JP2019008028A - Hydrophobic antireflection structure and manufacturing method of hydrophobic antireflection structure - Google Patents

Abstract

To provide a hydrophobic antireflection structure having excellent durability against abrasion while maintaining high low reflectivity and high water repellency.SOLUTION: A hydrophobic antireflection structure 1 comprises: a base portion 2; multiple truncated cone portions 3 formed on the surface of the base portion 2, which has a flat portion 31 at the front side; and a water-repellent layer 4 formed covering the multiple truncated cone portions 3. In plan view, the occupancy rate of the flat portions 31 of multiple truncated cone portions 3 to the surface of the base portion 2 is 6 to 40%; and the average width of the flat portions 31 of the multiple truncated cone portions 3 is 12 to 100 nm.SELECTED DRAWING: Figure 2

Description

  The present invention generally relates to a water-repellent antireflection structure and a method for producing a water-repellent antireflection structure, and more specifically, a base, a plurality of frustum-shaped protrusions formed on the surface of the base, and a plurality of The present invention relates to a water-repellent antireflective structure including a water-repellent layer provided so as to cover the frustum-shaped convex portion, and a method for producing the water-repellent antireflective structure.

  Conventionally, in order to reduce surface reflection of light and prevent adhesion of water, oil, dirt, etc. to the surface, surfaces of optical parts such as lenses and mirrors, surfaces of automobile windshields and rear windows, mobile phones, etc. A technique of providing a water-repellent antireflection structure on the surface of a screen of a display device such as a liquid crystal display is known.

  For example, Patent Literature 1 discloses a water-repellent antireflection coating including a base, a plurality of conical convex portions formed on the surface of the base, and a water repellent layer provided so as to cover the plurality of conical convex portions. A structure is disclosed. The base portion and the plurality of conical convex portions in Patent Document 1 are made of a transparent material having a refractive index of “1” or less, which is the refractive index of air. Further, the diameter of each bottom surface of the plurality of conical convex portions is equal to or smaller than the wavelength of light, and the plurality of conical convex portions are arranged at a pitch equal to or smaller than the wavelength of light. As a result, on the surface of the water-repellent antireflection structure, the refractive index of the material of the cone-shaped projection and the refractive index of the air between the cone-shaped projections are averaged, and the appearance of the water-repellent antireflection structure is apparent. The refractive index decreases, and the reflectance decreases.

  Moreover, the interface between air and water is made on the surface of the water-repellent antireflection structure by including air between the plurality of conical convex portions. The water repellency far exceeds the water repellency of the material of the cone-shaped projection itself by the effect of increasing the surface area by forming multiple cone-shaped projections and the effect of trapping air between adjacent cone-shaped projections. Can be realized. Such an effect is known as a lotus leaf effect.

  Furthermore, by providing a water-repellent water-repellent layer on the surface of the plurality of conical projections, the surface energy of the water-repellent antireflection structure is further reduced (the surface tension of the water-repellent antireflection structure is further increased). Therefore, the water repellency of the water-repellent antireflection structure is further improved.

  Thus, in the conventional water-repellent antireflection structure, a plurality of fine cone-shaped projections are formed on the surface of the base, and a water-repellent layer is provided so as to cover the plurality of cone-shaped projections. Thus, the water-repellent antireflection structure can be made low in reflection and high in water repellency. However, in such a conventional water-repellent antireflection structure, the tip portions of the plurality of conical convex portions are thin. In this case, when an arbitrary object comes into contact with the conventional water-repellent antireflection structure, the load per unit area applied to the tip of each of the plurality of cone-shaped convex portions increases, so that The aqueous antireflection structure has low durability against abrasion.

  Therefore, for example, when any object such as cloth, scrubbing brush, sponge, etc. comes in contact with the surface of the water-repellent antireflection structure, in order to wipe off water, oil, dirt, etc. adhering to the surface of the water-repellent antireflection structure, The tip portions of the plurality of cone-shaped convex portions are damaged, bent, or the like. As a result, it is difficult to maintain the low reflectivity and high water repellency of the water-repellent antireflection structure when there is wear on the water-repellent antireflection structure.

JP 2009-42714 A

  The present invention has been made in view of the above-described conventional problems, and an object thereof is to provide a water-repellent antireflection structure having excellent durability against abrasion while maintaining high low reflectivity and high water repellency. There is.

Such an object is achieved by the present inventions (1) to (9) below.
(1) a base;
A plurality of frustum-shaped convex portions formed on the surface of the base portion and having a flat portion on the tip side;
A water repellent layer provided to cover the plurality of frustum-shaped convex portions,
In a plan view, the occupation ratio of the flat portion of the plurality of frustum-shaped convex portions with respect to the surface of the base portion is 6 to 40%,
The water repellent antireflection structure, wherein an average value of the flat portions of the plurality of frustum-shaped convex portions is 12 to 100 nm.

  (2) The water-repellent antireflection structure according to (1), wherein an average value of angles formed by the flat portions and the side surfaces of the plurality of frustum-shaped convex portions is 90 to 120 °.

  (3) The water-repellent antireflection structure is configured such that the minimum value of the width of the flat portion of the plurality of frustum-shaped convex portions is 5 nm or more. Water repellent antireflection structure.

  (4) Any of the above (1) to (3), wherein the water-repellent antireflection structure is configured such that a maximum value of the width of the flat portion of the plurality of frustum-shaped convex portions is 150 nm or less. The water-repellent antireflection structure according to claim 1.

  (5) In the water-repellent antireflection structure, in any vertical cross-sectional view of the water-repellent antireflection structure, the total value of the widths of the flat portions of the plurality of frustum-shaped convex portions is The water-repellent antireflection structure according to any one of the above (1) to (4), which is configured to be 6 to 40% of the width.

  (6) The water repellency according to any one of (1) to (5), wherein the plurality of frustum-shaped convex portions having different widths of the flat portion are randomly arranged on the surface of the base portion. Anti-reflection structure.

  (7) The water-repellent antireflection structure according to (6), wherein the standard deviation of the width variation of the flat portion of the plurality of frustum-shaped convex portions is 5 to 30.

  (8) The repellency according to any one of (1) to (7), wherein the base and the plurality of frustum-shaped convex portions are made of an inorganic transparent material having a refractive index of 1.3 to 2.5. Aqueous antireflection structure.

(9) forming a base composed of a transparent material on the surface of the substrate;
Forming a pattern mask having a predetermined pitch on the surface of the base by sputtering;
Forming a plurality of frustum-shaped convex portions having a flat portion on the tip side on the surface of the base by etching the base on which the pattern mask is formed on the surface; and ,
Forming a water repellent layer to cover the plurality of frustum-shaped convex portions on the surface of the base, and
In a plan view, the occupation ratio of the flat portion of the plurality of frustum-shaped convex portions with respect to the surface of the base portion is 6 to 40%,
The average value of the width | variety of the said flat part of these frustum-shaped convex parts is 12-100 nm, The manufacturing method of the water-repellent antireflection structure characterized by the above-mentioned.

