Method for producing an ultrafine bubble-containing liquid, and apparatus for producing ultrafine bubbles

Abstract

To provide a technique for efficiently producing an ultrafine bubble-containing liquid containing predetermined gas.SOLUTION: Droplets D1 containing ultrafine bubbles containing first gas are made to fly in an atmosphere AT of second gas different from the first gas.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a technique for producing an ultrafine bubble-containing liquid.

Background Art

[0002] In recent years, the usefulness of ultrafine bubbles (Ultra Fine Bubble; hereinafter also referred to as "UFB") with a diameter of less than 1.0 μm has been confirmed in various fields. It has also been reported that UFB-containing liquids exhibit different functions depending on the type of gas constituting the UFB. For example, when nitrogen is used as the gas constituting the UFB, it has an anti-corrosion effect, and when oxygen is used, it has a growth-promoting effect. Furthermore, it has been reported that a sterilizing effect can be obtained by containing ozone in the constituent gas.

[0003] As a technique for producing such a UFB-containing liquid, Patent Document 1 discloses a fine bubble generator that generates fine bubbles containing a gas by ejecting a pressurized liquid in which a gas is pressurized and dissolved from a decompression nozzle.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the technique described in Patent Document 1, in the production of UFB, a method is adopted in which air or a desired gas is previously dissolved in a liquid to generate a gas-dissolved liquid, and then UFB is precipitated. Although bubbling is performed to generate the gas-dissolved liquid, in this case, most of the gas introduced into the liquid flows out into the atmosphere without being dissolved in the liquid, and the gas is wasted, so there is a problem that the production efficiency of the UFB-containing liquid is low.

[0006] The present invention aims to provide a technology for efficiently producing an ultrafine bubble-containing liquid containing a predetermined gas. [Means for solving the problem]

[0007] The present invention is a method for producing an ultrafine bubble-containing liquid, The method includes the steps of: flying a droplet containing ultrafine bubbles containing a first gas in an atmosphere of a second gas different from the first gas; recovering the droplet that has flown in the atmosphere using a recovery container filled with the second gas; and storing the recovery container in a storage chamber and supplying the first gas to the space in the storage chamber to form an atmosphere of the first gas in the storage chamber and in the recovery container communicating with the storage chamber. It is characterized by the following: [Effects of the Invention]

[0008] According to the present invention, it becomes possible to efficiently produce an ultrafine bubble-containing liquid containing a predetermined gas. [Brief explanation of the drawing]

[0009] [Figure 1] This figure shows the schematic configuration of the UFB-containing liquid manufacturing apparatus in this embodiment. [Figure 2] This is a schematic diagram illustrating the conceptual configuration of the discharge unit of a UFB generator. [Figure 3] This diagram shows the gas exchange between the liquid droplet and the atmosphere, and the gas exchange between the liquid droplet and the UFB (Ultraviolet Flux). [Figure 4] This is a schematic diagram of a typical UFB-containing liquid manufacturing apparatus. [Figure 5] This figure shows a first modified example of a UFB-containing liquid manufacturing apparatus. [Figure 6] This figure shows a second modified example of the UFB-containing liquid manufacturing apparatus. [Figure 7] This figure shows the manufacturing conditions and manufacturing results of the UFB-containing liquid in each example. [Modes for carrying out the invention]

[0010] Embodiments of the present invention will be described in detail below with reference to the attached drawings. Note that the following embodiments do not limit the present invention as defined in the claims, and not all combinations of features described in these embodiments are necessarily essential to the solution of the present invention. Furthermore, in the following description, ultrafine bubbles, which are bubbles with a diameter of less than 1.0 μm, are also referred to as "UFB," and the ultrafine bubble-containing liquid is also referred to as "UFB-containing liquid."

[0011] Figure 1 shows a schematic configuration of the UFB-containing liquid manufacturing apparatus 1 in this embodiment. The UFB-containing liquid manufacturing apparatus 1 comprises a supply unit 10 for supplying a gaseous dissolved liquid, a UFB generator 20, and a recovery container (recovery means) 30 for the UFB-containing liquid. In this embodiment, the gaseous dissolved liquid supply unit 10 generates a gaseous dissolved liquid (air-dissolved water) L10 by dissolving air (atmosphere) in the liquid (water in this example) supplied to the supply container 11, and supplies the generated gaseous dissolved liquid L10 to the UFB generator 20. The gaseous dissolved liquid L10 is generated by introducing air into the liquid supplied to the supply container 11 using a bubbling mechanism (not shown) or the like and stirring it. The gaseous dissolved liquid L10 generated in the supply container 11 is supplied to the UFB generator 20 via the supply channel 12. The gas (air) dissolved in the gaseous dissolved liquid L10 supplied to the UFB generator 20 is also referred to as the first gas in the following description. In this embodiment, air (atmosphere) is used as an example of the first gas, but the first gas is not limited to air and may be other gases.

[0012] The UFB generator 20 is equipped with multiple discharge units (discharge means) 21 that generate UFB in droplets by discharging air-dissolved water L10 supplied from the supply unit 10 as tiny droplets. The UFB generator 20 is installed on top of the recovery container 30 and discharges a large number of droplets D1 from the discharge units 21 toward the spatial region 31 of the recovery container 30. The spatial region 31 of the recovery container 30 is filled with a predetermined gas (hereinafter also referred to as the second gas) that is different from the first gas (air), and a predetermined gas atmosphere AT is formed. Therefore, the recovery container 30 also plays the role of an atmosphere-forming means in which a predetermined gas atmosphere AT is formed.

[0013] In this embodiment, "different gases" refers to gases in which at least one of the gaseous components and gaseous concentration (partial pressure) is different. That is, in two gases, if the gaseous components of one gas are different from those of the other gas, then the two gases are considered different. Furthermore, if one gas and the other gas have the same gaseous components, but the concentration (partial pressure) of the gaseous components of one gas is different from the concentration of the gaseous components of the other gas, then the two gases are considered different.

[0014] When droplet D1 is discharged from the discharge section 21, a rapid pressure change occurs in the liquid L10, and this pressure change generates UFB100 in the discharged droplet D1, with air as the gaseous component. The droplet D1 containing this UFB100 flies within the spatial region 31 of the recovery container 30, where an atmosphere AT of a predetermined gas (second gas) is formed. While flying within the atmosphere AT of the predetermined gas, gas exchange occurs between the gaseous component dissolved in droplet D1 and the predetermined gas, and the predetermined gas dissolves in droplet D1. Further gas exchange occurs between the predetermined gas dissolved in droplet D1 and the first gas (air) that constitutes the UFB present in droplet D1, and the UFB becomes a UFB with the first gas as the gaseous component. As a result, droplet D2 containing a UFB with the predetermined gas as the gaseous component is generated. This droplet D2 is recovered and stored in the recovery container 30. As a result, a UFB-containing liquid L20 containing UFB with a predetermined gas as a gaseous component is produced.

