A photothermal dual-curing phenyl epoxy silicone resin composition, its preparation method and application

Abstract

This invention discloses a photothermal dual-curing phenyl epoxy silicone resin composition, its preparation method, and its application, belonging to the field of organosilicon material technology. The photothermal dual-curing phenyl epoxy silicone resin composition, by weight, comprises: 40-60 parts of vinyl-terminated alkylphenyl polysiloxane; 20-40 parts of MDT-type phenyl hydrogen-containing silicone resin; 30-70 parts of epoxy resin; 1-5 parts of photoinitiator; 0.5-3 parts of latent thermal catalyst; and 2-10 parts of functional filler. This invention completely solves the problem of shadow areas and deep curing dead zones in LED packaging through a triple-time complementary mechanism of "photo-latent curing-thermal." Through the synergy of large steric groups and boron nitride nanosheets, it achieves simultaneous improvement in low shrinkage and high thermal conductivity, breaking the limitation of the opposition between these two in conventional technologies. Through optimization of phenyl content and fluoroalkyl modification, it achieves a balance between high refractive index and excellent hydrophobic self-cleaning properties.

Description

Technical Field

[0001] This invention relates to the field of organosilicon materials technology, specifically to a photothermal dual-curing phenyl epoxy silicone resin composition, its preparation method, and its application. Background Technology

[0002] The performance requirements for encapsulation coating materials in the LED packaging and high-end weather-resistant coating fields are becoming increasingly stringent. Currently, most mainstream LED encapsulation adhesives employ either single photocuring or single thermal curing methods. The former suffers from problems such as incomplete curing in shaded areas and incomplete deep curing; the latter is energy-intensive, has low production efficiency, and is difficult to adapt to heat-sensitive substrates. Weather-resistant coatings, on the other hand, generally suffer from poor UV aging resistance, insufficient adhesion, and inability to withstand high and low temperature cycling conditions.

[0003] To address these issues, the industry has attempted to develop a photothermal dual-curing system. However, existing dual-curing technologies still struggle to completely resolve the curing dead zone problem in the complex shadow areas of LED packaging, and material properties often present contradictions between high refractive index and low shrinkage, and high thermal conductivity and high transparency. For example, patent CN116063968B discloses a high-filler epoxy underfill adhesive, but its main component is an epoxy system with excessively high filler content, making it unsuitable for transparent packaging. Furthermore, the mainstream imported products of the same type are priced between 80,000 and 100,000 RMB per ton, while domestically produced alternatives generally suffer from unstable performance and poor batch consistency. Therefore, developing an organosilicon encapsulation coating material that can achieve complete curing (especially in shadow areas), high refractive index, ultra-low shrinkage, high thermal conductivity, excellent weather resistance, and controllable cost has significant industrial value and market potential. Summary of the Invention

[0004] The purpose of this invention is to provide a photothermal dual-curing phenyl epoxy silicone resin, its preparation method and application, to solve the technical problems of incomplete curing of LED encapsulants, poor resistance to high and low temperature cycling, and insufficient weather resistance and adhesion of weather-resistant coatings in the prior art.

[0005] To solve the above-mentioned technical problems, the technical solution of the present invention is as follows: A photothermal dual-curing phenyl epoxy silicone resin composition, comprising, by weight: 40-60 parts of vinyl-terminated alkylphenyl polysiloxane; 20-40 parts of MDT type phenyl hydrogen-containing silicone resin; 30-70 parts epoxy resin; 1-5 parts of photoinitiator; 0.5-3 parts of latent thermal catalyst; 2-10 parts of functional filler; The vinyl-terminated alkylphenyl polysiloxane has sterically hindered groups or fluoroalkyl groups introduced into its side chains; the MDT-type phenyl hydrogen-containing silicone resin has a phenyl content of 10%-30%; and the overall phenyl content of the composition is controlled at 15%-25%. The composition achieves complete curing through a triple time-complementary mechanism of "light-latent curing-heat": firstly, surface shaping is achieved by initiating free radical or cationic polymerization with ultraviolet light; then, unreacted alkoxy groups in the system are hydrolyzed and condensed in humid air at room temperature to 80°C to achieve deep curing in the shaded area; finally, the temperature is raised to >100°C to trigger a latent thermal catalyst to initiate deep crosslinking of the epoxy resin.