  According to the present invention, the water-repellent antireflection structure includes a base, a plurality of frustum-shaped convex portions formed on the surface of the base, and a water-repellent layer provided so as to cover the plurality of frustum-shaped convex portions. You can get a body. In such a water-repellent antireflection structure, the occupation ratio of the flat portions of the plurality of frustum-shaped convex portions with respect to the surface of the base portion in a plan view is 6 to 40%, and the plurality of frustum-shaped convex portions The average value of the width of the flat portion is 12 to 100 nm.

  With such a configuration, when an arbitrary object such as a cloth, a scrubbing brush, or a sponge comes into contact with the water-repellent antireflection structure of the present invention, each tip side of the plurality of frustum-shaped convex portions with respect to the arbitrary object The contact area of the (flat portion) increases, and the load per unit area for each of the plurality of frustum-shaped convex portions decreases. Therefore, each of the plurality of frustum-shaped convex portions is not easily damaged or bent. Therefore, according to the present invention, it is possible to provide a water-repellent antireflective structure having excellent durability against wear while maintaining high low reflectivity and high water repellency.

It is a perspective view which shows the external appearance of the water-repellent anti-reflective structure which concerns on this invention. It is a longitudinal cross-sectional view of the arbitrary positions of the water-repellent antireflection structure shown in FIG. It is a flowchart which shows the manufacturing method of the water-repellent antireflection structure which concerns on this invention. It is a figure for demonstrating each process of the manufacturing method of the water-repellent antireflection structure shown in FIG. It is an electron micrograph which shows one surface of the base in the manufacturing method of the water-repellent antireflection structure shown in FIG. It is a graph which shows the change of the reflectance of the light of wavelength 380-780 nm in each Example, a comparative example, and a reference example. It is a graph which shows the change of the contact angle of the water droplet by abrasion in each Example. It is a graph which shows the change of the contact angle of the water droplet by abrasion in a comparative example and a reference example.

  Hereinafter, the water-repellent antireflection structure and the method for producing the water-repellent antireflection structure of the present invention will be described based on preferred embodiments shown in the accompanying drawings. Each drawing referred to below is a schematic diagram prepared for explaining the present invention. For example, dimensions (length, width, thickness, etc.) of each component shown in the drawing are as follows. It does not necessarily reflect actual dimensions.

[Water-repellent antireflection structure]
First, the water-repellent antireflection structure of the present invention will be described with reference to FIGS. FIG. 1 is a perspective view showing an appearance of a water-repellent antireflection structure according to the present invention. FIG. 2 is a longitudinal sectional view of an arbitrary position of the water-repellent antireflection structure shown in FIG.

  The water-repellent antireflection structure 1 of the present invention shown in FIGS. 1 and 2 is formed on a base 2 and one surface of the base 2, and a plurality of frustum-shaped convex portions (having a flat portion 31 on the tip side) ( (Frustum-shaped pillar) 3 and a water-repellent layer 4 provided to cover the plurality of frustum-shaped projections 3.

  The water-repellent antireflection structure 1 has a high low reflection by a fine concavo-convex structure composed of a plurality of frustum-shaped convex portions 3 and a water-repellent layer 4 formed so as to cover the plurality of frustum-shaped convex portions 3. And high water repellency.

  Further, a flat portion 31 is formed on the tip side of the plurality of frustum-shaped convex portions 3. Compared with the conventional water-repellent antireflective structure in which a plurality of cone-shaped convex portions having a sharp point on the tip side are formed on the base by such a configuration, the cloth is made against the water-repellent antireflective structure 1. When an arbitrary object such as a scrubbing brush or sponge comes into contact, the contact area of each tip side (flat portion 31) of the plurality of frustum-shaped convex portions 3 with respect to the arbitrary object increases, and the plurality of frustum-shaped convex portions The load per unit area for each of the three is reduced. Therefore, in the water-repellent antireflection structure 1 of the present invention, each of the plurality of frustum-shaped convex portions 3 is not easily damaged or bent. Therefore, the durability of the water-repellent antireflection structure 1 against wear can be improved while maintaining the high low-reflectivity and high water repellency of the water-repellent antireflection structure 1.

  As shown in FIG. 2, the base 2 and the plurality of frustum-shaped convex portions 3 are integrally formed. The base 2 and the plurality of frustum-shaped convex portions 3 are made of the same type of inorganic transparent material. The inorganic transparent material constituting the base 2 and the plurality of frustum-shaped convex portions 3 has a refractive index of 1.3 to 2.5 when the refractive index of air is 1 and the light transmittance of air is 100%. An inorganic transparent material having a visible light transmittance of 70% or more is used.

Examples of such inorganic transparent materials include silicon oxide (SiO ₂ ), aluminum oxide (Al ₂ O ₃ ), titanium oxide (TiO ₂ ), zirconium oxide (ZrO ₂ ), and silicon nitride (Si ₃ N ₄ ). Among these, from the viewpoint of heat resistance and cost, it is preferable to configure the base 2 and the plurality of frustum-shaped convex portions 3 using silicon oxide or silicon nitride.

  The base 2 is a plate-like member made of the above-described inorganic transparent material. The thickness T of the base 2 is not particularly limited, but is, for example, about 100 to 500 nm. If the thickness T of the base 2 is less than the lower limit, the strength of the water-repellent antireflection structure 1 may be insufficient, and if the thickness T of the base 2 exceeds the upper limit, the water-repellent antireflection structure. The thickness and weight of the entire body 1 may increase more than necessary.

  A plurality of frustum-shaped convex portions 3 are integrally formed on one surface side of the base portion 2, and the other surface side of the base portion 2 is substantially flat. Each of the plurality of frustum-shaped convex portions 3 has a base end portion formed integrally with one surface of the base portion 2 and has a frustum shape having a flat portion 31 on the tip end side. The frustum shape here means that when viewed in a longitudinal sectional view as shown in FIG. 2, the width gradually decreases from the base end side toward the tip end side, and the flat portion 31 is formed on the tip end side. It means the shape that is formed. Therefore, the width Wb of the base end part of each frustum-shaped convex part 3 is larger than the width Wt of the flat part 31 on the front end side.

  In addition, the frustum shape of each frustum-shaped convex part 3 is not limited to mathematically exact frustum shape, and may be a substantially frustum shape including an error variation at the time of actual manufacturing. . For example, the frustum-shaped convex part of the frustum-shaped convex part 3 may have the shape which rounded the ridge part of the frustum.

