Side-incoming backlight module and display device

Abstract

The application provides a side-in backlight module and a display device, and relates to the technical field of display, and comprises a light guide plate, a rubber frame, a light source module and a fixing rubber layer; wherein the light source module comprises a substrate and a plurality of light emitting devices which are arranged at intervals on a first surface of the substrate, and the light emitting surface of the light emitting device faces the light guide plate; the fixing rubber layer is arranged on the first surface and fixedly connects the substrate with the light guide plate and the rubber frame; the fixing rubber layer comprises a plurality of rubber points, and the distribution density of the rubber points increases with the increase of the distance between the rubber points and the center point of any light emitting device; and / or the cross-sectional size of the rubber points increases with the increase of the distance between the rubber points and the center point. Based on the scheme, the brightness uniformity of the light entering side of the side-in backlight module can be effectively improved.

Description

Technical Field

[0001] This application relates to the field of display technology, and more specifically, to edge-lit backlight modules and display devices. Background Technology

[0002] As the LCD industry moves towards higher brightness, lower power consumption, and ultra-narrow bezels, edge-lit backlight modules have been widely used in the flat panel display field because they can effectively reduce the number of light-emitting diodes (LEDs) used and, when combined with light guide plates, achieve a thinner and lighter display structure.

[0003] In the conventional assembly of edge-lit backlight modules, white LED strip adhesive is typically used to bond the flexible circuit board of the LED strip to the light guide plate and the frame. However, with the current trend towards narrow bezel designs, the bottom bezel of the display screen has been significantly reduced, resulting in a substantial shortening of the light mixing distance between the LED light source and the effective display area. Within this limited light mixing space, the light emitted by the light source cannot achieve sufficient mixing and overlap on the light-incident side of the light guide plate, easily producing discrete hotspots and localized bright and dark bands at positions directly opposite each LED light source, severely deteriorating the brightness uniformity on the light-incident side. Summary of the Invention

[0004] This application provides an edge-lit backlight module and a display device, which can effectively improve the brightness uniformity of the light-incident side of the edge-lit backlight module.

[0005] In a first aspect, a side-lit backlight module is provided, comprising: a light guide plate, a frame, a light source module, and a fixing adhesive layer; wherein, the light source module includes a substrate and a plurality of light-emitting devices spaced apart on a first surface of the substrate, the light-emitting surfaces of the light-emitting devices facing the light guide plate; the fixing adhesive layer is disposed on the first surface and fixes the substrate to the light guide plate and the frame respectively; the fixing adhesive layer includes a plurality of adhesive dots, with the center point of any light-emitting device as a reference: the distribution density of the adhesive dots increases with the increase of the distance from the adhesive dot to the center point; and / or, the cross-sectional size of the adhesive dots increases with the increase of the distance from the adhesive dot to the center point.

[0006] In conjunction with the first aspect, in some implementations of the first aspect, the fixed adhesive layer includes a first region and a second region. The first region is a region that unfolds in a fan shape with the center point as the vertex and toward the light guide plate. The second region is a region located between two adjacent first regions. A plurality of first adhesive dots located in the first region are uniformly distributed. The distribution density and / or cross-sectional size of a plurality of second adhesive dots located in the second region increase with the increase of the distance from the second adhesive dot to the center point, and the distribution density and / or cross-sectional size of the second adhesive dots are both greater than the distribution density and / or cross-sectional size of the first adhesive dots.

[0007] In conjunction with the first aspect, in some implementations of the first aspect, the diameter of the first adhesive dot is 0.1 mm to 0.3 mm, and the center-to-center distance between adjacent first adhesive dots is 0.3 mm to 0.5 mm; the diameter of the second adhesive dot is 0.15 mm to 0.35 mm, and is greater than the diameter of the first adhesive dot, and the center-to-center distance between adjacent second adhesive dots gradually decreases from 0.4 mm to 0.2 mm as the distance from the second adhesive dot to the center point increases.

[0008] In conjunction with the first aspect, in some implementations of the first aspect, the fixing adhesive layer is a substrate-free white adhesive layer.

[0009] In conjunction with the first aspect, in some implementations of the first aspect, the reflectivity of the fixed adhesive layer is greater than 80%, and the thickness of the fixed adhesive layer is 15 μm to 25 μm.

[0010] In conjunction with the first aspect, in some implementations of the first aspect, the peel force of the fixed adhesive layer is greater than or equal to 2000gf / 25mm.

[0011] In conjunction with the first aspect, in some implementations of the first aspect, the fixed adhesive layer is doped with functional particles, including diffusion particles and / or color conversion particles.

[0012] In conjunction with the first aspect, in some implementations of the first aspect, the diffused particles are polymethyl methacrylate (PMMA) spherical particles.

[0013] In conjunction with the first aspect, in some implementations of the first aspect, the color-converting particles are quantum dot particles or phosphor particles, used to absorb blue light and emit red and / or green light.

[0014] In conjunction with the first aspect, in some implementations of the first aspect, the minimum overlap width between the substrate and the light guide plate is 0.3 mm.

[0015] In a second aspect, a display device is provided, comprising: a display panel, and an edge-lit backlight module as described in the second aspect, the edge-lit backlight module being located on the backlight side of the display panel. Attached Figure Description

[0016] Figure 1 This is a cross-sectional view of a conventional side-lit backlight module 100. Figure 2 This is a schematic diagram of the structure of a side-lit backlight module 200 proposed in an embodiment of this application; Figure 3 This is a schematic diagram of the adhesive dot distribution of a side-lit backlight module 200 according to an embodiment of this application; Figure 4This is a schematic diagram of the current external layout of the LED strip fixing adhesive for side-lit backlight modules. Figure 5 This is a schematic diagram of the simulation experiment results provided in this application; Figure 6 This is a schematic diagram of the assembly process of a side-lit backlight module 200 according to an embodiment of this application; Figure 7 This is a schematic diagram of a fixed adhesive coating process proposed in an embodiment of this application. Detailed Implementation

[0017] This application will present various aspects, embodiments, or features relating to a system comprising multiple devices, components, modules, etc. It should be understood and appreciated that individual systems may include additional devices, components, modules, etc., and / or may not include all the devices, components, modules, etc. discussed in conjunction with the accompanying drawings. Furthermore, combinations of these approaches are also possible. Furthermore, in the embodiments of this application, the words "exemplary," "for example," etc., are used to indicate that they are examples, illustrations, or descriptions. Any embodiment or design scheme described as "exemplary" in the embodiments of this application should not be construed as being better or more advantageous than other embodiments or design schemes. Specifically, the use of the term "exemplary" is intended to present the concept in a concrete manner. The business scenarios described in the embodiments of this application are for the purpose of more clearly illustrating the technical solutions of the embodiments of this application, and do not constitute a limitation on the technical solutions provided in the embodiments of this application. As those skilled in the art will know, with the evolution of technology and the emergence of new business scenarios, the technical solutions provided in the embodiments of this application are also applicable to similar technical problems.

