JP2008156716A - Manufacturing method of fine structure and fine structure - Google Patents

Abstract

The present invention provides a method for manufacturing a structure capable of obtaining a structure having micropores with excellent roundness in a short time.
[Solution]
(1) The process of forming the hollow which has a desired arrangement | sequence on the aluminum member surface,
(2) a step of anodizing the aluminum member to form an anodized film having micropores;
(3) a step of dissolving at least a part of the anodized film with an acid or an alkali, and (4) a step of anodizing, thereby growing new micropores in the depth direction in this order. A manufacturing method of a fine structure including the same.
[Selection figure] None

Description

  The present invention relates to a method for manufacturing a fine structure and a fine structure.

  In the technical fields of metal and semiconductor thin films, thin wires, dots, etc., the phenomenon of electrical, optical and chemical peculiarities can be seen by confining the movement of free electrons in a size smaller than a certain characteristic length. It has been known. Such a phenomenon is called “quantum mechanical size effect (quantum size effect)”. Research and development of functional materials applying such a unique phenomenon is being actively conducted. Specifically, a material having a structure finer than several hundred nm is referred to as a “microstructure” or “nanostructure”, and is one of the objects of material development.

  As a method for manufacturing such a fine structure, for example, a method for directly manufacturing a nano structure by a semiconductor processing technique including a fine pattern forming technique such as photolithography, electron beam exposure, and X-ray exposure can be given.

In particular, much research has been conducted on a method for manufacturing a microstructure having a regular microstructure.
For example, as a method for forming a regular structure in a self-regulating manner, an anodized alumina film (anodized film) obtained by subjecting aluminum to an anodizing treatment in an electrolytic solution can be mentioned. It is known that a plurality of fine pores (micropores) having a diameter of about several nm to several hundred nm are regularly formed in the anodized film. Using this self-ordering of the anodic oxide film to obtain a perfectly regular arrangement, theoretically, hexagonal prism cells with a regular hexagonal bottom surface are formed around the micropores, and adjacent micropores are formed. It is known that the connecting line forms an equilateral triangle.

As examples of applications of such an anodized film having micropores, optical functional nanodevices, magnetic devices, luminescent carriers, catalyst carriers and the like are known. For example, Patent Document 1 describes that a pore is sealed with a metal to generate localized plasmon resonance and applied to an apparatus for Raman spectroscopic analysis.
Patent Document 2 discloses an anodized porous alumina having a pore on the surface and having a tapered shape in which the pore diameter continuously changes by combining anodization and pore diameter enlargement treatment. Manufacturing is described.

Prior to the anodic oxidation treatment for forming such micropores, a method is known in which a depression that is a starting point for generating micropores in the anodic oxidation treatment is formed. By forming such depressions, it becomes easy to control the variation of the micropore arrangement and the pore diameter within a desired range.
As a general method for forming the depression, a self-ordering method using the self-ordering property of the anodized film is known. This is a method for improving the regularity by utilizing the property that the micropores of the anodized film are regularly arranged and removing the factors that disturb the regular arrangement.
In this self-ordering method, as described in Patent Document 1, after anodizing once, an immersion treatment in a mixed aqueous solution of phosphoric acid and hexavalent chromic acid is performed, and then the anodizing treatment is performed again in order. Is common.

JP 2005-307341 A JP 2005-156695 A

However, the film removal process using a mixed aqueous solution of phosphoric acid and hexavalent chromic acid usually requires a long time of several hours to several tens of hours, although it varies depending on the thickness of the anodized film. .
Further, depending on the application of the magnetic device or the like, not only a regular arrangement but also that the formed pores are close to a perfect circle is an indispensable condition, and the conventional manufacturing method requires further improvement.
Therefore, an object of the present invention is to provide a method for producing a microstructure having a regular arrangement and excellent roundness of pores in a short time, and a structure obtained thereby.

  As a result of diligent research to achieve the above object, the present inventor formed a recess having a desired arrangement on the surface of an aluminum member, and performed anodization, film dissolution, and anodization in this order in a short time. The inventors have found that a fine structure having highly circular micropores can be obtained, and have completed the present invention.

That is, the present invention provides the following (i) to (iv).
(I) A method for producing a microstructure including the following steps in this order:
(1) The process of forming the hollow which has a desired arrangement | sequence on the aluminum member surface,
(2) a step of anodizing the aluminum member to form an anodized film having micropores;
(3) a step of dissolving at least a part of the anodized film with an acid or an alkali;
(4) A step of anodizing to grow new micropores in the depth direction.
(Ii) A manufacturing method of the microstructure according to the manufacturing method of (i), further including (5) removing a part of the anodized film so that the cross-sectional shape of the micropore has a straight tube structure.
(Iii) Manufacturing method of fine structure including the following steps in this order:
(1) The process of forming the hollow which has a desired arrangement | sequence on the aluminum member surface,
(2) a step of anodizing the aluminum member to form an anodized film having micropores;
(3) a step of dissolving at least a part of the anodized film with an acid or an alkali;
(4) Anodizing, thereby growing new micropores in the depth direction;
(5) a step of removing a part of the anodized film so that the cross-sectional shape of the micropore has a straight tube structure;
(6) A step of repeating the step (4) and the step (5) at least once.
(Iv) A fine structure obtained by the method for producing a fine structure according to any one of (i) to (iii) above.

  According to the method for manufacturing a fine structure of the present invention, a fine structure having micropores with high roundness can be obtained in a short time.

The present invention is described in detail below.
The production method of the present invention comprises:
(I) A method for producing a microstructure including the following steps in this order:
(1) The process of forming the hollow which has a desired arrangement | sequence on the aluminum member surface,
(2) a step of anodizing the aluminum member to form an anodized film having micropores;
(3) a step of dissolving at least a part of the anodized film with an acid or an alkali;
(4) A step of anodizing to grow new micropores in the depth direction.
(Ii) The microstructure according to (i), further including (5) a step of removing a part of the anodized film so that a cross-sectional shape of the micropore has a straight tube structure. Manufacturing method.
(Iii) A step of further repeating the step (4) and the step (5) at least once in the step (ii).

