JP5438818B2 - Ozone generator and ozone generation method - Google Patents

Description

  The present invention relates to high performance and high efficiency of a plasma apparatus using silent discharge typified by an ozone generator and a carbon dioxide laser apparatus.

  An ozone generator will be described on behalf of a plasma device using silent discharge. The demand for ozone is increasing year by year, and in recent years it has been expanded not only to the water environment purification field such as water and sewage treatment but also to the field of pulp bleaching and semiconductor / liquid crystal manufacturing due to its usefulness as a powerful oxidizing agent. A common issue for each application is to increase the efficiency of high-concentration ozone generation. Various R & D activities are being carried out in various countries around the world to improve efficiency. In particular, high-concentration ozone generation technology using high-pressure, short-gap discharge with an extremely small discharge gap length under high gas pressure is innovative. Has been in the limelight (Patent Document 1). In improving efficiency, ozone generators are being considered to be more efficient when oxygen is used as the source gas (hereinafter referred to as oxygen source type) and when air is used as the source gas (hereinafter referred to as air source type). Development of higher efficiency is being promoted, centering on high-pressure short gap discharge. In particular, in the oxygen source type, the efficiency of ozone decomposition due to the generation efficiency of oxygen atoms and electron collisions, which are the starting points of ozone generation, and in the air source type, the ozone decomposition effect due to nitrogen oxides generated simultaneously with ozone is improved. It has become a point of focus.

  In recent years, it has been confirmed that an extremely interesting phenomenon occurs in an oxygen source type using high-purity oxygen gas. In a conventional ozone generator, it is known that when high-purity oxygen is used as a raw material gas, the ozone generation efficiency is extremely low, and it deteriorates with the operation time. Much research and development has been carried out to improve the ozone generation efficiency when using high-purity oxygen gas and to elucidate the physical phenomenon. Generally, a small amount of nitrogen is added to high-purity oxygen. Therefore, an empirical policy is adopted that avoids a decrease in ozone generation efficiency and deterioration over time. However, there are various theories on the mechanism of efficiency improvement by the addition gas such as nitrogen, and none of these theories have been proved correctly and the situation is not clear yet.

In the electronic device industry such as semiconductor and liquid crystal manufacturing processes, ozone is applied to the formation of insulating films and substrate cleaning. In such fields, the cleanliness of ozone gas is required, and the amount of metal contamination (hereinafter referred to as metal contamination) contained in ozone gas is regarded as a problem. In particular, heavy metal particles such as Cr and Fe caused by stainless steel, which is an electrode component of the ozone generator, are entrained in the ozone gas by sputtering of the electrode surface due to discharge and oxidative corrosion by ozone gas, and are taken into the device. It is a factor that deteriorates the characteristics. For this reason, it is generally practiced to reduce the generation of metal contamination from the electrode part by covering the surface with an insulator rich in sputtering resistance so as not to expose the metal part on the electrode surface. In the semiconductor deposition process, metal contamination quantity adsorbed on the silicon wafer is required and generally needs to be 10 ⁹ atoms / cm ² level, but only measures the electrode surface portion, 10 ¹¹ Metal contamination at a level of -10 ¹² atoms / cm ² is generated. This is because not only the metal contamination is generated from the electrode part, but also the nitrogen oxide generated together with ozone due to the nitrogen gas added to the raw material gas generates nitric acid by reaction with trace moisture, and this nitric acid This is due to the presence of metal contamination generated by corrosion of the metal gas flow part after the electrode part, for example, stainless steel piping material due to the influence. That is, even if the generation of metal contamination in the electrode part is reduced, as long as nitrogen is added to the source gas, in the process apparatus connected to the subsequent stage of the ozone generator, the generation of metal contamination cannot be suppressed, The amount of adhesion on the wafer cannot be satisfied.

  As described above, in the oxygen source type ozone generator for applications where cleanliness is required, the addition of nitrogen to the source gas is a big problem, and an ozone generator that does not add nitrogen to the source gas is desired. Yes. Against this background, so-called nitrogen-less ozone generation technology that does not add nitrogen gas has been actively developed. For example, anatase-type titanium oxide is installed on the electrode surface and ultraviolet light generated by discharge is used. It has been proposed to apply the photocatalytic effect of titanium oxide as a substitute for the effect of nitrogen on discharge and ozone generation (Patent Document 2). It has also been proposed to improve the activity of the photocatalyst by doping a noble metal such as platinum into the photocatalyst material (Patent Document 3). In both cases, it is said that by using the photocatalytic action of the electrode material, it is possible to improve the ozone generation efficiency when high purity oxygen is used as the source gas without adding nitrogen.

Japanese Patent No. 3545257 (paragraphs 0022 to 0026, FIG. 5) Japanese Patent No. 4069990 (paragraphs 0011 to 0021, FIG. 2) Republished Patent JP WO2005 / 080263 (0076 paragraph) Japanese Patent No. 4320637 (paragraph 0019) JP 2008-49280 A (paragraph 0010) Japanese Patent No. 2983153 (paragraphs 0111 to 0114)

  In an ozone generator that is a typical silent discharge plasma apparatus, the range of use of ozone is diverse, and further higher efficiency is required. However, at present, a significant increase in efficiency exceeding the high voltage short gap discharge disclosed in Patent Document 1 has not been realized, and the level cannot be achieved by simply optimizing the device structure and operating conditions. In other words, drastic reforms from the origin regarding plasma generation and maintenance are necessary, and optimization of the generation mechanism of high-concentration ozone in the currently required area and the power electronics technology that is the discharge physics and driving technology. is necessary. In addition, for the nitrogen-less ozone generation in the oxygen source type that has become apparent in recent years, even the role of nitrogen as an additive gas for ozone generation has not been clarified. It has not yet come to meet expectations. In the semiconductor / liquid crystal manufacturing field, the requirement specification for ozone gas is improved with the miniaturization of devices, so the establishment of an early nitrogen-less ozone generation technology is urgently required.

  For generating nitrogen-free ozone, for example, in Patent Document 2, an anatase-type titanium oxide thin film, which is a photocatalytic material, is formed on the electrode surface, and only high-purity oxygen (purity 99.9999% or more) is used as a source gas. In the conventional ozone generator, high-efficiency high-concentration ozone generation can be sufficiently realized without causing deterioration of ozone concentration with time. This is because the titanium oxide on the electrode surface absorbs the excitation energy of ozone molecules due to the photocatalytic action accompanying discharge, and returns to the ground state without changing the atomic structure of the ozone molecules, as in the case of adding nitrogen to the source gas. It is based on the idea that ozone can be prevented from returning to oxygen. However, the evaluation (operation) time disclosed in the literature is only about 30 hours.

  As a result of the inventors' verification test, after a long operating time, for example, 200 hours, a significant decrease in ozone generation efficiency was confirmed, and the generation of high-concentration ozone as disclosed could not be realized. This is considered because deterioration with time occurs in the photocatalytic ability of titanium oxide. Titanium oxide excited by receiving energy from ultraviolet light in the discharge field generates electrons and holes on its surface. However, since the recombination of electrons and holes is generated at the same time as the generation of electrons and holes on the titanium oxide surface, it is known that the photocatalytic ability decreases with time. Therefore, the photocatalytic material alone does not replace the effect of the additive gas such as nitrogen, and it is impossible to realize stable high-concentration ozone generation.

  Furthermore, in Patent Document 3, if a photocatalytic material having a predetermined band gap is doped with, for example, platinum, which is a noble metal, from the viewpoint of promoting its excitation capability, the effect of accumulating holes is increased. It has been shown that the ozone generation efficiency can be improved. However, there is no clear disclosure about the specific effect and the doping conditions of the noble metal material that brings about the effect, and the effect of the noble metal material is very unclear. Further, there is no relation between the electrode surface resistance and the ozone generation efficiency, and it is said that the ozone generation efficiency is determined only by the band gap of the photocatalytic material (Patent Document 3, paragraphs 0082 to 0085). There is no technical description, and the mechanism is not mentioned at all. Actually, the inventors conducted a verification test using the photocatalyst material with the specifications described, but it was not possible to reproduce the nitrogen-less ozone generation as described, and the ozone generation efficiency deteriorated over time. did. In addition, high-efficiency nitrogen-less ozone generation cannot be achieved simply by doping the described photocatalytic material with a noble metal.

  Further, in the carbon dioxide laser device which is another silent discharge plasma device, there is a problem of increasing its efficiency, that is, improving the laser oscillation efficiency or improving the plasma excitation efficiency. In addition, the apparatus cannot be operated for a long time in a state in which the gas is sealed off due to deterioration of the laser gas, and it is also necessary to improve that the gas needs to be replaced within a predetermined operation time. In addition, the gas is a mixed gas in which several gases are added to carbon dioxide, and the mixed gas tends to increase in cost as the number of mixed species increases, resulting in longer delivery times, lower costs, and shorter delivery times. The demand for is strong.

The ozone generator according to the present invention includes two electrodes arranged opposite to each other and at least one dielectric between the electrodes, and supplies gas containing oxygen between the electrodes and applies an alternating voltage to the gas. In an ozone generator for generating ozone by discharging ozone , at least one of the surfaces in contact with the discharge of the electrode or the dielectric is 0.05 wt% or more in weight ratio with respect to this oxide in titanium oxide or tungsten oxide as the thickness of the platinum fine particles such that to 10wt% is a semiconductive dispersed is provided below the discharge boundary layer 5 [mu] m, the ratio energy input to the discharge is operated in the following 20Wmin / NL more 800Wmin / NL I made it.

According to the present invention, catalytic activity with respect to the plasma excitation by the optimization of the discharge sustain form a discharge space boundary layer of the ozone generator, and the platinum fine particles to the discharge boundary layer so as not to inhibit the discharge stability is dispersed By utilizing this synergistic effect, the efficiency of the ozone generator can be dramatically improved. That is, the dramatic improvement in efficiency makes it possible to reduce the types of additive gases without using additive gases. Since it is not necessary to use an additive gas, Ru can provide very clean ozone gas which suppresses the occurrence of metallic contamination.

