JP2002286962A - Method for producing fine particle thin film - Google Patents

Abstract

(57) Abstract: Fine particles of an agglomerated phase are dispersed in a medium comprising a liquid mixture containing two or more liquids having different vapor pressures and surface tensions and having a uniform composition. The dispersion liquid is cast on a substrate surface to form a liquid film, and a part of the medium is vaporized and removed from the liquid film, whereby the fine particles are spread on the substrate surface in a single layer or a plurality of layers. According to the method for producing a fine particle thin film of the present invention,
The fine particles are regularly arranged on the substrate in a hexagonal lattice or a tetragonal lattice at an extremely high speed. Such a fine particle thin film is useful as a photochromic crystal material for optical applications such as an optical waveguide device.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for producing a fine particle thin film. According to the method for producing a fine particle thin film of the present invention,
For example, a fine particle thin film containing the fine particles in a useful regular arrangement such as a hexagonal lattice or a tetragonal lattice can be obtained at high speed. Such a fine particle thin film can be used as a photonic crystal material for various optical applications such as an optical waveguide device.

[0002]

2. Description of the Related Art In recent years, research and development on photonic crystals have been actively conducted. A photonic crystal means that light of a specific wavelength cannot exist inside a substance having a periodic change in refractive index with a dimension similar to the wavelength of light (for example, on the order of submicrons in the case of visible light). Is a material that makes use of the appearance of forbidden wavelengths, and is a term named because such forbidden wavelengths are exactly similar to the formation of electron transition forbidden bands in semiconductor crystals. Therefore, if a through-path of an arbitrary shape is provided in a material having a function as a photonic crystal, light of the forbidden wavelength can be guided only in the space of the through-path,
It becomes a means for forming an optical waveguide having a complicated and fine shape.

Although the concept of using a thin film in which fine particles are arranged in a lattice form as a photonic crystal is known, improvement of the performance requires that the particle diameters of the fine particles are uniform and the regularity of the lattice arrangement is high. It is desirable. Prior art documents relating to the arrangement of such fine particles include, for example, N.S. D. Den
Kov et al; Langmuir, 8, 3183 (19
92) and A. S. Dimitrov et al .; Langmui
r, vol. 12, p. 1303 (1996). In these techniques, for example, the aforementioned Dimitrov
Using the method described in the literature of the authors et al.
When a suspension having a particle diameter of 450 nm and a fine particle number concentration of 3.6 × 10 ¹⁷ particles / m ³ is used under the condition of 0%, a manufacturing process which requires a relatively long time of about 2 cm / hour as a coating linear velocity is required. For this reason, there were restrictions on industrial use.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for producing a fine particle thin film in which fine particles are highly arranged in a lattice at a high speed. Exist.

[0005]

Means for Solving the Problems The present inventors have found that when a fine particle dispersion liquid in which fine particles are dispersed in a mixture of two kinds of liquids having different vapor pressures and surface tensions as a medium is applied on a substrate in a thin film form, It is thought that high-speed diffusion of the fine particles driven by Marangoni instability caused by the difference in evaporation rate and surface tension of the liquid and the accumulation by the horizontal capillary force acting on the fine particles are possible. As a result, the inventors have found that a substrate is immersed in the fine particle dispersion and the substrate is pulled up under a certain condition to form a thin film structure in which fine particles are highly lattice-arranged, and the present invention has been achieved.

That is, a first gist of the present invention is to disperse aggregated phase fine particles in a medium comprising a liquid mixture containing two or more liquids having different vapor pressures and surface tensions and having a uniform composition. The fine particle dispersion is cast on a substrate surface to form a liquid film, and a part of the medium is vaporized and removed from the liquid film, whereby the fine particles are formed into a single layer or a plurality of layers on the substrate surface. The present invention resides in a method for producing a fine particle thin film characterized by being developed. Further, a second gist of the present invention resides in a fine particle thin film obtained by the above production method, wherein the fine particles are arranged in a hexagonal lattice or a tetragonal lattice on a substrate.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail. [Condensed phase fine particles] The fine particles in the present invention have a number average particle diameter of 0.001 to 10 µm, preferably 0.01 to 1 µm.
m are condensed phase fine particles. This is composed of a solid phase, a liquid phase, a gel or the like in a mixed state thereof, and is insoluble in a liquid medium described later, and forms a separated phase when dispersed in the liquid medium.

