KR102876111B1 - Coating film for solar cell module using organic-inorganic hybrid polymer coating composition - Google Patents

Abstract

The present invention relates to a coating film for a solar module using an organic-inorganic hybrid polymer coating composition. In one specific example, the coating film comprises a siloxane-based binder having a repeating structure represented by the following chemical formula 1; a fluorinated (meth)acrylate compound; a curing agent; and inorganic particles:
[Chemical Formula 1]

(The above chemical formula 1 is as defined in the detailed description).

Description

Coating film for solar cell module using organic-inorganic hybrid polymer coating composition

This patent application is related to the results of the project “Development of core materials for building-type solar power generation with guaranteed long-term reliability (over 25 years) and safety” (led by Sangbo Co., Ltd.; project number: 20213030010290) as part of the “New and Renewable Energy Core Technology Development Project” of the Ministry of Trade, Industry and Energy of the government of the Republic of Korea.

The present invention relates to a coating film for a solar module using an organic-inorganic hybrid polymer coating composition.

As the climate crisis intensifies, interest in clean, carbon-free energy and renewable energy sources is growing. Solar cells and their photovoltaic modules are currently the most widely used renewable energy devices.

In Korea, solar modules utilizing solar cells are rapidly spreading based on the Renewable Energy 3020 policy and implementation plan. In terms of quantity, Korea is known to rank 10th globally in terms of installed solar modules or panels. Due to Korea's limited land area, the land area available for solar panel installation is limited.

Accordingly, solar panels are being developed and installed in various forms of solar power systems, primarily for buildings, floating installations, and agricultural applications. Ground-mounted solar modules are manufactured using low-iron tempered glass on the front.

Low-iron tempered glass possesses the high transmittance and reliability required for the front surface of solar modules. However, its heavy weight hinders its widespread application in other types of solar power systems, such as buildings, telecommunications towers, and floating structures. Reducing the weight of solar modules is expected to expand their installation and distribution, as it will enable installation on previously impractical rooftops. Therefore, reducing the weight of solar modules is essential.

Research and development are underway for solar systems that utilize lightweight solar modules to replace glass, offering superior reliability and electrical output. The lighter weight of these lightweight solar systems reduces installation time and labor, thereby lowering installation costs. The higher the transmittance of a solar module's front panel material, the higher the module's electrical output.

Furthermore, to ensure normal power generation over the approximately 20-year lifespan of a solar module, it must withstand rapid outdoor temperature fluctuations (summer and winter), high UV rays, and humidity. Therefore, unreliable solar modules experience rapid output drops in harsh outdoor environments. Therefore, the front material of a solar module must ensure superior reliability, including not only transmittance but also UV stability and moisture permeability. Therefore, research and development of a plastic coating film with properties equivalent to or superior to those of the glass previously installed on the front of a solar module is required.

Background technology related to the present invention is disclosed in Korean Patent Publication No. 10-1983974 (published on September 3, 2019, title of the invention: Method for producing a polymer film and polymer film produced using the same).

One object of the present invention is to provide a coating film for solar modules having excellent light transmittance, light resistance, and moisture barrier properties.

Another object of the present invention is to provide a coating film for solar modules having excellent weather resistance, hydrophilicity, water repellency, and antifouling properties.

Another object of the present invention is to provide a coating film for solar modules having excellent scratch resistance and durability.

Another object of the present invention is to provide a coating film for solar modules that can be applied to solar cell elements or solar modules or panels at an economical cost while promoting an increase in the efficiency of solar modules.

Another object of the present invention is to provide a coating film for solar modules that can be applied to a substrate without an adhesive layer and has excellent adhesion to the substrate even when applied in a thin thickness.

Another object of the present invention is to provide a coating film for solar modules having excellent productivity and economic efficiency due to process simplification.

Another object of the present invention is to provide a solar module including the coating film for the solar module.

One aspect of the present invention relates to a coating film for a solar module using an organic-inorganic hybrid polymer coating composition. In one specific example, the coating film for a solar module is formed from an organic-inorganic hybrid polymer coating composition comprising a siloxane-based binder having a repeating structure represented by the following chemical formula 1; a fluorinated (meth)acrylate compound; a curing agent; and inorganic particles:

[Chemical Formula 1]

(In the above chemical formula 1, R ¹ , R ² and R ³ are each independently selected from a hydrogen atom, a C ₁ -C ₂₀ alkyl group, a C ₁ -C ₂₀ alkyl amino group, a vinyl group, a C ₁ -C ₂₀ alkyl vinyl group, a C ₁ -C ₂₀ alkyl (meth)acrylate group, a C ₃ -C ₂₀ alkyl (meth)acryloxy group, a C ₆ -C ₂₀ aryl group, a sulfonic acid group and a structure represented by the following chemical formula 2, wherein at least one of R ¹ , R ² and R ³ has a structure represented by the following chemical formula 2, and R ⁴ is a C ₁ -C ₂₀ alkyl group, a C ₂ -C ₂₀ alkenyl group, a C ₁ -C ₂₀ alkyl amino group, a C ₁ -C ₂₀ alkyl vinyl group, a C ₃ -C ₂₀ alkyl (meth)acrylate group, C ₃ -C ₂₀ alkyl (meth)acryloxy group, thiol group, C ₃ -C ₂₀ alkyl thiol group, glycidyloxy group, C ₁ -C ₂₀ alkyl glycidyloxy group, epoxy group, C ₁ -C ₂₀ alkyl epoxy group, C ₄ -C ₂₀ cycloalkyl epoxy group, C ₆ -C ₂₀ aryl epoxy group and C ₃ -C ₂₀ heteroaryl epoxy group, wherein m and n are each 0.1 to 0.9, and m + n = 1.

[Chemical Formula 2]

(In the above chemical formula 2, R ⁵ and R ⁶ are each independently selected from a C ₁ -C ₂₀ alkyl group, a C ₁ -C ₂₀ alkyl amino group, a hydroxy group, and a C ₁ -C ₂₀ alkoxy group, and R ⁷ is selected from a vinyl group, a C ₁ -C ₂₀ alkyl vinyl group, a C ₃ -C ₂₀ alkyl (meth)acrylate group, and a C ₃ -C ₂₀ alkyl (meth)acryloxy group, and * is a connecting portion.)

In one specific example, the organic-inorganic hybrid polymer coating composition may include 100 parts by weight of the siloxane-based binder, 1 to 30 parts by weight of a fluorinated (meth)acrylate compound, 0.1 to 15 parts by weight of a curing agent, and 2 to 40 parts by weight of inorganic particles.

In one specific example, the organic-inorganic hybrid polymer coating composition may include the fluorinated (meth)acrylate compound and inorganic particles in a weight ratio of 1:2 to 1:7.

In one specific example, the coating film may have an average surface roughness (Ra) of 0.05 to 0.25 μm.

In one specific example, the fluorinated (meth)acrylate compound may have a surface energy of 5 to 10 dyne/cm.

Another aspect of the present invention relates to a solar module comprising the coating film for the solar module. In one specific example, the solar module comprises: a solar cell element; a substrate layer formed on an upper surface of the solar cell element; and a coating film formed on an upper surface of the substrate layer.

The coating film for solar modules according to the present invention has excellent light transmittance, light resistance and moisture barrier properties, excellent weather resistance, hydrophilicity, water repellency and stain resistance, excellent scratch resistance and durability, can be applied to a substrate without an adhesive layer, and has excellent adhesion to the substrate even when applied in a thin thickness. Another object of the present invention is to provide a coating film for solar modules that has excellent productivity and economy due to process simplification, and can be applied to solar cell elements or solar modules or panels at an economical cost while promoting an increase in the efficiency of solar modules.

In addition, by applying the coating film of the present invention, the weight of the solar module can be reduced by about 65% or more compared to using glass material, and when installed on a building window, the constructability can be improved and the overall cost and load can be reduced.

