atomization device

Abstract

To provide an atomization device atomizing fluid by new structure, relative to conventional arts, and application equipment or the like using the atomization device.SOLUTION: An atomization device for atomizing fluid is provided, comprising: a film in which at least a part of a surface indicates affinity for atomization-target fluid, and which therefore enables a liquid film of the atomization-target fluid to be formed; and ultrasonic oscillation application means which comes in contact with the film to thereby apply ultrasonic oscillation to the film, wherein the atomization device applies ultrasonic wave to the liquid film formed on a surface of the film through the film, to thereby atomize the fluid included in the liquid film.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an atomizing device for atomizing a liquid, and a spray device, a coating device, a granulating device, etc. using the atomizing device.

Background Art

[0002] Conventionally, for various purposes, a technique of atomizing a liquid such as water using ultrasonic waves has been used. For example, in Patent Document 1, mainly for the purpose of humidification or the like, an ultrasonic vibrator is provided at the bottom of a container capable of holding a liquid such as water, and the liquid is atomized by the ultrasonic waves generated by the ultrasonic vibrator. A device is described.

[0003] Further, in Patent Document 2, as a nebulizer for making it easier for a patient to inhale a liquid medicine atomized when the atomized medicine for treating respiratory system diseases is inhaled by the patient, a device that atomizes and ejects a liquid by ultrasonic vibration is described. Further, in Patent Document 3, a device that atomizes a liquid by ultrasonic vibration is described in order to eject droplets composed of a paint used when performing spray coating. Further, in Patent Document 4, a spray drying device for producing fine powder by drying a mist-like solution sprayed by ultrasonic vibration is described.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0005] In a device described in Patent Document 1, which involves placing an ultrasonic transducer at the bottom of a liquid-holding container and using ultrasonic waves generated by the transducer to agitate the liquid inside the container and cause atomization, the surface of the liquid agitated by the ultrasonic waves becomes finely wavy, and a portion of the ripples of these waves breaks off from the liquid and is released into space, thereby causing the liquid to atomize. However, the atomization process produced by this mechanism varies depending on the shape of the container and the amount and depth of the liquid inside, making it difficult to consistently obtain mist (droplets) of a desired size.

[0006] In contrast, in so-called mesh-type atomizing devices, such as those described in Patent Documents 2 to 4, which have a mechanism for atomizing by vibrating an ultrasonic transducer near a diaphragm (partition) with fine through-holes, thereby intermittently releasing the liquid filled on the ultrasonic transducer side of the through-holes through the through-holes, it is possible to generate mist (droplets) of a desired size by adjusting the size of the through-holes and the strength of the applied ultrasonic waves. On the other hand, if the thickness of the diaphragm with through-holes is reduced or the density of the through-holes is increased for the purpose of reducing the release resistance when the liquid is released through the through-holes and increasing the amount of liquid released, the strength of the diaphragm decreases, causing the distance between the diaphragm and the ultrasonic transducer to fluctuate, resulting in a problem of fluctuating atomization performance.

[0007] The present invention aims to provide an atomizing device that produces liquid atomization by a novel mechanism, in contrast to the conventional technologies described above. Furthermore, the present invention aims to provide a coating device, etc., that utilizes this atomizing device. [Means for solving the problem]

[0008] To solve the above problems, the present invention provides the following means. (1) An atomizing device for atomizing a liquid, comprising a film capable of forming a liquid film of the liquid by having at least a part of its surface exhibit affinity for the liquid to be atomized, and an ultrasonic applying means capable of applying ultrasonic vibrations in contact with the film, wherein the device atomizes the liquid contained in the liquid film by applying ultrasonic waves to the liquid film formed on the surface of the film through the film. (2) Atomizing apparatus having a liquid supply means for supplying a liquid to be atomized onto the surface of the above film to form a liquid film. (3) The ultrasonic application means is an atomizing device that applies ultrasonic vibrations having a component perpendicular to the surface of the film. (4) A atomizing device having a voltage applying means capable of applying a voltage to a liquid film formed on the surface of the above film. (5) A atomizing device in which the thickness of the liquid film formed on the surface of the above film is 5 mm or less. (6) A spray device having the atomizing device described above. (7) A coating apparatus having the atomizing device described above. (8) A granulation apparatus having the atomizing device described above. [Effects of the Invention]

[0009] According to the atomizing device of the present invention, the liquid to be atomized can be efficiently atomized by utilizing the affinity that exists between the liquid to be atomized and the surface of a film that has affinity for the liquid. [Brief explanation of the drawing]

[0010] [Figure 1] This is a schematic diagram of the apparatus used in the study of the atomization method according to the present invention. [Figure 2] This is a schematic diagram illustrating the mechanism by which atomization occurs in the atomizing device according to the present invention. [Figure 3] This is a schematic diagram illustrating the mechanism by which atomization occurs in the atomizing device according to the present invention. [Figure 4] This figure shows an example of an embodiment of the atomizing device according to the present invention. [Figure 5]It is a diagram showing an example of a liquid supply means used in the atomization device according to the present invention. [Figure 6] It is a diagram showing an example of an ultrasonic generation means used in the atomization device according to the present invention. [Figure 7] It is a photograph showing a state where the paint atomized by the atomization device according to the present invention is sprayed onto a substrate. [Figure 8] It is a diagram showing a profile of the coating film thickness when the paint atomized by the atomization device according to the present invention is sprayed onto a substrate. [Figure 9] It is a diagram showing a change in the width of the coating film when the amount of paint atomized by the atomization device according to the present invention is changed. [Figure 10] It is a diagram showing a change in the charge amount of the coating film when the voltage applied to the liquid is changed during atomization by the atomization device according to the present invention. [Figure 11] It is a diagram showing a change in the width of the coating film when the voltage applied to the liquid is changed during atomization by the atomization device according to the present invention.

