WO2012082668A2

WO2012082668A2 - Patterned film and articles made therefrom

Info

Publication number: WO2012082668A2
Application number: PCT/US2011/064516
Authority: WO
Inventors: Guglielmo M. Izzi; Daniel R. Fronek; Thomas Herdtle; Nelson D. Sewall; Mieczyslaw H. Mazurek; Danny L. Fleming; Vivian W. Jones
Original assignee: 3M Innovative Properties Company
Priority date: 2010-12-13
Filing date: 2011-12-13
Publication date: 2012-06-21
Also published as: WO2012082667A2; WO2012082667A3

Abstract

A patterned film is disclosed. The patterned film includes at least a first patterned region and a non-patterned region juxtaposed with the first patterned region on a first surface of the patterned film. The patterned region has a series of substantially parallel peaks separated from each other by a series of substantially parallel valleys. The first patterned region and the non-patterned region extend side-by-side for the length of the patterned film in the machine direction, and the parallel peaks and parallel valleys in the first patterned region extend at an angle of at least five degrees to the machine direction. An article including an airfoil or hydrofoil have a seamless portion of the patterned film on its surface is also disclosed.

Description

PATTERNED FILM AND ARTICLES MADE THEREFROM

Cross Reference to Related Applications

This application claims priority to U. S. Provisional Application Nos. 61/422,395 and 61/422,406, both filed December 13, 2010, the disclosures of which are incorporated by reference herein in their entirety.

Background

It may be desirable to modify the surface of a body that passes through fluid media in use (e.g., an airplane that moves through air or a boat that moves through water). For example, protective films can be applied to a portion of the surface (e.g., to prevent abrasion of the surface). Also, some films applied to the surface may reduce the turbulent flow when the body passes through fluid media. Reducing turbulent flow can reduce drag, for example, and relatively small reductions in drag can significantly reduce the fuel needed to propel the body. Reduction in turbulent flow can also result in a reduction in noise, which is desirable for some applications.

Various films that can reduce turbulent flow are known and comprise a thermoplastic or thermoset polymeric film having a patterned surface that reduces drag, for example. Examples of these films can be found in U. S. Pat. Nos. 4,930,729 (Savill); 4,986,496 (Marentic et al.); 5,848,769 (Fronek et al.); 5,971,326 (Bechert); and 6,345,791 (McClure). These films, often referred to as riblet films, are typically prepared in continuous film processes with parallel grooves (also called riblets) extending in the machine direction. To apply such films, a tiling process is typically carried out in which the films are cut into strips and placed onto an airfoil or hydrofoil piece-by-piece to have the riblets correctly oriented in the main direction of fluid flow. Summary

The tiling process for applying riblet films to airfoils or hydrofoils can be time-consuming and labor-intensive. Very precise placement of the film pieces is necessary so that there are no gaps between pieces that can increase turbulence, resulting in increased noise or drag. Any protective film that may be desired (e.g., a protective film for the leading edge of the airfoil or hydrofoil) is typically separately applied, which provides further opportunities for gaps and exposed edges potentially detrimental to aerodynamic performance. The present disclosure provides a film that includes a patterned region and a non-patterned region, which may be useful, for example, both for reducing the turbulent flow at the surface of an airfoil or hydrofoil and for protecting at least a portion of the airfoil or hydrofoil. The patterned region of the film has a series of substantially parallel peaks separated from one another by a series of substantially parallel valleys, which are useful, for example, for reducing the turbulent flow at the surface of the article. The film is configured so that a portion of the airfoil or hydrofoil that is desired to be provided with a patterned surface (e.g., for drag reduction or noise reduction) may be covered with a single piece of film in which the substantially parallel peaks and substantially parallel valleys are oriented in the streamwise direction, where turbulence intensity is typically minimized. The non-patterned surface of the film can be useful for protecting a portion of the surface of the airfoil or hydrofoil that does not usually experience turbulent flow and may, for example, wrap around the leading edge of the airfoil or hydrofoil to provide protection (e.g., against abrasion).

The patterned film according to the present disclosure can be made, for example, by film processes in which the series of substantially parallel peaks separated from each other by a series of substantially parallel valleys are at an angle to the machine direction of the film. A piece large enough to cover the desired area of the airfoil or hydrofoil can then be cut and placed on the surface. This process eliminates the need for the time-consuming and labor-intensive tiling operation of applying riblet films. Since the film contains a non-patterned region that is useful, for example, for wrapping around the leading edge of an airfoil or hydrofoil, a separate protective tape need not be applied. Exposed edges of protective film are thereby advantageously eliminated as well as any edge tape that may be necessary to cover such exposed edges and thus eliminating undesirable turbulence formation.

In one aspect, the present disclosure provides a patterned film having an indefinite length in a machine direction, the patterned film comprising:

at least a first patterned region on a first surface of the patterned film, the patterned region comprising a series of substantially parallel peaks separated from each other by a series of substantially parallel valleys; and

a non-patterned region juxtaposed with the first patterned region on the first surface of the patterned film,

wherein the first patterned region and the non-patterned region extend side-by-side for the indefinite length of the patterned film in the machine direction, and wherein the parallel peaks and parallel valleys in the first patterned region extend at an angle of at least five degrees to the machine direction.

In some embodiments, the patterned film further comprises a second patterned region on the first surface of the patterned film, the second patterned region comprising a second series of substantially parallel peaks separated from each other by a second series of substantially parallel valleys, wherein the non-patterned region extends between and separates the first and second patterned regions on the first surface.

In another aspect, the present disclosure provides an article comprising an airfoil or hydrofoil having a leading edge; and

a patterned film according to the present disclosure on the airfoil or hydrofoil, wherein the first patterned region is on a surface of the airfoil or hydrofoil, wherein the non-patterned region wraps around the leading edge of the airfoil or hydrofoil. In another aspect, the present disclosure provides an article comprising:

an airfoil or hydrofoil having a leading edge and first and second opposing major surfaces; and a patterned film having first and second patterned regions on the airfoil or hydrofoil, wherein the first patterned region is on the first major surface of the airfoil or hydrofoil, wherein the non-patterned region wraps around the leading edge of the airfoil or hydrofoil, and wherein the second patterned region is on the second major surface of the airfoil or hydrofoil.

In another aspect, the present disclosure provides a roll comprising the patterned film disclosed herein.

In this application, terms such as "a", "an" and "the" are not intended to refer to only a singular entity, but include the general class of which a specific example may be used for illustration. The terms

"a", "an", and "the" are used interchangeably with the term "at least one". The phrase "at least one of followed by a list refers to any one of the items in the list and any combination of two or more items in the list. All numerical ranges are inclusive of their endpoints and non-integral values between the endpoints unless otherwise stated.

The term "substantially parallel" when referring to peaks and valleys means that the peaks and valleys can deviate from parallel by up to 5 (in some embodiments, up to 2.5 or 1) degrees. The substantially parallel peaks and valleys may be linear or may have a slight curvature or slight oscillation.

The oscillation or curvature may be to an extent such that it does not reduce the turbulence reduction properties of the seamless film.

The term "peaks" refers to surface features of the seamless film in the form of projecting edges, which typically are generally pointed at least at a portion of their apexes. The term "valleys" refers to the hollow spaces formed in between the peaks.

The term "machine direction" (MD) as used herein denotes the direction of a running, continuous film. When a portion of a continuous film is placed on the airfoil or hydrofoil, the machine direction corresponds to the long dimension "1" of the patterned film. As used herein, the terms machine direction and long dimension are typically used interchangeably. The term "cross-direction" (CD) as used above and below denotes the direction which is essentially perpendicular to the machine direction.

The term "spanwise direction" as used herein refers to the predominant direction of the span of the airfoil or hydrofoil. The airfoil or hydrofoil need not follow a straight line along its span. The "spanwise direction" can be determined, for example, with a vector passing through a point on each end of the airfoil or hydrofoil.

The term "film" as used herein refers to a self-supporting construction that is formed

independently from the airfoil or hydrofoil and can be handled on its own. Generally, the film disclosed herein is not an in-situ formed coating or layer on a surface.

