Zero-od high-brightness mini-led backlight module

Abstract

The utility model relates to the technical field of semiconductor display, concretely relates to a zero OD highlight Mini - LED backlight module, include: lamp board substrate, a plurality of Mini - COB chip are welded on the solder pad of lamp board substrate through the tin cream, light reflection structure is set up in the gap region between adjacent Mini - COB chip and is located lamp board substrate surface, plane colloid covers Mini - COB chip and light reflection structure and is glued with lamp board substrate as a whole, wherein, light reflection structure is used for breaking the total reflection path of big angle light in plane colloid inside, reduces light energy loss, and controls light exit position. Through setting scattering structure in the lamp board sealant, reduce light total reflection and energy loss, control light position supplement non - light - emitting area light intensity, improve display uniformity. Propose novel Mini - LED sealant structure zero OD backlight module design, after light - homogenizing optimization, realize highlight ultrathin display effect with less diaphragm.

Description

Technical Field

[0001] This utility model relates to the field of semiconductor display technology, specifically to a zero-OD high-brightness Mini-LED backlight module. Background Technology

[0002] COB (Chip-on-Board) packaging technology, also known as on-board chip packaging, is a process that directly mounts bare chips onto a printed circuit board (PCB). It achieves electrical interconnection between the chip and the substrate through precise wire bonding, and finally uses a special encapsulating colloid to cover the chip body and bonding wires, providing physical protection, environmental isolation, and mechanical support. Based on the coverage area of ​​the encapsulating colloid, COB packaging methods are mainly divided into two types: single-point encapsulation and full-surface encapsulation. Single-point encapsulation is typically used in backlight products with relatively large LED pitch, characterized by localized encapsulation of only a single LED chip and its surrounding leads. Full-surface encapsulation, on the other hand, is commonly used in backlight designs with high LED chip density, small chip pitch, and extremely thin overall thickness requirements, where the colloid covers the entire LED array area.

[0003] A well-designed single-point encapsulation structure can effectively reduce the obstruction and energy loss of light emitted by the chip by the encapsulating adhesive, helping to maintain high luminous efficiency. However, its significant drawback is that, limited by the minimum size required for each individual adhesive dot and the space it occupies cumulatively, the thickness and volume of the entire backlight module are difficult to further reduce, hindering the development of thinner and lighter products. Therefore, the industry practice is to use a design scheme with smaller COB chips and full-surface encapsulation. However, as the market demands for lower LED optical distance (OD) become increasingly stringent, the spacing between LEDs in the backlight module must be continuously reduced to achieve uniform display effects, resulting in a sharp increase in the number of LED chips required. This not only drives up material costs but also makes it more difficult to densely arrange a large number of chips in a smaller space, ultimately making it difficult to simultaneously achieve the two major development trends of thinner and lighter designs and lower costs.

[0004] On the other hand, while the conventional full-surface encapsulation design solves the space constraint problem, it introduces new optical challenges. When light is emitted from the side of the LED chip at a large angle, due to total internal reflection at the interface between the encapsulant and air, this portion of the light is confined within the encapsulant and undergoes multiple reflections and conductions. During this process, the light energy is gradually absorbed by the encapsulant material, resulting in a significant loss of backlight brightness. Furthermore, because the effective light emission position under the full-surface encapsulation structure is mainly concentrated in the top area of ​​the chip, rather than being uniformly diffused, it is very easy to form obvious "hot spots" in the display. To eliminate these uneven light spots and improve the display effect, additional optical films such as diffusion films and brightness enhancement films are usually required for light homogenization. This not only increases the design complexity of the backlight module, but also causes the overall backlight cost to continue to rise. Utility Model Content

[0005] To address the shortcomings of existing technologies, this utility model discloses a zero-OD high-brightness Mini-LED backlight module to solve the aforementioned problems.

