Backlight module

Abstract

The invention discloses a backlight module which comprises the following characteristics. The peep-proof sheet is arranged on a transmission path of a light beam of the light source assembly. The light guide plate is arranged on the side, back to the light source assembly, of the peep-proof piece and provided with a light incident face, a surface and a plurality of optical microstructures. The surface of the light incident surface faces the peep-proof sheet and is connected with the light incident surface. The optical microstructures are recessed or protruded out of the surface and are respectively provided with a first convex curved surface, a second convex curved surface and a fillet. The first convex curved surface and the second convex curved surface stand on the surface, and the fillet connects the first convex curved surface and the second convex curved surface. The first included angle between each first convex curved surface and the surface ranges from 30 degrees to 70 degrees, and the curvature radius of the fillet ranges from 0.001 mm to 0.005 mm. When the optical microstructure is recessed in the surface, the first convex curved surface faces the light incident surface. When the optical microstructures protrude out of the surface, the first convex curved surface is back to the light incident surface.

Description

Technical Field

[0001] The invention relates to an optical module, in particular to a backlight module. Background Art

[0002] The components of a liquid crystal display mainly include a backlight module, a display panel, and a frame. As liquid crystal displays are widely used in various occasions, many backlight modules will also provide an anti-peeping function. For example, when the backlight module is in the sharing state, more light beams will be emitted at a large angle, so that the backlight module can provide a larger viewing angle. On the contrary, when the backlight module is in the anti-peeping state, more light beams will be emitted at a small angle to reduce the viewing angle.

[0003] However, the existing backlight module still has the problem of insufficient brightness at large angles when in the sharing state, thus affecting the viewing angle in the sharing state. Increasing the light source brightness of the backlight module can slightly improve the problem of insufficient brightness at large angles, but it also makes the backlight module prone to overheating. In addition, the existing backlight module can only provide symmetrical viewing angles in the horizontal viewing angle when in the sharing state, resulting in limited application occasions. Summary of the invention

[0004] The invention provides a backlight module to improve the light output brightness at a large angle and provide an asymmetric viewing angle at a horizontal viewing angle.

[0005] To achieve one or part or all of the above purposes or other purposes, an embodiment of the present invention provides a backlight module, including a light source assembly, a privacy film, a first light-emitting element and a first light guide plate. The light source assembly is suitable for emitting a light beam. The privacy film is arranged on the transmission path of the light beam. The first light guide plate is arranged on the side of the privacy film that is opposite to the light source assembly. The first light guide plate has a first light incident surface, a surface and a plurality of optical microstructures. The first light incident surface is opposite to the first light-emitting element, and the surface faces the privacy film and is connected to the first light incident surface. The optical microstructure is recessed or protrudes from the surface, and has a first convex surface, a second convex surface and a rounded corner respectively. The first convex surface and the second convex surface stand on the surface, and the rounded corner connects the first convex surface and the second convex surface. The first angle between each first convex surface and the surface is between 30° and 70°, and the radius of curvature of the rounded corner is between 0.001 mm and 0.005 mm. When the optical microstructure is recessed in the surface, the first convex surface faces the first light incident surface and the second convex surface faces away from the first light incident surface. When the optical microstructure protrudes from the surface, the first convex curved surface faces away from the first light incident surface and the second convex curved surface faces toward the first light incident surface.

[0006] In an embodiment of the present invention, each of the first angles mentioned above is, for example, between 40° and 60°.

[0007] In one embodiment of the present invention, each of the optical microstructures has a vertex. Each first convex surface forms a first profile on the surface. Each first convex surface may have a first imaginary tangent line, and each optical microstructure may also have an imaginary cross section. Each imaginary cross section passes through each first vertex and is perpendicular to the first light incident surface and the surface. Each first imaginary tangent line passes through each first vertex and is located on each imaginary cross section, and a first angle may be formed between the first imaginary tangent line and the surface.

[0008] In an embodiment of the present invention, the second included angle between each of the second convex curved surfaces and the surface is, for example, between 20° and 40°.

