Resin surface structure and method for manufacturing the same

Abstract

To readily produce a surface structure imitating wings of Nasutitermitinae termites.SOLUTION: A resin surface structure has first pores with a depth of 1.5-30 μm and a pore size of 1-6 μm, and second pores with a depth of 1-5 μm and a pore size of 0.05-1 μm.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a resin surface structure and a method for manufacturing the same. [Background technology]

[0002] As global warming expands, arid regions are becoming increasingly severe, and water scarcity is a major challenge. In arid regions, groundwater sources are limited, while fog can form in the air. If fog can be efficiently collected, it could become a valuable water source. Fog droplets are small in weight and therefore easily adhere to surfaces, but their large surface area relative to their volume causes them to evaporate rapidly, making collection difficult.

[0003] The Australian termite, *Coptotermes venus*, flies during the rainy season to build its nests. The surface of this termite's wings has the function of attracting mist droplets, turning them into large water droplets, and then removing them from the surface (Non-Patent Literature 1). If this surface structure can be mimicked to efficiently collect mist droplets and convert them into liquid droplets, it is thought that this could be an effective measure against water shortages in arid regions.

[0004] Patent Document 1 describes diarylethene derivatives 1c and 2c [ka] [ka] This invention discloses that a surface structure mimicking the wings of the tengu termite can be formed, and that this surface structure can efficiently collect minute droplets. It also discloses a method for producing a mold using electroforming with this surface structure as the matrix. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2021-154712 [Non-patent literature]

[0006] [Non-Patent Document 1] ACS Nano 2010, 4, 1, 129-136 [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] According to Patent Document 1, a female mold can be made by electroforming using a surface structure having a diarylethene derivative as a matrix, and a surface structure mimicking the wings of the long-nosed termite can be made from this female mold. However, electroforming requires large-scale equipment such as metal film formation by vapor deposition or sputtering, and electroplating. The object of the present invention is to easily manufacture a surface structure mimicking the wings of the long-nosed termite. [Means for solving the problem]

[0008] The inventors of the present invention have discovered that a surface structure mimicking the wings of the Tengu termite can be easily manufactured by using a resin-based surface structure as a female mold, and have completed the present invention.

[0009] In other words, the present invention relates to a resin surface structure having first pores with a depth of 1.5 to 30 μm and a pore diameter of 1 to 6 μm, and second pores with a depth of 1 to 5 μm and a pore diameter of 0.05 to 1 μm.

[0010] The resin is preferably polyvinyl alcohol, polyvinylpyrrolidone, or polyacrylic acid.

[0011] The resin surface structure is preferably intended for use as a mold.

[0012] The present invention also relates to a method for manufacturing a resin surface structure, which includes a step of forming a resin layer on the surface of a sacrificial mold and a step of separating the resin layer from the sacrificial mold to obtain the resin surface structure. The sacrificial mold has, on a substrate, a first needle-like structure having a length of 1.5 to 30 μm and a diameter of 1 to 6 μm, and a second needle-like structure having a length of 1 to 5 μm and a diameter of 0.05 to 1 μm.

[0013] The present invention also relates to a method for manufacturing a resin surface structure, which includes a step of forming a resin layer on the surface of a sacrificial mold and a step of separating the resin layer from the sacrificial mold to obtain the resin surface structure. The sacrificial mold has, on a substrate, the following structural formula (3c):

Chemical formula

Chemical formula

[0014] The diarylethene closed-ring compound represented by structural formula (3c) is the following structural formula (1c): [ka] The compound is represented by the following structural formula (2c): [ka] It is preferable that the compound is represented by [formula].

[0015] Preferably, the length of the needle-shaped crystals of the diarylethene ring-closed product represented by structural formula (3c) is 8 times or more the length of the needle-shaped crystals of the diarylethene ring-closed product represented by structural formula (4c), and the diameter of the needle-shaped crystals of the diarylethene ring-closed product represented by structural formula (3c) is 7 times or more the diameter of the needle-shaped crystals of the diarylethene ring-closed product represented by structural formula (4c).

[0016] It is preferable that a layer containing needle-shaped crystals of a diarylethene ring-closed product represented by structural formula (3c) and needle-shaped crystals of a diarylethene ring-closed product represented by structural formula (4c) is formed on the surface of the substrate with a thickness in the range of 1 to 20 μm.

