A UV-curable LIPO encapsulating adhesive suitable for low-pressure injection molding (≤2MPa), its preparation method, and its application.

Abstract

This invention provides a UV-curable LIPO encapsulating adhesive suitable for low-pressure injection molding (≤2MPa), its preparation method, and its application. The UV-curable LIPO encapsulating adhesive, by weight, comprises the following components: 30-60 parts of modified photosensitive oligomer, 20-50 parts of gradient-compounded reactive diluent, 1-8 parts of composite photoinitiator, and 0.5-5 parts of functional additives. Compared with existing technologies, this invention has the following advantages: overcoming technical biases to achieve a perfect balance between low viscosity and high performance; achieving high-precision molding with extremely narrow borders, forming a generational advantage; second-level controllable curing, significantly improving production efficiency and yield; broad-spectrum high adhesion, with long-term reliability comprehensively surpassing existing technologies; green and environmentally friendly; simple process; and easy to scale up for mass production.

Description

Technical Field

[0001] This invention relates to the fields of polymer materials and electronic packaging technology, specifically to a UV-curable LIPO encapsulating adhesive adapted to extremely low injection pressures of ≤2MPa and capable of forming extremely narrow adhesive lines of 0.08mm, as well as its preparation method and application. Background Technology

[0002] As consumer electronics and automotive electronics rapidly iterate towards ultra-narrow bezels, thinness, and high integration, the narrow-bezel packaging of screens and mid-frames, and the sealing and bonding of precision electronic components, place unprecedentedly stringent requirements on the molding precision, curing efficiency, process adaptability, and long-term reliability of adhesives.

[0003] Currently, the mainstream technology in high-end electronic packaging is moisture-curing reactive polyurethane hot melt adhesive (PUR hot melt adhesive). However, it has inherent technical defects that cannot be overcome: First, the curing cycle is long, requiring 24-72 hours to complete cross-linking with moisture in the air, resulting in slow production line cycle time and the "two-meter problem" that prevents rework after curing, leading to a high scrap rate for defective products; Second, the molding precision is insufficient, with conventional adhesive line widths difficult to be less than 0.3mm, making it unsuitable for ultra-narrow bezels below 1.5mm; Third, the application pressure is as high as 8-15MPa, which can easily cause extrusion damage to precision structures such as screen glass and driver ICs; Fourth, it is highly sensitive to environmental temperature and humidity, resulting in poor batch stability.

[0004] UV-curable adhesives have gradually entered the electronic packaging field due to their advantages such as fast curing speed and strong controllability. However, existing technologies still have a core shortcoming: they cannot be adapted to LIPO low-pressure injection molding processes. The closest existing technologies are as follows: Prior art document 1 (CN121718298A) discloses a siloxane-modified polyurethane acrylate UV adhesive for electronic packaging, but it uses a single oligomer system and cannot achieve both low viscosity and high weather resistance. Its viscosity at 25°C is ≥12000mPa・s, requiring an injection pressure of ≥5MPa to fill the mold. The minimum molding line is only 0.2mm, which cannot be adapted to the LIPO low-pressure injection molding process with a pressure of ≤2MPa. Prior art document 2 (CN120230503A) discloses a low-pressure injection molding UV curing adhesive, but its active diluent is not designed with a gradient compounding, the curing shrinkage rate is ≥3%, and the adhesion retention rate is only about 70% after 1000h of humid heat aging, which cannot meet the long-term reliability requirements of IP68 waterproof sealing. Prior art document 3 (CN118908923A) discloses a fast-curing UV electronic adhesive, but it uses a single photoinitiator system, and the deep curing degree of the thick adhesive layer is less than 90%, requiring more than 30 seconds to fully cure, which cannot match the second-level curing cycle of the LIPO process.

[0005] In summary, existing technologies generally suffer from the technical bias of "low viscosity cannot be simultaneously achieved with high mechanical properties and high reliability," failing to meet the core requirements of ≤2MPa low-pressure compatibility, 0.08mm ultra-narrow adhesive line formation, 3-10s complete curing, and high stability under humid heat aging. This makes it difficult to fully replace PUR hot melt adhesives. Therefore, developing a UV-curable encapsulating adhesive that perfectly adapts to LIPO low-pressure injection molding processes and whose overall performance surpasses that of traditional PUR hot melt adhesives is a pressing technical problem to be solved in this field. Summary of the Invention

[0006] To address the above technical problems, this invention proposes a UV-curable LIPO encapsulating adhesive suitable for low-pressure injection molding of ≤2MPa, comprising the following components by weight: 30-60 parts of modified photosensitive oligomer, 20-50 parts of gradient compounded reactive diluent, 1-8 parts of composite photoinitiator, and 0.5-5 parts of functional additives.

