An epoxy resin material for LED encapsulation and a preparation method thereof

Abstract

The present application relates to a kind of epoxy resin materials for LED packaging and preparation method thereof, belong to LED packaging material technical field, hyperbranched polysiloxane and amino boron nitride are added to epoxy resin material, hyperbranched polysiloxane is bonded with ester group-containing epoxy resin matrix by virtue of three-dimensional branched structure, induces chemical microphase separation and forms nanoscale domain structure, dissipates energy by crack deflection, chain segment slip when being impacted, while its flexible siloxane segment effectively relieves curing internal stress, after modification of amino boron nitride by polyallylamine, surface amino and epoxy group form strong interface effect, not only inhibit crack propagation, but also can be used as rigid reinforcing phase to improve bearing capacity, the impact strength and flexural strength of the epoxy resin material for LED packaging are improved by the synergy of the two, adapt flexible LED application field.

Description

Technical Field

[0001] This invention belongs to the field of LED packaging material technology, and relates to an epoxy resin material for LED packaging and its preparation method. Background Technology

[0002] Light-emitting diodes (LEDs) have become the core light source in the lighting and display fields due to their advantages such as energy saving, high efficiency, and long lifespan. Encapsulation materials are key to ensuring the optical performance, heat resistance, and reliability of LEDs. Epoxy resin has become the preferred matrix material for low- and medium-power LED packaging due to its high light transmittance, excellent adhesion, low curing shrinkage, and controllable cost. However, as LEDs iterate towards high power, miniaturization, and Mini / Micro LEDs, the shortcomings of traditional bisphenol A epoxy encapsulation materials are becoming increasingly prominent: the glass transition temperature is relatively low, making it prone to thermal aging, yellowing, and light transmittance decay under long-term high-temperature conditions, which exacerbates light decay and color shift; the material has poor toughness and high internal stress, making it prone to cracking and interface debonding during thermal cycling, reducing the device's hermeticity; the filler has poor compatibility with the matrix, making it difficult to achieve a balance between high refractive index, high thermal conductivity, and low haze; residual impurities can easily corrode electrodes, causing electrochemical failure; and conventional blending and curing processes also have problems such as uneven dispersion and residual bubbles, further degrading device performance.

[0003] Chinese invention patent application CN104761871A discloses an epoxy resin encapsulation material for LED packaging and its preparation method. The material consists of component A and component B. Component A, by weight, contains 100 parts of epoxy resin mixture, 0.1-1 parts of antioxidant, 0.1-1 parts of light stabilizer, 0.01-1 parts of cationic accelerator, and 0.001-0.01 parts of dye. Component B, by weight, consists of 100 parts of acid anhydride, 0.1-1 parts of antioxidant, 10-30 parts of polyhexyl lactone polyol, and 0.5-1 parts of nucleophilic accelerator. The prepared epoxy resin encapsulation material for LED packaging has low viscosity, high light transmittance, excellent high-temperature resistance, excellent UV resistance, and excellent thermal shock resistance, meeting the performance requirements of white and blue LEDs operating in harsh environments.

[0004] The aforementioned technical solutions rely solely on the flexible segments of polyhexyl lactone polyol for toughening. This mechanism is limited to physical compatibility and segment slippage, failing to form chemical bonds with the epoxy resin matrix. This results in uneven polyol dispersion, making it difficult to form a uniform nanoscale domain structure and limiting toughening efficiency. Furthermore, single flexible segment toughening lacks synergistic rigidity reinforcement, failing to balance impact toughness and flexural strength. Insufficient internal stress relief makes it unsuitable for the stringent mechanical reliability requirements of flexible LEDs and high-power LEDs, and prone to cracking and debonding under complex operating conditions. Summary of the Invention

[0005] The purpose of this invention is to provide an epoxy resin material for LED packaging and its preparation method. By synergistically modifying ester-containing epoxy resin with aminoboron nitride and hyperbranched polysiloxane, the impact toughness, flexural strength and thermal conductivity of the material are improved simultaneously, the risk of yellowing is reduced, and it is suitable for flexible, high-power LED packaging requirements.

[0006] The objective of this invention can be achieved through the following technical solutions: A method for preparing an epoxy resin material for LED encapsulation includes the following steps: Step 1: Graft polyallylamine molecules onto the surface of boron nitride hydroxyl powder using electrostatic attraction to obtain boron nitride amino.

[0007] Step 2: γ-glycidoxypropyltrimethoxysilane is grafted onto the 1,6-hexanediol molecular chain via transesterification to obtain hyperbranched polysiloxane.

