JPWO2013125658A1 - Metal material, surface treatment method and apparatus - Google Patents

Abstract

The metal material includes a metal material substrate 2 and a modified layer formed on the surface of the metal material substrate 2, and the modified layer is viewed from a direction perpendicular to the surface of the metal material substrate 2. The average diameter is 1 μm or less, and three or more protrusions 3 projecting from the surface of the metal material base 2 are averaged within the range of 10 μm 2. The modified layer includes a base protruding from the surface of the metal material base 2 and a tip formed at the end of the base, and when viewed from a direction perpendicular to the surface of the metal material base 2 It is preferable that an average diameter is 1 μm or less, and an average of one or more protrusions having a constricted structure in which the outer diameter of the base is smaller than the outer diameter of the tip is within a range of 10 μm 2. Thereby, the metal material which has new functions, such as a hydrophilic property and a luminescent property, can be provided.

Description

  The present invention relates to a metal material, a surface treatment method for a metal material, a method for producing a water repellent material based on a metal material, a surface treatment apparatus for a conductive material, and a surface treatment method for a conductive material.

  In recent years, it has been strongly expected that new functions be imparted to metal materials. Specifically, in addition to the advantageous properties inherent in metal materials such as strength, workability, and corrosion resistance, new functions related to metal surfaces such as hydrophilic properties, water repellency properties, and luminescence properties mean that new fields of use of metal materials can be cultivated. It is highly expected. Against this background, recently, active research has been conducted to form a modified layer such as a plated layer, an oxide layer, a surface hardened layer, and a modified layer with improved surface roughness on the metal surface. As an example, there are a technique for forming a microstructure by anodizing a metal surface (see Non-Patent Document 1), a technique for forming a surface microstructure by electrolytic processing (see Non-Patent Document 2), and the like.

Hideaki Takahashi, Masatoshi Sakairi, Tatsuya Kikuchi, Jah Himendra Surface Technology Vol.60 (2009) No.3 p.14 Application and Theory of Electrochemical Machining for Micromachining Natsuhisa Surface Technology Vol.61 (2010) No.4 294

  In order to impart new functions such as hydrophilic characteristics, water repellency characteristics, and light emission characteristics to the metal material surface, it is necessary to design the structure and composition of the surface modification layer from a microscopic viewpoint of 1 μm or less. However, previous research has been aimed at improving functions such as workability and corrosion resistance, and has designed the structure and composition of the surface modification layer on the micron order, so it is not effective for the expression of new functions. It was enough. For example, as a method for improving the surface roughness, a method of pressing a roll having a dull structure on the surface of a metal material has been proposed. However, the unevenness on the surface of the metal material formed by this method has a size of micron order or more. For this reason, the metal material surface has the effect of improving workability by retaining oil and making the surface appearance uniform, but does not exhibit new functions. Further, as a method for improving the paint adhesion of an automobile outer plate, a method of forming phosphate crystals on the surface of a metal material has been proposed. However, the particle diameter of phosphate crystals formed by this method has a size of several microns. For this reason, the metal material surface does not exhibit a new function.

  On the other hand, among the already reported fine structure forming techniques, a technique for forming a fine structure by anodizing a metal surface, such as the technique described in Non-Patent Document 1, forms fine holes and can be applied. Functions are limited. Moreover, since the surface becomes an oxide layer, the surface physical properties are limited to the oxide species. In addition, a method using electrolytic processing such as the method described in Non-Patent Document 2 requires a very short distance between the surface to be processed and the counter electrode in order to form a surface microstructure. Control is very difficult.

  This invention is made | formed in view of the said subject, The objective is to provide the metal material which has new functions, such as a hydrophilic property and a luminescent property.

  Another object of the present invention is to provide a surface treatment method for a metal material capable of imparting high water repellency to the surface of the metal material without much labor and cost, and a water repellency based on the metal material. It is to provide a method for manufacturing a material.

  Furthermore, another object of the present invention is to provide a conductive material that can be efficiently manufactured at a low cost by conducting a process over a predetermined area of the surface or a large area of the surface to form a nano-level microstructure. The object is to provide a surface treatment apparatus and a surface treatment method.

The metal material according to the present invention includes a metal material substrate and a modified layer formed on the surface of the metal material substrate, and the modified layer is perpendicular to the surface of the metal material substrate. The average diameter when viewed from any direction is 1 μm or less, and the projections protruding from the surface of the metal material substrate have an average of 3 or more within a range of 10 μm ² .

The metal material according to the present invention is the metal material according to the above invention, wherein the modified layer includes a base portion protruding from a surface of the metal material base material, and a tip portion formed at an end portion of the base portion. The average diameter when viewed from the direction perpendicular to the surface of the substrate is 1 μm or less, and the protrusions having a constricted structure whose outer diameter of the base portion is smaller than the outer diameter of the tip portion are averaged within a range of 10 μm ^2. And one or more.

  The metal material according to the present invention is characterized in that, in the above-described invention, the average diameter of the protrusions when viewed from a direction perpendicular to the surface of the metal material substrate is 500 nm or less.

  The metal material according to the present invention is characterized in that, in the above-mentioned invention, the position where the protrusion is formed does not have periodicity in the in-plane direction of the metal material base material.

  The metal material according to the present invention is characterized in that, in the above-described invention, the modified layer includes a recess having an average diameter of 500 nm or less when viewed from a direction perpendicular to the surface of the metal material substrate.

  The metal material according to the present invention is characterized in that, in the above-mentioned invention, the metal material base material is formed of alloy steel.

  The metal material according to the present invention is characterized in that, in the above invention, the metal material base material is formed of a steel material.

  The metal material according to the present invention is characterized in that, in the above invention, the composition of the metal material substrate and the composition of the protrusions are different.

  The metal material according to the present invention is characterized in that, in the above-mentioned invention, the metal material substrate and the protrusion are continuously connected.

  The surface treatment method for a metal material according to the first aspect of the present invention includes a step of immersing a material to be treated as a cathode electrode made of a metal material having a surface to be treated and an anode electrode in an electrolytic solution; Forming a microstructure on the surface to be treated by applying a voltage in a range where the material to be treated is not oxidized or melted at 70 V or higher between the electrode and the anode electrode; and from the electrolytic solution, the material to be treated And cleaning the material to be processed, and performing a water repellent treatment on the surface to be processed of the cleaned material to be processed.

  The surface treatment method for a metal material according to the second aspect of the present invention includes a step of immersing a material to be treated as a cathode electrode made of a metal material having a surface to be treated and an anode electrode in an electrolytic solution; And applying a voltage of 70 V or more and 200 V or less between the anode electrode and the anode electrode, forming a microstructure on the surface to be processed, taking out the material to be processed from the electrolytic solution, And a step of performing a water repellent treatment on the treated surface of the treated material that has been washed.

  The method for producing a water-repellent material based on a metal material according to the present invention comprises immersing a metal material, which is a material to be treated as a cathode electrode having a surface to be treated, and an anode electrode in an electrolytic solution, A step of forming a fine structure on the surface of the metal material as the material to be treated by applying a voltage of 70 V or more and 200 V or less between the cathode electrode and the anode electrode; and taking out the metal material from the electrolytic solution And cleaning the metal material, and performing a water repellent treatment on the surface to be processed of the cleaned metal material.

  A surface treatment apparatus for a conductive material according to the present invention is interposed between an anode electrode and a cathode electrode made of a conductive material, which are immersed in an electrolytic solution so as to be separated from each other, and between the anode electrode and the cathode electrode, A shielding object having an opening for limiting a portion to be processed of the cathode electrode, and a power source for applying a voltage between the anode electrode and the cathode electrode.

  The surface treatment apparatus for a conductive material according to the present invention is characterized in that, in the above-mentioned invention, a mechanism for changing a position of the opening and / or a relative position between the anode electrode and the cathode electrode is provided.

  The surface treatment apparatus for a conductive material according to the present invention is characterized in that, in the above invention, the power source applies a voltage of 60 V or more and 300 V or less between the anode electrode and the cathode electrode.

  The surface treatment apparatus for conductive material according to the present invention is characterized in that, in the above invention, the shield is an insulating heat-resistant material having the opening covered on the surface of the cathode electrode.