[0018] References to "one embodiment" or "some embodiments" as described in this specification mean that one or more embodiments of this application include a specific feature, structure, or characteristic described in connection with that embodiment. Therefore, the phrases "in one embodiment," "in some embodiments," "in other embodiments," "in still other embodiments," etc., appearing in different parts of this specification do not necessarily refer to the same embodiment, but rather mean "one or more, but not all, embodiments," unless otherwise specifically emphasized. The terms "comprising," "including," "having," and variations thereof mean "including but not limited to," unless otherwise specifically emphasized.

[0019] In this application embodiment, "at least one" refers to one or more, and "more than one" refers to two or more. "And / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A alone, A and B simultaneously, and B alone, where A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects are in an "or" relationship. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of single or plural items. For example, at least one of a, b, or c can represent: a, b, c, ab, ac, bc, or abc, where a, b, and c can be single or multiple.

[0020] In the description of the embodiments of this application, the terms "upper," "lower," "left," "right," "inner," "outer," "vertical," and "horizontal," etc., indicate the orientation or positional relationship relative to the orientation or position of the components shown in the accompanying drawings. It should be understood that these directional terms are relative concepts, used for relative description and clarification, and not to indicate or imply that the device or component referred to must have a specific orientation, or be constructed and operated in a specific orientation. They can change accordingly depending on the orientation of the components in the accompanying drawings, and therefore should not be construed as limiting this application.

[0021] In the embodiments of this application, the same reference numerals are used to denote the same component or part. For the same part in the embodiments of this application, only one part or component may be labeled with reference numerals in the figures. It should be understood that the reference numerals also apply to other identical parts or components. In addition, the various parts in the figures are not drawn to scale, and the dimensions and sizes of the parts shown in the figures are only exemplary and should not be construed as limiting this application.

[0022] As the LCD industry moves towards higher brightness, lower power consumption, and ultra-narrow bezels, edge-lit backlight modules have been widely used in the flat panel display field because they can effectively reduce the number of LED light sources used and, when combined with light guide plates, achieve a thinner and lighter display structure.

[0023] Figure 1 This is a cross-sectional view of a conventional side-lit backlight module 100.

[0024] refer to Figure 1As shown, a conventional side-lit backlight module 100 typically includes a backplate 101, a frame 103, a light guide plate 105, a reflective sheet 107 disposed opposite to the light guide plate 105, and a light strip disposed on the light-incident side of the light guide plate 105, wherein the light strip includes a flexible printed circuit (FPC) and multiple surface-mounted LED light sources 109.

[0025] In traditional processes, a white LED strip fixing adhesive 108 with a certain thickness (e.g., 60μm) is typically used to bond and fix the fixing ends of the flexible circuit board to the edge of the light guide plate 105 and the adhesive frame 103. To ensure that stringent structural reliability requirements are met and to prevent the LED strip from delaminating with the light guide plate 105, the minimum overlap width between the flexible circuit board and the light guide plate 105 usually needs to be maintained at more than 0.4mm, which directly limits further reduction in the product bezel. In this type of traditional assembly architecture, the light emitted by each LED light source 109 is coupled into the interior of the light guide plate 105 through the light-incident end face of the light guide plate 105, and is converted into a surface light source output under the synergistic effect of the reflector 107 and the upper optical film.

[0026] However, with the current trend of narrow bezel designs, the bottom bezel size of the display screen has been significantly reduced, resulting in a significant shortening of the light mixing distance between the emitting surface of the LED light source 109 and the effective display area (AA). This spatial limitation leads to poor brightness uniformity on the light-incident side.

[0027] One specific reason for the aforementioned problem of poor brightness uniformity on the light-incident side is that, within the extremely short light mixing space, the light emitted by the discretely arranged LED light sources 109 has not yet achieved sufficient lateral divergence, mixing, and overlap at the light-incident side edge of the light guide plate 105 before directly entering the display area. This makes it very easy to generate discrete hotspots at the positions directly opposite each LED light source 109, while forming relatively dark areas in the gap area between two adjacent LED light sources 109, presenting obvious alternating bright and dark bands.

[0028] On the other hand, reference Figure 1As shown, the traditional white LED strip fixing adhesive 108 with a substrate has a relatively thick adhesive layer (approximately 60μm). While the rigid substrate does not contribute to adhesion, during the assembly and bonding of the backlight module 100, the rigid mechanical pressure easily causes uncontrollable lateral overflow or thickness deformation of the adhesive. Simultaneously, the thick adhesive layer results in significant assembly tolerances and height misalignments between the LED strip and the light guide plate 105 in the direction perpendicular to the display surface (Z-axis direction). This Z-axis height misalignment, typically reaching 60μm, causes some light emitted from the LED light source 109 at large angles to be unable to be effectively received by the light-incident end face of the light guide plate 105. Instead, it leaks through the misalignment gap and directly strikes the surface of the white LED strip fixing adhesive 108, causing approximately 3% light loss. This leaked light undergoes disordered stray reflection on the surface of the white LED strip fixing adhesive 108, further exacerbating localized abnormal brightness at the location directly opposite the LED light source 109. This severely deteriorates the brightness uniformity on the light-incident side, affecting the image quality of the terminal display product.

[0029] In view of this, the present application proposes a side-lit backlight module, which can effectively improve the brightness uniformity of the light-incident side of the side-lit backlight module.

