Composite light guide plate, preparation method thereof and backlight module

Abstract

The invention relates to the technical field of light guide plate manufacturing, and discloses a composite light guide plate, a preparation method thereof and a backlight module. The method comprises the following steps: providing a light guide plate mold with a variable-diameter micropore array, carrying out variable-pressure molding on a preset formula mixture to obtain a porous gradient matrix, imprinting the porous gradient matrix coated with the light curing agent based on a flexible prism array mold; a nested grating structure with direction selectivity is further formed through laser and plasma synergistic etching, an optical active layer and magnetron sputtering are sequentially formed on a nested grating base body, an optical active layer with the light-emitting regulation and wavelength conversion capacity is constructed, and through plasma activation and hot pressing, the light-emitting wavelength conversion structure with the light-emitting regulation and wavelength conversion capacity is obtained. The fluorinated polyimide film is combined with the tuning substrate, so that the overall structural strength of the composite light guide plate is enhanced, the multifunctional composite light guide plate with high interface bonding strength is formed, and the problems of interface delamination and stress concentration easily occurring in a multi-layer light guide structure are effectively solved.

Description

Technical Field

[0001] This invention relates to the field of light guide plate manufacturing technology, and more specifically, to a composite light guide plate and its preparation method, and a backlight module. Background Technology

[0002] With the rapid development of fields such as intelligent LCD display terminals, backlight modules, optical communication, and intelligent lighting, the performance requirements for light guide plates are constantly increasing, especially in achieving high luminous efficiency, high uniformity, thinness, and functional diversity, which has become a key focus of research and industrialization. Increasing research is concentrated on the construction of light guide plate microstructures, the introduction of functional materials, and the control of interface optical properties. Modern light guide plates not only perform light transmission but also integrate multiple optical tasks such as light emission modulation, wavelength conversion, and direction control, driving their structure to evolve from simple geometric patterns to multi-layered micro / nano structure composite systems.

[0003] In existing technologies, composite light guide plates typically employ multi-step processing to integrate structure and function. Specifically, this involves constructing micro-optical structures on a substrate and then introducing functional coatings. However, existing composite light guide plates often exhibit interlayer delamination, interface stress concentration, and even optical performance degradation at the interface between the microstructure layer and the functional coating due to material differences or surface energy mismatches. These poor interface stability issues are even more pronounced in light guide plates involving nested multi-functional layers and complex superimposed structures, directly impacting the long-term reliability and light output consistency of the device.

[0004] Therefore, there is a need to provide a composite light guide plate and its preparation method, as well as a backlight module, to solve the problem of poor interface stability of existing composite light guide plates. Summary of the Invention

[0005] The main objective of this invention is to provide a composite light guide plate and its preparation method, as well as a backlight module, in order to solve the technical problems mentioned in the background section.

[0006] The present invention adopts the following technical solution: A method for preparing a composite light guide plate includes: A light guide plate mold with a variable diameter micropore array is provided, and a pre-formulated mixture is subjected to pressure molding to obtain a porous gradient matrix; A photocuring agent is applied to the surface of the porous gradient substrate, and the porous gradient substrate coated with the photocuring agent is imprinted based on a flexible prism array mold to construct a curved prism array on the surface of the porous gradient substrate. The porous gradient substrate with the curved prism array is sequentially subjected to laser and plasma etching to obtain a nested grating substrate, and a photoactive layer is formed on the surface of the nested grating substrate based on a silane coupling agent solution. In an inert gas atmosphere, magnetron sputtering is performed on the surface of the photoactive layer based on a composite target to obtain a tuning substrate. A fluorinated polyimide film is then covered on the tuning substrate and hot-pressed for 10 to 15 minutes to obtain a composite light guide plate.

[0007] Furthermore, the preset formulation mixture includes a polymer substrate, nanofillers, and photorefractive additives; The polymer substrate is one of the following: a mixture of polycarbonate and polymethyl methacrylate in a mass ratio of 3:2, a mixture of polycarbonate and polystyrene in a mass ratio of 2:1, or a mixture of polymethyl methacrylate and polyetherimide in a mass ratio of 3:1. The nanofiller is one or more of nano-titanium dioxide, nano-zinc oxide, or nano-silicate, and the particle size of the nanofiller is 20-50 nanometers. The photorefractive agent is one or more of the following: benzotriazole UV absorbers, hindered amine light stabilizers, or nano zinc sulfide.

[0008] Further, the silane coupling agent solution is one or more of γ-aminopropyltriethoxysilane, γ-(2,3-epoxypropoxy)propyltrimethoxysilane, γ-methacryloyloxypropyltrimethoxysilane or vinyltrimethoxysilane, and the content of the silane coupling agent is 0.3 to 1.5 wt%.

[0009] Furthermore, the step of providing a light guide plate mold with a variable diameter micropore array, and performing variable pressure molding on a preset formula mixture to obtain a porous gradient matrix includes: The pre-formulated mixture is put into a mixer and stirred at 180 to 200°C for 30 to 50 minutes at a speed of 500 to 800 rpm. The preset formula mixture is melted by raising the temperature to 230 to 250°C, and the melt is injected into a light guide plate mold by an extruder in a vacuum environment for variable pressure molding. The inner wall of the light guide plate mold is provided with a variable diameter micropore array that gradually changes from 150 micrometers to 50 micrometers from the center to the edge and has a depth of 20 to 30 micrometers. During the molding process, a gas pressure of 0.5 to 0.7 MPa is applied, the molding pressure is 0.8 to 1 MPa, and the molding time is 10 to 15 minutes. The molded melt is subjected to gradient cooling treatment, which reduces the temperature from 230°C to room temperature at a cooling rate of 3°C / min, while applying a pressure of 0.2 to 0.3 MPa during the cooling process, and cooling for 40 to 60 minutes to obtain a porous gradient matrix.

[0010] Furthermore, the photocuring agent is an acrylic resin containing 5% photoinitiator; The step of coating the photocurable agent onto the surface of the porous gradient substrate and imprinting the photocurable agent-coated porous gradient substrate using a flexible prism array mold includes: The surface of the porous gradient substrate is subjected to plasma cleaning in an oxygen atmosphere for 30 to 40 seconds. The photocuring agent is spin-coated onto the surface of the cleaned porous gradient substrate at a spin speed of 400 to 600 rpm, and the coating thickness of the photocuring agent is 0.4 to 0.6 mm. Imprinting is performed on a porous gradient substrate coated with a photocurable agent using a flexible prism array mold. The flexible prism array mold is made of polydimethylsiloxane, and its surface has a prism array structure with a period of 100 to 200 micrometers and a radius of curvature of 50 to 80 micrometers. The imprinting pressure is 0.1 to 0.3 MPa. The imprinted porous gradient substrate is cured under ultraviolet light with an intensity of 15 milliwatts per square centimeter and a curing time of 15 to 30 seconds. During the curing process, a pressure of 0.2 to 0.4 MPa is applied simultaneously to form a curved prism array with a vertex angle of 60 to 80 degrees on the surface of the porous gradient substrate.