In addition, the coating film of the present invention has an average light transmittance of 90% or more in the main light conversion wavelength band of a solar module, a surface hardness of 3H or more, excellent weather resistance, and a moisture permeability of 3% or less. By applying the coating composition and coating film of the present invention, a solar module that is low cost and easy to install can be realized.

Figure 1 schematically illustrates a coating film formation process according to one specific example of the present invention.
Figure 2 illustrates a solar module according to one specific example of the present invention.
Figure 3 is a graph showing the transmittance measurement of the coating films of the examples and comparative examples.
Figure 4 is a photograph showing the results of the water contact angle measurement of the example.
Figure 5 is a photograph comparing the light transmittance of the coating films of the examples and comparative examples.

In describing the present invention, if it is determined that a detailed description of a related known technology or configuration may unnecessarily obscure the gist of the present invention, the detailed description will be omitted.

And the terms described below are terms defined in consideration of their functions in the present invention, and may vary depending on the intention or custom of the user or operator, so their definitions should be made based on the contents throughout this specification explaining the present invention.

In this specification, “upper (top surface)” and “lower (bottom)” are defined based on the drawing, and depending on the viewing point, “upper (top surface)” may be changed to “lower (bottom)” and “lower (bottom)” may be changed to “upper (top)”. In addition, in this specification, “on” or “on” may include not only the area directly above, but also cases where another structure is interposed in the middle.

In this specification, (meth)acrylic may mean “acrylic” and/or “methacrylic.”

Coating film for solar modules using organic-inorganic hybrid polymer coating composition

One aspect of the present invention relates to a coating film for a solar module using an organic-inorganic hybrid polymer coating composition.

Meanwhile, ethylene tetrafluoroethylene (ETFE) or ethylene chlorofluoroethylene (ECTFE) films, used to replace the tempered glass coating on the front surfaces of solar modules, cannot be synthesized under the Korean Chemical Substances Control Act, resulting in a complete reliance on imports. Furthermore, when these materials are processed at high temperatures using vapor-phase polymerization, large amounts of fluorine can leak, potentially causing serious damage, including explosions and deaths. Furthermore, because only a fixed ratio of raw materials can be adjusted, it's difficult to alter their physical properties.

The present inventors have completed the present invention by studying a coating film that is free from the risk of explosion and allows for free processing through coating and curing fixation using a liquid formulation. The present invention relates to a coating film for a solar module comprising a cured product of a coating composition that enables easy processing, lightweighting, and cost-effectiveness, and a solar module having the coating film attached to one surface of a solar cell element.

Furthermore, replacing the front glass of solar modules requires long-term weather resistance with minimal yellowing even after long-term use. Transparency, light transmittance, and durability are also important. The present invention can achieve these objectives, and this will be described in detail.

In one specific example, the coating film can be formed by coating an organic-inorganic hybrid polymer coating composition (hereinafter, “coating composition”) on one surface of a substrate and then curing the coating composition to obtain a cured product.

Figure 1 schematically illustrates a coating film formation process according to one specific example of the present invention. Referring to Figure 1, a coating composition (120) is applied to one surface of a substrate layer (110), and cured using at least one of heat and light, thereby forming a coating film (130) composed of a cured product of the coating composition (120).

The substrate layer (110) is not particularly limited in material as long as it is a transparent plastic film. For example, the substrate layer (110) may be made of a material selected from the group consisting of polyimide, polyester, polyethylene, polyetherimide, polyethylene naphthalate, polyethersulfone, polyethylene terephthalate, polyethylene terephthalate glycol, polycarbonate, polymethyl methacrylate, polymethyl methacrylimide, polyoxymethylene polypropylene, polyphenylene ether, polyphenylene sulfide, polyphenylene sulfone, polystyrene, polyether sulfone, polysulfone, polytetrafluoroethylene, polyurethane, polyvinyl chloride, polyvinylidene fluoride, polybutylene terephthalate, epoxy resin, copolymers thereof, or combinations thereof, but is not limited thereto.

In one specific example, a uniaxially or biaxially oriented film having excellent transparency and heat resistance, as well as excellent productivity and processability, may be used as a material constituting the substrate layer (110). The thickness of the substrate layer (110) may be 10 to 1000 μm, specifically 40 to 100 μm. If the thickness of the substrate layer (110) is less than 10 μm, the processability may be reduced, and if it exceeds 1000 μm, the optical properties may be reduced, or the weight of the coating film (130) may increase.

In one specific example, the coating film for the solar module is formed from an organic-inorganic hybrid polymer coating composition comprising a siloxane-based binder having a repeating structure of the following chemical formula 1; a fluorinated (meth)acrylate compound; a curing agent; and inorganic particles.

Hereinafter, the components of the organic-inorganic hybrid polymer coating composition will be described in detail.

Siloxane binder

The above siloxane-based binder (or organic-inorganic hybrid siloxane-based copolymer) comprises a repeating structure of the following chemical formula 1:

[Chemical Formula 1]

(In the above chemical formula 1, R ¹ , R ² and R ³ are each independently selected from a hydrogen atom, a C ₁ -C ₂₀ alkyl group, a C ₁ -C ₂₀ alkyl amino group, a vinyl group, a C ₁ -C ₂₀ alkyl vinyl group, a C ₁ -C ₂₀ alkyl (meth)acrylate group, a C ₃ -C ₂₀ alkyl (meth)acryloxy group, a C ₆ -C ₂₀ aryl group, a sulfonic acid group and a structure represented by the following chemical formula 2, wherein at least one of R ¹ , R ² and R ³ has a structure represented by the following chemical formula 2, and R ⁴ is a C ₁ -C ₂₀ alkyl group, a C ₂ -C ₂₀ alkenyl group, a C ₁ -C ₂₀ alkyl amino group, a C ₁ -C ₂₀ alkyl vinyl group, a C ₃ -C ₂₀ alkyl (meth)acrylate group, C ₃ -C ₂₀ alkyl (meth)acryloxy group, thiol group, C ₃ -C ₂₀ alkyl thiol group, glycidyloxy group, C ₁ -C ₂₀ alkyl glycidyloxy group, epoxy group, C ₁ -C ₂₀ alkyl epoxy group, C ₄ -C ₂₀ cycloalkyl epoxy group, C ₆ -C ₂₀ aryl epoxy group and C ₃ -C ₂₀ heteroaryl epoxy group, wherein m and n are each 0.1 to 0.9, and m + n = 1.

[Chemical Formula 2]

(In the above chemical formula 2, R ⁵ and R ⁶ are each independently selected from a C ₁ -C ₂₀ alkyl group, a C ₁ -C ₂₀ alkyl amino group, a hydroxy group, and a C ₁ -C ₂₀ alkoxy group, and R ⁷ is selected from a vinyl group, a C ₁ -C ₂₀ alkyl vinyl group, a C ₃ -C ₂₀ alkyl (meth)acrylate group, and a C ₃ -C ₂₀ alkyl (meth)acryloxy group, and * is a connecting portion.)

In one specific example, in the chemical formula 1, R ¹ , R ² and R ³ are each independently a hydrogen atom, a C ₁ -C ₁₀ alkyl group and a moiety composed of chemical formula 2, at least one of R ¹ , R ² and R ³ is a moiety composed of chemical formula 2, and R ⁴ may be a C ₁ -C ₁₀ alkyl group, but is not limited thereto.

The above C ₂ -C ₂₀ alkenyl group may include, for example, a vinyl group.

In addition, in the above chemical formula 2, R ⁵ and R ⁶ are each independently a hydroxy group or a C ₁ -C ₁₀ alkoxy group, and R ⁷ may be a C ₃ -C ₁₀ alkyl (meth)acryloxy group, but is not limited thereto.

In one specific example, 20 to 60 mol% of the hydroxyl groups, alkoxy groups and/or aryloxy groups forming the side chains of the backbone of the inorganic hybrid siloxane copolymer having the repeating structure of Chemical Formula 1 functioning as the binder may be substituted or modified with a moiety having the structure of Chemical Formula 2 via an ether bond. In addition, the siloxane binder, which is an organic-inorganic copolymer having the repeating structure of Chemical Formula 1, may have a weight average molecular weight (Mw) of 1,000 to 10,000 g/mol, but is not limited thereto.