Mode for Carrying Out the Invention

[0011] FIG. 1 shows a schematic diagram of an apparatus used for examining the atomization method according to the present invention. In the apparatus shown in FIG. 1, a resin ring 10 and a metal ring 11 each having an inner diameter of 16 mm are laminated, and various films 1 can be held by sandwiching them between the resin ring 10 and the metal ring 11. Then, with a predetermined amount of water droplets 2 supplied to the upper surface of the held film 1, a horn (tip cross-section: 12 mm × 2 mm) as a vibrator 3 is brought into contact with the lower surface of the film 1, and ultrasonic vibration can be applied in a direction perpendicular to the film surface as a vibration direction 5 with a predetermined amplitude.

[0012] Using the apparatus shown in Fig. 1, with (1) a hydrophilic film (manufactured by 3M Japan Ltd., SH2LHF (thickness 80 μm)) whose surface was hydrophilized, (2) a hydrophobic film (made of polyvinyl chloride, thickness 10 μm), and (3) an aluminum foil (thickness 10 μm) each held, a predetermined amount of water droplets was supplied to the surface of the film or the like, and the vibrator 3 was vibrated at a predetermined amplitude (oscillation frequency: 42.3 kHz) to rock the water droplets on the surface of the film or the like, attempting to atomize the water contained in the water droplets.

[0013] Among the above trials, when the aluminum foil was used, immediately after the start of applying ultrasonic waves, the aluminum foil in the portion immediately contacting the vibrator 3 melted, and it was difficult to continuously apply ultrasonic waves to the water droplets on the surface of the aluminum foil. On the other hand, by using the above hydrophilic film and hydrophobic film, ultrasonic waves could be continuously applied to the water droplets on the film. Table 1 shows the evaluation results regarding the state of the water droplets on the surfaces of the hydrophilic film and hydrophobic film, and the possibility of atomization, etc. when conducting the said evaluation. In Table 1, the symbols outside the parentheses indicate the state when the hydrophilic film was used, and the symbols inside the parentheses indicate the state when the hydrophobic film was used, respectively.

[0014] Also, in Table 1, "●" indicates that stable atomization of water occurred due to the applied ultrasonic vibration, and "▲" indicates that intermittent atomization of water occurred, respectively. On the other hand, "×" indicates that a water film with a substantially uniform thickness formed on the film surface during the application of ultrasonic waves and no atomization occurred. Also, "◇" indicates that due to the generation of a plurality of spherical water droplets, etc. during the application of ultrasonic waves, a water film with a substantially uniform thickness was not generated, and the said water droplets, etc. moved on the film surface and no atomization occurred. In Table 1, when assuming that the water droplets supplied in various amounts uniformly spread and wet the film surface, the thickness of the water film formed on the film surface is described inside the parentheses.

[0015] When a hydrophilic film was used, it was observed that water droplets supplied to the film surface rapidly spread and wet the film surface upon application of ultrasound, forming a water film (indicated by × in Table 1). Furthermore, it was observed that by applying ultrasonic vibrations with an amplitude greater than a predetermined value, minute droplets were released from the water film, resulting in water atomization (indicated by ● in Table 1). In other words, as shown by the symbols outside the parentheses in Table 1, it was observed that atomization occurred from water films with a thickness of approximately 1 mm or less when vibrations with an amplitude of approximately 10 μm were applied, and that atomization occurred from water films with a thickness of approximately 3.5 mm when the amplitude of the vibration was increased. From this, it was observed that water atomization occurs on the surface of a hydrophilic film when conditions such as the amplitude of the transducer and the thickness of the water film are met.

[0016] On the other hand, on the surface of the hydrophobic film, it was observed that applying ultrasound to water droplets dropped onto the film resulted in the formation of approximately spherical droplets with a large contact angle with the film surface over a wide range of conditions, and that these droplets moved along the film surface (◇ in Table 1). Furthermore, by increasing the amount of water supplied to the film, it was observed that the state transitioned from the formation of these spherical droplets to the formation of a water film of approximately uniform thickness (× in Table 1), but atomization of the water was not observed.

[0017] [Table 1]

[0018] Figure 2 schematically illustrates the various forces thought to be involved in the morphology of water droplets (water 2) present on the surface of various films 1. It is believed that a cohesive force 41 (surface tension) exists within the water droplets 2, acting to minimize their surface area. Furthermore, gravity 40 acts on the water droplets 2, acting to minimize their potential energy. Furthermore, if film 1 is hydrophilic (Figure 2(a)), an affinity force 42 exists between the film and water, and this affinity force 42 acts to wet the film surface. The morphology of the water 2 (water droplets) present on the surface of film 1 is thought to be determined mainly by gravity 40, cohesive force 41 (surface tension), and the affinity force 42 with the film.

