Optical member and method for manufacturing optical member

Abstract

An optical member provided with an optical substrate having a smooth surface and a silicon oxide film provided on the optical substrate, the silicon oxide film having a fine uneven structure on the surface, the surface of the fine uneven structure being provided with a waterproof film containing a fluorine compound, and the adhesion energy of the surface of the waterproof film being 0.2 mN / m to 6 mN / m.

Description

TECHNICAL FIELD

[0001] The present application relates to an optical member and a method for manufacturing an optical member. BACKGROUND

[0002] An optical member used in a camera or the like is required to have low reflectance of incident light. Also, in an optical member provided on a surface exposed to the outside, there is a demand to prevent water droplets such as raindrops from adhering, in order to suppress raindrop reflection into an image.

[0003] A glass laminate is disclosed in Japanese Patent Application Publication No. 2020-56866, which has an antireflection layer composed of a multilayer film containing a silicon oxide film on a concave-convex surface of a glass substrate having a concave-convex surface formed with fine concave-convex, and has a stain-proof layer on a surface of the antireflection layer.

[0004] A transparent substrate with a stain-proof film is disclosed in Japanese Patent Application Publication No. 2018-198050, which has an antiglare layer having concaves and convexes formed by applying and sintering an adhesive mainly composed of silicon oxide on a transparent substrate on a surface, and a stain-proof layer formed on the antiglare layer.

[0005] A method for forming fine concave-convex on a surface of a transparent substrate is disclosed in Japanese Patent Application Publication No. 2015-59977. SUMMARY

[0006] Technical Problem to be Solved by the Invention

[0007] An object of the present application is to provide an optical member having high water repellency and capable of suppressing water droplet adhesion, and a method for manufacturing an optical member.

[0008] Means for Solving the Technical Problem

[0009] The optical member of the present application has an optical substrate having a smooth surface and a silicon oxide film provided on the optical substrate, the silicon oxide film having a fine concave-convex structure on a surface, and a water-repellent film containing a fluorine compound provided on a surface of the fine concave-convex structure, the water-repellent film having an adhesion of 0.2 mN / m to 6 mN / m on a surface.

[0010] Preferably, the fluorine compound has a -(OCF2CF2)n- group (n is an integer of 1 or more) and does not contain a -(OCF2)m- group (m is an integer of 1 or more). n m Preferably, the fluorine compound has a -(OCF2CF2)n- group (n is an integer of 1 or more) and does not contain a -(OCF2)m- group (m is an integer of 1 or more).

[0011] Preferably, a sliding angle of a 5-μL water droplet on a surface of the water-repellent film is 10° or less.

[0012] ​Preferably, in the silicon oxide film, the content of aluminum is 0.25% by weight or less, the content of calcium is 2.0% by weight or less, the content of boron is 2.0% by weight or less, and the content of carbon is 6% by weight or less.

[0013] Preferably, the silicon oxide film is a sputtering film or an evaporation film.

[0014] Preferably, when the composition of the silicon oxide contained in the silicon oxide film is represented by SiOx, 1.90≤x≤2.00.

[0015] Preferably, the average height of the fine concave-convex structure from the bottom of the concave portion to the top of the convex portion is 150 nm to 600 nm, and the average period is 150 nm to 450 nm.

[0016] Preferably, in the optical member of the present application, the contact angle of water on the surface of the water-repellent film is 140° or more.

[0017] Preferably, the haze of the optical member of the present application is 2.5% or less.

[0018] Preferably, in the optical member of the present application, the average reflectance when light having a wavelength of 400 nm to 700 nm is perpendicularly incident on the surface is 1% or less.

[0019] Preferably, the optical member of the present application has a transmission wave aberration of λ / 5 or less for light having a wavelength of λ nm.

[0020] Preferably, the optical member of the present application has an intermediate layer between the optical substrate and the silicon oxide film, the intermediate layer having a different refractive index from the silicon oxide film for reducing the reflectance of incident light.

[0021] The method for manufacturing the optical member of the present application includes:

[0022] a film forming step of forming a silicon oxide film on one face of an optical substrate by a vapor phase film forming method;

[0023] a mask forming step of forming an etching mask on the silicon oxide film;

[0024] an etching step of forming a fine concave-convex structure on the surface of the silicon oxide film by etching the silicon oxide film through the etching mask by a vapor phase etching method; and

[0025] a coating step of forming a water-repellent film containing a fluorine compound on the surface of the fine concave-convex structure,

[0026] In the etching step, the etching is performed to a distance from the face of the optical substrate side of the silicon oxide film to the top of the largest convex portion of the fine concave-convex structure becomes smaller than the film thickness of the silicon oxide film immediately after the film formation.

[0027] Effects of the Invention

[0028] The optical member and the method for manufacturing the optical member according to the present application can provide an optical member having high water repellency and capable of suppressing water droplet adhesion. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 is a schematic cross-sectional view of an optical member according to an embodiment.

[0030] Figure 2 is a schematic cross-sectional view of an optical member according to a modification.

[0031] Figure 3 is a view showing a manufacturing process of an optical member according to an embodiment.

[0032] Figure 4 is a view showing details of a mask forming process.

[0033] Figure 5 is a view showing details of an etching process.

[0034] Figure 6 is a cross-sectional SEM image showing a change in surface shape of a silicon oxide film with the passage of time of a chemical etching.

[0035] Figure 7 is a view for explaining a measurement method of a water sliding angle.

[0036] Figure 8 is an image of a water droplet when a stage is tilted to 0° and 3.4°.

[0037] Figure 9 is a view for explaining a calculation method of an adhesion energy of a surface of an optical member.

[0038] Figure 10 is an explanatory view of a method for deriving an average height of a fine concavo-convex structure (1).

[0039] Figure 11 is an explanatory view of a method for deriving an average height of a fine concavo-convex structure (2).

[0040] In Fig. 12, Figure 12A is an example of an SEM image of a fine concavo-convex structure used when deriving an average period of a concavo-convex of a fine concavo-convex structure, Figure 12B is a spatial frequency spectrum derived from Figure 12A

[0041] In Fig. 13, Figure 13A and Figure 13B are views for explaining a sliding property evaluation method.

[0042] Figure 14 is a view showing a relationship between etching time and adhesion energy.​

[0043] Figure 15 is a graph showing the contact angle of water for each position on the X axis.

[0044] In Fig. 16, Figure 16A is a schematic view for explaining the area ratio of the SiO2 target and the optical glass sheet, Figure 16B is a schematic view showing a state in which the optical glass sheet is placed on the SiO2 target.

[0045] In Fig. 17, Figure 17A is a photographic image at the time of measuring the transmission wave aberration of sample 6-1, Figure 17B is a photographic image at the time of measuring the transmission wave aberration of sample 6-2, Figure 17C is a photographic image at the time of measuring the transmission wave aberration of sample 6-3, Figure 17D is a photographic image at the time of measuring the transmission wave aberration of sample 6-4.

[0046] Figure 18 is a graph showing the relationship between the physical etching time and the transmission wave aberration.

[0047] Figure 19 is a graph showing the wavelength dependency of the reflectance of samples 8-1A, 8-1B.

[0048] Figure 20 is a graph showing the wavelength dependency of the reflectance of samples 8-2A, 8-2B.

[0049] Figure 21 is a graph showing the wavelength dependency of the reflectance of samples 8-3A, 8-3B. DETAILED DESCRIPTION

[0050] Hereinafter, an embodiment of the present application will be described with reference to the drawings. Note that, in order to easily visually recognize, the film thicknesses of the respective layers and their ratios are appropriately changed and are not necessarily reflected on the actual film thicknesses and ratios. In the present specification, a numerical range indicated using "~" means a range including the numerical values recited before and after "~" as lower limit values and upper limit values.

[0051] Figure 1 is a cross-sectional view of an optical member of one embodiment. The optical member 1 includes an optical substrate 10 having a smooth surface, a silicon oxide film 20 provided on the optical substrate 10, and a water-repellent film 30 provided on the surface of the silicon oxide film 20. In the optical member 1, the adhesion energy of the surface of the water-repellent film 30 can be 0.2 mN / m to 6 mN / m. The adhesion energy is preferably 5.62 mN / m or less, more preferably 2.85 mN / m or less, and further preferably 0.29 mN / m to 1.29 mN / m.

[0052] The shape of the optical substrate 10 is not particularly limited and is a transparent substrate mainly used for optical devices such as a flat plate, a concave lens, or a convex lens. The optical substrate 10 can also be a substrate composed of a combination of a curved surface having a positive or negative curvature and a flat surface.

[0053] The silicon oxide film 20 has a fine concave-convex structure 22 on the surface. In the silicon oxide film 20, the content of aluminum is 0.25% by weight or less, the content of calcium is 2.0% by weight or less, the content of boron is 2.0% by weight or less, and the content of carbon is 6.0% by weight or less. The content of aluminum is preferably 0.1% by weight or less, the content of calcium is preferably 1.0% by weight or less, the content of boron is preferably 1.0% by weight or less, and the content of carbon is preferably 4.0% by weight or less. The contents of the contained components of the silicon oxide film 20 can be measured by X-ray photoelectron spectroscopy (XPS).

[0054] The silicon oxide film 20 is preferably a film produced by a vapor deposition method. Specifically, the silicon oxide film 20 is preferably a sputtered film produced by a sputtering method or an evaporated film produced by an evaporation method.

[0055] When the composition of the silicon oxide contained in the silicon oxide film 20 is represented by SiOx, 1.90≤x≤2.00 is preferable, and 1.95≤x≤2.00 is more preferable.

[0056] The fine concave-convex structure 22 formed on the surface of the silicon oxide film 20 preferably has an average height from the bottom of the concave portion to the top of the convex portion of 150 nm to 600 nm and an average period of the concave-convex structure of 150 nm to 450 nm. The average height is more preferably 150 nm to 450 nm, and further preferably 200 nm to 350 nm. The average period is more preferably 150 nm to 400 nm, and further preferably 150 nm to 350 nm.

[0057] The measurement method of the average height and the average period of the concave-convex structure will be described in the examples described later.

