JP4249094B2 - Method for manufacturing thin-film particulate assembly - Google Patents

Description

The present invention, various optical components are useful, such as in optical integrated circuits, it relates to the production how the thin film fine aggregate can also be used as a photonic crystal.

  As a prior art of a method for forming a fine particle aggregate utilizing the self-assembly phenomenon of fine particles, Kuniaki Nagayama has applied for a series of patents relating to a method for producing a fine particle aggregate utilizing the self-assembly phenomenon (Patent Document 1). ~ 7).

  Further, as for a manufacturing method that realizes a large area with a thick film, Vicki L. et al. Colvin and Yuri A. The research results of Vlasov are famous, and their representative papers include Non-Patent Documents 1 and 2.

  The Sato Group in the Kanagawa Regional Convergence Collaborative Research Project (KAST) is also working on the production of particulate aggregates using the self-assembly phenomenon of particulates, and the particulate aggregates are self-assembled between two opposing substrates. The method for forming the film is reported in the 2000 research result “Preparation and Evaluation of Externally Responsive Photonic Crystals”, and the same contents can be confirmed in Non-Patent Document 3.

  Non-Patent Document 4 also reports a lifting method in which the substrate is gradually lifted from the fine particle dispersion after dipping the fine particle dispersion in a state in which the substrate has good wettability.

In particular, Patent Document 1 forms a thin-film particulate assembly by bringing a dispersion liquid of fine particles into contact with a substrate and sweeping and moving the tip of a meniscus in a three-phase contact line formed by the atmosphere, the substrate, and the dispersion liquid. In this case, it is an invention to control the fine particle density and the total number of fine particles of the thin film fine particle aggregate using the moving speed of the meniscus tip, the volume fraction of fine particles, and the liquid evaporation rate as parameters.
Japanese Patent No. 2828386 Japanese Patent No. 2783487 Japanese Patent No. 2828374 Japanese Patent No. 28828375 Japanese Patent No. 2834416 Japanese Patent No. 2905712 JP-A-8-229474 Vicki L. Colvin et al., “Single-Crystal Colloidal Multilayers of Controlled bbbThickness” (Chem. Mater. 1999. 111, 1322-1140). Yurii A. Vlasov et al., “On-chip natural assembly of silicon photonic band gap crystals” “Nature”, November 15, 2001, Vol. 414, p. 289-293 Tadazawa, “Construction of functional photonic crystals”, [online], [Search June 10, 2004], Internet <URL: http: //www.kast.or. jp / kenkyu / seika / h15 / sato_2. pdf> Chem. Mater. 2002, 14, 760-765

  As described above, Kuniaki Nagayama et al. Have made a basic invention relating to the study of the self-assembly phenomenon of fine particles and the method of forming a fine particle assembly utilizing this phenomenon. In particular, in Patent Document 1, when forming a thin film-shaped fine particle aggregate, the fine particle density and the total number of fine particles of the thin film fine particle aggregate are determined using the moving speed of the meniscus tip, the volume fraction of the fine particles, and the liquid evaporation rate as parameters. It is an invention to control and is considered to be positioned as a superordinate concept of the present invention.

  However, Patent Document 1 is a patent for the basic research result of Kuniaki Nagayama and others, and only describes the basic and basic ones. The method of actually realizing the conditions required by Patent Document 1 is still a problem, and the method of obtaining industrially meaningful large-crystal thin-film fine particle aggregates is still a subject of research and development. . This is also reported in Non-Patent Document 1 or Non-Patent Document 4 published after Patent Document 1, while quoting the research results of Kuniaki Nagayama et al. It can be seen from what has been done.

  As described above, the method of actually obtaining a large-area thin-film fine particle aggregate is still a problem that has not been sufficiently solved even now.

  Next, the current state and problems of the method for forming a thin film particulate assembly utilizing the self-assembly phenomenon will be described. A method for forming a thin-film fine particle aggregate on a free-surface substrate by self-assembly of fine particles is described in Vicki L., et al. Colvin and Yuri A. It can be broadly divided into the so-called “Convective Self-Assembly” method that Vlasov is working on, and the pulling-up method performed in KAST and the like.

