High-hardness, high-flexibility and conductive optical protective coating with highly branched siloxane as construction element and preparation method of high-hardness, high-flexibility and conductive optical protective coating
By using an organic-inorganic hybrid film technology of highly branched siloxane and sulfobetaine siloxane, the contradiction between hardness and flexibility in optical protective coatings has been resolved, resulting in an optical protective coating with high hardness, high flexibility, and good conductivity, suitable for flexible displays and organic photoconductor drums.
Patent Information
- Application Number
- CN202511202226.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-08-26
- Publication Date
- 2025-11-25
AI Technical Summary
Existing optical protective coatings cannot simultaneously possess high hardness, high flexibility, and conductivity, and their poor compatibility during organic-inorganic hybridization leads to phase separation problems that affect optical and mechanical properties.
Using highly branched siloxanes as building blocks, and alkoxy compounds and sulfobetaine siloxanes as surfactants, an organic-inorganic hybrid film was prepared by sol-gel method. Lithium salts were added to improve conductivity, and a mild coating and curing process was adopted.
An optical protective coating with high hardness, good flexibility, and excellent conductivity was prepared. The bending radius can reach 1mm. It has good wear resistance and high transmittance, and is suitable for the protection of flexible displays and organic photoconductor drums.
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Figure CN121006149A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of ultra-hard flexible conductive optical protective coating preparation technology, specifically relating to a high-hardness, high-flexibility, conductive optical protective coating and its preparation method, which uses highly branched siloxanes as building blocks, co-hydrolyzes them with other alkoxy compounds, and uses sulfobetaine siloxanes as surfactants. Background Technology
[0002] Protective coatings are thin film materials applied to the surface of components to improve their wear resistance, corrosion resistance, and other properties, protecting the component surface from environmental damage. Optical protective coatings, on the other hand, are protective coatings with high optical transmittance that have little or no impact on the optical performance of the substrate, and are widely used in transparent optical devices such as displays. In recent years, with the development of flexible electronic devices, higher demands have been placed on the flexibility of optical protective coatings. Currently, flexible optical protective coatings on the market are mainly divided into two types: transparent polyimide film (CPI), which has good flexibility but slightly lower wear resistance; and ultra-thin flexible glass (UTG), which has high hardness but is brittle and has a complex manufacturing process. Therefore, it is crucial to invent an optical protective coating with high hardness and high flexibility.
[0003] However, hardness and flexibility are mutually exclusive properties. Polymer materials generally possess high flexibility but poor hardness and wear resistance; inorganic materials have high hardness and good wear resistance but poor flexibility. By hybridizing organic and inorganic components and designing a specific structure, coatings can achieve both high flexibility and high hardness—a contradictory combination. However, the poor compatibility between the organic and inorganic phases leads to phase separation during preparation, severely impacting the optical and mechanical properties of the coating. Therefore, selecting suitable organic-inorganic hybrid precursors and hybridization methods is crucial for preparing coatings with excellent optical and mechanical properties.
[0004] Furthermore, high-hardness, high-flexibility, and conductive optical protective coatings have enormous application potential in organic photoconductor drums. Organic photoconductor drums (OPCs) are core photoelectric conversion devices in office equipment such as laser printers and digital copiers. They typically employ a multi-layer structure, consisting of a charge blocking layer (BL), a charge generating layer (CGL), and a charge transport layer (CTL) sequentially coated onto a conductive aluminum tube. The outermost charge transport layer (CTL) protects all the coating layers; therefore, enhancing the hardness of the CTL while ensuring flexibility and conductivity is crucial for improving the OPC's lifespan. Simultaneously, OPCs operate at visible light wavelengths or laser light sources with wavelengths of 600–900 nm, thus the CTL needs to ensure high visible light transmittance. Additionally, high conductivity also allows the protected flexible electronic devices to possess higher sensitivity.
