Shielding-free dual-curing three-proofing glue and preparation method thereof

Abstract

The invention discloses a shielding-free dual-curing three-proofing adhesive and a preparation method thereof. The shielding-free dual-curing three-proofing adhesive comprises the following components in parts by weight: 40-65 parts of matrix resin; 20 to 40 parts of an acrylate monomer; 1 to 5 parts of a photoinitiator; 1-5 parts of an auxiliary agent; 1-5 parts of a rheological additive; the matrix resin comprises a urethane acrylate prepolymer A and a urethane acrylate prepolymer B, and the acrylate monomer comprises a phosphate modified acrylate monomer and two or more single-functional-group acrylate monomers. According to the shielding-free UV three-proofing adhesive provided by the invention, accurate coating, particularly accurate thick coating, of the three-proofing adhesive can be realized under the condition of no shielding, so that the production efficiency is improved, the cost is reduced, and high-precision production and processing are realized.

Description

Technical Field

[0001] The present invention relates to the processing field of three-proof glue, and particularly relates to a double-curing three-proof glue without masking and a preparation method thereof. Background Art

[0002] As a core component of electronic devices, printed circuit board assemblies (PCBA) are in harsh environments such as high humidity, salt spray, temperature shock, and mechanical vibration for a long time. In such an environment, PCBA is extremely prone to problems such as component corrosion, solder joint cracking, and insulation performance degradation. And the coating of three-proof glue (moisture-proof, salt-spray-proof, and mildew-proof) is a key process to improve the reliability of PCBA, which can significantly extend the service life of electronic products.

[0003] Since there are uncoatable areas such as connectors, sockets, heat sinks, high-power components, and sensors on PCBA, in order to avoid these areas being coated with glue, the existing solution is to pre-mask the non-glue-coated areas before spraying the three-proof glue. Common masking methods include: 1. Tape masking. For example, a weather-resistant and environmentally friendly masking tape disclosed in the invention patent with publication number CN118791980A. Although this masking tape improves the coordination and balance of peelability and adhesion performance compared with existing masking tape products, and the safety and environmental protection performance during high-temperature operation, there may still be a problem of local glue residue when the tape is peeled off; at the same time, attaching the tape before spraying glue and peeling the tape after spraying glue both need to be completed manually, which will prolong the processing time of the entire process, require a lot of time to cover the device with masking glue / tape, reduce the process efficiency, and increase the production cost; in addition, the sealing performance of the tape, especially at the edge of the tape, is insufficient, which may lead to masking failure.

[0004] 2. Coating peelable glue for masking. For example, a masking glue for three-proof coating applicable to connectors, its preparation method, and application method disclosed in the invention patent with authorization announcement number CN116496750B. This type of method has better sealing performance compared with tape masking, and at the same time, machines can be used to replace manual glue coating or peeling the glue layer, which relatively improves the production efficiency, but the coating, curing, and peeling of the masking glue still prolong the processing time, and there is still a risk of glue residue.

[0005] 3. Use prefabricated masking covers, masking films and other masking tools, for example: the invention patent with authorization announcement number CN114650664B discloses a printed circuit board three-conformal coating masking method and masking device, in which the printed circuit board can be set on the bearing surface, the positioning structure is used to position the printed circuit board, the three-conformal paint can be applied to the three-conformal coating area through the coating port, and the limiting raised layer is used to cover the shielding area; this method can improve the efficiency of three-conformal coating masking for specific models of products, but different types of products need to be molded separately, which is costly and less flexible. After replacing the PCBA product, the masking cover must be replaced or the mold must be redesigned.

[0006] The core idea of ​​the above process is to mask key components or areas in advance, and then remove the masking parts after the conventional spraying operation is completed, so as to achieve selective spraying of PCBA. These methods inevitably increase the work and consumables of masking and removing the masking.

[0007] By improving the precise positioning performance of the three-proof glue, it is possible to ensure that the three-proof glue is accurately applied without masking glue, thereby achieving the effect of improving production efficiency. However, existing three-proof glue products are usually difficult to achieve the above effects. Especially for some specific PCBA use environments, in order to adapt to extreme environments such as high humidity, salt spray, high temperature and mechanical vibration, thick three-proof glue is required to achieve the protection effect. The thickness of the three-proof glue of some products even needs to reach 0.5mm-3mm. The three-proof glue with low viscosity cannot achieve a larger thickness. At the same time, the fluidity of the colloid is good, and it is very easy to extend to the area where glue is not required, so accurate glue cannot be applied. The three-proof glue with high viscosity is difficult to apply evenly, resulting in poor appearance or even protection failure; in addition, the existing dual-curing three-proof glue requires a lot of time to complete moisture curing. At the same time, the hydrophobic properties of the product after curing, especially the steam resistance, are poor, which makes the coating unsuitable for high temperature and high humidity environments.

[0008] Therefore, there is an urgent need to propose a shielding-free UV three-proof adhesive, aiming to achieve precise coating of the three-proof adhesive under shielding conditions, especially precise thick coating, so as to improve production efficiency, reduce costs, and achieve high-precision production and processing. Summary of the invention

[0009] Therefore, in order to solve the above problems and realize the precise coating of the three-proof adhesive in an unshielded state, the present invention provides.

[0010] The present invention is achieved through the following technical solutions: The mask-free dual-curing conformal adhesive comprises the following raw material components in parts by weight: Main resin 40-65 parts; Acrylate monomer 20-40 parts; 1-5 parts of photoinitiator; 1 part - 5 parts of auxiliary agent; 1 part - 5 parts of rheological auxiliary agent; The main resin includes polyurethane acrylate prepolymer A and polyurethane acrylate prepolymer B. The viscosity of polyurethane acrylate prepolymer A is 9500 cps - 25000 cps, and the viscosity of polyurethane acrylate prepolymer B is 5000 cps - 10000 cps. The mass ratio of polyurethane acrylate prepolymer A to polyurethane acrylate prepolymer B is (1 - 3)∶1. The NCO content of both polyurethane acrylate prepolymer A and polyurethane acrylate prepolymer B is 0% - 1%. The acrylate monomer includes phosphate - modified acrylate monomer and two or more monofunctional acrylate monomers.

[0011] Preferably, the polyurethane acrylate prepolymer A is a branched - chain - structured polyurethane acrylate resin, which is prepared by reacting a polyfunctional polyol with a functionality of ≥3 and a diisocyanate at 70℃ - 90℃. The molar ratio of the polyfunctional polyol to the diisocyanate is 1∶(2.2 - 3.0). Then, the temperature is lowered to 50℃ - 60℃, and a hydrophobic branched - chain segment diol is added for reaction. The molar ratio of the hydrophobic branched - chain segment diol to the polyfunctional polyol is (0.8 - 1.2)∶1. Finally, a hydroxy acrylate monomer is slowly added for reaction. The molar ratio of the hydroxy acrylate monomer to the polyfunctional polyol is (0.5 - 1.5)∶1. The content of the residual NCO groups at the end of the polyurethane acrylate prepolymer A is ≤1% but not 0; and / or the polyurethane acrylate prepolymer B is a non - branched - chain - structured polyurethane acrylate resin, which is prepared by reacting a linear soft - segment polyol and a diisocyanate at 70℃ - 90℃. The molar ratio of the linear soft - segment polyol to the diisocyanate is 1∶(2.05 - 2.25). Then, a hydroxy acrylate is introduced for reaction. The molar ratio of the hydroxy acrylate to the linear soft - segment polyol is (1.00 - 1.15)∶1. The content of the residual NCO groups at the end of the polyurethane acrylate prepolymer B is ≤1% but not 0.