[0058] A waterproof membrane 30 is disposed on the surface of the fine uneven structure 22 of the silicon oxide film 20. The waterproof membrane 30 constitutes the outermost surface of the optical component 1. The waterproof membrane 30 contains a fluorinated compound. Examples of fluorinated compounds include SURFCLEAR (manufactured by Canon Optron, Inc.), OPTOOL (HD-1100TH: manufactured by DAIKIN INDUSTRIES, LTD.), Fluoro Surf (NL-1: manufactured by Fluoro Technology.), KY1091 (manufactured by Shin-Etsu Chemical Co., Ltd.), and NB05 (manufactured by KATSURAYAMA TECHNOLOGY INC.). A fluorinated compound having -(OCF2CF2) is more preferred as the fluorinated compound constituting the waterproof membrane 30. n -A functional group (where n is an integer greater than or equal to 1) and does not contain -(OCF2) m - A group (where m is an integer greater than or equal to 1). As shown in the examples described later, as a fluorine compound, it has -(OCF2) in its structure. m (OCF2CF2) n Compared to fluorine compounds containing the - functional group, compounds without -(OCF2) m -A group that only has -(OCF2CF2) n Fluorine compounds composed of - functional groups can achieve higher durability (see Table 11 below).

[0059] In optical component 1, the slip angle of a 5μL water droplet on the surface of the waterproof membrane 30 is preferably 10° or less.

[0060] The slip angle is set as a value measured by the following method. Optical component 1 is placed on a flat stage, and a water droplet with a volume of 5 μL is dropped onto the surface of its waterproof membrane 30. In this state, the stage is gradually tilted at 0.2° / second. The angle at which the tip of the water droplet begins to move is set as the slip angle.

[0061] In optical component 1, the water contact angle on the surface of the waterproof membrane 30 is preferably 140° or higher. The water contact angle can be measured using a commercially available contact angle meter. In this specification, the water contact angle is defined as the static contact angle measured with a water droplet volume of 2 mL.

[0062] The haze of optical component 1 is preferably 2.5% or less. Even lower haze is more preferable. As for optical component 1, the lower the haze, the less scattering within the optical component and the higher its quality; therefore, lower haze is more preferred. Haze can be measured using a commercially available haze meter.

[0063] The average reflectance of the optical member 1 when light having a wavelength of 400 nm to 700 nm is incident perpendicularly to the surface of the substrate is preferably 1% or less. The average reflectance refers to the average of the reflectance at each wavelength within the wavelength range of 400 nm to 700 nm. It is preferable that the reflectance be 1% or less at all wavelengths within the wavelength range of 400 nm to 700 nm. The lower the reflectance, the higher the antireflection performance.

[0064] The reflectance at each wavelength is measured by causing light to be incident on the optical member 1 at an incident angle of 0°. The wavelength dependence of the reflectance can be measured by a commercially available spectrometer.

[0065] The transmission wave aberration of the optical member 1 for light having a wavelength of λ nm is preferably λ / 5 or less. The transmission wave aberration can be measured using a commercially available laser interferometer.

[0066] As described above, the optical member 1 of the present embodiment has the optical substrate 10 having a smooth surface and the silicon oxide film 20 provided on the optical substrate 10, the silicon oxide film 20 having the fine irregular structure 22 on the surface, and the waterproof film 30 containing a fluorine compound provided on the surface of the fine irregular structure 22. By providing the waterproof film 30 on the surface of the fine irregular structure 22 formed on the silicon oxide film 20, a very high water repellency can be obtained compared to the case where the waterproof film 30 is provided on a flat surface. By providing the waterproof film 30 on the surface of the fine irregular structure, the surface area of the waterproof film can be increased. As a result, the difference between the surface free energy of water and the surface free energy of the optical member becomes large. The larger the difference between the surface free energy of water and the surface free energy of the optical member, the higher the water repellency. In the case where a waterproof film composed of a general fluorine compound is formed by coating on a flat substrate, the contact angle of water on the surface thereof is approximately 110° or so. In the present optical member 1, a contact angle of water exceeding 120°, and further a contact angle of 140° or more can be obtained, for example.

[0067] Furthermore, since the adhesion of the surface of the waterproof film 30 is 0.2 mN / m to 6 mN / m, a water droplet that is splashed does not easily remain on the surface of the optical member 1, and a lotus effect with high water run-off can be obtained. With good water run-off, the adhesion of a water droplet to the surface can be suppressed. Therefore, the optical member 1 is suitable for use as a lens filter provided on an exposed surface of a camera or the like.

[0068] According to the above structure, an optical member in which the run-off angle of a 5-μL water droplet on the surface of the waterproof film 30 is 10° or less can be realized. If the run-off angle of a water droplet is 10° or less, it can be said that the water droplet run-off is very good, and the adhesion of a water droplet to the surface can be further suppressed.

[0069] In the optical component 1 of this embodiment, the aluminum content in the silicon oxide film 20 is 0.25% by weight or less, the calcium content is 2.0% by weight or less, the boron content is 2.0% by weight or less, and the carbon content is 6% by weight or less. With this structure, when manufacturing the optical component 1, it is possible to suppress the generation of compounds that react with the etching gas and hinder etching during vapor-phase etching of the silicon oxide film 20 (refer to Experiment 2 described later). Therefore, it is easy to form a fine uneven structure 22.

[0070] In addition, when the silicon oxide film 20 is a film produced by a vapor phase film formation method, such as a sputtered film or a vapor-deposited film produced by a sputtering method or a vapor deposition method, it is possible to produce a film with sufficiently reduced impurity concentration.

[0071] When the composition (SiOx) of the silicon oxide contained in the silicon oxide film 20 is 1.90≤x≤2.00, the difference between the maximum and minimum values ​​of the in-plane distribution of the contact angle of water on the surface of the optical component 1, i.e. the surface of the waterproof film 30, can be suppressed to about 10% of the maximum value (refer to Experiment 3 described later).

[0072] When the average height of the micro-uneven structure formed on the surface of the silicon oxide film 20 of the optical component 1 from the bottom of the concave part to the top of the convex part is 150nm to 600nm and the average period is 150nm to 450nm, the water-repellent property can be further improved and the adhesion of water droplets can be further suppressed.

[0073] If the contact angle of water on the surface of the optical component 1 with the waterproof membrane 30 is 140° or more, very high water repellency can be obtained.

[0074] (Modified Example)

[0075] Figure 2 A cross-sectional view showing the modified optical component 2. Figure 2 In the middle, to and Figure 1 The same components are marked with the same symbols. The optical component 2 has an intermediate layer 12 between the optical substrate 10 and the silicon oxide film 20. The intermediate layer 12 has a different refractive index than the silicon oxide film 20 used to reduce the reflectivity of incident light. In this specification, "intermediate layer" refers to the layer disposed between the optical substrate 10 and the silicon oxide film 20.

[0076] The intermediate layer 12 can be a single layer or a multilayer film. When the intermediate layer 12 is a single layer, by setting it as a single-layer dielectric film with a refractive index between that of the optical substrate 10 and the silicon oxide film 20, an optical component 1 with a reflectivity of less than 1% for light from 400 nm to 700 nm can be achieved. When the intermediate layer 12 is a multilayer film, such as... Figure 2In (a), as shown in FIG. 1, high refractive index layers 12a having a relatively high refractive index and low refractive index layers 12b having a relatively low refractive index are preferably alternately laminated. In Figure 2 In (a), the low refractive index layers 12b and the high refractive index layers 12a are alternately laminated in six layers from the optical substrate 10 side, but the order of the high refractive index layers 12a and the low refractive index layers 12b can be reversed. The number of layers of the multilayer film is not particularly limited, and, for example, Figure 2 In (b), the intermediate layer 12 can have a three-layer structure.

[0077] The high refractive index layers 12a need only have a higher refractive index than the low refractive index layers 12b, and the low refractive index layers 12b need only have a lower refractive index than the high refractive index layers 12a, but it is more preferable that the high refractive index layers 12a have a higher refractive index than the optical substrate 10 and the low refractive index layers 12b have a lower refractive index than the optical substrate 10.

[0078] The refractive indices of the high refractive index layers 12a to each other or the low refractive index layers 12b to each other can be different, but from the viewpoint of suppressing the cost of materials and the cost of film formation and the like, it is preferable to use the same material and set the same refractive index.

[0079] As the material constituting the high refractive index layers 12a, niobium pentoxide (Nb2O5), titanium oxide (TiO2), zirconium oxide (ZrO2), tantalum pentoxide (Ta2O5), silicon oxynitride (SiON), silicon nitride (Si3N4), and silicon niobium oxide (SiNbO) and the like can be listed.

[0080] As the material constituting the low refractive index layers 12b, silicon oxide (SiO2), silicon oxynitride (SiON), gallium oxide (Ga2O3), aluminum oxide (Al2O3), lanthanum oxide (La2O3), lanthanum fluoride (LaF3), magnesium fluoride (MgF2), sodium aluminum fluoride (Na3AlF6), and the like can be listed.

[0081] Any compound can be film-formed so as to change the refractive index to some extent by controlling the ratio of constituent elements to deviate from the stoichiometric ratio or controlling the film formation density.

[0082] (Method of Manufacturing)

[0083] A method of manufacturing the optical member 1 of one embodiment will be described.

[0084] As shown in FIG. 1, the optical member 1 of one embodiment includes the optical substrate 10, the intermediate layer 12, and the multilayer film 20. Figure 3As shown, the manufacturing method of the optical member 1 includes processes A to D. Process A is a film forming process of forming the silicon oxide film 20 on the optical substrate 10. Process B is a mask forming process of forming the mask 40 on the silicon oxide film 20. Process C is an etching process of performing vapor phase etching of the silicon oxide film 20 using the mask 40 and using an etching gas G. Process D is a coating process of forming the water repellent film 30 on the surface of the etched silicon oxide film 20. An arrow F schematically indicates a coating treatment.