[0009] In one embodiment of the present invention, each of the second convex surfaces forms a second profile on the surface. Each second profile is a curve and has a second vertex that is protruding away from each first convex surface. Each second convex surface may have a second imaginary tangent line, and each optical microstructure may also have an imaginary cross section. Each imaginary cross section passes through each second vertex and is perpendicular to the first light incident surface and the surface. Each second imaginary tangent line passes through each second vertex and is located on each imaginary cross section, and a second angle may be formed between the second imaginary tangent line and the surface.

[0010] In one embodiment of the present invention, the maximum length of each of the optical microstructures in the normal direction of the first light incident surface may be between 0.005 mm and 0.050 mm.

[0011] In one embodiment of the present invention, the maximum width of each optical microstructure in a direction perpendicular to the normal direction of the first light incident surface is W. Each optical microstructure further has a vertex, each vertex is located on a side of each rounded corner facing away from the surface, and the maximum height of each optical microstructure between each vertex and the surface is H. 0.2≦H / W≦0.5.

[0012] In an embodiment of the present invention, each of the maximum widths may be between 0.002 mm and 0.050 mm.

[0013] In an embodiment of the present invention, each of the maximum heights is, for example, between 0.001 mm and 0.025 mm.

[0014] In one embodiment of the present invention, the light source assembly may include a second light guide plate and a second light emitting element. The second light guide plate has a second light incident surface and a light emitting surface connected to each other, the light emitting surface facing the privacy film. The second light emitting element is disposed opposite to the second light incident surface.

[0015] In one embodiment of the present invention, the light source assembly further includes a third light guide plate. The third light guide plate is disposed between the second light guide plate and the privacy film. The third light guide plate has a third light incident surface corresponding to the second light incident surface, and the second light emitting element is disposed relative to the second light incident surface and the third light incident surface.

[0016] In one embodiment of the present invention, the surface of the first light guide plate has a first edge and a second edge. The first edge is connected to the second edge, and the light emitting surface of the second light guide plate has a third edge corresponding to the first edge. The first light emitting element can be arranged along the second edge, and the second light emitting element can be arranged along the third edge.

[0017] In one embodiment of the present invention, the surface and the light-emitting surface are in the shape of a rectangle, the second side is a short side of the surface, and the third side is a long side of the light-emitting surface.

[0018] The backlight module of the present invention adopts a first light guide plate with an optical microstructure, wherein the first convex surface of the optical microstructure faces the first light incident surface when the optical microstructure is recessed in the surface, or faces away from the first light incident surface when the optical microstructure protrudes from the surface, so as to ensure that most of the light beams are incident on the first convex surface. Furthermore, the first angle between the first convex surface and the surface is between 30° and 70°, so that most of the light beams can be emitted from the first light guide plate at a large angle after being reflected by the first convex surface, thereby improving the large-angle light output brightness of the backlight module. In addition, because the first convex surface is located on the transmission path of most of the light beams, it can guide most of the light beams to be emitted at roughly similar angles, thereby providing an asymmetric viewing angle in the horizontal viewing angle of the backlight module. In addition, the first convex surface and the second convex surface are connected by a rounded corner, so that the rounded corner is located on the transmission path of part of the light beam, and the radius of curvature is between 0.001mm and 0.005mm. Therefore, the rounded corners can scatter part of the light beam out of the first light guide plate at a large angle, and the first convex surface can scatter the light beam by its own convex surface characteristics, thereby improving the light uniformity of the backlight module at a large angle. In this way, the optical quality of the backlight module in a shared state can also be improved.

[0019] In order to make the above and other purposes, features and advantages of the present invention more clearly understood, embodiments are given below with reference to the accompanying drawings for detailed description as follows. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 FIG. 4 is a side view of a backlight module according to an embodiment of the present invention.

[0021] Figure 2 yes Figure 1 A partial cross-sectional schematic diagram of a first light guide plate.

[0022] Figure 3 yes Figure 2 Schematic bottom view of the optical microstructure.

[0023] Figure 4 FIG. 4 is a schematic diagram of the light output brightness distribution of a backlight module according to an embodiment of the present invention.

[0024] Figure 5 FIG. 4 is a schematic diagram of a light output field pattern of a backlight module according to an embodiment of the present invention.

[0025] Figure 6 yes Figure 1 A bottom view of a first light emitting element and a first light guide plate.