[0008] Step 3: Hydrogenated cinnamic acid undergoes a Friedel-Crafts reaction with succinic anhydride under the catalysis of anhydrous aluminum chloride to obtain an intermediate acid; the intermediate acid and epichlorohydrin undergo a nucleophilic substitution reaction under the catalysis of tetrabutylammonium bromide to obtain an ester-containing epoxy resin.

[0009] Step 4: Add ester-based epoxy resin, curing agent, hyperbranched polysiloxane, amino boron nitride and curing accelerator to the reaction vessel, mix evenly to obtain epoxy resin material for LED encapsulation.

[0010] Furthermore, the specific preparation process of aminoboron nitride is as follows: Hydroxy boron nitride powder and deionized water were added to a reaction vessel, followed by a 30 wt% polyallylamine solution. The mixture was stirred at 20-25 °C and 300-500 r / min for 5-6 h, then centrifuged, washed, and dried to obtain amino boron nitride.

[0011] Furthermore, the ratio of boron hydroxynitride powder, deionized water, and polyallylamine solution is 10-15g: 5-6L: 60-80g.

[0012] Furthermore, the specific preparation process of hyperbranched polysiloxane is as follows: 1,6-hexanediol, γ-glycidoxypropyltrimethoxysilane, and p-toluenesulfonic acid were added to a reactor at 20-25℃ and reacted at 100-120℃ for 1-2 hours. The byproduct methanol was distilled off, and the distillation temperature was kept below 65℃. The temperature was then slowly increased to 160-170℃ at a rate of 10℃ / h, and the distillation temperature was maintained at 55℃-60℃. The mixture was allowed to cool naturally until the distillation temperature dropped below 50-60℃, at which point heating was stopped. The mixture was then dried and dialyzed to obtain hyperbranched polysiloxane.

[0013] Furthermore, the mass ratio of 1,6-hexanediol, γ-glycidyl etheroxypropyltrimethoxysilane, and p-toluenesulfonic acid is 390-420:487.30-527.30:3.52-5.52.

[0014] Furthermore, the specific preparation process of the intermediate acid is as follows: Hydrogenated cinnamic acid and dichloromethane were added to a reaction vessel and stirred until completely dissolved. Anhydrous aluminum chloride was slowly added at 0-2°C. After reacting for 30-40 minutes, succinic anhydride was slowly added to the system. The reaction was carried out under nitrogen protection at 20-25°C for 8-10 hours. After the reaction was completed, the mixture was poured into ice-cold deionized water, and 37wt% hydrochloric acid was added dropwise. The mixture was then filtered, purified, washed, and dried to obtain the intermediate acid.

[0015] Furthermore, the ratio of hydrogenated cinnamic acid, dichloromethane, anhydrous aluminum chloride, succinic anhydride, ice-cold deionized water, and hydrochloric acid is 52.5-62.5g: 530-730mL: 116.375-156.375g: 35-45g: 800-900mL: 28-32mL.

[0016] Furthermore, the specific preparation process of the ester-containing epoxy resin is as follows: Intermediate acid, epichlorohydrin, and tetrabutylammonium bromide were added to a reaction vessel and reacted at 80-85℃ under nitrogen protection for 1-3 hours. A 40wt% sodium hydroxide solution was added dropwise, and the reaction was continued for another hour. After the reaction was completed, the mixture was filtered, extracted, dried, and rotary evaporated to obtain an ester-containing epoxy resin.

[0017] Furthermore, the mass ratio of the intermediate acid, epichlorohydrin, tetrabutylammonium bromide, and sodium hydroxide solution is 25-35: 462.5-472.5: 1.9-2.2: 25-35.

[0018] Furthermore, the mass ratio of ester-based epoxy resin, curing agent, hyperbranched polysiloxane, aminoboron nitride, and curing accelerator is 10-12:7.80-9.80:0.8-1.2:1-1.5:0.384-0.484.

[0019] Furthermore, the curing agent is either methylhexahydrophthalic anhydride or methyltetrahydrophthalic anhydride.

[0020] Furthermore, the curing accelerator is either 1,5,7-triazabicyclo[4.4.0]dec-5-ene or 2-ethyl-4-methylimidazolium.

[0021] The present invention also provides an epoxy resin material for LED encapsulation, which is obtained by stirring an ester-based epoxy resin, a curing agent, a hyperbranched polysiloxane, an amino boron nitride, and a curing accelerator at 140-145°C and 500-600 r / min for 15-20 min until the mixture is homogeneous.

