Backlight module

Abstract

The invention discloses a backlight module which comprises a light source assembly, a peep-proof sheet, a light-emitting element and a light guide plate. The light source assembly emits light beams. The peep-proof sheet is arranged on a transmission path of the light beam. 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 inlet face, a surface and a plurality of optical microstructures. The light incident surface is opposite to the light-emitting element. The 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, a height is formed between each optical microstructure and the surface, and each height is gradually reduced in the normal direction of the light incident surface.

Description

Technical Field

[0001] The invention relates to a light source 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] Generally speaking, the backlight module can guide the light to be emitted at a large angle through the optical microstructure of the light guide plate, thereby providing a larger viewing angle in a shared state. However, the existing optical microstructure cannot guide the light to be emitted from the light guide plate evenly, resulting in the problem of poor optical quality of the backlight module. Summary of the invention

[0004] The invention provides a backlight module to improve optical quality.

[0005] To achieve one or part or all of the above purposes or other purposes, one 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 facing away from the light source assembly, and 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. 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 each optical microstructure has a height between it and the surface, wherein each height gradually decreases in the normal direction of the first light incident surface.

[0006] In one embodiment of the present invention, the above-mentioned surface may have a low light zone, an intermediate zone and a high light zone. The low light zone is connected to the first light incident surface. The first light guide plate has an end surface opposite to the first light incident surface, and the high light zone is connected to the end surface. The intermediate zone is located between the low light zone and the high light zone. The optical microstructure includes a plurality of low light microstructures, a plurality of intermediate microstructures and a plurality of high light microstructures. The low light microstructure is located in the low light zone, and there is a first maximum height difference between the low light microstructures. The intermediate microstructure is located in the intermediate zone, and there is a second maximum height difference between the intermediate microstructures. The high light microstructure is located in the high light zone, and there is a third maximum height difference between the high light microstructures. The second maximum height difference is greater than the first maximum height difference and the third maximum height difference.

[0007] In one embodiment of the present invention, two adjacent microstructures in the low beam have a first height difference along the normal direction. Two adjacent microstructures in the intermediate beam have a second height difference along the normal direction. Two adjacent microstructures in the high beam have a third height difference along the normal direction. The second height difference is greater than the first height difference and the third height difference.

[0008] In one embodiment of the present invention, the length of the surface of the first light guide plate in the normal direction is L, and the length of the middle area in the normal direction is L1. 0.2L≦L1≦0.7L.

[0009] In one embodiment of the present invention, at least a portion of the optical microstructures are arranged at unequal distances in the normal direction.

[0010] In one embodiment of the present invention, the optical microstructure may include a plurality of microstructures. The microstructures are arranged along a normal direction, and the spacing between two adjacent microstructures increases gradually along the normal direction.

[0011] In one embodiment of the present invention, the optical microstructure may include a plurality of microstructures. The microstructures are arranged along the normal direction and include two first microstructures and two second microstructures. The two first microstructures are adjacent to each other and separated by a distance D1, and the two second microstructures are adjacent to each other and separated by a distance D2. -6 ≦∣D1-D2∣ / D1≦10 -4 .

[0012] In one embodiment of the present invention, 0.1 nm≦|D1-D2|≦0.5 nm.

[0013] In one embodiment of the present invention, 0.01 mm≦D1≦0.07 mm, and 0.01 mm≦D2≦0.07 mm.

[0014] In one embodiment of the present invention, each optical microstructure has a vertex on the side facing away from the surface, and the maximum height of each optical microstructure between each vertex and the surface is MH. The maximum width of each optical microstructure in the normal direction is W, 0.2≦MH / W≦0.5.

[0015] In one embodiment of the present invention, the optical microstructures include a plurality of first-row microstructures and a plurality of second-row microstructures. The first-row microstructures and the second-row microstructures are arranged along the normal direction, and the first-row microstructures and the second-row microstructures are arranged side by side. The optical microstructure closest to the first light incident surface in the first-row microstructures is spaced apart from the first light incident surface by a first spacing, and the optical microstructure closest to the first light incident surface in the second-row microstructures is spaced apart from the first light incident surface by a second spacing. The first spacing is different from the second spacing.

