Backlight module

Abstract

The backlight module includes a light guide plate, a light source, an optical film, and first and second prism sheets. The light source is disposed on one side of a light incident surface of the light guide plate. The optical film overlaps a light exit surface of the light guide plate. The optical film includes a substrate, a plurality of optical microstructures, and a first diffusion structure layer. The light incident side of the substrate faces the light guide plate. The plurality of optical microstructures are disposed on the light incident side of the substrate and have extension directions intersecting the light incident surface of the light guide plate. Each optical microstructure has a top angle between its first and second inclined surfaces of between 50 and 90 degrees. The first diffusion structure layer is disposed on the light exit side of the substrate and overlaps the plurality of optical microstructures. The first diffusion structure layer has a haze value of between 20% and 90%. The first and second prism sheets overlap the optical film, each have a plurality of prism structures, and are located on the light exit side of the substrate. The first prism sheet is located between the optical film and the second prism sheet. The plurality of prism structures of the first and second prism sheets have extension directions intersecting each other. The backlight module has a high assembly yield and good light collection.

Description

[0001] This application is a divisional application of the invention patent application filed on May 29, 2019, entitled "Backlight Module" and with application number 201910455238.6. Technical Field

[0002] This invention relates to an optical module, and more particularly to a backlight module. Background Technology

[0003] With the increasing prevalence of non-self-emissive displays such as LCDs, backlight module designs need to be tailored to different usage scenarios. To improve the light energy utilization of the light source, backlight modules equipped with a Brightness Enhancement Film (BEF) have become one of the mainstream technologies in the market. Generally, such backlight modules are configured with a stacked structure of two Brightness Enhancement Films (such as two prisms with orthogonal extension directions), which can guide the light beam emitted from the light guide plate at a large angle to a specific angular range covering the viewing angle, thereby improving the overall light intensity of the backlight module near the viewing angle. However, this dual-layer BEF configuration limits the thinning of the backlight module.

[0004] To improve the light-gathering performance of backlight modules and overcome the aforementioned limitations in thinness, a light-gathering backlight module using a reverse prism to replace the two stacked optical brightness enhancement films has emerged. This type of backlight module can further enhance the overall light output near the viewing angle (i.e., it has a narrower angle range of light-gathering characteristics). Furthermore, because the number of optical film layers stacked in the light-gathering backlight module is smaller, its overall thickness can be effectively reduced, contributing to the thinning of the backlight module. However, from another perspective, when using this type of light-gathering backlight module, fine defects or tiny foreign objects (such as dust or lint introduced during assembly) between the various film layers are easily detected during subsequent quality control optical inspection. In other words, this type of backlight module, despite its excellent light-gathering performance, has poor concealment of minor defects, leading to a decrease in overall assembly yield. Therefore, balancing the light-gathering performance and concealment of backlight modules is one of the challenges that manufacturers face during design and development. Summary of the Invention

[0005] This invention provides a backlight module with high assembly yield and good light collection performance.

[0006] Other objects and advantages of the present invention can be further understood from the technical features disclosed herein.

[0007] To achieve one, some, or all of the above-mentioned objectives, or other objectives, an embodiment of the present invention provides a backlight module. The backlight module includes a light guide plate, a light source, an optical film, a first prism sheet, and a second prism sheet. The light guide plate has a connected light-emitting surface and a light-incident surface. The light source is disposed on one side of the light-incident surface of the light guide plate. The optical film is overlapped on the light-emitting surface of the light guide plate. The optical film includes a substrate, a plurality of optical microstructures, and a first diffusion structure layer. The substrate has opposing light-incident and light-emitting sides, with the light-incident side facing the light guide plate. The plurality of optical microstructures are disposed on the light-incident side of the substrate, and the extending directions of these optical microstructures intersect the light-incident surface of the light guide plate. The first diffusion structure layer is disposed on the light-emitting side of the substrate and overlaps the plurality of optical microstructures. The first prism sheet and the second prism sheet are overlapped on the optical film, and each has a plurality of prism structures. The first prism sheet and the second prism sheet are located on the light-emitting side of the substrate, with the first prism sheet located between the optical film and the second prism sheet. The extension directions of the multiple prism structures of the first prism sheet intersect the extension directions of the multiple prism structures of the second prism sheet.