[0022] The beneficial effects of this invention are: 1. This invention incorporates hyperbranched polysiloxane and aminoboron nitride into epoxy resin materials. The hyperbranched polysiloxane, with its three-dimensional branched structure, chemically bonds with the ester-containing epoxy resin matrix, inducing chemical microphase separation to form a nanoscale domain structure. Under impact, it dissipates energy through crack deflection and chain segment slippage. At the same time, its flexible siloxane segments effectively alleviate the internal stress during curing. After modification with polyallylamine, the aminoboron nitride forms a strong interfacial interaction between the surface amino and epoxy groups, which not only inhibits crack propagation but also acts as a rigid reinforcing phase to improve load-bearing capacity. The two work synergistically to improve the impact strength and flexural strength of epoxy resin materials for LED packaging, making them suitable for flexible LED applications.

[0023] 2. The aminoboron nitride of this invention exhibits significantly improved dispersion uniformity after modification with polyallylamine, constructing a continuous thermally conductive pathway in the matrix and effectively solving the heat accumulation problem of high-power LED chips. Simultaneously, the polar ester groups in the ester-containing epoxy resin matrix provide dipole polarization, and the three-dimensional structure of the hyperbranched polysiloxane optimizes the distribution of polar groups. The interfacial polarization formed between aminoboron nitride and the matrix further regulates the dielectric response, stabilizing the dielectric constant of the material at 2.9-3.1 (1kHz). The dielectric properties are adapted to the requirements of high-frequency signal transmission. This synergistic optimization of thermal conductivity and dielectric properties meets the dual requirements of heat dissipation and signal stability for high-density integrated LED packaging.

[0024] 3. The ester-based epoxy resin in this invention does not contain easily oxidized bisphenol A structure, resulting in stronger molecular chain stability. The siloxane segments of the hyperbranched polysiloxane have excellent resistance to oxygen aging and UV protection, which can inhibit the breakage of matrix molecular chains and oxidative discoloration. The inert surface of aminoboron nitride can block oxygen from contacting the matrix, slowing down the rate of thermo-oxidative aging. The three components work together to construct a multi-layer anti-aging protection system. After thermal aging, the yellowing index is lower than that of traditional epoxy materials, extending the service life of LED devices.

[0025] 4. The intermediate acid and ester-containing epoxy resin of this invention are prepared using bio-based raw materials such as hydrogenated cinnamic acid and succinic anhydride as the core, which reduces the dependence on petroleum resources. Moreover, the dynamic ester bonds in the material endow it with potential degradability, which is in line with the trend of green development. In the preparation process, the amount of raw materials and reaction parameters of each step are precisely matched. For example, the surface modification process of aminoboron nitride and the transesterification reaction conditions of hyperbranched polysiloxane are synergistic to ensure the compatibility of modified components and matrix. The viscosity of the material is controlled within the range suitable for conventional dispensing and molding processes. The segmented curing process reduces bubbles and internal stress residues, improves the packaging yield, and takes into account both environmental protection and industrial mass production requirements. Detailed Implementation

[0026] To further illustrate the technical means and effects of the present invention in achieving the intended purpose, the following detailed description of the specific implementation methods, features and effects of the present invention, in conjunction with preferred embodiments, is provided below.

[0027] Example 1: This example provides an epoxy resin material for LED encapsulation, which is prepared through the following steps: S1: Add 12.5g of boron nitride powder and 5.5L of deionized water to a reactor, add 70g of 30wt% polyallylamine solution, stir at 22℃ and 400r / min for 5.5h, centrifuge at 6100r / min for 12min, wash the precipitate with deionized water 4 times, and dry to obtain aminoboron nitride.

[0028] Polyallylamine molecules adsorb and bind to the negative potential points on the surface of boron hydroxynitride powder through electrostatic attraction, forming a stable ionic bond. This allows polyallylamine molecules to be grafted onto the surface of boron hydroxynitride powder, ultimately yielding amino boron nitride with surface-grafted amino groups.

[0029] S2: 405g of 1,6-hexanediol, 507.30g of γ-glycidyl etheroxypropyltrimethoxysilane and 4.52g of p-toluenesulfonic acid were added to a reaction vessel at 22℃ and reacted at 110℃ for 1.5h. The byproduct methanol was distilled off, and the distillation temperature was kept below 65℃. The temperature was slowly increased to 165℃ at a rate of 10℃ / h, and the distillation temperature was kept at 57℃. The temperature was allowed to cool naturally until it dropped below 55℃, at which point heating was stopped. The sample was then vacuum dried at 65℃ for 25h and dialyzed at 22℃ to remove low molecular weight molecules, yielding hyperbranched polysiloxane.

