Patent Description:
In a field of manufacturing electronic devices, an ultrasonic atomization apparatus is used in some cases. In the field of the electronic device manufacturing, the ultrasonic atomization apparatus atomizes a solution by using ultrasonic waves that are oscillated from an ultrasonic vibrator, and sends out the atomized solution to the outside by using transfer gas. When the source solution mist transferred to the outside is sprayed onto a substrate, a thin film for the electronic device is formed on the substrate.

Various solvents are used for the source solution used in the film formation, and in order to prevent erosion of the ultrasonic vibrator, a double chamber method, in which the source solution and the ultrasonic vibrator do not come into contact with each other, is used. In the double chamber method, in order to separate the ultrasonic vibrator and the source solution, a separator cup for accommodating the source solution is used separately for a water tank provided with the ultrasonic vibrator in its bottom surface. The separator cup is required to allow transmission of ultrasonic waves, and a material that easily transmits ultrasonic waves, such as polyethylene and polypropylene (PP), is used as its constituent material. Further, polyethylene and polypropylene have properties of being easily subjected to formation as well.

One example of the ultrasonic atomization apparatus employing the double chamber method described above is an atomization apparatus disclosed in <CIT>.

Other examples are described in <CIT>, <CIT> and <CIT>. The ultrasonic atomization apparatus described in <CIT> has the features specified in the preamble of the claim.

In general, toluene, ether, and the like, which are solvents high in solubility, are used as a solvent of the source solution. This is because toluene and ether have properties of high resin solubility.

However, when toluene and ether are used as a solvent of the source solution in a conventional ultrasonic atomization apparatus, the high resin solubility of the solvent may cause a leakage of the source solution due to swelling and deformation of the separator cup using polyethylene or polypropylene as its constituent material, or opening of a hole in the separator cup.

This results in deterioration of accommodation stability of the source solution in the conventional ultrasonic atomization apparatus, which poses a problem that the source solution mist of an appropriate atomization amount cannot be generated.

The present invention has an object to provide an ultrasonic atomization apparatus that solves the problem as described above, that is excellent in tolerance to a source solution, and that can generate a source solution mist of an appropriate atomization amount.

The above object is achieved by an ultrasonic atomization apparatus as specified in the claim.

These and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.

Description of Example not encompassed by the wording of the claim and Embodiment.

<FIG> and <FIG> are each an explanatory diagram schematically illustrating a configuration of an ultrasonic atomization apparatus <NUM> being an example outside the scope of the present claimed invention. <FIG> illustrates a case at the time of an initial state (No. <NUM>), and <FIG> illustrates a case at the time of generation of a source solution mist MT (No. <NUM>).

As illustrated in <FIG> and <FIG>, the ultrasonic atomization apparatus <NUM> includes a container <NUM>, an ultrasonic vibrator <NUM> being an atomizer, an internal hollow structure body <NUM>, and a gas supply unit <NUM>. Further, as illustrated in <FIG> and <FIG>, the container <NUM> has a structure in which an upper cup <NUM> and a separator cup <NUM> are coupled together by a connector <NUM>.

The upper cup <NUM> may have any shape as long as the upper cup <NUM> is a container having a space formed inside. In the ultrasonic atomization apparatus <NUM>, the upper cup <NUM> has a substantially cylindrical shape, and in the upper cup <NUM>, a space surrounded by a side surface being formed in a circular shape in plan view is formed.

Meanwhile, in the separator cup <NUM>, a source solution <NUM> is accommodated. The constituent material of the separator cup <NUM> is polytetrafluoroethylene (PTFE) being one of fluorocarbon resins, whose entire thickness is uniformly <NUM>. Specifically, the separator cup <NUM> uses PTFE as its constituent material, and has a bottom surface BP1 having a thickness of <NUM>.

As described above, the separator cup <NUM> according to the example has features in that the separator cup <NUM> satisfies a thin film condition that "the thickness of the bottom surface BP1 is <NUM> or less".

Further, in the example, the ultrasonic vibrator <NUM> applies ultrasonic waves to the source solution <NUM> in the separator cup <NUM>, and thereby atomizes the source solution <NUM>. Four ultrasonic vibrators <NUM> (only two of them are illustrated in <FIG> and <FIG>) are disposed in a bottom surface of a water tank <NUM>. Note that the number of ultrasonic vibrators <NUM> is not limited to four. One ultrasonic vibrator <NUM> or two or more ultrasonic vibrators <NUM> may be provided.

