A 9h optical film and a method of making the same

Abstract

This invention relates to a 9H optical film and its preparation method, belonging to the field of optical protective film technology. The optical film uses PET as a base film, with a high-hardness coating composed of epoxy silicone resin and modified fillers attached to its surface. The modified filler is prepared via a three-step process: KH-560 epoxidation, trifluorobutanol fluorination to introduce low surface energy segments, and epichlorohydrin to introduce terminal epoxy groups. During the staged curing process, the modified filler spontaneously migrates to the coating surface due to the low surface energy characteristics of the fluorinated segments, forming a filler concentration gradient distribution; its terminal epoxy groups participate in the cross-linking reaction, anchoring the filler in the resin network, thereby constructing a gradient structure with high filler enrichment on the surface and high cross-linking density internally. This gradient structure enables the coating surface to achieve a pencil hardness of 9H, while simultaneously imparting good flexibility and interfacial adhesion to the film material, solving the technical challenge of simultaneously achieving high hardness and flexibility.

Description

Technical Field

[0001] This invention belongs to the field of optical protective film technology, specifically, it relates to a 9H optical film and its preparation method. Background Technology

[0002] With the widespread adoption of consumer electronics, the screen, as the core interface for human-computer interaction, directly impacts user experience and product lifespan due to its surface protection performance. Screen protectors are widely used because they effectively prevent scratches and reduce the risk of screen breakage from drops. Traditional optical screen protectors are mostly based on glass. Glass has high surface hardness, effectively resisting scratches from daily use. However, its high density and brittleness make it prone to breakage under point impacts, and it increases the overall weight of the device, making it difficult to meet the demands for lightweight and thin electronic products. Screen protectors based on polymers such as polyethylene terephthalate (PET) and polyimide (PI) are lightweight, flexible, and have excellent impact resistance. However, their surface hardness is generally lower, resulting in insufficient wear and scratch resistance, making it difficult to provide effective physical protection for the screen.

[0003] To overcome the insufficient hardness of polymer base films, the industry commonly employs a technique of coating the polymer base film with a high-hardness coating. This approach achieves this by dividing the functions between the base film and the coating: the base film provides flexibility and support, while the coating provides surface hardness and scratch resistance, thus maintaining the overall flexibility of the film while imparting excellent surface protection properties. Introducing nanofillers into the coating is a common method to achieve high hardness. Nano-silica, due to its high hardness, high transparency, and good compatibility with organic resins, is widely used as a coating reinforcement filler. Traditional filler reinforcement methods involve uniformly dispersing nano-silica in the resin matrix, improving the overall hardness of the coating through physical filling. However, this uniformly dispersed system has significant limitations: the modulus difference between the filler and the resin matrix leads to stress concentration in filler-rich areas under bending stress, causing coating cracking. Especially when maintaining high surface hardness, a higher filler content exacerbates the hardening cracking problem. In comparison, surface modification technology, by introducing functional groups that can chemically react with the coating matrix material, can construct an organic-inorganic hybrid reinforcement system, which can alleviate brittle defects to some extent. However, it is still difficult to meet the toughness requirements under a surface hardness of 9H. Summary of the Invention

[0004] In order to solve the technical problems mentioned in the background art, the purpose of this invention is to provide a 9H optical film and its preparation method.

[0005] The objective of this invention can be achieved through the following technical solutions:

[0006] A 9H optical film includes a base film and a high-hardness coating on its surface;

[0007] The base film can be a single polymer film material or a composite film material with multiple functions (such as privacy protection, blue light protection, and glare protection). The implementation process of this invention is to study the performance of its coating. PET base film is selected to reduce the influence of other factors on optical performance. Hereinafter, it will be referred to as base film.

[0008] The high-hardness coating uses epoxy silicone resin and latent amine curing agent as film-forming substrates, with 3.8-5.5 wt% modified filler and no more than 1.5 wt% additives.

[0009] Furthermore, the epoxy equivalent of the epoxy silicone resin is no higher than 300 g / eq, and the high crosslinking density ensures the hardness of the film.

