Backlight modules and display devices

Abstract

This invention provides a backlight module with excellent light energy utilization efficiency and a display device employing this backlight module. [Solution] The backlight module BLM comprises a circuit board 100, a plurality of light-emitting elements, an anisotropic diffusion sheet 300, a plurality of Fresnel lenses 220, and an optical brightness enhancing film 400. The plurality of light-emitting elements are mounted on the circuit board. The anisotropic diffusion sheet is mounted on one side of the light-emitting surface 120es of each light-emitting element. The plurality of Fresnel lenses are mounted between the plurality of light-emitting elements and the anisotropic diffusion sheet, and are mounted so as to overlap these light-emitting elements. The optical brightness enhancing film is mounted on the side of the anisotropic diffusion sheet that faces away from the plurality of Fresnel lenses.

Description

Technical Field

[0001] The present invention relates to an optical module and an electronic device, and particularly to a backlight module and a display device.

Background Art

[0002] The application of in-vehicle displays has been gradually diversifying with the development of display technology. A head-up display that projects an image onto the front windshield of a vehicle is an example. Generally, in order to ensure safe driving, the reflectivity of the automotive front windshield is low, for example, 20%. Therefore, the illumination brightness of the head-up display needs to be significantly improved to meet the brightness requirements during display, resulting in an increase in the energy consumption of the operation and causing the problem of overheating. On the other hand, in order to avoid the adverse effect of the human eye directly looking at the display screen of the head-up display on the projection display effect, the display surface of the head-up display is generally arranged substantially parallel to the line-of-sight direction of the human eye or facing away from the human eye. However, many of the backlights currently used in head-up displays are of a type that concentrates light rays in the vertical direction of the display surface, so the utilization efficiency of light energy cannot be maximized.

[0003] Note that this "Background Art" paragraph is only for helping to understand the content of the present invention, so the content disclosed in this "Background Art" may include content that does not constitute well-known technology known to those skilled in the art. Therefore, the content disclosed in this "Background Art" does not mean that the above content, or the problems to be solved by one or more embodiments of the present invention, have already been well-known or recognized by those skilled in the art before the filing of the present invention.

Summary of the Invention

[0004] The present invention provides a backlight module and a display device with excellent light energy utilization efficiency.

[0005] Other purposes and advantages of the present invention can be further understood from the technical features disclosed herein.

[0006] To achieve some or all of the aforementioned objectives, or other objectives, one embodiment of the present invention provides a backlight module. The backlight module comprises a circuit board, a plurality of light-emitting elements, an anisotropic diffusion sheet, a plurality of Fresnel lenses, and an optical brightness-enhancing film. The plurality of light-emitting elements are mounted on the circuit board. The anisotropic diffusion sheet is mounted on one side of the light-emitting surface of each light-emitting element. The plurality of Fresnel lenses are mounted between the plurality of light-emitting elements and the anisotropic diffusion sheet, overlapping these light-emitting elements. The optical brightness-enhancing film is mounted on the side of the anisotropic diffusion sheet that faces away from the plurality of Fresnel lenses.

[0007] In one embodiment of the present invention, each Fresnel lens in the backlight module has an optical axis, and the multiple optical axes of the multiple Fresnel lenses each pass through multiple light-emitting elements.

[0008] In one embodiment of the present invention, the backlight module further comprises a light guide plate and a plurality of free-form lenses. The light guide plate is positioned between the plurality of light-emitting elements and the plurality of Fresnel lenses and covers the plurality of light-emitting surfaces of the plurality of light-emitting elements. The plurality of free-form lenses are installed on a first surface of the light guide plate that faces away from the circuit board and each overlaps the plurality of light-emitting elements.

[0009] In one embodiment of the present invention, the backlight module further comprises an auxiliary light-emitting element and a plurality of optical microstructures. The auxiliary light-emitting element is installed on one side of the light-receiving surface of the light guide plate. The plurality of optical microstructures are installed on the second surface of the light guide plate and are located between the plurality of light-emitting elements. The light-receiving surface is connected to the first surface and the second surface, and the second surface faces the direction of the circuit board.

[0010] In one embodiment of the present invention, the multiple optical microstructures in the backlight module do not overlap with the multiple free-form lenses along the normal direction of the second surface.

[0011] In one embodiment of the present invention, the plurality of light-emitting elements of the backlight module include a plurality of first light-emitting elements and a plurality of second light-emitting elements. Each Fresnel lens has an optical axis, and the plurality of optical axes of the plurality of Fresnel lenses each pass through the plurality of first light-emitting elements. Each second light-emitting element overlaps the connection between two adjacent Fresnel lenses along the direction normal to the light-emitting surface.

[0012] In one embodiment of the present invention, the optical brightness enhancing film of the backlight module is provided with a plurality of prism structures on the film surface facing away from the plurality of light-emitting elements.

[0013] In one embodiment of the present invention, each prism structure of the backlight module includes a first optical surface and a second optical surface connected to each other. The first bottom angle between the first optical surface and the film surface is greater than the second bottom angle between the second optical surface and the film surface. The multiple first optical surfaces and multiple second optical surfaces of the multiple prism structures are arranged alternately along one direction parallel to the film surface.