It is sectional drawing which shows the electrode structure of the ozone generator which is a silent discharge plasma apparatus by Embodiment 1 of this invention. It is sectional drawing which shows the electrode structure of another ozone generator which is a silent discharge plasma apparatus by Embodiment 1 of this invention. It is a figure for demonstrating the ozone generation characteristic of the ozone generator which is a silent discharge plasma apparatus by Embodiment 1 of this invention. It is a figure for demonstrating the weight ratio of the noble metal fine particle by Embodiment 1 of this invention. It is sectional drawing which shows the electrode structure of the ozone generator which is a silent discharge plasma apparatus by Embodiment 2 of this invention. It is sectional drawing which shows the electrode structure of the ozone generator which is a silent discharge plasma apparatus by Embodiment 3 of this invention. It is sectional drawing which shows another electrode structure of the ozone generator which is a silent discharge plasma apparatus by Embodiment 3 of this invention. It is sectional drawing which shows the electrode structure of the ozone generator which is a silent discharge plasma apparatus by Embodiment 4 of this invention. It is sectional drawing which shows the electrode structure of the ozone generator which is a silent discharge plasma apparatus by Embodiment 5 of this invention. It is sectional drawing which shows another electrode structure of the ozone generator which is a silent discharge plasma apparatus by Embodiment 5 of this invention. It is sectional drawing which shows the electrode structure of the ozone generator which is a silent discharge plasma apparatus by Embodiment 6 of this invention. It is sectional drawing which shows another electrode structure of the ozone generator which is a silent discharge plasma apparatus by Embodiment 6 of this invention. It is sectional drawing which shows the electrode structure of the ozone generator which is a silent discharge plasma apparatus by Embodiment 7 of this invention. It is sectional drawing which shows another electrode structure of the ozone generator which is a silent discharge plasma apparatus by Embodiment 7 of this invention. It is sectional drawing which shows another electrode structure of the ozone generator which is a silent discharge plasma apparatus by Embodiment 7 of this invention. It is sectional drawing which shows another electrode structure of the ozone generator which is a silent discharge plasma apparatus by Embodiment 7 of this invention. It is sectional drawing which shows the electrode structure of the ozone generator which is a silent discharge plasma apparatus by Embodiment 8 of this invention. It is sectional drawing which shows the electrode structure of the carbon dioxide laser apparatus which is a silent discharge plasma apparatus by Embodiment 9 of this invention. It is a figure for demonstrating the laser oscillation characteristic of the carbon dioxide laser device which is a silent discharge plasma apparatus by Embodiment 9 of this invention. It is a figure for demonstrating the laser oscillation characteristic by the carbon monoxide less gas of the carbon dioxide laser apparatus which is a silent discharge plasma apparatus by Embodiment 9 of this invention. It is sectional drawing which shows the electrode structure of the ozone generator which is a silent discharge plasma apparatus by Embodiment 10 of this invention. It is sectional drawing which shows another electrode structure of the ozone generator which is a silent discharge plasma apparatus by Embodiment 10 of this invention.

  The inventors have discovered that in an ozone generator typified by a silent discharge plasma device, the apparent discharge maintenance mode changes depending on the discharge gap length, gas pressure, and the like (Patent Document 4, paragraph 0019). In a conventional ozone generator having a discharge space with a relatively long gap, a discharge sustaining mode that is unique to silent discharge in which a highly insulating dielectric is interposed in the discharge space and a streamer-like fine discharge column exists Indicates. However, when the discharge gap length is shortened, the discharge maintenance mode is not always followed. It was found that when the discharge gap length is 0.3 mm or less, there is no apparent discharge column peculiar to silent discharge, and it is as if it approaches a glow-like uniform discharge maintenance form. This suggests that there is no need for a highly insulating boundary layer that is set to generate and maintain the discharge column, ie, has a high surface resistivity that traps the generated charge on its surface. However, high insulation is required in the thickness direction of the discharge boundary layer, that is, in the electric field direction. Despite the adoption of high-pressure short-gap discharge and innovative improvements in ozone generation efficiency, the relationship between the discharge maintenance mode and the discharge boundary layer has not been optimized at present. It is considered that there is a case where a predetermined ozone generation efficiency cannot be obtained unless the action of the additive gas is given.

In the present invention, a discharge boundary layer composed of noble metal fine particles and an oxide substrate is provided on the surface in contact with the discharge in the high-pressure short gap discharge space. Thereby, the surface resistivity of the surface in contact with the conventional discharge is 10 ¹² Ω or more, and the resistance is reduced to 10 ⁴ Ω or more and less than 10 ¹² Ω, which is a semiconducting region. The charge accumulation in the plasma is reduced, and the drift between the electrodes of the ions generated in the plasma that does not contribute to ozone generation and causes energy loss is suppressed. That is, the ozone generation and the discharge physical phenomenon in the high-pressure short gap discharge are optimized. In addition, the surface resistivity shown by this application is based on the measuring method based on JISC2141 "Ceramic material test method for electrical insulation."

  In the present invention, oxides such as yttrium, titanium, and indium are used for the oxide substrate, and palladium, rhodium, platinum, and the like are used as noble metal fine particles dispersed in the substrate. When the noble metal fine particles are dispersed in the oxide substrate used for the discharge boundary layer, the dispersibility of the noble metal fine particles and the weight ratio with respect to the oxide substrate are important parameters. In the present invention, the weight ratio (also referred to as the loading amount) refers to the weight ratio of the noble metal fine particles to the weight of the oxide as a substrate per unit volume of the discharge boundary layer, and produces the effect of the discharge boundary layer. Since this is the surface, it is sufficient that the noble metal particles have a predetermined weight ratio at least on the surface of the discharge boundary layer. Further, the particle diameter of the noble metal fine particles indicates the average particle diameter in the substrate, and the specific surface area which is one of the indicators of the catalytic activity is inversely proportional to the particle diameter as well as the weight ratio. In the silent discharge plasma apparatus, it is necessary to obtain a high and uniform dispersibility from the viewpoint of ensuring the stability of the discharge, and in order to effectively obtain the activity effect of the catalyst, the weight ratio of the noble metal fine particles is increased. There is a need. In order to obtain high dispersibility and activity, it is necessary to use noble metal fine particles having a small particle size (= specific surface area is increased), but there is a problem that the weight ratio with respect to the substrate becomes small. When further activity is expected, it is necessary to set a large weight ratio. However, if the weight ratio is simply increased, only the particle diameter of the noble metal fine particles is increased, resulting in a decrease in dispersibility, specific surface area, and stability. The possibility of inhibiting discharge increases. That is, the dispersibility and the weight ratio are in a trade-off relationship, and it is considered that the appropriate dispersibility and activity for the discharge are defined by the weight ratio and the particle diameter.

  In the present invention, the particle diameter that describes the dispersibility and the catalytic activity by the particle diameter that affects the dispersibility of the noble metal fine particles, and the specific surface area described by the particle diameter and the weight ratio corresponding to the number of the noble metal fine particles. And the weight ratio (the product of the reciprocal of the particle diameter and the weight ratio) are set in the range of 0.0005 to 20 wt% / nm. Further, the noble metal fine particles have a particle size of 100 nm or less, preferably 10 nm or less, and a weight ratio of 0.05 wt% or more, preferably 0.15 wt% or more, more preferably 3 wt% or more uniformly in the substrate. Is distributed. As described above, the noble metal fine particles do not aggregate in the vicinity of the surface of the discharge boundary layer or in the layer thickness direction, do not hinder a stable discharge state, and can effectively act as a highly active catalyst in the ozone generation field. . In a silent discharge plasma apparatus such as a conventional ozone generator, the arrangement of noble metal particles in the discharge space has not been studied from the viewpoint of ensuring the stability of the discharge. In addition, from the viewpoint of the use of noble metal catalysts in various industries, the weight ratio of noble metal fine particles has been discussed, but the dispersibility of noble metal fine particles in the substrate premised on use in discharge devices. It was not clarified.

  Patent Document 5 discloses that noble metal fine particles having a particle diameter of 1 to 10 nm and a weight ratio of 0.1 to 10 wt% are used in a plasma device. As for the operating conditions of the device, the specific input energy is 50 to 500 J / L (= 0.83 to 8.33 Wmin / L). Here, the specific input energy indicates a value obtained by dividing the discharge power by the gas flow rate. In this document, it is difficult to ensure the stability of discharge when used within the range of the above-mentioned specific input energy, and when used above the above range, it causes aggregation of noble metal fine particles as the temperature rises. It is disclosed that it cannot be used (Patent Document 5, paragraph 0010). On the other hand, the specific input energy of the plasma apparatus discussed in the present invention is 20 Wmin / NL to 800 Wmin / NL, preferably 20 Wmin / NL to 600 Wmin / NL, more preferably 30 Wmin / NL to 300 Wmin / NL, It is a region that is one digit larger than the specific input energy region of Reference 5 (where N is 1 atm and 0 ° C). In other words, in the present invention, in the specific input energy range for which application is denied in Patent Document 5, extremely stable discharge is maintained by using noble metal fine particles based on extremely high dispersibility and making the discharge boundary layer semiconductive. Furthermore, high activation of the catalyst can be realized, and furthermore, due to the cooling effect obtained from the structure of this plasma device, the temperature of the discharge boundary layer becomes 150 ° C. or lower, preferably 100 ° C. or lower. Such agglomeration of noble metal fine particles does not occur. That is, the present invention and Patent Document 5 show completely different apparatus forms / operation forms, and it is considered that the action exerted by the catalyst and the influence of the catalyst on the apparatus performance are greatly different.

  The specific input energy in this plasma device is limited by the following factors. The small specific input energy corresponds to a state where the input power is extremely small or the gas flow rate is extremely large. In this plasma device, when the specific input energy is less than 20 Wmin / NL, the discharge is difficult to spread uniformly in all discharge regions, the discharge is not stable, or the gas flow rate is too large, the pressure loss of the device increases, It is necessary to improve the capacity of the raw material gas supply device. On the other hand, a large specific input energy corresponds to a state in which the input power is extremely large or the gas flow rate is extremely small. In this plasma device, when the specific input energy exceeds 800 Wmin / NL, the temperature rise in the discharge space due to the increase in input power becomes significant, and in the case of an ozone generator, the effect of thermal decomposition of the generated ozone becomes large, There is a high possibility that stable ozone supply will be hindered. Further, in this device, the cooling effect due to the gas flow is also used for heat removal in the discharge space. If the gas flow velocity is extremely small, the effect cannot be effectively used. Therefore, the plasma device in the present invention is operated at a specific input energy of 20 Wmin / NL or more and 800 Wmin / NL or less.

