An optical film and its preparation method

Abstract

This application relates to an optical film and its preparation method, belonging to the field of optical film technology. The optical film comprises: a transparent base film, a high-refractive-index coating formed on the transparent base film, and a low-refractive-index coating formed on the high-refractive-index coating; wherein the low-refractive-index coating contains hollow nanoparticles and fluorosilane-modified secondary nanoparticles, the hollow nanoparticles being chemically bonded to the bulk of the low-refractive-index coating, the particle size of the hollow nanoparticles being smaller than the thickness of the low-refractive-index coating, and the particle size of the fluorosilane-modified secondary nanoparticles being larger than the thickness of the low-refractive-index coating, with a difference not exceeding 50 nm. This optical film exhibits good anti-reflection effect, excellent friction resistance, a low coefficient of dynamic friction, and good slip properties.

Description

Technical Field

[0001] This application relates to the field of optical film technology, and in particular to an optical film and its preparation method. Background Technology

[0002] When portable display devices are used outdoors, the strong outdoor light often causes the screen to reflect ambient light, reducing the color and clarity of the displayed content. To improve screen visibility, there are generally two methods: increasing screen brightness and reducing screen reflection. However, increasing brightness increases power consumption, further shortening the already short standby time of smart devices. Therefore, more and more display manufacturers are using anti-reflection (AR) films on the screen surface. This reduces reflected light from the outside environment when electronic products are used indoors and outdoors, solving the visibility problem under reflected light.

[0003] Anti-reflective coatings are made by depositing a layer of material with stacked high and low refractive indices onto the surface of a display screen. When light passes through different media, different refractive indices and film thicknesses result in different optical path differences. Through the design of the film structure and materials, interference can be created by the optical path differences reflected from different media, achieving an anti-reflective effect. There are generally two methods: one is to wet-coat a hard coating, a high-refractive-index coating, and a low-refractive-index coating; the other is to first wet-coat a hard coating, then dry-sputter-deposit multiple layers of high- and low-refractive-index coatings, and finally wet-coat an anti-fingerprint layer. Due to the high investment cost, high production cost, and low production efficiency of dry sputtering equipment, wet coating has gradually replaced sputtering and become the mainstream method.

[0004] The wet coating process for producing antireflective films involves first coating a 2-5 μm hard coating layer onto the surface of a transparent base film. Then, high-refractive-index and low-refractive-index coatings are applied over this hard coating. Alternatively, only a low-refractive-index coating layer may be applied over the hard coating. Since most 3C display devices, including mobile phones, tablets, e-readers, and automotive displays, use touchscreens for ease of use, the antireflective film applied to their surfaces requires not only optical antireflective performance but also surface scratch resistance, fingerprint wiping ease, and smoothness to improve operability and durability. A common practice is to add antifouling agents containing perfluoropolyethers (PFPE) to the antireflective coating to increase the water contact angle and reduce the coefficient of dynamic friction. However, after a period of use, hand sweat and dirt can easily remain on the antifouling film, reducing its antifouling performance, and its operability and durability remain insufficient. Summary of the Invention

[0005] To address the shortcomings identified above, the present application aims to provide an optical film and its preparation method that not only has excellent anti-reflection properties and improved scratch resistance of the anti-reflection coating surface, but also excellent slip properties.

[0006] In a first aspect, this application provides an optical film comprising: a transparent base film, a high refractive index coating formed on the transparent base film, and a low refractive index coating formed on the high refractive index coating; wherein the low refractive index coating contains hollow nanoparticles and fluorosilane-modified secondary nanoparticles, the hollow nanoparticles being chemically bonded to the main body of the low refractive index coating, the particle size of the hollow nanoparticles being smaller than the thickness of the low refractive index coating, and the particle size of the fluorosilane-modified secondary nanoparticles being larger than the thickness of the low refractive index coating, with the difference not exceeding 50 nm.

[0007] In the above technical solution, the addition of hollow nanoparticles, with a particle size smaller than the thickness of the low-refractive-index coating, can reduce the refractive index of the coating, thereby reducing the reflectivity of the low-refractive-index coating and improving its anti-reflection effect. At the same time, due to the chemical bond between the hollow nanoparticles and the main body of the low-refractive-index coating, the connection between the hollow nanoparticles and the main body of the low-refractive-index coating can be made stronger, thereby increasing the scratch resistance of the coating. The addition of fluorosilane-modified secondary nanoparticles, with a particle size larger than the thickness of the low-refractive-index coating, can form micro-protrusions on the surface of the coating, and fluorine functional groups are grafted on the micro-protrusions, thereby reducing the dynamic friction coefficient of the coating and giving it excellent slip properties.

[0008] In some embodiments of this application, the hollow nanoparticles are one or more of hollow silica, hollow alumina, hollow polymethyl methacrylate, and hollow polystyrene.

[0009] In some embodiments of this application, the fluorosilane-modified secondary nanoparticles are fluorosilane-modified silicon dioxide and / or fluorosilane-modified aluminum oxide.

[0010] In some embodiments of this application, the thickness of the high refractive index coating is 3-5 μm, the thickness of the low refractive index coating is 0.09-0.12 μm, the particle size of the hollow nanoparticles is 50-80 nm, and the particle size of the fluorosilane-modified secondary nanoparticles minus the thickness of the low refractive index coating is 3-30 nm.

[0011] The above technical solution can further reduce the dynamic friction coefficient of the optical film, making the optical film smoother and more effective at preventing reflection.

[0012] In a second aspect, this application provides a method for preparing an optical film, comprising the following steps: coating a transparent base film with a high refractive index coating liquid, then drying and UV curing to form a high refractive index coating; coating a high refractive index coating with a low refractive index coating liquid, then drying and UV curing to form a low refractive index coating.

[0013] The low-refractive-index coating liquid includes polyurethane acrylate, fluorine-modified resin, hollow nanoparticles, and fluorosilane-modified secondary nanoparticles. The surface of the hollow nanoparticles has acrylic double bonds. The weight of the hollow nanoparticles / (weight of polyurethane acrylate + weight of fluorine-modified resin) × 100% = 30-60%; the weight of the fluorosilane-modified secondary nanoparticles / (weight of polyurethane acrylate + weight of fluorine-modified resin) × 100% = 0.5-3.0%.

