High-transmittance, yellowing-resistant epoxy adhesive film and preparation method thereof

Abstract

This invention provides a high-transmittance, yellowing-resistant epoxy resin film and its preparation method. The epoxy resin film comprises the following raw materials in parts by weight: 30-35 parts liquid epoxy resin, 25-35 parts solid epoxy resin, 20-30 parts toughening agent, 5-8 parts aromatic diamine curing agent, 3-5 parts terminal amino triazine / Schiff base curing agent as shown in Formula I, 0.3-0.5 parts accelerator, 1-2 parts coupling agent, 0.1-0.3 parts defoamer, 0.5-0.8 parts thioester antioxidant, and 50-100 parts solvent. The curing agent as shown in Formula I, on the one hand, contains Schiff base bonds (C=N) and triazine ring structures with strong absorption and stabilizing ability for ultraviolet light, thus endowing the epoxy film with excellent UV aging resistance; on the other hand, it contains terminal amino groups that can participate in complex cross-linking reactions and increase the cross-linking density of the epoxy film, thereby overcoming the problem of precipitation and migration of small molecule anti-UV components under harsh environments.

Description

Technical Field

[0001] This invention belongs to the field of epoxy film technology, specifically relating to an epoxy film with high light transmittance and resistance to yellowing, and its preparation method. Background Technology

[0002] Epoxy film is a thin film material mainly composed of epoxy resin, curing agent, curing accelerator, diluent, and other additives. Due to its excellent adhesion, mechanical strength, and chemical resistance, it is widely used in printed circuit boards (PCBs), semiconductor components, LED light sources, optical devices, solar cells, electronic components, and other applications requiring connection, encapsulation, and protection. Examples include an epoxy film disclosed in patent CN103396742B and an epoxy resin film and its preparation method disclosed in patent CN107778774B.

[0003] Epoxy resin is the decisive component in the properties of epoxy films. Epoxy resins can be selected from alicyclic epoxy resins, bisphenol A type epoxy resins, linear thermoplastic phenolic epoxy resins, etc., among which bisphenol A type epoxy resin is the most widely used. The molecular structure of bisphenol A type epoxy resin contains aromatic rings that can absorb ultraviolet light and unstable unsaturated bonds. When exposed to sunlight for a long time, the aromatic rings are oxidized to carbonyl groups, forming chromophores, and the unsaturated bonds on the benzene rings break, causing the epoxy resin film to age and yellow. This not only reduces the transparency of the film and affects its aesthetics but may also shorten the product's lifespan. To overcome this problem, researchers often add appropriate amounts of components to the film raw materials to improve UV resistance. For example, patent CN103289317B discloses an LED encapsulation material, its preparation method, and its application. The patent uses a sulfur-containing benzotriazole compound as an ultraviolet absorber, which has excellent performance and good synergistic effects with antioxidants and ultraviolet stabilizers, and can be used as an ultraviolet absorber in LED encapsulation materials.

[0004] However, a significant issue is that the actual working environment of epoxy films is complex. Furthermore, epoxy resin itself is highly hygroscopic, and humid and hot environments easily accelerate the migration and precipitation of small-molecule UV-resistant components. Under the dual interaction of humid heat and UV irradiation, the UV resistance of epoxy films deteriorates rapidly. While the migration and precipitation of these UV-resistant components, due to their small dosage, do not significantly affect the mechanical properties of the epoxy film, they exacerbate yellowing and severely reduce its transparency and aesthetics in variable and harsh environments. This limits its application in fields with strict requirements for transparency and aesthetics, such as LED light sources and solar cell encapsulation. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a high-transmittance, yellowing-resistant epoxy resin film and its preparation method. The epoxy resin film raw material includes a terminal amino-triazine / Schiff base curing agent containing Schiff base bonds (C=N) and triazine rings in its molecular structure. This curing agent, on the one hand, imparts excellent UV aging resistance to the epoxy film due to its Schiff base bond (C=N) and triazine ring structure, which has strong absorption and stabilizing ability for ultraviolet light; on the other hand, it also overcomes the problem of precipitation and migration of small-molecule UV-resistant components under harsh conditions by containing terminal amino groups that can participate in complex cross-linking reactions and increase the cross-linking density of the epoxy film.