[0010] The modified filler is prepared by the following method:

[0011] Step A1: Mix silane coupling agent KH-560 and ethanol aqueous solution, acidify to pH 4-5, add nano silica to disperse and stir for 12 h, centrifuge to separate the solid phase and wash and dry to obtain the coupling matrix;

[0012] Step A2: Trifluorobutanol, triethylamine and anhydrous acetone are premixed, added to the coupling matrix for dispersion and heated to 55±2℃ and refluxed for 6-8h. After centrifugation to separate the solid phase, the mixture is dried to obtain the fluorinated matrix.

[0013] Step A3: Mix the fluorinated matrix, epichlorohydrin, tetrabutylammonium bromide and toluene, heat to 80-100℃ and stir for 4-6 hours. Then add sodium hydroxide aqueous solution and continue the reaction at 55-70℃ for 3-4 hours. Centrifuge to separate the solid phase and wash and dry to obtain the modified filler.

[0014] In step A1 above, the ratio of nano-silica, silane coupling agent KH-560, and ethanol aqueous solution is 10g: 2.7-3.5mL: 100-120mL. The silane coupling agent KH-560 hydrolyzes and couples with the nano-silica to form strong Si-O-Si covalent bonds, ensuring a strong connection between the modified layer and the inorganic core, and providing a solid interfacial strength substrate.

[0015] Furthermore, the average particle size of the nano-silica is in the range of 20-50 nm. Under this specification setting, the nanoparticles maintain good dispersion and migration ability, while providing high surface hardness.

[0016] In step A2 above, the ratio of coupling matrix, trifluorobutanol, triethylamine and anhydrous acetone is 10g: 2-2.5mL: 1-1.5mL: 50-70mL. The hydroxyl groups of trifluorobutanol undergo a ring-opening reaction with the epoxy groups on the surface of epoxy nano silica to form hydroxyl groups and introduce fluorine-containing structures.

[0017] In step A3 above, the ratio of fluorinated matrix, epichlorohydrin, tetrabutylammonium bromide, sodium hydroxide, and toluene is 10g:1.2-1.8mL:0.3-0.5g:2.5-3.5g:60-80mL. The small-molecule epichlorohydrin reacts with the hydroxyl groups on the surface of the fluorinated matrix, and then the ring is closed under the strong alkalinity of sodium hydroxide, thus introducing epoxy modification.

[0018] A method for preparing a 9H optical film is as follows:

[0019] Step S1: Premix epoxy silicone resin, latent amine curing agent and additives, then add modified filler, mix and vacuum degas to obtain coating liquid;

[0020] Step S2: The coating liquid is evenly coated onto the surface of the base film, pre-baked and set at 50-60℃, and then finally baked and cured at 80-95℃ to form a high-hardness coating on the surface of the base film, thus obtaining the 9H optical film.

[0021] Furthermore, the dry film thickness of the high-hardness coating is 30-50 μm, at which coating thickness, the overall performance of surface quality, hardness and toughness is superior.

[0022] The beneficial effects of this invention are:

[0023] The core innovation of the 9H optical film provided by this invention lies in the design of the molecular structure of the modified filler, which enables it to spontaneously construct a filler concentration gradient distribution during the coating curing process, thereby forming a gradient structure with varying degrees of cross-linking. This achieves a synergistic enhancement of high surface hardness and overall high toughness. Specifically:

[0024] This invention first involves a three-step chemical modification of nano-silica fillers. First, epoxy groups are introduced onto the surface of nano-silica using the silane coupling agent KH-560, forming epoxy-based nano-silica. Then, a ring-opening reaction between trifluorobutanol and the epoxy groups introduces fluorinated segments onto the particle surface, imparting extremely low surface energy to the filler. Finally, through the reaction of epichlorohydrin with surface hydroxyl groups and ring-closing treatment, epoxy groups are reintroduced at the outer ends of the fluorinated segments. This results in the modified filler possessing the following key characteristics: first, the extremely low surface energy of the fluorinated segments provides a thermodynamic driving force for subsequent gradient distribution; second, the terminal epoxy groups can participate in the epoxy-amine crosslinking reaction, anchoring the filler to the resin network through chemical bonds; and third, the overall multilayer structure ensures that the filler retains sufficient molecular mobility during the initial curing stage.

