JP2008135286A - Plasma surface treatment apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a plasma surface treatment apparatus capable of speeding up the surface treatment of an object to be treated. <P>SOLUTION: In the plasma surface treatment apparatus generating plasma by glow discharge, a porous body 9 is installed at the upstream of a discharge space 4 on at least one type of gas channel supplied to the discharge space 4, and the mist of an active material is contained in gas by passing the gas while the liquid active material is permeated to the porous body 9. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a plasma surface treatment apparatus using glow discharge, and more particularly to a plasma surface treatment apparatus that enables high-speed surface treatment of an object to be processed.

  In the fields of food processing, pharmaceutical production, medical treatment, etc., various sterilization methods have been conventionally employed as necessary.

  As sterilization methods classified as high-temperature sterilization methods, the pressurized steam method, in which the object is sealed in an autoclave and sterilized by exposure to pressurized steam at 120 ° C to 140 ° C for several minutes to several tens of minutes, is used. A high-temperature drying method or the like is used in which sterilization is performed by exposing an object to a high temperature of 160 to 190 ° C. for several minutes to several tens of minutes. These high-temperature sterilization methods are simple in equipment, and very high reliability has been recognized from the past use results. However, since the sterilization temperature is 120 ° C. or higher, they are used for non-heat-resistant products such as plastic products. Has the disadvantage of not being able to. For sterilization of such non-heat-resistant products, a low-temperature sterilization method using radiation or gas is mainly used.

  The radiation sterilization method using radiation is a method of sterilization by irradiating a target object with gamma rays for several hours, and can be sterilized at low temperature by the transmission power of radiation, and can also be applied to packages. is there. However, the radiation sterilization method is not suitable for a simple sterilization method of a low-priced object because a sterilization apparatus equipped with a radiation source costs several billion yen. Moreover, there is a problem that the control object is deteriorated by radiation.

  On the other hand, the low temperature sterilization method which is currently mainstream is a gas sterilization method using ethylene oxide gas. In the gas sterilization method, a sealed space is filled with ethylene oxide gas, and the object to be sterilized is fumigated for about several tens of hours to one week in this atmosphere. The gas sterilization method is the method most often used as a low temperature sterilization method. However, since the ethylene oxide gas used has extremely high toxicity and carcinogenicity, the ethylene oxide gas used for fumigation is recovered and recovered. New sterilization technology is not a simple and inexpensive sterilization method because it requires equipment for detoxification and also requires treatment for degassing the ethylene oxide gas soaked in the object to be sterilized. Development is desired.

  In recent years, a sterilization method using plasma has attracted attention because of the demand for such a simple and inexpensive sterilization technique. For example, the low-pressure plasma sterilization method is performed using various discharge forms such as microwave surface wave plasma and RF discharge, but has a problem that a vacuum chamber is essentially indispensable. The fact that a vacuum is necessary means that there is a limit to the size of the object and the number of objects to be processed. Therefore, in order to avoid such problems associated with vacuum, attention has been paid to the use of atmospheric pressure glow discharge.

So far, sterilization technology using atmospheric pressure glow discharge has been carried out by various research institutes. For example, glow discharge is generated at atmospheric pressure to generate plasma from a plasma generating gas, and toward the object to be processed. A plasma sterilization apparatus that blows out in a jet form (for example, see Patent Document 1) has been reported. In Patent Document 1, it is disclosed to use, as an inert gas, oxygen that generates active oxygen in the plasma, or vapor of H ₂ O or H ₂ O ₂ that generates hydroxy ions or hydroxy radicals, as the plasma generating gas. ing.

By the way, the source material that generates active molecular species such as ions and radicals in the plasma, such as oxygen, H ₂ O, or H ₂ O ₂ , is usually introduced into the plasma discharge space as a gas, and is a mist, that is, a liquid. There are few reports that it was supplied as fine particles. Regarding plasma surface treatment, a method using an OH-containing substance having OH in its chemical composition as a raw material has been reported (see, for example, Patent Document 2). Although it is mentioned that the OH-containing substance is supplied as a mist as an example, an example using an actually misted substance is not described.
JP2001-14589A (released on May 29, 2001) JP 2006-216468 (Released on August 17, 2006)

However, the atmospheric pressure plasma sterilization method reported so far does not have a sufficient bactericidal effect, and the D value for Bacillus atrophaeus, one of the most heat-resistant spore bacteria (the viable cell count is reduced to 1/10). However, there is a problem that a sterilization time of about 20 minutes is required even in direct plasma exposure of a He + O ₂ mixed gas.

  The present invention has been made in view of the above-mentioned problems, and the object thereof is a plasma sterilization apparatus capable of increasing the speed of sterilization of an object to be processed, and further, only sterilization processing. It is an object of the present invention to provide a plasma surface treatment apparatus capable of speeding up the surface treatment of an object to be processed.

  In order to solve the above problems, a plasma surface treatment apparatus according to the present invention generates a plasma by glow discharge and irradiates the plasma or a gas that has passed through the plasma to treat the surface of the workpiece. In the processing apparatus, a porous body for generating a liquid active substance as mist is installed on the flow path of at least one kind of gas supplied to the discharge space and upstream of the discharge space. A mist of the active substance is formed and contained in the gas by passing the at least one gas in a state where a liquid active substance generated as mist is infiltrated into the porous body. It is characterized by that.

  Here, the active substance means “a substance that contributes to realization of a desired surface treatment by being decomposed and / or activated in plasma”.

  According to the above configuration, it is possible to easily generate an appropriate amount and an optimal size of mist, compared to an ultrasonic mist generator or the like in which it is difficult to control the mist amount and the mist particle size depending on the physical properties of the liquid active substance. It becomes possible. Therefore, it is possible to increase the speed of the surface treatment of the workpiece.

  In the plasma surface treatment apparatus according to the present invention, the average pore diameter of the pores of the porous body is preferably 0.1 μm or more and 50 μm or less.

  By using a porous body having an average pore diameter of 50 μm or less, it is possible to avoid the disadvantage that droplets having an excessive particle diameter are generated and wet the surface of the non-processed product. Further, when a porous body having an average pore diameter of 50 μm or less is used as an electrode as will be described later, the distribution of electric field and the gas generated by evaporation of the active substance in the plasma in the pores and the non-pore portions are described. Concentration unevenness is unlikely to occur. Therefore, it is preferable from the viewpoint of the generated plasma and the in-plane uniformity of the surface treatment. Further, by using a porous body having an average pore diameter of 0.1 μm or more, it is possible to suitably generate mist without excessively reducing the speed at which the gas passes through the porous body.

  The plasma surface treatment apparatus according to the present invention may include a power application electrode and a ground electrode facing each other, and the porous body may also serve as the power application electrode.

  Since the porous body also serves as a power application electrode, the plasma generated in the discharge space between the power application electrode and the ground electrode is placed on the ground electrode or downstream of the ground electrode. It is possible to realize a configuration in which the light is uniformly irradiated. Therefore, the surface of the object to be processed can be processed uniformly.

  In such a case, the porous body is preferably a metal, a semiconductor, porous carbon, or porous silicon carbide.

  As a result, the porous body can be used as a power application electrode having a function of generating mist.

  The plasma surface treatment apparatus according to the present invention includes a power application electrode and a ground electrode facing each other, and the gas supplied to the discharge space is along the mutually facing surfaces of the power application electrode and the ground electrode facing each other. It may be introduced into the discharge space.

  Thereby, the structure which performs the surface treatment of a to-be-processed object outside the discharge space by the active chemical species contained in the gas that passes through the plasma and is discharged from the discharge space can be realized. Therefore, for example, it can be conveyed by a belt conveyor or the like to perform continuous processing, and can be suitably used for processing a large amount of objects to be processed.

  In such a case, the porous body is preferably carbon, glass, quartz, ceramics, organic polymer, or metal. Thereby, it becomes possible to generate a liquid active substance as mist.

  In the plasma surface treatment apparatus according to the present invention, it is preferable that liquid supply means for supplying the liquid active substance to the porous body is further provided.

