Reflection type polarized light brightness enhancement film capable of replacing diffusion plate and preparation method of reflection type polarized light brightness enhancement film

Abstract

The invention provides a reflective polarized brightness enhancement film capable of replacing a diffusion plate and a preparation method of the reflective polarized brightness enhancement film, and relates to the technical field of optical thin films. According to the reflective polarization brightness enhancement film, through the three-layer integrated design of the upper reflective polarization composite film, the middle micro-scattering dodging layer and the lower strong-scattering shielding layer, the reflective polarization brightness enhancement film can directly replace an independently-arranged diffusion plate in a liquid crystal display backlight module. Experiments prove that the reflective polarized brightness enhancement film disclosed by the invention has a relatively good shielding effect while keeping relatively high brightness. Besides, the reflection type polarized light brightness enhancement film can directly replace an independently-arranged diffusion plate in the liquid crystal display backlight module, the thickness of the backlight module can be reduced, the weight can be reduced, the material and assembly cost can be reduced, and light, thin and low-cost display product design can be achieved.

Description

Technical Field

[0001] This invention relates to the field of optical thin film technology, and in particular to a reflective polarizing brightening film that can replace a diffuser plate and its preparation method. Background Technology

[0002] Liquid crystal displays (LCDs) do not emit light themselves and rely on backlight modules to provide a uniform and bright surface light source. In typical edge-lit or direct-lit backlight modules, the light source (such as an LED), the light guide plate (LGP), and multiple optical films together constitute a complete optical system. Among them, the optical films mainly include diffuser plates, lower diffuser sheets, prism sheets (brightness enhancement films), and reflective polarizers (such as DBEFs), each performing its specific function to achieve a display effect with high brightness and high uniformity.

[0003] Reflective polarizing brightness enhancement films (such as multilayer co-extruded CPP structures based on PMMA and COC) are one of the key components in backlight modules, typically fabricated from multilayer polymer materials through a co-extrusion process. Their main function is to selectively transmit P-polarized light aligned with the absorption axis of the liquid crystal panel, while reflecting S-polarized light perpendicular to it back to the backlight system. The reflected S-polarized light, after scattering and polarization state conversion, can be emitted again, thus recovering light that would otherwise be absorbed, significantly improving the brightness and optical efficiency of the backlight system.

[0004] In traditional backlight design, the diffuser plate is also an indispensable component. Its main functions include: first, scattering the point or line light sources from the light guide plate or LED beads to form a uniform surface light source, eliminating optical defects such as "hot spots" or "light shadows"; second, shielding and blurring the internal structure of the backlight module, such as the dot pattern or LED arrangement on the light guide plate, preventing these structures from being directly observed by the user and ensuring the purity of the displayed image.

[0005] However, using a separate diffuser plate also brings a series of problems. First, diffuser plates typically have a certain thickness, generally between 0.5mm and 2mm, increasing the overall thickness and weight of the backlight module, which is detrimental to the development of thinner and lighter display devices. Second, as an additional material unit, the diffuser plate increases material costs and assembly process complexity, affecting production efficiency. Furthermore, light undergoes multiple volume scattering when passing through the diffuser plate. Although this achieves the goal of uniform light distribution, it inevitably causes a certain degree of light energy loss, negatively impacting the overall light extraction efficiency.

[0006] To overcome the aforementioned problems, the industry has been exploring technical solutions to reduce the number of optical films and achieve functional integration. Therefore, there is an urgent need to research and develop a new type of multifunctional optical film that integrates polarization enhancement, light uniformity, and internal structure shielding on a single film material, in order to meet the development needs of lightweight, thin, low-cost, and high-performance backlight modules.

[0007] In view of this, the present invention is hereby proposed. Summary of the Invention

[0008] The primary objective of this invention is to provide a reflective polarizing brightness enhancement film that can replace a diffuser plate. This reflective polarizing brightness enhancement film can directly replace a separately installed diffuser plate in a liquid crystal display backlight module. Furthermore, the reflective polarizing brightness enhancement film maintains high brightness while also providing superior shielding performance.

[0009] The second objective of this invention is to provide a method for preparing a reflective polarizing brightening film that can replace the diffuser plate.

[0010] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted: The present invention provides a reflective polarizing brightening film that can replace a diffuser plate, comprising an upper layer, a middle layer and a lower layer stacked from top to bottom; The upper layer is a reflective polarization composite film, used to selectively transmit P-polarized light and reflect S-polarized light; The middle layer is a micro-scattering homogenizing layer with a periodically arranged prism structure and micro-structural units on its surface, which are used to initially scatter the incident light to initiate the light homogenization process. The lower layer is a strong scattering shielding layer with a periodically arranged prism structure and microstructure units on its side, which are used to strongly scatter light to shield the optical discontinuities inside the backlight module. The three layers are connected by a transparent bonding layer to form an integrated thin film structure, and the reflective polarizing brightening film is used in the liquid crystal display backlight module to replace the independently set diffuser plate.

