Anti-sparkle film with randomized height map

Abstract

A structured surface includes first surface portions and second surface portions. Each of the first and second surface portions are continuous without any surface opening within an outermost perimeter. Each of the first surface portions has at least one peak. Each of the second surface portions has at least one valley. A highest peak of the first surface portions has height Hmax, and a deepest valley of the second surface portions has height Hmin. Each surface location in each of the first surface portions has a height not less than H1, and each surface location in each of the second surface portions has a height not greater than H2, where Hmin < H2 < H1 < Hmax. At least two of the first surface portions and at least two of the second surface portions have different shapes / sizes.

Description

PA102909W002ANTI-SPARKLE FILM WITH RANDOMIZED HEIGHT MAPSummary

[0001] In some aspects of the present description, a structured surface is provided, the structured surface including a plurality of spaced apart first surface portions and a plurality of spaced apart second surface portions. Each of the first and second surface portions are continuous without any surface opening within and across a closed outermost perimeter of the surface portion. Each of the first surface portions is spaced apart from each of the second surface portions. Each of the first surface portions includes at least one peak disposed within and away from the closed outermost perimeter of the first surface portion, and each of the second surface portions includes at least one valley disposed within and away from the closed outermost perimeter of the second surface portion. A highest peak of the at least one peak of all of the first surface portions has a height Hmax, and a deepest valley of the at least one valley of all the second surface portions has a height Hmin. Each surface location in each of the first surface portions has a height not less than Hl, and each surface location in each of the second surface portions has a height not greater than H2, where Hmin < H2 < Hl < Hmax. At least two of the first surface portions have different shapes and sizes, and at least two of the second surface portions have different shapes and sizes. Hl is selected such that between 10% and 30% of a total area of the structured surface is occupied by the first surface portions, and H2 is selected such that between 10% and 30% of a total area of the structured surface is occupied by the second surface portions.

[0002] In some aspects of the present description, a structured surface is provided, the structured surface including a plurality of spaced apart first surface portions and a plurality of spaced apart second surface portions. Each of the first and second surface portions is continuous without any surface opening within and across a closed outermost perimeter of the surface portion. Each of the first surface portions is spaced apart from each of the second surface portions. Each of the first surface portions includes at least one peak disposed within and away from the closed outermost perimeter of the first surface portion, and each of the second surface portions includes at least one valley disposed within and away from the closed outermost perimeter of the second surface portion. Between 10% and 20% of a total area of the structured surface is occupied by the first surface portions, and between 10% and 20% of a total area of the structured surface is occupied by the second surface portions. For each of at least one of the first surface portions and at least one of the second surface portions, the closed outermost perimeter of the surface portion has first and second perimeter portions that are convex toward each other defining a narrower portion of the surface portion joining two wider portions of the surface portion. A length of each of thefirst and second perimeter portions is at least 10% of a total length of the closed perimeter of the surface portion.

[0003] In some aspects of the present description, an aperiodic structured surface is provided, the aperiodic structured surface including a plurality of spaced apart first surface portions and a plurality of spaced apart second surface portions. Each of the first and second surface portions are continuous without any surface opening within and across a closed outermost perimeter of the surface portion. Each of the first surface portions is spaced apart from each of the second surface portions. Each of the first surface portions includes at least one peak disposed within and away from the closed outermost perimeter of the first surface portion, and each of the second surface portions includes at least one valley disposed within and away from the closed outermost perimeter of the second surface portion. At least two of the first surface portions have different shapes and sizes, and at least two of the second surface portions have different shapes and sizes. A magnitude squared of a Fourier transform of a height map of the first surface portions and second surface portions in the structured surface along one of the first and second directions, where at each spatial frequency the magnitude squared is integrated along the other one of the first and second directions, has a global peak having a first area under the curve Al at a first spatial frequency Fl and a second area under the curve A2 at a second spatial frequency F2, Fl and F2 in units of 1 / mm, where 5 < F2 < Fl, A1 / A2 < 100,000.

[0004] In some aspects of the present description, an aperiodic structured surface is provided, the aperiodic structured surface including a plurality of spaced apart first surface portions and a plurality of spaced apart second surface portions. Each of the first and second surface portions is continuous without any surface opening within and across a closed outermost perimeter of the surface portion. Each of the first surface portions is spaced apart from each of the second surface portions. Each of the first surface portions includes at least one peak disposed within and away from the closed outermost perimeter of the first surface portion, and each of the second surface portions includes at least one valley disposed within and away from the closed outermost perimeter of the second surface portion. At least two of the first surface portions have different shapes and sizes, and at least two of the second surface portions have different shapes and sizes. A magnitude squared of an azimuthally integrated Fourier transform of a height map of the first surface portions and second surface portions in the structured surface has a global peak having a first area under the curve Al at a first spatial frequency Fl, and a second area under the curve A2 at a second spatial frequency F2, Fl and F2 in units of 1 / mm, 5 < F2 < Fl, A1 / A2 < 100,000.Brief Description of the Drawings

[0005] FIGS. 1A and IB depict an optical film with randomized height maps, in accordance with an embodiment of the present description;

[0006] FIG. 2A shows additional details on a surface portion of an optical film, in accordance with an embodiment of the present description;

[0007] FIG. 2B shows a schematic view of a display system with an optical film with randomized height map, in accordance with an embodiment of the present description;

[0008] FIGS. 3A and 3B depict optical films with first and second surface portions, in accordance with embodiments of the present description;

[0009] FIGS. 4 A and 4B depict additional optical film variants with first and second surface portions, in accordance with embodiments of the present description;

[0010] FIGS. 5A and 5B depict even more optical film variants with first and second surface portions, in accordance with embodiments of the present description;

[0011] FIGS. 6A and 6B are charts showing structural characteristics of optical films with randomized height maps, in accordance with an embodiment of the present description;

[0012] FIG. 7 is an additional chart showing structural characteristics of optical films with randomized height maps, in accordance with an embodiment of the present description;

[0013] FIGS. 8A and 8B are alternate versions of the charts of FIGS. 6A and 7, respectively, showing structural characteristics of optical films with randomized height maps, in accordance with an embodiment of the present description; and

[0014] FIGS. 9A and 9B show optical sparkle and percent transmission for optical films with randomized height maps, in accordance with an embodiment of the present description.Detailed Description

[0015] 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.