The term "wall unit" refers to the non-dimension distances used to describe the height of peaks or the distance between peaks. Wall units are determined by multiplying the actual distance by the scalar quantity (square root of τ/ρ) divided by υ, where τ is the wall shear stress, p is the fluid density, and υ is the fluid kinematic viscosity.

The term "non-patterned region" as used herein means that the film in that region has no perceptible pattern of organized, structured features having a height of at least 0.1 wall unit or 1 micron. The "non-patterned region" is not required to be free of any surface roughness or texturing. The "non- patterned region" may be said to be free of a series of substantially parallel peaks separated from each other by a series of substantially parallel valleys.

As used herein, the term "polymer" encompasses both homopolymers, which are made from a single monomer, and copolymers, which are made from more than one monomer.

Brief Description of the Drawings

The disclosure may be more completely understood in consideration of the following detailed description of various embodiments of the disclosure in connection with the accompanying drawings, in which:

FIG. 1 is a perspective view of an embodiment of a patterned film according to the present disclosure;

FIG. 2 is an embodiment of a cross-sectional view taken along line 2-2 in FIG. 1 ;

FIG. 3 is a cross-sectional view similar to FIG. 2 but showing a different patterned surface useful in some embodiments of the present disclosure;

FIG. 4 is a cross-sectional view similar to FIG. 2 but showing another patterned surface useful in some embodiments of the present disclosure;

FIG. 5 is a cross-sectional view similar to FIG. 2 but showing yet another patterned surface useful in some embodiments of the present disclosure;

FIG. 6 is a cross-sectional view similar to FIG. 2 but showing yet another patterned surface useful in some embodiments of the present disclosure;

FIG. 7 is a fragmentary perspective of another embodiment of a patterned film according to the present disclosure where the peaks do not have a uniform height along their entire lengths;

FIG. 8 is a fragmentary perspective of another embodiment of a patterned film according to the present disclosure where the peaks progressively change in height along their lengths;

FIG. 9 is a fragmentary perspective of another embodiment of a patterned film according to the present disclosure where the peaks are not continuous across the film;

FIG. 10 is a schematic top view of a patterned film according to some embodiments of the present disclosure;

FIG. 1 1 is an embodiment of a cross-sectional view taken along line 1 1-1 1 in FIG. 10;

FIG. 12 is an exploded perspective view of an embodiment of an article including an airfoil or hydrofoil according to the present disclosure; FIG. 12A is an exploded side view of another embodiment of an article including an airfoil or hydrofoil according to the present disclosure; and

FIG. 13 is a schematic representation of a microrep Heating tool roll useful for making a patterned film according to the present disclosure.

Detailed Description

Reference will now be made in detail to embodiments of the disclosure, one or more examples of which are illustrated in the drawings. Features illustrated or described as part of one embodiment can be used with other embodiments to yield still a third embodiment. It is intended that the present disclosure include these and other modifications and variations.

A perspective view of an exemplary patterned film according to present disclosure is illustrated in FIG. 1. Patterned film 5 has at least a first patterned region 10 and a non-patterned region 15 juxtaposed with the first patterned region on the first surface of the patterned film. The first patterned region 10 has a series of substantially parallel peaks 20 separated from each other by a series of substantially parallel valleys 22. The substantially parallel peaks 20 and substantially parallel valleys 22 appear visible in

FIGS. 1 to 9, they are typically microscopic in size. The first patterned region 10 and the non-patterned region 15 extend side -by-side for the indefinite length of the patterned film in the machine direction (MD).

The substantially parallel peaks 20 and valleys 22 of patterned film 5 are oriented at an angle of at least five degrees to the machine direction "MD" of patterned film 5. In some embodiments, including the illustrated embodiment, the angle between the substantially parallel peaks 20 and valleys 22 and the machine direction "MD" of the patterned film 5 is at least 10, 20, 30, or 45 degrees and may be up to 90 degrees. In some embodiments, the angle between the substantially parallel peaks 20 and valleys 22 and the machine direction "MD" of the patterned film 5 is in a range from 20 to 90 degrees, 30 to 90 degrees, 60 to 90 degrees, or 75 to 90 degrees. In some embodiments, the substantially parallel peaks 20 and valleys 22 are perpendicular to the machine direction "MD" of the patterned film 5. Advantageously, the angle between the parallel peaks 20 and valleys 22 and the machine direction "MD" of the patterned film 5 can be tailored based on the aerodynamic or hydrodynamic requirements for a given application. For example, when the patterned film 5 is designed to be cut and placed on an airfoil or hydrofoil, it may be desirable to determine the shape of the airfoil, the angle of attack, and expected wind speeds in use and selecting a direction of the substantially parallel peaks and valleys 20 and 22 accordingly. In some embodiments, there is more than one series of substantially parallel peaks 20 separated from each other by a series of substantially parallel valleys 22 (e.g., in first patterned region 10) with each series oriented in a different direction. This may be useful, for example, depending on the aerodynamic requirements of the airfoil or the hydrodynamic requirements of the hydrofoil. The non-pattemed region 15 is intended to be a usable part of the film, and not simply edges of the film to be discarded. The patterned region(s) 10 and non-patterned region 15 are meant to be used together to provide different functions, for example, when the film 5 is cut in the cross-direction and applied to an airfoil or a hydrofoil. In some embodiments, the non-patterned region 15 forms at least 20 (in some embodiments, at least 30, 40, or 50) percent of the surface area of the film. In some

embodiments, the non-patterned region 15 forms up to 90 (in some embodiments, up to 80, 75, or 70) percent of the surface area of the film. In some embodiments, the non-patterned region 15 forms in a range from 20 to 90, 30 to 80, 30 to 75, 40 to 90, or 50 to 85 percent of the surface area of the film.

The patterned film has longitudinal side edges that extend in the machine direction. In some embodiments, the first patterned region 10 is located between (e.g., only between) one of the longitudinal side edges and a longitudinal center line of the patterned film. In some embodiments, the non-patterned region 15 is located in a central portion, which includes the longitudinal center, of the film and in some embodiments may extend from a central portion of the film to one of the longitudinal side edges.

In some embodiments, including the embodiment illustrated in FIG. 2, the patterned film 5 is a multilayer film. Either one or both of the first patterned region 10 and the non-patterned region 15 may be made up of multiple layers. And the first patterned region 10 and non-patterned region 15 need not be (and typically are not) identical in cross-section. An exemplary cross-sectional view of the first patterned region 10 taken along line 2-2 in FIG. 1 is shown in FIG. 2. In the embodiment shown in FIG. 2, the first patterned region 10 has a top layer 1 1 in which the series of substantially parallel peaks 20 and substantially parallel valleys 22 is provided. The multilayer first patterned region 10 further comprises optional tie layer 12 which is useful in some embodiments for promoting adhesion to base layer 13. In the illustrated embodiment, the film further comprises an adhesive layer 14 disposed between base layer 13 and an optional, removable liner 16. Exemplary materials useful for each component 1 1, 12, 13, 14, and 16 are described in detail, below.

The first patterned region 10 may have any arrangement of the series of substantially parallel peaks 20 separated from each other by the series of substantially parallel valleys 22 useful for reducing turbulent flow as a fluid (e.g., air, gas, water, or oil) flows over a body (such as an article according to the present disclosure) or as the body (such as the article according to the present disclosure) moves through a fluid. In cross-section, the first patterned region 10 may have a variety of wave forms. In FIG. 2, the first patterned region 10 has a symmetric saw tooth pattern, where each of the substantially parallel peaks 20 is identical as is each of the substantially parallel valleys 22. The base of the peak may be the same as the distance between peaks.

In the embodiment illustrated in FIG. 3, a series of substantially parallel, symmetric peaks 20 is separated by flat-bottomed valleys 26 in the first patterned region 10 of the patterned film. This configuration can be referred to as a skip tooth configuration. In a skip tooth configuration, the angle "a" between the side walls 25 and 27 of the peak cross-section may be the same or different for adjacent peaks 20. Useful angles "a" may be in the range from about 15 to 140 degrees, in some embodiments, in a range from 15 to 60 degrees. The distance between peaks 20 may be smaller or larger than the height of the peaks. In some embodiments, the distance between peaks is from 0.5 to 4 times the height of the peaks.

