A free radical cation hybrid red UV adhesive for wire bonding and a preparation method thereof

Abstract

This application relates to the field of UV adhesive materials, and more specifically to a free radical cationic hybrid red UV adhesive for ribbon cable bonding and its preparation method. The free radical cationic hybrid red UV adhesive for ribbon cable bonding comprises the following raw materials: cationic UV-curable resin monomer, free radical resin, free radical monomer, cationic photoinitiator, free radical photoinitiator, coupling agent, thixotropic agent, reinforcing agent, and red pigment. The red UV adhesive finally obtained by this application not only combines the advantages of two UV curing systems to achieve low energy, complete curing and rapid curing in both light-shaded and thick-layer applications, but also maintains excellent storage stability and environmental aging resistance, significantly improving the overall performance of this type of UV adhesive and enhancing its application quality and service life.

Description

Technical Field

[0001] This application relates to the field of UV adhesive materials, and more specifically to a free radical cation hybrid red UV adhesive for ribbon cable bonding and its preparation method. Background Technology

[0002] In existing technologies, ultraviolet (UV) curing adhesives have been widely used in the fields of ribbon cable bonding and electronic assembly due to their advantages such as rapid curing, environmental friendliness, and high energy efficiency. Among them, red UV adhesives have become an important sub-product due to their special requirements in ribbon cable marking, light shielding, and positioning.

[0003] As electronic components become increasingly miniaturized and high-density, ribbon cable bonding applications place more stringent demands on the performance of UV adhesives. Existing single-radical red UV adhesives are increasingly revealing their limitations in complex application scenarios. For example, in ribbon cable bonding, the shading effect caused by the ribbon cable structure or uneven UV irradiation, coupled with the sensitivity of the radical curing system to oxygen inhibition, can easily lead to incomplete surface curing and stickiness, affecting subsequent processing and reliability. Furthermore, to achieve the desired red color, organic or inorganic red pigments must be introduced into the formulation. These colorants significantly absorb and scatter UV light, severely hindering light penetration into the adhesive layer, resulting in insufficient curing depth. For ribbon cable applications with a certain thickness or requiring deep bonding, this light-shielding effect prevents the bottom of the adhesive from fully curing, significantly reducing bond strength and posing a risk of failure over long-term use.

[0004] To overcome the shortcomings of single curing systems, engineers explored cationic UV curing systems. These systems typically generate a superacid under light irradiation, catalyzing the ring-opening polymerization of epoxy or vinyl ether resins. Cationic polymerization offers advantages such as immunity to oxygen inhibition, low curing shrinkage, low internal stress, and post-curing effects, facilitating deep curing and achieving superior adhesion and heat resistance. However, cationic systems also suffer from moisture sensitivity, relatively slow curing rates, and a narrower range of raw material choices. When used alone, they struggle to achieve the optimal balance between the rapid positioning required for cable bonding and the final physical properties. Regardless of whether it's a single free radical, cationic, or a simple hybrid system, when applied to cable bonding, common technical problems include difficulties in deep curing due to the light-shielding effect of colorants, the inability to balance curing rate and final mechanical properties, and incomplete curing, poor storage stability, or insufficient resistance to environmental aging caused by poor synergy between the two curing mechanisms. Summary of the Invention

[0005] Therefore, in order to effectively solve the above-mentioned technical problems, the applicant, through in-depth research in the technical direction, finally proposed a free radical cationic hybrid red UV adhesive for ribbon cable bonding in this application. The red UV adhesive finally obtained by this application can not only combine the advantages of two UV curing systems to achieve low energy, complete curing and rapid curing of light and shadow areas and thick layers, but also maintain excellent storage stability and environmental aging resistance, thus greatly improving the overall performance of this type of UV adhesive and improving application quality and service life.

[0006] A free radical cationic hybrid red UV adhesive for bonding ribbon cables comprises, by weight, 40-65 parts of cationic UV-curable resin monomer, 20-35 parts of free radical resin, 15-25 parts of free radical monomer, 2-4 parts of cationic photoinitiator, 2-4 parts of free radical photoinitiator, 2-5 parts of coupling agent, 2-4 parts of thixotropic agent, 5-10 parts of reinforcing agent, 0.2-0.4 parts of defoamer, and 0.1-0.2 parts of red pigment.

