Superhydrophilic-Thermal Management Composite Transparent Coating Composition for Front Glass of a Photovoltaic Module, Coating Structure Including the Same, and Method for Forming the Same

Abstract

The present invention relates to a superhydrophilic-thermal management composite transparent coating composition for the front glass of a photovoltaic module, a coating structure including the same, and a method for forming the same, wherein convenience or efficiency of use is maximized due to ease of handling, use, maintenance, and repair derived from a structure differentiated from existing ones, such as by simultaneously realizing superhydrophilic properties that suppress the adhesion of contaminants and thermal management properties that reduce heat accumulation caused by the near-infrared region of solar radiation energy when applied to the front glass or transparent substrate surface of a photovoltaic module, thereby preventing module surface temperature rise and the resulting decrease in power generation efficiency and thermal degradation while maintaining visible light transmittance. The composition comprises 50 to 88 parts by weight of a water-soluble resin binder, 10 to 25 parts by weight of thermal management functional inorganic particles that selectively block radiation energy in the near-infrared region (800 to 1200 nm), 1 to 15 parts by weight of a superhydrophilic network forming component that maintains a surface contact angle of 10° or less, 0.5 to 5 parts by weight of a metal oxide for UV blocking, 0.5 to 5 parts by weight of an auxiliary additive including a dispersant, an antifoamer, and a stabilizer, and water. It is characterized by comprising an aqueous medium, and the coating film formed from the above composition maintains a transmittance of 90% or more in the visible light region (400 to 700 nm) while reducing the module surface temperature by 2 to 5°C or more under solar irradiation conditions.

Description

Technology Field

[0001] The present invention relates to surface modification and functional coating technology applied to photovoltaic power generation systems, and more specifically, to a superhydrophilic-thermal management composite transparent coating composition for the front glass of a photovoltaic module and a coating structure including the same, and a method for forming the same, which maximizes convenience or efficiency of use through ease of handling, use, maintenance, and repair derived from a structure differentiated from existing ones. This is achieved by simultaneously realizing superhydrophilic properties that suppress the adhesion of contaminants and thermal management properties that reduce heat accumulation caused by the near-infrared region of solar radiation energy, thereby preventing the rise in module surface temperature and the resulting decrease in power generation efficiency and thermal degradation while maintaining visible light transmittance. Background Technology

[0003] Solar modules are structured to generate electricity by concentrating sunlight through a front glass. Since they are installed and operated in outdoor environments for extended periods, dust, yellow dust, exhaust gas particles, organic pollutants, and moisture stains adhere to the surface of the front glass, causing a decrease in light transmittance. To address this, conventional technologies have been proposed to improve this by forming hydrophilic or water-repellent coatings on the front glass surface or performing periodic cleaning and maintenance.

[0005] However, these conventional technologies have limitations in that it is difficult to completely suppress the adhesion of contaminants, and the hydrophilic performance of the coating layer deteriorates thermally or drops within a short period as the surface temperature of the solar module rises, particularly under high temperature and strong radiation conditions. Furthermore, some near-infrared blocking coatings have limitations that negatively affect the power generation efficiency and manufacturing process applicability of solar modules due to reduced visible light transmittance, increased haze, or the requirement for high-temperature processes.

[0007] Accordingly, there is a demand for a new type of transparent coating technology that combines complementary superhydrophilic and thermal management functions to maintain stable self-cleaning performance even in long-term operating environments of photovoltaic modules, effectively suppress the rise in module surface temperature caused by solar radiation, and simultaneously ensure visible light transmittance and process compatibility. Prior art literature

[0009] Registered Patent Publication No. 10-1505322 "Spraying device for superhydrophilic anti-fouling coating material for solar cells" The problem to be solved

[0010] The present invention was created to more actively resolve the aforementioned problems, and its objective is to realize a stable superhydrophilic surface that effectively suppresses the adhesion of dust, fine particles, and organic contaminants exposed to the front glass surface of a solar module for a long period, while allowing contaminants to be naturally removed upon contact with rain or moisture.

[0012] In addition, the present invention has another objective of providing a thermal management function that suppresses the rise in surface temperature of a photovoltaic module by reducing heat accumulation caused by the near-infrared region of solar radiation energy, and thereby prevents the decrease in power generation efficiency and thermal degradation of the photovoltaic cell.

[0014] In addition, another problem addressed by the present invention is to provide a highly durable coating structure that suppresses thermal degradation or performance reduction of superhydrophilic performance even in high-temperature environments and under long-term solar irradiation conditions, thereby enabling the initial performance to be continuously maintained.

[0016] In addition, another problem addressed by the present invention is to provide a transparent coating composition and a coating film capable of suppressing optical loss of a photovoltaic module by minimizing the increase in haze while maintaining high transmittance in the visible light region.

