Plasma Sterilizer

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

[Technical field]

[0001] The present invention relates to an apparatus for sterilizing or disinfecting (hereinafter collectively referred to as sterilization) medical devices (instruments used in medical procedures defined in the Pharmaceutical and Medical Device Act, for example surgical instruments such as scissors and endoscopes, and diagnostic equipment used in medical procedures) using plasma. [Background technology]

[0002] The emergence of easily denatured and highly infectious viruses, such as the new coronavirus, and drug-resistant bacteria that are resistant to drugs such as antibiotics and alcohol, are becoming a threat to society. In order to prevent the outbreak of infectious diseases in medical institutions, it is important for medical device manufacturers to sterilize medical devices before shipping and for medical device remanufacturers to sterilize medical devices during the remanufacturing process. In addition, in the event of a pandemic, medical institutions may exceptionally reuse medical devices. In such cases, sterilization is required because there is a possibility that pathogens that cause infectious diseases may be attached to medical devices that have been used once.

[0003] Sterilization of such medical devices generally uses high-pressure steam or high-temperature dry air. However, some of the materials that make up the medical devices are not resistant to high temperatures and pressures, which can cause deformation, corrosion, and deterioration of the instrument surface. There are also methods that use sterilizing gases such as ethylene oxide gas and formalin, but with this method, there is a risk that the sterilizing gas will remain in the object after treatment, which may have a negative effect on the subsequent use of the object, and therefore post-treatment is required to remove the sterilizing gas.

[0004] Therefore, a method of sterilization using plasma has been attracting attention. In this method, raw materials are gasified in a sterilization chamber under reduced pressure, and then the gasified raw materials are turned into plasma, and the ions are irradiated onto objects in the sterilization chamber to perform sterilization. The raw material gas is turned into plasma by applying high-frequency power to an electrode installed in the sterilization chamber. For example, in Patent Document 1, a sterilizing agent such as gasified hydrogen peroxide is passed through a cylindrical mesh electrode installed in a treatment chamber (chamber), and the sterilizing agent is turned into plasma by applying high-frequency power to the electrode, thereby sterilizing an object placed in the electrode.

[0005] On the other hand, Patent Documents 2 and 3 disclose plasma sterilization devices that use flat plate electrodes arranged parallel to one another in a treatment chamber to generate plasma. These sterilization devices use highly safe water vapor as a raw material, and the activated species (mainly OH) generated by converting the water vapor into plasma are - Sterilization is carried out by irradiating the object with ultraviolet light (e.g., ions). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2000-308675 A [Patent Document 2] JP 2003-310719 A [Patent Document 3] JP 2008-188032 A Summary of the Invention [Problem to be solved by the invention]

[0007] OH - Sterilizing objects with ions does not have the problem of leaving harmful substances behind, but if the objects are continuously irradiated with ions during processing, the temperature of the objects increases due to the impact of the ions, making it unsuitable for sterilizing objects with low heat resistance.

[0008] The present invention has been made to solve such problems in the prior art, and its object is to provide a plasma device that can perform plasma processing on various objects, not limited to sterilization processing, with minimal increase in the temperature of the object. [Means for solving the problem]

[0009] In order to solve the above problems, the plasma processing apparatus according to the present invention comprises: a first electrode provided to face an object to be treated placed in the treatment chamber; a plate-shaped second electrode having a through hole and provided between the object to be processed and the first electrode; a gas supply unit that supplies a gas that becomes plasma between the first electrode and the second electrode; a power supply unit that supplies high-frequency power to the second electrode using the first electrode as a ground electrode to generate plasma from the gas; The present invention is characterized by comprising:

[0010] In the plasma processing apparatus according to the present invention, after placing the object to be processed in the processing chamber, a gas (plasma source gas) that will become plasma between the first electrode and the second electrode is supplied by the 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.

[0011] Then, the first electrode is grounded, and high frequency power is supplied to the second electrode by the power supply unit to convert the plasma source gas into plasma. The plasma source gas, which is fully or partially ionized (referred to as plasma gas), moves toward the object to be treated through the through-holes provided in the second electrode due to the back pressure of the plasma source gas supplied from the gas supply source. At this time, in the through-holes, some of the ions in the plasma gas are deprived of charge (electrons) or given charge (electrons) due to the potential of the high frequency power applied to the second electrode, becoming radicals. As a result, some of the ions irradiated to the object to be treated become radicals, so that a predetermined treatment 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.

