JP2022075126A - Plasma sterilizer - Google Patents

Abstract

To provide a plasma device capable of performing plasma treatment not only for sterilization, but also for various objects, with less temperature increase of the objects.SOLUTION: A plasma sterilizer 10 according to the present invention includes: a first electrode 13 that is provided so as to face an object to be treated 19 arranged in a treatment chamber 16; a plate-shaped second electrode 14 having through holes 141 that is provided between the object to be treated 19 and the first electrode 13; a gas supply unit 30 that supplies a plasma source gas between both electrodes 13 and 14; and a power supply unit 21 that supplies plasma generating high-frequency power to the second electrode 14 with using the first electrode 13 as a grounding electrode.SELECTED DRAWING: Figure 1

Description

The present invention sterilizes or sterilizes medical devices (instruments used for medical practices specified in the Pharmaceutical Machinery Law, such as surgical instruments such as swords and endoscopes and diagnostic instruments used for medical practices) using plasma (hereinafter collectively referred to as). It is called sterilization.)

Including the new coronavirus, viruses that are easily denatured and have strong infectivity, and drug-resistant bacteria that are resistant to drugs such as antibiotics and alcohol are emerging and are becoming a threat to society. In order to prevent the outbreak of infectious diseases in medical institutions, it is important to sterilize the medical device manufacturer before shipping and in the remanufacturing process by the medical device remanufacturer. In addition, in the event of a pandemic situation, medical equipment may be reused as a special case at medical institutions. In that case, it is necessary to sterilize the medical device once used because there is a possibility that a pathogen that causes an infectious disease may adhere to the medical device.

High-pressure steam or high-temperature dry air is generally used for sterilization of such medical devices. However, some of the constituent materials of medical devices do not have resistance to high temperature and high pressure, which causes deformation and corrosion and deterioration of the surface of the device. There is also a method of using a bactericidal gas such as ethylene oxide gas or formalin, but in this method, the bactericidal gas may remain on the object even after the treatment, which adversely affects the subsequent use of the object. Post-treatment is required to remove the bactericidal gas, as it can have an effect.

Therefore, attention is being paid to a method of sterilizing using plasma. In this method, a raw material is gasified in a sterilization chamber under reduced pressure, then the gasified raw material is turned into plasma, and the ions are irradiated to an object in the sterilization chamber to perform sterilization treatment. Plasma conversion of the raw material gas is performed by applying high frequency power to the electrodes installed in the sterilization chamber. For example, in Patent Document 1, a sterilizing agent such as gasified hydrogen peroxide is passed through a cylindrical reticulated electrode arranged in a processing chamber (chamber), and high-frequency power is applied to the electrode to generate plasma. As a result, the object placed in the electrode is sterilized.

On the other hand, Patent Document 2 and Patent Document 3 disclose a plasma sterilizer that turns into plasma by using flat plate electrodes arranged vertically in the processing chamber. These sterilizers use highly safe water vapor as a raw material, and sterilize the object by irradiating the object with active species (mainly OH ^- ions, etc.) generated by plasmaizing the water vapor.

Japanese Unexamined Patent Publication No. 2000-308675 Japanese Unexamined Patent Publication No. 2003-310719 Japanese Unexamined Patent Publication No. 2008-188032

If the object is sterilized with OH ^- ions, there is no problem that harmful substances remain, but if the ion is continuously irradiated during the treatment, there is a problem that the temperature of the object rises due to the impact of the ions. Therefore, it is not suitable for sterilization of objects with low heat resistance.

The present invention has been made to solve such a problem of the prior art, and an object thereof is not only in sterilization treatment but also in plasma treatment performed on various objects. It is an object of the present invention to provide a plasma apparatus capable of performing a process that does not raise the temperature.

The plasma processing apparatus according to the present invention made to solve the above problems is
The first electrode provided so as to face the object to be processed arranged in the processing chamber, and
A plate-shaped second electrode having a through hole provided between the object to be treated and the first electrode, and a plate-shaped second electrode.
A gas supply unit that supplies a gas that becomes plasma between the first electrode and the second electrode,
The first electrode is used as a grounding electrode, and the second electrode is provided with a power supply unit for supplying high-frequency power for turning the gas into plasma.

In the plasma processing apparatus according to the present invention, after arranging an object to be processed in the processing chamber, a gas that becomes plasma (plasma source gas) is supplied between the first electrode and the second electrode by a gas supply unit. This plasma source gas may be supplied between the first electrode and the second electrode, or may be supplied to the side of the first electrode opposite to the second electrode by providing a through hole in the first electrode. good.