[0005] In summary, developing a high-hardness, high-flexibility, and conductive optical protective coating is of great significance for applications in flexible displays, transparent optical devices, and CTL layers of organic photoconductor drums. Summary of the Invention
[0006] The purpose of this invention is to provide a high-hardness, high-flexibility, and conductive optical protective coating based on highly branched siloxanes and its preparation method. This optical protective coating is an organic-inorganic hybrid film material with good film-forming properties, uniform optical properties, good thermal stability, good flexibility (bending radius up to 1 mm), a maximum hardness of 9H, good wear resistance, and electrical conductivity. Under a load of approximately 0.15 kg, it showed no scratches when rubbed with steel wool. Figure 7 Furthermore, the preparation process is mild and simple. Therefore, this coating material has practical application value in the wear-resistant protection of flexible displays or organic light guide drums.
[0007] The present invention discloses a method for preparing a high-hardness, high-flexibility, and conductive optical protective coating using highly branched siloxanes as building blocks, comprising the following steps:
[0008] (1) Preparation of branched siloxanes by chemical reaction
[0009] Weigh pentaerythritol tetra(thioglycolic acid) ester and organosiloxane monomers (γ-glycidoxypropyltrimethoxysilane, 3-(isobutenoyloxy)propyltrimethoxysilane or propyltriethoxysilane) in a molar ratio of 1:4, then add 0.1-10 wt% of the catalyst triethylamine or dibutyltin dilaurate, and react at room temperature for 2-48 hours; the obtained product is washed repeatedly with petroleum ether to remove the catalyst, and then the petroleum ether is removed by vacuum distillation to obtain a branched siloxane with one of the following structural formulas;
[0010]
[0011] To facilitate the explanation of the specific reaction process of branched silanes, pentaerythritol tetra(thioglycolic acid) ester and 3-(isobutenoyloxy)propyltrimethoxysilane are used as examples (the reaction process of γ-glycidyl etheroxypropyltrimethoxysilane with pentaerythritol tetra(thioglycolic acid) ester is similar). Triethylamine is used as a catalyst (NEt3), and its reaction process is as shown in formula (II):
[0012]
[0013] In addition, the catalyst for the reaction of pentaerythritol tetra(thioglycolic acid) ester with propyltriethoxysilane isocyanate is dibutyltin dilaurate (DBTDL), and the reaction process is as shown in formula (III):
[0014]
[0015] (2) Preparation of surfactants using a mild method
[0016] Weigh propyltriethoxysilane isocyanate and N,N-dimethylethanolamine in a molar ratio of 1:1, and stir and heat at 50-70°C for 20-30 hours under nitrogen protection to obtain the intermediate 2-(dimethylamino)ethyl(3-(triethoxysilyl)propyl)carbamate.
[0017] Weigh 2-(dimethylamino)ethyl(3-(triethoxysilyl)propyl)carbamate and 1,3-propanesulfonic acid lactone in a molar ratio of 1:0.5-1.5, add diethyl ether and acetone in a volume ratio of 1:0.1-10, wherein the concentration of 2-(dimethylamino)ethyl(3-(triethoxysilyl)propyl)carbamate in the diethyl ether and acetone is 1-3 mmol / mL; stir the reaction at room temperature under nitrogen protection for 20-30 h, filter, take the white precipitate, wash with acetone 3-5 times, and dry to obtain the surfactant sulfobetaine siloxane;
[0018] (3) Obtain the stock solution by sol-gel method
[0019] The branched siloxane obtained in step (1) is dissolved in a mixed solvent of isopropanol and water at a molar ratio of 1:3 to 20:0 to 5 with alkoxy compounds (methyltriethoxysilane, tetraethoxysilane, zirconium propoxide, etc.) and surfactant sulfobetaine siloxane. The volume ratio of isopropanol to water is 1:0.1 to 1.5, and the concentration of branched siloxane in isopropanol and water is 0.006 to 0.1 mmol / mL. Then, acid or base with a final concentration of 0 to 5 wt% is added, and the mixture is aged at room temperature for 12 to 48 hours to obtain a colorless and transparent stock solution.
[0020] (4) Obtaining coating curing liquid by combining composite stock solution and lithium salt
[0021] Lithium salts such as lithium chloride or lithium nitrate with a final concentration of 0-10 wt% are added to the stock solution obtained in step (3) to obtain a coating curing solution;
[0022] (5) A composite film layer is obtained by coating and curing.