The internal hollow structure body <NUM> is a structure body including a hollow in side. In an upper surface part of the upper cup <NUM> of the container <NUM>, an opening part is formed, and as illustrated in <FIG> and <FIG>, the internal hollow structure body <NUM> is disposed in a manner of being inserted into the upper cup <NUM> through the opening part. Here, in a state in which the internal hollow structure body <NUM> is inserted in the opening part, a part between the internal hollow structure body <NUM> and the upper cup <NUM> is hermetically closed. In other words, the part between the internal hollow structure body <NUM> and the opening part of the upper cup <NUM> is sealed.

For the shape of the internal hollow structure body <NUM>, any shape may be adopted as long as the shape is a shape in which a hollow is formed inside. In the configuration example of <FIG> and <FIG>, the internal hollow structure body <NUM> has a flask-like cross-sectional shape without a bottom surface. More specifically, the internal hollow structure body <NUM> illustrated in <FIG> includes a tubular part 3A, a circular truncated cone part 3B, and a cylindrical part 3C.

The tubular part 3A is a tubular path part having a cylindrical shape, and the tubular part 3A extends from the outside of the upper cup <NUM> to the inside of the upper cup <NUM> in a manner of being inserted through the opening part provided in the upper surface of the upper cup <NUM>. More specifically, the tubular part 3A is divided into an upper tubular part disposed on the outside of the upper cup <NUM> and a lower tubular part disposed on the inside of the upper cup <NUM>. Further, the upper tubular part is attached from the outside of the upper surface of the upper cup <NUM>, and the lower tubular part is attached from the inside of the upper surface of the upper cup <NUM>, and in a state in which these are attached together, the upper tubular part and the lower tubular part communicate to each other through the opening part disposed on the upper surface of the upper cup <NUM>. One end of the tubular part 3A is connected to, for example, the inside of a thin-film film forming apparatus that forms a thin film by using a source solution mist MT, which is present on the outside of the upper cup <NUM>. In contrast, another end of the tubular part 3A is connected to an upper end side of the circular truncated cone part 3B inside the upper cup <NUM>.

The circular truncated cone part 3B has its external appearance (side wall surface) of a circular truncated cone shape, and has a hollow being formed inside. The circular truncated cone part 3B has its upper surface and bottom surface being opened. In other words, the hollow being formed inside is closed, and there are no upper surface and bottom surface. The circular truncated cone part 3B is present in the upper cup <NUM>, and as described above, the upper end side of the circular truncated cone part 3B connects (communicates) to the another end of the tubular part 3A, and a lower end portion side of the circular truncated cone part 3B is connected to the upper end side of the cylindrical part 3C.

Here, the circular truncated cone part 3B has a cross-sectional shape that is widened toward the end, that is, from the upper end side toward the lower end side. In other words, the diameter of the side wall on the upper end side of the circular truncated cone part 3B is the smallest (the same as the diameter of the tubular part 3A), the diameter of the side wall on the lower end side of the circular truncated cone part 3B is the largest (the same as the diameter of the cylindrical part 3C), and the diameter of the side wall of the circular truncated cone part 3B is smoothly increased from the upper end side toward the lower end side.

The cylindrical part 3C is a part having a cylindrical shape, and as described above, the upper end side of the cylindrical part 3C connects (communicates) to the lower end side of the circular truncated cone part 3B, and the lower end side of the cylindrical part 3C faces the bottom surface of the upper cup <NUM>. Here, in the configuration example of <FIG>, the lower end side of the cylindrical part 3C is released (specifically, does not have a bottom surface).

Here, in the configuration example of <FIG> and <FIG>, a central axis in a direction extending from the tubular part 3A to the cylindrical part 3C through the circular truncated cone part 3B in the internal hollow structure body <NUM> substantially matches a central axis of the upper cup <NUM> of the cylindrical shape. Note that the internal hollow structure body <NUM> may be an integral structure, or may be, as illustrated in <FIG> and <FIG>, configured by combining each member of the upper tubular part constituting a part of the tubular part 3A, the lower tubular part constituting the other part of the tubular part 3A, the circular truncated cone part 3B, and the cylindrical part 3C. In the configuration example of <FIG>, a lower end portion of the upper tubular part is connected to an outer upper surface of the upper cup <NUM>, an upper end portion of the lower tubular part is connected to an inner upper surface of the upper cup <NUM>, and a member consisting of the circular truncated cone part 3B and the cylindrical part 3C is connected to a lower end portion of the lower tubular part, and the internal hollow structure body <NUM> consisting of a plurality of members is thereby configured.