[0011] Furthermore, the upper reflective polarizing composite film is a multilayer co-extruded polymer film, and the material system includes at least one of PMMA (polymethyl methacrylate) and COC (cyclic olefin copolymer).

[0012] Preferably, the upper reflective polarizing composite film has prism structures on two surfaces, wherein the apex angle of the prism structure on one surface is 98°, 105° or 135°, and the apex angle of the prism structure on the other surface is 8°, 15° or 45°, forming an angle combination.

[0013] Furthermore, the cross-section of the prism structure in the middle layer is an isosceles triangle, and the microstructure unit is a circular or near-circular protrusion distributed on the prism surface; Preferably, the height of the isosceles triangular prism structure is 40~60μm, and the spacing between adjacent prisms is 50~210μm.

[0014] Preferably, the diameter of the circular or near-circular protrusions is 1~5μm, and they are uniformly or randomly distributed.

[0015] Furthermore, the lower prism structure has an isosceles trapezoidal cross-section, and the microstructure unit is a circular or near-circular protrusion distributed on the two sides of the isosceles trapezoid.

[0016] Preferably, the isosceles trapezoidal prism structure has an upper base width of 6~16μm, a lower base width of 54~70μm, and a height of 30~50μm.

[0017] Preferably, the interval between adjacent isosceles trapezoidal prism structures is 50~210μm; Preferably, the diameter of the circular or near-circular protrusions is 1~5μm, and they are uniformly or randomly distributed.

[0018] Furthermore, the bonding layer is a UV-curable adhesive with a thickness of 0.8~1.2μm.

[0019] Furthermore, the substrate used for each functional layer is a transparent flexible material selected from one or more combinations of polyethylene terephthalate, polycarbonate, polymethyl methacrylate, polyethylene, polystyrene, and polyamide resin.

[0020] Furthermore, the thickness of the substrate is 50~200μm.

[0021] The present invention provides a method for preparing the above-mentioned reflective polarizing brightening film, comprising the following steps: A light-diffusing layer with micro-scattering function and a shielding layer with strong scattering shielding function are prepared separately. Then, a transparent adhesive is applied between the light-diffusing layer, the shielding layer, the reflective polarization composite film, and the final composite interface. The shielding layer, the light-diffusing layer, and the upper reflective polarization composite film are then bonded together in a predetermined order to form an integrated multifunctional optical film.

[0022] Furthermore, the viscosity of the adhesive is in the range of 12~30 cps.

[0023] Furthermore, the coating line speed for applying the transparent adhesive is 8m / min to 12m / min.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows: The reflective polarizing brightness enhancement film provided by this invention, through a three-layer integrated design consisting of an upper reflective polarizing composite film, a middle micro-scattering uniform layer, and a lower strong scattering shielding layer, can directly replace a separately set diffuser plate in a liquid crystal display backlight module. Experimental results show that this film maintains high brightness while also exhibiting excellent shielding effect. Furthermore, eliminating the need for a separate diffuser plate helps reduce the thickness and weight of the backlight module, and decreases material and assembly costs, facilitating the design of thinner, lighter, and lower-cost display products.

[0025] The method for preparing a reflective polarizing brightening film provided by this invention involves separately preparing a light-uniforming layer with micro-scattering function and a shielding layer with strong scattering shielding function, and then using a micro-replication process combined with ultraviolet light curing to achieve structural molding, which can ensure high-precision replication of complex microstructures. Each functional layer is cured independently and then integrated through a bonding process, avoiding the process defects caused by multi-layer simultaneous molding. This method has the advantages of process stability and suitability for continuous production. Attached Figure Description

[0026] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0027] Figure 1 This is a schematic diagram of the shielding layer structure provided in Embodiment 1 of the present invention; Figure 2 This is a schematic diagram of the uniform light layer structure provided in Embodiment 1 of the present invention; Figure 3 This is a schematic diagram of the composite structure of the reflective polarizing brightening film that can replace the diffuser plate provided in Embodiment 1 of the present invention.

[0028] Icons: 101-Shielding layer; 102-Light homogenizing layer; 103-Adhesive layer; 104-Reflective polarizing composite film. Detailed Implementation

[0029] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] According to one aspect of the present invention, a reflective polarizing brightening film that can replace a diffuser plate includes an upper layer, a middle layer and a lower layer stacked sequentially from top to bottom; The upper layer is a reflective polarization composite film 104, which is used to selectively transmit P-polarized light and reflect S-polarized light. The middle layer is a micro-scattering homogenizing layer 102, which has a periodically arranged prism structure and micro-structure units on its surface, used to initially scatter the incident light to initiate the light homogenization process. The lower layer is a strong scattering shielding layer 101, which has a periodically arranged prism structure and microstructure units on its side, used to strongly scatter light to shield the optical discontinuities inside the backlight module. The upper, middle and lower layers are connected by a transparent bonding layer 103 to form an integrated thin film structure.