[0016] 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 faces the privacy film, and the second light emitting element is arranged opposite to the second light incident surface.

[0017] In one embodiment of the present invention, the light source assembly further includes a third light guide plate, which 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.

[0018] 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. The light emitting surface of the second light guide plate has a third edge aligned with 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.

[0019] In the backlight module of the present invention, the optical microstructure used in the first light guide plate has a characteristic of gradually decreasing height along the normal direction. In detail, the optical microstructure with gradually decreasing height along the normal direction can reduce the brightness of the light output on the side of the first light guide plate close to the first light incident surface, and increase the brightness of the light output on the side of the first light guide plate away from the first light incident surface. Based on the above, the optical microstructure can effectively improve the uniformity of the light output of the first light guide plate, thereby improving the optical quality of the backlight module.

[0020] 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

[0021] Figure 1 FIG. 4 is a side view of a backlight module according to an embodiment of the present invention.

[0022] Figure 2 yes Figure 1 Schematic diagram of an enlarged cross-sectional view of the optical microstructure.

[0023] Figure 3 yes Figure 1 A bottom view of a first light guide plate is shown.

[0024] Figure 4 yes Figure 1 Schematic diagram of the relationship between the height and position of the optical microstructure.

[0025] Figure 5 yes Figure 1 A schematic diagram of the relationship between the light output brightness and the horizontal viewing angle of a backlight module according to an embodiment of the present invention.

[0026] Figure 6 FIG. 1 is a bottom view of a first light guide plate of a backlight module according to another embodiment of the present invention.

[0027] Figure 7 FIG. 1 is a bottom view of a first light guide plate of a backlight module according to another embodiment of the present invention.

[0028] Figure 8 FIG. 1 is a bottom view of a first light guide plate of a backlight module according to another embodiment of the present invention.

[0029] Fig. 9 FIG. 4 is a side view of a backlight module according to another embodiment of the present invention.

[0030] Fig.10 yes Fig. 9 Schematic diagram of an enlarged cross-sectional view of the optical microstructure.

[0031] Fig.11 FIG. 4 is a side view of a backlight module according to another embodiment of the present invention.

[0032] Fig.12 FIG. 4 is a side view of a backlight module according to an embodiment of the present invention.

[0033] Fig.13 yes Fig.12 Schematic diagram of an enlarged cross-sectional view of the optical microstructure.

[0034] Wherein, the reference numerals are:

[0035] 100, 100a, 100b, 100c, 100d, 100e, 200: backlight module

[0036] 110, 110e: Light source assembly

[0037] 111: Second light guide plate

[0038] 112: Second light emitting element

[0039] 113: third light emitting element

[0040] 120: Privacy film

[0041] 130: first light emitting element

[0042] 140, 140a, 140b, 140c, 140d, 240: first light guide plate

[0043] 141, 241: first light incident surface

[0044] 143: Bright surface

[0045] 144: End face

[0046] 150:Reflective sheet

[0047] 1130: The third light incident surface

[0048] 1421: Low beam area

[0049] 1422: Middle Zone

[0050] 1423: High beam area

[0051] A1: First angle

[0052] A2: Second Angle

[0053] DH1: First maximum height difference

[0054] DH2: Second largest height difference

[0055] DH3: The third largest height difference

[0056] E1: First side

[0057] E2: Second side

[0058] E3: The Third Side

[0059] ES: Light emitting surface

[0060] G, D1, D2, D3: Spacing

[0061] G1: First spacing

[0062] G2: Second spacing

[0063] H: Height

[0064] IS: Second light incident surface

[0065] L0, L: length

[0066] L1, L2: beam

[0067] M, MF1, MF2, Md, M': optical microstructures

[0068] M1: Low beam microstructure

[0069] M1b: First microstructure

[0070] M2: Intermediate microstructure

[0071] M2b: Second microstructure

[0072] M3: High beam microstructure

[0073] Ma, Mb: microstructure

[0074] MH: Maximum height

[0075] ML: Maximum length

[0076] MR1: First row microstructure

[0077] MR2: Second row microstructure

[0078] N: Normal

[0079] P: Vertex

[0080] RC, RCd: rounded corners

[0081] S, 142, 242: Surface

[0082] S1, S1d: first convex surface

[0083] S2, S2d: second convex surface

[0084] W: Maximum width

[0085] X, Y, Z: direction DETAILED DESCRIPTION

[0086] 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.