[0085] In the film forming process (process A), the silicon oxide film 20 is formed on one face of the optical substrate 10 by a vapor phase film forming method. As the vapor phase film forming method, a sputtering method, a vacuum evaporation method, a chemical vapor deposition method, and the like can be listed, and a sputtering method is particularly preferable. By using the vapor phase film forming method, the mixing of impurities into the silicon oxide film 20 can be suppressed. That is, it can be said that a sputtered film formed by a sputtering method or an evaporated film formed by a vacuum evaporation method, and the like are films in which the mixing of elements other than the target material (i.e., impurities) is sufficiently suppressed.

[0086] When the film forming of the silicon oxide film 20 is performed by a sputtering method, a SiO2 target material is used, oxygen is introduced into a film forming chamber, and the flow rate of the oxygen is adjusted, whereby x of silicon oxide (SiOx) can be arbitrarily adjusted.

[0087] The film thickness of the silicon oxide film 20 is, for example, 500 nm to 1500 nm.

[0088] Details of the mask forming process (process B) are shown in Figure 4 . As an example, as Figure 4 shown, the mask forming process includes: process B-1, an Al-containing film forming process of forming an aluminum-containing thin film 42 (hereinafter referred to as an Al-containing thin film 42) on the silicon oxide film 20; and process B-2, a hot water treatment process of performing hot water treatment on the Al-containing thin film 42.

[0089] In the Al-containing film forming process (process B-1), the film forming of the Al-containing thin film 42 is performed using a vapor phase film forming method. As the vapor phase film forming method, a sputtering method, a vacuum evaporation method, a chemical vapor deposition method, and the like can be listed, and a sputtering method is particularly preferable. When the film forming of the silicon oxide film 20 is performed by a sputtering method, it is preferable to continuously perform the film forming of the Al-containing thin film 42 in the same chamber.

[0090] As the Al-containing thin film 42, an aluminum film, an aluminum oxide film, an aluminum nitride film, and the like can be listed. The film thickness of the Al-containing thin film 42 is preferably 0.5 to 60 nm, more preferably 2 to 40 nm, and further preferably 5 to 20 nm.

[0091] The warm water treatment in the warm water treatment step (step B-2) refers to a treatment of exposing for 1 minute or more in warm water of 60°C or higher. As the warm water treatment, for example, a method of boiling water after immersing a laminate in which the Al-containing film 42 is formed in water at room temperature (particularly preferably pure water), a method of immersing the above laminate in warm water maintained at a high temperature, or a method of exposing the Al-containing film 42 to high-temperature water vapor, or the like can be exemplified. In the present embodiment, the pure water 6 accommodated in the water tank 5 is heated, and the laminate composed of the optical substrate 10, the silicon oxide film 20, and the Al-containing film 42 is entirely immersed in the heated pure water 6 to perform the warm water treatment. The time of boiling or immersion is particularly preferably 3 minutes or more and 15 minutes or less. The temperature of the warm water is particularly preferably a high temperature of higher than 90°C. There is a tendency that the higher the temperature, the shorter the treatment time.

[0092] By the above warm water treatment, as shown in step B-3, the Al-containing film 42 becomes a concavo-convex structure layer mainly composed of an aluminum oxide hydrate. The concavo-convex structure layer corresponds to the mask 40. Hereinafter, the same meaning as the mask 40 is described as the concavo-convex structure layer 40. The aluminum oxide hydrate constituting the concavo-convex structure layer 40 refers to boehmite (indicated as AI2O3-H2O or AIOOH) which is a monohydrate aluminum oxide, gibbsite (indicated as AI2O3-3H2O or AI(OH)3) which is a trihydrate aluminum oxide (aluminum hydroxide), or the like.

[0093] The concavo-convex structure of the concavo-convex structure layer 40 is a random shape, and the size (size of an apex angle) and the orientation of the convex portion are various, but has a generally jagged cross section.

[0094] Details of the etching step (step C) are shown in Figure 5 . As an example, as shown in Figure 5 , the etching step includes: a physical etching step (step C-1) of physically etching the concavo-convex structure layer 40 in accordance with the shape thereof; and a reactive etching (chemical etching) step (step C-2) of selectively etching the silicon oxide film 20 exposed at the concave portion of the concavo-convex structure layer 40, which is performed thereafter.

[0095] In the physical etching step (step C-1), the concavo-convex structure layer 40 composed of the aluminum oxide hydrate is etched to expose the silicon oxide film 20 at the concave portion of the concavo-convex structure layer 40. Here, as the etching gas G1, for example, a mixed gas of argon (Ar) and CHF3 (trifluoromethane) is used. As the physical etching time t1, the ratio (t1 / t2) x 100 of the physical etching time t1 to the chemical etching time t2 of the subsequent step is preferably 0.56 to 2.22. Specifically, t1 is preferably 15 seconds to about 60 seconds, and more preferably 30 seconds to 45 seconds (see Test 6 described later).

[0096] In the chemical etching step (step C-2), the silicon oxide film 20 exposed at the recesses is etched. As the etching gas G2, for example, a mixed gas of SF6 (sulfur hexafluoride) and CHF3is used. In this case, SF6as a reactive gas is made to act on SiO2to generate SiF4and gasify it, thereby chemically etching SiO2. In this chemical etching step, the etching is performed until the distance d2from the surface of the optical substrate 10 side of the silicon oxide film 20 to the top of the largest convex portion of the fine irregular structure becomes smaller than the film thickness dl of the silicon oxide film 20 immediately after the film formation. As the chemical etching time t2, the etching time is preferably 600 seconds to 3600 seconds (10 minutes to 60 minutes), more preferably 900 seconds to 3000 seconds (15 minutes to 50 minutes), and particularly preferably 1800 seconds to 2700 seconds (30 minutes to 45 minutes) (see Test 1 described later).

[0097] In addition, after the chemical etching step, a cleaning treatment step (step C-3) is performed to remove the irregular structure layer 40 remaining on the surface of the silicon oxide film 20.

[0098] In the cleaning treatment step (step C-3), the irregular structure layer 40 is removed by SH3O3 (a mixed solution of sulfuric acid and hydrogen peroxide), and after drying, ultraviolet (UV) irradiation is performed.

[0099] In the coating step (step D), a water-repellent film 30 containing a fluorine compound is formed on the surface of the etched silicon oxide film 20. As the coating method, either dry coating or wet coating can be used. As the fluorine compound for dry coating, for example, SURFCLEAR (manufactured by Canon Optron Co., Ltd.) can be used, and as the fluorine compound for wet coating, for example, OPTOOL (HD-1100TH: manufactured by DAIKIN INDUSTRIES, LTD.), Fluoro Surf (NL-1: manufactured by Fluoro Technology.), KY1091 (manufactured by Shin-Etsu Chemical Co., Ltd.), and NB05 (manufactured by Katsurayama Technology Co., Ltd.) can be used.

[0100] By the above steps, the optical member 1 can be produced.

[0101] In addition, when the optical member 2 provided with the intermediate layer 12 is produced, the intermediate layer 12 is formed before the silicon oxide film 20 is formed on the optical substrate 10. As for the film formation of the intermediate layer 12, it is also preferable to use a vapor phase film formation method. By vapor deposition, a laminated structure of various refractive indexes and layer thicknesses can be easily formed.

[0102] Figure 6is a cross-sectional SEM image showing the change in the surface shape of the silicon oxide film with the passage of time accompanying the chemical etching time. In (1) to (5), a silicon oxide film having a film thickness of 1000 nm was formed on a substrate (1) to (5) are arranged in order of etching time, (1) is the sample with the shortest etching time, and (5) is the sample with the longest etching time. At the stage of a relatively short etching time such as (1) and (2), a state in which a recess is formed in a part of the surface is observed, and it cannot be said that the surface is uneven. The recess gradually increases with the increase in the etching time, and in (3), a state in which unevenness is formed on substantially the entire surface of the silicon oxide film is obtained. After the unevenness is formed on the whole, etching is performed in such a manner that the whole is removed on the premise that the unevenness shape is maintained. In (4), a flat portion is hardly observed on the surface of the silicon oxide film. Furthermore, in (5) which is the sample with the longest etching time, etching is performed until the distance from the surface of the optical substrate 10 side of the silicon oxide film 20 to the top of the largest convex portion of the fine uneven structure becomes smaller than the film thickness of the silicon oxide film 20 immediately after film formation. In (5), the distance from the surface of the optical substrate 10 side of the silicon oxide film to the top of the largest convex portion of the fine uneven structure is substantially 500 nm, which is substantially half of the original film thickness of 1000 nm. Figure 6

[0103] According to the research by the present inventors, as long as the samples shown in (3), (4), and (5), the antireflection effect can be sufficiently obtained, and super water repellency is exhibited by forming a water repellent film on the surface. However, it was found that in (5), water droplets do not adhere to the surface by the lotus effect, and thus a surface with high sliding property can be obtained, and in contrast, in (3) and (4), water droplets adhere to the surface by the petal effect, and thus a surface with low sliding property is obtained. This indicates that the adhesion energy of the surface in the uneven structure of (3) and (4) does not satisfy 0.2 mN / m to 6 mN / m.

[0104] By performing etching until the distance from the surface of the optical substrate 10 side of the silicon oxide film 20 to the top of the largest convex portion of the fine uneven structure becomes smaller than the film thickness of the silicon oxide film 20 immediately after film formation, a fine uneven structure having a cross-sectional structure as shown in (5) can be obtained. That is, an optical member in which the adhesion energy of the surface satisfies 0.2 mN / m to 6 mN / m can be realized.

[0105] ​In addition, when the above-described chemical etching is performed, if an impurity element that generates a compound that is not easily vaporized by reacting with the etching gas is contained in the silicon oxide film 20, the reaction of SiO2with the reactive gas can be hindered. If the reaction of SiO2with the reactive gas is hindered, problems such as a decrease in etching rate, a fluctuation in etching rate, or no etching progress can occur. As the impurity element that generates a fluorine compound that is not easily vaporized by reacting with SF6, aluminum, calcium, boron, and carbon can be listed. As described above, if the silicon oxide film 20 is formed by a vapor phase film formation method such as sputtering film formation using a SiO2target, the incorporation of these impurity elements can be sufficiently suppressed compared to the case where film formation is performed by a liquid phase film formation method such as sol-gel, and problems in which etching is hindered in the chemical etching step do not occur.