  Further, the flat portion 31 formed on the tip side of the frustum-shaped convex portion 3 is not limited to a strictly flat surface, and may be curved with a large radius of curvature in a range that can be regarded as substantially flat, You may have a micro unevenness | corrugation in the range which does not affect the effect of this invention.

  In addition, the frustum-shaped shape of the frustum-shaped convex part 3 is a truncated cone shape or a truncated pyramid shape such as a triangular frustum shape and a hexagonal frustum shape. The width of each height of the frustum-shaped convex portion 3 is such that the horizontal sectional shape of each height of the frustum-shaped convex portion 3 is circular or substantially circular (that is, the frustum-shaped convex portion 3 has a truncated cone shape). The diameter of the circular or substantially circular shape is the width of each height of the frustum-shaped convex portion 3. When the horizontal cross-sectional shape of each height of the frustum-shaped convex part 3 is a polygon or a substantially polygon (that is, when the frustum-shaped convex part 3 has a truncated pyramid shape), the polygon Alternatively, the diameter of the circle circumscribing the substantially polygonal shape is the width of each height of the frustum-shaped convex portion 3. Moreover, when the horizontal cross-sectional shape of each height of the frustum-shaped convex part 3 is indefinite, the largest delivery diameter in the cross-sectional shape is the width of each height of the frustum-shaped convex part 3.

  Therefore, in this specification, the phrase “width Wt of the flat portion 31 of the frustum-shaped convex portion 3” means that the flat portion 31 of the frustum-shaped convex portion 3 is viewed in plan (that is, the frustum-shaped convex portion 3). When the flat portion 31 has a circular or substantially circular shape (when the planar shape of the flat portion 31 of the portion 3 is viewed), the diameter of the circular or substantially circular shape is the flat portion 31 of the frustum-shaped convex portion 3. The width Wt. When the flat portion 31 has a polygonal shape, the diameter of the circle circumscribing the polygon or the substantially polygon is the width Wt of the flat portion 31 of the frustum-shaped convex portion 3. Further, when the flat portion 31 has an indefinite shape, the maximum passing diameter of the indefinite shape is the width Wt of the flat portion 31 of the frustum-shaped convex portion 3. The same applies to “the width Wb of the base end portion of the frustum-shaped convex portion 3”.

  In the water-repellent antireflection structure 1 of the present invention, each of the plurality of frustum-shaped convex portions 3 does not have a completely uniform frustum-shaped shape. That is, in the shape of the frustum-shaped convex portion 3, the width Wb (area) of the base end portion and the width Wt (tip) of the flat portion 31 on the front end side are excluded except for the height H from the base end portion to the flat portion 31 on the front end side. Area) and the angle θ formed by the flat portion 31 and the side surface of the frustum-shaped convex portion 3 have variations. In the water-repellent antireflection structure 1 of the present invention, a plurality of frustum-shaped convex portions 3 having such variations in shape are randomly arranged on one surface of the base portion 2.

  The height H of each frustum-shaped convex part 3 is substantially constant. In addition, the average value of the width Wb of the base end portions of the plurality of frustum-shaped convex portions 3 is preferably not more than the wavelength of visible light, specifically 50 to 380 nm, and more preferably 100 to 250 nm. preferable. If the average value of the width Wb of the base end portions of the plurality of frustum-shaped convex portions 3 is less than the lower limit value, the strength of the frustum-shaped convex portions 3 may not be sufficiently obtained, and the plurality of frustum-shaped convex portions 3 When the average value of the width Wb of the base end portion of the convex portion 3 exceeds the above upper limit value, light diffusion and diffraction by the plurality of frustum-shaped convex portions 3 occur, and the light of the water-repellent antireflection structure 1 The reflectivity may increase. Moreover, it is preferable that it is 12-100 nm, and, as for the average value of the width Wt of the flat part 31 of the some frustum-shaped convex part 3, it is more preferable that it is 15-25 nm.

  When the width Wt (area) of the flat part 31 of each frustum-shaped convex part 3 is small, the front end side of each frustum-shaped convex part 3 will be sharper. In this case, the low reflectivity and water repellency of the water repellent antireflection structure 1 are improved. In this case, when an arbitrary object such as cloth, scrubbing brush, sponge, or the like is in contact with the water-repellent antireflection structure 1, the contact area of the flat portion 31 of each frustum-shaped convex portion 3 with respect to the arbitrary object is small. Thus, the load per unit area for each of the plurality of frustum-shaped convex portions 3 is increased. As a result, the durability of the water repellent antireflection structure 1 against wear is reduced.

  On the other hand, when the width Wt (area) of the flat part 31 of each frustum-shaped convex part 3 is large, the front end side of each frustum-shaped convex part 3 becomes flatter. In this case, the low reflectivity and water repellency of the water repellent antireflection structure 1 are lowered. Further, in this case, when an arbitrary object such as cloth, scrubbing brush, sponge, or the like comes into contact with the water-repellent antireflection structure 1, the contact area of the flat portion 31 of each frustum-shaped convex portion 3 with respect to the arbitrary object is large. Thus, the load per unit area for each of the plurality of frustum-shaped convex portions 3 is reduced. Therefore, the durability against wear of the water repellent antireflection structure 1 is improved.

  Thus, the width Wt of the flat portion 31 of each frustum-shaped convex portion 3 is a parameter that greatly affects the low reflectivity and water repellency of the water repellent antireflection structure 1 and the durability against wear. For example, when the average value of the widths Wt of the flat portions 31 of the plurality of frustum-shaped convex portions 3 is less than the lower limit value, the water-repellent antireflection structure 1 has excellent low reflectivity and water repellency. In addition, the durability of the water repellent antireflection structure 1 against wear becomes insufficient. On the other hand, when the average value of the widths Wt of the flat portions 31 of the plurality of frustum-shaped convex portions 3 exceeds the upper limit, the water-repellent antireflection structure 1 has excellent durability against wear, The low reflectivity and water repellency of the antireflection structure 1 will be insufficient.

  For this reason, in the present invention, the average value of the widths Wt of the flat portions 31 of the plurality of frustum-shaped convex portions 3 is within the above range. Thereby, durability with respect to abrasion of the water repellent antireflection structure 1 can be improved while maintaining the high low reflectivity and high water repellency of the water repellent antireflective structure 1.

  In addition, the maximum value of the width Wt of the flat portions 31 of the plurality of frustum-shaped convex portions 3 is preferably 150 nm or less, and more preferably 50 nm or less. When the width Wt of the flat part 31 exceeds the upper limit, the frustum-shaped convex part 3 having such a flat part 31 contributes less to the low reflectivity and water repellency of the water-repellent antireflection structure 1. On the other hand, the minimum value of the width Wt of the flat portions 31 of the plurality of frustum-shaped convex portions 3 is preferably 5 nm or more, and more preferably 10 nm or more. When the width Wt of the flat part 31 is less than the above minimum value, the frustum-shaped convex part 3 having such a flat part 31 contributes less to improving the durability of the water-repellent antireflection structure 1 with respect to wear.