[0007] Preferably, the mass ratio of the cationic UV-curable resin monomer, the free radical resin, and the free radical monomer is (4.5~5):(2.2~2.8):(1.8~2.2).

[0008] Preferably, the mass ratio of the cationic UV-curable resin monomer, the free radical resin, and the free radical monomer is (4.6~4.8):(2.4~2.5):(2~2.1).

[0009] Preferably, the mass ratio of the cationic UV-curable resin monomer to the reinforcing agent is (4.6~4.8):(0.6~0.8).

[0010] Preferably, the cationic UV-curable resin monomer is a combination of bis((3,4-epoxycyclohexyl)methyl)adipate and oxetane.

[0011] Preferably, the mass ratio of bis((3,4-epoxycyclohexyl)methyl)adipic acid ester to oxetane is (2~2.2):(2.4~2.6).

[0012] Preferably, the free radical resin is an epoxy acrylate or a polyurethane acrylate.

[0013] Preferably, the free radical resin is a polyurethane acrylate.

[0014] Preferably, the free radical monomer is a combination of isobornyl methacrylate and tetrahydrofurfuryl acrylate.

[0015] Preferably, the mass ratio of isobornyl methacrylate to tetrahydrofurfuryl acrylate is (1~1.5):(1~1.5).

[0016] This application utilizes the aforementioned raw material formulation to construct a synergistic dual-curing system by introducing a specific ratio of cationic UV-curable resin monomers and corresponding cationic photoinitiators into a traditional free radical UV adhesive system. The core objective of this design is to comprehensively leverage the advantages of free radical polymerization—its rapid reaction rate and ability to achieve quick surface drying—and the characteristics of cationic polymerization—its insensitivity to oxygen, its "post-curing" effect, and its ability to initiate and sustain reactions at lower light energies. Through the complementarity and synergy of the two curing mechanisms, sufficient and complete curing is achieved even at lower UV irradiation energies, including the interior of the colloid, UV-shadowed areas, and thick layers where light intensity is insufficient due to the strong absorption of UV light by the red pigment (especially in the 350-450 nm band). This effectively solves the long-standing technical problem of incomplete local curing caused by the combined effects of physical shielding of the wire harness and the light-shielding effect of the colorant in ribbon cable bonding applications, ultimately improving the overall performance of the red UV adhesive.

[0017] Preferably, the cationic photoinitiator is at least one selected from iodonium salt, thionium salt, and ferrocene salt.

[0018] Preferably, the cationic photoinitiator is an aramid ferrocene salt.

[0019] Preferably, the free radical photoinitiator is TPO or TPO-L.

[0020] Preferably, the free radical photoinitiator is TPO.

[0021] Preferably, the coupling agent is at least one of KH550, KH560 and KH570.

[0022] Preferably, the coupling agent is KH550 or KH560.

[0023] Preferably, the coupling agent is KH560.

[0024] Preferably, the thixotropic agent is at least one selected from fumed silica, polyamide wax, bentonite, and diatomaceous earth.

[0025] Preferably, the thixotropic agent is fumed silica or polyamide wax.

[0026] Preferably, the thixotropic agent is fumed silica.

[0027] Preferably, the reinforcing agent is a combination of alicyclic epoxy resin and multifunctional polyurethane acrylate.

[0028] Preferably, the mass ratio of the alicyclic epoxy resin to the multifunctional polyurethane acrylate is (3~5):(1.5~2).

[0029] Preferably, the mass ratio of the alicyclic epoxy resin to the multifunctional polyurethane acrylate is (4~4.5):(1.8~2).

[0030] Preferably, the alicyclic epoxy resin is CY-179, sourced from Huntsman, USA.

[0031] Preferably, the multifunctional polyurethane acrylate is CN9010, sourced from Arkema, France.