[0014] In one embodiment of the present invention, the backlight module further comprises a light guide plate, an auxiliary light-emitting element, and a plurality of optical microstructures. The light guide plate is installed between the plurality of light-emitting elements and an anisotropic diffusion sheet. The light guide plate has a light-receiving surface and a first surface and a second surface connected to the light-receiving surface and facing away from each other. The auxiliary light-emitting element is installed on one side of the light-receiving surface of the light guide plate. The plurality of optical microstructures are installed on the second surface of the light guide plate and are located between the plurality of light-emitting elements. The plurality of Fresnel lenses are installed on the first surface of the light guide plate.

[0015] In one embodiment of the present invention, each Fresnel lens in the backlight module has an optical axis, and the multiple optical axes of the multiple Fresnel lenses do not pass through the multiple optical microstructures.

[0016] In one embodiment of the present invention, the backlight module further comprises a reflective structure layer having multiple openings, which is installed between a plurality of Fresnel lenses and a circuit board. Multiple light-emitting elements are installed within these openings.

[0017] In one embodiment of the present invention, the backlight module further comprises a light guide plate, auxiliary light-emitting elements, and a plurality of optical microstructures. The light guide plate is installed between the plurality of light-emitting elements and the plurality of Fresnel lenses and covers the plurality of light-emitting surfaces of these elements. The auxiliary light-emitting elements are installed on one side of the light-receiving surface of the light guide plate. The plurality of optical microstructures are installed on a second surface of the light guide plate and are located between the plurality of light-emitting elements. The second surface is connected to the light-receiving surface and faces the circuit board.

[0018] In one embodiment of the present invention, the optical brightness enhancing film of the backlight module is a reflective polarizing brightness enhancing film.

[0019] In one embodiment of the present invention, the backlight module further includes a reflective sheet installed on a circuit board and exposes a plurality of light-emitting elements.

[0020] To achieve some or all of the aforementioned objectives, or other objectives, an embodiment of the present invention provides a display device. The display device comprises a backlight module and a display panel. The backlight module comprises a circuit board, a plurality of light-emitting elements, an anisotropic diffusion sheet, a plurality of Fresnel lenses, and an optical brightness enhancing film. The plurality of light-emitting elements are mounted on the circuit board. The anisotropic diffusion sheet is mounted on one side of the light-emitting surface of each light-emitting element. The plurality of Fresnel lenses are mounted between the plurality of light-emitting elements and the anisotropic diffusion sheet, and are mounted so as to overlap these light-emitting elements. The optical brightness enhancing film is mounted on the side of the anisotropic diffusion sheet that faces away from the plurality of Fresnel lenses. The display panel is mounted on the side of the optical brightness enhancing film that faces away from the plurality of light-emitting elements.

[0021] In one embodiment of the present invention, the backlight module of the display device further comprises a light guide plate and a plurality of free-form surface lenses. The light guide plate is installed between a plurality of light-emitting elements and a plurality of Fresnel lenses and covers a plurality of light-emitting surfaces of these elements. The plurality of free-form surface lenses are installed on a first surface of the light guide plate that faces away from the circuit board and each overlaps with one of these light-emitting elements.

[0022] In one embodiment of the present invention, the plurality of light-emitting elements of the display device include a plurality of first light-emitting elements and a plurality of second light-emitting elements. Each Fresnel lens has an optical axis. The plurality of optical axes of the plurality of Fresnel lenses each pass through the plurality of first light-emitting elements, and each second light-emitting element overlaps the connection between two adjacent Fresnel lenses along the direction normal to the first surface.

[0023] In one embodiment of the present invention, when a plurality of first light-emitting elements of the display device are enabled and a plurality of second light-emitting elements are disabled, the display device operates in privacy mode. When a plurality of first light-emitting elements are disabled and a plurality of second light-emitting elements are enabled, the display device operates in shared mode.

[0024] Based on the above, in the backlight module and the display device according to an embodiment of the present invention, a plurality of Fresnel lenses, an anisotropic diffusion sheet, and an optical brightness enhancement film are installed in this order on the plurality of light-emitting surfaces of the plurality of light-emitting elements installed on the circuit board. The light diffusion ability of the anisotropic diffusion sheet can improve the quality of the backlight module, and the difference in the light diffusion ability in different directions satisfies the requirements of various light patterns, and can improve the utilization efficiency of the light energy of the backlight module.

[0025] As above, the present invention has been disclosed using embodiments, but the present invention is not limited thereto. Those skilled in the art can make some modifications without departing from the spirit scope of the present invention. Therefore, the protection scope of the present invention shall be limited by the appended claims.