[0011] Further, the step of immersing the nested grating substrate in a zinc sulfide quantum dot solution for electrophoretic deposition, and then immersing the deposited nested grating substrate in a silane coupling agent solution for impregnation, thereby forming a photoactive layer on the surface of the nested grating substrate, includes: The nested grating substrate was placed in a deionized aqueous solution containing 0.5-1% polyethylene glycol for electrophoretic deposition pretreatment. A pre-electric field of 1 volt / cm was applied at room temperature for 10 to 15 minutes to form a uniform charge distribution layer on the inner surface of the grating microgroove. The pretreated nested grating substrate was placed in a deionized aqueous solution containing 1.5-2.5% zinc sulfide quantum dots and 0.2-0.4% polyvinyl alcohol for electrophoretic deposition. An electric field of 3-5 V / cm was applied at 25°C for 15 to 25 minutes. The zinc sulfide quantum dots had a particle size of 4 to 7 nanometers. The nested grating substrate after electrophoretic deposition is impregnated with a toluene solution based on silane coupling agent and treated at 50 to 60°C for 10 to 15 minutes to form a uniform covalent bonded layer with a thickness of 0.2 to 0.4 micrometers on the nested grating substrate. The impregnated nested grating substrate is placed in a temperature-controlled oven, with the temperature set at 110 to 130°C and the heat treatment time at 15 to 25 minutes to form a photoactive layer.

[0012] Furthermore, the step of obtaining a tuned substrate by magnetron sputtering of the surface of the photoactive layer based on a composite target in an inert gas atmosphere includes: Under an argon and nitrogen atmosphere, the surface of the photoactive layer was pre-sputtered with an indium tin oxide and zinc oxide composite target to obtain a primary deposition substrate. Under an atmosphere of argon and oxygen, a gradient sputtering method is used to sputter the surface of the primary deposition substrate with a composite target of silicon oxide and zinc sulfide to obtain a multilayer tunable substrate. Thermal phase separation is performed on the multilayer tuned substrate to form a phase separation layer with a thickness of 0.6 to 0.8 micrometers and a refractive index that gradually changes from 1.5 to 1.9, thus obtaining the tuned substrate.

[0013] Further, the step of covering the fluorinated polyimide film onto the tuning substrate and hot-pressing it for 10 to 15 minutes to obtain the composite light guide plate includes: The tuning substrate was placed in a plasma chamber under a helium and ethylene atmosphere for plasma activation treatment, and a carbon nanochain structure was formed on the surface of the tuning substrate. The surface characteristics of the activated tuned substrate are obtained using a vision system, and the fluorinated polyimide film is pretreated with ultraviolet light according to the surface characteristics. In a vacuum environment, the activated tuning substrate is bonded to the fluorinated polyimide film that has been pretreated with ultraviolet light. Maintaining a vacuum environment, the bonded tuning substrate and fluorinated polyimide film are subjected to hot pressing treatment at a temperature of 80 to 90°C, a pressing pressure of 0.3 to 0.5 MPa, and a hot pressing time of 10 to 15 minutes to obtain a composite light guide plate.

[0014] The present invention also proposes a composite light guide plate, which is prepared by the method of any of the above-mentioned composite light guide plates. The composite light guide plate includes a porous gradient substrate, and the surface of the porous gradient substrate is provided with a variable diameter micropore array. The porous gradient substrate is formed with a nested grating layer, a photoactive layer and a tuning structure from the inside to the outside. The outer surface of the tuning structure is covered with a fluorinated polyimide film.

[0015] The present invention also proposes a backlight module, comprising the composite light guide plate as described above.

[0016] Beneficial effects: In this invention, a porous matrix with a spatial gradient pore structure is obtained by using a mold with a variable-diameter micropore array to perform variable pressure molding on a pre-formulated mixture. This not only helps to achieve uniform light propagation within the substrate but also provides a morphological basis for the subsequent nested construction of functional structures. A curved prism array is constructed on the surface of this porous gradient matrix, and a direction-selective nested grating structure is further formed through laser and plasma synergistic etching. This enhances the light guide plate's ability to control beam collimation and scattering. Furthermore, the layer-by-layer construction of the composite microstructure facilitates the deposition and interface of optical functional materials. Adhesion provides structural stability. Furthermore, by sequentially forming a photoactive layer and magnetron sputtering on the nested grating substrate, a photoactive layer with both light emission modulation and wavelength conversion capabilities is constructed. Through plasma activation and hot pressing, the fluorinated polyimide film is combined with the tuning substrate, enhancing the overall structural strength of the composite light guide plate. This results in a multifunctional composite light guide plate with high interfacial bonding strength, effectively solving the problems of interfacial delamination and stress concentration that easily occur in multilayer light guide structures. While maintaining excellent optical performance, it significantly improves the long-term stability and environmental adaptability of the composite light guide plate. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the overall steps of a method for preparing a composite light guide plate according to the present invention; Figure 2 This is a schematic diagram of the steps in an embodiment of the preparation method of a composite light guide plate according to the present invention; The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0018] It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0019] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of the stated features. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0020] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection, a direct connection, or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0021] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0022] Reference Figure 1 This invention proposes a method for preparing a composite light guide plate, comprising: S1: Provide a light guide plate mold with a variable diameter micropore array, and perform variable pressure molding on a preset formula mixture to obtain a porous gradient matrix; S2: Apply a photocuring agent to the surface of the porous gradient substrate, and imprint the photocuring agent-coated porous gradient substrate using a flexible prism array mold to construct a curved prism array on the surface of the porous gradient substrate. S3: The porous gradient substrate with the curved prism array is sequentially subjected to laser and plasma etching to obtain a nested grating substrate, and a photoactive layer is formed on the surface of the nested grating substrate based on the silane coupling agent solution. S4: In an inert gas atmosphere, magnetron sputtering is performed on the surface of the photoactive layer based on the composite target to obtain a tuning substrate, and a fluorinated polyimide film is covered on the tuning substrate and hot-pressed for 10 to 15 minutes to obtain a composite light guide plate.

