Preparation method and application of high-brightness coated optical reflection film

Abstract

The application relates to the technical field of reflective films, and discloses a preparation method and application of a high-brightness coated optical reflective film, which comprises the following steps: mixing and stirring acrylic ester adhesive, coated particles, fluorescent composite particles and an organic solvent according to a mass percentage ratio of 35-40%:3.5-4.2%:0.8-1.5%:50-60% to obtain a coating liquid; coating the coating liquid on a reflective film base film, and carrying out UV curing to obtain a coated optical reflective film; wherein the fluorescent composite particles are prepared by sequentially coating silica and a polymer on the surface of fluorescent powder. The brightness of the coated optical reflective film can be effectively improved by combining the fluorescent composite particles with the coated particles, meanwhile, the coated particles in the coating layer can also avoid scratching the light guide plate, so that the obtained reflective film can be better applied to optical elements.

Description

Technical Field

[0001] This invention relates to the technical field of optical thin films, and in particular to a method for preparing and applying a high-brightness coated optical reflective film. Background Technology

[0002] Backlight modules, comprising diffuser films, brightness enhancement films, and reflective films, are crucial components of displays. Backlight modules can be categorized into edge-lit and direct-lit types. Edge-lit backlight modules utilize a light guide plate to convert point light sources into surface light sources, with the reflective film in contact with the light guide plate. Uncoated reflective films suffer from adhesion problems, leading to shadows and other aesthetic defects; therefore, coating is typically applied. However, coating often reduces the reflectivity of the reflective film substrate, and coated optical reflective films generally have lower brightness than the substrate. Therefore, developing a high-brightness coated optical reflective film is necessary for its better application in optical components.

[0003] Chinese patent CN114637061A discloses a high-toughness and high-brightness reflective film and its preparation method. The reflective film consists of a reflective layer and an adhesive layer. First, an adhesive resin and quantum dot material are mixed in an organic solvent to prepare a coating solution. This coating solution is then applied to the surface of the reflective film substrate, and a quantum dot adhesive layer is formed through cross-linking and thermal curing, resulting in the high-toughness and high-brightness reflective film. This reflective film exhibits high reflectivity and high brightness, while also possessing high toughness and ease of assembly. However, the aforementioned patent uses UV adhesive or glue to encapsulate the quantum dot material (phosphor). Although this achieves water and oxygen barrier properties, the quantum dot material is inorganic. Directly adding it to the adhesive system results in poor compatibility between the quantum dot material and the adhesive, making uniform dispersion difficult. Furthermore, the adhesive system does not contain coating particles, which may scratch the light guide plate. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a method for preparing and applying a high-brightness coated optical reflective film. By combining fluorescent composite particles with coating particles, the brightness of the coated optical reflective film can be effectively improved. Simultaneously, the presence of coating particles in the coating also prevents scratches on the light guide plate. Furthermore, the fluorescent composite particles are obtained by sequentially coating the phosphor surface with silica and a polymer. This not only improves the compatibility between the phosphor and the adhesive system and reduces agglomeration, but also isolates the phosphor from external water and oxygen, increasing the phosphor's resistance to hydrolysis and aging.

[0005] The objective of this invention is achieved through the following technical solution:

[0006] In a first aspect, the present invention provides a method for preparing a high-brightness coated optical reflective film, comprising the following steps: mixing and stirring an acrylate adhesive, coating particles, fluorescent composite particles, and an organic solvent in a mass percentage ratio of 35-40%: 3.5-4.2%: 0.8-1.5%: 50-60% to obtain a coating liquid; coating the coating liquid onto a reflective film base film, and after UV curing, obtaining a coated optical reflective film; wherein, the fluorescent composite particles are obtained by sequentially coating the surface of phosphor with silica and a polymer; the polymer is obtained by reacting methacryloyloxypropylmethyldimethoxysilane, polyethylene glycol dimethacrylate, and a free radical initiator in a mass ratio of 0.2-0.4:1:0.002-0.003 in an organic solvent.

[0007] This invention involves mixing fluorescent composite particles, acrylate adhesive, and coating particles (organic coating particles) to obtain a coating liquid, which is then coated onto a reflective film base. After UV curing, a coated optical reflective film is obtained. The combination of fluorescent composite particles and coating particles effectively improves the brightness of the coated optical reflective film, while the presence of coating particles in the coating also prevents scratches on the light guide plate.

