Preparation method and application of high-brightness coating type optical reflecting film

Abstract

The invention relates to the technical field of reflecting films, and discloses a preparation method and application of a high-brightness coating type optical reflecting film, and the preparation method comprises the following steps: mixing and stirring an acrylate adhesive, coating particles, fluorescent composite particles and an organic solvent according to the mass percent of (35-40%): (3.5-4.2%): (0.8-1.5%): (50-60%) to obtain a coating liquid; the coating liquid is coated on a reflecting film base film, and after UV curing, the coating type optical reflecting film is obtained; wherein the fluorescent composite particles are prepared by coating the surface of fluorescent powder with silicon dioxide and a polymer in sequence. The fluorescent composite particles and the coating particles are combined, so that the brightness of the coating type optical reflecting film can be effectively improved, meanwhile, the coating particles exist in the coating, a light guide plate can be prevented from being scratched, and therefore the obtained reflecting film can be better applied to optical elements.

Description

Technical Field

[0001] The present invention relates to the technical field of optical films, and in particular to a preparation method and application of a high-brightness coated optical reflective film. Background Art

[0002] The backlight module, which includes components such as a diffusion film, a brightness enhancement film, and a reflective film, is one of the key components of a display. Backlight modules can be divided into edge-entry and direct-lit types. Edge-entry backlight modules use a light guide plate, which converts a point light source into a surface light source, and the reflective film is in contact with the light guide plate. Uncoated reflective films can experience adsorption issues, leading to appearance defects such as shadows, so they are generally coated. However, after coating, the reflective film substrate often decreases in reflectivity, and the brightness of the coated optical reflective film is not as good as that of the reflective film substrate. Therefore, it is necessary to develop a high-brightness coated optical reflective film for better application in optical components.

[0003] Patent publication number CN114637061A discloses a high-toughness, high-brightness reflective film and its preparation method. The reflective film consists of a reflective layer and an adhesive layer. An adhesive resin and a quantum dot material are first prepared in an organic solvent to form a coating solution. This coating solution is then applied to the surface of the reflective film substrate and then crosslinked and thermally cured to form a quantum dot adhesive layer, resulting in the high-toughness, high-brightness reflective film. This reflective film exhibits high reflectivity and brightness, along with high toughness and ease of assembly. However, the solution in the aforementioned patent uses UV glue or adhesive to encapsulate the quantum dot material (phosphor). While this achieves water and oxygen barrier properties, the quantum dot material is an inorganic material. 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 lacks coating particles, which could potentially scratch the light guide plate. Summary of the Invention

[0004] To address the aforementioned technical issues, the present invention provides a method for preparing and applying a high-brightness coated optical reflective film. By combining fluorescent composite particles with coated particles, the brightness of the coated optical reflective film is effectively enhanced. The presence of the coated particles in the coating also prevents scratches on the light guide plate. Furthermore, the fluorescent composite particles, obtained by sequentially coating the surface of phosphor powder with silica and then a polymer, not only improve the compatibility between the phosphor and the glue system, reducing agglomeration, but also isolate the phosphor from external water and oxygen, enhancing its resistance to hydrolysis and aging.

[0005] The purpose of the present invention is achieved through the following technical solutions: In a first aspect, the present invention provides a method for preparing a high-brightness coated optical reflective film, comprising the following steps: mixing an acrylate adhesive, coating particles, fluorescent composite particles, and an organic solvent in a mass percentage of 35-40%: 3.5-4.2%: 0.8-1.5%: 50-60% to obtain a coating liquid; applying the coating liquid on a reflective film base film, and UV curing to obtain a coated optical reflective film; wherein the fluorescent composite particles are obtained by sequentially coating the surface of a phosphor with silica and a polymer; and the polymer is obtained by adding methacryloyloxypropylmethyldimethoxysilane, polyethylene glycol dimethacrylate, and a free radical initiator to an organic solvent for reaction in a mass ratio of 0.2-0.4:1:0.002-0.003.

[0006] The present invention combines fluorescent composite particles with an acrylic adhesive and coating particles (organic coating particles) to create a coating solution, which is then applied to a reflective film base film. 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. The presence of the coating particles in the coating also prevents scratches on the light guide plate.