Brief Description of the Drawings

[0026] [Figure 1] FIG. ! is a cross-sectional view of a display device according to Embodiment 1 of the present invention. [Figure 2A] FIG. 2A is a top view of the Fresnel lens in FIG. 1. [Figure 2B] FIG. 2B is a top view of another embodiment of the Fresnel lens in FIG. 1. [Figure 3] FIG. 3 is a schematic diagram of the light diffusion effect of the anisotropic diffusion sheet in FIG. 1. [Figure 4] FIG. 4 is a cross-sectional view of a display device according to Embodiment 2 of the present invention. [Figure 5A] FIG. 5A is a perspective view of the free-form surface lens in FIG. 4. [Figure 5B] FIG. 5B is a perspective view of another embodiment of the free-form surface lens in FIG. 4. [Figure 6] FIG. 6 is a light output distribution diagram of the backlight module in FIG. 4. [Figure 7] FIG. 7 is a light output distribution diagram of the backlight module according to the comparative example. [Figure 8] FIG. 8 is a cross-sectional view of the display device according to the comparative example. It should be noted that there is an error in the "!" in the English translation of "FIG. ! is a cross-sectional view of a display device according to Embodiment 1 of the present invention. ", which should be "FIG. 1". The rest of the translation is adjusted according to the correct content. [Figure 9] Figure 9 is a cross-sectional view of a display device according to Embodiment 3 of the present invention. [Figure 10] Figure 10 is a magnified view of the optical brightness-enhancing film shown in Figure 9. [Figure 11] Figure 11 is a distribution diagram of normalized luminance with respect to viewing angle for the display device shown in Figure 9. [Figure 12] Figure 12 is a light emission distribution diagram of the backlight module shown in Figure 9. [Figure 13] Figure 13 shows the arrangement of the display device shown in Figure 9 when used as a head-up display. [Figure 14] Figure 14 is a cross-sectional view of a display device according to Embodiment 4 of the present invention. [Figure 15] Figure 15 is a cross-sectional view of a display device according to Embodiment 5 of the present invention. [Figure 16] Figure 16 is a cross-sectional view of a display device according to Embodiment 6 of the present invention. [Figure 17] Figure 17 is a cross-sectional view of a display device according to Embodiment 7 of the present invention. [Figure 18] Figure 18 is a light emission distribution diagram of the backlight module shown in Figure 17. [Figure 19] Figure 19 is a cross-sectional view of a display device according to Embodiment 8 of the present invention. [Figure 20A] Figure 20A is a cross-sectional view of the display device according to Embodiment 9 of the present invention when it is operating in privacy mode. [Figure 20B] Figure 20B is a cross-sectional view of the display device according to Embodiment 9 of the present invention when it is operating in shared mode. [Modes for carrying out the invention]

[0027] The above-mentioned and other technical details, features, and effects relating to the present invention will be clearly shown below in a detailed description with reference to one preferred embodiment in the attached drawings. The directional terms used in the following embodiments, such as "up," "down," "left," "right," "front," or "back," are merely for reference to the directions in the attached drawings. Therefore, these directional terms are used for illustrative purposes only and do not limit the present invention.

[0028] Figure 1 is a cross-sectional view of a display device according to Embodiment 1 of the present invention. Figure 2A is a top view of the Fresnel lens of Figure 1. Figure 2B is a top view of another embodiment of the Fresnel lens of Figure 1. Figure 3 is a schematic diagram of the light diffusion effect by the anisotropic diffusion sheet of Figure 1.

[0029] Referring to Figure 1, the display device 10 comprises a backlight module BLM and a display panel DP. The backlight module BLM comprises a circuit board 100 and a plurality of light-emitting elements 120. These light-emitting elements 120 are mounted on the circuit board 100 and electrically connected to the circuit board 100. For example, these light-emitting elements 120 are arranged in an array on the circuit board 100, and the circuit board 100 controls these light-emitting elements 120 individually to emit light. In other embodiments, the backlight module BLM has a local dimming function, but is not limited to this. In this embodiment, the light-emitting elements 120 are, for example, mini-LEDs (mini light-emitting diodes, mini-LEDs), but are not limited to this. In another embodiment, the light-emitting elements 120 may be micro-LEDs.

[0030] Each light-emitting element 120 has a light-emitting surface 120es facing away from the circuit board 100. The backlight module BLM further comprises a plurality of Fresnel lenses 220, an anisotropic diffusion sheet 300, and an optical brightness enhancing film 400 on one side of each light-emitting surface 120es of the plurality of light-emitting elements 120. The plurality of Fresnel lenses 220 are installed between the plurality of light-emitting elements 120 and the anisotropic diffusion sheet 300. The optical brightness enhancing film 400 is installed on the side of the anisotropic diffusion sheet 300 that faces away from these Fresnel lenses 220. The display panel DP is installed on the side of the optical brightness enhancing film 400 that faces away from these light-emitting elements 120. However, in another embodiment, the light-emitting surface of the light-emitting element is not limited to the surface facing away from the circuit board, but furthermore, the side of the light-emitting element, or both the surface facing away from the circuit board and the side of the light-emitting element, may be the light-emitting surface.

[0031] In this embodiment, the backlight module BLM further comprises a light guide plate 200. The light guide plate 200 is installed between a plurality of light-emitting elements 120 and an anisotropic diffusion sheet 300, and a plurality of Fresnel lenses 220 are installed on a first surface 200s1 of the light guide plate 200 that faces away from the circuit board 100. However, the present invention is not limited thereto. In another embodiment, these Fresnel lenses 220 may be installed on a second surface 200s2 of the light guide plate 200 that faces the circuit board 100, or they may be installed on both the first surface 200s1 and the second surface 200s2 of the light guide plate 200. The first surface 200s1 and the second surface 200s2 face in opposite directions to each other. For example, in this embodiment, the Fresnel lens 220 may have multiple stripe-shaped prisms arranged along one direction (e.g., direction X) parallel to the first surface 200s1 (see Figure 2A), that is, the Fresnel lens 220 in this embodiment is a one-dimensional lens structure. However, the present invention is not limited thereto. In another embodiment, the Fresnel lens 220A may have multiple annular prisms arranged in a concentric manner (see Figure 2B), that is, the Fresnel lens 220A is a two-dimensional lens structure.

