High abrasion and stain resistant optical coating based on photocuring technology

Abstract

The application relates to the technical field of optical protection, and specifically discloses a high-wear-resistance and high-stain-resistance optical coating based on a light curing technology, which comprises an alicyclic epoxy resin, an oxetane active diluent, a hexafunctional polyurethane acrylate oligomer, an environmentally-friendly short-chain perfluoropolyether modified diaryliodonium photoinitiator, a photosensitizer, a free radical photoinitiator and a hindered amine proton scavenger, etc. A preparation method comprises the following steps: dispersing raw materials in mixed solvents; pretreating a substrate; coating a coating liquid on the substrate; performing heat-induced self-assembly; performing long-wave photosensitive double curing; and performing post-curing treatment. The application adopts a composite initiation system of an environmentally-friendly short-chain perfluoropolyether modified diaryliodonium and a long-wave photosensitizer, and the low surface energy characteristics of the perfluoropolyether chain segment drive the enrichment of the iodonium salt on the surface, so that the surface crosslinking density and the pencil hardness of the coating are realized under an air atmosphere, and meanwhile, the flexibility of the internal free radical curing system is reserved.

Description

Technical Field

[0001] This application relates to the field of optical protection technology, and more specifically, to a highly wear-resistant and stain-resistant optical coating based on photocuring technology. Background Technology

[0002] With the rapid development of flexible display technology, touch modules, and automotive precision optics, optical thin film materials not only face challenges in terms of mechanical strength, but also face extremely stringent requirements regarding their optical quality and environmental compliance. In practical applications, such optical protective coatings are typically used as a pre-curing underlayer in vacuum coating processes.

[0003] In existing technologies, to meet scratch resistance requirements, optical coatings typically employ high-functionality acrylate or epoxy resin systems, achieving high surface hardness through high crosslinking density. However, this traditional hardened coating reveals three main technical bottlenecks in practical applications:

[0004] First, there are issues with optical compatibility and interface defects. The refractive index of traditional high-hardness coatings is often difficult to adjust, resulting in a significant refractive index difference between the coating and the substrate or subsequent inorganic oxide coatings. This refractive index mismatch produces noticeable optical interference fringes at the interface when light passes through, severely affecting the visual clarity and premium feel of display devices. Furthermore, over-cured coating surfaces are often too smooth and inert, leading to insufficient adhesion of subsequent PVD coatings and making them prone to peeling.

[0005] Secondly, there is a conflict between environmental compliance and durable stain resistance. To impart excellent hydrophobic, oleophobic, and fingerprint-resistant properties to optical coatings, existing technologies often add fluorinated surfactants or fluoropolymers. However, perfluorooctyl fluorocarbons, which are highly effective in traditional technologies, contain perfluorooctanoic acid and its salts or perfluorooctane sulfonic acid, exhibiting biocompatibility and potential toxicity. These have been strictly prohibited by the EU REACH regulation, the POPs Convention, and major global electronic device manufacturers. Although the industry has begun to experiment with short-chain (C6 or C4) fluorides or organosilicones as alternatives, these substitutes often suffer from limited surface energy reduction, poor abrasion resistance, and easy migration and performance degradation during physical friction, making it difficult to achieve the long-lasting anti-fouling performance of long-chain fluorides.

[0006] Finally, there is the trade-off between mechanical hardness and flexibility. The high-rigidity cross-linked network constructed to achieve high hardness results in a coating with high modulus and high brittleness. When applied to flexible foldable substrates, the curing shrinkage stress accumulated inside the coating cannot be released, which can easily lead to brittle cracking of the coating or delamination failure from the flexible substrate during bending. It is impossible to simultaneously achieve both hardness and bending resistance. Summary of the Invention

[0007] To address the problem that existing high-hardness photocurable coatings suffer from high rigidity and brittleness due to their high degree of cross-linking, making them prone to brittle cracking or peeling under stress and unable to simultaneously achieve a mechanical balance between high surface hardness, high impact toughness, and adhesion, this application provides a high wear-resistant and stain-resistant optical coating based on photocuring technology.

[0008] This application provides a high wear-resistant and stain-resistant optical coating based on photocuring technology, employing the following technical solution:

[0009] A high-wear-resistant and stain-resistant optical coating composition based on photocuring technology, characterized in that it is made from the following raw materials in parts by weight: 20-35 parts alicyclic epoxy resin; 5-15 parts oxetane reactive diluent; 30-50 parts hexafunctional polyurethane acrylate oligomer; 10-20 parts acrylate monomer; 1.5-4.0 parts environmentally friendly short-chain perfluoropolyether modified diaryliodonium salt; 0.2-0.8 parts photosensitizer; 2.0-4.0 parts free radical photoinitiator; 0.005-0.02 parts hindered amine proton scavenger; 0.1-0.3 parts leveling agent; and 60-100 parts organic mixed solvent.

[0010] After curing, the coating composition forms an optical interface layer with refractive index matching characteristics, with a light transmittance ≥91% and haze ≤1.0%.

[0011] By adopting the above technical solution, the hindered amine proton scavenger is used to chemically threshold-gated the photo-initiated cationic polymerization reaction. During the coating curing process, the hindered amine scavenger can effectively quench cationic active species inside the coating, limiting the cationic hardening reaction to only occur in the surface layer where the initiator is highly enriched. This establishes a step modulus gradient structure with an outer hardness and an inner toughness in the coating thickness direction. At the same time, by adopting a cationic-free radical hybrid curing system, the cationic polymerization of the surface layer endows the coating with excellent hardness and chemical resistance, while the free radical polymerization network of the bottom layer provides the required toughness and high adhesion, effectively solving the technical problem of the contradiction between high hardness, high toughness and high adhesion in the prior art.

[0012] Preferably, the alicyclic epoxy resin is 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexylcarboxylate; the oxetane reactive diluent is selected from at least one of 3-ethyl-3-hydroxymethyloxetane and bis(3-ethyl-3-oxetane)methyl ether; and the acrylate monomer is selected from at least one of dipentaerythritol hexaacrylate and tripropylene glycol diacrylate.

[0013] Preferably, the environmentally friendly short-chain perfluoropolyether modified diaryliodonium salt has a diphenyliodonium cationic center and an anion selected from hexafluorophosphate or hexafluoroantimonate. The environmentally friendly short-chain perfluoropolyether modified diaryliodonium salt is prepared by esterification reaction of short-chain perfluoropolyether acyl chloride with hydroxyl-containing iodonium salt. The perfluoropolyether segments are selected from repeating unit structures of perfluoromethyl ether, perfluoroethyl ether, or perfluorobutyl ether, and do not contain perfluorooctyl or longer chain structures, nor perfluorooctanoic acid or perfluorooctane sulfonic acid. The number average molecular weight of the perfluoropolyether segments is 400-600 g / mol.

[0014] Preferably, the photosensitizer is selected from at least one of 2-isopropylthioxanthone and 9,10-dibutoxyanthracene, and the characteristic absorption wavelength range of the photosensitizer covers 390-410 nm; the hindered amine proton scavenger is selected from at least one of bis(1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate and methyl-1,2,2,6,6-pentamethyl-4-piperidinyl sebacate.

[0015] Preferably, the organic mixed solvent is composed of propylene glycol methyl ether acetate and butanone in a mass ratio of 1:0.8-1.2.