[0023] In steps S1 to S4 above, the preparation process begins with providing a light guide plate mold with a variable-diameter micropore array. The micropore array exhibits a gradient in pore size, enabling the formation of a porous matrix with a spatially gradient pore structure during molding. Specifically, the pre-formulated mixture can be composed of polymeric materials (such as polycarbonate or polymethyl methacrylate) and specific additives (such as plasticizers or light-scattering particles) mixed in a certain proportion. After the mixture is injected into the mold, a variable pressure molding process is used, controlling the mold's closure and temperature changes at different pressure stages to ensure the mixture is fully filled and cured within the mold. During this process, the variable-diameter micropore array of the mold creates a porous structure with gradually varying pore sizes within the matrix. This structure not only facilitates uniform light scattering but also provides a stable morphological basis for the subsequent construction of functional layers. The pressure and temperature of the variable pressure molding process need to be precisely controlled, for example, gradually increasing within a pressure range of 80-120 MPa while maintaining the molding temperature near the material's glass transition temperature to ensure uniform pore distribution and the absence of significant defects in the matrix. The resulting porous gradient matrix has high pore connectivity, providing an ideal carrier for the penetration of photocuring agents and the construction of prism arrays.

[0024] In step S2, a photocurable agent is uniformly coated onto the surface of a porous gradient substrate. This process can employ spin coating or spray coating techniques to ensure that the photocurable agent can fully penetrate into the pores of the substrate. A flexible prism array mold is used to imprint the coated substrate. The imprinting process needs to be carried out under constant pressure (e.g., 5-10 MPa) and appropriate ultraviolet light irradiation to cure the photocurable agent and form a curved prism array on the substrate surface. The curved prism structure can effectively control the refraction and reflection angles of light, thereby improving the beam collimation capability of the light guide plate. In step S3, the substrate with the formed curved prism array is further processed through the synergistic effect of laser etching and plasma etching. Laser etching uses a high-energy laser beam to depict a periodic grating structure on the substrate surface, while plasma etching further modifies the morphology of the grating through reactive ion bombardment, forming a nested grating substrate. This nested grating structure has directional selectivity, enabling precise control of light scattering and propagation paths, thereby significantly improving the optical efficiency of the light guide plate. Furthermore, the nested grating substrate is electrophoretically deposited in a zinc sulfide quantum dot solution. The quantum dots are uniformly deposited on the substrate surface and within the pores under the influence of an electric field, forming a photoactive layer with wavelength conversion capabilities. The substrate is then immersed in a silane coupling agent solution to enhance the interfacial bonding between the quantum dots and the substrate through chemical bonding, further improving the stability of the photoactive layer. In step S4, a composite target (such as indium tin oxide or doped metal oxide) is used for magnetron sputtering in an inert gas atmosphere to deposit a uniform tuning layer on the surface of the photoactive layer. This tuning layer not only optimizes the luminous efficiency of the photoactive layer but also provides additional protection. The surface activity of the tuning substrate is further enhanced by plasma activation treatment. Subsequently, a fluorinated polyimide film is applied to the substrate surface and hot-pressed at 120-150°C for 10 to 15 minutes to ensure a tight bond between the film and the substrate, forming a composite light guide plate with high interfacial bonding strength. The composite light guide plate of this application not only possesses excellent optical performance, such as high luminous efficiency and uniform light distribution, but also exhibits outstanding mechanical strength and environmental stability due to the addition of fluorinated polyimide film. This effectively avoids the common interface delamination and stress concentration problems in multilayer structures, thereby significantly extending the service life of the light guide plate and improving its adaptability in complex environments.

[0025] In one embodiment, the pre-formulated mixture includes a polymer substrate, nanofillers, and a photorefractive agent; The polymer substrate is one of the following: a mixture of polycarbonate and polymethyl methacrylate in a mass ratio of 3:2, a mixture of polycarbonate and polystyrene in a mass ratio of 2:1, or a mixture of polymethyl methacrylate and polyetherimide in a mass ratio of 3:1. The nanofiller is one or more of nano-titanium dioxide, nano-zinc oxide, or nano-silicate, and the particle size of the nanofiller is 20-50 nanometers. The photorefractive agent is one or more of the following: benzotriazole UV absorbers, hindered amine light stabilizers, or nano zinc sulfide.

[0026] In the above embodiments, the pre-formulated mixture of the porous gradient matrix consists of a polymer substrate, nanofillers, and photorefractive agents, each component playing a unique role in improving the optical performance and structural stability of the light guide plate. The polymer substrate can be a mixture of polycarbonate and polymethyl methacrylate in a 3:2 mass ratio. This combination utilizes the high toughness and heat resistance of polycarbonate, combined with the excellent optical transparency of polymethyl methacrylate, to create a matrix that possesses both mechanical strength and light transmission efficiency. Alternatively, a mixture of polycarbonate and polystyrene in a 2:1 mass ratio can be used; the addition of polystyrene enhances the processing fluidity and surface smoothness of the substrate. Another option is a mixture of polymethyl methacrylate and polyetherimide in a 3:1 ratio. Polyetherimide provides excellent high-temperature resistance and chemical stability, ensuring the long-term stability of the substrate under complex environments.

[0027] Nanofillers, selected from nano-titanium dioxide, nano-zinc oxide, or nano-silicates, with particle sizes controlled between 20-50 nanometers, significantly enhance light scattering due to their small size and high specific surface area, improving the light uniformity of the light guide plate. Nano-titanium dioxide, with its high refractive index, effectively modulates the light propagation path, while nano-zinc oxide provides additional UV resistance, and nano-silicates enhance the mechanical strength of the substrate. Photorefractive agents, such as benzotriazole UV absorbers, effectively absorb UV light, protecting the substrate from photoaging. Hindered amine light stabilizers further improve material durability by capturing free radicals, and nano-zinc sulfide optimizes the refractive index to improve light distribution. These additives work synergistically to ensure the light guide plate maintains stable optical performance and structural integrity under high-intensity light.

[0028] In one example, the silane coupling agent solution is one or more of γ-aminopropyltriethoxysilane, γ-(2,3-epoxypropoxy)propyltrimethoxysilane, γ-methacryloyloxypropyltrimethoxysilane, or vinyltrimethoxysilane, and the content of the silane coupling agent is from 0.3 to 1.5 wt%.

[0029] In the above embodiments, the silane coupling agent solution serves as a key modifying component in the preparation of the composite light guide plate, used to enhance the interfacial bonding strength of the materials. The types of silane coupling agents include one or more combinations of γ-aminopropyltriethoxysilane, γ-(2,3-epoxypropoxy)propyltrimethoxysilane, γ-methacryloyloxypropyltrimethoxysilane, or vinyltrimethoxysilane. These silane coupling agents form chemical bonds with the polymer substrate and nanofillers through their active groups in their molecular structure, such as amino, epoxy, or vinyl groups, thereby improving the compatibility and overall stability of the composite material. γ-aminopropyltriethoxysilane, due to its strong amino group activity, can effectively enhance interfacial adhesion and improve the mechanical strength of the light guide plate. The epoxy groups of γ-(2,3-epoxypropoxy)propyltrimethoxysilane provide excellent chemical reactivity, enhancing the durability of the material under high temperature or humid environments.