  In plan view, the occupation ratio of the flat portions 31 of the plurality of frustum-shaped convex portions 3 with respect to one surface of the base 2 (in other words, the plurality of frustums with respect to the area of one surface of the base 2 in plan view) The ratio of the total area of the flat portions 31 of the convex portions 3) is preferably 6 to 40%, and more preferably 8 to 12%. When the occupation ratio of the flat portions 31 of the plurality of frustum-shaped convex portions 3 is less than the lower limit value, an effect of improving the durability against wear of the water-repellent antireflection structure 1 cannot be obtained. On the other hand, when the occupancy ratio of the flat portions 31 of the plurality of frustum-shaped convex portions 3 exceeds the upper limit value, the low reflectivity and water repellency of the water-repellent antireflection structure 1 are significantly lowered.

  Moreover, although the average value of the separation distance between the centers of the adjacent frustum-shaped convex part 3 is not specifically limited, For example, it is preferable that it is 50-350 nm, and it is more preferable that it is 100-250 nm. In addition, the standard deviation of the variation in the width Wt of the flat portion 31 of the plurality of frustum-shaped convex portions 3 is not particularly limited, but is preferably 5 to 30, and more preferably 6 to 12, for example. More preferably, it is 7-10.

  As described above, the width Wt (area) of the flat portion 31 of each frustum-shaped convex portion 3 has a great influence on the low reflectivity and water repellency of the water-repellent antireflection structure 1, and the durability against wear. . Further, in the water-repellent antireflection structure 1 of the present invention, the frustum-shaped convex portions 3 having different widths Wt (or areas) of the flat portion 31 on the front end side are randomly arranged on one surface of the base portion 2. Yes. With such a structure, in the water-repellent antireflection structure 1 of the present invention, the low reflectivity and water repellency are compared with the portion having low reflectivity and water repellency and relatively high durability against wear. A portion having a relatively high wear resistance and a relatively low durability against wear is randomly mixed. As a result, as the overall performance of the water-repellent antireflection structure 1, high low reflectivity and high water repellency and high durability against wear can be realized.

  Further, as described above, in the water-repellent antireflection structure 1 of the present invention, the frustum-shaped convex portions 3 having different widths Wt (or areas) of the flat portions 31 on the front end side on one surface of the base portion 2. Are randomly arranged. Therefore, in any (any) longitudinal sectional view of the water-repellent antireflection structure 1, the total value of the widths Wt of the flat portions 31 of the plurality of frustum-shaped convex portions 3 is the width of one surface of the base portion 2. It is 6 to 40%, more specifically 8 to 12%.

  For example, in a specific longitudinal sectional view of the water-repellent antireflection structure 1, when the total value of the widths Wt of the flat portions 31 of the plurality of frustum-shaped convex portions 3 is out of the above range, the specific In the direction of the cutting line for obtaining a longitudinal sectional view (straight line region), low reflectivity, water repellency, and durability against wear are reduced.

  In the water-repellent antireflection structure 1 of the present invention, the frustum-shaped convex portions 3 having different widths Wt (or areas) of the flat portion 31 are randomly arranged on one surface of the base portion 2, and In any (any) longitudinal sectional view of the water-repellent antireflection structure 1, the total value of the widths Wt of the flat portions 31 of the plurality of frustum-shaped convex portions 3 is within the above range. Therefore, the water-repellent antireflection structure 1 of the present invention has high low reflectivity, high water repellency, and high durability against wear in any direction (straight region).

  Moreover, although the average value of angle (theta) which each flat part 31 and the side surface of several frustum-shaped convex part 3 comprise is not specifically limited, For example, it is preferable that it is 90-120 degrees, and it is 100-110 degrees. More preferably. When the average value of the angles θ formed by the flat portions 31 and the side surfaces of the plurality of frustum-shaped convex portions 3 is out of the above range, the water-repellent antireflection structure 1 has a low reflection effect and a high water repellency effect. May be reduced. Moreover, it is preferable that the standard deviation of the dispersion | variation in angle (theta) which each flat part 31 and the side surface of the some frustum-shaped convex part 3 comprise is 4-6.

  The water-repellent layer 4 is provided so as to cover the plurality of frustum-shaped convex portions 3 and reduces the surface energy of the water-repellent antireflection structure 1 (increases the surface tension of the water-repellent antireflection structure 1). The water-repellent antireflection structure 1 has a function of improving the water repellency.

  The water repellent layer 4 is made of a water repellent material having a contact angle with respect to water droplets of 90 ° or more when applied to a smooth surface. Examples of such water-repellent materials include silicon-containing compounds (silane coupling agents). In particular, it is preferable to use a fluorine-containing silane compound as the water-repellent material for the water-repellent layer 4, and commercially available silanes. Compounds and fluorine-containing silane compounds can be widely used.

  Although the thickness of the water repellent layer 4 is not specifically limited, For example, it is preferable that it is 3-50 nm, and it is more preferable that it is 5-10 nm. When the thickness of the water repellent layer 4 is less than the above lower limit, sufficient film thickness uniformity cannot be maintained, and the water repellency improving effect of the water repellent antireflection structure 1 cannot be sufficiently obtained. There is. On the other hand, when the thickness of the water-repellent layer 4 exceeds the above upper limit, the ratio of the water-repellent layer 4 to the frustum-shaped convex portion 3 increases, and the gap between the plurality of frustum-shaped convex portions 3 is repelled. It may be filled with the water layer 4, and the low reflection effect of the water-repellent antireflection structure 1 may be hindered.

  As described in detail so far, in the water-repellent antireflection structure 1 of the present invention, the plurality of frustum-shaped convex portions 3 are formed on one surface of the base 2, and the antireflection structure 1 In plan view, the occupation ratio of the flat portions 31 of the plurality of frustum-shaped convex portions 3 with respect to one surface of the base portion 2 is 6 to 40%, and the flat portions 31 of the plurality of frustum-shaped convex portions 3 The average value of the width is 12 to 100 nm.

  With such a configuration, when an arbitrary object comes into contact with the water-repellent antireflection structure 1 of the present invention, the tip side (flat portion 31) of each of the plurality of frustum-shaped convex portions 3 with respect to the arbitrary object. The contact area increases, and the load per unit area for each of the plurality of frustum-shaped convex portions 3 decreases. Therefore, each of the plurality of frustum-shaped convex portions 3 is not easily damaged or bent. Therefore, according to the present invention, it is possible to provide the water-repellent antireflection structure 1 having excellent durability against wear while maintaining high low reflectivity and high water repellency.

[Application example]
Examples of the application of the water-repellent antireflection structure 1 of the present invention include an antireflection component and a water-repellent component including a substrate and the water-repellent antireflection structure 1 provided on at least one surface side of the substrate. Can do.