[0016] The present invention relates to optical films, and more specifically, to anti-sparkle films used in display systems to enhance visual quality by reducing display sparkle. Display systems, such as those used in televisions, computer monitors, and mobile devices, often suffer from a visual artifact known as "sparkle." Sparkle is a form of visual noise that manifests asrandom bright spots on the display, which can be distracting and reduce the overall image quality. This issue is particularly pronounced in high-resolution displays where the pixel density is high.

[0017] To mitigate sparkle, various types of anti-sparkle films have been developed. One effective approach involves the use of crossed-sinusoidal surface topographies. A crossed sinusoid is created by superimposing two orthogonal sinusoidal waves, resulting in a surface pattern that can scatter light in a controlled manner to reduce sparkle. These films have been successful in diminishing sparkle, thereby improving the visual experience for the user.

[0018] However, the periodic nature of crossed-sinusoidal patterns introduces its own set of challenges. The regularity of the sinusoidal waves can lead to periodic artifacts, which are repetitive and predictable distortions that can degrade the display quality. These artifacts are particularly problematic in applications requiring high visual fidelity, as they can be as distracting as the sparkle they are meant to eliminate.

[0019] Therefore, there is a need for improved anti-sparkle films that effectively reduce display sparkle while minimizing periodic artifacts. The present description addresses these needs by providing novel anti-sparkle films using crossed-sinusoidal height maps which have been randomized to approximate and achieve the anti-sparkle benefits of pure crossed-sinusoidal films while reducing or eliminating the optical artifacts associated with such films. It should be noted that the description of the films provided herein as cross-sinusoidal or approximations thereof is not meant to be limiting, and that other films which meet the limitations described and claimed herein are within the scope of the present description. The films described herein are aperiodic in that they are not purely periodic in nature (have at least some level of randomness over a pure periodic film such as a crossed-sinusoid) but also include a certain amount of near-periodicity or pseudo-periodicity over purely random films. This allows the anti-sparkle films described herein to avoid the optical artifacts of a pure crossed-sinusoid film while providing an improvement in optical characteristics such as sparkle over purely random films.

[0020] According to some aspects of the present description, a structured surface (e.g., the structured surface of an optical film) may include a plurality of spaced-apart first surface portions and a plurality of spaced-apart second surface portions. In some embodiments, each of the first and second surface portions may be continuous without any surface opening within and across a closed outermost perimeter of the surface portion (i.e., no area within the perimeter of the surface portion where the surface locations of the surface portion do not exist or have a zero height). In some embodiments, each of the first surface portions may be spaced apart from (i.e., do not overlap with) each of the second surface portions. In some embodiments, each of the first surface portions may include at least one peak disposed within and away from the closed outermost perimeter of the first surface portion, and each of the second surface portions may include at least one valleydisposed within and away from the closed outermost perimeter of the second surface portion. For the purposes of this discussion, a “peak” shall be defined as an area of the surface portion which has a local maximum height within that surface portion, and a “valley” shall be defined as an area of the surface portion which has a local minimum height within that surface portion. A surface portion may, in some embodiments, have two or more peaks (two or more regions which both have the same, maximum height, or a first peak and one or more other local peaks which are less than the first peak). Similarly, a surface portion may, in some embodiments, have two or more valleys (two or more regions which both have the same, minimum height, or a first valley and one or more other local valleys which are not as deep as the first valley).

[0021] In some embodiments, a highest peak of the at least one peak of all of the first surface portions has a height Hmax (i.e., a global maximum point across the entire surface), and a deepest valley of the at least one valley of all the second surface portions having a height Hmin (i.e., a global minimum point across the entire surface). It should be noted that “height” may be defined as a positive offset from a base layer, such as a substrate or sub-surface layer beneath the surface portions. In these cases, Hmin, though the lowest point in the structured surface, may be a positive offset from the base layer, albeit the minimum positive offset for the entire structured surface (see, e.g., the definition of heights shown in FIG. IB). In other embodiments, height can be measured as an offset from a mean height value for the entire structured surface, such that Hmax (for the peak) would be a positive offset from the mean height value and Hmin (for the valley) would be a negative offset from the mean height value (see, e.g., the scale presented in FIG. 1A). The relationships of the height values, as described and claimed herein, remain the same in either case, with only the reference height being different.

[0022] In some embodiments, each surface location in each of the first surface portions may have a height not less than Hl, and each surface location in each of the second surface portions may have a height not greater than H2, where Hmin < H2 < Hl < Hmax. In some embodiments, at least two of the first surface portions may have different shapes and sizes, and at least two of the second surface portions may have different shapes and sizes.

