Ultraviolet curing adhesive as well as preparation method, use method and application thereof

Abstract

The invention relates to an ultraviolet curing adhesive as well as a preparation method, a use method and application thereof. The ultraviolet curing adhesive is prepared from the following components in parts by weight: 10 to 70 parts of polyfunctional polyurethane acrylate prepolymer, 30 to 90 parts of acrylate reactive diluent, 1 to 10 parts of photoinitiator, 0.1 to 10 parts of thixotropic agent, 0.1 to 1 part of silane coupling agent, 0.1 to 1 part of defoaming agent, 0.1 to 1 part of antioxidant and 0.05 to 1 part of polymerization inhibitor. The multifunctional polyurethane acrylate prepolymer comprises a first prepolymer with the glass transition temperature Tg of 5-50 DEG C, the mass content of the first prepolymer in the multifunctional polyurethane acrylate prepolymer is 80%-100%, and the acrylate reactive diluent comprises an acrylate soft monomer and an acrylate hard monomer with the mass ratio of (0-0.5): 1. The adhesive is relatively high in curing speed, and has improved adhesive property and high temperature resistance.

Description

Technical Field

[0001] This invention relates to the field of organic adhesive technology, and in particular to ultraviolet-curable adhesives, their preparation methods, usage methods, and applications. Background Technology

[0002] Organic adhesives have a wide range of applications, including but not limited to the field of photovoltaic technology.

[0003] Solar energy, as a clean energy source, is being used more and more widely. In the field of solar power generation technology, solar cells are a crucial component. These cells utilize numerous main and auxiliary grid lines, which are made of silver paste. This silver paste typically contains 80% to 95% silver, making it very expensive. Furthermore, the arrangement of the grid lines affects the light-receiving area of ​​the cell; a poor grid arrangement results in high series resistance, significant power loss, and low output power. Therefore, to improve the photoelectric conversion efficiency of solar cells and reduce manufacturing costs, solder ribbon can be used to replace some of the grid lines during production. Most solder ribbon is copper-plated tin, without the expensive silver, thus reducing the cost of the cells. Simultaneously, solder ribbon has good conductivity and a small diameter (approximately 100-300 μm), which increases the solar-receiving area of ​​the cell.

[0004] Currently, there are two main types of welding strip processes.

[0005] One method is the traditional close-grid welding process, which uses a high-temperature encapsulation process. Flux is applied to the solder strip, and the solder on the surface of the solder strip is melted by heating to fix the solder strip to the surface of the cell. However, because the heating requires high temperature, and as the thickness of the cell becomes thinner, the encapsulation method of direct welding between the solder strip and the cell results in a large stress difference after welding, causing the cell to bend more. Therefore, the welded cell string will have a higher rate of defects such as solder desoldering and cell breakage.

[0006] Another process is the UV-cured adhesive welding process: Adhesive is applied to designated locations on the solar cell using dispensing or screen printing (silk screen or stencil printing). Then, solder ribbons are laid on these designated locations, bonding to the cell surface via the adhesive. Finally, the adhesive is cured by LED or UV lamps, completing the welding process. This welding process allows for low-temperature curing, minimizing impact on the solar cell. Furthermore, the cured adhesive exhibits a degree of toughness, reducing stress caused by deformation of the solder ribbons or solar cell, offering advantages over traditional welding methods. However, current optical tapes suffer from slow curing speeds, poor adhesion, and poor high-temperature resistance, leading to a tendency for delamination. Summary of the Invention

[0007] Therefore, it is necessary to provide a UV-curable adhesive with faster curing speed, improved adhesion and high temperature resistance, as well as its preparation method, application method and application.

[0008] One embodiment of this application provides a UV-curable adhesive, comprising the following components by weight: 10-70 parts of a multifunctional polyurethane acrylate prepolymer, 30-90 parts of an acrylate reactive diluent, 1-10 parts of a photoinitiator, 0.1-10 parts of a thixotropic agent, 0.1-1 parts of a silane coupling agent, 0.1-1 parts of a defoamer, 0.1-1 parts of an antioxidant, and 0.05-1 parts of a polymerization inhibitor; the multifunctional polyurethane acrylate prepolymer includes a first prepolymer with a glass transition temperature (Tg) of 5°C-50°C, and the mass content of the first prepolymer in the multifunctional polyurethane acrylate prepolymer is 80%-100%; the acrylate reactive diluent includes acrylate soft monomers and acrylate hard monomers in a mass ratio of 0-0.5:1.

