KR102577243B1 - Composite plastic film for replacing the front glass of a thin film solar module - Google Patents

Abstract

The present invention relates to a composite plastic film that replaces the front glass of a thin film solar module and a thin film solar module using the same. Specifically, the present invention relates to a composite plastic film that has excellent weather resistance and transmittance, can replace front glass, can provide thin film solar modules, and can reduce the weight of the solar module by more than 30%.

Description

Composite plastic film for replacing the front glass of a thin film solar module}

The present invention relates to a composite plastic film that replaces the front glass of a thin film solar module. Specifically, the present invention relates to a composite plastic film that has excellent weather resistance and transmittance, can replace front glass, can provide thin film solar modules, and can reduce the weight of the solar module by more than 30%.

Solar cells for solar power generation start from silicon or various compounds and can generate electricity once they are in the form of solar cells. However, since one cell does not provide sufficient output, each cell must be connected in series or parallel, and this connection is called a 'solar module'.

A solar module is composed of a front glass, a first sealant, a solar cell, a second sealant, and a back sheet. Ethylene vinyl acetate (EVA), etc. are used as the first and second sealing materials.

Recently, there have been many attempts to replace the glass used on the front of solar modules or to develop a use that replaces glass in buildings in order to achieve weight reduction and economic efficiency.

Among these attempts, many efforts have been made to replace glass using fluoropolymer (ETFE) films, but since fluoropolymer is expensive and has inherent limitations that prevent it from being widely used, research is underway to replace it with other lightweight materials.

Among these attempts, efforts were made to use polyester, specifically PET (polyethylene terephthalate), which is transparent, has high permeability, and has sufficient mechanical strength. However, PET film or sheet alone has limitations due to elongation retention, heat resistance, and yellowing phenomenon. It could not be practically replaced.

In particular, in order to replace the front glass of a solar module or the glass window of a building, long-term weather resistance is required with minimal yellowing even after long-term use, and transparency, transmittance, and durability are very important. We provide a film that satisfies all of these properties. There were limits to this.

Korean Patent Publication No. 10-2009-0045474 (2009.05.08) states that even when the sunlight incident on the solar module is not vertical, the sunlight incident on the surface of the solar cell is always transmitted regardless of changes in inclination angle and azimuth. We are launching an “optical sheet-attached solar module” to improve the power generation output efficiency of solar modules by making them vertical. The patent is a configuration of inserting an optical sheet or optical film designed between a solar cell and an encapsulant, and the optical sheet or optical film is provided with a vertical and horizontal prism sheet on the solar cell, and is provided on the prism sheet. It is configured to include a diffusion sheet. However, this use of multiple layers is not suitable for the trend of thinning solar cell modules due to the overall thickness of the solar cell module being thick. Additionally, there is a limit to achieving weight reduction due to the use of glass due to the configuration using tempered glass on the front. there is.

Korean Patent Publication No. 10-2009-0045474 (2009.05.08)

The purpose of the present disclosure is to reduce production costs and significantly reduce the weight of the solar module by replacing the front glass of the solar module with a plastic film.

In addition, we aim to provide a new composite plastic film with excellent weather resistance, less yellowing, and excellent durability even after long-term use, so that the front glass of solar modules can be replaced with a plastic film.

In addition, the purpose of the present invention is to provide a new composite plastic film that has light transmittance equivalent to or superior to that of existing glass and a solar cell employing the same.

One aspect of the present invention is a composite plastic film for replacing the front glass of a thin film solar cell,

A polyester base film facing the encapsulation material of the solar module; and

At least one light capture layer formed on the polyester base film and selected from a patterning layer and a mat coating layer;

Includes,

The polyester base film provides a composite plastic film containing a UV blocker that blocks UVA and UVB.

The composite plastic film according to one aspect of the present invention has excellent long-term weather resistance and high UV transmittance, so it can be applied to various fields as a replacement for glass.

Specifically, the composite plastic film according to one aspect of the present invention has a lower density than the glass used as the front glass in conventional solar modules, and by replacing it with the front glass, the weight of the transmissive amorphous thin film solar cell is reduced by about 30% or more. The degree can be reduced, and especially when installed in the windows of a building, the thickness can be thickened or the thickness of the glass can be thinned, and when used by laminating with the composite sheet of the present invention, constructability can be increased and costs and loads can be reduced. Also, problems such as damage can be minimized.

The composite plastic film according to one aspect of the present invention has a transmittance of 80% or more, and even better, 90% or more at 550 nm, but has almost no transmittance at short wavelengths. Specifically, for example, it has a transmittance of 50% or less at 400 nm, In terms of weather resistance, we can provide a film that satisfies △YI 5 or less after UVA 15kw/square irradiation, and MD elongation retention rate of 50% or more after 50 hours of PCT ((Pressure Cooker Test, 121℃, 1.4 atm, RH100%) treatment in durability. there is.

Hereinafter, the present invention will be described in more detail through specific examples or examples including the attached drawings. However, the following specific examples or examples are only a reference for explaining the present invention in detail, and the present invention is not limited thereto, and may be implemented in various forms.

Additionally, unless otherwise defined, all technical and scientific terms have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention pertains. The terminology used in the description herein is merely to effectively describe specific embodiments and is not intended to limit the invention.

Additionally, as used in the specification and the appended claims, the singular forms “a,” “an,” and “the” are intended to also include the plural forms, unless the context clearly dictates otherwise.

One aspect of the present invention is a composite plastic film for replacing the front glass of a thin film solar cell,

A polyester base film facing the encapsulation material of the solar module; and

At least one light capture layer formed on the polyester base film and selected from a patterning layer and a mat coating layer;

Includes,

The polyester base film provides a composite plastic film containing a UV blocker that blocks UVA and UVB.

