JP4229812B2 - Method for producing thin-film three-dimensional fine particle structure - Google Patents

Description

  The present invention relates to a method for manufacturing a thin-film three-dimensional particle structure, and for example, relates to a method for manufacturing a photonic crystal particle structure used for an optical component, an optical integrated circuit, or the like.

  Conventionally, a patent for improving the film thickness distribution of a thin-film three-dimensional fine particle structure by adding an electrolyte to the fine particle dispersion and controlling the temperature during the formation of the thin-film three-dimensional fine particle structure could not be found. .

  The following are known as prior arts related to a method for forming a thin-film three-dimensional fine particle structure utilizing the self-assembly phenomenon of fine particles.

  Kuniaki Nagayama is concerned with a method for producing a fine particle aggregate utilizing the self-assembly phenomenon, including Japanese Patent No. 28828386 (Patent Document 1), Japanese Patent No. 2784487 (Patent Document 2), and Japanese Patent No. 2828374. (Patent Document 3), Japanese Patent No. 2828375 (Patent Document 4), Japanese Patent No. 2834416 (Patent Document 5), Japanese Patent No. 29905712 (Patent Document 6), Japanese Patent Application Laid-Open No. 8-229474 (Patent Document 7). ) And other patents.

In addition, the research results of Vicki L. Colvin and Yurii A. Vlasov are well-known for the production methods with thick film and large area. Their typical papers are as follows.
(A) Vicki L. Colvin et al. “Single-Crystal Colloidal Multilayers of Controlled bbbThickness” (Chem. Mater. 1999, 11, 2132-2140) (Non-patent Document 1)
(B) Yurii A. Vlasov et al., “On-chip natural assembly of silicon photonic bandgap crystals” “Nature”, November 15, 2001, Vol. 414, p. 289-293 (Non-Patent Document 2)

  The Sato Group of Kanagawa Prefectural Concentration Collaborative Research Project (KAST) is also working on the production of fine particle aggregates using the self-assembly phenomenon of fine particles. As for the method of forming the film, the research result of 2000 “Fabrication and evaluation of externally responsive photonic crystals” (http: //home/ksp.or.jp/kast/kyodo/seika/index.html) It is reported in Patent Document 3).

  Also, a method of pulling up the substrate gradually from the fine particle dispersion after immersing the fine particle dispersion in a state where the substrate has good wettability is also described in Chem. Mater. 2002, 14, 760-765 (non- In Patent Literature 4), a report is made by Kanagawa Prefecture Regional Consolidation Joint Research Project (KAST).

  In particular, Japanese Patent No. 2828386 (Patent Document 1) discloses a method in which a dispersion liquid of fine particles is brought into contact with a substrate, and a meniscus tip portion in a three-phase contact line formed by the atmosphere, the substrate and the dispersion liquid is swept and moved. When forming a thin-film three-dimensional fine particle structure, the fine particle density and total number of fine particles of the thin-film three-dimensional fine particle structure are controlled by using the moving speed of the meniscus tip, the volume fraction of the fine particles, and the liquid evaporation rate as parameters. Is an invention. Since Japanese Patent No. 2828386 (Patent Document 1) is also deeply related to the present invention, the relationship with the present invention will be described again in the following description of “Problems to be Solved by the Invention”.

Japanese Patent No. 2828386 Japanese Patent No. 2783487 Japanese Patent No. 2828374 Japanese Patent No. 28828375 Japanese Patent No. 2834416 Japanese Patent No. 29905712 JP-A-8-229474

Vicki L. Colvin et al. “Single-Crystal Colloidal Multilayers of Controlled bbbThickness” (Chem. Mater. 1999, 11, 2132-2140) Yurii A. Vlasov et al., “On-chip natural assembly of silicon photonic bandgap crystals” “Nature”, November 15, 2001, Vol. 414, p. 289-293 Kei Tadazawa's work in 2000, “Fabrication and evaluation of field-responsive photonic crystals” (http: //home/ksp.or.jp/kast/kyodo/seika/index.html) Chem. Mater. 2002, 14, 760-765

  As described in the background section above, research on the self-assembly phenomenon of fine particles and a basic invention relating to a method of forming a fine particle aggregate using this phenomenon have been made energetically by Kuniaki Nagayama et al. In particular, in the above-mentioned Japanese Patent No. 2828386 (Patent Document 1), when forming a thin film-like three-dimensional fine particle structure, a thin film is formed using the moving speed of the meniscus tip, the volume fraction of fine particles, and the liquid evaporation rate as parameters. Disclosed is an invention for controlling the fine particle density and the total number of fine particles of a three-dimensional fine particle structure.

