JPH0795204B2 - Discharge device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a discharge device used for removing and charging in electrophotography, electrostatic recording and the like.

(Prior Art and Problems) Conventionally, as a device of this type, an AC voltage is applied between electrodes sandwiching a dielectric to generate a discharge in the vicinity of one electrode to generate positive and negative ions. Among the ions, a charging device that extracts ions of a predetermined polarity toward the member to be charged by an electric field formed by a bias voltage applied between the one electrode and the member to be charged and attaches to the member is, for example, It is known as shown in U.S. Pat. No. 4,155,093.

In this method, the electrode generating the discharge is exposed, and a strong discharge is generated in the vicinity of the exposed electrode, so that the electrode is easily corroded by the plasma etching action, the oxidation action, etc. due to the discharge. When such corrosion occurs, the discharge, and thus the removing / charging action becomes non-uniform, which is a problem in practical use.

On the other hand, it has a dielectric, at least two buried electrodes buried in the dielectric, and a bare bare electrode, and an AC voltage is applied between the buried electrodes, and the bare bare electrode is removed and charged. A bias voltage is applied between the members to generate an electric discharge in a part of the surface of the dielectric and in the vicinity of the surface of the bare electrode, and the generated ions are applied to the member to be removed / charged by the bias voltage. Discharge method to be applied (Japanese Patent Application Sho 61
No. -18954) has already been proposed by the applicant.

According to this method, an active creeping discharge is generated on the surface of the dielectric, so that the bare exposed electrode itself required for decharging / charging is not easily deteriorated by a strong discharge, and therefore durability is significantly improved. It became a result. That is, in the conventional discharge device that generated a strong discharge between the discharge electrode and the dielectric, the electrode deteriorates to the extent that it cannot withstand use in about 15 to 30 hours, but in this method, By using an inorganic material with high discharge resistance, it is possible to perform stable decharging / charging for a long period of time, for example, for about 150 to 200 hours until the dielectric is gradually etched and finally dielectric breakdown occurs. Become.

However, in order to further extend the durable life of this discharge device, it is sufficient to use a film having higher discharge resistance, that is, a film that is not easily etched by discharge plasma. A material having a high discharge property has a property that it is difficult to form a film by a vapor deposition or sputtering device, and even if it is attempted to perform this, the film formation speed is extremely slow and it is difficult to manufacture.

(Means for Solving Problems) The present invention aims to solve the problems of the above-mentioned conventional device and to dramatically improve the durability of the discharge device. For this purpose, A first dielectric, at least two first and second electrodes provided on the first dielectric, a second dielectric covering the first and second electrodes, and a second dielectric In a discharge device including a third electrode provided on the surface of a dielectric, the second dielectric is composed of three layers of an inorganic dielectric film including an inner layer, an intermediate layer and an outer layer, and the film quality is the same when forming the film. The inner layer is formed of a film with high adhesion, the intermediate layer is formed with easy film formation, and the outer layer is formed of a dense film with high discharge resistance. .

Embodiment An embodiment of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a sectional view of a discharge device as one embodiment.

The discharge device 1 is provided with at least two first and second electrodes 4 and 5 connected to an AC power source 11 on the surface of the first dielectric 2 and the electrodes 4 and 5 are the second dielectric 3 And is buried in the dielectric. A bare electrode 6 as a third electrode connected to a DC bias power source 12 is provided on the surface of the second dielectric 3.

A charged member 7 having a conductive substrate 9 to which a bias voltage is applied is arranged near the bare electrode 6 side of the discharge device 1. Reference numeral 8 denotes a photosensitive layer or a dielectric layer provided on the conductive substrate 9.

In the discharge device as described above, according to the present invention, the second dielectric 3 is formed by the three inorganic dielectric layers of the inner layer 31, the intermediate layer 32 and the outer layer 33, and the film quality is gradually or continuously formed during film formation. The inner layer 31 with a high adhesiveness, the intermediate layer 32
Is a film quality that facilitates film formation, and the outer layer 33 is formed with a dense film quality with high discharge resistance.

