Electronic paper edge sealing UV glue, and preparation method and application thereof

Abstract

This application relates to the field of photocurable adhesives, and discloses an electronic paper edge-sealing UV adhesive, its preparation method, and its application. The electronic paper edge-sealing UV adhesive of this application uses a resin matrix, functional fillers, photoinitiators, and additives as raw materials. The resin matrix includes fluorinated polyurethane acrylate resin and hyperbranched polyester acrylate; the functional fillers include modified flake boron nitride and fumed silica; the photoinitiator is a free radical photoinitiator; and the additives include silane coupling agents, flexible acrylate diluents, and polymerization inhibitors. The fluorine content of the fluorinated polyurethane acrylate resin is 1-5 wt%. Combined with the limitations on the composition and ratio of each raw material, the electronic paper edge-sealing UV adhesive of this application achieves a unified combination of low water absorption, low moisture permeability, high adhesive strength, resistance to thermal shock, and resistance to damp heat aging, fully meeting the stringent requirements of low moisture absorption, high reliability, and long durability for edge-sealing adhesives in electronic paper display edge encapsulation.

Description

Technical Field

[0001] This application relates to the field of light-curing adhesive technology, and in particular to a UV adhesive for sealing electronic paper edges, its preparation method, and its application. Background Technology

[0002] E-paper, also known as digital paper, is an ultra-thin, ultra-light display screen. It can be understood as a display screen that is as thin, flexible, and erasable as paper. Thanks to its paper-like display characteristics, e-paper has been widely used in many fields such as e-book readers, electronic tags, and wearable devices. This display technology has brought great convenience and entirely new experiences to people's reading, information display, and interaction with wearable devices, driving the development of related industries. As these application scenarios continue to expand and deepen, the market is placing higher demands on the performance and reliability of e-paper displays, making them more convenient, efficient, and environmentally friendly in information dissemination and acquisition.

[0003] Currently, to protect the microcapsules or electrophoretic solutions inside electronic paper from moisture, hot melt adhesives, epoxy resins, or UV adhesives are commonly used for edge sealing. However, these materials all have significant shortcomings. For example, hot melt adhesives achieve a certain degree of adhesion and sealing quickly in the initial stages of use, but their aging resistance and temperature resistance are poor, making the edges prone to aging and cracking under environments with large temperature fluctuations. Epoxy resins have a high water absorption rate, slow curing speed, and require high-temperature curing to achieve a good sealing effect. While UV adhesives cure quickly, they generally suffer from high water absorption, insufficient resistance to humid heat aging, rapid attenuation of bond strength after thermal shock, and a mismatch between their thermal expansion coefficient and that of the substrate, which can easily lead to stress cracking. Therefore, existing electronic paper edge sealing adhesives generally suffer from high moisture absorption, low bond strength retention, and insufficient durability, failing to meet the long lifespan requirements of electronic paper. Summary of the Invention

[0004] To at least overcome one of the problems existing in the prior art, one objective of this invention is to provide an electronic paper edge-sealing UV adhesive. This adhesive uses a resin matrix, functional fillers, a photoinitiator, and additives as raw materials. The resin matrix includes fluorinated polyurethane acrylate resin and hyperbranched polyester acrylate; the functional fillers include modified flake boron nitride and fumed silica; the photoinitiator is a free radical photoinitiator; and the additives include a silane coupling agent, a flexible acrylate diluent, and a polymerization inhibitor. The fluorine content of the fluorinated polyurethane acrylate resin is 1-5 wt%. Furthermore, the limitations on the composition and proportion of each raw material result in an electronic paper edge-sealing UV adhesive that possesses advantages such as low water absorption, strong resistance to damp heat aging, and high adhesion strength retention after thermal shock, thus meeting the requirements for edge-sealing adhesives in the edge encapsulation of electronic paper displays. A second objective of this invention is to provide a method for preparing the aforementioned electronic paper edge-sealing UV adhesive. A third objective of this application is to provide the application of the aforementioned electronic paper edge-sealing UV adhesive.

[0005] Therefore, the present invention adopts the following technical solution: A first aspect of the present invention provides an electronic paper edge-sealing UV adhesive, the raw material components of which include: a resin matrix, functional fillers, a photoinitiator, and additives; the resin matrix includes fluorinated polyurethane acrylate resin and hyperbranched polyester acrylate; the functional fillers include modified flake boron nitride and fumed silica; the photoinitiator is a free radical photoinitiator; the additives include a silane coupling agent, a flexible acrylate diluent, and a polymerization inhibitor; the fluorine content of the fluorinated polyurethane acrylate resin is 1~5 wt%.

[0006] In the raw materials of the electronic paper edge-sealing UV adhesive of this application, fluorinated polyurethane acrylate resin serves as the main film-forming substance, providing basic adhesion and flexibility. The fluorine atoms introduced into its molecular chain have low surface energy and high hydrophobicity, fundamentally reducing the water absorption tendency of the edge-sealing UV adhesive. Simultaneously, the 1-5 wt% fluorine content avoids problems such as decreased compatibility and insufficient adhesive strength caused by excessive fluorine content. Hyperbranched polyester acrylate facilitates cross-linking and copolymerization with the double bonds of other resins in the system during photocuring, thereby increasing the cross-linking density. Furthermore, its pre-branched spatial structure effectively inhibits overall curing volume shrinkage, thus reducing internal stress. Modified lamellar boron nitride... The components act as a barrier, dispersed within the edge-sealing UV adhesive. Their sheet-like structure extends the distance and time for moisture penetration, physically reducing water absorption. Combined with fumed silica, this imparts excellent rheological properties to the edge-sealing UV adhesive. The free-radical photoinitiator, by absorbing ultraviolet light and initiating a polymerization reaction, is key to achieving rapid and deep curing. The silane coupling agent enhances the adhesion strength and durability between the filler and resin, and between the adhesive layer and the electronic paper substrate during use. The flexible acrylate diluent also participates in the photocuring reaction, effectively absorbing and releasing thermal stress, reducing the risk of cracking. The polymerization inhibitor, acting as a stabilizer, primarily ensures the chemical stability of the edge-sealing UV adhesive during storage and transportation, preventing pre-polymerization. Through the synergistic effect of these components, the electronic paper edge-sealing UV adhesive of this application possesses excellent low water absorption, resistance to damp heat aging, and durability against thermal shock.