[0007] The fluorescent composite particles are obtained by sequentially coating the phosphor powder with silica and then a polymer. The silica coating isolates the phosphor from external water and oxygen, increasing its resistance to hydrolysis and aging. The silica layer also reduces light scattering caused by sudden changes in the refractive index between particles, improving light extraction efficiency. The polymer is then coated with a cross-linked network structure derived from the copolymerization of methacryloxypropylmethyldimethoxysilane and the double bonds of polyethylene glycol dimethacrylate (PEGDMA) in the presence of a free radical initiator. The polymer forms a denser and more stable coating. The silyl groups in the polymer hydrolyze to form -SiOH groups, which condense with the hydroxyl groups in the silica coating to form chemical bonds, further strengthening the bonding between the polymer and the phosphor. The resulting coating exhibits excellent toughness and wear resistance. Furthermore, the ester and ether bonds in the coating enhance the dispersibility of the phosphor in the acrylate adhesive system and reduce agglomeration.

[0008] Methacryloxypropylmethyldimethoxysilane and polyethylene glycol dimethacrylate have similar polarities and will not phase separate due to polarity differences, ensuring uniform dispersion of the pre-reaction product. If a silane coupling agent with excessive hydrophobicity is used to replace methacryloxypropylmethyldimethoxysilane, phase separation will occur, which is not conducive to the formation of a uniform and stable coating layer. The long-chain alkyl and methyl groups in methacryloxypropylmethyldimethoxysilane can reduce the surface energy of the coating layer and block the penetration of water molecules. If amino- or epoxy-containing silanes are used, they can only bind to PEGDMA through hydrogen bonds or physical adsorption, and cannot form a covalent cross-linked network, resulting in weak interfacial bonding. In addition, if methacryloxypropylmethyldimethoxysilane is used alone, it will directly condense with the modified phosphor, but will lack the buffering of the flexible chain segment. The resulting interface is rigid and prone to cracking, and it is bound by hydrogen bonds, so the interfacial bonding strength is weak. Moreover, the lack of a polyethylene glycol dimethacrylate coating layer will affect the dispersibility of the phosphor in the acrylate glue system, thereby affecting the brightness.

[0009] Preferably, the specific steps of preparing the fluorescent composite particles include: coating the surface of the phosphor with silicon dioxide to obtain a modified phosphor; adding the polymer and the modified phosphor to an ethanol aqueous solution for ultrasonic dispersion, and then stirring the mixture for reaction to obtain the fluorescent composite particles.

[0010] The polymer preferentially undergoes condensation reaction with the hydroxyl groups on the surface of the silica layer through the silane group at the end of its side chain (which becomes Si-OH group after hydrolysis) to form Si-O-Si covalent bonds, thereby firmly fixing the polymer network on the surface of the phosphor particles.

[0011] 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° C. for 6-8 hours.

[0012] Preferably, the specific steps of preparing the modified phosphor include: dispersing the phosphor in an ethanol aqueous solution, adjusting the pH to 4-5, adding ethyl silicate and ammonia water and stirring the mixture, and then centrifuging, drying, and calcining to obtain the modified phosphor.

[0013] Preferably, the mass ratio of the phosphor to the ethanol aqueous solution is 1:45-55; the mass ratio of the phosphor, ethyl silicate and ammonia water is 1:0.2-2:0.05-0.6; the stirring reaction is ultrasonic stirring at 60-65° C. for 6-8 hours; and the calcination is calcination at 400-500° C. for 2-3 hours.

[0014] Preferably, the thickness of the silicon dioxide coating layer in the fluorescent composite particles / modified phosphor is 15-25 nm.

[0015] Silica coating is formed by coating the phosphor surface with silica. However, if the silica coating is too thin, it will not provide sufficient hydroxyl groups, resulting in ineffective coating of the modified phosphor surface during subsequent polymer reaction coating. Furthermore, an overly thin silica coating is difficult to control during the coating process, resulting in uneven coating, which can affect subsequent polymer reaction coating. If the silica coating is too thick, it will increase light scattering on the phosphor surface, reducing the phosphor's luminous efficiency and, consequently, the brightness of the coated optical reflective film.

[0016] Preferably, the specific steps of preparing the polymer include: adding methacryloxypropylmethyldimethoxysilane to an ethanol aqueous 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, reacting for 6-8 hours, and finally centrifuging, washing, and drying to obtain a polymer.

