Liquid-repellent member and method for producing the same

Abstract

To provide a liquid-repellent member with excellent water-repellent performance and oil-repellent performance, and a method for producing the same.SOLUTION: A liquid-repellent member with a liquid-repellent surface on its surface comprises a metal member, and a liquid-repellent layer composed of a liquid-repellent material, the metal member having a boehmite film, and the liquid-repellent material containing at least either of a fluorine-containing compound and a silicon-containing compound. The boehmite film has a predetermined macro uneven portion on its surface and also has fine irregularities on the surface of the macro uneven portion. A method for producing the liquid-repellent member comprises: a thermal oxide film forming step for forming a predetermined thermal oxide film on a surface of a metal base that forms a metal member, by a laser treatment of irradiating the surface with laser beams; a boehmite film forming step for forming a boehmite film containing a hydroxyl group on the surface of the metal base by an immersion treatment of immersing the metal base in pure water having a conductivity of 10 mS / m or less and a temperature of 90°C or higher for 10 to 120 minutes; and a liquid-repellent layer forming step for forming a liquid-repellent layer on the outermost surface layer of the metal member by applying the liquid-repellent material to the boehmite film.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a liquid-repellent member having a liquid-repellent surface on its surface, and a method for manufacturing the same. More specifically, the present invention relates to a liquid-repellent member having a metal member and a liquid-repellent layer, in which the liquid-repellent surface is provided with a boehmite coating on the surface of a metal substrate forming the metal member, and a liquid-repellent layer on the outermost layer. The present invention also relates to a method for manufacturing a liquid-repellent member in which a boehmite coating is formed on the surface of a metal substrate by laser treatment in which the surface of the metal substrate is irradiated with laser light and then an immersion treatment, and then a liquid-repellent layer is provided. [Background technology]

[0002] There are various types of liquid-repellent materials available that have a liquid-repellent surface on their surface and have improved water-repellent properties, snow-, frost-, or ice-prevention properties (hereinafter collectively referred to as "water-repellent properties"), or oil-repellent properties.

[0003] Known examples of such liquid-repellent materials include a metal substrate made of a metal such as aluminum, iron, or copper, or an alloy thereof, on whose surface fine irregularities are formed, and a liquid-repellent layer made of a liquid-repellent material containing a fluorine-containing compound or a silicon-containing compound is provided.

[0004] As one method for forming fine irregularities on the surface of a metal substrate, for example, Patent Document 1 describes a water-repellent article having a water-repellent surface structure formed by laser treatment in which laser light is irradiated.

[0005] In Patent Document 1, the water-repellent surface structure is described as having a columnar structure separated by a plurality of grooves, with minute concave and convex portions alternately arranged at a predetermined pitch, forming a grating-like periodic structure, and the tip of the columnar structure has a cavity structure with a concave portion surrounded by an outer wall. Patent Document 1 also describes that water repellency can be improved by coating the surface of the water-repellent surface structure with a water-repellent agent such as a fluorine-based resin or a silicone-based resin, and the working examples specifically show that the sliding angle of the water-repellent surface is approximately 10 degrees when the droplet volume is 5 μL (see Figure 16 of Patent Document 1). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2019-155457 Summary of the Invention [Problem to be solved by the invention]

[0007] Liquid-repellent materials with water-repellent and oil-repellent properties are used in a variety of applications. Among these, those in which fine irregularities are formed on the surface of a metal substrate and the surface is provided with a liquid-repellent layer made of a liquid-repellent material containing a fluorine-containing compound or a silicon-containing compound are widely used because they are easy to apply to the formation of various parts and structures.

[0008] As in Patent Document 1 mentioned above, methods for forming fine irregularities on the surface of a metal substrate have been used, such as laser treatment or applying a water repellent agent such as a fluorine-based resin or a silicone-based resin to the surface to improve water repellency, but further improvements in water and oil repellency are desired.

[0009] The present invention has been made in view of the above circumstances, and has an object to provide a liquid-repellent member that has excellent oil-repellent properties in addition to water-repellent properties. Another object of the present invention is to provide a method for producing a liquid-repellent member that can obtain such a liquid-repellent member. [Means for solving the problem]

[0010] The present inventors have conducted extensive research into further improving both the water-repellent and oil-repellent properties of liquid-repellent members using metal substrates. As a result, they have discovered that by providing a boehmite coating on the surface of a metal substrate formed by laser treatment and immersion treatment with a predetermined macro-unevenness, and by further providing predetermined micro-unevenness on the surface of this macro-unevenness, the liquid-repellent layer provided on the boehmite coating has both improved water-repellent and oil-repellent properties compared to conventional coatings, and have completed the present invention.

[0011] That is, the gist of the present invention is as follows. (1) A liquid-repellent member having a liquid-repellent surface on its surface, the liquid-repellent member includes a metal member and a liquid-repellent layer containing a liquid-repellent material and covering the metal member; The metal member has a metal substrate made of metal and a boehmite coating containing hydroxyl groups formed on the surface of the metal substrate, the liquid-repellent surface is formed by forming the boehmite coating on the surface of the metal substrate and providing the liquid-repellent layer as the outermost layer of the liquid-repellent surface; the liquid-repellent material contains at least one of a fluorine-containing compound and a silicon-containing compound; The boehmite coating is The arrangement interval (I) is 10 to 300 μm, The depth (L) is 20 to 300 μm, The super-liquid-repellent angle is 20°≦θ≦60°, The surface has a macro uneven portion containing boehmite and having a fractal dimension of 1.22 to 1.4, and the macro uneven portion is composed of a plurality of uneven portions. The surface of the macro concave-convex portion has a micro concave-convex portion containing boehmite and having a thickness of 10 to 2000 nm, and the micro concave-convex portion has a plurality of openings of 10 to 50 nm. A liquid-repellent member characterized by: (2) The liquid-repellent member according to (1), wherein, when the boehmite coating is analyzed by glow discharge optical emission spectrometry from the surface in the depth direction, the ratio of the detected amount of hydroxyl groups to the total amount of the detected amount of metal constituting the metal base and the detected amount of hydroxyl groups is 50% or more and 90% or less. (3) The liquid-repellent member according to (1), wherein the metal forming the metal substrate is aluminum or an alloy containing aluminum. (4) The liquid-repellent member according to (1), wherein the liquid-repellent layer provided with the liquid-repellent material has a liquid-repellent performance in which the sliding angle when a 5 μL droplet of water is dropped is 7° or less, and when a 3 μL droplet of n-hexadecane is dropped, the sliding angle is 30° or less, exhibiting super water-repellent and super oil-repellent performance. (5) On the liquid-repellent surface, the boehmite coating is formed over the entire surface of the metal substrate that forms the metal member, the uneven portion is formed on the surface of the metal base material, the uneven portion being composed of a recess formed in a recessed shape from the surface in a depth direction and a protrusion formed in a protruding shape from the surface in a height direction around the recess, The liquid-repellent member described in (1), wherein the liquid-repellent surface has sharp ends formed in the area sandwiched between adjacent uneven portions on the surface of the metal member so that the convex portions included in each of the adjacent uneven portions come into contact with each other and become integrated.

[0012] (6) A method for manufacturing a liquid-repellent member having a liquid-repellent surface on its surface, comprising the steps of: the liquid-repellent member includes a metal member and a liquid-repellent layer containing a liquid-repellent material and covering the metal member; The metal member has a metal substrate made of metal and a boehmite coating containing hydroxyl groups formed on the surface of the metal substrate, a thermal oxide film forming step of forming a thermal oxide film containing hydroxyl groups on the surface of the metal base by laser treatment in which a laser beam is irradiated onto the surface of the metal base; a boehmite film forming step of immersing the metal base material on which the thermal oxide film has been formed in pure water having a conductivity of 10 mS / m or less and a temperature of 90°C or more for 10 to 120 minutes to form a boehmite film containing hydroxyl groups on the surface of the metal base material; a liquid-repellent layer forming step of applying the liquid-repellent material to the metal member on which the boehmite coating film has been formed, thereby forming the liquid-repellent layer on the outermost surface of the metal member, In the boehmite film forming step, the boehmite film is formed on the surface of the metal substrate at the liquid-repellent surface, In the liquid-repellent layer forming step, the liquid-repellent layer is formed on the outermost layer of the liquid-repellent surface, the liquid-repellent material contains at least one of a fluorine-containing compound and a silicon-containing compound; In the thermal oxide film forming step, the laser treatment The arrangement interval (I) is 10 to 300 μm, The depth (L) is 20 to 300 μm, The super-liquid-repellent angle is 20°≦θ≦60°, The surface has a macro uneven portion consisting of a plurality of uneven portions with a fractal dimension of 1.22 to 1.4, forming the thermally oxidized coating film having a micro-irregularity on the surface of the macro-irregularity, the micro-irregularity having a thickness of 10 to 1000 nm and a plurality of openings of 10 to 50 nm; In the boehmite film forming step, the thermal oxide film having the macro-irregularity and the micro-irregularity is converted into the boehmite film having the macro-irregularity and the micro-irregularity containing boehmite by the immersion treatment, The fine irregularities containing the boehmite have a thickness of 10 to 2000 nm. A method for producing a liquid-repellent member, comprising: (7) The conditions of the laser treatment are: output of 10 W or more; scanning speed of 50 to 2000 mm / s; and irradiation energy density of 0.4 to 10 J / mm 2 (6) The method for producing a liquid-repellent member according to (6), wherein the range is: (8) The method for producing a liquid-repellent member according to (7), wherein a ratio (P / D) of an irradiation interval P of the laser light to a beam diameter D of the laser light is 1 or more and 2 or less. (9) The surface of the metal substrate is formed with the uneven portion, which is composed of recesses formed by the metal constituting the metal substrate at the location irradiated with the laser light diffusing outward from the irradiation center of the laser light, and protrusions formed by the metal diffused from the recesses and accumulating around the recesses, The method for producing a liquid-repellent member according to (6), wherein the liquid-repellent surface has sharp edges formed so that the convex portions included in the adjacent concave-convex portions contact and integrate with each other in the areas sandwiched between the adjacent concave-convex portions on the surface of the metal member, and no untreated area is formed in which the metal base material is exposed before the irradiation of the laser light, and the boehmite coating is formed over the entire surface of the metal base material. [Effects of the Invention]

