is covered with the inorganic insulating film 121.
With such a configuration, a portion where a lot of ions are irradiated by corona discharge, that is, a lower layer portion 105-1 of the insulating film 105 is formed.
Since it is formed of an inorganic insulating film, it is possible to further suppress the receding of the side wall of the hole of the insulating film.

According to a third aspect of the invention, as shown in the conceptual diagram of FIG. 3, the line electrode formed on the surface of the insulating substrate 101.
102 and the dielectric film 10 formed on the surface of the line electrode 102.
3 and a finger electrode 104 formed on the dielectric film 103 and having a finger hole 107 for charge generation in the center.
And formed on the surface of the finger electrode 104 via an insulating film 105 having a hole for allowing charges to pass through in the center,
In the charge generation control element 100 consisting of the screen electrode 106 having the screen hole 108 for discharging charges in the center,
The lower layer portion 105-1 of the insulating film 105 is formed of an inorganic insulating film,
The upper layer 105-2 is formed of an organic insulating film, and the lower layer 10-2 is formed.
5-1 and the upper layer 105-2, the side wall of the hole of the insulating film 105 is covered with the inorganic insulating film 121, and the inorganic insulating film 122 is formed on the lower surface of the screen electrode 106 to form an insulating film made of an organic insulating film. The upper layer portion 105-2 of the film 105 is surrounded by the inorganic insulating film. With this configuration,
In addition to further suppressing the receding of the side wall of the hole of the insulating film 105,
It is possible to prevent the adhesion between the screen electrode 106 and the upper layer portion 105-2 made of the organic insulating film of the insulating film 105 from being lowered due to the ion irradiation. As a result, it is possible to realize various excellent properties such as having excellent durability and further excellent operational stability as compared with the conventional example.

According to a fourth aspect of the present invention, in the charge generation control element according to the first to third aspects, any one of a silicon oxide film, a silicon nitride film, and an alumina film is used as the inorganic insulating film covering the side wall of the hole of the insulating film 105. Is used. This provides a suitable inorganic insulating film that suppresses receding of the side wall of the hole of the insulating film.

[0015]

Next, an embodiment will be described. 4 to 14 are schematic cross-sectional structural views showing manufacturing steps for explaining the first embodiment of the charge generation control element according to the present invention. First, as shown in FIG. 4, a titanium film 202a for a line electrode having a thickness of about 0.5 micron is formed on an insulating substrate 201 made of quartz (or NA glass, Al ₂ O ₃ ) by a sputtering method or the like. To do. Next, FIG.
As shown in FIG.
By removing the part not covered by 3 by isotropic or anisotropic etching, the line electrode
Form 202. Next, as shown in FIG. 6, after removing the resist pattern 203, plasma CV is formed as a dielectric film 204.
A silicon oxide film is formed by a reaction such as monosilane (SiH ₄ ) and nitrous oxide (N ₂ O) by a method such as D method. The silicon oxide film needs to have a predetermined thickness (3 to 6 microns) that can withstand the high voltage applied between the line electrode 202 and the finger electrode described below.

Next, as shown in FIG. 7, a titanium film 205a for a finger electrode having a thickness of about 1.5 μm is formed by a sputtering method or the like. Next, as shown in FIG. 8, a portion of the titanium film 205a that is not covered with the resist pattern 206 is removed by isotropic or anisotropic etching to form a finger electrode 205 having finger holes 212. Form. Next, as shown in FIG. 9, an insulating film 207 made of an organic insulating film such as polyimide is formed to a thickness of about 50 μm by a screen printing method, and a hole portion 208 for allowing charges to pass is formed on the finger hole 212. After that, it is heat-treated at a temperature of about 300 ° C and solidified. Next, as shown in FIG. 10, a silicon oxide film 209a is formed on the entire surface of the insulating film 207 so as to have a predetermined film thickness by the CVD method or the sputtering method to a thickness of about 1 micron.

