JP5008865B2 - Thin film having surface fine uneven structure and method for producing the same - Google Patents

Description

  The present invention relates to a method for producing a thin film having a surface fine concavo-convex structure formed by self-organization without passing through a lithography process, and a thin film obtained thereby.

  In general, as a method for forming a fine concavo-convex structure, a lithography method for forming a fine relief shape by direct drawing using an electron beam resist or laser two-beam interference exposure method has been developed (for example, see Non-Patent Document 1). However, this method has a problem that it takes time for exposure and is not suitable for large area and mass production.

  Then, shape transfer methods, such as an injection molding method and a press processing method, are proposed as a method suitable for a large area and mass production (for example, refer nonpatent literature 1-2). This method uses a master in which a fine concavo-convex shape is formed on a resist material by the direct drawing method, and further produces a stamper (die) having a fine concavo-convex structure complementary to the master by electroforming. It is used to transfer to resin. However, the surface design using these technologies requires very advanced technology, the processing size is limited to about 1/10 micron, and the operation becomes more complicated as the processing size becomes smaller. There is a problem that a large investment is necessary.

  As another technique, a method using a microphase separation structure formed in a self-developed manner from a block copolymer has been reported as a method capable of easily performing nanometer-order patterning. For example, a sea-island micro phase separation membrane made of block polymer of polystyrene and polyisoprene is formed on a substrate, and osmium oxide is introduced into the polyisoprene phase by a gas phase reaction to improve etching resistance, and osmium oxide is selected. A method for forming a pattern using a chemically doped polyisoprene phase as a mask has been reported (for example, see Non-Patent Document 3).

  Such a method using a microphase separation structure of a block copolymer is simple and low-cost as compared with a lithography technique. However, ozone oxidation is complicated and the reaction time is relatively long, and it is difficult to improve the throughput. Moreover, since osmium oxide is highly toxic, its versatility is poor from the viewpoint of safety.

Hisao Kikuta The Institute of Electronics, Information and Communication Engineers J83-C (3), 173-181 (2000) A. Gombert, C.I. G. , Endeavor, 26, 79 (1967) M.M. park et al., Science, Vol. 276,1401-1406

  Accordingly, an object of the present invention is to provide a thin film having a fine concavo-convex structure that can be efficiently used in various fields, and a method for producing the same, in which a fine concavo-convex structure on the order of micrometers and nanometers can be efficiently obtained in a simple process It is in.

  The inventors of the present invention have intensively studied to achieve the above-mentioned object. After applying a crystalline polymer solution, in the thin film forming process for evaporating the solvent, various kinds of solvents can be used by changing the type of solvent and the solution concentration. The present inventors have found that a thin film having a surface fine concavo-convex structure having a size can be formed, and have completed the present invention.

That is, the method for producing a thin film of the present invention comprises a step of applying a solution obtained by dissolving polycaprolactone as a crystalline polymer in an organic solvent to a solid surface; And a step of forming a thin film having a surface fine concavo-convex structure by polymer crystallization accompanying evaporation.

  According to the method for producing a thin film of the present invention, the surface fine concavo-convex structure can be formed by a simple process without using a complicated process such as a resist or a vapor deposition method. At that time, a fine structure from the nanometer order to the micrometer order can be easily formed by a simple method of changing the boiling point or solution concentration of the organic solvent for dissolving the crystalline polymer. Furthermore, since a fine structure can be formed with less resources and energy than using a resist or a vapor deposition method in order to use the self-organization phenomenon of a solution, a manufacturing method that contributes to cost reduction can be provided. That is, according to the method for producing a thin film of the present invention, a fine uneven structure of micrometer order or nanometer order can be efficiently obtained by a simple process, and a thin film having a fine uneven structure usable in various fields is manufactured. Can do.

  As described above, in the thin film manufacturing method of the present invention, the crystallization speed can be changed by changing the boiling point of the organic solvent for dissolving the crystalline polymer and the solution concentration. The surface fine concavo-convex structure having an average concavo-convex period of 1 nm to 100 μm can be obtained.

  In the present invention, the evaporation rate of the solvent can be controlled by evaporating the solvent while rotating the solid surface.