Specific examples of the material of the fine particles include known radical polymerizable monomers such as styrene resins such as polystyrene and acrylic resins such as polymethyl methacrylate (PMMA), and polyethylene and polypropylene. Polymer, polycarbonate, polyamide (nylon 66, nylon 6T) obtained by coordination polymerization
), Polymers obtained by condensation polymerization of polyester, polyimide, polyphenylene ether, polyarylene sulfide, polyetherketone, polyetheretherketone, etc., polymers obtained by ring-opening polymerization of nylon 6, polycaprolactone, etc., pigments, etc. Organic crystals, amorphous inorganic substances such as silica, crystalline oxides such as alumina, titania, zirconia, zinc oxide, cadmium oxide, B
N, BP, BAs, AlN, AlP, AlAs, AlS
b, GaN, GaP, GaAs, GaSb, InN, I
Compounds (or III-V compound semiconductors) of Group 13 elements and Group 15 elements represented by compositional formulas such as nP, InAs, and InSb, and ZnS, ZnSe, and Z
nTe, CdS, CdSe, CdTe, HgS, HgS
e, a compound of a periodic table group 12 element and a periodic table group 16 element represented by a composition formula such as HgTe (or II-VI
Compound semiconductors such as group III compound semiconductors), carbon, silicon,
Single crystal semiconductors such as germanium, amorphous carbon, carbon black, any carbon material such as graphite, gold, silver, platinum,
Transition metals such as palladium, copper, nickel, cobalt, and iron are exemplified. These fine particles may have a composite structure of a plurality of compositions such as a core-shell structure and a mixed crystal structure, or may be a mixture of a plurality of types of fine particles.

For the purpose of controlling the refractive index of the fine particles assuming the use of the photonic crystal, the fine particles of the above-mentioned various polymers (preferably polymers obtained by radical polymerization such as polystyrene and PMMA) are added to the fine particles of the semiconductor crystal or transition. It is often effective to include a high refractive index substance such as a metal.

Among the various fine particles exemplified above, for example, silica, alumina, titania, zirconia, zinc oxide,
An oxide such as cadmium oxide can be synthesized by, for example, a so-called sol-gel method of hydrolyzing and condensing a corresponding metal alkoxide or metal halide. In addition, compound semiconductors, in addition to the above-described sol-gel method, for example, a high vacuum process such as molecular beam epitaxy method or CVD method, a raw material aqueous solution is present as a reverse micelle in a non-polar organic solvent, and in the reverse micelle phase. It can be synthesized by a method of growing crystals (so-called reverse micelle method), a method of injecting a thermally decomposable raw material into a high-temperature liquid-phase organic medium and growing crystals (so-called hot soap method), or the like. The carbon material can be produced, for example, by a method of burning benzene, naphthalene, an organic polymer having a relatively large carbon pigment, or the like as a carbon raw material. For the transition metal fine particles, see G.S. Sch
mid; "Clusters and Colloi
ds ", a method for producing a metal colloid utilizing a known oxidation-reduction reaction as reviewed by VCH (Weinheim, 1994) (for example, a transition metal ion compound such as chloroauric acid or silver nitrate or a salt thereof is converted to citric acid or a salt thereof). (Solution reaction in contact with a reducing agent such as a salt or a borohydride salt, etc.) For any fine particles, in addition to a pulverization method, a precipitation method from a solution or a reaction in a supercritical liquid is used. Physicochemical principles such as methods can also be used.

In order to disperse the fine particles as uniformly as possible without agglomeration, an organic ligand can be bonded to the surface. The effects of such organic ligands are particularly
It is large in the case of an inorganic substance such as a salt of a metal or a transition metal, and is particularly remarkable in the case of a semiconductor or a metal ultrafine particle. As a specific structure of an organic ligand, as described later, an organic molecule having a mercapto group (or thiol group; -SH) or a phosphine oxide group (P = O) strongly adheres to the surface of a semiconductor or metal ultrafine particle. It is preferable because they are combined. In addition, for example, Y. Shiraishi et al .;
J. Mol. Catal. 141, 1871 (1
As described in 999), a coordinating polymer such as polyacrylic acid is also an example of the organic ligand. In the case of fine particles of the above-mentioned various polymers, any surface treatment such as plasma treatment, corona discharge treatment, flame treatment, ozone treatment, or any other chemical surface treatment such as fluorine treatment is performed to disperse the particles in a liquid. Sex may be controlled.