[0017] Furthermore, the present invention relates to a method for manufacturing a water-repellent surface structure, which includes a step of bringing the resin surface structure into contact with a resin. [Effects of the Invention]

[0018] Since the surface structure of the present invention is made of resin, it can be easily manufactured by transferring a sacrificial surface structure. The water-repellent surface structure manufactured by using the surface structure of the present invention as a female mold has a surface structure that mimics the wings of the tengu termite and can efficiently collect minute droplets. [Brief explanation of the drawing]

[0019] [Figure 1] This document outlines the manufacturing method for resin-based surface structures. [Figure 2] The image shows a SEM image of a resin surface structure. [Figure 3]This document outlines the manufacturing method for a water-repellent surface structure. [Figure 4] The image shows a SEM image of a water-repellent surface structure. [Figure 5] This shows the contact angle between a water-repellent surface structure and water. [Figure 6] The SEM images of the sacrificial structure obtained in Example 1 and the surface structure obtained in Example 3, along with their water droplet adhesion properties, are shown. [Modes for carrying out the invention]

[0020] <<Resin Surface Structure>> The resin surface structure of the present invention has first pores and second pores having openings on the surface of a resin structure. In particular, the resin surface structure is characterized by having first pores with a depth of 1.5 to 30 μm and a pore diameter of 1 to 6 μm, and second pores with a depth of 1 to 5 μm and a pore diameter of 0.05 to 1 μm.

[0021] The depth of the first pore is 1.5 to 30 μm, but is preferably 10 to 30 μm, and more preferably 15 to 30 μm. The pore diameter of the first pore is 1 to 6 μm, but is preferably 1 to 3 μm, more preferably 1 to 2 μm, and still preferably 1.5 to 2 μm. The depth of the second pore is 1 to 5 μm, but is preferably 1.5 to 2 μm, and more preferably 1.8 to 2 μm. The pore diameter of the second pore is 0.05 to 1 μm, but is preferably 0.1 to 0.5 μm, more preferably 0.1 to 0.3 μm, and still preferably 0.1 to 0.2 μm. By structuring the first and second pores as described above, they can be suitably used as a mold for manufacturing the water-repellent surface structure described later. The resulting water-repellent surface structure can adhere small droplets but repel larger droplets.

[0022] The depth of the first pore is preferably 8 times or more the depth of the second pore, and more preferably 9 times or more. The diameter of the first pore is preferably 7 times or more the diameter of the second pore, and more preferably 8 times or more.

[0023] The first pore and the second pore each preferably have an inclination of 60° to 90° with respect to the surface of the resin-made surface structure and are formed from the surface opening of the resin-made surface structure toward the inside. The shapes of the first pore and the second pore are not particularly limited, and examples of their cross-sectional shapes include polygons, circles, and ellipses. The first pore and the second pore preferably have a substantially linear portion without curving from the surface opening of the resin-made surface structure toward the inside, and more preferably, the whole is substantially linear.

[0024] The density of the first pores on the surface of the resin-made surface structure is preferably 50,000 to 80,000 per 1 mm 2 more preferably 60,000 to 70,000, and even more preferably 65,000 to 70,000. Also, the density of the second pores is preferably 600,000 to 900,000 per 1 mm 2 more preferably 700,000 to 800,000. The density of each pore can be calculated by the number of surface openings on the resin-made surface structure.

[0025] The resin-made surface structure may optionally have a surface structure other than the first pore and the second pore as long as the surface structure produced using this as a mold has water repellency. Examples of arbitrary surface structures include a surface structure formed by laying plate-like crystals flat and pores other than the first pore and the second pore.

[0026] The structures of the first pore and the second pore can be observed and evaluated by SEM. Also, in the water-repellent surface structure obtained using this resin-made surface structure as a mold, since the surface structure of the resin-made surface structure is transferred, the structure of the resin-made surface structure can also be indirectly evaluated by observing the needle-like structure on the surface of the water-repellent surface structure by SEM.

[0027] The resin-made surface structure preferably has a thickness of 40 μm or more, more preferably 60 μm or more, so as to hold the first pore and the second pore inside. The upper limit of the thickness of the structure is not particularly limited, but is generally 100 μm or less.

