Inorganic component, and method for manufacturing an inorganic component

Abstract

Provided are an inorganic member and a method for manufacturing an inorganic member. The inorganic member is configured so that a fine uneveness can be formed on the surface thereof with a simple procedure, and by controlling the shape of the uneveness, it possible to realize an inorganic member that has excellent durablity and that has low water wettability, without the need to form an organic fluorine coating film (film formation).　At least a portion of a principal surface 1a (surface) has fine uneveness 2, and the skewness Ssk of the fine uneveness is -0.1 or less. The fine uneveness 2 is formed by performing a wet blasting treatment.

Description

Technical Field

[0001] The present invention relates to an inorganic member and a method for manufacturing the inorganic member.

Background Art

[0002] For example, in automobiles, railway vehicles, ships, aircraft, etc., by realizing a window panel with low wettability to water (i.e., difficult to wet), it becomes possible to omit mechanisms such as wipers, and cost reduction in manufacturing can be expected through reduction in the number of parts and shortening of the manufacturing process. Therefore, as a member of the window panel, the demand for an inorganic member with lower wettability to water has been increasing year by year. In addition, regarding inorganic members used for ophthalmic lenses and lenses of imaging devices, studies for realizing an inorganic member with lower wettability to water have been conventionally carried out.

[0003] By the way, as a method for controlling the wettability on the surface of a certain solid, for example, a method of varying the surface energy of the surface by forming a film or the like on the surface of the solid or forming irregularities on the surface of the solid is generally performed. Here, when irregularities are formed on the surface of a solid, the tendency of the wettability of the surface to water greatly differs depending on whether the nature of the solid is hydrophilic or hydrophobic. That is, in the case of a hydrophilic solid, by forming irregularities on the surface of the solid, the hydrophilicity is further improved, and the wettability of the surface to water gradually increases (i.e., it becomes easier to wet). On the other hand, in the case of a hydrophobic solid, by forming irregularities on the surface of the solid, the hydrophobicity is further improved, and the wettability of the surface to water gradually decreases (i.e., it becomes more difficult to wet), which has been proven by Wenzel's model. Therefore, if the surface of the inorganic member is hydrophilic and irregularities are formed on the surface, the hydrophilicity will be further improved, and the wettability of the surface to water will gradually increase (it will become easier to wet). For this reason, as a technique to realize an inorganic material surface with lower wettability (difficulty in wetting) with water, for example, a technique for forming a coating (film formation) made of an organofluorine compound or the like on the surface of an inorganic material is disclosed in Patent Document 1. However, the coatings formed (deposited) on the surface of such inorganic materials are extremely thin, and are easily worn away or peeled off by friction such as rubbing, making it difficult to maintain low wettability to water over a long period of time.

[0004] Therefore, instead of forming a coating (film deposition) as described above, a technique for creating a surface of an inorganic material that is less wettable (less wettable) to water by forming minute irregularities is disclosed in Patent Document 2. For example, this technique involves forming nanopillar structures with a high aspect ratio on the surface of an inorganic material. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 6-330363 [Patent Document 2] International Publication No. 2020 / 045668 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] However, even with the nanopillar structure having a high aspect ratio as described in Patent Document 2, the nanopillar structure may be damaged by friction such as rubbing, making it difficult to maintain low wettability with water. Furthermore, forming such complex and minute nanopillar structures requires multiple steps, making the manufacturing process complex and increasing production costs.

[0007] This invention has been made in view of the current problems, and provides an inorganic material that can have minute irregularities formed on its surface by a simple method, and by controlling the shape of these irregularities, can achieve excellent durability and low wettability to water without forming an organofluorine-based coating (film formation), as well as a method for manufacturing the inorganic material. [Means for solving the problem]

[0008] The problems that this invention aims to solve are as described above, and the means for solving these problems will now be explained.

[0009] In other words, the inorganic member according to the present invention is characterized in that it has minute irregularities on at least a part of its surface, and the skewness Ssk at said minute irregularities is -0.1 or less. In inorganic materials with such a structure, the microscopic irregularities formed on the surface have high rigidity and excellent durability, and can be easily formed, for example, by shot blasting. Furthermore, compared to a smooth surface without minute irregularities, it is possible to increase the contact angle of water droplets adhering to the surface of an inorganic material, thereby achieving lower wettability to water.

[0010] Furthermore, the inorganic component according to the present invention is preferably made of glass. By having such a configuration, it is possible to obtain an inorganic material that has high light transmittance and excellent processability.

[0011] Furthermore, in the inorganic member according to the present invention, it is preferable that the average length RSm of the roughness curve elements in the minute irregularities is 30 nm or more and 750 nm or less. This configuration simplifies the formation of minute irregularities on the surface of the inorganic material and prevents a decrease in the contact angle of water droplets adhering to the surface of the inorganic material.

[0012] Furthermore, in the inorganic member according to the present invention, it is preferable that the ratio (Rc / RSm) of the average height Rc of the roughness curve elements to the average length RSm of the roughness curve elements in the minute irregularities is 0.02 or more and 1.00 or less. This configuration improves the durability of the minute irregularities formed on the surface of the inorganic material, and prevents a decrease in the contact angle of water droplets adhering to the surface over a long period of time.

[0013] Furthermore, in the inorganic member according to the present invention, it is preferable that the arithmetic mean height Sa of the minute irregularities is 1 nm or more and 100 nm or less. By having such a configuration, it is possible to more reliably increase the contact angle of water droplets adhering to the surface of the inorganic material compared to a smooth plane without minute irregularities, thereby achieving lower wettability to water. Furthermore, it is possible to minimize light scattering caused by the uneven shape of the micro-irregularities, thereby more reliably ensuring the transparency of the surface of the inorganic material on which these micro-irregularities are formed.