[0007] Preferably, in the resin matrix, the weight ratio of the fluorinated polyurethane acrylate resin to the hyperbranched polyester acrylate is (4~9):(1~2). More preferably, in the resin matrix, the weight ratio of the fluorinated polyurethane acrylate resin to the hyperbranched polyester acrylate is (5~9):(1~2). Even more preferably, in the resin matrix, the weight ratio of the fluorinated polyurethane acrylate resin to the hyperbranched polyester acrylate is (5~9):(1.5~2).

[0008] Preferably, the hyperbranched polyester acrylate has a functionality of 5-12 and a number-average molecular weight of 2000-6000 g / mol. More preferably, the hyperbranched polyester acrylate has a functionality of 7-12 and a number-average molecular weight of 4500-6000 g / mol.

[0009] In the resin matrix, the high proportion of fluorinated polyurethane acrylate ensures the hydrophobicity of the adhesive layer and the bonding strength of the base, while hyperbranched polyester acrylate effectively increases the crosslinking density. The ratio of these two components in this application achieves sufficient crosslinking density to reduce curing shrinkage while maintaining adequate flexibility and elasticity in the adhesive layer, thereby inhibiting interfacial failure caused by adhesive layer cracking. Controlling the functionality of the hyperbranched polyester acrylate to 5-12 helps ensure efficient crosslinking during use and increases the crosslinking density, thus enhancing the mechanical strength of the adhesive layer and avoiding the increased brittleness caused by excessively high functionality. Hyperbranched polyester acrylate with a number average molecular weight in the range of 2000-6000 g / mol exhibits good compatibility and dispersibility, preventing self-aggregation.

[0010] Preferably, in the functional filler, the weight ratio of modified platen boron nitride to fumed silica is (2~4):(1~1.5). More preferably, in the functional filler, the weight ratio of modified platen boron nitride to fumed silica is (2.5~4):(1~1.5). Even more preferably, in the functional filler, the weight ratio of modified platen boron nitride to fumed silica is (3~4):(1~1.5).

[0011] The preparation method of the modified plate-like boron nitride includes the following specific steps: The surface of the modified boron nitride filler is modified by mixing flake boron nitride and silane coupling agent and heating.

[0012] Preferably, the surface hydrophobic modification temperature is 50~90℃ and the time is 0.5~3h. More preferably, the surface hydrophobic modification temperature is 60~90℃ and the time is 2~3h.

[0013] Preferably, the modified boron nitride has a sheet diameter of 50-300 nm and a thickness of 5-40 nm before modification. More preferably, the modified boron nitride has a sheet diameter of 100-300 nm and a thickness of 5-40 nm before modification. Even more preferably, the modified boron nitride has a sheet diameter of 100-300 nm and a thickness of 10-40 nm before modification.

[0014] Preferably, the fumed silica is hydrophobic fumed silica.

[0015] In the above technical solution, the weight percentage of modified flake boron nitride is higher than that of fumed silica. Sufficient modified flake boron nitride maximizes its labyrinth barrier effect. When the diameter of the unmodified flake boron nitride is controlled to be 50~300nm and the thickness to be 5~40nm, it is more conducive to uniform dispersion in the adhesive layer and the formation of a more tortuous penetration path, thereby extending the water vapor penetration path and improving the water vapor barrier effect on the sealing electronic paper. In addition, the flake boron nitride itself has good thermal conductivity and heat dissipation function, which can avoid the accelerated aging caused by excessive local temperature of the adhesive layer. The fumed silica uses hydrophobic fumed silica, which avoids the disadvantage of introducing a large number of hygroscopic silanol groups when using ordinary hydrophilic fumed silica. It mainly plays a thixotropic and reinforcing role, which helps to improve the mechanical strength and construction stability of the adhesive layer.

[0016] Preferably, in the additive, the weight ratio of the silane coupling agent, flexible acrylate diluent, and polymerization inhibitor is (1~3):(8~15):(0.02~0.1). More preferably, in the additive, the weight ratio of the silane coupling agent, flexible acrylate diluent, and polymerization inhibitor is (1.4~3):(10~15):(0.02~0.1). Even more preferably, in the additive, the weight ratio of the silane coupling agent, flexible acrylate diluent, and polymerization inhibitor is (1.4~3):(12~15):(0.02~0.1).

[0017] In the additives, 1-3 parts by weight of silane coupling agent fully act on the interface between the adhesive layer and the substrate, avoiding the risk of agglomeration or insufficient interfacial adhesion strength due to insufficient total amount of coupling agent, which can easily lead to peeling. 8-15 parts by weight of flexible acrylate diluent adjusts the viscosity and fully absorbs thermal stress, effectively resolving the contradiction between filler reinforcement and stress release. 0.02-0.1 parts by weight of polymerization inhibitor ensures storage stability without affecting the curing speed. The appropriate proportions of the three additives avoid performance shortcomings caused by excessive or insufficient amounts of a single additive, further enhancing the low water absorption, high adhesive strength, and resistance to damp heat aging properties of the edge-sealing UV adhesive, better meeting the stringent requirements of electronic paper edge sealing.