[0028] The resin material constituting the resin surface structure is not particularly limited as long as it can form the first and second pores, but from the viewpoint of ease of manufacture and moldability when the resin surface structure is used as a mold, thermoplastic resins are preferred, polyvinyl alcohol, polyvinylpyrrolidone, and polyacrylic acid are more preferred, and polyvinyl alcohol is even more preferred. The resin surface structure may be laminated with a substrate. The material of the substrate is not particularly limited, and metals, resins, glass, etc., can be used.

[0029] Since the resin surface structure has first and second pores, it can be suitably used as a mold, particularly a female mold, when manufacturing the water-repellent surface structure described later.

[0030] <<Manufacturing Method for Resin Surface Structures>> A resin surface structure can be manufactured by a process of forming a resin layer on the surface of a sacrificial mold, and a process of separating the resin layer from the sacrificial mold to obtain a resin surface structure.

[0031] <Sacrificial type (1)> The sacrificial type preferably has a first needle-like structure on the substrate having a length of 1.5 to 30 μm and a diameter of 1 to 6 μm, and a second needle-like structure having a length of 1 to 5 μm and a diameter of 0.05 to 1 μm.

[0032] The length of the first needle-like structure is 1.5 to 30 μm, but preferably 10 to 30 μm, and more preferably 15 to 30 μm. The diameter of the first needle-like structure is 1 to 6 μm, but preferably 1 to 3 μm, more preferably 1 to 2 μm, and even more preferably 1.5 to 2 μm. The length of the second needle-like structure is 1 to 5 μm, but preferably 1.5 to 2 μm, and more preferably 1.8 to 2 μm. The diameter of the second needle-like structure is 0.05 to 1 μm, but preferably 0.1 to 0.5 μm, more preferably 0.1 to 0.3 μm, and even more preferably 0.1 to 0.2 μm.

[0033] The length of the needle-like crystals in the first needle-like structure is preferably 8 times or more the length of the needle-like crystals in the second needle-like structure, and more preferably 9 times or more. Furthermore, the diameter of the first needle-like structure is preferably 7 times or more the diameter of the second needle-like structure, and more preferably 8 times or more.

[0034] The first needle-like structure and the second needle-like structure preferably have an inclination of 60° to 90° with respect to the substrate. Since the second needle-like structure may have this inclination, it is preferable that a layer consisting of the two needle-like structures is formed on the substrate surface with a thickness of 1.5 to 20 μm.

[0035] The density of the first needle-like structure on the substrate is 1 mm 2 The density of the second needle-like structure is preferably 50,000 to 80,000 needles per unit area, more preferably 60,000 to 70,000 needles, and even more preferably 65,000 to 70,000 needles. 2 A density of 600,000 to 900,000 plants per unit area is preferable, and 700,000 to 800,000 plants per unit area is more preferable.

[0036] The material of the base material is not particularly limited and includes, for example, metal, resin, glass, etc. From the viewpoint of manufacturing cost, it is preferable that it be made of the same material as the first and / or second needle-like structure.

[0037] The sacrificial type may have an arbitrary surface structure in addition to the first and second needle-like structures. An example of such a surface structure is one in which plate-like crystals are arranged upright and tiled.

[0038] <Sacrificial type (2)> Furthermore, the sacrificial type has the following structural formula (3c): [ka] Needle-shaped crystals of diarylethene ring-closed products represented by, The following structural formula (4c): [ka] It may have needle-shaped crystals of a diarylethene ring-closed product represented by .

[0039] In structural formulas (3c) and (4c), R A , and R B Each of these independently represents a methyl group, an ethyl group, a propyl group, an isopropyl group, a methoxy group, an ethoxy group, or a cyano group. E , and R F Each of these independently represents a methyl group, an ethyl group, a propyl group, or an isopropyl group. Among these, R A , and R B Each of these is preferably a methoxy group and a methyl group, R E , and R F A methyl group and an ethyl group are preferred, respectively.

[0040] R C , R D , R G , and R H Each of these independently represents a trimethylsilyl group, a t-butyl group, a neopentyl group, or an isopropyl group, but the trimethylsilyl group is more preferred.

