Coating composition, folding-resistant flexible coating, preparation method of folding-resistant flexible coating and flexible display equipment

Abstract

The invention discloses a coating composition, a folding-resistant flexible coating, a preparation method of the folding-resistant flexible coating and flexible display equipment, and belongs to the technical field of functional polymer coatings. The coating composition comprises a photoinitiator and a flatting agent, the polyurethane resin also comprises polysiloxane cross-linked resin containing carbon-carbon double bonds and thiol with the number-average molecular weight of 500-10000; the molar ratio of carbon-carbon double bonds in the polysiloxane cross-linked resin to sulfydryl in the mercaptan is 1: (0.5-1.2); the polysiloxane cross-linked resin is at least obtained by hydrolytic condensation of a silane monomer containing a carbon-carbon double bond; the mercaptan is dimercaptan and / or polymercaptan, and polyether, polyester, polysiloxane or long-chain aliphatic series are used as a skeleton. The prepared coating has the advantages of extremely low curing shrinkage rate, excellent anti-oxygen polymerization inhibition capability and uniform cross-linked network height, and can meet the requirements of flexible display equipment such as a folding screen on'softness, hardness, no warping and no crease 'of a surface protection layer.

Description

Technical Field

[0001] This invention relates to a coating composition, a flexible coating with folding resistance, a method for preparing the same, and a flexible display device, belonging to the field of functional polymer coating technology. Background Technology

[0002] Currently, the consumer electronics industry is undergoing a profound transformation towards flexibility and shape-shifting technologies, giving rise to cutting-edge products such as rollable displays and foldable communication terminals. The core requirement for these devices is that the display module can withstand high-frequency dynamic folding fatigue. Due to the inherent brittleness of its structure, traditional rigid silicate glass covers are completely inadequate for dynamic deformation scenarios.

[0003] Currently, the industry uses optical-grade flexible polymer films as the basic carrier material for flexible display devices, with colorless polyimide (CPI) and polyethylene terephthalate (PET) being the most representative. Although these two polymer substrates have occupied the mainstream market due to their excellent deformation resistance, extreme thinness, and excellent processing yield, their inherent physical defects such as low hardness and weak scratch resistance are difficult to overcome. They are prone to irreversible scratches and wear during daily interaction, which seriously restricts the long-term service life of the device and the screen texture.

[0004] In the absence of a new generation of high-rigidity, ultra-flexible substrates, a high-performance protective layer must be constructed on the surface of existing flexible substrates to address these shortcomings. Common substrate protective layers (primarily free-radical-initiated photocurable coatings of acrylate or polyurethane acrylate systems) cannot adequately withstand the extremely demanding repeated bending requirements of foldable screens because these protective layers suffer from fundamental, insurmountable defects in their underlying polymerization mechanisms.

[0005] 1. Severe oxygen inhibition reduces optical and surface properties. Traditional free radicals are easily captured by oxygen in the air to form inactive peroxide free radicals. This leads to incomplete curing of the coating surface and a sticky phenomenon, which not only significantly reduces the surface's fingerprint resistance and scratch resistance, but also easily causes light scattering, seriously affecting the optical transmittance required for screen display;

[0006] 2. High volume shrinkage and internal stress lead to substrate warping. Traditional acrylates use a "chain polymerization" mechanism, which cures extremely quickly and gels early, accompanied by severe volume shrinkage (typically as high as 5% to 15%) during the curing process. This huge internal shrinkage stress causes the flexible film substrate to undergo severe curling or warping deformation during coating curing, greatly increasing the difficulty of subsequent lamination processes;

[0007] 3. Uneven cross-linking network leads to a deadlock between hardness and flexibility. The cross-linking network formed by traditional chain polymerization often has "cross-link-rich areas" and "cross-link-poor areas," resulting in uneven stress on the microscopic surface and brittleness on the macroscopic surface. When the cross-linking density is increased in pursuit of high hardness, the coating is prone to whitening, creases, microcracks, or even direct breakage and peeling at stress concentration points under repeated folding, especially under extreme conditions where the inward / outward folding radius R < 1.5 mm.

