Preparation method and application of black high-transmittance resin composite board

Abstract

The invention relates to a preparation method and application of a black high-transmittance resin composite board, and belongs to the technical field of advertising materials. The resin is formed by compounding a black light-transmitting layer, a light guide layer and a diffusion layer, wherein the high-transmittance layer is prepared by modifying a carboxylated carbon nanotube with a silane coupling agent, polymerizing with a methyl methacrylate monomer, and directionally arranging in a magnetic field, so that high light transmittance and pure black appearance are realized; the light guide layer takes polycarbonate as a matrix, SiO2 microspheres are added, and the light transverse propagation efficiency is improved through hot press molding; the diffusion layer takes polymethyl methacrylate as a matrix, ZnO nanoparticles are added, a periodic microprism structure is processed on the surface, and uniform diffusion of light is realized. When applied to a lamp box, the light source is turned off to present a pure black appearance, and when turned on, the light source has high light transmittance and no mixed color, and is suitable for high-end advertisement display screens, vehicle-mounted lamp boxes and other scenes.

Description

Technical Field

[0001] The invention belongs to the technical field of advertising materials and relates to a preparation method and application of a black high-light-transmittance resin composite plate. Background Art

[0002] In modern light box production, material selection and design are crucial to the optical performance and durability of the final product. Traditional acrylic sheet materials face numerous technical challenges in light box applications. First, the colorant used in acrylic sheets often absorbs some light, resulting in insufficient light transmittance and brightness, which in turn wastes light energy. Since the primary function of a light box is to provide a uniform and efficient light source, this issue significantly impacts its overall performance. Furthermore, acrylic material itself has poor light scattering properties, preventing light from fully diffusing within the material and instead transmitting directly through the sheet. This directly transmitted light easily forms light spots, resulting in uneven light transmission across the light box and affecting the visual effect. This uneven light scattering not only reduces the light box's aesthetics but can also affect the clarity of information displayed in practice.

[0003] Secondly, acrylic's poor aging resistance is a significant technical shortcoming. The poor compatibility between acrylic and colorants easily leads to colorant precipitation, which in turn causes product aging and discoloration. After long-term environmental exposure, acrylic products often show noticeable discoloration, typically fading to white. This not only affects the appearance of the light box but can also reduce its service life. Furthermore, the material is prone to cracking after aging, further compromising the structural integrity and safety of the light box. This lack of aging resistance not only increases maintenance costs but can also lead to increased replacement frequency, impacting user experience and market competitiveness. Currently used black, translucent acrylic also has numerous drawbacks, primarily due to the colorants used in its formulation absorbing some of the color of white light, allowing only a limited range of visible light to pass through. This results in an impure color of the transmitted light. Especially when using white light as a backlight, the transmitted light often has a grayish, bluish, or reddish cast. This impure color can affect the accuracy of information conveyed in advertising displays.

[0004] In order to overcome these technical deficiencies, the development of new materials and manufacturing methods is particularly important. In recent years, with the advancement of nanotechnology and polymer chemistry, researchers have gradually explored the use of nanomaterials and chemical modification to optimize the optical properties and durability of light box materials. Summary of the Invention

[0005] The purpose of the present invention is to provide a preparation method and application of a black high-light-transmittance resin composite board, which has the characteristics of high light transmittance, no light spots, aging resistance and pure black appearance.

[0006] The purpose of the present invention can be achieved through the following technical solutions:

[0007] A black high-light-transmittance resin composite plate comprises an inner light-guiding layer, a middle diffusion layer, and an outer black light-transmitting layer; the preparation of the black light-transmitting layer comprises the following steps:

[0008] A1. Reflux the carbon nanotubes in a mixed concentrated acid to introduce carboxyl groups and hydroxyl groups on the surface through strong oxidation to obtain carboxylated carbon nanotubes, providing active sites for subsequent silane coupling agent grafting;

[0009] A2. The carboxylated carbon nanotubes prepared in step A1 are surface-modified with a silane coupling agent, KH-570. The methoxy groups of KH-570 are hydrolyzed to form silanols, which condense with the hydroxyl groups on the surface of the carbon nanotubes to form Si-OC covalent bonds. Meanwhile, the methacryloyloxy groups at the ends of KH-570 retain double bond activity, thereby obtaining surface-grafted double-bond carbon nanotubes.