[0030] In γ-glycidoxypropyltrimethoxysilane, the methoxy group in the molecule undergoes transesterification with the hydroxyl group in 1,6-hexanediol to generate a Si-OC covalent bond and release methanol as a byproduct. During the process, the distillation temperature is strictly controlled to not exceed 65°C to ensure efficient removal of methanol and prevent the raw material from volatilizing. The temperature is then increased and maintained to promote transesterification and branching of the molecular chain. The reversible reaction is driven forward by the gradual removal of methanol until the distillation temperature decreases, indicating that the reaction is complete. Unreacted low-molecular-weight monomers and catalyst residues are removed by dialysis, ultimately forming a hyperbranched polysiloxane with Si-OC as the main chain and epoxy and hydroxyl groups at the ends.

[0031] S3: Add 57.5g of hydrogenated cinnamic acid and 630mL of dichloromethane to a reaction vessel and stir until completely dissolved. Slowly add 136.375g of anhydrous aluminum chloride at 1℃. After reacting for 35min, slowly add 40g of succinic anhydride to the system. React for 9h under nitrogen protection and at 22℃. After the reaction is complete, pour it into 850mL of ice-cold deionized water and add 30mL of 37wt% hydrochloric acid dropwise. Filter the solution and dissolve the precipitate in tetrahydrofuran. Then place it in a mixed solution of ethyl acetate and n-hexane (ethyl acetate: n-hexane = 1:3) to precipitate a solid. Wash the precipitate four times with deionized water and dry it under vacuum at 62℃ for 13h to obtain the intermediate acid.

[0032] The active sites on the benzene ring of hydrogenated cinnamic acid are activated by anhydrous aluminum chloride (Lewis acid catalyst), and undergo a Friedel-Crafts reaction with succinic anhydride under low temperature conditions. Succinic anhydride acts as an acylation reagent to introduce acyl and carboxyl functional groups into the benzene ring, yielding an intermediate acid containing ester and carboxyl groups, which provides active sites for subsequent epoxidation reactions.

[0033] S4: Add 30g of intermediate acid, 467.5g of epichlorohydrin and 2.05g of tetrabutylammonium bromide to a reaction vessel and react at 82℃ under nitrogen protection for 2h. Add 30g of 40wt% sodium hydroxide solution dropwise and continue the reaction for 1h. After the reaction is complete, filter, collect the filtrate and extract it 4 times with saturated brine. Add anhydrous sodium sulfate to the separated organic phase, dry for 13h, filter, and rotary evaporate the filtrate to obtain ester-containing epoxy resin.

[0034] The carboxyl group in the intermediate acid undergoes a nucleophilic substitution reaction with excess epichlorohydrin under the catalysis of tetrabutylammonium bromide (phase transfer catalyst). Epichlorohydrin provides the epoxy group as a reaction reagent. The dropwise addition of 40wt% sodium hydroxide solution promotes the closure of the epoxy ring by removing HCl. The reaction is continued for 1 hour to ensure complete epoxidation, resulting in an ester-containing epoxy resin containing ester groups and epoxy groups.

[0035] S5: 11g of ester-based epoxy resin, 8.80g of curing agent methyltetrahydrophthalic anhydride, 1.0g of hyperbranched polysiloxane, 1.2g of aminoboron nitride, and 0.434g of curing accelerator 1,5,7-triazabicyclo[4.4.0]dec-5-ene were added to a reaction vessel and stirred for 17min at 142℃ and 550r / min to obtain epoxy resin material for LED encapsulation.

[0036] Example 2: This example provides an epoxy resin material for LED encapsulation, which is prepared through the following steps: S1: Add 10g of boron nitride powder and 5L of deionized water to a reactor, add 60g of 30wt% polyallylamine solution, stir for 5h at 20℃ and 300r / min, centrifuge for 10min at 6000r / min, wash the precipitate three times with deionized water, and dry to obtain aminoboron nitride.

[0037] S2: 390g of 1,6-hexanediol, 487.30g of γ-glycidyl etheroxypropyltrimethoxysilane and 3.52g of p-toluenesulfonic acid were added to a reaction vessel at 20℃ and reacted at 100℃ for 1h. The byproduct methanol was distilled off, and the distillation temperature was kept below 65℃. The temperature was slowly increased to 160℃ at a rate of 10℃ / h, and the distillation temperature was kept at 55℃. The temperature was allowed to cool naturally until it dropped below 50℃, at which point heating was stopped. The sample was then vacuum dried at 60℃ for 24h and dialyzed at 20℃ to remove low molecular weight molecules, yielding hyperbranched polysiloxane.