  However, the above-mentioned Japanese Patent No. 2828386 (Patent Document 1) is a patent of the basic research result of Nagayama et al., And only describes the basic and basic matters. The method of actually realizing the conditions required for the above is still unresolved. Therefore, a method for obtaining industrially meaningful large crystalline thin-film three-dimensional fine particle structures remains an object of research and development.

  This is because Chem. Mater. 1999, 11, 2132-2140 (Non-Patent Document 1) by Vicki L. Colvin et al. Published after Japanese Patent No. 2828386 (Patent Document 1) or Kanagawa Prefecture Regional Concentration Chem. Mater. 2002, 14, 760-765 (Non-patent Document 4) from the Joint Research Project (KAST) also reported on their film formation method, citing the research results of Nagayama et al. It is clear from the discussions.

  As described above, the method for actually obtaining a large-area thin-film three-dimensional fine particle structure is still a problem that has not been sufficiently solved.

  Next, the present situation and problems of the method for forming a thin-film three-dimensional fine particle structure using the self-assembly phenomenon will be described in more detail.

  The so-called Convective Self-Assembly method, which Vicki L. Colvin and Yurii A. Vlasov are working on, is used to form a thin-film three-dimensional fine particle structure on a free-surface substrate by the self-assembly phenomenon of fine particles. It is known as a method for obtaining crystals.

FIG. 8 is a diagram for explaining the principle of the Convective Self-Assembly method.
As shown in the figure, the Convective Self-Assembly method is a method in which a fine particle dispersion 202 in which fine particles 204 are dispersed is placed in a container 205 and a substrate 201 having good wettability is placed in the fine particle dispersion 202. When soaked (see FIG. 1A), the thin-film three-dimensional fine particle structure 203 is formed at the trace where the fine particle dispersion 202 evaporates and the wetting interface of the fine particle dispersion 202 recedes on the substrate 201. This is a method based on the principle of being formed (see FIG. 5B).

  In fact, using the Self-Assembly method based on the above principle using spherical monodispersed silica particles, a thin film-like three-dimensional fine particle structure with a uniform film thickness and large area is obtained under certain conditions. It can be confirmed that it is obtained.

  However, when the particle size is large (about 400 nm or more), the silica particles are precipitated in the raw material solution during the growth process, so that there is a problem that it is impossible to obtain a large-area thin-film three-dimensional fine particle structure. .

  For this reason, Yurii A. Vlasov et al. Prevent precipitation of silica particles in the raw material liquid during the growth process by creating a temperature difference between the upper and lower parts of the raw material liquid container in a temperature atmosphere higher than room temperature. (Yurii A. Vlasov et al., “On-chip natural assembly of silicon photonic bandgap crystals” “Nature”, November 15, 2001, Vol. 414, p. 289-293 (non- Patent Document 2)).

  Further, even if the silica particle has a particle size of 400 nm or less, for example, a particle size of about 300 nm, depending on the characteristics of the particle, the silica particle is precipitated in the raw material solution during the growth process. In some cases, a three-dimensional fine particle structure cannot be obtained.

  As described above, the thin film-like three-dimensional fine particle structure having a uniform film thickness and large area has been obtained by the Convective Self-Assembly method only by growth under certain specific conditions. In order to grow a thin film-like three-dimensional fine particle structure well when the conditions of the particles to be changed are changed, it has not been reported how the growth conditions should be.

  As described above, there has been a strong demand for a systematic control method for obtaining a thin-film three-dimensional fine particle structure having a uniform film thickness and a large area in the Convective Self-Assembly method.

  Accordingly, an object of the present invention is to provide a method for producing a large-area thin-film three-dimensional fine particle structure having a uniform film thickness in the Convective Self-Assembly method.