In order to effectively use the action of the catalyst by the noble metal fine particles used in the present invention, the characteristics of the oxide substrate in which the noble metal fine particles are dispersed have a great influence. In general, an oxide has low electron conductivity, and a catalyst using normal noble metal fine particles is dispersed in an insulator. Furthermore, even if the noble metal fine particles are simply dispersed in the oxide substrate according to the dispersibility and weight ratio shown in the present invention, the conductivity of the discharge boundary layer containing the noble metal fine particles maintains the insulation and hardly changes. However, the inventors of the present invention have confirmed that the catalytic action of the noble metal fine particles can be activated by adjusting the conductivity of the discharge boundary layer in the present invention. That is, in the present invention, the discharge boundary layer is made semiconductive from the viewpoints of both optimization of the high-pressure short gap discharge and activation of the noble metal fine particle catalyst. The surface resistivity of the discharge boundary layer can be easily controlled by temperature treatment or plasma treatment, and is set to 10 ⁴ Ω or more and less than 10 ¹² Ω. As a result, a dramatic ozone generation that exceeds the high-pressure short gap discharge is achieved by synergizing the catalytic action for plasma excitation by the installation of the optimal discharge boundary layer and the high activation of the noble metal fine particle catalyst in the high-pressure short gap discharge. Improvement of efficiency and generation of nitrogen-less ozone without using additive gas can be realized.

Embodiment 1 FIG.
1 and 2 are cross-sectional views showing the structure of an electrode portion of an ozone generator that is a silent discharge plasma apparatus according to Embodiment 1 of the present invention. 1 shows a parallel plate type electrode structure, and FIG. 2 shows a single electrode structure in a cylindrical tube type electrode structure. FIG. 2 also shows a cross-sectional view taken along line AA. The ozone generator shown in the figure introduces oxygen having a purity of 99.5% or more as a source gas into a discharge space 14 formed by two opposing electrodes, that is, a metal ground electrode 11 and a high voltage electrode 12 (see FIG. 2). (In this case, it flows from the left side to the right side of the page. Note that the figure is rotated 90 degrees for convenience, so the left side is down and the right side is up. The same applies to the subsequent rotating drawings.) A silent discharge is generated by applying an alternating high voltage (HV) to the discharge space 14 to generate ozone, and dielectrics 131 and 132 are disposed on the side facing the discharge space 14 of both electrodes. Has been. Further, discharge boundary layers 151 and 152 in which noble metal fine particles are uniformly dispersed in an oxide base are formed on the surfaces of the dielectrics 131 and 132. The interval between the discharge boundary layers 151 and 152 arranged opposite to each other, that is, the discharge gap length d is set to 0.3 mm or less. As an actual apparatus, a plurality of the electrode parts are connected in parallel and installed in a pressure vessel. The gas pressure P in the discharge space is equal to or higher than atmospheric pressure. Cooling of the discharge space 14 is realized by the ground electrode 11 being in contact with the cooling water 18. In FIG. 2, current is supplied from the power supply member 17 to the high voltage electrode 12, and the ozone outlet side of the dielectric 132 is closed. An electric field relaxation layer 16 is provided at the end of the high voltage electrode 12 on the ozone outlet side to prevent energy loss due to creeping discharge.

Discharging the boundary layer 151, 152, yttrium as a base, titanium, indium, tungsten, Yuji pin um, erbium, zirconium, oxide of any one of tantalum is used as the main component. Precious metal fine particles are uniformly dispersed in the oxide substrate. As the noble metal fine particles, fine particles of palladium, rhodium, platinum, ruthenium, osmium, gold, antimony, or a mixture of these fine particles are used. The discharge boundary layers 151 and 152 by the above combination bring about an optimum discharge maintenance state and catalytic action for silent discharge, and contribute to a significant improvement in ozone generation efficiency.

  The discharge boundary layers 151 and 152 are thin layers having a thickness of 5 μm or less, preferably 3 μm or less. Further, the noble metal fine particles in the discharge boundary layer are in a weight ratio (hereinafter simply referred to as a weight ratio) of 0.05 wt% or more and 10 wt% or less with respect to the oxide as the substrate per unit surface area of the discharge boundary layer. It is uniformly dispersed and contained on the surface of the discharge boundary layer, preferably 0.15 wt% or more, more preferably 3 wt% or more. Here, the ratio between the particle diameter and the weight ratio described above satisfies 0.0005 to 20 wt% / nm. Furthermore, the particle diameter of the noble metal fine particles used here is 100 nm or less, preferably 10 nm or less. The discharge boundary layers 151 and 152 are formed by a general coating method such as a dip coating method or a spin coating method.

The surface resistivity of a dielectric used in a conventional ozone generator has a high insulating property of 10 ¹² Ω or more. In the present invention, the dielectrics 131 and 132 have a surface resistivity of 10 such as glass or ceramics. An insulating bulk material of ¹² Ω or more is used. Of course, the dielectric may be formed by coating such as thermal spraying, sputtering and glass lining in addition to the bulk material. In addition, when noble metal fine particles having the above specifications are simply dispersed in the oxide base shown above, the surface resistivity of the discharge boundary layer is 10 ¹² Ω or more due to the insulating properties of the oxide and the high dispersibility of the noble metal fine particles. Become. That is, in the simple dispersion of the noble metal fine particles on the oxide base, the conductivity as the surface of the discharge boundary layer is hardly affected, and the insulation is maintained. However, in the present invention, the discharge boundary layers 151 and 152 are not perfect insulators but are formed so as to have semiconductivity. After the noble metal fine particles are dispersed in the oxide substrate, the surface resistivity as the discharge boundary layer is set to 10 ⁴ Ω or more and less than 10 ¹² Ω by performing resistance control treatment. By this treatment, both the discharge maintenance mode and the catalyst activity can be optimized.

FIG. 3 shows an ozone generation characteristic in an ozone generator having discharge boundary layers 151 and 152 in which titanium oxide is used for the oxide substrate, platinum is used for the noble metal fine particles, and the surface resistivity is controlled to be 10 ⁴ Ω or more and less than 10 ¹² Ω. Indicates. In the figure, the change in ozone generation characteristics with respect to the weight ratio of platinum is described, the horizontal axis indicates the input energy per unit gas amount (specific input energy), and the vertical axis indicates the ozone concentration. The source gas is liquid oxygen with a purity of 99.5% or higher, and no additive gas such as nitrogen is used. That is, ozone generation characteristics in a so-called nitrogen-less state are shown. However, a very small amount of nitrogen is contained as an impurity in the liquid oxygen cylinder. Moreover, each characteristic shows the characteristic after 200 hours or more of continuous operation time. Here, “no discharge boundary layer” represents a case where the discharge boundary layers 151 and 152 are not provided, and the above-described dielectrics 131 and 132 having high insulation form the boundary of the discharge space. In the figure, the slope of the tangent line in the low input energy region of each characteristic curve (shown as a one-dot chain line in the curve without the discharge boundary layer as an example) is called the maximum ozone generation efficiency. Represent. The maximum ozone generation efficiency is defined as being equivalent to the generation efficiency of oxygen atoms, which is the initial process of ozone generation.

  From the figure, it can be seen that when the discharge boundary layer in the present invention is not installed, the ozone generation efficiency is very low, and the generation of high concentration ozone itself is impossible. In this characteristic, deterioration of ozone concentration with time is observed, and it has been confirmed that the characteristic is further deteriorated from the result shown in the figure along with the operation time. Further, when noble metal fine particles are dispersed in the oxide substrate, which is the greatest feature of the present invention, and the discharge boundary layers 151 and 152 having a predetermined surface resistivity are used as the boundary surfaces of the discharge space, the weight ratios are 0.15 wt% and 3 wt%. %, A rapid increase in ozone generation efficiency was confirmed, and it became clear that deterioration with time in ozone concentration was completely eliminated.

  FIG. 4 shows the relationship between the change amount of the maximum ozone generation efficiency and the weight ratio of platinum when there is no discharge boundary layer. From the figure, the maximum ozone generation efficiency starts to improve when the weight ratio is 0.01 wt% or more, but when the weight ratio is less than 0.05 wt%, problems such as the dispersion state of platinum and the boundary layer of the discharge boundary layer In some cases, the characteristics of the discharge boundary layer are not stable due to insufficient effects on ozone generation. However, at a weight ratio of 0.05 wt% or more, which is the inflection point of the curve in the figure, the ozone generation characteristics were extremely stable and reproducible.

Further, when the discharge boundary layers 151 and 152 are made of titanium oxide alone (predetermined resistance control) in which the weight ratio is 0%, that is, platinum is not dispersed, the ozone generation efficiency is 0.01 wt%. It was equivalent. Furthermore, when the weight ratio was 0.15 wt% or more and 3 wt% or more, it was confirmed that the ozone generation efficiency was further improved stably as the weight ratio increased. However, if it exceeds 10 wt%, the activity of platinum will increase too much, so it is not preferable to increase the weight ratio from the viewpoint of safety during the production of the discharge boundary layer. Therefore, from the above results, platinum having a weight ratio of at least 0.05 wt% or more, preferably 0.15 wt% or more, more preferably 3 wt% or more is uniformly dispersed in the titanium oxide substrate, and the surface resistivity is 10 ⁴ Ω. By providing a semiconductive discharge boundary layer of less than 10 ¹² Ω, an extremely high efficiency and stability can be obtained when the source gas is made of only high-purity oxygen gas without using an additive gas such as nitrogen. It became clear that high-concentration ozone generation, so-called nitrogen-less ozone generation, can be realized.

  In addition to the liquid oxygen having a purity of 99.5% or more, the same evaluation as described above was performed for high-purity oxygen having a purity of 99.9999% or more. As a result, it was confirmed that the same result as above was obtained. Naturally, the amount of impurities contained in high purity oxygen having a purity of 99.9999% or more is overwhelmingly small. That is, the result of FIG. 4 proves that high efficiency ozone generation without nitrogen can be realized by the present invention, not high efficiency due to nitrogen as an impurity contained in the source gas.

