JP2011161415A - Microparticle with controlled size and shape as well as method for manufacturing this microparticle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a microparticle which enables a highly efficient making of the microparticle with controlled size and shape, as well as the microparticle with controlled size and shape manufactured by this method. <P>SOLUTION: This method for manufacturing the microparticle with controlled size and shape features that the projecting part of an uneven pattern formed on the surface of a base by imprinting process, is isolated as the microparticle. Also, the microparticle manufactured by this method is provided. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method of producing fine particles having a controlled size and shape by using an imprint process, and fine particles produced by the method.

  Submicron to nanometer-sized microparticles have recently become increasingly important as starting materials for producing various functional devices. Various properties of fine particles vary depending on the size and shape of the fine particles. To optimize the properties of the fine particles, fine particles with controlled size and shape and excellent size uniformity are produced. It is required to do.

  Various methods such as a liquid phase method and a gas phase method have been reported as a method for producing fine particles, but it is not easy to produce fine particles having a controlled size and shape. Even when monodispersed fine particles with controlled size can be formed, such as polystyrene fine particles and silica fine particles, the shape of the obtained fine particles is often spherical, and it is difficult to produce fine particles with a controlled geometric shape. It is. According to a fine particle synthesis method using crystal growth like metal fine particles, it is possible to obtain fine particles having a cylindrical shape or the like, but in this case, it is difficult to make the sizes uniform.

  A mold process has been proposed as a method for producing fine particles whose size and shape are highly controlled. In the casting process, a nano-ordered structure material such as anodized porous alumina obtained by anodizing aluminum in an acidic bath is used as a casting mold. Filling the substance makes it possible to form fine particles with a controlled size and shape (Non-patent Document 1). However, since it is necessary to dissolve and remove the template in order to collect the fine particles formed in the pores, the template cannot be repeatedly used, and it is difficult to efficiently produce fine particles. Also, after forming a dot pattern by drawing on a two-layer resist using photolithography, it is reported that fine particles with excellent size uniformity can be formed by selectively dissolving and removing only the resist layer at the bottom. (Non-Patent Document 2). However, in photolithography, it is difficult to obtain a pattern with a large area with high throughput, and it is difficult to efficiently produce fine particles. In addition, applicable materials are limited to materials that can be used as a photoresist. There was a problem.

M. T. Tierney and C. R. Martin, J. Phys. Chem., 93, 2878 (1989) J. H. Moon, A. J. Kim, J. C. Crocker, and S. Yang, Adv. Mater., 19, 2508 (2007)

  As described above, it is difficult to efficiently produce monodispersed fine particles having a controlled size and shape by existing fine particle production processes represented by a liquid phase method and a gas phase method. On the other hand, if the mold process is used, it is possible to produce fine particles with controlled size and geometric shape, and in addition, it is applicable to a wide range of materials. However, in order to recover the fine particles formed using the template process, it is necessary to dissolve and remove the template, which has a problem of low throughput.

  Accordingly, an object of the present invention is to solve the problems of the conventional mold method and to imprint a process in which a mold as a starting structure can be repeatedly used for the purpose of producing fine particles with controlled size and shape with high efficiency. It is an object of the present invention to provide a method capable of efficiently producing fine particles having a controlled size and shape with high throughput, and a fine particle having a controlled size and shape produced by the method.

  In order to solve the above-mentioned problems, the present invention has been made as a result of intensive studies on a method for producing fine particles with controlled size and shape at high throughput. That is, the method for producing fine particles having a controlled size and shape according to the present invention comprises a method characterized in that the protrusions of the concavo-convex pattern formed on the substrate surface by the imprint process are isolated as fine particles. In addition, in the shape of the fine particles whose size and shape are controlled in the present invention, in addition to the granular shape such as a cylindrical shape, a cylindrical shape, a cone shape, a rectangular tube shape, a prismatic shape, a partial hollow shape, etc. Even relatively large fiber forms are included, and can include virtually any shape.

  In the method according to the present invention, a regular concavo-convex pattern is once formed on the substrate surface by an imprint process using a mold having a submicron to nanoscale fine pattern, and then the formed concavo-convex pattern is formed. By selectively peeling only the protrusions and collecting them as fine particles, it is possible to produce fine particles having a controlled size and shape.