[0023] In some embodiments, the value of Hl may be selected such that between 10% and 30% of a total area of the structured surface is occupied by the first surface portions, and the value of H2 may be selected such that between 10% and 30% of a total area of the structured surface is occupied by the second surface portions. For example, if Hmin (the lowest valley on the entire structured surface) is defined to be 0.5 microns, and Hmax (the highest peak on the entire structured surface) is defined as 8.5 microns, Hl may be defined as 7 microns, and H2 may be defined as 2 microns. In this example, the first surface portions would be defined as all surface locations on the structured surface with have a height greater than 7 microns (defining the “peaks”of the structured surface), and the second surface portions would be defined as all surface locations on the structured surface with have a height less than 2 microns (defining the “valleys” of the structured surface).

[0024] In some embodiments, the structured surface may be a structured surface of an optical film, such as an optical film for reducing optical sparkle (e.g., as may be used in a display system). In some embodiments, the optical film may have a first major surface which is or which includes the structured surface as described herein, and an opposing second major surface (e.g., an unstructured “back” surface, or a second structured surface).

[0025] In some embodiments, the optical film may further include an optically clear material disposed on the first major surface and substantially covering the first and second plurality of surface portions. In some such embodiments, the optically clear material may encapsulate and substantially planarize at least a portion of the first surface portions and the second surface portions on the structured surface. In some embodiments, the optically clear material may be an optically clear adhesive. 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 may be an optically clear adhesive. In some embodiments, the use of an optically clear adhesive may allow the optical film with the structured surface to be laminated to or otherwise included with a display as part of a display system.

[0026] In some embodiments, the optical film may further include a substrate, wherein the first surface portions and the second surface portions are disposed on a first major surface of the substrate. In some such embodiments, the substrate may have an optical retardation of less than about 20 nanometers (nm), or less than about 10 nm, or less than about 5 nm.

[0027] For the purposes of this description, optical retardation in an optical film refers to the phase difference introduced between different polarization components of light as it passes through an optical film. This phase difference is typically caused by the birefringence of the material, which means that the material has different refractive indices for different polarization directions of light. Birefringent materials have two distinct refractive indices depending on the polarization direction of the light. When light enters such a material, it splits into two rays, each polarized perpendicularly to the other and traveling at different speeds. As the two rays travel through the material, they accumulate a phase difference due to their different speeds. This phase difference is known as optical retardation. Optical retardation is typically measured in nanometers (nm) and is a function of the thickness of the film and the difference in refractive indices (birefringence). As used in the present description, it is important that the optical retardation introduced by any substrate included with the optical film be relatively low, such that the polarization state of an image generated by a display is substantially maintained after passing through the substrate.

[0028] In some embodiments, a display system may include a display (e.g., a liquid crystal display) configured to emit an image for viewing by an eye of a viewer, and the optical film 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 20%, or at least 30%, or at least 40%, or at least 50%.

[0029] In some embodiments, magnitude squared of a Fourier transform of a height map of the first surface portions and second surface portions in the structured surface along one of the first and second directions, where at each spatial frequency the magnitude squared is integrated along the other one of the first and second directions, may have a global peak having a first area under the curve, Al, at a first spatial frequency Fl and a second area under the curve, A2, at a second spatial frequency F2, where Fl and F2 are in units of 1 / mm, and 5 < F2 < Fl, A1 / A2 may be less than or equal to 100,000, or less than or equal to 50,000, or less than or equal to 10,000, or less than or equal to 5,000, or less than or equal to 1,000, or less than or equal to 500, or less than or equal to 100, or less than or equal to 80, or less than or equal to 60, or less than or equal to 40, or less than or equal to 20, or less than or equal to 10, or less than or equal to 8, or less than or equal to 6, or less than or equal to 4, or less than or equal to 2, or less than or equal to 1.

[0030] According to some aspects of the present description, a structured surface (e.g., the structured surface of an optical film) may include a plurality of spaced-apart first surface portions and a plurality of spaced-apart second surface portions. In some embodiments, each of the first and second surface portions may be continuous without any surface opening within and across a closed outermost perimeter of the surface portion. In some embodiments, each of the first surface portions may be spaced apart from (not overlapping with) each of the second surface portions. In some embodiments, each of the first surface portions may include at least one peak disposed within and away from the closed outermost perimeter of the first surface portion, and each of the second surface portions may include at least one valley disposed within and away from the closed outermost perimeter of the second surface portion. In some embodiments, between 10% and 20% of a total area of the structured surface may be occupied by the first surface portions, and between 10% and 20% of the total area of the structured surface may be occupied by the second surface portions.

[0031] In some embodiments, for each of at least one of the first surface portions and at least one of the second surface portions, the closed outermost perimeter of the surface portion may have first and second perimeter portions that are convex toward each other defining a narrower portion of the surface portion joining two wider portions of the surface portion. In some embodiments, alength of each of the first and second perimeter portions may be at least 10%, or at least 15%, or at least 20%, or at least 25%, or at least 30%, or at least 40% of a total length of the closed perimeter of the surface portion.

[0032] In some embodiments, the structured surface may be a structured surface of an optical film, such as an optical film for reducing optical sparkle (e.g., as may be used in a display system). In some embodiments, the optical film may have a first major surface which is or which includes the structured surface as described herein, and an opposing second major surface (e.g., an unstructured “back” surface, or a second 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 first surface portions and second surface portions. In some such embodiments, the optically clear material may encapsulate and substantially planarize at least a portion of the first surface portions and second surface portions on the structured surface. In some embodiments, the optically clear material may be an optically clear adhesive. 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 may be an optically clear adhesive. In some embodiments, the use of an optically clear adhesive may allow the optical film with the structured surface to be laminated to or otherwise included with a display as part of a display system.