FIGS. 4 and 5 illustrate different shaped peaks that can be useful in a skip tooth configuration. In the embodiment illustrated in FIG. 4, the peaks 40 have a pencil shape. That is, the side walls 45 and 47 of the peaks 40 are substantially parallel to each other near the flat-bottomed valleys and then converge to form a sharp ridges. The angle "b" between the side walls 45 and 47 depends, for example, on the distance between the side walls 45 and 47 when they are converging and may be in the range from about 15 to 140 degrees, in some embodiments, 15 to 60 degrees. In FIG. 4, angle "b" is about 30 degrees. In FIG. 5, the side walls 55 and 57 of peaks 50 also change direction. Near the flat-bottomed valleys, the angle "d" between side walls 55 and 57 is larger than the angle "c"' between side walls 55 and 57 at the apex. Again, useful angles "c" and "d" may be in the range from about 15 to 140 degrees, or 15 to 60 degrees. In FIG. 5, angle "c" is about 30 degrees, and angle "d" is about 53 degrees. The shape of peaks 50 shown in FIG. 5 can also be useful in a saw tooth configuration where there are not flat-bottomed valleys between peaks.

In some embodiments, some of the substantially parallel peaks when viewed in cross-section are larger in height than others of the parallel peaks. For example, FIG. 6 shows a series of parallel peaks 28 and 30 that are of different heights, separated by a series of parallel valleys 22.

Other variations in cross-sectional shape are envisioned. For example, each of the peaks and valleys may be asymmetric (e.g., have side walls with different lengths). The peaks and valleys may also be rounded (e.g., they may have concave side walls). Adjacent peaks may have the same height with different widths, or adjacent peaks may be different in both height and width.

In some embodiments, at least some of the parallel peaks vary in height along the length of the peaks. For example, in the fragmentary, perspective view of the top patterned surface of film 71 illustrated in FIG. 7, peaks 70 are features that extend along the surface substantially in the x-direction. In the embodiment shown, the maximum height in the z-direction and spacing in the y-direction of peaks 70 are substantially uniform. Each peak 70 has a generally triangular cross-section in the y-z-plane. The height at the top edge 75 of the peaks 70 varies along the x-axis to form peaks 77 and valleys 79 in the x- z plane. The peaks 77 and valleys 79 are symmetrically spaced apart from one another along the top edge 75 of each peak 70. Peaks 77 and valleys 79 may have a variety of shapes. In the illustrated

embodiment, each peak 77 has a generally arcuate shape in the x-z-plane, and each valley 79 has a substantially flat shape in the x-z-plane. In addition, the peaks 77 align with each other in the y-direction, and the valleys 79 align with each other in the y-direction. In other embodiments, peaks 77 may be offset from each other in the y-direction, and valleys 79 may be offset from each other in the y-direction.

Positioning of peaks 77 and valleys 79 can be optimized to reduce turbulent flow across the surface of the article. In some embodiments, in terms of wall units, the spacing between peaks 77 in the x-direction is between 10 and 100.

While in FIG. 7, the height of the peaks is undulating along the length of the peaks, the embodiment of FIG. 8 illustrates peaks 80 that progressively change in height. In FIG. 8, the peaks 80 of patterned film 81 have a constant base width, but their height increases continuously along their length to give them an increasingly sharper triangular profile. In some embodiments, the substantially parallel peaks progressively decrease in height as they approach the non-patterned region. In these embodiments, the substantially parallel peaks ultimately disappear into the non-patterned region. In some embodiments, the peaks are faired into the wall surface. The valleys may either narrow or widen as the peak or valley progresses from one end of the article to the other. In some embodiments, the height and/or width of a given peak or valley may change as the peak or valley progresses from one end of the article to the other.

In some embodiments, at least some of the parallel peaks are discontinuous across the patterned film. For example, the peaks and valleys may terminate for a portion of the patterned film. In the embodiment illustrated in FIG. 9, the peaks 90 of patterned film 91 have short cross-direction-extending gaps 99. The gaps may be less than the boundary layer thickness in the streamwise direction. In other embodiments, the substantially parallel peaks and valleys may terminate for a portion of the patterned film in the machine direction. This may be advantageous, for example, when it is desirable to have a portion of the span of an airfoil or hydrofoil to not be provided with substantially parallel peaks and valleys.

The optimum dimensions of the peaks 20, 40, 50, 70, 80, or 90 are somewhat dependent upon the speed at which the surface to be covered passes through the fluid (or the speed at which the fluid passes over the surface). The size of the peaks may be selected, for example, to achieve maximum efficiency in the specific area of a selected airfoil or hydrofoil and may depend on, for example, the local wind speed, the Reynolds number, the shape of the airfoil, and the angle of attack of the fluid over the airfoil. For more discussion on this topic with regard to drag reduction, see AIAA-88-0138, "Drag Reduction for

External Boundary Layers Using Riblets and Polymers," L. W. Reidy and G. W. Anderson, presented at the AIAA 26th Aerospace Sciences Meeting, Jan. 1 1-14, 1988 at Reno, Nev. In some embodiments, the peaks may have a height of about 10 to 400 microns (about 0.4 to 16 mils) above the valleys. In some embodiments, when the patterned film is provided for drag reduction, the peaks may be about 20 to 150 microns (about 0.8 to 6 mils) high for high speed uses (e.g., aircraft). Higher peak heights (e.g., in the range from about 150 microns to 400 microns (about 6 to 16 mils) may be useful for noise reduction applications. In some embodiments, the peaks increase in size as they approach the trailing edge of the airfoil or hydrofoil. In some of these embodiments, the peaks may have a height useful for noise reduction near the trailing edge of the airfoil or hydrofoil, and they may have a height useful for drag reduction in other regions. The peak-to-peak spacing between adjacent peaks likewise may be adjusted depending on the application. A spacing of about 10 to 300 microns (about 0.4 to 12 mils) may be useful. In some embodiments (e.g., aircraft applications) a spacing of about 20 to 150 microns (about 0.8 to 6 mils) may be desirable for drag reduction.

A top view of another embodiment of a patterned film according to present disclosure is illustrated in FIG. 10. Patterned film 105 has first patterned region 1 10a and second patterned region 1 10b on the first surface of the patterned film. The first patterned region comprises a first series of substantially parallel peaks separated from each other by a first series of substantially parallel valleys 20,22, and the second patterned region comprises a second series of substantially parallel peaks separated from each other by a second series of substantially parallel valleys. Non-patterned region 1 15 extends between and separates the first and second patterned regions 1 10a and 1 10b. The first patterned region 1 10a, the non-patterned region 15, and the second patterned region 110b extend side-by-side for the indefinite length of the patterned film in the machine direction (MD). The series of substantially parallel peaks and the series of substantially parallel valleys in the first patterned region may be different from the second series of substantially parallel peaks and the series of substantially parallel valleys in the second patterned region. For example, the difference may be in at least one of height of the substantially parallel peaks, the angle between the substantially parallel peaks and the machine direction, the length of the substantially parallel peaks, or the spacing between the substantially parallel peaks. Also the second series of substantially parallel peaks and valleys may have a different configuration of peaks and valleys or a different progressively changing pattern (e.g., in height, direction, or spacing) than the first series of substantially parallel peaks. A cross-section of the first patterned region or the second patterned region taken through the peaks may have any of the configurations shown in FIGS. 2 to 6, for example.