In order to achieve the above object, the present invention has the following configuration.
a) According to the first aspect of the present invention, the substrate is immersed in a fine particle dispersion in which fine particles are dispersed in a dispersion medium, and the wetting film of the fine particle dispersion on the surface of the substrate due to the evaporation of the dispersion medium is utilized on the substrate. A manufacturing method for forming a thin-film three-dimensional fine particle structure , wherein a step of performing a desalting treatment of the fine particle dispersion and a step of adding an electrolyte are performed before the formation of the thin-film three-dimensional fine particle structure. during the formation of a three-dimensional fine structure is characterized by a step of controlling the ambient temperature constant.

b ) The invention according to claim 2 , wherein the substrate is immersed in a fine particle dispersion in which fine particles are dispersed in a dispersion medium, and the wetting film of the fine particle dispersion on the surface of the substrate due to the evaporation of the dispersion medium is used on the substrate. a manufacturing method for forming a thin film three-dimensional fine structure, prior to formation of the thin film-like three-dimensional fine structure, and performing desalination of the particulate dispersion, and adjusting the hydrogen ion concentration, It is characterized in that the step of adding an electrolyte is performed, and the step of controlling the ambient temperature to be constant is performed during the formation of the thin-film three-dimensional fine particle structure.

c ) In the invention according to claim 3, the step of performing the desalting treatment of the fine particle dispersion is a step of using an ion exchange resin, and the invention of claim 4 is a method of performing the desalting treatment of the fine particle dispersion. It is a process using centrifugation.
d ) The invention according to claim 5 is characterized in that the step of controlling the atmospheric temperature to be constant is a step performed using a thermostatic bath.

According to the method for producing a thin-film three-dimensional fine particle structure according to claim 1 , by performing a desalting treatment before adding the electrolyte to the fine particles, depending on the amount of the electrolyte to be added, The electrolyte concentration can be controlled. As a result, the speed of precipitation of the fine particles can be controlled, and a thin-film three-dimensional fine particle structure having a uniform film thickness distribution can be obtained.

According to the method for producing a thin-film three-dimensional fine particle structure according to claim 2 , the present invention is applied to fine particles of a material having an isoelectric point of around 7 by adjusting the pH value of the fine particle dispersion. It becomes possible.

The method for producing a thin-film three-dimensional fine particle structure according to claim 3 presents a specific method (ion exchange) of the desalting treatment in the present invention.

The method for producing a thin-film three-dimensional fine particle structure according to claim 4 presents a specific method (centrifugation) of desalting treatment in the present invention.

The method for producing a thin-film three-dimensional fine particle structure according to claim 5 presents a specific method (a constant temperature bath) for controlling the ambient temperature during the formation of the thin-film three-dimensional fine particle structure in the present invention to be constant. Is.

  The present invention controls the temperature during the addition of an electrolyte to a fine particle dispersion and the formation of a thin film-like three-dimensional fine particle structure, thereby controlling the speed of precipitation of the fine particles and having a uniform film thickness distribution. An original fine particle structure is obtained.

First, the principle of the method for producing a thin-film three-dimensional fine particle structure in the present invention will be described.
In the method for forming a thin film three-dimensional fine particle structure using the self-assembly phenomenon of fine particles, the growth rate of the thin film three-dimensional fine particle structure is governed by the drying rate of the dispersion medium. This will be explained by Dimitrov and Nagayama's theory (Langmuir 1997, 12, 11303) used to explain the self-assembly phenomenon of fine particles.

According to their theory, thin film formation by self-assembly of fine particles follows the following formula.
h = (βLjφ) / (0.605dv (1-φ))
As shown in FIG. 2, h is the number of particle layers, v is the growth rate of the particle film, φ is the volume fraction of the particles, j is the evaporation rate of the dispersion medium, and L is the wetting of the substrate surface. The length of the film, d, means the particle diameter. Note that β in the formula represents a ratio between the speed of the fine particles in the dispersion medium and the flow speed of the dispersion medium, which are generated when the dispersion medium evaporates.

  In accordance with the above equation, in the Self-Assembly method, the volume fraction of particles (fine particles) in the fine particle dispersion is controlled when controlling the film thickness (number of particle layers h) of the thin-film three-dimensional fine particle structure. Dispersion concentration) φ is adjusted and controlled.

  However, the Convective Self-Assembly method uses evaporation of the dispersion medium to cause wetting film receding on the substrate, so at the beginning of the growth process, the particle dispersion concentration is as intended. As the time elapses, the concentration of the fine particle dispersion gradually increases as the dispersion medium evaporates.

  According to the above formula, as the concentration of the fine particle dispersion increases, the film thickness of the thin-film three-dimensional fine particle structure should gradually increase. A three-dimensional fine particle structure may be widely obtained.

