JP2000117097A - Forming method of particle thin film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a forming method of a particle thin film by which a particle thin film of high density having uniform density of particles can be fast formed by an easy and safe method. SOLUTION: A liquid 2 with particles 1 floating on the surface is vibrated to spread the particles 1 on the liquid surface to form a thin film of particles 1 on the surface of the liquid 2. Or, by applying ultrasonic vibration on the liquid, or by producing a flow from the inside of the liquid to the surface, the liquid surface is partially raised to spread the particles on the liquid surface to form a particle thin film on the liquid surface.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a thin film applicable to various fields such as electronics and biotechnology, and more particularly to a method for forming a thin film sensor, a porous film, a display, and a recording material. The present invention relates to a method for forming a particle thin film.

[0002]

2. Description of the Related Art In various fields such as electronics and biotechnology, the appearance of new functional materials and new devices realizing advanced functions is expected. As one of the candidate materials and devices, a high-performance device in which functional fine particles are integrated has attracted attention, and a technique for forming a thin film using the fine particles has been actively studied.

[0003] Conventional thin film forming methods using fine particles can be broadly divided into two methods when focusing on a thin film forming support. One is a method using a solid surface as a support for forming a thin film, and the other is a method using a liquid surface as a support. The method of using a solid surface as a support for forming a thin film of fine particles, for example, on a substrate such as a glass horizontally installed,
A liquid in which the desired fine particles are dispersed is applied in a thin layer by spin coating or the like, and a drying method of forming a particle thin film by drying the solution, or a substrate such as glass is immersed in the liquid in which the fine particles are dispersed, An adsorption method for immobilizing the fine particles adsorbed on the substrate surface by utilizing the deposition phenomenon of the fine particles is generally known. As one type of the adsorption method, Japanese Patent Application Laid-Open No. 8-229474 proposes a particle thin film forming method called advection accumulation method. This involves forming a single-particle film and a multi-particle film on a substrate by immersing a flat substrate that is easily compatible with the solvent in a liquid in which fine particles are dispersed, and controlling the atmosphere, humidity, particle concentration, and substrate pulling speed. Is what you do. Also,
As a method of forming a relatively large particle thin film, a cascade method in which an adhesive layer is provided on the substrate surface, particles are supplied one after another on the substrate, the particles are brought into contact with the substrate, and the particles are attached to the substrate surface is also generally used. Is known.

On the other hand, as a method of using a liquid surface as a support for forming a thin film of fine particles, there is a method to which the LB method (Langmuir-Blodgett method) is applied. In this method, particles are spread on a liquid surface, and the expanded particles are compressed in the direction of the liquid surface to form a single layer of high-density particle thin film, which is transferred to a solid substrate and fixed. Also, JP-A-7-18
No. 5311 discloses that a high-density liquid is used as a support for forming a thin film of fine particles, a dispersion liquid of the fine particles is spread on the surface of the high-density liquid, and the developed thickness is controlled, whereby the fine particles are deposited on the high-density liquid. A method has been proposed in which a two-dimensionally aggregated and formed particle thin film is transferred to a solid substrate and fixed on the substrate. According to this method, a high-density particle thin film, particularly a single-layer particle thin film, can be formed at a relatively high speed.

[0005]

The above-mentioned conventional method for forming a particle thin film has several problems as described below. For example, in the drying method, a dispersion liquid of fine particles is used. The particle concentration in the dispersion liquid is uniform when viewed macroscopically, but the concentration is not uniform microscopically. When a thin layer of a particle dispersion having a non-uniform concentration is applied to a substrate, the concentration of the particles in the thin layer tends to be further non-uniform. Further, since the thickness of the particle thin film (the number of particle layers) is determined by the dispersion concentration of the particles in the liquid to be used and the coating amount, unless an ideal state in which the dispersion concentration is uniform is formed, a high-density layer is formed. Formation of a particle thin film is not possible.

In addition, in the adsorption method, unevenness of thickness and density of the particle thin film easily occurs in principle due to low flatness and low cleanliness of the solid surface. Since it is difficult to increase the speed of the control, the formation speed of the particle thin film cannot be increased. JP-A-8-2294
In the particle thin film forming method called advection accumulation method disclosed in Japanese Patent Publication No. 74-74, the thin film forming speed is several μm / sec.
For example, it takes one hour or more to form a thin film of particles on a substrate of 10 cm square. Also, in the cascade method, particles that have once adhered to the substrate cannot move on the substrate.For example, when the interval between multiple particles that have previously adhered to the substrate surface is slightly smaller than the particle diameter, particles are retained in the gaps. Therefore, it is impossible to form a dense particle thin film.

