Patent Grant
10293309
The present invention relates to a method for, a bubble generating nozzle for, and an apparatus for generating micro-nano bubbles, wherein the method, the nozzle, and the apparatus use water hammering.
Washing or sterilizing by micro-nano bubbles is a method that uses only water, air, and additives of a trace quantity, offering a reduced environmental load. Due to this, such method has attracted attention as an alternative to a conventional method for washing or sterilizing that uses materials like detergents and chemicals. In addition, because of such method being highly safe, an application as a sterilization method for vegetables and foods has been studied. Conventional methods for generating micro-nano bubbles have been known in three fashions: the gas-liquid two-phase swirl flow method, the venturi tube method, and the pressure dissolution method. (For example, refer to Patent Literatures 1 and 2 for the gas-liquid two-phase swirl flow method and the pressure dissolution method.)
Such methods are however not satisfactory because the number of micro-nano bubbles generated by each of such methods is still not large enough. Although each of such conventional three methods can easily produce micro-bubble water, nucleating agents like base and magnesium must be added to the micro-nano water for generating a sufficient number of micro-nano bubbles. Addition of the nucleating agents has been a major obstacle in expansion of application to washing and sterilization of such as semiconductor devices and food. At present however, it is very difficult to generate a large amount of micro-nano bubbles using pure water.
Pumps of various types are employable as the driving pump in an apparatus that generates bubbles using water, air, and additives of a trace quantity. However, washing and sterilization of semiconductor devices and foods require that all the pertinent apparatus components including the driving pump should operate without causing metal contamination. For example, when devices such as semiconductor wafers are to be washed without metal contamination, all the wetted parts of pumps to be used in an apparatus for generating micro-nano bubbles should be made of those which do not generate any metal ions; and further, such pumps must operate stably at a discharge pressure of 0.3 to 0.6 MPa.
In consideration for these, the inventors of the present invention have proposed an apparatus that employs a compressed-air driven bellows-cylinder pump as a pump that feeds liquid without using rotating movements (Patent Literatures 3 and 4). All the wetted parts of the proposed pump are made of fluorine resin to avoid the feared metal contamination that will occur in a rotating type pump. To achieve the goal of performing a clean washing without the influence of contamination, technical development is desired on application of plastic by use of such as fluorine resin to all the related constituent units for generating micro-bubbles, including not only pumps but also nozzles.
{Patent Literature 1}
Laid-open patent application TOKKAI 2009-274045
{Patent Literature 2}
Laid-open patent application TOKKAI 2008-264771
{Patent Literature 3}
U.S. Pat. No. 4,547,451
{Patent Literature 4}
U.S. Pat. No. 4,924,907
In conventional technologies, it is extremely difficult to generate a large amount of micro-nano bubbles only with pure water but without using any nucleating agents. Granted that addition of the nucleating agents is intended, the agents are required to be used in a significantly reduced amount. In addition, if micro-nano bubbles can be generated in an amount considerably larger than a quantity that conventional technologies will generate, great improvement in washing and sterilization can be expected and, further, the broadening of application of such technique to various usages becomes practicable. Thus, a method for generating micro-nano bubbles by a new technique instead of prior techniques and an apparatus for generating micro-nano bubbles capable of actualizing such new technique have been strongly desired.
In the technical field to which the present invention relates, constructing a system capable of generating micro-nano bubbles without metal contamination is still being sought as in the past. As stated above, a prospect that this problem can be solved by employing a compressed-air driven bellows-cylinder pump, in which all the wetted parts thereof are made of fluorine resin, is obtained. Moreover, if micro-nano bubbles can be generated in an amount considerably larger than a conventional quantity using a micro-nano bubble generating apparatus that employs the pump of such configuration, it is expected that such bubble-generating method will be a useful washing method as a response to a demand by technical movements toward the fining of wiring in manufacturing semiconductor devices. At present however, a high performance apparatus of metal-free material that can generate an increased amount of bubbles has not been available.