[0012] Preferably, the hydrophobic branched - chain segment diol includes C12 - C18 long - chain aliphatic diols.

[0013] Preferably, the mass ratio of the monofunctional acrylate monomer to the phosphate - modified acrylate monomer is (20 - 50)∶1.

[0014] Preferably, the monofunctional acrylate monomer includes an acrylate monomer with Tg > 50℃ and an acrylate monomer with Tg < 25℃. The mass ratio of the acrylate monomer with Tg > 50℃ to the acrylate monomer with Tg < 25℃ is (4 - 12)∶1.

[0015] Preferably, the acrylate monomers with Tg > 50 °C include but are not limited to one or more of 4-tert-butylcyclohexyl acrylate, isobornyl acrylate, acryloylmorpholine, N,N-dimethylacrylamide, cyclohexyl methacrylate, isobornyl methacrylate, methyl methacrylate, phenyl methacrylate; and / or the acrylate monomers with Tg < 25 °C include but are not limited to one or more of 2-phenoxyethyl acrylate, trimethylolpropane formal acrylate, tetrahydrofurfuryl acrylate, lauric acid acrylate, ethoxyethoxyethyl acrylate, tetrahydrofurfuryl ethoxyacrylate; and / or the phosphate-modified acrylate monomers include but are not limited to one or more of 2-hydroxyethyl methacrylate phosphate, bis(2-methacryloyloxyethyl) hydrogen phosphate, bis(2-acryloyloxyethyl) phosphate, epoxyethane-modified diphosphoric acid diacrylate.

[0016] Preferably, the photoinitiator includes but is not limited to two or more of methyl benzoylformate, 2-hydroxy-2-methyl-1-phenyl-1-propanone, 2,4,6-trimethylbenzoyl diphenylphosphine oxide, ethyl 2,4,6-trimethylbenzoyl phenylphosphinate, bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, methyl o-benzoylbenzoate.

[0017] Preferably, the additives include one or more of fluorescent agents, silane coupling agents, wetting agents, and the rheology additive is hydrophobic fumed silica.

[0018] A preparation method of a maskless dual-curing three-proof adhesive, comprising the following steps: Step S1: Preparation of raw materials: Prepare the raw materials of the maskless dual-curing three-proof adhesive as described above; Step S2: Pretreatment of raw materials: Preheat the polyurethane acrylate prepolymer A and the polyurethane acrylate prepolymer B in an oven at 60 °C - 90 °C for 30 minutes respectively to reduce the viscosity of the prepolymers; Step S3: Mixing and dispersion of raw materials: Step S31: Under a yellow light environment, add the polyurethane acrylate prepolymer A and the polyurethane acrylate prepolymer B with a mass ratio of (1 - 3)∶1 into a stirring kettle, and sequentially add acrylate monomers, photoinitiator and additives, and stir the above raw materials at a rotation speed of 50 RPM - 500 RPM for 1 hour - 2 hours to make the raw materials mix evenly; Step S32: Under the stirring state of Step S31, slowly add the rheological aid into the stirring kettle, and turn on the high-speed dispersion disc of the stirring kettle to disperse the raw materials after the rheological aid, where: use a high-speed dispersion disc with a rotation speed ≥ 1000 RPM, the processing time is 1 hour - 2 hours, and the peripheral linear velocity of the high-speed dispersion disc ≥ 15 m / s; or use a three-roll mill with a roll spacing of 5 μm - 40 μm for processing, the grinding speed < 150 RPM, and grind at least twice; after dispersion, a three-proof glue with a viscosity of 2000 cps - 6000 cps and a thixotropic index of 2 - 6 is obtained.

[0019] Preferably, it further includes: Step S4: Defoaming and packaging of the three-proof glue: Directly put the packaging container filled with the three-proof glue prepared in Step S3 into the homogenizer, and defoam for ≥ 5 minutes at a vacuum degree ≤ -0.080 MPa and a rotation speed ≥ 600 RPM, and then encapsulate; or first put the three-proof glue prepared in Step S3 into a turnover barrel, put the turnover barrel into the homogenizer, defoam for ≥ 5 minutes at a vacuum degree ≤ -0.080 MPa and a rotation speed ≥ 600 RPM, then pour the three-proof glue into the packaging container, and then use a vacuum barrel for secondary vacuum treatment for 10 - 20 minutes and then encapsulate, and the vacuum degree of the vacuum barrel ≤ -0.095 Mpa.

[0020] The beneficial effects of the technical solution of the present invention are mainly reflected in: 1. The double-curing three-proof glue without masking of the present invention precisely controls the synergistic ratio of two polyurethane acrylate prepolymers with different viscosities, acrylic monomers and rheological aids, so that the three-proof glue has an appropriate viscosity (2000 - 6000 cps) and thixotropic properties (thixotropic index 2 - 6); the above characteristics enable the three-proof glue to reduce its viscosity under the action of shear force during dispensing, which is convenient for rapid dispensing and ensures the uniformity of dispensing; after dispensing, the three-proof glue can restore high viscosity in a static state, instantly forming a stable structure, avoiding the three-proof glue from flowing or spreading along the dispensing boundary, so as to ensure that the three-proof glue precisely maintains the coating shape before curing; in addition, for the uneven areas of printed circuit components, by precisely controlling the thixotropic index of the three-proof glue, it is possible to avoid excessive sagging caused by too high thixotropic index, thereby avoiding the problem of poor coverage of the three-proof glue and ensuring that the coating area is precisely controllable.

[0021] 2. The non-concealing dual-curing three-proof glue is formulated by blending a high-viscosity polyurethane acrylate prepolymer A and a low-viscosity polyurethane acrylate prepolymer B to form a dual-resin system. The polyurethane acrylate prepolymer A is used to provide structural support, while the polyurethane acrylate prepolymer B is used to optimize the rheological properties. The dual-resin system avoids the influence of the viscosity fluctuation of a single resin on the overall viscosity of the product. At the same time, with the synergistic effect of acrylic monomers, rheological aids, and other additives (such as silane coupling agents), it can not only enhance the thixotropic performance but also improve the storage stability, avoiding delamination or sedimentation after long-term storage, thus constructing a three-proof glue system with system stability and batch consistency, ensuring the reliability of the product and enabling the three-proof glue to meet the requirements of precise dispensing.

[0022] 3. The non-concealing dual-curing three-proof glue uses a polyurethane acrylate resin system with a low NCO content and combines a surface-layer / deep-layer composite system of photoinitiator combinations to achieve rapid curing under UV radiation. After curing, the hardness is ≥D65, and subsequent production processes can be carried out immediately after UV curing. The residual NCO groups of the resin provide moisture-assisted curing for local shadow areas, ensuring that complete cross-linking can still be achieved in areas with insufficient UV light. A dual-curing system of rapid UV curing and moisture curing can be realized, improving production efficiency. At the same time, the volume shrinkage rate of the coating after curing is <1%, avoiding phenomena such as cracking and warping caused by shrinkage, which reduce the coating effect.