[0087] Figure 1 FIG. 4 is a side view of a backlight module according to an embodiment of the present invention. Figure 2 yes Figure 1 Schematic diagram of an enlarged cross-sectional view of the optical microstructure. Figure 3 yes Figure 1 A bottom view of a first light guide plate is shown. Figure 4 yes Figure 1 Schematic diagram of the relationship between the height and position of the optical microstructure. Please refer to Figure 1 , 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 away from the light source assembly 110, and the first light guide plate 140 has a first light incident surface 141, a surface 142 and a plurality of optical microstructures M. The first light incident surface 141 is opposite to the first light-emitting element 130. The surface 142 faces the privacy film 120 and is connected to the first light incident surface 141. The optical microstructure M is recessed in the surface 142, and each optical microstructure M has a height H with respect to the surface 142, wherein each height H decreases gradually in the normal direction N of the first light incident surface 141. Specifically, the height H may be the distance between each optical microstructure M and the surface 142 on an imaginary cross-section (XZ plane) perpendicular to the first light incident surface 141 and the surface 143 .

[0088] The light source assembly 110 may include an edge-entry backlight module or a direct-type backlight module, and the present embodiment takes an 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. The light exit surface ES faces the privacy film 120, and 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, wherein the second light-emitting element 112 may include a light-emitting diode (LED). The second light guide plate 111 may be a rectangular parallelepiped, and the second light-emitting element 112 is, for example but not limited to, arranged on the long side of the second light guide plate 111. 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, for example but not limited to, protrude from the surface S and may be triangular prism-shaped or spherical. Incidentally, a reflective sheet 150 may be disposed on the side of the second light guide plate 111 facing away from the privacy film 120 to improve the light utilization of the backlight module 100. However, in the embodiment where the light source assembly 110 adopts a direct-type backlight module 100, the reflective sheet 150 may be omitted from the backlight module 100.

[0089] The privacy film 120 of this embodiment 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 of this embodiment includes, for example, a grating. In one embodiment, the privacy film 120 may include a liquid crystal layer, and the light emission angle is reduced by controlling the rotation of the liquid crystal molecules.

[0090] 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. Figure 1 and Figure 3 , the surface 142 of the first light guide plate 140 has a first edge E1 and a second edge E2, and the first edge E1 is connected to the second edge E2. The light emitting surface ES of the second light guide plate 111 has a third edge E3 aligned with the first edge E1. The first light emitting element 130 can be arranged along the second edge E2, and the second light emitting element 112 can be arranged along the third edge E3. In detail, the first edge E1 and the third edge E3 can extend along the direction X, and the second edge E2 can extend along the direction Y. Furthermore, the shape of the surface 142 can be rectangular, and the first edge E1 can be the long side of the surface 142 (see Figure 3), the second side E2 may be the short side of the surface 142. The first light incident surface 141 may be connected to the short side. In other words, the first light emitting element 130 may be, for example but not limited to, disposed along the short side of the first light guide plate 140, and the first light emitting element 130 and the second light emitting element 112 may be disposed on different sides of the first light guide plate 111 and the second light guide plate 140, respectively. In detail, the second light emitting element 112 may be disposed on the long side (i.e., the third side E3) of the light emitting surface ES of the second light guide plate 140, and the first light emitting element 130 may be disposed on the short side (i.e., the second side E2) of the first light guide plate 111, so as to control the light output brightness of the backlight module 100 at a horizontal viewing angle.

[0091] Please refer to Figure 1 and Figure 2 , 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 143. In detail, the optical microstructure M of the first light guide plate 140 can guide the light beam L2 to be emitted from the light emitting surface 143 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 sharing state).

