Low reflectivity removable lens stack

Abstract

A removable lens stack includes a base layer, a first removable lens layer, and a second removable lens layer. The base layer may include a substrate and a moth-eye coating. The first removable lens layer may include a substrate, a single-layer or multi-layer interference anti-reflection coating on a first side of the substrate, and a fluoropolymer coating on a second side of the substrate. The first removable lens layer may be laminated on top of the base layer, with the fluoropolymer coating shaped to match the moth-eye coating. The second and any subsequent removable lens layers may include a substrate, a single-layer or multi-layer interference anti-reflection coating on a first side of the substrate, and an acrylic or polyurethane adhesive on a second side of the substrate. The second removable lens layer may be laminated on top of the first removable lens layer, and so on.

Description

[Technical Field]

[0001] The present invention relates to a low reflectance removable lens stack. [Background technology]

[0002] In various environments where protective eyewear, such as goggles, visors, and face shields, is used, maintaining visibility as debris accumulates on the eyewear is important. For example, participants in off-road sports such as motocross racing need to maintain visibility of the course as mud, insects, and other debris accumulate on their goggles or helmet visors. Similarly, in operating room environments, debris can impair the surgeon's or other practitioner's vision during procedures. In response to these needs, peel-off films, either individually or in laminated stacks, are commonly applied to goggle lenses, visors, or face shields. When debris accumulates on the outermost peel-off film or the outermost peel-off film becomes damaged, the wearer simply peels it off to reveal a fresh layer underneath.

[0003] To ensure good vision through such laminated lenses, it is desirable to minimize internal reflections. One promising technology for reducing reflections is the so-called moth-eye (ME) coating, which mimics the anti-reflective properties of moth eyes by forming a pattern of microscopic bumps that effectively eliminates the refractive index interface between the lens and air. Unfortunately, in the case of multi-lens laminates, adhesives used between layers tend to fill in around the bumps of the ME coating, significantly increasing the peel strength of each layer (e.g., from about 2.50 N / cm to about 4.13 N / cm (650 g / in to 1,070 g / in)). This makes the layers difficult to peel apart, and the force required to remove them may exceed the tensile strength of the lens material, rendering the laminate unusable. Summary of the Invention [Problem to be solved by the invention]

[0004] The present disclosure contemplates various apparatus and methods for overcoming the shortcomings associated with the related art. [Means for solving the problem]

[0005] One aspect of an embodiment of the present disclosure is a removable lens stack. The removable lens stack may include a base layer comprising a substrate having a first surface and a second surface opposite the first surface, the base layer further comprising a moth-eye coating on the first surface of the substrate. The removable lens stack may further include one or more removable lens layers, each comprising a substrate having a first surface and a second surface opposite the first surface, a moth-eye coating on the first surface of the substrate, and a fluoropolymer coating on the second surface of the substrate. The one or more removable lens layers may be laminated on top of the base layer such that the second surface of the substrate of each removable lens layer faces the first surface of the substrate of the immediately preceding layer among the base layer and the one or more removable lens layers. Each of the fluoropolymer coatings may be shaped to match the moth-eye coating of the immediately preceding layer.

[0006] In each of the one or more removable lens layers and the base layer, the moth-eye coating may comprise a polymer. On each of the one or more removable lens layers and the base layer, the moth-eye coating may form a pattern of protrusions having a half-wavelength pitch.

[0007] On each of the one or more removable lens layers and the base layer, the moth-eye coating may form a pattern of protrusions having a height of half a wavelength.

[0008] On each of the one or more removable lens layers and the base layer, the moth-eye coating may form a pattern of cones. The base layer may further comprise a moth-eye coating on the second surface of the substrate.

[0009] In each of the one or more removable lens layers and the base layer, the substrate may comprise polyethylene terephthalate (PET). The removable lens stack may further include an adhesive treatment between the substrate and the moth-eye coating in each of the one or more removable lens layers and the base layer, and the adhesive treatment may include a pressure-sensitive adhesive.

[0010] The removable lens stack may further comprise an adhesive treatment between the substrate and the fluoropolymer coating in each of the one or more removable lens layers, and the adhesive treatment may comprise a pressure-sensitive adhesive.

[0011] The peel strength of each of the one or more removable lens layers may be less than about 100 grams per inch. The peel strength of each of the one or more removable lens layers may be between about 15 grams per inch and about 50 grams per inch, and more particularly between about 15 grams per inch and about 30 grams per inch.