[0023] 4. The polyurethane acrylate prepolymer A of the non-concealing dual-curing three-proof glue can adopt a hydrophobic branched-chain structure, and the polyurethane acrylate prepolymer B can adopt a linear structure. By strictly controlling the mass ratio between the polyurethane acrylate prepolymer A and the polyurethane acrylate prepolymer B, and coordinating the use of phosphate-modified acrylate and the optimized ratio of acrylate monomers with Tg>50°C and acrylate monomers with Tg<25°C, a three-proof glue system with good comprehensive performance is constructed. The cured three-proof glue coating has a Shore hardness ≥D65 mechanical hardness, while maintaining good flexibility, with an elongation at break ≥150% and a tensile strength ≥4 MPa. The adhesion to the PCBA substrate can reach 5B, combining excellent mechanical properties and adhesion.

[0024] 5. The non-concealing dual-curing three-proof glue can adopt a polyurethane acrylate prepolymer A with a hydrophobic branched-chain structure, and at the same time select polyurethane acrylate prepolymers A and B with a low NCO content, so that the cured three-proof glue coating has good hydrophobicity. At the same time, combined with the appropriate viscosity and thixotropic performance of the three-proof glue, the coating thickness of the three-proof glue can reach 0.5 mm - 3 mm. Therefore, compared with the thin coating (≤100μm) design of conventional three-proof glue, the non-concealing dual-curing three-proof glue has good resistance to heat and humidity, chemical resistance, high and low temperature shock resistance, and steam shock resistance, ensuring long-term and reliable protection.

[0025] 6. In the preparation method of the non-concealing dual-curing three-proof glue, the polyurethane acrylate prepolymer A and the polyurethane acrylate prepolymer B are preheated to reduce the viscosity of the prepolymers, facilitating subsequent uniform dispersion. At the same time, to avoid the presence of air bubbles in the three-proof glue, degassing treatment and vacuum packaging are carried out during the packaging of the three-proof glue, thereby avoiding the generation of air bubbles during subsequent storage and transportation, ensuring the stability of continuous dispensing and the denseness of the coating, improving the protection effect of the coating, providing guarantee for precise dispensing, achieving high-thickness and high-precision dispensing, and avoiding contamination of non-coated areas. Detailed implementation manners

[0026] To clearly and detailedly present the objectives, advantages, and features of the present invention, the following preferred embodiments will be used for explanation. These embodiments are merely typical examples of applying the technical solutions of the present invention, and any technical solutions formed by equivalent substitution or equivalent transformation fall within the scope of protection required by the present invention.

[0027] At the same time, it is declared that the meaning of the term "a plurality" in this solution is two or more, unless otherwise specifically defined.

[0028] The present invention discloses a non-concealing dual-curing three-proof glue, which comprises the following raw material components by weight: Main resin: 40 parts - 65 parts; Acrylate monomer: 20 parts - 40 parts; Photoinitiator: 1 part - 5 parts; Auxiliary agent: 1 part - 5 parts; Rheological auxiliary agent: 1 part - 5 parts; The main resin includes polyurethane acrylate prepolymer A and polyurethane acrylate prepolymer B. The viscosity of polyurethane acrylate prepolymer A is 9500 cps - 25000 cps, and the viscosity of polyurethane acrylate prepolymer B is 5000 cps - 10000 cps. Specifically, the viscosity ranges of the above-mentioned resin A and resin B refer to the viscosity value ranges of resin A and resin B at 60 °C. The mass ratio of polyurethane acrylate prepolymer A to polyurethane acrylate prepolymer B is (1 - 3):1. High-viscosity polyurethane acrylate prepolymer A and low-viscosity polyurethane acrylate prepolymer B are used. Among them, polyurethane acrylate prepolymer A is used to provide structural support, and polyurethane acrylate prepolymer B is used to optimize rheological properties. The dual-resin system avoids the influence of the viscosity fluctuation of a single resin on the overall viscosity of the product, facilitating the precise adjustment of the overall viscosity of the shadow-free dual-curing three-proof adhesive. The acrylate monomer includes a phosphate-modified acrylate monomer and two or more monofunctional acrylate monomers. Among them, the monofunctional acrylate monomer provides flexibility to ensure the cohesive strength of the coating / adhesive layer, and the phosphate-modified acrylate monomer can enhance the crosslinking density of the three-proof adhesive and optimize mechanical properties. The phosphate group can also strengthen the interfacial bonding.

[0029] Among them, the NCO content of both polyurethane acrylate prepolymer A and polyurethane acrylate prepolymer B is 0% - 1%. Due to the use of a polyurethane acrylate resin system with a low NCO content and the application of a photoinitiator, rapid photocuring can be achieved without consuming a large amount of time waiting for moisture curing. At the same time, a small amount of isocyanate can perform moisture curing treatment on local shaded areas that cannot be irradiated by UV light during photocuring, thereby improving the overall curing performance of the coating. In addition, the resin system with a low NCO content can facilitate the improvement of the hydrophobic property of the coating after curing to adapt to extreme environments of high temperature and high humidity.

[0030] In some embodiments, the polyurethane acrylate prepolymer A is a branched-chain polyurethane acrylate resin, which is prepared by reacting a polyfunctional polyol with a functionality of ≥3 with a diisocyanate at 70 °C - 90 °C. The molar ratio of the polyfunctional polyol to the diisocyanate is 1:(2.2 - 3.0). Then, the temperature is lowered to 50 °C - 60 °C, and a hydrophobic branched-chain segment diol is added for reaction. The molar ratio of the hydrophobic branched-chain segment diol to the polyfunctional polyol is (0.8 - 1.2):1. Finally, a hydroxy acrylate monomer is slowly added for reaction. The molar ratio of the hydroxy acrylate monomer to the polyfunctional polyol is (0.5 - 1.5):1. The content of the residual NCO group at the end of the polyurethane acrylate prepolymer A is ≤1% but not 0. In a preferred embodiment, the hydrophobic branched-chain segment diol includes a long-chain aliphatic diol with C12 - C18. The polyurethane acrylate prepolymer A further improves the hydrophobic property of the product by adopting a hydrophobic branched-chain structure.

[0031] In some other embodiments, the polyurethane acrylate prepolymer A may also directly adopt existing products that meet the viscosity and NCO content requirements of the polyurethane acrylate prepolymer A, such as: LuCure8674 produced by Guangzhou Runao Chemical Materials Co., Ltd., DM88A produced by Double Bond Chemical Co., Ltd., or A2888-1 of Guangzhou Handong New Materials Technology Co., Ltd. In addition, other products in the prior art that meet the viscosity and NCO content requirements of the polyurethane acrylate prepolymer A may also be used as substitutes for the above-mentioned products. Therefore, these specific product grades should not be used as limitations on the scope of protection of the present invention.