[0008] Based on the above, in a backlight module according to an embodiment of the present invention, the optical film located between the prism sheet and the light guide plate has multiple optical microstructures disposed on the light-emitting surface side of the light guide plate, and the extending directions of the optical microstructures intersect the light-incident surface of the light guide plate, which can increase the overall light output of the backlight module near the positive viewing angle (that is, improve the light-gathering ability of the backlight module). On the other hand, by providing a diffusion structure layer on the side of the optical film away from the optical microstructures, the obfuscation of the backlight module can be improved, thereby improving the assembly yield of the backlight module. In other words, the process latitude of each component of the backlight module can also be increased.

[0009] To make the above features and advantages of the present invention more apparent and understandable, specific embodiments are described below in conjunction with the accompanying drawings. Attached Figure Description

[0010] Figure 1 This is a schematic diagram of the backlight module according to the first embodiment of the present invention.

[0011] Figure 2 yes Figure 1 A side view of the backlight module.

[0012] Figure 3 yes Figure 1 A top view of the backlight module.

[0013] Figure 4 yes Figure 1 A cross-sectional schematic diagram of the optical film.

[0014] Figures 5 to 8 This is a cross-sectional schematic diagram of an optical film according to other embodiments of the present invention.

[0015] Figure 9A This is a top view schematic diagram of the backlight module according to the second embodiment of the present invention.

[0016] Figure 9B This is a top view schematic diagram of the backlight module according to the third embodiment of the present invention.

[0017] Figure 10A This is a top view schematic diagram of the backlight module according to the fourth embodiment of the present invention.

[0018] Figure 10B This is a top view schematic diagram of the backlight module according to the fifth embodiment of the present invention.

[0019] Figure 11 This is a schematic diagram of the backlight module according to the sixth embodiment of the present invention.

[0020] Figure 12 yes Figure 11 A side view of the backlight module.

[0021] Figure 13 yes Figure 11 A cross-sectional schematic diagram of the second prism.

[0022] Figure 14 This is a cross-sectional schematic diagram of the second prism sheet according to another embodiment of the present invention. Detailed Implementation

[0023] The foregoing and other technical contents, features, and effects of this invention will be clearly presented in the following detailed description of a preferred embodiment with reference to the accompanying drawings. The directional terms used in the following embodiments, such as up, down, left, right, front, or back, are merely for reference to the directions in the drawings. Therefore, the directional terms used are for illustrative purposes and not for limiting the invention.

[0024] Figure 1 This is a schematic diagram of the backlight module according to the first embodiment of the present invention. Figure 2 yes Figure 1 A side view of the backlight module. Figure 3 yes Figure 1 A top view of the backlight module. Figure 4 yes Figure 1 A cross-sectional schematic diagram of the optical film. It should be noted that, for clarity, Figure 3 Only shown Figure 2 The light guide plate 100, the light source 110, and the optical microstructure 122.

[0025] Please refer to Figure 1 and Figure 2The backlight module 50 includes a light guide plate 100, a light source 110, and an optical film 120. The light guide plate 100 has a light-emitting surface 100a and a light-incident surface 100b, and the light-emitting surface 100a and the light-incident surface 100b are connected. The optical film 120 is overlapped on the light-emitting surface 100a of the light guide plate 100. The light source 110 is disposed on one side of the light-incident surface 100b of the light guide plate 100. That is, the backlight module 50 in this embodiment is a side-lit backlight module. However, the present invention is not limited thereto. According to other embodiments, the backlight module can also be a direct-lit backlight module. It should be noted that in this embodiment, the number of light sources 110 is illustrated by example as five, and does not mean that the present invention is limited to the content disclosed in the drawings. In other embodiments, the number of light sources 110 can be adjusted according to the optical design of the backlight module.