On the other hand, in the method using the LB method in which the liquid surface is used as a support for forming a thin film, the size of the particles used is limited. For example, when fine particles having a size of several hundred nm to several tens μm are used. In addition, the cohesive force between the particles is increased, and the aggregated particles cannot be developed simply by supplying the particles to the liquid surface, and the thin film may not be formed. In Japanese Patent Application Laid-Open No. 7-185311 using a high-density liquid, a step of dispersing particles in the high-density liquid, a step of controlling the film thickness of the particle dispersion supplied on the high-density liquid with high accuracy, and the like are described. Required and the equipment becomes very large. In this method, the high-density liquid used is mercury or the like,
There is concern about the effects on the human body, etc., and there is a safety problem.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide a method for easily and safely forming a particle thin film having a uniform density and a high density.

[0009]

According to a first aspect of the present invention, a liquid in which particles are levitated on a surface is caused to vibrate, the particles are spread on the surface of the liquid, and a thin film composed of particles is formed on the surface of the liquid. It is a method of forming a particle thin film including a step of forming. After the particles are spread on the surface of the liquid, it is preferable to gradually reduce the amplitude of the vibration acting on the liquid, since a particle thin film can be formed more quickly and stably.

According to a second aspect of the present invention, an ultrasonic vibration is applied to a liquid having particles floating on the surface so that a part of the surface of the liquid is raised, and the particles are developed on the liquid surface, and the particles are spread from the particles. Forming a thin film on the surface of a liquid. A part of the surface of the liquid is raised, and the ultrasonic vibration is applied to the liquid so that the raised part moves, or the ultrasonic vibration is transmitted so that the transmission direction of the ultrasonic vibration is not perpendicular to the surface of the liquid. Is preferably applied to a liquid because a particle thin film can be formed more efficiently. Furthermore, it is preferable to gradually reduce the amplitude of the ultrasonic vibration applied to the liquid after the particles have been spread on the liquid surface, because a defect-free particle thin film can be formed more quickly and more stably.

According to a third aspect of the present invention, a liquid having particles floating on its surface is provided with a flow in the liquid so that a part of the surface of the liquid is raised and the shape of the apex of the raised portion is disturbed. This is a method for forming a particle thin film including a step of generating the particles, developing the particles on the surface of the liquid, and forming a thin film composed of the particles on the surface of the liquid. A part of the surface of the liquid is raised, and the flow is generated in the liquid so that the raised part moves,
It is preferable to generate a flow in the liquid such that the direction of the flow is not perpendicular to the surface of the liquid, because a particle thin film can be formed more efficiently. Furthermore, it is preferable to gradually reduce the flow rate of the liquid generated after the particles are spread on the surface of the liquid, because a particle thin film without defects can be formed more quickly and more stably.

In the first to third aspects of the present invention, the charged particles are levitated on the surface of the liquid, or the particles are charged after the particles are levitated on the surface of the liquid, and the thin film comprising the particles is formed of the liquid. It is preferable to apply an electric field to the particles before the particles are formed on the surface or after the thin film composed of the particles is formed, because excess particles can be efficiently removed and the particle thin film can be formed more stably. Further, it is preferable to apply a weak vibration to the liquid when removing the particles, since excess particles can be removed more efficiently.

According to the first to third aspects of the present invention, after a thin particle film is formed on a liquid surface, the thin film is brought into contact with the surface of a solid substrate, transferred and fixed, whereby a thin film composed of particles can be easily formed on the substrate surface. Can be formed. By repeating this operation, a particle thin film having a desired thickness can be formed on the substrate.

[0014]

FIG. 1 is an example of a thin film forming apparatus used in a thin film forming method according to a first embodiment of the present invention. The liquid 2 is held in a holding container 5. The bottom surface of the holding container 5 is formed by a vibrating plate 6, and the vibration from a vibrator 4 a made of ceramics, plastic, or the like disposed in contact with the vibrating plate 6 is transmitted to the entire bottom surface of the liquid 2. Has become. The vibrator 4a is connected to a high frequency power supply 7 so that a high frequency voltage can be applied.

The particles 1 float on the surface of the liquid 2.
In this state, when a high-frequency voltage is applied from the high-frequency power supply 7 to the vibrator 4a, the vibrator 4a vibrates, and this vibration is transmitted to the entire liquid 2 via the vibration plate 6. Vibration is holding container 5
From the bottom surface in the liquid 2 toward the liquid surface, and when the vibration reaches the liquid surface, the particles 1 develop on the surface of the liquid 2 and a monolayer of particles is formed on the surface of the liquid 2 .

In FIG. 1, the process in which the particles 1 are spread on the surface of the liquid 2 and the thin film composed of the particles is formed on the surface of the liquid 2 is schematically shown in FIGS. The particles 1 are floating on the surface of the liquid 2 in an aggregated state (FIG. 2A).
The particles 1a in contact with the liquid have an adhesive force F with the liquid 2
1 and particles 1b are acting. Liquid 2
The particles 1b that are not directly in contact with the particles and the particles 1c that are located further above have an adhesion force F2 between the particles. Since the adhesive force between the two objects tends to increase as the area where the objects are in contact increases, usually, F2 <F1
Holds (FIG. 2B).