  Furthermore, since the liquid supply means for supplying the liquid agent to the porous body is provided, there is an additional effect that the amount of the liquid agent to be permeated into the porous body can be suitably adjusted. .

  In the plasma surface treatment apparatus according to the present invention, it is preferable to generate plasma under atmospheric pressure.

  By generating plasma under atmospheric pressure, it is possible to easily surface-treat the workpiece without requiring an expensive vacuum apparatus.

  In the plasma surface treatment apparatus according to the present invention, it is preferable that the contact angle (wetting angle) between the substance constituting the porous body and the liquid active substance is an acute angle. Here, an acute angle means an angle of less than 90 °.

  Since the contact angle (wetting angle) between the substance constituting the porous body and the liquid active substance exhibits an acute angle, the liquid active substance efficiently penetrates into the pores of the porous body. Is possible. Therefore, mist can be suitably generated.

  In the plasma surface treatment apparatus according to the present invention, the at least one gas supplied to the discharge space includes at least one gas selected from the group consisting of He, Ar, Ne, Kr, Xe, and nitrogen. Is preferred.

  The at least one gas supplied to the discharge space contains at least one gas selected from the group consisting of He, Ar, Ne, Kr, Xe, and nitrogen, so that these gases become porous. Without reacting with the permeated liquid active substance, it is extruded from the pores to form mist, so that it is possible to suitably generate mist.

  The plasma surface treatment apparatus according to the present invention is preferably a sterilization treatment apparatus, an oxidation treatment apparatus, a nitridation treatment apparatus, a reduction treatment apparatus, an etching treatment apparatus, or a CVD treatment apparatus.

  In the plasma surface treatment apparatus according to the present invention, the liquid active substance is preferably water, hydrogen peroxide water, ozone water, carbonated water, an organic solvent, or silicone oil.

  The plasma surface treatment apparatus according to the present invention is preferably (i) an organometallic compound or an inorganic metal compound that is liquid at normal temperature and pressure, or (ii) a solution of an organometallic compound or an inorganic metal compound.

  As described above, the plasma surface treatment apparatus according to the present invention generates a liquid active substance as a mist on the flow path of at least one gas supplied to the discharge space and upstream of the discharge space. The porous body is installed, and the mist of the active substance is formed by passing the gas in a state in which the porous substance is infiltrated with the liquid active substance generated as mist. Therefore, it is possible to easily generate an appropriate amount and an optimal size of mist, and to introduce the generated liquid active agent mist together with the gas into the discharge space. Thus, it is possible to increase the speed of the surface treatment of the workpiece.

  In order to solve the above problems, the inventors of the present invention may increase the speed of surface treatment of an object to be processed by supplying a liquid agent in the form of mist between electrodes that generate plasma. As a result, when a sterilization treatment experiment was performed using a mixed gas of carrier gas and oxygen containing a mist of water generated by an ultrasonic vibrator, as shown in Comparative Example 3 described later, The speed of the surface treatment of the workpiece was the same as when no mist was supplied. Therefore, further studies have been made to solve the above-mentioned problems. As a result, a liquid working substance is infiltrated into the porous body, and the liquid working substance is extruded by a mixed gas of carrier gas and oxygen. It has been found that the surface treatment speed of the treated product is remarkably improved, and the present invention has been completed.

  An embodiment of the present invention will be described below with reference to FIGS.

<First Embodiment>
FIG. 1 shows an embodiment of a plasma surface treatment apparatus according to the present invention.

  A chamber 1 of the plasma surface treatment apparatus is provided with a power application electrode 2 and a ground electrode 3 facing each other, and plasma is generated by glow discharge in a discharge space 4 between the power application electrode 2 and the ground electrode 3. It is supposed to be generated. In addition, in the Example mentioned later, although the rectangular chamber made from an acrylic resin is used, the shape of the chamber 1 is not limited to a rectangle, Moreover, the material of the chamber 1 is not limited to an acrylic resin.

  These electrodes are made of aluminum, stainless steel, copper or the like. The edge portion of the electrode plane facing the plasma is preferably processed to have a radius of curvature of 1 mm or more. Thereby, generation | occurrence | production of the abnormal discharge by electric field concentration can be prevented. Further, ceramics such as alumina and boron nitride may be coated on the surface of these metal members forming the electrodes by a plasma spraying method or a CVD method. The thickness of the ceramic coating is preferably 70 to 120 μm, more preferably around 100 μm.

  The power application electrode 2 is connected to a plasma generation power source 6 via a matching circuit 5 that adjusts the circuit impedance to be constant.

  Here, it is preferable that the power application electrode 2 and the ground electrode 3 are arranged at an interval such that glow discharge is maintained even under atmospheric pressure, and for that purpose, the interval may be about 200 μm or more and 8 mm or less. However, it is more preferably 500 μm or more and 4 mm or less. Since the space between the power application electrode 2 and the ground electrode 3 is 200 μm or more, a space larger than the mean free path of charged particles can be formed, so that glow discharge can be stably maintained. Moreover, since the space | interval of the power application electrode 2 and the ground electrode 3 is 8 mm or less, the excessive generation | occurrence | production of a secondary electron is suppressed and a glow discharge can be maintained stably, without changing to an arc discharge.

  In this way, plasma generation under atmospheric pressure is possible by making the distance between the power application electrode 2 and the ground electrode 3 smaller than the conventional low-pressure plasma. Therefore, it is not necessary to use a large vacuum apparatus, and surface treatment can be performed easily. Further, since it is not necessary to perform the surface treatment in a vacuum, it becomes possible to carry out the continuous treatment by conveying the workpiece 7 by a belt conveyor or the like as shown in FIG. It can be suitably used for processing a large amount of the object 7 to be processed.

  A gas introduction pipe (not shown) is provided in the upper part of the chamber 1, and a carrier gas or a mixed gas of a carrier gas and a working gas is supplied from the gas supply unit 8. A carrier gas or mixed gas from a gas supply unit 8 such as a gas cylinder is supplied into the chamber 1 from a gas introduction pipe via a pressure regulator, a flow rate regulator, an on-off valve, and the like.

  Here, the working gas refers to a working gas that is a substance that contributes to the realization of a desired surface treatment by being decomposed and / or activated in plasma. Refers to an inert gas that does not contribute to the realization of the desired surface treatment.

  A liquid active substance is generated as a mist between a portion where a carrier gas or a mixed gas of a carrier gas and a working gas is introduced from a gas introduction pipe (not shown) at the top of the chamber 1 and the discharge space 4. A porous body 9 is provided. The porous body 9 is installed in close contact with the inner periphery of the chamber 1 on the flow path of the carrier gas introduced into the chamber 1 or the mixed gas of the carrier gas and the working gas, upstream of the discharge space 4. ing. For this reason, the carrier gas or the mixed gas passes through the porous body 9 and flows into the discharge space 4.

  Here, in the present specification, “mist” refers to fine liquid particles, and the average particle diameter thereof is in the range of 0.01 to 50 μm.

  The porous body 9 is preferably installed in close contact with the inner periphery of the chamber 1, but it is sufficient that the carrier gas or the mixed gas flows downward through the porous body 9. It is not always necessary to be in close contact with the inner periphery of the chamber 1.

  Further, the porous body 9 may be provided on the flow path of the carrier gas or the mixed gas of the carrier gas and the working gas, and may be provided upstream of the discharge space 4, and is necessarily provided in the chamber 1. There is no. The porous body 9 may be installed, for example, between the gas supply unit 8 and the gas introduction pipe into the chamber 1. In such a case, the porous body 9 may be further installed on the gas flow path before mixing when the carrier gas or the mixed gas of the carrier gas and the working gas is a mixture of a plurality of gases, It may be installed on a later gas flow path.

  The porous body 9 is not particularly limited as long as it is a porous body having pores into which a liquid active substance can enter. For example, carbon, glass, quartz, ceramics, metal sintered bodies, organic high A molecule or the like can be used. Also, as the carbon porous body, a carbon particle sintered body can be suitably used.