[0008] Although researchers have attempted to balance hardness and flexibility by introducing inorganic nanocomponents to prepare organic-inorganic hybrid coatings, the high shrinkage and susceptibility to fatigue cracking remain unresolved as long as the underlying curing network still relies on traditional acrylate chain polymerization. Therefore, there is an urgent need to develop a novel coating system that combines extremely low curing shrinkage, excellent antioxidant inhibition, and a highly uniform crosslinked network, starting from the underlying photocuring chemical mechanism, to meet the requirements of flexible display devices such as foldable screens for a surface protective layer that is both flexible and rigid, without warping or creases. Summary of the Invention

[0009] To address the aforementioned shortcomings of existing technologies, this invention proposes a coating composition, a flexible coating with fold resistance, a preparation method thereof, and a flexible display device. This coating exhibits extremely low curing shrinkage, excellent antioxidant and polymerization resistance, and a highly uniform crosslinked network, thus meeting the requirements of flexible display devices such as foldable screens for a surface protective layer that is "both flexible and rigid, without warping or creases."

[0010] The first aspect of the present invention relates to a coating composition comprising a photoinitiator and a leveling agent;

[0011] It also includes polysiloxane crosslinked resins containing carbon-carbon double bonds and thiols with a number average molecular weight of 500 to 10,000;

[0012] The molar ratio of carbon-carbon double bonds to mercapto groups in the polysiloxane crosslinked resin is 1:0.5-1.2;

[0013] The polysiloxane crosslinked resin is obtained by hydrolysis and condensation of at least a silane monomer containing a carbon-carbon double bond;

[0014] The thiols are dithiols and / or polythiols, with polyethers, polyesters, polysiloxanes or long-chain aliphatic compounds as the backbone.

[0015] A second aspect of this invention relates to a method for preparing a flexurally resistant flexible coating, comprising:

[0016] Weigh out a polysiloxane crosslinking resin containing carbon-carbon double bonds and a thiol with a number average molecular weight of 500 to 10000 according to a carbon-carbon double bond to mercapto molar ratio of 1:0.5 to 1.2. Add a photoinitiator and a leveling agent and mix thoroughly to obtain a mixture.

[0017] A bubble-free mixture is coated onto the surface of a flexible substrate and then photocured by ultraviolet light to obtain a flexible coating that is resistant to bending.

[0018] A third aspect of the present invention relates to a flexible coating that is resistant to bending, prepared using the method described above.

[0019] A fourth aspect of the present invention relates to a flexible display device comprising the aforementioned fold-resistant flexible coating.

[0020] Technical effect

[0021] 1. The polysiloxane crosslinked resin containing carbon-carbon double bonds and dithiol in the coating composition can be combined under the action of a photocuring agent; the polysiloxane crosslinked resin containing carbon-carbon double bonds has a highly crosslinked dense network, which can provide microscopic rigidity and macroscopic hardness, and scratch resistance, while the high molecular weight dithiol (polythiol) can provide a flexible skeleton, dissipate stress, and resist folding.

[0022] 2. The highly cross-linked, rigid polysiloxane nodes in the folding-resistant flexible coating provide the coating with microscopic rigidity and macroscopic hardness (scratch resistance), while the mercapto-containing macromolecules with flexible skeletons act as cross-linking agents, building an ultra-flexible "bridge" between the polysiloxane nodes. When subjected to severe bending (such as inward bending of a folding screen), the flexible skeleton chain segments can quickly dissipate stress through conformational changes in the molecular chains, preventing brittle fracture between inorganic nodes.

[0023] 3. After the introduction of thiol groups, the reaction mechanism during photocuring changes from a simple chain reaction to a mixed chain / stepwise polymerization involving thiols. The chain transfer effect of thiol groups greatly delays the arrival of the crosslinking gel point, releases the internal stress of the system, and ensures that the coating on the film maintains perfect smoothness. At the same time, it consumes the oxygen generated during the reaction, avoids surface stickiness, and ensures that the coating has optical-grade transparency. Detailed Implementation

[0024] The embodiments of the present invention will now be described in detail. Experimental methods not specifically described in the embodiments were performed according to conventional methods and conditions.

[0025] This invention relates to a flexible coating that is resistant to folding, and its preparation process is as follows:

[0026] Weigh out a polysiloxane crosslinking resin containing carbon-carbon double bonds and a thiol with a number average molecular weight of 500 to 10000 according to a carbon-carbon double bond to mercapto molar ratio of 1:0.5 to 1.2. Add a photoinitiator and a leveling agent and mix thoroughly to obtain a mixture.