[0016] A process for preparing a highly wear-resistant and stain-resistant optical coating based on photocuring technology includes the following steps:

[0017] S1. Substrate pretreatment: Select optical grade substrates, clean and dry their surfaces, and then perform corona treatment or plasma treatment to make the surface tension of the substrate reach more than 42dyn / cm.

[0018] S2, Coating liquid film: The coating composition is mixed evenly to obtain a coating liquid, which is then coated onto the substrate surface by spin coating or wire rod coating, and the wet film thickness is controlled within the range of 8-15μm;

[0019] S3. Thermally induced self-assembly: The coated substrate is placed on a heating platform or oven for infrared heating treatment at a temperature of 60-80℃ for 60-120 seconds, which causes the environmentally friendly short-chain perfluoropolyether modified diaryliodonium to migrate and accumulate at the gas-liquid interface and evaporate the solvent.

[0020] S4. Photosensitive curing: The heat-treated coating is irradiated with a UV-LED single-wavelength light source. The center wavelength of the light source is 395nm±5nm or 405nm±5nm. During the irradiation process, surface cationic polymerization and internal free radical polymerization are initiated.

[0021] S5. Post-curing treatment: The coated material after light exposure is placed in an oven for heat treatment at a temperature of 60-80℃ for 10-30 minutes. After cooling, a gradient-cured coating is obtained.

[0022] Preferably, in step S1, the cleaning and drying process includes ultrasonic cleaning with anhydrous ethanol for 5-10 minutes, followed by drying with nitrogen gas.

[0023] Preferably, in step S2, the spin coating is performed in a segmented spin coating manner, firstly at a low speed of 500 rpm for 3-5 seconds, and then at a high speed of 1500-3000 rpm for 20-30 seconds.

[0024] Preferably, in step S4, the UV-LED single-wavelength light source has an illumination intensity of 300-800 mW / cm² on the coating surface, a total exposure energy of 800-2000 mJ / cm², and the curing environment is an air atmosphere.

[0025] Preferably, the power of the corona treatment or plasma treatment in step S1 is 300-500W, and the treatment time is 10-30 seconds.

[0026] In summary, this application has the following beneficial effects:

[0027] 1. Because this application uses an environmentally friendly short-chain perfluoropolyether modified diaryliodonium iodide combined with a long-wavelength photosensitizer, the low surface energy of the perfluoropolyether segments drives the iodium salt to accumulate on the surface, and the photosensitizer initiates cationic polymerization on the surface through an electron transfer mechanism that is not affected by oxygen inhibition. This achieves the effect of extremely high crosslinking density and pencil hardness on the coating surface in an air atmosphere, while retaining the flexibility of the internal free radical curing system.

[0028] 2. In this application, hindered amine compounds are preferably used as proton scavengers. Because they are uniformly distributed in the coating and set the chemical reaction threshold of cationic polymerization, they can instantly quench trace acidic substances generated by photosensitization in the bulk phase, thereby cutting off the internal cationic reaction path. This achieves the effect of a step-like distribution of surface hardness and internal toughness, effectively solving the problems of internal stress cracking and poor adhesion that are prone to occur in high-hardness coatings.

[0029] 3. The method of this application modifies diaryliodonium with environmentally friendly short-chain perfluorinated polyether and initiates polymerization by photolysis to produce acid, while directly incorporating fluorinated segments into the cationic crosslinking network backbone in the form of covalent bonds. Therefore, the effect of chemically anchoring fluorinated functional components to the coating surface is obtained, which significantly improves the long-term stability and non-migration of the coating's hydrophobic and oleophobic properties during long-term mechanical friction. Attached Figure Description

[0030] Figure 1 This is a flowchart of a high wear-resistant and stain-resistant optical coating preparation process based on photocuring technology provided in this application. Detailed Implementation

[0031] The present application will be further described in detail below with reference to the accompanying drawings and embodiments.

[0032] Technical concept:

[0033] Traditional free radical photopolymerization systems, while curing quickly, are highly susceptible to oxygen inhibition in air, resulting in low crosslinking density and poor abrasion resistance on the outermost surface of the coating. Forcibly increasing the crosslinking density generates significant volumetric shrinkage stress, causing the coating to curl or crack on flexible substrates. Furthermore, to impart fingerprint resistance, fluorinated surfactants are typically added physically. However, these additives are prone to physical migration and detachment from the coating surface and often lead to increased haze due to poor compatibility with the base resin.

[0034] To address the aforementioned technical problems, this invention proposes a gradient curing technology based on photosensitized electron transfer and chemical threshold gating mechanisms. The core concept of this solution lies in utilizing the synergistic control of thermodynamics and kinetics to achieve binary differentiation of coating properties along the thickness direction under a single coating and single-light-irradiation process.

[0035] The specific technical methods are as follows:

[0036] First, a modified diaryliodomonium salt (component A) with a long-chain structure of perfluoropolyether (PFPE) was designed and synthesized. Utilizing the extremely low surface energy of the PFPE segments, component A was driven to spontaneously migrate from the bulk phase of the coating to the gas-liquid interface and become highly enriched during the infrared leveling stage after coating, thereby establishing a steep concentration gradient within the coating.

[0037] Secondly, a long-wavelength photosensitizer (component B) that is mismatched with the absorption wavelength of component A and a trace amount of hindered amine proton scavenger (component C) are introduced. During the photocuring stage, the decomposition of component A to produce acid is initiated using an "electron transfer sensitization" mechanism. On the coating surface, due to the high enrichment of component A, the concentration of the generated superacid instantly exceeds the neutralization threshold of component C, initiating cationic polymerization of the alicyclic epoxy resin unaffected by oxygen inhibition, forming a surface layer with high hardness and chemically anchored fluorine segments.

[0038] Finally, in the bulk coating phase, due to the extremely low concentration of component A, the trace acidic substances generated by sensitization are completely quenched by component C, and cationic polymerization is inhibited; at the same time, long-wave ultraviolet light initiates free radical initiators, driving the polyurethane acrylate system to undergo free radical polymerization, forming a high-toughness stress-dissipating layer.

[0039] The main raw materials and reagents used in the following examples and comparative examples have the following sources and specifications. Reagents not specifically mentioned are all commercially available analytical grade or higher grade products.

[0040] Alicyclic epoxy resin (UVR-6110): Chemical name is 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexylcarboxylate, CAS number: 2386-87-0;

[0041] Oxycyclobutane reactive diluent (OXT-101): Chemical name is 3-ethyl-3-hydroxymethyloxycyclobutane, CAS number: 3047-32-3;

[0042] Hexafunctional polyurethane acrylate oligomer (EBECRYL1290): Aliphatic polyurethane acrylate with a weight-average molecular weight of approximately 1000 g / mol.

[0043] Acrylate monomer (DPHA-58-9);

[0044] Iodonium salt precursor: Chemical name is (4-hydroxyphenyl)phenyliodonium hexafluorophosphate, CAS number: 105372-25-2, purity >98%;

[0045] Environmentally friendly short-chain perfluoropolyether precursors: Solvay Fluorolink series or similar products are selected, and SGS testing shows no PFOA / PFOS residues.