  For example, it requires an antireflection function such as the surface of optical parts such as lenses and mirrors, the surface of automobile windshields and rear windows, the surface of screens of display devices such as mobile phones and liquid crystal displays, and water, The water-repellent antireflective structure 1 of the present invention can be provided on the surface where there is a risk of adhesion of oil, dirt and the like.

  Also, a water repellent antireflection film can be obtained by using a base film instead of the substrate and forming the water repellent antireflection structure 1 of the present invention on the base film.

[Production method]
Next, with reference to FIGS. 3-5, the manufacturing method of the water-repellent anti-reflective structure of this invention is explained in full detail. FIG. 3 is a flowchart showing a method for manufacturing a water-repellent antireflection structure according to the present invention. FIG. 4 is a diagram for explaining each step of the method for producing the water-repellent antireflection structure shown in FIG. FIG. 5 is an electron micrograph showing one surface of the base in the method for producing the water-repellent antireflection structure shown in FIG.

  As shown in FIG. 3, the manufacturing method S <b> 100 of the water-repellent antireflection structure 1 of the present invention includes a step S <b> 110 for forming a base 2 on a plate-like substrate 10, and a plurality of methods on one surface of the base 2. A step S120 for forming the frustum-shaped convex portion 3 and a step S130 for forming the water repellent layer 4 so as to cover the plurality of frustum-shaped convex portions 3 are included.

  In step S110, first, as shown in FIG. 4A, the substrate 10 is prepared. The substrate 10 is made of a heat resistant material such as a glass material, a metal material, or a heat resistant plastic material, and functions as a base for forming the water repellent antireflection structure 1.

  In the illustrated embodiment, the upper surface of the substrate 10 is flat or substantially flat, but the present invention is not limited to this. For example, the upper surface of the substrate 10 may be a curved surface. Hereinafter, for the sake of explanation, the upper surface of the substrate 10 will be described as being substantially flat. However, an aspect in which the upper surface of the substrate 10 is a curved surface is also within the scope of the present invention.

  Next, as shown in FIG. 4B, the base portion 2 made of the above-described inorganic transparent material is formed on one surface of the substrate 10. The method for forming the base 2 on one surface of the substrate 10 is not particularly limited. For example, a physical vapor deposition method such as sputtering, vapor deposition, or ion plating (Physical Vapor Deposition), plasma CVD, Examples thereof include chemical vapor deposition such as ALD (Atomic Layer Deposition).

  The thickness of the base 2 formed on the substrate 10 in the step S110 is set such that the thickness T of the base 2 of the water-repellent antireflection structure 1 after completion described above and the height H of the plurality of frustum-shaped convex portions 3 are as follows. In order to ensure, it is about 160 nm or more.

  When the base portion 2 is formed on the substrate 10, next, as shown in FIG. 4C, a predetermined pitch is formed on the surface of the base portion 2 that is not in contact with the substrate 10 by a heat sputtering method. An island-shaped pattern mask 20 is formed.

  FIG. 5A shows an electron micrograph of the pattern mask 20 formed on the surface of the base 2 in step S110. As shown in FIG. 4C and FIG. 5A, the pattern mask 20 is composed of a plurality of discontinuous islands 21 having various sizes and randomly arranged. The surface of the base 2 is partially exposed from the gap between the island-like objects 21.

As a constituent material of the island-shaped object 21 of the pattern mask 20, an etching rate slower than that of the constituent material of the base 2 (the above-mentioned inorganic transparent material) in etching processing for forming a plurality of truncated cone-shaped convex portions 3 described later. A material having is used. Examples of such materials include aluminum (Al), aluminum oxide (Al ₂ O ₃ ), tin (Sn), indium (In), zinc (Zn), silver (Ag), gold (Au), and mixtures thereof. Is mentioned.

  In step S110, the average value of the pitch of the pattern mask 20 formed on the surface of the substrate 10, that is, the average value of the separation distance between adjacent islands 21 is preferably 30 to 150 nm, and more preferably. 70 to 120 nm. In addition, the thickness of the pattern mask 20 formed on the surface of the substrate 10 (the average value of the thickness of the islands 21) is preferably 3 to 50 nm, and more preferably 10 to 25 nm.

  In the sputtering method in step S110, an inert gas such as argon gas or nitrogen gas ionized by applying a voltage is introduced into the chamber in which the substrate 10 having the base 2 formed on the surface is disposed, and the chamber The pattern mask 20 is placed on the surface of the base 2 by colliding with the sputtering target that is disposed inside and colliding with the sputtering target made of the constituent material of the island-like material 21 and stacking the knocked-out target atoms on the surface of the base 2. Formed on the surface.

Ultimate vacuum in the chamber at the time of performing sputtering is preferably ^{1 × 10 -5 ~1 × 10 -3} Pa, to be ^{1 × 10 -5 ~1 × 10 -4} Pa and more preferable. Moreover, it is preferable that the pressure of the inert gas introduce | transduced in a chamber is 0.1-3.0 Pa, and it is more preferable that it is 0.1-0.5 Pa. Further, the flow rate of the inert gas is preferably 5 to 100 sccm (standard cubic centimeter per minute), and more preferably 10 to 30 sccm. Moreover, it is preferable that the temperature of the base 2 is 100-400 degreeC, and it is more preferable that it is 250-350 degreeC. Moreover, it is preferable that the processing time of sputtering processing is 0.5 to 10 minutes, and it is more preferable that it is 1 to 5 minutes.

  By executing the sputtering method under such sputtering conditions, the pattern mask 20 having the above average value of thickness and pitch can be formed on the surface of the base 2.

  Returning to FIG. 3, when the pattern mask 20 is formed on the surface of the base 2 in step S110, the manufacturing method S100 proceeds to step S120. In step S120, as shown in FIG. 4D, the base portion 2 on which the pattern mask 20 is formed is etched, and a plurality of frustum-shaped convex portions 3 are formed on the surface of the base portion 2. Is formed.

  FIG. 5B shows an electron micrograph of the plurality of frustum-shaped convex portions 3 formed on the surface of the base portion 2 in step S120. FIG. 5C shows a TEM (transmission electron microscope) photograph of the plurality of frustum-shaped convex portions 3 formed on the surface of the base 2 in step S120. As shown in FIG. 5B and FIG. 5C, the plurality of frustum-shaped convex portions 3 have a flat portion 31 on the distal end side, and further, on one surface of the base portion 2, The frustum-shaped convex portions 3 having different widths Wt (areas) of the flat portion 31 on the front end side are randomly arranged.

  In order to form such a plurality of frustum-shaped convex portions 3, reactive ion etching can be used as an etching process performed on the base portion 2 on which the pattern mask 20 is formed.