[0007] Further, by weight, it includes the following components: 40-50 parts of modified photosensitive oligomer, 25-40 parts of gradient compounded reactive diluent, 2-5 parts of composite photoinitiator, and 1-3 parts of functional additives.

[0008] Further, the modified photosensitive oligomer is composed of a main oligomer and an auxiliary oligomer in a mass ratio of 7-9:1-3; the photosensitive oligomer is a siloxane-modified aliphatic polyurethane acrylate with a number average molecular weight of 1000-5000 and a rotational viscosity of 500-5000 mPa·s at 25°C; the auxiliary oligomer is at least one of alicyclic epoxy acrylate or bisphenol A epoxy acrylate; the gradient compounded reactive diluent is composed of monofunctional acrylate, difunctional acrylate, and polyfunctional acrylate in a mass ratio of 6-8:1.5-3.5:0-0.5; the composite photoinitiator is composed of a surface-drying photoinitiator and a deep-curing photoinitiator in a mass ratio of 1-3:1. The siloxane-modified aliphatic polyurethane acrylate is prepared by stepwise polymerization of hydroxyl-terminated polysiloxane, aliphatic diisocyanate, polycarbonate diol, and hydroxy acrylate under the action of a catalyst. The ends of the molecular chain are grafted with acrylate photosensitive groups, and the sides are grafted with polydimethylsiloxane segments and C6-C12 long-chain alkyl flexible segments.

[0009] Further, the monofunctional acrylate is at least one of isobornyl acrylate, isobornyl methacrylate, isodecyl acrylate, and lauryl acrylate; the difunctional acrylate is at least one of 1,6-hexanediol diacrylate, tripropylene glycol diacrylate, and tripropylene glycol diacrylate; and the polyfunctional acrylate is at least one of trimethylolpropane triacrylate and pentaerythritol triacrylate. The surface-drying photoinitiator is at least one of 2-hydroxy-2-methyl-1-phenylacetone, 1-hydroxycyclohexylphenyl ketone, and benzophenone; the deep-curing photoinitiator is at least one of 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, ethyl 2,4,6-trimethylbenzoylphenylphosphonate, and bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide.

[0010] Further, the functional additives, by weight, include 0.2-2 parts of adhesion promoter, 0.1-0.5 parts of leveling agent, 0.1-0.5 parts of defoamer, 0.05-0.2 parts of polymerization inhibitor, and 0.05-1.8 parts of weather stabilizer; Further, the adhesion promoter is at least one of γ-glycidoxypropyltrimethoxysilane, γ-methacryloyloxypropyltrimethoxysilane, vinyltrimethoxysilane, and phosphate ester adhesion promoters; the leveling agent is at least one of organosilicon leveling agents or acrylate leveling agents; the defoamer is a non-silicone polymer defoamer; and the polymerization inhibitor is at least one of p-hydroxyanisole, hydroquinone, and 2,6-di-tert-butyl-p-cresol. The weather stabilizer is a mixture of hindered amine light stabilizer and benzotriazole ultraviolet absorber in a mass ratio of 2:1.

[0011] This invention also provides a method for preparing the UV-curable LIPO encapsulating adhesive suitable for ≤2MPa low-pressure injection molding, which is carried out entirely in a light-shielded environment and includes the following steps: S1 According to the formula, add the modified photosensitive oligomer into the light-proof reactor, control the temperature at 25-40℃, stabilize the vacuum at -0.095±0.005MPa, and stir at 300-500rpm for 10-20min until the system is uniform and free of agglomeration. S2 Add the gradient compound active diluent of the formula to the reactor, maintain the temperature and vacuum conditions, and continue stirring for 20-30 minutes until the system is mixed evenly. S3. Lower the system temperature to 25-35℃, add the prescribed amount of composite photoinitiator, and stir under vacuum and light-proof conditions for 20-30 minutes until the photoinitiator is completely dissolved. S4 Add the formulated amount of functional additive to the reactor, maintain vacuum and light-proof conditions, and continue stirring for 15-20 minutes. After completion, perform vacuum degassing for 10-15 minutes, filter the material through a 1000-mesh filter cloth for two stages, and store it in a light-proof and sealed container to obtain the UV-curable LIPO encapsulating adhesive.

