JP2004298667A - Thin film deposition apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an apparatus with which a thin film having prescribed thickness is deposited on the whole surfaces of a substrate in a short period of time. <P>SOLUTION: The apparatus for depositing a thin film having uniform film thickness on the substrate by atomizing a liquid material to produce mist and depositing the mist on the substrate by electrostatic force is composed of a mist producing part for atomizing the liquid material to produce the mist, a mist electrifying part for electrifying the mist, a deceleration part for decelerating the flow rate of the electrified mist electrified in the electrifying part and a electrostatic coating part for inducing charge having polarity counter to the polarity of the electrification of the electrified mist on the substrate and causing the substrate to adsorb the electrified mist. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an apparatus for forming a thin film having a uniform thickness by applying a mist obtained by atomizing a liquid substance to a substrate by electrostatic force.
[0002]
[Prior art]
As a technique for forming a thin film on a substrate, various techniques have been known for a long time. For example, apply paint uniformly to a substrate such as an iron plate or synthetic resin plate using a brush or a roll coater to form a coating, or apply a paint mist to the substrate using an electrostatic coating gun to apply the coating. A method of forming, or a method of immersing a substrate in a cloud of powder paint formed into a cloud using an electrostatic fluidized immersion layer, attaching the powder to the substrate by electrostatic force, and baking to form a coating film, etc. Are known.
[0003]
In recent years, a spin coating technique of forming a thin film using a centrifugal force by high-speed rotation to form a protective film on a substrate of an optical disc or a recording film has been widely used, and is not so large. It is relatively effective for disk-shaped substrates. The spin coating technique is also used when forming a thin film on a square substrate having a large area such as a liquid crystal panel.
[0004]
[Problems to be solved by the present invention]
However, in the former method of applying with a brush or a roll coater, it is very difficult to adjust the thickness of the coating film. In particular, it is impossible to adjust the film thickness from 1 μm to several μm. The same applies to the method using electrocoating, but it is said that the electrostatic coating method using the electrostatic fluidized immersion layer can relatively adjust the thickness of the coating film. However, since powder coating is used in the electrostatic coating, a baking step is required. In this step, high-temperature processing is performed, and thus many of the optical discs and liquid crystal panels cannot be applied.
[0005]
In addition, in the case of a method using the spin coating technique as described above, in the case of a square substrate such as a liquid crystal panel having a relatively large area, the film thickness at the corners becomes large, and the film thickness cannot be uniform. There was a point.
[0006]
Therefore, in the present invention, a suitable liquid substance is formed into a mist (mist) having a relatively uniform particle size, the mist is charged to one polarity (usually negative), and the directivity due to the flow of air is minimized. Another object of the present invention is to form a uniform thin film having a predetermined thickness by causing a charge mist to adhere to a substrate by electrostatic force.
[0007]
Means and Action for Solving the Problems
In order to solve the above problems, the invention according to claim 1 of the present application generates a mist by atomizing a liquid substance, adheres the mist to a substrate by electrostatic force, and forms a thin film having a uniform thickness on the substrate. In the forming device, a mist generating section that generates a mist by atomizing the liquid substance, a mist charging section that charges the mist, and a flow rate of the charged mist charged by the mist charging section is reduced, A charge mist decelerating unit that increases the concentration of the charge mist near the substrate, and an electrostatic coating that induces a charge having a polarity opposite to the polarity of the charge of the charge mist on the substrate to attract the charge mist to the substrate. And a thin film forming apparatus comprising:
[0008]
According to the thin film forming apparatus of the first aspect, a thin film having a predetermined thickness can be formed on the entire surface of the substrate in a short time.
[0009]
According to a second aspect of the present invention, in the first aspect, the charging mist decelerating unit has the same polarity as the polarity of the charging mist, and generates a repulsive force between the charging mist and the adhesion of the charging mist. An object of the present invention is to provide a thin film forming apparatus including an electrostatic repulsion filter that allows air to pass therethrough.