[0030] The content of silane coupling agents is controlled between 0.3 and 1.5 wt% to ensure that they can fully exert their modifying effect in the material system without affecting the transparency and optical properties of the substrate. γ-methacryloyloxypropyltrimethoxysilane promotes cross-linking between polymers through its acryloyl groups, further optimizing the structural toughness of the light guide plate, while the vinyl group of vinyltrimethoxysilane enhances the copolymerization ability with the polymer substrate, contributing to the formation of a uniform composite network. The synergistic effect of the various silane coupling agents significantly improves the interfacial bonding effect within the light guide plate material, thereby enhancing its optical uniformity and long-term stability.

[0031] In one example, the step of providing a light guide plate mold with a variable diameter micropore array and performing variable pressure molding on a preset formula mixture to obtain a porous gradient matrix includes: The pre-formulated mixture is put into a mixer and stirred at 180 to 200°C for 30 to 50 minutes at a speed of 500 to 800 rpm. The preset formula mixture is melted by raising the temperature to 230 to 250°C, and the melt is injected into a light guide plate mold by an extruder in a vacuum environment for variable pressure molding. The inner wall of the light guide plate mold is provided with a variable diameter micropore array that gradually changes from 150 micrometers to 50 micrometers from the center to the edge and has a depth of 20 to 30 micrometers. During the molding process, a gas pressure of 0.5 to 0.7 MPa is applied, the molding pressure is 0.8 to 1 MPa, and the molding time is 10 to 15 minutes. The molded melt is subjected to gradient cooling treatment, which reduces the temperature from 230°C to room temperature at a cooling rate of 3°C / min, while applying a pressure of 0.2 to 0.3 MPa during the cooling process, and cooling for 40 to 60 minutes to obtain a porous gradient matrix.

[0032] In the above embodiments, a pre-formulated mixture is added to a mixer and stirred at 500 to 800 rpm for 30 to 50 minutes at 180 to 200°C to achieve uniform mixing of polymer components and additives. One polymer matrix combination is selected, with polycarbonate and polymethyl methacrylate mixed in a 3:2 mass ratio, and added to a high-speed mixer. The temperature is set to 180°C, and the mixture is stirred at 800 rpm for 30 minutes to ensure sufficient entanglement of the two polymer molecular chains, forming a uniform polymer premix. Then, 5 wt% of nano-titanium dioxide particles (20 to 30 nm in diameter) are added to the premix, and stirring continues for 40 minutes at 200°C and 500 rpm to ensure uniform dispersion of the nanoparticles in the polymer matrix, enhancing the light scattering properties of the mixture. Maintaining a temperature of 180 to 200°C softens the polymer without inducing degradation, while the stirring speed and time range ensure moderate viscosity and uniform component distribution.

[0033] After stirring, the temperature of the pre-formulated mixture is raised to 230-250°C for melting. The melt is then injected into a light guide plate mold with a variable-diameter microporous array in a vacuum environment via an extruder for pressure molding, forming a preliminary matrix. The nanocomposite mixture is placed in a twin-screw extruder at a set temperature of 230°C and a screw speed of 300 rpm. Extrusion melting ensures a uniform melt state, while a vacuum degassing device simultaneously removes air bubbles and volatile impurities, ensuring consistent melt viscosity and no defects. The melt is then injected into a custom mold. The mold's inner wall features a variable-diameter microporous array with a diameter gradually decreasing from 150 micrometers to 50 micrometers from the center to the edge, and a depth of 20-30 micrometers. During molding, a pressure of 0.6 MPa and a molding pressure of 0.9 MPa are applied for 15 minutes. High-temperature melting ensures moderate material fluidity, the variable-diameter micropore array of the mold imparts a gradient pore structure to the matrix, and precise control of air pressure and molding pressure optimizes the uniformity of pore distribution, providing a structural basis for the optical performance of the light guide plate.

[0034] After molding, the pre-molded substrate undergoes gradient cooling, decreasing from 230°C to room temperature at a rate of 3°C / min while applying a pressure of 0.2 to 0.3 MPa for 40 to 60 minutes, resulting in a porous gradient matrix with a stable gradient pore structure. The molded substrate is then placed in a temperature-controlled cooling device, with an initial temperature of 230°C, and gradually cooled to room temperature at a rate of 3°C / min for 60 minutes. A constant pressure of 0.2 MPa is applied during cooling to maintain the integrity of the internal pore structure and prevent deformation or micropore collapse due to thermal stress. Gradient cooling ensures the ordered arrangement of the material's molecular chains, enhancing the substrate's mechanical strength and optical transparency, while stabilizing the gradient pore structure formed in the mold. Precise control of the cooling rate and pressure maintains structural consistency during curing, preserving the gradual change in pore size from 150 micrometers at the center to 50 micrometers at the edge, ensuring the light scattering and guiding performance of the light guide plate. By curing the pre-molded substrate, a porous gradient matrix with excellent optical properties is formed.

[0035] refer to Figure 2 In one example, the photocuring agent is an acrylate resin containing 5% photoinitiator; The step of coating the photocurable agent onto the surface of the porous gradient substrate and imprinting the photocurable agent-coated porous gradient substrate using a flexible prism array mold includes: S21: The surface of the porous gradient substrate is subjected to plasma cleaning treatment in an oxygen atmosphere for 30 to 40 seconds. S22: Spin-coat the UV-curing agent onto the surface of the cleaned porous gradient substrate. The spin-coating speed is set to 400 to 600 rpm, and the coating thickness of the UV-curing agent is 0.4 to 0.6 mm. S23: Imprinting a porous gradient substrate coated with a photocurable agent using a flexible prism array mold, wherein the flexible prism array mold is made of polydimethylsiloxane, and the surface of the flexible prism array mold has a prism array structure with a period of 100 to 200 micrometers and a radius of curvature of 50 to 80 micrometers, and the imprinting pressure is 0.1 to 0.3 MPa. S24: The imprinted porous gradient substrate is placed in an ultraviolet light environment for curing. The ultraviolet light intensity is 15 milliwatts per square centimeter, and the curing time is 15 to 30 seconds. During the curing process, a pressure of 0.2 to 0.4 MPa is applied simultaneously to form a curved prism array with a vertex angle of 60 to 80 degrees on the surface of the porous gradient substrate.

