Low-stress and low-displacement uv heat-curable adhesive for optical devices and preparation method thereof

Abstract

The application discloses a kind of low stress low displacement UV thermosetting glue for optical device and preparation method thereof, by weight parts, the curing glue includes the following raw materials: first epoxy resin 10-35 parts, second epoxy resin 25-60 parts, UV curing agent 2-4 parts, thermosetting agent 3-5 parts, active diluent 7-15 parts, reinforcing filler 8-14 parts;Wherein, the second epoxy resin is obtained using organic silicon modified bisphenol A type epoxy resin;The reinforcing filler includes layered aluminum magnesium silicate and spherical silica.The curing glue of the application can realize UV+heat double curing, with high toughness, low volatility, heat and humidity resistance, high bonding strength characteristics.

Description

Technical Field

[0001] This invention belongs to the field of adhesive technology, specifically relating to a low-stress, low-displacement UV thermosetting adhesive for optical devices and its preparation method. Background Technology

[0002] With the rapid development of optical communication technology, optical devices play a crucial role in numerous fields such as modern communication networks, data centers, intelligent transportation, and medical equipment. From optical modules and couplers in fiber optic communication to optical components in lidar and various high-end sensors, the performance of optical devices directly determines the information transmission efficiency, accuracy, and reliability of the entire system. In the manufacturing process of these optical devices, curing adhesives, as key encapsulation materials, are used to fix optical components, seal optical paths, and provide mechanical support; their performance has a profound impact on the overall performance of the optical devices.

[0003] Traditional single-component thermosetting epoxy adhesives on the market have the following problems: ① High curing temperature (120-150℃), which can cause thermal damage to temperature-sensitive optical chips (such as InP and LiNbO3); ② Rapid increase in modulus during curing, and residual stress of 5-15MPa due to CTE mismatch during the cooling stage, causing lens floating or fiber displacement; ③ Short room temperature storage period (usually <48 h), requiring cold chain transportation, resulting in high production costs. Traditional UV-curable adhesives also have some obvious limitations. The curing shrinkage rate of UV-curable adhesives is usually high, making it difficult to achieve complete curing for some deep-cavity structures or thick-layer encapsulated optical devices. To overcome the limitations of single UV-curable or thermosetting adhesives, some UV-thermal dual-curable adhesives have emerged on the market. However, existing UV-thermal dual-curable adhesives still have some problems. On the one hand, their curing shrinkage rate is still high, making it difficult to meet the requirements of high-precision optical devices for low stress and low displacement; on the other hand, their residual stress after curing is large, which may cause micro-displacement of optical components during long-term use, affecting the reliability of optical devices.

[0004] Therefore, there is an urgent need to develop a high-performance adhesive that can maintain low stress and low displacement during both UV curing and thermal curing processes, in order to meet the high-performance requirements of the optical device industry for packaging materials and promote the further development of optical device technology. Summary of the Invention

[0005] The purpose of this invention is to overcome the defects in the prior art and provide a low-stress, low-displacement UV thermosetting adhesive and method for optical devices, so that the adhesive can maintain low stress and low displacement during both UV curing and thermosetting processes, while possessing good toughness and resistance to damp heat, thus meeting the packaging requirements of high-precision optical devices.

