A flexible, scratch-resistant transparent coating, its preparation method and application

Abstract

This invention discloses a flexible, scratch-resistant transparent coating, its preparation method, and its applications. The flexible, scratch-resistant transparent coating of this invention comprises a type A polysilsesquioxane, a type B polysilsesquioxane, and a polyurethane acrylate in a mass ratio of 1–5:1:1–6. The type A polysilsesquioxane contains at least one of epoxy-based side chains and unsaturated double-bond side chains; the type B polysilsesquioxane contains mercapto-containing side chains; and the polyurethane acrylate contains unsaturated double-bond side chains. The flexible, scratch-resistant transparent coating of this invention possesses advantages such as excellent optical properties, excellent scratch resistance, high flexibility, strong impact resistance, and performance that can be controlled within a wide range. It is suitable for use in foldable displays. Furthermore, its preparation method is simple, the raw materials are widely available, the cost is low, the process conditions are easy to control, and the production efficiency is high, making it suitable for large-scale industrial production and application.

Description

Technical Field

[0001] This invention relates to the field of advanced coating technology, specifically to a flexible, scratch-resistant transparent coating, its preparation method, and its application. Background Technology

[0002] Foldable displays represent a significant innovation in the electronics field, driving the continuous evolution of mobile terminal form factors. Flexible cover glass is a key component of foldable displays, primarily used for surface protection of the display panel while balancing light transmittance and bending reliability. In recent years, ultra-thin glass (UTG), with its high hardness, excellent light transmittance, and good wrinkle resistance, has gradually replaced colorless polyimide (CPI) as the mainstream candidate material for flexible cover glass. However, UTG is prone to internal residual stress during manufacturing and processing, and its low impact resistance results in insufficient drop impact resistance, posing a significant risk of breakage in practical use.

[0003] Currently, the main approach to improving the impact resistance of UTG (Ultra-Touch Glass) and reducing the risk of fragmentation is to laminate protective films such as polyethylene terephthalate (PET) onto the surface. However, the improvement in impact resistance of PET film is very limited, and its surface scratch resistance is relatively poor, making it difficult to meet the durability requirements of foldable terminals under high-frequency touch and daily friction scenarios. Therefore, it is necessary to construct a transparent surface protective coating on the PET film to synergistically improve the overall scratch resistance and impact reliability.

[0004] The surface coating of the UTG system differs significantly from existing trapezoidal or cage-like polysilsesquioxane (PSQ) surface protective coatings, which are mainly used for CPI cover plates (e.g., Adv. Mater. 2017, 29, 1700205; CN 114479665 A). Besides requiring excellent optical properties, high scratch resistance, and high flexibility, it also needs to significantly improve impact resistance to adapt to the brittle characteristics and drop conditions of glass substrates. However, existing coating materials generally only achieve one of the properties: high scratch resistance, high flexibility, or high impact resistance. Achieving all three properties synergistically within the same transparent coating system remains a major challenge. The key reason is that there is an inherent contradiction between high hardness and high flexibility, and between high hardness and high impact resistance, making it difficult to achieve both simultaneously.

[0005] Currently, research reports on high-performance transparent protective coatings for UTG surfaces are relatively limited. Kim et al. reported an alicyclic epoxy functionalized polysilsesquioxane coating for UTG, which can achieve a nanoindentation hardness of about 0.7 GPa (Prog. Org. Coat. 2024, 187, 108162). However, this coating system was originally designed for CPI flexible cover plates, and the material is relatively brittle and lacks an effective energy dissipation mechanism, so its effect on improving the impact resistance of UTG is very limited.

[0006] Therefore, it is of great significance to develop a transparent surface protective coating with excellent optical properties, excellent scratch resistance, high flexibility, strong impact resistance, and performance that can be adjusted within a wide range. Summary of the Invention

[0007] The purpose of this invention is to provide a flexible, scratch-resistant transparent coating, its preparation method, and its application.

[0008] The technical solution adopted in this invention is: A flexible, scratch-resistant transparent coating comprises A-type polysilsesquioxane, B-type polysilsesquioxane, and polyurethane acrylate in a mass ratio of 1-5:1:1-6. The A-type polysilsesquioxane contains at least one of epoxy side chains and unsaturated double bond side chains, the B-type polysilsesquioxane contains mercapto-containing side chains, and the polyurethane acrylate contains unsaturated double bond side chains.

[0009] Preferably, the epoxy side chain is at least one of glycidyl ether group and alicyclic epoxy group.

[0010] Preferably, the unsaturated double bond side chain is at least one of methacrylate, acrylate, and vinyl groups.

[0011] Preferably, the thiol-containing side chain is at least one of mercaptopropyl and mercaptoethyl.