<Aluminum member>
The aluminum member used in the present invention has an aluminum substrate and an anodized film having micropores present on the surface of the aluminum substrate. This aluminum member can be obtained by anodizing at least one surface of an aluminum substrate.

  1 and 2 are schematic end views of an aluminum member and a microstructure for explaining the method for manufacturing a microstructure according to the present invention.

<Aluminum substrate>
The aluminum substrate is not particularly limited. For example, a pure aluminum plate; an alloy plate containing aluminum as a main component and containing a small amount of foreign elements; a substrate obtained by depositing high-purity aluminum on low-purity aluminum (for example, recycled material); silicon Examples of the substrate include a substrate in which high purity aluminum is coated on the surface of a wafer, quartz, glass or the like by a method such as vapor deposition or sputtering; a resin substrate in which aluminum is laminated.

  Of the aluminum substrate, the surface on which the anodized film is provided by anodizing treatment preferably has an aluminum purity of 99.5% by mass or more, more preferably 99.9% by mass or more, and 99.99% by mass. % Or more is more preferable. When the aluminum purity is in the above range, the regularity of the pore arrangement is sufficient.

  The shape of the aluminum substrate is not particularly limited. For example, an aluminum web may be sufficient and a sheet-like sheet may be sufficient.

<Conveying web by roll>
When the aluminum substrate is an aluminum web, it is preferable to perform film dissolution treatment, anodizing treatment, and straight tube treatment, which will be described later, while conveying the aluminum web.
In the conveyance of the aluminum web, from the viewpoint of carrying a large amount and stably, it is preferable that the radius of curvature of the conveyance roll used therein is 50 mm or more, more preferably 70 mm or more, and further more preferably 100 mm or more. preferable. When it is within the above range, the aluminum web is less likely to be cut by applying a strong pressure to the transport roll.

  The width of the aluminum web is preferably 50 mm or more, more preferably 100 mm or more, and further preferably 150 mm or more from the viewpoint of mass conveyance. When it is in the above range, there is little possibility that the aluminum web will be cut by tension.

The conveyance speed is preferably 1 mm / min to 150 m / min from the viewpoint of mass conveyance, more preferably 10 mm / min to 100 m / min, and still more preferably 50 mm / min to 50 m / min. . Within the above range, there is little possibility that the aluminum web will be cut because the conveying speed is too high, and the productivity is not too low because the conveying speed is too slow.
The method of conveyance may be either continuous or discontinuous.

  The surface of the aluminum substrate is preferably subjected to degreasing and mirror finishing in advance.

  Moreover, when using the microstructure obtained by this invention for the use using a light transmittance, it is preferable to heat-process an aluminum substrate previously. By heat treatment, a region having a high regularity of pore arrangement is widened.

<Heat treatment>
When heat treatment is performed, it is preferably performed at 200 to 350 ° C. for about 30 seconds to 2 minutes. Thereby, the regularity of the arrangement | sequence of the micropore produced | generated by the anodic oxidation process mentioned later improves.
The aluminum substrate after the heat treatment is preferably cooled rapidly. As a method of cooling, for example, a method of directly feeding into water or the like can be mentioned.

<Degreasing treatment>
Degreasing treatment uses acids, alkalis, organic solvents, etc. to dissolve and remove organic components such as dust, fat, and resin that adhere to the aluminum surface, and causes defects in each treatment described later due to the organic components. This is done for the purpose of preventing the occurrence of.
A conventionally known degreasing agent can be used for the degreasing treatment. Specifically, for example, various commercially available degreasing agents can be used by a predetermined method.

Especially, the following each method is illustrated suitably.
A method in which an organic solvent such as alcohol (for example, methanol), ketone, benzine, volatile oil or the like is brought into contact with the aluminum surface at room temperature (organic solvent method); a solution containing a surfactant such as soap or neutral detergent at a temperature from 80 to 80 A method in which the aluminum surface is contacted at a temperature up to ℃, and then washed with water (surfactant method); a sulfuric acid aqueous solution having a concentration of 10 to 200 g / L is brought into contact with the aluminum surface at a temperature from room temperature to 70 ° C for 30 to 80 seconds. Then, a method of washing with water; while a sodium hydroxide aqueous solution having a concentration of 5 to 20 g / L was brought into contact with the aluminum surface at room temperature for about 30 seconds, a direct current having a current density of 1 to 10 A / dm ² was passed with the aluminum surface as a cathode. And then neutralizing with a nitric acid aqueous solution having a concentration of 100 to 500 g / L; various known anodizing electrolytes are usually used. In while in contact with the aluminum surface, the aluminum surface by applying a direct current of a current density of 1 to 10 A / dm ² in the cathode, or a method of electrolysis by passing an alternating current; the alkaline aqueous solution in the concentration of 10 to 200 g / L A method of bringing the aluminum surface into contact at 40 to 50 ° C. for 15 to 60 seconds, and then neutralizing by contacting with an aqueous nitric acid solution having a concentration of 100 to 500 g / L; a surfactant, water or the like was mixed with light oil or kerosene. A method in which the emulsion is brought into contact with the aluminum surface at a temperature from room temperature to 50 ° C. and then washed with water (emulsion degreasing method); a mixed solution of sodium carbonate, phosphates, surfactants, etc. is brought to a temperature from room temperature to 50 ° C. The aluminum surface is brought into contact with the aluminum surface for 30 to 180 seconds and then washed with water (phosphate method).

  The degreasing treatment is preferably a method in which the fat on the aluminum surface can be removed while aluminum is hardly dissolved. In this respect, the organic solvent method, the surfactant method, the emulsion degreasing method, and the phosphate method are preferable.

<Mirror finish processing>
The mirror finishing process is performed to eliminate unevenness on the surface of the aluminum substrate and improve the uniformity and reproducibility of the particle forming process by an electrodeposition method or the like. As an unevenness | corrugation of the surface of an aluminum member, the rolling rebar generated at the time of rolling in the case where an aluminum member is manufactured through rolling is mentioned, for example.
In the present invention, the mirror finish is not particularly limited, and a conventionally known method can be used. Examples thereof include mechanical polishing, chemical polishing, and electrolytic polishing.
Examples of the mechanical polishing include a method of polishing with various commercially available polishing cloths, and a method of combining various commercially available abrasives (for example, diamond, alumina) and a buff. Specifically, a method in which the method using an abrasive is performed by changing the abrasive used from coarse particles to fine particles over time is preferably exemplified. In this case, the final polishing agent is preferably # 1500. Thereby, the glossiness can be 50% or more (in the case of rolled aluminum, both the rolling direction and the width direction are 50% or more).

