BACKLIGHT HAVING MULTIPLE HIGH DEFINITION OPTICAL FILMS

Abstract

A backlight for a display includes an array of individual light sources and a plurality of optical films disposed between the display and the light sources. Each film includes a regular array of intersecting ridges that define a plurality of through holes. Each of the through holes extends between a first open end and a second open end of the through hole. A cross-section of the optical film in a plane parallel to the thickness of the film includes two adjacent ridges in the array of ridges and a through hole therebetween. The film has a maximum thickness h max and the through hole includes a sidewall having a substantially vertical portion connected to a first open end of the through hole and a substantially horizontal portion extending from the substantially vertical portion and connected to a second open end, the substantially horizontal portion having a minimum thickness h at a location between two adjacent ridges. min h max / h min ≧2.

Description

Summary of the Invention

[0001] In some aspects herein, a backlight is provided for providing illumination along a first direction to a display disposed on the backlight, the backlight including a plurality of spaced apart individual light sources arranged in rows and columns of light sources and configured to face the display, and an optical film disposed on the light sources and proximately disposed below a first plane. The optical film and the first plane are configured to be disposed between the display and the light sources. The optical film includes a plurality of through holes arranged in rows and columns of through holes and extending between a first major surface and a second major surface of the optical film. Each through hole has a first opening at the first major surface having a first open area A1 and a second opening at the second major surface having a second open area A2. Each through hole has a length H along the first direction, and a ratio of H / A2 is about 0.13 or greater. When all of the light sources emit light, the light emitted by all of the light sources has a first overall peak intensity measured at a first plane and a first luminance uniformity measured across the first plane. Without the optical film, the light emitted by all of the light sources has a second overall peak intensity measured at the first plane and a second luminance uniformity measured across the first plane. The first overall peak intensity and the second overall peak intensity differ by less than about 20%, and the first luminance uniformity shows at least a 2.8% improvement over the second luminance uniformity.

[0002] In some aspects herein, an optical film is provided, the optical film including a structured first major surface opposite a second major surface, the first major surface including a plurality of posts arranged in rows and columns and a plurality of ridges extending between and recessed relative to the posts, a plurality of through holes extending between the first major surface and the second major surface, each through hole including a first opening in the first major surface defined by and recessed relative to some of the ridges and having a first maximum dimension, and a second opening in the second major surface having a second maximum dimension different from the first maximum dimension.

[0003] In some aspects herein, an optical film is provided, the optical film including a structured first major surface opposite a second major surface. The first major surface includes a plurality of posts arranged in rows and columns, a plurality of ridges extending between and recessed relative to the posts, and a plurality of recesses extending thicknesswise from the first major surface into the optical film. Each recess includes a first open end at the first major surface defined by and recessed relative to some of the ridges and having a first maximum dimension, and a second closed end recessed a distance D from the first open end and having a second maximum dimension different from the first maximum dimension.

[0004] In some aspects herein, a backlight is provided for providing illumination along a first direction to a display disposed on the backlight, the backlight including a plurality of spaced apart individual light sources arranged in rows and columns of light sources and configured to face the display, and an optical film having a structured first major surface opposite the second major surface and a plurality of through holes extending between the first major surface and the second major surface. The optical film is disposed on the light source and disposed proximately below the first plane. The optical film and the first plane are configured to be disposed between the display and the light source. When the optical film is disposed such that the first major surface faces the light source, the average luminance in the first plane is smaller and the first luminance uniformity value is smaller, and when the optical film is disposed such that the second major surface faces the light source, the first average luminance in the first plane is larger and the first luminance uniformity value is larger, and the luminance uniformity value is calculated by dividing the maximum luminance value in the first plane by the minimum luminance value in the first plane.

[0005] In some aspects herein, a backlight for providing illumination to a display panel is provided, the backlight including a two-dimensional array of spaced apart individual light sources and a plurality of optical films disposed over the light sources and configured to be disposed between the display panel and the light sources. Each of the optical films includes a regular two-dimensional array of intersecting ridges defining a plurality of through-holes therebetween. Each of the through-holes extends between a first open end and a second open end of the through-hole on respective opposite first and second major surfaces of the optical film. In a first cross-section of the optical film in a first plane that is parallel to the thickness direction of the optical film and includes two adjacent ridges in the array of ridges and the through-holes therebetween, the optical film has a maximum thickness h maxThe through hole includes a sidewall having a substantially vertically oriented portion connected to a first open end of the through hole and a substantially horizontally oriented portion extending from the substantially vertically oriented portion and connected to a second open end. The substantially horizontally oriented portion has a minimum thickness h at a location disposed between two adjacent ridges. min h max / h min is about 2 or more.

[0006] In some aspects herein, a backlight is provided for providing illumination along a first direction to a display disposed on the backlight, the backlight including a plurality of spaced apart individual light sources arranged in rows and columns of light sources and configured to face the display, an optical stack including two or more optical films disposed on the light sources and proximately disposed below a first plane, the optical stack and the first plane configured to be disposed between the display and the light sources, and a diffusing layer disposed between the optical stack and the display. Each optical film in the optical stack includes a plurality of through holes arranged in rows and columns of through holes and extending between a first major surface and a second major surface of the optical film. Each through hole has a first opening at the first major surface having a first open area A1 and a second opening at the second major surface having a second open area A2. Each through hole has a height H along the first direction, and a ratio of H / A2 is about 0.13 or greater. When all of the light sources emit light, the light emitted by all of the light sources has a first average luminance in a first plane, and when the optical stack is absent, the light emitted by all of the light sources has a second average luminance in the first plane, the first average luminance being greater than the second average luminance. [Brief description of the drawings]