Acting force F3 due to vibration on particle 1a
However, a high-frequency voltage is applied to the vibrator 4a so that F2 <F3 <F1. Although the particle 1a receives an acting force F3 from the liquid surface due to vibration, the particle 1a is held on the liquid surface because F1 is larger than F3. On the other hand, the particle 1b receives an acting force F3 ′ due to vibration via the particle 1a,
Since 3 ′ is larger than F2, there is no restriction due to the adhesive force F2 with the particle 1a, and contact / non-contact with the particle 1a is repeated. Further, the particles 1c located in the upper layer have many interparticle gaps and a large degree of freedom of the particles, so that the acting force F3 ″ due to vibration on the particles 1c is attenuated, and F3 ″ becomes smaller than F2. ing. As a result, as shown in FIG. 2C, the particles 1b and 1c
Moves on the particle 1a while maintaining the aggregation state. Thereafter, the aggregated particles such as the particles 1b sequentially reach the surface of the liquid 2 where the particles 1a are not present, and are held on the surface of the liquid 2 by the adhesive force F1 with the liquid 2, thereby forming a part of the particle thin film. Become like

As shown in FIG. 2D, the particles 1a in contact with the surface of the liquid 2 move two-dimensionally on the surface of the liquid 2 (in FIG. At the surface of the liquid 2 by the cohesive force F4, which is the combined force of the inter-particle attractive force between the particles 1a and the liquid crosslinking force (capillary force due to the wetting of the solid and the liquid). 2
Dimensionally aggregated. Therefore, the particles 1 which have floated on the surface of the liquid 2 in an aggregated state are developed on the surface of the liquid 2 and have a high density arrangement. As a result, a thin film composed of the particles 1 having a high density and a uniform density (hereinafter, may be referred to as a “particle thin film”) is formed on the liquid surface 2.

The frequency of the vibration applied to the liquid may be appropriately determined depending on the properties of the liquid or particles used. Vibration applied to the liquid is preferably high-frequency vibration because a thin particle film can be stably formed.
Preferably, it is about kHz. Further, when the acting force F3 due to the vibration becomes larger than the cohesive force F4, the density of the particle thin film may decrease. Therefore, it is preferable to determine the magnitude of F3 so that F3 <F4. The acting force F3 of the vibration can be set to a desired magnitude by adjusting the amplitude, and in FIG. 1, can be set to a preferable range by adjusting the voltage applied to the vibrator 4a.

Further, when a low-density thin film is formed on the surface of the liquid, the particles may aggregate non-uniformly and the thin film may be cracked. On the other hand, once the particles are spread on the surface of the liquid and F3 is gradually reduced, the two-dimensional aggregation of the particle thin film (FIG. 2D) is promoted, and the thin film is densified. can do. Therefore, while the particles are being spread on the surface of the liquid (FIGS. 2A to 2C), the acting force F of the vibration is applied.
3, the thin film is efficiently formed at high speed and efficiently, and after the development, the acting force F3 of the vibration is reduced step by step, and the density of the thin film is increased. It is preferable because it is possible. The acting force F3 of the vibration can be set to a desired magnitude by adjusting the amplitude in the same manner as described above, and in FIG. 1, it is set to a preferable range by adjusting the voltage applied to the vibrator 4a. can do.

The direction in which vibration is applied to the liquid is not particularly limited, and vibrations in various directions can be applied.
For example, as shown in FIG.
May be applied to apply vibration that travels in a direction parallel to the surface of the liquid 2. A plurality of vibration sources may be provided. For example, as shown in FIG. 4, the bottom surface of the liquid holding container 5 may be divided, and the vibration plate 6 and the vibrator 4 may be arranged for each division.

FIG. 5 shows an example of a thin film forming apparatus used in the thin film forming method according to the second embodiment of the present invention. The liquid 2 is held in a holding container 5. On the bottom surface of the holding container 5, a piezoelectric element 4b made of ceramic is arranged.
The ultrasonic vibration from b is transmitted to the liquid 2. The piezoelectric element 4b is connected to the high-frequency power source 7,
A high-frequency voltage is applied.

The particles 1 float on the surface of the liquid 2.
When a high-frequency voltage is applied to the piezoelectric element 4b from the high-frequency power supply 7 in this state, the piezoelectric element 4b vibrates ultrasonically, and the ultrasonic vibration is transmitted to the liquid 2 from the bottom surface of the holding container 5. When the ultrasonic vibration reaches the surface of the liquid 2, a bulge 3a is formed on a part of the surface of the liquid 2 by a radiation pressure generated by the ultrasonic wave. As a result, the particles 1 spread on the surface of the liquid 2, and a monolayer of the particles is formed on the surface of the liquid 2.