[0010]
According to the thin-film forming apparatus of the second aspect, the flow rate of the charging mist can be effectively reduced, and the maintenance-free reduction section is provided.
[0011]
A third aspect of the present invention is an apparatus for forming a mist by atomizing a liquid substance, and applying the mist to a substrate by electrostatic force to form a thin film having a uniform film thickness on the substrate. A mist generating unit that generates a mist, a mist charging unit that charges the mist, and induces a charge having a polarity opposite to the polarity of the charging mist on the substrate, and attracts the charged mist to the substrate. An electrostatic coating portion for causing the charged mist to have the same polarity as the charged mist and to generate a repulsive force with the charged mist, thereby preventing the charged mist from adhering or passing therethrough. A thin film forming apparatus provided with an electrostatic repulsion filter that allows air to pass therethrough to increase the concentration of the charged mist in an atmosphere near the substrate.
[0012]
According to the thin film forming apparatus of the third aspect, since the concentration of the charged mist can be effectively concentrated in the atmosphere near the substrate and the concentration thereof can be increased, the thin film having a predetermined thickness can be formed on the entire surface of the substrate in a short time. An electrostatic repulsion filter that can and does its job is very easy to maintain.
[0013]
According to a fourth aspect of the present invention, in any one of the first to third aspects, the electrostatic coating unit includes an annular correction member at a position surrounding the substrate, and has a same polarity as the polarity of the charge on the substrate. An object of the present invention is to provide a thin film forming apparatus for applying a voltage.
[0014]
According to the thin film forming apparatus of the fourth aspect, since the concentration of the electric field can be reduced and made uniform, a thin film having a uniform thickness can be formed on the entire surface of the substrate.
[0015]
According to a fifth aspect of the present invention, in any one of the first to fourth aspects, the electrostatic coating unit includes a DC power supply capable of supplying a variable voltage capable of adjusting a charge amount induced or applied to the substrate. And a thin film forming apparatus capable of adjusting the voltage to adjust the thickness of the thin film.
[0016]
According to the thin film forming apparatus of the fifth aspect, it is possible to form a film having a desired thickness by adjusting the voltage value.
[0017]
According to a sixth aspect of the present invention, in any one of the first to fifth aspects, the mist charging portion has a discharge electrode, and the discharge electrode is surrounded by a tube, and is disposed inside the tube toward a tip end of the discharge electrode. The present invention provides a thin film forming apparatus that prevents the mist from adhering to the discharge electrodes by flowing air.
[0018]
According to the thin film forming apparatus of claim 6, since no mist adheres to the discharge electrode, the time required for maintenance of the discharge electrode can be greatly reduced.
[0019]
According to a seventh aspect of the present invention, in any one of the first to sixth aspects, a duct that separates mist from the mist generation unit is connected to a stage subsequent to the mist generation unit, and the duct has a predetermined particle diameter. An object of the present invention is to provide a thin film forming apparatus having a height and a length capable of removing most of the mist having a large particle diameter.
[0020]
According to the thin film forming apparatus of the seventh aspect, since a mist having a relatively small particle diameter can be formed by removing a mist having a large particle diameter, a thin film having a highly accurate thickness can be formed.
[0021]
[Embodiment of the present invention]
An embodiment of the present invention will be described. FIG. 1 shows an embodiment of a charging mist coater according to the present invention. The charging mist coater 100 is roughly divided into a mist generating unit 1 and a mist generating unit that convert a liquid substance such as an organic dye serving as a paint or a recording material into mist, that is, mist-like fine mist droplets (hereinafter, referred to as mist). Since the particle size of the mist from 1 is various, the mist from the mist separation unit 2 and the mist from the mist separation unit 2 that leave the mist with a smaller particle size than the predetermined particle size and remove the mist with a larger particle size Mist charging unit 3 for negatively charging the mist, charging mist deceleration unit 4 for reducing the flow velocity of the charged mist, and electrostatic charging for covering the substrate S having a positive surface charge opposite to the charging polarity of the charging mist. The coating unit 5 includes a mist collecting unit 6 that collects the charged mist that has not adhered to the substrate S for reuse.