[0026] Figure 7 yes Figure 1 A schematic top view of a second light guide plate.

[0027] Figure 8 FIG. 4 is a side view of a backlight module according to another embodiment of the present invention.

[0028] Fig. 9 yes Figure 8 A partial cross-sectional schematic diagram of a first light guide plate.

[0029] Fig.10 FIG. 4 is a side view of a backlight module according to another embodiment of the present invention.

[0030] Wherein, the reference numerals are:

[0031] 100, 100a, 100b: backlight module

[0032] 110, 110b: light source assembly

[0033] 111: Second light guide plate

[0034] 112: Second light emitting element

[0035] 113: Third light guide plate

[0036] 120: Privacy film

[0037] 130: first light emitting element

[0038] 140, 140a: first light guide plate

[0039] 141: First light incident surface

[0040] 143, 143a: Optical microstructure

[0041] 144: Bright side

[0042] 150:Reflective sheet

[0043] 1130: The third light incident surface

[0044] A1: First angle

[0045] A2: Second Angle

[0046] C1: First contour

[0047] C2: Second contour

[0048] D: Direction

[0049] E1: First side

[0050] E2: Second side

[0051] E3: The Third Side

[0052] ES: Light emitting surface

[0053] H: Maximum height

[0054] IC: Imaginary cross section

[0055] IL1: First imaginary tangent

[0056] IL2: Second imaginary tangent

[0057] IS: Second light incident surface

[0058] L: Maximum length

[0059] L1, L2: beam

[0060] N: Normal

[0061] P, Pa: Vertex

[0062] P1: First vertex

[0063] P2: Second vertex

[0064] RC, RCa: fillet

[0065] S, 142: Surface

[0066] S1, S1a: first convex surface

[0067] S2, S2a: second convex surface

[0068] W: Maximum width

[0069] X, Y, Z: direction DETAILED DESCRIPTION

[0070] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments, but is not intended to limit the present invention.

[0071] Figure 1 FIG. 4 is a side view of a backlight module according to an embodiment of the present invention. Figure 2 yes Figure 1A partial cross-sectional schematic diagram of a first light guide plate. Figure 3 yes Figure 2 Schematic diagram of the optical microstructure from above. Figure 1 and Figure 2 The backlight module 100 includes a light source assembly 110, a privacy film 120, a first light-emitting element 130 and a first light guide plate 140. The light source assembly 110 is suitable for emitting a light beam L1. The privacy film 120 is disposed on the transmission path of the light beam L1. The first light guide plate 140 is disposed on the side of the privacy film 120 that is opposite to the light source assembly 110. The first light guide plate 140 has a first light incident surface 141, a surface 142 and a plurality of optical microstructures 143. The first light incident surface 141 is opposite to the first light-emitting element 130, and the surface 142 faces the privacy film 120 and is connected to the first light incident surface 141. The optical microstructure 143 is recessed in the surface 142 and has a first convex surface S1, a second convex surface S2 and a rounded corner RC, respectively. The first convex surface S1 and the second convex surface S2 stand on the surface 142, and the rounded corner RC connects the first convex surface S1 and the second convex surface S2. The first convex surface S1 faces the first light incident surface 141 and the second convex surface S2 faces away from the first light incident surface 141. A first included angle A1 between each first convex surface S1 and the surface 142 is between 30° and 70°, and a radius of curvature of the fillet RC is between 0.001 mm and 0.005 mm.

[0072] Please continue to refer to Figure 1 The light source assembly 110 of this embodiment may include an edge-type backlight module or a direct-type backlight module. Figure 1 Take the edge-entry backlight module as an example. For example, the light source assembly 110 may include a second light guide plate 111 and a second light-emitting element 112. The second light guide plate 111 has a second light-incident surface IS and a light-exit surface ES connected to each other, and the light-exit surface ES faces the privacy film 120. The second light-emitting element 112 is arranged opposite to the second light-incident surface IS. In detail, the second light-emitting element 112 can generate a light beam L1 to enter the second light guide plate 111, and the second light guide plate 111 guides the light beam L1 to exit from the light-exit surface ES. In this embodiment, the second light-emitting element 112 may include a light-emitting diode (LED). In one embodiment, the surface S of the second light guide plate 111 facing away from the light-exit surface ES may have a plurality of optical microstructures (not shown), and the optical microstructures may be, for example but not limited to, protruding from the surface S and may be triangular prism-shaped or spherical. By the way, in this embodiment, a reflective sheet 150 may be arranged on the side of the second light guide plate 111 facing away from the privacy film 120 to improve the light utilization rate of the backlight module 100. However, in the embodiment where the light source assembly 110 adopts a direct-lit backlight module 100 , the reflective sheet 150 may be omitted from the backlight module 100 .