[0041] R1 to R8 each independently represent a hydrogen atom, an optionally substituted linear or cyclic alkyl group, or a halogen atom. C1 to C4 alkyl groups are preferred. Examples of substituents on alkyl groups include hydrogen atoms, methyl groups, trimethylsilyl groups, ethyl groups, isopropyl groups, tert-butyl groups, methoxy groups, and ethoxy groups. Examples of halogen atoms include fluorine, iodine, and chlorine. Among the above, hydrogen atoms, methyl groups, trimethylsilyl groups, ethyl groups, isopropyl groups, tert-butyl groups, and methoxy groups are preferred for R1 to R8.

[0042] The diarylethene ring-closed compound represented by structural formula (3c) is shown in structural formula (1c): [ka] It is preferable that the compound is represented by the following structural formula (4c). Furthermore, the diarylethene ring-closed product represented by structural formula (2c) is preferred. [ka] It is preferable that the compound is represented by [formula].

[0043] The needle-shaped crystals of the diarylethene ring-closed compound represented by structural formula (3c) are coated on a substrate with structural formula (3o): [ka] It can be formed by irradiating microcrystals of the ring-opened diarylethene represented by [formula] with ultraviolet light.

[0044] The diarylethene ring-opened compound represented by structural formula (3o) is shown in structural formula (1o): [ka] It is preferable that the compound is represented by [formula].

[0045] The needle-shaped crystals of the diarylethene ring-closed compound represented by structural formula (4c) are coated on a substrate with structural formula (4o): [ka] These can be formed by irradiating microcrystals of the diarylethene ring-opened compound represented by with ultraviolet light. Needle-shaped crystals of (3c) and (4c) grow epitaxially on the crystal lattices of (3o) and (4o) on the substrate, regardless of the type of substrate.

[0046] The diarylethene ring-opened compound represented by structural formula (4o) is shown in structural formula (2o): [ka] It is preferable that the compound is represented by [formula].

[0047] (3o), (3c), (4o), and (4c) are all photoresponsive; when the open ring (3o) is irradiated with ultraviolet light, it becomes the closed ring (3c), and when the closed ring (3c) is irradiated with visible light, it becomes the open ring (3o). Similarly, when the open ring (4o) is irradiated with ultraviolet light, it becomes the closed ring (4c), and when the closed ring (4c) is irradiated with visible light, it becomes the open ring (4o).

[0048] The surface on the substrate where microcrystalline ring-open bodies of structural formulas (3o) and (4o) exist is smooth. When ultraviolet light is irradiated onto this surface, the ring-open bodies change into closed-ring bodies of structural formulas (3c) and (4c), needle-like crystals grow from the surface of the layer, and the smooth crystal planes disappear.

[0049] Furthermore, when visible light is irradiated onto the surface of the layer where the needle-shaped crystals have grown, the closed-ring body changes to the open-ring body, the needle-shaped crystals disappear, and the crystal returns to its original smooth state. In the sacrificial form having needle-shaped crystals of diarylethene closed-ring bodies, it is preferable to avoid exposure to visible light in order to maintain the needle-shaped crystals, and in particular, it is preferable to avoid exposure to light with wavelengths of 360 to 830 nm.

[0050] In the sacrificial form having needle-shaped crystals of the diarylethene ring-closed product, the length of the needle-shaped crystal of structural formula (3c) is preferably 1.5 to 30 μm, more preferably 10 to 30 μm, and more preferably 15 to 30 μm. The diameter of the needle-shaped crystal of structural formula (3c) is preferably 1 to 6 μm, more preferably 1 to 3 μm, even more preferably 1 to 2 μm, and even more preferably 1.5 to 2 μm. The length of the needle-shaped crystal of structural formula (4c) is preferably 1 to 5 μm, more preferably 1.5 to 2 μm, and even more preferably 1.8 to 2 μm. The diameter of the needle-shaped crystal of structural formula (4c) is preferably 0.05 to 1 μm, more preferably 0.1 to 0.5 μm, even more preferably 0.1 to 0.3 μm, and even more preferably 0.1 to 0.2 μm.

[0051] The length of the needle-shaped crystals of structural formula (3c) is preferably 8 times or more, and more preferably 9 times or more, than the length of the needle-shaped crystals of structural formula (4c). Furthermore, the diameter of the needle-shaped crystals of the diarylethene ring-closed product represented by structural formula (3c) is preferably 7 times or more, and more preferably 8 times or more, than the diameter of the needle-shaped crystals of the diarylethene ring-closed product represented by structural formula (4c).