As chemical polishing, for example, “Aluminum Handbook”, 6th edition, edited by Japan Aluminum Association, 2001, p. Various methods described in 164 to 165 may be mentioned.
Further, phosphoric acid - nitric acid method, Alupol I method, Alupol V method, Alcoa R5 _{method, H 3 PO 4 -CH 3 COOH} -Cu _{method, H 3 PO 4 -HNO 3 -CH} 3 COOH method are preferable. Of these, the phosphoric acid-nitric acid method, the H ₃ PO ₄ —CH ₃ COOH—Cu method, and the H ₃ PO ₄ —HNO ₃ —CH ₃ COOH method are preferable.
By chemical polishing, the glossiness can be made 70% or more (in the case of rolled aluminum, both the rolling direction and the width direction are 70% or more).

As electrolytic polishing, for example, “Aluminum Handbook”, 6th edition, edited by Japan Aluminum Association, 2001, p. Various methods described in 164 to 165 may be mentioned.
Moreover, the method described in US Pat. No. 2,708,655 is preferable.
“Practical Surface Technology”, vol. 33, no. 3, 1986, p. The method described in 32-38 is also preferably exemplified.
By electropolishing, the gloss can be 70% or more (in the case of rolled aluminum, both the rolling direction and the width direction are 70% or more).

  These methods can be used in appropriate combination. For example, a method of using an abrasive is preferably performed by changing the abrasive to be used from coarse particles to fine particles over time, and then performing electrolytic polishing.

By mirror finishing, for example, a surface having an average surface roughness R _{a of} 0.1 μm or less and a glossiness of 50% or more can be obtained. The average surface roughness _Ra is preferably 0.03 μm or less, and more preferably 0.02 μm or less. Further, the glossiness is preferably 70% or more, and more preferably 80% or more.
The glossiness is a regular reflectance obtained in accordance with JIS Z8741-1997 “Method 3 60 ° Specular Gloss” in the direction perpendicular to the rolling direction. Specifically, using a variable angle gloss meter (for example, VG-1D, manufactured by Nippon Denshoku Industries Co., Ltd.), when the regular reflectance is 70% or less, the incident reflection angle is 60 degrees and the regular reflectance is 70%. In the case of exceeding, the incident / reflection angle is 20 degrees.

<(1) The process of forming the hollow which has a desired arrangement | sequence on the aluminum member surface>
Before the anodic oxidation treatment for forming micropores on the aluminum surface, a depression that is the starting point for generating micropores in the anodic oxidation treatment is formed. By forming such depressions, it becomes easy to control the arrangement of micropores and the roundness of the pore diameter, which will be described later, within a desired range.

The method for forming the depression is not particularly limited, and examples thereof include a physical method including a transfer method, a particle beam method, a block copolymer method, and a resist pattern / exposure / etching method.
Electrochemical micropores are not formed. As a result, the starting points of the micropores formed by anodic oxidation can be arranged in any desired arrangement, and the roundness of the resulting structure can be increased.

<Physical method>
For example, a method using an imprint method (a transfer method or a press patterning method in which a substrate or a roll having a protrusion is pressed against an aluminum plate to form a recess) can be used. Specifically, a method of forming a depression by pressing a substrate having a plurality of protrusions on the surface thereof against the aluminum surface can be mentioned. For example, a method described in JP-A-10-121292 can be used.
Another example is a method in which polystyrene spheres are arranged in a dense state on the aluminum surface, SiO ₂ is vapor-deposited thereon, then the polystyrene spheres are removed, and the substrate is etched using the vapor-deposited SiO ₂ as a mask to form depressions. It is done.

<Particle beam method>
The particle beam method is a method in which a hollow is formed by irradiating the aluminum surface with a particle beam. The particle beam method has an advantage that the position of the depression can be freely controlled.
Examples of the particle beam include a charged particle beam, a focused ion beam (FIB), and an electron beam.
As the particle beam method, for example, a method described in JP-A-2001-105400 can be used.

<Block copolymer method>
The block copolymer method is a method in which a block copolymer layer is formed on an aluminum surface, a sea-island structure is formed in the block copolymer layer by thermal annealing, and then an island portion is removed to form a depression.
As a block copolymer method, the method described in Unexamined-Japanese-Patent No. 2003-129288 can be used, for example.

<Resist pattern, exposure, etching method>
In the resist pattern / exposure / etching method, the resist on the surface of the aluminum plate is exposed and developed by photolithography or electron beam lithography to form a resist pattern, which is then etched. In this method, a resist is provided and etched to form a recess penetrating to the aluminum surface.

  Among the above-described methods for forming various depressions, a physical method, an FIB method, and a resist pattern / exposure / etching method are desirable.

In the present invention, when a plurality of depressions are formed on the surface of the aluminum plate at a predetermined interval and arrangement, and particularly when a very fine porous anodized alumina film having a pore interval of around 0.1 μm is produced, the aluminum plate In order to artificially form fine depressions on the surface regularly, it is necessary to use high-resolution micromachining technology using electron beam lithography, X-ray lithography, etc. Since it is not economical to apply it every time it is manufactured, a transfer (imprint) method of pressing a substrate having a plurality of protrusions on the surface of an aluminum plate to be anodized is preferable.
Specifically, it can be carried out by bringing a substrate or roll having protrusions into close contact with an aluminum plate and applying pressure using a hydraulic press or the like. The arrangement (pattern) of the protrusions provided on the substrate is made to correspond to the arrangement of the pores of the porous anodized alumina film formed by anodic oxidation, not to mention the regular hexagonal periodic arrangement, but the periodic arrangement. It is also possible to use an arbitrary pattern that lacks a part of. Further, it is desirable that the substrate on which the protrusion is formed has a mirror surface and has a strength and a hardness that are not broken by the pressing pressure and the arrangement of the protrusion is not deformed. For this purpose, it is possible to use a general-purpose silicon substrate that is easy to finely process, including a metal substrate such as aluminum or tantalum. However, a substrate made of high-strength diamond or silicon carbide is repeatedly used. Since the number of times of use can be increased, it is more desirable. Thus, if one substrate or roll having protrusions is prepared, a regular array of depressions can be efficiently formed on a large number of aluminum plates by repeatedly using the substrate or roll.