The constituent unit represented by the mole fraction m in the above chemical formula 1 can be derived from a silane monomer having four hydrolysable alkoxy groups.

In one specific example, the silane monomer having the four hydrolyzable functional groups may be selected from the group consisting of tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, tetrabuthoxysilane, tetraisopropoxysilane, methoxytriethoyxsilane, dimethoxydiethoxysilane, and ethoxytrimethoxysilane, but is not limited thereto.

Additionally, the constituent unit represented by the mole fraction n in the above chemical formula 1 may be derived from a silane monomer having three hydrolyzable functional groups, namely an alkoxy group. For example, the silane monomers having the three hydrolyzable functional groups are methyltriethoxysilane (MTES), ethyltriethoxysilane (ETES), n-propyltriethoxysilane (PTES), octyltriethoxysilane (OTES), vinyltrimethoxysilane (VTMS), vinyltriethoxysilane (VTES), vinyltriisopropoxysilane (VTIPS), 3-aminopropyltrimethoxysilane (APTMS), 3-aminopropyltriethoxysilane (APTES), 3-(2-Aminoethylamino)propyltrimethoxysilane (AEPTMS), (3-Acryloxypropyl)trimethoxysilane (APTMS), Methacryloxymethyltriethoxysilane (MMS), 3-Methacryloxypropyltrimethoxysilane (MPTMS), 3-Methacryloxypropyltriethoxysilane (MPTES), 3-Mercaptopropyltriethoxysilane (MPTES), 3-Isocyanatopropyltriethoxysilane (ICPTES), It may be selected from the group consisting of 2-(3,4-epoxycyclohexyl)ethyltriethoxysilane (ECETMS), 3-glycidyloxypropyltrimethoxysilane (GPTMOS), 3-glycidyloxypropyltriethoxysilane (GPTEOS), phenyltrimethoxysilane (PTES), (4-chlorophenyl)triethoxysilane (CPTES), and [3-(phenylamino)propyl]trimethoxysilane (PAPTMS), but is not limited thereto.

Meanwhile, at least one silane-based material having a moiety having a structure of Chemical Formula 2 may be condensed on at least some of the side chains constituting the backbone of the inorganic hybrid siloxane copolymer having the repeating structure of Chemical Formula 1. The silane-based material condensed on the side chain of Chemical Formula 1 may have at least one hydrolyzable functional group connected to a silicon atom, and at least one vinyl group, a C ₁ -C ₂₀ alkyl vinyl group, a C ₃ -C ₂₀ alkyl (meth)acrylate group, and/or a C ₃ -C ₂₀ alkyl (meth)acryloxy group.

For example, silane-based materials that can be condensed on at least a portion of the side chain of the backbone of an inorganic hybrid siloxane copolymer having a repeating structure of Chemical Formula 1 include vinyltrimethoxysilane (VTMS), vinyltriethoxysilane (VTES), vinyltriiosproposysilane (VTIPS), chloromethylphenylvinylsilane, (3-acryloxypropyl)trimethoxysilane (APTMS), methacryloxymethyltriethoxysilane (MMS), 3-methacryloxypropyltrimethoxysilane (PTMS), It may include, but is not limited to, 3-methacryloxypropyltriethoxysilane (MPTES).

An organic-inorganic hybrid siloxane copolymer having a repeating structure of Chemical Formula 1 can be manufactured through a polymerization reaction in which a solvent and, if necessary, a catalyst are added to the starting materials, which are silane monomers, to hydrolyze them, induce a condensation reaction, and optionally perform a hydration reaction by adding heating and hydrogen peroxide.

In one specific example, the polymerization reaction may be performed through a hydrolysis reaction and a condensation reaction by a sol-gel process at a temperature of 25 to 100°C for 2 to 24 hours, but is not limited thereto. At this time, the weight average molecular weight of the ultimately synthesized organic-inorganic hybrid siloxane copolymer can be controlled depending on the amount of polymerization solvent used and the reaction time. By performing the polymerization reaction for 2 to 24 hours, a copolymer having a repeating structure of Chemical Formula 1 and having a weight average molecular weight suitable for use as a binder in a coating composition can be prepared.

In one specific example, the polymerization solvent in which the silane-based starting material is dispersed may be any polymerization solvent capable of mediating a polymerization reaction between the starting materials. Typically, the polymerization step may be conducted in a soluble solvent capable of forming a homogeneous solution.

In one specific example, the polymerization solvent may be selected from the group consisting of aliphatic hydrocarbon solvents, ether solvents, acetate solvents, alcohol solvents, ketone solvents, amide solvents, silicone solvents, and combinations thereof. For example, the polymerization solvent may include, but is not limited to, one or more of propylene glycol monomethyl ether acetate (PGMEA), propylene glycol monomethyl ether (PGME), butyl cellosolve (BC), methyl cellosolve (MC), ethylene glycol (EG), propylene glycol (PG), N-methyl-2-pyrrolidone (NMP), dimethylacetamide (DMAc), propylene glycol diacetate (PGDA), propylene glycol normal propyl ether (PnP), tetrahydrofuran, toluene, xylene, butyl acetate, acetone, methyl ethyl ketone, methyl isobutyl ketone, methanol, ethanol, n-propanol, isopropanol, butanol, butoxyethanol, pentanol, octanol, hexane, heptane, ethers, and ketones.

In the above polymerization reaction, as long as the aforementioned starting materials can be uniformly dissolved in the polymerization solvent, the content of the polymerization solvent is not particularly limited. In one exemplary aspect, the amount of the polymerization solvent used in the polymerization reaction can be adjusted to a range of about 5 to 60 parts by weight, preferably about 20 to 50 parts by weight, based on the total content of each reactant including the polymerization solvent.

Additionally, acid catalysts and/or basic catalysts may be used to promote hydrolysis and/or condensation reactions. For example, these catalysts may be used in an aqueous solution form.

For example, the acid catalyst may include, but is not limited to, one or more of inorganic acids such as hydrochloric acid, sulfuric acid, and nitric acid; and organic acids such as toluenesulfonic acid, formic acid, acetic acid, butyric acid, palmitic acid, oxalic acid, and tartaric acid. In addition, the basic catalyst may include, but is not limited to, alkali metal hydroxides such as sodium hydroxide, lithium hydroxide, and potassium hydroxide; alkaline earth metal compounds such as barium hydroxide, barium hydroxide monohydrate, barium hydroxide octahydrate, calcium hydroxide, and magnesium hydroxide; and quaternary ammonium compounds such as tetramethylammonium hydroxide, tetramethylammonium chloride, tetraethylammonium hydroxide, tetrabutylammonium hydroxide, tetrabutylammonium fluoride, benzyltrimethylammonium hydroxide, and benzyltriethylammonium hydroxide. It may include, but is not limited to, one or more of ammonia, triethylamine, tripropylamine, n-butylamine, di-n-butylamine, tri-n-butylamine, imidazole, pyridine, 3-methylpyridine, 4-dimethylaminopyridine, N,N-diisopropylethylamine, and ammonium perchlorate.

Fluorinated (meth)acrylate compounds

The above fluorinated (meth)acrylate compound includes a fluorinated (meth)acrylate monomer and/or a fluorinated (meth)acrylate oligomer. In one specific example, the fluorinated (meth)acrylate compound may have a surface energy of 5 dyne/cm to 10 dyne/cm. As the number of carbon fluorides increases, the water contact angle of the surface may increase and the surface energy may decrease. A coating film with improved weather resistance and durability may be formed. Therefore, a coating film obtained from the coating composition according to the present invention can maximize stability even when used outdoors for a long period of time under high temperature and high humidity conditions.