An exemplary cross-sectional view of the patterned film 105 taken along line 1 1-1 1 in FIG. 10 is shown in FIG. 1 1. In the illustrated embodiment, the patterned film 105 is a multilayer film in each of the first and second patterned regions 1 10a and 1 10b and in the non-patterned region 1 15. The first and second patterned region 1 10a and 1 10b and non-patterned region 1 15 are not identical in cross-section. In some embodiments, the multilayer film comprises at least first and second layers of different materials, and wherein the first and second layers have different thicknesses relative to each other in the non- patterned region and in the first patterned region. In the illustrated embodiment, the patterned film 105 has a layer 1 1 1 in which the series of substantially parallel peaks and substantially parallel valleys (not shown in FIG. 1 1) is provided in the patterned regions. The layer 1 1 1 is continuous through the first patterned region 1 10a, the non-patterned region 115, and the second patterned region 110b, but it is thinner in the first and second patterned regions 110a and 1 10b than in the non-patterned region 1 15. Patterned film 105 also has a base layer 1 13. Base layer 1 13 is continuous through the first patterned region 1 10a, the non-patterned region 1 15, and the second patterned region 1 10b, and in the illustrated embodiment has a substantially uniform thickness. In the illustrated embodiment, the film further comprises an adhesive layer 1 14 disposed between base layer 13 and optional, removable liner 1 16. The multilayer patterned film 105 may optionally further comprise a tie layer 1 12 which is useful in some embodiments for promoting adhesion between layer 1 1 1 and base layer 1 13. The substantially parallel peaks and substantially parallel valleys may be provided as a separate thin layer (not shown in FIG. 1 1) in first and second patterned regions 110a and 1 10b. In yet other embodiments, a separate thin layer on top of layer 1 1 1 (not shown in FIG. 1 1) may be continuous across the first and second patterned region 1 10a and 1 10b and non-patterned region 1 15 and contain the substantially parallel peaks and substantially parallel valleys in the patterned regions. Exemplary materials useful for each component 1 1 1, 1 12, 1 13, 1 14, and 1 16 are described in detail, below.

In some embodiments, including embodiments where the patterned film 5 and 105 is a multilayer film, the entire thickness of patterned film 5 and 105 is in a range from about 50 to 500 microns thick (about 2 to 20 mils). However, in some embodiments, at least a portion of the non-patterned region 15 and 1 15 may be thicker than the first and/or second patterned regions 10, 1 10a, and 1 10b and may have a thickness in a range from about 250 to 914 microns (about 10 to 36 mils), in some embodiments, about 250 to 500 microns (about 10 to 20 mils), or about 250 to 400 microns (about 10 to 16 mils). In some of these embodiments, the first and/or second patterned region 10, 110a, and 1 10b may have a thickness in a range from about 50 to 400 microns thick (about 2 to 16 mils), in some embodiments, about 75 to 150 microns (about 3 to 6 mils). The thickness of the patterned film may progressively taper from the first patterned region to the non-patterned region and optionally into the second patterned region. In some embodiments, it may be useful for at least a portion of the non-patterned region to be thicker than the first and/or second patterned regions, for example, to provide adequate abrasion protection for a leading edge of an airfoil or hydrofoil.

In general, the patterned film according to the present disclosure has a first patterned surface where the second surface, opposite the first surface, is not provided with a pattern. That is, the second surface may be considered non-patterned as defined above. The pattern on the first surface of the film is also typically not carried through the entire film thickness. That is, the film typically does not bear the substantially parallel peaks and substantially parallel valleys that carry through its entire thickness. In some embodiments, the second surface of the film, opposite the first patterned surface, is flat.

The present disclosure provides, in some aspects, an airfoil or a hydrofoil having a seamless portion of a patterned film disclosed herein on at least a portion of the airfoil or hydrofoil. FIG. 12 is an exploded perspective view of an embodiment of an article including an airfoil or hydrofoil according to the present disclosure. Article 200 includes an airfoil or hydrofoil 201 with a seamless patterned film 205 on its surface. The airfoil may be, for example, an airplane wing, helicopter blade, wind turbine, propeller, or other rotor blade. The hydrofoil may be, for example, a boat hull or propeller. Airfoil or hydrofoil 201 has a leading edge 207 and a trailing edge 209. The first patterned region 210 is typically positioned on one of the first or second opposing major surfaces of the airfoil 201, and, in the illustrated embodiment, the non-pattemed region 215 wraps around the leading edge 207 of the airfoil or hydrofoil 201. In some embodiments, seamless patterned film 205 has a second patterned region (not shown in FIG. 12). In some of these embodiments, the first patterned region 210 is on the first major surface of the airfoil or hydrofoil 201, the non-patterned region 215 wraps around the leading edge 207 of the airfoil or hydrofoil 201, and the second patterned region (not shown) is on the second major surface of the airfoil or hydrofoil 201. However, the seamless patterned film 205 need not cover the entire first major surface or second major surface of the airfoil or hydrofoil 201.

The first patterned region 210 of the seamless portion of the patterned film may be positioned on the airfoil or hydrofoil 201 such that it will minimize the turbulence intensity. In some embodiments, the substantially parallel peaks and substantially parallel valleys 220, 222 extend over the length of the turbulent region on the upper surface of the airfoil or hydrofoil. There may be a smooth transition between the patterned region 210 and to the non-patterned region 215 to a patterned region on the first surface of the film 205, as described above, where the peaks decrease in height from the patterned region progressively into the non-patterned region and ultimately disappear. The non-patterned region can begin at any desired point in the laminar region of the airfoil or hydrofoil 201. In some embodiments, the substantially parallel peaks and substantially parallel valleys extend over the length of the turbulent region on both the upper surface and lower surface of the airfoil or hydrofoil. In some embodiments, the peaks 220 increase in size as they approach the trailing edge 209 of the airfoil or hydrofoil 201.

Seamless patterned film 205 has a long dimension "1" that is long enough to cover the entire span of the airfoil or hydrofoil 201 or any desirable portion of the airfoil in the spanwise direction "s" of airfoil or hydrofoil 201 and is substantially aligned with the spanwise direction. In some embodiments, the long dimension "1" of the seamless film is at least 2, 4, 6, 10, 15, or 20 meters long and may be up to 40, 60, 80, or 100 meters long or longer. The seamless patterned film 205 has a short dimension "w" that may have any width suitable for covering a desired portion surface of the airfoil or hydrofoil in the streamwise direction. For example, the short dimension "w" of the seamless film may be up to about 1 or 1.5 meter wide, which are common maximum widths for continuous film, but may be as small as 25, 10, or 5 centimeters. It should be understood by a person having ordinary skill in the art that the long dimension "1" is longer than the short dimension "w" of the seamless patterned film portion.

FIG. 12A is an exploded side view of another exemplary embodiment of an article including an airfoil or hydrofoil according to the present disclosure. Article 300 includes an airfoil or hydrofoil 301 as described above in FIG. 12 with a seamless patterned film 305 on its surface. Airfoil or hydrofoil 301 has a leading edge 307 and a trailing edge 309. The first patterned region 310 is near the trailing edge 309 of the airfoil or hydrofoil 301, and, in the illustrated embodiment, the non-patterned region 315 wraps around the leading edge 307 of the airfoil or hydrofoil 301. The non-patterned region is thicker in the vicinity of the leading edge 307. In some embodiments, the first patterned region extends around the trailing edge of the airfoil or hydrofoil 301 to provide substantially parallel peaks and substantially parallel valleys on both the top and bottom of the airfoil or hydrofoil 301.

In some embodiments, a seamless portion of the patterned film 205 disclosed herein may be stretched, if desired, to conform to the substrate surface and to remove unwanted wrinkles and air bubbles. Providing perforations or other discontinuities (e.g., slits) in the film can facilitate applying the film to the airfoil or hydrofoil 201 and accommodates the passage of moisture and vapors through the film.

In some embodiments, the first surface of the patterned film 5, 105, 205, and 305, which may be provided on a top layer 1 1 and 1 1 1 of a multilayer film as shown in FIGS. 2 to 7 and 1 1, is typically sufficiently resistant to chemical and weather exposure to permit the use of patterned film 5, 105, and 205 on a variety of airfoils and hydrofoils 201. For example, materials for at least the top layer 1 1 and 1 1 1 of the patterned film 5, 105, and 205 can be selected so that the film can withstand extended exposure to water, oil, fuel, solvents, and hydraulic fluids without a noticeable deterioration in its physical properties, performance, or appearance. Further, materials for the top layer 1 1 and 1 1 1 can be selected so that the film 5, 105, 205, and 305 is not appreciably affected by rain, sand or particle erosion, or other harsh environmental agents to which the airfoil or hydrofoil 201 may be exposed during normal use. In some embodiments, it is desirable for the patterned film 5, 105, 205, and 305, particularly the top layer 1 1 and 1 1 1, to be resistant to degradation by ultraviolet (UV) light and weatherable. Photo- oxidative degradation caused by UV light (e.g., in a range from 280 to 400 nm) may result in color change and deterioration of optical and mechanical properties of polymeric films. It is also typically desirable for patterned film 5, 105, 205, and 305 to show no substantial change in appearance or removability, even when subjected to accelerated weathering (e.g., ultraviolet radiation and moisture) for 500 hours according to the procedure described in ASTM G 53-95 "Standard Practice for Operating Light-and Water-Exposure Apparatus (Fluorescent UV Condensation Type) for Exposure of Non-Metallic Materials."