In one aspect of the present invention, the composite plastic film includes a first in-line coating layer on one side of the polyester base film to improve adhesion to the encapsulant, and a second in-line coating layer to improve adhesion to the light capture layer on the other side. It may further include an in-line coating layer.

In one aspect of the present invention, the polyester base film may be made of a polyester resin having an intrinsic viscosity of 0.7 to 1.0 dL/g.

In one aspect of the present invention, the polyester base film has a thickness of 50 to 350 ㎛, a UV transmittance of 30% or less at 400 nm, a UV transmittance of 85% or more at 550 nm, a total light transmittance of 80% to 90%, and a haze. may be 2% or less, the b* value obtained from the CIE1976L*a*b* color system may be 10 or less, and the yellowness may be 15 or less.

In one aspect of the present invention, the composite plastic film has a total thickness of 50 to 500 ㎛, a UV transmittance of 30% or less at 400 nm, a UV transmittance of 85% or more at 550 nm, a total light transmittance of 90% to 99%, and a haze. is more than 80%, the b* value obtained from the CIE1976L*a*b* color system is 20 or less, the yellowness is 20 or less, and the elongation and elongation retention rate in the machine direction before and after 50 hours of PCT (121℃, 1.4 atm, RH100%) treatment. This may be more than 50%.

In one aspect of the present invention, the polyester base film may contain 0.5 to 5% by weight of a UV blocker that blocks UVA and UVB.

In one aspect of the present invention, the UV blocker may be used by mixing a polyoxyalkylene-based compound and a benzoxazine-based compound.

In one aspect of the present invention, the patterning layer is made of polymer resin and includes a light-collecting protrusion, and the light-collecting protrusion may have a hemispherical or hexagonal array lens structure.

In one aspect of the present invention, the light-collecting protrusion may have a diameter of 20 to 30 ㎛ and a height of 10 to 15 ㎛.

In one aspect of the present invention, the mat coating layer includes a polymer resin and organic particles, and the organic particles include methyl methacrylate, ethyl methacrylate, isobutyl methacrylate, normal butyl methacrylate, and normal butyl methyl methacrylate. Crylate, acrylic acid, methacrylic acid, hydroxyethyl methacrylate, hydroxypropyl methacrylate, hydroxyethyl acrylate, acrylamide, methyl acrylamide, glycidyl methacrylate, ethyl acrylate, isobutyl Beads and silicone-based spherical particles made of homopolymers, copolymers, or terpolymers of monomers selected from acrylate, normal butylacrylate, and 2-ethylhexyl acrylate, polyethylene, polystyrene, polypropylene, and copolymers of acrylic and olefin. It may be any one or two or more organic particles selected from the group consisting of.

In one aspect of the present invention, the organic particles may have an average particle diameter of 1 to 50 ㎛.

In one aspect of the present invention, the polyester base film may be made of polyethylene terephthalate resin.

By manufacturing the composite plastic film as described above, the inventors of the present invention have excellent long-term weather resistance and durability enough to replace the glass placed on the front of a thin film solar module, and have excellent light transmittance to improve the efficiency of the solar module. The present invention was completed by discovering that it could be done.

More specifically, the inventors of the present invention studied to replace glass and use it as a front sheet of solar modules for a long period of time. As a result, when used as a polyester film, it has the advantage of being lighter in weight and transparent compared to glass, but is exposed to sunlight for a long period of time. Accordingly, it was confirmed that there was a problem of deterioration of long-term weather resistance, such as yellowing due to aging. Accordingly, research was conducted to improve this long-term weather resistance to maintain a lifespan of more than 10 years even when exposed to ultraviolet rays. As a result, the UV transmittance was less than 30% at 400 nm, the UV transmittance was more than 85% at 550 nm, and the total light transmittance was 90% ~ 99%, haze is 80% or more, b* value obtained from CIE1976L*a*b* color system is 20 or less, yellowness is 20 or less, PCT (121℃, 1.4 atm, RH100%) treatment for 50 hours It was discovered that replacement is possible within the range that satisfies all physical properties such as pre- and post-machine direction elongation and elongation retention rate of 50% or more. Accordingly, a composite plastic film with a specific laminated structure that satisfies all of these properties was developed.

In other words, the composite plastic film of the present invention not only has long-term weather resistance, but also improves light transmittance despite having long-term weather resistance, so that the efficiency of solar modules can be shown to be equivalent to that of existing glass. In addition, it is lightweight and relatively cheaper than fluoropolymer, so productivity can be further improved.

Hereinafter, the configuration of the present invention will be described in more detail.

Specifically, the first aspect of the composite plastic film includes a polyester base film facing the encapsulation material of the solar module; and at least one light capture layer formed on the polyester base film and selected from a patterning layer and a mat coating layer.

The second aspect of the composite plastic film includes a first in-line coating layer to improve adhesion to an encapsulant; A polyester base film facing the encapsulation material of the solar module; a second in-line coating layer to improve adhesion to the light trapping layer; And it may include at least one light trapping layer selected from the patterning layer and the mat coating layer.

The first and second aspects are intended to specifically illustrate the composite plastic film according to one aspect of the present invention, but are not limited thereto.

[Polyester base film]

In one aspect of the present invention, it is desirable for the polyester base film to prevent aging and deterioration, and to this end, it may contain a polyester resin and a UV blocker that blocks UVA and UVB. More specifically, from the viewpoint of developing long-term weather resistance, it is desirable to use a UV blocker that can block both short-wavelength ultraviolet rays of UVA (320-400 nm) and UVB (280-320 nm). More specifically, it is desirable to use a UV blocker that can ensure that the UV transmittance at 400 nm is 50% or less, more specifically 30% or less, and even more specifically 1 to 30%.