[0019] On the other hand, when film 1 is hydrophobic (Figure 2(b)), the interaction between the film and water is small, and the morphology of water 2 (water droplets) present on the surface of film 1 is mainly determined by gravity 40 and cohesive force 41 (surface tension). In particular, a large cohesive force 41 exists for water, and it is observed that water droplets with a large contact angle are formed between the film and the water according to the balance between gravity 40 and cohesive force 41, and the contact area between water and film is reduced. This state can also be observed as if a repulsive force 43 is acting between the water and the film, causing the water to be repelled.

[0020] As shown in Table 1, the mechanism by which the form of water on the film surface vibrated by the vibrator 3 and whether or not it can be atomized differs depending on whether the film surface is hydrophilic or hydrophobic is considered to be as follows. The mechanism by which the affinity force 42 between the film and water shown in Figure 2(a) is generated is presumed to be as follows: When water comes into contact with a hydrophilic surface, the surface generally hydrates and various bonds are formed with water molecules, resulting in water molecules being confined to the surface. These confined water molecules then have a cohesive force 41 (surface tension) with the surrounding water molecules. As a result, water on the hydrophilic surface is subjected to a predetermined confining force, which is observed as the affinity force 42 that causes hydrophilicity (wettability). Furthermore, it is thought that this affinity force 42 counteracts the cohesive force 41 (surface tension) of water, allowing water to be retained in the form of a water film with a large specific surface area.

[0021] When vibration is applied to the film on which the water film is formed by the vibrator 3, the restraining force mainly due to the affinity force 42 present between the film and the water functions as a coupling for transmitting the vibration, and it is thought that the energy of the vibration can be supplied to the water film. As a result, it is presumed that the water film can be made to oscillate by supplying vibration energy through the film, and when the conditions for water droplet formation are met, some of the water constituting the water film is torn away from the film to form minute water droplets, resulting in the phenomenon shown in Table 1.

[0022] On the other hand, on hydrophobic surfaces, the interaction between the surface and water is small, and it is presumed that a state is formed where water droplets, which tend to become spherical due to the cohesive force 41 (surface tension), are pressed against the film surface mainly by gravity 40 acting on the water (Figure 2(b)). Furthermore, in this state, even though the water droplets and the film are in contact, there is no effective restraining force at the interface between the water droplets and the film, and they can displace each other freely. Therefore, when vibration is applied to the film 1 by the vibrator 3, it is thought that the energy of the vibration is not easily introduced into the water droplets. In addition, it is presumed that the vibration of the film causes the water droplets to be repelled upward, resulting in the sphericalization of the water droplets due to the cohesive force (surface tension) 41 and a reduction in the contact area between the film and the water droplets, as shown by "◇" in Table 1.

[0023] Furthermore, even on a hydrophobic film, an increase in water volume leads to an increase in the gravitational force acting on the water (indicated by "×" in Table 1), but atomization does not occur due to reasons such as the lack of sufficient restraining force at the interface between the water droplet and the film.

[0024] The atomizing device according to the present invention utilizes the above-mentioned findings and uses a film 1 having a surface that exhibits affinity for the liquid to be atomized. With a liquid film 2 formed on the surface by the liquid to be atomized, ultrasonic vibrations are applied to the liquid film 2 through the film 1, causing the liquid film on the film surface to agitate and atomizing a portion of the liquid constituting the liquid film into droplets 20. In other words, the atomizing device according to the present invention is characterized by using the bond (affinity force) that occurs between the liquid to be atomized and the film surface that exhibits affinity for the liquid as a connector for transmitting ultrasonic vibrations, thereby agitating the liquid film constrained on the film surface by the affinity force and causing atomization.

[0025] Figures 1 and 2 illustrate an example in which a liquid such as water is supplied to the upper surface of a film placed approximately horizontally. However, the present invention is not limited to this, and the film surface can be positioned at any angle with respect to the vertical direction, as long as a liquid film of approximately uniform thickness can be formed on the film surface. In other words, for example, a liquid film may be formed on the lower surface of a horizontally positioned film, and the liquid constituting the liquid film may be atomized. Alternatively, the film surface may be positioned parallel to the vertical direction, and atomization may occur from the liquid film formed on that surface. In this specification, "liquid film" refers to a form of liquid, and is used to distinguish it from "liquid droplets," which are formed when the liquid is repelled by the film due to insufficient affinity between the liquid and the film.

[0026] Figure 3 schematically shows an example of the configuration of the atomizing device according to the present invention. In the configuration shown in Figure 3, a film 1 having affinity for the liquid to be atomized is used on the lower surface side to form a liquid film 2 consisting of the liquid on the lower surface of the film 1, and a vibrator 3 is brought into contact with the upper surface of the film 1 to atomize the liquid contained in the liquid film as droplets 20. In this configuration, by continuously supplying the liquid along the film 1, it is possible to maintain the thickness of the liquid film in the portion oscillated by the vibrator 3, and atomization can be performed continuously.