[0010] A3. After mixing the surface-grafted double-bond carbon nanotubes prepared in step A2, methyl methacrylate monomer, anti-aging agent, and cross-linking agent, a free radical initiator is added, and ultrasonic dispersion polymerization is performed under nitrogen protection. The free radical initiator decomposes to generate free radicals that attack the double bonds of the methyl methacrylate monomer, initiating a chain polymerization reaction. The surface-grafted double-bond carbon nanotubes also participate in the copolymerization reaction of the monomer through their terminal double bonds; a magnetic field is applied to align the surface-grafted double-bond carbon nanotubes;

[0011] A4: Pour the mixture obtained in A3 into a mold and solidify it.

[0012] As a preferred technical solution of the present invention, the mixed concentrated acid in step A1 is 98% concentrated sulfuric acid and 68% concentrated nitric acid in a volume ratio of 2-4:1.

[0013] As a preferred technical solution of the present invention, the reflux temperature in step A1 is 75-85° C., and the reflux time is 5-7 h.

[0014] As a preferred technical solution of the present invention, in step A2, the mass ratio of the carboxylated carbon nanotubes to the silane coupling agent KH-570 is 1:4-6; the reaction temperature is 50-70° C., and the reaction time is 3-5 hours.

[0015] As a preferred technical solution of the present invention, the anti-aging agent in step A3 is a benzotriazole ultraviolet absorber and a hindered amine light stabilizer in a mass ratio of 1:0.5-1.5; the cross-linking agent is ethylene glycol dimethacrylate; and the free radical initiator is azobisisobutyronitrile.

[0016] As a preferred technical solution of the present invention, the mass ratio of the methacrylic acid monomer, surface-grafted double-bond carbon nanotubes, anti-aging agent, crosslinking agent, and free radical initiator in step A3 is 100:0.005-0.05:0.3-0.8:0.5-2:0.1-0.5.

[0017] Furthermore, the method for preparing the black high-light-transmittance resin composite plate is characterized by comprising the following preparation steps:

[0018] (1) Prepare a black light-transmitting layer according to steps A1-A4, and the sp 2 The hybrid carbon structure has a wide spectrum absorption characteristic, absorbing the entire visible light band through the quantum confinement effect, avoiding the color distortion caused by the selective absorption of traditional color pastes;

[0019] (2) Polycarbonate (refractive index 1.58) and SiO2 microspheres (refractive index 1.45) are mixed evenly. The refractive index difference forms a total reflection interface. Light undergoes multiple total reflections on the surface of the microspheres, increasing the lateral propagation distance. The light guide layer is then laminated to the black light-transmitting layer and hot-pressed.

[0020] (3) The diffusion layer is prepared by mixing polymethyl methacrylate and ZnO nanoparticles, and then laminating them on the light guide layer and hot pressing them to obtain the diffusion layer.

[0021] As a preferred technical solution of the present invention, the particle size of the SiO2 microspheres in step (2) is 3-10 μm, and the content is 0.1-0.5 wt% of the light guiding layer.

[0022] As a preferred technical solution of the present invention, the ZnO particle size in step (3) is 50-200nm, and the content is 0.1-0.5wt% of the diffusion layer; the surface of the diffusion layer has a micro-prism structure with a period of 30-100μm and an angle of 45-75°, which is attached to the other side of the light-guiding layer. Through the refraction and diffraction effects, the light diffusion angle is increased, and the uniformity of the light intensity distribution is better than that of the planar structure.

[0023] Furthermore, the black high-light-transmittance resin composite board is used for preparing a light box; the light-guiding layer is the inner layer close to the light source, the diffusion layer is the middle layer, and the black light-transmitting layer is the outermost layer.

[0024] Beneficial effects of the present invention:

[0025] (1) Carbon nanotubes have a wide spectrum absorption capacity. The present invention carboxylates carbon nanotubes and grafts silane coupling agents to mix the carbon nanotubes evenly in the resin, and then aligns them in a magnetic field to reduce local aggregation and light scattering caused by random distribution. With an extremely low addition amount of carbon nanotubes, full-band light absorption is achieved, achieving the synergy of high light transmittance and pure black appearance.

[0026] (2) The SiO2 microspheres in the light-guiding layer guide the light to propagate laterally through total reflection. Combined with the gradient distribution of ZnO nanoparticles and microprism structure in the diffusion layer, the light diffusion angle is increased and the light spot is eliminated.

