Epoxydized polyurethane acrylate prepolymer, preparation method thereof, uv photocuring sunscreen adhesive prepared from the same and application

Abstract

The application relates to the technical field of light-cured adhesives and display materials, and discloses an epoxidized polyurethane acrylate prepolymer, a preparation method thereof, UV light-cured light-shielding glue prepared from the epoxidized polyurethane acrylate prepolymer and application. The epoxidized polyurethane acrylate prepolymer is prepared from the reaction of an epoxidized hydroxyl-terminated polybutadiene, isophorone diisocyanate and a hydroxyl-containing acrylate monomer, and simultaneously contains an epoxy group and an acrylate double bond on a molecular chain. The light-shielding glue prepared from the epoxidized polyurethane acrylate prepolymer prepared by the application has the performances of low shrinkage, high curing depth, excellent adhesion and high and low temperature impact resistance through a cationic / radical hybrid curing mechanism, and is suitable for the fields of display device frame light shielding and optical element packaging.

Description

Technical Field

[0001] This invention relates to the field of photocurable adhesives and display materials, specifically to an epoxy polyurethane acrylate prepolymer and its preparation method, a UV-curable light-shielding adhesive prepared therefrom, and its applications. The UV-curable light-shielding adhesive is suitable for light shielding of display device bezels and for the encapsulation of optical components. Background Technology

[0002] As display technology advances towards full-screen and narrow-bezel designs, higher demands are being placed on side-shielding materials. An ideal light-shielding material must possess high light-shielding properties (optical density OD value), low curing shrinkage, high cross-linking density, excellent adhesion, water resistance, chemical corrosion resistance, and resistance to high and low temperature impacts. Currently, most light-shielding materials utilize ultraviolet (UV) curing systems, primarily including free radical curing, cationic curing, and hybrid curing systems.

[0003] Free radical curing systems have fast curing speeds, but suffer from problems such as large curing shrinkage, oxygen inhibition, and incomplete curing in shaded areas, affecting coating adhesion and long-term reliability. Cationic curing systems have low shrinkage, no oxygen inhibition, and strong post-curing effects, but are sensitive to environmental humidity and have relatively slow curing rates.

[0004] CN116162431A discloses a photothermal hybrid curing adhesive, which achieves photothermal dual curing by combining modified epoxidized polybutadiene with modified anhydride-modified polybutadiene, thereby improving resistance to damp heat. However, this system has limited curing depth and complex composition, posing challenges to storage stability. CN114292607A discloses an adhesive containing polyphenylene ether and epoxidized polybutadiene, aiming for low dielectric properties, but it is not optimized for high curing depth and environmental resistance in light-shielding applications.

[0005] In existing technologies, simple free radical or cationic curing opacifiers cannot simultaneously meet the stringent requirements of low shrinkage, high curing depth (e.g., 5mm or more), and high weather resistance. Especially in the dispensing process, deep curing of thick adhesive layers is a major technical challenge. Existing hybrid curing systems also suffer from insufficient curing depth and weather resistance. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art and provide an epoxidized polyurethane acrylate prepolymer, its preparation method, a UV-curable light-blocking adhesive prepared therefrom, and its applications.

[0007] The light-shielding adhesive provided by this invention, through a unique epoxidized polyurethane acrylate prepolymer synthesis design, combined with a cationic and free radical hybrid curing mechanism, can achieve low shrinkage, high crosslinking density, and extremely high curing depth (up to 5 mm or more), while also endowing the coating with excellent water resistance, acid and alkali resistance, and high and low temperature impact resistance.

[0008] To achieve the above objectives, the first aspect of the present invention provides a method for preparing an epoxidized polyurethane acrylate prepolymer, wherein the method includes the following steps: (1) In the presence of a catalyst, the epoxidized hydroxyl-terminated polybutadiene and isophorone diisocyanate undergo a first reaction. The reaction is stopped when the difference between the NCO content values ​​obtained from two consecutive sampling titrations is less than 0.1%. (2) After the first reaction is completed, hydroxyl-containing acrylate monomers are added, the temperature is raised to carry out the second reaction, and the characteristic infrared absorption peak of NCO is monitored until it disappears, and the epoxidized polyurethane acrylate prepolymer is obtained.