[0007] [Figure 1A] FIG. 2 is a side view of a backlight for providing illumination to a display according to one embodiment herein. [Figure 1B]FIG. 2 is a side view of a backlight for providing illumination to a display according to one embodiment herein. [Figure 2A] FIG. 2 is a side view of a detail of an optical film according to an embodiment herein. [Figure 2B] FIG. 2 is a side view of a detail of an optical film according to an embodiment herein. [Figure 3A] 2A-2D are further details and embodiments of an optical film according to an embodiment of the present disclosure. [Figure 3B] 2A-2D are further details and embodiments of an optical film according to an embodiment of the present disclosure. [Figure 3C] 2A-2D are further details and embodiments of an optical film according to an embodiment of the present disclosure. [Figure 4] FIG. 2 is a side view of an optical film according to an alternative embodiment herein. [Figure 5A] 1 is a magnified image of an optical film having microreplicated features according to an embodiment herein. [Figure 5B] 1 is a magnified image of an optical film having microreplicated features according to one embodiment herein. [Figure 6A] 11 is an additional close-up image of an optical film having high definition features according to an embodiment herein. [Figure 6B] 11 is an additional close-up image of an optical film having high definition features according to an embodiment herein. [Figure 7] 11 is a plot illustrating luminance performance for various configurations of high definition features according to alternative embodiments herein. [Figure 8] 1 is a plot comparing peak luminance values ​​of a display with and without an optical film disposed over a backlight, according to an embodiment herein. [Figure 9A] 1 is a plot comparing display uniformity performance of a display with and without an optical film disposed over a backlight, according to one embodiment of the present description. [Figure 9B] 1 is a plot comparing display uniformity performance of a display with and without an optical film disposed over a backlight, according to one embodiment of the present description. [Figure 10] 11 is an additional close-up image of an optical film having high definition features according to an embodiment herein. [Figure 11] FIG. 1 illustrates a backlight for providing illumination to a display, featuring two or more optical films, according to an embodiment of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] In the following description, reference is made to the accompanying drawings, which 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 disclosure. Accordingly, the following detailed description is not to be taken in a limiting sense.

[0009] According to some aspects herein, a backlight for providing illumination along a first direction (e.g., a thickness direction or z-axis of the backlight) to a display disposed on the backlight includes a plurality of spaced apart individual light sources (e.g., light emitting diodes) arranged in rows (e.g., along the x-axis of the backlight) and columns (e.g., along the y-axis of the backlight) of the light sources and configured to face the display, and an optical film disposed over the light sources and adjacently disposed below a first plane. The optical film and the first plane are configured to be disposed between the display and the light sources.

[0010] In some embodiments, the optical film may include a plurality of through holes arranged in rows and columns of through holes and extending between a first (e.g., top) major surface and a second (e.g., bottom) major surface of the optical film. In some embodiments, each through hole has a first opening at the first major surface having a first open area A1 and a second opening at the second major surface having a second open area A2. In some embodiments, each through hole has a length H along a first direction, and a ratio of H / A2 is about 0.13 or greater.

[0011] In some embodiments, the shape of at least a portion of each through-hole may be substantially a truncated pyramid, or a truncated cone, or a cylinder, or a prism, or any other suitable shape. In some embodiments, the slope of any of the inner walls of each of the through-holes may be substantially vertical (e.g., for a cylindrical or prism shape). In other embodiments (e.g., for a truncated pyramid or a prism shape), the slope of any of the inner walls of each of the through-holes may be within ±15 degrees, or within ±10 degrees, or within ±8 degrees in a first direction (e.g., along the z-axis).

[0012] In some embodiments, the open area A1 may be greater than the open area A2. In other embodiments, A1 may be less than A2. In yet other embodiments, A1 and A2 may be substantially equal. In some embodiments, when A1 is greater than A2 and the optical film is positioned such that A1 faces the light source, the first average luminance in the first plane may be smaller and the first luminance uniformity may be greater. In other embodiments, when A1 is greater than A2 and the optical film is positioned such that A2 faces the light source, the first average luminance in the first plane is greater and the first luminance uniformity is greater. Stated another way, if A1 and A2 have different areas, then positioning the film with the larger holes "up" (i.e., toward the display) and the smaller holes "down" (i.e., toward the light source) can exhibit a relatively brighter average luminance and a relatively greater luminance uniformity value when compared to values ​​that may exhibit a relatively smaller average luminance and a relatively smaller luminance uniformity value (i.e., more uniform display luminance) measured when the film is reversed (larger holes "down" and smaller holes "up").

[0013] When all the light sources emit light, the light emitted by all the light sources has a first overall peak intensity measured at the first plane and a first luminance uniformity measured across the first plane. Without the optical film, the light emitted by all the light sources has a second overall peak intensity measured at the first plane and a second luminance uniformity measured across the first plane. The first overall peak intensity and the second overall peak intensity differ by less than about 20%, and the first luminance uniformity shows at least a 2.8% improvement over the second luminance uniformity. In some embodiments, the light emitted by all the light sources can have a first average luminance in the first plane, and without the optical film, the light emitted by all the light sources can have a second average luminance in the first plane, and the first average luminance is equal to or greater than the second average luminance.

[0014] For purposes of this specification, "luminance uniformity" (or simply "uniformity") shall be defined as the maximum luminance value divided by the minimum luminance value when measured across the display or portion of the display being measured. That is, as used herein, the term "uniformity" is a specific measurement for a display or portion of a display, and only has meaning when compared against a second measured uniformity value. For example, a larger value of uniformity calculated in this manner is less desirable than a smaller value. That is, a larger uniformity value represents an increase in "luminance unevenness", or uneven spots on the display. For purposes of this specification, the terms "ununiformity" and "luminance unevenness" may be used interchangeably and shall describe undesirable visible luminance effects on a display, such as spots on a display that are noticeably brighter or darker than the surrounding areas of the display.

[0015] In the above example, if "the first luminance uniformity shows an improvement of at least 2.8% over the second luminance uniformity," this means that the measured value for the first luminance uniformity is at least 2.8% smaller (has less luminance unevenness) than the measured value for the second luminance uniformity.

