High-refractive-index UV curing adhesive glue as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of adhesive preparation, aims to solve the technical problem that the adhesive property and the humidity and heat resistance of the traditional UV (ultraviolet) curing adhesive glue need to be further improved, and provides UV curing adhesive glue and a preparation method thereof. According to the invention, copolymerizable zirconium-phosphate coordination oxygen cluster resin and triazine nuclear tri (hydroxyethyl methylacrylate) etherate are introduced into a UV curing process through free radical reaction, a curing system composed of an organic network, a coordination embedded structure and a multifunctional crosslinking unit in a synergistic manner is constructed, and the formed curing adhesive layer has a continuous and stable network structure; the bonding degree of an interface and a body is high, the structural response is uniform under the action of illumination, damp heat and external load, and the adhesive is suitable for high-stability bonding application between optical elements.

Description

High refractive index UV-curable adhesives, their preparation methods and applications Technical Field

[0001] This invention relates to the field of adhesive preparation technology, specifically to high refractive index UV-curable adhesives, their preparation methods, and applications. Background Technology

[0002] UV-curable adhesives are a class of functional materials that rely on ultraviolet light irradiation to trigger a cross-linking reaction and achieve rapid curing. They are widely used in optical device assembly, electronic component packaging, and precision structural bonding. In existing technologies, these adhesives typically use acrylate monomers or oligomers as the main reactive components, combined with a photoinitiator system, to form a cross-linked network structure under ultraviolet irradiation. By controlling the molecular structure, functionality, and ratio of the organic components, cured adhesive layers with different viscosity characteristics, curing behaviors, and mechanical responses can be obtained. In optical applications, UV-curable adhesives are often used for bonding transparent substrates. After curing, the structure undergoes a certain degree of structural evolution under environmental factors such as light, humidity, heat, and external loads. Therefore, a relatively systematic research and industrialization foundation has been formed for the network construction method, structural stability, and performance under long-term service conditions in the cured system.

[0003] Currently, most UV-curable adhesives use a single or a few organic acrylate components to construct the curing network. During the formation process, their cross-linking structure often exhibits localized concentration or uneven distribution. When such adhesive layers are subjected to external loads such as tensile shear, the degree of force participation between the interface region and the bulk structure is prone to differ. Internal stress accumulates in local areas, resulting in discontinuous structural adjustment and abrupt changes in stress response with load.

[0004] On the other hand, the cured network formed in traditional processes is prone to local relaxation or rearrangement of its internal structure under long-term humid and hot conditions. The structural changes are often concentrated in specific areas, making it difficult for the overall state of the adhesive layer to maintain continuous evolution. In addition, the composition of some systems changes significantly before and after curing, and the distribution of optical components is easily adjusted during the curing process. This leads to significant fluctuations in the refractive index and appearance after curing under subsequent light or heat conditions, affecting its long-term stability in optical bonding scenarios. Summary of the Invention

[0005] The purpose of this invention is to provide a high refractive index UV-curable adhesive, its preparation method, and its application, in order to solve the technical problem that the bonding performance and moisture and heat resistance of UV-curable adhesives in the prior art need to be further improved.

[0006] The objective of this invention can be achieved through the following technical solution: a high refractive index UV-curable adhesive, comprising the following raw material components by weight: 55-65 parts of sulfide-enriched binary oligomer, 8-12 parts of copolymerizable zirconium-phosphate coordinated oxygen cluster resin, 12-15 parts of triazine nucleotris(hydroxyethyl methacrylate) ether, and 1 part of photoinitiator, wherein the photoinitiator is ethyl 2,4,6-trimethylbenzoylphenylphosphonate;

[0007] The sulfide-enriched binary oligomer was prepared by the following method:

[0008] A1. Add sulfide polyol resin, dibutyltin dilaurate and a calculated amount of isophorone diisocyanate to a reaction vessel and stir. Under nitrogen protection, heat the reaction vessel to 60-80℃ and stir for 2-4 hours to obtain isocyanate-terminated sulfide polyurethane prepolymer.

[0009] A2. Add isocyanate-terminated sulfide polyurethane prepolymer, hydroxyethyl methacrylate and 4-methoxyphenol to a reaction vessel and stir. Under nitrogen protection, heat the reaction vessel to 40-60℃ and keep it at this temperature for 2-3 hours. After the reaction is complete, degas under vacuum for 10 minutes and pass through a 100-mesh stainless steel filter to obtain sulfide-enriched binary oligomer.

[0010] The reaction principle for preparing sulfide-enriched binary oligomers is as follows:

[0011] The hydroxyl groups in the thioether polyol molecule undergo an addition reaction with the isocyanate groups in isophorone diisocyanate under the catalysis of dibutyltin dilaurate, forming a polyurethane segment structure linked by urethane bonds. Under the condition of relative excess isocyanate, an oligomeric intermediate with isocyanate end groups is obtained. Subsequently, the end group isocyanate reacts further with the hydroxyl groups in the hydroxyethyl methacrylate molecule to achieve end group capping and introduce methacrylate structural units. In this process, 4-methoxyphenol maintains the chemical stability of the system by inhibiting unnecessary free radical reactions, so that the resulting oligomer simultaneously contains thioether segments, polyurethane bonding units and methacrylate end group features in its molecular structure, and finally prepares a thioether-enriched binary oligomer.