  In the imprint process, a thermal imprint method in which a mold is pressed against a thermoplastic resin under a heating condition to transfer a fine pattern, or a photoimprint method using a photocurable resin can be used. Moreover, the method of imprinting on the precursor of metal oxides including silica and titanium oxide can also be used. According to the present invention, fine particles having a diameter of 500 nm or less and excellent in size uniformity can be produced as the fine particles to be isolated.

  In order to selectively peel and isolate only the protrusions of the concavo-convex pattern formed by the imprint process, a technique of mechanically scraping with a scraper or the like, or a technique of peeling with an adhesive tape can be used. In addition, the imprint mold in the imprint process is peeled off from the base material together with the protrusion-forming material of the concavo-convex pattern filled in the recess of the mold, and filled into the recess from the peeled mold recess. It is also possible to use a method of taking out the substances that have been used as fine particles.

  In addition, a solution containing a polymer is applied to the surface of the substrate on which the concavo-convex pattern is formed, and after the coating film is dried, only the protrusions of the concavo-convex pattern are selectively separated as fine particles from the substrate surface The fine particles can be recovered by isolating and dissolving the coating film. For example, it is also possible to use a technique in which a sacrificial layer that can be dissolved by post-processing is provided on the surface of the substrate after imprinting, and then peeled after the sacrificial layer is solidified. When the sacrificial layer is peeled off, only the protrusions of the concavo-convex pattern embedded therein can be selectively peeled off from the substrate. Further, if the peeled sacrificial layer is dissolved by post-treatment, the peeled fine particles can be collected. A polymer or an elastomer can be used for the sacrificial layer for peeling the fine particles, and the sacrificial layer can be easily formed by applying a solution in which these are dissolved to the substrate surface and drying. The sacrificial layer used in the present invention needs to use a material that can selectively dissolve the fine particle material in an insoluble solvent so that only the fine particles can be selectively recovered in the post-treatment. For example, fine particles produced using a photocurable resin are insoluble in an organic solvent such as acetone, and thus can be used as a sacrificial layer as long as the material is soluble in acetone.

  In the nanoimprint process, not only fine particles made of a resin or the like but also fine particles made of a metal oxide or metal can be produced. That is, the fine particles are produced on the assumption that the material of the protrusions of the concavo-convex pattern includes at least one of resin, metal oxide, or metal. It is also possible to obtain fine particles made of a metal oxide, a metal, or the like by forming a fine pattern using these materials and then performing a separation and recovery operation using the sacrificial layer in the same manner.

  In addition, by using two or more kinds of materials for forming an uneven pattern by imprinting, composite fine particles having a controlled size and shape can be easily produced. That is, the material of the projections of the concavo-convex pattern is made of two or more kinds of substances, and composite particles are produced by isolating the projections. For example, by forming a pillar array by photoimprinting using a monomer in which metal fine particles are dispersed and selectively isolating the pillar portion, metal fine particles / polymer composite fine particles having a controlled size and shape can be obtained. . In addition, by forming a concavo-convex pattern by imprinting on a thin film in which different polymers are layered, the formation of fine particles with a layered structure and the formation of fine particles by combining substances that can be selectively dissolved by post-processing It is also possible to form porous fine particles by dissolving a dissolvable substance by post-treatment.

  In addition, as a mold used for the imprint process, a mold produced by various lithography techniques can be used, but anodized porous alumina obtained by anodizing aluminum in an acid bath can also be used. Anodized porous alumina can control the pore diameter and pore depth with high precision on a nanoscale by changing the anodizing conditions. In addition, it is possible to form fine particles whose shape is highly controlled at the nanoscale. That is, a method using an anodized porous alumina or a positive mold produced using the same as a mold is applied as an imprint mold in the imprint process. Furthermore, since the anodized porous alumina can have a large area, the present invention can be implemented in a large area, and fine particles can be produced more efficiently.