[0034] In some embodiments, the optical film may further include a substrate, wherein the first surface portions and second surface portions are disposed on a first major surface of the substrate. In some such embodiments, the substrate may have an optical retardation of less than about 20 nanometers (nm), or less than about 10 nm, or less than about 5 nm.

[0035] In some embodiments, a display system may include a display (e.g., a liquid crystal display) configured to emit an image for viewing by an eye of a viewer, and the optical film 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 20%, or at least 30%, or at least 40%, or at least 50%.

[0036] In some embodiments, a magnitude squared of a Fourier transform of a height map of the first surface portions and second surface portions in the structured surface along one of the first and second directions, where at each spatial frequency the magnitude squared is integrated along the other one of the first and second directions, has a global peak having a first area under the curve Al at a first spatial frequency Fl and a second area under the curve A2 at a second spatial frequency F2, Fl and F2 in units of 1 / mm, 5 < F2 < Fl, A1 / A2 may be less than or equal to100,000, or less than or equal to 50,000, or less than or equal to 10,000, or less than or equal to 5,000, or less than or equal to 1,000, or less than or equal to 500, or less than or equal to 100, or less than or equal to 80, or less than or equal to 60, or less than or equal to 40, or less than or equal to 20, or less than or equal to 10, or less than or equal to 8, or less than or equal to 6, or less than or equal to 4, or less than or equal to 2, or less than or equal to 1.

[0037] According to some aspects of the present description, an aperiodic structured surface (e.g., the structured surface of an optical film) may include a plurality of spaced-apart first surface portions and a plurality of spaced-apart second surface portions. In some embodiments, each of the first and second surface portions may be continuous without any surface opening within and across a closed outermost perimeter of the surface portion. In some embodiments, each of the first surface portions may be spaced apart from (not overlap with) each of the second surface portions. In some embodiments, each of the first surface portions may include at least one peak disposed within and away from the closed outermost perimeter of the first surface portion, and each of the second surface portions may include at least one valley disposed within and away from the closed outermost perimeter of the second surface portion. In some embodiments, at least two of the first surface portions may have different shapes and sizes, and at least two of the second surface portions may have different shapes and sizes.

[0038] In some embodiments, a magnitude squared of a Fourier transform of a height map of the first surface portions and second surface portions in the structured surface along one of the first and second directions, where at each spatial frequency the magnitude squared is integrated along the other one of the first and second directions, may have a global peak having a first area under the curve Al at a first spatial frequency Fl and a second area under the curve A2 at a second spatial frequency F2, Fl and F2 in units of 1 / mm, where 5 < F2 < Fl, and A1 / A2 may be less than or equal to 100,000, or less than or equal to 50,000, or less than or equal to 10,000, or less than or equal to 5,000, or less than or equal to 1,000, or less than or equal to 500, or less than or equal to 100, or less than or equal to 80, or less than or equal to 60, or less than or equal to 40, or less than or equal to 20, or less than or equal to 10, or less than or equal to 8, or less than or equal to 6, or less than or equal to 4, or less than or equal to 2, or less than or equal to 1.

[0039] In some embodiments, the structured surface may be a structured surface of an optical film, such as an optical film for reducing optical sparkle (e.g., as may be used in a display system). In some embodiments, the optical film may have a first major surface which is or which includes the structured surface as described herein, and an opposing second major surface (e.g., an unstructured “back” surface, or a second structured surface).

[0040] In some embodiments, the optical film may further include an optically clear material disposed on the first major surface and substantially covering the first surface portions and secondsurface portions. In some such embodiments, the optically clear material may encapsulate and substantially planarize at least a portion of the first surface portions and second surface portions on the structured surface. In some embodiments, the optically clear material may be an optically clear adhesive. 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 may be an optically clear adhesive. In some embodiments, the use of an optically clear adhesive may allow the optical film with the structured surface to be laminated to or otherwise included with a display as part of a display system.

[0041] In some embodiments, the optical film may further include a substrate, wherein the first surface portions and second surface portions are disposed on a first major surface of the substrate. In some such embodiments, the substrate may have an optical retardation of less than about 20 nanometers (nm), or less than about 10 nm, or less than about 5 nm.

[0042] In some embodiments, a display system may include a display (e.g., a liquid crystal display) configured to emit an image for viewing by an eye of a viewer, and the optical film 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 20%, or at least 30%, or at least 40%, or at least 50%.

[0043] According to some aspects of the present description, an aperiodic structured surface (e.g., the structured surface of an optical film) may include a plurality of spaced apart first surface portions and a plurality of spaced apart second surface portions. In some embodiments, each of the first and second surface portions may be continuous without any surface opening within and across a closed outermost perimeter of the surface portion. In some embodiments, each of the first surface portions may be spaced apart from (not overlapping with) each of the second surface portions. In some embodiments, each of the first surface portions may include at least one peak disposed within and away from the closed outermost perimeter of the first surface portion, and each of the second surface portions may include at least one valley disposed within and away from the closed outermost perimeter of the second surface portion. In some embodiments, at least two of the first surface portions may have different shapes and sizes, and at least two of the second surface portions may have different shapes and sizes.

[0044] In some embodiments, a magnitude squared of an azimuthally integrated Fourier transform of a height map of the first surface portions and second surface portions in the structured surface may have a global peak having a first area under the curve Al at a first spatial frequency Fl, and a second area under the curve A2 at a second spatial frequency F2, Fl and F2 in units of1 / mm, 5 < F2 < Fl, A1 / A2 may be less than or equal to 100,000, or less than or equal to 50,000, or less than or equal to 10,000, or less than or equal to 5,000, or less than or equal to 1,000, or less than or equal to 500, or less than or equal to 100, or less than or equal to 80, or less than or equal to 60, or less than or equal to 40, or less than or equal to 20, or less than or equal to 10, or less than or equal to 8, or less than or equal to 6, or less than or equal to 4, or less than or equal to 2, or less than or equal to 1.

