KR102544688B1 - Backsheet for pv module and manufacturing method thereof - Google Patents

Abstract

The present invention relates to a back sheet for a solar module and a method for manufacturing the same, and can be replaced with a single-layer polyester film in a conventional fluorine film/PET film/fluorine film or PET/PET/PE laminated structure, and a roof top (Rooftop) can satisfy the aesthetics required for products, and the heat absorption of the solar cell is low, and the power conversion efficiency is high. It relates to a new backsheet for solar modules.

Description

Photovoltaic module backsheet and its manufacturing method {BACKSHEET FOR PV MODULE AND MANUFACTURING METHOD THEREOF}

The present invention relates to a back sheet for a solar module and a method for manufacturing the same, in a structure in which a conventional fluorine film/PET film/fluorine film or white polyester film/transparent polyester film/white polyethylene film is laminated, a single-layer polyester film It can be replaced with, and it relates to a back sheet for a photovoltaic module that can satisfy the aesthetics required for a roof top product, including a printing layer containing a black pigment.

A solar cell for photovoltaic power generation starts from silicon or various compounds and can generate electricity when it is in the form of a solar cell. However, since sufficient output cannot be obtained with one cell, each cell must be connected in series or parallel, and this connected state is called a 'solar module'.

A solar module is composed of laminated glass, a first sealing material, a solar cell, a second sealing material, and a back sheet. As the first sealing material and the second sealing material, ethylene vinyl acetate (EVA) or the like is used.

Conventionally, a TPT (Tedlar/PET/Tedlar) type backsheet requires a lamination process through an adhesive to laminate a Tedlar film and a PET film. Even in the white polyester film/transparent polyester film/white polyethylene film type backsheet, a lamination process using an adhesive is required to laminate each film. The Tedlar film used in the existing backsheet is expensive, so it accounts for more than 50% of the current backsheet manufacturing process cost, thereby increasing the cost of the backsheet.

Therefore, in order to lower the manufacturing cost, research to realize the same effect as using fluorine film without using expensive fluorine film, which is not in smooth supply and demand, and reducing the number of laminated films to reduce the price of the film constituting the backsheet and Research to reduce process costs is being attempted.

In addition, the growth of roof top products is currently prominent in photovoltaic products, and appearance aesthetics are required due to installation on the roof.

In the conventional backsheet, a colored film is used to impart external aesthetics, or a colored pigment is added to an encapsulant to improve aesthetic degradation due to a color difference with a solar cell. In particular, black color It is typically used. In the case of using such a colored film, the temperature of the solar cell is increased due to easy absorption of heat during the photovoltaic power generation process, thereby reducing the power generation efficiency and consequently lowering the power generation efficiency of the solar module. And if you want to express the color by putting a colored pigment in the encapsulant, there is a disadvantage in that it also lowers the power generation efficiency by interfering with the absorption of sunlight.

In Korean Patent Publication Nos. 10-2016-0025244 and 10-2016-0026107, a surface layer is placed on one or both sides of the substrate layer, and a reflective layer of a certain pattern is placed thereon to increase solar energy efficiency and to realize an aesthetic effect, Republic of Korea In Patent Publication No. 10-2016-0028101, a reflective layer is placed on one side or both sides of the base layer, and a black pattern layer is placed thereon to improve solar efficiency using reflected light and to realize aesthetic effects using the black pattern layer. Compared to the back sheet manufacturing process, it is impossible to reduce the lamination process, and the adhesive strength of the surface layer and the reflective layer or the reflective layer and the black pattern layer, which are bonded in direct contact with the encapsulant ethylene vinyl acetate (EVA), is low, resulting in peeling from the back sheet. easy to occur

An object of the present invention is to provide a backsheet that can be changed to a single-layer film structure of the present invention, from a structure in which a transparent film and a white film are conventionally laminated to a backsheet, which is a core material for protecting a solar module. That is, the purpose is to enable the expression of physical properties equivalent to those of using a conventional laminated film while being made of a single layer.

In addition, when applied to a solar module, a printed layer is formed only on a portion to show the same color as the solar cell, and the solar cell is positioned in a portion where the printed layer is not formed, so that the temperature of the solar cell increases due to heat absorption. The purpose is to prevent this, and to have excellent aesthetics by applying a back sheet of the same color as the solar cell in appearance.

In addition, when the polyester base film is made of a single layer film of a transparent film, the part where the solar cell is located is transparent so that it can be used not only for the front light receiving type solar module but also for the double side light receiving type solar module, and has excellent visible light transmittance, It is intended to provide a backsheet for a solar module that has excellent UV blocking properties and excellent moisture resistance, thereby increasing the light receiving efficiency of the solar module and preventing aging and deterioration of the polyester base film.

In addition, it is intended to provide a back sheet for a photovoltaic module having improved adhesion to an encapsulant.

The present invention includes a polyester base film and a printed layer formed on one side or both sides of the polyester base film and formed only on a portion of the surface of the polyester base film, wherein the printed layer includes a black pigment. It relates to a backsheet for an optical module.

In addition, the present invention includes a) a first compounding chip containing a polyester resin having an intrinsic viscosity of 0.80 to 1.40 dl/g and a light stabilizer, and a polyester resin having an intrinsic viscosity of 0.80 to 1.40 dl/g and inorganic particles. preparing an unstretched sheet by melt-extruding any one selected from a second compounding chip or a mixture thereof and a polyester resin having an intrinsic viscosity of 0.63 to 0.90 dl/g;

b) preparing a film by uniaxially stretching the unstretched sheet in the longitudinal direction and then biaxially stretching in the width direction; and

c) forming a printed layer by applying a composition for a printed layer including a binder resin, an organic solvent and a black pigment to only a portion of the surface of the base film;

It relates to a method for manufacturing a back sheet for a solar module comprising a.