[0006] The objective of this invention can be achieved through the following technical solutions: The present invention provides a low-stress, low-displacement UV thermosetting adhesive for optical devices. By weight, the adhesive comprises the following raw materials: 10-35 parts of first epoxy resin, 25-60 parts of second epoxy resin, 2-4 parts of UV curing agent, 3-5 parts of thermosetting agent, 7-15 parts of reactive diluent, and 8-14 parts of reinforcing filler. The preparation method of the second epoxy resin includes the following steps: Q1. Mix arylsilane, methacryloxysilane, isopropanol and water, adjust the pH to acidic, heat to 45-65℃ and keep the reaction at this temperature for 4-8 hours, cool, wash and dry to obtain the reactants; Q2. Mix the reactants obtained in step Q1, bisphenol A epoxy resin, and toluene, stir, add azobisisobutyronitrile, heat to 70-105℃ and keep the reaction at this temperature for 4-8 hours, distill under reduced pressure, and cool to obtain the second epoxy resin. The method for preparing the reinforcing filler includes the following steps: P1. The layered magnesium aluminum silicate and spherical silica are vacuum dried and cooled for later use; P2. Mix the dried layered magnesium aluminum silicate obtained in step P1, the dried spherical silica, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, anhydrous ethanol and water, stir, adjust the pH to 3-5, introduce nitrogen gas, heat to 45-75℃ and react for 8-10 h, then add mercaptopropyltrimethoxysilane, keep the reaction at this temperature for 4-6 h, distill under reduced pressure, dry, grind and sieve to obtain the reinforcing filler; wherein the particle size of the layered magnesium aluminum silicate is 100-500 nm and the particle size of the spherical silica is 10-150 nm.

[0007] In some embodiments of the present invention, the first epoxy resin is F-44 type phenolic epoxy resin.

[0008] In some embodiments of the present invention, the UV curing agent is any one or more of triphenylsulfonium chloride, diaryliodomonium chloride, and triphenylsulfonium hexafluorophosphate.

[0009] In some embodiments of the present invention, the thermosetting agent is a cationic latent thermosetting agent.

[0010] In some embodiments of the present invention, the active diluent is any one or more of 1,4-bis[(glycidoxy)methyl]cyclohexane, butyl glycidyl ether, 2-ethylhexyl glycidyl ether, and 4-nonylphenyl glycidyl ether.

[0011] In some embodiments of the present invention, the molar ratio of arylsilane to methacryloxysilane in step Q1 is 1:(0.9-1.4).

[0012] In some embodiments of the present invention, the mass ratio of the reactant to the bisphenol A type epoxy resin in step Q2 is 1:(0.5-0.8).

[0013] In some embodiments of the present invention, the mass ratio of dried layered magnesium aluminum silicate, dried silica, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane and mercaptopropyltrimethoxysilane in step P2 is (0.25-0.5):1:(0.3-0.7):(0.15-0.45).

[0014] In some embodiments of the present invention, the reagents used to adjust the pH to acidity in steps Q1 and P2 include, but are not limited to, glacial acetic acid.

[0015] The research mechanism of this invention is as follows: 1. Epoxy resin cured adhesives have been widely used in many fields due to their excellent bonding properties, good mechanical properties, and chemical stability. However, epoxy resin cured adhesives themselves have problems such as high brittleness and poor resistance to damp heat. To solve these problems, this invention uses a composite epoxy resin (F-44 type phenolic epoxy resin and silicone-modified epoxy resin) to improve the overall performance of the cured adhesive.

[0016] This invention uses two different types of silanes (arylsilane and methacryloxysilane) to modify the resin. The rigid aromatic ring structure of arylsilane significantly increases the glass transition temperature of the resin and reduces water absorption, thus improving moisture resistance. Meanwhile, the introduction of methacryloxysilane effectively reduces curing shrinkage and improves toughness. Furthermore, the introduction of double bonds in the silanes endows the resin with UV free radical polymerization capabilities, enabling rapid localized curing and improving bond strength.

[0017] 2. Reinforcing fillers: If layered magnesium aluminum silicate is directly blended with spherical silica, although the toughening effect can be achieved by the slippage of the lamellars and the viscosity reduction by the spherical beads, the polar surface will adsorb water vapor and has poor compatibility with epoxy. Under humid heat, the interface will de-adhere first. Therefore, silanization modification is crucial.