[0014] Furthermore, in the inorganic member according to the present invention, it is preferable that the maximum height Sz of the minute irregularities is 30 nm or more and 500 nm or less. By having such a configuration, it is possible to more reliably increase the contact angle of water droplets adhering to the surface of the inorganic material compared to a smooth plane without minute irregularities, thereby achieving lower wettability to water. Furthermore, it is possible to more reliably minimize light scattering caused by the uneven shape of the micro-irregularities, thereby more reliably ensuring the transparency of the surface of the inorganic material on which these micro-irregularities are formed.

[0015] Furthermore, the inorganic member according to the present invention may be characterized in that at least a portion of its surface has minute irregularities, and the ratio of the average height Rc of the roughness curve elements in the minute irregularities to the average length RSm of the roughness curve elements (Rc / RSm) is 0.03 or more and 1.00 or less. In the case of an inorganic member having such a configuration, at least the durability of the minute irregularities formed on the surface of the inorganic member can be improved, and the decrease in the contact angle of the water droplets adhering to the surface can be prevented over a long period of time.

[0016] And the manufacturing method of the inorganic member according to the present invention is a method for manufacturing any of the above-described inorganic members, and is characterized in that minute irregularities are formed by performing wet blasting treatment on at least a part of the surface of the inorganic member. According to the manufacturing method having such a configuration, an inorganic member having minute irregularities formed on the surface can be obtained, and the contact angle of the water droplets adhering to the surface is increased as compared with a smooth plane having no such minute irregularities, and an inorganic member having a lower wettability to water is realized.

Effects of the Invention

[0017] As effects of the present invention, the following effects are exhibited. That is, according to the inorganic member and the manufacturing method of the inorganic member according to the present invention, minute irregularities can be formed on the surface of the inorganic member by a simple method, and by controlling the shape of the irregularities, excellent durability can be achieved without forming (film-forming) an organic fluorine-based film, and low wettability to water can be realized.

Brief Description of the Drawings

[0018] [Figure 1] It is a side cross-sectional view showing the configuration of an inorganic member according to an embodiment of the present invention. [Figure 2] It is a diagram for explaining various parameters representing surface roughness in minute irregularities formed on an inorganic member, where (a) is a diagram for explaining skewness Ssk, (b) is a diagram for explaining the average height Rc of roughness curve elements and the average length RSm of roughness curve elements, and (c) is a diagram for explaining the arithmetic mean height Sa and the maximum height Sz. [Figure 3] It is an enlarged side cross-sectional view schematically showing a state where water droplets adhere to minute irregularities formed on an inorganic member. [Modes for carrying out the invention]

[0019] Next, embodiments of the inorganic material and the method for manufacturing the inorganic material according to the present invention will be described with reference to Figures 1 to 3.

[0020] [Configuration of Inorganic Component 1] First, the configuration of the inorganic member 1 in this embodiment will be explained using Figures 1 to 3. The inorganic component 1 is, for example, a rectangular flat plate-shaped component, and is mainly composed of glass, ceramics, metal, etc.

[0021] When the inorganic component 1 is made of glass, examples of glass materials include soda-lime glass, alkali-free glass, aluminosilicate glass, borosilicate glass, quartz glass, and chalcogenide glass. Furthermore, when the inorganic component 1 is made of ceramics, examples of materials for the ceramic component include sapphire and spinel. Furthermore, if the inorganic component 1 is made of metal, examples of materials for the metal component include germanium and silicon.

[0022] Furthermore, the inorganic component 1 is preferably made of glass because it has high light transmittance and excellent processability. Furthermore, the shape of the inorganic member 1 is not limited to this embodiment, and may be any of the following: a flat plate with a circular or polygonal outline, a flat plate that is curved overall, or a spherical or aspherical lens shape. Furthermore, it is preferable that the inorganic member 1 has light transmittance in at least a portion of the wavelength range between the ultraviolet and infrared regions.

[0023] As shown in Figure 1, in the inorganic member 1, minute irregularities 2 are formed on one surface (in this embodiment, the main surface 1a). The minute irregularities 2 are primarily applied to the surface of the inorganic member 1 with the aim of reducing its wettability with water (i.e., making it less wettable). Therefore, the minute irregularities 2 only need to be formed in at least a portion of the main surface 1a where low wettability to water is required, depending on the final usage state of the inorganic member 1, and in this embodiment, they are formed over the entire surface of the main surface 1a.

[0024] The minute irregularities 2 formed on the main surface 1a of the inorganic member 1 consist of shapes determined by various surface parameters as shown below (skewness Ssk, average length RSm of roughness curve elements, ratio of average height Rc of roughness curve elements to average length RSm of roughness curve elements (Rc / RSm), arithmetic mean height Sa, and maximum height Sz).

[0025] Specifically, the minute surface irregularities 2 are set such that the skewness Ssk is -0.1 or less (Ssk ≤ -0.1), the average length RSm of the roughness curve elements is between 30 nm and 750 nm (30 nm ≤ RSm ≤ 750 nm), the ratio of the average height Rc of the roughness curve elements to the average length RSm of the roughness curve elements (Rc / RSm) is between 0.02 and 1.00 (0.02 ≤ (Rc / RSm) ≤ 1.00), the arithmetic mean height Sa is between 1 nm and 100 nm (1 nm ≤ Sa ≤ 100 nm), and the maximum height Sz is between 30 nm and 500 nm (30 nm ≤ Sz ≤ 500 nm).