[0046] Free radical photoinitiator (TPO): Chemical name 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, CAS number: 75980-60-8;

[0047] Photosensitizer (ITX): Chemical name is 2-isopropylthioxanthone, CAS number: 5495-84-1;

[0048] Hindered amine proton scavenger (Tinuvin292): Chemical name is bis(1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate, CAS number: 41556-26-7;

[0049] Leveling agent (BYK-333): Polyether modified polydimethylsiloxane, CAS No.: 134180-76-0;

[0050] Thionyl chloride: CAS No.: 7719-09-7, analytical grade;

[0051] Triethylamine: CAS No.: 121-44-8, analytical grade;

[0052] Propylene glycol methyl ether acetate (PGMEA): CAS No.: 108-65-6, purity >99.5%, industrial grade.

[0053] Butanone (MEK): CAS No.: 78-93-3, purity >99.5%, industrial grade.

[0054] Hydrofluoroether (HFE-7100): Chemical name is methoxynonafluorobutane, CAS number: 163702-07-6.

[0055] Since the environmentally friendly short-chain perfluoropolyether modified diaryliodonium (component A) used in the embodiments of the present invention cannot be obtained directly through commercial means, the following preparation example 1 details the synthesis process of this core component.

[0056] Preparation Example 1: Synthesis of Perfluoropolyether Modified Diaryliodonium Hexafluorophosphate

[0057] Step S1: In a 250 mL three-necked flask equipped with a reflux condenser, thermometer, and mechanical stirrer, add 50.0 g (approximately 0.1 mol) of short-chain perfluoropolyether carboxylic acid (PFPE-COOH, structural unit: perfluoroethyl ether / perfluorobutyl ether, without C8 long chain), and add 100 mL of hydrofluoroether (HFE-7100) to completely dissolve it. Then, slowly add 23.8 g (0.2 mol) of thionyl chloride dropwise through a constant-pressure dropping funnel. After the addition is complete, add 0.1 mL of N,N-dimethylformamide (DMF) as a catalyst.

[0058] The reaction system was heated to 65°C and stirred under reflux for 5 hours, during which acidic gas was observed to escape. After the reaction was completed, the reaction solution was transferred to a rotary evaporator and distilled under reduced pressure at 60°C and -0.09 MPa to remove the solvent and excess thionyl chloride, yielding a colorless, transparent, oily liquid, which is the perfluoropolyether acyl chloride intermediate, with a yield of 98%.

[0059] Step S2: In a 500mL light-proof three-necked flask equipped with a constant pressure dropping funnel and a mechanical stirrer, add 10.5g (0.02mol) (4-hydroxyphenyl)phenyliodomonium hexafluorophosphate, dissolve it in 150mL of anhydrous dichloromethane, and add 3.0g (0.03mol) triethylamine.

[0060] The flask was cooled in an ice-water bath at 0°C. Under vigorous stirring, an anhydrous dichloromethane solution (30 mL) containing 12.0 g (approximately 0.024 mol) of the perfluoropolyether acyl chloride intermediate prepared in step S1 was slowly added dropwise through a dropping funnel. The dropping rate was controlled to keep the system temperature below 5°C and the reaction was stirred for 18 hours.

[0061] Step S3: After the reaction is complete, transfer the reaction mixture to a separatory funnel and wash three times with 100 mL of deionized water to remove the byproduct triethylamine hydrochloride and unreacted water-soluble impurities. Collect the lower organic phase and dry it with anhydrous magnesium sulfate for 12 hours. After filtering to remove the drying agent, remove the dichloromethane solvent by rotary evaporation under reduced pressure at 30 °C to obtain a viscous amber-colored waxy solid.

[0062] The obtained solid was dispersed in 50 mL of n-hexane and ultrasonically cleaned for 10 minutes to remove unreacted free perfluoropolyether. After centrifugation, the lower solid layer was collected. Finally, the solid was placed in a vacuum drying oven and dried at 40 °C for 24 hours to obtain 16.5 g of perfluoropolyether-modified diaryliodonium hexafluorophosphate, with a yield of 80%.

[0063] Product structure confirmation: LC-MS (liquid chromatography-mass spectrometry) analysis of the product showed that perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS) were not detected (detection limit <5 ppb), confirming that the product complies with the EU REACH and POPs regulations. Additionally, infrared spectroscopy analysis showed that the product structure was within a certain range at 1780 cm⁻¹. -1 A distinct stretching vibration peak of the ester carbonyl group (C=O) was observed, and the carboxyl peak of the raw material perfluoropolyether was at 1775 cm⁻¹. -1 The peak of acyl chloride is 1805 cm⁻¹ -1 The disappearance confirms that the esterification reaction was completed and the product structure is as expected.

[0064] The present invention will be further disclosed below with reference to embodiments: Example

[0065] Please see the appendix Figure 1 This embodiment provides a high wear-resistant and stain-resistant optical coating composition based on photocuring technology and its preparation process.

[0066] The following parts by weight of raw materials were added to a light-proof stirred tank: 28 parts of alicyclic epoxy resin, 10 parts of oxetane reactive diluent, 40 parts of hexafunctional polyurethane acrylate oligomer, 15 parts of acrylate monomer, 2.8 parts of the environmentally friendly short-chain perfluoropolyether modified diaryliodonium obtained in Preparation Example 1, 0.5 parts of photosensitizer, 3.0 parts of free radical photoinitiator, 0.012 parts of hindered amine proton scavenger, and 0.2 parts of leveling agent.

[0067] Subsequently, 80 parts of an organic mixed solvent were added, which was a mixture of propylene glycol methyl ether acetate (PGMEA) and butanone (MEK) in a mass ratio of 1:1.

[0068] Stir at 500 rpm for 30 minutes at room temperature until a uniform and transparent coating solution is formed. Filter the solution using a 0.45 μm PTFE membrane for later use.

[0069] Coating preparation process:

[0070] S1. Substrate Pretreatment: A 125μm thick optical-grade PET film was selected, cleaned and dried with anhydrous ethanol, and then subjected to corona treatment. The treatment power was 400W, and the treatment time was 20 seconds, until the surface tension of the substrate reached above 42 dyn / cm.

[0071] S2. Coating liquid film: The above coating liquid is dropped onto the surface of the substrate and a segmented spin coating process is adopted: first spin coating at 500 rpm for 5 seconds, and then spin coating at 2000 rpm for 25 seconds.

[0072] S3, Thermally Induced Self-Assembly: The coated substrate is placed on a heating platform at 70°C and heated for 90 seconds to evaporate the solvent and drive the surface migration of fluorine-containing components.

[0073] S4. Photosensitive Curing: The heat-treated coating is placed on a UV-LED conveyor belt and irradiated in an air atmosphere. The center wavelength of the light source is 395nm, the light intensity is 500mW / cm², and the total exposure energy is 1500mJ / cm².

[0074] S5. Post-curing treatment: Place the light-exposed coating in an oven and heat-treat at 70°C for 20 minutes, then cool to room temperature to obtain a cured coating.

[0075] Example 2

[0076] This embodiment aims to verify the technical effect under high cationic component content and high fluorine content.

[0077] The raw material composition is as follows: 35 parts of alicyclic epoxy resin, 15 parts of oxetane reactive diluent, 30 parts of hexafunctional polyurethane acrylate oligomer, 10 parts of acrylate monomer, 4.0 parts of environmentally friendly short-chain perfluoropolyether modified diaryliodonium obtained in Preparation Example 1, 0.8 parts of photosensitizer, 2.0 parts of free radical photoinitiator, 0.02 parts of hindered amine proton scavenger, and 0.3 parts of leveling agent.