[0052] The needle-shaped crystals of structural formula (3c) and structural formula (4c) preferably have an inclination of 60° to 90° with respect to the substrate. Since each needle-shaped crystal may have this inclination, it is preferable that a layer consisting of two needle-shaped crystals is formed on the substrate surface with a thickness of 1.5 to 20 μm.

[0053] The material of the substrate supporting the needle-shaped crystals is not limited as long as needle-shaped crystals of diarylethene ring-closed bodies can be grown on it, and examples include glass, metal, and resin. Examples of metals include nickel, iron, stainless steel, and aluminum. Examples of resins include polypropylene, polystyrene, polydimethylsiloxane, polymethyl methacrylate (PMMA), polyolefin, polycarbonate, melamine resin, and epoxy resin.

[0054] The sacrificial type may have any surface structure in addition to the needle-shaped crystals of structural formulas (3c) and (4c), as long as it has the desired water repellency. An example of such a surface structure is one in which plate-like crystals are arranged upright and tiled.

[0055] The sacrificial type can be produced by (a) applying a solution containing microcrystals of the ring-open diarylethene represented by structural formula (3o) and microcrystals of the ring-open diarylethene represented by structural formula (4o) onto a substrate, and (b) irradiating the applied surface with ultraviolet light to form needle-shaped crystals of the ring-closed diarylethene represented by structural formula (3c) and needle-shaped crystals of the ring-closed diarylethene represented by structural formula (4c).

[0056] Examples of solvents for the solution used in step (a) include chloroform, dichloromethane, benzene, toluene, and THF. In the solution, the molar ratio (3o:4o) of the compound with structural formula (3o) to the compound with structural formula (4o) is preferably 80:120 to 120:80, more preferably 95:105 to 105:95, and most preferably equimolar. Furthermore, the concentrations of the microcrystals of structural formula (3o) and structural formula (4o) are preferably 100 to 500 mg / mL, respectively.

[0057] In step (a), it is preferable to coat the solution containing microcrystals and then dry the solvent. The drying conditions are not particularly limited and may be at room temperature under normal pressure.

[0058] In step (b), the wavelength of the ultraviolet light irradiated is preferably 254 to 313 nm. The energy of the ultraviolet light irradiated is preferably 5 to 30 W. Furthermore, after irradiation with ultraviolet light, it is preferable to hold the sample at a temperature in the range of 30 to 40°C for 24 hours to 1 week, which promotes the growth of needle-shaped crystals. The needle-shaped crystals of structural formulas (3c) and (4c) tend to increase in size and decrease in water-repellent effect when the holding temperature is increased, so it is preferable to hold them at a temperature within the aforementioned range.

[0059] When manufacturing a resin surface structure using a sacrificial mold having needle-shaped crystals of diarylethene ring-closed bodies, it is preferable to pre-form a metal coating of Au-Pd, Au, Pt, Pt-Pd, etc., on the surface of the sacrificial mold. These coatings can be formed by general methods such as sputtering.

[0060] <Process for forming the resin layer> In the step of forming a resin layer on the surface of the sacrificial mold, a resin solution is laminated onto the surface of the sacrificial mold, and the solvent is removed by drying or heating. The resin is preferably a thermoplastic resin, more preferably polyvinyl alcohol, polyvinylpyrrolidone, or polyacrylic acid, and even more preferably polyvinyl alcohol. The solvent of the resin solution is not particularly limited, but examples include water, alcohol, acetic acid, and chloroform. The method of removing the solvent is not particularly limited, but static drying at 15-30°C is preferred, and static drying at room temperature is more preferred. Through this step, the surface structure of the sacrificial mold is transferred to the resin layer.

[0061] <Separation process of the resin layer> In the step of separating the resin layer from the sacrificial mold to obtain a resin surface structure, the specific method of separating the resin layer is not particularly limited as long as it can be separated. For example, if a thin film of polyvinyl alcohol is formed on the surface of the sacrificial mold, chloroform may be dropped onto the thin film to facilitate the peeling of the thin film from the sacrificial mold. Also, if the sacrificial mold consists of needle-shaped crystals of a diarylethene ring-closed product, the sacrificial mold may be dissolved by applying a solvent for needle-shaped crystals such as chloroform, dichloromethane, benzene, toluene, or THF. Through this step, a resin surface structure is obtained in which the surface structure of the sacrificial mold has been transferred.