[0012] Furthermore, in step A1, the ratio of sulfide polyol resin to dibutyltin dilaurate is 40g:0.1g, wherein the amount of isophorone diisocyanate added is 0.55-0.60 times the molar amount of hydroxyl groups in the reaction system.

[0013] Furthermore, in step A2, the ratio of isocyanate-terminated sulfide polyurethane prepolymer, hydroxyethyl methacrylate, and 4-methoxyphenol is 50-60g:8-10mL:0.03-0.05g.

[0014] Furthermore, the preparation method of the sulfide polyol is as follows: pentaerythritol tetrakis(3-mercaptopropionic acid) and diethylene glycol monoallyl ether are added to a reaction vessel and stirred until uniform. Under nitrogen protection, the temperature of the reaction vessel is controlled at 25-35℃. An initiator is added and the reaction is kept at this temperature for 2-4 hours. After the reaction is completed, the mixture is degassed under vacuum for 10 minutes to obtain the sulfide polyol.

[0015] The reaction equation for preparing thioether polyols is as follows:

[0016]

[0017] In the formula: ; ;

[0018] .

[0019] The reaction principle for preparing thioether polyols is as follows:

[0020] The tetra(3-mercaptopropionic acid) pentaerythritol ester molecule contains multiple thiol active sites, while diethylene glycol monoallyl ether provides carbon-carbon double bond reaction sites. Under an inert atmosphere, the two can undergo a thiol-to-alkene addition reaction. This process is essentially a free radical-initiated thiol-alkene addition reaction pathway. Under the action of an azo initiator, the system generates free radicals and induces the thiol to generate sulfur free radicals. The sulfur free radicals add to the allyl carbon-carbon double bond and achieve chain reaction propagation through hydrogen transfer. Accompanied by the construction of SC bonds, the allyl double bond is consumed and transformed into a thioether bond linkage structure, thereby forming a polymer system containing thioether segments and polyhydroxy structural units, yielding a thioether polyol.

[0021] Furthermore, in the preparation of thioether polyols, the ratio of the amount of pentaerythritol tetrakis(3-mercaptopropionic acid), diethylene glycol monoallyl ether, and initiator is 18-20g:20-24mL:0.2g, wherein the initiator is azodimethoxyisoheptanenitrile.

[0022] Furthermore, the copolymerizable zirconium-phosphate coordinated oxygen cluster resin is prepared by the following method:

[0023] B1. Add methacryloyloxyethyl phosphate and isopropanol to a reaction vessel and stir. After mixing evenly, add triethylamine while controlling the temperature of the reaction vessel at 20-30℃. Continue stirring for 1-2 hours to obtain a phosphate-based triethylamine salt solution.

[0024] B2. Add zirconium n-propoxide and isopropanol to a reaction vessel and stir. Control the temperature of the reaction vessel to 20-30℃ and add phosphate-based triethylamine salt solution. After stirring for 1-2 hours, add deionized water in five batches. Then, raise the temperature of the reaction vessel to 40-45℃ and keep it at that temperature for 2-4 hours. After the reaction is completed, collect the filtrate through a 200-mesh stainless steel sieve to obtain copolymerizable zirconium-phosphate-coordinated oxygen cluster resin.

[0025] The reaction principle for preparing copolymerizable zirconium-phosphate coordinated oxygen cluster resin is as follows:

[0026] The phosphate group in the methacryloyloxyethyl phosphate molecule has a strong coordination electron-donating ability. Under the action of triethylamine, it undergoes deprotonation to form a phosphate anion, thereby increasing its tendency to complex with the metal center. Furthermore, zirconium propoxide, as a zirconium source, has a zirconium center with high Lewis acidity, which easily coordinates with the oxygen atom of the phosphate ester to form a stable Zr-OP coordination structure. At the same time, the introduction of trace amounts of water into the system can induce controlled hydrolysis of zirconium alkoxide to generate zirconium-oxygen cluster units with bridging oxygen structures. Under the stabilizing effect of the phosphate ester ligand, the cluster structure is assembled and solidified, ultimately forming an organic-inorganic coordination network system with zirconium-oxygen clusters as inorganic nodes and phosphate esters as coordination links, thus obtaining a copolymerizable zirconium-phosphate ester coordinated oxygen cluster resin.

[0027] Furthermore, in step B1, the ratio of methacryloyloxyethyl phosphate, isopropanol, and triethylamine is 8-10 g: 60 mL: 4 mL.

[0028] Furthermore, in step B2, the ratio of zirconium propoxide, isopropanol, triethylamine phosphate salt solution, and deionized water is 18-20g:30mL:60mL:0.8-1.0g.

[0029] Furthermore, the preparation method of the triazine nucleotri(hydroxyethyl methacrylate) ether is as follows: under ice bath conditions, cyanuric chloride and anhydrous acetone are added to a reaction vessel and stirred. After the mixture is uniform, hydroxyethyl methacrylate and triethylamine are added in sequence. Then the reaction vessel is heated to 40-50°C and kept at this temperature for 2-4 hours with stirring. After the reaction is completed, the mixture is filtered and distilled under reduced pressure until no liquid is collected, thus obtaining the triazine nucleotri(hydroxyethyl methacrylate) ether.

[0030] The reaction equation for the preparation of triazine nucleotris(hydroxyethyl methacrylate) ether is as follows:

[0031]

[0032] In the formula: .