  In the present invention, titanium oxide, which is an oxide substrate, has photocatalytic properties, receives ultraviolet light generated by silent discharge, and generates electrons and holes. The generated electrons are supplied (oxidized) to the discharge space and act on dissociation of oxygen molecules, so that an increase in oxygen atom generation efficiency is realized in the ozone generator. However, on the titanium oxide surface, electrons and holes generated due to photocatalytic properties will eventually recombine, and the photocatalytic performance will deteriorate over time. In the present invention, platinum is provided on the surface of titanium oxide in order to suppress a decrease in photocatalytic activity, that is, recombination of electrons and holes. Noble metal fine particles such as platinum have an action of attracting electrons (reduction action), and have the ability to dissociate oxygen molecules to generate oxygen atoms. Electrons generated on the surface of the titanium oxide by the photocatalytic ability are supplied to the discharge space or attracted to platinum and do not easily recombine with holes. Accordingly, the time-dependent deterioration of the photocatalytic ability due to electron-hole recombination is suppressed, and the supply of electrons to the discharge space is continuously performed, assisting the generation of oxygen atoms in the discharge space. Furthermore, since the generation of oxygen atoms is promoted by the catalytic activity of platinum, it is thought that the ozone generation efficiency has been dramatically improved.

When the gap length of the discharge space is extremely short, 0.3 mm or less, the diameter of the discharge column showing the streamer-like discharge characteristic of silent discharge becomes extremely small, and the number density of the discharge columns increases rapidly, so it seems Then, it comes closer to a glow-like discharge maintenance mode. In other words, in the discharge space of 0.3 mm or less, the state is approaching the state where there is no longer any discharge column. Conventionally, the dielectric used for the ozone generator in order to maintain and promote the generation of the discharge column has been set to a high surface resistivity of 10 ¹² Ω or higher. However, in a discharge that occurs in a short gap length, the presence of the discharge column itself is not apparent, so there is no need to maintain and promote its generation. In other words, the surface resistivity of the dielectric used does not need to be increased unlike conventional devices. Rather, in order to remove unnecessary ions that do not contribute to ozone generation on the dielectric surface (suppressing drift between electrodes of unnecessary ions), it is preferable that the surface resistivity of the dielectric is small, and energy loss related to ozone generation is reduced. Can be relaxed. That is, in silent discharge with a short gap length, it is preferable to set the surface resistivity of the dielectric small, which contributes to improvement in ozone generation efficiency. However, if the surface resistivity is made too small, such as less than 10 ⁴ Ω, it is necessary to be careful since the discharge maintenance itself becomes unstable. The above is based on the knowledge previously found by the inventors.

Further, the noble metal fine particle catalyst is generally dispersed or supported on an insulating oxide base, and its activity is limited by the low conductivity of the oxide. In the present invention, by adjusting the conductivity of the discharge boundary layer, the electron conductivity is greatly improved, and the surface resistivity is set to 10 ⁴ Ω or more and less than 10 ¹² Ω. As a result, the catalytic activity of platinum has been improved.

  In the present invention, from the viewpoint of increasing the efficiency of ozone generation, the discharge resistivity corresponding to the discharge gap length is specified, and the surface resistivity of the discharge space boundary surface is defined by the activity of the noble metal fine particle catalyst, and the surface resistivity is In order to satisfy this condition, a discharge boundary layer made of oxide and noble metal fine particles and controlled in resistance to a predetermined value was installed. As a result, the ozone generation efficiency has been dramatically improved by effectively utilizing both the photocatalytic property of the oxide substrate and the catalytic action of the noble metal fine particles while maintaining the optimal discharge state. .

The above phenomenon can realize the same highly efficient generation of nitrogen-less ozone in any combination of the above-described materials regardless of only the combination in which the oxide base is titanium oxide and the noble metal fine particles are platinum. In particular, when the substrate is a titanium oxide or tungsten oxide, the photocatalytic properties of the substrate and the combined effect of the noble metal fine particles are synergized with the optimization of maintaining the discharge state in other oxide substrates. To do. That is, by using a semiconductive discharge boundary layer containing at least 0.05 wt% or more of noble metal fine particles in each oxide base material, nitrogen having a discharge space gap length of 0.3 mm or less is not added. It can be concluded that highly efficient nitrogen-less ozone generation can be realized. When the surface resistivity of the discharge boundary layer formed by dispersing the noble metal on the above-described oxide substrate shows a high insulation property of 10 ¹² Ω or more, or when the conductivity is too low below 10 ⁴ Ω, Efficient nitrogen-less ozone generation is impossible, and the effects shown in the present embodiment cannot be achieved only by containing precious metal fine particles.

  In this embodiment, the ratio between the particle diameter and the weight ratio is 0.0005 to 20 wt% / nm, and the particle diameter of the noble metal fine particles is limited to 100 nm or less. It was found that the optimum range of the above ratio was not established when the particle diameter exceeded 100 nm. At such a particle size, the effect between particles becomes too great, and the dispersibility in the oxide substrate is extremely low, and aggregation of noble metal fine particles easily occurs, so a uniform discharge boundary layer is formed. Can not. The non-uniform discharge boundary layer adversely affects the discharge state and ozone generation characteristics, and the predetermined ozone generation characteristics cannot be obtained. In order to sufficiently improve the dispersibility of noble metal fine particles and their catalytic effect, and use in a discharge field, it is necessary to make the particle diameter 100 nm or less, and the noble metal fine particle diameter is further reduced in the oxide substrate. Dispersing at a high density can cause more catalytic effect of the noble metal fine particles to act on ozone generation. Therefore, preferably noble metal fine particles of 10 nm or less are used. The thickness of the discharge boundary layer is 5 μm or less. Naturally, the thick film is less likely to be damaged by the discharge, and the possibility of disappearance of the discharge boundary layer is reduced. However, excessive film thickness exceeding 5 μm may cause delamination due to loss of adhesion to the dielectric surface, which is the base material, and production costs such as increased use of noble metal fine particles. Therefore, it is preferable that the discharge boundary layer is thin. From these viewpoints, in this embodiment, a thin film having a film thickness of 0.2 μm or more and 5 μm or less, preferably 3 μm or less is used.

  In addition, the dispersibility of the noble metal fine particles is desirably uniform in one discharge space from the viewpoint of maintaining the stability of discharge and ozone generation characteristics and forming the discharge boundary layer. There is no problem even if the discharge boundary layer having s is formed in the same direction of gas flow. That is, the dispersibility of the noble metal fine particles in the vicinity of the raw material gas inlet side of the discharge space in FIGS. 1 and 2 may be set to be higher than the dispersibility of the noble metal fine particles from the subsequent to the ozone outlet side. Thereby, it is considered that the generation efficiency of oxygen atoms is further improved.

In the present embodiment, a noble metal fine particle is formed on an oxide substrate as a boundary surface of the discharge space at a weight ratio of 0.05 wt% to 10 wt%, and the particle diameter is 100 nm or less, and the discharge is formed based on extremely high and uniform dispersibility. Since the boundary layer is placed on the dielectric, and the surface resistivity of the discharge boundary layer is controlled to 10 ⁴ Ω or more and less than 10 ¹² Ω, extremely stable discharge can be maintained in a wide range of specific input energy regions. Further, it is possible to provide a silent discharge ozone generator that generates high-concentration ozone with high efficiency only with high-purity oxygen without using an additive gas such as nitrogen as a raw material gas. Further, since the boundary of the discharge space is constituted by the discharge boundary layer, it is possible to provide a clean ozone gas in which the electrode metal portion is not exposed to the discharge space and the metal contamination is not contained in the ozone gas. You can also.

Embodiment 2. FIG.
FIG. 5 is a cross-sectional view showing a structure of an electrode portion of an ozone generator that is a silent discharge plasma apparatus according to Embodiment 2 of the present invention. In the ozone generator shown in the figure, a tubular ground electrode 11 and a high voltage electrode 12 are arranged concentrically, and only oxygen having a purity of 99.5% or more is introduced as a source gas into a discharge space 14 formed by both electrodes, Silent discharge is generated by applying an alternating high voltage to the discharge space 14 to generate ozone, and the high voltage electrode 12 corresponding to the boundary of the discharge space 14 has a dielectric on the side facing the discharge space 14. A body 132 is installed. The dielectric 132 is made of a bulk material such as glass or ceramic, and its end on the ozone outlet side (the right side in FIG. 5) is closed. Further, the discharge boundary layers 151 and 152 shown in the first embodiment are formed on the surfaces of the ground electrode 11 and the dielectric 132, and the gap length d of the discharge space 14 is set to 0.3 mm or less. Further, the discharge space 14 is cooled by the ground electrode 11 side coming into contact with the cooling water 18.

  That is, the present embodiment is different from the first embodiment in that the discharge boundary layer 151 is directly formed on the surface of the ground electrode 11 side without using a dielectric. Also in this electrode structure, the ozone generation characteristics similar to those of the first embodiment can be confirmed, and high-concentration ozone can be generated with high efficiency and stability even when the additive gas is not used and the source gas is only oxygen.

  The thicknesses of the discharge boundary layers 151 and 152 used here are 5 μm or less, and are excellent in adhesion to electrodes and dielectrics. Therefore, the discharge boundary layers 151 and 152 are sputtered even during long-time operation. There is almost no peeling or weight loss. If peeling or the like occurs in the discharge boundary layer 151 on the surface of the ground electrode 11 and the underlying metal electrode surface is exposed to the discharge space, the metal electrode is formed on the surface of the discharge boundary layer 152 on the opposite side by sputtering and oxidation. The material and its oxide are deposited and adhered. When the discharge boundary layer 152 is covered with the metal electrode material and its oxide, the surface of the discharge boundary layer 152 does not directly contact the discharge space, and its catalytic ability does not affect ozone generation. That is, deterioration over time is observed in the ozone generation characteristics.

  In addition, the metal electrode material generated from the metal electrode and its oxide are also entrained in the generated ozone gas, and it is discharged from the ozone generator while being contained in the ozone gas as a metal contaminant, resulting in a decrease in the cleanliness of the ozone gas. Forced. On the other hand, since the discharge boundary layer 152 disposed on the high voltage electrode 12 side is provided with the dielectric 132, there is no such concern.

  As described above, since the discharge boundary layers 151 and 152 in the present embodiment have a sufficient film thickness and excellent adhesion to the electrode and the dielectric, such a phenomenon does not occur. There is no change over time in the ozone generation characteristics, and the cleanliness of ozone gas does not decrease. Further, FIG. 5 shows only the structure of the tubular electrode, but the parallel plate electrode structure shown in FIG. 1 of Embodiment 1 does not have the dielectric 131 on the ground electrode 11 side, and similar ozone generation characteristics are obtained. Needless to say.