[0073] In this embodiment, the privacy film 120 can reduce the emission angle of the light beam L1, so that when the light source assembly 110 is turned on and the first light-emitting element 130 is turned off, the backlight module 100 can provide a smaller viewing angle (i.e., the privacy state). The privacy film 120 includes, for example, a grating, but other embodiments are not limited thereto. For example, in one embodiment, the privacy film 120 may include a liquid crystal layer, and the emission angle of the light beam L1 may be reduced by controlling the rotation of the liquid crystal molecules.

[0074] In this embodiment, the first light emitting element 130 can provide the light beam L2 required by the backlight module 100 in the sharing state. The first light emitting element 130 can include a light emitting diode (LED), but the present invention is not limited thereto.

[0075] The first light guide plate 140 can guide the light beam L2 of the first light emitting element 130 to be emitted from the light emitting surface 144, wherein the light emitting surface 144 is opposite to the surface 142. In detail, the optical microstructure 143 of the first light guide plate 140 can guide the light beam L2 to be emitted from the light emitting surface 144 at a large angle, so when the first light emitting element 130 is activated, the backlight module 100 can provide a larger viewing angle (i.e., a shared state). In addition, when the first light emitting element 130 and the second light emitting element 112 are activated together, the backlight module 100 can simultaneously have the advantages of a large viewing angle and high brightness of forward light emission.

[0076] Please refer to Figure 1 and Figure 2 , the first convex surface S1 of the optical microstructure 143, for example, protrudes toward the first light incident surface 141, so that the first convex surface S1 can slightly scatter the light beam L2, so that the brightness of the light emitted from the first light guide plate 140 is more uniform. The fillet RC, for example, stands on the surface 142 in a slightly arched shape, and the fillet RC has a curved surface protruding toward the light emitting surface 144 to scatter the incident light beam L2, thereby further improving the uniformity of the light emitted from the first light guide plate 140. The second convex surface S2 can protrude in the direction away from the first light incident surface 141 to scatter part of the light beam L2 to the light emitting surface 144, so that the brightness of the light emitted from the first light guide plate 140 is more uniform. By the way, part of the light beam L2 generated by the first light-emitting element 130 can be directly incident on the first convex surface S1 and the fillet RC from the first light incident surface 141, and the other part can be incident on the second convex surface S2 and the fillet RC after total reflection on the light emitting surface 144, but the present invention does not impose many restrictions on the transmission path of the light beam L2.

[0077] Please refer to Figure 2 and Figure 3In the present embodiment, each first convex surface S1 forms a first contour C1 on the surface 142. Each first contour C1 is a curve and has a first vertex P1 protruding away from each second convex surface S2. Each first convex surface S1 may have a first imaginary tangent line IL1, and each optical microstructure 143 may also have an imaginary section IC. Each imaginary section IC passes through each first vertex P1 and is perpendicular to the first light incident surface 141 and the surface 142. Each first imaginary tangent line IL1 passes through each first vertex P1 and is located on each imaginary section IC, and a first angle A1 may be sandwiched between the first imaginary tangent line IL1 and the surface 142, respectively. The imaginary section IC is, for example, substantially parallel to the XZ plane. In other words, the first angle A1 is sandwiched between the first imaginary tangent line IL1 and the surface 142. In detail, the first convex surface S1 may be approximately a conical surface, and the connection between the conical surface and the surface 142 forms the first contour C1. Furthermore, the first contour C1 is, for example, substantially in the form of a parabola and protrudes toward the first light incident surface 141, and the first vertex P1 may be the vertex of the parabola. In one embodiment, each first angle A1 is, for example, between 40° and 60°, so that the light output brightness of the backlight module 100 in the shared state at a horizontal viewing angle of approximately between -60° and -40° can be increased. Incidentally, in another embodiment, the radius of curvature of each fillet RC is R, and 0.001mm<R<0.005mm, for example but not limited to 0.001mm, 0.002mm, 0.003mm, 0.004mm and 0.005mm, so as to further enhance the light output uniformity of the first light guide plate 140. In addition, the curvature of the first convex surface S1 may be less than or equal to 0.011mm, but the present invention is not limited thereto.