[0033] The reaction principle for preparing triazine nucleotris(hydroxyethyl methacrylate) ether is as follows:

[0034] In the reaction system, the triazine ring in the cyanuric chloride molecule has electronic defect characteristics, and its chlorinated substituents are prone to nucleophilic substitution reactions under alkaline conditions. Among them, the hydroxyl group in the hydroxyethyl methacrylate molecule acts as a nucleophile and is activated in the presence of triethylamine, which gradually substitutes the chlorine atom on the triazine ring to form a stable triazine nucleoether bond structure. Triethylamine mainly plays the role of capturing the hydrogen chloride generated in the reaction, thereby promoting the reaction towards substitution and maintaining the chemical equilibrium of the system, and finally preparing the triazine nucleotri(hydroxyethyl methacrylate) ether.

[0035] Furthermore, in the preparation of triazine nucleotris(hydroxyethyl methacrylate) ether, the ratio of cyanuric chloride, anhydrous acetone, hydroxyethyl methacrylate, and triethylamine is 9-12g:80-100mL:18-24mL:10mL.

[0036] The present invention also discloses a method for preparing a high refractive index UV-curable adhesive, comprising the following steps: adding a sulfide-enriched binary oligomer, a copolymerizable zirconium-phosphate coordinated oxygen cluster resin, and a triazine nucleotris(hydroxyethyl methacrylate) ether to a stirred tank; heating the stirred tank to 30-40°C; stirring for 10-15 minutes; adding a photoinitiator; vacuum degassing for 10 minutes; and passing the mixture through a 100-mesh stainless steel filter to obtain the UV-curable adhesive.

[0037] The reaction principle for preparing UV-curable adhesives is as follows:

[0038] The sulfide-enriched binary oligomers, copolymerizable zirconium-phosphate coordinated oxygen cluster resins, and triazine nucleus tri(hydroxyethyl methacrylate) ethers all contain methacrylate unsaturated groups and polar functional groups in their molecular structures. Under heating and stirring conditions, they can form a homogeneous molecular-level mixed system. In this system, the metal-oxygen coordination structure in the zirconium-phosphate coordinated oxygen clusters and the organic oligomers achieve stable coexistence through coordination and intermolecular interactions. The triazine nucleus structure participates in the system construction through its multiple functional sites. The photoinitiator exists in a molecularly dispersed state in this system and does not participate in chemical bonding. It is only embedded in the organic-inorganic composite network as a potential reaction source, thereby forming a photoresponsive resin system with homogeneous composition and synergistic structure. Finally, a UV-curable adhesive is prepared.

[0039] The present invention also discloses the application of high refractive index UV-curable adhesive, wherein the high refractive index UV-curable adhesive prepared by the above-mentioned preparation method is applied to the bonding of optical instruments and the encapsulation of optoelectronic devices.

[0040] The present invention has the following beneficial effects:

[0041] 1. In the UV-curable adhesive system of the present invention, triazine nucleotris(hydroxyethyl methacrylate) ether participates in the reaction and gradually builds a cross-linking network during the UV curing process, so that the adhesive layer forms a continuous stress-bearing structural framework after curing. Under tensile and shear loads, the interface region and the bulk structure can participate in bearing the load synchronously. At the same time, in this stress-bearing structure, the sulfide-rich binary oligomer exists in a continuous distribution state, so that the internal stress of the adhesive layer is uniformly distributed along the bulk direction during the stress process. Furthermore, the copolymerizable zirconium-phosphate coordinated oxygen cluster resin is embedded in the cross-linking network in a copolymer form. Under the continuous action of tensile and shear loads, it forms a dispersed constraint on the deformation process of the internal structure of the adhesive layer, so that the structural adjustment of the adhesive layer tends to be gradual during the stress process. Thus, the adhesive layer exhibits continuous stress response characteristics under tensile and shear conditions.

[0042] 2. In the UV-curable adhesive system of the present invention, the copolymerizable zirconium-phosphate coordinated oxygen cluster resin is distributed in the cross-linking network in a copolymeric manner during the curing process. This allows the internal structural adjustment process of the adhesive layer to be dispersed and constrained under the continuous action of a humid and hot environment, making it difficult for local structural changes to occur in a concentrated manner. In this network structure, the multifunctional cross-linking framework constructed by triazine nucleotris(hydroxyethyl methacrylate) ether provides the basic structural morphology of the adhesive layer, enabling the adhesive layer to maintain the continuity of the overall network under humid and hot conditions. On this basis, the sulfide-enriched binary oligomers are continuously distributed in the cured network, so that when moisture and heat act on the adhesive layer, their influence on the overall structure gradually unfolds along the bulk phase direction. Thus, the structural change process of the adhesive layer in a humid and hot environment exhibits a gradual characteristic, and the overall state continues to evolve with the environmental effects.