Even if the inorganic dielectric material 3 is made of the same material, the characteristics of the film can be variously changed by changing the film forming method or the film forming conditions such as the film forming speed during film forming. In general, when the film formation speed is changed, for example, the lower the film formation speed and the slower and denser the film is, the better the adhesion to the substrate and the higher the discharge resistance are. The easier the film is, the lower the properties such as adhesion and discharge resistance tend to be. (The difference in the denseness of such a film can be determined by the difference in the etching rate due to, for example, wet etching with hydrofluoric acid or dry etching with an alcon gas. Generally, the denser the film, the slower the etching rate.) Therefore, when the inorganic dielectric film 3 is formed, a dense film having excellent adhesiveness to the substrate 4 is used as the inner layer 31 to be a relatively thin film so that the adhesiveness can be sufficiently secured, and the intermediate layer 32 is formed, for example. The film can be formed by increasing the film speed to be a film thick enough to withstand the discharge voltage, and the outer layer 33 can be a dense film having a high discharge resistance and a relatively thin film that can secure the discharge resistance.

Next, each part of the apparatus of this embodiment as described above will be specifically described including its material and the like.

First, in FIG. 1, the first dielectric 2 as a support is
There is no particular limitation as long as it is a fixed dielectric such as a glass substrate, a ceramic substrate, or a resin substrate. The first and second electrodes 4,5 need only be conductors, for example Al, Cr, Au, Cu, Ni.
Metals such as can be used. As the third electrode 6,
Metals with strong corrosion resistance and oxidation resistance, such as Ti, W, Cr, Ta, Mo, Fe, C
It is possible to use u, Co, Ni, Au, Pt, etc., or an alloy or oxide containing these metals.

Next, as the dielectric film 3 covering the first and second electrodes 4 and 5, the thickness is 1 μm or more and 500 μm or less, preferably 3 μm.
An inorganic dielectric material having a high discharge resistance of not less than 200 μm and not more than 200 μm is used. For example, glass, ceramic, SiO ₂ , MgO, Al ₂
Oxides such as O ₃ and Ta ₂ O ₅ , or silicon nitride, aluminum nitride, as well as aluminum and silicon are formed by a vapor deposition method, an ion plating method, a sputter film forming method, a CVD method, or the like.

At this time, in the present invention, the dielectric film 3 is divided into three layers, and the film formation conditions such as the film formation rate are changed so that the inner layer 31 having excellent adhesion to the support substrate 2 can be formed with a minimum film thickness. The intermediate layer 32 having a film thickness sufficient for the discharge withstand voltage is formed on the condition that the film is relatively easy to be formed. Only the thickness of the outer layer 33
To be selected as.

In the device of the present embodiment as described above, when an AC voltage is applied between the first and second electrodes 4 and 5 by the AC power supply 11,
An AC discharge region 10 is formed on the surface of the dielectric 3. The electric field strength of the discharge region 10 is stronger toward the center and gradually weakens toward the outside. At that time, the inner layer 31 maintains the adhesion strength of the film, the intermediate layer 32 sufficiently secures the discharge withstand voltage, and the outer layer 33 guarantees the discharge resistance, so that the durability is remarkably improved.

If the dielectric withstanding film 3 is formed as a single layer film without using the present invention, the following problems occur. For example, the compactness of the film,
If a film that emphasizes discharge durability is attempted to be formed, it generally takes a significantly long time to form the film, which is very costly if not impossible. Therefore, if a film is formed under conditions that make it relatively easy to form, the film is likely to peel off at the bonding surface with the substrate, and the discharge resistance at the surface is poor, and etching or deterioration of the film due to discharge progresses. However, there is a problem such as that, and it is difficult to obtain a practical product.

Therefore, the results of the implementation of the present invention will be shown below.

An alumina ceramic substrate was used as the first dielectric 2 serving as a support, Cr electrodes were used as the first and second electrodes 4 and 5, and a Ti electrode was used as the third electrode. Then, as the second dielectric, an Al ₂ O ₃ film, which is relatively difficult to form but has excellent discharge resistance, was formed to a thickness of 10 μm by an ion plating method. At that time, as the inner layer, first, the film formation rate was about 50 Å / min.
3μm thick film, then 9μ at about 750Å / min as an intermediate layer
The film was formed to a thickness of m and an outer layer was formed to a thickness of 0.7 μm at about 50Å / min.

Then, a continuous discharge endurance test was conducted by applying a sine wave of 1.7 KVp _- p, 35 KHZ as an AC voltage, and stable discharge continued for about 1000 hours or longer.

On the other hand, in the case of a single-layer discharge device not according to the present invention, for example, SiO ₂ which is relatively easy to form a film as the second dielectric is used.
When a 10 μm-thick sputter film was formed at 800 Å / min and a discharge test was conducted under the same conditions, the dielectric film was etched by discharge plasma in about 150 to 200 hours, and eventually dielectric breakdown occurred.