[0015] Here, we will describe the discharge section 21 provided in the UFB generator 20 applied to this embodiment. Figure 2 is a schematic diagram showing the conceptual configuration of three types of discharge sections 22 to 24 that can be applied as the discharge section 21 of the UFB generator 20 of this embodiment. In Figure 2, (a) shows a pressure-type discharge section 22, (b) shows a thermal-type discharge section 23, and (c) shows a piezo-type discharge section 24.

[0016] The pressure-type discharge unit 22 shown in Fig. 2(a) includes a discharge port forming member 22c in which a plurality of minute discharge ports 22b for discharging the liquid L10 supplied into the flow path 22a as droplets are formed, and a pressurizing unit (pressure generating means) 22d for applying pressure to the liquid L10 in the flow path 22a. In the present embodiment, the discharge port forming member 22c has a metal plate in which a plurality of discharge ports 22b are formed. The gas-dissolved liquid (liquid L10) supplied from the above-described supply container 11 (Fig. 1) is supplied to the flow path 22a (Sa1). In the present embodiment, water in which air (gas with an oxygen partial pressure of 21%) is saturated and dissolved is supplied to the flow path 22a as the gas-dissolved liquid. The liquid L10 filled in the flow path 22a is pressurized by the pressurizing unit 22d (Sa2). Thereby, droplets D1 are discharged from the discharge ports 22b (Sa3). In the process of discharging the droplets D1, immediately before being discharged from the discharge ports 22b, the pressure (water pressure) of the liquid L10 increases. And when the liquid L10 is discharged to the outside from the discharge ports 22b and becomes the droplets D1, the pressure of the liquid L10 decreases. Thus, a steep pressure change occurs in the liquid L10 before and after being discharged from the discharge ports 22b. Thereby, the dissolved gas (air) precipitates in the droplets D1 composed of the gas-dissolved liquid, and the UFB100 having air as the gas component is generated.

[0017] The thermal-type discharge unit 23 shown in Fig. 2(b) includes a heating element 23d that converts electrical energy into thermal energy as the pressure generating means. When power is supplied to the heating element 23d provided at a position facing the discharge port 23b in a state (Sb1) where the flow path 23a is filled with the gas-dissolved liquid (liquid L10), film boiling occurs in the liquid L10 in the flow path 23a due to the heat generation of the heating element 23d (Sb2). Due to the pressurizing force of the bubbles BL generated by the film boiling, the liquid L10 in the flow path 23a is discharged from the discharge port 23b as the droplets D1 (Sb3). The steep pressure change of the liquid L10 at this time generates the UFB100 in the droplets D1. Further, in this thermal-type discharge unit 23, in addition to the pressure change of the liquid L10 before and after discharge as described above, shock waves generated along with the temperature rise and disappearance of the film boiling of the liquid L10 are also considered to contribute to the formation of the UFB100.

[0018] Also, in the piezo-type discharge unit 24 shown in Fig. 2(c), a voltage is applied to the piezo element 24d in a state (Sc1) where the gas-dissolved liquid (liquid L10) is filled in the flow path 24a. As a result, the piezo element 24d is deformed to pressurize the liquid L10 in the flow path 24a (Sc2), and the droplet D1 is discharged from the discharge port 24b (Sc3). Due to the steep pressure change before and after the discharge, UFB100 having air as a gas component is generated in the droplet D1.

[0019] Fig. 3 is a diagram showing the state of gas exchange between the droplet D1 and the atmosphere AT, and the gas exchange between the droplet D1 and the UFB100 contained in the droplet D1. As described above, the recovery container 30 is filled with a predetermined gas, and a predetermined gas atmosphere AT is formed. A large number of droplets D1 containing UFB100 are discharged from the discharge unit 21 into this atmosphere AT and are in a spray state. This state is shown in Fig. 3(a).

[0020] Immediately after being discharged from the discharge unit 21, the droplet D1 has UFB100 having air as a gas component. However, while flying in the space region 31, gas exchange accompanied by equilibration of partial pressures occurs between the gas (here, air) dissolved inside and the predetermined gas (second gas) forming the atmosphere AT. Since the droplet D1 is minute and has a large gas-liquid interface area (specific surface area) per unit volume, this gas exchange is efficiently performed. Furthermore, the predetermined gas (second gas) that has undergone gas exchange and dissolved in the droplet D1 also undergoes gas exchange with the gas component (in this example, air) of the UFB100 formed in the droplet D1, resulting in a droplet D2 containing UFB200 containing the predetermined gas. This state is shown in Fig. 3(b). Since the specific surface area of the UFB is extremely large, the gas exchange of the UFB is performed more efficiently. Thereafter, the droplet that has flown through the space region 31 is recovered in the recovery container 30 and becomes a UFB-containing liquid L20 containing UFB200 replaced with the predetermined gas, as shown in Fig. 3(c).

[0021] Next, we will describe in more detail an example of the production of UFB-containing liquid. Here, we will describe an example in which general-purpose purified water containing dissolved air is used as a raw material, and a UFB-containing liquid containing UFB made of air (atmosphere) is discharged using a piezoelectric discharge unit 24 into a recovery container 30 with an oxygen partial pressure of 100%, thereby producing a UFB-containing liquid with a high oxygen concentration.