[0031] The reflective polarizing brightening film provided by this invention integrates the reflective polarization function and the light-shielding function of the diffuser plate into a single film, achieving the following technical effects: 1. It can directly replace a separate diffuser plate, simplifying the backlight module structure: By integrating a middle micro-scattering uniform layer 102 with gradient scattering capability and a lower strong scattering shielding layer 101 below a traditional CPP composite film, this film can effectively eliminate hot spots and light shadows caused by LED beads, light guide plate dots, etc., without relying on an external diffuser plate.

[0032] 2. Maintaining high optical efficiency while achieving high shielding performance: Although this invention integrates strong scattering functionality, it effectively controls light energy loss by employing surface microstructure modulation rather than volume scattering, and by designing a gradient path that combines initial scattering in the middle layer with strong shielding in the lower layer.

[0033] 3. It facilitates the thinning and cost reduction of backlight modules: By eliminating the traditional independent diffuser plate, the overall thickness and weight of the backlight module are significantly reduced, aligning with the trend towards thinner and lighter display devices. At the same time, reducing the number of optical film layers helps lower material costs and assembly processes, improving production efficiency.

[0034] 4. The three-layer structure works in tandem to enhance system-level optical performance: The upper CPP layer is responsible for the transmission of P-light and the recovery of S-light, improving light utilization efficiency; the middle layer gently scatters light to initiate the light mixing process and avoid local overbrightness; the lower layer achieves strong scattering through complex microstructures, completely blurring the internal structure image. The three layers work together to give the emitted light high brightness, high uniformity, and high purity, meeting the optical requirements of high-end LCD products.

[0035] In summary, the reflective polarizing brightness enhancement film provided by this invention, through its three-layer integrated design—an upper reflective polarizing composite film 104, a middle micro-scattering uniform layer 102, and a lower strong scattering shielding layer 101—can directly replace a separately installed diffuser plate in a liquid crystal display backlight module. Experimental results show that this film maintains high brightness while also exhibiting excellent shielding performance. Furthermore, eliminating the need for a separate diffuser plate helps reduce the thickness and weight of the backlight module, and decreases material and assembly costs, facilitating the design of thinner, lighter, and lower-cost display products.

[0036] In a preferred embodiment of the present invention, the upper reflective polarizing composite film 104 is a multilayer co-extruded polymer film, and the material system includes at least one of PMMA and COC.

[0037] Preferably, the upper reflective polarizing composite film 104 has prism structures on two opposite surfaces to form a double-sided light control structure, wherein the apex angle of the prism structure on one surface is 98°, 105° or 135°, and the apex angle of the prism structure on the other surface is 8°, 15° or 45°, forming corresponding angle combinations.

[0038] As a preferred embodiment, the upper reflective polarization composite film 104 of the present invention is made of a multilayer co-extruded polymer material containing at least one of PMMA and COC, which can achieve efficient polarization selective separation and improve light recovery efficiency.

[0039] Furthermore, the reflective polarizing composite film 104 has a double-sided light control structure, where one surface has a prism apex angle of 98°, 105°, or 135°, and the other surface has an apex angle of 8°, 15°, or 45°, forming a specific angle combination. This design can improve the directional distribution of emitted light while maintaining high brightness output, and works in conjunction with the middle and lower layer scattering structure to achieve a better balance of optical performance.

[0040] In a preferred embodiment of the present invention, the cross-section of the prism structure in the middle layer is mainly an isosceles triangle, and the microstructure unit is a circular or near-circular protrusion distributed on the prism surface. In the preferred embodiment described above, the height of the isosceles triangular prism structure is 40~60μm, and the spacing between adjacent prisms is 50~210μm.

[0041] As an optional implementation, the height of the isosceles triangular prism structure is 40–60 μm, for example, it can be 40 μm, 45 μm, 50 μm, 55 μm, or 60 μm, or any value between 40 and 60 μm, such as 42.3 μm, 48.7 μm, or 56.9 μm; the spacing between adjacent prisms is 50–210 μm, for example, it can be 50 μm, 100 μm, 150 μm, 200 μm, or 210 μm, or any value between 50 and 210 μm, such as 65.4 μm, 123.8 μm, or 187.5 μm.

[0042] In the preferred embodiment described above, the diameter of the circular or near-circular protrusions is 1~5μm, and they are uniformly or randomly distributed.

[0043] As an optional implementation, the particle size of the circular or near-circular protrusions is 1 to 5 μm, for example, it can be 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, or any value between 1 and 5 μm, such as 1.8 μm, 2.5 μm, 3.7 μm, 4.9 μm, etc.; the protrusions are uniformly distributed or randomly distributed on the surface.