[0013] According to the present invention, it is possible to obtain a liquid-repellent member that is superior in both water-repellency and oil-repellency compared to conventional materials. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 1 is a cross-sectional SEM image (magnification: 100 times) of the liquid-repellent member according to Example 1. As shown in FIG. [Figure 2] FIG. 2 is a diagram for explaining the super-liquid-repellent manifestation angle (θ) of the macro concave-convex portion. [Figure 3] FIG. 3 is a schematic diagram showing the relationship between the beam diameter of the laser light and the irradiation interval. [Figure 4] FIG. 4 is a planar SEM image (magnification: 10,000 times) of the liquid-repellent member according to Example 1. As shown in FIG. [Figure 5] FIG. 5 is a cross-sectional SEM image (magnification: 10,000 times) of the liquid-repellent member according to Example 1. As shown in FIG. [Figure 6] FIG. 6 is a planar SEM (magnification: 100 times) of the liquid-repellent member according to Example 1. [Figure 7]FIG. 7 is a cross-sectional SEM image (magnification: 100 times) of the liquid-repellent member according to Example 2. [Figure 8] FIG. 8 is a cross-sectional SEM image (magnification: 100 times) of the liquid-repellent member according to Comparative Example 1. As shown in FIG. [Figure 9] FIG. 9 is a cross-sectional SEM image (magnification: 100 times) of the liquid-repellent member according to Comparative Example 2. DETAILED DESCRIPTION OF THE INVENTION

[0015] The liquid-repellent member of the present invention will be described in detail together with its manufacturing method. The components of the present invention described below can be combined in part or in whole as appropriate.

[0016] [1. Liquid-repellent material] The liquid-repellent member of the present invention has a liquid-repellent surface, and includes a metal member and a liquid-repellent layer covering the metal member, the liquid-repellent layer comprising a liquid-repellent material. The metal member includes a metal substrate and a boehmite film containing hydroxyl groups formed on the surface of the metal substrate. The liquid-repellent surface includes the boehmite film formed on the surface of the metal substrate, and the liquid-repellent layer formed on the outermost surface of the liquid-repellent surface. The liquid-repellent material includes at least one of a fluorine-containing compound and a silicon-containing compound. The boehmite film has a macroscopic uneven surface, consisting of a plurality of uneven portions, with an arrangement interval (I) of 10 to 300 μm, a depth (L) of 20 to 300 μm, a super-liquid-repellent angle of 20°≦θ≦60°, and a fractal dimension of 1.22 to 1.4. The macroscopic uneven surface also has a microscopic uneven surface, with a plurality of openings of 10 to 50 nm and a thickness of 10 to 2,000 nm.

[0017] [1-1. Metallic Components] <Metal base material> The liquid-repellent member of the present invention includes a metal member and a liquid-repellent layer covering the metal member, the metal member comprising a liquid-repellent material. The metal member includes a metal substrate made of metal and a boehmite coating containing hydroxyl groups formed on the surface of the metal substrate. Examples of metal substrates used for the metal member include aluminum, copper, iron, titanium, and alloys containing these metals. However, to provide the boehmite coating, it is preferable that at least the metal substrate on the liquid-repellent surface is aluminum or an alloy containing aluminum. More preferably, an aluminum substrate made of aluminum or an alloy containing aluminum is used. There are various aluminum substrates available, ranging from 100% pure aluminum to aluminum alloys containing different types and amounts of alloying elements. The material of the aluminum substrate is not limited and can be determined based on the application of the liquid-repellent member to be formed using the metal substrate and the various physical properties required for that application, such as strength, corrosion resistance, and processability. Furthermore, processed materials obtained by appropriately processing into a desired shape, as well as combinations of processed materials, can also be used.

[0018] Among these, when considering cases such as forming a component forming a refrigerator compartment or a laptop computer housing, a wrought material that has excellent thermal conductivity and is easy to process is desirable, and among these, it is preferable to use 1000 series alloys, 3000 series alloys, 5000 series alloys, and 6000 series alloys. Furthermore, although there are no particular limitations as it depends on the application of the liquid-repellent member, a metal substrate with a thickness of about 0.3 mm to 10 mm can generally be used.

[0019] <Boehmite film> The metal substrate is provided with a boehmite coating having hydroxyl groups on its surface. As described below, this boehmite coating is formed by a dipping treatment in which a thermal oxide coating formed by laser treatment, in which the surface of the metal substrate is irradiated with laser light, is immersed in pure water having a conductivity of 10 mS / m or less and a temperature of 90°C or higher for 10 to 120 minutes. That is, the boehmite coating is formed by converting the thermal oxide coating formed on the surface of the metal substrate by the laser treatment through the dipping treatment. The boehmite coating has macro-irregularities and micro-irregularities containing boehmite, which are formed by converting a macro-irregularity consisting of multiple irregularities generated by the laser treatment when the thermal oxide coating is formed, and a micro-irregularity formed on the surface of the macro-irregularity, through the dipping treatment.

[0020] (Macro uneven part, macro uneven part containing boehmite) The macro-irregularity has an irregular shape on the order of μm. The macro-irregularity has a structure consisting of recesses formed by perforating the metal substrate upon irradiation with laser light and protrusions based on metal oxide deposits formed during laser light irradiation. The macro-irregularity has a repeating structure consisting of recesses and protrusions formed by adjacently irradiating the metal substrate with laser light multiple times. The macro-irregularity can be confirmed by observing the surface or cross section of the metal member using, for example, a scanning electron microscope (SEM). The immersion treatment converts the macro-irregularity into a macro-irregularity containing boehmite. The macro-irregularity containing boehmite contains aluminum oxide hydroxide (γ-AlO(OH)), which is boehmite, and may also contain a metal hydroxide, metal oxide hydroxide, or metal oxide as described below. In this specification, boehmite is understood to include pseudo-boehmite.

[0021] It is important that the macroscopic unevenness containing boehmite has a predetermined arrangement interval (I) and depth (L) determined by the procedure described with reference to Fig. 1. That is, the arrangement interval (I) of the unevenness in the macroscopic unevenness is 10 µm or more, preferably 30 µm or more, more preferably 60 µm or more, and even more preferably 80 µm or more. On the other hand, the arrangement interval (I) of the unevenness in the macroscopic unevenness is 300 µm or less, preferably 220 µm or less, more preferably 150 µm or less, and even more preferably 100 µm or less. If the arrangement interval (I) of the unevenness in the macroscopic unevenness is within these ranges, it is possible to ensure the formation of a liquid-repellent layer containing a liquid-repellent material more effectively.

[0022] To calculate the arrangement interval (I) and depth (L), a cross-section of the metal member or the liquid-repellent member after the liquid-repellent layer is observed using an SEM, and a cross-sectional photograph is taken that includes multiple concave-convex portions formed by laser irradiation, in which at least 12 concave portions and 11 convex portions are alternately and continuously arranged.The arrangement interval (I) and depth (L) can then be calculated from the multiple concave-convex portions included in this cross-sectional photograph.

[0023] Specifically, as shown in FIG. 1, the depth is determined by drawing the following lines on the cross-sectional photograph. First, for 12 arbitrarily selected consecutive recesses in the cross-sectional photograph, the deepest of the lowest points of each recess is designated as the minimum recess Pb1. A reference line RL1 is drawn that passes through this minimum recess Pb1 or a position lower than Pb1 and passes through the position where the sum of the distances from the respective bottom points of each recess is smallest. Next, on this cross-sectional photograph, the highest convex point among the convex points sandwiched between the 12 recesses is designated as the highest convex point Pt1. A reference line RL2 is drawn that passes through this highest convex point Pt1 and is parallel to the reference line RL1. Drawing the reference lines RL1 and RL2 in this manner prevents the depth (L) of the uneven portion from being calculated as being excessively larger or smaller than the actual value.

