Epoxy adhesive film with high light transmittance and yellowing resistance and preparation method thereof

Abstract

The invention provides an epoxy resin adhesive film with high light transmittance and yellowing resistance and a preparation method thereof. The epoxy resin adhesive film comprises the following raw materials in parts by weight: 30-35 parts of liquid epoxy resin, 25-35 parts of solid epoxy resin, 20-30 parts of a toughening agent, 5-8 parts of an aromatic diamine curing agent, 3-5 parts of an amino-terminated triazine / Schiff base curing agent shown as a formula I, 0.3-0.5 part of an accelerant, 1-2 parts of a coupling agent, 0.1-0.3 part of a defoaming agent, 0.5-0.8 part of a thioester antioxidant and 50-100 parts of a solvent. On one hand, the curing agent shown in the formula I has a Schiff base bond (C = N) and a triazine ring structure which have relatively strong absorption and stabilization capabilities on ultraviolet rays, so that the epoxy adhesive film is endowed with excellent ultraviolet aging resistance; on the other hand, due to the fact that amino-terminated groups which can participate in complex cross-linking reaction and improve the cross-linking density of the epoxy adhesive film are contained, the problems that micromolecular anti-ultraviolet components are separated out and migrated in a harsh environment can be solved.

Description

Technical Field

[0001] The invention belongs to the technical field of epoxy films, and in particular relates to an epoxy film with high light transmittance and yellowing resistance and a preparation method thereof. Background Art

[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 bonding performance, 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 occasions that require connection, packaging and protection, such as the epoxy film disclosed in patent CN103396742B, the epoxy resin film disclosed in patent CN107778774B and the preparation method thereof.

[0003] Epoxy resin is the decisive component of the properties of epoxy film. Epoxy resin can be selected from alicyclic epoxy resin, bisphenol A epoxy resin, linear thermoplastic novolac epoxy resin, etc. Among them, bisphenol A epoxy resin is the most widely used. The molecular structure of bisphenol A epoxy resin contains aromatic rings and unstable unsaturated bonds that can absorb ultraviolet rays. When exposed to ultraviolet rays for a long time in the sun, the aromatic ring will be oxidized to carbonyl to form a chromophore, and the unsaturated bonds on the benzene ring will break, causing the epoxy resin film to age and turn yellow, which will not only reduce the transparency of the film and affect the aesthetics, but also may shorten the service life of the product. In order to overcome this problem, researchers often add an appropriate amount of ingredients to improve the anti-ultraviolet properties to the raw materials of the film, such as a LED packaging material and its preparation method and application disclosed in patent CN103289317B. The patent uses a sulfur-containing benzotriazole compound ultraviolet light absorber, which has excellent performance and has a good synergistic effect with antioxidants and ultraviolet light stabilizers. It can be used as an ultraviolet light absorber for LED packaging materials.

[0004] However, one problem that cannot be ignored is that the actual working environment of epoxy film is complex. In addition, epoxy resin itself has strong hygroscopicity. The humid and hot environment can easily accelerate the migration and precipitation of small molecule anti-ultraviolet components. The anti-ultraviolet performance of epoxy film deteriorates rapidly under the dual interactive environment of humid and hot / ultraviolet radiation. Due to the small amount of anti-ultraviolet components used, their migration and precipitation will not have much effect on the mechanical properties of epoxy film, but will aggravate the yellowing of the film, seriously reducing the transparency and aesthetics of epoxy film in changeable and harsh environments, limiting its application in fields with strict requirements on transparency and aesthetics, such as LED light sources, solar cell packaging and other fields. Summary of the invention

[0005] In order to solve the above technical problems, the present invention provides an epoxy resin film with high light transmittance and yellowing resistance and a preparation method thereof. The epoxy resin film raw material comprises an amino-terminated triazine / Schiff base curing agent containing a Schiff base bond (C=N) and a triazine ring in its molecular structure. On the one hand, the curing agent contains a Schiff base bond (C=N) and a triazine ring structure with strong absorption and stabilization capabilities for ultraviolet rays, thereby giving the epoxy film excellent resistance to ultraviolet aging; on the other hand, because it contains an amino-terminated group that can participate in complex cross-linking reactions and increase the cross-linking density of the epoxy film, it can overcome the problem of precipitation and migration of small molecule anti-ultraviolet components under harsh environments.