[0008] The fluorescent composite particles are obtained by sequentially coating the phosphor surface with silica and then with a polymer. The silica coating isolates the phosphor from external water and oxygen, increasing its resistance to hydrolysis and aging. Simultaneously, the silica layer reduces light scattering caused by abrupt changes in refractive index between particles, improving light extraction efficiency. Further coating with a polymer, obtained by copolymerizing the double bonds in methacryloyloxypropylmethyldimethoxysilane and polyethylene glycol dimethacrylate (PEGDMA) under the action of a free radical initiator, results in a cross-linked network structure that forms a denser and more stable coating layer. Furthermore, the silane groups in the polymer hydrolyze to generate -SiOH groups, which condense with the hydroxyl groups in the silica coating to form chemical bonds, further enhancing the adhesion between the polymer and the phosphor. The resulting coating layer exhibits excellent toughness and wear resistance. Additionally, the ester and ether groups in the coating layer improve the dispersibility of the phosphor in acrylate adhesive systems, reducing agglomeration.

[0009] Methacryloxypropylmethyldimethoxysilane and polyethylene glycol dimethacrylate have similar polarities, preventing phase separation due to polarity differences and ensuring uniform dispersion of the pre-reaction product. However, if a highly hydrophobic silane coupling agent is used instead of methacryloxypropylmethyldimethoxysilane, phase separation will occur, hindering the formation of a uniform and stable coating layer. The long-chain alkyl and methyl groups in methacryloxypropylmethyldimethoxysilane reduce the surface energy of the coating layer, preventing water molecule penetration. If amino- or epoxy-containing silanes are used, they can only bind to PEGDMA through hydrogen bonding or physical adsorption, failing to form a covalent cross-linked network, resulting in weak interfacial bonding. Furthermore, if methacryloxypropylmethyldimethoxysilane is used alone, it will directly condense with the modified phosphor, but lacking the buffer of flexible segments, the resulting interface is rigid, prone to cracking, and weak due to hydrogen bonding. Furthermore, the lack of a polyethylene glycol dimethacrylate coating layer will affect the dispersibility of phosphor in the acrylate adhesive system, thereby affecting brightness.

[0010] Preferably, the specific steps for preparing the fluorescent composite particles include: coating the surface of the phosphor with silica to obtain modified phosphor; adding the polymer and modified phosphor to an ethanol aqueous solution for ultrasonic dispersion, followed by stirring reaction to obtain fluorescent composite particles.

[0011] The polymer preferentially undergoes a condensation reaction with the hydroxyl groups on the surface of the silica layer through the silyl groups at the end of its side chain (which are hydrolyzed into Si-OH groups) to form Si-O-Si covalent bonds, thereby firmly fixing the polymer network to the surface of the phosphor particles.

[0012] Preferably, the mass ratio of the polymer to the modified phosphor is 0.03~0.05:1; the mass ratio of the modified phosphor to the ethanol aqueous solution is 1:10~20; and the stirring reaction is carried out at 50~60℃ for 6~8 hours.

[0013] Preferably, the specific steps for preparing the modified phosphor include: dispersing the phosphor in an aqueous ethanol solution, adjusting the pH to 4-5, adding ethyl silicate and ammonia and stirring the reaction, and then centrifuging, drying, and calcining to obtain the modified phosphor.

[0014] Preferably, the mass ratio of the phosphor to the aqueous ethanol solution is 1:45~55; the mass ratio of the phosphor, ethyl silicate, and ammonia is 1:0.2~2:0.05~0.6; the stirring reaction is performed by ultrasonic stirring at 60~65℃ for 6~8h; and the calcination is performed by calcination at 400~500℃ for 2~3h.

[0015] Preferably, the thickness of the silica coating layer in the fluorescent composite particles / modified phosphor is 15~25nm.

[0016] Coating phosphors with silica yields a silica coating layer. However, if the silica coating layer is too thin, it cannot provide enough hydroxyl groups, resulting in ineffective coating of the modified phosphor surface during subsequent polymer reactions. Furthermore, an excessively thin silica coating layer is difficult to control during the coating process, easily leading to uneven coating, which also affects subsequent polymer reactions. Conversely, if the silica coating layer is too thick, it increases light scattering on the phosphor surface, reducing the phosphor's luminous efficiency and consequently decreasing the brightness of the coated optical reflective film.

