Brightness enhancing film and preparation method thereof

Abstract

This application belongs to the technical field of functional films and specifically discloses a brightness-enhancing film and its preparation method. The brightness-enhancing film of the present application comprises, from the outside to the inside, a brightness-enhancing layer, a substrate layer, and a protective layer. A first coating layer is disposed between the brightness-enhancing layer and the substrate layer, and a second coating layer is disposed between the substrate layer and the protective layer. Both the first coating layer and the second coating layer are made of a modified polyurethane acrylate adhesive. By configuring both the first coating layer and the second coating layer of the brightness-enhancing film to be a modified polyurethane acrylate adhesive with high fastness properties, the prepared brightness-enhancing film achieves the function of converging light while maintaining a more secure connection between the various layers and meeting water-boiling resistance standards.

Description

Technical Field

[0001] The present application relates to the technical field of functional films, and in particular to a brightness enhancement film and a preparation method thereof. Background Art

[0002] Brightness enhancement film is a new type of high-performance optical film used in TFT and LCD backlight modules to improve the luminous efficiency of the backlight system. Its principle is to refract and reflect light through a micro-prism structure, so that light that meets a certain angle is emitted. In other words, the light emission angle is controlled. Light that does not meet the angle is refracted by the prism and returned to the backlight module to be reused. Ultimately, the light that is emitted outside the observer's field of view is focused within the observer's field of view, enhancing the observer's normal brightness, thereby improving the luminous efficiency of the light-emitting module and the light energy utilization rate of the light source.

[0003] Existing brightness-enhancing films utilize a molding process, where a unique prismatic structure is attached to a substrate coated with the brightness-enhancing film. This creates a film that can enhance light source brightness and adjust the angle of light beam convergence. Currently, brightness-enhancing films are widely used in LCD displays, such as televisions, monitors, and mobile phone screens, to increase display brightness and conserve battery life.

[0004] In response to the aforementioned technology, the inventors believe that most existing brightness enhancement film products have poor bonding strength between the brightness enhancement layer and the substrate layer, and often fail to meet boiling water resistance standards, which significantly affects the lifespan of the brightness enhancement film. Therefore, it is necessary to develop a brightness enhancement film with excellent bonding strength between the layers. Summary of the Invention

[0005] In order to improve the connection strength between the various layer structures in the brightness enhancement layer, the present application provides a brightness enhancement film and a preparation method thereof.

[0006] In the first aspect, the present application provides a brightness enhancement film, which adopts the following technical solution:

[0007] A brightness enhancing film comprises, from the outside to the inside, a brightness enhancing layer, a substrate layer and a protective layer. A first coating layer is provided between the brightness enhancing layer and the substrate layer, and a second coating layer is provided between the substrate layer and the protective layer. Both the first coating layer and the second coating layer are modified polyurethane acrylate adhesive.

[0008] By adopting the above technical solution, a highly adhesive modified polyurethane acrylate adhesive is applied to both sides of a polyester blend substrate layer. A prismatic brightness enhancement layer and a polyester blend protective layer are then assembled and bonded to each side of the substrate layer. The brightness enhancement layer converges light penetrating from the bottom, thereby enhancing the brightness of the brightness enhancement film. The protective layer prevents damage to the functional layer structure of the brightness enhancement film during installation in the backlight module. A modified polyurethane acrylate adhesive layer is formed on both sides of the substrate layer to enhance the bonding strength of the composite film structure within the brightness enhancement film. Furthermore, relevant water-boiling-resistant functional materials are introduced into the substrate layer and the modified polyurethane acrylate adhesive layer for modification to further ensure that the brightness enhancement film product meets water-boiling-resistant test standards.

[0009] Preferably, the modified polyurethane acrylate rubber material comprises the following raw materials in parts by weight: 25-40 parts of dimethylol propionic acid, 42-48 parts of isophorone diisocyanate, 45-56 parts of trihydroxy polyoxypropylene ether, 14-18 parts of 3-methacryloxypropyltrimethoxysilane, 8-10 parts of tridecafluoroheptanol, 4-10 parts of 1-methyl-2-pyrrolidone, 3-6 parts of trimethylolpropane, 40-50 parts of acrylate oligomer, 1-1.8 parts of catalyst, 3-5 parts of defoaming agent, 4-8 parts of salt-forming agent, and 1.5-3 parts of inorganic particles;

[0010] Wherein, the catalyst is an organotin catalyst;

[0011] The defoaming agent is tetramethyldecynediol;

[0012] The salt-forming agent is triethylamine;

[0013] The inorganic particles are one or more of chromium oxide and nickel oxide.

[0014] By adopting the above technical solution, the modified polyurethane acrylate adhesive is prepared by using isophorone diisocyanate, trihydroxy polyoxypropylene ether and acrylate oligomer as main raw materials to synthesize polyurethane acrylate polymer. While having strong adhesion of polyurethane adhesive, the prepared adhesive also has good water boiling resistance due to the hydrophilic groups contained in the acrylate monomer; the main colloid is compositely modified with dimethylol propionic acid and silane coupling agent, firstly using dimethylol propionic acid to extend the chain of the prepolymer and at the same time introducing the hydrophilic group carboxyl group, so that the hydrophilic group of the molecular chain is reduced. Increasing the water content enhances the hydration of polymer molecules, reduces intertwining of molecular chains, and promotes microphase dispersion of the polymer phase, increasing the number of latex particles and correspondingly reducing their particle size, enabling better self-emulsification of the prepolymer. 3-Methacryloxypropyltrimethoxysilane and tridecafluoroheptanol are then used to synthesize a silane coupling agent for modification. The hydrolysis reaction generates silanol groups, one end of which condenses with the hydroxyl groups in the polyester components of the brightening layer, substrate layer, and protective layer to form silanol bonds, forming a cross-linked or interpenetrating network structure, improving the connectivity between the functional layers. The other end connects to the main body of the colloid, transforming the original hydrophilic surface into a lipophilic surface, effectively preventing particle agglomeration and improving its dispersibility.