  The surface treatment apparatus for a conductive material according to the present invention is characterized in that, in the above invention, the conductive material is a metal material.

  The surface treatment method for a conductive material according to the present invention is characterized in that the surface of the conductive material is treated using the surface treatment apparatus for a conductive material according to the present invention.

  The metal material according to the present invention can provide a metal material having new functions such as hydrophilic characteristics and light emission characteristics.

  According to the surface treatment method for a metal material and the method for producing a water repellent material based on a metal material according to the present invention, high water repellency can be imparted to the surface of the metal material without much labor and cost. it can.

  According to the surface treatment apparatus and the surface treatment method for a conductive material according to the present invention, a conductive material in which a nano-level microstructure is formed over a predetermined area of the surface or a large area of the surface is efficiently manufactured at low cost. can do.

FIG. 1A is a plan view showing a configuration of a metal material according to an embodiment of the present invention. 1B is a cross-sectional view taken along line AA in FIG. 1A. FIG. 2 is an SEM photograph showing an example of a protrusion formed on the surface of a cold-rolled steel sheet. FIG. 3 is a schematic diagram for explaining a method of calculating the outer diameter of the protrusion. FIG. 4 is a schematic diagram for explaining the constriction structure of the protrusion. FIG. 5 is an SEM photograph showing an example of a protrusion having a constricted structure formed on a cold-rolled steel sheet. FIG. 6 is a cross-sectional TEM photograph showing an example of a protrusion having a constricted structure formed on a cold-rolled steel sheet. FIG. 7 is an SEM photograph showing an example of a recess formed on the surface of stainless steel. FIG. 8 is an SEM photograph showing an example of a recess formed on the surface of stainless steel. FIG. 9 is a cross-sectional TEM photograph showing an example of a protrusion having a composition different from that of the substrate. FIG. 10 is a cross-sectional TEM photograph showing a state where protrusions are continuously formed on the cold-rolled steel sheet. FIG. 11 is a flowchart showing a flow of surface treatment of a metal material according to an embodiment of the present invention. FIG. 12 is a schematic diagram showing a configuration example of an apparatus used in the metal material surface treatment method according to an embodiment of the present invention. FIG. 13 is a SEM photograph showing the surface of the surface-treated SUS316L stainless steel. FIG. 14 is a view of the state in which distilled water is dropped on the surface of the stainless steel surface shown in FIG. FIG. 15 is a schematic diagram showing a configuration of a conductive material surface treatment apparatus according to an embodiment of the present invention. FIG. 16 is a schematic view showing a modification of the surface treatment apparatus shown in FIG. FIG. 17 is a schematic view showing a modification of the surface treatment apparatus shown in FIG. FIG. 18 is a diagram illustrating a configuration of the opening. FIG. 19A is a diagram showing a secondary electron image on the left side in the length direction of the opening when 150 V is applied between the anode electrode and the cathode electrode. FIG. 19B is a diagram showing a secondary electron image of the central portion in the length direction of the opening when 150 V is applied between the anode electrode and the cathode electrode. FIG. 19C is a diagram illustrating a secondary electron image on the right side in the length direction of the opening when 150 V is applied between the anode electrode and the cathode electrode. FIG. 20 is a diagram showing the appearance of the cathode electrode after processing with the size of the opening being 5 mm × 5 mm and 5 mmφ. FIG. 21 is a diagram showing an SEM image of the surface of the cathode electrode after processing with the size of the opening being 5 mmφ. FIG. 22 is a view showing an SEM image of the surface of the cathode electrode not subjected to surface treatment.

〔Metal material〕
1A and 1B are a plan view showing a configuration of a metal material according to an embodiment of the present invention and a cross-sectional view taken along line AA in FIG. 1A, respectively. As shown to FIG. 1A and 1B, the metal material 1 which is one Embodiment of this invention is equipped with the base material 2 and the projection part 3 as a modified layer formed on the surface of the base material 2. As shown in FIG. Yes. The base material 2 is formed of a metal material. Examples of metal materials include alloy steels including stainless steel, steel materials such as cold-rolled steel sheets containing Fe and C and a trace amount of alloy elements of about 3% by mass or less as required, soft steel sheets, high tensile strength of 2 GPa class Examples include high strength steel plates and hot rolled steel plates. The shape of the substrate 2 is not particularly limited, and a plate shape, a rod shape, a line shape, a pipe shape, or the like can be used. Moreover, the base material 2 may be obtained by welding a plurality of members. Moreover, when the base material 2 is plate-shaped, the plate | board thickness is not limited and it can utilize from 100 micrometers or less metal foil to the thick steel plate of thickness 3mm or more.

The protrusion 3 is formed by a microstructure protruding from the surface of the substrate 2 having an average diameter R as viewed from a direction perpendicular to the surface of the substrate 2 of 1 μm, preferably 500 nm or less. FIG. 2 is a scanning electron microscope (SEM) photograph showing an example of a protrusion formed on the surface of a cold-rolled steel sheet. In the figure, the protrusion 3 is shown by an arrow. The protrusion 3 is formed by energizing at 135 V for 30 minutes in a K ₂ CO ₃ aqueous solution having a concentration of 0.3 mol / L using a cold-rolled steel plate and a platinum electrode as a cathode electrode and an anode electrode, respectively. In this case, as shown in FIG. 3, the average diameter R of the protrusion 3 when viewed from a direction perpendicular to the surface of the cold-rolled steel sheet is a circle C having the same area as the area surrounded by the outline of the protrusion 3. Is calculated by calculating the diameter R of the circle C. By forming three or more such protrusions 3 on the average within a range of 10 μm ² , light emission characteristics and hydrophilic characteristics can be imparted to the surface of the substrate 2. By increasing the hydrophilic properties, it becomes difficult to form droplets on the metal surface. As a result, it has a cleaning action that makes it difficult to get dirt such as organic matter. I can expect. Although the in-plane distribution of the protrusions 3 is not limited, it is advantageous in manufacturing that there is no particular periodicity. For example, in order to produce a surface in which the protrusions 3 have periodicity in a row, an excessive process is required, which is disadvantageous in production.

As shown in FIG. 4, the protrusion 3 has a structure in which the outer diameter Lrmin of the base 3a is smaller than the outer diameter Lrmax of the tip 3b, that is, a constricted structure, compared with a case without a constricted structure, The specific surface area of the substrate 2 and the internal voids are apparently increased. Therefore, the hydrophilic property etc. which are affected by the specific surface area can be further improved. Moreover, the protrusion part 3 which has a constriction structure gives the chemical reaction on the surface and its promotion function to the surface of the base material 2, and improves adhesiveness with the thin film layer formed on the surface of the base material 2. Can be expected. For this reason, it is desirable to form one or more protrusions 3 having a constricted structure with an outer diameter Lrmin of the base portion 3a smaller than the outer diameter Lrmax of the distal end portion 3b on average within a range of 10 μm ² . Since the hydrophilic property is higher as the specific surface area is larger, it is advantageous to reduce the protrusion size and increase the number of protrusions, and the surface area with a constricted protrusion structure increases the specific surface area, further improving the hydrophilic property. To do.

  The projecting portion 3 having a constricted structure (1) A cross-sectional sample of the surface of a metal material is manufactured by FIB (Focused Ion Beam) method or the like, and the cross-sectional sample is observed with an SEM or a transmission electron microscope (TEM). It can be confirmed by a method, (2) a method in which a metal material is tilted and observed by SEM. FIG. 5 is an SEM photograph showing an example of the protrusion 3 having a constricted structure formed on the cold-rolled steel sheet. This is an image taken by tilting the sample by 70 degrees. FIG. 6 is a cross-sectional TEM photograph showing an example of a protrusion 3 having a constricted structure formed on a cold-rolled steel sheet. The protrusion having a constricted structure has an outer diameter Lrmin of the base portion 3a of 90% or less of the size of the outer diameter Lrmax of the distal end portion 3b as shown in the following formula (1), preferably the following formula (2): Thus, it means a structure in which the outer diameter Lrmin of the base portion 3a is 80% or less of the outer diameter Lrmax of the distal end portion 3b. In the example shown in FIG. 5, the value of Lrmin / Lrmax was 0.38, and in the example shown in FIG. 6, the value of Lrmin / Lrmax was 0.62. The outer diameter Lrmin of the base portion 3a is the minimum outer diameter of the base portion 3a when the base portion 3a is viewed from a direction perpendicular to the surface of the metal material substrate, and the outer diameter Lrmax of the tip portion 3b is equal to that of the metal material substrate. It is the maximum outer diameter of the tip 3b when viewed from a direction perpendicular to the surface.