[0022]
Here, the substrate S is a substrate used for a liquid crystal panel or a substrate used for forming a next-generation large-capacity optical disk, and the thin film formed according to the present invention is a substrate used for a liquid crystal panel. This is a protective film and can be used as a light transmission protective layer in the case of a next-generation large-capacity optical disk. In addition, various substrates such as glass and lenses may be used as the substrate S.
[0023]
The mist generating section 1 can be formed by various methods such as a commonly known atomizing method using ultrasonic vibration and a spraying method using a spray nozzle. In the present invention, compressed air is sent to the nozzle 11 and coating from the liquid tank 12 is performed. The liquid is supplied, and mist is generated from the nozzle 11. With respect to this nozzle, a coating gun of a spray-type coating machine suitable for the present invention is used as a nozzle, and the flow of the air stream at the outlet of the mist generating section 1 is made as small as possible. Here, the liquid to be mist preferably does not contain a substance such as a pigment having a particle diameter of 10 μm or more.
[0024]
In order to form a thin film having a more uniform thickness, the mist sorting section 2 needs to create an atmosphere of mist having a particle diameter as small as possible or less as much as possible. The mist is separated by a predetermined value due to the combined effects of mist inertia, centrifugal force, gravity, surface energy difference due to mist particle size difference, and repulsion force due to electrification. The above mist can be removed. The main members constituting the mist separation unit 2 are trapped in a duct 21 made of a conductive material such as a metal material, a DC power supply 22 for outputting a relatively high DC voltage for applying a negative voltage to the duct 21, and the duct 21. It comprises a drain 23 for discharging the liquid by mist, a drain tank 24 for storing the liquid, and the like.
[0025]
The duct 21 has a mountain-like height higher than the connection point with the mist generating unit 1, and the mist having a large particle diameter comes into contact with the inner wall of the duct 21 due to its inertia, gravity, and the like, and is removed. The height and length of the duct 21 are determined by the size of the particle diameter and the speed of the air flow from the mist generating unit 1. The duct 21 may have a spiral shape, or portions having a large cross-sectional area of the flow path and narrow portions may be alternately arranged.
[0026]
The mist from the mist generating section 1 is weakly negatively charged, and the mist having a smaller particle diameter is more likely to be trapped on the inner wall of the duct 21 under the influence of the mist. Therefore, by fixing the duct 21 to a negative polarity potential, A mist having a small particle diameter and a small influence of inertia force and gravity is difficult to be trapped, and a mist having a large particle diameter has a larger influence of inertia force and gravity than the influence of potential. Be trapped. In this way, most of the mist having a large particle diameter is removed, and the mist having a small particle diameter is sent to the mist charging section 3.
[0027]
The mist charging unit 3 includes a first discharge electrode 31 to which a negative DC high voltage is applied, a second discharge electrode 32 disposed to face the first discharge electrode 31 at a distance, and connected to a ground potential; A DC high-voltage power supply 33 that applies a negative DC high voltage to the first discharge electrode 31, a mist guide 34 that concentrates mist from the mist separation unit 2 and sends the mist to the gap between the discharge electrodes 31 and 32, and the duct 21. It is composed of a partition member 35 connected to form a mist flow path.
[0028]
Corona discharge is generated in the gap between the discharge electrodes 31 and 32, and the mist passing through the gap is effectively negatively charged by the corona discharge. Although FIG. 1 shows a pair of upper and lower discharge electrodes, a plurality of pairs of discharge electrodes are arranged in front and back directions on the paper.