  On the other hand, the thin film of the present invention is a thin film having a surface fine concavo-convex structure obtained by any of the thin film production methods described above. Since the thin film of the present invention has a micro uneven structure of micrometer order or nanometer order, it can be used as a functional material capable of exhibiting new functions such as electronic properties, conductive properties, and optical properties. Alternatively, the fine concavo-convex pattern provides a cell adhesion surface and can be used as a cell culture substrate serving as a cell support substrate and a nutrient supply route.

  Hereinafter, the best mode for carrying out the present invention will be described in detail.

  The method for producing a thin film of the present invention includes a step of applying a solution obtained by dissolving a crystalline polymer in an organic solvent to a solid surface. The polymer used in the present invention is not particularly limited as long as it is a crystalline polymer, and examples thereof include engineering plastics such as polyethylene, polypropylene, polyester, polycarbonate, polyamide, polyacetal, and polyvinyl alcohol, and general-purpose polymers. When used as a general industrial porous membrane, it is desirable to use an engineering plastic from the viewpoint of high strength, high elastic modulus, and flexibility.

  In addition, examples of the crystalline polymer include biodegradable polymers such as polylactic acid, polyhydroxybutyric acid, polycaprolactone, polyethylene adipate, and polybutylene carbonate, which are desirable from the viewpoint of being absorbed in the living body when used for medical purposes. . Of these, polybutylene carbonate, polyethylene carbonate and the like are preferable from the viewpoint of solubility in an organic solvent. Polylactic acid and polycaprolactone are desirable from the viewpoints of availability, price, and the like.

  The solvent that can be used in the present invention is not particularly limited as long as it dissolves the polymer to be used. Examples of organic solvents include halogenated organic solvents such as chloroform and methylene chloride, aromatic hydrocarbons such as benzene, toluene and xylene, esters such as ethyl acetate and butyl acetate, ketones such as acetone and methyl isobutyl ketone, Examples include ethers such as tetrahydrofuran, carbon disulfide and the like. These organic solvents may be used alone or in combination as a mixed solvent.

  The crystalline polymer solution preferably has a polymer concentration of 0.01 to 200 g / L, more preferably 0.1 to 100 g / L. If the polymer concentration is lower than 0.01 g / L, the resulting thin film tends to have insufficient mechanical strength. On the other hand, if the polymer concentration is higher than 200 g / L, the concentration tends to be too high and the periodic structure tends to collapse.

  As a base material that forms a solid surface, inorganic materials such as glass, metal, silicon wafers, or polymers having excellent organic solvent resistance such as polypropylene, polyethylene, and polyetherketone can be used. From the viewpoint of smoothness, it is desirable to use an inorganic material for the substrate.

  The method for applying the polymer solution may be any coating method, and examples thereof include spray coating, dip coating, drop coating, cast coating (cast), and spin coating. Although the temperature of the solution at the time of application | coating may be room temperature, you may heat to the glass transition temperature of the polymer used from 30 degreeC.

  The thickness of the solution at the time of application is preferably set so that the thickness of the thin film after evaporation of the solvent is 50 nm to 100 μm.

  The method for producing a thin film of the present invention includes a step of forming a thin film having a fine surface relief structure by evaporating the solvent in an open system or a closed system. By applying a polymer solution and evaporating the solvent on the substrate, a fine concavo-convex structure can be formed by polymer crystallization accompanying the evaporation of the solvent.

  At this time, the fine unevenness size can be controlled by controlling the solvent evaporation rate according to the boiling point of the solvent or the evaporation conditions. More specifically, the lower the boiling point of the solvent, the faster the solvent evaporation rate, and the smaller the fine unevenness size.

  As for the evaporation environment, there is a method for controlling the solvent evaporation rate depending on whether the application atmosphere is an open system in the atmosphere or a closed system, and a coating substrate is installed on a rotating body and a high There is a method of evaporating the solvent while rotating the substrate after dropping the molecular solution.

  The temperature of the solution during evaporation may be room temperature, but in order to increase the solvent evaporation rate, it may be heated to 30 ° C. to the glass transition temperature of the polymer used. When the solvent is evaporated while rotating the base material, the solvent evaporation rate can be made faster than the open system in the atmosphere by setting the rotation speed to 500 to 3000 rpm.