[0027] (3) The compound anti-aging agent (benzotriazole UV absorber + hindered amine light stabilizer) works synergistically with the chemically bonded carbon nanotubes. The benzotriazole compound absorbs ultraviolet light through intramolecular hydrogen bonds, and the hindered amine light stabilizer inhibits resin chain breakage and yellowing by capturing free radicals and regenerating them; thus extending the service life of the resin. DETAILED DESCRIPTION

[0028] In order to further illustrate the technical means and effects adopted by the present invention to achieve the predetermined purpose of the invention, the specific implementation methods, structures, features and effects of the present invention are described in detail below in combination with the embodiments.

[0029] The sources of raw materials involved in the following examples and comparative examples are as follows: the polycarbonate was purchased from Ruihe New Materials Co., Ltd.; carbon nanotubes were purchased from Turing New Materials Co., Ltd.; polymethyl methacrylate was purchased from Jiangyuxin Plastics Co., Ltd.; and carbon black paste was purchased from Zhengzhou Lixing Chemical Products Co., Ltd.

[0030] Example 1

[0031] A black high-light-transmittance resin composite plate comprises an inner light-guiding layer, a middle diffusion layer, and an outer black light-transmitting layer; the preparation of the black light-transmitting layer comprises the following steps:

[0032] A1. Control the temperature of carbon nanotubes in mixed concentrated acid at 80°C and reflux for 6 hours to obtain carboxylated carbon nanotubes;

[0033] A2, surface-modifying the carboxylated carbon nanotubes obtained in step A1 with a silane coupling agent KH-570 to obtain surface-grafted double-bond carbon nanotubes;

[0034] A3, after mixing the surface-grafted double-bond carbon nanotubes prepared in step A2, methyl methacrylate monomer, anti-aging agent, and cross-linking agent, adding a free radical initiator, ultrasonically dispersing and polymerizing under nitrogen protection, and applying an 800 Gs magnetic field to align the surface-grafted double-bond carbon nanotubes;

[0035] A4: Pour the mixture obtained in A3 into a mold and solidify it.

[0036] The mixed concentrated acid in step A1 is 98% concentrated sulfuric acid and 68% concentrated nitric acid in a volume ratio of 3:1.

[0037] In step A2, the mass ratio of the carboxylated carbon nanotubes to the silane coupling agent KH-570 is 1:5; the reaction temperature is 60° C., and the reaction time is 4 hours.

[0038] The anti-aging agent in step A3 is a UV absorber Tinuvin 326 and a light stabilizer Tinuvin 770 in a mass ratio of 1:1; the crosslinking agent is ethylene glycol dimethacrylate; and the free radical initiator is azobisisobutyronitrile.

[0039] The mass ratio of the methacrylic acid monomer, the surface-grafted double-bond carbon nanotubes, the anti-aging agent, the crosslinking agent, and the free radical initiator in step A3 is 100:0.03:0.6:1.2:0.3.

[0040] The method for preparing a black high-light-transmittance resin composite plate is characterized by comprising the following preparation steps:

[0041] (1) Prepare a black light-transmitting layer with a thickness of 0.3 mm according to steps A1-A4;

[0042] (2) Polycarbonate and SiO2 microspheres were mixed evenly and then laminated to the black light-transmitting layer by hot pressing to obtain a light-guiding layer with a thickness of 2 mm;

[0043] (3) The diffusion layer is prepared by mixing polymethyl methacrylate and ZnO nanoparticles, and then laminating them on the light guide layer and hot pressing them to obtain a diffusion layer with a thickness of 1.5 mm.

[0044] The SiO2 microspheres in step (2) have a particle size of 3-10 μm and a content of 0.3 wt% of the light-guiding layer.

[0045] The ZnO particle size in step (3) is 50-200 nm, and the content is 0.3 wt% of the diffusion layer; the surface of the diffusion layer has a micro-prism structure with a period of 60 μm and an angle of 60°, which is attached to the other side of the light guide layer.

[0046] The black high-light-transmittance resin composite board is used for preparing a light box; the light-guiding layer is the inner layer close to the light source, the diffusion layer is the middle layer, and the black light-transmitting layer is the outermost layer.