[0029]
A basic specific example of the mist charging unit 3 will be described with reference to FIG. The discharge electrodes 31 and 32 are surrounded by tubes 31a and 32a, respectively, in order to prevent mist from adhering to the discharge electrodes 31 and 32, and weak air flows through the tubes 31a and 32a. The air is preferably as weak as possible as long as mist does not adhere to the discharge electrodes 31 and 32. The voltage of the DC high-voltage power supply 33 varies depending on the distance between the discharge electrodes 31 and 32 and the like, but is usually a negative voltage of several kilovolts to tens of kilovolts. The corona discharge is generated between the discharge electrodes 31 and 32 by this voltage, and the mist passes through the corona discharge, thereby being charged effectively.
[0030]
Next, another basic specific example of the mist charging unit 3 will be described with reference to FIG. This specific example is a charging method in which negatively charged air is supplied into the partition member 35 from outside the partition member 35 forming the mist flow path, and the mist is negatively charged. This is composed of a cylindrical body 36 capable of supplying air from the outside to the inside of the partition member 35, and discharge electrodes 37 and 38 provided at locations in the cylindrical body 36 near the partition member 35. A negative DC high voltage (-HV) is applied to the discharge electrode 37, and the discharge electrode 38 is connected to the ground potential.
[0031]
Corona discharge is formed between the discharge electrodes 37 and 38, and the air passing through the corona discharge atmosphere is negatively ionized. The negatively ionized air gives negative ions to the mist in the partition wall member 35 and charges the mist negatively. In this example, it is not necessary to install a discharge electrode to which a high voltage is applied in the partition, and it is only necessary to introduce negative ionized air outside the partition 35 into the partition 35, so that mist adheres to the discharge electrode. Needless to say, there is a margin in designing the apparatus.
[0032]
The charged mist charged in this manner is attached to the substrate surface by electrostatic attraction caused by the positive charge induced on the substrate S in a subsequent electrostatic coating process. Since the flow rate of the mist is small and the electrostatic attraction acting on the charging mist is small, if the flow rate of the charging mist is large, the amount of the charging mist adhering to the substrate S decreases. Therefore, it is preferable that the flow rate of the charging mist is as small as possible, and ideally, it is omnidirectional. For this reason, in this embodiment, the charging mist deceleration unit 4 that decelerates the charging mist before the electrostatic coating step is provided.
[0033]
As a method of reducing the flow velocity of the charging mist, there are two methods as shown in FIG. The method (1) for changing the cross-sectional area of the flow path is a widely known method, and by increasing the cross-sectional area of the flow path, the flow rate of the charging mist is reduced by the ratio of the cross-sectional area. However, this method is to increase the cross-sectional area of the flow path at the location where the substrate S is present, and increases the amount of charged mist that passes away from the substrate S. Therefore, in the case of the present invention, this method is not so large. Not valid.
[0034]
A second method of reducing the flow velocity of the charging mist by passing only air is to exhaust only air from the flow path and leave the charging mist as it is in the flow path. This method increases the cross-sectional area of the flow path. This is an effective idea because the flow rate of the charging mist can be considerably reduced without increasing the flow rate, and the concentration of the charging mist in the flow path after the flow rate is reduced increases. Therefore, in this embodiment, the second deceleration method is used.
[0035]
A specific example of the charging mist reduction unit for realizing the second method will be described with reference to FIG. This feature is that the electrostatic repulsion filter 7 is provided so as to close a part of the flow path formed by the partition member 41 which is an extension of the partition member 35 of the mist charging unit 3, and air is discharged from the flow path through the electrostatic repulsion filter 7. By providing an exhaust pipe 42 and an exhaust device 43 for exhausting the gas, the charged mist is not removed from the flow path, but only the air is exhausted to reduce the flow velocity of the charged mist and to reduce the flow rate of the charged mist. It increases the concentration of mist.
[0036]
Here, in a filter that does not use a normal electrostatic force, particles to be removed are filtered by a filter and only air is passed. In addition, an electrostatic filter using a woven cloth having electrostatic characteristics, an electrostatic filter using an electrostatic space between positive and negative electrodes used in an air purifier, or an electrostatic filter combining these, The filter is attached to and removed from the filter using electrostatic attraction, and only the purified air is passed. In other words, each of such electrostatic filters has a polarity opposite to that of the charged particles charged negatively or positively, and removes the charged particles by attracting the charged particles to the electrostatic filter using electrostatic attraction. , Through which only air passes.