[0045] In some embodiments, the structured surface may be a structured surface of an optical film, such as an optical film for reducing optical sparkle (e.g., as may be used in a display system). In some embodiments, the optical film may have a first major surface which is or which includes the structured surface as described herein, and an opposing second major surface (e.g., an unstructured “back” surface, or a second structured surface).

[0046] In some embodiments, the optical film may further include an optically clear material disposed on the first major surface and substantially covering the first surface portions and second surface portions. In some such embodiments, the optically clear material may encapsulate and substantially planarize at least a portion of the first surface portions and second surface portions on the structured surface. In some embodiments, the optically clear material may be an optically clear adhesive. 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 may be an optically clear adhesive. In some embodiments, the use of an optically clear adhesive may allow the optical film with the structured surface to be laminated to or otherwise included with a display as part of a display system.

[0047] In some embodiments, the optical film may further include a substrate, wherein the first surface portions and second surface portions are disposed on a first major surface of the substrate. In some such embodiments, the substrate may have an optical retardation of less than about 20 nanometers (nm), or less than about 10 nm, or less than about 5 nm.

[0048] For the purposes of this description, optical retardation in an optical film refers to the phase difference introduced between different polarization components of light as it passes through an optical film. This phase difference is typically caused by the birefringence of the material, which means that the material has different refractive indices for different polarization directions of light. Birefringent materials have two distinct refractive indices depending on the polarization direction of the light. When light enters such a material, it splits into two rays, each polarized perpendicularly to the other and traveling at different speeds. As the two rays travel through the material, they accumulate a phase difference due to their different speeds. This phase difference is known as optical retardation. Optical retardation is typically measured in nanometers (nm) and is a function of the thickness of the film and the difference in refractive indices (birefringence). Asused in the present description, it is important that the optical retardation introduced by any substrate included with the optical film be relatively low, such that the polarization state of an image generated by a display is substantially maintained after passing through the substrate.

[0049] In some embodiments, a display system may include a display (e.g., a liquid crystal display) configured to emit an image for viewing by an eye of a viewer, and the optical film 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 20%, or at least 30%, or at least 40%, or at least 50%.

[0050] Turning now to the figures, FIGS. 1A and IB depict an embodiment of a structured surface on an optical film using randomized height maps, according to the present description. It may be helpful to examine both FIGS. 1A and IB together for the following discussion.

[0051] Optical film 300 includes a first major surface 11, which is a structured surface 10, and an opposing second major surface 12. In some embodiments, structured surface 10 may include a plurality of first surface portions 30 and second surface portions 40. Each of first surface portions 30 may include one or more peaks 20 (highest point(s) on the surface), and each of the second surface portions 40 may include one or more valleys 25 (lowest point(s) on the surface). The peak 20 is disposed within the first surface portion 30 and away from the outer perimeter 31 of the first surface portion 30 (not near the outer perimeter of the first surface portion 30). Similarly, the valley 25 is disposed within the second surface portion 40 and away from the outer perimeter 41 of the second surface portion 40 (not near the outer perimeter of the second surface portion 40).

[0052] In some embodiments, a highest peak 21a of the at least one peak 20 of all of the first surface portions 30 may have a height Hmax, and a deepest valley 21b of the at least one valley 25 of all the second surface portions 40 may have a height Hmin. In some embodiments, the first surface portions 30 are defined such that each surface location in each of the first surface portions 30 has a height not less than a height Hl, and each surface location in each of the second surface portions 40 has a height not greater than a height H2, where Hmin < H2 < Hl < Hmax. At least two of the first surface portions 30 may have different shapes and sizes, and at least two of the second surface portions 40 may have different shapes and sizes. In some embodiments, Hl is selected such that between 10% and 30% of a total area of the structured surface is occupied by the first surface portions 30, and H2 is selected such that between 10% and 30% of a total area of the structured surface is occupied by the second surface portions 40. See, for example, FIG. 3A, for additional details on the area.

[0053] In some embodiments, optical film 300 may include a substrate 14 disposed on second major surface 12, such that the first surface portions 30 and second surface portions 40 may be disposed on substrate 14. In some embodiments, the substrate may be configured to have a relatively low optical retardation (e.g., less than about 20 nm, or about 10 nm, or about 5 nm) such that a polarity of light (e.g., an image light) passing through substrate 14 is substantially maintained.

[0054] FIG. 2A shows the details of a surface portion on an embodiment of an optical film, according to the present description. In some embodiments, structured surface 10 (see surface 10, e.g., FIG. 1 A) may include a plurality of spaced-apart first surface portions 30 and a plurality of spaced-apart second surface portions 40.

[0055] In some embodiments, each of the first 30 and second 40 surface portions may be continuous without any surface opening (such as opening 30a, 40a) within and across a closed outermost perimeter 31, 41 of surface portion 30, 40. In some embodiments, each of the first surface portions 30 may be spaced apart from (non-overlapping with) each of the second surface portions 40. Additional details of first surface portions 30 and second surface portions 40, and how they are disposed relative to optical film 300, may be found in the discussion of FIGS. 3A through 5B elsewhere herein.

[0056] FIG. 2B shows a schematic view of an embodiment of a display system with an optical film with randomized height map, according to the present description. In some embodiments, display system 400 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 300 of FIG. 1A) with structured surface 10 as described herein. The 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 300. In some embodiments, optical film 300 may further include an optically clear material 40a disposed on the structured surface 10 and substantially covering the first surface portions 30 and second surface portions 40. 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 the first surface portions 30 and second surface portions 40, as shown in FIG. 2B. In other embodiments, optically clear material 40a may be a conformal layer which substantially follows the contours of structured surface 10 and first surface portions 30 and second surface portions 40.

