JP2001255720A - Charging device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a charging device with supreme charging performance, being made stably usable over a long period. SOLUTION: In the charging device 10 composed of a base plate 1 consisting of insulator, exciting electrodes 2 formed on the surface of the base plate 1, and dielectric body layer 3 covering the surface of the base plate 1 that the exciting electrodes 2 is respectively formed, moreover the discharging electrode 4 provided with an open part 5 on the position corresponding to the exciting electrode 2 formed on the surface of the dielectric body layer 3, the discharging electrode 4 is, made of a material consisting of at least, one kind of metal provided with fusing point beyond 900 deg.C and at least, one kind of metal provided with ionizing energy below 8 eV.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charging device used in an image forming apparatus such as an electrostatic recording system and an electrophotographic recording system.

[0002]

2. Description of the Related Art Conventionally, various charging devices have been used in image forming apparatuses such as an electrostatic recording system and an electrophotographic recording system. Among them, as a representative method as a charging device for charging an image carrier such as a photoconductor, (1) a corotron that uses a corotron charger or a scorotron charger and charges the photoconductor by corona discharge from a corotron wire Method (2) Surface creeping discharge including a linear excitation electrode formed on an alumina substrate and a planar discharge electrode formed by being embedded in the dielectric layer at a position facing the linear excitation electrode via the dielectric layer. There are widely known two methods, a method using a solid-state charging device for charging a photoreceptor by performing creeping corona discharge by an element.

In recent years, colorization has been advanced in the field of copiers and printers, and the non-uniform charging, which has not been a problem in the case of black-and-white images, has a problem in the case of a color image forming apparatus. If there is non-uniformity, when a solid image of halftone is output, it cannot follow a continuous density change and appears as a step-like image quality defect. Coveted.

In the case of the corotron method (1), since the deterioration of the charging characteristics gradually progresses continuously with time,
It is not impossible to keep track of the corotron wire replacement time individually by recording the rise in the drive voltage. Therefore, it is possible to replace each corotron wire at an appropriate time without uniformly setting the replacement time, which is advantageous from the viewpoint of maintenance cost.

On the other hand, in a system using a solid charging device, the charging characteristics are not limited to continuously deteriorating, and when the driving voltage is adjusted, the charging device suddenly stops functioning. It is difficult to know the replacement time individually.

However, a corotron-type charging device includes:
There are problems such as the need for a high-voltage power supply device and the generation of a large amount of harmful gases such as nitrogen oxides and ozone. Recently, solid-state charging devices have tended to be widely used.

[0007]

As a solid charging device used in an image forming apparatus, for example, Japanese Patent Application Laid-Open No. H10-313
No. 45 discloses an insulating substrate such as alumina, a dielectric layer formed on the surface of the insulating substrate on the side to be charged (such as a photoreceptor), an induction electrode covered with the dielectric layer, and a dielectric layer. A discharge electrode provided on the opposite side of the induction electrode with an opening formed to form a discharge area; a discharge power supply for applying an AC voltage between the induction electrode and the discharge electrode; a discharge electrode and a member to be charged; And a bias power supply for applying a predetermined bias voltage between the surface corona discharger.

In this creeping corona discharger, a high-frequency voltage is applied between a planar excitation electrode and a linear discharge electrode to generate a creeping corona discharge at a discharge electrode end of a discharge area. In this method, ions having positive and negative charges are generated to charge an object to be charged such as a photoreceptor, but the generated ions not only travel toward the object to be charged but also toward the charging device itself. Some will collide. The discharge electrode on the surface of the charging device is scraped off by the sputtering action due to the ion collision, which contributes to shortening the life of the charging device.

In addition to the electrode destruction due to such ion collision, there are many causes for shortening the life of the charging device. In general, the life of a solid state discharger is attributed to deterioration of the discharge electrode, deterioration or destruction of the insulating layer between the excitation electrode and the discharge electrode, and deterioration of the discharge performance due to disconnection of the excitation electrode.

Japanese Patent No. 2665903 discloses a method of protecting the surface of a discharge electrode formed on a charging device with a glass material in order to extend the life of the solid charging device. Also, JP-A-8-82980 discloses that
As a method for preventing deterioration of the insulating layer and wear of the electrode due to ion bombardment, an insulating substrate, an ion generating electrode provided on the insulating substrate and covered with the insulating layer, and an ion generating electrode on the insulating substrate And an induction electrode provided on both sides of the ion generation electrode at substantially the same level as the above.