Then, the first electrode is grounded, and high-frequency power is supplied to the second electrode by the power supply unit to turn the plasma source gas into plasma. The plasma source gas, which is wholly or partially ionized (this is called plasma gas), is directed toward the object to be processed through the through hole provided in the second electrode by the rear pressure of the plasma source gas supplied from the gas supply source. And move. At that time, in this through hole, due to the potential of the high frequency power applied to the second electrode, some of the ions in the plasma gas are deprived of electric charges (electrons) or are given electric charges (electrons), and are radicals. Will be. As a result, a part of the ions irradiated to the object to be treated becomes radicals, so that a predetermined process such as sterilization of the object to be treated is performed, while the temperature rise of the object to be treated is reduced or suppressed.

Here, it is desirable that the volume of the through hole of the second electrode is large enough to resonate the ions in the plasma gas corresponding to the frequency of the high frequency power and the plasma gas.

By doing so, when the plasma gas passes through the through hole, the ions in the plasma gas are likely to stay in the through hole, and the radicalization is promoted.

It is desirable that a plurality of the through holes are provided in the second electrode. As a result, the efficiency of the radicalization is increased, and more ions are radicalized so that the object to be treated is irradiated.

As an example of the plasma gas, water vapor can be mentioned.

When the plasma processing apparatus according to the present invention is used for the purpose of sterility or cleaning, there is no problem even if the plasma gas remains on the object to be treated by doing so. In addition, for the purpose of sterility, OH ^- ions generated by plasma conversion of plasma gas and OH radicals radicalized from the OH-ions have a strong sterility effect, so effective sterility treatment should be performed. Can be done.

In the plasma processing apparatus according to the present invention, since a part of the ions irradiated on the object to be processed becomes radicals, the predetermined plasma treatment on the object to be processed is performed, while the temperature rise of the object to be processed is reduced or suppressed. To. Therefore, it is possible to perform plasma treatment even on a treatment target having low heat resistance. The treatment targeted by the plasma processing apparatus according to the present invention includes not only sterilization treatment but also cleaning treatment for various treatment objects, and is further applicable to etching, film formation and the like.

The figure which shows typically the cross section of the main body of the plasma sterilization apparatus which is one Embodiment of the plasma processing apparatus which concerns on this invention, and various peripheral devices connected to it. FIG. 3 is an enlarged cross-sectional view of an upper electrode and a lower electrode of the plasma sterilizer according to the embodiment of FIG. The figure which shows typically the cross section of the main body of the plasma sterilization apparatus which is another embodiment of the plasma processing apparatus which concerns on this invention, and various peripheral devices connected to it. FIG. 3 is an enlarged cross-sectional view of an upper electrode and a lower electrode of the plasma sterilizer according to the embodiment of FIG. Enlarged plan view of the lower electrode. Explanatory drawing which shows one method for making a honeycomb-shaped electrode (plate). Flow chart when sterilizing the object to be treated. A table of the results of investigating the quality of plasma generation when the size of the through hole of the lower electrode and the pressure in the processing space are changed in various ways. Plan views of lower electrodes of various embodiments, in which circular through holes are densely arranged (a), rectangular nets are arranged (b), triangular through holes are densely arranged (c), and slits are formed. The through holes are arranged (d), the through holes whose slit widths change regularly (e), and the cross-shaped through holes are arranged regularly (f).

The plasma sterilizer 10 which is an embodiment of the plasma processing apparatus according to the present invention will be described with reference to the drawings.

<1. Configuration of plasma sterilizer>
FIG. 1 schematically shows a cross section of the main body of the plasma sterilizer 10 of the present embodiment and various peripheral devices connected to the cross section. As is clear from FIG. 1, the plasma sterilizer 10 is a parallel plate type (capacitive coupling type) plasma processing device, and is arranged substantially parallel to the upper part of the processing table 12 provided in the sealable housing 11. It has two electrodes (upper electrode 13 and lower electrode 14). The upper electrode 13 corresponds to the first electrode, and the lower electrode 14 corresponds to the second electrode. Of these, the lower electrode 14 facing the processing object 19 placed on the processing table 12 is in contact with the peripheral wall of the housing 11 via an insulator, and partitions the upper space in the housing 11. ing. A large number of through holes 141 are formed in the lower electrode 14. The lower electrode 14 will be described in detail later. A door 15 for loading and removing the object 19 to be processed is provided on the side wall of the housing 11 below the lower electrode 14. The space below the lower electrode 14 in the housing 11 is called a processing space 16.

An introduction pipe 31 for introducing a plasma source gas is provided between both electrodes 13 and 14 of the housing 11. The introduction pipe 31 is connected to the water tank 32, and the introduction pipe 31 between the water tank 32 and the outlet in the housing 11 is provided with a vaporizer (vaporizer) 33, a mass flow controller 34, and a valve 35 in this order. These constitute the plasma source gas supply unit 30.