[0012] Preferably, the Si-O-Si network structure of the type A polysilsesquioxane (PSQ) is one of the following: trapezoidal structure, cage structure, random structure, and hyperbranched structure.

[0013] Preferably, the degree of condensation of the type A polysilsesquioxane is 75% to 99%, and the number-average molecular weight is 1500 g / mol to 20000 g / mol.

[0014] Preferably, the type B polysilsesquioxane further comprises at least one of epoxy side chains and unsaturated double bond side chains.

[0015] Preferably, the Si-O-Si network structure of the B-type polysilsesquioxane is one of the following: trapezoidal structure, cage structure, random structure, and hyperbranched structure.

[0016] Preferably, the degree of condensation of the type B polysilsesquioxane is 80% to 99%, and the number-average molecular weight is 1500 g / mol to 170000 g / mol.

[0017] Preferably, the polyurethane acrylate (PUA) has a functionality of 2 to 6, a number of urethane bonds of 2 to 10, and a number-average molecular weight of 800 g / mol to 2500 g / mol.

[0018] Preferably, the thickness of the flexible, scratch-resistant transparent coating is 20 nm to 500 μm.

[0019] A method for preparing the flexible, scratch-resistant transparent coating as described above includes the following steps: 1) Dissolve type A polysilsesquioxane, type B polysilsesquioxane and polyurethane acrylate in an organic solvent, then add an initiator and mix evenly to obtain a prepolymer solution; 2) Apply the prepolymer liquid to the substrate surface, dry and cure it to obtain a flexible, scratch-resistant, transparent coating.

[0020] Preferably, the organic solvent in step 1) is at least one of toluene, xylene, tetrahydrofuran, dichloromethane, chloroform, acetone, ethyl acetate, and butanone.

[0021] Preferably, the initiator in step 1) is at least one of a photoinitiator and a thermal initiator.

[0022] Preferably, the photoinitiator is at least one of a free radical photoinitiator and a cationic ring-opening photoinitiator.

[0023] Preferably, the free radical photoinitiator is at least one selected from 1-hydroxycyclohexylphenyl ketone, 2-hydroxy-2-methyl-1-phenylpropanone, 2-hydroxy-2-methyl-1-[4-(methylthio)phenyl]propanone, diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide, bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, and diethoxyphenylphosphine oxide.

[0024] Preferably, the cationic ring-opening photoinitiator is at least one of diphenyliodonium hexafluorophosphate, diphenyliodonium tetrafluoroborate, di(4-methylphenyl)iodonium hexafluoroantimonate, triphenylthionium hexafluoroantimonate, triphenylthionium hexafluorophosphate, triphenylthionium tetrafluoroborate, and di(4-methylphenyl)phenylthionium hexafluoroantimonate.

[0025] Preferably, the amount of photoinitiator is 0.1% to 5% of the total mass of type A polysilsesquioxane, type B polysilsesquioxane, and polyurethane acrylate.

[0026] Preferably, the thermal initiator is at least one selected from triethylamine, N,N-dimethylbenzylamine, 2-methylimidazole, 1-methylimidazole, and 2-ethyl-4-methylimidazole.

[0027] Preferably, the amount of the thermal initiator is 0.5% to 2% of the total mass of type A polysilsesquioxane, type B polysilsesquioxane, and polyurethane acrylate.

[0028] Preferably, the coating method in step 2) is at least one of spin coating, blade coating, bar coating, dip coating, spray coating, slot coating, roller coating, and curtain coating.

[0029] Preferably, the substrate in step 2) is one of polyethylene terephthalate (PET) substrate, polyethylene naphthalate (PEN) substrate, colorless polyimide (PI) substrate, polycarbonate (PC) substrate, polymethyl methacrylate (PMMA) substrate, polyethylene (PE) substrate, polypropylene (PP) substrate, and polyurethane (PU) substrate.

[0030] Preferably, the drying temperature in step 2) is 10℃~150℃.

[0031] Preferably, the curing method in step 2) is at least one of ultraviolet curing and thermal curing.

[0032] Preferably, the energy density of the UV curing is 20 mJ / cm². 2 ~5000mJ / cm 2 .

[0033] Preferably, the curing temperature of the thermosetting process is 40℃~150℃.

[0034] A foldable display comprising the aforementioned flexible, scratch-resistant, transparent coating.

[0035] The beneficial effects of the present invention are as follows: The flexible scratch-resistant transparent coating of the present invention has the advantages of excellent optical performance, excellent scratch resistance, high flexibility, strong impact resistance, and performance that can be adjusted within a wide range. It is suitable for use in foldable displays. Moreover, its preparation method is simple, the raw materials are widely available, the cost is low, the process conditions are easy to control, and the production efficiency is high, making it suitable for large-scale industrial production and application.