[0006] A high-transmittance, yellowing-resistant epoxy resin film comprises the following raw materials in parts by weight: 30-35 parts liquid epoxy resin, 25-35 parts solid epoxy resin, 20-30 parts toughening agent, 5-8 parts curing agent, 3-5 parts amino-triazine / Schiff base curing agent, 0.3-0.5 parts accelerator, 1-2 parts coupling agent, 0.1-0.3 parts defoamer, 0.5-0.8 parts thioester antioxidant, and 50-100 parts solvent. The structure of the amino-triazine / Schiff base curing agent is shown in Formula I.

[0007] Formula I: .

[0008] The terminal aminotriazine / Schiff base curing agent is prepared by a method comprising the following steps:

[0009] 1) Under an inert atmosphere, 1,3,5-triazine-2,4,6-tricarboxaldehyde and N-(4-aminophenyl)maleimide were dissolved in an organic solvent and heated to reflux for reaction. After the reaction was completed, the mixture was cooled and alcohol was added until no precipitate was formed. The mixture was filtered, washed, and dried to obtain intermediate 1 for later use.

[0010] 2) Protect the amino group on the aminobenzylthiophenol derivative to obtain intermediate 2, for later use;

[0011] 3) Mix intermediate 1, intermediate 2 and organic solvent evenly, and react under controlled temperature. After the reaction is complete, add alcohol until no precipitate is formed. Filter, wash and dry to obtain intermediate 3.

[0012] 4) Deprotecting intermediate 3 yields a terminal aminotriazine / Schiff base curing agent.

[0013] Step 1) The organic solvent is selected from one or more combinations of benzene, toluene, carbon tetrachloride, dichloromethane, and chloroform. The reaction time is 4-6 hours. The alcohol is selected from one or more combinations of methanol, ethanol, and isopropanol. The washing is performed 1-3 times with alcohol. The drying is performed at 80-100°C. The molar ratio of 1,3,5-triazine-2,4,6-tricarboxaldehyde to N-(4-aminophenyl)maleimide is 1:3.25-3.35. Step 1) involves the Schiff base reaction of 1,3,5-triazine-2,4,6-tricarboxaldehyde and N-(4-aminophenyl)maleimide to generate an intermediate containing a Schiff base structure.

[0014] Step 2) The amino protection reaction specifically involves dissolving the aminobenzylthiophenol derivative in an alcohol, adding an amino protecting agent (ethyl trifluoroacetate), and conducting the reaction under controlled temperature. After the reaction, the mixture is filtered, washed, and dried to obtain intermediate 2 for later use. The aminobenzylthiophenol derivative is selected from one or more combinations of 4-aminobenzylthiophenol, 2-aminobenzylthiol, and 3-aminobenzylthiophenol. The alcohol is selected from one or more combinations of methanol, ethanol, and isopropanol. The molar ratio of the aminobenzylthiophenol derivative to the amino protecting agent is 1:1-1.06. The controlled temperature reaction is conducted at 20-25℃ for 10-24 hours. The washing is performed by alternating washing with alcohol and water 1-3 times. The drying is carried out at 80-100℃. Step 2) is the reaction in which ethyl trifluoroacetate protects the amino group on the aminobenzylthiophenol derivative.

[0015] Step 3) The organic solvent is a mixture of benzene and methyl ethyl ketone in a volume ratio of 10:3-5. The reaction is carried out at 20-30℃ for 3-6 hours, and the molar ratio of intermediate 1 to intermediate 2 is 1:3.2-3.4. The washing is performed by alternating washing with methyl ethyl ketone and water 1-3 times, and the drying is performed at 80-100℃. Step 3) involves a Michael addition reaction between the unsaturated double bonds and thiol groups on intermediates 1 and 2 to generate an amino-protected-terminal aminotriazine / Schiff base curing agent.