  On the surface of the base material 2, in addition to the protrusions 3, recesses having an average diameter of 1 μm or less, preferably 500 nm or less when viewed from a direction perpendicular to the surface of the base material 2 are desirably formed. . Since the surface area of the metal material can be increased by forming the recesses in addition to the protrusions 3, the light emission characteristics and the hydrophilic characteristics of the metal material surface can be further improved. In addition, the presence of the concave portions in addition to the convex portions allows more lubricating oil and functional liquid to be retained for a longer time, so that a new function can be imparted to the surface of the substrate 2.

7 and 8 are SEM photograph diagrams showing an example of a recess formed on the surface of stainless steel. FIG. 7 shows a state in which the metal material is observed from directly above the surface of the metal material, and FIG. 8 shows a state in which the metal material is observed by tilting the metal material by 60 degrees. The recesses shown in FIGS. 7 and 8 are formed by energizing SUS430 stainless steel and platinum electrodes at 115 V for 30 minutes in a 0.1 mol / L aqueous K ₂ CO ₃ solution using a cathode electrode and an anode electrode, respectively. It is. The arrow in the figure indicates a recess. As is apparent from FIGS. 7 and 8, recesses having a size of about 200 nm to 500 nm are formed all over the stainless steel surface.

  The substance which forms the protrusion part 3 may have the same composition as the base material 2, a different composition, and can be used properly according to the objective. FIG. 9 is a cross-sectional TEM photograph showing an example of the protrusion 3 having a composition different from the composition of the substrate 2. In the example shown in FIG. 9, the base material 2 is made of SUS316 stainless steel, but the Cr concentration in the protrusion 3 is smaller than the Cr concentration in the base material 2. According to such a structure, it is expected that the catalytic function of Ni can be utilized more effectively while utilizing the advantages of SUS316 stainless steel. As an example, there is a possibility that it can be used as it is as a steam reforming catalyst containing Ni as an active ingredient. In this case, since Cr is known to lower the catalyst performance, it can be expected that the influence of Cr can be reduced. Moreover, since the protrusion structure of this invention has a large specific surface area, it is excellent in heat exchange property. This is also advantageous as a catalytic reaction substrate.

  It is desirable that the base material 2 and the protruding portion 3 are continuous bodies. By the base material 2 and the protrusion part 3 being a continuous body, the intensity | strength of the protrusion part 3 can be raised. FIG. 10 is a cross-sectional TEM photograph showing a state where protrusions are continuously formed on the cold-rolled steel sheet. Although not shown, when the crystal orientation was analyzed for the region R1 of the protrusion 3 and the region R2 of the substrate 2, the protrusion 3 was a single crystal and had almost the same crystal orientation as the substrate 2. Such a continuous structure is stable against mechanical action and chemical action, and in addition to the protrusion 3 being difficult to fall off, it is also effective when it is not desired to use a different substance or different element for the protrusion 3. It is. Such a continuous structure can be formed by using a steel material or metal having a low content of an easily oxidizable alloy element (for example, Cr) as the base material 2.

  As an example of the manufacturing method of the metal material 1 which has such a structure, it can manufacture by utilizing the discharge in electrolyte solution. Specifically, a direct current voltage of about 60 to 140 V is applied to the electrode in the electrolytic solution using a material to be treated and an inert metal such as platinum as a cathode electrode and an anode electrode, respectively. The range of the applied voltage varies depending on the material to be processed, but can be easily determined while confirming the surface structure of the material to be processed by SEM. By changing the processing time and the applied voltage within a suitable range, the average diameter of the protrusions can be controlled. Specifically, in the case of the same material, the average diameter of the protrusion can be increased as the applied voltage is increased, the treatment time is increased, and the position deeper from the electrolytic solution liquid surface.

  However, when the applied voltage reaches a value that causes a complete plasma state, the surface of iron or stainless steel is excessively melted or oxidized. It is difficult to form a fine protrusion structure. In order to impart a constricted structure, it is necessary to select a condition where the discharge energy density is high as long as the surface is not excessively melted or oxidized. As an example, it is effective to set the applied voltage higher or reduce the processing target region so that the electric field is concentrated. In this case as well, a suitable condition can be determined by comparing the result of observing the treated surface with an SEM with the treated condition. Further, the protrusion structure in which Ni is concentrated and Cr is deficient as shown in FIG. 9 can be formed by setting the discharge voltage higher. In addition to this, it is possible to provide a new element on the surface by preparing a protrusion structure and then supplying the element in a solution. The “complete plasma state” refers to a state in which light emission mixed with orange or light emission mainly composed of orange covers the cathode electrode surface during discharge.

[Example 1]
A soft cold-rolled steel sheet (CRS, size 2 mm × 20 mm × 0.7 mm) and Pt were immersed in an aqueous solution of K ₂ CO _{3 with} a concentration of 0.3 mol / L as a cathode electrode and an anode electrode, respectively, and different energizing voltages were applied to the cathode A sample was prepared by energizing the electrode and the anode electrode. And the surface of the soft cold-rolled steel plate after electricity supply was observed by SEM, and the average diameter and density of the projection part currently formed in the surface were evaluated. At that time, in order to observe how the treatment differs depending on the depth from the liquid level of the aqueous solution, for some samples, the sample was cut out from the soft cold-rolled steel sheet at the portion where the depth from the liquid level was different. The surface was observed. The average diameter of the protrusions is an average value of the diameters of 20 protrusions arbitrarily selected within a range of 12 μm × 9 μm arbitrarily selected, and the density is the number of protrusions within the above range of 108 μm. ^This is a result of dividing the number by ² (= 12 μm × 9 μm) and multiplying by 10 μm ² to obtain the number of protrusions per 10 μm ² . The evaluation results are shown in Table 1 below. Experiment No. 1 shown in Table 1. Sample 1-7 is a soft cold-rolled steel sheet before energization in the above aqueous solution. Experiment No. 1 shown in Table 1. Samples 1-1 to 1-6 and Experiment No. As is clear from the comparison with the sample No. 1-7, it was confirmed that the modified layer having the protrusions according to the present invention can be obtained by the energization treatment. It was also confirmed that by reducing the applied voltage, the average diameter of the protrusions can be reduced and the density of the protrusions can be increased. In addition, Experiment No. It was confirmed that the average diameter of the protrusions can be reduced and the density of the protrusions can be increased by shortening the distance from the liquid surface to the treatment surface as in the sample 1-6.

[Example 2]
SUS316 stainless steel (size: 25 mm × 2.5 mm × 0.8 mm) and Pt were immersed in an aqueous solution of K ₂ CO _{3 with} a concentration of 0.3 mol / L as a cathode electrode and an anode electrode, respectively, and different energization voltages were applied to the cathode electrode. A sample was prepared by energizing the anode electrode. And the surface of the SUS316 stainless steel after electricity supply was observed by SEM, and the average diameter and density of the projection part currently formed in the surface were evaluated similarly to Example 1. FIG. At that time, in order to observe how the treatment differs depending on the depth from the liquid level of the aqueous solution, for some samples, the sample was cut out from the soft cold-rolled steel sheet at the portion where the depth from the liquid level was different. Observations were made. Moreover, the photoluminescence of the surface of SUS316 stainless steel after energization was measured. As an apparatus, FP6200 manufactured by JASCO Corporation was used, and measurement was performed at a start wavelength of 350 nm, an end wavelength of 600 nm, and an excitation wavelength of 435 nm. Specifically, in the photoluminescence spectrum obtained from the stainless steel surface after energization, an emission peak centered around a wavelength of about 430 nm that is not found in the photoluminescence spectrum obtained from the stainless steel surface before energization was confirmed. It was done. Therefore, in this example, the intensity of the emission peak was measured in the photoluminescence measurement. Experiment No. 1 in which the maximum emission intensity was obtained in this example. Experiment No. 2 in which the emission peak height of 2-5 was 10, untreated, and no corresponding emission peak was observed. The height of the emission peak of 2-7 was evaluated as 0. The evaluation results are shown in Table 2 below. As shown in Table 2, the stainless steel surface having the protrusions according to the present invention (samples of Experiment Nos. 2-1 to 2-5) is an untreated stainless steel surface having no protrusions (Experiment No. Sample No. 2-7), or experiment no. It was confirmed that the sample had high emission characteristics as compared with the 2-6 sample. The emission characteristics increase as the size of the protrusions decreases, and particularly high emission characteristics are obtained when the average diameter of the protrusions is 500 nm or less. From this result, it is expected that the stainless steel having the protrusions according to the present invention can be used as a metal material of a display element or an element using light in the visible light region.