However, in the method of protecting the electrode surface of the charging device by covering it with an insulating layer such as a glass material as in these charging devices, the life of the electrode is prolonged, but the charging performance is deteriorated and the cost required for discharging is reduced. There is a problem that is up.

Japanese Patent Application Laid-Open No. 9-80878 discloses that
In an image forming apparatus including a charging device that charges a recording medium by generated ions, a variation in charging of the recording medium by the charging device is monitored, and a voltage applied to the charging device is adjusted according to the degree of variation in charging. The disclosed image forming apparatus is disclosed. However, in this image forming apparatus, the charging device is replaced when the limit of adjustment is reached while the device is being used while adjusting the applied voltage while monitoring the variation in charging. Since there is no limit point for adjustment in the charger and the discharge does not occur suddenly, there is a problem that a solid charging device that can be used is replaced as soon as possible after a certain period of time, resulting in wasteful cost.

In general, the life of the solid-state charging device varies depending on manufacturing conditions, for example, the temperature during firing, and the life of each solid-state charging device varies. Therefore, it is necessary to predict the replacement time of the charging device. Can not. For this reason, there is a case where the charging device is replaced with a new charging device in about half of the original life for safety. Therefore, in order to eliminate such waste, there is a demand for a solid-state charging device capable of estimating the lifetime.

In view of the above circumstances, an object of the present invention is to provide a charging device which can be used stably for a long time and has excellent charging performance.

[0015]

According to a first aspect of the present invention, there is provided a charging device comprising a substrate made of an insulator, a plurality of excitation electrodes formed on the surface of the substrate, and the excitation electrodes. And a discharge electrode formed on the dielectric layer surface and having an opening at a position corresponding to the excitation electrode, and applying a voltage between the excitation electrode and the discharge electrode. A discharge region is formed between the opening and the surface of the excitation electrode corresponding to the opening, and the charging device charges the member to be charged with charged particles generated by the discharge in the discharge region. Are characterized by comprising at least one kind of metal having a melting point of 900 ° C. or more and at least one kind of metal having an ionization energy of 8 eV or less.

Here, 900 ° C. contained in the discharge electrode
It is preferable that the content ratio of the metal having the above melting point is 20 wt% or more and 80 wt% or less.

Further, a second charging device of the present invention for achieving the above object comprises a substrate made of an insulator, a plurality of excitation electrodes formed on the substrate surface, and a substrate surface on which the excitation electrodes are formed. A covering dielectric layer, and a discharge electrode formed on the surface of the dielectric layer and having an opening at a position corresponding to the excitation electrode, wherein a voltage is applied between the excitation electrode and the discharge electrode, A discharge region is formed between the opening and the surface of the excitation electrode corresponding to the opening, and in a charging device for charging an object to be charged with charged particles generated by discharge in the discharge region, a part of the discharge region In the discharge region, the time until the dielectric breakdown, the dielectric breakdown detection unit is set to be set shorter than the time until the dielectric breakdown of the discharge region other than the partial discharge region is formed, That.

Here, the dielectric breakdown detecting section is formed by forming the dielectric layer of the dielectric layer to have a thickness smaller than that of the discharge region other than the partial discharge region. Preferably, it is formed.

The dielectric breakdown detecting section may have an opening area larger than an opening formed in a discharge region other than the partial discharge region. It is also a preferred embodiment that the opening is formed by forming the opening having the following.

It is also a preferable embodiment that a life determining means for measuring the discharge current of the insulation breakdown detecting section and determining the life of the charging device based on the measured value is provided.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, an embodiment of the first charging device of the present invention will be described.

FIG. 1 is a schematic configuration diagram showing an embodiment of a first charging device of the present invention.

As shown in FIG. 1, this charging device 10
A substrate 1 made of an insulator such as alumina; an excitation electrode 2 formed on the surface of the substrate 1; a dielectric layer 3 covering the surface of the substrate 1 on which the excitation electrode 2 is formed; And a discharge electrode 4 having an opening 5 at a position corresponding to the excitation electrode 2. The discharge is performed by applying an AC driving voltage from a driving power supply 6 between the excitation electrode 2 and the discharge electrode 4. Then, the charged particles P generated by the discharge are transferred to the charged body 7 by the action of the bias voltage applied from the bias power supply 8, and the charged body 7 is charged.

FIG. 2 is a top view (a) of the charging device shown in FIG. 1 and a cross-sectional view taken along line AA of FIG.