[0022] The liquid supplied to the discharge unit 24 is purified water with dissolved air. Therefore, the partial pressure of oxygen in the purified water before it is discharged from the discharge unit 24 is 21%, and the dissolved oxygen content at room temperature is 7.6 ppm. When this purified water is discharged into the recovery container 30 as a droplet D1, UFB100, which is made up of air, is generated within the droplet D1. The droplet D1 containing this UFB100 flies through the spatial region 31 of the recovery container 30 and is finally recovered by the recovery container 30, becoming the UFB-containing liquid L20. An atmosphere AT filled with 100% oxygen partial pressure is formed in the spatial region 31 of the recovery container 30. As a result, gas exchange proceeds so that the oxygen partial pressure equilibrium between the atmosphere AT with 100% oxygen partial pressure and the droplet D1 with 21% oxygen partial pressure, and the dissolved oxygen concentration in droplet D1 increases. Furthermore, as the dissolved oxygen concentration in droplet D1 increases and the oxygen partial pressure rises, gas exchange also occurs between droplet D1 and the UFB100 contained in droplet D1. That is, before gas exchange occurs, UFB100 is air, and the oxygen partial pressure is 21%. Therefore, as the oxygen partial pressure of droplet D1 increases due to gas exchange with the atmosphere AT, gas exchange also occurs between droplet D1 and UFB100 so that the oxygen partial pressure becomes equilibrium. Since the specific surface area of ​​UFB100 is even larger than that of droplet D1, gas exchange between droplet D1 and UFB100 is performed even more efficiently. In this embodiment, the dissolved oxygen concentration of the fine bubble-containing water recovered in the recovery container 30 is 20 ppm (equivalent to an oxygen partial pressure of 50%), making it possible to produce oxygen-rich UFB-containing liquid (UFB-containing water), and a UFB200 with a high oxygen concentration can be obtained.

[0023] Figure 4 is a schematic diagram of a typical UFB-containing liquid manufacturing apparatus. In this UFB-containing liquid manufacturing apparatus, a predetermined gas 300 is supplied from a high-pressure cylinder 109 to water stored in a supply container 110 to perform bubbling and generate gas-dissolved water L110. Furthermore, the generated gas-dissolved water L110 is supplied to a UFB generator 120 to generate UFB and produce UFB-containing liquid L120, which is stored in a predetermined recovery container 130. An existing UFB generator 120 is used for the UFB generator 120.

[0024] In such a UFB-containing liquid manufacturing apparatus, it is necessary to supply a predetermined gas from a high-pressure cylinder 109 to the water in the supply container 110 and perform bubbling to produce a gas-dissolved liquid L110 in which the predetermined gas is dissolved. Therefore, gas loss occurs when the predetermined gas 300 is released into the atmosphere during the stage of producing the gas-dissolved liquid L110, resulting in low efficiency in producing a gas-dissolved liquid in which the predetermined gas is dissolved at the desired concentration. In addition, it is necessary to keep the high-pressure cylinder 109 installed at all times, which raises concerns about the overall size of the apparatus.

[0025] In contrast, the UFB-containing liquid production apparatus 1 of this embodiment shown in Figure 1 discharges droplets D1 with a large specific surface area into a recovery container 30 filled with a predetermined gas, and performs gas exchange between droplets D1 and the atmosphere AT. This makes it possible to produce droplets D2 in which a predetermined gas (oxygen in the above example) is dissolved at a high concentration while suppressing the wasteful consumption of the predetermined gas. Furthermore, gas exchange also occurs between the UFB 100, which consists of the dissolved high-concentration predetermined gas and the atmosphere, in droplet D2. This makes it possible to efficiently produce a UFB-containing liquid L20 containing UFB 200 which contains a high concentration of the predetermined gas.

[0026] Next, a modified example of the UFB-containing liquid manufacturing apparatus 1 of this embodiment, shown in Figure 1, will be described based on Figures 5 and 6.

[0027] <First variation> Figure 5 shows a first modified example of the UFB-containing liquid manufacturing apparatus shown in Figure 1. The UFB-containing liquid manufacturing apparatus 1A shown in Figure 5 is equipped with a stirring mechanism (stirring means) 40 in the recovery container 30 of the UFB-containing liquid manufacturing apparatus 1 shown in Figure 1. The stirring mechanism 40 comprises a stirrer 41 provided on the outer bottom surface of the recovery container 30 and a stirring bar 42 provided inside the recovery container 30. The stirrer 41 has a magnet that rotates with a motor, and the magnetic field generated by the magnet rotates the stirring bar 42 inside the recovery container 30. This rotation of the stirring bar 42 can stir the UFB-containing liquid recovered in the recovery container 30.

[0028] In the first modified example, similar to the above embodiment, droplets D2 containing UFB200 with a predetermined gas are generated, and these droplets D2 are collected in the recovery container 30 to become UFB-containing liquid L20. Furthermore, in the first modified example, the liquid L20 collected in the recovery container 30 is stirred by the agitator 42. This further promotes gas exchange at the interface between the collected liquid L20 and the atmosphere AT. Gas exchange is governed by the surface area of ​​the interface between the liquid L20 and UFB200 and the molecular motion near the interface. When the liquid L20 stored in the recovery container 30 is at rest, the gas concentration at the gas-liquid interface surface becomes saturated and localized, making it difficult for further gas dissolution to proceed. However, as in this modified example, by stirring the liquid stored in the recovery container 30 with the agitator 42, the gas concentration at the gas-liquid interface surface does not become localized, and gas exchange at the interface between the liquid L20 and the atmosphere AT can be further promoted. This allows for further gas exchange between the UFB100 and UFB20 present in liquid L20 and liquid L20. Therefore, according to this modified example, it becomes possible to produce a UFB-containing liquid containing a predetermined gas more efficiently.

[0029] <Second variation> Figure 6 shows a second modified example of the UFB-containing liquid manufacturing apparatus 1 shown in Figure 1. The UFB-containing liquid manufacturing apparatus 1B shown in Figure 6 includes a storage chamber 50 having a space for storing a recovery container 30 and a UFB generator 20. A predetermined gas is supplied to the storage chamber 50 from a gas supply unit 51 located at the top, and the pressure inside the storage chamber 50 is maintained at a higher pressure (positive pressure) than the pressure outside the storage chamber 50 (in this case, atmospheric pressure). The recovery container 30 stored in the storage chamber 50 has an open top, and the space area 31 of the recovery container 30 is in communication with the space inside the storage chamber 50. Therefore, a predetermined gas atmosphere is formed in the space area 31 of the recovery container 30, similar to the space inside the storage chamber 50. In addition, a discharge window (gas discharge unit) 52 for discharging gas is formed on the upper wall surface of the storage chamber 50. Furthermore, the storage chamber 50 is provided with a pressure gauge (pressure detection means) 53 for detecting the internal pressure. Based on the pressure measured by this pressure gauge 53, the supply of gas from the gas supply source connected to the gas supply unit 51 is controlled, and the pressure inside the storage chamber 50 is maintained at a constant pressure (positive pressure).