[0032] Furthermore, the core advantage of the reinforcing additive scheme adopted in this application lies in the synergistic effect of alicyclic epoxy resin and trifunctional polyurethane acrylate, which significantly improves the curing completeness, bonding strength, and long-term reliability of the adhesive. The two raw materials respectively enhance the cationic and free radical curing processes of the system, forming an interpenetrating polymer network. Under ultraviolet light irradiation, the polyurethane acrylate, with its high reactivity, rapidly constructs a network framework that maintains initial strength; while the alicyclic epoxy resin, exhibiting its oxygen-inhibited and post-curing properties, continues to react even after light exposure ceases. This characteristic allows the curing reaction to continue in weak light areas and deep regions caused by wire harness obstruction or light absorption by red pigments, thus ensuring complete overall curing. Simultaneously, the excellent properties of both resins jointly enhance the adhesion, flexibility, and aging resistance of the cured adhesive layer, ultimately effectively solving the problem of incomplete curing caused by insufficient light in ribbon cable bonding.

[0033] Preferably, the defoamer is at least one of silicone defoamers.

[0034] A method for preparing a free radical cationic hybrid red UV adhesive for ribbon cable bonding includes the following steps: S1: In a light-shielding reactor, cationic UV-curable resin monomer, free radical resin, free radical monomer and reinforcing agent are added sequentially, and stirred at 200-300 rpm for 20-25 min at room temperature to obtain a premix; S2: Thixotropic agent, coupling agent and defoamer are added to the premix, and the stirring speed is increased to 400-500 rpm for high-speed dispersion for 40-50 min until no visible particles are found; S3: The stirring speed is reduced to 200-300 rpm and the remaining raw materials are added, and stirring is continued for 20-30 min. Stirring is stopped, the reactor is connected to a vacuum system, and bubbles are removed under a vacuum of -0.095 MPa to -0.1 MPa for 20-30 min until the adhesive is clear and transparent with no visible bubbles.

[0035] The beneficial effects of this application are:

[0036] 1. The red UV adhesive finally obtained in this application not only combines the advantages of two UV curing systems to achieve low energy, complete curing and rapid curing of light-shaded areas and thick layers, but also maintains excellent storage stability and environmental aging resistance, which greatly improves the overall performance of this type of UV adhesive and enhances application quality and service life.

[0037] 2. This application constructs a synergistic dual-curing system by introducing a specific ratio of cationic UV-curable resin monomers and corresponding cationic photoinitiators into a traditional free radical UV adhesive system. This system comprehensively utilizes the advantages of free radical polymerization, such as its fast reaction rate and rapid surface drying, as well as the characteristics of cationic polymerization, such as its insensitivity to oxygen, its "post-curing" effect, and its ability to initiate and sustain the reaction at lower light energies. Through the complementarity and synergy of the two curing mechanisms, sufficient and complete curing is achieved at lower UV irradiation energies, including the interior of the colloid, UV-shadowed areas, and thick layers where light intensity is insufficient due to the strong absorption of UV light by the red pigment (especially in the 350-450 nm band). This ultimately improves the overall application performance of the red UV adhesive.

[0038] 3. The core advantage of the reinforcing additive scheme adopted in this application lies in the synergistic effect of alicyclic epoxy resin and trifunctional polyurethane acrylate, which significantly improves the curing completeness, bonding strength, and long-term reliability of the adhesive. The two raw materials respectively enhance the cationic and free radical curing processes of the system, forming an interpenetrating polymer network. Under ultraviolet light irradiation, the polyurethane acrylate, with its high reactivity, rapidly constructs a network framework that maintains initial strength. This characteristic allows the curing reaction to continue in weak light areas and deep regions caused by wire beam obstruction or light absorption by red pigments, thereby ensuring complete overall curing and ultimately improving its comprehensive performance. Attached Figure Description

[0039] Figure 1 This is a photograph of the free radical cation hybrid red UV adhesive for bonding ribbon cables prepared in Example 1 of this application. Detailed Implementation

[0040] Example 1

[0041] A free radical cationic hybrid red UV adhesive for bonding ribbon cables comprises, by weight, 46 parts of cationic UV-curable resin monomer, 25 parts of free radical resin, 20 parts of free radical monomer, 2.5 parts of cationic photoinitiator, 2.5 parts of free radical photoinitiator, 2.9 parts of coupling agent, 2.9 parts of thixotropic agent, 7.5 parts of reinforcing agent, 0.3 parts of defoamer, and 0.1 parts of red pigment.