[0062] <<Method for manufacturing a water-repellent surface structure>> A water-repellent surface structure can be manufactured by a method that includes a step of bringing the resin surface structure into contact with a resin. The contact between the resin surface structure and the resin is preferably carried out by laminating a resin solution onto the resin surface structure. After lamination of the resin solution, the solvent is removed by drying or heating.

[0063] Examples of resins include thermoplastic resins such as polystyrene, polydimethylsiloxane, polymethyl methacrylate (PMMA), poly(n-butyl methacrylate), polymethyl acrylate, polyolefin, and cycloolefin polymer (Zeonex polymer). Among these, polystyrene and polydimethylsiloxane are preferred. The constituent materials of the two needle-like structures do not need to be the same, but it is preferable from the viewpoint of manufacturing cost.

[0064] The solvent for the resin solution is not particularly limited, but examples include chloroform, benzene, acetone, and cyclohexane. The method for removing the solvent is not particularly limited, but static drying at 15-30°C is preferred, and static drying at room temperature is more preferred. Through this process, the surface structure of the resin surface structure is transferred to the resin layer.

[0065] Following the step of bringing a resin surface structure into contact with a resin, the resin layer is separated from the resin surface structure to obtain a water-repellent surface structure. The method for separating the resin layer is not particularly limited.

[0066] The water-repellent surface structure obtained by the above method has the surface structure of the sacrificial type transferred to it, and therefore, similar to the sacrificial type, it is preferable to have a first needle-like structure with a length of 1.5 to 30 μm and a diameter of 1 to 6 μm, and a second needle-like structure with a length of 1 to 5 μm and a diameter of 0.05 to 1 μm. The dimensions, shape, density, etc. of the first needle-like structure and the second needle-like structure are as described above for the sacrificial type.

[0067] The water-repellent surface structure may be laminated with other materials, as long as a sacrificial structure is transferred to the surface. Examples of other materials include metals, resins, and glass. For example, when the water-repellent surface structure is used for collecting mist droplets, the water-repellent surface structure can be supported on a support such as a net or a plate.

[0068] The surface of a water-repellent surface structure preferably has a contact angle of 90° or more for water droplets, and more preferably 100° or more. Generally, surfaces with a contact angle of less than 90° for water droplets are classified as hydrophilic, while those with a contact angle of 90° or more are classified as water-repellent. Furthermore, surfaces with a contact angle exceeding 150° are said to be water-repellent. A typical example of such a water-repellent surface is the surface of a lotus leaf, and this water repellency is sometimes called the "lotus effect."

[0069] The water-repellent surface structure may have any surface structure in addition to the first and second needle-like structures. An example of such a surface structure is one in which plate-like crystals are arranged upright and tiled.

[0070] <<Method for collecting microdroplets>> The microdroplets can be recovered by a method that includes a first step of adsorbing microdroplets onto a water-repellent surface structure, and a second step of recovering the adsorbed microdroplets.

[0071] The water-repellent surface structure mimics the surface structure of the wings of the long-nosed termite and therefore has the property of adsorbing minute droplets, similar to the wings of the long-nosed termite. The size of the minute droplets adsorbed onto the water-repellent surface structure in the first step is preferably 1 to 200 μm, and more preferably 10 to 180 μm. Minute droplets larger than 200 μm tend to be repelled by the water-repellent surface structure. Water is preferred as the minute droplet. A specific example is mist droplets. Furthermore, the space in which the minute droplets exist is not particularly limited as long as gas is present and it is not a vacuum, but it is preferable that it is a space in which air is present.

[0072] Methods for adsorbing microdroplets include spraying a gas containing microdroplets onto a water-repellent surface structure, or supporting a water-repellent surface structure in a space where a gas containing microdroplets is present. For example, by placing a water-repellent surface structure in a space where fog is generated, fog droplets can be adsorbed onto the surface of the water-repellent surface structure.

