JP4701413B2 - Plasma sterilization apparatus and plasma sterilization method using the apparatus - Google Patents

Description

  The present invention relates to an apparatus for sterilizing or sterilizing (hereinafter referred to as sterilization) bacteria that adhere to a sterilization treatment body such as a medical instrument using plasma, and more particularly, to sterilizing plasma-based ions. The present invention relates to a device for sterilizing bacteria that are injected into a treatment body and adheres to a medical instrument and the like, and a sterilization method using the device.

  Recently, sterilization and sterilization are required for medical instruments and containers used in hospitals and dental clinics. As the target device, for example, a container in which bacteria must not grow inside, such as an infusion container, a medicine bottle, or a pure water sealed container, or a medical device in which bacteria must not adhere to the outside, such as a scalpel For example, a laboratory instrument in which bacteria should not be present inside and outside, such as a flask.

  Also, dealing with crimes that attach bacteria that release extremely harmful toxins to the surface of postal envelopes addressed to government officials has become an urgent issue to combat international terrorism.

  It is important to reliably and drastically reduce the number of bacteria present on the surface including the inner surface of the object to be sterilized, bacteria attached to daily goods, and mold.

  Conventionally, various methods have been studied as a technique for sterilizing an object to be sterilized such as a medical instrument.

  For example, a method using high-pressure steam or dry hot air is most widely used. However, such a method may cause deformation of the medical device or oxidation of the surface of the device due to steam or heat. There is a possibility that it cannot be sterilized.

  Further, in the method using ethylene oxide gas or formalin, there is a risk that a toxic residue is left in the sterilization target, which may have a serious adverse effect on a patient in contact with the sterilization target. For this reason, an additional step of removing toxic residues remaining on the sterilization target is required, which has a disadvantage of being costly or time consuming.

As one of the methods for solving such a drawback, there is known a system for injecting plasma ions into an object to be sterilized to sterilize. In the plasma system, a method using hydrogen peroxide as a precursor of a reactive species is known (Patent Document 1). A method of sterilizing by plasma ion implantation using argon gas is also known (Patent Document 2). There is also known a technique for sterilizing plasma ions by using water vapor without using hydrogen peroxide (Patent Document 3).
Japanese Patent Laid-Open No. 2-62261 Japanese Patent No. 2774193 JP 2003-310719 A

  In the case of using hydrogen peroxide as in Patent Document 1, since the purchase cost of hydrogen peroxide is high, the sterilization cost is expensive, which is not desirable in terms of running cost. Also, hydrogen peroxide requires care in storage and handling, and is difficult to maintain and manage.

  In Patent Document 2 using an inert gas such as argon gas, it is easy to handle, but the most effective oxygen atom for sterilization is not generated or is rarely obtained, and high sterilization is difficult to obtain. was there.

  In Patent Document 3, since ion implantation by plasma is performed, the sterilization effect can be further enhanced by utilizing the physical energy of the particles of the plasma, not only by the chemical effect of the highly diffusible plasma. . Further, by using the DC electrode and the AC electrode in combination, electrons or ions are accelerated and driven into the cells of the sterilization target, and radicals are driven into the cells or the surface layer of the cells thermally regardless of whether the electrodes are positive or negative. As a result, a plasma sheath is generated in the vicinity of the periphery of the DC electrode, and acceleration of electrons or ions due to Coulomb force against the DC electrode occurs, so that the sterilizing effect is remarkably excellent. However, it is necessary to generate a large amount of water vapor outside the treatment room and send it to the sterilization treatment room together with the carrier gas, which has the disadvantage that the equipment cost becomes high and the equipment becomes large. In addition, in the atmosphere of water vapor, the pressure conditions and voltage conditions that can be sterilized are stricter than those of hydrogen peroxide, and it is difficult to stably sterilize by generating plasma in the sterilization treatment chamber.

  In addition, a method of injecting plasma ions into an object to be sterilized using hydrogen peroxide, argon gas, and moisture has attracted attention as a sterilization technique for the object to be sterilized, but uses hydrogen peroxide, argon gas, and moisture. In either method, a large amount of reaction gas is generated outside, and is supplied to and discharged from the sterilization treatment chamber. Therefore, in the conventional one, the equipment becomes large, resulting in increased costs.

  In the present invention, in consideration of safety in order to reduce costs, research has been repeated on the premise that water is used instead of hydrogen peroxide or ethylene gas as a processing gas. In particular, by using a plasma-based ion implantation method with high sterilization treatment results using water, a large amount of plasma can be generated around the sterilization target, and plasma ions can be implanted into the sterilization target. It was noted that it was not necessary to generate plasma throughout the body.