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

[0007] Formula I:

[0008] The amino-terminated triazine / 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 are dissolved in an organic solvent, and the temperature is raised to reflux state for reaction. After the reaction is completed, the mixture is cooled, and alcohol is added until no precipitation is generated. The mixture is filtered, washed, and dried to obtain intermediate 1 for standby use;

[0010] 2) protecting the amino group on the aminothiophenol derivative to obtain intermediate 2 for later use;

[0011] 3) Mix intermediate 1, intermediate 2 and an organic solvent evenly, control the temperature to react, add alcohol after the reaction until no precipitation is produced, filter, wash and dry to obtain intermediate 3;

[0012] 4) Deprotecting the intermediate 3 to obtain an amino-terminated triazine / Schiff base curing agent.

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

[0014] The amino protection reaction in step 2) is specifically as follows: dissolving an aminothiophenol derivative in alcohol, adding an amino protection agent, preferably ethyl trifluoroacetate, reacting at a controlled temperature, filtering, washing, and drying after the reaction to obtain intermediate 2 for standby use. The aminothiophenol derivative is selected from one or a combination of two or more of 4-aminothiophenol, 2-aminobenzenethiol, and 3-aminothiophenol. The alcohol is selected from one or a combination of two or more of methanol, ethanol, and isopropanol. The molar ratio of the aminothiophenol derivative to the amino protection agent is 1:1-1.06, the temperature control reaction is to react at 20-25°C for 10-24h, the washing is to wash alternately with alcohol and water for 1-3 times, and the drying is to dry at 80-100°C. Step 2) is a reaction for protecting the amino group on the aminothiophenol derivative with ethyl trifluoroacetate.

[0015] 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 control reaction condition is 20-30°C for 3-6h, and the molar ratio of intermediate 1 to intermediate 2 is 1:3.2-3.4. The washing is washing with methyl ethyl ketone and water alternately for 1-3 times, and the drying is drying at 80-100°C. Step 3) is the unsaturated double bonds on intermediates 1 and intermediates 2 and the thiol groups undergo Michael addition reaction to generate amino-protected terminal amino triazine / Schiff base curing agent.

[0016] Step 4) The deprotection reaction is specifically as follows: taking intermediate 3 and adding it to potassium carbonate solution, controlling the temperature to react, adjusting the pH to 3-5 after the reaction, distilling to remove the solvent, re-dissolving the obtained solid in water, adjusting the pH to 10-12, extracting with ethyl acetate, and distilling to obtain a terminal amino triazine / Schiff base curing agent. The concentration of the potassium carbonate solution is 5-10wt%, 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, and the mass volume ratio of the intermediate 2 to the potassium carbonate solution is (70-100) g: (250-300) mL. The temperature control reaction is to control the temperature at 20-30°C for 10-24h. The pH is adjusted to 3-5 by using hydrochloric acid with a concentration of 30-37wt%, and the pH is adjusted to 10-12 by using saturated ammonia water. Step 3) Deprotection of intermediate 2 is used to prepare the final product terminal amino triazine / Schiff base curing agent.

[0017] The thioester antioxidant is selected from one or a combination of two or more of dilauryl thiodipropionate (antioxidant DLTP), octadecyl thiodipropionate (antioxidant DSTP), ditetradecyl thiodipropionate (antioxidant DMTDP).

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

[0019] The solid epoxy resin is a bisphenol A 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 a combination of two or more of tertiary amine accelerators, phenol accelerators and imidazole accelerators.

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

[0023] The coupling agent is selected from one or a combination of two or more of triethoxy [4- (trifluoromethyl) phenyl] silane, trimethoxy (3,3,3-trifluoropropyl) silane 3,3,3-trifluoropropyl triethoxy silane, methyl (3,3,3-trifluoropropyl) diethoxy silane, β- (3,4-epoxycyclohexyl) ethyl trimethoxy silane, 3-glycidyl ether oxypropyl trimethoxy silane, 3- [(2,3) - epoxypropyloxy] propyl methyl dimethoxy silane. Preferably, triethoxy [4- (trifluoromethyl) phenyl] silane is used.

[0024] The defoaming agent is not particularly limited and may be either silicon-based or non-silicon-based defoaming agent. Specifically, the defoaming agent may be selected from one or a combination of two or more of BYK-1790, BYK-1794, BYK-1795, BYK-088, and Shin-Etsu's KS-603.