The pressure when using the above transfer method is preferably 0.001 to 100 tons / cm ² , more preferably 0.01 to 75 tons / cm ² , although depending on the type of substrate. 50 tons / cm ² is particularly preferred.
Moreover, as temperature at the time of press, 0-300 degreeC is preferable, 5-200 degreeC is more preferable, 10-100 degreeC is especially preferable, As time of a press, 2 seconds-30 minutes are preferable, and 5 seconds-15 Minute is more preferable, and 10 seconds to 5 minutes is particularly preferable.
Further, from the viewpoint of fixing the surface shape after pressing, a method for cooling the aluminum surface portion can also be added as a post-treatment.

  As shown in FIG. 1A, an aluminum substrate 12 is formed by pressing a substrate 13 having a desired protrusion on the surface, for example, in the direction of an arrow, and applying the desired surface to the surface as shown in FIG. A recess 15 having the following arrangement is formed.

<(2) Step of forming anodized film having micropores by anodizing aluminum member, anodizing>
As the anodizing treatment, a conventionally known method can be used. Specifically, high-purity aluminum is used, and an anodized film is formed at a low speed over a long period of time (for example, several hours to several tens of hours) at a voltage according to the type of the electrolytic solution.
In this method, since the pore diameter depends on the voltage, a desired pore diameter can be obtained to some extent by controlling the voltage.

The average flow rate during the anodizing treatment is preferably 0.5 to 20.0 m / min, more preferably 1.0 to 15.0 m / min, and 2.0 to 10.0 m / min. More preferably, it is min. By performing anodizing treatment at a flow rate in the above range, uniform and high regularity can be obtained.
Moreover, the method of flowing the electrolytic solution under the above-mentioned conditions is not particularly limited, but, for example, a method using a general stirring device such as a stirrer is used. It is preferable to use a stirrer that can control the stirring speed with a digital display because the average flow rate can be controlled. As such a stirring apparatus, for example, magnetic stirrer HS-50D manufactured by AS ONE can be mentioned.

  For the anodizing treatment, for example, a method in which an aluminum substrate is used as an anode in a solution having an acid concentration of 1 to 10% by mass can be used. The solution used for the anodizing treatment is preferably an acid solution, more preferably sulfuric acid, phosphoric acid, chromic acid, oxalic acid, sulfamic acid, benzenesulfonic acid, amidosulfonic acid, etc., among which sulfuric acid, phosphoric acid, Oxalic acid is particularly preferred. These acids can be used alone or in combination of two or more.

The conditions for anodizing treatment vary depending on the electrolyte used, and therefore cannot be determined unconditionally. In general, however, the electrolyte concentration is 0.1 to 20% by mass, the solution temperature is -10 to 30 ° C., and the current density. 0.01 to 20 A / dm ² , voltage 3 to 300 V, electrolysis time 0.5 to 30 hours are preferable, electrolyte concentration 0.5 to 15% by mass, liquid temperature −5 to 25 ° C., current density 0 0.05 to 15 A / dm ² , voltage 5 to 250 V, electrolysis time 1 to 25 hours are more preferable, electrolyte concentration 1 to 10% by mass, solution temperature 0 to 20 ° C., current density 0.1 to 10 A / More preferably, dm ² , voltage of 10 to 200 V, and electrolysis time of 2 to 20 hours are used.
The thickness of the anodized film is preferably 1 to 300 μm, more preferably 5 to 150 μm, and still more preferably 10 to 100 μm.

  The treatment time for the anodizing treatment is preferably 0.5 minutes to 16 hours, more preferably 1 minute to 12 hours, and further preferably 2 minutes to 8 hours.

  The anodizing treatment can be performed by changing the voltage intermittently or continuously in addition to being performed under a constant voltage. In this case, it is preferable to decrease the voltage sequentially. As a result, the resistance of the anodized film can be lowered, and can be made uniform when the electrodeposition treatment is performed later.

The average pore density is preferably 50-1500 / μm ² .

  The area ratio occupied by the micropores is preferably 20 to 50%. The area ratio occupied by the micropores is defined by the ratio of the total area of the micropore openings to the area of the aluminum surface.

  As shown in FIG. 1C, the anodized aluminum member 10 a has an anodized film 14 a having micropores 16 a on the surface of the aluminum substrate 12. A barrier layer 18a exists on the aluminum substrate 12 side of the anodized film 14a.

<(3) Step of dissolving at least a part of the anodized film with acid or alkali>
In the dissolution treatment, a part of the anodized film is dissolved. Also called pore wide processing.

  The step of dissolving a part of the anodized film is a process of dissolving a part of the anodized film of the aluminum member described above. Preferably, when an image with a magnification of 20000 is observed with an FE-SEM, the micropores are dissolved to such an extent that they appear more regular. Specifically, it is a treatment for dissolving so that a part of the anodized film and the barrier layer remain. The anodized film may be almost dissolved and removed.

  By this film dissolution treatment, a part of the irregularly arranged surface of the anodic oxide film is partially dissolved, so that the regularity of the micropore array becomes high. On the other hand, a part of the inside of the micropore of the anodic oxide film is similarly dissolved, and becomes a starting point of an anodic oxidation process described later.

  As shown in FIG. 2A, the film dissolution treatment dissolves the surface of the anodized film 14a and the inside of the micropores 16a (the barrier layer 18a and the porous layer) shown in FIG. An aluminum member 10b having an anodic oxide film 14b having micropores 16b on the substrate 12 is obtained.

