Method for preparing metal pattern on flexible substrate

Abstract

The invention provides a method for preparing a metal pattern on a flexible substrate. A peelable solid layer is selectively formed on a patterned surface of a flexible substrate by applying a liquid solution on the patterned surface. The metal pattern on the flexible substrate may be formed by removing the peelable solid layer after metallization. In some cases, a peelable solid layer may be transferred from the patterned surface to a transfer layer having a metal pattern formed therein.

Description

[0001] This application is a divisional application of an invention patent application with an application date of June 27, 2019, application number 201980042635.9 (international application number PCT / IB2019 / 055466), and invention name “Method for preparing a metal pattern on a flexible substrate”. Technical Field

[0002] The present disclosure relates to methods of making metal patterns / features on flexible substrates, and devices made by the methods. Background Art

[0003] Metal patterns can be prepared on a substrate by various techniques. For example, in one typical process, poly(methyl methacrylate) (PMMA) can be first patterned on a substrate by a hot embossing lithography process, followed by reactive ion etching; then metal is deposited onto the entire surface; the PMMA is washed away along with the metal on the PMMA with acetone; and only the metal deposited onto the substrate remains. A typical hot embossing lithography process is described, for example, in U.S. Pat. No. 5,772,905 (Chou et al.). In another typical process, polyvinyl alcohol (PVA) resin is used instead of PMMA, so that water can be used for the wash-off step. Summary of the invention

[0004] Briefly, in one aspect, the present disclosure describes a method for forming a metal pattern on a flexible substrate. The method includes: providing a patterned surface on the flexible substrate. The patterned surface includes one or more recessed features and one or more platform features adjacent to the recessed features. The method also includes: coating the patterned surface with a liquid solution to at least partially fill the recessed features; hardening the liquid solution to form a strippable solid layer in the recessed features; etching the patterned surface after hardening the liquid solution; providing a metal layer to cover the patterned surface; and removing the solid layer in the recessed features together with the metal layer on the solid layer from the flexible substrate to form a metal pattern on the platform features of the flexible substrate.

[0005] In another aspect, the present disclosure describes a device made according to the above method. The device includes the metal pattern disposed only on the top surface of the platform feature. The platform feature has an average line width of about 50 nm to about 5 microns and an average height of about 50 nm to about 5 microns.

[0006] In another aspect, the present disclosure describes a method for forming a metal pattern. The method includes: providing a patterned surface, the patterned surface including one or more recessed features and one or more platform features adjacent to the recessed features; coating the patterned surface with a liquid solution to at least partially fill the recessed portions; hardening the liquid solution to form a peelable solid layer in the recessed portions; providing a transfer layer to adhere to the patterned surface; and removing the transfer layer from the patterned surface to form a patterned structure on the transfer layer. The solid layer is transferred from the patterned surface to the transfer layer, and one or more platform features of the patterned structure are formed. The method also includes: providing a metal layer on the patterned structure of the transfer layer; and removing the solid layer from the patterned structure together with the metal layer on the solid layer to form a metal pattern on the transfer layer.

[0007] In another aspect, the present disclosure describes a device made according to the above method. The device includes: the transfer layer, the transfer layer having a patterned surface, the patterned surface including one or more recessed features and one or more platform features adjacent to the recessed features; and the metal pattern, the metal pattern is only disposed in the recessed features. The recessed features have an average line width of about 50 nm to about 5 microns and an average depth of about 50 nm to about 5 microns.

[0008] Various unexpected results and advantages are obtained in the exemplary embodiments of the present disclosure. One such advantage of the exemplary embodiments of the present disclosure is that the liquid solution can be uniformly coated on the patterned surface. After the liquid solution hardens, a strippable solid layer can be selectively formed on the patterned surface for an effective stripping process after metallization.

[0009] Various aspects and advantages of the exemplary embodiments of the present disclosure have been summarized. The above summary of the invention is not intended to describe each illustrated embodiment or every implementation of the current certain exemplary embodiments of the present disclosure. The following drawings and detailed description more specifically illustrate certain preferred embodiments using the principles disclosed herein. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The present disclosure may be more fully understood by considering the following detailed description of various embodiments of the present disclosure in conjunction with the accompanying drawings, in which:

[0011] Figure 1A is a cross-sectional view of a flexible substrate having a patterned surface according to one embodiment.

[0012] Figure 1B A process according to one embodiment is shown Figure 1AA process for forming a release coating on a patterned surface.

[0013] Figure 1C According to one embodiment, a liquid solution is applied to Figure 1B process on a patterned surface.

[0014] Figure 1D Shown is a drying method according to one embodiment Figure 1C The process of converting a liquid solution into a solid layer.

[0015] Figure 2A The metal layer is provided to the Figure 1D process on a patterned surface.

[0016] Figure 2B According to one embodiment, Figure 2A The process of removing a solid layer together with the metal layer on the solid layer.

[0017] Figure 3A An etching process according to one embodiment is shown. Figure 1D The process of patterning a surface.

[0018] Figure 3B The metal layer is provided to the Figure 3A process on a patterned surface.

[0019] Figure 3C According to one embodiment, Figure 3B The process of removing a solid layer together with the metal layer on the solid layer.

[0020] Figure 4A The transfer layer is shown in accordance with one embodiment. Figure 1D process on a patterned surface.

[0021] Figure 4B According to one embodiment, Figure 4A A cross-sectional view of the transfer layer after being removed from the patterned surface together with the solid layer to form a patterned structure on the patterned surface.

[0022] Figure 5A According to one embodiment, Figure 4B A process for providing a metal layer on a patterned structure.

[0023] Figure 5B A method of removing a solid layer from a substrate together with a metal layer on the solid layer is shown according to one embodiment. Figure 5A The process of removing the patterned structure.

[0024] Fig. 6AAn etching process according to one embodiment is shown. Figure 4B The process of patterning a surface.

[0025] Figure 6B The metal layer is provided to the Fig. 6A process on a patterned surface.

[0026] Figure 6C According to one embodiment, Figure 6B The process of removing a solid layer together with the metal layer on the solid layer.

[0027] Figure 7 is a top plan view of a schematic diagram of a metal pattern on a substrate according to one embodiment.

[0028] Figure 8 Microscopic images of Example 8 are shown.

[0029] Fig. 9 Microscopic images of Example 9 are shown.