[0057] In some embodiments, optical film 300 may further include an optically clear material 40b disposed on second major surface 12 of optical film 300. In some such embodiments, optically clear material 40b may be an optically clear adhesive, although this is not intended to be limitingin any way. In some embodiments, optically clear materials 40a and 40b may be optically clear adhesives configured to laminate optical film 300 to other layers in the display system 400 (e.g., to display 70, or to other optical layers above optical film 300, such as diffusing layers, protective layers, light enhancement layers, etc.). For example, in some embodiments, display system 400 may further include an anti-glare film 65. It should be noted that a slight gap is shown between some layers of the display system 400 in FIG. 2B to help distinguish the layers from the adjacent layers. However, in practice, there may be no gap between layers.

[0058] FIGS. 3A-5B depict various embodiments of optical films with first and second surface portions and randomized or adjusted height maps, according to the present description. Each of the optical films 300a through 300e were created using an algorithm which adjusts or “randomizes” the heights of an otherwise crossed-sinusoid anti-sparkle film in order to reduce or eliminate any optical artifacts created by the regularity of the unadjusted crossed-sinusoid pattern. Each of the optical films shown in FIGS. 3-5B are labeled with a constant, K, which defines the amount of “randomness” applied to the algorithm which defines the appearance and design of the optical film, with a K of 0 being the smallest adjustment (amount of “randomization”) and a K of 0.5 being the largest adjustment. It should be noted that a K value of 0 means there is no randomization, and the resulting optical film 250 (shown in FIG. 3A) would be a perfect crossed- sinusoid film of the prior art and is not within the scope of the present description.

[0059] For example, and not intended to be limiting in any way, one algorithm that might be used to generate a randomized, crossed-sinusoid, height map which meets the limitations taught herein may include the following steps:

[0060] Select the pitch p and amplitude A for the crossed sinusoid.

[0061] Generate a square grid of coordinates in an x-y plane with spacing of p / 2 in the x and y directions.

[0062] Assign heights 0 or h = 2A to the grid points so that no horizontal and no vertical neighbor are the same height.

[0063] Randomly move each grid point by r*p*K, where r is a random number between -1 and 1 and K is a constant between 0 and 0.5 that controls the degree of randomization.

[0064] Generate a height map by using Voronoi tessellation (for example) and assign the height within each tile the value assigned to its grid point.

[0065] Apply a two-dimensional bandpass Fourier filter to the height map with a spatial filter function g(f) that peaks near f = 1 / p, or which has a low-pass cutoff near 1 / p.

[0066] FIGS. 3B through 5B show the results of using such an algorithm and varying the K value to obtain various embodiments of optical films as described herein. Each of FIGS. 3B through 5B (as well as FIG. 3A, showing film 250 for comparison purposes) includes a table ofvalues which include the value of K, the maximum height of the structures on the structured surface, the minimum height, and user defined values of R1 and R2, which correspond respectively to heights Hl and H2, as described herein and in the following description.

[0067] Looking first at FIG. 3A, and for a K value of 0 (indicating zero randomization) and values of R1(H1) and R2(H2) of 7 microns and 2 microns respectively, it can be seen that a plurality of first surface portions 30 and second surface portions 40 are generated from the originally crossed-sinusoidal optical film. Each of the first surface portions 30 and second surface portions 40 contain no surface openings within an outer perimeter 31, 41 of the first surface portions 30 and second surface portions 40. Each of the first surface portions 30 is defined by the value of R1(H1), which is, in this example, 7 microns, which means that the shape of any first surface portion 30 is defined by drawing a boundary (outer perimeter 31) around groups of structures which have a height equal to or greater than the Hl value, which in this case is 7 microns. Similarly, each of the second surface portions 40 is defined by the value of R2(H2), which is, in this example, 2 microns, which means that the shape of any second surface portion 40 is defined by drawing a boundary (outer perimeter 41) around groups of structures which have a height equal to or less than the H2 value, which in this case is 2 microns.

[0068] Stated another way, each of the structures in each of the first surface portions 30 has a height not less than Hl (7 microns), and each of the structures in each of the second surface portions 40 has a height not greater than H2 (2 mic), wherein Hmin (0.91 microns in this example) < H2 < Hl < Hrnax (8.91 microns in this example. In the embodiments of FIGS. 3B through 5B, at least two of the first surface portions 30 have different shapes and sizes, and at least two of the second surface portions have different shapes and sizes (indicating some degree of “randomization” beyond a pure crossed-sinusoid film, and first surface portions 30 and second surface portions 40 do not overlap (i.e., are spaced apart from each other). In the embodiment of FIG. 3A, however, each of the first surface portions 30 have the same size and shape, as this is a “pure” crossed-sinusoid film 250 of the prior art. The same is true for second surface portions 40, which are substantially identical to each other in the pure crossed-sinusoid film 250.

[0069] This same description can be applied to FIGS. 3B through 5B (optical film embodiments 300a through 300e), but now the amount of randomization (defined by the constant K) is increased with each successful embodiment. Increasing the value of K in each embodiment has the effect of increasing the amount of randomization applied to each embodiment (increases the “effect” of the randomization). Moving from FIG. 3A to FIGS. 3B, 4A, 4B, 5A, and finally to 5B, the amount of randomization becomes more pronounced, as shown in these figures. In this way, the desired optical properties (such as the amount of reduction in sparkle, or the amount oftransmission of light through the optical film) can be “tuned” to achieve an optimum balance based on the desired optical properties of the resulting optical films.