[0027] A bubble-free mixture is coated onto the surface of a flexible substrate and then photocured by ultraviolet light to obtain a flexible coating that is resistant to bending.

[0028] The polysiloxane crosslinked resin containing carbon-carbon double bonds is obtained by hydrolysis and condensation of silane monomers containing carbon-carbon double bonds.

[0029] For some preferred embodiments, the molar ratio of carbon-carbon double bonds to mercapto groups can be 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9, 1:1, 1:1.1, 1:1.2, etc.

[0030] In some preferred embodiments, the number average molecular weight of the thiol can be 500, 1000, 2000, 3000, 4000, 5000, 6000, 7000, 8000, 9000, 10000, etc.

[0031] In some preferred embodiments, the carbon-carbon double-bonded silane monomer is selected from at least one of methacryloxyalkyltrialkoxysilane, acryloyloxyalkyltrialkoxysilane, vinyltrialkoxysilane, and allyltrialkoxysilane. More preferably, the methacryloxyalkyltrialkoxysilane is γ-methacryloyloxypropyltrimethoxysilane, the acryloyloxyalkyltrialkoxysilane is γ-acryloyloxypropyltrimethoxysilane, and the vinyltrialkoxysilane is vinyltrimethoxysilane and / or vinyltriethoxysilane.

[0032] In some preferred embodiments, the polysiloxane crosslinking resin containing carbon-carbon double bonds is prepared by adding silane monomers containing carbon-carbon double bonds to a mixed solvent of water and alcohol, adding an alkaline catalyst, and performing a hydrolysis-condensation reaction at 40-60°C for 4-12 hours, followed by purification or vacuum distillation to remove the solvent.

[0033] Of course, the polysiloxane crosslinking resin containing carbon-carbon double bonds can also be obtained by adding silane monomers containing carbon-carbon double bonds and silane monomers without carbon-carbon double bonds together to a mixed solvent of water and alcohol, adding an alkaline catalyst, and performing a hydrolysis-condensation reaction at 40-60°C for 4-12 hours, followed by purification or vacuum distillation to remove the solvent.

[0034] Further preferably, the silane monomer that does not contain carbon-carbon double bonds is at least one of tetraethyl orthosilicate (TEOS), methyltrimethoxysilane (MTMS), and dimethyldimethoxysilane (DMDMS), which can reduce the crosslinking density of the polysiloxane crosslinking resin to a certain extent, so as to balance the hardness and flexibility of the coating.

[0035] More preferably, the mass ratio of water to alcohol in the mixed solvent is 1:0.75 to 3, for example, the mass ratio can be 1:0.75, 1:1, 1:1.5, 1:2, 1:2.5, 1:3, etc.

[0036] Further preferably, the addition of an alkaline catalyst maintains the initial pH of the reaction system between 8.0 and 10.5. By controlling the alkaline catalytic conditions, the silane condensation rate exceeds the hydrolysis rate, resulting in the directional formation of a highly cross-linked, dense inorganic siloxane network, providing excellent coating hardness and scratch resistance. The alkaline catalyst can be ammonia, sodium hydroxide solution, or amine solution. The reaction temperature for the hydrolysis-condensation reaction can be 40℃, 45℃, 50℃, 55℃, or 60℃, and the reaction time can be controlled at 4h, 5h, 6h, 7h, 8h, 9h, 10h, 11h, or 12h.

[0037] The thiols are dithiols and / or polythiols, with polyethers, polyesters, polysiloxanes or long-chain aliphatic compounds as the backbone.

[0038] In some preferred embodiments, the photoinitiator is at least one of 1-hydroxycyclohexylphenyl ketone (Irgacure184), 2-hydroxy-2-methyl-1-phenyl-1-propanone (Darocur1173), and TPO.

[0039] In some preferred embodiments, the amount of photoinitiator added is 1.0% to 4.0% of the total mass of the polysiloxane crosslinked resin and thiol, and this amount can be 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, etc.

[0040] In some preferred embodiments, the bubble-free mixture is obtained by vacuum stirring or vacuum degassing.