[0027] Furthermore, the film 1 constituting the atomizing device according to the present invention is not particularly limited as long as it has a surface on which at least a portion of its surface exhibits affinity for the liquid to be atomized and exhibits flexibility to the extent that it can follow the displacement caused by the vibration of the vibrator 3.

[0028] Furthermore, the liquid atomized by the atomizing device according to the present invention is not limited to water or aqueous solutions. For example, by using a film whose surface at least exhibits lipophilicity, it is possible to atomize organic solvents or solutions using organic solvents as solvents. On the other hand, the atomizing device according to the present invention is preferably used for atomizing liquids having a predetermined cohesive force (surface tension), and is particularly preferably used for atomizing water and aqueous solutions.

[0029] In order to retain the atomized liquid in the form of a liquid film, the film 1 constituting the atomizing device according to the present invention is preferably one that exhibits a predetermined affinity for the liquid. The magnitude of the affinity between the film and the liquid can be evaluated, for example, by the ease with which a liquid film is formed when ultrasonic vibrations are applied while the film and the liquid are in contact.

[0030] For example, a film that exhibits sufficient affinity to form a liquid film with a thickness of 0.5 mm or less, more preferably 0.3 mm or less, when a liquid is dropped onto the film surface and ultrasonic vibrations are applied, without forming droplets with a large contact angle, can be preferably used as a film constituting the atomizing device according to the present invention. By using such a film, a liquid film constrained by the affinity with the film surface can be formed on the film surface, and atomization can be produced by agitating this liquid film with ultrasonic vibrations.

[0031] The film 1 constituting the atomizing device according to the present invention may be made of a material that exhibits affinity for the liquid to be atomized as a whole, or affinity may be imparted to the surface portion of a film made of a predetermined material by various methods. For example, affinity for the liquid may be imparted only to the surface that forms a liquid film with the liquid to be atomized, or a film in which affinity for the liquid is imparted only to a part of the surface may be used.

[0032] In an atomizing apparatus, such as the one described in Patent Document 1, which atomizes a large volume of bulk water held in a tank by applying oscillation with an ultrasonic transducer, the large volume of water being agitated inevitably results in a large amount of energy being wasted due to internal friction and other factors, making it difficult to atomize. In contrast, the atomizing apparatus according to the present invention applies oscillation with an ultrasonic transducer to a minute volume of liquid, and is therefore generally expected to achieve high energy efficiency. Furthermore, when atomizing continuously, the atomizing apparatus according to the present invention makes it possible to obtain a mist containing droplets of a predetermined size at all times by keeping the volume of the liquid being agitated constant.

[0033] Furthermore, in the atomizing device described in Patent Document 1, a portion of the water stored in the water tank is atomized, and the atomized water droplets released are dispersed above the water surface. In contrast, in the atomizing device according to the present invention, by arranging the film in a plane perpendicular to the direction in which the droplets are to be released, it becomes possible to release the droplets in any direction other than upwards.

[0034] Furthermore, according to the mesh-type atomizing apparatus described in Patent Documents 2 to 4, it is possible to release atomized droplets in any direction, for example. On the other hand, as explained above, in the present invention, since droplets are generated by agitating the liquid film formed on the film surface, the diaphragm (mesh) with through holes that is essential in the atomizing apparatus described in Patent Documents 2 to 4 is unnecessary, and the resistance to liquid ejection caused by the diaphragm is reduced, making it possible to improve atomization efficiency.

[0035] Figure 4 shows an example of an embodiment of the atomizing device according to the present invention. In Figure 4, the film 1 for generating the liquid film 2 is attached to and fixed to a film support 6 having an opening, thereby holding the film 1 under a predetermined tension. The film 1 used is not particularly limited as long as it has resistance to the liquid to be atomized, has a predetermined flexibility that allows it to deform in accordance with the operation of the vibrator 3, and has a tension that does not cause macroscopic slack within the film 1.

[0036] Furthermore, the side of the film 1 that forms the liquid film 2 preferably exhibits affinity for the liquid forming the liquid film 2. Preferably, the film 1 is used if it exhibits an affinity such that the liquid spreads when the liquid to be used is dropped onto the surface of the film 1 and ultrasound is applied, causing the liquid to wet the surface.

[0037] The shape and material of the film support 6 that supports the film 1 are not particularly limited, as long as it has sufficient strength to prevent deformation or resonance when the film 1 vibrates due to the operation of the vibrator 3. Furthermore, as described below, when applying an electric potential to the liquid forming the liquid film 2, it is preferable to make the film support 6 out of a conductive material such as metal and to electrically ground it to stabilize the electric potential.

[0038] In Figure 4, a liquid supply means 7 is provided on the surface of the film 1 attached to the film support 6 in order to form a liquid film 2 on the film 1 surface. The liquid supply means 7 is used to form a liquid film 2 on the surface of the film 1 by bringing the liquid supplied from the liquid supply pump 10 into contact with the surface of the film 1, thereby utilizing the surface tension of the liquid.