[0092] The optical microstructure M can reflect the light beam L2 to the light emitting surface 143 of the first light guide plate 140, and each optical microstructure M can provide different light receiving amounts through different heights H, and then provide different light reflection amounts, so as to improve the light emitting uniformity of the first light guide plate 140. In this way, the optical taste of the backlight module 100 in a shared state can be improved. Further, each optical microstructure M has a vertex P on the side facing away from the surface 142, and the maximum height of each optical microstructure M between each vertex P and the surface 142 is MH. The height H of each optical microstructure M is, for example, the maximum height MH. Further, the vertex P can be located on the aforementioned imaginary section (XZ plane), and the maximum height MH of each optical microstructure M is, for example, the maximum distance between the vertex P and the surface 142 on the aforementioned imaginary section. In one embodiment, the maximum height MH of each optical microstructure M may be between 0.001 mm and 0.025 mm, such as 0.001 mm, 0.002 mm, 0.005 mm, 0.01 mm, 0.015 mm, 0.02 mm and 0.025 mm, but the present invention is not limited thereto.

[0093] Please refer to Figure 1 and Figure 3In the present embodiment, the surface 142 of the first light guide plate 140 may have a low light zone 1421, a middle zone 1422 and a high light zone 1423. The low light zone 1421 is connected to the first light incident surface 141. The first light guide plate 140 has an end surface 144 opposite to the first light incident surface 141, and the high light zone 1423 is connected to the end surface 144. The middle zone 1422 is located between the low light zone 1421 and the high light zone 1423. The optical microstructure M includes a plurality of low light microstructures M1, a plurality of middle microstructures M2 and a plurality of high light microstructures M3. The low light microstructure M1 is located in the low light zone 1421, and there is a first maximum height difference DH1 between the low light microstructures M1. It should be noted that the first maximum height difference DH1 is the maximum height minus the minimum height among the heights of all the low light microstructures M1 relative to the surface 142, and is not limited to Figure 1 The adjacent two low beam microstructures M1 are shown. The intermediate microstructures M2 are located in the intermediate area 1422, and there is a second maximum height difference DH2 between the intermediate microstructures M2. Similarly, the second maximum height difference DH2 is the maximum height minus the minimum height among all the intermediate microstructures M2 relative to the surface 142, and is not limited to Figure 1 The adjacent two intermediate microstructures M2 are shown. The high beam microstructures M3 are located in the high beam area 1423, and there is a third maximum height difference DH3 between the high beam microstructures M3. The second maximum height difference DH2 is greater than the first maximum height difference DH1 and the third maximum height difference DH3. The third maximum height difference DH3 is the maximum height minus the minimum height among all the high beam microstructures M3 relative to the surface 142, and is not limited to Figure 1 Two adjacent high beam microstructures M3 are shown.

[0094] In short, the variation of the height H of each intermediate microstructure M2 located in the intermediate area 1422 is greater than that of the low-beam microstructure M1 located in the low-beam area 1421 and the high-beam microstructure M3 located in the high-beam area 1423. In this way, the light output angle of the light beam L2 after being reflected by the intermediate microstructure M2 can have more variation than that of the low-beam microstructure M1 and the high-beam microstructure M3, thereby improving the light output uniformity of the light output surface 143 corresponding to the intermediate area 1422. In addition, compared with the intermediate microstructure M2 and the high-beam microstructure M3, the low-beam microstructure M1 can reduce the amount of reflection of the light beam L2 by a lower average height, thereby reducing the light output brightness of the light output surface 143 corresponding to the low-beam area 1421. In addition, compared with the intermediate microstructure M2 and the low-beam microstructure M1, the high-beam microstructure M3 can increase the amount of reflection of the light beam L2 by a higher average height, thereby improving the light output brightness of the light output surface 143 corresponding to the high-beam area 1423.

[0095] In the present embodiment, two adjacent ones of the low beam microstructure M1 along the normal direction N have a first height difference, wherein the first height difference may, for example, be less than or equal to the first maximum height difference DH1. Similarly, two adjacent ones of the intermediate microstructure M2 along the normal direction N have a second height difference, and the second height difference of the present embodiment may, for example, be less than or equal to the second maximum height difference DH2. Similarly, two adjacent ones of the high beam microstructure M3 along the normal direction N have a third height difference, and the third height difference may, for example, be less than or equal to the third maximum height difference DH3. The second height difference is greater than the first height difference and the third height difference. In one embodiment, the first height difference, the second height difference and the third height difference may be different from the first maximum height difference DH1, the second maximum height difference DH2 and the third maximum height difference DH3, respectively.