[0023] The coating curing liquid obtained in step (4) is spin-coated, dip-coated or sprayed onto the surface of a substrate (e.g., glass slide, polyethylene terephthalate, polymethyl methacrylate, etc.) that has been treated with Plasma for 3 to 5 minutes. After evaporating the solvent, it is cured at 60 to 160°C for 0.5 to 5 hours to obtain the high-hardness, high-flexibility, and conductive optical protective coating of the present invention.
[0024] The sol-gel reaction process is similar in principle to the curing process. Taking the branched siloxane synthesized in (II) with tetraethoxysilane as an example (the reaction process of other siloxanes or zirconium propoxide with branched siloxane is similar), the reaction principle is shown in formula (IV):
[0025] Attached Figure Description
[0026] Figure 1 Fourier transform infrared spectra of the unreaction mixture of pentaerythritol tetra(thioglycolic acid) ester and 3-(isobutenoyloxy)propyltrimethoxysilane, and branched siloxane 1.
[0027] Figure 2 : 1H NMR spectrum of branched siloxane 2;
[0028] Figure 3 Fourier transform infrared spectra of pentaerythritol tetra(thioglycolic acid) ester and branched siloxane 3;
[0029] Figure 4 1H NMR spectrum of 2-(dimethylamino)ethyl(3-(triethoxysilyl)propyl)carbamate;
[0030] Figure 5 : 1H NMR spectrum of sulfobetaine siloxane;
[0031] Figure 6 Transmission spectra of coatings 1 to 7;
[0032] Figure 7 Optical microscope image of coating 1 after it has been scratched with a 9H pencil;
[0033] Figure 8 Optical microscope images of polyethylene terephthalate film (left) and coating 1 (right) after being repeatedly scratched with steel wool;
[0034] Figure 9 Fourier transform infrared spectra of coating 3 and curing liquid 3;
[0035] Figure 10 Electrochemical impedance spectroscopy of coatings 4 to 7;
[0036] Table 1: Performance data of coatings prepared in the examples
[0037]
[0038] Detailed Implementation
[0039] The present invention will be further described in detail below with reference to specific embodiments, but the present invention is not limited thereto.
[0040] Example 1
[0041] Pentaerythritol tetra(thioglycolic acid) ester (0.4325 g, 1 mmol) and 3-(isobutenoyloxy)propyltrimethoxysilane (0.9934 g, 4 mmol) were weighed into a 10 mL Erlenmeyer flask, and then triethylamine (100 mg, 0.99 mmol) was added. The mixture was stirred at room temperature for 24 hours. After the reaction was complete, the product was washed three times with petroleum ether to remove the triethylamine catalyst, and then the petroleum ether was removed by vacuum distillation to obtain 1.3943 g of branched siloxane 1. Its Fourier transform infrared spectrum is shown below. Figure 1 As shown. (Through) Figure 1 Branched silane 1 at 2570cm -1 The thiol peak and at 1640 cm⁻¹ -1 The carbon-carbon double bond peaks are significantly less intense at the same positions in the unreacted mixture compared to the peaks at the same positions, indicating a higher degree of reaction.
[0042] Example 2
[0043] Pentaerythritol tetra(thioglycolic acid) ester (0.4325 g, 1 mmol) and propyltriethoxysilane isocyanate (0.9880 g, 4 mmol) were weighed into a 10 mL Erlenmeyer flask, and then dibutyltin dilaurate (100 mg, 0.15 mmol) was added. The mixture was stirred at room temperature for 48 hours. The product was washed three times with petroleum ether to remove dibutyltin dilaurate, and then the petroleum ether was removed by vacuum distillation to obtain 1.4063 g of branched siloxane 2, the 1H NMR spectrum of which is shown below. Figure 2 As shown, from Figure 2 We can see that every hydrogen atom on our branched siloxane 2 can be found on the NMR spectrum, and there are few impurity peaks, which indicates that we have successfully synthesized branched siloxane 2 with a very high yield.