[0018] Preferably, the radical photoinitiator is selected from at least one of 2,4,6-trimethylbenzoylphosphonate, diphenyl-(2,4,6-trimethylbenzoyl)phosphine oxide, 1-hydroxycyclohexylphenyl ketone, 2-hydroxy-2-methyl-1-phenyl-1-propanone, 2-methyl-1-(4-methylthiophenyl)-2-morpholino-1-propanone, and bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide. More preferably, the radical photoinitiator is selected from at least one of 2,4,6-trimethylbenzoylphosphonate, diphenyl-(2,4,6-trimethylbenzoyl)phosphine oxide, 2-hydroxy-2-methyl-1-phenyl-1-propanone, 2-methyl-1-(4-methylthiophenyl)-2-morpholino-1-propanone, and bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide.

[0019] Preferably, the silane coupling agent is selected from at least one of KH-560, KH-570, KH-590, and A-171. More preferably, the silane coupling agent is selected from at least one of KH-560, KH-570, and KH-590.

[0020] Preferably, the flexible acrylate diluent is a multifunctional acrylate monomer containing ethoxy or propoxy segments. More preferably, the multifunctional acrylate monomer containing ethoxy segments is selected from at least one of ethoxylated trimethylolpropane triacrylate, ethoxylated pentaerythritol tetraacrylate, and polyethylene glycol diacrylate; and the multifunctional acrylate monomer containing propoxy segments is selected from at least one of propoxylated glycerol triacrylate and propoxylated trimethylolpropane triacrylate.

[0021] Preferably, the polymerization inhibitor is selected from at least one of phenolic polymerization inhibitors, quinone polymerization inhibitors, and aromatic amine polymerization inhibitors. More preferably, the polymerization inhibitor is selected from at least one of p-hydroxyanisole, 2,6-di-tert-butyl-p-cresol, hydroquinone, tetrachlorobenzoquinone, and phenothiazine. Even more preferably, the polymerization inhibitor is selected from at least one of p-hydroxyanisole, 2,6-di-tert-butyl-p-cresol, hydroquinone, and phenothiazine.

[0022] Under the aforementioned free radical photoinitiator, UV light can penetrate the adhesive layer, achieving deep curing of the edge-sealing UV adhesive and avoiding sealing failure caused by incomplete curing. The flexible acrylate diluent endows the multifunctional acrylate monomers containing ethoxy or propoxy segments with excellent flexibility, allowing stress buffering functionality to be embedded within the crosslinking network, thereby ensuring the durability and reliability of the edge-sealing UV adhesive.

[0023] Preferably, in the raw materials of the electronic paper edge sealing UV adhesive, the weight ratio of resin matrix, functional filler and photoinitiator is (40~55):(5~13):(2~6).

[0024] Preferably, in the raw materials of the electronic paper edge sealing UV adhesive, the weight ratio of resin matrix, functional filler, photoinitiator and additives is (40~55):(5~13):(2~6):(10~21).

[0025] In the raw material composition of the electronic paper edge-sealing UV adhesive of this application, 40-55 parts by weight of resin matrix fully ensure the film-forming properties, hydrophobicity, and adhesive foundation of the adhesive layer; 5-13 parts by weight of functional filler effectively play a barrier and reinforcement role without affecting the flexibility of the adhesive layer; 2-6 parts by weight of photoinitiator facilitates rapid and efficient curing, avoiding the risk of incomplete curing due to insufficient dosage or residual odor and yellowing due to excessive dosage; 10-21 parts by weight of additives can fully play the functions of interfacial adhesion, stress release, and storage stability; the synergistic effect of each component enables the edge-sealing UV adhesive to take into account low water absorption, low shrinkage, high adhesion, and aging resistance, solving the problem that existing electronic paper edge-sealing UV adhesives have outstanding individual properties but poor overall performance due to the imbalance of component dosage.

[0026] A second aspect of the present invention provides a method for preparing the electronic paper edge-sealing UV adhesive according to the first aspect of the present invention, comprising the following steps: S1. Vacuum mixing: Under light-protected conditions, the raw material components are mixed under vacuum to obtain a mixture. S2. Filtering and storage: Filter the mixture and store it in a light-proof package to obtain the electronic paper sealing UV adhesive.

[0027] Preferably, in step S1, the vacuum degree of the vacuum mixing is not higher than -0.09 MPa, and the mixing time is 20~60 min. More preferably, in step S1, the vacuum degree of the vacuum mixing is not higher than -0.09 MPa, and the mixing time is 35~60 min.

[0028] Preferably, in step S2, the pore size of the filter bag or filter element used for filtration is 0.5~10μm. More preferably, in step S2, the pore size of the filter bag or filter element used for filtration is 1~10μm.

[0029] The preparation method of the electronic paper edge-sealing UV adhesive in this application involves vacuum mixing, filtration, and storage steps, combined with optimization of preparation method parameters. Specifically, step S1, vacuum mixing under light-protected conditions, prevents premature decomposition of the photoinitiator and removes air bubbles generated during mixing, preventing pore formation in the adhesive layer during edge-sealing curing and thus sealing failure, while also improving the density of the adhesive layer. Step S2, filtration, removes impurity particles, preventing adhesion defects or stress concentration caused by impurities. Light-protected packaging ensures the performance stability of the edge-sealing UV adhesive during storage. Through synergistic optimization of each step, the components are uniformly mixed, ultimately resulting in an electronic paper edge-sealing UV adhesive with low water absorption, resistance to damp heat aging, and durability against thermal shock.