[0009] The aforementioned UV-curable adhesive, through the synergistic effect of specific component ratios, particularly the use of a multifunctional polyurethane acrylate prepolymer with a specific glass transition temperature (Tg) and control of the specific mass ratio of the multifunctional polyurethane acrylate prepolymer, can improve the curing speed and adhesion of the UV-curable adhesive to solder ribbons. After curing, it exhibits good mechanical properties such as tensile strength and elongation at break, as well as good high-temperature resistance. Therefore, it has a wide range of applications and can be used in photovoltaic modules to improve the problem of easy delamination, thus helping to extend the service life of photovoltaic modules.

[0010] In some embodiments, the acrylate soft monomers include at least one selected from ethoxyethoxyethyl acrylate, ethoxyethoxyethyl methacrylate, n-butyl acrylate, 2-ethylhexyl acrylate, dodecyl acrylate, tetrahydrofuran acrylate, tetrahydrofuran methacrylate, and isodecyl acrylate; and / or,

[0011] The acrylate hard monomers include at least one selected from N,N-dimethylacrylamide, acrylmorpholine, isoborneol acrylate, methyl acrylate, methyl methacrylate, isoborneol methacrylate, and methyl methacrylate; and / or,

[0012] The mass ratio of the acrylate soft monomer to the acrylate hard monomer is 0.1~0.5:1.

[0013] In some embodiments, each of the multifunctional polyurethane acrylate prepolymers has 2 to 4 acrylate groups independently.

[0014] In some embodiments, at least one of the following conditions is satisfied:

[0015] (1) The photoinitiator includes at least one of 1-hydroxycyclohexylphenyl ketone, 2-hydroxy-2-methyl-1-phenyl-1-propanone, 2,2-dimethoxy-2-phenylacetophenone, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, tetrakis(2,4-di-tert-butylphenyl)-4,4'-biphenyl bisphosphite, 2-methyl-1-(4-methylthiophenyl)-2-morpholino-1-propanone, 2-phenylbenzyl-2-dimethylamino-1-(4-morpholinobenzylphenyl)butanone, isopropylthioxanthone, benzophenone, and ethyl 4-dimethylaminobenzoate; optionally, the photoinitiator includes at least one of 1-hydroxycyclohexylphenyl ketone and 2,4,6-trimethylbenzoyl-diphenylphosphine oxide.

[0016] (2) The thixotropic agent includes at least one of fumed silica or organobentonite;

[0017] (3) The silane coupling agent includes at least one of KH-550, KH-560 and KH-570;

[0018] (4) The defoamer includes at least one of BYK-1795, BYK-535 and BYK-525;

[0019] (5) The antioxidants include at least one of antioxidant 1010, antioxidant DLTP, antioxidant 1076, antioxidant CA, antioxidant 164 and antioxidant TPP;

[0020] (6) The polymerization inhibitor includes at least one of p-hydroxyanisole, hydroquinone, 2,5-dimethylhydroquinone and 1,4-naphthol.

[0021] In some embodiments, the UV-curable adhesive has a viscosity of 2000~30000 mPa·s at a rotation speed of 30 rpm and a temperature of 25°C; and / or,

[0022] The thixotropic index of the UV-curable adhesive is 3 to 12. The thixotropic index is the ratio of the viscosity at 0.5 rpm to the viscosity at 5 rpm at a temperature of 25°C.

[0023] One embodiment of this application provides a method for preparing a UV-curable adhesive, comprising the following steps:

[0024] The UV-curable adhesive is obtained by mixing the components of any of the above-mentioned UV-curable adhesives in parts by weight.

[0025] In some embodiments, the mixing is performed using a planetary mixer with a revolution stirring speed of 15 r / min to 25 r / min and a dispersion speed of 300 r / min to 800 r / min; and / or,

[0026] The mixing time is 1 to 2 hours.

[0027] One embodiment of this application provides a method for using a UV-curable adhesive, comprising the following steps:

[0028] The above-mentioned UV-curable adhesives are cured under UV light to obtain a cured UV-curable adhesive layer.

[0029] In some embodiments, the irradiation energy of the ultraviolet light is 500 mJ / cm². 2 ~2000mJ / cm 2 .

[0030] One embodiment of this application provides a UV-curable adhesive layer, which is formed by curing any of the above-mentioned UV-curable adhesives with UV light.