[0012] Furthermore, the system temperature shall not exceed 40℃ throughout steps S1-S4, and the stirring speed shall not fluctuate by more than ±50 rpm. The two-stage filtration in step S4 uses 1000 mesh + 1500 mesh filter cloths in series for filtration. The filtration process is conducted in the dark and at a constant temperature of 30°C throughout.

[0013] The present invention also provides an application of the UV-curable LIPO encapsulating adhesive adapted for ≤2MPa low-pressure injection molding, wherein the UV-curable LIPO encapsulating adhesive is applied to the low-pressure injection molding UV curing encapsulation process of electronic devices, including smartphone ultra-narrow bezel display modules, wearable device precision components, automotive Mini-LED display modules, and AR / VR head-mounted display optical encapsulation components; Furthermore, the parameters of the low-pressure injection molding UV curing encapsulation process are: injection pressure ≤2MPa, injection temperature 25-40℃, 365-405nm UV-LED light source for curing, light source power density 30-50mW / cm², and curing time 3-10s. The packaging process has a frame-closing and pressure-holding time of ≤5s. After closing, there is no need for static curing, and the process can be directly transferred to the next step.

[0014] Compared with the prior art, the present invention has the following beneficial effects:

[0015] This invention overcomes the technical bias of existing technologies that "low-viscosity UV adhesives inevitably lead to a decline in mechanical properties and weather resistance" by using a modified photosensitive oligomer compound system with a specific ratio. The system's rotational viscosity at 25°C is precisely controlled between 1000-8000 mPa·s, and complete mold filling can be achieved under extremely low injection pressure of ≤2MPa, without defects such as bubbles, sagging, or insufficient adhesive. At the same time, the tensile shear strength of the adhesive layer is ≥8MPa, and the 180° peel strength is ≥15N / 25mm. This invention solves the core problem that a single oligomer system cannot simultaneously achieve both flowability and mechanical properties.

[0016] This invention reduces the minimum molding line width to 0.08mm and achieves a glue thickness control accuracy of ±0.01mm through the synergistic effect of a gradient compounded reactive diluent system and leveling agent. This far exceeds the glue line limit of ≥0.2mm in existing technologies, enabling the bezel width of terminal products to be compressed to below 1.38mm and the screen ratio to exceed 95%. At the same time, it completely avoids the squeezing damage to precision components caused by high-pressure gluing, and reduces the product's hidden defect rate by more than 90%.

[0017] This invention utilizes a composite photoinitiator system adapted to UV-LED light sources, achieving complete curing in 3-10 seconds at a low power density of 30-50mW / cm², with a curing degree ≥98%. It eliminates the need for post-curing, completely resolving the "two-meter problem" of traditional PUR hot melt adhesives, which suffer from long curing cycles (24-72 hours), high environmental sensitivity, and difficulty in rework. Production efficiency is increased by over 80%, and product yield is improved from 95% for traditional PUR to over 99.5%. After assembly, the product can immediately proceed to the next process, significantly shortening production and inventory cycles.

[0018] This invention achieves broad-spectrum strong adhesion to commonly used electronic packaging substrates such as glass, aluminum alloy, stainless steel, PC, and PMMA through the synergistic effect of siloxane-modified oligomers and various types of adhesion promoters. After 1000 hours of humid heat aging at 85℃ / 85% RH, the adhesion retention rate is ≥90%. After 1000 cycles of high and low temperature cycling from -40℃ to 125℃, there is no cracking or delamination. The IP68 waterproof test pass rate is 100%, fully meeting the long-term reliability requirements of consumer electronics and automotive electronics.

[0019] The system of this invention has no solvent addition and no VOC emissions, and complies with RoHS and REACH environmental standards. The preparation process can be completed at room temperature and pressure, with low energy consumption, good batch stability, and an overall production cost that is more than 20% lower than that of high-end imported PUR hot melt adhesives. It has the conditions for large-scale industrial application and can completely replace the application of traditional PUR hot melt adhesives in the field of high-end electronic packaging. Attached Figure Description

[0020] Figure 1 is a comparison chart of curing rates. The horizontal axis represents curing time (unit: s / h), and the vertical axis represents degree of curing (unit: %). Curve 1 represents Example 1, and curve 2 represents Comparative Example 1.