  The film dissolution treatment is performed by bringing the aluminum member into contact with an acid aqueous solution or an alkali aqueous solution. The method of making it contact is not specifically limited, For example, the immersion method and the spray method are mentioned. Of these, the dipping method is preferred.

When an acid aqueous solution is used for the film dissolution treatment, it is preferable to use an aqueous solution of an inorganic acid such as sulfuric acid, phosphoric acid, nitric acid, hydrochloric acid, or a mixture thereof. Especially, the aqueous solution which does not contain chromic acid is preferable at the point which is excellent in safety | security. The concentration of the acid aqueous solution is preferably 1 to 10% by mass. The temperature of the acid aqueous solution is preferably 25 to 60 ° C.
When an alkaline aqueous solution is used for the film dissolution treatment, it is preferable to use an aqueous solution of at least one alkali selected from the group consisting of sodium hydroxide, potassium hydroxide and lithium hydroxide. The concentration of the alkaline aqueous solution is preferably 0.1 to 5% by mass. The temperature of the alkaline aqueous solution is preferably 20 to 35 ° C.
Specifically, for example, 50 g / L, 40 ° C. phosphoric acid aqueous solution, 0.5 g / L, 30 ° C. sodium hydroxide aqueous solution or 0.5 g / L, 30 ° C. potassium hydroxide aqueous solution is preferably used. .
The immersion time in the acid aqueous solution or alkali aqueous solution is preferably 8 to 120 minutes, more preferably 10 to 90 minutes, and still more preferably 15 to 60 minutes.

  In the film dissolution treatment, the amount of dissolution of the anodized film is such that the irregularity of the arrangement of the surface of the anodized film can be dissolved to increase the regularity of the arrangement of the micropores, and the bottom part of the micropores It is possible to leave the starting point of the anodizing treatment described later by leaving the anodized film without dissolving.

<(4) Anodizing treatment, thereby growing new micropores in the depth direction, anodizing treatment>
The anodizing treatment is performed after the above-described film dissolution treatment. Thereby, the oxidation reaction of the aluminum substrate proceeds, and new micropores grow in the depth direction from the anodized film partially dissolved by the film dissolution treatment.

  As shown in FIG. 2 (B), the oxidation reaction of the aluminum substrate 12 shown in FIG. 2 (A) proceeds by the anodic oxidation treatment, and the micropores deeper than the micropores 16b are formed on the aluminum substrate 12. The microstructure 20a having the anodic oxide film 14c having 16c is obtained.

For the anodic oxidation treatment after the film dissolution treatment, a conventionally known method can be used, but it is preferable that the anodic oxidation treatment is performed under the same conditions as the above-described anodization treatment before the film dissolution treatment.
Also, a method of repeatedly turning on and off the current intermittently while keeping the DC voltage constant, and a method of repeatedly turning on and off the current while intermittently changing the DC voltage can be suitably used. According to these methods, fine micropores are generated in the anodic oxide film, which is preferable in that uniformity is improved particularly when sealing treatment is performed by electrodeposition.
In the above-described method of intermittently changing the voltage, it is preferable to decrease the voltage sequentially. As a result, the resistance of the anodized film can be lowered, and can be made uniform when the electrodeposition treatment is performed later.

The amount of increase in the thickness of the anodized film is preferably from 0.1 to 100 μm, and more preferably from 0.5 to 50 μm. Within the above range, the regularity of the pore arrangement can be further increased.
The thickness of the barrier layer is preferably 1 to 90 nm, and more preferably 5 to 60 nm.

<(5) A step of removing a part of the anodized film such that the cross-sectional shape of the micropore has a straight tube structure, a straight tube step>
In the straight tube process, a part of the anodized film is removed so that the cross-sectional shape of the micropore has a straight tube structure. To remove a part of the anodic oxide film so that the cross-sectional shape of the micropore has a straight tube structure, for example, the anodic oxide film before and after immersion in the treatment solution is photographed by FE-SEM from the cross-sectional direction in advance. Can be dissolved under predetermined dissolution conditions. More specifically, by forming a fracture surface of the aluminum member and observing with a FE-SEM at a magnification of 20000 times, the anodized film on the surface side from the inflection point in the depth direction of the inner diameter of the cross section of the micropore is formed. Conditions that allow dissolution and removal. As a result, the surface of the anodized film is dissolved, and the straightness of the micropores is increased. As a result, a microstructure having a high roundness of the micropores can be obtained.

  As shown in FIG. 2C, the inside of the micropore 16c on the surface side from the inflection point of the anodized film 14c shown in FIG. Thus, the microstructure 20b having the anodic oxide film 14d having the straight tubular micropore 16d is obtained.

Since the straight tube process can be basically performed under the same conditions as the film dissolution treatment, only the differences will be described below.
In the straight tube process, a part of the anodized film is removed so that the cross-sectional shape of the micropore has a straight tube structure. In order to dissolve and remove the anodic oxide film on the surface side from the inflection point in the depth direction of the inner diameter of the cross section of the micropore, for example, 1) The anodic oxide film before and after immersion in the treatment solution is previously removed from the cross-sectional direction by FE-SEM. The dissolution conditions can be determined by photographing, and the dissolution treatment can be performed under the predetermined dissolution conditions. Or 2) The position of the inflection point in the depth direction is estimated in advance from the previous anodic oxidation conditions, and the anodized film is dissolved to the estimated position of 1 to 70 nm, preferably 2 to 60 nm, more preferably 3 to 50 nm. To do. Or 3) The surface of the anodic oxide film is observed by FE-SEM and dissolved to a depth where the arrangement of micropores on the surface becomes almost regular.

In the straight tube process, the dissolution amount of the anodic oxide film is not particularly limited, and is preferably 0.01 to 30% by mass, and more preferably 0.1 to 15% by mass.
In the straight tube process, the immersion time in the aqueous acid solution or aqueous alkali solution is preferably 8 to 90 minutes, more preferably 10 to 60 minutes, and still more preferably 15 to 45 minutes.