  The thin film of the present invention is preferably obtained by the production method of the present invention as described above, and is a thin film having a surface fine concavo-convex structure. Examples of the surface fine concavo-convex structure include those having an average concavo-convex period of 1 nm to 100 μm observed with an atomic force microscope.

  The surface fine concavo-convex structure of the obtained thin film can be observed more clearly with an atomic force microscope (AFM) photograph, but a structure in which a plurality of spherulites grow and their boundary lines become concave portions, and fine particles are connected. And a structure in which pores are formed therebetween, a structure in which fibrillated crystals are aggregated, and the like.

  The thin film of the present invention is a separation membrane used for microfiltration, food cleaning treatment, etc., industrial materials such as battery separators, medical materials such as bandages and paper diapers, rainy clothing, gloves, etc. It can be suitably used for preparation materials, pharmaceutical materials such as films that can contain a drug in the pores, cell culture, scaffolding materials, optical materials, and electronic materials for forming three-dimensional tissue bodies from cells. it can.

  Examples and the like specifically showing the configuration and effects of the present invention will be described below. In addition, the average uneven | corrugated period of the surface fine uneven structure observed with an atomic force microscope was measured as follows.

  The surface of the thin film was observed using an atomic force microscope (Nano Scope 3A-MMAFM manufactured by Nippon Bico Co., Ltd.), and the atomic force acting between the microprobe and the sample surface at that time was detected by the displacement of the cantilever. The amount of displacement was detected as the amount of laser beam displacement, the average unevenness period was analyzed, and the surface unevenness was analyzed.

Example 1
Poly ε-caprolactone (manufactured by Wako Pure Chemical Industries, Ltd., weight average molecular weight: 70,000 to 100,000) is dissolved in four solvents such as chloroform, ethyl acetate, tetrahydrofuran (hereinafter THF), or acetone, and the concentration is 1 g / L, 10 g / L, and 50 g / L. These solutions were cast on a glass petri dish, the solvent was evaporated in an open system and a closed system, and then vacuum dried at room temperature for 2 days to obtain a thin film (thickness: 100 nm to 1 μm). Details about the solvents used are given in Table 1.

A scanning electron microscope (SEM) photograph of the thin film thus obtained is shown in FIGS. 1 to 2, and an atomic force microscope (AFM) photograph of the thin film is shown in FIGS. Tables 2 to 3 show the results of analyzing surface irregularities from the results of AFM observation.

Example 2
Polyε-caprolactone (manufactured by Wako Pure Chemical Industries, Ltd., weight average molecular weight: 70,000 to 100,000) was dissolved in chloroform to prepare a concentration of 10 g / L. This solution was dropped on a glass substrate placed on a rotating body and rotated under the condition of a rotational speed of 1000 rpm × 10 seconds to evaporate the solvent and obtain a thin film. FIG. 5 shows the SEM photograph, AFM photograph, and surface roughness analysis result of the thin film (thickness 200 nm) thus obtained.

Scanning electron microscope (SEM) photograph of the thin film obtained in Example 1 (open system) Scanning electron microscope (SEM) photograph of the thin film obtained in Example 1 (sealed system) Atomic force microscope (AFM) photograph of the thin film obtained in Example 1 (open system) Atomic force microscope (AFM) photograph of the thin film obtained in Example 1 (sealed system) Scanning electron microscope (SEM) photograph and atomic force microscope (AFM) photograph of the thin film obtained in Example 2 (rotary evaporation method)

Claims (4)

A step of applying a solution obtained by dissolving polycaprolactone as an crystalline polymer in an organic solvent to a solid surface, and evaporating the solvent in an open system or a closed system, and crystallization of the polymer accompanying the solvent evaporation to form a surface fine uneven structure Forming a thin film comprising: a method for producing a thin film.   2. The method for producing a thin film according to claim 1, wherein an average concavo-convex period of the surface fine concavo-convex structure observed with an atomic force microscope is 1 nm to 100 μm.   The method for producing a thin film according to claim 1, wherein the solvent is evaporated while rotating the solid surface. The thin film which has the surface fine concavo-convex structure obtained by the manufacturing method of the thin film in any one of Claims 1-3.

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