When the internal hollow structure body <NUM> having the above-described shape is disposed in a manner of being inserted into the upper cup <NUM>, the inside of the upper cup <NUM> is divided into two spaces. The first space is a hollow part being formed inside the internal hollow structure body <NUM>. The hollow part is hereinafter referred to as an "atomization space <NUM>". The atomization space <NUM> is a space surrounded by the inner side surface of the internal hollow structure body <NUM>.

The space is a space formed by an inner surface of the upper cup <NUM> and an outer side surface of the internal hollow structure body <NUM>. The space is hereinafter referred to as a "gas supply space <NUM>". As described above, the inside of the upper cup <NUM> is sectioned into the atomization space <NUM> and the gas supply space <NUM>.

Further, the atomization space <NUM> and the gas supply space <NUM> are connected through a lower opening part of the cylindrical part 3C.

Further, in the configuration example of <FIG> and <FIG>, as can be seen from the shape of the internal hollow structure body <NUM> and the shape of the upper cup <NUM>, the gas supply space <NUM> is the widest on the upper side of the upper cup <NUM> and is gradually narrower toward the lower side of the upper cup <NUM>. In other words, a part of the gas supply space <NUM> that is surrounded by an outer side surface of the tubular part 3A and an inner side surface of the upper cup <NUM> is the widest, and a part of the gas supply space <NUM> that is surrounded by an outer side surface of the cylindrical part 3C and an inner side surface of the upper cup <NUM> is the narrowest.

The gas supply unit <NUM> is disposed in the upper surface of the upper cup <NUM>. Through the gas supply unit <NUM>, a carrier gas G4 for transferring the source solution mist MT (see <FIG>) being atomized by the ultrasonic vibrator <NUM> to the outside through the tubular part 3A of the internal hollow structure body <NUM> is supplied. As the carrier gas G4, for example, a high-concentration inert gas can be adopted. Further, as illustrated in <FIG> and <FIG>, the gas supply unit <NUM> is provided with a supply port 4a, and the carrier gas G4 is supplied into the gas supply space <NUM> of the container <NUM> through the supply port 4a present in the container <NUM>.

The carrier gas G4 supplied from the gas supply unit <NUM> is supplied into the gas supply space <NUM> and fills the gas supply space <NUM>, and is then introduced to the atomization space <NUM> through the lower opening part of the cylindrical part 3C.

Further, in the ultrasonic atomization apparatus <NUM> of the example, the separator cup <NUM> of the container <NUM> has a cup-like shape, and accommodates the source solution <NUM> inside. The bottom surface BP1 of the separator cup <NUM> is gently inclined from a side surface part toward the center, and is formed into a spherical surface shape having a predetermined curvature.

Further, the water tank <NUM> is filled with ultrasonic wave conveyance water <NUM>, which serves as an ultrasonic wave conveyance medium. The ultrasonic wave conveyance water <NUM> has a function of conveying ultrasonic vibration that is generated from the ultrasonic vibrator <NUM> disposed in the bottom surface of the water tank <NUM> to the source solution <NUM> in the separator cup <NUM>.

In other words, the ultrasonic wave conveyance water <NUM> is accommodated in the water tank <NUM> so as to be able to convey, to the inside of the separator cup <NUM>, vibration energy of ultrasonic waves applied from the ultrasonic vibrator <NUM>.

As described above, in the bottom surface BP1 of the separator cup <NUM>, the source solution <NUM> to be atomized is accommodated, and a liquid level 15A of the source solution <NUM> is positioned lower than the position at which the connector <NUM> is disposed (see <FIG> and <FIG>).

Further, regarding the separator cup <NUM>, the positions of the separator cup <NUM> and the water tank <NUM> are set so that the entire bottom surface BP1 is immersed in the ultrasonic wave conveyance water <NUM>. Specifically, the bottom surface BP1 of the separator cup <NUM> is disposed above the bottom surface of the water tank <NUM> without touching the bottom surface of the water tank <NUM>, and the ultrasonic wave conveyance water <NUM> is present between the bottom surface BP1 of the separator cup <NUM> and the bottom surface of the water tank <NUM>.