[0009] A second aspect of the present invention provides an epoxidized polyurethane acrylate prepolymer obtained according to the method of the first aspect.

[0010] A third aspect of the present invention provides the use of the epoxidized polyurethane acrylate prepolymer according to the second aspect in the preparation of UV-curable light-shielding adhesive.

[0011] The fourth aspect of the present invention provides a UV-curable light-blocking adhesive, wherein the light-blocking adhesive comprises the following components in parts by weight: 30-60 parts of the epoxy polyurethane acrylate prepolymer described in the second aspect; 30-50 parts of the reactive diluent monomer; 6-13 parts of the photoinitiator; 0.5-2 parts of the light-blocking agent; and 1-3 parts of the additives.

[0012] The fifth aspect of this invention provides the application of the UV-curable light-shielding adhesive described in the fourth aspect in the fields of light-shielding for display device bezels or packaging for optical components.

[0013] The beneficial technical effects achieved by the present invention through the above technical solution are as follows: (1) Low shrinkage and high crosslinking density: The inherent volume expansion or low shrinkage characteristics of cationic ring-opening polymerization, together with free radical polymerization, form an interpenetrating network (IPN) or synergistic network, which significantly reduces the overall curing shrinkage of the system, reduces internal stress, and improves the adhesion and impact resistance of the coating to the substrate. The high crosslinking network endows the coating with excellent hardness and acid and alkali resistance.

[0014] (2) Extremely high curing depth: Cationic polymerization is not affected by oxygen inhibition and has a post-curing effect, which can continuously initiate deep curing. By optimizing the prepolymer structure and selecting long-wavelength free radical initiators, the light-shielding adhesive of the present invention can achieve complete curing of thicknesses of 5 mm and above under irradiation by a 405 nm LED light source, solving the core problem of thick adhesive layer applications.

[0015] (3) Excellent environmental resistance: The polybutadiene backbone is highly hydrophobic and the epoxy-acrylate hybrid network is dense, which makes the coating have extremely low water absorption, excellent water resistance, acid and alkali resistance and high and low temperature impact resistance (no cracking after cycling at -40℃~85℃).

[0016] (4) Good process adaptability: The viscosity of the system is adjustable, and it is suitable for various processes such as dispensing, spraying, and scraping. The surface is quickly set after light exposure, and the deep layer is fully cured by cationic post-curing, which is suitable for light-shielding and sealing of complex structural parts or shaded areas. Detailed Implementation

[0017] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0018] The first aspect of this invention provides a method for preparing an epoxidized polyurethane acrylate prepolymer, wherein the method includes the following steps: (1) In the presence of a catalyst, the epoxidized hydroxyl-terminated polybutadiene and isophorone diisocyanate undergo a first reaction. The reaction is stopped when the difference between the NCO content values ​​obtained from two consecutive sampling titrations is less than 0.1%. (2) After the first reaction is completed, hydroxyl-containing acrylate monomers are added, the temperature is raised to carry out the second reaction, and the characteristic infrared absorption peak of NCO is monitored until it disappears, and the epoxidized polyurethane acrylate prepolymer is obtained.

[0019] In this invention, the NCO group on the isophorone diisocyanate (IPDI) ring has higher activity than the NCO group on the side chain, and this difference is amplified in the presence of a catalyst (e.g., dibutyltin dilaurate DBTDL). In step (1), both hydroxyl groups of the epoxidized hydroxyl-terminated polybutadiene are capped by the NCO group on the IPDI ring. After the first reaction, the NCO group on the IPDI side chain is almost not consumed. In step (2), after adding the hydroxyl-containing acrylate monomer and heating, the NCO activity of the side chain increases, thereby reacting with the hydroxyl-containing acrylate and resulting in a free radical photocuring effect.

[0020] In this invention, isophorone diisocyanate may be in excess. The first reaction is preferably carried out in dry air (atmosphere).