[0030] Figure 2 This is a schematic diagram of the structure of a side-lit backlight module 200 according to an embodiment of this application. Figure 2 (a) in the figure is used to represent a cross-sectional view of the side-lit backlight module 200. Figure 2 (b) in the figure is used to represent a longitudinal cross-sectional view of the side-lit backlight module 200.

[0031] refer to Figure 2 As shown in (a), the side-lit backlight module 200 includes a light guide plate 210, a frame 220, a light source module 230, and a fixing adhesive layer 240. The light source module 230 includes a substrate 231 and a plurality of light-emitting devices 232 spaced apart on the first surface 01 of the substrate 231, with the light-emitting surface 02 of the light-emitting devices 232 facing the light guide plate 210; a fixing adhesive layer 240 is disposed on the first surface 01 and fixes the substrate 231 to the light guide plate 210 and the adhesive frame 220 respectively.

[0032] refer to Figure 2 As shown in (b), the above-mentioned fixed adhesive layer 240 includes a plurality of adhesive dots 241, with the center point O1 of any light-emitting device 232 as a reference: the distribution density of adhesive dots 241 increases with the increase of the distance from adhesive dots 241 to the center point O1, and / or, the cross-sectional size of adhesive dots 241 increases with the increase of the distance from adhesive dots 241 to the center point O1.

[0033] In the hardware structure of the aforementioned side-lit backlight module 200, the first surface 01 of the substrate 231 refers to the welding bearing surface of the substrate 231 facing the light guide plate 210 and the frame 220, i.e., the surface of the FPC-mounted light-emitting device 232. The light-emitting device 232 (such as an LED bead) can be fixed to the first surface 01 by surface mounting process and electrically connected through reserved electrode pins. The light-emitting surface 02 of the light-emitting device 232 can directly contact or maintain a very small assembly gap with the edge light-incident end face of the light guide plate 210 to ensure that large-angle emitted light can be coupled into the interior of the light guide plate 210 to the maximum extent. The aforementioned fixing adhesive layer 240 serves as a functional adhesive medium and can be directly applied to the area on the first surface 01 excluding the light-emitting device 232, the pads, and the necessary safety spacing. It spans between the light guide plate 210 and the frame 220. One end of the fixing adhesive layer 240 is bonded to the light-incident edge surface of the light guide plate 210, and the other end is bonded to the surface of the frame 220, thereby securing the light source module 230 as a whole between the two.

[0034] It should be noted that the phrase "taking the center point of any light-emitting device 232 as a reference" means that, in the extending direction of the substrate 231, the distribution density and cross-sectional size of the adhesive dots 241 gradually increase with the increase of the vertical distance from the light-emitting center line of the light-emitting device 232. In other words, on the surface of the substrate 231, the closer to the front of the light-emitting device 232, the sparser the distribution of adhesive dots 241 and the smaller the area of ​​each individual dot; while the farther away from the front of the light-emitting device 232 (i.e., the area near the gap between two adjacent light-emitting devices 232), the denser the distribution of adhesive dots 241 and the larger the area of ​​each individual dot.

[0035] The higher the distribution density of adhesive dots 241 per unit area, or the larger the cross-sectional size of a single adhesive dot 241, the higher the coverage of the adhesive layer 240 in that area. Since the adhesive layer 240 itself has high reflectivity, the reflectivity of that area increases accordingly. Conversely, when the distribution density of adhesive dots 241 per unit area decreases, or the size of a single adhesive dot 241 decreases, the coverage of the adhesive layer 240 in that area decreases, the exposed surface area of ​​the substrate 231 increases, and the reflectivity of that area decreases accordingly. In this way, the spatial density and size variations of the adhesive dots 241 can be transformed into a spatially variable reflectivity distribution on the surface of the substrate 231.

[0036] When each light-emitting device 232 is lit, the light emitted by the device itself is not uniform in space. Specifically, the light is strongest and most concentrated in the area directly opposite the center line of the device 232, while the light is weakest in the gap area between adjacent devices 232, away from the center line. Traditional uniformly coated adhesive layers (such as…) Figure 1 As shown, the inherent light-emitting defects of the light source cannot be changed, resulting in excessive light emission and bright spots in the area directly facing the light source. However, in the side-lit backlight module 200 proposed in this application embodiment, by changing the density and size distribution of the adhesive dots 241, an optical functional structure whose reflectivity changes accordingly at different positions is constructed on the surface of the substrate 231, thereby adjusting the intensity of the light source.

[0037] For example, in the region directly opposite the center line of the light-emitting device 232 (i.e., the region with the strongest light), the adhesive dots 241 are sparsely distributed and small in size. This reduces the coverage of the fixing adhesive layer 240 on the surface of the substrate 231 in this region, thereby actively weakening the light reflection capability of this region and avoiding the formation of hotspots due to excessive local light concentration. In contrast, in the region far from the center line and close to the gap between two adjacent light-emitting devices 232 (i.e., the region with the weakest light), the adhesive dots 241 are densely distributed and larger in size. This increases the coverage of the fixing adhesive layer 240 in this region, and multiple adjacent adhesive dots 241 exhibit a more continuous morphology, thereby enhancing the light reflection capability of this region and reflecting the weak light in this region back into the light guide plate 210, thus increasing the light contribution of this region. By using this optical functional structure that reduces light reflection in strong light areas and increases light reflection in weak light areas, the backlight intensity that ultimately enters the light guide plate 210 can be made smoother and more uniform overall, thus fundamentally solving the problem of alternating bright and dark bands on the light-incident side caused by the shortened light mixing distance in ultra-narrow bezel products.

[0038] Based on the above technical solution, the edge-lit backlight module achieves a correspondence between the spatial distribution of adhesive dots and the reflectivity of the substrate surface by setting a non-uniformly gradient distributed array of adhesive dots on the substrate surface. This reduces reflectivity in high-light areas and increases reflectivity in low-light areas, thereby effectively compensating for the uniformity of light distribution within the light guide plate space. This solution does not require damaging the structure of the light guide plate itself or introducing additional complex optical films. While ensuring the strength and reliability of the backlight module assembly structure, it effectively improves the brightness uniformity on the light-incident side, solving the problem of dotted bright spots and alternating bright and dark bands caused by the shortened light mixing distance in narrow-bezel edge-lit backlight products. This provides a reliable spatial basis for narrowing the bezel size of the display module.