[0025] During the coating curing process, the fluorinated segments on the surface of the modified filler, due to their extremely low surface energy, spontaneously migrate towards the air-coating interface, following the principle of minimizing thermodynamic surface free energy. The staged curing process of this invention provides a sufficient time window for this migration: in the pre-curing stage, the system viscosity is low, allowing the filler to fully accumulate on the surface; as the temperature rises, the resin begins to crosslink but is not yet fully cured, and the filler still has limited migration space; finally, high-temperature curing fixes the formed gradient distribution structure. The resulting coating exhibits a gradient distribution characteristic where the filler content gradually decreases from the surface towards the base film, i.e., a rich nano-silica reinforcement layer forms on the surface, the filler content gradually decreases internally, and the filler content is lowest in the interface region.

[0026] Because the epoxy groups carried at the ends of the modified fillers participate in the epoxy-amine crosslinking reaction, the fillers are not only physical reinforcing agents but also chemical crosslinking points of the crosslinking network. The gradient distribution of fillers in the coating directly leads to the gradient distribution of the crosslinking network density. Specifically, the surface layer of the coating has high surface hardness due to filler enrichment, but the steric hindrance effect of the fluorinated segments and their weak interactions result in a relatively low degree of crosslinking in this region. Inside the coating, the filler content decreases, and crosslinking mainly relies on the functional groups of the epoxy silicone resin itself to form a relatively dense crosslinking network. The filler content is lowest at the interface between the coating and the base film, where the resin maintains high flexibility and good affinity with the base film.

[0027] This gradient structure, characterized by "high filler content and low cross-linking degree on the surface" and "low filler content and high cross-linking degree internally," closely matches the stress distribution pattern of the optical film during bending. When the film is bent, the coating surface experiences the greatest tensile deformation. The lower initial cross-linking degree on the surface endows it with good deformation capacity, preventing brittle cracking. Meanwhile, the higher cross-linking degree inside the coating provides sufficient structural support, preventing the overall collapse of the coating. At the same time, the interface region, with its lowest filler content and the resin remaining flexible, ensures a strong bond between the coating and the base film. It is this gradient structure that enables the coating to achieve a 9H surface hardness while possessing excellent bending resistance. The fluorinated segments enriched on the surface also endow the coating with good hydrophobic and antifouling properties.

[0028] Compared to existing reinforcement schemes that rely on uniformly dispersed fillers, the gradient distribution structure constructed in this invention fundamentally solves the contradiction between hardness and flexibility in traditional filler-reinforced systems. In uniformly dispersed systems, the modulus difference between the filler and the resin matrix leads to stress concentration during bending. However, this invention, through gradient distribution, concentrates high-filler content areas on the surface, while the interior consists of a flexible layer with low filler content. This achieves a synergistic balance between high surface hardness and overall high toughness, providing a high-performance and economical technical solution for the field of optical protective films. Detailed Implementation

[0029] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0030] The following information pertains to the raw materials used in the composite system during the implementation process:

[0031] Example 1: Preparation of 9H optical film. The specific implementation process is as follows:

[0032] 1. Preparation of modified fillers

[0033] Step A1: Prepare a 60% (v / v) ethanol-water solution using industrial ethanol and deionized water. Mix the silane coupling agent KH-560 with the ethanol-water solution, add hydrochloric acid to acidify to pH 4.2, then add nano-silica (average particle size 50 μm), and disperse using ultrasound for 10 min, followed by stirring at 60 rpm for 12 h. The ratio of nano-silica, silane coupling agent KH-560, and ethanol-water solution is 10 g: 2.7 mL: 100 mL. Finally, centrifuge to separate the solid phase, wash with deionized water, and dry with hot air to obtain the coupling matrix.

[0034] Step A2: Add trifluorobutanol, triethylamine and anhydrous acetone and stir to premix. Then add the coupling matrix and disperse by ultrasonication. Heat to 55±2℃ and reflux for 6 hours. The ratio of coupling matrix, trifluorobutanol, triethylamine and anhydrous acetone is 10g:2.5mL:1.5mL:70mL. Finally, centrifuge to separate the solid phase and dry with hot air to obtain the fluorinated matrix.