[0047] Example 2

[0048] A black high-transmittance resin composite plate, characterized by comprising an inner light-guiding layer, a middle diffusion layer, and an outer black light-transmitting layer; the preparation of the black light-transmitting layer comprises the following steps:

[0049] A1. reflux carbon nanotubes in a mixed concentrated acid at 75° C. for 5 h to obtain carboxylated carbon nanotubes.

[0050] A2, surface-modifying the carboxylated carbon nanotubes obtained in step A1 with a silane coupling agent KH-570 to obtain surface-grafted double-bond carbon nanotubes;

[0051] A3, after mixing the surface-grafted double-bond carbon nanotubes prepared in step A2, methyl methacrylate monomer, anti-aging agent, and cross-linking agent, adding a free radical initiator, ultrasonically dispersing and polymerizing under nitrogen protection, and applying an 800 Gs magnetic field to align the surface-grafted double-bond carbon nanotubes;

[0052] A4: Pour the mixture obtained in A3 into a mold and solidify it.

[0053] The mixed concentrated acid in step A1 is 98% concentrated sulfuric acid and 68% concentrated nitric acid in a volume ratio of 2:1.

[0054] In step A2, the mass ratio of the carboxylated carbon nanotubes to the silane coupling agent KH-570 is 1:4; the reaction temperature is 60° C., and the reaction time is 3 h.

[0055] The anti-aging agent in step A3 is the ultraviolet absorber Chimassorb 81 and the light stabilizer Chimassorb 944 in a mass ratio of 1:0.5; the cross-linking agent is ethylene glycol dimethacrylate; and the free radical initiator is azobisisobutyronitrile.

[0056] The mass ratio of the methacrylic acid monomer, the surface-grafted double-bond carbon nanotubes, the anti-aging agent, the crosslinking agent, and the free radical initiator in step A3 is 100:0.005:0.3:0.5:0.1.

[0057] The method for preparing a black high-light-transmittance resin composite plate comprises the following preparation steps:

[0058] (1) Prepare a black light-transmitting layer with a thickness of 0.3 mm according to steps A1-A4;

[0059] (2) Polycarbonate and SiO2 microspheres were mixed evenly and then laminated to the black light-transmitting layer by hot pressing to obtain a light-guiding layer with a thickness of 2 mm;

[0060] (3) The diffusion layer is prepared by mixing polymethyl methacrylate and ZnO nanoparticles, and then laminating them on the light guide layer and hot pressing them to obtain a diffusion layer with a thickness of 1.5 mm.

[0061] The SiO2 microspheres in step (2) have a particle size of 3-10 μm and a content of 0.1 wt% of the light-guiding layer.

[0062] The ZnO particle size in step (3) is 50-200 nm, and the content is 0.1 wt% of the diffusion layer; the surface of the diffusion layer has a micro-prism structure with a period of 30 μm and an angle of 45°, which is attached to the other side of the light guide layer.

[0063] The black high-light-transmittance resin composite board is used for preparing a light box; the light-guiding layer is the inner layer close to the light source, the diffusion layer is the middle layer, and the black light-transmitting layer is the outermost layer.

[0064] Example 3

[0065] A black high-light-transmittance resin composite plate comprises an inner light-guiding layer, a middle diffusion layer, and an outer black light-transmitting layer; the preparation of the black light-transmitting layer comprises the following steps:

[0066] A1, reflux the carbon nanotubes in a mixed concentrated acid for 7 hours to obtain carboxylated carbon nanotubes;

[0067] A2, surface-modifying the carboxylated carbon nanotubes obtained in step A1 with a silane coupling agent KH-570 to obtain surface-grafted double-bond carbon nanotubes;

[0068] A3, after mixing the surface-grafted double-bond carbon nanotubes prepared in step A2, methyl methacrylate monomer, anti-aging agent, and cross-linking agent, adding a free radical initiator, ultrasonically dispersing and polymerizing under nitrogen protection, and applying an 800 Gs magnetic field to align the surface-grafted double-bond carbon nanotubes;

[0069] A4: Pour the mixture obtained in A3 into a mold and solidify it.

[0070] The mixed concentrated acid in step A1 is 98% concentrated sulfuric acid and 68% concentrated nitric acid in a volume ratio of 4:1.

[0071] In step A2, the mass ratio of the carboxylated carbon nanotubes to the silane coupling agent KH-570 is 1:6; the reaction temperature is 70° C., and the reaction time is 5 h.