[0043] 3. In the UV-curable adhesive system of the present invention, the sulfide-rich binary oligomer is one of the main organic components in the system. During the mixing and curing process, it forms a continuous phase distribution in the system, so that the adhesive layer maintains a relatively consistent optical composition before and after curing. This continuous phase structure has a continuous influence on the formation of the refractive index of the adhesive layer after curing. As the UV curing process progresses, the triazine nucleotris(hydroxyethyl methacrylate) ether participates in the reaction and gradually builds a cross-linking network, so that the system changes from a fluid dynamic to a solid structure. The formation process of the network in space is relatively balanced, which is conducive to the stability of the refractive index distribution inside the adhesive layer. At the same time, during this process, the zirconium-phosphate ester coordinated oxygen cluster resin can be copolymerized and embedded into the network structure, so that the composition of the adhesive layer maintains a continuous transition state before and after curing. Under the action of subsequent light and heat environment, the internal structure adjustment of the adhesive layer shows a gradual change characteristic, and the refractive index change and the yellowing process of appearance unfold relatively slowly over time. Detailed Implementation

[0044] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0045] Example 1

[0046] This embodiment provides a method for preparing sulfide-enriched binary oligomers, including the following steps:

[0047] Step I: Preparation of thioether polyols

[0048] Weigh out 18.0g of pentaerythritol tetrakis(3-mercaptopropionic acid) and 20.0mL of diethylene glycol monoallyl ether, add them to the reaction vessel and stir until homogeneous. Under nitrogen protection, control the temperature of the reaction vessel at 25℃, add 0.2g of azodimethoxyisoheptanenitrile and keep the reaction at this temperature for 2-4 hours. After the reaction is complete, degas under vacuum for 10 minutes to obtain thioether polyol.

[0049] Step II: Preparation of isocyanate-terminated sulfide polyurethane prepolymer

[0050] Weigh out 40.0g of sulfide polyol resin, 0.1g of dibutyltin dilaurate, and 0.55 times the molar amount of hydroxyl groups in the reaction system of isophorone diisocyanate, add them to the reaction vessel and stir. Under nitrogen protection, heat the reaction vessel to 60℃ and keep it at this temperature for 2 hours to obtain isocyanate-terminated sulfide polyurethane prepolymer.

[0051] Step III: Preparation of sulfide-enriched binary oligomers

[0052] Weigh out 50.0g of isocyanate-terminated sulfide polyurethane prepolymer, 8.0mL of hydroxyethyl methacrylate and 0.03g of 4-methoxyphenol and add them to the reaction vessel. Stir the mixture and heat the reaction vessel to 40℃ under nitrogen protection. Keep the mixture at this temperature and stir for 2 hours. After the reaction is complete, degas the mixture under vacuum for 10 minutes and pass it through a 100-mesh stainless steel filter to obtain sulfide-enriched binary oligomers.

[0053] Example 2

[0054] This embodiment provides a method for preparing sulfide-enriched binary oligomers, including the following steps:

[0055] Step I: Preparation of thioether polyols

[0056] Weigh out 20.0g of pentaerythritol tetrakis(3-mercaptopropionic acid) and 24.0mL of diethylene glycol monoallyl ether, add them to the reaction vessel and stir until homogeneous. Under nitrogen protection, control the temperature of the reaction vessel at 35℃, add 0.2g of azodimethoxyisoheptanenitrile and keep the reaction at this temperature for 4h. After the reaction is complete, degas under vacuum for 10min to obtain thioether polyol.

[0057] Step II: Preparation of isocyanate-terminated sulfide polyurethane prepolymer

[0058] Weigh out 40.0g of sulfide polyol resin, 0.1g of dibutyltin dilaurate, and 0.60 times the molar amount of hydroxyl groups in the reaction system of isophorone diisocyanate, add them to the reaction vessel and stir. Under nitrogen protection, heat the reaction vessel to 80℃ and keep it at this temperature for 4 hours to obtain isocyanate-terminated sulfide polyurethane prepolymer.

[0059] Step III: Preparation of sulfide-enriched binary oligomers

[0060] Weigh out 60.0g of isocyanate-terminated sulfide polyurethane prepolymer, 10.0mL of hydroxyethyl methacrylate and 0.05g of 4-methoxyphenol and add them to the reaction vessel. Stir the mixture and heat the reaction vessel to 60℃ under nitrogen protection. Keep the mixture at this temperature and stir for 3 hours. After the reaction is complete, degas the mixture under vacuum for 10 minutes and pass it through a 100-mesh stainless steel filter to obtain sulfide-enriched binary oligomers.

[0061] Example 3

[0062] This embodiment provides a method for preparing sulfide-enriched binary oligomers, including the following steps:

[0063] Step I: Preparation of thioether polyols

[0064] Weigh out 19.0g of pentaerythritol tetrakis(3-mercaptopropionic acid) and 21.0mL of diethylene glycol monoallyl ether, add them to the reaction vessel and stir until homogeneous. Under nitrogen protection, control the temperature of the reaction vessel at 30℃, add 0.2g of azodimethoxyisoheptanenitrile and keep the reaction at this temperature for 3h. After the reaction is complete, degas under vacuum for 10min to obtain thioether polyol.

[0065] Step II: Preparation of isocyanate-terminated sulfide polyurethane prepolymer

[0066] Weigh out 40.0g of sulfide polyol resin, 0.1g of dibutyltin dilaurate, and 0.58 times the molar amount of hydroxyl groups in the reaction system of isophorone diisocyanate, add them to the reaction vessel and stir. Under nitrogen protection, heat the reaction vessel to 70℃ and keep it at this temperature for 3 hours to obtain isocyanate-terminated sulfide polyurethane prepolymer.