[0035] Step A3: Add fluorinated matrix, epichlorohydrin, tetrabutylammonium bromide and toluene to the mixture and stir. Heat to 100℃ and stir for 4 hours. Then add sodium hydroxide to prepare a 10% aqueous solution and continue the reaction at 70℃ for 3 hours. The ratio of fluorinated matrix, epichlorohydrin, tetrabutylammonium bromide, sodium hydroxide and toluene is 10g:1.8mL:0.5g:3.5g:80mL. Finally, centrifuge to separate the solid phase, wash with acetone and deionized water in sequence, and dry to obtain the modified filler.

[0036] 2.9H optical film preparation

[0037] Step S1: Using epoxy silicone resin (model: SEI-2030P, epoxy equivalent approximately 190g / eq) and latent amine curing agent (model: EH-5031S) as film-forming substrates, feed them at a weight ratio of 1:0.65. Then add 0.4wt% leveling agent (model: BYK-333) and 0.2wt% defoamer (model: BYK-055) to the film-forming substrate. Premix at high speed of 600rpm for 3min, then reduce the speed to 60rpm, add 5wt% modified filler to the film-forming substrate and mix for 30min. Vacuum degassing for 1h to obtain the coating liquid.

[0038] Step S2: Select a 125μm PET optical film as the base film with a surface tension of about 55 dyne / cm. Use slit extrusion coating to evenly coat the coating liquid onto the surface of the PET base film. First, pre-bake and set it at 50℃ for 20min, and then finally bake and cure it at 80℃ for 8min to form a high-hardness coating on the surface of the base film. The dry film thickness is measured to be 45μm, and the optical film is obtained.

[0039] Example 2: Preparation of 9H optical film, the specific implementation process is as follows:

[0040] 1. Preparation of modified fillers

[0041] Step A1: Prepare a 60% (v / v) ethanol-water solution using industrial ethanol and deionized water. Mix the silane coupling agent KH-560 with the ethanol-water solution, add hydrochloric acid to acidify to pH 4.5, then add nano-silica (average particle size 50 μm), and disperse using ultrasound for 10 min, then switch to stirring at 60 rpm for 12 h. The ratio of nano-silica, silane coupling agent KH-560, and ethanol-water solution is 10 g: 3 mL: 120 mL. Finally, centrifuge to separate the solid phase, wash with deionized water, and dry with hot air to obtain the coupling matrix.

[0042] Step A2: Add trifluorobutanol, triethylamine and anhydrous acetone and stir to premix. Then add the coupling matrix and disperse by ultrasonication. Heat to 55±2℃ and reflux for 7h. The ratio of coupling matrix, trifluorobutanol, triethylamine and anhydrous acetone is 10g:2.5mL:1mL:60mL. Finally, centrifuge to separate the solid phase and dry with hot air to obtain the fluorinated matrix.

[0043] Step A3: Add fluorinated matrix, epichlorohydrin, tetrabutylammonium bromide and toluene to the mixture and stir. Heat to 90℃ and stir for 5 hours. Then add sodium hydroxide to prepare a 10% aqueous solution and continue the reaction at 60℃ for 3.5 hours. The ratio of fluorinated matrix, epichlorohydrin, tetrabutylammonium bromide, sodium hydroxide and toluene is 10g:1.5mL:0.4g:3g:80mL. Finally, centrifuge to separate the solid phase, wash with acetone and deionized water in sequence, and dry to obtain the modified filler.

[0044] 2.9H optical film preparation

[0045] Step S1: Using epoxy silicone resin (model: SEI-2030P, epoxy equivalent approximately 190g / eq) and latent amine curing agent (model: EH-5031S) as film-forming substrates, feed them at a weight ratio of 1:0.6. Then add 0.5wt% leveling agent (model: BYK-333) and 0.2wt% defoamer (model: BYK-055) to the film-forming substrate. Premix at high speed of 600rpm for 3min, then reduce the speed to 60rpm, add 5.5wt% modified filler to the film-forming substrate and mix for 30min. Vacuum degassing for 1h to obtain the coating liquid.