  The contact angle (wetting angle) between the substance constituting the porous body used here and the liquid active substance used is preferably an acute angle, and more preferably a combination that provides a contact angle (wetting angle) of 2 to 40 °. Is desirable. Thereby, a liquid active substance can be efficiently infiltrated into the pores of the porous body.

  Here, the contact angle (wetting angle) between the substance constituting the porous body to be used and the liquid agent to be used constitutes the porous body in the liquid agent under the environment where the earth gravity field acts. A method for measuring the shape of a meniscus formed when a board made of a material is immersed, or 50 μl of a liquid active substance is dropped on the surface of a material constituting a porous body, and a contact angle (wetting) is obtained from a droplet image. It is a value measured by a method of measuring (angle).

  The average pore diameter of the pores of the porous body 9 is preferably 0.1 μm to 50 μm, more preferably 0.2 μm to 10 μm, and further preferably 0.2 μm to 5 μm. By using the porous body 9 having an average particle size of 50 μm or less, it is possible to avoid the disadvantage that droplets having an excessive particle size are generated and the surface of the non-processed product is wetted. Further, by using a porous body having an average particle size of 0.1 μm or more, it becomes possible to suitably generate mist without excessively reducing the speed at which the carrier gas or mixed gas passes through the porous body. .

  The porosity of the porous body is preferably 10 to 70%, more preferably 10 to 50%, and further preferably 15 to 40%. When the porosity is 70% or less, the mechanical strength of the porous body is not significantly reduced, and the structure itself can be suitably held. On the other hand, when the porosity is 10% or more, it is possible to efficiently generate mist without excessively reducing the passage of the carrier gas. Here, the porosity means a value measured using a porosity meter.

  For example, when the porous body 9 is a carbon particle sintered body, the average particle size of the sintered carbon particles is preferably 0.5 to 350 μm, and more preferably 1 to 40 μm. When the average particle diameter of the carbon particles is 350 μm or less, it is possible to avoid the inconvenience that droplets having an excessive particle diameter are generated and wet the surface of the non-processed product. Further, when the average particle size is 0.5 μm or more, it becomes possible to suitably generate mist without excessively reducing the speed at which the carrier gas or mixed gas passes through the porous body.

  Here, the average particle size of the carbon particles of the carbon particle sintered body is a value determined by the following method. First, a carbon particle sintered body as a sample is observed with a scanning electron microscope, and for each of a total of 50 or more carbon particles, the major axis diameter of one target particle, that is, the shape of the particle is determined. The dimension in the direction of the largest dimension is measured from the micrograph. Of the 50 or more measured values, the average particle diameter in the present invention is a value obtained by averaging the measurement values of 60% of the total number of measurement values excluding the upper and lower 20% as the number of measurement values.

  The porous body 9 may be subjected to a surface treatment for making the contact angle (wetting angle) an acute angle so that the liquid active substance can efficiently enter the pores. For example, when the active substance is water, a porous body 9 that has been subjected to a treatment for making the surface hydrophilic can be suitably used. As such surface treatment, for example, when the porous body 9 is carbon such as a carbon particle sintered body, the carbon particle sintered body is used to efficiently infiltrate water as an active substance into the pores. An example is a method in which silicon is deposited by thermal CVD to a thickness of 10 to 200 nm, more preferably about 20 to 100 nm, and then a natural oxide film is grown on the deposited silicon surface by dipping in water containing dissolved oxygen.

  The porous body 9 is supplied with a liquid active substance generated as mist from the liquid supply unit 10. The liquid supply unit 10 includes a storage container for a liquid active substance, a supply pipe, an on-off valve, a flow rate regulator, and the like.

  The liquid supply unit 10 may be anything as long as it can supply the liquid active substance to the porous body 9, and the liquid active substance is directly applied to the porous body 9 from the storage container. It may be supplied or supplied to the porous body 9 through a supply pipe. Further, any method may be used for supplying the porous body 9, for example, a structure in which the porous body 9 is dropped on the porous body 9, a structure in which the porous body 9 is sucked by capillary action, The structure etc. which cool to below a dew point and aggregate the vapor | steam in the gas previously containing vapor | steam on the particle | grain surface etc. can be mentioned.

  By supplying the liquid active substance from the liquid supply unit 10 to the porous body 9, the liquid active substance that has permeated the porous body 9 enters the pores of the porous body 9 and is subdivided. become. When the carrier gas or mixed gas passes through the porous body 9 in which the liquid active substance has permeated, the liquid active substance that has penetrated into the pores due to the pressure of the carrier gas or mixed gas becomes the carrier gas or mixed gas. At the same time, it is extruded from the porous body 9 to form mist. The formed carrier gas or mixed gas containing mist is introduced into the discharge space 4 between the power application electrode 2 and the ground electrode 3 to generate plasma by glow discharge.

  The average particle diameter of the supplied mist is preferably 0.01 μm to 50 μm, more preferably 0.05 μm to 5 μm, and further preferably 0.05 μm to 3 μm. By using a mist having an average particle size of 50 μm or less, it is possible to avoid the disadvantage that droplets having an excessive particle size are generated and the surface of the non-processed product is wetted. Further, when a mist having an average particle size of 0.01 μm or more is used, the active substance is efficiently transported and the speed of the surface treatment can be increased.

  Since the mist is composed of a liquid, molecules of the active substance having a very high concentration are introduced between the electrodes as compared with the vapor which is a gas. Since the mist introduced in this way is heated by collision with gas molecules in the plasma generated between the electrodes, it vaporizes according to its vapor pressure, and a large amount of active substance molecules are put into the plasma. Supply is possible. Therefore, it is possible to shorten the surface treatment of the workpiece.

  In the present invention, the liquid active substance includes an active substance that is liquid at normal temperature and pressure and a solution of the active substance. Moreover, normal temperature means the temperature range of 5 to 40 degreeC, and normal pressure means atmospheric pressure and the pressure of the vicinity.

  In addition, it is conceivable to supply such high-concentration active substances in the form of steam, but high-concentration steam will cause condensation unless the temperature of the container, piping and gas is controlled at a high temperature. Are complicated and require high temperatures.

  Further, when glow discharge plasma is generated using the formed mist by the ultrasonic mist generator, the effect of the present invention of shortening the surface treatment time of the object to be processed cannot be obtained. The reason for this is not clear, but for example, power was insufficient due to excessive supply of mist such as water, and the effect of annihilation by recombination of radicals generated in plasma increased, and the particle size of the supplied mist It is conceivable that the transpiration effect in plasma was not obtained.

A large amount of active substance molecules generated in the plasma are decomposed by charged particles in the plasma to generate various reaction products. For example, when a mixed gas of helium and oxygen and a mist of water are supplied into the plasma, it is considered that a reaction product is generated through the following reaction.
H ₂ O → OH + H
H ₂ O + e: → H ₂ + O or 2H + O
H ₂ O + O → H ₂ O ₂
O ₂ + O → O ₃
Of these reaction products, OH radicals, atomic oxygen, H ₂ O ₂ , and O ₃ are all active chemical species having oxidizing power, and are considered to play an important role in the surface treatment of the object 7 to be treated. It is done. For example, these active chemical species can be sterilized by oxidizing live bacteria, and can oxidize the surface of the workpiece 7. In this specification, an active chemical species refers to a chemical species that is generated in plasma and contributes to the realization of surface treatment, such as excited molecules, radicals, and ions.

  The lower end of the chamber 1 coincides with the lower end of the discharge space 4 between the power application electrode 2 and the ground electrode 3, and the lower end of the discharge space 4 is an opening 11 that opens toward the outside. Thus, the gas that has passed through the plasma generated in the discharge space 4 between the power application electrode 2 and the ground electrode 3 is released to the outside from the opening 11. An object to be processed 7 is disposed downstream of the opening 11 and is subjected to surface treatment by irradiation with a gas containing an active chemical species released from the opening 11. The distance from the opening 11 to the workpiece 7 is preferably 0 or more and 30 mm or less. If the distance from the opening 11 to the workpiece 7 is 30 mm or less, the active chemical species contributing to the realization of the desired surface treatment reaches the workpiece 7 without disappearing, and the surface treatment capability is increased. It can be demonstrated.