[0032] In some embodiments, the polyurethane acrylate prepolymer B is a polyurethane acrylate resin with an unbranched structure, which is formed by reacting a linear soft segment polyol with a diisocyanate at 70°C-90°C, wherein the molar ratio of the linear soft segment polyol to the diisocyanate is 1:(2.05-2.25), and then introducing a hydroxy acrylate for reaction, wherein the molar ratio of the hydroxy acrylate to the linear soft segment polyol is (1.00-1.15):1, and the residual NCO group content at the end of the polyurethane acrylate prepolymer B is ≤1% but not 0; the polyurethane acrylate prepolymer B adopts a linear structure, its molecular chains are linearly arranged, there is no cross-linking or only weak physical cross-linking, it has good flexibility and ductility, and has good mechanical properties.

[0033] In some embodiments, the polyurethane acrylate prepolymer B may also directly adopt existing products that meet the viscosity and NCO content requirements of the polyurethane acrylate prepolymer B, for example: FSP8394 produced by Guangzhou Runao Chemical Materials Co., Ltd. or DM5212 produced by Double Bond Chemical Co., Ltd. Other products in the prior art that meet the viscosity and NCO content requirements of the polyurethane acrylate prepolymer B may also be used as substitutes for the above-mentioned products. Therefore, these specific product grades should not be used as limitations on the scope of protection of the present invention.

[0034] In some embodiments, the mass ratio of the monofunctional acrylate monomer to the phosphate-modified acrylate monomer is (20-50):1, and the hydrophobicity of the conformal adhesive is ensured by limiting the added content of the phosphate-modified acrylate monomer.

[0035] In some embodiments, the monofunctional acrylate monomer includes an acrylate monomer with Tg > 50°C and an acrylate monomer with Tg < 25°C. Among them, the higher Tg monomer provides rigidity, improves scratch resistance, strength, and high hydrophobic performance. The low Tg monomer imparts flexibility, impact resistance, and ductility, reduces brittle fracture by dispersing stress, and is suitable for environments with dynamic loads or large temperature differences, avoiding the problems of a single material being too brittle or too soft. The mass ratio of the acrylate monomer with Tg > 50°C to the acrylate monomer with Tg < 25°C is preferably (4 - 12)∶1.

[0036] In some embodiments, the acrylate monomer with Tg > 50°C includes, but is not limited to, one or more of 4-tert-butylcyclohexyl acrylate (TBCHA), isobornyl acrylate (IBOA), acryloylmorpholine (ACMO), N,N-dimethylacrylamide (DMAA), cyclohexyl methacrylate (CHMA), isobornyl methacrylate (IBOMA), methyl methacrylate (MMA), phenyl methacrylate (PhMA); and / or the acrylate monomer with Tg < 25°C includes, but is not limited to, one or more of 2-phenoxyethyl acrylate (PHEA), cyclotrimethylolpropane formal acrylate (CTFA), tetrahydrofurfuryl acrylate (THFA), lauryl acrylate (LA), ethoxyethoxyethyl acrylate (EOEOEA), tetrahydrofurfuryl ethoxy acrylate (THFEOA).

[0037] In some embodiments, the phosphate-modified acrylate monomer includes, but is not limited to, one or more of 2-hydroxyethyl methacrylate phosphate, bis(2-methacryloyloxyethyl) hydrogen phosphate, bis(2-acryloyloxyethyl) phosphate, and ethylene oxide-modified diphosphoric acid diacrylate.

[0038] In some embodiments, the photoinitiator includes, but is not limited to, two or more of methyl benzoylformate (MBF), 2-hydroxy-2-methyl-1-phenylpropan-1-one (UV1173), 2,4,6-trimethylbenzoyl diphenylphosphine oxide (TPO), ethyl 2,4,6-trimethylbenzoyl phenylphosphinate (TPO-L), bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (BAPO), methyl o-benzoylbenzoate (OMBB), etc.

[0039] In some embodiments, the additives include one or more of fluorescent agents, silane coupling agents, and wetting agents. The rheology additive is fumed silica, and hydrophobic fumed silica is preferably used.

[0040] According to the above raw material ratios, the following Examples 1 - 6 are provided, and at the same time, Comparative Examples 1 - 8 for comparison with the Examples are added. The raw material ratios of Examples 1 - 6 and Comparative Examples 1 - 8 are as follows: Example 1:

[0041] It includes the following raw material components by weight: Polyurethane acrylate prepolymer A: 35 parts; Polyurethane acrylate prepolymer B: 20 parts; Acrylate monomer with Tg > 50°C: 30 parts; Acrylate monomer with Tg < 25°C: 5 parts; Phosphate-modified acrylate monomer: 1 part; Photoinitiator: 4 parts; Auxiliary agent: 2 parts; Rheology modifier: 3 parts; In this example, LuCure8674 produced by Guangzhou Run'ao Chemical Materials Co., Ltd. is used as the polyurethane acrylate prepolymer A, and FSP8394 produced by Guangzhou Run'ao Chemical Materials Co., Ltd. is used as the polyurethane acrylate prepolymer B. The acrylate monomer with Tg > 50°C is acryloylmorpholine (ACMO, Tg = 145°C) and isobornyl acrylate (IBOA, Tg = 88°C), and the ratio of the two is m(ACMO)∶ m (IBOA) = 2∶1; The acrylate monomer with Tg < 25°C used in this example is tetrahydrofurfuryl acrylate (THFA, Tg = -20°C); The phosphate-modified acrylate monomer used in this example is 2-hydroxyethyl methacrylate phosphate; The photoinitiators used in this example are 2-hydroxy-2-methyl-1-phenyl-1-propanone (UV1173) and bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (BAPO), and the ratio is m (UV1173)∶ m (BAPO) = 1∶1; The auxiliary agent combination used in this example is a combination of a fluorescent agent, a silane coupling agent, and a wetting agent. Among them, the fluorescent agent is 0.1 part by mass, the silane coupling agent is 1 part by mass, and the wetting agent is 0.9 part by mass. Example 2:

[0042] It includes the following raw material components by weight: Polyurethane acrylate prepolymer A: 30 parts; Polyurethane acrylate prepolymer B: 30 parts; Acrylate monomer with Tg > 50°C: 25 parts; Acrylate monomer with Tg < 25°C: 5 parts; Phosphate-modified acrylate monomer: 1 part; Photoinitiator: 4 parts; Auxiliary agent: 2 parts; Rheology modifier: 3 parts; In this example, the acrylate monomer with Tg > 50°C is isobornyl methacrylate (IBOMA, Tg = 155°C); other raw materials are the same as those in Example 1. Example 3:

[0043] It includes the following raw material components by weight: Polyurethane acrylate prepolymer A: 45 parts; Polyurethane acrylate prepolymer B: 20 parts; Acrylate monomer with Tg > 50°C: 21 parts; Acrylate monomer with Tg < 25°C: 2 parts; Phosphate-modified acrylate monomer: 0.5 part; Photoinitiator: 4.5 parts; Auxiliary agent: 2 parts; Rheology modifier: 5 parts; In this example, the polyurethane acrylate prepolymer A is DM88A produced by Double Bond Chemical Co., Ltd. The acrylate monomer with Tg < 25°C in this example is ethoxyethoxyethyl acrylate (EOEOEA, Tg = -56°C); the photoinitiator is a combination of methyl benzoylformate (MBF), 2-hydroxy-2-methyl-1-phenyl-1-propanone (UV1173), and 2,4,6-trimethylbenzoyl diphenylphosphine oxide (TPO), and the ratio is m (MBF)∶ m (UV1173)∶ m (TPO)=1∶1∶1; other raw materials used in this example are the same as those in Example 1. Example 4:

[0044] It includes the following raw material components by weight: Polyurethane acrylate prepolymer A: 30 parts; Polyurethane acrylate prepolymer B: 17 parts; Acrylate monomer with Tg > 50°C: 33 parts; Acrylate monomer with Tg < 25°C: 5 parts; Phosphate-modified acrylate monomer: 2 parts; Photoinitiator: 5 parts; Auxiliary agent: 4.5 parts; Rheology modifier: 1.5 parts; Except for the above ratios, the raw materials used in this example are the same as those in Example 3. Example 5:

[0045] It includes the following raw material components by weight: Polyurethane acrylate prepolymer A: 20 parts; Polyurethane acrylate prepolymer B: 20 parts; Acrylate monomer with Tg > 50°C: 16 parts; Acrylate monomer with Tg < 25°C: 3 parts; Phosphate-modified acrylate monomer: 1 part; Photoinitiator: 1 part; Auxiliary agent: 1 part; Rheology modifier: 1 part; Except for the above ratios, the raw materials used in this example are the same as those in Example 1. Example 6:

[0046] It includes the following raw material components by weight: Polyurethane acrylate prepolymer A: 45 parts; Polyurethane acrylate prepolymer B: 20 parts; Acrylate monomer with Tg > 50°C: 34 parts; Acrylate monomer with Tg < 25°C: 5 parts; Phosphate-modified acrylate monomer: 1 part; Photoinitiator: 5 parts; Auxiliary agent: 5 parts; Rheology modifier: 5 parts; Except for the above ratios, the raw materials used in this example are the same as those in Example 3.

[0047] Comparative Example 1: It includes the following raw material components by weight: Polyurethane acrylate prepolymer A: 55 parts; Acrylate monomer with Tg > 50°C: 30 parts; Acrylate monomer with Tg < 25°C: 5 parts; Phosphate-modified acrylate monomer: 1 part; Photoinitiator: 4 parts; Auxiliary agent: 2 parts; Rheology modifier: 3 parts; In this comparative example, except for not adding polyurethane acrylate B, the other raw materials are the same as those in Example 1.

[0048] Comparative Example 2: It includes the following raw material components by weight: Polyurethane acrylate prepolymer A: 35 parts; Polyurethane acrylate prepolymer B: 20 parts; Acrylate monomer with Tg < 25°C: 35 parts; Phosphate-modified acrylate monomer: 1 part; Photoinitiator: 4 parts; Auxiliary agent: 2 parts; Rheological auxiliary agent: 3 parts; In this comparative example, except for not adding acrylate monomer with Tg > 50°C, the other raw materials are the same as those in Example 1.

[0049] Comparative Example 3: Comprising the following raw material components by weight: Polyurethane acrylate prepolymer A: 35 parts; Polyurethane acrylate prepolymer B: 20 parts; Acrylate monomer with Tg > 50°C: 31 parts; Acrylate monomer with Tg < 25°C: 5 parts; Photoinitiator: 4 parts; Auxiliary agent: 2 parts; Rheological auxiliary agent: 3 parts; In this comparative example, except for not adding phosphate-modified acrylate monomer, the other raw materials are the same as those in Example 1.

[0050] Comparative Example 4: Comprising the following raw material components by weight: Polyurethane acrylate prepolymer A: 30 parts; Polyurethane acrylate prepolymer B: 27 parts; Acrylate monomer with Tg > 50°C: 25 parts; Acrylate monomer with Tg < 25°C: 5 parts; Phosphate-modified acrylate monomer: 1 part; Photoinitiator: 4 parts; Auxiliary agent: 2 parts; Rheological auxiliary agent: 6 parts; In this comparative example, except for the above ratios, the other raw materials used in this comparative example are the same as those in Example 1.

[0051] Comparative Example 5: Comprising the following raw material components by weight: Polyurethane acrylate prepolymer A: 36 parts; Polyurethane acrylate prepolymer B: 27 parts; Acrylate monomer with Tg > 50°C: 25 parts; Acrylate monomer with Tg < 25°C: 4.5 parts; Phosphate-modified acrylate monomer: 1 part; Photoinitiator: 4 parts; Auxiliary agent: 2 parts; Rheology aid: 0.5 part; In this comparative example, except for the above ratios, the remaining raw materials used in this comparative example are the same as those in Example 1.

[0052] Comparative Example 6: In this comparative example, the polyurethane acrylate prepolymers are respectively a combination of polyurethane acrylate prepolymer C and polyurethane acrylate prepolymer D, wherein polyurethane acrylate prepolymer C is Desmodur® VPLS 2371 produced by Covestro; polyurethane acrylate prepolymer D is DM5212 produced by Double Bond Chemical Co., Ltd. The remaining raw materials used in this comparative example are the same as those in Example 1.

[0053] Comparative Example 7: Comprising the following raw material components by weight: Polyurethane acrylate prepolymer B: 55 parts; Acrylate monomer with Tg > 50 °C: 30 parts; Acrylate monomer with Tg < 25 °C: 5 parts; Phosphate-modified acrylate monomer: 1 part; Photoinitiator: 4 parts; Auxiliary agent: 2 parts; Rheology aid: 3 parts; In this comparative example, except for not adding polyurethane acrylate A, the remaining raw materials are the same as those in Example 1.

[0054] Comparative Example 8: Comprising the following raw material components by weight: Polyurethane acrylate prepolymer A: 20 parts; Polyurethane acrylate prepolymer B: 35 parts; Acrylate monomer with Tg > 50 °C: 30 parts; Acrylate monomer with Tg < 25 °C: 5 parts; Phosphate-modified acrylate monomer: 1 part; Photoinitiator: 4 parts; Auxiliary agent: 2 parts; Rheology aid: 3 parts; In this comparative example, except for replacing the mass ratio of polyurethane acrylate A and polyurethane acrylate prepolymer B, the remaining raw materials are the same as those in Example 1.

[0055] The present invention also simultaneously discloses a preparation method of a mask-free dual-curing three-proof adhesive, comprising the following steps: Step S1: Preparation of raw materials: Prepare the raw materials of the non-shielded dual-curing three-proof glue as described above; Step S2: Pretreatment of raw materials: Preheat the polyurethane acrylate prepolymer A and the polyurethane acrylate prepolymer B in an oven at 60°C - 90°C for 30 minutes respectively to reduce the viscosity of the prepolymers; Step S3: Mixing and dispersion of raw materials: Step S31: Under a yellow light environment, add the polyurethane acrylate prepolymer A and the polyurethane acrylate prepolymer B with a mass ratio of (1 - 3)∶1 into a stirring kettle, and then sequentially add acrylate monomer, photoinitiator and additives, and stir the above raw materials at a speed of 50 - 500 RPM for 1 hour - 2 hours to make the raw materials mix evenly; Step S32: Under the stirring state of Step S31, slowly add the rheological aid into the stirring kettle, and turn on the high-speed dispersion disk of the stirring kettle to disperse the raw materials after the rheological aid. Among them: use a high-speed dispersion disk with a speed ≥1000 RPM, the treatment time is 1 hour - 2 hours, and the peripheral linear speed of the high-speed dispersion disk ≥15 m / s; or use a three-roll mill with a roll spacing of 5μm - 40μm for treatment, the grinding speed <150 RPM, and grind at least twice; after dispersion, a three-proof glue with a viscosity of 2000 cps - 6000 cps and a thixotropic index of 2 - 6 is obtained.