[0036] In the above embodiments, to ensure the porous gradient substrate surface is clean and has good adhesion performance, it needs to be subjected to plasma cleaning treatment. The porous gradient substrate is placed in a plasma cleaning device, the vacuum degree is set to 10 Pa, and oxygen is introduced to form an oxygen atmosphere. A 100-watt radio frequency power is used to generate plasma to bombard the substrate surface, and the cleaning time is controlled between 30 and 40 seconds. This process effectively removes organic contaminants, grease, and micro-dust particles from the substrate surface, while simultaneously introducing hydroxyl functional groups into the surface through plasma action, enhancing surface activity. These hydroxyl functional groups significantly improve the adhesion of subsequent photocurable agents, providing a clean and chemically active surface for spin coating processes. After cleaning, the substrate is immediately transferred to a dust-free environment to avoid secondary contamination and ensure the surface condition is suitable for the next step of photocurable agent coating.

[0037] Acrylic resin containing 5% photoinitiator was selected as the UV curing agent. The resin was uniformly applied to the cleaned substrate surface using a spin coater at a speed of 400 to 600 rpm, with the coating thickness controlled between 0.4 and 0.6 mm. Precise control of the spin coater speed during the process ensured uniform coating thickness, avoiding localized accumulation or excessive thinness. The coated substrate was then pre-baked in an 80°C vacuum oven for 30 seconds to remove micro-air bubbles and preliminarily stabilize the resin structure. This step provides a smooth, defect-free surface for subsequent embossing processes, ensuring the molding accuracy of the prism array structure.

[0038] A preliminary prism array structure is formed on a substrate coated with a UV-curable material using a flexible prism array mold. The mold is made of polydimethylsiloxane and has a prism array structure with a period of 100 to 200 micrometers and a radius of curvature of 50 to 80 micrometers. During the imprinting process, a low pressure of 0.1 to 0.3 MPa is applied, causing the mold to make light contact with the coated substrate for 10 seconds. This ensures that the UV-curable material fully fills the microstructure of the mold while avoiding air bubbles or coating deformation. The flexibility of the polydimethylsiloxane mold allows it to fit tightly to the substrate surface, ensuring accurate transfer of the prism pattern.

[0039] To ensure complete curing of the UV-curable agent after imprinting and the formation of a stable curved prism array, further UV curing is required. The pre-formed substrate is placed under a 365 nm UV light source with an irradiation intensity of 15 mW / cm² and a curing time of 15 to 30 seconds. During curing, a uniform pressure of 0.2 to 0.4 MPa is applied simultaneously to ensure complete molding of the UV-curable agent within the prism structure of the flexible mold, resulting in a curved prism array with a vertex angle of 60 to 80 degrees. After curing, demolding is performed by slowly heating to 50 degrees Celsius to prevent deformation of the prism structure, resulting in a curved prism substrate with a high-precision optical structure.

[0040] Furthermore, the curved prism substrate undergoes plasma surface modification. Specifically, under an argon atmosphere, the surface of the curved prism substrate is bombarded with plasma at a power of 50 watts for 15 seconds to fine-tune the surface roughness of the prism array and introduce trace active sites, while maintaining the integrity of the prism structure and enhancing the adhesion of the photoactive layer in subsequent processes. The surface-optimized porous gradient substrate is then placed in a nitrogen-protected annealing furnace and annealed at 100 degrees Celsius for 20 minutes to eliminate any residual internal stress that may have remained during UV curing, while also optimizing the structural stability of the curved prism array and ensuring its geometric accuracy and optical performance.

[0041] In one example, the step of forming a photoactive layer on the surface of the nested grating substrate based on a silane coupling agent solution includes: The nested grating substrate was placed in a deionized aqueous solution containing 0.5-1% polyethylene glycol for electrophoretic deposition pretreatment. A pre-electric field of 1 volt / cm was applied at room temperature for 10 to 15 minutes to form a uniform charge distribution layer on the inner surface of the grating microgroove. The pretreated nested grating substrate was placed in a deionized aqueous solution containing 1.5-2.5% zinc sulfide quantum dots and 0.2-0.4% polyvinyl alcohol for electrophoretic deposition. An electric field of 3-5 V / cm was applied at 25°C for 15 to 25 minutes. The zinc sulfide quantum dots had a particle size of 4 to 7 nanometers. The nested grating substrate after electrophoretic deposition is impregnated with a toluene solution based on silane coupling agent and treated at 50 to 60°C for 10 to 15 minutes to form a uniform covalent bonded layer with a thickness of 0.2 to 0.4 micrometers on the nested grating substrate. The impregnated nested grating substrate is placed in a temperature-controlled oven, with the temperature set at 110 to 130°C and the heat treatment time at 15 to 25 minutes to form a photoactive layer.

[0042] In the above embodiments, the nested grating substrate is first pre-cleaned by placing it in a plasma cleaning device and using a mixed plasma of argon and oxygen at a pressure of 200 Pa and a power of 100 watts for 5 minutes to remove organic impurities and oxides from the surface, while activating the surface of the grating microgroove to enhance the adhesion of subsequent quantum dot deposition.

[0043] The nested grating substrate was pretreated for electrophoretic deposition by immersing it in a deionized aqueous solution containing 0.5-1% polyethylene glycol. A pre-electric field of 1 volt / cm was applied at room temperature for 10-15 minutes to form a uniform charge distribution layer on the inner surface of the grating microgrooves. Specifically, the charge distribution on the substrate surface was optimized through the dispersion effect of polyethylene glycol and the driving force of the electric field, providing a uniform electric field environment for the subsequent deposition of zinc sulfide quantum dots. Polyethylene glycol, as a stabilizer, effectively prevented charge accumulation on the substrate surface, ensuring the formation of a consistent charge layer on the inner surface of the microgrooves, thereby improving the uniformity and adhesion of quantum dot deposition. The nested grating substrate was then fixed to the electrodes of the electrophoretic deposition apparatus and immersed in the solution; the electric field strength was set to 1 volt / cm, maintained at room temperature, and continuously applied for 10-15 minutes; after treatment, the substrate surface was gently rinsed with deionized water and dried for later use.

[0044] The pretreated nested grating substrate was electrophoretically deposited in a deionized aqueous solution containing 1.5–2.5% zinc sulfide quantum dots and 0.2–0.4% polyvinyl alcohol. An electric field of 3–5 V / cm was applied at 25°C for 15–25 minutes, controlling the zinc sulfide quantum dot particle size to 4–7 nm. This process utilizes the electric field to drive the directional deposition of quantum dots within the grating microgrooves, forming a dense quantum dot layer. Polyvinyl alcohol acts as a dispersant and binder, enhancing the stability of the quantum dots in solution, preventing aggregation, and promoting uniform distribution of quantum dots within the microgrooves. Subsequently, the quantum dot deposition substrate was immersed in a 99.9% pure ethanol solution and ultrasonically cleaned at 40°C for 3 minutes to remove unbonded quantum dots and solution residues. A toluene solution based on a silane coupling agent is used to impregnate the electrophoretically deposited nested grating substrate, followed by treatment at 50–60°C for 10–15 minutes to form a uniform covalently bonded layer with a thickness of 0.2–0.4 micrometers. This process involves a chemical reaction between the silane coupling agent and the quantum dots and substrate surface to form stable covalent bonds, enhancing the adhesion between the quantum dot layer and the substrate, while simultaneously providing protection for the photoactive layer. After treatment, the substrate is rinsed with pure toluene to remove unreacted silane coupling agent; subsequently, the substrate is dried in a nitrogen stream to ensure surface cleanliness.