When a fine particle thin film obtained by the production method of the present invention is used for a photonic crystal described below,
It is desirable that the particle size distribution of the fine particles is as small as possible,
Specifically, the standard deviation of the particle size of the fine particles is 1 of the number average particle size.
Desirably, it is 0% or less. Such a standard deviation is more preferably 7% or less, and still more preferably 5% or less.

[Fine particle thin film] The fine particle thin film in the present invention is a thin film mainly composed of the above fine particles and is formed on an arbitrary substrate. The thin film may be a monolayer of the aforementioned fine particles (Monolayer, that is, a single layer having no overlapping in the thickness direction of the fine particles) or a two-particle layer (Bilayer
and a plurality of layers (layers in which the above-mentioned single layers are overlapped with each other).

The above-mentioned fine particle thin film usually has a thickness of 0.1 μm.
The thickness is about 001 to 1000 μm, and the thickness is preferably 0.01 to 100 μm, more preferably 0.05 to 100 μm.
About 50 μm. The film thickness may be changed continuously or discontinuously in the fine particle thin film as needed. Such a fine particle thin film may contain components other than the fine particles. For example, a material such as a synthetic resin such as a thermoplastic resin or a crosslinkable cured resin, or a wax may be contained as a matrix for filling the gaps between the fine particles. There is no limitation on the arrangement state of the fine particles in the fine particle thin film, but when the fine particle thin film is used as a photonic crystal, the fine particles have a hexagonal (Hexagonal) lattice shape or a tetragonal (Tetragonal) lattice shape. Preferably, they are arranged. Among them, the hexagonal lattice arrangement is most preferable in terms of the lattice arrangement homogeneity.

[Substrate for Thin Film] A solid substrate is usually used as a substrate on which the fine particle thin film is formed. Examples of the material include resin, organic crystal, paper, wood, diamond, glass, ceramics, and inorganic crystal. , Metals, semiconductors and the like. Such a substrate does not necessarily have to be planar, and may be in the form of a long belt for the purpose of increasing continuous productivity. When such a belt-like substrate is used, the above-mentioned fine particle thin film may be formed and then cut into a desired size.

[Formation of Fine Particle Thin Film] The present invention provides a method for producing the above fine particle thin film at a high speed.
The effects considered to be the source of the effect are as follows: (1) the action of rapidly spreading the fine particles on the liquid film surface due to Marangoni instability of the surface tension generated on the liquid film surface of the fine particle dispersion liquid cast on the substrate; (2) There are two points of the accumulation action by the horizontal capillary force acting on the fine particles as the volume fraction of one liquid constituting the medium decreases from the liquid film.

That is, a fine particle dispersion in which the fine particles are dispersed in a medium mainly composed of a mixture of at least two liquids having different vapor pressures and surface tensions is used, and a film is formed on the substrate using the above two actions. How to The Marangoni instability of the surface tension that occurs on the surface of the liquid film here means that the chemical composition distribution on the liquid phase surface is in a non-equilibrium state because the vaporization rate of each liquid molecule is different on the liquid phase surface of multiple liquid mixtures. This is a phenomenon in which a non-equilibrium state in which the surface tension distribution on the liquid phase surface is unstable due to the non-equilibrium state appears. Since the appearance of the Marangoni instability is a relatively fast non-equilibrium process, it is possible to spread the fine particles on the surface of the liquid film very quickly due to the difference in surface tension caused by this.

Further, the above-mentioned accumulation action by the lateral capillary force means that the fine particles spread on the substrate surface very quickly by utilizing the above-mentioned Marangoni instability, together with the mass transfer of the medium molecules caused by the capillary effect in the gap, the substrate. This is the action of accumulating each other in the surface direction (that is, the lateral direction). That is,
When the liquid phase thickness of the liquid film on the substrate surface of the medium starts to become smaller than the diameter of the fine particles due to the vaporization of the medium molecules, the liquid surface of the liquid phase forms a curved surface near the fine particles due to the meniscus effect. The above-mentioned transverse capillary force is a large driving force for promoting mass transfer of a medium necessary for forming a curved surface.