[0030] A third aspect of this application provides the application of an electronic paper edge-sealing UV adhesive in the edge encapsulation of an electronic paper display, wherein the electronic paper edge-sealing UV adhesive is the aforementioned electronic paper edge-sealing UV adhesive, or is prepared by the aforementioned preparation method.

[0031] Compared with the prior art, the present invention has at least the following beneficial effects: 1) The raw material components of this application include a resin matrix, functional fillers, photoinitiators, and additives; wherein, the resin matrix includes fluorinated polyurethane acrylate resin and hyperbranched polyester acrylate; the functional fillers include modified flake boron nitride and fumed silica; the photoinitiator is a free radical photoinitiator; the additives include silane coupling agents, flexible acrylate diluents, and polymerization inhibitors; the fluorine content of the fluorinated polyurethane acrylate resin is 1~5wt%. The fluorinated polyurethane acrylate fully ensures the hydrophobicity of the adhesive layer and the bonding strength of the base during edge sealing and curing, while the hyperbranched polyester acrylate effectively increases the crosslinking density. Combined with the barrier path effect established by modified flake boron nitride, the thixotropic reinforcement of fumed silica, and the synergistic effect of various additives, the resulting electronic paper edge sealing UV adhesive possesses extremely low water absorption, resistance to damp heat aging, and durability against thermal shock. Its saturated water absorption rate is as low as 0.30%, and its water vapor transmission rate is as low as 1.6 g·mm / (m²). 2 • After 24 hours, the initial bonding strength is ≥8.4MPa, the strength retention rate after 240 hours of thermal shock is ≥90.7%, and the strength retention rate after 1296 hours of high temperature and high humidity aging is ≥92.4%, which effectively solves the problems of high water absorption, insufficient durability and easy stress cracking of existing electronic paper sealing adhesives.

[0032] 2) In the preparation method of the electronic paper edge-sealing UV adhesive of this application, the steps of vacuum mixing, filtration and preservation, and optimization of the preparation method parameters ensure that the functional filler is uniformly dispersed and well compatible with the resin matrix, effectively eliminating air bubbles and making the prepared electronic paper edge-sealing UV adhesive more stable. This preparation method is simple, requires no complex equipment, is suitable for large-scale production, and helps to form a uniform and stable electronic paper edge-sealing UV adhesive. Detailed Implementation

[0033] The present invention will be further described in detail below through specific embodiments, comparative examples and tables, but is not limited to all the discussions and data.

[0034] Fluorinated polyurethane acrylate resin is sourced from Guangzhou Songda New Material Technology Co., Ltd., with fluorine content of 2wt%, 3wt%, and 6wt%; hyperbranched polyester acrylate is sourced from Guangdong Boxin New Material Technology Co., Ltd., with a functionality of 6 and a number-average molecular weight of 3500~4500 g / mol; flake boron nitride is sourced from Xinyang Defupeng New Material Co., Ltd., with a flake diameter of 50~100 nm and a thickness of 5~20 nm; hydrophobic fumed silica is sourced from Degussa, model R812S; ethoxylated trimethylolpropane triacrylate is sourced from Wuhan Jushun Chemical Co., Ltd., CAS number 28961-43-5.

[0035] Example of preparation of modified plate-shaped boron nitride: Preparation Example 1: The preparation method of modified plate-like boron nitride includes the following steps: In a three-necked flask equipped with a stirrer and a reflux condenser, 20g of flake boron nitride, 1.2g of silane coupling agent KH-570, and 100mL of anhydrous ethanol were added. Stirring was started to fully disperse the powder and form a uniform suspension. The temperature was raised to 80℃, and the mixture was refluxed at this temperature for 2.5h to perform surface hydrophobic modification. The mixture was then transferred to a rotary evaporator to remove the anhydrous ethanol. The resulting slurry was dried at 70℃, ground, and passed through a 200-mesh sieve to obtain modified flake boron nitride.

[0036] Preparation Example 2: The preparation method of modified plate-like boron nitride includes the following steps: In a three-necked flask equipped with a stirrer and a reflux condenser, 20g of flake boron nitride, 1.6g of silane coupling agent KH-570, and 100mL of anhydrous ethanol were added. Stirring was started to fully disperse the powder and form a uniform suspension. The temperature was raised to 80℃, and the mixture was refluxed at this temperature for 2.5h to perform surface hydrophobic modification. The mixture was then transferred to a rotary evaporator to remove the anhydrous ethanol. The resulting slurry was dried at 70℃, ground, and passed through a 200-mesh sieve to obtain modified flake boron nitride.

[0037] Example of resin matrix preparation: Preparation Example 3: The method for preparing the resin matrix includes the following steps: The resin matrix was prepared by uniformly mixing 50g of fluorinated polyurethane acrylate resin with a fluorine content of 2wt% and 10g of hyperbranched polyester acrylate.

[0038] Preparation Example 4: The method for preparing the resin matrix includes the following steps: The resin matrix was prepared by uniformly mixing 50g of fluorinated polyurethane acrylate resin with a fluorine content of 3wt% and 10g of hyperbranched polyester acrylate.

[0039] Preparation Example 5: The method for preparing the resin matrix includes the following steps: The resin matrix was prepared by uniformly mixing 90g of fluorinated polyurethane acrylate resin with a fluorine content of 2wt% and 15g of hyperbranched polyester acrylate.

