Improved water-repellent coated glass and manufacturing method thereof

Abstract

The present invention relates to a method for manufacturing coated glass having superhydrophobicity of 152° or higher through a composite coating composition using fluoroalkylsilane and nanoparticles and sequential plasma-UV treatment. Specifically, a glass substrate having fine folds of an average depth of 50-300 nm formed on its surface is surface-activated with a silane-based pretreatment solution containing 3-aminopropyltriethoxysilane to introduce amino group terminals, and a coating composition comprising a fluoroalkylsilane having a perfluoroalkyl group having 8-10 carbon atoms and silica nanoparticles with an average particle size of 20-40 nm is applied by spin coating to form a primary coating layer with a thickness of 200-400 nm. Subsequently, argon plasma treatment followed by 254 nm UV irradiation is sequentially performed to form a nanoprotrusion structure with a height of 80-150 nm on the surface and to improve the water contact angle to 152° or higher according to the KS M ISO 15989 method, and then stepwise at 60-85°C in a nitrogen atmosphere The final water-repellent coated glass is completed by heating and drying / curing. According to the present invention, unlike conventional simple chemical coating methods, excellent superhydrophobicity and durability can be simultaneously secured by applying surface modification technology through nanostructure control, and economical and practical mass production is possible using commercially available materials and general equipment.

Description

Technology Field

[0001] The following examples relate to coated glass having improved water repellency and a method for manufacturing the same. Background Technology

[0002] Glass is widely used in various fields, including architectural exterior materials, automotive windshields, electronic device displays, and solar panels. However, typical glass surfaces are hydrophilic, causing water droplets to adhere easily. This results in various problems, such as the accumulation of contaminants, difficulty maintaining visibility, and the hassle of cleaning and maintenance.

[0003] To solve these problems, technologies for applying water-repellent coatings to glass surfaces have been developed. Conventional water-repellent coating technologies have mainly used chemical treatment methods using fluorine-based compounds or physical coating methods using silicone-based polymers. However, these existing technologies failed to secure sufficient water repellency, with a water-repellent contact angle remaining around 130 degrees, and suffered from performance degradation during long-term use due to insufficient durability of the coating layer.

[0004] In particular, some existing glass coating technologies utilize a method of forming a coating layer on the microfolds of the glass surface by using the chemical bonding of hydroxyl groups and silane compounds. While this approach contributes to improving basic water repellency, it has limitations in that it is difficult to secure consistent and excellent water repellency performance due to limited control of the surface microstructure.

[0005] In addition, conventional coating technologies using chemical vapor deposition or physical vapor deposition methods have limitations in achieving reproducible water-repellent performance because it is difficult to precisely control the thickness of the coating layer or surface roughness. In particular, forming a uniform coating that corresponds to the unique microfold structure of the glass surface while simultaneously controlling the surface structure at the nano level has been recognized as a technically difficult challenge.

[0006] Recently, biomimetic technology mimicking the surface structure of a lotus leaf has garnered attention, and it is known to be capable of achieving superhydrophobicity of over 150 degrees through micro and nano-sized hierarchical structures. However, the development of practical and economical manufacturing methods to precisely implement such structures on glass surfaces remains a technical challenge. Prior art literature

[0007] Korean Registered Patent 10-1327901 Korean Published Patent 10-2007-0013712 Korean Published Patent 10-2015-0046683 Korean Published Patent 10-2018-0125642 The problem to be solved

[0008] The first problem that the present invention aims to solve is to overcome the limitations of water-repellent performance of existing water-repellent coating technologies and to provide coated glass having excellent superhydrophobicity of 152 degrees or higher.

[0009] The second task is to provide a manufacturing method that can form a uniform and stable coating layer on the microfolds of the glass surface, while simultaneously implementing a regular nanostructure on the surface to maximize water-repellent performance.

[0010] The third task is to provide a technology that can improve the durability and chemical resistance of a coating layer while maintaining optical transparency by using a composite coating composition containing fluoroalkylsilane and nanoparticles.

[0011] The fourth task is to provide a method for precisely controlling the nanostructure through a surface modification process that sequentially applies plasma treatment and UV irradiation, thereby ensuring reproducible and consistent water-repellent performance.

[0012] The fifth task is to establish a practical manufacturing process capable of economical and mass production using commercially available materials and general equipment. means of solving the problem

[0013] The present invention relates to a method for manufacturing coated glass having improved water repellency, comprising: a) a step of introducing amino group terminals by surface activation treatment with a silane-based pretreatment solution containing 3-aminopropyltriethoxysilane on a glass substrate having fine folds formed on the surface with an average depth of 50-300 nm and a width of 100-800 nm; b) a step of forming a primary coating layer with a thickness of 200-400 nm by spin coating a coating composition comprising a fluoroalkylsilane having a perfluoroalkyl group having 8-10 carbon atoms and silica nanoparticles with an average particle size of 20-40 nm on the surface-activated glass substrate; c) a step of sequentially performing argon plasma treatment followed by 254 nm ultraviolet irradiation on the primary coating layer to form a nanoprotrusion structure with a height of 80-150 nm on the surface and improving the water contact angle to 152 degrees or more according to the KS M ISO 15989 method; and d) a step of drying and curing the coating layer having the nanostructure formed thereon by stepwise heating to 60-85°C in a nitrogen atmosphere and cooling to complete a water-repellent coated glass satisfying a water contact angle of 152°C or more and a surface roughness Ra of 100-250 nm; characterized by including the above steps.

[0014] At this time, the above step a) comprises: a1) a step of pre-treating the glass substrate with an aqueous sodium hydroxide solution having a pH of 12.0-12.5 for 5-10 minutes to remove surface contaminants and alkali ions; a2) a step of preparing a total of 1,000 parts by weight of a silane-based pre-treatment solution composed of 15 parts by weight of 3-aminopropyltriethoxysilane, 5 parts by weight of polyethylene glycol monomethyl ether, and 980 parts by weight of deionized water, by adjusting the pH to 9.0-9.3; a3) a step of immersing the glass substrate in the pre-treatment solution at 45-55°C for 15-25 minutes while applying ultrasound at a frequency of 42 kHz with an output of 300 W to allow silane molecules to penetrate into the interior of the microfolds; a4) a step of forming an aminosilane monolayer by washing the immersed glass substrate 5 times with deionized water and then drying the surface with nitrogen gas having a purity of 99.5% or higher.

[0015] At this time, step b) comprises: b1) a step of preparing a fluoroalkylsilane mixture by mixing 25 parts by weight of 1H,1H,2H,2H-perfluorooctyltriethoxysilane and 15 parts by weight of 1H,1H,2H,2H-perfluorodecyltriethoxysilane; b2) a step of preparing a nanoparticle dispersion by ultrasonically dispersing 8 parts by weight of hydrophobic silica nanoparticles having an average particle size of 30 nm and a specific surface area of ​​200-300 m² / g in a mixed solvent of 400 parts by weight of isopropanol and 100 parts by weight of ethanol for 30 minutes; b3) a step of mixing 40 parts by weight of the fluoroalkylsilane mixture, 508 parts by weight of the nanoparticle dispersion, and 2 parts by weight of acetic acid as an acid catalyst to form a coating composition of a total of 550 parts by weight, and stirring at 600 rpm for 45 minutes; b4) a step of spin-coating the coating composition onto the surface-activated glass substrate at 1500-2500 rpm for 40-50 seconds to form a primary coating layer with a thickness of 200-400 nm and pre-drying at room temperature for 30 minutes; characterized by including the above steps.

[0016] At this time, step c) comprises: c1) a step of treating the surface of the primary coating layer for 60 seconds by generating a mixed plasma of 85 vol% argon gas and 15 vol% oxygen gas under conditions of 13.56 MHz frequency, 200 W output, and pressure 0.3-0.5 Torr; c2) a step of activating the Si-O bonds of the fluoroalkylsilane by irradiating the plasma-treated coating layer with ultraviolet light having a wavelength of 254 nm and an intensity of 20 mW / cm² for 10 minutes while controlling the temperature to 30℃; c3) a step of forming a conical nanoprotrusion structure with a height of 80-150 nm and a diameter of 50-120 nm on the surface by additionally treating with 99.9% pure argon plasma under conditions of 100 W output and pressure 0.2 Torr for 20 seconds after the ultraviolet irradiation; c4) After the formation of the nanoprotrusion structure is completed, drop 2 μL of pure water according to the KS M ISO 15989 method to measure the contact angle and confirm that 152 degrees or more is achieved, and if it is not achieved, perform the above c3) step for an additional 5 seconds; characterized by including the above step.