[0021] The prepolymer prepared by this invention combines the low polarity, flexibility and low hygroscopicity of polybutadiene segments, the cationic curing characteristics (low shrinkage, deep curing) brought by epoxy groups, and the rapid free radical curing characteristics brought by acrylate double bonds.

[0022] In some embodiments of the present invention, the temperature of the first reaction is 5-25°C.

[0023] In some embodiments of the present invention, the temperature of the second reaction is 60-90°C, preferably 80°C.

[0024] In some embodiments of the present invention, the catalyst is selected from at least one of dibutyltin dilaurate and stannous octoate.

[0025] In some embodiments of the present invention, the number average molecular weight of the epoxidized hydroxyl-terminated polybutadiene is 1400-3000, preferably 1450 or 3000.

[0026] In some embodiments of the present invention, the epoxidized hydroxyl-terminated polybutadiene is Polybd. ® 605E and Polybd ® 700i.

[0027] In some embodiments of the present invention, the hydroxyl-containing acrylate monomer is hydroxyethyl acrylate (HEA) and / or hydroxyethyl methacrylate (HEMA).

[0028] In some embodiments of the present invention, the molar ratio of the epoxidized hydroxyl-terminated polybutadiene, isophorone diisocyanate and hydroxyl-containing acrylate monomer is 1:1.5-2:1-2, preferably 1:2:2.

[0029] According to a particularly preferred embodiment of the present invention, a method for preparing an epoxidized polyurethane acrylate prepolymer includes: Under a dry atmosphere, epoxidized hydroxyl-terminated polybutadiene and IPDI are added to a reactor, along with 0.05-0.1% of a catalyst (e.g., dibutyltin dilaurate) and 0.1-0.2% of a polymerization inhibitor (e.g., BHT). The epoxidized hydroxyl-terminated polybutadiene and IPDI react at 5-25°C. The reaction is monitored by di-n-butylamine titration until the isocyanate content change rate is <0.1%. Then, hydroxyl-containing acrylate monomers are added to continue the reaction until the characteristic infrared absorption peak of the isocyanate group disappears, yielding an epoxidized polyurethane acrylate prepolymer.

[0030] A second aspect of the present invention provides an epoxy polyurethane acrylate prepolymer obtained according to the method of the first aspect. The epoxy polyurethane acrylate prepolymer molecular chain simultaneously contains an epoxy group capable of cationic curing and an acrylate double bond capable of free radical curing.

[0031] A third aspect of the present invention provides the use of the epoxidized polyurethane acrylate prepolymer according to the second aspect in the preparation of UV-curable light-shielding adhesive.

[0032] The fourth aspect of this invention provides a UV-curable light-blocking adhesive, wherein the light-blocking adhesive comprises the following components in parts by weight: 30-60 parts (e.g., 30, 35, 40, 45, 50, 55, or 60 parts) of the epoxy polyurethane acrylate prepolymer described in the second aspect; 30-50 parts (e.g., 30, 34, 40, 44, or 50 parts) of reactive diluent monomer; 6-13 parts of photoinitiator; 0.5-2 parts of light-blocking agent; and 1-3 parts of additives.

[0033] In some embodiments of the present invention, the reactive diluent monomer is used to adjust the viscosity of the system and participate in the curing network, including 5-15 parts of cationic curing diluent monomer and 25-45 parts of free radical curing diluent monomer; the free radical curing diluent monomer preferably includes 20-40 parts of monofunctional acrylate monomer and 2-5 parts of polyfunctional acrylate monomer.

[0034] In some embodiments of the present invention, the cationic curing diluent monomer is selected from at least one of vinyl ethers, epoxy compounds, cyclic ethers, and lactones, preferably from at least one of 1,4-cyclohexanediethanol divinyl ether, diethylene glycol monovinyl ether, 1,4-butanediol diglycidyl ether, tetrahydrofuran, and ε-caprolactone, and more preferably diethylene glycol monovinyl ether. Diethylene glycol monovinyl ether can participate in both free radical curing and cationic curing reactions, exhibiting a fast reaction rate. It is a substance, other than epoxidized polyurethane acrylate prepolymers, that enables crosslinking through both free radical curing and cationic curing. Its preferred weight percentage is 5 parts.