[0072] The anti-aging agent in step A3 is a UV absorber Tinuvin 326 and a light stabilizer Chimassorb 944 in a mass ratio of 1:1.5; the crosslinking agent is ethylene glycol dimethacrylate; and the free radical initiator is azobisisobutyronitrile.

[0073] The mass ratio of the methacrylic acid monomer, the surface-grafted double-bond carbon nanotubes, the anti-aging agent, the crosslinking agent, and the free radical initiator in step A3 is 100:0.05:0.8:2:0.5.

[0074] The method for preparing a black high-light-transmittance resin composite plate comprises the following preparation steps:

[0075] (1) Prepare a black light-transmitting layer with a thickness of 0.3 mm according to steps A1-A4;

[0076] (2) Polycarbonate and SiO2 microspheres were mixed evenly and then laminated to the black light-transmitting layer by hot pressing to obtain a light-guiding layer with a thickness of 2 mm;

[0077] (3) The diffusion layer is prepared by mixing polymethyl methacrylate and ZnO nanoparticles, and then laminating them on the light guide layer and hot pressing them to obtain a diffusion layer with a thickness of 1.5 mm.

[0078] The SiO2 microspheres in step (2) have a particle size of 3-10 μm and a content of 0.5 wt% of the light-guiding layer.

[0079] As a preferred technical solution of the present invention, the ZnO particle size in step (3) is 50-200nm, and the content is 0.5wt% of the diffusion layer; the surface of the diffusion layer has a micro-prism structure with a period of 100μm and an angle of 75°, which is attached to the other side of the light guide layer.

[0080] The black high-light-transmittance resin composite board is used for preparing a light box; the light-guiding layer is the inner layer close to the light source, the diffusion layer is the middle layer, and the black light-transmitting layer is the outermost layer.

[0081] Comparative Example 1

[0082] On the basis of Example 1, the magnetic field is removed in step A3, and the carbon nanotubes are randomly dispersed. The rest is consistent with Example 1.

[0083] Comparative Example 2

[0084] On the basis of Example 1, the carbon nanotubes were not subjected to the carboxylation treatment in step A1, and the rest were the same as in Example 1.

[0085] Comparative Example 3

[0086] On the basis of Example 1, the carbon nanotubes were not subjected to the silane coupling agent grafting treatment in step A2, and the rest were the same as in Example 1.

[0087] Comparative Example 4

[0088] On the basis of Example 1, the carbon nanotubes were not subjected to the treatments in steps A1 and A2, and the rest were the same as in Example 1.

[0089] Comparative Example 5

[0090] On the basis of Example 1, carbon nanotubes were not added and carbon black paste was used instead. The rest of the steps were the same as in Example 1.

[0091] Comparative Example 6

[0092] On the basis of Example 1, the surface of the diffusion layer is flat and has no micro-prism structure, and the rest is consistent with Example 1.

[0093] Performance testing:

[0094] The light transmittance of the samples prepared in the examples and comparative examples was tested according to ASTM D1003 standard;

[0095] The blackness L value of the examples and comparative examples was measured according to the ASTM E308 color test standard, ranging from 0 (pure black) to 100 (pure white);

[0096] The laser beam divergence angles of the examples and comparative examples were tested according to ISO 13694.

[0097] The samples prepared in the examples and comparative examples were subjected to light aging according to ISO 4892 standard, and the transmittance decrease rate and yellowing index after aging were tested.

[0098] Transmittance / % Blackness L value Light diffusion angle / ° Transmittance decrease / % Yellowing index / ΔYI Example 1 88 8.2 165 3 2.5 Example 2 85 9.5 160 4 3.0 Example 3 86 7.8 170 5 2.8 Comparative Example 1 82 12.4 140 8 5.3 Comparative Example 2 75 18.3 130 15 7.7 Comparative Example 3 78 16.7 135 12 6.4 Comparative Example 4 70 20.1 120 20 9.1 Comparative Example 5 58 22.6 110 23 11.6 Comparative Example 6 80 8.5 90 4 3.2

[0099] The test results show that the transmittance and blackness of the embodiment are significantly higher than those of comparative examples 1-4, indicating that chemical bonding reduces the agglomeration of carbon nanotubes and avoids scattering loss, and the magnetic field orientation makes the carbon nanotubes orderly distributed, thereby lowering the absorption threshold; it can be seen from comparative example 5 that the transmittance and blackness are significantly reduced when the carbon nanotubes are replaced by color paste, and the yellowing index after aging is significantly higher than that of the embodiment, which may be because the organic dye in the color paste is easily photodegraded; comparative example 6 has no microprism structure, and the light diffusion angle is significantly reduced. It can be seen that the microprism structure significantly expands the light through refraction and diffraction effects to eliminate light spots.