[0016] In some embodiments, the backlight can further include a diffusion film disposed between the light source and the optical film. In some embodiments, the backlight may further include one or more brightness enhancing films (e.g., prism films) disposed between the optical film and the display.

[0017] According to some aspects herein, the optical film may include a structured first major surface opposite the second major surface. The first major surface may include a plurality of posts arranged in rows and columns (e.g., arranged along the x-axis and y-axis of the optical film) and a plurality of ridges extending between and recessed relative to the posts. In some embodiments, a plurality of through holes may extend between the first major surface and the second major surface, each through hole including a first opening in the first major surface defined by and recessed relative to some of the ridges and a second opening in the second major surface. In some embodiments, the first opening may have a first maximum dimension and the second opening may have a second maximum dimension different from the first maximum dimension. In some embodiments, the first opening of each through hole is defined by and surrounded by four of the ridges. In some embodiments, each through hole of the plurality of through holes can define a distance H between a first opening and a second opening, and the second opening can have an open area A2, where the ratio of H / A2 is greater than or equal to about 0.13.

[0018] In some embodiments, the shape of at least a portion of each through-hole may be substantially a truncated pyramid, or a truncated cone, or a cylinder, or a prism, or any other suitable shape. In some embodiments, the slope of any of the inner walls of each of the through-holes may be substantially vertical. In other embodiments, the slope of any of the inner walls of each of the through-holes may be within ±15 degrees, or within ±10 degrees, or within ±8 degrees in a first direction (e.g., along the z-axis).

[0019] According to some aspects herein, a backlight for providing illumination to a display can include a plurality of spaced apart individual light sources arranged in rows (e.g., on the x-axis) and columns (e.g., on the y-axis) of light sources and configured to face the display, and any of the optical films including through holes described herein disposed over the plurality of spaced apart individual light sources and positioned closely below a first plane.

[0020] In some embodiments, when all the light sources emit light, the light emitted by all the light sources has a first overall peak intensity at the first plane and a first luminance uniformity across the first plane. In the absence of the optical film, the light emitted by all the light sources may have a second overall peak intensity at the first plane and a second luminance uniformity across the first plane, such that the first overall peak intensity and the second overall peak intensity differ by less than about 20%, or less than about 15%, or less than about 10%, and the first luminance uniformity shows at least a 2.8% improvement over the second luminance uniformity. In some embodiments, the light emitted by all the light sources may have a first average luminance at the first plane, and in the absence of the optical film, the light emitted by all the light sources may have a second average luminance at the first plane, the first average luminance being equal to or greater than the second average luminance.

[0021] According to some aspects herein, the optical film includes a structured first major surface opposite the second major surface. In some embodiments, the first major surface may include a plurality of posts arranged in rows and columns (e.g., the x-axis and y-axis of the optical film), a plurality of ridges extending between and recessed relative to the posts, and a plurality of recesses extending from the first major surface into the optical film in a thickness direction (e.g., the z-axis of the optical film). In some embodiments, each recess may include a first open end at the first major surface defined by and recessed relative to some of the ridges, and a second closed end recessed a distance D from the first open end. The first open end may have a first maximum dimension and the second closed end may have a second maximum dimension different from the first maximum dimension. In some embodiments, the first open end of each recess may be defined by and surrounded by four of the ridges. In some embodiments, the second closed end of each recess may have a surface area A4, where the ratio of D / A4 is greater than or equal to about 0.13.

[0022] In some embodiments, the shape of at least a portion of each of the recesses may be a truncated pyramid, or a truncated cone, or a cylinder, or a prism. In some embodiments, the slope of at least one inner wall of each of the recesses may be substantially vertical. In other embodiments, the slope of at least one inner wall of each of the recesses may be within ±15 degrees (or within ±10 degrees, or within ±8 degrees) in the thickness direction of the optical film.

[0023] According to some aspects herein, a backlight for providing illumination to a display can include a plurality of spaced apart individual light sources arranged in rows (e.g., on the x-axis) and columns (e.g., on the y-axis) of light sources and configured to face the display, and any of the optical films including recesses described herein disposed over the plurality of spaced apart individual light sources and adjacently disposed below a first plane.

[0024] In some embodiments, when all the light sources emit light, the light emitted by all the light sources has a first overall peak intensity at the first plane and a first luminance uniformity across the first plane. In the absence of the optical film, the light emitted by all the light sources may have a second overall peak intensity at the first plane and a second luminance uniformity across the first plane, such that the first overall peak intensity and the second overall peak intensity differ by less than about 20%, or less than about 15%, or less than about 10%, and the first luminance uniformity shows at least a 2.8% improvement over the second luminance uniformity. In some embodiments, the light emitted by all the light sources may have a first average luminance at the first plane, and in the absence of the optical film, the light emitted by all the light sources may have a second average luminance at the first plane, the first average luminance being equal to or greater than the second average luminance.

[0025] According to some aspects herein, a backlight for providing illumination along a first direction to a display disposed thereon may include a plurality of spaced apart individual light sources (e.g., light emitting diodes) arranged in rows and columns of light sources (e.g., x-axis and y-axis) and configured to face the display, a structured first major surface opposite the second major surface, and an optical film having a plurality of through holes extending between the first major surface and the second major surface. In some embodiments, the optical film may be disposed over the light sources and adjacently disposed below the first plane. In some embodiments, the optical film and the first plane are configured to be disposed between the display and the light sources.

[0026] In some embodiments, when the optical film is positioned with a first major surface facing the light source, the average luminance in the first plane is smaller and the first luminance uniformity value is smaller, and when the optical film is positioned with a second major surface facing the light source, the first average luminance in the first plane is greater and the first luminance uniformity value is greater, and the luminance uniformity value is calculated by dividing the maximum luminance value in the first plane by the minimum luminance value in the first plane.