<(6) Step of repeating step (4) and step (5) at least once>
Next, preferably, the process including the above-described (4) anodizing treatment and the subsequent (5) straight tube process is performed once or more. By repeating, the cross-sectional shape of the micropore described above becomes a straight tube structure. In this respect, this step is preferably repeated 3 to 10 times, more preferably 5 to 7 times.
When the above steps are repeated twice or more, the conditions of each anodizing treatment and straight tube step may be the same or different. Among these, from the viewpoint of improving the roundness, it is one of preferred embodiments that the voltages are different in two or more anodic oxidation treatments. In that case, it is more preferable to gradually change to a high voltage condition from the viewpoint of improving roundness.

<Microstructure>
The microstructure of the present invention can be obtained by the above-described method for manufacturing a microstructure of the present invention.
The fine structure of the present invention preferably has an average pore density of 50 to 1500 / μm ² .
In the microstructure of the present invention, the area ratio occupied by the micropores is preferably 20 to 50%.
Furthermore, the fine structure of the present invention preferably has a roundness defined by the following formula (1) of micropores of 0.1 or less. More preferably, it is 0.08 or less, and further 0.06 or less.

Specifically, the obtained oxide film was photographed by FE-SEM from the surface side, and all the hole shapes in 1 μm ² were extracted by image analysis software (Note that the arrangement of the micropores itself is an example. 1 to 5 and Comparative Examples 1 and 2 all had a honeycomb arrangement.) The equivalent circular radius, maximum radius, and minimum radius of each hole were determined, and the roundness parameter T was calculated according to the following general formula. The smaller the value, the closer to a perfect circle.
General formula (1): T = Σ (S _max −S _min ) ÷ ΣS
Here, S represents an equivalent circular radius when the hole is observed from the surface direction, S _max represents the maximum radius, and S _min represents the minimum radius.

<Other processing>
Further, other processes can be performed as necessary.
For example, when the microstructure of the present invention is used as a sample stage and the aqueous solution is dropped to form a film, a hydrophilic treatment may be performed in order to reduce the contact angle with water. The hydrophilic treatment can be performed by a conventionally known method.
In addition, when the microstructure of the present invention is used as a sample stage to target a protein that is denatured or decomposed with an acid, it is used for pore-wide treatment and neutralizes the acid remaining on the aluminum surface. Therefore, neutralization treatment may be performed. The neutralization treatment can be performed by a conventionally known method.

The fine structure of the present invention can also remove the aluminum substrate depending on the application.
The method for removing the aluminum substrate is not particularly limited, but for example, a method in which alumina is hardly soluble or insoluble, and is immersed in a solvent in which aluminum is soluble is preferable.
Types of solvents include halogen solvents such as bromine and iodine; acidic solvents such as dilute sulfuric acid, phosphoric acid, oxalic acid, sulfamic acid, benzenesulfonic acid and amidosulfonic acid; sodium hydroxide, potassium hydroxide, calcium hydroxide, etc. The alkaline solvent is preferably exemplified. Of these, bromine and iodine are preferable.

The microstructure of the present invention can also carry a catalyst on the micropores of the anodized film depending on the application.
Although a catalyst will not be specifically limited if it has a catalyst function, For example, the following are mentioned.

AlCl ₃ , AlBr ₃ , Al ₂ O ₃ , SiO ₂ , SiO ₂ —Al ₂ O ₃ , Si zeolite, SiO ₂ —NiO, activated carbon, PbO / Al ₂ O ₃ , LaCoO ₃ , H ₃ PO ₄ , H ₄ P ₂ O ₇ , Bi ₂ O ₃ —MoO ₃ , Sb ₂ O ₅ , SbO ₅ —Fe ₂ O ₃ , SnO ₂ —Sb ₂ O ₅ , Cu, CuO ₂ —Cr ₂ O ₃ , Cu—Cr ₂ O ₃ — ZnO, Cu / SiO ₂ , CuCl ₂ , Ag / α-Al ₂ O ₃ , Au, ZnO, ZnO—Cr ₂ O ₃ , ZnCl ₂ , ZnO—Al ₂ O ₃ —CaO, TiO ₂ , TiCl ₄ .Al ( _{C 2 H 5) 3, Pt} / TiO 2, V 2 O 5, V 2 O 5 -P 2 O 5, V 2 O 5 / TiO 2, Cr 2 O 3, Cr 2 O 3 / Al 2 O 3, MoO ₃ , MoO ₃ —SnO ₂ , Co · Mo / Al ₂ O ₃ , Ni · Mo / Al ₂ O ₃ , MoS ₂ , Mo—Bi _{-O, MoO 3 -Fe 2 O 3} , H 3 PMo 12 O 40, WO 3, H 3 PW 12 O 40, MnO 2, Fe-K 2 O-Al 2 O 3, Fe 2 O 3 -Cr 2 O ₃ , Fe ₂ O ₃ —Cr ₂ O ₃ —K ₂ O, Fe ₂ O ₃ , Co, Co / activated carbon, Co ₃ O ₄ , Co carbonyl complex, Ni, RaneyNi, Ni / support, modified Ni, Pt, Pt _{/ Al 2 O 3, Pt-} Rh-Pd / _{support, Pd, Pd / SiO 2,} Pd / Al 2 O 3, PdCl 2 -CuCl 2, Re, Re-Pt / Al 2 O 3, Re 2 O 7 / Al ₂ O ₃ , Ru, Ru / Al ₂ O ₃ , Rh, Rh complex.

The method for supporting is not particularly limited, and a conventionally known method can be used.
For example, an electrodeposition method; a method in which a dispersion of catalyst particles is applied to an aluminum member having an anodized film and dried is preferably mentioned. The catalyst is preferably a single particle or an aggregate.
As the electrodeposition method, a conventionally known method can be used. Specifically, for example, in the case of gold electrodeposition, an aluminum member is immersed in a dispersion at 30 ° C. containing 1 g / L HAuCl ₄ and 7 g / L H ₂ SO _4, and a constant voltage of 11 V ( (Adjusted with slidac), and a method of electrodeposition treatment for 5 to 6 minutes.
As the electrodeposition method, Hyundai Kagaku, January 1997, p. Examples using copper, tin and nickel are described in detail in 51-54, and this method can also be used.