[0067] Step III: Preparation of sulfide-enriched binary oligomers

[0068] Weigh out 55.0g of isocyanate-terminated sulfide polyurethane prepolymer, 9.0mL of hydroxyethyl methacrylate and 0.04g of 4-methoxyphenol and add them to the reaction vessel. Stir the mixture and heat the reaction vessel to 50℃ under nitrogen protection. Keep the mixture at this temperature and stir for 3 hours. After the reaction is complete, degas the mixture under vacuum for 10 minutes and pass it through a 100-mesh stainless steel filter to obtain sulfide-enriched binary oligomers.

[0069] Example 4

[0070] This embodiment provides a method for preparing a copolymerizable zirconium-phosphate coordinated oxygen cluster resin, comprising the following steps:

[0071] Step ①: Prepare phosphate ester-based triethylamine salt solution

[0072] Weigh out 8.0 g of methacryloyloxyethyl phosphate and 60.0 mL of isopropanol and add them to the reaction vessel. Stir and mix well. Then, add 4.0 mL of triethylamine while controlling the temperature of the reaction vessel at 20 °C and continue stirring for 1 h to obtain a phosphate-based triethylamine salt solution.

[0073] Step ②: Preparation of copolyzirconium-phosphate coordinated oxygen cluster resin

[0074] Weigh 18.0g of zirconium n-propoxide and 30.0mL of isopropanol and add them to the reaction vessel. Stir the reaction vessel at 20℃ and add 60.0mL of phosphate-based triethylamine salt solution. After stirring for 1 hour, add 0.8g of deionized water in five batches. Then, heat the reaction vessel to 40℃ and keep it at that temperature for 2 hours. After the reaction is complete, collect the filtrate through a 200-mesh stainless steel sieve to obtain a copolymerizable zirconium-phosphate-coordinated oxygen cluster resin.

[0075] Example 5

[0076] This embodiment provides a method for preparing a copolymerizable zirconium-phosphate coordinated oxygen cluster resin, comprising the following steps:

[0077] Step ①: Prepare phosphate ester-based triethylamine salt solution

[0078] Weigh out 10.0g of methacryloyloxyethyl phosphate and 60.0mL of isopropanol and add them to the reaction vessel. Stir and mix well. Then, add 4.0mL of triethylamine while controlling the temperature of the reaction vessel at 30℃ and continue stirring for 2 hours to obtain a phosphate-based triethylamine salt solution.

[0079] Step ②: Preparation of copolyzirconium-phosphate coordinated oxygen cluster resin

[0080] Weigh 20.0g of zirconium n-propoxide and 30.0mL of isopropanol and add them to the reaction vessel. Stir the reaction vessel at 30℃ and add 60.0mL of phosphate-based triethylamine salt solution. After stirring for 2 hours, add 1.0g of deionized water in five batches. Then, heat the reaction vessel to 45℃ and keep it at that temperature for 4 hours. After the reaction is complete, collect the filtrate through a 200-mesh stainless steel sieve to obtain a copolymerizable zirconium-phosphate-coordinated oxygen cluster resin.

[0081] Example 6

[0082] This embodiment provides a method for preparing a copolymerizable zirconium-phosphate coordinated oxygen cluster resin, comprising the following steps:

[0083] Step ①: Prepare phosphate ester-based triethylamine salt solution

[0084] Weigh out 9.0 g of methacryloyloxyethyl phosphate and 60.0 mL of isopropanol and add them to the reaction vessel. Stir and mix well. Then, add 4.0 mL of triethylamine while controlling the temperature of the reaction vessel at 25 °C and continue stirring for 2 h to obtain a phosphate-based triethylamine salt solution.

[0085] Step ②: Preparation of copolyzirconium-phosphate coordinated oxygen cluster resin

[0086] Weigh 19.0g of zirconium n-propoxide and 30.0mL of isopropanol and add them to the reaction vessel. Stir the reaction vessel at 25℃ and add 60.0mL of phosphate-based triethylamine salt solution. After stirring for 2 hours, add 1.0g of deionized water in five batches. Then, heat the reaction vessel to 45℃ and keep it at that temperature for 3 hours. After the reaction is complete, collect the filtrate through a 200-mesh stainless steel sieve to obtain a copolymerizable zirconium-phosphate-coordinated oxygen cluster resin.

[0087] Example 7

[0088] This embodiment provides a method for preparing a high refractive index UV-curable adhesive, including the following steps:

[0089] Step 1: Preparation of triazine nucleotris(hydroxyethyl methacrylate) ether.

[0090] Under ice bath conditions, 9.0 g of cyanuric chloride and 80.0 mL of anhydrous acetone were weighed and added to the reaction vessel and stirred. After the mixture was homogeneous, 18.0 mL of hydroxyethyl methacrylate and 30.0 mL of triethylamine were added sequentially. The reaction vessel was then heated to 40 °C and stirred for 2 h. After the reaction was completed, the mixture was filtered and distilled under reduced pressure until no liquid was collected, yielding triazine nucleotris(hydroxyethyl methacrylate) ether.