[0045] The impregnated nested grating substrate is placed in a temperature-controlled oven at 110-130°C for 15-25 minutes to form a photoactive layer. This high-temperature treatment further solidifies the chemical bonds between the silane coupling agent, quantum dots, and the substrate, optimizing the refractive index and light transmission performance of the photoactive layer, ensuring layer thickness stability, and improving optical performance. After treatment, the substrate is slowly cooled to room temperature to avoid thermal stress-induced damage to the layer structure; the substrate surface is then inspected to ensure the photoactive layer is uniform and free of cracks.

[0046] In one example, the step of obtaining a tuned substrate by magnetron sputtering of the surface of a photoactive layer based on a composite target in an inert gas atmosphere includes: Under an argon and nitrogen atmosphere, the surface of the photoactive layer was pre-sputtered using an indium tin oxide and zinc oxide composite target to obtain a primary deposition substrate. Under an atmosphere of argon and oxygen, a gradient sputtering method is used to sputter the surface of the primary deposition substrate with a composite target of silicon oxide and zinc sulfide to obtain a multilayer tunable substrate. Thermal phase separation is performed on the multilayer tuned substrate to form a phase separation layer with a thickness of 0.6 to 0.8 micrometers and a refractive index that gradually changes from 1.5 to 1.9, thus obtaining the tuned substrate.

[0047] In the above embodiments, the surface of the photoactive layer is pre-sputtered to form a uniform primary deposition substrate. The pre-sputtering is carried out in an inert gas atmosphere with an argon-nitrogen ratio of 3:1 and a pressure of 0.3 Pa. An indium tin oxide and zinc oxide composite target is used, the sputtering power is set to 100 watts, the substrate temperature is controlled at 100 degrees Celsius, and sputtering is carried out continuously for 5 minutes. The low-energy sputtering method ensures that a uniform primary deposition film is formed on the surface of the photoactive layer. The film structure is stable and well bonded to the substrate, providing a smooth deposition surface.

[0048] Gradient sputtering was performed on the surface of the primary deposited substrate to form a multilayer tunable substrate with a gradual refractive index change, further optimizing the refractive index distribution of the light guide plate. Gradient sputtering was performed in an inert gas atmosphere with an argon-oxygen ratio of 5:1 and a pressure of 0.5 Pa, using a silicon oxide and zinc sulfide composite target. The sputtering power was gradually increased from 120 W to 180 W, while the substrate temperature was gradually increased from 110°C to 160°C, with sputtering continued for 8 minutes. Gradient control resulted in a multilayer structure with a continuous refractive index change in the deposited layer, enhancing the optical performance of the light guide plate. The formation of the multilayer tunable substrate ensured the gradual refractive index change.

[0049] Thermally induced phase separation was performed on the multilayer tuned substrate to form a phase-separated layer with a thickness of 0.6 to 0.8 micrometers and a refractive index that gradually varied from 1.5 to 1.9, resulting in the final tuned substrate. The thermally induced phase separation was carried out in a heat treatment chamber with a vacuum of 10^-3 Pa, with the temperature gradually increased from 150°C to 200°C and held for 10 minutes. By inducing micro-segmentation of the material components in the multilayer structure through heat treatment, a phase-separated layer with a gradually varying refractive index was formed, optimizing the optical performance of the light guide plate and giving it better light transmission efficiency and refractive index matching characteristics.

[0050] Furthermore, the phase-separated tuned substrate can be subjected to plasma-assisted sputtering. Under an inert gas atmosphere with an argon-helium ratio of 4:1 and a pressure of 0.4 Pa, an alumina and indium oxide composite target is used. The sputtering power is 150 watts combined with radio frequency plasma assistance, maintaining the substrate temperature at 170 degrees Celsius for 6 minutes. This deposits a 0.3 to 0.5 micrometer thick reinforcing film on the phase-separated tuned substrate surface, optimizing surface smoothness and refractive index distribution. Annealing is then performed. The reinforced tuned substrate is placed in a nitrogen-atmosphere annealing furnace, and the annealing temperature is controlled to rise from 180 degrees Celsius to 220 degrees Celsius, with a holding time of 12 minutes. Annealing eliminates internal stress in the reinforced tuned substrate and optimizes the crystal structure, stabilizing the refractive index of the reinforcing film within the range of 1.7 to 1.9. Finally, surface modification sputtering is performed under an argon atmosphere at a pressure of 0.2 Pa, using a silicon oxide and magnesium fluoride composite target, sputtering at a low power of 80 watts for 3 minutes, with the substrate temperature controlled at 130 degrees Celsius, to deposit a modification layer with a thickness of 0.1 to 0.2 micrometers on the surface of the stable tuning substrate, further optimizing the optical properties and refractive index matching of the tuning substrate surface, and obtaining a better tuning substrate.

[0051] In one embodiment, the step of covering the fluorinated polyimide film onto the tuning substrate and hot-pressing it for 10 to 15 minutes to obtain the composite light guide plate includes: The tuning substrate was placed in a plasma chamber under a helium and ethylene atmosphere for plasma activation treatment, and a carbon nanochain structure was formed on the surface of the tuning substrate. The surface characteristics of the activated tuned substrate are obtained using a vision system, and the fluorinated polyimide film is pretreated with ultraviolet light according to the surface characteristics. In a vacuum environment, the activated tuning substrate is bonded to the fluorinated polyimide film that has been pretreated with ultraviolet light. Maintaining a vacuum environment, the bonded tuning substrate and fluorinated polyimide film are subjected to hot pressing treatment at a temperature of 80 to 90°C, a pressing pressure of 0.3 to 0.5 MPa, and a hot pressing time of 10 to 15 minutes to obtain a composite light guide plate.

[0052] In the above embodiment, the tuned substrate is placed in a plasma cleaning chamber containing argon and oxygen in a 4:1 ratio for pre-cleaning by plasma bombardment at 80 watts for 3 minutes. Then, the tuned substrate is placed in a plasma chamber under a helium and ethylene atmosphere for plasma activation treatment, forming carbon nanochain structures on the surface of the tuned substrate. Specifically, the pre-cleaned tuned substrate is placed in a plasma chamber, and a mixed gas of helium and ethylene in a 3:1 ratio is introduced, maintaining the chamber pressure at 10 Pa. The plasma generator power is set to 90 watts, and the processing time is 5 minutes. Helium provides a stable plasma environment, and ethylene molecules dissociate under the action of high-energy plasma, generating active carbon groups that are grafted onto the surface of the tuned substrate, forming carbon nanochain structures. This significantly improves surface chemical activity and enhances the interfacial bonding with the subsequent fluorinated polyimide film.