[0018] This invention first modifies the surface of the reinforcing filler with N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, and then further modifies it with mercaptopropyltrimethoxysilane. On one hand, the modified reinforcing filler exhibits better compatibility with the system; on the other hand, the amino groups in N-(2-aminoethyl)-3-aminopropyltrimethoxysilane react with the epoxy groups in the epoxy resin to form chemical bonds, enhancing the bonding force between the filler and the matrix. More importantly, the mercapto groups in mercaptopropyltrimethoxysilane undergo a thiol-epoxy click reaction with the epoxy groups in the epoxy resin, further improving the interfacial bonding force. Furthermore, the antioxidant and metal chelating effects of the mercapto groups may also improve the resistance to damp heat. Simultaneously, the second epoxy resin formed by organosilicon-modified bisphenol A type epoxy resin contains C=C double bonds, and click chemistry occurs between the mercapto groups and the C=C double bonds, resulting in a fast reaction rate and high selectivity, thus improving the UV curing rate. Moreover, the mercapto-alkene reaction is a stepwise polymerization mechanism, resulting in less volume shrinkage compared to chain polymerization. Through this surface modification, the reinforcing filler not only forms stable chemical bonds with the epoxy resin, but also improves the dispersibility and compatibility with the matrix through the synergistic effect of amino and mercapto groups. This reduces internal stress while improving the toughness of the cured adhesive, achieving the goals of low volatility, resistance to damp heat, and high bond strength.

[0019] Another aspect of the present invention provides a method for preparing a low-stress, low-displacement UV thermosetting adhesive for optical devices, comprising the following steps: S1. The first epoxy resin, the second epoxy resin, the UV curing agent, and the reactive diluent are mixed and added to the reaction vessel to obtain a mixture; S2. Add reinforcing filler to the mixture obtained in step S1, stir, then add thermosetting agent, mix, and degas under vacuum to obtain cured adhesive.

[0020] Compared with the prior art, the present invention has the following outstanding advantages: 1. This invention uses F-44 type phenolic epoxy resin and a specific organosilicon-modified epoxy resin as a composite, and improves flexibility, reduces curing stress and shrinkage, and enhances resistance to damp heat through a specific organosilicon compound, making it suitable for packaging precision devices such as optical modules.

[0021] 2. This invention combines layered aluminum magnesium silicate with spherical silica through a silane coupling agent. Through the synergistic effect of amino and mercapto groups, namely, the ring-opening bond between amino groups and epoxy resin, and the click reaction between mercapto groups and the C=C double bonds in epoxy resin and second epoxy resin, the filler-matrix chemical anchoring is achieved, improving dispersibility and interfacial strength, thereby enhancing the overall performance of the cured adhesive. Detailed Implementation

[0022] The present invention will now be described in detail with reference to specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0023] The present invention will be described below with reference to specific embodiments. It should be noted that the following embodiments are examples of the present invention and are used only to illustrate the invention, not to limit it. Other combinations and various modifications within the scope of the present invention can be made without departing from its spirit or scope.

[0024] Each cured adhesive was prepared according to the proportions and preparation methods of the raw materials specified in the following examples and comparative examples.

[0025] To facilitate implementation of this invention by those skilled in the art, the manufacturers of some raw materials for the embodiments and comparative examples are described below: Bisphenol A type epoxy resin: model E-51; Thermosetting agent: Cationic latent thermosetting agent, model ICAM-8409; Unless otherwise specified, all other raw materials can be purchased from the market.

[0026] Preparation Example 1 The preparation method of the second epoxy resin A includes the following steps: Q1. Mix 0.2 mol of 1,5-divinyl-3,3-diphenyl-1,1,5,5-tetramethyltrisiloxane, 0.24 mol of methacryloyloxypropylmethyldiethoxysilane, 25 g of isopropanol and 10 g of water, adjust the pH to 4.0, heat to 55 °C and keep the reaction at that temperature for 6 h, cool to room temperature, wash three times with water, and dry with anhydrous Na2SO4 to obtain the reactant; Q2. Mix 15g of reactant obtained in step Q1, 10g of bisphenol A type epoxy resin E-51, and 30g of toluene, stir evenly, add 0.1g of azobisisobutyronitrile, heat to 85℃ and keep warm for 6h, distill under reduced pressure, and cool to room temperature to obtain the second epoxy resin A.