[0017] At this time, the above step d) comprises: d1) a step of naturally drying the coating layer with the formed nanostructure at room temperature for 90 minutes in a nitrogen gas atmosphere with a purity of 99.5% or higher while controlling the relative humidity to 40% or less; d2) a step of removing residual solvent and moisture by heating the naturally dried coating layer to 60°C at a heating rate of 2°C / min and maintaining it for 45 minutes; d3) a step of forming complete cross-linking of the fluoroalkylsilane by further heating the coating layer to 85°C at a heating rate of 1°C / min and finally curing it for 20 minutes; d4) a step of slowly cooling the cured coated glass to room temperature at a cooling rate of 3°C / min and then verifying whether it satisfies all criteria according to the KS M ISO 15989 method, such as a water contact angle of 152° or higher, an Ra value of 100-250nm measured by a surface roughness meter, and a coating layer thickness of 200-400nm measured by an ellipsometer; It is characterized by including Effects of the invention

[0018] The method for manufacturing an improved water-repellent coated glass according to the present invention achieves the following significant effects.

[0019] First, by uniformly introducing amino group terminals into the microfolds of the glass surface through surface activation treatment using 3-aminopropyltriethoxysilane, the chemical bonding strength with the subsequent coating layer can be significantly improved, thereby ensuring coating stability.

[0020] Second, by using a composite coating composition comprising a fluoroalkylsilane having a perfluoroalkyl group having 8-10 carbon atoms and silica nanoparticles with an average particle size of 20-40 nm, excellent water repellency and durability compared to existing technology can be achieved simultaneously.

[0021] Third, through a surface modification process that sequentially performs argon plasma treatment followed by 254 nm ultraviolet irradiation, a regular nanostructure with a height of 80-150 nm can be precisely formed, thereby stably achieving superhydrophobicity of 152 degrees or higher.

[0022] Fourth, the chemical resistance and durability of the coating layer can be significantly improved by forming complete cross-linking of the fluoroalkylsilane through a stepwise heating drying process in a nitrogen atmosphere.

[0023] Fifth, by applying a quality management system according to the KS M ISO 15989 standard method, consistent and reproducible water-repellent performance can be guaranteed, which provides significant technical value for industrial applications.

[0024] Sixth, by establishing a practical manufacturing process capable of economical and mass production using commercially available materials and standard coating equipment, immediate application in industrial settings is possible.

[0025] Seventh, unlike the conventional simple coating method using hydroxyl groups and dimethyldichlorosilane, by introducing surface modification technology through nanostructure control, water repellency performance can be significantly improved from the existing level of 130 degrees to over 152 degrees. Specific details for implementing the invention

[0026] Hereinafter, embodiments are described in detail with reference to the attached drawings. However, various modifications may be made to the embodiments, and thus the scope of the patent application is not limited or restricted by these embodiments. It should be understood that all modifications, equivalents, and substitutions to the embodiments are included within the scope of the rights.

[0027] Specific structural or functional descriptions of the embodiments are disclosed for illustrative purposes only and may be modified and implemented in various forms. Accordingly, the embodiments are not limited to the specific disclosed forms, and the scope of this specification includes modifications, equivalents, or substitutions that fall within the technical concept.

[0028] Terms such as "first" or "second" may be used to describe various components, but these terms should be interpreted solely for the purpose of distinguishing one component from another. For example, the first component may be named the second component, and similarly, the second component may be named the first component.

[0029] When it is stated that a component is "connected" to another component, it should be understood that it may be directly connected to or joined to that other component, or that there may be other components in between.

[0030] The terms used in the embodiments are for illustrative purposes only and should not be interpreted as intended to be limiting. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this specification, terms such as "comprising" or "having" are intended to indicate the existence of the features, numbers, steps, actions, components, parts, or combinations thereof described in the specification, and should be understood as not precluding the existence or addition of one or more other features, numbers, steps, actions, components, parts, or combinations thereof.

[0031] Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as generally understood by those skilled in the art to which the embodiments pertain. Terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the relevant technology, and should not be interpreted in an ideal or overly formal sense unless explicitly defined in this application.

[0032] The advantages and features of the present invention and the methods for achieving them will become clear by referring to the embodiments described below in detail together with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below but may be implemented in various different forms. These embodiments are provided merely to ensure that the disclosure of the present invention is complete and to fully inform those skilled in the art of the scope of the invention, and the present invention is defined only by the scope of the claims.

[0033] In the embodiments of the present invention, unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as generally understood by those skilled in the art to which the present invention pertains. Terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the relevant technology, and should not be interpreted in an ideal or overly formal sense unless explicitly defined in the embodiments of the present invention.

[0034] The shapes, sizes, ratios, angles, numbers, etc. disclosed in the drawings for explaining embodiments of the present invention are exemplary, and therefore the present invention is not limited to the depicted details. Furthermore, in describing the present invention, if it is determined that a detailed description of related known technology may unnecessarily obscure the essence of the present invention, such detailed description is omitted. Where terms such as "includes," "has," or "is made up" are used in this specification, other parts may be added unless "only" is used. Where a component is expressed in the singular, it includes cases where it includes the plural unless specifically stated otherwise.

[0035] In interpreting the components, they are interpreted to include a margin of error even in the absence of a separate explicit statement.

[0036] The size and thickness of each component shown in the drawings are illustrated for convenience of explanation, and the present invention is not necessarily limited to the size and thickness of the illustrated components.

[0037] The features of each of the various embodiments of the present invention may be combined or combined with one another, either partially or wholly, and as will be fully understood by those skilled in the art, various technical interlocking and operation are possible, and each embodiment may be implemented independently of one another or together in an interlocking relationship.

[0038] The present invention relates to a method for manufacturing coated glass having improved water repellency, comprising: a) a step of introducing amino group terminals by surface activation treatment with a silane-based pretreatment solution containing 3-aminopropyltriethoxysilane on a glass substrate having fine folds formed on the surface with an average depth of 50-300 nm and a width of 100-800 nm; b) a step of forming a primary coating layer with a thickness of 200-400 nm by spin coating a coating composition comprising a fluoroalkylsilane having a perfluoroalkyl group having 8-10 carbon atoms and silica nanoparticles with an average particle size of 20-40 nm on the surface-activated glass substrate; c) a step of sequentially performing argon plasma treatment followed by 254 nm ultraviolet irradiation on the primary coating layer to form a nanoprotrusion structure with a height of 80-150 nm on the surface and improving the water contact angle to 152 degrees or more according to the KS M ISO 15989 method; and d) a step of drying and curing the coating layer having the nanostructure formed thereon by stepwise heating to 60-85°C in a nitrogen atmosphere and cooling to complete a water-repellent coated glass satisfying a water contact angle of 152°C or more and a surface roughness Ra of 100-250 nm; characterized by including the above steps.

[0039] At this time, the above step a) comprises: a1) a step of pre-treating the glass substrate with an aqueous sodium hydroxide solution having a pH of 12.0-12.5 for 5-10 minutes to remove surface contaminants and alkali ions; a2) a step of preparing a total of 1,000 parts by weight of a silane-based pre-treatment solution composed of 15 parts by weight of 3-aminopropyltriethoxysilane, 5 parts by weight of polyethylene glycol monomethyl ether, and 980 parts by weight of deionized water, by adjusting the pH to 9.0-9.3; a3) a step of immersing the glass substrate in the pre-treatment solution at 45-55°C for 15-25 minutes while applying ultrasound at a frequency of 42 kHz with an output of 300 W to allow silane molecules to penetrate into the interior of the microfolds; a4) a step of forming an aminosilane monolayer by washing the immersed glass substrate 5 times with deionized water and then drying the surface with nitrogen gas having a purity of 99.5% or higher.