[0030] In the accompanying drawings, similar reference numerals indicate similar elements. Although the above-identified drawings, which may not be drawn to scale, set forth various embodiments of the present disclosure, other embodiments as mentioned in the detailed description are also conceivable. In all cases, the present disclosure describes the currently disclosed disclosure in the manner of representation of exemplary embodiments rather than by expressing limitations. It should be understood that those skilled in the art may devise many other modifications and embodiments that fall within the scope and essence of the present disclosure. DETAILED DESCRIPTION

[0031] For the following Glossary of defined terms, these definitions shall govern throughout this application, unless a different definition is provided in the claims or elsewhere in the specification.

[0032] Glossary

[0033] Certain terms are used throughout the specification and claims, which, although mostly well known, may require some explanation. It should be understood that:

[0034] By using orientation terms such as "atop," "on," "over," "overlying," "uppermost," "under," and the like, with respect to the positions of various elements in the disclosed coated articles, we refer to the relative position of the elements with respect to a horizontally disposed, upwardly facing substrate. However, unless otherwise indicated, the present invention is not intended that a substrate or article should have any particular spatial orientation during or after manufacture.

[0035] By using the term "overlying" to describe the position of a layer relative to a substrate or other element of an article of the present disclosure, we refer to the layer as being on top of the substrate or other element, but not necessarily adjacent to the substrate or other element.

[0036] By using the term “separated by” to describe the position of a layer relative to other layers, we refer to the layer as being positioned between two other layers, but not necessarily contiguous or adjacent to either layer.

[0037] The term "about" or "approximately" with respect to a value or shape means + / -5% of that value or characteristic or feature, but explicitly includes the exact value. For example, a viscosity of "about" 1 Pa-sec means a viscosity from 0.95 Pa-sec to 1.05 Pa-sec, but also explicitly includes a viscosity of just 1 Pa-sec. Similarly, a "substantially square" perimeter is intended to describe a geometric shape having four side edges, wherein the length of each side edge is 95% to 105% of the length of any other side edge, but also includes a geometric shape in which each side edge has exactly the same length.

[0038] The term "substantially" with respect to a property or characteristic means that the property or characteristic is exhibited to a greater extent than the opposite of the property or characteristic is exhibited. For example, a "substantially" transparent substrate is one that transmits more radiation (e.g., visible light) than it does not transmit (e.g., absorbs and reflects). Thus, a substrate that transmits more than 50% of visible light incident on its surface is substantially transparent, but a substrate that transmits 50% or less of visible light incident on its surface is not substantially transparent.

[0039] As used in this specification and the accompanying embodiments, the singular forms "a", "an", and "the" include plural referents unless the content clearly indicates otherwise. Thus, for example, reference to a fine fiber comprising "a compound" includes a mixture of two or more compounds. As used in this specification and the accompanying embodiments, the term "or" is generally used in its sense including "and / or" unless the content clearly dictates otherwise.

[0040] As used in this specification, the recitations of numerical ranges by endpoints include all numbers subsumed within that range (eg, 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.8, 4, and 5).

[0041] Unless otherwise specified, all numerals of the expression amount or composition, characteristic measurement, etc. used in this specification and embodiment should be understood to be modified by the term "about" in all cases. Therefore, unless otherwise specified, the numerical parameters shown in the above specification and the attached embodiment list can vary according to the desired characteristics sought to be obtained by those skilled in the art using the teaching content of the present disclosure. At the very least, and without attempting to limit the application of the principle of equivalents to the scope of the embodiment protected by the claims, each numerical parameter should be interpreted at least according to the reported significant digits and by applying the usual rounding method.

[0042] Various exemplary embodiments of the present disclosure will now be described with specific reference to the accompanying drawings. Various modifications and changes may be made to the exemplary embodiments of the present disclosure without departing from the spirit and scope of the present disclosure. Therefore, it should be understood that the embodiments of the present disclosure are not limited to the exemplary embodiments described below, but should be controlled by the limiting factors shown in the claims and any equivalents thereof.

[0043] Figure 1A 4 is a cross-sectional view of a flexible substrate having a patterned surface according to one embodiment. The patterned surface 40 is formed on the main surface of the flexible substrate 2. The patterned surface 40 includes one or more recessed features 42 and one or more platform features 44 adjacent to the recessed features 42. In some embodiments, the platform features 44 may form a grid configuration, such as Figure 7 Grid 52 is shown. Grids as described herein are generally understood to mean pattern geometries having connecting traces separated by open areas 54 to form cells. Illustrative examples of grids having linear traces include, for example, grids having hexagonal and square cells. In some embodiments, the open area of ​​the grid may be, for example, greater than 90%, greater than 95%, or greater than 98%. The platform features 44 may have an average line width in the range of, for example, about 50 nm to about 5 microns or about 100 nm to about 3 microns; and an average height in the range of, for example, about 50 nm to about 5 microns or about 100 nm to about 3 microns.

[0044] In some embodiments, substrate 2 can be a flexible substrate, such as a web of indefinite length polymer material. When moving along the web path, the flexible substrate or web can be stretched (e.g., longitudinally and / or transversely). The flexible substrate can include, for example, polyethylene terephthalate (PET), polyethylene, polystyrene, polyurethane, etc. The process described herein can be performed on a roll-to-roll device including one or more rollers to convey the web along the web path. Substrate 2 can have, for example, a thickness of about 2 mm or less, about 1 mm or less, about 500 microns or less, or about 200 microns or less.

[0045] In some embodiments, patterned surface 40 can be formed directly on flexible substrate 2. Figure 1A In the depicted embodiment of , patterned surface 40 is formed on patterned layer 4 disposed on substrate 2 .

[0046] In some embodiments, the patterned surface 40 can be formed on the substrate 2 by a micro-replication process. In some embodiments, a layer of curable material can be disposed on the substrate 2 to form the patterned layer 4. The curable material can include, for example, polydimethylsiloxane (PDMS), epoxy resin, UV-curable acrylate resin, etc. A micro-replication stamp can be provided to press against the curable material layer to form a replicated feature on the curable material layer. The curable material can be cured by various methods, including, for example, heat, UV, electron beam radiation, etc. It should be understood that the patterned surface 40 can be formed on the substrate 2 by any suitable method (such as, for example, embossing, micro-molding, micro-matching, laser etching, 3D printing, etc.).

[0047] In some embodiments, the patterned layer 4 may include one or more release coating materials that exhibit relatively low surface adhesion strength. Such release coating materials may include, for example, siloxane, silicone, polytetrafluoroethylene, etc.