[0046] Step S2: Select a 125μm PET optical film as the base film with a surface tension of about 55 dyne / cm. Use slit extrusion coating to evenly coat the coating liquid onto the surface of the PET base film. First, pre-bake and set it at 50℃ for 20min, and then finally bake and cure it at 90℃ for 6min to form a high-hardness coating on the surface of the base film. The dry film thickness is measured to be 48μm, and the optical film is obtained.

[0047] Example 3: Preparation of 9H optical film, the specific implementation process is as follows:

[0048] 1. Preparation of modified fillers

[0049] Step A1: Prepare a 60% (v / v) ethanol-water solution using industrial ethanol and deionized water. Mix the silane coupling agent KH-560 with the ethanol-water solution, add hydrochloric acid to acidify to pH 5, then add nano-silica (average particle size 25 μm), and disperse using ultrasound for 10 min, then switch to stirring at 60 rpm for 12 h. The ratio of nano-silica, silane coupling agent KH-560, and ethanol-water solution is 10 g: 3.5 mL: 100 mL. Finally, centrifuge to separate the solid phase, wash with deionized water, and dry with hot air to obtain the coupling matrix.

[0050] Step A2: Add trifluorobutanol, triethylamine and anhydrous acetone and stir to premix. Then add the coupling matrix and disperse by ultrasonication. Heat to 55±2℃ and reflux for 8 hours. The ratio of coupling matrix, trifluorobutanol, triethylamine and anhydrous acetone is 10g:2mL:1.5mL:50mL. Finally, centrifuge to separate the solid phase and dry with hot air to obtain the fluorinated matrix.

[0051] Step A3: Add fluorinated matrix, epichlorohydrin, tetrabutylammonium bromide and toluene to the mixture and stir. Heat to 80℃ and stir for 6 hours. Then add sodium hydroxide to prepare a 10% aqueous solution and continue the reaction at 55℃ for 4 hours. The ratio of fluorinated matrix, epichlorohydrin, tetrabutylammonium bromide, sodium hydroxide and toluene is 10g:1.2mL:0.3g:2.5g:60mL. Finally, centrifuge to separate the solid phase, wash with acetone and deionized water in sequence, and dry to obtain the modified filler.

[0052] 2.9H optical film preparation

[0053] Step S1: Using epoxy silicone resin (model: SEI-8030, epoxy equivalent approximately 270 g / eq) and latent amine curing agent (model: EH-5031S) as film-forming substrates, feed them at a weight ratio of 1:0.48. Then add 0.8 wt% leveling agent (model: BYK-333) and 0.3 wt% defoamer (model: BYK-055) to the film-forming substrate. Premix at high speed of 600 rpm for 3 min, then reduce the speed to 60 rpm, add 3.8 wt% modified filler to the film-forming substrate and mix for 30 min. Vacuum degassing for 1 h to obtain the coating liquid.

[0054] Step S2: Select a 125μm PET optical film as the base film with a surface tension of about 55 dyne / cm. Use slit extrusion coating to evenly coat the coating liquid onto the surface of the PET base film. First, pre-bake and set it at 55℃ for 15 min, and then finally bake and cure it at 95℃ for 5 min to form a high-hardness coating on the surface of the base film. The dry film thickness is measured to be 32μm, and the optical film is obtained.

[0055] Example 4: Preparation of 9H optical film. The specific implementation process is as follows:

[0056] 1. Preparation of modified fillers

[0057] Step A1: Prepare a 60% (v / v) ethanol-water solution using industrial ethanol and deionized water. Mix the silane coupling agent KH-560 with the ethanol-water solution, add hydrochloric acid to acidify to pH 4.7, then add nano-silica (average particle size 25 μm), and disperse using ultrasound for 10 min, then switch to stirring at 60 rpm for 12 h. The ratio of nano-silica, silane coupling agent KH-560, and ethanol-water solution is 10 g: 3.2 mL: 100 mL. Finally, centrifuge to separate the solid phase, wash with deionized water, and dry with hot air to obtain the coupling matrix.