[0016] Step 4) The deprotection reaction specifically involves: adding intermediate 3 to a potassium carbonate solution, reacting under controlled temperature, adjusting the pH to 3-5 after the reaction, removing the solvent by distillation, redissolving the resulting solid in water, adjusting the pH to 10-12, extracting with ethyl acetate, and distilling to obtain the terminal aminotriazine / Schiff base curing agent. The concentration of the potassium carbonate solution is 5-10 wt%, and the solvent of the potassium carbonate solution is a mixture of tetrahydrofuran, alcohol, and water in a volume ratio of 5-8:1:1-3. The mass-to-volume ratio of intermediate 2 to potassium carbonate solution is (70-100) g:(250-300) mL. The temperature-controlled reaction is carried out at 20-30℃ for 10-24 h. The pH is adjusted to 3-5 using 30-37 wt% hydrochloric acid, and the pH is adjusted to 10-12 using saturated ammonia. Step 3) involves deprotecting intermediate 2 to prepare the final product, the terminal aminotriazine / Schiff base curing agent.

[0017] The thioester antioxidant is selected from one or more combinations of dilauryl thiodipropionate (antioxidant DLTP), octadecyl thiodipropionate (antioxidant DSTP), and di(tetradecyl) thiodipropionate (antioxidant DMTDP).

[0018] The liquid epoxy resin is a bisphenol A type epoxy resin with an epoxy equivalent of 130-200 g / eq, specifically selected from one or more of Mitsubishi YL-980, Mitsui R-139, and Mitsui R-140P.

[0019] The solid epoxy resin is a bisphenol A type epoxy resin with an epoxy equivalent of 475-800 g / eq, specifically selected from one or a combination of two of Dow DER671, DER662E, DER663E, and DER663UE.

[0020] The aromatic diamine curing agent is selected from one or more combinations of m-phenylenediamine, diaminodiphenylmethane, m-phenylenediamine, diaminodiphenyl sulfone, and 4,4'-diaminodiphenyl ether; preferably diaminodiphenylmethane.

[0021] The accelerator is selected from one or more combinations of tertiary amine accelerators, phenolic accelerators, and imidazole accelerators.

[0022] The toughening agent is a thermoplastic resin selected from one or more of Mitsubishi's BR-106 and BR-117, Degussa's DYNAPOL-L411, and Toyobo's GK590, GK-360, and 673.

[0023] The coupling agent is selected from one or more of the following: triethoxy[4-(trifluoromethyl)phenyl]silane, trimethoxy(3,3,3-trifluoropropyl)silane, 3,3,3-trifluoropropyltriethoxysilane, methyl(3,3,3-trifluoropropyl)diethoxysilane, β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidyl etheroxypropyltrimethoxysilane, and 3-[(2,3)-epoxypropoxy]propylmethyldimethoxysilane. Triethoxy[4-(trifluoromethyl)phenyl]silane is preferred.

[0024] There are no particular restrictions on the defoamer; both silicone and non-silicone defoamers are acceptable. Specifically, it can be selected from one or more of BYK-1790, BYK-1794, BYK-1795, BYK-088, and Shin-Etsu KS-603.

[0025] The solvent is selected from one or more of organic benzenes, ketones, and ethers; specifically, the solvent is selected from one or more of toluene, xylene, butanone, N-methyl-2-pyrrolidone, cyclohexanone, and methyl isobutyl ketone.

[0026] This invention also provides a method for preparing the above-mentioned high light transmittance and yellowing-resistant epoxy resin film, comprising the following steps:

[0027] T1) Dissolve the toughening agent in the solvent, then add liquid epoxy resin, solid epoxy resin, coupling agent, defoamer, and thioester antioxidant, heat and mix evenly to obtain a mixture;

[0028] T2) Heat the mixture, stir it evenly, then cool it down, add the curing agent, terminal aminotriazine / Schiff base curing agent, and accelerator, mix evenly, degas, coat it onto the release film, and bake off the solvent to obtain an epoxy resin film with high light transmittance and resistance to yellowing.