[0048] In some embodiments, patterned surface 40 may be treated to reduce its surface adhesive strength. Figure 1B In the depicted embodiment, according to one embodiment, processing Figure 1A The patterned surface 40 is formed by a plasma deposition process. The peeling coating 46 is formed on the patterned surface. In some embodiments, the peeling coating 46 can be formed by a plasma deposition process. Gaseous hexamethyldisiloxane (HMDSO) can be introduced into the reaction chamber, and the peeling coating is formed on the patterned surface 40 in the presence of plasma. The peeling coating can have a thickness of, for example, less than about 500 nm, less than about 200 nm, or less than 100 nm. Exemplary plasma deposition processes and apparatus are described in WO 2018 / 005109 (Yu et al.), which is incorporated herein by reference.

[0049] The liquid solution may be disposed on the patterned surface 40 to selectively form a strippable solid layer on the patterned surface. Figure 1C In the embodiment of FIG. 4 , after the release coating 46 is formed, the liquid solution 6 is disposed on the patterned surface 40 . The liquid solution 6 fills the recessed features 42 and covers the terrace features 44 . Figure 1C In the depicted embodiment of , the liquid solution 6 has a surface level 61 above the land features 44. It should be understood that in some embodiments, the liquid solution 6 may have a surface level 61 below the land features 44 and only be present in the recessed features 42.

[0050] In some embodiments, the liquid solution 6 may be a poly(vinyl alcohol) (PVA) solution in water. It should be understood that the liquid solution may contain other solutes, such as, for example, polyvinyl butyral (PVB), curable acrylates, film formers, etc. The liquid solution may be dissolved in any combination of common solvents such as water, isopropanol, methyl ethyl ketone, hexane, ethyl acetate. The surface energy of the liquid composition may be increased by adding a surfactant such as, for example, polyethylene glycol p-(1,1,3,3-tetramethylbutyl)-phenyl ether (available under the trade name Triton ™ X-100 was commercially available from Sigma-Aldrich Chemical Company, Milwaukee, WI) to modify the

[0051] The liquid solution 6 is then hardened to form a peelable solid layer 62 in the recessed feature 42. In some embodiments, the liquid solution 6 can be hardened by drying at a temperature of, for example, about 25° C. to about 175° C. or about 50° C. to about 100° C. The patterned surface 40 has a relatively low surface adhesive strength, so that the solid layer 62 can be separated or peeled from the recessed feature 42, for example, by peeling or washing. Figure 1D In the depicted embodiment of FIG. 4 , after hardening, hardening product residues 64 remain on the land features 44. The dry thickness of the hardening product residues 64 is thinner than the dry thickness of the solid layer 62 in the recessed features. In some embodiments, the dry thickness of the hardening product residues 64 can be, for example, about ½ or less, about 1 / 3 or less, about 1 / 5 or less, or about 1 / 10 or less of the dry thickness of the solid layer 62 in the recessed features.

[0052] In the depicted embodiment, the platform features 44 each have a flat top surface. In some embodiments, the platform features 44 may have various protruding shapes, such as, for example, a prism or pyramid shape, a hemispherical shape, a bullet-like shape, etc. Various protruding features are described in U.S. Pat. No. 8,703,232 (Stay et al.), which is incorporated herein by reference. In some embodiments, the platform features 44 may have a protruding shape that allows the liquid solution 6 to flow from the platform features into the recessed features 42 to reduce the amount of hardened product residue 64 on the platform features 44. In some embodiments, the platform features 44 may have a hydrophobic surface property that repels the liquid solution 6 from flowing from the platform features into the recessed features.

[0053] After forming the strippable solid layer 62 in the recessed features, a conductive layer may be disposed on the patterned surface. The conductive layer may be, for example, a metal layer, or include any suitable conductive material. Figure 2A According to one embodiment, a metal layer 8 is provided to cover Figure 1D The first portion 82 of the metal layer 8 is disposed in the recessed feature 42 ; and the second portion 84 of the metal layer 8 is disposed on the top surface of the platform feature 44 .

[0054] The metal layer 8 can be formed by any desired process, including, for example, evaporation, sputtering, electron beam deposition, physical vapor deposition, chemical vapor deposition, liquid coating, etc. In some embodiments, the metal layer can include multiple layers, for example, including a bonding layer to be in direct contact with the patterned surface and another metal (e.g., copper, silver, gold, aluminum, etc.) layer on top of the bonding layer. The bonding layer (also known as an adhesive or adhesion promotion layer) can include chromium, chromium oxide, ITO, AZO, nickel, titanium, etc. It should be understood that the metal layer can include any suitable conductive material.

[0055] In some embodiments, the metal layer 8 may have an average thickness of, for example, about 0.01 micrometers to about 2 micrometers, about 0.02 micrometers to about 1 micrometer, or about 0.025 micrometers to about 0.5 micrometers. In some embodiments, the metal layer 8 may be continuous, have one or more surfaces that conform to the surface morphology of the patterned surface, and have a generally uniform thickness. In some embodiments, the metal layer 8 may have a non-uniform thickness. For example, as Figure 2A As shown, metal layer 8 may have a reduced thickness or even be discontinuous at step 66 .

[0056] After the metal layer is formed on the patterned surface, a stripping process may be performed to remove the strippable solid layer 62 in the recessed features together with the metal layer 82 on the strippable solid layer from the patterned surface. The remaining metal layer 84 on the patterned surface 40 forms a metal pattern, such as Figure 2B shown.

[0057] In some embodiments, the solid layer 62 may be a water-soluble polymer layer that can be removed from the patterned surface 40 by, for example, pressure washing, ultrasonic cleaning, etc. When the solid layer 62 comprises poly(vinyl alcohol) (PVA), the solid layer 62 can be dissolved and peeled off from the substrate by water washing. In some embodiments, the solid layer 62 can be removed by peeling. In one embodiment, a curable resin layer (e.g., an acrylate resin) can be coated on the patterned surface 40. The curable resin layer can be cured together with the metal layer in the recessed features and the strippable solid layer, and peeled off from the patterned surface 40. The curable resin material can have a suitable affinity for the metal layer so that the metal layer on the top of the platform can remain on the patterned surface, and the strippable solid layer can be removed together with the metal layer on the strippable solid layer. In some embodiments, the metal layer can be applied in such a way that the metal layer is more strongly bonded to the patterned surface, such as, for example, deposition using sputtering and / or using a bonding layer.