[0006] Key reaction mechanism: The vinyl groups in the vinyl-terminated alkylphenyl polysiloxane and the silicon-hydrogen bonds in the MDT-type phenyl hydrogen-containing silicone resin undergo a silicon addition reaction under the action of a photoinitiator or thermal catalyst to form a three-dimensional network structure of phenyl silicone resin prepolymer. After physical blending of the prepolymer with epoxy resin, a composition that can be cured multiple times is formed.

[0007] Triple temporal complementary solidification mechanism: Photocuring (surface / shallow layer setting): Under ultraviolet light (365-405nm) irradiation, the vinyl groups in vinyl-terminated alkylphenyl polysiloxanes and the silicon-hydrogen bonds (Si-H) in MDT-type phenyl hydrogen-containing silicone resin undergo a hydrosilylation reaction in the presence of a photoinitiator to form a three-dimensional network structure of phenyl silicone resin prepolymer, achieving rapid surface setting.

[0008] Latent curing (shaded areas / deep filling): After light exposure, unreacted alkoxysilane groups (from the polysiloxane backbone or side chains) in the system undergo hydrolysis and condensation reactions using trace amounts of moisture in the environment at temperatures ranging from room temperature to 80°C, achieving "dark area curing" in shaded areas and deep layers. This step is one of the core innovations of this invention, overcoming the fundamental defects of traditional photocuring and photothermal dual curing.

[0009] Thermosetting (final property impartation): Heating to >100℃ triggers a latent thermal catalyst, causing the epoxy resin and curing agent to undergo ring-opening polymerization, forming a high-density cross-linked network, which imparts the final heat resistance, mechanical properties and adhesive properties to the material.

[0010] To achieve a balance between high performance and low temperature performance, this invention modifies the polysiloxane by functionalizing its side chains: introducing sterically hindered groups (adamantyl or norbornene) into the side chains of vinyl-terminated alkylphenyl polysiloxanes to reduce curing shrinkage; or introducing fluoroalkyl side chains to improve water self-cleaning properties. By precisely controlling the phenyl content at 15%-25% (based on the total mass of the polysiloxane), both high refractive index (>1.52) and low-temperature resistance are achieved.

[0011] Wherein, the fluoroalkyl group is C1-C10 Perfluoroalkyl or perfluoropolyether group.

[0012] The vinyl-terminated alkylphenyl polysiloxane incorporates sterically hindered groups or fluoroalkyl groups into its side chains, comprising the following steps: anionic ring-opening copolymerization of a functionalized cyclosiloxane with octamethylcyclotetrasiloxane, methylphenylcyclosiloxane, and a vinyl-termining agent in a single pot to directly obtain a vinyl-terminated alkylphenyl polysiloxane with sterically hindered groups and / or fluoroalkyl groups in its side chains; wherein the functionalized cyclosiloxane is a cyclotri / cyclotetrasiloxane containing sterically hindered groups or a cyclotrisiloxane containing fluoroalkyl groups.

[0013] The functional filler is boron nitride nanosheets grafted with a silicon coupling agent or modified zinc oxide; the average particle size of the boron nitride nanosheets is 50-200 nm, and the particle size of the modified zinc oxide is 20-100 nm. Using boron nitride nanosheets grafted with a silane coupling agent instead of conventional nano-silica utilizes its high thermal conductivity and two-dimensional sheet structure to produce a synergistic effect with the aforementioned large-position cation groups: the large-position cation groups inhibit excessive growth in crosslinking density, reduce shrinkage stress, and simultaneously provide steric hindrance for the uniform dispersion of boron nitride nanosheets, preventing agglomeration, thereby improving thermal conductivity while reducing shrinkage.

[0014] The boron nitride nanosheets grafted with the silicon coupling agent are prepared by the following method: using hexagonal boron nitride as raw material, a silane coupling agent and an activating agent are added simultaneously during ball milling, and then ball milled to obtain the nanosheets; the silane coupling agent is KH-560 (X-(2,3-epoxypropoxy)propyltrimethoxysilane), and the amount used is 3-20% of the mass of hexagonal boron nitride; the activating agent is low molecular weight polyethylene glycol or triethanolamine, and the amount used is 0.5-2% of the mass of hexagonal boron nitride.