[0017] By controlling the reactant ratio and reaction conditions, a polymer with a suitable molecular chain structure, containing silane, ester, and ether bonds, can be obtained. This polymer not only reacts with the surface hydroxyl groups of the modified phosphor but also facilitates its dispersion in the acrylate adhesive system, reducing agglomeration. Simultaneously, by synergistically controlling the molecular weight of polyethylene glycol dimethacrylate, the polymer's molecular chain size and steric hindrance can be adjusted, facilitating a good coating effect of the polymer on the surface of the modified phosphor.

[0018] Preferably, the mass ratio of the methacryloxypropylmethyldimethoxysilane to the ethanol aqueous 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).

[0019] Preferably, the coating particles are PU particles with a particle size of 3 to 8 μm; and the organic solvent is one or more of ethyl acetate, butyl acetate and butanone.

[0020] Coating particles are flexible particles. Excessive particle size can hinder the phosphor's brightness enhancement, affecting brightness. Furthermore, excessive amounts of coating particles can scatter light, reducing the coating's reflectivity and also lowering brightness. Excessive addition of fluorescent composite particles can shift color coordinates, giving the film a yellowish tint. Excessive additions can lead to a limited brightness enhancement.

[0021] Preferably, the coating thickness is 6-7 μm; the UV curing is performed at 80-90°C for 2-4 minutes, and then UV curing is performed, and the UV energy is controlled at 300-500 mJ / cm 2 .

[0022] If the coating is too thin, the phosphor may be partially exposed outside the adhesive layer, which may easily scratch the light guide plate during the subsequent backlight unit assembly process. If the coating is too thick, it will not match the UV curing parameters, resulting in incomplete curing. At the same time, the brightness of the reflective film may be reduced due to the excessive coating thickness.

[0023] In a second aspect, the present invention further provides an application of a high-brightness coating type optical reflective film in an optical element.

[0024] Compared with the prior art, the present invention has the following beneficial effects: (1) The combination of fluorescent composite particles and coating particles can effectively improve the brightness of the coated optical reflective film. At the same time, due to the presence of coating particles in the coating, scratches on the light guide plate can also be avoided. (2) The surface of the phosphor is coated with silica, which can isolate the phosphor from the contact with external water and oxygen, increase the anti-hydrolysis and anti-aging capabilities of the phosphor, and at the same time, the silica layer on the surface can reduce the light scattering caused by the sudden change of the refractive index between particles, and improve the light extraction efficiency; then coated with a polymer containing multiple functional groups (silane groups, ester groups and ether bonds, etc.), which can improve the dispersion of the phosphor in the acrylic glue system, reduce the agglomeration phenomenon, and further improve the brightness of the coated optical reflective film. DETAILED DESCRIPTION

[0025] The technical solutions of the present invention are described below with specific embodiments, but the protection scope of the present invention is not limited thereto.

[0026] The method for preparing the high-brightness coated optical reflective film of the present invention comprises the following steps: (1) The phosphor is dispersed in an ethanol-water solution at a mass ratio of 1:45-55 to obtain a mixed solution; the pH of the mixed solution is adjusted to 4-5, ethyl silicate and ammonia water are added, and the mass ratio of the phosphor, ethyl silicate and ammonia water is 1:0.2-2:0.05-0.6, and ultrasonic stirring is carried out at 60-65°C for 6-8 hours; after centrifugal separation and drying, calcination is carried out at 400-500°C for 2-3 hours to obtain a modified phosphor, wherein the thickness of the silica coating layer in the modified phosphor is 15-25 nm; (2) Methacryloxypropylmethyldimethoxysilane was added to an ethanol aqueous 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 mixed solution; polyethylene glycol dimethacrylate (average molecular weight of 400-600) was dissolved in tetrahydrofuran at a mass ratio of 1:10-15 and then added to the mixed solution, 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, and the mixture was heated to 65-80°C under nitrogen protection for 6-8 hours. After the reaction was completed, the mixture was centrifuged, washed and dried to obtain a polymer; (3) The polymer and the modified phosphor were added to an ethanol aqueous solution at a mass ratio of 0.03-0.05:1, and the mass ratio of the modified phosphor to the ethanol aqueous solution was 1:10-20. After ultrasonic dispersion, the pH was adjusted to 6.5-7.5, and then stirred at 50-60 °C for 6-8 h. After the reaction was completed, the mixture was centrifuged, washed, and dried to obtain fluorescent composite particles. (4) Based on the 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 liquid; the coating liquid is applied on the reflective film base film to a coating thickness of 6~7 μm, and then cured at 80~90°C for 2~4 minutes, and then UV cured, with the UV energy controlled at 300~500 mJ / cm 2 , and obtain a coated optical reflective film.