[0036] Specifically: 1) The flexible scratch-resistant transparent coating of the present invention comprises PSQ and PUA. Compared with the pure PSQ coating, its impact resistance is significantly improved (PUA has dynamic hydrogen bonding, which can effectively dissipate energy under impact load, thereby effectively improving the impact resistance of the coating; at the same time, by selecting PUA with higher functionality and co-crosslinking with PSQ network, the significant decrease in coating hardness caused by the introduction of PUA can be effectively avoided). It also maintains high scratch resistance and has a smaller bending radius, making it suitable for applications with high requirements for durability and bending resistance, such as flexible displays. 2) The flexible scratch-resistant transparent coating of the present invention can be designed and controlled within a wide range by adjusting parameters such as the Si-O-Si network structure, degree of condensation, crosslinking method and molar ratio of side chain functional groups of PSQ, combined with structural parameters such as the side chain functionality of PUA and the ratio of PSQ to PUA, so as to meet the usage requirements of different application scenarios. 3) The preparation method of the flexible scratch-resistant transparent coating of the present invention has the advantages of simple process flow, wide availability of raw materials, low cost and easy control of process conditions. It is suitable for use with coating processes such as spin coating, blade coating, slot coating and roller coating, and can realize continuous production, which is conducive to reducing production costs and improving production efficiency, and is suitable for large-scale industrial applications. Attached Figure Description

[0037] Figure 1 The image shows the UV-Vis spectrum of the flexible, scratch-resistant transparent coating of Example 4.

[0038] Figure 2 The image shows the test results of the scratch resistance performance of the flexible scratch-resistant transparent coating in Example 4. Detailed Implementation

[0039] The present invention will be further explained and described below with reference to specific embodiments.

[0040] Example 1: A flexible, scratch-resistant transparent coating is prepared as follows: 1) A type of polysilsesquioxane (Guangzhou Jinxian New Materials Co., Ltd.; degree of condensation 95%, Si-O-Si network structure is ladder-like, number-average molecular weight Mn=9500g / mol, side chain contains acrylate groups), a type of polysilsesquioxane (Guangzhou Jinxian New Materials Co., Ltd.; degree of condensation 96%, Si-O-Si network structure is ladder-like, number-average molecular weight Mn=8000g / mol, side chain contains mercaptopropyl groups), and a type of polyurethane acrylate (Guangzhou Jinxian New Materials Co., Ltd.; number-average molecular weight Mn=8000g / mol, side chain contains mercaptopropyl groups) were combined. The poly(methyl methacrylate) with an average molecular weight of Mn = 1000 g / mol, a functionality of 6, and 2 urethane bonds was dissolved in toluene under stirring at room temperature. The mass ratio of poly(methyl methacrylate) type A, poly(methyl methacrylate) type B, and polyurethane acrylate was 3:1:4. 2-hydroxy-2-methyl-1-phenylpropanone was then added and stirred until homogeneous. The amount of 2-hydroxy-2-methyl-1-phenylpropanone used was 2% of the total mass of poly(methyl methacrylate) type A, poly(methyl methacrylate) type B, and polyurethane acrylate to obtain a prepolymer solution (homogeneous and transparent). 2) Spin-coat the prepolymer onto the PET substrate surface, then bake in an oven at 60°C for 20 minutes, followed by UV curing for 2 minutes. The UV curing energy density is 2000 mJ / cm². 2 A flexible, scratch-resistant, transparent coating is obtained.

[0041] Example 2: A flexible, scratch-resistant transparent coating is prepared as follows: 1) A type of polysilsesquioxane (Guangzhou Jinxian New Materials Co., Ltd.; degree of condensation 95%, random Si-O-Si network structure, number-average molecular weight Mn=5500g / mol, side chain containing acrylate groups), a type of polysilsesquioxane (Guangzhou Jinxian New Materials Co., Ltd.; degree of condensation 96%, random Si-O-Si network structure, number-average molecular weight Mn=6500g / mol, side chain containing mercaptopropyl groups), and a type of polyurethane acrylate (Guangzhou Jinxian New Materials Co., Ltd.; number-average molecular weight Mn=6500g / mol, side chain containing mercaptopropyl groups) were combined. The poly(methyl methacrylate) with an average molecular weight of Mn = 1000 g / mol, a functionality of 6, and 2 urethane bonds was dissolved in toluene under stirring at room temperature. The mass ratio of poly(methyl methacrylate) type A, poly(methyl methacrylate) type B, and polyurethane acrylate was 3:1:4. 2-hydroxy-2-methyl-1-phenylpropanone was then added and stirred until homogeneous. The amount of 2-hydroxy-2-methyl-1-phenylpropanone used was 2% of the total mass of poly(methyl methacrylate) type A, poly(methyl methacrylate) type B, and polyurethane acrylate to obtain a prepolymer solution (homogeneous and transparent). 2) Spin-coat the prepolymer onto the PET substrate surface, then bake in an oven at 60°C for 20 minutes, followed by UV curing for 2 minutes. The UV curing energy density is 2000 mJ / cm². 2 A flexible, scratch-resistant, transparent coating is obtained.