[0021] Figure 2 The images show the molding effect of the adhesive thread. Area A is a metallographic microscope image of the 0.08mm adhesive thread in Example 1, and Area B is a metallographic microscope image of the 0.3mm adhesive thread in Comparative Example 1. Figure 3The image shows the appearance of the adhesive layer after 1000 high and low temperature cycles in Example 1. There is no cracking or delamination. Figure 4 shows the appearance of the adhesive layer after 1000 high and low temperature cycles in Comparative Example 1, where edge debonding and microcracks are visible.

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0023] The raw materials used in the embodiments and comparative examples of this invention are all commercially available electronic-grade products that comply with RoHS environmental standards; the testing methods all follow current national standards and industry-standard specifications, as detailed below: Viscosity test: ASTM D2196-2020, tested at 25℃ and 10 rpm; Curing degree test: Differential scanning calorimeter (DSC) test, 395nm UV-LED light source, power density 40mW / c²; Tensile shear strength: GB / T 7124-2008, universal testing machine test for aluminum-aluminum substrate; 180° peel strength: GB / T 2792-2014, tested on glass, aluminum alloy, and PC substrates; Damp heat aging test: SJ / T 11187-2023, 85℃ / 85% RH for 1000h, test the adhesion retention rate; High and low temperature cycling test: GB / T 2423.22-2012, -40℃~125℃, hold at high and low temperatures for 30 minutes each, cycle 1000 times; Molding accuracy testing: High-precision metallographic microscope is used to test the minimum glue line width and glue thickness accuracy; Waterproof performance test: GB / T 4208-2017, IP68 rating (immersion in 1.5m water for 30 minutes).

[0024] Preparation of Siloxane-Modified Aliphatic Polyurethane Acrylates Under nitrogen protection, 100 parts by weight of isophorone diisocyanate (IPDI) and 0.05 parts by weight of dibutyltin dilaurate catalyst were added to a reactor. The mixture was heated to 50°C, and 30 parts by weight of hydroxyl-terminated polydimethylsiloxane (number average molecular weight 2000) was slowly added dropwise. The reaction was maintained at this temperature for 2 hours. Then, 120 parts by weight of polycarbonate diol (number average molecular weight 2000) was added dropwise, and the reaction was maintained at this temperature for 3 hours. The temperature was lowered to 45°C, and a mixture of 40 parts by weight of hydroxyethyl acrylate and 0.1 parts by weight of p-hydroxyanisole was added dropwise. The reaction was maintained at this temperature for 4 hours. The -NCO content was determined by di-n-butylamine titration to be 0.08%, at which point the reaction was stopped, yielding the target product. The product's rotational viscosity at 25°C was 3200 mPa·s, and its number average molecular weight was 3500. Example 1

[0025] This embodiment provides a UV-curable LIPO encapsulating adhesive suitable for low-pressure injection molding with pressure ≤2MPa. The formulation is as follows by weight: 45 parts of modified photosensitive oligomer (36 parts of siloxane-modified aliphatic polyurethane acrylate and 9 parts of alicyclic epoxy acrylate prepared in the preparation example, with a compounding ratio of 8:2), 38 parts of gradient compounded reactive diluent (26 parts of isoborneol acrylate, 11 parts of 1,6-hexanediol diacrylate, and 1 part of trimethylolpropane triacrylate, with a compounding ratio of 7.2:2.5:0.3), 3 parts of composite photoinitiator (2 parts of 1-hydroxycyclohexylphenyl ketone and 1 part of 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, with a compounding ratio of 2:1), 4 parts of functional additives (1.5 parts of γ-glycidoxypropyltrimethoxysilane, 0.3 parts of acrylate leveling agent, 0.2 parts of non-silicone defoamer, 0.1 parts of p-hydroxyanisole, and 1.2 parts of hindered amine light stabilizer). (0.7 parts of benzotriazole UV absorber).

[0026] The preparation method is as follows: S1 According to the formula, add the modified photosensitive oligomer to the light-proof reactor, control the temperature at 30℃, the vacuum degree at -0.095MPa, and stir at 400rpm for 15min until the system is uniform and free of agglomeration; S2 Add the gradient compounded active diluent according to the formula, maintain the temperature and vacuum conditions, and continue stirring for 25 minutes until the mixture is uniform; S3 is cooled to 30°C, the composite photoinitiator is added, and the mixture is stirred for 25 minutes under vacuum and light-proof conditions until completely dissolved. Add functional additives to S4, maintain vacuum and light-proof conditions, stir for 18 minutes, vacuum degas for 12 minutes, filter through 1000 mesh + 1500 mesh two-stage filter cloth, store in a light-proof and sealed environment throughout the process.