  The conductive Self-Assembly method is a method in which a finely wet dispersion substrate is immersed in a fine particle dispersion, the fine particle dispersion evaporates, and the wet interface of the fine particle dispersion retreats on the substrate. In this method, an array thin film is formed (FIG. 7). The pulling-up method is a method in which the substrate is gradually lifted from the fine particle dispersion after the substrate having good wettability is immersed in the fine particle dispersion.

  Both methods make it possible to obtain a particle aggregate having a face-centered cubic structure relatively easily by utilizing the self-assembly phenomenon of fine particles. Since the method uses the cohesive force between the fine particles generated when the raw material liquid in which the fine particles are dispersed dries, the growth rate of the thin-film fine particle aggregate is governed by the drying rate of the dispersion medium.

  Further, in the case of the reactive self-assembly method, the growth rate is usually 0.1 μm / s or less. Therefore, if a thin film-like fine particle aggregate having a size of several centimeters is to be formed, It takes a long time. In the case of the pulling method, the substrate is mechanically lifted from the fine particle dispersion. However, unlimited high-speed pulling growth is not possible, and even in the pulling method, the self-accumulation rate of the fine particles is dispersed. Since it is governed by the evaporation rate of the medium, it can be lifted only at a rate within the range of conditions in which the fine particles self-assemble. Therefore, if an attempt is made to obtain a thin film-like fine particle aggregate having a certain thickness, the pulling speed is almost the same as the retraction speed of the wetting interface due to drying of the dispersion medium. End up.

  The present invention has been made in view of the above points, and its object is to obtain a sufficient film thickness in a shorter time than before without degrading the quality of the fine particle aggregate. It is an object of the present invention to provide a method for producing a thin film-like fine particle aggregate utilizing self-assembly of fine particles.

  As a result of various studies to achieve the above object, the present inventor made a contact between a part of a substrate and a fine particle dispersion obtained by dispersing fine particles in a dispersion medium, and then the substrate, fine particle dispersion The above-mentioned problem is achieved by making the temperature of the substrate higher than the temperature of the fine particle dispersion when the three-phase contact line of the meniscus tip formed in the atmosphere of the liquid, the substrate and the fine particle dispersion is swept and expanded. As a result, the present invention has been completed.

That is, in the method for producing a thin-film fine particle assembly according to claim 1, after a part of a substrate is brought into contact with a fine particle dispersion obtained by dispersing fine particles in a dispersion medium, the substrate and the fine particles are obtained. A method for producing a thin-film fine particle assembly in which a three-phase contact line of a meniscus tip formed in an atmosphere of a dispersion, the substrate and the fine particle dispersion is swept and developed to produce a fine particle aggregate, The temperature of the substrate is made higher than the temperature of the fine particle dispersion , and the polarization state of adjacent beams is orthogonalized by using multiple beams at any position of the wetting film on the substrate surface formed in the vicinity of the three-phase contact line. And heating by changing the degree of heating .

The method for producing a thin-film fine particle assembly according to claim 2 is the method for producing a thin-film fine particle assembly according to claim 1, wherein the temperature of the fine particle dispersion is set in the atmosphere of the substrate and the fine particle dispersion. It is characterized by being higher than the temperature.

The method for producing a thin-film fine particle assembly according to claim 3 is the method for producing a thin-film fine particle assembly according to claim 1, wherein the temperature of the atmosphere of the substrate and the fine particle dispersion is higher than the temperature of the substrate. It is characterized by.

4. The method for manufacturing a thin film particulate assembly according to claim 4 , wherein the heating uses an energy beam generator in the manufacturing method of the thin film particulate assembly according to any one of claims 1 to 3. It is characterized by.

  In the method of manufacturing a thin film particulate assembly according to claim 1, since the temperature of the substrate is higher than the temperature of the particulate dispersion liquid, the evaporation from the wet film on the substrate surface is more than the evaporation from the reservoir of the particulate dispersion liquid. It becomes dominant, a high growth rate can be obtained, and a sufficient film thickness can be obtained in a shorter time than before without degrading the quality of the fine particle aggregate.

