BC battery uv isolating glue and preparation method thereof

Abstract

This invention provides a UV-blocking adhesive for BC batteries and its preparation method. The UV-blocking adhesive for BC batteries comprises the following raw materials in parts by weight: 20-50 parts of hydrogenated bisphenol A epoxy acrylate resin, 10-30 parts of alicyclic epoxy resin, 10-40 parts of hydrogenated epoxy resin, 10-20 parts of laurate acrylate resin, 2-10 parts of diol, 2-4 parts of composite photoinitiator, and 0.5-2 parts of additives. The hydrogenated bisphenol A epoxy acrylate resin is obtained by ring-opening esterification reaction of hydrogenated bisphenol A epoxy resin and acrylic monomer. The composite photoinitiator includes a free radical photoinitiator and a cationic photoinitiator. The additives include a UV absorber, a hindered amine light stabilizer, and an antioxidant. This invention can improve the high-temperature stability, aging resistance, surface drying effect of thin coatings, and insulation performance of the UV-blocking adhesive.

Description

Technical Field

[0001] This invention belongs to the field of photovoltaic cell auxiliary encapsulation materials technology, specifically relating to a UV separator for BC cells and its preparation method. Background Technology

[0002] BC (Back Contact) cells offer advantages such as unshaded front, excellent low-light response, superior high-temperature performance, strong anti-shading capability, and aesthetically pleasing appearance. Their theoretical photoelectric conversion efficiency can reach 29.56%, with mass production efficiencies consistently ranging from 25.5% to 26.5%. This makes them one of the platform technologies with the highest efficiency ceiling among current crystalline silicon photovoltaic cells, and they can be combined with PERC, TOPCon, HJT, and tandem cell technologies for enhanced efficiency. Furthermore, the BC cell encapsulation utilizes a back-side linear solder strip structure, improving microcrack resistance by 48%. This aligns with the trend towards larger, thinner silicon wafers, giving them high-value-added application potential in BIPV, high-end industrial and commercial, and residential photovoltaic markets.

[0003] Currently, in the production, transportation, and packaging processes of BC batteries, protective paper or UV-resistant adhesive is commonly used. For the paper solution, the thinning, large-size, and precision electrode structure characteristics of BC batteries place high demands on process protection, typically using 45~60 g / m². 2 Dust-free isolation paper is a disposable consumable, and the cost of consumables for large-scale mass production is high. At the same time, isolation paper relies on forest resources, resulting in a large amount of solid waste and a high environmental burden. Moreover, in the production process, isolation paper needs to be padded and picked up separately, which has poor automation adaptability and is prone to paper jams, paper residue, and dust pollution. This can cause defects such as scratches on battery cells, yellowing of slurry, and increased breakage rate, which restricts the speed of the production line. For UV isolation adhesive solutions, existing technologies mostly use a single acrylate curing system, which has a simple formula, but has the following problems: (1) poor high temperature stability. Under high temperature and high pressure conditions, the battery lamination is prone to softening, flowing, sticking, and cracking, and the risk of electrode insulation failure is high; (2) insufficient aging resistance. Under long-term ultraviolet, high temperature and high humidity conditions, it is prone to yellowing, delamination, and blistering. It is difficult to pass the DH3000h high temperature and high humidity, TC600 cold and hot cycles, and UV 60kwh / m 2 UV aging test; (3) The curing system is single, the surface drying effect of the thin coating is poor, and it is easy to stick to the mesh and equipment, polluting the automated production line; (4) The insulation strength and dimensional stability are limited, making it difficult to adapt to the precision insulation and isolation requirements of the dense interdigitated electrodes on the back of the BC battery, which can easily cause micro short circuits and leakage problems. Summary of the Invention

[0004] In view of this, the present invention provides a UV separator for BC batteries and its preparation method, which can improve the high temperature stability, aging resistance, surface drying effect of thin coating and insulation performance of UV separator.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides a UV separator for BC batteries, comprising the following raw materials in parts by weight: 20-50 parts of hydrogenated bisphenol A epoxy acrylate resin, 10-30 parts of alicyclic epoxy resin, 10-40 parts of hydrogenated epoxy resin, 10-20 parts of laurate acrylate resin, 2-10 parts of diol, 2-4 parts of composite photoinitiator, and 0.5-2 parts of additives; wherein the hydrogenated bisphenol A epoxy acrylate resin is obtained by ring-opening esterification reaction of hydrogenated bisphenol A epoxy resin and acrylic monomer; the composite photoinitiator includes a free radical photoinitiator and a cationic photoinitiator; and the additives include a UV absorber, a hindered amine light stabilizer, and an antioxidant.