Example 3
SUS316 stainless steel (thickness 1 mm × width 2.5 mm × length 30 mm) was used. The surface was mirror-polished with Diawrap ML-150P. The stainless steel and Pt were immersed in 300 cm ^{3 of a} 0.1 mol / L K ₂ CO ₃ aqueous solution as a cathode electrode and an anode electrode, respectively, and the cathode and anode electrodes were energized for 15 minutes at different energizing voltages. Produced. After the experiment, the electrode (SUS316 stainless steel) was thoroughly rinsed with distilled water and then sufficiently dried to conduct contact angle measurement experiments on the surfaces of three portions at a depth of 30 mm, 28 mm, and 26 mm from the liquid surface. Distilled water (made by Wako Pure Chemical Industries, Ltd.) was dropped with a micropipette, and each water drop was photographed from the side with a camera (EOS Kiss X2 made by Canon). The length (l) is measured, the respective contact angles (θ _R ) are calculated from θ _R = 2tan ⁻¹ (2h / l), the average value is calculated, and the contact angle at a depth of 30 mm from the liquid surface did.

  After the contact angle measurement experiment was completed, the sample was sufficiently dried, and the average diameter and density of the protrusions formed on the surface were evaluated in the same manner as in Example 1. Further, in order to evaluate how much the surface area of the obtained sample is increased with respect to the smooth surface, the surface area of the sample when the surface area of the smooth surface is 1 is defined as the specific surface area, and the following assumption is made: Based on the calculation. That is, assuming that the hemispherical protrusions having the average diameter obtained above exist on the smooth surface at the density obtained above, the number of times of the increase relative to the smooth surface was calculated. The results are shown in Table 3 below. As shown in Table 3, in the examples within the scope of the present invention, the samples (experiment No. 3-1) which are untreated and do not have the modified layer of the present invention or the properties of the modified layer are out of the scope of the present invention. It can be seen that the contact angle is small compared with the sample (Experiment No. 3-6) and the hydrophilic property is improved.

Example 4
A soft cold-rolled steel sheet (size: 1.5 mm × 20 mm × 0.7 mm) and Pt were immersed in an aqueous solution of K ₂ CO ₃ having a concentration of 0.3 mol / L as a cathode electrode and an anode electrode, respectively, and a cathode with an energization voltage of 110V A sample was prepared by energizing the electrode and the anode electrode for 30 minutes. In this example, the width of the sample was set to 1.0 mm different from those in Examples 1 and 2 in order to concentrate the electric field. And after electricity supply, the contact angle of one place was measured by the method similar to Example 3 regarding the 15-mm depth part from the liquid level. The result was a contact angle of 45 °. Further, after the contact angle measurement, the sample was dried, the surface of the same part was observed with SEM, and the average diameter and density of the protrusions formed on the surface were evaluated in the same manner as in Example 1. A typical SEM photograph is shown in FIG. As a result of the evaluation, the average diameter of the protrusions as viewed from above was 350 nm. Further, the density of the protrusions having a constricted structure was evaluated. Density of projections having a constricted structure, counted the number of projections having a constricted configuration in the same parts as of the evaluation of the average diameter and density of the projections (range), similar to the density of the projections, per 10 [mu] m ² The average number of was calculated. As a result, it was confirmed that there were three on average.

Example 5
A soft cold-rolled steel plate (size 1.5 mm × 20 mm × 0.7 mm) and Pt were immersed in an aqueous solution of K ₂ CO ₃ having a concentration of 0.3 mol / L as a cathode electrode and an anode electrode, respectively, and the cathode was set at an energizing voltage of 95V. A sample was prepared by energizing the electrode and the anode electrode for 10 minutes. And after electricity supply, the contact angle of one place was measured by the method similar to Example 3 regarding the 15-mm depth part from the liquid level. The result was a contact angle of 60 °. In addition, after measuring the contact angle, it was dried and the surface of the same part was observed by SEM, and the average diameter and density of the protrusions formed on the surface and the density of the protrusions having a constricted structure were evaluated in the same manner as in Example 1. did. As a result of the evaluation, it was confirmed that the average diameter of the protrusions as viewed from above was 350 nm, and an average of one protrusion having a constricted structure was present within 10 μm ² .

Example 6
A 6 mass% C-2 mass% Si-2 mass% Cr steel was rolled and the cross section was evaluated for Vickers strength of 25 g, which was 900, which was confirmed to be a 2GPa class ultra high strength steel. The steel material cut into a size of 1 mm × 20 mm × 0.7 mm and Pt were immersed in an aqueous solution of K ₂ CO _{3 with} a concentration of 0.1 mol / L as a cathode electrode and an anode electrode, respectively, and the cathode voltage was set at 110V. The anode electrode was energized for 30 minutes. After energization, the surface of the soft cold-rolled steel sheet having a depth of 18 mm from the liquid surface was observed by SEM, and the average diameter of the protrusions formed on the surface and the density of the protrusions having a constricted structure were evaluated. As a result of the evaluation, it was confirmed that the average diameter of the protrusions seen from above was 400 nm, and ^two protrusions having a constricted structure exist on average within 10 μm ² .

[Surface treatment method for metal materials]
FIG. 11 is a flowchart showing a flow of surface treatment of a metal material according to an embodiment of the present invention. FIG. 12 is a schematic diagram showing a configuration example of an apparatus used in the metal material surface treatment method according to an embodiment of the present invention. As shown in FIG. 11, in the surface treatment of a metal material according to an embodiment of the present invention, first, a material to be treated as a cathode electrode, which is a metal material, and an anode electrode are immersed in an electrolytic solution, and the cathode electrode By applying a voltage between the anode electrode and the anode electrode, a fine structure is formed on the surface of the material to be processed (step S1). Specifically, as shown in FIG. 12, the anode electrode 13 and the material to be processed 14 are immersed in the electrolytic solution 12 in the container 11, and the anode electrode 13 and the electrode 13 are connected from the power source 16 through a conductive wire 15 such as a copper wire. By applying a voltage to the material 14 to be processed, a fine structure is formed on the surface of the material 14 to be processed.

The electrolytic solution 12 is not particularly limited, and has electrical conductivity. When the surface treatment of the material to be treated 14 is performed, the surface of the material to be treated 14 is excessively etched, or the anode electrode 13 and the material to be treated are treated. It is a solution that hardly adheres to or precipitates on the surface of the material 14 or forms a precipitate. Examples of the electrolyte of the electrolytic solution 12 include potassium carbonate (K ₂ CO ₃ ), sodium carbonate (Na ₂ CO ₃ ), sodium hydrogen carbonate (NaHCO ₃ ), ammonium carbonate ((NH ₄ ) ₂ CO ₃ ), water Lithium oxide (LiOH), sodium hydroxide (NaOH), potassium hydroxide (KOH), ammonium hydroxide (NH ₄ OH), sodium chloride (NaCl), potassium chloride (KCl), ammonium chloride (NH ₄ Cl), sulfuric acid Such as sodium salt, sulfuric acid potassium salt, sulfuric acid ammonium salt, nitric acid sodium salt, nitric acid potassium salt, nitric acid ammonium salt, sodium citrate (NaH ₂ (C ₃ H ₅ O (COO) ₃ )) Sodium salt of acid, potassium salt of citric acid, ammonium salt of citric acid, nitric acid, hydrochloric acid, etc. It can be exemplified.