  In the method for producing a thin-film fine particle assembly according to claim 2, since the temperature of the fine particle dispersion is higher than the temperature of the atmosphere of the substrate and the fine particle dispersion, the convection of the fine particle dispersion becomes active, and the fine particles are dispersed in the fine particle dispersion. It is possible to effectively suppress precipitation in the medium.

  In the method of manufacturing a thin film particulate assembly according to claim 3, since the temperature of the atmosphere of the substrate and the particulate dispersion liquid is equal to or higher than the temperature of the substrate, the temperature condition is that the temperature of the substrate is higher than the temperature of the particulate dispersion liquid. It can be realized stably.

  In the method of manufacturing a thin film-like fine particle assembly according to claim 4, the temperature of the wet film on the substrate surface is easily increased because an arbitrary position of the wet film on the substrate surface formed in the vicinity of the three-phase contact line is heated. Can be raised.

  In the method for manufacturing a thin film particulate assembly according to claim 5, since the heating is performed by the energy beam generator, the temperature at any position of the wet film on the substrate surface or in the vicinity thereof can be more easily increased. .

  In the method of manufacturing a thin film particulate assembly according to claim 6, since the degree of heating differs depending on the position of the wet film on the surface of the substrate on which the thin film particulate aggregate is formed, Defects can be generated, and the generation of defects in the thin-film fine particle aggregate growing from a region where the degree of heating is strong can be prevented.

  As described above, in the method for forming the thin-film fine particle assembly 8 using the self-assembly phenomenon of the fine particles 6, the growth rate of the thin-film fine particle assembly 8 is governed by the drying speed of the dispersion medium 7.

  According to Dimitrov and the theory by Kuniaki Nagayama (Langmuir 1997, 12, 11303) used for explaining the self-assembly phenomenon of the fine particles 6, k = βLjφ / (0.605 dv (1 -Φ)) is established. Where k: number of particle layers, v: growth rate of particle film, φ: volume fraction of fine particles 6, j: evaporation rate of dispersion medium 7, L: length of wet film on substrate 1 surface, β: dispersion The ratio between the particle velocity and the flow velocity in the medium 7, d: the particle diameter of the fine particles 6 (see FIG. 2). The above equation can be rewritten as v = βLjφ / (0.605dk (1-φ)).

  Thus, the growth rate v of the particle film is proportional to the evaporation rate j of the dispersion medium 7. As can be seen from the above equation, in order to increase the growth rate v, the length L of the wetting film on the surface of the substrate 1 is increased (wetting the surface of the substrate 1 is improved), and the evaporation rate j of the dispersion medium 7 is increased. There is a method of increasing the volume fraction φ of the fine particles 6 (increasing the particle concentration). This point is as described in Patent Document 1.

  However, in practice, since it is difficult to control the length L of the wet film on the surface of the substrate 1, it is usually controlled by the concentration of the fine particle dispersion 2. In addition, the evaporation rate j of the dispersion medium 7 can be increased by increasing the temperature condition of the surface of the substrate 1, but the fine particle dispersion liquid can be increased simply by increasing the temperature condition of the surface of the substrate 1 during growth. Since the evaporation from the liquid reservoir 2 also increases, the concentration of the fine particle dispersion 2 increases during the growth of the film, and the growth conditions gradually shift (FIG. 9).

  Therefore, in the present invention, the temperature of the substrate 1 is set higher than the temperature of the fine particle dispersion 2. As a result, it is possible to increase the evaporation rate j from the wet film on the surface of the substrate 1 while preventing evaporation from the liquid reservoir of the fine particle dispersion 2, thereby realizing a large growth rate (FIG. 1). .

  In order to realize the condition that the temperature of the substrate 1 is higher than the temperature of the fine particle dispersion 2, it is preferable that the temperature of the fine particle dispersion 2 is higher than the temperature of the atmosphere 3 of the substrate 1 and the fine particle dispersion 2. This is because the convection of the fine particle dispersion 2 becomes active and the precipitation of the fine particles 6 in the fine particle dispersion 2 can be effectively suppressed.