[0026] The configuration of the minute irregularities 2 is not limited to this embodiment, and as long as the skewness Ssk is within the range of the above setting, other parameters, namely the average length RSm of the roughness curve elements, the ratio of the average height Rc of the roughness curve elements to the average length RSm of the roughness curve elements (Rc / RSm), the arithmetic mean height Sa, and / or the maximum height Sz, may be outside the range of the above setting. Alternatively, with respect to the configuration of the minute irregularities 2, at least the ratio of the average height Rc of the roughness curve elements to the average length RSm of the roughness curve elements (Rc / RSm) is within the range of the above setting, so other parameters, namely the skewness Ssk, the average length RSm of the roughness curve elements, the arithmetic mean height Sa, and / or the maximum height Sz, may be outside the range of the above setting.

[0027] "Skewness Ssk" is a parameter defined by ISO 25178, which represents the symmetry between the peaks and valleys of the uneven shape constituting the main surface 1a of the inorganic member 1, when centered on the average plane (the dashed line in Figure 2(a)). Specifically, as shown in Figure 2(a), when the skewness Ssk is a negative value (Ssk < 0), the histogram of the height distribution of the minute irregularities 2 that make up the surface takes on a shape that is biased upwards relative to the average plane. On the other hand, when the skewness Ssk is a positive value (Ssk > 0), the histogram of the height distribution of the minute irregularities 2 that make up the surface will have a shape that is biased downwards relative to the mean plane. Furthermore, when the skewness Ssk is 0 (or more precisely, a value close to 0) (Ssk=0), the histogram of the height distribution of the minute irregularities 2 that make up the surface takes on a shape that is symmetrically distributed with respect to the mean plane.

[0028] In this embodiment, as described above, the skewness Ssk in the minute irregularities 2 is -0.1 or less, and the main surface 1a of the inorganic member 1 is provided with minute irregularities 2 (see Figure 3) in which multiple valleys Ya Ya Ya are provided between multiple peaks Xa Xa, with the valleys being closer together than the peaks Xa.

[0029] As a result, as shown in Figure 3, when water droplets W adhere to the main surface 1a of the inorganic member 1, air layers Q·Q··· are easily formed within the multiple recesses 21·21··· blocked by the water droplets W, increasing the contact angle θ of the water droplets W, and thus lowering the wettability of the main surface 1a of the inorganic member 1 to water (i.e., making it more difficult to wet).

[0030] In this embodiment, the upper limit of the skewness Ssk is set to -0.1, but -0.2 is preferred, and -0.3 is more preferred. Furthermore, while there are no particular limitations on the lower limit of the skewness Ssk, it is subject to technical factors such as the reduction in strength of the inorganic material 1 and the method of forming minute irregularities 2 (for example, the wet blasting treatment described later). In practice, it will be -10 or higher, but -5 or higher is preferred, -3 or higher is more preferred, -2 or higher is even more preferred, and -1.5 or higher is particularly preferred.

[0031] The "average length RSm of the roughness curve elements" is a parameter defined by JIS B0601:2013, and represents the average pitch between adjacent recesses and protrusions in the uneven shape that constitutes the roughness curve 2a. Specifically, as shown in Figure 2(b), the roughness curve 2a is formed by a series of consecutive contour curves 2a1·2a1···, and each contour curve 2a1 is composed of adjacent peaks Xb and valleys Yb. The peaks Xb and valleys Yb described above each have multiple minute irregularities. However, if these minute irregularities fall below a predetermined threshold (for example, 10% of the highest height (or highest depth) of the peak Xb (or valley Yb)), they are considered noise and recognized as part of the peak Xb or valley Yb. The average length RSm of the roughness curve element is then expressed by the average length of these multiple contour curves 2a1·2a1··· (RSm = (RSm1 + RSm2 + ···RSmn) / n).

[0032] In this embodiment, as described above, the average length RSm of the roughness curve elements in the minute irregularities 2 is between 30 nm and 750 nm. Here, a smaller average length RSm of the roughness curve element is preferable because it results in denser micro-irregularities 2 formed on the main surface 1a of the inorganic material 1. However, this is limited by technical factors related to the method of forming the micro-irregularities 2 (for example, the wet blasting process described later), and in practice, it is limited to the lower limit of 30 nm. In this embodiment, the lower limit of the average length RSm of the roughness curve elements is set to 30 nm, but 60 nm is preferred, 90 nm is more preferred, 120 nm is even more preferred, and 150 nm is particularly preferred.

[0033] Furthermore, in this embodiment, the upper limit of the average length RSm of the roughness curve elements is set to 750 nm, but 700 nm is preferred, 600 nm is more preferred, 500 nm is even more preferred, and 400 nm is particularly preferred. Furthermore, if the average length RSm of the roughness curve elements exceeds the upper limit of 750 nm, liquid is more likely to penetrate into the recesses 21 of the micro-irregularities 2 (see Figure 3). As a result, in Figure 3, when water droplets W adhere to the main surface 1a of the inorganic member 1, it becomes difficult to maintain the air layers Q Q Q within the multiple recesses 21 21 ... that are blocked by the water droplets W. This reduces the contact angle θ of the water droplets W, and the wettability of the main surface 1a of the inorganic member 1 to water increases (i.e., it becomes easier to wet), which is undesirable.

[0034] The ratio of the average height Rc of the roughness curve elements to the average length RSm of the roughness curve elements (Rc / RSm) represents the virtual aspect ratio in the micro-undulation 2. Furthermore, the "average height Rc of the roughness curve elements" mentioned above is a parameter defined by JIS B0601:2013, and represents the average distance between the lower end of adjacent concave parts and the upper end of convex parts in the uneven shape that constitutes the roughness curve 2a. Specifically, as shown in Figure 2(b), the average height Rc of an element is expressed by the average distance between the lower end P1 of the valley Yb and the upper end P2 of the peak Xb in each of the contour curves 2a1 described above (Rc = (Rc1 + Rc2 + ...Rcn) / n).