[0044] In a preferred embodiment, the intermediate light-homogenizing layer 102 adopts a prism structure with an isosceles triangular cross-section, and circular or near-circular protrusions with a particle size of 1~5μm are provided on its surface. This allows for gentle initial scattering of incident light without causing significant light loss, thus initiating the light homogenization process. This light-homogenizing layer 102 structure helps alleviate hotspot phenomena and works in conjunction with the lower shielding layer 101.

[0045] In a preferred embodiment of the present invention, the cross-section of the lower prism structure is an isosceles trapezoid, and the microstructure unit is a circular or near-circular protrusion distributed on the two sides of the isosceles trapezoid.

[0046] In a preferred embodiment, the lower shielding layer 101 adopts a prism structure with an isosceles trapezoidal cross-section, and has circular or near-circular protrusions with a particle size of 1~5μm distributed on the two waist surfaces, which can form a high-intensity, asymmetric scattering field within a unit area, effectively blurring the LED light shadows and light guide plate dot patterns inside the backlight module.

[0047] In the preferred embodiment described above, the width of the upper base of the isosceles trapezoidal prism structure is 6~16μm, the width of the lower base is 54~70μm, and the height is 30~50μm.

[0048] As an optional implementation, the width of the upper base of the isosceles trapezoidal prism structure is 6–16 μm, for example, it can be 6 μm, 8 μm, 10 μm, 12 μm, 14 μm, or 16 μm, or any value between 6 and 16 μm, such as 7.5 μm, 11.2 μm, or 15.8 μm; the width of the lower base is 54–70 μm, for example, it can be 54 μm, 58 μm, 60 μm, 65 μm, or 70 μm, or any value between 54 and 70 μm, such as 56.3 μm, 62.7 μm, or 68.9 μm; the height is 30–50 μm, for example, it can be 30 μm, 35 μm, 40 μm, 45 μm, or 50 μm, or any value between 30 and 50 μm, such as 32.4 μm, 38.6 μm, or 47.5 μm.

[0049] In the preferred embodiment described above, the interval between adjacent isosceles trapezoidal prism structures is 50~210μm; As an optional implementation, the interval between adjacent isosceles trapezoidal prism structures is 50 to 210 μm, for example, it can be 50 μm, 100 μm, 150 μm, 200 μm, 210 μm, or any value between 50 and 210 μm, such as 75.3 μm, 120.8 μm, 185.6 μm, etc.

[0050] In the preferred embodiment described above, the diameter of the circular or near-circular protrusions is 1~5μm, and they are uniformly or randomly distributed.

[0051] As an optional implementation, the particle size of the circular or near-circular protrusions is 1 to 5 μm, for example, it can be 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, or any value between 1 and 5 μm, such as 1.8 μm, 2.5 μm, 3.7 μm, 4.9 μm, etc.; the protrusions are uniformly distributed or randomly distributed on the surface.

[0052] As an optional implementation, the bonding layer 103 is a UV-curable adhesive with a thickness of 0.8 to 1.2 μm, for example, it can be 0.8 μm, 0.9 μm, 1.0 μm, 1.1 μm, or 1.2 μm, or any value between 0.8 and 1.2 μm, such as 0.85 μm, 0.98 μm, or 1.15 μm.

[0053] In a preferred embodiment of the present invention, the substrate used for each functional layer is a transparent flexible material selected from one or more combinations of polyethylene terephthalate (PET), polycarbonate (PC), polymethyl methacrylate (PMMA), polyethylene (PE), polystyrene (PS), and polyamide resin (PA). In a preferred embodiment of the present invention, the thickness of the substrate is 50~200μm.

[0054] As an optional implementation, the thickness of the substrate is 50 to 200 μm, for example, it can be 50 μm, 100 μm, 150 μm, 200 μm, or any value between 50 and 200 μm, such as 75 μm, 120 μm, 180 μm, etc.

[0055] According to one aspect of the present invention, a method for preparing the above-mentioned reflective polarizing brightening film includes the following steps: (A) Prepare a light-diffusing layer 102 with micro-scattering function and a shielding layer 101 with strong scattering shielding function respectively: use micro-replication process to coat the surface of the patterned mold with photocurable resin, pre-cur it with ultraviolet light, demold it and transfer it to the substrate, and then perform complete curing. (B) Apply transparent adhesive between the functional layers and at the final composite interface; (C) The shielding layer 101, the light-diffusing layer 102 and the upper reflective polarization composite film 104 are sequentially bonded in a predetermined order to form an integrated multifunctional optical film. The multifunctional optical film is configured to replace the independent diffuser plate in the backlight module.

[0056] The method for preparing a reflective polarizing brightening film provided by this invention involves separately preparing a light-uniforming layer 102 with micro-scattering function and a shielding layer 101 with strong scattering shielding function, and then using a micro-replication process combined with ultraviolet light curing to achieve structural molding, which can ensure high-precision replication of complex microstructures. Each functional layer is cured independently and then integrated through a bonding process, avoiding the process defects caused by multi-layer synchronous molding. This method has the advantages of stable process and suitability for continuous production.

