Anti-reflective articles and methods for manufacturing the same

Abstract

An article having an anti-reflective structure is provided. The antireflective article includes a substrate having a surface and a bulk, and an array of antireflective nanostructures along the surface of the substrate. Each antireflective nanostructure in the array of antireflective nanostructures is supported by the bulk of the material. Each antireflective nanostructure in the array of antireflective nanostructures tapers from the bulk of the substrate to define a respective peak. At least some of the antireflective nanostructures in the array of antireflective nanostructures are connected to adjacent antireflective nanostructures in the array of antireflective nanostructures via respective interconnects. Each interconnect is added to the bulk of the substrate supporting the antireflective nanostructures. Each interconnect is located at or on a midpoint between the peak of the antireflective nanostructure and the bulk of the substrate.

Description

Technical Field

[0001] The present invention disclosed herein generally relates to antireflective surfaces. Cross-reference to related applications

[0002] This application claims priority to U.S. Provisional Application No. 63 / 105,673, filed on October 26, 2020, entitled "Antireflection with Interconnect Structure", the entire disclosure of which is hereby expressly incorporated by reference herein.

Background Art

[0003] Antireflective surfaces have been used in a variety of situations, including solar modules, solar collectors, optical components, and displays. Antireflection techniques applied to the covers of solar panels can increase the transmission of light into the module. Solar concentrators benefit from a reduction in light reflection or an increase in transmission to enhance the capture or conversion of solar energy into thermal energy. In optical components, reflection and scattering contribute to noise such as lens flare, which can degrade signal quality. In the case of electronic displays, reflection of light from the surface of the cover can interfere with light specifically emitted or reflected by the display.

[0004] Specular reflection of incident light or other electromagnetic radiation occurs at an interface where there is a sharp change in refractive index from one medium to a second medium. This change results in refraction and transmission in addition to reflection. The amount of reflection increases as the difference in refractive indices of the two materials increases. Also, reflection increases as the angle of incidence increases from perpendicular to the surface.

[0005] Various attempts have been made to reduce reflection. Conventional thin-film dielectric coatings add a layer of material to the surface, but generally cannot substantially compensate for large reflections at wide angles from the normal. Other approaches include surface texturing and the use of nanoparticles. However, when the surface texture and particle feature size are close to or larger than the wavelength of the incident electromagnetic radiation, high scattering can still occur without increasing transmittance.

[0006] Conventional anti-reflective techniques use thin film coatings of dielectric materials such as solid or porous MgF2, SiO2, ZnSe, SnO2, and ZnS. When deposited to a thickness of half or a quarter of the target wavelength, such layers can particularly reduce reflections near that wavelength. However, the anti-reflective effect for other non-specific wavelengths is limited. Furthermore, such anti-reflective effects are typically tuned to perpendicular incidence, where light strikes a surface perpendicular to the surface. Such anti-reflective coatings lack the ability to neutralize the increase in Fresnel reflection as the angle of incidence deviates from the normal. In addition, since such layers may have a different coefficient of thermal expansion than the substrate, thermal cycling can lead to delamination, delamination, or other damage.

[0007] Microstructured surfaces have also been used to scatter incident light. Microstructures are effective at various angles. However, light scattering contributes to high haze and can accumulate dirt inside the structure without necessarily increasing transmittance.

[0008] Subwavelength nanostructured surfaces exhibited haze adjustment depending on their physical dimensions. However, due to their anti-reflective optical effects, such structures typically have a large depth-to-width ratio, making them mechanically fragile. The structures are also subjected to abrasion and tearing in the environment. Furthermore, the structural integrity of the structures poses challenges during assembly, transportation, and field application. Thus, the small subwavelength features of such nanostructured surfaces can be mechanically damaged in multiple ways. Nanopillars and similar structures with large depth-to-width ratios are particularly susceptible to such damage. While larger structures have higher mechanical resistance, such larger structures scatter light without increasing transmittance, and fragments can accumulate on their surface. [Overview of the project]

[0009] According to one aspect of the present disclosure, an anti-reflective article comprises a substrate including a surface and bulk, and an array of anti-reflective nanostructures (sometimes referred to as “anti-reflective nanostructures”) along the surface of the substrate. Each anti-reflective nanostructure in the array of anti-reflective nanostructures is supported by the bulk of the substrate. Each anti-reflective nanostructure in the array of anti-reflective nanostructures tapers away from the bulk of the substrate, defining its respective peak (sometimes referred to as “peaks”). At least some of the anti-reflective nanostructures in the array of anti-reflective nanostructures are connected to adjacent anti-reflective nanostructures in the array of anti-reflective nanostructures via their respective interconnections, each interconnection being added to the bulk of the substrate supporting the anti-reflective nanostructure. Each interconnection is located at or on an intermediate point between the peak of the anti-reflective nanostructure and the bulk of the substrate.

[0010] According to another aspect of the present disclosure, an anti-reflective article comprises a substrate having a surface and bulk, and an array of anti-reflective nanostructures along the surface of the substrate. Each anti-reflective nanostructure in the array of anti-reflective nanostructures is supported by the bulk of the substrate. Each anti-reflective nanostructure in the array of anti-reflective nanostructures tapers away from the bulk of the substrate, defining its respective peak. The height at which adjacent anti-reflective nanostructures in the array of anti-reflective nanostructures are connected by interconnections varies across the substrate. At least some of the interconnections are located equidistant from the peaks of the anti-reflective nanostructures and the bulk of the substrate.

[0011] According to yet another aspect of this disclosure, an anti-reflective article comprises a substrate including a surface and bulk, and an array of anti-reflective nanostructures along the surface of the substrate. Each anti-reflective nanostructure in the array of anti-reflective nanostructures is supported by the bulk of the substrate. Each anti-reflective nanostructure in the array of anti-reflective nanostructures tapers off from the bulk of the substrate, defining its respective peak or summit. Some of the anti-reflective nanostructures in the array of anti-reflective nanostructures are connected to adjacent anti-reflective nanostructures in the array of anti-reflective nanostructures via a portion of the substrate, in addition to the bulk of the substrate. This portion defines a saddle-shaped portion of the surface.

[0012] According to yet another aspect of the present disclosure, an anti-reflective article comprises a substrate having a surface and a bulk, the surface being shaped to define an array of anti-reflective nanostructures, each anti-reflective nanostructure in the array tapering from the bulk of the substrate to define its respective peak, thereby defining a distribution of material across the entire surface of the substrate. Part of the material distribution is located between adjacent anti-reflective nanostructures in the array of anti-reflective nanostructures such that adjacent anti-reflective nanostructures in the array of anti-reflective nanostructures are interconnected by part of the material distribution.

[0013] According to yet another aspect of the present disclosure, a method for manufacturing an anti-reflective article includes the steps of forming a mask having a lamellar nanopattern on a substrate and etching the substrate through openings in the mask defined by the lamellar nanopattern. Etching the substrate includes performing anisotropic etching such that an arrangement of tapered nanostructures is formed according to the lamellar pattern.

[0014] According to yet another aspect of the present disclosure, a method for manufacturing an anti-reflective article comprises forming a mask having a nanopattern of holes on a substrate and etching the substrate through the holes in the mask defined by the nanopattern. Etching the substrate involves performing anisotropic etching such that an arrangement of tapered nanostructures is formed according to the nanopattern of holes. The nanopattern of holes is configured such that the arrangement of tapered nanostructures has saddle-shaped surfaces at the interconnections between adjacent tapered nanostructures in the arrangement of tapered nanostructures.