[0027] In some embodiments, each through-hole can have a first opening disposed on the first major surface and having an open area A1 and a second opening disposed on the second major surface and having an open area A2. In some embodiments, each through-hole of the plurality of through-holes defines a distance H between the first opening and the second opening such that H / A2 is about 0.13 or greater. In some embodiments, at least one of the first opening and the second opening can include a lip that protrudes outward from the periphery of the opening toward the center of the opening. In some embodiments, light passing through the through-hole can be scattered by the lip.

[0028] According to some aspects herein, a backlight for providing illumination to a display panel includes a two-dimensional array of spaced apart individual light sources and a plurality of optical films disposed over the light sources and configured to be disposed between the display panel and the light sources. In some embodiments, the plurality of optical films can include at least two, or at least three, or at least four, or at least five films.

[0029] In some embodiments, each of the optical films includes a regular two-dimensional array of intersecting ridges that define a plurality of through holes therebetween. In some embodiments, each of the through holes extends between a first open end and a second open end of the through hole on each of the first and second opposing major surfaces of the optical film. In some embodiments, a first cross-section of the optical film in a first plane parallel to the thickness direction of the optical film (e.g., the z-axis of the film as shown in FIG. 11 ) includes two adjacent ridges in the array of ridges and a through hole therebetween. In some embodiments, the optical film has a maximum thickness h max and the through hole includes a sidewall having a substantially vertically oriented portion connected to a first open end of the through hole and a substantially horizontally oriented portion extending from the substantially vertically oriented portion and connected to a second open end. In some embodiments, the substantially horizontally oriented portion has a minimum thickness h at a location disposed between two adjacent ridges. min may have a ratio h max / h min is about 2 or more, or about 3 or more, or about 4 or more, or about 5 or more, or about 6 or more, or about 7 or more, or about 8 or more, or about 9 or more, or about 10 or more.

[0030] In some embodiments, the backlight can further include a diffusing layer disposed between the plurality of optical films and the display panel. In such embodiments, the surface of the diffusing layer can include a plurality of microstructures (e.g., a plurality of square pyramid shapes).

[0031] In some embodiments, one of the first open end and the second open end of each of the through holes of the plurality of through holes may be larger than the other of the first open end and the second open end. In some embodiments, the inclination of the inner wall of each of the through holes of the plurality of through holes may be within ±15 degrees in the thickness direction. In some embodiments, the shape of each of the through holes may be, but is not limited to, a rectangular column, a truncated pyramid, a cylinder, and a truncated cone. In some embodiments, each of the through holes of the plurality of through holes defines a distance H between the first opening and the second opening. In some embodiments, the second opening may have an open area A2, and a ratio of H / A2 may be about 0.13 or greater.

[0032] In some embodiments, each optical film of the plurality of optical films may be oriented similarly to each of the other optical films in the plurality of optical films. In some embodiments, each optical film of the plurality of optical films may be oriented such that the larger of the first and second open ends faces the display. In other embodiments, each optical film of the plurality of optical films may be oriented such that the larger of the first and second open ends faces the two-dimensional array of spaced apart individual light sources.

[0033] In some embodiments, the regular two-dimensional array of intersecting ridges of each of the optical films may form orthogonal rows and columns of posts (e.g., a two-dimensional grid). In some such embodiments, at least one row of the optical films may form an angle of less than about 20 degrees, or less than about 15 degrees, or less than about 10 degrees, or less than about 5 degrees with at least one other row of the plurality of optical films (e.g., the films may be substantially aligned with one another or may be rotated only slightly with respect to one another). In other such embodiments, at least one row of the optical films may form an angle of between about 10 degrees and about 80 degrees, or between about 20 degrees and about 70 degrees, or between about 30 degrees and about 60 degrees, or between about 40 degrees and about 60 degrees with at least one other row of the plurality of optical films.

[0034] According to some aspects herein, a backlight for providing illumination along a first direction to a display disposed on the backlight includes a plurality of spaced apart individual light sources, the plurality of spaced apart individual light sources arranged in rows and columns of light sources and configured to face the display, an optical stack disposed on the light sources and including two or more optical films disposed proximately below a first plane, the optical stack and the first plane configured to be disposed between the display and the light source, and a diffusing layer disposed between the optical stack and the display. In some embodiments, the optical stack may include two optical films, or three optical films, or four optical films, or five or more optical films.

[0035] In some embodiments, each optical film in the optical stack can include a plurality of through holes arranged in rows and columns of through holes and extending between a first major surface and a second major surface of the optical film. In some embodiments, each through hole can have a first opening at the first major surface having a first open area A1 and a second opening at the second major surface having a second open area A2. In some embodiments, each through hole can have a height H along a first direction, and a ratio of H / A2 is about 0.13 or greater. In some embodiments, when all light sources emit light, the light emitted by all light sources has a first average brightness in a first plane, and when the optical stack is absent, the light emitted by all light sources has a second average brightness in the first plane. In some embodiments, the first average brightness is greater than the second average brightness.

[0036] In some embodiments, the first open area A1 may be greater than the second open area A2. In some such embodiments, each optical film in the optical stack may be positioned such that A1 faces the multiple spaced apart, discrete light sources. In other such embodiments, each optical film in the optical stack may be positioned such that A1 faces the display. In yet other such embodiments, at least one optical film in the optical stack may be positioned such that A1 faces the display and at least one other optical film in the optical stack may be positioned such that A1 faces the multiple spaced apart, discrete light sources.

[0037] In some embodiments, the surface of the diffusing layer may include a plurality of microstructures, hi some such embodiments, each microstructure within the plurality of microstructures may have a square pyramid shape.