[0078] The amount of organic mixed solvent used is 60 parts, and the solvent composition is a mixture of PGMEA and MEK at a mass ratio of 1:0.8.

[0079] The preparation process is the same as in Example 1.

[0080] Coating preparation process:

[0081] S1. Substrate pretreatment: Corona treatment power is 500W, and treatment time is 30 seconds.

[0082] S2, Coating liquid film: The high-speed spin coating stage has a rotation speed of 3000 rpm and a time of 30 seconds.

[0083] S3, Thermally Induced Self-Assembly: The heating platform temperature is 80℃, and the heating time is 120 seconds.

[0084] S4. Photosensitive curing: The center wavelength of the light source is 395nm, the light intensity is 800mW / cm², the total exposure energy is 2000mJ / cm², and the atmosphere is air.

[0085] S5. Post-curing treatment: Heat treatment at 80℃ for 20 minutes.

[0086] Example 3

[0087] This embodiment aims to verify the technical effect under conditions of high free radical component content and low fluorine content.

[0088] The raw material composition is as follows: 20 parts of alicyclic epoxy resin, 5 parts of oxetane reactive diluent, 50 parts of hexafunctional polyurethane acrylate oligomer, 20 parts of acrylate monomer, 1.5 parts of environmentally friendly short-chain perfluoropolyether modified diaryliodonium obtained in Preparation Example 1, 0.2 parts of photosensitizer, 4.0 parts of free radical photoinitiator, 0.005 parts of hindered amine proton scavenger, and 0.1 parts of leveling agent.

[0089] The amount of organic mixed solvent used is 100 parts, and the solvent composition is a mixture of PGMEA and MEK at a mass ratio of 1:1.2.

[0090] The preparation process is the same as in Example 1.

[0091] Coating preparation process:

[0092] S1. Substrate pretreatment: Corona treatment power is 300W, and treatment time is 10 seconds.

[0093] S2, Coating liquid film: The high-speed spin coating stage has a rotation speed of 1500 rpm and a time of 20 seconds.

[0094] S3, Thermally Induced Self-Assembly: The heating platform temperature is 60℃, and the heating time is 60 seconds.

[0095] S4. Photosensitive curing: The center wavelength of the light source is 395nm, the light intensity is 300mW / cm², the total exposure energy is 800mJ / cm², and the atmosphere is air.

[0096] S5. Post-curing treatment: Heat treatment at 60℃ for 20 minutes.

[0097] Example 4

[0098] This embodiment selects low-value boundary conditions for each raw material component and process parameter.

[0099] The raw material composition is as follows: 20 parts of alicyclic epoxy resin, 5 parts of oxetane reactive diluent, 50 parts of hexafunctional polyurethane acrylate oligomer, 20 parts of acrylate monomer, 1.5 parts of environmentally friendly short-chain perfluoropolyether modified diaryliodonium obtained in Preparation Example 1, 0.2 parts of photosensitizer, 2.0 parts of free radical photoinitiator, 0.005 parts of hindered amine proton scavenger, and 0.1 parts of leveling agent.

[0100] The amount of organic mixed solvent used is 60 parts, and the solvent composition is a mixture of PGMEA and MEK in a mass ratio of 1:1.

[0101] The preparation process is the same as in Example 1.

[0102] Coating preparation process:

[0103] S1. Substrate pretreatment: Corona treatment power is 300W, and treatment time is 10 seconds.

[0104] S2, Coating liquid film: The high-speed spin coating stage has a rotation speed of 1500 rpm and a time of 20 seconds.

[0105] S3, Thermally Induced Self-Assembly: The heating platform temperature is 60℃, and the heating time is 60 seconds.

[0106] S4. Photosensitive curing: The center wavelength of the light source is 395nm, the light intensity is 300mW / cm², the total exposure energy is 800mJ / cm², and the atmosphere is air.

[0107] S5. Post-curing treatment: Heat treatment at 60℃ for 20 minutes.

[0108] Example 5

[0109] This embodiment selects high-value boundary conditions for each raw material component and process parameter.

[0110] The raw material composition is as follows: 35 parts of alicyclic epoxy resin, 15 parts of oxetane reactive diluent, 30 parts of hexafunctional polyurethane acrylate oligomer, 10 parts of acrylate monomer, 4.0 parts of environmentally friendly short-chain perfluoropolyether modified diaryliodonium obtained in Preparation Example 1, 0.8 parts of photosensitizer, 4.0 parts of free radical photoinitiator, 0.02 parts of hindered amine proton scavenger, and 0.3 parts of leveling agent.

[0111] The amount of organic mixed solvent used is 100 parts, and the solvent composition is a mixture of PGMEA and MEK at a mass ratio of 1:1.2.

[0112] The preparation process is the same as in Example 1.

[0113] Coating preparation process:

[0114] S1. Substrate pretreatment: Corona treatment power is 500W, and treatment time is 30 seconds.

[0115] S2, Coating liquid film: The high-speed spin coating stage has a rotation speed of 3000 rpm and a time of 30 seconds.

[0116] S3, Thermally Induced Self-Assembly: The heating platform temperature is 80℃, and the heating time is 120 seconds.

[0117] S4. Photosensitive curing: The center wavelength of the light source is 395nm, the light intensity is 800mW / cm², the total exposure energy is 2000mJ / cm², and the atmosphere is air.

[0118] S5. Post-curing treatment: Heat treatment at 80℃ for 20 minutes.

[0119] Comparative Example 1:

[0120] Compared with Example 1, the difference is that the environmentally friendly short-chain perfluoropolyether modified diaryliodonium (2.8 parts) obtained in Preparation Example 1 was removed, and instead 1.4 parts of unmodified iodonium salt and 1.4 parts of unmodified perfluoropolyether were physically mixed and added. The remaining components and process parameters are the same as in Example 1.

[0121] Comparative Example 2:

[0122] Compared with Example 1, the difference is that the hindered amine proton scavenger is removed, while the other components and process parameters are the same as in Example 1.

[0123] Comparative Example 3:

[0124] Compared with Example 1, the difference is that the S3 thermally induced self-assembly step is omitted (i.e., after coating, the 70°C heating treatment is not performed, but the S4 photosensitive curing is performed directly). The remaining components and process parameters are the same as those in Example 1.

[0125] Comparative Example 4:

[0126] Compared to Example 1, the difference lies in the removal of all cationic curing components (alicyclic epoxy resin, oxetane reactive diluent, and modified iodonium salt), while correspondingly increasing the polyurethane acrylate oligomer to 70 parts and the acrylate monomer to 25 parts, and physically adding 1.4 parts of unmodified perfluoropolyether as a hydrophobic additive. The formulation does not contain proton scavengers or photosensitizers; only free radical initiators are used, and the process parameters are the same as in Example 1.

[0127] Comparative Example 5:

[0128] Compared with Example 1, the difference is that in the S4 photosensitization curing step, a 365nm high-pressure mercury lamp light source is used instead of a 395nm UV-LED light source, and the total exposure energy is kept at 1500mJ / cm². The other components and process parameters are the same as in Example 1.

[0129] Comparative Example 6:

[0130] Compared with Example 1, the difference is that the hexafunctional polyurethane acrylate oligomer is replaced with ordinary low-refractive-index aliphatic polyurethane acrylate (refractive index nD is about 1.48), while the other components and process parameters are the same as in Example 1.