[0018] In addition, another problem addressed by the present invention is to provide a coating technology based on an aqueous composition that can be formed at room temperature or low temperature processes and applied to large-area glass substrates, thereby offering excellent applicability to photovoltaic module manufacturing processes and on-site construction processes. means of solving the problem

[0020] To achieve the above-mentioned problem, the superhydrophilic-thermal management composite transparent coating composition for the front glass of a photovoltaic module proposed in the present invention, the coating structure including the same, and the method for forming the same are as follows.

[0022] The present invention relates to a superhydrophilic-thermal-managing transparent coating composition formed on the front glass or transparent substrate surface of a solar module to suppress the adhesion of contaminants and simultaneously reduce the temperature rise caused by solar radiation, wherein the composition comprises 50 to 88 parts by weight of a water-soluble resin binder, 10 to 25 parts by weight of thermal-managing functional inorganic particles that selectively block radiant energy in the near-infrared region (800 to 1200 nm), 1 to 15 parts by weight of a superhydrophilic network forming component that maintains a surface contact angle of 10° or less, 0.5 to 5 parts by weight of a metal oxide for blocking ultraviolet rays, 0.5 to 5 parts by weight of an auxiliary additive including a dispersant, an antifoaming agent, and a stabilizer, and an aqueous medium containing water, wherein the coating film formed from the composition maintains a transmittance of 90% or more in the visible light region (400 to 700 nm) while reducing the module surface temperature by 2 to 5°C or more under solar irradiation conditions.

[0024] In addition, the above-mentioned water-soluble resin binder is characterized by comprising one or more of a vinyl acetate-ethylene copolymer (VAE), an acrylic emulsion, and a silica sol or a siloxane-based inorganic binder.

[0026] In addition, the thermal management functional inorganic particles are characterized by comprising one or more of timony-doped tin oxide (ATO), indium-doped tin oxide (ITO), aluminum-doped zinc oxide (AZO), and cesium-doped tungsten oxide.

[0028] In addition, the average particle size of the thermal management functional inorganic particles is controlled to a range of 20 to 80 nm, characterized in that the haze of the coating film is maintained at 5% or less.

[0030] In addition, the superhydrophilic network forming component comprises one or more of a silica sol, a titanium oxide (TiO₂) photocatalyst, and a hydrophilic silane or a hydrophilic polymer, and is characterized by forming a hydrophilic inorganic-organic composite network on the surface.

[0032] In addition, the titanium oxide is characterized by having self-restoring superhydrophilic properties in which surface hydrophilicity is restored upon UV irradiation.

[0034] The coating structure formed on the front glass substrate of the solar module of the present invention comprises: a thermal management functional layer formed by penetrating the surface layer of the glass substrate and suppressing a temperature rise caused by solar radiation through a near-infrared blocking function; and a superhydrophilic surface control layer formed on the upper part of the thermal management functional layer to allow moisture to diffuse in the form of a continuous water film; wherein the thermal degradation of the superhydrophilic surface control layer is suppressed by the thermal management functional layer.

[0036] In addition, the thermal management functional layer is characterized by being chemically bonded to a glass substrate by including a silica-based inorganic network.

[0038] In addition, the superhydrophilic surface control layer is characterized by maintaining a contact angle of 15° or less upon contact with water.

[0040] The method for forming a superhydrophilic-thermal management coating film on the front glass of a solar module according to the present invention comprises: a substrate cleaning step (S10) of cleaning and drying a glass substrate; a functional layer forming step (S20) of forming a penetrating thermal management functional layer on the surface layer of the glass substrate by applying a thermal management composition having a near-infrared blocking function; and a control layer forming step (S30) of forming a superhydrophilic surface control layer on top of the thermal management functional layer by applying a superhydrophilic composition.

[0042] In addition, the functional layer forming step (S20) and the control layer forming step (S30) are characterized by being performed at room temperature or at a low temperature of 120°C or lower.

[0044] In addition, the coating film is characterized by having a thickness in the range of 50 to 500 nm.

[0046] Meanwhile, the present invention may further include the following technical features.

[0047] First, the superhydrophilic network forming component further includes a water-trapping hydrophilic nanomaterial that forms a stable hydration layer through multiple hydrogen bonds upon contact with moisture, thereby forming a water-based buffer layer between the contaminant and the surface of the coating film, which is characterized by inhibiting the direct attachment of the contaminant.

[0049] In addition, the superhydrophilic network forming component includes a charge-retaining hydrophilic auxiliary material that forms a fixed charge on the surface to induce alignment of water molecules, thereby maintaining a continuous adsorption state of water molecules on the surface of the coating film.

[0051] In addition, the superhydrophilic network forming component includes a lubricating hydrophilic auxiliary material that swells in the presence of moisture to form a low-friction hydrated layer on the surface, characterized in that contaminants can be detached by washing water or rain with low shear force. Effects of the invention

[0053] According to the present invention, which is configured as described above, by forming a superhydrophilic-thermal management composite coating on the front glass or transparent substrate surface of a solar module, the phenomenon of dust and contaminants adhering to the surface is significantly suppressed, and contaminants are removed along with a continuous water film upon contact with rain or moisture, thereby ensuring stable self-cleaning performance for a long period.