[0057] As an optional implementation, the viscosity range of the coating liquid for the bonding layer 103 prepared in step (A) is 12~30 cps, for example, it can be 12 cps, 15 cps, 20 cps, 25 cps, 30 cps, or any value between 12 and 30 cps, such as 13.5 cps, 17.8 cps, 22.4 cps, etc.

[0058] As an optional implementation, the coating line speed in step (B) is 8~12m / min, for example, it can be 8m / min, 9m / min, 10m / min, 11m / min, 12m / min, or any value within this range, such as 8.5m / min, 9.2m / min, 10.8m / min, 11.7m / min, etc.

[0059] The advantages and effects of this application compared to the prior art can also be summarized as follows: 1. Structural innovation: Three-layer integrated architecture.

[0060] Breaking away from the single-function limitations of traditional reflective polarizing films (CPP), a creative three-layer integrated structure from top to bottom was designed: Top layer: Conventional CPP reflective polarization layer → responsible for polarized light recovery and brightening.

[0061] Middle layer: Micro-scattering homogenizing layer 102 → responsible for the initial homogenization of the optical path.

[0062] Bottom layer: Strong scattering shielding layer 101 → responsible for final light uniformation and structural shielding.

[0063] The essence of innovation: integrating the functions previously achieved by three different film materials (diffuser plate, lower diffuser sheet, and reflective polarizing brightening film) into a single thin film.

[0064] 2. Functional innovation: From "brightening" to "brightening + uniform light + masking".

[0065] The thin film of this invention is no longer merely a "brightness enhancement" element, but a multifunctional optical engine. It proactively undertakes the core tasks that originally had to be performed by the diffuser plate: eliminating hot spots, mixing light, and shielding the internal structure.

[0066] Meanwhile, the three layers are not simply stacked, but work together. The bottom layer provides strong shading, the middle layer provides gentle homogenization to suppress excessive light loss, and the top layer provides efficient brightening, ultimately outputting an extremely uniform surface light source while ensuring high brightness.

[0067] 3. Performance Innovation: Optimization and balance of optical performance.

[0068] Efficient light management: By first shielding and homogenizing the light, and then recovering the polarization, the reflected S-polarized light has already undergone homogenization processing by the lower structure when it circulates in the backlight system, which improves the light utilization efficiency and light output uniformity.

[0069] Low-loss uniform light: Unlike the inevitable light loss caused by strong volume scattering of independent diffusers, this invention uses a two-layer structure to finely control the degree of scattering, aiming to achieve the required uniform light and shielding effect with the lowest light energy loss, thereby maintaining high brightness at the system level.

[0070] 4. Application Innovation: Leading the transformation of module design and manufacturing.

[0071] Simplified module architecture: This allows the backlight module to completely eliminate the need for a separate diffuser plate, which is a revolution in traditional backlight architecture.

[0072] Thin design: One of the thickest components in the backlight module has been removed, providing core technological support for manufacturing thinner and lighter display devices.

[0073] Process optimization: Reduced material types, inventory management, and assembly steps directly led to lower costs and improved production efficiency.

[0074] The technical solution of the present invention will be further described below with reference to the embodiments.

[0075] Example 1 Figure 1 This is a schematic diagram of the shielding layer 101 structure provided in Embodiment 1 of the present invention.

[0076] Figure 2 This is a schematic diagram of the uniform light layer 102 structure provided in Embodiment 1 of the present invention.

[0077] Figure 3 This is a schematic diagram of the composite structure of the reflective polarizing brightening film that can replace the diffuser plate provided in Embodiment 1 of the present invention.

[0078] See Figures 1-3 This embodiment provides a reflective polarizing brightening film that can replace a diffuser plate. The optical film comprises, from top to bottom: a CPP composite film (upper layer), a light-diffusing layer 102 (middle layer), and a shielding layer 101 (lower layer). The functional layers are connected by an adhesive layer to form an integrated composite structure.

[0079] 1. The upper layer is a multilayer co-extruded reflective polarizing composite film 104 (i.e., CPP composite film), with microprism structures on its two main surfaces. The prism angles are matched at 105° / 15° to achieve directional control and brightness enhancement of the emitted light.

[0080] The CPP composite film has the function of selectively transmitting P-polarized light and reflecting S-polarized light, thereby improving the light utilization efficiency of the backlight system.

[0081] 2. The middle layer is a light-diffusing layer 102 with micro-scattering capability, disposed below the CPP composite film. This light-diffusing layer 102 is composed of several parallel prism strips, the main cross-section of which is an isosceles right triangle with a base length of 50 μm. Circular protrusions are distributed on the surface of the prism structure, and the particle size of the protrusions is randomly distributed, ranging from 1 to 3 μm.

[0082] The homogenizing layer 102 structure can initially scatter incident light from below, initiating the light mixing process, which helps to eliminate local light intensity unevenness while maintaining high light transmittance and reducing light energy loss. The prism strips of the middle homogenizing layer 102 are arranged at an angle of 0° / 0°.