[0024] Next, in this cross-sectional photograph, for 12 consecutive recesses, including the bottommost recess Pb1, 12 straight lines are drawn perpendicular to the reference line RL2 from the bottom of each recess, and these lines are designated as lines a to l, respectively. Next, medians are drawn between two adjacent perpendicular lines on the lines a to l, and these median lines are designated as lines A to K. The spacing between adjacent lines A to K is designated as arrangement intervals I1 to I10. The distance from the reference line RL2 to the deepest point in each recess is designated as depths L1 to L10, respectively. The arrangement intervals I1 to I10 and depths L1 to L10 correspond to the arrangement intervals I1 to I10 and depths L1 to L10 of the 10 recesses through which lines b to k pass, excluding the lines a and l at both ends, of the lines a to l.

[0025] In this way, the depths L1 to L10 and the spacings I1 to I10 can be obtained for the 10 recesses through which lines b to k pass. Furthermore, the Smirnoff-Grubbs test is used to detect outliers among the depths L1 to L10 and the spacings I1 to I10. To detect outliers, the absolute deviation is calculated by subtracting the value of each depth L for the 10 recesses with depths L1 to L10 by the average value of the depths L1 to L10. The calculated absolute deviation is then divided by the unbiased standard deviation of the depths L1 to L10 to calculate the test statistic t. Next, a p-value is calculated, which represents the probability that the test statistic t will be that value. Any p-value less than 5% is detected as an outlier. If an outlier is detected, the depth L of the recess where the outlier was detected is excluded from the 10 recesses with depths L1 to L10, and outlier detection is performed again for the remaining depths L of the recesses. This process is repeated until no outliers are detected. Similarly, outliers are detected for the spacings I1 to I10. Furthermore, for 10 recesses through which lines b to k included in this cross-sectional photograph pass, average depths and average arrangement intervals are calculated from the depths and arrangement intervals of the remaining recesses, excluding recesses for which outliers were detected at either or both of the depths L1 to L10 and the arrangement intervals I1 to I10. The average depth of the macroscopic unevenness containing boehmite obtained in this manner is defined as the depth (L), and the average arrangement interval is defined as the arrangement interval (I).

[0026] Furthermore, for each recess in the macroscopic unevenness containing boehmite whose arrangement interval (I) and depth (L) have been determined as described above, the arctan ((I / 2) / L) can be calculated as shown in FIG. 2 , and the average value can be defined as the super-liquid-repellent angle (θ) of the unevenness in the macroscopic unevenness. This super-liquid-repellent angle (θ) is 20° or more, preferably 30° or more, and more preferably 40° or more. On the other hand, this super-liquid-repellent angle (θ) is 60° or less, preferably 55° or less, more preferably 50° or less, and even more preferably 45° or less. When the super-liquid-repellent angle (θ) of the unevenness in the macroscopic unevenness falls within these ranges, the depth of the unevenness becomes sufficiently deep and pointed relative to the opening diameter of the unevenness. This prevents liquid droplets from seeping into the recess from near the surface to the bottom, making it easier to maintain the space formed by the unevenness. When calculating arctan((I / 2) / L), if an outlier as described above is detected at any of the recess depths L1 to L10, that recess is excluded from the calculation of the average value.

[0027] Furthermore, the fractal dimension of the macroscopic unevenness containing boehmite is 1.22 to 1.4, preferably 1.23 to 1.3, more preferably 1.24 to 1.28, and even more preferably 1.25 to 1.26. When the fractal dimension of the macroscopic unevenness is within this range, the entire surface of the unevenness and a portion thereof have a self-similar shape, and the surface shape of the unevenness becomes complex. This makes it easier to prevent droplets from adhering to the surface of the unevenness when they are dropped onto the liquid-repellent surface. Here, the fractal dimension of the macroscopic unevenness can be calculated by the box-counting method using image analysis software such as ImageJ. However, in the present invention, the calculation was performed under the condition of 0.5 / (unit pixel length (μm / pixel), in other words, a setting of 0.5 μm per pixel. Specifically, it can be determined as follows. ImageJ is open source and can be obtained from the following link (https: / / imagej.nih.gov / ij / download.html).

[0028] First, a cross-sectional SEM image (JPEG file) of the macroscopic irregularities containing boehmite for which fractal dimension is to be calculated is loaded into image software such as PowerPoint. A line corresponding to the length of the scale bar on the cross-sectional SEM is drawn to calculate the unit pixel length (μm / pixel). The cross-sectional SEM image (JPEG file before correction) of the macroscopic irregularities is then adjusted so that the corrected image has a resolution of 0.5 μm / pixel [JPEG file (after correction) = JPEG file (before correction) × 0.5 / (unit pixel length (μm / pixel))]. The corrected data (JPEG file) is then imported into ImageJ and converted to 8-bit data. A range is then specified to include the irregularities for which fractal dimension is to be calculated. The specified range is then cropped and binarized. As shown in Figure 1, a threshold is set to distinguish the metal substrate forming the macroscopic irregularities from the background color, allowing the irregular shape of the macroscopic irregularities to be extracted. The metal substrate, excluding the areas involved in the surface shape, is then filled with the same color as the background, and fractal structure analysis is performed. In this case, BoxSizes were left at the default settings (2,3,4,6,8,12,16,32,64).

[0029] The boehmite-containing macro-texture is formed continuously on the surface of the metal substrate along the irradiation path of the laser beam. When a metal substrate is irradiated with a laser, the energy from the laser irradiation melts, diffuses, and vaporizes the metal substrate. The metal diffuses and vaporizes from the center of the irradiation outward, creating holes, which form the bases of depressions, and the areas on both sides (adjacent) of the depressions that are not irradiated with the laser become the bases of protrusions. At the same time, the molten metal is oxidized in part or in whole to form metal oxide, which diffuses around the irradiated areas that will become depressions, deposits, and solidifies, forming protrusions.

[0030] The boehmite-containing macro-irregularity portion comprises recesses formed in a depth direction from the surface of the metal substrate and protrusions formed in a height direction from the surface around the recesses. The regions sandwiched between adjacent recesses preferably have sharp edges formed so that the protrusions included in the adjacent recesses come into contact with each other and are integrated. On the other hand, it is preferable to prevent the formation of exposed areas (untreated areas) of the metal substrate on the surface of the macro-irregularity portion, which correspond to unirradiated areas that have not been irradiated with a laser. For example, as shown in Figure 1, the protrusions come into contact with each other to form sharp edges in the area corresponding to the midline G.

[0031] Since the non-laser-irradiated area does not have any unevenness, the area where the non-laser-irradiated area spreads will have a flat shape, and therefore, no contribution to liquid repellency can be expected. Furthermore, the area where the non-laser-irradiated area spreads will have a flat shape, resulting in a decrease in fractal dimension. Therefore, on the liquid-repellent surface, a cross-sectional photograph of the metal member or the liquid-repellent member after the liquid-repellent layer has been formed is taken using an SEM, and of 10 consecutive convex portions arbitrarily selected in the cross-sectional photograph, preferably 5 or more convex portions form sharp ends, more preferably 7 or more convex portions form sharp ends, even more preferably 9 or more convex portions form sharp ends, and particularly preferably 10 or more convex portions form sharp ends.

[0032] (Fine unevenness, fine unevenness containing boehmite) The fine irregularities have an irregular shape of nm order size and are formed on the surface of the macro irregularities. The fine irregularities appear on the surface of a thermally oxidized film when a metal substrate is irradiated with a laser to form a molten metal layer having a thermally oxidized film. The fine irregularities can be confirmed by observing the surface or cross section of the metal member using an SEM or the like. The immersion treatment converts the fine irregularities into fine irregularities containing boehmite.

[0033] The boehmite-containing fine irregularities have a plurality of nano-sized openings of 10 nm to 50 nm and a fine structure with a film thickness of 10 nm to 2000 nm. When observed with an SEM, the fine irregularities are observed as a spongy structure with fine openings of the above size. In the present invention, the liquid-repellent surface has the fine irregularities on the surface of the boehmite-containing macro irregularities. In this way, the nano-order fine irregularities are provided on the surface of the micron-order macro irregularities containing boehmite, thereby increasing the surface area and improving the liquid repellency. Preferably, in the liquid-repellent surface of the liquid-repellent member of the present invention, a boehmite coating including the boehmite-containing macro irregularities and the fine irregularities is formed over the entire surface of the metal substrate that forms the metal member. The micro-irregularities containing boehmite contain aluminum oxide hydroxide (γ-AlO(OH)), which is boehmite, in the same manner as the macro-irregularities containing boehmite described above, and may also contain a metal hydroxide, a metal oxide hydroxide, or a metal oxide as described below.