[0042] Example 3: A flexible, scratch-resistant transparent coating is prepared as follows: 1) A type of polysilsesquioxane (Guangzhou Jinxian New Materials Co., Ltd.; degree of condensation 80%, Si-O-Si network structure is ladder-like, number-average molecular weight Mn=2600g / mol, side chain contains acrylate groups), a type of polysilsesquioxane (Guangzhou Jinxian New Materials Co., Ltd.; degree of condensation 82%, Si-O-Si network structure is ladder-like, number-average molecular weight Mn=3500g / mol, side chain contains mercaptopropyl groups), and polyurethane acrylate (Guangzhou Jinxian New Materials Co., Ltd.; number-average molecular weight Mn=3500g / mol, side chain contains mercaptopropyl groups) were combined. The poly(methyl methacrylate) with an average molecular weight of Mn = 1000 g / mol, a functionality of 6, and 2 urethane bonds was dissolved in toluene under stirring at room temperature. The mass ratio of poly(methyl methacrylate) type A, poly(methyl methacrylate) type B, and polyurethane acrylate was 3:1:4. 2-hydroxy-2-methyl-1-phenylpropanone was then added and stirred until homogeneous. The amount of 2-hydroxy-2-methyl-1-phenylpropanone used was 2% of the total mass of poly(methyl methacrylate) type A, poly(methyl methacrylate) type B, and polyurethane acrylate to obtain a prepolymer solution (homogeneous and transparent). 2) Spin-coat the prepolymer onto the PET substrate surface, then bake in an oven at 60°C for 20 minutes, followed by UV curing for 2 minutes. The UV curing energy density is 2000 mJ / cm². 2 A flexible, scratch-resistant, transparent coating is obtained.

[0043] Example 4: A flexible, scratch-resistant transparent coating is prepared as follows: 1) A type of polysilsesquioxane (Guangzhou Jinxian New Materials Co., Ltd.; degree of condensation 95%, Si-O-Si network structure is ladder-like, number-average molecular weight Mn=9500g / mol, side chain contains acrylate groups), a type of polysilsesquioxane (Guangzhou Jinxian New Materials Co., Ltd.; degree of condensation 96%, Si-O-Si network structure is ladder-like, number-average molecular weight Mn=8000g / mol, side chain contains glycidyl ether groups, acrylate groups and mercaptopropyl groups, the molar ratio of glycidyl ether groups, acrylate groups and mercaptopropyl groups is 1:1:1), and polyurethane acrylate (Guangzhou Jinxian New Materials Co., Ltd.) are combined. Materials Co., Ltd.; Number average molecular weight Mn=1000g / mol, functionality is 6, number of urethane bonds is 2) Dissolved in toluene under stirring at room temperature, the mass ratio of type A polysilsesquioxane, type B polysilsesquioxane and polyurethane acrylate is 3:1:4, then 2-hydroxy-2-methyl-1-phenylpropanone and triphenylthionium hexafluoroantimonate are added and stirred evenly, the amount of 2-hydroxy-2-methyl-1-phenylpropanone and triphenylthionium hexafluoroantimonate is 2% of the total mass of type A polysilsesquioxane, type B polysilsesquioxane and polyurethane acrylate, to obtain a prepolymer liquid (uniform and transparent); 2) Spin-coat the prepolymer onto the PET substrate surface, then bake in an oven at 60°C for 20 minutes, followed by UV curing for 2 minutes. The UV curing energy density is 4000 mJ / cm². 2 A flexible, scratch-resistant, transparent coating is obtained.