[0015] In addition, the organic tin catalyst selected as the catalyst can avoid side reactions during the catalytic process, and does not require post-processing after the reaction is complete, which can shorten the production cycle and maintain relatively high and stable catalytic efficiency; tetramethyldecynediol selected as the defoaming agent has a high surface tension difference and can quickly destroy the elastic membrane of the bubble, and has good compatibility with other surfactants in the system and will not cause foaming; triethylamine selected as the salt-forming agent has strong alkalinity to completely neutralize the reaction and promote emulsification in the system to obtain a better emulsion effect; chromium oxide and nickel oxide are selected as inorganic particles to fill the adhesive layer, which can effectively capture free radicals generated during thermal aging to prevent the oxidation of molecular chain side groups, thereby improving the heat resistance of the adhesive layer.

[0016] Preferably, the preparation method of the modified polyurethane acrylate rubber material comprises the following steps:

[0017] S1. Mix dimethylolpropionic acid and trihydroxy polyoxypropylene ether under a vacuum degree of less than 0.36 kPa, and heat to 105-110° C. to remove moisture for 1-1.5 hours to prepare a mixed initial solution;

[0018] S2, cooling the mixed initial solution in step S1 to 70-80° C., adding isophorone diisocyanate, 1-methyl-2-pyrrolidone and a catalyst, and mixing and reacting for 2-4 hours to obtain a reaction solution;

[0019] S3, adding acrylate oligomer to the reaction solution in step S2 and reacting for 1-2 hours, then adding trimethylolpropane and mixing evenly, reacting for 20-30 minutes to obtain a cross-linked mixture;

[0020] S4. Cool the crosslinked mixed solution in step S3 to 55-60° C., add 3-methacryloxypropyltrimethoxysilane, tridecafluoroheptanol and a salt-forming agent, and mix and react for 30-40 minutes. Then, add inorganic particles with stirring at a speed of 60-80 r / min, add a defoaming agent and mix evenly, and then add water for emulsification to obtain a modified polyurethane acrylate rubber material.

[0021] By adopting the above technical solution, dimethylolpropionic acid, trihydroxy polyoxypropylene ether and isophorone diisocyanate are initially reacted to increase the hard segment content in the polymer, increase the probability of the -NCO group on the end group of the prepolymer to react with water, and generate more urea bonds, biuret, etc. during emulsification, thereby increasing the cohesive force in the molecule, thereby improving the adhesion and peel strength of the adhesive layer; then, a silane coupling agent is introduced to make the relative molecular mass in the emulsion moderate, which can not only ensure the wettability of the adhesive to the substrate layer, but also provide sufficient cohesive strength, so that the product adhesive layer has good initial adhesion; finally, other additives are added to further improve the comprehensive performance of the modified polyurethane acrylate adhesive.

[0022] Preferably, the brightness enhancement layer comprises a plurality of prisms arranged side by side and attached to the first coating layer, wherein the prisms comprise the following raw materials in parts by weight: 20-60 parts of monomer, 30-70 parts of oligomer, and 5-10 parts of photoinitiator;

[0023] wherein the monomer is one or more of ditrimethylolpropane tetraacrylate and dipentaerythritol pentaacrylate;

[0024] The oligomer is a polyester acrylate oligomer;

[0025] The photoinitiator is an oxime ester type photoinitiator.

[0026] By adopting the above technical solution, the use of ditrimethylolpropane tetraacrylate and dipentaerythritol pentaacrylate as multifunctional monomers not only adjusts the viscosity of the system by dissolving and diluting the oligomers, but also influences the cure rate of the brightening layer by participating in the photocuring process. Polyester acrylate oligomers, as relatively low-molecular-weight photosensitive polymers, possess groups that undergo photocuring reactions. They are typically derived from the esterification of polyester polyols with acrylic acid. The resulting brightening layer exhibits excellent solvent and heat resistance. Furthermore, polyester acrylate oligomers enhance the elasticity of the brightening layer, addressing the issue of easily damaged prismatic structures on its surface. Because the imino groups in polyurethane can form hydrogen bonds with carbonyl groups and ester carbonyl groups, hydrogen bonding between polymer chains effectively improves the elasticity and strength of the brightening layer. Secondly, since polyurethane is a copolymer composed of alternating soft segments and hard segments, the hard segments are dispersed in the soft segment matrix to act as physical cross-links, which can also make the brightening layer exhibit rubber-like elastic properties; oxime ester photoinitiators have high photosensitivity. Under light excitation, the weak NO bond in the oxime ester breaks, generating unstable acyloxy free radicals, which release carbon dioxide after decarboxylation to produce highly active free radical initiation reactions, thereby having high photoinitiation performance.

[0027] Preferably, the method for preparing the polyester acrylate oligomer comprises the following steps:

[0028] S1. Add toluene and 9,9-bis[4-(2-hydroxyethoxy)phenyl]fluorene and mix evenly. After they are completely dissolved, add phthalic anhydride, p-toluenesulfonic acid, and 2,6-di-tert-butyl-p-cresol in sequence, heat to 65-80°C, and react for 2-3 hours to obtain an initial reaction solution.

[0029] S2, cooling the initial reaction solution in step S1 to 40-50° C., sequentially adding 2,6-di-tert-butyl-p-cresol and hydroxyethyl acrylate to the mixture for reaction, sampling and testing the acid value every 1 h, and stopping the reaction when the acid value drops to 40 mgKOH / g to obtain a reaction intermediate solution;

[0030] S3. Add 30 wt.% of o-phenylphenoxyethyl acrylate monomer to the reaction intermediate solution in step S2, heat to 60-70° C., react for 40-50 minutes, and obtain the polyester acrylate oligomer after vacuum distillation and filtration purification.