  In the preparation of anodized porous alumina, a sulfuric acid electrolyte is used, a conversion voltage is 10V to 120V, a oxalic acid electrolyte is used, and a formation voltage is 30V to 130V. If anodization is performed under conditions of a voltage of 180 V to 220 V, porous alumina with regularly arranged pores of uniform size can be produced. By adopting these porous alumina as a mold for nanoimprinting, In addition, it is possible to produce fine particles whose size and shape are highly controlled.

  In addition, after anodizing under constant voltage conditions, once the oxide film is dissolved and removed, anodized porous alumina obtained by the technique of anodizing again under the same conditions, By using a highly ordered porous alumina obtained by forming a fine depression on the surface and anodizing it as a starting point for pore generation during anodization, the size and shape of the resulting fine particles can be increased with higher accuracy. It can also be controlled. Further, in the method of forming depressions in aluminum prior to anodic oxidation, it is possible to obtain porous alumina having triangular openings or square openings by controlling the arrangement pattern of the depressions. By using these porous aluminas, fine particles having a controlled cross-sectional geometry can also be formed. In addition, a sample having tapered pores can be obtained by employing a method in which anodization and wet etching are repeated a plurality of times during the production of porous alumina. If these are used as a mold, it is possible to obtain fine particles whose shape is controlled in the length direction in addition to the cross-sectional geometric shape, such as obtaining fine particles having a cone shape.

  Furthermore, anodized porous alumina formed on the surface of roll-shaped aluminum, or a roll-shaped mold prepared using the same as a mold can also be used as a continuous imprint mold. For example, if an aluminum round bar is anodized, it is possible to produce a roll-shaped nanoimprint mold with a regular hole array pattern formed on the surface. If imprinting is performed while rotating this, higher throughput is achieved. In addition, a nanopillar array pattern can be formed. By continuously applying and peeling the sacrificial phase to the nanopattern thus obtained, it becomes possible to form fine particles with higher throughput.

  The fine particles having a controlled size and shape according to the present invention are produced by a method using the imprint process as described above.

  As described above, according to the present invention, by using an imprint process in which a template as a starting structure can be repeatedly used, the protrusions of the concavo-convex pattern formed by the imprint process are selectively isolated to form fine particles. By doing so, it becomes possible to efficiently produce desired fine particles having a controlled size and shape with high throughput.

It is a schematic diagram which shows the basic concept of the manufacturing method of the microparticles | fine-particles based on this invention based on the imprint process. It is a schematic diagram of the isolation process of the microparticles | fine-particles by the mechanical scraping method in this invention. It is a schematic diagram of the isolation process of microparticles | fine-particles by the adhesive tape in this invention. It is a schematic diagram of the process which isolates microparticles | fine-particles after peeling a filling substance from a base material with the mold in this invention. It is a schematic diagram of the isolation process of microparticles | fine-particles by the sacrificial layer in this invention. It is the figure which showed the fine particle preparation using the anodized porous alumina in this invention typically by the sacrificial layer process. It is the figure which showed typically preparation of the cone-shaped microparticles | fine-particles using the anodized porous alumina which has a taper-shaped pore in this invention by a sacrificial phase process. It is a schematic diagram of the manufacturing process of the composite microparticles in the present invention. It is the figure which showed typically the manufacturing process of the composite fine particle using the technique of imprinting on the multilayer resist in this invention. It is the figure which showed typically the manufacturing process of the microparticles | fine-particles which have a hollow part in this invention. It is a figure which shows the observation result by the electron microscope of the fiber-like polymer microparticles | fine-particles obtained in Example 1. FIG. It is a figure which shows the observation result by the electron microscope of the cone-shaped polymer microparticles | fine-particles obtained in Example 2. FIG. It is a figure which shows the observation result by the electron microscope of the cone-shaped polymer fine particle obtained in Example 3. FIG.

Embodiments of the fine particle production method of the present invention will be described below in detail with reference to the drawings.
FIG. 1 schematically shows the basic concept of the fine particle production method of the present invention based on the nanoimprint process. In FIG. 1, reference numeral 1 denotes an imprint mold, and an uneven pattern 3 is formed on the surface of a substrate 2 by an imprint process using the imprint mold 1. Only the protrusions 4 of the concavo-convex pattern 3 are selectively isolated as fine particles, and fine particles 5 having a controlled size and shape are obtained after the isolation.