6 (a) and 6 (b) show the flow of the liquid 2 in the raised portion 3a of FIG. 5, and FIG. 6 (c) shows how the particles 1 expand in the raised portion 3a. Is shown. When ultrasonic vibration is applied from the inside of the liquid 2 toward the surface of the liquid 2, a radiation pressure is generated in the liquid 2, and FIG.
As shown in (a), a bump 3a is formed on the surface of the liquid 2. A vortex flow as shown in FIG. 6B is generated in the protruding portion 3a, and the particles 1 floating on the surface of the liquid move together with the flow as an aggregate of a plurality of particles. .

The particles 1 moving in accordance with the flow of the raised portion 3a are subjected to the same acting force of F1 to F4 as described above, and further, as shown in FIG. And the acting force F6 of its own weight is acting. While the particles 1 are moving as agglomerates in the vertex direction of the ridge 3a, the particles 1b and 1c slide down the inclined surface of the ridge 3a while maintaining the aggregation state, and only the particles 1a Held on the surface,
It is possible to move to the top of the raised portion 3a (FIG. 6)
(C)). After the particles 1b and the like slide down the protruding portion 3a,
The particles 1a reach the surface of the liquid 2 where no particles exist, and are held on the surface of the liquid 2 by the adhesive force F1 with the liquid 2, thereby forming a part of the particle thin film. Thereafter, the particles 1 are two-dimensionally aggregated on the surface of the liquid 2 by the aggregation force F4, and a particle thin film having a high density and a uniform density is formed on the surface of the liquid 2. In addition, the raised part 3 by radiation pressure
The frequency of the ultrasonic vibration forming a is several hundred kHz to
It is in the range of several hundred MHz, especially 1 MHz to 100
When it is in the range of MHz, a particle thin film can be efficiently formed.

In the method of forming a thin film according to the second aspect, when the particles (particles 1b and 1c) slide down on the inclined surface of the raised portion in the process of forming the thin film, the action of their own weight is also added. The acting force of vibration can be reduced, and loss of particles due to flying can be prevented.

It is preferable to move the raised portion formed on the surface of the liquid because the speed of forming the particle thin film can be improved. Raised part 3 of liquid surface due to ultrasonic radiation pressure
In the method using a, the flow rate of the thin film is determined by the flow generated on the surface of the liquid, and the flow is slow at a position far from the raised portion 3a, so that it takes time to form a thin film having a large area. By moving the raised portion 3a, a particle thin film having a large area can be formed at a high speed. As a method of moving the raised portion formed on the liquid surface, for example, as shown in FIG. 7, a slide mechanism in which a piezoelectric element 4b which is a source of ultrasonic vibration is installed on the bottom surface of the liquid holding container 5 is used. And a method of reciprocating to the left and right while being fixed to the transporting means 8.

It is preferable that the ultrasonic vibration is applied to the liquid so that the transmission direction of the ultrasonic vibration is not perpendicular to the surface of the liquid, because a thin particle film having a large area can be efficiently formed. By applying ultrasonic vibration in this way, the range of the generated flow can be increased,
As a result, the formation speed of the particle thin film is increased. For example,
As shown in FIG. 8, the transmission direction of the ultrasonic vibration is set to the liquid surface by making the piezoelectric element 4b, which is the source of the ultrasonic vibration, have an angle (α) with respect to the bottom surface of the liquid holding container 5. So that they are not vertical.

The number of piezoelectric elements 4b may be plural, and plural piezoelectric elements 4b may be arranged in a line on the bottom surface of a holding container (not shown) as shown in FIG.
If this is further fixed to the transporting means having the slide mechanism shown in FIG. 7 and moved to the left and right, a particle thin film can be formed more efficiently. The piezoelectric element may be installed inside the holding container or may be installed outside. However, when the piezoelectric element is installed outside, the bottom surface of the holding container is transmitted so that ultrasonic vibration of the piezoelectric element is transmitted to the liquid. Needs to be selected.

After the particles have been spread on the surface of the liquid, it is preferable to gradually reduce the amplitude of the ultrasonic vibration since a high-density particle thin film can be formed more stably and quickly. If the ultrasonic vibration is stopped immediately after the particles are spread on the surface of the liquid, a large wave is generated on the liquid surface when the ridge formed on the surface of the liquid disappears, and the particle thin film partially overlaps Or cracks may occur in the particle thin film. When the ultrasonic vibration is gradually reduced, the ridges gradually disappear, so that the large waves as described above are not generated, and it is possible to prevent the defect of the particle thin film which is likely to be generated at the ridge portion. it can.
Note that the amplitude of the ultrasonic vibration can be set in a preferable range in FIG. 5, for example, by adjusting the voltage applied to the piezoelectric element 4b.

FIG. 10 shows an example of a thin film forming apparatus used in the thin film forming method according to the third embodiment of the present invention. The liquid 2 is held in a holding container 5. A pump 9 for generating a flow from the bottom to the top in the drawing is arranged on the inner bottom surface of the holding container 5 so that a flow from the bottom to the top in the liquid 2 can be generated. When the pump 9 is operated in a state where the particles 1 are levitated on the surface of the liquid 2, a flow is generated from the bottom to the top, and when this flow reaches the surface, a bump 3 b is generated on the surface of the liquid 2. . The protrusions 3 b cause the particles 1 to spread on the surface of the liquid 2, and a monolayer of particles is formed on the surface of the liquid 2.