[0031] By adopting the above-mentioned technical solution, the introduction of 9,9-bis[4-(2-hydroxyethoxy)phenyl]fluorene into the structure of polyester acrylate oligomers can impart a high refractive index to the oligomers, while also possessing excellent properties such as high heat resistance, high transparency, and low cure shrinkage. When synthesizing polyester acrylate oligomers with a fluorene backbone, a diol with a fluorene backbone is first subjected to a semi-esterification reaction with an intracyclic monoanhydride, which results in an anhydride ring-opening reaction. Subsequently, an esterification reaction is performed with a monoalcohol with an acrylic acid structure and the residual carboxyl groups in the reaction product from the previous step. This allows for excellent control of the molecular weight of the oligomer, resulting in a polyester acrylate oligomer with low viscosity and a high refractive index.

[0032] Preferably, the material of the substrate layer includes polyethylene terephthalate (PET), polyethylene naphthalate (PEN), glass fiber and a compatibilizer, the mass ratio of the polyethylene terephthalate, the polyethylene naphthalate and the glass fiber is 1: (0.40-0.70): (0.05-0.10), and the compatibilizer is polypropylene grafted maleic anhydride.

[0033] By adopting the above technical solution, polyethylene naphthalate (PE) and polyethylene terephthalate (PET) are melt-blended as the main raw materials to produce the substrate layer. Due to their similar structures, PEN and PET exhibit good compatibility. In the PEN molecular structure, the benzene rings found in PET are replaced by the more rigid naphthalene rings, which have a more stable resonance structure than benzene rings. This results in a more rigid molecular chain and a more planar structure, resulting in a PET / PEN blend with higher glass transition temperature, crystallization temperature, and melting point. The addition of alkali-free glass fiber and a thermally stable compatibilizer enhances the boiling resistance of the organic polymer layer. Due to the hydrophilic hydroxyl groups on the glass fiber surface and the hydrophilicity of the polypropylene-grafted maleic anhydride compatibilizer, water molecules are less likely to penetrate the organic polymer within the temperature range and disrupt the glass fiber bonding structure. Furthermore, the incorporation of glass fiber imparts a certain haze to the substrate layer, which can be used to mask imperfections in the backlight module.

[0034] Preferably, the material of the protective layer includes polyethylene terephthalate (PET), polycarbonate (PC) and an organosilicon compound, and the mass ratio of the polyethylene terephthalate, the polycarbonate and the organosilicon compound is 1:1:(0.05-0.15).

[0035] By adopting the above technical solution, colorless, transparent, and dimensionally stable polycarbonate is melt-blended with polyethylene terephthalate to produce a protective layer. Because PET and PC share similar end groups in their structures, they exhibit good compatibility. Blending PET with PC not only improves the stability of the melt within the protective layer, imparting high mechanical strength to the layer structure for improved processing performance, but also enhances the transparency of the protective layer, preventing light from being obstructed as it passes through it, reducing refraction and reflection, and further enhancing the focusing effect of the brightening layer. The PET / PC blend is modified using an organosilicon compound. The intermolecular interactions between organosilicon molecules are weak, and a linear relationship exists between their cross-linking degree and their hardness and flexibility. By modifying the structure of the organosilicon polymer to adjust the hardness and flexibility of the protective layer, the friction coefficient of the outer surface of the protective layer is further reduced, enhancing wear resistance. Furthermore, organosilicon compounds can significantly reduce the internal stress of the PET / PC blend, thereby improving the heat resistance of the protective layer.

[0036] In a second aspect, the present application provides a method for preparing a brightness enhancement film, comprising the following steps:

[0037] S1. Pre-treat the surface of the stretched substrate layer, evenly apply the modified polyurethane acrylate adhesive to one side of the substrate layer, then attach the stretched protective layer to the side of the substrate layer coated with the modified polyurethane acrylate adhesive, and cool and cure at room temperature for 1-1.5 hours;

[0038] S2, the modified polyurethane acrylate adhesive is evenly coated on the other side of the substrate layer, the brightening layer is coated on the side of the substrate layer coated with the modified polyurethane acrylate adhesive, and the brightness is enhanced at 400-600 MJ / cm 2 Under UV light irradiation, the brightness enhancement layer is rolled by a roller with a prism structure, and is shaped and cured for 20-30 minutes to obtain the brightness enhancement film.

[0039] By adopting the above technical solution, a substrate layer and a protective layer with stable quality are produced through a stretching film-forming process, and the modified polyurethane acrylate adhesive is evenly coated on both sides of the substrate layer, so that each layer structure is assembled and bonded in the order of its function. Then, by controlling the appropriate temperature and pressure, the curing speed of the modified polyurethane acrylate adhesive layer is accelerated; the brightening layer is quickly cured by a UV curing process, and the optical structure on the roller is copied to the brightening layer. It has the technical advantages of low production energy consumption (compared to thermal curing), low solvent emissions, excellent performance of the cured brightening layer, and high molding precision.