[0032] In this embodiment, it is important to note that each of the multiple Fresnel lenses 220 has an optical axis OA, and each of these multiple optical axes OA of the Fresnel lenses 220 passes through each of the multiple light-emitting elements 120. In other words, each of these Fresnel lenses 220 is installed to correspond to each of the multiple light-emitting elements 120, that is, they are installed to overlap with the multiple light-emitting elements 120. The Fresnel lenses 220 are used to convert the light rays emitted from the light-emitting elements 120 into collimated light.

[0033] The anisotropic diffusion sheet 300 has different light diffusion capabilities in different dimensions parallel to the film surface 300s. For example, in this embodiment, the anisotropic diffusion sheet 300 expands the optical shape of the light ray L along a specific direction (e.g., axial AD1) and maintains the optical shape of the light ray L in a direction perpendicular to the specific direction (e.g., axial AD2) (see Figure 3). Therefore, by installing the anisotropic diffusion sheet 300, not only is the quality of the backlight module BLM improved, but various optical shape requirements are also satisfied, and the utilization efficiency of the light energy of the backlight module BLM can be further improved.

[0034] On the other hand, in this embodiment, the optical brightness enhancement film 400 is, for example, a reflective polarizing brightness enhancement film (Dual Brightness Enhancement Film, DBEF), which gives a single polarization state to the passing light rays and improves the transmittance of the light rays emitted from the backlight module BLM through the display panel DP. However, the present invention is not limited thereto. In another embodiment, the optical brightness enhancement film 400 may further consist of two prism sheets whose prism stretching directions are orthogonal to each other.

[0035] In this embodiment, in order to increase the light emission efficiency of the light-emitting elements 120, the backlight module BLM further includes a reflective sheet 140 installed on the circuit board 100 and not overlapping with the light-emitting elements 120. From another perspective, this reflective sheet 140 is positioned between the multiple light-emitting elements 120, exposing these light-emitting elements 120. The reflective sheet 140 reflects the light rays emitted from the light-emitting elements 120 toward the circuit board 100 toward the display panel DP.

[0036] The present disclosure will be described in detail below with reference to other embodiments. The same reference numerals will be used for the same components, and the same technical details will be omitted. Note that for omitted parts, you can refer to the previously described embodiments, and redundant explanations will be omitted below.

[0037] Figure 4 is a cross-sectional view of a display device according to Embodiment 2 of the present invention. Figure 5A is a perspective view of the free-form surface lens of Figure 4. Figure 5B is a perspective view of another embodiment of the free-form surface lens of Figure 4. Figure 6 is a light emission distribution diagram of the backlight module of Figure 4. Figure 7 is a light emission distribution diagram of a backlight module according to a comparative example. Figure 8 is a cross-sectional view of a display device according to a comparative example.

[0038] Referring to Figure 4, compared to the display device 10 of Figure 1, the backlight module BLM-A of the display device 10A in this embodiment further comprises a light guide plate 250 and a plurality of free-form lenses 255. The light guide plate 250 is positioned between a plurality of light-emitting elements 120 and a plurality of Fresnel lenses 220, covering a plurality of light-emitting surfaces 120es of these light-emitting elements 120. These free-form lenses 255 are positioned on a first surface 250s1 of the light guide plate 250 that faces away from the circuit board 100, and each of them overlaps with these light-emitting elements 120 along the normal direction (e.g., direction Z) of the first surface 250s1. In other words, the plurality of free-form lenses 255 are positioned so that each corresponds to a plurality of light-emitting elements 120.

[0039] The free-form surface lens 255 is used to focus the light ray L1 emitted from the light-emitting element 120 in the direction normal to the first surface 250s1 (for example, direction Z). The Fresnel lens 220 is used to convert the light ray L1 from the free-form surface lens 255 into collimated light. For example, in this embodiment, the free-form surface lens 255 may be a one-dimensional lens structure such as a cylindrical lens, as shown in Figure 5A. However, the present invention is not limited thereto. In another embodiment, the free-form surface lens 255A may further be a two-dimensional lens structure (see Figure 5B). In this embodiment, the light-emitting element 120 is embedded in the light guide plate 250. More specifically, with respect to the surface on the circuit board 100 on which the light-emitting element 120 is provided as the reference plane, the height of the light-emitting surface 120es of the light-emitting element 120 is higher than the height of the second surface 250s2 of the light guide plate 250 facing the circuit board 100, but is not limited thereto. In another embodiment, the light-emitting element 120 is not embedded in the light guide plate 250. More specifically, when the surface on the circuit board 100 on which the light-emitting element 120 is provided is taken as the reference plane, the height of the light-emitting surface 120es of the light-emitting element 120 is less than or equal to the height of the second surface 250s2 of the light guide plate 250 that faces the circuit board 100.

