JP2009068076A - Fine structure and manufacturing method - Google Patents

Abstract

[Problem] To provide a fine structure that can be used as a porous alumina membrane filter having an excellent filtration flow rate and excellent precision fractionation, and a method for producing the fine structure, with respect to a filtration system for an aqueous solvent liquid.
A microstructure comprising an aluminum anodized film and having micropore through-holes, wherein the pore diameter dispersion of the micropore through-holes is within 8% of the average diameter, A microstructure having a surface imparted with a substance that improves the hydrophobicity of the surface of the anodic oxide film.
[Selection figure] None

Description

  The present invention relates to a microstructure and a manufacturing method thereof.

  Filter membranes put into practical use in the field of microfiltration include organic membranes and inorganic membranes, and organic membranes are widely used in practice. Many of these organic membranes do not have independent pores, and the pore size distribution is relatively wide. Therefore, research to further improve the accuracy of separation of specific substances, which is the most important function of the filter, has been conducted. It is proceeding in the direction.

  In order to solve such problems, for example, in Non-Patent Document 1, etc., the organic film made of a polymer is irradiated with high energy particles generated from a nuclear reactor, and the tracks through which the particles have passed through the organic film are etched to form pores. A so-called track etching method is known. This track etching method can obtain independent pores with a narrow pore diameter distribution that are perpendicular to the organic film, but in order to avoid the generation of double holes due to the incidence of particles overlapping during track formation, There was a problem that the density, so-called porosity, could not be increased.

  On the other hand, as an inorganic membrane, for example, as known in Non-Patent Document 2, etc., a porous alumina membrane filter using an anodized aluminum film is known. By anodizing aluminum in an acidic electrolyte, independent pores with a narrow pore size distribution are arranged with a high porosity, so a membrane filter with a high filtration flow rate per hour can be manufactured at low cost. Can do.

T.A. D. Block, Membrane Filtration, Sci. Tech, Inc. , Madison (1983) Hideki Masuda, “New Technology of Porous Membrane Using Anodization”, Altopia, July 1995

  Therefore, the present invention relates to an aqueous solvent liquid filtration system, and provides a fine structure that can be used as a porous alumina membrane filter having an excellent filtration flow rate and excellent precision fractionation, and a method for producing the fine structure. For the purpose.

  As a result of intensive studies to achieve the above object, the present inventor has given the present invention to the surface of the aluminum anodic oxide film forming the microstructure by adding a substance that improves the hydrophobicity of the surface of the anodic oxide film. Completed.

That is, the present invention provides the following (i) to (iv).
(I) a microstructure comprising an aluminum anodized film and having micropore through-holes, wherein the pore diameter dispersion of the micropore through-holes is within 8% of the average diameter, and the surface of the aluminum anodized film And a substance for improving the hydrophobicity of the surface of the anodic oxide film.
(Ii) at least on the aluminum substrate;
(A) Treatment for forming an oxide film having micropores by anodization treatment,
(B) Treatment for removing aluminum from the oxide film obtained in (A) above,
(C) treatment for penetrating the micropores of the oxide film obtained in (A) above, and (D) treatment for imparting a substance that improves the hydrophobicity of the oxide film surface to the oxide film surface,
The fine structure according to the above (i), which is formed by applying the materials in this order.
(Iii) The microstructure according to (i) or (ii) above, wherein the substance that improves hydrophobicity is a compound that acts as a surfactant having an HLB value of 9 or less.
(Iv) The microstructure according to (i) to (iii) above, wherein the degree of ordering defined by the following formula (1) is 50% or more for the micropore through hole.
Ordering degree (%) = B / A × 100 (1)
In the above formula (1), A represents the total number of micropore through holes in the measurement range. B, when a circle with the shortest radius inscribed in the edge of the other micropore through hole is drawn around the center of gravity of the one micropore through hole, other than the one micropore through hole inside the circle This represents the number of the one micropore through hole in the measurement range that includes the six gravity centers of the micropore through holes.

  ADVANTAGE OF THE INVENTION According to this invention, regarding the filtration system of the liquid of an aqueous solvent, the fine structure which can be used as a porous alumina membrane filter excellent in the filtration flow volume and excellent in the precision fractionation property can be obtained.

The present invention is described in detail below.
The microstructure of the present invention is a microstructure having an anodized aluminum film and having micropore through-holes, and the pore diameter dispersion of the micropore through-holes is within 8% of the average diameter. The surface of the anodized film is provided with a substance that improves the hydrophobicity of the surface of the anodized film.

The microstructure of the present invention is preferably
On the aluminum substrate, at least
(A) Treatment for forming an oxide film having micropores by anodization treatment,
(B) Treatment for removing aluminum from the oxide film obtained in (A) above,
(C) treatment for penetrating the micropores of the oxide film obtained in (A) above, and (D) treatment for imparting a substance that improves the hydrophobicity of the oxide film surface to the oxide film surface,
Are formed in this order.

<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 micropore array is sufficient.

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

<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 by contacting with a nitric acid aqueous solution having a concentration of 100 to 500 g / L; various known electrolytic solutions for anodizing treatment 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 content on the aluminum surface can be removed while aluminum dissolution hardly occurs. 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. Examples of the irregularities on the surface of the aluminum substrate include rolling stripes generated during rolling in the case where the aluminum substrate is manufactured through rolling.
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. Among 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.

<Process (A): Micropore formation process by anodic oxidation>
In process (A), an aluminum substrate is anodized to form an oxide film having micropores on the surface of the aluminum substrate.
As the anodizing treatment, a conventionally known method can be used. Specifically, it is preferable to use the self-ordering method described later.

The self-ordering method is a method of 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. 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.

  In order to form micropores by the self-ordering method, anodizing treatment (a-1) described later may be performed, but preferably anodizing treatment (a-1) described later, film removal treatment (a- It is preferable to form by the method of implementing 2) and re-anodizing treatment (a-3) in this order.

<Anodizing treatment (a-1)>
The average flow rate during the anodizing treatment (a-1) is preferably 0.5 to 20.0 m / min, more preferably 1.0 to 15.0 m / min, and 2.0 More preferably, it is -10.0 m / 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. In particular, 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. Examples of such a stirring apparatus include “Magnetic Stirrer HS-50D (manufactured by AS ONE)” and the like.