[0040] In summary, this application has the following beneficial effects:

[0041] 1. In the present application, the modified polyurethane acrylate adhesive is prepared by synthesizing a polyurethane acrylate polymer using isophorone diisocyanate, trihydroxy polyoxypropylene ether and acrylate oligomers as main raw materials. While having strong adhesion of polyurethane adhesive, the prepared adhesive also has good boiling resistance due to the hydrophilic groups contained in the acrylate monomers; the main colloid is compositely modified with dimethylolpropionic acid and silane coupling agent, and dimethylolpropionic acid is first used to extend the chain of the prepolymer while introducing hydrophilic groups such as carboxyl groups to increase the hydrophilicity of the molecular chain. The hydration of polymer molecules is increased, reducing the entanglement between molecular chains, which is beneficial to the microphase dispersion of the polymer phase, increasing the number of latex particles and correspondingly reducing the particle size, making the prepolymer more self-emulsifiable. 3-Methacryloxypropyltrimethoxysilane and tridecafluoroheptanol are then used to synthesize a silane coupling agent for modification. The silanol group generated by the hydrolysis reaction condenses with the hydroxyl groups in the polyester components of the brightening layer, substrate layer, and protective layer to form a silanol bond, forming a cross-linked or interpenetrating network structure, improving the connection between the functional layers. The other end connects to the main body of the colloid, transforming the original hydrophilic surface into a lipophilic surface, which can effectively prevent the aggregation of particles and improve their dispersion.

[0042] 2. In the present application, the prisms on the brightening layer are formed by using ditrimethylolpropane tetraacrylate and dipentaerythritol pentaacrylate as multifunctional monomers. This not only allows the viscosity of the system to be adjusted by dissolving and diluting the oligomers, but also affects the curing rate of the brightening layer by participating in the photocuring process. The polyester acrylate oligomers impart good solvent resistance and heat resistance to the prepared brightening layer, and also enhance the elasticity of the brightening layer, thereby resolving the problem of the prism structure on its surface being easily damaged. Since the imino groups in the polyurethane can form hydrogen bonds with the carbonyl groups and the ester carbonyl groups, the elasticity and strength of the brightening layer can be effectively improved through hydrogen bonding between the polymer chains. The oxime ester photoinitiator has high photosensitivity. Under light excitation, the weak NO bond in the oxime ester breaks, generating unstable acyloxy radicals. After decarboxylation, carbon dioxide is released to generate highly active free radical initiation reactions, thereby having high photoinitiation performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 This is a schematic diagram of the layer structure of a brightness enhancement film of the present application.

[0044] Description of reference numerals:

[0045] 1. Brightness enhancement layer; 2. Base material layer; 3. Protective layer; 4. First coating layer; 5. Second coating layer; 6. Prism body. DETAILED DESCRIPTION

[0046] The present application is further described in detail below with reference to the embodiments.

[0047] The raw materials used in the examples and comparative examples can all be obtained commercially.

[0048] Preparation Example

[0049] Preparation of modified polyurethane acrylate rubber

[0050] Preparation Example 0-1, a method for preparing a modified polyurethane acrylate rubber material, is prepared by the following method:

[0051] (1) Under a vacuum of less than 0.36 kPa, 32 g of dimethylol propionic acid and 50 g of trihydroxy polyoxypropylene ether were mixed and heated to 108° C. to remove moisture for 1.3 h to prepare a mixed initial solution;

[0052] (2) cooling the mixed initial solution in step (1) to 75° C., adding 45 g of isophorone diisocyanate, 7 g of 1-methyl-2-pyrrolidone and 1.4 g of a catalyst, and mixing and reacting for 3 h to obtain a reaction solution;

[0053] (3) adding 45 g of acrylate oligomer to the reaction solution in step (2) and reacting for 1.5 h, then adding 4.5 g of trimethylolpropane and mixing evenly, and reacting for 25 min to obtain a cross-linked mixed solution;

[0054] (4) The crosslinked mixed solution in step (3) was cooled to 58° C., 16 g of 3-methacryloyloxypropyltrimethoxysilane, 9 g of tridecafluoroheptanol and 6 g of a salt-forming agent were added and mixed for 35 min, 2.2 g of inorganic particles were added at a stirring speed of 70 r / min, and 4 g of a defoaming agent was added and mixed evenly, and then water was added for emulsification to obtain a modified polyurethane acrylate rubber material.

[0055] Preparation Example 0-2, a method for preparing a modified polyurethane acrylate rubber compound, is prepared by the following method:

[0056] (1) Under a vacuum of less than 0.36 kPa, 40 g of dimethylol propionic acid and 56 g of trihydroxy polyoxypropylene ether were mixed and heated to 110° C. to remove moisture for 1.5 hours to prepare a mixed initial solution;

[0057] (2) cooling the mixed initial solution in step (1) to 80° C., adding 48 g of isophorone diisocyanate, 10 g of 1-methyl-2-pyrrolidone and 1.8 g of a catalyst, and mixing and reacting for 4 h to obtain a reaction solution;

[0058] (3) adding 50 g of acrylate oligomer to the reaction solution in step (2) and reacting for 2 h, then adding 6 g of trimethylolpropane and mixing evenly, and reacting for 30 min to obtain a cross-linked mixed solution;

[0059] (4) The crosslinked mixed solution in step (3) was cooled to 60° C., 18 g of 3-methacryloyloxypropyltrimethoxysilane, 10 g of tridecafluoroheptanol and 8 g of a salt-forming agent were added and mixed for 40 min, 3 g of inorganic particles were added at a stirring speed of 80 r / min, and 5 g of a defoaming agent was added and mixed evenly, and then water was added for emulsification to obtain a modified polyurethane acrylate rubber material.

[0060] Preparation Example 0-3, a method for preparing a modified polyurethane acrylate rubber compound, is prepared by the following method:

[0061] (1) Under a vacuum degree of less than 0.36 kPa, 25 g of dimethylol propionic acid and 45 g of trihydroxy polyoxypropylene ether were mixed and heated to 105° C. to remove moisture for 1 hour to prepare a mixed initial solution;

[0062] (2) cooling the mixed initial solution in step (1) to 70° C., adding 42 g of isophorone diisocyanate, 4 g of 1-methyl-2-pyrrolidone and 1 g of a catalyst, and mixing and reacting for 2 h to obtain a reaction solution;

[0063] (3) adding 40 g of acrylate oligomer to the reaction solution in step (2) and reacting for 1 h, then adding 3 g of trimethylolpropane and mixing evenly, and reacting for 20 min to obtain a cross-linked mixed solution;

[0064] (4) The crosslinked mixed solution in step (3) was cooled to 55° C., 14 g of 3-methacryloyloxypropyltrimethoxysilane, 8 g of tridecafluoroheptanol and 4 g of a salt-forming agent were added and mixed for 30 min, 1.5 g of inorganic particles were added at a stirring speed of 60 r / min, and 3 g of a defoaming agent was added and mixed evenly, and then water was added for emulsification to obtain a modified polyurethane acrylate rubber material.