[0040] Furthermore, the backlight module BLM-A further comprises an auxiliary light-emitting element 260 and a plurality of optical microstructures OMS. The auxiliary light-emitting element 260 is installed on one side of the light-receiving surface 250is of the light guide plate 250, the light-receiving surface 250is connecting a first surface 250s1 and a second surface 250s2. The plurality of optical microstructures OMS are installed on the second surface 250s2 of the light guide plate 250. For example, in this embodiment, the optical microstructures OMS may be protruding structures that project outward from the second surface 250s2 of the light guide plate 250, but are not limited thereto. In another embodiment, the optical microstructures may further be recessed structures that are recessed inward from the second surface 250s2 of the light guide plate 250.

[0041] It should be noted that the multiple optical microstructures OMS are located between the multiple light-emitting elements 120. More specifically, in the direction normal to the second surface 250s2 of the light guide plate 250 (e.g., direction Z), these optical microstructures OMS do not overlap with the multiple free-form lenses 255. In this embodiment, the light rays L2 emitted from the auxiliary light-emitting element 260 propagate within the light guide plate 250 and are reflected by the multiple optical microstructures OMS and propagated into the space between the multiple free-form lenses 255. This increases the amount of light emitted in the dark areas formed between the multiple light-emitting elements 120 of the backlight module BLM-A, and reduces the impact of these dark areas on display quality.

[0042] Figure 8 shows a comparative example display device 11C. Referring to Figures 4 and 8, the comparative example backlight module BLM'' does not have the light guide plate 250, the multiple free-form surface lenses 255, the auxiliary light-emitting element 260, and the multiple Fresnel lenses 220 of the backlight module BLM-A in this embodiment. In the comparative example backlight module BLM'', the diffusion sheet 300'' has the same light diffusion capability in any direction parallel to the film surface, that is, there is no anisotropy in the light diffusion capability of the diffusion sheet 300'' in the comparative example. On the other hand, in the comparative example backlight module BLM'', a prism sheet 450 is further installed between the diffusion sheet 300'' and the optical brightness-enhancing film 400, and the prism sheet 450 has multiple prism structures 455, and these prism structures 455 are arranged along direction X.

[0043] As is clear from Figures 6 and 7, the BLM-A backlight module of this embodiment has significantly superior light-gathering capabilities compared to the BLM'' backlight module of the comparative example. Furthermore, the front brightness of the BLM-A backlight module of this embodiment reaches 4.2 times that of the BLM'' backlight module of the comparative example.

[0044] Referring to Figures 4 and 6, in this embodiment, the anisotropic diffusion sheet 300 expands the optical shape of the light ray along direction Y and maintains the optical shape in direction X. That is, the axial directions AD1 and AD2 in Figure 3 are parallel to directions Y and X in Figure 4, respectively.

[0045] Figure 9 is a cross-sectional view of a display device according to Embodiment 3 of the present invention. Figure 10 is an enlarged view of the optical brightness enhancement film in Figure 9. Figure 11 is a normalized brightness distribution diagram with respect to viewing angle in the display device of Figure 9. Figure 12 is a light emission distribution diagram of the backlight module in Figure 9. Figure 13 is a diagram showing the arrangement when the display device of Figure 9 is used as a head-up display.

[0046] Referring to Figures 9 and 10, compared to the display device 10A in Figure 4, the optical brightness enhancement film 400A in the backlight module BLM-B of the display device 10B of this embodiment has a further plurality of prism structures 420 installed on the film surface 400s facing away from the plurality of light-emitting elements 120. In this embodiment, these prism structures 420 are arranged along direction X and extend in direction Y. Each of these prism structures 420 comprises a first optical surface 420s1 and a second optical surface 420s2 that are connected to each other. The angle of the first bottom angle A1 formed between the first optical surface 420s1 and the film surface 400s is greater than the angle of the second bottom angle A2 formed between the second optical surface 420s2 and the film surface 400s.

[0047] The multiple first optical surfaces 420s1 and the multiple second optical surfaces 420s2 in the multiple prism structures 420 are arranged alternately along one direction (e.g., direction X) parallel to the film surface 400s. From another perspective, all of the multiple first optical surfaces 420s1 in these prism structures 420 face one side of the optical brightness-enhancing film 400A, and all of the multiple second optical surfaces 420s2 face the other side of the optical brightness-enhancing film 400A.

[0048] The installation of these prism structures 420 makes it possible to deflect the light rays passing through the optical brightness enhancement film 400A from the normal direction of the film surface 400s and guide them to a specific viewing angle. For example, the peak value of the emitted light shape of the backlight module BLM-B in this embodiment is deflected at the viewing angle θ by the installation of the prism structure 420. The viewing angle θ is, for example, in the range of 10 to 20 degrees (see Figure 11). Comparing Figures 6 and 12, it can be seen that the emitted light distribution of the backlight module BLM-B in this embodiment is deflected at least 10 degrees vertically compared to the emitted light distribution of the backlight module BLM-A in Figure 4.

[0049] Based on the emission characteristics described above, the display device 10B of this embodiment is used as a head-up display for automobiles (see Figure 13). The display image of the display device 10B is projected onto the vehicle's windshield WS for the driver's DVR to view. Because the light emission distribution of the backlight module BLM-B of this embodiment is deflected by a specific angle (i.e., viewing angle θ) from the front, the display surface DS of the display device 10B does not need to be positioned directly facing the projection path. For example, the normal direction of the display surface DS can be deflected at least 10 degrees from the projection path (or the projection path can be positioned directly facing the viewing angle θ of the display device 10B). In this way, the display surface DS of the display device 10B can be positioned as far as possible toward the windshield WS, reducing or avoiding the impact on driving safety caused by the driver's DVR directly viewing the display screen. At the same time, the light emission distribution deflected from the front further maximizes the display efficiency when using the display device 10B as a head-up display.