[0055] In addition, the present invention provides another effect of improving overall power generation efficiency by mitigating the output degradation and thermal degradation of solar cells occurring in high-temperature environments, as it can effectively reduce the module surface temperature under solar irradiation conditions through a thermal management function that selectively blocks solar radiation energy in the near-infrared region.

[0057] In addition, the present invention has another effect of achieving excellent durability in which the initial hydrophilic properties are maintained for a long period by adopting a layered structure in which the thermal management functional layer and the superhydrophilic surface control layer act complementarily, thereby suppressing the thermal degradation of superhydrophilic performance even under high temperature and prolonged solar irradiation conditions.

[0059] In addition, the coating composition according to the present invention is designed to maintain high transmittance in the visible light region and suppress the increase in haze, thereby having another effect of minimizing optical loss of the solar module without compromising the appearance quality.

[0061] Furthermore, since the present invention enables the formation of a coating film at room temperature or low temperature conditions based on an aqueous composition, it offers excellent process applicability to the front glass of large-area solar modules and provides another effect of simultaneously ensuring reduced energy consumption in the manufacturing process and ease of on-site construction. Brief explanation of the drawing

[0063] FIG. 1 is a flowchart briefly illustrating, in steps, a method for forming a superhydrophilic-thermal management coating film on the front glass of a photovoltaic module constructed according to a preferred embodiment of the present invention. Specific details for implementing the invention

[0064] Hereinafter, the structure of the present invention and the resulting operation and effects will be described collectively with reference to the attached drawings.

[0066] 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 can 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. Furthermore, throughout the entire specification, the same reference numerals refer to the same components.

[0068] The present invention relates to surface modification and functional coating technology applied to photovoltaic power generation systems.

[0070] In particular, the present invention relates to a superhydrophilic-thermal management composite transparent coating composition for the front glass of a solar module, a coating structure including the same, and a method for forming the same, wherein convenience of use or efficiency is maximized due to ease of handling, use, maintenance, and repair derived from a structure differentiated from existing ones, such as by simultaneously realizing superhydrophilic properties that suppress the adhesion of contaminants and thermal management properties that reduce heat accumulation caused by the near-infrared region of solar radiation energy when applied to the front glass or transparent substrate surface of a solar module, thereby preventing the rise in module surface temperature and the resulting decrease in power generation efficiency and thermal degradation while maintaining visible light transmittance.

[0072] FIG. 1 is a flowchart briefly illustrating, in steps, a method for forming a superhydrophilic-thermal management coating film on the front glass of a photovoltaic module configured according to a preferred embodiment of the present invention.

[0074] 1. Superhydrophilic-thermal management transparent coating composition

[0075] The superhydrophilic-thermal management transparent coating composition according to the present invention is a functional transparent coating composition designed to be applied to the front glass or other transparent substrate surface of a photovoltaic module to suppress the adhesion of dust, fine particles, organic contaminants, and moisture residues introduced by the external environment, while simultaneously reducing the temperature rise of the photovoltaic module surface by selectively controlling thermal energy in the near-infrared region contained in solar radiation energy.

[0076] The above coating composition is based on an environmentally friendly aqueous medium with excellent process stability, and each component within the composition is combined to achieve a balance of optical transparency, thermal management performance, surface hydrophilicity, and long-term durability.

[0078] Specifically, the above composition includes the following components.

[0079] (a) Water-soluble resin binder

[0080] The above-mentioned water-soluble resin binder is a basic framework component for securing continuous film formation, mechanical strength, adhesion to the substrate, and visible light transmission characteristics of the coating film, and it is preferable to include 50 to 88 parts by weight based on 100 parts by weight of the total composition.

[0081] The above water-soluble resin binder may be used alone or in combination with one or more of vinyl acetate-ethylene copolymer (VAE), acrylic emulsion, silica sol, or siloxane-based inorganic binder, and among these, silica sol or siloxane-based inorganic binder is particularly advantageous for improving the weather resistance, water resistance, and heat resistance of the coating film by forming chemical bonds through condensation reactions with siloxane bonds or hydroxyl groups on the surface of the glass substrate.

[0082] Furthermore, when organic and inorganic binders are used in combination, the organic binder ensures the flexibility and crack resistance of the coating film, while the inorganic binder complements heat resistance and long-term durability, enabling the stable maintenance of the coating film even under the conditions of repeated temperature changes in solar modules.

[0084] (b) Thermal management functional inorganic particles

[0085] The above thermal management functional inorganic particles are a key component for reducing thermal energy transferred to the surface of a photovoltaic module by exhibiting absorption or reflection characteristics in the near-infrared region of 800 to 1200 nm of solar radiation energy, and it is preferable to include 10 to 25 parts by weight based on 100 parts by weight of the total composition.