[0027] Preparation Example 2 The preparation method of the second epoxy resin B is the same as that of Preparation Example 1, except that the amount of bisphenol A type epoxy resin added is 15g.

[0028] Preparation Example 3 The preparation method of reinforcing filler A includes the following steps: P1. 400 nm layered magnesium aluminum silicate and 50 nm spherical silica were vacuum dried at 100 °C to constant weight and then cooled for later use. P2. Mix 7.5g of dried layered magnesium aluminum silicate, 20g of dried spherical silica, 10g of N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, 500mL of anhydrous ethanol and 100mL of water, stir well, adjust the pH to 4, introduce nitrogen gas, heat to 60℃ and react for 8h, then add 6g of mercaptopropyltrimethoxysilane, keep the reaction at this temperature for 5h, distill under reduced pressure, dry at 80℃ for 6h, grind through a 200-mesh sieve to obtain reinforcing filler A.

[0029] Preparation Example 4 The preparation method of reinforcing filler B includes the following steps: P1. 50nm spherical silica was vacuum dried at 100℃ to constant weight and then cooled for later use; P2. Mix 27.5g of dried spherical silica, 10g of N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, 500mL of anhydrous ethanol and 100mL of water, stir well, adjust the pH to 4, introduce nitrogen gas, heat to 60℃ and react for 8h, then add 6g of mercaptopropyltrimethoxysilane, keep the reaction at this temperature for 5h, distill under reduced pressure, dry at 80℃ for 6h, grind through a 200-mesh sieve to obtain reinforcing filler B.

[0030] Preparation Example 5 The preparation method of reinforcing filler C is the same as that of preparation example 3, except that the amount of mercaptopropyltrimethoxysilane added is 2g.

[0031] Example 1 A low-stress, low-displacement UV thermosetting adhesive for optical devices, comprising, by weight, the following raw materials: 22.5 parts of F-44 type phenolic epoxy resin, 42.5 parts of second epoxy resin A, 3 parts of UV curing agent triphenylsulfonium chloride, 4 parts of thermosetting agent ICAM-8409, 11 parts of 1,4-bis[(glycidoxy)methyl]cyclohexane, and 11 parts of reinforcing filler A; The preparation method of the curing adhesive in this embodiment includes the following steps: S1. F-44 type phenolic epoxy resin, second epoxy resin A, UV curing agent triphenylsulfonium chloride, and 1,4-bis[(glycidoxy)methyl]cyclohexane are mixed and added to a reaction vessel to obtain a mixture; S2. Add reinforcing filler A to the mixture obtained in step S1, stir evenly, then add thermosetting agent ICAM-8409, mix evenly, and then degas under vacuum to obtain cured adhesive.

[0032] Example 2 A low-stress, low-displacement UV thermosetting adhesive for optical devices, comprising, by weight, the following raw materials: 10 parts of F-44 type phenolic epoxy resin, 25 parts of second epoxy resin A, 2 parts of UV curing agent triphenylsulfonium chloride, 3 parts of thermosetting agent ICAM-8409, 7 parts of 1,4-bis[(glycidoxy)methyl]cyclohexane, and 8 parts of reinforcing filler A; The preparation method of the curing adhesive in this embodiment is the same as that in Example 1.