[0006] Preferably, the diol comprises at least one selected from 1,4-cyclohexanediethanol, 2,2-bis(4-hydroxycyclohexyl)propane, 1,3-cyclohexanediethanol, 1,4-cyclohexanediol, 1,3-cyclohexanediol, tricyclodecanediethanol, dicyclopentadienediethanol, norbornanediethanol, 1,2-cyclohexanediethanol, ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,8-octanediol, and 1,9-nonanediol.

[0007] Preferably, in the composite photoinitiator, the mass ratio of the free radical photoinitiator to the cationic photoinitiator is (1~4):1.

[0008] Preferably, the additives further include leveling agents, defoamers, and silane coupling agents.

[0009] Preferably, the preparation method of the hydrogenated bisphenol A epoxy acrylate resin includes the following steps: S11. Add hydrogenated bisphenol A epoxy resin to the reactor, heat to 90~100 ℃, and stir until melted; S12. Add the tertiary amine catalyst and polymerization inhibitor to the reactor, and then add acrylic monomer dropwise to the reactor. After the addition is complete, heat to 110~120 ℃ to carry out the reaction until the acid value of the system is ≤5 mgKOH / g, and obtain hydrogenated bisphenol A epoxy acrylate resin.

[0010] Preferably, in step S12, the mass ratio of the tertiary amine catalyst, the polymerization inhibitor, and the acrylic monomer is (0.8~1.2):(0.05~0.15):100.

[0011] Preferably, in step S12, the molar ratio of the carboxyl group of the acrylic monomer to the epoxy group of the hydrogenated bisphenol A epoxy resin is (1~1.08):1.

[0012] Preferably, in step S12, the acrylic monomer is added dropwise over a period of 1.5 to 2 hours.

[0013] Preferably, in step S12, the reaction time is 4 to 6 hours.

[0014] Secondly, the present invention provides a method for preparing the UV-blocking adhesive for BC batteries, comprising the following steps: S1. Prepare the hydrogenated bisphenol A epoxy acrylate resin; S2. The hydrogenated bisphenol A epoxy acrylate resin, the alicyclic epoxy resin, the hydrogenated epoxy resin, the laurate acrylate resin, and the diol are stirred once at room temperature, and then heated to 30-50°C for a second stirring to obtain a mixture; wherein the stirring speed of the first stirring is 800-1000 r / min and the time is 20-30 min; the stirring speed of the second stirring is 600-2000 r / min and the time is 20-60 min; S3. Cool to room temperature, add the composite photoinitiator and the additive in the dark, stir, filter, and degas under vacuum to obtain UV separator for BC batteries; wherein, the stirring speed is 500~600 r / min, and the time is 15~20 min; the filtration uses a 200~300 mesh filter; the vacuum degree of the vacuum degassing is -0.08~-0.1 MPa, and the time is 10~15 min.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: In this invention, a ternary resin composite matrix composed of hydrogenated bisphenol A epoxy acrylate resin, alicyclic epoxy resin, and hydrogenated epoxy resin, prepared by ring-opening esterification reaction of hydrogenated bisphenol A epoxy resin and acrylic monomer, is used, along with laurate acrylate resin and diol. A composite photoinitiator containing free radical photoinitiators and cationic photoinitiators, as well as additives containing an anti-yellowing system, are employed to improve the high-temperature stability, aging resistance, surface drying effect of thin coating, and insulation performance of the UV release adhesive. Detailed Implementation

[0016] The present invention will now be described in further detail with reference to specific embodiments, so that those skilled in the art can more clearly understand the present invention.

[0017] In a first aspect, the present invention provides a UV separator for BC batteries, comprising the following raw materials in parts by weight: 20-50 parts of hydrogenated bisphenol A epoxy acrylate resin, 10-30 parts of alicyclic epoxy resin, 10-40 parts of hydrogenated epoxy resin, 10-20 parts of laurate acrylate resin, 2-10 parts of diol, 2-4 parts of composite photoinitiator, and 0.5-2 parts of additives; wherein the hydrogenated bisphenol A epoxy acrylate resin is obtained by ring-opening esterification reaction of hydrogenated bisphenol A epoxy resin and acrylic monomer; the composite photoinitiator includes a free radical photoinitiator and a cationic photoinitiator; and the additives include a UV absorber, a hindered amine light stabilizer, and an antioxidant.