[0106] Further, in an optical substrate used in a cover glass or a lens, etc., a metal other than Si (for example, Al, Ca) can be contained to lower the softening point or adjust the refractive index, etc. Therefore, if the surface of the optical substrate is etched to directly form a concavo-convex structure on the surface of the optical member, the above-described problems can occur in the chemical etching step of Step C-2, and it can take time to form the concavo-convex structure or it can not be possible to form a concavo-convex structure of sufficient depth. In the manufacturing method of the present optical member 1, since the silicon oxide film 20 is formed on the optical substrate 10, problems do not occur even if an impurity element is incorporated into the optical substrate 10, and the method can be applied regardless of the material of the optical substrate 10.

[0107] Further, in an optical member in which the silicon oxide film 20 is provided on the optical substrate 10 and the fine concavo-convex structure 22 is provided on the surface of the silicon oxide film 20 but the water-repellent film 30 is not provided, the surface of the fine concavo-convex structure 22 exhibits superhydrophilicity. In the case of an optical member in which the fine concavo-convex structure 22 having superhydrophilicity is provided, water wets and spreads on the surface, and it is possible to suppress the adhesion of water to the surface. As a result, it is possible to obtain an effect of preventing the adhesion of raindrops, etc. However, in a camera in which an optical member having such a superhydrophilic film is used as a lens filter, during photographing, when the water that wets and spreads on the lens filter dries, the drying can be non-uniform and wet and dry portions can occur, and thus the visible image can deteriorate. By providing the water-repellent film 30 as in the optical member 1, it is possible to obtain an effect of repelling raindrops, etc., and thus it is possible to obtain an antifouling effect compared to the case where water wets and spreads, and it is possible to prevent the above-described image deterioration when used as a lens filter for a camera, and thus it is very preferable in terms of practical use.

[0108] Example

[0109] Samples of the optical member of the example and the comparative example were produced, various tests were performed, and the results of verifying the optical member of the present application are described.

[0110] As a film forming apparatus, an RF magnetron sputtering apparatus BMS-800II (SHINCRON CO., LTD.) was used in producing the samples used in each experiment. The film forming conditions of each film will be described later.

[0111] The properties of each sample were measured by the following measurement methods.

[0112] (reflectance)

[0113] A microspectrophotometer (USPM-PU: Olympus Corporation) was used in the measurement of reflectance. The reflectance of each wavelength was measured when light was incident at an incident angle of 0° (normal incidence) on the optical member.

[0114] (contact angle of water)

[0115] A contact angle meter (DM300: Kyowa Interface Science Co., Ltd.) was used in the measurement of the contact angle of water. Here, the water droplet amount was set to 2 μL, and the static contact angle was measured.

[0116] (sliding angle of water)

[0117] Reference Figure 7 The measurement method of the sliding angle of water will be described. The optical member 1 was placed on an unillustrated stage having a flat surface, and a water droplet 50 of a volume amount of 5 μL was dropped on the surface (surface of the water repellent film) la of the optical member 1. In this state, the stage was gradually inclined at 0.2° / sec to gradually raise one end side (left side in the figure) of the optical member 1, thereby inclining the optical member 1. In Figure 7 the inclination angle is represented by θ. The inclination angle θ was gradually increased, and the angle at which the end portion 50e of the water droplet 50 started to move was set as the sliding angle. Figure 8 the image 52 is an image of the water droplet 50 on the optical member 1 when the plane of the stage was horizontal, i.e., the inclination angle θ = 0°, Figure 8 the image 54 is an image of the water droplet 50 on the optical member 1 when the plane of the stage was inclined at an inclination angle θ = 3.4°. Here, in Figure 8 the optical member 1 was inclined toward the right side of the paper as down and the left side as up. As shown by the dotted line, the position of the water droplet 50 at θ = 0° was shifted from the position of the water droplet 50 at θ = 3.4°. The position change of the end portion of the right side of the water droplet 50, i.e., the side inclined downward, was measured. Figure 9 one example in which the relationship between the inclination angle [°] of the stage and the position (droplet position) of the end portion 50e of the water droplet 50 was measured is shown. As shown in Figure 9 the droplet position changed greatly, the angle was set as the sliding angle. In Figure 9In the example shown, the sliding angle changes greatly between the greatly changed inclination angle 3.4° and the immediately preceding inclination angle 3.0°, and therefore the intermediate angle 3.2° between the measurement points is set as the sliding angle. In addition, the sliding angle is measured 10 times for each 1 optical member, and the average of the 10 times is taken as the sliding angle of the optical member.

[0118] (adhesion energy)

[0119] The adhesion energy is calculated from the sliding angle of water described above and using the following equation (1).

[0120] As shown in Figure 7 , it is assumed that the surface la of the optical member 1 is a flat surface, and the contact surface of the water droplet 50 that contacts the surface la of the optical member is circular, and the radius of the contact surface is set as r. The sliding angle obtained by the above steps is set as a. If the weight of the water droplet 50 is set as m, the volume of the water droplet 50 is set as V, and the density of the water droplet 50 is set as p, the gravitational force component acting downward on the water droplet 50 at the instant of sliding can be expressed as follows:

[0121] mg•sin a = Vpg•sin a

[0122] If the adhesion energy of the surface la of the optical member 1 is set as E, the force with which the surface la of the optical member 1 supports the water droplet 50 is 2πrE.

[0123] At the instant of sliding of the liquid droplet, the gravitational force component and the force supporting the water droplet reach equilibrium. That is, the following relationship holds:

[0124] Vpg•sin a = 2πrE

[0125] Therefore, the adhesion energy E is expressed by equation (1).

[0126] E = Vpg•sin a / 2πr (1)

[0127] In addition, in the present embodiment, the adhesion energy E is calculated using the sliding angle a measured using a water droplet having a volume V of 5 μL. Here, the sliding angle a is a value that varies depending on the volume V of the water droplet 50, and the adhesion energy E does not depend on the volume V of the water droplet 50.

[0128] (haze)

[0129] A haze meter (NDH5000: NIPPON DENSHOKU INDUSTRIES Co., LTD.) was used in the measurement of the haze.

[0130] is expressed by the following equation.

[0131] Haze [%] = (diffuse transmittance amount / (perpendicular transmittance amount + diffuse transmittance amount)) x 100

[0132] The greater the haze, the greater the amount of diffused transmitted light.

[0133] (Average height of the concavo-convex)

[0134] The average height of the concavo-convex is the average height from the bottom of the concave portion to the top of the convex portion of the fine concavo-convex structure formed on the surface of the silicon oxide film, and is derived as follows. Referring to Figure 10 The explanation will be given.

[0135] First, a cross section of the optical member was photographed at a magnification of 50,000 times by a scanning electron microscope (SEM) to obtain an SEM image (213 x 320 [pix]) (S1). This corresponds to a region of 1.7 μm long x 2.56 μm wide. In Figure 10 , the vertical and horizontal axes in each image represent the number of pixels. The SEM image was binarized to detect the edge of the concavo-convex structure (S2), a filling process of filling the concave portion was performed (S3), noise was removed (S4), and the surface of the concavo-convex, that is, the boundary between air and the concavo-convex was determined (S5). Through the processes of S1 to S5, for example, the boundary line of the concavo-convex with the deepest position shown in Figure 11 as the height 0 can be obtained. As shown in Figure 11 , the height of the concavo-convex is random, the vertex of the largest convex portion is about 310 nm, and if the concavo-convex height is accumulated and averaged, the average height of the concavo-convex of the example shown in Figure 11 is 168 nm indicated by a broken line. In addition, Figure 11 is data related to Sample 1-4 of Test 1 described later.

[0136] (Average period of the concavo-convex)

[0137] With respect to the average period, the spatial frequency spectrum was obtained, the spatial frequency value at which the maximum intensity was taken was obtained, and the period was obtained from the spatial frequency value. In detail, the SEM image of the fine concavo-convex structure under plan view observation was obtained at a magnification of 10,000 times by a scanning electron microscope (refer to Figure 12A ), a range of 1000 x 680 pixels was cut out from the SEM image, and two-dimensional Fourier transform was performed. In addition, in Figure 12A the image, 1 pixel corresponds to 10 nm. The obtained two-dimensional spatial frequency square intensity spectrum was integrated in the azimuthal angle direction, the intensity of the spectrum corresponding to the magnitude of the spatial frequency was obtained, and thus the relationship between the one-dimensional spatial frequency and the spectrum intensity was calculated. Then, the spatial frequency value at which the maximum intensity (peak value) was taken was obtained by fitting the vicinity of the vertex with a Gaussian function (refer to Figure 12B ). For example, when the spatial frequency value at which the maximum intensity is represented is 5 μm -1The period [μm] was 1 / 5 = 0.2, and the average period was 200 nm.

[0138] "Test 1"

[0139] Samples 1-1 to 1-10 of optical members each having a silicon oxide film on an optical substrate, a fine concavo-convex structure on the surface of the silicon oxide film, and a water-repellent film on the fine concavo-convex structure were produced, and various evaluations were performed.

[0140] (Sample production method)

[0141] The production method of Samples 1-1 to 1-10 was as follows.

[0142] As the optical substrate, a white plate substrate (B270i: manufactured by SCHOTT Corporation) having a diameter of 80 mm and a thickness of 2.5 mm was used. On the white plate substrate, a 1000-nm-thick silicon oxide film was formed by a sputtering method, and further a 10-nm-thick aluminum film was formed by a sputtering method. Then, warm water treatment of immersing the white plate substrate on which the silicon oxide film and the aluminum film were laminated in warm water at 100°C for 3 minutes was performed. By this, the aluminum film was changed into a fine concavo-convex layer composed of a hydrate of aluminum oxide.

[0143] A SiO2 target was used in the film formation of the silicon oxide film, and an Al target was used in the film formation of the aluminum film. The sputtering conditions were as follows.