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

[0026] The present 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) dissolving a toughening agent in a solvent, and then adding a liquid epoxy resin, a solid epoxy resin, a coupling agent, a defoaming agent, and a thioester antioxidant, heating and mixing uniformly to obtain a mixture;

[0028] T2) heating the mixture, stirring evenly, cooling it down, adding a curing agent, an amino-terminated triazine / Schiff base curing agent, and an accelerator, mixing evenly, degassing, coating on a release film, and drying off the solvent to obtain an epoxy resin film with high light transmittance and yellowing resistance.

[0029] In step T1), the temperature is raised to 40-60°C

[0030] In step T2), the temperature is raised to 70-80° C., and the temperature is lowered to 30-50° C. The temperature for drying out the solvent is 75-90° C., the time is 10-20 min, and the thickness of the adhesive film is 20-50 um.

[0031] The epoxy resin film curing condition is baking at 80-120° C. for 2-5 hours.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] The epoxy resin film raw material of the present invention comprises a terminal amino triazine / Schiff base curing agent containing a Schiff base bond (C=N) and a triazine ring in the molecular structure. On the one hand, the curing agent contains a Schiff base bond (C=N) and a triazine ring structure with strong absorption and stabilization capabilities for ultraviolet rays, thereby giving the epoxy film excellent resistance to ultraviolet aging; on the other hand, because it contains a terminal amino group that can participate in complex cross-linking reactions and increase the cross-linking density of the epoxy film, it can overcome the problem of precipitation and migration of small molecule anti-ultraviolet components under harsh environments. DETAILED DESCRIPTION

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

[0035] Example 1

[0036] 1) Under nitrogen atmosphere, 0.1 mol 1,3,5-triazine-2,4,6-tricarbaldehyde and 0.325 mol N-(4-aminophenyl)maleimide were dissolved in 100 mL benzene, and the temperature was raised to reflux state to react for 5 h. After the reaction was completed, the mixture was cooled to room temperature, methanol was added until no precipitation was produced, filtered, washed with ethanol for 3 times, and dried at 80°C to constant weight to obtain intermediate 1, which was set aside;

[0037]

[0038] 2) 0.1 mol of 4-aminothiophenol was dissolved in 100 mL of ethanol, and 0.1 mol of ethyl trifluoroacetate was added. The reaction was carried out at 25° C. for 12 h. After the reaction was completed, the mixture was filtered, washed with ethanol three times, and dried at 80° C. to constant weight to obtain intermediate 2, which was set aside;

[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 in a volume ratio of 10:3, mix them evenly, control the temperature at 25°C to react for 6 hours, pour methanol into the mixture after the reaction is completed until no precipitation is produced, filter, wash with methyl ethyl ketone and water alternately for 3 times, and dry at 80°C to constant weight to obtain intermediate 3;

[0041]

[0042] 4) 70 g of intermediate 3 was added to a 7 wt % potassium carbonate solution (the solvent was a mixture of tetrahydrofuran, ethanol and water in a volume ratio of 8:1:3) at a mass volume ratio of 70 g:250 mL, and the temperature was controlled at 30° C. for 24 h. After the reaction, the pH was adjusted to 3 with 37 wt % hydrochloric acid, and the solvent was distilled off. The obtained solid was redissolved in water, the pH was adjusted to 12 with saturated ammonia water, extracted with ethyl acetate, and distilled to obtain an amino-terminated triazine / Schiff base curing agent.

[0043]

[0044] 5) Dissolve 30 g of toughening agent Toyobo GK590 in 100 mL of butanone, then add 35 g of liquid epoxy resin Mitsubishi YL-980, 30 g of solid epoxy resin Dow DER671, 2 g of coupling agent triethoxy [4- (trifluoromethyl) phenyl] silane, 0.1 g of defoaming agent BYK-1790, and 0.8 g of antioxidant DLTP, heat to 60 ° C and mix well to obtain a mixture;

[0045] 6) The mixture was heated to 80°C, stirred evenly, then cooled to 30°C, 8g of curing agent diaminodiphenylmethane, 5g of terminal amino triazine / Schiff base curing agent, and 0.3g of accelerator dimethylimidazole were added and mixed evenly, degassed, coated on the release film, heated to 80°C and dried to remove the solvent for 20 minutes to obtain a 25 μm thick epoxy resin film with high light transmittance and yellowing resistance.

[0046] Example 2

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

[0048] Example 3

[0049] The rest is the same as Example 1, except that in step 2), 4-aminothiophenol is replaced by an equal molar amount of 2-aminothiophenol.