[0035] In some embodiments of the present invention, the monofunctional acrylate monomer is used to reduce shrinkage and improve toughness, and is selected from at least one of isobornyl acrylate (IBOA), hydroxyethyl acrylate (HEA), tetrahydrofuran acrylate (THFA), and acrylmorpholine (ACMO), preferably isobornyl acrylate (IBOA) and acrylmorpholine (ACMO). The monofunctional acrylate monomer is preferably 26 parts isobornyl acrylate (IBOA) and 10 parts acrylmorpholine (ACMO) to achieve a balanced reaction rate and adhesive layer hardness.

[0036] In some embodiments of the present invention, the multifunctional acrylate monomer is used to improve the crosslinking density and curing rate, and is selected from at least one of trimethylolpropane triacrylate (TMPTA) and dipentaerythritol hexaacrylate (DPHA), preferably trimethylolpropane triacrylate (TMPTA). Preferably, the multifunctional acrylate monomer is 3 parts of trimethylolpropane triacrylate (TMPTA).

[0037] In some embodiments of the present invention, the photoinitiator comprises 1-3 parts of a cationic photoinitiator and 5-10 parts of a free radical photoinitiator.

[0038] In some embodiments of the present invention, the cationic photoinitiator is selected from diaryliodomonium salts (such as Irgacure 250) or triarylthionium salts (such as CPI-210S), preferably diaryliodomonium salts. The cationic photoinitiator is preferably 2 parts of Irgacure 250.

[0039] In some embodiments of the present invention, the free radical photoinitiator is selected from at least one of acylphosphine oxide photoinitiators (e.g., TPO, Irgacure 819). α-hydroxy ketones (e.g., Irgacure 184) can be added to enhance surface curing. The free radical photoinitiator is preferably a combination of 5 parts Irgacure 819 and 1 part TPO to improve the curing depth.

[0040] An opaque agent is a pigment (paste or colorant) that reflects or absorbs visible light wavelengths but allows ultraviolet light to pass through. Preferably, it is a colorant or paste with good solubility or dispersibility in the system. In some embodiments of the invention, the opaque agent is a carbon black paste or black colorant. In some embodiments of the invention, the opaque agent is selected as 0.5-2 parts of Special Black 250; preferably 1 part of Special Black 250, ensuring opacity while maintaining good curing depth.

[0041] In some embodiments of the present invention, the additive is selected from at least one of leveling agents, coupling agents, defoamers, and antioxidants.

[0042] In some embodiments of the present invention, the leveling agent is used to improve the wetting and leveling of the opaque adhesive on the substrate, and is selected from at least one of modified polydimethylsilane and polyether polyester modified organosiloxane, preferably polyether modified polysiloxane. In the present invention, the leveling agent can be selected at 0.1-1 parts, and in some embodiments of the present invention, 0.5 parts of polyether modified polysiloxane (BYK-3505) is preferred.

[0043] In some embodiments of the present invention, the coupling agent can participate in the photocuring reaction to improve adhesion and water resistance to substrates such as glass and metal. It is γ-(2,3-epoxypropoxy)propyltrimethoxysilane (KH560) and / or γ-methacryloyloxypropyltrimethoxysilane (KH570), preferably γ-(2,3-epoxypropoxy)propyltrimethoxysilane (KH560). In the present invention, the coupling agent can be selected as 0.5-3 parts. In some embodiments of the present invention, 1.5 parts of γ-(2,3-epoxypropoxy)propyltrimethoxysilane (KH560) are preferred, as it can both crosslink with the epoxidized polyurethane acrylate prepolymer and react with the hydroxyl groups of substrates such as glass and metal.

[0044] In this invention, the light-shielding adhesive can be prepared by the following method: under light-shielding conditions, the reactive diluent monomer, photoinitiator, additive and light-shielding agent are mixed evenly according to the formula; then the epoxidized polyurethane acrylate prepolymer is added and stirred or dispersed until uniform; finally, the UV-curable light-shielding adhesive is obtained by degassing and filtration.