In the present embodiment, a noble metal fine particle is formed on an oxide substrate as a boundary surface of the discharge space at a weight ratio of 0.05 wt% to 10 wt%, and the particle diameter is 100 nm or less, and the discharge is formed based on extremely high and uniform dispersibility. Since the boundary layer is disposed on the ground electrode surface and the dielectric surface, and the discharge boundary layer is subjected to resistance control processing so that the surface resistivity is 10 ⁴ Ω or more and less than 10 ¹² Ω, in a wide range of specific input energy regions, It is possible to provide a silent discharge type ozone generator that can maintain extremely stable discharge and generates high-concentration ozone with high efficiency only with oxygen without using an additive gas such as nitrogen as a raw material gas. In addition, since the boundary of the discharge space is constituted by the discharge boundary layer, the catalytic action of the discharge boundary layer on the generation of ozone is not accompanied by a change with time, and the electrode metal part is exposed to the discharge space. Therefore, it is possible to provide clean ozone gas that does not contain metal contamination without using an additive gas such as nitrogen.

Embodiment 3 FIG.
6 and 7 are cross-sectional views showing the structure of the electrode part of an ozone generator that is a silent discharge plasma apparatus according to Embodiment 3 of the present invention. FIG. 6 shows a parallel plate electrode structure, and FIG. 7 shows a structure of an electrode portion of a cylindrical tube electrode structure ozone generator. In both cases, only oxygen having a purity of 99.5% or more is introduced as a source gas into a discharge space 14 formed between the ground electrode 11 and the high voltage electrode 12, and silent discharge is caused by applying an alternating high voltage to the discharge space 14. To generate ozone.

  FIG. 6 shows a configuration substantially similar to that shown in FIG. 1 shown in the first embodiment, but the cooling method of the discharge space 14 is different. In the present embodiment, the ground electrode 11 and the high voltage electrode 12 are provided with the discharge boundary layers 151 and 152 shown in the first embodiment on the surfaces facing the discharge space 14 via the dielectrics 131 and 132, respectively. Prepare. A cooling plate 20 having the same structure as the ground electrode is disposed on the side of the high voltage electrode 12 that does not face the discharge space 14 with an insulating plate 19 interposed therebetween. The same cooling water circulates through the ground electrode 11 and the cooling plate 20 to cool the discharge space 14 from both the ground side and the high voltage side. Here, since the cooling plate 20 is arranged via the insulating plate 19 and the cooling plate 20 is grounded, pure water or ion-exchanged water is not generated without causing an electrical short circuit due to the conductivity of the cooling water. Not only general tap water can be used as cooling water. As in the second embodiment, there is no problem even if the dielectric 131 is not installed. The dielectrics 131 and 132 may be dielectric films formed by coating such as bulk material such as glass and ceramics or thermal spraying on the electrode surface, sputtering and glass lining.

  7 also differs from FIG. 2 in that cooling is performed from both sides of the discharge space 14 in the same manner. In this embodiment, ion exchange water or pure water circulates inside the ground electrode 11 and the high voltage electrode 12. The discharge boundary layer 151 shown in the first embodiment is provided on the discharge space 14 side of the ground electrode 11 via the dielectric 131, and the discharge boundary layer 152 is directly formed on the surface of the high voltage electrode 12. The dielectric 131 may be a dielectric film formed by a bulk material such as glass or ceramics or a coating such as thermal spraying on the electrode surface, sputtering or glass lining. In FIG. 7, the cooling water 18 and the high voltage electrode 12 are in direct contact, but an insulating layer is provided between them so that the cooling water 18 and the high voltage electrode 12 are not in direct (electrical) contact. In this case, not only ion-exchanged water and pure water but also general tap water can be used as the cooling water 18.

  6 and 7, the discharge boundary layers 151 and 152 shown in the first embodiment are formed on the surfaces of the ground electrode 11 and the high voltage electrode 12 facing the discharge, and the gap length of the discharge space is 0.3 mm. It is set as follows. The film thickness of the discharge boundary layers 151 and 152 used here is 5 μm or less. Furthermore, the discharge space 14 is cooled by both the ground electrode 11 side and the high voltage electrode 12 side being in contact with the cooling water 18. That is, the cooling capacity of the discharge space 14 is improved as compared with the configuration shown in the first embodiment, and the temperature rise of the discharge space 14 can be further suppressed. Therefore, the power that can be input per unit discharge area can be increased, which can contribute to downsizing of the apparatus.

  Even in such an electrode structure, the same ozone generation characteristics as in the first embodiment can be realized, and high-concentration ozone can be generated efficiently and stably even when the source gas is only oxygen without using the additive gas. Further, since the discharge boundary layers 151 and 152 are excellent in adhesion to electrodes and dielectrics, even if a discharge boundary layer is provided directly on the surface of the high voltage electrode 12 as shown in FIG. In operation, the discharge boundary layer is hardly peeled off or reduced by sputtering or the like. Therefore, the surface of the electrode metal is not directly exposed to the discharge field during the generation of ozone, and the ozone generation characteristics and the cleanliness of the ozone gas are not deteriorated. In FIG. 6, the same thing can be said when the discharge boundary layer is formed directly on the surface of the ground electrode 11 without installing the dielectric 131.

In the present embodiment, a noble metal fine particle is formed on an oxide substrate as a boundary surface of the discharge space at a weight ratio of 0.05 wt% to 10 wt%, and the particle diameter is 100 nm or less, and the discharge is formed based on extremely high and uniform dispersibility. Since the boundary layer is disposed on the electrode surface or the dielectric surface, and the discharge boundary layer is subjected to resistance control treatment so that the surface resistivity is 10 ⁴ Ω or more and less than 10 ¹² Ω, It is possible to provide a silent discharge type ozone generator that can maintain stable discharge and generate high-concentration ozone with high efficiency only by oxygen without using an additive gas such as nitrogen as a raw material gas. In addition, since the boundary of the discharge space is constituted by the discharge boundary layer, the catalytic action of the discharge boundary layer on the generation of ozone is not accompanied by a change with time, and the electrode metal part is exposed to the discharge space. Therefore, it is possible to provide clean ozone gas that does not contain metal contamination without using an additive gas such as nitrogen. In addition, since the discharge space is cooled from both sides of the electrode, the cooling efficiency of the discharge space can be improved and the apparatus can be reduced in size.

Embodiment 4 FIG.
FIG. 8 is a sectional view showing a structure of an electrode portion of an ozone generator which is a silent discharge plasma apparatus according to Embodiment 4 of the present invention. In the ozone generator shown in the figure, a tubular ground electrode 11 and a high voltage electrode 12 are arranged concentrically, and only oxygen having a purity of 99.5% or more is introduced as a source gas into a discharge space 14 formed by both electrodes, Silent discharge is generated by applying an alternating high voltage to the discharge space 14 to generate ozone, and the high voltage electrode 12 corresponding to the boundary of the discharge space 14 has a dielectric on the side facing the discharge space 14. A body 132 is installed. The dielectric 132 is made of a bulk material having excellent insulating properties such as ceramics and glass, and the end portion on the ozone outlet side is closed. Further, the discharge boundary layer 151 shown in the first embodiment is formed on the surface of the ground electrode 11, and the gap length of the discharge space is set to 0.3 mm or less. Further, the discharge space 14 is cooled by the ground electrode 11 being in contact with the cooling water 18.

  That is, the present embodiment is different from the first embodiment in that the discharge boundary layer shown in the first embodiment is installed only on the surface of the ground electrode 11 that is one boundary surface of the discharge space 14. This electrode structure also exhibits substantially the same ozone generation characteristics as in the first embodiment. However, since the surface area of the discharge boundary layer in contact with the discharge space 14 is reduced as compared with the first and second embodiments, the ozone generation efficiency shown in the first embodiment is not reached slightly. However, compared to an electrode structure in which no discharge boundary layer is installed, extremely high-efficiency nitrogen-less ozone generation can be realized, and even when oxygen is used as the source gas without using an additive gas, high-concentration ozone is highly efficient and Can be generated stably.

  Since the thickness of the discharge boundary layer 151 used here is 5 μm or less and has excellent adhesion to the ground electrode 11, the discharge boundary layer 151 is peeled off or reduced by sputtering due to discharge even during long-time operation of the apparatus. The ground electrode 11 is not exposed to the discharge space 14. In addition, the dielectric 132 serving as the opposing surface of the discharge boundary layer 151 is made of a bulk material. Due to the influence of sputtering due to discharge, the dielectric constituent material / element is not adhered or deposited on the surface of the discharge boundary layer 151. Very few. Therefore, the discharge boundary layer 151 can always maintain the state exposed to the discharge, and its catalytic ability does not decrease with time, so that stable ozone generation can be realized. In FIG. 8, only the structure of the tubular electrode is shown, but the same ozone is applied to the parallel plate electrode structure and the structure in which only the discharge boundary layer 151 on the ground electrode 11 side is installed as shown in the first embodiment. Needless to say, the generation characteristics can be realized.

In the present embodiment, a noble metal fine particle is formed on an oxide substrate as a boundary surface of the discharge space at a weight ratio of 0.05 wt% to 10 wt%, and the particle diameter is 100 nm or less, and the discharge is formed based on extremely high and uniform dispersibility. Since the boundary layer is installed on the surface of the ground electrode, and the discharge boundary layer is subjected to resistance control treatment so that the surface resistivity is 10 ⁴ Ω or more and less than 10 ¹² Ω, an extremely stable discharge can be obtained in a wide range of specific input energy regions. It is possible to provide a silent discharge type ozone generator capable of maintaining high concentration ozone with high efficiency only with oxygen without using an additive gas such as nitrogen as a raw material gas. In addition, since the boundary of the discharge space is composed of a discharge boundary layer and a dielectric material made of a bulk material, the catalytic effect of the discharge boundary layer on the generation of ozone does not change with time, and the electrode in the discharge space Since the metal part is not exposed, a clean ozone gas that does not contain metal contamination can be provided without using an additive gas such as nitrogen. Further, since the discharge boundary layer is installed only on one boundary surface of the discharge space, there is a slight decrease in the ozone generation efficiency compared to the first and second embodiments, but the discharge boundary layer is not installed at all. In comparison, a significant improvement in ozone generation efficiency can be realized. In addition, the cost for manufacturing the discharge boundary layer can be reduced because the installation area is reduced.