  The electrolytic solution 12 can have any pH and concentration as long as the surface of the material to be treated 14 can be modified. For example, when an aqueous potassium carbonate solution is used as the electrolytic solution 12, the concentration thereof is not particularly limited and can be 0.001 mol / L or more, more preferably 0.005 mol / L or more. This is because if the concentration of the electrolytic solution 12 is too low, it may be difficult to maintain a suitable discharge state when a voltage is applied between the anode electrode 13 and the workpiece 14. The upper limit of the concentration of the electrolytic solution 12 is not particularly provided, but can be, for example, 0.5 mol / L or less. Further, the pH of the electrolytic solution 12 can be set to an arbitrary value as long as the electrode does not cause excessive corrosion or etching, and can be set to, for example, pH 10 to 12.

  The anode electrode 13 is formed of a material that is thermally and chemically stable during discharge. Examples of such an anode electrode 13 include Pt, Ir, and graphite.

  The material to be treated 14 is not particularly limited as long as it is a metal material, and a cold-rolled material, a hot-rolled material, or a cast material, and a processed product thereof (including welding) can be used if it is a steel material. The steel type is not particularly limited, and carbon steel, low alloy steel, stainless steel, or the like can be used. Also, plated steel sheets including electrogalvanized steel sheets can be used. Moreover, the shape of the to-be-processed material 14 is not specifically limited, A plate shape, linear shape, rod shape, a pipe shape, or a processed component can be utilized. Moreover, the to-be-processed material 14 needs to be immersed in the electrolyte solution 12, and needs to be deeper than 1 mm from a liquid level at least.

  As the discharge condition, a range from a partial plasma state to a complete plasma state where unevenness is formed on the surface of the material to be processed 14 can be used. However, it is necessary to carry out in a voltage range lower than the voltage at which the workpiece 14 melts. Specifically, when the discharge voltage is increased, light emission that can be confirmed with the naked eye in the dark starts, and is a state from a voltage indicating orange point light emission to immediately before the entire material becomes red hot. The applied voltage is preferably in the range of about 70 to 200 V, and more preferably in the range of 80 to 150 V, when the size of the workpiece 14 is 1 mm × 1 mm × 20 mm. This voltage range is applicable to most steel materials including alloy steels such as stainless steel. However, since this voltage range changes depending on the type and arrangement of the material 14 to be processed, it is preferable to determine by observing the surface of the material 14 to be processed by changing the voltage condition with an SEM.

  It is a necessary condition that the discharge voltage is a voltage for forming fine protrusions on the surface of the steel material. If the voltage is lower than the lower limit voltage, fine protrusions are not formed on the surface. Therefore, it can be determined by confirming the presence or absence of the fine protrusions by SEM. If the upper limit is exceeded, the surface to be treated will melt. Therefore, the upper limit can be determined as the voltage at which the surface melts. However, it is more desirable not to oxidize the surface. In that case, the voltage at which the surface is oxidized can be easily determined by examining the SEM and an energy dispersive X-ray spectrometer (EDS) attached to the SEM. When oxygen is detected with the same X-ray intensity as the oxide of the material 14 to be processed, it can be determined that the surface is oxidized. Further, with respect to the X-ray intensity of oxygen normalized by the intensity of the Fe L-line of the oxide of the object to be treated 14 (for example, it means an oxide of Fe in a cold rolled steel sheet or low alloy steel), the material to be treated 14 The X-ray intensity normalized with the Fe-L line intensity of oxygen at 1 is required to be 1/3 or less. The surface inspection is performed by changing the voltage and discharging for 30 minutes, taking out the material 14 to be processed, washing it with water, drying it, introducing it into the SEM, and observing it.

  The discharge processing time needs 3 seconds or more. However, the discharge treatment time may be as long as, for example, 60 minutes. However, if the discharge treatment time is too long, the material to be treated 14 may be worn out, so a treatment time of 30 minutes or longer is not preferable. Within the desired voltage range, it has been found that the higher the applied voltage, the higher the water repellency of the surface after the final step. Therefore, the most preferable condition is to select an applied voltage close to the upper limit of the preferable condition range.

FIG. 13 shows an example in which a SUS316L stainless steel plate having a thickness of 0.8 mm is processed. This SUS316L stainless steel plate was cut to a width of 2 mm and a length of 30 mm, and was made conductive with a copper wire to form a cathode electrode. The anode electrode used was a 50-cm long Pt wire bent so as not to contact each other and formed into a planar shape. The connecting part between the SUS316L stainless steel plate and the copper wire was heat-pressed with a heat-resistant resin so that the copper wire did not touch the electrolytic solution, and the 20 mm long portion of the electrode was immersed in the electrolytic solution. The electrolytic solution was an aqueous solution of K ₂ CO ₃ having a concentration of 0.1 mol / L, the voltage was set to 130V, and the electric discharge was performed for 10 minutes.

  As a result, as shown in FIG. 13, it was confirmed that a fine protrusion structure having an average diameter of 1 μm or less was formed on the surface of the SUS316L stainless steel plate. Moreover, it was confirmed by the elemental analysis by EDS that the surface of the SUS316L stainless steel plate was not oxidized. In addition, at an applied voltage exceeding 160 V, the tip of the SUS316L stainless steel plate was melted. For this reason, the upper limit value of the applied voltage could be obtained as 160V. In addition, since it was confirmed by EDS elemental analysis that the surface of the SUS316L stainless steel plate was not oxidized at an applied voltage of 140 V or lower, it was found that the preferable upper limit of the applied voltage was 140 V in this experimental condition and test material. . On the other hand, the lower limit value of the applied voltage could be determined to be 80 V from the presence or absence of the protrusion structure. The most preferable applied voltage could be determined to be 140V.

  Returning to FIG. Once the microstructure is formed on the surface of the material to be processed 14 as described above, the material to be processed 14 is then taken out from the electrolytic solution 12 and the material to be processed 14 is cleaned (step S2). Finally, a water repellent treatment is performed on the treated surface of the treated material 14 that has been cleaned (step 3). The cleaning method is performed for the purpose of removing the electrolytic solution on the surface, and includes a method of immersing in pure water or spraying. In addition to pure water, a weak acid or an alkaline solution may be used as long as the fine structure on the surface is not broken. At that time, electrolysis can be applied. After washing, it may be dried, or depending on the subsequent water repellent treatment, it may proceed to the next step without being dried. As the water repellent treatment method, a method of applying a water repellent spray, a method of adsorbing an organic substance having a water repellent function such as a fluorine-based resin in a liquid phase or a gas phase, and the like can be adopted. In this embodiment, nanopro (component: fluorocarbon resin, silicon resin) manufactured by Coronyl Co., Ltd. is sprayed on the surface of the material to be treated 14 and dried for 12 hours or more, so that the surface of the material to be treated 14 is subjected to water repellent treatment. did. Thereby, a series of surface treatments are completed.

  FIG. 14 shows the result of observing the state in which distilled water was dropped from the sample surface shown in FIG. As a result of observation, the contact angle of water was measured to be 152 °, and it was confirmed that super water-repellency was realized. The contact angle of water in the sample not subjected to the water repellent treatment was 51 °. Further, when the same water repellent treatment was performed on the material that was not subjected to plasma discharge in the solution, the contact angle of water was 125 °. Therefore, in order to obtain a super water-repellent surface, it was confirmed that both plasma discharge in solution and water-repellent treatment were necessary.

