JP-7855244-B2 - Edge-lit backlight unit with improved efficiency

JP7855244B2JP 7855244 B2JP7855244 B2JP 7855244B2JP-7855244-B2

Inventors

ウォーカー，ケニスエル．
シェン，ビンエー．
ポープ，マシューケー．

Assignees

ブライトビューテクノロジーズ，インコーポレイテッド

Dates

Publication Date: 20260508
Application Date: 20211216
Priority Date: 20201218

Claims (20)

An edge-lit backlight unit for a backlit display, wherein the edge-lit backlight unit is Reflector, An edge-light type light guide film positioned above the reflector, wherein the edge-light type light guide film has a length and a width, and the combination of the edge-light type light guide film and the reflector is configured to provide a peak optical dispersion of 15° to 20° and a full-width half-maximum diffusion angle of 25° to 45°, A diffuser film positioned above the edge-lit light guide film, wherein the diffuser film has a plurality of parallel prism microstructures on one side facing the edge -lit light guide film, and a plurality of diffuser microstructures on the opposite side of the diffuser film , at least some of the plurality of parallel prism microstructures having an apex angle of 78° to 92° and being formed from a material having a refractive index of 1.49 to 1.58, and the plurality of diffuser microstructures having a total width half-maximal diffusion angle of 30° to 60° , and A pair of crossed luminance-enhancing films positioned above the diffuser film, wherein at least one of the pair of crossed luminance-enhancing films has a plurality of parallel minute prisms on one side facing away from the diffuser film, and the plurality of parallel minute prisms of one of the pair of crossed luminance-enhancing films is oriented perpendicular to the plurality of parallel minute prisms of the other of the pair of crossed luminance -enhancing films . Equipped with, The plurality of parallel prism microstructures of the diffuser film are substantially aligned with the plurality of parallel microprisms of at least one of the pair of intersecting brightness-enhancing films . An edge-lit backlight unit in which each of the plurality of diffuser microstructures is formed in a square pyramidal shape, and at least some faces of the square pyramidal shape of each of the plurality of diffuser microstructures are oriented at approximately 45° with respect to the plurality of parallel prism microstructures of the diffuser film .
The edge -lit backlight unit according to claim 1, wherein at least one of the pair of intersecting brightness-enhancing films comprises a plurality of parallel minute prisms oriented to be most closely aligned with the light direction.
The edge-light type backlight unit according to claim 2, wherein at least one of the pair of crossed brightness-enhancing films is positioned on top of the edge-light type backlight unit.
The edge-lit backlight unit according to claim 1 , wherein the square pyramidal shape has an apex angle of approximately 110°.
The edge-lit backlight unit according to claim 1 , wherein the square pyramidal shape has an apex angle of approximately 90°.
The edge-lit backlight unit according to claim 1 , wherein each of the plurality of diffuser microstructures is formed from a material having a refractive index of approximately 1.57.
The edge-lit backlight unit according to claim 1, further comprising a plurality of LEDs positioned along the width of the edge-lit light guide film.
An edge-lit backlight unit for a backlit display, wherein the edge-lit backlight unit is Diffuse reflector, An edge-light type light guide film positioned above the diffuse reflector, wherein the edge-light type light guide film has a length and a width, and the combination of the edge-light type light guide film and the diffuse reflector is configured to provide a peak optical dispersion of 30° to 50° and a full-width half-maximum diffusion angle of 55° to 85°, A diffuser film positioned above the edge-lit light guide film, wherein the diffuser film has a plurality of parallel prism microstructures on one side facing the edge -lit light guide film, and a plurality of diffuser microstructures on the opposite side of the diffuser film , at least some of the plurality of parallel prism microstructures having an apex angle of 75° to 85° and a refractive index of 1.59 to 1.67 , and the plurality of diffuser microstructures having a total width half-maximum diffusion angle of less than 20° , and A pair of crossed luminance-enhancing films positioned above the diffuser film, wherein at least one of the pair of crossed luminance-enhancing films has a plurality of parallel minute prisms on one side facing away from the diffuser film, and the plurality of parallel minute prisms of one of the pair of crossed luminance-enhancing films is oriented perpendicular to the plurality of parallel minute prisms of the other of the pair of crossed luminance-enhancing films. Equipped with, The plurality of parallel prism microstructures of the diffuser film are substantially aligned with the plurality of parallel microprisms of at least one of the pair of intersecting brightness-enhancing films . An edge-lit backlight unit in which each of the plurality of diffuser microstructures is formed in a square pyramidal shape, and at least some faces of the square pyramidal shape of each of the plurality of diffuser microstructures are oriented at approximately 45° with respect to the plurality of parallel prism microstructures of the diffuser film .
