JP2005135716A - Discharge element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve a problem that in the conventional discharge element, moisture is condensed in a recessed part on the surface of porcelain and ammonium nitrate or the like is dissolved in the moisture, resulting in deterioration of durability. <P>SOLUTION: A protective layer with a surface roughness Ra of 10μm or less is provided on the discharge element. Therefore, condensation of moisture on the surface of the protective layer is suppressed and the adhesion of ammonium nitrate to the protective layer is restricted, and a discharge element having a long life with high output is obtained. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a discharge element used for an ozone generator, an ion generator or the like.

  As shown in FIG. 3, this type of discharge element has a linear discharge electrode 13 provided on the surface of a discharge element 18 made of ceramics, and a planar induction electrode 14 embedded in the discharge element 18. Patent Documents 1 to 4 describe that a high frequency high voltage is applied between the electrodes to generate creeping corona discharge on the substrate surface. In particular, Patent Documents 3 and 4 show a method of removing ammonium nitrate, which is a discharge inhibitor attached to the discharge surface of the discharge element 18, by heating the discharge element 18.

  The protective layer 15 of the conventional discharge element 18 is a ceramic single layer or a single glass layer and is formed by a manufacturing method such as printing or lamination, but voids due to pinholes in the manufacturing process or poor lamination with the discharge electrode 13. The surface roughness is increased due to grain removal and grain growth during firing. It is known that when such a conventional discharge element 18 having a large surface roughness is used in the atmosphere for a long period of time, water-absorbing ammonium sulfate is generated on the discharge electrode 13 to inhibit discharge.

This is because the nitrogen oxide produced by the discharge reacts with a small amount of ammonia present in the atmosphere, and it enters the uneven portions of the ceramics on and around the discharge electrode 13 as white needle-like crystals and precipitates. It is. Since this ammonium sulfate has a small effect of inhibiting discharge in a dry state, there is a method in which a heating element pattern built in the discharge element 18 or a small heater attached to the back surface of the discharge element 18 is heated to 100 to 350 ° C. These are proposed in the aforementioned Patent Documents 3 and 4.
Japanese Patent Publication No. 22-22998 Japanese Patent Publication No. 3-49198 JP-A-5-166578 JP 11-139810 A

  However, in the conventional method, there is a risk in terms of safety because there is a risk that dust or dust that has fallen on the discharge device, a device that supports the discharge device, or a nearby device may ignite.

  Further, in the conventional discharge element having a large surface roughness (Ra), moisture condenses in the recesses on the porcelain surface, and ammonium nitrate or the like dissolves in the water, so that the critical humidity related to the condensation of moisture near the recesses is increased. It has been found that there is a problem that water content tends to adhere to the surface of the discharge element, and the function of the discharge element is lowered. In addition, the ammonium nitrate dissolved in the moisture in the recesses in this way is concentrated due to a change in the surrounding humidity, and there is a problem that the protective layer is eroded and deteriorated.

  The discharge element of the present invention is a discharge element in which a discharge electrode is provided on the surface of a ceramic substrate, a dielectric electrode is embedded in the substrate, and the discharge electrode and the dielectric electrode are opposed to each other through a dielectric layer. A protective layer having a surface roughness Ra of 10 μm or less is provided on the discharge electrode.

  The discharge element of the present invention is characterized in that the protective layer on the discharge electrode has a multilayer structure based on a ceramic layer.

  In the discharge element of the present invention, the protective layer has a thickness of 20 to 100 μm.

  The discharge element of the present invention is characterized in that the surface of the protective layer is formed of non-crystallized glass.

  In the discharge element of the present invention, the surface of the protective layer is formed of a polyimide resin having a thickness of 10 μm or less.

  The discharge element of the present invention is characterized in that the lowermost layer of the protective layer is formed of a ceramic layer having a thickness of 10 m or more.

  According to the present invention, a plurality of discharge electrodes are provided on the surface of a substrate made of ceramic, embedded in the substrate with a planar dielectric electrode, and the discharge electrode and the planar dielectric electrode are interposed via a dielectric layer. In the discharge element opposed to each other, by providing a protective layer having a surface roughness Ra of 10 μm or less on the discharge electrode, the condensation of moisture on the surface of the protective layer is suppressed, so that ammonium nitrate adheres to the protective layer. Thus, a long-life high-output discharge element can be obtained.

  Moreover, durability can be further improved by making the said protective layer into the multilayered structure based on a ceramic layer.

  Further, by setting the thickness of the protective layer to 20 to 100 μm, the durability can be further improved without suggesting the amount of ozone or ions generated.