[0058] It should be understood that the strippable solid layer 62 can be any suitable resist that can be removed from the patterned surface 40 by applying, for example, a solvent, heat, cooling, stripping, etc. In some embodiments, the release coating 46 below the solid layer 62 in the recessed features can be completely or partially removed along with the solid layer 62.

[0059] In some embodiments, prior to providing a metal layer on the platform feature, the hardening product residue 64 remaining on the platform feature 44 after hardening can be removed (see, e.g., Figure 1D ).exist Figure 3A In the depicted embodiment of FIG, the residue 64 has been removed from the platform feature 44' by etching. Any suitable etching process may be used, including, for example, reactive ion etching (RIE), such as oxygen or octafluoropropane plasma etching. After removing the hardened product residue 64 from the platform feature 44, the etching process may continue to remove the underlying lift-off coating 46 (see FIG. Figure 1B ), to expose the top surface of the platform feature 44. In some embodiments, RIE can remove the hardening product residue and then modify the chemistry of the underlying release coating 46. Etching can also slightly reduce the thickness of the solid layer 62' in the recessed features. In some embodiments, the thickness of the solid layer 62' can be reduced, for example, by less than 20%, less than 10%, or less than 5%.

[0060] The etching process used herein can be used to modify the chemistry of the release coating 46 (on the platform features). Such modifications can be beneficial to improve the adhesion of the metal layer disposed on the release coating. The etching process used herein can be well controlled so that it can not cause crosslinking in the strippable solid layer, which can cause the solid layer to adhere more strongly to the substrate and be less soluble in water. The process described herein can be technically superior to conventional hot imprint lithography processes, such as the process described in U.S. Pat. No. 5,772,905 (Chou et al.), in which the heavy reactive ion etching process can degrade the substrate surface and the metal / substrate interface formed thereafter.

[0061] After etching, a conductive layer may be disposed onto the patterned surface. Figure 3B According to one embodiment, a metal layer 8' is provided to cover Figure 3A The process of patterning the surface of the substrate. The first portion 82' of the metal layer 8' is disposed on the strippable solid layer 62' in the recessed feature; and the second portion 84' of the metal layer 8' is disposed directly on the top surface of the platform feature 44'. The stripping process can be performed to remove the solid layer 62' in the recessed feature together with the metal layer 82' on the solid layer. Figure 3C is a cross-sectional view of a metal pattern 84 ′ on a platform feature 44 ′.

[0062] In some embodiments, the coating is provided with a selectively formed peelable solid layer (such as Figure 1D The patterned surface of the structure shown in FIG. 1 can be used as a molding surface to prepare a metallization pattern. It should be understood that the patterned surface can be made of other suitable materials such as, for example, metal. Figure 4A The transfer layer is shown in accordance with one embodiment. Figure 1D In some embodiments, before providing the transfer layer on the platform feature, the hardening product residue 64 remaining on the platform feature 44 after hardening can be removed (see, for example, Figure 1D ), such as Figure 3A The embodiment shown.

[0063] The transfer layer 7 includes an adhesive layer 74 in direct contact with the patterned surface of the patterned layer 4. The adhesive layer 74 is supported by a flexible backing layer 72. In some embodiments, the adhesive layer 74 can be formed by placing a curable liquid on the patterned surface to form a cured product. In some embodiments, the adhesive layer can be at least partially formed by re-dissolving the peelable solid layer 62 and using the re-dissolved layer as at least a portion of the adhesive layer. The adhesive layer can also be solvent-coated onto the backing 72 or on top of the patterned surface.

[0064] Adhesive layer 74 may include any suitable adhesive material having desired properties. Adhesive layer 74 may be releasable or stretch releasable, and may be releasable from the patterned surface of substrate 2. In some embodiments, the adhesive may include at least one of a rubber, silicone, or acrylic adhesive. In some embodiments, the adhesive may include a tackified rubber adhesive, such as natural rubber; olefins; silicones such as silicone polyureas or silicone block copolymers; synthetic rubber adhesives such as polyisoprene, polybutadiene, and styrene-isoprene-styrene, styrene-ethylene-butylene-styrene, and styrene-butadiene-styrene block copolymers and other synthetic elastomers; and tackified or untackified acrylic adhesives, such as copolymers of isooctyl acrylate and acrylic acid, which can be polymerized by radiation, dissolution, suspension, or emulsion techniques; polyurethanes; silicone block copolymers; and combinations thereof. The adhesive may be, for example, any of the adhesives described in any of the following patent applications, all of which are incorporated herein by reference: PCT Patent Publication Nos. 2015 / 035556, 2015 / 035960, and US Patent Publication No. 2015 / 034104.

[0065] In some embodiments, the backing layer 72 may have sufficient flexibility so that the transfer layer 7 can provide conformability and resilience properties, which are helpful when the adhesive layer 74 is bonded to the patterned surface of the patterned layer 4 and when it is removed from the patterned surface by peeling. In some embodiments, the flexible backing layer 72 may include a flexible polymer film. The flexible backing layer 72 may include, for example, polyethylene terephthalate (PET), polyethylene, polystyrene, polyurethane, etc. The process described herein may be performed on a roll-to-roll device including one or more rollers to convey the web along a web path. The transfer layer 7 may have a thickness of, for example, about 2 mm or less, about 1 mm or less, about 500 microns or less, or about 200 microns or less.

[0066] When the transfer layer 7 is peeled off from the substrate 2 , the peelable solid layer 62 and, in some embodiments, the hardened product residue 64 may be attached to the adhesive layer 74 and transferred from the patterned layer 4 to the transfer layer 7 . Figure 4B A cross-sectional view of a transferred layer 7 forming a patterned structure 54 is shown. In the depicted embodiment, the patterned structure 54 may be Figure 1A The negative protrusions of the patterned surface 40. The patterned structure 54 includes a corresponding Figure 1A The protruding features 542 of the recessed features 42 of the patterned surface 40 and the corresponding Figure 1A The protruding feature 542 has a top portion including the peelable solid layer 62 and a bottom portion of the material including the adhesive layer 74. The hardened product residue 64 is attached to the bottom surface of the recessed portion 544. It should be understood that the release coating 46 (see Figure 1B ) may be at least partially transferred from the patterned layer 4 to the transfer layer 7 along the solid layer 62 and the hardened product residue 64, thereby covering the solid layer 62 and the hardened product residue 64, respectively.