[0086] One or more of the following may be used as the above-mentioned inorganic particles: timony-doped tin oxide (ATO), indium-doped tin oxide (ITO), aluminum-doped zinc oxide (AZO), and cesium-doped tungsten oxide (Cs-doped WO₃). These doped metal oxides are characterized by having plasmon absorption or reflection properties in the near-infrared region through the control of free electron concentration.

[0087] It is preferable that the average particle size of the above thermal management functional inorganic particles be controlled within the range of 20 to 80 nm, because if the particle size is less than 20 nm, the near-infrared blocking efficiency may not be sufficiently secured, and if it exceeds 80 nm, there is a concern that the transparency of the coating film may be reduced due to increased haze caused by visible light scattering.

[0088] In the present invention, by controlling the particle size, the haze of the coating film can be maintained at 5% or less while stably securing a near-infrared blocking effect.

[0090] (c) Superhydrophilic network forming component

[0091] The above superhydrophilic network forming component is a key functional component for maintaining a contact angle of 10° or less upon contact with water by forming hydrophilic active points on the surface of the coating film where water molecules can be uniformly diffused, and is included in an amount of 1 to 15 parts by weight.

[0092] The above components may include one or more of silica sol, titanium oxide (TiO₂) photocatalyst, hydrophilic silane, or hydrophilic polymer, and these components form an inorganic-organic composite network structure on the surface of the coating film or the surface layer, thereby preventing localized condensation of moisture and inducing diffusion in the form of a continuous water film.

[0093] In particular, when a TiO₂ photocatalyst is included, oxygen vacancies on the surface are activated by UV irradiation, and hydroxyl groups (-OH) are reformed, thereby enabling self-restoring superhydrophilic properties in which hydrophilicity is restored by UV exposure even when hydrophilicity has decreased.

[0094] This self-restoring mechanism contributes to stably maintaining superhydrophilic performance in long-term outdoor operating environments of photovoltaic modules.

[0096] (d) Metal oxide for UV protection

[0097] The above-mentioned metal oxide for blocking ultraviolet rays may be included in an amount of 0.5 to 5 parts by weight as a protective component to suppress photodegradation of the coating film, molecular chain cleavage of the resin binder, and deterioration of surface function that may occur due to the ultraviolet region of sunlight.

[0098] One or more of the above metal oxides may be used, including cerium oxide (CeO₂), zinc oxide (ZnO), and titanium oxide (TiO₂), and prevent organic components inside the coating film from being exposed to direct ultraviolet rays through ultraviolet absorption or scattering functions.

[0099] However, since excessive content may lead to a decrease in transmittance in the visible light region, it is desirable to control the content within the above range.

[0101] (e) auxiliary additives

[0102] The above auxiliary additive is a component for ensuring the physical stability and process suitability of the composition, and includes dispersants, defoaming agents, stabilizers, etc., and may be included in an amount of 0.5 to 5 parts by weight.

[0103] These dispersants prevent the aggregation of thermal management functional inorganic particles and superhydrophilic components, ensuring a uniform dispersion state even during long-term storage, while defoaming agents remove bubbles that may occur during the coating process, thereby suppressing the occurrence of defects in the coating film.

[0104] The above stabilizer prevents changes in viscosity and precipitation of the composition, thereby enabling the maintenance of consistent quality even during repeated process applications.

[0106] (f) aqueous medium

[0107] The above aqueous medium contains water as a medium for uniformly dispersing each of the above components, and by not using organic solvents, worker safety, environmental friendliness, and compatibility with the solar module manufacturing process can be ensured.

[0108] In addition, by adopting a water-based system, it is possible to form a stable coating film even under room or low temperature conditions, thereby minimizing energy consumption.

[0110] 2. Superhydrophilic-thermal management coating structure

[0111] The superhydrophilic-thermal management coating structure according to the present invention is formed on a front glass substrate of a photovoltaic module and has a functionally separated and layered double-layer structure so that the function of suppressing heat accumulation caused by solar radiation energy and the function of controlling surface hydrophilicity can be stably expressed without mutual interference.

[0113] Specifically, the coating structure includes a thermal management functional layer formed by penetrating the surface layer of a glass substrate, and a superhydrophilic surface control layer formed on top of the thermal management functional layer and directly exposed to the external environment.

[0114] At this time, the thermal management functional layer is formed such that a composition containing thermal management functional inorganic particles having selective absorption or reflection characteristics in the near-infrared region partially penetrates and is fixed to the micro-irregularities or surface layer of the glass substrate, thereby forming a stable functional layer with excellent mechanical and chemical bonding strength with the substrate.

[0116] The above-mentioned thermal management functional layer effectively blocks or mitigates energy in the near-infrared region of solar radiation during solar irradiation, thereby reducing the heat inflow into the glass substrate and coating film; consequently, localized temperature rise and heat concentration phenomena occurring on the surface of the solar module are suppressed.