[0042] The combination of cationic UV-curable resin monomers bis((3,4-epoxycyclohexyl)methyl) adipate and oxetane in a mass ratio of 2.1:2.5.

[0043] The free radical resin is polyurethane acrylate, L-6290D, sourced from Guangzhou Lankelu New Materials Co., Ltd., China.

[0044] The free radical monomer is a combination of isobornyl methacrylate and tetrahydrofurfuryl acrylate in a mass ratio of 1:1.

[0045] The cationic photoinitiator is ferromagnesian salt, UYRACURE-261, from Shenzhen Youyang Technology Co., Ltd.

[0046] The free radical photoinitiator is TPO; the coupling agent is KH560; the thixotropic agent is fumed silica, fumed silica H18, from Wacker Chemie, Germany; the red pigment is ULOM RD1254, from Shanghai Juncai, China; and the defoamer is silicone defoamer BYK-066N.

[0047] The reinforcing agent is a combination of alicyclic epoxy resin and multifunctional polyurethane acrylate, with a mass ratio of 4.2:1.8.

[0048] The alicyclic epoxy resin is specifically CY-179, sourced from Huntsman, USA; the multifunctional polyurethane acrylate is specifically CN9010, sourced from Arkema, France.

[0049] A method for preparing a free radical cationic hybrid red UV adhesive for ribbon cable bonding includes the following steps: S1: In a light-shielding reactor, cationic UV-curable resin monomer, free radical resin, free radical monomer and reinforcing agent are added sequentially, and stirred at 240 rpm for 25 min at room temperature to obtain a premix; S2: Thixotropic agent, coupling agent and defoamer are added to the premix, and the speed is increased to 480 rpm for high-speed dispersion for 45 min until no visible particles are found; S3: The speed is reduced to 240 rpm and the remaining raw materials are added, and stirring is continued for 25 min. Stirring is stopped, the reactor is connected to a vacuum system, and bubbles are removed under a vacuum of -0.095 MPa for 30 min until the adhesive is clear and transparent with no visible bubbles.

[0050] The physical sample of the free radical cationic hybrid red UV adhesive for ribbon cable bonding prepared in this embodiment is shown below. Figure 1 As shown.

[0051] Example 2

[0052] This embodiment differs from Embodiment 1 only in the following way: A free radical cationic hybrid red UV adhesive for ribbon cable bonding, by weight, comprises the following raw materials: 50 parts cationic UV curable resin monomer, 28 parts free radical resin, 18 parts free radical monomer, 2.5 parts cationic photoinitiator, 2.5 parts free radical photoinitiator, 2.9 parts coupling agent, 2.9 parts thixotropic agent, 7.5 parts reinforcing agent, 0.3 parts defoamer, and 0.1 parts red pigment.

[0053] The remaining implementation methods are the same.

[0054] Example 3

[0055] This embodiment differs from Embodiment 1 only in the following way: A free radical cationic hybrid red UV adhesive for ribbon cable bonding, by weight, comprises the following raw materials: 46 parts cationic UV curable resin monomer, 25 parts free radical resin, 20 parts free radical monomer, 2.5 parts cationic photoinitiator, 2.5 parts free radical photoinitiator, 2.9 parts coupling agent, 2.9 parts thixotropic agent, 6 parts reinforcing agent, 0.3 parts defoamer, and 0.1 parts red pigment.

[0056] The remaining implementation methods are the same.