  Since the islands 21 of the pattern mask 20 formed on the surface of the base 2 are made of a material having an etching rate lower than that of the constituent material of the base 2, the islands 21 are exposed from between the islands 21 of the pattern mask 20. The exposed portion of the base portion 2 is etched at a faster rate than the portion of the pattern mask 20 where the islands 21 are disposed. Due to this difference in etching rate, the height of the base portion 2 varies, and as a result, a plurality of frustum-shaped convex portions 3 are formed on the base portion 2.

  On the surface of the base 2, the portion of the pattern mask 20 where the islands 21 are arranged becomes the flat part 31 of the frustum-shaped convex part 3, and the base 2 exposed from between the islands 21 of the pattern mask 20. The amount of etching of the exposed portion becomes the height H of the frustum-shaped convex portion 3. Further, since the islands 21 of the pattern mask 20 have different sizes, the flat portions 31 of the frustum-shaped convex portions 3 to be formed have different widths Wt (areas).

  In the etching process in step S120, an etching gas is introduced into the chamber in which the base 2 having the pattern mask 20 formed on the surface is disposed, and the etching gas is turned into plasma by applying a voltage to the etching gas. A high frequency voltage is applied to the electrode on which (base 2) is placed.

  As a result, a potential difference is generated between the surface of the base 2 and the pattern mask 20 and the plasma, and ions in the plasma are accelerated toward the surface of the base 2 and the pattern mask 20 to collide with the surface of the base 2 and the pattern mask 20. To do. At this time, etching is performed on the surface of the base 2 and the pattern mask 20.

Etching gases used in this etching process include argon (Ar), nitrogen (N ₂ ), sulfur hexafluoride (SF ₆ ), carbon tetrafluoride (CF ₄ ), trifluoromethane (CHF ₃ ), helium (He ), it can be used krypton (Kr), neon (Ne), and mixed gas thereof with oxygen _{(O 2).}

Further, in the etching process, the ultimate vacuum in the chamber is preferably ^{1 × 10 -5 ~1 × 10 -3} Pa, more preferably ^{1 × 10 -5 ~1 × 10 -4} Pa . Further, the pressure of the etching gas introduced into the chamber is preferably 1 to 10 Pa, and more preferably 1 to 5 Pa. Further, the flow rate of the etching gas is preferably 10 to 100 sccm, and more preferably 30 to 60 sccm. Moreover, it is preferable that the temperature of the base 2 is 30-100 degreeC, and it is more preferable that it is 30-50 degreeC. Moreover, it is preferable that the processing time of an etching process is 10 to 40 minutes, and it is more preferable that it is 10 to 20 minutes.

  Returning to FIG. 3, when the pattern mask 20 is formed on the surface of the base 2 in step S120, the manufacturing method S100 proceeds to step S130. In step S <b> 130, as shown in FIG. 4E, the water repellent layer 4 is formed so as to cover the plurality of frustum-shaped convex portions 3 on the surface of the base portion 2.

  In step S <b> 130, first, impurities are removed from the plurality of frustum-shaped convex portions 3 on the surface of the base portion 2 by vacuum ultraviolet (Vaccum Ultra Violet) cleaning. Thereafter, a water-repellent layer 4 is formed by applying a water-repellent agent containing a water-repellent material to the surfaces of the plurality of frustum-shaped convex portions 3 and then applying heat treatment. As a method of applying a water repellent containing a water repellent material, a method used in a normal coating operation such as spray coating, bar coater coating, spin coating, dip coating, roll coating coating or the like can be used.

  The heating temperature in this heat treatment is preferably 70 to 120 ° C, and more preferably 80 to 100 ° C. Further, the heating time is preferably 30 to 90 minutes, and more preferably 50 to 70 minutes.

  In addition, the method for forming the water repellent layer 4 in step S130 is not limited to the above-described application and heating method, and may be any method as long as it does not fill the gaps between the plurality of frustum-shaped convex portions 3. The known film forming method can be used.

  Through the steps S110 to S130, the base 2, the plurality of frustum-shaped convex portions 3 formed on the surface of the base 2, and having the flat portion 31 on the front end side, and the plurality of frustum-shaped The water repellent antireflection structure 1 of the present invention including the water repellent layer 4 provided so as to cover the convex portion 3 is formed.

  The water-repellent antireflection structure and the method for producing the water-repellent antireflection structure according to the present invention have been described based on the illustrated embodiment, but the present invention is not limited to this. Each component of the present invention can be replaced with any component that can exhibit the same function, or any component of the present invention can be added to each component of the present invention.

  For example, the number and type of the layers of the water-repellent antireflection structure 1 shown in FIGS. 1 and 2 are merely illustrative examples, and the present invention is not necessarily limited thereto. It is also within the scope of the present invention for any layer to be added or combined without departing from the principles and intent of the present invention.

  For example, the water repellent antireflection structure 1 may further include an ultraviolet absorbing layer for preventing deterioration due to light, an impact absorbing layer for absorbing an impact on the water repellent antireflective structure 1, and the like.

  Further, the number and types of steps of the manufacturing method S100 shown in FIG. 3 are merely illustrative examples, and the present invention is not necessarily limited thereto. It is within the scope of the present invention that any step can be added or combined for any purpose or any step can be deleted without departing from the principle and intention of the present invention.

  Next, the present invention will be described in detail based on examples, comparative examples, and reference examples with reference to FIGS. 6 to 8, but the present invention is not limited thereto. Further, “%” shown in each example, comparative example, and reference example represents “% by weight”.

  FIG. 6 is a graph showing changes in the reflectance of light having a wavelength of 380 to 780 nm in each of the examples, comparative examples, and reference examples. FIG. 7 is a graph showing changes in the contact angle of water droplets due to wear in each example. FIG. 8 is a graph showing changes in the contact angle of water droplets due to wear in the comparative example and the reference example.

Example 1
A glass plate having a width of 2 cm, a length of 2 cm, and a thickness of 0.1 cm was prepared as the substrate 10, and the substrate 10 was placed in a chamber of a commercially available film forming apparatus (“FHS-280” manufactured by Fuji R & D). . Using this film forming apparatus, the base 2 made of silicon oxide (SiO ₂ ) was formed on the surface of the substrate 10. The thickness of the base 2 formed on the surface of the substrate 10 was 400 nm.

  Next, the substrate 10 having the base 2 formed on the surface was placed in a chamber of a commercially available sputtering apparatus (“FHS-280” manufactured by Fuji R & D). In this example, Ar was used as an inert gas used in a sputtering apparatus, and an aluminum target was used as a sputtering target.