In the case of forming a plurality of layers of fine particles according to the present invention, it is possible to advance the inter-particle aggregation by increasing the particle concentration due to the vaporization of the medium molecules earlier than the above-mentioned particle accumulation process due to the lateral capillary force. become. The formation of such a plurality of layers is performed, specifically, by using an additive such as a surfactant or a polymer substance or adjusting the hydrogen ion concentration (pH) in order to adjust the dependence of the cohesive force between particles on the particle concentration. It can be optimized by controlling physicochemical conditions such as temperature and temperature.

[Liquid Medium] As the liquid constituting the medium, two or more liquids having different vapor pressures and surface tensions are selected. Further, it is necessary that the two or more liquids form a homogeneously dissolved composition having mutually infinite solubility at a liquid film forming temperature. The difference in vapor pressure between the two liquids is usually about 1.5 to 20, preferably about 2 to 8, and more preferably about 3 to 7 as a ratio of the vapor pressure at the liquid film forming temperature (that is, the vapor pressure is about 3 to 7). The pressure ratio refers to the vapor pressure of the larger vapor pressure when the vapor pressure of the liquid having the smaller vapor pressure is set to 1.) The difference in surface tension between the two liquids is usually 1.5 to 2 as a ratio of the surface tension.
0, preferably about 2 to 10, and more preferably about 3 to 7 (that is, the ratio of the surface tension is the surface tension of the larger surface tension when the surface tension of the liquid having the smaller surface tension is 1). When the liquid film forming temperature exceeds the boiling point of one liquid medium, the surface tension value that can be measured or calculated in a temperature range of 5 ° C. lower than the boiling point is used instead.)

The vapor pressure ratio is selected from the above range in order to obtain Marangoni instability caused by one of the liquids evaporating quickly. If the ratio is less than the above range, sufficient Marangoni instability does not occur. On the other hand, if the vapor pressure ratio is too different, it is difficult to favorably disperse fine particles due to excessively rapid vaporization of components having a low vapor pressure. In the relationship between the vapor pressure and the surface tension, it is preferable that the surface tension of the medium liquid having a high vapor pressure is smaller than the surface tension of the medium liquid having a low vapor pressure. That is, it is preferable that the surface tension of the remaining medium liquid is larger than the surface tension of the medium liquid that evaporates.

There are no particular restrictions on the combination of the two liquids meeting the above conditions, and various combinations can be used. The polarity of the liquid is appropriately selected in consideration of the wettability with the fine particles to be dispersed. For example, a combination of water and lower alcohols (for example, alcohols having 3 or less carbon atoms such as methanol, ethanol, n-propyl alcohol, and isopropyl alcohol), and water and lower ketones (for example, having 4 or less carbon atoms such as acetone and methyl ethyl ketone). Ketones), a combination of water and lower ethers (eg, ethers having 4 or less carbon atoms such as diethyl ether and tetrahydrofuran), esters with water and 4 or less carbon atoms (eg, n-butyl formate, isopropyl formate, ethyl acetate, A combination using water such as methyl acetate, methyl propionate, etc .; instead of the water, an amide solvent such as N, N-dimethylformamide (abbreviated as DMF) or a nitrogen-containing organic compound such as nitrogen-containing aromatics such as pyridine. Combination using solvents; D
A highly polar liquid mixture system such as a combination of water and a nitrogen-containing organic solvent such as MF or pyridine. In these combinations, the organic solvent having a high vapor pressure has a lower surface tension than that of the remaining water, which is preferable.

On the other hand, examples of combinations of high-boiling hydrocarbons and low-boiling hydrocarbons include octane, isooctane,
Combination of relatively high-boiling aliphatic hydrocarbons having about 8 to 10 carbon atoms such as nonane and decane with relatively low-boiling aliphatic hydrocarbons having about 5 to 7 carbon atoms such as pentane, hexane and heptane , A combination of relatively high-boiling aromatic hydrocarbons such as xylene and chlorobenzene with relatively low-boiling aromatic hydrocarbons such as toluene and benzene, and xylene, chlorobenzene, and aromatic hydrocarbons such as toluene Combinations with relatively low-boiling aliphatic hydrocarbons such as pentane, hexane, heptane and the like which are easy to volatilize, and the like, and further, these hydrocarbons and the lower alcohols, lower ketones, lower ethers, and carbon number Combination with any polar organic solvent such as 4 or less esters, nitrogen-containing organic solvents, or halogenated hydrocarbons such as chloroform and methylene chloride Allowed, combinations between polar organic solvent is also illustrated.