  In the present invention, in the Self-Assembly method, the conditions under which a thin film-like three-dimensional fine particle structure having a uniform film thickness can be widely obtained have been clarified by examining the correlation between the growth conditions and the film thickness distribution. Hereinafter, detailed description will be given using specific examples.

  Centrifugation is carried out on silica particles having a particle diameter of 310 nm in an ethanol dispersion medium, the supernatant is removed, ethanol is added to the precipitate, and the spherical monodispersed silica particles are dispersed again in ethanol. The dispersion is centrifuged in the same manner, and the supernatant is removed, ethanol is added, and redispersion is performed. The above process is performed three times, and the final liquid addition is performed by adjusting the particle concentration to 4 wt% as a raw material liquid (fine particle dispersion) 102.

  The substrate 101 is first subjected to ultrasonic cleaning with acetone, and then immersed in a mixed solution of concentrated sulfuric acid and hydrogen peroxide solution for 1 hour, rinsed with pure water, and then dried.

  Using the raw material liquid 102 and the substrate 101, as shown in FIG. 1, the raw material liquid 102 is placed in a container 105 and immersed in the raw material liquid 102 in a state where the substrate 101 is upright. In this state, the dispersion medium evaporates from the raw material liquid 102, and the wet film of the raw material liquid 102 on the surface of the substrate 101 moves backward, so that the thin-film three-dimensional fine particle structure 103 grows (for the growth process) (See FIG. 8 above).

  However, under these conditions, since the silica particles in the raw material liquid are precipitated in about 1 to 1 and a half days, the subsequent growth is not performed, and it is possible to obtain a large-area thin film three-dimensional fine particle structure 103. Can not.

  However, in more detail, depending on the nature of the silica particles, even if the particle size is about 300 nm, no obvious precipitation occurs for more than one week. The body 103 may continue to grow.

  This is explained above when a dispersion liquid is formed because the density of the silica particles is small or the amount of the electrolyte contained therein is small depending on the synthesis conditions for obtaining the silica particles and the subsequent treatment method. This is because it is harder to precipitate than the silica particles, and the growth after the second day may be possible.

  As described above, since the growth conditions of the thin film-like three-dimensional fine particle structure 103 vary depending on the characteristics of the particles, how to obtain a good thin-film three-dimensional fine particle structure 103 in a wide area in each case, It becomes important.

  The ethanol dispersion liquid of silica particles 4 wt% having a particle diameter of 310 nm described above precipitates in one day to one and a half days at room temperature, so that the raw material liquid (fine particle dispersion liquid) 102 is placed in a container as shown in FIG. When the substrate 101 is put up and then immersed in the raw material liquid 102 in a state where the substrate 101 is erected, it is put into a 50 ° C. constant temperature bath (incubator) 106 and grown. As a result, the thin film three-dimensional fine particle structure 103 is growing. The film-like three-dimensional fine particle structure 103 could be obtained up to the end of the substrate 101 without stopping.

  The thin-film three-dimensional fine particle structure 103 is formed on both surfaces of the substrate 101. When one surface is wiped off to obtain a light transmission spectrum, a spectrum as shown in FIG. 3 is obtained. In the vicinity of the wavelength of 730 nm, a dip (A) due to the periodic structure of the thin-film three-dimensional fine particle structure 103 is seen.

  In addition, a vibration component (B) is observed in the vicinity of a wavelength of 800 to 1000 nm. This is a vibration component generated from the film thickness of the thin-film three-dimensional fine particle structure 103, and this vibration component is Fourier-decomposed. By doing so, the film thickness of the thin-film three-dimensional fine particle structure 103 can be derived.

  Using this, the film thickness was derived by sequentially changing the position in steps of about 1 mm from the growth start point toward the downstream side of growth (from the upper side to the lower side of the substrate 101 in FIG. 1). FIG. 4 is a diagram showing the film thickness distribution (part 1) obtained in this way. In the figure, point a on the horizontal axis indicates the measurement position on the most upstream side, and point m indicates the measurement position on the most downstream side.

  The film thickness distribution (part 1) shows that the film thickness increases from the upstream side to the downstream side of the growth, that is, from the measurement position a point to the m point. This result is obtained during the growth process. This is consistent with the fact that the concentration of the raw material liquid 102 gradually increases.

  While the growth after the second day was not performed at room temperature, the growth after the second day was continued by performing the growth process in a constant temperature bath (incubator) 106 at 50 ° C., and FIG. It can be considered that the film thickness distribution as described above is obtained because the precipitation of silica particles in the raw material liquid during the growth process is prevented.