[0083] 3. The lower layer is a shielding layer 101 with strong scattering and shielding functions, located at the bottom layer. This shielding layer 101 is also composed of periodically arranged prism strips, with its main cross-section being an isosceles trapezoid. The upper base width is 4μm, the lower base width is 60μm, and the height is 40μm. The spacing between adjacent prism strips is 150μm. Circular protrusions are provided on the two side surfaces of the isosceles trapezoid. The protrusions have different particle sizes, ranging from 1 to 3μm, and are randomly arranged.

[0084] The aforementioned reflective polarizing brightness enhancement film composite microstructure can generate a strong asymmetric scattering effect, effectively blurring the dot pattern and internal structure of the LED beads on the light guide plate, preventing them from being directly observed in the display screen, and achieving excellent visual masking effect.

[0085] The specific preparation process is as follows: First, prism adhesive is coated on the surface of a copper roller engraved with the target pattern. After pre-curing under low-pressure ultraviolet light, the roller is demolded and transferred to a 100μm thick polyethylene terephthalate (PET) substrate. Then, it is completely cured under high-pressure ultraviolet light to form a stable microstructure surface. Subsequently, UV-curable acrylic adhesive is coated on the other side of the substrate or the surface of an adjacent film layer as an adhesive layer 103. The shielding layer 101, the light-diffusing layer 102, and the upper CPP composite film are then laminated together in sequence to finally obtain an integrated multifunctional optical film.

[0086] Example 2 The difference between this embodiment and Embodiment 1 is that, except for the fact that "the spacing between adjacent isosceles trapezoidal prism strips is 210μm" in the shielding layer 101, the rest is the same as in Embodiment 1.

[0087] Example 3 The only difference between this embodiment and embodiment 2 is that the prism strip arrangement angle of the middle light-diffusing layer 102 is adjusted from 0° / 0° to 0° / 135°, that is, the two sets of prism structures are at a 135-degree angle; the rest of the structure, material selection and preparation method are the same as in embodiment 2.

[0088] Example 4 The only difference between this embodiment and Embodiment 3 is that the base length of the isosceles right-angled triangular prism structure of the middle light-diffusing layer 102 is increased from 50μm to 75μm; the rest of the structure, material selection and preparation process are the same as in Embodiment 3.

[0089] Example 5 The only difference between this embodiment and embodiment 3 is that the structural parameters of the isosceles trapezoidal prism of the lower shielding layer 101 have changed. Specifically, the width of the upper base has increased from 4μm to 5μm, the width of the lower base has decreased from 60μm to 54μm, and the height remains 40μm while maintaining the same height structure. All other parts are the same as in embodiment 3.

[0090] Example 6 The only difference between this embodiment and embodiment 3 is that the distribution range of the circular protrusions on the surface of the shielding layer 101 and the light-diffusing layer 102 is adjusted from 1~3μm to 3~5μm; the rest of the structure, materials and preparation methods are the same as in embodiment 3.

[0091] Comparative Example 1 As a comparative reference, this comparative example provides a conventional CPP composite film with the same structure as the upper CPP composite film in the above embodiments, with prism angles of 105° / 15° and a substrate of 100μm thick PET.

[0092] In actual backlight module testing, this CPP film needs to be used in conjunction with an independent diffuser plate to achieve basic light uniformity and shielding functions.

[0093] Comparative Example 2 This comparative example provides a reflective polarizing brightening film, which differs from Example 1 in that: the middle layer micro-scattering uniform layer 102 is omitted, and the lower strong scattering shielding layer 101 and the upper reflective polarizing composite film 104 are directly connected by a transparent adhesive layer.

[0094] Comparative Example 3 This comparative example provides a reflective polarizing brightening film, which differs from Example 1 in that the lower strong scattering shielding layer 101 is omitted, and the middle micro-scattering uniform light layer 102 and the upper reflective polarizing composite film 104 are directly connected by a transparent adhesive layer.

[0095] Comparative Example 4 This comparative example provides a reflective polarizing brightening film, which differs from Example 1 in that the order of the middle and lower functional layers is reversed. The specific structure is as follows: The bottom layer (original lower layer position): is set as micro-scattering homogenizing layer 102, with an isosceles triangular prism structure in cross-section, 40 μm high and about 56.6 μm at the base; the surface is distributed with circular protrusions with a particle size of 1~3 μm, which are randomly distributed; the spacing between adjacent prisms is 50 μm; Intermediate layer (original middle layer position): set as strong scattering shielding layer 101, with a cross-section of isosceles trapezoidal prism structure, upper base width 4μm, lower base width 60μm, and height 40μm; circular protrusions with a particle size of 1~3μm are provided on the two waist surfaces, which are randomly distributed; the spacing between adjacent prisms is 150μm; The top layer is still a multilayer co-extruded reflective polarizing composite film 104, with the prism angle combination of the two surfaces being 105° / 15°, and the substrate being PET (100μm).