As the third liquid, any kind of liquid that can be uniformly mixed with the two liquid systems may be additionally mixed with the combination of the two liquids exemplified here. For example, water-methanol-tetrahydrofuran, water-DMF-methyl acetate, hexane-octane-toluene, benzene-chlorobenzene-chloroform and the like are exemplified. Further, a third liquid that promotes uniform mixing may be additionally mixed with two types of liquid systems that do not completely dissolve in each other. For example, a system in which an aromatic hydrocarbon is additionally mixed with a water-containing alcohol system such as water-methanol-benzene or water-methanol-toluene, and a linear aliphatic ether is added to a water-containing alcohol system such as water-methanol-diethyl ether. Examples thereof include a mixed system and a system in which a fatty acid ester is additionally mixed with a water-containing alcohol system such as water-methanol-ethyl acetate.

Of these examples, the case where water is used as an essential liquid is preferred in terms of low environmental load and low pollution and the surface tension of the liquid mixture (ie, the above-mentioned transverse capillary force). And the above-mentioned lower alcohols are more preferred, and the combination of water and methanol is one of the most preferred.

The mixing ratio in the combination of the at least two liquids is adjusted by the properties of the fine particles used (surface wettability, specific gravity, etc.) and the various conditions described later (temperature, substrate drawing speed, drawing angle, etc.). Is done. Generally, a liquid having a low surface tension is 5 to 5000 parts by weight, preferably 10 to 100 parts by weight of a liquid having a high surface tension.
１０００1000 parts by weight are used. For example, when a combination of water and methanol is used, the weight ratio of water to methanol is usually 1: 0.1 to 1:50, preferably 1: 0.5.
１ ： 1: 20, more preferably about 1: 1１〜1: 10.

[Preparation of Dispersion] The amount of the fine particles in the fine particle dispersion in which the fine particles are dispersed in a medium mainly composed of a mixture of at least two liquids described above depends on the properties of the fine particles used (surface wettability). And specific gravity, etc.) and various conditions (temperature, drawing speed and drawing angle of the substrate, etc.) described later, but are usually 0.01 to 30% by weight, preferably 0.1 to 20% by weight, and more preferably 0.1 to 20% by weight as a weight percentage. Preferably, it is about 1 to 10% by weight.

In the manufacturing method of the present invention, it is preferable that the repulsive force between the surfaces of the fine particles applied to the substrate is within an appropriate range. This is because if the repulsive force is too small during coating, the fine particles are likely to be fixed in the initial arrangement state which takes kineticly during the coating process, so that they are not rearranged in a highly regular array, and conversely, the repulsive force is too large. Even at a certain moment, even if a highly regular arrangement can be achieved, it is presumed to be due to a mechanism that the ability to maintain the arrangement is small and the probability of changing to an undesirable irregular arrangement again increases. As a preferable repulsion condition between the surfaces of the fine particles, the zeta potential of the surface of the fine particles measured in the fine particle dispersion is usually -20 to -85 millivolt (mV). This value is preferably -30 to -80 mV, more preferably -40.
The range is about -75 mV. Such zeta potential is
When the medium forming the continuous phase of the fine particle dispersion is proton dissociating, such as a mixture of water and methanol, it can be suitably controlled by the hydrogen ion concentration (pH). The pH value is usually in the range of about 4 to 12, preferably 5 to 11, and more preferably about 6 to 10.

[Pull Out of Substrate] Next, various conditions in the operation of pulling out the substrate will be described below. Note that the conditions exemplified below are not limited to the following description because they may vary greatly depending on, for example, the boiling point of the medium. The temperature condition depends on the freezing point and boiling point of the medium, but the liquid temperature of the fine particle dispersion is usually -30 to 150 ° C, preferably 0 to 100 ° C.
More preferably, the temperature is about 10 to 70 ° C. Note that the ambient temperature, that is, the temperature of the gas phase in contact with the fine particle dispersion is not necessarily the same as the liquid temperature of the fine particle dispersion, and the temperature of the liquid such as humidity may be controlled for the purpose of controlling the vaporization rate of the liquid. Adjustment of steam pressure and ventilation measures may be taken.