  When the temperature of the fine particle dispersion 2 is higher than the temperature of the atmosphere 3 of the substrate 1 and the fine particle dispersion 2, the temperature of the container containing the fine particle dispersion 2 may be controlled. The temperature of the substrate 1 in the vicinity of the liquid 2 is set to be higher than the temperature of the atmosphere 3 of the substrate 1 and the fine particle dispersion 2, and as a result, the temperature of the fine particle dispersion 2 is higher than the temperature of the atmosphere 3 of the substrate 1 and the fine particle dispersion 2. May be higher.

  In order to realize the condition that the temperature of the substrate 1 is higher than the temperature of the fine particle dispersion 2, the temperature of the atmosphere of the substrate 1 and the fine particle dispersion 2 is set to be higher than the temperature of the substrate 1 in addition to the above-described method. preferable. This is because the temperature condition that the temperature of the substrate 1 is higher than the temperature of the fine particle dispersion 2 can be stably realized.

  When the temperature of the substrate 1 is made higher than the temperature of the fine particle dispersion 2, the temperature of the substrate 1 may be directly heated, and the temperature of the fine particle dispersion 2 and the atmosphere 3 of the substrate 1 and the fine particle dispersion 2 As a result, the temperature of the substrate 1 may be higher than the temperature of the fine particle dispersion 2.

  In order to realize the condition that the temperature of the substrate 1 is higher than the temperature of the fine particle dispersion 2, it is more preferable to heat an arbitrary position of the wetting film on the surface of the substrate 1 formed in the vicinity of the three-phase contact line 9. preferable. This is because the temperature of the wet film on the surface of the substrate 1 can be easily increased.

  It is more preferable to use an energy beam generator for the heating here. This is because the temperature of the wet film on the surface of the substrate 1 can be increased more easily. As an energy beam generator, the carbon dioxide laser irradiation apparatus 15 etc. are mentioned, for example.

  Further, it is more preferable that the degree of heating is changed depending on the position of the wet film on the surface of the substrate 1. An energy beam generator was used for heating to an arbitrary position of the wet film on the surface of the substrate 1 formed in the vicinity of the three-phase contact line 9 (hereinafter referred to as “in the vicinity of the growth front of the thin-film fine particle assembly 8”). Taking advantage of the feature, by creating a portion having a high degree of heating and a portion having a weak degree of heating in the vicinity of the growth front of the thin film-like fine particle assembly 8, defects are generated in the thin film-like fine particle assembly 8 growing from the region 27 having a low degree of heating. This is because it is possible to prevent generation of defects in the thin-film fine particle aggregate 8 that is generated and grows from the region 26 where the degree of heating is high.

  When the thin-film fine particle aggregate 8 formed by the conventional method shown in FIGS. 7 and 8 or the method of the present invention shown in FIGS. 1 and 3 is observed with a microscope, the growth direction is usually as shown in FIG. Boundary 20 parallel to is seen. Since the position where such a boundary 20 is generated is random, it may not be convenient when the thin-film fine particle assembly 8 is applied to a device or the like. Therefore, utilizing the feature of heating by the energy beam generator, a portion where the degree of heating is strong and weak as shown in FIG. 6 is created. By doing so, the growth front near the region 26 where the degree of heating is strong has a high evaporation rate of the dispersion medium 7, and the growth front near the region 27 where the degree of heating is weak compared with here. A state with a slow evaporation rate can be created. As a result, the growth starts from the position where the evaporation rate of the dispersion medium 7 is fast, and the position where the evaporation rate of the dispersion medium 7 is slow grows after this, and the thin film-like fine particle accumulation growing from the region 26 where the degree of heating is strong. Defects do not occur in the body 8, and defects can be collected in the thin-film fine particle assembly 8 that grows from the region 27 where the degree of heating is weak (FIG. 6).

  As a method of changing the degree of heating depending on the position of the wet film on the surface of the substrate 1, for example, by using a plurality of energy beam generators and superposing a plurality of laser beams, the degree of heating as shown in FIG. The strong region 26 and the weak region 27 can be formed. When superimposing laser beams, if the polarization states of adjacent laser beams are orthogonal to each other, the laser beams can be neatly superimposed.