[0031] According to one embodiment of this application, a photovoltaic module is provided, including an adhesive layer, wherein the adhesive layer includes any of the above-described ultraviolet-curable adhesive layers. Detailed Implementation

[0032] To facilitate understanding of the present invention, a more comprehensive description is provided below, along with preferred embodiments. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. It should be understood that these embodiments are provided to provide a thorough and complete understanding of the disclosure of the present invention.

[0033] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0034] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0035] One embodiment of this application provides a UV-curable adhesive, comprising the following components by weight: 10-70 parts of a multifunctional polyurethane acrylate prepolymer, 30-90 parts of an acrylate reactive diluent, 1-10 parts of a photoinitiator, 0.1-10 parts of a thixotropic agent, 0.1-1 parts of a silane coupling agent, 0.1-1 parts of a defoamer, 0.1-1 parts of an antioxidant, and 0.05-1 parts of a polymerization inhibitor; the multifunctional polyurethane acrylate prepolymer includes a first prepolymer with a glass transition temperature (Tg) of 5°C-50°C, and the mass content of the first prepolymer in the multifunctional polyurethane acrylate prepolymer is 80%-100%; the acrylate reactive diluent includes acrylate soft monomers and acrylate hard monomers in a mass ratio of 0-0.5:1.

[0036] The aforementioned UV-curable adhesive, through the synergistic effect of specific component ratios, particularly the use of a multifunctional polyurethane acrylate prepolymer with a specific glass transition temperature (Tg) and control of the specific mass ratio of the multifunctional polyurethane acrylate prepolymer, can improve the curing speed and adhesion of the UV-curable adhesive to solder ribbons. After curing, it exhibits good mechanical properties such as tensile strength and elongation at break, as well as good high-temperature resistance. Therefore, it has a wide range of applications and can be used in photovoltaic modules to improve the problem of easy delamination, thus helping to extend the service life of photovoltaic modules.

[0037] In this application, acrylate soft monomers and acrylate hard monomers have the general meaning in the art. acrylate soft monomers have a glass transition temperature (Tg) of -10°C to 25°C for their homopolymers, while acrylate hard monomers have a glass transition temperature (Tg) of significantly higher than room temperature, typically above 80°C.

[0038] In some embodiments, the acrylate soft monomers include at least one of ethoxyethoxyethyl acrylate (EOEOEA), ethoxyethoxyethyl methacrylate, n-butyl acrylate (BA), 2-ethylhexyl acrylate (2-EHA), dodecyl acrylate (LA), tetrahydrofuran acrylate (THFA), tetrahydrofuran methacrylate, and isodecyl acrylate (IDA).

[0039] In some embodiments, the acrylate hard monomers include at least one of N,N-dimethylacrylamide (DMAA), acrylmorpholine (ACMO), isobornyl acrylate (IBOA), methyl acrylate, methyl methacrylate, isobornyl methacrylate, and methyl methacrylate (MMA).

[0040] As an example, the mass ratio of acrylate soft monomers to acrylate hard monomers is 0, 0.05:1, 0.1:1, 0.15:1, 0.2:1, 0.3:1, 0.4:1, 0.5:1, or any value within the range formed by any two of the above point values ​​as endpoints; it can be selected as 0.05:1 to 0.5:1, and further can be 0.1 to 0.5:1.

[0041] As an example, by weight, the acrylate reactive diluent may be 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, or any value within the range formed by any two of the above point values ​​as endpoints.

[0042] In some embodiments, the UV-curable adhesive further comprises a functional monomer, including at least one of hydroxyethyl acrylate (HEA), hydroxyethyl methacrylate (HEMA), hydroxypropyl acrylate (HPA), hydroxypropyl methacrylate (HPMA), and acrylic acid (AA).

[0043] In some embodiments, the number of acrylate groups in each multifunctional polyurethane acrylate prepolymer is independently 2 to 4, for example 2, 3, or 4.

[0044] In this application, the first prepolymer is also a multifunctional polyurethane acrylate prepolymer, and its glass transition temperature Tg is 5℃, 6℃, 7℃, 8℃, 9℃, 10℃, 11℃, 12℃, 13℃, 14℃, 15℃, 16℃, 17℃, 18℃, 19℃, 20℃, 21℃, 22℃, 23℃, 24℃, 25℃, 26℃, 27℃, 28℃, 29℃, 30℃, 31℃, 32℃, 33℃, 34℃, 35℃, 36℃, 37℃, 38℃, 39℃, 40℃, 41℃, 42℃, 43℃, 44℃, 45℃, 46℃, 47℃, 48℃, 49℃, 50℃ or any value within the range formed by any two of the above points as endpoints, further being 8℃~20℃.