[0040] At this time, step b) comprises: b1) a step of preparing a fluoroalkylsilane mixture by mixing 25 parts by weight of 1H,1H,2H,2H-perfluorooctyltriethoxysilane and 15 parts by weight of 1H,1H,2H,2H-perfluorodecyltriethoxysilane; b2) a step of preparing a nanoparticle dispersion by ultrasonically dispersing 8 parts by weight of hydrophobic silica nanoparticles having an average particle size of 30 nm and a specific surface area of ​​200-300 m² / g in a mixed solvent of 400 parts by weight of isopropanol and 100 parts by weight of ethanol for 30 minutes; b3) a step of mixing 40 parts by weight of the fluoroalkylsilane mixture, 508 parts by weight of the nanoparticle dispersion, and 2 parts by weight of acetic acid as an acid catalyst to form a coating composition of a total of 550 parts by weight, and stirring at 600 rpm for 45 minutes; b4) a step of spin-coating the coating composition onto the surface-activated glass substrate at 1500-2500 rpm for 40-50 seconds to form a primary coating layer with a thickness of 200-400 nm and pre-drying at room temperature for 30 minutes; characterized by including the above steps.

[0041] At this time, step c) comprises: c1) a step of treating the surface of the primary coating layer for 60 seconds by generating a mixed plasma of 85 vol% argon gas and 15 vol% oxygen gas under conditions of 13.56 MHz frequency, 200 W output, and pressure 0.3-0.5 Torr; c2) a step of activating the Si-O bonds of the fluoroalkylsilane by irradiating the plasma-treated coating layer with ultraviolet light having a wavelength of 254 nm and an intensity of 20 mW / cm² for 10 minutes while controlling the temperature to 30℃; c3) a step of forming a conical nanoprotrusion structure with a height of 80-150 nm and a diameter of 50-120 nm on the surface by additionally treating with 99.9% pure argon plasma under conditions of 100 W output and pressure 0.2 Torr for 20 seconds after the ultraviolet irradiation; c4) After the formation of the nanoprotrusion structure is completed, drop 2 μL of pure water according to the KS M ISO 15989 method to measure the contact angle and confirm that 152 degrees or more is achieved, and if it is not achieved, perform the above c3) step for an additional 5 seconds; characterized by including the above step.

[0042] At this time, the above step d) comprises: d1) a step of naturally drying the coating layer with the formed nanostructure at room temperature for 90 minutes in a nitrogen gas atmosphere with a purity of 99.5% or higher while controlling the relative humidity to 40% or less; d2) a step of removing residual solvent and moisture by heating the naturally dried coating layer to 60°C at a heating rate of 2°C / min and maintaining it for 45 minutes; d3) a step of forming complete cross-linking of the fluoroalkylsilane by further heating the coating layer to 85°C at a heating rate of 1°C / min and finally curing it for 20 minutes; d4) a step of slowly cooling the cured coated glass to room temperature at a cooling rate of 3°C / min and then verifying whether it satisfies all criteria according to the KS M ISO 15989 method, such as a water contact angle of 152° or higher, an Ra value of 100-250nm measured by a surface roughness meter, and a coating layer thickness of 200-400nm measured by an ellipsometer; It is characterized by including

[0043] Reasons for Material Selection and Technical Basis

[0044] Rationale for Selecting 3-Aminopropyltriethoxysilane (APTES)

[0045] The reason 3-aminopropyltriethoxysilane was selected as the surface activation agent in this invention is due to the following technical characteristics. First, APTES possesses both an ethoxy group (-OEt) and an amino group (-NH2) within its molecular structure; the ethoxy group can form strong siloxane bonds (Si-O-Si) through hydrolysis and condensation reactions with the silanol group (Si-OH) on the glass surface, while the amino group provides a chemical bonding point with the subsequent fluoroalkylsilane. Second, the propyl group (-C3H6-) of APTES has an appropriate carbon chain length, providing a balance of flexibility and stability, which enables high penetration into the fine folds of the glass surface and the formation of a uniform coating. Third, the basic nature of the amino group promotes the hydrolysis of the fluoroalkylsilane used in the subsequent process, thereby strengthening the chemical bonding force between the coating layers.

[0046] Basis for Selection of Perfluoroalkylsilane Compounds

[0047] In the present invention, the reason for using a mixture of 1H,1H,2H,2H-perfluorooctyltriethoxysilane and 1H,1H,2H,2H-perfluorodecyltriethoxysilane is to optimize water repellency and coating stability. First, perfluoroalkyl groups exhibit extremely low surface energy due to the strong electronegativity difference of carbon-fluorine bonds, which minimizes interaction with water molecules and provides excellent water repellency. Second, the mixed use of octyl groups (C8) and decyl groups (C10) creates a complementary effect due to different chain lengths; the short chains provide durability through high crosslinking density, while the long chains ensure excellent water repellency. Third, the triethoxysilane terminal groups maximize the adhesion of the coating layer through multi-point bonding with the substrate, and at the same time form a dense network structure through crosslinking reactions between silane molecules. Fourth, the 1H,1H,2H,2H- structure is designed to maintain water-repellent properties while ensuring chemical stability by placing a methylene group between the silane group and the perfluoroalkyl group.

[0048] Basis for selecting silica nanoparticles

[0049] The technical rationale for selecting hydrophobic silica nanoparticles with an average particle size of 30 nm and a specific surface area of ​​200-300 m² / g lies in controlling surface roughness and improving coating performance. First, the particle size of 30 nm is significantly smaller than the wavelength of visible light (380-780 nm), which minimizes Rayleigh scattering and maintains the optical transparency of the coating layer. Second, the addition of nanoparticles creates fine roughness on the coating surface, enhancing the air trapping effect. This forms a complex interface according to the Cassie-Baxter model, thereby improving water repellency. Third, the high specific surface area of ​​200-300 m² / g maximizes the contact area with fluoroalkylsilanes, enabling strong physical adsorption and chemical bonding. Fourth, the hydrophobic surface-treated silica improves dispersion stability in organic solvents and increases compatibility with fluoroalkylsilanes, promoting the formation of a uniform coating film. Fifth, the inorganic properties of silica enhance the heat and chemical resistance of the coating layer, ensuring durability in long-term usage environments.

[0050] Basis for selecting polyethylene glycol monomethyl ether

[0051] The reason polyethylene glycol monomethyl ether was selected as a surfactant is to control the hydrolysis of silane compounds and improve coating quality. First, the ether bonds and hydroxyl groups of this compound form hydrogen bonds with water molecules, appropriately controlling the hydrolysis rate of silanes and preventing gelation caused by rapid reactions. Second, its amphiphilic structure reduces interfacial tension between hydrophobic nanoparticles and hydrophilic solvents, promoting uniform dispersion and preventing precipitation. Third, due to its relatively low molecular weight, it is easily removed from the final coating layer without adversely affecting coating performance, and it completely volatilizes during the drying process, leaving no residue.

[0052] Rationale for selecting the acetic acid catalyst

[0053] The technical basis for using acetic acid as an acid catalyst lies in the precise control of the hydrolysis and condensation reactions of silanes. First, the weak acidity of acetic acid (pKa=4.76) promotes the hydrolysis of ethoxy groups in silanes at an appropriate rate, thereby extending the pot life of the coating solution and improving workability. Second, by providing milder reaction conditions compared to strong acids, it prevents substrate damage and suppresses the aggregation of nanoparticles. Third, its high volatility ensures complete removal during the drying process, guaranteeing the chemical purity of the final coating layer. Fourth, the chelation effect of carboxyl groups removes metal ion impurities, thereby improving the optical transparency and chemical stability of the coating layer.

[0054] Rationale for Selecting Isopropanol-Ethanol Mixed Solvent

[0055] The reason for selecting a 4:1 mixing ratio of 400 parts by weight of isopropanol to 100 parts by weight of ethanol is to optimize solubility parameters and evaporation rates. First, the low surface tension (23.0 mN / m) of isopropanol provides excellent wettability to the glass substrate, thereby promoting the formation of a uniform coating film. Second, the addition of ethanol improves the solubility of the silane compound and supplies the moisture necessary for hydrolysis. Third, the appropriate difference in evaporation rates between the two solvents ensures a leveling time, thereby minimizing surface defects and enabling the formation of a coating layer of uniform thickness. Fourth, the Hansen solubility parameter of the mixed solvent provides appropriate solubility for both the fluoroalkylsilane and the nanoparticles, maintaining a stable dispersion system.

[0056] Rationale for selecting argon gas

[0057] The technical rationale for selecting argon as the gas for plasma treatment lies in its inertness and plasma generation efficiency. First, the chemical inertness of argon enables pure physical surface modification while preventing unwanted chemical reactions with the coating layer. Second, the appropriate mass of argon ions (39.95 amu) is optimized for nanostructure formation via surface sputtering, allowing for the creation of precise surface textures without excessive damage. Third, the low ionization energy of argon (15.76 eV) enables stable plasma generation even at relatively low power, thereby improving the economic efficiency and reproducibility of the process. Fourth, the addition of 15 volume% oxygen enhances the effectiveness of subsequent treatment through the removal of organic contaminants from the surface and surface activation.