[0039] Figure 5 schematically shows an example of a liquid supply means 7 used in the atomizing device according to the present invention. In the liquid supply means 7 shown in Figure 5, a recess with an opening 7a is provided on the side surface of one end of a plate-like body, and liquid can be supplied to the recess from the outside via a liquid supply path 7b. The surface 7c on the recess side of the liquid supply means 7 shown in Figure 5 is held in contact with the surface of the film 1, and liquid is supplied through the liquid supply path 7b at an appropriate flow rate to fill the recess with liquid, and the liquid can then be supplied by flowing out from the opening 7a along the surface of the film 1.

[0040] Furthermore, as described below, when applying a potential to the liquid forming the liquid film 2, at least the portion of the liquid supply means 7 that comes into contact with the liquid can be made of metal, and the potential can be applied to the liquid by an externally provided voltage application means 8 using the metal portion as an electrode.

[0041] The liquid supply means 7 used in the atomizing device according to the present invention is not limited to the form shown in Figure 4. Any means that can supply liquid to the surface of the film 1 at a constant rate to form and maintain a liquid film 2 is also possible, such as supplying liquid to the surface of the film 1 by spraying.

[0042] The liquid supply pump 10 for supplying liquid to the surface of the film 1 is not particularly limited as long as it is a pump capable of supplying liquid by pressurizing it at a constant rate, and a tube pump or the like with an appropriate capacity can be used as the liquid supply pump 10.

[0043] As shown in Figure 4, by applying ultrasonic vibrations generated by the ultrasonic generating means 4 using the transducer 3 to the back side of the film 1 on which the liquid film 2 is formed on the surface, through the opening of the film support 6, it is possible to oscillate the liquid film 2, thereby breaking up a portion of the liquid constituting the liquid film 2 and forming minute droplets 20 that constitute a liquid mist.

[0044] In the configuration shown in Figure 4, when forming minute droplets 20 from the liquid constituting the liquid film 2, the droplets 20 can be formed successfully if ultrasonic vibrations are applied to the film 1 by contacting the back surface of the film 1 with the transducer 3. Furthermore, for purposes such as stabilizing the vibration of the film 1, the transducer 3 can be attached to the back surface of the film 1 by appropriate means.

[0045] Furthermore, in the configurations shown in Figures 3 and 4, by vibrating the transducer 3 in contact with the film 1, the portion of the film in contact with the transducer 3 generates vibrations substantially identical to those of the transducer 3, allowing for the formation of minute droplets 20 from the liquid film 2. On the other hand, as the ultrasonic vibrations within the film rapidly attenuate as it moves away from the contact area with the transducer 3, droplets 20 do not form on the film surface in areas other than the contact area with the transducer 3, making it possible to generate droplets 20 substantially only from the film surface in the portion in contact with the transducer 3.

[0046] Furthermore, by using a vibrator 3 with a vibration direction 5 perpendicular to the film surface, the generated droplets 20 will have a predetermined velocity perpendicular to the film surface, and the generated droplets 20 will have a flux that is substantially the same as, or similar in cross-section to, the contact surface between the vibrator 3 and the film 1. Utilizing these characteristics, the atomizing device according to the present invention can be suitably used not only for purposes such as supplying atomized liquid into space, but also as a spray head for a drawing means that utilizes the flux of the droplets 20 to spray the droplets 20 onto a predetermined position on the surface of an object.

[0047] Furthermore, as shown in Figures 3 and 4, by forming minute droplets 20 from the liquid film 2, the amount of liquid contained in the liquid film 2 on the film surface in contact with the vibrator 3 decreases, and the thickness of the liquid film 2 decreases. In the atomizing device according to the present invention, it is possible to continuously generate droplets 20 by supplying liquid to the film surface in contact with the vibrator 3 using the liquid supply means 7.

[0048] For example, in the configurations shown in Figures 3 and 4, the supply of liquid 21 to the film surface in contact with the vibrator 3 can be driven primarily by the surface tension of the liquid. In other words, when the thickness of the liquid film 2 on the film surface in contact with the vibrator 3 decreases, the surface tension of the liquid causes a flow of liquid within the film in a direction that makes it the same thickness as the surrounding liquid film, thereby maintaining the thickness of the liquid film 2 in contact with the vibrator 3.

[0049] Therefore, from the viewpoint of facilitating the supply of liquid 21 to the surface of the contact portion of the film with the vibrator 3 and maintaining the amount of liquid droplets 20 generated, it is desirable to maintain the thickness of the liquid film 2 in the vicinity of the contact portion. For example, it is desirable to reduce the liquid flow distance by arranging the opening 7a of the liquid supply means 7, as shown in Figure 5, in the vicinity of the contact portion.