In addition, as described above, it is desirable to provide a film with high transmittance by blocking short wavelengths as much as possible while well transmitting long wavelengths exceeding 400 nm in order to improve the efficiency of solar modules. Therefore, it is desirable to satisfy the physical properties of UV transmittance of 85% or more at 550 nm, total light transmittance of 80% to 90%, and haze of 2% or less.

In addition, from the viewpoint of long-term weather resistance, the b* value obtained from the CIE1976L*a*b* colorimetric system is 10 or less, the yellowness is 15 or less, and the machine direction elongation before and after 50 hours of PCT (121℃, 1.4 atm, RH100%) treatment. It is desirable to satisfy all physical properties with an elongation retention rate of 50% or more.

By satisfying all of the above physical properties, it is possible to provide a composite plastic film that has excellent long-term weather resistance and, more specifically, can be used for more than 10 years as a replacement for the front glass of a solar module.

Any UV blocker that can satisfy all of the above physical properties can be used without limitation. Specifically, for example, benzophenone-based compounds, benzotriazole-based compounds, benzooxazinone-based compounds, benzoate-based compounds, phenyl salicylate-based compounds, polyoxyalkylene-based compounds, benzoxazine-based compounds, and hindered amine-based compounds. It may include any one or two or more selected from the group consisting of, but is not limited thereto.

More specifically, it may be a mixture of a polyoxyalkylene-based compound and a benzoxazine-based compound, and their mixing ratio may be 2 to 8:8 to 2 weight ratio, specifically 3 to 6:6 to 3 weight ratio, and the above physical properties It can be used by adjusting it to satisfy, so it is not limited to this. As a commercialized example, a film that satisfies all of the above physical properties can be provided by using a mixture of Solvay's CYASORB UV-3638F and Millken's ClearShield 390B.

The content of the UV blocker can be used without limitation as long as it satisfies all of the above physical properties. Specifically, for example, 0.1 to 10% by weight, specifically 0.5 to 5% by weight, of the content of the polyester base film, More specifically, 0.8 to 3% by weight may be used.

The UV blocker is preferably added when manufacturing a polyester base film, and more preferably, the dispersibility of the UV blocker can be improved by preparing a compounding chip containing a UV blocker, mixing it with a polyester chip, and melt-extruding the film to produce the film. can be made even better.

The polyester base film is preferably made of polyester resin with an intrinsic viscosity of 0.7 to 1.0 dL/g, and has excellent durability and weather resistance within the above range, so it can be used for a long period of time when applied to solar modules.

In addition, after 50 hours of PCT (121℃, 1.4 atm, RH100%), it is recommended that the elongation retention rate in the machine direction is 50% or more, specifically 50 to 80%, preferably 60 to 80%, and if it is less than 50%, Physical properties deteriorate rapidly over time, which can reduce long-term weather resistance.

In addition, the polyester base film may have a thickness of 50 to 350 ㎛, more specifically 150 to 300 ㎛, and is suitable for use as a thin film solar module backsheet at this thickness, but is not limited thereto.

In one aspect of the present invention, the polyester resin can be used without limitation as long as it is commonly used in the production of polyester films, and specifically, for example, polyethylene terephthalate, polyethylene phthalate, polybutylene naphthalate, etc. It can be used, but is not limited to this.

The polyester resin is a general term for polymers in which the monomer residue, which is the main bond in the main chain, and the covalent bond connecting the monomer residues are ester bonds. Usually, it is a dicarboxylic acid compound, a dihydroxy compound, or a dicarboxylic acid ester derivative and a dihydride. It can be obtained by condensation polymerization of a hydroxy compound.

Here, dicarboxylic acid compounds include, for example, terephthalic acid, 2,6-naphthalenedicarboxylic acid, isophthalic acid, diphenyldicarboxylic acid, diphenylsulfonedicarboxylic acid, diphenoxyethanedicarboxylic acid, 5- Aromatic dicarboxylic acids such as sodium sulfoisophthalic acid and phthalic acid, aliphatic dicarboxylic acids such as oxalic acid, succinic acid, adipic acid, sebacic acid, dimer acid, maleic acid, and fumaric acid, alicyclic dicarboxylic acids such as cyclohexane dicarboxylic acid, Oxycarboxylic acids such as paraoxybenzoic acid, etc. can be mentioned. In addition, dicarboxylic acid ester derivatives include esterified products of the above dicarboxylic acid compounds, such as dimethyl terephthalate, diethyl terephthalate, 2-hydroxyethylmethyl terephthalate, 2,6-naphthalenedicarboxylic acid dimethyl, and isophthalic acid. Examples include dimethyl, dimethyl adipate, dimethyl maleate, and dimethyl dimer acid.

Examples of the hydroxy compounds include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6 -Aliphatic hydroxy compounds such as hexanediol and neopentyl glycol, polyoxyalkylene glycols such as diethylene glycol, polyethylene glycol, polypropylene glycol, and polytetramethylene glycol, and alicyclic dimethyl compounds such as 1,4-cyclohexanedimethanol. and aromatic dihydroxy compounds such as hydroxy compounds, bisphenol A, and bisphenol S.

Among these, terephthalic acid, 2,6-naphthalenedicarboxylic acid, isophthalic acid, etc. can be preferably used as dicarboxylic acid compounds, and neopentyl glycol, ethylene glycol, 1,3-propanediol, 1, 4-Butanediol, polytetramethylene glycol, 1,4-cyclohexanedimethanol, etc. can be preferably used.

Among these, it is particularly preferable to use polyethylene terephthalate (PET), which consists of terephthalic acid or dimethyl terephthalate and ethylene glycol.

In one aspect of the present invention, the polyester base film having excellent hydrolysis resistance may be used, or a film having excellent hydrolysis resistance may be manufactured and used, or a commercially available product may be used. For example, the polyester film with excellent hydrolysis resistance can be used with a low content of oligomers generated during condensation polymerization. In addition, heat treatment to improve the known hydrolysis resistance can be additionally applied to the polyester film to reduce the moisture content of the polyester and reduce the shrinkage rate, thereby further improving the hydrolysis resistance.