Therefore, it is strongly desired to establish a new method for generating micro-nano bubbles and to develop a high-performance apparatus for generating micro-nano bubbles, by general optimization of structures and shapes of constituents including pumps and other constituting parts such as a bubble generating nozzle, a gas-liquid mixing vessel, and a liquid-feeding device. Ultimately, it is necessary to construct a system capable of generating micro-nano bubbles without metal contamination.
In view of the background described above, an object of the present invention is to provide an apparatus for generating micro-nano bubbles to construct a system that performs clean washing and sterilizing with a large amount of micro-nano bubbles generated using pure water only and can generate micro-nano bubbles without metal contamination. The apparatus intended to be provided, including a bubble generating nozzle and an auto-regulating gas-liquid mixing vessel is to operate on a new method, which is different from conventional arts, for generating micro-nano bubbles using water hammering.
The basic idea for solving the problem described above is use of violent water hammering to generate a large amount of micro-nano bubbles that contains dissolved gas, wherein the water hammering occurs in collision of water, a non-compressive substance. To actualize this, the inventors of the present invention has been led to the present art through, in the method for generating micro-nano bubbles and the apparatus therefor, optimizing the structure and the shape of the bubble generating nozzle so that the water hammering power will work to its utmost extent and constructing an apparatus for generating micro-nano bubbles having a configuration that accelerates generating a large amount of micro-nano bubbles.
Thus, the configuration of the present invention is as follows:
(2) The present invention provides a method for generating micro-nano bubbles using water hammering power, the method comprising:
producing jets of a gas-including liquid by injecting the liquid from the outside of a cylinder via two or more through-holes in the cylinder at a pressure higher than the atmospheric pressure, providing the cylinder having such two or more through-holes with a diameter of 0.1 to 6.0 mm, arrayed in the circumferential direction thereof with such a configuration that the respective openings of such two or more small through-holes are arranged facing each other in the same plane;
creating a collision of the jets of the gas-including liquid inside the cylinder; and
generating micro-nano bubbles by the mutual collision of the jets of the gas-including liquid, wherein, in order to maintain the inflow direction of the gas-including liquid unchanged until reaching the inlet position of the through holes,
the cylinder is arranged perpendicular to an inflow direction of the gas-including liquid so as to align the openings of the through-holes with the inflow direction thereof, or arranged in parallel to the inflow direction of the gas-including liquid using a cylinder which has one end formed into a closed tube-like shape and an outer wall with a smaller cross-sectional area than that of an introduction port of the gas-including liquid, provided inside a nozzle case for feeding the gas-including liquid to the cylinder.
(3) The present invention provides the method for generating micro-nano bubbles as described in the paragraph (2), further comprising:
a sucking process that sucks a gas and a liquid;
a pressurization process that pressurizes the gas and the liquid;
a dissolved gas enriching process, wherein the pressurized gas-including liquid is mixed with another new gas;
a dissolved gas miniaturization process that generates micro-nano bubbles,
wherein the pressurized gas-including liquid prepared at the dissolved gas enriching process is injected from the outside of the cylinder having two or more through-holes with the diameter of 0.1 to 6.0 mm, arrayed in the circumferential direction thereof with such a configuration that the respective openings of such two or more through-holes are arranged facing each other in the same plane via such through-holes at a pressure higher than the atmospheric pressure to produce jets of the liquid, and the jets are collided mutually inside the cylinder.
(4) The present invention provides the method for generating micro-nano bubbles as described in the paragraph (2), wherein the pressure higher than the atmospheric pressure at the time of squirting is between 0.2 and 0.6 MPa, and the diameter of the small through-holes at the part leading to the hollow of the cylinder is between 0.1 and 0.3 mm.
(5) The present invention provides the method for generating micro-nano bubbles as described in the paragraph (2), wherein the liquid of the gas-including liquid comprises at least one substance selected from the group consisting of ozone, oxygen, hydrogen peroxide, chloric acid, perchloric acid, and potassium permanganate.