[0015] In relation to any one of the embodiments described herein, the articles and / or methods described herein may or may not otherwise include, or may not include, one or more combinations of the following embodiments or features: The substrate includes each interconnection. The interconnection is provided by a portion of the substrate between adjacent anti-reflective nanostructures in an array of anti-reflective nanostructures. The portion of the substrate defines a saddle-shaped portion of the surface. The anti-reflective article further includes a distribution of nanoparticles arranged across the surface of the substrate such that each interconnection is provided by each subset (sometimes referred to as a “subset”) of the nanoparticle distribution. The nanoparticles in each subset closest to a peak are larger than the nanoparticles in each subset closest to the bulk. The anti-reflective article further includes a distribution of flakes across the substrate. Each flake in the flake distribution is in contact with a peak of linked anti-reflective nanostructures in an array of anti-reflective nanostructures such that each flake in the flake distribution provides one or more interconnections. The anti-reflective article further includes a filler that crosses a substrate placed in a cavity defined by an array of anti-reflective nanostructures, such that each interconnection is provided by the respective portion of the filler. The anti-reflective article further includes a continuous film that extends across the array of anti-reflective nanostructures, such that the continuous film provides interconnections between the peaks of the anti-reflective nanostructures. The arrangement of the anti-reflective nanostructures is configured such that a pair of adjacent anti-reflective nanostructure peaks in the arrangement are spaced at a distance smaller than the wavelength of light incident on the anti-reflective article. The arrangement of the anti-reflective nanostructures establishes the effective refractive index of light incident on the anti-reflective article. Each anti-reflective nanostructure in the array of anti-reflective nanostructures is configured such that the effective refractive index exhibits a continuous gradient from each peak of the anti-reflective nanostructure to the base of the anti-reflective nanostructure. The substrate includes a base substrate and a layer supported by the base substrate. The layer includes an array of anti-reflective nanostructures. The surface of the substrate is shaped to define the arrangement of anti-reflective nanostructures. Each pair of adjacent anti-reflective nanostructures in the array of anti-reflective nanostructures is interconnected by the respective parts of the substrate. Adjacent anti-reflective nanostructures in the array of anti-reflective nanostructures define a saddle-shaped surface.The anti-reflective article further includes multiple nanoparticles dispersed across the array of anti-reflective nanostructures such that each pair of adjacent anti-reflective nanostructures in the array of anti-reflective nanostructures is interconnected by a subset of multiple nanoparticles. The number of nanoparticles in each subset varies as the depth at which adjacent anti-reflective nanostructures in the array of anti-reflective nanostructures are interconnected changes. The arrangement of nanoparticles in each subset varies as the depth at which adjacent anti-reflective nanostructures in the array of anti-reflective nanostructures are interconnected changes. Each subset includes nanoparticles of various sizes. The material distribution includes multiple nanoparticles arranged within cavities defined by the array of anti-reflective nanostructures. The material distribution includes a distribution of flakes across the substrate such that each flake in the flake distribution interconnects two or more of the peaks of the anti-reflective nanostructures. The material of the distribution includes fillers arranged across the substrate within cavities defined by the arrangement of anti-reflective nanostructures. The distribution material includes a continuous film that extends across the array of anti-reflective nanostructures, such that the continuous film provides interconnections between the peaks of the anti-reflective nanostructures.

[0016] For a more complete understanding of this disclosure, the following detailed description and accompanying drawings should be referenced. In the drawings, similar elements are identified by the same reference numeral. [Brief explanation of the drawing]

[0017] [Figure 1] This is a schematic side view of an anti-reflective article having an array of interconnected nanostructures, as an example. [Figure 2] This figure shows the anti-reflective article according to claim 1, relating to light at a different angle of incidence. [Figure 3] This is a graph plot of the light transmittance of an anti-reflective article for various incident angles, and the anti-reflective article has an arrangement of interconnected nanostructures on both sides of the substrate, according to one embodiment. [Figure 4] This figure shows planar and cross-sectional scanning electron microscope (SEM) images of an array of interconnected nanostructures according to one embodiment. [Figure 5] This figure shows a planar SEM image of an interconnected nanostructure array obtained from an etching procedure in which the level of selectivity between the etching mask and the substrate is varied, according to one embodiment. [Figure 6] These are a top view and a cross-sectional view of an anti-reflective article having an array of nanostructures interconnected at various depths, according to one embodiment. [Figure 7] This figure shows cross-sectional and planar SEM images of an array of interconnected nanostructures according to one embodiment. [Figure 8] This figure shows a schematic side view of an anti-reflective article having an array of interconnected nanostructures at various depths according to one embodiment, and a schematic plan view of a hole-based mask used to manufacture the nanostructures. [Figure 9] This figure shows cross-sectional and planar SEM images of an anti-reflective article having an array of interconnected nanostructures at various depths, according to one embodiment. [Figure 10] This figure shows a cross-sectional SEM image of an example of an anti-reflective article having an array of nanostructures interconnected at various depths. [Figure 11] This figure shows oblique cross-sectional SEM images of an anti-reflective article having an array of nanostructures interconnected at various depths, according to another embodiment. [Figure 12] This figure shows a planar SEM image of an example of an anti-reflective article having an array of nanostructures with a shallow etching depth. [Figure 13] This is a schematic cross-sectional view of an anti-reflective article having an arrangement of nanostructures interconnected by multiple nanoparticles, according to one embodiment. [Figure 14] This figure shows a cross-sectional SEM image of an anti-reflective article having an interconnected arrangement of nanoparticles in a nanostructure according to one embodiment. [Figure 15] This is a schematic cross-sectional view of an anti-reflective article having an array of nanostructures interconnected by fillers in each cavity or gap within the array, according to one embodiment. [Figure 16] This is a schematic cross-sectional view of an anti-reflective article having an array of nanostructures interconnected by a continuous blanket or film, according to one embodiment. [Figure 17] FIG. is a SEM image of an anti-reflection article having an array of nanostructures interconnected by a continuous blanket according to one embodiment. [Figure 18] FIG. is a schematic cross-sectional view of an anti-reflection article having an array of nanostructures interconnected by a distribution of flakes according to one embodiment. [Figure 19] FIG. is a schematic plan view of an anti-reflection article having an array of nanostructures interconnected by a distribution of flakes according to one embodiment. [Figure 20] FIG. is a side view of a superhydrophobic glass substrate having interconnected nanostructures and deposited hydrophobic fluorocarbon molecules to show the water contact angle on its surface according to one embodiment. DETAILED DESCRIPTION

[0018] Embodiments of the disclosed articles, systems, and methods can take various forms. Specific embodiments are shown in the drawings and the content described below, and it should be understood that what is intended by the present disclosure is illustrative. That is, the present disclosure is not intended to limit the present invention to the specific embodiments described and illustrated herein.

[0019] Anti-reflective articles having interconnected nanostructures are described. Methods for manufacturing such articles are also described. The interconnections between adjacent nanostructures provide mechanical stability without adversely affecting optical performance. Thus, a robust subwavelength array of nanostructures is provided. The interconnections are also configured so that the gradual change in refractive index provided by the nanostructures is still provided. The interconnections also maintain the self-cleaning properties of the anti-reflective article. These properties and other characteristics of the anti-reflective article are maintained despite the interconnections being located at or above the midpoints of the nanostructures. As described and illustrated herein, each interconnection is located at or above the midpoint between the peak of the nanostructure and the bulk of the substrate on which the nanostructures extend. The interconnected nanostructured surface is provided to be compatible with a surface configured for superhydrophilic or superhydrophobic properties and / or oleophobicity and other surface characteristics.

[0020] The disclosed articles and methods can provide various types of interconnections. In some cases, the interconnection is an integral portion of the substrate on which the nanostructure is formed. In such cases, the depth to which the substrate is etched to form the nanostructure varies. Thus, the surface of the substrate may be saddle-shaped, as shown and described herein. Alternatively or additionally, the interconnection is provided by nanoparticles dispersed throughout the substrate. In some cases, the size of the nanoparticles gradually increases with increasing distance from the substrate bulk. Thus, cavities between adjacent nanostructures can be filled more effectively. Alternatively or additionally, the interconnection may be provided by a distribution of flakes in contact with the peaks of the nanostructure. Further options include fillers placed in the cavities and / or continuous blankets or other films across the peaks. In each of these cases, the interconnection may consist of, or otherwise include, a material such that the anti-reflective properties and performance of the disclosed article are maintained.

[0021] The disclosed anti-reflective articles include an array of nanostructures that provide a refractive index gradient. The refractive index gradient may be configured to be presented by moth-eye and / or other nanostructure arrays. Thus, the disclosed anti-reflective articles can provide a broad-spectrum, omnidirectional anti-reflective surface that can self-clean while maintaining mechanical and thermal durability.

[0022] The disclosed anti-reflective articles can be applied as covers for solar panels. The anti-reflective properties result in greater light transmission, enabling higher energy generation. The self-cleaning properties of the disclosed anti-reflective articles reduce the need for frequent cleaning, ensuring maximum energy generation at all times. The mechanical and thermal stability of the disclosed anti-reflective articles is beneficial in several respects, including, for example, during manufacturing, assembly, transportation, installation, and use. Therefore, their durability matches that of solar panels, resulting in a long operating life.

[0023] The disclosed anti-reflective articles are not limited to use in solar panels and are useful for a wide range of applications. For example, the disclosed anti-reflective articles can be used in connection with devices and systems such as optical components, lenses, laser components, windows, picture frames, display boxes, LED and OLED lighting, and electronic displays. In electronic displays, the durable reduction of reflections provided by the disclosed articles does not introduce haze. Therefore, it can provide an increased contrast ratio for both light-emitting and reflective displays.

[0024] As described below, the anti-reflective surface of the disclosed anti-reflective article may include subwavelength nanostructures along the surface having transmission or absorption properties over a range of electromagnetic wavelengths. The structures have peaks to establish a gradual change in refractive index, which is in contrast to flat peaks that may produce, for example, discrete step changes in refractive index. The structures are interconnected at or below the peaks to enhance high mechanical resistance. The structures may exhibit self-cleaning properties. Furthermore, a self-cleaning surface is desirable when the substrate is used as a cover material.