It is necessary that the top portion of the raised portion 3b is disturbed. Since the turbulence of the raised portion 3b is accompanied by vibration, the same effect can be obtained by applying a flow to the liquid as if ultrasonic vibration was applied to the liquid. The particles floating on the liquid surface receive an acting force F3 due to vibration. As a result, the particles 1 behave similarly to the case where they are placed on a bulge due to the radiation pressure of ultrasonic vibration, and a high-density and uniform-density particle thin film is formed on the surface of the liquid 2. You.

When a bulge formed on the surface of the liquid is moved or a flow is generated so that the direction of the flow in the liquid is not perpendicular to the surface of the liquid, the particle thin film having a large area can be efficiently used. It is preferable because it can be formed in a uniform manner. As a method of moving the raised portion, for example, as shown in FIG. 11, a pump 9 which is a source of flow is fixed to a transporting means 8 having a slide mechanism installed on the bottom surface of the liquid holding container 5, and left and right. And the like.
As a method of giving an angle to the direction of the flow, a method of inclining a pump or the like, which is a source of the flow, on the bottom surface of the holding container in a non-horizontal manner may be used. The reason why the particle thin film formation is more efficient is similar to the case where ultrasonic vibration is applied.

After the particles have been spread on the surface of the liquid, it is preferable to gradually reduce the speed of the generated flow since a high-density particle thin film can be formed more stably and quickly. If the flow is stopped immediately after the particles are spread on the surface of the liquid, a large wave will be generated on the liquid surface when the ridge formed on the surface of the liquid disappears, and the particle thin film may partially overlap. In some cases, cracks may occur in the particle thin film. When the flow speed is reduced stepwise, the ridges are also gradually disappeared, so the large waves as described above are not generated, and the defect of the particle thin film which is likely to be generated at the ridge portion is prevented. Can be.

In the first to third aspects, when the amount of particles floating on the liquid surface is excessive, or when particles overlap due to disturbance or the like after forming a particle thin film,
It is preferable to remove excess particles and particles in the overlapping portion. As a method of removal, for example, the particles are preliminarily triboelectrically charged, or charged by corona discharge or the like in a state where a particle thin film is formed on the surface of the liquid, and then the particles are spread on the liquid surface. While you are
Alternatively, after the thin particle film is formed on the liquid surface, an electrostatic field can be applied to the thin particle film to electrostatically remove particles and the like remaining on the thin film. This method is generally
The adhesive force F1 between the particles 1a and the liquid is equal to the adhesive force F2 between the particles.
It utilizes the fact that it is much larger than the electrostatic attraction force (Coulomb force) F7 that acts to remove particles.
May be set so that F2 <F7 <F1.
When vibration is applied to the surface of the liquid at the same time as the electrostatic field is applied, the action F3 of the vibration and the electrostatic force F7 can be simultaneously applied, and the unnecessary particles can be removed more efficiently. FIG. 12A schematically shows a state in which particles are charged by the corona discharger 12, and FIG. 12B schematically shows a state in which particles are removed by applying an electrostatic field to the charged particles by the electrode plate 13. Show.

The particle thin film formed on the surface of the liquid by the first to third thin film forming methods is transferred to a solid substrate and transferred and fixed, whereby a high-density particle thin film can be easily formed on the solid substrate. Can be formed. More specifically, referring to FIG. 13, the solid substrate 14 is held by holding means 15 having a vertical sliding mechanism. By sliding the holding means 15 downward, the solid substrate 14 is gradually immersed in the liquid 2 on which the particle thin film 20 is formed (FIG. 13A). Next, the solid substrate 14 is gradually pulled up from the liquid 2 by sliding the holding means 15 in the upward direction.
The particle thin film 20 transfers to the upper part (FIG. 13B). By repeating this operation a plurality of times, a particle thin film having a desired thickness can be formed on the solid substrate. Then, if desired,
By heating and drying the solid substrate 14, the particle thin film 20 is dried.
Can be fixed on a solid substrate. It is not necessary to immerse the entire solid substrate in the liquid, for example, by holding the surface of the solid substrate on which the particle thin film is formed in parallel with the liquid surface, contacting only this surface with the particle thin film, and then peeling off. ,
The particle thin film can be transferred to a solid substrate.

The material, size, etc. of the particles used in the first to third thin film forming methods are not particularly limited, and are chemically stable, hardly wet with the liquid used, and
What is necessary is just to select so that it may float on the surface of the liquid. Even particles that originally have a large surface energy and are easily wettable by the liquid to be used, can be suitably used by subjecting the surface of the particles to a chemical treatment such as a hydrophobic treatment. The liquid used is not particularly limited, and various liquids can be used in combination with the particles.