[0044] Example 5: A flexible, scratch-resistant transparent coating is prepared as follows: 1) A type of polysilsesquioxane (Guangzhou Jinxian New Materials Co., Ltd.; degree of condensation 95%, Si-O-Si network structure is ladder-like, number-average molecular weight Mn=9500g / mol, side chains contain glycidyl ether groups and acrylate groups, the molar ratio of glycidyl ether groups to acrylate groups is 1:1), a type of polysilsesquioxane (Guangzhou Jinxian New Materials Co., Ltd.; degree of condensation 96%, Si-O-Si network structure is ladder-like, number-average molecular weight Mn=8000g / mol, side chains contain mercaptopropyl groups), and polyurethane acrylate (Guangzhou Jinxian) were combined. New Materials Co., Ltd.; Number average molecular weight Mn=1000g / mol, functionality is 6, number of urethane bonds is 2) Dissolved in toluene under stirring at room temperature, the mass ratio of type A polysilsesquioxane, type B polysilsesquioxane and polyurethane acrylate is 3:1:4, then 2-hydroxy-2-methyl-1-phenylpropanone and triethylamine are added and stirred evenly, the amount of 2-hydroxy-2-methyl-1-phenylpropanone and triethylamine is 2% of the total mass of type A polysilsesquioxane, type B polysilsesquioxane and polyurethane acrylate, to obtain a prepolymer liquid (uniform and transparent); 2) Spin-coat the prepolymer onto the PET substrate surface, then bake in an oven at 120°C for 120 minutes, followed by UV curing for 2 minutes. The UV curing energy density is 2000 mJ / cm². 2 A flexible, scratch-resistant, transparent coating is obtained.

[0045] Example 6: A flexible, scratch-resistant transparent coating is prepared as follows: 1) A type of polysilsesquioxane (Guangzhou Jinxian New Materials Co., Ltd.; degree of condensation 95%, Si-O-Si network structure is ladder-like, number-average molecular weight Mn=9500g / mol, side chain contains acrylate groups), a type of polysilsesquioxane (Guangzhou Jinxian New Materials Co., Ltd.; degree of condensation 96%, Si-O-Si network structure is ladder-like, number-average molecular weight Mn=8000g / mol, side chain contains glycidyl ether groups, acrylate groups and mercaptopropyl groups, the molar ratio of glycidyl ether groups, acrylate groups and mercaptopropyl groups is 1:1:1), and polyurethane acrylate (Guangzhou Jinxian New Materials Co., Ltd.) are combined. Materials Co., Ltd.; Number average molecular weight Mn=2150g / mol, functionality is 6, number of urethane bonds is 6) Dissolved in toluene at room temperature with stirring. The mass ratio of type A polysilsesquioxane, type B polysilsesquioxane and polyurethane acrylate is 3:1:4. Then, 2-hydroxy-2-methyl-1-phenylpropanone and triphenylthionium hexafluoroantimonate are added and stirred evenly. The amount of 2-hydroxy-2-methyl-1-phenylpropanone and triphenylthionium hexafluoroantimonate is 2% of the total mass of type A polysilsesquioxane, type B polysilsesquioxane and polyurethane acrylate to obtain a prepolymer solution (uniform and transparent). 2) Spin-coat the prepolymer onto the PET substrate surface, then bake in an oven at 60°C for 20 minutes, followed by UV curing for 2 minutes. The UV curing energy density is 4000 mJ / cm². 2 A flexible, scratch-resistant, transparent coating is obtained.

[0046] Example 7: A flexible, scratch-resistant transparent coating is prepared as follows: 1) A type of polysilsesquioxane (Guangzhou Jinxian New Materials Co., Ltd.; degree of condensation 95%, Si-O-Si network structure is ladder-like, number-average molecular weight Mn=9500g / mol, side chain contains acrylate groups), a type of polysilsesquioxane (Guangzhou Jinxian New Materials Co., Ltd.; degree of condensation 96%, Si-O-Si network structure is ladder-like, number-average molecular weight Mn=8000g / mol, side chain contains glycidyl ether groups, acrylate groups and mercaptopropyl groups, the molar ratio of glycidyl ether groups, acrylate groups and mercaptopropyl groups is 1:1:1), and polyurethane acrylate (Guangzhou Jinxian New Materials Co., Ltd.) are combined. Materials Co., Ltd.; Number average molecular weight Mn=2500g / mol, functionality is 6, number of urethane bonds is 10) Dissolved in toluene at room temperature with stirring. The mass ratio of type A polysilsesquioxane, type B polysilsesquioxane and polyurethane acrylate is 3:1:4. Then, 2-hydroxy-2-methyl-1-phenylpropanone and triphenylthionium hexafluoroantimonate are added and stirred evenly. The amount of 2-hydroxy-2-methyl-1-phenylpropanone and triphenylthionium hexafluoroantimonate is 2% of the total mass of type A polysilsesquioxane, type B polysilsesquioxane and polyurethane acrylate to obtain a prepolymer solution (uniform and transparent). 2) Spin-coat the prepolymer onto the PET substrate surface, then bake in an oven at 60°C for 20 minutes, followed by UV curing for 2 minutes. The UV curing energy density is 4000 mJ / cm². 2 A flexible, scratch-resistant, transparent coating is obtained.