[0073] In the second step, the specific method of recovery of the microdroplets adsorbed in the first step is not particularly limited, as long as they can be recovered. For example, they can be recovered by gravity by tilting the water-repellent surface structure. If the microdroplets adsorbed in the first step are too small, they may be brought into contact with each other to form larger droplets before recovery. [Examples]

[0074] (Example 1) Sacrificial type fabrication The ring-open structures (1o) and (2o) were weighed in equimolar ratios (1o: 8.4 mg, 2o: 10.3 mg) and dissolved in 30 μL of chloroform. This solution was dropped onto a 2 cm square polypropylene substrate and dried at atmospheric pressure at room temperature in the dark to create a mixed thin film containing microcrystals of structures (1o) and (2o). The water contact angle in this thin film was 123°. This thin film was irradiated with ultraviolet light (wavelength 313 nm) for 5 minutes. Subsequently, needle-shaped crystals were grown by storing it in the dark at 30°C for 9 days, and a sacrificial form was obtained.

[0075] (Example 2) Fabrication of a resin surface structure Using the sacrificial mold obtained in Example 1, a resin surface structure was fabricated using the process shown in Figure 1. After coating the surface containing the needle-shaped crystals of the sacrificial mold with Au, a 10 wt% PVA aqueous solution was dropped onto it, and ultrasonic waves were irradiated for 30 seconds to remove air bubbles. After the surface was covered with the PVA aqueous solution, it was dried for one day to evaporate the water and obtain a surface structure made of PVA. A few drops of chloroform were dropped onto this to peel the PVA surface structure from the substrate. After washing the surface of the structure with chloroform, SEM observation was performed. In the SEM image (Figure 2), it was observed that the structure of the sacrificial mold from Example 1 had been transferred as a female mold. In Figure 2, the scale bars are (a) 20.0 μm, (b) 10.0 μm, (c) 5.0 μm, and (d) 2.0 μm, respectively.

[0076] (Example 3) Fabrication of a water-repellent surface structure A water-repellent surface structure was fabricated using the process described in Figure 3. Specifically, a 15 wt% polystyrene chloroform solution was dropped onto the resin surface structure obtained in Example 2 and dried for one day. After drying, the mixed film was immersed in DMSO (dimethyl sulfoxide) to dissolve and remove the PVA surface structure, thereby obtaining a water-repellent surface structure. Subsequently, after coating with Au, SEM observation was performed.

[0077] Figure 4 shows SEM images of the obtained water-repellent surface structure. In Figure 4, the scale bars are (a) 20.0 μm, (b) 10.0 μm, (c) 5.0 μm, and (d) 2.0 μm, respectively. In Figure 4, the water-repellent surface structure transferred to polystyrene reproduced the microstructure of the sacrificial surface (see Figure 6(a)). As shown in Figure 5, the contact angle of the water-repellent surface structure was 145.2°.

[0078] (Measurement Example 1) Adhesion of water droplets to a water-repellent surface structure In Example 3, pure water was sprayed onto the surface of the polystyrene surface structure using a commercially available spray bottle, and the moment when the minute water droplets collided with the surface was captured using a high-speed camera (1000fps).

[0079] The lower right of Figure 6 shows the distribution of the number of water droplets that were adsorbed onto the surface of the surface structure obtained in Example 3 and were not repelled (Non-bouncing), the number of water droplets released from spray bottle 1 (which generates microdroplets with a diameter of 40-400 μm) and repelled from the surface (Bouncing (Spr. 1)), and the number of water droplets released from spray bottle 2 (which generates microdroplets with a diameter of 400-1000 μm) and repelled from the surface (Bouncing (Spr. 2)), along with the diameter of the water droplets. Figure 6(b) shows an SEM image of the surface of the surface structure obtained in Example 3.

[0080] Similar measurements were also performed on the sacrificial surface obtained in Example 1. The distribution of the number of water droplets and their diameters is shown in the lower left of Figure 6. Figure 6(a) shows the SEM image of the surface.

[0081] The water-repellent surface structure transferred to polystyrene, shown in Figure 6(b), reproduced the microstructure of the sacrificial surface shown in Figure 6(a). The surface structure obtained in Example 3 (bottom right of Figure 6) exhibited the ability to hold a large number of water droplets of mist particle size (diameter 40-100 μm), demonstrating that resin-based surface structures can also adequately hold water droplets of mist particle size. Furthermore, compared to the sacrificial surface obtained in Example 1 (bottom left of Figure 6), the surface structure obtained in Example 3 (bottom right of Figure 6) showed less overlap between the distribution of Non-bouncing and Bouncing (Spr.1) for all water droplets, indicating a stronger tendency to specifically hold water droplets of mist particle size (diameter 40-100 μm).