The amount of the particles levitated on the surface of the liquid is calculated in accordance with the particle diameter and the size of the opening of the liquid holding container, and the amount necessary for the close-packed arrangement is calculated. The arrangement may be appropriately determined in consideration of the fact that the arrangement deviates from the ideal close-packed arrangement. Excess particles can be removed by applying an electrostatic field as described above.

[0039]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited thereto. Example 1 An apparatus similar to that of FIG.
After water is poured into a container 5 mm, a polystyrene-based latex (spherical, spherical diameter: 3.0 μm, particle size distribution (GSD
Values) 1.02 to 1.03) were supplied and floated on the water surface. Ceramic piezoelectric element 4a (resonance point is 700H
z, 1.8 kHz, 11.6 kHz, and 22.4 kHz
Hz), a sine wave voltage ± 30 V was applied from the power supply 7 at a frequency of 22.4 kHz, and high-frequency vibration was applied to pure water. By the action of the vibration, the polystyrene latex particles spread over the entire surface of the water, and a thin film composed of the polystyrene latex particles was formed on the water surface in about 80 seconds. Next, FIG.
As shown in (1), a voltage of -6 kV was applied to the corona discharger 12 to scan the particle thin film while performing corona discharge, thereby negatively charging the polystyrene latex particles.
Subsequently, a voltage of ± 15 V is applied to the piezoelectric element 4a to vibrate the piezoelectric element 4a, and as shown in FIG. 12B, a voltage is applied to the electrode plate 13 in the range of 1 kV to 2 kV, A minute distance from the water surface (about 2m
m), an electrostatic field was applied to a thin film composed of polystyrene latex particles. As a result, the surplus latex particles adhered to the electrode plate 13 without being destroyed, and were removed from the particle thin film.

Next, when this thin film was observed with a microscope, it was confirmed that no cracks or particles were overlapped in the thin film, and that the thin film had a uniform structure. Further, the formed polystyrene latex particle thin film was taken in by a CCD camera, and the particle arrangement density was calculated by image processing. As a result, assuming that the case where perfectly spherical particles are arranged in the closest density is 1, it was found that the film was a thin film in which particles were arranged at a density of about 0.7. Considering the particle size distribution of the latex particles, it was demonstrated that the density of the obtained particle thin film was very high.

Example 2 A thin particle film was formed in the same manner as in Example 1 except that the sine wave voltage from the power supply 7 was changed from ± 30 V to ± 20 V. The time until the thin film was formed was about 4 minutes. Further, the density of the particle arrangement (the density when the closest arrangement is 1) obtained in the same manner as in Example 1 was about 0.7. Example 3 A thin particle film was formed in the same manner as in Example 1 except that the sine wave voltage from the power supply 7 was changed from ± 30 V to ± 40 V. The time until the thin film was formed was about 40 seconds. The density of the particle arrangement determined in the same manner as in Example 1 (the density when the closest arrangement is 1)
Was about 0.62.

Example 4 A thin particle film was formed in the same manner as in Example 1 except that the application of the voltage to the piezoelectric element 4a was changed as follows. ± 30 sinusoidal voltage from power supply 7
V was changed to ± 40V, a voltage was applied to the piezoelectric element 4a for 40 seconds, and the polystyrene latex particles were developed into pure water by the action of vibration. Then, the voltage was reduced to a sine wave voltage of ± 30V, and the voltage was increased for about 10 seconds. The voltage was applied to the piezoelectric element 4a. The density of the obtained particle thin film is the same as in Example 1, and
Since the time required for forming the thin film was about 50 seconds, it was proved that when the magnitude of the vibration was gradually reduced, a high-density particle thin film could be formed more quickly.

Example 5 An apparatus similar to that of FIG.
After injecting pure water into a 5 mm container 5, a polystyrene latex (spherical, spherical diameter: 3.0 μm, particle size distribution (GSD
Values) 1.02 to 1.03) were supplied and floated on the water surface. Piezoelectric element 4b (resonance point is 5 MHz, circle: diameter 30)
mm), a sine wave voltage ± 2 from the power source 7 at a frequency of 5 MHz.
5 V was applied, and ultrasonic vibration was applied to pure water. Due to the radiation pressure of ultrasonic vibration, a cone shape (diameter of cone bottom: about 30
mm, height: about 10 mm, the tip of the cone was rounded, and the shape was not disturbed. ) Was visually confirmed that the raised portion 3a was formed on the water surface. The polystyrene latex particles spread on the water surface, and after about 5 minutes, a thin film composed of the polystyrene latex particles was formed on the water surface. When the structure of the thin film was observed with a microscope in the same manner as in Example 1, no particles were overlapped and no crack was generated in the thin film.
Further, the density of the particle arrangement (the density when the closest arrangement is 1) obtained in the same manner as in Example 1 was about 0.7.