[0035] In this embodiment, as described above, the ratio (Rc / RSm) of the average height Rc of the roughness curve elements in the minute irregularities 2 to the average length RSm of the roughness curve elements is 0.02 or more and 1.00 or less. Here, a larger value for the above ratio (Rc / RSm) is preferable. In this embodiment, the lower limit is set at 0.02, but 0.03 is preferable, 0.05 is more preferable, 0.07 is even preferable, and 0.09 is particularly preferable. If the above ratio (Rc / RSm) value is less than the lower limit of 0.02, liquid is more likely to penetrate into the recesses 21 of the minute irregularities 2 (see Figure 3). As a result, similar to the case described above where the average length RSm of the elements exceeds the upper limit of 750 nm, the wettability of the main surface 1a of the inorganic member 1 to water increases (i.e., it becomes easier to wet), which is undesirable.

[0036] On the other hand, if the value of the above ratio (Rc / RSm) exceeds the upper limit of 1.00, light scattering due to the uneven shape of the minute irregularities 2 becomes more likely, which not only impairs the transparency of the main surface 1a of the inorganic material 1 but also makes it more susceptible to damage due to wear and other factors, thus reducing the durability of the minute irregularities 2, which is undesirable. In this embodiment, the upper limit of the ratio (Rc / RSm) is set to 1.00, but 0.50 is preferred, 0.30 is more preferred, 0.20 is even more preferred, and 0.18 is particularly preferred.

[0037] The "arithmetic mean height Sa" is a parameter defined by ISO 25178, which extends the elements of the roughness curve 2a, which is a line, to a surface. Specifically, as shown in Figure 2(c), the arithmetic mean height Sa represents the average of the absolute distances between each point of the uneven shape constituting the minute unevenness 2 (for example, the height Xh to the peak of the peak Xc and the depth Yh to the peak of the valley Yc) with respect to the average surface Z on the main surface 1a of the inorganic member 1 (Sa = ((Xh1 + Xh2 + ... + Xhn) + (-1)(Yh1 + Yh2 + ... + Yhn)) / 2n).

[0038] In Figure 3, if the value of the arithmetic mean height Sa becomes too small, when water droplets W adhere to the main surface 1a of the inorganic member 1, it becomes difficult to maintain the air layers Q Q Q in the multiple recesses 21 21 ... that are blocked by the water droplets W. This reduces the contact angle θ of the water droplets W, and the wettability of the main surface 1a of the inorganic member 1 to water increases (i.e., it becomes easier to wet), which is undesirable. On the other hand, if the value of the arithmetic mean height Sa becomes too large, light scattering due to the uneven shape of the minute irregularities 2 becomes more likely, impairing the transparency of the main surface 1a of the inorganic material 1, which is undesirable.

[0039] For these reasons, in this embodiment, as described above, the arithmetic mean height Sa of the minute irregularities 2 is between 1 nm and 100 nm. The lower limit of the arithmetic mean height Sa is set at 1 nm, but 2 nm is preferred, 3 nm is more preferred, 4 nm is even more preferred, and 5 nm is particularly preferred. Furthermore, while the upper limit of the arithmetic mean height Sa is set at 100 nm, 80 nm is preferred, 60 nm is more preferred, 40 nm is even more preferred, and 30 nm is particularly preferred.

[0040] "Maximum height Sz" is a parameter defined by ISO 25178, similar to the arithmetic mean height Sa mentioned above, and is a parameter that extends the elements of the roughness curve 2a, which is a line, to a surface. Specifically, as shown in Figure 2(c), the maximum height Sz represents the sum of the absolute values ​​of the maximum distances between points of the uneven shape constituting the minute unevenness 2 (for example, the height Xh(MAX) to the peak of the largest peak Xc(MAX), and the depth Yh(MAX) to the peak of the valley Yc(MAX)) with respect to the average surface Z on the main surface 1a of the inorganic member 1 (Sz = (Xh(MAX) + (-1)(Yh(MAX))).

[0041] In Figure 3, if the value of the maximum height Sz becomes too small, when a water droplet W adheres to the main surface 1a of the inorganic member 1, it becomes difficult to maintain the air layer Q Q Q within the multiple recesses 21 21 ... that are blocked by the water droplet W. This reduces the contact angle θ of the water droplet W, and the wettability of the main surface 1a of the inorganic member 1 to water increases (i.e., it becomes easier to wet), which is undesirable. On the other hand, if the value of the maximum height Sz becomes too large, light scattering due to the uneven shape of the minute irregularities 2 becomes more likely, which not only impairs the transparency of the main surface 1a of the inorganic material 1 but also makes it more susceptible to damage due to wear and reduces the durability of the minute irregularities 2, which is undesirable.

[0042] For these reasons, in this embodiment, as described above, the maximum height Sz of the minute irregularities 2 is between 30 nm and 500 nm. The lower limit of the maximum height Sz is set at 30 nm, but 40 nm is preferred, 50 nm is more preferred, 80 nm is even more preferred, and 110 nm is particularly preferred. Furthermore, while the upper limit of the maximum height Sz is set at 500 nm, 450 nm is preferred, 400 nm is more preferred, 350 nm is even more preferred, and 330 nm is particularly preferred.

[0043] By the way, the contact angle θ of the main surface 1a of the inorganic member 1 on which minute irregularities 2 are formed is preferably 60° or more, more preferably 70° or more, even more preferably 75° or more, and particularly preferably 80° or more. Furthermore, there is no particular upper limit to the contact angle θ; for example, it can be 180°.

[0044] On the main surface 1a of the inorganic member 1, which has minute irregularities 2 having the shape described above, it is possible to form (deposit) a water-repellent film that lowers the surface energy of the main surface 1a, with the aim of further reducing its wettability to water (i.e., making it difficult to wet).