[0067] In some embodiments, the recesses 544 may form a grid configuration, such as Figure 7 Grid 52 is shown. Grids as described herein are generally understood to mean pattern geometries having connecting traces separated by open areas to form cells. Illustrative examples of grids having linear traces include, for example, grids having hexagonal and square cells. Recesses 544 may have an average line width in the range of, for example, about 50 nm to about 5 microns and an average depth in the range of, for example, about 50 nm to about 5 microns.

[0068] A metal layer may be disposed onto the patterned configuration of the transfer layer. Figure 5A According to one embodiment, Figure 4B5. The metal layer includes a first portion 92 disposed on the top surface of the protruding feature 542 and a second portion 94 disposed on the bottom surface of the recessed portion 544.

[0069] The metal layer can be formed by any desired process including, for example, evaporation, sputtering, electron beam deposition, physical vapor deposition, chemical vapor deposition, liquid coating, etc. In some embodiments, the metal layer can include multiple layers, for example, including a bonding layer (e.g., nickel or titanium) to be in direct contact with the patterned surface and another metal (e.g., copper, silver, gold, aluminum, etc.) layer on top of the bonding layer.

[0070] like Figure 5A As shown, the first portion 92 and the second portion 94 of the metal layer are disconnected from each other. That is, the metal layer is not conformally formed on the side of the protruding feature 542. It should be understood that the metal layer can be at least partially formed on the side of the protruding feature 542 with reduced thickness.

[0071] In some embodiments, the metal layer 94 in the recess 544 can have an average thickness of, for example, about 0.01 micrometers to about 2 micrometers, about 0.02 micrometers to about 1 micrometer, or about 0.025 micrometers to about 0.5 micrometers. In some embodiments, the metal layer 94 in the recess 544 can be continuous, have one or more surfaces that conform to the surface morphology of the bottom surface of the recess 544, and have a substantially uniform thickness. In some embodiments, the metal layer 94 can have a non-uniform thickness.

[0072] After forming the metal layer on the transfer layer 7, a peeling process may be performed to remove the solid layer 62 on the protruding features 542 together with the metal layer 92 on the solid layer. In some embodiments, the solid layer 62 may be a water-soluble polymer layer that can be removed from the transfer layer 7 by, for example, pressure washing. When the solid layer 62 includes poly(vinyl alcohol) (PVA), the solid layer 62 may be dissolved and peeled off from the substrate by water washing. In some embodiments, the solid layer 62 may be removed by peeling. In one embodiment, a curable resin layer may be coated on the transfer layer 7. The curable resin layer may be cured together with the metal layer and the solid layer on the protruding features, and peeled off from the patterned structure 54. Figure 5B is a cross-sectional view of the remaining metal pattern 94 in the recess 544 .

[0073] In some embodiments, the hardening product residues 64 remaining in the recesses 544 of the transfer layer 7 may be removed before the metal layer is disposed on the transfer layer 7 (see, e.g. Figure 4B ).exist Fig. 6AIn the depicted embodiment of , the hardening product residue 64 has been removed by etching from the bottom surface of the recess 544. Any suitable etching process may be used including, for example, reactive ion etching (RIE), such as oxygen or octafluoropropane plasma etching.

[0074] In some embodiments, etching may first remove the release coating 46 on the surface (if applicable), and continue to remove the underlying hardened product residue 64 to expose the bottom surface of the recess 544. Etching may also slightly reduce the thickness of the solid layer 62 of the protruding feature 522. In some embodiments, the thickness of the solid layer 62 may be reduced, for example, by less than 20%, less than 10%, or less than 5%.

[0075] After etching, the metal layer can be placed Fig. 6A On the patterned structure 54'. Figure 6B According to one embodiment, a metal layer is provided to cover Fig. 6A The first portion 92' of the metal layer is disposed on the solid layer 62 of the protruding feature; and the second portion 94' of the metal layer is disposed directly on the bottom surface of the recessed portion 544'. A lift-off process may be performed to remove the solid layer 62' together with the metal layer 92' on the solid layer from the transfer layer 7. Figure 6C is a cross-sectional view of the metal pattern 94 ′ in the recessed portion 544 ′ of the transfer layer 7 .

[0076] The metal patterns described herein (e.g., Figure 2B 84 of them Figure 3C 84', Figure 5B 94 of them Figure 6C 94' in) can be applied to various devices. In some embodiments, the metal pattern may be disposed only on the platform features of the patterned surface to form a grid shape on the flexible substrate. In some embodiments, the metal pattern may be disposed only in the recessed portion of the patterned surface to form a grid shape on the flexible substrate. The metal pattern may have a thickness of, for example, about 20nm to 500nm. In some embodiments, the flexible substrate having a patterned surface supporting a metal pattern may be transparent. In some embodiments, the patterned surface having a metal pattern may be backfilled with a material that matches the refractive index of the top layer of the structured layer. Exemplary backfill materials are described in U.S. Patent 8,703,232 (Stay et al.), which is incorporated herein by reference.

[0077] Although the above description provides a grid pattern of metal or other conductive materials on a flexible substrate, it should be understood that other material patterns can be formed on a flexible substrate in a similar manner. For example, the material used for such a pattern may include ceramics, inks, or any suitable optical material. In addition, similar processes / methods can be used to prepare suitable patterns other than grids on a flexible substrate.

[0078] The processes described herein, such as, for example, microreplication, plasma coating, etching, coating, hardening / drying, lamination, stripping, metal deposition (e.g., sputtering), metal evaporation, etc., can be performed in a continuous or roll-to-roll manner. An exemplary continuous or roll-to-roll microreplication process is described in U.S. Pat. No. 9,759,663 (Halverson et al.). An exemplary continuous or roll-to-roll process of plasma coating and etching is described in U.S. Pat. No. 8,460,568 (David et al.). An exemplary continuous or roll-to-roll process of coating and drying is described in U.S. Pat. No. 8,623,140 (Yapel et al.). Lamination and stripping of the web can be added after the coating step. An exemplary continuous or roll-to-roll process of metal deposition is described in U.S. Pat. No. 6,172,810 (Fleming et al.).

[0079] Various modifications and changes may be made to the exemplary embodiments of the present disclosure without departing from the spirit and scope of the present disclosure. Therefore, it should be understood that the embodiments of the present disclosure are not limited to the exemplary embodiments described below, but should be controlled by the limiting factors shown in the claims and any equivalents thereof.