[0014] In the above technical solution, because the low refractive index coating liquid contains hollow nanoparticles with acrylic double bonds, the particle size of the hollow nanoparticles is smaller than the thickness of the low refractive index coating. After curing, it forms a low refractive index coating, which can reduce the refractive index of the coating and increase the scratch resistance of the coating. At the same time, the addition of fluorosilane-modified secondary nanoparticles, whose particle size is larger than the thickness of the low refractive index coating, can form micro-protrusions on the surface of the coating. Fluorine functional groups are grafted on the micro-protrusions and cooperate with the fluorine functional groups in the fluorine-modified resin, thereby reducing the dynamic friction coefficient of the coating and giving it excellent slip properties.

[0015] In some embodiments of this application, the method for preparing fluorosilane-modified secondary nanoparticles includes: firstly, hydrolyzing one end of the fluorosilane coupling agent -Si-X into -Si-OH; then, causing a dehydration reaction between some hydroxyl groups on the surface of the hydrophilic nanoparticles and the hydroxyl groups in -Si-OH, thereby grafting the hydrophilic nanoparticles with the fluorosilane coupling agent, drying, and obtaining fluorosilane-modified nanoparticle powder; and then dispersing the nanoparticle powder in a solvent to obtain a fluorosilane-modified secondary nanoparticle dispersion.

[0016] In the above technical solution, fluorosilane-modified secondary nanoparticles can be obtained, and they are added in the form of a dispersion, which can make the secondary nanoparticles more uniformly dispersed, thereby further reducing the dynamic friction coefficient of the coating and further improving the smoothness of the coating.

[0017] In some embodiments of this application, the fluorosilane coupling agent solution is first hydrolyzed for 5 hours or more at a pH of 4.0–5.0, causing one end of the fluorosilane coupling agent, -Si-X, to hydrolyze into -Si-OH. Then, hydrophilic nanoparticles are added, and the reaction is carried out at 60–80°C for 0.5–2 hours, causing some of the hydroxyl groups on the surface of the hydrophilic nanoparticles to undergo a dehydration reaction with the hydroxyl groups in -Si-OH. The solvent in the fluorosilane coupling agent solution includes water and ethanol, and the mass ratio of the fluorosilane coupling agent to the hydrophilic nanoparticles is (0.2–0.6):1.

[0018] The above technical solution can improve the hydrolysis effect of fluorosilane coupling agents and allow more fluorosilane coupling agents to be grafted onto hydrophilic nanoparticles for modification.

[0019] In some embodiments of this application, the mass ratio of fluorosilane coupling agent to water and ethanol is 1:(0.8-1.2):(15-25).

[0020] In the above technical solution, the addition of a large amount of ethanol can enable the silane coupling agent to achieve better hydrolysis.

[0021] In some embodiments of this application, the fluorosilane coupling agent is one or more of the following: trimethoxy(1H,1H,2H,2H-heptadecyl)silane, 1H,1H,2H,2H-perfluorooctyltrimethoxysilane, 1H,1H,2H,2H-perfluorooctyltriethoxysilane, 1H,1H,2H,2H-perfluorodecyltrimethoxysilane, 1H,1H,2H,2H-perfluorodecyltriethoxysilane, and tridecafluorooctyltriethoxysilane.

[0022] In some embodiments of this application, the primary particle size of the hydrophilic nanoparticles is 5–50 nm.

[0023] In the above technical solution, the hydrophilic nanoparticles have a very small particle size, making it easier to graft with fluorosilane coupling agents. Furthermore, after forming secondary particles, the portion protruding from the low refractive index coating can have more fluorine functional groups, thereby further improving the slip properties of the optical film. Attached Figure Description

[0024] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 A process flow diagram of the method for preparing the optical film provided in the embodiments of this application;

[0026] Figure 2 This is a schematic diagram of the structure of the optical film provided in an embodiment of this application.

[0027] Icons: 110 - Transparent base film; 120 - High refractive index coating; 130 - Low refractive index coating; 131 - Hollow nanoparticles; 132 - Fluorosilane-modified secondary nanoparticles. Detailed Implementation

[0028] Figure 1 A process flow diagram illustrating the fabrication method of the optical film provided in this application embodiment. Please refer to [link / reference]. Figure 1 The method for preparing the optical film provided in this application includes the following steps:

[0029] S110, Preparation of high refractive index coating: A high refractive index coating liquid is coated on a transparent base film, and then dried and UV cured to form a high refractive index coating.

[0030] The high refractive index coating liquid comprises: 25-35 parts by weight of UV-curable oligomer, 4-10 parts by weight of active monomer, 1-3 parts by weight of initiator, 60-80 parts by weight of solvent, and 0.1-0.2 parts by weight of leveling agent, and the weight of initiator / (weight of UV-curable oligomer + weight of active monomer) × 100% = 3-6%.

[0031] As an example, in the high-refractive-index coating, the amount of UV-curable oligomer added is 25 parts by weight, 30 parts by weight, or 35 parts by weight; the amount of reactive monomer added is 4 parts by weight, 5 parts by weight, 6 parts by weight, 7 parts by weight, 8 parts by weight, 9 parts by weight, or 10 parts by weight; the amount of initiator added is 1 part by weight, 1.5 parts by weight, 2 parts by weight, 2.5 parts by weight, or 3 parts by weight; the amount of solvent added is 60 parts by weight, 65 parts by weight, 70 parts by weight, 75 parts by weight, or 80 parts by weight; the amount of leveling agent added is 0.1 parts by weight, 0.15 parts by weight, or 0.2 parts by weight; and the weight of initiator / (weight of UV-curable oligomer + weight of reactive monomer) × 100% is 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, or 6%.

[0032] The UV-curable oligomer can be one or more of polyurethane acrylates, epoxy acrylates, polyester acrylates, and pure acrylic acid.