[0017] Preferably, the specific steps for preparing the polymer include: adding methacryloyloxypropylmethyldimethoxysilane to an aqueous ethanol solution, adjusting the pH to 4-5, stirring at room temperature for 3-5 hours, then adding a tetrahydrofuran solution containing polyethylene glycol dimethacrylate and a free radical initiator, heating to 65-80°C under nitrogen protection and reacting for 6-8 hours, and finally centrifuging, washing and drying to obtain the polymer.

[0018] By controlling the reactant ratio and reaction conditions, polymers with suitable molecular chain structures can be obtained, containing silane groups, ester groups, and ether bonds. These polymers not only react with the surface hydroxyl groups of the modified phosphor but also facilitate the dispersion of the phosphor in the acrylate adhesive system, reducing agglomeration. Furthermore, by synergistically controlling the molecular weight of polyethylene glycol dimethacrylate, the molecular chain size and steric hindrance of the polymer can be determined, which is beneficial for achieving a good coating effect on the modified phosphor surface.

[0019] Preferably, the mass ratio of the methacryloyloxypropylmethyldimethoxysilane to the aqueous ethanol solution is 1:20-25; the mass ratio of the polyethylene glycol dimethacrylate to tetrahydrofuran is 1:10-15; the average molecular weight of the polyethylene glycol dimethacrylate is 400-600; and the free radical initiator is azobisisobutyronitrile (AIBN).

[0020] Preferably, the coating particles are PU particles with a particle size of 3-8 μm; the organic solvent is one or more of ethyl acetate, butyl acetate and butanone.

[0021] The coated particles are flexible; excessively large particle sizes can hinder the phosphor's brightening effect, thus affecting luminance. Furthermore, excessive addition of coated particles can scatter light, reducing the coating's reflectivity and also decreasing luminance. Over-addition of fluorescent composite particles can cause color coordinate shifts, resulting in a yellowish film appearance, while insufficient addition will not significantly improve luminance.

[0022] Preferably, the coating thickness is 6-7 μm; the UV curing involves first curing at 80-90°C for 2-4 minutes, followed by UV curing, with the UV energy controlled at 300-500 mJ / cm². 2 .

[0023] If the coating thickness is too thin, the phosphor may be partially exposed outside the adhesive layer, which can easily scratch the light guide plate during subsequent backlight module assembly. If the coating thickness is too thick, it will not match the UV curing conditions, resulting in incomplete curing. At the same time, the brightness of the reflective film may be reduced due to the excessive coating thickness.

[0024] Secondly, the present invention also provides an application of a high-brightness coated optical reflective film in optical elements.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] (1) The combination of fluorescent composite particles and coated particles can effectively improve the brightness of coated optical reflective film. At the same time, the presence of coated particles in the coating can also prevent scratches on the light guide plate.

[0027] (2) The surface of the phosphor is coated with silica, which can isolate the phosphor from the contact with water and oxygen in the outside world, increase the phosphor’s resistance to hydrolysis and aging, and at the same time, the silica layer on the surface can reduce light scattering caused by the abrupt change in refractive index between particles and improve the light extraction efficiency. Then, the polymer containing multifunctional groups (silyl groups, ester groups and ether bonds, etc.) is coated, which can improve the dispersibility of the phosphor in the acrylate adhesive system, reduce the agglomeration phenomenon, and further improve the brightness of the coated optical reflective film. Detailed Implementation

[0028] The technical solution of the present invention will be illustrated below with specific embodiments, but the scope of protection of the present invention is not limited thereto.

[0029] The method for preparing the high-brightness coated optical reflective film in this invention includes the following steps:

[0030] (1) Disperse the phosphor in an ethanol aqueous solution at a mass ratio of 1:45~55 to obtain a mixture; adjust the pH of the mixture to 4~5, add ethyl silicate and ammonia, the mass ratio of phosphor, ethyl silicate and ammonia is 1:0.2~2:0.05~0.6, and ultrasonically stir at 60~65℃ for 6~8h; after centrifugation and drying, calcine at 400~500℃ for 2~3h to obtain modified phosphor, the thickness of the silica coating layer in the modified phosphor is 15~25nm;