[0131] Test Example 1: Comprehensive Physical Properties and Surface Characteristics Test of Coating

[0132] This test example comprehensively tests the coating thickness, pencil hardness, adhesion, contact angle, and abrasion resistance of the optical coatings prepared in the above embodiments and comparative examples. The specific test steps are as follows:

[0133] First, the basic physical parameters of the coating were determined. Using an Elcometer 456 digital film thickness gauge, 10 measurement points were randomly selected at the center and edge of the coating sample. The coating thickness values ​​were read and the arithmetic mean was calculated. Pencil hardness testing was performed according to ASTM D3363 standard. A Mitsubishi standard hardness pencil was used, and under a 750g load, the pencil was pushed across the coating surface at a 45-degree angle. The highest hardness rating that did not break the coating was recorded. Adhesion testing was performed according to Method B of ASTM D3359 standard. A special cross-cutting tool was used to cut 100 1mm × 1mm grids on the coating surface. 3M 600 pressure-sensitive adhesive tape was applied and quickly peeled off at a 180-degree angle. The degree of peeling off the grid areas was observed and rated.

[0134] Subsequently, surface wettability and wear resistance durability tests were conducted. Using a contact angle meter, at 23℃ and 50% relative humidity, the static water contact angle and hexadecane contact angle of the coating surface were measured, with the droplet volume set to 2μL. The equilibrium value after 30 seconds of droplet contact with the surface was recorded as the initial contact angle. Wear resistance testing was performed using a Heidong-9820 reciprocating friction testing machine. 0000# steel wool was used as the wear medium, the friction head diameter was 20mm, and a vertical load of 1000g was applied. The coating surface was rubbed reciprocally 3000 times at a frequency of 60 times / minute. After friction, the worn area was gently wiped with ethanol to remove debris. After drying, the water contact angle and hexadecane contact angle of the area were measured again. The difference between these values ​​and the initial values ​​characterized the wear resistance durability of the coating.

[0135] The specific data from the above tests are summarized in Table 1.

[0136] Table 1 Summary of Performance Test Data for Examples and Comparative Examples

[0137]

[0138] A comparison of the data from Examples 1 to 5 with Comparative Example 2 shows that hindered amine compounds play a decisive role in constructing the modulus gradient along the coating thickness direction. Example 1 achieved an adhesion level of 5B while maintaining a pencil hardness of 6H, while Comparative Example 2, due to the absence of hindered amines, experienced highly cross-linked cationic polymerization both inside and on the surface of the coating, leading to internal stress accumulation and a significant decrease in adhesion to 1B. This result confirms that the chemical reaction threshold established using hindered amines can effectively quench trace amounts of acidic active species generated by long-wavelength photosensitization in the bulk phase, limiting the cationic hardening reaction to occur only in the initiator-rich surface layer. This preserves a tough network primarily based on free radical curing within the coating, achieving a mechanical balance between high surface hardness and high substrate adhesion.

[0139] The difference in contact angle changes between Example 1 and Comparative Example 1 after abrasion resistance testing verifies the effectiveness of the chemical anchoring technique for the fluorinated component. Comparative Example 1 introduced the unmodified fluorinated component through physical blending. Although its initial contact angle was similar to that of Example 1, after 3000 cycles of steel wool friction, its hexadecane contact angle significantly decreased from 75.0 degrees to 61.2 degrees, indicating that free fluorinated molecules detached and migrated under mechanical friction. In contrast, the coatings of Examples 1 to 5 showed no significant decrease in contact angle after abrasion. This is because the perfluoropolyether segments are directly covalently linked to the cationic initiator. Accompanying the initiator's pyrolysis and polymerization reactions, the fluorinated segments are chemically bonded and locked within the high-crosslink density polymer backbone of the surface layer, thus endowing the coating with durable and stable hydrophobic and oleophobic properties.

[0140] The comparison results between Example 1 and Comparative Examples 3 and 4 illustrate the necessity of thermally induced self-assembly processes and composite curing systems. Comparative Example 3 omitted the heating step, resulting in insufficient migration and enrichment of the fluorinated initiator to the surface, leading to insufficient cationic reaction sites on the coating surface, an initial water contact angle of only 98.4 degrees, and a hardness as low as 2H. Comparative Example 4 used only a free radical curing system; due to the inhibitory effect of oxygen in the air on free radical polymerization, the coating surface was not fully cured, and the hardness was only HB. This invention solves the problems of surface stickiness and poor underlayer curing in traditional photocuring systems by thermodynamically driving the enrichment of fluorinated components on the surface, combining the oxygen-insensitive characteristic of surface cationic polymerization, and the effective excitation of the underlying free radical initiator by a long-wavelength light source.

[0141] Test Example 2: Optical Properties and Environmental Reliability Testing

[0142] This test case primarily evaluates the component compatibility of the coating composition and its structural stability under humid and hot conditions, with a focus on the impact of the gradient structure on optical transparency and the ability of the interfacial adhesion to be maintained under extreme conditions.

[0143] Optical performance testing: Tests were conducted according to ASTM D1003 standard. A haze meter was used to measure the coating samples of each embodiment and comparative example. Five points were selected at the center and perimeter of each sample, and the total light transmittance and haze were measured at each point. The arithmetic mean of the five points was recorded. This test characterizes the dispersion state and compatibility of the fluorine-containing components in the coating; a higher haze value indicates the presence of phase separation or microscopic defects within the coating.

[0144] Boiling water resistance test: Immerse each coating sample completely in a beaker containing deionized water, heat the water to boiling, and maintain the boiling point for 60 minutes. Remove the sample, blot the surface moisture with a lint-free cloth, and allow it to stand at room temperature for 1 hour to recover. Then observe whether the coating surface shows whitening, blistering, or peeling.

[0145] Adhesion tests were performed again on the restored sample surface, and the adhesion level after boiling water treatment was recorded to evaluate the interlayer bonding stability of the coating under hygrothermal stress.

[0146] Solvent resistance wiping test: Using cotton balls soaked in methyl ethyl ketone (MEK), the coating surface was repeatedly wiped under a 500g load. The number of wiping cycles was set to 200. After wiping, the coating surface was observed for signs of dissolution, loss of gloss, or damage, which was used to evaluate the resistance of the cured cross-linked network of the coating to chemical solvent erosion.

[0147] Table 2. Optical and Reliability Test Data for Examples and Comparative Examples

[0148]

[0149] The differences in optical transmittance and haze data between the examples and the comparative examples reflect the influence of the fluorinated component introduction method on the microcompatibility of the coating. The haze values ​​of Examples 1 to 5 were all controlled between 0.45% and 0.83%, and the transmittance was all above 91.5%, indicating that the perfluoropolyether-modified iodonium salt, as a single molecular component, forms a uniform enriched layer on the surface through a thermally induced self-assembly process, without generating macroscopic phase separation structures in the bulk coating that would cause light scattering. Conversely, Comparative Example 1, which introduced unmodified perfluoropolyether and iodonium salt through physical mixing, experienced agglomeration and precipitation during curing due to the significant difference in surface energy between the fluorocarbon segments and the hydrocarbon resin matrix, and the lack of chemical bonding constraints. This resulted in a significant increase in haze to 3.15% accompanied by a decrease in transmittance, confirming the necessity of molecular-level chemical modification for ensuring the transparency of optical-grade coatings.