[0033] The active monomer may be one or more of o-phenylphenoxyethyl acrylate, ethylene glycol dimethacrylate, propoxylated neopentyl glycol diacrylate, propoxylated glycerol triacrylate, 1,4-butanediol diacrylate, 1,6-hexanediol diacrylate, trimethylolethane triacrylate, ethoxylated pentaerythritol tetraacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, dipentaerythritol tetraacrylate, dipentaerythritol pentaacrylate, and dipentaerythritol hexaacrylate.

[0034] The photoinitiators are 1-hydroxycyclohexylphenyl ketone (184), 1,1'-(methylenedi-4,1-phenylene)bis[2-hydroxy-2-methyl-1-propanone] (127), 2-hydroxy-methylphenylpropane-1-one (1173), 2-methyl-1-(4-methylthiophenyl)-2-morpholino-1-propanone (907), benzoin dimethyl ether (651), 2,4,6-(trimethylbenzoyl)diphenylphosphine oxide (TPO), etc.

[0035] The solvent can be one or more of alcohols, ketones, and esters; among which, alcohols include one or more of methanol, ethanol, n-propanol, isopropanol, n-butanol, and isobutanol; ketones include one or more of acetone, butanone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; and esters include one or more of methyl acetate, ethyl acetate, propyl acetate, and butyl acetate.

[0036] The leveling agent may be one or more of fluorinated leveling agents, organosiloxane leveling agents, and organosilicone-modified acrylic leveling agents. Optionally, the leveling agent may be one or more of the following: BYK-UV 3500, BYK-UV 3505, BYK-UV 3530, BYK-UV 3535, BYK-UV 3560, BYK-UV 3565; TEGO Flow 300, Flow 375, Flow 425, TEGO Glide415, Glide 450; NIO's FTERGENT 602A; and Dai Nippon Ink Chemical's F-445, F-470, F-479, F-553, F-556.

[0037] After applying the high-refractive-index coating, the high-refractive-index coating is dried at an environment of 60–110°C for 2–3 minutes. For example, the drying temperature of the high-refractive-index coating is 60°C, 70°C, 80°C, 90°C, 100°C, or 110°C; the drying time is 2 minutes, 2.2 minutes, 2.5 minutes, 2.8 minutes, or 3 minutes.

[0038] After drying, it is UV cured with an energy of 200–350 mJ / cm². 2As an example, the UV curing energy is 200 mJ / cm². 2 250mj / cm 2 300mj / cm 2 or 350mj / cm 2 .

[0039] High-refractive-index coatings can be applied using methods such as slot coating, microgravure coating, doctor blade coating, Mayer bar coating, roller coating, and blade coating. Choosing microgravure coating or slot coating methods can result in better coating effects.

[0040] In this application, the solid content of the high refractive index coating liquid is 20-40%, and the coating amount of the high refractive index coating liquid is 15-30 g / m². 2 By adjusting the solid content and coating amount, the thickness of the high-refractive-index coating can be maintained between 3 and 5 μm. For example, the solid content of the high-refractive-index coating liquid is 20%, 25%, 30%, 35%, or 40%; the coating amount is 20 g / m². 2 25g / m 2 30g / m 2 35g / m 2 or 42g / m 2 The thickness of the high refractive index coating is 3μm, 3.5μm, 4μm, 4.5μm or 5μm.

[0041] S120, Preparation of a low-refractive-index coating: A low-refractive-index coating liquid is coated onto a high-refractive-index coating, then dried and UV-cured to form a low-refractive-index coating. The low-refractive-index coating contains hollow nanoparticles and fluorosilane-modified secondary nanoparticles. The hollow nanoparticles are chemically bonded to the main body of the low-refractive-index coating. The particle size of the hollow nanoparticles is smaller than the thickness of the low-refractive-index coating, while the particle size of the fluorosilane-modified secondary nanoparticles is larger than the thickness of the low-refractive-index coating, with a difference not exceeding 50 nm.

[0042] Because the low-refractive-index coating contains hollow nanoparticles with acrylic double bonds, and the particle size of the hollow nanoparticles is smaller than the thickness of the low-refractive-index coating, the low-refractive-index coating is formed after curing, which can reduce the refractive index of the coating and increase its scratch resistance. At the same time, the addition of fluorosilane-modified secondary nanoparticles, whose particle size is larger than the thickness of the low-refractive-index coating, can form micro-protrusions on the surface of the coating. Fluorine functional groups are grafted on the micro-protrusions and cooperate with the fluorine functional groups in the fluorine-modified resin, thereby reducing the dynamic friction coefficient of the coating and giving it excellent slip properties.

[0043] In this application, the low-refractive-index coating liquid comprises: polyurethane acrylate, fluorine-modified resin, hollow nanoparticles, and fluorosilane-modified secondary nanoparticles. The hollow nanoparticles have acrylic double bonds on their surface. The weight of the hollow nanoparticles / (weight of polyurethane acrylate + weight of fluorine-modified resin) × 100% = 30-60%; the weight of the fluorosilane-modified secondary nanoparticles / (weight of polyurethane acrylate + weight of fluorine-modified resin) × 100% = 0.5-3.0%.

[0044] As an example, the weight of hollow nanoparticles / (weight of polyurethane acrylate + weight of fluorinated resin) × 100% is 30%, 35%, 40%, 45%, 50%, 55%, or 60%; the weight of fluorosilane-modified secondary nanoparticles / (weight of polyurethane acrylate + weight of fluorinated resin) × 100% is 0.5%, 1%, 1.5%, 2%, 2.5%, or 3.0%.

[0045] Optionally, the low-refractive-index coating liquid comprises: 0.7 to 1.0 parts by weight of polyurethane acrylate, 0.7 to 1.0 parts by weight of fluorine-modified resin, 0.5 to 1.2 parts by weight of hollow nanoparticles with acrylic double bonds, 0.01 to 0.05 parts by weight of fluorosilane-modified secondary nanoparticles, 90 to 100 parts by weight of solvent, 0.1 to 0.2 parts by weight of leveling agent, 0.05 to 0.1 parts by weight of initiator, 0.05 to 0.2 parts by weight of antifouling agent, and 0.1 to 0.3 parts by weight of leveling agent.