Several polymers are useful for making the patterned film 5, 105, 205, and 305. In some embodiments, at least the top layer 1 1 and 1 1 1 or the entire patterned film 5, 105, 205, and 305 is made from a thermoplastic. In some embodiments, at least the top layer 1 1 and 1 1 1 or the entire patterned film 5, 105, and 205 is made from a thermoset. Useful materials for making the patterned film in any of its layers include polyurethanes, polyesters, polycarbonates, polyethers, polyimides, polyolefins, fluoropolymers, silicones, and combinations thereof. A variety of stabilizers may be added to the patterned film 5, 105, 205, and 305 (e.g., in at least the top layer 1 1 and 1 1 1) to improve its resistance to UV light. Examples of such stabilizers include at least one of ultra violet absorbers (UVA) (e.g., red shifted UV absorbers (e.g., the TINUVTN family of stabilizers available from Ciba-Geigy Corp.)), hindered amine light stabilizers (HALS), or anti-oxidants. In some embodiments, a easy-to-clean coating may be applied to the top layer of the patterned film. The easy-to-clean coating may be a hydrophobic coating which includes a polymer matrix (e.g., a silicone or fluoropolymer) and nanoparticles dispersed therein. The nanoparticles may be, for example, polymer (e.g., fluoropolymer) particles, particles of a dielectric material (e.g., silica, alumina, zirconia, titania, or indium tin oxide particles), or metal (e.g., gold) particles. Further details regarding such hydrophobic coatings are described, for example, in copending applications with serial numbers 61/407820 and 61/407806, both filed October 28, 2010, the disclosures of which are incorporated by reference herein. In some embodiments, the easy-to-clean coating may comprise nanosilica and may be coated out of water. Further details of such coatings are described in copending applications with serial numbers 61/390501 and 61/390498, both filed October 6, 2010, the disclosures of which are incorporated by reference herein. The patterned film 5, 105, 205, and 305 in its various layers may also optionally include fillers such as glass, ceramic or polymeric bubbles; pigments; processing aids; and fire retardants.

In some embodiments, at least the top layer 1 1 and 1 1 1 of the patterned film 5, 105, 205, and 305 comprises a fluoropolymer. Fluoropolymers typically are resistant to UV degradation even in the absence of stabilizers such as UVA, HALS, and anti-oxidants. Useful fluoropolymers include ethylene- tetrafluoroethylene copolymers (ETFE), tetrafluoroethylene-hexafluoropropylene copolymers (FEP), tetrafluoroethylene-hexafluoropropylene-vinylidene fluoride copolymers (THV), polyvinylidene fluoride (PVDF), blends thereof, and blends of these and other fluoropolymers. Fluoropolymers, in particular those that contain polymerized units of vinylidene fluoride, have been found to have good chemical resistance and weatherability.

At least the top layer 1 1 and 1 1 1 of the patterned film 5, 105, 205, 305 may be made from a blend of a fluoropolymer and a non-fluorinated polymer. Acrylic polymers, in particular those that contain polymerized units of short chain alkyl methacrylates, have been found to have good bonding properties and handling characteristics. Accordingly, in some embodiments, at least the top layer 1 1 and 1 1 1 of the patterned film 5, 105, 205, 305 may be made from a blend of a fluoropolymer and an acrylic polymer. For example, a blend of polyvinylidene fluoride and polymethyl methacrylate can be used. At least the top layer 1 1 and 1 1 1 of the patterned film 5, 105, 205, 305 may comprise a blend of 70% to 100% by weight fluoropolymer and 0% to 30% by weight acrylic polymer, 70% to 90% by weight fluoropolymer and 10% to 30% by weight acrylic polymer, or about 90% by weight fluoropolymer and about 10% by weight acrylic polymer.

Referring again to FIG. 1 1, in some embodiments, a separate thin layer (not shown in FIG. 1 1) comprising the substantially parallel peaks and substantially parallel valleys in first and second patterned regions 1 10a and 1 10b may comprise a fluoropolymer or a blend of a fluoropolymer and a non- fluorinated polymer as described above.

In some embodiments, including the embodiments illustrated in FIGS. 2, 3, and 6, the patterned film 5 andl05 is a multilayer film that includes optional tie layer 12. The composition of the tie layer can be selected, for example, depending on the composition of the top layer 1 1 and the optional base layer 13 so that good adhesion and handling ability can be obtained. In some embodiments, tie layer 12 is made from a blend of a fluoropolymer and an acrylic polymer. In some of these embodiments, the same fluoropolymer and acrylic polymer that make up the top layer 1 1 also make up the tie layer 12, but in different ratios. Tie layer 12 typically has a higher percentage of acrylic polymer, for example. Tie layer 12 may comprise, for example, a blend of 70% to 100% by weight acrylic polymer and 0% to 30% by weight fluoropolymer, 70% to 90% by weight acrylic polymer and 10% to 30% by weight fluoropolymer, or about 90% by weight acrylic polymer and 10% by weight fluoropolymer.

In embodiments described above for a patterned film comprising acrylic polymers, various acrylic polymers may be useful. For example, medium to low molecular weight acrylic resins having a weight average molecular weight below 750,000, including blends or copolymers comprising at least two materials selected from the group consisting of methyl methacrylate, ethyl methacrylate, butyl methacrylate, and methacrylate copolymers may be useful.

In some embodiments wherein the patterned film is a multilayer film, the layer including first patterned surface 1 1 may be about 5 to 250 microns (about 0.2 to 10 mils) thick or about 10 to 40 microns (about 0.5 to 1.5 mils) thick at least in the first and/or second patterned regions. Tie layer 12 may be about 2.5 to 75 microns (about 0.1 to 3 mils) thick or about 3 to 12 microns (about 0.1 to 0.5 mils) thick at least in the first and/or second patterned regions. Overall, the combined thickness of layers 1 1 and 12 in at least the first and/or second patterned regions may be about 7.5 to 325 microns (about 0.3 to 13 mils) or about 15 to 50 microns (about 0.6 to 2.0 mils). The thicknesses of the layers 1 1 and 12 in the non- patterned region, if present, may be considerably thinner.

Referring now to FIGS. 2, 3, 4, 5, 6, and 1 1, typically, a multilayer, patterned film may comprise optional base layer 13 and 1 13. Base layer 13 and 1 13 may be useful, for example, for providing strength and elongation to the patterned film, which can contribute to easy installation and removal of the patterned film. In some embodiments, base layer 13 and 1 13 is made from a material selected from thermoplastic urethanes, silicones, and poly(vinyl chloride). Examples of thermoplastic urethanes include polyester-urethane, polyether-urethane, and polycaprolactone-urethane. The base layer 13 and 1 13 can include UV stabilizers, antioxidants, fillers, pigments, and post-crosslinking additives.

In some embodiments, the material that forms the base layer 13 and 1 13 is the most elastic material in the multilayer film. The term "elastic" refers to any material that exhibits recovery from stretching or deformation. A material that is more elastic than another material has a higher tendency to recover from stretching or deformation. In some embodiments, the material that forms the reinforcing layer has an elongation of at least about 300%, without breaking. "Elongation" in terms of percent refers to [(the extended length-the initial length)/the initial length] multiplied by 100.

Base layer 13 and 1 13 may be about 35 to 300 microns (about 1.5 to 12 mils) or about 50 to 100 microns (about 2 to 4 mils) thick in at least the first and second patterned regions. Base layer 13 and 1 13 may, in some embodiments, be considerably thicker (e.g., up to about 914 microns (36 mils)) in a least a portion of the non-patterned region 115. In some embodiments of the patterned film according to the present disclosure, the first and optionally second patterned region comprises a fluoropolymer, and the non-patterned region comprises at least one of a polyurethane, a silicone, or a fluoropolymer (in some embodiments a polyurethane, which may be a crosslinked polyurethane or a thermoplastic polyurethane). In some embodiments, the patterned film is a multilayer film comprising a layer of the fluoropolymer and a layer of the polyurethane, wherein the layer of the polyurethane is thicker in the non-patterned region than in the first and optionally second patterned region. Likewise, the layer of fluoropolymer can be thicker in the first and optionally second patterned regions than in the non-patterned region.