(6) The present invention provides the method for generating micro-nano bubbles as described in the paragraph (2), wherein the gas of the gas-including liquid comprises at least one substance selected from the group consisting of carbon dioxide, hydrogen gas, and nitrogen gas.
(7) The present invention provides an apparatus for generating micro-nano bubbles using water hammering power created by a mutual collision of jets of a gas-including liquid, comprising:
a gas port, a liquid pipe and a regulating valve for sucking each of a gas and a liquid;
a pump for pressurizing the gas and the liquid in a mixture and transferring them;
a gas-liquid mixing vessel for enriching the dissolved gas by mixing the transferred liquid, which includes the gas, with another new gas; and
a bubble generating nozzle for generating micro-nano bubbles using the gas-including liquid prepared in the gas-liquid mixing vessel,
wherein the bubble generating nozzle comprises:
a hollow cylinder having two or more through-holes with a diameter of 0.1 to 6.0 mm, arrayed in the circumferential direction thereof with such a configuration that the respective openings of each of such two or more through-holes faces each other in the same plane; and a micro-nano bubble discharge port provided on at least one end of the hollow cylinder,
wherein the through-holes are arranged so that all of their extension lines passing through respective center of the cross-section of each of the through-holes intersect each other in the inside of the hollow of the cylinder,
wherein, in order to maintain the inflow direction of the gas-including liquid unchanged until reaching the inlet position of the through-holes,
the hollow cylinder is arranged perpendicular to an inflow direction of the gas-including liquid so as to align the openings of the through-holes with the inflow direction thereof, or arranged in parallel to the inflow direction of the gas-including liquid using a cylinder which has one end formed into a closed tube-like shape and an outer wall with a smaller cross-sectional area than that of an introduction port of the gas-including liquid, provided inside a nozzle case for feeding the gas-including liquid to the cylinder.
(8) The present invention provides the apparatus for generating micro-nano bubbles as described in the paragraph (7), wherein the bubble generating nozzle has two or more numbers of hollow cylinders.
(10) The present invention provides the apparatus for generating micro-nano bubbles as described in the paragraph (7), wherein the hollow cylinder has, in its longitudinal direction, two or more rows of the through-holes, each of such rows consisting of two or more through-holes with a diameter of 0.1 to 6.0 mm.
(11) The present invention provides the apparatus for generating micro-nano bubbles as described the paragraph (7), wherein the diameter of the through-holes that lead to the hollow of the hollow cylinder is between 0.1 and 0.3 mm.
(12) The present invention provides the apparatus for generating micro-nano bubbles as described in the paragraph (7), wherein the diameter of the micro-nano bubble discharge port provided on at least one end of the hollow cylinder is equal to or larger than the diameter of a part of the hollow cylinder, wherein such part is such a part where the through-holes are arranged in a circumferential direction.
(14) The present invention provides the apparatus for generating micro-nano bubbles as described in the paragraph (7), wherein, in the bubble generating nozzle for generating micro-nano bubbles, the gas-including liquid is squirted at a pressure of 0.2 to 0.6 MPa through the through-holes of the bubble generating nozzle.
(15) The present invention provides the apparatus for generating micro-nano bubbles as described in the paragraph (7), wherein the gas-liquid mixing vessel has the bubble generating nozzle for generating micro-nano bubbles, and the liquid that includes the gas transferred by the means for pressurizing and transferring is discharged into the gas-liquid mixing vessel by the bubble generating nozzle.
(16) The present invention provides the apparatus for generating micro-nano bubbles as described in the paragraph (7), wherein the gas-liquid mixing vessel has a float valve inside or outside the vessel to maintain the volume of the gas and the liquid and the internal pressure inside the vessel always within a prescribed range by discharging excess gas from the vessel.
(17) The present invention provides the apparatus for generating micro-nano bubbles as described in the paragraph (7), wherein a pump or piping, or both, through which the gas-including liquid flows, is made of plastic.
(18) The present invention provides the apparatus for generating micro-nano bubbles as described in the paragraph (17), wherein a pump or piping, or both, through which the gas-including liquid flows, is made of fluorine resin.