[0025] The interconnects and other elements of the disclosed anti-reflective articles may function across a broad spectrum and at various angles of incidence. In some cases, the disclosed anti-reflective articles provide a highly transparent surface with controlled variable haze. Adjustable haze is important for controlling the level of transparency of the transparent substrate.

[0026] Interconnected nanostructures may feature lateral dimensions smaller than the wavelength of light. For example, the lateral spacing between peaks of a nanostructure may be less than 100 nanometers (nm). The vertical dimensions of a nanostructure may be comparable to or greater than the wavelength of light. For example, a nanostructure may have a height greater than 100 nm.

[0027] The nanostructure is characterized by sub-wavelength transverse dimensions, and the effective refractive index can be averaged over the surface cross-sectional area and varies over the depth (or vertical dimension) of the nanostructure. Further details are shown in relation to the example in Figure 1.

[0028] The nanostructure establishes an interface between two media characterized by a continuous gradient of effective refractive index from the first medium through the surface nanotexture to the second medium, creating a broad-spectrum anti-reflection effect.

[0029] The nanostructure has sufficient depth relative to the wavelength of light at any incident angle, creating a continuous gradient of refractive index for incident light at all angles, resulting in an omnidirectional anti-reflective effect characterized by high transmittance at all angles. Further details are shown in relation to the example in Figure 2.

[0030] Nanostructures feature sub-wavelength transverse dimensions, allowing for haze control, such as minimizing haze at smaller dimensions.

[0031] The nanostructures are interconnected to provide mechanical stability while maintaining a continuous gradient of the effective refractive index from the top to the bottom of the structure. The nanostructures may be connected at various depths, either intermediate, at the top, or a combination of both.

[0032] Nanostructures may include surface deposition of molecules or elements with high or low surface energy to impart surface superhydrophilicity or superhydrophobic properties, respectively, as well as other surface features such as oleophobicity.

[0033] Another aspect of the present invention teaches a method for fabricating thermally and mechanically stable interconnected subwavelength nanostructures on at least one surface of a substrate such as glass, polymer, semiconductor, ceramic, and other materials, thereby creating a broad-spectrum and omnidirectional anti-reflective surface that may be characterized by surface properties such as superhydrophobicity, superhydrophilicity, and oleophobicity.

[0034] Nanostructures can be fabricated within a substrate using reactive ion etching or any other dry or wet etching method, such that the nanostructures are interconnected and also provide anti-reflective properties.

[0035] Using hard masks of various designs, nanostructures can be etched at the top, center, or in combination at different parts of the nanostructure, or at interconnected nanostructures. The top view of the hard mask contains separate islands or a continuous network of interconnected shapes. In some cases, the two-dimensional shape may include one or a combination of regular geometric shapes such as circular and / or parabolic shapes and / or various irregular shapes.

[0036] The hard mask can vary in composition, density, and thickness across different regions of the surface. Varying the composition of the hard mask features can primarily alter its selectivity or durability to the substrate when exposed to etching. Varying the density or thickness of the mask can lead to varying etching rates. Variations in mask degradation across different lateral regions allow the substrate surface to be exposed for different periods of time, thus enabling surface etching to create a variety of interconnected nanostructures with varying etching depths and geometric shapes. Furthermore, using a combination of isotropic and anisotropic etching of the substrate material can establish longer durations of lateral etching on the top of the nanostructures, creating tapered etching shapes.

[0037] The disclosed method may include modifying the surface of the nanostructure. For example, the composition of the nanostructure can be changed.

[0038] Nanoparticles, porous materials, and polymers can be deposited between nanostructures to connect them, provide anti-reflective properties, and enhance mechanical durability. Deposition methodologies may include solution-based deposition, vapor deposition, or chemical vapor deposition, or vacuum-based deposition such as plasma-enhanced deposition or atomic layer deposition.

[0039] The tops of the nanostructures may be connected via the deposition of a material that covers and connects multiple nanostructures. The deposition methodology may include solution-based deposition of planar particles, vacuum-based deposition such as chemical vapor deposition and sputtering, and contract printing.

[0040] Figure 1 shows an article 100 having interconnected nanostructures 102 with interconnections 104 at various heights and depths according to one embodiment. Article 100 establishes an interface containing a medium, the substrate 106 having a refractive index of n2, and the external medium having a refractive index of n1. Cross sections CS1, CS2, and CS3 show the cross sections (CS) of the nanostructure 102 at various depths when light strikes the surface with perpendicular incidence (perpendicular to the surface). White circles represent the substrate material having a refractive index of n2, and the shaded areas represent the external medium having a refractive index of n1. Due to the subwavelength characteristics of the nanostructure 102, the wavefront shows the cross-sectional average of the refractive index. As a result, the effective refractive index changes continuously from n1 to n2 as the light travels from the top to the bottom of the nanostructure 102. Figure 1 also includes a graph plot 108 showing various possible continuous gradients in refractive index. The vertical lines in the refractive index diagram represent different profiles or depths of the changing refractive index, which depend on the shape and height of the nanostructure 102.

[0041] Figure 2 shows a pair of cross-sections CS1 and CS2 of article 100 when light strikes the surface of article 100 at an oblique angle (not perpendicular to the surface). The continuous gradient and effective refractive index in the cross-sectional region can be observed with respect to the distance along the path of light. Cross-sections CS1 and CS2 refer to planes perpendicular to the path of light.

[0042] Figure 3 shows a graph plot of total light transmittance for a glass substrate treated with nanotexturing on both surfaces. Transmittance is graphed as a function of wavelength at various incidence angles. Normal incidence is represented as 90 degrees, and other incidence angles are also measured as the angle of the beam relative to the substrate surface. In other words, 70 degrees from the normal is represented as 160 degrees (90 + 70 = 160 degrees) in this figure.

[0043] Part A of Figure 4 shows a top SEM image of an example article 400. Article 400 includes nanostructures 402 interconnected within a substrate 404 fabricated by etching a material (in this case, glass) via the use of a hard mask having a pattern similar to that of white or brighter areas. Examples of masks and further details on how to fabricate such masks are provided below. Part B of Figure 4 shows a cross-section of article 400 to illustrate how the nanostructures 402 are interconnected at various depths. In this embodiment, the cross-sectional regions of the nanostructures 402 may resemble, or include, peaks 406, walls 408, or double peaks 410.

[0044] Figure 5 shows SEM images of top views of exemplary articles 500 (part A), 502 (part B), 504 (part C), and 506 (part D), each having interconnected nanostructures fabricated by etching the substrate through hard masks of different mask shapes using an etchant that changes the selectivity between the mask and the substrate.

[0045] Figure 6 shows a top view and a cross-sectional view of article 600 having interconnected nanostructures 602-605, where nanostructures 602 are interconnected at varying depths within the nanostructure 602. In this embodiment, nanostructures 602-605 also have varying heights. For simplicity, only nanostructures 602 and 603 are shown in the top view. As shown in the top view, nanostructures 602-605 have a layered or Mazzey-like layered pattern. One or more of the interconnections define a hyperbolic paraboloid where the peaks of nanostructure 602 intersect each other at the center.

[0046] Figure 7 shows interconnected nanostructures on the surface of a glass substrate fabricated by a hard mask having a shape similar to an array of islands. The nanostructures are characterized by varying heights and depths, and are interconnected at various depths. In this example, part A of Figure 7 shows a cross-section perpendicular to the surface. Part B of Figure 7 shows a cross-section at an angle not perpendicular to the surface, revealing pores and interconnected substrate material in the diagonal cross-section. Part C of Figure 7 shows a view at 30 degrees to the surface. Part D of Figure 7 shows a top view of the nanostructured substrate surface, which also resembles the geometric shape of the hard mask.

[0047] Figure 8 shows a cross-sectional view of an article 800 having interconnected nanostructures 802 within a substrate 804 having a network matrix. When viewed from above, article 800 exhibits a perforated geometric shape. Figure 8 also shows a schematic top view of article 800 during manufacturing. In the top view, the darkened areas 806 represent valleys within the nanostructures 802 and roughly correspond to areas of the substrate 804 not protected by the mask for etching. The cross-sectional view along the dashed line features a double peak 808 connected in the center by a hyperbolic paraboloid (saddle-shaped) surface 810. In the top view, the bright areas are regions where the surface was covered by the mask during etching, and the dark areas are regions where holes were formed during etching. The hyperbolic surface is formed due to differences in the lateral dimensions of the mask in the intermediate portion. Moving along the dashed line in the top view changes the lateral dimensions of the mask perpendicular to the dashed line.

[0048] Part A of Figure 9 shows an SEM image of the top surface of interconnected structures on the substrate surface. Part B of Figure 9 shows a top view of the same nanostructured surface, where darker areas indicate deeper valleys in the nanostructure. The bright, network-like areas also resemble the geometric shape of a mask used to etch such nanostructures. Part B of Figure 9 shows an SEM cross-section of the same structure. The peaks are interconnected and do not resemble grass-like or needle-like structures.