[0045] The above water-repellent film can be formed (film-forming) by bonding a silane compound containing alkyl groups or fluoroalkyl groups to the surface (main surface 1a) of the inorganic member 1. Furthermore, when forming a water-repellent film on the main surface 1a of the inorganic member 1, minute irregularities (minute irregularities with a shape similar to the minute irregularities 2 described above) are formed on the main surface 1a in advance so that the surface irregularities of the water-repellent film after formation will have a shape set by the various parameters described above (skewness Ssk, average length RSm of roughness curve elements, ratio of average height Rc of roughness curve elements to average length RSm of roughness curve elements (Rc / RSm), arithmetic mean height Sa, and maximum height Sz).

[0046] The inorganic component 1 may be provided with an anti-reflective coating, a reflective coating, a half-mirror coating, or the like. Anti-reflective coatings include, for example, low-refractive-index films with a refractive index lower than that of the glass substrate, and dielectric multilayer films in which low-refractive-index layers and high-refractive-index layers are alternately stacked. Reflective films and half-mirror films often utilize dielectric multilayer films in which layers with relatively low refractive index and layers with relatively high refractive index are alternately stacked. Anti-reflective coatings, reflective coatings, and half-mirror coatings can be formed, for example, by sputtering or CVD methods.

[0047] [Method for manufacturing inorganic material 1] Next, the manufacturing method of the inorganic component 1 will be explained using Figure 1. The minute irregularities 2 formed on at least a portion of the surface (main surface 1a) of the inorganic member 1 are formed by applying a wet blasting treatment or the like to the main surface 1a.

[0048] Wet blasting is a process in which abrasive particles, composed of solid particles such as alumina, are uniformly mixed with a liquid such as water to form a slurry, which is then sprayed at high speed from a spray nozzle onto a workpiece made of inorganic material 1 using compressed air, thereby creating fine irregularities on the workpiece.

[0049] In wet blasting, when a high-speed ejected slurry collides with a workpiece, the abrasive particles in the slurry scrape, strike, and rub against the surface of the workpiece, creating fine irregularities on the workpiece surface. In this case, the abrasive particles sprayed onto the workpiece, as well as the fragments of the workpiece removed by the abrasive particles, are washed away by the liquid sprayed onto the workpiece, resulting in fewer particles remaining on the workpiece.

[0050] The surface roughness (skewness Ssk, average length RSm of roughness curve elements, ratio of average height Rc of roughness curve elements to average length RSm (Rc / RSm), arithmetic mean height Sa, and maximum height Sz) of the minute irregularities 2 formed on the main surface 1a of the workpiece (inorganic material 1) by wet blasting can be adjusted mainly by the particle size distribution of the abrasive grains contained in the slurry, the spray pressure when spraying the slurry onto the workpiece, and the processing speed during nozzle movement.

[0051] In wet blasting, when slurry is sprayed onto the workpiece, the liquid carries the abrasive particles to the workpiece. Compared to dry blasting, this allows for the use of finer abrasive particles, and the impact when the abrasive particles collide with the workpiece is reduced, enabling precise machining. In this way, by applying a wet blast treatment to the workpiece (inorganic member 1), it is easy to form appropriately sized irregular shapes on the main surface 1a of the inorganic member 1, and without impairing the transparency of the inorganic member 1, the contact angle θ of water droplets W adhering to the main surface 1a is increased, making it possible to further reduce the wettability of the main surface 1a of the inorganic member 1 to water (i.e., make it more difficult to wet).

[0052] In dry blasting, heat is generated in the workpiece due to friction when the sprayed abrasive particles collide with the workpiece. However, in wet blasting, the liquid constantly cools the surface of the workpiece during the process, so the workpiece is not heated by the blasting.

[0053] Furthermore, it is possible to form minute irregularities 2 on the main surface 1a of the inorganic material 1 by dry blasting, but in dry blasting, the impact when the abrasive grains collide with the main surface 1a of the inorganic material 1 is too great, which tends to increase the surface roughness of the main surface 1a on which the minute irregularities 2 are formed, and the transparency of the inorganic material 1 is easily impaired.

[0054] By the way, in addition to wet blasting, chemical etching, sol-gel method, nanoimprint method, etc. can be used to form minute irregularities 2 on the main surface 1a of the inorganic material 1. Here, chemical etching is a process in which the main surface 1a of the inorganic material 1 is chemically etched with hydrogen fluoride (HF) gas, acids such as hydrofluoric acid, hydrochloric acid, or sulfuric acid, or alkaline aqueous solutions such as sodium hydroxide. [Examples]

[0055] Next, the inorganic material having minute irregularities formed according to the present invention will be described in detail using examples and comparative examples. The configuration of the inorganic member according to the present invention is not limited to the embodiments shown below.

[0056] [Sample preparation] First, samples 1 to 14 and 20 to 22 were prepared as examples of the inorganic material according to the present invention, and samples 15 to 19 were prepared as comparative examples to these examples. For samples 1, 2, 7-15, and 18-20, "Glass 1" was selected as alkali-free glass (manufactured by Nippon Electric Glass Co., Ltd., product name: OA-10G) consisting of rectangular plates with a thickness of 0.5 mm. Furthermore, for samples 3, 4, 16, 21, and 22, aluminosilicate glass (manufactured by Nippon Electric Glass Co., Ltd., product name: T2X-1) consisting of a rectangular plate with a thickness of 0.5 mm was used as "glass 2". Furthermore, for samples 5, 6, and 17, we decided to use borosilicate glass (manufactured by Nippon Electric Glass Co., Ltd., product name: BDA) consisting of rectangular plates with a thickness of 0.5 mm as "glass 3".