[0026] Furthermore, the optical film 120 includes a substrate 121, a plurality of optical microstructures 122, and a first diffusion structure layer 123. The substrate 121 has opposing light-incident sides 121a and emitting sides 121b, wherein the light-incident side 121b faces the light guide plate 100, and the optical microstructures 122 are disposed on the light-incident side 121b of the substrate 121, wherein the extending directions of the optical microstructures 122 intersect the light-incident surface 100b of the light guide plate 100, and the optical microstructures 122 can selectively contact the light guide plate 100. In this embodiment, the substrate 121 may be made of polyethylene terephthalate (PET) or polycarbonate (PC). The optical microstructures 122 may be made of UV-curable adhesive (UV glue) or other suitable polymers.

[0027] In this embodiment, the optical microstructure 122 of the optical film 120 can be arranged on the substrate 121 along the X direction and extend in the Y direction. For example, the cross-sectional profile of the optical microstructure 122 in a plane perpendicular to the extension direction (i.e., the Y direction) (i.e., the XZ plane) can be triangular. That is, the optical microstructure 122 in this embodiment can be a triangular prism strip, but the present invention is not limited to this. In other embodiments, the cross-sectional profile of the optical microstructure 122 in the XZ plane can also be adjusted according to the actual light pattern requirements (or beam splitting effect). More specifically, please refer to Figure 2Each of these optical microstructures 122 has a first inclined plane 122s1 and a second inclined plane 122s2, and the boundary between the first inclined plane 122s1 and the second inclined plane 122s2 defines a ridge line RL of the optical microstructure 122. In this embodiment, the optical microstructure 122 has a vertex angle θ between the first inclined plane 122s1 and the second inclined plane 122s2, and the vertex angle θ can be between 50 degrees and 90 degrees, but the present invention is not limited thereto. In other embodiments, the vertex angle θ of the optical microstructure can also be 90 degrees or between 90 degrees and 130 degrees.

[0028] Please refer to Figure 3 In this embodiment, the extension direction (i.e., direction Y) of the vertical projection of the ridge line RL (i.e., the extension path) of the optical microstructure 122 onto the light-emitting surface 100a of the light guide plate 100 can be selectively perpendicular to the light-incident surface 100b of the light guide plate 100. However, the invention is not limited thereto. According to other embodiments, the extension direction of the vertical projection of the ridge line RL of the optical microstructure 122 onto the light guide plate 100 may not be perpendicular to the light-incident surface 100b of the light guide plate 100. For example, the angle between the extension direction of the vertical projection of the ridge line RL of the optical microstructure 122 onto the light guide plate 100 and the light-incident surface 100b of the light guide plate 100 can be between 45 degrees and 90 degrees. Accordingly, the overall light output of the backlight module near the positive viewing angle can be increased.

[0029] Please refer to Figure 1 and Figure 4 The first diffusion structure layer 123 of the optical film 120 is disposed on the light-emitting side 121b of the substrate 121, and overlaps multiple optical microstructures 122 in the normal direction (i.e., direction Z) of the light-emitting surface 100a of the light guide plate 100. For example, the first diffusion structure layer 123 of the optical film 120 may selectively include a photosensitive adhesive layer 1231 and multiple diffusion particles 1232, wherein these diffusion particles 1232 are covered by the photosensitive adhesive layer 1231 (e.g., ...). Figure 4 (As shown). In this embodiment, the photosensitive adhesive layer 1231 is made of, for example, a UV-curable adhesive (UV glue) or other suitable transparent photosensitive adhesive. The diffusion particles 1232 may be made of polymethyl methacrylate (PMMA), polystyrene (PS), or a copolymer of the above materials. On the other hand, in this embodiment, the plurality of diffusion particles 1232 of the first diffusion structure layer 123 may be spherical and have various particle sizes, but the present invention is not limited thereto. In other embodiments, the plurality of diffusion particles 1232 may also have substantially the same particle size.