[0012] Here, it is desirable that the through hole of the second electrode has a volume large enough to resonate with the ions in the plasma gas in response to the frequency of the high frequency power and the plasma gas.

[0013] By doing so, when the plasma gas passes through the through-holes, the ions therein tend to remain within the through-holes, promoting the formation of the radicals.

[0014] It is preferable that a plurality of the through holes are provided in the second electrode, which increases the efficiency of the radicalization, so that a larger number of ions are radicalized and irradiated onto the object to be treated.

[0015] An example of the plasma gas is water vapor.

[0016] When the plasma processing apparatus according to the present invention is used for the purpose of sterilization or cleaning, there is no problem even if the plasma gas remains on the object to be processed. - The ions and the OH radicals produced by the ions have a strong sterilizing effect, making it possible to carry out an effective sterilization process. Effect of the Invention

[0017] In the plasma processing apparatus according to the present invention, some of the ions irradiated to the object to be processed become radicals, so that the predetermined plasma processing is performed on the object to be processed while the temperature rise of the object to be processed is reduced or suppressed. Therefore, it is possible to perform plasma processing on objects with low heat resistance. Processing that can be performed by the plasma processing apparatus according to the present invention includes sterilization processing, cleaning processing for various objects to be processed, and can also be applied to etching, film formation, etc. [Brief description of the drawings]

[0018] [Figure 1] 1 is a schematic cross-sectional view of a main body of a plasma sterilization apparatus, which is one embodiment of a plasma processing apparatus according to the present invention, and various peripheral devices connected thereto; [Diagram 2] FIG. 2 is an enlarged cross-sectional view of the upper electrode and the lower electrode of the plasma sterilization apparatus according to the embodiment of FIG. 1. [Diagram 3] FIG. 13 is a schematic cross-sectional view of a main body of a plasma sterilization apparatus, which is another embodiment of a plasma processing apparatus according to the present invention, and various peripheral devices connected thereto. [Figure 4] FIG. 4 is an enlarged cross-sectional view of the upper electrode and the lower electrode of the plasma sterilization apparatus of the embodiment of FIG. 3. [Diagram 5] FIG. [Figure 6] FIG. 2 is an explanatory diagram showing one method for producing a honeycomb-shaped electrode (plate). [Figure 7] 11 is a flowchart showing a process for sterilizing an object to be treated. [Figure 8] 13 is a table showing the results of an investigation into the quality of plasma generation when the size of the through hole in the lower electrode and the pressure in the processing space are changed in various ways. [Figure 9] Plan views of various types of lower electrodes, including (a) a dense arrangement of circular through-holes, (b) a rectangular mesh-like arrangement, (c) a dense arrangement of triangular through-holes, (d) an arrangement of slit-shaped through-holes, (e) an arrangement of through-holes with regularly varying slit widths, and (f) a regular arrangement of cross-shaped through-holes. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] A plasma sterilization apparatus 10, which is one embodiment of a plasma processing apparatus according to the present invention, will be described with reference to the drawings.

[0020] <1. Plasma sterilization device configuration> FIG. 1 is a schematic diagram showing a cross section of the main body of the plasma sterilization device 10 of this embodiment and various peripheral devices connected thereto. As is clear from FIG. 1, the plasma sterilization device 10 is a parallel plate type (capacitively coupled type) plasma processing device, and has two electrodes (upper electrode 13 and lower electrode 14) arranged approximately parallel to each other above a processing stage 12 provided in a sealable housing 11. 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 stage 12 is in contact with the peripheral wall of the housing 11 via an insulator, and divides the upper space in the housing 11. The lower electrode 14 is perforated with a large number of through holes 141. The lower electrode 14 will be described in detail later. A door 15 for loading and unloading the processing object 19 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 the processing space 16.

[0021] An introduction pipe 31 for introducing a plasma source gas is provided between the two electrodes 13, 14 of the housing 11. The introduction pipe 31 is connected to a water tank 32, and a vaporizer 33, a mass flow controller 34, and a valve 35 are provided in this order in the introduction pipe 31 between the water tank 32 and an outlet inside the housing 11, which constitute a plasma source gas supply unit 30.

[0022] 3 and 4, the introduction pipe 31 may be provided between the housing 11 and the upper electrode 132. In this case, an 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 uniformly supplied to the space between the upper electrode 132 and the lower electrode 13 while diffusing.

[0023] An exhaust pipe 41 is provided below the housing 11 (that is, below the processing space 16), and an opening / closing valve 42 and an exhaust pump 43 are provided in the exhaust pipe 41. These constitute an exhaust unit 40.