[0038] S3: Add 52.5g of hydrogenated cinnamic acid and 530mL of dichloromethane to a reaction vessel and stir until completely dissolved. Slowly add 116.375g of anhydrous aluminum chloride at 0℃. After reacting for 30min, slowly add 35g of succinic anhydride to the system. React for 8h under nitrogen protection and at 20℃. After the reaction is complete, pour it into 800mL of ice-cold deionized water and add 28mL of 37wt% hydrochloric acid dropwise. Filter the solution and dissolve the precipitate in tetrahydrofuran. Then place it in a mixed solution of ethyl acetate and n-hexane (ethyl acetate: n-hexane = 1:3) to precipitate a solid. Wash the precipitate three times with deionized water and dry it under vacuum at 60℃ for 12h to obtain the intermediate acid.

[0039] S4: Add 25g of intermediate acid, 462.5g of epichlorohydrin and 1.9g of tetrabutylammonium bromide to a reaction vessel and react at 80℃ under nitrogen protection for 1h. Add 25g of 40wt% sodium hydroxide solution dropwise and continue the reaction for 1h. After the reaction is complete, filter, collect the filtrate and extract it three times with saturated brine. Add anhydrous sodium sulfate to the separated organic phase, dry for 12h, filter, and rotary evaporate the filtrate to obtain ester-containing epoxy resin.

[0040] S5: Add 10g of ester-based epoxy resin, 7.80g of curing agent methyltetrahydrophthalic anhydride, 0.8g of hyperbranched polysiloxane, 1g of amino boron nitride, and 0.384g of curing accelerator 1,5,7-triazabicyclo[4.4.0]dec-5-ene to a reaction vessel and stir for 15min at 140℃ and 500r / min to obtain epoxy resin material for LED encapsulation.

[0041] Example 3: This example provides an epoxy resin material for LED encapsulation, which is prepared through the following steps: S1: Add 15g of boron nitride powder and 6L of deionized water to a reactor, add 80g of 30wt% polyallylamine solution, stir for 6h at 25℃ and 500r / min, centrifuge for 15min at 6200r / min, wash the precipitate 5 times with deionized water, and dry to obtain amino boron nitride.

[0042] S2: 420g of 1,6-hexanediol, 527.30g of γ-glycidyl etheroxypropyltrimethoxysilane and 5.52g of p-toluenesulfonic acid were added to a reaction vessel at 25℃ and reacted at 120℃ for 2h. The byproduct methanol was distilled off, and the distillation temperature was kept below 65℃. The temperature was slowly increased to 170℃ at a rate of 10℃ / h, and the distillation temperature was kept at 60℃. The temperature was allowed to cool naturally until it dropped below 60℃, at which point heating was stopped. The sample was then vacuum dried at 70℃ for 26h and dialyzed at 25℃ to remove low molecular weight molecules, yielding hyperbranched polysiloxane.

[0043] S3: Add 62.5g of hydrogenated cinnamic acid and 730mL of dichloromethane to a reaction vessel and stir until completely dissolved. Slowly add 156.375g of anhydrous aluminum chloride at 2℃. After reacting for 40min, slowly add 45g of succinic anhydride to the system. React for 10h under nitrogen protection and at 25℃. After the reaction is complete, pour it into 900mL of ice-cold deionized water and add 32mL of 37wt% hydrochloric acid dropwise. Filter and dissolve the precipitate in tetrahydrofuran. Then place it in a mixed solution of ethyl acetate and n-hexane (ethyl acetate: n-hexane = 1:3) to precipitate a solid. Wash the precipitate 5 times with deionized water and dry it under vacuum at 65℃ for 14h to obtain the intermediate acid.

[0044] S4: Add 35g of intermediate acid, 472.5g of epichlorohydrin and 2.2g of tetrabutylammonium bromide to a reaction vessel and react at 85℃ under nitrogen protection for 3h. Add 35g of 40wt% sodium hydroxide solution dropwise and continue the reaction for 1h. After the reaction is complete, filter, collect the filtrate and extract it 5 times with saturated brine. Add anhydrous sodium sulfate to the separated organic phase, dry for 14h, filter, and rotary evaporate the filtrate to obtain ester-containing epoxy resin.

[0045] S5: 12g of ester-based epoxy resin, 9.80g of curing agent methyltetrahydrophthalic anhydride, 1.2g of hyperbranched polysiloxane, 1.5g of aminoboron nitride, and 0.484g of curing accelerator 1,5,7-triazabicyclo[4.4.0]dec-5-ene were added to a reaction vessel and stirred for 20min at 145℃ and 600r / min to obtain epoxy resin material for LED encapsulation.

[0046] Example 4: This example provides an epoxy resin material for LED encapsulation. The difference from Example 1 is that methyl hexahydrophthalic anhydride is used instead of methyl tetrahydrophthalic anhydride in step S5.