[0045] In the multifunctional polyurethane acrylate prepolymer, the mass content of the first prepolymer is 80%, 85%, 90%, 95%, 100%, or any value within the range formed by any two of the above points as endpoints.

[0046] Understandably, multifunctional polyurethane acrylate prepolymers may also include other multifunctional polyurethane acrylate prepolymers whose glass transition temperature (Tg) is not in the range of 5–50°C, but is, for example, greater than or equal to 5°C. In other words, the glass transition temperature (Tg) of the multifunctional polyurethane acrylate prepolymers in UV-curable adhesives is greater than or equal to 5°C, and further less than or equal to 105°C. Further, other multifunctional polyurethane acrylate prepolymers have a glass transition temperature (Tg) greater than 50°C and less than or equal to 105°C.

[0047] Optionally, the multifunctional polyurethane acrylate prepolymer includes at least one of CN996NS, CN989NS, CN9013, and 8602. Further, CN996NS has a glass transition temperature (Tg) of 8°C, CN989NS has a glass transition temperature (Tg) of 72°C, CN9013 has a glass transition temperature (Tg) of 102°C, and 8602 has a glass transition temperature (Tg) of 20°C.

[0048] In some embodiments, the multifunctional polyurethane acrylate prepolymer includes CN996NS, and optionally includes at least one of CN989NS, CN9013 and 8602; further, the mass ratio of at least one of CN989NS, CN9013 and 8602 to CN996NS is 1:8 to 10, for example 1:8, 1:9, 1:10 or any value within the range formed by any two of the above point values ​​as end values.

[0049] As an example, by weight, the multifunctional polyurethane acrylate prepolymer can be 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, or any value within the range formed by any two of the above point values ​​as endpoints.

[0050] In some embodiments, the photoinitiator includes at least one selected from 1-hydroxycyclohexylphenyl ketone, 2-hydroxy-2-methyl-1-phenyl-1-propanone, 2,2-dimethoxy-2-phenylacetophenone, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, tetrakis(2,4-di-tert-butylphenyl)-4,4'-biphenyl bisphosphite, 2-methyl-1-(4-methylthiophenyl)-2-morpholino-1-propanone, 2-phenylbenzyl-2-dimethylamino-1-(4-morpholinobenzylphenyl)butanone, isopropylthioxanthone, benzophenone, and ethyl 4-dimethylaminobenzoate; optionally, the photoinitiator includes at least one selected from 1-hydroxycyclohexylphenyl ketone and 2,4,6-trimethylbenzoyl-diphenylphosphine oxide.

[0051] As an example, the photoinitiator, by weight, can be 1, 1.5, 2, 3, 4, 5, 6, 7, 8, 9, 10, or any value within the range formed by any two of the above point values ​​as endpoints.

[0052] In some embodiments, the mass ratio of the multifunctional polyurethane acrylate prepolymer to the acrylate reactive diluent is 0.8 to 1.2:1; for example, 0.8:1, 0.9:1, 1:1, 1.1:1, 1.2:1, or any value within the range formed by any two of the above point values ​​as endpoints.

[0053] In some embodiments, the thixotropic agent comprises at least one of fumed silica or organobentonite, optionally Degussa fumed silica AEROSIL 380. As an example, the thixotropic agent, by weight, may be 0.1, 0.2, 0.5, 0.6, 0.8, 1, 2, 3, 4, 4.5, 5, 6, 7, 8, 9, 10, or any value within a range formed by any two of the above point values ​​as endpoints.

[0054] In some embodiments, the silane coupling agent includes at least one of 3-aminopropyltriethoxysilane (KH-550), 3-glycidoxypropyltrimethoxysilane (KH-560), and 3-methacryloyloxypropyltrimethoxysilane (KH-570), optionally KH-560. As an example, the silane coupling agent may be 0.1, 0.2, 0.5, 0.6, 0.8, 1 parts by weight, or any value within the range formed by any two of the above points as endpoints.

[0055] In some embodiments, the defoamer includes at least one of BYK-1795, BYK-535, and BYK-525, with BYK-1795 being optional. As an example, the defoamer may be present in parts by weight of 0.1, 0.2, 0.5, 0.6, 0.8, 1, or any value within a range defined by any two of the above points as endpoints.