[0018] In this invention, a ternary resin composite matrix composed of hydrogenated bisphenol A epoxy acrylate resin, alicyclic epoxy resin, and hydrogenated epoxy resin, prepared by ring-opening esterification reaction of hydrogenated bisphenol A epoxy resin and acrylic monomer, is used, along with laurate acrylate resin and diol. A composite photoinitiator containing free radical photoinitiators and cationic photoinitiators, as well as additives containing an anti-yellowing system, are employed to improve the high-temperature stability, aging resistance, surface drying effect of thin coating, and insulation performance of the UV release adhesive.

[0019] It should be noted that UV-resistant insulating adhesive can be used for front protection, inter-cell isolation, back electrode insulation, passivation layer protection, and pollution prevention in automated mass production of BC cells. It can replace photovoltaic cell separator paper and is suitable for large-scale, paperless, and intelligent manufacturing of high-efficiency crystalline silicon BC cells. BC cells refer to interdigitated back contact (IBC) cells, which are high-efficiency photovoltaic cells with zero grid lines on the front and all positive and negative electrodes integrated on the back of the cell. They are widely used in high-end distributed photovoltaics, BIPV (Building Integrated Photovoltaics), flexible photovoltaic modules, and other fields.

[0020] Hydrogenated bisphenol A epoxy acrylate resin is one of the matrix components of ternary resin composites. It is prepared by ring-opening esterification reaction of hydrogenated bisphenol A epoxy resin and acrylic monomer. Hydrogenated bisphenol A epoxy acrylate resin has a fully saturated molecular structure without benzene ring unsaturated bonds and incorporates flexible aliphatic segments. It has the characteristics of low color, high light transmittance, low yellowing index, low curing shrinkage, high flexibility, high heat resistance, high weather resistance, and high insulation. It can be adapted for 4~6 μm thin-layer precision screen printing. After curing, it has no internal stress and excellent toughness. It can bend and deform with thin silicon wafers and flexible battery substrates without easily cracking or delamination. It can meet the mass production needs of flexible BC batteries and large-size thin-film batteries. At the same time, it effectively improves the problem of long-term yellowing and degradation failure of coatings at the substrate level, matching the photovoltaic-grade weather resistance and high light transmittance requirements of BC batteries.

[0021] Alicyclic epoxy resin is one of the matrix materials for ternary resin compounding. It can form a dense interpenetrating cross-linked network with hydrogenated epoxy resin, which can further improve the high-temperature dimensional stability, bonding strength and media resistance of the adhesive layer. It can solve the problems of softening, flowing and cracking of single resin system at high temperature.

[0022] Hydrogenated epoxy resin is one of the matrix components for ternary resin blends. It has a fully saturated molecular structure, high optical transparency, and excellent UV aging resistance. It can work synergistically with alicyclic epoxy resins to further improve heat resistance and anti-blocking ability.

[0023] Laurate acrylate resin is an active diluent with high light transmittance, low shrinkage, high yellowing resistance, and good compatibility with hydrogenated bisphenol A epoxy acrylate resin. It can adjust the viscosity of the adhesive to 15,000~30,000 cps (25℃) and is suitable for screen printing coating processes of 4~6 μm. At the same time, it can participate in UV cross-linking and curing, forming a uniform and dense cross-linking network with the main resin, further improving the light transmittance, smoothness and aging resistance of the coating, without the precipitation of small molecules and without affecting the photovoltaic-grade weather resistance index.

[0024] Diols can improve adhesion and the flexibility of the coating.

[0025] The composite photoinitiator is a combination of free radical photoinitiator and cationic photoinitiator, which can achieve both rapid surface drying and complete deep curing. It has uniform crosslinking density, reduces curing stress, and ensures long-term stable adhesion. It is suitable for LED 365 nm light source and thin coating curing needs, and has no risk of yellowing in the later stage.

[0026] UV absorbers, hindered amine light stabilizers, and antioxidants form an anti-yellowing system in the additives, which can inhibit photo / thermal aging.

[0027] In some embodiments, the diol comprises at least one selected from 1,4-cyclohexanediethanol, 2,2-bis(4-hydroxycyclohexyl)propane, 1,3-cyclohexanediethanol, 1,4-cyclohexanediol, 1,3-cyclohexanediol, tricyclodecanediethanol, dicyclopentadienediethanol, norbornanediethanol, 1,2-cyclohexanediethanol, ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,8-octanediol, and 1,9-nonanediol. Further, the diol is 1,4-cyclohexanediethanol. It should be noted that 1,4-cyclohexanediethanol contains a dihydroxyl polar group, a saturated cyclohexane ring, and a flexible alkyl chain. The hydroxyl group can form hydrogen bonds / chemical bonds with silicon wafers, passivation layers, and metal electrodes, significantly improving interfacial adhesion. The cyclohexane ring can improve high-temperature anti-sticking properties and structural rigidity. The alkyl chain can improve the toughness and flexibility of the coating, effectively preventing cracking and peeling under thermal cycling and mechanical action. It has high optical purity and does not affect light transmission or yellowing resistance.