[0046] As an example, the amount of polyurethane acrylate added is 0.7 parts by weight, 0.8 parts by weight, 0.9 parts by weight, or 1.0 parts by weight; the amount of fluorinated modified resin added is 0.7 parts by weight, 0.8 parts by weight, 0.9 parts by weight, or 1.0 parts by weight; the amount of hollow nanoparticles added is 0.5 parts by weight, 0.7 parts by weight, 0.9 parts by weight, 1.1 parts by weight, or 1.2 parts by weight; the amount of fluorosilane-modified secondary nanoparticles added is 0.01 parts by weight, 0.02 parts by weight, 0.03 parts by weight, 0.04 parts by weight, or 0.05 parts by weight; and the amount of solvent added... The amounts are 90 parts by weight, 92 parts by weight, 94 parts by weight, 96 parts by weight, 98 parts by weight, or 100 parts by weight; the amount of leveling agent added is 0.1 parts by weight, 0.15 parts by weight, or 0.2 parts by weight; the amount of initiator added is 0.05 parts by weight, 0.06 parts by weight, 0.07 parts by weight, 0.08 parts by weight, 0.09 parts by weight, or 0.1 parts by weight; the amount of antifouling additive added is 0.05 parts by weight, 0.10 parts by weight, 0.15 parts by weight, or 0.2 parts by weight; and the amount of leveling agent added is 0.1 parts by weight, 0.2 parts by weight, or 0.3 parts by weight.

[0047] The solvent can be a solvent in a high-refractive-index coating liquid, the leveling agent can be a leveling agent in a high-refractive-index liquid, and the initiator can be an initiator in a high-refractive-index coating liquid; these details will not be elaborated here. Antifouling additives can be RS-90, KY-1203, etc.

[0048] In this application, hollow nanoparticles can be added in the form of a dispersion to achieve a more uniform distribution in the low-refractive-index coating. This hollow nanoparticle dispersion is commercially available, and the weight percentage of the hollow nanoparticles added represents the effective components of the dispersion, excluding the solvent. Fluorosilane-modified secondary nanoparticles can also be added in the form of a dispersion to achieve a more uniform distribution in the low-refractive-index coating. The weight percentage of the fluorosilane-modified secondary nanoparticles added represents the effective components of the dispersion, excluding the solvent. The preparation method of the fluorosilane-modified secondary nanoparticle dispersion is described in detail below.

[0049] The process involves first hydrolyzing one end of the fluorosilane coupling agent, -Si-X, into -Si-OH; then, causing some of the hydroxyl groups on the surface of the hydrophilic nanoparticles to undergo a dehydration reaction with the hydroxyl groups in -Si-OH, thereby grafting the hydrophilic nanoparticles with the fluorosilane coupling agent. After drying, fluorosilane-modified nanoparticle powder is obtained; the nanoparticle powder is then added to a solvent for dispersion to obtain a fluorosilane-modified secondary nanoparticle dispersion.

[0050] The fluorosilane coupling agent is one or more of the following: trimethoxy(1H,1H,2H,2H-heptadecyl)silane, 1H,1H,2H,2H-perfluorooctyltrimethoxysilane, 1H,1H,2H,2H-perfluorooctyltriethoxysilane, 1H,1H,2H,2H-perfluorodecyltrimethoxysilane, 1H,1H,2H,2H-perfluorodecyltriethoxysilane, and tridecafluorooctyltriethoxysilane.

[0051] Optionally, the fluorosilane coupling agent solution is first hydrolyzed at a pH of 4.0–5.0 for 5 hours or more, causing the -Si-X end of the fluorosilane coupling agent to hydrolyze into -Si-OH; then, hydrophilic nanoparticles with a particle size of 5–50 nm are added, and the reaction is carried out at 60–80 °C for 0.5–2 hours, causing some of the hydroxyl groups on the surface of the hydrophilic nanoparticles to undergo a dehydration reaction with the hydroxyl groups in -Si-OH; wherein the solvent in the fluorosilane coupling agent solution includes water and ethanol, the mass ratio of fluorosilane coupling agent to hydrophilic nanoparticles is (0.2–0.6):1, and the mass ratio of fluorosilane coupling agent to water and ethanol is 1:(0.8–1.2):(15–25).

[0052] As an example, the pH value of the hydrolysis of the fluorosilane coupling agent is 4.0, 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9 or 5.0; the hydrolysis time of the fluorosilane coupling agent is 5h, 5.5h, 6h, 6.5h, 7h, 7.5h or 8h; the mass ratio of the added fluorosilane coupling agent, water and ethanol is 1:0.8:15, 1:1:15, 1:1.2:15, 1:0.8:20, 1:0.8:25, 1:1:20, 1:1:25, 1:1.2:20 or 1:1.2:25.

[0053] As an example, the primary particle size of the hydrophilic nanoparticles is 7 nm, 12 nm, 13 nm, 14 nm, 16 nm, 20 nm, 40 nm, or 50 nm; the temperature of the dehydration reaction is 60 °C, 65 °C, 70 °C, 75 °C, or 80 °C; the time of the dehydration reaction is 0.5 h, 1 h, 1.5 h, or 2 h; and the mass ratio of the fluorosilane coupling agent to the hydrophilic nanoparticles is 0.2:1, 0.3:1, 0.4:1, 0.5:1, or 0.6:1.

[0054] After applying the low-refractive-index coating, dry it at 70–100°C for 1–3 minutes, then dry it at an oxygen concentration of less than 500 ppm and a light dose of 300–500 mJ / cm. 2 Under ultraviolet irradiation conditions, a low refractive index coating was obtained.

[0055] Alternatively, the low-refractive-index coating liquid can be applied using methods such as slot coating, microgravure coating, blade coating, Mayer bar coating, roller coating, and doctor blade coating to form the coating. Choosing microgravure coating or slot coating as the application method can result in better coating effects.