More preferably, the intrinsic viscosity of the polyester resin used in manufacturing the compounding chip of polyester resin and UV blocker is preferably 0.80 to 1.40 dl/g, and the polyester resin used with the compounding chip in manufacturing the base film The intrinsic viscosity of the ester resin is preferably 0.63 to 0.90 dl/g. When manufacturing compounding chips, if the intrinsic viscosity of the polyester resin used is less than 0.80 dl/g, processability may be reduced due to a decrease in the viscosity of the compounding chip during film manufacturing, durability may be weakened, and durability may be weakened during film manufacturing. If the intrinsic viscosity of the resin is less than 0.63 dl/g, the viscosity decreases as the shear stress during processing decreases due to the low intrinsic viscosity, and although processability improves, improvements in durability and weather resistance cannot be expected, and 0.90 dl/g If it exceeds the existing polyethylene terephthalate resin production expectations, productivity may deteriorate due to high discharge pressure during manufacturing and breakage during stretching.

In one aspect of the present invention, the polyester base film has a thickness of 50 to 350 ㎛, a UV transmittance of 30% or less at 400 nm, a UV transmittance of 85% or more at 550 nm, a total light transmittance of 80% to 90%, and a haze. is less than 2%, and satisfies all physical properties such as a b* value of 10 or less and a yellowness of 15 or less obtained from the CIE1976L*a*b* colorimetric system, thereby providing a solar module with excellent long-term weather resistance and efficiency. .

As explained above, the polyester base film has excellent long-term weather resistance and is transparent, so it can be used as a replacement for existing front glass. However, when applied as is to solar modules, it has low total light transmittance and low light collection efficiency, making it difficult to use the solar module. Efficiency may decrease. Therefore, by providing a light blocking layer on the polyester film as shown below, light collection efficiency is increased and light transmittance is increased to improve the efficiency of the solar module.

[Light capture layer]

The composite plastic film according to one aspect of the present invention includes at least one light trapping layer selected from a patterning layer and a mat coating layer on the polyester film in order to further improve light collection efficiency and total light transmittance. .

As described above, for long-term weather resistance, the total light transmittance may be somewhat lowered as a UV blocker is included to block UVA and UVB so that the UV transmittance at 400 nm is 30% or less. Accordingly, from the viewpoint of further improving light collection and transmission efficiency while being stable to ultraviolet rays, it includes at least one light trapping layer selected from the patterning layer and the mat coating layer.

Specifically, by providing the light trapping layer, the composite plastic film has a total thickness of 50 to 500 ㎛, a UV transmittance of 30% or less at 400 nm, a UV transmittance of 85% or more at 550 nm, and a total light transmittance of 90% to 99%. %, haze is 80% or more, b* value obtained from CIE1976L*a*b* color system is 20 or less, yellowness is 20 or less, and machine direction before and after 50 hours of PCT (121℃, 1.4 atm, RH100%) treatment. This may be to satisfy all physical properties with an elongation retention rate of 50% or more. Within the range that satisfies all of the above ranges, all physical properties including long-term weather resistance, durability, and solar module efficiency can be satisfied.

The patterning layer is made of polymer resin and includes light-collecting protrusions, and the light-collecting protrusions may have a hemispherical or hexagonal array lens structure.

In one aspect of the present invention, the patterning layer is a pattern layer having irregularities that increase light scattering and improve light absorption, and may have various types of patterns by embossing, or may be a coating layer containing light scattering particles. The pattern layer having an uneven pattern on the surface without light scattering particles is mainly a method of obtaining a transparent synthetic resin film. For example, in the case of thermoplastic synthetic resin, a method of providing an uneven pattern on the surface of the extruded synthetic resin at the same time as extrusion is used. there is. Additionally, the method of forming an uneven pattern on a synthetic resin layer using this method using a substrate includes the so-called polysand method and the embossing cooling roll method. The polysand method is a method in which a synthetic resin is extruded into a film form between a shaping sheet having an uneven pattern in advance and a base material, and then after cooling, the shaping sheet is peeled off and the uneven pattern of the shaping sheet is transferred to the synthetic resin film. In the embossing cooling roll method, synthetic resin is extruded between a base material and an embossing cooling roll using an embossing cooling roll and a press roll provided with an uneven pattern, and is pressed between the embossing cooling roll and a press roll to transfer the uneven pattern of the embossing cooling roll to the synthetic resin film. This is the way to do it.

On the other hand, when using a thermosetting synthetic resin, one method is to apply the thermosetting synthetic resin to the surface of the substrate and provide an uneven pattern on the surface of the resin during the semi-curing stage.

In the present invention, the size of the pattern of the pattern layer or the light scattering particles of the coating layer is not particularly limited, but may range from several nanometers to several millimeters.

In the present invention, the patterning layer is not particularly limited if the material exhibits the physical properties targeted by the present invention, but may be, for example, a thermoplastic or thermosetting pattern layer selected from polyester resin and acrylic resin.

In one aspect of the present invention, the diameter of the light-collecting protrusion formed on the patterning layer may be 20 to 30 ㎛ and the height may be 10 to 15 ㎛, and the transmittance can be further improved in the above range, so it is preferable, but limited thereto. That is not the case.

The mat coating layer includes a polymer resin and organic particles, and the organic particles include methyl methacrylate, ethyl methacrylate, isobutyl methacrylate, normal butyl methacrylate, normal butyl methyl methacrylate, acrylic acid, and methacrylic acid. Acid, hydroxyethyl methacrylate, hydroxypropyl methacrylate, hydroxyethyl acrylate, acrylamide, methyl acrylamide, glycidyl methacrylate, ethyl acrylate, isobutyl acrylate, normal butyl acrylate and any one selected from the group consisting of homopolymers, copolymers or terpolymers of monomers selected from 2-ethylhexyl acrylate, beads made of polyethylene, polystyrene, polypropylene, acrylic and olefin-based copolymers, and silicon-based spherical particles. Or, it may be two or more organic particles.