Although the embodiment illustrated in FIG. 1 1 shows a multilayer film construction that has continuous layers 1 1 1 and 1 13 extending through the patterned region(s) and non-patterned region, the different regions may be made from different materials or different combinations of materials or layers and may not have continuous layers. For example, the patterned region(s) may have the multilayer construction described above with any of the materials listed for layers 1 1 1, 112, and 1 13. The non- patterned region may be made, for example, from multiple layers of polyurethane or silicone polymers.

Referring again to FIG. 1 1 , the top layer 1 1 1 and base layer 1 13 of the patterned film 105 may comprise first and second polyurethane layers. The first polyurethane layer 11 1 may comprise a solvent- based or water-based polyurethane, which may be a polyester-based polyurethane, a polycarbonate -based polyurethane or a combination or blend of both. A water-based polyurethane can be made from an aqueous-based polyurethane dispersion, and a solvent-based polyurethane can be made from a solvent- based polyurethane solution. The solvent-based and water-based polyurethanes may be lightly crosslinked. The second polyurethane layer (base layer 1 13 in the illustrated embodiment) may comprise a thermoplastic polyurethane (e.g., polycaprolactone-based thermoplastic polyurethane).

The polyurethane in the first and/or second polyurethane layers 1 1 1 and 1 13 can be the reaction product of one or more polyols (e.g., a polyester polyol, a polycarbonate polyol, or a combination thereof); one or more diisocyanates (e.g., isophorone diisocyanate, bis (4-isocyanato-cyclohexyl) methane or a combination of both); and optionally up to 10%, based on the total weight of the reaction

components, of triisocyanates. In some embodiments, the polyurethane in the first or second

polyurethane layers is made from one or a combination of aliphatic polyols, aliphatic diisocyanates, and aliphatic triisocyanates. Suitable useful materials for making polyurethane films are described further in U.S. Pat. App. Pub. No. 2008/0199704 (Ho et al.).

Patterned film 5, 105, 205, and 305 may carry or bear a continuous or discontinuous graphic layer (e.g., graphic design, logo, or alpha-numeric characters) that can be aesthetic and/or functional. Graphic layers may be provided as an ink (e.g., a pigment dispersed in a compatible binder) and applied to any layer of the first patterned region, non-patterned region, or, in some embodiments, the second patterned region using any suitable printing technique. Referring again to FIGS. 2-6 and 1 1, patterned film 5 and 105, in some embodiments, further comprises an adhesive layer 14 and 1 14 disposed on a second surface of the patterned film, opposite the first surface of the patterned film. In some embodiments, the adhesive layer comprises a pressure sensitive adhesive (PSA). PSAs are well known to those of ordinary skill in the art to possess properties including the following: (1) aggressive and permanent tack, (2) adherence with no more than finger pressure, (3) sufficient ability to hold onto an adherend, and (4) sufficient cohesive strength to be cleanly removable from the adherend. Materials that have been found to function well as PSAs are polymers designed and formulated to exhibit the requisite viscoelastic properties resulting in a desired balance of tack, peel adhesion, and shear holding power.

Exemplary useful PSAs include polyacrylates, such as those that comprise a polymer of an acrylate ester of acrylic acid with a non-tertiary alcohol. In some embodiments, the PSA comprises the polymerization product of 85 to 98% by weight of one or more (co)polymerizable acrylate ester monomers and 2 to 15% by weight of a copolymerizable acid or amide. Multifunctional acrylates, copolymerizable photoinitiators, or combinations of the two may also be present in a total amount of up to 0.5% by weight to provide some crosslinking, which can contribute to easy removability, better fluids resistance, and improved high temperature performance of the article. The adhesive layer may have any useful thickness and may be about 10 to 125 microns (about 0.4 to 5 mils), or about 12 to 50 microns (about 0.5 to 2 mils). Ultimately, removability is a balance among the peel adhesion, the degree of crosslinking, and the thickness of the bonding layer, and the toughness of the seamless film.

In some embodiments, the adhesive layer 14 and 1 14 comprises a curable adhesive (e.g., a thermally curable adhesive or moisture curable adhesive composition). Exemplary curable adhesives include silicones, epoxies, acrylates, cyano-acrylates, and urethanes. Several useful curable adhesives are commercially available. Exemplary useful epoxy adhesives include epoxy resin adhesives available from 3M Company, St. Paul, Minn. Under the trade designation "3M SCOTCH- WELD". Exemplary useful curable acrylates and cyanoacrylates include acrylate adhesives available under the trade designation "3M SCOTCH- WELD DP8005" and cyano-acrylate adhesives available under the trade designation

"PRONTO INSTANT ADHESIVES", both from 3M Company. Exemplary useful urethane adhesives include those that cure by exposure to moisture such as curable adhesives available from 3M Company under the trade designations "3M SCOTCH- WELD", grades "DP-605NS", "3592", "3535", and "3549".

Suitable adhesives for adhesive layer 14 and 114, including PSAs and curable adhesives, are described in further detail in U. S. Pat. Appl. Pub. No. 2004/0126541 (Dietz et al.).

Referring again to FIGS. 2-6 and 1 1, patterned film 5 and 105, in some embodiments, further comprises an optional, removable liner 16 and 1 16 disposed on the adhesive layer 14 and 1 14. The removable liner 16 and 1 16 can be applied to protect adhesive layer 14 and 114 from contamination by dirt and other materials and can be removed shortly before the film is applied to a surface. The liner may be, for example, an untreated polyolefin sheet or a silicone- or fluorosilicone -treated paper or plastic sheet. In some embodiments, the release liner is a microstructured release liner or the adhesive layer is provided with a microstructure. See, e.g., U.S. Pat. App. Pub. Nos. US2007-021235 (Sherman et al.) and US2003-129343 (Galkiewicz et al.) and PCT Int. Appl. Pub. No. WO09/058466 (Sherman et al.) and WO04/000569 (Graham et al.). Microstructured release liners and adhesives may be useful, for example, for preventing air bubbles from being trapped in the adhesive layer 14 and 1 14 when it is applied to a surface. In some embodiments, including the embodiment illustrated in FIG. 11, the liner 16 and 1 16 has variations in thickness to complement the patterned film thickness. This may be useful, for example, for simplifying handling and manufacturing processes (e.g., for stabilizing the patterned film when it is wound about a core into roll form for easy storage and shipping).

A variety of techniques are useful for making a patterned film according to the present disclosure.

In embodiments wherein the seamless film is a multilayer film, almost any combination of layers may be coextruded then joined to the remaining layers. The different layers may also be assembled by various sequential or tandem coating methods. Combinations of coating and extrusion may also be useful. It is useful for materials in adjacent, contacting layers to be compatible and either adhere together by themselves or be capable of being adhered together so as to provide sufficient interlayer adhesion that the seamless, multilayer film does not delaminate during normal use. In some embodiments, a large proportion of acrylic polymer in tie layer 12 promotes good adhesion between top layer 1 1 and base layer 13.

The substantially parallel peaks and valleys pattern may be imparted to the patterned region(s) of the patterned film during the formation of a film, or alternatively, a pre-formed web comprising one or more layers may be provided and the substantially parallel peaks and valleys pattern formed in the surface layer to form the patterned film. In some embodiments, the patterned first surface of the film is made by embossing (e.g., utilizing heat and/or pressure). In some embodiments, the patterned first surface of the film is made by microreplication.