[0030] It is worth mentioning that by providing a first diffusion structure layer 123 on the light-emitting side 121b through the optical film 120, the optical film 120 can have a specific haze value. For example, the haze value of the first diffusion structure layer 123 (or the optical film 120) can be between 20% and 90%. Accordingly, the opacity of the backlight module can be improved, thereby increasing the assembly yield of the backlight module. In other words, the process latitude of each component of the backlight module can also be increased. On the other hand, since the first diffusion structure layer 123 (or the optical film 120) has a specific haze value, the number of diffusers in the backlight module 50 can be further reduced, which helps to reduce production costs.

[0031] It should be noted that, to meet specific concealing requirements and maximize the overall light output of the backlight module near the positive viewing angle, the apex angle θ of the optical microstructure 122 can be adjusted according to the haze value of the first diffusion structure layer 123. For example, in one embodiment, the haze value of the first diffusion structure layer 123 is 20%, and the apex angle θ of the optical microstructure is 90 degrees; in another embodiment, the haze value of the first diffusion structure layer 123 is 50%, and in order to obtain the same level of positive brightness, the apex angle θ of the optical microstructure needs to be designed to be less than 70 degrees.

[0032] Furthermore, the backlight module 50 also includes a first prism sheet 130 and a second prism sheet 140. The first prism sheet 130 and the second prism sheet 140 overlap the optical film 120 in the normal direction (i.e., direction Z) of the light-emitting surface 100a of the light guide plate 100, and are located on the light-emitting side 121b of the substrate 121 of the optical film 120 (that is, the side of the optical film 120 where the first diffusion structure layer 123 is provided). The first prism sheet 130 is located between the optical film 120 and the second prism sheet 140. Specifically, the first prism sheet 130 has a substrate 131 and a plurality of prism structures 132. These prism structures 132 are arranged along the direction Y on the surface of the substrate 131 away from the optical film 120 and extend in the direction X. Similarly, the second prism sheet 140 has a substrate 141 and a plurality of prism structures 142. These prism structures 142 are arranged along the X direction on the side surface of the substrate 141 away from the first prism sheet 130 and extend in the Y direction.

[0033] Following the above, in this embodiment, the extending direction (i.e., direction X) of the plurality of prism structures 132 of the first prism sheet 130 may be perpendicular to the extending direction (i.e., direction Y) of the plurality of prism structures 142 of the second prism sheet 140. However, the present invention is not limited to this. In other embodiments, the extending direction of the plurality of prism structures 132 of the first prism sheet 130 may also be neither perpendicular nor parallel to the extending direction of the plurality of prism structures 142 of the second prism sheet 140. That is, the angle between the extending direction of the plurality of prism structures 132 of the first prism sheet 130 and the extending direction of the plurality of prism structures 142 of the second prism sheet 140 may be greater than 0 degrees and less than 90 degrees. In this embodiment, the refractive index of the plurality of prism structures 132 of the first prism sheet 130 and the plurality of prism structures 142 of the second prism sheet 140 may be between 1.62 and 1.75. In this way, the overall light output of the backlight module 50 near the positive viewing angle can be further improved.

[0034] Please continue to refer to Figure 1 The backlight module 50 may optionally include a diffuser 150, but the invention is not limited thereto. The diffuser 150 is overlapped with the second prism sheet 140 and located on the side of the second prism sheet 140 away from the first prism sheet 130. Further, the backlight module 50 may also include a reflector 160, and the light guide plate 100 has a bottom surface 100c opposite to the light-emitting surface 100a, with the reflector 160 disposed on the side of the light guide plate 100 where the bottom surface 100c is located. Since some of the light beam emitted by the light source 110 will exit from the bottom surface 100c of the light guide plate 100 during transmission through the light guide plate 100, resulting in light energy loss, the reflector 160 can reflect this portion of the light beam back to the light guide plate 100, thereby improving the light energy utilization rate of the light source 110. However, the invention is not limited thereto; in other embodiments, the backlight module may not have a reflector 160.

