Optical film with randomized surface domains

Abstract

A structured surface defines a first surface direction and an orthogonal second surface direction, the structured surface including a plurality of adjacent, non-overlapping surface domains. Each of the surface domains has a closed outermost perimeter, such that a shape of no more than 10% of the closed outermost perimeters are the same. Each surface domain includes a plurality of structures disposed within the closed outermost perimeter of the surface domain. The structures disposed within each surface domain are arranged along a first domain direction and a second domain direction local to the surface domain, and the arrangement of structures within at least 10% of the surface domains is periodic or near periodic. The plurality of structures of no more than about 10% of the surface domains have the same arrangement of structures.

Description

PA103613W002OPTICAL FILM WITH RANDOMIZED SURFACE DOMAINSSummary

[0001] In some aspects of the present description, a structured surface is provided, the structured surface defining a first surface direction and an orthogonal second surface direction. The structured surface includes a plurality of adjacent, non -overlapping surface domains. Each of the surface domains has a closed outermost perimeter 24, such that a shape of no more than about 10% of the closed outermost perimeters are the same. Each surface domain includes a plurality of structures disposed within the closed outermost perimeter of the surface domain. The structures of the plurality of structures disposed within each surface domain are arranged along a first domain direction and an orthogonal second domain direction local to the surface domain. The arrangement of structures within at least 10% of the surface domains is periodic or near periodic. The plurality of structures of no more than about 10% of the surface domains have the same arrangement of structures.

[0002] In some aspects of the present description, an optical film is provided, the optical film having a first major surface including at least one structured surface, and an opposing second major surface. The at least one structured surface defines a first surface direction and an orthogonal second surface direction, and includes a plurality of adjacent, non-overlapping surface domains. Each surface domain includes a plurality of structures disposed within a closed outermost perimeter of the surface domain. The structures of the plurality of structures disposed within each surface domain are arranged along a first domain direction and an orthogonal second domain direction. The first domain direction and second domain direction defined relative to the surface domain, and the arrangement of structures within at least about 10 % of the surface domains is periodic or near periodic. The plurality of structures of no more than about 10% of the surface domains have the same arrangement.

[0003] In some aspects of the present description, an optical film is provided, the optical film including a plurality of adjacent, non-overlapping structured surfaces. Each structured surface of the plurality of structured surfaces includes a plurality of adjacent, non-overlapping surface domains. An arrangement of the plurality of surface domains within at least two of the structured surfaces is substantially identical. Each structured surface of the plurality of structured surfaces defines a first surface direction and an orthogonal second surface direction. Each surface domain within each structured surface has a closed outermost perimeter 24, such that a shape of no more than about 10% of the closed outermost perimeters within a structured surface are the same. Each surface domain within a structured surface includes a plurality of structures disposed within the closed outermost perimeter of the surface domain. The structures of the plurality of structures disposed within each surface domain are arranged along a first domain direction and an orthogonal second domain direction, wherein the first domain direction and the second domain direction defined relative to the surface domain. The arrangement of structures within at least about 10% of the surface domains isperiodic or near periodic. The plurality of structures of no more than about 10% of the surface domains within a structured surface have the same arrangement of structures.

[0004] In some aspects of the present description, an optical film is provided, the optical film including a plurality of adjacent, non-overlapping structured surfaces. Each structured surface of the plurality of structured surfaces includes a plurality of adjacent, non-overlapping surface domains, and an arrangement of the plurality of surface domains within at least two of the structured surfaces is substantially identical. Each structured surface of the plurality of structured surfaces defines a first surface direction and an orthogonal second surface direction. The surface domains of each structured surface have a closed outermost perimeter, such that a shape of no more than about 10% of the closed outermost perimeters within a structured surface are the same. Each surface domain within a structured surface includes a plurality of structures disposed within the closed outermost perimeter of the surface domain. The structures of the plurality of structures disposed within each surface domain are arranged, either periodically or aperiodically, along a first domain direction and an orthogonal second domain direction, the first domain direction and the second domain direction defined relative to the surface domain. The plurality of structures of no more than about 10% of the surface domains within a given structured surface have the same arrangement of structures, and at least some of the surface domains at an edge of the given structured surface are configured to substantially align with and substantially match an arrangement of structures within the corresponding surface domains at an edge of an adjacent structured surface.Brief Description of the Drawings

[0005] FIGS. 1A and IB provide top, plan views of a structured surface with surface domains, in accordance with an embodiment of the present description;

[0006] FIGS. 2A and 2B show an optical film featuring structured surfaces with surface domains, in accordance with an embodiment of the present description;

[0007] FIGS. 3A and 3B show additional details on the surface domains of a structured surface, in accordance with an embodiment of the present description;

[0008] FIG. 4 is a side view of a display system including an optical film with surface domains, in accordance with an embodiment of the present description;

[0009] FIGS. 5A and 5B are plots of an autocorrelation function of an optical film, in accordance with an embodiment of the present description;

[0010] FIGS. 6A and 6B detail steps in a method of making an optical film with surface domains, in accordance with an embodiment of the present description; and

[0011] FIGS. 7A and 7B illustrate optical films with tiled structured surfaces which have surface domains that align with the corresponding surface domains of an adjacent structured surface, in accordance with an embodiment of the present description.Detailed Description

[0012] In the following description, reference is made to the accompanying drawings that form a part hereof and in which various embodiments are shown by way of illustration. The drawings are not necessarily to scale. It is to be understood that other embodiments are contemplated and may be made without departing from the scope or spirit of the present description. The following detailed description, therefore, is not to be taken in a limiting sense.