(19) The present invention provides the apparatus for generating micro-nano bubbles as described in the paragraph (7), wherein the pump for pressurizing and transferring the liquid that includes the gas is a compressed-air driven or an electric motor driven bellows cylinder pump.
(20) The present invention provides the apparatus for generating micro-nano bubbles as described in the paragraph (7), wherein the liquid of the gas-including liquid comprises at least one substance selected from the group consisting of ozone, oxygen, hydrogen peroxide, chloric acid, perchloric acid, and potassium permanganate.
(21) The present invention provides the apparatus for generating micro-nano bubbles as described in the paragraph (7), wherein the gas of the gas-including liquid comprises at least one substance selected from the group consisting of carbon dioxide, hydrogen gas, and nitrogen gas.
(22) The present invention provides the apparatus for generating micro-nano bubbles according to the paragraph (20), wherein the gas of the gas-including liquid additionally comprises at least one substance selected from the group consisting of carbon dioxide, hydrogen gas, and nitrogen gas.
The method for generating micro-nano bubbles by the present invention generates micro-nano bubbles using the water hammering power. Therefore, the method is able to generate micro-nano bubbles in a large amount using pure water only without use of substances which are not necessarily needed such as nucleating agents. Accordingly, the method can realize a clean washing and sterilization. Since this water hammering power is maximized by the use of a bubble-generating nozzle having an optimized structure and shape, the use of such optimized nozzle makes it possible to perform the continuous and stable generation of bubbles in an efficient manner. Thereby, the amount of generation of small-size bubbles, not only of the size of micrometer order but also of nanometer order, can be increased together. This feature enhances the capability and function in the washing and sterilizing more than those in conventional techniques.
The apparatus for generating micro-nano bubbles by the present invention has a bubble generating nozzle and equipment configuration that permits the generating of bubbles in a large amount stably; therefore, the apparatus is usable in a set of equipment for clean washing and sterilizing with pure water.
On the other hand in the gas-liquid mixing vessel that dissolves gas in liquid, transferring a gas and a liquid in a mixture by a pump may sometimes prevent generating uniform micro-nano bubbles. This is because the occurrence of a phenomenon in which the volume of the gas increases, causes the inside of the gas-liquid mixture vessel to become full of the gas and the volume of the liquid in the vessel to be lessened, and the gas not dissolved in liquid is fed to the bubble generating nozzle in an as-gas-state, resulting in an unstable generation of micro-nano bubbles. This problem is solvable by discharging an excess gas from the gas-liquid mixing vessel through a float valve provided inside or outside the vessel. With this float valve, the volume of the gas and the liquid are always maintained within a prescribed range and thereby the amount of generation of the micro-nano bubbles becomes constant.
Further, for a clean washing that is incompatible with metal ions which a wetted part generates, configuring a pump or piping, or both, in a washing apparatus with plastic or preferably with fluorine resin makes the apparatus become to have a high reliability and a clean feature.
The method and the apparatus by the present invention contribute to constructing a micro-nano bubble generating system that generates bubbles without metal contamination. For example, application of the present invention to washing such as semiconductor wafers simplifies such washing process compared to conventional processes that perform complicated washing using such as drug solutions. Further, the invention is cable of reducing an environmental load because the invented method does not need use of materials such as drug solutions. Moreover, the use of the invention for sterilization of foods such as vegetables makes it possible to perform reliable and safe sterilization.
The following describes the best mode for carrying out the present invention, referring to drawings.
These constituents are arranged as illustrated in a perspective view
Next, the gas and the liquid are agitated by the pump 15 and are force-fed to the gas-liquid mixing vessel 14. The pump 15 used is mainly a bellows cylinder pump of compressed-air driven type but an electric motor driven type may be used. The gas and the liquid in the gas-liquid mixing vessel 14 are under the pressure generated by the pump 15; therefore, the gas is easily dissolved. The pressure that force-feeds the gas and the liquid from the pump 15 is watched by the pressure sensor 12. Increasing the quantity of the dissolved gas with this manner, the preparations are made for increasing the amount of generation of the micro-nano bubbles. In the micro-nano bubble generating system by the present invention, it is a practical manner to use the bellows cylinder pump as the pump 15. Depending on the use purpose however, conventionally known pumps are applicable. The applicable pumps include a reciprocating pump such as a piston pump, a plunger pump, or a diaphragm pump; or a rotary pump such as a gear pump, an eccentric pump, or a screw pump.