[0012] The removable lens stack may have a visible light transmission (VLT) of greater than 95%, and more particularly greater than 98%. Another aspect of an embodiment of the present disclosure is a method for manufacturing a removable lens stack. The method may include providing a base layer comprising a substrate having a first surface and a second surface opposite the first surface, the base layer further comprising a moth-eye coating on the first surface of the substrate. The method may further include laminating one or more removable lens layers on top of the base layer, each removable lens layer comprising a substrate having a first surface and a second surface opposite the first surface, a moth-eye coating on the first surface of the substrate, and a fluoropolymer coating on the second surface of the substrate. The one or more removable lens layers may be laminated on top of the base layer such that the second surface of the substrate of each removable lens layer faces the first surface of the substrate of the immediately preceding layer among the base layer and the one or more removable lens layers. The method may further comprise a laminating step of laminating the one or more stacked removable lens layers to the base layer, each of the fluoropolymer coatings being shaped to match the moth-eye coating of the immediately preceding layer.

[0013] The laminating step may include laminating the one or more laminated removable lens layers to the base layer under pressure at a temperature of less than 40°C. The method may further comprise applying a corona treatment between the substrate and the moth-eye coating in each of the one or more removable lens layers.

[0014] The method may further comprise applying a corona treatment between the substrate and the fluoropolymer coating in each of the one or more removable lens layers. Another aspect of the present disclosure is a removable lens laminate comprising a base layer, a first removable lens layer, and a second removable lens layer. The base layer may comprise a substrate and a moth-eye coating on a first surface of the substrate. The first removable lens layer may comprise a substrate, a single-layer or multi-layer interference anti-reflection coating on a first surface of the substrate, and a fluoropolymer coating on a second surface of the substrate opposite the first surface. The first removable lens layer may be laminated on top of the base layer such that the second surface of the substrate of the first removable lens layer faces the first surface of the substrate of the base layer, and the fluoropolymer coating is shaped to match the moth-eye coating. The second removable lens layer may comprise a substrate, a single-layer or multi-layer interference anti-reflection coating on a first surface of the substrate, and an acrylic adhesive or polyurethane adhesive on a second surface of the substrate opposite the first surface. The second removable lens layer may be laminated on top of the first removable lens layer such that the second surface of the substrate of the second removable lens layer faces the first surface of the substrate of the first removable lens layer.

[0015] The moth-eye coating may include a polymer. The moth-eye coating may form a pattern of multiple protrusions having a half-wavelength pitch. The moth-eye coating may form a pattern of multiple protrusions having a half-wavelength height. The moth-eye coating may form a pattern of multiple cones.

[0016] The base layer may comprise a moth-eye coating on a second side of the substrate opposite the first side. In each of the base layer, the first removable lens layer, and the second removable lens layer, the substrate may comprise polyethylene terephthalate (PET).

[0017] The removable lens stack may further include a third removable lens layer comprising a substrate, a single- or multi-layer interference anti-reflection coating on a first side of the substrate, and an acrylic or polyurethane adhesive on a second side of the substrate opposite the first side. The third removable lens layer may be laminated on top of the second removable lens layer such that the second side of the substrate of the third removable lens layer faces the first side of the substrate of the second removable lens layer. The removable lens stack may further include a fourth removable lens layer comprising a substrate, a single- or multi-layer interference anti-reflection coating on a first side of the substrate, and an acrylic or polyurethane adhesive on a second side of the substrate opposite the first side. The fourth layer may be laminated on top of the third removable lens layer such that the second side of the substrate of the fourth removable lens layer faces the first side of the substrate of the third removable lens layer.

[0018] The peel strength of the first removable lens layer may be less than about 100 grams per inch. The peel strength of the first removable lens layer may be between about 15 grams per inch and about 50 grams per inch. The peel strength of the first removable lens layer may be between about 15 grams per inch and about 30 grams per inch.

[0019] The removable lens stack may have a visible light transmission (VLT) of greater than 95%. The removable lens stack may have a VLT of greater than 98%. Another aspect of the present disclosure is a method for producing a removable lens laminate. The method may include a step of providing a base layer comprising a substrate and a moth-eye coating on a first surface of the substrate, and a first lamination step of laminating a first removable lens layer on top of the base layer, the first removable lens layer comprising a substrate, a single-layer or multi-layer interference anti-reflection coating on the first surface of the substrate, and a fluoropolymer coating on a second surface of the substrate opposite the first surface. The first removable lens layer may be laminated on top of the base layer such that the second surface of the substrate of the first removable lens layer faces the first surface of the substrate of the base layer. The method may further include a lamination step of laminating the laminated first removable lens layer to the base layer, the fluoropolymer coating being shaped to conform to the moth-eye coating. The method may further comprise a second lamination step of laminating a second removable lens layer on top of the first removable lens layer, the second removable lens layer comprising a substrate, a single-layer or multi-layer interference anti-reflection coating on a first side of the substrate, and an acrylic adhesive or a polyurethane adhesive on a second side of the substrate opposite the first side, the second removable lens layer being laminated on top of the first removable lens layer such that the second side of the substrate of the second removable lens layer faces the first side of the substrate of the first removable lens layer.