  Hereinafter, the embodiment will be described in detail.

Example 1
The fine particle dispersion 2 was prepared as follows. Centrifugation was performed by dispersing spherical monodispersed silica particles having a particle diameter of 300 nm in an ethanol dispersion medium, and the supernatant was removed. Then, ethanol was added to the precipitate, and the spherical monodispersed silica particles were 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 was performed three times, and the fine particle dispersion was prepared by adjusting the concentration of the particles to 5% by weight upon the final addition of ethanol.

  The substrate 1 was 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 (rinse), and then dried.

  The pulling device 5 was disposed in the atmosphere 3 controlled to a temperature T3 = 25 ° C. The pulling device 5 has a drive mechanism capable of pulling up at a constant speed. The pulling device 5 includes a carbon dioxide laser irradiation device 15 for heating the vicinity of the growth front of the thin film particle assembly 8 and the thin film particle assembly 8. A radiation thermometer 19 for measuring the temperature in the vicinity of the growth front and a feedback mechanism 16 for feeding back the measured value of the radiation thermometer 19 to the carbon dioxide laser irradiation device 15 were provided. The temperature in the vicinity of the growth front of the thin film particulate assembly 8 was controlled to T1 (FIG. 3).

  In this embodiment, a carbon dioxide laser is used as an energy beam generator for heating, and the temperature of the substrate and the vicinity of the fine particle dispersion is T1 = 50 at the temperature T3 = 25 ° C. of the atmosphere of the fine particle dispersion. The temperature of the fine particle dispersion was set to a temperature T2 higher than the temperature T3 of the atmosphere of the substrate and the fine particle dispersion (T3 <T2 <T1). In FIG. 3, the temperature control mechanism of the container containing the fine particle dispersion is not described.

  Using the fine particle dispersion 2, the substrate 1, and the pulling device 5 described above, a part of the substrate 1 is brought into contact with the fine particle dispersion 2 as shown in FIG. 3, and then the substrate is pulled at a pulling rate of 1.0 μm / s. Raised one. The fine particle dispersion 2 was stabilized during growth at a temperature slightly higher than 25 ° C., which is the temperature of the atmosphere 3.

  As a result of growing under these conditions, a thin film-like fine particle assembly 8 having a length of about 1 cm could be obtained in 3 hours.

(Example 2)
The same fine particle dispersion 2 and substrate 1 as in Example 1 were used.

  The pulling device 5 was disposed in the atmosphere 3 controlled to a temperature T3. Further, the pulling device 5 has a drive mechanism that can be pulled at a constant speed, and has a cooling bath mechanism 11 that makes the temperature T2 of the fine particle dispersion 2 lower than the temperature T1 of the substrate 1. used. The cooling bath mechanism 11 was configured to cover as much as possible the liquid storage container containing the fine particle dispersion 2, so that the fine particle dispersion was not warmed from the atmosphere. Further, the upper surface of the liquid reservoir was covered (covered) 12 except for the portion where the substrate 1 was pulled up to prevent evaporation from the surface of the fine particle dispersion 2 (FIG. 4).

  In this example, the temperature adjustment of the cooling bath mechanism for cooling the reservoir of fine particle dispersion 2 is set to 25 ° C. in atmosphere 3 at temperature T3 = 50 ° C., and the temperature of fine particle dispersion 2 is determined from T3. The substrate 1 was pulled up from the fine particle dispersion 2 having a low temperature T2. Since the portion of the substrate 1 pulled up from the fine particle dispersion 2 is immediately exposed to the atmosphere of the temperature T3, T2 <T1 at the substrate position in the vicinity of the growth front of the thin film particle aggregate 8 during the pulling. It was stabilized at T1 where ≦ T3 (FIG. 4).

  Under this condition, as shown in FIG. 4, after a part of the substrate 1 was brought into contact with the fine particle dispersion 2, the substrate 1 was pulled up at a pulling rate of 1.0 μm / s.