[0034] (hydroxyl group) The boehmite coating is formed on the surface of the metal substrate and terminates with hydroxyl groups. The hydroxyl groups can be confirmed by detecting hydroxyl groups present near the surface of the metal substrate using glow discharge optical emission spectrometry (GD-OES). The proportion of hydroxyl groups (hydroxyl group abundance) can be determined by analyzing the metal substrate from the surface to the depth direction using glow discharge optical emission spectrometry, and is determined as the ratio of the detected amount of hydroxyl groups to the total amount of the detected amount of metal constituting the metal substrate and the detected amount of hydroxyl groups.

[0035] Specifically, first, the emission intensity (V) derived from the main metal and hydroxyl groups constituting the metal substrate is measured using GD-OES. Then, the amount of detected main metal constituting the metal substrate is calculated from the integrated value (area) of the emission intensity derived from the main metal. The amount of detected hydroxyl groups is measured from the integrated value of the emission intensity derived from the hydroxyl groups. Furthermore, the ratio of the amount of detected hydroxyl groups to the total amount of detected main metal and hydroxyl groups is calculated as the hydroxyl group abundance. In the emission spectrum obtained by GD-OES, the peaks appearing at 281 nm and 309 nm are considered to be peaks derived from hydroxyl groups.

[0036] The emission intensity near the surface of a metal substrate can be measured using GD-OES to a depth of 200 nm from the surface. Specifically, the measurement range is from the detection of the emission intensity derived from the main metal elements and hydroxyl groups that make up the metal substrate to the time required for sputtering 200 nm corresponding to the main metal elements. This measurement range (time) can be determined by measuring the sputtering rate (μm / min) of a standard sample containing the main metal element to be measured at a high purity. Measuring emission intensity using GD-OES allows the detection and evaluation of not only the components present in the outermost surface layer of the metal substrate, but also components present deep enough to contribute to bonding with the liquid-repellent material described below.

[0037] In the boehmite coating, the ratio of the detected amount of hydroxyl groups to the total amount of detected metals and hydroxyl groups detected by the glow discharge optical emission spectrometry (hydroxyl group abundance) is preferably 50% or more, more preferably 55% or more, more preferably 60% or more, and particularly preferably 65% ​​or more. When this ratio is equal to or greater than the lower limit mentioned above, the number of hydroxyl groups present near the surface of the metal substrate increases, strengthening the effect of chemical bonding with functional groups in the liquid-repellent material, thereby enabling the stable and reliable formation of a liquid-repellent layer. Meanwhile, the upper limit of the ratio of the detected amount of hydroxyl groups to the total amount of detected metals and hydroxyl groups is not particularly limited, but is preferably 90% or less, more preferably 85% or less, more preferably 80% or less, and particularly preferably 75% or less.

[0038] The hydroxyl groups in the boehmite coating may be formed from aluminum oxide hydroxide (γ-AlO(OH)), which is boehmite, or from hydroxides (metal hydroxides) of metals forming the metal substrate, such as aluminum hydroxide (Al(OH)), copper hydroxide (Cu(OH)), iron(II) hydroxide (Fe(OH)), or iron(III) oxide hydroxide (FeO(OH)), depending on the aluminum or aluminum-containing alloy forming the metal substrate of the liquid-repellent surface. Furthermore, the boehmite coating may contain oxides (metal oxides) of metals forming the metal substrate, such as aluminum oxide (AlO), copper(I) oxide (CuO), copper(II) oxide (CuO), iron(II) oxide (FeO), iron(II,III) oxide (FeO), or iron(III) oxide (FeO), depending on the metal forming the metal substrate.

[0039] In consideration of the above-mentioned purposes and properties, the boehmite film is preferably 0.1 μm or more and 3 μm or less, more preferably 0.5 μm or more and 2.5 μm or less.

[0040] [1-2. Liquid repellent layer] <Liquid repellent material> The liquid-repellent member of the present invention comprises the metal member described above and a liquid-repellent layer covering the metal member and containing a liquid-repellent material. That is, in the liquid-repellent member of the present invention, the boehmite film described above is formed on the surface of the metal substrate constituting the metal member at the liquid-repellent surface, and a liquid-repellent layer is provided on the outermost layer of the liquid-repellent surface. The liquid-repellent material that forms the liquid-repellent layer can be one containing at least one of a fluorine-containing compound and a silicon-containing compound.

[0041] Among these, the fluorine-containing compound is an organic compound containing a fluorine atom, and examples thereof include a fluorine-containing coupling agent, a fluorine-based surfactant, a fluorine resin, a fluorine-based lubricating oil, etc. Specific examples of the fluorine-containing compound include a fluorine-containing silane coupling agent such as perfluorododecyltrichlorosilane (FTCS) and perfluoroalkoxysilane; a fluorine-based surfactant having a perfluoroalkyl group, a fluorine resin such as polytetrafluoroethylene (PTFE), polychlorotrifluoroethylene (PCTFE), and perfluoroalkoxyalkane (PFA); a fluorine-based lubricating oil such as perfluoropolyether (PFPE); and the like.

[0042] The silicon-containing compound is an organic compound containing a silicon atom, and examples thereof include a silicon-containing coupling agent, a silicone surfactant, a silicone resin, a silicone oil, a silicone elastomer, etc. Specific examples of the silicon-containing compound include a silicon-containing silane coupling agent such as octyltriethoxysilane or dodecyltriethoxysilane; a silicone surfactant in which a hydrophilic substituent has been introduced into a portion of a silicone having a siloxane bond in the main skeleton; a silicone resin; a silicone oil; a silicone elastomer; etc.

[0043] Examples of the coupling agent include fluorine-containing coupling agents containing fluorine atoms and silicon-containing coupling agents containing silicon atoms. Furthermore, preferred coupling agents are silane-containing coupling agents having a structure in which a hydrolyzable group is bonded to a silicon atom. Among fluorine-containing coupling agents, fluorine-containing silane coupling agents are preferred. Among silicon-containing coupling agents, silicon-containing silane coupling agents are preferred. These silane-containing coupling agents have an alkoxy group, such as an ethoxy group, a methoxy group, or a butoxy group, as a hydrolyzable group, and preferably have an alkoxysilyl group, such as an ethoxysilyl group, a methoxysilyl group, or a butoxysilyl group, in which the hydrolyzable group is bonded to a silicon atom. By using a silane-containing coupling agent, the alkoxy group of the silane-containing coupling agent is hydrolyzed to generate a silanol group. The silanol group of the silane-containing coupling agent and the hydroxyl group present on the surface of the thermally oxidized coating form a hydrogen bond or a siloxane bond via a dehydration condensation reaction. In other words, the use of a silane-containing coupling agent preferably allows the liquid-repellent material to be more stably present on the surface of the metal member.

[0044] <Liquid repellency> In the present invention, the liquid-repellent layer provided with the liquid-repellent material preferably has the following super water-repellent and super oil-repellent properties. Specifically, with regard to water repellency, the sliding angle when a 5 μL droplet of water is dropped is 7° or less, preferably 6° or less, more preferably 5° or less, and even more preferably 4° or less. There is no particular restriction on the lower limit of the sliding angle when water is dropped, but it is essentially 2° or more. Meanwhile, with regard to oil repellency, the sliding angle when a 3 μL droplet of n-hexadecane is dropped is 30° or less, preferably 25° or less, more preferably 20° or less, and even more preferably 10° or less. There is no particular restriction on the lower limit of the sliding angle when n-hexadecane is dropped, but it is essentially 5° or more. As described above, by providing a boehmite coating over the entire surface of a metal component, the action of chemical bonding between the hydroxyl groups of the boehmite coating and the functional groups in the liquid-repellent material is exerted over the entire surface structure of the liquid-repellent surface, stabilizing the liquid-repellent layer and improving the liquid-repellent performance. Furthermore, with regard to water repellency, the contact angle with water is preferably 160° or greater. With regard to liquid repellency, the contact angle with n-hexadecane is preferably 120° or greater, more preferably 150° or greater.

[0045] [1-3.Application] The liquid-repellent member of the present invention is a member that exhibits water repellency to prevent water adhesion and oil repellency to prevent oil adhesion. In this case, the targets of adhesion prevention include not only liquid water and oil, but also solid water and oil, as well as snow, frost, ice, mist, and the like formed by condensation of water and oil (vapor) in the air. Furthermore, since the liquid-repellent member of the present invention uses a metal substrate, it is advantageous in terms of processability. Therefore, the liquid-repellent member of the present invention has a wide variety of uses, including, but not limited to, anti-condensation, anti-snow, anti-frost, and anti-icing components that require water repellency; precision machinery, clothing (fabrics), cooking utensils, kitchenware, and processing equipment that require oil repellency; and construction, automobiles, industrial products, and the like that require stain resistance. More specifically, it can be used to form walls, ceilings, floors, shelves, and heat exchangers in the refrigerator compartment of a refrigerator, indoor units of an air conditioner, etc., to prevent condensation; heat exchangers in the indoor units of refrigeration devices used in refrigerated freezer trucks and refrigerator freezers, and heat exchangers in the outdoor units of air conditioners, etc., to prevent frost; buildings, traffic signs, traffic lights, power lines, steel towers, bridge girders, etc., used outdoors, to prevent snow and ice; housings of precision instruments such as laptops and electronic devices; cooking utensils such as pots and frying pans; automobile bodies and interior and exterior parts; equipment and processing tools used in factories, etc.