The edge-lit backlight unit according to claim 8 , wherein the plurality of parallel minute prisms of at least one of the pair of intersecting brightness-enhancing films are oriented to be most closely aligned with the light direction.
The edge-light type backlight unit according to claim 9 , wherein at least one of the pair of crossed brightness-enhancing films is positioned on top of the edge-light type backlight unit.
The edge-lit backlight unit according to claim 8 , wherein each of the plurality of diffuser microstructures is configured to have a total width half-maximal diffusion angle of less than 10° or equal to 10° .
The edge-lit backlight unit according to claim 8 , wherein each of the plurality of diffuser microstructures is configured to have a total width half-maximal diffusion angle of less than 5° or equal to 5° .
A backlight unit, wherein the backlight unit is Reflector, A light guide film positioned above the reflector, wherein the light guide film is configured to guide light along the direction of light, A diffuser film positioned above the light guide film, wherein the diffuser film has a plurality of parallel prism microstructures on one side facing the light guide film , at least some of the plurality of parallel prism microstructures having a prism vertex direction , and the diffuser film further has a plurality of pyramidal microstructures on the opposite side, at least some of the plurality of pyramidal microstructures having a common pyramidal vertex direction, A first brightness-enhancing film positioned above the diffuser film, wherein the first brightness-enhancing film has a plurality of parallel prism microstructures on one side of the first brightness-enhancing film facing away from the diffuser, and at least some of the plurality of parallel prism microstructures of the first brightness-enhancing film have a common prism vertex direction, A second brightness-enhancing film is positioned above the first brightness-enhancing film, wherein the second brightness-enhancing film has a plurality of parallel prism microstructures on one side of the second brightness-enhancing film facing away from the first brightness-enhancing film, and at least some of the plurality of parallel prism microstructures of the second brightness-enhancing film have a common prism vertex direction, comprising: A backlight unit in which the common prism vertex direction of at least one of the first brightness-enhancing film and the second brightness-enhancing film is substantially oriented along the light direction, the common prism vertex direction of the diffuser film is substantially oriented along the common prism vertex direction of at least one of the first brightness-enhancing film and the second brightness-enhancing film , and the common pyramidal vertex direction of the diffuser film is oriented at a desired angle with respect to the common prism vertex direction of the diffuser film , the desired angle being substantially 45° .
The backlight unit according to claim 13, wherein the common prism vertex direction of at least one of the first brightness-enhancing film and the second brightness-enhancing film, which have a prism vertex direction substantially oriented along the light direction, has a prism vertex direction that is less than 10 degrees from the light direction.
The backlight unit according to claim 13, wherein the common prism vertex direction of at least one of the first brightness-enhancing film and the second brightness-enhancing film, which have a prism vertex direction substantially oriented along the light direction, has a prism vertex direction that is less than 20 degrees from the light direction.
The backlight unit according to claim 13, wherein the other of the first brightness-enhancing film and the second brightness-enhancing film has a prism vertex direction that is oriented substantially perpendicular to the prism vertex direction of the at least one of the first brightness-enhancing film and the second brightness-enhancing film.
The backlight unit according to claim 13, wherein at least one of the first brightness-enhancing film and the second brightness-enhancing film, which have a prism vertex direction substantially oriented along the light direction, is positioned on top of the backlight unit.
The backlight unit according to claim 13 , wherein at least some of the plurality of parallel prism microstructures of the diffuser film have apex angles of 78° to 94°.
The backlight unit according to claim 13 , wherein at least some of the plurality of parallel prism microstructures of the diffuser film are formed from a material having a refractive index of 1.5 to 1.66.
The backlight unit according to claim 13 , wherein at least some of the plurality of pyramidal microstructures of the diffuser film have an apex angle of 84° to 114°.