For the anodizing treatment (a-1), for example, a method in which an aluminum substrate is used as an anode in a solution having an acid concentration of 0.01 to 5 mol / L can be used.
The solution used for the anodizing treatment (a-1) is preferably an acid solution, and sulfuric acid, phosphoric acid, chromic acid, oxalic acid, sulfamic acid, benzenesulfonic acid, amidosulfonic acid, glycolic acid, tartaric acid, Malic acid, citric acid, and the like are more preferable, and sulfuric acid, phosphoric acid, and oxalic acid are particularly preferable. These acids can be used alone or in combination of two or more.

The conditions for the anodizing treatment (a-1) vary depending on the electrolyte used, and thus cannot be determined unconditionally. In general, however, the electrolyte concentration is 0.01 to 5 mol / L, and the solution temperature is -10 to 10. It is preferably 30 ° C., current density 0.01 to 20 A / dm ² , voltage 3 to 300 V, electrolysis time 0.5 to 30 hours, electrolyte concentration 0.05 to 3 mol / L, liquid temperature −5 to 25 It is more preferable that it is C, current density 0.05-15A / dm < ² >, voltage 5-250V, electrolysis time 1-25 hours, electrolyte concentration 0.1-1 mol / L, liquid temperature 0-20 degreeC, current More preferably, the density is 0.1 to 10 A / dm ² , the voltage is 10 to 200 V, and the electrolysis time is 2 to 20 hours.

  The treatment time for the anodizing treatment (a-1) is preferably 0.5 minutes to 16 hours, more preferably 1 minute to 12 hours, and even more preferably 2 minutes to 8 hours.

  The anodizing treatment (a-1) can be performed under a constant voltage, or a method of changing the voltage intermittently or continuously. In this case, it is preferable to decrease the voltage sequentially. This makes it possible to reduce the resistance of the anodized film, and fine micropores are formed in the anodized film, which is preferable in terms of improving uniformity, particularly when sealing treatment is performed by electrodeposition. .

  In the present invention, the thickness of the anodized film formed by such anodizing treatment (a-1) is preferably 0.1 to 2000 μm, more preferably 1 to 1000 μm. More preferably, it is -500 micrometers.

Furthermore, in the present invention, the average pore density of the micropores formed by such anodizing treatment (a-1) is preferably 50 to 1500 / μm ² .
Furthermore, the area ratio occupied by the micropores formed by such anodizing treatment (a-1) is preferably 20 to 50%.
Here, the area ratio occupied by the micropores is defined by the ratio of the total area of the openings of the micropores to the area of the aluminum surface.

<Film removal treatment (a-2)>
The film removal process (a-2) is a process for dissolving and removing the anodized film formed on the surface of the aluminum substrate by the anodizing process (a-1).
After forming the anodized film on the surface of the aluminum substrate by the anodizing treatment (a-1), the processing (B) (aluminum removing treatment) described later may be performed immediately, but the anodizing treatment (a-1) Thereafter, it is preferable to perform a film removal process (a-2) and a re-anodization process (a-3) described later in this order, and then perform a process (B) (aluminum removal process) described later.

  Since the anodic oxide film has higher regularity as it gets closer to the aluminum substrate, the anodic oxide film once removed by this film removal treatment (a-2) and remaining on the surface of the aluminum substrate. The bottom portion can be exposed on the surface to obtain regular depressions. Therefore, in the film removal process (a-2), aluminum is not dissolved, but only the anodized film made of alumina (aluminum oxide) is dissolved.

  Alumina solution includes chromium compound, nitric acid, phosphoric acid, zirconium compound, titanium compound, lithium salt, cerium salt, magnesium salt, sodium fluorosilicate, zinc fluoride, manganese compound, molybdenum compound, magnesium compound, barium compound and An aqueous solution containing at least one selected from the group consisting of simple halogens is preferred.

Specific examples of the chromium compound include chromium (III) oxide and anhydrous chromium (VI) acid.
Examples of the zirconium-based compound include zircon ammonium fluoride, zirconium fluoride, and zirconium chloride.
Examples of the titanium compound include titanium oxide and titanium sulfide.
Examples of the lithium salt include lithium fluoride and lithium chloride.
Examples of the cerium salt include cerium fluoride and cerium chloride.
Examples of the magnesium salt include magnesium sulfide.
Examples of the manganese compound include sodium permanganate and calcium permanganate.
Examples of the molybdenum compound include sodium molybdate.
Examples of magnesium compounds include magnesium fluoride pentahydrate.
Examples of barium compounds include barium oxide, barium acetate, barium carbonate, barium chlorate, barium chloride, barium fluoride, barium iodide, barium lactate, barium oxalate, barium perchlorate, barium selenate, selenite. Examples thereof include barium, barium stearate, barium sulfite, barium titanate, barium hydroxide, barium nitrate, and hydrates thereof. Among the barium compounds, barium oxide, barium acetate, and barium carbonate are preferable, and barium oxide is particularly preferable.
Examples of halogen alone include chlorine, fluorine, and bromine.

Among them, the alumina solution is preferably an aqueous solution containing an acid. Examples of the acid include sulfuric acid, phosphoric acid, nitric acid, hydrochloric acid, and the like, and a mixture of two or more acids may be used.
The acid concentration is preferably 0.01 mol / L or more, more preferably 0.05 mol / L or more, and still more preferably 0.1 mol / L or more. There is no particular upper limit, but generally it is preferably 10 mol / L or less, more preferably 5 mol / L or less. An unnecessarily high concentration is not economical, and if it is higher, the aluminum substrate may be dissolved.

  The alumina solution is preferably −10 ° C. or higher, more preferably −5 ° C. or higher, and still more preferably 0 ° C. or higher. In addition, since the starting point of ordering will be destroyed and disturbed if it processes using the boiling alumina solution, it is preferable to use it without boiling.

  The alumina solution dissolves alumina and does not dissolve aluminum. Here, the alumina solution may not dissolve aluminum substantially or may dissolve it slightly.

  The film removal treatment (a-2) is performed by bringing the aluminum substrate on which the anodized film is formed into contact with the above-described alumina 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.

The dipping method is a treatment in which an aluminum substrate on which an anodized film is formed is dipped in the above-described alumina solution. Stirring during the dipping process is preferable because a uniform process is performed.
The dipping treatment time is preferably 10 minutes or longer, more preferably 1 hour or longer, and further preferably 3 hours or longer and 5 hours or longer.