[0013] The present description relates to optical films, particularly those used in display systems to reduce optical artifacts such as sparkle. More specifically, it pertains to surface topographies that minimize visible artifacts while maintaining the anti-sparkle properties of the film, and methods of making the same.

[0014] In the field of display technology, optical films are widely used to enhance the visual quality of displays by reducing undesirable artifacts such as sparkle. Sparkle is a visual phenomenon that occurs when light is scattered by the surface of the display, leading to a grainy or glittery appearance that can detract from the viewing experience. One common approach to mitigate sparkle involves the use of structured surfaces on optical films disposed between the display and a viewer.

[0015] A known method to reduce display sparkle involves the use of a crossed sinusoid surface topography, which consists of a sum of two orthogonal sinusoids. This approach has proven effective in reducing sparkle due to its periodic structure. However, the periodicity of the crossed sinusoids introduces other undesirable display artifacts, such as moire patterns and other visual distortions, which can compromise the overall display quality.

[0016] Efforts to address these artifacts have included dithering the positions of the peaks and valleys of the sinusoids. While dithering can reduce some of the display artifacts, it does not eliminate them entirely. The persistence of these artifacts indicates that the current methods are insufficient for achieving the desired level of visual clarity in display systems.

[0017] Given the limitations of existing technologies, there is a clear need for improved surface topographies for anti-sparkle films. Such improved surface topographies should effectively reduce display sparkle while minimizing or eliminating the associated visual artifacts. The new approach should provide a more randomized structure that retains the anti-sparkle properties without introducing periodicity-related distortions. This would enhance the visual quality of displays, providing a clearer and more pleasant viewing experience for users.

[0018] Optical films based on such improvements may include one or more structured surfaces. Each such structured surface would introduce an amount of randomization according to the present description. However, if the optical film thus created includes more than one structured surface tiled across the optical film, each structured surface may, in some embodiments, be substantially identical to each other structured surface (i.e., the “randomness” introduced as described herein is present within each structured surface, but one structured surface could be identical to another structured surface). In some embodiments, the structured surfaces themselves may be divided into a number ofnon-overlapping surface domains, with each surface domain having a different arrangement of structures from the other surface domains (or at least different than some subset of the other surface domains).

[0019] According to some aspects of the present description, a structured surface defines a first surface direction (e.g., an x-axis relative to the entire structured surface) and an orthogonal second surface direction (e.g., the y-axis of the structured surface.). In some embodiments, the structured surface may include a plurality of adjacent, non-overlapping surface domains. In some such embodiments, each of the surface domains includes a closed outermost perimeter, such that a shape of no more than about 10%, or about 15%, or about 20%, or about 25% of the closed outermost perimeters are the same.

[0020] For the purposed of this description, a surface domain is defined as a sub-region of the larger structured surface. By way of analogy, the structured surface may be compared to a country, and the surface domains may be compared to the provinces, states, or regions into which the country is divided. In at least some embodiments, the entire structured surface may be divided into surface domains, with one surface domain bordering on one or more other surface domains, but not overlapping with those other surface domains.

[0021] In some embodiments, each surface domain of the structured surface may include a plurality of structures disposed within the closed outermost perimeter of the surface domain. In some embodiments, these structures may be peaks and valleys in the surface, members (e.g., posts, pyramids, bumps, etc.) extending above a substrate or other surface, or any other appropriate topology in which the “structures” can be represented by heights in a height map of the surface domain (or of the entire structured surface).

[0022] In some such embodiments, the structures of the plurality of structures may be disposed within each surface domain and arranged along a first domain direction (e.g., a “local” x-direction, relative to the surface domain, which may be different than the first surface direction) and an orthogonal second domain direction (e.g., a y-direction local to the surface domain. Stated another way, the first domain direction and the second domain direction are defined relative to the surface domain itself, and these domain directions may not be the same as the first and second surface directions). In some embodiments, the arrangement of structures within at least about 10%, or at least about 15%, or at least about 20%, or at least about 30%, or at least about 40%, or at least about 50% of the surface domains is periodic or near periodic.

[0023] Regarding the definitions of the terms “periodic” and “near periodic” as used herein, in the field of optical films and other structured surfaces, it is helpful to determine the degree of periodicity or near periodicity to understand and control the visual properties of the surface. One effective method to assess this periodicity is through the use of an autocorrelation function (ACF).