[0027] From the appendix Figure 1 It can be seen that the proposed solution, using a 365-405nm UV-LED light source with a power density of 30-50mW / cm², achieves a curing time of 3-10s, which is significantly shorter than that of Comparative Example 1, enabling instant curing. Furthermore, the curing degree of this solution is also more thorough than that of Comparative Example 1.

[0028] From the appendix Figure 2 It can be seen that the minimum molding line width of this solution is 0.08mm, and the glue thickness control accuracy is ±0.01mm, while the minimum molding line width of the comparative example is 0.3mm. From the appendix Figure 3 It can be seen that, under the condition of 1000 cycles of high and low temperature testing from -40℃ to 125℃, the interface between the adhesive layer and the glass and metal frame of Comparative Example 1 showed large-area debonding, and a large number of micro-cracks were generated inside the adhesive layer, which extended to the bonding interface between the adhesive layer and the substrate.

[0029] From the appendix Figure 4 As can be seen, under the same conditions as Comparative Example 1, which were subjected to 1000 cycles of high and low temperature cycling from -40℃ to 125℃, the adhesive layer of this solution remained intact without cracking, and the interface between it and the glass and metal frame was tightly bonded without any delamination. Example 2

[0030] The formula in this embodiment is expressed in parts by weight as follows: 50 parts of modified photosensitive oligomer (40 parts of the preparation example product, 10 parts of bisphenol A epoxy acrylate, compounding ratio 8:2), 35 parts of gradient compound reactive diluent (24 parts of isoborneol methacrylate, 10 parts of tripropylene glycol diacrylate, 1 part of pentaerythritol triacrylate, compounding ratio 6.9:2.8:0.3), 4 parts of composite photoinitiator (2.5 parts of 2-hydroxy-2-methyl-1-phenylacetone, 1.5 parts of bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, compounding ratio 1.7:1), 3 parts of functional additives (1.2 parts of γ-methacryloyloxypropyltrimethoxysilane, 0.4 parts of organosilicon leveling agent, 0.2 parts of non-silicone defoamer, 0.1 parts of 2,6-di-tert-butyl-p-cresol, 0.7 parts of hindered amine light stabilizer). (0.4 parts of benzotriazole UV absorber).

[0031] The preparation method is the same as in Example 1. Example 3

[0032] The formula in this embodiment is expressed in parts by weight as follows: 40 parts of modified photosensitive oligomer (32 parts of the preparation example product, 8 parts of alicyclic epoxy acrylate, compounding ratio 8:2), 40 parts of gradient compound reactive diluent (28 parts of isodecyl acrylate, 12 parts of tripropylene glycol diacrylate, compounding ratio 7:3:0), 5 parts of composite photoinitiator (3 parts of 1-hydroxycyclohexylphenyl ketone, 2 parts of ethyl 2,4,6-trimethylbenzoylphenylphosphonate, compounding ratio 1.5:1), 2 parts of functional additives (1 part of phosphate ester adhesion promoter, 0.3 parts of acrylate leveling agent, 0.2 parts of non-silicone defoamer, 0.05 parts of p-hydroxyanisole, 0.3 parts of hindered amine light stabilizer, 0.15 parts of benzotriazole UV absorber).

[0033] The preparation method is the same as in Example 1. Example 4

[0034] The formula in this embodiment is expressed in parts by weight as follows: 30 parts of modified photosensitive oligomer (27 parts of the preparation example product, 3 parts of alicyclic epoxy acrylate, compounding ratio 9:1), 50 parts of gradient compound reactive diluent (35 parts of lauryl acrylate, 14 parts of 1,6-hexanediol diacrylate, 1 part of trimethylolpropane triacrylate, compounding ratio 7:2.8:0.2), 8 parts of composite photoinitiator (5 parts of benzophenone, 3 parts of 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, compounding ratio 1.7:1), 5 parts of functional additives (2 parts of vinyltrimethoxysilane, 0.5 parts of organosilicon leveling agent, 0.5 parts of non-silicone defoamer, 0.2 parts of hydroquinone, 1.2 parts of hindered amine light stabilizer, 0.6 parts of benzotriazole UV absorber).