  Based on this focus, in the present invention, a large amount of water vapor is not supplied to the entire sterilization treatment chamber, but a small amount of water is present around the sterilization target body, which is converted into water vapor to I thought that it would be possible to sterilize by generating plasma from water vapor in the surroundings, rather than supplying water vapor from the outside, water for generating water vapor was set in the sterilization treatment chamber, and this water was evaporated while plasma was The object is to make the device compact by sterilizing the object to be sterilized.

  Specifically, the present invention, for example, puts a glass with a small amount of water into the sterilization chamber and regulates the glass so that it does not evaporate in large quantities at one time when evacuated. In order to create a state in which a slight amount of water vapor continues to be supplied even when the pressure reaches the pressure, and in that state, voltage is applied to inject ions generated from the water vapor into the sterilization target to sterilize. It is a thing.

Specifically, the invention of claim 1
A sterilization chamber that generates plasma;
A cradle disposed in the sterilization treatment chamber and supporting a sterilization target;
Voltage application means connected to the cradle and applying a DC voltage to the cradle;
Connected to the sterilization chamber, and vacuuming means for evacuating the sterilization chamber;
A water container disposed in the sterilization chamber and containing a predetermined amount of water;
A ceramic filter, a polymer polymer filter, or a porous ceramic which is provided in a discharge portion where the water in the water container is discharged into the sterilization treatment chamber and slows the release rate of the water released toward the sterilization treatment chamber A restriction member composed of
A control means connected to the vacuum means and the voltage application means for controlling the operation of the vacuum means and the voltage application means,
The control means operates the vacuum means to evacuate to a predetermined pressure, and when the sterilization treatment chamber reaches a predetermined pressure, operates the voltage application means to apply a predetermined voltage and hold it for a predetermined time. Thus, plasma is generated to sterilize the object to be sterilized placed on the cradle.

  According to a second aspect of the present invention, in the plasma sterilization apparatus according to the first aspect, the regulating member comprises a porous filter.

  According to a third aspect of the present invention, in the plasma sterilization apparatus according to the first or second aspect, the vacuum means is controlled by the control means to control the pressure in the sterilization treatment chamber and the discharge amount from the sterilization treatment chamber. Thus, the amount of moisture released from the discharge part of the water container is stably regulated within a predetermined range.

According to a fourth aspect of the present invention, in the plasma sterilization apparatus according to the third aspect, the control means causes the pressure P in the sterilization treatment chamber to be within a range of P = 0.1 Pa to 50 Pa and the gas from the sterilization treatment chamber. By controlling the vacuum means so that the exhaust amount S is in the range of S = 50 L / min to 3,000 L / min, the moisture release amount Q from the water container is reduced.
Q (g / min) = 0.0008 * 10 ⁻² * P (Pa) * S (L / min).

  According to a fifth aspect of the present invention, in the plasma sterilization apparatus according to the fourth aspect, the direct-current applied voltage applied to the cradle is controlled in the range of 3 kV to 20 kV by the control means. .

The invention of claim 6 is the plasma sterilizer according to any one of claims 1 to 5,
The voltage applying means is means for applying a pulse voltage.

  A seventh aspect of the present invention is the plasma sterilization apparatus according to the sixth aspect, wherein the voltage applying means further includes a high frequency power source for applying an alternating current.

The invention of claim 8 includes a sterilization treatment chamber that generates plasma and a pedestal to be placed and a cradle formed as a direct current electrode, and a water container that discharges water into the sterilization treatment chamber, The discharge part of the water container is equipped with a regulating member made of a ceramic filter, a polymer polymer filter, or porous ceramics that regulates the amount of water released,
The amount of water discharged from the water container to the sterilization chamber is controlled within a predetermined range by reducing the pressure in the sterilization chamber by a vacuum means to a predetermined pressure and controlling the exhaust amount from the sterilization chamber to a predetermined exhaust amount. To regulate,
In this state, a predetermined pulse voltage is applied to the DC electrode for a predetermined time and held for a predetermined time,
Forms plasma caused by static electricity around the object to be sterilized,
Ions in the plasma are implanted toward the object to be sterilized to sterilize the object to be sterilized.

The invention of claim 9 is the plasma sterilization method of claim 8,
By controlling the pressure in the sterilization chamber to be in the range of 0.1 Pa to 50 Pa, and controlling the exhaust amount in the sterilization chamber to be in the range of 50 L / min to 3,000 L / min, The amount Q of water released from the water container is regulated and applied so as to be a value calculated as Q (g / min) = 0.0008 * 10 ⁻² * P (Pa) * S (L / min) The voltage is applied in the range of 3 kV to 20 kV.

  According to the present invention, in the present invention, the water container is arranged in the sterilization treatment chamber, and the steam is released little by little from the water in the water container by the regulating member. However, a high voltage can be applied while maintaining an appropriate pressure. As a result, high-density plasma can be generated in the sterilization treatment chamber, and the sterilization target can be effectively sterilized.

