JP5762686B2 - Method for producing fine particles - Google Patents

Description

The present invention relates to a method of manufacturing a controlled particle size and shape by using the imprint process.

  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.

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 according to the present invention applies a solution containing a polymer to a substrate surface on which an uneven pattern has been formed by an imprint process, and after drying the coating film, the unevenness is removed from the substrate surface. It consists of a method characterized in that only the projections of the pattern are selectively peeled off as fine particles, and the fine particles are recovered by dissolving the coating film. 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 size uniformity can be produced as fine particles.

The order to selectively stripping only the protrusions of the uneven pattern formed by imprinting process filling, and methods scraping mechanically by scraper or the like, the imprint mold in the imprint process, in a recess of the mold The method of removing the material filled in the dents from the base of the mold with the concavo-convex pattern projection portion forming material peeled off from the base of the peeled mold can be considered, but in the present invention, in particular, The following method is adopted.

As the above method, a solution containing a polymer is applied to the surface of the substrate on which the concavo-convex pattern is formed, and after drying the coating film, only the protrusions of the concavo-convex pattern are selectively selected as fine particles from the substrate surface. Fine particles can be collected by peeling 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 substances, and the projections are peeled from the surface of the base material to produce composite fine particles. For example, by forming a pillar array by photoimprinting using a monomer in which metal fine particles are dispersed and selectively peeling off 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.

Controlled microparticles of definitive size and shape to the present invention are those produced by the 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 peeled to form fine particles. This makes it 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 a fine particle peeling process by a mechanical scraping technique as a reference example of the present invention. It is a schematic diagram of the peeling process of microparticles | fine-particles by the adhesive tape as a reference example of this invention. It is a schematic diagram of the process which peels microparticles | fine-particles after peeling a filling substance from a base material with the mold as a reference example of this invention. It is a schematic diagram of the fine particle peeling process by the sacrificial layer in the present invention. It is the figure which showed typically microparticle preparation using the anodized porous alumina in this invention 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 layer 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 method 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, as a reference example of the present invention, by mechanically scraping 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. The method of peeling as the fine particles 5 is schematically shown. In the illustrated example, a scraper 6 is used for mechanical scraping.

FIG. 3 shows, as a reference example of the present invention, the protrusion 4 of the concavo-convex pattern 3 formed on the surface of the substrate 2 using the imprint mold 1 as shown in FIG. The method of peeling as the fine particles 5 by peeling is schematically shown.

FIG. 4 shows a concavo-convex pattern 3 on a layer 2a for forming a concavo-convex 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 imprint mold 1 is peeled 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 from the inside of the recess 1a of the peeled mold 1, A method of separating the fine particles 5 by taking out the substance 4a filled in the hollow 1a and formed into a 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 peeled 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 removing the sacrificial layer 8 together with the protrusions 4 and then dissolving the sacrificial layer 8 to obtain the separated 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 peeled 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 substrate 2, and the imprint mold 1 is formed on the surface of the composite material layer 23 in the same manner as shown in FIG. The uneven pattern 3 is formed by the imprint process used. Only the protrusions 4 of the concavo-convex pattern 3 are selectively peeled as fine particles. After peeling, the size and shape are controlled, and composite fine particles 24 in which the substance B (22) is mixed in the substance A (21) are obtained. It is done.

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 fine particles 35 having a multilayer structure by peeling off as fine particles.

In FIG. 10, for example, an anodized porous alumina 41 is used for imprinting to form a concavo-convex pattern 44 having protrusions 43 including particles 42, and the protrusions 43 including particles 42 are peeled 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. After the elastomer was applied and dried and solidified toluene solution of the surface of the formed substrate by nanoimprint, peeling the elastomeric layer was subjected to a peeling of the 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 peeled 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 [Production 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 peel off the 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, then immersed in chromic phosphoric acid mixed solution, only oxide film The porous alumina having tapered pores is obtained by selectively dissolving and removing, performing anodization again for 25 seconds under the same conditions, and then performing an etching operation for 7 minutes in a 5 wt% 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. After the elastomer to the surface of the fabricated nano pattern was applied and dried and solidified toluene solution of, peeling the elastomeric layer was subjected to a peeling of the 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 Having Multilayer Structure 42 Particle 45 Fine Particle 46 Containing Particle Hollow Part 47 Fine Part Having Hollow Part

Claims (11)

The solution containing the polymer is applied to the imprint process concavo-convex pattern formed surface of the substrate, selectively peeled after drying the coating film, only the protrusions of the uneven pattern from the substrate surface by peeling the fine particles And collecting the fine particles by dissolving the coating film.   The method for producing fine particles according to claim 1, wherein the diameter of the fine particles is 500 nm or less.   The method for producing fine particles according to claim 1 or 2, wherein the material of the protrusions of the concavo-convex pattern includes at least one of resin or metal oxide. The material of the protrusion part of the said uneven | corrugated pattern consists of two or more types of substances, and composite fine particle is produced by peeling this protrusion part from the base-material surface, The one in any one of Claims 1-3 characterized by the above-mentioned. Method for producing fine particles.   The method for producing fine particles according to any one of claims 1 to 4, wherein anodized porous alumina or a positive mold produced using the same as a mold is used as an imprint mold in the imprint process.   6. The method for producing fine particles according to claim 5, 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.   6. The method for producing fine particles according to claim 5, wherein anodized porous alumina using oxalic acid as an electrolytic solution and regularly formed with pores prepared at a conversion voltage of 30 V to 130 V is used.   6. The method for producing fine particles according to claim 5, wherein phosphoric acid is used as an electrolytic solution, and anodized porous alumina in which pores prepared at a conversion voltage of 180 to 220 V are regularly arranged is used.   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 according to any one of claims 5 to 8, which is characterized by the following.   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 pore generation during anodization is used. A method for producing the fine particles according to claim 1.   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.

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