One useful technique for making a microreplicating tool roll using for producing the patterned region(s) on the first surface of the patterned film according to the present disclosure is by using a fly- cutting head adapted to move while cutting a groove down the length of a tool roll as described, for example, in U. S. Pat. Appl. Pub. No. 2009/0038450 (Campbell et al.). A schematic illustration of an exemplary tool roll 1 14, which can be made, for example, using this technique is shown in FIG. 13. In FIG. 13, tool roll 1 14 can be prepared by holding the roll stationary, and moving a fly-cutting head down the length of the tool roll to form a groove 150 that is the negative of peaks 20, 40, 50, 80, 90 described herein. At the completion of a single pass down the length of the tool roll, the tool roll may be indexed and the process repeated to form an adjacent groove 150. The position of the cutting elements can be controlled relatively precisely, and the position of a groove cut into the roll surface during a second or subsequent pass down the roll can be coordinated with the position of grooves or other features cut into the roll surface during a preceding pass, as shown in FIG. 13 at 155. On a large or "macro-" scale, surface features cut into a tool roll may or may not extend uninterrupted across the length, width, or around the perimeter of the tool roll. For example, as schematically shown in FIG. 13, a tool roll may have a first pattern 150 on one portion of the roll and a second pattern 155 on a different portion of the roll with a transition zone (shown as the dots in FIG. 13) where the first pattern 150 may progressively change into the second pattern 155. The first pattern 150 and second pattern 155 may be any of those in FIGS. 2 to 9. Features can be cut into a tool roll at any desirable angle with respect to the axis of rotation (or an axis of symmetry) of the tool roll, such as at a 45 degree angle to that axis. The angle selected for the features may be based, for example, on aerodynamic requirements obtained for the airfoil (or hydrodynamic requirements of the hydrofoil).

Multiple features can be cut into a tool roll in successive passes of a fly-cutting head, or multiple features can be cut into a tool roll by successive passes of each cutting element during a single pass (such as a shallower groove cut by one cutting element and a deeper groove cut by the next succeeding cutting element). Multiple groove shapes and heights may also be incorporated by using a cutting tool with multiple tips such as those described in U.S. Pat. No. 7,140,812 (Bryan et al.).

A patterned film disclosed herein can be made from a microreplication tool (e.g., such as that shown in FIG. 13) using several techniques (e.g., casting and curing a polymeric material on the tool, embossing, extrusion, compression molding, and injection molding). In other embodiments, the structure of the tool roll (a master tool) can be transferred on other media, such as to a belt or web of polymeric material, by a cast and cure process to form a tooling sheet. The tooling sheet can be laminated to a film (e.g., a multilayer film) using heat and/or pressure in order to impart the pattern of the tooling sheet to a surface of patterned film 5, 105, 205, and 305 to form the first and optionally second patterned regions. This results in a film having a patterned surface that corresponds to the surface of the master tool. The tooling sheet can also act as a carrier web to protect the patterned surface through any additional processing operations such as corona treating, substrate bonding layer attaching, slitting, or perforating. It can be removed at any time during the manufacture of article according to the present disclosure.

In some embodiments, patterned film can be made by forming a rolling bank of a film precursor material, wherein the rolling bank contacts first and second substrates; passing the first and second substrates with the precursor material disposed therebetween through a nip (e.g., formed by nip roll(s), bars, platen(s), knife edge(s), or a combination thereof); heating the film precursor material (e.g., using infrared lamps, ovens, microwave radiation, or heated platens) under conditions such that it forms a film layer in contact with the first and second substrates; and optionally removing at least one of the first or second substrates from the film layer to expose an outer surface of the film layer to which additional layers may be laminated, or on which subsequent layers may be provided, for example. The first or second substrate may be provided with a pattern comprising a series of substantially parallel peaks separated from each other by a series of substantially parallel valleys. For further details regarding this process, see, e.g., PCT Int. Appl. Pub. No. WO 2008/042883 (Ho et al.). In some embodiments, the patterned film disclosed herein further comprises an adhesive layer 14 and 1 14 disposed on a second surface of the film, opposite the patterned first surface of the film. The adhesive layer can be useful, for example, for applying the patterned film to the surface of an airfoil or hydrofoil 201 by contacting the surface of the airfoil or hydrofoil with the adhesive layer 14 and 1 14. In some embodiments, adhesive layer 14 and 1 14 can be coated onto the second surface of the film. In some of these embodiments, the film is a multilayer film (e.g., comprising layers that have been previously joined together). The removable, protective liner 16 and 1 16 may then be laminated to adhesive layer 14 and 1 14. In other embodiments, adhesive layer 14 and 1 14 can be coated onto a release liner and transfer laminated to the second surface of a film. In some of these embodiments, the patterned film and the adhesive layer-coated release liner can be passed between rubber rolls, which may optionally be heated.

The patterned film according to the present disclosure may also be useful, for example, is useful as a master, wherein the patterned film bears the negative of the pattern imparted to the surface of the airfoil or hydrofoil 201. In these embodiments, the patterned film can be applied to a surface of a mold with the first surface of the film exposed, forming a cavity between the patterned first surface of the film and a surface of an airfoil or hydrofoil, wherein the machine direction of the film is aligned with the spanwise direction of the airfoil or hydrofoil, providing a curable resin in the cavity, and curing the curable resin. Additional information about such manufacturing techniques can be found in U.S. Pat. No. 4,576,850 (Martens), U.S. Pat. No. 5,183,597 (Lu), and U.S. Pat. No. 5,468,540 (Lu).

The methods described herein are in contrast to conventional methods of forming a series of peaks and valleys in a surface, which generally involve forming grooves running in the machine direction of the film. Since web-forming production lines typically have a width of up to about 1 or 1.5 meter wide, it is not possible to provide a seamless film with a width of greater than 1 or 1.5 meter using conventional, machine-direction-groove-forming processes. This has resulted in the aforementioned disadvantageous tiling process due to the size limit of a film that can be provided to an airfoil or hydrofoil with peaks and valleys extending in the streamwise direction. The patterned film according to the present disclosure provides a solution to these problems.

Selected Embodiments of the Disclosure:

In a first embodiment, the present disclosure provides a patterned film having an indefinite length in a machine direction, the patterned film comprising:

a non-patterned region juxtaposed with the first patterned region on the first surface of the patterned film, wherein the first patterned region and the non-patterned region extend side-by-side for the indefinite length of the patterned film in the machine direction, and wherein the parallel peaks and parallel valleys in the first patterned region extend at an angle of at least five degrees to the machine direction.

In a second embodiment, the present disclosure provides a patterned film according to the first embodiment, wherein in at least the first patterned region, the substantially parallel peaks progressively decrease in height as they approach the non-patterned region.

In a third embodiment, the present disclosure provides an article according to the first or second embodiment, wherein the non-patterned region forms at least 20 percent of the surface area of the patterned film.

In a fourth embodiment, the present disclosure provides a patterned film according to any one of the first to third embodiments, wherein the angle between the parallel peaks and valleys to the machine direction is in a range from seventy- five to ninety degrees.

In a fifth embodiment, the present disclosure provides a patterned film according to any one of the first to fourth embodiments, wherein the parallel peaks and valleys are perpendicular to the machine direction.

In a sixth embodiment, the present disclosure provides a patterned film according to any one of the first to fifth embodiments, wherein some of the parallel peaks when viewed in cross-section are larger in height than others of the parallel peaks.

In a seventh embodiment, the present disclosure provides a patterned film according to any one of the first to sixth embodiments, wherein at least some of the parallel peaks vary in height along their lengths.

In an eighth embodiment, the present disclosure provides a patterned film according to any one of the first to seventh embodiments, wherein the patterned film is thicker in the non-patterned region than in the first patterned region.

In a ninth embodiment, the present disclosure provides a patterned film according to any one of the first to eighth embodiments, wherein at least some of the parallel peaks are interrupted by spanwise- extending gaps.

In a tenth embodiment, the present disclosure provides a patterned film according to any one of the first to ninth embodiments, wherein at least some of the parallel valleys are flat-bottomed.

In an eleventh embodiment, the present disclosure provides a patterned film according to any one of the first to tenth embodiments, wherein at least some of the parallel peaks have shapes with side-walls that change direction.

In a twelfth embodiment, the present disclosure provides a patterned film according to any one of the first to eleventh embodiments, wherein there is more than one series of substantially parallel peaks separated from each other by a series of substantially parallel valleys in the first patterned region with each series oriented in a different direction.

In a thirteenth embodiment, the present disclosure provides a patterned film according to any one of the first to twelfth embodiments, wherein the patterned film is a multilayer film.