<Re-anodizing treatment (a-3)>
After removing the anodic oxide film by the film removal treatment (a-2) to form regular depressions on the surface of the aluminum substrate, the degree of ordering of the micropores is higher by performing the anodic oxidation treatment again. An anodized film can be formed.
For the re-anodizing treatment (a-3), a conventionally known method can be used, but it is preferably performed under the same conditions as the above-described anodizing treatment (a-1).
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.

When the re-anodizing treatment (a-3) is performed at a low temperature, the arrangement of micropores becomes regular and the pore diameter becomes uniform.
On the other hand, by performing the re-anodizing treatment (a-3) at a relatively high temperature, the arrangement of the micropores can be disturbed, and the variation in pore diameter can be made within a predetermined range. Also, the pore diameter variation can be controlled by the processing time.

  In the present invention, the thickness of the anodized film formed by such re-anodizing treatment (a-3) is preferably 0.1 to 1000 μm, more preferably 1 to 500 μm, More preferably, it is 10-500 micrometers.

In the present invention, the pore diameter of the micropore formed by such anodizing treatment (a-3) is preferably 0.01 to 0.5 μm.
Further, the micropores formed by such re-anodizing treatment (a-3) preferably have a pore diameter dispersion within 8% of the average diameter within a range of 1 μm ^2. It is more preferable.

Furthermore, in the present invention, the average pore density of the micropores formed by such anodizing treatment (a-3) is preferably 50 to 1500 / μm ² .
Furthermore, the area ratio occupied by the micropores formed by such anodizing treatment (a-3) is preferably 20 to 50%.

  In the present invention, instead of the above-described anodic oxidation treatment (a-1) and film removal treatment (a-2), for example, a physical method, a particle beam method, a block copolymer method, a resist pattern / exposure / etching method, etc. Thus, a depression that is a starting point for generating micropores by the re-anodizing treatment (a-3) described above may be formed.

<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.

Moreover, in this invention, the oxide film which has a micropore on the aluminum substrate surface by giving the process of following (1)-(4) in this order as said process (A) (micropore formation process by anodization). May be formed.
(1) Step of forming an anodic oxide film having micropores on the surface of the aluminum substrate by anodizing the surface of the aluminum substrate (2) Step of partially dissolving the anodic oxide film using acid or alkali (3) A step of growing the micropores in the depth direction by performing anodization treatment (4) A step of removing the anodized film above the inflection point of the cross-sectional shape of the micropores

<Step (1)>
In the step (1), at least one surface of the aluminum substrate is anodized to form an anodized film having micropores on the surface of the aluminum substrate.
Step (1) can be carried out in the same procedure as in the anodizing treatment (a-1).
FIG. 1 is a schematic end view of an aluminum substrate and an anodized film formed on the aluminum substrate.
FIG. 1A shows a state in which the anodized film 14a having the micropores 16a is formed on the surface of the aluminum substrate 12a by the step (1).

<Step (2)>
In step (2), the anodized film formed in step (1) is partially dissolved using acid or alkali.
Here, partially dissolving the anodic oxide film does not completely dissolve the anodic oxide film formed in the step (1), but on the aluminum substrate 12a as shown in FIG. 1A shows that the surface of the anodized film 14a shown in FIG. 1A and the inside of the micropore 16a are partially dissolved so that the anodized film 14b having the micropores 16b remains.
Further, the dissolution amount of the anodized film is preferably 0.001 to 50% by mass of the whole anodized film, more preferably 0.005 to 30% by mass, and 0.01 to 15% by mass. More preferably. When the dissolution amount is in the above range, the irregular part of the surface of the anodic oxide film can be dissolved to increase the regularity of the micropore array, and the anodic oxide film is formed on the bottom part of the micropore. Thus, the starting point of the anodizing treatment performed in the step (3) can be left.

  Step (2) is performed by bringing the anodized film formed on the aluminum substrate into contact with an aqueous acid solution or an aqueous alkali 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 in step (2), 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 0.01 to 1 mol / L. The temperature of the acid aqueous solution is preferably 25 to 60 ° C.
When an alkaline aqueous solution is used in step (2), 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 0.01 to 1 mol / L. The temperature of the alkaline aqueous solution is preferably 20 to 35 ° C.
Specifically, for example, 0.5 mol / L, 40 ° C. phosphoric acid aqueous solution, 0.05 mol / L, 30 ° C. sodium hydroxide aqueous solution or 0.05 mol / L, 30 ° C. potassium hydroxide aqueous solution is suitable. 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.

<Step (3)>
In step (3), the anodization process is again performed on the aluminum substrate in which the anodized film is partially dissolved in step (2) to grow micropores in the depth direction.
As shown in FIG. 1 (C), the oxidation reaction of the aluminum substrate 12a shown in FIG. 1 (B) proceeds by the anodizing treatment in the step (3), and the aluminum substrate 12b is more than the micropores 16b. An anodic oxide film 14c having micropores 16c grown in the depth direction is formed.

A conventionally known method can be used for the anodizing treatment, but it is preferably performed under the same conditions as the above-described anodizing treatment (a-1).
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. When the increase amount is in the above range, the regularity of the pore arrangement can be further increased.

<Process (4)>
In step (4), the anodized film above the inflection point 30 in the cross-sectional shape of the micropore 16c shown in FIG. As shown in FIG. 1C, the micropore formed by the self-ordering method has a substantially straight tube shape in cross section except for the upper portion of the micropore 16c. In other words, a portion (a deformed portion) 20 having a cross-sectional shape different from that of the remaining portion of the micropore 16c exists in the upper portion of the micropore 16c. In step (4), the anodized film above the inflection point 30 of the cross-sectional shape of the micropore 16c is removed in order to eliminate the deformed portion 20 existing on the upper portion of the micropore 16c.
Here, the inflection point 30 refers to a portion where the shape changes remarkably with respect to the main shape (here, a substantially straight pipe shape) formed by the cross-sectional shape of the micropore 16c. In the cross-sectional shape of 16c, it refers to a portion where the continuity of the shape is lost with respect to the main shape (substantially straight pipe shape).
By removing the anodized film above the inflection point 30 of the cross-sectional shape of the micropore 16c, the entire micropore 16d has a substantially straight tube shape as shown in FIG.

  In the step (4), the inflection point 30 of the cross-sectional shape of the micropore 16c is specified by photographing an FE-SEM of the anodized film 14c after the execution of the step (3) from the cross-sectional direction. The anodic oxide film above may be removed.