[0056] In some embodiments, the antioxidant includes at least one of antioxidant 1010 (i.e., pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]), antioxidant DLTP (dilauryl thiodipropionate), antioxidant 1076 (octadecyl β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate), antioxidant CA (1,1,3-tris(2-methyl-4-hydroxy-5-tert-butylphenyl)butane), antioxidant 164, and antioxidant TPP (triphenyl phosphite), optionally antioxidant 1010. As an example, the antioxidant may be 0.1, 0.2, 0.5, 0.6, 0.8, 1 parts by weight, or any value within the range formed by any two of the above points as endpoints.

[0057] In some embodiments, the polymerization inhibitor includes at least one selected from p-hydroxyanisole, hydroquinone, 2,5-dimethylhydroquinone, and 1,4-naphthol, optionally p-hydroxyanisole. As an example, the polymerization inhibitor may be 0.05, 0.1, 0.2, 0.5, 0.6, 0.8, 1 parts by weight, or any value within a range consisting of any two of the above points as endpoints.

[0058] In some embodiments, the UV-curable adhesive has a viscosity of 2000~30000 mPa·s at a rotation speed of 30 rpm and a temperature of 25°C. As an example, this viscosity can be 2000, 3000, 4000, 5000, 6000, 7000, 8000, 9000, 10000, 11000, 12000, 13000, 14000, 15000, 16000, 17000, 18000, 19000, 20000, 21000, 22000, 23000, 24000, 25000, 26000, 27000, 28000, 29000, 30000 mPa·s, or any value within a range defined by any two of the above points as endpoints.

[0059] In some embodiments, the thixotropic index of the UV-curable adhesive is 3 to 12. The thixotropic index is the ratio of the viscosity at 25°C and a rotation speed of 0.5 rpm to the viscosity at a rotation speed of 5 rpm. As an example, the thixotropic index of the UV-curable adhesive can be 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, or any value within the range formed by any two of the above points as endpoints.

[0060] Understandably, in this application, the viscosity of the UV-curable adhesive refers to the viscosity tested when stirred at the corresponding rotation speed, and the viscosity of the adhesive at different shear rates can be measured using a rotational rheometer.

[0061] One embodiment of this application provides a method for preparing a UV-curable adhesive, comprising the following steps:

[0062] The UV-curable adhesive is obtained by mixing the components of any of the above UV-curable adhesives in parts by weight.

[0063] By mixing the above components, a UV-curable adhesive can be obtained.

[0064] In some embodiments, mixing is carried out using a planetary mixer with a revolution stirring speed of 15 r / min to 25 r / min and a dispersion speed of 300 r / min to 800 r / min.

[0065] As an example, the revolution stirring speed of the planetary mixer is 15 r / min, 18 r / min, 20 r / min, 22 r / min, 25 r / min, or any value within the range formed by any two of the above points as endpoints.

[0066] As an example, the dispersion speed is 300 r / min, 400 r / min, 500 r / min, 600 r / min, 700 r / min, 800 r / min, or any value within the range formed by any two of the above point values ​​as endpoints.

[0067] In some embodiments, the mixing time is 1 to 2 hours.

[0068] In some embodiments, the above mixing includes the following steps: first, mixing all components except the thixotropic agent for 0.5 to 1.5 hours, and then adding the thixotropic agent and mixing for 0.5 to 1 hour.

[0069] In some embodiments, a centrifugal degassing step is included after mixing, which may be performed using a vacuum centrifuge.

[0070] One embodiment of this application provides a method for using a UV-curable adhesive, comprising the following steps:

[0071] The above-mentioned UV-curable adhesives are cured under UV light to obtain a cured UV-curable adhesive layer.

[0072] When the aforementioned UV-curable adhesive is irradiated with UV light, the photoinitiator absorbs energy and decomposes into free radicals, initiating a free radical polymerization reaction between the acrylate double bonds on the polyurethane acrylate molecules and the double bonds on the acrylate reactive diluents. In this way, the long-chain molecules of the polyurethane acrylate and the small molecules of the acrylate reactive diluent monomers interconnect, rapidly forming a three-dimensional cross-linked network structure. The originally liquid adhesive then cures, achieving its adhesive effect. The entire process involves no solvent evaporation, relying on photo-initiated free radical polymerization for curing. Simultaneously, through the use of silane coupling agents and other components, the cured UV-curable adhesive layer possesses excellent mechanical properties such as tensile strength and elongation at break, as well as good high-temperature resistance. Therefore, it has a wide range of applications, particularly in photovoltaic modules, where it addresses the problem of easy delamination, thus improving the lifespan of photovoltaic modules.