[0027] In a specific embodiment of the present invention, in step (1), the phosphor is YAG phosphor.

[0028] In a specific embodiment of the present invention, in step (1), the heating rate of calcination is 1-10°C / min.

[0029] In a specific embodiment of the present invention, in step (1), step (2) and step (3), the volume ratio of ethanol to water in the ethanol aqueous solution is 7:3.

[0030] 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 to 8 μm and an average particle size of 5 μm; the organic solvent is one or more of ethyl acetate, butyl acetate and butanone; and the reflective film base film is our company's homemade EST150 reflective film.

[0031] Example 1 (1) The phosphor was dispersed in an ethanol-water solution at a mass ratio of 1:50 and ultrasonically dispersed for 1 h to obtain a mixed solution; the pH of the mixed solution was adjusted to 4-5, ethyl silicate and ammonia water were added, and the mass ratio of phosphor, ethyl silicate and ammonia water was 1:1.2:0.35, and ultrasonic stirring was carried out at 60 °C for 7 h; after centrifugal separation and drying, the mixture was heated at a heating rate of 2 °C / min and calcined at 450 °C for 2 h to obtain a modified phosphor. The thickness of the silica coating layer in the modified phosphor was 17±1 nm; (2) Methacryloxypropylmethyldimethoxysilane was added to an ethanol aqueous 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 mixed solution; polyethylene glycol dimethacrylate (average molecular weight of 600) was dissolved in tetrahydrofuran at a mass ratio of 1:10 and added to the mixed solution, 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 a polymer; (3) The polymer and the modified phosphor were added to an ethanol aqueous solution at a mass ratio of 0.036:1, and the mass ratio of the modified phosphor to the ethanol aqueous solution was 1:10. After ultrasonic dispersion for 30 minutes, the pH was adjusted to 6.5-7.5, and then stirred at 60 ° C for 6 hours. After the reaction was completed, the mixture was centrifuged, washed and dried to obtain fluorescent composite particles; (4) Based on the total mass percentage of 100%, the acrylic adhesive, coating particles, fluorescent composite particles and organic solvent (ethyl acetate) were mixed and stirred in a ratio of 38.5%: 3.6%: 1%: 56.9%, with a stirring rate of 1000 r / min and a stirring time of 1 h to obtain a coating liquid; the coating liquid was coated on the reflective film base film with a coating thickness of 6.4 ± 0.1 μm, and then cured at 85 ° C for 2 min, and then UV cured, with the UV energy controlled at 400 mJ / cm 2 , and obtain a coated optical reflective film.

[0032] Example 2 The difference from Example 1 is that the amount of fluorescent composite particles added is 0.8%. Specifically, based on the total mass percentage of 100%, the acrylic adhesive, coating particles, fluorescent composite particles, and solvent (ethyl acetate) were 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 hour to obtain a coating solution.

[0033] Example 3 (1) The phosphor was dispersed in an ethanol-water solution at a mass ratio of 1:50 and ultrasonically dispersed for 1 h to obtain a mixed solution; the pH of the mixed solution was adjusted to 4-5, ethyl silicate and ammonia water were added, and the mass ratio of phosphor, ethyl silicate and ammonia water was 1:1.2:0.35, and ultrasonic stirring was carried out at 60 °C for 7 h; after centrifugal separation and drying, the mixture was heated at a heating rate of 2 °C / min and calcined at 450 °C for 2 h to obtain a modified phosphor. The thickness of the silica coating layer in the modified phosphor was 17±1 nm; (2) Methacryloxypropylmethyldimethoxysilane was added to an ethanol aqueous 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 mixed solution; polyethylene glycol dimethacrylate (average molecular weight of 600) was dissolved in tetrahydrofuran at a mass ratio of 1:10 and added to the mixed solution, and 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 a polymer; (3) The polymer and the modified phosphor were added to an ethanol aqueous solution at a mass ratio of 0.044:1, and the mass ratio of the modified phosphor to the ethanol aqueous solution was 1:10. After ultrasonic dispersion for 30 minutes, the pH was adjusted to 6.5-7.5, and then stirred at 60 ° C for 6 hours. After the reaction was completed, the mixture was centrifuged, washed and dried to obtain fluorescent composite particles; (4) Based on the total mass percentage of 100%, the acrylic adhesive, coating particles, fluorescent composite particles and organic solvent (ethyl acetate) were mixed and stirred in a ratio of 38.5%: 3.6%: 1%: 56.9%, with a stirring rate of 1000 r / min and a stirring time of 1 h to obtain a coating liquid; the coating liquid was coated on the reflective film base film with a coating thickness of 6.4 ± 0.1 μm, and then cured at 85 ° C for 2 min, and then UV cured, with the UV energy controlled at 400 mJ / cm 2 , and obtain a coated optical reflective film.