[0058] Step A2: Add trifluorobutanol, triethylamine and anhydrous acetone and stir to premix. Then add the coupling matrix and disperse by ultrasonication. Heat to 55±2℃ and reflux for 7h. The ratio of coupling matrix, trifluorobutanol, triethylamine and anhydrous acetone is 10g:2.2mL:1.2mL:60mL. Finally, centrifuge to separate the solid phase and dry with hot air to obtain the fluorinated matrix.

[0059] Step A3: Add fluorinated matrix, epichlorohydrin, tetrabutylammonium bromide and toluene to the mixture and stir. Heat to 95℃ and stir for 4.5h. Then add sodium hydroxide to prepare a 10% aqueous solution and continue the reaction at 65℃ for 3.5h. The ratio of fluorinated matrix, epichlorohydrin, tetrabutylammonium bromide, sodium hydroxide and toluene is 10g:1.5mL:0.4g:2.8g:75mL. Finally, centrifuge to separate the solid phase, wash with acetone and deionized water in sequence, and dry to obtain the modified filler.

[0060] 2.9H optical film preparation

[0061] Step S1: Using epoxy silicone resin (model: SEI-8030, epoxy equivalent approximately 270 g / eq) and latent amine curing agent (model: EH-5031S) as film-forming substrates, feed them at a weight ratio of 1:0.52. Then add 0.7 wt% leveling agent (model: BYK-333) and 0.5 wt% defoamer (model: BYK-055) to the film-forming substrate. Premix at high speed of 600 rpm for 3 min, then reduce the speed to 60 rpm, add 4.3 wt% modified filler to the film-forming substrate and mix for 30 min. Vacuum degassing for 1 h to obtain the coating liquid.

[0062] Step S2: Select a 125μm PET optical film as the base film with a surface tension of about 55 dyne / cm. Use slit extrusion coating to evenly coat the coating liquid onto the surface of the PET base film. First, pre-bake and set it at 60℃ for 20min, and then finally bake and cure it at 90℃ for 7min to form a high-hardness coating on the surface of the base film. The dry film thickness is measured to be 35μm, and the optical film is obtained.

[0063] Comparative Example 1 follows the same implementation process as in Example 4, but the modified filler is replaced in equal amounts with a coupling matrix of surface-grafted epoxy structure, while the rest remains identical.

[0064] Comparative Example 2, based on the test results of Comparative Example 1 above, used as a control, increased the amount of coupling matrix to 12 wt% of the film-forming substrate, with the rest being exactly the same.

[0065] Comparative Example 3 follows the same implementation process as Example 4, except that the modified filler is replaced in equal amounts with fluorine-modified nano silica (model: SF-BKT-001, native silica particle size is 20nm), and all other aspects are exactly the same.

[0066] The prepared optical films were tested according to ASTM D3363-22 for surface pencil hardness, ASTM D7334-08 for surface water contact angle, and ASTM D1003-21 for light transmittance and haze. The specific test results are shown in Table 1.

[0067] Table 1

[0068] Pencil hardness / H Water contact angle / ° transmittance / % Haze / % Example 1 ≥9 106 90.2 0.7 Example 2 ≥9 109 89.7 0.8 Example 3 ≥9 113 91.4 0.6 Example 4 ≥9 115 90.8 0.7 Comparative Example 1 5 86 88.1 0.5 Comparative Example 2 ≥9 84 85.3 0.7 Comparative Example 3 8 117 90.5 0.8

[0069] As shown in Table 1, the test results indicate that the prepared optical film has a surface pencil hardness of 9H, which is excellent and provides the surface protection capability of glass. The surface water contact angle is above 100°, which provides good anti-fouling capability. The light transmittance is around 90%, which meets the requirements for optical protective film. The overall haze is relatively high, but it still meets the requirement of not exceeding 1%.

[0070] The optical film prepared above was subjected to adhesion testing according to ASTM D3359-23 standard, and minimum bending radius testing according to ASTM D522-17 standard. The coated surface was rubbed with 500g of 0000# steel wool for 1000 cycles, and the surface condition was observed. Specific test results are shown in Table 2.