[0040] Example of preparation of functional fillers: Preparation Example 6: The preparation method of functional fillers includes the following steps: 25g of modified boron nitride flakes from Preparation Example 1 and 10g of hydrophobic fumed silica were mixed evenly to obtain the functional filler.

[0041] Preparation Example 7: The preparation method of functional fillers includes the following steps: The functional filler was prepared by uniformly mixing 40g of the modified sheet boron nitride from Preparation Example 2 and 13g of hydrophobic fumed silica.

[0042] Example of preparation of auxiliary agents: Preparation Example 8: The preparation method of the auxiliary agent includes the following steps: The additive was prepared by mixing 1.2g of silane coupling agent KH-570, 14g of ethoxylated trimethylolpropane triacrylate and 0.08g of 2,6-di-tert-butyl-p-cresol evenly.

[0043] Comparative examples of resin matrix preparation: Preparation of Comparative Example 1: The method for preparing the resin matrix includes the following steps: The resin matrix was prepared by uniformly mixing 50g of fluorinated polyurethane acrylate resin with a fluorine content of 6wt% and 10g of hyperbranched polyester acrylate.

[0044] Preparation of Comparative Example 2: The method for preparing the resin matrix includes the following steps: The resin matrix was prepared by uniformly mixing 50g of fluorinated polyurethane acrylate resin with a fluorine content of 2wt% and 30g of hyperbranched polyester acrylate.

[0045] Comparative examples of the preparation of functional fillers: Preparation of Comparative Example 3: The preparation method of functional fillers includes the following steps: The functional filler was prepared by mixing 25g of 8000-mesh calcium carbonate and 10g of hydrophobic fumed silica evenly.

[0046] Preparation of Comparative Example 4: The preparation method of functional fillers includes the following steps: The functional filler was prepared by uniformly mixing 25g of flake boron nitride and 10g of hydrophobic fumed silica.

[0047] It is particularly important to emphasize that, unless otherwise specified, the raw materials, reagents or devices used in this invention can be obtained from conventional commercial sources.

[0048] Examples of UV adhesive for sealing electronic paper edges: An electronic paper edge-sealing UV adhesive is prepared through the following steps: S1. Vacuum mixing: Under light-protected conditions, add 40-55g of resin matrix, 5-13g of functional filler, 2-6g of photoinitiator, and 10-21g of additives to a vacuum planetary mixer in sequence. Evacuate the mixture to a vacuum degree not higher than -0.09MPa and continue mixing for 20-60 minutes to obtain the mixture. S2. Filtration and preservation: The mixture is filtered through a filter device with a filter bag or filter element with a pore size of 0.5~10μm, and the filtrate is preserved in a light-proof package to obtain the electronic paper sealing UV adhesive.

[0049] Regarding step S1, in some specific embodiments, the resin matrix includes fluorinated polyurethane acrylate resin and hyperbranched polyester acrylate, wherein the weight ratio of fluorinated polyurethane acrylate resin to hyperbranched polyester acrylate can be 4:1, 5:1, 8:1.5, 9:2 or 9:1.5, the fluorine content of the fluorinated polyurethane acrylate resin can be 1wt%, 2wt%, 3wt%, 4wt% or 5wt%, the functionality of the hyperbranched polyester acrylate can be 5, 6, 8, 9, 10 or 12, and the number average molecular weight can be 2000 g / mol, 3500 g / mol, 4000 g / mol, 5000 g / mol or 6000 g / mol. The functional fillers include modified sheet boron nitride and fumed silica. The modified sheet boron nitride is prepared by mixing sheet boron nitride and a silane coupling agent and heating to perform surface hydrophobic modification, thereby obtaining the modified boron nitride filler. Before modification, the sheet diameter of the modified boron nitride can be 50nm, 100nm, 150nm, 200nm, or 300nm, and the thickness can be 5nm, 10nm, 15nm, 20nm, 30nm, or 40nm. The weight ratio of modified sheet boron nitride to fumed silica can be 2:1, 2.5:1, 3:1, 4:1.3, or 4:1.5. The photoinitiator is a free radical photoinitiator, which can be selected from at least one of 2,4,6-trimethylbenzoylphosphonate, diphenyl-(2,4,6-trimethylbenzoyl)phosphine oxide, 1-hydroxycyclohexylphenyl ketone, 2-hydroxy-2-methyl-1-phenyl-1-propanone, 2-methyl-1-(4-methylthiophenyl)-2-morpholino-1-propanone, and bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide. The additives include silane coupling agents, flexible acrylate diluents, and polymerization inhibitors; the silane coupling agent may be selected from at least one of KH-560, KH-570, KH-590, and A-171; the flexible acrylate diluent is a multifunctional acrylate monomer containing ethoxy or propoxy segments, the multifunctional acrylate monomer containing ethoxy segments may be selected from at least one of ethoxylated trimethylolpropane triacrylate, ethoxylated pentaerythritol tetraacrylate, and polyethylene glycol diacrylate, the multifunctional acrylate monomer containing propoxy segments may be selected from at least one of propoxylated glycerol triacrylate and propoxylated trimethylolpropane triacrylate; the polymerization inhibitor may be selected from at least one of phenolic polymerization inhibitors, quinone polymerization inhibitors, and aromatic amine polymerization inhibitors, and the polymerization inhibitor may be selected from at least one of p-hydroxyanisole, 2,6-di-tert-butyl-p-cresol, hydroquinone, tetrachlorobenzoquinone, and phenothiazine.The amount of resin matrix can be 40g, 42g, 50g or 55g, the amount of functional filler can be 5g, 8g, 10g or 13g, the amount of photoinitiator can be 2g, 3g, 4.5g, 5g or 6g, the amount of additives can be 10g, 14g, 18g or 21g, and the stirring and mixing time can be 20min, 30min, 45min or 60min.