[0037]
It is possible to reduce the flow rate of the charged mist using such a filter, but since a part or a large part of the charged mist is removed, the concentration of the charged mist in the atmosphere near the substrate S is reduced, It cannot be expected to form a thin film in a short time. That is, it is actually impossible to use a conventional electrostatic filter.
[0038]
Therefore, in the specific example of the charging mist reduction unit, the electrostatic repulsion filter 7 is used. Here, the electrostatic repulsion filter has the opposite polarity to that of the conventional electrostatic filter, that is, it has the same polarity as that of the charged mist, and generates a repulsive force between the charged mist and the charged mist. This is for allowing air to pass without adhering and of course not passing. Usually, the mist is overwhelmingly negatively charged in the electrostatic repulsion filter 7, and therefore, a woven fabric having a negative electrostatic property or a negative direct current high voltage And the like.
[0039]
In FIG. 5, by exhausting a part of the air in the flow path through which the charged mist passes through the electrostatic repulsion filter 7, the flow velocity of the charged mist after the exhaust is reduced, and thereby the concentration of the charged mist is increased. ing. For example, the flow rate 2 exhausted by the exhaust mechanisms 42 and 43 through the electrostatic repulsion filter 7 is subtracted from the flow rate 1 of air per unit time before exhaustion (an amount substantially equal to the air ejection amount of the nozzle 11 in FIG. 1). The flow rate after the exhaust is the flow rate 3, and the reduction ratio of the flow rate of the charging mist can be easily obtained from the ratio of the flow rate 1 to the flow rate 3. For example, if the flow rate 2 is の of the flow rate 1, the flow rate 3 is １ ／ of the flow rate 1. If the cross-sectional area of the flow path is the same, the flow rate of the charging mist is almost １ ／. Become. As a result, if the charge mist is not exhausted, the charge mist exists at almost twice the density in the subsequent stage of the charge mist reduction mechanism. Such a charging mist deceleration mechanism is provided between the mist charging unit 3 and the electrostatic coating unit 5 in FIG. 1, and reduces the flow rate of the charging mist from the mist charging unit 3 and increases the concentration of the charging mist. And supplied to the electrostatic coating unit 5 to help the charged mist adhere to the substrate S effectively.
[0040]
As shown in FIG. 6, the electrostatic coating unit 5 is connected to the housing member 51 connected to the partition wall member 41 of the charge mist reduction unit 4 and to the substrate S of the charge mist due to non-uniformity and partial concentration of the electric field intensity. In order to prevent the uneven thickness of the thin film formed on the substrate S from being caused by the non-uniform adhesion, the correcting member 52 made of a metal material or the like provided around the window 54 is provided. It comprises a DC power supply 53 for applying a negative voltage, a charge application section 55 for applying a positive charge to the substrate S placed on the window 54 of the housing member 51, and the like. Note that the correction member 52 is provided outside the housing member 51 and has a shape suitable for the size and shape of the substrate S, for example, a shape having a square or circular cross section.
[0041]
The charge applying section 55 includes a variable DC power supply 55a capable of applying a regulated voltage, an electrode plate 55b to which a positive DC voltage of the variable DC power supply 55a is applied, and an electrical insulation between the electrode plate 55b and the housing member 51. And an electrical insulating member 55c. The electric insulating member 55c can serve as a lid for opening and closing the window 54, and has a well-known suction structure having a plurality of suction holes communicating with an air suction mechanism (not shown), so that the substrate S can be suction-held. Those with functions are convenient.
