A method for preparing a black high-transmittance resin composite board and its application

Abstract

This invention relates to a method for preparing a black high-transparency resin composite board and its application, belonging to the field of advertising materials technology. The resin of this invention is composed of a black transparent layer, a light-guiding layer, and a diffusion layer. The high-transparency layer uses carboxylated carbon nanotubes modified with a silane coupling agent, polymerized with methyl methacrylate monomers, and magnetically oriented to achieve high light transmittance and a pure black appearance. The light-guiding layer uses polycarbonate as a matrix, adding SiO2 microspheres, and improves the lateral light propagation efficiency through hot pressing. The diffusion layer uses polymethyl methacrylate as a matrix, adding ZnO nanoparticles, and processing a periodic microprism structure on the surface to achieve uniform light diffusion. When applied to light boxes, it presents a pure black appearance when the light source is off, and exhibits high light transmittance without any impurities when on, making it suitable for high-end advertising displays, vehicle-mounted light boxes, and other scenarios.

Description

Technical Field

[0001] This invention belongs to the field of advertising materials technology, and relates to a method for preparing a black high-transparency resin composite board and its application. Background Technology

[0002] In modern lightbox manufacturing, material selection and design are crucial to the optical performance and durability of the final product. Traditional acrylic sheets face several technical challenges in lightbox applications. First, the pigments used in acrylic sheets typically absorb some light, directly leading to insufficient light transmittance and brightness, thus wasting light energy. Since the primary function of a lightbox 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 diffusing sufficiently within the material and causing it to pass directly through the sheet. This direct light transmission easily forms light spots, resulting in uneven light transmission and affecting the visual effect. This uneven light scattering not only reduces the lightbox's aesthetics but can also affect the clarity of information display in practical applications.

[0003] Secondly, the poor aging resistance of acrylic materials is also a significant technical shortcoming. The poor compatibility between acrylic and colorant makes it prone to colorant precipitation, leading to product aging and fading. Acrylic products often exhibit noticeable fading after prolonged environmental exposure, typically turning white, which not only affects the appearance of the lightbox but may also reduce its lifespan. Furthermore, aging materials are prone to cracking, further impacting the structural integrity and safety of the lightbox. This lack of aging resistance not only increases maintenance costs but may also lead to more frequent replacements, affecting user experience and market competitiveness. Currently used black translucent acrylic also has several shortcomings, primarily because the colorant used in its formulation absorbs some of the color of white light, allowing only certain wavelengths of visible light to pass through. This results in impure light colors, especially when using white light as a backlight, where the transmitted light often appears grayish, bluish, or reddish. This impurity in light color can affect the accuracy of information delivery in advertising displays.

[0004] To overcome these technological shortcomings, the development of new materials and manufacturing methods is particularly important. In recent years, with the advancement of nanotechnology and polymer chemistry, researchers have been gradually exploring ways to optimize the optical properties and durability of light box materials through nanomaterials and chemical modifications. Summary of the Invention

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

[0006] The objective of this invention can be achieved through the following technical solutions:

[0007] A black high-transmittance resin composite board 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 includes the following steps:

[0008] A1. Carbon nanotubes are refluxed in a mixed concentrated acid, and carboxyl and hydroxyl groups are introduced on the surface through strong oxidation to obtain carboxylated carbon nanotubes, which provide active sites for subsequent silane coupling agent grafting.

[0009] A2. The carboxylated carbon nanotubes obtained in step A1 are surface modified with silane coupling agent KH-570. The methoxy group of KH-570 is hydrolyzed to generate silanol, which condenses with the hydroxyl group on the surface of carbon nanotubes to form Si-OC covalent bonds. At the same time, the methacryloyloxy group at the end of KH-570 retains the double bond activity, thus obtaining surface-grafted double bond carbon nanotubes.

[0010] A3. After mixing the surface-grafted double-bonded carbon nanotubes prepared in step A2, methyl methacrylate monomer, anti-aging agent, and crosslinking agent, a free radical initiator is added. The mixture is then ultrasonically dispersed and polymerized 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-bonded carbon nanotubes also participate in the copolymerization reaction of the monomers through the double bonds at their ends. A magnetic field is applied to orient the surface-grafted double-bonded carbon nanotubes.