[0050] Regarding step S2, in some specific implementations, the pore size of the filter bag or filter element can be 0.5μm, 1μm, 5μm or 10μm. Example 1

[0051] An electronic paper edge-sealing UV adhesive is prepared through the following steps: S1. Vacuum mixing: Under light-protected conditions, 45g of the resin matrix of Preparation Example 3, 8g of the functional filler of Preparation Example 6, 3g of diphenyl-(2,4,6-trimethylbenzoyl)phosphine oxide, and 14g of the additive of Preparation Example 8 were added sequentially to a vacuum planetary mixer. The vacuum was evacuated to a vacuum degree not higher than -0.09MPa, and the mixture was stirred continuously for 30min to obtain a mixture. S2. Filtration and Preservation: The mixture is filtered through a filter device with a 5μm pore size filter element, and the filtrate is preserved in a light-proof package to obtain electronic paper sealing UV adhesive. Example 2

[0052] The preparation method of an electronic paper edge sealing UV adhesive is the same as that in Example 1, except that the resin matrix in Preparation Example 3 in Example 2 is replaced by the resin matrix in Preparation Example 4 in equal amounts. Example 3

[0053] The preparation method of an electronic paper edge sealing UV adhesive is the same as that in Example 1, except that the resin matrix of Preparation Example 3 is replaced by the resin matrix of Preparation Example 5 in equal amounts. Example 4

[0054] The preparation method of an electronic paper edge-sealing UV adhesive is the same as that in Example 1, except that the functional filler in Preparation Example 6 is replaced by the functional filler in Preparation Example 7 in the same amount in Example 4.

[0055] Comparative Example 1: The preparation method of an electronic paper edge sealing UV adhesive is the same as that in Example 1, except that the resin matrix of Preparation Example 3 in Comparative Example 1 is replaced by the resin matrix of Preparation Example 1 in equal amounts.

[0056] Comparative Example 2: The preparation method of an electronic paper edge sealing UV adhesive is the same as that in Example 1, except that the resin matrix of Preparation Example 3 in Comparative Example 2 is replaced by the resin matrix of Preparation Example 2.

[0057] Comparative Example 3: The preparation method of an electronic paper edge-sealing UV adhesive is the same as that in Example 1, except that the functional filler in Preparation Example 6 of Comparative Example 3 is replaced by the functional filler in Preparation Example 3.

[0058] Comparative Example 4: The preparation method of an electronic paper edge-sealing UV adhesive is the same as that in Example 1, except that the functional filler in Preparation Example 6 in Comparative Example 4 is replaced with the functional filler in Preparation Example 4.

[0059] Comparative Example 5: The preparation method of an electronic paper edge sealing UV adhesive is the same as in Example 1, except that the amount of resin matrix used in Preparation Example 3 in Comparative Example 5 is changed to 60g.

[0060] Material performance testing: The electronic paper edge-sealing UV adhesives of Examples 1-4 and Comparative Examples 1-5 were cured under the following UV conditions: 365nm UV light, 2000mj / cm². 2 The adhesive layer was obtained after curing at 25℃ / 50%RH for 24 hours using curing energy. Various performance tests were then performed on the adhesive layer using the following methods: 1. Saturated water absorption rate: Referring to GB / T 1034-2008 standard, the electronic paper edge-sealing UV adhesive was injected into the mold and cured under the above UV curing conditions to form a circular sample with a diameter of 50±1mm and a thickness of 1.0±0.1mm. The sample was then immersed in deionized water at 25℃ for 168h. After removal, the surface water droplets were quickly wiped away with absorbent paper. The masses of the adhesive layer before and after immersion, m1 and m0, were recorded. The saturated water absorption rate (W) was calculated using the following formula. m = (m1-m0) / m0×100%. Perform three parallel tests and take the average value.

[0061] 2. Water Vapor Transmission Rate (WVTR): Referring to GB / T 21529-2008 standard, the electronic paper edge-sealing UV adhesive was uniformly coated onto a smooth PTFE plate. The wet film thickness was controlled using a coater, and the film was cured under the aforementioned UV curing conditions to form a uniform film with a thickness of 100±5μm. A circular sample with a diameter of 74 mm was cut from the center of the film and placed into the test chamber of the water vapor transmission rate tester. The test was conducted at a temperature of 38±0.5℃ and a relative humidity of 90±2%, and the mass of water vapor transmitted through the film per unit area and per unit time was recorded. Three parallel tests were performed, and the average value was taken.

[0062] 3. Adhesive Strength (Tensile Shear Strength): Referring to GB / T 7124-2008 standard, using a 1.0 mm thick PET sheet as the standard substrate, cut into 100 mm × 25 mm rectangular test pieces. Apply electronic paper edge-sealing UV adhesive evenly to the overlapping end of one PET test piece (overlap area 12.5 mm × 25 mm), immediately align and overlap it with another PET test piece, and fix it with clamps to control the adhesive layer thickness at 0.1 ± 0.02 mm. After UV curing the overlapping area under the above conditions, apply shear force to the overlapping specimen on a universal testing machine at a constant tensile speed of 10 ± 1 mm / min until the specimen fails. Record the maximum failure load F, and calculate the tensile shear strength using the following formula: τ = F / (12.5 × 25). Perform 5 parallel tests and take the average value.