The liquid entered under force-feeding into the gas-liquid mixing vessel 14 mixes with a gas to dissolve the gas thereinto and then is transferred to the micro-nano bubble generating nozzle attachment part 11. The micro-nano bubble generating nozzle attachment part 11 is a part to which a nozzle connects, wherein the nozzle generates, from the gas-including liquid, micro-nano bubbles in a large amount having a diameter of 60 μm or smaller, preferably to be 15 μm or smaller.
At that time, the pressure sensor 12 senses variations of the liquid pressure at the section between the micro-nano bubble generating nozzle attachment part 11 and the gas-liquid mixing vessel 14 to watch the dissolving conditions of the gas-liquid mixture. By this, a constant pressure condition needed for stable generation of micro-nano bubbles is actualized.
The process to be performed by the apparatus for generating micro-nano bubbles to which the present invention is applied is as follows. Treatments that the gas sucking port 16, the liquid sucking pipe 17, and the gas sucking regulating valve 18 perform are the gas- and liquid-sucking process. The pressure is regulated by the pressure sensor 12. Next, the gas-including liquid is pressurized using the bellows cylinder pump 15; this treatment is the gas-liquid pressurization process. Following this process, the pressurized gas-including liquid is mixed with another new gas using the pump controller 13 and the gas-liquid mixing vessel 14; this treatment is the dissolved gas enriching process. After this, the bubble generating nozzle by the present invention, which nozzle will be mentioned later, is connected to the micro-nano bubble generating nozzle attachment part 11 to generate micro-nano bubbles. This process is referred to as the dissolved liquid miniaturization process, in which the micro-nano bubbles are generated by injecting the gas-including liquid from the outside of a cylinder, which has two or more small through-holes, via such small through-holes at a pressure higher than the atmospheric pressure to produce jets of the liquid, and the jets are collided mutually at one point inside the cylinder.
Next, explanation follows to describe a method for generating micro-nano bubbles in a large amount from the gas-including liquid that is in a gas-dissolved state.
The following explains how to generate the micro-nano bubbles using the water stream squirted from the high-speed liquid jet squirting nozzle. The gas-including liquid is discharged from the high-speed liquid jet squirting nozzle at the discharge pressure of 0.2 MPa to 0.6 MPa given by the high-pressure pump 15. The discharged liquid rapidly releases its pressure and collides violently each other producing a water hammering power. The explosive water hammering smashes the gas-including liquid and makes the liquid to be in a state that a large amount of micro-nano bubbles is involved therein. It should be noted that, depending on the method of release, there is a case where the amount of generation of micro-nano bubbles becomes reduced. However, the micro-nano bubbles can be generated in a large amount with the method and the apparatus by the present invention.
The reason of feeding the liquid at a high-pressure is to increase the speed of the liquid in squirting from the small-hole. This means that making the liquid collision high-speed increases the impact energy and that a large amount of micro-nano bubbles of more minute size can be generated thereby.
Assume that F is the power of collision. Also assume that the density of a liquid is ρ, the size of a small-hole S, and the velocity of a liquid V. Then, the relationship of F=ρSV2 holds. For the optimal value of F, the optimum design that considers the relation between the size of hole S and the velocity V is needed.
What is important here is that, if a pump capable of generating a higher pressure is used, there is a possibility that a further-large amount of micro-nano bubbles can be generated. For example, it is available to use a high-pressure pump that generates pressures of 0.5 to 250 MPa or so. If a pump of this kind is used, the liquid velocity V increases proportionally to the pressure and the amount of generation of micro-nano bubbles greatly increases because the impact power of the water hammering power F increases with the square of V. However, for the application of such high-pressure pump to an apparatus for generating micro-nano bubbles, it is difficult to meet various demands such as light weight, small size, metal-free, and low maintenance cost.