[0041] Example 1

[0042] 43.5g of γ-methacryloxypropyltrimethoxysilane (KH-570, 1.75×10) was added. -1 mol) was added to 10 mL of water and 15 mL of anhydrous ethanol, and then 90 mg of 25% ammonia water was added. The mixture was stirred vigorously at 1500 rpm for 10 h to generate V-POSQ, a polysiloxane crosslinking resin containing carbon-carbon double bonds.

[0043] After the reaction was completed, volatile components were removed by rotary evaporation. The remaining viscous solution was then dissolved in 300 mL of dichloromethane. The organic layer was washed alternately with water and saturated NaCl solution until the pH of the water became neutral after washing.

[0044] After washing, an appropriate amount of anhydrous magnesium sulfate was added to the organic layer to remove excess water, followed by filtration. After filtration, rotary evaporation was performed again to remove the remaining solvent, yielding V-POSQ. V-POSQ was dissolved in butyl acetate at a weight ratio of 1:1 to obtain a V-POSQ solution.

[0045] 65 mg of V-POSQ solution was added to 0.30 mL of propylene glycol methyl ether acetate. Then, 25 mg of polyethylene glycol dithiol (SH-PEG-SH, Mn=2000) was added at a 1:1 molar ratio of mercapto to double bond. 2 mg of the free radical photoinitiator 1-hydroxycyclohexylphenyl ketone (Irgacure184) was added to the solution. After mixing thoroughly, the mixture was coated onto a 2.5 cm × 2.5 cm × 50 μm PET film and placed in a 60 °C vacuum drying oven to remove excess solvent. Finally, the film was irradiated with a 500 W mercury lamp with a 280 nm filter for 2 min to achieve UV curing, thus obtaining a transparent coating.

[0046] Example 2

[0047] The only difference between this embodiment and Embodiment 1 is the synthesis process of V-POSQ:

[0048] 43.5g of γ-methacryloxypropyltrimethoxysilane (KH-570, 1.75×10) was added. -1 1.25 g of methyltrimethoxysilane (MTMS, 9.21 × 10⁻⁶ mol) and 1.25 g of methyltrimethoxysilane (MTMS, 9.21 × 10⁻⁶ mol). -3 99 mg of ammonia solution (25% by mass) was added to 11 mL of water and 16.5 mL of anhydrous ethanol, and then 99 mg of ammonia solution (25% by mass) was added. The mixture was stirred vigorously at 1500 rpm for 10 h.

[0049] Example 3

[0050] The only difference between this embodiment and Embodiment 1 is the synthesis process of V-POSQ:

[0051] 43.5g of γ-methacryloxypropyltrimethoxysilane (KH-570, 1.75×10) was added. -1 2.64 g of methyltrimethoxysilane (MTMS, 1.94 × 10⁻⁶ mol) and 2.64 g of methyltrimethoxysilane (MTMS, 1.94 × 10⁻⁶ mol). -2 1 mol) was added together with 12 mL of water and 18 mL of anhydrous ethanol, and then 108 mg of 25% ammonia water was added. The mixture was stirred vigorously at 1500 rpm for 10 h.

[0052] Example 4

[0053] The only difference between this embodiment and Embodiment 1 is the synthesis process of V-POSQ:

[0054] 43.5g of γ-methacryloxypropyltrimethoxysilane (KH-570, 1.75×10) was added. -1 4.21 g of methyltrimethoxysilane (MTMS, 3.09 × 10⁻⁶ mol) and 4.21 g of methyltrimethoxysilane (MTMS, 3.09 × 10⁻⁶ mol). -21 mol) was added together with 13 mL of water and 19.5 mL of anhydrous ethanol, and then 117 mg of 25% ammonia water was added. The mixture was stirred vigorously at 1500 rpm for 10 h.

[0055] Example 5

[0056] The only difference between this embodiment and Embodiment 1 is the synthesis process of V-POSQ:

[0057] 43.5g of γ-methacryloxypropyltrimethoxysilane (KH-570, 1.75×10) was added. -1 5.97 g of methyltrimethoxysilane (MTMS, 4.38 × 10⁻⁶ mol) and 5.97 g of methyltrimethoxysilane (MTMS, 4.38 × 10⁻⁶ mol). -2 1 mol) was added together with 14 mL of water and 21 mL of anhydrous ethanol, and then 126 mg of 25% ammonia water was added. The mixture was stirred vigorously at 1500 rpm for 10 h.