  It is also possible to form the surface of the protective layer of the discharge element of the present invention with polyimide having a thickness of 10 μm or less. In this case, durability can be improved by forming the thickness of the lowermost layer of a protective layer with a ceramic layer of 10 micrometers or less.

  Embodiments of the present invention will be described below.

  FIG. 1 is a developed perspective view of the discharge element of the present invention, and FIG. 2 is a cross-sectional view of the discharge element of the present invention.

  The discharge element 8 of the present invention includes an induction electrode 4 built in the ceramic sheets 1 and 2, a discharge electrode 3 formed on the surface of the ceramic sheet 2, and a protective layer 5 formed on the surface of the discharge electrode 3. Have The discharge electrode 3 and the induction electrode 4 are formed so as to face each other, and the ceramic sheet 2 sandwiched between the discharge electrode 3 and the induction electrode 4 acts as a dielectric layer. By applying a high frequency voltage of about 1 to 3 kV to the discharge electrode 3 and the induction electrode 4, a corona discharge is generated on the surface of the discharge electrode 3, thereby generating ozone and ions. .

  Hereinafter, features of the present invention will be described in order.

  In the discharge element 8 of the present invention, a discharge electrode 3 is provided on the surface of a substrate made of ceramics, a dielectric electrode 4 is embedded in the substrate, and the discharge electrode 3 and the dielectric electrode 3 are interposed via a dielectric layer. In the discharge element 8 facing each other, a protective layer 5 having a surface roughness Ra of 10 μm or less is provided on the discharge electrode 3. Thereby, the amount of moisture generated in the recesses on the surface of the protective layer 5 is reduced, the ammonium nitrate which is a discharge inhibitor is dissolved in the moisture in the recesses, and the critical humidity affecting the moisture condensation in the recesses is reduced, It is possible to prevent the amount of water generated on the surface of the protective layer 5 from increasing and the amount of ozone and ions generated from decreasing. Thus, the phenomenon that the critical humidity related to the condensation of moisture in the concave portion due to the radius of curvature of the concave portion is also applied to the humidity sensor. In addition, by reducing the amount of moisture condensed on the surface of the protective layer 5, the amount of ammonium nitrate deposited on the surface of the protective layer 5 can be reduced, and the durability of the discharge element 8 can be improved.

  On the other hand, when the surface roughness Ra of the protective layer 5 exceeds 10 μm, the amount of water condensed in the concave portions on the surface of the protective layer 5 increases, and ammonium nitrate as a discharge inhibitor precipitates on the concave and convex portions of the protective layer 5. However, it is not preferable because the water absorption causes a problem that the discharge is inhibited.

  The surface roughness Ra of the protective layer 5 is more preferably 3.0 μm or less, and ideally 1.0 μm or less.

  In the discharge element 8 of the present invention, the protective layer 5 preferably has a multilayer structure based on a ceramic layer. As a result, it is possible to select a material having a surface roughness Ra of 10 μm or less, and it is possible to reduce irregularities such as pinholes and voids by forming a multilayer, and the effect that the discharge efficiency is hardly deteriorated can be expected. . On the other hand, when the protective layer 5 has a single-layer structure, surface roughness is caused by voids due to poor stacking with pinholes or discharge electrodes 3 in the manufacturing process such as printing and stacking, degranulation during firing, and grain growth. Is undesirably caused by the problem that ammonium nitrate, which is a discharge inhibiting substance, is deposited on the concavo-convex portion and the water absorption absorbs discharge.

  Specifically, the inner base layer 5a serving as the base of the protective layer 5 is preferably a ceramic layer, and the surface layer 5b made of glass or polyimide is formed on the surface thereof. By doing in this way, it becomes possible to make the protective layer 5 with a smooth surface and good durability.

  Moreover, it is preferable that the discharge element 8 of this invention sets the whole thickness of the said protective layer 5 to 20-100 micrometers. If the thickness of the protective layer 5 is less than 20 μm, there arises a problem that the protective layer 5 or the ceramic sheet 2 that is a dielectric layer is broken by discharge. On the other hand, when the thickness of the protective layer 5 exceeds 100 μm, it is not preferable because the discharge efficiency is lowered and the discharge does not occur.

  More preferably, it is preferable to set it as 20-50 micrometers. By reducing the thickness of the protective layer 5, it is possible to increase the amount of ozone and ions generated.