[0080] List of Exemplary Embodiments

[0081] It should be understood that any of Embodiments 1 to 16, Embodiments 17 to 27, and Embodiments 28 to 30 may be combined.

[0082] Embodiment 1 is a method for forming a metal pattern on a flexible substrate, the method comprising:

[0083] providing a patterned surface on the flexible substrate, the patterned surface comprising one or more recessed features and one or more land features adjacent to the recessed features;

[0084] coating the patterned surface with a liquid solution to at least partially fill the recessed features;

[0085] hardening the liquid solution to form a peelable solid layer in the recessed feature;

[0086] etching the patterned surface after hardening the liquid solution;

[0087] providing a metal layer to cover the etched patterned surface; and

[0088] The solid layer in the recessed features is removed from the flexible substrate along with the metal layer on the solid layer to form a metal pattern on the land features of the flexible substrate.

[0089] Embodiment 2 is a method according to embodiment 1, the method further comprising: before applying the liquid solution, treating the patterned surface to form a release coating on the patterned surface.

[0090] Embodiment 3 is a method according to embodiment 1 or 2, wherein the liquid layer also covers the platform features on the patterned surface.

[0091] Embodiment 4 is a method according to any one of embodiments 1 to 3, wherein after the hardening, a hardening product residue remains on the platform feature portion, and the dry thickness of the hardening product residue is at most ½ of the thickness of the solid layer in the recessed feature portion.

[0092] Embodiment 5 is a method according to embodiment 4, wherein the hardened product residue has a dry thickness of about 200 nm or less.

[0093] Embodiment 6 is a method according to any one of embodiments 2 to 5, wherein the etching is capable of removing or modifying the release coating.

[0094] Embodiment 7 is a method according to any one of embodiments 1 to 6, wherein the metal layer is provided together with the bonding layer by sputtering deposition.

[0095] Embodiment 8 is a method according to any one of embodiments 1 to 7, wherein removing the solid layer further comprises: coating the metal layer with a curable resin, and curing the curable resin to form a cured resin layer.

[0096] Embodiment 9 is the method according to embodiment 8, the method further comprising: peeling off the cured resin layer to remove the solid layer in the recessed feature together with the metal layer on the solid layer from the flexible substrate.

[0097] Embodiment 10 is the method according to any one of embodiments 1 to 9, wherein providing a patterned surface on the flexible substrate comprises forming microreplicated features on the flexible substrate.

[0098] Embodiment 11 is a method according to embodiment 9, wherein the microreplicated features are formed on a patterned surface layer of the flexible substrate.

[0099] Embodiment 12 is the method according to any one of embodiments 2 to 10, wherein the release coating is formed by a plasma deposition process using hexamethyldisiloxane (HMDSO).

[0100] Embodiment 13 is a method according to any one of embodiments 1 to 12, wherein the liquid solution comprises poly(vinyl alcohol) (PVA).

[0101] Embodiment 14 is a method according to any one of embodiments 1 to 13, wherein the metal pattern on the platform features of the flexible substrate forms a grid shape having an open area greater than 95%.

[0102] Embodiment 15 is a method according to any one of embodiments 1 to 14, wherein the patterned surface having the metal pattern is backfilled with a material that matches the refractive index of the patterned surface.

[0103] Embodiment 16 is a device made according to the method of any one of embodiments 1 to 15, the device comprising:

[0104] the flexible substrate;

[0105] the metal pattern being disposed only on the top surface of the platform feature to form a grid shape on the flexible substrate,

[0106] The terrace features have an average line width of about 50 nm to about 5 microns and an average height of about 50 nm to about 5 microns.

[0107] Embodiment 17 is a method for forming a metal pattern, the method comprising:

[0108] providing a patterned surface comprising one or more recessed features and one or more platform features adjacent to the recessed features;

[0109] coating the patterned surface with a liquid solution to at least partially fill the recesses;

[0110] hardening the liquid solution to form a peelable solid layer in the recessed portion;

[0111] providing a transfer layer to adhere to the patterned surface;

[0112] removing the transfer layer from the patterned surface to form a patterned configuration on the transfer layer, the solid layer being transferred from the patterned surface to the transfer layer and forming one or more land features of the patterned configuration;

[0113] providing a metal layer on the patterned structure of the transferred layer; and

[0114] The solid layer together with the metal layer on the solid layer is removed from the patterned structure to form a metal pattern on the transfer layer.

[0115] Embodiment 18 is a method according to embodiment 17, the method further comprising: treating the patterned surface to form a release coating on the patterned surface.

[0116] Embodiment 19 is a method according to embodiment 17 or 18, wherein the transfer layer includes an adhesive layer, and the adhesive layer is a cured product of a curable liquid applied to the patterned surface.

[0117] Embodiment 20 is the method according to embodiment 19, wherein the transfer layer further comprises a flexible backing layer to support the adhesive layer.

[0118] Embodiment 21 is a method according to any one of embodiments 17 to 20, the method further comprising: etching the patterned surface before providing the transfer layer.

[0119] Embodiment 22 is a method according to any one of embodiments 17 to 21, the method further comprising: etching the patterned structure before providing the metal layer on the patterned structure.

[0120] Embodiment 23 is a method according to any one of embodiments 17 to 22, wherein the metal layer is provided together with the bonding layer by sputtering deposition.

[0121] Embodiment 24 is the method according to any one of embodiments 17 to 23, wherein the solid layer and the metal layer on the solid layer are removed by water washing.

[0122] Embodiment 25 is a method according to any one of embodiments 17 to 24, wherein the solid layer and the metal layer on the solid layer are removed by peeling.

[0123] Embodiment 26 is a method according to any one of embodiments 17 to 25, wherein the patterned surface having the metal pattern is backfilled with a material that matches the refractive index of the patterned surface.

[0124] Embodiment 27 is a device made according to the method of any one of embodiments 17 to 26, the device comprising:

[0125] the transfer layer having a patterned surface including one or more recessed features and one or more protruding features adjacent to the recessed features; and

[0126] the metal pattern, the metal pattern being disposed only in the recessed portion to form a grid shape,

[0127] The depressed portions have an average line width of about 50 nm to about 5 microns and an average depth of about 50 nm to about 5 microns.

[0128] Embodiment 28 is a method for forming a conductive grid pattern on a flexible substrate, the method comprising:

[0129] providing a patterned surface including recessed portions and land features, the land features forming a grid pattern;

[0130] coating the patterned surface with a liquid solution to at least partially fill the recesses;

[0131] hardening the liquid solution to form a peelable solid layer,

[0132] The thickness of the peelable solid layer in the recessed portion is at least 2 times, at least 5 times, or at least 10 times the thickness on the platform feature portion.