Description

(Cross-reference of related applications) This application claims priority to U.S. Provisional Patent Application No. 63/127,325, filed on 18 December 2020, and U.S. Provisional Patent Application No. 63/214,730, filed on 24 June 2021. The entire contents of those applications are incorporated herein by reference. This invention relates to an edge-lit backlight unit for a backlit display, which has improved efficiency and enables increased visible brightness without increasing power to the display. An edge-lit backlight unit (BLU), as shown in Figure 1, typically uses a light guide film 100 with a plurality of light-emitting diodes (LEDs) 110 positioned along one side of the light guide film 100. The light guide film 100 has a width W and a length L, and the LEDs 110 are positioned at one edge along the width W of the light guide film 100 and are configured to emit light into the light guide film 100 so that the light travels along the length L of the light guide film 100, as shown in Figure 2, which is a cross-section obtained along line 2-2 in Figure 1. The light guide film 100 typically has a miniature structure on its upper and/or bottom surface that externally couples the light to the light guide film 100. Ideally, the structure is apodized so that the externally coupled light of the light guide film 100 has a spatially uniform intensity. Generally, the light externally coupled to the light guide film 100 is externally coupled with angular dispersion, directed away from the light input edge of the light guide film 100, as shown in Figure 2. This general direction away from the light guide film 100 nominally extends along the length L of the light guide film 100 and is referred to as the optical direction of the light guide film 100. For backlight units used in edge-lit displays, it is desirable to maximize light efficiency, that is, to increase visible brightness without increasing the power supplied to the backlight unit. The components of the following figures are not necessarily drawn to scale, although at least one of them may be drawn to scale. They are illustrated to emphasize the general principles of this disclosure and are not necessarily drawn to scale. Reference numerals designating the corresponding components are repeated throughout the figures as needed for consistency and clarity. Figure 1 is a schematic top view of an edge-lit light guide film with multiple light-emitting diode (LED) light sources for use in an edge-lit backlight unit for a backlit display. Figure 2 is a schematic cross-sectional view of Figure 1 obtained along line 2-2. Figure 3A is a schematic exploded cross-sectional view of a backlight unit for a backlit display, including the light guide film shown in Figures 1 and 2 and an LED. Figure 3B is a schematic diagram of a brightness-enhancing film for a backlit display, which has a prismatic microstructure and includes details of the apex and base angles. Figure 3C is a schematic diagram of a stacked pair of brightness-enhancing films for a backlit display having a prismatic microstructure, illustrating the right-angle orientation of the two films. Figure 3D is a schematic diagram of a gain-enhancing film for a backlit display, having a prismatic microstructure on one side and including details of the apex and base angles. Figure 3E is a schematic diagram of a gain-enhancing film for a backlit display, having a prismatic microstructure on one side, where the prismatics are formed at a desired angle with respect to the long axis of the film. Figure 3F is a schematic diagram of a gain-enhancing film for a backlit display, having an inverted pyramidal microstructure on one side and a prism on the opposite side, and including details of the apex and base angles of the inverted pyramidal structure. Figure 3G is a schematic diagram of a gain-enhancing film for a backlit display, having a pyramidal microstructure on one side and a prism on the opposite side, where the pyramidal axis is formed at a desired angle with respect to the major axis of the film, and the prism on the opposite side is aligned with the diagonal of the base of the pyramid. Figure 3H is a schematic top view of an edge-lit light guide film with multiple light-emitting diode (LED) light sources, showing the orientation in the optical direction, the desired orientation of the pyramid on the top of the first brightness-enhancing film, the desired orientation of the prism on the top of the second brightness-enhancing film, and the desired orientation of the prism on the bottom of the gain-enhancing film. Figure 4 shows a two-dimensional plot of the dispersion of light emitted from an LED as a function of angle, as measured by a light distribution meter, and a two-dimensional plot of the dispersion of light emitted from an LED as a function of angle, as measured by a light distribution meter, after the light has passed through a pair of intersecting brightness-enhancing films. Figure 5A is a three-dimensional rep