In the ultrasonic atomization apparatus <NUM> having the configuration as described above, when the ultrasonic vibrators <NUM> apply ultrasonic vibration, vibration energy of the ultrasonic waves is conveyed to the source solution <NUM> in the separator cup <NUM> through the ultrasonic wave conveyance water <NUM> and the bottom surface BP1 of the separator cup <NUM>.

Then, as illustrated in <FIG>, liquid columns <NUM> are raised from the liquid level 15A, and the source solution <NUM> transition to liquid particles and to mist, producing the source solution mist MT in the atomization space <NUM>. The source solution mist MT generated in the gas supply space <NUM> is supplied to the outside through an upper opening part of the tubular part 3A by the carrier gas G4 supplied from the gas supply unit <NUM>.

<FIG> and <FIG> are each an explanatory diagram schematically illustrating a configuration of a conventional ultrasonic atomization apparatus <NUM>. <FIG> illustrates a case at the time of an initial state (No. <NUM>), and <FIG> illustrates a case at the time of generation of a source solution mist MT (No. <NUM>).

In the following, parts similar to those of the ultrasonic atomization apparatus <NUM> according to the example illustrated in <FIG> and <FIG> are denoted by the same reference signs and general description thereof will be omitted.

A container <NUM> corresponding to the container <NUM> of the ultrasonic atomization apparatus <NUM> is made of a combined structure of an upper cup <NUM> and a separator cup <NUM>. The upper cup <NUM> is configured similarly to the upper cup <NUM>.

A conventional separator cup <NUM> corresponding to the separator cup <NUM> of the example adopts polypropylene (PP) that easily transmits ultrasonic waves as its constituent material, whose entire thickness is uniformly <NUM>.

In order to make the thickness of the separator cup <NUM> as thin as possible with the aim of maintaining transmissiveness of the ultrasonic waves (preventing attenuation of vibration energy of the ultrasonic waves) and maintaining the shape of the separator cup <NUM>, the thickness of the separator cup <NUM> is set to <NUM>.

<FIG> is a graph showing effects of the example. In <FIG>, the horizontal axis represents a flow rate [L/min] of the carrier gas G4, and the vertical axis represents an atomization amount [g/min] of the generated source solution mist MT.

<FIG> shows experimental results of an experiment performed on the condition that distilled water at <NUM> was used as the source solution <NUM>, four ultrasonic vibrators <NUM>, which are models NB-<NUM>-<NUM>-<NUM> manufactured by TDK Corporation, were disposed in the bottom surface of the water tank <NUM>, and vibration frequency of the four ultrasonic vibrators <NUM> was set to <NUM>. Note that a nitrogen gas is used as the carrier gas G4.

In <FIG>, atomization amount variation L1 shows a case in which the constituent material of the separator cup <NUM> is PTFE, and film thickness t of the bottom surface BP1 is <NUM>. Atomization amount variation L2 shows a case in which the constituent material of the separator cup <NUM> is PTFE, and the film thickness t of the bottom surface BP1 is <NUM>. Atomization amount variation L3 shows a case in which the constituent material of the separator cup <NUM> is PTFE, and the film thickness t of the bottom surface BP1 is <NUM>. Specifically, the atomization amount variations L1 to L3 are experimental results related to the ultrasonic atomization apparatus <NUM> according to the example.

Meanwhile, atomization amount variation L4 shows a case in which the constituent material of the separator cup <NUM> is PP, and film thickness t of a bottom surface BP6 is <NUM>. Specifically, the atomization amount variation L4 is experimental results related to the conventional ultrasonic atomization apparatus <NUM>.

As shown by the atomization amount variation L3 of <FIG>, when PTFE is adopted as the constituent material of the separator cup <NUM> and the film thickness of the bottom surface BP1 is <NUM>, transmissiveness of ultrasonic waves in the bottom surface BP1 of the separator cup <NUM> is not excellent, and the source solution mist MT cannot be substantially obtained.

However, when the film thickness of the bottom surface BP1 is set to <NUM>, specifically, when the bottom surface BP1 satisfies the thin film condition described above as shown by the atomization amount variation L2 of <FIG>, transmissiveness of ultrasonic waves in the bottom surface BP1 of the separator cup <NUM> is improved, and the source solution mist MT can be obtained with an effective atomization amount.

In addition, when the film thickness of the bottom surface BP1 is set to <NUM> as shown by the atomization amount variation L1 of <FIG>, transmissiveness of ultrasonic waves in the bottom surface BP1 of the separator cup <NUM> is significantly improved, and the source solution mist MT can be obtained with an atomization amount that excels the conventional ultrasonic atomization apparatus <NUM> shown by the atomization amount variation L4.