[0046] [2. Method for manufacturing liquid-repellent material] In the present invention, the method for producing a liquid-repellent member having a liquid-repellent surface includes a thermal oxide film forming step of forming a thermal oxide film on the surface of a metal substrate by laser treatment, in which a laser beam is irradiated onto the surface of the metal substrate; a boehmite film forming step of forming a hydroxyl-containing boehmite film on the surface of the metal substrate by immersing the metal substrate with the thermal oxide film formed thereon in pure water having a conductivity of 10 mS / m or less and a temperature of 90°C or higher for 10 to 120 minutes; and a liquid-repellent layer forming step of forming a liquid-repellent layer on the outermost surface of the metal member by applying a liquid-repellent material to the metal member with the boehmite film formed thereon. In the thermal oxide film forming step, a thermal oxide film is formed on the surface of the metal substrate at the liquid-repellent surface. In the boehmite film forming step, a boehmite film is formed on the surface of the metal substrate at the liquid-repellent surface. In the liquid-repellent layer forming step, a liquid-repellent layer is formed on the outermost surface of the liquid-repellent surface. The liquid-repellent material includes at least one of a fluororesin and a silicone resin. In the thermal oxide film forming step, the laser treatment forms a thermal oxide film having a macroscopic unevenness on its surface, which is made up of a plurality of unevennesses, with an arrangement interval (I) of 10 to 300 μm, a depth (L) of 20 to 300 μm, a super-liquid-repellent angle of 20°≦θ≦60°, and a fractal dimension of 1.22 to 1.4, and also having a microscopic unevenness on its surface, which has a plurality of openings of 10 to 50 nm and a thickness of 10 to 1,000 nm. Furthermore, in the boehmite film forming step, the immersion treatment converts the thermal oxide film having the macroscopic unevenness and the microscopic unevenness into a boehmite film having the macroscopic unevenness and the microscopic unevenness containing boehmite, thereby forming a microscopic unevenness containing boehmite and a thickness of 10 to 2,000 nm.

[0047] [2-1. Thermal oxide film formation process] First, in the thermal oxide film forming step, a thermal oxide film is formed on the surface of the metal base material by laser processing in which the surface of the metal base material is irradiated with laser light.

[0048] <Laser treatment> In this laser treatment, a thermally oxidized coating having the macro- and micro-irregularities described above is formed on the surface of the metal substrate. Specifically, it is believed that metal at the irradiated area of ​​the laser light diffuses outward from the center of the laser light irradiation, forming depressions. The metal diffused from these depressions accumulates around the depressions, forming protrusions, resulting in the development of macro-irregularities with micrometer-order irregularities. Furthermore, micro-irregularities with nanometer-order irregularities are formed on the surface of the macro-irregularities. As described above, when the macro-irregularities are closely observed, sharp edges can be seen in the areas sandwiched between adjacent irregularities, where the protrusions included in each of the adjacent irregularities come into contact and merge.

[0049] The principle of formation of a thermal oxide film by laser processing can be inferred as follows. That is, the metal substrate is melted and evaporated by the energy of laser irradiation, and the spaces created by the evaporation become the bases of recesses, and the areas on both sides (neighboring sides) of the recesses that are not irradiated by the laser become the bases of protrusions. At the same time, the molten metal portion is oxidized in part or in whole to become metal oxide, which deposits around the irradiated areas that become recesses, forming protrusions. The deposits made of metal oxide are formed in the form of a film that covers the recesses and protrusions. In this way, the deposits made of metal oxide formed on the surface of the metal substrate form a molten metal layer that forms the uneven shape of the macro-unevenness. Furthermore, metal oxides have at least some partial ionicity, and metal ions (e.g., Al in the case of Al) are present on the ionic surface of the metal oxide. 3+ ) and oxide ions (O 2- ) are present. Due to their electrostatic neutrality, they react with moisture in the air to hydroxylate the metal oxides present on the surface of the metal fusion layer, and the surface of the metal fusion layer becomes covered with hydroxyl groups. In this way, a thermal oxide film containing hydroxyl groups is thought to be formed on the outermost surface of the metal fusion layer.

[0050] The thermal oxide film contains the hydroxide (metal hydroxide) or oxide hydroxide (metal oxide hydroxide) of the metal forming the metal base, as described above, depending on the metal forming the metal base. The thermal oxide film may also contain the oxide (metal oxide) of the metal forming the metal base, as described above, depending on the metal forming the metal base.

[0051] Although known lasers can be used for this laser treatment, it is preferable to use a pulsed laser, such as a YAG laser, a YVO4 laser, a semiconductor laser, or a fiber laser, because this is convenient for spot processing of the metal substrate.

[0052] Furthermore, when performing laser treatment, it is preferable to avoid leaving untreated areas that expose the metal substrate before laser light irradiation, so that a thermal oxide film is formed over the entire surface of the metal substrate. If there are unirradiated areas of the metal substrate that are not irradiated with laser light, no metal molten layer is formed in the unirradiated areas of the metal substrate, and no thermal oxide film is present. Typically, an oxide film similar to the natural oxide film of aluminum is formed on the surface of a metal substrate, but since it does not contain hydroxyl groups, chemical bonding due to this is not expected. Furthermore, if there are many unirradiated areas, the proportion of flat areas will increase. Therefore, in order to form as much of a liquid-repellent layer containing a liquid-repellent material as possible, it is preferable to perform laser treatment so that as few untreated areas that expose the metal substrate before laser light irradiation remain as possible.

[0053] Here, laser processing is affected by the irradiation energy of the laser beam per unit area (hereinafter also referred to as "irradiation energy density"). The irradiation energy density represents the laser output that the laser-irradiated portion of the object to be laser-processed (workpiece, in this invention, metal substrate) receives per unit area and per unit time. The irradiation energy density (J / mm 2) is expressed by the following formula (A1) using the laser light output W (W), the number of laser light scans N (times), the laser light irradiation interval P (mm), the laser light scanning speed V (mm / s), the length of the laser irradiated area perpendicular to the irradiation direction of the laser light Length, and the width of the laser irradiated area parallel to the irradiation direction of the laser light Width. Irradiation energy density = ((((Length / P) × Width × N) / V) × W) / (Length × Width) Formula (A1) By modifying this formula (A1), the following formula (A2) is obtained: The irradiation energy density can be calculated using formula (A2). Irradiation energy density = (W × N) / (P × V) Equation (A2)

[0054] In the present invention, the irradiation energy density is 0.4 J / mm 2 It is preferably equal to or greater than 1.0 J / mm 2 More preferably, 1.5 J / mm 2 More than 2.0 J / mm 2 That's all. Also, 10J / mm 2 It is preferably less than or equal to 5 J / mm 2 Less than 3 J / mm 2 The irradiation energy density is 0.4 J / mm or less. 2 If the irradiation energy density is 10 J / mm or more, a thermal oxide film having hydroxyl groups is easily formed on the surface of the metal member subjected to laser treatment, and a thermal oxide film having a predetermined hydroxyl group abundance ratio can be obtained. 2 If the thickness is less than this, the recesses of the macro unevenness in the thermal oxide film can be made sufficiently deep.

[0055] Here, the laser conditions (laser processing conditions) for the laser processing may be appropriately set so as to achieve the aforementioned irradiation energy density. Parameters of the laser processing conditions include the laser beam output (W), laser beam frequency (kHz), laser beam diameter (μm), laser beam irradiation interval (μm), laser beam scanning speed (mm / s), and the number of laser beam scans (times). Of these, the laser beam output is preferably 10 W or more, more preferably 30 W or more. Conversely, the laser beam output is preferably 100 W or less, more preferably 70 W or less. Furthermore, the laser beam scanning speed is preferably 50 mm / s or more, more preferably 100 mm / s or more, and even more preferably 300 mm / s or more. Conversely, the laser beam scanning speed is preferably 2000 mm / s or less, more preferably 1000 mm / s or less, and even more preferably 500 mm / s or less. The number of scans refers to the number of times that the laser light is repeatedly irradiated along the same irradiation locus.

[0056] The relationship between the beam diameter D and the irradiation interval P of the laser beam will be explained with reference to FIG. 3. The irradiation interval P of the laser beam refers to the interval P between the trajectory 1 of one laser beam irradiated onto the target and the trajectory 1' of another laser beam irradiated adjacent to the laser. Specifically, the irradiation interval of the laser beam refers to the distance between either end of the trajectory 1 of the one laser beam in a direction perpendicular to the scanning direction 2 and the end of the trajectory 1' of the other laser beam on the same side as the one laser beam. When a pulsed laser is irradiated, the trajectory of the laser beam is represented as a continuous trajectory of pores formed by individual laser pulses. In this case, the irradiation interval P of the laser beam corresponds to the sum of the width of the region sandwiched between the trajectories of the laser beam formed by the continuous pores and the size of the beam diameter D. In the present invention, it is preferable that the ratio (P / D) of the irradiation interval P of the laser beam to the beam diameter D of the laser beam is 1 or more and 2 or less.