  According to the second aspect, the amount of water discharge can be reliably regulated with a simple structure. In particular, since there is no need for a member such as a control valve for controlling the discharge amount, and a control mechanism for controlling the member, it is only necessary to place the water container and this restricting member in the sterilization treatment chamber, and to have a simple configuration. Can do.

  According to the third aspect, by controlling the pressure and the exhaust amount, the amount of water vapor generated can be regulated reliably and easily, so that the pressure can be effectively generated and sterilized. Can be sterilized with high functionality.

  According to the fourth aspect, by setting the pressure and the exhaust amount within appropriate ranges, the amount of water vapor generated can be reliably and easily within the appropriate ranges, so that plasma can be generated effectively and sterilized. It can be pressure and can be sterilized with high functionality.

  According to the fifth aspect, since the applied voltage can be applied at a high voltage, the plasma can be effectively generated and the function of sterilization is excellent.

  According to the sixth aspect, plasma ions can be effectively implanted into the sterilization object.

  According to the seventh aspect, plasma can be generated at a high density, and the sterilization function is excellent.

  According to the present invention, in the present invention, the water container is arranged in the sterilization treatment chamber, and the water vapor is gradually released from the water in the water container by the regulating member, so that no atmospheric gas is introduced from the outside. However, a high voltage can be applied while maintaining an appropriate pressure. As a result, high-density plasma can be generated in the sterilization treatment chamber, and the sterilization target can be effectively sterilized.

In the prior art, the inside of the sterilization treatment chamber is temporarily reduced to a vacuum pressure of 7.0 * 10 ⁻⁴ Pa using, for example, a vacuum pump, and then the pressure is increased to 2.0 to 7.0 Pa while introducing the reaction gas. The vacuum pump or the like is adjusted so that

On the other hand, in the present invention, it is not necessary to once reduce the pressure to 7.0 * 10 ⁻⁴ Pa using the vacuum pump, and when the pressure is reduced from the atmospheric pressure using the vacuum pump. In addition, when the pressure as described above, that is, 2.0 to 7.0 Pa, the water in the water container evaporates little by little, so that it can be maintained in the pressure range. By applying a high voltage in this state, the object to be sterilized can be sterilized effectively, so that the method can be simplified as compared with the conventional method.

  According to the invention of claim 9, it is possible to generate a higher density plasma in the sterilization treatment chamber and effectively sterilize the object to be sterilized.

In the present invention, the term “sterilization” means a process of destroying or removing all living organisms of microorganisms from an object to be sterilized. In practice, the term “survival probability” conventionally defines the degree of sterilization (or sterility). As an expression indicating a specific sterilization amount, for example, measuring as 10 ⁻³ , 10 ⁻⁶ , and 10 ⁻¹² is conventionally used as a practical sterilization or sterilization target for sterilization treatment. In order to simplify the explanation, sterilization or sterilization is used as a representative for the sake of simplicity.

  In the present invention, the pressure in the sterilization chamber is set to a range of 0.1 Pa to 50 Pa because it is difficult to generate plasma if the pressure is reduced too much, and plasma is not generated even if the pressure is insufficient. In particular, the range of 0.2 Pa to 10 Pa is particularly preferable.

  Moreover, although the effect which can sterilize can be anticipated, so that the applied voltage is high, since it cannot make it very high in relation to a pressure, it is preferable to set it as the range of 3kV-20kV, and it is preferable to set it as the range of 6kV-15kV especially.

  The amount of discharge S varies greatly depending on the size of the equipment, but at present, it is preferably in the range of 50 to 3,000 (L / min), particularly 100 to 500 (L / min) as a highly feasible one. ) Is preferable.

  In particular, if the amount of moisture released from the water container is too large (or too fast), it is difficult to maintain the plasma generation pressure. If the amount released is too small, the amount of water vapor is insufficient and sufficient plasma ions are generated. Since it cannot be obtained, it is preferable to regulate the amount of water discharge to be within an appropriate range.

The amount of water released Q is
Q (g / min) = 0.0008 * 10 ⁻² * P (Pa) * S (L / min)
By controlling the pressure in the sterilization chamber to be in the range of 0.1 Pa to 50 Pa, and controlling the exhaust amount in the sterilization chamber to be in the range of 50 L / min to 3,000 L / min, The amount Q of water released from the water container is regulated to be a value calculated as Q (g / min) = 0.0008 * 10 ⁻² * P (Pa) * S (L / min), and the applied voltage Is preferably applied in the range of 3 kV to 20 kV.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. It should be noted that the following description of the preferred embodiment is merely illustrative in nature, and is not intended to limit the present invention, its application, or its use.