[0039] Figure 3 This is a schematic diagram of the adhesive dot distribution of a side-lit backlight module 200 proposed in an embodiment of this application.

[0040] In some possible embodiments, reference Figure 3 As shown, based on the above adhesive dot distribution design, the fixed adhesive layer 240 can be divided into two regions, namely the first region A1 and the second region A2. The first region A1 is a fan-shaped region extending towards the light guide plate 210 with the center point O1 of any light-emitting device 232 as its vertex. The second region A2 is the region located between two adjacent first regions A1. Multiple first adhesive dots 2411 within the first region A1 are uniformly distributed. The distribution density and / or cross-sectional size of multiple second adhesive dots 2412 within the second region A2 increases with the distance from the second adhesive dots 2412 to the center point O1, and the distribution density and / or cross-sectional size of the second adhesive dots 2412 are both greater than the distribution density and / or cross-sectional size of the first adhesive dots 2411.

[0041] The first region A1 is a fan-shaped area extending towards the light guide plate 210 with the center point O1 of any light-emitting device 232 as its vertex. This region corresponds to the core beam region with the strongest light intensity in the light emitted by a single light-emitting device 232. Since the spatial light intensity within the first region A1 is at its peak, to avoid excessive local light concentration and the generation of bright spots on the light-incident side of the light guide plate 210, the multiple first adhesive dots 2411 located within the first region A1 are arranged in a relatively low density and uniformly distributed. Under this arrangement, the adhesive layer coverage within the first region A1 remains at a constant and low level, thereby providing a uniform and low surface reflectivity within the core strong beam range, reducing the local reflectivity of this high-intensity concentrated area, and suppressing the generation of bright spots.

[0042] The second region A2 is located between two adjacent first regions A1, corresponding to the weak light region or dark region between two adjacent light-emitting devices 232. Within this region, since the spatial light intensity directly radiated by the light source is at a low point, to prevent local dark areas from appearing due to the shortened light mixing distance, the multiple second adhesive dots 2412 within the second region A2 employ a gradient design for the adhesive dot distribution density and / or increasing cross-sectional size. That is, the distribution density and / or cross-sectional size of the second adhesive dots 2412 increase with the increase of the distance from the second adhesive dot 2412 to the center point O1. Moreover, the overall distribution density and cross-sectional size of the second adhesive dots 2412 within the second region A2 are greater than the distribution density and cross-sectional size of the first adhesive dots 2411 within the first region A1. This results in a higher coverage of the fixing adhesive layer 240 within the second region A2 compared to the first region A1, thereby forming a highly reflective optical functional layer in the dark region of space. This enhances the light reflection capability of the second region A2, allowing more light within the second region A2 to be reflected back into the light guide plate 210.

[0043] Based on the design of the glue dot distribution and geometric parameters in the first region A1 and the second region A2, the brightness uniformity on the incident light side can be improved.

[0044] In some possible embodiments, the spatial emission angle of the first region A1, which is fan-shaped, can be adjusted according to the half-value angle characteristics of the light-emitting device 232.

[0045] For example, the area of ​​the fan-shaped expansion can be defined as a spatial emission angle region of 45° on each side of the light-emitting center line of the light-emitting device 232; or refer to Figure 3 As shown, the region is defined as a spatial emission angle region of 60° on each side of the light-emitting center line of the light-emitting device 232. Within this angle range, by maintaining the uniform distribution of the first adhesive dots 2411 (for example, fixing the diameter r0 of the first adhesive dots 2411 within the range of 0.1 mm to 0.3 mm, and keeping the center-to-center distance p0 between adjacent first adhesive dots 2411 constant within the range of 0.3 mm to 0.5 mm), the main angle range of strong light emitted by the light-emitting device 232 can be effectively covered, thereby providing a uniform and low reflectivity in this region, directly weakening the excessively strong light directly facing the light-emitting device 232, and suppressing the generation of dot-shaped bright spots.

[0046] In some possible embodiments, the gradient increase pattern of the second adhesive point 2412 within the second region A2 can be adjusted in segments.

[0047] For example, at the boundary near the edge of the first region A1, the cross-sectional size of the second adhesive dot 2412 can be fixed to a first diameter r1 (e.g., 0.25 mm), while the distance between its adjacent centers gradually decreases from 0.4 mm near the boundary to 0.3 mm. As it moves further away from the center line until it reaches the exact center of the two adjacent light-emitting devices 232, the cross-sectional size of the second adhesive dot 2412 can be further increased to a second diameter r2 (e.g., 0.35 mm) larger than the first diameter r1, and the distance between its centers p1 is further compressed to 0.2 mm. In this arrangement, as it extends towards the junction area of ​​the two adjacent light-emitting devices 232 (i.e., the area with the weakest light), the spacing between the second adhesive dots 2412 gradually decreases, eventually forming a nearly continuous adhesive layer in the junction area. Ultimately, the coverage area of ​​the fixed adhesive layer 240 is larger in areas with weaker light, thereby reflecting more weak light that would otherwise be missed back into the light guide plate 210, further improving the brightness of the dark area.

[0048] Based on the above technical solution, it is possible to adjust the uniformity of the spatial light intensity distribution of the light source, thereby improving the brightness uniformity of the side-lit backlight module. Moreover, while ensuring the structural connection strength, it effectively eliminates the problem of dot-shaped bright spots caused by the shortened light mixing distance in narrow-bezel side-lit backlight products.

[0049] Furthermore, considering that the conventional solutions commonly used in the industry typically employ white LED strip mounting adhesive with a substrate, applied in a continuous, zigzag pattern to the surface of the LED strip FPC, this white adhesive has a low reflectivity, usually only around 70%. When light emitted from LED devices at large angles strikes the adhesive surface, significant light loss occurs, thus limiting the overall luminous efficacy of the backlight module.

[0050] To address the light loss problem caused by the low reflectivity of traditional lamp adhesives, the industry has proposed an optimization scheme aimed at improving light efficiency.

[0051] Figure 4 This is a schematic diagram of the current external layout of the LED strip fixing adhesive for side-lit backlight modules. Figure 4 (a) in the figure represents the current layout of the continuous square-shaped full-coated LED strip fixing adhesive. Figure 4 (b) in the diagram is a layout scheme for the LED strip fixing adhesive used to solve the problem of light loss caused by the low reflectivity of traditional LED adhesive.