  FIG. 2 shows a method for isolating the protrusions 4 of the concavo-convex pattern 3 formed on the surface of the substrate 2 using the imprint mold 1 as shown in FIG. Is schematically shown. In the illustrated example, a scraper 6 is used for mechanical scraping.

  FIG. 3 shows the fine particles 5 by peeling off the protrusions 4 of the concavo-convex pattern 3 formed on the surface of the substrate 2 using the imprint mold 1 as shown in FIG. A method for isolation is schematically shown.

  FIG. 4 shows an imprint pattern 3 formed on a surface 2a for forming an uneven pattern on the surface of a substrate 2 by using an imprint mold 1 having a recess 1a similar to that shown in FIG. The mold 1 is peeled off from the base material 2 together with the protrusion forming material 4a of the uneven pattern 3 filled in the recess 1a of the mold 1, and the recess 1a is filled from the peeled recess 1a of the mold 1; A method of isolating the fine particles 5 by taking out the substance 4a formed in the fine particle shape as the desired fine particles 5 having a controlled size and shape is schematically shown.

  FIG. 5 shows a case where a dissolvable sacrificial layer 8 is applied on the concavo-convex pattern 3 having the protrusions 4 formed on the surface of the substrate 2 using the imprint mold 1 as shown in FIG. The layer 8 is dried and solidified, and then the sacrificial layer 8 is peeled off together with the protrusions 4, and then the sacrificial layer 8 is dissolved to obtain the isolated fine particles 5.

  FIG. 6 shows, as an imprint mold, anodized porous alumina 10 in which pores 9 having a controlled size and shape are arranged with high regularity, and has protrusions 4 formed on the surface of the substrate 2. The uneven pattern 3 is formed. After removing the anodized porous alumina 10 as an imprint mold, a dissolvable sacrificial layer 8 is applied onto the concave / convex pattern 3 in the same manner as shown in FIG. 4, and the sacrificial layer 8 is dried and solidified. The method for separating the sacrificial layer 8 together with the protrusions 4 and then dissolving the sacrificial layer 8 to obtain the isolated fine particles 5 is schematically shown.

  7 uses an anodized porous alumina 12 having tapered pores 11 as an imprint mold, and has tapered pores 11 on the surface of the substrate 2 as compared with the embodiment shown in FIG. As a structure transfer layer of the anodized porous alumina 12, a concavo-convex pattern 13 having a cone-shaped protrusion 14 is formed. After removing the anodized porous alumina 12 as an imprint mold, a dissolvable sacrificial layer 15 is applied onto the uneven pattern 13 in the same manner as shown in FIG. 5, and the sacrificial layer 15 is dried and solidified. Then, the sacrificial layer 15 is peeled off together with the protrusions 14, and then the sacrificial layer 15 is dissolved to obtain isolated cone-shaped fine particles 16.

  FIG. 8 schematically shows an example of the formation process of the composite fine particles. A composite material layer 23 of the substance A (21) and the substance B (22) is provided on the base material 2 (substrate), and on the surface of the composite material layer 23, as shown in FIG. The uneven pattern 3 is formed by an imprint process using the mold 1. Only the protrusions 4 of the concavo-convex pattern 3 are selectively isolated as fine particles, and after the isolation, the composite fine particles 24 in which the size and shape are controlled and the substance B (22) is mixed in the substance A (21). Is obtained.

  In FIG. 9, the multilayer resist 31 is imprinted using, for example, anodized porous alumina 32 to form a concavo-convex pattern 34 having a protrusion 33 in which the configuration of the multilayer resist 31 remains, and then the protrusion 33 3 schematically shows a process for producing a microparticle 35 having a multilayer structure by isolating the microparticles as microparticles.

  FIG. 10 shows an imprint using, for example, anodized porous alumina 41 to form a concavo-convex pattern 44 having protrusions 43 including particles 42, and the protrusions 43 including particles 42 are isolated to form fine particles including particles 42. 45 schematically illustrates a process for producing a fine particle 47 (fine particle having a hollow portion) in which a hollow portion 46 is formed by dissolving and removing particles 42 contained therein by post-processing. is there.