[0020] The laminating step may include laminating the first removable lens layer to the base layer under pressure at a temperature of less than 40° C. The laminating step may occur before the second laminating step.

[0021] The method may further comprise applying a corona treatment between the substrate and the moth-eye coating of the base layer and / or between the substrate and the fluoropolymer coating of the first removable lens layer.

[0022] The method may further include laminating a third removable lens layer on top of the second removable lens layer, the third removable lens layer comprising a substrate, a single- or multi-layer interference anti-reflection coating on a first side of the substrate, and an acrylic or polyurethane adhesive on a second side of the substrate opposite the first side. The third removable lens layer may be laminated on top of the second removable lens layer such that the second side of the substrate of the third removable lens layer faces the first side of the substrate of the second removable lens layer. The method may further include laminating a fourth removable lens layer on top of the third removable lens layer, the fourth removable lens layer comprising a substrate, a single- or multi-layer interference anti-reflection coating on a first side of the substrate, and an acrylic or polyurethane adhesive on a second side of the substrate opposite the first side. The fourth removable lens layer may be laminated on top of the third removable lens layer such that the second side of the substrate of the fourth removable lens layer faces the first side of the substrate of the third removable lens layer.

[0023] These and other features and advantages of the various embodiments disclosed herein may be better understood with regard to the following description and drawings, in which like numerals refer to like parts throughout. [Brief explanation of the drawings]

[0024] [Figure 1] FIG. 1 is a cross-sectional view of one base layer and two removable lens layers in a removable lens stack according to one embodiment of the present disclosure. [Figure 2] 2 is a cross-sectional view of a removable lens stack having the layers of FIG. 1. [Figure 3] FIG. 10 is a cross-sectional view of a base layer and multiple removable lens layers in a removable lens stack according to another embodiment of the present disclosure. [Figure 4] 4 is a cross-sectional view of a removable lens stack having the layers of FIG. 3. DETAILED DESCRIPTION OF THE INVENTION

[0025] The present disclosure encompasses various embodiments of a removable lens laminate and a method for manufacturing the same. The detailed description set forth below in connection with the accompanying drawings is intended as a description of some currently contemplated embodiments and is not intended to represent the only manner in which the disclosed invention may be deployed or utilized. The description describes functions and features in connection with the illustrated embodiments. It may be understood that the same or equivalent functions may be achieved by various embodiments, which are, however, also intended to be encompassed within the scope of the present disclosure. It is further understood that the use of relational terms such as first and second is used only to distinguish one entity from another entity and does not necessarily require or imply any actual such order or relationship between such entities.

[0026] FIG. 1 is a cross-sectional view of a base layer 100 and two removable lens layers 200, which may be laminated together to form a removable lens stack 10, as shown in cross-section in FIG. 2. The base layer 100 of the removable lens stack 10 may be attached to a surface, such as, for example, a goggle lens or visor, or a transparent window in a surgical helmet, hood, or gown, or may be attached to a frame around its periphery (i.e., without being attached to a surface), such that the removable lens stack 10 itself functions as a lens, visor, face shield, or the like. In the example of FIGS. 1 and 2, two removable lens layers 200 are shown, which are laminated to the base layer 100 to form the removable lens stack 10. However, it is envisioned that there may be more than two removable lens layers 200, or only one removable lens layer 200. As shown, each of the removable lens layers 200 may comprise a substrate 210 and a moth-eye coating 220 on its first surface 212. The base layer 100 may similarly comprise a substrate 110 with a moth-eye coating 120a on a first surface 112 thereof and an optional moth-eye coating 120b on a second surface 114 opposite the first surface 112. The moth-eye coatings 120a, 120b, 220 enable the removable lens stack 10 to have very low reflectivity and thus exhibit a visible light transmission (VLT) of greater than 95%, or in some cases greater than 98% (e.g., greater than 99% with reflectivity less than 1%).