[0052] contrast Figure 4 (a) and Figure 4 As shown in (b), the core idea of ​​the current solution to address the light loss problem caused by the low reflectivity of traditional LED strip adhesive is to change the shape and layout of the LED strip fixing adhesive, eliminating the edge tape on the side facing the light-emitting device in the conventional U-shaped structure, thereby creating a partially open opening. This opening design exposes the white polyimide (PI) surface of the flexible circuit board, which was originally covered by the LED strip adhesive. Since the white PI surface of the FPC itself has a reflectivity of approximately 80%, significantly higher than the 70% reflectivity of traditional white LED strip fixing adhesive, exposing the higher reflectivity FPC surface can improve light utilization to a certain extent, increasing the overall luminous efficacy of the backlight module by approximately 3%.

[0053] However, the above-mentioned aperture optimization scheme still faces obvious technical bottlenecks in practical industrial applications, namely, the improvement in light efficiency is very limited.

[0054] Specifically, while the aforementioned optimized opening scheme eliminates an edge adhesive strip on the side of the light-emitting device to improve luminous efficiency by exposing the white PI surface, this opening design essentially sacrifices the rigid bonding area between the FPC and the light guide plate. Therefore, to ensure basic structural robustness and prevent adhesive separation issues during subsequent reliability testing, the opening area of ​​the LED strip fixing adhesive cannot be expanded indefinitely. This limits the improvement in backlight module luminous efficiency by this optimized scheme to approximately 3%, preventing a significant breakthrough in luminous efficiency and introducing the contradiction between luminous efficiency improvement and structural reliability found in existing solutions.

[0055] Furthermore, the aforementioned aperture optimization scheme exacerbates the risk of spot brightness in ultra-narrow bezel products. This is because this localized aperture design further increases the reflectivity of the light-emitting surface area of ​​the light-emitting device (i.e., the area with already strong light intensity), while the reflectivity between two adjacent light-emitting devices (i.e., the area with relatively weak light intensity) remains unchanged. This further intensifies the uneven distribution of light intensity on the incident side within an extremely short light mixing space, thereby deteriorating the overall optical image performance.

[0056] Therefore, the adhesive used in the fixing adhesive layer 240 of the side-lit backlight module 200 proposed in this application embodiment can be a substrate-free white adhesive layer, such as a UV-curable substrate-free white adhesive layer, prepared based on UV-curable adhesive.

[0057] Traditional LED strip fixing adhesives include rigid plastic substrates, such as polyethylene terephthalate (PET) sheets. These substrates typically only serve a passive auxiliary role, supporting the adhesive and facilitating manual assembly and tape winding; the material itself contributes nothing to the actual interfacial adhesion. Furthermore, because the rigid substrate occupies a large portion of the tape's volume, the proportion of effective adhesive per unit volume is significantly reduced, limiting the overall shear strength. In contrast, the substrate-free white adhesive layer used in this embodiment completely eliminates the substrate in its material structure. This allows the space of the fixing adhesive layer 240 after pressing to be entirely filled with a mechanically adhesive cross-linked polymer network, resulting in a significantly higher overall adhesion per unit volume compared to traditional LED strip fixing adhesives.

[0058] For example, in addition to the UV-curable adhesive mentioned above, in practical applications, heat-curable white glue or moisture-curable white glue can also be used as materials to form the above-mentioned fixing adhesive layer 240.

[0059] In some possible embodiments, due to the significant increase in the overall adhesion of the adhesive layer 240 of the side-lit backlight module 200 per unit volume, the high adhesion of the adhesive layer 240 in the height direction perpendicular to the screen surface allows its overall thickness to be significantly compressed to an ultra-thin level of 15μm to 25μm. Within this thickness range, because the interior of the adhesive layer 240 is completely filled with a highly active adhesive network, the peel strength of the adhesive layer 240 can still stably reach above 2000gf / 25mm.

[0060] In traditional LED strip fixing adhesives, the thickness of the substrate adhesive is fixed at around 60 μm. This results in a misalignment of up to 60 μm in the thickness direction between the light-emitting surface of the light-emitting device and the edge light-incident surface of the light guide plate, leading to approximately 3% light leakage loss. However, this embodiment reduces the thickness of the fixing adhesive layer 240 to 15 μm to 25 μm (e.g., around 20 μm), thereby minimizing the misalignment in the thickness direction between the light-emitting device 232 and the light guide plate 210. In other words, the thinning of the fixing adhesive layer 240 effectively reduces light leakage caused by the misalignment gap between the light-emitting device 232 and the light guide plate 210, thus reducing this light loss and improving the luminous efficiency of the side-lit backlight module 200.

[0061] Furthermore, due to the increased adhesive strength per unit area of ​​the adhesive layer 240, the bonding length of the adhesive layer 240 in the planar dimension can be reduced. This is because the adhesive layer 240 provides sufficient mechanical bonding strength on a smaller contact surface, and the planar bonding length between the substrate 231 and the light guide plate 210 no longer needs to rely on traditional large-area overlaps. The minimum overlap width between the two can be safely reduced from 0.4 mm in the conventional solution to 0.3 mm.

[0062] In summary, the embodiments of this application utilize a substrate-free curing adhesive design to improve the overall adhesion of the fixing adhesive layer 240. While achieving an ultra-thin thickness of 15μm to 25μm, the minimum overlap width between the substrate 231 and the light guide plate 210 is reduced to 0.3mm. This not only ensures the reliability of the high-strength adhesive structure but also increases the physical bezel space of the side-lit backlight module to adapt to the narrow bezel requirements, and effectively improves the light efficiency of the side-lit backlight module 200.

[0063] In some possible embodiments, for products that require high brightness but do not require narrow bezels, a full coating process can be performed using only a substrate-free fixing adhesive layer 240, without adopting the adhesive dot distribution design proposed in the above embodiments.

[0064] In addition, in order to further improve the brightness uniformity and high color gamut display effect of the side-lit backlight module 200, the present application embodiment has made the following design to the fixing adhesive layer 240, thereby increasing the optical function of the fixing adhesive layer 240.

[0065] In some possible embodiments, the fixative layer 240 is doped with functional particles, including diffuse particles.