[0150] The boiling water resistance test results revealed the mechanism by which the gradient-cured structure alleviates internal stress and resists humid heat erosion. Example 1 showed no change in appearance and maintained a 5B adhesion level after being boiled in 100°C for 60 minutes. In contrast, Comparative Example 2, although initially exhibiting poor adhesion, developed microcracks and completely lost adhesion after boiling water treatment. This indicates that the lack of hindered amine regulation in the system, under high temperature and humidity conditions, prevents the release of internal stress caused by excessive cross-linking, leading to brittle cracking and interfacial peeling of the coating. Furthermore, Comparative Example 4 showed edge lifting and decreased adhesion after the boiling water test, indicating that the interfacial stability of a single free radical cured network after water absorption and swelling is inferior to the interpenetrating polymer network structure constructed in this invention.

[0151] Solvent wiping tests further verified the high crosslinking density of the surface cationic cured layer. The sample in the example remained undamaged after 200 wipings with methyl ethyl ketone (MEK), indicating that the surface alicyclic epoxy resin formed a dense solvent-resistant barrier under the initiation of a superacid. Comparative Example 3, although using the same formulation, omitted the thermal induction step, resulting in insufficient migration of the fluorinated iodonium salt to the surface, leading to insufficient concentration of the surface cationic initiator and reduced curing density. Therefore, it exhibited gloss loss under solvent wiping. This result indirectly confirms the crucial role of the thermally induced self-assembly step in establishing high-concentration initiation centers on the coating surface and initiating efficient cationic polymerization, thereby endowing the coating with excellent chemical resistance.

[0152] Test Example 3: Long-wavelength light curing efficiency and curing rate test

[0153] This test case aims to quantitatively evaluate the impact of the long-wavelength photosensitive system used in this invention on curing efficiency, especially in comparison with wavelength mismatch of the light source and a single curing system, so as to objectively verify the effectiveness of the "long-wavelength photosensitive electron transfer" mechanism in achieving deep curing of coatings.

[0154] Curing rate test: The photocuring kinetics of the wet coatings in each embodiment and comparative example were monitored in real time using a Fourier transform infrared spectrometer equipped with a fast scanning accessory. The wet coating samples were placed on the sample stage of the photocuring accessory, and the light source wavelength was set to 395 nm (except for Comparative Example 5), and the light intensity was 500 mW / cm².

[0155] The degree of curing of cationic polymerization is monitored by observing the characteristic absorption peak of alicyclic epoxy groups (approximately 800 cm⁻¹). -1 The degree of curing of free radical polymerization was characterized by monitoring the real-time disappearance of the characteristic absorption peak of the acrylate double bond (approximately 810 cm⁻¹). -1 The real-time disappearance of the cation was characterized, and the cation solidification conversion rate of each system was recorded after a 3-second exposure time.

[0156] Curing depth test: Each sample was cured at different total exposure energies. After curing, the coating was cut open and peeled off using a blade.

[0157] A solvent wiping test was performed on the residual undercoat on the substrate: using a cotton ball soaked in propylene glycol methyl ether acetate, the residual undercoat was wiped under slight pressure. The minimum exposure energy required for the coating not to be removed was recorded. This value is an objective indicator of the deep curing efficiency of the undercoat. The lower the critical curing energy, the higher the curing efficiency.

[0158] Table 3 Summary of Curing Efficiency and Curing Rate Test Results for Examples and Comparative Examples

[0159]

[0160] The comparison of the critical curing energies of Examples 1 to 5 with Comparative Examples 3 and 5 strongly verifies the high curing efficiency of the present invention under long-wavelength light sources. The photosensitive electron transfer mechanism employed in this invention utilizes the photophysical interaction between the photosensitizer (ITX) and the iodonium salt component, enabling the iodonium salt, which does not absorb the 395nm wavelength, to be effectively activated and decomposed to produce acid. Comparative Example 5, with the same formulation as Example 1, only changed the curing light source from 395nm to 365nm, and its critical curing energy significantly increased from 800mJ / cm² to 1300mJ / cm². This indicates that the penetration power of the 365nm short-wavelength light source is insufficient to effectively activate the deep initiation system, and its compatibility with the sensitization mechanism is low. This result confirms that the combination of a long-wavelength photosensitizer and light source is a necessary technical means to achieve rapid deep curing of coatings.

[0161] The test data from Comparative Example 4 reveals the necessity of using a hybrid curing system. Comparative Example 4, employing a pure free radical system, showed a free radical conversion rate of only 45.1% within a 3-second exposure time. Furthermore, in the critical curing energy test, even at exposure energies exceeding 1500 mJ / cm², the coating substrate could not be completely cured and was wiped off by the solvent. This phenomenon was due to severe inhibition of polymerization of the coating bulk phase by oxygen from the air, resulting in incomplete curing. Examples 1 to 5 showed significantly higher free radical conversion rates than Comparative Example 4 within 3 seconds, indicating that the exothermic reaction of cationic polymerization can effectively increase the internal temperature of the coating, partially overcoming the oxygen inhibition effect, thereby achieving rapid deep free radical curing. This synergistic effect effectively solves the technical problem of insufficient curing depth in traditional photocuring under air atmosphere.

[0162] The differences in curing conversion rates between Examples 1 and Examples 2 and 3 confirm the regulatory effect of the coating component ratio on the cationic and free radical polymerization rates. Example 2 exhibited the highest cationic conversion rate at 3 seconds, while also having the lowest critical curing energy, indicating that increasing the proportion of cationic components helps to improve the surface hardening rate and curing efficiency. Example 3, on the other hand, exhibited the highest free radical conversion rate, indicating that the formation rate of the bulk high-toughness network was accelerated. This difference in curing rate achieved by adjusting the ratio of the two types of resin components provides an objective process basis for preparing gradient coatings with different mechanical biases, supporting the flexibility of controlling the final coating performance through formulation adjustments.

[0163] Test Example 4: Proton Scavenger Concentration Gradient Control and Interfacial Adhesion Stability Test

[0164] This test case aims to quantitatively investigate the effect of the dosage of hindered amine proton scavenger on the overall performance of the coating, especially its influence on the key parameter of modulus gradient, and to verify the role of substrate surface corona pretreatment in improving the interfacial bonding strength of the coating.

[0165] The effect of proton scavenger concentration was tested: The formulation of Example 1 was used as a base, but the corona pretreatment of Preparation Example 1 was not performed. The amount of proton scavenger (Tinuvin 292) was adjusted from 0.005 parts to 0.030 parts. After the coating was prepared, pencil hardness and adhesion tests were performed to determine the precise effect of this key component on the balance point of hardness and adhesion.

[0166] Test on the effect of pretreatment on adhesion: Coating formulations of Example 1, Comparative Example 1, and Comparative Example 2 were selected, and samples were prepared under the following two substrate pretreatment conditions:

[0167] Condition A: Perform corona pretreatment as described in Example 1.

[0168] Condition B: Cleaning with ethanol only, without corona pretreatment. After preparation, all samples underwent initial adhesion testing and post-boiling adhesion testing.

[0169] UV aging resistance test: Samples from Example 1, Example 4, and Comparative Example 2 were placed in an accelerated UV aging chamber. The irradiation intensity was set to 0.77 W / m² / nm, the black panel temperature was 60℃, and continuous light aging was carried out for 1000 hours.