[0047] Comparative Example 1: A transparent coating is prepared by the following method: 1) Dissolve type A polysilsesquioxane (Guangzhou Jinxian New Materials Co., Ltd.; degree of condensation 95%, Si-O-Si network structure is ladder structure, number average molecular weight Mn=9500g / mol, side chain contains acrylate groups) and type B polysilsesquioxane (Guangzhou Jinxian New Materials Co., Ltd.; degree of condensation 96%, Si-O-Si network structure is ladder structure, number average molecular weight Mn=8000g / mol, side chain contains mercaptopropyl groups) in toluene at room temperature by stirring. The mass ratio of type A polysilsesquioxane to type B polysilsesquioxane is 3:1. Then add 2-hydroxy-2-methyl-1-phenylpropanone and stir until homogeneous. The amount of 2-hydroxy-2-methyl-1-phenylpropanone is 2% of the total mass of type A polysilsesquioxane and type B polysilsesquioxane to obtain a prepolymer solution (homogeneous and transparent). 2) Spin-coat the prepolymer onto the PET substrate surface, then bake in an oven at 60°C for 20 minutes, followed by UV curing for 2 minutes. The UV curing energy density is 2000 mJ / cm². 2 A transparent coating is obtained.

[0048] Comparative Example 2: A transparent coating is prepared by the following method: 1) Dissolve type A polysilsesquioxane (Guangzhou Jinxian New Materials Co., Ltd.; degree of condensation 95%, Si-O-Si network structure is ladder structure, number average molecular weight Mn=9500g / mol, side chain contains acrylate groups) in toluene under stirring at room temperature, then add 2-hydroxy-2-methyl-1-phenylpropanone and stir until uniform. The amount of 2-hydroxy-2-methyl-1-phenylpropanone is 2% of the mass of type A polysilsesquioxane to obtain a prepolymer solution (uniform and transparent). 2) Spin-coat the prepolymer onto the PET substrate surface, then bake in an oven at 60°C for 20 minutes, followed by UV curing for 2 minutes. The UV curing energy density is 2000 mJ / cm². 2 A transparent coating is obtained.

[0049] Comparative Example 3: A transparent coating is prepared by the following method: 1) Dissolve type B polysilsesquioxane (Guangzhou Jinxian New Materials Co., Ltd.; degree of condensation 96%, Si-O-Si network structure is ladder structure, number average molecular weight Mn=8000g / mol, side chain contains mercaptopropyl groups) in toluene under stirring at room temperature, then add 2-hydroxy-2-methyl-1-phenylpropanone and stir until uniform. The amount of 2-hydroxy-2-methyl-1-phenylpropanone is 2% of the mass of type B polysilsesquioxane to obtain a prepolymer solution (uniform and transparent). 2) Spin-coat the prepolymer onto the PET substrate surface, then bake in an oven at 60°C for 20 minutes, followed by UV curing for 2 minutes. The UV curing energy density is 2000 mJ / cm². 2 Because the system contains only thiol groups, it cannot be cured, and a transparent coating cannot be obtained.

[0050] Comparative Example 4: A transparent coating is prepared by the following method: 1) Dissolve polyurethane acrylate (Guangzhou Jinxian New Materials Co., Ltd.; number average molecular weight Mn=1000g / mol, functionality 6, number of urethane bonds 2) in toluene at room temperature by stirring. Then add 2-hydroxy-2-methyl-1-phenylpropanone and stir until homogeneous. The amount of 2-hydroxy-2-methyl-1-phenylpropanone is 2% of the mass of polyurethane acrylate to obtain a prepolymer solution (homogeneous and transparent). 2) Spin-coat the prepolymer onto the PET substrate surface, then bake in an oven at 60°C for 20 minutes, followed by UV curing for 2 minutes. The UV curing energy density is 2000 mJ / cm². 2 A transparent coating is obtained.

[0051] Comparative Example 5: A transparent coating is prepared by the following method: 1) Dissolve polyurethane acrylate (Guangzhou Jinxian New Materials Co., Ltd.; number average molecular weight Mn=2150g / mol, functionality 6, number of urethane bonds 6) in toluene at room temperature by stirring. Then add 2-hydroxy-2-methyl-1-phenylpropanone and stir until homogeneous. The amount of 2-hydroxy-2-methyl-1-phenylpropanone is 2% of the mass of polyurethane acrylate to obtain a prepolymer solution (homogeneous and transparent). 2) Spin-coat the prepolymer onto the PET substrate surface, then bake in an oven at 60°C for 20 minutes, followed by UV curing for 2 minutes. The UV curing energy density is 2000 mJ / cm². 2 A transparent coating is obtained.