[0066] In some possible embodiments, the diffused particles described above are PMMA spherical particles.

[0067] PMMA material itself possesses good optical transparency and anti-yellowing properties, and the difference between the refractive index of PMMA material (approximately 1.49) and the refractive index of the main adhesive layer 240 is small. When light enters the adhesive layer 240 and comes into contact with the PMMA spherical particles, this small difference in refractive index allows the light to undergo efficient multi-angle scattering at the particle interface, rather than being completely blocked or absorbed. This multi-angle scattering can disrupt the light beam that originally propagated along a fixed direction, thus smoothing the spatial reflectivity and making the brightness transition on the light-incident side of the side-lit backlight module 200 more gradual.

[0068] For example, the particle size of the aforementioned PMMA spherical particles can be controlled between 1 μm and 5 μm (e.g., around 3 μm). If the particle size is too small (less than 1 μm), the scattering cross-section for red, green, and blue visible light will be insufficient, and it will not play a significant role in diffusion and light control. If the particle size is too large (greater than 5 μm), it will easily lead to an abnormal increase in the surface roughness of the ultrathin fixing adhesive layer 240 (15 μm to 25 μm), thereby affecting the strength of the adhesive structure of the assembled bonding.

[0069] For example, the mass doping concentration of the aforementioned PMMA spherical particles in the fixing adhesive layer 240 can be limited to between 3% and 8% (e.g., around 5%). When the doping concentration is below 3%, the bright and dark bands cannot be effectively eliminated; while when the doping concentration is above 8%, the excessive aggregation of inorganic / organic particles will block the cross-linking and curing of the colloidal polymer network, resulting in a decrease in the overall mechanical peel strength of the fixing adhesive layer 240 after curing, and causing the risk of delamination under narrow borders.

[0070] For example, the aforementioned diffusion particles are not limited to PMMA particles, but can also be replaced with at least one of polystyrene (PS) particles, silicone resin particles, silica particles, titanium dioxide particles, or zinc oxide particles. These alternative particles can also achieve the effect of improving the brightness uniformity of the side-lit backlight module 200.

[0071] Based on the above technical solution, by doping PMMA diffusion particles of specific particle size and concentration into the fixed adhesive layer, the spatial distribution of reflected light intensity can be further smoothed by utilizing the particle scattering effect, thereby improving the brightness uniformity of the backlight module on the light-incident side without sacrificing the reliability of the adhesive structure.

[0072] In some possible embodiments, the functional particles doped in the fixative layer 240 may be color-converting particles, which may be quantum dot (QD) particles or phosphor particles.

[0073] The aforementioned color-conversion particles are used to absorb the blue light emitted by the light-emitting device 232 and, after being excited, emit red and / or green light, which mixes with the unabsorbed blue light to form high color gamut white light. Since some of the blue light emitted by the light-emitting device 232 at a large angle would originally directly hit the fixing adhesive layer 240 and be absorbed and lost by the surface, by doping the fixing adhesive layer 240 with color-conversion particles of high color saturation, this part of the stray blue light that could not originally enter the light guide plate 210 can be converted into an excitation source, and high monochromatic red and / or green light is generated on-site and injected into the light guide plate 210. This solution utilizes the fixed adhesive layer 240 to directly convert and recover stray light, making full use of the light energy that would otherwise be lost. This not only significantly improves the overall light efficiency of the side-lit backlight module 200, but also effectively shortens the physical mixing distance of high color gamut white light by using the fixed adhesive layer 240 to directly convert and recover stray light through the fixed adhesive layer 240 before the red, green, and blue light enters the light guide plate 210. This achieves high color gamut color performance of the backlight module under an ultra-narrow bezel architecture.

[0074] For example, the median particle size of the aforementioned color conversion particles can be controlled between 2 nm and 15 nm (when quantum dot particles are used), or between 1 μm and 10 μm (when phosphor particles are used). If the particle size is too small, the quantum yield or excitation efficiency of the particles will decrease significantly, making it impossible to form a high color gamut color adjustment; if the particle size is too large, it will also cause the surface flatness of the ultrathin fixing adhesive layer 240 (15 μm to 25 μm) to deteriorate, resulting in stress concentration inside the fixing adhesive layer 240 and weakening the interfacial bonding strength between the substrate and the light guide plate.

[0075] For example, the mass doping concentration of the aforementioned color conversion particles in the fixative layer 240 can be limited to between 2% and 6% (e.g., around 4%). When the doping concentration is below 2%, the absorption and conversion of stray blue light at large angles is insufficient, failing to achieve the expected improvement in high color gamut coverage. When the doping concentration is above 6%, it not only leads to a severe fluorescence self-absorption effect within the fixative layer 240, thereby reducing luminous efficiency, but also, due to the excessively high proportion of inorganic particles, it blocks the cross-linking and interweaving of the main polymer network of the fixative layer 240 during the curing process, reducing the overall mechanical peel strength of the fixative layer 240 after curing and increasing the risk of delamination under narrow-frame structures.

[0076] For example, the aforementioned color conversion particles are not limited to single-color conversion particles, but can also be mixed particles of red and green light conversion particles. These alternatives or combinations can also achieve the effect of improving the 200 color gamut coverage and overall light effect of the side-lit backlight module.

[0077] Based on the above technical solution, by doping color conversion particles of specific size and concentration into the fixed adhesive layer, and utilizing the in-situ wavelength conversion and stray light recovery mechanism, the overall light efficiency of the side-lit backlight module is significantly improved while ensuring the reliability of the bonding structure, and excellent high color gamut color performance is achieved.

[0078] In some possible embodiments, the functional particles incorporated into the aforementioned fixed adhesive layer 240 may include both the aforementioned diffusion particles and color conversion particles.

[0079] To further and more intuitively verify the effects of the technical solution of this application on improving backlight efficiency, optimizing the uniformity of brightness on the incident light side, and enhancing structural reliability, the embodiments of this application also provide a set of simulation experimental data and comparative test results.

[0080] This experiment set up four control groups for testing, namely: the conventional method (i.e., Figure 4 Scheme (a) shown in the figure), conventional optimization scheme (i.e. Figure 4 The scheme shown in (b) of this application), the first embodiment of this application (i.e., the scheme of using substrate-free white glue for full coating) and the second embodiment of this application (i.e., the scheme of using substrate-free white glue and combined with a non-uniform gradient distribution glue dot array).