[0057] For the inorganic materials of samples 1-14 and 20-22, which serve as examples, microscopic irregularities were formed on one of the main surfaces by wet blasting. Specifically, a slurry was prepared by uniformly stirring abrasive particles made of alumina (Al2O3) and water as an abrasive. A wet blast was then performed on the entire surface of one main surface of each inorganic component, scanning it while moving a nozzle at a predetermined processing speed, and spraying the prepared slurry from the nozzle using air at a predetermined processing pressure.

[0058] Here, polygonal abrasive grains of #8000 were used for the inorganic materials of samples 1-12 and 20, polygonal abrasive grains of #4000 were used for the inorganic materials of samples 13, 14 and 21, and polygonal abrasive grains of #2000 were used for the inorganic material of sample 22. Furthermore, the processing pressure of the air in the nozzle was set to 0.22 MPa for inorganic materials of samples 1 to 6, 0.15 MPa for inorganic materials of samples 7 and 8, 0.13 MPa for inorganic materials of samples 9 to 12, 0.10 MPa for inorganic material of sample 13, 0.20 MPa for inorganic material of sample 14, 0.30 MPa for inorganic material of sample 20, and 0.25 MPa for inorganic materials of samples 21 and 22. Furthermore, the processing speed for nozzle movement was set to 10 mm / s for inorganic materials of samples 1, 3, 5, 7, 10, and 20; 5 mm / s for inorganic materials of samples 2, 4, 6, 8, 11, 13, 14, 21, and 22; 20 mm / s for inorganic material of sample 9; and 1 mm / s for inorganic material of sample 12.

[0059] For the inorganic materials of comparative examples 15-17, one of the main surfaces was left untreated. In other words, the inorganic materials of samples 15-17 were left untreated without the use of abrasives.

[0060] For the inorganic material of sample 18, which serves as a comparative example, microscopic irregularities were formed on one of the main surfaces by wet etching with hydrofluoric acid. Specifically, microscopic irregularities were formed by immersing one main surface of an inorganic material in a hydrofluoric acid solution (30°C) adjusted to a concentration of 5 wt% for 2000 seconds.

[0061] For the inorganic material of sample 19, which served as a comparative example, a silica coating was applied by the sol-gel method to create minute irregularities on one of the main surfaces. Specifically, a silica-containing liquid was sprayed onto the surface, and the applied silica-containing liquid was dried to form microscopic irregularities consisting of a silica coating film on the main surface.

[0062] Table 1 describes the material properties, the method for forming micro-irregularities, and the conditions for the abrasive (abrasive grains), processing air pressure, and processing speed used when applying wet blasting treatment to the inorganic components of samples 1 to 19 shown above.

[0063] [Table 1]

[0064] [Measurement of contact angle θ] Next, to confirm the water wettability of the inorganic materials of samples 1 to 22, the contact angle θ was measured on each main surface where minute irregularities were formed. The contact angle θ was measured using the static drop method (so-called θ / 2 approximation method) as specified in JIS R3257:1999. Approximately 2 μL of pure water was dropped onto each inorganic component, which was placed horizontally with its main surface, where minute irregularities were formed, facing upwards. The water droplet was then photographed from the side using a digital scope (Keyence Corporation, product name VHX-500F) to measure the contact angle θ. Specifically, as shown in Figure 3, based on the image data of the captured water droplet W, the (θ / 2) between the virtual line L1 connecting the endpoint W1 and vertex W2 of the water droplet W and the virtual horizontal line L2 on the main surface 1a of the inorganic member 1 was calculated, and the contact angle θ was derived based on the following formula 1.

[0065] θ=2tan-1(h / r)...(Formula 1) h: Height of vertex W2 r: radius of the base of the water droplet W

[0066] [Surface roughness measurement] Next, the surface roughness of the main surfaces of the inorganic materials of samples 1 to 22 was measured. Surface roughness was measured on the main surface of samples 1-14 and 20-22 after wet blasting, on one of the main surfaces of samples 15-17, on the main surface of sample 18 after wet etching with hydrofluoric acid, and on the main surface of sample 19 with a silica coating.

[0067] The parameters of surface roughness measured were the skewness Ssk, the average length RSm of the roughness curve elements, the average height Rc of the roughness curve elements, the arithmetic mean height Sa, and the maximum height Sz of the formed micro-irregularities. These measurements were performed using an atomic force microscope (AFM). For sample 19, measurements were performed using a laser microscope. Furthermore, based on the above measurements, the ratio (Rc / RSm) of the average height Rc of the roughness curve elements to the average length RSm of the roughness curve elements was derived.

[0068] The atomic force microscope (AFM) used for the measurements was a Bruker product (product name (SPM unit): Dimension Icon, product name (Controller unit): Nano Scope V), and the measurements were performed in accordance with JIS B0601:2013 and ISO 25178. Furthermore, the measurement conditions were as follows: tapping mode was used, and the scan rate was set to 1 Hz and the number of acquired data points to 512 x 512 for a measurement area of ​​5 x 5 μm.

[0069] Furthermore, the laser microscope used for the measurements was a Keyence Corporation laser microscope (product name: VK-X250), and the measurements were performed in accordance with JIS B0601:2013 and ISO 25178. Furthermore, the measurement conditions were set so that the cutoff value of the high-pass filter λc was 50 μm, and the cutoff value of the low-pass filter λs was 0.5 μm, and the measurement was performed so that the number of acquired data points was 2048 × 1536 pixels for a measurement area of ​​approximately 287 × 215 μm.

[0070] [Measurement results of contact angle θ and surface roughness] The results of the contact angle θ and surface roughness measurements performed on samples 1 to 22 are described below. The contact angle θ was measured as shown in Table 2 below, and the surface roughness was measured as shown in Tables 2 and 3 below.