[0035] The preparation method is the same as in Example 1. Example 5

[0036] The formula in this embodiment is expressed in parts by weight as follows: 60 parts of modified photosensitive oligomer (42 parts of the preparation example product, 18 parts of alicyclic epoxy acrylate, compounding ratio 7:3), 20 parts of gradient compounded reactive diluent (16 parts of isobornyl acrylate, 4 parts of tripropylene glycol diacrylate, compounding ratio 8:2:0), 1 part of composite photoinitiator (0.75 parts of 1-hydroxycyclohexylphenyl ketone, 0.25 parts of ethyl 2,4,6-trimethylbenzoylphenylphosphonate, compounding ratio 3:1), 0.5 parts of functional additives (0.2 parts of γ-glycidoxypropyltrimethoxysilane, 0.1 parts of acrylate leveling agent, 0.1 parts of non-silicone defoamer, 0.05 parts of p-hydroxyanisole, 0.03 parts of hindered amine light stabilizer, 0.02 parts of benzotriazole UV absorber).

[0037] The preparation method is the same as in Example 1.

[0038] Comparative Example 1: Commercially available high-end mobile phone packaging PUR hot melt adhesive (Henkel, Germany), compared with traditional technology; Comparative Example 2: Commercially available ordinary electronic packaging UV adhesive (domestic brand), and existing UV adhesive technology comparison; Comparative Example 3: The UV adhesive prepared in Example 1 of Comparative Document 1 (CN121718298A) is closest to the prior art; Comparative Example 4: The only difference from Example 1 is that the modified photosensitive oligomer compound ratio is 6:4 (deviating from the range of 7-9:1-3 of this invention), and the rest of the formulation and preparation method are the same as in Example 1; Comparative Example 5: The only difference from Example 1 is that the modified photosensitive oligomer compound ratio is 10:0 (deviating from the scope of this invention), and the rest of the formulation and preparation method are the same as in Example 1; Comparative Example 6: The only difference from Example 1 is that the ratio of reactive diluent is 5:4:1 (deviating from the range of 6-8:1.5-3.5:0-0.5 of this invention), and the rest of the formulation and preparation method are the same as in Example 1; Comparative Example 7: The only difference from Example 1 is that the composite photoinitiator ratio is 4:1 (deviating from the 1-3:1 range of this invention), and the rest of the formulation and preparation method are the same as in Example 1;

[0039] Comprehensive performance tests were conducted on Examples 1-5 and Comparative Examples 1-7, and the results are shown in the table below:

[0040] Test Result Analysis Examples 1-5 of this invention comprehensively surpass traditional PUR hot melt adhesives (Comparative Example 1) and the closest existing technology (Comparative Example 3) in terms of core performance such as injection pressure, curing efficiency, molding accuracy, and long-term reliability, forming a significant generational advantage and fully realizing the need to replace PUR hot melt adhesives.

[0041] Comparative Examples 4-7, when deviating from the core compounding ratio range of this invention, exhibited a significant decrease in overall performance: deviations in the oligomer compounding ratio made it impossible to balance low viscosity and mechanical properties, resulting in a substantial increase in the required injection pressure; deviations in the reactive diluent ratio increased curing shrinkage, significantly reducing molding accuracy and damp heat aging stability; and deviations in the photoinitiator ratio resulted in insufficient deep curing, significantly prolonged curing time, and decreased long-term reliability. These results fully demonstrate that the specific ratio range of this invention is not a conventional parameter adjustment in the art, but rather a key to achieving the core technical effect, and thus possesses non-obviousness.

[0042] Embodiment 1 of the present invention achieves an extremely low injection pressure of ≤1.2MPa, an ultra-narrow adhesive line of 0.08mm, complete curing in 5 seconds, and a 93.5% adhesion retention rate under wet heat aging. Its comprehensive performance reaches the industry-leading level and has extremely strong industrial application value.

[0043] Industrial application examples The LIPO encapsulant prepared in Example 1 was applied to the mass production line of a 6.78-inch smartphone ultra-narrow bezel display module. The encapsulation process parameters were: injection pressure 1.5MPa, injection temperature 30℃, 395nm UV-LED light source curing, power density 40mW / cm², curing time 5s, and frame holding pressure time 3s.