[0033] Example 3 A low-stress, low-displacement UV thermosetting adhesive for optical devices, comprising, by weight, the following raw materials: 35 parts of F-44 type phenolic epoxy resin, 60 parts of second epoxy resin A, 4 parts of UV curing agent diaryliodonium salt, 95 parts of thermosetting agent ICAM-840, 15 parts of 2-ethylhexyl glycidyl ether, and 14 parts of reinforcing filler A; The preparation method of the curing adhesive in this embodiment includes the following steps: S1. Add F-44 type phenolic epoxy resin, second epoxy resin A, UV curing agent diaryliodonium salt, and 2-ethylhexyl glycidyl ether to a reaction vessel to obtain a mixture; S2. Add reinforcing filler A to the mixture obtained in step S1, stir evenly, then add thermosetting agent ICAM-8409, mix evenly, and then degas under vacuum to obtain cured adhesive.

[0034] Example 4 A low-stress, low-displacement UV thermosetting adhesive for optical devices and its preparation method are disclosed. The specific implementation method is the same as in Example 1, except that an equal amount of second epoxy resin B is used to replace second epoxy resin A.

[0035] Example 5 A low-stress, low-displacement UV thermosetting adhesive for optical devices and its preparation method are disclosed. The specific implementation method is the same as in Example 1, except that an equal amount of reinforcing filler B is used instead of reinforcing filler A.

[0036] Example 6 A low-stress, low-displacement UV thermosetting adhesive for optical devices and its preparation method are disclosed. The specific implementation method is the same as in Example 1, except that an equal amount of reinforcing filler C is used to replace reinforcing filler A.

[0037] Comparative Example 1 A low-stress, low-displacement UV thermosetting adhesive for optical devices and its preparation method are disclosed. The specific implementation method is the same as in Example 1, except that an equal amount of F-44 type phenolic epoxy resin is used to replace the second epoxy resin A.

[0038] Effect evaluation: The cured adhesives prepared in Examples 1-6 and Comparative Example 1 were tested and analyzed. The specific results are shown in Table 1. The shear strength of the adhesives prepared in Examples 1-3 was tested and analyzed. The specific results are shown in Table 2.

[0039] Performance testing: (1) Water absorption rate test Referring to HG / T 3856-2006(2017) "Determination of Water Absorption Rate of Insulating Varnish Film", the sample was cured under UV (1000mW) @ 45s + 85℃ @ 60min conditions to form a cured block of 25mm × 25mm × 2mm. After curing, the block was placed in the same space at 25℃ for 12h. The weight M0 of the cured block was measured using an analytical balance. Then, the block was immersed in 100℃ distilled water for 2h. After removing the block, the surface moisture was wiped clean, and the weight M1 of the cured block after immersion was measured again using an analytical balance. The data was calculated as a percentage using the formula: Wt = (M1-M0) / M0×100%; (2) Elongation at break test Referring to GB / T 528-2009 "Determination of Tensile Stress-Strain Properties of Vulcanized Rubber or Thermoplastic Rubber", specifically, Type 2 specimens were used, with a gauge length of 20 mm, a thickness of 1 mm, and a tensile speed of 5 mm / min. The test substrate was a dumbbell-shaped sample (dog bone), and the testing instrument was a computerized universal testing machine. The curing conditions were UV (1000 mW) @ 45 s + 85℃ @ 60 min.

[0040] Table 1 ; (3) Shear strength test Referring to the test method in GB / T 7124-2008 "Determination of Tensile Shear Strength of Adhesives (Rigid Material to Rigid Material)", and according to the company's internal testing standard XB-QCT-016, the shear strength at 110℃ was tested, specifically as follows: a. The test substrate is an AL-glass overlap sheet. A standard aluminum sheet (100mm*27.9mm*1.5mm) is polished and then the surface to be bonded is cleaned with a cleaning solvent. b. Weigh 2mg of adhesive sample onto the bonding surface, place 100μm copper wire as a spacer to set the adhesive layer thickness, then cover with 5*5*1mm glass, press firmly, cure under UV (1000mW)@45s+85℃@60min, and leave at room temperature for 24h. c. Perform a shear force test on the sample at 110℃ in the oven of a computer-controlled universal testing machine, with a shearing speed of 100 mm / min. After the aluminum sheet is pulled apart, measure the actual area of ​​the adhesive layer with a micrometer. d. Calculate tensile shear strength = breaking force (Newtons) / adhesive layer area (mm²)2 ).