[0063] 4. Bond strength retention rate after thermal shock: Referring to GB / T 2423.22-2012 standard, prepare and test the bond strength in parallel 5 times according to the above test method. Calculate the average tensile-shear strength and record it as τ0. Prepare another set of samples (5 in parallel) in the same way and place them in a thermal shock test chamber. Set the high temperature chamber temperature to 60℃ and the low temperature chamber temperature to -20℃. Keep them in the high and low temperature chambers for 30 minutes each, with a transition time of less than 5 minutes. Repeat this cycle 240 times. Remove the samples and allow them to recover at 23±2℃ and 50±5%RH for 2 hours. Measure their tensile-shear strength and record the average value as τ1. Calculate the bond strength retention rate after thermal shock using the following formula: Bond strength retention rate after thermal shock = (τ1 / τ0)×100%.

[0064] 5. Bond strength retention rate after high temperature and high humidity aging: According to GB / T 2423.3-2016 standard, after preparing and testing the bond strength in parallel for 5 times according to the above bond strength test method, the average tensile shear strength is calculated and recorded as τ0. Another set of samples (5 in parallel) is prepared in the same way and placed in a constant temperature and humidity test chamber. The conditions are set as temperature 60℃ and relative humidity 80% for continuous aging for 1296h. After taking them out, they are restored at 23±2℃ and 50±5% RH for 24h. The tensile shear strength is measured and the average value is recorded as τ2. The bond strength retention rate after thermal shock is calculated according to the following formula: Bond strength retention rate after thermal shock = (τ2 / τ0)×100%.

[0065] The performance of the UV adhesive for electronic paper edge sealing after curing in Examples 1-4 and Comparative Examples 1-5 is shown in Table 1 below:

[0066] The electronic paper edge-sealing UV adhesives in Examples 1-4 achieve a balance of low water absorption, low moisture permeability, high bond strength, thermal shock resistance, and humid heat aging resistance through a rational ratio and synergistic effect among the raw material components, including the resin matrix, functional fillers, photoinitiators, and additives. Specifically, the use of fluorinated polyurethane acrylate resin with a fluorine content of 1-5 wt%, a specifically formulated resin matrix, silane coupling agent-modified flake boron nitride, and hydrophobic fumed silica, along with these components, results in a UV adhesive that meets the stringent requirements of low moisture absorption, low water vapor transmission rate, high bond strength, and resistance to thermal shock and humid heat aging. The results show that its saturated water absorption rate is as low as 0.30%, its water vapor transmission rate is as low as 1.6 g·mm / (m²·24h), its initial bond strength is ≥8.4 MPa, its strength retention rate after 240 h of thermal shock is ≥90.7%, and its strength retention rate after 1296 h of high temperature and high humidity aging is ≥92.4%. This fully meets the stringent requirements of low moisture absorption, high reliability, and long durability for edge-sealing adhesives in electronic paper display edge encapsulation.

[0067] Compared with Example 1, Comparative Example 1 was prepared using the same method and with the same amount of raw materials. The difference was that the resin matrix in Comparative Example 1 was replaced with a fluorinated polyurethane acrylate resin with a fluorine content of 6 wt%. The results showed that although the saturated water absorption rate and water vapor transmission rate of the electronic paper sealing UV adhesive in Comparative Example 1 were slightly lower, its initial bond strength was significantly reduced to only 6.3 MPa, which was 74% of the initial bond strength of Example 1. The strength retention rates after thermal shock and high-temperature and high-humidity aging were also significantly lower, at only 78.5% and 76.3%, respectively. This may be because the fluorine content of the fluorinated polyurethane acrylate resin was too high, leading to decreased compatibility with the hyperbranched polyester acrylate and insufficient uniform dispersion in the system. This, in turn, disrupted the continuity of the crosslinked network structure, preventing the formation of a stable adhesive interface and ultimately resulting in a significant decrease in its bond strength and aging resistance.

[0068] Compared with Example 1, Comparative Example 2 was prepared using the same method and with the same amount of raw materials. The difference was that the resin matrix in Comparative Example 2 was replaced with an excess of hyperbranched polyester acrylate. The results showed that although the initial adhesive strength of the electronic paper sealing UV adhesive in Comparative Example 2 was slightly higher, its saturated water absorption rate increased to 0.43%, and its water vapor transmission rate increased to 2.3 g·mm / (m²·24h). Furthermore, the strength retention rate after thermal shock and after high-temperature and high-humidity aging was significantly lower than that in Example 1. This indicates that an excessive amount of hyperbranched polyester acrylate may lead to an excessively high crosslinking density, increased brittleness of the adhesive layer, and greater internal stress, making it difficult to absorb and release the thermal stress generated under alternating thermal and high-temperature and high-humidity conditions. Additionally, excessive hyperbranched polyester acrylate can weaken the hydrophobic effect of the fluorinated components, resulting in increased water absorption and decreased aging resistance.

[0069] Compared with Example 1, Comparative Example 3 was prepared using the same method and with the same amount of raw materials. The difference was that the functional filler in Comparative Example 3 was replaced with a mixture of calcium carbonate and hydrophobic fumed silica. The results showed that the electronic paper edge-sealing UV adhesive of Comparative Example 3 exhibited varying degrees of performance degradation. Its saturated water absorption rate reached 0.81%, water vapor transmission rate increased to 5.7 g·mm / (m²·24h), and initial bond strength was 7.2 MPa. Furthermore, the strength retention rates after thermal shock and high-temperature, high-humidity aging were also low. This may be because calcium carbonate lacks the labyrinthine barrier structure and hydrophobic properties of modified boron nitride, thus failing to effectively block water vapor penetration. Additionally, its compatibility with the resin matrix is ​​generally poor, easily leading to defects within the adhesive layer, thereby significantly weakening the hydrophobic barrier properties, bond strength, and aging resistance of the edge-sealing adhesive.