[0058] Example 6

[0059] The only difference between this embodiment and Embodiment 1 is the synthesis process of V-POSQ:

[0060] 43.5g of γ-methacryloxypropyltrimethoxysilane (KH-570, 1.75×10) was added. -1 7.94 g of methyltrimethoxysilane (MTMS, 5.83 × 10⁻⁶ mol) and 7.94 g of methyltrimethoxysilane (MTMS, 5.83 × 10⁻⁶ mol). -2 1 mol) was added together with 15 mL of water and 22.5 mL of anhydrous ethanol, and then 135 mg of 25% ammonia water was added. The mixture was stirred vigorously at 1500 rpm for 10 h.

[0061] Example 7

[0062] The only difference between this embodiment and Embodiment 1 is the synthesis process of V-POSQ:

[0063] 43.5g of γ-methacryloxypropyltrimethoxysilane (KH-570, 1.75×10) was added. -1 10.2 g of methyltrimethoxysilane (MTMS, 7.5 × 10⁻⁶ mol) and 10.2 g of methyltrimethoxysilane (MTMS, 7.5 × 10⁻⁶ mol). -2 1 mol) was added together with 16 mL of water and 24 mL of anhydrous ethanol, and then 144 mg of 25% ammonia water was added. The mixture was stirred vigorously at 1500 rpm for 10 h.

[0064] Example 8

[0065] The only difference between this embodiment and Embodiment 1 is the synthesis process of V-POSQ:

[0066] 43.5g of γ-methacryloxypropyltrimethoxysilane (KH-570, 1.75×10) was added. -1 12.8 g of methyltrimethoxysilane (MTMS, 9.42 × 10⁻⁶ mol) and 12.8 g of methyltrimethoxysilane (MTMS, 9.42 × 10⁻⁶ mol). -2 1 mol) was added together with 17 mL of water and 25.5 mL of anhydrous ethanol, and then 153 mg of 25% ammonia water was added. The mixture was stirred vigorously at 1500 rpm for 10 h.

[0067] Comparative Example 1

[0068] The only difference between this comparative example and Example 1 is the synthesis process of V-POSQ:

[0069] 43.5g of γ-methacryloxypropyltrimethoxysilane (KH-570, 1.75×10) was added. -1 15.9 g of methyltrimethoxysilane (MTMS, 1.17 × 10⁻⁶ mol) and 15.9 g of methyltrimethoxysilane (MTMS, 1.17 × 10⁻⁶ mol). -1 1 mol) was added together with 18 mL of water and 27 mL of anhydrous ethanol, and then 162 mg of 25% ammonia water was added. The mixture was stirred vigorously at 1500 rpm for 10 h.

[0070] Comparative Example 2

[0071] The only difference between this comparative example and Example 1 is the synthesis process of V-POSQ:

[0072] 43.5g of γ-methacryloxypropyltrimethoxysilane (KH-570, 1.75×10) was added. -1 19.5 g of methyltrimethoxysilane (MTMS, 1.43 × 10⁻⁶ mol) and 19.5 g of methyltrimethoxysilane (MTMS, 1.43 × 10⁻⁶ mol). -1 171 mg of ammonia solution with a mass percentage concentration of 25% was added to 19 mL of water and 28.5 mL of anhydrous ethanol, and then 171 mg of ammonia solution with a mass percentage concentration of 25% was added. The mixture was stirred vigorously at 1500 rpm for 10 h.

[0073] Comparative Example 3

[0074] The only difference between this comparative example and Example 1 is the synthesis process of V-POSQ:

[0075] 43.5g of γ-methacryloxypropyltrimethoxysilane (KH-570, 1.75×10) was added. -1 23.8 g of methyltrimethoxysilane (MTMS, 1.75 × 10⁻⁶ mol) and 23.8 g of methyltrimethoxysilane (MTMS, 1.75 × 10⁻⁶ mol). -1 1 mol) was added together with 20 mL of water and 30 mL of anhydrous ethanol, and then 180 mg of 25% ammonia water was added. The mixture was stirred vigorously at 1500 rpm for 10 h.

[0076] The coatings prepared in the above embodiments and comparative examples were subjected to performance tests. The test methods and testing standards are as follows, and the results are shown in Table 1.