When the substrate immersed in the fine particle dispersion is pulled out, the drawing linear velocity is usually 5 to 5,000.
0 cm / hour, preferably about 10 to 10000 cm / hour. At this time, the angle at which the substrate is pulled out (the angle between the tangent line at the portion where the target coating thin film comes into contact with the liquid surface and the liquid surface of the fine particle dispersion liquid with the coating substrate interposed therebetween. The angle formed between the surface of the substrate opposite to the thin film and the liquid surface of the fine particle dispersion is not limited as long as the entire surface of the substrate is not immersed in the fine particle dispersion.
0 °, preferably 5 to 90 °, more preferably 5 to 60
°.

[Addition treatment of thin film] The fine particle thin film may be coated with a layer, if necessary, for example, a protective layer for preventing mechanical damage of the coated surface due to friction and abrasion, a light absorbing layer, moisture and oxygen gas. And the like, may be provided with a transmission shielding layer, an antiglare layer, an antireflection layer, a low refractive index layer and the like for suppressing or preventing the transmission of reactive low molecules such as. Further, a multilayer structure may be provided by providing an optional additional functional layer such as an undercoat layer or an electrode layer for improving the adhesion between the substrate and the fine particle thin film. The fine particle thin film may have a multilayer structure in which a film forming step described later is performed a plurality of times, or may have a two-layer structure in which two separately manufactured fine particle thin films are bonded. . In such a multilayer structure, the fine particles constituting each layer may be the same or different from each other.

[Use of Fine Particle Thin Film] The fine particle thin film is refracted in a space occupied by the fine particles contained therein (hereinafter referred to as “fine particle space”) and in a space other than the space (hereinafter referred to as “matrix space”). When there is an index difference, the thin film has a periodic change in the refractive index, and thus has a function as a photonic crystal. In performing such a design, the refractive index of the fine particle space may be designed to be larger or smaller than the refractive index of the matrix space. The refractive index of the matrix space is suitably controlled, for example, by occupying the matrix space with a synthetic resin or liquid having an appropriate refractive index.

[0033]

EXAMPLES Specific examples of the present invention will be described in more detail with reference to the following Examples, which should not be construed as limiting the scope of the invention. [Measurement device] (1) Ultra-high resolution scanning electron microscope (SEM): S-900 manufactured by Hitachi, Ltd. was used. The electron gun was a cold cathode field emission electron gun, and the acceleration voltage was 5 kV. (2) Electrophoretic light scattering photometer: ELS manufactured by Otsuka Electronics Co., Ltd.
-800 was used. The light source used was a He-Ne laser (10 milliwatts), and the Doppler of the scattered light was used.
By determining the shift amount, the electrophoretic velocity of the particles was determined, and the zeta potential was determined from the value.

[Examples 1 to 3] In Examples 1 to 3, the influence of the temperature during the formation of the liquid film was considered. Aqueous dispersion of silica particles (number average particle size 4 supplied by Nippon Shokubai Co., Ltd.)
(30 nm ± 3%), water and methanol were added so that the particle concentration was 5% by weight and the weight ratio of water to methanol was 1: 1 to prepare a fine particle dispersion. 50 minutes after the preparation, this fine particle dispersion (0.9 mL) was poured into a Petri dish (3 cm inside diameter) on a hot stirrer, and washed with a 30% chromic acid mixed acid for at least one day to prepare a silicon wafer substrate (1c).
mx 4 cm) at a 30 ° angle. The liquid temperature was changed to 15 ° C. (Example 1), 49 ° C. (Example 2), and 93 ° C. (Example 3) by adjusting the temperature of the hot stirrer. In each case, 10 seconds after the start of immersion. The substrate was picked up with tweezers, pulled up, and dried in an air atmosphere (temperature: 15 ° C., humidity: 44%) while maintaining the same angle as that at the time of immersion, to obtain a fine particle array structure on the silicon wafer substrate. The three photographs shown in FIG. 1 show, by SEM, a region in which the coating ratio of particles is relatively low in each of the arrangement structures obtained in these three examples in which the liquid temperature was changed. As the liquid temperature increases, 2
The area of the region forming the dimensional array increases, and the liquid temperature 9 of the third embodiment increases.
At 3 ° C., a densely packed thin film of a monolayer (Monolayer) and a bipartite layer (Bilayer) was formed with an area of approximately 5 mm ² . This was interpreted as that the coating linear velocity was on the order of 10,000 cm / hour, because the evaporation rate increased due to the temperature rise, and the accompanying increase in the speed of diffusion of fine particles and the thinning of the liquid film were caused. Tables 1 and 2 show the vapor pressure and surface tension of water and methanol at 15 ° C., 49 ° C., and 93 ° C.