[0058] Basis for selecting nitrogen gas

[0059] The reason for using a nitrogen atmosphere in the drying and curing processes is to prevent oxidation and protect coating quality. First, the inert nature of nitrogen prevents the thermal oxidation of fluoroalkylsilanes during high-temperature curing, thereby maintaining the chemical stability of the coating layer. Second, by removing oxygen, radical reactions are suppressed, preventing unwanted side reactions and preserving the optical transparency of the coating layer. Third, a dry nitrogen atmosphere blocks atmospheric moisture, preventing further hydrolysis of silanes and providing consistent curing conditions. Fourth, the use of high-purity nitrogen of 99.5% or higher prevents coating defects caused by trace impurities, ensuring the quality consistency of the final product.

[0060] Critical significance of component range

[0061] Microfold dimensional range of glass substrates

[0062] Limiting the microfolds on the surface of a glass substrate to an average depth of 50-300 nm and a width of 100-800 nm is a critical factor directly linked to the success of the subsequent coating process. If the depth is less than 50 nm, the surface roughness is insufficient, which limits the anchoring effect of the coating composition and significantly reduces the adhesion of the coating layer, particularly during long-term use, and there is a high risk of delamination. On the other hand, if the depth exceeds 300 nm, it is difficult for the coating composition to fully penetrate to the deep parts of the folds, resulting in the formation of an incomplete coating, which leads to non-uniformity in water-repellent performance and reduced durability. Regarding the width, if it is less than 100 nm, excessive penetration of the coating liquid due to capillary action occurs, impairing surface flatness, while if it exceeds 800 nm, optical transparency is damaged and scattering phenomena increase due to large irregularities.

[0063] Critical range of component ratios in silane-based pretreatment solutions

[0064] A concentration of 15 parts by weight of 3-aminopropyltriethoxysilane is the optimal value considering both surface modification effects and economic feasibility. Below 10 parts by weight, the reaction with silanol groups on the glass surface is insufficient, resulting in a low density of amino group terminal introduction, which leads to a decrease in binding strength with subsequent fluoroalkylsilanes. If it exceeds 20 parts by weight, the excessive silane concentration causes active self-condensation reactions within the solution, leading to gelation; this impairs the storage stability of the coating solution and hinders the formation of a uniform coating. 5 parts by weight of polyethylene glycol monomethyl ether is a critical concentration for controlling the hydrolysis rate of the silane and ensuring the dispersion stability of nanoparticles; if this range is exceeded, the surfactant effect becomes insufficient or excessive, adversely affecting the coating quality.

[0065] Critical Significance of Fluoralkylsilane Mixing Ratio

[0066] The mixing ratio of 25 parts by weight of 1H,1H,2H,2H-perfluorooctyltriethoxysilane and 15 parts by weight of 1H,1H,2H,2H-perfluorodecyltriethoxysilane is precisely designed to achieve an optimal balance of water repellency and durability. If the proportion of octylsilane is reduced to less than 20 parts by weight, the high crosslinking density effect due to the short chain is insufficient, resulting in a decrease in the mechanical strength and wear resistance of the coating layer. If it exceeds 30 parts by weight, water repellency is limited due to the relatively short fluoroalkyl chain, making it difficult to achieve the target contact angle of 152 degrees. In the case of decylsilane, if it is less than 10 parts by weight, the water repellency effect of the long chain is insufficient, making it difficult to achieve superhydrophobicity, and if it exceeds 20 parts by weight, intermolecular entanglement occurs due to the excessively long chain, impairing the uniformity of the coating film.

[0067] Critical range of nanoparticle size and concentration

[0068] An average particle size of 30 nm for silica nanoparticles is a threshold that provides the optimal combination of optical transparency and surface roughness effects. Below 20 nm, the particles are excessively small, resulting in a negligible surface roughness formation effect, which cannot sufficiently exhibit the air layer trapping effect according to the Casley-Baxter model. Exceeding 50 nm increases scattering interactions with visible light, leading to reduced transparency and increased turbidity. A concentration of 8 parts by weight serves as a balance point between improved water repellency and the maintenance of coating film transparency; below 5 parts by weight, the surface roughness effect is insufficient, while exceeding 12 parts by weight results in coating defects and deterioration of optical properties due to nanoparticle aggregation.

[0069] Critical significance of execution conditions at each process stage

[0070] Criticality of surface activation treatment conditions

[0071] Pretreatment using an aqueous sodium hydroxide solution with a pH of 12.0–12.5 is a key process for maximizing the silanol group density on the glass surface. Below pH 11.5, the alkaline etching effect is insufficient, limiting the formation of surface active sites; conversely, above pH 13.0, excessive etching damages the glass surface, degrading optical properties. Ultrasonic treatment at a frequency of 42 kHz promotes the penetration of silane molecules into microfolds through cavitation, while simultaneously creating a uniform reaction environment by removing bubbles. An output of 300 W represents the optimal condition for achieving effective mass transfer without excessive heat generation; below 200 W, the penetration effect is insufficient, while exceeding 400 W leads to premature condensation of silane due to overheating.

[0072] Conditions for Preparation and Application of Coating Composition

[0073] A stirring condition of 600 rpm for 45 minutes is a critical condition for uniform dispersion between fluoroalkylsilane and nanoparticles and the formation of a stable suspension. Below 500 rpm, mixing is insufficient, leading to component separation, while exceeding 800 rpm promotes nanoparticle aggregation due to excessive shear stress, thereby reducing dispersion stability. The stirring time of 45 minutes is the minimum required time to achieve uniform mixing at the molecular level; below 30 minutes, coating non-uniformity occurs due to incomplete mixing, and above 60 minutes, the self-condensation reaction of the silane proceeds, shortening the pot life. In spin coating, a rotation speed of 1500–2500 rpm is the optimal condition for forming a uniform coating film with a thickness of 200–400 nm, achieving both leveling and thickness control simultaneously through the balance of centrifugal force and viscous force.

[0074] Criticality of Plasma-Ultraviolet Sequential Processing

[0075] In argon plasma treatment, a frequency of 13.56 MHz is an industrial standard RF frequency that ensures stable plasma generation and a uniform ion density distribution. An output of 200 W and pressure conditions of 0.3-0.5 Torr are optimized parameters for nanostructure formation via surface sputtering; below 150 W, ion energy is insufficient, resulting in minimal structure formation, while above 250 W, excessive damage destroys the chemical bonds of the coating layer. A treatment time of 60 seconds serves as a balance point between surface modification and damage prevention, during which the rearrangement of surface atoms and the formation of microstructures are completed.

[0076] 254 nm ultraviolet irradiation is a specific wavelength for activating the Si-O bonds of fluoroalkylsilanes; since this energy level exactly matches the dissociation energy of siloxane bonds, selective bond activation is possible. Irradiation at an intensity of 20 mW / cm² for 10 minutes is a condition that simultaneously achieves chemical bond activation and prevents thermal damage; below 15 mW / cm², the activation effect is insufficient, and if it exceeds 30 mW / cm², molecular decomposition occurs due to excessive energy.

[0077] Critical Significance of the Stepwise Curing Process

[0078] Stepwise temperature curing in a nitrogen atmosphere is an essential process for the complete crosslinking reaction and stress relief of fluoroalkylsilanes. Controlling relative humidity to 40% or lower prevents additional hydrolysis reactions caused by atmospheric moisture, ensuring consistent curing conditions, which is essential for securing reproducible coating quality. Natural drying for 90 minutes prevents stress concentration within the coating film and achieves a uniform density distribution through the gradual evaporation of the solvent. A heating rate of 2°C / min is the optimal condition for inducing the stepwise condensation reaction of silanes while minimizing interfacial stress caused by differences in thermal expansion; heating faster than this leads to bubble formation and coating defects due to rapid solvent evaporation.

[0079] Intermediate curing at 60°C for 45 minutes is a critical step for removing residual solvent and completing the primary crosslinking reaction; this temperature is the optimal point for preventing excessive thermal stress while ensuring complete evaporation of the solvent. Final curing at 85°C for 20 minutes is a condition for achieving the complete polymerization reaction of the fluoroalkylsilane and maximum crosslinking density; at this temperature, the siloxane network is completed and optimal mechanical properties are exhibited.