[0015] The latent thermal catalyst is a blocked isocyanate or microencapsulated amine catalyst with a thermal triggering temperature of 100-130℃.

[0016] The composition has a viscosity of 50-100 Pa·s, a refractive index >1.52 after curing, a shrinkage rate ≤0.8%, and a thermal conductivity >1.5 W / m·K.

[0017] The method for preparing the photothermal dual-curing phenyl epoxy silicone resin composition includes the following steps: S1: Mix and stir the vinyl-terminated alkylphenyl polysiloxane, MDT-type phenyl hydrogen-containing silicone resin, photoinitiator, and latent thermal catalyst at 50-90°C for 10-30 min to carry out the pre-reaction; S2: Add the formulated amount of functional filler to the mixture obtained in S1, and grind it to a fineness of ≤20um using a homogenizing grinding equipment; S3: Add the prescribed amount of epoxy resin to the mixture obtained in S2, and continue stirring at room temperature to 100°C for 20-40 minutes, controlling the viscosity of the composition to ≤100 Pa·s, to obtain the photothermal dual-curing phenyl epoxy silicone resin composition.

[0018] The application of the aforementioned photothermal dual-curing phenyl epoxy silicone resin composition in LED encapsulation materials or weather-resistant coatings includes the following curing process: UV curing: wavelength 365-405nm, irradiation time 5-10 minutes; Latent curing: Place at room temperature to 80°C for 10-60 min to allow hydrolysis and condensation reactions to occur using the alkoxy groups in the system; Thermosetting: Heat to 100-130℃ and hold for 30-60 minutes to trigger the latent thermal catalyst to complete deep cross-linking.

[0019] The LED encapsulation material, after curing, shows no failure after 1800 hours at 85°C / 85%RH and no cracking after 50 cycles at temperatures ranging from -60 to 200°C; the weather-resistant coating, after curing, shows no rust after ≥1000 hours of salt spray testing and no yellowing after ≥500 hours of UV aging testing.

[0020] Compared with the prior art, the present invention has the following beneficial effects: 1. Breakthrough in complete curing: Through the triple time-complementary mechanism of "light-latent curing-heat", the problem of shadow areas and deep curing dead zones in LED packaging is completely solved, which cannot be achieved by single or dual curing technologies.

[0021] 2. Synergistic Performance Enhancement: Through the synergistic effect of sterically hindered groups and boron nitride nanosheets, low shrinkage (≤0.8%) and high thermal conductivity (>1.5 W / m·K) are simultaneously improved, breaking the limitation of the opposition between the two in conventional technologies. By optimizing the phenyl content and fluoroalkyl modification, a balance is achieved between high refractive index (>1.52) and excellent hydrophobic self-cleaning properties (contact angle ≥110°).

[0022] 3. Cost and Industrialization Advantages: Overall cost is reduced by more than 50% compared to imported products. Single-component design (viscosity ≤80Pa·s) is suitable for automated dispensing processes, with good batch consistency (failure rate <0.02ppm). Detailed Implementation

[0023] The technical solution of the present invention will be clearly and completely described below with reference to specific 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.

[0024] Testing standards: Refractive index: ASTM D542 Shrinkage rate: ASTM D2566 Thermal conductivity: ASTM D5470 Double 85 Test: JESD22-A101 High and low temperature cycling: GB / T 2423.22 Salt spray test: GB / T-10125 UV aging: GB / T 16422.3 Example 1 (LED encapsulating adhesive) This embodiment provides a photothermal dual-curing phenyl epoxy silicone resin composition, comprising, by weight: 50 parts of vinyl-terminated alkylphenyl polysiloxane with adamantyl side chain, 30 parts of MDT-type phenyl hydrogen-containing silicone resin (total phenyl content 15%), 40 parts of epoxy resin, 2 parts of photoinitiator (Irgacure·184), 1 part of blocked isocyanate latent thermal catalyst, and 5 parts of boron nitride nanosheets grafted with silane coupling agent.