(Embodiment 1)
1 and 2 show Embodiment 1 of the present invention. As shown in FIG. 1, a plasma generator 2 is arranged in a sterilization treatment chamber 1 serving as a vacuum container. The plasma generator 2 includes a non-diffusive plasma generator 3 that generates plasma in which diffusion is suppressed. The non-diffusive plasma generator 3 is electrically connected to a direct current pulse power source 41 that is a voltage application means and a sterilization target T, and the sterilization target T is placed thereon to convert the processing target itself into an electrode (direct current). Electrode) 5. The direct current electrode 5 is disposed in the sterilization treatment chamber 1 and connected to a direct current pulse power supply 41 disposed outside the sterilization treatment chamber 1 via a current introduction terminal 6 attached to the wall of the sterilization treatment chamber 1. is doing.

  The sterilization treatment chamber 1 is provided with an exhaust port 7 and connected to a vacuum pump 8. It is desirable that a filter (not shown) that prevents bacteria-attached dust particles from entering the sterilization treatment chamber 1 is interposed in the exhaust port 7.

  A sterilization object T is placed on the cradle 5 of the sterilization treatment chamber 1 and a water container 10 is placed thereon. As shown in FIG. 2, the water container 10 is a container for storing water W, and a discharge member 11 is provided with a regulating member 12 made of a ceramic porous filter. The restriction member 12 restricts the evaporation amount (or evaporation rate) when the water in the water container 10 evaporates as water vapor. The reason will be described later.

  The control means 20 controls the operation of the vacuum pump 8 and the application voltage and application time of the pulse voltage application means 41.

  FIG. 6 shows a preferable power waveform of the DC pulse power supply 41. The direct-current pulse 42 of the direct-current pulse power supply 41 has an electrical ability to generate plasma in a region near the surface of the sterilization target T by its own self-discharge. As shown in FIG. 6, the DC pulse power supply 41 generates a DC pulse 42 having a DC negative voltage of V and a pulse width of t1 with a period (charging time) t2. By adjusting the duty ratio determined by the number of repetitions of the pulse of the period t2, it is possible to more effectively control the sterilization treatment speed that is an ion flux incident on the sterilization target T per unit time.

  A positive voltage may be used instead of the negative voltage of the DC pulse 42, and in this case as well, a bactericidal effect substantially equivalent to the negative voltage can be obtained.

  The magnitude of such a parameter depends on the charge transfer speed on the surface of the sterilization target T (in this case, the insulator) that affects the pulse width t1 of the DC pulse 42, the sterilization target T and the particles in the plasma. It is determined in consideration of the charge elimination speed caused by the collision. The width of the DC pulse 42 is preferably on the order of several μs to several ms, and the voltage is preferably about several kV to several tens kV. However, it is preferable that the peak value of the current be adjusted so as to be equal to or less than the set value of the circuit component. The repetition width t2 of the DC pulse 42 is preferably about several hundred pps to several thousand pps.

  The operating state of the first embodiment will be described.

  After the water container 10 is set in the sterilization treatment chamber 1 and the sterilization target T is placed on the cradle 5, the vacuum pump 8 is operated based on the signal from the control means 20, and the exhaust port 7, the air in the sterilization treatment chamber 1 is discharged. Then, when the inside of the sterilization treatment chamber 1 is depressurized to a predetermined pressure, the operation of the vacuum pump 8 is controlled so that the predetermined pressure is maintained. In this state, the DC pulse power 42 is input from the DC pulse power supply 41 to the pulse voltage application unit 5 under the application conditions described above based on the signal from the control unit 20.

  In the above operating state, in terms of the sterilization function, generally, the higher the applied pressure, the better the sterilization effect. However, in order to generate plasma by increasing the applied voltage, the condition is also affected by the pressure in the sterilization treatment chamber 1, so it is important to maintain the pressure at an appropriate value. The relationship between the pressure in the sterilization treatment chamber 1 and the applied voltage is, as can be seen from FIG. 8, a voltage in the range of 1.0 Pa to 50 Pa (particularly 2.0 to 10 Pa), particularly in the range of 3 kV to 20 kV. Can be sterilized effectively. It should be noted that at 1.0 Pa or less, since the current value suddenly decreases, the power value decreases rapidly. In this case, the voltage (or power) in the plasma generation region is kept high by forming a magnetic field or the like. It is possible to sterilize.

  In that case, the range of 0.1 Pa to 10 Pa (particularly 0.2 Pa to 10 Pa) is suitable.

  In order to maintain the sterilization treatment chamber 1 in the above pressure range while reducing the pressure with the vacuum pump 8, it is necessary to appropriately control the amount of water vapor discharged into the sterilization treatment chamber 1 and the amount of exhaust discharged from the sterilization treatment chamber 1. is there.