Also, if an Al ₂ O ₃ film with excellent discharge resistance is to be formed as a single layer, it takes about 30 to 40 hours if a dense film is formed by the ion plating method at a rate of about 50 Å / min as described above. Of course, discharge durability is secured for 1000 hours or more, but it takes a long time for film formation and is not practical. So with a single layer film
If the film is formed at a high speed of 750 Å / min, the denseness of the film cannot be secured as it is, and the surface resistance of the film tends to decrease due to the influence of humidity, and stable discharge cannot be performed, or the film durability is poor There are problems that dielectric breakdown occurs and film peeling occurs in a short time.

Thus, according to the present invention, by forming the second dielectric by the inorganic dielectric film in the above-mentioned three layers, not only the film can be easily formed in a short time, the durability is significantly improved, and uniform It became possible to maintain a stable discharge for a long period of time.

Further, in the embodiment shown in FIG. 1, the film quality of the dielectric film 3 is divided into three layers, but this does not necessarily mean that the film quality is strictly divided into three layers, and the inner layer 31 and the intermediate layer 31 are not separated. Layer 32,
Alternatively, it is also possible to gradually change the film quality between the intermediate layer 32 and the outer layer 33.

FIG. 2 shows another embodiment of the present invention described above. In the figure, the film quality of the dielectric 3 is not strictly divided into three layers, and the film quality gradually changes from the inner layer to the intermediate layer to the outer layer. The results of the implementation at this time will be described by taking the case of using the Al ₂ O ₃ film described above as an example. Similarly, an Al ₂ O ₃ film having excellent discharge resistance was formed to a total thickness of 10 μm by the ion plating method. At that time, the inner layer was formed at a film forming rate of about 50 Å / min, then the film forming rate was gradually changed to an intermediate layer at about 750 Å / min, and finally the film forming rate was gradually changed. The outer layer is formed at 50 Å / min, and the inner layer −
The ratio of the thickness of the middle layer to the outer layer is approximately 0.3 μm-9 μm.
It was formed as -0.7 μm. Then, when a continuous discharge durability test was performed under the same conditions, a stable discharge continued for about 1000 hours or longer.

According to this configuration, it is possible to disperse the generation of stress due to the difference in the film quality between the layers of the dielectric 3 (for example, the stress due to the difference in the coefficient of thermal expansion, etc.) by gradually changing the film quality, and thus more stable. The dielectric film 3 can be formed.

When the device of the present invention is applied to a copying machine, a laser beam printer, or the like, it becomes possible to perform uniform and stable charging for a long time, which is impossible with a conventional corona charger or the like.

It should be noted that the present invention is not limited to the above-described embodiment, and as shown in other embodiments of FIGS. 3 to 6, there are three or more embedded electrodes (see FIGS. 3 to 6), and Two or more bare electrodes (first
Of course, it can be implemented even when provided.

(Effects of the Invention) As described above, the present invention uses an inorganic dielectric layer composed of three layers as the second dielectric, an inner layer having high adhesion, a middle layer having easy film formation, and an outer layer having discharge resistance. By using a film having a high property, the function of preventing corrosion such as etching is improved, and uniform and stable decharging / charging can be performed for a long period of time. As a result, the performance of the device using the device of the present invention is improved. Moreover, the above-mentioned relatively thick intermediate layer can be easily formed, and the inner layer and the outer layer can be formed very thinly, so that the production is easy.

[Brief description of drawings]

FIG. 1 is a sectional view of an apparatus according to an embodiment of the present invention, and FIGS.
Each of the drawings is a cross-sectional view showing an apparatus according to another embodiment of the present invention. 1 ... Discharge device 2 ... First dielectric 3 ... Second dielectric 31 ... Inner layer 32 ... Intermediate layer 33 ... Outer layer 4,5 ... First and second electrodes 6 ... Third electrode

Claims (1)

[Claims] 1. A first dielectric, at least two first and second electrodes provided on the first dielectric, and a second dielectric covering the first and second electrodes. And a third electrode provided on the surface of the second dielectric, wherein the second dielectric is composed of three layers of an inorganic dielectric film including an inner layer, an intermediate layer and an outer layer. Sometimes the film quality is changed stepwise or continuously with the same material, the inner layer is a film with high adhesion, the intermediate layer is a film that can be easily formed, and the outer layer is formed with a dense film with high discharge resistance. A discharge device characterized by the above.