[0080] Critical Significance of Achieving a Water Contact Angle of 152 Degrees or More

[0081] Achieving a water contact angle of 152 degrees or higher according to the KS M ISO 15989 method is not merely a numerical target but a physicochemical critical point for realizing superhydrophobicity. Unlike the contact angle of typical water-repellent surfaces, which ranges from 90 to 130 degrees, 152 degrees is the minimum critical value at which a composite interface in the Kasey-Baxter state is stably formed; at this level, a state is achieved where water droplets barely come into contact with the surface and float on a layer of air. This superhydrophobicity exhibits complex functions such as self-cleaning, antifouling, and anti-freezing effects, and below 151 degrees, these effects decrease rapidly, significantly reducing their practical value.

[0082] Criticality of surface roughness Ra in the range of 100-250 nm

[0083] A surface roughness Ra value of 100–250 nm represents the optimal balance between the water-repellent effect and optical transparency provided by the nanostructure. Below 100 nm, the surface roughness is insufficient, limiting the air layer trapping effect and making it difficult to maintain a perfect spherical shape of water droplets. Above 250 nm, scattering interactions with visible light increase, degrading transparency, while excessive roughness increases vulnerability to mechanical wear. Within this range, the nanoprotrusion structure forms an optimal structure that effectively blocks the penetration of water molecules while maintaining visual transparency.

[0084] Critical range of coating layers with a thickness of 200-400 nm

[0085] A coating layer thickness of 200–400 nm is the optimal range considering both water-repellent performance and optical interference effects. Below 200 nm, the coating layer is excessively thin, making it difficult to completely cover fine folds and resulting in reduced durability due to pinhole formation. Above 400 nm, internal stress increases due to the thick coating layer, raising the risk of delamination, and color changes caused by optical interference are observed, degrading optical properties. Within this thickness range, the molecular orientation of fluoroalkylsilanes and the dispersion of nanoparticles are optimized, allowing for the simultaneous achievement of excellent water repellency and transparency.

[0086] Examples and Comparative Examples

[0087] Specific details for implementing the invention

[0088] Example 1

[0089] A soda-lime glass substrate having fine folds formed on its surface with an average depth of 180 nm and a width of 350 nm was pretreated with an aqueous sodium hydroxide solution with a pH of 12.2 for 7 minutes, and then washed with deionized water. A silane-based pretreatment solution consisting of 15 parts by weight of 3-aminopropyltriethoxysilane, 5 parts by weight of polyethylene glycol monomethyl ether, and 980 parts by weight of deionized water was prepared by adjusting the pH to 9.1 for a total of 1,000 parts by weight. The glass substrate was immersed in the pretreatment solution at 50°C for 20 minutes while ultrasonic waves with a frequency of 42 kHz were applied at an output of 300 W, after which it was washed 5 times with deionized water and dried with nitrogen gas.

[0090] A fluoroalkylsilane mixture was prepared by mixing 25 parts by weight of 1H,1H,2H,2H-perfluorooctyltriethoxysilane and 15 parts by weight of 1H,1H,2H,2H-perfluorodecyltriethoxysilane. A nanoparticle dispersion was prepared by ultrasonically dispersing 8 parts by weight of hydrophobic silica nanoparticles with an average particle size of 30 nm and a specific surface area of ​​250 m² / g in a mixed solvent of 400 parts by weight of isopropanol and 100 parts by weight of ethanol for 30 minutes. A coating composition of a total of 550 parts by weight was prepared by mixing 40 parts by weight of the fluoroalkylsilane mixture, 508 parts by weight of the nanoparticle dispersion, and 2 parts by weight of acetic acid, and stirred at 600 rpm for 45 minutes.

[0091] The coating composition was spin-coated onto a surface-activated glass substrate at 2000 rpm for 45 seconds to form a primary coating layer with a thickness of 300 nm, and pre-dried at room temperature for 30 minutes. A mixed plasma of 85 vol% argon gas and 15 vol% oxygen gas was generated under conditions of 13.56 MHz frequency, 200 W output, and 0.4 Torr pressure, and the surface of the primary coating layer was treated for 60 seconds. Subsequently, ultraviolet light with a wavelength of 254 nm and an intensity of 20 mW / cm² was irradiated at 30°C for 10 minutes. Afterward, the surface was further treated with an argon plasma under conditions of 100 W output and 0.2 Torr pressure for 20 seconds to form a nanoprotrusion structure.

[0092] The nanostructured coating layer was air-dried at room temperature for 90 minutes in a nitrogen gas atmosphere while controlling the relative humidity to 35%, then heated to 60°C at a heating rate of 2°C / min and maintained for 45 minutes. Afterward, it was further heated to 85°C at a heating rate of 1°C / min and finally cured for 20 minutes, then slowly cooled to room temperature at a cooling rate of 3°C / min to complete the water-repellent coated glass.

[0093] Example 2

[0094] The procedure was carried out in the same manner as in Example 1, but a pretreatment solution composed of 20 parts by weight of 3-aminopropyltriethoxysilane, 3 parts by weight of polyethylene glycol monomethyl ether, and 977 parts by weight of deionized water was used. The fluoroalkylsilane mixture was composed of 30 parts by weight of 1H,1H,2H,2H-perfluorooctyltriethoxysilane and 10 parts by weight of 1H,1H,2H,2H-perfluorodecyltriethoxysilane, and 6 parts by weight of hydrophobically treated silica nanoparticles with an average particle size of 25 nm and a specific surface area of ​​280 m² / g were used. Spin coating was performed at 1800 rpm for 50 seconds to form a coating layer with a thickness of 250 nm.

[0095] Example 3

[0096] The procedure was carried out in the same manner as in Example 1, but a fluoroalkylsilane mixture was prepared using 20 parts by weight of 1H,1H,2H,2H-perfluorooctyltriethoxysilane and 20 parts by weight of 1H,1H,2H,2H-perfluorodecyltriethoxysilane. 10 parts by weight of silica nanoparticles with an average particle size of 35 nm and a specific surface area of ​​220 m² / g were used, and spin coating was performed at 2200 rpm for 40 seconds to form a coating layer with a thickness of 350 nm. Plasma treatment was performed at an output of 180 W.

[0097] Comparative Example 1

[0098] The procedure was carried out in the same manner as in Example 1, but a pretreatment solution composed of 8 parts by weight of 3-aminopropyltriethoxysilane, 2 parts by weight of polyethylene glycol monomethyl ether, and 990 parts by weight of deionized water was used. Only 35 parts by weight of 1H,1H,2H,2H-perfluorooctyltriethoxysilane was used as the fluoroalkylsilane, and silica nanoparticles were not added. Plasma treatment was not performed, and only UV irradiation was carried out for 15 minutes.

[0099] Comparative Example 2

[0100] The procedure was carried out in the same manner as in Example 1, but 30 parts by weight of 1H,1H,2H,2H-perfluorodecyltriethoxysilane was used alone. 15 parts by weight of silica nanoparticles with an average particle size of 60 nm were used, and no acetic acid was added to the coating composition. Plasma treatment was performed for 120 seconds at a high power of 300 W.

[0101] Comparative Example 3

[0102] The procedure was carried out in the same manner as in Example 1, but the surface activation treatment was omitted and the coating composition was applied directly. The fluoroalkylsilane mixture was composed of 15 parts by weight of 1H,1H,2H,2H-perfluorooctyltriethoxysilane and 25 parts by weight of 1H,1H,2H,2H-perfluorodecyltriethoxysilane, and only 3 parts by weight of silica nanoparticles with an average particle size of 15 nm were used. The curing temperature was limited to a maximum of 50°C.

[0103] Composition Comparison Table

[0104] division Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 APTES (parts by weight) 15 20 15 8 15 - PEG-MME (parts by weight) 5 3 5 2 5 5 Deionized water (parts by weight) 980 977 980 990 980 995 Octylsilane (parts by weight) 25 30 20 35 - 15 Decylsilane (parts by weight) 15 10 20 - 30 25 Silica particle size (nm) 30 25 35 - 60 15 Silica content (parts by weight) 8 6 10 - 15 3 Acetic acid (parts by weight) 2 2 2 2 - 2 Plasma output (W) 200 200 180 - 300 200 Final curing temperature (°C) 85 85 85 85 85 50

[0105] Technical analysis of examples and comparative examples

[0106] The 15 parts by weight of 3-aminopropyltriethoxysilane used in Example 1 is the optimal concentration capable of forming a high-density amino terminal layer through sufficient reaction with the silanol groups on the glass surface, which ensures a strong chemical bond with the subsequent fluoroalkylsilane. On the other hand, the 8 parts by weight of Comparative Example 1 has a significantly lower surface modification density, resulting in insufficient adhesion of the coating layer, which is a major cause of reduced long-term durability.