[0144] - Sputtering conditions of the silicon oxide film -

[0145] Target input power: 500 W

[0146] Degree of vacuum: 0.2 Pa, Ar / O2 mixed atmosphere (O2 flow rate: 200 seem)

[0147] No substrate heating

[0148] - Sputtering conditions of the aluminum film -

[0149] Target input power: 600 W

[0150] Degree of vacuum: 0.2 Pa, Ar atmosphere (Ar flow rate: 200 seem)

[0151] No substrate heating

[0152] Then, etching treatment was performed using the fine concavo-convex layer as a mask. First, physical etching was performed, and then chemical etching was performed. The recesses of the fine concavo-convex layer were perforated by the physical etching to expose the silicon oxide layer. Then, the silicon oxide film exposed at the recesses of the fine concavo-convex layer was etched by the chemical etching. The conditions of the physical etching and the chemical etching were as follows, respectively.

[0153] - Physical etching conditions -

[0154] ICP (Inductively Coupled Plasma) output power: 300 W, bias output power: 120 W

[0155] Etching pressure: 3 Pa

[0156] Etching gas: Ar (100 sccm), CHF3(10 sccm)

[0157] Substrate temperature: 10°C

[0158] Etching time: 45 seconds

[0159] - Chemical etching conditions -

[0160] ICP output power: 500 W, bias output power: 15 W

[0161] Etching pressure: 0.6 Pa

[0162] Etching gas: SF6(40 sccm), CHF3(40 sccm)

[0163] Substrate temperature: 10°C

[0164] Etching time: 5 minutes to 70 minutes (varies depending on the sample)

[0165] The etching time for each of samples 1-1 to 1-10 is shown in Table 1 described later.

[0166] By the etching treatment, a waterproof film was formed by dip-coating a fluorine coating (trade name Fluoro Surf NL-1: manufactured by Fluorotechnology Co., Ltd.) on the concave-convex structure formed on the surface of the silicon oxide film.

[0167] With respect to samples 1-1 to 1-10 produced in the above-described manner, the calculated adhesion energy and the evaluation results of the water sliding properties on the surface of each sample are shown in Table 1.

[0168] (Water sliding property evaluation)

[0169] The evaluation method for the water sliding property is described. First, the number of residual water droplets was measured according to the following steps.

[0170] 1) Pure water was added to an empty spray container of a commercially available FUJIFILM Corporation Hydro Ag alcohol spray.

[0171] 2) As Figure 13AAs shown, the sample S (samples 1-1 to 1-10) was vertically stood using a jig not shown, and the spray container 56 was disposed in such a manner that the distance from the surface of the sample S to the center of the bottom of the spray container 56 was 150 mm.

[0172] 3) The spray rod was pressed 3 times in this state, and pure water was sprayed to the surface of the sample S.

[0173] 4) Then, the sample S was horizontally placed, and the number of water droplets remaining on the surface was counted. The surface of the sample S was observed at 5 times magnification using a stereomicroscope. As shown, a range of 40 x 40 mm centered on the center O of the sample S was divided into 4 parts, and the water droplets in each of a 20 x 20 mm region in the 1st quadrant, a 20 x 20 mm region in the 2nd quadrant, a 20 x 20 mm region in the 3rd quadrant, and a 20 x 20 mm region in the 4th quadrant were counted, and the average number of water droplets in the 4 regions was taken as the number of residual water droplets. Figure 13B

[0174] The number of residual water droplets was evaluated according to the following criteria for each of the samples 1-1 to 1-10. The results of the evaluation of the water slideability are shown in Table 1.

[0175] A: The number of residual water droplets was 2 or less

[0176] B: The number of residual water droplets was 3 or more and 5 or less

[0177] C: The number of residual water droplets was 6 or more and 10 or less

[0178] D: The number of residual water droplets exceeded 10

[0179] [Table 1]

[0180]

[0181] In the samples 1-2 to 1-9 in which the adhesion energy satisfied 0.2 mN / m to 6 mN / m, the slideability of C or more was obtained. In contrast, in the samples 1-1 and 1-10 in which the adhesion energy did not satisfy 0.2 mN / m to 6 mN / m, the evaluation of the slideability was D. The samples 1-2 to 1-9 correspond to the embodiments of the optical member of the present application, and the samples 1-1 and 1-10 correspond to the comparative examples. Good slideability was obtained when the adhesion energy was 5.62 mN / m or less, better slideability was obtained when the adhesion energy was 2.85 mN / m or less, and very good slideability was obtained when the adhesion energy was 0.29 mN / m to 1.29 mN / m.

[0182] Figure 14 ​The etching time dependence based on the adhesion energy of Table 1 is shown in FIG. 1. In this Test 1, the chemical etching time for achieving good slip-off properties is 10 minutes to 60 minutes. Also, by setting the chemical etching time to 15 minutes to 50 minutes, better slip-off properties can be obtained, and by setting it to 30 minutes to 45 minutes, very good slip-off properties can be obtained. In Figure 14 In FIG. 1, the range indicated by the double-headed arrow is the range for achieving good slip-off properties. It is thought that when the etching time is less than 5 minutes, the formation of the concavo-convex structure will be insufficient due to under-etching, and it is thought that when it exceeds 60 minutes, the concavo-convex structure that has been formed will be destroyed due to over-etching.

[0183] Here, the water contact angle β, the water slip-off angle α, the reflectance R, and the haze H were evaluated for Samples 1-1 to 1-7, respectively. The evaluation criteria are shown in Table 2, and the evaluation results are shown in Table 3. Also, in Table 3, the evaluation of slip-off properties and the adhesion energy shown in Table 1 are shown together.

[0184] [Table 2]

[0185]

[0186] The evaluation criteria shown in Table 2 are also the same after Test 2.

[0187] [Table 3]

[0188]

[0189] As shown in Table 3, the evaluation of water slip-off properties coincides with the evaluation of the water slip-off angle. When the adhesion energy is in the range of 0.29 mN / m to 1.29 mN / m, all evaluations are B or higher.

[0190] "Test 2"

[0191] Samples 2-1 to 2-7 of optical members having a fine concavo-convex structure on the surface of an optical substrate and a water-repellent film on the fine concavo-convex structure were produced, and various evaluations were performed. In terms of not having a silicon oxide film, Samples 2-1 to 2-7 are equivalent to Comparative Examples of the optical member of the present application.

[0192] (Sample Production Method)

[0193] The production method of Samples 2-1 to 2-7 is as follows.

[0194] As the optical substrate, a white plate substrate (B270i: manufactured by SCHOTT Corporation) having a diameter of 80 mm and a thickness of 2.5 mm was used. An aluminum film of 10 nm was formed on the white plate substrate by a sputtering method. Then, warm water treatment of immersing the white plate substrate on which the aluminum film was laminated in warm water at 100°C for 3 minutes was performed. By this, the aluminum film was changed into a fine concavo-convex layer composed of a hydrate of aluminum oxide.

[0195] In the film formation of the aluminum film, an Al target was used, and the sputtering conditions were the same as those of Test 1.

[0196] Then, etching treatment was performed using the fine concavo-convex layer as a mask. First, physical etching was performed, and then chemical etching was performed. The concave portions of the fine concavo-convex layer were perforated by the physical etching to expose the surface of the white plate substrate. Then, the white plate substrate exposed at the concave portions of the fine concavo-convex layer was etched by the chemical etching. The conditions of the physical etching and the chemical etching were the same as those of Test 1. In addition, the chemical etching time was different between 5 minutes and 45 minutes depending on the sample. The chemical etching time in each sample is shown in Table 4.

[0197] By the etching treatment, a waterproof film was formed by dip coating a fluorine coating layer (trade name: Fluoro Surf NL-1: manufactured by Fluoro Technology Co., Ltd.) on the concavo-convex structure formed on the surface of the white plate substrate.

[0198] The water contact angle β, the water sliding angle α, the reflectance R, and the haze H were evaluated for the samples 2-1 to 2-7 produced in the above-described manner, respectively, in accordance with the evaluation criteria shown in Table 2. The evaluation results are shown in Table 4.

[0199] [Table 4]

[0200]

[0201] All of the samples 2-1 to 2-7 resulted in low sliding properties. In addition, analysis (XPS: X-ray photoelectron spectroscopy) was performed on the surface of the samples, and as a result, Al and F were detected on the surface. From the results of the surface analysis, it was inferred that Al in the white plate substrate reacted with the etching gas to form AlF3 having a low vapor pressure and remained on the surface to hinder the etching.

[0202] "Test 3"

[0203] The composition dependency on the etching distribution of the SiOx film was investigated.

[0204] (Method for producing samples)

[0205] As the optical substrate, a white plate substrate (B270i: manufactured by SCHOTT Corporation) having a diameter of 80 mm and a thickness of 2.5 mm was used. On the white plate substrate, a 1000-nm-thick silicon oxide film (SiOx film) was formed by a sputtering method, and further, a 10-nm-thick aluminum film was formed by a sputtering method. The film formation conditions of the silicon oxide film will be described later. The film formation conditions of the aluminum film were the same as those of Test 1. Then, warm water treatment of immersing the white plate substrate on which the silicon oxide film and the aluminum film were laminated in warm water at 100°C for 3 minutes was performed. Thereby, the aluminum film was made into a fine concavo-convex layer composed of a hydrate of aluminum oxide. x The film formation conditions of the silicon oxide film will be described later. The film formation conditions of the aluminum film were the same as those of Test 1. Then, warm water treatment of immersing the white plate substrate on which the silicon oxide film and the aluminum film were laminated in warm water at 100°C for 3 minutes was performed. Thereby, the aluminum film was made into a fine concavo-convex layer composed of a hydrate of aluminum oxide.

[0206] Then, etching treatment was performed using the fine concavo-convex layer as a mask. First, physical etching was performed, and then chemical etching was performed. The concave portions of the fine concavo-convex layer were perforated by the physical etching to expose the silicon oxide layer. Then, the silicon oxide film exposed at the concave portions of the fine concavo-convex layer was etched by the chemical etching. As for the conditions of the physical etching and the chemical etching, the etching time of the chemical etching was set to 30 minutes in all the samples, and the other conditions were the same as those of Test 1.