[0073] Furthermore, silane coupling agents can also improve the adhesion of adhesives in high humidity environments. Specifically, in high humidity environments, one end of the silane coupling agent bonds with the acrylate, while the other end forms a chemical bond with the substrate, thereby improving the adhesion of the acrylate-based adhesive to the substrate.

[0074] Optionally, the irradiation energy of ultraviolet light is 500 mJ / cm.2 ~2000mJ / cm 2 For example, 500, 600, 700, 800, 900, 1000, 1100, 1200, 1300, 1400, 1500, 1600, 1700, 1800, 1900, 2000 mJ / cm³ 2 Or any value within the range formed by any two of the above point values ​​as endpoints.

[0075] One embodiment of this application provides a UV-curable adhesive layer, which is formed by curing any of the above-mentioned UV-curable adhesives with UV light.

[0076] According to one embodiment of this application, a photovoltaic module is provided, including an adhesive layer, which includes any of the above-described ultraviolet-curable adhesive layers.

[0077] In some embodiments, the photovoltaic module includes a photovoltaic device, which includes a solar cell, and the solar cell includes at least one of crystalline silicon solar cells and heterojunction solar cells. The aforementioned UV-curable adhesive layer not only cures quickly but also has high light transmittance, making it suitable for bonding various solar cells, including but not limited to the surfaces and solder ribbons of ordinary crystalline silicon solar cells and heterojunction solar cells.

[0078] In some embodiments, the photovoltaic module further includes solder ribbons disposed on the surface of the photovoltaic device, the solder ribbons being connected to the surface of the photovoltaic device via an adhesive layer, the adhesive layer including any of the above-mentioned ultraviolet-curable adhesive layers.

[0079] In some embodiments, the photovoltaic module manufacturing process requires lamination, and after lamination, it needs to be placed at 200°C for 4 hours. This process can easily lead to the optical adhesive delaminating. Applying any of the above-mentioned UV-curable adhesive layers can improve this delamination problem, enhance the device stability of the photovoltaic module, and extend its service life.

[0080] To make the objectives, technical solutions, and advantages of this invention clearer and more concise, the invention is described using the following specific embodiments, but the invention is by no means limited to these embodiments. The embodiments described below are merely preferred embodiments of the invention and can be used to describe the invention, but should not be construed as limiting the scope of the invention. It should be noted that any modifications, equivalent substitutions, and improvements made within the spirit and principles of this invention should be included within the protection scope of this invention.

[0081] To better illustrate the present invention, the following description, in conjunction with specific embodiments, further clarifies the content of the invention. The following are specific embodiments.

[0082] 1. Example of preparation of UV-curable adhesive.

[0083] Weigh each component according to the parts by weight shown in Table 1. Then, add the multifunctional polyurethane acrylate prepolymer, acrylate reactive diluent, photoinitiator, silane coupling agent, defoamer, antioxidant, and polymerization inhibitor into a planetary mixer. Turn on the planetary stirring (stirring speed of 20 r / min) and high-speed dispersion (stirring speed of 600 r / min) and continue stirring for 1 hour to ensure the system is uniformly mixed. Then add the thixotropic agent and continue stirring for 0.5 hours. After completion, filter out the material and transfer it to a vacuum centrifuge for degassing under vacuum to obtain the UV-curable adhesive for photovoltaic applications. The prepared product is sealed in black or dark-colored opaque UV-resistant packaging and stored at room temperature.

[0084] Among them, the multifunctional polyurethane acrylate prepolymer selected is one or more of the following from SARTOMER (USA): CN996NS (8℃), CN989NS (72℃), CN9013 (102℃), CN8888NS (-32℃), CN9004NS (-76℃), and 8602 (20℃) from Guangzhou Songda New Materials. The temperature in parentheses is the glass transition temperature of the prepolymer.

[0085] The photoinitiators selected were Irgacure 184 and LUCIRIN TPO from BASF, Germany.

[0086] The silane coupling agent used is KH560 from Shanghai Kaiyin Chemical Co., Ltd.

[0087] The defoamer used is BYK-1795 from BYK Chemicals in Germany.

[0088] The thixotropic powder used is CARBOT TS720 fumed silica from the USA.

[0089] The antioxidant used is Irganox 1010 from BASF in Germany.

[0090] The polymerization inhibitor used is Merck Sigma-Aldrich MEHQ.

[0091] 2. Performance testing.