[0042]
In the electrostatic coating unit 5, when the positive DC voltage of the variable DC power supply 55a is applied to the electrode plate 55b, the side of the electrical insulating member 55c that contacts the electrode plate 55b is negative, and the side that contacts the substrate S is the negative side. Positive charges are induced, and negative and positive charges are similarly induced when the substrate S is made of an electrically insulating material. Therefore, a positive charge is induced on the lower surface of the substrate S, and the negatively charged mist is electrostatically attracted, so that a thin film having a thickness of several tens μm or less can be efficiently formed. When the substrate S is made of a conductive material, a positive voltage is applied to the electrode plate 55b as described above, so that the substrate S has a positive polarity.
[0043]
Here, the variable DC power supply 55a can supply a positive DC voltage of several hundred volts or more to the electrode plate 55b, and the film thickness can be adjusted by changing the magnitude of the DC voltage. By increasing the voltage of the variable DC power supply 55a, the electric field formed between the electrode plate 55b and the ground increases, and the amount of charge on the substrate S increases. Can be made thicker. On the other hand, if the voltage of the variable DC power supply 55a is reduced, the amount of charge on the substrate S is reduced, so that the amount of charge mist adhering to the substrate S is reduced, and the thickness of the coating film is reduced.
[0044]
Next, an embodiment of the electrostatic coating unit 5 having a preferable structure will be described with reference to FIG. The same symbols as those used in FIGS. 1 and 6 indicate members having the same names. In FIG. 7, an insulating plate 56 made of an electrically insulating material or a high-resistance material is provided on a bottom plate of the housing member 51, and an electrostatic repulsion filter 7 indicated by a chain line is provided thereon. The electrostatic repulsion filter 7 does not reduce the flow velocity of the charging mist, but concentrates the charging mist near the substrate S, thereby increasing the concentration of the charging mist in the atmosphere near the substrate.
[0045]
The electrostatic repulsion filter 7 includes a mesh-shaped metal member 7a having an infinite number of meshes of an appropriate size, and a DC power supply 7b for applying a negative DC voltage to the mesh-shaped metal member 7a. The mesh-like metal member 7a has its lower end fixed on the bottom plate of the housing member 51, rises at an angle, for example, about 60 degrees, and has a height of about 1/2 to 3/4 from the bottom plate of the housing member 51. It is bent so as to be almost parallel to the S plane. In the mesh-shaped metal member 7a, the ratio between the open area and the closed area of the entire mesh is determined, and the size of each mesh is determined so as to minimize the flow of air.
[0046]
The magnitude of the negative DC voltage of the DC power supply 7b is determined by the size of the mesh. This voltage is determined so that a negative electrostatic curtain is formed in the mesh of each mesh, so that non-ionized air can pass through but not a negatively charged mist. Usually, it is several kilovolts to several tens of kilovolts.
[0047]
Therefore, the charging mist sent from the charging mist decelerating unit 4 does not adsorb or pass through the mesh-shaped metal member 7a, and does not pass therethrough. As a result, the concentration of the charged mist existing in the space near the bottom of the substrate S is increased. On the other hand, since the air passes through the mesh of the mesh-shaped metal member 7a of the electrostatic repulsion filter 7, the flow of the charging mist existing in the space near and below the substrate S is not accelerated. Due to such operations of the charging mist reduction section 4 and the electrostatic repulsion filter 7, the amount of charging mist adsorbed on the substrate S per unit time is further increased, and a thin film can be formed in a shorter time.
[0048]
When such an electrostatic repulsion filter 7 is provided in the electrostatic coating section 5, it is not always necessary to provide the charging mist reduction section 4. In this case, although not shown, it is conceivable to provide a wind direction plate at the entrance of the electrostatic coating unit 5 for directing the air flow obliquely downward to reduce the air flow near the substrate S. In this case, the flow of the air and the charging mist is directed downward by the wind direction plate, the air passes through the electrostatic repulsion filter 7 as it is, and the charging mist flows near the substrate S along the inclination of the electrostatic repulsion filter 7. Rise to the department. Accordingly, the flow of air near the substrate S is greatly slowed, and the concentration of the charged mist is increased.