[0029] In step T1), the temperature increase is to raise the temperature to 40-60℃.

[0030] In step T2), the temperature is raised to 70-80℃, and the temperature is lowered to 30-50℃. The solvent removal temperature is 75-90℃, the time is 10-20 minutes, and the film thickness is 20-50 μm.

[0031] The epoxy resin film is cured at 80-120℃ for 2-5 hours.

[0032] Compared with the prior art, the beneficial effects of the present invention are:

[0033] The epoxy resin film raw material of this invention contains a terminal amino triazine / Schiff base curing agent with a Schiff base bond (C=N) and a triazine ring in its molecular structure. This curing agent, on the one hand, endows the epoxy film with excellent UV aging resistance due to the Schiff base bond (C=N) and triazine ring structure with strong absorption and stabilization ability for ultraviolet light; on the other hand, it can overcome the problem of precipitation and migration of small molecule anti-UV components under harsh conditions by containing terminal amino groups that can participate in complex cross-linking reactions and increase the cross-linking density of epoxy film. Detailed Implementation

[0034] The present invention will be further described below with reference to specific embodiments, but is not limited to the contents of the specification. Unless otherwise specified, all "parts" mentioned in the embodiments of the present invention are parts by weight. All reagents used are commercially available in the art.

[0035] Example 1

[0036] 1) Under a nitrogen atmosphere, 0.1 mol of 1,3,5-triazine-2,4,6-tricarboxaldehyde and 0.325 mol of N-(4-aminophenyl)maleimide were dissolved in 100 mL of benzene. The mixture was heated to reflux and reacted for 5 h. After the reaction was completed, the mixture was cooled to room temperature, and methanol was added until no precipitate was formed. The mixture was filtered, washed three times with ethanol, and dried at 80 °C to constant weight to obtain intermediate 1, which was then used for later use.

[0037] ;

[0038] 2) Dissolve 0.1 mol of 4-aminobenzylthiophenol in 100 mL of ethanol, add 0.1 mol of ethyl trifluoroacetate, and react at 25 °C for 12 h. After the reaction is complete, filter, wash three times with ethanol, and dry at 80 °C to constant weight to obtain intermediate 2 for later use.

[0039] ;

[0040] 3) Take 0.1 mol of intermediate 1, 0.34 mol of intermediate 2, and 150 mL of a mixed solvent of benzene and methyl ethyl ketone at a volume ratio of 10:3. Mix them evenly and react at 25℃ for 6 h. After the reaction is complete, add methanol until no precipitate is formed. Filter, wash with methyl ethyl ketone and water three times alternately, and dry at 80℃ to constant weight to obtain intermediate 3.

[0041] ;

[0042] 4) Take 70g of intermediate 3 and add it to a 7wt% potassium carbonate solution (the solvent is a mixture of tetrahydrofuran, ethanol and water in a volume ratio of 8:1:3) at a mass-to-volume ratio of 70g:250mL. The reaction is carried out at 30℃ for 24h. After the reaction is completed, adjust the pH to 3 with 37wt% hydrochloric acid, remove the solvent by distillation, redissolve the obtained solid in water, adjust the pH to 12 with saturated ammonia, extract with ethyl acetate, and distill to obtain the terminal aminotriazine / Schiff base curing agent.

[0043] ;

[0044] 5) Dissolve 30g of toughening agent Toyobo GK590 in 100mL of methyl ethyl ketone, then add 35g of liquid epoxy resin Mitsubishi YL-980, 30g of solid epoxy resin Dow DER671, 2g of coupling agent triethoxy[4-(trifluoromethyl)phenyl]silane, 0.1g of defoamer BYK-1790, and 0.8g of antioxidant DLTP. Heat to 60℃ and mix thoroughly to obtain a mixture.

[0045] 6) Heat the mixture to 80℃, stir evenly, then cool to 30℃, add 8g of curing agent diaminodiphenylmethane, 5g of terminal aminotriazine / Schiff base curing agent, and 0.3g of accelerator dimethylimidazole, mix evenly, degas, coat onto release film, heat to 80℃ to remove solvent for 20min, and obtain a 25μm thick epoxy resin film with high light transmittance and yellowing resistance.