Next, as shown in FIG. 11, anisotropic etching is performed on the finger holes 212 and the finger electrodes 205.
Of the insulating film 207, and the insulating film 207
Only the silicon oxide film 209a formed above is removed by etching, and the inorganic insulating film 209 is left only on the side wall of the hole of the insulating film 207. Next, as shown in FIG. 12, a metal thin plate 21 such as Ti, Ti N, Mo, W, or SUS, which is a screen electrode material, is formed.
Stick 0a with an adhesive. Next, as shown in FIG.
The resist 211 is patterned by photolithography, and the thin metal plate 210a for a screen electrode in a region not covered by the resist 211 is removed by an anisotropic dry etching method to form a screen electrode 210 having a screen hole 213. To form. Finally, the resist
By removing 211, the charge generation control element having the configuration shown in FIG. 14, that is, FIG. 1 is completed.

The reason why anisotropic dry etching is used for processing the screen electrode in the above manufacturing process is that the screen electrode 210 is formed from the metal thin plate 210a, so that the film thickness is several tens of microns, and the sputtering method is used. Much thicker than formed. Therefore, an etching method that avoids side etching is desirable.

Although titanium films formed by the sputtering method are used as the line electrodes, finger electrodes and screen electrodes, these electrodes are not limited to titanium films and may be metal films that can withstand high voltage and corona discharge. For example, materials such as Mo and W are sputtered or CVD
You may form using the method. Furthermore, plasma C is used for the dielectric film.
Although the one using the silicon oxide film by the VD method is shown, it is not limited to this, and it is rather that the inorganic insulating film formed on the side wall of the hole of the insulating film has a different quality when the inorganic insulating film is etched. The end point detection is good. Therefore, any film can be used as long as it has a withstand voltage, such as boron (B), phosphorus (P), aluminum (Al), silicon (Si),
Titanium (Ti), tantalum (Ta), tungsten (W), zirconium (Zr), calcium (Ca),
Hafnium (Hf), Vanadium (V), Niobium (Nb
), Chromium (Cr), magnesium (Mg), lead (Pb)
), Tin (Sn), or other oxides, carbides, nitrides, or fluorides, or a composite film of these compounds.

Although a silicon oxide film is used as the inorganic insulating film formed on the side wall of the hole of the insulating film, the insulating film is not limited to this and may be any insulating film that can withstand ion irradiation.
For example, a silicon nitride film or an alumina film may be used. Also,
The processing method of the finger electrode may be isotropic or anisotropic, but in order to expose the finger hole side wall of the finger electrode on the surface during anisotropic etching of the inorganic insulating film formed on the side wall of the hole part of the insulating film. It is desirable that the side wall of the finger hole of the finger electrode is inclined by isotropic etching.

In the present embodiment, since the inorganic insulating film having ion irradiation resistance is selectively formed on the side wall of the hole of the insulating film, there is a conventional problem of receding the side wall of the hole of the insulating film due to ion irradiation. It is possible to suppress the charge and to provide etching resistance to products such as nitric acid, so that the electric charge that contributes to latent image formation can be stably supplied for a long time, and the reliability of the electric charge generation control element is improved. Can be made.

Next, a second embodiment of the present invention will be described with reference to FIG.
~ It demonstrates based on the manufacturing process drawing shown in FIG. First, by the same method as the manufacturing process of the first embodiment, as shown in FIG.
As shown in Fig. 1, after the line electrode 302 and the dielectric film 304 are formed on the insulating substrate 301, 1.
A finger electrode 305 having finger holes 312 made of a titanium film having a thickness of about 5 microns is formed. Next, as shown in FIG. 16, a silicon oxide film 307a to be a lower layer portion of the insulating film is formed on the entire surface of the substrate by plasma CVD to a thickness of about 3.0 μm by the same method as the formation of the dielectric film 304. . Next, as shown in FIG. 17, finger electrodes
A lower layer portion 30 of an insulating film made of a silicon oxide film 307a is formed on 305.
Wet the resist pattern 308 so that the silicon oxide film 307a on the finger holes 312 is removed, leaving 7
Alternatively, dry etching is performed. Next, as shown in FIG. 18, after removing the resist 308, the upper layer portion 309 of the insulating film made of an organic insulating film such as polyimide is screen-printed.
A thickness of about 50 μm is formed, and a hole portion for allowing an electric charge to pass is formed on the finger hole 312. After that, it is heat-treated at a temperature of about 300 ° C. and baked.