In the present invention, by using the nozzle having a structure as illustrated in
The micro-nano bubble generating nozzle by the present invention needs to have a diameter of 0.1 to 6 mm at its nozzle parts 3b and 4b shown in
The small-hole flow passages 3a and 4a are enough when they are such a device as has a stream-narrowing function for feeding the gas-including liquid in a form of a high-speed jet; and when they are taper-shaped continuously toward the nozzle parts 3b and 4b, they may also be enough. The amount of generation of micro-nano bubbles is determined mainly by the dimension of the diameter of the nozzle parts 3b and 4b; therefore, the small-hole flow passages 3a and 4a may be omitted in the present invention.
An example of another method for colliding the gas-dissolved liquid will be explained referring to
The experiment told that controlling the velocity of liquid V made the amount of generated micro-nano bubbles increased and the life of bubbles prolonged. When the velocity V exceeds 25 m/s as a guideline, the nozzle generates micro-nano bubbles stably.
The same effect will be obtained at a lower liquid velocity by squirting the liquid toward center from every direction concentrating the water hammering at the center. This means that when the water hammering is given from every direction, the same or more effect will be produced even if the velocity is reduced to ½. For example, since F=2ρSV2, when eight holes are arranged so that the hammering among the jets concentrates in the center, the force at the center becomes F=ρS(½)2×8=2ρSV2. Thus, when the small-hole of the nozzle is provided in a plural number for concentrating the water hammering produced by the liquid collision, the energy of the liquid collision becomes same even if the velocity V is low because the flowing quantity of liquid increases. Since the amount of generation of micro-nano bubbles will be acceptably same if the energy in the collisions of the liquid is same, the pressure of discharging the liquid can be lowered and the amount of generation of micro-nano bubbles will be secured as desired.
Discharging the liquid from a plurality of holes, as the nozzle illustrated in
Then, as illustrated in
A float 31 illustrated in
Mixing the gas and the liquid requires its method to increase the dissolving efficiency of the gas into the liquid by enlarging the contact area of the gas and the liquid. If the efficiency lowers, shortage of the generation amount occurs due to a shortage of the gas, which is a fatal problem in the generating of micro-nano bubbles.
We examined how much the amount of generated micro-nano bubbles will be increased depending on the degree of control over the amount of the gas and the liquid. As a result, it was understood that the following are points of interest. If the amount of the liquid in the volume ratio inside the gas-liquid mixing vessel occupies 60% and the amount of the gas occupies 40%, the gas-liquid ratio is the ideal balance of amounts. To stabilize the amount of generation of the micro-nano bubbles and to increase the amount of generated bubbles, it is necessary that the condition of the mixing of the gas to be dissolved and the liquid should be optimized by exhausting the excess gas from an excess gas exhausting port 48 of a float socket 47 using the buoyancy of the float 31 caused by the liquid for controlling their ratio automatically. In the present invention, for the purpose of increasing greatly the amount of generation of micro-nano bubbles, it is preferable to control the volume ratio of the gas and the liquid in the gas-liquid mixing vessel within the range of gas to liquid ratio=50:50 to 5:95 so that the liquid will occupy more part in the volume ratio. Also in the present invention, the float 31 may be installed outside the gas-liquid mixing vessel, instead of installing inside. In this arrangement, connecting the inside and outside of the gas-liquid mixing vessel using such as a communication pipe permits controlling the volume ratio of the gas and the liquid.
In
When using a conventional apparatus that generates a less amount of micro-nano bubbles, a major method for generating an increased amount of micro-nano bubbles is as follows. The method is comprised of processes of: generating micro-nano bubbles once in a water tank; pumping up micro-nano bubbles generated in the water tank again; injecting an additional gas to be dissolved into the pumped bubble-containing liquid at the gas-liquid mixing vessel; and circulating the gas-injected bubble-containing liquid multiple times to bring the bubble-containing liquid to a state in which a large amount of micro-nano bubbles are involved. Thereby, micro-nano bubbles are generated in an increased amount.