[0035] It should be noted that the backlight module (e.g., backlight module 50) of this embodiment is suitable for use with a non-self-emissive display panel, such as a liquid crystal display (LCD) panel or an electrophoretic display (EPD) panel, to assemble an electronic device (i.e., a display device) that can display images. In other words, any display device that includes a non-self-emissive display panel and uses the backlight module of this embodiment still falls within the technical solutions that can be adopted by this disclosure and does not depart from the scope of protection intended by this disclosure.

[0036] Figures 5 to 8 This is a cross-sectional schematic diagram of an optical film according to other embodiments of the present invention. It should be particularly noted that... Figures 5 to 8 Any optical film can replace Figure 1 The optical film 120 is used to form backlight modules of different embodiments. Please refer to... Figure 5 In this embodiment, the optical film 120A and Figure 4 The main difference in the optical film 120 lies in the composition and structure of the first diffusion structure layer. In this embodiment, the first diffusion structure layer 123A of the optical film 120A does not have diffusion particles, and the surface 123s of the first diffusion structure layer 123A away from the substrate 121 has a microstructure. It should be noted that the microstructure described here is illustratively illustrated by an irregular (or randomly distributed) uneven structure, and does not represent that the present invention is limited to the content disclosed in the drawings. In some embodiments, the microstructure of the first diffusion structure layer may also be an uneven structure with a periodic distribution, and these uneven structures can be fabricated by creating a mold using photolithography, or the uneven structure can be fabricated directly on the first diffusion structure layer 123A using a photolithography and etching process. That is, the material of the first diffusion structure layer 123A may include a UV-curable adhesive (UV glue) or a photoresist. It is worth mentioning that the manufacturing method of these uneven structures is not limited to the above method. In other embodiments, the surface of the mold can be made uneven by sandblasting, and then UV forming can be performed to create the first diffusion layer.

[0037] Please refer to Figure 6 In this embodiment, the optical film 120B and Figure 5The main difference between the optical film 120A and the optical microstructure is the composition of the optical microstructure and the first diffusion structure layer. In this embodiment, the optical microstructure 122A of the optical film 120B may include multiple diffusion particles 1222 (i.e., the optical microstructure 122A may also have a specific haze value). On the other hand, a mold (e.g., a roller) with randomly distributed uneven microstructures can be used to form an uneven microstructure with a randomly distributed pattern on the light-emitting side 121b of the substrate 121 and then cured to form the first diffusion layer 123B; or the method of forming the first diffusion structure layer 123B may include a step of roughening the surface of the light-emitting side 121b of the substrate 121 using ultraviolet light or plasma, that is, the material of the first diffusion structure layer 123B and the substrate 121 may be the same. For example, the haze value of the optical microstructure 122A may be less than the haze value of the first diffusion structure layer 123B. However, the present invention is not limited thereto. In other embodiments, the relationship between the haze value of the optical microstructure 122A and the haze value of the first diffusion structure layer 123B may also be determined according to the overall haze requirement of the optical film 120B. In another embodiment, the first diffusion structure layer of the optical film may not have a microstructure or the optical film may not have a first diffusion structure layer; that is, the required haze of the optical film is provided by a plurality of optical microstructures 122A containing diffusion particles 1222.

[0038] Please refer to Figure 7 and Figure 8 , Figure 7 Optical film 120C, Figure 8 Optical film 120D and Figure 5 The main difference between the optical films 120A and 120D lies in the configuration of the optical microstructures. Specifically, the cross-sectional profile of the optical microstructure 122B of the optical film 120C is arc-shaped, while the cross-sectional profile of the optical microstructure 122C of the optical film 120D is polygonal (i.e., the cross-sectional profile of the optical microstructure 122C has multiple broken line segments). However, the present invention is not limited to the above embodiments. The different compositions and structures of the first diffusion structure layer, the compositions and configurations of the optical microstructures, and other embodiments can be combined and applied according to the overall haze requirements of the optical film.