[0044] Example 3
[0045] Pentaerythritol tetra(thioglycolic acid) ester (0.4325 g, 1 mmol) and γ-glycidyl etheroxypropyltrimethoxysilane (0.9454 g, 4 mmol) were weighed into a 10 mL Erlenmeyer flask, and then triethylamine (20.24 mg, 0.2 mmol) was added. The reaction was carried out at room temperature for 48 hours. After the reaction was completed, the product was washed three times with petroleum ether to remove triethylamine, and then the petroleum ether was removed by vacuum distillation to obtain 1.2673 g of branched siloxane 3. Its Fourier transform infrared spectrum is shown below. Figure 3 As shown in the figure, pentaerythritol tetra(thioglycolic acid) ester at 2570 cm⁻¹ -1 The sample exhibits a strong thiol peak, while branched siloxane 3 shows virtually no thiol peak, indicating that we successfully synthesized branched siloxane 3.
[0046] Example 4
[0047] 0.494 g (2 mmol) of propyltriethoxysilane isocyanate and 0.178 g (2 mmol) of N,N-dimethylethanolamine were weighed into a glass vial and heated at 60 °C for 24 h under nitrogen protection to obtain 0.672 g of the intermediate 2-(dimethylamino)ethyl(3-(triethoxysilyl)propyl)carbamate. Its 1H NMR spectrum is shown below. Figure 4 As shown; Figure 4 We can see that 2-(dimethylamino)ethyl(3-(triethoxysilyl)propyl)carbamate was successfully synthesized. We can also see that the product has very few impurity peaks. Since our product was not purified, the reaction has a very high yield.
[0048] Weigh 0.672 g (2 mmol) of 2-(dimethylamino)ethyl(3-(triethoxysilyl)propyl)carbamate and 0.244 g (2 mmol) of 1,3-propanesulfonic acid lactone into a glass vial. Add 1 mL of diethyl ether and 0.2 mL of acetone. Stir the mixture at room temperature for 24 h under nitrogen protection. After filtration, collect the white precipitate, wash it three times with acetone, and dry it to obtain 0.632 g of the surfactant sulfobetaine siloxane. Its 1H NMR spectrum is as follows: Figure 5 As shown. Figure 5 We can see that we have successfully synthesized sulfobetaine siloxane with very few impurities.
[0049] Example 5
[0050] Branched siloxane 2 (0.1422 g, 0.1 mmol), tetraethoxysilane (0.3744 g, 1.8 mmol), and sulfobetaine siloxane (0.01145 g, 0.025 mmol) were weighed and dissolved in a mixed solvent of 6 mL of deionized water and isopropanol (volume ratio 1:1) without adding acid or alkali to obtain solution 1. This solution was aged at room temperature for 48 hours to obtain colorless and transparent stock solution 1. Without adding lithium chloride or lithium nitrate, colorless and transparent coating curing solution 1 was obtained.
[0051] Coating curing solution 1 was spin-coated onto the surface of a glass slide that had been treated with Plasma for 4 minutes. The solvent was evaporated at 60°C, and then cured at 120°C for 2 hours to obtain coating 1. The light transmittance of coating 1 is above 90%. Figure 6 This indicates that coating 1 has good transmittance, and the pencil hardness of coating 1 is 9H. Figure 7 This indicates that coating 1 has high hardness and can resist the abrasion of steel wool, effectively protecting the polymer from scratches. Figure 8Meanwhile, electrochemical impedance spectroscopy was performed on coating 1, and the conductivity of coating 1 was estimated using the Randle equivalent circuit, revealing that its conductivity was poor. The performance of coating 1 is summarized in Table 1.
[0052] Example 6
[0053] Branched siloxane 2 (0.1422 g, 0.1 mmol), tetraethoxysilane (0.3744 g, 1.8 mmol) and sulfobetaine siloxane (0.02290 g, 0.05 mmol) were weighed and dissolved in a mixed solvent of 6 mL of deionized water and isopropanol (volume ratio 1:1) without adding acid or alkali to obtain solution 2. This solution was aged at room temperature for 48 hours to obtain colorless and transparent stock solution 2. Without adding lithium chloride or lithium nitrate, colorless and transparent coating curing solution 2 was obtained.
[0054] Coating curing solution 2 was applied dropwise to the surface of a glass slide that had been treated with Plasma for 4 minutes. The solvent was evaporated at 60°C and then cured at 120°C for 2 hours to obtain coating 2. The performance is summarized in Table 1.