  The flow rate of the gas that has passed through the plasma in the opening 11 is preferably 1 to 100 m / s. When the flow velocity of the gas that has passed through the plasma is 1 m / s or more, the active chemical species that contribute to the realization of the desired surface treatment reaches the workpiece 7 without disappearing, and the surface treatment capability is improved. It can be demonstrated. If it is 100 m / s or less, an excessive increase in the chamber internal pressure can be prevented, and the structure of the apparatus can be simplified.

  Here, the flow rate of the gas that has passed through the plasma is adjusted by changing the flow rate of introducing the carrier gas or mixed gas into the chamber 1 and / or the interval between the power application electrode 2 and the ground electrode 3. be able to.

  Moreover, although the temperature of the plasma irradiated to the to-be-processed object 7 is about 120-130 degreeC in an Example, since the length of a plasma can be shortened as shown in the reference example 3 mentioned later, it is 50. It can be lowered to about ~ 100 ° C. Therefore, it can be suitably used for non-heat resistant products such as plastics.

  In the present invention, the surface treatment is not particularly limited as long as it is a surface treatment of the object 7 to be processed by the generated plasma. For example, sterilization treatment, oxidation treatment, nitriding treatment, etching treatment, reduction treatment, CVD And the like.

  In FIG. 1, the workpiece 7 is disposed downstream of the opening 11 of the chamber 1. However, the workpiece 7 is a portion in contact with the discharge space 4 of the ground electrode 3 as shown in FIG. 2. That is, you may install in the part facing a power application electrode. Even in such a case, the object 7 can be surface-treated with the generated plasma. In this case, the generated plasma is directly irradiated to the workpiece 7.

  The plasma generating power source 6 is preferably a commercially available power source such as 13.56 MHz, 27 MHz, or 40 MHz, but any frequency may be used as long as it is a power source that generates plasma. The range of the applied frequency is preferably 200 KHz to 2.45 GHz, and more preferably 10 MHz to 200 MHz. In particular, when the frequency is 10 MHz or more, it is preferable because the frequency is relatively easy to generate and maintain a discharge. In particular, a frequency of 200 MHz or less is preferable because a simple impedance matching circuit can be easily formed.

The applied power applied between the power application electrode 2 and the ground electrode 3 is preferably 8 W / cm ^{3 to 1} kW / cm ³ depending on the type of target surface treatment, and is preferably 15 to 200 W / cm ^3. It is more preferable that When the applied power is 1 kW / cm ³ or less, the temperature of the plasma does not increase excessively, and the surface treatment of the non-heat-resistant product can be suitably performed. Further, when the applied power is 8 W / cm ³ or more, sufficient plasma can be generated for the surface treatment of the workpiece 7.

  The gas supply unit 8 such as a gas cylinder is filled with a carrier gas and, if necessary, a working gas. As the carrier gas, a rare gas such as helium, argon, neon, krypton, or xenon; an inert gas such as nitrogen can be used. These gases may be used alone or in combination of two or more. The working gas may be appropriately selected according to the type of surface treatment. For example, when sterilizing the surface of the object 7 to be treated, oxygen, carbon dioxide, hydrogen peroxide, ozone, or the like is oxidized. Oxygen, carbon dioxide, ozone, hydrogen peroxide, etc., nitrogen, ammonia, hydrazine, etc. for nitriding, hydrogen, etc. for reduction, and fluorine-containing substances for etching. Can be used. In the present invention, since a liquid active substance is supplied as a mist as an active substance involved in plasma generation, the working gas may be used as necessary.

  These gases are supplied into the chamber 1 as a combined gas mixture by controlling opening and closing of the respective opening valves as necessary. Here, when the working gas is used, the mixing ratio of the carrier gas and the working gas is preferably 0.001 to 80 vol% with respect to the carrier gas, and 0.001 to 50 vol. % Is more preferable. When the ratio of the working gas is 0.001 vol% or more, a reaction product is remarkably generated between the mist substance and the working gas substance by mixing with the mist, which is preferable. Further, when the ratio of the working gas is 80 vol% or less, it is preferable because the discharge is stable and the electric power for obtaining a sufficient reaction product does not become excessive.

  The liquid active substance supplied as the mist may be appropriately selected according to the type of surface treatment. For example, when sterilizing the surface of the object 7 to be treated, water, hydrogen peroxide water, ozone water Water, hydrogen peroxide water, ozone water, carbonated water, etc. when performing oxidation treatment with carbonated water, etc. Trimethylaluminum, trimethylgallium, dimethylzinc, titanium (IV), etc. when performing CVD treatment A metal compound that is liquid at room temperature and normal pressure; a metal compound solution such as a polyaluminum chloride aqueous solution; an organic solvent such as alcohol or acetone; a silicone oil or the like can be used. By mixing these liquid active substances with the appropriate working gas, it is possible to form semiconductor thin films such as aluminum nitride and gallium nitride; oxide semiconductor thin films such as zinc oxide; and compound thin films such as titanium oxide. Further, in the film formation using an organic solvent, a low dielectric constant organic thin film can be formed. On the other hand, when silicone oil is used, it is possible to form a silicon oxide film without using silane gas by mixing oxygen into the working gas.

  The material forming the chamber 1 may be an insulating material or a conductive material. In the case where the material forming the chamber 1 is a conductive material, each electrode may be insulated and provided. As a material for forming the chamber 1, for example, plastics such as acrylic resin and vinyl chloride; quartz; alumina; ceramics such as glass and the like can be suitably used.

  FIG. 3A is an example of the present embodiment more specifically showing FIG. 1, and FIG. 3B shows a change in the arrangement method of objects to be processed in the plasma processing apparatus of FIG. This is an example. In the example of FIG. 3A, the liquid supply unit 10 supplies the liquid active substance to the porous body 9 via the supply pipe 14 from the tank 13 that stores the liquid active substance 12. The supply pipe 14 is located at a position between the porous body 9 and a portion where the carrier gas or a mixed gas of the carrier gas and the working gas is introduced from a gas introduction pipe (not shown) at the top of the chamber 1. The liquid active substance is dropped onto the porous body 9 from the end thereof. The liquid active substance is supplied into the chamber 1 from the supply pipe 14 via a flow rate regulator and an on-off valve. As a result, a liquid active substance can be dropped onto the porous body 9 at regular intervals to stably generate mist of the active substance.

  In the example of FIG. 3A, the carrier gas or mixed gas from the gas supply unit 8 is branched into a path i for maintaining pressure equilibrium and a path ii as a process gas, and the process gas component is It is introduced into the chamber 1.

  In the example of FIG. 3A, the ground electrode 3 is formed in the entire length direction on the container wall on one side of the chamber 1, and the power application electrode 2 projects into the chamber from the container wall on the opposite side of the chamber 1. It has a configuration. However, the configuration of the electrodes is not limited to these, and any configuration may be used. In addition, the power application electrode 2 is connected to the matching circuit 5 via a metal plate or a metal rod. However, the configuration of the power application electrode 2 is not limited to this, and the power application electrode 2 is connected via the matching circuit. Any configuration may be used as long as it is connected to the plasma generating power source. Further, in FIG. 3A, the chamber 1 is further installed in an insulating container 15 in order to prevent the reaction product produced as a result of the experiment from diffusing indoors. . In addition, the plasma processing apparatus of this invention does not necessarily need to be equipped with this function. In addition, when such a function is given, the configuration is not limited to this.

  In FIG. 3A, the object 7 is disposed downstream of the opening 11 and irradiated with a gas containing active chemical species released from the opening 11 to be surface-treated. However, the to-be-processed object 7 may be conveyed with a belt conveyor as FIG.3 (b) shows. Thereby, it becomes possible to perform the continuous process of the to-be-processed object 7, and can use it suitably for a process of a large amount of to-be-processed objects.