Although it is not limited, light collection can be performed more efficiently by using organic particles having a refractive index in the range of 1.4 to 1.52.

The average particle diameter of the organic particles may be 1 to 50 ㎛, more specifically 5 to 40 ㎛, and is preferred because the light collection efficiency is excellent in this range, but is not limited thereto. In addition, from the perspective of further improving light collection efficiency, two types of organic particles with different average particle diameters may be mixed and used, specifically, for example, first organic particles with an average particle diameter of 30 to 50 ㎛, and It may be used by mixing the second organic particles of 5 to 20 ㎛. Their mixing ratio may be 3:7 to 7:3 by weight, but is not limited thereto.

The content of the organic particles may be 1 to 60% by weight, more specifically 10 to 50% by weight, of the weight of the mat coating layer.

The polymer resin used in the mat coating layer can be used without limitation as long as it is a thermosetting polymer resin or a photocurable polymer resin, and can be used without limitation as long as it is for well fixing the organic particles to the polyester base film.

In one aspect of the present invention, the thickness of the light trapping layer may be 10 to 200 ㎛, more specifically 50 to 150 ㎛, but is not limited thereto.

[First in-line coating layer and second in-line coating layer]

In one aspect of the present invention, the polyester base film may include a first in-line coating layer on the surface in contact with the encapsulant of the solar module to further improve adhesion to the encapsulant.

In one aspect of the present invention, the second in-line coating layer may be formed on the polyester base film to further improve adhesion with the light capture layer.

In one aspect of the present invention, the first in-line coating layer and the second in-line coating layer may be applied in-line during a uniaxial or biaxial stretching process when manufacturing a polyester base film, and may be cured and dried during a heat treatment process after stretching to form a coating film. More specifically, it may be formed by applying a primer coating composition to one or both sides before stretching or after uniaxial stretching. At this time, the first in-line coating layer and the second in-line coating layer may be formed of the same or different compositions, and may be used without limitation as long as they have excellent adhesion to the target encapsulant and light capture layer.

In one aspect of the present invention, the primer coating composition may be selected from acrylic resin, polyester resin, and polyurethane resin.

The acrylic resin may be an acrylic resin such as methyl methacrylate, ethyl methacrylate, isobutyl methacrylate, normal butyl methyl methacrylate, and a copolymer or terpolymer of acrylic acid and methacrylic acid.

More specifically, the primer coating composition is prepared by preparing an aqueous dispersion composition containing 2 to 20% by weight of the acrylic resin, 0.1 to 1.0% by weight of a silicone wetting agent, 0.1 to 1.0% by weight of silica particles, and the remaining amount of water and applied on the base film. After application, it is preferable to go through stretching and heat treatment processes to have a dry coating thickness of 30 to 120 nm. The application method is not limited as long as it is a known application method such as the Meyer bar method or the gravure method.

The polyester resin may be a copolymerization of a dicarboxylic acid component containing a sulfonic acid alkali metal salt compound and a glycol component containing diethylene glycol.

As the dicarboxylic acid component, aromatic dicarboxylic acid and sulfonic acid alkali metal salt compound can be used. The dicarboxylic acid component is an aromatic dicarboxylic acid such as phthalic acid, terephthalic acid, dimethyl terephthalate, isophthalic acid, dimethyl isophthalate, 2,5-dimethyl terephthalic acid, 2,6-naphthalene dicarboxylic acid, and biphenyldicarboxylic acid. Acids, aliphatic dicarboxylic acids such as adipic acid and sebacic acid, and alicyclic dicarboxylic acids such as cyclohexane dicarboxylic acid can be used, but are not necessarily limited thereto.

Examples of the sulfonic acid alkali metal salt compound include alkali metal salts such as sulfoterephthalic acid, 5-sulfoisophthalic acid, 4-sulfoisophthalic acid, and 4-sulfonaphthalenic acid-2,7-dicarboxylic acid, preferably may be included in 6 to 20 mol% of the total acid components. When used at less than 6 mol%, the dispersion time of the resin in water becomes longer and dispersibility is low, and when used at more than 20 mol%, water resistance may decrease.

The glycol component may include diethylene glycol and an aliphatic glycol with 2 to 8 carbon atoms or an alicyclic glycol with 6 to 12 carbon atoms. For example, ethylene glycol, 1,3-propanediol, 1,2-propylene glycol, neopentyl glycol, 1,4-butanediol, 1,4-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1, 2-cyclohexanedimethanol, 1,6-hexanediol, p-xylene glycol, triethylene glycol, etc. can be used, but are not necessarily limited thereto. At this time, it is preferable to contain 20 to 80 mol% of diethylene glycol out of the total glycol components.

More specifically, the primer coating composition is prepared by preparing an aqueous dispersion composition to include 2 to 20% by weight of the polyester resin, 0.1 to 1.0% by weight of a silicone wetting agent, 0.1 to 1.0% by weight of silica particles, and the remaining amount of water to form a base film. After applying it on the surface, it is preferable to go through stretching and heat treatment processes to have a dry coating thickness of 30 to 120 nm. The application method is not limited as long as it is a known application method such as the Meyer bar method or the gravure method.

The polyurethane-based resin can be manufactured by blocking a prepolymer obtained by polymerizing a linear diol, a branched glycol having three or more terminal groups, and an isocyanate-based monomer with an inorganic acid base to enable water dispersion. The branched glycol refers to glycol with 3 or more functional groups.