[0031] (2) Methacryloxypropylmethyldimethoxysilane was added to an aqueous ethanol solution at a mass ratio of 1:20~25, the pH was adjusted to 4~5, and the mixture was stirred at room temperature for 3~5 hours to obtain a mixture; polyethylene glycol dimethacrylate (average molecular weight of 400~600) was dissolved in tetrahydrofuran at a mass ratio of 1:10~15 and added to the mixture, and then a free radical initiator was added. The mass ratio of methacryloxypropylmethyldimethoxysilane, polyethylene glycol dimethacrylate and free radical initiator was 0.2~0.4:1:0.002~0.003. The mixture was heated to 65~80℃ under nitrogen protection and reacted for 6~8 hours. After the reaction was completed, the mixture was centrifuged, washed and dried to obtain the polymer.

[0032] (3) Add the polymer and modified phosphor to an ethanol aqueous solution at a mass ratio of 0.03~0.05:1. The mass ratio of modified phosphor to ethanol aqueous solution is 1:10~20. After ultrasonic dispersion, adjust the pH to 6.5~7.5, and then stir at 50~60℃ for 6~8h. After the reaction is completed, centrifuge, wash and dry to obtain fluorescent composite particles.

[0033] (4) Based on a total mass percentage of 100%, the acrylic adhesive, coating particles, fluorescent composite particles, and organic solvent are mixed and stirred in a ratio of 35~40%: 3.5~4.2%: 0.8~1.5%: 50~60% to obtain a coating solution; the coating solution is applied to the reflective film base film, and the coating thickness is 6~7μm. Then, it is first cured at 80~90℃ for 2~4min, and then UV cured, with the UV energy controlled at 300~500mJ / cm. 2 A coated optical reflective film was obtained.

[0034] In a specific embodiment of the present invention, in step (1), the phosphor is YAG phosphor.

[0035] In a specific embodiment of the present invention, in step (1), the heating rate of calcination is 1~10℃ / min.

[0036] In a specific embodiment of the present invention, in steps (1), (2) and (3), the volume ratio of ethanol to water in the ethanol aqueous solution is 7:3.

[0037] In a specific embodiment of the present invention, in step (4), the acrylate adhesive is a UV-type acrylate adhesive, model UV50LV, purchased from Anshiao Trading (Shenzhen) Co., Ltd.; the coating particles are PU particles with a particle size of 3~8μm and an average particle size of 5μm; the organic solvent is one or more of ethyl acetate, butyl acetate and butanone; the reflective film base film is our company's self-made EST150 reflective film.

[0038] Example 1

[0039] (1) The phosphor was dispersed in an ethanol aqueous solution at a mass ratio of 1:50 and ultrasonically dispersed for 1 h to obtain a mixture; the pH of the mixture was adjusted to 4~5, and ethyl silicate and ammonia were added. The mass ratio of phosphor, ethyl silicate and ammonia was 1:1.2:0.35, and the mixture was ultrasonically stirred at 60℃ for 7 h; after centrifugation and drying, the mixture was heated at a heating rate of 2℃ / min and calcined at 450℃ for 2 h to obtain modified phosphor. The thickness of the silica coating layer in the modified phosphor was 17±1 nm.

[0040] (2) Methacryloxypropylmethyldimethoxysilane was added to an aqueous ethanol solution at a mass ratio of 1:20, the pH was adjusted to 4-5, and the mixture was stirred at room temperature for 3 hours to obtain a mixture; polyethylene glycol dimethacrylate (average molecular weight of 600) was dissolved in tetrahydrofuran at a mass ratio of 1:10 and added to the mixture, and then a free radical initiator was added. The mass ratio of methacryloxypropylmethyldimethoxysilane, polyethylene glycol dimethacrylate and free radical initiator was 0.4:1:0.003. The mixture was heated to 70°C under nitrogen protection and reacted for 7 hours. After the reaction was completed, the mixture was centrifuged, washed and dried to obtain the polymer.

[0041] (3) The polymer and modified phosphor were added to an ethanol aqueous solution at a mass ratio of 0.036:1 and the mass ratio of modified phosphor to ethanol aqueous solution was 1:10. After ultrasonic dispersion for 30 min, the pH was adjusted to 6.5~7.5 and then stirred at 60℃ for 6 h. After the reaction was completed, the fluorescent composite particles were obtained by centrifugation, washing and drying.