[0096] Incidentally, in the present embodiment, the length of the surface 142 of the first light guide plate 140 in the normal direction N is L, and the length of the middle area 1422 in the normal direction N is L0. 0.2L≦L0≦0.7L. In other words, the length of the middle area 1422 may be between 0.2L and 0.7L, the length of the low beam area 1421 in the normal direction N may be within approximately 0.2L, and the length of the high beam area 1423 in the normal direction N may be between 0.7L and L. In one embodiment, the variation of the height H of the low beam microstructure M1, the middle microstructure M2, and the high beam microstructure M3 is, for example, Figure 4 As shown, the present invention is not limited thereto.

[0097] Please refer to Figure 2 and Figure 3 In this embodiment, the maximum width of each optical microstructure M in the normal direction N is W, 0.2≦MH / W≦0.5. Further, because the first light guide plate 140 is located on the transmission path of the light beam L1 of the light source assembly 110, the above-mentioned range of aspect ratio (i.e., MH / W) can not only control the emission angle of the light beam L1, but also reduce the size of the optical microstructure M, thereby reducing the light beam L1 (drawn in Figure 1) The bright spots generated by the optical microstructures M can improve the light uniformity of the backlight module 100 in the anti-peeping state. In one embodiment, the maximum width W of each optical microstructure M is, for example, between 0.005 mm and 0.050 mm, such as approximately 0.005 mm, 0.01 mm, 0.015 mm, 0.02 mm, 0.025 mm, 0.03 mm, 0.035 mm, 0.04 mm, 0.045 mm and 0.05 mm. In addition, the maximum length ML of each optical microstructure M in the direction D perpendicular to the normal N can be between 0.002 mm and 0.050 mm, such as approximately 0.005 mm, 0.008 mm, 0.01 mm, 0.015 mm, 0.02 mm, 0.025 mm, 0.03 mm, 0.035 mm, 0.04 mm, 0.045 mm and 0.05 mm, but the present invention does not impose any restrictions on the above values.

[0098] Compared with the prior art, in the backlight module 100 of the present embodiment, the optical microstructure M used in the first light guide plate 140 has a characteristic that the height H gradually decreases along the normal direction N. In detail, the optical microstructure M with a gradually decreasing height along the normal direction N can reduce the brightness of the light emitted from the side of the first light guide plate 140 close to the first light incident surface 141, and increase the brightness of the light emitted from the side of the first light guide plate 140 far from the first light incident surface 141. Based on the above, the optical microstructure M can effectively improve the uniformity of the light emitted from the first light guide plate 140, thereby improving the optical quality of the backlight module 100.

[0099] By the way, please refer to Figure 1 and Figure 2, the optical microstructure M 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. In detail, the light beam L2 generated by the first light-emitting element 130 can be partially incident on the first convex surface S1 and the rounded corner RC directly from the first light incident surface 141. Therefore, the height H of each optical microstructure M can affect the amount of light received by the first convex surface S1, thereby changing the amount of light reflected by each optical microstructure M to the light beam L2. The other part is incident on the second convex surface S2 and the rounded corner RC after total reflection on the light emitting surface 143. Furthermore, the first convex surface S1 of the optical microstructure M, 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 143 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 143, so that the brightness of the light emitted from the first light guide plate 140 is more uniform.