[0039] Figure 9A This is a top view schematic diagram of the backlight module according to the second embodiment of the present invention. Figure 9B This is a top view schematic diagram of the backlight module according to the third embodiment of the present invention. Please refer to... Figure 9A The backlight module 50A in this embodiment and Figure 3The difference in the backlight module 50 lies in the configuration of the optical microstructure. In this embodiment, the vertical projection of the ridge line RL-A (i.e., the extension path) of the optical microstructure 122D of the optical film 120E onto the light-emitting surface 100a of the light guide plate 100 is a broken line. Specifically, although the extension path of the optical microstructure 122D is broken line, the vertical projection of its ridge line RL-A onto the light guide plate 100 is still limited to between two virtual straight lines IL.

[0040] More specifically, the vertical projections of the multiple bends of the ridge line RL-A of the optical microstructure 122D onto the light guide plate 100 are respectively tangent to two virtual straight lines IL, and the extension directions of these two virtual straight lines IL are perpendicular to the light incident surface 100b of the light guide plate 100. That is, although the extension path of the optical microstructure 122D is zigzag, its extension direction is still approximately perpendicular to the light incident surface 100b of the light guide plate 100 (i.e., direction Y). It is worth mentioning that the vertical projection of the optical microstructure 122D onto the light emitting surface 100a of the light guide plate 100 has a back-and-forth bending shape, which can effectively suppress the bright and dark patterns, i.e., moiré patterns, generated between the optical film 120E and the two prisms (e.g., the first prism 130 and the second prism 140). In other words, it can improve the light emission uniformity of the backlight module 50A.

[0041] Please refer to Figure 9B The backlight module 50A-1 in this embodiment and Figure 9A The difference between the backlight module 50A and the previous one lies in the configuration of the optical microstructure. In this embodiment, the two adjacent prisms RL-A of the optical microstructure 122D-1 of the optical film 120E-1 are projected onto the light guide plate 100 in a mirror manner as two vertical projections. Accordingly, the bright and dark fringes generated between the optical film 120E-1 and the two prism sheets (e.g., the first prism sheet 130 and the second prism sheet 140) can be further suppressed.

[0042] Figure 10A This is a top view schematic diagram of the backlight module according to the fourth embodiment of the present invention. Figure 10B This is a top view schematic diagram of the backlight module according to the fifth embodiment of the present invention. Please refer to... Figure 10A The backlight module 50B in this embodiment and Figure 9A The difference between the backlight module 50A and the previous one lies in the configuration of the optical microstructure. In this embodiment, the vertical projection of the ridge line RL-B (i.e., the extension path) of the optical microstructure 122E of the optical film 120F onto the light-emitting surface 100a of the light guide plate 100 is wavy. Similar to the optical microstructure 122D in the previous embodiment (e.g.... Figure 9AAs shown), in this embodiment, although the extension path of the optical microstructure 122E is wavy (e.g., a sine / cosine curve), its extension direction is still generally perpendicular to the light-incident surface 100b of the light guide plate 100 (i.e., direction Y). However, the invention is not limited to this; according to other embodiments, the extension path of the optical microstructure can also be a non-periodic bending curve. It is worth mentioning that the vertical projection of the optical microstructure 122E onto the light-emitting surface 100a of the light guide plate 100 has a back-and-forth bending shape, which can effectively suppress the interaction between the optical film 120F and the prism sheet (e.g., ...). Figure 1 The bright and dark stripe phenomenon generated between the first prism sheet 130 and the second prism sheet 140 shown is called a moiré pattern. In other words, it can improve the light emission uniformity of the backlight module 50B.