[0050] Figure 14 is a cross-sectional view of a display device according to Embodiment 4 of the present invention. Figure 15 is a cross-sectional view of a display device according to Embodiment 5 of the present invention. Referring to Figure 14, the difference between the display device 10C of this embodiment and the display device 10B of Figure 9 is that the arrangement of the auxiliary light-emitting element and the optical microstructure is different.

[0051] Specifically, in this embodiment, the auxiliary light-emitting element 260 of the backlight module BLM-C is installed on one side of the light-receiving surface 200is of the light guide plate 200, and the multiple optical microstructures OMS are installed on the second surface 200s2 of the light guide plate 200 facing the circuit board 100 and are located between the multiple light-emitting elements 120. The first surface 200s1 and the second surface 200s2 are connected to the light-receiving surface 200is. It should be noted that the multiple optical axes OA of the multiple Fresnel lenses 220 installed on the first surface 200s1 of the light guide plate 200 do not pass through these optical microstructures OMS.

[0052] The technical effects that the auxiliary light-emitting element 260 and the multiple optical microstructures OMS in this embodiment have on the backlight module BLM-C are similar to the technical effects that the auxiliary light-emitting element 260 and the multiple optical microstructures OMS have on the backlight module BLM-B in Figure 9. For a detailed explanation, please refer to the relevant paragraphs in the above-mentioned embodiment. A detailed explanation will not be repeated here.

[0053] However, the present invention is not limited thereto. In another embodiment of the display device 10D, the backlight module BLM-D omits the installation of the light guide plate 250 and the multiple free-form surface lenses 255 shown in Figure 14 (see Figure 15).

[0054] Figure 16 is a cross-sectional view of a display device according to Embodiment 6 of the present invention. Referring to Figure 16, compared to the display device 10D of Figure 15, the backlight module BLM-E of the display device 10E of this embodiment further comprises a reflective structural layer 180 for improving the light emission efficiency of the light-emitting element 120. The reflective structural layer 180 is installed between a plurality of Fresnel lenses 220 and a circuit board 100 and has a plurality of openings 180op. The plurality of light-emitting elements 120 are installed within these openings 180op. In this embodiment, the reflective structural layer 180 is, for example, a reflective grid, but is not limited thereto.

[0055] Figure 17 is a cross-sectional view of a display device according to Embodiment 7 of the present invention. Figure 18 is a light emission distribution diagram of the backlight module in Figure 17. Referring to Figure 17, in the display device 10F of this embodiment, the multiple prism structures 420 shown in Figure 16 are not installed on the optical brightness enhancement film 400 of the backlight module BLM-F. From Figures 7 and 18, it can be seen that the backlight module BLM-F of this embodiment has significantly better light focusing ability compared to the backlight module BLM'' of the comparative example. Furthermore, it can be seen that the front brightness of the backlight module BLM-F of this embodiment reaches 2.2 times that of the backlight module BLM'' of the comparative example.

[0056] Figure 19 is a cross-sectional view of a display device according to Embodiment 8 of the present invention. Referring to Figure 19, in the display device 10G of this embodiment, the backlight module BLM-G omits the installation of the multiple free-form surface lenses 255 shown in Figure 9. The other components of the backlight module BLM-G of this embodiment and the technical effects resulting therefrom are similar to those of the backlight module BLM-B in Figure 9. For a detailed explanation, please refer to the relevant paragraphs of the above-mentioned embodiments. A detailed explanation will not be repeated here.

[0057] Figures 20A and 20B are cross-sectional views of the display device according to Embodiment 9 of the present invention when it is operating in privacy mode and sharing mode, respectively. Referring to Figures 20A and 20B, the main difference between the display device 10H of this embodiment and the display device 10A of Figure 4 is that the arrangement of the light-emitting element and the free-form surface lens is different.

[0058] Specifically, in this embodiment, the multiple light-emitting elements 120A in the backlight module BLM-H include multiple first light-emitting elements 121 and multiple second light-emitting elements 122. Multiple optical axes OA of the multiple Fresnel lenses 220 each pass through the multiple first light-emitting elements 121. Multiple second light-emitting elements 122 each overlap the connection between two adjacent Fresnel lenses 220 along the normal direction (e.g., direction Z) of the light-emitting surface 120es.

[0059] It should be noted that a free-form lens 255 is installed correspondingly on the light-emitting surface 120es of each of the multiple first light-emitting elements 121 and the multiple second light-emitting elements 122. In other words, in this embodiment, some of the free-form lenses 255 are not installed on the multiple optical axes OA of the multiple Fresnel lenses 220.