[0011] A4. Pour the mixture obtained in A3 into the mold and let it cure.

[0012] As a preferred embodiment 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 embodiment of the present invention, the reflux temperature in step A1 is 75-85℃ and the reflux time is 5-7h.

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

[0015] As a preferred embodiment 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 crosslinking agent is ethylene glycol dimethacrylate; and the free radical initiator is azobisisobutyronitrile.

[0016] As a preferred embodiment of the present invention, the mass ratio of the methacrylic acid monomer, surface-grafted double-bonded 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-transmittance resin composite board is characterized by comprising the following preparation steps:

[0018] (1) A black transparent layer was prepared according to steps A1-A4, and the sp of carbon nanotubes was obtained. 2 Hybrid carbon structures have broad-spectrum absorption characteristics, absorbing the entire visible light band through quantum confinement effect, thus avoiding color distortion caused by the selective light absorption of traditional pigments.

[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 obtained by hot pressing it onto the black light-transmitting layer.

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

[0021] As a preferred embodiment of the present invention, 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 guide 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 microprism structure with a period of 30-100μm and an angle of 45-75°, which is attached to the other side of the light guide layer. Through the refraction and diffraction effect, the light diffusion angle is increased, and the uniformity of light intensity distribution is better than that of the planar structure.

[0023] Furthermore, the aforementioned black high-transmittance resin composite board is used in 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.

[0024] The beneficial effects of this invention are:

[0025] (1) Carbon nanotubes have a wide spectrum absorption capability. In this invention, carbon nanotubes are mixed evenly in resin by carboxylating carbon nanotubes and grafting silane coupling agents, and then oriented by magnetic field to reduce local aggregation and light scattering caused by random distribution. Full-band light absorption is achieved with extremely low carbon nanotube addition, achieving a synergy of high light transmittance and pure black appearance.

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

[0027] (3) The compound anti-aging agent (benzotriazole ultraviolet absorber + hindered amine light stabilizer) works synergistically with chemically bonded carbon nanotubes. Benzotriazole compounds absorb ultraviolet light through intramolecular hydrogen bonds, and hindered amine light stabilizers inhibit resin chain breakage and yellowing by capturing free radicals and regenerating them, thus extending the service life of the resin. Detailed Implementation

[0028] To further illustrate the technical means and effects of the present invention in achieving its intended purpose, the following detailed description of the specific implementation methods, structures, features, and effects of the present invention, in conjunction with embodiments, is provided below.

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

[0030] Example 1

[0031] A black high-transmittance resin composite board 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 includes the following steps:

[0032] A1. Carbon nanotubes were refluxed in a mixed concentrated acid at a controlled temperature of 80°C for 6 hours to obtain carboxylated carbon nanotubes.

[0033] A2. The carboxylated carbon nanotubes obtained in step A1 are surface-modified with silane coupling agent KH-570 to obtain surface-grafted double-bonded carbon nanotubes.

[0034] A3. After mixing the surface-grafted double-bonded carbon nanotubes prepared in step A2, methyl methacrylate monomer, anti-aging agent, and crosslinking agent, add a free radical initiator, and then ultrasonically disperse and polymerize under nitrogen protection while applying an 800 Gs magnetic field to orient the surface-grafted double-bonded carbon nanotubes.

[0035] A4. Pour the mixture obtained in A3 into the mold and let it cure.

[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 carboxylated carbon nanotubes to silane coupling agent KH-570 is 1:5; the reaction temperature is 60℃ and the reaction time is 4h.

[0038] The anti-aging agent in step A3 is a mixture of ultraviolet absorber Tinuvin 326 and 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, surface-grafted double-bonded carbon nanotubes, anti-aging agent, crosslinking agent, and free radical initiator in step A3 is 100:0.03:0.6:1.2:0.3.

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

[0041] (1) A black transparent layer with a thickness of 0.3 mm is prepared according to steps A1-A4;

[0042] (2) After the polycarbonate and SiO2 microspheres are mixed evenly, they are bonded to the black light-transmitting layer and hot-pressed to obtain a light guide layer with a thickness of 2mm.

[0043] (3) The diffusion layer is prepared by mixing polymethyl methacrylate and ZnO nanoparticles and then bonding them to the light guide layer and hot pressing 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 guide layer.