However, the deformed portion is generated in the micropore mainly when the anodized film 14a is newly formed on the aluminum substrate 12a as in the step (1). Therefore, in order to remove the anodic oxide film above the inflection point 30 of the cross-sectional shape of the micropore 16c and eliminate the deformed portion 20 above the micropore 16c, the anodic oxide film formed in the step (1) is used. May be removed in step (4).
As will be described later, when the step (3) and the step (4) are repeated twice or more, the deformed portion 20 is eliminated in the anodized film 14d after the step (4) is performed, and the cross-sectional shape of the micropore 16d is obtained. Since the whole has a substantially straight pipe shape, a new micropore is formed above the micropore formed in step (3) (hereinafter referred to as “step (3 ′)”) following step (4). A deformed part occurs in Therefore, in the step (4) (hereinafter referred to as “step (4 ′)” in this paragraph) to be performed following the step (3 ′), a new upper portion of the micropore formed in the step (3 ′) is added. It is necessary to remove the deformed part. Therefore, in step (4 ′), it is necessary to remove the anodized film above the inflection point of the micropore formed in step (3 ′).

  In the step (4), the process for removing the anodic oxide film above the inflection point of the cross-sectional shape of the micropore 16c may be a polishing process such as mechanical polishing, chemical polishing, and electrolytic polishing. However, as in the step (2), a treatment for dissolving the anodized film using an acid or an alkali is preferable. In this case, as shown in FIG. 1D, an anodic oxide film 14d having a thickness smaller than that of the anodic oxide film 14c shown in FIG. 1C is formed.

  In the step (4), when the anodized film is partially dissolved using acid or alkali, the dissolved amount of the anodized film is not particularly limited, and the total amount of the anodized film is not limited. It is preferable that it is 0.01-30 mass%, and it is more preferable that it is 0.1-15 mass%. When the dissolution amount is in the above range, the irregular portion of the surface arrangement of the anodized film can be dissolved, and the regularity of the arrangement of the micropores can be increased. Moreover, when performing a process (3) and a process (4) repeatedly 2 times or more, the starting point of the anodizing process in the process (3) implemented next can be left.

It is preferable to repeat the step (3) and the step (4) twice because the regularity of the pore arrangement is high, more preferably 3 times or more, and more preferably 4 times or more. Is more preferable.
When the above steps are repeated twice or more, the conditions of each step (3) and step (4) may be the same or different. From the viewpoint of improving the degree of ordering, the step (3) is preferably performed by changing the voltage every time. In this case, it is more preferable to gradually change to a high voltage condition from the viewpoint of improving the degree of ordering.

In the state shown in FIG. 1D, the average pore density is preferably 50 to 1500 / μm ² , and the area ratio occupied by the micropores is preferably 20 to 50%.

  FIG. 2 is a partial cross-sectional view showing a state after the above process (A) (micropore formation process by anodization). As shown in FIG. 2, an anodic oxide film 14 having micropores 16 is formed on the surface of the aluminum substrate 12.

<Process (B): Aluminum removal process>
In the process (B), the aluminum substrate 12 is dissolved and removed from the state shown in FIG. FIG. 3 is a partial cross-sectional view showing the state after the main treatment, and shows a fine structure made of the anodized film 14 having the micropores 16.
Therefore, in the aluminum removal treatment, a treatment solution that does not dissolve alumina but dissolves aluminum is used.

The treatment liquid is not particularly limited as long as it does not dissolve alumina and dissolves aluminum. For example, an aqueous solution such as mercury chloride, bromine / methanol mixture, bromine / ethanol mixture, aqua regia, hydrochloric acid / copper chloride mixture, etc. Etc.
As a density | concentration, 0.01-10 mol / L is preferable and 0.05-5 mol / L is more preferable.
As processing temperature, -10 degreeC-80 degreeC are preferable, and 0 degreeC-60 degreeC is preferable.

  The aluminum removal treatment is performed by contacting with the treatment liquid described above. 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. The contact time at this time is preferably 10 seconds to 5 hours, and more preferably 1 minute to 3 hours.

  The film thickness of the anodized film after the aluminum removal treatment is preferably 1 to 1000 μm, and more preferably 10 to 500 μm.

  After the aluminum removal treatment, the anodized film is preferably washed with water before the treatment (C) (micropore penetration treatment) described later. In order to suppress changes in the pore diameter of the micropores due to hydration, the water washing treatment is preferably performed at 30 ° C. or lower.

<Process (C): Micropore penetration process>
In the process (C), the anodic oxide film 14 having the micropores 16 shown in FIG. 3 is immersed in an acid aqueous solution or an alkali aqueous solution to partially dissolve the anodic oxide film 14. Thereby, the anodic oxide film 14 at the bottom of the micropore 16 is removed, and the micropore 16 penetrates (a micropore through hole 18 is formed). FIG. 4 is a partial cross-sectional perspective view showing a state after the micropore penetrating process, and shows a fine structure made of the anodic oxide film 14 having the micropore through-hole 18.
With this treatment, the penetration rate of the micropores is preferably 70% or more, more preferably 85% or more, and particularly preferably 95% or more.

When an acid aqueous solution is used for the micropore penetration 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. 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 40 ° C.
When an alkaline aqueous solution is used for the micropore penetration 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.

  The thickness of the anodic oxide film after the penetration treatment is preferably 1 to 1000 μm, and more preferably 10 to 500 μm.

  Moreover, it is preferable to wash with water after the penetration treatment. In order to suppress changes in the pore diameter of the micropores due to hydration, the water washing treatment is preferably performed at 30 ° C. or lower.

<Treatment (D): Treatment for imparting a substance that improves the hydrophobicity of the oxide film surface>
In the treatment (D), the hydrophobicity of the surface of the oxide film on the surface of the anodized film including the inside of the micropore with respect to the microstructure formed of the anodized film 12 having the micropore through-holes 16 shown in FIG. The substance which improves is given. Here, it is preferable to apply a substance that improves the hydrophobicity of the surface of the oxide film over the entire surface of the anodized film including the inside of the micropore.
Treatment (D) improves the hydrophobicity of the oxide film surface. Specifically, the treatment (D) makes the contact angle of the oxide film surface with water 100 ° or more, preferably 125 ° or more, more preferably 150 ° or more.

In the treatment (D), the substance to be applied to the oxide film surface is not particularly limited as long as the substance is applied to the oxide film surface to improve the hydrophobicity of the oxide film.
In the treatment (D), it is preferable to improve the hydrophobicity of the oxide film by applying a hydrophobic substance to the surface of the oxide film. Here, as a hydrophobic substance imparted to the oxide film surface in the treatment (D), a compound that acts as a surfactant having a low HLB value, specifically, a compound that acts as a surfactant having an HLB value of 9 or less. preferable.