[0025] This invention provides a method for preparing a photothermal dual-curing phenyl epoxy silicone resin composition, comprising the following steps: S1: The formulated amounts of vinyl-terminated alkylphenyl polysiloxane, MDT-type phenyl hydrogen-containing silicone resin, photoinitiator, and latent thermal catalyst are mixed and stirred at 60°C for 20 min to carry out a pre-reaction; S2: Add the formulated amount of boron nitride nanosheets grafted with silane coupling agent to the mixture obtained in S1, and grind them to a fineness of 12 μm using a homogenizing grinding equipment; S3: Add the prescribed amount of epoxy resin to the mixture obtained in S2, and continue stirring at 80°C for 40 min, controlling the viscosity of the composition to 75 Pa·s, to obtain the photothermal dual-curing phenyl epoxy silicone resin composition.

[0026] This invention provides the application of the above-mentioned photothermal dual-curing phenyl epoxy silicone resin composition in LED encapsulation materials, including the following curing process: UV curing: wavelength 365nm, illumination time 10s; Latent curing: Place at room temperature to 80°C for 30 min to allow hydrolysis and condensation reactions to occur using the alkoxy groups in the system; Thermosetting: Heat to 105℃ and hold for 60 minutes to trigger the latent thermal catalyst to complete deep cross-linking.

[0027] Performance: Refractive index 1.54, shrinkage rate 0.7%, thermal conductivity 1.6W / m·K, no failure after 1800h of double 85 testing, no cracking after 50 cycles of high and low temperatures, and complete curing in the shaded area.

[0028] In this embodiment, the vinyl-terminated alkylphenyl polysiloxane with adamantyl side chain is prepared by the following method: 1. Preparation of adamantyl ethyl dimethylchlorosilane: 1-Vinyladamantane and dimethylchlorosilane were subjected to a hydrosilylation reaction in the presence of a platinum catalyst (Krstedt catalyst, Pt amount 10~20ppm). The conditions were: toluene as solvent, 60~80℃, N2 protection, reaction time 6~10h. The conversion rate of 1-vinyladamantane was monitored. The product fraction was collected by vacuum distillation to obtain adamantyl ethyl dimethylsilane.

[0029] 2. Preparation of 1,3,5-trimethyl-1,3,5-tris(adamantylethyl)cyclotrisiloxane (Ad3-D3) by hydrolysis and cyclization: The above chlorosilane was slowly added dropwise to a deionized water / diethyl ether mixture and hydrolyzed at 0-5°C. Then, a small amount of hydrochloric acid was added to catalyze cyclization. The mixture was stirred overnight at room temperature. The organic phase was separated, washed with water until neutral, dried, and then distilled under reduced pressure to collect the target product Ad3-D3.

[0030] 3. Preparation of functionalized polysiloxanes by ring-opening copolymerization: In a 1L polymerization reactor, 370g of D4, 60g of methylphenylcyclosiloxane, 35g of Ad3-D3, and 3.5g of 1,3-divinyltetramethyldisiloxane were added, along with 0.2g of tetramethylammonium hydroxide alkali gel. The mixture was reacted at 110℃ for 10h. After removing low-boiling substances, a modified polysiloxane with a vinyl content of 0.32 mmol / g, an adamantyl molar content of approximately 4.2%, and a fluoroalkyl molar content of approximately 5.6% was obtained.

[0031] In this embodiment, the method for preparing silane coupling agent-grafted boron nitride nanosheets is as follows: Among them, hexagonal boron nitride powder (h-BN, particle size 5~30µm, purity ≥99%), silane coupling agent: kH-560 (γ-(2,3-epoxypropoxy)propyltrimethoxysilane): introduces epoxy groups, suitable for epoxy-modified systems; activating agent: low molecular weight polyethylene glycol (FEG-400) or triethanolamine, the amount of which is 0.5%~2% of the mass of h-BN; dispersion medium: anhydrous ethanol or acetone, added in small amounts to improve material flowability, the amount added during wet ball milling is 10%~30% of the total mass of solid phase; feeding ratio: the mass ratio of h-BN to silane coupling agent is 100: (3~20), preferably 100: (5~12).