As shown in FIGS. 3 and 4, the introduction pipe 31 may be provided between the housing 11 and the upper electrode 132. In this case, the upper electrode 132 having a large number of through holes 131 is used so that the water vapor introduced from the introduction pipe 31 is diffused and uniformly supplied to the space between the upper electrode 132 and the lower electrode 13.

An exhaust pipe 41 is provided below the housing 11 (that is, below the processing space 16), and the exhaust pipe 41 is provided with an on-off valve 42 and an exhaust pump 43. These form the exhaust unit 40.

Of the two electrodes, the upper electrode 13 is grounded and the lower electrode 14 is connected to the high frequency power supply 21. A matching unit 22 for performing impedance matching is provided between the high frequency power supply 21 and the lower electrode 14.

The wall surface of the housing 11 has a pressure gauge (P) 51 for measuring the pressure in the processing space 16, and the processing table 12 has a thermometer (T) for measuring the temperature of the object 19 to be processed. ) 52 is provided.

The plasma sterilizer 10 is also provided with a control unit (CTRL) 50, which receives signals from sensors such as the pressure gauge 51 and the thermometer 52, and according to a program given in advance, the plasma source gas supply unit 30. By controlling each part such as the exhaust part 40 and the high frequency power supply 21, the object to be processed 19 is sterilized.

<2. Configuration of lower electrode>
As described above, the lower electrode 14 is perforated with a large number of through holes 141 (FIG. 2). As shown in FIG. 5, the through hole 141 has a regular hexagonal shape, and the through holes 141 are densely arranged in the lower electrode 14 (that is, as a honeycomb shape) in the entire lower electrode 14. It is desirable to make the ratio of the area of the through hole 141 as large as possible. This improves the efficiency of the sterilization treatment of the object 19 to be treated with plasma gas.

Such a honeycomb-shaped electrode (plate) may be produced by drilling through holes 141 in a metal plate material, but as shown in FIG. 6, elongated metal plates are formed at regular intervals of 120 degrees. It can be manufactured by stacking a large number of parts 142 bent on the front and back. As the metal of the electrode, aluminum, copper, silver or the like can be used as in the conventional case.

As the lower electrode 14, in addition to the honeycomb-shaped one, as shown in FIG. 9, the circular through holes are densely arranged (a), the rectangular net-like one (b), and the triangular through holes are densely arranged. Arranged (c), slit-shaped through holes arranged (d), through holes with regularly changing slit width (e), cross-shaped through holes arranged regularly (f) etc. may be used. By making the shape of the through hole into these shapes, it is possible to widen the accommodation frequency band when ions stay in the through hole.

<3. Operation of plasma sterilizer>
The flow of sterilizing the object 19 to be processed using the plasma sterilizer 10 of the present embodiment will be described with reference to the flowchart of FIG. First, the door 15 of the housing 11 is opened, and the object 19 to be processed is placed on the processing table 12 (step S1). Then, the door 15 is closed, and the inside of the housing 11 is sufficiently exhausted by the exhaust unit 40 (step S2).

Next, the plasma source gas supply unit 30 introduces water vapor (H ₂ O) into the space between the upper electrode 13 and the lower electrode 14 at a predetermined flow rate (step S3), and plasma the water vapor at that flow rate into the lower electrode 14. High-frequency power is applied to make the plasma (step S4). As a result, the water vapor in the space between the upper electrode 13 and the lower electrode 14 is turned into plasma, and ions such as OH- ^, H ⁺ , and H ₃ O ⁺ generated by plasma formation and H ₂ O, etc. that have not yet been turned into plasma. Becomes the mixed plasma gas 18. The plasma gas 18 is sequentially sent to the processing space 16 through the through hole 141 of the lower electrode 14 by the pressure of the water vapor introduced from the introduction pipe 31 (FIG. 2), and is irradiated to the processing object 19.

Here, when the plasma gas 18 passes through the through hole 141, energy is received again from the lower electrode 14, and the ion dissociation of water vapor (H ₂ O) proceeds. In addition, most of the hydrogen ions (H ⁺ ) during plasma formation collide with the wall surface of the lower electrode 14 (through hole 141) and disappear, while the hydroxy ions (OH ⁻ ) are extinguished by the lower electrode 14 (through hole 141). ), When it comes into contact with the wall surface or the like, an electron (e ⁻ ) is emitted there by a high frequency voltage applied to the lower electrode 14, and it becomes a neutral hydroxy radical (OH ^* ). Since this hydroxyl radical has a strong sterilizing action, the plasma sterilizing apparatus 10 of the present embodiment can perform a strong sterilizing treatment on the object 19 to be treated. Further, since the ratio of radicals in the plasma gas 18 irradiated to the object 19 to be processed increases, the temperature of the object 19 to be processed is less likely to be raised than when only ions are irradiated.