The compound that acts as a surfactant used in the treatment (D) is not particularly limited as long as the HLB value is 9 or less, a compound that acts as an anionic surfactant, a compound that acts as a cationic surfactant, Any compound that acts as a nonionic surfactant can be used. In addition, since the HLB value of the compound acting as a surfactant varies depending on the structure, the structure is selected and used so that the HLB value is 9 or less.
Among the compounds that act as the above-mentioned surfactants, compounds that act as nonionic surfactants are particularly preferred because of the small influence that the HLB value fluctuates during the filtration treatment.

When a compound that acts as a nonionic surfactant is used, the structure is not particularly limited, and examples thereof include ether type, ester type, amino ether type, ether ester type, alkanolamide type, and the like. Specific examples of the compound acting as a nonionic surfactant include polyoxyethylene alkyl ether, polyoxyethylene alkyl allyl ether, polyoxyethylene derivative, oxyethylene / oxypropylene block copolymer, polyethylene glycol fatty acid ester, sorbitan fatty acid. Esters, polyoxyethylene sorbitan fatty acid esters, polyoxyethylene sorbitol fatty acid esters, glycerin fatty acid esters, polyoxyethylene fatty acid esters, polyoxyethylene alkylamines, alkyl alkanolamides, polyoxyethylene alkylamino ethers, pentaerythritol fatty acid esters, polyethylene glycol , Polyoxypropylene polyoxyethylene alkyl ether, polyoxye Len polyoxypropylene ether derivative, polyoxypropylene glyceryl ether, methoxypolyethylene glycol, glycerol borate fatty acid ester, polyoxyethylene alkylamine, polyoxyethylene glycerol borate fatty acid ester, polyoxyethylene fatty acid alkanolamide, polyglycerin fatty acid ester, Propylene glycol fatty acid ester, polyoxyethylene sorbit fatty acid ester, polyoxyethylene phytosterol, polyoxyethylene phytostanol, polyoxyethylene vegetable oil, polyoxyethylene lanolin, polyoxyethylene lanolin alcohol, polyoxyethylene beeswax derivative, polyoxyethylene alkylphenyl Examples include formaldehyde condensates.
Among these compounds that act as nonionic surfactants, polyoxyethylene alkyl ether, polyoxyethylene alkylphenyl ether, polyoxyethylene / polyoxypropylene block polymer, polyoxyethylene sorbit fatty acid ester, polyoxyethylene sorbitan Fatty acid ester, polyethylene glycol, polyoxyethylene glycerin fatty acid ester, polyethylene glycol fatty acid ester, glycerin fatty acid ester, sorbitan fatty acid ester, pentaerythritol fatty acid ester, propylene glycol fatty acid ester, polyglycerin fatty acid ester adjust HLB value by alkyl chain length It is preferable because it is easy to do.

  Among these, polyoxyethylene alkyl ether, polyoxyethylene sorbite fatty acid ester, polyoxyethylene sorbitan fatty acid ester, polyglycerin fatty acid ester, polyethylene glycol, polyethylene glycol fatty acid ester are adsorptive to alumina which is the main component of oxide film Is preferable, and polyoxyethylene sorbite fatty acid ester and polyethylene glycol fatty acid ester are particularly preferable. As described above, since the HLB value of a compound that acts as a surfactant varies depending on its structure, the compound acting as a surfactant in the above-described case has an HLB value due to the difference in its structure even if it is of the same type. Different. For example, even if it is a compound as a surfactant having an oxyethylene repeating unit, the HLB value varies depending on the number of repeating oxyethylene repeating units, so the structure is selected so that the HLB value is 9 or less. To do.

In addition to the above surfactants, compounds acting as nonionic surfactants as described in JP-A-62-251740 and JP-A-3-208514, JP-A-59-121044 Compounds acting as amphoteric surfactants as described in JP-A-4-13149, and compounds acting as fluorine-based surfactants as described in JP-A-62-170950. Can be added. Specific examples of the compound that acts as the nonionic surfactant include sorbitan tristearate, sorbitan monopalmitate, sorbitan trioleate, stearic acid monoglyceride, polyoxyethylene nonylphenyl ether and the like. Specific examples of the compound acting as an amphoteric surfactant include alkyldi (aminoethyl) glycine, alkylpolyaminoethylglycine hydrochloride, 2-alkyl-N-carboxyethyl-N-hydroxyethylimidazolinium betaine, and N- Examples include tetradecyl-N, N-betaine type (for example, trade name “Amogen K” manufactured by Daiichi Kogyo Co., Ltd.).
Similarly, these surfactants having a HLB value of 9 or less are selected and used.

A commercially available surfactant having an HLB value of 9 or less can be used. As specific examples of the surfactant having an HLB value of 9 or less, for example, the following surfactants can be used.
“Brownon N-502 (HLB value 5.7)”, “Brownon N-503 (HLB value 7.4)”, “Brownon N-504 (HLB value 8.9)”, “Brownon EL-1502” .2 (HLB value 6.3) ”,“ Fine Surf OE-40 (HLB value 7.9) ”,“ Brownon EL-1503P (HLB value 8.3) ”,“ Cocosurf HG-30 (HLB value 8. 3) "," Finesurf D-1303 (HLB value 9.0) ".
“Peletex (registered trademark) PC-2418 (HLB value 5.8)”, “Peletex (registered trademark) PC-2419 (HLB value 6.4)”, “Peletex (registered trademark) PC-2420 (HLB)” Value 7.0) "," Peletex (registered trademark) PC-2421 (HLB value 8.3) "," Peletex (registered trademark) PC-2422 (HLB value 9.0) "," Peletex (registered trademark) PC ". -2319 (HLB value 6.2) "," Peletex (registered trademark) PC-2320 (HLB value 6.9) "," Peletex (registered trademark) PC-2321 (HLB value 8.1) "," Peletex ( (Registered trademark) PC-2322 (HLB value 9.0) ".
"Emulgen (registered trademark) 103 (HLB value 8.1)" manufactured by Kao, "Emulgen (registered trademark) 404 (HLB value 8.8)".
“Leocol (registered trademark) TD-30 (HLB value 8.0)”, “LEOX (registered trademark) TC-35 (HLB value 7.4)”, “LEOX (registered trademark) CC-30 (HLB value) manufactured by Lion 8.0) "," LEOX (registered trademark) CCN-20 (HLB value 6.2) "," LEOX (registered trademark) CCN-30 (HLB value 8.0) ".