[0065] Preparation Example 0-4 is a method for preparing a modified polyurethane acrylate rubber material, which differs from Preparation Example 0-1 in that dimethylolpropionic acid is not added in step (1).

[0066] Preparation Example 0-5 is a method for preparing a modified polyurethane acrylate rubber material, which differs from Preparation Example 0-1 in that trimethylolpropane is not added in step (3).

[0067] Preparation Example 0-6, a method for preparing a modified polyurethane acrylate rubber compound, differs from Preparation Example 0-1 in that 3-methacryloxypropyltrimethoxysilane and tridecafluoroheptanol are not added in step (4).

[0068] Preparation of polyester acrylate oligomers

[0069] Preparation Example 1-1, a method for preparing a polyester acrylate oligomer, is prepared by the following method:

[0070] (1) Add 30 g of toluene and 42 g of 9,9-bis[4-(2-hydroxyethoxy)phenyl]fluorene and mix them evenly. After they are completely dissolved, add 32 g of phthalic anhydride, 26 g of p-toluenesulfonic acid, and 20 g of 2,6-di-tert-butyl-p-cresol in sequence, heat to 72°C, and react for 2.5 hours to obtain an initial reaction solution.

[0071] (2) Cooling the initial reaction solution in step (1) to 45° C., sequentially adding 30 g of 2,6-di-tert-butyl-p-cresol and 18 g of hydroxyethyl acrylate to the mixture for reaction, sampling and detecting the acid value every 1 h, and stopping the reaction when the acid value drops to 40 mgKOH / g to obtain a reaction intermediate solution;

[0072] (3) Add 44 g of 30 wt.% o-phenylphenoxyethyl acrylate monomer to the reaction intermediate solution in step (2), heat to 65° C., react for 45 minutes, and obtain polyester acrylate oligomers after vacuum distillation and filtration purification.

[0073] Preparation Example 1-2, a method for preparing a polyester acrylate oligomer, is prepared by the following method:

[0074] (1) Add 35 g of toluene and 44 g of 9,9-bis[4-(2-hydroxyethoxy)phenyl]fluorene and mix them evenly. After they are completely dissolved, add 36 g of phthalic anhydride, 30 g of p-toluenesulfonic acid, and 23 g of 2,6-di-tert-butyl-p-cresol in sequence, heat to 80°C, and react for 3 h to obtain an initial reaction solution.

[0075] (2) The initial reaction solution in step (1) was cooled to 50° C., 34 g of 2,6-di-tert-butyl-p-cresol and 19 g of hydroxyethyl acrylate were added in sequence for mixed reaction, and the acid value was detected every 1 h. When the acid value dropped to 40 mgKOH / g, the reaction was stopped to obtain a reaction intermediate solution;

[0076] (3) Add 46 g of 30 wt.% o-phenylphenoxyethyl acrylate monomer to the reaction intermediate solution in step (2), heat to 70° C., react for 50 min, and obtain polyester acrylate oligomers after vacuum distillation and filtration purification.

[0077] Preparation Example 1-3, a method for preparing a polyester acrylate oligomer, is prepared by the following method:

[0078] (1) Add 25 g of toluene and 40 g of 9,9-bis[4-(2-hydroxyethoxy)phenyl]fluorene and mix them evenly. After they are completely dissolved, add 28 g of phthalic anhydride, 22 g of p-toluenesulfonic acid, and 17 g of 2,6-di-tert-butyl-p-cresol in sequence, heat to 65°C, and react for 2 h to obtain an initial reaction solution.

[0079] (2) The initial reaction solution in step (1) was cooled to 40° C., 26 g of 2,6-di-tert-butyl-p-cresol and 17 g of hydroxyethyl acrylate were added in sequence and mixed for reaction. The acid value was detected every 1 h. When the acid value dropped to 40 mgKOH / g, the reaction was stopped to obtain a reaction intermediate solution.

[0080] (3) Add 42 g of 30 wt.% o-phenylphenoxyethyl acrylate monomer to the reaction intermediate solution in step (2), heat to 60° C., react for 40 min, and obtain polyester acrylate oligomers after vacuum distillation and filtration purification.

[0081] Preparation Example 1-4, a method for preparing a polyester acrylate oligomer, differs from Preparation Example 1-1 in that in step (2), samples are taken every 1 hour to detect the acid value. When the acid value drops to 55 mgKOH / g, the reaction is stopped to obtain a reaction intermediate solution.

[0082] Example

[0083] Example 1, a brightness enhancement film, a method for preparing the brightness enhancement film, comprising the following steps:

[0084] (1) The stretched substrate layer was subjected to surface pretreatment, and the modified polyurethane acrylate adhesive was evenly coated on one side of the substrate layer. Then, the stretched protective layer was attached to the side of the substrate layer coated with the modified polyurethane acrylate adhesive, and cooled and cured at room temperature for 1.2 hours;

[0085] (2) The modified polyurethane acrylate adhesive is evenly coated on the other side of the substrate layer, and the brightening layer is coated on the side of the substrate layer coated with the modified polyurethane acrylate adhesive. 2 Under UV light, the brightening layer is rolled by a roller with a prism structure, and the brightening layer is formed and cured for 25 minutes to obtain a brightening film.