[0081] Figure 5 This is a schematic diagram of the simulation experiment results provided in this application.

[0082] In addition, the experimental data and performance indicators of each scheme are shown in Table 1 below: Table 1

[0083] Combination Figure 5 The simulation results are illustrated in the diagram and the test data are shown in Table 1. The optical and physical characteristics of each scheme are analyzed in detail below: First, regarding the backlight luminous efficacy index, the luminous efficacy of the conventional solution is set as a baseline value of 100%. The conventional optimization solution slightly improves the luminous efficacy to 103% by exposing the white PI surface of the circuit board through partial openings. However, in Embodiment 1 of this application, due to the use of ultra-thin substrate-free white adhesive of 15μm to 25μm, the thickness direction height misalignment between the light-emitting device and the light guide plate is significantly reduced, eliminating light leakage loss caused by the misalignment gap, and its backlight luminous efficacy is significantly increased to 106%. In Embodiment 2 of this application, after introducing non-uniform gradient adhesive dots, although the adhesive layer coverage area is reduced, its luminous efficacy is still stably maintained at a high level of 104.6%, which represents a significant breakthrough in luminous efficacy compared to the prior art.

[0084] Secondly, the uniformity of brightness on the incident light side can be characterized by the ratio of maximum brightness to minimum brightness. A value closer to 1 indicates smoother and more uniform brightness. The uniformity value of the conventional scheme is 1.21. The conventional optimized scheme, due to localized openings causing abrupt changes in reflectivity at the point directly opposite the light source, exacerbates the alternation of light and dark, worsening its uniformity value to 1.33. In simulation images, this manifests as obvious dot-like bright spots on the edge of the light strip. In contrast, the uniformity value of Embodiment 1 in this application is 1.22. Embodiment 2 of this application, by employing a zoned adhesive dot arrangement that reduces reflectivity in strong light areas and increases reflectivity in weak light areas, compensates for the spatial light intensity distribution of the light source itself, significantly converging its incident light side brightness uniformity value to 1.08.

[0085] according to Figure 5 As can be seen from the simulation diagram, the brightness transition of Embodiment 2 of this application is smooth throughout the entire light strip side, effectively eliminating the phenomenon of dotted bright spots and alternating bright bands.

[0086] Furthermore, in terms of adhesive strength and structural design, conventional optimization schemes, due to the hollowing out of some of the adhesive, result in damaged bonding area, leading to a significant decrease in mechanical peel strength and an inability to reduce the minimum overlap width to 0.4mm. In contrast, both Embodiment 1 and Embodiment 2 of this application employ a substrate-free material design, allowing the adhesive layer to be completely filled with a high-viscosity network. This ensures that even with the adhesive layer thickness reduced to a maximum of 15μm to 25μm, the overall adhesive strength is still significantly improved compared to traditional solutions. Not only is there no risk of delamination, but the minimum planar overlap width between the LED strip and the light guide plate can also be rigidly reduced from 0.4mm to 0.3mm.

[0087] In summary, the second embodiment of this application, through the synergy of a substrate-free fixing adhesive layer and a partitioned non-uniform adhesive dot distribution, achieves a light efficiency gain of over 4.6% while maintaining high bonding strength and successfully releasing the frame space to 0.3mm. It also significantly optimizes the uniformity of the incident light brightness to 1.08, thereby meeting the performance requirements of narrow-bezel products.

[0088] In addition, this application embodiment also provides an assembly process for a side-lit backlight module 200 to complete the assembly between the components.

[0089] Figure 6 This is a schematic diagram of the assembly process of a side-lit backlight module 200 proposed in an embodiment of this application.

[0090] refer to Figure 6 As shown, the assembly process includes the following operations: S601: Substrate bare board processing and light-emitting device mounting.

[0091] For example, the bare board processing of substrate 231 (i.e., light source module FPC) can be completed first, including the fabrication of circuits on the surface of substrate 231, surface treatment of pads, and processing of process positioning holes. Then, multiple light-emitting devices 232 are precisely surface-mounted and fixed to the first surface 01 of substrate 231 using a surface mount process to ensure the electrical connection accuracy and mechanical bonding reliability between the light-emitting devices 232 and substrate 231.

[0092] S602: First application of white glue.

[0093] For example, depending on the narrow bezel and optical function requirements of different terminal products, the corresponding coating scheme (such as full coating process or non-uniform gradient dispensing patterning process) can be selected to complete the first white glue coating on the surface of substrate 231.

[0094] S603: First assembly, bonding, and full curing.

[0095] For example, the light-emitting surface of the light-emitting device 232 can be kept facing upwards, and a visual alignment system can be used to achieve precise coupling and alignment between the substrate 231 and the light guide plate 210. After alignment, the first mechanical pressing and bonding is performed. The pressing parameters can be adjusted to (0.25±0.05) MPa, and the holding time is set to (3±1) s. Under this pressing control, the substrate-free white adhesive can be spread controllably at the bonding interface, and the bonding thickness is compressed to the limit and stably controlled between 15μm and 25μm, while keeping the minimum overlap width between the two planes at 0.3mm. After pressing, the adhesive is irradiated in situ with a preset wavelength ultraviolet light source to complete the first full curing treatment, thus constructing an integrated structure of the substrate 231 and the light guide plate 210.

[0096] S604: Second white glue coating.

[0097] For example, in addition to the integrated structure of the substrate 231 and the light guide plate 210 already formed, a second linear pattern of substrate-free white adhesive can be applied to a specific bonding surface of the frame 220 (or the integrated adhesive and iron piece) to form an adhesive structure for fixing the adhesive layer 240 to the frame side.

[0098] S605: Second assembly, bonding, and full curing.

[0099] For example, the integrated structure of the substrate 231 and the light guide plate 210 can be flipped so that the light-emitting device 232 faces downwards, completing the precise secondary alignment and bonding between the integrated structure and the adhesive frame 220. The mechanical pressing parameters during bonding are also limited to (0.25±0.05) MPa, and the holding time is constantly controlled at (3±1) s. After pressing, the adhesive is subjected to a second full curing treatment using an ultraviolet light source, so that the polymer network spanning both ends of the fixed adhesive layer 240 is completely cross-linked and cured. After removing the pressing force, the rigid assembly of the whole machine is completed.