[0047] Example 5: This example provides an epoxy resin material for LED encapsulation. The difference from Example 1 is that 2-ethyl-4-methylimidazolium is used instead of 1,5,7-triazabicyclo[4.4.0]dec-5-ene in step S5.

[0048] Comparative Example 1: This comparative example provides an epoxy resin material for LED packaging. The difference from Example 1 is that hyperbranched polysiloxane and amino boron nitride are removed in step S5.

[0049] Comparative Example 2: This comparative example provides an epoxy resin material for LED packaging. The difference from Example 1 is that hyperbranched polysiloxane is removed in step S5.

[0050] Comparative Example 3: This comparative example provides an epoxy resin material for LED packaging. The difference from Example 1 is that amino boron nitride is removed in step S5.

[0051] Comparative Example 4: This comparative example provides an epoxy resin material for LED packaging. The difference from Example 1 is that in step S5, bisphenol A type epoxy resin E51 is used instead of ester-containing epoxy resin.

[0052] The specifications and sources of the raw materials used in the above embodiments and comparative examples are as follows: Boron hydroxynitride powder: particle size 300-500nm, purity 95%, purchased from Shaanxi Xingbei Aike Biotechnology Co., Ltd.

[0053] Polyallylamine: 99% purity, purchased from Wuhan Smike Biotechnology Co., Ltd.

[0054] 1,6-Hexanediol: 99.5% purity, purchased from Shanghai Maclean Biochemical Technology Co., Ltd.

[0055] γ-glycidoxypropyltrimethoxysilane: purity 97%, purchased from Shanghai Maclean Biochemical Technology Co., Ltd.

[0056] p-Toluenesulfonic acid: 99% purity, purchased from Shanghai Maclean Biochemical Technology Co., Ltd.

[0057] Hydrogenated cinnamic acid: 99% purity, purchased from Wuhan Lanabai Pharmaceutical Chemical Co., Ltd.

[0058] Dichloromethane: purity ≥ 99.9%, purchased from Shanghai Maclean Biochemical Technology Co., Ltd.

[0059] Anhydrous aluminum chloride: purity 99.99%, purchased from Shanghai Maclean Biochemical Technology Co., Ltd.

[0060] Succinic anhydride: 98% purity, purchased from Shanghai Maclean Biochemical Technology Co., Ltd.

[0061] Tetrahydrofuran: purity ≥99.9%, purchased from Shanghai Maclean Biochemical Technology Co., Ltd.

[0062] Ethyl acetate: purity 99.8%, purchased from Shanghai Maclean Biochemical Technology Co., Ltd.

[0063] n-Hexane: 99.5% purity, purchased from Shanghai Maclean Biochemical Technology Co., Ltd.

[0064] Epichlorohydrin: 99% purity, purchased from Shanghai Maclean Biochemical Technology Co., Ltd.

[0065] Tetrabutylammonium bromide: 99% purity, purchased from Shanghai Maclean Biochemical Technology Co., Ltd.

[0066] Methyltetrahydrophthalic anhydride: 98% purity, purchased from Shanghai Maclean Biochemical Technology Co., Ltd.

[0067] 1,5,7-Triazabicyclo[4.4.0]dec-5-ene: purity 97%, purchased from Shanghai Aladdin Reagent Co., Ltd.

[0068] Methylhexahydrophthalic anhydride: 98% purity, purchased from Shanghai Maclean Biochemical Technology Co., Ltd.

[0069] 2-Ethyl-4-methylimidazole: 99% purity, purchased from Shanghai Maclean Biochemical Technology Co., Ltd.

[0070] Bisphenol A type epoxy resin E51: purity ≥95, purchased from Shenzhen Yoshida Chemical Co., Ltd.

[0071] The epoxy resin materials for LED encapsulation prepared in Examples 1-5 and Comparative Examples 1-4 were transferred into a mold and cured at 90°C for 2 hours, then heated to 110°C and cured for 2 hours, then heated to 140°C and cured for 2 hours, and finally cooled naturally to room temperature to obtain a sample. The obtained sample was then subjected to performance testing. Impact performance test: The test was conducted using an XCJ-4 type simply supported beam impact tester, in accordance with the GB / T 1843-2008 test standard. The sample size was 80mm × 10mm × 4mm, without notches, and the final result was the average of at least 5 tests.

[0072] Bending performance test: The test was conducted on a WSM-50 KN universal testing machine according to the GB / T 9341-2000 test standard. The test rate was 2 mm / min, and the span was 64 mm. The specimen size was 80 mm × 10 mm × 4 mm. The final result was the average of at least 5 tests.