  From the above, it can be seen that in order to obtain the thin film three-dimensional fine particle structure 103 having a uniform film thickness distribution, it is effective to control the speed of precipitation of silica particles during the growth process.

  The present invention is characterized in that the speed of precipitation of silica particles is controlled by adding an electrolyte to the fine particle dispersion 102 serving as a raw material liquid and by controlling the atmospheric temperature during the growth process to be constant.

  Although the above explanation has been made on silica particles, it is effective to adjust the speed of precipitation of particles during the growth process in order to obtain a thin-film three-dimensional fine particle structure having a uniform film thickness distribution. The same is true for any particle.

  Hereinafter, the method for producing a thin film three-dimensional fine particle structure having a uniform film thickness distribution according to the present invention will be described in more detail using actual specific examples.

Example 1
In this embodiment, according to claim 1, the example was carried out the invention of claims 4 and 5 will be described.

The preparation of the raw material liquid (fine particle dispersion) 102 is performed according to the following procedure in the same manner as described above.
Centrifugation is performed by dispersing spherical monodispersed silica particles having a particle diameter of 310 nm in ethanol, the supernatant is removed, ethanol is added to the precipitate, and the spherical monodispersed silica particles are dispersed again in ethanol. The dispersion is centrifuged in the same manner, and the supernatant is removed, ethanol is added, and redispersion is performed.

  The above steps were repeated three times, and 8 ml of a 9 ml container (vial) was prepared by adjusting the concentration of the particles to 4 wt% at the time of the final addition of ethanol, and further 2 μl of 0.01 N sodium chloride aqueous solution. In addition, the raw material liquid (fine particle dispersion) 102 is subjected to ultrasonic dispersion.

  The substrate 101 is first subjected to ultrasonic cleaning with acetone, and then immersed in a mixed solution of concentrated sulfuric acid and hydrogen peroxide solution for 1 hour, rinsed with pure water, and then dried.

  As shown in FIG. 1, the substrate 101 after washing is immersed in a raw material liquid (fine particle dispersion) 102 placed in a container 105 and placed in a constant temperature bath (incubator) 106 at 50 ° C. Made growth. The growth was completed in about 4 days, and a thin film three-dimensional fine particle structure 103 having a length of about 2 cm was obtained.

  By changing the position of this thin film-like three-dimensional fine particle structure 103 in steps of about 1 mm from the growth start point toward the downstream side of the growth in the same manner as described above, the light transmission spectrum is obtained. The film thickness was derived by Fourier analysis of data in the vicinity of a wavelength of 800 to 1000 nm. FIG. 5 is a diagram showing the film thickness distribution (part 2) obtained in this way.

  As can be seen from FIG. 5, it can be seen that a substantially uniform film thickness distribution is obtained except for a and b near the growth start point and q and r near the growth end point. The variation in film thickness in the region showing a uniform film thickness distribution corresponds to ± 1 particle layer.

  In this way, the principle that a uniform film thickness distribution can be obtained is that the sedimentation speed of the silica particles in the raw material liquid during the growth process is appropriately adjusted. This is because the film thickness distribution of the thin-film three-dimensional fine particle structure 103 in which the same growth is performed in a constant temperature bath (incubator) 106 at 40 ° C. is shown in FIG. While the thickness is reduced, the film thickness distribution of the thin-film three-dimensional fine particle structure 103 performed in a constant temperature bath (incubator) 106 at 60 ° C. is shown in FIG. This can also be confirmed from the increase in thickness. This is because, as the temperature rises, the Brownian motion in the raw material liquid becomes active, the silica particles are less likely to precipitate, and the effect of concentrating the raw material liquid 102 is more strongly reflected in the film thickness distribution. It is.

  The addition of sodium chloride to the raw material liquid 102 has the effect of compressing the thickness of the electric double layer around the silica particles in the raw material liquid 102 and facilitating the precipitation of the silica particles. The speed can be controlled.

However, when the addition amount of sodium chloride was further increased 10 times as compared with the present example (concentration: 2.5 × 10 ⁻⁵ mol / l), precipitates were conspicuous in the thin-film three-dimensional fine particle structure 103. Thus, it was not possible to obtain a good thin film three-dimensional fine particle structure 103. When the rate of precipitation of silica particles is controlled by the amount of sodium chloride added, it is desirable to control it at a concentration of this example or less (about 2.5 × 10 ⁻⁶ mol / l).