[0056] As an example, the drying conditions for the low refractive index coating are: drying at 70°C for 3 min; or drying at 85°C for 2 min; or drying at 100°C for 1 min; and the ultraviolet irradiation conditions are: an oxygen concentration of 100 ppm and a light dose of 350 mJ / cm². 2 Under conditions of ultraviolet irradiation; or under conditions of oxygen concentration of 200 ppm and light dose of 400 mJ / cm². 2 Under conditions of ultraviolet irradiation; or under conditions of oxygen concentration of 300 ppm and light dose of 450 mJ / cm². 2 Under conditions of ultraviolet irradiation; or under conditions of oxygen concentration of 400 ppm and light dose of 500 mJ / cm². 2 Under conditions of ultraviolet irradiation.

[0057] Optionally, the solid content of the low-refractive-index coating liquid is 2-3%, and the coating amount of the low-refractive-index coating liquid is 3-10 g / m².2 By combining this solid content and this coating amount, the thickness of the low-refractive-index coating is achieved to be 0.09–0.12 μm. As an example, the solid content of the low-refractive-index coating liquid is 2%, 2.2%, 2.4%, 2.6%, 2.8%, or 3.0%; the coating amount of the low-refractive-index coating liquid is 3 g / m³. 2 5g / m 2 8g / m 2 or 10g / m 2 The thickness of the low refractive index coating can be 0.09μm, 0.10μm, 0.11μm or 0.12μm.

[0058] Optical films can be prepared using the methods described above. Figure 2 This is a schematic diagram of the optical film provided in an embodiment of this application. Please refer to... Figure 2 The optical film includes a transparent base film 110, a high-refractive-index coating 120 formed on the transparent base film 110, and a low-refractive-index coating 130 formed on the high-refractive-index coating 120. The low-refractive-index coating 130 contains hollow nanoparticles 131 and fluorosilane-modified secondary nanoparticles 132. The particle size of the hollow nanoparticles 131 is smaller than the thickness of the low-refractive-index coating 130, and the particle size of the fluorosilane-modified secondary nanoparticles 132 is larger than the thickness of the low-refractive-index coating 130, with a difference not exceeding 50 nm.

[0059] The low-refractive-index coating 130 contains hollow nanoparticles 131, and the particle size of the hollow nanoparticles 131 is smaller than the thickness of the low-refractive-index coating 130. This reduces the refractive index of the coating, thereby reducing its reflectivity and improving its anti-reflection effect. Simultaneously, the chemical bonds between the hollow nanoparticles 131 and the main body of the low-refractive-index coating 130 strengthen the bond, increasing the coating's scratch resistance. The addition of fluorosilane-modified secondary nanoparticles 132, with a particle size larger than the thickness of the low-refractive-index coating 130, forms micro-protrusions on the coating surface. These micro-protrusions are grafted with fluorine functional groups, reducing the coefficient of dynamic friction and providing excellent slip properties.

[0060] Optionally, the thickness of the transparent base film 110 is 15–250 μm; alternatively, the thickness of the transparent base film 110 is 25–80 μm, 80–150 μm, or 150–250 μm. As an example, the thickness of the transparent base film 110 is 25 μm, 38 μm, 40 μm, 50 μm, 60 μm, 80 μm, 100 μm, 125 μm, 188 μm, or 250 μm.

[0061] The transparent base film 110 can be made of plastic film; the plastic film is selected from one of the following: polyethylene terephthalate film (PET), colorless transparent polyimide film (CPI), norbornene film (COP), cellulose triacetate film (TAC), polyethylene naphthalate film (PEN), polycarbonate film (PC), polymethyl methacrylate film (PMMA), terpolymer of acrylonitrile (A)-butadiene (B)-styrene (S) (ABS), ABS and PET composite film, PC and PMMA composite film, and polyetheretherketone film (PEEK).

[0062] Optionally, the hollow nanoparticles 131 are one or more of hollow silica, hollow alumina, hollow polymethyl methacrylate, and hollow polystyrene, and the particle size of the hollow nanoparticles 131 is 50-80 nm. As an example, the particle size of the hollow nanoparticles 131 is 50 nm, 60 nm, 70 nm, or 80 nm.

[0063] Further, the fluorosilane-modified secondary nanoparticles 132 are fluorosilane-modified silicon dioxide and / or fluorosilane-modified alumina. The high-refractive-index coating 120 has a thickness of 3–5 μm, and the low-refractive-index coating 130 has a thickness of 0.09–0.12 μm. The particle size of the fluorosilane-modified secondary nanoparticles 132 minus the thickness of the low-refractive-index coating 130 is 3–30 nm. As an example, the particle size of the fluorosilane-modified secondary nanoparticles 132 minus the thickness of the low-refractive-index coating 130 is 3 nm, 5 nm, 10 nm, 15 nm, 20 nm, 25 nm, or 30 nm.

[0064] In this application, the high refractive index coating 120 has a refractive index that is 0.05 to 0.3 greater than that of the low refractive index coating 130, which can improve its anti-reflection effect. Optionally, the high refractive index coating 120 has a refractive index that is 0.07 to 0.15 greater than that of the low refractive index coating 130.

[0065] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0066] Example

[0067] This embodiment provides an optical film comprising a transparent base film and a high-refractive-index coating adhered to the transparent base film, and a low-refractive-index coating adhered to the high-refractive-index coating, stacked sequentially from bottom to top. The method for preparing the optical film includes:

[0068] (1) Coating a high refractive index coating liquid onto a transparent base film, drying it at 100°C for 2 min, and then irradiating it with ultraviolet light to obtain a high refractive index coating.

[0069] (2) Apply the low-refractive-index coating liquid onto the high-refractive-index coating, dry at 80℃ for 2 min, and then dry at an oxygen concentration of 200 ppm and a light dose of 350 mJ / cm. 2 A low-refractive-index coating is obtained under ultraviolet irradiation by a high-pressure mercury lamp.