[0117] Due to the presence of such a thermal management functional layer, thermal degradation, such as binder degradation, rearrangement of surface functional components, or loss of hydrophilic active sites, is significantly suppressed in the superhydrophilic surface control layer located on top, even when exposed to a high-temperature environment.

[0119] Meanwhile, the superhydrophilic surface control layer comprises a silica sol, a titanium oxide photocatalyst, and a hydrophilic silane or hydrophilic polymer component, and controls the continuous diffusion of water molecules across the surface by forming a hydrophilic inorganic-organic composite network on the surface of the coating film.

[0120] Accordingly, when external moisture comes into contact with the surface, the water does not form localized water droplets but diffuses as a continuous water film, thereby realizing a self-cleaning effect in which dust and contaminants are naturally removed during this process.

[0122] In particular, in the coating structure of the present invention, while the thermal management functional layer and the superhydrophilic surface control layer each perform independent functions, a structural synergy effect occurs in which the thermal stability of the superhydrophilic surface control layer is indirectly reinforced by the thermal management functional layer.

[0123] Accordingly, the superhydrophilic surface control layer can stably maintain hydrophilic properties with a contact angle of 15° or less upon contact with water, even under conditions of long-term solar irradiation and repeated high and low temperature cycles, and long-term reliability is ensured without degradation of initial performance.

[0125] In addition, the above double-layer structure has the advantage of being able to independently control the thickness, composition, and formation conditions of each layer, thereby optimizing thermal management performance and superhydrophilic performance simultaneously without reducing visible light transmittance or increasing haze.

[0127] 3. Method for forming a superhydrophilic-thermal management coating film

[0128] The method for forming a superhydrophilic-thermal management coating film according to the present invention is a process for implementing a double-layer coating structure in which thermal management functions and superhydrophilic functions interact complementarily on a front glass substrate of a photovoltaic module, wherein each step is configured to stably secure thermal management performance and surface hydrophilicity without reducing visible light transmittance.

[0130] The above method for forming a coating film includes the following steps.

[0131] (a) Substrate cleaning step (S10)

[0132] The above substrate cleaning step (S10) is a pretreatment step to ensure adhesion between the coating film and the glass substrate and uniformity of the coating film, and is performed to remove oil, dust, fine particles, and organic contaminants remaining on the surface of the front glass substrate of the solar module.

[0133] The above cleaning may be applied individually or in combination with one or more of ultrasonic cleaning, alkaline cleaning, neutral cleaning, or pure water cleaning. For example, organic contaminants and inorganic foreign substances can be effectively removed by performing pure water cleaning after cleaning with an alkaline cleaning solution.

[0134] Subsequently, residual moisture on the surface of the cleaned glass substrate is removed through hot air drying, infrared drying, or natural drying; during this process, the density of hydroxyl groups (-OH) on the glass surface increases, thereby improving the chemical bonding with the subsequently formed coating film.

[0136] (b) Thermal management functional layer formation step (S20)

[0137] The above functional layer formation step (S20) is a step of forming a penetrating thermal management functional layer on the surface layer of a glass substrate to reduce the heat inflow in the near-infrared region of solar radiation energy.

[0138] In the above functional layer formation step (S20), a thermal management composition containing thermal management functional inorganic particles having a near-infrared blocking function is applied to the surface of a glass substrate, and the application method may be spray coating, roll coating, dip coating, slot die coating, or a combination thereof.

[0139] At this time, the thermal management composition is adjusted to have low viscosity and excellent wettability so that it partially penetrates into the fine irregularities or surface layer of the glass substrate, and subsequently, during the drying or low-temperature heat treatment process, an inorganic network is formed and stably fixed to the substrate.

[0140] The above thermal management functional layer can be chemically bonded to the glass substrate not only through physical bonding but also through siloxane bonding or condensation reactions between hydroxyl groups, and accordingly, the thermal management functional layer is stably maintained without peeling or deterioration even under long-term operating conditions.

[0142] (c) Step of forming a superhydrophilic surface control layer (S30)

[0143] The above control layer formation step (S30) is a step of forming a functional surface layer to impart superhydrophilic properties to the upper part of the thermal management functional layer.

[0144] In the above control layer formation step (S30), a superhydrophilic composition comprising silica sol, titanium oxide photocatalyst, hydrophilic silane, or hydrophilic polymer is applied to the upper surface of the thermal management functional layer, and the application method may preferably be a spray, roll coating, or slot die coating method.

[0145] The applied superhydrophilic composition forms an inorganic-organic composite network structure during the drying and low-temperature heat treatment processes, thereby realizing a superhydrophilic surface control layer having a high density of hydrophilic active sites on the surface of the coating film.