[0027] Unlike conventional removable lenses, each removable lens layer 200 may further comprise a fluoropolymer coating 230 on a second surface 214 of the substrate 210 opposite the first surface 212. Thus, when the removable lens layer 200 is laminated on top of the base layer 100 with the second surface 214 of each substrate 210 facing the first surface 112, 212 of the immediately preceding substrate 110, 210 (which may be the substrate 210 of the immediately preceding removable lens layer 200 or the substrate 110 of the base layer 100, as the case may be), the fluoropolymer coating 230 may abut the moth-eye coating 120 a, 220. Thus, when the laminated removable lens layers 200 are laminated to the base layer 100, each fluoropolymer coating 230 may be molded to match the moth-eye coating 120 a, 220 of the immediately preceding layer 100, 200. The resulting mechanical interlock between the moth-eye coating 120a, 220 and the corresponding molded female pattern formed in the adjacent fluoropolymer coating 230 can function similar to a zipper to secure the adjacent layers together. This mechanical interlocking can completely avoid the use of acrylic or other tacky adhesives in the moth-eye coating 120a, 220, thereby preventing the increased peel strength associated with such conventional adhesives pooling around the protrusions of the moth-eye coating 120a, 220. Thus, the removable lens layer 200 can advantageously have a much lower peel strength, which may be less than about 100 grams per inch, such as between about 15 grams per inch and about 50 grams per inch, and more specifically between about 15 grams per inch and about 30 grams per inch (e.g., about 25 grams per inch), allowing the wearer to remove each layer 200 as desired with a reasonable amount of pulling force.(Note that base layer 100 does not need to be removable, and therefore there may be no problem with using a tacky adhesive to attach base layer 100 to a surface, provided the increased peel strength caused by adhesive buildup around the protrusions of optional moth-eye coating 120b is acceptable.) The substrate 110, 210 of each layer 100, 200 may comprise a transparent polymer such as polyethylene terephthalate (PET) and may be about 1 mil to 10 mils thick, e.g., approximately 2 mils thick, for the substrate 210 of each removable lens layer 200, while the substrate 110 of the base layer 100 may be the same thickness or typically thicker (e.g., about 7 mils). The moth-eye coating 220 of each removable lens layer 200 and the moth-eye coatings 120a, 120b of the base layer 100 may comprise a polymer, typically made of a hard polymer such as glassy carbon having a Mohs hardness of 7. The moth-eye coatings 120a, 120b, and 220 can form a pattern of nano-sized micro-protrusions or protrusions (e.g., transparent cones) on the surface of the substrate 110 or 210, with dimensions (e.g., half-wavelength pitch and / or half-wavelength height) on the order of the wavelength of light (e.g., visible light), thereby creating an anti-reflection effect. For example, the pitch and / or height of the protrusions can be 200 nm-375 nm. The protrusions of the moth-eye coatings 120a, 120b, and 220 can have various shapes, including rounded or rectangular protrusion surfaces instead of cones.

[0028] The moth-eye coatings 120a, 120b, 220 may be refractive index matched (e.g., within 0.2) to the substrates 110, 210, the fluoropolymer coating 230, and any adhesives (described below) that may be used so that the entire removable lens stack 10 may have a consistent refractive index (e.g., within 0.2). However, because the refractive index interface between air and the removable lens stack 10 may be effectively eliminated by the outermost moth-eye coating 220 (because the interface appears to incident light as a gradient rather than an abrupt change in material), it is not necessary to match the refractive index of the removable lens stack 10 to air (n=1). Thus, it is contemplated that a wide variety of materials may be used for the substrates 110, 210 and other components of the removable lens stack 10.

[0029] Generally, when constructing a conventional removable lens stack, a removable bonding material is used to wet each pair of adjacent surfaces together. The term "wetting" in this context may refer to when two surfaces come into close contact with each other, such that contact expels all air between them, thereby enabling good bonding. While simply placing one lens on top of another does not disperse the air trapped between the lenses, an acrylic-based removable adhesive can be used to wet the surfaces together and promote bonding. By matching the refractive index of the adhesive to that of the lenses (e.g., within 0.2), visible light can remain at a constant velocity at the interface, thereby minimizing reflection. An example of such a system may be found in U.S. Pat. No. 9,295,297, entitled "Adhesive Mountable Stack of Removable Layers," the entire contents of which are expressly incorporated herein by reference. However, problems arise when bonding two surfaces together, one or both of which have a moth-eye coating, because the adhesive is sticky to the touch. In particular, as noted above, the adhesive seals around the microprotrusions of the moth-eye coating, dramatically increasing the peel strength beyond that which is functionally suitable for a removable lens laminate.