[0032] Steps: Mechanochemical ball milling in-situ grafting: h-BN powder, silane coupling agent, and activating agent ethanol are added to a planetary ball mill in a specific ratio (zirconia or silicon nitride are used for the jar and grinding balls to avoid metal contamination). The mass ratio of h-BN to silane coupling agent is 100:9, and the amount of activating agent ethanol added is 20% of the total mass of the solid phase.

[0033] Grinding ball configuration: Large balls (10mm), medium balls (5mm), and small balls (2mm) are mixed in a mass ratio of 1:2:3, with a ball-to-material ratio of 20:140:1. Ball milling process parameters: rotation speed: 500 rpm, time: 6 h, alternating forward and reverse rotation every 30 min, stop and cool for 15 min every 2 h to avoid local overheating that could cause self-polymerization of silane coupling agent.

[0034] Atmosphere: N2 protection.

[0035] Example 2 (LED encapsulating adhesive) This embodiment provides a photothermal dual-curing phenyl epoxy silicone resin composition, comprising, by weight: 45 parts of vinyl-terminated alkylphenyl polysiloxane with norbornene-containing side chains, 35 parts of MDT-type phenyl hydrogen-containing silicone resin (total phenyl content 20%), 50 parts of epoxy resin, 3 parts of photoinitiator (Irgacure·184), 1.5 parts of microencapsulated latent thermal catalyst, and 8 parts of boron nitride nanosheets grafted with silane coupling agent.

[0036] The present invention provides a method for preparing the above-mentioned photothermal dual-curing phenyl epoxy silicone resin composition, comprising the following steps: S1: The formulated amounts of vinyl-terminated alkylphenyl polysiloxane with nobornene side chains, MDT-type phenyl hydrogen-containing silicone resin, photoinitiator and latent thermal catalyst are mixed and stirred at 50°C for 30 min to carry out pre-reaction; S2: Add the formulated amount of boron nitride nanosheets grafted with silane coupling agent to the mixture obtained in S1, and grind them to a fineness of 10 μm using a homogenizing grinding equipment; S3: Add the prescribed amount of epoxy resin to the mixture obtained in S2, and continue stirring at 100°C for 20 minutes. Control the viscosity of the composition to 70 Pa·s to obtain the photothermal dual-curing phenyl epoxy silicone resin composition.

[0037] This invention provides the application of the above-mentioned photothermal dual-curing phenyl epoxy silicone resin composition in LED encapsulation materials, including the following curing process: UV curing: wavelength 405nm, irradiation time 5s; Latent curing: Place at 80℃ for 60 min, and utilize the alkoxy groups in the system to carry out hydrolysis and condensation reactions; Thermosetting: Heat to 130℃ and hold for 30 minutes to trigger the latent thermal catalyst to complete deep cross-linking.

[0038] Performance: Refractive index 1.55, shrinkage rate 0.6%, thermal conductivity 1.7W / m·K, tested for 2000 hours without failure, and no cracking after 50 high and low temperature cycles.

[0039] In this embodiment, the vinyl-terminated alkylphenyl polysiloxane with norbornene groups in the side chain is prepared by the following method: 1) Preparation of norbornene-enylethyldimethylchlorosilane: 5-norbornen-2-ylethyldimethylchlorosilane was subjected to a hydrosilylation reaction with dimethylchlorosilane in the presence of a platinum catalyst (Karstedt catalyst, Pt amount 10~20ppm). The conditions were: toluene as solvent, 70~90℃, N2 protection, reaction time 8~12h. The reaction endpoint was determined by gas chromatography when the conversion rate of 5-norbornen-2-ylvinyl was ≥98%. Post-treatment: the target fraction was collected by vacuum distillation to obtain norbornenen-ethyldimethylchlorosilane.

[0040] 2) Hydrolysis and cyclization to prepare 1,3,5-trimethyl-1,3,5-tris(norbornenylethyl)cyclotrisiloxane (Nb3-D3): The above-mentioned chlorosilane was slowly added dropwise to a deionized water / diethyl ether mixture and hydrolyzed at a low temperature of 0-5°C. Then, a small amount of trifluoromethanesulfonic acid was added to catalyze cyclization. The mixture was stirred overnight at room temperature, the organic phase was separated, washed with deionized water until neutral, dried with anhydrous sodium sulfate, and then distilled under reduced pressure to collect the target product Nb3-D3.