[0030] In the modified UFB-containing liquid manufacturing apparatus 1B, the spatial region 31 of the recovery container 30 is also formed with a predetermined gas atmosphere AT. Therefore, the droplet D1 discharged from the UFB generator 20 undergoes gas exchange with the predetermined gas, similar to the apparatus shown in Figure 1, and is then recovered in the recovery container 30, producing a UFB-containing liquid L20 containing UFB with the predetermined gas as its gaseous component. Furthermore, the gas discharged from the droplet D2 or liquid L20 through gas exchange with the predetermined gas is released into the spatial region 31 of the recovery container 30 and the storage chamber 50. This gas is discharged to the outside through the discharge window 52 due to the pressure difference between the storage chamber 50 and the external pressure, and therefore does not remain in the storage chamber 50 or the recovery container 30. Consequently, the gas concentration of the predetermined gas in the recovery container 30 gradually increases. Therefore, the droplets discharged in a mist-like form into the spatial area 31 of the recovery container 30 are constantly and efficiently exchanged with the predetermined gas atmosphere AT supplied to the storage chamber 50.

[0031] There are no particular restrictions on the gas to be filled into the recovery container 30. For example, hydrogen, helium, nitrogen, methane, fluorine, neon, carbon dioxide, ozone, argon, chlorine, ethane, propane, air, clean air, and medical air are suitable. It is also possible to use a multi-component mixed gas, such as air. [Examples]

[0032] Here, specific examples of the production of UFB-containing liquid using the UFB-containing liquid production apparatus shown in the above embodiment will be described in the following 1st to 14th examples. The production conditions and results of the UFB-containing liquid in each example are shown in Figure 7.

[0033] <First Example> In the first embodiment, a UFB-containing liquid was manufactured using the UFB-containing liquid manufacturing apparatus 1B shown in Figure 5. A pressure-type discharge unit 22 shown in Figure 2(a) was used as the discharge unit 21 for discharging droplets. The discharge unit 22 is equipped with a discharge port forming member having a metal plate with 2000 openings (discharge ports 22b) capable of discharging 50 μm droplets. A saturated aqueous solution in which air is dissolved was supplied to the flow path 22a of this discharge unit 22, and pressure was applied to the saturated aqueous solution L10 by the pressurizing unit 22d to discharge droplets D1 from the discharge ports 22b. At this time, the pressure applied to the saturated aqueous solution L10 by the pressurizing unit 22d was set to a pressure such that 20 pl of droplets were discharged from each discharge port 22b. To efficiently exchange gas between the gas dissolved in the droplet immediately discharged from the discharge port 22b (air in this example) and the gas in the atmosphere AT inside the recovery container 30 (oxygen in this embodiment), it is preferable that the droplet discharged from the discharge port 22b be 100 pl or less. For this reason, in this embodiment, the pressure applied to the saturated solution L10 was set so that droplets of about 20 pl were discharged from the discharge port 22b.

[0034] Meanwhile, the spatial region 31 of the collection container 30 was filled with oxygen gas as a predetermined gas. The droplets D1 discharged from the discharge port 22b became a mist and flew through the spatial region 31 of the collection container 30 before being collected in the collection container 30.

[0035] In this example, the size of the droplets D1 and D2 flying within the spatial region 31 of the collection container 30 was calculated by microscopic observation. The calculation results confirmed that the volume of the discharged droplet was approximately 20 pl.

[0036] Furthermore, the average particle size, concentration, and UFB of the UFB contained in the liquid recovered by the recovery container 30 were measured. A measuring instrument (model SALD-7500) manufactured by Shimadzu Corporation was used for the measurements. The measurement results showed that the average particle size was 110 nm, the volume-average particle diameter (mv) was 380 nm, and the number-average particle diameter (dn) of the UFB was 110 nm, with a ratio of 3.45 between the two (mv / dn). The UFB concentration in the UFB-containing liquid was 0.2 billion particles / ml.

[0037] Furthermore, UFB has a volume-average particle diameter (mv) and a number-average particle diameter (dn) of 20 μm or less, and it is preferable from the viewpoint of long-term storage that the ratio of the volume-average particle diameter (mv) to the number-average particle diameter (dn) (mv / dn) is 3.5 or less. In this example, since the measurement results of the UFB satisfy the above-mentioned preferred conditions, it is determined that UFB with excellent long-term storage properties has been produced.

[0038] For the analysis of gas species, a DO meter (manufactured by HAC Corporation) was used for oxygen, a Pack Test (manufactured by Kyoritsu Chemical Laboratory Co., Ltd.) was used for ozone, and gas chromatography (manufactured by Shimadzu Corporation) was used for hydrogen, nitrogen, helium, and oxygen.

[0039] Furthermore, the amount of dissolved oxygen in the UFB-containing liquid L20 after it was recovered in the recovery container 30 was measured by analyzing the type of gas. The measurement results showed that the amount of dissolved oxygen in the recovered UFB-containing liquid L20 was 20 ppm, which was higher than the amount of dissolved oxygen in the gas-dissolved liquid L10 (8 ppm), confirming that it contained a higher concentration of oxygen. From this result, it became clear that at least a portion of the gas dissolved in the gas-dissolved liquid L10 before droplet discharge was exchanged from air to oxygen while the droplets were flying through the oxygen atmosphere AT inside the recovery container 30. In addition, since the dissolved oxygen concentration of the recovered UFB-containing liquid L20 exceeded the solubility of oxygen in water, it also became clear that the gas of UFB200 contained in the UFB-containing liquid L20 was exchanged for oxygen.

[0040] Furthermore, by stirring the recovered UFB-containing liquid L20 using a stirring bar 42 installed in the recovery container 30, the dissolved oxygen concentration of the UFB-containing liquid L20 was increased to 25 ppm while maintaining the UFB concentration and particle size. This increase in the dissolved oxygen concentration of the UFB-containing liquid L20 clearly indicated that gas exchange of UFB200 contained in the UFB-containing liquid L20 was further advanced.

[0041] <Second Example> The second embodiment is the same as the first embodiment, but with the droplet discharge unit changed from the discharge unit 22 to the piezoelectric discharge unit 24 shown in Figure 2(c) in the UFB-containing liquid manufacturing apparatus 1B used in the first embodiment. A piezoelectric discharge device (KJ-4B: manufactured by Kyocera Corporation) was used as the piezoelectric discharge unit 24. The droplet volume of the droplet D1 discharged from the discharge port 24b of the discharge unit 24 was set to 25 pl. The UFB-containing liquid L20 was manufactured under the same manufacturing conditions as in the first embodiment.