[0038] Referring now to the drawings, FIG. 1A is a side view of a backlight for providing illumination to a display according to the present disclosure. In some embodiments, a backlight 300 for providing illumination 80 to a display 50 may include a plurality of spaced apart individual light sources 60 and an optical film 100. In some embodiments, the individual light sources 60 face the display (i.e., emit light 80 toward the display in the z-direction shown in FIG. 1A) and are arranged in rows and columns of light sources 60 (e.g., a matrix of light emitting diodes having rows in the x-axis and columns in the y-axis as shown in FIG. 1A). The optical film 100 is disposed above or proximate to the light sources 60 and proximately below a first plane 70 (i.e., a reference plane for purposes of illustration). In some embodiments, the optical film 100 includes a plurality of through-holes 40 arranged in rows (e.g., x-axis) and columns (e.g., y-axis) of the optical film. Each of the plurality of through-holes 40 extends between a first major surface 10 and a second major surface 11 of the optical film 100. In some embodiments, each through hole 40 can have a first opening 41 having a first open area A1 at the first major surface 10 and a second opening 43 having a second open area A2 at the second major surface 11. Each through hole has a length H along a first direction (i.e., along the z-axis, or "thickness direction" as shown in FIG. 1A).

[0039] In some embodiments of the optical film, when configured such that the ratio of H / A2 is about 0.13 or greater, light 80 provided by light source 60 passing through optical film 100 provides a first overall peak intensity (e.g., brightest spot) at first plane 70 and a first luminance uniformity (e.g., point-to-point variations in luminance causing "bright" and "dark" spots) across first plane 70. Without optical film 100, light 80 has a second overall peak intensity at first plane 70 and a second luminance uniformity across first plane 70 such that the first overall peak intensity and the second overall peak intensity differ by less than about 20%, or less than about 15%, or less than about 10%, and the first luminance uniformity represents an improvement over the second luminance uniformity of at least about 2.8%, or at least about 3.0%, or at least about 5%, or at least about 10%.

[0040] In some embodiments, the optical film 100 may include a plurality of posts 20 arranged in rows (e.g., on the x-axis) and columns (e.g., on the y-axis) of the optical film. In some embodiments, the optical film 100 may also include a plurality of ridges 30 extending between and recessed relative to the posts (i.e., recessed below the highest point of the posts 20 relative to the first major surface 10 of the optical film 100). In some embodiments, the first opening 41 of each through hole 40 may be defined and surrounded by four ridges 30. Further details of the posts 20 and ridges 30 can be seen in Figures 5A-6B.

[0041] In some embodiments, the backlight 300 can further include a diffusion film 67 disposed between the light source 60 and the optical film 100. In some embodiments, the backlight 300 may further include one or more other optical films 65 (e.g., brightness enhancing films, "prism" films, pyramidal convex prism films, pyramidal concave prism films, reflective polarizer films, diffusion films, microlens films, and / or light recycling films) disposed between the optical film 100 and the display 50.

[0042] FIG. 1B illustrates an alternative embodiment of the optical film 100 of FIG. 1A. More specifically, FIG. 1B illustrates an embodiment where the orientation of the optical film 100 is arranged in an opposite orientation to that of the optical film 100 illustrated in FIG. 1A, with the second openings 43 now facing the first plane 70 (i.e., the optical film 100 of FIG. 1B is "upside down" relative to the optical film 100 of FIG. 1A). Other than the orientation of the optical film 100, a backlight using the embodiment illustrated in FIG. 1B may be otherwise identical to the backlight 300 of FIG. 1A. Depending on the size of the first openings 41 and the second openings 43 relative to each other, the optical performance measured at the first plane 70 may differ based on the orientation of the optical film 100. For example, when the optical film 100 is positioned such that the first opening 41 (and first open area A1) faces the light source 60 (as shown in FIG. 1A), the first average luminance across the first plane 70 may be relatively small and the first luminance uniformity may be relatively large, and when the optical film 100 is positioned such that the second opening 43 (and second open area A2) faces the light source 60 (as shown in FIG. 1B), the first average luminance at the first plane 70 may be relatively large and the first luminance uniformity may be relatively small.

[0043] 2A and 2B provide side views of the optical film 100 of FIG. 1A, featuring further details according to the present specification. FIG. 1A shows an enlarged view of one of the through holes 40 of the optical film 100, with the first open area A1 and the second open area A2 being different (i.e., different areas). It should be noted that while FIG. 2A shows one possible embodiment in which the first opening 41 is larger than the second opening 43, other embodiments are possible, as described elsewhere herein. For example, in some embodiments, the first opening 41 may be smaller than or equal to the second opening 43.

[0044] When the first open area 41 and the second open area A2 are different, one or more of the sidewalls 47 may have a draft angle θ that is within ±15 degrees, or within ±10 degrees, or within ±8 degrees in the thickness direction (i.e., the z direction as shown in FIG. 2A ). In embodiments in which the first open area 41 and the second open area A2 are substantially equal, the draft angle θ may be substantially equal to 0 (i.e., the sidewalls may be substantially vertical).

[0045] 2B illustrates an alternative embodiment of through-hole 40 in optical film 100. In some embodiments, at least one of first opening 41 and second opening 43 can include a lip 24 that protrudes outward from the periphery of the opening toward the center of the opening. In some embodiments, light passing through lip 24 can be scattered as shown in FIG.