[0006] This utility model is achieved through the following technical solution:

[0007] This utility model provides a zero-OD high-brightness Mini-LED backlight module, including:

[0008] Light board substrate;

[0009] Multiple Mini-COB chips are soldered onto the pads of the lamp board substrate using solder paste;

[0010] A light-reflecting structure is disposed on the surface of the lamp board substrate and located in the gap area between adjacent Mini-COB chips;

[0011] A planar colloid covers the Mini-COB chip and the light-reflecting structure and is bonded to the lamp board substrate;

[0012] The light-reflecting structure is used to disrupt the total internal reflection path of large-angle light rays inside the planar colloid, reduce light energy loss, and regulate the light emission position.

[0013] Furthermore, the light-reflecting structure is formed by mixing reflective particles with silicon-based resin, including titanium dioxide, which has a reflectivity greater than 95%.

[0014] Furthermore, the shape of the light-reflecting structure is at least one of the following: a dotted scattering network, a hemispherical shape, a prism, a cylinder, or a pyramid.

[0015] Furthermore, when the light reflection structure is a dotted scattering mesh, its dimensions satisfy: height H ≤ 0.25 mm, and the height-to-width ratio satisfies 0.1 ≤ H / W ≤ 0.5.

[0016] Furthermore, the arrangement of the light reflection structure can be any of the following: a dotted arrangement distributed according to the Bessel equation, a uniform arrangement, an offset rectangular arrangement, a radial polynomial arrangement, a grid arrangement, or a random arrangement.

[0017] Furthermore, the refractive index n1 of the planar colloid satisfies 1.47≤n1≤1.55, and the thickness H satisfies 0.15mm≤H≤0.5mm.

[0018] Furthermore, an optical film assembly is stacked on the light-emitting side of the lamp board substrate, and the optical film assembly includes at least a combination of a light-diffusing film, a diffuser plate, a light conversion film, a lower diffuser film, a light-enhancing prism film, and a polarizing light-enhancing film.

[0019] Furthermore, the optical film assembly comprises, from bottom to top, a light-diffusing film, a light-converting film, a lower diffuser film, a light-enhancing prism film, and a polarizing light-enhancing film.

[0020] Furthermore, the spacing between the Mini-COB chips is ≤3.5mm, and the light reflection structure increases the uniformity of backlight illuminance to ≥76.2% by expanding the single-point light-emitting area.

[0021] The beneficial effects of this utility model are as follows:

[0022] This invention significantly reduces the number of total internal reflections of LED light rays at large angles within the encapsulation by incorporating a series of scattering structures on the surface of the lamp panel. This reduces energy loss due to the encapsulation and lamp panel. Furthermore, by adjusting the design and distribution of these scattering structures, the light emission position is controlled, supplementing the light emission from non-light-emitting areas and improving the uniformity of the displayed image. Benefiting from the optimized light-uniformity design of the encapsulation structure, this invention achieves excellent uniformity with fewer film layers, resulting in a high-brightness, ultra-thin Mini-LED backlight module. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 This is a schematic diagram of a Mini-LED light panel;

[0025] Figure 2(a) is a schematic diagram of the emitted light rays from a conventional planar sealant.

[0026] Figure 2(b) is a simulation diagram of the chip's light emission angle and conventional planar encapsulation optics;

[0027] Figure 3 This is a schematic diagram of the emitted light rays from a new type of planar sealant containing reflective dots;

[0028] Figure 4 This is a diagram of the dot-scattering white glue dot structure;

[0029] Figure 5 This is a schematic diagram of several scattering dot arrangements in a new type of planar sealant;

[0030] Figure 6(a) shows the chip light emission angle and the optical simulation diagram of the novel planar encapsulation.

[0031] Figure 6(b) shows the chip light emission angle and the optical simulation diagram of the novel planar encapsulation.

[0032] Figure 7(a) is an optical simulation diagram of conventional planar sealing;

[0033] Figure 7(b) is an optical simulation diagram of the novel planar sealant;

[0034] Figure 8(a) is a diagram of the architecture of a high-brightness Mini-LED backlight module with zero OD;

[0035] Figure 8(b) is an optical simulation diagram of a zero-OD high-brightness Mini-LED backlight module. Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of the embodiments of this utility model clearer, the technical solutions of the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this utility model, not all embodiments. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this utility model.