In a fourteenth embodiment, the present disclosure provides a patterned film according to the thirteenth embodiment, wherein the multilayer film comprises at least first and second layers of different materials, and wherein the first and second layers have different thicknesses relative to each other in the non-patterned region and in the first patterned region.

In a fifteenth embodiment, the present disclosure provides a patterned film according to the fourteenth embodiment, wherein the multilayer film comprises a layer of fluoropolymer and a layer of polyurethane, wherein the layer of the polyurethane is thicker in the non-patterned region than in the first patterned region.

In a sixteenth embodiment, the present disclosure provides a patterned film according to any one of the first to fourteenth embodiments, wherein the first patterned region comprises a fluoropolymer, and wherein the non-patterned region comprises at least one of a polyurethane, a silicone, or a fluoropolymer.

In a seventeenth embodiment, the present disclosure provides a patterned film according to any one of the first to sixteenth embodiments, wherein at least some of the substantially parallel peaks vary progressively in spacing between the peaks.

In an eighteenth embodiment, the present disclosure provides a patterned film according to any one of the first to seventeenth embodiments having longitudinal side edges, wherein the first patterned region is located between one of the longitudinal side edges and a longitudinal center line of the patterned film.

In a nineteenth embodiment, the present disclosure provides a patterned film according to any one of the first to eighteenth embodiments, further comprising an adhesive layer disposed on a second surface of the patterned film, opposite the first surface of the patterned film.

In a twentieth embodiment, the present disclosure provides a patterned film according to any one of the first to nineteenth embodiments, wherein the series of substantially parallel peaks separated from each other by the series of substantially parallel valleys are made by microreplication.

In a twenty-first embodiment, the present disclosure provides a patterned film according to any one of the first to nineteenth embodiments, wherein the series of substantially parallel peaks separated from each other by the series of substantially parallel valleys are made by embossing.

In a twenty-second embodiment, the present disclosure provides an article comprising:

an airfoil or hydrofoil having a leading edge; and

a seamless portion of a patterned film according to any one of the first to twenty- first embodiments on the airfoil or hydrofoil, wherein the first patterned region is on a surface of the airfoil or hydrofoil, wherein the non-patterned region wraps around the leading edge of the airfoil or hydrofoil. In a twenty -third embodiment, the present disclosure provides the article according to the twenty- second embodiment, wherein the machine direction of the patterned film is aligned with a spanwise direction of the airfoil or hydrofoil.

In a twenty-fourth embodiment, the present disclosure provides the article according to the twenty-second or twenty-third embodiment, wherein the seamless portion of the patterned film has a long dimension that is at least two meters long.

In a twenty-fifth embodiment, the present disclosure provides a patterned film according to any one of the first to twenty- first embodiments, further comprising a second patterned region on the first surface of the patterned film, the second patterned region comprising a second series of substantially parallel peaks separated from each other by a second series of substantially parallel valleys, wherein the non-patterned region extends between and separates the first and second patterned regions on the first surface.

In a twenty-sixth embodiment, the present disclosure provides a patterned film according to the twenty- fifth embodiment, wherein the series of substantially parallel peaks and the series of substantially parallel valleys in the first patterned region are different from the second series of substantially parallel peaks and the series of substantially parallel valleys in the second patterned region in at least one of height of the substantially parallel peaks, the angle between the substantially parallel peaks and the machine direction, the length of the substantially parallel peaks, or the spacing between the substantially parallel peaks.

In a twenty-seventh embodiment, the present disclosure provides an article comprising:

an airfoil or hydrofoil having a leading edge and first and second opposing major surfaces; and a seamless portion of the patterned film according to the twenty-fifth or twenty-sixth embodiment on the airfoil or hydrofoil, wherein the first patterned region is on the first major surface of the airfoil or hydrofoil, wherein the non-patterned region wraps around the leading edge of the airfoil or hydrofoil, and wherein the second patterned region is on the second major surface of the airfoil or hydrofoil.

In a twenty-eighth embodiment, the present disclosure provides the article according to the twenty-seventh embodiment, wherein the machine direction of the patterned film is aligned with a spanwise direction of the airfoil or hydrofoil.

In a twenty -ninth embodiment, the present disclosure provides the article according to the twenty- seventh or twenty-eighth embodiment, wherein the seamless portion of the patterned film has a long dimension that is at least two meters long.

In a thirtieth embodiment, the present disclosure provides a roll comprising the patterned film according to any one of the first to twenty-first, twenty-fifth, and twenty-sixth embodiments.

In a thirty- first embodiment, the present disclosure provides a roll according to the thirtieth embodiment, further comprising a liner with variations in thickness to complement the patterned film thickness. In a thirty-second embodiment, the present disclosure provides a roll according to the thirtieth or thirty-first embodiment, wherein the liner is structured.

All patents and publications referred to herein are hereby incorporated by reference in their entirety. Various modifications and alterations of this disclosure may be made by those skilled in the art without departing from the scope and spirit of this disclosure, and it should be understood that this disclosure is not to be unduly limited to the illustrative embodiments set forth herein.

Claims

What is claimed is:

1. A patterned film having an indefinite length in a machine direction, the patterned film comprising: at least a first patterned region on a first surface of the patterned film, the patterned region comprising a series of substantially parallel peaks separated from each other by a series of substantially parallel valleys; and

wherein the first patterned region and the non-patterned region extend side -by-side for the indefinite length of the patterned film in the machine direction, and wherein the parallel peaks and parallel valleys in the first patterned region extend at an angle of at least five degrees to the machine direction.

2. The patterned film according to claim 1, wherein in at least the first patterned region, the substantially parallel peaks progressively decrease in height as they approach the non-patterned region.

3. The patterned film according to claim 1 or 2, wherein the non-patterned region forms at least 20 percent of the surface area of the film.

4. A patterned film according to any one of claims 1 to 3, wherein the patterned film is thicker in the non-patterned region than in the first patterned region.

5. A patterned film according to any one of claims 1 to 4, wherein there is more than one series of substantially parallel peaks separated from each other by a series of substantially parallel valleys in the first patterned region with each series oriented in a different direction.

6. A patterned film according to any one of claims 1 to 5, wherein the patterned film is a multilayer film.

7. A patterned film according to claim 6, wherein the multilayer film comprises at least first and second layers of different materials, and wherein the first and second layers have different thicknesses relative to each other in the non-patterned region and in the first patterned region.

8. A patterned film according to any one of claims 1 to 7, wherein at least some of the substantially parallel peaks vary progressively in spacing between the peaks.

9. A patterned film according to any one of claims 1 to 8, further comprising an adhesive layer disposed on a second surface of the patterned film, opposite the first surface of the patterned film.

10. An article comprising:

an airfoil or hydrofoil having a leading edge; and

a seamless portion of the patterned film according to any one of claims 1 to 9 on the airfoil, wherein the first patterned region is on a surface of the airfoil or hydrofoil, wherein the non-patterned region wraps around the leading edge of the airfoil or hydrofoil.

1 1. A patterned film according to any one of claims 1 to 9, further comprising a second patterned region on the first surface of the patterned film, the second patterned region comprising a second series of substantially parallel peaks separated from each other by a second series of substantially parallel valleys, wherein the non-patterned region extends between and separates the first and second patterned regions on the first surface.

12. A patterned film according to claim 1 1, wherein the series of substantially parallel peaks and the series of substantially parallel valleys in the first patterned region are different from the second series of substantially parallel peaks and the series of substantially parallel valleys in the second patterned region in at least one of height of the substantially parallel peaks, the angle between the substantially parallel peaks and the machine direction, length of the substantially parallel peaks, or spacing between the substantially parallel peaks.

13. An article comprising:

an airfoil or hydrofoil having a leading edge and first and second opposing major surfaces; and a seamless portion of the patterned film according to claim 1 1 or 12 on the airfoil or hydrofoil, wherein the first patterned region is on the first major surface of the airfoil or hydrofoil, wherein the non- patterned region wraps around the leading edge of the airfoil or hydrofoil, and wherein the second patterned region is on the second major surface of the airfoil or hydrofoil.

14. A roll comprising the patterned film according to any one of claims 1 to 9, 1 1, and 12.

15. A roll according to claim 14, further comprising a liner with variations in thickness to complement the patterned film thickness.