[0050] On the other hand, as shown in Figure 4, by applying a potential to the liquid supplied to the film surface using a voltage application means 8, and by constructing the oscillator 3 from metal and maintaining it at ground potential, a potential difference is created between the liquid film 2 and the oscillator 3, thereby promoting the supply 21 of liquid to the contact area between the film 1 and the oscillator 3 through electrostatic force. Furthermore, the electrostatic force generated by creating a potential difference between the liquid film 2 and the oscillator 3 also acts as a restraining force that constrains the liquid film to the film 1, and by increasing the thickness of the liquid film 2, the amount of liquid droplets 20 generated can be increased. Furthermore, by applying a voltage to the liquid film on the surface of film 1, an electric charge is imparted to the liquid within the film and to the droplets produced by atomization. In particular, by creating a predetermined electric field distribution in the space containing the atomized droplets, it becomes possible to control the flow (flux) of the droplets.

[0051] When a potential difference is created between the liquid film 2 and the vibrator 3 by the voltage application means 8, it is preferable to use a film 1 made of a material that can ensure insulation even when in contact with the liquid. Figure 4 shows an example in which a potential is applied to the liquid film 2 by the voltage application means 8 while the vibrator 3 is grounded, but the present invention is not limited to this, and by applying a potential to the vibrator 3 side, an electrostatic force can be generated between it and the liquid film, thereby improving the efficiency of liquid supply to the contact area between the film 1 and the vibrator 3 and increasing the thickness of the liquid film 2.

[0052] The ultrasonic generating means 4 can be used without particular limitation as long as it has an output that corresponds mainly to the area of ​​the contact area between the film 1 and the transducer 3. Figure 6 schematically shows an example of the structure of the ultrasonic generating means 4 used in the present invention. As shown in Figure 6, an ultrasonic transducer can be constructed by providing electrodes 30 on both sides of a piezoelectric material 31 that expands / contracts when a voltage is applied, and applying an AC voltage of a predetermined frequency from an AC power supply device 33 to generate vibrations in a direction that expands / contracts the distance between the electrodes. Furthermore, by attaching a horn 32 exhibiting appropriate acoustic characteristics to one side of the electrodes of the ultrasonic transducer, the amplitude of the sound waves emitted from the ultrasonic transducer can be adjusted.

[0053] In the ultrasonic generating means 4 configured as shown in Figure 6, vibrations perpendicular to the tip surface of the horn 32 can be generated. However, the ultrasonic generating means used in the atomizing device according to the present invention is not limited to this. An ultrasonic generating means that generates vibrations parallel to the tip surface of the horn 32, or an ultrasonic generating means that generates vibrations by mixing perpendicular and horizontal vibrations relative to the tip surface of the horn 32, can be used. On the other hand, when the atomizing device according to the present invention is used as the head portion of the drawing means, it is preferable to use an ultrasonic generating means that can apply vibrations perpendicular to the film surface, from the viewpoint of aligning the flux of the generated droplets.

[0054] In the atomizing apparatus according to the present invention, the transducer 3, which is an ultrasonic applying means that contacts the film and applies ultrasonic vibrations, may be the horn 32 of the ultrasonic generating means shown in Figure 6 and brought into contact with the film 1 as the transducer 3, or a member further connected to the horn 32 may also be used as the transducer 3.

[0055] The amplitude of the ultrasonic vibration applied by the transducer 3 to the film 1 can be appropriately determined according to the surface tension of the liquid being atomized and the amount of liquid atomized per unit time. In particular, using a transducer with an amplitude of 10 μm or more makes it possible to atomize liquids with high surface tension, such as water, and using a transducer with an amplitude of 20 μm or more makes it possible to atomize water films with a thickness of about 3 mm. Further increasing the amplitude expands the conditions under which atomization can occur.

[0056] Furthermore, while the frequency of the ultrasonic vibration applied to the film 1 by the transducer 3 is not particularly limited, relatively low-frequency ultrasound can be used because the amplitude described above can be easily obtained. For example, by using ultrasound with a frequency of 20k to 100kHz, or ultrasound with a frequency of 20k to 50kHz, vibrations with the above-mentioned amplitude can be easily obtained.

[0057] To verify the atomization of liquid using the atomizing device shown in Figure 4, the atomization stability and other factors were evaluated by spraying the droplets 20 produced by the atomizing device shown in Figure 4 onto the substrate 11 using the method described below.

[0058] A 2mm thick aluminum plate with a 20mm x 10mm opening was used as the film support 6. A film (3M Japan, SH2LHF (80μm thick)) with one side being a hydrophilic surface was attached to the film support 6 with adhesive, with the back side of the hydrophilic surface facing the film support 6. Furthermore, an aluminum liquid supply means 7 (width of opening 7a: 20mm, depth of recess: 1mm) as shown in Figure 5 was positioned on the hydrophilic film surface so that its opening 7a coincided with the long side of the opening of the film support 6, and was fixed to the film support 6 from the outside with clips.

[0059] The film support 6 was fixed to the stand so that the hydrophilic surface of the film faced downwards and was roughly horizontal, and the film support 6 was grounded. In addition, the horn portion (tip cross-section: 12 mm x 2 mm) of the ultrasonic generator (Sharp UW-A2) was fixed in contact with the back surface of the film via the center of the opening of the film support 6. The tip of the horn portion of the ultrasonic generator has a frequency of 38 kHz and an amplitude of approximately 12 μm, generating vibrations perpendicular to the surface of the film.