[0024] The autocorrelation function (ACF) is a mathematical tool used to measure the similarity of a “signal” or, in this case, the pattern of a structured surface to a “shifted” version of itself. In signalprocessing, for example, one can compare a waveform to various versions of itself which have been delayed (or shifted) in time (for example, comparing a sinusoidal signal waveform to copies of the same signal shifted by 1 millisecond (ms), 2 ms, 3 ms, etc.). When the results of these comparisons are plotted, a waveform with a higher amount of periodicity will produce a higher number of peaks (“hills” within the plot which rise to a summit above some level) on the resulting plot (while a purely random waveform will have only a single peak located at zero. The higher number of peaks in the plot indicate a higher amount of periodicity in the waveform. When applied to a structured surface, such as an optical film, the ACF can reveal the periodic or near-periodic nature of the surface topography.

[0025] For example, to determine the periodicity of a structured surface, an ACF can be calculated for a height map of the structured surface (holding the heights and locations of the structures within the structured surface). This involves taking the Fourier transform of the surface topography data, computing the power spectral density (PSD), and then performing an inverse Fourier transform to obtain the ACF. Then the resulting ACF is plotted, and the presence of distinct peaks in the plot is analyzed. These peaks indicate the degree of periodicity in the surface structure.

[0026] If the ACF plot shows at least three distinct peaks (two distinct peaks in addition to the peak at the origin), the surface is considered to have some degree of periodicity. The presence of multiple peaks suggests that the surface topography repeats at regular intervals.

[0027] For surfaces with near-periodic (or “quasi-periodic” or “pseudo-periodic”) structures (for example, a height map of a surface created by crossed sinusoids, to which some amount of randomization has been applied to the points in the height map), the ACF plot may show peaks which indicate a repeating pattern. If there are at least three distinct collinear peaks in a given direction (for any line that passes through the center of the surface), the surface is considered to have near-periodic properties in that given direction.

[0028] In some embodiments, the plurality of structures of no more than about 10%, or about 15%, or about 20%, or about 25% of the surface domains have the same arrangement. Stated another way, the arrangement of structures within each surface domain may be different than the arrangement of structures within at least some of the other surface domains.

[0029] For example, the arrangement of structures of a first surface domain may differ from the arrangement of structures of a second, different surface domain by at least one of an angular difference between the first domain direction (e.g., the domain’s “local” first direction) and the first surface direction of the structured surface (in other words, rotation or translation of the structures within the domain relative to the overall surface), the pitches between neighboring structures, the relative amplitudes of the structures, and a relative position of the structures to each other (e.g., the pattern of the structures within each surface domain).

[0030] For example, a structured surface of the present description may be generated by taking a surface with a purely periodic arrangement of structures, such as a surface with alternating peaks and valleys representing a 2D crossed sinusoid, and breaking that overall surface into smaller surfacedomains. Then, the periodic pattern within each surface domain (or within at least a subset of the surface domains) may be separately rotated relative to the first and second surface directions. That is, each surface domain will still contain structures in a crossed-sinusoid pattern, but the rotation (or the point-to-point translation) of the pattern within each surface domain may be different from the starting rotation of the original structured surface. In some embodiments, all of the surface domains may have a unique rotation angle relative to the original structured surface. In other embodiments, only a subset of the surface domains may have a unique rotation angle. It should be noted that this example is for discussion purposes only, and the arrangement of the structures among the surface domains may vary in other ways, as described herein.

[0031] In some embodiments, the shape of at least 30%, or at least 40%, or at least 50% of the closed outermost perimeters of the structured domains of a structured surface may be an irregular polygon. In other embodiments, the closed outermost perimeters may have any other appropriate shape, including circles, ovals, regular polygons, curved shapes, etc.

[0032] According to some aspects of the present description, an optical film has a first major surface including at least one structured surface of any of the embodiments described herein, and an opposing second major surface. In some embodiments, the at least one structured surface may include two or more structured surfaces tiled across the optical film. In some such embodiments, at least some of the two or more structured surfaces may be substantially identical to each other. For example, each structured surface in the optical film may include substantially identical surface domains as described herein. The surface domains of a given structured surface (e.g., a structured surface “tile”) may be arranged such that the surface domains on one edge of one structured surface substantially align with the surface domains on a corresponding edge of an adjacent structured surface.

[0033] In some embodiments, the optical film may further include an optically clear material disposed on the first major surface and substantially covering the at least one structured surface. In some such embodiments, the optically clear material is an optically clear adhesive. In some such embodiments, the optically clear material may encapsulate and substantially planarize at least a portion of the at least one structured surface. In some embodiments, the optical film may further include an optically clear material disposed on the second major surface. In some such embodiments, the optical material on the second major surface may be an optically clear adhesive. For example, in some embodiments, the optical clear material on either the first major surface or the second major surface, or both, may be useful in laminating the optical film to other layers in an optical stack, such as an optical stack for use in a display system.

[0034] In some embodiments, the optical film may further include a substrate. In some such embodiments, the structures of the surface domains disposed on a first major surface of the substrate. In some such embodiments, the substrate may have an optical retardation less than about 20 nm.