In one specific example, the fluorine-based (meth)acrylate compound is trifluoroethyl (meth)acrylate (e.g., 2,2,2-trifluoroethyl (meth)acrylate), pentafluoropropyl (meth)acrylate (e.g., 2,2,3,3,3-pentafluoropropyl (meth)acrylate), tetrafluoropropyl (meth)acrylate (e.g., 2,2,3,3-tetrafluoropropyl (meth)acrylate), hexafluoroisopropyl (meth)acrylate (e.g., 1,1,1,3,3,3-hexafluoroisopropyl (meth)acrylate), hexafluorobutyl (meth)acrylate (e.g., 2,2,3,4,4,4-hexafluorobutyl (meth)acrylate), heptafluorobutyl (meth)acrylate (e.g., 2,2,3,3,4,4,4-heptafluorobutyl (meth)acrylate), octafluoropentyl (meth)acrylate, octafluoro-5-(trifluoromethyl)hexyl (meth)acrylate, dodecafluoroheptyl (meth)acrylate, trifluoro-2-(trifluoromethyl)-2-hydroxy-4-methyl-5-pentyl (meth)acrylate, tridecafluorooctyl (meth)acrylate, perfluorooctyl (meth)acrylate (e.g., 1H,1H-perfluoro-n-octyl (meth)acrylate), dodecafluoro-2-hydroxy-8-(trifluoromethyl)nonyl (meth)acrylate, hexadecafluoro-9-(trifluoromethyl)decyl (meth)acrylate, heptadecafluorodecyl (meth)acrylate, perfluorodecyl (meth)acrylate, heneicosafluorododecyl (meth)acrylate, icosafluoro-11-(trifluoromethyl)dodecyl (meth)acrylate, dodecafluoro-7-(trifluoromethyl)octyl (meth)acrylate, combinations thereof, and oligomers thereof, but is not limited thereto.

In one specific example, the fluorinated (meth)acrylate compound may be included in an amount of 1 to 30 parts by weight based on 100 parts by weight of the siloxane-based binder. When included in the above content range, the surface hardness and durability of the coating film may be prevented from deteriorating, while the water contact angle may be improved, resulting in excellent water repellency, reduced surface energy, and excellent weather resistance. For example, the compound may be included in an amount of 1 to 10 parts by weight.

hardener

The above coating composition may include at least one of a photopolymerization initiator and a thermal curing agent as a curing agent. The photopolymerization initiator may induce a photopolymerization reaction of a siloxane-based binder, a fluorine-based (meth)acrylate-based compound, etc. in the coating composition by irradiation with an appropriate light source such as ultraviolet (UV) rays.

In one specific example, the photopolymerization initiator is 1) an acetophenone-based photopolymerization initiator such as 2,2'-diethoxyacetophenone, 2,2'-dibutoxyacetophenone, 2-hydroxy-2-methylpropiophenone, p-t-butyltrichloroacetophenone, p-t-butyldichloroacetophenone, 4-chloroacetophenone, 2,2'-dichloro-4-phenoxyacetophenone, 2) benzophenone, 4,4'-dimethylaminobenzophenone, 4,4'-dichlorobenzophenone, 3,3'-dimethyl-2-methoxybenzophenone, 4-phenyl benzophenone, hydroxy benzophenone, acrylated benzophenone, 4,4'-bis(dimethylamino)benzophenone, 4,4'-bis(diethyl 3) Thioxanthone-based photopolymerization initiators such as thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, isopropyl thioxanthone, 1-[9-ethyl-6-(2-methylbenzoyl)-9H-carbazol-3-3-yl]-1-(O-acetyloxime), 2,4-diethyl thioxanthone, 2,4-diisopropyl thioxanthone, 2-chloro thioxanthone, 2-dodecyl thioxanthone, 2,4-dimethyl thioxanthone, 2,4-diethyl thioxanthone, etc. 4) Benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin Benzoin-based photopolymerization initiators such as isobutyl ether, benzyl dimethyl ketal, and methyl benzoyl formate, 5) 2,4,6-trichloro-s-triazine, 2-phenyl-4,6-bis(trichloromethyl)-s-triazine, 2,4-trichloromethyl-6-triazine, bis(trichloromethyl)-6-styryl-s-triazine, 2-4-trichloromethyl(piperonyl)-6-triazine, 2-4-trichloromethyl(4'-methoxystyryl)-6-triazine, 2-(3',4'-dimethoxystyryl)-4,6-bis(trichloromethyl)-s-triazine, 2-(4'-methoxy naphthyl)-4,6-bis(trichloromethyl)-s-triazine, 2,4-trichloromethyl-4-methylnaphthyl-6-triazine, 2-(p-methoxyphenyl)-4,6-bis(trichloromethyl)-s-triazine, 2-p-methoxystyryl-4,6-bistrichloromethyl-s-triazine, 2-piphenyl-4,6-bis(trichloromethyl)-s-triazine, 2,4-bistrichloromethyl-6-p-methoxystyryl-s-triazine, etc.; 6) At least one of photopolymerization initiators such as diphenyl-(2,4,6-trimethylbenzoyl)phosphine oxide, ethyl(2,4,6-trimethylbenzoyl)phenylphosphinate, 2,2-bis(2-chlorophenyl)-4,4,5,5-tetraphenyl-1,2-biimidazole may be included.

For example, the photopolymerization initiators sold commercially include Irgacure 369 (2-Benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone-1, hereinafter, manufactured by Ciba Specialty Chemical Co.), Irgacure 651 (2,2-Dimethoxy-1,2-diphenylethan-1-one), Irgacure 907 (2-Methyl-1-(4-methyl thio) phenyl-2-(4-morpholinyl)-1-propanone), Irgacure 819 (Bis(2,4,6-trimethylbenzoyl)-phenylphosphineoxide), Irgacure 184 (1-Hydroxy-cyclohexyl-phenyl-ketone), Irgacure 250 (Iodonium, (4-methylphenyl)[4-(2-methylpropyl) phenyl]-, hexafluorophosphate(1-)), Irgacure 127 (2-Hydroxy-1-{4-[4-(2-hydroxy-2-methyl-propionyl)-benzyl]-phenyl}-2-methyl-propan-1-one), etc.

The above-mentioned thermosetting agent may be a latent thermosetting agent that does not cure at low temperatures but cures at high temperatures. The latent thermosetting agent may include at least one of an amine-based, imidazole-based, dihydrazide-based, and organic peroxide-based thermosetting agent.

In one specific example, the curing agent may be included in an amount of 0.1 to 15 parts by weight based on 100 parts by weight of the siloxane-based binder. When included in the above range, the composition's mixability and curing reaction rate can be easily controlled, resulting in excellent curing efficiency and preventing defects such as yellowing of the coating film. For example, the curing agent may be included in an amount of 0.1 to 8 parts by weight.

inorganic particles

The above inorganic particles may be included for the purpose of increasing hardness and light transmittance. For example, the above inorganic particles may include metal or non-metal oxide particles, or metal or non-metal nitride particles.

The above-mentioned inorganic particles may be spherical, ellipsoidal, polyhedral or irregularly shaped. For example, they may be spherical.

In one specific example, the inorganic particles may have an average particle diameter (d50) of 10 nm to 1.5 μm. Under the above conditions, the optical properties of the coating film may be excellent. For example, the average particle diameter may be 15 nm to 1.0 μm.

In one specific example, the inorganic particles may include at least one of silica-based inorganic particles and polystyrene-based inorganic particles.

In one specific example, the silica-based inorganic particles may be in the form of colloidal silica, in which silica is dispersed in an organic solvent. Under the above conditions, the particles may exhibit excellent dispersibility and workability, while also improving hardness and light transmittance.

The above inorganic particles may be used by mixing two types of inorganic particles with different average particle diameters to further improve the light collection efficiency of the coating film layer.

For example, it may include first inorganic particles having an average particle diameter of 100 nm to 1.5 μm and second inorganic particles having an average particle diameter of 10 nm to 50 nm. Under the above conditions, the light collection efficiency of the coating film may be excellent.