  In the discharge element 8 of the present invention, the surface layer 5b of the protective layer 5 is preferably formed of non-crystallized glass. Thereby, the surface roughness Ra becomes 10 μm or less, and the effect that the discharge efficiency is hardly deteriorated can be expected. On the other hand, when the surface layer 5b of the protective layer 5 is made of crystallized glass, the surface roughness becomes rough due to crystallization and grain growth of the glass component after sintering, so that ammonium sulfate is liable to precipitate during discharge, resulting in durability. The problem that is inferior occurs.

  In the discharge element 8 of the present invention, the surface layer 5b of the protective layer 5 on the discharge electrode 3 is preferably formed of a polyimide resin having a thickness of 10 μm or less. As a result, an effect that the discharge efficiency is hardly deteriorated can be expected. On the other hand, when the thickness of the polyimide resin exceeds 10 μm, it is not preferable because a problem that the discharge efficiency is lowered due to the hygroscopic property of the polyimide itself occurs.

  In the discharge element 8 of the present invention, the base layer 5a of the protective layer 5 on the discharge electrode 3 is preferably formed of a ceramic layer having a thickness of 10 m or more. Thereby, the effect that the discharge efficiency is hardly deteriorated can be expected. On the other hand, if the thickness of the ceramic layer is 10 μm or less, there is a problem that cracks occur in the protective layer 5 due to the impact of discharge, which is not preferable.

  Hereinafter, a method for producing the discharge element 8 of the present invention will be described.

  First, a planar dielectric electrode 4 pattern is printed on the surface of the ceramic sheet 1 by metallizing ink by screen printing. If the thickness of the dielectric electrode 4 after firing is 5 μm or less, unevenness during printing occurs and disconnection tends to occur. Conversely, if the thickness of the planar dielectric electrode 4 exceeds 50 μm, it becomes difficult to remove the metallized ink during firing, and bubbles are generated in the ceramic laminate.

  Next, the ceramic sheet 1 and the ceramic sheet 2 to be a dielectric layer are laminated by thermocompression bonding. The ceramic sheet 2 desirably has a thickness after firing of 20 μm or more. If the thickness after firing of the ceramic sheet 2 is less than 20 μm, there is a risk of dielectric breakdown when a high voltage is applied. In order to increase the discharge efficiency, the thickness after firing of the ceramic sheet 2 is desirably 300 μm or less.

  Next, the linear discharge electrode 3 pattern 3 is printed with metallized ink on the surface of the ceramic sheet 2 by screen printing. The discharge electrode 3 becomes a highly efficient discharge element 8 by providing a plurality of protrusions on the periphery of the discharge electrode 3 or by forming a grid or a plurality of linear electrodes. The thickness of the discharge electrode 3 is preferably designed to be 5 to 50 μm after firing. If the thickness of the discharge electrode 3 is less than 5 μm, unevenness at the time of printing occurs and unevenness of discharge may occur. Moreover, when the thickness of the discharge electrode 3 is less than 5 μm, it can be expected that the life is shortened due to deterioration due to discharge. On the other hand, if the thickness of the discharge electrode 3 exceeds 50 μm, it becomes difficult to remove the metallized ink at the time of firing, bubbles are generated in the protective layer 5, and the discharge efficiency is lowered.

  Next, the power feeding portions 7a and 7b are formed by printing on the back surface of the ceramic green sheet 1 with metallized ink. Desirably, the thickness of the power feeding portions 7a and 7b after firing is designed to be 5 to 50 μm. If the thickness is less than 5 μm, unevenness occurs during printing, and electrical connection cannot be obtained. Conversely, the thickness of the wiring circuit is 50 μm. If it exceeds, it will be difficult to remove the metallized ink at the time of firing, bubbles will be generated in the power feeding part, and the strength of the power feeding part will be easily estimated.

  Finally, the protection of the multilayer structure in which the ceramic layer is used as the base layer 5a on the discharge electrode 3 and the surface layer 5b is overlaid with a ceramic, fine-crystallized glass layer, or polyimide layer having a fine material particle size as the surface layer 5b. Layer 5 is formed. The protective layer 5 is formed by printing or sheet adhesion. It can be easily estimated that when the particle size of the raw material forming the protective layer 5 is made fine, the surface roughness becomes small. When the thickness of the protective layer 5 after firing is 10 μm or less, the protective layer 5 is destroyed by discharge, and when the thickness of the protective layer 5 is increased, the discharge efficiency is deteriorated. Therefore, the thickness is preferably 20 to 100 μm or less. In addition, the ammonium sulfate as a discharge inhibiting substance generated by discharge enters the uneven portions of the ceramic on and around the discharge electrode 3 and grows as white needle-like crystals. Therefore, in order to suppress the precipitation, the surface roughness of the protective layer 5 is desirably Ra 10 μm or less. Further, as a method for reducing the Ra of the protective layer 5, processing by blasting, polishing, or the like is possible, but it is difficult to manage the thickness of the protective layer 5.