The polyurethane-based primer coating layer consists of 10 to 75% by weight of a linear prepolymer having two isocyanate end groups that are partially or entirely blocked with an inorganic acid base group and 25 to 75% by weight of a branched prepolymer having three or more isocyanate end groups that are partially or entirely blocked with an inorganic acid group. It can be formed by applying a polyurethane coating composition containing 90% by weight of a water-dispersible polyurethane resin and water. By ensuring that the content of the branched prepolymer satisfies the above range, a coating film having excellent adhesion to the encapsulant can be formed. In addition, if the content of the branched prepolymer exceeds 90% by weight, the viscosity rises rapidly due to excessive gelation, making it difficult to prepare an aqueous dispersion composition, and defects in surface appearance such as cracks occurring on the surface of the film when coated. This can happen.

The method for producing the water-dispersible polyurethane resin is, for example, reacting 39 to 45% by weight of polyol, 0.3 to 1.2% by weight of trimethylol propane, and 50 to 57% by weight of an isocyanate compound to prepare a prepolymer having isocyanate as a terminal group. , it can be prepared by reacting 3 to 4% by weight of an inorganic acid salt to block the ionic group of sulfate at the end of the isocyanate, but is not limited thereto.

The polyol may be polyester-based polyol or polyether-based polyol, and polyester-based polyol is preferably used. Polyester-based polyols include polyols produced from the reaction of carboxylic acid, sebacic acid, or acid anhydride and polyhydric alcohol. More specifically, the polyol may be polyethylene adipate diol.

The trimethylol propane is used to produce a prepolymer having a trifunctional group, and is preferably used in an amount of 0.3 to 1.2% by weight. If used in less than 0.3% by weight, the crosslinking density may decrease and anti-blocking properties may decrease, and if used in excess of 1.2% by weight, the crosslinking density will become too high and stretchability may deteriorate, resulting in poor coating appearance. This is not excellent and the adhesion may deteriorate.

The isocyanate compound is not limited, but hexamethylene diisocyanate is preferably used. A prepolymer having a tri-functional group can be produced within the range of 50 to 57% by weight.

It is preferable to use sodium hydrogen sulfate as the inorganic acid salt, and its content is preferably 3 to 4% by weight.

More specifically, the primer coating composition is an aqueous dispersion composition containing 2 to 20% by weight of the polyurethane resin prepared by the above method, 0.1 to 1.0% by weight of a silicone wetting agent, 0.1 to 1.0% by weight of silica particles, and the remaining amount of water. After manufacturing and applying it on a base film, it is preferable to go through stretching and heat treatment processes to have a dry coating thickness of 30 to 120 nm. The application method is not limited as long as it is a known application method such as the Meyer bar method or the gravure method.

Additionally, a primer coating layer can be formed using a mixture of the polyester resin and the polyurethane resin, and in this case, the mixing ratio of the polyester resin and the polyurethane resin may be 9:1 to 6:4 by weight. An aqueous dispersion composition was prepared to include 2 to 20% by weight of a mixture of the polyester resin and polyurethane resin, 0.1 to 1.0% by weight of a silicone wetting agent, 0.1 to 1.0% by weight of silica particles, and the remaining amount of water, and formed on a base film. After application, it is preferable to go through stretching and heat treatment processes to have a dry application thickness of 30 to 120 nm. The application method is not limited as long as it is a known application method such as the Meyer bar method or the gravure method.

In one aspect of the present invention, the first in-line coating layer and the second in-line coating layer may include a UV blocker capable of simultaneously blocking UVA and UVB, similar to the polyester base film.

The present invention will be described in more detail below based on examples and comparative examples. However, the following Examples and Comparative Examples are only one example to explain the present invention in more detail, and the present invention is not limited by the following Examples and Comparative Examples.

Hereinafter, the physical properties of the present invention were measured as follows.

1) Intrinsic viscosity

After dissolving the sample in Ortho Chloro Phenol at 160 ± 2°C, measure the sample viscosity in a viscosity tube using an automatic viscosity meter (Skyvis-4000) at 25°C, and calculate the sample by formula 1 below. The intrinsic viscosity (I.V.) was obtained. The unit of intrinsic viscosity is dl/g.

[Calculation Formula 1]

Intrinsic viscosity (IV) = {(0.0242× Rel)+0.2634}× F

2) Ultraviolet and visible light transmittance

Using a UV spectrometer (Agilent, Cary5000 UV-VIS-NIIR Spectrophotometer), transmittance was measured at a wavelength of 200 nm to 800 nm, and UVA transmittance was evaluated through the average transmittance of 280 to 320 nm and UVB transmittance through the transmittance at 400 nm. did. And the visible light transmittance was evaluated through the 550nm transmittance.

3) Weather resistance

To evaluate resistance to UV, QUV treatment was performed under the conditions below using Q-LAB's QUV tester, and the Yellow Index over time was measured using a Color Meter (Konica Minolta. CM-512m3).

Lamp: UVA-340

Typical Irradiance: 0.77 W/㎡ (at 340nm)

Temp. : 70℃

Additionally, ΔY.I was calculated as follows.

△YI = YI ₂ - YI ₁

In the above formula, YI ₁ is the yellowness of the film before inputting it into the QUV tester, and YI ₂ is the yellowness of the film after QUV treatment after inputting it into the QUV tester.

Weather resistance is satisfactory within the range where ΔY.I is 5 or less.

4) Color and yellowness

The film color was confirmed using a color meter. The measurement method was using Konica Minolta (CM-512m3) equipment, measuring 30 sheets (480㎛) of 16㎛ film overlapping and comparing the film color with b*, which indicates the color of the film.

5) Durability: After PCT (Pressure Cooker Test), MD direction elongation retention rate

The PCT test is performed at 121°C, 1.4 atm, and 100% RH for 50 hours, and the unit of elongation retention in the MD direction is %.