In one specific example, the inorganic particles may be included in an amount of 2 to 40 parts by weight relative to 100 parts by weight of the siloxane-based binder. Within this content range, the coating film may exhibit excellent mechanical properties such as wear resistance, scratch resistance, and pencil hardness while preventing appearance defects and reduced flexibility. For example, the inorganic particles may be included in an amount of 10 to 35 parts by weight.

In one specific example, the organic-inorganic hybrid polymer coating composition may include the fluorinated (meth)acrylate compound and the inorganic particles in a weight ratio of 1:2 to 1:5. When included in the above weight ratio range, the coating composition has excellent mixing and dispersibility, and may simultaneously have excellent mechanical properties such as light transmittance, water repellency, and hardness. For example, it may be included in a weight ratio of 1:4 to 1:6.

additives

In one specific example, the coating composition may further comprise one or more additives selected from the group consisting of a leveling agent, a filler, and a surfactant.

In one specific example, the coating composition may further include a leveling agent to improve applicability to a substrate. The leveling agent may be a commercially available silicone-type leveling agent, a fluorine-type leveling agent, an acrylic-type leveling agent, or the like, and is not particularly limited to a specific leveling agent.

In one specific example, the leveling agent may be a nonionic surfactant such as a polyether-modified polydimethylsiloxane, a polyester-modified polydimethylsiloxane, a polyether-modified hydroxy-functional polydimethylsiloxane, a polyether-ester-modified hydroxy-functional polydimethylsiloxane, an acrylic-functional polyester-modified polydimethylsiloxane, a polyoxyethylene alkyl ether, a polyoxyethylene octylphenyl ether, a polyoxyethylene nonylphenyl ether, a polyoxyethylene alkyl allyl ether, a polyoxyethylene polyoxypropylene block copolymer, a sorbitan fatty acid ester, or a polyoxyethylene sorbitan fatty acid ester.

In one specific example, the additive may be included in an amount of 0.01 to 20 parts by weight based on 100 parts by weight of the siloxane-based binder, but is not limited thereto. For example, it may be included in an amount of 0.05 to 5 parts by weight, and for another example, it may be included in an amount of 0.1 to 1 part by weight.

For example, the leveling agent may be included in an amount of 0.01 to 20 parts by weight relative to 100 parts by weight of the siloxane-based binder, but is not limited thereto. For example, it may be included in an amount of 0.05 to 5 parts by weight, or, for another example, 0.1 to 1 part by weight. When included in the above content range, the applicability to the substrate may be excellent.

solvent

The above coating composition may further include a solvent. The solvent is not particularly limited. For example, the solvent may include one or more of propylene glycol monomethyl ether acetate (PGMEA), propylene glycol monomethyl ether (PGME), butyl cellosolve (BC), methyl cellosolbu (MC), ethylene glycol (EG), propylene glycol (PG), N-methyl-2-pyrrolidone (NMP), dimethylacetamide (DMAc), propylene glycol diacetate (PGDA), propylene glycol normal-propyl ether (PnP), tetrahydrofuran, toluene, xylene, butyl acetate, acetone, methyl ethyl ketone, methyl isobutyl ketone, methanol, ethanol, n-propanol, isopropanol, butanol, butoxyethanol, pentanol, octanol, hexane, heptane, ethers, and ketones. When used with the above solvent, the adhesion of the coating film to the substrate can be improved. For example, methyl ethyl ketone can be included.

In one specific example, the solvent may be included in an amount of 20 to 400 parts by weight based on 100 parts by weight of the siloxane-based binder. Within this content range, the durability and chemical resistance of the coating film are prevented from deteriorating, while the coating composition exhibits excellent mixing and dispersibility, and the viscosity of the composition can be easily controlled, thereby forming a coating film of uniform thickness. For example, the solvent may be included in an amount of 80 to 300 parts by weight.

Non-fluorinated (meth)acrylate compounds

In one specific example, the coating composition may further comprise a non-fluorinated (meth)acrylate compound.

The above non-fluorinated (meth)acrylate compound may include a non-fluorinated (meth)acrylate monomer and/or a non-fluorinated (meth)acrylate oligomer.

For example, the non-fluorine-based (meth)acrylate compound may include a monofunctional (meth)acrylate compound and/or a polyfunctional (meth)acrylate compound.

In one specific example, the monofunctional (meth)acrylate compound is an aliphatic (meth)acrylate compound substituted with a C _{1 to} C ₂₀ alkyl group, a C ₂ to C ₂₀ alkenyl group, a C ₂ to C ₂₀ alkynyl group, a C ₁ to C ₂₀ alkoxy group, a C ₁ to C ₂₀ alkoxyalkyl group, a C 1 to C ₂₀ alkoxyallyl group, an epoxy group, or the like; a C ₅ to C ₈ cycloalkyl (meth)acrylate compound unsubstituted or substituted with a C ₁ to C ₁₀ alkyl group, a C ₂ to C ₁₀ alkenyl group, a C ₂ to C ₁₀ alkynyl group, or a C ₁ -C ₁₀ alkoxy group; It may be selected from the group consisting of C ₅ to C ₂₀ aryl (meth)acrylate compounds which are unsubstituted or substituted with a _{C 1 to C 10} alkyl group, a C ₂ to C ₁₀ alkenyl group, a C ₂ to C ₁₀ alkynyl group, or a C ₁ to C ₁₀ alkoxy group; allyl alkoxylate compounds having a C 1 to C 20 alkoxy group; urethane (meth)acrylate compounds, and combinations thereof.

In one specific example, the C ₂ to C ₂₀ alkenyl (meth)acrylate compound may be selected from the group consisting of butadiene (meth)acrylate, hexadiene (meth)acrylate, octadiene (meth)acrylate, combinations thereof, and oligomers thereof, but is not limited thereto.

In one specific example, the C ₁ -C ₂₀ alkoxy (meth)acrylate compound may be selected from the group consisting of, but is not limited to, 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, ethylene glycol methyl ether (meth)acrylate, ethylene glycol phenyl ether (meth)acrylate, diethylene glycol methyl ether (meth)acrylate, diethylene glycol ethyl ether (meth)acrylate, 1,3-butylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, combinations thereof, and oligomers thereof.

In one specific example, the C ₁ -C ₂₀ alkoxyalkyl (meth)acrylate compound may be selected from the group consisting of, but is not limited to, 2-hydroxy-ethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, 2-hydroxy-propyl (meth)acrylate, 2-hydroxy-butyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 2-butoxyethyl (meth)acrylate, trimethoxybutyl (meth)acrylate, combinations thereof, and oligomers thereof.

In one specific example, the epoxy (meth)acrylate compound may be selected from the group consisting of epoxy (meth)acrylate, epoxycyclohexylmethyl (meth)acrylate, glycidyl (meth)acrylate, methyl glycidyl (meth)acrylate, combinations thereof, and oligomers thereof, but the present invention is not limited thereto.

In one specific example, the C ₅ -C ₈ cycloalkyl (meth)acrylate compound may be selected from the group consisting of, but is not limited to, cyclohexyl (meth)acrylate, dicyclopentanyl (meth)acrylate, isobornyl (meth)acrylate, combinations thereof, and oligomers thereof.

In one specific example, the C ₅ -C ₂₀ aryl (meth)acrylate compound may be selected from the group consisting of, but is not limited to, benzyl (meth)acrylate, phenoxyethyl (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, combinations thereof, and oligomers thereof.

In one specific example, the allyl alkoxylate compound may be selected from the group consisting of allyl propoxylate, allyl monopropoxylate, combinations thereof, and oligomers thereof, but is not limited thereto.

In one specific example, the urethane-based (meth)acrylate-based compound may be a radical polymerizable unsaturated group-containing oligomer or prepolymer obtained by reacting a polyisocyanate-based compound having a plurality of isocyanate groups with a polyol-based compound having a plurality of hydroxyl groups, and then reacting the polyisocyanate-based compound with a (meth)acrylate-based compound containing hydroxyl groups.