[0207] By the etching treatment, a waterproof film was formed by dip coating a fluorine coating layer (trade name: Fluoro Surf NL-1: manufactured by Fluorotechnology Co., Ltd.) on the concavo-convex structure formed on the surface of the silicon oxide film.

[0208] - Film formation of silicon oxide film -

[0209] In the film formation of the silicon oxide film, a SiO2 target was used, and the target input power and the oxygen O2 flow rate were changed, whereby samples having SiOx films with different x were produced. The composition ratio x and the target input power and the oxygen flow rate are shown in Table 5. The other conditions were the same as those of Test 1.

[0210] [Table 5]

[0211]

[0212] In addition, the composition ratio x was measured using a Rutherford Backscattering Spectroscopy (RBS) device. An RBS device (device main body: 3SDH-R10, accelerator: 3SDH Pelletron) manufactured by NEC Corporation was used in the measurement, and RBS-400 manufactured by CE&A Corporation was used as a data analysis software.

[0213] The contact angle distribution within the substrate surface was measured for each sample. Taking the center of the 80mm diameter sample as the origin, the water contact angle was measured at 5mm intervals on the orthogonal biaxial axes, namely the X-axis and Y-axis. The measurement results are shown in Table 6. (1) represents the water contact angle [°] at each position X on the X-axis of each sample, and (2) represents the water contact angle [°] at each position Y on the Y-axis of each sample.

[0214]

[0215] In this example, the contact angle distribution has approximately the same symmetry in the X-axis and Y-axis directions. Figure 15 The diagram shows the relationship between position on the X-axis and contact angle. For example... Figure 15 As shown, the contact angle decreases as it moves outward from the center (position 0) of the substrate. It is possible to make the difference between the contact angle at the center position 0 and the ±35mm position approximately 10% of the contact angle at the center position 0mm within the range of 1.9 ≤ x ≤ 2.0. That is, if the range is 1.95 ≤ x ≤ 2.0, the difference between the inner and outer contact angles can be further reduced, which is therefore preferable.

[0216] In vapor phase etching, it is a known phenomenon that the etching amount differs between the center and the edges of a substrate. This is believed to occur because the plasma, which is the result of the etching gas dissociating into electrons and ions, is unevenly distributed across the substrate, concentrating around the periphery (edges). Consequently, the etching amount at the edges of the substrate is greater than that at the center.

[0217] Furthermore, the results in Table 6 show that, based on SiO x The composition ratio x affects the difference in etching amount between the center and ends of the substrate. When the oxygen composition in the silicon oxide film decreases, the relative Si concentration increases. In chemical etching, the etching rate of the etching gas SF6+CH3F is Si>SiO. x Si-enriched films are easier to etch. It is believed that, through the synergistic effect of this tendency and the phenomenon that plasma tends to concentrate around the substrate, the in-plane etching amount distribution depends on SiO₂. x The composition of x changes.

[0218] For each sample, the results of measuring the height of the unevenness at three locations on the X-axis are shown in Table 7: the center of the substrate, the middle part (1 / 2 part) between the center and the end, and the end of the substrate. In Table 7, the unevenness height is expressed as a normalized value with the highest unevenness height (the unevenness height at the center of the substrate of the sample with a composition ratio of x=2) set to 1.

[0219] [Table 7]

[0220]

[0221] As shown in Table 7, when the composition ratio x is 1.8 or less, the difference in the etching amount between the central portion of the substrate and the end portion of the substrate becomes significant. The in-plane distribution of the unevenness height has a correlation with the in-plane distribution of the contact angle shown in Table 6, and thus it is considered that the in-plane distribution of the unevenness height is a main cause of the in-plane distribution of the contact angle.

[0222] "Test 4"

[0223] In Test 2, it was shown that when a white plate substrate (B270i: manufactured by SCHOTT Corporation) was used as an optical substrate and the surface thereof was to be etched to form a fine uneven structure, the etching was hindered and the uneven structure could not be formed. As Test 4, a sample in which an impurity was added when a silicon oxide film was formed on an optical substrate was prepared, and an experiment in which the impurity concentration at which the etching is not hindered was defined was performed.

[0224] Elements that can form a compound by reacting with SF6 as an etching gas are boron (B), calcium (Ca), aluminum (Al), and carbon (C). Thus, these elements (hereinafter, collectively referred to as impurity elements) were investigated. By placing an optical glass sheet containing any one of Al, Ca, and B or a carbon sheet as a special product on a SiO2 target when forming a silicon oxide film, a silicon oxide film containing an impurity element was prepared.

[0225] The concentration of the impurity element was changed by adjusting the area of the optical glass sheet or the carbon sheet placed on the SiO2 target. The thickness of the optical glass sheet and the carbon sheet was set to 1 mm. Figure 16A is a schematic plan view of a SiO2 target 60 of a 6-inch size. As shown in Figure 15 As shown in A, the area of the SiO2 target 60 was divided into 16 equal parts, and an optical glass sheet 62 or a carbon sheet was placed on the SiO2 target 60 so that the area thereof becomes 1 / 16, 2 / 16,..., n / 16 of the area of the SiO2 target 60. Figure 16B is a schematic view showing a state in which two optical glass sheets 62 are placed on the SiO2 target 60.

[0226] (Sample preparation method)

[0227] As the optical substrate, a whiteboard substrate having a diameter of 80 mm and a thickness of 2.5 mm was used, on which a 1000-nm-thick silicon oxide film was formed by a sputtering method, and further a 10-nm-thick aluminum film was formed by a sputtering method. As described above, when the silicon oxide film was formed, the optical glass sheet 62 or the carbon sheet was disposed on the SiO2 target 60 to produce a plurality of samples having different impurity concentrations. The warm water treatment was performed under the same conditions as in Test 1, and the etching treatment was performed under the same conditions as in Test 1. Finally, a waterproof film was formed by dip-coating a fluorine coating (trade name Fluorosurf NL-1: manufactured by Fluoro Technology Co., Ltd.) on the concave-convex structure formed on the surface of the whiteboard substrate, as in the case of Test 1.

[0228] As the optical glass sheet 62, B270i (manufactured by SCHOTT), H-ZF52 (manufactured by Chengdu Guangming Optical Materials Co., Ltd.), or S-LHA58 (manufactured by OHARA INC.) was used. B270i contains Al, H-ZF52 contains Ca, and S-LHA58 contains B. In Table 8, the area ratio of the sheet, the type of optical glass, the impurity element, and the concentration [wt%] of the impurity are shown for each sample. For each sample, the composition was analyzed by XPS after the formation of the silicon oxide film and before the etching, and the impurity concentration was calculated.

[0229] (Evaluation)

[0230] The etching state was evaluated for each sample. The etching state was evaluated based on the contact angle of water measured at the central portion of the substrate. This is because it is considered that if the etching state is good, the water repellency will be high. In this example, evaluation was performed using the following evaluation criteria. A: The contact angle was 140° or more

[0231] B: The contact angle was less than 140° and 120° or more

[0232] C: The contact angle was less than 120°

[0233] The evaluation results are shown in Table 8.

[0234] [Table 8]

[0235]

[0236] As shown in Table 8, when the impurity contained in the silicon oxide film is aluminum, it is preferable to be 0.25 wt% or less, and further preferable to be 0.10 wt% or less. When the impurity contained in the silicon oxide film is calcium, it is preferable to be 2.00 wt% or less, and further preferable to be 1.00 wt% or less. When the impurity contained in the silicon oxide film is boron, it is preferable to be 2.00 wt% or less, and further preferable to be 1.00 wt% or less. When the impurity contained in the silicon oxide film is carbon, it is preferable to be 6.0 wt% or less, and further preferable to be 4.0 wt% or less.

[0237] In the case where the fine concavo-convex structure is formed directly on the surface of the optical substrate, as described above, the etching process can sometimes be hindered by the influence of the element bonded to fluorine contained in the optical substrate. In view of this, since the silicon oxide film is formed on the optical substrate by the vapor deposition capable of suppressing the mixing of impurities and the fine concavo-convex structure is formed on the surface thereof, even when the optical substrate contains an element bonded to fluorine in the composition, the problem of hindering the etching process does not occur, and thus various optical substrates can be used without considering the kind.

[0238] "Test 5"

[0239] In the sample production method of Test 1, a sample group in which the average height and the average period of the concavo-convex structure were changed by changing the chemical etching conditions was produced, and the reflectance R, the haze H, and the water sliding property were evaluated. The results are shown in Table 9.

[0240]

[0241] According to the results of Table 9, as the average height and the average period of the concavo-convex, by the combination of both, the average height can take a range of 100 nm to 600 nm, and the average period can take a range of 100 nm to 450 nm. As the average height, 150 nm to 600 nm is preferable, 150 nm to 450 nm is more preferable, and 200 nm to 350 nm is particularly preferable. Also, as the average period, 150 nm to 450 nm is preferable, 150 nm to 400 nm is more preferable, and 150 nm to 350 nm is particularly preferable. As the combination, when the average height is 100 nm to 150 nm, the average period is preferably 300 nm to 450 nm. When the average height is 150 nm to 200 nm, the average period can take a range of 100 nm to 450 nm, preferably 100 nm to 350 nm, and more preferably 100 nm to 200 nm. When the average height is 200 nm to 500 nm, the average period can take a range of 100 nm to 450 nm, and preferably 100 nm to 350 nm. Particularly preferably, the average height is 200 nm to 350 nm and the average period is 100 nm to 350 nm. When the average height is 500 nm to 600 nm, the average period is preferably 100 nm to 350 nm, and more preferably 100 nm to 200 nm.

[0242] "Test 6"

[0243] The present inventors found that, in the production process of the optical member of the present application, when a silicon oxide film having a concavo-convex surface is formed on a flat optical substrate, the quality of the transmitted wavefront (contour interval) varies depending on the etching treatment conditions. In Test 6, the transmitted wave aberration required to obtain a good image was investigated.

[0244] In the sample production method of Test 1, samples 6-1 to 6-4 were produced by changing the time ratio of the etching time of physical etching to the etching time of chemical etching. The other conditions were produced in accordance with the sample production method of Test 1. The physical etching time t1, the chemical etching time t2, and the etching time ratio (t1 / t2) x 100) of each sample 6-1 to 6-4 are shown in Table 10.