[0086] The modified polyurethane acrylate rubber material is derived from Preparation Example 0-1, and the polyester acrylate oligomer is derived from Preparation Example 1-1.

[0087] Example 2, a brightness enhancement film, a method for preparing the brightness enhancement film, comprising the following steps:

[0088] (1) The stretched substrate layer was subjected to surface pretreatment, and the modified polyurethane acrylate adhesive was evenly coated on one side of the substrate layer. Then, the stretched protective layer was attached to the side of the substrate layer coated with the modified polyurethane acrylate adhesive, and cooled and cured at room temperature for 1.5 hours;

[0089] (2) The modified polyurethane acrylate adhesive is evenly coated on the other side of the substrate layer, and the brightening layer is coated on the side of the substrate layer coated with the modified polyurethane acrylate adhesive. 2Under UV light, the brightening layer is rolled by a roller with a prism structure, and the brightening layer is formed and cured for 30 minutes to obtain a brightening film.

[0090] The modified polyurethane acrylate rubber material is derived from Preparation Example 0-1, and the polyester acrylate oligomer is derived from Preparation Example 1-1.

[0091] Example 3, a brightness enhancement film, a method for preparing the brightness enhancement film, comprising the following steps:

[0092] (1) The stretched substrate layer was subjected to surface pretreatment, and the modified polyurethane acrylate adhesive was evenly coated on one side of the substrate layer. Then, the stretched protective layer was attached to the side of the substrate layer coated with the modified polyurethane acrylate adhesive, and cooled and cured at room temperature for 1 hour;

[0093] (2) The modified polyurethane acrylate adhesive is evenly coated on the other side of the substrate layer, and the brightening layer is coated on the side of the substrate layer coated with the modified polyurethane acrylate adhesive. 2 Under UV light irradiation, the brightening layer is rolled by a roller with a prism structure, and the brightening layer is formed and cured for 20 minutes to obtain a brightening film.

[0094] The modified polyurethane acrylate rubber material is derived from Preparation Example 0-1, and the polyester acrylate oligomer is derived from Preparation Example 1-1.

[0095] Example 4 is a brightness enhancement film, which differs from Example 1 in that the modified polyurethane acrylate adhesive is derived from Preparation Example 0-2, and the polyester acrylate oligomer is derived from Preparation Example 1-2.

[0096] Example 5 is a brightness enhancement film, which differs from Example 1 in that the modified polyurethane acrylate adhesive is derived from Preparation Examples 0-3, and the polyester acrylate oligomer is derived from Preparation Examples 1-3.

[0097] Example 6 is a brightness enhancement film, which differs from Example 1 in that the modified polyurethane acrylate adhesive is derived from Preparation Example 0-4.

[0098] Example 7, a brightness enhancement film, differs from Example 1 in that the modified polyurethane acrylate adhesive is derived from Preparation Example 0-5.

[0099] Example 8 is a brightness enhancement film, which differs from Example 1 in that the modified polyurethane acrylate adhesive is derived from Preparation Example 0-6.

[0100] Example 9 is a brightness enhancement film, which is different from Example 1 in that the polyester acrylate oligomer is derived from Preparation Example 1-4.

[0101] Example 10 is a brightness enhancement film, which differs from Example 1 in that glass fiber and compatibilizer are not added to the material of the substrate layer.

[0102] Example 11 is a brightness enhancement film, which differs from Example 1 in that no organosilicon compound is added to the material of the protective layer.

[0103] Comparative Example

[0104] Comparative Example 1 is a brightness enhancement film, which differs from Example 1 in that, in the preparation method of the modified polyurethane acrylate rubber compound, dimethylolpropionic acid is replaced by an equal amount of 3,5-dimethylthiotoluenediamine.

[0105] Comparative Example 2 is a brightness enhancement film, which differs from Example 1 in that, in the preparation method of the modified polyurethane acrylate adhesive, 3-methacryloxypropyltrimethoxysilane and tridecafluoroheptanol are replaced by an equal amount of carbodiimide.

[0106] Comparative Example 3 is a brightness enhancement film, which differs from Example 1 in that, in the preparation method of the polyester acrylate oligomer, an equal amount of 2-phenoxyethyl acrylate is used as the monomer instead of ditrimethylolpropane tetraacrylate and dipentaerythritol pentaacrylate.

[0107] Comparative Example 4 is a brightness enhancement film, which differs from Example 1 in that, in the preparation method of the polyester acrylate oligomer, an equal amount of acylphosphine oxide photoinitiator (TPO or TEPO) is used as the photoinitiator instead of the oxime ester photoinitiator.

[0108] Performance testing: Brightness-enhancing films were prepared according to the methods described in each Example and Comparative Example. Each film was cut into several standard squares measuring 50 cm x 50 cm. The standard squares were tested for peel strength, boiling water resistance, abrasion resistance, and light transmittance. For each Example or Comparative Example, three samples were tested, and the average results are reported in Table 1. The testing methods are as follows:

[0109] 1. Peel strength: Referring to GB / T 2970-1995, an electronic peeling machine was used to test the peel strength between the brightness enhancement layer and the substrate layer of the standard square. The test results are shown in Table 1.

[0110] 2. Boiling resistance: Place the standard cube in a beaker filled with an appropriate amount of deionized water, and then place the beaker in a constant temperature oil bath at 80°C. After 24 hours, observe whether the surface of the substrate has whitening, bubbling or falling off. The test results are shown in Table 1.

[0111] 3. Wear resistance: A 600-grit sandpaper loaded with a 100-g weight was rubbed evenly on the protective layer surface of the blank and standard squares at a constant speed 100 times. The weight was measured every 20 times, and the total wear weight loss was calculated. The test results are shown in Table 1.