[0045] The fifth aspect of this invention provides the application of the UV-curable light-shielding adhesive described in the fourth aspect in the fields of light-shielding for display device bezels or packaging for optical components.

[0046] The present invention will be described in detail below through embodiments.

[0047] Unless otherwise specified in the following examples and comparative examples, all conditions were performed under standard conditions or conditions recommended by the manufacturer. Reagents or instruments used, unless otherwise specified, are all commercially available products.

[0048] Example 1 This embodiment illustrates the preparation of epoxidized polyurethane acrylate prepolymer and UV-curable light-shielding adhesive.

[0049] (1) Under dry air protection, add 500g (about 0.35mol) of Polybd to a four-necked flask equipped with a stirrer, thermometer and condenser. ® 605E, 0.1g dibutyltin dilaurate, and 0.2g 2,6-di-tert-butyl-p-cresol (BHT) were added dropwise at a constant temperature of ≤25℃. 155.6g (0.70mol) isophorone diisocyanate (IPDI) was added dropwise over 3 hours. After the addition was complete, samples were taken at 5-minute intervals, and the NCO content was determined using the di-n-butylamine method (HG / T 2409-2023). After two sampling tests showed an NCO content change rate <0.1%, 81.3g (0.70mol) hydroxyethyl acrylate (HEA) was added, and the reaction was carried out at 80℃. The characteristic peak of NCO (2260cm⁻¹) was monitored by infrared spectroscopy every hour. -1Continue cooling until the peak completely disappears; cool to below 50°C and discharge to obtain a light yellow viscous liquid, denoted as prepolymer A.

[0050] (2) Preparation of light-shielding adhesive According to the formula (parts by weight) shown in Table 1, add the reactive diluent monomer, photoinitiator, opaque agent, leveling agent and coupling agent in sequence to a brown glass container, and stir until the photoinitiator is completely dissolved; then add prepolymer A, disperse it in a planetary mixer at 2000 rpm for 10 min, and then degas it under vacuum and filter it through a 5μm filter bag to obtain a uniform and fine UV-curable opaque.

[0051] Example 2 The difference from Example 1 is that: in step (1), hydroxyethyl acrylate (HEA) is replaced with an equal molar amount of hydroxyethyl methacrylate (HEMA), and the resulting product is denoted as prepolymer B; in step (2), prepolymer A is replaced with an equal part by weight of prepolymer B.

[0052] Example 3 The difference from Example 1 is that: in step (1), the amount of isophorone diisocyanate (IPDI) is 116.7g (0.525mol) and the amount of hydroxyethyl acrylate (HEA) is 40.6g (0.35mol), and the resulting product is denoted as prepolymer H; the formulation of the light-shielding adhesive in step (2) is different (as shown in Table 1).

[0053] Example 4 The difference from Example 1 is that the formulation of the light-shielding adhesive in step (2) is different (as shown in Table 1).

[0054] Example 5 The difference from Example 1 is that Polybd in step (1) is removed. ® Replace 605E with 1050g (0.35mol) of Polybd. ® 700i (number average molecular weight = 3000), the product obtained is denoted as prepolymer E; replace prepolymer A in step (2) with an equal part by weight of prepolymer E.

[0055] Comparative Example 1 The difference from Example 1 is that isophorone diisocyanate (IPDI) in step (1) is replaced with an equimolar amount of dicyclohexylmethane diisocyanate (HMDI), and the resulting product is denoted as prepolymer C; prepolymer A in step (2) is replaced with an equimolar amount of prepolymer C.

[0056] Comparative Example 2 The difference from Comparative Example 1 is that: in step (1), hydroxyethyl acrylate (HEA) is replaced with an equal molar amount of hydroxyethyl methacrylate (HEMA), and the resulting product is denoted as prepolymer D; in step (2), prepolymer A is replaced with an equal part by weight of prepolymer D.