[0170] After aging, the surface of the sample was observed, and the water contact angle and adhesion of the aged area were measured again.

[0171] Table 4. Results of tests on the effects of proton scavenger concentration, pretreatment, and aging resistance.

[0172]

[0173] Test data from samples A to C confirm the mechanism by which hindered amine scavengers regulate the coating modulus gradient. As the amount of hindered amine increased from 0.005 parts to 0.030 parts, the surface pencil hardness of the coating gradually decreased from 5H to 3H, while the adhesion remained at 5B. This result indicates that hindered amine scavengers act as quenchers of cationic curing reactions in the coating. Higher amine dosage leads to higher scavenging efficiency for bulk acidic active species, resulting in lower cationic polymerization within the coating and a dominant free radical curing network, thus reducing the overall modulus while maintaining high toughness. This trend quantitatively verifies that by adjusting the amount of proton scavenger, the balance point between coating hardness and toughness can be precisely controlled, meeting the customized requirements of different applications for "external hardness and internal toughness."

[0174] A comparison of the adhesion data between Example 1 and Sample D clarifies the crucial role of substrate pretreatment in interfacial bonding. Example 1 exhibited an initial adhesion of 5B after corona treatment, which remained at 5B after 1000 hours of UV aging. In contrast, Sample D initially showed an adhesion of only 3B, which further decreased to 2B after aging. Corona treatment, through high-energy corona discharge, effectively increased the density of polar functional groups on the PET substrate surface, enabling the cationic polymer components and acrylate monomers in the coating to form strong chemical crosslinks or physical anchors with the hydroxyl and carboxyl groups on the substrate surface. This pretreatment step significantly improved the bonding energy and durability of the coating-substrate interface, particularly enhancing interfacial stability under aging stress.

[0175] The UV aging test results demonstrated the synergistic stabilizing effect of the modified iodonium salt and the hindered amine scavenger. In Examples 1 and 4, after 1000 hours of UV aging, the water contact angle (WCA) decreased only slightly, and the adhesion level remained unchanged. However, in Comparative Example 1, the WCA decreased from an initial 114.9° to 99.5° after aging, indicating that the un-chemically anchored fluorinated components underwent degradation or migration under long-term UV irradiation and photothermal effects. Furthermore, both the cationic initiator and the hindered amine scavenger of this invention possess anti-photodegradation structures, and their presence in the system provides additional photothermal oxidation stabilization protection for the coating, enabling it to maintain hydrophobic and stain-resistant properties even under long-term outdoor use.

[0176] Test Example 5: Thermal Shock and Mechanical Shock Toughness Test

[0177] This test case aims to quantitatively evaluate the ability of the "hard on the outside, tough on the inside" gradient structure of the coating of this invention to resist thermal and mechanical shock stresses. The gradient structure provides a stress buffer layer in the thickness direction, which is of great significance to the reliability of the coating in harsh environments.

[0178] Thermal shock stability test: The coating samples of each embodiment and comparative example were placed in a high and low temperature cycling test chamber for thermal shock test.

[0179] The thermal shock cycle is set as follows: maintain a constant temperature of −40°C for 30 minutes, then rapidly transfer to a constant temperature of 85°C for 30 minutes. One such cycle is counted as one period.

[0180] The samples were subjected to 200 cycles of thermal shock treatment. After the cycles were completed, the samples were removed and allowed to recover at room temperature for 2 hours.

[0181] Subsequently, observe the coating surface for signs of blistering, delamination, or cracking. Perform adhesion tests on the samples and record the adhesion level after thermal shock treatment.

[0182] Falling ball impact test: The test was conducted according to the falling ball impact method in GB / T9279-2007. Using a standard impact apparatus, each coating sample was fixed on an impact base. A steel ball with a diameter of 1 / 2 inch and a mass of 112g was selected. The steel ball was released from different heights and allowed to fall freely onto the coating surface. The minimum impact height required to cause cracks or peeling of the coating was recorded; this height value was used to characterize the coating's resistance to mechanical impact.

[0183] Optical property testing after wear resistance: Samples from Example 1 and Comparative Example 4 were selected. Using a reciprocating friction tester, the sample surface was rubbed 1000 times with 0000# steel wool and a pressure of 1000g. In the friction area, the haze was measured again using a haze meter after wear. The increase in haze value was used to objectively evaluate the coating's ability to maintain optical clarity after mechanical damage.

[0184] Table 5 Summary of thermal shock and mechanical toughness test results for the examples and comparative examples

[0185]

[0186] The test data of Examples 1 to 5, compared with those of Comparative Examples 2 and 4, objectively verified the technical advantages of the modulus gradient structure constructed in this invention in resisting thermal and mechanical stress. In the thermal shock test, the sample from the examples showed no defects in appearance and maintained a stable adhesion level after experiencing 200 cycles of drastic temperature changes from -40°C to 85°C. Conversely, Comparative Example 2 developed microcracks and completely lost its adhesion after thermal shock, while Comparative Example 4 showed edge lifting. This indicates that the hindered amine-regulated external hard-internal tough gradient structure allows the free radical-dominated network inside the coating to act as a stress buffer layer, effectively absorbing and dissipating the enormous thermal stress generated by thermal expansion mismatch, thus preventing brittle failure of the hard surface layer.

[0187] The drop ball impact test results directly quantified the high toughness effect brought about by the gradient structure. The minimum fracture height of Example 3 reached 125.1 cm, significantly higher than the 40.0 cm of Comparative Example 4 and the 55.0 cm of Comparative Example 2. This result confirms that by precisely controlling the ratio of free radical curing components to cationic curing components, the overall mechanical impact resistance of the coating can be significantly improved without sacrificing surface hardness. In particular, the comparison with Comparative Example 2 highlights the technical disadvantage of excessive crosslinking severely reducing coating toughness, further demonstrating the necessity of hindered amine scavengers for maintaining the inner toughness structure.

[0188] The haze test results after wear resistance revealed the contribution of the composite cured network structure to the optical retention capability. Comparative Example 4 showed a haze increase to 7.30% after 1000 cycles of light friction, indicating that its cured network was not dense enough and was prone to microscopic scratches and scattering defects under mechanical wear. In contrast, Example 1's haze value only increased to 1.15% under the same wear conditions.

[0189] This indicates that the dual-curing hybrid network structure used in this invention, especially the high-density epoxy / oxetane network initiated by cations on the surface, can provide higher resistance to micro-scratches and surface structure stability, ensuring that the coating can maintain high optical clarity even after long-term wear.

[0190] Test Example 6: Environmental Compliance and Compatibility Test with Optical Vacuum Coating

[0191] This test case aims to highlight the technical advantages of the coating composition described in this application in meeting stringent environmental regulations and adapting to downstream optical vacuum coating processes.

[0192] The coating sample prepared in Example 1 was selected as the experimental group. Comparative Example 6 was also set up, the only difference from Example 1 being the replacement of the high-refractive-index hexafunctional polyurethane acrylate oligomer with a common low-refractive-index aliphatic polyurethane acrylate (refractive index approximately 1.48). Comparative Example 1 was also selected as the control group for long-chain fluorinated materials.

[0193] First, PFAS content and environmental compliance tests were conducted. Referring to the CEN / TS15968 standard, organic solvent extraction was performed on the cured coating using liquid chromatography-tandem mass spectrometry, and the residual amounts of perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) were analyzed.