[0070] It should be noted that too much randomization (for example, with K equal to 0.5) may increase the randomization too much, so that the anti-sparkle property of the film essentially goes away (as the film becomes closer to a purely random film). However, an appropriate value of K may be found for various embodiments, based on the requirements of the application, and this statement is not meant to be limiting.

[0071] In some embodiments, such as the embodiments shown in FIGS. 4 A and 4B, unique signatures appear in some of the surface portions of the optical films. For example, looking at FIGS. 4A and 4B together for the following discussion, and embodiments 300b and 300c of the optical film, for each of at least one 30b of the first surface portions 30 and at least one 40b of the second surface portions, the closed outermost perimeter of the surface portion has first 31a, 41a and second 31b, 41b perimeter portions that are convex toward each other defining a narrower portion 42a of the surface portion joining two wider portions 42b and 42c of the surface portion. In some such embodiments, a length of each of the first 31a, 41a and second 31b, 41b perimeter portions may be at least 10%, or at least 15%, or at least 20%, or at least 25%, or at least 30%, or at least 40% of a total length of the closed perimeter 31, 41 of the surface portion 30b, 40b.

[0072] FIGS. 6A and 6B are charts showing structural characteristics of embodiments of optical films with randomized height maps, according to the present description. Specifically, these figures represent graphs of magnitude squared (magnitude2) of the Fourier transform of a height may of the first and second surface portions in the structured surface along one of first and second directions (fx for FIG. 6A, fy for FIG. 6B).

[0073] In some embodiments, a magnitude2 PSD(fx), PSD(fy) of a Fourier transform of a height map of the first and second surface portions in the structured surface along one of the first and second directions, where at each spatial frequency the amplitude is integrated along the other one of the first and second directions, has a global peak 50x, 50y having a first amplitude Al (Alx, Aly) (for example, for the plotline representing a K value equal to 0.3 in FIGS. 6A and 6B) at a first spatial frequency Fl (Fix, Fly) and a second amplitude A2 (A2x, A2y) at a second spatial frequency F2, where Fl and F2 in units of 1 / mm, such that 5 < F2 < Fl, A1 / A2 < 100,000.

[0074] FIG. 8A shows the same basic relationship as FIG. 6A, but in simplified terms and defined in a slightly different way. Based on FIG. 8A, the a magnitude squared of a Fourier transform of a height map of the first surface portions and second surface portions in the structured surface along one of the first and second directions, where at each spatial frequency the magnitude squared is integrated along the other one of the first and second directions, has a global peak having a first area under the curve Al at a first spatial frequency Fl and a second area under thecurve A2 at a second spatial frequency F2, Fl and F2 in units of 1 / mm, 5 < F2 < Fl, A1 / A2 < 100,000. This approach more specifically uses the area under the curve of Al and A2, as shown in FIG. 8A, to define the distribution of the first and second surface portions. Although not specifically shown, a similar graph to FIG. 8 A can be applied to the graph of FIG. 6B.

[0075] Similarly, FIG. 7 provides a graph of a Fourier transform of a distribution of the structures in the structured surface as a function of a spatial frequency, wherein, a magnitude squared PSD(fq) of the Fourier transform, where at each spatial frequency the magnitude squared is integrated over all azimuthal angles (e.g., from 0-360 degrees), has a global first peak 50q having a first amplitude A3 (for example, for the plotline representing a K value equal to 0.3 in FIG. 7) at a first spatial frequency F3 and a second peak 51 having a second amplitude A4 at a second spatial frequency F4, wherein F3 and F4 are in units of 1 / mm, and 5 < F4 < F3, A3 / A4 < 100,000. It should be noted that variables A3, A4, F3, and F4 are used in the description here, but may be expressed as Al, A2, Fl, and F2 in the corresponding claim presented herein. The variable names are changed in this section to distinguish them from the previous discussion, but are otherwise interchangeable.

[0076] As with FIG. 8A, FIG. 8B shows an alternate approach to characterizing the periodicity of the optical films, similar to that of FIG. 7, but based on the areas under the curves. In FIG. 8B, a magnitude squared of an azimuthally integrated Fourier transform of a height map of the first surface portions and second surface portions in the structured surface has a global peak having a first area under the curve A3 at a first spatial frequency F3, and a second area under the curve A4 at a second spatial frequency F4, F3 and F4 in units of 1 / mm, 5 < F4 < F3, A3 / A4 < 100,000.

[0077] Finally, FIGS. 9A and 9B show optical sparkle and percent transmission for embodiments of optical films with randomized height maps, according to the present description. Looking first at FIG. 9A, this graph provides the results of measurements for three example films, Filml, Film2, and Film3, which are films configured according to the present description. These three films are compared to values measured from the image only (Image Only, with no optical film at all present), with only a commercially available anti-glare film (AG Only) between the image and the viewer, and with an anti-glare film on a PET substrate (AG PET, which represents how a typical display might appear with only an anti-glare film and substrate between the image and the viewer).

[0078] In FIG. 9A, it can be seen that the amount of sparkle present with just the image only is at or near 1 on the normalized scale showing amount of sparkle. When the anti-glare film is introduced (either by itself, AG Only, or with a PET substrate, AG PET), a significant amount ofsparkle (relative to Image Only) is introduced. The amount of sparkle is reduced as shown when each of Filml, Film2, and Film3 is introduced in addition to the AG PET layer.