[0034] Comparative Example 1 Difference from Example 1: No fluorescent composite particles were added.

[0035] Based on the total mass percentage of 100%, the acrylic adhesive, coating particles and organic solvent (ethyl acetate) were mixed and stirred in a ratio of 38.5%:4.6%:56.9%, with a stirring rate of 1000 r / min and a stirring time of 1 h to obtain a coating liquid; the coating liquid was coated on the reflective film base film with a coating thickness of 6.4±0.1 μm, and then cured at 85°C for 2 min, and then UV cured, with the UV energy controlled at 400 mJ / cm 2 , and obtain a coated optical reflective film.

[0036] Comparative Example 2 The difference from Example 1 is that the added phosphor is not processed in any way.

[0037] Based on the total mass percentage of 100%, the acrylate adhesive, coating particles, phosphor and organic solvent (ethyl acetate) were mixed and stirred in a ratio of 38.5%: 3.6%: 1%: 56.9%, with a stirring rate of 1000 r / min and a stirring time of 1 h to obtain a coating liquid; the coating liquid was coated on the reflective film base film with a coating thickness of 6.4±0.1 μm, and then cured at 85°C for 2 min, and then UV cured, with the UV energy controlled at 400 mJ / cm 2 , and obtain a coated optical reflective film.

[0038] Comparative Example 3 Difference from Example 1: other silane coupling agents containing double bonds (vinyltrimethoxysilane) are used instead of methacryloxypropylmethyldimethoxysilane.

[0039] (1) The phosphor was dispersed in an ethanol-water solution at a mass ratio of 1:50 and ultrasonically dispersed for 1 h to obtain a mixed solution; the pH of the mixed solution was adjusted to 4-5, ethyl silicate and ammonia water were added, and the mass ratio of phosphor, ethyl silicate and ammonia water was 1:1.2:0.35, and ultrasonic stirring was carried out at 60 °C for 7 h; after centrifugal separation and drying, the mixture was heated at a heating rate of 2 °C / min and calcined at 450 °C for 2 h to obtain a modified phosphor. The thickness of the silica coating layer in the modified phosphor was 17±1 nm; (2) Vinyl trimethoxysilane was added to an ethanol aqueous 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 mixed solution; polyethylene glycol dimethacrylate (average molecular weight of 600) was dissolved in tetrahydrofuran at a mass ratio of 1:10 and added to the mixed solution, and then a free radical initiator was added. The mass ratio of vinyl trimethoxysilane, 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 a polymer; (3) The polymer and the modified phosphor were added to an ethanol aqueous solution at a mass ratio of 0.036:1, and the mass ratio of the modified phosphor to the ethanol aqueous solution was 1:10. After ultrasonic dispersion for 30 minutes, the pH was adjusted to 6.5-7.5, and then stirred at 60 ° C for 6 hours. After the reaction was completed, the mixture was centrifuged, washed and dried to obtain fluorescent composite particles; (4) Based on the total mass percentage of 100%, the acrylic adhesive, coating particles, fluorescent composite particles and organic solvent (ethyl acetate) were mixed and stirred in a ratio of 38.5%: 3.6%: 1%: 56.9%, with a stirring rate of 1000 r / min and a stirring time of 1 h to obtain a coating liquid; the coating liquid was coated on the reflective film base film with a coating thickness of 6.4 ± 0.1 μm, and then cured at 85 ° C for 2 min, and then UV cured, with the UV energy controlled at 400 mJ / cm 2 , and obtain a coated optical reflective film.