[0100] Figure 5 yes Figure 1 A schematic diagram showing the relationship between the light output brightness and the horizontal viewing angle of a backlight module in an embodiment of the present invention. Figure 1 and Figure 5 , the viewing angles 1, 2 and 3 are all viewed from the side of the end surface 144 of the first light guide plate 140. Further, based on the normal direction (direction Z) of the light emitting surface 143, the angle between the viewing angle 1 and the direction Z is about 60 degrees, the angle between the viewing angle 2 and the direction Z is about 50 degrees, and the angle between the viewing angle 3 and the direction Z is about 40 degrees. Please refer to Figure 1 , Figure 2 and Figure 5In one embodiment, the first angle A1 between each 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°. In one embodiment, the first angle A1 is, for example, between 40° and 60°, which can increase the light output brightness of the backlight module 100 at a horizontal viewing angle of about -60° to -40°, so that the backlight module 100 can provide an asymmetric viewing angle in the sharing state. In another embodiment, the first angle A1 can be between 47° and 53°, and 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, thereby increasing the light output brightness of the backlight module 100 at a horizontal viewing angle of about -80° to -20°. On the other hand, 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 L2 to be emitted from the first light guide plate 140 at a large angle, thereby increasing the viewing angle of the backlight module 100. The radius of curvature of the fillet RC is, for example, between 0.001 mm and 0.005 mm, so as to further improve the uniformity of light emission from the first light guide plate 140. In another embodiment, the radius of curvature of the fillet RC may be approximately 0.001 mm, 0.002 mm, 0.003 mm, 0.004 mm, and 0.005 mm, but the present invention is not limited thereto.

[0101] Figure 6 is a bottom view schematic diagram of a first light guide plate of a backlight module according to another embodiment of the present invention. 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 6 , at least part of the optical microstructures M are arranged in unequal intervals in the normal direction N. For example, the optical microstructure M may include a plurality of microstructures Ma. The microstructures Ma are arranged along the normal direction N, and the spacing G between two adjacent microstructures Ma increases gradually along the normal direction N. In this way, the brightness of the light emitted from the side of the first light guide plate 140a away from the first light incident surface 141 can be increased, and the brightness of the light emitted from the side of the first light guide plate 140a close to the first light incident surface 141 can be reduced, so that the brightness of the light emitted from the first light guide plate 140a is more uniform, thereby further improving the optical quality of the backlight module 100a.

[0102] Figure 7 is a bottom view schematic diagram of a first light guide plate 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 Figure 7, at least part of the optical microstructures M may be arranged at unequal distances in the normal direction N of the first light incident surface 141, and the present embodiment takes the optical microstructures M as an example of random arrangement in the normal direction N. Further, in the first light guide plate 140b of the present embodiment, the microstructure Mb may include two first microstructures M1b and two second microstructures M2b. The two first microstructures M1b are adjacent to each other and separated by a distance D1, and the two second microstructures M2b are adjacent to each other and separated by a distance D2, 10 -6 ≦∣D1-D2∣ / D1≦10 -4 For example, in this embodiment, 0.1nm≦|D1-D2|≦0.5nm. In short, the arrangement of the microstructure Mb in this embodiment can be achieved by Figure 3 This is achieved by increasing or decreasing the spacing between the optical microstructures M. For example, Figure 3 The spacing between two adjacent optical microstructures M is D3, and by increasing or decreasing each spacing D3 by any value within a predetermined range, the following can be obtained: Figure 7 The aforementioned predetermined range may include 0.1nm to 0.5nm, that is, |D3-D2| may be between 0.1nm and 0.5nm, but is not limited thereto. In one embodiment, 0.01mm≦D1≦0.07mm, and 0.01mm≦D2≦0.07mm. It is understood that the aforementioned range of |D1-D2| is not limited to Figure 7 The arrangement of the optical microstructure M. For example, the microstructure Mb can be as follows Figure 3 , Figure 6 and Figure 8 The present invention does not impose any limitation on this.

[0103] Figure 8 is a bottom view of a first light guide plate of a backlight module according to another embodiment of the present invention. The structure and advantages of the backlight module 100c 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, the optical microstructure M includes a plurality of first-row microstructures MR1 ​​and a plurality of second-row microstructures MR2. The first-row microstructures MR1 ​​and the second-row microstructures MR2 are arranged along the normal direction N, and the first-row microstructures MR1 ​​and the second-row microstructures MR2 are arranged side by side with each other. The optical microstructure MF1 closest to the first light incident surface 141 in the first-row microstructures MR1 ​​is separated from the first light incident surface 141 by a first spacing G1, and the optical microstructure MF2 closest to the first light incident surface 141 in the second-row microstructures MR2 is separated from the first light incident surface 141 by a second spacing G2. The first spacing G1 is different from the second spacing G2. In this way, the optical microstructures MF1 and MF2 can reflect light beams at different positions to reduce the bright lines formed on the first light guide plate 140c due to the concentrated emission of light beams, thereby improving the light emission uniformity on the side of the first light guide plate 140c close to the first light incident surface 141. In the present embodiment, the first spacing G1 is, for example, the spacing between the optical microstructure MF1 and the first light guide plate 140c in the normal direction N, and the second spacing G2 may be the spacing between the optical microstructure MF2 and the first light guide plate 140c in the normal direction N. In addition, the first row of microstructures MR1 ​​and the second row of microstructures MR2 may be arranged approximately equidistantly along the normal direction N, but in other embodiments, the first row of microstructures MR1 ​​and the second row of microstructures MR2 may be arranged unequally along the normal direction N. Incidentally, the arrangement of the optical microstructures M in the present embodiment may be changed by increasing or decreasing Figure 3 The method is obtained by dividing the distances D3 by , and the detailed method has been described above, so the related description is omitted here.