[0077] Transmittance: According to ASTM D1003 standard, the transmittance of the sample was measured using a haze meter under visible light irradiation at a wavelength of 550 nm on a 50 μm thick high-transmittance PET film.

[0078] Pencil hardness test: According to ASTM D3363 standard, a Zhonghua brand test pencil is used to scratch the coated surface at a 45° angle under a 750g load. The maximum pencil hardness that does not produce plough marks is used as the evaluation result.

[0079] Warpage: The coating solution is evenly applied to a 10cm×10cm×50μm PET film. After light curing, the film is placed flat on a glass plate, and the maximum height (mm) of the four corners of the film warping off the glass surface is measured. The lower the height, the smaller the curing shrinkage stress.

[0080] Inward folding test: Fix the sample to both ends of the bending machine and bend it inward along the functional layer of the material. The bending radius is controlled at 1mm. After holding the bend for 1 second, return it to a straight state and observe whether the coating cracks.

[0081] Dynamic bending fatigue test: The coating sample was fixed on a dynamic folding tester, with a bending radius R = 1.5 mm, a bending angle of 180°, and a test frequency of 60 times / minute. After 200,000 consecutive bends (inward folds), the surface of the coating was recorded to determine whether microcracks, whitening of creases, or peeling occurred.

[0082] Table 1 Light transmittance Pencil hardness Warp Fold in Dynamic bending fatigue test Example 1 99.1±0.2% 4H <3.0mm OK Passed (no cracks, no creases) Example 2 98.1±0.2% 4H <1.5mm OK Passed (no cracks, no creases) Example 3 97.4±0.3% 4H <1.5mm OK Passed (no cracks, no creases) Example 4 97.8±0.2% 3H <1.0mm OK Passed (no cracks, no creases) Example 5 97.1±0.3% 3H <1.0mm OK Passed (no cracks, no creases) Example 6 97.0±0.2% 3H <1.0mm OK Passed (no cracks, no creases) Example 7 96.3±0.3% 2H <5.0mm OK Passed (no cracks, no creases) Example 8 96.2±0.2% 2H <5.0mm OK Passed (no cracks, no creases) Comparative Example 1 96.0±0.3% 2H >10mm NG Failed (cracks, no creases) Comparative Example 2 95.7±0.2% 1H >10mm NG Failed (cracks, no creases) Comparative Example 3 95.0±0.3% 1H >10mm NG Failed (cracks, creases)

[0083] In summary, this invention successfully developed a novel functional coating that combines excellent hardness, ultra-high flexibility, and extremely low shrinkage. This functional coating ingeniously combines alkaline hydrolysis condensation with a thiol-ene click reaction: first, a dense inorganic nano-rigid core rich in carbon-carbon double bonds is constructed; then, under the action of a free radical photoinitiator, the highly efficient stepwise polymerization reaction between thiol groups and double bonds, "thiol-ene," precisely bridges highly compliant polyethylene glycol (PEG) long chains into the cross-linked network, forming a unique cross-linked structure of "rigid inorganic core - flexible organic long chain." Combined with the inherent low polymerization shrinkage internal stress and antioxidant polymerization inhibition properties of the thiol-ene system, this completely breaks through the technical barriers of traditional acrylate photocuring systems, which are characterized by high brittleness, easy stickiness, and a high tendency to warp flexible substrates. The final coating not only possesses optical-grade transmittance but also perfectly dissipates stress concentration under extremely small folding radii, perfectly resisting high-frequency dynamic bending fatigue. Furthermore, according to the test results, silane monomers without carbon-carbon double bonds can reduce the crosslinking density of polysiloxane crosslinking resins to a certain extent. Adding an appropriate amount can balance the hardness and flexibility of the coating, while adding too much will result in an overly soft coating that cannot meet the requirements for use.

[0084] It should be emphasized that the above are merely preferred embodiments of the present invention and are not intended to limit the present invention in any way. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention shall still fall within the scope of the technical solution of the present invention.