[0050] Example 4

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

[0052] Example 5

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

[0054] 2) 0.1 mol of 4-aminothiophenol was dissolved in 100 mL of ethanol, and 0.106 mol of ethyl trifluoroacetate was added. The reaction was carried out at 25° C. for 12 h. After the reaction was completed, the mixture was filtered, washed with ethanol three times, and dried at 80° C. to constant weight to obtain intermediate 2, which was set aside;

[0055] 3) 0.1 mol of the intermediate, 0.32 mol of the amino-protected aminothiophenol derivative, and 150 mL of a mixed solvent of benzene and methyl ethyl ketone in a volume ratio of 10:5 were mixed evenly, and the reaction was carried out at 25°C for 6 hours. After the reaction was completed, methanol was added until no precipitation was produced, filtered, washed with methyl ethyl ketone and water alternately for 3 times, and dried at 80°C to constant weight to obtain intermediate 3;

[0056] 4) 100 g of intermediate 3 was added to a 7 wt % potassium carbonate solution (the solvent was a mixture of tetrahydrofuran, ethanol and water in a volume ratio of 8:1:3) at a mass volume ratio of 100 g:300 mL, and the temperature was controlled at 30 ° C for 24 h. After the reaction, the pH was adjusted to 3 with 37 wt % hydrochloric acid, and the solvent was distilled off. The obtained solid was redissolved in water, the pH was adjusted to 12 with saturated ammonia water, extracted with ethyl acetate, and distilled to obtain an amino-terminated triazine / Schiff base curing agent.

[0057] Example 6

[0058] The rest is the same as Example 1, except that in step 5), an equal amount of 3-glycidyloxypropyltrimethoxysilane is used to replace triethoxy[4-(trifluoromethyl)phenyl]silane.

[0059] Example 7

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

[0061] 6) The mixture was heated to 80°C, stirred evenly, then cooled to 30°C, 5 g of curing agent diaminodiphenylmethane, 5 g of terminal amino triazine / Schiff base curing agent, and 0.3 g of accelerator dimethylimidazole were added and mixed evenly, degassed, coated on the release film, heated to 80°C and dried to remove the solvent for 20 minutes to obtain a 25 μm thick epoxy resin film with high light transmittance and yellowing resistance.

[0062] Comparative Example 1

[0063] The rest is the same as Example 1, except that the amino-terminated triazine / Schiff base curing agent is replaced by an equal mass of diaminodiphenylmethane.

[0064] Comparative Example 2

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

[0066] The epoxy films prepared in the above examples and comparative examples were cured by baking at 120°C for 2 hours and then tested for the following properties:

[0067] Light transmittance: measured in accordance with standard GB / T2410, wavelength 400nm-1200nm.

[0068] Determination of ΔYI of wet heat / ultraviolet interaction aging: wet heat aging: soak in 85℃ water for 2h; ultraviolet aging: ultraviolet radiation aging test is carried out according to the requirements of the International Electrotechnical Commission standard IEC61345, the sample surface temperature is 60±5℃; the wavelength is in the range of 280-400nm, and the irradiation intensity is 15KW·h / m 2 , UV irradiation time is 2000hr. Re-measure the transmittance. According to the standard GB / T 2409 plastic yellow index test method, the change ΔYI of the yellow index of the sample before and after aging is measured. The higher the change index, the more obvious the yellowing phenomenon.

[0069] Elongation at break: DMA method test, tensile rate is 0.3mm / min, test temperature is 25℃.

[0070] Table 1 Performance test results

[0071]

[0072]

[0073] As can be seen from Table 1, the epoxy film containing amino-terminated triazine / Schiff base curing agent prepared by the present invention has significantly improved elongation at break and anti-yellowing performance by adding amino-terminated triazine / Schiff base curing agent, which has great industrial advantages.

[0074] From Examples 1-4 and Comparative Example 2, it can be seen that the amino-terminated triazine / Schiff base curing agent of the present invention and the thioester antioxidant have an obvious synergistic effect of improving the anti-yellowing performance.

[0075] The above detailed description is a specific description of one feasible embodiment of the present invention. The embodiment is not intended to limit the patent scope of the present invention. Any equivalent implementation or modification that does not deviate from the present invention should be included in the scope of the technical solution of the present invention.