Example 1 [Formation of Isolated Polymer Fiber by Photoimprint Process]
A SiC mold having a structure in which protrusions were regularly arranged with a period of 500 nm was pressed against the surface of an aluminum plate having a purity of 99.99% to form a fine uneven pattern on the surface. The textured aluminum plate was anodized in an aqueous phosphoric acid solution adjusted to a concentration of 0.1 M at a bath temperature of 0 ° C. under a direct current of 200 V for 5 minutes, 10 minutes, and 30 minutes. Thereafter, the substrate was immersed in a 10% by weight phosphoric acid aqueous solution for 60 minutes, and subjected to pore diameter expansion treatment. The produced anodized porous alumina was immersed in a fluoroalkylsilane solution and subjected to a surface release treatment. The produced anodized porous alumina was used as a mold for photoimprinting on a photocurable resin, and a nanofiber array was formed on the surface of the substrate. A toluene solution in which an elastomer was dissolved was applied to the surface of a substrate formed by nanoimprinting and dried and solidified, and then the elastomer layer was peeled off to isolate nanofibers. The peeled elastomer film was immersed in toluene, dissolved and removed, and then recovered by filtering the polymer fiber fine particles dispersed in toluene into a filter. From observation with a scanning electron microscope, it was confirmed that the obtained isolated polymer fiber had a diameter of 250 nm and a length of 2 μm, 4 μm, and 6 μm, respectively. FIG. 11 shows the observation results of the obtained polymer fibers (fiber-like polymer fine particles) with an electron microscope.

Example 2 (Preparation of cone-shaped polymer fine particles)
A SiC mold having a structure in which protrusions were regularly arranged with a period of 500 nm was pressed against the surface of an aluminum plate having a purity of 99.99% to form a fine uneven pattern on the surface. A textured aluminum plate is anodized in a phosphoric acid aqueous solution adjusted to a concentration of 0.1 M at a bath temperature of 0 ° C. under a direct current of 200 V for 3 minutes, and then a 10 wt% phosphoric acid aqueous solution, bath temperature. An operation of immersing in 30 ° C. for 25 minutes was repeated 5 times to obtain anodized porous alumina having tapered pores. The produced anodized porous alumina was immersed in a fluoroalkylsilane solution and subjected to a surface release treatment. The produced anodized porous alumina was used as a mold to perform photoimprinting on a photocurable resin, thereby forming a tapered pillar array on the surface of the substrate. A toluene solution in which an elastomer was dissolved was applied to the surface of a substrate formed by nanoimprinting and dried and solidified, and then the elastomer layer was peeled off to isolate cone-shaped polymer particles. The peeled elastomer film was immersed in toluene, dissolved and removed, and then collected by filtering the cone-shaped polymer fine particles dispersed in toluene into a filter. The observation result by the electron microscope of the obtained cone-shaped polymer fine particles is shown in FIG.

Example 3 [Fine particle formation from polymer pattern prepared by continuous imprint process]
Anodized aluminum roll with a diameter of 75 mm and a length of 90 mm under conditions of 0.3M oxalic acid bath, bath temperature 17 ° C, formation voltage 40V, and then immersed in the chromic phosphate mixed solution, the oxide film only The porous alumina having tapered pores is obtained by selectively dissolving and removing, anodizing again for 25 seconds under the same conditions, and then performing an etching operation for 5 minutes in a 5% by weight phosphoric acid aqueous solution 5 times. Formed. The surface of the produced porous alumina was immersed in a fluoroalkylsilane solution, and the surface was subjected to mold release treatment to form a roll mold. A taper-shaped polymer pillar array having a diameter of 70 nm and a protrusion height of 200 nm was continuously formed by imprinting the photocurable resin while rotating the obtained roll-shaped mold. A toluene solution in which an elastomer was dissolved was applied to the surface of the prepared nanopattern and dried and solidified, and then the elastomer layer was peeled off to isolate cone-shaped polymer particles. The peeled elastomer film was immersed in toluene, dissolved and removed, and then collected by filtering the cone-shaped polymer fine particles dispersed in toluene into a filter. The observation result of the obtained cone-shaped polymer fine particles with an electron microscope is shown in FIG.