[0112] 4. Light transmittance: The standard square was tested using the German BYK AT-4725 haze meter according to ASTM D1003. The test results are shown in Table 1.

[0113] Table 1

[0114]

[0115] Combining Examples 1-3, Comparative Example 1, and Table 1, the brightness enhancement films prepared from Examples 1-3 all exhibited superior peel strength to that of the brightness enhancement film prepared from Comparative Example 1. The brightness enhancement films prepared from Examples 1-3 also exhibited superior water boiling resistance to that of the brightness enhancement film prepared from Comparative Example 1, and the brightness enhancement films prepared from Examples 1-3 all exhibited superior light transmittance to that of the brightness enhancement film prepared from Comparative Example 1. The higher the peel strength, the stronger the adhesion between the layers. Test results indicate that dimethylolpropionic acid, as a hydrophilic chain extender, exhibits excellent compatibility with the system, effectively promoting emulsification of the prepolymer emulsion, exhibiting good hydrophilicity and adhesion, and producing uniform particle size. However, 3,5-dimethylthiotoluenediamine, containing two methylthio groups and two amino groups, can produce odorous sulfur-containing small molecules during prolonged reaction or at relatively high temperatures. It is also prone to degradation, resulting in a darker color of the adhesive layer, which not only affects the light transmittance of the brightness enhancement film product but also reduces its physical and mechanical properties. The brightness enhancement film prepared from Example 1 exhibits the best overall performance.

[0116] Combining Examples 1-3, Comparative Example 2, and Table 1, the peel strength of the brightness enhancement films prepared in Examples 1-3 was superior to that of the brightness enhancement film prepared in Comparative Example 2. The water boiling resistance of the brightness enhancement films prepared in Examples 1-3 was superior to that of the brightness enhancement film prepared in Comparative Example 2. Furthermore, the light transmittance of the brightness enhancement films prepared in Examples 1-3 was superior to that of the brightness enhancement film prepared in Comparative Example 2. The test results indicate that carbodiimide has poor compatibility with the system, making it ineffective in modifying the emulsion and affecting the effectiveness of other additives, resulting in a significant decrease in the water boiling resistance of the brightness enhancement film product.

[0117] Combining Examples 1-3, Comparative Example 3, and Table 1, the peel strength of the brightness enhancing films prepared in Examples 1-3 was superior to that of the brightness enhancing film prepared in Comparative Example 3, and the light transmittance of the brightness enhancing films prepared in Examples 1-3 was superior to that of the brightness enhancing film prepared in Comparative Example 3. These test results indicate that the use of monofunctional monomers instead of multifunctional monomers in the preparation of polyester acrylate oligomers does not result in the desired light-focusing effect of the resulting brightness enhancing films.

[0118] Combining Examples 1-3, Comparative Example 4, and Table 1, the peel strength of the brightness-enhancing films prepared in Examples 1-3 was superior to that of the brightness-enhancing film prepared in Comparative Example 3, and the light transmittance of the brightness-enhancing films prepared in Examples 1-3 was superior to that of the brightness-enhancing film prepared in Comparative Example 4. The test results indicate that acylphosphine oxide photoinitiators are cleavage-type photoinitiators, and their effective absorption wavelength is not ideal for absorption and initiation during UV curing of the brightness-enhancing layer. During the photoinitiation process, the cleavage of the PC bond within the chromophore within the molecule causes the original yellow color of the acylphosphine oxide to fade, resulting in photobleaching of the brightness-enhancing layer structure. Furthermore, acylphosphine oxide photoinitiators are relatively expensive, increasing production costs.

[0119] Combining Examples 1-3, 4, and 5 with Table 1, the overall performance of the brightness enhancement films prepared in Examples 1-3 is superior to that of the brightness enhancement films prepared in Examples 4 and 5. The test results show that the amount of each raw material added and the reaction conditions in the preparation of each layer of the brightness enhancement film have peak values ​​within the set ranges. Changing the reaction conditions or approaching the end values ​​of the material additions will affect the yield and performance.

[0120] Combining Examples 1-3, Examples 6-8, and Table 1, the peel strength of the brightness enhancement films prepared in Examples 1-3 was superior to that of the brightness enhancement film prepared in Example 6; the water boiling resistance of the brightness enhancement films prepared in Examples 1-3 was superior to that of the brightness enhancement films prepared in Examples 7 and 8. The test results indicate that dimethylolpropionic acid, as a direct crosslinking agent, has a direct impact on the adhesion of the modified rubber compound, while the combined modification of dimethylolpropionic acid and a silane coupling agent also has a significant impact on the water boiling resistance of the adhesive layer.

[0121] Combining Examples 1-3, Example 9 and Table 1, the transmittance of the brightness enhancement films prepared in Examples 1-3 is significantly better than that of the brightness enhancement film prepared in Example 9. The test results show that the preparation of the brightness enhancement layer has specific requirements for the calculation of the acid value of the reaction process.

[0122] Combining Examples 1-3, Example 10, and Table 1, the brightness enhancement films prepared in Examples 1-3 all exhibit significantly better water boiling resistance than the brightness enhancement film prepared in Example 9. The test results demonstrate that the alkali-free glass fiber and the thermally stable compatibilizer enhance the water boiling resistance of the organic polymer layer structure. Due to the hydrophilic hydroxyl groups on the glass fiber surface and the hydrophilicity of the polypropylene-grafted maleic anhydride compatibilizer, water molecules are less likely to penetrate the organic polymer within the temperature range and disrupt the glass fiber binding structure.

[0123] Combining Examples 1-3, Example 11, and Table 1, the brightness enhancement films prepared in Examples 1-3 all exhibit significantly better abrasion resistance than the brightness enhancement film prepared in Example 11. These test results demonstrate that modifying the structure of the organosilicon polymer to adjust the hardness and flexibility of the protective layer can further reduce the coefficient of friction on the outer surface of the protective layer and enhance its abrasion resistance.