[0053] The surface properties of the activated tunable substrate were acquired using a vision system, and the fluorinated polyimide film was pretreated with ultraviolet light based on these properties. Specifically, a high-resolution vision system was used to scan the surface of the activated tunable substrate, analyzing the distribution and density of carbon nanochain structures to generate surface property data. Based on this data, a 0.1 mm thick fluorinated polyimide film was selected and placed in an ultraviolet irradiation device with a wavelength of 254 nm for 10 minutes. Ultraviolet light induced the breaking of molecular bonds on the film surface, generating hydroxyl and carboxyl functional groups, enhancing the chemical bonding between the film and the activated substrate while maintaining optical transparency. The vision system accurately identified the surface properties, ensuring that the parameters of the ultraviolet pretreatment matched the substrate properties.

[0054] The activated and tuned substrate and the pretreated fluorinated film were placed in a vacuum chamber, with the vacuum level controlled at 0.01 Pa. A mechanical pressing device was used to smoothly cover the surface of the activated substrate with the pretreated fluorinated film, ensuring tight contact between the two. During the bonding process, the pressing speed and force were precisely controlled to avoid the generation of air bubbles or interface defects. The vacuum environment effectively eliminated air interference, ensuring the uniformity and stability of the bonding interface. Initial contact was achieved between the carbon nanochains on the surface of the activated substrate and the functional groups of the pretreated film.

[0055] Maintaining a vacuum environment, the bonded tuning substrate and fluorinated polyimide film were hot-pressed to obtain a composite light guide plate. The substrate was placed in a hot press at a vacuum of 0.01 Pa, a pressing temperature of 85°C, a pressing pressure of 0.3 MPa, and a pressing time of 12 minutes. During the hot pressing process, carbon nanochains on the surface of the tuning substrate chemically bonded to the functional groups of the fluorinated film. The fluorinated polyimide film was uniformly embedded into the substrate surface under high temperature and pressure, forming a high-strength interfacial bond. The vacuum environment prevented oxidation or impurity interference, ensuring the structural uniformity and optical transparency of the composite light guide plate.

[0056] Furthermore, the formed composite light guide plate can be post-annealed to obtain a composite light guide plate. The pre-formed composite light guide plate is placed in an annealing furnace under nitrogen protection and annealed at 100 degrees Celsius for 30 minutes. Annealing eliminates the internal stress generated during hot pressing, further optimizes the interfacial bonding stability between the fluorinated polyimide film and the tuning substrate, and enhances the mechanical strength and optical uniformity of the composite light guide plate, ultimately resulting in a composite light guide plate with excellent optical performance and structural stability.

[0057] A composite light guide plate is prepared by the method described in any one of the preceding claims. The composite light guide plate includes a porous gradient substrate. The surface of the porous gradient substrate is provided with an array of variable diameter micropores. The porous gradient substrate is formed with a nested grating layer, a photoactive layer and a tuning structure from the inside to the outside. The outer surface of the tuning structure is covered with a fluorinated polyimide film.

[0058] In the above embodiments, the porous gradient substrate is formed through precision machining technology, exhibiting a continuous pore gradient with gradually increasing pore size from the inner to the outer layer. This optimizes light scattering and transmission paths, improving light utilization efficiency. The fine and uniform grating lines in the nested grating layer effectively guide light direction, enhancing the light-guiding effect. The photoactive layer's composition and structure are precisely controlled through the aforementioned electrophoretic deposition and heat treatment processes, ensuring excellent optical performance and stability. The tuning structure enables the composite light guide plate to possess excellent light control capabilities at different angles and wavelengths, further improving display quality. The fluorinated polyimide film, as the outermost layer of the composite light guide plate, not only possesses excellent optical transparency and chemical stability but also effectively resists environmental corrosion, protecting the internal structure from damage. Its close bonding with the tuning substrate through plasma activation ensures the integrity and durability of the composite light guide plate. The prepared composite light guide plate can be widely used in various display devices, such as liquid crystal displays and organic light-emitting diode displays, significantly improving display effects, reducing energy consumption, and enhancing product market competitiveness.

[0059] This application embodiment also provides a backlight module, including the composite light guide plate as described above, and further comprising a light source assembly and a reflector. Specifically, the light source assembly is disposed on one side of the composite light guide plate for providing backlight. The reflector is disposed on the other side of the composite light guide plate for reflecting light emitted from the light source assembly that is not directly utilized by the composite light guide plate, thereby improving light utilization. The backlight module further includes a light guide plate frame for fixing the composite light guide plate, the light source assembly, and the reflector, ensuring the stability of their relative positions, thereby improving the overall performance and reliability of the backlight module. The light source assembly is preferably an LED light source, which has the advantages of energy saving, environmental protection, and long lifespan. The reflector is made of a high-reflectivity material, such as a silver-white aluminized film or a white polyester film, to maximize light reflection. The composite light guide plate, the light source assembly, the reflector, and the light guide plate frame are combined together through a precision assembly process to form a compact and high-performance backlight module. This backlight module can uniformly illuminate the display area, providing a high-quality backlight effect. It is suitable for various display devices, such as LCD panels and electronic paper, providing stable and uniform backlight support for display devices, improving display quality, and reducing energy consumption.

[0060] The above description is merely a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A method for preparing a composite light guide plate, characterized in that, include: A light guide plate mold with a variable diameter micropore array is provided, and a pre-formulated mixture is subjected to pressure molding to obtain a porous gradient matrix; A photocuring agent is applied to the surface of the porous gradient substrate, and the porous gradient substrate coated with the photocuring agent is imprinted based on a flexible prism array mold to construct a curved prism array on the surface of the porous gradient substrate. The porous gradient substrate with the curved prism array is sequentially subjected to laser and plasma etching to obtain a nested grating substrate, and a photoactive layer is formed on the surface of the nested grating substrate based on a silane coupling agent solution. In an inert gas atmosphere, magnetron sputtering is performed on the surface of the photoactive layer based on a composite target to obtain a tuning substrate. A fluorinated polyimide film is then covered on the tuning substrate and hot-pressed for 10 to 15 minutes to obtain a composite light guide plate.