[0044] Mass production verification shows that the phone bezel width can be compressed to 1.38mm, achieving a screen-to-body ratio of 95.8%. After frame assembly, no static curing is required; the phone can be directly transferred to the next process. The production line cycle time has been reduced from 28 seconds per unit in the traditional PUR process to 12 seconds per unit, increasing production efficiency by 133%. The mass production yield rate reaches 99.6%, an improvement of 4.6 percentage points compared to the traditional PUR process. The disassembly and rework yield rate reaches 98%, reducing the cost of scrapping defective products by 85%. After reliability testing of 1,000 mass production prototypes, 100% of them passed the IP68 waterproof test. After 1,000 hours of humid heat aging at 85℃ / 85% RH, there was no delamination or water ingress, fully meeting the mass production requirements of high-end smartphones.

[0045] These are merely preferred embodiments of the present invention and are not intended to limit the scope of the patent. Any equivalent structural transformations made using the contents of the specification and drawings of the present invention under the inventive concept of the present invention, or direct / indirect applications in other related technical fields, are included within the scope of patent protection of the present invention.

Claims

1. A UV-curing LIPO encapsulation glue suitable for < 2 MPa low pressure injection molding, characterized in that, The modified photosensitive oligomer is prepared by gradually polymerizing hydroxy-terminated polysiloxane, aliphatic diisocyanate, polycarbonate dihydric alcohol, and hydroxy acrylate under the action of a catalyst, grafting acrylate photosensitive groups at both ends of the molecular chain, and grafting polydimethylsiloxane segments and C6-C12 long-chain alkyl flexible segments on the side.

2. The UV-curing LIPO encapsulation glue of claim 1, wherein, The modified photosensitive oligomer is prepared by gradually polymerizing hydroxy-terminated polysiloxane, aliphatic diisocyanate, polycarbonate dihydric alcohol, and hydroxy acrylate under the action of a catalyst, grafting acrylate photosensitive groups at both ends of the molecular chain, and grafting polydimethylsiloxane segments and C6-C12 long-chain alkyl flexible segments on the side.

3. The UV-curing LIPO encapsulation adhesive suitable for < 2 MPa low pressure injection molding according to claim 2, characterized in that, The modified photosensitive oligomer is prepared by gradually polymerizing hydroxy-terminated polysiloxane, aliphatic diisocyanate, polycarbonate dihydric alcohol, and hydroxy acrylate under the action of a catalyst, grafting acrylate photosensitive groups at both ends of the molecular chain, and grafting polydimethylsiloxane segments and C6-C12 long-chain alkyl flexible segments on the side. The modified photosensitive oligomer is prepared by gradually polymerizing hydroxy-terminated polysiloxane, aliphatic diisocyanate, polycarbonate dihydric alcohol, and hydroxy acrylate under the action of a catalyst, grafting acrylate photosensitive groups at both ends of the molecular chain, and grafting polydimethylsiloxane segments and C6-C12 long-chain alkyl flexible segments on the side.

4. The UV-curing LIPO encapsulation glue according to claim 3, wherein, The modified photosensitive oligomer is prepared by gradually polymerizing hydroxy-terminated polysiloxane, aliphatic diisocyanate, polycarbonate dihydric alcohol, and hydroxy acrylate under the action of a catalyst, grafting acrylate photosensitive groups at both ends of the molecular chain, and grafting polydimethylsiloxane segments and C6-C12 long-chain alkyl flexible segments on the side. The modified photosensitive oligomer is prepared by gradually polymerizing hydroxy-terminated polysiloxane, aliphatic diisocyanate, polycarbonate dihydric alcohol, and hydroxy acrylate under the action of a catalyst, grafting acrylate photosensitive groups at both ends of the molecular chain, and grafting polydimethylsiloxane segments and C6-C12 long-chain alkyl flexible segments on the side.