[0073] Nanoindentation test: The test was conducted using an MTS 100BA-1C nanoindenter with a typical load-hold-unload cycle. The test sample surface was polished and the indentation depth was 2µm.

[0074] Dielectric property testing: The dielectric properties of the silver paste-coated sample were tested using an E4980A impedance analyzer under RT conditions.

[0075] Thermal conductivity test: Referencing ASTM D5470 standard, a laser flash thermal conductivity meter (LFA 467) was used. The sample size was 10mm×10mm×2mm, and the test temperature was 25℃. The thermal diffusivity, specific heat capacity, and density were recorded. The thermal conductivity was calculated using the formula "thermal diffusivity = thermal diffusivity × specific heat capacity × density".

[0076] Yellowing resistance test: The sample was placed in a 150℃ heat aging chamber for 1000h. The transmittance at 450nm wavelength before and after aging was measured using a UV-Vis spectrophotometer, and the yellowing index was measured using a colorimeter.

[0077] The performance test results are shown in the table below: Table 1 Performance Test Overview As shown in Table 1, the impact strength of Examples 1-5 is higher than that of Comparative Examples 1-4. This may be because the three-dimensional branched structure of the hyperbranched polysiloxane chemically bonds with the epoxy matrix, inducing chemical microphase separation and forming a uniformly dispersed nanoscale domain structure. When subjected to impact, energy can be dissipated through crack deflection, branching, and chain segment slip. At the same time, its flexible siloxane chain segments can alleviate the internal stress of curing and reduce stress concentration. The strong interfacial interaction between aminoboron nitride and epoxy matrix can inhibit crack propagation. The two work together to improve the impact strength of the samples.

[0078] As shown in Table 1, the flexural strength of Examples 1-5 is higher than that of Comparative Examples 1-4. This may be because the ester groups and epoxy groups in the ester-containing epoxy resin matrix form a dense cross-linked network, providing rigid support for the aromatic ring structure of hydrogenated cinnamic acid. The multifunctional groups of hyperbranched polysiloxane fully cross-link with the epoxy group, improving the network density. Boron nitride amino reacts with the surface amino groups and epoxy groups to achieve a strong bond between the filler and the matrix, enhancing the load-bearing capacity.

[0079] As shown in Table 1, the dielectric constants of Examples 1-5 are greater than those of Comparative Examples 1-4. This may be because the ester groups in the ester-containing epoxy resin matrix are polar functional groups, which can provide dipole polarization and improve dielectric response. The three-dimensional structure of the hyperbranched polysiloxane makes the polar groups uniformly distributed, reducing polarization loss. Boron nitride amino is an inorganic polar filler, and the interfacial polarization formed by the amino groups and epoxy groups on its surface further enhances the dielectric properties.

[0080] As shown in Table 1, the thermal conductivity of Examples 1-5 is greater than that of Comparative Examples 1-3. This may be because boron nitride amino, as a high thermal conductivity filler, has significantly improved compatibility with epoxy matrix after surface modification with polyallylamine. It can be uniformly dispersed and form a continuous thermally conductive path to quickly transfer heat. The Si-OC main chain of hyperbranched polysiloxane has better thermal conductivity than the CC main chain of traditional epoxy and can optimize the interfacial contact between the filler and the matrix, reducing the interfacial thermal resistance.

[0081] As shown in Table 1, the yellowing index of Examples 1-5 is lower than that of Comparative Examples 1-4. This may be because the ester-containing epoxy resin uses bio-based hydrogenated cinnamic acid as raw material, does not contain easily oxidized and degraded bisphenol A structure, and has higher molecular chain stability. The siloxane segments of the hyperbranched polysiloxane have excellent resistance to oxygen aging and UV protection, which can inhibit the breakage of matrix molecular chains and oxidative discoloration. The inert surface of aminoboron nitride can block oxygen from contacting the matrix and slow down the rate of thermo-oxidative aging.

[0082] It should be noted that, in this document, terms such as “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus.

[0083] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention.

Claims

1. A method for preparing an epoxy resin material for LED encapsulation, characterized in that, Includes the following steps: Step 1: Graft polyallylamine molecules onto the surface of boron nitride hydroxyl powder using electrostatic attraction to obtain boron nitride amino. Step 2: γ-glycidoxypropyltrimethoxysilane is grafted onto the 1,6-hexanediol molecular chain via transesterification to obtain hyperbranched polysiloxane. Step 3: Hydrogenated cinnamic acid undergoes a Friedel-Crafts reaction with succinic anhydride under the catalysis of anhydrous aluminum chloride to obtain intermediate acid; the intermediate acid and epichlorohydrin undergo a nucleophilic substitution reaction under the catalysis of tetrabutylammonium bromide to obtain ester-containing epoxy resin. Step 4: Add ester-based epoxy resin, curing agent, hyperbranched polysiloxane, amino boron nitride and curing accelerator to the reaction vessel, mix evenly to obtain epoxy resin material for LED encapsulation.