[0042] (4) Based on a total mass percentage of 100%, the acrylic adhesive, coating particles, fluorescent composite particles, and organic solvent (ethyl acetate) are mixed and stirred in a ratio of 38.5%:3.6%:1%:56.9% at a stirring rate of 1000 r / min for 1 h to obtain a coating solution. The coating solution is then applied to the reflective film base film, with a coating thickness of 6.4 ± 0.1 μm. After curing at 85 °C for 2 min, UV curing is performed, with the UV energy controlled at 400 mJ / cm². 2 A coated optical reflective film was obtained.

[0043] Example 2

[0044] The difference from Example 1 is that the amount of fluorescent composite particles added is 0.8%. Specifically, based on a total mass percentage of 100%, the acrylate adhesive, coating particles, fluorescent composite particles, and solvent (ethyl acetate) are mixed and stirred in a ratio of 38.5%:3.8%:0.8%:56.9% at a stirring rate of 1000 r / min for 1 h to obtain the coating solution.

[0045] Example 3

[0046] (1) The phosphor was dispersed in an ethanol aqueous solution at a mass ratio of 1:50 and ultrasonically dispersed for 1 h to obtain a mixture; the pH of the mixture was adjusted to 4~5, and ethyl silicate and ammonia were added. The mass ratio of phosphor, ethyl silicate and ammonia was 1:1.2:0.35, and the mixture was ultrasonically stirred at 60℃ for 7 h; after centrifugation and drying, the mixture was heated at a heating rate of 2℃ / min and calcined at 450℃ for 2 h to obtain modified phosphor. The thickness of the silica coating layer in the modified phosphor was 17±1 nm.

[0047] (2) Methacryloxypropylmethyldimethoxysilane was added to an aqueous ethanol solution at a mass ratio of 1:20, the pH was adjusted to 4-5, and the mixture was stirred at room temperature for 3 hours to obtain a mixture. Polyethylene glycol dimethacrylate (average molecular weight of 600) was dissolved in tetrahydrofuran at a mass ratio of 1:10 and added to the mixture. Then a free radical initiator was added. The mass ratio of methacryloxypropylmethyldimethoxysilane, polyethylene glycol dimethacrylate and free radical initiator was 0.35:1:0.002. The mixture was heated to 65°C under nitrogen protection and reacted for 6 hours. After the reaction was completed, the mixture was centrifuged, washed and dried to obtain the polymer.

[0048] (3) The polymer and modified phosphor were added to an ethanol aqueous solution at a mass ratio of 0.044:1 and the mass ratio of modified phosphor to ethanol aqueous solution was 1:10. After ultrasonic dispersion for 30 min, the pH was adjusted to 6.5~7.5 and then stirred at 60℃ for 6 h. After the reaction was completed, the fluorescent composite particles were obtained by centrifugation, washing and drying.

[0049] (4) Based on a total mass percentage of 100%, the acrylic adhesive, coating particles, fluorescent composite particles, and organic solvent (ethyl acetate) are mixed and stirred in a ratio of 38.5%:3.6%:1%:56.9% at a stirring rate of 1000 r / min for 1 h to obtain a coating solution. The coating solution is then applied to the reflective film base film, with a coating thickness of 6.4 ± 0.1 μm. After curing at 85 °C for 2 min, UV curing is performed, with the UV energy controlled at 400 mJ / cm². 2 A coated optical reflective film was obtained.

[0050] Comparative Example 1

[0051] Difference from Example 1: No fluorescent composite particles were added.

[0052] Based on a total mass percentage of 100%, the acrylic adhesive, coating particles, and organic solvent (ethyl acetate) were mixed and stirred at a ratio of 38.5% : 4.6% : 56.9% at a stirring rate of 1000 r / min for 1 h to obtain the coating solution. The coating solution was then applied to the reflective film base film to form a coating thickness of 6.4 ± 0.1 μm. The coating was first cured at 85℃ for 2 min, followed by UV curing at a UV energy of 400 mJ / cm². 2 A coated optical reflective film was obtained.

[0053] Comparative Example 2

[0054] The difference from Example 1: the added phosphor was not treated in any way.