2. The method for preparing a composite light guide plate according to claim 1, characterized in that, The preset formulation mixture includes a polymer substrate, nanofillers, and photorefractive additives; The polymer substrate is one of the following: a mixture of polycarbonate and polymethyl methacrylate in a mass ratio of 3:2, a mixture of polycarbonate and polystyrene in a mass ratio of 2:1, or a mixture of polymethyl methacrylate and polyetherimide in a mass ratio of 3:

1. The nanofiller is one or more of nano-titanium dioxide, nano-zinc oxide, or nano-silicate, and the particle size of the nanofiller is 20-50 nanometers. The photorefractive agent is one or more of the following: benzotriazole UV absorbers, hindered amine light stabilizers, or nano zinc sulfide.

3. The method for preparing a composite light guide plate according to claim 1, characterized in that, The silane coupling agent solution is one or more of γ-aminopropyltriethoxysilane, γ-(2,3-epoxypropoxy)propyltrimethoxysilane, γ-methacryloyloxypropyltrimethoxysilane or vinyltrimethoxysilane, and the content of the silane coupling agent is 0.3 to 1.5 wt%.

4. The method for preparing a composite light guide plate according to claim 1, characterized in that, The step of providing a light guide plate mold with a variable diameter micropore array and performing variable pressure molding on a preset formula mixture to obtain a porous gradient matrix includes: The pre-formulated mixture is put into a mixer and stirred at 180 to 200°C for 30 to 50 minutes at a speed of 500 to 800 rpm. The preset formula mixture is melted by raising the temperature to 230 to 250°C, and the melt is injected into a light guide plate mold by an extruder in a vacuum environment for variable pressure molding. The inner wall of the light guide plate mold is provided with a variable diameter micropore array that gradually changes from 150 micrometers to 50 micrometers from the center to the edge and has a depth of 20 to 30 micrometers. During the molding process, a gas pressure of 0.5 to 0.7 MPa is applied, the molding pressure is 0.8 to 1 MPa, and the molding time is 10 to 15 minutes. The molded melt is subjected to gradient cooling treatment, which reduces the temperature from 230°C to room temperature at a cooling rate of 3°C / min, while applying a pressure of 0.2 to 0.3 MPa during the cooling process, and cooling for 40 to 60 minutes to obtain a porous gradient matrix.

5. The method for preparing a composite light guide plate according to claim 1, characterized in that, The photocuring agent is an acrylic resin containing 5% photoinitiator; The step of coating the photocurable agent onto the surface of the porous gradient substrate and imprinting the photocurable agent-coated porous gradient substrate using a flexible prism array mold includes: The surface of the porous gradient substrate is subjected to plasma cleaning in an oxygen atmosphere for 30 to 40 seconds. The photocuring agent is spin-coated onto the surface of the cleaned porous gradient substrate at a spin speed of 400 to 600 rpm, and the coating thickness of the photocuring agent is 0.4 to 0.6 mm. Imprinting is performed on a porous gradient substrate coated with a photocurable agent using a flexible prism array mold. The flexible prism array mold is made of polydimethylsiloxane, and its surface has a prism array structure with a period of 100 to 200 micrometers and a radius of curvature of 50 to 80 micrometers. The imprinting pressure is 0.1 to 0.3 MPa. The imprinted porous gradient substrate is cured under ultraviolet light with an intensity of 15 milliwatts per square centimeter and a curing time of 15 to 30 seconds. During the curing process, a pressure of 0.2 to 0.4 MPa is applied simultaneously to form a curved prism array with a vertex angle of 60 to 80 degrees on the surface of the porous gradient substrate.

6. The method for preparing a composite light guide plate according to claim 1, characterized in that, The step of forming a photoactive layer on the surface of the nested grating substrate based on a silane coupling agent solution includes: The nested grating substrate was placed in a deionized aqueous solution containing 0.5-1% polyethylene glycol for electrophoretic deposition pretreatment. A pre-electric field of 1 volt / cm was applied at room temperature for 10 to 15 minutes to form a uniform charge distribution layer on the inner surface of the grating microgroove. The pretreated nested grating substrate was placed in a deionized aqueous solution containing 1.5-2.5% zinc sulfide quantum dots and 0.2-0.4% polyvinyl alcohol for electrophoretic deposition. An electric field of 3-5 V / cm was applied at 25°C for 15 to 25 minutes. The zinc sulfide quantum dots had a particle size of 4 to 7 nanometers. The nested grating substrate after electrophoretic deposition is impregnated with a toluene solution based on silane coupling agent and treated at 50 to 60°C for 10 to 15 minutes to form a uniform covalent bonded layer with a thickness of 0.2 to 0.4 micrometers on the nested grating substrate. The impregnated nested grating substrate is placed in a temperature-controlled oven, with the temperature set at 110 to 130°C and the heat treatment time at 15 to 25 minutes to form a photoactive layer.

7. The method for preparing a composite light guide plate according to claim 1, characterized in that, The step of obtaining a tuned substrate by magnetron sputtering of the surface of the photoactive layer based on a composite target in an inert gas atmosphere includes: Under an argon and nitrogen atmosphere, the surface of the photoactive layer was pre-sputtered with an indium tin oxide and zinc oxide composite target to obtain a primary deposition substrate. Under an atmosphere of argon and oxygen, a gradient sputtering method is used to sputter the surface of the primary deposition substrate with a composite target of silicon oxide and zinc sulfide to obtain a multilayer tunable substrate. Thermal phase separation is performed on the multilayer tuned substrate to form a phase separation layer with a thickness of 0.6 to 0.8 micrometers and a refractive index that gradually changes from 1.5 to 1.9, thus obtaining the tuned substrate.

8. The method for preparing a composite light guide plate according to claim 1, characterized in that, The step of covering the activated tuning substrate with a fluorinated polyimide film and hot-pressing it for 10 to 15 minutes to obtain the composite light guide plate includes: The tuning substrate was placed in a plasma chamber under a helium and ethylene atmosphere for plasma activation treatment, and a carbon nanochain structure was formed on the surface of the tuning substrate. The surface characteristics of the activated tuned substrate are obtained using a vision system, and the fluorinated polyimide film is pretreated with ultraviolet light according to the surface characteristics. In a vacuum environment, the activated tuning substrate is bonded to the fluorinated polyimide film that has been pretreated with ultraviolet light. Maintaining a vacuum environment, the bonded tuning substrate and fluorinated polyimide film are subjected to hot pressing treatment at a temperature of 80 to 90°C, a pressing pressure of 0.3 to 0.5 MPa, and a hot pressing time of 10 to 15 minutes to obtain a composite light guide plate.

9. A composite light guide plate, characterized in that, The composite light guide plate is prepared by the method described in any one of claims 1 to 8. The composite light guide plate includes a porous gradient substrate, the surface of which is provided with an array of variable diameter micropores. The porous gradient substrate is formed with a nested grating layer, a photoactive layer and a tuning structure from the inside to the outside. The outer surface of the tuning structure is covered with a fluorinated polyimide film.

10. A backlight module, characterized in that, Including the composite light guide plate as described in claim 9.

Images