[0079] FIG. 9B is provided to show the percentage of light transmission that is present for these same conditions. The graph of FIG. 9B is normalized so that the amount of light transmission is at 100% for the image with an anti-glare film with PET substrate and no other optical film. It can be seen that, in the embodiments shown, the introduction of Filml, Film2, and Film3 can have an impact on the amount of light that is transmitted through the optical stack (which includes the AG PET layer and the corresponding optical film of the present description). Each of the optical films configured according to the present description can be “tuned” or optimized according to the requirements of the application to find the appropriate balance between the amount of sparkle reduction and loss in light transmission. For example, Film3 provides a significant reduction in sparkle (over 35% relative to the AG PET value) but a relatively low loss in light transmission. These measured values are examples only and are not intended to be limiting. Other configurations of optical films within the scope of the present description may have other sparkle and transmission characteristics.

[0080] For the purposes of this description, the sparkle can be determined as a ratio of standard deviation to a mean of an intensity distribution of a light output of a display panel low pass filtered to remove display pixel modulation from the intensity distribution. The sparkle can be expressed as a percent by multiplying the ratio by 100%. The sparkle can be determined according to IEC 62977-3-9 (2023). Annex B2 of that test standard describes suitable low pass filtering to remove the display pixel modulation from the intensity distribution. A suitable instrument for measuring sparkle is the SMS- 1000 Sparkle Measurement System available from Display - Messtechnik & Systeme, Rottenburg am Neckar, Germany. The SMS- 1000 can also determine a distinctiveness of image (DOI) which is defined as a modulation transfer factor (MTF) for a spatial frequency of the pixel pattern of the display as a percent of a reference MTF at the same spatial frequency determined from the display without the sparkle reduction optical film and without the antiglare cover glass of the display. The percentage reduction in MTF at the pixel spatial frequency can be determined as the percentage reduction in DOI determined by the SMS- 1000.

[0081] 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 anddescribed 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.

[0082] 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 30 degrees of parallel. Directions or surfaces described as substantially parallel to one another may, in some embodiments, be within 20 degrees, or within 10 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.

[0083] 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.

[0084] 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 comprising a plurality of spaced apart first surface portions and a plurality of spaced apart second surface portions, each of the first and second surface portions being continuous without any surface opening within and across a closed outermost perimeter of the surface portion, each of the first surface portions spaced apart from each of the second surface portions, each of the first surface portions comprising at least one peak disposed within and away from the closed outermost perimeter of the first surface portion, and each of the second surface portions comprising at least one valley disposed within and away from the closed outermost perimeter of the second surface portion, a highest peak of the at least one peak of all of the first surface portions having a height Hmax, and a deepest valley of the at least one valley of all the second surface portions having a height Hrnin; each surface location in each of the first surface portions having a height not less than Hl, each surface location in each of the second surface portions having a height not greater than H2, Hmin < H2 < Hl < Hmax, at least two of the first surface portions having different shapes and sizes, and at least two of the second surface portions having different shapes and sizes; and wherein Hl is selected such that between 10% and 30% of a total area of the structured surface is occupied by the first surface portions, and H2 is selected such that between 10% and 30% of a total area of the structured surface is occupied by the second surface portions.

2. An optical film comprising a first major surface comprising the structured surface of claim 1, and an opposing second major surface.

3. 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 2, disposed between the display and the eye of the viewer.

4. The optical film of claim 2, further comprising an optically clear material disposed on the first major surface and substantially covering the first surface portions and the second surface portions.

5. The optical film of claim 4, wherein the optically clear material is an optically clear adhesive.

6. The optical film of claim 4, wherein the optically clear material encapsulates and substantially planarizes at least a portion of the first surface portions and the second surface portions.

7. The optical film of claim 2, further comprising an optically clear material disposed on the second major surface.

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

9. The optical film of claim 2, further comprising a substrate, the first surface portions and the second surface portions disposed on a first major surface of the substrate.

10. The optical film of claim 8, wherein the substrate has an optical retardation less than about 20 nm.

11. The display system of claim 3, 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.

12. The display system of claim 11, wherein the reduction in optical sparkle is at least 10%.

13. The structured surface of claim 1, wherein a magnitude squared of a Fourier transform of a height map of the first surface portions and second surface portions in the structured surface along one of the first and second directions, where at each spatial frequency the magnitude squared is integrated along the other one of the first and second directions, has a global peak having a first area under the curve Al at a first spatial frequency Fl and a second area under the curve A2 at a second spatial frequency F2, Fl and F2 in units of 1 / mm, 5 < F2 < Fl, A1 / A2 < 100,000.

14. A structured surface comprising a plurality of spaced apart first surface portions and a plurality of spaced apart second surface portions, each of the first and second surface portions being continuous without any surface opening within and across a closed outermost perimeter of the surface portion, each of the first surface portions spaced apart from each of the second surface portions, each of the first surface portions comprising at least one peak disposed within and away from the closed outermost perimeter of the first surface portion, and each of the second surface portions comprising at least one valley disposed within and away from the closed outermost perimeter of the second surface portion;wherein between 10% and 20% of a total area of the structured surface is occupied by the first surface portions, and between 10% and 20% of a total area of the structured surface is occupied by the second surface portions; and wherein for each of at least one of the first surface portions and at least one of the second surface portions, the closed outermost perimeter of the surface portion has first and second perimeter portions that are convex toward each other defining a narrower portion of the surface portion joining two wider portions of the surface portion, and wherein a length of each of the first and second perimeter portions is at least 10% of a total length of the closed perimeter of the surface portion.

15. An optical film comprising a first major surface comprising the structured surface of claim 14, and an opposing second major surface.

Images