[0146] In particular, when a titanium oxide photocatalyst is included, a self-restoring mechanism in which surface hydrophilicity is restored by UV irradiation is activated, maintaining stable superhydrophilic performance even in long-term operating environments.

[0148] (d) Process conditions and coating film characteristics

[0149] The above substrate cleaning step (S10), thermal management functional layer formation step (S20), and superhydrophilic surface control layer formation step (S30) can all be performed at room temperature or at a low temperature of 120°C or lower, which is advantageous for minimizing energy consumption and preventing substrate damage when applied to a photovoltaic module manufacturing process or on-site construction process.

[0150] In addition, it is preferable that the thickness of the entire coating film formed through the above process be controlled to a range of 50 to 500 nm, and within this range, thermal management performance and superhydrophilic performance can be secured simultaneously while maintaining high transmittance and low haze characteristics in the visible light region.

[0152] In the following, specific examples are described that actually implement the composition, coating structure, and formation method described in detail above, and examples and comparative examples are explained to enable a clearer understanding of the technical scope and effects of the present invention.

[0153] However, the following examples are merely illustrative to aid in understanding the present invention, and the scope of the present invention is not limited thereto.

[0155] 4. Examples

[0156] Example 1: Formation of a superhydrophilic-thermal management composite coating film

[0157] After preparing the front glass of the solar module (low-iron tempered glass, thickness 3.2 mm), it was cleaned in an ultrasonic cleaner for 10 minutes using a neutral cleaning solution, rinsed thoroughly with pure water, and then dried with 80°C hot air to remove moisture and contaminants from the surface of the substrate.

[0158] Subsequently, a thermal management composition of the following composition was prepared to form a thermal management functional layer.

[0159] - Water-soluble silica sol binder: 60 parts by weight

[0160] - ATO (timony-doped tin oxide) nanoparticles (average particle size 40 nm): 20 parts by weight

[0161] - Cerium oxide for UV protection: 2 parts by weight

[0162] - Dispersant and stabilizer: 2 parts by weight

[0163] - Water: Remaining amount

[0164] After uniformly applying the above composition to the surface of a glass substrate using a spray coating method, a low-temperature heat treatment was performed at 100°C for 10 minutes to form a penetrating thermal management functional layer on the surface of the glass substrate.

[0166] Next, a superhydrophilic composition of the following composition was prepared to form a superhydrophilic surface control layer.

[0167] - Silica sol: 8 parts by weight

[0168] - TiO₂ photocatalyst (anatase type, average particle size 15 nm): 3 parts by weight

[0169] - Hydrophilic silane coupling agent: 2 parts by weight

[0170] - Dispersant and antifoaming agent: 1 part by weight

[0171] - Water: Remaining amount

[0172] After applying the above superhydrophilic composition to the thermal management functional layer using a roll coating method, a superhydrophilic surface control layer was formed by drying at 90°C for 10 minutes.

[0173] The thickness of the entire coating film formed at this time was about 180 nm.

[0175] Example 2: Coating film according to change in composition ratio

[0176] The same process as in Example 1 was performed, but cesium-doped tungsten oxide (Cs-doped WO₃, average particle size 60 nm) was used as the thermal management functional inorganic particle and the content was adjusted to 25 parts by weight.

[0177] Other process conditions were maintained the same as in Example 1.

[0179] 5. Comparative Example

[0180] Comparative Example 1: Superhydrophilic monolayer coating film

[0181] The same glass substrate as in Example 1 was used, but the step of forming a thermal management functional layer (S20) was omitted and only the superhydrophilic surface control layer was formed as a single layer.

[0182] The thickness of the formed coating film was about 120 nm.

[0184] Comparative Example 2: Thermal management single-layer coating film

[0185] The same glass substrate as in Example 1 was used, but the step of forming a superhydrophilic surface control layer (S30) was omitted and only the thermal management functional layer was formed as a single layer.

[0186] The thickness of the formed coating film was about 150 nm.

[0188] 6. Performance Evaluation and Effects

[0189] The following items were evaluated for the coating films formed according to the examples and comparative examples.

[0190] 1) Visible light transmittance

[0191] As a result of measuring the average transmittance in the 400–700 nm range using a spectrophotometer, Examples 1 and 2 both maintained a transmittance of 90% or higher, whereas Comparative Examples 1 and 2 showed relatively large fluctuations in transmittance due to the application of hydrophilic components or inorganic particles alone, respectively.

[0193] 2) Surface contact angle

[0194] As a result of measuring the water contact angle, the initial contact angle of Examples 1 and 2 was 10° or less, and remained at 15° or less even after 1,000 hours of simulated sunlight irradiation.

[0195] On the other hand, in Comparative Example 1, the contact angle increased to 30° or more under high temperature conditions, and deterioration of superhydrophilic performance was observed.