[0052] Comparative Example 6: A transparent coating is prepared by the following method: 1) Dissolve polyurethane acrylate (Guangzhou Jinxian New Materials Co., Ltd.; number average molecular weight Mn=2500g / mol, functionality 6, number of urethane bonds 10) in toluene at room temperature by stirring. Then add 2-hydroxy-2-methyl-1-phenylpropanone and stir until homogeneous. The amount of 2-hydroxy-2-methyl-1-phenylpropanone is 2% of the mass of polyurethane acrylate to obtain a prepolymer solution (homogeneous and transparent). 2) Spin-coat the prepolymer onto the PET substrate surface, then bake in an oven at 60°C for 20 minutes, followed by UV curing for 2 minutes. The UV curing energy density is 2000 mJ / cm². 2 A transparent coating is obtained.

[0053] Comparative Example 7: A transparent coating is prepared by the following method: 1) Dissolve polyurethane acrylate (Guangzhou Jinxian New Materials Co., Ltd.; number average molecular weight Mn=1000g / mol, functionality 2, number of urethane bonds 2) in toluene at room temperature by stirring. Then add 2-hydroxy-2-methyl-1-phenylpropanone and stir until homogeneous. The amount of 2-hydroxy-2-methyl-1-phenylpropanone is 2% of the mass of polyurethane acrylate to obtain a prepolymer solution (homogeneous and transparent). 2) Spin-coat the prepolymer onto the PET substrate surface, then bake in an oven at 60°C for 20 minutes, followed by UV curing for 2 minutes. The UV curing energy density is 2000 mJ / cm². 2 A transparent coating is obtained.

[0054] Performance testing: 1) The UV-Vis spectrum of the flexible, scratch-resistant transparent coating (approximately 40 μm thick, with a glass substrate) of Example 4 is shown below. Figure 1 As shown.

[0055] Depend on Figure 1 It can be seen that the transmittance of the flexible, scratch-resistant transparent coating can reach 90% at a wavelength of 550nm, indicating that it has good optical transparency.

[0056] 2) The flexible scratch-resistant transparent coating (approximately 100 μm thick, PET substrate) of Example 4 was subjected to 2000 reciprocating rubbing cycles using #0000 grade steel wool under an average vertical pressure of approximately 4 kPa. The scratch resistance test results were then observed using an optical microscope and a scanning electron microscope. Figure 2 (Uncoated PET substrate is shown as a control).

[0057] Depend on Figure 2 It can be seen that no obvious scratches were observed on the surface of the flexible scratch-resistant transparent coating after 2000 cycles of reciprocating rubbing, indicating that it has excellent scratch resistance.

[0058] 3) The performance test data of the flexible scratch-resistant transparent coatings of Examples 1-7 and the transparent coatings of Comparative Examples 1-7 are shown in the table below: Table 1 Performance test data of the flexible scratch-resistant transparent coatings of Examples 1-7 and the transparent coatings of Comparative Examples 1-7

[0059] Note: Pencil hardness: The test was conducted in accordance with "GB / T 6739-2022 Pencil method for determining the hardness of paint and varnish". The sample was a coating on a PET substrate. The width of the sample was 50mm±5mm, the length was 50mm±5mm, and the coating thickness was 100μm±5μm.

[0060] Bending radius: The test was conducted in accordance with "GB / T 6742-2007 Paint and Varnish Bending Test (Cylindrical Shaft)". The sample was a coating on a PET substrate. The width of the sample was 50mm ± 5mm, the length was 50mm ± 5mm, and the coating thickness was 100μm ± 5μm. In the inward bending radius test, 0.25mm is the minimum bending radius that can be achieved / measured under this test condition (test lower limit). The values ​​in the table are the minimum values ​​when no visible cracks / peeling are found in the sample.

[0061] Drop height: The test was conducted in accordance with "GB / T 1732-2020 Test method for impact resistance of coating film". The sample was a coating applied to a PET substrate. The width of the sample was 50mm±5mm, the length was 50mm±5mm, and the coating thickness was 100μm±5μm.

[0062] Comparative Example 3 failed to obtain a transparent coating, therefore no corresponding performance test data is available.