As shown in FIGS. 2A and 2B, the excitation electrodes 2 are formed on the substrate 1 in a plurality of lines in parallel, and the excitation electrodes 2 are formed. Substrate 1
Is covered by the dielectric layer 3. Further, a discharge electrode 4 is formed on the dielectric layer 3, and the discharge electrode 4 is formed.
In the position corresponding to the excitation electrode 2, a plurality of openings 5 are formed. A creeping discharge is generated in a discharge region formed between the hole of the opening 5 of the discharge electrode 4 and the surface of the excitation electrode 2 located immediately below the hole. This charging device 1
The material of the discharge electrode 4 of at least 0
A metal having a melting point of 00 ° C. or more and at least one kind of 8
A material composed of a metal having an ionization energy of eV or less is used.

By forming the discharge electrode 4 from such a material, it is possible to obtain a charging device which is suitable for the purpose of the present invention, can be used stably for a long period of time, and has excellent charging performance.

In order to extend the life of the discharge electrode of the solid-state charging device, it is effective to use a metal having a high melting point, and in terms of discharge performance, it is effective to use a metal having a small ionization energy. Therefore, in order to achieve both life and discharge performance, it is necessary to use a high melting point metal having a melting point of 900 ° C. or more and a small ionization energy metal having an ionization energy of 8 eV or less as a discharge electrode.

According to the experiments of the present inventors, when the content ratio of the metal having a melting point of 900 ° C. or more contained in the discharge electrode is set to 20 wt% or more and 80 wt% or less, the charging device of the present embodiment is used. It has been found to be extremely effective in extending life.

Next, a method of forming the charging device will be described.

FIG. 3 is a diagram showing a method of forming the charging device shown in FIGS. 1 and 2.

First, as shown in FIG. 3A, a plurality of linear (see FIG. 2A) excitation electrodes 2 are formed at predetermined positions on the alumina substrate 1. The excitation electrode 2 is formed by printing a material such as Au, Ag, or AgPd on the alumina substrate 1 by a thick film printing method and firing the material. In addition, as a method for forming the excitation electrode 2, a conductive film such as Au, AgPd, chromium, copper, tungsten, aluminum, platinum, or titanium is formed by a sputtering method or the like, and a thin film method of re-patterning by a photolithographic etching method is used. It may be formed.

Next, as shown in FIG. 3B, a dielectric layer 3 is formed so as to cover the surface of the substrate 1 on which the excitation electrodes 2 are formed. The dielectric layer 3 is preferably formed of a dielectric layer having a low dielectric constant.

Further, the dielectric layer 3 is formed by a thick film printing method so that a pattern (see FIG. 2A) in which a plurality of holes (openings) 5 are formed at positions corresponding to the excitation electrodes 2.
The re-discharge electrode 4 is formed thereon by a thick film printing method.

Here, in the first charging device of the present invention, as the material of the discharge electrode 4, at least one kind of metal having a melting point of 900 ° C. or more and at least one kind of metal having an ionization energy of 8 eV or less are used. Is used.

In this embodiment, AgPd is used as the material of the discharge electrode 4. That is, Pd is selected as a metal having a melting point of 900 ° C. or more used to extend the life, and Ag is selected as a metal having an ionization energy of 8 eV or less used to secure discharge performance.

Table 1 shows the composition of the discharge electrode material of the charging device according to the first embodiment of the present invention.

[0037]

[Table 1]

As shown in Table 1, seven kinds of discharge electrodes in which the composition of Ag and Pd (the number is wt%) were prepared.
A discharge test was performed on the charging device having the discharge electrodes of these seven types formed thereon to evaluate the performance.

In addition to the above combination of Ag and Pd, for example, a combination of Ag and Ni can provide good results. Further, various combinations of materials such as Au, Ag, Ni, and Al were evaluated.

In the discharge test, AC 2 kV (peak to peak) 1 was applied between the excitation electrode 2 (see FIG. 1) and the discharge electrode 4.
By applying 00 kHz, a creeping discharge is caused in the vicinity of the opening 5 to ionize the gas in the air, and the ions are applied by the bias potential applied between the discharge electrode 4 and the charged member 7.
It was transferred from the opening 5 to the surface of the member 7 to be charged, and the current flowing at that time and the amount of gas generated were measured.

FIG. 4 is a diagram showing the discharge characteristics of the discharge electrodes of the groups A, B and C shown in Table 1.