  Next, plasma surface treatment will be described. First, the workpiece 7 is placed at a predetermined position at the lower end of the chamber 1. Next, a liquid active substance generated as mist is supplied from the liquid supply unit 10 to the porous body 9, penetrates the porous body 9, and enters the pores of the porous body 9. Subsequently, the carrier gas or a mixed gas of the carrier gas and the working gas is introduced into the chamber 1 from the gas introduction pipe, passes through the porous body 9, and enters the pores of the porous body 9. The active substance is extruded from the porous body 9 to form a mist. While introducing the carrier gas containing the mist of the liquid active substance thus formed or a mixed gas of the carrier gas and the working gas into the discharge space 4 between the power application electrode 2 and the ground electrode 3, An electric field is applied between the power application electrode 2 and the ground electrode 3 to generate plasma by glow discharge under atmospheric pressure. The active chemical species in the plasma generated in this way is discharged from the lower end of the chamber 1 which is the lower end of the discharge space 4 and irradiated on the surface of the object 7 to be surface-treated.

<Second Embodiment>
4 and 5 show another embodiment of the plasma surface treatment apparatus according to the present invention. 4B is a plan view of the plasma surface treatment apparatus of FIG. 4A viewed from the direction of arrow A, and FIG. 5 is a portion surrounded by a circle of the plasma surface treatment apparatus of FIG. FIG.

  The bottom of the chamber 21 of the plasma surface treatment apparatus is a power application electrode 22, and plasma is generated by glow discharge in the discharge space 24 between the power application electrode 22 and the ground electrode 23 facing the power application electrode 22. Yes.

  Here, the power application electrode 22 is formed of a porous body. That is, in this embodiment, the power application electrode 22 having the function of the porous body used in the first embodiment is used as the power application electrode. Here, the porous body constituting the power application electrode 22 is not particularly limited as long as it is a porous body having conductivity. For example, a metal, a semiconductor, porous carbon, porous silicon carbide, or the like is used. Can be mentioned. The ground electrode 23 is made of aluminum, stainless steel, copper or the like.

  The power application electrode 22 is connected to a plasma generation power source (not shown) through a matching circuit (not shown) that adjusts the circuit impedance to be constant. In FIG. 4A, the chamber 21 is made of metal, and the power application electrode 22 is connected to the matching circuit via the metal and a metal rod 29 made of copper, aluminum, stainless steel, or the like. However, the configuration of the power application electrode is not limited to this, and may be any configuration as long as the power application electrode 22 is connected to the plasma generation power source via the matching circuit. . 4A, the ground electrode 23 is connected to the grounded shield 30 and connected to the conductive or insulating flanges (31, 32). However, the configuration of the ground electrode is also limited to this. Any configuration may be used as long as the ground electrode 23 is grounded. Further, in FIG. 4A, the ground electrode 23 is preferably a mesh plate as shown in FIG. 4B. Thereby, in the configuration in which the object to be processed is disposed in the discharge space 24 such as on the ground electrode 23, the gas that has passed through the plasma after irradiation is discharged. Further, when the object to be processed is disposed downstream of the ground electrode 23, the gas that has passed through the plasma can be emitted through the holes in the mesh and irradiated to the object to be processed. However, the configuration of the ground electrode 23 is not limited to this.

  Here, it is preferable that the power application electrode 22 and the ground electrode 23 are arranged at intervals such that glow discharge is maintained even under atmospheric pressure. For this purpose, the interval may be about 200 μm to 8 mm. However, it is more preferably 500 μm or more and 4 mm or less. When the distance between the power application electrode 22 and the ground electrode 23 is 200 μm or more, glow discharge can be maintained. Further, it is preferable that the distance between the power application electrode 22 and the ground electrode 23 is 8 mm or less because excessive generation of secondary electrons is suppressed and transition to arc discharge does not occur.

  Thus, by reducing the distance between the power application electrode 22 and the ground electrode 23, plasma processing under atmospheric pressure is possible. Therefore, it is not necessary to use a large vacuum apparatus, and surface treatment can be performed easily.

  The chamber 21 is provided with a gas introduction pipe 27 so that a carrier gas or a mixed gas of a carrier gas and a working gas is supplied from a gas supply unit (not shown). Carrier gas or mixed gas from a gas supply unit such as a gas cylinder is supplied from the gas introduction pipe 27 into the chamber 21 via a pressure regulator, a flow rate regulator, and an on-off valve.

  Further, the chamber 21 is provided with a liquid introduction pipe 28, and a liquid active substance generated as mist is supplied from a liquid supply section (not shown). The liquid supply unit includes a storage container for a liquid active substance, a supply pipe, an on-off valve, a flow rate regulator, and the like.

  The liquid active substance introduced into the chamber 21 from the liquid introduction tube 28 is dropped onto the power application electrode 22 formed of a porous body. As a result, the active substance that has permeated the power application electrode 22 enters the pores of the power application electrode 22 and is subdivided. When the carrier gas or mixed gas passes through the power application electrode 22 in which the liquid agent has permeated, the liquid agent that has penetrated into the pores due to the pressure of the carrier gas or mixed gas becomes the carrier gas or mixed gas. At the same time, the mist is formed by being pushed out from the power application electrode 22. The carrier gas or mixed gas containing the formed mist is introduced into the discharge space 24 between the power application electrode 22 and the ground electrode 23 to generate plasma by glow discharge.

  The porous body constituting the power application electrode 22 is not particularly limited as long as it has pores into which a liquid active substance can enter, but the average pore diameter of the pores is 0.1 μm to 50 μm. Preferably, the thickness is 0.2 μm to 10 μm, and more preferably 0.2 μm to 5 μm. By using the porous body 9 having an average particle size of 50 μm or less, it is possible to avoid the inconvenience that droplets having an excessive particle size are generated and the surface of the non-processed product is wetted. Further, by using a porous body having an average particle size of 0.1 μm or more, it is possible to suitably generate mist without reducing the speed at which the carrier gas or mixed gas passes through the porous body.

  As the porous carbon, a carbon particle sintered body can be suitably used. For example, when the porous carbon is a carbon particle sintered body, the average particle size of the sintered carbon particles is preferably 0.5 to 350 μm, and more preferably 1 to 40 μm. When the average particle diameter of the carbon particles is 350 μm or less, it is possible to avoid the inconvenience that droplets having an excessive particle diameter are generated and wet the surface of the non-processed product. If the average particle size is 0.5 μm or more, the carrier gas or a mixed gas of the carrier gas and the working gas can suitably generate mist without decreasing the speed of passing through the power application electrode 22. It becomes.

  Further, the porous body may be subjected to a surface treatment for making the contact angle (wetting angle) an acute angle so that the liquid active substance can efficiently enter the pores. For example, when the active substance is water, porous carbon that has been subjected to a treatment for making the surface hydrophilic can be suitably used. Since this surface treatment is as described in <Embodiment 1>, description thereof is omitted here.

  The interval between the power application electrode 22 and the ground electrode 23 is as described above. However, in the example shown in FIG. 4 or 5, the interval is maintained by the interval holding member 25. The spacing member 25 also has a function of insulating the power application electrode 22 and the ground electrode 23. As the spacing member 25, quartz, alumina, glass, ceramics such as boron nitride, heat resistant plastic, or the like can be suitably used. However, the structure for maintaining and insulating the gap between the power application electrode 22 and the ground electrode 23 is not limited to this, and any structure having both functions of the gap and the insulation can be used. Good.

  In FIGS. 4 and 5, the power application electrode 22, the spacing member 25 and the ground electrode 23 are fixedly held by a fixing member 26. As the fixing member 26, for example, an insulating screw such as ceramics can be suitably used. However, the method of fixing and holding the power application electrode 22, the spacing member 25, and the ground electrode 23 is not limited to this, and any method may be used.

  In the plasma surface treatment apparatus according to the present embodiment, the workpiece 7 can be disposed on the ground electrode 23 or downstream of the ground electrode 23.

  When the workpiece 7 is disposed on the ground electrode 23, it is possible to uniformly irradiate the workpiece with the plasma generated in the discharge space 24 between the power application electrode 22 and the ground electrode 23, In the portion where the plasma is irradiated, the surface of the object to be processed can be processed uniformly and at a higher speed. In addition, when arrange | positioning the to-be-processed object 7 on the ground electrode 23, the to-be-processed object 7 is arrange | positioned so that the gas which passed through the plasma after irradiation can be discharged | emitted.