[0107] The mixed use of 1H,1H,2H,2H-perfluorooctyltriethoxysilane and 1H,1H,2H,2H-perfluorodecyltriethoxysilane applied in the examples exhibits complementary effects due to their different chain lengths. The relatively short chain of octylsilane provides mechanical strength through high crosslinking density, while the long chain of decylsilane ensures excellent water repellency. When only a single silane is used, as in Comparative Examples 1 and 2, these synergistic effects cannot be expected, and thus the overall coating performance is limited.

[0108] The silica nanoparticles used in the examples, with an average particle size in the range of 25-35 nm, are of an optimal size that can sufficiently exhibit surface roughness effects while minimizing visible light scattering. In particular, the 30 nm particles of Example 1 are of an ideal size that maintains optical transparency while maximizing the air layer trapping effect according to the Kasey-Baxter model. On the other hand, the 60 nm particles of Comparative Example 2 have reduced transparency due to increased light scattering caused by their excessive size, and the 15 nm particles of Comparative Example 3 do not contribute to the improvement of water repellency because the surface roughness effect is negligible.

[0109] The 200W plasma output applied in the examples represents a balance between forming nanostructures through surface sputtering and preventing excessive damage. Under these conditions, regular nanoprotrusion structures with a height of 80-150nm are formed, minimizing the contact area of ​​water droplets. The 300W high output of Comparative Example 2 destroys the chemical bonds of the coating layer due to excessive energy, thereby causing performance degradation; furthermore, if plasma treatment is omitted as in Comparative Example 1, the formation of surface nanostructures becomes impossible, making it difficult to achieve superhydrophobicity.

[0110] The addition of an acetic acid catalyst appropriately controls the hydrolysis rate of silane to improve the storage stability of the coating solution while inducing a uniform reaction. When the acid catalyst is omitted, as in Comparative Example 2, the non-uniform hydrolysis of silane impairs the uniformity of the coating film and causes localized performance variations.

[0111] The final curing temperature of 85°C applied in the examples is the minimum required temperature for the complete crosslinking reaction of fluoroalkylsilane, at which the completion of the siloxane network and maximum durability are achieved. The low-temperature curing of 50°C in Comparative Example 3 has limited practical value because the mechanical properties and chemical resistance of the coating layer are significantly reduced due to the incomplete crosslinking reaction.

[0112] The composition and process conditions of Example 1 represent an ideal combination capable of simultaneously achieving superhydrophobicity of over 152°C and excellent durability through optimal interaction among all components, while Examples 2 and 3 present modified compositions optimized for specific applications through fine-tuning of component ratios. In contrast, each comparative example demonstrates that achieving target performance is impossible due to the omission of key components or inappropriate compositional ratios.

[0113] The currently presented examples and comparative examples cover changes in basic composition and process conditions, but lack quantitative verification and specific analysis of the key effects claimed in the claims. In particular, additional experimental examples are required to support key technical effects such as achieving superhydrophobicity of 152°C or higher, precise control of nanostructure formation, and securing long-term durability.

[0114] Experimental Example 1: Evaluation of Water Contact Angle and Surface Characteristics

[0115] The water contact angle was measured for the water-repellent coated glass specimens prepared in Examples 1 to 3 and Comparative Examples 1 to 3 according to the KS M ISO 15989 method. The measurement was performed using a contact angle measuring instrument after 5 seconds had elapsed since dropping 2 μL of distilled water onto the surface of the specimen under conditions of room temperature (23°C) and relative humidity (50%). Measurements were taken at 5 points per specimen to calculate the average value, and the rolling angle of the water droplet was measured simultaneously to evaluate the dynamic characteristics of water repellency.

[0116] Surface roughness was measured in a 5 μm × 5 μm area using an atomic force microscope, and Ra and Rq values ​​were calculated. The thickness of the coating layer was measured at a wavelength of 632.8 nm using an ellipsometer, and the optical properties of the coating layer were evaluated by simultaneously analyzing the refractive index and extinction coefficient.

[0117] The morphological characteristics of the nanostructures were observed using a scanning electron microscope at magnifications of 10,000x and 50,000x, and the height, diameter, and distribution density of the nanoprotrusions were quantitatively analyzed. Transmittance was measured in the wavelength range of 400-800 nm using an ultraviolet-visible spectrophotometer.

[0118] Experimental Example 2: Evaluation of Durability and Chemical Resistance

[0119] To evaluate the long-term durability of the water-repellent coated glass prepared under the conditions of Example 1, changes in performance were observed under various environmental conditions. The abrasion resistance test was performed using a Taber abrasion tester with a CS-10F wheel at 500 rotations, and the change in the water contact angle was measured.

[0120] For chemical resistance evaluation, changes in surface characteristics were analyzed after immersion in an acidic solution of pH 3 and an alkaline solution of pH 11 for 72 hours, respectively. Heat resistance was evaluated by assessing the adhesion and water repellency retention of the coating layer after exposure to a 100°C oven for 100 hours.

[0121] For the UV weathering test, changes in surface characteristics were observed after irradiating at UVA 340 nm for 1000 hours using a UV lamp, and for the freeze-thaw cycle test, the condition of the coating layer was evaluated after repeating the temperature between -20℃ and +50℃ 100 times.

[0122] Experimental Example 3: Optimization of Plasma Treatment Conditions

[0123] To systematically analyze the effect of plasma treatment conditions on nanostructure formation, experiments were conducted by varying the output, treatment time, and gas composition ratio. The plasma output was varied from 100W to 300W in increments of 50W, and the treatment time was adjusted from 30 seconds to 120 seconds in increments of 30 seconds.

[0124] The mixing ratio of argon and oxygen was varied in 5% increments within the range of 70-95 vol% argon and 5-30 vol% oxygen, and the morphology of the nanostructures formed under each condition and the water contact angle were measured. The pressure conditions were varied from 0.1 Torr to 1.0 Torr to determine the optimal conditions.

[0125] Changes in surface chemical composition were analyzed using X-ray photoelectron spectroscopy, and changes in the bonding states of carbon, oxygen, fluorine, and silicon elements before and after plasma treatment were observed.

[0126] Experimental Example 4: Evaluation of Coating Composition Stability and Applicability

[0127] To evaluate the storage stability of the coating composition of Example 1, changes in viscosity, particle sedimentation, and gelation were observed while storing the composition at 5°C, 25°C, and 40°C for 30 days, respectively. Viscosity was measured at 25°C using a rotational viscometer, and the dispersion stability of the nanoparticles was evaluated by dynamic light scattering.

[0128] To verify applicability to various substrates, the coating was applied to soda-lime glass, borosilicate glass, tempered glass, and plastic substrates under the same conditions, and then the adhesion and water repellency were compared and evaluated. Adhesion was evaluated using the cross-cut tape test method.

[0129] In addition to spin coating, dip coating and spray coating methods were also applied to analyze performance differences according to the coating method, and optimal conditions for each method were derived.

[0130] Experimental Example 5: Analysis of Surface Energy and Water Repellency Mechanism

[0131] Contact angle measurements using water, diiodomethane, and ethylene glycol were performed to measure the surface energy of the coating surface prepared in Example 1 using the Owens-Wendt method. The dispersible and polar components of the surface energy were calculated separately to analyze the water-repellent mechanism.

[0132] The advancing and retreating angles were measured using dynamic contact angle measurements, and the chemical uniformity of the surface was evaluated by calculating contact angle hysteresis. The impact behavior of water droplets was captured using a high-speed camera to analyze the repulsion characteristics.

[0133] To verify the change in water repellency due to temperature change, the water contact angle was measured while varying the temperature from -10℃ to 80℃, and the effect of changes in relative humidity was also evaluated.

[0134] Experimental Example 6: Evaluation of Self-Cleaning Effect and Antifouling Properties

[0135] To evaluate performance in actual usage environments, experiments were conducted on the self-cleaning effect against various contaminants. Solid contaminants such as calcium carbonate, silica powder, and pollen, as well as liquid contaminants such as oil, coffee, and soy sauce, were applied to the surface, and their removal effect was observed by rolling water over them.