In this method, it is difficult to control the amount of generation of the micro-nano bubbles. Further, a circulating technique invites trouble such as occurrence of contamination. Because of that, an apparatus that is capable of generating a large amount of micro-nano bubbles in one process without use of a circulation technique is desired.
Therefore, it is intended to generate micro-nano bubbles, without circulation in the gas-liquid mixing vessel to be used in the present invention, by a liquid-collision in the gas-liquid mixture state under the working of the micro-nano bubble generating nozzle 38, which is held on a nozzle holder 39, having a structure same as illustrated in
In this situation, it is the requisite condition that the nozzle 38 arranged inside the gas-liquid mixing vessel should issue the liquid of the gas-liquid mixture state at a flow rate more than that of the nozzle 11 arranged at the distal end to increase the pressure inside the gas-liquid mixing vessel. If the flow rate of the nozzle 38 is smaller, micro-nano bubbles sometimes may not be generated from the nozzle attached at the distal end.
The effect of the installing of the nozzle 38 inside the gas-liquid mixing vessel is that one-path of processing along the gas-liquid mixing vessel to the nozzle permits a stable generation of a large amount of micro-nano bubbles. Thereby, such technique enables provision of an apparatus suitable for washing process in semiconductor manufacturing line for example.
In the present invention, configuring gas-liquid mixing vessels in a multi-stage cascade makes it possible to generate a larger amount of micro-nano bubbles; this is a useful means for generating a large amount of bubbles.
As can be seen in
Bubbles like this produced by the water hammering gives less damage to the nozzle structure, because collision occurs only between the liquid. Therefore, it is possible to make a bubble generating apparatus have a longer service life.
The significant feature of the method and the apparatus for generating micro-nano bubbles by the present invention is that they are compatible with using pure water as a gas-including liquid that does not include any foreign matters such as nucleating agents in an application to washing and sterilization of semiconductor devices and food. Granted that a use of the nucleating agents, or the like, is needed to increase the amount of generation of micro-nano bubbles, the quantity of addition of such material into pure water can be considerably reduced. In the present invention, tap water, well water, or spring water such as natural water other than pure water can be used in consideration of the supply state or usability. Further in the present invention, the strengthening of the oxidizing action of the dissolved liquid and the reformulating of the liquid for enhancing permeability required for impurity removing action may be practicable to increase the effectiveness of the washing and sterilizing.
The method for strengthening the oxidizing action of the dissolved liquid stated above includes the use of the gas-including liquid which is an aqueous solution prepared by adding, to pure water, at least one of oxidant selected from the group consisting of ozone, oxygen, hydrogen peroxide, chloric acid, perchloric acid, and potassium permanganate. Among these oxidant, ozone and oxygen are preferable oxidant for the present invention, because they have little adverse effect as an additive and their environmental load is very small.
As the method for enhancing the permeability for impurity removing action in the gas-including liquid stated above, it is a preferable method to add a gas selected from the group consisting of carbon dioxide, hydrogen gas, and nitrogen gas, which has excellent permeability for impurity removing action. On generation of micro-nano bubbles, carbon dioxide, hydrogen gas, or nitrogen gas invades easily the boundary surfaces between a semiconductor device and impurities, such as residuals of resist, adhering to its surface. Thereby, the effectiveness of the washing is largely increased. Further, since carbon dioxide or nitrogen gas is harmless to human body, such gas is suitable for the present invention as a reformulating additive.
The structure and shape of the micro-nano bubble generating nozzle by the present invention will be detailed referring to concrete embodiments.
A liquid-collision nozzle illustrated in
A liquid-collision nozzle illustrated in
A liquid-collision nozzle illustrated in
A liquid-collision nozzle illustrated in
As stated above, micro-nano bubbles, which were not generated without a high-pressure pump, can be generated in a large amount by optimizing the structure and arrangement of the through-hole of the liquid-collision nozzle even if the pump pressure is 0.2 MPa; thus this technique is able to actualize energy-saving.