  In addition, even when the object 7 is disposed downstream of the ground electrode 23, the direction of discharge and the direction of gas passing through the plasma are the same as in the first embodiment shown in FIG. Therefore, it is possible to uniformly irradiate the object to be processed with the gas that has passed through the plasma, and the surface of the object to be processed can be uniformly processed. Further, in such a case, since it is possible to realize a configuration in which the surface treatment of the object to be processed is performed outside the discharge space, for example, it is possible to carry out a continuous treatment by being conveyed by a belt conveyor or the like. It can use suitably for the process of the to-be-processed object.

  Further, when the object 7 is disposed downstream of the ground electrode 23, the distance from the lower end of the ground electrode 23 to the object 7 is preferably 0 or more and 30 mm or less. If the distance from the lower end of the ground electrode 23 to the workpiece 7 is 30 mm or less, the active chemical species contributing to the realization of the desired surface treatment reaches the workpiece 7 without disappearing, and the surface treatment is performed. Can demonstrate ability.

  Moreover, it is preferable that the flow velocity of the gas that has passed through the plasma at the lower end of the ground electrode 23 is 0.1 to 80 m / s, regardless of the position of the object 7 to be processed. When the flow rate of the gas that has passed through the plasma is 0.1 m / s or more, mist generation from the porous body is effectively performed, which is preferable. Further, when the processing object 7 is disposed downstream of the ground electrode 23 at a gas flow rate of 1 m / s or more, the active chemical species contributing to the realization of the desired surface treatment reaches the processing object 7 without disappearing. The ability of surface treatment can be demonstrated. In addition, when the flow velocity of the gas that has passed through the plasma is 80 m / s or less, an excessive increase in the chamber internal pressure can be prevented, and the device structure can be simplified.

  In addition, although the power application electrode 22 and the ground electrode 23 are fixedly held in FIG. 4, they are not necessarily fixedly held. For example, as illustrated in FIG. 6, only the power application electrode 22 may be fixed and held in the chamber 21 by a fixing member 26, for example. FIG. 6 is a view showing a CVD processing apparatus having a configuration in which the ground electrode 23 ′ also has the function of a substrate heater. However, the present invention is not limited to the CVD processing apparatus, and may be applied to other plasma processing apparatuses. Can do. In the CVD processing apparatus of FIG. 6, a substrate which is the object to be processed 7 is disposed on the ground electrode 23 '.

  Since the frequency of the plasma generation power source, the applied power, the gas used as the carrier gas or working gas, the mixing ratio of the carrier gas and the working gas, and the liquid working substance are as described in <Embodiment 1>, here Then, explanation is omitted.

  The material for forming the chamber 21 is metal in FIG. 4 or FIG. 5, but is not limited to metal when other means for connecting the power application electrode 22 to the plasma generation power source is provided. Alternatively, for example, an insulating material such as plastic, glass, or ceramics may be used.

  The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope shown in the claims, and embodiments obtained by appropriately combining technical means disclosed in different embodiments. Is also included in the technical scope of the present invention.

[Example 1: Sterilization treatment using plasma surface treatment apparatus (sterilization apparatus) of the present invention]
<Sterilization treatment using the plasma surface treatment apparatus (sterilization apparatus) of the present invention>
Sterilization was performed using the plasma surface treatment apparatus shown in FIG. A mixed gas of He and oxygen is introduced into a rectangular chamber 1 formed by an acrylic spacer, and connected to a ground electrode 3 made of a grounded stainless steel substrate and a 13.56 MHz RF power source 6 via a matching box 5. A 1 mm gap was formed between the aluminum power application electrodes 2 thus formed, and atmospheric pressure plasma was generated in the discharge space 4. The electrode area was 30 × 30 mm ² . In a rectangular chamber 1, a carbon particle sintered body (porous body) 9 subjected to surface treatment is installed between the discharge space 4 and the inflow portion of the mixed gas, and ultrapure water of about 25 μl per minute is provided on the upper surface thereof. Were sequentially dropped and water mist was generated by flowing He + O ₂ gas. The flow rates of He and O ₂ were controlled by a mass flow controller.

  As the carbon particle sintered body, a carbon sintered body (Nisshinbo Co., Ltd.) having an average particle diameter of 70 μm was used. The surface treatment was performed by depositing 100 nm of silicon on the carbon particle sintered body by thermal CVD, and then immersing it in water containing dissolved oxygen for 24 hours to grow a natural oxide film on the deposited silicon surface. .

Bacillus subtilis (Bacillus atrophaeus ATCC # 9372) supplied from Raven was used as the indicator fungus to be treated. Bacillus subtilis is excellent in non-pathogenicity and heat resistance, and is often used as an indicator bacterium for sterilization techniques. The B. subtilis, on a stainless steel dish and 10 ⁶ cells / dish quantification.

  Three stainless steel dishes on which the indicator bacteria were placed were placed downstream of the plasma, that is, 1 cm downstream of the opening 11 of the chamber 1 and sterilized.

  Plasma generation conditions are: input power: 80 W, total flow rate: 20 SLM, oxygen concentration in the mixed gas: 0.5 vol%, irradiation time of the gas that has passed through the plasma (hereinafter, in Examples, Comparative Examples, and Reference Examples, The irradiation of the gas that has passed through the plasma is also abbreviated as “plasma irradiation” and “plasma irradiation time” for convenience.): Sterilization was performed for 15 minutes. The measurement was performed by exposing three stainless steel dishes to one irradiation at the same time.

<Evaluation of sterilization: confirmation of the presence of viable bacteria with a pH detection reagent>
After the plasma irradiation, Bacillus subtilis in a stainless steel dish was cultured at 32 ° C. for 7 days in a dedicated medium (Raven) mixed with a pH detection reagent. The presence or absence of viable bacteria is determined by utilizing the fact that the pH in the medium changes due to the life activity of viable bacteria and the color of the pH detection reagent changes from reddish brown to yellow when viable bacteria remain. This was confirmed by the color change of the liquid.

<Evaluation results>
When mist was supplied in Example 1, the pH detection reagent was reddish brown and no color change was observed. This indicates that sterilization is complete. In contrast, in Comparative Example 1 described later, when no mist was supplied, the pH detection reagent turned yellow in any medium, and sterilization was not completed after 15 minutes of plasma irradiation. I understood. From the above, it was confirmed that high speed sterilization was achieved by supplying mist.

[Comparative Example 1]
The plasma surface treatment apparatus used in Example 1 was used to irradiate the Bacillus subtilis with plasma in the same manner as in Example 1 except that ultrapure water was not supplied to the porous body 9 and no mist was generated. went.

[Example 2: Sterilization treatment using plasma surface treatment apparatus (sterilization apparatus) of the present invention]
<Sterilization treatment using the plasma surface treatment apparatus (sterilization apparatus) of the present invention>
Sterilization was performed in the same manner as in Example 1 except that the plasma irradiation time was variously changed.

<Evaluation of sterilization: Evaluation by D value>
After the plasma irradiation, the stainless steel dish on which Bacillus subtilis was placed was immersed in a specified amount of ultrapure water and suspended by ultrasonic irradiation. A predetermined amount of the obtained suspension was taken out and cultured on an agar medium at 32 ° C. for 2 days, and then colonies formed by viable bacteria were counted. The number of viable bacteria was identified by using the colony counting method described in “Anti-bacterial fungus 26 No. 9 p511 (1998), Biotechnology Experiments Japan Society for Biotechnology [Baifukan]”.

  The number of colonies identified by the above method at each irradiation time was plotted against the irradiation time to create a survival curve, and the D value was determined from the slope.

<Evaluation results>
FIG. 7 (b) shows the survival curve of the indicator bacterium obtained in Example 2, and FIG. 7 (a) shows the indicator bacterium obtained when Comparative Example 2 described later did not supply mist. The survival curve is shown. From the slopes of the straight lines in FIGS. 7A and 7B, the D value when the mist is not supplied is 3.2 minutes, whereas the D value when the mist is supplied is 1.5 minutes. It was confirmed that it was greatly shortened.