[0042] In this example, the UFB concentration in the UFB-containing liquid L20 produced was 500 million particles / ml. Furthermore, it was confirmed that a high concentration of oxygen (18 ppm) was dissolved in the UFB-containing liquid L20. This result clearly indicates that while droplet D1 was flying through the oxygen atmosphere AT inside the recovery container 30, at least a portion of the gas dissolved in droplet D1 was exchanged from air to oxygen. Additionally, since the dissolved oxygen concentration in the recovered UFB-containing liquid L20 exceeded the solubility of oxygen in water, it was also clear that the gas of UFB200 contained in the UFB-containing liquid L20 was exchanged from air to oxygen. In this example, the volume-average particle diameter (mv) of UFB200 contained in the UFB-containing liquid L20 was 220 nm, and the number-average particle diameter (dn) was 110 nm, with a ratio of 2.00 (mv / dn). Therefore, in this example as well, UFB with excellent long-term storage properties was produced.

[0043] <Third Example> In the third embodiment, the UFB-containing liquid L20 was produced using the UFB-containing liquid production apparatus 1B used in the second embodiment, with the droplet volume of droplet D1 set to 100 pl, and all other production conditions being the same as in the second embodiment.

[0044] In this example, the UFB concentration in the UFB-containing liquid L20 produced was 0.5 billion particles / ml. Furthermore, it was confirmed that a high concentration of oxygen (14 ppm) was dissolved in the UFB-containing liquid L20. This result clearly indicates that while droplet D1 was flying through the oxygen atmosphere AT in the recovery container 30, at least a portion of the gas dissolved in the droplet was exchanged from air to oxygen. Additionally, in this example, the dissolved oxygen concentration in the recovered UFB-containing liquid L20 exceeded the solubility of oxygen in water, indicating that the gas from the UFB contained in the UFB-containing liquid L20 was also exchanged from air to oxygen. In this example, the volume-average particle diameter (mv) of the UFB contained in the UFB-containing liquid L20 was 380 nm, the number-average particle diameter (dn) was 115 nm, and the ratio of the two (mv / dn) was 3.30.

[0045] <Fourth Example> In the fourth embodiment, the gas filled in the recovery container 30 of the UFB-containing liquid production apparatus 1B used in the second embodiment was changed from oxygen to 0.6 ppm ozone-containing air, and the droplet volume was set to 2 pl. The other production conditions were the same as in the second embodiment to produce the UFB-containing liquid L20.

[0046] In this example, the UFB concentration in the UFB-containing liquid L20 produced was 500 million particles / ml. Furthermore, it was confirmed that a high concentration of ozone (3 ppm) was dissolved in the UFB-containing liquid L20. From these results, it became clear that at least a portion of the gas dissolved in droplet D1 was exchanged from air to ozone-containing air while it was flying through the ozone atmosphere AT in the recovery container 30. Additionally, since the dissolved ozone concentration in the recovered UFB-containing liquid L20 exceeded the solubility of ozone in water, it became clear that the gas of UFB200 contained in the UFB-containing liquid L2 was exchanged from air to ozone-containing air. In this example, the volume-average particle diameter (mv) of the UFB contained in the UFB-containing liquid L20 was 210 nm, and the number-average particle diameter (dn) was 110 nm, with a ratio of 1.91 (mv / dn). Therefore, in this embodiment as well, UFB with excellent long-term storage properties was produced.

[0047] <Example 5> In the fifth embodiment, the UFB-containing liquid production apparatus 1B used in the second embodiment was used, but the dissolved gas in the gaseous dissolved water L10 before UFB generation was changed from air to nitrogen, and the other production conditions were the same as in the second embodiment to produce the UFB-containing liquid L20.

[0048] In this example, the UFB concentration in the UFB-containing liquid L20 produced was 500 million particles / ml. Furthermore, it was confirmed that a high concentration of oxygen (18 ppm) was dissolved in the UFB-containing liquid. This result clearly indicates that at least a portion of the gas dissolved in the droplet D1 was converted from nitrogen to oxygen while it was flying through the oxygen atmosphere AT in the recovery container 30. Additionally, since the dissolved oxygen concentration in the recovered UFB-containing liquid L20 exceeded the saturation solubility of oxygen in water, it was clear that the gas in the UFB200 contained in the UFB-containing liquid L20 was converted from nitrogen to oxygen. In this example, the volume-average particle diameter (mv) of the UFB contained in the UFB-containing liquid was 220 nm, the number-average particle diameter (dn) was 105 nm, and the ratio of the two (mv / dn) was 2.10. Therefore, in this example as well, UFB with excellent long-term storage properties was produced.

[0049] <Sixth Example> In the sixth embodiment, the UFB-containing liquid L20 was produced in the UFB-containing liquid production apparatus 1B used in the second embodiment, but with the gas filled in the recovery container 30 changed from oxygen to helium, and the other production conditions were the same as in the second embodiment.

[0050] In this example, the UFB concentration in the UFB-containing liquid L20 produced was 500 million particles / ml. Furthermore, it was confirmed that the UFB-containing liquid contained a high concentration of helium at 3000 ppm. From these results, it became clear that at least a portion of the gas dissolved in droplet D1 was exchanged from air to helium while it was flying through the helium atmosphere in the recovery container 30. Additionally, since the dissolved helium concentration in the recovered UFB-containing liquid L20 exceeded the solubility of helium in water, it became clear that the gas of UFB200 contained in the UFB-containing liquid L20 was exchanged from air to helium. In this example, the volume-average particle diameter (mv) of the UFB contained in the UFB-containing liquid was 210 nm, the number-average particle diameter (dn) was 108 nm, and the ratio of the two (mv / dn) was 1.94. Therefore, in this example as well, UFB with excellent long-term storage properties was produced.

[0051] <Example 7> In the seventh embodiment, in the UFB-containing liquid production apparatus 1B used in the second embodiment described above, the dissolved gas in the gaseous dissolved water L10 before UFB generation was changed from air to oxygen, and the gas filled into the recovery container 30 was changed from oxygen to carbon dioxide (CO2). The other production conditions were the same as in the second embodiment to produce the UFB-containing liquid L20.

[0052] In this example, the UFB concentration in the UFB-containing liquid L20 produced was 500 million particles / ml. Furthermore, it was confirmed that a high concentration of 800 ppm of carbon dioxide was dissolved in the UFB-containing liquid L20. From these results, it became clear that at least a portion of the gas dissolved in droplet D1 was exchanged from oxygen to carbon dioxide while it was flying through the carbon dioxide atmosphere in the recovery container 30 as droplet D1. Additionally, since the concentration of carbon dioxide dissolved in the recovered UFB-containing liquid L20 exceeded the solubility of carbon dioxide in water, it became clear that the gas of UFB200 contained in the UFB-containing liquid L20 was exchanged from oxygen to carbon dioxide. In this example, the volume-average particle diameter (mv) of the UFB contained in the UFB-containing liquid L20 was 210 nm, and the number-average particle diameter (dn) was 110 nm, with a ratio of 1.91 (mv / dn). Therefore, in this example as well, UFB with excellent long-term storage properties was produced.