[0041] 3) Preparation of functionalized polysiloxanes by ring-opening copolymerization: In a 1L polymerization reactor, 360g of octamethylcyclotetrasiloxane (D4), 65g of methylphenylcyclosiloxane, 42g of Nb3-D3, and 4.2g of 1,3-divinyltetramethyldisiloxane were added, along with 0.25g of tetramethylammonium hydroxide alkali gel as a catalyst. The reaction was carried out at 110℃ for 12h. The temperature was then raised to 180℃ to decompose the catalyst. After removing unreacted rings and low-boiling substances under reduced pressure, a modified polysiloxane with a vinyl content of 0.30mmol / g, a norbornene molar content of approximately 5.0%, and a phenyl molar content of approximately 12.5% ​​was obtained, with a viscosity of approximately 5500mPa·s (25℃).

[0042] Example 3 (Weather-resistant coating) This embodiment provides a photothermal dual-curing phenyl epoxy silicone resin composition, which, by weight, comprises: 60 parts of vinyl-terminated alkylphenyl polysiloxane with perfluoroalkyl side chains, 20 parts of DT type phenyl hydrogen-containing silicone resin (total phenyl content 25%), 70 parts of organosilicon hybrid epoxy resin, 1 part of photoinitiator (Irgacure·184), 3 parts of blocked isocyanate catalyst, and 2 parts of modified zinc oxide.

[0043] The present invention provides a method for preparing the above-mentioned photothermal dual-curing phenyl epoxy silicone resin composition, comprising the following steps: S1: Mix and stir the formulated amounts of vinyl-terminated alkylphenyl polysiloxane with perfluoroalkyl side chains, MDT-type phenyl hydrogen-containing silicone resin, photoinitiator and latent thermal catalyst at 90°C for 10 min to carry out pre-reaction; S2: Add the formulated amount of functional filler to the mixture obtained in S1, and grind it to a fineness of 14 μm using a homogenizing grinding equipment; S3: Add the prescribed amount of epoxy resin to the mixture obtained in S2, and continue stirring at 130°C for 30 min, controlling the viscosity of the composition to 78 Pa·s, to obtain the photothermal dual-curing phenyl epoxy silicone resin composition.

[0044] This invention also provides the application of the above-mentioned photothermal dual-curing phenyl epoxy silicone resin composition in weather-resistant coatings, including the following curing process: UV curing: wavelength 365nm, illumination time 10s; Latent curing: After being placed at room temperature for 60 minutes, hydrolysis and condensation reactions are carried out using the alkoxy groups in the system; Thermosetting: Heat to 100℃ and hold for 60 minutes to trigger the latent thermal catalyst to complete deep cross-linking.

[0045] Performance: Elongation at break 450%, adhesion grade 1, no rust after 1200h salt spray test, no yellowing after 550h UV aging, contact angle 112°.

[0046] In this embodiment, the preparation method of vinyl-terminated alkylphenyl polysiloxane with perfluoroalkyl side chains is as follows: In a 1L polymerization reactor, 350g of octamethylcyclotetrasiloxane (D4), 70g of methylphenylcyclosiloxane, 55g of perfluoroalkylethylmethylcyclotrisiloxane (F3-D3, perfluorohexylethylmethylcyclotrisiloxane), and 3.8g of 1,3-divinyltetramethyldisiloxane were added, along with 0.15g of trifluoromethanesulfonic acid as an initiator. The ring-opening polymerization reaction was carried out at 40-50℃ for 6-8h, and then the temperature was raised to 80℃. Deionized water was added to terminate the reaction, and the mixture was stirred for another 2h to allow the trifluoromethanesulfonic acid to be fully hydrolyzed. The mixture was allowed to stand and the lower acidic water layer was removed. The organic layer was washed with deionized water until neutral, and low-boiling substances and residual rings were removed by vacuum distillation to obtain vinyl-terminated alkylphenyl polysiloxane with a vinyl content of approximately 0.28 mmol / g, a perfluoroalkyl molar content of approximately 5.8%, and a phenyl molar content of approximately 13.2%, and a viscosity of approximately 4800 mPa·s (25℃). The perfluoroalkyl group in the perfluoroalkyl ethyl methyl cyclotrisiloxane is perfluorohexyl ethyl or perfluorobutyl ethyl. The introduction of the fluoroalkyl side chain endows the material with excellent hydrophobic self-cleaning properties and low surface energy characteristics.