  The discharge element 8 thus formed is fired in a reducing gas atmosphere at 1400 ° C. to 1600 ° C. After firing, the power supply unit 7 is plated and connected to the power supply line by brazing or soldering. When exposed to the influence of ozone and ions generated by discharge for a long time, it is possible to sufficiently predict that the plating, solder, brazing material, wiring, etc. of the power supply section will be oxidized and cause a failure such as disconnection. 7b are preferably provided on the back surface of the discharge surface. This is to prevent corona discharge from occurring near the power feeding units 7a and 7b and the deterioration of the power feeding units 7a and 7b. It is also effective to take measures to prevent oxidation with silicon or the like on the wired power supply portions 7a and 7b.

  When a high-frequency AC high voltage is applied to the power feeding units 7 a and 7 b by a high-frequency AC power source, a high-frequency corona discharge is generated from the periphery of the discharge electrode 3. By this discharge, plasma containing positive and negative ions is formed on the discharge surface.

  It is well known that this type of discharge element 8 becomes an ozone generation discharge element when a voltage of 5 kV or more is applied, and can be used as an ion generation discharge element when a voltage of 1.2 KV is applied. is there.

  An induction electrode 4 having a width of 10 mm and a length of 40 mm made of tungsten ink is printed on a ceramic sheet 2 made of alumina having a purity of 96%, and the ceramic sheet 2 serving as a dielectric layer is adhered to the ceramic electrode 2. A discharge electrode 3 is formed on the surface facing the induction electrode 4, a protective layer 5 is further formed on the surface of the discharge electrode 3, cut to a predetermined size, and then fired at 1550 ° C. for 3 hours to form a discharge element. 8 was produced. Here, the surface roughness of the protective layer 5, the material of the protective layer 5, and the thickness of the protective layer 5 were changed as shown in Table 1, and 27 types of discharge elements 8 were prepared.

  The surface roughness of the protective layer 5 was adjusted by changing the particle size of the raw material powder contained in the paste forming the protective layer 5 or polishing with a sand paste or the like.

  Moreover, the discharge element 8 produced with the following method was evaluated.

  First, for evaluation of overvoltage resistance, a high-frequency high-voltage power supply of 8 kV (PP) and 60 kHz was used for 1 minute. An overvoltage resistance evaluation was performed by applying an overvoltage. In this evaluation, the dielectric breakdown, the degree of deterioration of the protective layer 5 and the like were observed.

  Next, as a durability evaluation, continuous discharge was performed using a high-frequency high-voltage power supply for acceleration evaluation of 5 kV (PP) and 40 kHz in a high-temperature and high-humidity state of 40 ° C.-95% RH. And it extracted at fixed time and measured the time-dependent change of ozone generation amount. When measuring the amount of ozone generated, the amount of ozone generated under an environmental condition of 25 ° C.-60% RH was measured using a 3 kV (PP), 10 kHz high frequency high voltage power supply. In the measurement method, a high voltage is applied to and discharged from the discharge element 8 in a cylinder having an air flow rate of 20 L / min and an inner diameter of 52 mm in a constant temperature and humidity chamber, and an ozone concentration measuring device (manufactured by Dailex Corporation) is provided downstream. (DY-1500 type) sampling tube was installed and measured. An ozone adsorption honeycomb was placed downstream of the sampling tube to prevent ozone from staying in the constant temperature and humidity chamber. In the measurement, the concentration after 1 minute was applied to the discharge element 8 as a measured value. In the present invention, the amount of ozone generated after 60 hours of continuous energization was determined to be 60% or more of the amount of ozone generated at the beginning of the durability evaluation.

The results are shown in Table 1.

  It can be seen that Sample Nos. 11 to 27 which are outside the scope of the claims of the present invention have problems in the discharge state and durability. In particular, Sample Nos. 13 to 19 whose surface roughness of the protective layer 5 is rougher than Ra 10 μm are such that ammonium sulfate is deposited on the surface of the protective layer 5 and inhibits discharge, so that the amount of ozone generated after continuous discharge is 70% or less of the initial value. Therefore, the durability was judged to be inferior. On the other hand, Sample Nos. 1 to 10, 21 and 24 to 27 having a surface roughness Ra of the protective layer 5 of 10 μm or less showed good durability with a small decrease in the amount of ozone generated after durability. Further, if the surface roughness Ra is 3 μm or less, the ozone generation amount after durability can be made 90% or more of the initial value, and if the surface roughness Ra is 1 μm or less, the durability after durability is increased. It was found that the amount of ozone generated can be 95% or more.