For example,
Pressure in sterilization treatment chamber: P (Pa: Pascal)
Volume in sterilization chamber: V (L: liter)
Discharge from sterilization treatment room: S (L / min)
Amount of water vapor released into the sterilization chamber: Q (g / min)
Then,
In order to perform sterilization effectively, as can be seen from FIG. 8, it is important to keep the voltage value and current value high and to keep the pressure within a predetermined range. For example, when the pressure P = 4 Pa, as can be seen from FIG. 8, the voltage value and the current value can be maintained high. Therefore, if this pressure is maintained at 4 Pa, it is necessary to regulate the amount of gas (water vapor discharge amount) Q and the discharge amount S released into the sterilization treatment chamber 1 to predetermined values. Here, for simplicity, the relationship between the pressure P in the sterilization treatment chamber and the amount of water vapor released into the sterilization treatment chamber is calculated with the discharge amount S as a constant value.

Specifically, the amount of water released Q is
Q = P * S
Are in a relationship.

Therefore, for example, when P = 4 Pa and S = 300 (L / min), Q (g / min) is calculated as follows.
Q (g / min) = 9.87 * 10 ⁻⁶ * 4 (Pa) * 300 (L / min) * 18 / 22.4
= 0.0095 (g / min)
Q (g / min) = 0.95 * 10 ⁻² (g / min)
As calculated.

  The volume when 1 mol of water is vaporized is 22.4, the molecular weight of water is 18, and in this case, the pressure of water is 1 atm.

Accordingly, the amount of water vapor released from the water container 10 may be regulated by the regulating member 12 so as to be 0.95 * 10 ⁻² (g / min).

That is, when the water evaporation amount Q is (g / min), the pressure P is (Pa), and the exhaust amount S is (L / min), the following relational expression is obtained.
Q (g / min) = 0.0008 * 10 ⁻² * P (Pa) * S (L / min).

  Therefore, the emission amount S varies greatly depending on the size of the facility, but as a highly feasible one, a range of 50 to 3,000 (L / min) is currently used. If the pressure range of the sterilization treatment chamber is 0.1 Pa to 50 Pa, the regulating member is calculated from the above relational expression so as to obtain a water discharge amount Q suitable for it as shown in FIG. It is good to provide.

In particular, the discharge amount S is preferably in the range of 100 to 500 (L / min). When the pressure range of the sterilization treatment chamber is 0.2 Pa to 10 Pa in this range, the water discharge amount Q (g 9b, point A [10 Pa, 6.67 * 10 ⁻² (g / min)], point B [0.2 Pa, 0.12 * 10 ⁻² (g / min) ], Point C [0.2 Pa, 0.03 * 10 ⁻² (g / min)], and point D [10 Pa, 1.33 * 10 ⁻² (g / min)]. preferable.

  In the present invention, as described above, since the evaporation amount of the water contained in the water container is controlled to be slowly evaporated by the regulating member, the pressure in the sterilization treatment chamber 1 can be maintained at an appropriate value. As a result, plasma could be generated effectively, and the results of actual sterilization tests will be described later as Example 1, but could be sterilized with high probability.

(Embodiment 2)
A second embodiment will be described with reference to FIG. The second embodiment is different from the first embodiment only in that the water container 10a has a different structure, and the other configurations are the same as those of the first embodiment. In the second embodiment, description of the same parts as those of the first embodiment is omitted, and only different parts will be described. The discharge portion at the upper part of the water container 10a was narrowed, the porous filter 12a was formed in a columnar shape, and was in a state of protruding into the water Wa in the water container 10.

  In the second embodiment, an excellent sterilizing function can be exhibited as in the first embodiment.

(Embodiment 3)
A third embodiment will be described with reference to FIG. The third embodiment is different from the first embodiment only in that the water container 10b has a different structure, and the other configuration is the same as that of the first embodiment. In the third embodiment, description of the same parts as those in the first embodiment is omitted, and only different parts will be described.

  In the third embodiment, the water container 10b is the same as the water container 10a of the second embodiment, and the arrangement position of the water container 10b is changed. In the third embodiment, unlike in the first embodiment, the entire water container 10b is not disposed inside the sterilization treatment chamber 1, but the upper end of the cylindrical porous filter 12b is positioned in the sterilization treatment chamber 1. Is provided.

  In the present invention, as in the third embodiment, the case where only the water evaporation portion in the water container is provided in the sterilization treatment chamber is included in the expression that the water container is disposed in the sterilization treatment chamber. Define as

(Embodiment 4)
A fourth embodiment will be described with reference to FIG. In the fourth embodiment, as compared with the first embodiment, only a DC application unit 45 is added to the direct current pulse application unit 41 as a voltage application unit, and the other configurations are the same as those in the first embodiment. . In the fourth embodiment, description of the same parts as those in the first embodiment is omitted, and only different parts will be described.