In one specific example, the polyisocyanate compound may be selected from the group consisting of, but is not limited to, 2,4-trylene diisocyanate and isomers thereof, diphenylmethane diisocyanate, hexamethylene diisocyanate, hydrogenated xylylene diisocyanate, isophorone diisocyanate, dicyclohexylmethane diisocyanate, naphthalene diisocyanate, triphenylmethane triisocyanate, and combinations thereof.

In one specific example, the polyol compound may be a polyhydroxy compound selected from the group consisting of polycarbonate polyols, polyester polyols, polyether polyols, polycaprolactone polyols, and combinations thereof. For example, the polyhydroxy compound can be selected from the group consisting of glycerin-ethylene oxide adduct, glycerin-propylene oxide adduct, glycerin-tetrahydrofuran adduct, glycerin-ethylene oxide-propylene oxide adduct, trimethylolpropane-ethylene oxide adduct, trimethylolpropane-propylene oxide adduct, trimethylolpropane-tetrahydrofuran adduct, trimethylolpropane-ethylene oxide-propylene oxide adduct, dipentaerythritol-ethylene oxide adduct, dipentaerythritol-propylene oxide adduct, dipentaerythritol-tetrahydrofuran adduct, dipentaerythritol-ethylene oxide-propylene oxide adduct, and combinations thereof.

In one specific example, the polyol compound may be a polyhydric alcohol. For example, the polyhydric alcohol may be selected from the group consisting of ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, polypropylene glycol, 2-methyl-1,3-propanediol, 1,3-butanediol, an adduct of bisphenol A and propylene oxide or ethylene oxide, 1,2,3,4-tetrahydroxybutane, glycerin, trimethylolpropane, 1,2-cyclohexane glycol, 1,3-cyclohexane glycol, 1,4-cyclohexane glycol, paraxylene glycol, bicyclohexyl-4,4-diol, 2,6-decarin glycol, 2,7-decarin glycol, and combinations thereof.

In one specific example, the hydroxyl group-containing (meth)acrylate compound may be selected from the group consisting of 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate, polyethylene glycol mono(meth)acrylate, polypropylene glycol mono(meth)acrylate, tris(hydroxyethyl)isocyanuric acid di(meth)acrylate, pentaerythritol tri(meth)acrylate, and combinations thereof, but is not limited thereto.

In one specific example, the multifunctional (meth)acrylate compound may be added for the purpose of improving solvent resistance, hardness, etc. For example, the multifunctional (meth)acrylate compound may be selected from the group consisting of pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol tri(meth)acrylate, dipentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, t-butylpropane tri(meth)acrylate, combinations thereof, and oligomers thereof, but is not limited thereto.

In one specific example, the non-fluorinated (meth)acrylate compound may be included in an amount of 10 to 350 parts by weight based on 100 parts by weight of the siloxane binder. When included in the above content range, the occurrence of defects such as cracks in the coating film can be prevented, while the hardness can be excellent.

The method for applying the coating composition to the substrate is not particularly limited. For example, spin coating such as the central drop spin method, roll coating, spray coating, bar coating, knife coating, casting coating, dip coating, gravure coating, slit coating using a slit nozzle such as the discharge nozzle method, or a dispensing method may be used, and the coating composition may be applied to the substrate by combining two or more methods.

In one specific example, the coating film may have an average surface roughness (Ra) of 0.05 to 0.25 μm. Under the above conditions, the surface may have excellent water-repellent properties and light transmittance.

In one specific example, a coating composition (120) applied to a substrate may be cured using a light source, such as an LED lamp, that emits light of an ultraviolet wavelength, to form a coating film on the substrate. For example, the coating film may have a thickness of 0.1 to 500 μm, but is not limited thereto.

In one specific example, the coating composition may be cured by soft baking the substrate on one surface thereof at a temperature of 70 to 100°C and/or irradiating the substrate with ultraviolet rays having an intensity of 300 to 1000 mJ/cm ² . Optionally, a drying step for evaporating a solvent included in the coating composition may be performed prior to the UV irradiation. The drying step may be performed at a lower temperature than the curing step, and by performing the drying step, a coating film may be firmly formed on the substrate.

The present invention enables the reactive functional groups of an organic/inorganic hybrid siloxane copolymer (binder) and a fluorinated (meth)acrylate compound contained in a coating composition to form cross-linking bonds through a curing process. Accordingly, a coating film comprising the cured product having a mutual network structure can be formed.

The coating film manufactured according to the present invention is manufactured through a liquid formulation, thus avoiding the risk of explosion and allowing for free processing. Furthermore, the coating film not only exhibits excellent light transmittance, hardness, and moisture resistance, but also exhibits minimal yellowing, resulting in superior weatherability. Therefore, the coating film can be utilized as a replacement material for tempered glass attached to the front surface of solar modules.

Solar modules including coating films for solar modules

Another aspect of the present invention relates to a solar module comprising the coating film for the solar module. In one specific example, the solar module (200) comprises a solar cell element (210); a substrate layer (110) formed on the upper surface of the solar cell element (210); and a coating film (130) formed on the upper surface of the substrate layer (110) and formed from the coating composition.

The above-mentioned substrate layer can be the same as that described above.

The above solar cell element can be used without limitation as one used in the art.

In one specific example, the coating film may have a thickness of 0.1 to 500 μm, for example, 1 to 10 μm.

In one specific example, the coating film may have an average light transmittance of 90% or more at a wavelength ranging from 400 nm to 1100 nm, for example, 90 to 100%.

In one specific example, the coating film may have a pencil hardness of 3H to 9H. The hardness and durability may be excellent within the above range.

In one specific example, the coating film may have a yellowing index (△YI) of less than 2% as measured according to KS M ISO 4892-3. Under the above conditions, the coating film may have excellent yellowing resistance. For example, the coating film may have a yellowing index of, for example, 0% to 1.95%.

In one specific example, the coating film may have a moisture vapor transmission rate of 3.0 g/m 2 ㆍ24 hr or less, measured under conditions of 36±2°C, 100 RH% relative humidity, and 24 hours using a test device Permatran-W 3/33 MA (Mocon, USA) in accordance with ASTM F1249 or the above standard. For example, the moisture vapor transmission rate may be 0 ^to 3.0 g/m ² ㆍ24 hr.

In one specific example, the solar cell device may have the substrate layer and the coating film sequentially formed on one surface, and an encapsulating material for sealing the solar cell device and a backsheet for protecting the encapsulating material from ultraviolet rays, etc. may be sequentially formed on the other surface of the solar cell device. For example, the encapsulating material may include an ethylene vinyl acetate (EVA)-based resin.

In one specific example, the backsheet may be manufactured by pressing a polyvinyl fluoride (PVF) adhesive layer on both sides of a polyethylene terephthalate (PET) film, or by pressing a polyethylene naphthalate (PEN) or polyvinylidene fluoride (PVDF) film with an adhesive layer.

For example, a solar module can be manufactured by forming a coating film according to the present invention on the upper surface of a substrate on one side of a solar cell element, sequentially laminating a sealant and a back sheet on the other side of the solar cell element, and then heating and pressing to form an integrated structure. The coating film of the present invention not only has excellent light transmittance, hardness, weather resistance, and moisture permeability, but also has excellent lightness due to its low weight compared to glass, and can be utilized as a material to replace glass on the front surface of a solar cell element.

In the case of a conventional structural film manufacturing process, a separate frame is required for pattern formation, whereas the present invention can form a structural film using only the coating composition.

In particular, the present invention (A) has the advantage of ease of process by enabling formation of unevenness on the film surface by applying inorganic particles rather than a complex process such as nanoimprinting, and (B) can have the effect of an invention formed by a single process of forming a single layer rather than a multilayer.

Hereinafter, the structure and operation of the present invention will be described in more detail through preferred embodiments. However, these are presented as preferred examples of the present invention and should not be construed as limiting the present invention in any way. Details not described herein are technically feasible to those skilled in the art, and therefore, their description will be omitted.