In this way, after irradiating the treatment object 19 with the plasma gas 18 for a predetermined time (step S5), the input of high-frequency power and the introduction of steam are stopped, and the sterilization treatment is completed. The exhaust unit 40 continues to operate for a while even after the input of high-frequency power and the introduction of water vapor are stopped, and the bactericidal gas is discharged from the inside of the housing 11. It goes without saying that appropriate detoxification treatment is performed for the discharged gas. After the end processing is completely completed, the object 19 to be processed is taken out from the inside of the housing 11 (step S6).

<4. Example>
In order to sufficiently sterilize the object 19 to be treated by the above-mentioned action, plasma must be stably formed. Since the lower electrode 14 is provided with a through hole 141 in the plasma sterilizer 10, it was decided to search for conditions for stable plasma formation.

The size of the lower electrode 14 of the plasma sterilizer 10 used is 338 × 648 mm, and the thickness is 10 mm. Circular through holes 141 of various sizes were densely provided in the lower electrode 14. Specifically, the diameter Φ of the through holes was set to 10, 15, 20, 25, 30, 35, 40 mm, and the distance d between adjacent through holes was set to 2.5 mm. When the through holes are of their size (and the distance d between adjacent through holes is 2.5 mm), the area of each through hole, the area ratio of the through hole to the area of the lower electrode (opening ratio), and each through hole. The volume of the holes is shown in FIG. The opening rate of the through hole in the lower electrode is preferably 40 to 90%, more preferably 60 to 90%. The volume of each through hole is preferably 100 to 20000 mm ³ , more preferably 100 to 15000 mm ³ .

Then, for each lower electrode 14, the magnitude of the high frequency power (frequency is 13.56 MHz) to be input is set to 300 W (0.136 W / cm ² ), and the flow rate of water vapor introduced between both electrodes 13 and 14 is set to 20 sccm. While fixing each, the pressure in the processing space 16 was changed to 50, 80, 90, 120 Pa by changing the exhaust strength by the exhaust unit 40, and the quality of plasma generation in each case was visually examined. The results are shown in the table of FIG. In the table of FIG. 8, ◯ indicates that the plasma was stably generated and the state in which the high concentration was maintained in the through hole 141 continued. By continuing such a state, the plasma gas can stay in the through hole 141 for a slightly long time, so that a relatively large amount of ions in the plasma gas are easily converted into radicals. In the table of FIG. 8, x indicates that the plasma generation was not stable, the plasma gas rapidly flowed out toward the processing space 16, and the plasma gas did not stay in the through hole 141 very much. Δ indicates that the plasma gas was retained in the through hole 141, but the thickness in the through hole 141 was reduced and the concentration was low.

The retention of plasma gas in the through hole 141 is the mass-to-charge ratio of ions in the plasma gas (m / z), the frequency (f) of the high frequency voltage applied to the lower electrode 14, and the size of the through hole 141. It is considered to depend on (diameter Φ or volume V). In the case of this embodiment, the main ion in the plasma gas is hydroxy ion (OH ⁻ ), but in that case, the conditions in the range of ○ in the table of FIG. 8 are effective in plasma treatment such as sterilization. It turns out that it is a condition that works.

10 ... Plasma sterilizer 11 ... Housing 12 ... Processing table 13, 132 ... Upper electrode 14 ... Lower electrode 131, 141 ... Through hole 15 ... Door 16 ... Processing space 18 ... Plasma gas 19 ... Processing object 21 ... High frequency power supply 22 ... Matching unit 30 ... Plasma source gas supply unit 40 ... Exhaust unit 50 ... Control unit

Claims (7)

The first electrode provided so as to face the object to be processed arranged in the processing chamber, and
A plate-shaped second electrode having a through hole provided between the object to be treated and the first electrode, and a plate-shaped second electrode.
A gas supply unit that supplies a gas that becomes plasma between the first electrode and the second electrode,
A plasma processing apparatus comprising the first electrode as a grounding electrode and a power supply unit for supplying high-frequency power for converting the gas into plasma to the second electrode. The plasma processing apparatus according to claim 1, wherein the gas supply unit supplies the gas between the first electrode and the second electrode. The plasma processing apparatus according to claim 1, wherein the first electrode has a through hole, and the gas supply unit supplies the gas to the side of the first electrode opposite to the second electrode. The plasma processing apparatus according to any one of claims 1 to 3, wherein a plurality of through holes of the second electrode are provided in the second electrode. The plasma processing apparatus according to claim 4, wherein the planar shape of the through hole of the second electrode is a regular hexagon, and the second electrode is densely provided. The plasma processing apparatus according to claim 4, wherein the through hole of the second electrode has a circular planar shape and is densely provided on the second electrode. The plasma processing apparatus according to any one of claims 1 to 6, wherein the gas is steam (H ₂ O).

Images