As can be understood from the experimental results of <FIG>, it was confirmed that the atomization amount of the source solution mist MT reaches a practical level regarding transmissiveness of ultrasonic waves if the film thickness of PTFE adopted as the constituent material of the separator cup <NUM> was set to <NUM> or less.

In addition, it was confirmed that the atomization amount of the source solution mist MT reaches a high standard excelling the related art regarding transmissiveness of ultrasonic waves if the film thickness of PTFE adopted as the constituent material of the separator cup <NUM> was set to <NUM> or less.

Note that transmissiveness of ultrasonic waves is determined by acoustic impedance. Acoustic impedance of fluorocarbon resins, including PTFE, is approximately <NUM> [× <NUM><NUM> kg/m<NUM>s], and thus it is estimated that results similar to those of the case shown in <FIG> can be obtained if fluorocarbon resin is used as the constituent material of the separator cup <NUM>.

As described above, regarding the ultrasonic atomization apparatus <NUM> according to the example, a configuration that the thin film condition regarding the separator cup <NUM> that "the thickness of the bottom surface BP1 is <NUM> or less" is satisfied is referred to as a basic configuration, and a configuration that a limited thin film condition regarding the separator cup <NUM> that "the thickness of the bottom surface BP1 is <NUM> or less" is satisfied is referred to as a limited configuration. Specifically, the thin film condition described above includes the limited thin film condition described above.

As described above, the constituent material of the separator cup <NUM> in the ultrasonic atomization apparatus <NUM> according to the example is PTFE being fluorocarbon resin. The fluorocarbon resin as typified by PTFE has properties of having relatively high tolerance to various solvents. Thus, the separator cup <NUM> of the ultrasonic atomization apparatus <NUM> can exert relatively high tolerance to the source solution <NUM>.

In addition, through satisfaction of the thin film condition that "the thickness of the bottom surface BP1 is <NUM> or less", the separator cup <NUM> having the basic configuration according to the example enhances transmissiveness of ultrasonic waves in the bottom surface BP1, and can thus generate the source solution mist MT with the atomization amount at the practical level.

As a result, the basic configuration of the ultrasonic atomization apparatus <NUM> according to the example produces effects of enabling generation of the source solution mist MT that is excellent in tolerance to the source solution <NUM> and that has an approximate atomization amount.

In addition, through satisfaction of the limited thin film condition that "the thickness of the bottom surface BP1 is <NUM> or less", the separator cup <NUM> having the limited configuration of the ultrasonic atomization apparatus <NUM> according to the example can further enhance transmissiveness of ultrasonic waves in the bottom surface BP1 and generate the source solution mist MT with a higher atomization amount.

<FIG> is an explanatory diagram illustrating a cross-sectional structure of a separator cup 12B in an ultrasonic atomization apparatus <NUM> being an embodiment of the present invention. <FIG> is a plan view illustrating a planar structure of the bottom surface BP2 of the separator cup 12B illustrated in <FIG>. <FIG> illustrates a plan view as seen from the bottom surface BP2 side.

In <FIG> and <FIG>, constituent elements similar to those of the ultrasonic atomization apparatus <NUM> according to the example are denoted by the same reference signs to omit description thereof as appropriate, and features of the embodiment will mainly be described.

As illustrated in <FIG> and <FIG>, the separator cup 12B is different from the separator cup <NUM> according to the example in that the bottom surface BP2 does not have a uniform film thickness but has two types of film thicknesses. This will be described below in detail.

The bottom surface BP2 is separated into four thin film regions R1 each having a relatively small film thickness of <NUM> or less, and a thick film region R2 having a relatively large film thickness of larger than <NUM>.

The four thin film regions R1 are set to correspond to the four ultrasonic vibrators <NUM>. Each of the four thin film regions R1 is set in a region including the entire ultrasonic wave transmission region through which the ultrasonic waves applied from a corresponding ultrasonic vibrator <NUM> transmit. Further, in the bottom surface BP2, the entire region except for the four thin film regions R1 is set to the thick film region R2. Further, the film thickness of the side surface and the upper surface of the separator cup <NUM> is also set to the same film thickness as the thick film region R2.