[Example 1]
A commercially available 0.8 mm thick stainless steel SUS316L steel sheet was cut into 2 mm width and 30 mm length and degreased by immersing in dilute hydrochloric acid, and then conducting through a copper wire to obtain a cathode electrode. The anode electrode was formed by bending a 0.5 mmφ Pt wire having a length of 50 cm so as not to contact each other and forming it into a planar shape. The connecting portion between the cathode electrode and the copper wire was heat-pressed with a heat-resistant resin, so that the copper wire did not touch the electrolytic solution, and the 20 mm long portion of the electrode was immersed in the electrolytic solution. The electrolytic solution was a K ₂ CO ₃ aqueous solution having a concentration of 0.1 mol / L, the applied voltage was set within the range of 60 to 180 V, the electric discharge was performed for 10 minutes, and after completion, the plate was washed with pure water and dried. Then, water repellent treatment was performed by spraying Nanopro manufactured by Coronyl on the surface of the material to be treated and drying for 12 hours or more, and the water wettability was investigated. Water wettability was obtained by dropping distilled water at 6 locations 1 μm at a regular interval onto the electrode surface using a micropipette and shooting from the side using Canon's digital camera EOS Kiss X2. The contact angle was measured from the photograph taken and evaluated by taking the average of 6 locations. Distilled water 049-16787 manufactured by Wako Pure Chemical Industries, Ltd. was used. Table 4 shows the test results. As shown in Table 4, it was confirmed that all of the inventive examples exhibited a high contact angle compared to the untreated material. Particularly in Invention Examples 3, 4 and 5 where the applied voltage is in the range of 120 to 140V, super water repellency with a contact angle of 150 ° or more is realized, and in Invention Example 5 where the applied voltage is 140V, the most is 153.6 °. It was confirmed that a high contact angle was exhibited.

[Surface treatment equipment for conductive materials]
The inventors of the present invention consider that it is conventionally impossible to form a nano-level microstructure for the purpose of efficiently producing a conductive material having a nano-level microstructure formed on the surface at a low cost. Intensive research was conducted, including the examination of the possibility of using plasma discharge in liquid. As a result, the inventors of the present invention have found that a nano-level microstructure can be formed on the surface of the conductive material by partially causing plasma discharge in liquid using the conductive material as a cathode electrode. It was. In addition, the inventors of the present invention have studied a method of forming a nano-level microstructure on a specific portion of the surface of the conductive material, and the treated portion of the conductive material is immersed in an electrolyte solution together with the anode electrode, It was found that a nano-level microstructure can be formed in a specific portion of the surface of the conductive material by installing a shield having an opening between the conductive material and the anode electrode. Furthermore, the inventors of the present invention can change the relative position between the opening of the shielding object and / or the anode electrode and the conductive material, so that the surface of the conductive material continuously or discretely has nano-level fineness. It has been found that a structure can be formed.

  FIG. 15 is a schematic diagram showing a configuration of a conductive material surface treatment apparatus according to an embodiment of the present invention. As shown in FIG. 15, the surface treatment apparatus 21 for a conductive material according to an embodiment of the present invention includes a modification treatment cell 22, an electrolytic solution 23 stored in the modification treatment cell 22, and an electrolytic solution 23. The anode electrode 24 and the cathode electrode 25 made of a conductive material to be processed are provided, and the anode electrode 24 and the DC power source 26 connected to the cathode electrode 25 are provided. The cathode electrode 25 is covered with a box 27 made of an insulating material, and the box 27 is formed with an opening 28 for limiting a portion to be processed of the cathode electrode 25. The box 27 is arranged so that the upper part is higher than the liquid level of the electrolytic solution 23. The upper part of the box 27 may be opened, or may have a lid with a hole through which a conducting wire connecting the cathode electrode 25 and the DC power source 26 is passed.

  As the modification treatment cell 22, a known cell made of a material that is stable with respect to the electrolytic solution 23, for example, a cell made of glass, Teflon (registered trademark), or polyethyl ether ketone (PEEK) can be used. A ceramic cell can also be used as the modification treatment cell 22. In the surface treatment apparatus 21 shown in FIG. 16 to be described later, a metallic cell can be used.

The electrolytic solution 23 has electrical conductivity, and a voltage is applied between the anode electrode 24 and the cathode electrode 25 to form a nano-level microstructure on the surface to be processed (the surface of the cathode electrode 25). Further, it is a solution that hardly etches the surface to be treated, adheres to or precipitates on the surfaces of the anode electrode 24 and the cathode electrode 25, or forms a precipitate. Such electrolytic solution 23, for example, potassium carbonate _(K 2 _CO 3), sodium carbonate _(Na 2 _CO 3), sodium bicarbonate (NaHCO _3), ammonium carbonate _{((NH 4) 2 CO 3} ), water Lithium oxide (LiOH), sodium hydroxide (NaOH), magnesium hydroxide (Mg (OH) ₂ ), potassium hydroxide (KOH), ammonium hydroxide (NH ₄ OH), sodium chloride (NaCl), potassium chloride (KCl ), Magnesium chloride (MgCl ₂ ), ammonium chloride (NH ₄ Cl), lithium sulfate, sodium sulfate, magnesium sulfate, potassium sulfate, ammonium sulfate, lithium nitrate, sodium nitrate, Magnesium nitrate, potassium nitrate, ammonium nitrate, lithium Citrate um, citrate sodium, such as sodium citrate _{(NaH 2 (C 3 H 5} O (COO) 3)), citrate magnesium, citrate potassium citrate ammonium, An aqueous solution containing at least one selected from the group consisting of sulfuric acid, nitric acid, hydrochloric acid, and citric acid can be used.

  The electrolytic solution 23 can have any pH and concentration as long as the surface treatment of the cathode electrode 25 can be performed. For example, when an aqueous potassium carbonate solution is used as the electrolytic solution 23, the concentration is particularly limited. It can be 0.001 mol / L or more, more preferably 0.005 mol / L or more without any problems. This is because if the concentration is too low, it may be difficult to maintain a suitable discharge state when a voltage is applied between the anode electrode 24 and the cathode electrode 25. The upper limit of the concentration is not particularly provided, but can be set to 0.5 mol / L or less, for example. Further, the pH of the electrolytic solution 23 can be set to any value as long as the electrode is not excessively corroded or etched, for example, pH 5 to 12.

  The anode electrode 24 is ionized and dissolved in the electrolytic solution 23 when a voltage is applied between the anode electrode 24 and the cathode electrode 25 to form a nano-level microstructure on the surface to be processed. It is an insoluble anode electrode made of an electrode material that is deposited on the surface and does not hinder the formation of a nano-level microstructure. As such an anode electrode 24, for example, a platinum (Pt) electrode, a palladium (Pd) electrode, an iridium (Ir) electrode, an electrode whose surface is coated with Pt, Pd, or Ir, or a graphite electrode can be used.

  The cathode electrode 25 is a material to be processed whose surface is modified by application of a voltage, and is made of a conductive material (conductive material) such as a metal material or an alloy material. Examples of the material to be processed that functions as the cathode electrode 25 include a carbon steel material, an alloy steel material, a stainless steel material, and a nickel material. Further, the shape of the cathode electrode 25 (material to be processed) is not particularly limited, and can be a component having a plate shape, a belt shape, or a conductive material portion. The material to be treated can be used as the cathode electrode 25 after the surface is optionally mirror-polished with sandpaper or the like.

  The direct current power source 26 applies a voltage required for the modification process of the surface of the cathode electrode 25 that is a material to be processed, for example, a voltage of 60 V or more and 300 V or less between the anode electrode 24 and the cathode electrode 25. A known power source can be used as the DC power source 26.

  In the present embodiment, the cathode electrode 25 is covered by the box 27. However, as shown in FIG. 16, the anode electrode 24 may be covered by the box 27 in which the opening 28 is formed. Further, the portion to be processed of the cathode electrode 25 is not limited by the box 27 having the opening 28, but as shown in FIG. 17, at least the surface of the cathode electrode 25 immersed in the electrolytic solution 23 is heat resistant resin, glass or the like. The insulating portion may be covered with an insulating heat-resistant material, and an opening 28 for limiting a portion to be processed of the cathode electrode 25 may be formed in a part of the heat-resistant material.

  The shape and size of the opening 28 are not particularly limited, and the box 27 may have a plurality of openings. When a plurality of openings 28 are provided, the openings 28 are not limited to the same surface of the cathode electrode 25. For example, the openings 28 may be provided on the front surface side and the back surface side of the cathode electrode 25. In addition, as shown in FIG. 18, an inclined portion 28 a may be provided at an upper end (liquid level side) end of the opening 28. By providing the inclined portion 28a, the gas generated from the portion to be processed can be efficiently released into the electrolytic solution 23.