[0078] Compared with the prior art, the backlight module 100 of the present embodiment adopts a first light guide plate 140 having an optical microstructure 143, wherein the first convex surface S1 of the optical microstructure 143 faces the first light incident surface 141 when the optical microstructure 143 is recessed in the surface 142, so as to ensure that most of the light beam L2 is incident on the first convex surface S1. Further, the first angle A1 between the first convex surface S1 and the surface 142 is between 30° and 70°, such as but not limited to 30°, 35°, 40°, 45°, 50°, 55°, 60°, 65° and 70°, so that most of the light beam L2 can be reflected by the first convex surface S1 and emitted from the first light guide plate 140 at a large angle, thereby improving the large-angle light output brightness of the backlight module 100. In addition, because the first convex surface S1 is located on the transmission path of most of the light beam L2, it can guide most of the light beam L2 to emit at a roughly similar angle, thereby allowing the backlight module 100 to provide an asymmetric viewing angle in the horizontal viewing angle. In addition, the first convex surface S1 and the second convex surface S2 are connected by a fillet RC, so that the fillet RC is located on the transmission path of part of the light beam L2, and the radius of curvature is between 0.001mm and 0.005mm. Therefore, the fillet RC can scatter part of the light beam L2 out of the first light guide plate 140 at a large angle, and the first convex surface S1 can scatter the light beam L2 through the characteristics of its own convex surface, thereby improving the uniformity of the light output of the backlight module 100 at a large angle. In this way, the optical taste of the backlight module 100 in a shared state can also be improved.

[0079] Figure 4 FIG. 4 is a schematic diagram of the light output brightness distribution of a backlight module according to an embodiment of the present invention. Figure 5 FIG. 1 is a schematic diagram of a light output field of a backlight module according to an embodiment of the present invention, wherein Figure 5 (a) is a schematic diagram of the light output field in the anti-peep state. Figure 5 (b) is a schematic diagram of the light field type in the sharing state. Please refer to Figures 1 to 5 ,in Figure 4 and Figure 5Take the first angle A1 between 47° and 53° as an example. When the backlight module 100 is in the anti-peeping state, the light output brightness is concentrated in the horizontal viewing angle between approximately -20° and +20°. On the contrary, when the backlight module 100 is in the sharing state, part of the light beam L2 is reflected by the first convex surface S1 and emitted from the first light guide plate 140 at a large angle. Therefore, compared with the anti-peeping state, the light output brightness of the backlight module 100 in the horizontal viewing angle between approximately -80° and -20° is significantly increased. It is worth mentioning that the light output brightness of the backlight module 100 between the horizontal viewing angle of 20° and 80° does not increase as significantly as that of -80° to -20°, so that the backlight module 100 provides an asymmetric viewing angle. In one embodiment, the backlight module 100 can be applied to a vehicle display device. For example, the vehicle display device can be installed in front of the driver's seat. In this way, when the backlight module 100 is in the sharing state, the asymmetric viewing angle can facilitate the driver to view the screen of the vehicle display device, and can also prevent the light emitted by the screen from reflecting from the window next to the driver's seat and affecting the driver's rearview mirror. It can be understood that the above application of the backlight module 100 is only an example and is not intended to limit the present invention.