[0060] When multiple first light-emitting elements 121 are enabled and multiple second light-emitting elements 122 are disabled, the range of emission angles of the light rays La emitted from each first light-emitting element 121, after their optical path is altered by passing through the free-form surface lens 255 and the Fresnel lens 220, converges when they are emitted from the backlight module BLM-H compared to the range of emission angles when the light rays La are emitted from each first light-emitting element 121. At this time, user USR1, who is viewing the display device 10H from the front, is positioned exactly on the positive optical path of the light rays La emitted from the multiple first light-emitting elements 121 and can see the display screen of the display panel DP. However, users USR2 and USR3, who are viewing the display device 10H from an oblique direction, are positioned outside the positive optical path of the light rays La and cannot see the display screen (see Figure 20A). In other words, the display device 10H is operating in privacy mode at this time.

[0061] When multiple first light-emitting elements 121 are disabled and multiple second light-emitting elements 122 are enabled (see Figure 20B), the light rays Lb emitted from each second light-emitting element 122 in the figure have their optical paths altered by passing through the free-form lens 255 and the Fresnel lens 220, and are then emitted from the backlight module BLM-H at a large angle, far from the normal direction of the light-emitting surface 120es. Therefore, users USR2 and USR3, who view the display device 10H from an oblique direction, are positioned exactly on the oblique optical path of the light rays Lb emitted from the multiple second light-emitting elements 122, and can see the display screen of the display panel DP. However, user USR1, who views the display device 10H from the front, is positioned outside the oblique optical path of the light rays Lb and cannot see the display screen. In other words, the display device 10H is operating in shared mode at this time.

[0062] In other words, by switching the open / closed state of the first light-emitting element 121 and the second light-emitting element 122, it is possible to switch the operating mode of the display device 10H between privacy mode and shared mode. On the other hand, the backlight module BLM-H of this embodiment does not have the auxiliary light-emitting element 260 and multiple optical microstructures OMS shown in Figure 4. However, the present invention is not limited to the shared mode described above. In another shared mode, multiple first light-emitting elements 121 and multiple second light-emitting elements 122 are enabled simultaneously. At this time, user USR1, who is viewing the display device 10H from the front, and users USR2 and USR3, who are viewing the display device 10H from an angle, can all see the display screen of the display panel DP.

[0063] In summary, in one embodiment of the present invention, a backlight module and display device are provided in the following order on multiple light-emitting surfaces of multiple light-emitting elements mounted on a circuit board: multiple Fresnel lenses, an anisotropic diffusion sheet, and an optical brightness-enhancing film. The light diffusion capability of the anisotropic diffusion sheet can improve the quality of the backlight module, and the differences in its light diffusion capability in different directions can satisfy the requirements of various optical shapes and improve the utilization efficiency of the light energy of the backlight module.

[0064] The above description is merely a preferred embodiment of the present invention, and the scope of implementation of the present invention is not limited thereto. Simple and equivalent changes and modifications based on the claims and specifications of the present invention also fall within the scope of the present invention. Furthermore, any single embodiment or claim of the present invention does not necessarily have to achieve all the purposes, advantages, or features disclosed by the present invention. In addition, the abstract and the title of the invention are provided solely for patent search purposes and are not intended to limit the scope of the claims of the present invention. Moreover, terms such as "first," "second," etc., mentioned in this specification or the claims of the present invention are merely names for elements or for distinguishing different embodiments or scopes, and do not limit the upper or lower limits on the quantity of elements. [Explanation of Symbols]

[0065] 10, 10A, 10B, 10C, 10D, 10E, 10F, 10G, 10H, 11C: Display device 100: Circuit board 120, 120A, 121, 122: Light-emitting elements 121: First light-emitting element 122: Second light-emitting element 120es:Idemitsu surface 140: Reflective sheet 180: Reflective structure layer 180op: opening 200, 250: Light guide plate 200is, 250is: Light entrance surface 200s1, 250s1: First surface 200s2, 250s2: Second surface 220, 220A: Fresnel lens 255, 255A: Free-form surface lenses 260: Auxiliary light-emitting element 300: Anisotropic diffusion sheet 300″: Diffusion Sheet 300s, 400s: Film surface 400, 400A: Optical brightness enhancement film 420, 455: Prism structure 420s1: 1st optical surface 420s2: 2nd optical surface 450: Prism Sheet A1: First base angle A2: Second base angle AD1, AD2: Axial direction BLM, BLM-A, BLM-B, BLM-C, BLM-D, BLM-E, BLM-F, BLM-G, BLM-H, BLM″: Backlight Module DP: Display Panel DS:Display surface DVR: Driver L, L1, L2, La, Lb: Ray OA: optical axis OMS: Optical Microstructure USR1, USR2, USR3: User WS: Windshield X, Y, Z: direction θ: viewing angle

Claims

1. Circuit board and Multiple light-emitting elements are installed on the circuit board, An anisotropic diffusion sheet is installed on one side of the light-emitting surface of each of the plurality of light-emitting elements, A plurality of Fresnel lenses are installed between the plurality of light-emitting elements and the anisotropic diffusion sheet, and are installed so as to overlap the plurality of light-emitting elements. An optical brightness enhancing film is installed on the side of the anisotropic diffusion sheet facing away from the plurality of Fresnel lenses, A backlight module characterized by comprising the following features.

2. The backlight module according to claim 1, characterized in that each of the plurality of Fresnel lenses has an optical axis, and each of the plurality of optical axes of the plurality of Fresnel lenses passes through the plurality of light-emitting elements.