Claims

1. A coating composition comprising a photoinitiator and a leveling agent; characterized in that: It also includes polysiloxane crosslinked resins containing carbon-carbon double bonds and thiols with a number average molecular weight of 500 to 10,000; The molar ratio of carbon-carbon double bonds to mercapto groups in the polysiloxane crosslinked resin is 1:0.5-1.2; The polysiloxane crosslinked resin is obtained by hydrolysis and condensation of at least a silane monomer containing a carbon-carbon double bond; The thiols are dithiols and / or polythiols, with polyethers, polyesters, polysiloxanes or long-chain aliphatic compounds as the backbone.

2. The coating composition according to claim 1, characterized in that: The polysiloxane crosslinked resin is further obtained by co-hydrolysis and condensation of silane monomers containing carbon-carbon double bonds and silane monomers without carbon-carbon double bonds.

3. A method for preparing a flexible coating that is resistant to folding, characterized in that: Weigh out a polysiloxane crosslinking resin containing carbon-carbon double bonds and a thiol with a number average molecular weight of 500 to 10000 according to a carbon-carbon double bond to mercapto molar ratio of 1:0.5 to 1.

2. Add a photoinitiator and a leveling agent and mix thoroughly to obtain a mixture. A bubble-free mixture is coated onto the surface of a flexible substrate and then cured by ultraviolet light to obtain a flexible coating that is resistant to bending. The polysiloxane crosslinked resin containing carbon-carbon double bonds is obtained by hydrolysis and condensation of silane monomers containing carbon-carbon double bonds; The thiols are dithiols and / or polythiols, with polyethers, polyesters, polysiloxanes or long-chain aliphatic compounds as the backbone.

4. The preparation method according to claim 3, characterized in that: The polysiloxane crosslinking resin containing carbon-carbon double bonds is prepared by adding silane monomers containing carbon-carbon double bonds to a mixed solvent of water and alcohol, adding an alkaline catalyst, and performing a hydrolysis-condensation reaction at 40-60°C for 4-12 hours, followed by purification or vacuum distillation to remove the solvent.

5. The preparation method according to claim 3, characterized in that: The polysiloxane crosslinking resin containing carbon-carbon double bonds is prepared by adding silane monomers containing carbon-carbon double bonds and silane monomers without carbon-carbon double bonds to a mixed solvent of water and alcohol, adding an alkaline catalyst, and performing a hydrolysis-condensation reaction at 40-60°C for 4-12 hours. The solvent is then removed by purification or vacuum distillation.

6. The preparation method according to claim 4 or 5, characterized in that: The carbon-carbon double bond-containing silane monomer is selected from at least one of methacryloyloxyalkyltrialkoxysilane, acryloyloxyalkyltrialkoxysilane, vinyltrialkoxysilane, and allyltrialkoxysilane.

7. The preparation method according to claim 6, characterized in that: The methacryloyloxyalkyltrialkoxysilane is γ-methacryloyloxypropyltrimethoxysilane, the acryloyloxyalkyltrialkoxysilane is γ-acryloyloxypropyltrimethoxysilane, and the vinyltrialkoxysilane is vinyltrimethoxysilane and / or vinyltriethoxysilane.

8. The preparation method according to claim 5, characterized in that: The silane monomer without carbon-carbon double bonds is at least one of tetraethyl orthosilicate, methyltrimethoxysilane, and dimethyldimethoxysilane, and the molar ratio of the silane monomer without carbon-carbon double bonds to the silane monomer with carbon-carbon double bonds does not exceed 0.

6.

9. The preparation method according to claim 3, characterized in that: The mass ratio of water to alcohol in the mixed solvent is 1:0.75 to 3.

10. The preparation method according to claim 3, characterized in that: The addition of an alkaline catalyst keeps the initial pH of the reaction system between 8.0 and 10.

5.

11. The preparation method according to claim 3, characterized in that: The photoinitiator is at least one of 1-hydroxycyclohexylphenyl ketone, 2-hydroxy-2-methyl-1-phenyl-1-propanone, and TPO.

12. The preparation method according to claim 3 or 11, characterized in that: The amount of photoinitiator added is 1.0% to 4.0% of the total mass of the polysiloxane crosslinked resin and thiol.

13. The preparation method according to claim 3, characterized in that: The bubble-free mixture is obtained by vacuum stirring or vacuum degassing.

14. A flexible coating that withstands folding, characterized in that: It is prepared by any one of the preparation methods described in claims 3 to 13.

15. A flexible display device, characterized in that: Includes the flexural flexible coating as described in claim 14.