[0055] Example 7
[0056] Branched siloxane 2 (0.1422 g, 0.1 mmol), tetraethoxysilane (0.3744 g, 1.8 mmol), and sulfobetaine siloxane (0.04580 g, 0.1 mmol) were weighed and dissolved in 6 mL of a mixed solvent of deionized water and isopropanol (volume ratio 1:1), without adding acid or alkali, to obtain solution 3. This solution was aged at room temperature for 48 hours to obtain colorless and transparent stock solution 3. Without adding lithium chloride or lithium nitrate, a colorless and transparent coating curing solution 3 was obtained, and its Fourier transform spectrum is shown below. Figure 9 As shown.
[0057] Three drops of the coating curing solution were applied to the surface of a glass slide that had been treated with Plasma for 4 minutes. The solvent was evaporated at 60°C, and then cured at 120°C for 2 hours to obtain coating 3. The performance of the coating is summarized in Table 1, and its Fourier transform spectrum is shown in the figure. Figure 9 As shown. From Figure 9 We can see that solution 3 at 940 cm -1 Silyl groups and at 1183cm -1 The proportion of silicon-oxygen-silicon bonds in the coating is significantly higher than that in coating 3, indicating that the silicon hydroxyl groups further dehydrate and crosslink during the heating and curing process to form a silicon-oxygen-silicon crosslinking network, thereby giving the coating higher mechanical properties.
[0058] Example 8
[0059] Branched siloxane 2 (0.1422 g, 0.1 mmol), tetraethoxysilane (0.3744 g, 1.8 mmol) and sulfobetaine siloxane (0.09160 g, 0.2 mmol) were weighed and dissolved in a mixed solvent of 6 mL of deionized water and isopropanol (volume ratio 1:1) without adding acid or alkali to obtain solution 4. This solution was aged at room temperature for 48 hours to obtain colorless and transparent stock solution 4. Without adding lithium chloride or lithium nitrate, colorless and transparent coating curing solution 4 was obtained.
[0060] Coating curing solution 4 was drop-coated onto the surface of a glass slide treated with Plasma for 4 minutes. The solvent was evaporated at 60°C, and then cured at 120°C for 2 hours to obtain coating 4. Electrochemical impedance spectroscopy (EIS) of coating 4 was performed, and its EIS spectrum is shown in Figure 10. The conductivity of coating 4 was obtained by simulating the EIS spectrum using the Randle equivalent circuit. Performance is summarized in Table 1.
[0061] Example 9
[0062] Branched siloxane 2 (0.1422 g, 0.1 mmol), tetraethoxysilane (0.3744 g, 1.8 mmol), and sulfobetaine siloxane (0.1832 g, 0.4 mmol) were weighed and dissolved in a mixed solvent of 6 mL of deionized water and isopropanol (volume ratio 1:1) without adding acid or alkali to obtain solution 5. This solution was aged at room temperature for 48 hours to obtain colorless and transparent stock solution 5. Without adding lithium chloride or lithium nitrate, colorless and transparent coating curing solution 5 was obtained.
[0063] The coating curing solution 5 was transferred to the surface of a glass slide that had been treated with Plasma for 4 minutes by drop casting. The solvent was evaporated at 60°C and then cured at 120°C for 2 hours to obtain coating 5. The performance is summarized in Table 1.
[0064] Example 10
[0065] Branched siloxane 2 (0.1422 g, 0.1 mmol), tetraethoxysilane (0.3744 g, 1.8 mmol) and sulfobetaine siloxane (0.09160 g, 0.2 mmol) were weighed and dissolved in a mixed solvent of 6 mL of deionized water and isopropanol (volume ratio 1:1) without adding acid or base to obtain solution 6. This solution was aged at room temperature for 18 hours to obtain colorless and transparent stock solution 6.
[0066] The colorless and transparent stock solution 6 was compounded with 20 mg of lithium chloride to obtain the coating curing solution 6. The solution was then dropped onto the surface of a glass slide treated with 1 Plasma for 4 minutes. The solvent was evaporated at 60°C and then cured at 120°C for 2 hours to obtain the coating 6. The performance is summarized in Table 1.