[0043] For example, a method for forming the optical microstructure 122E of the optical film 120F may include coating a UV-curable adhesive layer (or other suitable resin layer) onto a substrate 121 and imprinting the UV-curable adhesive layer using a mold with a pre-formed imprinting pattern (e.g., wavy or zigzag texture), while simultaneously curing the UV-curable adhesive layer located between the mold and the substrate 121 using a UV source. However, the invention is not limited thereto. In other embodiments, the method for forming the optical microstructure may also include sculpting the UV-curable adhesive layer using a tool with a specific shaped cutting head. Specifically, during the sculpting process on the UV-curable adhesive layer, the cutting head and the substrate 121 move relative to each other in the horizontal direction (i.e., direction X) of the cutting head's travel direction (i.e., direction Y). Accordingly, the periodicity of the wavy distribution in the extended direction of the formed optical microstructure can be determined according to the period of the cutting head's back-and-forth movement. In another embodiment, during the etching process on the UV-curable adhesive layer, the cutting head moves back and forth perpendicular to the substrate direction. By varying the degree of pressure applied by the cutting head, a gourd-shaped wave-like deposition pattern can be created, such as... Figure 10B The backlight module 50B-1 is shown. That is, the two adjacent prisms RL-B of the optical microstructure 122E-1 of the optical film 120F-1 are projected onto the light guide plate 100 in a mirror manner. Accordingly, the bright and dark fringes generated between the optical film 120F-1 and the two prism sheets (e.g., the first prism sheet 130 and the second prism sheet 140) can be further suppressed.

[0044] Figure 11 This is a schematic diagram of the backlight module according to the sixth embodiment of the present invention. Figure 12 yes Figure 11 A side view of the backlight module. Figure 13 yes Figure 11 A cross-sectional view of the second prism. Please refer to... Figures 11 to 13 The backlight module 50C in this embodiment and Figure 1The difference in the backlight module 50 lies in the configuration of the second prism sheet. In this embodiment, the second prism sheet 140A also has a second diffusion structure layer 143, which is disposed on the side of the second prism sheet 140A facing the first prism sheet 130, and overlaps with a plurality of prism structures 142 in the Z direction.

[0045] For example, the second diffusion structure layer 143 of the second prism sheet 140A may selectively include a photosensitive adhesive layer 1431 and a plurality of diffusion particles 1432, wherein these diffusion particles 1432 are coated by the photosensitive adhesive layer 1431 (e.g., Figure 13 (As shown). In this embodiment, the photosensitive adhesive layer 1431 is made of, for example, a UV-curable adhesive (UV glue) or other suitable transparent photosensitive adhesive. The diffusion particles 1432 may be made of polymethyl methacrylate (PMMA), polystyrene (PS), or a copolymer of the above materials. On the other hand, in this embodiment, the plurality of diffusion particles 1432 of the second diffusion structure layer 143 may be spherical and have various particle sizes, but the present invention is not limited thereto. In other embodiments, the plurality of diffusion particles 1432 may also have approximately the same particle size. On the other hand, since the second diffusion structure layer 143 (or the second prism sheet 140A) has a specific haze value, the backlight module 50C may not have such a haze value. Figure 1 The diffuser sheet 150 helps reduce production costs. However, the embodiments of the second diffusion structure layer of the present invention are not limited to the above embodiments. The second diffusion structure layer may also be implemented without diffusion particles, but with a microstructured surface.

[0046] Figure 14 This is a cross-sectional schematic diagram of the second prism sheet according to another embodiment of the present invention. Please refer to... Figure 14 The second prism sheet 140B in this embodiment and Figure 13 The main difference between the second prism sheet 140A and the second prism sheet 140B lies in the composition of the prism structure and the configuration of the second prism sheet. In this embodiment, the prism structure 142A of the second prism sheet 140B may include multiple diffusing particles 1422. That is, the prism structure 142A may have a specific haze value. On the other hand, the side of the second prism sheet 140B away from the prism structure 142A may not have a second diffusing structure layer 143 (e.g., Figure 13 (As shown). That is, the haze required by the second prism sheet 140B is provided by a plurality of prism structures 142A containing diffusion particles 1422. However, the embodiments of the second prism sheet of the present invention are not limited to the above embodiments, and the second prism sheet may also be implemented in a composition including a second diffusion structure layer with a microstructured surface and a prism structure with diffusion particles.

[0047] In summary, in the backlight module of one embodiment of the present invention, the optical film located between the prism sheet and the light guide plate has multiple optical microstructures disposed on the light-emitting surface side of the light guide plate, and the extending directions of the optical microstructures intersect the light-incident surface of the light guide plate, which can increase the overall light output of the backlight module near the positive viewing angle (that is, improve the light-gathering ability of the backlight module). On the other hand, by providing a diffusion structure layer on the side of the optical film away from the optical microstructures, the obfuscation of the backlight module can be improved, thereby improving the assembly yield of the backlight module. In other words, the process latitude of each component of the backlight module can also be increased.