[0096] Comparative Example 5 This comparative example provides a reflective polarizing brightening film, which differs from Example 1 in that: the middle and lower layers in this comparative example are both micro-scattering uniform light layers 102, that is, the two micro-scattering uniform light layers 102 in Example 1 are connected to the upper reflective polarizing composite film 104 through a transparent adhesive layer.

[0097] Comparative Example 6 This comparative example provides a reflective polarizing brightening film, which differs from Example 1 in that: the middle and lower layers in this comparative example are both strong scattering shielding layers 101, that is, the two strong scattering shielding layers 101 in Example 1 are connected to the upper reflective polarizing composite film 104 through a transparent adhesive layer.

[0098] Experimental Example 1 To verify whether the reflective polarizing brightening film provided by the present invention can replace the independent diffuser plate, the optical performance of the optical film samples prepared in Examples 1 to 6 and Comparative Example 1 was tested, focusing on their brightness and shielding effect level. The test results are shown in Table 1.

[0099] Table 1 shows the brightness and shading effects provided in the examples and comparative examples:

[0100] The luminance was based on the light output brightness of Comparative Example 1 (standard CPP composite film + independent diffuser plate) (set as 100%), and the test values ​​of the other samples were relative percentages. The shading effect level evaluation criteria are as follows: Level 1: Comparable to the existing DP+CPP scheme; Level 2: Fairly good, with slightly visible structures that do not affect viewing; Level 3: Significantly superior, completely eliminating the visibility of the internal structure.

[0101] The test results show that: All embodiments achieved good masking effects without the independent diffuser plate. Among them, the masking effect of Embodiment 1 reached level 3, which was better than Comparative Example 1 and other embodiments, indicating that it has better visual purity. Although the luminance of each embodiment is slightly lower than that of Comparative Example 1 (up to 97.0%), it is within an acceptable range, and some embodiments (such as Example 4) maintain a level of shading effect of 1 while achieving a luminance close to the optimal level. Compared with Example 1, Example 2 has a slightly lower luminance while achieving a slightly lower shading effect, indicating that a trade-off between shading performance and optical efficiency can be achieved by adjusting the density of the prism in the shading layer 101.

[0102] Comparative Example 2 omits the middle micro-scattering homogenizing layer 102, retaining only the structure where the upper reflective polarizing composite film 104 and the lower strong scattering shielding layer 101 are directly bonded. Although it achieves light shielding to a certain extent (shielding effect level 1), its luminance is 92.6%, lower than all other embodiments. In contrast, each embodiment introduces the middle micro-scattering homogenizing layer 102 to perform preliminary light field homogenization based on the lower strong scattering layer, effectively alleviating the problem of excessive light energy divergence caused by single strong scattering, thereby significantly improving the output brightness while maintaining good shielding performance (luminance of Examples 1-6 is 94.8%~97.0%).

[0103] Comparative Example 3 omits the lower strong scattering shielding layer 101, retaining only the upper reflective polarizing composite film 104 and the middle micro-scattering homogenizing layer 102. Its luminance is 91.43%, which is close to the level of some embodiments, but the shielding effect is only level 1, significantly lower than Embodiments 1-3 and Embodiments 4-6 (shielding level 1 but higher brightness). In contrast, each embodiment significantly enhances the ability to blur the optical discontinuities within the backlight module by setting the lower strong scattering shielding layer 101 with a trapezoidal prism structure and sidewall microstructures.

[0104] Comparative Example 4 swapped the positions of the middle micro-scattering homogenizing layer 102 and the lower strong scattering shielding layer 101, i.e., the micro-scattering homogenizing layer 102 was placed at the bottom and the strong scattering shielding layer 101 was placed in the middle layer, while the rest of the structure remained unchanged. Test results showed that its luminance was 93.03%, and the shielding effect level was 2, both lower than those of the other embodiments. In contrast, the embodiment employs a layer sequence design with the strong scattering shielding layer 101 at the bottom and the micro-scattering homogenizing layer 102 in the middle. This allows the incident light to first undergo high-intensity scattering to effectively blur the internal structure, then undergoes gentle homogenization in the middle layer to regulate the light field distribution, and finally the upper reflective polarization composite film 104 efficiently recovers the S-polarized light, achieving an optimal balance between brightness and shielding. This comparison demonstrates that the spatial arrangement order of the functional layers has a decisive influence on optical performance; reversing the layer sequence will disrupt the optical path coordination mechanism, leading to a decrease in overall performance.

[0105] Comparative Example 5 employs a structure consisting of two layers, both of which are micro-scattering homogenizing layers 102. That is, both the middle and lower layers have the same micro-scattering functional layers as in Example 1. Its luminance is 95.48%, approaching the level of some examples, but its shading effect is only level 1, significantly lower than Example 1. This comparison shows that relying solely on a dual weak scattering structure cannot achieve the required shading intensity; a lower layer structure with high-intensity asymmetric scattering characteristics must be introduced to achieve excellent visual purity.