[0045] The ZnO particles in step (3) have a particle size of 50-200 nm and a content of 0.3 wt% of the diffusion layer; the surface of the diffusion layer has a microprism 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 aforementioned black high-transmittance resin composite board is used in 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.

[0047] Example 2

[0048] A black high-transmittance resin composite board, characterized in that it 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 includes the following steps:

[0049] A1. Carbon nanotubes were refluxed in a mixed concentrated acid at a controlled temperature of 75°C for 5 hours to obtain carboxylated carbon nanotubes.

[0050] A2. The carboxylated carbon nanotubes obtained in step A1 are surface-modified with silane coupling agent KH-570 to obtain surface-grafted double-bonded carbon nanotubes.

[0051] A3. After mixing the surface-grafted double-bonded carbon nanotubes prepared in step A2, methyl methacrylate monomer, anti-aging agent, and crosslinking agent, add a free radical initiator, and then ultrasonically disperse and polymerize under nitrogen protection while applying an 800 Gs magnetic field to orient the surface-grafted double-bonded carbon nanotubes.

[0052] A4. Pour the mixture obtained in A3 into the mold and let it cure.

[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 carboxylated carbon nanotubes to silane coupling agent KH-570 is 1:4; the reaction temperature is 60℃ and the reaction time is 3h.

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

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

[0057] The preparation method of the black high-transmittance resin composite board includes the following preparation steps:

[0058] (1) A black transparent layer with a thickness of 0.3 mm is prepared according to steps A1-A4;

[0059] (2) After the polycarbonate and SiO2 microspheres are mixed evenly, they are bonded to the black light-transmitting layer and hot-pressed to obtain a light guide layer with a thickness of 2mm.

[0060] (3) The diffusion layer is prepared by mixing polymethyl methacrylate and ZnO nanoparticles and then bonding them to the light guide layer and hot pressing 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 guide layer.

[0062] The ZnO particles in step (3) have a particle size of 50-200 nm and a content of 0.1 wt% of the diffusion layer; the surface of the diffusion layer has a microprism 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 aforementioned black high-transmittance resin composite board is used in the manufacture 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.

[0064] Example 3

[0065] A black high-transmittance resin composite board 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 includes the following steps:

[0066] A1. Carbon nanotubes were refluxed in a mixed concentrated acid for 7 hours to obtain carboxylated carbon nanotubes.

[0067] A2. The carboxylated carbon nanotubes obtained in step A1 are surface-modified with silane coupling agent KH-570 to obtain surface-grafted double-bonded carbon nanotubes.

[0068] A3. After mixing the surface-grafted double-bonded carbon nanotubes prepared in step A2, methyl methacrylate monomer, anti-aging agent, and crosslinking agent, add a free radical initiator, and then ultrasonically disperse and polymerize under nitrogen protection while applying an 800 Gs magnetic field to orient the surface-grafted double-bonded carbon nanotubes.

[0069] A4. Pour the mixture obtained in A3 into the mold and let it cure.

[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 carboxylated carbon nanotubes to silane coupling agent KH-570 is 1:6; the reaction temperature is 70℃ and the reaction time is 5h.

[0072] The anti-aging agent in step A3 is a mixture of ultraviolet absorber Tinuvin 326 and 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, surface-grafted double-bonded carbon nanotubes, anti-aging agent, crosslinking agent, and free radical initiator in step A3 is 100:0.05:0.8:2:0.5.

[0074] The preparation method of the black high-transmittance resin composite board includes the following preparation steps:

[0075] (1) A black transparent layer with a thickness of 0.3 mm is prepared according to steps A1-A4;

[0076] (2) After the polycarbonate and SiO2 microspheres are mixed evenly, they are bonded to the black light-transmitting layer and hot-pressed to obtain a light guide layer with a thickness of 2mm.

[0077] (3) The diffusion layer is prepared by mixing polymethyl methacrylate and ZnO nanoparticles and then bonding them to the light guide layer and hot pressing 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 guide 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 microprism 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 aforementioned black high-transmittance resin composite board is used in the manufacture 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.

[0081] Comparative Example 1

[0082] Based on Example 1, step A3 removes the magnetic field, and the carbon nanotubes are randomly dispersed, while the rest remains the same as in Example 1.