[0040] Comparative Example 4 Difference from Example 1: polyethylene glycol dimethacrylate was not added.

[0041] (1) The phosphor was dispersed in an ethanol-water solution at a mass ratio of 1:50 and ultrasonically dispersed for 1 h to obtain a mixed solution; the pH of the mixed solution was adjusted to 4-5, ethyl silicate and ammonia water were added, and the mass ratio of phosphor, ethyl silicate and ammonia water was 1:1.2:0.35, and ultrasonic stirring was carried out at 60 °C for 7 h; after centrifugal separation and drying, the mixture was heated at a heating rate of 2 °C / min and calcined at 450 °C for 2 h to obtain a modified phosphor. The thickness of the silica coating layer in the modified phosphor was 17±1 nm; (2) Methacryloxypropylmethyldimethoxysilane was added to an ethanol aqueous 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 mixed solution; a free radical initiator was added to the mixed solution, the mass ratio of methacryloxypropylmethyldimethoxysilane to the free radical initiator was 0.4:0.003, and the mixture was heated to 70°C under nitrogen protection for 7 hours. After the reaction was completed, the mixture was centrifuged, washed, and dried to obtain a polymer; (3) The polymer and the modified phosphor were added to an ethanol aqueous solution at a mass ratio of 0.036:1, and the mass ratio of the modified phosphor to the ethanol aqueous solution was 1:10. After ultrasonic dispersion for 30 minutes, the pH was adjusted to 6.5-7.5, and then stirred at 60 ° C for 6 hours. After the reaction was completed, the mixture was centrifuged, washed and dried to obtain fluorescent composite particles; (4) Based on the total mass percentage of 100%, the acrylic adhesive, coating particles, fluorescent composite particles and organic solvent (ethyl acetate) were mixed and stirred in a ratio of 38.5%: 3.6%: 1%: 56.9%, with a stirring rate of 1000 r / min and a stirring time of 1 h to obtain a coating liquid; the coating liquid was coated on the reflective film base film with a coating thickness of 6.4 ± 0.1 μm, and then cured at 85 ° C for 2 min, and then UV cured, with the UV energy controlled at 400 mJ / cm 2 , and obtain a coated optical reflective film.

[0042] Comparative Example 5 The difference from Example 1 is that the molecular weight of polyethylene glycol dimethacrylate is too large and the added amount is too much.

[0043] (1) The phosphor was dispersed in an ethanol-water solution at a mass ratio of 1:50 and ultrasonically dispersed for 1 h to obtain a mixed solution; the pH of the mixed solution was adjusted to 4-5, ethyl silicate and ammonia water were added, and the mass ratio of phosphor, ethyl silicate and ammonia water was 1:1.2:0.35, and ultrasonic stirring was carried out at 60 °C for 7 h; after centrifugal separation and drying, the mixture was heated at a heating rate of 2 °C / min and calcined at 450 °C for 2 h to obtain a modified phosphor. The thickness of the silica coating layer in the modified phosphor was 17±1 nm; (2) Methacryloxypropylmethyldimethoxysilane was added to an ethanol aqueous 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 mixed solution; polyethylene glycol dimethacrylate (average molecular weight 750) was dissolved in tetrahydrofuran at a mass ratio of 1:15 and added to the mixed solution, 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 a polymer; (3) The polymer and the modified phosphor were added to an ethanol aqueous solution at a mass ratio of 0.036:1, and the mass ratio of the modified phosphor to the ethanol aqueous solution was 1:10. After ultrasonic dispersion for 30 minutes, the pH was adjusted to 6.5-7.5, and then stirred at 60 ° C for 6 hours. After the reaction was completed, the mixture was centrifuged, washed and dried to obtain fluorescent composite particles; (4) Based on the total mass percentage of 100%, the acrylic adhesive, coating particles, fluorescent composite particles and organic solvent (ethyl acetate) were mixed and stirred in a ratio of 38.5%: 3.6%: 1%: 56.9%, with a stirring rate of 1000 r / min and a stirring time of 1 h to obtain a coating liquid; the coating liquid was coated on the reflective film base film with a coating thickness of 6.4 ± 0.1 μm, and then cured at 85 ° C for 2 min, and then UV cured, with the UV energy controlled at 400 mJ / cm 2 , and obtain a coated optical reflective film.