[0035] According to some aspects of the present description, a display system may include a display configured to emit an image for viewing by an eye of a viewer, and any of the embodimentsthe optical film with structured surfaces described herein, disposed between the display and the eye of the viewer. In some such embodiments, the display system may provide a reduction in optical sparkle when compared to a comparative display system which is identical to the display system except it does not include the optical film. In some such embodiments, the reduction in optical sparkle may be at least 10%, or at least 15%, or at least 20%.

[0036] According to some aspects of the present description, an optical film may include a plurality of adjacent, non-overlapping structured surfaces, such as any of the embodiments of structured surfaces with surface domains described herein. In some embodiments, each structured surface of the plurality of structured surfaces may include a plurality of adjacent, non-overlapping surface domains. In some such embodiments, an arrangement of the plurality of surface domains within at least two of the structured surfaces is substantially identical. Stated another way, at least two or more of the structured surfaces may be substantially identical.

[0037] In some embodiments, each structured surface of the plurality of structured surfaces may define a first surface direction (e.g., an x-axis defined in terms of the structured surface) and an orthogonal second surface direction (e.g., a y-axis defined for the structured surface). In some embodiments, the surface domains of each structured surface have a closed outermost perimeter. In some embodiments, a shape of no more than about 10%, or about 15%, or about 20% of the closed outermost perimeters of the surface domains within a structured surface are the same. Stated another way, the shapes of the closed outermost perimeters of the surface domains may be unique with only a small percentage (including zero percent) repeats in the shapes per surface structure.

[0038] In some embodiments, each surface domain within a structured surface may include a plurality of structures disposed within the closed outermost perimeter of the surface domain. In some such embodiments, the structures disposed within each surface domain may be arranged along a first domain direction and an orthogonal second domain direction, where both the first domain direction and second domain direction are defined relative to the surface domain (rather than relative to the surface structure), and the first domain direction and second domain direction may be different than the first surface direction and second surface direction, respectively. In some embodiments, the arrangement of structures within at least about 10%, or about 20%, or about 30%, or about 40%, or about 50% of the surface domains may be periodic or near periodic, as defined elsewhere herein. In some embodiments, the plurality of structures of no more than about 10%, or about 15%, or about 20% of the surface domains within a structured surface have the same arrangement of structures.

[0039] For example, for each structured surface, the arrangement of structures of a first surface domain within the structured surface differs from the arrangement of structures of a second, different surface domain within the structured surface by at least one of an angular difference between the first domain direction and the first surface direction of the structured surface (i.e., the arrangement may be “rotated” in the XY plane relative to the structured surface), a pitch between neighboring structures, an average pitch between neighboring structures, the relative amplitudes of the structures, an averageamplitude of the structures, and a relative position of the structures relative to each other (e.g., the “pattern” the structures within a surface domain form, e.g., a rectangular grid, a circular arrangement, specific locations within the surface domain, etc.).

[0040] In some embodiments, each of the structured surfaces of the plurality of structured surfaces, or each of at least 30%, or at least 40%, or at least 50%, or at least 60% of the structured surfaces, may be substantially identical. In some such embodiments, the structured surfaces of the plurality of structured surfaces may be tiled across the optical film.

[0041] According to some aspects of the present description, a display system may include a display configured to emit an image for viewing by an eye of a viewer, and any of the embodiments the optical film with structured surfaces described herein, disposed between the display and the eye of the viewer. In some such embodiments, the display system may provide a reduction in optical sparkle when compared to a comparative display system which is identical to the display system except it does not include the optical film.

[0042] As discussed previously herein, one application of surface domains in an optical film (or structured surfaces thereof) is to “break up” or add randomness to a periodic or near periodic arrangement of structures. This randomization through surface domains can reduce or eliminate any optical artifacts (such as moire) that may be introduced by the periodicity of the surfaces. However, there are other uses of surface domains that can be applied to non-periodic surface structures that fall within the scope of the present description. For example, an optical film may be created by “tiling” a series of structured surfaces together to make a larger surface, such as the surface of an optical film. In this case, the tiling of structured surfaces (even structured surfaces which are substantially random or substantially aperiodic) can introduce a regular pattern of discontinuities (e.g., a grid) at the locations where the tiles butt up against each other. This regular pattern of seams between tiles can also introduce optical artifacts.

[0043] One way of addressing the issue of seam lines (discontinuity lines between structured surfaces) is to apply the concept of surface domains, as discussed herein, to the non-periodic or low periodicity surfaces, while ensuring that the surface domains at one edge of the structured surface align with and match the corresponding surface domains at the abutting edge of the adjacent structured surface.

[0044] According to some aspects of the present description, an optical film includes a plurality of adjacent, non-overlapping structured surfaces (e.g., a grid of structured surfaces tiled across the optical film). Each structured surface of the plurality of structured surfaces includes a plurality of adjacent, non-overlapping surface domains, wherein an arrangement of the plurality of surface domains within at least two of the structured surfaces is substantially identical (i.e., at least two of the structured surfaces may be substantially the same).