Example 6 A particle thin film was formed in the same manner as in Example 5, except that a thin film forming apparatus similar to that shown in FIG. 7 was used instead of the thin film forming apparatus similar to that shown in FIG. The piezoelectric element 4b is moved 10 m
It was reciprocated at m / sec. It was visually confirmed that the raised portion having the same shape as that of Example 5 moved on the water surface.
A particle thin film was formed in about 2 minutes. When the thin film structure and the array density were examined in the same manner as in Example 1, it was confirmed that, as in Example 5, a thin film having a high density and a uniform structure was formed.

Embodiment 7 The piezoelectric element 4b of the thin film forming apparatus used in Embodiment 5 (FIG. 5)
Is disposed so as to form an angle (α), not horizontal, with respect to the bottom surface of the holding container 5 (FIG. 8).
Was used to form a particle thin film. When α was changed from 20 degrees to 50 degrees to expand the polystyrene latex particles, the range in which the flow was acting was larger than the range of the raised portion 3a formed in Example 5 at any angle. Has been confirmed to be expanded. A particle thin film was formed in about 3 minutes. When the thin film structure and the array density were examined in the same manner as in Example 1, it was confirmed that, as in Example 5, a thin film having a high density and a uniform structure was formed.

Example 8 Using the same thin film forming apparatus as in Example 5, polystyrene latex particles were developed in the same manner as in Example 5. While the particles are being spread on the water surface, a sine wave voltage of ± 4 is applied to the piezoelectric element 4b.
Although 0 V was applied, after the development, the voltage was gradually decreased by ± 5 V per second. As a result of the stepwise reduction of the voltage as described above, when the voltage was lowered instantaneously, cracks and overlaps occurred at the protruding portion of the particle thin film at a rate of about once every 4 to 5 times. Even when the thin film was continuously formed 10 times or more, the thin film did not crack or overlap, and the particle thin film could be formed more stably.

Embodiment 9 Using the same apparatus as that shown in FIG.
After injecting pure water into a 0 mm container 5, polystyrene-based latex (spherical, spherical diameter: 3.0 μm, particle size distribution (GS
D value) of 1.02 to 1.03) was supplied and floated on the water surface. The pump 9 was provided with an inlet 10 and an outlet 11 integrally, and the outlet 11 of the pump was a circle having a diameter of 10 mm. The pump was operated to generate a flow from the bottom surface to the water surface. It was visually confirmed that the flow caused disturbance with vibration on the water surface. The polystyrene latex particles moved and developed on the ridge 3b on the water surface, and a thin film composed of the polystyrene latex particles was formed on the water surface after about 5 minutes. When the structure of the thin film was observed with a microscope in the same manner as in Example 1, no particles were overlapped and no crack was generated in the thin film. Also,
The density of the particle arrangement determined in the same manner as in Example 1 (the closest arrangement is 1
Was about 0.6 to 0.65.

COMPARATIVE EXAMPLE 1 A flow was applied to a liquid using the same apparatus as in Example 9 except that the pump flow rate was reduced. The raised portion was formed on the water surface, but the shape of the vertex of the raised portion was not disturbed. In this state, the polystyrene latex particles were merely moving along the ridges according to the flow as aggregates, but no particle thin film was formed.

Example 10 A particle thin film was formed in the same manner as in Example 9, except that a thin film forming apparatus similar to that shown in FIG. 11 was used instead of the thin film forming apparatus similar to that shown in FIG. Pump 10 is moved by transporting means 8 to 10
It was reciprocated at mm / sec. It could be visually confirmed that the raised portion having the same shape as in Example 10 moved on the water surface. A particle thin film was formed in about 2 minutes. When the thin film structure and the arrangement density were examined in the same manner as in Example 1, it was confirmed that, as in Example 9, a thin film having a high density and a uniform structure was formed.

Embodiment 11 The pump 10 of the thin film forming apparatus (FIG. 10) used in Embodiment 9
Was formed using a thin film forming apparatus arranged so as to form an angle (β) instead of being horizontal with respect to the bottom surface of the holding container 5. When the polystyrene latex particles were developed by changing β from 20 degrees to 50 degrees, the range in which the flow was acting was larger than the range of the raised portion 3b formed in Example 9 at any angle. Has been confirmed to be expanded. A particle thin film was formed in about 3 minutes. When the thin film structure and the arrangement density were examined in the same manner as in Example 1, it was confirmed that, as in Example 9, a thin film having a high density and a uniform structure was formed.

Example 12 Using the same thin film forming apparatus as in Example 9, polystyrene latex particles were developed in the same manner as in Example 9. After the particles were spread on the water surface, the flow rate was gradually reduced over about 3 seconds.
As a result of the stepwise reduction in the flow rate, a particle thin film having no cracks and no overlap at the protruding portions of the particle thin film could be formed stably.

After forming a particle thin film composed of polystyrene latex particles in Examples 1 to 12, the particle thin film was fixed on a glass substrate using an apparatus shown in FIG.
Each of the particle thin films was transferred onto a glass substrate without disturbing the structure.