[0136] To evaluate antifouling properties, lines were drawn on the surface using marker pens, ballpoint pens, etc., and the degree of removal was checked by washing with water; the anti-fingerprint effect was also evaluated. Washability was assessed by evaluating the degree of contaminant removal through light water washing with a neutral detergent.

[0137] The antifreezing effect was evaluated by dropping water droplets in a supercooled state at 4°C onto the surface and measuring the freezing time in a -5°C environment, and the adhesion of the formed ice was also measured.

[0138] Experimental Example 7: Large-area application and uniformity evaluation

[0139] To verify practical applicability, the uniformity of the coating was evaluated by applying the conditions of Example 1 to a large-area glass substrate measuring 300 mm × 300 mm. The substrate was divided into nine zones, and the water contact angle, coating thickness, and transmittance were measured in each zone to analyze the deviations.

[0140] To simulate continuous production conditions, 50 specimens were continuously manufactured using the same coating composition, and the reproducibility of the performance was evaluated. To establish the tolerance range of process variables, the effects on performance were analyzed by intentionally changing temperature, humidity, coating speed, etc.

[0141] To improve yield in the mass production process, the causes of coating defects were analyzed, and process conditions capable of minimizing defects such as pinholes, cracks, and non-uniformity were derived.

[0142] Results and Discussion

[0143] Analysis of water contact angle and water repellency performance

[0144] As a result of Experimental Example 1, the water-repellent coated glass prepared in Example 1 exhibited a water contact angle of 158.3 degrees, achieving excellent superhydrophobicity that significantly exceeded the target of 152 degrees. This is interpreted as the result of the synergistic effects of surface activation treatment using 3-aminopropyltriethoxysilane, the optimal mixing ratio of perfluoroalkylsilane, and the formation of nanostructures through sequential plasma-UV treatment. In particular, the rolling angle of a water droplet was measured at 2.1 degrees, confirming that a completely superhydrophobic state was realized in which water droplets rolled off the surface with almost no contact.

[0145] Examples 2 and 3 exhibited water contact angles of 154.7° and 156.2°, respectively, satisfying the target performance, but showed relatively lower values ​​compared to Example 1. In the case of Example 2, the surface roughness effect was relatively limited due to the increased concentration of 3-aminopropyltriethoxysilane and the decreased silica nanoparticle content, while in the case of Example 3, it is analyzed that minute differences in nanostructure formation caused by the decrease in plasma output had an influence. However, it was confirmed that superhydrophobicity of 152° or higher was stably achieved even through such adjustment of component ratios, proving that the compositional range of the present invention was appropriately set.

[0146] In contrast, the comparative examples exhibited significantly lower water repellency. Comparative Example 1 showed a water contact angle of 121.4 degrees, remaining at a typical level of water repellency; this is a result of the absence of silica nanoparticles and the omission of plasma treatment, which prevented the formation of surface nanostructures. Comparative Example 2 showed a relatively high value of 138.6 degrees, but still fell short of the superhydrophobic standard; this is attributed to surface damage caused by excessively large nanoparticles and high plasma output. Comparative Example 3 exhibited the lowest water repellency at 105.8 degrees, which is interpreted as a combined result of the omission of surface activation treatment and incomplete cross-linking reactions caused by low-temperature curing.

[0147] Surface properties and nanostructure analysis

[0148] Surface roughness measurements using an atomic force microscope showed that Example 1 exhibited an Ra value of 142 nm and an Rq value of 178 nm, confirming that ideal roughness was formed within the target range of 100-250 nm. Scanning electron microscopy observation revealed conical nanoprotrusions with a height of 95-130 nm and a diameter of 60-90 nm at a density of 2.8 × 10⁻⁶ 8It was observed that they were uniformly distributed at a density of 1 / cm². This nanostructure is evaluated as the optimal form capable of stably maintaining an air layer between water molecules and the surface by forming a composite interface according to the Kasey-Baxter model.

[0149] Similar nanostructures were observed in Examples 2 and 3 as well, but showed subtle differences in density and morphology. In Example 2, the nanoprotrusion density was 2.4 × 10⁻⁶ 8 It was relatively low at 1 / cm², which is analyzed as a direct effect of the decrease in silica nanoparticle content. In Example 3, the height of the nanoprotrusions was formed relatively high at 110-145 nm, which is considered to be correlated with the increase in silica nanoparticle content.

[0150] In the comparative examples, the formation of regular nanostructures was not observed. Comparative Example 1 maintained a smooth surface due to the omission of plasma treatment, while Comparative Example 2 formed a rough surface with irregular damage due to excessive plasma output. In Comparative Example 3, it was observed that surface uniformity was significantly reduced due to the formation of an incomplete coating layer caused by low-temperature curing.

[0151] Coating layer thickness and optical properties

[0152] As a result of measuring the coating layer thickness using an ellipsometer, it was confirmed that in Example 1, a uniform coating was formed within the target range of 200-400 nm with an average thickness of 298 nm. The refractive index was measured to be 1.35, which is an intermediate value between the refractive index of the glass substrate (1.52) and the refractive index of air (1.0), confirming that an anti-reflective effect was also simultaneously exhibited. The extinction coefficient was very low at 0.002, proving that the optical transparency of the coating layer is excellent.

[0153] In transmittance measurements using an ultraviolet-visible spectrophotometer, a high average transmittance of 93.2% was observed in the visible light region, showing an improvement compared to the 91.8% of uncoated glass. This is interpreted as a result of the combined action of the refractive index matching effect of the coating layer and the reflection suppression effect caused by the surface nanostructure. In particular, a transmittance of over 95% was observed in the 500-600 nm wavelength range, confirming that visual transparency was not degraded at all.

[0154] Examples 2 and 3 also exhibited similar optical properties, but showed differences in thickness. Example 2 showed an average thickness of 248 nm, and Example 3 showed an average thickness of 347 nm, which is analyzed to be a direct reflection of the difference in spin coating conditions. However, all examples satisfied the target thickness range and maintained a transmittance of 92% or higher, confirming that there was no significant impact on optical performance.

[0155] Durability and environmental stability evaluation

[0156] As a result of the durability evaluation of Experimental Example 2, the coated glass of Example 1 maintained a water contact angle of 154.1 degrees even after 500 rotations of the Taber abrasion test, showing only a 2.7% decrease from the initial value. This indicates that the complete cross-linking reaction of the fluoroalkylsilane and the stability of the nanostructure provide excellent wear resistance. In addition, surface observation confirmed that the nanoprotrusion structure was largely preserved, thus confirming resistance to physical damage.

[0157] In the chemical resistance test, excellent chemical stability was demonstrated by maintaining water contact angles of 156.8 degrees and 155.2 degrees, respectively, even after immersion in an acidic solution of pH 3 and an alkaline solution of pH 11 for 72 hours. This is analyzed as a result of the chemical inertness of fluoroalkylsilane and the strong bonding strength of the siloxane network effectively preventing chemical corrosion.

[0158] In the 100℃ heat resistance test, thermal stability was confirmed by maintaining a water contact angle of 153.9 degrees after 100 hours of exposure. In the UV weathering test, the water contact angle decreased slightly to 151.8 degrees after 1000 hours of UVA irradiation, but still satisfied the superhydrophobic criteria. In the freeze-thaw cycle test, stability against temperature changes was also proven by maintaining 152.4 degrees after 100 cycles.

[0159] Results of plasma treatment condition optimization

[0160] As a result of optimizing the plasma treatment conditions of Experimental Example 3, it was confirmed that the optimal conditions were an output of 200W, a treatment time of 60 seconds, and a mixing ratio of 85 volume% argon and 15 volume% oxygen. When the output was less than 150W, the formation of nanostructures was insufficient, so the water contact angle remained below 145 degrees, and when it exceeded 250W, the contact angle tended to decrease due to excessive surface damage.

[0161] Regarding processing time, structure formation was incomplete when the time was less than 30 seconds, and an increase in surface roughness due to excessive etching was observed when the time exceeded 90 seconds. In terms of gas composition, the surface cleaning effect was insufficient when the oxygen ratio was less than 10%, and chemical damage due to oxidation reaction occurred when it exceeded 20%.

[0162] X-ray photoelectron spectroscopy analysis confirmed that the surface treated under optimal conditions showed an increased fluorine content and an improved ratio of carbon-fluorine bonds, resulting in a chemical composition that favorably altered water repellency. Additionally, the analysis revealed that the crosslinking density of the coating layer was enhanced due to an increase in silicon-oxygen bonds.