[0049] Part A of Figure 10 shows an SEM image of a perspective view of interconnected nanostructures on a substrate surface with interconnected peaks at various depths. The oblique cross-section reveals pores within the interconnected matrix of the substrate material and reveals the interconnected nature of the nanostructures. Part B of Figure 10 shows an interconnected nanostructure surface with a shallower etching depth.

[0050] Parts A and B of Figure 11 show oblique cross-sectional SEM images of a substrate having interconnected nanostructures on its surface. The oblique cross-section reveals a series of pores within the matrix of the interconnected substrate material, revealing the interconnected nature of the nanostructures.

[0051] Parts A and B in Figure 12 are similar to the examples in Figures 9 to 12, but show a top view of a nanostructured surface with a shallow etching depth.

[0052] Part A of Figure 13 shows a schematic cross-sectional view of article 1300 having nanostructures 1302 interconnected with particles 1304 connected to the upper region of nanostructures 1302. Part B of Figure 13 shows a schematic cross-sectional view of article 1306 having nanostructures 1308 interconnected with heterogeneous (different) particles 1310 filling the gaps between nanostructures 1308.

[0053] Figure 14 shows a cross-sectional SEM image of an article having a substrate with interconnected nanostructures on its surface. In this embodiment, the article includes nanoparticles that interconnect separate nanostructures composed of a substrate material.

[0054] Figure 15 shows a schematic cross-sectional view of an article 1500 having a substrate 1502 having interconnected nanostructures 1504 on its surface. In this example, the gaps between the nanostructures 1504 are filled with different materials 1506.

[0055] Figure 16 shows a schematic cross-sectional view of an article 1600 including a substrate 1602 having interconnected nanostructures 1604 on its surface. In this embodiment, the article 1600 includes a continuous film 1606 or blanket of material connecting a plurality of nanostructures 1604.

[0056] Parts A and B of Figure 17 show SEM images of an exemplary article having interconnected nanostructures within a substrate, where the peaks of the nanostructures are interconnected by a continuous blanket of material. Part A of Figure 17 shows the surface relief in the blanket of material, characterized by raised peaks and recessed valleys.

[0057] Figure 18 shows a schematic cross-sectional view of an article 1800 including a substrate 1802 having nanostructures 1804 interconnected on its surface. In this embodiment, a subset or more of the nanostructures 1804 are interconnected by respective flakes 1806 of nano- or micro-scale material.

[0058] Figure 19 shows a schematic top view of article 1800 shown in Figure 18.

[0059] Figure 20 shows the water contact angle on a superhydrophobic glass substrate characterized by interconnected nanostructures and hydrophobic fluorocarbon molecules deposited on their surface. In this example, the contact angle is measured to be as low as 162 degrees.

[0060] The disclosed articles and methods may provide substrates having high transparency, low reflectivity, or both high transparency at all angles and a broad wavelength, while maintaining high mechanical and thermal stability. The disclosed articles and methods are applicable to a variety of rigid or flexible substrates, including plastics or polymers, glass, and semiconductors. Nanostructures are etched onto one or more surfaces of the substrate. The surface treatment may be applied to a homogeneous substrate or a composite substrate, for example, one coated with an additional material, and then the treatment is applied to the coated material. Thus, the term “substrate” is used herein to include a substrate having a base substrate and one or more layers supported by the base substrate.

[0061] Nanostructures are sub-wavelengths in lateral dimensions, where “sub-wavelength” refers to a physical dimension smaller than the wavelength of the incident light or electromagnetic wave. The wavelength of the incident light may be within or beyond the visible spectrum. The disclosed articles are useful in relation to a wide range of wavelengths.

[0062] The nanostructure is smaller than the wavelength of light such that at each depth of the nanostructure, there exists an effective refractive index that averages across the entire cross-section at that depth. For light striking the surface at a non-perpendicular or "wide-angle" setting, the cross-section of the effective refractive index is perpendicular to the angle of incidence. Figures 1 and 2 illustrate how subwavelength nanostructures generate a continuous gradient of the effective refractive index from one medium to a second medium through the nanostructure. Figure 1 shows incident light at perpendicular incidence, and Figure 2 shows incident light at a wide angle that is not perpendicular to the surface. Due to the subwavelength lateral dimension of nanostructure 102, the effective refractive index gradient is averaged across multiple nanostructures 102. An example of a high transmission spectrum of nanotextured glass is shown in Figure 3, demonstrating high transmittance and, consequently, low reflectance across a wide spectrum at various angles of incidence.

[0063] Nanostructures consist of or are formed within a substrate, which includes polymers and plastics, glass, semiconductors, ceramics, and other materials. Examples of polymers and plastics include, but are not limited to, polycarbonate, polyethylene, polylactic acid, and polyethylene terephthalate. Glass may include, among other things, borosilicates, soda lime, aluminosilicates, and fused silica. Examples of other materials include silicon, gallium arsenide, perovskites, oxides, nitrides, and carbides.

[0064] Nanostructures are interconnected. This interconnected nature of nanostructures provides mechanical durability to fragile nanostructures that are susceptible to mechanical fracture.

[0065] The lateral dimensions of the structure (e.g., the spacing between peaks) can be configured to control scattering, and therefore haze. Larger dimensions produce haze, while dimensions much smaller than the wavelength of the relevant light do not scatter and therefore do not produce haze. The depth of the nanostructure is comparable to or greater than the relevant wavelength of light, such that there is an effective continuous change in refractive index along the relevant optical path length of the light. For light in the visible spectrum, for example, the depth may be as small as 100 nanometers. In other cases, other depths may be used.

[0066] Nanostructures are fabricated by etching or nanoimprinting onto a target substrate. Etching can include wet etching such as acid etching, dry etching such as reactive ion etching, or plasma etching under vacuum or atmospheric pressure. Various geometric shapes of nanostructures can be etched using masks of various geometric shapes.

[0067] In Figures 4 and 5, lamellar or maze-like masks can be used in conjunction with reactive ion etching to create interconnected structures throughout the top and interior of the nanostructure, creating interconnected structures that are roughly equivalent to a range of peaks. The top view of the nanostructure may look like elongated islands or interconnected mazes. Peaks and ridges are connected at various depths. The height and depth of the structure may be modified (for example, as shown in Figure 6). Tapered structures with a small upper cross-section and a large lower cross-section are created to generate a continuous gradient of the effective refractive index, for example, as shown in Figure 1.

[0068] Figure 7 shows that interconnected nanostructures can be etched using a masking pattern with circular or irregularly shaped islands, where the structures are tapered and their height and depth may vary to produce a continuous gradient of the effective refractive index. Variation in island size and separation distance allows for variations in the etching initiation time for different regions of the surface, where the island edges can be gradually removed by the etchant.

[0069] In Figures 8 to 12, interconnected mask patterns with holes that expose the substrate can be used to etch interconnected nanostructures, and the interiors of the structures are connected at various depths. The nanostructures are tapered, and the height and depth of the structures can be modified to generate interconnected structures with a continuous gradient of effective refractive index.

[0070] By using an etching process that simultaneously performs isotropic etching (chemical reaction) and anisotropic etching (ionic bombardment), tapered interconnect nanostructures can be fabricated using a single etching step. Such etching recipes vary depending on the substrate and masking material. The etchant contains at least one component that chemically reacts with the substrate. The etchant can also etch the substrate and mask at different rates, where the etchant is more chemically reactive with the substrate than with the mask. The rates of anisotropic and isotropic etching with respect to the mask differ from those of the substrate. Once the region of the substrate between the mask begins to etch, isotropic etching contributes in the lateral etching direction. Simultaneously, anisotropic etching etches downwards the substrate in areas not protected by the mask. Using this strategy, conical or irregular tapered shapes can be achieved, where the cross-sectional area of ​​the substrate is smaller at the top (peak) of the nanostructure and larger at the bottom (base).

[0071] Alternatively, a mask with varying composition, thickness, density, or combinations of the three on the surface can be used to etch such tapered structures, primarily using anisotropic etching. Lateral variations in the mask's composition, thickness, and / or density generate varying etching rates for different regions, allowing for substrate exposure at different times. This approach enables the initiation of substrate etching at different times for different regions of the surface, thus allowing for the creation of nanostructured surfaces where peaks are interconnected at varying depths and the height and depth of the nanostructures vary.

[0072] A mask pattern having patterned polymer domains can be used as a mask. However, to increase the selectivity for etching compared to the substrate, additional material can be impregnated into target polymer groups on the surface of the substrate. The target polymer groups can form various patterns, such as labyrinthine structures, island or hole patterns, through the self-assembly of polymers on the surface. Impregnation of the masking material can be by continuous impregnation synthesis, vapor-based impregnation in a chamber, or liquid-based impregnation in a solution. The masking material can include a variety of materials having different etching selectivity than the substrate, and can include inorganic materials or compounds, including metals, metalloids, semiconductors, or their oxides or other compounds. For example, inorganic materials or compounds can include aluminum oxide, titanium dioxide, zinc oxide, silicon dioxide, hafnium dioxide, zirconium dioxide, and tungsten.