[0070] The high-refractive-index coating and the low-refractive-index coating are shown in the table below:

[0071] Table 1. Composition of high refractive index coating HC-1

[0072]

[0073] Table 2 Composition of high refractive index coating HC-2

[0074]

[0075] Table 3 Composition of high refractive index coating HC-3

[0076]

[0077]

[0078] Table 4. Composition of low refractive index coating LR-1

[0079]

[0080] Table 5. Composition of antireflective coating LR-2

[0081]

[0082]

[0083] Table 6. Composition of Antireflective Coating LR-3

[0084]

[0085] Table 7 Composition of Antireflective Coating LR-4

[0086]

[0087]

[0088] Table 8. Composition of Antireflective Coating LR-5

[0089]

[0090] Table 9. Composition of Antireflective Coating LR-6

[0091]

[0092]

[0093] Table 10 Composition of Antireflective Coating LR-7

[0094]

[0095] Table 11 Composition of Antireflective Coating LR-8

[0096]

[0097]

[0098] Table 12 Composition of Antireflective Coating LR-9

[0099]

[0100] Table 13 Composition of Antireflective Coating LR-10

[0101]

[0102]

[0103] Table 14 Composition of Antireflective Coating LR-11

[0104]

[0105] Table 15 Composition of Antireflective Coating LR-12

[0106]

[0107]

[0108] Table 16 Composition of Antireflective Coating LR-13

[0109]

[0110] Table 17 Composition of Antireflective Coating LR-14

[0111]

[0112]

[0113] Table 18 Composition of Antireflective Coating LR-15

[0114]

[0115] The preparation method of dispersion-A (Example 1 and Example 2) is as follows:

[0116] Mix 10g of fluorosilane coupling agent SCA-F13C8M, 10g of water, and 180g of ethanol. Add a certain amount of oxalic acid to the mixture to adjust the pH to between 4.0 and 4.5. Stir and hydrolyze for 5.5 hours to obtain fluorosilanol. Place Evonik Degussa's hydrophilic silica powder Aerosil 130, with a native particle size of 16nm, into a blower dryer and dry at 100°C for 12 hours. Then, add 30g of silica powder to the above fluorosilanol solution and stir at 60°C for 1 hour. Centrifuge the mixture and dry it at 60°C for 12 hours to obtain surface-modified silica powder.

[0117] Take 15g of the modified silica powder and put it into 85g of methyl isobutyl ketone. After dispersing it in a ball mill for 3.5h, the secondary particle size was measured to be 0.11μm. This is fluorine-modified silica dispersion-A.

[0118] The preparation method of dispersion-B (Examples 3 and 4) is as follows:

[0119] Mix 10g of fluorosilane coupling agent SCA-F13C8M, 10g of water, and 180g of ethanol. Add a certain amount of oxalic acid to the mixture to adjust the pH to between 4.0 and 4.5. Stir and hydrolyze for 6 hours to obtain fluorosilanol. Place Evonik Degussa's hydrophilic silica powder Aerosil 200, with a native particle size of 12nm, into a blower dryer and dry at 100°C for 12 hours. Then, add 25g of silica powder to the above fluorosilanol solution and stir at 60°C for 1 hour. Centrifuge the mixture and dry it at 60°C for 12 hours to obtain surface-modified silica powder.

[0120] Take 15g of the modified silica powder and put it into 85g of methyl isobutyl ketone. After dispersing it in a ball mill for 2.5h, the secondary particle size was measured to be 0.125μm. This is fluorine-modified silica dispersion-B.

[0121] The preparation method of dispersion-C (Examples 5 and 6) is as follows:

[0122] Mix 10g of Evonik Degussa F8261 fluorosilane coupling agent, 10g of water, and 180g of ethanol. Add a certain amount of oxalic acid to the mixture to adjust the pH to between 4.0 and 4.5. Stir and hydrolyze for 7 hours to obtain fluorosilanol. Place Evonik Degussa Aerosil 300 hydrophilic silica powder with a native particle size of 7nm into a blower dryer and dry at 100°C for 12 hours. Then, add 20g of silica powder to the above fluorosilanol solution and stir at 60°C for 1 hour. Centrifuge the mixture and dry it at 60°C for 12 hours to obtain surface-modified silica powder.

[0123] Take 10g of the modified silica powder and put it into 90g of propylene glycol methyl ether. After dispersing it in a ball mill for 3 hours, the secondary particle size was measured to be 0.118μm. This is the fluorine-modified silica dispersion-C.

[0124] The preparation method of dispersion-D (Examples 7 and 8) is as follows:

[0125] Mix 10g of Shin-Etsu Chemical KBM-7803 fluorosilane coupling agent, 10g of water, and 180g of ethanol. Add a certain amount of oxalic acid to the mixture to adjust the pH to between 4.0 and 4.5. Stir and hydrolyze for 6.5 hours to obtain fluorosilanol. Place Evonik Degussa hydrophilic alumina powder (Aeroxide Aluc), with a native particle size of 13nm, into a blower dryer and dry at 100°C for 12 hours. Then, add 50g of alumina powder to the above fluorosilanol solution and stir at 60°C for 1 hour. Centrifuge the mixture and dry it at 60°C for 12 hours to obtain surface-modified alumina powder.

[0126] Take 20g of the modified alumina powder and put it into 80g of propylene glycol methyl ether. After dispersing it in a ball mill for 5 hours, the secondary particle size was measured to be 0.128μm. This is the fluorine-modified alumina dispersion-D.

[0127] The preparation method of dispersion-E (comparative example 2) is as follows:

[0128] 15g of unmodified Evonik Degussa hydrophilic silica powder Aerosil 130 was placed in 85g of methyl isobutyl ketone and dispersed in a ball mill for 3.5h. The secondary particle size was measured to be 0.115μm. This is the unmodified silica dispersion-E.

[0129] The preparation method of dispersion-F (comparative example 5) is as follows:

[0130] 35g of the modified silica powder obtained during the preparation of dispersion-A was placed in 70g of methyl isobutyl ketone and dispersed in a ball mill for 1 hour. The secondary particle size was measured to be 0.155μm. This is fluorine-modified silica dispersion-F.

[0131] The preparation method of dispersion-G (comparative example 6) is as follows:

[0132] 10g of the modified silica powder obtained during the preparation of dispersion-A was placed in 90g of methyl isobutyl ketone and dispersed in a ball mill for 8 hours. The secondary particle size was measured to be 0.075μm. This is fluorine-modified silica dispersion-G.