[0030] Thus, a fluoropolymer coating 230 may be provided on the second side 214 of each substrate 210 to wet and integrate the surfaces of the substrates 110, 210 and to achieve the desired peel strength in the disclosed removable lens laminate 10. The fluoropolymer coating 230 may be a refractive index-matched (e.g., within 0.2) soft fluoropolymer (such as fluorinated ethylene-propylene copolymer (FEP), perfluoroalkoxyalkane (PFA), or tetrafluoroethylene perfluoro(methyl vinyl ether) (MFA)) that is non-tacky to the touch yet moldable under lamination pressure to produce a debossed (negative) pattern that corresponds to the protrusions of the abutting moth-eye coating 120a, 220.

[0031] In some cases, an adhesive treatment 140a, 240 may be provided between the substrate 110 and the moth eye coating 120a of the base layer 100 and / or between the substrate 210 and the moth eye coating 220 of each removable lens layer 200. Similarly, if the substrate 110 of the base layer 100 further comprises a moth eye coating 120b on its second surface 114, an adhesive treatment 140b may be provided between the substrate 110 and the moth eye coating 120b. In each removable lens layer 200, an adhesive treatment 250 may likewise be provided between the substrate 210 and the fluoropolymer coating 230. The adhesive treatments 140a, 140b, 240, and 250 may include a pressure-sensitive adhesive such as a silicone adhesive (e.g., a polydimethyl / methylvinylsiloxane polymer and resin dispersed in toluene / isopropyl alcohol, such as adhesives sold by The Dow Chemical Company under the designations DOWSIL® 7655 Adhesive or DOWSIL® 7656 Adhesive). The adhesive may be refractive index matched (e.g., within 0.2) to the substrates 110 and 210 and other elements of the removable lens stack 10, as described above.

[0032] The base layer 100 and one or more removable lens layers 200 may be manufactured by coating the respective substrates 110, 210 with the moth-eye coatings 120a, 120b, 220 and fluoropolymer coatings 230, which may optionally be attached to the substrates 110, 210 by adhesive treatments 140a, 140b, 240, 250 as described above. It is also envisioned that a corona treatment may be applied between the substrates 110, 210 and the moth-eye coatings 120a, 120b, 220 and / or between the substrate 210 and the fluoropolymer coating 220 to improve adhesion. This may ensure, for example, that the fluoropolymer coating 220 remains with the outermost removable lens layer 200 when the outermost removable lens layer 200 is removed from the removable lens stack 10. Corona treatment may be applied instead of or in addition to the adhesive treatments 140a, 140b, 240, 250 described above. The removable lens layers 200 may then be laminated on top of the base layer 100 such that the second surface 214 of the substrate 210 of each removable lens layer 200 faces the first surface 112, 212 of the substrate 110, 210 of the immediately preceding layer in the base layer 100 and one or more removable lens layers 200 (as the case may be). In the illustrated example shown in Figures 1 and 2, a first removable lens layer 200 (shown in the center of each figure) is laminated to the base layer 100, and a second removable lens layer 200 (shown on the left side of each figure) is laminated to the first removable lens layer 200. Additional removable lens layers 200 may be similarly provided and added to the laminate.

[0033] The removable lens layer 200 may then be laminated to the base layer 100 under pressure with or without heat (e.g., under pressure at a temperature less than 40°C). Note that the base layer 100 and removable lens layer 200 may be laminated together in a single lamination process or multiple lamination processes, e.g., each removable lens layer 200 is added to the stack in a separate lamination process (or multiple removable lens layers 200 are laminated together before being laminated to the base layer 100). As a result of lamination, each fluoropolymer coating 230 may be shaped to match the moth-eye coating 120a, 220 of the immediately preceding layer. In particular, the hard protrusions of the moth-eye coating 120a, 220 may be pressed into the soft fluoropolymer coating 230 to create a corresponding debossed (negative) pattern in the fluoropolymer coating 230. In this way, the aforementioned mechanical interlocking between the layers 100, 200 can be achieved to generate the desired peel strength (e.g., approximately 0.097 N / cm (25 grams / inch)) without the use of a tacky adhesive between the layers 100, 200, which could otherwise fill the gaps between the protrusions and excessively increase the peel strength. At the same time, air between the layers 100, 200 can be evacuated during the lamination process, allowing the opposing layers 100, 200 to wet (and consequently bond slightly) while effectively eliminating refractive index interfaces due to the refractive index gradient created by the architecture of the moth-eye coatings 120a, 220. The visible light transmittance (VLT) of the resulting removable lens laminate 10 can be greater than 95% (e.g., 96% with 4% reflectance), as opposed to 92% with 8% reflectance that can be found in uncoated lenses. In some cases, particularly when the moth-eye coating 120b is provided such that the moth-eye coatings 120a, 120b, 220 are present on both sides of the laminate 10, the VLT may be greater than 98% (eg, greater than 99%).