[0056] This preparation method further includes Step S4: Defoaming and packaging of the three-proof glue: Directly put the packaging container filled with the three-proof glue prepared in Step S3 into a homogenizer, and defoam for ≥5 minutes at a vacuum degree ≤ -0.080 MPa and a speed ≥600 RPM and then seal; or first put the three-proof glue prepared in Step S3 into a turnover barrel, put the turnover barrel into a homogenizer, defoam for ≥5 minutes at a vacuum degree ≤ -0.080 MPa and a speed ≥600 RPM, then pour the three-proof glue into the packaging container, and then use a vacuum barrel for secondary vacuum treatment for 10 minutes - 20 minutes and then seal, and the vacuum degree of the vacuum barrel ≤ -0.095 Mpa.

[0057] Based on the raw material ratios of the above embodiments and comparative examples, and the above preparation method, a three-proof glue product is prepared by the following preparation steps: Under yellow light environment, add each raw material except the rheology aid into a stirring kettle, stir at a speed of 100 ± 10 RPM for 1 hour to ensure uniform mixing of the materials; under the stirring state, add the rheology aid into the stirring kettle, turn on the high-speed dispersing disk of the stirring kettle, with a speed of 1200 ± 50 RPM, disperse for 1 hour, and the linear velocity at the edge of the dispersing disk ≥ 15 m / s. After dispersion, a three-proof adhesive is prepared. Subsequently, degassing treatment is performed on the three-proof adhesives prepared in each example and comparative example. Pour the three-proof adhesive after dispersion into an opaque packaging container, and then place it in a homogenizing degassing machine. Degas for 5 minutes under a vacuum degree ≤ -0.080 MPa and a speed ≥ 600 RPM to obtain the finished three-proof adhesive; the packaging container used in Example 3 is a non-cylindrical container and cannot be directly degassed by a homogenizer. Therefore, first use a turnover barrel to degas in a homogenizer under a vacuum degree ≤ -0.080 MPa and a speed ≥ 600 RPM for 5 minutes, then pour it into the packaging container, and use a vacuum barrel with a vacuum degree of -0.095 MPa for secondary vacuum treatment for 10 minutes to obtain the finished three-proof adhesive.

[0058] Meanwhile, a comparative example 9 with a degassing treatment method different from the above method is also provided. The raw materials, their ratios, and the dispersion steps of the raw materials in this comparative example 9 are the same as those in Example 1. However, when preparing this three-proof adhesive, only degas the three-proof adhesive in a vacuum barrel with a vacuum degree of -0.095 MPa for 20 minutes, and then pour it into the packaging container.

[0059] Subsequently, use a precision dispensing machine with a nozzle diameter of 0.1 mm to dispense the finished three-proof adhesives prepared in each example and comparative example on three different PCB test boards respectively. The dispensing thickness is 1 mm. After dispensing, use a UV lamp with a radiation energy of 2000 mJ / cm 2 for curing.

[0060] After the finished three-proof adhesives prepared in each example and comparative example are cured on different PCB test boards, the following performance tests are respectively carried out: 1. Rheological property test: (1) Viscosity test: Use a Brookfield DV2T type rotational viscometer (14# rotor) to measure the viscosity at a constant temperature of 25 ± 1 °C and a speed of 20 RPM; (2) Thixotropy index: Use a Brookfield DV2T type rotational viscometer (14# rotor) to detect the viscosity value (η1) at a speed of 2 RPM and the viscosity value (η2) at a speed of 20 RPM at a temperature of 25 ± 1 °C. The Ti = η1 / η2 viscosity value; The rheological property test results of Examples 1 - 6 and Comparative Examples 1 - 9 are shown in Table 1: Table 1: Rheological property test results of the three-proof adhesive:

[0061] 2. Mechanical properties test: (1) Adhesion test: Refer to ASTM D3359 and GB / T 9286-2021 standards and use the cross-cut method for test evaluation; (2) Hardness test: Refer to GB / T 2411-2008 and use a Shore D hardness tester to measure the hardness of the cured coating; (3) Elongation at break: Tested in accordance with GB / T 1040.1-2018 standard; (4) Tensile strength: Tested in accordance with GB / T 1040.1-2018 standard; The mechanical properties test results of Examples 1-6 and Comparative Examples 1-9 are shown in Table 2: Table 2: Test results of mechanical properties of three-proof adhesive:

[0062] 3. Process suitability test (1) Flat dispensing performance: The test was conducted on a bare PCB board without components. A precision dispensing machine was used to apply 1 mm thick non-shielding three-proof adhesive lines (3 cm) and square patterns (3 cm × 3 cm). The dispensing status was observed with the naked eye and a microscope. The test contents included line width uniformity, square pattern uniformity, area comparison before and after dispensing for 10 minutes, and bubble conditions. (2) PCBA dispensing performance: The test was conducted on a PCBA panel containing devices. A 1 mm thick conformal adhesive coating was applied on the PCBA board using a precision dispensing machine. The dispensing time was recorded. The dispensing status of the coating after UV curing was observed with the naked eye and a microscope, as well as the consistency of each micro-board. The test content included observing with the naked eye and a microscope whether there were bubbles in the coating, whether the conformal adhesive had overflowed, and whether there was excessive sagging. The PCBA panel consisted of 20 small / micro PCBA boards, and the size of the entire board was 13 cm × 35 cm.

[0063] The process applicability test results of Examples 1-6 and Comparative Examples 1-9 are shown in Table 3: Table 3: Test results of the applicability of the three-proof adhesive process:

[0064] in: D represents the average width of the dispensing line, in mm; ΔD represents the width difference between the widest and narrowest parts of the dispensing line, in mm; δD represents the line width deviation, δD=ΔD / D; A0 represents the area of ​​the dispensing area, in cm 2; A 10 represents the area 10 minutes after dispensing, with the unit of cm 2 ; ΔA represents the area difference, with the unit of cm 2 ; δA represents the area deviation before and after 10 minutes of dispensing, δA = ΔA / A0; T represents the dispensing time of the PCBA panel, with the unit of s.

[0065] In the above tests, due to the problem of insufficient addition amount of the rheological aid in Comparative Example 5, the viscosity and thixotropy are both low, so the dispensing thickness cannot reach 1 mm. In the above test results, the dispensing thickness used in Comparative Example 5 is 0.3 mm.