  As described in the above embodiments, the rate of precipitation of silica particles in the raw material liquid 102 during the growth process is controlled by controlling the amount of sodium chloride added to the raw material liquid 102 and the temperature during the growth process. The thin film-like three-dimensional fine particle structure 103 having a uniform film thickness can be formed.

  The sodium chloride used in this example can be used easily and is used as a typical electrolyte, and it goes without saying that the same effect can be obtained even if other electrolytes are used. Absent.

(Example 2)
In this embodiment, according to claim 1, the example was carried out the invention of claims 3 and 5 will be described.

In the present embodiment, the method of adjusting the raw material liquid 102 is different from that in the first embodiment.
An ion exchange resin is added to a spherical monodispersed silica particle dispersion having a particle diameter of 310 nm, and the mixture is allowed to rest for about one month, and the electrolyte incorporated in the silica particles is removed. The dispersion medium used at this time may be water or ethanol. Thereafter, the amount of silica dispersion used is taken out and filtered to remove the ion exchange resin in the liquid.

  After this, if the dispersion medium is water, centrifuge, remove the supernatant, repeat the procedure of adding ethanol to the precipitate and redispersing in ethanol. Finally, the dispersion medium is replaced with ethanol. The silica particle concentration is adjusted to 4 wt%. Moreover, when the dispersion medium in the process using an ion exchange resin is ethanol, it is only necessary to adjust the concentration after filtering to 4 wt%.

  8 ml of the silica dispersion liquid whose concentration was adjusted in this way was put into a container (vial) having a capacity of 9 ml, and 2 μl of 0.01N sodium chloride aqueous solution was further added, followed by ultrasonic dispersion. Liquid) 102.

  The method for cleaning the substrate 101 and the method for the film formation process are the same as those in the first embodiment. Further, the thin film-like three-dimensional fine particle structure 103 obtained thereby has a similar film thickness distribution.

  The method of this example is considered to be a method that is more faithful to the principle of the present invention than the method of Example 1. That is, the electrolyte taken in the silica particles cannot be removed sufficiently even after repeated centrifugation. This can also be seen from the well-known fact that the silica particle dispersion liquid subjected to the ion exchange resin treatment is less likely to precipitate the silica particles than the silica particle dispersion liquid subjected to only the centrifugal separation treatment.

  Therefore, removing the electrolyte in the silica particles as much as possible first, and then adding only the amount of electrolyte necessary to control the precipitation rate of the silica particles is the most faithful method to the principle of the present invention. Conceivable.

  However, in the thin film-like three-dimensional fine particle structure 103 actually obtained, no significant difference is recognized between the methods of Example 1 and Example 2. Therefore, the method of Example 1 is usually sufficient for practical use.

(Example 3)
In the present embodiment, examples in which the inventions of claims 1 , 2, 4 , and 5 are implemented will be described.

  In this example, a case where particles other than silica particles are used will be described. In practice of the present invention, it is basically necessary to control the speed of precipitation of fine particles while fine particles are well dispersed in the dispersion medium. This is because a good thin-film three-dimensional fine particle structure cannot be formed under conditions where the fine particles easily aggregate.

  Here, the concept of an isoelectric point that determines the quality of fine particle dispersion in the dispersion medium will be described. When inorganic fine particles are dispersed in a dispersion medium, the surface of the fine particles has a charge, and an interface potential is generated on the surface of the fine particles. This interfacial potential varies depending on the hydrogen ion concentration (pH) of the dispersion medium, and there is a pH value at which the interfacial potential becomes zero. This pH value is called the isoelectric point.

  At this isoelectric point, since the fine particles in the dispersion medium do not wear a charge garment, they are very likely to aggregate. In order to produce a fine particle dispersion in which fine particles are well dispersed, it is necessary to adjust the pH value as far as possible from the isoelectric point.

  Here, looking back at the steps of Example 1 and Example 2 using silica particles, the pH value of the fine particle dispersion is close to 7 due to centrifugation or ion exchange resin. It is said that the isoelectric point of colloidal silica is around 2, and a pH value far from the isoelectric point is realized in the above process.

  However, when a fine particle material having an isoelectric point near 7 is used, it is necessary to adjust the pH value in order to ensure good dispersion of the fine particles in the dispersion medium. Here, the raw material liquid adjustment method of spherical monodisperse particles with a particle diameter of 300 nm of titanium oxide, which is said to have an isoelectric point of 5 to 6, will be described.