[0045] In some embodiments, each structured surface of the plurality of structured surfaces may define a first surface direction and an orthogonal second surface direction. The surface domains ofeach structured surface include a closed outermost perimeter, wherein the shapes of the closed outermost perimeters of a percentage of the surface domains (e.g., at least about 60%, or at least about 70%, or at least about 80%, or at least about 90%) is unique.

[0046] In some embodiments, each surface domain within a structured surface includes a plurality of structures disposed within the closed outermost perimeter of the surface domain. In some embodiments, the structures of the plurality of structures disposed within each surface domain are arranged along a first domain direction and an orthogonal second domain direction which are defined relative to the surface domain rather than the overall structured surface.

[0047] In some embodiments, the plurality of structures of no more than about 10% of the surface domains within a given structured surface have the same arrangement of structures, and wherein at least some of the surface domains at an edge of the given structured surface are configured to substantially align with and substantially match an arrangement of structures within the corresponding surface domains at an edge of an adjacent structured surface. Stated another way, while the surface domains within a given structured surface should have a low percentage of repetition (e.g., different outermost perimeters, different arrangements of structures, etc.), each structured surface should be configured such that the surface domains at any one edge of the structured surface correspond to (align with, have similar arrangement of structures within) as the surface domains at the edge of an adjacent structured surface. In some embodiments, the arrangement of structures within at least some of the structured surfaces is substantially non-periodic or aperiodic.

[0048] According to some aspects of the present description, a display system may include a display configured to emit an image for viewing by an eye of a viewer, and any of the embodiments the optical film with structured surfaces (having substantially aperiodic surface domains) described above, disposed between the display and the eye of the viewer. In some such embodiments, the display system may provide a reduction in optical sparkle when compared to a comparative display system which is identical to the display system except it does not include the optical film.

[0049] Turning now to the figures, FIGS. 1 A and IB provide top, plan views of an embodiments of a structured surface with surface domains, according to the present description. Both FIGS. 1 A and IB should be examined simultaneously for the following discussion.

[0050] In some embodiments, a structured surface 300 defines a first surface direction (e.g., see the x-axis shown in FIGS. 1A and IB) and an orthogonal second surface direction (e.g., the y-axis). In some embodiments, structured surface 300 includes a plurality of adjacent, non-overlapping surface domains 20. In some embodiments, each of surface domains 20 has a closed outermost perimeter 24 (see FIG. IB). In some embodiments, a shape of no more than about 10% of the closed outermost perimeters 24 are the same (i.e., most of the shapes of the surface domains 20 are unique within the structured surface 300).

[0051] In some embodiments, each surface domain 20 may include a plurality of structures 30 (e.g., peaks and valleys, posts, bumps, beads, etc.) disposed within the closed outermost perimeter 24of the surface domain. In some embodiments, structures 30 within each surface domain 20 may be arranged along a first domain direction (see, e.g., xl, x2 in FIG. IB) and an orthogonal second domain direction (e.g., yl, y2). In some embodiments, first domain direction xl, x2 and second domain direction yl, y2 are defined relative to each surface domain 20, rather than relative to the structured surface 300. In some embodiments, first domain direction xl, x2 and second domain direction yl, y2 may be different than first surface direction x and second surface direction y. In other embodiments, the first domain direction xl, x2 and second domain direction yl, y2 of at least some of the surface domains 20 may be substantially identical to first surface direction x and second surface direction y.

[0052] In some embodiments, the arrangement of structures 30 within at least about 10% (and up to about 100%) of surface domains 20 is periodic or near periodic, as defined elsewhere herein. In some embodiments, the plurality of structures of no more than about 10%, or about 20%, or about 30% of surface domains 20 have the same arrangement. As noted elsewhere herein, the arrangement of structures 30 within surface domains 20 may be different than the arrangement of structures 30 in other surface domains 20 in a variety of ways (e.g., relative rotation within the XY plane, pitch between structures 30, amplitude of structures 30, pattern of structures 30, and even type of structures.) The specific shapes and arrangement of surface domains 20 shown in the figures herein are meant as examples only, and not intended to be limiting. In the embodiment shown in FIGS. 1 A and IB, the shapes of the closed outermost perimeters 24 of the surface domains 20 are irregular polygons. However, any appropriate shapes may be used and be within the scope of the present description.

[0053] An optical film, such as the embodiment of optical film 400 illustrated in FIGS. 2A and 2B, may include a number of structured surfaces 300 tiled across its surface. In some embodiments, the surface domains 20 within a given surface domain 300 may each have a unique shape or arrangement (or at least a significant percentage of the surface domains 20 are unique). However, in some embodiments, each structured surface 300 may be substantially identical to each other structured surface 300 across optical film 400 (or at least a significant percentage of the structured surfaces 300 may be substantially identical.) In the embodiment shown in FIG. 2A, the shapes of structured surfaces 300 appear to be rectangular or square, but any appropriate shapes may be used for structured surfaces 300 (e.g., regular polygons, irregular polygons, random shapes, circles, ovals, concentric shapes, etc.)