[0049]
In this embodiment, in the electrostatic coating section 5, a DC voltage 55a applies an appropriate positive voltage to the electrode 55b from the DC power supply 55a to induce a positive charge on the surface of the substrate S through the electric insulating member 55c. The negatively charged mist adhering to the substrate S without repelling and overlapping each other is instantaneously neutralized, and is further positively charged by the voltage of the DC power supply 55a, so that the negatively charged mist adheres thereon. Becomes possible. Thus, a thin film having a predetermined thickness of several tens μm or less is formed. Note that, similarly to the above embodiment, the thickness of the thin film can be adjusted by adjusting the voltage of the DC power supply 55a.
[0050]
At this time, the voltage of the DC power supply 55a applied to the electrode 55b forms an electric field, but the electric field is not uniform. Generally, the electric field concentrates on a point having a sharp shape such as a corner of an electrode, and the intensity of the electric field is increased, so that a region having a strong electric field and a region having a weak electric field are generated. The correction member 52 corrects this phenomenon and makes the electric field intensity relatively uniform. By optimizing the shape of the correction member 52 and optimizing the potential at the same time, the electric field becomes highly uniform, and a thin film having a uniform thickness can be formed on the entire surface of the substrate S. .
[0051]
Then, as shown in FIG. 1, the charged mist that has not adhered to the substrate S is collected in the mist collection unit 6 and reused. The mist collection unit 6 includes a collection case 61, an electrostatic repulsion filter 62 as described above, a mist collection tank 63, an exhaust device 64 that exhausts substantially only air through the electrostatic repulsion filter 62, and the like. The description of the drying step and the like is omitted.
[0052]
As described above, the electrostatic repulsion filter used in the present invention does not substantially adsorb the charged mist, and therefore does not cause contamination due to the charged mist, and therefore requires little maintenance.
[0053]
In addition, as for the structure of the discharge electrode of the mist charging section, various structures can be considered in addition to the above embodiment. A few preferable examples in which the mist can be effectively charged will be described. The discharge electrode is comb-shaped, teeth are alternately inserted into the gaps between the teeth of a pair of comb-shaped discharge electrodes, and a corona discharge is generated between each tooth. The mist can be effectively charged by passing the mist through the gap. In order to further enhance the charging effect, such a comb-shaped discharge electrode may be provided in multiple layers in the direction in which the mist flows.
[0054]
As another example, a metal wire having a large number of sharp protrusions in the middle, such as a barbed wire, is used, and a plurality of metal wire units in which a plurality of such metal wires are arranged in parallel, the mist flows. The mist can be effectively charged even if the mist is arranged in the direction and a predetermined voltage is applied between the metal units to generate corona discharge.
[0055]
In addition to the above, various kinds of combinations such as a combination of a wire net-like discharge electrode and a discharge wire passing through the center of the mesh are conceivable. In these cases, mist adheres, so that maintenance is sometimes required.
[0056]
In the above-described embodiment, the DC power supply 55a is used as a means for applying electric charge to the substrate S. However, the electric charge may be applied to the substrate S in advance by various known charging methods without using the DC power supply. In this case, when the charge mist having the same charge amount as the charge amount previously given to the substrate S is attached to the substrate S, the substrate S is neutralized.
[0057]
In the drawing, the window 54 of the electrostatic coating unit 5 is provided on the ceiling of the housing member 51 and the substrate S is disposed on the upper part. However, the window 54 is provided on the side wall or the bottom plate of the housing member, or the mist collecting unit 6 of FIG. And the substrate S may be arranged at that position, and the same effect can be obtained.
[0058]
【The invention's effect】
As described above, according to the present invention, a thin film having a predetermined thickness can be formed on the entire surface of a substrate in a short time.
[Brief description of the drawings]
FIG. 1 schematically shows a thin film forming apparatus according to an embodiment of the present invention.
FIG. 2 shows an example of a mist charging section in the thin film forming apparatus according to the present invention.
FIG. 3 shows another example of the mist charging section in the thin film forming apparatus according to the present invention.