[0106] Comparative Example 6 employs a double-layer structure consisting of a strong scattering shielding layer 101. That is, both the middle and lower layers have the same strong scattering functional layers as in Example 1. Its shielding effect reaches level 3, comparable to Example 1, but its luminance is only 93.65%, significantly lower than the other examples (94.80%~97.0%). This comparison shows that simply enhancing scattering intensity, while beneficial for shielding, leads to a decrease in optical efficiency. The present invention, through a gradient scattering design of a strong scattering shielding layer 101 + a micro-scattering homogenizing layer 102, achieves a better balance between shielding effect and light transmittance.

[0107] Therefore, the results of Comparative Examples 1 to 6 show that omitting any functional layer, reversing the layer order, or using a homogenized structure cannot reproduce the comprehensive optical performance achieved by the present invention, thus confirming the necessity and non-obviousness of the three-layer integrated architecture and its spatial arrangement of the present invention.

[0108] In summary, the integrated reflective polarizing brightness enhancement film provided by this invention can still provide comprehensive optical performance that is superior to or equivalent to that of traditional architectures without the need for an independent diffuser plate, fully meeting the requirements of liquid crystal display backlight modules for high brightness, high uniformity and high shielding.

[0109] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention 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 or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A reflective polarizing brightening film that can replace a diffuser plate, characterized in that, This includes an upper layer, a middle layer, and a lower layer that are stacked from top to bottom; The upper layer is a reflective polarization composite film (104) used to selectively transmit P-polarized light and reflect S-polarized light; The middle layer is a micro-scattering homogenizing layer (102), which has a periodically arranged prism structure and micro-structure units on its surface, used to initially scatter the incident light to initiate the light homogenization process. The lower layer is a strong scattering shielding layer (101), which has a periodically arranged prism structure and microstructure units on its side, used to strongly scatter light to shield the optical discontinuities inside the backlight module. The upper, middle and lower layers are connected by a transparent bonding layer (103) to form an integrated thin film structure.

2. The reflective polarizing brightening film according to claim 1, characterized in that, The upper reflective polarizing composite film (104) is a multilayer co-extruded polymer film, and the material system includes at least one of PMMA and COC; Preferably, the reflective polarizing composite film (104) has prism structures on two surfaces respectively, wherein: the apex angle of the prism structure on one surface is 98°, 105° or 135°, and the apex angle of the prism structure on the other surface is 8°, 15° or 45°, forming an angle combination.

3. The reflective polarizing brightening film according to claim 1, characterized in that, The cross-section of the prism structure in the middle layer is an isosceles triangle, and the microstructure unit is a circular or near-circular protrusion distributed on the prism surface; Preferably, the height of the isosceles triangular prism structure is 40~60μm, and the spacing between adjacent prisms is 50~210μm; Preferably, the diameter of the circular or near-circular protrusions is 1~5μm, and they are uniformly or randomly distributed.

4. The reflective polarizing brightening film according to claim 1, characterized in that, The lower prism structure has an isosceles trapezoidal cross-section, and the microstructure unit is a circular or near-circular protrusion distributed on the two sides of the isosceles trapezoid. Preferably, the isosceles trapezoidal prism structure has an upper base width of 6~16μm, a lower base width of 54~70μm, and a height of 30~50μm; Preferably, the spacing between adjacent isosceles trapezoidal prism structures is 50~210μm; Preferably, the diameter of the circular or near-circular protrusions is 1~5μm, and they are uniformly or randomly distributed.

5. The reflective polarizing brightening film according to claim 1, characterized in that, The bonding layer (103) is a UV-curable adhesive with a thickness of 0.8~1.2μm.

6. The reflective polarizing brightening film according to claim 1, characterized in that, The substrate used for each functional layer is a transparent flexible material selected from one or more combinations of polyethylene terephthalate, polycarbonate, polymethyl methacrylate, polyethylene, polystyrene, and polyamide resin.

7. The reflective polarizing brightening film according to claim 6, characterized in that, The thickness of the substrate is 50~200μm.

8. A method for preparing a reflective polarizing brightening film according to any one of claims 1 to 7, characterized in that, Includes the following steps: A light-diffusing layer (102) with micro-scattering function and a shielding layer (101) with strong scattering shielding function are prepared respectively. Then, a transparent adhesive is applied between the light-diffusing layer (102), the shielding layer (101), the reflective polarization composite film (104), and the final composite interface. The shielding layer (101), the light-diffusing layer (102), and the upper reflective polarization composite film (104) are sequentially bonded in a predetermined order to form an integrated multifunctional optical film.

9. The preparation method according to claim 8, characterized in that, The viscosity range of the adhesive is 12~30 cps.

10. The preparation method according to claim 8, characterized in that, The coating line speed for applying the transparent adhesive is 8m / min to 12m / min.

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