[0046] 3A-3C provide further details and embodiments of the optical film 100. FIG. 3A shows light rays 80a and 80b passing through the optical film 100 when the optical film 100 is positioned such that the first opening 41 is larger than the second opening 43. The light ray 80a, which is already substantially collimated (i.e., already substantially aligned in the z-direction), passes directly through the second opening 43 and then through the first opening 41 without being reflected or redirected by the sidewall 47. However, the light ray 80b enters the second opening 43 at an angle, hits the sidewall 47, and is redirected upwards from the first opening 41. The effect of the through-hole 40 is to generally collimate the light ray 80 before it illuminates the display. In other embodiments, a similar collimation effect can occur for the light ray 80 if the first opening 41 is smaller than the second opening 43, or if the optical film of FIG. 3A is inverted as shown in FIG. 3B. However, if an opening (such as second opening 43 in FIG. 3B) includes a lip 24 surrounding the periphery of the opening, the lip 24 can have the effect of scattering light rays (such as light ray 80c in FIG. 3B) as the light passes through. This light scattering can increase the uniformity of the light 80 as it enters the first plane 70 (see FIG. 1) by adding a diffusion effect. Depending on the requirements of the backlight application, this can be a desirable effect. Comparing the embodiments of FIG. 3A and FIG. 3B, the embodiment of optical film 100 in FIG. 3A can have a better average brightness relative to that of FIG. 3B, but both embodiments can show an improvement in average brightness (i.e., an increase in brightness) relative to a similar backlight without optical film 100. Similarly, the embodiment of optical film 100 in FIG. 3B can have a better brightness uniformity relative to that of FIG. 3A (due to the scattering / diffusion effect of lip 24), but both embodiments can show an improvement in uniformity relative to a similar backlight without optical film 100.

[0047] FIG. 3C illustrates some of the possible shapes of through-hole 40, including a prism 40a, a truncated pyramid 40b, a cylinder 40c, and a truncated cone 40d. The shapes depicted in FIG. 3C are representative of some of the possible shapes formed by the sidewalls of through-hole 40, but are not meant to be limiting. Other shapes are possible. Also, note that the shape of through-hole 40 may have imperfections or variations (e.g., lip 24, sidewall angle and surface variations, curves, etc.) and may not be completely represented by the shape depicted in FIG. 3C. That is, the shape of at least a portion of through-hole 40 may be substantially equal to a truncated pyramid (for example), but may not be a perfect truncated pyramid.

[0048] FIG. 4 shows a side view of an alternative embodiment of a backlight 300a. The embodiment shown in FIG. 4 is similar to the embodiment of the backlight 300 of FIG. 1A and has many common (similarly numbered) components. The function of any component in FIG. 4 with a corresponding similarly numbered component in FIG. 1A shall be assumed to have a similar function and description unless otherwise specified and may not be further described herein. The backlight 300a is configured to provide illumination 80 to the display 50. The backlight 300a includes an optical film 100a, which differs from the optical film 100 of FIG. 1A primarily in that the optical film 100a includes a plurality of recesses 45 (rather than through holes 40 as shown in FIG. 1A). The recess 45 has a first open end 41a at the first major surface 10a, a second closed end 43a at the second major surface 11a, and a depth D extending from the first open end 41a to the inner surface 43b of the second closed end 43a (i.e., the recess 45 does not extend all the way to the second major surface 11a). Each first open end 41a has a first open area A3, and each second closed end 43a has a second closed area A4 (i.e., the area of ​​the inner surface 43b). In experiments, it has been demonstrated that the optical film 100a having the recess 45 exhibits similar optical performance improvements as the optical film 100 having the through holes 40 (see FIG. 1A). It should also be noted that the optical film 100a may be arranged in a reverse orientation, with the second closed end 43a facing the display 50, similar to the embodiment of the film 100 shown in FIG. 1B, with similar optical performance advantages. 3C are also applicable to recesses 45 of optical film 100a. In some embodiments, the ratio of depth D to closed area A4 may be greater than or equal to about 0.13.

[0049] 5A, 5B, 6A, and 6B are actual close-up images of an optical film having high-definition features according to the present disclosure. These figures show the features of the optical film 100 in cross-section from various angles (FIGS. 5B, 6A, and 6B). These figures should be viewed together for the following discussion, and features common across two or more of these figures (i.e., similarly numbered components) shall be assumed to have similar functions unless otherwise specified. FIG. 5A shows a "top view" of the optical film 100 and a plurality of through-holes 40. Each through-hole 40 has a first opening 41 having a first maximum dimension 42 and a second opening 43 having a second maximum dimension 44. In the embodiment shown in FIG. 5A, each of the first openings 41 is surrounded and defined by four ridges 30 that extend between and are recessed relative to the plurality of posts 20. A lip 24 can be seen surrounding each second opening 43.

[0050] 5B shows a cross-sectional image of optical film 100 cut halfway through through hole 40, showing posts 20 and the ridges 30 spanning between them. The posts 20 extend above the ridges 30 and above the first major surface 10. A second opening 43 on the second major surface 11 features a lip 24 that extends from the sidewall of the hole into the opening.

[0051] 6A and 6B are additional cross-sectional images showing through hole 40 surrounded (on three sides, since it is a cross section) by ridge 30 that defines a perimeter of first opening 41 on first major surface 10. Lip 24 extends outwardly from second opening 43 and defines a maximum dimension 44 of second opening 43. Sidewalls 47 may have a slope, typically with a slight draft within ±10 degrees of vertical. In some embodiments, sidewalls 47 may be substantially flat, while in other embodiments, sidewalls 47 may have curvature or other non-planar features and / or deformations, especially as they approach lip 24.

[0052] 7 is a plot showing the luminance improvement (i.e., the luminance ratio compared to a reference value measured without the optical film present or structure, which represents 100%) versus the value of the ratio H / A2 (i.e., the ratio of the height H of the through hole to the open area A2 of the second opening). The three points shown are point 92, which represents an approximate value of H / A2 of 0.13, point 94, which represents an approximate value of H / A2 of 0.5, and point 96, which represents an approximate value of H / A2 of 1.0. The plot of FIG. 7 shows an increase in performance (i.e., an increase in the luminance ratio) starting from an H / A2 value of about 0.13 and increasing to an increase of nearly 18% as the ratio approaches 1.0.