FIG. 4 is a diagram for explaining a basic concept of a charging mist deceleration method according to the present invention.
FIG. 5 is a diagram illustrating an example of a charging mist reduction mechanism according to the present invention.
FIG. 6 shows an example of an electrostatic coating unit in the thin film forming apparatus according to the present invention.
FIG. 7 is a view showing one embodiment of an electrostatic coating unit in the thin film forming apparatus according to the present invention.
[Explanation of symbols]
1: Mist generation part
11 ... Nozzle
12 ... Liquid tank
2… Mist sorting part
21 ... duct
22 DC power supply
23 ... Drain
24 ... Drain tank
3: Mist charging part
31, 32 ... discharge electrode
33… DC high voltage power supply
34 ... Mist guide
35 ... partition member
4: Charge mist reduction unit
41 ... partition member
42 ... exhaust pipe
43… Exhaust device
5 ... Electrostatic coating part
51 ... housing member
52 ... Correction member
53 ... DC power supply
54 ... Window
55 ... Charge giving section
55a ... DC power supply
55b ... electrode plate
55c ... electric insulation member
56 ... insulating plate
6: Mist collection unit
61 ... Collection case
62 ... Electrostatic repulsion filter
63… Mist collection tank
64 ... exhaust device
7 ... Electrostatic repulsion filter
7a: mesh metal member
7b ... DC power supply
S ... substrate

Claims (7)

In an apparatus for generating a mist by atomizing a liquid substance, attaching the mist to a substrate by electrostatic force, and forming a thin film having a uniform thickness on the substrate,
A mist generator that generates a mist by atomizing the liquid substance,
A mist charging unit that charges the mist,
A charging mist reducing unit that reduces the flow rate of the charging mist charged by the mist charging unit and increases the concentration of the charging mist near the substrate;
An electrostatic coating unit that induces a charge having a polarity opposite to the polarity of the charge of the charge mist on the substrate, and causes the charge mist to be attracted to the substrate,
An apparatus for forming a thin film, comprising: In claim 1,
The charging mist reduction unit has the same polarity as the polarity of the charging mist, and generates a repulsive force between the charging mist and the charging mist. A thin film forming apparatus comprising: In an apparatus for generating a mist by atomizing a liquid substance, attaching the mist to a substrate by electrostatic force, and forming a thin film having a uniform thickness on the substrate,
A mist generator that generates a mist by atomizing the liquid substance,
A mist charging unit that charges the mist,
An electrostatic coating unit that induces a charge having a polarity opposite to the polarity of the charge of the charge mist on the substrate, and causes the charge mist to be attracted to the substrate,
With
The electrostatic coating portion has the same polarity as the polarity of the charged mist, generates a repulsive force with the charged mist, does not allow the charged mist to adhere or pass, and allows air to pass therethrough, and A thin film forming apparatus comprising: an electrostatic repulsion filter that increases the concentration of the charged mist in a nearby atmosphere. In any one of claims 1 to 3,
The thin film forming apparatus, wherein the electrostatic coating unit includes an annular correction member at a position surrounding the substrate, and applies a voltage having the same polarity as the polarity of the charge on the substrate. In any one of claims 1 to 4,
The electrostatic coating unit has a DC power supply that can supply a variable voltage that can adjust the amount of charge induced or applied to the substrate, and adjusts the voltage to adjust the thickness of the thin film. A thin film forming apparatus characterized by the above-mentioned. In any one of claims 1 to 5,
The mist charging unit has a discharge electrode,
The discharge electrode is surrounded by a tube,
An apparatus for forming a thin film, wherein the mist is prevented from adhering to the discharge electrode by flowing air toward the tip of the discharge electrode in the tube. In any one of claims 1 to 6,
A duct that separates mist from the mist generating section is connected to a stage subsequent to the mist generating section, and the duct has a height and a length that can remove most of the mist having a particle diameter larger than a predetermined particle diameter. An apparatus for forming a thin film, comprising:

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