[0057] Comparative Example 1

[0058] This comparative example differs from Example 1 only in the following way: A free radical cationic hybrid red UV adhesive for ribbon cable bonding, by weight, comprises: 60 parts cationic UV curable resin monomer, 22.5 parts free radical resin, 7.5 parts free radical monomer, 2.5 parts cationic photoinitiator, 2.5 parts free radical photoinitiator, 2.9 parts coupling agent, 2.9 parts thixotropic agent, 7.5 parts reinforcing agent, 0.3 parts defoamer, and 0.1 parts red pigment.

[0059] The remaining implementation methods are the same.

[0060] Comparative Example 2

[0061] This comparative example differs from Example 1 only in the following way: A free radical cationic hybrid red UV adhesive for ribbon cable bonding, by weight, comprises: 46 parts cationic UV curable resin monomer, 25 parts free radical resin, 20 parts free radical monomer, 2.5 parts cationic photoinitiator, 2.5 parts free radical photoinitiator, 2.9 parts coupling agent, 2.9 parts thixotropic agent, 1.5 parts reinforcing agent, 0.3 parts defoamer, and 0.1 parts red pigment.

[0062] The remaining implementation methods are the same.

[0063] Comparative Example 3

[0064] This comparative example differs from Example 1 only in the following way: the combination of cationic UV-curable resin monomers bis((3,4-epoxycyclohexyl)methyl) adipate and oxetane in a mass ratio of 3:1.

[0065] The remaining implementation methods are the same.

[0066] Comparative Example 4

[0067] This comparative example differs from Example 1 only in the following way: the free radical monomer is a combination of isobornyl methacrylate and tetrahydrofurfuryl acrylate in a mass ratio of 4:1.

[0068] The remaining implementation methods are the same.

[0069] Comparative Example 5

[0070] This comparative example differs from Example 1 only in the following way: the reinforcing agent is a combination of alicyclic epoxy resin and multifunctional polyurethane acrylate in a mass ratio of 1:2.

[0071] The remaining implementation methods are the same.

[0072] Comparative Example 6

[0073] This comparative example differs from Example 1 only in the following way: the reinforcing agent is a combination of alicyclic epoxy resin and multifunctional polyurethane acrylate in a mass ratio of 5:0.5.

[0074] The remaining implementation methods are the same.

[0075] Performance testing

[0076] 1. Adhesion: The test was conducted according to GB / T 7124-2008. A 25mm wide and 1.6mm thick 304 stainless steel strip was solvent-cleaned and polished. Then, a 0.1mm thick layer of red UV adhesive was uniformly applied to the overlapping area of ​​the strip, with an overlap area of ​​12.5mm × 25mm. A UV point light source with a rated wavelength of 365nm and a light intensity of 100mW / cm² was used to irradiate the overlapping area for 20 seconds. After curing, the sample was placed in a standard laboratory environment (23±2°C, 50±5%RH) for 24 hours. Then, a shear strength test was performed on a universal testing machine at a tensile speed of 5mm / min. The result was the average of 10 tests.

[0077] 2. Curing performance: The UV adhesive was irradiated for 20 seconds using a hybrid system of cationic UV curing material and free radical system, with a rated wavelength of 365nm and a light intensity of 100mW / cm². The curing status of the UV adhesive was observed, and the presence of thixotropic surface shadows or incomplete curing at the bottom was noted. If any of these were present, the product was considered unqualified; otherwise, it was considered qualified. 50 samples were tested in each group, and the pass rate was recorded in Table 1.

[0078] 3. Environmental aging resistance: The test is conducted in accordance with ASTM D1183. The cured bonded sample is placed in a constant temperature and humidity chamber at 85°C and 85% relative humidity for 500 hours. The bond shear strength before and after the test is obtained, and the shear strength retention rate is obtained. The average value of 10 tests is recorded in Table 1.

[0079] 4. Stability test: 50g of uncured adhesive sample was sealed in an opaque plastic container and placed in a constant temperature oven at 60℃ for accelerated aging. The sample was taken out every week, cooled to room temperature, and its appearance was observed. The viscosity before and after the test was measured with a viscometer and compared with the initial value. The test period was 28 days, and the viscosity change rate was recorded. The average value of 10 tests was recorded in Table 1.