[0053] <Eighth Example> In the eighth embodiment, in the UFB-containing liquid production apparatus 1B used in the second embodiment described above, the dissolved gas in the gas-dissolved water L10 before UFB generation was changed from air to oxygen, and the gas filled into the recovery container 30 was changed from oxygen to hydrogen. The UFB-containing liquid L20 was produced under the same production conditions as in the second embodiment.

[0054] In this example, the UFB concentration in the UFB-containing liquid L20 produced was 500 million particles / ml. Furthermore, it was confirmed that a high concentration of hydrogen (0.8 ppm) was dissolved in the UFB-containing liquid L20. This result clearly indicates that at least a portion of the gas dissolved in droplet D1 was converted from oxygen to hydrogen while it was floating in the hydrogen atmosphere within the recovery container 30. Additionally, since the dissolved hydrogen concentration in the recovered UFB-containing liquid L20 exceeded the solubility of hydrogen in water, it was clear that the gas of UFB200 contained in the UFB-containing liquid L20 was converted from oxygen to hydrogen. In this example, the volume-average particle diameter (mv) of the UFB contained in the UFB-containing liquid L20 was 210 nm, and the number-average particle diameter (dn) was 112 nm, with a ratio of 1.88 (mv / dn). Therefore, in this example as well, UFB with excellent long-term storage properties was produced.

[0055] <Example 9> In the ninth embodiment, in the UFB-containing liquid production apparatus 1B used in the second embodiment described above, the dissolved gas in the gas-dissolved water L10 before UFB generation was changed from air to oxygen, and the gas filled into the recovery container 30 was changed from oxygen to nitrogen. The UFB-containing liquid L20 was produced under the same production conditions as in the second embodiment.

[0056] In this example, the UFB concentration in the UFB-containing liquid L20 was 500 million particles / ml. Furthermore, it was confirmed that a high concentration of 10 ppm of nitrogen was dissolved in the UFB-containing liquid L20. From these results, it became clear that at least a portion of the gas dissolved in droplet D1 was exchanged from oxygen to nitrogen while it was flying through the nitrogen atmosphere in the recovery container 30. Additionally, since the dissolved nitrogen concentration in the recovered UFB-containing liquid L20 exceeded the solubility of nitrogen in water, it became clear that the gas of UFB200 contained in the UFB-containing liquid L20 was exchanged from oxygen to nitrogen. In this example, the volume-average particle diameter (mv) of UFB200 contained in the UFB-containing liquid L20 was 215 nm, and the number-average particle diameter (dn) was 110 nm, with a ratio of 1.95 between the two (mv / dn). Therefore, in this example as well, UFB with excellent long-term storage properties was produced.

[0057] <Tenth Example> In the tenth embodiment, the UFB-containing liquid production apparatus used in the second embodiment was modified by changing the dissolved gas in the gaseous dissolved water L10 before UFB generation from air to nitrogen. The UFB-containing liquid L20 was produced under the same production conditions as in the second embodiment.

[0058] In this example, the UFB concentration in the UFB-containing liquid L20 was 500 million particles / ml. Furthermore, it was confirmed that a high concentration of 15 ppm of oxygen was dissolved in the UFB-containing liquid L20. From these results, it became clear that at least a portion of the gas dissolved in droplet D1 was exchanged from nitrogen to oxygen while it was floating in the oxygen atmosphere within the recovery container 30. Additionally, since the dissolved oxygen concentration in the recovered UFB-containing liquid L20 exceeded the solubility of oxygen in water, it became clear that the gas of UFB200 contained in the UFB-containing liquid L20 was exchanged from nitrogen to oxygen. In this example, the volume-average particle diameter (mv) of UFB200 contained in the UFB-containing liquid L20 was 380 nm, and the number-average particle diameter (dn) was 110 nm, with a ratio of 3.45 (mv / dn). Therefore, in this example as well, UFB with excellent long-term storage properties was produced.

[0059] <11th Example> In the 11th embodiment, the UFB-containing liquid manufacturing apparatus 1B used in the second embodiment was modified by changing the droplet D1 discharge unit 21 from the aforementioned piezoelectric discharge unit 24 to a thermal discharge unit 23 using the heating element 23d shown in Figure 2(b). The UFB-containing liquid L20 was manufactured under the same conditions as in the second embodiment.

[0060] In this example, the UFB concentration in the UFB-containing liquid L20 produced was 600 million particles / ml. Furthermore, it was confirmed that a high concentration of oxygen (18 ppm) was dissolved in the UFB-containing liquid L20. From these results, it became clear that at least a portion of the gas dissolved in droplet D1 was exchanged from air to oxygen while it was flying through the oxygen atmosphere AT in the recovery container 30. Additionally, since the dissolved oxygen concentration in the recovered UFB-containing liquid L20 exceeded the solubility of oxygen in water, it became clear that the gas of UFB200 contained in the UFB-containing liquid L20 was exchanged from air to oxygen. In this example, the volume-average particle diameter (mv) of UFB200 contained in the UFB-containing liquid L20 was 210 nm, and the number-average particle diameter (dn) was 110 nm, with a ratio of 1.91 between the two (mv / dn). Therefore, in this example as well, UFB with excellent long-term storage properties was produced.

[0061] <Example 12> In the 12th embodiment, the gas filled into the recovery container 30 of the UFB-containing liquid production apparatus 1B used in the second embodiment was changed from oxygen to clean air. Clean air has a higher oxygen concentration than the air dissolved in water. The UFB-containing liquid L20 was produced under the same production conditions as in the second embodiment.

[0062] In this example, the UFB concentration in the UFB-containing liquid L20 was 600 million particles / ml. It was confirmed that the UFB-containing liquid L20 contained oxygen at a higher concentration (9.0 ppm oxygen) than the oxygen concentration of the air dissolved in liquid L10. From this result, it became clear that when droplet D1 was flying through the clean air in the recovery container 30, the gas dissolved in droplet D1 was exchanged from air to clean air. Furthermore, since the dissolved oxygen concentration of L20 in the recovered UFB-containing liquid exceeded the solubility of oxygen in water, it became clear that the gas (air) of the UFB contained in the UFB-containing liquid L20 was exchanged for clean air. In this example, the volume-average particle diameter (mv) of UFB200 contained in the UFB-containing liquid L20 was 230 nm, and the number-average particle diameter (dn) was 105 nm, with a ratio of 2.2 (mv / dn). Therefore, in this example as well, UFB with excellent long-term storage properties was produced.