[0053] 8 is a plot comparing peak luminance values ​​for displays with and without an optical film described herein disposed over a backlight. Plot 95 represents a plot of the peak luminance shown for an LED without an optical film in place, approximately 21000 cd / m 2 (candela per square meter, also known as nits) for the peak luminance value. Plot 97 represents a plot of the peak luminance shown for the same LED with an optical film disposed over the LED, at approximately 23,000 cd / m 2 5A , which represents an approximate gain in peak luminance value of 8.7%. Note that the luminance value measured at any given point on the optical film may vary based on the alignment of a particular LED with the through-hole, and that the peak luminance value with the optical film in place may occur when the LED is substantially aligned with the through-hole. At other times, such as when a post (such as post 20 as shown in FIG. 5A ) is aligned with the LED, the luminance value may decrease significantly from the peak luminance value shown here. It is the combination of increased peak luminance from some LEDs and increased scattering from other LEDs that contributes to both the overall increase in average luminance across the display and the corresponding increase in uniformity across the display.

[0054] 9A and 9B are plots comparing display uniformity performance of displays with and without an optical film disposed on the backlight. FIG. 9A shows a plot of luminance values ​​99 measured across a display for a backlight featuring a high definition optical film according to the present disclosure, and values ​​measured across a display for a backlight in which the high definition film is replaced with an optically clear unstructured film of polyethylene terephthalate (PET). The value 99 for the high definition optical film shows both an increase in luminance value across the display relative to the featureless PET film, as well as an increase in uniformity (i.e., a smaller contrast difference between the minimum and maximum luminance values). FIG. 9B shows another exemplary measurement using a high definition optical film 98 and a featureless PET film 91. The minimum and maximum luminance values ​​shown by these plots, as well as the LD luminance uniformity values ​​they represent, are summarized in Table 1. Note that in terms of uniformity, smaller contrast values ​​are better than larger contrast values. As shown in Table 1, the measured performance for a high definition optical film (i.e., for example, a film featuring through holes in FIG. 1A) showed an approximate improvement in contrast of about 2.88%. Similar example films were measured and showed an improvement of at least 2.88%, and in many cases even greater improvement values. These examples are described in more detail elsewhere herein.

[0055] [Table 1]

[0056] Figure 10 is an additional close-up image of an optical film with high definition features highlighting further details of one embodiment of the optical film. In some embodiments, the optical film 100 includes a regular two-dimensional array of intersecting ridges 30 that define a plurality of through-holes 40 therebetween (see, for example, Figure 5A). Figure 10 shows a cross-sectional view of the optical film 100 showing a plane P1 (i.e., the plane of Figure 10) parallel to the thickness direction of the optical film 100 (i.e., the z-axis shown in Figure 10). The cross-section of plane P1 includes two adjacent ridges 30a, 30b in the array of ridges and the through-hole 40 therebetween.

[0057] In some embodiments, the optical film 100 has a maximum thickness h max In some embodiments, the through hole 40 extends between a first open end 41 and a second open end 43 of the through hole 40 on opposite first and second major surfaces 101 and 102 of the optical film 100, respectively. In some embodiments, the through hole 40 has a sidewall 47 that is a substantially vertically oriented portion connected to the first open end 41 of the through hole 40. In some embodiments, the through hole 40 also has a substantially horizontally oriented portion 24 (e.g., a lip) extending from the substantially vertically oriented portion 47 and connected to the second open end 43 of the through hole 40. In some embodiments, the substantially horizontally oriented portion 27 has a minimum thickness h at a location 103 disposed between two adjacent ridges 30a and 30b. min and the ratio h max / h min is about 2 or more, or about 3 or more, or about 4 or more, or about 5 or more, or about 6 or more, or about 7 or more, or about 8 or more, or about 9 or more, or about 10 or more.

[0058] Finally, FIG. 11 is an embodiment of a backlight for providing illumination to a display, featuring two or more optical films. It should be noted that FIG. 1A and FIG. 11 share many similarly numbered elements, and similarly numbered elements should be assumed to have similar functions unless otherwise specified. The description of elements from FIG. 1A applies equally to those similarly numbered elements of FIG. 11, and these elements may not be described in the discussion of FIG. 11. FIG. 11 is a side view of a backlight 300a for providing illumination to a display 50. In some embodiments, the backlight 300a provides illumination 80 to the display 50. In some embodiments, the backlight 300a may include a plurality of spaced apart individual light sources 60 and an optical stack 150 having two or more optical films 100. In some embodiments, the individual light sources 60 face the display (i.e., emit light 80 toward the display in the z-direction shown in FIG. 11 ) and are arranged in rows and columns of light sources 60 (e.g., a matrix of light emitting diodes having rows in the x-axis and columns in the y-axis). The optical stack 150 may be disposed on or proximate to the light sources 60 and proximately below the first plane 70 (i.e., a reference plane for purposes of illustration). In some embodiments, each of the optical films 100 in the optical stack 150 may include a plurality of through-holes 40 arranged in rows (e.g., on the x-axis) and columns (e.g., on the y-axis) of each optical film. Each of the plurality of through-holes 40 extends between the first major surface 101 and the second major surface 103 of the optical film 100. In some embodiments, each through hole 40 can have a first opening 41 having a first open area A1 at the first major surface 101 and a second opening 43 having a second open area A2 at the second major surface 103. Each through hole has a length H along a first direction (i.e., along the z-axis, or "thickness direction" as shown in FIG. 11).

[0059] In some embodiments of the optical film, the ratio of H / A2 is configured to be about 0.13 or greater. In some embodiments, when the light sources 60 emit light 80, the light 80 emitted by all of the light sources 60 can have a first average luminance at the first plane 70, and in the absence of the optical stack 150, the light 80 emitted by all of the light sources 60 can have a second average luminance at the first plane 70, the first average luminance being greater than the second average luminance.

[0060] In some embodiments, the backlight 300a may further include a diffusing layer 200 having a plurality of microstructures 210. In some embodiments, each microstructure 210 may have a square pyramid shape.