In this manner, the bottom surface BP2 of the separator cup 12B includes four thin film regions R1 corresponding to the four ultrasonic vibrators <NUM>. Each of the four thin film regions R1 includes an ultrasonic wave transmission region that allows transmission of the ultrasonic waves generated from a corresponding ultrasonic vibrator <NUM> out of the four ultrasonic vibrators <NUM>.

Further, the separator cup 12B of the ultrasonic atomization apparatus <NUM> according to the embodiment has its thickness (≤ <NUM>) of the four thin film regions R1 set smaller than the thickness (> <NUM>) of the other region.

In this manner, in the bottom surface of the separator cup 12B according to the embodiment, each of the four thin film regions R1 satisfies the thin film condition that "the thickness is <NUM> or less" and the thick film region R2 does not satisfy the thin film condition described above.

<FIG> is an explanatory diagram illustrating a cross-sectional structure of the conventional ultrasonic atomization apparatus <NUM>. <FIG> is a plan view illustrating a planar structure of the bottom surface BP6 of the separator cup <NUM> illustrated in <FIG>. <FIG> illustrates a plan view as seen from the bottom surface BP6 side.

In <FIG> and <FIG>, constituent elements similar to those of the ultrasonic atomization apparatus <NUM> illustrated in <FIG> and <FIG> are denoted by the same reference signs to omit description thereof as appropriate.

As illustrated in <FIG> and <FIG>, the separator cup <NUM> has a uniform film thickness in the bottom surface BP6 as well. Specifically, the bottom surface BP6 is uniformly set to <NUM>. Further, the film thickness of the side surface and the upper surface of the separator cup <NUM> is also set to the same film thickness (<NUM>).

In this manner, the ultrasonic atomization apparatus <NUM> according to the embodiment has features in that, in the bottom surface BP2 of the separator cup 12B, the four thin film regions R1 (at least one thin film region) satisfy the thin film condition described above, and the thick film region R2 being the other region except for the four thin film regions R1 does not satisfy the thin film condition described above.

Regarding the ultrasonic atomization apparatus <NUM> according to the embodiment, owing to the features described above, by setting the film thickness of the thick film region R2 to be relatively large of larger than <NUM> in the separator cup 12B, tolerance to the source solution <NUM> can be enhanced to the maximum.

In addition, the ultrasonic atomization apparatus <NUM> according to the embodiment satisfies the thin film condition that the four thin film regions R1 each including the ultrasonic wave transmission region has a "thickness of <NUM> or less", similarly to the ultrasonic atomization apparatus <NUM> according to the example.

Thus, the ultrasonic atomization apparatus <NUM> according to the embodiment produces effects of enabling generation of the source solution mist MT with an appropriate atomization amount, similarly to the ultrasonic atomization apparatus <NUM> according to the example.

Note that, as a matter of course, the source solution mist MT of a higher atomization amount can be generated in the embodiment as well by setting the thickness of the four thin film regions R1 to <NUM> or less so as to achieve satisfaction of the limited thin film condition as in the limited configuration according to the example.

Claim 1:
An ultrasonic atomization apparatus comprising:
a container (<NUM>) including a separator cup (<NUM>) configured to accommodate a source solution at a lower part;
an internal hollow structure body (<NUM>) including a hollow inside being provided above said separator cup (<NUM>) in said container (<NUM>); and
a water tank (<NUM>) configured to accommodate an ultrasonic wave conveyance medium (<NUM>) inside, said water tank (<NUM>) and said separator cup (<NUM>) being positioned so that a bottom surface of said separator cup (<NUM>) is immersed in said ultrasonic wave conveyance medium (<NUM>),
a plurality of ultrasonic vibrators (<NUM>) provided in a bottom surface of said water tank (<NUM>),
characterized in that
said separator cup (<NUM>) uses fluorocarbon resin as a constituent material, and includes a bottom surface having a thickness satisfying a thin film condition, said thin film condition being that "said thickness of said bottom surface is <NUM> or less",
said bottom surface of said separator cup (<NUM>) includes a plurality of thin film regions corresponding to said plurality of ultrasonic vibrators (<NUM>), and each of said plurality of thin film regions includes an ultrasonic wave transmission region allowing transmission of ultrasonic waves applied from a corresponding ultrasonic vibrator out of said plurality of ultrasonic vibrators (<NUM>), and
in said bottom surface of said separator cup (<NUM>), said plurality of thin film regions each satisfies said thin film condition, and the other region except for said plurality of thin film regions does not satisfy said thin film condition.