[0133] The preparation method of dispersion-H (comparative example 7) is as follows:

[0134] 10g of silane coupling agent Shin-Etsu Chemical KBM-503, 10g of water, and 180g of ethanol were mixed. A certain amount of oxalic acid was added dropwise to the mixture to adjust the pH value to between 4.0 and 4.5. After stirring and hydrolyzing for 5.5 hours, the product was silanol. Evonik Degussa's hydrophilic silica powder Aerosil 130, with a native particle size of 16nm, was placed in a blower dryer and dried at 100°C for 12 hours. Then, 20g of silica powder was added to the above silanol solution and stirred at 60°C for 1 hour. The mixture was then centrifuged and finally dried at 60°C for 12 hours to obtain surface-modified silica powder.

[0135] Take 15g of the modified silica powder and put it into 85g of methyl isobutyl ketone. After dispersing it in a ball mill for 4 hours, the secondary particle size was measured to be 0.105μm. This is a silane-modified silica dispersion containing methacrylic acid double bonds - H.

[0136] Experimental Example 1

[0137] The preparation conditions of the optical films provided in Examples 1-8 and Comparative Examples 1-7 are shown in Table 19, and the performance of the optical films is shown in Table 20. The calculation methods or testing methods for each parameter in Tables 19 and 20 are as follows:

[0138] Table 19 Summary of Preparation Conditions for Optical Films

[0139]

[0140]

[0141] 1. Coating thickness test:

[0142] The thickness of the high-refractive-index coating and the low-refractive-index coating of the optical film were measured using the Metis LITE coating thickness gauge from NXT GmbH, Germany, based on the principle of optical diffraction.

[0143] 2. Transmittance (%), Haze (%):

[0144] According to JIS K-7105 standard, the transmittance and haze of the optical film were measured using a Japanese Denshoku NDH 2000N haze meter by means of transmitted light method.

[0145] 3. Coating adhesion:

[0146] According to the standard ASTM D-3359, draw a grid pattern on the surface of the optical film using a cross-cutting tool. Then, apply 3M 600 tape to the grid pattern and quickly peel off the tape at a 180-degree angle. Use a magnifying glass to observe the removal of the grid pattern.

[0147] 5B: The coating has not peeled off at all;

[0148] 4B: Cross-cut coating peeling area <5%;

[0149] 3B: 5%–15% of the cross-cut coating has peeled off.

[0150] 2B: 15%–35% of the cross-cut coating has peeled off.

[0151] 1B: 35%–65% of the cross-cut coating has peeled off.

[0152] 0B: Cross-cut coating peeling area >65%.

[0153] 4. Pencil hardness:

[0154] According to JISK-5600 standard, the pencil hardness of the optical film was measured using an Elcometer 3086 pencil hardness tester. Measurement method: Using a Mitsubishi pencil with a hardness of H to 4H, five lines were drawn under a 500g load. The optical film coating was then observed for scratches, and the following criteria were used for judgment.

[0155] [Judgment Criteria]

[0156] 0-2 scratches result in a "Pass" rating.

[0157] 3-5 scratches are considered "NG" (Not Acceptable).

[0158] 5. Resistant to steel wool abrasion:

[0159] Using the Shenzhen Zhijia Instruments ZJ-339-GSR steel wool resistance tester, under a load of 1000g, Japanese Bonstar#0000 steel wool with a 2cm×2cm friction head was used to rub back and forth on the surface of the anti-reflective film at 60Hz to confirm the scratches on the coating surface.

[0160] [Judgment Criteria]

[0161] No scratches after 300 or fewer friction cycles;

[0162] No scratches after 200 friction cycles, scratches after 300 friction cycles Δ;

[0163] Scratches are present if the friction count is less than 200 times ×.

[0164] 6. Rubber resistance test:

[0165] Using a Korean Minoan eraser, with a load of 500g, a friction speed of 40 cycles / min, a stroke of 40mm, and 1000 cycles, the water contact angle of the optical film was measured.

[0166] 7. Water contact angle (°):

[0167] Using the JC2000D water contact angle meter from Shanghai Zhongchen Digital Technology Equipment Co., Ltd., pure water was injected into one end of the measuring needle connecting tube, and water droplets flowed out from the other end of the needle. A 1cm×3cm piece of the hard coating to be tested was placed horizontally on the measuring platform with the coated side facing up and secured with tape. The button was rotated to squeeze out a droplet from the needle (set to 2.0μL). The platform with the hard coating to be tested was raised until it came into contact with the droplet. The water contact angle was calculated using the goniometric method through the measuring software.

[0168] 8. Average reflectance (%):

[0169] The optical film sample was cut into 8cm×8cm pieces, and black tape was attached to the back of the coating. The average reflectance at a 6-degree angle in the visible light region of 380-780nm was measured using a Shimadzu UV-2600i UV-Vis spectrophotometer.

[0170] 9. Coefficient of kinetic friction:

[0171] Using the PARAM MXD-02 friction coefficient tester from Jinan Langguang Electromechanical, the antireflective film sample was cut into a length of 200-250mm and a width of 100-130mm, placed on the testing table, and fixed with a clamp. The test medium was a balance paper, and the test was performed at an area of ​​2×2cm, a load of 200±20g, a test speed of 100mm / min, and a stroke of 70mm.

[0172] 10. Particle size determination of dispersion:

[0173] The average particle size of the nano-dispersion was determined using a Bettersize2600 laser particle size analyzer manufactured by Dandong Bettersize Instruments Co., Ltd., based on the principle of laser diffraction.

[0174] Table 20 Performance of Optical Films

[0175]

[0176] As can be seen from Tables 19 and 20, the optical films provided in Examples 1 to 8 of this application have good anti-reflection effect, good friction resistance, low coefficient of dynamic friction, and good slip properties.

[0177] Compared to Examples 1 to 4 and Example 6, the optical films provided in Examples 5, 7 and 8 have a weight of fluorosilane-modified secondary nanoparticles / (weight of polyurethane acrylate + weight of fluorine-modified resin) × 100% = 2 to 3.0%, which can improve the rubber resistance test performance, reduce the dynamic friction coefficient and improve the slip properties of the optical films.