<Evaluation of sterilization: Evaluation by electron microscope observation of indicator bacteria after sterilization>
The indicator bacteria after sterilization treatment when the plasma irradiation time was 4 minutes and 10 minutes were observed with an electron microscope.

<Evaluation results>
FIG. 8 (c) shows an indicator bacterium sterilized with an irradiation time of 4 minutes and 10 minutes in Example 2, and FIG. 8 (b) shows 4 minutes when mist is not supplied in Comparative Example 2 described later. And (a) shows the result of electron microscopic observation of the indicator bacteria before sterilization, of the indicator bacteria sterilized with an irradiation time of 10 minutes. From FIG. 8B and FIG. 8C, the reduction of bacteria was observed as the plasma irradiation time became longer. Moreover, when the sterilization process is performed by supplying mist (c), it can be seen that the outer shape of the bacteria is largely broken in the plasma irradiation time of 10 minutes. On the other hand, when the mist is not supplied (b), the outer shape of the bacteria is not broken even during the plasma irradiation time of 10 minutes, and the sterilization effect is improved by supplying the mist and performing the sterilization treatment. It was confirmed. Although not shown in the figure, when Bacillus subtilis is sterilized by heat, the bacterium does not shrink and releases toxin (endotoxin) in the incorporated living body. On the other hand, sterilization by plasma irradiation is excellent in that there is no such problem.

[Comparative Example 2]
Using the plasma surface treatment apparatus used in Example 1, plasma was irradiated to Bacillus subtilis in the same manner as in Example 2 except that ultrapure water was not supplied to the porous body 9 and no mist was generated, and sterilization was evaluated. went.

[Comparative Example 3: Sterilization using mist generated by ultrasonic transducer]
In the plasma surface treatment apparatus shown in FIG. 3A, instead of the porous body 9 and the liquid supply unit 10, a mist by an ultrasonic vibrator is provided between the gas supply unit 8 and the introduction unit of the mixed gas into the chamber 1. Sterilization treatment was performed in the same manner as in Example 2 except that the apparatus provided with the generating means was used.

That is, the mixed gas of He and O ₂ mixed at a predetermined ratio by the mass flow controller is an acrylic in which an ultrasonic vibrator (HM-303N, manufactured by Honda Electronics Co., Ltd.) that forms a mist with a diameter of 3 μm is immersed in water. The piping was connected so as to pass through the resin container. The mixed gas after passing through the acrylic resin container was introduced into the chamber 1 after removing excessively coarse mist by a liquid trap.

  A survival curve was prepared in the same manner as in Example 2, and the D value was determined from the slope. FIG. 7C shows the survival curve of the indicator bacterium obtained in Comparative Example 3. From the slope of the straight line in FIG. 7C, it can be seen that the D value when the mist generated by the ultrasonic transducer is used is 3.1 minutes, which is similar to the case where no mist is generated. This is thought to be due to the lack of power due to excessive densification of the water mist and the effect of extinction due to recombination of radicals generated in the plasma.

[Reference Example 1]
Chemical species to be a sterilization element at the time of each plasma irradiation when mist generated using the plasma surface treatment apparatus of the present invention is used, when mist is not generated, and when mist generated by an ultrasonic transducer is used In order to identify this, the atmosphere in the downstream part of the plasma was collected in a gas concentration detector tube (manufactured by Gastec Corporation, 32, 18M) and measured. The measurement was carried out under the same conditions as in Examples 1 and 2 and Comparative Examples 1, 2, and 3 after 15 minutes from the generation of plasma. Moreover, since measurement is possible only for chemical species having a relatively long life, the measurement object is limited to H ₂ O ₂ and O ₃ . The measurement results are shown in Table 1 below.

As shown in Table 1, when no mist was generated, H ₂ O ₂ was below the detection limit, but the O ₃ concentration was increased to 12 ppm. On the other hand, in the case of using the mist generated using the plasma surface treatment apparatus of the present invention, in the case of using the mist generated by the ultrasonic vibrator, H ₂ O ₂ rises to ₂ ppm, and O ₃ The concentration was 0.3 to 0.4 ppm. In both cases, despite the fact that H ₂ O ₂ is equivalent, a large difference is observed in the obtained D value, so that it is considered that H ₂ O ₂ is not the main factor of sterilization.

  Therefore, the temperature of the workpiece during plasma irradiation was measured with a thermocouple. The results are also shown in Table 1. As a result, when the mist generated using the plasma surface treatment apparatus of the present invention was used and when the mist generated by the ultrasonic vibrator was used, a temperature increase was observed up to around 130 ° C. There is almost no difference in the temperature of the object to be processed at the time of plasma irradiation between the two, and it cannot be considered that the cause of the large difference in the D value is the temperature. Then, next, the active chemical species which becomes a sterilization element at the time of plasma irradiation was identified.

[Reference Example 2]
In the case of supplying water in the form of mist by generating mist by the method of the present invention, in the case of not supplying water, and in the case of supplying water in the form of mist by generating mist with an ultrasonic vibrator, In order to identify active chemical species that are sterilization elements during plasma irradiation, a spectroscope (Ocean Optics, USB2000) was attached at a position 1 cm downstream of the plasma, and emission spectroscopic analysis of each plasma was performed. The measurement was performed under the same conditions as in Examples 1 and 2 and Comparative Examples 1, 2, and 3.

  In FIG. 9, (a) when mist is generated by an ultrasonic vibrator and water is supplied in the form of mist, (b) when mist is generated by the method of the present invention and water is supplied in the form of mist, (C) An emission spectrum of plasma generated when water is not supplied is shown. As shown in (c), when water is not supplied, very strong light emission from atomic oxygen is observed. This is presumed to be generated by dissociation of oxygen supplied in the plasma. On the other hand, as shown in (b), when water is supplied in the form of mist by generating mist by the method of the present invention, light emission from OH radical is strongest, followed by He, Luminescence from atomic oxygen and atomic hydrogen is observed. However, as shown in (a), when water is supplied in the form of mist by generating mist with an ultrasonic transducer, the emission from OH radicals is the strongest compared to the case of (b). However, the overall emission intensity is weak, and it can be seen that light emission from atomic oxygen can hardly be observed. From the above results, it is considered that there is a high possibility that the strong sterilization effect when the mist is supplied using the method of the present invention, that is, the porous material, is caused by a reaction involving OH radicals.

  Thus, when using the mist generated by the ultrasonic vibrator, the tendency that the emission of OH radicals is the strongest is the same as when using a porous body, but the overall emission intensity is low. Therefore, the slow rate of sterilization when using mist generated by an ultrasonic transducer is due to power shortage due to excessive mist supply and reduced transpiration effect in plasma due to excessive mist size. It is thought that. That is, when generating mist using the porous body of the present invention, it was considered that good control over the amount and size of the generated mist produced good results. When the apparatus of the present invention is used, many conditions considered to be related to the generation of mist, such as the supply rate of the liquid active substance, the average particle diameter of the pores of the porous body, the surface characteristics of the porous body (hydrophilic Etc.), the flow rate of gas passing through the porous body, the porosity of the porous body, and the like can be used for controlling the generation of mist. Therefore, it is considered that it is possible to increase the speed of the surface treatment by generating an appropriate amount and an optimal size of mist.

[Reference Example 3]
Whether the amount of OH radicals in the plasma changes between upstream and downstream of the plasma under the same conditions as in Examples 1 and 2 was measured by emission spectroscopic analysis upstream and downstream from the side of the discharge space 4, The amount of OH radicals was the same upstream and downstream of the plasma. From this, even when the distance between the upstream and downstream of the plasma is reduced, the amount of OH radicals reaching the workpiece 7 is the same and the same sterilization effect can be obtained. The distance can be reduced. As a result, it is possible to reduce the electric power used, and the temperature of the plasma treatment can be further lowered.