[0133] Embodiment 29 is a method according to embodiment 28, the method also including: providing a metal layer to cover the patterned surface; and removing the solid layer in the recess together with the metal layer on the solid layer to form a grid metal pattern on the platform feature portion.

[0134] Embodiment 30 is a method according to embodiment 28, further comprising:

[0135] providing a transfer layer to adhere to the patterned surface;

[0136] removing the transfer layer from the patterned surface to form a patterned configuration on the transfer layer, the solid layer being transferred from the patterned surface to the transfer layer and forming one or more land features of the patterned configuration;

[0137] providing a metal layer on the patterned structure of the transferred layer; and

[0138] The solid layer is removed from the patterned construction together with the metal layer on the solid layer to form a mesh metal pattern on the transferred layer.

[0139] The operation of the present disclosure will be further described with reference to the examples described in detail below. These examples are provided to further illustrate various specific and preferred embodiments and techniques. However, it should be understood that many variations and modifications may be made and still fall within the scope of the present disclosure.

[0140] Example

[0141] These embodiments are for illustrative purposes only and are not intended to unduly limit the scope of the appended claims. Although the numerical ranges and parameters showing the broad scope of the present disclosure are approximate, the numerical values ​​shown in the specific examples are reported as accurately as possible. However, any numerical value inherently contains certain errors, and the standard deviation existing in its respective test measurements will inevitably cause such errors. At the very least, and without attempting to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should at least be interpreted based on the reported significant digits and by applying conventional rounding methods.

[0142] Materials Summary

[0143] Unless otherwise specified, all parts, percentages, ratios, etc. in the examples and the rest of this specification are by weight. Table 1 provides the abbreviations and sources of all materials used in the following examples:

[0144] Table 1

[0145]

[0146] Solution mixture

[0147] "Mixture 1" is a combination of 75 wt% aliphatic urethane diacrylate, 25 wt% diacrylate, and 0.5% photoinitiator.

[0148] "Mix 2" is a solution of 3%-10% PVA, 10% isopropyl alcohol, 0.05% Tergitol in DI water.

[0149] Base

[0150] Two types of patterned surfaces were used. Both patterned surfaces were formed by roll-to-roll microreplication. Mel 454 was coated with Mix 1, rolled against a structured tool, cured using UV light, and then peeled from the tool.

[0151] The first pattern is Figure 7 The "pseudo-random meander" pattern depicted. The lines in the figure represent features with nearly vertical sidewalls that are 2 microns high and 2 microns wide. The average pitch of the cells is 200 microns.

[0152] The second pattern is the hexagonal pattern of US Patent Publication No. 2013 / 0306359 depicted in Figure 1. The lines in the figure represent features that are 2 microns high, 2 microns wide at the peak, and 4 microns wide at the base. The pitch of the hexagons is 200 microns.

[0153] Coating and etching methods

[0154] On the patterned surface, one or more layers are added or subtracted using known coating and etching techniques.

[0155] Hexamethyldisiloxane (HMDSO) was deposited using plasma coating techniques. Here, a homemade parallel plate capacitively coupled plasma reactor was used to lift-off the surface. The chamber had a surface area of ​​18.3 ft 2 The central cylindrical powered electrode of the reactor was placed on the powered electrode. After the structured film was placed on the powered electrode, the reaction chamber was pumped down to a base pressure of less than 1.3 Pa (2 mTorr). HMDSO was evaporated into the chamber through a ½ tube without restriction. Processing was performed using a plasma enhanced CVD method by coupling RF power into the reactor at a frequency of 13.56 MHz and an applied power of 2000 watts. Processing time was controlled by moving the microstructured film through the reaction zone at a rate of 30 feet per minute.

[0156] The die coating technique is a roll-to-roll technique for depositing liquid solutions. The solution is coated using a slot die at a speed of 10 feet per minute and dried between 70°C and 110°C in an oven approximately 6m long. The solution concentration and feed rate are adjusted to achieve the correct dry thickness.

[0157] The solutions were coated onto monolithic specimens using the Mayer rod technique. The solution concentration and the Mayer rod were adjusted to achieve the correct dry thickness. These solutions were allowed to dry at room temperature.

[0158] "Sputtered" silver was deposited using a known vacuum sputtering method. Silver was deposited by evaporation using a known electron beam evaporation method. For both methods, a 10 nm layer of Cr was deposited as a bonding layer. These systems can be run in batch or roll-to-roll form.

[0159] The single-piece sample was etched using a batch etching method. A vacuum was drawn in a Plasmatherm model 3032 capacitor plasma reactor and oxygen was flowed in at a rate of 500 standard cubic centimeters per minute. The reactor power was set to 1350 watts. The amount of etching was controlled by adjusting the time the reactor was turned on.

[0160] The etching was continuous using a roll-to-roll etching method. The samples were etched in a home-made chamber with a web path of approximately 3 meters. The web speed and number of passes were adjusted to vary the residence time in the reactor. Octafluoropropane flowed at a rate of 250 standard cubic centimeters per minute, and oxygen flowed at a rate of 750 standard cubic centimeters per minute. The reactor power was set to 6000 watts.

[0161] Test Method

[0162] The following test methods were used to evaluate some of the embodiments of the present disclosure. Transmittance, haze, and clarity were measured using BYK-Gardner haze-gardplus. Conductivity was measured using a two-point probe between two lines coated with TEC-PR-041 (Ink Tec Inc. Newton, NC) or using a custom probe (two one-centimeter contacts separated by one centimeter). Microscope images were obtained using an Olympus MX61L.

[0163] Table 1

[0164]

[0165] Example

[0166] Examples of the preparation of various release coatings on patterned surfaces according to the present disclosure are illustrated below, along with one or more comparative examples.

[0167] Example 1

[0168] The pseudo-random curved pattern was plasma coated with HDMSO. Mix 2 was die coated to a dry thickness of 0.5 microns. Silver was sputtered in a batch process to a thickness of 200 nanometers. The silver layer was laminated to Mel454 with Mix 1 and then cured with UV light and then peeled to remove the solid layer from the recessed features.

[0169] Example 2

[0170] The pseudo-random curved pattern was plasma coated with HDMSO. Mixture 2 was die coated to a dry thickness of 0.5 micrometers. Silver was sputtered to a thickness of 200 nanometers in a batch process. The substrate was placed under an ultrasonic horn for 10 seconds to remove the solid layer.