[0092] 2.1 Curing Time Test Method: The curing time is tested using the finger-touch method. Lightly touch the adhesive surface with your finger; if it feels slightly sticky but no adhesive remains on your finger, the surface is considered dry (refer to GB1728-79 Method for Determining the Drying Time of Paint Films and Putty Films). Experimental Conditions: The LED UV curing equipment provides 250W UV lamp irradiation at a wavelength of 365nm, with a lamp distance of 5cm. The unit of measurement is seconds (s).

[0093] 2.2 Thixotropic value refers to the ratio of viscosity at 0.5 rpm to viscosity at 5 rpm under conditions of 25℃. The viscometer used for viscosity measurement is a Brookfield DV2T viscometer.

[0094] 2.3 Tensile strength and elongation at break were determined in accordance with GB / T529-2009.

[0095] 2.4 High Temperature Resistance Test Method: First, adhesive is applied along the long side of the solar cell (16.6mm*8.2mm) using a dispensing machine to form three equally spaced lines. The dimensions of the lines are controlled to be 1-2mm wide, ≤300μm thick, and 15mm long. The cells are then fully cured under LED UV curing equipment. After curing, the solar cells with the adhesive lines are laminated and encapsulated at a pressure of 5kgf. After cooling, the laminated components are placed at 200℃ for an aging test. After 4 hours, the cells are removed and the appearance of the adhesive line area is observed. NG indicates the presence of bubbles or yellowing at the adhesive line, while OK indicates no bubbles or yellowing.

[0096] 2.5 Test method for adhesive strength: Refer to GB / T 31985-2015 and ASTM D903. The sample consists of a solar cell + UV-cured adhesive + solder ribbon, with the adhesive applied and UV cured. The testing equipment is a tensile testing machine, which clamps the solder ribbon and the solar cell, with a pulling speed of 50 mm / min and an angle of 90° between the solder ribbon and the solar cell.

[0097] Table 1

[0098]

[0099] Table 2

[0100]

[0101] As can be seen from Tables 1 and 2, the multifunctional polyurethane acrylate prepolymers of the UV-curable adhesives in Comparative Examples 1 and 2 are all CN8888NS (-32℃) or CN9004NS (-76℃), which have low glass transition temperatures. As a result, the UV-curable adhesives prepared have poor high-temperature resistance (NG) after curing, and bubbles or yellowing appear on the adhesive lines.

[0102] In Comparative Example 3, the ratio of soft monomers to hard monomers in the UV-curable adhesive was 1. The resulting UV-curable adhesive had low tensile strength and poor cohesion after curing, which led to low bonding strength between the battery cell and the solder ribbon.

[0103] In Comparative Example 4, the multifunctional polyurethane acrylate prepolymer of the UV-curable adhesive was all CN989NS (72℃), which had a glass transition temperature that was too high. As a result, the UV-curable adhesive had a low elongation at break after curing, was too brittle, and had poor bonding performance.

[0104] The test results of Examples 1-8 show that using a high-Tg multifunctional polyurethane acrylate prepolymer and controlling the ratio of soft monomers to hard monomers at 0-0.5 results in an adhesive that not only cures quickly but also exhibits high tensile strength and elongation at break after UV curing, as well as high bonding strength and toughness. It also has good high-temperature resistance and can withstand temperatures up to 200°C after being encapsulated into photovoltaic modules, with no bubbles or yellowing after 4 hours.

[0105] As can be seen from Examples 1-2 and Comparative Example 3, the lower the proportion of soft monomers, the lower the elongation at break. However, increasing the proportion of soft monomers will lead to a decrease in tensile strength. In the examples, the proportion of soft and hard monomers was adjusted to 0-0.5, and the UV-curable adhesive obtained after curing has both high tensile strength and elongation at break.

[0106] As can be seen from Examples 7 and 8, the ratio of multifunctional polyurethane acrylate prepolymer to acrylate reactive diluent is feasible within a certain range, and the amount used can be adjusted according to specific requirements.

[0107] Furthermore, the thixotropic value affects the efficiency of the adhesive applicator and also the shape of the adhesive dots. Therefore, by adjusting the amount of thixotropic agent, the thixotropic value of the adhesive can be made more suitable for production. In addition, the amount of photoinitiator directly affects the curing speed of the adhesive. To improve the curing speed, a certain proportion of photoinitiator needs to be added.

[0108] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0109] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims, and the specification can be used to interpret the content of the claims.