[0046] Example 2

[0047] The rest is the same as in Example 1, except that in step 6), the amount of terminal aminotriazine / Schiff base curing agent is 3g and the amount of diaminodiphenylmethane is 10g.

[0048] Example 3

[0049] The rest is the same as in Example 1, except that in step 2), 4-aminobenzylthiophenol is replaced with an equimolar amount of 2-aminobenzylthiophenol.

[0050] Example 4

[0051] The rest is the same as in Example 1, except that in step 5), the amount of antioxidant DLTP is 0.5g.

[0052] Example 5

[0053] The rest is the same as in Example 1, except that: 1) under a nitrogen atmosphere, 0.1 mol of 1,3,5-triazine-2,4,6-tricarboxaldehyde and 0.335 mol of N-(4-aminophenyl)maleimide were dissolved in 100 mL of toluene, and the mixture was heated to reflux and reacted for 6 h. After the reaction was completed, the mixture was cooled to room temperature, and methanol was added until no precipitate was formed. The mixture was filtered, washed three times with ethanol, and dried at 80 °C to constant weight to obtain intermediate 1 for later use.

[0054] 2) Dissolve 0.1 mol of 4-aminobenzylthiophenol in 100 mL of ethanol, add 0.106 mol of ethyl trifluoroacetate, and react at 25 °C for 12 h. After the reaction is complete, filter, wash three times with ethanol, and dry at 80 °C to constant weight to obtain intermediate 2 for later use.

[0055] 3) Take 0.1 mol of intermediate, 0.32 mol of amino-protected aminobenzenethiophenol derivative, and 150 mL of a mixed solvent of benzene and methyl ethyl ketone in a volume ratio of 10:5. Mix them evenly and react at 25℃ for 6 h. After the reaction is complete, add methanol until no precipitate is formed. Filter, wash with methyl ethyl ketone and water three times alternately, and dry at 80℃ to constant weight to obtain intermediate 3.

[0056] 4) Take 100g of intermediate 3 and add it to a 7wt% potassium carbonate solution (the solvent is a mixture of tetrahydrofuran, ethanol and water in a volume ratio of 8:1:3) at a mass-to-volume ratio of 100g:300mL. The reaction is carried out at 30℃ for 24h. After the reaction is completed, adjust the pH to 3 with 37wt% hydrochloric acid, remove the solvent by distillation, redissolve the obtained solid in water, adjust the pH to 12 with saturated ammonia, extract with ethyl acetate, and distill to obtain the terminal aminotriazine / Schiff base curing agent.

[0057] Example 6

[0058] The rest is the same as in Example 1, except that in step 5), triethoxy[4-(trifluoromethyl)phenyl]silane is replaced with an equal mass of 3-glycidyl etheroxypropyltrimethoxysilane.

[0059] Example 7

[0060] The rest is the same as in Example 1, except that, in step 5), 25g of toughening agent Toyobo GK590 is dissolved in 100mL of butanone, and then 30g of liquid epoxy resin Mitsubishi YL-980, 25g of solid epoxy resin Dow DER671, 1g of coupling agent triethoxy[4-(trifluoromethyl)phenyl]silane, 0.1g of defoamer BYK-1790 and 0.5g of antioxidant DLTP are added. The mixture is heated to 60°C and mixed evenly to obtain a mixture.

[0061] 6) Heat the mixture to 80℃, stir evenly, then cool to 30℃, add 5g of curing agent diaminodiphenylmethane, 5g of terminal aminotriazine / Schiff base curing agent, and 0.3g of accelerator dimethylimidazole, mix evenly, degas, coat onto release film, heat to 80℃ to remove solvent for 20min, and obtain a 25μm thick epoxy resin film with high light transmittance and yellowing resistance.

[0062] Comparative Example 1

[0063] The rest is the same as in Example 1, except that an equal mass of diaminodiphenylmethane is used instead of the terminal aminotriazine / Schiff base curing agent.