First, the inside of the chamber is depressurized until the degree of vacuum in the chamber of the sputtering apparatus reaches 5 × 10 ⁻⁵ Pa, and then 100 W of electric power is supplied to the inert gas, and the inert gas converted into plasma is 0.4 Pa. The pattern mask 20 (multiple islands 21) made of aluminum was formed on the base 2 with the pressure of 30 sccm and an inflow of 30 sccm. At this time, the temperature of the base 2 was 300 ° C., and the processing time of the sputtering process was 2 minutes. The thickness of the pattern mask 20 formed on the surface of the base 2 was 15 nm, and the average pitch of the pattern mask 20 was 100 nm.

Next, the substrate 10 having the base 2 with the pattern mask 20 formed on the surface was placed in the chamber of a commercially available etching processing apparatus (“RIE-200NL” manufactured by Samco Corporation). In this example, a mixed gas of CF ₄ and O ₂ was used as an etching gas used in the etching processing apparatus. The mixing ratio of O ₂ in this mixed gas was 20%.

First, the pressure in the chamber is reduced until the degree of vacuum in the chamber of the etching processing apparatus reaches 5 × 10 ⁻⁵ Pa, and then 100 W of electric power is supplied to the etching gas. An inflow of 50 sccm is introduced into the chamber, and further, a high frequency voltage of 13.56 MHz is applied to the electrode on which the substrate 10 (base 2) is placed, whereby the surface of the base 2 and the pattern mask 20 are etched. And a plurality of frustum-shaped convex portions 3 were formed on the surface of the base portion 2. The temperature of the base 2 at this time was 40 ° C., and the processing time for the etching process was 15 minutes.

  The parameters regarding the width Wt of the flat part 31 of the obtained frustum-shaped convex part 3 were as follows.

Average value of width Wt of flat portion 31: 21.6 nm
Maximum value of the width Wt of the flat portion 31: 38.5 nm
Minimum value of the width Wt of the flat portion 31: 5.8 nm
Standard deviation of variation in width Wt of flat portion 31: 9.3272
In a plan view, the occupation ratio of the flat portions 31 of the plurality of frustum-shaped convex portions 3 with respect to one surface of the base portion 2 is 9.4%.

  Next, the surface of the plurality of frustum-shaped convex portions 3 obtained in this way was subjected to vacuum ultraviolet (VUV) cleaning for 10 minutes to remove impurities from the surface of the frustum-shaped convex portions 3. . Thereafter, a commercially available water repellent (“DS-5210TH” manufactured by Harves Co., Ltd.) was applied to the surfaces of the plurality of frustum-shaped convex portions 3, and heat treatment was performed at 100 ° C. for 60 minutes to form the water repellent layer 4. . The thickness of the obtained water repellent layer 4 was 5 to 10 nm.

(Example 2)
A water-repellent antireflection structure 1 of Example 2 was obtained in the same manner as in Example 1 except that the processing time in the etching process was changed to 13 minutes.

  Parameters relating to the width Wt of the flat portion 31 of the frustum-shaped convex portion 3 in the water-repellent antireflection structure 1 of Example 2 were as follows.

Average value of width Wt of flat portion 31: 23.5 nm
Maximum value of the width Wt of the flat portion 31: 36.5 nm
Minimum value of the width Wt of the flat portion 31: 11.2 nm
Standard deviation of variation in width Wt of flat portion 31: 7.5749
In a plan view, the occupation ratio of the flat portions 31 of the plurality of frustum-shaped convex portions 3 with respect to one surface of the base portion 2 is 10.2%.

  In particular, in the water-repellent antireflection structure 1 of Example 2, the minimum value of the width Wt of the flat portion 31 was 10 nm or more.

(Comparative example)
A comparative water-repellent antireflection structure was obtained in the same manner as in Example 1 except that the processing time in the sputtering process was changed to 3 minutes and the processing time in the etching process was changed to 10.5 minutes. .

  Parameters regarding the width of the flat portion of the frustum-shaped convex portion in the water-repellent antireflection structure of the comparative example were as follows.

Average width of flat part: 10.7nm
Maximum width of flat part: 23.1 nm
Minimum width of flat part: 5.8 nm
Standard deviation of variation in flat portion width: 4.4442
In a plan view, the occupancy ratio of the flat portion of the plurality of frustum-shaped convex portions with respect to one surface of the base portion: 5.0%

(Reference example)
In place of the sputtering method and the etching process in Example 1 described above, a method using a transfer mold (stamper) that has been generally used in the past to create a water-repellent antireflection structure is used on the base. A water-repellent antireflection structure of a reference example was obtained in the same manner as in Example 1 except that a plurality of convex portions were formed.

  First, using a commercially available electron beam drawing apparatus, the surface of the transfer mold (stamper) has the same overall shape (height and width) as the frustum-shaped convex portion 3 of the present invention, but the tip portion is The cone-shaped recesses corresponding to the sharply-pointed cone-shaped projections are formed in a hexagonal close-packed arrangement. Note that the density of the conical concave portions formed on the transfer mold is the same as the density of the frustum-shaped convex portions 3 of the present invention.

  Next, the base formed on the surface of the substrate is melted or softened by heating or the like, the transfer mold is pressed against the melted or softened base, and a plurality of hexagonal close-packed arrays are formed on the surface of the base. The cone-shaped convex part of was formed.

  Next, in the same manner as in Example 1, a water repellent layer was formed so as to cover the plurality of formed cone-shaped convex portions, and a water repellent antireflection structure of a reference example was obtained on a substrate.

  Parameters relating to the width of the tip of the cone-shaped convex portion in the water-repellent antireflection structure of the comparative example thus obtained were as follows.

Average value of tip width: 3.0 nm
Maximum value of tip width: 5.0 nm
Minimum width of tip: 2.0 nm
Standard deviation of variation in tip width: 1.2792
In plan view, the occupation ratio of the tip portions of the plurality of cone-shaped convex portions with respect to one surface of the base portion: 3.0%

[Evaluation method]
Next, a method for measuring the low reflectivity, water repellency, and durability against wear of the water-repellent antireflection structures of each Example, Comparative Example and Reference Example will be described.

1. Low reflectivity The average reflectance of light with a wavelength of 380 to 780 nm of a raw sample in a state where a base (silicon oxide S: thickness 400 nm) is formed on a substrate (glass plate) is measured. Comparison was made with the average reflectance of light having a wavelength of 380 to 780 nm of the water-repellent antireflection structure of the reference example. Thereafter, according to the following criteria, the low reflectivity of the water-repellent antireflection structures of each Example, Comparative Example, and Reference Example was evaluated according to how much the average reflectance of light having a wavelength of 380 to 780 nm decreased.

A: Decrease in average reflectance of light having a wavelength of 380 to 780 nm is greater than 3% O: Decrease in average reflectance of light having a wavelength of 380 to 780 nm is 1.5 to 3%
X: The amount of decrease in average reflectance of light having a wavelength of 380 to 780 nm is smaller than 1.5%.