  Since the fine particles having a controlled size and shape obtained by the present invention can be efficiently produced with high throughput, they can be applied to any application that requires fine particles having excellent size uniformity industrially.

DESCRIPTION OF SYMBOLS 1 Imprint mold 1a Mold hollow 2 Base material 2a Uneven pattern formation layer 3, 13, 34, 44 Uneven pattern 4, 14, 33, 43 Protrusion 4a Protrusion formation material 5, 16 Fine particle 6 Scraper 7 Adhesive tape 8, 15 Sacrificial layer 9, 11 Pore 10, 12, 32, 41 Anodized porous alumina 21 Substance A
22 Substance B
23 Composite Material Layer 24 Composite Fine Particle 31 Multilayer Resist 35 Fine Particle 42 with Multilayer Structure Particle 45 Particle Fine Particle 46 Hollow Part 47 Fine Part with Hollow

Claims (16)

  A method for producing fine particles having a controlled size and shape, characterized in that protrusions of a concavo-convex pattern formed on a substrate surface by an imprint process are isolated as fine particles.   The method for producing fine particles having a controlled size and shape according to claim 1, wherein the diameter of the fine particles to be isolated is 500 nm or less.   The method for producing fine particles with controlled size and shape according to claim 1 or 2, wherein the protrusions of the concavo-convex pattern are isolated by mechanically scraping.   The method for producing fine particles with controlled size and shape according to claim 1 or 2, wherein the protrusions of the concavo-convex pattern are isolated by peeling with an adhesive tape.   The imprint mold in the imprint process was peeled off from the base material together with the projection forming material of the concavo-convex pattern filled in the recess of the mold, and was filled in the recess from the peeled mold recess The method for producing fine particles with controlled size and shape according to claim 1 or 2, wherein the substance is taken out as fine particles.   By applying a solution containing a polymer to the surface of the substrate on which the concavo-convex pattern is formed, drying the coating film, and then peeling the coating film, only the protrusions of the concavo-convex pattern are selectively isolated as fine particles from the substrate surface The method for producing fine particles having a controlled size and shape according to claim 1 or 2, wherein the fine particles are collected by dissolving the coating film.   The size and shape-controlled fine particle production according to any one of claims 1 to 6, wherein the material of the projections of the concavo-convex pattern includes at least one of a resin and a metal oxide. Method.   The material according to any one of claims 1 to 7, wherein a material of the projection part of the concavo-convex pattern is made of two or more kinds of materials, and the composite fine particles are produced by isolating the projection part. A method for producing fine particles having a controlled shape.   9. Fine particles with controlled size and shape according to any one of claims 1 to 8, wherein an anodized porous alumina or a positive mold produced using the same as a mold is used as an imprint mold in the imprint process. Manufacturing method.   The size- and shape-controlled fine particles according to claim 9, wherein sulfuric acid is used as an electrolytic solution and anodized porous alumina having pores regularly arranged at a conversion voltage of 10V to 120V is used. Production method.   The fine particles with controlled size and shape according to claim 9, wherein oxalic acid is used as an electrolytic solution and anodized porous alumina having pores regularly arranged at a conversion voltage of 30V to 130V is used. Manufacturing method.   The fine particles with controlled size and shape according to claim 9, wherein phosphoric acid is used as an electrolytic solution, and anodized porous alumina having pores regularly arranged at a chemical conversion voltage of 180V to 220V is used. Manufacturing method.   After anodizing at a constant voltage, once the oxide film is dissolved and removed, anodized porous alumina in which pores prepared by anodizing again under the same conditions are regularly arranged from the surface side should be used. The method for producing fine particles having controlled size and shape according to any one of claims 9 to 12.   The anodized porous alumina prepared by forming a fine depression on the surface of aluminum prior to anodization and using this as a starting point for generating pores during anodization is used. A method for producing fine particles having a controlled size and shape.   The anodized porous alumina formed on the surface of roll-shaped aluminum, or a roll-shaped mold prepared using the same as a mold is used as a mold for continuous imprinting. A method for producing fine particles having a controlled size and shape.   Microparticles having a controlled size and shape, produced by the method according to claim 1.

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