[0194] Next, optical compatibility and rainbow effect tests were conducted. The coatings of Example 1, Comparative Example 1, and Comparative Example 6 were coated onto optical-grade PET films with a refractive index of 1.60 and cured. The samples were placed under a D65 standard light source and a three-band fluorescent lamp, and the coating surface was visually observed at different incident angles. If no colored interference fringes were observed, it was recorded as no rainbow effect; if obvious red and green alternating fringes were observed, it was recorded as having a rainbow effect. At the same time, a refractometer was used to test the refractive index of the cured coating.

[0195] Finally, the adhesion of the vacuum coating was tested. A 100 nm thick indium tin oxide (ITO) conductive film was deposited on the surface of the above samples using magnetron sputtering. Subsequently, a cross-cut adhesion test was performed using 3M 600 tape to evaluate the bonding strength between the coating as a base layer and the vacuum-deposited layer.

[0196] The test results are as follows:

[0197] The test results of Example 1 showed that the contents of PFOA and PFOS were undetectable (below the detection limit of 5 ppb), which confirms that the short-chain perfluoropolyether modification technology used in this application fully complies with the EU REACH regulation and the POPs Convention's restrictions on organofluorine compounds. In terms of optical properties, the coating of Example 1 has a refractive index of 1.58, which matches well with the PET substrate, and no rainbow-like pattern was observed. In the vacuum coating test, the ITO film layer and the coating were tightly bonded, with adhesion reaching level 5B, and no peeling occurred.

[0198] Although Comparative Example 1 performed reasonably well in terms of physical properties, it was found to contain more than 500 ppb of PFOA in environmental testing, which did not meet environmental compliance requirements.

[0199] Comparative Example 6, due to the use of a low-refractive-index resin, has a cured coating with a refractive index of only 1.49, resulting in a significant refractive index difference with the substrate. This led to a visually observed severe rainbow-like effect, severely impacting the optical display performance. This specific embodiment is merely an explanation of this application and is not intended to limit it. Those skilled in the art, after reading this specification, can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A highly wear-resistant and stain-resistant optical coating composition based on photocuring technology, characterized in that, It is made from the following raw materials in parts by weight: 20-35 parts alicyclic epoxy resin; 5-15 parts oxetane reactive diluent; 30-50 parts hexafunctional polyurethane acrylate oligomer; 10-20 parts acrylate monomer; 1.5-4.0 parts environmentally friendly short-chain perfluoropolyether modified diaryliodonium salt; 0.2-0.8 parts photosensitizer; 2.0-4.0 parts free radical photoinitiator; 0.005-0.02 parts hindered amine proton scavenger; 0.1-0.3 parts leveling agent; and 60-100 parts organic mixed solvent. After curing, the coating composition forms an optical interface layer with refractive index matching characteristics, exhibiting a light transmittance ≥91% and a haze ≤1.0%. The environmentally friendly short-chain perfluoropolyether modified diaryliodonium salt has a diphenyliodonium cationic center and an anion selected from hexafluorophosphate or hexafluoroantimonate. The environmentally friendly short-chain perfluoropolyether modified diaryliodonium salt is prepared by esterification reaction of short-chain perfluoropolyether acyl chloride with hydroxyl-containing iodonium salt. The perfluoropolyether segments are selected from repeating unit structures of perfluoromethyl ether, perfluoroethyl ether, or perfluorobutyl ether, and do not contain perfluorooctyl or longer chain structures, nor perfluorooctanoic acid or perfluorooctane sulfonic acid. The number average molecular weight of the perfluoropolyether segments is 400-600 g / mol.

2. The high wear-resistant and stain-resistant optical coating composition based on photocuring technology according to claim 1, characterized in that: The alicyclic epoxy resin is 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexylcarboxylate; the oxetane reactive diluent is selected from at least one of 3-ethyl-3-hydroxymethyloxetane and bis(3-ethyl-3-oxetane)methyl ether; the acrylate monomer is selected from at least one of dipentaerythritol hexaacrylate and tripropylene glycol diacrylate.

3. The high wear-resistant and stain-resistant optical coating composition based on photocuring technology according to claim 1, characterized in that: The photosensitizer is selected from at least one of 2-isopropylthioxanthone and 9,10-dibutoxyanthracene, and the characteristic absorption wavelength range of the photosensitizer covers 390-410 nm; the hindered amine proton scavenger is selected from at least one of bis(1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate and methyl-1,2,2,6,6-pentamethyl-4-piperidinyl sebacate.

4. The high wear-resistant and stain-resistant optical coating composition based on photocuring technology according to claim 1, characterized in that: The organic mixed solvent is composed of propylene glycol methyl ether acetate and butanone in a mass ratio of 1:0.8-1.

2.

5. A preparation process for a high wear-resistant and stain-resistant optical coating based on photocuring technology, characterized in that, The high wear-resistant and stain-resistant optical coating composition based on photocuring technology as described in any one of claims 1-4 comprises the following steps: S1. Substrate pretreatment: Select optical grade substrates, clean and dry their surfaces, and then perform corona treatment or plasma treatment to make the surface tension of the substrate reach more than 42dyn / cm. S2, Coating liquid film: The coating composition is mixed evenly to obtain a coating liquid, which is then coated onto the substrate surface by spin coating or wire rod coating, and the wet film thickness is controlled within the range of 8-15μm; S3. Thermally induced self-assembly: The coated substrate is placed on a heating platform or oven for infrared heating treatment at a temperature of 60-80℃ for 60-120 seconds, which causes the environmentally friendly short-chain perfluoropolyether modified diaryliodonium to migrate and accumulate at the gas-liquid interface and evaporate the solvent. S4. Photosensitive curing: The heat-treated coating is irradiated with a UV-LED single-wavelength light source. The center wavelength of the light source is 395nm±5nm or 405nm±5nm. During the irradiation process, surface cationic polymerization and internal free radical polymerization are initiated. S5. Post-curing treatment: The coated material after light exposure is placed in an oven for heat treatment at a temperature of 60-80℃ for 10-30 minutes. After cooling, a gradient-cured coating is obtained.

6. The preparation process of a high wear-resistant and stain-resistant optical coating based on photocuring technology according to claim 5, characterized in that: In step S1, the cleaning and drying process includes ultrasonic cleaning with anhydrous ethanol for 5-10 minutes, followed by drying with nitrogen gas.

7. The preparation process of a high wear-resistant and stain-resistant optical coating based on photocuring technology according to claim 5, characterized in that: In step S2, the spin coating is performed in a segmented spin coating manner. First, the spin coating is performed at a low speed of 500 rpm for 3-5 seconds, and then at a high speed of 1500-3000 rpm for 20-30 seconds.

8. The preparation process of a high wear-resistant and stain-resistant optical coating based on photocuring technology according to claim 5, characterized in that: In step S4, the illuminance of the UV-LED single-wavelength light source on the coating surface is 300-800 mW / cm². 2 The total exposure energy is 800-2000 mJ / cm. 2 The solidified environment is an air atmosphere.

9. The preparation process of a high wear-resistant and stain-resistant optical coating based on photocuring technology according to claim 5, characterized in that: In step S1, the power of the corona treatment or plasma treatment is 300-500W, and the treatment time is 10-30 seconds.

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