[0060] Furthermore, a substrate 11 (made of Sus430), which is the target onto which droplets 20 formed by the atomization of the liquid are sprayed, is positioned 30 mm from the film support 6, parallel to the film support 6, and is electrically grounded so that it can move at a predetermined speed in the direction of the short side of the horn section.

[0061] In the above state, a syringe pump acting as the liquid supply pump 10 was used to supply a water-based paint (viscosity: 25 mPa·sec) containing the dissolved dye to the liquid supply means 7 at a constant rate to form a liquid film on the hydrophilic surface of the film. At the same time, a predetermined voltage was applied to the liquid supply means 7 by the voltage application means 8, and the ultrasonic generator was operated to cause atomization from the liquid film.

[0062] Figure 7 shows the appearance of a substrate to which droplets 20 of water-based paint have been sprayed, with a water-based paint supply rate of 0.03 ml / sec, a substrate movement speed of 3.0 cm / s, and a voltage of -6 kV applied to the liquid supply means 7. As shown in Figure 7, atomization was performed using the atomizing device shown in Figure 4 while the substrate was being moved. It was verified that there was no color unevenness in the direction of the substrate's movement, and a striped coating film 12 with a constant width in the direction perpendicular to the direction of the substrate's movement was formed. The above results demonstrate that atomization using the atomizing device shown in Figure 4 is continuous and uniform. Furthermore, it is shown that by utilizing the mist generated by this atomization, it is possible to create a spray device that ejects mist consisting of various liquids, or a coating device that applies paint or the like to the surface of various objects.

[0063] In the evaluation of the atomizing device described above, a liquid film is formed on the lower surface of the film. In the liquid film formed on the lower surface of the film, a predetermined, substantially uniform thickness can be maintained regardless of the presence of gravity acting on the liquid in the film. Therefore, it is considered that the liquid film is held in place by the affinity between the film and the liquid. Furthermore, the continuous formation of uniform stripes on the substrate surface is considered to indicate that ultrasonic vibrations can be transmitted to the liquid film (liquid) held in place by the affinity between the film and the liquid, thereby causing atomization, and that the thickness of the liquid film can be maintained by supplying liquid through the liquid supply means 7.

[0064] Figure 8 shows the results of measuring the thickness profile of the coating film in the width direction after drying the striped coating film formed using the above apparatus, with a water-based paint supply rate of 0.03 ml / sec, a voltage applied to the liquid supply means 7 of 9 kV, and the moving speed of the substrate 11 changed to 1.0, 3.0, and 5.0 cm / s. As shown in Figure 8(c), it was observed that when the substrate was moved at a speed of 5.0 cm / s, the width of the formed stripe was approximately 14 mm, which is close to the width of the horn section (12 mm). This suggests that, at least in the width direction of the horn section, the droplets produced by the atomizing device shown in Figure 4 travel in a straight line almost perpendicular to the film surface.

[0065] Furthermore, as shown in Figures 8(a) and 8(b), it was observed that reducing the movement speed of the substrate widened the width of the striped coating and made the thickness of the coating more uniform. This is presumed to be because reducing the movement speed of the substrate increases the amount of liquid adhering per unit area, resulting in the liquid droplets adhering to the substrate wetting and spreading out. It was considered that the width of the stripes drawn under similar conditions reflects the amount of liquid adhering per unit area.

[0066] Figure 9 shows the change in the width of the striped coating film drawn on the substrate surface when the voltage applied to the liquid supply means 7 is 9 (kV), the substrate movement speed is 3.0 (cm / s), and the supply speed of the paint supplied from the syringe pump (liquid supply pump 10) to the liquid supply means 7 is changed using the above apparatus. As shown in Figure 9, it was observed that increasing the supply speed of the paint supplied to the liquid supply means 7 increased the width of the stripes drawn. From this, it was inferred that increasing the supply speed of the paint supplied to the liquid supply means 7 increases the thickness of the liquid film on the film surface, and thus increases the amount of droplets produced by atomization.

[0067] On the other hand, when the supply rate of the paint supplied to the liquid supply means 7 was set to below a certain value (less than 0.01 ml / sec in Figure 8), continuous atomization became difficult, and evaluation of the stripe width became difficult. This suggests that when the paint supply rate is below a certain value, the thickness of the liquid film on the film surface becomes thinner, making it difficult for minute droplets to be uniformly generated by the fluctuation of the liquid film.

[0068] Furthermore, when the paint supply rate was increased above a certain value (0.05 ml / sec or higher in Figure 8), a phenomenon was observed where the paint dripped from the liquid film on the film surface as macroscopic droplets, making it difficult to maintain good atomization.

[0069] Figure 10 shows the amount of charge (specific charge: mC / kg) attached per unit weight of paint sprayed onto the substrate when a striped coating film was drawn on a grounded substrate surface in the same manner as described above, using the above apparatus, with the substrate moving speed set to 3.0 cm / s, the water-based paint supply rate set to 0.05 ml / sec, and the voltage applied to the liquid supply means 7 by the voltage application means 8 being varied. The amount of charge attached per unit weight of paint was measured by measuring the current flowing between the substrate and the ground when a predetermined amount of paint was sprayed onto a metal substrate. Figure 11 shows the change in the width of the striped coating film drawn on the substrate surface in the above case.