[0034] When the removable lens stack 10 is incorporated into eyewear and worn, a wearer can easily peel away the outermost removable lens layer 200 to expose the clean removable lens layer 200 (or base layer 100) underneath. For a removable lens stack 10 having multiple removable lens layers 200, the pulling force used to remove the outermost removable lens layer 200 may generally include an initial outward force (perpendicular to the stack 10) as the wearer lifts the outermost removable lens layer 200 from one side of the stack 10 (e.g., by grasping an easily accessible tab on one side of the stack 10) to separate the outermost removable lens layer 200 from the other removable lens layers 200, followed by a continuous lateral force (with a component parallel to the stack 10) as the wearer peels the outermost removable lens layer 200 away. It is envisioned that the continuous lateral forces that are responsible for the majority of separation of the removable lens layers 200 may be more likely to lift the outermost removable lens layer 200 than to separate the underlying subsequent layers 200. Thus, the wearer can easily peel one layer 200 at a time without accidentally peeling off additional layers 200 of the removable lens stack 10.

[0035] Hybrid stacks are also envisioned that may combine one or more layers having a moth-eye coating with one or more layers having alternative types of anti-reflection coatings, such as single-layer or multi-layer interference anti-reflection coatings. By way of example, FIG. 3 shows a cross-sectional view of the same base layer 100 as FIG. 1 , but now with one removable lens layer 300 and two removable lens layers 400, which may be laminated together to form the removable lens stack 20 shown in cross-section in FIG. 4. The base layer 100 of the removable lens stack 20 may be the same as the base layer of the removable lens stack 10 shown in FIGS. 1 and 2 and may be similarly attached to a surface, such as a goggle lens or visor, or a transparent window in a surgical helmet, hood, or gown, or may be attached to a frame around its periphery so that the removable lens stack 20 itself functions as a lens, visor, face shield, or the like. Advantageously, the removable lens stack 20 uses a moth-eye coating on some, but not all, layers, thereby reducing the difficulty and expense associated with producing a moth-eye coating. In the illustrated embodiment, for example, the base layer 100 is the only layer having a moth-eye coating, and the removable lens layers 300, 400 instead have a single-layer or multi-layer interference anti-reflection coating 340, 440, which may be less costly to produce (e.g., by spin coating, dip coating, or vacuum deposition). In particular, the first removable lens layer 300 may comprise a substrate 310, a single-layer or multi-layer interference anti-reflection coating 340 on a first surface 312 of the substrate 310, and a fluoropolymer coating 330 (with optional adhesive treatment 350) on a second surface 314 of the substrate 310 opposite the first surface 312. With the first removable lens layer 300 laminated on top of the base layer 100 and the second surface 314 of the substrate 310 facing the first surface 112 of the substrate 110 of the base layer 100, the fluoropolymer coating 330 may be shaped to conform to the moth-eye coating 120a, as described above.

[0036] One or more additional removable lens layers 400 may also be added to the stack, each comprising a substrate 410, a single- or multi-layer interference anti-reflective coating 440 on a first side 412, and an adhesive 450, such as an acrylic or polyurethane adhesive, on a second side 414. One such removable lens layer 400 may be laminated to a removable lens layer 300 such that the second side 414 of the substrate 410 faces the first side 312 of the substrate 300. Further removable lens layers 400 may be laminated thereon, with the second side 414 of each substrate 410 facing the first side 412 of the respective preceding substrate 400. It is also possible to use anti-reflective coatings 340, 440 that do not have protrusions (such as the moth-eye coating 120a), thereby avoiding any concerns about the adhesive 450 filling in around the protrusions and undesirably increasing the peel strength. As a result, various types of adhesives 450 may be used, including acrylic or polyurethane adhesives such as pressure-sensitive adhesives (PSAs), which may adhere (e.g., by applying pressure) to the anti-reflective coatings 340, 440 of the previous layers 300, 400. A hybrid removable lens stack 20 can effectively achieve the superior anti-reflective properties of a moth-eye by incorporating it into one or more layers, while simultaneously benefiting from one or more layers having less expensive anti-reflective coatings 340, 440 and / or adhesives 450. Thus, a hybrid removable lens stack 20 can represent a "best of both worlds" compromise that balances the need for high anti-reflective properties with manufacturing costs.