[0071] [Table 2]

[0072] [Table 3]

[0073] As shown in Table 2, in the inorganic materials of Examples 1-14 and 20-22, the contact angle θ of the main surface on which minute irregularities were formed was high, ranging from 81° to 96°, indicating good results in that the wettability to water was low (i.e., difficult to wet). On the other hand, in the inorganic materials of comparative examples, samples 15 to 19, the contact angle θ of one of the main surfaces (in sample 18, the main surface subjected to wet etching with hydrofluoric acid; in sample 19, the main surface with a silica coating film) was 14° to 50°, which is considerably lower than in the above examples, indicating poor results that show high wettability (i.e., easy wetting) to water. Based on the above results, we will discuss the surface roughness measurement results for the inorganic materials of samples 1 to 22.

[0074] The skewness Ssk was within the range of -1.9 to -0.4 for the inorganic materials of the examples, samples 1-14 and 20-22. On the other hand, in the inorganic components of samples 15-17 (untreated comparative examples), sample 18 (wet etching with hydrofluoric acid), and sample 19 (with a silica coating film), the skewness Ssk was in the range of 0-1.0, or 0 or a positive value.

[0075] Furthermore, the average length RSm of the roughness curve elements is within the range of 158.4 nm to 582.5 nm for the inorganic materials of examples 1 to 14 and 20 to 22. The value of this average length RSm tends to increase as the air processing pressure increases or as the nozzle processing speed decreases during wet blasting. On the other hand, in the inorganic components of sample 18, which was subjected to wet etching with hydrofluoric acid, and sample 19, which had a silica coating film, the average length RSm of the elements in the roughness curve was 1057.5 nm and 11080 nm, respectively, which were considerably larger than those in the above examples.

[0076] Furthermore, the ratio of the average height Rc of the roughness curve elements to the average length RSm of the roughness curve elements (Rc / RSm) is in the range of 0.05 to 0.16 for the inorganic materials of examples 1 to 14 and 20 to 22. This ratio (Rc / RSm) tends to increase as the air processing pressure increases or as the nozzle processing speed decreases during wet blasting. On the other hand, in the inorganic material of sample 18 that underwent wet etching with hydrofluoric acid, the ratio of the average height Rc of the roughness curve elements to the average length RSm of the roughness curve elements (Rc / RSm) was 0.01, which was a smaller value compared to the above example. Furthermore, in the inorganic component of sample 19, which was provided with a silica coating film, the ratio of the average height Rc of the roughness curve elements to the average length RSm of the roughness curve elements (Rc / RSm) was 0.02, which was a smaller value compared to the above example.

[0077] As shown in Table 3, the arithmetic mean height Sa for the inorganic materials of Examples 1-14 and 20-22 is in the range of 3.9 nm to 42.3 nm, and the value of the arithmetic mean height Sa tends to increase as the air processing pressure increases or as the nozzle processing speed decreases during wet blasting. On the other hand, in the inorganic materials of the untreated comparative examples, samples 15-17, and sample 18, which underwent wet etching with hydrofluoric acid, the arithmetic mean height Sa was in the range of 0.2 nm to 3.6 nm, which was smaller than that of the above examples. Furthermore, in the inorganic component of sample 19, which was provided with a silica coating film, the arithmetic mean height Sa was 120 nm, which was considerably larger than that of the above-mentioned examples.

[0078] Furthermore, the maximum height Sz for the inorganic materials of examples 1-14 and 20-22 is within the range of 117-371 nm, and the value of this maximum height Sz tends to increase as the air treatment pressure during wet blasting increases. On the other hand, in the inorganic materials of the untreated comparative examples, samples 15-17, and sample 18, which underwent wet etching with hydrofluoric acid, the maximum height Sz was in the range of 2 nm to 42 nm, which was considerably smaller than that of the above examples. Furthermore, in the inorganic component of sample 19, which was provided with a silica coating film, the maximum height Sz was 2080 nm, which was considerably larger than that of the above-mentioned examples.

[0079] [effect] As described above, the inorganic member 1 in this embodiment is characterized in that it has minute irregularities 2 on at least a part of its main surface 1a (surface), and the skewness Ssk at the minute irregularities 2 is -0.1 or less.

[0080] Thus, in this embodiment, the skewness Ssk of the formed minute irregularities 2 is a negative value, and as shown in Figure 2(a), the minute irregularities 2 have an uneven shape in which valleys Ya·Ya··· have narrower spacing between each peak Xa1 compared to the peak Xa. Therefore, it has high rigidity and excellent durability, and can be easily formed by impacting the main surface (surface) 1a of the inorganic member 1 with granular material, for example, by shot blasting. Furthermore, as shown in Figure 3, on the main surface (surface) 1a of the inorganic member 1 on which minute irregularities 2 are formed, an air layer Q is maintained in the recesses 21 of the minute irregularities 2. Therefore, compared to a smooth plane without minute irregularities 2, it is possible to increase the contact angle θ of water droplets W adhering to the main surface (surface) 1a, thereby achieving lower wettability to water.

[0081] Furthermore, it is preferable that the inorganic member 1 in this embodiment is made of glass.

[0082] By having such a configuration, an inorganic component 1 with high light transmittance and excellent processability can be obtained.

[0083] Furthermore, in this embodiment, it is preferable that the inorganic member 1 has an average length RSm of the roughness curve elements in the minute irregularities 2 that is between 30 nm and 750 nm.

[0084] In this way, by setting the range of the average length RSm of the roughness curve elements as described above, the formation of minute irregularities 2 can be made simpler, and it is possible to prevent water droplets W adhering to the main surface (surface) 1a of the inorganic material 1 from entering the recesses 21 of the minute irregularities 2 and reducing the contact angle θ.