The dispersion used in the method using catalyst particles can be obtained by a conventionally known method. For example, it can be obtained by a method for producing fine particles by a low vacuum evaporation method or a method for producing a catalyst colloid in which an aqueous solution of a catalyst salt is reduced.
The catalyst colloidal particles preferably have an average particle size of 1 to 200 nm, more preferably 1 to 100 nm, and even more preferably 2 to 80 nm.
As the dispersion medium used in the dispersion, water is preferably used. In addition, a solvent that can be mixed with water, for example, alcohol such as ethyl alcohol, n-propyl alcohol, i-propyl alcohol, 1-butyl alcohol, 2-butyl alcohol, t-butyl alcohol, methyl cellosolve, butyl cellosolve, and water These mixed solvents can also be used.

  In the method using the catalyst colloidal particles, the coating method is not particularly limited, and examples thereof include bar coater coating, spin coating, spray coating, curtain coating, dip coating, air knife coating, blade coating, and roll coating.

As the dispersion liquid used in the method using the catalyst colloid particles, for example, a gold colloid particle dispersion liquid and a silver colloid particle dispersion liquid are preferably used.
As the dispersion of colloidal gold particles, for example, those described in JP-A-2001-89140 and JP-A-11-80647 can be used. Commercial products can also be used.
The dispersion of silver colloidal particles preferably contains silver and palladium alloy particles in that they are not affected by the acid eluted from the anodized film. In this case, the palladium content is preferably 5 to 30% by mass.

  After applying the dispersion, it is appropriately washed with a solvent such as water. As a result, only the catalyst particles supported on the micropores remain in the anodic oxide film, and the catalyst particles not filled in the micropores are removed.

Adhesion amount of the catalyst after carrying treatment is preferably from 10 to 1000 mg / m ^2, more preferably from 50 to 800 mg / m ^2, particularly preferably from 100 to 500 mg / m ^2.
Further, the surface porosity after the supporting treatment is preferably 70% or less, more preferably 50% or less, and particularly preferably 30% or less. The surface porosity after the supporting treatment is a ratio of the total area of the openings of the unsupported micropores to the area of the aluminum surface.

  The catalyst colloidal particles used in the dispersion usually have a variation in particle size distribution of about 10 to 20% as a coefficient of variation. In the present invention, by setting the pore diameter variation within a specific range, colloidal particles having a variation in particle size distribution can be efficiently used for sealing.

  When the pore diameter is 50 nm or more, a method using catalyst colloidal particles is preferably used. Moreover, when a pore diameter is less than 50 nm, an electrodeposition method is used suitably. A method of combining both is also preferably used.

  Since the microstructure of the present invention has micropores with high roundness, it can be applied to various uses.

The present invention will be specifically described below with reference to examples. However, the present invention is not limited to these.
1. Fabrication of microstructure (Examples 1 to 5 and Comparative Examples 1 and 2)
Each substrate was mirror-finished, and each microstructure was obtained by the method described below.

(1) Substrate The substrate used for the production of the fine structure was a high-purity aluminum substrate (manufactured by Sumitomo Light Metal Industries, Ltd., purity 99.99 mass%, thickness 0.4 mm). This high-purity aluminum substrate was used after being cut into such a size that the portion to be anodized could be made into a square having a side of 10 cm.

(2) Mirror finish treatment The substrate was subjected to a mirror finish treatment.
<Mirror finish processing>
By performing polishing using a polishing cloth, buffing and electrolytic polishing in this order, a mirror finish was applied. After buffing, it was washed with water.
Polishing using a polishing cloth uses a polishing machine (Struers Abramin, manufactured by Marumoto Kogyo Co., Ltd.) and a water-resistant polishing cloth (commercially available), and the number of the water-resistant polishing cloth is # 200, # 500, # 800, # 1000 and The change was made in the order of # 1500.
The buffing was performed using a slurry-like abrasive (FM No. 3 (average particle size 1 μm) and FM No. 4 (average particle size 0.3 μm), both manufactured by Fujimi Incorporated).
The electrolytic polishing was performed for 2 minutes using an electrolytic solution (temperature: 70 ° C.) having the following composition, using the anode as a substrate and the cathode as a carbon electrode at a constant current of 130 mA / cm ² . As a power source, GP0110-30R (manufactured by Takasago Seisakusho) was used.

<Electrolyte composition>
-660 mL of 85% by mass phosphoric acid (reagent manufactured by Wako Pure Chemical Industries)
・ Pure water 160mL
・ Sulfuric acid 150mL
・ Ethylene glycol 30mL

(3) Process (1) Indentation forming process A positive electron beam resist (ZEP-520: trade name of Nippon Zeon Co., Ltd.) is spin-coated on a silicon substrate to a thickness of 0.1 μm, and an electron beam exposure apparatus Then, after exposing a dot pattern in which peripheral protrusions were arranged in a regular hexagonal shape with a period of 0.1 μm with respect to each protrusion, this was developed to open pores having a diameter of about 25 nm in the resist. On this, chromium having a thickness of 50 nm is deposited using an electron beam deposition apparatus, immersed in diglyme as a solvent, ultrasonic waves are applied, and chromium on the resist is removed together with the resist, thereby removing about 25 nm. Chromium protrusions with a diameter of 50 nm were formed. Then, using this chromium as a mask, the silicon substrate was etched to a depth of 60 nm by a reactive dry etching method using CF ₄ gas. Thereafter, chromium was removed with oxygen plasma, and a substrate in which protrusions having a diameter of about 25 nm and a height of 60 nm were regularly arranged with a period of 0.1 μm was produced. Then, the silicon substrate on which the above-described protrusions were formed was placed on the aluminum after the mirror finish, and a depression was formed on the surface of the aluminum plate by applying a pressure of 3 ton / cm ² using a hydraulic press.

(4) Step (2) Anodizing treatment An electrolytic solution of 0.50 mol / L oxalic acid aqueous solution was used for the treated aluminum substrate under the conditions of a voltage of 40 V, a liquid temperature of 15 ° C., and a liquid flow rate of 3.0 m / min. Anodizing was performed for 5 hours. The cathode used was a stainless steel electrode, and GP0110-30R (manufactured by Takasago Seisakusho Co., Ltd.) was used as the power source. In addition, NeoCool BD36 (manufactured by Yamato Kagaku Co.) was used as the cooling device, and Pair Stirrer PS-100 (manufactured by EYELA) was used as the stirring and heating device. The flow rate of the electrolyte was measured using a vortex flow monitor FLM22-10PCW (manufactured by AS ONE).