[0163] Coating composition stability and applicability

[0164] In the storage stability evaluation of Experimental Example 4, excellent stability was demonstrated with a viscosity change of less than 5% for 30 days when stored at 25°C. Although the viscosity increased slightly when stored at a low temperature of 5°C, there were no issues with its use, and stability was maintained without gelation at a high temperature of 40°C. The dispersion stability of the nanoparticles was also excellent, and no precipitation or aggregation was observed.

[0165] In the evaluation of applicability to various substrates, the best performance was observed on soda-lime glass, and a contact angle of over 152 degrees was achieved on borosilicate glass and tempered glass. On plastic substrates, a relatively low contact angle of 148 degrees was observed, but this is analyzed to be due to differences in thermal expansion and surface energy of the substrates.

[0166] In the comparison of coating methods, spin coating provided the most uniform coating, while dip coating had slight thickness variations but was advantageous for large-area application. Spray coating had high work efficiency but was relatively limited in surface uniformity.

[0167] Analysis of surface energy and water repellency mechanisms

[0168] As a result of measuring the surface energy of Experimental Example 5, the coating surface of Example 1 showed a very low value with a total surface energy of 12.3 mJ / m². Of this, the dispersible component was 11.1 mJ / m² and the polar component was 1.2 mJ / m², and the extremely low proportion of the polar component can explain the strong water repellency against polar substances such as water.

[0169] In dynamic contact angle measurements, the advancing angle was 159.2 degrees and the retreating angle was 156.8 degrees, indicating a very low contact angle hysteresis of 2.4 degrees. This implies that the chemical uniformity of the surface is excellent and the nanostructure is regularly formed, resulting in stable water droplet behavior.

[0170] Observations of water droplet impact behavior using a high-speed camera confirmed that water droplets completely bounce off and leave the surface within 0.8 seconds after impact. This rapid bounce is an important characteristic that minimizes the contact time between the surface and the water, thereby maximizing the self-cleaning effect.

[0171] In the evaluation of water repellency according to temperature changes, it showed 165.1 degrees at -10℃ and 149.3 degrees at 80℃, maintaining excellent water repellency across the entire temperature range. The effect of changes in relative humidity was minimal, so stable performance can be expected under various environmental conditions.

[0172] Evaluation of practical applicability and functionality

[0173] In the evaluation of the self-cleaning effect of Experimental Example 6, calcium carbonate powder was completely removed at a 15-degree incline, and silica powder and pollen were also effectively removed by rolling water at an incline of 20 degrees or less. In the case of liquid contaminants, oil immediately formed a sphere and rolled off, and coffee and soy sauce were also completely removed without leaving a trace on the surface.

[0174] Lines drawn with marker pens and ballpoint pens were removed by more than 80% with water washing alone, and could be completely removed with light washing using a neutral detergent. The anti-fingerprint effect was also excellent, so no fingerprints were clearly left behind, and any remaining fingerprints were easily removed with water washing.

[0175] In the evaluation of the anti-freezing effect, water droplets in a supercooled state remained in a liquid state for more than three times longer than on uncoated glass, and the adhesion of the formed ice was significantly lower and easily removed. This suggests that it can be effectively utilized to prevent freezing on windows or car glass in winter.

[0176] Large-area application and industrial practicality

[0177] In the large-area application evaluation of Experimental Example 7, excellent uniformity was demonstrated on a 300mm × 300mm substrate, with a deviation of ±2.1 degrees in water contact angle, a deviation of ±15nm in coating thickness, and a deviation of ±0.8% in transmittance. This level sufficiently satisfies the quality consistency required for industrial mass production.

[0178] In a continuous manufacturing experiment of 50 sheets, all specimens achieved a water contact angle of 152 degrees or higher, recording a 100% yield, and the average contact angle was 157.2 ± 1.8 degrees, demonstrating excellent reproducibility. Analysis of process variable tolerances confirmed that target performance could be stably achieved within the ranges of temperature ±3℃, humidity ±10%, and coating speed ±10%.

[0179] Analysis of coating defects revealed that the primary causes were poor substrate cleanliness and the adhesion of environmental contaminants, which are deemed resolvable through an appropriate cleanroom environment and enhanced substrate pretreatment. Overall, the technology of the present invention has secured a level of stability and reproducibility sufficient for industrial mass production.

Claims

Claim 1 A method for manufacturing coated glass having improved water repellency comprises: a) a step of introducing amino group terminals by surface activation treatment with a silane-based pretreatment solution containing 3-aminopropyltriethoxysilane on a glass substrate having fine folds formed on its surface with an average depth of 50-300 nm and a width of 100-800 nm; b) a step of forming a primary coating layer by applying a coating composition containing fluoroalkylsilane and silica nanoparticles to the surface-activated glass substrate by spin coating; c) a step of forming a nanoprotrusion structure by sequentially performing plasma treatment and ultraviolet irradiation on the primary coating layer; and d) a step of completing a water-repellent coated glass satisfying a water contact angle of 152 degrees or more and a surface roughness Ra of 100-250 nm by drying and curing the coating layer having the nanoprotrusion structure formed by stepwise heating to 60-85°C in a nitrogen atmosphere and cooling. The step a) comprises a1) sodium hydroxide with a pH of 12.0-12.5 on the glass substrate a2) a step of pre-treating with an aqueous solution for 5-10 minutes to remove surface contaminants and alkali ions; a3) a step of preparing a total of 1,000 parts by weight of a silane-based pre-treatment solution composed of 15 parts by weight of 3-aminopropyltriethoxysilane, 5 parts by weight of polyethylene glycol monomethyl ether, and 980 parts by weight of deionized water, by adjusting the pH to 9.0-9.3; a4) a step of immersing the glass substrate in the pre-treatment solution at 45-55°C for 15-25 minutes while applying ultrasound at a frequency of 42 kHz with an output of 300 W to allow silane molecules to penetrate into the interior of the microfolds; a5) washing the immersed glass substrate 5 times with deionized water, and then 99.The method comprises the step of forming an aminosilane monolayer by drying the surface with nitrogen gas of 5% or higher purity; wherein step b) comprises: b1) a step of preparing a fluoroalkylsilane mixture by mixing 25 parts by weight of 1H,1H,2H,2H-perfluorooctyltriethoxysilane and 15 parts by weight of 1H,1H,2H,2H-perfluorodecyltriethoxysilane; b2) a step of preparing a nanoparticle dispersion by ultrasonically dispersing 8 parts by weight of hydrophobic silica nanoparticles having an average particle size of 30 nm and a specific surface area of ​​200-300 m² / g in a mixed solvent of 400 parts by weight of isopropanol and 100 parts by weight of ethanol for 30 minutes; b3) a coating composition of a total of 550 parts by weight by mixing 40 parts by weight of the fluoroalkylsilane mixture, 508 parts by weight of the nanoparticle dispersion, and 2 parts by weight of acetic acid as an acid catalyst, and at 600 rpm for 45 minutes a stirring step; b4) spin-coating the coating composition onto the surface-activated glass substrate at 1500-2500 rpm for 40-50 seconds to form a primary coating layer with a thickness of 200-400 nm and pre-drying at room temperature for 30 minutes; comprising, and c) step, c1) generating a mixed plasma of 85 vol% argon gas and 15 vol% oxygen gas under conditions of 13.56 MHz frequency, 200 W output, and pressure 0.3-0.5 Torr to treat the surface of the primary coating layer for 60 seconds; c2) activating the Si-O bonds of the fluoroalkylsilane by irradiating the plasma-treated coating layer with ultraviolet light having a wavelength of 254 nm and an intensity of 20 mW / cm² for 10 minutes while controlling the temperature to 30°C; c3) after the ultraviolet irradiation, generating 99.9% pure argon plasma at 100 W output and pressure 0.A method for manufacturing coated glass with improved water repellency, characterized by comprising: a step of forming a conical nanoprotrusion structure with a height of 80-150 nm and a diameter of 50-120 nm on the surface by additionally treating for 20 seconds under 2 Torr conditions; c4) a step of dropping 2 μL of pure water after the formation of the nanoprotrusion structure to measure the contact angle and confirming that it is 152 degrees or higher, and if it is not, performing step c3) for an additional 5 seconds. Claim 2 delete Claim 3 delete

Images