[0124] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make non-creative modifications to the present embodiment as needed, but as long as they are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. A brightness enhancement film, characterized in that: The invention relates to a coating material comprising a brightness enhancement layer (1), a substrate layer (2) and a protective layer (3) in sequence from the outside to the inside, wherein a first coating layer (4) is provided between the brightness enhancement layer (1) and the substrate layer (2), and a second coating layer (5) is provided between the substrate layer (2) and the protective layer (3), and both the first coating layer (4) and the second coating layer (5) are modified polyurethane acrylate adhesive. The modified polyurethane acrylate rubber material comprises the following raw materials in parts by weight: 25-40 parts of dimethylol propionic acid, 42-48 parts of isophorone diisocyanate, 45-56 parts of trihydroxy polyoxypropylene ether, 14-18 parts of 3-methacryloxypropyltrimethoxysilane, 8-10 parts of tridecafluoroheptanol, 4-10 parts of 1-methyl-2-pyrrolidone, 3-6 parts of trimethylolpropane, 40-50 parts of acrylate oligomer, 1-1.8 parts of catalyst, 3-5 parts of defoaming agent, 4-8 parts of salt-forming agent, and 1.5-3 parts of inorganic particles; Wherein, the catalyst is an organotin catalyst; The defoaming agent is tetramethyldecynediol; The salt-forming agent is triethylamine; The inorganic particles are one or more of chromium oxide and nickel oxide; The brightness enhancement layer (1) comprises a plurality of prisms (6) arranged side by side and attached to the first coating layer (4), wherein the prisms (6) comprise the following raw materials in parts by weight: 20-60 parts of monomer, 30-70 parts of oligomer, and 5-10 parts of photoinitiator; wherein the monomer is one or more of ditrimethylolpropane tetraacrylate and dipentaerythritol pentaacrylate; The oligomer is a polyester acrylate oligomer; The photoinitiator is an oxime ester type photoinitiator; The preparation method of the polyester acrylate oligomer comprises the following steps: S1. Add toluene and 9,9-bis[4-(2-hydroxyethoxy)phenyl]fluorene and mix evenly. After they are completely dissolved, add phthalic anhydride, p-toluenesulfonic acid, and 2,6-di-tert-butyl-p-cresol in sequence, heat to 65-80°C, and react for 2-3 hours to obtain an initial reaction solution. S2, cooling the initial reaction solution in step S1 to 40-50° C., sequentially adding 2,6-di-tert-butyl-p-cresol and hydroxyethyl acrylate to the mixture for reaction, sampling and testing the acid value every 1 h, and stopping the reaction when the acid value drops to 40 mgKOH / g to obtain a reaction intermediate solution; S3. Add 30 wt.% of o-phenylphenoxyethyl acrylate monomer to the reaction intermediate solution in step S2, heat to 60-70° C., react for 40-50 min, and obtain the polyester acrylate oligomer after vacuum distillation and filtration purification.

2. A brightness enhancement film according to claim 1, characterized in that: The preparation method of the modified polyurethane acrylate rubber material comprises the following steps: S1. Mix dimethylolpropionic acid and trihydroxy polyoxypropylene ether under a vacuum degree of less than 0.36 kPa, and heat to 105-110° C. to remove moisture for 1-1.5 hours to prepare a mixed initial solution; S2, cooling the mixed initial solution in step S1 to 70-80° C., adding isophorone diisocyanate, 1-methyl-2-pyrrolidone and a catalyst, and mixing and reacting for 2-4 hours to obtain a reaction solution; S3, adding acrylate oligomer to the reaction solution in step S2 and reacting for 1-2 hours, then adding trimethylolpropane and mixing evenly, reacting for 20-30 minutes to obtain a cross-linked mixture; S4. Cool the crosslinked mixed solution in step S3 to 55-60° C., add 3-methacryloxypropyltrimethoxysilane, tridecafluoroheptanol and a salt-forming agent, and mix and react for 30-40 minutes. Then, add inorganic particles with stirring at a speed of 60-80 r / min, add a defoaming agent and mix evenly, and then add water for emulsification to obtain a modified polyurethane acrylate rubber material.

3. A brightness enhancement film according to claim 1, characterized in that: The material of the substrate layer (2) includes polyethylene terephthalate (PET), polyethylene naphthalate (PEN), glass fiber and a compatibilizer, wherein the mass ratio of the polyethylene terephthalate, the polyethylene naphthalate and the glass fiber is 1: (0.40-0.70): (0.05-0.10), and the compatibilizer is polypropylene grafted with maleic anhydride.

4. The brightness enhancement film according to claim 1, characterized in that: The material of the protective layer (3) includes polyethylene terephthalate (PET), polycarbonate (PC) and an organosilicon compound, and the mass ratio of the polyethylene terephthalate, the polycarbonate and the organosilicon compound is 1:1:(0.05-0.15).

5. A method for preparing a brightness enhancement film according to any one of claims 1 to 3, characterized in that: The following steps are involved: S1, subjecting the stretched substrate layer (2) to surface pretreatment, uniformly coating the modified polyurethane acrylate adhesive on one side of the substrate layer (2), and then attaching the stretched protective layer (3) to the side of the substrate layer (2) coated with the modified polyurethane acrylate adhesive, and cooling and curing at room temperature for 1-1.5 hours; S2. The modified polyurethane acrylate adhesive is evenly coated on the other side of the substrate layer (2), and the brightening layer (1) is coated on the side of the substrate layer (2) coated with the modified polyurethane acrylate adhesive. Under irradiation with a 400-600 MJ / cm2 UV lamp, the brightening layer (1) is rolled by a roller with a prism body (6) structure, and is formed and cured for 20-30 minutes to obtain the brightening film.

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