Claims

1. A high light transmittance, yellowing-resistant epoxy resin film, characterized in that: The invention comprises the following raw materials in parts by weight: 30-35 parts of liquid epoxy resin, 25-35 parts of solid epoxy resin, 20-30 parts of toughening agent, 5-8 parts of aromatic diamine curing agent, 3-5 parts of amino-terminated triazine / Schiff base curing agent, 0.3-0.5 parts of accelerator, 1-2 parts of coupling agent, 0.1-0.3 parts of defoaming agent, 0.5-0.8 parts of thioester antioxidant, and 50-100 parts of solvent. The amino-terminated triazine / Schiff base curing agent has a structure as shown in Formula I.

2. The high light transmittance, yellowing-resistant epoxy resin film according to claim 1, characterized in that: The amino-terminated triazine / 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 are dissolved in an organic solvent, and the temperature is raised to reflux state for reaction. After the reaction is completed, the mixture is cooled, and alcohol is added until no precipitation is generated. The mixture is filtered, washed, and dried to obtain intermediate 1 for standby use; 2) protecting the amino group on the aminothiophenol derivative to obtain intermediate 2 for later use; 3) Mix intermediate 1, intermediate 2 and an organic solvent evenly, control the temperature to react, add alcohol after the reaction until no precipitation is produced, filter, wash and dry to obtain intermediate 3; 4) Deprotecting the intermediate 3 to obtain an amino-terminated triazine / Schiff base curing agent.

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

35.

4. The high light transmittance, yellowing-resistant epoxy resin film according to claim 2, characterized in that: Step 2) The amino protection reaction is specifically as follows: dissolving an aminothiophenol derivative in alcohol, adding an amino protection reagent, preferably ethyl trifluoroacetate, reacting under temperature control, filtering, washing, and drying after the reaction to obtain an intermediate 2 for standby use; the aminothiophenol derivative is selected from one or a combination of two or more of 4-aminothiophenol, 2-aminobenzenethiol, and 3-aminothiophenol; and the molar ratio of the aminothiophenol derivative to the amino protection reagent is 1:1-1.

06.

5. The high light transmittance, yellowing-resistant epoxy resin film 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 control reaction condition is 20-30°C for 3-6h, 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 yellowing resistance according to claim 2, characterized in that: Step 4) The deprotection reaction is specifically as follows: taking the intermediate 3 and adding it to a potassium carbonate solution, controlling the temperature to react, adjusting the pH to 3-5 after the reaction, distilling off the solvent, re-dissolving the obtained solid in water, adjusting the pH to 10-12, extracting with ethyl acetate, and distilling to obtain the amino-terminated triazine / Schiff base curing agent.

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

8. The high light transmittance, yellowing-resistant epoxy resin film according to claim 1, characterized in that: The liquid epoxy resin is a bisphenol A epoxy resin with an epoxy equivalent of 130-200 g / eq, specifically selected from Mitsubishi YL-980, Mitsui R-139, Mitsui R-140P, or a combination of two or more thereof; the solid epoxy resin is a bisphenol A epoxy resin with an epoxy equivalent of 475-800 g / eq, specifically selected from Dow DER671, DER662E, DER663E, DER663UE, or a combination of two or more thereof; the accelerator is selected from tertiary amine accelerators, phenol accelerators, and imidazole accelerators, or a combination of two or more thereof.

9. The high light transmittance, yellowing-resistant epoxy resin film according to claim 1, characterized in that: The coupling agent is selected from one or a combination of two or more of triethoxy [4- (trifluoromethyl) phenyl] silane, trimethoxy (3,3,3-trifluoropropyl) silane 3,3,3-trifluoropropyl triethoxy silane, methyl (3,3,3-trifluoropropyl) diethoxy silane, β- (3,4-epoxycyclohexyl) ethyl trimethoxy silane, 3-glycidyl ether oxypropyl trimethoxy silane, 3- [(2,3) - epoxypropoxy] propyl methyl dimethoxy silane; preferably triethoxy [4- (trifluoromethyl) phenyl] silane.

10. The method for preparing the epoxy resin film with high light transmittance and yellowing resistance according to any one of claims 1 to 9, characterized in that: The steps include: T1) dissolving a toughening agent in a solvent, and then adding a liquid epoxy resin, a solid epoxy resin, a coupling agent, a defoaming agent, and a thioester antioxidant, heating and mixing uniformly to obtain a mixture; T2) heating the mixture, stirring evenly, cooling it down, adding a curing agent, an amino-terminated triazine / Schiff base curing agent, and an accelerator, mixing evenly, degassing, coating on a release film, and drying off the solvent to obtain an epoxy resin film with high light transmittance and yellowing resistance.

Images