[0037] The examples of FIGS. 3 and 4 show one removable lens layer 300 (having a non-ME AR coating 340 and a fluoropolymer coating 330 for connecting with the moth-eye coating 120 a of the base layer 100) and two removable lens layers 400 (having a non-ME AR coating 440 and an acrylic or polyurethane adhesive 450) laminated to the base layer 100 to form the removable lens laminate 20. However, hybrid laminates of various other combinations of layers are also envisioned. For example, more or fewer removable lens layers 400 may be used. Also, one or more removable lens layers 200 (see FIGS. 1 and 2) may be added between the base layer 100 and the removable lens layers 300, in which case the fluoropolymer coating 330 of the removable lens layer 300 may contact the moth-eye coating 220 of the outermost removable lens layer 200 instead of directly contacting the moth-eye coating 120 a of the base layer 100. Alternatively, a substrate having a moth-eye coating may be incorporated further out in the stack with one or more substrates having an underlying non-ME AR coating. To this end, a modification layer 400 having a moth-eye coating may be used in place of the non-ME AR coating 440 (although an acrylic or polyurethane adhesive 450 would still be used to connect with the underlying non-ME AR coating). Hybrid removable lens stacks 20 of various configurations can be economically designed and produced according to the specific needs of manufacturers and consumers, both in terms of the degree of anti-reflection required and the desired unit cost.

[0038] It should also be noted that the use of moth-eye coatings on both sides of a layer (i.e., a forward-facing moth-eye pattern and a rear-facing moth-eye pattern) is not necessarily limited to the base layer 100. Either of the removable lens stacks 10, 20 may have such double-sided moth-eye layers at any position in the stack. For example, the stack may consist of multiple layers 100 stacked on top of each other (in some cases, they may be the only type of layer in the stack, such as a stack of three layers 100). A fluoropolymer coating may be applied between each pair of adjacent layers 100, which may be molded into the shape of a moth-eye coating as described above. However, in this case, the fluoropolymer coating may be molded into the shape of two moth-eye coatings facing each other with the fluoropolymer coating interposed therebetween. As one exemplary method for stacking multiple such double-sided moth-eye layers 100, a fluoropolymer coating may be coated onto the forward-facing moth-eye coating 120a of a first layer 100, thereby forming one side of the fluoropolymer coating into the shape of the forward-facing moth-eye coating 120a, and then a second layer 100 may be laminated onto the fluoropolymer coating, thereby forming the other side of the fluoropolymer coating into the shape of the rear-facing moth-eye coating 120b of the second layer 100. Stacking of additional layers 100 can continue in the same manner (or in combination with other types of layers, as described above), with the fluoropolymer coating being formed into the shape of two adjacent moth-eye coatings whenever necessary. Preferably, a release treatment may be applied to each forward-facing moth-eye coating 120a, an adhesion-promoting treatment may be applied to each rear-facing moth-eye coating 120b, or both, thereby promoting the fluoropolymer coating to peel away with each layer 100 when the layers 100 are removed from the stack. By using the moth-eye layers on both sides in this manner, it is possible to obtain a high degree of anti-reflection properties.Furthermore, depending on the moth-eye fabrication process used, producing two moth-eye coatings 120a, 120b on the same substrate 110 may be more cost-effective than producing individual moth-eye coatings on separate substrates, making the use of double-sided moth-eye layers potentially more efficient. The manufacturing process can also be simplified (and cost reduced) by using the same repeating layer 100 instead of multiple different layers.

[0039] The above description is given by way of example, not limitation. Given the above disclosure, those skilled in the art will be able to devise variations that are within the scope and spirit of the invention disclosed herein. Furthermore, the various features of the embodiments disclosed herein can be used alone or in varying combinations with each other and are not intended to be limited to the specific combinations described herein. Therefore, the scope of the claims should not be limited by the embodiments shown.

Claims

1. A removable lens stack, comprising: a base layer comprising a substrate and a moth-eye coating on a first surface of the substrate; a first removable lens layer comprising a substrate, a single-layer or multi-layer interference anti-reflection coating on a first side of the substrate, and a fluoropolymer coating on a second side of the substrate opposite the first side, the first removable lens layer being laminated on top of the base layer such that the second side of the substrate of the first removable lens layer faces the first side of the substrate of the base layer, the fluoropolymer coating being shaped to conform to the moth-eye coating; a second removable lens layer comprising a substrate, a single or multi-layer interference anti-reflection coating on a first side of the substrate, and an acrylic or polyurethane adhesive on a second side of the substrate opposite the first side, the second removable lens layer being laminated on top of the first removable lens layer such that the second side of the substrate of the second removable lens layer faces the first side of the substrate of the first removable lens layer.