[0028] In some embodiments, the mass ratio of the free radical photoinitiator to the cationic photoinitiator in the composite photoinitiator is (1~4):1.

[0029] In some embodiments, the additives further include leveling agents, defoamers, and silane coupling agents. It should be noted that silane coupling agents can build interfacial "molecular bridges," further enhancing adhesion, while leveling agents and defoamers can optimize printing appearance and coating effects.

[0030] In some embodiments, the method for preparing the hydrogenated bisphenol A epoxy acrylate resin includes the following steps: S11. Add hydrogenated bisphenol A epoxy resin to the reactor, heat to 90~100 ℃, and stir until melted; S12. Add the tertiary amine catalyst and polymerization inhibitor to the reactor, and then add acrylic monomer dropwise to the reactor. After the addition is complete, heat to 110~120 ℃ to carry out the reaction until the acid value of the system is ≤5 mgKOH / g, and obtain hydrogenated bisphenol A epoxy acrylate resin.

[0031] Understandably, the reactor can be equipped with stirring, temperature control, and reflux condensation; the addition of a polymerization inhibitor is to prevent the acrylic monomer from self-polymerizing and changing color at high temperatures, and the polymerization inhibitor can be a high-temperature resistant polymerization inhibitor; the acid value of the system can be monitored throughout the reaction, and the reaction endpoint is determined when the acid value of the system is ≤5 mgKOH / g, and heating is stopped; the resulting hydrogenated bisphenol A epoxy acrylate resin is water-white and transparent.

[0032] In some embodiments, in step S12, the mass ratio of the tertiary amine catalyst, the polymerization inhibitor, and the acrylic monomer is (0.8~1.2):(0.05~0.15):100.

[0033] In some embodiments, in step S12, the molar ratio of the carboxyl group of the acrylic monomer to the epoxy group of the hydrogenated bisphenol A epoxy resin is (1~1.08):1.

[0034] In some embodiments, in step S12, the acrylic monomer is added dropwise over a period of 1.5 to 2 hours.

[0035] In some embodiments, the reaction time in step S12 is 4 to 6 hours.

[0036] In some embodiments, in step S12, when the acid value of the system is ≤5 mgKOH / g, the temperature is lowered to below 60°C, and the mixture is filtered to obtain hydrogenated bisphenol A epoxy acrylate resin. It is understood that filtration is performed to remove trace impurities from the system.

[0037] In some embodiments, the acrylic monomer is acrylic acid.

[0038] In some embodiments, the tertiary amine catalyst is N,N-dimethylbenzylamine.

[0039] In some embodiments, the polymerization inhibitor is p-tert-butylcatechol.

[0040] Secondly, the present invention also provides a method for preparing the UV-blocking adhesive for BC batteries, comprising the following steps: S1. Prepare the hydrogenated bisphenol A epoxy acrylate resin; S2. The hydrogenated bisphenol A epoxy acrylate resin, the alicyclic epoxy resin, the hydrogenated epoxy resin, the laurate acrylate resin, and the diol are stirred once at room temperature, and then heated to 30-50°C for a second stirring to obtain a mixture; wherein the stirring speed of the first stirring is 800-1000 r / min and the time is 20-30 min; the stirring speed of the second stirring is 600-2000 r / min and the time is 20-60 min; S3. Cool to room temperature, add the composite photoinitiator and the additive in the dark, stir, filter, and degas under vacuum to obtain UV separator for BC batteries; wherein, the stirring speed is 500~600 r / min, and the time is 15~20 min; the filtration uses a 200~300 mesh filter; the vacuum degree of the vacuum degassing is -0.08~-0.1 MPa, and the time is 10~15 min.

[0041] It should be noted that in step S2, the first stirring is to ensure that the polar components are evenly dispersed, and the second stirring is to ensure that each resin and the diol are fully miscible, so as to simultaneously improve the coating adhesion, flexibility and high temperature stability. In step S3, the composite photoinitiator and additives are added at room temperature and away from light, and stirred at low speed, in order to avoid the generation of bubbles and the premature failure of the photoinitiator and additives.