[0057] Comparative Example 3 (1) Under dry air protection, add 500g (about 0.35mol) of Polybd to a four-necked flask equipped with a stirrer, thermometer and condenser. ® 605E, 0.1g dibutyltin dilaurate, 0.2g 2,6-di-tert-butyl-p-cresol (BHT); maintain temperature ≤45℃; add 89.7g (approximately 0.87mol) ethyl isocyanate acrylate (AOI) dropwise at a uniform rate; after the addition is complete, monitor the NCO characteristic peak (2260cm) using infrared spectroscopy every 1 hour. - ¹), until the peak completely disappears; a light yellow viscous liquid is obtained, denoted as prepolymer F.

[0058] (2) Replace the prepolymer A in step (2) of Example 1 with an equal part by weight of prepolymer F.

[0059] Comparative Example 4 (1) Under dry air protection, add 500g (about 0.35mol) of Polybd to a four-necked flask equipped with a stirrer, thermometer and condenser. ® 605E, 0.1g dibutyltin dilaurate, 0.2g 2,6-di-tert-butyl-p-cresol (BHT); maintain temperature ≤45℃; uniformly add 135g (approximately 0.87mol) of ethyl isocyanate 2-methacrylate (MOI). After the addition is complete, monitor the NCO characteristic peak (2260cm) using infrared spectroscopy every 1 hour. - ¹), until the peak completely disappears; a light yellow viscous liquid is obtained, denoted as prepolymer G.

[0060] (2) Replace the prepolymer A in step (2) of Example 1 with an equal part by weight of prepolymer G.

[0061] Table 1

[0062] Test case The UV-curable light-blocking adhesives prepared in Examples 1-5 and Comparative Examples 1-4 were subjected to performance tests. The specific test methods, standards, and results are as follows.

[0063] Test methods and standards: Viscosity: Measured at 25°C using a Brookfield DV-II viscometer.

[0064] Curing depth: Inject the adhesive sample into a transparent PE tube (10mm inner diameter) and cure it under a 405nm LED light (1000mW / cm²). 2 Irradiate for 60 seconds, keep at a constant temperature of 25℃ for 24 hours, then remove and scrape off the uncured soft part, and measure the length of the cured part. Test each sample 5 times and take the average value.

[0065] Volume shrinkage rate: The density change before and after curing is measured using the hydrometer bottle method, and the volume shrinkage rate is calculated. According to GB / T 39818-2021, the shrinkage rate (%) is calculated as follows: = (1 - density before curing / density after curing) × 100%.

[0066] Shear strength: Glass / glass overlap specimens were prepared, fully cured under a 405nm LED lamp, and placed at a constant temperature of 25℃ for 24 hours. Shear strength was then tested according to GB / T 7124-2008.

[0067] Adhesion: The adhesive layer was applied to a glass substrate, and the sample was tested under a 405nm LED light (light intensity 1000mW / cm²). 2 Irradiate for 60 seconds, keep at a constant temperature of 25°C for 24 hours, and after curing, use a cross-cutting tool to score the surface and then peel it off with 3M tape. ASTM D3359-23 rating standard: 5B (completely smooth cutting edge), 0B (peeling area >65%).

[0068] Hardness: Sample under 405nm LED light (light intensity 1000mW / cm²) 2 Irradiate for 60 seconds, then keep at a constant temperature of 25℃ for 24 hours to allow for complete curing. After curing, test the sample using a Shore hardness tester. Test the Shore D hardness according to GB / T 2411-2008.

[0069] Glass transition temperature (Tg): Tested using a dynamic thermomechanical analyzer (DMA).

[0070] Water absorption rate: Sample under 405nm LED light (light intensity 1000mW / cm²) 2 Irradiate for 60 seconds, then place at a constant temperature of 25℃ for 24 hours. Dry the cured sample (uniform size) at 50℃ to constant weight (W0), then immerse it in deionized water at 25℃ for 24 hours. Remove, wipe off surface moisture, and weigh (W1). Calculate the water absorption rate (%) according to ISO 62:2008: (W1-W0) / W0×100%.

[0071] High and low temperature shock resistance: Place the cured glass-to-glass adhesive sample in a thermal shock test chamber and maintain it at -40℃ for 30 minutes. Then, raise the temperature to 85℃ within 1 minute and maintain it for 30 minutes. This constitutes one cycle. After 100 cycles, observe whether there is cracking or delamination, and test the shear strength retention rate.