[0171] Example 3

[0172] The hexagonal pattern was plasma coated with HDMSO. Mixture 2 was die coated to a dry thickness of 1 micron. The patterned surface was roll-to-roll etched for 30 seconds. Silver was sputtered to a thickness of 200 nanometers in a roll-to-roll process. The silver layer was laminated to Mel454 with Mixture 1 and then cured with UV light and then peeled to remove the solid layer from the recessed features.

[0173] Example 4

[0174] The metallization pattern from Example 1.2 was backfilled with Mixture 1, laminated to the COP, and cured with UV light.

[0175] Example 5

[0176] The hexagonal pattern was plasma coated with HDMSO. Mixture 2 was coated with a Meyer rod to a dry thickness of 1 micron. The pattern was etched in a batch process for 30 seconds. Silver was sputtered in a batch process to a thickness of 200 nanometers. The silver layer was laminated to Mel454 with Mixture 1 and then cured with UV light and then stripped to remove the solid layer from the recessed features.

[0177] Comparative Example 6

[0178] The hexagonal pattern was plasma coated with HDMSO. Mix 2 was die coated to a dry thickness of 0.5 microns. Silver was sputtered to a thickness of 200 nanometers in a batch process. The silver layer was laminated to Mel454 with Mix 1 and then cured with UV light and then peeled off to remove the solid layer from the recessed features.

[0179] Comparative Example 7

[0180] Mix 2 was coated with a Mayer rod to a dry thickness of 1 micron on a hexagonal pattern. The pattern was etched in a batch process for 30 seconds. Silver was sputtered in a batch process to a thickness of 200 nanometers. The silver layer was laminated to Mel454 with Mix 1 and then cured with UV light and then peeled to remove the solid layer from the recessed features.

[0181] Table 2

[0182]

[0183] Example 8

[0184] The hexagonal pattern was plasma coated with HDMSO. Mixture 2 was die coated to a dry thickness of 2 microns. The pattern was transferred to Mel454 by coating Mixture 1, curing with UV light, and then stripping. The patterned structure was etched for 30 seconds in a batch process. Silver was sputtered to a thickness of 200 nanometers in a batch process. A silver layer was laminated to Mel454 with Mixture 1, then cured with UV light, and then stripped to remove the solid layer from the recessed features.

[0185] Comparative Example 9

[0186] The hexagonal pattern was plasma coated with HDMSO. Mix 2 was die coated to a dry thickness of 2 microns. The pattern was transferred to Mel454 by coating Mix 1, curing with UV light, and then peeling. Silver was sputtered to a thickness of 200 nanometers in a batch process. A silver layer was laminated to Mel454 with Mix 1, then cured with UV light, and then peeled to remove the solid layer from the recessed features.

[0187] Product characteristics

[0188] The transmittance, haze, clarity, and conductivity of Examples 1 to 7 are reported in Table 3.

[0189] Table 3

[0190]

[0191] None of the samples from Examples 8 or 9 were conductive, but Figure 8 and Fig. 9 As can be seen from the micrographs shown, Example 8 contains more metal on the traces.

[0192] References throughout this specification to "one embodiment", "certain embodiments", "one or more embodiments" or "an embodiment", whether or not the term "exemplary" is included before the term "embodiment", mean that the particular features, structures, materials or characteristics described in conjunction with the embodiment are included in at least one embodiment of certain exemplary embodiments of the present disclosure. Therefore, phrases such as "in one or more embodiments", "in certain embodiments", "in one embodiment" or "in an embodiment" appearing throughout this specification do not necessarily refer to the same embodiment in certain exemplary embodiments of the present disclosure. Furthermore, specific features, structures, materials or characteristics may be combined in any suitable manner in one or more embodiments.

[0193] Although this specification has described certain exemplary embodiments in detail, it should be understood that those skilled in the art can easily think of changes, modifications and equivalents of these embodiments after understanding the above. Therefore, it should be understood that the present disclosure should not be unduly limited to the exemplary embodiments shown above. In particular, as used herein, the numerical range expressed by the end value is intended to include all numerical values ​​contained in the range (for example, 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4 and 5). In addition, all numbers used herein are considered to be modified by the term "about".

[0194] In addition, all publications and patents cited herein are incorporated herein by reference in their entirety, just as if each individual publication or patent was specifically and individually indicated to be incorporated by reference. Various exemplary embodiments have been described. These and other embodiments are within the scope of the following claims.

Claims

1. A method for forming a metal pattern on a flexible substrate, the method comprising: providing a patterned surface on the flexible substrate, the patterned surface comprising one or more recessed features and one or more land features adjacent to the recessed features; treating the patterned surface to form a release coating thereon; applying a liquid solution over the release coating on the patterned surface to at least partially fill the recessed features and cover the land features; hardening the liquid solution to form a peelable solid layer in the recessed features and a hardened product residue on the land features, wherein the hardened product residue has a dry thickness of at most one-half the thickness of the peelable solid layer in the recessed features; etching the patterned surface after hardening the liquid solution to remove the hardening product residues from the mesa features; providing a metal layer to cover the etched patterned surface; as well as removing the peelable solid layer in the recessed features together with the metal layer on the peelable solid layer from the flexible substrate to form a pattern of the metal layer on the land features of the flexible substrate; Wherein etching the patterned surface after hardening the liquid solution further comprises chemically modifying the release coating on the mesa features to increase adhesion to the metal layer.

2. The method of claim 1, wherein removing the solid layer further comprises: coating the metal layer with a curable resin and curing the curable resin to form a cured resin layer; and separating the cured resin layer from the flexible substrate to remove the peelable solid layer in the recessed feature together with the metal layer on the peelable solid layer from the flexible substrate. 3 . The method of claim 1 , wherein providing a patterned surface on the flexible substrate comprises forming microreplicated features on the flexible substrate. The method according to claim 1 , wherein the release coating is formed by a plasma deposition process using hexamethyldisiloxane (HMDSO).

5. The method of claim 1, wherein the liquid solution comprises poly(vinyl alcohol) (PVA). 6 . The method of claim 1 , wherein the metal pattern on the land features of the flexible substrate forms a grid shape having an open area greater than 95%.

7. The method of claim 1, wherein the patterned surface having the metal pattern is backfilled with a material having a refractive index matching that of the patterned surface.

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