  The surface treatment apparatus 21 may have a heating means such as a heater for heating the electrolytic solution 23 or a thermometer for measuring the temperature of the electrolytic solution 23. Further, the angle at which the cathode electrode 25 is installed may be perpendicular to the liquid surface of the electrolytic solution 23, but is not limited thereto. Further, for the purpose of promoting plasma generation on the surface of the cathode electrode 25, a mechanism for supplying a gas such as hydrogen, argon, water vapor or the like to the surface of the cathode electrode 25 may be provided.

  The surface treatment apparatus 21 having such a configuration produces a surface-modified conductive material as follows. Hereinafter, a surface treatment method for a conductive material using the surface treatment apparatus 21 will be described.

[Surface treatment method of conductive material]
When manufacturing the surface-modified conductive material using the surface treatment device 21, first, the box 27 is immersed in the electrolytic solution 23 stored in the modification treatment cell 22, and then the anode electrode 24 and the cathode electrode 25 are immersed separately, and the system (surface modification processing system) which performs the surface modification process of the cathode electrode 25 is constructed | assembled. At that time, the cathode electrode 25 is immersed in the box 27 so that the portion to be processed can be seen from the opening 28 of the box 27. The surface modification treatment of the cathode electrode 25 is performed on the portion exposed from the opening 28 to the electrolytic solution 23 side. In the configuration of the surface treatment apparatus 21 shown in FIG. 16, the anode 27 is placed in the box 27, and the box 27 is installed so that the opening 28 of the box 27 faces the portion to be treated of the cathode electrode 25. Since the part to be processed becomes larger than the opening part as the part to be processed is separated from the opening part 28, the interval (distance) between the part to be processed between the opening part 28 and the cathode electrode 25 is usually preferably 5 mm or less. 1 mm or less is more preferable.

  Next, a predetermined voltage is applied between the anode electrode 24 and the cathode electrode 25 to modify the surface of the cathode electrode 25 (surface modification treatment step). The predetermined voltage is a voltage that can be determined in a preliminary experiment, and can be determined by the following method. That is, first, the voltage applied to the surface modification treatment system and the treatment time are changed within a desired range. If the processing time is not specified, it may be performed for 15 minutes. The range in which the voltage is changed may be about 50 to 300V. Next, the treated surface is observed with an SEM, and a protrusion structure having an average of 1 μm or less is formed on the surface, the surface is not oxidized (excluding a natural oxide layer having a thickness of several nanometers), Confirm that it has not been melted, and determine the conditions. Whether or not the surface is oxidized can be confirmed by using EDS in the SEM.

  The voltage range varies somewhat depending on the type of the cathode electrode 25, but is in the range of 60V to 300V, preferably in the range of 80 to 180V. The lower limit voltage corresponds to the voltage at which plasma is generated. The upper limit voltage is determined by oxidation of the surface due to high temperature or melting of the surface and disappearing of the fine protrusion structure. Although a preferable voltage range can be determined as described above, a higher applied voltage may be set when it is desired to process for a short time or to increase the protrusion structure.

A specific example will be described. In this specific example, the surface modification treatment system shown in FIG. 15 was constructed using a stainless steel plate (SUS316) as the cathode electrode 25. The size of the opening 28 was set to 25 mm × 4 mm. Then, a 0.1 mol / L potassium carbonate (K ₂ CO ₃ ) aqueous solution was energized as an electrolytic solution 23 for 15 minutes. When the surface of the stainless steel plate after the treatment with SEM was observed, the lower limit voltage was found to be 80V. Moreover, it turned out that an upper limit voltage is 250V. Secondary electron images of (a) left part, (b) center part, and (c) right part in the length direction of the opening 28 when 150 V is applied between the anode electrode 24 and the cathode electrode 25, respectively. It is shown in FIGS. 19A, 19B, and 19C.

  As shown in FIGS. 19A, 19B, and 19C, it was confirmed that a fine protrusion structure having a diameter of 1 μm or less was formed on the surface of the stainless steel plate. Moreover, since the same protrusion structure was seen in the left part of the opening part 28 of the length direction, the right part, and the center part, it has confirmed that the appropriate process was performed in the whole opening part. It was also confirmed that the lower the voltage within the desired voltage range, the smaller the size of the protrusion structure and the number of protrusion structures. For this reason, the applied voltage may be adjusted according to the required surface characteristics. For example, when it is desired to obtain the light emission characteristics, the protrusion structure should be small, so the applied voltage may be set low.

  Although the principle of forming the fine protrusion is not clarified, it is presumed that the fine protrusion is formed by partial plasma discharge in liquid near the cathode electrode 25. That is, in this method, if the voltage applied between the anode electrode 24 and the cathode electrode 25 is less than the lower limit voltage, the partial plasma discharge in the liquid does not sufficiently occur and fine protrusions are not formed, and the voltage is higher than the upper limit voltage. Then, the generation of complete plasma melts the surface of the cathode electrode 25, which is disadvantageous for the formation of fine protrusions.

  In plasma discharge in liquid, plasma discharge occurs in the gas phase when the temperature of the electrolytic solution 23 in the vicinity of the cathode electrode 25 locally exceeds the boiling point due to application of a voltage and a gas phase is generated in the vicinity of the cathode electrode 25. This is thought to be caused by the occurrence of For this reason, it is possible to apply a voltage from room temperature, but it is more effective if the temperature of the entire electrolytic solution 23 or the vicinity of the cathode electrode 25 is set in the range of 80 ° C. to 100 ° C. This is because the temperature in the vicinity of the cathode electrode 25 can be efficiently raised to efficiently cause plasma discharge in liquid. The voltage application time can be any time, for example, 1 second or more and 30 minutes or less. The shorter the voltage application time, the smaller the size of the fine protrusions to be formed. Therefore, the voltage application time may be appropriately selected according to the desired surface shape and characteristics.

  As is apparent from the above description, according to this surface treatment method, the voltage applied between the anode electrode 24 and the cathode electrode 25 immersed in the electrolytic solution 23 without using an expensive apparatus and advanced technology. It is possible to efficiently produce a conductive material having a nano-level microstructure formed on the surface at low cost simply by controlling the above. A conductive material having a nano-level microstructure formed on the surface can exhibit various functions due to the microstructure. Surface modification can be performed for a wider area of the cathode electrode 25 by moving the cathode electrode 25 with the box 27 fixed or by moving the box 27 with the cathode electrode 25 fixed. Moreover, a continuous processing surface is obtained by moving continuously while processing. Moreover, it is also possible to give a discrete pattern by moving in steps or repeating movement and discharge. In particular, in the surface treatment apparatus 21 shown in FIG. 16, it is not necessary to cover the cathode electrode 25 with the box 27, so that the cathode electrode 25 can be expanded to a continuous processing facility and a continuous processing method by using a large sample or a strip-shaped sample. is there.

[Example 1]
Boxes 27 having various sizes of openings (5 mm × 5 mm, 5 mmφ, 10 mmφ, 10 mm × 2 mm, and 20 mm × 1 mm) on an alumina plate having a thickness of 1.7 mm were produced. The upper end surface of the opening 28 was processed obliquely by 30 degrees as shown in FIG. A SUS316 stainless steel with a thickness of 1 mm is used as the cathode electrode 25, and Pt is immersed in a 0.3 mol / L K ₂ CO ₃ aqueous solution as the anode electrode 24 to construct a surface modification treatment system as shown in FIG. did. A voltage was applied between the cathode electrode 25 and the anode electrode 24. And the surface of the SUS316 stainless steel after voltage application was observed by SEM. FIG. 20 shows an example of an external appearance photograph of the cathode electrode 25 after processing with the size of the opening 28 being 5 mm × 5 mm and 5 mmφ. The applied voltage is 160 V and the application time is 15 minutes. As shown in FIG. 20, it was confirmed that the surface of the cathode electrode 25 was processed into the shape of the opening 28.