As shown in FIG. 4, the discharge characteristics of these discharge electrodes can be classified into the following three patterns.
That is, group A: those whose initial current amount is large and whose current values are stable for a long time without dropping the head, group B: those whose initial current amount is small and whose head drops in a short time : The initial current amount is large, but the head drops immediately. Of course, among the above three patterns, the group A is the most suitable as the performance of the charging device. Group A corresponds to two of the seven types of samples in Table 1 above.
From the second sample, that is, high melting point Ag of 20% and small ionization energy of Pd of 80% to the sixth sample, that is, five kinds of samples from Ag 80% and Pd to 20%.

Based on the results of this test, an example of a material candidate that can be used for the discharge electrode of the first charging device of the present invention will be described below.

Table 2 is a table in which candidate materials for the discharge electrode are arranged in the order of ionization energy.

[0045]

[Table 2]

As shown in Table 2, the ionization energy 8e
Examples of the metal of V or less include Ni, Ag, and Al.

Table 3 is a table in which candidate materials for the discharge electrode are arranged in the order of the melting point.

[0048]

[Table 3]

As shown in Table 3, metals having a melting point of 900 ° C. or higher include Ag, Au, Ni, Pd and the like.

As described above, the discharge electrode of the first charging device of the present invention is composed of at least one kind of metal having a melting point of 900 ° C. or more and at least one kind of metal having an ionization energy of 8 eV or less. Thus, it can be seen that it is possible to obtain a charging device which can be used stably for a long period and has excellent charging performance.
Further, it is shown that it is preferable to set the content ratio of the metal having a melting point of 900 ° C. or more contained in the discharge electrode to 20% by weight or more and 80% by weight or less in terms of life and charging performance.

Next, an embodiment of the second charging device of the present invention will be described.

The second charging device of the present invention has a structure similar to that of the typical solid-state charging device shown in FIG. 1 as in the first embodiment, and its forming method is also shown in FIG. 3) to 3 (c), except that the second charging device of the present invention discharges a part of the discharge region formed between the opening and the corresponding excitation electrode surface. In the region, a dielectric breakdown detecting unit is formed in which the time until the dielectric breakdown is set shorter than the time until the dielectric breakdown in the discharge region other than the partial discharge region.

FIG. 5 is a sectional view showing an embodiment of the second charging device of the present invention.

As shown in FIG. 5, in the charging device 20 of the second embodiment, a part of the discharge region 27 of the discharge region 27 formed between the opening 25 and the corresponding surface of the excitation electrode 22 is formed. The dielectric breakdown detecting section 2 in which the thickness of the dielectric layer 23 ′ is reduced to 20 μm with respect to the designed value of the dielectric layer 23 of the discharge region 27 having the charging function of 30 μm.
8 are formed.

FIG. 6 is an enlarged view of the vicinity of the discharge region in the initial state and after long-time continuous driving of the second charging device of the present invention.

As shown in FIG. 6A, in the initial state,
Although no abnormality is observed in the dielectric layer 3 of the charging device 10, the charging device 10 'after long-time continuous driving includes:
As shown in FIG. 6B, the dielectric layer 3 'near the opening 5 is formed.
The deteriorated portion 3a occurs in a part of. This deteriorated part 3
The depth a is proportional to the magnitude of the discharge. Under the same driving conditions (driving voltage and frequency), the thinner the dielectric layer 3, the lower the discharge starting voltage and the stronger the discharge. Is early.

FIG. 7 is a graph showing the relationship between the thickness of the dielectric layer and the firing voltage in the charging device according to the second embodiment.

As shown in FIG. 7, when the thickness of the dielectric layer is reduced, the firing voltage is reduced. Therefore,
In the charging device according to the second embodiment, as shown in FIG.
In addition, the time until the dielectric breakdown of the discharge region 27 is reached,
The dielectric breakdown detecting section 28 is formed in this portion by reducing the thickness of the dielectric layer 23 'so as to shorten the time until dielectric breakdown.

FIG. 8 is a plan view of the charging device according to the second embodiment.

As shown in FIG. 8, in the charging device 20 of the second embodiment, a location B outside the effective charging range A
Further, there is provided a discharge life detecting pattern 29 in which the above-mentioned insulation breakdown detecting section 28 is formed. in this way,
In a place B outside the effective charging range A,
Is formed, it is possible to evaluate the lifetime without deteriorating the uniformity of charging.

In the second embodiment, an example is shown in which the dielectric breakdown detecting section is formed in which the time until the dielectric breakdown in the discharge region is set short by reducing the thickness of the dielectric layer. The breakdown detecting section is formed as an opening having an opening area larger than an opening formed in a discharge region other than the partial discharge region, the opening formed in the dielectric breakdown detecting portion of the openings. It is good also as what is formed by this.