[0061] In some embodiments, each film 100 in the optical stack 150 may be oriented the same as each of the other optical films 100 in the optical stack 150. For example, each film 100 may be oriented such that the first opening 41 faces the display 50 and the second opening 43 faces the light source 60 (as shown in FIG. 11 ). In another example, each film 100 may be oriented such that the first opening 41 faces the light source 60 and the second opening 43 faces the display 50. In another embodiment, at least one of the optical films 100 may be oriented such that the first opening 41 faces the display 50, while at least one other of the optical films 100 may be oriented such that the first opening 41 faces the light source 60 (i.e., some of the films 100 may be inverted relative to the other films 100). EXAMPLES

[0062] Table 2 shows the results of luminance contrast measurements made on several example films. Each of the example films listed in Table 2 was made using a high definition process, and all luminance measurements were made using a Konica Minolta CA-2500 2D color analyzer. All example high definition films measured showed an improvement in luminance contrast ranging from at least about 2.88% to about 11.29%. The reference film used in each of the following examples was a featureless (no through holes or structures) optically clear polyethylene terephthalate (PET) film.

[0063] [Table 2-1]

[0064] [Table 2-2]

[0065] Terms such as "about" will be understood by those of skill in the art in the context in which they are used and described herein. Unless otherwise clear to one of skill in the art in the context in which they are used and described herein, the use of "about" as applied to quantities describing feature sizes, amounts, and physical properties will be understood to mean within 10 percent of the particular value. An amount given as about a particular value may be exactly that particular value. For example, unless otherwise clear to one of skill in the art in the context in which they are used and described herein, an amount having a value of about 1 means that the amount has a value between 0.9 and 1.1, and may even be 1.

[0066] Terms such as "substantially" will be understood by those of skill in the art in the context in which they are used and described herein. If the use of "substantially equal" is not clear to those of skill in the art in the context in which they are used and described herein, "substantially equal" means approximately equal, with about as above. If the use of "substantially parallel" is not clear to those of skill in the art in the context in which they are used and described herein, "substantially parallel" means 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 clear to those of skill in the art in the context in which they are used and described herein, "substantially aligned" means aligned within 20% of the width of the objects being aligned. Objects described as substantially aligned may, in some embodiments, be aligned within 10% or within 5% of the width of the objects being aligned.

[0067] All references, patents, or patent applications referenced above are hereby incorporated by reference in their entirety. In the event of any inconsistency or contradiction between any of the incorporated references and this application, the information in the foregoing description shall prevail.

[0068] Descriptions of elements in a figure should be understood to apply equally to corresponding elements in other figures unless otherwise indicated. Although specific embodiments have been illustrated and described herein, those skilled in the art will appreciate that the specific embodiments illustrated and described may be replaced by various alternative and / or equivalent implementations 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. Accordingly, it is intended that the present disclosure be limited only by the claims and the equivalents thereof.

Claims

1. 1. A backlight for providing illumination to a display panel, comprising: a two-dimensional array of spaced apart individual light sources; a plurality of optical films disposed over the light source and configured to be disposed between the display panel and the light source, each of the optical films including a regular two-dimensional array of intersecting ridges defining a plurality of through-holes therebetween, each of the through-holes extending between first and second open ends of the through-hole on opposite first and second major surfaces of the optical film, the through-holes being parallel to a thickness direction of the optical film and including two adjacent ridges in the array of ridges and a through-hole therebetween, the optical film having a maximum thickness h ｍａｘ the through-hole includes a sidewall including a substantially vertically oriented portion connected to the first open end of the through-hole and a substantially horizontally oriented portion extending from the substantially vertically oriented portion and connected to the second open end, the substantially horizontally oriented portion having a minimum thickness h at a location disposed between the two adjacent ridges. ｍｉｎ and h ｍａｘ / h ｍｉｎ and a plurality of optical films, wherein the number of optical films is ≧2; Backlight.

2. The backlight of claim 1 , wherein the plurality of optical films comprises at least three optical films.

3. The backlight of claim 1 , further comprising a diffusing layer disposed between the plurality of optical films and the display panel.

4. The backlight of claim 3 , wherein the surface of the diffusing layer comprises a plurality of microstructures.

5. The backlight of claim 4 , wherein each microstructure in the plurality of microstructures has a square pyramidal shape.

6. The backlight of claim 1 , wherein one of the first open end and the second open end of each of the plurality of through holes is larger than the other of the first open end and the second open end.

7. The backlight according to claim 1 , wherein the inclination of the inner wall of each of the plurality of through holes is within ±15 degrees in the thickness direction.

8. 2. The backlight of claim 1, wherein each through hole of the plurality of through holes defines a distance H between the first opening and the second opening, the second opening having an open area A2, and a ratio of H / A2 is greater than or equal to about 0.

13.

9. The backlight of claim 6 , wherein each optical film of the plurality of optical films is oriented the same as each other optical film in the plurality of optical films.

10. The backlight of claim 9 , wherein each optical film of the plurality of optical films is oriented so that the larger of the first open end and the second open end faces the display.

11. 10. The backlight of claim 9, wherein each optical film of the plurality of optical films is oriented so that a larger of the first open end and the second open end faces the two-dimensional array of spaced-apart individual light sources.

12. The backlight of claim 1 , wherein the regular two-dimensional array of intersecting ridges in each of the optical films forms orthogonal rows and columns of posts.

13. 13. The backlight of claim 12, wherein for at least two of the optical films in the plurality of optical films, the row of one of the two optical films forms an angle of less than about 20 degrees with the row of the other of the two optical films.

14. 13. The backlight of claim 12, wherein for at least two of the optical films in the plurality of optical films, the row of one of the two optical films forms an angle of about 10 degrees to about 80 degrees with the row of the other of the two optical films.

Images