Claims

1. First pores having a depth of 10-30 μm and a pore diameter of 1-6 μm, It has a second pore with a depth of 1 to 5 μm and a pore diameter of 0.05 to 1 μm. A resin surface structure, A resin surface structure wherein the resin is polyvinyl alcohol or polyvinylpyrrolidone.

2. A first pore having a depth of 1.5 to 30 μm and a pore diameter of 1 to 6 μm, It has a second pore with a depth of 1 to 5 μm and a pore diameter of 0.05 to 0.5 μm. A resin surface structure, A resin surface structure wherein the resin is polyvinyl alcohol or polyvinylpyrrolidone.

3. A resin surface structure according to claim 1 or 2 for use as a mold.

4. A process of laminating a resin solution containing polyvinyl alcohol or polyvinylpyrrolidone, with water or alcohol as the solvent, onto a sacrificial surface, removing the solvent to form a resin layer, and The process includes separating the resin layer from the sacrificial mold to obtain a resin surface structure, The sacrificial type has a first needle-like structure on the substrate having a length of 10 to 30 μm and a diameter of 1 to 6 μm, and a second needle-like structure having a length of 1 to 5 μm and a diameter of 0.05 to 1 μm, or The sacrificial type has a first needle-like structure on the substrate having a length of 1.5 to 30 μm and a diameter of 1 to 6 μm, and a second needle-like structure having a length of 1 to 5 μm and a diameter of 0.05 to 0.5 μm. A method for manufacturing a resin surface structure according to any one of claims 1 to 3.

5. A process of laminating a resin solution containing polyvinyl alcohol or polyvinylpyrrolidone, with water or alcohol as the solvent, onto a sacrificial surface, removing the solvent to form a resin layer, and The process includes separating the resin layer from the sacrificial mold to obtain a resin surface structure, The aforementioned sacrificial type, On the substrate, the following structural formula (3c): 【Chemistry 1】 Needle-shaped crystals of diarylethene ring-closed products represented by, The following structural formula (4c): 【Chemistry 2】 A method for producing a resin surface structure according to any one of claims 1 to 3, having needle-shaped crystals of a diarylethene ring-closed body represented by [the specified formula]. (In structural formulas (3c) and (4c), R Ａ , and R Ｂ Each of these independently represents a methyl group, an ethyl group, a propyl group, an isopropyl group, a methoxy group, an ethoxy group, or a cyano group. R Ｅ , and R Ｆ Each of these independently represents a methyl group, an ethyl group, a propyl group, or an isopropyl group. R Ｃ , R Ｄ , R Ｇ , and R Ｈ Each of these independently represents a trimethylsilyl group, a t-butyl group, a neopentyl group, or an isopropyl group. R １ to R ８ each independently represents a hydrogen atom, a linear or cyclic alkyl group which may be substituted, or a halogen atom.)

6. The diarylethene ring-closed compound represented by structural formula (3c) is shown in structural formula (1c): 【Transformation 3】 It is a compound represented by the following: The diarylethene ring-closed compound represented by structural formula (4c) is shown in structural formula (2c): 【Chemistry 4】 The compound represented by A method for manufacturing a resin surface structure according to claim 5.

7. The length of the needle-shaped crystals of the diarylethene ring-closed product represented by structural formula (3c) is 8 times or more the length of the needle-shaped crystals of the diarylethene ring-closed product represented by structural formula (4c). The diameter of the needle-shaped crystals of the diarylethene ring-closed product represented by structural formula (3c) is seven times or more the diameter of the needle-shaped crystals of the diarylethene ring-closed product represented by structural formula (4c). A method for manufacturing a resin surface structure according to claim 5 or 6.

8. A method for producing a resin surface structure according to any one of claims 5 to 7, characterized in that a layer containing needle-shaped crystals of a diarylethene ring-closed body represented by structural formula (3c) and needle-shaped crystals of a diarylethene ring-closed body represented by structural formula (4c) is formed on the surface of a substrate with a thickness in the range of 1 to 20 μm.

9. A method for manufacturing a resin surface structure according to any one of claims 4 to 8, wherein in the step of forming the resin layer, the solvent is removed by static drying at 15°C to 30°C.

10. The process includes bringing a resin surface structure according to any one of claims 1 to 3 into contact with a resin, A method for manufacturing a water-repellent surface structure.

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