[0047] Comparative Example 1 (no latent curing, only photothermal dual curing) The formula is the same as in Example 2, but the "latent curing" step is omitted in the curing process, that is, heat curing is performed directly after UV curing.

[0048] Results: After 30 cycles of high and low temperatures, microcracks appeared at the edge of the LED support (shade area); after 1200 hours of dual 85 testing, the light transmittance decreased by 15%. This proves that the latent curing mechanism is indispensable for stress release and deep curing in the shaded area.

[0049] Comparative Example 2 (Conventional nano-silica replacing boron nitride) The formulation is basically the same as in Example 1, except that boron nitride nanosheets are replaced with an equal mass of unmodified nano-silica.

[0050] Results: The thermal conductivity was only 0.6 W / m·K, and the shrinkage rate was 0.8%. Compared with Example 1, this demonstrates that boron nitride nanosheets have better compatibility and thermal conductivity enhancement with this system, without compromising the low shrinkage performance.

[0051] Comparative Example 3 (total phenyl content exceeds the range, at 35%) The formulation is basically the same as in Example 2, but the base content of the MDT-type phenyl hydrogen-containing silicone resin is adjusted to 35%, and the overall phenyl content is about 30%.

[0052] Results: The refractive index increased to 1.58, but cracking occurred after 35 high and low temperature cycles. The hardness was too high at -60°C, and the flexibility decreased. This demonstrates that the phenyl content needs to be strictly controlled within the range specified in this invention to balance temperature resistance and flexibility.

[0053] Comparative Example 4 (Vinyl-terminated alkylphenyl polysiloxane side chain without norbornene group) The formulation is basically the same as in Example 2, but the vinyl-terminated alkylphenyl polysiloxane with norbornene group in the side chain is changed to vinyl-terminated alkylphenyl polysiloxane.

[0054] Results: The shrinkage rate after curing increased from 0.6% in Example 2 to 0.92%. Cracking occurred after 40 cycles of high and low temperature cycling (Example 2 showed no cracking after 50 cycles). Cross-sectional SEM showed a significant increase in stress patterns within the cross-linked network, and localized aggregation of boron nitride nanosheets. This demonstrates that the introduction of sterically hindered side chain groups (norbornene groups) effectively reduces cross-linking shrinkage stress and provides steric hindrance assistance for the uniform dispersion of boron nitride nanosheets, playing a crucial synergistic role in simultaneously maintaining low shrinkage rate and high thermal conductivity.

[0055] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A photothermal dual-curing phenyl epoxy silicone resin composition, characterized in that, Included by weight parts: 40-60 parts of vinyl-terminated alkylphenyl polysiloxane; 20-40 parts of MDT type phenyl hydrogen-containing silicone resin; 30-70 parts epoxy resin; 1-5 parts of photoinitiator; 0.5-3 parts of latent thermal catalyst; 2-10 parts of functional filler; The vinyl-terminated alkylphenyl polysiloxane has sterically hindered groups or fluoroalkyl groups introduced into its side chains; the MDT-type phenyl hydrogen-containing silicone resin has a phenyl content of 10%-30%; and the overall phenyl content of the composition is controlled at 15%-25%. The composition achieves complete curing through a triple time-complementary mechanism of "light-latent curing-heat": firstly, surface shaping is achieved by initiating free radical or cationic polymerization with ultraviolet light; then, unreacted alkoxy groups in the system are hydrolyzed and condensed in humid air at room temperature to 80°C to achieve deep curing in the shaded area; finally, the temperature is raised to >100°C to trigger a latent thermal catalyst to initiate deep crosslinking of the epoxy resin.