[0073] Masks with varying lateral thicknesses in nanodomains can be fabricated by changing the thickness of the target polymer. For example, this can be achieved by removing one domain of the polymer before penetration, so that the remaining domains take on a dome shape or a tapered edge shape.

[0074] Masks with laterally diverse densities within nanodomains can be fabricated by partial penetration of target polymer domains to prevent penetration saturation. Therefore, the penetration density near the polymer surface is higher than in regions further from the surface.

[0075] Masks with laterally diverse compositions can be fabricated by using multiple domains of a polymer, such as using a C homopolymer or an AB block copolymer mixed with an ABC block copolymer, in which case different materials permeate different polymer domains.

[0076] Polymer patterns can be formed by the self-assembly of block copolymers, in which one or more domains of the block copolymer are composed of target polymers that have specificity for a penetrating agent. The self-assembly of block copolymers can form a variety of domain patterns depending on the polymer composition and self-assembly conditions such as temperature, pressure, and the chemical composition of the environment.

[0077] The distance between peaks in a nanostructure can be controlled by changing the polymer. Polymer chain length can be increased to increase the distance between polymer domains before etching, resulting in increased distance between peaks in the nanostructure on the etched surface. For example, in the case of a 30:70 molar ratio polystyrene-block-polymethyl methacrylate (PS-b-PMMA) polymer forming PS columns within a PMMA web, the distance between polystyrene columns can be increased by increasing the polymer chain length or decreased by decreasing the polymer chain length while maintaining the molar ratio. Similarly, a 70:30 ratio PMMA-b-PS polymer forms PMMA columns within a PS web. Likewise, instead of extending the length of specific domains in a block copolymer, homopolymers consisting of one or more domains, or one chemically similar to one domain, may be added to the mixture, and the composition ratio affects the lateral dimensions of the pattern. A polymer composed of three polymer domains, or a polymer mixture containing such three polymer domains, can be used in the formation of a triblock polymer containing three domains, or via a mixture of block copolymers having two domains, each having a homopolymer with similar chemical properties to one of the block copolymer domains, or between two domains. Examples of polymer domains used in such self-assembly include, among others, polyvinylpyridine such as PS, PMMA, P2VP and P4VP, polybutadiene, and polyethylene oxide (PEO).

[0078] After the nanostructure is etched onto the substrate, additional elements, molecules, or particles can be deposited. This deposition can create additional interconnections between structures to enhance mechanical durability, or the deposition can modify the surface energy of the surface to create various properties, such as superhydrophobicity, superhydrophilicity, and oleophobicity.

[0079] Nanoparticles or films smaller than the distance between nanostructures can be deposited between nanostructures (see, for example, Figures 13, 14, and 15). Such particles can connect one nanostructure to another. A matrix having an effective refractive index between the refractive indices of two media may also be deposited between or on top of the structures such that there is a continuous gradient of the effective refractive index from the top to the bottom of the nanostructure. Such materials may consist of or include solid materials such as MgF2, silicon dioxide, or polymers, or porous matrices whose pore size is smaller than the wavelength of light to which they belong.

[0080] As shown in Figures 16-19, particles or films can be deposited on nanostructures, where particles can connect multiple nanostructures. Such particles can take on various geometric shapes, such as planar structures like films (Figures 16 and 17), plate-like structures connecting a limited number of nanostructures (Figures 18 and 19), and spherical structures (Figures 13 and 14). The structures may also have irregular shapes or other geometric shapes.

[0081] Such deposition can be carried out via liquid deposition techniques such as droplet casting, sol-gel, Langmuir-Blodgett, or other methods. Particles may also be deposited by vacuum-based processes such as sputtering, physical vapor deposition, chemical vapor deposition, passivation, atomic layer deposition, and other similar approaches. The particle or film composition may include polymers, metals, or metal oxides, or other materials, examples of which include polystyrene, titanium dioxide, silicon dioxide, and fluorinated compounds.

[0082] Particles or films may be chemically bonded to a structure via functional groups on the surface of the particles or nanostructure. Particles may also be bonded to the structure via heat treatment. Particles may also be simply held in place via other forces, such as van der Waals interactions.

[0083] The particles or film may be composed of a low surface energy material that imparts properties to the surface, such as superhydrophobic functional groups. One example is a fluorinated compound such as polytetrafluoroethylene. Another example is titanium dioxide in the form of nanoparticles or composites. The particles or film may be composed of a high surface energy material that imparts properties to the surface, such as superhydrophilicity. Such surface properties can give the surface a self-cleaning effect.

[0084] Herein, we describe some embodiments of the disclosed articles and methods.

[0085] Example 1: An anti-reflective glass substrate having nanostructures on its surface, wherein the nanostructures are interconnected at various depths and manufactured with a gradient of effective refractive index from the top to the bottom of the nanostructures (Figure 9). PS-b-P2VP block copolymer deposited on the glass surface can be induced to form nanopatterns via tetrahydrofuran vapor annealing, forming domains of PS islands with a diameter of approximately 25 nm in the interconnected P2VP matrix on the substrate surface. Anionic metal salts, such as tetrachloroaurate ions, can selectively penetrate and electrostatically bond to the positively charged P2VP blocks via liquid release. The penetrated metals pattern the P2VP domains on the surface of the glass substrate, forming a network of nanopatterned hard masks. The glass surface is etched with the hard mask using plasma etching based on a fluorine-based gas mixture. A CHF3-oxygen mixed gas in an 8:1 ratio was used at a pressure of 10 mTorr with ICP and RIE outputs of 1000 W and 100 W to induce a mixture of isotropic and anisotropic etching mechanisms. Gas mixtures consisting of CF4, C4F8, and SF6 can also be used. The lateral dimensions of the mask can decrease over etching time, allowing newly exposed glass surfaces to begin etching at different times in the process. This combination of isotropic and anisotropic etching generates nanostructures with distinct peaks, characterized by varying heights and depths. The nanostructures are interconnected at various depths, and hyperbolic paraboloid shapes exist at such interconnections.

[0086] Example 2: The nanostructures are interconnected with additional material deposition, such as MgF2 nanoparticles (Figure 14 shows one with a particle-linked structure), providing additional resistance to mechanical wear. As above, PS-b-PMMA can be used to generate PMMA islands within a network of PS on the surface of a glass surface. Alumina or gallium-based masks can be infiltrated into PMMA domains using the trimethyl form of the metal, which is done alternately with vapor-based exposure using water vapor, resulting in continuous infiltration synthesis to form a metal-containing or organometallic nanoisland hard mask. Reactive ion etching using inductively coupled plasma is used for etching using simultaneous isotropic and anisotropic mechanisms. A mixture of halogen gas and oxygen gas, e.g., a mixture of 45 sccm of CF4-5 sccm of oxygen at a pressure of 25 mTorr, is used for etching. 1000W, 100W ICP, and RIE power supplies are used. Figure 14 shows conical structures of various heights and depths etched onto a glass substrate. MgF2 particles with a diameter of less than 40 nm are deposited by sputtering at a rate of 1 nm per second. Flash heating can be used to further fuse the particles and nanostructures. As a result, an interconnected nanostructure surface is obtained, characterized by tapered or conical glass structures interconnected by MgF2 nanoparticles or nanostructures, which feature a continuous gradient in the cross-sectional area from the top to the bottom of the nanostructure.

[0087] Example 3: Polystyrene nanoparticles are assembled in a two-dimensional array on the surface of a glass substrate. 50 nm diameter nanoparticles, spin-coated to the surface, form a monolayer across the substrate surface. Gold is then deposited on the entire surface using sputtering, depositing metal on the substrate between the nanoparticles. The nanoparticles are then removed using toluene, and the gold deposited on the substrate forms a hard mask. The glass surface is etched using a plasma etching method similar to that described in Example 1, with a fluorinated gas mixture of oxygen, allowing the gold to act as a hard mask. A 10:1 ratio SF6-oxygen gas mixture is used at a pressure of 20 mTorr with ICP and RIE powers of 1000 W and 150 W to generate interconnected peaks on the surface of the glass substrate, exhibiting hyperbolic parabolas between each peak. After the formation of this nanotexturing, graphene oxide nanoflakes with a width of approximately 100 nanometers and a thickness of less than 30 nanometers are deposited using spin coating. As a result, a glass substrate with a nanotexture is obtained on a surface having multiple nanostructures linked by nanoflakes (Figures 18 and 19).