  FIG. 6 shows the measured reflectance of the raw sample and the light-repellent antireflective structures of Examples, Comparative Examples, and Reference Examples having a wavelength of 380 to 780 nm.

2. Water Repellency The initial contact angle of 10 μl water droplets on the surface of the water-repellent antireflection structure of each Example, Comparative Example and Reference Example was measured, and the water-repellent reflection of each Example, Comparative Example and Reference Example was performed according to the following criteria The water repellency of the prevention structure was evaluated.

A: Initial contact angle of 10 μl of water is larger than 140 ° O: Initial contact angle of 10 μl of water is 125-140 °
×: Initial contact angle of 10 μl of water is smaller than 125 °

  In each example, comparative example, and reference example, the initial contact angle of a 10 μl water droplet with respect to the surface of the unprocessed sample was 116.1 °.

3. Durability against wear When the water-repellent antireflection structure is worn by pressing the friction material under the following conditions and reciprocating a plurality of times against the water-repellent antireflection structure of each Example, Comparative Example and Reference Example, The number of wear (the number of reciprocating strokes) was measured when the contact angle of 10 μl of water droplets on the surface of the water-repellent antireflection structure was less than 125 °.

Friction material: palm fiber strain Load: 320 gf
Stroke length: 100mm
Friction speed: 50 reciprocations / minute

  Based on the number of wears when the contact angle of 10 μl of water droplets with respect to the surface of the water repellent antireflective structure is less than 125 °, the water repellent antireflective structures of each of the examples, comparative examples, and reference examples are based on the following criteria. The durability against wear was evaluated.

A: The contact angle of 10 μl water droplets was less than 125 ° after 1000 wears. ○: The contact angle of 10 μl water droplets was less than 125 ° after 100 to 1000 wears. The contact angle of 10 μl water droplets was less than 125 ° with less wear times.

[Evaluation results]
Table 1 below shows the evaluation results of the low-reflectivity, water-repellency, and durability against wear of the water-repellent antireflection structures of the embodiments, comparative examples, and reference examples evaluated as described above.

  As is clear from Table 1, it can be seen that the water-repellent antireflection structures of Examples 1 and 2 have high low reflectivity, high water repellency, and high durability against abrasion. On the other hand, in the comparative example in which the occupation ratio of the flat portion is out of 6 to 40% which is a preferable range of the present invention, and the average value of the width of the flat portion is out of 12 to 100 nm which is a preferable range of the present invention. The water-repellent antireflection structure has any of low reflectivity, water repellency, and durability against abrasion. Moreover, the reference example obtained by the conventionally used manufacturing method has insufficient durability against wear.

  Further, Table 2, FIG. 7 and FIG. 8 show the change due to the above-described wear of the contact angle of a 10 μl water droplet to the surface of the water-repellent antireflection structure of each embodiment, comparative example, and reference example. .

  Thus, in Example 1 and Example 2, against the water-repellent antireflection structure, the friction material of palm fiber was pressed against the water-repellent antireflection structure and reciprocated 100 times to obtain the water-repellent antireflection structure. When worn, the reduction amount of the contact angle of 10 μl of water droplets on the surface of the water-repellent antireflection structure is 3 ° or less. From this, it can be seen that the water-repellent antireflection structures of Example 1 and Example 2 have very high durability against wear.

  Thus, in the water-repellent antireflection structures of the first and second embodiments of the present invention, the occupation ratio of the flat portions of the plurality of frustum-shaped convex portions with respect to the surface of the base portion in the plan view is 6 to 40%. In addition, the average value of the widths of the flat portions of the plurality of frustum-shaped convex portions is 12 to 100 nm. Thereby, the outstanding durability with respect to abrasion is realizable, maintaining high low reflectivity and high water repellency.

  DESCRIPTION OF SYMBOLS 1 ... Water-repellent antireflection structure 2 ... Base part 3 ... Frustum-shaped convex part 31 ... Flat part 4 ... Water-repellent layer 10 ... Substrate 20 ... Pattern mask 21 ... Island-like thing H ... Height of frustum-shaped convex part T ... thickness of base part Wt ... width of flat part Wb ... width of base end part θ ... angle S100 ... manufacturing method S110, S120, S130 ... process

Claims (9)

The base,
A plurality of frustum-shaped convex portions formed on the surface of the base portion and having a flat portion on the tip side;
A water repellent layer provided to cover the plurality of frustum-shaped convex portions,
In a plan view, the occupation ratio of the flat portion of the plurality of frustum-shaped convex portions with respect to the surface of the base portion is 6 to 40%,
The water repellent antireflection structure, wherein an average value of the flat portions of the plurality of frustum-shaped convex portions is 12 to 100 nm.   2. The water-repellent antireflection structure according to claim 1, wherein an average value of angles formed by the flat portions and side surfaces of the plurality of frustum-shaped convex portions is 90 to 120 °.   3. The water-repellent antireflection structure according to claim 1, wherein the water-repellent antireflection structure is configured such that a minimum value of the flat portion of the plurality of frustum-shaped convex portions is 5 nm or more. body.   4. The water repellent structure according to claim 1, wherein the water repellent antireflection structure is configured so that a maximum value of the width of the flat portion of the plurality of frustum-shaped convex portions is 150 nm or less. 5. Anti-reflection structure.   In the water-repellent antireflection structure, in any vertical cross-sectional view of the water-repellent antireflection structure, a total value of the widths of the flat portions of the plurality of frustum-shaped convex portions is a width of the base portion. The water-repellent antireflection structure according to any one of claims 1 to 4, wherein the water-repellent antireflection structure is configured to be -40%.   6. The water-repellent antireflection structure according to claim 1, wherein the plurality of frustum-shaped convex portions having different widths of the flat portion are arranged at random on the surface of the base portion.   The water repellent antireflection structure according to claim 6, wherein a standard deviation of the variation in the width of the flat portion of the plurality of frustum-shaped convex portions is 5 to 30.   The water repellent antireflection structure according to claim 1, wherein the base and the plurality of frustum-shaped convex portions are made of an inorganic transparent material having a refractive index of 1.3 to 2.5. Forming a base composed of a transparent material on the surface of the substrate;
Forming a pattern mask having a predetermined pitch on the surface of the base by sputtering;
Forming a plurality of frustum-shaped convex portions having a flat portion on the tip side on the surface of the base by etching the base on which the pattern mask is formed on the surface; and ,
Forming a water repellent layer to cover the plurality of frustum-shaped convex portions on the surface of the base, and
In a plan view, the occupation ratio of the flat portion of the plurality of frustum-shaped convex portions with respect to the surface of the base portion is 6 to 40%,
The average value of the width | variety of the said flat part of these frustum-shaped convex parts is 12-100 nm, The manufacturing method of the water-repellent antireflection structure characterized by the above-mentioned.

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