[0083] Comparative Example 2

[0084] Based on Example 1, the carbon nanotubes are not subjected to step A1 carboxylation treatment, and the rest is consistent with Example 1.

[0085] Comparative Example 3

[0086] Based on Example 1, the carbon nanotubes are not treated with silane coupling agent in step A2, and the rest is the same as in Example 1.

[0087] Comparative Example 4

[0088] Based on Example 1, the carbon nanotubes are not subjected to steps A1 and A2, and the rest remains the same as in Example 1.

[0089] Comparative Example 5

[0090] Based on Example 1, carbon nanotubes were not added, but carbon black paste was used instead, while the rest remained the same as in Example 1.

[0091] Comparative Example 6

[0092] Based on Example 1, the surface of the diffusion layer is planar and has no microprism structure, while the rest remains the same as in Example 1.

[0093] Performance testing:

[0094] The transmittance of the samples was tested according to the ASTM D1003 standard test examples and comparative examples.

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

[0096] The laser beam spread angle of the test examples and comparative samples were determined according to ISO 13694 standard.

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

[0098] Light transmittance / % L value of blackness Light diffusion angle / ° Light 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 example are significantly higher than those of comparative examples 1-4, indicating that chemical bonding reduces carbon nanotube aggregation and avoids scattering loss, and magnetic field orientation makes carbon nanotubes distributed in an orderly manner, reducing the light absorption threshold. Comparative example 5 shows that replacing carbon nanotubes with pigment paste significantly reduces both transmittance and blackness, and the yellowing index after aging is significantly higher than that of the example, possibly because the organic dyes in the pigment paste are easily photodegraded. Comparative example 6 has no microprism structure, and the light diffusion angle is significantly reduced, indicating 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 is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any indirect modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A black high-transmittance resin composite board, characterized in that: It comprises an inner light-guiding layer, a middle diffusion layer, and an outer black light-transmitting layer; the method for preparing the material of the black light-transmitting layer includes the following steps: A1. Carbon nanotubes are refluxed in a mixed concentrated acid to obtain carboxylated carbon nanotubes; A2. Carboxylated carbon nanotubes were prepared in step A1 and surface-modified with silane coupling agent KH-570 to obtain surface-grafted double-bonded carbon nanotubes. A3. After mixing the surface-grafted double-bonded carbon nanotubes prepared in step A2, methyl methacrylate monomer, anti-aging agent, and crosslinking agent, add a free radical initiator, and then ultrasonically disperse and polymerize under nitrogen protection while applying a magnetic field to orient the surface-grafted double-bonded carbon nanotubes. A4. Pour the mixture obtained in A3 into a mold and let it cure. In step A3, the anti-aging agent is a benzotriazole ultraviolet absorber and a hindered amine light stabilizer in a mass ratio of 1:0.5-1.

5. The preparation method of the aforementioned black high-transmittance resin composite board includes the following preparation steps: (1) A black light-transmitting layer is prepared according to steps A1-A4; (2) After uniformly mixing polycarbonate and SiO2 microspheres, the mixture is bonded to a black light-transmitting layer and hot-pressed to obtain a light guide layer. (3) The diffusion layer is prepared by mixing polymethyl methacrylate and ZnO nanoparticles and then bonding them to the light guide layer and hot pressing to obtain the diffusion layer. In step (2), the SiO2 microspheres have a particle size of 3-10 μm and a content of 0.1-0.5 wt% of the light guide layer. In step (3), the ZnO nanoparticles have a particle size of 50-200 nm and a content of 0.1-0.5 wt% of the diffusion layer; the surface of the diffusion layer has a microprism 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.

2. The black high-transmittance resin composite board 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-transmittance resin composite board according to claim 1, characterized in that: The reflux temperature in step A1 is 75-85℃, and the reflux time is 5-7h.

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

5. The black high-transmittance resin composite board according to claim 1, characterized in that: The crosslinking agent in step A3 is ethylene glycol dimethacrylate; the free radical initiator is azobisisobutyronitrile.

6. The black high-transmittance resin composite board according to claim 1, characterized in that: The mass ratio of methyl methacrylate monomer, surface-grafted double-bonded 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.

7. A black high-transmittance resin composite board as described in any one of claims 1-6, characterized in that: It is used in the manufacture 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.