[0080] Please refer to Figure 2 and Figure 3 , to illustrate other features of the optical microstructure 143. In one embodiment, the second angle A2 between each second convex surface S2 and the surface 142 is, for example, between 20° and 40°, so as to reflect a portion of the light beam to be emitted from the first light guide plate 140 at a large angle, thereby increasing the viewing angle of the backlight module 100. In this embodiment, each second convex surface S2 forms a second contour C2 on the surface 142. Each second contour C2 is a curve and has a second vertex P2 protruding away from each first convex surface S1. Each second convex surface S2 may have a second imaginary tangent IL2. Each imaginary section IC passes through each second vertex P2. Each second imaginary tangent IL2 passes through each second vertex P2 and is located on each imaginary section IC, and a second angle A2 may be sandwiched between the second imaginary tangent IL2 and the surface 142. In other words, the second angle A2 is sandwiched between the second imaginary tangent IL2 and the surface 142. Similarly, the second convex surface S2 may be similar to a cone, and the connection between the cone and the surface 142 forms a second contour C2. Furthermore, the second contour C2 may be substantially parabolic and convex away from the first light incident surface 141, and the second vertex P2 may be the vertex of the parabola.

[0081] The maximum length L of each optical microstructure 143 in the normal direction N of the first light incident surface 141 may be between 0.005 mm and 0.050 mm, wherein the normal direction N is, for example, substantially parallel to the direction X. On the other hand, the maximum width of each optical microstructure 143 in a direction D perpendicular to the normal direction N of the first light incident surface 141 is W, wherein the direction D is, for example, substantially parallel to the direction Z. Each optical microstructure 143 may also have a vertex P. Each vertex P is located on the side of each fillet RC facing away from the surface 142, and the maximum height of each optical microstructure 143 between each vertex P and the surface 142 is H, wherein 0.2≦H / W≦0.5, such as 0.2, 0.25, 0.3, 0.35, 0.4, 0.45 and 0.5. For example, the maximum width W may be between 0.002 mm and 0.050 mm. Specifically, since the optical microstructure 143 is located at the light source component 110 (drawn in Figure 1 ) on the transmission path of the light beam L2, so the maximum length L and the maximum width W of each optical microstructure 143 are designed to be between the above ranges, which can greatly reduce the area of ​​the orthographic projection of each optical microstructure 143 on the surface 142, so as to reduce the interference of the optical microstructure 143 on the light beam L2, thereby further improving the light uniformity of the backlight module 100. In one embodiment, the maximum length L can be, for example, approximately 0.005mm, 0.008mm, 0.01mm, 0.015mm, 0.02mm, 0.025mm, 0.03mm, 0.035mm, 0.04mm, 0.045mm and 0.05mm, and in another embodiment, the maximum width W can be, for example, approximately 0.005mm, 0.01mm, 0.015mm, 0.02mm, 0.025mm, 0.03mm, 0.035mm, 0.04mm, 0.045mm and 0.05mm. In addition, the curvature of the second convex surface S2 may be less than or equal to 0.037 mm, but the present invention does not impose any restrictions on the specific numerical value.

[0082] In this embodiment, each maximum height H is, for example, between 0.001 mm and 0.025 mm, so that the light receiving area of ​​the first convex surface S1 can be increased, thereby further increasing the light output brightness of the backlight module 100 at a large viewing angle. In one embodiment, the maximum height H can be, for example, approximately 0.001 mm, 0.002 mm, 0.005 mm, 0.01 mm, 0.015 mm, 0.02 mm, and 0.025 mm, but other embodiments are not limited thereto.

[0083] Figure 6 yes Figure 1 A bottom view of a first light emitting element and a first light guide plate. Figure 7 yes Figure 1 Please refer to the top view of the second light guide plate. Figure 1 , Figure 6and Figure 7 Incidentally, in the present embodiment, the surface 142 of the first light guide plate 140 has a first side E1 and a second side E2. The first side E1 is connected to the second side E2, and the light emitting surface ES of the second light guide plate 111 has a third side E3 corresponding to the first side E1. The first light emitting element 130 may be arranged along the second side E2, and the second light emitting element 112 may be arranged along the third side E3. In other words, the first light emitting element 130 and the second light emitting element 112 may be arranged on different sides of the first light guide plate 140 and the second light guide plate 111 relative to each other. Further, the shape of the surface 142 and the light emitting surface ES is, for example, a rectangle. The second side E2 is the short side of the surface 142, and the third side E3 is the long side of the light emitting surface ES. In other words, the first light emitting element 130 may be, for example but not limited to, arranged along the short side of the first light guide plate 140, and the second light emitting element 112 may be, for example but not limited to, arranged along the long side of the second light guide plate 111.