  Next, from the results of sample numbers 1, 2, 7, 12, and 20, it can be seen that the total thickness of the protective layer 5 is desirably 20 μm or more and 100 μm or less. When the thickness of the protective layer 5 was less than 20 μm, cracks occurred in the protective layer 5 due to the impact of discharge in the overvoltage evaluation. Further, when the thickness of the ceramic layer serving as the base layer 5a of the protective layer 5a was 100 μm or more, no discharge occurred. This is because the protective layer 5 is too thick to inhibit discharge. In addition, about 12, 20, and 23 where the thickness of the protective layer 5 exceeds 100 micrometers, generation | occurrence | production of ozone has been confirmed if the voltage to apply is 10 kV.

  In addition, from the results of sample numbers 1, 7, 11, and 12, it can be seen that the thickness of the ceramic layer serving as the base layer 5a is preferably 5 μm or more and 100 μm or less. When the thickness of the ceramic layer serving as the base layer 5a is less than 5 μm, cracks are generated in the protective layer 5 due to the impact of discharge in overvoltage evaluation. It can be easily estimated that the durability deteriorates due to the crack. Further, when the thickness of the ceramic layer serving as the base layer 5a exceeded 100 μm, no discharge occurred. This is also because the protective layer 5 is too thick to inhibit discharge.

  Next, from the results of Sample Nos. 1 and 19, it can be seen that the non-crystallized glass is more durable than the crystallized glass. Crystallized glass has a rough surface due to crystallization and grain growth of the glass component after sintering, so that ammonium sulfate is liable to precipitate during discharge, resulting in poor durability.

  Further, from the results of sample numbers 1, 7, 11, 12, 21, 22 it can be seen that the thickness of the ceramic layer to be the base layer 5a is preferably 5 μm or more and 100 μm or less. When the thickness of the ceramic layer serving as the base layer 5a is less than 5 μm, cracks occur in the protective layer 5 due to the impact of discharge. It can be easily estimated that the durability deteriorates due to the crack. Further, when the thickness of the ceramic layer serving as the base layer 5a was 100 μm or more, no discharge occurred. It can be seen from the results of sample numbers 1 to 10, 21, 23, 25 to 27 that the base layer 5a is desirably a ceramic layer. Further, when the thickness of the glass layer is 20 μm or less, the protective layer 5 is not able to withstand the impact of discharge, and when the thickness exceeds 100 μm, the discharge tends to be difficult. If the polyimide layer that becomes the surface layer 5b has a thickness of 20 μm or more, the amount of ozone generated tends to decrease after durability. This is expected to be difficult to discharge because the polyimide itself has water absorption. Therefore, it is desirable that the thickness of the polyimide serving as the surface layer be 10 μm or less.

  Moreover, although the sample which attached the heating element to the back surface of the discharge element 8 was evaluated as a comparison, although the surface roughness Ra is 10 μm or more, the generation of ammonium nitrate is suppressed by the heating effect, and the amount of ozone generated after durability evaluation The difference in change is small. However, when the heating element was not operated, ammonium nitrate was precipitated, resulting in poor durability.

  In comparison, it can be seen that there is no difference in the change in the amount of ozone generated after the durability evaluation by comparing the sample numbers 1 to 10 within the scope of the present invention with the sample with the heating element of the prior art.

It is a development perspective view of the discharge element of the present invention. It is sectional drawing of the discharge element of this invention. It is a development perspective view of the conventional discharge element.

Explanation of symbols

1, 2 Ceramic sheet 3 Discharge electrode 4 Dielectric electrode 5 Protective layer 8 Discharge element

Claims (6)

In a discharge element in which a discharge electrode is provided on the surface of a substrate made of ceramics, a dielectric electrode is embedded in the substrate, and the discharge electrode and the dielectric electrode are opposed to each other through a dielectric layer, the surface is disposed on the discharge electrode. A discharge element provided with a protective layer having a roughness Ra of 10 μm or less. The discharge element according to claim 1, wherein the protective layer has a multilayer structure based on a ceramic layer. The discharge element according to claim 1, wherein the protective layer has a thickness of 20 to 100 μm. The discharge element according to claim 1 or 2, wherein the surface of the protective layer is formed of non-crystallized glass. The discharge element according to claim 1, wherein the surface of the protective layer is formed of a polyimide resin having a thickness of 10 μm or less. 3. The discharge element according to claim 1, wherein the lowermost layer of the protective layer is formed of a ceramic layer having a thickness of 10 m or more.

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