[0066] 4. Environmental reliability test (1) Power-on immersion test: Coat a 1-mm three-proof glue coating on the circuit board with a Debug indicator light. After UV curing, connect the circuit board to a 10V small power supply. When the power is on, the Debug indicator light is on. Immerse it in water at 25 ± 1°C and observe for 72 hours to see if the coating changes color and if the Debug light goes out; (2) Vapor shock test: Coat a 1-mm three-proof glue coating on the circuit board with a Debug indicator light. After UV curing, connect the circuit board to a 10V small power supply. When the power is on, the Debug indicator light is on. Spray the circuit board with saturated water vapor for 8 hours and observe if the coating changes color and if the Debug light goes out; (3) Thermal shock test: Cure the coating on a certain type of PCBA panel with a coating thickness of 1 mm. Place the PCBA board in a high and low temperature alternating test chamber at a temperature of -60 - 125°C, with one cycle every 30 minutes, and do 100 cycles; After the test, observe whether there are any phenomena such as cracking, delamination, and separation on the coating appearance; (4) Temperature and humidity endurance test: Cure the coating on an IPC B25A comb-shaped electrode plate with a coating thickness of 1 mm and place it in a temperature and humidity chamber at 85°C / 85%RH for 1000 h; After the test, observe whether there are any phenomena such as white spots, blisters, pinholes, cracks, wrinkles, peeling, separation, and color change on the coating appearance; (5) Salt spray resistance test: Cure the coating on a certain type of PCBA panel with a coating thickness of 1 mm. Place the PCBA board in a salt spray test chamber and observe whether there are any adverse phenomena such as blisters, rust spots, creep, whitening, blackening, and peeling on the coating appearance after the test.

[0067] The environmental reliability test results of Examples 1 - 6 and Comparative Examples 1 - 9 are shown in Table 4: Table 4: Environmental reliability of the mask-free three-proof glue:

[0068] In the above test results, "failure" means that the Debug lamp goes out or the coating shows abnormalities during the experiment; meanwhile, in the above test, the dispensing thickness used in Comparative Example 5 is 0.3 mm. The coating thickness of Comparative Example 5 is 0.3 mm.

[0069] By analyzing the test results in Tables 1-4, it can be seen that Examples 1-6 use appropriate raw materials and ratios to control the viscosity within the range of 2000 cps - 6000 cps and the thixotropic index within the suitable range of 2-6; this enables Examples 1-4 to achieve a balance between toughness and strength and have good performance in terms of mechanical properties, dispensing process applicability, and environmental reliability.

[0070] Compared with Examples 1-6, each comparative example has deficiencies in different aspects: Comparative Example 1 only uses polyurethane acrylate resin A with high viscosity and a branched structure as the main resin. This choice makes the viscosity of Comparative Example 1 relatively higher and the thixotropic index relatively lower. At the mechanical property level, due to the lack of the regulating effect of linear polyurethane acrylate resin B with a soft segment, Comparative Example 1 shows characteristics of high hardness, high strength but relatively poor toughness. Although it performs excellently in terms of process performance, in terms of environmental reliability, especially in the thermal shock test, cracking occurs at the pin positions of the PCBA device, indicating that the toughness of Comparative Example 1 is insufficient and it cannot adapt to extreme environments.

[0071] Comparative Example 2 only uses THFA with Tg < 25°C as the acrylate monomer, and the formulation lacks monomers with high Tg points. Although Comparative Example 2 has similar effects to Examples 1-4 in terms of rheological properties and dispensing processability, due to only using low-Tg monomers, the overall strength of the material is relatively low. Without the synergistic effect of high-Tg monomers with high hydrophobicity and rigid structures, the waterproof performance of the coating is relatively weak, and it performs poorly under the harsh environmental conditions of steam shock and double 85 shock.

[0072] Comparative Example 3 does not add phosphate-modified acrylate monomers to the formulation system. This monomer plays a key role in promoting the adhesion between the coating and the substrate and improving the coating adhesion; due to the absence of this key component, in the cross-cut test of Comparative Example 3, there is a small amount of peeling at the intersection positions.

[0073] The addition amount of the rheology additive in Comparative Example 4 was too large, resulting in a relatively high overall viscosity and thixotropy index. Although the addition of a high amount of rheology additive gave Comparative Example 4 higher mechanical strength, it also brought the disadvantages of excessive strength and decreased toughness. In addition, due to the relatively high viscosity and thixotropy, the dispensing speed became slower, and the dispensing line width became narrower, resulting in a significant decrease in the dispensing efficiency for coatings of the same area when using Comparative Example 4. Moreover, due to excessive thixotropy, obvious shrinkage of the glue occurred after dispensing. In the PCBA spraying application, insufficient coverage caused by shrinkage of the glue may increase the risk of product failure. In the dispensing test of PCBA panel, the phenomenon of excessive glue hanging was found, and bubbles and even gaps appeared at the bottom of high components, affecting the protection effect of Comparative Example 4 in the environmental reliability test.

[0074] There was a problem of insufficient addition amount of the rheology additive in Comparative Example 5, resulting in relatively low viscosity and thixotropy. During the test, in the actual dispensing process of Comparative Example 5, the line width was too wide and the maintainability of the dispensing area was poor, and there was a risk of glue overflow in the PCBA application. In the PCBA panel dispensing test, glue overflowed into the V-CUT in Comparative Example 5, seriously affecting production. At the same time, due to the low thixotropy index, Comparative Example 5 could not be dispensed to a thickness of 1 mm like other materials, and the maximum thickness could only reach 0.3 mm, which also led to a decrease in the material protection performance of Comparative Example 5, mainly manifested as poor performance in the water resistance-related tests.

[0075] Comparative Example 6 used a polyurethane acrylate prepolymer with the same configuration but a higher NCO content. It also had good dispensing and processability similar to those of Examples 1-6 at the dispensing processability level. However, due to the high NCO content of the main resin, it could not quickly reach the curing effect after UV curing and needed to wait an additional 5-7 days to reach the final curing hardness, affecting production efficiency. And the curing hardness was relatively low, and the corresponding coating strength was also relatively low. At the same time, the use of the resin with a high NCO content led to poor performance in the water resistance-related tests of the coating.

[0076] Comparative Example 7 only used the low-viscosity linear-structured polyurethane acrylate prepolymer B as the main resin. This choice made the coating relatively soft, with poor toughness and high strength under the same ratio conditions. However, at the same time, the coating prepared from this comparative example showed poor performance in the water resistance-related tests.

[0077] Although Comparative Example 8 also used two kinds of polyurethane acrylate prepolymers A and polyurethane acrylate prepolymer B, but with the linear polyurethane acrylate as the main resin, so under the same ratio of other materials, the hardness of the cured coating was relatively low, the tensile strength decreased, and the coating strength was also low. In terms of hydrophobicity, it was also inferior to the sample with polyurethane acrylate prepolymer A as the main body.

[0078] In Comparative Example 9, only vacuum barrel degassing was used in the preparation process, and a homogenizer was not used for degassing. This difference in the process led to poor performance of the finished product during dispensing, and there were more bubbles inside after dispensing; the appearance of a large number of bubbles weakened the protective effect of the coating. During steam impact, thermal shock, damp heat test, and salt spray test, the protective effect was weakened due to the appearance of a large number of bubbles, affecting the reliability and stability of the material.

[0079] There are still various implementation manners of the present invention. All technical solutions formed by equivalent transformation or equivalent substitution fall within the protection scope of the present invention.