[0084] Figure 8 FIG. 4 is a side view of a backlight module according to another embodiment of the present invention. Fig. 9 yes Figure 8 The structure and advantages of the backlight module 100a of this embodiment are similar to those of Figure 1 The following is an example of an embodiment of the present invention, and only the differences are described below. Please refer to Figure 8 and Fig. 9 , the optical microstructure 143a protrudes from the surface 142. The first convex surface S1a is opposite to the first light incident surface 141 and the second convex surface S2a is facing the first light incident surface 141. Furthermore, after most of the light beam L2 enters the first light guide plate 140a from the first light incident surface 141, it can be totally reflected to the first convex surface S1a via the light emitting surface 144, and then reflected to the light emitting surface 144 via the first convex surface S1a, and then emitted from the light emitting surface 144 at a large angle. Similarly, part of the light beam L2 is reflected to the light emitting surface 144 via the fillet RCa and the second convex surface S2a. It should be noted that the first angle A1 is located on the side of the optical microstructure 143a that is opposite to the first light incident surface 141, the fillet RCa protrudes away from the light emitting surface 144, and the second angle A2 is located on the side of the optical microstructure 143a that is facing the first light incident surface 141. Other features of the optical microstructure 143a are the same. Figure 1 Therefore, the related description is omitted here.

[0085] Fig.10 is a side view schematic diagram of a backlight module according to another embodiment of the present invention. The structure and advantages of the backlight module 100b of this embodiment are similar to those of Figure 1 The following is an example of an embodiment of the present invention, and only the differences are described below. Please refer to Fig.10, the light source assembly 110b, for example, further includes a third light guide plate 113. The third light guide plate 113 is disposed between the second light guide plate 111 and the privacy film 120. The third light guide plate 113 has a third light incident surface 1130 corresponding to the second light incident surface IS, and the second light emitting element 112 is disposed relative to the second light incident surface IS and the third light incident surface 1130. In short, the second light emitting element 112 can emit a light beam toward the second light incident surface IS and the third light incident surface 1130 at the same time, and the second light guide plate 111 can guide the light beam to be incident on the third light guide plate 113, and the third light guide plate 113 can guide the light beam to be incident on the privacy film 120. Incidentally, the number of the third light guide plate 113 in this embodiment may be one, but in other embodiments, the number of the third light guide plate 113 may be multiple, and the present invention does not impose any restrictions on the specific number of the third light guide plate 113.

[0086] In summary, the backlight module of the present invention adopts a first light guide plate with an optical microstructure, wherein the first convex surface of the optical microstructure faces the first light incident surface when the optical microstructure is recessed in the surface, or faces away from the first light incident surface when the optical microstructure protrudes from the surface, so as to ensure that most of the light beams are incident on the first convex surface. Furthermore, the first angle between the first convex surface and the surface is between 30° and 70°, so that most of the light beams can be emitted from the first light guide plate at a large angle after being reflected by the first convex surface, thereby improving the large-angle light output brightness of the backlight module. In addition, because the first convex surface is located on the transmission path of most of the light beams, it can guide most of the light beams to be emitted at roughly similar angles, thereby providing an asymmetric viewing angle in the horizontal viewing angle of the backlight module. In addition, the first convex surface and the second convex surface are connected by a rounded corner, so that the rounded corner is located on the transmission path of part of the light beam, and the radius of curvature is between 0.001mm and 0.005mm. Therefore, the rounded corners can scatter part of the light beam out of the first light guide plate at a large angle, and the first convex surface can scatter the light beam by its own convex surface characteristics, thereby improving the light uniformity of the backlight module at a large angle. In this way, the optical quality of the backlight module in a shared state can also be improved.

[0087] Although the present invention has been disclosed as above by way of embodiments, it is not intended to limit the present invention. A person having ordinary knowledge in the technical field to which the present invention belongs may make some changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention shall be determined by the scope of the attached patent application.