[0054] FIG. 2B shows an edge view of an embodiment of optical film 400. A number of structured surfaces 300 can be seen aligned (adjacent, non-overlapping) across a base layer 10 (base layer 10 having a first, “top” surface 11 and a second, “bottom” surface 12). In some embodiments, base layer 10 may be integral to optical film 400 (e.g., a unitary construction including base layer 10 and structured surfaces 300). In some embodiments, optical film 400 may be disposed on an additional substrate 14, depending on manufacturing and application requirements. Each structured surface 300 may include a number of surface domains 20, and at least some of the surface domains 20within a structured surface 300 may have a unique arrangement of structures. Structures 30 may, for example, have unique average heights (as measured above first surface 11, for example), or unique structure-to-structure distances (structure pitches, or be distinguished by any number of different arrangement schemes such as those described elsewhere herein. In some embodiments, structures 30 may be unique projections from first surface 11, or may include peaks 30p and valleys 30v within the surface domain 20, or any combination of structure types appropriate to the application.

[0055] FIGS. 3A and 3B show additional embodiments of structure types that may be seen within surface domains 20 of a structured surface. The embodiments of structures 30 shown herein are examples only, intended to illustrate concepts and definitions used herein, and not intended to be limiting in any way. FIG. 3A shows one possible surface domain 20 with structures 30 that appear to be posts of varying amplitudes (in this case, heights) Al, A2. Structures 30 as shown in the embodiment of FIG. 3 A may have a unique structure-to-structure spacing or pitch, P. In some embodiments, the pitch P may be consistent or may vary while still exhibiting some periodic nature (e.g., the precise location of structures 30 may have been adjusted by a small amount to introduce some level of randomness to the arrangement of structures 30, so it may be useful to look at the average pitch across the structures 30 within a surface domain 20, rather than individual pitch values). Amplitudes or heights (Al, A2) may also vary across the structure 30 within a surface domain 20 (e.g., their may be more height levels, a single height level, etc.) such that an average amplitude across the surface domain 20 may be more useful when comparing the structures to structures of a different surface domain 20. In some embodiments, such as the embodiment of FIG. 3B, the structures may include peaks 30p and valleys 30v in a sinusoidal or near- sinusoidal surface topography.

[0056] FIG. 4 is a side view of an embodiment of a display system including an optical film with surface domains, according to the present description. In some embodiments, display system 500 may include a display 70 (e.g., a liquid crystal display and backlight, an LED display, an OLED display, etc.) and an optical film such as any of the optical films (such as optical film 400 of FIG. 2A) described herein.

[0057] Display 70 may be configured to emit an image as light rays 75, the image intended for viewing by an eye of a viewer 90 after passing through optical film 400. In some embodiments, optical film 400 may further include an optically clear material 40a disposed on structured surfaces 300 and substantially covering the surface domains within the structured surface 300. In some such embodiments, the optically clear material 40a may be an optically clear adhesive, but this is not intended to be limiting. In some such embodiments, the optically clear material 40a may encapsulate and substantially planarize at least a portion of surface domains, as shown in FIG. 4. In other embodiments, optically clear material 40a may be a conformal layer which substantially follows the contours of the structures within the surface domains.

[0058] In some embodiments, optical film 400 may further include an optically clear material40b disposed on second major surface 12 of optical film 400. In some such embodiments, opticallyclear material 40b may be an optically clear adhesive, although this is not intended to be limiting in any way. In some embodiments, optically clear materials 40a and 40b may be optically clear adhesives configured to laminate optical film 400 to other layers in the display system 500 (e.g., to display 70, or to other optical layers above or below optical film 400, such as diffusing layers, protective layers, light enhancement layers, etc.). For example, in some embodiments, display system 500 may further include an anti-glare layer 65 (e.g., an anti-glare coating, film, glass, etc). It should be noted that a slight gap is shown between some layers of the display system 500 in FIG. 4 to help distinguish the layers from the adjacent layers. However, in practice, there may be no gap between layers.

[0059] FIGS. 5A and 5B are plots of an example autocorrelation function (ACF) for an embodiment of an optical film, according to the present description. FIG. 5A shows the plot of an ACF completed (as described elsewhere herein) in an “x direction” for three example optical films (the ACF calculated for the x-axis of the film, passing through the film’s center point, or origin). FIG. 5B shows a similar plot of an ACF completed in a “y direction” for the same three example optical films (calculated for the y-axis of the film, passing through the film’s center point, or origin).

[0060] In each of FIG. 5A and 5B, there are ACF plotlines for three different films. The first, labeled “Crossed Sinusoid”, is a film without the surface domains as described herein, and represents a “pure” 2D surface topology created by crossing two orthogonal sinusoids. The remaining films, Example 01 and Example 02, are both example films having the varying surface domains as described herein.