[0088] Example 4: Figures 4, 5, and 6 show lamellar or maze-like geometric shapes in top views obtained by scanning electron microscopy. Self-assembly of block copolymers with interconnected mesostructure nanopatterns resembling a world map is achieved on a glass surface through control of chain length and domain molar ratio. One domain of the polymer pattern is infiltrated with metal to form a lamellar hard mask nanopattern. Reactive ion etching is used to etch the substrate. Instead of conical nanostructures, the substrate formation resulting from plasma etching is sharp-edged with hyperbolic surfaces interconnected in the center, which can be described as interconnected mountain-like ridges. From the top view, these nanostructures resemble a maze-like or lamellar structure where alternating materials are provided layer by layer (Figure 6). After etching, from side or cross-sectional views, the structure appears as a single peak, double peak, or wall, depending on the angle of intersection with the structure (Figure 4). When a single feature of a labyrinthine mask appears as a curve with variable thickness in its top view, the etching process removes thinner parts of the line more quickly, and therefore the underlying structure is exposed to the etching solution sooner than other parts, thus initiating etching earlier. This varied exposure to the etchant creates variable height and depth over the entire length of the single feature, producing double peaks and hyperbolas.

[0089] Example 5: To increase surface haze, the inter-peak distance of the nanostructure can be increased to about 100 nanometers, and the etching depth can be increased to about 200 nm to scatter light. Increasing the etching depth increases light scattering in the shorter wavelength regions of ultraviolet and visible light, and therefore increases haze, improving the anti-reflective properties for near-infrared and infrared wavelengths. Conversely, an inter-peak distance of 40 nanometers provides a surface with no visible or detectable scattering in visible light.

[0090] Example 6: Nanostructured surfaces can improve some surface properties of the same non-nanostructured material. For example, a relatively flat or featureless hydrophobic surface can become superhydrophobic through a combination of hydrophobic surface and nanotexturing. It is also possible to change the surface properties of a nanotextured material by applying a specific coating after nanotexturing. For example, by coating a hydrophobic layer on a nanostructured substrate such as glass, the hydrophobic layer becomes superhydrophobic. After texturing the glass surface, a hydrophobic fluorocarbon polymer was deposited by vacuum deposition of fluorocarbon using a C4F8 passivation gas. Deposition was performed in a deep reactive ion etching (DRIE) chamber under a vacuum of 12 mTorr, with outputs of 10 W and 450 W relative to the RIE and ICP outputs, respectively, using a continuous flow of 65 sccm of C4F8. After deposition, the water contact angle was measured at 162 degrees (Figure 20), and a nanotextured anti-reflective glass surface with superhydrophobic self-cleaning properties was obtained.

[0091] Example 7: A superhydrophobic surface can be fabricated by depositing elements or molecules after etching a nanostructured surface. Prior to deposition on the glass, the glass surface may be activated for hydroxyl groups using oxygen plasma, UV-ozone treatment, or other cleaning procedures, and any step may be used to ensure the highest quality of deposition. After any cleaning step, 0.1 mM octadecyltrichlorosilane was dissolved in hexane. The solution was then dropped onto the surface or the surface was immersed in the solution for 4 hours, followed by heating at 120°C for 1 hour. This procedure forms an alkyl-functionalized nanostructured surface characterized by superhydrophobic surface properties in which the water contact angle can exceed 150 degrees.

[0092] Example 8: Copolymers of two or more domains can be used for microphase separation when creating patterned surfaces on substrates such as glass. An example of a two-domain system is PS-b-PMMA, with a molar ratio of 30-70, which is annealed, for example, at about 200°C to form columns of PS within a PMMA matrix. An example of a three-domain block copolymer system is polystyrene-block-polybutadiene-block-polytetobutyl metallate, which can also form column-like structures with three domains when exposed to THF vapor at room temperature. The formation of vertical domains allows for the selective penetration of metals or metal oxides via sequential infiltration synthesis, such as using TMA to form alumina. Multiple domains allow for varying degrees of penetration and thus change the density or composition of the formation of metal or metal oxide compositions. Patterns of such masks with varying selectivity for the substrate allow for varying levels of protection against etching for various parts of the surface. Such masks allow for varying etching initiation times. When etched under a single-step reactive ion etching, the patterned mask on the surface allows etching to various depths on different parts of the substrate, enabling the generation of nanostructures having hyperbolas characterized by distinct peaks and valleys of varying heights and depths, where the peaks are connected to each other at various depths (Figure 7C).

[0093] Example 9: A hard mask with varying density at different lateral positions allows for variations in the etching rate of the mask, thus creating different start times for exposure and etching of the substrate surface. A PS-b-PMMA block copolymer film is used to impregnate alumina by continuous infiltration synthesis. Three cycles are used for each precursor with an infiltration period of three minutes to prevent saturation of the infiltration within the polymer domains. Thus, the infiltrated polymer domains near the surface have a higher metallic density compared to the interior of the target domain. Then, mainly directional physical etching can be used for the etching process. The variation in density of the hard mask allows for different etching rates of the mask. In the case of island-shaped masks, the sides of the islands are gradually etched away in physical etching, thus gradually exposing more of the substrate surface. This forms a tapered nanostructured surface. For regions where the distance between islands is small, etching in those regions may be slower than in regions where the distance between islands is large. This allows for a variety of etching depths, such that the former case has a shallower etching depth. This strategy of unsaturated penetration, which generates variable density within a hard mask, enables an anisotropic etching approach to create anti-reflective nanostructures with a continuously varying cross-sectional area from top to bottom of the structure, where the structures are interconnected at various depths and have varying heights and depths.

[0094] Example 10: After forming etched nanostructures on the surface of a substrate, a porous material may be added between the structures for mechanical stability, where the effective refractive index of the added material is between the substrate and another medium such as air. For example, interconnections between nanostructures fabricated on glass can be fabricated using PS-b-PMMA block copolymer. If necessary, additional PMMA homopolymer may be added to the polymer solution to increase porosity. The PS-b-PMMA block copolymer is deposited on the surface and fills the gaps between the peaks of the nanostructures. The PMMA is then washed away with an acetic acid solvent to form a porous scaffold between the nanopeaks, improving mechanical stability. Before applying acetic acid, the PMMA may be decomposed by exposure to UV light to facilitate removal. The porous structure has a refractive index between air and glass, and this refractive index can be controlled by the porosity of the polymer. The porosity of the polymer is controlled by the ratio of PS-b-PMMA in the coating layer. A higher ratio of PMMA polymer chains results in higher porosity. An optional step is to use a short oxygen plasma treatment to further create additional porosity on top of the glass nanostructure peaks or to remove excess polymer. The final result is a surface with a continuous effective refractive index from air to glass, where the porous polymer connects multiple glass nanostructures, improving mechanical durability and omnidirectional anti-reflective properties.

[0095] Example 11: Figure 17 shows interconnected nanostructures fabricated by adding a blanket of MgF2 on top of a nanostructure. The nanostructure is etched onto a fused silica substrate using a penetrating hard mask, and a thin film of MgF2 is deposited on top using a sputtering method by controlling the deposition rate and time. The MgF2 thin film blanket can have a porous structure, and the peaks of the fused silica nanostructure create bumps or physical features on the thin film blanket. The heterogeneous surface morphology creates a gradual transition of the effective refractive index from a first medium such as air to the top of the MgF2 glass material. The refractive index of MgF2 is less than 1.2, especially when porous, and lies between the refractive index of air (1) and the refractive index of fused silica glass (approximately 1.5). From the top to the bottom of the nanostructure, the cross-sectional area of ​​the glass, i.e., the high refractive index medium, increases, while the cross-sectional area of ​​air and MgF2, i.e., the low effective refractive index medium, decreases. This creates a continuously changing effective refractive index without an abrupt transition from the top of the surface to the interior of the substrate. Therefore, this creates an anti-reflective surface with a blanket of material that interconnects nanostructures composed of native substrate materials.

[0096] The etchant may vary in other cases. For example, in substrates such as soda-lime glass, the etching solution may contain a mixture of a fluorinated gas, an oxidizing agent, and a heavy noble gas such as argon.