[0091] Step 2: Preparation of UV-curable adhesive

[0092] By weight, 55 parts of the sulfide-enriched binary oligomer prepared in Example 1, 8 parts of the copolymerizable zirconium-phosphate coordinated oxygen cluster resin, and 12 parts of the triazine nucleotris(hydroxyethyl methacrylate) ether prepared in Example 4 were weighed and added to a stirred tank. The stirred tank was heated to 30°C and stirred for 10 min. Then, 1 part of ethyl 2,4,6-trimethylbenzoylphenylphosphonate was added and vacuum degassing was performed for 10 min. After passing through a 100-mesh stainless steel filter, the UV-curable adhesive was obtained.

[0093] Example 8

[0094] This embodiment provides a method for preparing a high refractive index UV-curable adhesive, including the following steps:

[0095] Step 1: Preparation of triazine nucleotris(hydroxyethyl methacrylate) ether.

[0096] Under ice bath conditions, 12.0 g of cyanuric chloride and 100.0 mL of anhydrous acetone were weighed and added to the reaction vessel and stirred. After the mixture was homogeneous, 24.0 mL of hydroxyethyl methacrylate and 30.0 mL of triethylamine were added sequentially. The reaction vessel was then heated to 50 °C and stirred for 4 h. After the reaction was completed, the mixture was filtered and distilled under reduced pressure until no liquid was collected, yielding triazine nucleotris(hydroxyethyl methacrylate) ether.

[0097] Step 2: Preparation of UV-curable adhesive

[0098] By weight, 65 parts of the sulfide-enriched binary oligomer prepared in Example 2, 12 parts of the copolymerizable zirconium-phosphate coordinated oxygen cluster resin, and 15 parts of the triazine nucleotris(hydroxyethyl methacrylate) ether prepared in Example 5 were weighed and added to a stirred tank. The stirred tank was heated to 40°C and stirred for 15 minutes. Then, 1 part of ethyl 2,4,6-trimethylbenzoylphenylphosphonate was added and vacuum degassing was performed for 10 minutes. After passing through a 100-mesh stainless steel filter, the UV-curable adhesive was obtained.

[0099] Example 9

[0100] This embodiment provides a method for preparing a high refractive index UV-curable adhesive, including the following steps:

[0101] Step 1: Preparation of triazine nucleotris(hydroxyethyl methacrylate) ether.

[0102] Under ice bath conditions, 10.0 g of cyanuric chloride and 90.0 mL of anhydrous acetone were weighed and added to the reaction vessel and stirred. After the mixture was homogeneous, 21.0 mL of hydroxyethyl methacrylate and 30.0 mL of triethylamine were added sequentially. The reaction vessel was then heated to 45 °C and stirred for 3 h. After the reaction was completed, the mixture was filtered and distilled under reduced pressure until no liquid was collected, yielding triazine nucleotris(hydroxyethyl methacrylate) ether.

[0103] Step 2: Preparation of UV-curable adhesive

[0104] By weight, 60 parts of the sulfide-enriched binary oligomer prepared in Example 3, 10 parts of the copolymerizable zirconium-phosphate coordinated oxygen cluster resin, and 13 parts of the triazine nucleotris(hydroxyethyl methacrylate) ether prepared in Example 6 were weighed and added to a stirred tank. The stirred tank was heated to 35°C and stirred for 12 minutes. Then, 1 part of ethyl 2,4,6-trimethylbenzoylphenylphosphonate was added and vacuum degassing was performed for 10 minutes. After passing through a 100-mesh stainless steel filter, the UV-curable adhesive was obtained.

[0105] Comparative Example 1

[0106] The difference between this comparative example and Example 9 is that the thioether enriched binary oligomer used in step two is removed, and the isocyanate-terminated thioether polyurethane prepolymer prepared in step II is used to replace the thioether enriched binary oligomer in an equal amount.

[0107] Comparative Example 2

[0108] The difference between this comparative example and Example 9 is that the copolyzirconia-phosphate coordination oxygen cluster resin is omitted in step two.

[0109] Comparative Example 3

[0110] The difference between this comparative example and Example 9 is that the use of triazine nucleotris(hydroxyethyl methacrylate) ether was omitted in step two.

[0111] Performance testing:

[0112] Two square quartz glass pieces with sides of 5cm and a thickness of 0.5cm were placed in a clean environment. The bonding surfaces of the two quartz glass pieces were wiped with a lint-free cloth soaked in anhydrous ethanol, and then subjected to ultraviolet ozone activation treatment for 5 minutes. Subsequently, the UV-curable adhesive prepared in Examples 7-9 and Comparative Examples 1-3 was dotted onto the bonding surface of one of the quartz glass pieces, and the adhesive layer thickness was controlled to be 20μm. The other quartz glass piece was aligned and bonded together, and a pressure of 0.1MPa was applied at 25°C for 30s. While the pieces were bonded together, they were cured by irradiation with 365nm ultraviolet light at an intensity of 150mW / cm2 for 30s. After the irradiation was completed, the external force was released and the bonded assembly was placed in a drying oven at 50°C for 20 minutes to release internal stress, thus obtaining a quartz glass-quartz glass bonded assembly.

[0113] The refractive indices of the UV-curable adhesives prepared in Examples 7-9 and Comparative Examples 1-3 after curing were tested in accordance with the standard GB / T 6488-2022 "Determination of Refractive Index of Liquid Chemical Products".

[0114] Referring to the standard GB / T 39822-2021 "Determination of Yellow Index and its Change Value of Plastics", the yellow index change values ​​of the UV-curable adhesives prepared in Examples 7-9 and Comparative Examples 1-3 after curing were tested.