Within a length range of 5 m in the longitudinal direction of the film roll, two measurement samples of 300 mm × 200 mm in size are collected with the vertical direction in the MD direction of the film and the horizontal direction in the TD direction. First, a sample for measuring physical properties was made with the length of the MD and TD directions being 300mm -up speed) Using a universal tensile test machine (Instron's Tensile Test Machine) at 500 mm/min, the cutting elongation in the machine direction (MD) of the film before PCT treatment was measured 10 times, excluding the maximum and minimum values. The average value was obtained.

For another sample taken at 300 mm in the MD direction and 200 mm in the TD direction, cut the sample with a knife to a length of 200 mm in the MD direction at intervals of 15 mm continuously in the TD direction based on one corner, and repeat this 10 times. After the cut film with a sample size (MD After hanging it in an autoclave so that it is not submerged in water, the sample is aged for 50 hours under high temperature and high humidity conditions of 121°C × 100% RH × 1.4 atm. When aging is complete, take it out of the autoclave and leave it at room temperature for 24 hours. Then, take a small sample of 200mm , Cutting elongation in the machine direction (MD) of the film after PCT treatment using a universal tensile test machine (Instron's Tensile Test Machine) with a gauge length of 50mm and a cross head-up speed of 500mm/min. After measuring 10 times, the average value was obtained excluding the maximum and minimum values.

Using the elongation values in the MD direction before and after the PCT treatment, the elongation retention rate in the MD direction after PCT was calculated according to the following calculation formula 2.

[Calculation Formula 2]

6) Haze and total light transmittance

A specimen of the deposited film was measured using a HAZE METER (Model name: Nipon denshoku, Model NDH 5000).

[Example 1]

1) Manufacture of compounding chips

79.6% by weight of polyethylene terephthalate (intrinsic viscosity 0.69 dl/g) chips, 20% by weight of UV blocker (mix CYASORB UV-3638F from Solvay and ClearShield 390B from Millken in a 1:1 weight ratio), antioxidant (Irganox 1010 from Basf) 0.2% by weight and 0.2% by weight of thickener (GPA ZE-105E, Goulston technologies, Inc.) were mixed in a ribbon mixer at 30 rpm for 10 minutes.

The mixture was melt-extruded using a co-rotating twin-screw extruder with two supply ports and one vent port. In the case of polyethylene terephthalate, it was ground to a size with an average diameter of 100㎛ or less to improve mixing with other additives.

During melt extrusion, the screw of the twin screw extruder was rotated at 200 rpm and the discharge amount per hour was set to 200 kg/hr. The vent port for removing water and organic compounds with a boiling point of 240°C or lower was maintained at a vacuum of 10 Torr, and the screw Considering heat generation due to shear stress, the temperature was set to 240°C and the resin temperature was melt-extruded at 270°C, and the L/D of the twin screw extruder was 60.

In addition, a 400-mesh screen filter was used at the tip of the twin screw extruder to remove unmelted coagulant and improve shear force to produce compounding chips. The intrinsic viscosity of the manufactured compounding chip was 0.62dl/g.

2) Manufacture of composite plastic film

95% by weight of polyester resin chips with an intrinsic viscosity of 0.80 dl/g and 5% by weight of the compounding chips were placed in an extruder and melted at 280°C. Afterwards, an unstretched sheet was manufactured on a casting roll at 20°C while extruding through a T-die. After stretching it 3.3 times in the longitudinal direction at 95°C, a first primer coating composition to form a first in-line coating layer is applied to one side, and a second primer coating composition to form a second in-line coating layer is applied to the other side. , a film with a total thickness of 155㎛ was produced by stretching 3.9 times in the width direction at 135°C. The thickness of the first in-line coating layer was 100 nm, and the thickness of the second in-line coating layer was 100 nm.

The first primer coating composition contains 8% by weight of a polyester binder (Z-695 from GOO Chemical), 8% by weight of an oxazoline-based curing agent (C-K05 from TAKEMOTO), and 0.2% by weight of a silicone-based wetting agent (Q2-5212 from Dow Corning). % by weight and balance of water.

The second primer coating composition contains 3% by weight of a polyester binder (Z-695 from GOO Chemical), 12% by weight of a urethane binder (X-007 from DKS), 0.1% by weight of a tin catalyst (CAT-21 from DKS), It contains 1% by weight of a blocked isocyanate-based curing agent (WM44 from Asahi Kasei), 0.2% by weight of a silicone-based wetting agent (Wet250 from Tego), 0.3% by weight of colloidal silica particles (average particle diameter 0.08 ㎛), and the remaining amount of water.

3) Formation of light trapping layer

After applying the mat coating composition on the second in-line coating layer of the composite plastic film prepared above, it was photocured to form a light trapping layer with a thickness of 25 ㎛.

The mat coating composition contains 25.0% by weight of binder resin (acrylic type, Aekyung Chemical Co., Ltd., AA-914), 5.0% by weight of hardener (urethane type, Aekyung Chemical Co., Ltd., AH2100), and organic particles (acrylic particles, Soken's MT5R-10HH (average particle diameter) 15 ㎛) and MR-7GC (average particle diameter 6 ㎛) mixed in a 1:1 weight ratio) and 45% by weight of methyl ethyl ketone.

[Example 2]

In Example 1, the composite plastic film was manufactured in the same manner as Example 1, except that 90% by weight of polyester resin chips with an intrinsic viscosity of 0.80 dl/g and 10% by weight of the compounding chips were used.

[Example 3]

In Example 1, the composite plastic film was manufactured in the same manner as Example 1, except that 85% by weight of polyester resin chips with an intrinsic viscosity of 0.80 dl/g and 15% by weight of the compounding chips were used.

[Comparative Example 1]

It was prepared in the same manner as Example 1, except that the light trapping layer was not formed.

[Comparative Example 2]

It was prepared in the same manner as Example 1, except that Solvay's CYASORB UV-3638F was used alone as a UV blocker.

Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Total thickness (㎛) 180 180 180 155 180 Total light transmittance
(%) 98.1 97.7 97.1 88.9 97.9 Haze (%) 87.6 87.3 87.9 2.5 87.5 UV transmittance 400nm UV transmittance (%) 12.9 2.8 1.3 1.0 84.4 550nm UV transmittance (%) 96.3 95.9 95.5 87.4 95.7 color L 92.3 92.7 92.5 94.5 92.7 b* 10.2 12.4 14.7 9.3 10.5 Yellowness (Y.I.) 13.8 15.4 17.8 12.5 11.7 Weather resistance (△Y.I) 4.7 3.8 3.3 3.1 7.2 durability(%) 72 69 67 65 70

As shown in the table above, the composite plastic film of the present invention has a UV transmittance of 30% or less at 400 nm, a UV transmittance of 85% or more at 550 nm, a total light transmittance of 90% to 99%, a haze of 80% or more, and CIE1976L* The b* value obtained from the a*b* colorimetric system is 20 or less, the yellowness is 20 or less, and the machine direction elongation and elongation retention rate of 50% or more before and after 50 hours of PCT (121℃, 1.4 atm, RH100%) treatment are all satisfied. was confirmed.

In addition, when the composite plastic film of Examples 1 to 3 was used to replace the front glass of a solar module, the weight of the solar module could be reduced by 35%, and the long-term weather resistance evaluation was also passed. It was confirmed that the efficiency was equivalent to that of using existing glass.

In the case where the light trapping layer was not formed as in Comparative Example 1, the total light transmittance was low and the 550nm UV transmittance was low, so it was confirmed that the efficiency was reduced to 60% when applied to a solar module.

In addition, it was confirmed that when the UV blocker is used alone as in Comparative Example 2, the weather resistance is poor and the lifespan is less than 5 years, so it cannot be used as a replacement for the front glass of a solar module.

As described above, the present invention has been described with specific details, limited embodiments, and drawings, but these are provided only to facilitate a more general understanding of the present invention, and the present invention is not limited to the above embodiments, and the present invention Anyone skilled in the art can make various modifications and variations from this description.

Accordingly, the spirit of the present invention should not be limited to the described embodiments, and the scope of the patent claims described below as well as all modifications that are equivalent or equivalent to the scope of this patent claim shall fall within the scope of the spirit of the present invention. .

Claims (12)

A composite plastic film for replacing the front glass of a thin film solar cell,
A polyester base film facing the encapsulation material of the solar module; and
It is formed on the polyester base film and includes at least one light capture layer selected from a patterning layer and a mat coating layer,
The polyester base film contains a UV blocker that blocks UVA and UVB,
The polyester base film is manufactured by manufacturing a compounding chip containing the UV blocker, mixing it with a polyester chip, and then melting and extruding it,
The UV blocker is a composite plastic film that is a mixture of polyoxyalkylene-based compounds and benzoxazine-based compounds at a weight ratio of 2 to 8:8 to 2. According to clause 1,
The composite plastic film further includes a first in-line coating layer on one side of the polyester base film to improve adhesion to the encapsulant, and a second in-line coating layer to improve adhesion to the light trapping layer on the other side. Phosphorus composite plastic film. According to clause 1,
The polyester base film is a composite plastic film made of polyester resin with an intrinsic viscosity of 0.7 to 1.0 dL/g. According to clause 1,
The polyester base film has a thickness of 50 to 350 ㎛, a UV transmittance of 30% or less at 400 nm, a UV transmittance of 85% or more at 550 nm, a total light transmittance of 80% to 90%, a haze of 2% or less, and CIE1976L *A composite plastic film with a b* value of 10 or less and a yellowness of 15 or less obtained from the a*b* colorimetric system. According to clause 1,
The composite plastic film has a total thickness of 50 to 500 ㎛, a UV transmittance of 30% or less at 400 nm, a UV transmittance of 85% or more at 550 nm, a total light transmittance of 90% to 99%, a haze of 80% or more, and CIE1976L *a*b*A composite plastic film with a b* value of 20 or less, a yellowness of 20 or less obtained from the colorimetric system, and a machine direction elongation and elongation retention rate of 50% or more before and after 50 hours of PCT (121℃, 1.4 atm, RH100%) treatment. . According to clause 1,
The polyester base film is a composite plastic film containing 0.5 to 5% by weight of a UV blocker that blocks UVA and UVB. delete According to clause 1,
The patterning layer is made of polymer resin and includes light-collecting protrusions,
A composite plastic film wherein the light-collecting protrusion has a hemispherical or hexagonal array lens structure. According to clause 8,
A composite plastic film wherein the light-collecting protrusion has a diameter of 20 to 30 ㎛ and a height of 10 to 15 ㎛. According to clause 1,
The mat coating layer includes polymer resin and organic particles,
The organic particles include methyl methacrylate, ethyl methacrylate, isobutyl methacrylate, normal butyl methacrylate, normal butyl methyl methacrylate, acrylic acid, methacrylic acid, hydroxyethyl methacrylate, and hydroxypropyl methacrylate. Homopolymers of monomers selected from acrylates, hydroxyethyl acrylates, acrylamide, methyl acrylamide, glycidyl methacrylate, ethyl acrylate, isobutyl acrylate, n-butyl acrylate and 2-ethylhexyl acrylate. A composite plastic film comprising one or more organic particles selected from the group consisting of copolymers or terpolymers, polyethylene, polystyrene, polypropylene, beads made of acrylic and olefin-based copolymers, and silicon-based spherical particles. According to clause 10,
A composite plastic film wherein the average particle diameter of the organic particles is 1 to 50 ㎛. According to clause 1,
The polyester base film is a composite plastic film made of polyethylene terephthalate resin.