[0104] Fig. 9 FIG. 4 is a side view of a backlight module according to another embodiment of the present invention. Fig.10 yes Fig. 9 The structure and advantages of the backlight module 100d 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. 9 and Fig.10 , the optical microstructure Md protrudes from the surface 142. The first convex surface S1d is opposite to the first light incident surface 141 and the second convex surface S2d is toward the first light incident surface 141. Furthermore, after most of the light beam L2 enters the first light guide plate 140d from the first light incident surface 141, it can be totally reflected to the first convex surface S1d via the light emitting surface 143, and then reflected to the light emitting surface 143 via the first convex surface S1d, and then emitted from the light emitting surface 143 at a large angle. Similarly, part of the light beam L2 is reflected to the light emitting surface 143 via the fillet RCd and the second convex surface S2d. It should be noted that the first angle A1 is located on the side of the optical microstructure Md that is opposite to the first light incident surface 141, the fillet RCd protrudes away from the light emitting surface 143, and the second angle A2 is located on the side of the optical microstructure Md that is facing the first light incident surface 141. Other features of the optical microstructure Md are the same. Figure 1It is understood that the transmission path of the light beam L2 shown in this embodiment is only for illustration and is not intended to limit the present invention.

[0105] Fig.11 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 100e 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.11 , the light source assembly 110e, for example, further includes a third light guide plate 113, and the third light guide plate 113 is disposed between the second light guide plate 111 and the privacy film. 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. Further, 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 plates 113 in this embodiment may be one, but in other embodiments, the number of the third light guide plates 113 may be multiple, and the present invention does not impose more restrictions on the specific number of the third light guide plates 113.

[0106] Fig.12 FIG. 4 is a side view of a backlight module according to an embodiment of the present invention. Fig.13 yes Fig.12 Schematic diagram of the enlarged cross-section of the optical microstructure. Please refer to Fig.12 and Fig.13 , the backlight module 200 includes a light source assembly 110, a privacy film 120, a first light emitting element 130, and a first light guide plate 240. The maximum height between each optical microstructure M' of the first light guide plate 240 and the surface 242 is MH, and the maximum width of each optical microstructure M' in the normal direction N of the first light incident surface 241 is W, 0.2≦MH / W≦0.5. In addition, in one embodiment, the maximum height MH of each optical microstructure M' can be gradually reduced in the normal direction, that is, Figure 1 The other features of the optical microstructure M' are the same as Figure 1 Similarly, the other features of the light source assembly 110, the privacy film 120, and the first light emitting element 130 are the same. Figure 1 Therefore, the related description is omitted here.

[0107] Compared with the prior art, in the backlight module 200 of the present embodiment, the optical microstructure M' used in the first light guide plate 240 has a characteristic of an aspect ratio (MH / W) between 0.2 and 0.5. Specifically, within the above aspect ratio range of 0.2 to 0.5, the height of each optical microstructure M' can be adjusted according to the distance between each optical microstructure M' and the first light incident surface 241 to change the amount of light reflected by each optical microstructure M', thereby adjusting the amount of light emitted from different positions of the first light guide plate 240. In addition, the first light guide plate 240 is located on the transmission path of the light beam L1 of the light source assembly 110, and through the above aspect ratio range, not only the emission angle of the light beam L1 can be controlled, but also the size of the optical microstructure M' can be reduced, thereby reducing the bright spot generated by the light beam L1 passing through the optical microstructure M'. Based on the above, the optical microstructure M' can effectively improve the light uniformity of the first light guide plate 240, thereby improving the optical taste of the backlight module 200.