[0041] Table 2 ; The data above show that the cured adhesives prepared in Examples 1-3 have high moisture resistance, high toughness, good adhesion to optical devices, and still have suitable shear strength even after high-temperature curing.

[0042] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A low-stress, low-displacement UV thermosetting adhesive for optical devices, characterized in that, By weight, the cured adhesive comprises the following raw materials: 10-35 parts of first epoxy resin, 25-60 parts of second epoxy resin, 2-4 parts of UV curing agent, 3-5 parts of thermosetting agent, 7-15 parts of reactive diluent, and 8-14 parts of reinforcing filler. The preparation method of the second epoxy resin includes the following steps: Q1. Mix arylsilane, methacryloxysilane, isopropanol and water, adjust the pH to acidic, heat to 45-65℃ and keep the reaction at this temperature for 4-8 hours, cool, wash and dry to obtain the reactants; Q2. Mix the reactants obtained in step Q1, bisphenol A epoxy resin, and toluene, stir, add azobisisobutyronitrile, heat to 70-105℃ and keep the reaction at this temperature for 4-8 hours, distill under reduced pressure, and cool to obtain the second epoxy resin. The method for preparing the reinforcing filler includes the following steps: P1. The layered magnesium aluminum silicate and spherical silica are vacuum dried and cooled for later use; P2. Mix the dried layered magnesium aluminum silicate obtained in step P1, the dried spherical silica, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, anhydrous ethanol and water, stir, adjust the pH to 3-5, introduce nitrogen gas, heat to 45-75℃ and react for 8-10 h, then add mercaptopropyltrimethoxysilane, keep the reaction at this temperature for 4-6 h, distill under reduced pressure, dry, grind and sieve to obtain the reinforcing filler; wherein the particle size of the layered magnesium aluminum silicate is 100-500 nm and the particle size of the spherical silica is 10-150 nm.

2. The low-stress, low-displacement UV thermosetting adhesive for optical devices according to claim 1, characterized in that, The first epoxy resin is F-44 type phenolic epoxy resin.

3. The low-stress, low-displacement UV thermosetting adhesive for optical devices according to claim 1, characterized in that, The UV curing agent is any one or more of triphenylsulfonium chloride, diaryliodomonium chloride, and triphenylsulfonium hexafluorophosphate.

4. The low-stress, low-displacement UV thermosetting adhesive for optical devices according to claim 1, characterized in that, The thermosetting agent is a cationic latent thermosetting agent.

5. The low-stress, low-displacement UV thermosetting adhesive for optical devices according to claim 1, characterized in that, The active diluent is any one or more of 1,4-bis[(glycidoxy)methyl]cyclohexane, butyl glycidyl ether, 2-ethylhexyl glycidyl ether, and 4-nonylphenyl glycidyl ether.

6. The low-stress, low-displacement UV thermosetting adhesive for optical devices according to claim 1, characterized in that, In step Q2, the mass ratio of the reactant to the bisphenol A epoxy resin is 1:(0.5-0.8).

7. The low-stress, low-displacement UV thermosetting adhesive for optical devices according to claim 1, characterized in that, In step P2, the mass ratio of dried layered magnesium aluminum silicate, dried silica, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane and mercaptopropyltrimethoxysilane is (0.25-0.5):1:(0.3-0.7):(0.15-0.45).

8. A method for preparing a low-stress, low-displacement UV thermosetting adhesive for optical devices according to any one of claims 1-7, characterized in that, It includes the following steps: S1. The first epoxy resin, the second epoxy resin, the UV curing agent, and the reactive diluent are mixed and added to the reaction vessel to obtain a mixture; S2. Add reinforcing filler to the mixture obtained in step S1, stir, then add thermosetting agent, mix, and degas under vacuum to obtain cured adhesive.