That is, when the opening area of the opening (the size of the discharge hole) is reduced, the time until the dielectric breakdown in the discharge region becomes longer, and as the opening area of the opening is increased, the time until the dielectric breakdown occurs. Can be set to a desired dielectric breakdown time by appropriately designing the opening area of the opening of the dielectric breakdown detector.

If the opening area (size of the discharge hole) of the opening of the discharge region is too large, the life is shortened due to dielectric breakdown, and if the size of the discharge hole is too small, the life is shortened due to discharge deterioration. I know that.

Further, the method of each of the above methods, for example,
The dielectric breakdown detecting unit may be formed by adjusting the firing time of the dielectric layer.

FIG. 9 is a graph showing the relationship between the length of firing time of the dielectric layer and the firing voltage in the charging device of the second embodiment.

As shown in FIG. 9, it can be seen that the firing voltage of the samples A and B under different experimental conditions decreases as the firing time of the dielectric layer decreases. this is,
If the firing time of the dielectric layer is shortened, many defects are generated in the dielectric layer, and the time until the dielectric breakdown is shortened. It may be.

When the charging device according to the second embodiment was manufactured, as a pretreatment, bubbles contained in the paste material were removed by kneading and defoaming a printing paste material for the dielectric layer. However, there was no significant difference in the experimental range.

Next, the life determining means provided in the second charging device of the present invention will be described.

FIG. 10 is a schematic diagram showing an embodiment of the life determining means provided in the second charging device of the present invention.

As shown in FIG. 10, the charging device 30 includes an induction electrode 32, a dielectric layer 33 having a normal thickness, and a charging portion 37 including a discharge electrode 34.
2 ', a dielectric layer 33' having a thickness of about half the normal layer thickness,
And a discharge determination unit 38 including a discharge electrode 34 ′, and a life determining unit that measures a discharge current in the dielectric breakdown detection unit 38 and determines the life of the charging device 30 based on the measured value. ing.

The life determining means includes a dielectric breakdown detecting section 38.
Photoconductor 50 and charging device 3 arranged at a position facing
Discharge current measuring electrode 4 for measuring a discharge current between 0
1 and an ammeter 42, the circuit is switched by a switch 43, the discharge current is measured, and when the current value is out of the range of the current value assumed in advance, it is determined that the insulation breakdown detection unit 38 has been broken.

The discharge electrode 34 of the dielectric breakdown detector 38
An AC voltage is applied between the AC power supply 44 and the induction electrode 32, and the frequency and voltage (peak-to-peak value) of the AC power supply 44 are measured. May be determined to have been destroyed, or the capacitance of the dielectric breakdown detector 38 may be measured, and if the capacitance deviates from a preset range, it may be determined that dielectric breakdown has occurred. You may. If it is determined that the dielectric breakdown has occurred once, the simultaneous driving of the dielectric breakdown detecting unit 38 and the charging unit 37 is stopped, and the dielectric breakdown detecting unit 38 is stopped.
Therefore, the charging unit 37 is not adversely affected.

As described above, when it is determined that the dielectric breakdown detector 38 has been broken down, the depth of the deteriorated portion 33a ′ generated in the dielectric layer 33 ′ of the dielectric breakdown detector 38 is temporarily induced. Even if it reaches the electrode 32 ′, the depth of the deteriorated portion 33 a generated in the dielectric layer 33 on the charged portion does not reach the induction electrode 32, and the normal image forming process can be continued. In this way, since it is detected that the charging device is approaching the end of its life, the charging device can be replaced at an appropriate time without causing any trouble in an image forming process performed using the charging device. .

In the above example, an example was described in which the life of the dielectric breakdown detecting section 38 was set to about half the life of a normal charging section. However, for example, a plurality of steps such as 75%, 50%, and 25% were used. By forming a plurality of types of insulation breakdown detectors set for the same life time and recording the time until each actual insulation breakdown, it is possible to more accurately estimate the life.

In addition, the driving time of the charging device is recorded, and after the breakdown detection unit is broken, the driving time is subtracted from the time recorded up to that time, and the predetermined time is reached. Sometimes, it is possible to inform the user that the life of the charging device is approaching.

[0076]

As described above, according to the first charging device of the present invention, at least one type of 9
A metal having a melting point of 00 ° C. or more and at least one kind of 8
By using a metal having an ionization energy of eV or less, it is possible to realize a charging device having excellent charging performance, which can be used stably for a long period of time.