[0245] The transmitted wave aberration, the image evaluation, and the anti-splashing function were evaluated for each sample, and the results are shown in Table 10. The evaluation methods are as follows, respectively.

[0246] (Measurement method of transmitted wave aberration)

[0247] The transmitted wave aberration was measured using a laser interferometer (FUJIFILM F601). The measurement light was set to light with a wavelength λ = 633 nm. The measurement was performed by irradiating the measurement light onto the surface of the optical member having a concavo-convex structure. In Table 10, the PV value is shown as the transmitted wave aberration.

[0248] exist Figure 17A to Figure 17D The image shows the surface images of the optical components during the transmission aberration measurement of samples 6-1 to 6-4. The portion shown in the central black circle represents the optical components.

[0249] (Image evaluation methods)

[0250] Samples 6-1 to 6-4 were used as lens filters and mounted on a general-purpose handheld television camera (body: Sony HDC-4300, lens: Fujinon UA18×7.6BERD). The subjects were photographed, and the photographic images were displayed on a monitor. The photographic images were then evaluated according to the following evaluation criteria.

[0251] A: Able to clearly identify what the subject is.

[0252] B: Although the photographic image is displayed, the subject cannot be identified.

[0253] C: Unable to obtain photographic images.

[0254] (Evaluation of water slipperiness)

[0255] In addition, the slipperiness of water was evaluated for samples 6-1 to 6-4 using the same method as in test 1.

[0256] [Table 10]

[0257]

[0258] As shown in Table 10, the transmitted wave aberration is preferably λ / 5 or less, and more preferably λ / 5 to λ / 8.

[0259] Figure 18 This represents the relationship between physical etching time t1 and wavefront aberration PV value. The dashed line represents the fitted curve y = 0.0582e 0.0283x R 2 The value is R 2 =0.9984. For example... Figure 18 As shown, there is a tendency for the wavefront aberration PV value to be larger as the physical etching time t1 is longer.

[0260] Sample 6-4, which had poor image evaluation and slippage evaluation results, was analyzed.

[0261] For SEM observation, SEM images of samples were prepared using the same manufacturing method as samples 6-4, after physical etching and before chemical etching, and cross-sectional SEM images were captured. The results showed that the mask (a layer with an uneven structure composed of alumina hydrate) had recesses that penetrated through it, and that portions of the underlying silicon oxide film were etched, as well as portions where the uneven structure of the mask was destroyed and disappeared.

[0262] For elemental analysis, analytical samples were prepared using the same manufacturing method as samples 6-1 to 6-4, up to the chemical etching process, and fluorescence X-ray analysis was performed. The results showed that the Ar concentration (wt%) in the silicon oxide film of sample 6-4 was approximately 15 times higher than that of samples 6-1 to 6-3.

[0263] Typically, transmission wavefront aberration is correlated with substrate deformation. It is speculated that during physical etching with Ar, accelerated Ar mixes into the silicon oxide film, causing distortion of the Si-O-Si network structure of the SiO2 film. As a result, the film stress of the SiO2 film increases, and this high stress leads to substrate deformation, thereby degrading the transmission wavefront (increasing transmission wavefront aberration).

[0264] Based on the above analysis results and the relationship between physical etching time t1 and wavefront aberration (PV) value shown in Figure 17, the physical etching time t1 is preferably 60 seconds or less, more preferably 45 seconds or less. Furthermore, to improve water repellency, the physical etching time t1 is preferably set to 30 seconds or more. The etching time ratio (t1 / t2) × 100, which is the ratio of physical etching time t1 to chemical etching time t2, is preferably 2.22 or less, more preferably 1.67 or less. The etching time ratio (t1 / t2) × 100 is particularly preferably 1.11 to 1.67.

[0265] "Experiment 7"

[0266] Fluorine compounds, which are particularly preferred from the viewpoint of durability, were studied as constituent materials of waterproof membranes.

[0267] (Sample preparation method)

[0268] Using the same sample fabrication method as in Experiment 3, wherein the SiO2 film is set as a silicon oxide film. x With x=2, etching was performed. Samples 7-1 to 7-4, each coated with a different fluorine compound, were prepared during the waterproof film formation process. Sample 7-1 used -(OCF2CF2) manufactured by Company A. n - As a fluorine compound with a functional group, sample 7-2 used -(OCF2CF2) manufactured by Company B. n - As a functional group, fluorine compounds, such as -(OCF2) manufactured by Company C, were used in Sample 7-3. m (OCF2CF2) n - As a functional group, fluorine compounds, such as -(OCF2) manufactured by Company D, were used in samples 7-4. m (OCF2CF2) n - Fluorine compounds as functional groups.

[0269] Each sample was continuously irradiated with 150 W xenon lamp light (manufactured by Kenko Tokina Co., Ltd.: Super Bright 152S), and the water contact angle was measured periodically. The xenon lamp light-emitting surface was disposed facing the sample surface, and the distance between the two was set to 10 mm.

[0270] The number of days for the contact angle to decrease by 3% and 5% from the initial value is summarized in Table 11. In addition, for each sample, N = 4 were produced. The contact angle and the number of days in Table 11 are averages for N = 4.

[0271] [Table 11]

[0272]

[0273] In Table 11, "not confirmed" means that the decrease by 5% was not confirmed even after 150 days. Both n and m in the table are integers of 1 or more.

[0274] As shown in Table 11, in the samples 7-1 and 7-2 in which the fluorine compound has a -(OCF2CF2) n group, n is an integer of 1 or more, and -(OCF2) m group is not included, and m is an integer of 1 or more, the time for the contact angle to decrease by 5% from the initial value was very long, and the durability was high.

[0275] "Test 8"

[0276] The effect of having an intermediate layer between the optical substrate and the silicon oxide film was verified.

[0277] (Sample production method)

[0278] ((Sample 8-1A))

[0279] Sample 8-1A was produced as follows. As the optical substrate, a white plate substrate (FDS90: manufactured by SCHOTT) having a diameter of 80 mm and a thickness of 2.5 mm was used. The refractive index n of FDS90 for light having a wavelength of 633 nm was 1.839. An intermediate layer was formed on the white plate substrate by a sputtering method. Then, a 1000-nm-thick silicon oxide film was formed on the intermediate layer by a sputtering method, and further, a 10-nm-thick aluminum film was formed by a sputtering method. Then, warm water treatment of immersing the white plate substrate on which the silicon oxide film and the aluminum film were stacked in warm water at 100°C for 3 minutes was performed. By this, the aluminum film became a fine concavo-convex layer composed of a hydrate of aluminum oxide. The film formation conditions of the silicon oxide film and the film formation conditions of the aluminum film were set to be the same as those of the sample production method of Test 1.

[0280] Then, the micro-uneven layer was used as a mask for etching. The etching process was performed under the same physical and chemical etching conditions as the sample preparation method in Experiment 1, with the chemical etching time set to 45 minutes.

[0281] Furthermore, a waterproof membrane was formed on the uneven structure formed on the surface of the silicon oxide film using the same method as in Experiment 1.

[0282] The intermediate layer is a monolayer silicon oxynitride (SiO2) film with a refractive index of 1.515 for light with a wavelength of 633 nm. x N y ).

[0283] ((Sample 8-1B))

[0284] Sample 8-1B was fabricated, which has the same structure as sample 8-1A, but does not have an intermediate layer. Regarding sample 8-1B, the fabrication method of sample 8-1A does not include the step of forming an intermediate layer; instead, a silicon oxide film is directly formed on the surface of the white board substrate. Apart from this, it was fabricated using the same method as sample 8-1A.

[0285] ((Sample 8-2A))

[0286] As the optical substrate, a white board substrate (H-ZLAF90: manufactured by SCHOTT) with a diameter of 80 mm and a thickness of 2.5 mm was used. The refractive index n of H-ZLAF90 for light with a wavelength of 633 nm is 1.9928. As the intermediate layer, a multilayer film with a 5-layer structure consisting of alternating layers of low-refractive-index dielectric films and high-refractive-index dielectric films was formed. Except for changing the type of optical substrate, setting the intermediate layer to a multilayer film, and setting the chemical etching time to 30 minutes, sample 8-2A was fabricated using the same fabrication method as sample 8-1A.

[0287] Regarding the intermediate layer, a silicon oxynitride (SiO) film is used. x N y Niobium oxide (Nb2O) is used as a low-refractive-index dielectric film. 5-x The film is a high-refractive-index dielectric film. The refractive index and thickness of each film are shown in Table 12 below. In Table 12, the intermediate layers are shown as layer 1 closest to the silicon oxide film and layer 5 closest to the substrate.

[0288] [Table 12]

[0289]

[0290] ((Sample 8-2B))

[0291] Sample 8-2B was fabricated, which has the same structure as sample 8-2A, but lacks an intermediate layer. Regarding sample 8-2B, the fabrication method of sample 8-2A does not include the step of forming an intermediate layer; instead, a silicon oxide film is directly formed on the surface of the white board substrate. Apart from this, it was fabricated using the same method as sample 8-2A.

[0292] ((Sample 8-3A))

[0293] As the optical substrate, a white board substrate (BaFD7: manufactured by SCHOTT) with a diameter of 80 mm and a thickness of 2.5 mm was used. The refractive index n of BaFD7 for light with a wavelength of 633 nm is 1.698. As the intermediate layer, a multilayer film with a three-layer structure consisting of alternating layers of low-refractive-index dielectric films and high-refractive-index dielectric films was formed. Except for changing the type of optical substrate, setting the intermediate layer to a multilayer film, and setting the chemical etching time to 50 minutes, sample 8-3A was fabricated using the same fabrication method as sample 8-1A.

[0294] Regarding the intermediate layer, a silicon oxynitride (SiO2) film is used. x N y Niobium oxide (Nb2O) is used as a low-refractive-index dielectric film. 5-x The film is a high-refractive-index dielectric film. The refractive index and thickness of each film are shown in Table 13 below. In Table 13, the intermediate layers are shown as layer 1 with the side closest to the silicon oxide film and layer 3 with the side closest to the substrate.