  In the treatment (D), a compound that acts as a surfactant to be used can be appropriately selected according to the degree of improving the hydrophobicity of the oxide film surface. In order to further improve the hydrophobicity of the oxide film surface, it is preferable to use a compound that acts as a surfactant having an HLB value of 8 or less, and more preferably to use a compound that acts as a surfactant having an HLB value of 6 or less. .

  In the treatment (D), after immersing the oxide film in a solution in which a compound that acts as a surfactant having an HLB value of 9 or less is dissolved in a solvent, only the solvent is volatilized by heat treatment, whereby the HLB is formed on the surface of the oxide film. A method of imparting a compound that acts as a surfactant having a value of 9 or less is preferred. The type of the solvent is not particularly limited as long as the compound acting as a surfactant dissolves, but water, ethylene dichloride, cyclohexanone, methyl ethyl ketone, methanol, ethanol, propanol, ethylene glycol monomethyl ether, 1-methoxy-2 -Propanol, 2-methoxyethyl acetate, 1-methoxy-2-propyl acetate, dimethoxyethane, methyl lactate, ethyl lactate, N, N-dimethylacetamide, N, N-dimethylformamide, tetramethylurea, N-methylpyrrolidone, Dimethyl sulfoxide, sulfolane, γ-butyrolactone, toluene and the like are preferable. The reason why the above method is preferred is that not only the solvent volatilizes during the heat treatment, but also the oxide film and the compound acting as a surfactant are chemically bonded. The concentration of the compound acting as a surfactant in the solution dissolved in the solvent is preferably 0.1 to 20 wt%, more preferably 0.5 to 10 wt% in order to uniformly treat the entire oxide film surface. Moreover, as heat processing temperature, 40-400 degreeC is preferable and 60-300 degreeC is more preferable. The heat treatment time is preferably 30 seconds to 12 hours, more preferably 1 minute to 8 hours, and particularly preferably 10 minutes to 4 hours.

  In addition to the method of heat treatment after immersing the oxide film in a solution in which a compound acting as a surfactant having an HLB value of 9 or less as described above is dissolved in a solvent, a polymer, preferably a water-insoluble polymer, and After immersing in the surface of the oxide film in a solution in which a compound that acts as a surfactant having an HLB value of 9 or less is dissolved in an organic solvent, only the solvent is volatilized by heat treatment, so that the surface of the oxide film has an HLB value of 9 or less. A compound that acts as a surfactant can also be added. In this case, the polymer, preferably a water-insoluble polymer, functions as a protective film that prevents the hydration of the oxide film. Hereinafter, in this specification, after immersing the oxide film in a solution in which a polymer and a compound that acts as a surfactant are dissolved in an organic solvent, the compound that acts as a surfactant is applied to the surface of the oxide film by heat treatment. This method is called a protective film forming method. On the other hand, after immersing an oxide film in a solution in which a compound that acts as a surfactant is dissolved in a solvent, a method of imparting a compound that acts as a surfactant to the surface of the oxide film by heat treatment is also referred to as a direct imparting method. .

Examples of the water-insoluble polymer include polyvinylidene chloride, poly (meth) acrylonitrile, polysulfone, polyvinyl chloride, polyethylene, polycarbonate, polystyrene, polyamide, cellophane and the like.
Examples of the organic solvent include ethylene dichloride, cyclohexanone, methyl ethyl ketone, methanol, ethanol, propanol, ethylene glycol monomethyl ether, 1-methoxy-2-propanol, 2-methoxyethyl acetate, 1-methoxy-2-propyl acetate, dimethoxyethane. , Methyl lactate, ethyl lactate, N, N-dimethylacetamide, N, N-dimethylformamide, tetramethylurea, N-methylpyrrolidone, dimethyl sulfoxide, sulfolane, γ-butyrolactone, toluene, and the like. The surfactant concentration and the polymer concentration in the liquid dissolved in the organic solvent are each preferably 0.1 to 50 wt%, more preferably 1 to 30 wt%.
Moreover, as heat processing temperature at the time of solvent volatilization, 30-300 degreeC is preferable and 50-200 degreeC is more preferable.

By subjecting the aluminum substrate to at least the above-described treatments (A) to (D) in this order, the fine structure of the present invention obtained has a pore diameter of micropores existing in the oxide film of 0.01 to 0.00. It is preferably 5 μm. Here, the micropore refers to a micropore through hole.
Further, in the micropore, in the range of 1 μm ² , the pore diameter dispersion is preferably within 8% of the average diameter, and more preferably within 5%. In addition, the average diameter and dispersion | distribution of a pore diameter can each be calculated | required by a following formula.
Average diameter: μx = (1 / n) ΣXi
Dispersion: σ ² = (1 / n) (ΣXi ² ) −μx ²
Dispersion / average diameter = σ / μx ≦ 0.03
Here, Xi is the pore diameter of one micropore measured in the range of 1 μm ² .

  Moreover, it is preferable that the degree of ordering defined by the following formula (1) is 50% or more for the micropores present in the oxide film in the microstructure of the present invention.

    Ordering degree (%) = B / A × 100 (1)

  In the above formula (1), A represents the total number of micropores in the measurement range. B is centered on the center of gravity of one micropore, and when a circle with the shortest radius inscribed in the edge of another micropore is drawn, the center of gravity of the micropore other than the one micropore is placed inside the circle. This represents the number in the measurement range of the one micropore to be included.

FIG. 5 is an explanatory diagram of a method for calculating the degree of ordering of pores. The above formula (1) will be described more specifically with reference to FIG.
The micropore 1 shown in FIG. 5A draws a circle 3 (inscribed in the micropore 2) having the shortest radius and centering on the center of gravity of the micropore 1 and inscribed in the edge of another micropore. In this case, the center of the circle 3 includes six centroids of micropores other than the micropore 1. Therefore, the micropore 1 is included in B.
The micropore 4 shown in FIG. 5 (B) draws a circle 6 (inscribed in the micropore 5) having the shortest radius and centering on the center of gravity of the micropore 4 and inscribed in the edge of the other micropore. In this case, the center of gravity of the micropores other than the micropores 4 is included inside the circle 6. Therefore, the micropore 4 is not included in B. In addition, the micropore 7 shown in FIG. 5B is centered on the center of gravity of the micropore 7 and has the shortest radius 9 inscribed in the edge of another micropore (inscribed in the micropore 8). Is drawn, the circle 9 includes seven centroids of micropores other than the micropore 7. Therefore, the micropore 7 is not included in B.