[0061] The ACF for each film was completed by measuring the heights of structures at an initial, zero position, and then shifting the film in a direction (the X direction for FIG. 5A, the Y direction for FIG. 5B) a small amount (e.g., 0.5 micron, or 1 micron, etc.) and measuring the heights of the structures again. In practice, best results are obtained by shifting the films over at least 20 periods in each direction (measuring the heights each time the films are shifted). The examples in FIGS. 5A and 5B were created by shifting the height may over about 22 periods of the structures (note: it may take multiple “shifts” to move the film one full period).

[0062] The plotlines show the crossed sinusoid is the most “periodic”, as it shows high correlation between points after each shift, creating multiple peaks in the ACF plot, many of which show a correlation above 0.8 (indicating a high amount of periodicity). The term “crossed sinusoid” is used in this example to refer to a film that was designed based on crossed sinusoid waveforms; however imperfections may have been introduced in the manufacture of the film being measured, and the shape of the “peaks” may differ from the shape of the “valleys”. Therefore, the term crossed sinusoid, as used to describe the film in FIGS. 5A and 5B, is only a label indicating that film had a higher degree of periodicity than the other examples (closest to a “pure” crossed sinusoid in design).

[0063] The plotlines for Example 01 and Example 02 also show multiple peaks across the ACF, indicating they still each have a significant amount of periodicity, even though the structures of thosefilms have been “randomized” to different extents. For example, the Example 02 film has an ACF in the x direction (FIG. 5A) with multiple peaks that are above at least 0.3 (indicating a certain level of periodicity, but not as much as the periodicity seen in the crossed sinusoid film, with peaks above about 0.8).

[0064] It is important that some percentage (e.g., at least 20%, or at least 30%, or at least 40%) of the surface domains in the structured surfaces described herein have some level of periodicity, as the periodicity of a film can be used to reduce sparkle (as in an anti-sparkle film). However, as described previously herein, “perfectly” periodic or near periodic film structures can introduce other optical artifacts such as moire. By breaking the periodic or near periodic surface into a number of surface domains, as describe herein, and varying the arrangement of the structures across the different domain sections, a level of randomness can be introduced through the different domain arrangements, while allowing a significant percentage of the surface domains to still be periodic or near periodic in nature. This allows the periodic nature of the different domains to reduce sparkle in a display system, while the variation between domains reduces the occurrence of other optical artifacts.

[0065] FIGS. 6 A and 6B detail steps in one embodiment of a method of making an optical film with surface domains, according to the present description. It should be noted that the method described in these figures in an example only and not intended to be limiting in any way. There are various ways to create the optical films and structured surfaces described herein that are within the scope of the present description.

[0066] In a first step of this embodiment, as shown in FIG. 6 A, an existing structured surface 100 has structures 30 (e.g., peaks and valleys in a crossed-sinusoidal film) which have a periodic arrangement (e.g., an ACF of at least about 0.7, or 0.8, or above). The heights and / or locations of the structures in a height map of structured surface 100 may be randomized (by any of a variety of methods) to create a partially randomized structured surface 100a with structures 30a that have been “tweaked” (e.g., moved, shortened, made taller, rotated, etc.) to add some level of randomization.

[0067] As shown in FIG. 6B, the steps of FIG. 6A may be repeated any number of times to produce additional “versions” of original structured surface 100 (e.g., structured surfaces 100a- lOOe as shown in FIG. 6B), each with its own unique arrangement of structures. In the example of FIG. 6B, five different height map variations were generated, but this is not meant to be limiting. A domain map 105 is then applied to the collection of height maps 100a- lOOe. For example, as shown in FIG. 6B, domain map 105 has five different domain types (each represented as a different gray shade in FIG. 6B). Each of the different height maps 100a- lOOe is then mapped to a specific domain type in domain map 105. For example, the structures of height map 100a may be “copied” to domain type 105a (the white domains) in domain map 105, the structures of height map 100b may be “copied” to domain type 105b, and so on, to piece together the resulting structured surface 300, which is an amalgamation of all 5 height maps, wherein the structured domains in structured surface 300 were created from five different randomized height maps.

[0068] Finally, FIGS. 7A and 7B illustrate how the surface domains of adjacent (tiled) structured surfaces may align to “break up” long seams between adjacent structured surfaces which may cause optical artifacts in a resulting optical film.

[0069] FIG. 7A shows three structured surfaces having surface domains 20. Surface domains 20 may have structures within them which are arranged with some level of periodicity (as described previously herein) or with substantially no periodicity. As shown in FIG. 7A, the structured surfaces 300 are configured such that the surface domains 20a at one edge of a structured surface 300 substantially line up with, and have a substantially similar arrangement of structures within, the corresponding surface domains 20b of an adjacent structured surface 300. The double arrows show between adjacent structured surfaces 300 indicate areas where the surface domains of one structured surface are intended to align with the surface domains of an adjacent structured surface.

[0070] FIG. 7B shows the resulting optical film 400 when four of these structured surfaces 300 are tiled together, where the surface domains at the edges appear to “bleed over” or extend from one structured surface to the adjacent one. This technique may be used to “break up” or add randomization to the seams between adjacent structured surfaces, making them visible in the finished display output.