[0295] [Table 13]

[0296]

[0297] ((Sample 8-3B))

[0298] Sample 8-3B was fabricated, which has the same structure as sample 8-3A, but lacks an intermediate layer. Regarding sample 8-3B, the fabrication method of sample 8-3A does not include the step of forming an intermediate layer; instead, a silicon oxide film is directly formed on the surface of the white board substrate. Apart from this, it was fabricated using the same method as sample 8-A.

[0299] For samples 8-1A and 8-1B, the measurement results of the wavelength dependence of reflectance are shown below. Figure 19 .exist Figure 19 In the diagram, the solid line represents the wavelength dependence of the reflectance of sample 8-1A with an intermediate layer, and the dashed line represents the wavelength dependence of the reflectance of sample 8-1B without an intermediate layer.

[0300] The average reflectance in the wavelength range of 400 nm to 700 nm was 0.1% for the sample 8-1A and 1.83% for the sample 8-1B. It is considered that the sample 8-1A reduced the reflectance by having the intermediate layer having a refractive index between the refractive index of the optical substrate and the refractive index (n = 1.46) of the silicon oxide film, and reducing the difference in the refractive index between the layers.

[0301] The measurement results of the wavelength dependence of the reflectance for the samples 8-2A and 8-2B are shown in Figure 20 In Figure 20 , the solid line indicates the wavelength dependence of the reflectance of the sample 8-2A having the intermediate layer, and the broken line indicates the wavelength dependence of the reflectance of the sample 8-2B not having the intermediate layer.

[0302] The average reflectance in the wavelength range of 400 nm to 700 nm was 0.1% for the sample 8-2A and 2.8% for the sample 8-2B. The sample 8-2A had the intermediate layer composed of a multilayer film between the optical substrate and the silicon oxide film, and the reflected light generated at the boundaries of the respective films interfered with each other by the intermediate layer, and it is considered that the reflectance was reduced by this effect.

[0303] The measurement results of the wavelength dependence of the reflectance for the samples 8-3A and 8-3B are shown in Figure 21 In Figure 21 , the solid line indicates the wavelength dependence of the reflectance of the sample 8-3A having the intermediate layer, and the broken line indicates the wavelength dependence of the reflectance of the sample 8-3B not having the intermediate layer.

[0304] The average reflectance in the wavelength range of 400 nm to 700 nm was 0.1% for the sample 8-3A and 2.8% for the sample 8-3B. The sample 8-3A had the intermediate layer composed of a multilayer film between the optical substrate and the silicon oxide film, and the reflected light generated at the boundaries of the respective films interfered with each other by the intermediate layer, and it is considered that the reflectance was reduced by this effect.

[0305] The test 8 showed that the reflectance was greatly reduced by having the intermediate layer.

[0306] With respect to the above embodiments, the following notes are further disclosed.

[0307] (Note 1)

[0308] An optical element having an optical substrate having a smooth surface and a silicon oxide film provided on the optical substrate,

[0309] The silicon oxide film has a fine uneven structure on the surface,

[0310] The waterproof film containing a fluorine compound is provided on the surface of the fine uneven structure,

[0311] The adhesion of the surface of the water-repellent film can be 0.2 mN / m to 6 mN / m.

[0312] (Note 2)

[0313] The optical member according to Note 1, wherein

[0314] The fluorine compound has a -(OCF2CF2) n group (n is an integer of 1 or more) and does not include a -(OCF2) m group (m is an integer of 1 or more).

[0315] (Note 3)

[0316] The optical member according to Note 1 or 2, wherein

[0317] The sliding-off angle of a 5-μL water droplet on the surface of the water-repellent film is 10° or less.

[0318] (Note 4)

[0319] The optical member according to any one of Notes 1 to 3, wherein

[0320] In the silicon oxide film, the content of aluminum is 0.25% by weight or less, the content of calcium is 2.0% by weight or less, the content of boron is 2.0% by weight or less, and the content of carbon is 6% by weight or less.

[0321] (Note 5)

[0322] The optical member according to any one of Note 1 to Note 4, wherein

[0323] The silicon oxide film is a sputtering film or an evaporation film.

[0324] (Note 6)

[0325] The optical member according to any one of Notes 1 to 5, wherein

[0326] When the composition of the silicon oxide contained in the silicon oxide film is represented by SiOx, 1.90 ≤ x ≤ 2.00.

[0327] (Note 7)

[0328] The optical member according to any one of Note 1 to Note 6, wherein

[0329] The average height of the fine concavo-convex structure from the bottom of the concave portion to the top of the convex portion is 150 nm to 600 nm, and the average period is 150 nm to 450 nm.

[0330] (Note 8)

[0331] The optical member according to any one of the following notes 1 to 8, wherein

[0332] The contact angle of water on the surface of the water-repellent film is 140° or more.

[0333] (Note 9)

[0334] The optical member according to any one of the following notes 1 to 8, wherein

[0335] The haze of the optical member is 2.5% or less.

[0336] (Note 10)

[0337] The optical member according to any one of the following notes 1 to 9, wherein

[0338] The average reflectance when light having a wavelength of 400 nm to 700 nm is perpendicularly incident on the surface is 1% or less.

[0339] (Note 11)

[0340] The optical member according to any one of the following notes 1 to 10, wherein

[0341] The transmitted wave aberration for light having a wavelength of λ nm is λ / 5 or less.

[0342] (Note 12)

[0343] The optical member according to any one of the following notes 1 to 11, wherein

[0344] An intermediate layer having a different refractive index from the silicon oxide film for reducing the reflectance of incident light is provided between the optical substrate and the silicon oxide film.

[0345] (Note 13)

[0346] A method for manufacturing an optical member, comprising:

[0347] A film forming step of forming a silicon oxide film on one face of an optical substrate by a vapor phase film forming method;

[0348] A mask forming step of forming an etching mask on the silicon oxide film;

[0349] An etching step of forming a fine concavo-convex structure on the surface of the silicon oxide film by etching the silicon oxide film through the etching mask by a vapor phase etching method; and

[0350] A coating step of forming a water-repellent film containing a fluorine compound on the surface of the fine concavo-convex structure,

[0351] In the etching step, the distance of etching to the top of the largest convex portion of the fine concavo-convex structure from the surface of the optical substrate side of the silicon oxide film becomes smaller than the film thickness of the silicon oxide film immediately after film formation.

[0352] In addition, the disclosure of Japanese Patent Application No. 2023-054253 filed on March 29, 2023, is incorporated by reference herein in its entirety. All documents, patent applications, and technical standards cited in this specification are incorporated by reference to the same extent as if each individual document, patent application, or technical standard were specifically and individually indicated to be incorporated by reference.

[0353] Symbol Explanation

[0354] 1, 2 - optical member, 1a - surface of optical member, 5 - water tank, 6 - pure water, 10 - optical substrate, 12 - intermediate layer, 12a - high refractive index layer, 12b - low refractive index layer, 20 - silicon oxide film, 22 - fine concavo-convex structure, 30 - water repellent film, 40 - concavo-convex structure layer (mask), 42 - Al-containing thin film, 50 - water droplet, 50e - end portion of water droplet, 52, 54 - image of water droplet, 60 - SiO2 target, 62 - optical glass sheet.

Claims

1. An optical member comprising an optical substrate having a smooth surface and a silicon oxide film provided on the optical substrate, the silicon oxide film has a fine concavo-convex structure on a surface, a water-repellent film containing a fluorine compound is provided on a surface of the fine concavo-convex structure, an adhesion of the surface of the water-repellent film is 0.2 mN / m to 6 mN / m.

2. The optical member according to claim 1, wherein The fluorine compound has a -(OCF2CF2) n group and does not include a -(OCF2) m group, wherein n is an integer of 1 or more, and m is an integer of 1 or more.

3. The optical member according to claim 1, wherein a sliding angle of a 5 μL water droplet on the surface of the water-repellent film is 10° or less.

4. The optical member according to claim 1, wherein in the silicon oxide film, an aluminum content is 0.25% by weight or less, a calcium content is 2.0% by weight or less, a boron content is 2.0% by weight or less, and a carbon content is 6% by weight or less.

5. The optical member according to any one of claims 1 to 4, wherein the silicon oxide film is a sputtering film or an evaporation film.

6. The optical member according to any one of claims 1 to 4, wherein when a composition of the silicon oxide contained in the silicon oxide film is represented by SiOx, 1.90 ≤ x ≤ 2.

00.

7. The optical member according to any one of claims 1 to 4, wherein an average height from a bottom of a concave portion to a top of a convex portion of the fine concavo-convex structure is 150 nm to 600 nm, and an average period is 150 nm to 450 nm.

8. The optical member according to claim 1, wherein a contact angle of water on the surface of the water-repellent film is 140° or more.

9. The optical member according to any one of claims 1 to 4, wherein a haze of the optical member is 2.5% or less.

10. The optical member according to any one of claims 1 to 4, wherein an average reflectance when light having a wavelength of 400 nm to 700 nm is perpendicularly incident on the surface is 1% or less.

11. The optical member according to any one of claims 1 to 4, wherein a transmission wave aberration for light having a wavelength of λ nm is λ / 5 or less.

12. The optical member according to any one of claims 1 to 4, wherein an intermediate layer having a different refractive index from the silicon oxide film for reducing a reflectance of incident light is provided between the optical substrate and the silicon oxide film.

13. A method for manufacturing an optical member, comprising: a film forming step of forming a silicon oxide film on one face of an optical substrate by a vapor phase film forming method; a mask forming step of forming an etching mask on the silicon oxide film; an etching step of forming a fine concavo-convex structure on a surface of the silicon oxide film by etching the silicon oxide film through the etching mask by a vapor phase etching method; and a coating step of forming a water-repellent film containing a fluorine compound on a surface of the fine concavo-convex structure, in the etching step, etching is performed to a distance from a surface of the optical substrate side of the silicon oxide film to a top of a maximum convex portion of the fine concavo-convex structure becomes smaller than a film thickness of the silicon oxide film immediately after film formation.

Images