[0080] Table 1 Performance Test Results

[0081]

[0082] Based on the final performance test results of the embodiments and comparative examples, Examples 1-3 achieved superior performance results compared to Comparative Examples 1-6. This is mainly because the cationic UV-curable resin monomers and corresponding cationic photoinitiators and reinforcing additives used in Examples 1-3, as specified in this application, enhanced the cationic and free radical curing process of the system, forming an interpenetrating polymer network. Under ultraviolet light irradiation, polyurethane acrylate, with its high reactivity, rapidly constructs a network framework that maintains its initial strength. This characteristic allows the curing reaction to continue in the weak light areas and deep regions caused by beam obstruction or light absorption by the red pigment, thereby ensuring complete curing and ultimately improving its overall performance.

Claims

1. A free radical cationic hybrid red UV adhesive for bonding ribbon cables, characterized in that: By weight, the raw materials include: 40-65 parts cationic UV-curable resin monomer, 20-35 parts free radical resin, 15-25 parts free radical monomer, 2-4 parts cationic photoinitiator, 2-4 parts free radical photoinitiator, 2-5 parts coupling agent, 2-4 parts thixotropic agent, 5-10 parts reinforcing agent, 0.2-0.4 parts defoamer, and 0.1-0.2 parts red pigment; The cationic UV-curable resin monomer is a combination of bis((3,4-epoxycyclohexyl)methyl)adipate and oxetane, with a mass ratio of (2~2.2):(2.4~2.6). The free radical resin is epoxy acrylate or polyurethane acrylate; The free radical monomer is a combination of isobornyl methacrylate and tetrahydrofurfuryl acrylate in a mass ratio of (1~1.5):(1~1.5). The cationic UV-curable resin monomer has a mass ratio of free radical resin to free radical monomer of (4.5~5):(2.2~2.8):(1.8~2.2). The mass ratio of the cationic UV-curable resin monomer to the reinforcing agent is (4.6~4.8):(0.6~0.8). The reinforcing agent is a combination of alicyclic epoxy resin and multifunctional polyurethane acrylate, with a mass ratio of (3~5):(1.5~2).

2. The free radical cationic hybrid red UV adhesive for ribbon cable bonding according to claim 1, characterized in that: The cationic photoinitiator is at least one of iodonium salt, thionium salt, and ferrocene salt.

3. The free radical cationic hybrid red UV adhesive for ribbon cable bonding according to claim 2, characterized in that: The free radical photoinitiator is TPO or TPO-L.

4. The free radical cationic hybrid red UV adhesive for ribbon cable bonding according to claim 3, characterized in that: The coupling agent is at least one of KH550, KH560 and KH570.

5. The free radical cationic hybrid red UV adhesive for ribbon cable bonding according to claim 4, characterized in that: The thixotropic agent is at least one of fumed silica, polyamide wax, bentonite, and diatomaceous earth.

6. The free radical cationic hybrid red UV adhesive for ribbon cable bonding according to claim 5, characterized in that: The alicyclic epoxy resin is specifically CY-179; the multifunctional polyurethane acrylate is specifically CN9010.

7. The method for preparing the free radical cationic hybrid red UV adhesive for ribbon cable bonding according to any one of claims 1 to 6, characterized in that: Specifically, the following steps are included: S1: In a light-shielding reactor, cationic UV-curable resin monomer, free radical resin, free radical monomer and reinforcing agent are added in sequence, and stirred at 200~300 rpm for 20~25 min at room temperature to obtain a premix. S2: Add thixotropic agent, coupling agent and defoamer to the premix, and increase the speed to 400~500 rpm for high-speed dispersion for 40~50 min until no visible particles are present; S3: Reduce the speed to 200~300 rpm and add the remaining raw materials, continue stirring for 20~30 min, stop stirring, connect the reactor to the vacuum system, and remove bubbles under a vacuum of -0.095MPa to -0.1MPa for 20~30 min until the liquid is clear and transparent with no visible bubbles.

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