[0064] Comparative Example 2

[0065] The rest is the same as in Example 1, except that an equal mass of phenolic antioxidant 1010 is used instead of antioxidant DLTP.

[0066] The epoxy films prepared in the above examples and comparative examples were cured at 120°C for 2 hours and then subjected to the following performance tests:

[0067] Transmittance: Measured according to standard GB / T2410, with wavelengths ranging from 400nm to 1200nm.

[0068] Determination of ΔYI for damp heat / UV alternating aging: Damp heat aging: immersion in water at 85℃ for 2 hours; UV aging: UV irradiation aging test according to the requirements of International Electrotechnical Commission standard IEC61345, with sample surface temperature of 60±5℃; wavelength range of 280-400nm; irradiation intensity of 15KW·h / m 2 The ultraviolet irradiation time was 2000 hours. The transmittance was retested. The change in yellow index (ΔYI) of the samples before and after aging was determined according to the standard GB / T 2409, "Test Method for Yellow Index of Plastics." A higher yellow index indicates more pronounced yellowing.

[0069] Elongation at break: Tested by DMA method, with a tensile rate of 0.3 mm / min and a test temperature of 25℃.

[0070] Table 1 Performance Test Results

[0071] .

[0072] As can be seen from Table 1, the epoxy film containing terminal aminotriazine / Schiff base curing agent prepared by the present invention has significantly improved both elongation at break and anti-yellowing properties, and has great industrial advantages.

[0073] Examples 1-4 and Comparative Example 2 show that the terminal aminotriazine / Schiff base curing agent of the present invention and the thioester antioxidant have a significant synergistic effect in improving the anti-yellowing performance.

[0074] The above detailed description is a specific description of one of the feasible embodiments of the present invention. This embodiment is not intended to limit the patent scope of the present invention. All equivalent implementations or modifications that do not depart from the present invention should be included within the scope of the technical solution of the present invention.

Claims

1. A high-transmittance, yellowing-resistant epoxy resin film, characterized in that, The raw materials comprise the following parts by weight: 30-35 parts liquid epoxy resin, 25-35 parts solid epoxy resin, 20-30 parts toughening agent, 5-8 parts aromatic diamine curing agent, 3-5 parts terminal aminotriazine / Schiff base curing agent, 0.3-0.5 parts accelerator, 1-2 parts coupling agent, 0.1-0.3 parts defoamer, 0.5-0.8 parts thioester antioxidant, and 50-100 parts solvent. The structure of the terminal aminotriazine / Schiff base curing agent is shown in Formula I. Formula I: .

2. The epoxy resin film with high light transmittance and resistance to yellowing according to claim 1, characterized in that, The terminal aminotriazine / Schiff base curing agent is prepared by a method comprising the following steps: 1) Under an inert atmosphere, 1,3,5-triazine-2,4,6-tricarboxaldehyde and N-(4-aminophenyl)maleimide were dissolved in an organic solvent and heated to reflux for reaction. After the reaction was completed, the mixture was cooled and alcohol was added until no precipitate was formed. The mixture was filtered, washed, and dried to obtain intermediate 1 for later use. 2) Protect the amino group on the aminobenzylthiophenol derivative to obtain intermediate 2, for later use; 3) Mix intermediate 1, intermediate 2 and organic solvent evenly, and react under controlled temperature. After the reaction is complete, add alcohol until no precipitate is formed. Filter, wash and dry to obtain intermediate 3. 4) Deprotecting intermediate 3 yields a terminal aminotriazine / Schiff base curing agent.

3. The epoxy resin film with high light transmittance and resistance to yellowing according to claim 2, characterized in that, Step 1) The organic solvent is selected from one or more of benzene, toluene, carbon tetrachloride, dichloromethane, and chloroform. The reaction time is 4-6 h. The molar ratio of 1,3,5-triazine-2,4,6-tricarboxaldehyde to N-(4-aminophenyl)maleimide is 1:3.25-3.

35.