[0037] like Figure 1As shown, this embodiment provides a Mini-LED light board 100, which consists of a planar colloid 101, a Mini-COB chip 102, a light-reflecting structure 103, and a light board substrate 104. The planar colloid 101 is made of optical-grade material and is integrally formed with the light board substrate 104 through a precision bonding process. The Mini-COB chip 102 is precisely soldered to designated pad positions on the substrate 104 using solder paste to ensure reliable electrical connection. The light-reflecting structure 103 is fixed to the surface of the substrate 104 to guide and optimize light distribution. Throughout the assembly process, the chip 102 and the light-reflecting structure 103 are completely embedded inside the planar colloid 101, forming a smooth and flat encapsulation surface.

[0038] In this embodiment, as shown in Figure 2(a), the thickness H of the conventional planar sealant is set to be between 0.15 mm and 0.5 mm (i.e., 0.15 mm ≤ H ≤ 0.5 mm), and its refractive index n1 is between 1.47 and 1.55 (i.e., 1.47 ≤ n1 ≤ 1.55). Based on Snell's law, the total internal reflection angle α of the emitted light from the mini-LED in the planar sealant can be calculated using the formula n1sinα=n0sin90°, where n0 is the refractive index of air, approximately 1.0, therefore α=arcsin(n0 / n1). Substituting the refractive index range, the value of α is between 40.2° and 42.9°, which means that the angle of the emitted light from the LED must be less than α in order to effectively escape from the interior of the sealant and avoid total internal reflection.

[0039] However, current LED devices typically have a high viewing angle of up to 160°, and the maximum luminous intensity angle is usually concentrated around 60°. Therefore, a large number of large-angle rays (exceeding the α range) generated by the LED cannot directly exit the planar adhesive, but instead propagate repeatedly within the adhesive via total internal reflection, resulting in luminous efficiency loss. As shown in Figure 2(b), optical simulations using LED data with a 160° emission angle clearly verify the above phenomenon: the light forms multiple reflection trajectories within the adhesive, while only small-angle rays successfully exit.

[0040] In one embodiment, optical density is a property of a material that ideally describes its ability to absorb the energy (radiant energy) of light transmitted within it. According to the Lambert-Beer Law, when light passes through a homogeneous medium, the optical density OD is linearly related to the optical path length.

[0041] OD=A×L=lg(Io / It)=-log10(T);

[0042] A is the linear absorption coefficient of the adhesive (unit: cm⁻¹), which is determined by the material properties;

[0043] L is the optical path length (unit: cm-1);

[0044] Io is the incident radiation intensity, and It is the transmitted radiation intensity;

[0045] The relationship between transmittance and optical path length: T = 10 - OD = 10 - AL;

[0046] The transmittance T1 of existing planar adhesives with high transparency is usually between 95% and 97%, and the tested thickness (optical path) L1 is 0.2 mm. It can be deduced that A = -log10(T1) / L1.

[0047] Furthermore, the transmittance T2 and OD2 of the medium under different optical path lengths L2 (thicknesses) are:

[0048] OD2=A×L2=-log10(T1)×(L2 / L1); T2=10-A×L2=10log10(T1)×(L2 / L1)

[0049] With T1 set to 97%, when the optical path length L2 is 100 times that of L1, i.e., 20 mm, the transmittance T2 is approximately 4.7%, meaning that 95.3% of the light energy is absorbed by the colloid.

[0050] In summary, it can be seen that the transmittance of a uniform medium decreases exponentially with the optical path (thickness). In conventional planar encapsulation, a large amount of total internal reflection light is not only absorbed by the colloid, but the reflectivity of the lamp board is generally <90%, which further aggravates the light energy loss and significantly reduces the backlight brightness. At the same time, the light is concentrated at the top of the chip and emitted, resulting in poor image uniformity.

[0051] Furthermore, it is known that for certain media materials, reducing the light propagation path length can effectively reduce light energy loss. Therefore, such as... Figure 3 As shown, a series of light-reflecting structures 103 were designed. This structure uses a white colloid formed by mixing a silicone resin with a high proportion of reflective particles (such as titanium dioxide), which is coated onto the surface of the lamp board at the gap of the LED pitch using a dispensing process.