[0035]

[Table 1]

[0036]

[Table 2]

[Embodiments 4 and 5] Embodiments 4 and 5 consider the influence of the substrate pull-out angle. Under the application conditions of Example 1 (liquid temperature of 15 ° C.), the immersion angle and the drying angle of the substrate were matched (hereinafter simply referred to as “substrate angle”), and the substrate angle was set to 15 ° (Example 4) and 30 ° (described above). Example 1) and 90 ° (Example 5) were subjected to the same coating experiment. When the angle of the substrate was changed, the result of observing the monolayer region having relatively high regularity in each obtained array structure by SEM is shown in three photographs of FIG.
As the substrate angle becomes smaller, the area of one domain (region unit formed only by a continuous regular structure without defects; the same applies hereinafter) increases, and the mono is highly regular.
A layer was formed. This was interpreted as that the influence of gravity on the diffusion of the particles was reduced by reducing the angle of pulling out the substrate, and that the force (packing pressure) for the particles to closely pack each other was large.

[Examples 6 to 9] In Examples 6 to 9, the influence of the pH of the fine particle dispersion was considered. Under the application conditions of Example 1, the pH of the particle dispersion was changed by replacing a part of the added water with 0.01 N dilute hydrochloric acid or 0.1 N sodium hydroxide aqueous solution. That is,
pH = 4 (Example 6), pH = 8 (Example 7), pH =
9 (Example 8) and pH = 12 (Example 9) were prepared. The operations of Examples 6 to 9 were performed under the condition that the air temperature and the liquid temperature were 15
3 ° C. and a humidity of 35%, and the other conditions were the same as in Example 1. In each of the obtained array structures, a monolayer region having relatively high regularity was observed by SEM. It is a photograph of. As shown in the photographs of Examples 6 to 8, the area of one domain increases and the regularity of the particle arrangement increases as the pH increases up to pH = 9 until pH = 9. Gender has decreased. This is because, as the pH rises, the amount of charge on the particle surface increases and the repulsion between the particles increases (see Reference Example 1 below), so that the rearrangement of the particles is promoted by an appropriate repulsion between the particles up to about pH = 9. It became easy to fit into a highly ordered particle array structure, but if the repulsion was too strong (pH = 1
2) It was interpreted that the ability to form a highly ordered particle array structure was too weak.

Reference Example 1 In this reference example, the zeta potential of each silica particle under different pH conditions was considered.
The silica particles used in the above example were diluted with water and methanol so that the particle concentration was 0.002% by weight and the weight ratio of water to methanol was 1: 5. Example 6
The pH of the solution was changed to 4, 8, 10, and 12 by the method used in 〜9. For these particle dispersions, the zeta potential of each of the dispersed silica particles was measured by the electrophoretic light scattering photometer described above. As the physical property values of the solvent, those obtained by linearly approximating the physical property values of a mixed solution of water and methanol described in Chemical Handbook (Maruzen) were used. That is, the relative dielectric constant is 38.73 (83.3% by weight of methanol at 25 ° C.) and the refractive index is 1.3371.
(83.3% by weight of methanol, 18 ° C.), viscosity: 0.9
A value of 314 (83.3% by weight of methanol, 25 ° C.) was used. Note that the temperature difference only in the refractive index is 18
This is because only the value at ° C was described. The measurement was carried out at 25 ° C. with circulating water. Further, since it took time for the value to stabilize, an average of data after 50 minutes after preparation was taken. FIG. 4 shows each zeta potential of the silica particles under different pH conditions. As the pH increased, the absolute value of the zeta potential increased. That is, it was found that the interparticle repulsion due to the electrostatic potential was increased. This was interpreted as a weakening of the shielding effect by hydrogen ions.