Embodiment 5 FIG.
FIG. 9 is a sectional view showing a structure of an electrode portion of an ozone generator which is a silent discharge plasma apparatus according to Embodiment 5 of the present invention. The ozone generator shown in the drawing introduces only oxygen having a purity of 99.5% or more as a source gas into a discharge space 14 formed by a tubular ground electrode 11 and a high voltage electrode 12 and applies an alternating high voltage to the discharge space 14. Thus, silent discharge is generated to generate ozone, and a dielectric 131 is provided on the side of the ground electrode 11 corresponding to the boundary of the discharge space facing the discharge space 14. The dielectric 131 uses a bulk material having excellent insulating properties such as ceramics and glass. Further, the discharge boundary layers 151 and 152 shown in the first embodiment are formed on the surfaces of the dielectric 131 and the high voltage electrode 12, and the gap length d of the discharge space 14 is set to 0.3 mm or less. Further, the ground electrode 11 side is in contact with the cooling water 18, and the discharge space 14 is cooled via the dielectric 131.

  The ground electrode 11 in the present embodiment is a conductive layer provided on the outer surface of the dielectric 131, and a protective film for the cooling water 18 may be provided on the surface of the conductive layer. In the present embodiment, the source gas passes through the inside 21 of the high voltage electrode 12 from the power supply member 17 side, is discharged from the end of the high voltage electrode 12, further changes direction, and flows into the discharge space 14. That is, the gas flow direction in the discharge space 14 is opposite to the cylindrical tube electrode structure shown in the first to fourth embodiments.

  Although not shown in FIG. 9, the left end portion of the electrode part is taken out so that the raw material gas and the generated ozone gas are not mixed. Also in this electrode structure, the ozone generation characteristics similar to those of the first embodiment can be realized. The film thickness of the discharge boundary layers 151 and 152 is 5 μm or less, and has excellent adhesion to the dielectric 131 and the high voltage electrode 12, so that the discharge boundary layers 151 and 152 are caused by discharge even during long-time operation. There is no peeling or weight loss by sputtering, and in particular, in the discharge boundary layer 152, the surface of the high voltage electrode 12 is not exposed to the discharge space. That is, since no metal contamination is contained in the ozone gas and the surfaces of the discharge boundary layers 151 and 152 are not covered by sputtering of the dielectric 131 and the high-voltage electrode 12, the discharge boundary layer 151, The catalytic ability of 152 does not cause deterioration over time.

  FIG. 10 shows an electrode structure when the discharge boundary layer is removed from the surface of the dielectric 131 in FIG. In this structure, the discharge boundary layer shown in the first embodiment is provided only on the surface of the high voltage electrode 12 (outer tube surface) which is one boundary surface of the discharge space 14. When the discharge boundary layer is formed in a tubular shape, it is much easier and less expensive to form it on the outer surface than on the inner surface of the tube. Even in this electrode structure, ozone generation characteristics substantially similar to those of the first embodiment can be realized as in the case of FIG.

  However, as shown in the fourth embodiment, in the structure of FIG. 10, the surface area of the discharge boundary layer in contact with the discharge space 14 is reduced as compared with the first embodiment. The ozone generation efficiency does not reach a little. However, compared to the electrode structure shown in the first embodiment in which no discharge boundary layer is provided, extremely highly efficient generation of nitrogen-less ozone can be realized. In addition, the dielectric 131 that is the facing surface of the discharge boundary layer 152 is made of a bulk material, and the dielectric 131 is sputtered by discharge, and the constituent material of the dielectric 131 adheres to and accumulates on the surface of the discharge boundary layer 152. There is very little. Therefore, the discharge boundary layer 152 can always maintain the state exposed to the discharge, and its catalytic ability does not decrease with time, so that stable ozone generation can be realized.

In the present embodiment, a noble metal fine particle is formed on an oxide substrate as a boundary surface of the discharge space at a weight ratio of 0.05 wt% to 10 wt%, and the particle diameter is 100 nm or less, and the discharge is formed based on extremely high and uniform dispersibility. Since the boundary layer is installed only on the surface of the high voltage electrode and the dielectric surface or the surface of the high voltage electrode, and the discharge boundary layer is subjected to resistance control treatment so that the surface resistivity is 10 ⁴ Ω or more and less than 10 ¹² Ω, It is possible to provide a silent discharge type ozone generator that can maintain a very stable discharge in a specific input energy range and can generate high-concentration ozone with only oxygen without using an additive gas such as nitrogen as a raw material gas. . In addition, since the boundary of the discharge space is composed of a discharge boundary layer or a dielectric, the catalytic effect of the discharge boundary layer on the generation of ozone is not accompanied by a change with time, and the electrode metal portion is not present in the discharge space. Since it is not exposed, clean ozone gas which does not contain metal contamination can be provided without using an additive gas such as nitrogen. Furthermore, when the discharge boundary layer is installed only on the outer peripheral surface of the tubular high-voltage electrode, it is much easier and less expensive than forming the discharge boundary layer on the inner surface of the tubular member. Even if the discharge boundary layer is installed only on the surface, the ozone generation efficiency can be greatly improved.

Embodiment 6 FIG.
FIG. 11 is a sectional view showing the structure of an electrode part of an ozone generator which is a silent discharge plasma apparatus according to Embodiment 6 of the present invention. The ozone generator shown in the drawing introduces only oxygen having a purity of 99.5% or more as a source gas into a discharge space 14 formed by the ground electrode 11 and the high voltage electrode 12 and applies an alternating high voltage to the discharge space 14. Dielectric discharge is generated to generate ozone, and a dielectric 132 is provided on the side of the high-voltage electrode 12 facing the discharge space 14 corresponding to the boundary of the discharge space. The dielectric 132 is made of a bulk material that is difficult to be sputtered, such as glass or ceramics, and the ozone outlet side is closed. Further, the discharge boundary layers 151 and 152 shown in the first embodiment are formed on the surfaces of the ground electrode 11 and the dielectric 132 facing the discharge space. Cooling of the discharge space 14 is realized by the ground electrode 11 side being in contact with the cooling water 18. The electrode structure in the present embodiment is almost the same as the structure shown in the second embodiment, but the discharge space 14 is filled with a gas permeable wire knit 22 having high electrical and thermal conductivity. The point is different. Even in such an electrode structure, ozone generation characteristics equivalent to or higher than those of the first embodiment can be realized.

  FIG. 12 shows an electrode structure in which the wire knit shown in FIG. The dielectric 132 is made of a bulk material that is difficult to be sputtered, such as glass or ceramics, and both ends are open ends. That is, the source gas also flows inside the dielectric 132 and generates a discharge. Furthermore, the discharge boundary layer shown in the first embodiment is formed on the surface facing the discharge space, that is, the surface on the discharge space side of the ground electrode 11, the outer and inner surfaces of the dielectric 132, and the surface of the high voltage electrode 12. 151, 152a, 152b, and 152c. Cooling of the discharge space 14 is realized by the ground electrode 11 side being in contact with the cooling water 18. In the electrode structure in FIG. 12, the gas permeability is high in electrical conductivity and thermal conductivity in the discharge space 14 a between the ground electrode 11 and the dielectric 132 and in the discharge space 14 b between the dielectric 132 and the high voltage electrode 12. Each of the wire knits 22a and 22b is filled. Even in such an electrode structure, ozone generation characteristics equivalent to or higher than those of the first embodiment can be realized.

  Due to the installation of the wire knits 22, 22a, 22b, turbulent flow is generated in the discharge spaces 14, 14a, 14b, and gas molecules collide with the cooled electrode surface. Therefore, the heat of the gas can be dissipated well. Further, the wire knits 22, 22 a, and 22 b also function as expansion materials for center alignment of the ground electrode 11, the high voltage electrode 12, and the dielectric 132. Furthermore, since the wire knits 22, 22a, and 22b are filled, it is easy to shorten the gap length of each discharge space, and due to the hollow cathode effect (concentrated discharge plasma in the hollow space of the same potential), The ozone yield can be further improved. It is more effective to form the same material as that of the discharge boundary layer shown in the first embodiment on the surfaces of the wire knits 22, 22a and 22b.

In the present embodiment, a noble metal fine particle is formed on an oxide substrate as a boundary surface of the discharge space at a weight ratio of 0.05 wt% to 10 wt%, and the particle diameter is 100 nm or less, and the discharge is formed based on extremely high and uniform dispersibility. A boundary layer is installed, and the surface resistivity of the discharge boundary layer is controlled to be 10 ⁴ Ω or more and less than 10 ¹² Ω, so that a very stable discharge can be maintained in a wide range of specific input energy regions. It is possible to provide a silent discharge ozone generator that generates high-concentration ozone with high efficiency using only oxygen without using an additive gas such as nitrogen as a gas. In addition, since the boundary of the discharge space is constituted by the discharge boundary layer, the catalytic action of the discharge boundary layer on the generation of ozone is not accompanied by a change with time, and the electrode metal part is exposed to the discharge space. Therefore, a clean ozone gas that does not contain metal contamination can be provided without using an additive gas such as nitrogen. Further, the ozone generation efficiency can be further improved by the fine adjustment function of the gap length by wire knit, the enhanced cooling of the gas, and the hollow cathode effect.

Embodiment 7 FIG.
FIG. 13 is a sectional view showing the structure of an electrode part of an ozone generator which is a silent discharge plasma apparatus according to Embodiment 7 of the present invention. The ozone generator shown in the figure introduces oxygen having a purity of 99.5% or more as a source gas into a discharge space formed by the ground electrode 11 and the high voltage electrode 12 and applies silent high voltage to the discharge space by applying an alternating high voltage. Ozone is generated, and a dielectric 132a is installed on the side of the high voltage electrode 12 facing the discharge space. Furthermore, a dielectric 132b is provided on the surface of the dielectric 132a on the ozone outlet side (the right side of the paper in FIG. 13). Note that a bulk material that is difficult to be sputtered such as glass or ceramic is selected for the dielectric 132a, and the dielectric 132b is formed on the dielectric 132a by thermal spraying, sputtering, glass lining, or the like.