[0100] In addition, for the first white glue coating (i.e., S602) in the above-mentioned whole machine assembly process, this application embodiment also provides a corresponding fixing glue coating process.

[0101] Figure 7 This is a schematic diagram of a fixed adhesive coating process proposed in an embodiment of this application.

[0102] refer to Figure 7 As shown, the adhesive application process may include the following steps: S701: Colloidal configuration and particle doping.

[0103] For example, a UV-curable adhesive matrix (or other thermosetting or moisture-curing adhesive matrix) of a preset viscosity can be prepared. Diffusion particles with a particle size between 1 μm and 5 μm (e.g., PMMA spherical particles with a mass concentration of approximately 5%) and / or color-converting particles with a median particle size between 2 nm and 15 nm (e.g., quantum dot particles with a mass concentration of approximately 4%) are added to the adhesive matrix according to the aforementioned defined mass doping concentration. The mixture is then mixed and degassed under vacuum using a planetary high-speed mixer to uniformly disperse the functional particles within the polymer network of the adhesive matrix, resulting in a functionalized mixed adhesive matrix.

[0104] S702: Adaptive graphical layout.

[0105] For example, the functionalized mixed adhesive configured in S701 can be loaded into the dispensing system of the dispensing equipment, and any of the following patterned coating schemes can be selected according to the actual needs of the product: Solution A: For products that require high brightness but not narrow bezels, control the dispensing equipment to fully coat and crosslink the functionalized mixed adhesive on the first surface 01 of the substrate 231 to form a continuous and uniform thin adhesive layer.

[0106] Option B: For products with ultra-narrow bezels and the need to eliminate bright spots, a high-precision inkjet printing process or micro-contact transfer printing process is adopted. During the coating process, the inkjet frequency and / or droplet volume of the inkjet head at different coordinate positions are adjusted by digital graphic control software. Local dispensing is performed strictly according to the aforementioned non-uniform gradient arrangement law of "sparse and small size in strong light areas and dense and large size in weak light areas". This directly forms a first region A1 composed of multiple discrete first adhesive dots 2411 and a second region A2 composed of multiple gradient-increasing second adhesive dots 2412 on the first surface 01.

[0107] Furthermore, this application also proposes a display device, which may include a display module and an edge-lit backlight module proposed in this application, wherein the edge-lit backlight module is disposed on the backlight side of the display panel.

[0108] In some possible embodiments, the above-described display device can be applied to various electronic devices such as smartphones, tablets, laptops, televisions, automotive displays, and industrial control displays.

[0109] Those skilled in the art will understand that, for the sake of convenience and brevity, the specific working processes of the systems, devices, and units described above can be referred to the corresponding processes in the foregoing method embodiments, and will not be repeated here.

[0110] In the several embodiments provided in this application, it should be understood that the disclosed systems, apparatuses, and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative; for instance, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces; the indirect coupling or communication connection between apparatuses or units may be electrical, mechanical, or other forms.

[0111] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A side-lit backlight module, characterized in that, include: Light guide plate, frame, light source module and fixing adhesive layer; The light source module includes a substrate and a plurality of light-emitting devices spaced apart on a first surface of the substrate, wherein the light-emitting surfaces of the light-emitting devices face the light guide plate. The fixing adhesive layer is disposed on the first surface and fixes the substrate to the light guide plate and the adhesive frame respectively; the fixing adhesive layer includes a plurality of adhesive dots, with the center point of any of the light-emitting devices as a reference: the distribution density of the adhesive dots increases with the increase of the distance from the adhesive dots to the center point; and / or, the cross-sectional size of the adhesive dots increases with the increase of the distance from the adhesive dots to the center point.

2. The side-lit backlight module according to claim 1, characterized in that, The fixing adhesive layer includes a first region and a second region. The first region is a region that extends in a fan shape towards the light guide plate with the center point as the vertex. The second region is a region located between two adjacent first regions. The multiple first adhesive dots located in the first region are evenly distributed; The distribution density and / or cross-sectional size of the plurality of second adhesive dots located in the second region increase with the increase of the distance from the second adhesive dot to the center point, and the distribution density and / or cross-sectional size of the second adhesive dots are all greater than the distribution density and / or cross-sectional size of the first adhesive dots.

3. The side-lit backlight module according to claim 2, characterized in that, The diameter of the first adhesive dot is 0.1 mm to 0.3 mm, and the center-to-center distance between adjacent first adhesive dots is 0.3 mm to 0.5 mm; The diameter of the second adhesive dot is 0.15 mm to 0.35 mm, which is larger than the diameter of the first adhesive dot. The center-to-center distance between adjacent second adhesive dots gradually decreases from 0.4 mm to 0.2 mm as the distance from the second adhesive dot to the center point increases.

4. The side-lit backlight module according to any one of claims 1 to 3, characterized in that, The fixing adhesive layer is a substrate-free white adhesive layer.

5. The side-lit backlight module according to any one of claims 1 to 4, characterized in that, The reflectivity of the fixing adhesive layer is greater than 80%, and the thickness of the fixing adhesive layer is 15μm to 25μm.

6. The side-lit backlight module according to any one of claims 1 to 5, characterized in that, The peel force of the fixing adhesive layer is greater than or equal to 2000gf / 25mm.

7. The side-lit backlight module according to any one of claims 1 to 6, characterized in that, The fixed adhesive layer is doped with functional particles, including diffusion particles and / or color conversion particles.

8. The side-lit backlight module according to claim 7, characterized in that, The diffused particles are polymethyl methacrylate (PMMA) spherical particles.

9. The side-lit backlight module according to claim 7 or 8, characterized in that, The color-converting particles are quantum dot particles or phosphor particles, used to absorb blue light and emit red and / or green light.

10. The side-lit backlight module according to any one of claims 1 to 9, characterized in that, The minimum overlap width between the substrate and the light guide plate is 0.3 mm.

11. A display device, characterized in that, include: The display panel, and the side-lit backlight module as described in any one of claims 1 to 10, wherein the side-lit backlight module is disposed on the backlight side of the display panel.

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