[0097] This specification describes articles having interconnected antireflective nanostructures formed on one or more surfaces of a substrate. The articles and / or methods described herein may, alternatively or additionally, include, or be accompanied by, one or more combinations of the following embodiments or features: The substrate comprises one or more of polymers, glass, sapphire, ceramics, or semiconductor materials and has a top and a bottom surface. The nanostructures are interconnected on a hyperbolic parabolic geometric surface such that connections occur at various depths. The nanostructures consist of or contain the material of the substrate. The nanostructures have defined peaks across the entire surface with an inter-peak distance less than 100 nm, and the distance or height of the highest peak to the lowest trough is greater than 100 nm. The cross-sectional area of ​​the structure is nearly zero at the top of the structure and increases continuously with depth until it reaches 100% at the bottom of the structure. One or more optical properties of the structure include a continuous gradient of the effective refractive index from outside the top surface of the nanostructure to inside the substrate below the bottom of the nanostructure. The effective hardness of the nanostructured surface exceeds 2 mohs. Anti-reflective properties maintain less than 1% specular reflection at perpendicular incidence for wavelengths of 450–1100 nm, and less than 20% specular reflection at an incidence angle of 70 degrees from the perpendicular. The structure is formed by chemical etching, nanoimprinting, or reactive ion etching. The top view of the nanostructure includes a continuous network of separate islands or interconnected shapes. The two-dimensional shape includes one or a combination of regular or irregular shapes, such as circular or parabolic shapes. Additional molecules or elements can be deposited on the surface of the nanostructure to impart additional surface effects, such as superhydrophobicity, in the case of low-energy surfaces or hydrophobic materials, and to impart additional surface effects, such as superhydrophilicity, in the case of high-energy surface materials.

[0098] This specification describes articles having interconnected antireflective nanostructures formed on one or more surfaces of a substrate. The articles and / or methods described herein may, alternatively or additionally, include, or be accompanied by, one or more combinations of the following embodiments or features: The substrate comprises one or more of polymers, glass, sapphire, ceramics, or semiconductor materials and has a top and a bottom surface. The cross-sectional area of ​​the nanostructure material varies continuously from the top to the bottom of the surface of the nanostructure. The nanostructures are interconnected by multiple particles having distinct peaks at various depths of the nanostructure, or by porous materials filling gaps between the nanostructures, or by particles on top of the nanostructures connecting the multiple peaks, or by thin-film blanket-like structures connecting the multiple peaks, or by a combination of these four. The particles on top of the nanostructures may be planar, flake-like, or irregular in shape in the geometric form connecting multiple nanostructures having thicknesses ranging from atomic thickness to 100 nanometers. The thin-film blanket has a thickness of less than 100 nm and may have peaks and valleys on the surface of the thin film. Particles, porous materials, and thin films may include two-dimensional materials comprising graphene and graphene oxide, metals, metal oxides, metal compounds, polymers, semiconductors, semiconductor compounds, or combinations of several such materials. One or more optical properties of the structure include a continuous gradient of effective refractive index from the outside of the top surface of the nanostructure to the inside of the substrate beneath the bottom of the nanostructure. The effective hardness of the nanostructured surface is greater than 2 mohs. The anti-reflective properties maintain less than 1% specular reflectance for normal incidence and less than 20% specular reflectance for incident light at 70 degrees from the normal for wavelengths of 450–1100 nm. The nanostructures are formed from chemical etching, nanoimprinting, or reactive ion etching. The top view of the nanostructure includes a continuous network of distinct islands or interconnected shapes. The two-dimensional shape may include one or a combination of regular geometric shapes such as circular or parabolic shapes or irregular shapes.Additional molecules or elements can be deposited on the surface of nanostructures to impart additional surface effects such as superhydrophobicity in the case of low-energy surfaces or hydrophobic materials, and to impart additional surface effects such as superhydrophilicity in the case of high-energy surface materials.

[0099] This specification describes a method for producing an anti-reflective article having an anti-reflective nanostructure on a substrate, comprising forming a polymer layer on the substrate, wherein the polymer layer comprises one or more polymers comprising at least one block copolymer, the polymer layer comprises a pattern, the patterned polymer layer comprises at least a first polymer domain and a second polymer domain, and one or more precursors are applied on the patterned polymer layer on the substrate to form a patterned mask of an inorganic material or inorganic compound comprising a metal, a metalloid, a semiconductor, or a composite thereof on the substrate, wherein the precursor does not infiltrate at least one polymer domain, and the precursor infiltrates at least one polymer domain to form an inorganic material within the polymer domain, and the infiltrated material produces a variety of etching rates or selectivity with respect to the etching solution, 50 Having diverse densities, thicknesses, or compositions in the lateral direction within a lateral dimension of 0 nanometers, the substrate is etched, and polymer domains that do not contain the infiltrated inorganic material are first removed by the etching solution, in which case localized areas of the substrate are etched, and various parts of the mask decrease in size laterally during etching or expose the masked area to the etching agent at various points, resulting in varying etching depths across the entire masked area at the end of the etching process, and the etching is performed under an etching time long enough for the inorganic material mask to lift off or erode, generating a nanostructured surface of the substrate material, where there is a continuous gradient in the cross-sectional region from the top to the base of the nanostructure, and the peaks of the nanostructure are interconnected at various depths such that they form hyperbolic or saddle-like surfaces at the interconnection points.

[0100] The methods described herein may, alternatively or additionally, include, or involve, one or more combinations of the following embodiments or features: One or more precursors penetrate two or more polymer domains, and the precursors generate inorganic materials in polymer domains having different densities, thicknesses, or compositions to create varying resistances or selectivity to the etching agent. The inorganic materials or inorganic compounds include metals, metalloids, semiconductors, or compounds thereof, including aluminum oxide, titanium dioxide, zinc oxide, silicon dioxide, hafnium dioxide, zirconium dioxide, and tungsten. Two or more precursors are used for penetration, which selectively penetrates different polymer domains. The precursors are gases, or the formation of liquids or plasmas. One or more domains resemble points, mazes, spider webs, parallel lines, bees, or helices. One or more of the domains form an interconnected network. Additional layers or particles or nanoflakes or nanoplates are deposited on the etched surface, resulting in the creation of additional interconnections between the peaks of the nanostructure. Heat treatment or chemical treatment stabilizes the structure or improves the adhesion of deposited materials. This method involves additional surface treatment or deposition of elements or molecules with gas, liquid, or plasma to create hydrophobic, hydrophilic, or oleophobic properties. The top view of the mask geometric shape and nanostructure includes a continuous network of distinct islands or interconnected shapes, and the two-dimensional shape may include one or a combination of regular geometric shapes such as circular, parabolic, or irregular shapes.

[0101] This disclosure is intended to be illustrative and is written with reference to specific embodiments not intended to limit this disclosure. The embodiments may be modified, added to, and / or deleted without departing from the spirit and scope of this disclosure.