[0063] <Example 13> In the 13th embodiment, a showerhead (product name: Bollina, manufactured by Tanaka Metal Co., Ltd.) was used as the discharge unit 21 for discharging droplets D1. Saturated dissolved water from the air (atmosphere) was discharged from the showerhead into a recovery container filled with oxygen as a predetermined gas, and recovered. This showerhead employs a swirling flow method that generates fine bubbles by repeatedly separating and merging the gas-liquid mixture using a mixing unit. The recovery container 30 was also filled with oxygen.

[0064] In this 13th embodiment, photographic evidence confirmed that the droplets discharged from the showerhead included droplets larger than 100 pL. The UFB concentration in the recovered liquid was 200 million particles / ml.

[0065] It was confirmed that a high concentration of oxygen (oxygen concentration of 7.8 ppm) was dissolved in the UFB-containing liquid L20 recovered in the recovery container 30. From this result, it became clear that while droplet D1 was flying through the oxygen atmosphere inside the recovery container 30, the gas dissolved in droplet D1 was exchanged from air to oxygen. Furthermore, the dissolved oxygen concentration of the recovered UFB-containing liquid L20 was 7.8 ppm, which exceeds the oxygen solubility in water of 7.6, so it also became clear that the gas of UFB200 contained in UFB-containing liquid L20 was exchanged from air to clean air. In this comparative example, the volume-average particle diameter (mv) of UFB contained in UFB-containing liquid L20 was 600 nm, the number-average particle diameter (dn) was 135 nm, and the ratio of the two (mv / dn) was 4.44.

[0066] Thus, in the 13th embodiment as well, it was found that gas exchange occurred in which the gaseous component of the droplets discharged into the recovery container 30 was replaced from air to oxygen, and consequently, the gaseous component of the UFB in droplet D1 was also replaced from air to oxygen. However, the droplets discharged from the showerhead included droplets larger than 100 pL, and because these droplets have a small specific surface area, gas exchange was difficult to proceed with. For this reason, the dissolved oxygen concentration of the UFB-containing liquid was lower than in the second embodiment. Furthermore, the discharged droplets also contained bubbles other than UFB, such as microbubbles and millibubbles, which may float to the surface of the liquid in the recovery container and disappear over time, and the UFB may disappear as a result.

[0067] <Example 14> In the 14th embodiment, a spray-type discharge unit was used as the discharge unit 21 for discharging droplet D1. Specifically, water saturated with air was discharged by spray (product name e-3X, manufactured by MTG Co., Ltd.) and collected. Oxygen was filled into the collection container 30 as a predetermined gas. Photographs confirmed that the droplets discharged from the spray included droplets larger than 100 pL.

[0068] In this 14th example, photographic evidence confirmed that the droplets discharged from the spray included droplets larger than 100 pL. The UFB concentration in the recovered liquid was 500 million particles / ml. It was confirmed that a high concentration of oxygen of 10.71 ppm was dissolved in this UFB-containing liquid L20. From these results, it became clear that while droplet D1 was flying through the oxygen atmosphere in the recovery container 30, the gas dissolved in droplet D1 was exchanged from air to oxygen. Furthermore, since the dissolved oxygen concentration in the recovered UFB-containing liquid L20 exceeded the oxygen solubility in water, it also became clear that the gas of UFB200 contained in UFB-containing liquid L20 was exchanged from air to oxygen. In this comparative example, the volume-average particle diameter (mv) of UFB200 contained in UFB-containing liquid L20 was 1500 nm, the number-average particle diameter (dn) was 140 nm, and the ratio of the two (mv / dn) was 10.71.

[0069] Thus, in this embodiment as well, it became clear that gas exchange occurred in which the gaseous component of droplet D1 discharged into the recovery container 30 was replaced from air to oxygen, and consequently, the gaseous component of UFB within droplet D1 was also replaced from air to oxygen. However, the droplets discharged from the spray also include droplets larger than 100 pL. Since these droplets have a small specific surface area, gas exchange is difficult to proceed with. For this reason, the dissolved oxygen concentration of the UFB-containing liquid was lower than in the second embodiment. Furthermore, since the discharged droplets also contain bubbles other than UFB, such as microbubbles and millibubbles, these may float to the surface of the liquid in the recovery container and disappear over time, and the UFB may disappear as a result. In other words, it is preferable that the droplets be 100 pL or less.

[0070] As described above, according to the first to fourteenth embodiments, it is possible to produce a UFB-containing liquid containing UFB with a predetermined gas as the gaseous component by flying minute droplets containing UFB in a predetermined gas atmosphere. Compared to conventional methods in which a predetermined gas is dissolved in a liquid and then UFB is generated in the resulting solution to produce a UFB-containing liquid, this manufacturing method reduces the outflow loss of the predetermined gas and makes it possible to produce a UFB-containing liquid extremely efficiently.

[0071] (Other embodiments) In the above embodiments and examples, an example was shown in which a droplet containing UFB is evacuated in a predetermined gas atmosphere to exchange the UFB within the droplet for the predetermined gas, and the UFB-containing liquid with the exchanged gas is collected in a collection container. However, the invention is not limited to this. It is also possible to directly apply the UFB-containing liquid to the object to be coated without collecting the droplet that has evacuated in the predetermined gas atmosphere in a collection container.

[0072] Furthermore, while the above embodiments and examples show examples of generating ultrafine bubbles by precipitating dissolved gas within a droplet due to pressure changes when a droplet is discharged from a minute discharge port, the invention is not limited to this. Alternatively, UFBs may be generated in a gas solution containing a first gas such as air by a predetermined method to produce a UFB-containing liquid, and this UFB-containing liquid may be discharged as a droplet from a minute-diameter discharge port, and the droplet may be allowed to fly in an atmosphere of a predetermined gas (second gas). In this case as well, gas exchange can be performed between the droplet containing the first gas and the atmosphere of the predetermined gas (second gas), and further gas exchange can be performed between the gas-exchanged droplet and the UFB contained in the droplet. In other words, it becomes possible to produce a UFB-containing liquid containing UFBs that contain the second gas. [Explanation of symbols]

[0073] 1, 1A, 1B UFB-containing liquid production equipment AT atmosphere D1,D2 droplet

Claims

1. A method for producing an ultrafine bubble-containing liquid, A step of flying a droplet containing ultrafine bubbles containing a first gas in an atmosphere of a second gas different from the first gas, A step of collecting the droplets that have flown in the aforementioned atmosphere using a recovery container filled with the second gas, The steps include: storing the recovery container in a storage chamber and supplying the first gas to the space within the storage chamber to form an atmosphere of the first gas within the storage chamber and within the recovery container communicating with the storage chamber; A method for producing an ultrafine bubble-containing liquid, characterized by having the following characteristics.