[0108] In summary, in the backlight module of the present invention, the optical microstructure used in the first light guide plate has a characteristic of gradually decreasing height along the normal direction. In detail, the optical microstructure with gradually decreasing height along the normal direction can reduce the brightness of the light output on the side of the first light guide plate close to the first light incident surface, and increase the brightness of the light output on the side of the first light guide plate away from the first light incident surface. Based on the above, the optical microstructure can effectively improve the uniformity of the light output of the first light guide plate, thereby improving the optical quality of the backlight module.

[0109] 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 is arranged on the side of the privacy film facing away from the light source component, and 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 microstructures are recessed or protruded from the surface, and each of the optical microstructures has a height with the surface, wherein each of the heights gradually decreases in a normal direction of the first light incident surface.

2. The backlight module according to claim 1, wherein: The surface has a low light area, a middle area and a high light area, the low light area is connected to the first light incident surface, the first light guide plate has an end surface opposite to the first light incident surface, and the high light area is connected to the end surface, the middle area is located between the low light area and the high light area, the optical microstructures include multiple low light microstructures, multiple middle microstructures and multiple high light microstructures, the low light microstructures are located in the low light area, and there is a first maximum height difference between the low light microstructures, the middle microstructures are located in the middle area, and there is a second maximum height difference between the middle microstructures, the high light microstructures are located in the high light area, and there is a third maximum height difference between the high light microstructures, and the second maximum height difference is greater than the first maximum height difference and the third maximum height difference.

3. The backlight module according to claim 2, wherein: Among the low beam microstructures, two adjacent to each other along the normal direction have a first height difference, among the intermediate microstructures, two adjacent to each other along the normal direction have a second height difference, and among the high beam microstructures, two adjacent to each other along the normal direction have a third height difference, and the second height difference is greater than the first height difference and the third height difference.

4. The backlight module according to claim 2, wherein: The length of the surface of the first light guide plate in the normal direction is L, the length of the middle area in the normal direction is L1, and 0.2L≦L1≦0.7L.

5. The backlight module according to claim 1, wherein: At least some of the optical microstructures are arranged with unequal distances in the normal direction.

6. The backlight module according to claim 5, characterized in that: The optical microstructures include a plurality of microstructures, the microstructures are arranged along the normal direction, and the spacing between two adjacent microstructures increases gradually along the normal direction.

7. The backlight module according to claim 5, wherein: The optical microstructures include a plurality of microstructures, which are arranged along the normal direction and include two first microstructures and two second microstructures, wherein the two first microstructures are adjacent to each other and separated by a distance D1, and the two second microstructures are adjacent to each other and separated by a distance D2, 10 -6 ≦∣D1-D2∣ / D1≦10 -4 .

8. The backlight module according to claim 7, wherein: Among them, 0.1nm≦∣D1-D2∣≦0.5nm.

9. The backlight module according to claim 7, wherein: Among them, 0.01mm≦D1≦0.07mm, and 0.01mm≦D2≦0.07mm.

10. The backlight module according to claim 1, wherein: Each of the optical microstructures has a vertex on a side facing away from the surface, and each of the optical microstructures has a maximum height MH between each of the vertices and the surface, and each of the optical microstructures has a maximum width W in the normal direction, 0.2≦MH / W≦0.

5.

11. The backlight module according to claim 1, wherein: The optical microstructures include a plurality of first-row microstructures and a plurality of second-row microstructures, the first-row microstructures and the second-row microstructures are arranged along the normal direction, and the first-row microstructures and the second-row microstructures are arranged side by side with each other, an optical microstructure among the first-row microstructures that is closest to the first light incident surface is spaced apart from the first light incident surface by a first spacing, and an optical microstructure among the second-row microstructures that is closest to the first light incident surface is spaced apart from the first light incident surface by a second spacing, and the first spacing is different from the second spacing.

12. 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.

13. The backlight module according to claim 12, 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.

14. The backlight module according to claim 13, 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 aligned with 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.

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