[0044] Table 1

[0045] Note: The relative center brightness of each embodiment / comparative example is the percentage of the center brightness of each embodiment / comparative example relative to the center brightness of the EST150 base film; the relative average brightness of each embodiment / comparative example is the percentage of the average brightness of each embodiment / comparative example relative to the average brightness of the EST150 base film.

[0046] As shown in Table 1, the coated optical reflective film in Comparative Example 1 lacks phosphor, resulting in a slightly lower luminance than the EST150 base film. While phosphor is added to the coated optical reflective film in Comparative Example 2, the untreated phosphor has poor dispersion in the adhesive system, leading to agglomeration and formation of large clusters, which exacerbate light scattering and reduce luminance. In contrast, Examples 1-3 of the present invention utilize surface-treated fluorescent composite particles, resulting in coated optical reflective films with higher luminance and uniformity.

[0047] In addition, in Comparative Example 3, other silane coupling agents containing double bonds are used. Due to their fast reaction rate, the polymer molecular weight is easily out of control, the system viscosity increases dramatically, the phosphor is easily agglomerated, and light scattering is enhanced, resulting in lower brightness and poor uniformity.

[0048] In Comparative Example 4, since methacryloxypropylmethyldimethoxysilane is used alone, it will directly condense with the phosphor, lack the buffering of the flexible chain segment, easily crack, and is not conducive to the formation of the coating layer. In addition, the dispersibility of the phosphor in the glue system will be reduced, resulting in lower brightness and uniformity.

[0049] In Comparative Example 5, the molecular weight of polyethylene glycol dimethacrylate is too large and the amount added is too much, which will result in a larger molecular chain of the polymer and greater steric hindrance. In addition, the silane group in the molecular chain is difficult to effectively react with the hydroxyl group on the surface of the modified phosphor, resulting in poor uniformity of the coating layer of the fluorescent composite particles, and low brightness and uniformity.

[0050] The above are only preferred embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the description of the present invention, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A method for preparing a high-brightness coating type optical reflective film, characterized in that: The method comprises the following steps: mixing an acrylic adhesive, coating particles, fluorescent composite particles, and an organic solvent in a mass ratio of 35-40%: 3.5-4.2%: 0.8-1.5%: 50-60% to obtain a coating liquid; applying the coating liquid on a reflective film base film, and performing UV curing to obtain a coating-type optical reflective film; Among them, the fluorescent composite particles are prepared by sequentially coating the surface of the phosphor with silica and polymer; the polymer is prepared by adding methacryloxypropylmethyldimethoxysilane, polyethylene glycol dimethacrylate and free radical initiator into an organic solvent in a mass ratio of 0.2~0.4:1:0.002~0.003 for reaction.

2. The method for preparing a high-brightness coating type optical reflective film according to claim 1, characterized in that: The specific steps of preparing the fluorescent composite particles include: coating the surface of the fluorescent powder with silicon dioxide to obtain a modified fluorescent powder; adding the polymer and the modified fluorescent powder into an ethanol aqueous solution for ultrasonic dispersion, and then stirring the mixture for reaction to obtain the fluorescent composite particles.

3. The method for preparing a high-brightness coating type optical reflective film according to claim 1 or 2, characterized in that: The thickness of the silicon dioxide coating layer in the fluorescent composite particles is 15-25 nm.

4. The method for preparing a high-brightness coating type optical reflective film according to claim 2, wherein: 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° C. for 6-8 hours.

5. The method for preparing a high-brightness coating type optical reflective film according to claim 1 or 2, characterized in that: The specific steps of preparing the polymer include: adding methacryloxypropylmethyldimethoxysilane to an ethanol aqueous 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, reacting for 6-8 hours, and finally centrifuging, washing, and drying to obtain the polymer.

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

7. The method for preparing a high-brightness coating type optical reflective film according to claim 1, characterized in that: 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.

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

9. The method for preparing a high-brightness coating type optical reflective film according to claim 1 or 7, characterized in that: The UV curing is carried out at 80-90°C for 2-4 minutes, and then UV curing is carried out, and the UV energy is controlled at 300-500 mJ / cm 2 .

10. Use of the high-brightness coating type optical reflective film prepared by the preparation method according to any one of claims 1 to 9 in optical elements.

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