[0048] Although the present invention has been disclosed above by way of embodiments, it is not intended to limit the present invention. Any person skilled in the art may make some modifications and refinements without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention shall be determined by the appended claims.

[0049] Explanation of reference numerals in the attached figures: 50, 50A~50C: Backlight module 100: Light guide plate 100a: Light-emitting surface 100b: Light-receiving surface 100c: Bottom surface 110: Light source 120, 120A~120F: Optical films 121, 131, 141: Substrate 121a: Receiver side 121b: Light-emitting side 122, 122A~122E: Optical microstructures 122s1, 122s2: Inclined surface 1222, 1232, 1422, 1432: Diffused particles 123, 123A, 123B: First diffusion structure layer 123s: Surface 1231, 1431: Photosensitive adhesive layer 130: First Prism Slide 132, 142, 142A: Prism structure 140, 140A, 140B: Second prism sheet 143: Second diffusion structure layer 150: Diffusion sheet 160: Reflector IL: Virtual Line RL, RL-A, RL-B: Edges X, Y, Z: Direction θ: Vertex angle.

Claims

1. A backlight module, characterized in that, The backlight module includes a light guide plate, a light source, an optical film, a first prism sheet, and a second prism sheet, wherein: The light guide plate has a light-emitting surface and a light-incident surface connected together; The light source is disposed on one side of the light incident surface of the light guide plate; The optical film is overlapped on the light-emitting surface of the light guide plate, and the optical film includes a substrate, multiple optical microstructures, and a first diffusion structure layer, wherein: The substrate has a light-incident side and a light-outcident side, wherein the light-incident side faces the light guide plate; The plurality of optical microstructures are disposed on the light-incident side of the substrate, wherein the extending directions of the plurality of optical microstructures intersect the light-incident surface of the light guide plate, and each optical microstructure has a first inclined surface and a second inclined surface, wherein the apex angle of each optical microstructure between the first inclined surface and the second inclined surface is between 50 degrees and 90 degrees; and The first diffusion structure layer is disposed on the light-emitting side of the substrate and overlaps the plurality of optical microstructures; the haze value of the first diffusion structure layer is between 20% and 90%. The first prism sheet and the second prism sheet are overlapped on the optical film and each has multiple prism structures. The first prism sheet and the second prism sheet are located on the light-emitting side of the substrate, and the first prism sheet is located between the optical film and the second prism sheet. The extending directions of the multiple prism structures of the first prism sheet intersect the extending directions of the multiple prism structures of the second prism sheet.

2. The backlight module according to claim 1, characterized in that, The extension direction of the plurality of optical microstructures of the optical film is perpendicular to the light incident surface of the light guide plate.

3. The backlight module according to claim 1, characterized in that, The optical microstructures of the optical film include multiple diffused particles.

4. The backlight module according to claim 1, characterized in that, The cross-section of each of the plurality of optical microstructures of the optical film is a triangle or a polygon.

5. The backlight module according to claim 1, characterized in that, The extension paths of each optical microstructure of the optical film are wavy or zigzag-shaped when projected vertically onto the light-emitting surface of the light guide plate.

6. The backlight module according to claim 1, characterized in that, The material of the first diffusion structure layer includes multiple diffusion particles.

7. The backlight module according to claim 1, characterized in that, One surface of the first diffusion structure layer has a microstructure.

8. The backlight module according to claim 1, characterized in that, The second prism sheet also has a second diffusion structure layer disposed on the side of the second prism sheet facing the first prism sheet.

9. The backlight module according to claim 1, characterized in that, The plurality of prism structures of the second prism sheet include a plurality of diffusing particles.

10. The backlight module according to claim 1, characterized in that, The refractive index of the plurality of prism structures of the first prism sheet and the second prism sheet is between 1.62 and 1.75.

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