[0055] Based on a total mass percentage of 100%, acrylic adhesive, coating particles, phosphor, and organic solvent (ethyl acetate) were mixed and stirred in a ratio of 38.5%:3.6%:1%:56.9% at a stirring rate of 1000 r / min for 1 h to obtain a coating solution. The coating solution was then applied to the reflective film base film, resulting in a coating thickness of 6.4 ± 0.1 μm. The coating was first cured at 85℃ for 2 min, followed by UV curing at a UV energy of 400 mJ / cm². 2 A coated optical reflective film was obtained.

[0056] Comparative Example 3

[0057] The difference from Example 1 is that other silane coupling agents containing double bonds (vinyltrimethoxysilane) are used instead of methacryloyloxypropylmethyldimethoxysilane.

[0058] (1) The phosphor was dispersed in an ethanol aqueous solution at a mass ratio of 1:50 and ultrasonically dispersed for 1 h to obtain a mixture; the pH of the mixture was adjusted to 4~5, and ethyl silicate and ammonia were added. The mass ratio of phosphor, ethyl silicate and ammonia was 1:1.2:0.35, and the mixture was ultrasonically stirred at 60℃ for 7 h; after centrifugation and drying, the mixture was heated at a heating rate of 2℃ / min and calcined at 450℃ for 2 h to obtain modified phosphor. The thickness of the silica coating layer in the modified phosphor was 17±1 nm.

[0059] (2) Add vinyltrimethoxysilane to an aqueous ethanol solution at a mass ratio of 1:20, adjust the pH to 4-5, stir at room temperature for 3 hours to obtain a mixture; dissolve polyethylene glycol dimethacrylate (average molecular weight of 600) in tetrahydrofuran at a mass ratio of 1:10 and add it to the mixture, then add a free radical initiator. The mass ratio of vinyltrimethoxysilane, polyethylene glycol dimethacrylate and free radical initiator is 0.4:1:0.003. Heat to 70°C under nitrogen protection and react for 7 hours. After the reaction is completed, centrifuge, wash and dry to obtain the polymer.

[0060] (3) The polymer and modified phosphor were added to an ethanol aqueous solution at a mass ratio of 0.036:1 and the mass ratio of modified phosphor to ethanol aqueous solution was 1:10. After ultrasonic dispersion for 30 min, the pH was adjusted to 6.5~7.5 and then stirred at 60℃ for 6 h. After the reaction was completed, the fluorescent composite particles were obtained by centrifugation, washing and drying.

[0061] (4) Based on a total mass percentage of 100%, the acrylic adhesive, coating particles, fluorescent composite particles, and organic solvent (ethyl acetate) are mixed and stirred in a ratio of 38.5%:3.6%:1%:56.9% at a stirring rate of 1000 r / min for 1 h to obtain a coating solution. The coating solution is then applied to the reflective film base film, with a coating thickness of 6.4 ± 0.1 μm. After curing at 85 °C for 2 min, UV curing is performed, with the UV energy controlled at 400 mJ / cm². 2 A coated optical reflective film was obtained.

[0062] Comparative Example 4

[0063] Difference from Example 1: No polyethylene glycol dimethacrylate was added.

[0064] (1) The phosphor was dispersed in an ethanol aqueous solution at a mass ratio of 1:50 and ultrasonically dispersed for 1 h to obtain a mixture; the pH of the mixture was adjusted to 4~5, and ethyl silicate and ammonia were added. The mass ratio of phosphor, ethyl silicate and ammonia was 1:1.2:0.35, and the mixture was ultrasonically stirred at 60℃ for 7 h; after centrifugation and drying, the mixture was heated at a heating rate of 2℃ / min and calcined at 450℃ for 2 h to obtain modified phosphor. The thickness of the silica coating layer in the modified phosphor was 17±1 nm.

[0065] (2) Methacryloxypropylmethyldimethoxysilane was added to an aqueous ethanol solution at a mass ratio of 1:20, the pH was adjusted to 4-5, and the mixture was stirred at room temperature for 3 hours to obtain a mixture. A free radical initiator was added to the mixture, and the mass ratio of methacryloxypropylmethyldimethoxysilane to the free radical initiator was 0.4:0.003. The mixture was heated to 70°C under nitrogen protection and reacted for 7 hours. After the reaction was completed, the mixture was centrifuged, washed and dried to obtain a polymer.