[0057] By setting the P / D ratio at or above the lower limit, it is possible to prevent excessive accumulation of metals that diffuse from adjacent (parallel) marking patterns during laser irradiation, resulting in voids (sparse areas) between the deposits, thereby improving the bond strength and airtightness between the metal member and the object to be joined. Furthermore, by setting the P / D ratio at or below the upper limit, laser irradiation does not result in the formation of non-irradiated areas (untreated areas) without unevenness on the surface of the metal substrate between adjacent (parallel) marking patterns, thereby improving the bond strength and airtightness between the metal member and the object to be joined. The lower limit of the P / D ratio is preferably 1.2, more preferably 1.3, and even more preferably 1.5. The upper limit of the P / D ratio is preferably 1.9, more preferably 1.8, and even more preferably 1.6.

[0058] Note that the higher the melting point and the greater the thermal diffusion of the metal that makes up the metal substrate, the less susceptible the metal substrate tends to be to the effects of laser light. Therefore, it is desirable to set the irradiation energy density according to the type of metal substrate to be laser treated. Table 1 shows examples of assumed laser treatment conditions for cases where the main metal of the metal substrate to be laser treated is aluminum, iron, or copper.

[0059] [Table 1]

[0060] [2-2. Boehmite film formation process] Next, in the boehmite film forming step, the metal substrate on which the thermal oxide film has been formed, obtained in the thermal oxide film forming step, is immersed in pure water having a conductivity of 10 mS / m or less and a temperature of 90°C or more for 10 to 120 minutes, thereby forming a boehmite film containing hydroxyl groups on the surface of the metal substrate.

[0061] <Immersion treatment> In the boehmite film-forming step, the thermal oxide film having macro-concave and micro-concave portions obtained in the thermal oxide film-forming step is converted into a boehmite film having macro-concave and micro-concave portions containing boehmite by the immersion treatment. The formation of the boehmite film can be confirmed by, for example, X-ray diffraction measurement.

[0062] The immersion treatment uses pure water with a conductivity of 10 mS / m or less. It is preferably 5 mS / m or less, and more preferably 1 mS / m or less. While there is no lower limit for the conductivity, taking into consideration the cost of producing pure water and practicality, it is preferably 0.01 mS / m or more, more preferably 0.02 mS / m or more, and even more preferably 0.05 mS / m or more. If the conductivity exceeds 10 mS / m, the boehmite film may not be formed, the film formation rate may be slowed, and the presence of impurities may make the film more susceptible to defects.

[0063] Furthermore, the immersion treatment uses pure water at a temperature of 90°C or higher, preferably 95°C or higher. By setting the temperature within this range, the reaction to form a boehmite film can occur, and a higher temperature is preferable because it tends to shorten the immersion treatment time. There is no upper limit to the temperature, but it is preferably 100°C or lower in order to avoid exceeding the boiling point and avoiding excessive reaction.

[0064] The immersion time is 10 to 120 minutes, preferably 30 to 90 minutes. The immersion time can be adjusted appropriately depending on the conductivity and temperature of the pure water. By setting the immersion time within this range, the reaction to form a boehmite film can occur, and it is possible to prevent the reaction from becoming excessive or the boehmite film from becoming too thick and becoming brittle.

[0065] Prior to the immersion treatment described above, the surface of the metal substrate on which the thermal oxide film has been formed in the thermal oxide film forming step may be pretreated. The pretreatment may be selected from known methods, such as blasting, degreasing, etching, desmutting, chemical polishing, and electrolytic polishing.

[0066] By immersion treatment under these conditions, the thermally oxidized film having macro- and micro-irregularities is converted into a boehmite film containing boehmite and having macro- and micro-irregularities. Because the thermally oxidized film is relatively thin, it is believed that the entire film is converted into a boehmite film. Here, the thickness of the micro-irregularities containing boehmite obtained through the boehmite film formation process is set to 10 to 2000 nm. This is because the immersion treatment generates a boehmite film by reacting water with the metal oxide of aluminum contained in the thermally oxidized film, and the boehmite film grows over time due to the reaction of water with the metallic aluminum contained in the metal substrate.

[0067] [2-3. Liquid repellent layer formation process] In the liquid-repellent layer forming step, a liquid-repellent material is applied to a metal member on which a boehmite film has been formed on the surface of the metal substrate in the boehmite film forming step, thereby forming the above-mentioned liquid-repellent layer on the outermost layer of the metal member.

[0068] The liquid-repellent material used in this liquid-repellent layer-forming step is made of either a fluorine-containing compound or a silicon-containing compound, or both, as described above. The specific means for the liquid-repellent layer-forming step are not particularly limited as long as they can form a liquid-repellent layer on the outermost surface of the metal member on which the boehmite film has been formed. Known methods such as spraying, coating, and immersion can be used. After the liquid-repellent treatment with the liquid-repellent material, the liquid-repellent layer can be formed on the surface of the thermal oxide film by natural drying, or by heating and drying at approximately 100°C to 300°C, or a combination of these methods can be used.

[0069] [2-4. Pre-treatment process] A pretreatment step of treating the metal substrate may be provided prior to the thermal oxide film forming step, the boehmite film forming step, or the liquid-repellent layer forming step described above. The pretreatment step may be performed together with the pretreatment for the immersion treatment described above. Such pretreatment steps include washing and degreasing of the metal substrate. Of these, washing can be performed using a surfactant, acid, alkali, or the like. Degreasing can be performed using an organic solvent such as acetone, alcohol, or ethanol, or alkali, or the like. When performing these washing and degreasing steps, rinsing with pure water may be performed as necessary.

[0070] [3. Action and Effects] The liquid-repellent member of the present invention has a boehmite coating on a metal member covered with a liquid-repellent layer, which has a macro-uneven portion containing boehmite in which the scale of the unevenness, the shape of the recesses, and the complexity of the surface shape of the uneven portion are controlled, and the surface of this macro-uneven portion has a micro-uneven portion containing boehmite, so that the liquid-repellent member has enhanced liquid repellency.

[0071] In particular, when the super-liquid-repellent angle of the concave-convex portions of the macro-convex portion containing boehmite is within a predetermined numerical range, the depth of the concave portions is sufficiently deep and sharp relative to the opening diameter of the concave portions, and when droplets of liquid are dropped onto the surface of the liquid-repellent surface, the droplets do not penetrate from near the surface to the bottom of the concave portions, making it easier to maintain the space formed by the concave-convex portions. Furthermore, since the fractal dimension of the unevenness in the macro unevenness is within a predetermined range, the entire surface of the unevenness and part of it have a self-similar shape, and the surface shape of the unevenness becomes complex, so when droplets are dropped onto the surface of the liquid-repellent surface, it becomes easier to prevent the droplets from adhering to the surface of the unevenness. Furthermore, in the present invention, the liquid-repellent surface has a fine unevenness containing boehmite on the surface of the macro unevenness. In this way, the surface of the micron-order macro unevenness is provided with a fine unevenness of nano-order, thereby increasing the surface area and improving the liquid repellency.

[0072] Therefore, as shown in the examples described later, the liquid-repellent member of the present invention exhibits super-water-repellency, with a water contact angle of 160° or more, preventing water from adhering to the surface, and a sliding angle of 7° or less when a 5 μL drop of water is applied. Moreover, the contact angle with n-hexadecane is 120° or more, and the sliding angle is 30° or less when a 3 μL drop of n-hexadecane is applied. This means that the liquid-repellent member not only repels water but also oil, providing an unprecedented liquid-repellent member with excellent water and oil repellency.

[0073] Furthermore, in the liquid-repellent member according to the present invention, the metal member has a boehmite coating containing hydroxyl groups formed on the surface of the metal substrate, and the liquid-repellent surface has a boehmite coating formed on the surface of the metal substrate and a liquid-repellent layer formed on the outermost layer of the liquid-repellent surface. By providing the boehmite coating on the surface of the metal substrate, the proportion of hydroxyl groups present near the surface layer of the metal substrate (hydroxyl group abundance rate) is increased. This strengthens the interaction between the hydroxyl groups of the boehmite coating and the fluorine-containing compound and silicon-containing compound contained in the liquid-repellent material, thereby improving the liquid-repellency of the liquid-repellent material. [Example]

[0074] Preferred embodiments of the present invention will be specifically described below based on examples and comparative examples, but the present invention should not be construed as being limited thereto. Table 3 summarizes the manufacturing conditions for each example and comparative example, and various evaluations of the obtained liquid-repellent members.

[0075] [1. Evaluation] <Cross-sectional SEM observation> The liquid-repellent member was cut in the thickness direction, embedded in an epoxy resin, and then wet-polished to prepare a sample for evaluating the bonding cross-section. The thickness-direction cross-section of the sample for evaluating the bonding cross-section was observed with a scanning electron microscope (manufactured by JEOL Ltd., JSM-7200F) at magnifications of 100 to 500 times. From the obtained observed cross-section, the arrangement interval (I), depth (L), super-liquid-repellent expression angle (θ), and fractal dimension of the macro uneven portions were determined. In doing so, all of these values were determined as described above. Also, the thickness of the fine uneven portions formed on the surface of the macro uneven portions was determined by observing the cross-section SEM at 10,000 times magnification.