  By performing this conditional growth, a thin film-like fine particle assembly 8 having a length of about 1 cm could be obtained in 3 hours.

(Example 3)
The same fine particle dispersion 2 and substrate 1 as in Example 1 were used. The pulling device 5 has substantially the same structure as that shown in FIG. 3, but a plurality of carbon dioxide laser generators are used in order to create a portion where the degree of heating is strong and a portion where heating is weak. A plurality of laser beams were superposed to form a region 26 having a high degree of heating and a region 27 having a weak degree as shown in FIG.

  Using the fine particle dispersion 2, the substrate 1, and the pulling device 5 described above, the average temperature of the substrate 1 in the vicinity of the growth front of the thin-film fine particle aggregate 8 is set to T1 = The substrate was pulled up at a pulling rate of 1.0 μm / s under control of 50 ° C. The temperature of the fine particle dispersion 2 was stabilized during the growth (T3 <T2 <T1) in a state slightly higher than 25 ° C., which is the temperature of the atmosphere 3.

  By growing under these conditions, a thin film-like fine particle assembly 8 having a length of about 1 cm could be obtained in 3 hours. Further, the boundary 20 generated in the obtained thin film-shaped fine particle assembly 8 is swept away to the region 27 where the degree of heating is weak, and the generation of the boundary cannot be recognized in the region 26 where the degree of heating is strong. It was.

It is a partial schematic sectional drawing which shows an example of the apparatus used for the manufacturing method of the thin film-form microparticle aggregate | assembly of this invention. It is a figure explaining each parameter governing a fine particle accumulation phenomenon. It is a schematic sectional drawing which shows an example of the apparatus used for the manufacturing method of the thin film-form microparticle aggregate | assembly of this invention. It is a schematic sectional drawing which shows another example of the apparatus used for the manufacturing method of the thin-film particulate assembly of this invention. It is explanatory drawing which shows the boundary seen in a thin film-form microparticle aggregate. It is explanatory drawing which shows the spatial modulation of a heating and sweeping of a boundary. It is the schematic which shows an example of the Conductive Self-Assembly method. It is the schematic which shows an example of the raising method. It is a figure explaining the subject which the present invention tends to solve.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Substrate 2 Fine particle dispersion 3 Atmosphere of substrate and fine particle dispersion 5 Lifting device 6 Fine particle 7 Dispersion medium 8 Thin film fine particle aggregate 9 Three-phase contact line 10 Meniscus 11 Cooling bath mechanism 12 Lid 15 Carbon dioxide laser irradiation device 16 Feedback mechanism ( Laser power)
17 Introduction Window 18 Condenser Lens 19 Radiation Thermometer 20 Boundary 21 Growth Upstream 22 Growth Downstream 23 Growth Direction 24 Crystal Phase of Fine Particle Aggregate 25 Liquid Phase of Fine Particle Aggregate 26 Region of High Heating 27 Region of Low Heating

Claims (4)

After bringing a part of the substrate into contact with the fine particle dispersion obtained by dispersing the fine particles in the dispersion medium, the tip of the meniscus formed in the atmosphere of the substrate, the fine particle dispersion, the substrate and the fine particle dispersion A method for producing a thin-film particulate assembly, in which a three-phase contact line is swept and developed to produce a particulate assembly,
The temperature of the substrate is higher than the temperature of the fine particle dispersion ,
Heating at any position of the wetting film on the substrate surface formed in the vicinity of the three-phase contact line with a plurality of beams so that the polarization states of adjacent beams are orthogonal to each other and changing the degree of heating. A method for producing a thin-film particulate assembly characterized by the above.   2. The method for producing a thin-film fine particle assembly according to claim 1, wherein the temperature of the fine particle dispersion is higher than the temperature of the atmosphere of the substrate and the fine particle dispersion.   2. The method for producing a thin film particulate assembly according to claim 1, wherein the temperature of the atmosphere of the substrate and the particulate dispersion is set to be equal to or higher than the temperature of the substrate. The method of manufacturing a thin film particulate assembly according to any one of claims 1 to 3 , wherein an energy beam generator is used for the heating.

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