Next, as shown in FIG. 19, a silicon oxide film 310a is formed on the side wall of the hole of the insulating film composed of the lower layer portion 307 and the upper layer portion 309 by CVD or sputtering so as to have a predetermined thickness. Form about 1 micron. Next, Fig. 20
As shown in FIG. 3, anisotropic etching is performed to form the lower layer portion 30 of the insulating film on the finger holes 312 and the finger electrodes 305.
The portion not covered with 7 and the silicon oxide film 310a formed on the upper layer portion 309 of the insulating film are removed by etching, and only the side wall of the hole of the insulating film composed of the upper layer portion 309 and the lower layer portion 307 is filled with silicon. Inorganic insulating film 31 made of oxide film
Leave 0 Next, as shown in FIG. 21, a thin metal plate 311a such as Ti, Ti N, Mo, W or SUS, which is a screen electrode material, is bonded with an adhesive or the like. Next, as shown in FIG. 22, a resist 313 is patterned by a photolithography method, and the metal thin plate 311a for a screen electrode in a region not covered by the resist 313 is removed by an anisotropic dry etching method. Screen hole 31
A screen electrode 311 with 4 is formed. Finally, the resist 313 is removed to complete the charge generation control element having the structure shown in FIG. 23, that is, FIG.

In the present embodiment, an inorganic insulating film having ion irradiation resistance is selectively formed on the side wall of the hole of the insulating film, and the lower layer of the insulating film having strong ion irradiation is formed of the inorganic insulating film. Therefore, it is possible to suppress the receding of the side wall of the hole of the insulating film due to the ion irradiation, which has been a problem in the past, and to provide etching resistance to products such as nitric acid. The charge can be stably supplied over a long period of time, and the reliability of the charge generation control element can be improved.

Next, the third embodiment of the present invention will be described with reference to FIG.
A description will be given based on the sectional structure diagram shown in FIG. In this embodiment, the line electrode 402 and the dielectric film 403 are formed on the insulating substrate 401, the finger electrodes 404 are formed, and then the silicon oxide film is formed by the same method as the manufacturing process of the second embodiment. The inorganic insulating film 407 is formed only on the side wall of the hole of the insulating film formed by the lower layer portion 405 made of and the upper layer portion 406 made of an organic insulating film such as polyimide. Then, a thin metal plate for a screen electrode on which the inorganic insulating film 408 is formed in advance is bonded with an adhesive or the like. Finally, the thin metal plate for a screen electrode and the inorganic insulating film 408 on the lower surface thereof are etched by a photolithography method to form a screen hole 411.
Forming a screen electrode 409 having a structure similar to that shown in FIG. 3 to complete the charge generation control element.

In the present embodiment, an inorganic insulating film having ion irradiation resistance is selectively formed on the side wall of the hole of the insulating film composed of the upper layer portion and the lower layer portion, and the insulating film lower layer portion having strong ion irradiation is formed. Since it is formed of an inorganic insulating film, and the inorganic insulating film is formed between the screen electrode and the upper layer of the insulating film, there is a conventional problem of retreating the hole side wall of the insulating film due to ion irradiation. It is possible to suppress it and to provide etching resistance to products such as nitric acid. Further, since it is possible to prevent the screen electrode and the insulating film from peeling off due to a temperature rise due to ion irradiation, it is possible to stably supply charges that contribute to latent image formation for a long period of time.
The reliability of the charge generation control element can be improved.