5. The UV-curing LIPO encapsulation glue according to claim 3, wherein, The modified photosensitive oligomer is prepared by gradually polymerizing hydroxy-terminated polysiloxane, aliphatic diisocyanate, polycarbonate dihydric alcohol, and hydroxy acrylate under the action of a Catalyst, grafting acrylate photosensitive groups at both ends of the molecular chain, and graft polydimethylsiloxane segments and C6-C12 long-chain alkyl flexible segments on one side. The modified photosensitive oligomer is prepared by gradually polymerizing hydroxy-terminated polysulfoxane, aliphatic diisocyanate, polycarbonate dihydric alcohol and hydroxy acrylate under the action of a catalyst, grafting acrylate photosensitivity groups at both ends of the molecular chain, and grafting polydimethylsiloxane segments with C6-C12 long-chain alkyl flexible segments on the side. The modified photosensitive oligomers are prepared by gradually polymerizing hydroxy-terminated polysiloxane, aliphatic diisocyante, polycarbonate dihydric alcohol, and hydroxy acrylate under the actionof a catalyst, grafting acrylate photosensitive groups at both ends of the molecular chain, grafting polydimethylsiloxane segments and C6-C12 long-chain alkyl flexible chain segments on the side. The modified photosensitive oligomer is prepared by gradually polymerizing hydroxy terminated polysiloxane, aliphatic diisocyanate, polycarbonate dihy dric alcohol, and hydroxy acrylate under the action of a catalyst, grafting ac rylate photosensitive groups at both ends of the molecular chain, and grafting polydimethylsiloxanes segments and C6-C12 long-chain alkyl flexible segments on the side. The functional additives include, by weight fraction, 0.2-2 parts of an adhesion promoter, 0.1-0.5 parts of a leveling agent, 0.1-0.5 parts of a defoaming agent, 0.05-0.2 parts of a polymerization inhibitor, and 0.05-1.8 parts of a weather-resistant stabilizer.

6. The UV-curing LIPO encapsulation glue according to claim 3, wherein, The adhesion promoter is at least one of γ-glycidoxypropyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, vinyltrimethoxysilane, and phosphate adhesion promoter; the leveling agent is at least one of silicone leveling agent or acrylate leveling agent; the defoaming agent is a non-silicon polymer defoaming agent; the polymerization inhibitor is at least one of p-hydroxyanisole, hydroquinone, and 2,6-di-tert-butyl-p-cresol; The weather-resistant stabilizer is a complex of a hindered amine light stabilizer and a benzotriazole ultraviolet absorber at a mass ratio of 2:

1.

7. A process for the preparation of a UV-curing LIPO encapsulation glue suitable for low pressure injection molding at ≤ 2 MPa according to any one of claims 1 to 6, characterized in that, The whole process is carried out in a yellow light environment, including the following steps: S1. According to the formula, add the modified photosensitive oligomer to the light-proof reaction kettle, control the temperature at 25-40℃, and stabilize the vacuum degree at -0.095±0.005MPa, stir at a speed of 300-500rpm for 10-20min, until the system is uniform and there is no agglomeration; S2. Add the gradient-compounded active diluent to the reaction kettle according to the formula, keep the temperature and vacuum conditions, and continue to stir for 20-30min, until the system is uniformly mixed; S3. Reduce the system temperature to 25-35℃, add the composite photoinitiator according to the formula, and stir under vacuum and light-proof conditions for 20-30min, until the photoinitiator is completely dissolved; S4. Add the functional additive to the reaction kettle according to the formula, keep the vacuum and light-proof conditions, and continue to stir for 15-20min, then vacuum degassing for 10-15min, filter out the material through 1000 mesh filter cloth in two stages, and store it in a light-proof sealed manner, to obtain the UV curing LIPO packaging glue.

8. The method of claim 7, wherein, The system temperature in steps S1-S4 does not exceed 40℃, and the stirring speed fluctuation does not exceed ±50rpm; The two-stage filtration in step S4 uses 1000 mesh + 1500 mesh filter cloth in series, and the whole filtration process is carried out in the light-proof and constant temperature 30℃.

9. Use of a UV-curing LIPO encapsulation glue according to any one of claims 1 to 6 for low pressure injection molding at < 2 MPa, characterized in that, The UV curing LIPO packaging glue is applied to the low-pressure injection molding UV curing packaging process of electronic devices, including smart phone extremely narrow frame display modules, wearable device precision components, vehicle-mounted Mini-LED display modules, and AR / VR head-mounted optical packaging components.

10. The use of a UV-curing LIPO encapsulation glue according to claim 9, characterized in that, The parameters of the low-pressure injection molding UV curing packaging process are: injection pressure ≤2MPa, injection temperature 25-40℃, using 365-405nm UV-LED light source for curing, light source power density 30-50mW / cm², and curing time 3-10s; The frame bonding and pressure maintaining time of the packaging process is ≤5s, and there is no need for standing and curing after frame bonding, which can be directly transferred to the next process.

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