  Here, the discharge spaces formed between the ground electrode 11 and the dielectrics 132a and 132b are referred to as discharge spaces 14a and 14b, respectively. Further, the discharge boundary layers 151 and 152 shown in the first embodiment are formed on the surfaces facing the discharge spaces 14a and 14b so as to follow the shapes of the ground electrode 12 and the dielectrics 132a and 132b. In the present embodiment, the ground electrode 11 side is in contact with the cooling water 18, and the discharge spaces 14a and 14b are cooled. The electrode structure in FIG. 13 is substantially the same as the structure shown in the second embodiment, but differs in that the discharge space 14a and the discharge space 14b having different gap length dimensions in the gas flow direction are arranged in series. Yes. In the discharge space 14a on the source gas inlet side (left side in FIG. 13), the gap length is set to 1.2 to 0.3 mm in order to optimize the oxygen atom generation efficiency, and on the ozone outlet side (right side in FIG. 13). In the discharge space 14b, a dielectric 132b is provided so as to have a gap length of 0.3 mm or less in order to suppress decomposition of ozone generated by electron collision and heat. In such an electrode structure, ozone generation characteristics equivalent to or better than those of the first embodiment can be realized.

  FIG. 14 shows another electrode structure having two types of discharge gap lengths in series as in FIG. The surface of the tubular high-voltage electrode 12 is coated with a dielectric 132 by spraying, sputtering, glass lining, etc., and the discharge boundary layers 151 and 152 shown in the first embodiment are arranged on the surface and the surface of the ground electrode 11. Yes. Even in this electrode structure, ozone generation characteristics similar to those described above can be realized. Here, the diameter of the high voltage electrode 12 is changed in the gas flow direction (length direction), and the discharge spaces 14a and 14b are formed by installing the dielectric 132 and the discharge boundary layer 152 so as to follow the shape of the high voltage electrode 12. Is forming.

  FIG. 15 shows still another electrode structure having two types of discharge gap lengths in series as in FIGS. A dielectric 132 is formed on the surface of the high voltage electrode 12 having a certain diameter by thermal spraying, sputtering, glass lining, etc., and the discharge boundary layers 151 and 152 shown in the first embodiment are formed on the surface and the surface of the ground electrode 11. It is arranged. Even in this electrode structure, ozone generation characteristics similar to those described above can be realized. Here, the discharge spaces 14 a and 14 b are formed by changing the thickness of the dielectric 132 in the gas flow direction and installing the discharge boundary layer 152 along the shape of the dielectric 132.

  Further, in FIG. 16, by providing a plurality of high voltage electrodes 12a, 12b, 12c having different diameters with respect to one ground electrode 11, discharge spaces 14a, 14b, 14c having three types of discharge gap lengths in series. The electrode structure which forms is shown. Dielectrics 132a, 132b, and 132c are formed on the surfaces of the high-voltage electrodes 12a, 12b, and 12c by thermal spraying, sputtering, glass lining, and the like, and the discharge boundary layers 152a, 152b, and 152c shown in the first embodiment are further formed on the surfaces. Is installed. A discharge boundary layer 151 is also formed on the surface of the ground electrode 11 on the discharge space side. The high voltage electrodes 12 a, 12 b and 12 c are connected in series and supplied with current from the power supply member 17. In FIG. 16, the gap length of the discharge space 14c arranged closest to the ozone outlet is 0.3 mm or less, the gap length of the central discharge space 14b is 0.6 mm or less, and the gap length of the discharge space 14a on the source gas inlet side is 1.2 mm. The following. As a result, also in this electrode structure, the ozone generation characteristics similar to the above can be realized with extremely high efficiency.

In the present embodiment, a noble metal fine particle is formed on an oxide substrate as a boundary surface of the discharge space at a weight ratio of 0.05 wt% to 10 wt%, and the particle diameter is 100 nm or less, and the discharge is formed based on extremely high and uniform dispersibility. Since the boundary layer is installed on the surface of the ground electrode, and the discharge boundary layer is subjected to resistance control treatment so that the surface resistivity is 10 ⁴ Ω or more and less than 10 ¹² Ω, an extremely stable discharge can be obtained in a wide range of specific input energy regions. It is possible to provide a silent discharge type ozone generator capable of maintaining high concentration ozone with high efficiency only with oxygen without using an additive gas such as nitrogen as a raw material gas. In addition, since the boundary of the discharge space is constituted by the discharge boundary layer, the catalytic action of the discharge boundary layer on the generation of ozone is not accompanied by a change with time, and the electrode metal part is exposed to the discharge space. Therefore, a clean ozone gas that does not contain metal contamination can be provided without using an additive gas such as nitrogen. In addition, since the formation of discharge spaces suitable for each ozone generation process such as oxygen atom generation and ozone generation was realized individually, the part that contributes to oxygen atom generation is formed with a relatively long gap length, in other words, rough, and ozone decomposition is performed. Since it is only necessary to form the gap length with high accuracy only in the portion that suppresses and generates high-concentration ozone, it is effective in reducing the cost of the ozone generator.

Embodiment 8 FIG.
FIG. 17 is a sectional view showing a structure of an electrode portion of an ozone generator which is a silent discharge plasma apparatus according to Embodiment 8 of the present invention. In the ozone generator shown in the figure, a tubular ground electrode 11 and a high voltage electrode 12 are concentrically arranged, and only oxygen having a purity of 99.5% or more is introduced as a source gas into a discharge space 14 formed by the two electrodes. A silent discharge is generated by applying an alternating high voltage to the discharge space 14 to generate ozone. On the side of the high voltage electrode 12 corresponding to the boundary of the discharge space 14 facing the discharge space 14, A dielectric 132 is provided. The dielectric 132 is made of a bulk material such as glass or ceramic, and the end of the ozone outlet side (the right side in FIG. 17) is closed. Further, the discharge boundary layers 151 and 152 shown in the first embodiment are formed on the surfaces of the ground electrode 11 and the dielectric 132, and the gap length d of the discharge space 14 is set to 0.3 mm or less. The discharge space 14 is cooled by the ground electrode 11 side being in contact with the cooling water 18.

  Further, the spacer 23 is installed at the source gas inlet of the dielectric 132 (left side of the paper in FIG. 17) so as not to stop the gas flow. Also in this electrode structure, ozone generation characteristics similar to those of the first embodiment can be realized, and high-concentration ozone can be generated efficiently and stably even when the source gas is only oxygen without using an additive gas. In the ozone generator as shown in FIG. 17, the discharge space 14 is cooled by the ground electrode 11 being directly cooled by the cooling water, but the cooling water does not directly contact the ground tube at the tube plate 24 portion. Cooling efficiency decreases. In this part, the gas temperature or the temperature rise of the dielectric 132 is larger than that in the region where the ground electrode that is directly cooled is present. Therefore, the spacer 23 is partially disposed in the same sectional area of the discharge space. There is an effect of reducing heat generation due to. Moreover, in the gas inlet section, the flow velocity and flow rate of the gas flowing in can be changed by installing the spacer 23 and adjusting the size and position thereof. That is, when a large number of electrode tubes are connected in parallel, the material gas is allowed to flow evenly through the electrode tubes.

In the present embodiment, a noble metal fine particle is formed on an oxide substrate as a boundary surface of the discharge space at a weight ratio of 0.05 wt% to 10 wt%, and the particle diameter is 100 nm or less, and the discharge is formed based on extremely high and uniform dispersibility. Since the boundary layer is disposed on the ground electrode surface and the dielectric surface, and the discharge boundary layer is subjected to resistance control treatment so that the surface resistivity is 10 ⁴ Ω or more and less than 10 ¹² Ω, It is possible to provide a silent discharge type ozone generator that can maintain stable discharge and generate high-concentration ozone with high efficiency only by oxygen without using an additive gas such as nitrogen as a raw material gas. In addition, since the boundary of the discharge space is constituted by the discharge boundary layer, the catalytic action of the discharge boundary layer on the generation of ozone is not accompanied by a change with time, and the electrode metal part is exposed to the discharge space. Therefore, a clean ozone gas that does not contain metal contamination can be provided without using an additive gas such as nitrogen. Further, since the spacer is disposed at the source gas inlet, the gas temperature or dielectric temperature of the portion corresponding to the ground electrode that is not directly water-cooled can be reduced. Further, the gas can be evenly supplied to a large number of electrode tubes by the uniform distribution action of the raw material gas, which is effective in improving the efficiency and reliability of the ozone generator.

Embodiment 9 FIG.
FIG. 18 is a cross-sectional view showing a structure of an electrode portion of a carbon dioxide laser device which is a silent discharge plasma apparatus according to Embodiment 9 of the present invention. The carbon dioxide laser device shown in the figure introduces a mixed gas of carbon dioxide, carbon monoxide, nitrogen and helium as a raw material gas into a discharge space 14 formed by a ground electrode 11 and a high voltage electrode 12, and an AC high voltage is introduced into the discharge space 14. A silent discharge is generated by applying a voltage to excite carbon dioxide to realize laser amplification and laser oscillation. In the discharge space of the ground electrode 11 and the high voltage electrode 12 corresponding to the boundary of the discharge space 14. Dielectrics 131 and 132 are installed on the facing side. Therefore, since the deterioration of the laser gas due to the sputtering of the electrode surface is suppressed, the gas sealing operation for about 24 hours is possible.

The present inventors conducted an experiment in which the discharge boundary layer of the present invention was applied to this silent discharge type carbon dioxide laser device. That is, in the carbon dioxide laser device that is a silent discharge plasma device according to the ninth embodiment, the discharge boundary layers 151 and 152 shown in the first embodiment are provided on the surfaces of the dielectrics 131 and 132. As with the ozone generator that is a silent discharge plasma apparatus in the previous embodiments, the discharge boundary layers 151 and 152 use titanium oxide for the oxide base and platinum for the noble metal fine particles, and the surface resistivity is 10 ⁴ Ω. The resistance control processing is performed so as to be less than 10 ¹² Ω. The platinum weight ratio is 0.05 wt% or more, and the film thickness is 5 μm or less. In the present embodiment, both the ground electrode 11 side and the high-voltage electrode 12 side are in contact with the cooling water, and the discharge space 14 is cooled to exhibit the same structure as the ozone generator shown in the third embodiment. ing. The distance between the discharge boundary layers 151 and 152 arranged opposite to each other, that is, the discharge gap length d is set to 30 mm or more, and the gas pressure P in the discharge space is less than atmospheric pressure. The drive frequency is 100 kHz or higher.