[0027]

As described above based on the embodiments, according to the present invention, the side wall of the hole of the insulating film is prevented from receding by forming and covering the side wall of the hole of the insulating film with the inorganic insulating film. Suppressed and stable output characteristics can be obtained. Further, by suppressing the receding of the side wall of the hole of the insulating film, it is possible to reduce cracks and the like in the hole of the screen electrode, and it is possible to realize a charge generation control element having excellent reliability and durability.

[Brief description of the drawings]

FIG. 1 is a cross-sectional configuration diagram showing a configuration of a charge generation control element according to a first aspect of the invention.

FIG. 2 is a cross-sectional configuration diagram showing a configuration of a charge generation control element according to a second aspect of the invention.

FIG. 3 is a cross-sectional configuration diagram showing a configuration of a charge generation control element according to a third aspect of the invention.

FIG. 4 is a diagram showing a manufacturing process of the charge generation control device (first embodiment) shown in FIG. 1.

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

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

FIG. 15 is a diagram showing a manufacturing process of the charge generation control device (second embodiment) shown in FIG. 2.

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

23 is a diagram showing a manufacturing process that follows the manufacturing process shown in FIG. 22.

FIG. 24 is a diagram showing a manufacturing process of the charge generation control element (third embodiment) shown in FIG. 3.

FIG. 25 is a cross-sectional configuration diagram showing a configuration example of a conventional charge generation control element.

FIG. 26 is an explanatory diagram for explaining a problem of the conventional example shown in FIG. 25.

[Explanation of symbols]

 101,201,301,401 Insulating substrate 102,202,302,402 Line electrode 103,204,304,403 Dielectric film 104,205,305,404 Finger electrode 105,207 Insulating film 106,210,311,409 Screen electrode 107,212,312,410 Finger hole 108,213,314,411 Screen hole 105-1,307,121 Insulating film Lower layer 105-2,309,407 Insulating layer, Insulating film, Insulating layer Inorganic insulation film 208 Charge passage hole

Claims (4)

[Claims] 1. A line electrode formed on the surface of an insulating substrate, a dielectric film formed on the surface of the line electrode, and a hole for charge generation in the center formed on the dielectric film. In a charge generation control element comprising a finger electrode and a screen electrode having a hole for discharging charge in the center, which is formed through an insulating film having a hole for allowing the charge to pass through in the center of the finger electrode, A charge generation control element, wherein a side wall of a hole portion of the insulating film for allowing charges to pass through is covered with an inorganic insulating film. 2. A line electrode formed on the surface of an insulating substrate, a dielectric film formed on the surface of the line electrode, and a hole for charge generation in the center formed on the dielectric film. In a charge generation control element comprising a finger electrode and a screen electrode having a hole for discharging charge in the center, which is formed through an insulating film having a hole for allowing the charge to pass through in the center of the finger electrode, The lower layer of the insulating film is formed of an inorganic insulating film, the upper layer of the insulating film is formed of a thick organic insulating film, and the side wall of the hole of the insulating film for allowing charges to pass through is covered with the inorganic insulating film. A charge generation control element characterized by the above. 3. A line electrode formed on the surface of an insulating substrate, a dielectric film formed on the surface of the line electrode, and a hole for charge generation in the center formed on the dielectric film. In a charge generation control element comprising a finger electrode and a screen electrode having a hole for discharging charge in the center, which is formed through an insulating film having a hole for allowing the charge to pass through in the center of the finger electrode, The lower layer of the insulating film is formed of an inorganic insulating film, the upper layer of the insulating film is formed of a thick organic insulating film, and the side wall of the hole of the insulating film for allowing charges to pass through is covered with the inorganic insulating film. A charge generation control element, wherein an inorganic insulating film is formed on the lower surface of the screen electrode, and the organic insulating film forming the upper layer of the insulating film is surrounded by the inorganic insulating film. 4. The inorganic insulating film covering the side wall of the hole for allowing the charge of the insulating film to pass therethrough is any one of a silicon oxide film, a silicon nitride film and an alumina film. 2. The charge generation control element according to item 1.