Examples and Comparative Examples

Synthesis examples 1-6

Synthesis Example 1: Synthesis of an organic-inorganic hybrid siloxane copolymer (siloxane binder)

Propylene glycol monomethyl ether acetate (101.9 g), tetraethoxysilane (0.9 mol, 189.4 g), and methyltrimethoxysilane (0.1 mol, 14.3 g) were placed in a reaction vessel and stirred at 25°C for 30 minutes. A mixed solvent of distilled water and 1 N HNO ₃ (70.3 g) was slowly added to this mixture. After the addition was complete, the reaction vessel was sealed, nitrogen gas was purged at a rate of 25 cc/min, and the reaction mixture was stirred for 30 minutes. The temperature inside the reaction vessel was increased to 30°C over approximately 10 minutes and stirred for an additional 2 hours to thoroughly mix the reaction mixture. Thereafter, the temperature inside the reaction vessel was increased to 85°C over approximately 30 minutes and stirred for an additional 2 hours to obtain a copolymer.

The reaction product including the copolymer was cooled to 60°C over about 30 minutes, and 3-methacryloxypropyltrimethoxysilane (0.5 mol, 124.7 g) was added over about 2 hours. Upon completion of the addition, the temperature was raised to 85°C over about 30 minutes and stirred for an additional 2 hours. Propylene glycol monomethyl ether acetate (101.9 g) was added again to the reactor, and the mixture was slowly cooled to room temperature while stirring again to obtain an organic-inorganic hybrid siloxane copolymer (siloxane binder) as a binder. The siloxane binder had a weight average molecular weight of 1,200 g/mol. The prepared siloxane binder solution was placed in a polypropylene container, sealed around the container, purged with nitrogen, and stored in a refrigerator.

Synthesis Example 2: Synthesis of an organic-inorganic hybrid siloxane copolymer (siloxane binder)

Tetraethoxysilane (0.5 mol, 105.2 g) and methyltrimethoxysilane (0.5 mol, 71.7 g) were added to a reaction vessel and stirred at 25°C for 30 minutes. Thereafter, an organic-inorganic hybrid siloxane copolymer (siloxane binder) was obtained in the same manner as in Synthesis Example 1. The siloxane binder had a weight average molecular weight of 2,300 g/mol. The prepared siloxane binder solution was placed in a polypropylene vessel, sealed around the vessel, purged with nitrogen, and then cooled and stored.

Synthesis Example 3: Synthesis of an organic-inorganic hybrid siloxane copolymer (siloxane binder)

Tetraethoxysilane (0.1 mol, 21.0 g) and methyltrimethoxysilane (0.9 mol, 129.1 g) were added to a reaction vessel and stirred at 25°C for 30 minutes. Thereafter, an organic-inorganic hybrid siloxane copolymer (siloxane binder) was obtained in the same manner as in Synthesis Example 1. The siloxane binder had a weight average molecular weight of 4,700 g/mol. The prepared siloxane binder solution was placed in a polypropylene vessel, sealed around the vessel, purged with nitrogen, and then cooled and stored.

Synthesis Example 4: Synthesis of an organic-inorganic hybrid siloxane copolymer (siloxane binder)

In a reaction vessel, 113.0 g of propylene glycol monomethyl ether acetate, tetraethoxysilane (0.6 mol, 126.3 g), and 3-methacryloxypropyltrimethoxysilane (0.4 mol, 99.7 g) were placed and stirred at 25°C for 30 minutes. To this mixture, a mixed solvent of distilled water and 1 N HNO ₃ (69.9 g) was slowly added. After the addition was complete, the reaction vessel was sealed, nitrogen gas was purged at a rate of 25 cc/min, and the reaction mixture was stirred for 30 minutes. The temperature inside the reaction vessel was increased to 30°C over approximately 10 minutes and stirred for an additional 2 hours to thoroughly mix the reaction mixture. Thereafter, the temperature inside the reaction vessel was increased to 85°C over approximately 30 minutes and stirred for an additional 2 hours to obtain a copolymer (siloxane-based binder). The above siloxane-based binder had a weight average molecular weight of 2,200 g/mol. The prepared siloxane-based binder solution was placed in a polypropylene container, sealed, purged with nitrogen, and then stored in a refrigerator.

Synthesis Example 5: Synthesis of an organic-inorganic hybrid siloxane copolymer (siloxane binder)

Propylene glycol monomethyl ether acetate (93.3 g), tetraethoxysilane (0.6 mol, 126.3 g), and vinyltrimethoxysilane (0.4 mol, 60.5 g) were placed in a reaction vessel and stirred at 25°C for 30 minutes. A mixed solvent of distilled water and 1 N HNO ₃ (69.9 g) was slowly added to this mixture. After the addition was complete, the reaction vessel was sealed, nitrogen gas was purged at a rate of 25 cc/min, and the reaction mixture was stirred for 30 minutes. The temperature inside the reaction vessel was increased to 30°C over approximately 10 minutes and stirred for an additional 2 hours to thoroughly mix the reaction mixture. Thereafter, the temperature inside the reaction vessel was increased to 85°C over approximately 30 minutes and stirred for an additional 2 hours to obtain a copolymer (siloxane-based binder). The above siloxane-based binder had a weight average molecular weight of 2,100 g/mol. The prepared siloxane-based binder solution was placed in a polypropylene container, sealed, purged with nitrogen, and then stored in a refrigerator.

Synthesis Example 6: Synthesis of an organic-inorganic hybrid siloxane copolymer (siloxane binder)

Propylene glycol monomethyl ether acetate (91.8 g), tetraethoxysilane (0.6 mol, 126.2 g), and methyltrimethoxysilane (0.4 mol, 57.4 g) were placed in a reaction vessel and stirred at 25°C for 30 minutes. A mixed solvent of distilled water and 1 N HNO ₃ (66.3 g) was slowly added to this mixture. After the addition was complete, the reaction vessel was sealed, nitrogen gas was purged at a rate of 25 cc/min, and the reaction mixture was stirred for 30 minutes. The temperature inside the reaction vessel was increased to 30°C over approximately 10 minutes and stirred for an additional 2 hours to thoroughly mix the reaction mixture. Thereafter, the temperature inside the reaction vessel was increased to 85°C over approximately 30 minutes and stirred for an additional 2 hours to obtain a copolymer.

The reaction product including the above copolymer was cooled to 60°C over about 30 minutes, and vinyltrimethoxysilane (0.4 mol, 60.5) g was added over about 2 hours. Upon completion of the addition, the temperature was raised to 85°C over about 30 minutes and stirred for an additional 2 hours. Propylene glycol monomethyl ether acetate (91.8 g) was added again to the reactor, and the mixture was slowly cooled to room temperature while stirring again to obtain an organic-inorganic hybrid siloxane copolymer (siloxane binder) as a binder. The siloxane binder had a weight average molecular weight of 2,000 g/mol. The prepared siloxane binder solution was placed in a polypropylene container, sealed around the container, purged with nitrogen, and stored in a refrigerator.

Examples and Comparative Examples

The components used in the above examples and comparative examples are as follows.

(A) Siloxane monomer: The siloxane monomer prepared in the above synthesis examples 1 to 6 was used.

(B) Fluorinated (meth)acrylate compounds: (B-1) 2,2,2-trifluoroethyl methacrylate (manufactured by Sigma) was used. (B-2) 2,2,3,3,3-pentafluorobutyl methacrylate (manufactured by Sigma) was used. (B-3) 2,2,3,3,4,4,4-heptafluorobutyl methacrylate (manufactured by Sigma) was used.

(C) Curing agent: Irgacure 184 (manufactured by JM Tech) was used as a photopolymerization initiator.

(D) Inorganic particles: Polystyrene beads (PS/polystyrene, manufactured by Sigma) with an average particle diameter of 50 nm to 1 μm were used.

(E) Additive: BYK307 (manufactured by BYK) was used as a leveling agent.

(F) Solvent: Methyl ethyl ketone (manufactured by Daejung Chemical) was used.