[0071] There are various other ways to create the structured surface 300, and various alternate embodiments of the structured surface within the scope of the present description. For example, in one embodiment, adjacent surface domains within a structured surface may each have a different type of structure (e.g., one domain may have cylindrical posts, while an adjacent domain has the peaks and valleys of a sinusoidal surface). Other embodiments are possible.

[0072] Terms such as “about” will be understood in the context in which they are used and described in the present description by one of ordinary skill in the art. If the use of “about” as applied to quantities expressing feature sizes, amounts, and physical properties is not otherwise clear to one of ordinary skill in the art in the context in which it is used and described in the present description, “about” will be understood to mean within 10 percent of the specified value. A quantity given as about a specified value can be precisely the specified value. For example, if it is not otherwise clear to one of ordinary skill in the art in the context in which it is used and described in the present description, a quantity having a value of about 1, means that the quantity has a value between 0.9 and 1.1, and that the value could be 1.

[0073] Terms such as “substantially” will be understood in the context in which they are used and described in the present description by one of ordinary skill in the art. If the use of “substantially equal” is not otherwise clear to one of ordinary skill in the art in the context in which it is used and described in the present description, “substantially equal” will mean about equal where about is as described above. If the use of “substantially parallel” is not otherwise clear to one of ordinary skill in the art in the context in which it is used and described in the present description, “substantially parallel” will mean within 10 degrees, or within 5 degrees, of parallel. Directions or surfaces described as substantially parallel to one another may, in some embodiments, be within 10 degrees, orwithin 5 degrees of parallel, or may be parallel or nominally parallel. If the use of “substantially aligned” is not otherwise clear to one of ordinary skill in the art in the context in which it is used and described in the present description, “substantially aligned” will mean aligned to within 20% of a width of the objects being aligned. Objects described as substantially aligned may, in some embodiments, be aligned to within 10% or to within 5% of a width of the objects being aligned.

[0074] All references, patents, and patent applications referenced in the foregoing are hereby incorporated herein by reference in their entirety in a consistent manner. In the event of inconsistencies or contradictions between portions of the incorporated references and this application, the information in the preceding description shall control.

[0075] Descriptions for elements in figures should be understood to apply equally to corresponding elements in other figures, unless indicated otherwise. Although specific embodiments have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that a variety of alternate and / or equivalent implementations can be substituted for the specific embodiments shown and described without departing from the scope of the present disclosure. This application is intended to cover any adaptations or variations of the specific embodiments discussed herein. Therefore, it is intended that this disclosure be limited only by the claims and the equivalents thereof.

Claims

What is claimed:

1. A structured surface defining a first surface direction and an orthogonal second surface direction, the structured surface comprising a plurality of adjacent, non-overlapping surface domains, each of the surface domains comprising a closed outermost perimeter, such that a shape of no more than about 10% of the closed outermost perimeters are the same; wherein each surface domain comprises a plurality of structures disposed within the closed outermost perimeter of the surface domain, the structures of the plurality of structures disposed within each surface domain arranged along a first domain direction and an orthogonal second domain direction, the first domain direction and second domain direction defined relative to the surface domain, and the arrangement of structures within at least about 10% of the surface domains is periodic or near periodic; and wherein the plurality of structures of no more than about 10% of the surface domains have the same arrangement.

2. The structured surface of claim 1, wherein the arrangement of structures of a first surface domain differs from the arrangement of structures of a second, different surface domain by at least one of an angular difference between the first domain direction and the first surface direction of the structured surface, a pitch between neighboring structures, an average pitch between neighboring structures, relative amplitudes of the structures, an average amplitude of the structures, and a relative position of the structures to each other.

3. The structured surface of claim 1, wherein the shape of at least 30%, or at least 40%, or at least 50% of the closed outermost perimeters is an irregular polygon.

4. An optical film comprising a first major surface comprising at least one structured surface of claim 1, and an opposing second major surface.

5. The optical film of claim 4, wherein the at least one structured surface comprises two or more structured surfaces tiled across the optical film.

6. A display system, comprising: a display configured to emit an image for viewing by an eye of a viewer; and the optical film of claim 4, disposed between the display and the eye of the viewer.

7. The optical film of claim 4, further comprising an optically clear material disposed on the first major surface and substantially covering the at least one structured surface.

8. The optical film of claim 7, wherein the optically clear material is an optically clear adhesive.

9. The optical film of claim 7, wherein the optically clear material encapsulates and substantially planarizes at least a portion of the at least one structured surface.

10. The optical film of claim 4, further comprising an optically clear material disposed on the second major surface.

11. The optical film of claim 10, wherein the optical material is an optically clear adhesive.

12. The optical film of claim 4, further comprising a substrate, the structures of the surface domains disposed on a first major surface of the substrate.

13. The optical film of claim 12, wherein the substrate has an optical retardation less than about 20 nm.

14. The display system of claim 6, wherein the display system provides a reduction in optical sparkle when compared to a comparative display system which is identical to the display system except it does not include the optical film.

15. The display system of claim 14, wherein the reduction in optical sparkle is at least 10%.

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