  The microstructure of the present invention more preferably has a degree of ordering defined by the above formula (1) of 60% or more with respect to the micropores present in the oxide film.

  Moreover, the fine structure of the present invention can also carry organic compounds, inorganic compounds, metal fine particles, and the like in the micropores of the anodized film depending on the application.

  The present invention will be specifically described below with reference to examples. However, the present invention is not limited to these.

[Example 1]
1. Electropolishing treatment A high-purity aluminum substrate (manufactured by Sumitomo Light Metal Co., Ltd., purity 99.99 mass%, thickness 0.4 mm) is cut so that it can be anodized in an area of 10 cm square, and an electropolishing liquid having the following composition is used. The electropolishing treatment was performed under the conditions of a voltage of 25 V, a liquid temperature of 65 ° C., and a liquid flow rate of 3.0 m / min. The cathode was a carbon electrode, and GP0110-30R (manufactured by Takasago Seisakusho) was used as the power source. The flow rate of the electrolyte was measured using a vortex flow monitor FLM22-10PCW (manufactured by AS ONE).

<Electrolytic polishing liquid composition>
-660 mL of 85% phosphoric acid (reagent manufactured by Wako Pure Chemical Industries, Ltd.)
・ Pure water 160mL
・ Sulfuric acid 150mL
・ Ethylene glycol 30mL

2. Treatment (A): Micropore formation treatment by anodic oxidation The sample after the polishing treatment obtained above was treated with an electrolytic solution of 0.30 mol / L sulfuric acid, voltage 25 V, liquid temperature 15 ° C., liquid flow rate 3.0 m / min. And anodizing for 1 hour. Furthermore, the obtained sample was immersed for 20 minutes under a condition of 40 ° C. using a mixed aqueous solution of 0.5 mol / L phosphoric acid to remove the film.
After this treatment was repeated four times, re-anodization treatment was performed for 5 hours with an electrolyte solution of 0.30 mol / L sulfuric acid at a voltage of 25 V, a liquid temperature of 15 ° C., and a liquid flow rate of 3.0 m / min. The micropores 16 are arranged in the form of a straight tube and a honeycomb on the surface of the aluminum substrate 12 shown in FIG. 2 by dipping for 20 minutes under a condition of 40 ° C. using a mixed aqueous solution of L phosphoric acid (film removal treatment). An anodic oxide film 14 was formed.
In both the anodizing treatment and the re-anodizing treatment, a stainless steel electrode was used as the cathode, and GP0110-30R (manufactured by Takasago Seisakusho) was used as the power source. Further, NeoCool BD36 (manufactured by Yamato Kagaku Co.) was used as the cooling device, and Pear 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).

3. Treatment (B): Aluminum removal treatment The sample obtained above was immersed in a mixed aqueous solution of 20% by mass hydrochloric acid and 0.1 mol / L cupric chloride at 25 ° C. for 20 minutes to obtain an aluminum substrate 12. Was dissolved to remove, and a fine structure made of the anodic oxide film 14 having the micropores 16 shown in FIG. 3 was produced.

4). Treatment (C): Micropore penetration treatment The sample obtained above was immersed in a 0.10 mol / L potassium chloride aqueous solution at 25 ° C for 2 minutes, and then penetrated using 0.10 mol / L potassium hydroxide. The surface to be contacted was subjected to a contact treatment at 20 ° C. for 10 minutes, and the micropores were allowed to penetrate therethrough, so that a fine structure composed of the anodized film 14 having the micropore through holes 16 shown in FIG.

5). Treatment (D): Treatment for imparting a substance that improves the hydrophobicity of the oxide film surface The sample obtained above is immersed in a solution having the following composition for 5 minutes, and then heat-treated at 200 ° C. for 30 minutes, A compound that acts as a surfactant was applied to the surface of the oxide film by a direct application method that volatilizes and removes the solvent.
・ GO-4: Polyoxyethylene sorbitol tetraoleate (Nikko Chemicals)
* HLB value: 8.5 0.025g
・ Methyl ethyl ketone 30.00g

6). Shape analysis of porous alumina membrane filter A surface photograph (magnification 20000 times) was taken with FE-SEM, and the average diameter and the standard deviation of the diameter were calculated by the following formula for 300 arbitrary micropores in a 1 μm × 1 μm field of view. / The average diameter was determined. As a result, the dispersion of the pore diameter with respect to the average diameter was 2.7%.
Average diameter: μx = (1 / n) ΣXi
Dispersion: σ ² = (1 / n) (ΣXi ² ) −μx ²

Standard deviation = σ =

Standard deviation / average diameter = σ / μx
Here, Xi and x are pore diameters of one micropore measured in the range of 1 μm ² .
Similarly, the degree of ordering defined by the following formula (1) was determined using 300 arbitrary micropores. As a result, the degree of ordering was 90%.
Ordering degree (%) = B / A × 100 (1)
In the above formula (1), A represents the total number of micropores in the measurement range. B is centered on the center of gravity of one micropore, and when a circle with the shortest radius inscribed in the edge of another micropore is drawn, the center of gravity of the micropore other than the one micropore is placed inside the circle. This represents the number in the measurement range of the one micropore to be included.

The filtration flow rate of the fine structure of Example 1 obtained above was evaluated. Specifically, the filtration flow rate per unit time of 20 ° C. pure water at a driving pressure of 1.0 kgf · cm ⁻² was obtained. The results are shown in Table 1.

[Example 2]
2. Treatment (A): Implemented in the same manner as in Example 1 except that the electrolyte used in the micropore formation treatment by anodization was an electrolyte of 0.50 mol / L oxalic acid and the voltage was 40V. The microstructure of Example 2 was obtained. As a result of the shape analysis, the dispersion of the pore diameter with respect to the average diameter was 2.9%, and the degree of ordering was 90%. In addition, the filtration flow rate test was implemented also in this fine structure like Example 1. FIG. The results are shown in Table 1.