Examples 1 to 12 and Comparative Examples 1 to 2

Manufacturing of coating film: A coating composition containing the ingredients and contents as shown in Table 1 above was stirred for 30 minutes, and applied to one surface of a primer-treated plastic (PET) substrate (substrate layer) using a Meyer bar to a thickness of 1 to 50 μm. Then, the coating composition was cured by exposing it to a light source of 500 mJ/cm2 at 80°C for 1 minute, thereby manufacturing a coating film having a surface roughness (Ra, arithmetic mean roughness) of 0.05 to 0.15 μm and a thickness of 5 (±0.5) μm.

Meanwhile, in Table 1, Comparative Example 2 is a coating film manufactured in the same manner as Example 1, except that 100 parts by weight of acrylate monomer (M3, manufactured by Miwon Corporation) was used instead of the siloxane binder (A) manufactured in the manufacturing example.

Comparative Example 3

Only a primer-treated transparent plastic substrate (50㎛ thick) was applied.

Comparative Example 4

Low-iron glass (iron content less than 0.02 wt%) was applied for the solar front.

Experimental example

(1) Light transmittance: The relative total light transmittance (Total Transmittance) of the coating films of the above examples and comparative examples was measured, and the results are shown in Table 2 below. At this time, the total light transmittance was measured for Examples 1 to 4 and Comparative Example 3, each of which formed an anti-reflection (AR) layer, and the results are shown in Figure 3 below.

(2) Hardness: For the coating films of the above examples and comparative examples, the pencil hardness was measured for a load of 500 g using a pencil hardness tester according to the PET standard method (pencil hardness measurement method), and the results are shown in Table 2 below.

(3) Measurement of contamination resistance (water contact angle): The water contact angle was measured for the coating films of the above examples and comparative examples using a contact angle measuring device, and the results are shown in Table 2 below.

(4) Measurement of yellowing degree: In order to evaluate the resistance to ultraviolet (UV) rays for the coating films of the above examples and comparative examples, the yellowing degree, which is the rate of change in yellowness (△YI), was measured in accordance with the KS M ISO 4892-3 standard, and the results are shown in Table 2 below.

(5) Haze value measurement: The Haze value of the coating films of the above examples and comparative examples was measured using a measuring device (Spectrophotometer, CM-5 (KONICA MINOLTA, INC.)), and the results are shown in Table 2 below.

(6) Water vapor transmission ratio (WVTR, g/m ² ㆍ24 hr): The water vapor transmission rate (WVTR) of the coating films of the examples and comparative examples was measured using a moisture vapor transmission rate measuring device (OX-TRAN 2/21MD) of MOCON. The examples and comparative examples were cut to a size of 100 mm x 100 mm, and measured by inserting them into a jig with a hole in the center. The measurement was performed for 24 hours under conditions of 36℃ and 100%RH. If the WVTR is 3.0 g/m ² ㆍ24 hr or less, it was evaluated as good (indicated by ○ in Table 2), and if the WVRT exceeds 3.0 g/m ² ㆍ24 hr, it was evaluated as poor (indicated by X in Table 2).

Fig. 3 is a graph showing the transmittance measurement of the coating films of Examples and Comparative Examples. In Fig. 3, the graphs are each measured when an anti-reflection layer (AR) is formed on the surface of the coating film (Comparative Example 3 and Examples 1 to 4) and when an anti-reflection layer is not formed (Comparative Example 3 and Example 1). In addition, Fig. 4 is a photograph showing the results of the water contact angle measurement of Example 3, and Fig. 5 is a photograph comparing the light transmittance of the coating films of Comparative Example 3, Examples 3, and Examples 12.

Referring to the results of FIGS. 3 to 5 and Table 2, the surface energy of the coating film manufactured in Comparative Example 1 without adding a fluorinated acrylate compound increased, resulting in a decrease in the water contact angle. It was found that the coating film manufactured in Comparative Example 2 without adding the siloxane-based binder of the present invention was difficult to adhere to a substrate, and thus was not suitable as a coating film. In particular, it was found that through Examples 1 to 4, as the content of the inorganic component increased, the transmittance of the coating film increased by 1 to 3% compared to Comparative Example 3, and the degree of yellowing decreased. In addition, in the case of the coating films manufactured in Examples 1 to 12, it was found that as the content of the fluorinated acrylate compound increased or the number of fluorine substituents increased, the water contact angle of the coating film improved, and the light transmittance improved due to the refractive index decreasing depending on the electronegativity of the fluorine group. In addition, when examples using polymer binders having different weight average molecular weights were compared, it was found that although the polymer binder having a weight average molecular weight of about 2,300 g/mol had excellent hardness, sufficient hardness was secured even when using polymer binders having different weight average molecular weights.

In addition, it was confirmed that Examples 1 to 12, compared to the coating films manufactured in Comparative Examples 1 and 2, not only had superior pencil hardness, water repellency, and yellowing degree, but also had excellent light transmittance and moisture permeability overall. In addition, compared to the coating film manufactured in Comparative Example 4, it was confirmed that the weight of the solar module could be reduced by more than 65%, and that it exhibited equivalent effects such as long-term weather resistance evaluation and light transmittance, and thus it was confirmed that it could be applied to replace the front glass of the solar module.

The present invention has been described above, focusing on specific embodiments. Those skilled in the art will appreciate that the present invention can be implemented in modified forms without departing from its essential characteristics. Therefore, the disclosed embodiments should be considered illustrative rather than limiting. The scope of the present invention is set forth in the claims, not the foregoing description, and all differences within the scope equivalent thereto should be construed as being encompassed by the present invention.

110: Substrate layer 120: Coating composition
130: Coating film 200: Solar module
210: Solar cell element

Claims (6)

A siloxane-based binder comprising a repeating structure of the following chemical formula 1;
Fluorinated (meth)acrylate compounds;
hardener; and
A coating film formed from an organic-inorganic hybrid polymer coating composition comprising inorganic particles;
[Chemical Formula 1]

(In the above chemical formula 1, R ¹ , R ² and R ³ are each independently selected from a hydrogen atom, a C ₁ -C ₂₀ alkyl group and a structure of the following chemical formula 2, wherein at least one of R ¹ , R ² and R ³ has a structure of the following chemical formula 2,
The above R ⁴ is selected from a C ₁ -C ₂₀ alkyl group, a vinyl group, a C ₁ -C ₂₀ alkyl vinyl group, a C ₃ -C ₂₀ alkyl (meth)acrylate group, and a C ₃ -C ₂₀ alkyl (meth)acryloxy group,
The above m and n are each 0.1 to 0.9, and the above m + n = 1.
[Chemical Formula 2]

(In the above chemical formula 2, R ⁵ and R ⁶ are each independently selected from a C ₁ -C ₂₀ alkyl group, a hydroxy group, and a C ₁ -C ₂₀ alkoxy group,
The above R ⁷ is selected from a vinyl group, a C ₁ -C ₂₀ alkyl vinyl group, a C ₃ -C ₂₀ alkyl (meth)acrylate group, and a C ₃ -C ₂₀ alkyl (meth)acryloxy group, and the * is a connecting moiety.
In the first paragraph, the organic-inorganic hybrid polymer coating composition is a coating film comprising 100 parts by weight of the siloxane-based binder, 1 to 30 parts by weight of a fluorinated (meth)acrylate compound, 0.1 to 15 parts by weight of a curing agent, and 2 to 40 parts by weight of inorganic particles.
In the second paragraph, the organic-inorganic hybrid polymer coating composition is a coating film comprising the fluorine-based (meth)acrylate compound and inorganic particles in a weight ratio of 1:2 to 1:7.
In the first paragraph, the coating film is a coating film having an average surface roughness (Ra) of 0.05 to 0.25 ㎛.
In the first paragraph, the fluorine-based (meth)acrylate compound is a coating film having a surface energy of 5 to 10 dyne/cm.
solar cell device;
A substrate layer formed on the upper surface of the solar cell element; and
A solar module comprising a coating film formed on the upper surface of the substrate layer and according to any one of claims 1 to 5.