[0178] In Comparative Example 1, the optical film obtained without the addition of a dispersion containing fluorosilane-modified secondary nanoparticles exhibited poor resistance to steel wool and rubber, a high coefficient of dynamic friction, and poor slip properties. In Comparative Example 2, the optical film obtained without using a fluorosilane coupling agent to modify silica also showed poor resistance to steel wool and rubber, a high coefficient of dynamic friction, and poor slip properties. In Comparative Example 3, the amount of fluorosilane-modified secondary nanoparticle dispersion added was too small, resulting in a relatively poor resistance to steel wool and rubber, a high coefficient of dynamic friction, and poor slip properties. Comparative Example 4... In Comparative Example 5, the excessive addition of the dispersion of fluorosilane-modified secondary nanoparticles resulted in a high degree of haze in the obtained optical film. In Comparative Example 6, the excessively large particle size of the fluorosilane-modified secondary nanoparticles resulted in a high degree of haze in the obtained optical film. In Comparative Example 7, the excessively small particle size of the fluorosilane-modified secondary nanoparticles resulted in poor resistance to steel wool and rubber, a high coefficient of dynamic friction, and poor slip properties in the obtained optical film. In Comparative Example 7, the use of a silane coupling agent (without fluorine groups) to modify silica resulted in a relatively poor resistance to steel wool and rubber, a high coefficient of dynamic friction, and poor slip properties in the obtained optical film.

[0179] The embodiments described above are some, but not all, of the embodiments of this application. The detailed description of the embodiments of this application is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

Claims

1. An optical film, characterized in that, include: A transparent base film, a high refractive index coating formed on the transparent base film, and a low refractive index coating formed on the high refractive index coating; The low-refractive-index coating contains polyurethane acrylate, fluorine-modified resin, hollow nanoparticles, and fluorosilane-modified secondary nanoparticles. The hollow nanoparticles are chemically bonded to the main body of the low-refractive-index coating. The particle size of the hollow nanoparticles is smaller than the thickness of the low-refractive-index coating, and the particle size of the fluorosilane-modified secondary nanoparticles is larger than the thickness of the low-refractive-index coating, with a difference of no more than 50 nm. The weight of the fluorosilane-modified secondary nanoparticles / (weight of polyurethane acrylate + weight of fluoro-modified resin) × 100% = 2~3.0%, and the fluorosilane-modified secondary nanoparticles are fluorosilane-modified silicon dioxide and / or fluorosilane-modified aluminum oxide.

2. The optical film according to claim 1, characterized in that, The hollow nanoparticles are one or more of hollow silica, hollow alumina, hollow polymethyl methacrylate, and hollow polystyrene.

3. The optical film according to claim 1 or 2, characterized in that, The thickness of the high-refractive-index coating is 3~5 μm, and the thickness of the low-refractive-index coating is 0.09~0.12 μm; The hollow nanoparticles have a particle size of 50-80 nm, and the particle size of the fluorosilane-modified secondary nanoparticles minus the thickness of the low-refractive-index coating is 3-30 nm.

4. A method for preparing the optical film according to any one of claims 1 to 3, characterized in that, Includes the following steps: A high refractive index coating is formed by coating a transparent base film with a high refractive index liquid, drying it, and then UV curing it. A low-refractive-index coating is applied to the high-refractive-index coating, and then dried and UV cured to form the low-refractive-index coating. The low-refractive-index coating comprises polyurethane acrylate, fluorinated resin, hollow nanoparticles, and fluorosilane-modified secondary nanoparticles. The hollow nanoparticles have acrylic double bonds on their surface. The weight of the hollow nanoparticles is 30-60% (weight of polyurethane acrylate + weight of fluorinated resin) × 100%. The weight of the fluorosilane-modified secondary nanoparticles is 2-3.0% (weight of polyurethane acrylate + weight of fluorinated resin) × 100%. The fluorosilane-modified secondary nanoparticles are fluorosilane-modified silica and / or fluorosilane-modified alumina.

5. The preparation method according to claim 4, characterized in that, The method for preparing the fluorosilane-modified secondary nanoparticles includes: First, hydrolyze one end of the fluorosilane coupling agent, -Si-X, into -Si-OH; Then, some of the hydroxyl groups on the surface of the hydrophilic nanoparticles undergo a dehydration reaction with the hydroxyl groups in -Si-OH, causing the hydrophilic nanoparticles to be grafted with a fluorosilane coupling agent. After drying, the fluorosilane-modified secondary nanoparticles are obtained. The secondary nanoparticles were dispersed in a solvent to obtain a fluorosilane-modified dispersion of the secondary nanoparticles.

6. The preparation method according to claim 5, characterized in that, First, control the hydrolysis of the fluorosilane coupling agent solution at a pH of 4.0~5.0 for 5 h or more, so that one end of the fluorosilane coupling agent -Si-X is hydrolyzed into -Si-OH; Then the hydrophilic nanoparticles are added, and the reaction is carried out at 60~80℃ for 0.5~2 h, so that some of the hydroxyl groups on the surface of the hydrophilic nanoparticles undergo a dehydration reaction with the hydroxyl groups in -Si-OH. The solvent in the fluorosilane coupling agent solution includes water and ethanol, and the mass ratio of the fluorosilane coupling agent to the hydrophilic nanoparticles is (0.2~0.6):

1.

7. The preparation method according to claim 6, characterized in that, The mass ratio of the fluorosilane coupling agent to water and ethanol is 1:(0.8~1.2):(15~25).

8. The preparation method according to claim 6, characterized in that, The fluorosilane coupling agent is one or more of the following: trimethoxy(1H,1H,2H,2H-heptadecyl)silane, 1H,1H,2H,2H-perfluorooctyltrimethoxysilane, 1H,1H,2H,2H-perfluorooctyltriethoxysilane, 1H,1H,2H,2H-perfluorodecyltrimethoxysilane, 1H,1H,2H,2H-perfluorodecyltriethoxysilane, and tridecafluorooctyltriethoxysilane.

9. The preparation method according to any one of claims 5 to 8, characterized in that, The primary particle size of the hydrophilic nanoparticles is 5~50 nm.

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