[0067] Example 11
[0068] Branched siloxane 2 (0.1422 g, 0.1 mmol), tetraethoxysilane (0.3744 g, 1.8 mmol) and sulfobetaine siloxane (0.1832 g, 0.4 mmol) were weighed and dissolved in a mixed solvent of 6 mL of deionized water and isopropanol (volume ratio 1:1) without adding acid or base to obtain solution 7. This solution was aged at room temperature for 18 hours to obtain colorless and transparent stock solution 7.
[0069] The colorless and transparent stock solution 7 was compounded with 20 mg of lithium nitrate to obtain the coating curing solution 7. The solution was then dripped onto the surface of a glass slide that had been treated with Plasma for 4 minutes. The solvent was evaporated at 60°C and then cured at 120°C for 2 hours to obtain the coating 7. The performance is summarized in Table 1.
[0070] Example 12
[0071] Branched siloxane 1 (0.1426 g, 0.1 mmol), tetraethoxysilane (0.3744 g, 1.8 mmol) and sulfobetaine siloxane (0.02290 g, 0.05 mmol) were weighed and dissolved in a mixed solvent of 6 mL of deionized water and isopropanol (volume ratio 1:1) without adding acid or alkali to obtain solution 8. This solution was aged at room temperature for 48 hours to obtain colorless and transparent stock solution 8. Without adding lithium chloride or lithium nitrate, a colorless and transparent coating curing solution 8 was obtained.
[0072] Colorless and transparent stock solution 8 was applied dropwise to the surface of a glass slide that had been treated with Plasma for 4 minutes. The solvent was evaporated at 60°C and then cured at 120°C for 2 hours to obtain coating 8. The performance of the coating is summarized in Table 1.
[0073] Example 13
[0074] Branched siloxane 3 (0.1378 g, 0.1 mmol), tetraethoxysilane (0.3744 g, 1.8 mmol) and sulfobetaine siloxane (0.02290 g, 0.05 mmol) were weighed and dissolved in a mixed solvent of 6 mL of deionized water and isopropanol (volume ratio 1:1) without adding acid or alkali to obtain solution 9. This solution was aged at room temperature for 48 hours to obtain colorless and transparent stock solution 9. Without adding lithium chloride or lithium nitrate, a colorless and transparent coating curing solution 9 was obtained.
[0075] Coating curing solution 9 was applied dropwise to the surface of a glass slide that had been treated with Plasma for 4 minutes. The solvent was evaporated at 60°C and then cured at 120°C for 2 hours to obtain coating 9. The performance is summarized in Table 1.
[0076] Example 14
[0077] Branched siloxane 2 (0.1422 g, 0.1 mmol), methyltriethoxysilane (0.3204 g, 1.8 mmol), and sulfobetaine siloxane (0.02290 g, 0.05 mmol) were weighed and dissolved in a mixed solvent of 6 mL of deionized water and isopropanol (volume ratio 1:1) without adding acid or alkali to obtain solution 10. This solution was aged at room temperature for 48 hours to obtain colorless and transparent stock solution 10. Without adding lithium chloride or lithium nitrate, colorless and transparent coating curing solution 10 was obtained.
[0078] Coating curing solution 10 was applied dropwise to the surface of a glass slide that had been treated with Plasma for 4 minutes. The solvent was evaporated at 60°C and then cured at 120°C for 2 hours to obtain coating 10. The performance is summarized in Table 1.
[0079] Example 15
[0080] Weigh out branched siloxane 2 (0.3555g, 0.25mmol) and zirconium n-propoxide (0.4905g, 1.5mmol) and dissolve them in 4mL of isopropanol without adding acid or alkali to obtain solution 11. Let it stand at room temperature for 24 hours to age to obtain colorless and transparent stock solution 11; without adding lithium chloride or lithium nitrate, colorless and transparent coating curing solution 11 is obtained.
[0081] The coating curing solution 11 was transferred to the surface of a glass slide that had been treated with Plasma for 4 minutes by spin coating. The solvent was evaporated at 60°C and then cured at 120°C for 2 hours to obtain coating 11. The performance is summarized in Table 1.