According to the second charging device of the present invention,
In a part of the discharge region, a part of the discharge region was formed with a dielectric breakdown detection unit in which the time until the dielectric breakdown was set to be shorter than the time until the part of the discharge region other than the partial discharge region reached the dielectric breakdown. This makes it possible to predict the life of the charging device, to obtain a charging device with excellent charging performance that can be used stably for a long period of time, and to replace the charging device at an appropriate time. As a result, waste of resources can be reduced.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of a first charging device of the present invention.

FIG. 2A is a top view of the charging device shown in FIG. 1 and FIG.

FIG. 3 is a diagram showing a method of forming the charging device shown in FIGS. 1 and 2.

4 is a diagram showing discharge characteristics of discharge electrodes of groups A, B and C3 shown in Table 1. FIG.

FIG. 5 is a sectional view showing an embodiment of a second charging device of the present invention.

FIG. 6 is an enlarged view of the vicinity of a discharge region in an initial state and after long-time continuous driving of a second charging device of the present invention.

FIG. 7 is a graph showing a relationship between a dielectric layer thickness and a discharge starting voltage in the charging device according to the second embodiment.

FIG. 8 is a plan view of a charging device according to a second embodiment.

FIG. 9 is a graph showing a relationship between a firing time of a dielectric layer and a discharge starting voltage in the charging device according to the second embodiment.

FIG. 10 is a schematic configuration diagram illustrating an embodiment of a life determining unit provided in a second charging device of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2, 22, 32, 32 'Excitation electrode 3, 23, 23', 33, 33 'Dielectric layer 3a, 33a, 33a' Deterioration part 4, 34, 34 'Discharge electrode 5, 25 Opening 6 Drive power supply 7 Charged body (photosensitive body) 10, 10 ', 20, 30 Charging device 27 Discharge area 28, 38 Dielectric breakdown detection section (discharge area) 29 Discharge life detecting pattern 41 Discharge current measuring electrode 42 Ammeter 43 Switch 44 AC Power supply 50 Photoconductor P Charged particles

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Takeshi Kengawa 2274 Hongo, Ebina-shi, Kanagawa Prefecture F-Xerox Corporation Ebina Works F-term (reference) 2H003 AA11 CC08 DD03 EE06 EE10

Claims (6)

[Claims] A substrate formed of an insulator, a plurality of excitation electrodes formed on the substrate surface, a dielectric layer covering the substrate surface on which the excitation electrodes are formed, and a dielectric layer formed on the dielectric layer surface. A discharge electrode having an opening at a position corresponding to the excitation electrode, between the opening and the surface of the excitation electrode corresponding to the opening by applying a voltage between the excitation electrode and the discharge electrode. In a charging device in which a discharge region is formed and a member to be charged is charged by charged particles generated by discharge in the discharge region, the discharge electrode includes at least one kind of metal having a melting point of 900 ° C. or more and at least one kind of metal. And a metal having an ionization energy of 8 eV or less. 2. The content ratio of a metal having a melting point of 900 ° C. or more contained in the discharge electrode is 20 wt% or more and 80 w / w.
2. The charging device according to claim 1, wherein said charging device is at most t%. 3. A substrate made of an insulator, a plurality of excitation electrodes formed on the substrate surface, a dielectric layer covering the substrate surface on which the excitation electrodes are formed, and a dielectric layer formed on the dielectric layer surface. A discharge electrode having an opening at a position corresponding to the excitation electrode, between the opening and the surface of the excitation electrode corresponding to the opening by applying a voltage between the excitation electrode and the discharge electrode. In a charging device in which a discharge region is formed and a member to be charged is charged by charged particles generated by a discharge in the discharge region, a part of the discharge region in the discharge region has a time until dielectric breakdown, A charging device, comprising: a dielectric breakdown detecting unit which is set to be shorter than a time required until dielectric breakdown occurs in a discharge region other than a partial discharge region. 4. The dielectric breakdown detecting section is formed by forming a portion of the dielectric layer in which the dielectric breakdown detecting section is thinner than a portion of a discharge region other than the partial discharge region. The charging device according to claim 3, wherein the charging device is used. 5. The dielectric breakdown detecting section, wherein an opening formed in the dielectric breakdown detecting section of the opening is larger than an opening area formed in a discharge region other than the partial discharge region. 4. The charging device according to claim 3, wherein the charging device is formed by being formed as an opening having: 6. A charging device according to claim 3, further comprising a life determining means for measuring a discharge current of said insulation breakdown detecting section and for determining a life of the charging device based on the measured value. .