[0024] Of the two electrodes, the upper electrode 13 is grounded, and the lower electrode 14 is connected to a high-frequency power source 21. Between the high-frequency power source 21 and the lower electrode 14, a matching section 22 is provided for impedance matching.

[0025] A pressure gauge (P) 51 for measuring the pressure inside the processing space 16 is provided on the wall of the housing 11, and a thermometer (T) 52 for measuring the temperature of the object 19 to be processed is provided on the processing table 12.

[0026] The plasma sterilization apparatus 10 is also provided with a control unit (CTRL) 50, which receives signals from sensors such as the pressure gauge 51 and thermometer 52, and controls each part such as the plasma source gas supply unit 30, exhaust unit 40, and high-frequency power supply 21 according to a pre-given program, thereby sterilizing the treatment object 19.

[0027] <2. Configuration of the bottom electrode> As described above, a large number of through holes 141 are drilled in the lower electrode 14 (FIG. 2). As shown in FIG. 5, it is desirable that the through holes 141 have a regular hexagonal planar shape and are densely arranged in the lower electrode 14 (i.e., in a honeycomb shape) to maximize the proportion of the area of ​​the through holes 141 in the entire lower electrode 14. This improves the efficiency of sterilization of the treatment object 19 by the plasma gas.

[0028] Such a honeycomb-shaped electrode (plate) may be produced by drilling through holes 141 in a metal plate, but it can also be produced by stacking a large number of parts 142 made by bending a long, thin metal plate at 120 degrees on both sides at regular intervals, as shown in Fig. 6. As for the metal of the electrode, aluminum, copper, silver, etc. can be used, as in the conventional case.

[0029] The lower electrode 14 may be, in addition to such a honeycomb shape, a dense arrangement of circular through-holes (a), a rectangular net-like shape (b), a dense arrangement of triangular through-holes (c), an arrangement of slit-shaped through-holes (d), an arrangement of through-holes whose slit widths regularly change (e), or a regular arrangement of cross-shaped through-holes (f), as shown in Fig. 9. By forming the through-holes into these shapes, the frequency band that can be accommodated when ions are retained in the through-holes can be expanded.

[0030] <3. Operation of the plasma sterilizer> The flow of sterilization of the treatment object 19 using the plasma sterilization device 10 of this embodiment will be described with reference to the flowchart in Fig. 7. First, the door 15 of the housing 11 is opened, and the treatment object 19 is placed on the treatment table 12 (step S1). Then, the door 15 is closed, and the inside of the housing 11 is sufficiently evacuated by the exhaust unit 40 (step S2).

[0031] Next, water vapor (H2O) is introduced into the space between the upper electrode 13 and the lower electrode 14 at a predetermined flow rate by the plasma source gas supply unit 30 (step S3), while high frequency power is applied to the lower electrode 14 to convert the water vapor at the predetermined flow rate into plasma (step S4). As a result, the water vapor in the space between the upper electrode 13 and the lower electrode 14 is converted into plasma, and the OH generated by the plasma is - Or H + , H3O + and HO that has not yet been converted into plasma form. The plasma gas 18 is sequentially sent to the processing space 16 through the through-holes 141 of the lower electrode 14 by the pressure of the water vapor introduced from the introduction tube 31 (FIG. 2), and is irradiated onto the processing object 19.

[0032] Here, when the plasma gas 18 passes through the through-holes 141, it receives energy from the lower electrode 14 again, and the ion dissociation of the water vapor (H2O) progresses. In addition, the hydrogen ions (H + ) are mostly destroyed by colliding with the wall surface of the lower electrode 14 (through hole 141), while hydroxy ions (OH -When the electrons (e) contact the wall of the lower electrode 14 (through hole 141), the high frequency voltage applied to the lower electrode 14 causes electrons (e - ) and releases the neutral hydroxyl radical (OH * ) Since these hydroxyl radicals have a strong sterilizing effect, the plasma sterilization device 10 of this embodiment can perform a strong sterilization treatment on the treatment object 19. In addition, since the ratio of radicals in the plasma gas 18 irradiated to the treatment object 19 increases, the temperature of the treatment object 19 is not increased as much as when only ions are irradiated.