[0197] 3) Temperature reduction effect

[0198] As a result of measuring the module surface temperature under a solar simulator, Examples 1 and 2 showed a temperature reduction effect of 2 to 5°C or more compared to uncoated glass, whereas Comparative Example 1 did not show a significant temperature reduction effect.

[0200] From the above results, it can be confirmed that the superhydrophilic-thermal management composite coating structure according to the present invention simultaneously achieves superhydrophilic performance and thermal management performance, while maintaining stable performance for a long period even in high-temperature environments.

[0202] Meanwhile, the present invention may further include the following technologies.

[0203] In the superhydrophilic-thermal management composite transparent coating composition according to the present invention, the superhydrophilic network forming component is not composed of a single hydrophilic material, but is formed as a multifunctional superhydrophilic amplification network in which a plurality of hydrophilic auxiliary materials having different operating principles are combined.

[0204] Specifically, the superhydrophilic network forming component includes water-trapping hydrophilic nanomaterials, charge-retaining hydrophilic auxiliary materials, and lubricating hydrophilic auxiliary materials, and these materials mutually complementarily amplify superhydrophilic performance through different physical and chemical mechanisms.

[0205] The above water-trapping hydrophilic nanomaterial is configured to stably capture water molecules at the nanoscale through multiple hydrogen bonds upon contact with moisture by including a high density of multiple hydroxyl groups (-OH), phosphate groups, sulfonic acid groups, or similar hydrophilic functional groups on its surface or inside. As a result, a structurally stabilized hydration layer is formed on the surface of the coating film, rather than a simply diffusing water film, and the hydration layer acts as a water-based buffer interface between the contaminant and the surface of the coating film. Accordingly, direct contact or chemical adsorption of contaminants, such as fine dust, organic pollutants, or airborne particles, onto the surface of the coating film is suppressed, and the initial attachment of contaminants is structurally blocked.

[0206] The charge-retaining hydrophilic auxiliary material described above consists of a hydrophilic polymer or an inorganic / organic hybrid material designed to maintain a fixed state of positive or negative charges on the surface or near-surface region of the coating film. By maintaining the charge state even after the formation of the coating film, the auxiliary material induces the dipole moments of water molecules to align with the charge upon contact with moisture, thereby stably maintaining a state in which water molecules are continuously adsorbed on the surface of the coating film. This electrical attraction-based moisture alignment mechanism prevents a rapid deterioration of the superhydrophilic state even in environments involving repeated drying and rewetting, compared to cases relying on simple chemical hydrophilicity, and effectively suppresses the increase in contact angle over time.

[0207] The above lubricating hydrophilic auxiliary material is configured such that, in the presence of moisture, molecular chains swell to form polymer domains in a highly fluid, hydrated state. As a result, a low-friction hydrated lubricating layer combined with moisture is formed on the surface of the coating film, and the lubricating layer plays a role in significantly reducing the coefficient of friction between the contaminant and the surface. Consequently, even if contaminants are temporarily attached to the surface of the coating film, they can be easily detached by fluid flows with low shear force, such as rain, washing water, or condensation water, and a natural cleaning effect is achieved without separate mechanical cleaning.

[0208] In particular, the present invention can induce synergistic effects through a composite superhydrophilic network. For example, the three hydrophilic auxiliary materials do not each act independently, but rather form a composite network structure within the coating film to implement a stepwise and continuous superhydrophilic operation mechanism.

[0209] In other words, a structural synergy is manifested in which the initial approach and adhesion of contaminants are suppressed by water-trapping hydrophilic nanomaterials, the superhydrophilic state of the surface is stably maintained for a long time by charge-retaining hydrophilic auxiliary materials, and the detachment of residual contaminants is facilitated by lubricating hydrophilic auxiliary materials. Through the combination of such multiple mechanisms, the coating film according to the present invention provides a highly reliable superhydrophilic surface that goes beyond merely having a low initial contact angle, with simultaneously improved contamination resistance, ease of cleaning, and maintenance of superhydrophilic performance even in long-term operating environments.

[0211] According to the present invention, which is configured as described above, the adhesion of contaminants is suppressed and self-cleaning performance is maintained for a long period by a superhydrophilic-thermal management composite coating formed on the front glass or transparent substrate surface of a solar module. At the same time, the reduction in module surface temperature due to near-infrared blocking alleviates the decrease in power generation efficiency and thermal degradation. Furthermore, even in high-temperature environments, the thermal degradation of superhydrophilic performance is suppressed and visible light transmittance is maintained, thereby minimizing optical losses. Additionally, the invention provides the effect of improving large-area applicability and process efficiency through a low-temperature process based on an aqueous composition.