[0052] In this embodiment, a dispensing process is used to place scattering white adhesive dots into the gaps between the chip pitches, forming a light guide plate-like dot array structure. The dimensions of the dotted scattering white adhesive dots are as follows: Figure 4 As shown, the height H ≤ 0.25 mm, and satisfies 0.1 ≤ H / W ≤ 0.5.

[0053] In one embodiment, the total internal reflection light is scattered by the dotted white adhesive dots, forming outgoing light at the dot locations. Given that the white adhesive dot material has a reflectivity >95%, this design effectively improves the reflectivity of the LED panel and shortens the light propagation path while controlling the light to exit above the dots, thereby compensating for the brightness between LED pitches and improving image uniformity. The arrangement of the white adhesive scattering dots can be of different geometric shapes, such as... Figure 5 As shown.

[0054] The arrangement of scattering dots within the arrangement area can be set according to the Bessel equation:

[0055]

[0056] Different dot arrangements can also be used, such as uniform, offset rectangle, radial polynomial, grid, random number, list, etc.

[0057] The reflective structure 103 can be hemispherical, or it can be prism, cylinder, pyramid, etc. As shown in Figure 6(a), the reflective structure in Example 2 is a cylindrical curved surface. Figure 6(b) uses LED data with a 160° emission angle for optical simulation. It can be seen that the light emitted by the chip is emitted from the colloid, and the area of ​​the emission position is much larger than that of the conventional encapsulation structure.

[0058] Optical simulations were performed to compare the novel sealant using the scattering structure of Example 2 with conventional sealants. The simulated optical results of the lamp board are shown in Figures 7(a) and 7(b). The corresponding optical performance parameters are summarized in Table 1.

[0059] Table 1 Comparison of Optical Simulation Performance of Conventional & Novel Planar Sealant

[0060] Radiant flux Central Illuminance average deviation Illumination uniformity Conventional flat sealing 558.76 118430 0.501 49.9％ New type of flat sealant 1033.5 148970 0.238 76.2％

[0061] Wherein, standard deviation: u represents the average illuminance value in the simulated grid, xi represents the simulated illuminance value in each grid; average deviation: standard deviation / average value; illuminance uniformity: 1 - average deviation.

[0062] In this embodiment, it can be seen that the emitted light flux of the novel planar encapsulation with scattering structure is increased by 85% compared with conventional planar encapsulation, and the illuminance uniformity is improved by 26.3%. More emitted light means higher brightness, and higher illuminance uniformity means fewer films are needed for the backlight and a thinner module architecture.

[0063] Figure 8(a) shows a schematic diagram of a high-brightness Mini-LED backlight module with zero OD. The backlight module includes a mini-LED lamp board 104, multiple COB LEDs 102, a planar sealant 101, and a reflective structure 103. It also includes a series of film structures: a uniform light-diffusing film 201 at the bottom of the film assembly, followed by a diffuser plate 202, a light conversion film 203, a lower diffuser film 204, a brightness-enhancing prism film 205, and a polarizing brightness-enhancing film 206. This film stack can meet the design requirements of a lamp board with a chip pitch ≤3.5mm. The simulated structure is shown in Figure 8(b), and the image is uniform with no display defects.