  Centrifugation is performed by dispersing spherical monodispersed titanium oxide particles having a particle diameter of 300 nm in ethanol, the supernatant is removed, ethanol is added to the precipitate, and spherical monodispersed titanium oxide particles are dispersed again in ethanol. The dispersion is centrifuged in the same manner, and the supernatant is removed, ethanol is added, and redispersion is performed.

  The above steps were repeated three times, and the fine particle dispersion with a pH value of 10 by adding an appropriate amount of aqueous ammonia to the particle concentration adjusted to 4 wt% at the time of the final ethanol addition was added to a container (9 ml capacity). 8 ml is added to a vial), and 2 μl of a 0.01 N sodium chloride aqueous solution is added and subjected to ultrasonic dispersion to obtain a raw material liquid (fine particle dispersion) 102.

  The method for cleaning the substrate 101 is the same as that in the first embodiment. The film forming process is the same as that in Example 1 except that the temperature of the thermostatic chamber (incubator) 106 is set to 65 ° C. Thereby, a thin film-like three-dimensional fine particle structure 103 of spherical monodispersed titanium oxide particles having a good film thickness distribution can be obtained.

It is a figure which shows the growth method in the thermostat (incubator) which concerns on this invention. It is a figure which shows each parameter which dominates the fine particle accumulation phenomenon. It is a figure which shows the light transmission spectrum example of a thin film-shaped three-dimensional fine particle structure. It is a figure which shows the film thickness distribution (the 1) of a thin film-like three-dimensional fine particle structure (problem to be solved by the present invention). It is a figure which shows the film thickness distribution (the 2) of a thin film-like three-dimensional fine particle structure. It is a figure which shows the film thickness distribution (the 3) of a thin film-like three-dimensional fine particle structure. It is a figure which shows the film thickness distribution (the 4) of a thin film-shaped three-dimensional fine particle structure. It is a figure for demonstrating the principle of Convective Self-Assembly method.

Explanation of symbols

101, 201: Substrate 102, 202: Fine particle dispersion (raw material liquid)
103, 203: Thin-film three-dimensional fine particle structure 104, 204: Fine particle 105, 205: Container 106: Thermostatic bath (incubator)

Claims (5)

A substrate is immersed in a fine particle dispersion in which fine particles are dispersed in a dispersion medium, and a thin film-like three-dimensional fine particle structure is formed on the substrate by utilizing the retraction of the wet film of the fine particle dispersion on the substrate surface by evaporation of the dispersion medium. A manufacturing method comprising:
Before the formation of the thin-film three-dimensional fine particle structure, a step of desalting the fine particle dispersion and a step of adding an electrolyte are performed, and the ambient temperature is kept constant during the formation of the thin-film three-dimensional fine particle structure. A method for producing a thin film-like three-dimensional fine particle structure, characterized in that the step of controlling is performed. A substrate is immersed in a fine particle dispersion in which fine particles are dispersed in a dispersion medium, and a thin film-like three-dimensional fine particle structure is formed on the substrate by utilizing the retraction of the wet film of the fine particle dispersion on the substrate surface by evaporation of the dispersion medium. A manufacturing method comprising:
Before formation of the thin film-like three-dimensional fine structure, and performing desalination of the particulate dispersion liquid were and adjusting the hydrogen ion concentration, the step of adding an electrolyte, a thin-film three-dimensional fine structure A method for producing a thin-film three-dimensional fine particle structure comprising performing a step of controlling the atmospheric temperature constant during formation. In the manufacturing method of the thin film-shaped three-dimensional fine particle structure according to claim 1 or 2 ,
The method for producing a thin-film three-dimensional fine particle structure is characterized in that the step of desalting the fine particle dispersion is a step of using an ion exchange resin. In the manufacturing method of the thin film-shaped three-dimensional fine particle structure according to claim 1 or 2 ,
The method for producing a thin-film three-dimensional fine particle structure is characterized in that the step of desalting the fine particle dispersion is a step of using centrifugation. In the manufacturing method of the thin film-shaped three-dimensional fine particle structure according to any one of claims 1 to 4 ,
The method for producing a thin-film three-dimensional fine particle structure is characterized in that the step of controlling the atmospheric temperature to be constant is a step performed using a thermostatic bath.

Images