[0033] After the object 19 to be treated has been irradiated with the plasma gas 18 for a predetermined time (step S5), the application of high frequency power and the introduction of water vapor are stopped, and the sterilization process is terminated. Note that the exhaust unit 40 continues to operate for a while after the application of high frequency power and the introduction of water vapor are stopped, and the sterilizing gas is discharged from the housing 11. Of course, the discharged gas is subjected to an appropriate detoxification process. After the termination process is completely completed, the object 19 to be treated is removed from the housing 11 (step S6).

[0034] <4. Examples> Plasma must be generated stably in order to sufficiently sterilize the treatment object 19 by the above-mentioned action. Since the lower electrode 14 of the present plasma sterilization device 10 is provided with a through hole 141, we decided to explore the conditions for stable plasma generation.

[0035] The size of the lower electrode 14 of the plasma sterilization device 10 used was 338×648 mm, and the thickness was 10 mm. Circular through-holes 141 of various sizes were densely provided in this lower electrode 14. Specifically, the diameters Φ of the through-holes were set to 10, 15, 20, 25, 30, 35, and 40 mm, and the distance d between adjacent through-holes was all 2.5 mm. The area of ​​each through-hole, the area ratio of the through-holes to the area of ​​the lower electrode (aperture ratio), and the volume of each through-hole when the through-holes were set to these sizes (and the distance d between adjacent through-holes was set to 2.5 mm) are shown in FIG. 8. The aperture ratio of the through-holes in the lower electrode is preferably 40 to 90%, more preferably 60 to 90%. The volume of each through-hole was 100 to 20,000 mm. 3 It is desirable to set the distance between the center of the plate and the ground. 3 is more desirable.

[0036] The magnitude of the high-frequency power (frequency: 13.56 MHz) applied to each lower electrode 14 was set to 300 W (0.136 W / cm 2 ), the flow rate of water vapor introduced between the electrodes 13 and 14 was fixed at 20 sccm, and the pressure in the processing space 16 was changed to 50, 80, 90, and 120 Pa by changing the exhaust strength of 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. 8. In the table of FIG. 8, ○ indicates that the plasma was generated stably and maintained at a high concentration in the through hole 141 for a long time. By continuing such a state, the plasma gas can be retained in the through hole 141 for a relatively long time, so that ions in the plasma gas are easily converted into radicals in a relatively large amount. In the table of FIG. 8, × indicates that the plasma generation was not stable, the plasma gas quickly flowed out toward the processing space 16, and did not retain much in the through hole 141. △ indicates that the plasma gas was retained in the through hole 141, but the thickness in the through hole 141 decreased, resulting in a low concentration.

[0037] The retention of the plasma gas in the through-hole 141 is considered to depend on the mass-to-charge ratio (m / z) of the ions in the plasma gas, the frequency (f) of the high-frequency voltage applied to the lower electrode 14, and the size (diameter Φ or volume V) of the through-hole 141. In this embodiment, the main ions in the plasma gas are hydroxy ions (OH - ), in which case it can be seen that the conditions in the range marked with ○ in the table of FIG. 8 are effective conditions for plasma treatment such as sterilization. [Explanation of symbols]

[0038] 10. Plasma sterilization device 11…Housing 12... Processing table 13, 132...Top electrode 14…Lower electrode 131, 141...Through holes 15…Door 16... Processing space 18...Plasma gas 19...Materials to be processed 21...High frequency power supply 22…Matching section 30...Plasma source gas supply unit 40…Exhaust section 50...Control unit

Claims

1. a first electrode provided to face an object to be treated placed in the treatment chamber; a plate-shaped second electrode having a through hole and provided between the object to be processed and the first electrode; a gas supply unit that supplies a gas that becomes plasma between the first electrode and the second electrode; a power supply unit that supplies high-frequency power to the second electrode using the first electrode as a ground electrode for converting the gas into plasma; a grounded processing table for placing the object to be processed; A plasma processing apparatus comprising:

2. The plasma processing apparatus according to claim 1 , wherein the gas supply unit supplies the gas between the first electrode and the second electrode.

3. 2 . 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 a side of the first electrode opposite to the second electrode.

4. 4. The plasma processing apparatus according to claim 1, wherein the second electrode has a plurality of through holes formed therein.

5. 5. The plasma processing apparatus according to claim 4, wherein the through holes of the second electrode have a regular hexagonal planar shape and are densely arranged in the second electrode.

6. 5. The plasma processing apparatus according to claim 4, wherein the through holes of the second electrode have a circular planar shape and are densely arranged in the second electrode.

7. The gas is water vapor (H 2 7. The plasma processing apparatus according to claim 1, wherein the plasma processing apparatus is a plasma processing apparatus according to claim 1.

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