[0042] The sources of raw materials used in the following examples and comparative examples are explained below: Hydrogenated bisphenol A epoxy resin: Mitsubishi Chemical, Japan, jER™ YX8000; Alicyclic epoxy resin: Daicel, Japan, 2021P; Hydrogenated epoxy resin: Mitsubishi Chemical, Japan, jER™ YX8043; Epoxy acrylate: Boxin New Materials, B-151DM; Free radical photoinitiators: IGM, Omnirad TPO; Cationic photoinitiator: Guangren Huitong, HRcure 2074; UV absorber: BASF, Tinuvin 400; Hindered amine light stabilizer: BASF, Tinuvin 292; Antioxidant: BASF, Irganox® 1010; Leveling agent: TEGO Rad 2100; Defoamer: BYK-141; Silane coupling agent: Evonik, Dynasylan MEMO.

[0043] Example 1 This embodiment provides a UV-blocking adhesive for BC batteries, composed of the following raw materials in parts by weight: 40 parts hydrogenated bisphenol A epoxy acrylate resin, 10 parts alicyclic epoxy resin, 20 parts hydrogenated epoxy resin, 10 parts laurate acrylate resin, 5 parts 1,4-cyclohexanediol, 3 parts composite photoinitiator, and 2 parts additives; wherein, the composite photoinitiator is composed of a free radical photoinitiator and a cationic photoinitiator, with a mass ratio of 2:1; the additives are composed of a UV absorber, a hindered amine light stabilizer, an antioxidant, a leveling agent, an antifoaming agent, and a silane coupling agent, with a mass ratio of 2:2:5:5:5:10.

[0044] The preparation steps of hydrogenated bisphenol A epoxy acrylate resin are as follows: 1. Feeding and melting: Add hydrogenated bisphenol A epoxy resin to a reactor equipped with stirring, reflux condensation and temperature control, heat to 95°C, and stir at a constant temperature until the resin is completely transparent and melted; 2. Addition of catalyst and polymerization inhibitor: Add 1.0% of N,N-dimethylbenzylamine (Aladdin Chemical Reagent) by total mass of acrylic acid and 0.1% of p-tert-butylcatechol (Aladdin Chemical Reagent) by total mass of acrylic acid. 3. Dropping reaction: Acrylic acid was slowly added dropwise according to the equimolar ratio of epoxy groups to carboxyl groups, with a dropping time of 1.8 h; 4. Temperature control reaction: After the addition is complete, heat to 115℃ and maintain the temperature for 5 hours, while monitoring the acid value of the system in real time; 5. Endpoint determination: Stop heating when the acid value of the system is ≤5 mgKOH / g; 6. Post-treatment: Cool to below 60℃, filter to remove impurities, and obtain hydrogenated bisphenol A epoxy acrylate resin. The product is water-white and transparent.

[0045] The preparation steps of the UV-resistant separator for BC batteries are as follows: 1. Matrix premixing: Add alicyclic epoxy resin, hydrogenated epoxy resin, hydrogenated bisphenol A epoxy acrylate resin, laurate acrylate resin and 1,4-cyclohexanediethanol sequentially to the reactor and stir at 900 r / min for 25 min at room temperature. 2. Mix the system: Heat to 45℃ and stir at 1300 r / min for 35 min; 3. Addition of photoinitiator and additives: Cool to room temperature, add composite photoinitiator and additives in the dark, and stir at 550 r / min for 18 min in the dark; 4. Filtration and degassing: The product is filtered using a 250-mesh precision filter and degassed under vacuum at -0.09 MPa for 12 minutes to obtain the finished UV separator for BC batteries.

[0046] Example 2 This embodiment provides a UV-blocking adhesive for BC batteries. The raw materials differ from those in Example 1 in that: 30 parts of hydrogenated bisphenol A epoxy acrylate resin, 20 parts of alicyclic epoxy resin, and 30 parts of hydrogenated epoxy resin are used.

[0047] The preparation steps of hydrogenated bisphenol A epoxy acrylate resin are the same as in Example 1.

[0048] The preparation steps for the UV-blocking adhesive for BC batteries are the same as in Example 1.

[0049] Example 3 This embodiment provides a UV-blocking adhesive for BC batteries. The raw materials differ from those in Example 1 in that: 20 parts of hydrogenated bisphenol A epoxy acrylate resin, 30 parts of alicyclic epoxy resin, and 40 parts of hydrogenated epoxy resin are used.