Claims

1. A UV-curable adhesive, characterized in that, The product comprises, by weight parts, the following components: 10-70 parts of multifunctional polyurethane acrylate prepolymer, 30-90 parts of acrylate reactive diluent, 1-10 parts of photoinitiator, 0.1-10 parts of thixotropic agent, 0.1-1 parts of silane coupling agent, 0.1-1 parts of defoamer, 0.1-1 parts of antioxidant, and 0.05-1 parts of polymerization inhibitor; wherein the multifunctional polyurethane acrylate prepolymer includes a first prepolymer with a glass transition temperature (Tg) of 5°C-50°C, and the mass content of the first prepolymer in the multifunctional polyurethane acrylate prepolymer is 80%-100%; wherein the acrylate reactive diluent includes acrylate soft monomers and acrylate hard monomers in a mass ratio of 0-0.5:

1.

2. The UV-curable adhesive as described in claim 1, characterized in that, The acrylate soft monomers include at least one selected from ethoxyethoxyethyl acrylate, ethoxyethoxyethyl methacrylate, n-butyl acrylate, 2-ethylhexyl acrylate, dodecyl acrylate, tetrahydrofuran acrylate, tetrahydrofuran methacrylate, and isodecyl acrylate; and / or, The acrylate hard monomers include at least one selected from N,N-dimethylacrylamide, acrylmorpholine, isoborneol acrylate, methyl acrylate, methyl methacrylate, isoborneol methacrylate, and methyl methacrylate; and / or, The mass ratio of the acrylate soft monomer to the acrylate hard monomer is 0.1~0.5:

1.

3. The UV-curable adhesive as described in claim 1, characterized in that, Each of the multifunctional polyurethane acrylate prepolymers has 2 to 4 acrylate groups.

4. The UV-curable adhesive as described in claim 1, characterized in that, At least one of the following conditions must be met: (1) The photoinitiator includes at least one of 1-hydroxycyclohexylphenyl ketone, 2-hydroxy-2-methyl-1-phenyl-1-propanone, 2,2-dimethoxy-2-phenylacetophenone, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, tetrakis(2,4-di-tert-butylphenyl)-4,4'-biphenyl bisphosphite, 2-methyl-1-(4-methylthiophenyl)-2-morpholino-1-propanone, 2-phenylbenzyl-2-dimethylamino-1-(4-morpholinobenzylphenyl)butanone, isopropylthioxanthone, benzophenone and ethyl 4-dimethylaminobenzoate; (2) The thixotropic agent includes at least one of fumed silica or organobentonite; (3) The silane coupling agent includes at least one of KH-550, KH-560 and KH-570; (4) The defoamer includes at least one of BYK-1795, BYK-535 and BYK-525; (5) The antioxidants include at least one of antioxidant 1010, antioxidant DLTP, antioxidant 1076, antioxidant CA, antioxidant 164 and antioxidant TPP; (6) The polymerization inhibitor includes at least one of p-hydroxyanisole, hydroquinone, 2,5-dimethylhydroquinone and 1,4-naphthol.

5. The UV-curable adhesive according to any one of claims 1 to 4, characterized in that, The UV-curable adhesive has a viscosity of 2000~30000 mPa·s at a rotation speed of 30 rpm and a temperature of 25°C; and / or, The thixotropic index of the UV-curable adhesive is 3 to 12. The thixotropic index is the ratio of the viscosity at 0.5 rpm to the viscosity at 5 rpm at a temperature of 25°C.

6. A method for preparing a UV-curable adhesive, characterized in that, Includes the following steps: The components of the UV-curable adhesive according to any one of claims 1 to 5 are mixed in parts by weight to obtain the UV-curable adhesive.

7. The method for preparing the UV-curable adhesive as described in claim 6, characterized in that, The mixing is carried out using a planetary mixer, wherein the planetary mixer has a revolution stirring speed of 15 r / min to 25 r / min and a dispersion speed of 300 r / min to 800 r / min; and / or, The mixing time is 1 to 2 hours.

8. A method for using a UV-curable adhesive, characterized in that, Includes the following steps: The UV-curable adhesive according to any one of claims 1 to 5 is photocured under UV light to obtain a cured UV-curable adhesive layer.

9. A UV-curable adhesive layer, characterized in that, It is formed by curing the UV-curable adhesive according to any one of claims 1 to 5 with UV light.

10. A photovoltaic module, characterized in that, It includes an adhesive layer, wherein the adhesive layer includes the UV-curable adhesive layer of claim 9.

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