[0115] The tensile shear strength of the quartz glass-quartz glass bonded assemblies prepared with UV-cured adhesives in Examples 7-9 and Comparative Examples 1-3 was tested in accordance with the standard GB / T 7124-2008 "Determination of tensile shear strength of adhesives (rigid material to rigid material)".

[0116] The tensile shear strength change rate of quartz glass-quartz glass bonded components prepared by UV-cured adhesives in Examples 7-9 and Comparative Examples 1-3 after aging at 45°C and 95%RH for 10 days was tested in accordance with standard GB / T 2423.3-2016 "Environmental Testing - Part 2: Test Methods - Test Cab: Constant Humidity and Heat Test". The specific data are shown in Table 1.

[0117] Table 1 - Performance Test Data for Each Sample

[0118]

[0119] Data Analysis:

[0120] Comparing the data in Table 1, it can be found that the UV-curable adhesive prepared in this invention has a refractive index of 1.53 and a yellow index change of 0.5 after curing. Furthermore, the tensile shear strength of the quartz glass-quartz glass bonded assembly using this UV-curable adhesive is 12.6 MPa, and the tensile shear strength change rate of this assembly after aging at 45℃ and 95% RH for 10 days is -4.7%. All these data are superior to the comparative example, indicating that…

[0121] In Comparative Example 1, the organic component used in step two was replaced by the isocyanate-terminated sulfide polyurethane prepolymer prepared in step II, which replaced the sulfide-enriched binary oligomer prepared in step III. This caused the system to lose the polymerizable double bond structural units introduced and stably retained by the subsequent end-capping reaction during the UV curing process. Since the organic main phase is difficult to form an effective intercalation with the free radical crosslinking network during the curing stage, its participation in the cured adhesive layer is reduced, which affects the continuity of the network structure in the bulk direction. As a result, under the influence of light and humid heat, the internal structure adjustment of the cured adhesive layer is more likely to occur along local areas, and the overall structural state shows more obvious changes with the environment. At the same time, under the action of tensile shear load, the continuity of the force path in the adhesive layer is weakened, and stress concentration is more likely to occur during the stress transmission process, thus causing changes in the overall performance of the sample in multiple performance tests.

[0122] In Comparative Example 2, no copolymerizable zirconium-phosphate coordinated oxygen cluster resin was introduced during the preparation of the UV-curable adhesive in step two. This resulted in the absence of copolymerized embedded units formed by inorganic coordination structures in the cured system. Since such structures are originally distributed in a dispersed manner in the cured network and participate in the collaborative construction of the spatial structure, their absence weakens the constraint ability of the crosslinking network on the adjustment of the microstructure. After curing, under the influence of a humid and hot environment, the structural changes caused by moisture and thermal disturbance are more likely to accumulate in local areas and gradually extend to the overall structure, thus affecting the stability of the adhesive layer. At the same time, under light conditions, the cumulative effect of internal structural changes will be further reflected in the evolution of the optical state. Furthermore, under tensile and shear loads, due to the lack of dispersed constraint nodes, the deformation process of the adhesive layer is more likely to be concentrated and unfold, causing changes in the overall stability of the sample in multi-performance tests.

[0123] In Comparative Example 3, the addition of triazine nucleotris(hydroxyethyl methacrylate) ether in step two altered the multifunctional network framework formed by the crosslinking reaction in the curing system. Since this type of structure originally participated in constructing the spatial crosslinking skeleton during curing, its absence led to a decrease in the density of crosslinking points and network continuity in the cured adhesive layer. Consequently, the degree to which the interface region and bulk structure were fixed during the curing stage was weakened. Under light, heat, or humid conditions, the internal structure of the adhesive layer was more prone to readjustment, and this readjustment process exhibited a certain cumulative characteristic, thus affecting the overall structural stability. Under tensile shear load conditions, due to insufficient integrity of the network skeleton, the stress transmission path tended to be shortened and discontinuous, making local structural deformation more likely to occur, thereby altering the overall performance of the sample in multiple performance tests.

[0124] Ultimately, this demonstrates that when the construction methods of different structural units in a UV-cured adhesive system change, the morphology of the network structure formed during curing and its subsequent evolutionary behavior also change. Specifically, in Comparative Example 1, the path of the organic main phase participating in the construction of the crosslinking network is adjusted, affecting the spatial continuity between the bulk structure and the cured network. In Comparative Example 2, the lack of dispersed embedded units formed by coordination structures in the network alters the curing structure's ability to respond to environmental disturbances. In Comparative Example 3, the change in the degree of construction of the crosslinking network skeleton leads to adjustments in the distribution of crosslinking points and network continuity. These changes collectively result in differences in the structural response of the cured adhesive layer under light, humidity, heat, and external load conditions, thus reflecting changes in the overall performance of the samples in multiple performance tests.