The plasma generator 2 includes a non-diffusive plasma generator 3 (41) that generates a plasma whose diffusion is suppressed, and assists the generation of the plasma in the non-diffusion region of the plasma, It consists of an auxiliary plasma generator 3a that increases the amount.
The auxiliary plasma generator 3a is physically the same as the plasma generator of the known apparatus, and a high frequency power source is used. The auxiliary plasma generator 3 a is formed of a first high frequency power supply (RF) 43 and the electrode 5. The electrode 5 of the auxiliary plasma generator 3 a is shared with the electrode 5 of the non-diffusive plasma generator 3, and the electrode of the auxiliary plasma generator 3 a is identical to the electrode of the non-diffusible plasma generator 3. is there. The sterilization treatment chamber 1 is grounded. The first high frequency power supply 43 is connected to the cradle 5 (electrode) 5 via the current introduction terminal 6.

  Furthermore, a wide area plasma generator 44 for generating a plasma in the entire sterilization treatment chamber 1 (wide area) is provided. The wide area plasma generator 44 is formed of a second high frequency power supply (RF) 45 and a wide area plasma generation electrode 46. The wide-area plasma generation electrode 46 is disposed in the sterilization treatment chamber 1 and is a second high-frequency power source disposed outside the sterilization treatment chamber 1 via a current introduction terminal 47 attached to the wall of the sterilization treatment chamber 1. 45 is connected.

  7A and 7B show preferable power waveforms of the DC pulse power supply 41 and the first high-frequency power supply 43. FIG. As shown in FIG. 2B, the direct-current pulse power supply 41 generates a direct-current pulse 42 having a direct-current negative voltage V and a pulse width t1 at a period (charge time) t2. The first high frequency power supply 43 generates the AC pulse 47 periodically or continuously. As the rf condition of the AC pulse 47, the frequency is set to f, the peak voltage is set to K, and the pulse width is set to t3.

  The DC pulse 42 rises with a time delay of Δt from the rise time of the AC pulse 47.

  By adjusting the parameters constituting the negative voltage pulse condition and the rf condition and adjusting the ion implantation energy distribution, energy peak, and plasma density, the sterilization time until the specified sterilization rate is obtained can be controlled. . By adjusting the duty ratio determined by the number of repetitions of the pulse of the period t2, it is possible to more effectively control the sterilization treatment speed that is the ion flux incident on the sterilization treatment target T per unit time.

  By using a positive voltage instead of the negative voltage of the DC pulse 42, a substantially equivalent sterilizing effect can be obtained.

  The magnitude of such a parameter depends on the charge transfer speed on the surface of the sterilization target T (in this case, the insulator) that affects the pulse width t1 of the DC pulse 42, the sterilization target T and the particles in the plasma. It is determined in consideration of the charge elimination speed caused by the collision.

  An AC pulse 47 is applied to the electrode 5 prior to the DC pulse 42 in time. Plasma is generated in the vicinity of the sterilization target T of the electrode 5 and the conductor that is electrically joined to the electrode 5. The DC pulse 42 is applied to the electrode 5 with a time delay of Δt with respect to the application of the AC pulse 47. The positive ions and electrons of the plasma P around the sterilization target T receive an electrostatic force. The electrons are strongly repelled from the surface of the sterilization target T or near the surface and moved away from the sterilization target T, and positive ions are attracted to the sterilization target T and remain around the sterilization target T. By the sheath, the ionized positive ions are strongly accelerated toward the sterilization target T. The positive ions thus accelerated damage the microbial cells present on the surface of the sterilization target T. Such damage is caused by ions having kinetic energy, which is physical energy, being driven into the cell or into the cell wall. When the electrode 5 is positively charged, electrons are driven into the cell or into the cell wall. Thus, microorganisms are killed by physical effects.

  During the direct current pulse 42 of the period t2, the ion sheath is eliminated, and the radicals present in the vicinity of the sterilization target T that are activated in the plasma P by the afterglow are highly efficient. The microorganisms are killed by reaching the surface of the sterilization target T. Such killing is based on a chemical effect that is the same as the action of known devices.

  As described above, according to the fourth embodiment, the number of cells present can be reduced on the order of 6 digits by the combined effect of the physical effect and the chemical effect.

  The direct-current pulse 42 has an electric ability to generate plasma in a region near the surface of the sterilization target T by self-discharge of itself. The AC pulse 47 further increases the excitation energy of the plasma generated by the DC pulse 42 to increase the amount of excited species / radicals in an auxiliary and wide area. The plasma sheath formed by the self-discharge of the direct current pulse 42 applied to the same electrode that generates the plasma in the presence of the plasma is an electrical acceleration that uniformly injects positive ions or electrons into the surface layer of the sterilization target T. Create a field. The addition of the wide area plasma generating electrode 46 increases the excited species of plasma generated in a wider area, and a larger amount of radicals diffused in a wide area are injected into the sterilization target T, thereby increasing the sterilization efficiency and setting the death rate. It is possible to shorten the processing time until the is obtained.

  The wide area plasma generating electrode 46 can be replaced with a light source. The light source preferably emits light of various wavelengths from infrared to ultraviolet.