[Example 3]
5. above. Treatment (D): Implemented in the same manner as in Example 1 except that the compound acting as a surfactant used in the treatment for imparting a substance that improves the hydrophobicity of the oxide film surface was changed to the following. The microstructure of Example 3 was obtained. As a result of the shape analysis, the dispersion of the pore diameter with respect to the average diameter was 2.7%, and the degree of ordering was 90%. In addition, the filtration flow rate test was implemented also in this fine structure like Example 1. FIG. The results are shown in Table 1.
・ Olein alcohol / OE-20 (Aoki Yushi Kogyo Co., Ltd.)
* HLB value: 5.0 0.040g

[Example 4]
5. above. Treatment (D): Implemented in the same manner as in Example 1 except that the compound acting as a surfactant used in the treatment for imparting a substance that improves the hydrophobicity of the oxide film surface was changed to the following. The microstructure of Example 4 was obtained. As a result of the shape analysis, the dispersion of the pore diameter with respect to the average diameter was 2.7%, and the degree of ordering was 90%. In addition, the filtration flow rate test was implemented also in this fine structure like Example 1. FIG. The results are shown in Table 1.
・ Alkylphenol / nonylphenol / N-503 (Aoki Yushi Kogyo Co., Ltd.)
* HLB value: 7.4 0.050g

[Example 5]
5. above. Treatment (D): Implemented in the same manner as in Example 1 except that the compound acting as a surfactant used in the treatment for imparting a substance that improves the hydrophobicity of the oxide film surface was changed to the following. The microstructure of Example 5 was obtained. As a result of the shape analysis, the dispersion of the pore diameter with respect to the average diameter was 2.7%, and the degree of ordering was 90%. In addition, the filtration flow rate test was implemented also in this fine structure like Example 1. FIG. The results are shown in Table 1.
・ N-decyl alcohol / Fine Surf / D-1303 (Aoki Yushi Kogyo Co., Ltd.)
* HLB value: 9.0 0.025g

[Example 6]
5. above. Treatment (D): In the same manner as in Example 1 except that the treatment for imparting a substance that improves the hydrophobicity of the oxide film surface was carried out by a protective film formation method using a liquid having the following composition: 6 microstructures were obtained. The immersion time and heat treatment conditions are the same as in Example 1. As a result of the shape analysis, the dispersion of the pore diameter with respect to the average diameter was 6.6%, and the degree of ordering was 75%. In addition, the filtration flow rate test was implemented also in this fine structure like Example 1. FIG. The results are shown in Table 1.
・ GO-4: Polyoxyethylene sorbitol tetraoleate (Nikko Chemicals)
* HLB value: 8.5 0.025g
・ Polyvinylidene chloride 0.200g
・ Methyl ethyl ketone 30.00g

[Comparative Example 1]
5. above. Treatment (D): A microstructure of Comparative Example 1 was obtained in the same manner as in Example 1 except that the treatment for imparting a substance that improves the hydrophobicity of the oxide film surface was omitted. As a result of the shape analysis, the dispersion of the pore diameter with respect to the average diameter was 2.7%, and the degree of ordering was 90%. In addition, the filtration flow rate test was implemented also in this fine structure like Example 1. FIG. The results are shown in Table 1.

[Comparative Example 2]
2. Treatment (A): In micropore formation treatment by anodization, anodization treatment was performed for 1 hour with an electrolyte of 0.30 mol / L sulfuric acid under conditions of a voltage of 25 V, a liquid temperature of 15 ° C., and a liquid flow rate of 3.0 m / min. The same method as in Example 1 except that the obtained sample was immersed in a mixed solution of 0.5 mol / L phosphoric acid at 40 ° C. for 20 minutes to omit the repeated film removal treatment four times. Thus, the microstructure of Comparative Example 2 was obtained. As a result of the shape analysis, the dispersion of the pore diameter with respect to the average diameter was 11.2%, and the degree of ordering was 18%. In addition, the filtration flow rate test was implemented also in this fine structure like Example 1. FIG. The results are shown in Table 1.

[Comparative Example 3]
5. above. Treatment (D): Comparison was made in the same manner as in Example 1 except that the compound acting as a surfactant used in the treatment for imparting a substance that improves the hydrophobicity of the oxide film surface was changed to the following. The microstructure of Example 3 was obtained. As a result of the shape analysis, the dispersion of the pore diameter with respect to the average diameter was 2.7%, and the degree of ordering was 90%. In addition, the filtration flow rate test was implemented also in this fine structure like Example 1. FIG. The results are shown in Table 1.
・ Alkylphenol / nonylphenol / N-505 (Aoki Yushi Kogyo Co., Ltd.)
* HLB value: 10.0 0.025g

FIG. 1 is a schematic end view of an aluminum substrate and an anodized film formed on the aluminum substrate. FIG. 2 is a partial cross-sectional view showing a state after the anodizing treatment (A). FIG. 3 is a partial cross-sectional view showing a state after the separation process (B). FIG. 4 is a partial cross-sectional view showing a state after the penetration process (C). FIG. 5 is an explanatory diagram of a method for calculating the degree of ordering of pores.

Explanation of symbols

1, 2, 4, 5, 7, 8 Micropore 3, 6, 9 Circle 12, 12a, 12b, Aluminum substrate 14, 14a, 14b, 14c, 14d Anodized film 16, 16a, 16b, 16c, 16d Micropore 18: Micropore through hole 20 Deformed portion 30 Inflection point

Claims (4)

  A microstructure comprising an aluminum anodized film and having micropore through-holes, wherein the pore diameter dispersion of the micropore through-holes is within 8% of the average diameter, A fine structure characterized by being provided with a substance that improves the hydrophobicity of the surface of the anodized film. On the aluminum substrate, at least
(A) Treatment for forming an oxide film having micropores by anodization treatment,
(B) Treatment for removing aluminum from the oxide film obtained in (A) above,
(C) treatment for penetrating the micropores of the oxide film obtained in (A) above, and (D) treatment for imparting a substance that improves the hydrophobicity of the oxide film surface to the oxide film surface,
The fine structure according to claim 1, which is formed by applying the components in this order.   The microstructure according to claim 1 or 2, wherein the substance that improves hydrophobicity is a compound that acts as a surfactant having an HLB value of 9 or less. The microstructure according to any one of claims 1 to 3, wherein the degree of ordering defined by the following formula (1) is 50% or more for the micropore through hole.
Ordering degree (%) = B / A × 100 (1)
In the above formula (1), A represents the total number of micropore through holes in the measurement range. B, when a circle with the shortest radius inscribed in the edge of the other micropore through hole is drawn around the center of gravity of the one micropore through hole, other than the one micropore through hole inside the circle This represents the number of the one micropore through hole in the measurement range that includes the six gravity centers of the micropore through holes.