[0050] Comparative Example 1 This comparative example provides a UV separator for BC batteries, composed of the following raw materials in parts by weight: 50 parts epoxy acrylate, 20 parts cyclotrimethylolpropane methyl acetal acrylate (CTFA), 10 parts tetrahydrofuran acrylate (THFA), 20 parts isobornyl acrylate (IBOA), 3 parts free radical photoinitiator, and 2 parts additives; wherein the additives consist of leveling agent, defoamer, and silane coupling agent, and the mass ratio of leveling agent, defoamer, and silane coupling agent is 1:1:2.

[0051] The preparation steps of the UV-resistant separator for BC batteries are as follows: Epoxy acrylate, cyclotrimethylolpropane methyl acetal acrylate, tetrahydrofuran acrylate and isobornyl acrylate were added sequentially to the reactor and stirred at 350 r / min for 20 min at room temperature. Keep the stirring speed constant, add the defoamer and leveling agent in sequence, stir for 10 min, then add the silane coupling agent and stir for 15 min; Reduce the stirring speed to 250 r / min, add the free radical photoinitiator in the dark, and stir in the dark for 30 min to obtain the finished UV separator for BC batteries.

[0052] Performance Tests and Results The UV-blocking adhesives prepared in Examples 1-3 and Comparative Example 1 were subjected to the following performance tests, and the results are shown in Table 1.

[0053] (1) Viscosity: Refer to GB / T 13217.4-2008.

[0054] (2) Fineness before curing: The fineness is tested by a fineness plate. Specifically, use a paint mixing knife to take a sample and drip it into the deepest part of the groove. The amount of sample should slightly overflow the groove, but not too much. Hold both ends of the scraper with both hands, press the blade vertically against the plane of the fineness plate, and make sure the long side of the scraper is perpendicular to the groove. Scrape from the deep end to the shallow end (0 mark direction) at a uniform speed in one go, for a total of 1~3 seconds, without stopping or scraping back. Apply uniform pressure to ensure that the groove is completely filled. Observe the reading within 5 seconds after scraping.

[0055] (3) Transmittance: Refer to IEC 62788-2016, the adhesive layer thickness is 100 μm, and the spectral scanning band is 380~1100nm.

[0056] (4) Cross-cut adhesion test: Refer to GB / T 9286-1998, use a cross-cut knife to cut 10×10 squares, stick 3M 600# tape and quickly tear it vertically, and observe the coating peeling.

[0057] (5) Volume resistivity: Refer to ASTM D257.

[0058] (6) Electrical strength: Refer to GB / T 1408.1-2006.

[0059] (7) Hardness: Refer to JIS K5400.

[0060] (8) Warpage after curing: First, lay the BC cell with the adhesive side facing up and mark 5 measuring points (four corners + center of the long side). Measure the height of each point and calculate the initial maximum warpage (highest point - lowest point). Then, apply the release liner to the BC cell with a spreader and cure it at 23±2 ℃ and 50±10% RH to form a film layer with a thickness of 20 μm. After curing, let it stand at room temperature for more than 30 min. Then, remeasure the height at the same measuring point and calculate the maximum warpage after curing. Finally, calculate the warpage after curing (maximum warpage after curing - initial maximum warpage).

[0061] Table 1 Performance test results of UV release adhesives in Examples 1-3 and Comparative Example 1

[0062] As shown in Table 1, compared with Comparative Example 1, the UV-blocking adhesives of Examples 1-3 showed significantly reduced fineness before curing and warpage after curing, while significantly improved transmittance, cross-cut adhesion test grade, volume resistivity, electrical strength, and hardness. Furthermore, the UV-blocking adhesives of Examples 1-3 achieved a viscosity of 15000-30000 cps at 25°C, a fineness <10 μm before curing, transmittance ≥90%, a cross-cut adhesion test grade of 0 / 1, and a volume resistivity ≥10 ppm. 14 Technical requirements: Ω•cm, electrical strength ≥15 kV / mm, hardness ≥70 Shore D, and warpage ≤0.5 mm after curing.

[0063] In addition, the results of the cross-cut adhesion test of the UV isolation adhesives of Examples 1-3 and Comparative Example 1 are described as follows: The edges of the squares in Example 1 were intact, with no peeling or shedding, and were rated as Grade 0, indicating excellent adhesion and the best coating flexibility; The interfacial bonding force in Example 2 was balanced, with no peeling or shedding, and was rated as Grade 0, indicating the most balanced overall performance; Example 3 had no peeling, and was rated as Grade 0, indicating the best adhesion; The coating of Comparative Example 1 only had physical adhesion, with large-area peeling (peeling percentage > 15%), and was rated as Grade 3, indicating that the adhesion did not meet the standard.