[0082] From the data in Table 1, we can see that coatings 1 to 11 all have high hardness. However, with the addition of sulfobetaine siloxane, the hardness of coatings 1 to 7 decreases. The bending radius of the coating is 1 mm, indicating that the coating has high flexibility. With the addition of sulfobetaine siloxane, the conductivity of coatings 1 to 7 increases. Furthermore, the addition of lithium salt can significantly improve the conductivity of the material.
Claims
1. A method for preparing a high-hardness, high-flexibility, and conductive optical protective coating using highly branched siloxanes as building blocks, comprising the following steps: (1) Preparation of branched siloxanes by chemical reaction Weigh pentaerythritol tetra(mercaptoacetic acid) ester and organosiloxane monomer in a molar ratio of 1:4, then add 0.1-10 wt% of the catalyst triethylamine or dibutyltin dilaurate, and react at room temperature for 2-48 hours; the product is washed repeatedly with petroleum ether to remove the catalyst, and then the petroleum ether is removed by vacuum distillation to obtain a branched siloxane with one of the following structural formulas; the organosiloxane monomer is γ-glycidoxypropyltrimethoxysilane, 3-(isobutenoyloxy)propyltrimethoxysilane, or propyltriethoxysilane isocyanate; (2) Preparation of surfactants using a mild method Weigh propyltriethoxysilane isocyanate and N,N-dimethylethanolamine in a molar ratio of 1:1, and stir and heat at 50-70°C for 20-30 hours under nitrogen protection to obtain the intermediate 2-(dimethylamino)ethyl(3-(triethoxysilyl)propyl)carbamate. Weigh 2-(dimethylamino)ethyl(3-(triethoxysilyl)propyl)carbamate and 1,3-propanesulfonic acid lactone in a molar ratio of 1:0.5-1.5, add diethyl ether and acetone in a volume ratio of 1:0.1-10; stir the reaction at room temperature under nitrogen protection for 20-30 h, filter, take the white precipitate, wash with acetone 3-5 times, and dry to obtain the surfactant sulfobetaine siloxane; (3) Obtain the stock solution by sol-gel method The branched siloxane obtained in step (1) is dissolved in a mixed solvent of isopropanol and water at a molar ratio of 1:3 to 20:0 to 5, with the volume ratio of isopropanol to water being 1:0.1 to 1.
5. Then, an acid or base with a final concentration of 0 to 5 wt% is added, and the mixture is aged at room temperature for 12 to 48 hours to obtain a colorless and transparent stock solution. (4) Obtaining coating curing liquid by combining composite stock solution and lithium salt Lithium chloride or lithium nitrate with a final concentration of 0-10 wt% is added to the stock solution obtained in step (3) to obtain a coating curing solution; (5) A composite film layer is obtained by coating and curing. The coating curing liquid obtained in step (4) is spin-coated, dip-coated or sprayed onto the substrate surface that has been treated with Plasma for 3 to 5 minutes. After evaporating the solvent, it is cured at 60 to 160°C for 0.5 to 5 hours to obtain the high-hardness, high-flexibility, and conductive optical protective coating.
2. The method for preparing a high-hardness, high-flexibility, and conductive optical protective coating using highly branched siloxanes as building blocks as described in claim 1, characterized in that: In step (2), the concentration of 2-(dimethylamino)ethyl(3-(triethoxysilyl)propyl)carbamate in diethyl ether and acetone is 1-3 mmol / mL.
3. The method for preparing a high-hardness, high-flexibility, and conductive optical protective coating using highly branched siloxanes as building blocks as described in claim 1, characterized in that: The alkoxy compound in step (3) is methyltriethoxysilane, tetraethoxysilane or zirconium propoxide; the concentration of isopropanol and branched siloxane in water is 0.006 to 0.1 mmol / mL.
4. The method for preparing a high-hardness, high-flexibility, and conductive optical protective coating using highly branched siloxanes as building blocks as described in claim 1, characterized in that: The substrate for step (5) is a glass slide, polyethylene terephthalate, or polymethyl methacrylate.
5. A high-hardness, high-flexibility, and conductive optical protective coating using highly branched siloxanes as building blocks, characterized in that: It is prepared by the preparation method described in any one of claims 1 to 4.