[0066] (3) The polymer and modified phosphor were added to an ethanol aqueous solution at a mass ratio of 0.036:1 and the mass ratio of modified phosphor to ethanol aqueous solution was 1:10. After ultrasonic dispersion for 30 min, the pH was adjusted to 6.5~7.5 and then stirred at 60℃ for 6 h. After the reaction was completed, the fluorescent composite particles were obtained by centrifugation, washing and drying.

[0067] (4) Based on a total mass percentage of 100%, the acrylic adhesive, coating particles, fluorescent composite particles, and organic solvent (ethyl acetate) are mixed and stirred in a ratio of 38.5%:3.6%:1%:56.9% at a stirring rate of 1000 r / min for 1 h to obtain a coating solution. The coating solution is then applied to the reflective film base film, with a coating thickness of 6.4 ± 0.1 μm. After curing at 85 °C for 2 min, UV curing is performed, with the UV energy controlled at 400 mJ / cm². 2 A coated optical reflective film was obtained.

[0068] Comparative Example 5

[0069] The difference from Example 1 is that the molecular weight of polyethylene glycol dimethacrylate is too large and the amount added is too much.

[0070] (1) The phosphor was dispersed in an ethanol aqueous solution at a mass ratio of 1:50 and ultrasonically dispersed for 1 h to obtain a mixture; the pH of the mixture was adjusted to 4~5, and ethyl silicate and ammonia were added. The mass ratio of phosphor, ethyl silicate and ammonia was 1:1.2:0.35, and the mixture was ultrasonically stirred at 60℃ for 7 h; after centrifugation and drying, the mixture was heated at a heating rate of 2℃ / min and calcined at 450℃ for 2 h to obtain modified phosphor. The thickness of the silica coating layer in the modified phosphor was 17±1 nm.

[0071] (2) Methacryloxypropylmethyldimethoxysilane was added to an aqueous ethanol solution at a mass ratio of 1:20, the pH was adjusted to 4-5, and the mixture was stirred at room temperature for 3 hours to obtain a mixture; polyethylene glycol dimethacrylate (average molecular weight of 750) was dissolved in tetrahydrofuran at a mass ratio of 1:15 and added to the mixture, and then a free radical initiator was added. The mass ratio of methacryloxypropylmethyldimethoxysilane, polyethylene glycol dimethacrylate and free radical initiator was 0.4:1.5:0.003. The mixture was heated to 70°C under nitrogen protection and reacted for 7 hours. After the reaction was completed, the mixture was centrifuged, washed and dried to obtain the polymer.

[0072] (3) The polymer and modified phosphor were added to an ethanol aqueous solution at a mass ratio of 0.036:1 and the mass ratio of modified phosphor to ethanol aqueous solution was 1:10. After ultrasonic dispersion for 30 min, the pH was adjusted to 6.5~7.5 and then stirred at 60℃ for 6 h. After the reaction was completed, the fluorescent composite particles were obtained by centrifugation, washing and drying.

[0073] (4) Based on a total mass percentage of 100%, the acrylic adhesive, coating particles, fluorescent composite particles, and organic solvent (ethyl acetate) are mixed and stirred in a ratio of 38.5%:3.6%:1%:56.9% at a stirring rate of 1000 r / min for 1 h to obtain a coating solution. The coating solution is then applied to the reflective film base film, with a coating thickness of 6.4 ± 0.1 μm. After curing at 85 °C for 2 min, UV curing is performed, with the UV energy controlled at 400 mJ / cm². 2 A coated optical reflective film was obtained.

[0074] Table 1

[0075]

[0076] Note: The relative center luminance of each embodiment / comparative example is the percentage of the center luminance of each embodiment / comparative example relative to the center luminance of the EST150 base film; the relative average luminance of each embodiment / comparative example is the percentage of the average luminance of each embodiment / comparative example relative to the average luminance of the EST150 base film.

[0077] As shown in Table 1, the coated optical reflective film in Comparative Example 1 did not contain phosphor, therefore its brightness was slightly lower than that of the EST150 base film. In Comparative Example 2, although phosphor was added to the coated optical reflective film, the phosphor was not treated, resulting in poor dispersion in the adhesive system. This caused the phosphor to agglomerate into larger clusters, exacerbating light scattering and leading to reduced brightness. In contrast, Examples 1-3 of this invention used surface-treated fluorescent composite particles, resulting in coated optical reflective films with higher brightness and uniformity.