[0076] <Planar SEM Observation> The surface of the liquid-repellent member was observed with a scanning electron microscope (manufactured by JEOL Ltd., JSM-7200F) at magnifications of 100 to 10,000 times. By observing the planer SEM at 10,000 times magnification, the size of the openings of the fine uneven portions formed on the surface of the macro uneven portions was confirmed.

[0077] <Measurement of Static Contact Angle and Sliding Angle> For the measurement of the static contact angle, an automatic contact angle meter (DMo-602 manufactured by Kyowa Interface Science Co., Ltd.) was used, and the contact angles of the water droplets or liquid droplets immediately after dropping 5 μL of ion-exchanged water and 3 μL of n-hexadecane droplets, respectively, onto the surface of the horizontally placed liquid-repellent member were measured. Note that with this automatic contact angle meter, when the contact angle becomes super-liquid-repellent of 160° or more, the water droplets (liquid droplets) do not adhere.

[0078] Also, for the measurement of the sliding angle, a static friction coefficient measuring machine (automatic contact angle meter DMo-602 manufactured by Kyowa Interface Science Co., Ltd.) was used, and 5 μL of ion-exchanged water droplets were dropped onto the surface of the horizontally placed liquid-repellent member, and the angle at which the water droplets began to slide when the liquid-repellent member was tilted at a speed of about 2° / second was determined. Similarly, 3 μL of n-hexadecane droplets were dropped onto the surface of the horizontally placed liquid-repellent member, and the angle at which the liquid droplets began to slide when the liquid-repellent member was tilted at a speed of about 2° / second was determined.

[0079] <GD-OES Surface Analysis> The liquid-repellent material was subjected to surface analysis using a glow discharge optical emission spectrometry (GD-OES) (Horiba, Ltd.: GD-Profiler2). The measurement conditions were: analysis diameter (anode diameter): 4 mmφ, gas pressure: 600 Pa, RF power: 35 W, acquisition interval: 0.1 s, measured elements: Al (measurement wavelength: 396.157 nm, photomultiplier tube high voltage: 600 V), measured elements: Fe (measurement wavelength: 374.954 nm), measured elements: Cu (measurement wavelength: 324.759 nm), measured elements: OH group (measurement wavelength: 306.775 nm, photomultiplier tube high voltage: 900 V). The measurement method involved sputtering the sample with Ar plasma and then performing elemental analysis by atomic emission of the sputtered atoms. The hydroxyl group abundance was calculated from the emission intensity detected from the time from the detection of the metal substrate or hydroxyl groups to the time required for 200 nm sputtering corresponding to the major elements (Al, Cu, and Fe) constituting the metal substrate. The time required for 200 nm sputtering was determined from the sputtering rate (μm / min) obtained by measuring each standard sample containing the above elements at high purity (Al: A995 manufactured by Nippon Light Metal Co., Ltd.; Cu: Cu-113514 manufactured by Nilaco Corporation; Fe: Fe-223469 manufactured by Nilaco Corporation) in advance using the same equipment and analytical conditions as above. The purity of each standard sample, as well as the sputtering rate and time required for 200 nm sputtering, are shown in Table 2 below. In the examples and comparative examples described below, an aluminum base material is used as the metal base material, and therefore, the emission intensity derived from the main metal constituting the metal base material was measured only for Al.

[0080] [Table 2]

[0081] <Surface roughness measurement> The surface roughness of the liquid-repellent member was measured using a Mitutoyo SURFTEST SJ-210 device. The arithmetic mean height (Ra), maximum height (Rz), and arithmetic mean slope (RΔa) were measured for the liquid-repellent members of the examples and comparative examples. The arithmetic mean height (Ra) and maximum height (Rz) were measured in accordance with JIS B 0601-2013. The arithmetic mean slope (RΔa) was measured in accordance with JIS B 0601-2001.

[0082] [2. Sample Preparation] [Example 1] A test aluminum plate (A5052-H18) measuring 50 mm × 50 mm × 1 mm thick was prepared as the aluminum substrate. This test aluminum plate was subjected to laser treatment by irradiating it with a laser under the following conditions to form a thermal oxide film on the surface of the test aluminum plate (aluminum substrate) (thermal oxide film formation step). The surface (one of the main surfaces) of the test aluminum plate was irradiated with laser light along the longitudinal direction of the test aluminum plate and along the lateral direction, so that the trajectories of the laser light intersected within a rectangular region measuring 55 mm in the longitudinal direction and 55 mm in the lateral direction.

[0083] [Laser treatment conditions] Equipment: Keyence 3Axis Fiber laser marker (model: MDF-5200) Laser wavelength: 1090nm Transmission method: Pulse Output: 40W Frequency: 60kHz Beam diameter (D): 60 μm ·Irradiation interval (P): 90μm Scanning speed: 400mm / s Scanning method: Cross Number of scans (irradiations): 1 Energy density: 2.22J / mm 2

[0084] Next, the test aluminum plate (aluminum substrate) obtained as described above and having a thermal oxide film formed on its surface was first subjected to a pretreatment in which it was immersed in a 30% by mass aqueous nitric acid solution at room temperature for 3 minutes. Thereafter, the pretreated substrate was thoroughly washed with ion-exchanged water having a conductivity of 1.0 mS / m, and then immersed in warm ion-exchanged water at 95°C having the same conductivity of 1.0 mS / m for 60 minutes to convert the thermal oxide film into a boehmite film, thereby obtaining a test aluminum plate (aluminum substrate) having a hydroxyl group-containing boehmite film formed on its surface (boehmite film formation step).

[0085] Next, a liquid-repellent material was applied to the test aluminum member (aluminum member) having the boehmite coating formed on the surface of the test aluminum plate (aluminum substrate) obtained as described above, to form a liquid-repellent layer on the surface (outermost layer) (liquid-repellent layer-forming step). Here, the liquid-repellent material was a fluorine-based surfactant (U-201 manufactured by Unichem Co., Ltd.; solvent isopropyl alcohol, solids content 2%) consisting of a perfluoroalkyl group phosphate ester compound, applied at a concentration of approximately 50 μg / cm 2 The coating was applied in an amount of 100 ml and dried at 120°C for 60 minutes.

[0086] The boehmite coating of the test liquid-repellent member according to Example 1 obtained as described above had a macroscopic unevenness (a macroscopic unevenness containing boehmite) consisting of multiple unevennesses, each consisting of a concave portion extending from the surface in a depth direction and a convex portion extending from the surface in a height direction around the concave portion, as shown in FIG. 1 . Furthermore, in the region between adjacent unevennesses, sharp edges were observed, where the convex portions included in adjacent unevennesses contacted and integrated with each other. Furthermore, planar SEM imaging at 10,000x magnification shown in FIG. 4 confirmed the formation of a microscopic unevenness (a microscopic unevenness containing boehmite) with openings of approximately 80 to 250 nm on the surface of the macroscopic unevenness of the boehmite coating according to Example 1. Furthermore, cross-sectional SEM imaging at 10,000x magnification shown in FIG. 5 revealed that the thickness of the microscopic unevenness was approximately 400 nm. Figure 6 shows a planar SEM image (magnification 100x) of this boehmite film, which allows us to confirm the state of the irradiation trajectories of the intersecting laser beams.

[0087] The spacing (I), depth (L), and super-liquid repellency angle (θ) of these macroscopic irregularities were determined using the cross-sectional SEM (magnification 100x) shown in Figure 1, and were specified using the method described above. Furthermore, to determine the fractal dimension, the cross-sectional SEM image shown in Figure 1 was imported into Microsoft PowerPoint, and calculations were performed using ImageJ with the box-counting method. The various settings were as described above. The various evaluation results described above are summarized in Table 3.

[0088] [Table 3]

[0089] [Example 2] A test liquid-repellent member according to Example 2 was obtained under the same conditions as in Example 1, except that the laser beam scanning speed in the thermal oxide film formation step was set to 1000 mm / s. Figure 7 shows a cross-sectional SEM image (magnification: 100x) of the obtained test liquid-repellent member. Based on this, the arrangement interval (I), depth (L), super-liquid-repellent angle (θ), and fractal dimension of the macroscopic irregularities were determined. Furthermore, the microscopic irregularities were evaluated in the same manner as in Example 1, and the liquid-repellent performance was also evaluated. The results are shown in Table 3.