Example 10 By continuously pulling up the substrate at a constant speed under the conditions of Example 4 described above, it was possible to continuously produce a coating film having a highly ordered particle arrangement structure similar to Example 4. .

[0041]

According to the method for producing a fine particle thin film of the present invention,
The fine particles are regularly arranged on the substrate in a hexagonal lattice or a tetragonal lattice at an extremely high speed. Such a fine particle thin film is useful as a photochromic crystal material for optical applications such as an optical waveguide device.

[Brief description of the drawings]

FIG. 1 shows the microparticle array structure obtained in Examples 1 to 3
It is the photograph observed by M.

FIG. 2 is a photograph obtained by observing a monolayer region having relatively high regularity in a fine particle array structure obtained in Examples 4, 1 and 5 by SEM.

FIG. 3 shows that the monolayer region having relatively high regularity in the fine particle array structure obtained in Examples 6 to 9 was identified by SEM.
It is a photograph observed in.

FIG. 4 is a graph in which the zeta potential of each silica particle is plotted under different pH conditions in Reference Example 1.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G02B 6/12 G02B 6/12 NZ (72) Inventor Manabu Kawa 1000 Kamoshida-cho, Aoba-ku, Yokohama-shi, Kanagawa-ken Address Mitsubishi Chemical Corporation Yokohama Research Laboratory F-term (reference) 2H047 KA03 LA18 PA06 TA41 4D075 AB03 AB35 AB56 BB22X BB24Z BB93X CA47 CB01 DA03 DA06 DB01 DB13 DB14 DB18 DB21 DB31 DC24 EA06 EA10 EB01 EB05 EB13 EB37 EB37 EC30 EC51 4G072 AA25 BB05 BB09 BB10 DD04 DD05 DD06 EE01 EE06 EE07 GG03 HH14 LL06 LL11 LL13 LL14 LL15 MM21 MM31 NN21 TT01 UU30 4G075 AA24 BB02 BB08 CA02 FB01

Claims (14)

[Claims] An agglomerate phase fine particle is dispersed in a medium comprising a liquid mixture containing two or more liquids having different vapor pressures and surface tensions and having a uniform composition. A fine particle thin film, wherein the fine particles are spread on the surface of the substrate in a single layer or a plurality of layers by forming a liquid film by casting on the liquid film and vaporizing and removing a part of the medium from the liquid film. Manufacturing method. 2. The method according to claim 1, wherein the number average particle diameter of the aggregated phase fine particles is 0.001 to 0.001.
The method for producing a fine particle thin film according to claim 1, wherein the thickness is 10 µm. 3. The method according to claim 1, wherein the ratio of the vapor pressure of the medium liquid at the liquid film forming temperature is 1.5 to 20. 4. The method according to claim 1, wherein the ratio of the surface tension of the medium liquid at the liquid film forming temperature is 1.5 to 20. 5. The method for producing a fine particle thin film according to claim 1, wherein the surface tension of the medium liquid having a high vapor pressure is smaller than the surface tension of the medium liquid having a low vapor pressure. 6. The method for producing a fine particle thin film according to claim 1, wherein the liquid film forming temperature is -30 to 150 ° C. 7. The method for producing a fine particle thin film according to claim 1, wherein the medium liquid is a mixture of water and a polar organic solvent. 8. The method for producing a fine particle thin film according to claim 1, wherein the polar organic solvent is an alcohol, an ether or a nitrogen-containing organic solvent. 9. The method for producing a fine particle thin film according to claim 1, wherein the substrate has a drawing angle of 5 to 150 °. 10. The method for producing a fine particle thin film according to claim 1, wherein the zeta potential of the surface of the fine particles measured in the fine particle dispersion is -20 to -85 mV. 11. The method for producing a fine particle thin film according to claim 1, wherein the aggregate phase fine particles are fine silica. 12. The method according to claim 1, wherein the aggregated phase fine particles are arranged in a hexagonal lattice or a tetragonal lattice on the substrate. 13. The method for producing a fine particle thin film according to claim 1, wherein the standard deviation of the particle diameter of the aggregated phase fine particles is 10% or less of the number average particle diameter. 14. A fine particle thin film comprising aggregated phase fine particles arranged in a hexagonal lattice or a tetragonal lattice on a substrate by the method according to claim 1.