[0078] In addition, in Comparative Example 3, other silane coupling agents containing double bonds were used. Due to their excessively fast reaction rate, the polymer molecular weight was easily out of control, the system viscosity increased dramatically, the phosphor was prone to agglomeration, and the light scattering was enhanced, resulting in lower brightness and poorer uniformity.

[0079] In Comparative Example 4, because methacryloyloxypropylmethyldimethoxysilane was used alone, it directly condensed with the phosphor. Lacking the buffer of flexible segments, it was prone to cracking, which was not conducive to the formation of the coating layer. Furthermore, the dispersibility of the phosphor in the adhesive system was reduced, resulting in lower brightness and uniformity.

[0080] In Comparative Example 5, the excessive molecular weight and excessive amount of polyethylene glycol dimethacrylate resulted in a large polymer molecular chain and greater steric hindrance. Furthermore, the silane groups in the molecular chain were difficult to react effectively with the hydroxyl groups on the surface of the modified phosphor, leading to poor uniformity of the coating layer of the fluorescent composite particles and low brightness and uniformity.

[0081] The above are merely preferred embodiments of the present invention and do not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made using the present invention specification, 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 high-brightness coated optical reflective film, characterized in that, The process includes the following steps: mixing and stirring acrylate adhesive, coating particles, fluorescent composite particles and organic solvent in a mass percentage ratio of 35~40%: 3.5~4.2%: 0.8~1.5%: 50~60% to obtain a coating liquid; coating the coating liquid onto the reflective film base film, and after UV curing, obtaining a coated optical reflective film; The fluorescent composite particles are prepared by sequentially coating the surface of phosphor with silica and polymer. The thickness of the silica coating layer in the fluorescent composite particles is 15~25nm. The polymer is prepared by reacting methacryloyloxypropylmethyldimethoxysilane, polyethylene glycol dimethacrylate and free radical initiator in an organic solvent at a mass ratio of 0.2~0.4:1:0.002~0.

003. The average molecular weight of the polyethylene glycol dimethacrylate is 400~600.

2. The method for preparing the high-brightness coated optical reflective film according to claim 1, characterized in that, The specific steps for preparing the fluorescent composite particles include: coating the surface of the phosphor with silica to obtain modified phosphor; adding the polymer and modified phosphor to an ethanol aqueous solution for ultrasonic dispersion, followed by stirring reaction to obtain fluorescent composite particles.

3. The method for preparing the high-brightness coated optical reflective film according to claim 2, characterized in that, The mass ratio of the polymer to the modified phosphor is 0.03~0.05:1; the mass ratio of the modified phosphor to the ethanol aqueous solution is 1:10~20; the stirring reaction is carried out at 50~60℃ for 6~8h.

4. The method for preparing a high-brightness coated optical reflective film according to claim 1 or 2, characterized in that, The specific steps for preparing the polymer include: adding methacryloyloxypropylmethyldimethoxysilane to an aqueous ethanol solution, adjusting the pH to 4-5, stirring at room temperature for 3-5 hours, then adding a tetrahydrofuran solution containing polyethylene glycol dimethacrylate and a free radical initiator, heating to 65-80°C under nitrogen protection and reacting for 6-8 hours, and finally centrifuging, washing and drying to obtain the polymer.

5. The method for preparing the high-brightness coated optical reflective film according to claim 4, characterized in that, The mass ratio of the methacryloyloxypropylmethyldimethoxysilane to the aqueous ethanol solution is 1:20~25; the mass ratio of the polyethylene glycol dimethacrylate to tetrahydrofuran is 1:10~15.

6. The method for preparing the high-brightness coated optical reflective film according to claim 1, characterized in that, The coating particles are PU particles with a particle size of 3~8μm; the organic solvent is one or more of ethyl acetate, butyl acetate and butanone.

7. The method for preparing a high-brightness coated optical reflective film according to claim 1 or 6, characterized in that, The coating thickness is 6~7μm.

8. The method for preparing a high-brightness coated optical reflective film according to claim 1 or 6, characterized in that, The UV curing process involves first curing at 80-90℃ for 2-4 minutes, followed by UV curing, with the UV energy controlled at 300-500 mJ / cm². 2 .

9. The application of a high-brightness coated optical reflective film prepared by any one of claims 1-8 in optical components.

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