[0070] Compared with Example 1, Comparative Example 4 was prepared using the same method and with the same amount of raw materials. The difference was that the functional filler in Comparative Example 4 was replaced with a mixture of unmodified flake boron nitride and hydrophobic fumed silica. The results showed that the saturated water absorption rate of the electronic paper sealing UV adhesive in Comparative Example 4 was 0.67%, and the water vapor transmission rate was 3.4 g·mm / (m²·24h). Initial bond strength, thermal shock resistance, and strength retention after high-temperature and high-humidity aging all decreased. This indicates that the flake boron nitride without silane coupling agent surface hydrophobic modification has a strong surface polarity, poor compatibility with the hydrophobic resin matrix, insufficient dispersion uniformity, and cannot form an effective water vapor barrier labyrinth path. Furthermore, its interfacial bonding with the resin matrix is ​​weak, easily leading to interfacial defects, which in turn causes a decrease in its hydrophobic barrier performance, bond strength, and aging resistance.

[0071] Compared with Example 1, Comparative Example 5 was prepared using the same method and with the same types of raw materials, except that the amount of resin matrix in Comparative Example 5 was increased to 60g. The results showed that the saturated water absorption rate (0.52%) and water vapor transmission rate (2.8 g·mm / (m²·24h)) of the electronic paper sealing UV adhesive in Comparative Example 5 were both higher than those in Example 1. However, the initial bond strength was lower than that of Example 1. Although the strength retention rate after thermal shock was close to that of Example 1, the strength retention rate after high-temperature and high-humidity aging was still lower than that of Example 1. This indicates that excessive resin matrix content leads to a decrease in the relative proportion of functional fillers in the system, preventing the full utilization of the water vapor barrier effect of modified lamellar boron nitride and the thixotropic reinforcing effect of fumed silica. Furthermore, excessive resin matrix also results in uneven cross-linking network density and decreased adhesive layer compactness, thereby weakening its hydrophobic barrier properties, bond strength, and resistance to humid heat aging.

[0072] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. For those skilled in the art, other variations or modifications can be made based on the above description. Any obvious variations or modifications derived from the technical solutions of the present invention are still within the protection scope of the present invention.

Claims

1. A UV adhesive for sealing electronic paper edges, characterized in that, Its raw material components include: resin matrix, functional filler, photoinitiator and additives; The resin matrix includes fluorinated polyurethane acrylate resin and hyperbranched polyester acrylate; The functional fillers include modified sheet-like boron nitride and fumed silica; The photoinitiator is a free radical type photoinitiator; The additives include silane coupling agents, flexible acrylate diluents, and polymerization inhibitors; The fluorine content of the fluorinated polyurethane acrylate resin is 1~5wt%.

2. The electronic paper edge-sealing UV adhesive according to claim 1, characterized in that, In the resin matrix, the weight ratio of the fluorinated polyurethane acrylate resin to the hyperbranched polyester acrylate is (4~9):(1~2).

3. The electronic paper edge-sealing UV adhesive according to claim 1 or 2, characterized in that, The hyperbranched polyester acrylate has a functionality of 5-12 and a number-average molecular weight of 2000-6000 g / mol.

4. The electronic paper edge-sealing UV adhesive according to claim 1, characterized in that, In the functional filler, the weight ratio of the modified plate boron nitride to fumed silica is (2~4):(1~1.5).

5. The electronic paper edge-sealing UV adhesive according to claim 1 or 4, characterized in that, The modified boron nitride flakes had a diameter of 50-300 nm and a thickness of 5-40 nm before modification. And / or, the fumed silica is hydrophobic fumed silica.

6. The electronic paper edge-sealing UV adhesive according to claim 1, characterized in that, In the additives, the weight ratio of the silane coupling agent, the flexible acrylate diluent, and the polymerization inhibitor is (1~3):(8~15):(0.02~0.1).

7. The electronic paper edge-sealing UV adhesive according to claim 1, characterized in that, The free radical photoinitiator is selected from at least one of 2,4,6-trimethylbenzoylphosphonate, diphenyl-(2,4,6-trimethylbenzoyl)phosphine oxide, 1-hydroxycyclohexylphenyl ketone, 2-hydroxy-2-methyl-1-phenyl-1-propanone, 2-methyl-1-(4-methylthiophenyl)-2-morpholino-1-propanone, and bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide; And / or, the flexible acrylate diluent is a multifunctional acrylate monomer containing ethoxy or propoxy segments.

8. The electronic paper edge-sealing UV adhesive according to any one of claims 1 to 7, characterized in that, Its raw materials include the following components in parts by weight: 40-55 parts of resin matrix; 5-13 parts of functional filler; 2-6 parts of photoinitiator; Additives: 10-21 parts.

9. A method for preparing an electronic paper edge-sealing UV adhesive as described in any one of claims 1 to 8, characterized in that, Includes the following steps: S1. Vacuum mixing: Under light-protected conditions, the raw material components are mixed under vacuum to obtain a mixture. S2. Filtering and storage: Filter the mixture and store it in a light-proof package to obtain the electronic paper sealing UV adhesive.

10. The application of an electronic paper edge-sealing UV adhesive as described in any one of claims 1 to 8 or an electronic paper edge-sealing UV adhesive prepared by the preparation method as described in claim 9 in the edge encapsulation of an electronic paper display.

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