[0213] The present invention described above has been explained with reference to an exemplary embodiment illustrated in the drawings, but this is merely illustrative, and it should be made clear to those skilled in the art that various modifications and equivalent alternative embodiments are possible therefrom. Accordingly, the true technical scope of protection of the present invention should be interpreted by the appended claims, and all technical ideas within an equivalent scope should be interpreted as being included within the scope of rights of the present invention. Explanation of the symbols

[0215] S10. Substrate cleaning step S20. Functional layer formation step S30. Control layer formation step

Claims

Claim 1 A superhydrophilic-thermal management composite transparent coating composition comprising 50 to 88 parts by weight of a water-soluble resin binder, 10 to 25 parts by weight of thermal management functional inorganic particles that selectively block radiant energy in the near-infrared region (800 to 1200 nm), 1 to 15 parts by weight of a superhydrophilic network forming component that maintains a surface contact angle of 10° or less, 0.5 to 5 parts by weight of a metal oxide for UV blocking, 0.5 to 5 parts by weight of an auxiliary additive including a dispersant, an antifoaming agent, and a stabilizer, and an aqueous medium containing water, wherein the superhydrophilic network forming component comprises at least one of a silica sol, a titanium oxide (TiO₂) photocatalyst, a hydrophilic silane, or a hydrophilic polymer to form a hydrophilic inorganic-organic composite network on the surface of the coating film, wherein the titanium oxide photocatalyst has a self-restoring superhydrophilic characteristic in which surface hydrophilicity is restored by UV irradiation, and A superhydrophilic-thermal management composite transparent coating composition for a solar module front glass, characterized in that the superhydrophilic network forming component further includes a water-trapping hydrophilic nanomaterial that forms a stable hydration layer through multiple hydrogen bonds upon contact with moisture, thereby forming a water-based buffer layer between the contaminant and the coating film surface to suppress direct adhesion of the contaminant, the superhydrophilic network forming component further includes a charge-retaining hydrophilic auxiliary material that forms a fixed charge on the surface to induce alignment of water molecules, thereby maintaining a continuous adsorption state of water molecules on the coating film surface, and the superhydrophilic network forming component further includes a lubricating hydrophilic auxiliary material that swells in the presence of moisture to form a low-friction hydration layer on the surface, thereby allowing the contaminant to be easily detached by washing water or rain with low shear force. Claim 2 A superhydrophilic-thermal management composite transparent coating composition for a front glass of a photovoltaic module according to claim 1, characterized in that the water-soluble resin binder comprises one or more of a vinyl acetate-ethylene copolymer (VAE), an acrylic emulsion, and a silica sol or a siloxane-based inorganic binder. Claim 3 A superhydrophilic-thermal management composite transparent coating composition for a solar module front glass, characterized in that, in claim 1, the thermal management functional inorganic particles comprise one or more of timony-doped tin oxide (ATO), indium-doped tin oxide (ITO), aluminum-doped zinc oxide (AZO), and cesium-doped tungsten oxide. Claim 4 A superhydrophilic-thermal management composite transparent coating composition for a solar module front glass, characterized in that, in claim 1, the average particle size of the thermal management functional inorganic particles is controlled to a range of 20 to 80 nm so that the haze of the coating film is maintained at 5% or less. Claim 5 delete Claim 6 delete Claim 7 A superhydrophilic-thermal management coating structure for a photovoltaic module, comprising: a thermal management functional layer formed by penetrating the surface layer of the glass substrate with the thermal management composition of claim 1 and suppressing a temperature rise caused by solar radiation by blocking near-infrared rays; and a superhydrophilic surface control layer formed by applying the superhydrophilic composition of claim 1 on the upper surface of the thermal management functional layer and allowing surface moisture to diffuse in the form of a continuous water film; wherein the thermal management functional layer is configured to suppress thermal degradation of the superhydrophilic surface control layer by reducing the heat transferred to the superhydrophilic surface control layer. Claim 8 A superhydrophilic-thermal management coating structure for a photovoltaic module, characterized in that, in claim 7, the thermal management functional layer comprises a silica-based inorganic network and is chemically bonded to a glass substrate. Claim 9 A superhydrophilic-thermal management coating structure for a photovoltaic module according to claim 7, characterized in that the superhydrophilic surface control layer maintains a contact angle of 15° or less upon contact with water. Claim 10 A method for forming a superhydrophilic-thermal management coating film on the front glass of a solar module, comprising: (a) a substrate cleaning step (S10) of cleaning and drying a glass substrate; (b) a thermal management functional layer forming step (S20) of applying the thermal management composition of claim 1 to the glass substrate to form a thermal management functional layer penetrated into the surface layer of the glass substrate; and (c) a superhydrophilic surface control layer forming step (S30) of applying the superhydrophilic composition of claim 1 to the top of the thermal management functional layer to form a superhydrophilic surface control layer. Claim 11 A method for forming a superhydrophilic-thermal-management coating film according to claim 10, wherein the functional layer forming step (S20) and the control layer forming step (S30) are performed at room temperature or at a low temperature of 120°C or lower. Claim 12 A method for forming a superhydrophilic-thermal management coating film according to claim 10, characterized in that the coating film has a thickness in the range of 50 to 500 nm.

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