(Example)
Experiments were actually conducted to confirm the bactericidal effect with the structure of the first embodiment.

  A pedestal connected to the negative pole of the DC power supply was installed near the bottom of the sterilization treatment chamber of Embodiment 1 so that the sterilization treatment body could be placed thereon. Bacteria that form spores with Bacillus bacteria that have a high probability of survival by various sterilization treatments (Bacillus pumilus) were used as indicator bacteria to evaluate sterilization performance. Bacteria after sterilization treatment was diluted and cultured, and the number of surviving bacteria was measured from the number of generated colonies. The sterilized treatment body to which the spore bacteria adhere on the order of 10 7 is placed on the cradle of the sterilization treatment room, and 1 cc is placed in a cylindrical cup (height: 10 mm, top opening diameter: 80 mm) as a water container. We put water and put this cylindrical cup on the cradle together. The opening part which is a discharge | release part on this cylindrical cup was covered with the ceramic filter in which the porous was formed so that discharge | release amount Q = 0.01 (g / min). As a result, the exhaust amount S = 300 (L / min) when evacuated by the vacuum pump 8 can be stably maintained when the pressure P in the sterilization treatment chamber is reduced to about 4 Pa when evacuated. It was. At this time, the applied voltage was set to V = 10 kv to the DC power source, a pulse with a frequency: t2 = 500 pps and a pulse width: t1 = 5 μsec was applied and maintained for 1 minute, 5 minutes, and 10 minutes. Moreover, the voltage was set to 5 kV and the same processing was performed. These experimental results are shown in Table 1 as Samples 1-6.

(Comparative example)
A sterilization treatment chamber and a cylindrical cup similar to those in Example 1 were prepared. The difference from the example is that nothing is provided in the opening on the upper surface of the cylindrical cup, and in this comparative example, the opening diameter of the upper surface of the cylindrical cup: 80 mm, without any restriction member, it is opened as it is. It was in a state.

  In the same manner as in the example, a DC voltage of 10 kv was applied, a pulse having a frequency of 500 pps and a pulse width of 5 μsec was applied, and maintained for about 1 minute, 5 minutes, and 10 minutes. These were designated as Comparative Examples 1 to 6. In the comparative example, the above time varied without being stable, and the value is described below.

  The sterilization results of Examples (Samples 1 to 6 and Comparative Examples 1 to 6) are shown in Table 1 below.

  In the examples (samples 1 to 6) of the present invention, all could be sterilized. In particular, the result was that sterilization was more effective when the applied voltage was higher, 10 kV, and the treatment time was longer. From these facts, if water is placed in the sterilization treatment chamber and evaporated in a small amount calculated, plasma can be generated stably and high voltage can be applied during that time, so it can be sterilized with high capacity. I understood.

  On the other hand, in the comparative example, only 10 kV was able to be sterilized for one digit, but 5 kV was still in the order of 10 7 and could not be sterilized. When the pressure in the sterilization chamber is reduced to reduce the vacuum, the water in the cup evaporates at once and is discharged directly. Even if a voltage is applied in this pressure state, the power value of ions and the like on the surface of the sterilized body cannot be obtained as a power value that can be sterilized. It is guessed. In some cases, even if plasma was generated, there was a moment during that time, and it was not possible to maintain a sterilizable state. That is, in the comparative example, the bactericidal effect was not obtained, and the voltage for generating plasma was unstable and varied.

  In the present invention, an appropriate amount of water in the water container may be added, and it may be added every time sterilization is performed, or after several sterilizations, the water is replenished and replaced. May be.

The regulating member that regulates the amount of water released may be any material as long as the amount of evaporation is kept as constant as possible and can be evaporated slightly. For example, a ceramic filter, a polymer polymer filter, a porous filter, etc. Filters that can easily control the permeation amount of porous ceramics and porous bodies can be used. Further, when the entire water container is placed in the sterilization treatment chamber, there is no need to change the sterilization apparatus itself, which is excellent in that it can be easily set and replaced. However, only the filter may be placed in the sterilization chamber and the water container situation may be placed outside the sterilization chamber.
The arrangement position of the water container may be arranged at any position in the sterilization treatment room. However, it is more effective to increase the ion density around the object to be sterilized when it is close to the object to be sterilized, and it is preferable to place the object together with the object to be sterilized on the cradle.

  As described above, the plasma sterilization apparatus and method according to the present invention can be used in medical instruments used in hospitals, dental clinics, etc., such as infusion containers, medicine bottles, and pure water sealed containers. Containers that should not be propagated, medical equipment that should not have bacteria attached to the outside, such as a scalpel, laboratory equipment that must not have bacteria on the inside or outside, such as flasks, or government officials Applicable to postal envelope safety measures.