2. A method for producing an ultrafine bubble-containing liquid according to claim 1, further comprising the step of stirring the ultrafine bubble-containing liquid consisting of the droplets collected in the collection container.

3. The method for producing an ultrafine bubble-containing liquid according to claim 1 or 2, wherein the storage chamber comprises a gas supply unit for supplying the second gas from the outside and a gas discharge unit for discharging the gas inside the storage chamber to the outside.

4. A method for producing an ultrafine bubble-containing liquid according to claim 3, wherein the second gas is supplied from the gas supply unit such that the pressure in the storage chamber is greater than the pressure outside the storage chamber.

5. A method for producing an ultrafine bubble-containing liquid according to any one of claims 1 to 4, wherein the ultrafine bubbles have a volume-average particle diameter (mv) and a number-average particle diameter (dn) of 20 μm or less, and the ratio of the volume-average particle diameter (mv) to the number-average particle diameter (dn) (mv / dn) is 3.5 or less.

6. The second gas in the aforementioned atmosphere contains a predetermined gaseous component different from that of the first gas. A method for producing an ultrafine bubble-containing liquid according to any one of claims 1 to 5, wherein the ultrafine bubbles contained in the droplets that fly in the aforementioned atmosphere contain the predetermined gaseous component.

7. The second gas in the aforementioned atmosphere contains the same gaseous components as the first gas, but at a different concentration. A method for producing an ultrafine bubble-containing liquid according to any one of claims 1 to 5, wherein the ultrafine bubbles contained in the droplets that have flown through the aforementioned atmosphere change to a concentration different from that of the first gas.

8. The method for producing an ultrafine bubble-containing liquid according to any one of claims 1 to 7, wherein the droplets are produced by the liquid in which the first gas is dissolved being discharged from a minute-diameter discharge port provided in the discharge unit.

9. The method for producing an ultrafine bubble-containing liquid according to claim 8, wherein the ultrafine bubbles are generated by a change in the pressure of the liquid before and after it is discharged as droplets from the discharge port.

10. The method for producing an ultrafine bubble-containing liquid according to claim 8 or 9, wherein the discharge unit discharges a liquid containing the first gas-containing ultrafine bubbles as droplets into the atmosphere from the discharge port and allows them to fly.

11. The method for producing an ultrafine bubble-containing liquid according to any one of claims 8 to 10, wherein the discharge unit comprises a discharge port forming member on which the discharge port is formed, and a pressurizing unit that pressurizes the liquid in which the first gas is dissolved to discharge droplets from the discharge port.

12. The method for producing an ultrafine bubble-containing liquid according to any one of claims 8 to 10, wherein the discharge unit comprises a piezoelectric element that applies pressure to the liquid in which the first gas is dissolved to discharge the droplets from the discharge port.

13. The method for producing an ultrafine bubble-containing liquid according to any one of claims 8 to 10, wherein the discharge unit comprises a heating element that generates thermal energy for discharging the droplets from the discharge port into the liquid in which the first gas is dissolved.

14. The method for producing an ultrafine bubble-containing liquid according to any one of claims 8 to 13, wherein the discharge unit has a plurality of discharge ports.

15. The method for producing an ultrafine bubble-containing liquid according to any one of claims 1 to 14, wherein the droplet is a droplet of 100 pl or less.

16. A method for producing an ultrafine bubble-containing liquid according to any one of claims 1 to 15, wherein the second gas comprises at least one gaseous component of oxygen, nitrogen, ozone, carbon dioxide, and hydrogen.

17. An apparatus for producing an ultrafine bubble-containing liquid, The ultrafine bubbles have a volume-average particle diameter (mv) and a number-average particle diameter (dn) of 20 μm or less, and the ratio of the volume-average particle diameter (mv) to the number-average particle diameter (dn) (mv / dn) is 3.5 or less. A dispensing unit that dispenses droplets containing ultrafine bubbles containing a first gas, The system comprises an atmosphere-forming means for forming an atmosphere of a second gas different from the first gas, The apparatus for producing an ultrafine bubble-containing liquid is characterized in that the discharge unit discharges the liquid droplets into the atmosphere and causes them to fly.

18. The atmosphere forming means is comprised of a collection container for collecting the droplets, The apparatus for producing an ultrafine bubble-containing liquid according to claim 17, wherein the recovery container is filled with the second gas to form the atmosphere, and the flying droplets are recovered in the atmosphere.

19. An apparatus for producing an ultrafine bubble-containing liquid, A dispensing unit that dispenses droplets containing ultrafine bubbles containing a first gas, A recovery means for collecting the droplets discharged by the discharge unit into a recovery container in an atmosphere of a second gas different from the first gas, A storage chamber is formed in which the atmosphere of the first gas is formed inside the recovery container that is in communication with the space in which the recovery container is housed by supplying the first gas to the space, An apparatus for producing an ultrafine bubble-containing liquid, characterized by comprising the following features.

20. The apparatus for producing an ultrafine bubble-containing liquid according to any one of claims 17 to 19, wherein the droplets are formed when the liquid in which the first gas is dissolved is discharged from a minute-diameter discharge port provided in the discharge unit.

21. The apparatus for producing an ultrafine bubble-containing liquid according to claim 20, wherein the ultrafine bubbles are generated by a change in the pressure of the liquid before and after the droplet is discharged from the discharge port.

22. The apparatus for producing an ultrafine bubble-containing liquid according to claim 20 or 21, wherein the discharge unit discharges a liquid containing the first gas-containing ultrafine bubbles as droplets into the atmosphere from the discharge port and causes them to fly.

23. The apparatus for producing an ultrafine bubble-containing liquid according to claim 20 or 21, wherein the discharge unit is equipped with a piezoelectric element that applies pressure to the liquid in which the first gas is dissolved to discharge the droplets from the discharge port.

24. The apparatus for producing an ultrafine bubble-containing liquid according to claim 20 or 21, wherein the discharge unit is equipped with a heating element that generates thermal energy for discharging the droplets from the discharge port into the liquid in which the first gas is dissolved.

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