Claims

1. A double-curing three-proof adhesive without masking, characterized in that: Comprising the following raw material components by weight parts: Main resin 40 parts - 65 parts; Acrylate monomer 20 parts - 40 parts; Photoinitiator 1 part - 5 parts; Auxiliary agent 1 part - 5 parts; Rheology aid 1 part - 5 parts; The main resin includes polyurethane acrylate prepolymer A and polyurethane acrylate prepolymer B. The viscosity of polyurethane acrylate prepolymer A is 9500 cps - 25000 cps, and the viscosity of polyurethane acrylate prepolymer B is 5000 cps - 10000 cps. The mass ratio of polyurethane acrylate prepolymer A to polyurethane acrylate prepolymer B is (1 - 3)∶1, and the NCO content of both polyurethane acrylate prepolymer A and polyurethane acrylate prepolymer B is 0% - 1%; the acrylate monomer includes phosphate-modified acrylate monomer and two or more monofunctional acrylate monomers.

2. The double-curing three-proof glue without masking according to claim 1, wherein: The polyurethane acrylate prepolymer A is a polyurethane acrylate resin with a branched structure, which is prepared by reacting a polyfunctional polyol with a functionality of ≥3 and a diisocyanate at 70℃ - 90℃. The molar ratio of the polyfunctional polyol to the diisocyanate is 1∶(2.2 - 3.0). Then, the temperature is lowered to 50℃ - 60℃ and a hydrophobic branched-chain segment diol is added for reaction. The molar ratio of the hydrophobic branched-chain segment diol to the polyfunctional polyol is (0.8 - 1.2)∶1. Finally, a hydroxyacrylate monomer is slowly added for reaction. The molar ratio of the hydroxyacrylate monomer to the polyfunctional polyol is (0.5 - 1.5)∶1. The content of the residual NCO group at the end of the polyurethane acrylate prepolymer A is ≤1% but not 0; and / or the polyurethane acrylate prepolymer B is a polyurethane acrylate resin without a branched structure, which is prepared by reacting a linear soft-segment polyol and a diisocyanate at 70℃ - 90℃. The molar ratio of the linear soft-segment polyol to the diisocyanate is 1∶(2.05 - 2.25). Then, a hydroxyacrylate is introduced for reaction. The molar ratio of the hydroxyacrylate to the linear soft-segment polyol is (1.00 - 1.15)∶1. The content of the residual NCO group at the end of the polyurethane acrylate prepolymer B is ≤1% but not 0.

3. The double-curing three-proof glue without masking according to claim 2, wherein: The hydrophobic branched-chain segment diol includes C12 - C18 long-chain aliphatic diols.

4. The double-curing three-proof glue without masking according to claim 1, characterized in that: The mass ratio of the monofunctional acrylate monomer to the phosphate-modified acrylate monomer is (20 - 50)∶1.

5. The double-curing three-proof glue without masking according to claim 4, wherein: The monofunctional acrylate monomer includes an acrylate monomer with Tg > 50℃ and an acrylate monomer with Tg < 25℃. The mass ratio of the acrylate monomer with Tg > 50℃ to the acrylate monomer with Tg < 25℃ is (4 - 12)∶1.

6. The double-curing three-proof glue without masking according to claim 5, characterized in that: The acrylate monomers with Tg > 50°C include, but are not limited to, one or more of 4-tert-butylcyclohexyl acrylate, isobornyl acrylate, acryloylmorpholine, N,N-dimethylacrylamide, cyclohexyl methacrylate, isobornyl methacrylate, methyl methacrylate, phenyl methacrylate; and / or the acrylate monomers with Tg < 25°C include, but are not limited to, one or more of 2-phenoxyethyl acrylate, trimethylolpropane formal acrylate, tetrahydrofurfuryl acrylate, lauryl acrylate, ethoxyethoxyethyl acrylate, tetrahydrofurfuryl ethoxy acrylate; and / or the phosphate-modified acrylate monomers include, but are not limited to, one or more of 2-hydroxyethyl methacrylate phosphate, bis(2-methacryloyloxyethyl) hydrogen phosphate, bis(2-acryloyloxyethyl) phosphate, ethylene oxide-modified diphosphate acrylate.

7. The double-curing three-proof glue without masking according to claim 6, characterized in that: The photoinitiators include, but are not limited to, two or more of methyl benzoylformate, 2-hydroxy-2-methyl-1-phenyl-1-propanone, 2,4,6-trimethylbenzoyl diphenylphosphinate, ethyl 2,4,6-trimethylbenzoyl phenylphosphinate, bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, methyl o-benzoylbenzoate.

8. The double-curing three-proof glue without masking according to claim 1, characterized in that: The additives include one or more of fluorescent agents, silane coupling agents, wetting agents, and the rheology additive is hydrophobic fumed silica.

9. Preparation method of a shielding-free dual-curing three-proof adhesive, characterized in that: It includes the following steps: Step S1: Preparation of raw materials: Prepare the raw materials of the mask-free dual-curing three-proof glue as described in any one of claims 1-8. Step S2: Pretreatment of raw materials: Preheat the polyurethane acrylate prepolymer A and the polyurethane acrylate prepolymer B in an oven at 60°C - 90°C for 30 minutes respectively to reduce the viscosity of the prepolymers. Step S3: Mixing and dispersion of raw materials: Step S31: Under a yellow light environment, add the polyurethane acrylate prepolymer A and the polyurethane acrylate prepolymer B with a mass ratio of (1-3):1 into a stirring kettle, and sequentially add acrylate monomers, photoinitiators, and additives, and stir the above raw materials at a speed of 50RPM - 500RPM for 1 hour - 2 hours to make the raw materials evenly mixed. Step S32: Under the stirring state of Step S31, slowly add the rheology additive into the stirring kettle, and turn on the high-speed dispersion disk of the stirring kettle to disperse the raw materials after adding the rheology additive, where: use a high-speed dispersion disk with a speed ≥ 1000RPM, the treatment time is 1 hour - 2 hours, and the peripheral linear velocity of the high-speed dispersion disk ≥ 15m / s; or use a three-roll mill with a roll spacing of 5μm - 40μm for treatment, the grinding speed < 150RPM, and grind at least twice; after dispersion, a three-proof glue with a viscosity of 2000 cps - 6000cps and a thixotropic index of 2 - 6 is obtained.

10. The preparation method of the unshielded dual-curing three-proof adhesive according to claim 9, characterized in that: It also includes: Step S4: Degassing and packaging of the three-proof glue: directly put the packaging container containing the three-proof glue prepared in step S3 into the homogenizer, degas for ≥5 minutes at a vacuum degree ≤-0.080MPa and a rotation speed ≥600RPM, and then package it; alternatively, first put the three-proof glue prepared in step S3 into a turnover barrel, put the turnover barrel into the homogenizer, degas for ≥5 minutes at a vacuum degree ≤-0.080MPa and a rotation speed ≥600RPM, and then pour the three-proof glue into the packaging container, and then use a vacuum barrel for secondary vacuum treatment for 10-20 minutes before packaging, and the vacuum degree of the vacuum barrel is ≤-0.095Mpa.

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