3. A light guide plate is installed between the plurality of light-emitting elements and the plurality of Fresnel lenses, and covers the plurality of light-emitting surfaces of the plurality of light-emitting elements. A plurality of free-form surface lenses are installed on the first surface of the light guide plate facing away from the circuit board, and each of the plurality of light-emitting elements overlaps with the plurality of light-emitting elements, The backlight module according to claim 1, further comprising the following:

4. An auxiliary light-emitting element is installed on one side of the light-receiving surface of the light guide plate, The system further comprises a plurality of optical microstructures, which are placed on the second surface of the light guide plate and located between the plurality of light-emitting elements, The light-receiving surface connects the first surface and the second surface, and the second surface faces the circuit board. The backlight module according to claim 3.

5. The backlight module according to claim 4, wherein the plurality of optical microstructures do not overlap with the plurality of free-form surface lenses along the normal direction of the second surface.

6. The backlight module according to claim 3, wherein the plurality of light-emitting elements include a plurality of first light-emitting elements and a plurality of second light-emitting elements, each of the plurality of Fresnel lenses has an optical axis, each of the plurality of optical axes of the plurality of Fresnel lenses passes through the plurality of first light-emitting elements, and each of the plurality of second light-emitting elements overlaps the connection between two adjacent Fresnel lenses along the normal direction of the light-emitting surface.

7. The backlight module according to claim 1, characterized in that the optical brightness enhancing film has a plurality of prism structures provided on the film surface facing away from the plurality of light-emitting elements.

8. The backlight module according to claim 7, characterized in that each of the plurality of prism structures includes a first optical surface and a second optical surface connected to each other, the first bottom angle between the first optical surface and the film surface is greater than the second bottom angle between the second optical surface and the film surface, and the plurality of first optical surfaces and the plurality of second optical surfaces of the plurality of prism structures are alternately arranged along one direction parallel to the film surface.

9. A light guide plate is installed between the plurality of light-emitting elements and the anisotropic diffusion sheet, and has a light-receiving surface and a first surface and a second surface connected to the light-receiving surface and facing away from each other. An auxiliary light-emitting element is installed on one side of the light surface of the light guide plate, The light guide plate further comprises a plurality of optical microstructures, which are placed on the second surface of the light guide plate and located between the plurality of light-emitting elements. The backlight module according to claim 1, wherein the plurality of Fresnel lenses are installed on the first surface of the light guide plate.

10. The backlight module according to claim 9, wherein each of the plurality of Fresnel lenses has an optical axis, and the plurality of optical axes of the plurality of Fresnel lenses do not pass through the plurality of optical microstructures.

11. The backlight module according to claim 1, further comprising a reflective structure layer having a plurality of openings, which is installed between the plurality of Fresnel lenses and the circuit board, and wherein the plurality of light-emitting elements are installed within the plurality of openings.

12. A light guide plate is installed between the plurality of light-emitting elements and the plurality of Fresnel lenses, and covers the plurality of light-emitting surfaces of the plurality of light-emitting elements. An auxiliary light-emitting element is installed on one side of the light-receiving surface of the light guide plate, The system further comprises a plurality of optical microstructures, which are placed on the second surface of the light guide plate and located between the plurality of light-emitting elements, The backlight module according to claim 1, wherein the second surface is connected to the light-receiving surface and faces the circuit board.

13. The backlight module according to claim 1, wherein the optical brightness-enhancing film is a reflective polarizing brightness-enhancing film.

14. The backlight module according to claim 1, further comprising a reflective sheet installed on the circuit board and exposing the plurality of light-emitting elements.

15. It includes a backlight module, and the backlight module is Circuit board and Multiple light-emitting elements are installed on the circuit board, An anisotropic diffusion sheet is installed on one side of the light-emitting surface of each of the plurality of light-emitting elements, A plurality of Fresnel lenses are installed between the plurality of light-emitting elements and the anisotropic diffusion sheet, and are installed so as to overlap the plurality of light-emitting elements. The anisotropic diffusion sheet comprises an optical brightness enhancing film installed on the side facing away from the plurality of Fresnel lenses, A display device further characterized by comprising a display panel installed on the side of the optical brightness-enhancing film that faces away from the plurality of light-emitting elements.

16. The backlight module further, A light guide plate is installed between the plurality of light-emitting elements and the plurality of Fresnel lenses, and covers the plurality of light-emitting surfaces of the plurality of light-emitting elements. A plurality of free-form surface lenses are installed on the first surface of the light guide plate facing away from the circuit board, and each of the plurality of light-emitting elements overlaps with the plurality of free-form surface lenses, The display device according to claim 15, characterized by comprising:

17. The display device according to claim 16, wherein the plurality of light-emitting elements include a plurality of first light-emitting elements and a plurality of second light-emitting elements, each of the plurality of Fresnel lenses has an optical axis, each of the plurality of optical axes of the plurality of Fresnel lenses passes through each of the plurality of first light-emitting elements, and each of the plurality of second light-emitting elements overlaps with the connection between two adjacent Fresnel lenses along the direction normal to the first surface.

18. The display device according to claim 17, characterized in that when the plurality of first light-emitting elements are enabled and the plurality of second light-emitting elements are disabled, the display device operates in privacy mode, and when the plurality of first light-emitting elements are disabled and the plurality of second light-emitting elements are enabled, the display device operates in shared mode.

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