[0072] Chemical resistance (acid and alkali resistance): The fully cured adhesive layer was immersed in 10% H2SO4 and 10% NaOH aqueous solutions respectively for 24 hours at room temperature, and the changes in the appearance of the adhesive layer were observed. Record whether there was swelling, dissolution, discoloration or peeling.

[0073] Optical density (light-shielding property): The sample is coated into a thin film of fixed thickness (50 μm) and cured. It is then scanned using a UV-Vis spectrophotometer within the visible light wavelength range of 400-700 nm. Optical density OD = Log(incident light intensity / transmitted light intensity). The higher the OD value, the better the light-shielding property.

[0074] The performance test results are shown in Table 2.

[0075] Table 2

[0076] Continued from Table 2

[0077] According to the test results in Table 2, the free radical / cationic hybrid curing light-shielding adhesive prepared by using epoxidized polyurethane acrylate prepolymer synthesized from cationic curable epoxidized hydroxyl-terminated polybutadiene and hydroxyl-containing acrylate as raw materials has good curing depth, while maintaining low volume shrinkage rate, good resistance to high and low temperature impact, good acid and alkali resistance, good adhesion to glass substrate, and high optical density value.

[0078] The light-shielding adhesives prepared in Comparative Examples 1 and 2 showed higher 24-hour water absorption rates and significantly lower high and low temperature impact strength compared to Example 1. This is because the diisocyanate used in the synthesis of the prepolymer was HMDI, whose two isocyanate groups have no difference in activity, resulting in low selectivity in the reaction with epoxidized hydroxyl-terminated polybutadiene. During the reaction, a large number of the two isocyanate groups in HMDI may react with the epoxidized hydroxyl-terminated polybutadiene, leading to the grafting of acrylate without free radical curing, resulting in a lower crosslinking network density after photocuring. Due to the deeper curing depth, the initial reaction mainly involves cationic reactions, and the curing depth is not significantly different from other examples.

[0079] The prepolymers synthesized in Comparative Examples 3 and 4 were prepolymers of epoxidized hydroxyl-terminated polybutadiene directly polymerized with the isocyanate groups of AOI and MOI, introducing free radical curing groups. The light-shielding adhesives prepared in Comparative Examples 3 and 4 were inferior to those in Example 1 in terms of acid and alkali resistance and high and low temperature impact resistance. The reason for the higher volume shrinkage rate after curing is that the AOI structure is flexible, has no steric hindrance, and is easy to pack tightly, while the MOI structure has α-methyl steric hindrance, is rigid, and is loosely packed. However, the IPDI alicyclic structure has good rigidity, and the network is not easy to collapse. Overall, the light-shielding adhesives prepared by combining IPDI with HEA / HEMA (Examples 1 and 2) have a lower volume shrinkage rate after photocuring than those of AOI and MOI.

[0080] The UV-curable light-shielding adhesive prepared in this invention, through a unique epoxidized polyurethane acrylate prepolymer design and a cationic / free radical hybrid curing system, successfully achieves low shrinkage, extremely high curing depth (>5mm), and excellent environmental resistance. Its comprehensive performance is superior to existing technology products, and it fully meets the application requirements of light-shielding for high-end display device bezels and optical component packaging.

[0081] This invention provides a high-performance UV-curable light-shielding adhesive, which is particularly suitable for applications requiring high curing depth, low stress, and high reliability, such as light-shielding of display device frames and sealing of optical components, and has broad prospects for industrial applications.

[0082] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for preparing an epoxidized polyurethane acrylate prepolymer, characterized in that, The method includes the following steps: (1) In the presence of a catalyst and in a dry atmosphere, the epoxidized hydroxyl-terminated polybutadiene and isophorone diisocyanate undergo a first reaction. The reaction is stopped when the difference between the NCO content values ​​obtained from two consecutive sampling titrations is less than 0.1%. (2) After the first reaction is completed, hydroxyl-containing acrylate monomers are added, the temperature is raised to carry out the second reaction, and the characteristic infrared absorption peak of NCO is monitored until it disappears, and the epoxidized polyurethane acrylate prepolymer is obtained.