1 is a schematic view of a plasma sterilization apparatus according to Embodiment 1 of the present invention. Sectional drawing of the water container of Embodiment 1 is shown. The same figure as FIG. 2 is shown regarding Embodiment 2. FIG. The same figure as FIG. 1 in connection with Embodiment 3 is shown. The same figure as FIG. 1 in connection with Embodiment 4 is shown. FIG. 4 is a waveform diagram showing a power wave of an applied voltage related to the first embodiment. FIGS. 7A and 7B are waveform diagrams related to the fourth embodiment and showing a power wave of an applied voltage. In this invention, it is a graph which shows the relationship between an applied voltage and the pressure of a sterilization treatment chamber. 9a and 9b are graphs showing the relationship between the evaporation amount of water and the pressure in the sterilization treatment chamber in the present invention.

Explanation of symbols

T object to be sterilized 1 sterilization treatment chamber 2 plasma generator 3 plasma generator 4 voltage applying means 41 pulse voltage applying means 42 DC pulse 43 AC applying means (high frequency power supply)
5 cradle (DC electrode)
6 Current introduction terminal 7 Exhaust port 8 Vacuum means 10 Water container 11 Discharge portion 12 Restricting member 20 Control means

Claims (9)

A sterilization chamber that generates plasma;
A cradle disposed in the sterilization treatment chamber and supporting a sterilization target;
Voltage application means connected to the cradle and applying a DC voltage to the cradle;
Connected to the sterilization chamber, and vacuuming means for evacuating the sterilization chamber;
A water container disposed in the sterilization chamber and containing a predetermined amount of water;
A ceramic filter, a polymer polymer filter, or a porous ceramic which is provided in a discharge portion where the water in the water container is discharged into the sterilization treatment chamber and slows the release rate of the water released toward the sterilization treatment chamber A restriction member composed of
A control means connected to the vacuum means and the voltage application means for controlling the operation of the vacuum means and the voltage application means,
The control means operates the vacuum means to evacuate to a predetermined pressure, and when the sterilization treatment chamber reaches a predetermined pressure, operates the voltage application means to apply a predetermined voltage and hold it for a predetermined time. Thus, a plasma sterilization apparatus is characterized in that plasma is generated to sterilize an object to be sterilized placed on the cradle. The plasma sterilizer according to claim 1,
The plasma sterilizer characterized in that the regulating member comprises a porous filter. In the plasma sterilizer according to claim 1 or 2,
By controlling the vacuum means by the control means to control the pressure in the sterilization treatment chamber and the discharge amount from the sterilization treatment chamber, the amount of moisture released from the discharge portion of the water container is within a predetermined range. A plasma sterilizer characterized by being stably regulated. The plasma sterilizer according to claim 3,
By the control means, the pressure P in the sterilization treatment chamber is in the range of P = 0.1 Pa to 50 Pa, and the gas exhaust amount S from the sterilization treatment chamber is in the range of S = 50 L / min to 3,000 L / min. By controlling the vacuum means such that the water release amount Q from the water container is Q (g / min) = 0.0008 * 10-2 * P (Pa) * S (L / min) Plasma sterilizer characterized by being controlled to become. The plasma sterilizer according to claim 4,
The plasma sterilizer characterized in that the control means controls the DC applied voltage applied to the cradle within a range of 3 kV to 20 kV. In the plasma sterilizer according to any one of claims 1 to 5,
The plasma sterilizing apparatus, wherein the voltage applying means is means for applying a pulse voltage. The plasma sterilizer according to claim 6,
The plasma sterilizer, wherein the voltage applying means further comprises a high frequency power source for applying an alternating current. A sterilization treatment chamber that generates plasma is provided with a cradle for placing a sterilization target and formed as a direct current electrode, a water container that discharges water into the sterilization treatment chamber, and water in a discharge portion of the water container. Equipped with a ceramic filter that regulates the release amount, a polymer filter, or a regulating member made of porous ceramics ,
The amount of water discharged from the water container to the sterilization chamber is controlled within a predetermined range by reducing the pressure in the sterilization chamber by a vacuum means to a predetermined pressure and controlling the exhaust amount from the sterilization chamber to a predetermined exhaust amount. To regulate,
In this state, a predetermined pulse voltage is applied to the DC electrode for a predetermined time and held for a predetermined time,
Forms plasma caused by static electricity around the object to be sterilized,
A plasma sterilization method, characterized in that ions in the plasma are implanted toward a sterilization target body to sterilize the sterilization target body. The plasma sterilization method according to claim 8,
By controlling the pressure in the sterilization chamber to be in the range of 0.1 Pa to 50 Pa, and controlling the exhaust amount in the sterilization chamber to be in the range of 50 L / min to 3,000 L / min, The water release amount Q from the water container is regulated and applied so as to be a value calculated as Q (g / min) = 0.0008 * 10-2 * P (Pa) * S (L / min) A plasma sterilization method, wherein a voltage is applied in a range of 3 kV to 20 kV.

Images