[0063] As shown in Table 1: a) The transparent coatings of Comparative Examples 1-2 did not introduce the PUA component, which can dissipate energy through hydrogen bonding, and therefore had poor impact resistance, with a drop height of only 7cm-10cm. In contrast, the drop height of the flexible scratch-resistant transparent coatings of Examples 1-6 increased to 16cm-21cm, indicating that introducing the PUA component into the polysilsesquioxane system can significantly improve the impact resistance of the coating. At the same time, the flexible scratch-resistant transparent coatings of Examples 1-6 still maintained a high pencil hardness grade (3H-9H) and a small inward bending radius (0.25mm), indicating that the present invention can maintain the scratch resistance and flexibility of the coating while improving the impact resistance, and the above properties can be designed and controlled within a wide range. b) Compared with the transparent coatings of Comparative Examples 4 to 6, the flexible scratch-resistant transparent coatings of Examples 1 to 7 have a smaller inward bending radius (0.25 mm) and a significantly improved pencil hardness (3H to 9H). This indicates that a single PUA coating is difficult to meet the requirements of both flexibility and scratch resistance at the same time. However, by constructing a PSQ-PUA composite system, this invention can achieve higher hardness and excellent scratch resistance while maintaining high flexibility, thus achieving a synergistic improvement in performance. c) Compared with the flexible scratch-resistant transparent coatings of Examples 1-6, the transmittance of the flexible scratch-resistant transparent coating of Example 7 decreased. This is presumably related to the higher content of urethane bonds in its system. Excessive urethane bonds will enhance intermolecular forces and change the polarity of the system, leading to a decrease in the compatibility between PUA and PSQ and an increase in the difference in solubility parameters, thereby inducing phase separation and resulting in enhanced light scattering, which ultimately manifests as a decrease in transmittance. d) The pencil with the flexible, scratch-resistant transparent coating of Example 4 has a hardness of up to 9H and an inward bending radius of 0.25mm, exhibiting the best overall performance; e) The outward bending radius of the flexible scratch-resistant transparent coatings in Examples 1 to 6 is generally in the range of 13 mm to 19 mm, while the outward bending radius of the transparent coating in Comparative Example 2 reaches 25 mm. This shows that after introducing Class B PSQ, the coating system of the present invention can significantly improve the outward bending adaptability while maintaining high pencil hardness, thereby improving the overall reliability of the coating in actual bending application scenarios.

[0064] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A flexible, scratch-resistant, transparent coating, characterized in that, The composition includes a type A polysilsesquioxane, a type B polysilsesquioxane, and a polyurethane acrylate in a mass ratio of 1–5:1:1–6; the type A polysilsesquioxane contains at least one of epoxy side chains and unsaturated double bond side chains; the type B polysilsesquioxane contains a side chain containing a thiol group; and the polyurethane acrylate contains an unsaturated double bond side chain.

2. The flexible, scratch-resistant transparent coating according to claim 1, characterized in that: The type B polysilsesquioxane further includes at least one of epoxy side chains and unsaturated double bond side chains.

3. The flexible, scratch-resistant transparent coating according to claim 1 or 2, characterized in that: The epoxy side chain is at least one of glycidyl ether group and alicyclic epoxy group; the unsaturated double bond side chain is at least one of methacrylate group, acrylate group and vinyl group; the mercapto-containing side chain is at least one of mercaptopropyl group and mercaptoethyl group.

4. The flexible, scratch-resistant transparent coating according to claim 1 or 2, characterized in that: The Si-O-Si network structure of the Class A polysilsesquioxane is one of the following: trapezoidal structure, cage structure, random structure, or hyperbranched structure.

5. The flexible, scratch-resistant transparent coating according to claim 1 or 2, characterized in that: The degree of condensation of the type A polysilsesquioxane is 75% to 99%, and the number average molecular weight is 1500 g / mol to 20000 g / mol.

6. The flexible, scratch-resistant transparent coating according to claim 1 or 2, characterized in that: The Si-O-Si network structure of the B-type polysilsesquioxane is one of the following: trapezoidal structure, cage structure, random structure, or hyperbranched structure.

7. The flexible, scratch-resistant transparent coating according to claim 1 or 2, characterized in that: The degree of condensation of the B-type polysilsesquioxane is 80%–99%, and the number-average molecular weight is 1500 g / mol–170000 g / mol.

8. The flexible, scratch-resistant transparent coating according to claim 1 or 2, characterized in that: The polyurethane acrylate has a functionality of 2-6, a number of urethane bonds of 2-10, and a number-average molecular weight of 800 g / mol to 2500 g / mol.

9. A method for preparing a flexible, scratch-resistant, transparent coating as described in any one of claims 1 to 8, characterized in that, Includes the following steps: 1) Dissolve type A polysilsesquioxane, type B polysilsesquioxane and polyurethane acrylate in an organic solvent, then add an initiator and mix evenly to obtain a prepolymer solution; 2) Apply the prepolymer liquid to the substrate surface, dry and cure it to obtain a flexible, scratch-resistant, transparent coating.

10. A foldable display, characterized in that, It includes the flexible, scratch-resistant, transparent coating as described in any one of claims 1 to 8.

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