2. The method according to claim 1, wherein, The temperature of the first reaction is 5-25℃; Preferably, the temperature of the second reaction is 60-90°C, and more preferably 80°C.

3. The method according to claim 1 or 2, wherein, The catalyst is selected from at least one of dibutyltin dilaurate and stannous octoate; Preferably, the number-average molecular weight of the epoxidized hydroxyl-terminated polybutadiene is 1400-3000, more preferably 1450 or 3000; Preferably, the epoxidized hydroxyl-terminated polybutadiene is Polybd. ® 605E and Polybd ® 700i; Preferably, the hydroxyl-containing acrylate monomer is hydroxyethyl acrylate and / or hydroxyethyl methacrylate; Preferably, the molar ratio of the epoxidized hydroxyl-terminated polybutadiene, isophorone diisocyanate, and hydroxyl-containing acrylate monomer is 1:1.5-2:1-2, and more preferably 1:2:

2.

4. The epoxidized polyurethane acrylate prepolymer obtained by the method according to any one of claims 1-3.

5. The application of the epoxy polyurethane acrylate prepolymer according to claim 4 in the preparation of UV-curable light-shielding adhesive.

6. A UV-curable light-blocking adhesive, characterized in that, The light-shielding adhesive comprises the following components in parts by weight: 30-60 parts of the epoxidized polyurethane acrylate prepolymer as described in claim 4; 30-50 parts of the reactive diluent monomer; 6-13 parts of the photoinitiator; 0.5-2 parts of the light-shielding agent; and 1-3 parts of the additives.

7. The light-blocking adhesive according to claim 6, wherein, The reactive diluent monomer comprises 5-15 parts of cationic curable diluent monomer and 25-45 parts of free radical curable diluent monomer; the free radical curable diluent monomer preferably comprises 20-40 parts of monofunctional acrylate monomer and 2-5 parts of polyfunctional acrylate monomer. Preferably, the cationic curing diluent monomer is selected from at least one of vinyl ethers, epoxy compounds, cyclic ethers and lactones, more preferably from at least one of 1,4-cyclohexanediethanol divinyl ether, diethylene glycol monovinyl ether, 1,4-butanediol diglycidyl ether, tetrahydrofuran and ε-caprolactone, and more preferably diethylene glycol monovinyl ether. Preferably, the monofunctional acrylate monomer is selected from at least one of isobornyl acrylate, hydroxyethyl acrylate, tetrahydrofuran acrylate, and acrylomorpholine, and more preferably isobornyl acrylate and acrylomorpholine; Preferably, the multifunctional acrylate monomer is selected from at least one of trimethylolpropane triacrylate and dipentaerythritol hexaacrylate, and more preferably trimethylolpropane triacrylate.

8. The light-blocking adhesive according to claim 6 or 7, wherein, The photoinitiator comprises 1-3 parts of a cationic photoinitiator and 5-10 parts of a free radical photoinitiator; Preferably, the cationic photoinitiator is selected from diaryliodonium salts or triarylthionium salts, and more preferably diaryliodonium salts; Preferably, the free radical photoinitiator is selected from at least one of acylphosphine oxide photoinitiators; Preferably, the opacifier is a carbon black paste or a black colorant.

9. The light-blocking adhesive according to any one of claims 6-8, wherein, The additive is selected from at least one of leveling agents, coupling agents, defoamers, and antioxidants; Preferably, the leveling agent is selected from at least one of modified polydimethylsilane and polyether polyester modified organosiloxane, and more preferably polyether modified polysiloxane; Preferably, the coupling agent is γ-(2,3-epoxypropoxy)propyltrimethoxysilane and / or γ-methacryloyloxypropyltrimethoxysilane, more preferably γ-(2,3-epoxypropoxy)propyltrimethoxysilane.

10. The application of the UV-curable light-shielding adhesive according to any one of claims 6-9 in the field of light shielding for display device bezels or encapsulation of optical components.

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