(5) Step (3) Anodized film dissolution treatment The sample after the anodization treatment obtained above was immersed in a phosphoric acid aqueous solution at a temperature of 40 ° C and 0.50 mol / L for 25 minutes.

(6) Step (4) Anodizing treatment The sample after the above treatment was subjected to conditions of a voltage of 40 V, a liquid temperature of 15 ° C., and a liquid flow rate of 3.0 m / min using an electrolyte of 0.50 mol / L oxalic acid aqueous solution. Anodizing was performed for 5 hours. The same electrode and apparatus as those used in the above step (2) were used.

(7) Process (5) Anodized film dissolution treatment (straight tubular process)
The sample after the anodizing treatment obtained above was immersed in an aqueous phosphoric acid solution at a temperature of 40 ° C. and 0.50 mol / L for 25 minutes to obtain a sample of Example 1.

(Example 2)
In the said Example 1, the projection board | substrate for the hollow formation process of a process (1) was created with the method of the following description. Specifically, an electron beam negative resist (SNR-M5: trade name of Tosoh Corporation) is spin-coated on a silicon carbide substrate on which a diamond thin film is deposited to a thickness of 0.5 μm, and approximately 0.1 μm is applied by electron beam exposure. Protrusions having a diameter of 25 nm and a height of 70 nm were regularly arranged with a period of 100 nm.
After that, a silicon carbide substrate with projections is brought into close contact with the mirror-finished aluminum substrate surface prepared by the same method as in Example 1, and aluminum is applied by applying a pressure of 4 ton / cm ² using a hydraulic press. A depression was formed on the plate surface.
Thereafter, the processes of steps (2) to (5) were performed in the same manner as in Example 1 to obtain a sample of Example 2.

(Example 3)
In Example 1 above,
The period of the protruding substrate in step (1) is 62.5 nm, the treatment liquid is 0.30 mol / L sulfuric acid in steps (2) and (4), the voltage is 25 V, and steps (3) and (5) In the same manner as in Example 1 except that the processing time was set to 20 minutes, the processes of Steps (1) to (5) were sequentially performed to obtain a sample of Example 3.

Example 4
In the said Example 1, the process of (1)-(4) was performed in order by the method similar to Example 1 except having omitted the process (5), and the sample of Example 4 was obtained.

(Example 5)
A sample of Example 5 was obtained in the same manner as in Example 1 except that Steps (4) / (5) were added twice more in Example 1 above.

(Comparative Example 1)
In Example 1, except that Steps (3), (4), and (5) were omitted, Steps (1) and (2) were sequentially performed in the same manner as in Example 1, and Comparative Example 1 A sample was obtained.

(Comparative Example 2)
In Example 1, except that steps (4) and (5) were omitted, the steps (1) to (3) were sequentially performed in the same manner as in Example 1 to obtain a sample of Comparative Example 2. It was.

2. Shape analysis of structure The roundness of the micropore when viewed from the surface direction of the structure samples of Examples 1 to 5 and Comparative Examples 1 and 2 obtained as described above was evaluated.
Specifically, the obtained oxide film was photographed by FE-SEM from the surface side, and all the hole shapes in 1 μm ² were extracted by image analysis software (Note that the arrangement of the micropores itself is an example. 1 to 5 and Comparative Examples 1 and 2 all had a honeycomb arrangement.) The equivalent circular radius, maximum radius, and minimum radius of each hole were determined, and the roundness parameter T was calculated according to the following general formula. The smaller the value, the closer to a perfect circle. The results are shown in Table 1.
General formula (1): T = Σ (S _max −S _min ) ÷ ΣS
Here, S represents an equivalent circular radius when the hole is observed from the surface direction, S _max represents the maximum radius, and S _min represents the minimum radius.

  As apparent from Table 1, the fine structure manufacturing method (Examples 1 to 5) of the present invention has a small roundness parameter and obtains a fine structure that is closer to a perfect circle than Comparative Examples 1 and 2. be able to.

FIGS. 1A, 1B, and 1C are schematic end views of an aluminum member and a microstructure for explaining the method of manufacturing a microstructure according to the present invention. 2A, 2B, and 2C are schematic end views of an aluminum member and a microstructure for explaining the manufacturing method of the microstructure of the present invention.

Explanation of symbols

1, 2, 4, 5, 7, 8, 16a, 16b, 16c, 16d Micropore 10a, 10b, 10c Aluminum member 12 Aluminum substrate 13 Substrate 14a, 14b, 14c, 14d Anodized film 15 Recess 18a, 18b, 18c 18d Barrier layer 20a, 20b Fine structure

Claims (4)

A method for producing a microstructure comprising the following steps in this order:
(1) The process of forming the hollow which has a desired arrangement | sequence on the aluminum member surface,
(2) a step of anodizing the aluminum member to form an anodized film having micropores;
(3) a step of dissolving at least a part of the anodized film with an acid or an alkali;
(4) A step of anodizing to grow new micropores in the depth direction.   Furthermore, (5) The manufacturing method of the microstructure of Claim 1 including the process of removing a part of an anodic oxide film so that the cross-sectional shape of the said micropore may become a straight pipe structure. A method for producing a microstructure comprising the following steps in this order:
(1) The process of forming the hollow which has a desired arrangement | sequence on the aluminum member surface,
(2) a step of anodizing the aluminum member to form an anodized film having micropores;
(3) a step of dissolving at least a part of the anodized film with an acid or an alkali;
(4) Anodizing, thereby growing new micropores in the depth direction;
(5) a step of removing a part of the anodized film so that the cross-sectional shape of the micropore has a straight tube structure;
(6) A step of repeating the step (4) and the step (5) at least once.   The fine structure obtained by the manufacturing method of the fine structure in any one of the said Claims 1-3.

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