  FIG. 19 shows laser output characteristics when laser oscillation is performed in this electrode structure. In the figure, the laser output characteristics of the carbon dioxide laser device using the discharge boundary layers 151 and 152 in the present embodiment and the conventional device (when the discharge boundary layers 151 and 152 are not installed) are compared, and the horizontal axis represents the input power, The vertical axis represents the laser output. From the figure, it can be understood that the carbon dioxide laser device shown in the present embodiment using the discharge boundary layers 151 and 152 has higher oscillation characteristics than the conventional device. The carbon dioxide laser device differs from the ozone generator in the discharge gap length, the gas pressure in the discharge space, and the type of gas. However, as a result of experiments, it has been found that the oscillation efficiency is improved by using the above discharge boundary layer. It is considered that the laser oscillation efficiency was improved by the photocatalytic ability of the discharge boundary layer and the catalytic activity of the noble metal fine particles.

  FIG. 20 shows the laser output characteristics of the carbon dioxide laser device in this embodiment and the conventional device when the laser gas composition is a mixed gas of carbon dioxide, nitrogen and helium, that is, so-called carbon monoxide (CO) -less. From the figure, the carbon dioxide laser device in the present embodiment using the discharge boundary layer has the same oscillation characteristics as the conventional device without the discharge boundary layer when carbon monoxide is included, even if it does not include carbon monoxide. I understand that. On the other hand, when carbon monoxide is not used in a conventional device having no discharge boundary layer, it can be seen that the oscillation efficiency is lower than that in the present embodiment. This is considered to be because the carbon dioxide concentration in the laser gas can be maintained at a high concentration by the photocatalytic ability of the discharge boundary layer and the catalytic activity of the noble metal fine particles, and the laser oscillation characteristics are improved. That is, according to the carbon dioxide laser device of the present embodiment, carbon monoxide can be removed from the laser gas, the conventional four-type mixed gas can be reduced to at least three types, and the cost and delivery time can be reduced. Shows the effect of. Further, in the present embodiment, when carbon monoxide is added, carbon dioxide can be similarly maintained at a high concentration, and deterioration of the laser gas is suppressed, so that the conventional apparatus takes about 24 hours. The gas sealing operation can be further extended.

In the present embodiment, the discharge boundary layer formed on the basis of the extremely high and uniform dispersibility of the noble metal fine particles on the oxide substrate at a weight ratio of 0.05 wt% to 10 wt% and a particle diameter of 100 nm or less is formed on the ground electrode surface. It was found that a carbon dioxide laser device having excellent oscillation efficiency can be provided because the discharge boundary layer is provided on the dielectric surface and the discharge boundary layer is subjected to resistance control treatment so that the surface resistivity is 10 ⁴ Ω or more and less than 10 ¹² Ω. In addition, highly efficient oscillation characteristics can be obtained without adding carbon monoxide to the laser gas. In addition, since the boundary of the discharge space is constituted by the discharge boundary layer, the catalytic action of the discharge boundary layer on the laser oscillation does not change with time, and the electrode metal part is exposed to the discharge space. Therefore, a clean laser output can be obtained, and a gas sealing operation for a long time can be performed.

  As described above, if the discharge boundary layer of the present invention is applied to the silent discharge plasma apparatus, it is confirmed that the efficiency improvement effect can be obtained not only in the ozone generator but also in the carbon dioxide laser apparatus. The layer can be expected to exhibit effects such as improved efficiency in various silent discharge plasma devices.

Embodiment 10 FIG.
FIG. 21 is a sectional view showing a structure of an electrode portion of an ozone generator which is a silent discharge plasma apparatus according to Embodiment 10 of the present invention. The ozone generator shown in the figure generates ozone by generating creeping discharge by a pair of electrodes 25 and 26 and a dielectric 133 formed on the same plane.

  In the figure, a pair of electrodes 25 and 26 are arranged side by side with a distance d1 of 0.1 mm or less (corresponding to the discharge gap length d in each of the above embodiments) on the surface of the dielectric 134. The electrodes 25 and 26 are covered with a dielectric 133. The dielectric 134 is in contact with the heat sink 27 and is cooled by a cooling fluid such as water flowing in the heat sink 27. Further, a discharge boundary layer 153 similar to that shown in the first embodiment is arranged on the upper layer of the dielectric 133, that is, the surface of the dielectric 133 opposite to the dielectric 134. The discharge boundary layer 153 is in contact with the guide plate 29 via a sealing material 28 such as packing, and forms a gas space (discharge space) 14 into which a source gas containing only oxygen having a purity of 99.5% or more is introduced.

  In the ozone generator having such an electrode configuration, an alternating high voltage is applied between the pair of electrodes 25 and 26, and creeping discharge is generated on the surface of the discharge boundary layer 153. Ozone is generated by this creeping discharge. As the dielectric 134, glass, alumina, or the like having a sufficiently large volume resistivity and dielectric strength was used, and its thickness was set to be sufficiently thicker than d1. Similarly, an insulating material having a sufficiently large volume resistivity and dielectric strength is used for the dielectric 133. As the guide plate 29, for example, a metal such as stainless steel or a fluororesin such as PTFE (polytetrafluoroethylene) is used in order to suppress the occurrence of metal contamination. Even in such an ozone generator, ozone generation characteristics substantially similar to those of the first embodiment can be realized. Further, by arranging a plurality of combinations of the electrode portions 25 and 26 without overlapping each other on one dielectric 134, or by stacking a plurality of electrode portions shown in FIG. 21, the amount of ozone generated can be easily increased. It becomes possible.

  Also, as shown in FIG. 22, the same effect can be obtained by omitting the dielectric 133 shown in FIG. 21 and covering the electrodes 25 and 26 with the discharge boundary layer 153.

In the present embodiment, a discharge boundary layer formed based on extremely high and uniform dispersibility of noble metal fine particles on an oxide substrate as a boundary surface of a discharge space at a weight ratio of 0.05 wt% to 10 wt% and a particle diameter of 100 nm or less. In addition, since the surface resistivity of the discharge boundary layer is controlled to be 10 ⁴ Ω or more and less than 10 ¹² Ω, extremely stable discharge can be maintained in a wide range of specific input energy range, and the material gas can be maintained. It is possible to provide a silent discharge ozone generator that generates high-concentration ozone with only oxygen without using an additive gas such as nitrogen. In addition, since the boundary of the discharge space is constituted by the discharge boundary layer, the catalytic action of the discharge boundary layer on the generation of ozone is not accompanied by a change with time, and the electrode metal part is exposed to the discharge space. Therefore, a clean ozone gas that does not contain metal contamination can be provided without using an additive gas such as nitrogen. Further, since the electrode portion can be formed extremely compactly, it is effective for reducing the size and cost of the ozone generator.

Embodiment 11 FIG.
In Embodiments 1-8 and 10, the oxygen source type ozone generator was shown, but in the same structure as the above embodiment, by providing the discharge boundary layer in the present invention in the air source type ozone generator, The efficiency of ozone generation can be increased. In the air feed type, unlike the oxygen feed type, the consumption of generated ozone by nitrogen oxide (NOx) generated with ozone is generated, and the ozone generation efficiency is significantly reduced compared to the oxygen feed type. It has been. In the air feed type, simply shortening the gap in the discharge space (increasing the electric field strength) is not a good idea to improve the generation efficiency of NOx, but appropriately sets the Pd value represented by the product of the gap length d and the gas pressure P In addition, suppression of NOx generation by increasing the gas pressure in the discharge space is effective for increasing efficiency (Patent Document 6, paragraphs 0111 to 0114). In the present invention, the gap length is set to 0.6 mm or less and the above gas pressure is increased, and the discharge boundary layer shown in the first embodiment is provided to suppress NOx generation and improve the generation efficiency of oxygen atoms. And further increase in ozone generation efficiency can be expected.

  When noble metal fine particles such as platinum constituting the discharge boundary layer and oxides in which the fine particles are dispersed have photocatalytic properties (for example, oxides such as titanium and tungsten), the oxides may be alkali metals or alkaline earths. When a NOx storage alloy composed of metal or the like is contained, it is considered that generation of NOx is further suppressed and ozone generation efficiency is improved.

In the present embodiment, a discharge boundary layer formed based on extremely high and uniform dispersibility of noble metal fine particles on an oxide substrate as a boundary surface of a discharge space at a weight ratio of 0.05 wt% to 10 wt% and a particle diameter of 100 nm or less. In addition, the discharge boundary layer is subjected to resistance control treatment so that the surface resistivity is 10 ⁴ Ω or more and less than 10 ¹² Ω, so that extremely stable discharge can be maintained in a wide range of specific input energy regions, and high concentration ozone can be maintained. It is possible to provide a silent discharge type ozone generator that generates a high efficiency.

11: Ground electrode 12: High voltage electrode 131, 132: Dielectric 14: Discharge space 151, 152: Discharge boundary layer

Claims (8)

Two electrodes arranged opposite to each other and at least one dielectric between the electrodes are provided. A gas containing oxygen is supplied between the electrodes and an alternating voltage is applied to discharge the gas containing oxygen. In the ozone generator for generating ozone , at least one of the surfaces in contact with the discharge of the electrode or the dielectric is 0.05 wt% or more and 10 wt% in titanium oxide or tungsten oxide with respect to the oxide. A discharge boundary layer having a thickness of 5 μm or less, in which platinum fine particles are dispersed so as to be less than or equal to 5%, is provided so that the specific input energy to the discharge is 20 Wmin / NL or more and 800 Wmin / NL or less. A featured ozone generator . The ozone generator according to claim 1, wherein the platinum fine particles have a particle size of 100 nm or less. 2. The ozone generator according to claim 1 , wherein the discharge boundary layer has a surface resistivity of 10 ⁴ Ω or more and less than 10 ¹² Ω. At least one dielectric is provided between two electrodes arranged opposite to each other, and a gas containing oxygen is supplied between the electrodes, and at least one of the surfaces of the electrode or the dielectric contacting the gas containing oxygen On the surface, a discharge having a thickness of 5 μm or less that is semiconductive in which platinum fine particles are dispersed in titanium oxide or tungsten oxide in a weight ratio of 0.05 wt% to 10 wt% with respect to this oxide. providing boundary layer, ozone generation method characterized by the gas by applying an AC voltage between said electrodes, and by discharging at the following ratios input energy 20Wmin / NL more 800Wmin / NL to generate ozone. The ozone generation method according to claim 4 , wherein the platinum fine particles have a particle size of 100 nm or less. Ozone generation method according to claim 4, wherein the surface resistivity of the discharge boundary layer is less than 10 ⁴ Omega least 10 ¹² Omega. The ozone generation method according to claim 4 , wherein the gas containing oxygen is an oxygen gas having a purity of 99.5% or more. The ozone generation method according to claim 6 , wherein the gas containing oxygen is air.

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