[0064] (9) Aging reliability test The UV-blocking adhesives prepared in Examples 1-3 and Comparative Example 1 were subjected to DH 3000 h high temperature and high humidity aging test, TC 600 cycles of hot and cold cycling aging test, and UV 60 kWh / m test. 2 The results of the UV aging test are as follows.

[0065] After 3000 hours of high temperature and high humidity aging, the coatings of Examples 1 to 3 showed no blistering, delamination, bubbles, or discoloration, and the tensile adhesion was all >19 N / cm. The cross-cut adhesion test results were all still 0, and the adhesion did not decrease. The coating of Comparative Example 1 showed obvious yellowing and local blistering, with a tensile adhesion of 7.2 N / cm and a cross-cut adhesion test result that dropped to 4.

[0066] After 600 cycles of thermal aging, the coatings of Examples 1-3 all showed good toughness, which could offset the temperature alternating stress. The coatings were tightly bonded to the substrate, and there were no changes in appearance or cross-cut adhesion test grade. The coating of Comparative Example 1 became brittle, with large-area delamination at the edges, and the cross-cut adhesion test grade was 3.

[0067] UV 60kwh / m 2 After UV aging, the transmittance of Examples 1-3 decreased by less than 1%, with no obvious yellowing; while the transmittance of Comparative Example 1 decreased by 7.8%, with severe yellowing.

[0068] (10) High temperature anti-adhesion test The UV-resistant adhesives prepared in Examples 1-3 and Comparative Example 1 were subjected to a high-temperature anti-adhesion test (standing at 200 °C for 30 min). The coatings of Examples 1-3 were all dry, without adhesion or deformation, while the coating of Comparative Example 1 softened and adhered.

[0069] (11) Printing process compatibility test The UV-isolating adhesives prepared in Examples 1-3 and Comparative Example 1 were screen-printed with a coating thickness of 5 μm. A 365nm LED curing light source was used, with a light energy of 5000 mJ and a curing time of 2 s. The UV-isolating adhesives of Examples 1-3 were all suitable for screen printing, exhibiting fine coatings, good wetting effects, and no defects such as screen sticking, missing prints, or pinholes. The coating of Comparative Example 1 had poor surface drying and was prone to screen sticking.

[0070] The implementation effects of Examples 1-3 and Comparative Example 1 are summarized as follows: For Example 1, the formulation features the highest proportion of hydrogenated bisphenol A epoxy acrylate resin and the lowest proportions of alicyclic epoxy resin and hydrogenated epoxy resin; performance characteristics include optimal light transmittance and coating flexibility, and adhesion, insulation performance and hardness all meet technical requirements; it is suitable for flexible BC batteries, ultra-thin silicon wafers and applications with stringent light transmittance requirements.

[0071] For Example 2, the formulation features a moderate proportion of hydrogenated bisphenol A epoxy acrylate resin, alicyclic epoxy resin, and hydrogenated epoxy resin, with a balanced gradient. Performance characteristics include moderate viscosity, excellent and balanced performance in light transmittance, adhesion, hardness, coating flexibility, aging resistance, and high-temperature anti-blocking properties, stable at grade 0 in cross-cut adhesion testing, and optimal compatibility with printing processes, making it the optimal solution for general mass production of BC batteries.

[0072] For Example 3, the formulation features: the proportion of hydrogenated bisphenol A epoxy acrylate resin is the lowest, while the proportions of alicyclic epoxy resin and hydrogenated epoxy resin are the highest; performance: the coating rigidity, electrical strength, and adhesion are the best in the three groups, and the high-temperature anti-sticking and aging resistance are outstanding; it is suitable for long-term high-temperature processes, rigid BC battery cells, and harsh outdoor working conditions.

[0073] For Comparative Example 1, the formulation characteristics are: ordinary single-system UV isolation adhesive; performance is: adhesion is not up to standard, high temperature anti-blocking and aging resistance are poor, the coating is hard and brittle, and it cannot meet the requirements of paperless mass production and long-term service of BC batteries.

[0074] In summary, this invention employs a ternary resin composite matrix composed of hydrogenated bisphenol A epoxy acrylate resin, alicyclic epoxy resin, and hydrogenated epoxy resin, obtained by ring-opening esterification of hydrogenated bisphenol A epoxy resin and acrylic monomer, combined with laurate acrylate resin and 1,4-cyclohexanediethanol. The synergistic effect of the multiple resins enhances heat resistance, weather resistance, and insulation properties. High adhesion is achieved through the polar hydroxyl groups of 1,4-cyclohexanediethanol, and the flexible chain segments improve coating toughness. The formulation has a clear gradient, allowing for flexible selection based on the flexible / rigid and conventional / high-temperature operating conditions of BC batteries. It can replace separator paper, enabling low-cost, high-yield, and green production of BC batteries.