2. The removable lens laminate of claim 1 , wherein the moth-eye coating comprises a polymer.

3. The removable lens laminate of claim 1 , wherein the moth-eye coating forms a pattern of protrusions having a half-wavelength pitch.

4. The removable lens laminate of claim 1 , wherein the moth-eye coating forms a pattern of protrusions having a height of half a wavelength.

5. The removable lens laminate of claim 1 , wherein the moth-eye coating forms a pattern of cones.

6. The removable lens laminate of claim 1 , wherein the base layer comprises a moth-eye coating on a second surface of the substrate opposite the first surface.

7. 10. The removable lens stack of claim 1, wherein in each of the base layer, the first removable lens layer, and the second removable lens layer, the substrate comprises polyethylene terephthalate (PET).

8. 10. The removable lens stack of claim 1, further comprising a third removable lens layer comprising a substrate, a single or multi-layer interference anti-reflection coating on a first side of the substrate, and an acrylic or polyurethane adhesive on a second side of the substrate opposite the first side, the third removable lens layer laminated on top of the second removable lens layer such that the second side of the substrate of the third removable lens layer faces the first side of the substrate of the second removable lens layer.

9. 9. The removable lens stack of claim 8, further comprising a fourth removable lens layer comprising a substrate, a single or multi-layer interference anti-reflection coating on a first side of the substrate, and an acrylic or polyurethane adhesive on a second side of the substrate opposite the first side, the fourth layer laminated on top of the third removable lens layer such that the second side of the substrate of the fourth removable lens layer faces the first side of the substrate of the third removable lens layer.

10. 10. The removable lens laminate of claim 1, wherein the first removable lens layer has a peel strength of less than about 100 grams per inch.

11. 11. The removable lens laminate of claim 10, wherein the peel strength of the first removable lens layer is between about 15 grams / inch and about 50 grams / inch.

12. 12. The removable lens stack of claim 11, wherein the peel strength of the first removable lens layer is between about 15 grams / inch and about 30 grams / inch.

13. 10. The removable lens laminate of claim 1, wherein the visible light transmission (VLT) is greater than 95%.

14. 14. The removable lens stack of claim 13, wherein the VLT is greater than 98%.

15. 1. A method of manufacturing a removable lens stack, comprising: providing a base layer comprising a substrate and a moth-eye coating on a first surface of the substrate; a first lamination step of laminating a first removable lens layer on top of the base layer, the first removable lens layer comprising a substrate, a single-layer or multi-layer interference anti-reflection coating on a first side of the substrate, and a fluoropolymer coating on a second side of the substrate opposite the first side, the first removable lens layer being laminated on top of the base layer such that the second side of the substrate of the first removable lens layer faces the first side of the substrate of the base layer; a laminating step of laminating the first removable lens layer to the base layer, wherein the fluoropolymer coating is shaped to conform to the moth-eye coating; a second lamination step of laminating a second removable lens layer on top of the first removable lens layer, the second removable lens layer comprising a substrate, a single-layer or multi-layer interference anti-reflection coating on a first side of the substrate, and an acrylic adhesive or a polyurethane adhesive on a second side of the substrate opposite the first side, the second removable lens layer being laminated on top of the first removable lens layer such that the second side of the substrate of the second removable lens layer faces the first side of the substrate of the first removable lens layer.

16. 16. The method of claim 15, wherein the laminating step comprises laminating the laminated first removable lens layer to the base layer under pressure at a temperature of less than 40°C.

17. The method of claim 15 , wherein the laminating step occurs before the second laminating step.

18. 16. The method of claim 15, further comprising applying a corona treatment between the substrate of the base layer and the moth-eye coating.

19. 16. The method of claim 15, further comprising applying a corona treatment between the substrate and the fluoropolymer coating of the first removable lens layer.

20. 16. The method of claim 15, further comprising laminating a third removable lens layer on top of the second removable lens layer, the third removable lens layer comprising a substrate, a single or multi-layer interference anti-reflection coating on a first side of the substrate, and an acrylic or polyurethane adhesive on a second side of the substrate opposite the first side, the third removable lens layer being laminated on top of the second removable lens layer such that the second side of the substrate of the third removable lens layer faces the first side of the substrate of the second removable lens layer.

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