[Example 3: Oxidation treatment of Si surface using plasma surface treatment apparatus of the present invention]
<Oxidation treatment of Si surface using plasma surface treatment apparatus of the present invention>
As shown in FIG. 2, using the same apparatus as in Example 1 except that the Si substrate 7 is disposed in the portion of the ground electrode 3 that is in contact with the discharge space 4, that is, the portion facing the power application electrode 2, Oxidation treatment was performed. The Si substrate is in contact with the ground electrode 3 and is connected to the ground.

A mixed gas of He and oxygen flows into a rectangular chamber formed by an acrylic spacer, a stainless steel substrate provided with a Si substrate and grounded, and an aluminum electrode connected to a 13.56 MHz RF power source via a matching box A 1 mm gap was formed between them, and atmospheric pressure plasma was generated in this space. The electrode area was 30 × 30 mm ² . A porous carbon surface-treated in the same manner as in Example 1 was installed in the middle of a rectangular chamber, and about 25 μl of ultrapure water per minute was sequentially dropped onto the upper surface, and a He + O ₂ gas was allowed to flow to mist the water. Was generated. The flow rates of He and O ₂ were controlled by a mass flow controller.

  Oxidation was performed with plasma generation conditions of input power: 80 W, total flow rate: 10 SLM, oxygen concentration in the mixed gas: 0.5 vol%, and plasma irradiation time: 75 minutes.

<Evaluation of oxidation treatment>
Infrared absorption of the portion corresponding to the upstream, middle and downstream portions of the gas flow including mist in the discharge space 4 of the Si substrate after the oxidation treatment is measured using FTIR (manufactured by Shimadzu Corporation, PC-8600). The results are shown in FIG. The upper part of the figure shows the spectrum of the upstream Si substrate, the middle part of the figure shows the spectrum of the middle Si substrate, and the lower part of the figure shows the spectrum of the downstream Si substrate. In any spectrum, an absorption peak due to the Si—O bond was observed at wavelengths of 1100 to 1200 cm ⁻¹ , confirming the growth of the oxide film.

  As described above, the plasma surface treatment apparatus according to the present invention allows the carrier gas or the mixed gas to pass through in a state in which the porous substance is infiltrated with the liquid substance to be generated as mist. Since the mist is formed and mixed with the carrier gas or the mixed gas, the surface treatment of the workpiece can be speeded up. In addition, since glow discharge plasma at atmospheric pressure is used, an expensive vacuum apparatus is not required and surface treatment can be performed at a low temperature, and such surface treatment can be performed at high speed.

  Therefore, it is very useful as a simple and inexpensive sterilization method for non-heat-resistant products such as plastic products in food processing, pharmaceutical manufacturing, medical fields and the like. In addition, it is very useful for oxidation treatment, nitriding treatment, reduction treatment, CVD treatment, etc., and not only can it be used in various manufacturing industries that perform these surface treatments, but also incorporates surface treated materials. However, it can be used in the electronic equipment manufacturing industry that manufactures various products, and is considered to be very useful.

It is a figure which shows one Embodiment of the plasma surface treatment apparatus concerning this invention. It is a figure showing one embodiment of a plasma surface treatment apparatus concerning the present invention. It is a figure showing one embodiment of a plasma surface treatment apparatus concerning the present invention. It is a figure showing one embodiment of a plasma surface treatment apparatus concerning the present invention. It is a figure showing one embodiment of a plasma surface treatment apparatus concerning the present invention. It is a figure showing one embodiment of a plasma surface treatment apparatus concerning the present invention. It is a graph which shows the survival curve of the indicator bacteria obtained as a result of the sterilization process performed in the Example and the comparative example, (a) is a graph which shows the survival curve of the indicator bacteria obtained when mist was not supplied. And (b) is a graph showing the survival curve of the indicator fungus obtained when using the mist generated using the plasma surface treatment apparatus of the present invention, and (c) is a graph generated by an ultrasonic transducer. It is a graph which shows the survival curve of the indicator microbe obtained when using mist. It is a figure which shows the result of the electron microscope observation of the indicator microbe before and after the sterilization process performed in the Example and the comparative example, (a) is a figure which shows the result of the electron microscope observation of the indicator microbe before the sterilization process, (b) is a figure which shows the result of the electron microscope observation of the indicator microbe after the sterilization processing obtained when not supplying mist, (c) is the mist generated using the plasma surface treatment apparatus of this invention It is a figure which shows the result of the electron microscopic observation of the indicator microbe after the sterilization process obtained when using. It is a diagram showing an emission spectrum of plasma generated in Examples and Comparative Examples, (a) is a diagram showing an emission spectrum when water is supplied in the form of mist by generating mist with an ultrasonic vibrator, (B) is a figure which shows the emission spectrum at the time of generating mist by the method of this invention, and supplying water in the form of mist, (c) is a figure which shows the emission spectrum of the plasma produced | generated when not supplying water. It is. In an Example, it is a figure which shows the result of having measured the infrared absorption of the part applicable to the upstream of the gas flow containing the mist in the discharge space, the middle flow, and the downstream part of the Si substrate after an oxidation process by FTIR.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Chamber 2 Electric power application electrode 3 Ground electrode 4 Discharge space 5 Matching circuit 6 Power source for plasma generation 7 Processed object 8 Gas supply part 9 Porous body 10 Liquid supply part 11 Opening part 12 Liquid active substance 13 Tank 14 Supply pipe 15 Insulating container 21 Chamber 22 Power application electrode 23 Ground electrode 24 Discharge space 25 Spacing material 26 Fixing member 27 Gas introduction pipe 28 Liquid introduction pipe 29 Metal rod 30 Shield 31 Flange 32 Flange

Claims (13)

In a plasma surface treatment apparatus for treating a surface of an object to be processed by generating plasma by glow discharge and irradiating the plasma or a gas that has passed through the plasma,
A porous body for generating a liquid active substance as a mist is provided on the flow path of at least one gas supplied to the discharge space and upstream of the discharge space. A mist of the active substance is formed and contained in the gas by passing the at least one gas in a state in which the liquid active substance generated as mist is infiltrated. Plasma surface treatment equipment.   2. The plasma surface treatment apparatus according to claim 1, wherein an average pore diameter of the pores of the porous body is 0.1 μm or more and 50 μm or less. It has a power application electrode and a ground electrode facing each other,
The plasma surface treatment apparatus according to claim 1, wherein the porous body also serves as a power application electrode.   The plasma surface treatment apparatus according to claim 3, wherein the porous body is a metal, a semiconductor, porous carbon, or porous silicon carbide. It has a power application electrode and a ground electrode facing each other,
3. The plasma surface according to claim 1, wherein the gas supplied to the discharge space is introduced into the discharge space in a direction along a mutually opposing surface of the power application electrode and the ground electrode facing each other. Processing equipment.   6. The plasma surface treatment apparatus according to claim 5, wherein the porous body is made of carbon, glass, quartz, ceramics, organic polymer, or metal.   The plasma surface treatment apparatus according to claim 1, further comprising liquid supply means for supplying the liquid active substance to the porous body.   The plasma surface treatment apparatus according to claim 1, wherein plasma is generated under atmospheric pressure.   9. The contact angle (wetting angle) between the substance constituting the porous body and the liquid active substance is an acute angle, according to any one of claims 1 to 8. Plasma surface treatment equipment.   The at least one gas supplied to the discharge space includes at least one gas selected from the group consisting of He, Ar, Ne, Kr, Xe, and nitrogen. The plasma surface treatment apparatus according to any one of the above.   The plasma surface treatment apparatus according to any one of claims 1 to 10, which is a sterilization treatment apparatus, an oxidation treatment apparatus, a nitridation treatment apparatus, a reduction treatment apparatus, an etching treatment apparatus, or a CVD treatment apparatus.   The plasma surface treatment according to claim 1, wherein the liquid active substance is water, hydrogen peroxide water, ozone water, carbonated water, an organic solvent, or silicone oil. apparatus.   11. The liquid active substance is (i) an organometallic compound or an inorganic metal compound that is liquid at room temperature and normal pressure, or (ii) a solution of an organometallic compound or an inorganic metal compound. The plasma surface treatment apparatus according to any one of the above.