[0100] The above description is merely a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Although the present invention has been disclosed as a preferred embodiment as above, it is not intended to limit the present invention. Any person skilled in the art can make some changes or modifications to equivalent embodiments using the technical contents disclosed above without departing from the scope of the technical solution of the present invention. However, any indirect modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A black high-transmittance resin composite sheet, characterized by: It comprises an inner light-guiding layer, a middle diffusion layer and an outer black light-transmitting layer; the material preparation method of the black light-transmitting layer comprises the following steps: A1. refluxing carbon nanotubes in a mixed concentrated acid to obtain carboxylated carbon nanotubes; A2, surface-modifying the carboxylated carbon nanotubes prepared in step A1 with a silane coupling agent KH-570 to obtain surface-grafted double-bond carbon nanotubes; A3, mixing the surface-grafted double-bond carbon nanotubes prepared in step A2, methyl methacrylate monomer, anti-aging agent, and cross-linking agent, adding a free radical initiator, performing ultrasonic dispersion polymerization under nitrogen protection, and applying a magnetic field to align the surface-grafted double-bond carbon nanotubes; A4: Pour the mixture obtained in A3 into a mold and solidify it.

2. The black high-transmittance resin composite sheet according to claim 1, characterized in that: The mixed concentrated acid in step A1 is 98% concentrated sulfuric acid and 68% concentrated nitric acid in a volume ratio of 2-4:

1.

3. The black high-light-transmittance resin composite sheet according to claim 1, characterized in that: The reflux temperature in step A1 is 75-85° C., and the reflux time is 5-7 h.

4. The black high-light-transmittance resin composite sheet according to claim 1, characterized in that: In step A2, the mass ratio of the carboxylated carbon nanotubes to the silane coupling agent KH-570 is 1:4-6; the reaction temperature is 50-70° C., and the reaction time is 3-5 hours.

5. The black high-light-transmittance resin composite sheet according to claim 1, characterized in that: The anti-aging agent in step A3 is a benzotriazole ultraviolet absorber and a hindered amine light stabilizer in a mass ratio of 1:0.5-1.5; the crosslinking agent is ethylene glycol dimethacrylate; and the free radical initiator is azobisisobutyronitrile.

6. The black high-light-transmittance resin composite sheet according to claim 1, characterized in that: The mass ratio of the methacrylic acid monomer, the surface-grafted double-bond carbon nanotubes, the anti-aging agent, the crosslinking agent, and the free radical initiator in step A3 is 100:0.005-0.05:0.3-0.8:0.5-2:0.1-0.

5.

7. A method for preparing the black high-light-transmittance resin according to claim 1, characterized in that: The method comprises the following preparation steps: (1) Prepare a black light-transmitting layer according to steps A1-A4; (2) mixing polycarbonate and SiO2 microspheres uniformly and laminating them to the black light-transmitting layer by hot pressing to obtain a light-guiding layer; (3) The diffusion layer is prepared by mixing polymethyl methacrylate and ZnO nanoparticles, and then laminating them on the light guide layer and hot pressing them to obtain the diffusion layer.

8. The method for preparing a black high-light-transmittance resin composite sheet according to claim 7, characterized in that: The SiO2 microspheres in step (2) have a particle size of 3-10 μm and a content of 0.1-0.5 wt% of the light-guiding layer; 9. The method for preparing a black high-light-transmittance resin composite sheet according to claim 7, characterized in that: The ZnO particle size in step (3) is 50-200 nm, and the content is 0.1-0.5 wt% of the diffusion layer; the surface of the diffusion layer has a micro-prism structure with a period of 30-100 μm and an angle of 45-75°, which is attached to the other side of the light guide layer.

10. A black high-light-transmittance resin composite sheet according to any one of claims 1 to 9, characterized in that: Applicable to the preparation of light boxes; the light guide layer is the inner layer close to the light source, the diffusion layer is the middle layer, and the black light-transmitting layer is the outermost layer.