4. The epoxy resin film with high light transmittance and resistance to yellowing according to claim 2, characterized in that, Step 2) The amino protection reaction is specifically as follows: dissolve the aminobenzylthiophenol derivative in alcohol, add an amino protecting reagent, which is ethyl trifluoroacetate, and carry out the reaction under controlled temperature. After the reaction is completed, filter, wash, and dry to obtain intermediate 2 for later use. The aminobenzylthiophenol derivative is selected from one or more combinations of 4-aminobenzylthiophenol, 2-aminobenzylthiol, and 3-aminobenzylthiophenol. The molar ratio of the aminobenzylthiophenol derivative to the amino protecting reagent is 1:1-1.

06.

5. The epoxy resin film with high light transmittance and resistance to yellowing according to claim 2, characterized in that, Step 3) The organic solvent is a mixed solvent of benzene and methyl ethyl ketone in a volume ratio of 10:3-5; the temperature-controlled reaction conditions are 20-30℃ for 3-6 hours, and the molar ratio of intermediate 1 to intermediate 2 is 1:3.2-3.

4.

6. The epoxy resin film with high light transmittance and resistance to yellowing according to claim 2, characterized in that, Step 4) The deprotection reaction is specifically as follows: intermediate 3 is added to potassium carbonate solution, the temperature is controlled and the reaction is carried out. After the reaction is completed, the pH is adjusted to 3-5, the solvent is removed by distillation, the obtained solid is redissolved in water, the pH is adjusted to 10-12, ethyl acetate is extracted, and the terminal aminotriazine / Schiff base curing agent is obtained by distillation.

7. The epoxy resin film with high light transmittance and resistance to yellowing according to claim 1, characterized in that, The thioester antioxidant is selected from one or more of dilauryl thiodipropionate, octadecyl thiodipropionate, and di(tetradecyl) thiodipropionate; the aromatic diamine curing agent is selected from one or more of m-phenylenediamine, diaminodiphenylmethane, m-phenylenediamine, diaminodiphenyl sulfone, and 4,4'-diaminodiphenyl ether.

8. The epoxy resin film with high light transmittance and resistance to yellowing according to claim 1, characterized in that, The liquid epoxy resin is a bisphenol A type epoxy resin with an epoxy equivalent of 130-200 g / eq; the solid epoxy resin is a bisphenol A type epoxy resin with an epoxy equivalent of 475-800 g / eq; and the accelerator is selected from one or more combinations of tertiary amine accelerators, phenolic accelerators, and imidazole accelerators.

9. The epoxy resin film with high light transmittance and resistance to yellowing according to claim 8, characterized in that, The bisphenol A type epoxy resin with an epoxy equivalent of 130-200 g / eq is selected from one or more of Mitsubishi YL-980, Mitsui R-139, and Mitsui R-140P; the bisphenol A type epoxy resin with an epoxy equivalent of 475-800 g / eq is selected from one or two of Dow DER671, DER662E, DER663E, and DER663UE.

10. The epoxy resin film with high light transmittance and resistance to yellowing according to claim 1, characterized in that, The coupling agent is selected from one or more combinations of triethoxy[4-(trifluoromethyl)phenyl]silane, trimethoxy(3,3,3-trifluoropropyl)silane, 3,3,3-trifluoropropyltriethoxysilane, methyl(3,3,3-trifluoropropyl)diethoxysilane, β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidyl etheroxypropyltrimethoxysilane, and 3-[(2,3)-epoxypropoxy]propylmethyldimethoxysilane.

11. A method for preparing the high light transmittance and yellowing-resistant epoxy resin film according to any one of claims 1-10, characterized in that, Includes the following steps: T1) Dissolve the toughening agent in the solvent, then add liquid epoxy resin, solid epoxy resin, coupling agent, defoamer, and thioester antioxidant, heat and mix evenly to obtain a mixture; T2) Heat the mixture, stir it evenly, then cool it down, add the curing agent, terminal aminotriazine / Schiff base curing agent, and accelerator, mix evenly, degas, coat it onto the release film, and bake off the solvent to obtain an epoxy resin film with high light transmittance and resistance to yellowing.

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