[0075] Unless otherwise specified, all raw materials used in this invention are existing substances that can be purchased directly from the market.

[0076] The above are merely preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A UV-resistant insulating adhesive for BC batteries, characterized in that, The raw materials include the following parts by weight: 20-50 parts of hydrogenated bisphenol A epoxy acrylate resin, 10-30 parts of alicyclic epoxy resin, 10-40 parts of hydrogenated epoxy resin, 10-20 parts of laurate acrylate resin, 2-10 parts of diol, 2-4 parts of composite photoinitiator, and 0.5-2 parts of additives. The hydrogenated bisphenol A epoxy acrylate resin is prepared by ring-opening esterification reaction of hydrogenated bisphenol A epoxy resin and acrylic monomer; the composite photoinitiator includes a free radical photoinitiator and a cationic photoinitiator; the additives include a UV absorber, a hindered amine light stabilizer and an antioxidant.

2. The UV-resistant insulating adhesive for BC batteries according to claim 1, characterized in that, The diols include at least one selected from 1,4-cyclohexanediethanol, 2,2-bis(4-hydroxycyclohexyl)propane, 1,3-cyclohexanediethanol, 1,4-cyclohexanediol, 1,3-cyclohexanediol, tricyclodecanediethanol, dicyclopentadienediethanol, norbornanediethanol, 1,2-cyclohexanediethanol, ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,8-octanediol, and 1,9-nonanediol.

3. The UV-resistant adhesive for BC batteries according to claim 1, characterized in that, In the composite photoinitiator, the mass ratio of the free radical photoinitiator to the cationic photoinitiator is (1~4):

1.

4. The UV-resistant insulating adhesive for BC batteries according to claim 1, characterized in that, The additives also include leveling agents, defoamers, and silane coupling agents.

5. The UV-resistant insulating adhesive for BC batteries according to claim 1, characterized in that, The preparation method of the hydrogenated bisphenol A epoxy acrylate resin includes the following steps: S11. Add hydrogenated bisphenol A epoxy resin to the reactor, heat to 90~100 ℃, and stir until melted; S12. Add the tertiary amine catalyst and polymerization inhibitor to the reactor, and then add acrylic monomer dropwise to the reactor. After the addition is complete, heat to 110~120 ℃ to carry out the reaction until the acid value of the system is ≤5 mgKOH / g, and obtain hydrogenated bisphenol A epoxy acrylate resin.

6. The UV-resistant insulating adhesive for BC batteries according to claim 5, characterized in that, In step S12, the mass ratio of the tertiary amine catalyst, the polymerization inhibitor, and the acrylic monomer is (0.8~1.2):(0.05~0.15):

100.

7. The UV-resistant insulating adhesive for BC batteries according to claim 5, characterized in that, In step S12, the molar ratio of the carboxyl group of the acrylic monomer to the epoxy group of the hydrogenated bisphenol A epoxy resin is (1~1.08):

1.

8. The UV-resistant insulating adhesive for BC batteries according to claim 5, characterized in that, In step S12, the acrylic monomer is added dropwise over a period of 1.5 to 2 hours.

9. The UV-resistant insulating adhesive for BC batteries according to claim 5, characterized in that, In step S12, the reaction time is 4 to 6 hours.

10. The method for preparing the UV-blocking adhesive for BC batteries according to any one of claims 1-9, characterized in that, Includes the following steps: S1. Prepare the hydrogenated bisphenol A epoxy acrylate resin; S2. The hydrogenated bisphenol A epoxy acrylate resin, the alicyclic epoxy resin, the hydrogenated epoxy resin, the laurate acrylate resin, and the diol are stirred once at room temperature, and then heated to 30-50 °C for a second stirring to obtain a mixture; wherein the stirring speed of the first stirring is 800-1000 r / min and the time is 20-30 min; the stirring speed of the second stirring is 600-2000 r / min and the time is 20-60 min; S3. Cool to room temperature, add the composite photoinitiator and the additive in the dark, stir, filter, and degas under vacuum to obtain UV separator for BC batteries; wherein, the stirring speed is 500~600 r / min, and the time is 15~20 min; the filtration uses a 200~300 mesh filter; the vacuum degree of the vacuum degassing is -0.08~-0.1 MPa, and the time is 10~15 min.

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