[0053]

According to the present invention, it is possible to easily and safely form a particle thin film having a uniform fine particle density.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of an example of a particle thin film forming apparatus used in a first embodiment of a particle thin film forming method of the present invention.

FIG. 2 is a view schematically showing a process of forming a particle thin film in the method of forming a particle thin film of the present invention.

FIG. 3 is a schematic cross-sectional view of an example of a particle thin film forming apparatus used in the first embodiment of the particle thin film forming method of the present invention.

FIG. 4 is a schematic sectional view of an example of a particle thin film forming apparatus used in the first embodiment of the particle thin film forming method of the present invention.

FIG. 5 is a schematic cross-sectional view of an example of a particle thin film forming apparatus used in the second embodiment of the particle thin film forming method of the present invention.

FIG. 6 is a diagram schematically showing a process of forming a particle thin film in the method for forming a particle thin film of the present invention.

FIG. 7 is a schematic cross-sectional view of another example of the particle thin film forming apparatus used in the second embodiment of the particle thin film forming method of the present invention.

FIG. 8 is a schematic cross-sectional view of another example of the particle thin film forming apparatus used in the second embodiment of the particle thin film forming method of the present invention.

FIG. 9 is a perspective view showing a partial structure of another example of the particle thin film forming apparatus used in the second embodiment of the particle thin film forming method of the present invention.

FIG. 10 is a schematic cross-sectional view of an example of a particle thin film forming apparatus used in the third embodiment of the particle thin film forming method of the present invention.

FIG. 11 is a schematic sectional view of another example of the particle thin film forming apparatus used in the third embodiment of the particle thin film forming method of the present invention.

FIG. 12 is a schematic cross-sectional view of an apparatus used for removing surplus particles in the method for forming a particle thin film of the present invention.

FIG. 13 is a schematic sectional view of an apparatus used for transferring a particle thin film onto a solid substrate in the method for forming a particle thin film of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Particle 2 Liquid 3a Raised part 3b Raised part 4a Vibrator 4b Piezoelectric element 5 Liquid holding container 6 Vibrating plate 7 High frequency power supply 8 Transport means (slide mechanism) 9 Pump 10 Pump inlet 11 Pump outlet 12 Corona discharger 13 Plate electrode 14 Solid substrate 15 Holding member

Claims (13)

[Claims] 1. A method of forming a particle thin film, comprising the steps of: applying a vibration to a liquid having particles floating on a surface thereof, developing the particles on the surface of the liquid, and forming a thin film of particles on the surface of the liquid. 2. The method of forming a thin particle film according to claim 1, further comprising the step of reducing the amplitude of vibration applied to the liquid in a stepwise manner after the particles have been spread on the surface of the liquid. 3. An ultrasonic vibration is applied to a liquid having particles floating on its surface so that a part of the surface of the liquid is raised,
A method of forming a particle thin film, comprising: developing particles on a surface of a liquid to form a thin film of the particles on the surface of the liquid. 4. A part of the surface of the liquid is raised,
The method according to claim 3, wherein ultrasonic vibration is applied to the liquid so that the protrusion moves. 5. The method according to claim 3, wherein the ultrasonic vibration is applied to the liquid such that the transmission direction of the ultrasonic vibration is not perpendicular to the surface of the liquid. . 6. The method according to claim 3, further comprising the step of reducing the amplitude of ultrasonic vibration applied to the liquid in a stepwise manner after the particles are spread on the surface of the liquid. 2. The method for forming a particle thin film according to claim 1. 7. A flow is generated in the liquid in which particles are levitated on the surface so that a part of the surface of the liquid is raised and the shape of the apex of the raised part is disturbed.
A method of forming a particle thin film, comprising: developing particles on a liquid surface to form a thin film of particles on the surface of the liquid. 8. A part of the surface of the liquid is raised,
The method according to claim 7, wherein a flow is generated in the liquid so that the protrusion moves. 9. The method according to claim 7, wherein the flow is generated in the liquid such that the direction of the flow is not perpendicular to the surface of the liquid. 10. The method according to claim 7, further comprising a step of gradually reducing the speed of the flow generated in the liquid after the particles have been spread on the surface of the liquid. 2. The method for forming a particle thin film according to claim 1. 11. Floating charged particles on the surface of a liquid, or charging particles after floating the particles on the surface of a liquid, before forming a thin film of particles on the surface of the liquid. An electric field is applied to the particles after a thin film composed of the particles is formed.
The method for forming a thin particle film according to any one of claims 1 to 10. 12. A thin film made of particles is formed on a liquid surface by the method of forming a thin particle film according to any one of claims 1 to 11, and the thin film is transferred to a surface of a solid substrate by contact. And forming a thin film composed of particles on the surface of the substrate by fixing. 13. A method for forming a particle thin film according to claim 12, wherein the method is repeated a plurality of times.