[0071] Table 2

[0072] Adhesion rating Minimum bending radius / mm Surface state after friction Example 1 5B 3 Minor scratches Example 2 5B 3 Minor scratches Example 3 5B 2 Minor scratches Example 4 5B 2 Minor scratches Comparative Example 1 5B 2 Severe scratches Comparative Example 2 4B 5 Obvious scratches Comparative Example 3 2B 6 Obvious scratches

[0073] As shown in Table 2, the optical films prepared in the examples all achieved an adhesion grade of 5B for their high-hardness coatings, with a minimum bending radius of 2-3 mm. After 1000 rubs, only slight scratches appeared. Compared to the comparative examples, Comparative Example 1 had a lower surface hardness and developed severe scratches after rubbing, resulting in insufficient protective performance. In Comparative Example 2, increasing the amount of filler led to a decrease in adhesion, a significant increase in the minimum bending radius, and a significant deterioration in toughness. Comparative Example 3 used fluorinated fillers, which increased surface hardness, but severely deteriorated the surface properties of the coating, resulting in obvious cracks during the cross-cutting process, a decrease in adhesion grade, and a higher minimum bending radius, failing to meet the toughness requirements.

[0074] In the description of this specification, the references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0075] The above description is merely an example and illustration of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described, or use similar methods to replace them, as long as they do not deviate from the invention or exceed the scope defined in the claims, all of which should fall within the protection scope of the present invention.

Claims

1. A 9H optical film comprising a base film and a high hardness coating on a surface thereof, characterized in that, The high-hardness coating is prepared from an epoxy silicone resin and a latent amine curing agent as a film-forming base material, with 3.8-5.5 wt% of a modified filler and not more than 1.5 wt% of an auxiliary agent added; The modified filler is prepared by the following method: Step A1: mix silane coupling agent KH-560 and an aqueous ethanol solution, acidify to a pH value of 4-5, add nano-silica dispersion, stir for 12 h, centrifugally separate the solid phase and wash and dry, to obtain a coupling matrix; Step A2: pre-mix trifluorobutanol, triethylamine and anhydrous acetone, add the coupling matrix dispersion and heat to 55±2℃ to reflux for 6-8 h, centrifugally separate the solid phase and dry, to obtain a fluorinated matrix; Step A3: mix the fluorinated matrix, epichlorohydrin, tetrabutylammonium bromide and toluene, heat to 80-100℃ and stir for 4-6 h, then add an aqueous sodium hydroxide solution, control the temperature to 55-70℃ and continue to react for 3-4 h, centrifugally separate the solid phase and wash and dry, to obtain the modified filler.

2. The 9H optical film of claim 1, wherein, The amount ratio of nano-silica, silane coupling agent KH-560 and aqueous ethanol solution is 10 g: 2.7-3.5 mL: 100-120 mL.

3. The 9H optical film of claim 2, wherein, The average particle size of the nano-silica is 20-50 nm.

4. The 9H optical film of claim 2, wherein, The amount ratio of the coupling matrix, trifluorobutanol, triethylamine and anhydrous acetone is 10 g: 2-2.5 mL: 1-1.5 mL: 50-70 mL.

5. The 9H optical film of claim 3, wherein, The amount ratio of the fluorinated matrix, epichlorohydrin, tetrabutylammonium bromide, sodium hydroxide and toluene is 10 g: 1.2-1.8 mL: 0.3-0.5 g: 2.5-3.5 g: 60-80 mL.

6. The 9H optical film of claim 1, wherein The epoxy equivalent weight of the epoxy silicone resin is not higher than 300 g / eq.

7. The method of claim 1-6, wherein the 9H optical film is prepared by the steps of: Specifically: Step S1: pre-mix the epoxy silicone resin, the latent amine curing agent and the auxiliary agent, then add the modified filler and mix and vacuum deaerate, to obtain a coating liquid; Step S2: uniformly coat the coating liquid on the surface of the base film, first pre-bake and shape at 50-60℃, then final-bake and cure at 80-95℃, to form a high-hardness coating on the surface of the base film, to obtain a 9H optical film.

8. The method of claim 7, wherein the 9H optical film is prepared by the steps of: The dry film thickness of the high-hardness coating is 30-50 µm.