2. The photothermal dual-curing phenyl epoxy silicone resin composition according to claim 1, characterized in that, The sterically hindered group is adamantyl or norbornene; the fluoroalkyl group is C1-C6. 10 Perfluoroalkyl or perfluoropolyether group.

3. The photothermal dual-curing phenyl epoxy silicone resin composition according to claim 1, characterized in that, The side chain of the vinyl-terminated alkylphenyl polysiloxane is introduced with a sterically hindered group or a fluoroalkyl group, comprising the following steps: anionic ring-opening copolymerization of a functionalized cyclosiloxane with octamethylcyclotetrasiloxane, methylphenylcyclosiloxane, and a vinyl-termining agent in one pot to directly obtain a vinyl-terminated alkylphenyl polysiloxane with a sterically hindered group and / or a fluoroalkyl group in the side chain; wherein the functionalized cyclosiloxane is a cyclotri / cyclotetrasiloxane containing a sterically hindered group or a cyclotrisiloxane containing a fluoroalkyl group.

4. The photothermal dual-curing phenyl epoxy silicone resin composition according to claim 1, characterized in that, The functional filler is boron nitride nanosheets grafted with a silicon coupling agent or modified zinc oxide; the average particle size of the boron nitride nanosheets is 50-200 nm, and the particle size of the modified zinc oxide is 20-100 nm.

5. The photothermal dual-curing phenyl epoxy silicone resin composition according to claim 4, characterized in that, The boron nitride nanosheets grafted with the silane coupling agent are prepared by the following method: using hexagonal boron nitride as raw material, a silane coupling agent and an activating agent are added simultaneously during ball milling, and then ball milled to obtain the nanosheets; the silane coupling agent is KH-560, and the amount used is 3-20% of the mass of hexagonal boron nitride; the activating agent is low molecular weight polyethylene glycol or triethanolamine, and the amount used is 0.5-2% of the mass of hexagonal boron nitride.

6. The photothermal dual-curing phenyl epoxy silicone resin composition according to claim 1, characterized in that, The latent thermal catalyst is a blocked isocyanate or microencapsulated amine catalyst with a thermal triggering temperature of 100-130℃.

7. The photothermal dual-curing phenyl epoxy silicone resin composition according to claim 1, characterized in that, The composition has a viscosity of 50-100 Pa·s, a refractive index >1.52 after curing, a shrinkage rate ≤0.8%, and a thermal conductivity >1.5 W / m·K.

8. A method for preparing the photothermal dual-curing phenyl epoxy silicone resin composition according to any one of claims 1-7, characterized in that... Includes the following steps: S1: Mix and stir the vinyl-terminated alkylphenyl polysiloxane, MDT-type phenyl hydrogen-containing silicone resin, photoinitiator, and latent thermal catalyst at 50-90°C for 10-30 min to carry out the pre-reaction; S2: Add the formulated amount of functional filler to the mixture obtained in S1, and grind it to a fineness of ≤20um using a homogenizing grinding equipment; S3: Add the prescribed amount of epoxy resin to the mixture obtained in S2, and continue stirring at room temperature to 100°C for 20-40 minutes, controlling the viscosity of the composition to ≤100 Pa·s, to obtain the photothermal dual-curing phenyl epoxy silicone resin composition.

9. The application of the photothermal dual-curing phenyl epoxy silicone resin composition according to any one of claims 1-7 in LED encapsulation materials or weather-resistant coatings, characterized in that, The following curing processes are included: UV curing: wavelength 365-405nm, irradiation time 5-10s; Latent curing: Place at room temperature to 80°C for 10-60 min to allow hydrolysis and condensation reactions to occur using the alkoxy groups in the system; Thermosetting: Heat to 100-130℃ and hold for 30-60 minutes to trigger the latent thermal catalyst to complete deep cross-linking.

10. The application according to claim 9, characterized in that, After curing, the LED encapsulation material showed no failure after 1800 hours at 85°C / 85%RH and no cracking after 50 temperature cycles from -60 to 200°C. After curing, the weather-resistant coating showed no rust after ≥1000 hours of salt spray testing and no yellowing after ≥500 hours of UV aging testing.