2. The method for preparing an epoxy resin material for LED encapsulation according to claim 1, characterized in that, The specific preparation process of aminoboron nitride described in step one is as follows: Hydroxy boron nitride powder and deionized water were added to a reaction vessel, followed by a 30 wt% polyallylamine solution. The mixture was stirred at 20-25 °C and 300-500 r / min for 5-6 h, then centrifuged, washed, and dried to obtain amino boron nitride. The ratio of boron nitride powder, deionized water, and polyallylamine solution is 10-15g: 5-6L: 60-80g.

3. The method for preparing an epoxy resin material for LED encapsulation according to claim 1, characterized in that, The specific preparation process of the hyperbranched polysiloxane in step two is as follows: 1,6-hexanediol, γ-glycidoxypropyltrimethoxysilane, and p-toluenesulfonic acid were added to a reactor at 20-25℃ and reacted at 100-120℃ for 1-2 hours. The byproduct methanol was distilled off, and the distillation temperature was kept below 65℃. The temperature was then slowly increased to 160-170℃ at a rate of 10℃ / h, and the distillation temperature was maintained at 55℃-60℃. The mixture was allowed to cool naturally until the distillation temperature dropped below 50-60℃, at which point heating was stopped. The mixture was then dried and dialyzed to obtain hyperbranched polysiloxane.

4. The method for preparing an epoxy resin material for LED encapsulation according to claim 3, characterized in that, The mass ratio of 1,6-hexanediol, γ-glycidyl etheroxypropyltrimethoxysilane, and p-toluenesulfonic acid is 390-420:487.30-527.30:3.52-5.

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5. The method for preparing an epoxy resin material for LED encapsulation according to claim 1, characterized in that, The specific preparation process of the intermediate acid mentioned in step three is as follows: Hydrogenated cinnamic acid and dichloromethane were added to a reaction vessel and stirred until completely dissolved. Anhydrous aluminum chloride was slowly added at 0-2°C. After reacting for 30-40 minutes, succinic anhydride was slowly added to the system. The reaction was carried out under nitrogen protection at 20-25°C for 8-10 hours. After the reaction was completed, the mixture was poured into ice-cold deionized water, and 37wt% hydrochloric acid was added dropwise. The mixture was then filtered, purified, washed, and dried to obtain the intermediate acid.

6. The method for preparing an epoxy resin material for LED encapsulation according to claim 5, characterized in that, The ratio of hydrogenated cinnamic acid, dichloromethane, anhydrous aluminum chloride, succinic anhydride, ice-cold deionized water, and hydrochloric acid is 52.5-62.5g: 530-730mL: 116.375-156.375g: 35-45g: 800-900mL: 28-32mL.

7. The method for preparing an epoxy resin material for LED encapsulation according to claim 1, characterized in that, The specific preparation process of the ester-containing epoxy resin mentioned in step three is as follows: Intermediate acid, epichlorohydrin, and tetrabutylammonium bromide were added to a reaction vessel and reacted at 80-85℃ under nitrogen protection for 1-3 hours. A 40wt% sodium hydroxide solution was added dropwise, and the reaction was continued for another hour. After the reaction was completed, the mixture was filtered, extracted, dried, and rotary evaporated to obtain an ester-containing epoxy resin.

8. The method for preparing an epoxy resin material for LED encapsulation according to claim 7, characterized in that, The mass ratio of the intermediate acid, epichlorohydrin, tetrabutylammonium bromide, and sodium hydroxide solution is 25-35: 462.5-472.5: 1.9-2.2: 25-35.

9. The method for preparing an epoxy resin material for LED encapsulation according to claim 1, characterized in that, The mass ratio of the ester-containing epoxy resin, curing agent, hyperbranched polysiloxane, amino boron nitride, and curing accelerator in step four is 10-12. 7.80-9.80：0.8-1.2：1-1.5：0.384-0.484； The curing agent is either methylhexahydrophthalic anhydride or methyltetrahydrophthalic anhydride; The curing accelerator is any one of 1,5,7-triazabicyclo[4.4.0]dec-5-ene and 2-ethyl-4-methylimidazolium.

10. An epoxy resin material for LED encapsulation, characterized in that, It is prepared by the method for preparing an epoxy resin material for LED encapsulation as described in any one of claims 1-9.

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