[0125] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to specific implementations. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A high refractive index UV-curable adhesive, characterized in that, The raw material composition includes the following parts by weight: 55-65 parts of sulfide-enriched binary oligomer, 8-12 parts of copolymerizable zirconium-phosphate coordinated oxygen cluster resin, 12-15 parts of triazine nucleotris(hydroxyethyl methacrylate) ether, and 1 part of photoinitiator; the sulfide-enriched binary oligomer is prepared by the following method: A1, adding sulfide polyol resin, dibutyltin dilaurate, and a calculated amount of isophorone diisocyanate to a reaction vessel and stirring, and then, under nitrogen protection... The reactor is heated to 60-80℃ and stirred for 2-4 hours to obtain isocyanate-terminated sulfide polyurethane prepolymer; A2, the isocyanate-terminated sulfide polyurethane prepolymer, hydroxyethyl methacrylate and 4-methoxyphenol are added to the reactor and stirred. Under nitrogen protection, the reactor is heated to 40-60℃ and stirred for 2-3 hours. After the reaction is completed, vacuum degassing is performed for 10 minutes, and the mixture is passed through a 100-mesh stainless steel filter to obtain sulfide-enriched binary oligomer.

2. The high refractive index UV-curable adhesive according to claim 1, characterized in that, The photoinitiator is ethyl 2,4,6-trimethylbenzoylphenylphosphonate; in step A1, the ratio of sulfide polyol resin to dibutyltin dilaurate is 40g:0.1g, wherein the amount of isophorone diisocyanate added is 0.55-0.60 times the molar amount of hydroxyl groups in the reaction system; in step A2, the ratio of isocyanate-terminated sulfide polyurethane prepolymer, hydroxyethyl methacrylate, and 4-methoxyphenol is 50-60g:8-10mL:0.03-0.05g.

3. The high refractive index UV-curable adhesive according to claim 1, characterized in that, The preparation method of the thioether polyol is as follows: pentaerythritol tetrakis(3-mercaptopropionic acid) and diethylene glycol monoallyl ether are added to a reaction vessel and stirred until homogeneous. Under nitrogen protection, the temperature of the reaction vessel is controlled at 25-35℃. An initiator is added and the reaction is kept at this temperature for 2-4 hours. After the reaction is completed, the mixture is degassed under vacuum for 10 minutes to obtain the thioether polyol.

4. The high refractive index UV-curable adhesive according to claim 3, characterized in that, In the preparation of thioether polyols, the ratio of pentaerythritol tetrakis(3-mercaptopropionic acid) ester, diethylene glycol monoallyl ether, and initiator is 18-20g:20-24mL:0.2g, wherein the initiator is azodimethoxyisoheptanenitrile.

5. The high refractive index UV-curable adhesive according to claim 1, characterized in that, The copolymerizable zirconium-phosphate coordination oxygen cluster resin is prepared by the following method: B1. Methacryloxyethyl phosphate and isopropanol are added to a reaction vessel and stirred. After mixing evenly, triethylamine is added while the temperature of the reaction vessel is controlled at 20-30℃. Stirring is continued for 1-2 hours to obtain a phosphate-based triethylamine salt solution; B2. Zirconium n-propoxide and isopropanol are added to a reaction vessel and stirred. The temperature of the reaction vessel is controlled at 20-30℃ and the phosphate-based triethylamine salt solution is added. After stirring for 1-2 hours, deionized water is added in five batches. Then, the temperature of the reaction vessel is raised to 40-45℃ and kept at this temperature for 2-4 hours. After the reaction is completed, the filtrate is collected through a 200-mesh stainless steel sieve to obtain the copolymerizable zirconium-phosphate coordination oxygen cluster resin.

6. The high refractive index UV-curable adhesive according to claim 5, characterized in that, In step B1, the ratio of methacryloyloxyethyl phosphate, isopropanol, and triethylamine is 8-10 g: 60 mL: 4 mL; in step B2, the ratio of zirconium n-propoxide, isopropanol, phosphate-based triethylamine salt solution, and deionized water is 18-20 g: 30 mL: 60 mL: 0.8-1.0 g.

7. The high refractive index UV-curable adhesive according to claim 1, characterized in that, The preparation method of the triazine nucleotri(hydroxyethyl methacrylate) ether is as follows: under ice bath conditions, cyanuric chloride and anhydrous acetone are added to a reaction vessel and stirred. After the mixture is uniform, hydroxyethyl methacrylate and triethylamine are added in sequence. Then the reaction vessel is heated to 40-50℃ and stirred for 2-4 hours. After the reaction is completed, the mixture is filtered and distilled under reduced pressure until no liquid is collected to obtain the triazine nucleotri(hydroxyethyl methacrylate) ether.

8. The high refractive index UV-curable adhesive according to claim 7, characterized in that, In the preparation of triazine nucleotris(hydroxyethyl methacrylate) ether, the ratio of cyanuric chloride, anhydrous acetone, hydroxyethyl methacrylate and triethylamine is 9-12g:80-100mL:18-24mL:10mL.

9. The method for preparing the high refractive index UV-curable adhesive as described in any one of claims 1-8, characterized in that, Includes the following steps: The sulfide-enriched binary oligomer, copolyzirconium-phosphate coordinated oxygen cluster resin, and triazine nucleotris(hydroxyethyl methacrylate) ether were added to a stirred tank. The stirred tank was heated to 30-40℃ and stirred for 10-15 minutes. After adding the photoinitiator, the mixture was vacuum degassed for 10 minutes. The mixture was then passed through a 100-mesh stainless steel filter to obtain the UV-curable adhesive.

10. The application of high refractive index UV-curable adhesives, characterized in that, The high refractive index UV-curable adhesive prepared by the method described in claim 9 is applied to the bonding of optical instruments and the encapsulation of optoelectronic devices.

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