Claims

1. A backlight module, characterized in that: include: A light source assembly, adapted to emit a light beam; A privacy film, disposed on the transmission path of the light beam; a first light emitting element; as well as a first light guide plate, disposed on a side of the privacy film facing away from the light source assembly, the first light guide plate having a first light incident surface, a surface and a plurality of optical microstructures, the first light incident surface being opposite to the first light emitting element, the surface facing the privacy film and connected to the first light incident surface, the optical microstructures being recessed or protruding from the surface, and respectively having a first convex surface, a second convex surface and a fillet, the first convex surface and the second convex surface being vertically disposed on the surface, and the fillet connecting the first convex surface and the second convex surface, a first angle between each of the first convex surfaces and the surface being between 30° and 70°, and a radius of curvature of the fillet being between 0.001 mm and 0.005 mm; When the optical microstructures are recessed in the surface, the first convex surfaces face the first light incident surface and the second convex surfaces are away from the first light incident surface; when the optical microstructures are protruding from the surface, the first convex surfaces are away from the first light incident surface and the second convex surfaces face the first light incident surface.

2. The backlight module according to claim 1, wherein: Each of the first angles is between 40° and 60°.

3. The backlight module according to claim 1, wherein: Each of the first convex surfaces forms a first contour on the surface, each of the first contours is a curve and has a first vertex protruding away from each of the second convex surfaces, each of the first convex surfaces has a first imaginary tangent, and each of the optical microstructures has an imaginary section, each of the imaginary sections passes through each of the first vertices and is perpendicular to the first light incident surface and the surface, each of the first imaginary tangents passes through each of the first vertices and is located on each of the imaginary sections, and the first angles are respectively formed between the first imaginary tangents and the surface.

4. The backlight module according to claim 1, wherein: A second included angle between each of the second convex surfaces and the surface is between 20° and 40°.

5. The backlight module according to claim 4, wherein: Each of the second convex surfaces forms a second contour on the surface, each of the second contours is curved and has a second vertex protruding away from each of the first convex surfaces, each of the second convex surfaces has a second imaginary tangent, and each of the optical microstructures has an imaginary section, each of the imaginary sections passes through each of the second vertices and is perpendicular to the first light incident surface and the surface, each of the second imaginary tangents passes through each of the second vertices and is located on each of the imaginary sections, and the second angles are respectively formed between the second imaginary tangents and the surface.

6. The backlight module according to claim 1, wherein: A maximum length of each of the optical microstructures in a normal direction to the first light incident surface is between 0.005 mm and 0.050 mm.

7. The backlight module according to claim 1, wherein: Each of the optical microstructures has a maximum width W in a direction perpendicular to a normal direction of the first light incident surface, and each of the optical microstructures further has a vertex, each of the vertices is located on a side of each of the rounded corners facing away from the surface, and a maximum height of each of the optical microstructures between each of the vertices and the surface is H, 0.2≦H / W≦0.

5.

8. The backlight module according to claim 7, wherein: Each of the maximum widths is between 0.002 mm and 0.050 mm.

9. The backlight module according to claim 7, wherein: Each of the maximum heights is between 0.001 mm and 0.025 mm.

10. The backlight module according to claim 1, wherein: The light source assembly includes a second light guide plate and a second light emitting element. The second light guide plate has a second light incident surface and a light emitting surface connected to each other. The light emitting surface faces the privacy film. The second light emitting element is arranged opposite to the second light incident surface.

11. The backlight module according to claim 10, wherein: The light source assembly further includes a third light guide plate, which is arranged between the second light guide plate and the privacy film. The third light guide plate has a third light incident surface corresponding to the second light incident surface, and the second light-emitting element is arranged relative to the second light incident surface and the third light incident surface.

12. The backlight module according to claim 10, wherein: The surface of the first light guide plate has a first edge and a second edge, the first edge is connected to the second edge, the light emitting surface of the second light guide plate has a third edge corresponding to the first edge, the first light-emitting element is arranged along the second edge, and the second light-emitting element is arranged along the third edge.

13. The backlight module according to claim 12, wherein: The surface and the light-emitting surface are in the shape of a rectangle, the second side is a short side of the surface, and the third side is a long side of the light-emitting surface.

Images