Referring to
A liquid-collision nozzle illustrated in
In the present invention, either of the nozzles having the structure illustrated in
Regarding a liquid-collision nozzle illustrated in
Thus, the diameter of the small through-holes of the liquid-collision nozzle is an important factor that determines the performance of the micro-nano bubbles. Although there is a difference in behavior depending on the nature of the liquid and the gas to be dissolved, the tendency is as described in the above. Therefore, the amount of micro-nano bubbles can be controlled by adjusting the diameter of the small through-holes of the liquid-collision nozzle.
As can be known from
Micro-nano bubbles were generated using distilled water as the gas-including liquid with the apparatus for generating micro-nano bubbles by the present invention as illustrated in
Comparison of the results shown in
As stated above, the method for generating micro-nano bubbles by the present invention generates micro-nano bubbles using the water hammering power. Therefore, the method is able to generate micro-nano bubbles in a large amount using pure water only without use of substances which are not necessarily needed such as nucleating agents. Accordingly, the method can realize a clean washing and sterilization. Since this water hammering power is maximized by the use of a bubble generating nozzle having an optimized structure and shape and by an apparatus that is able to stably perform the generation of a large amount of bubbles, the application of such combination makes it possible to perform the continuous and stable generation of bubbles in an efficient manner. Thereby, the amount of generation of small-size bubbles, not only of the size of micrometer order but also of nanometer order, can be increased together. This feature enhances the capability and function in the washing and sterilizing more than those in conventional techniques.
Further, for a clean washing that is incompatible with metal ions which a wetted part generates, configuring a pump or piping, or both, in a washing apparatus with plastic or preferably with fluorine resin makes the apparatus become to have a high reliability and a clean feature. Thus, the apparatus for generating micro-nano bubbles by the present invention is applicable to the clean washing for such as semiconductor wafers. Conventionally, the washing of semiconductor wafers has used processing with such as strong acid treatment, alkaline neutralization, and pure water rinsing. The process therefore has been complicated and the environmental load has been large because, for example, the process uses drug solutions. However, the present invention is able to solve this problem. Further, the process burden such as in the disposal of drug solutions is eliminated and the required scale for semiconductor manufacturing equipment becomes small and related process is made compact; these are a great industrial value.
Further, in the semiconductor wafer washing, the use of a micro-nano bubble-generated liquid, other than pure water, improves the washing effect largely and makes the washing process very simple with the washing equipment downsized. The micro-nano bubble-generated liquid for such use is prepared by adding a gas having excellent oxidizing ability like oxygen or a permeable impurity removal agent such as carbon dioxide or nitrogen gas, and then followed by the micro-nano bubble generation process by the present invention. Thereby, the washing becomes environment friendly. Further, the process burden such as in the disposal of drug solutions is eliminated and the required scale for semiconductor manufacturing equipment becomes small and related process is made compact; these are a great industrial value.
The micro-nano bubble generating system by the present invention is applicable to a medical use, because the system uses micro-nano bubbles generated by a clean system that uses pumps and wetted part made of fluorine resin. Therefore, it is expected that the field of the application of the invented system will expand greatly.
Further, the capability of the washing and sterilization by micro-nano bubbles that uses oxygen or ozone as its constitution gas can be applied not only to the semiconductor field but also to fields of foods and vegetables. Thus, there is a possibility in that the application range may expand to the fields such as agriculture and fisheries; and the method for generating micro-nano bubbles, the bubble generating nozzle, and the apparatus for generating micro-nano bubbles by the present invention have a very high superiority in such field expansion movement.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2013/066902 | 6/13/2013 | WO | 00 |
| Publishing Document | Publishing Date | Country | Kind |
|---|---|---|---|
| WO2014/199525 | 12/18/2014 | WO | A |
| Number | Name | Date | Kind |
|---|---|---|---|
| 4994242 | Rae | Feb 1991 | A |
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