[0090] [Example 3] A test liquid-repellent member according to Example 3 was obtained in the same manner as in Example 1, except that, among the laser processing conditions in the thermal oxide film formation step, the scanning speed of the laser light was set to 1000 mm / s and a phosphate ester group-containing fluorine coating agent (Fluorotechnology Co., Ltd., FG5093; solvent: fluorine-based solvent, solids content: 0.5%) was used as the liquid-repellent material. The arrangement spacing (I), depth (L), super-liquid-repellent angle (θ), and fractal dimension of the macroscopic unevenness were determined based on cross-sectional SEM images of the obtained test liquid-repellent member. Furthermore, the fine unevenness was evaluated in the same manner as in Example 1, and the liquid-repellent performance was also evaluated. The results are shown in Table 3.

[0091] [Comparative Example 1] A test liquid-repellent member according to Comparative Example 1 was obtained under the same conditions as in Example 1, except that the laser beam scanning speed in the thermal oxide film formation step was set to 6,000 mm / s. Figure 8 shows a cross-sectional SEM image (magnification: 100x) of the obtained test liquid-repellent member. Based on this, the arrangement interval (I), depth (L), super-liquid-repellent angle (θ), and fractal dimension of the macroscopic irregularities were determined. Furthermore, the microscopic irregularities were evaluated in the same manner as in Example 1, and the liquid-repellent performance was also evaluated. The results are shown in Table 3.

[0092] Comparative Example 2 A test liquid-repellent member according to Comparative Example 2 was obtained under the same conditions as in Example 1, except that the laser beam scanning speed in the thermal oxide film formation step was set to 3,000 mm / s. Figure 9 shows a cross-sectional SEM image (magnification: 100x) of the obtained test liquid-repellent member. Based on this, the arrangement interval (I), depth (L), super-liquid-repellent angle (θ), and fractal dimension of the macroscopic irregularities were determined. Furthermore, the microscopic irregularities were evaluated in the same manner as in Example 1, and the liquid-repellent performance was also evaluated. The results are shown in Table 3.

[0093] [3. Consideration] Cross-sectional observation of the liquid-repellent members of Examples 1 and 2 using an SEM confirmed that macroscopic irregularities containing boehmite and having micrometer-order irregularities were formed over the entire surface of the aluminum substrate. It is presumed that macroscopic irregularities were also formed in Example 3, which was subjected to laser treatment under the same conditions as Example 2. It was also confirmed that nanoscopic irregularities containing boehmite of nanometer-order irregularities were formed on the surface of the macroscopic irregularities. In other words, the boehmite coating on the aluminum member had macroscopic irregularities in which the complexity of the surface shape of the irregularities was controlled based on the scale of the irregularities, the shape of the recesses, and the fractal dimension. Furthermore, the presence of nanoscopic irregularities on the surface of the macroscopic irregularities enabled the formation of a liquid-repellent member with enhanced liquid repellency not only with water but also with n-hexadecane, which has a lower surface free energy than water and is therefore more easily wetted.

[0094] In contrast, in Comparative Example 1 and Comparative Example 2, which do not satisfy the super-liquid-repellent angle and fractal dimension specified for the liquid-repellent member according to the present invention, the static contact angle with water was not different from Examples 1 to 3, but there was a large difference in the sliding angle. Also, when n-hexadecane was used, the static contact angle was not different from Examples 1 to 3, but there was a large difference in the sliding angle, and the liquid-repellent performance was inferior. [Explanation of symbols]

[0095] 1(1')...laser light trajectory, 2...scanning direction, P...irradiation interval, D...beam diameter, Pt1: highest convex part, Pb1: lowest concave part, RL1, RL2: reference lines.

Claims

1. A liquid-repellent member having a liquid-repellent surface on its surface, the liquid-repellent member includes a metal member and a liquid-repellent layer containing a liquid-repellent material and covering the metal member; The metal member has a metal substrate made of metal and a boehmite coating containing hydroxyl groups formed on the surface of the metal substrate, the liquid-repellent surface is formed by forming the boehmite coating on the surface of the metal substrate and providing the liquid-repellent layer as the outermost layer of the liquid-repellent surface; the liquid-repellent material contains at least one of a fluorine-containing compound and a silicon-containing compound; The boehmite coating is The arrangement interval (I) is 10 to 300 μm, The depth (L) is 20 to 300 μm, The super-liquid-repellent exhibiting angle is 20°≦θ≦60°, The surface has a macro uneven portion containing boehmite and consisting of a plurality of uneven portions, and the fractal dimension of the macro uneven portion is 1.22 to 1.4, a micro-concave and convex portion containing boehmite having a thickness of 10 to 2000 nm and having a plurality of openings of 10 to 50 nm on the surface of the macro-concave and convex portion; A liquid-repellent member characterized by:

2. 2. The liquid-repellent member according to claim 1, wherein, when the boehmite coating is analyzed by glow discharge optical emission spectrometry from the surface in a depth direction, a ratio of the detected amount of hydroxyl groups to a total amount of the detected amount of metal forming the metal base and the detected amount of hydroxyl groups is 50% or more and 90% or less.

3. The liquid-repellent member according to claim 1 , wherein the metal forming the metal substrate is aluminum or an alloy containing aluminum.

4. 2. The liquid-repellent member according to claim 1, wherein the liquid-repellent layer comprising the liquid-repellent material has liquid-repellent properties in such a manner that a sliding angle of 7° or less when a 5 μL droplet of water is dropped onto the liquid-repellent layer, and a sliding angle of 30° or less when a 3 μL droplet of n-hexadecane is dropped onto the liquid-repellent layer, thereby achieving super-water-repellent and super-oil-repellent properties.

5. the boehmite coating is formed on the liquid-repellent surface over the entire surface of the metal substrate that forms the metal member, the uneven portion is formed on the surface of the metal base material, the uneven portion being composed of a recess formed in a recessed shape from the surface in a depth direction and a protrusion formed in a protruding shape from the surface in a height direction around the recess, The liquid-repellent member according to claim 1, wherein the liquid-repellent surface has sharp edges formed in the area sandwiched between adjacent uneven portions on the surface of the metal member so that the convex portions included in each of the adjacent uneven portions come into contact and become integrated.

6. A method for manufacturing a liquid-repellent member having a liquid-repellent surface on its surface, comprising: the liquid-repellent member includes a metal member and a liquid-repellent layer containing a liquid-repellent material and covering the metal member; The metal member has a metal substrate made of metal and a boehmite coating containing hydroxyl groups formed on the surface of the metal substrate, a thermal oxide film forming step of forming a thermal oxide film containing hydroxyl groups on the surface of the metal base by laser treatment in which a laser beam is irradiated onto the surface of the metal base; a boehmite film forming step of immersing the metal base material on which the thermal oxide film has been formed in pure water having a conductivity of 10 mS / m or less and a temperature of 90°C or more for 10 to 120 minutes to form a boehmite film containing hydroxyl groups on the surface of the metal base material; a liquid-repellent layer forming step of applying the liquid-repellent material to the metal member on which the boehmite coating film has been formed, thereby forming the liquid-repellent layer on the outermost surface of the metal member, In the boehmite film forming step, the boehmite film is formed on the surface of the metal substrate at the liquid-repellent surface, In the liquid-repellent layer forming step, the liquid-repellent layer is formed on the outermost layer of the liquid-repellent surface, the liquid-repellent material contains at least one of a fluorine-containing compound and a silicon-containing compound; In the thermal oxide film forming step, the laser treatment The arrangement interval (I) is 10 to 300 μm, The depth (L) is 20 to 300 μm, The super-liquid-repellent exhibiting angle is 20°≦θ≦60°, The surface has a macro uneven portion consisting of a plurality of uneven portions, and the fractal dimension is 1.22 to 1.4, forming the thermally oxidized coating film having a micro-concave portion on the surface of the macro-concave portion, the micro-concave portion having a thickness of 10 to 1000 nm and a plurality of openings of 10 to 50 nm; In the boehmite film forming step, the thermal oxide film having the macro-irregularity and the micro-irregularity is converted into the boehmite film having the macro-irregularity and the micro-irregularity containing boehmite by the immersion treatment, The fine irregularities containing boehmite have a thickness of 10 to 2000 nm. A method for producing a liquid-repellent member, comprising:

7. The conditions for the laser treatment are an output of 10 W or more, a scanning speed of 50 to 2000 mm / s, and an irradiation energy density of 0.4 to 10 J / mm 2 The method for producing a liquid-repellent member according to claim 6 , wherein the range is:

8. The method for producing a liquid-repellent member according to claim 7 , wherein a ratio (P / D) of an irradiation interval P of the laser light to a beam diameter D of the laser light is 1 or more and 2 or less.

9. the surface of the metal substrate is formed with the uneven portion, which is composed of recesses formed by the metal forming the metal substrate at the location irradiated with the laser light diffusing outward from the irradiation center of the laser light, and protrusions formed by the metal diffused from the recesses and accumulating around the recesses; 7. The method for manufacturing a liquid-repellent member according to claim 6, wherein, in the liquid-repellent surface, in an area on the surface of the metal member between adjacent concave-convex portions, sharp edges are formed so that the convex portions included in the adjacent concave-convex portions come into contact with each other and become integrated, no untreated area is formed in which the metal base material is exposed before the irradiation of the laser light, and the boehmite coating is formed over the entire surface of the metal base material.

Images