  FIG. 21 shows an example of an SEM image of the surface of the cathode electrode 25 after processing with the size of the opening 28 being 5 mmφ. As shown in FIG. 21, it was confirmed that a fine protrusion structure having a diameter of 1 μm or less that was not formed on the surface that was not subjected to the surface treatment (see FIG. 22) was formed on the surface of the cathode electrode 25. Further, it was found that the fine protrusion structure could be formed with an applied voltage of 90 to 200V even when other shapes of the opening 28 were used, but the fine protrusion structure decreased at 220V or more. This is presumed to be due to surface melting. Further, when a uniform water repellent treatment was performed on the entire surface of the cathode electrode 25 shown in FIG. 20, it was possible to obtain a higher water repellency than a surface not subjected to the surface treatment. Further, in an experiment in which 170 V (application time is 15 minutes) was applied using a box 27 having 5 mmφ and 5 mm × 5 mm openings 28 on both sides, a fine protrusion structure was formed on both sides by SEM observation, and surface modification treatment was performed. It has been confirmed that can be carried out simultaneously on both sides.

[Example 2]
A stainless steel plate (SUS316) is used as a cathode electrode, and the anode electrode 24 is covered with a box 27 made of alumina (thickness 1.7 mm) provided with an opening 28 of 1 mm (longitudinal direction) × 20 mm (lateral direction). A surface modification system as shown was constructed. The surface with the opening 28 was placed 1 mm away from the cathode electrode 25. The applied voltage between the electrodes was 140V and 220V. A voltage was applied between the electrodes for 5 minutes, then the stainless steel plate was moved 5 mm upward (longitudinal direction), and the voltage was applied again for 5 minutes. The upward movement and voltage application were repeated 10 times. Two kinds of experiments were conducted, in which the applied voltage between the electrodes was 140V and 220V. As a result, it was possible to obtain a stainless steel plate having a region where a fine projection structure exists at intervals of 5 mm.

Example 3
The anode electrode 24 is covered with a box 27 made of alumina (thickness 1.7 mm) provided with an opening 28 of 1 mm (longitudinal direction) × 20 mm (lateral direction) using a Zn-plated steel plate as a cathode electrode, as shown in FIG. A simple surface modification treatment system was constructed. The surface with the opening 28 was placed 1 mm away from the cathode electrode 25. The applied voltage between the electrodes was 120 V, and the Zn-plated steel sheet was moved 20 mm downward (longitudinal direction) at a speed of 1 mm / min while applying a voltage between the electrodes. A Zn-plated steel sheet with a treated area of 20 mm × 20 mm could be produced. When this surface was subjected to a methylene blue decolorization reaction test, a significantly higher photocatalytic effect was obtained as compared with the surface not subjected to surface treatment.

Example 4
A commercially available cold-rolled steel sheet having a thickness of 0.8 mm was cut into a length of 80 mm and a width of 6 mm to obtain a cathode electrode. Bending was performed in the width direction so that the length direction was an axis, and the cross-section in the width direction was processed into an arc shape with a local radius of 10 mm. A heat-resistant resin was applied to the surface of the cathode electrode 25 except for the connection portion with the electrode, and an opening 28 having a width of 2 mm and a width of 4 mm and a length of 25 mm was formed on one curved surface. A voltage of 150 V was applied between the cathode electrode 25 of Pt. In both samples, a fine protrusion structure having an average diameter of 1 μm or less was formed on the surface of the opening 28.

  According to the present invention, it is possible to provide a metal material having new functions such as hydrophilic characteristics and light emission characteristics.

  According to the present invention, a surface treatment method for a metal material capable of imparting high water repellency to the surface of the metal material without much labor and cost, and a method for producing a water repellent material based on the metal material Can be provided.

  According to the present invention, a surface treatment apparatus for a conductive material capable of efficiently producing a conductive material formed with a nano-level fine structure by performing treatment over a predetermined place on the surface or a large area of the surface, and A surface treatment method can be provided.

DESCRIPTION OF SYMBOLS 1 Metal material 2 Base material 3 Protrusion part 11 Container 12 Electrolytic solution 13 Anode electrode 14 To-be-processed material (cathode electrode)
DESCRIPTION OF SYMBOLS 15 Conductor 16 Power supply 17 Thermometer 21 Surface treatment apparatus 22 Modification process cell 23 Electrolytic solution 24 Anode electrode 25 Cathode electrode (material to be processed)
26 DC power supply 27 Box 28 Opening 28a Inclined part

Claims (18)

A metal material substrate;
A modified layer formed on the surface of the metal material substrate;
With
The modified layer has an average diameter of 1 μm or less when viewed from a direction perpendicular to the surface of the metal material base, and a protrusion protruding from the surface of the metal material base within a range of 10 μm ^2. A metal material characterized by comprising three or more on average. The modified layer includes a base projecting from the surface of the metal material base and a tip formed at an end of the base, as viewed from a direction perpendicular to the surface of the metal material base. The average diameter is 1 μm or less, and an average of one or more protrusions having a constricted structure in which the outer diameter of the base is smaller than the outer diameter of the tip is within a range of 10 μm ^2. Item 4. The metal material according to Item 1.   3. The metal material according to claim 1, wherein an average diameter of the protrusion when viewed from a direction perpendicular to the surface of the metal material substrate is 500 nm or less.   4. The metal material according to claim 1, wherein a position where the protrusion is formed does not have periodicity in an in-plane direction of the metal material substrate. 5.   The said modified layer is provided with a recessed part with an average diameter of 500 nm or less when it sees from the direction perpendicular | vertical with respect to the surface of the said metal material base material, In any one of Claims 1 thru | or 4 characterized by the above-mentioned. The metal material described.   The metal material according to any one of claims 1 to 5, wherein the metal material substrate is made of alloy steel.   The metal material according to claim 6, wherein the metal material base material is formed of a steel material.   The metal material according to any one of claims 1 to 7, wherein a composition of the metal material substrate and a composition of the protrusions are different.   The metal material according to any one of claims 1 to 7, wherein the metal material substrate and the protrusion are continuously connected. A step of immersing a material to be treated as a cathode electrode made of a metal material having a surface to be treated and an anode electrode in an electrolytic solution;
Forming a microstructure on the surface to be treated by applying a voltage in a range where the material to be treated is not oxidized or melted at 70 V or higher between the cathode electrode and the anode electrode;
Removing the material to be treated from the electrolytic solution and washing the material to be treated;
Applying a water repellent treatment to the treated surface of the treated material that has been cleaned;
A surface treatment method for a metal material, comprising: A step of immersing a material to be treated as a cathode electrode made of a metal material having a surface to be treated and an anode electrode in an electrolytic solution;
Forming a microstructure on the surface to be treated by applying a voltage of 70V to 200V between the cathode electrode and the anode electrode;
Removing the material to be treated from the electrolytic solution and washing the material to be treated;
Applying a water repellent treatment to the treated surface of the treated material that has been cleaned;
A surface treatment method for a metal material, comprising: Immersing a metal material, which is a material to be treated as a cathode electrode having a surface to be treated, and an anode electrode in an electrolytic solution;
Forming a microstructure on the surface of the metal material that is the material to be treated by applying a voltage of 70 V or more and 200 V or less between the cathode electrode and the anode electrode;
Removing the metallic material from the electrolytic solution and washing the metallic material;
Performing a water repellent treatment on the treated surface of the washed metal material;
A method for producing a water-repellent material using a metal material as a base material. An anode electrode immersed in the electrolytic solution at a distance from each other and a cathode electrode made of a conductive material;
A shielding object interposed between the anode electrode and the cathode electrode and having an opening that limits a portion to be processed of the cathode electrode;
A power source for applying a voltage between the anode electrode and the cathode electrode;
A surface treatment apparatus for a conductive material, comprising:   The surface treatment apparatus for a conductive material according to claim 13, further comprising a mechanism for changing a position of the opening and / or a relative position between the anode electrode and the cathode electrode.   The surface treatment apparatus for conductive material according to claim 13 or 14, wherein the power source applies a voltage of 60 V or more and 300 V or less between an anode electrode and a cathode electrode.   The surface of the conductive material according to claim 13, wherein the shield is an insulating heat-resistant material having the opening covered on the surface of the cathode electrode. Processing equipment.   The surface treatment apparatus for a conductive material according to claim 13, wherein the conductive material is a metal material.   A surface treatment method for a conductive material, wherein the surface of the conductive material is modified using the surface treatment apparatus for a conductive material according to any one of claims 13 to 17.