[0085] Furthermore, in this embodiment, it is preferable that the ratio (Rc / RSm) of the average height Rc of the roughness curve elements to the average length RSm of the roughness curve elements (Rc / RSm) in the minute irregularities 2 of the inorganic member 1 is 0.02 or more and 1.00 or less.

[0086] Thus, by setting the range of the ratio (Rc / RSm) of the average height Rc and average length RSm of the roughness curve elements, which is a virtual aspect ratio in the micro-irregularity 2, as described above, the height of the protrusions in the irregular shape of the micro-irregularity 2 can be suppressed, making it possible to suppress damage due to wear and other factors, improving the durability of the micro-irregularity 2, and preventing a decrease in the contact angle of water droplets W adhering to the main surface 1a of the inorganic material 1 over a long period of time.

[0087] Furthermore, in this embodiment, it is preferable that the inorganic member 1 has an arithmetic mean height Sa of 1 nm or more and 100 nm or less in the minute irregularities 2.

[0088] In this way, by setting the range of the arithmetic mean height Sa as described above, it becomes possible to more effectively maintain the air layer Q in the recesses 21 of the minute irregularities 2. Compared to a smooth plane without minute irregularities 2, it is possible to more reliably increase the contact angle θ of the water droplets W adhering to the main surface (surface) 1a of the inorganic member 1, thereby achieving lower wettability to water. Furthermore, it is possible to minimize light scattering due to the uneven shape of the minute irregularities 2, and to more reliably ensure the transparency of the main surface 1a of the inorganic material 1 on which the minute irregularities 2 are formed.

[0089] Furthermore, in this embodiment, it is preferable that the inorganic member 1 has a maximum height Sz of 30 nm or more and 500 nm or less in the minute irregularities 2.

[0090] In this way, by setting the maximum height Sz range as described above, it becomes possible to more effectively maintain the air layer Q in the recesses 21 of the minute irregularities 2. Compared to a smooth plane without minute irregularities 2, this makes it possible to more reliably increase the contact angle θ of water droplets W adhering to the main surface (surface) 1a of the inorganic member 1, thereby achieving lower wettability to water. Furthermore, it is possible to further reliably minimize light scattering due to the uneven shape of the minute irregularities 2, and to more reliably ensure the transparency of the main surface 1a of the inorganic material 1 on which the minute irregularities 2 are formed.

[0091] Furthermore, the inorganic member 1 in this embodiment may have minute irregularities 2 on at least a part of its main surface 1a (surface), and without having the features described above, it may be characterized by having at least a ratio (Rc / RSm) of the average height Rc of the roughness curve elements and the average length RSm of the roughness curve elements in the minute irregularities 2 being 0.02 or more and 1.00 or less.

[0092] With an inorganic member 1 having such a configuration, at the very least, the durability of the minute irregularities 2 formed on the main surface 1a (surface) of the inorganic member 1 is improved, and the decrease in the contact angle of water droplets W adhering to the main surface 1a can be prevented over a long period of time.

[0093] Furthermore, the method for manufacturing the inorganic member 1 in this embodiment is a method for manufacturing any of the inorganic member 1 described above, characterized in that minute irregularities 2 are formed by performing a wet blast treatment on at least a part of the main surface (surface) 1a of the inorganic member 1.

[0094] According to a manufacturing method with such a configuration, an inorganic member 1 having fine irregularities 2 formed on its main surface 1a can be obtained, in which the contact angle θ of water droplets W adhering to the main surface 1a of the inorganic member 1 is increased compared to a smooth plane without the fine irregularities 2, thereby achieving lower wettability to water. [Industrial applicability]

[0095] The inorganic material and method for manufacturing the inorganic material according to the present invention can be used as an inorganic material with lower wettability to water in fields such as window panels for automobiles, railway vehicles, ships, and aircraft, as well as eye lenses and lenses for imaging devices. [Explanation of symbols]

[0096] 1. Inorganic component 1a Main surface (front surface) 2 Microscopic irregularities 2a Roughness curve RSm Roughness Curve Average Length Average height of Rc roughness curve element Sa arithmetic mean height SSK Skewness Sz Maximum Height

Claims

1. The surface has microscopic irregularities on at least a portion of it, The skewness Ssk in the minute irregularities is -0.1 or less. In the aforementioned minute irregularities, The ratio of the average height Rc of the roughness curve elements to the average length RSm of the roughness curve elements (Rc / RSm) is between 0.02 and 1.

00. An inorganic component characterized by the following features.

2. The inorganic component is made of glass. The inorganic member according to claim 1, characterized in that

3. In the aforementioned minute irregularities, The average length RSm of the roughness curve elements is between 30 nm and 750 nm. The inorganic member according to claim 1 or claim 2, characterized in that

4. In the aforementioned minute irregularities, The arithmetic mean height Sa is between 1 nm and 100 nm. An inorganic member according to any one of claims 1 to 3, characterized in that...

5. In the aforementioned minute irregularities, The maximum height Sz is between 30 nm and 500 nm. An inorganic member according to any one of claims 1 to 4, characterized in that...

6. The surface has microscopic irregularities on at least a portion of it, The ratio (Rc / RSm) of the average height Rc of the roughness curve elements to the average length RSm of the roughness curve elements in the said minute irregularities is 0.03 or more and 1.00 or less. An inorganic component characterized by the following features.

7. A method for manufacturing an inorganic component according to any one of claims 1 to 6, The minute irregularities are formed by performing a wet blasting treatment on at least a portion of the surface of the inorganic member. A method for manufacturing an inorganic component, characterized by the above.

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