[0102] The above explanation is provided solely to clarify understanding, and no unnecessary limitations should be assumed from it. (Note 1) An anti-reflective article comprising a substrate including a surface and bulk, and an arrangement of a plurality of anti-reflective nanostructures along the surface of the substrate, Each anti-reflective nanostructure in the array of anti-reflective nanostructures is supported by the bulk of the substrate, and each anti-reflective nanostructure tapers off from the bulk of the substrate, forming a peak. At least several anti-reflective nanostructures in the array of anti-reflective nanostructures are connected to adjacent anti-reflective nanostructures in the array of anti-reflective nanostructures via interconnections, and these interconnections are added to the bulk of the substrate supporting the anti-reflective nanostructures. An anti-reflective article wherein the interconnection portion is located at or on an intermediate point between the peak of the anti-reflective nanostructure and the bulk of the substrate. (Note 2) The anti-reflective article according to Appendix 1, wherein the substrate includes the interconnection portion. (Note 3) The anti-reflective article according to Appendix 1, wherein the interconnection portion is provided by a portion of the substrate between adjacent anti-reflective nanostructures in the arrangement of anti-reflective nanostructures. (Note 4) The anti-reflective article described in Appendix 3, wherein a portion of the substrate forms a saddle-shaped surface portion. (Note 5) The anti-reflective article according to Appendix 1, further comprising a distribution of nanoparticles arranged across the surface of the substrate, wherein each interconnection portion is provided by a subset of the nanoparticle distribution. (Note 6) The anti-reflective article according to Appendix 5, wherein the nanoparticles in the subset closest to the peak are larger than the nanoparticles in the subset closest to the bulk. (Note 7) The anti-reflective article according to Appendix 1, further comprising a distribution of flakes across the substrate, wherein each flake in the distribution of flakes is in contact with the peaks of linked anti-reflective nanostructures in the arrangement of anti-reflective nanostructures, and each flake provides one or more interconnections. (Note 8) The anti-reflective article according to Appendix 1, further comprising a filler traversing the substrate disposed within a cavity defined by the arrangement of the anti-reflective nanostructures, wherein each interconnection is provided by a corresponding portion of the filler. (Note 9) The anti-reflective article according to Appendix 1, further comprising a continuous film extending across the arrangement of the anti-reflective nanostructures, wherein the continuous film provides interconnections between the peaks of the plurality of anti-reflective nanostructures. (Note 10) The anti-reflective article according to Appendix 1, wherein the arrangement of the anti-reflective nanostructures is configured such that the peaks of each pair of adjacent anti-reflective nanostructures within the arrangement of the anti-reflective nanostructures are spaced apart by a distance smaller than the wavelength of light incident on the anti-reflective article. (Note 11) The arrangement of the anti-reflective nanostructure establishes an effective refractive index for light incident on the anti-reflective article. The anti-reflective article according to Appendix 1, wherein each anti-reflective nanostructure in the array of anti-reflective nanostructures is configured such that the effective refractive index exhibits a continuous gradient from the corresponding peak of the anti-reflective nanostructure to the base of the anti-reflective nanostructure. (Note 12) The substrate includes a base substrate and a layer supported by the base substrate. The anti-reflective article according to Appendix 1, wherein the layer comprises the arrangement of the anti-reflective nanostructures. (Note 13) The anti-reflective article according to Appendix 1, wherein the surface of the substrate is molded to form an arrangement of the anti-reflective nanostructures. (Note 14) An anti-reflective article comprising a substrate including a surface and bulk, and an arrangement of a plurality of anti-reflective nanostructures along the surface of the substrate, Each anti-reflective nanostructure in the array of anti-reflective nanostructures is supported by the bulk of the substrate, and each anti-reflective nanostructure tapers off from the bulk of the substrate, forming a peak. The height at which adjacent anti-reflective nanostructures in the aforementioned arrangement are connected by interconnections varies across the substrate. An anti-reflective article wherein at least some interconnections are positioned equidistant from the peaks of the anti-reflective nanostructures and the bulk of the substrate. (Note 15) The anti-reflective article according to Appendix 14, wherein each pair of adjacent anti-reflective nanostructures in the array of anti-reflective nanostructures is interconnected by the corresponding portion of the substrate. (Note 16) The anti-reflective article according to Appendix 14, wherein adjacent anti-reflective nanostructures in the arrangement of the anti-reflective nanostructures form a saddle-shaped surface. (Note 17) The anti-reflective article according to Appendix 14, comprising a plurality of nanoparticles dispersed across an array of anti-reflective nanostructures, wherein each pair of adjacent anti-reflective nanostructures in the array of anti-reflective nanostructures is interconnected by corresponding subsets of the plurality of nanoparticles. (Note 18) The anti-reflective article according to Appendix 17, wherein the number of nanoparticles in each subset changes such that the depth to which adjacent anti-reflective nanostructures in the array of anti-reflective nanostructures are interconnected changes. (Note 19) The anti-reflective article according to Appendix 17, wherein the position of nanoparticles in each subset changes such that the depth to which adjacent anti-reflective nanostructures in the array of anti-reflective nanostructures are interconnected changes. (Note 20) Each of the aforementioned subsets comprises nanoparticles of various sizes, as described in Appendix 17, for the anti-reflective article. (Note 21) An anti-reflective article comprising a substrate including a surface and bulk, and an arrangement of a plurality of anti-reflective nanostructures along the surface of the substrate, Each anti-reflective nanostructure in the array of anti-reflective nanostructures is supported by the bulk of the substrate, and each anti-reflective nanostructure tapers off from the bulk of the substrate, forming a peak. An anti-reflective article in which some anti-reflective nanostructures in the array of anti-reflective nanostructures are connected to adjacent anti-reflective nanostructures in the array of anti-reflective nanostructures via a portion of the substrate, in addition to the bulk of the substrate. (Note 22) The invention comprises a substrate including a surface and bulk, and a dispersion of a material across the surface of the substrate, The surface is shaped to form an array of anti-reflective nanostructures, each anti-reflective nanostructure in the array is supported by the bulk of the substrate, and each anti-reflective nanostructure tapers off from the bulk of the substrate, forming a peak. An anti-reflective article wherein a portion of the distribution of the material is located between adjacent anti-reflective nanostructures in an array of anti-reflective nanostructures, and adjacent anti-reflective nanostructures in the array of anti-reflective nanostructures are interconnected by a portion of the material. (Note 23) The anti-reflective article according to Appendix 22, wherein the distribution of the material includes a plurality of nanoparticles arranged within a cavity defined by the arrangement of the anti-reflective nanostructures. (Note 24) The anti-reflective article according to Appendix 22, wherein the distribution of the material includes a distribution of flakes across the substrate, and each flake in the distribution of flakes interconnects the peaks of two or more anti-reflective nanostructures. (Note 25) The anti-reflective article according to Appendix 21, wherein the distribution of the material includes a filler that crosses the substrate, which is located in a cavity defined by the arrangement of the anti-reflective nanostructures. (Note 26) The anti-reflective article according to Appendix 21, wherein the material of the distribution includes a continuous film extending across the arrangement of the anti-reflective nanostructures, the continuous film providing interconnections between the peaks of the anti-reflective nanostructures. (Note 27) A method for manufacturing anti-reflective articles, A step of forming a mask having a lamellar nanopattern on a substrate, The process includes etching the substrate through the openings of the mask defined by the lamellar nanopattern, A method for manufacturing an anti-reflective article, comprising etching the substrate such that an anisotropic etching is performed so that an arrangement of tapered nanostructures is formed according to the lamellar nanopattern. (Note 28) A method for manufacturing anti-reflective articles, A step of forming a mask having a nano-pattern of holes on a substrate, The process includes etching the substrate through holes in the mask defined by the nanopattern, The etching of the substrate includes performing anisotropic etching such that an arrangement of tapered nanostructures is formed according to the nanopattern of the holes, A method for manufacturing an anti-reflective article, wherein the nanopattern of the holes is configured such that the arrangement of tapered nanostructures has saddle-shaped surfaces at the interconnections between adjacent tapered nanostructures within the arrangement of tapered nanostructures.

Claims

1. An anti-reflective article comprising a substrate including a surface and bulk, an arrangement of a plurality of anti-reflective nanostructures along the surface of the substrate, and a distribution of flakes across the substrate, Each anti-reflective nanostructure in the array of anti-reflective nanostructures is supported by the bulk of the substrate, and each anti-reflective nanostructure tapers off from the bulk of the substrate, forming a peak. At least several anti-reflective nanostructures in the array of anti-reflective nanostructures are connected to adjacent anti-reflective nanostructures in the array of anti-reflective nanostructures via interconnections. An anti-reflective article in which each flake in the distribution of the flakes is an interconnection and is in contact with the peaks of linked anti-reflective nanostructures in the arrangement of anti-reflective nanostructures.

2. The anti-reflective article according to claim 1, wherein the substrate includes the interconnection portion.

3. The anti-reflective article according to claim 1, wherein the interconnection portion is provided by a portion of the substrate between adjacent anti-reflective nanostructures in the arrangement of anti-reflective nanostructures.

4. The anti-reflective article according to claim 3, wherein a part of the substrate forms a saddle-shaped surface portion.

5. The anti-reflective article according to claim 1, further comprising a distribution of nanoparticles arranged across the surface of the substrate, wherein each interconnection portion is provided by a subset of the nanoparticle distribution.

6. The anti-reflective article according to claim 5, wherein the nanoparticles in the subset closest to the peak are larger than the nanoparticles in the subset closest to the bulk.

7. The anti-reflective article according to claim 1, further comprising a filler that crosses the substrate and is disposed within a cavity defined by the arrangement of the anti-reflective nanostructures, wherein each interconnection is provided by a corresponding portion of the filler.

8. The anti-reflective article according to claim 1, wherein the arrangement of the anti-reflective nanostructures is configured such that the peaks of each pair of adjacent anti-reflective nanostructures within the arrangement of the anti-reflective nanostructures are spaced apart by a distance smaller than the wavelength of light incident on the anti-reflective article.

9. The arrangement of the anti-reflective nanostructure establishes an effective refractive index for light incident on the anti-reflective article. The anti-reflective article according to claim 1, wherein each anti-reflective nanostructure in the array of anti-reflective nanostructures is configured such that the effective refractive index exhibits a continuous gradient from the corresponding peak of the anti-reflective nanostructure to the base of the anti-reflective nanostructure.

10. The substrate includes a base substrate and a layer supported by the base substrate. The anti-reflective article according to claim 1, wherein the layer comprises the arrangement of the anti-reflective nanostructures.

11. The anti-reflective article according to claim 1, wherein the surface of the substrate is molded to form an arrangement of the anti-reflective nanostructures.

12. A substrate comprising a surface and bulk, and a distribution of material across the surface of the substrate, The surface is shaped to form an array of anti-reflective nanostructures, each anti-reflective nanostructure in the array is supported by the bulk of the substrate, and each anti-reflective nanostructure tapers off from the bulk of the substrate, forming a peak. A portion of the distribution of the material is located between adjacent anti-reflective nanostructures in the array of anti-reflective nanostructures, and adjacent anti-reflective nanostructures in the array of anti-reflective nanostructures are interconnected by a portion of the distribution of the material. The distribution of the material includes a distribution of flakes across the substrate, wherein each flake in the distribution interconnects the peaks of two or more anti-reflective nanostructures, in an anti-reflective article.

13. The anti-reflective article according to claim 12, wherein the distribution of the material includes a plurality of nanoparticles disposed within a cavity defined by the arrangement of the anti-reflective nanostructures.

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