[0070] As shown in Figure 10, by applying a voltage to the liquid film via the liquid supply means 7 using the voltage application means 8, it is possible to attach electric charge to the droplets of sprayed paint, and it has been shown that the amount of attached charge increases in proportion to the voltage value.

[0071] As shown in Figure 11, when no voltage was applied to the liquid film, the width of the striped coating created by the atomization of the paint was approximately 18 mm, which tended to be wider than the width of the horn section (12 mm). On the other hand, by applying a voltage of approximately 1 kV to the liquid film, the width of the stripes became approximately the same as the width of the horn section, suggesting that the diffusion of flux from the atomized droplets due to electrostatic force was prevented.

[0072] On the other hand, it was observed that increasing the voltage applied to the liquid film beyond 1kV tended to widen the stripe width. This was presumed to be because the amount of charge adhering to the sprayed paint increased, and this charge created a repulsive force between the droplets, causing the droplet flux to spread.

[0073] The above results demonstrate that, in the atomizing device according to the present invention, by applying a voltage to the liquid film formed on the film surface, a predetermined amount of charge can be imparted to the droplets generated from the liquid film on the film surface, thereby changing the spray state of the droplets. Furthermore, the atomizing device according to the present invention can be used as an atomizing device for so-called electrostatic coating, in which droplets are attached to a substrate held at a predetermined potential by electrostatic force.

[0074] As described above, the atomizing device according to the present invention can atomize a liquid in a stable amount over time to generate a flux of minute droplets. Furthermore, the atomizing device according to the present invention can eject the directional droplet flux in any desired direction, and this can be used to construct a spray device that ejects a mist consisting of various liquids.

[0075] Furthermore, the above-described spray device can be used to configure a coating device for spraying paints, etc., which are composed of dispersed and dissolved predetermined dyes, etc., in a liquid onto an object to form a coating film. In this coating device, since the atomized droplets fly with a predetermined direction during the atomization process, there is no need to use the flow of air, etc., to impart directionality to the droplets, as in general air sprays, and coating using a so-called airless method becomes possible. Because airless coating does not reduce the paint adhesion rate due to air blowback, coating can be performed with high coating efficiency.

[0076] The atomizing device according to the present invention is capable of generating a flux of droplets having substantially the same cross-sectional shape as an ultrasonic application means, such as a transducer that applies ultrasonic vibrations for atomizing a liquid. Depending on the shape of the ultrasonic application means, it is possible to apply paint or the like to a fine area, and by atomizing the paint while moving the device within the surface of the object to be coated, it is possible to coat a large area. Furthermore, efficient coating can be achieved by arranging multiple atomizing devices according to the present invention in parallel.

[0077] Furthermore, by adding a mechanism to the atomizing device according to the present invention that atomizes a solution obtained by dissolving a predetermined solute, and then evaporates and removes the solvent from the droplets generated by atomization, a granulation device can be constructed to produce fine particles composed of the solute. The granulation device can take various forms, including one in which the solvent is evaporated and removed by heating the atomized space of the solution to produce fine particles within that space, or another in which the solution is sprayed onto the surface of a substrate that does not have affinity for the solution, droplets made of the solution are generated and grown, and then the solvent is evaporated and removed. [Industrial applicability]

[0078] The atomizing device according to the present invention makes it possible to efficiently atomize various liquids and easily generate a mist consisting of the liquid. In particular, by using this mist, it is possible to apply paints and the like with a high coating rate, and also to use the mist to granulate various fine particles. [Explanation of Symbols]

[0079] 1 film 2 Water (water droplets, liquid film) 3. Oscillator 4. Ultrasonic generating means 5. Direction of vibration 6 Film support 7 Liquid supply means 8 Voltage application means 10 Liquid supply pumps 11 Base material 12. Coating film 20 droplets (mist) 30 electrodes 31 Piezoelectric material 32 horns 33 AC power supply equipment 40 Gravity 41 Cohesive force (surface tension) 42. Affinity between the film surface and the liquid

Claims

1. A atomizing device for atomizing liquids, A film capable of forming a liquid film of a liquid by exhibiting affinity for a liquid in which at least a portion of the surface is atomized, It has ultrasonic application means capable of applying ultrasonic vibrations by contacting the film, An atomizing device characterized by atomizing the liquid contained in a liquid film formed on the surface of the film by applying ultrasonic waves through the film.

2. The atomizing apparatus according to claim 1, characterized in that it has a liquid supply means for supplying a liquid to be atomized onto the surface of the above film to form a liquid film.

3. The atomizing apparatus according to claim 1 or 2, characterized in that the ultrasonic application means applies ultrasonic vibrations having a component perpendicular to the surface of the film.

4. The atomizing apparatus according to any one of claims 1 to 3, characterized in that it has a voltage applying means capable of applying a voltage to a liquid film formed on the surface of the above film.

5. A spray device characterized by having an atomizing device according to any one of claims 1 to 4.

6. A coating apparatus characterized by having an atomizing device according to any one of claims 1 to 4.

7. A granulation apparatus characterized by having an atomizing device according to any one of claims 1 to 4.

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