[0064] In the specific implementation process, the selection and arrangement order of the optical film group are crucial to achieving a backlight effect with high uniformity and high brightness. The light-diffusing film 201 is positioned close to the light-emitting surface of the lamp panel 104. Its main function is to initially diffuse the light emitted from the lamp panel, breaking up residual small light spots and laying the foundation for subsequent optical processing. The diffuser plate 202 is located above the light-diffusing film 201, further scattering the light, improving the spatial uniformity of the light, and supporting the upper film. The light conversion film 203 is used to optimize the color gamut performance of the backlight. Its contained fluorescent material can convert some blue light into red and green light, thereby improving the white light color temperature and color rendering index. The lower diffuser film 204 is placed above the light conversion film 203, and its main function is to soften the light and eliminate any minor unevenness that may be caused by the prism structure or color conversion layer. The brightness enhancement prism film 205 is typically a BEF (Brightness Enhancement Film) structure. Its precise prism array effectively collects large-angle light and focuses it in a direction perpendicular to the screen, significantly improving axial brightness. The topmost polarization-type brightness enhancement film 206 (such as DBEF) utilizes polarization recovery technology to recover polarized light components that would otherwise be absorbed in the backlight module, further improving light energy utilization and overall brightness output efficiency. Through this carefully designed film stack combination, combined with the innovative reflective structure 103 on the lamp board 104 for effective control of the light emission position and path, this zero-OD high-brightness Mini-LED backlight module can successfully achieve high brightness output and high screen uniformity (≥76.2%) in a compact design with a chip pitch ≤3.5mm. At the same time, it effectively suppresses the "hot spot" phenomenon, significantly reduces the dependence on additional homogenizing film layers, simplifies the module structure, and controls costs.

[0065] The above embodiments are only used to illustrate the technical solutions of this utility model, and are not intended to limit it. Although this utility model has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this utility model.

Claims

1. A zero-OD high-brightness Mini-LED backlight module, characterized in that, include: Lamp board substrate (104); Multiple Mini-COB chips (102) are soldered onto the pads of the lamp board substrate (104) using solder paste; A light-reflecting structure (103) is disposed on the surface of the lamp board substrate (104) and located in the gap area between adjacent Mini-COB chips; A planar colloid (101) covers the Mini-COB chip (102) and the light-reflecting structure (103) and is bonded to the lamp board substrate (104) as a whole; The light reflection structure (103) is used to disrupt the total internal reflection path of large-angle light rays inside the planar colloid (101), reduce light energy loss, and regulate the light emission position.

2. The zero-OD high-brightness Mini-LED backlight module according to claim 1, characterized in that, The light-reflecting structure (103) is formed by mixing reflective particles with silicon-based resin, including titanium dioxide, which has a reflectivity greater than 95%.

3. The zero-OD high-brightness Mini-LED backlight module according to claim 1 or 2, characterized in that, The light-reflecting structure (103) is at least one of the following: a dotted scattering mesh, a hemispherical shape, a prism, a cylinder, or a pyramid.

4. The zero-OD high-brightness Mini-LED backlight module according to claim 3, characterized in that, When the light reflecting structure (103) is a dotted scattering mesh, its dimensions satisfy: height H≤0.25mm, and the height-to-width ratio satisfies 0.1≤H / W≤0.

5.

5. The zero-OD high-brightness Mini-LED backlight module according to claim 1, characterized in that, The arrangement of the light reflection structure (103) can be any of the following: a dotted arrangement distributed according to the Bessel equation, a uniform arrangement, an offset rectangular arrangement, a radial polynomial arrangement, a grid arrangement, or a random arrangement.

6. The zero-OD high-brightness Mini-LED backlight module according to claim 1, characterized in that, The refractive index n1 of the planar colloid (101) satisfies 1.47≤n1≤1.55, and the thickness H satisfies 0.15mm≤H≤0.5mm.

7. The zero-OD high-brightness Mini-LED backlight module according to claim 1, characterized in that, The light-emitting side of the lamp board substrate (104) is provided with an optical film group, which includes at least a combination of a light-diffusing film (201), a diffuser plate (202), a light conversion film (203), a lower diffuser film (204), a light-enhancing prism film (205), and a polarizing light-enhancing film (206).

8. The zero-OD high-brightness Mini-LED backlight module according to claim 7, characterized in that, The optical film assembly includes, from bottom to top, a light-diffusing film (201), a diffuser plate (202), a light conversion film (203), a lower diffuser film (204), a light-enhancing prism film (205), and a polarizing light-enhancing film (206).

9. The zero-OD high-brightness Mini-LED backlight module according to claim 1, characterized in that, The spacing of the Mini-COB chips (102) is ≤3.5mm, and the light reflection structure (103) increases the uniformity of backlight illuminance to ≥76.2% by expanding the single-point light-emitting area.

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