The back sheet for a photovoltaic module of the present invention is made of a single-layer polyester film, so manufacturing costs are reduced, and there are advantages in that it can be applied to both a front-side light-receiving photovoltaic module as well as a double-side light-receiving photovoltaic module.

In addition, by allowing the printing layer containing the black pigment to be printed only on a portion thereof, it is possible to prevent the temperature of the solar cell from rising due to heat absorption, and a backsheet of the same color as the solar cell is applied to improve aesthetics. It works.

In addition, the back sheet for a solar module according to the present invention has an effect of improving the power change efficiency of the module by 5% or more because the temperature rise in the module due to solar heat absorption is small.

In addition, the back sheet for a solar module according to the present invention has an effect of improving durability and improving workability by forming a printed layer having excellent adhesion to an encapsulant and excellent flexibility.

1 shows one aspect of the back sheet for a solar module of the present invention.
Figure 2 shows one aspect of the back sheet for a solar module of the present invention.
Figure 3 shows one aspect of the back sheet for a solar module of the present invention.
4 is a cross-sectional view showing one aspect of the back sheet for a solar module of the present invention.
FIG. 5 shows details of a printed pattern to which the aspect of FIG. 2 is applied, and shows one aspect of the entire printed pattern.
FIG. 6 shows details of a printed pattern to which the aspect of FIG. 3 is applied, and shows one aspect of the entire printed pattern.

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

Also, unless defined otherwise, all technical and scientific terms have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Terms used in the description in the present invention are merely to effectively describe specific embodiments and are not intended to limit the present invention.

Also, the singular forms used in the specification and appended claims may be intended to include the plural forms as well, unless the context dictates otherwise.

One aspect of the present invention includes a polyester base film and a printed layer formed on one or both surfaces of the polyester base film and formed only on a portion of the surface of the polyester base film, wherein the printed layer includes a black pigment It is a back sheet for a solar module.

In one aspect of the present invention, the polyester base film comprises a polyester film and one or both surfaces thereof selected from polyurethane-based resins and polyester-based resins, or a mixture thereof. A primer coating layer may be formed.

In one aspect of the present invention, the polyester base film has a whiteness of 80 or more, an intrinsic viscosity of 0.60 to 0.85 dl / g, a machine direction heat shrinkage of 2.0% or less after 30 minutes at 150 ° C, 121 ° C, RH 100% White film (A) with a retention rate of elongation in the machine direction of 40% or more after 50 hours or UV transmittance of 5% or less at 360 nm, an intrinsic viscosity of 0.60 to 0.85 dl/g, and a heat shrinkage rate in the machine direction after 30 minutes at 150 ° C. It may be a transparent film (B) having a machine direction elongation retention rate of 40% or more after 50 hours at 2.0% or less, 121 ° C., RH 100%.

In one aspect of the present invention, the polyester film may include any one or a mixture of two or more selected from light stabilizers and inorganic particles.

In one aspect of the present invention, the content of the light stabilizer may be 0.15 to 1.5% by weight of the total weight of the polyester film, and the content of the inorganic particles may be 3 to 20% by weight of the total weight of the polyester film.

In one aspect of the present invention, the polyester base film may have a thickness of 150 to 350 μm, and the print layer may have a thickness of 1 to 35 μm.

In one aspect of the present invention, the printing layer includes a thermosetting resin having a glass transition temperature of 10 ° C. or higher as a binder resin, or a mixed resin of the thermosetting resin and a thermoplastic resin having a glass transition temperature of 40 ° C. or higher, and the black pigment is carbon it could be black

In one aspect of the present invention, the printing layer may include a mixed resin of a polyurethane-based resin having a glass transition temperature of 10° C. or higher and a polyvinyl chloride-based resin having a glass transition temperature of 40° C. or higher.

In one aspect of the present invention, the black pigment may be included in 5 to 60% by weight in the printing layer.

In one aspect of the present invention, the printed layer includes: i) a printed layer formed by being spaced apart on only a portion of the surface of the polyester base film, ii) a printed layer formed on only a portion of the surface of the polyester base film and having a continuous pattern, iii) a printed layer formed only on a portion of the surface of the polyester base film along the edge of the solar cell, and iv) a printed layer formed only on a portion of the surface of the polyester base film in the form of a sea island.

In one aspect of the present invention, the printed layer may partially overlap a solar cell of a solar module.

In addition, the present invention relates to a method for manufacturing a back sheet for a photovoltaic module, and one aspect of the manufacturing method of the present invention is a) a first comp comprising a polyester resin having an intrinsic viscosity of 0.80 to 1.40 dl/g and a light stabilizer Founding chip, any one selected from a polyester resin having an intrinsic viscosity of 0.80 to 1.40 dl/g and a second compounding chip containing inorganic particles, or a mixture thereof, and a polyester resin having an intrinsic viscosity of 0.63 to 0.90 dl/g Melting and extruding to prepare an unstretched sheet;

b) preparing a film by uniaxially stretching the unstretched sheet in the longitudinal direction and then biaxially stretching in the width direction; and

c) forming a printed layer by applying a composition for a printed layer including a binder resin, an organic solvent and a black pigment to only a portion of the surface of the base film;

It may contain.

In one aspect of the manufacturing method of the present invention, in the step b), before the stretching or after the uniaxial stretching, the step of applying a primer coating composition to one or both surfaces further comprising it could be

In one aspect of the manufacturing method of the present invention, the coating in step c) may be selected from screen printing, offset, digital printing, roll coating, gravure coating, reverse coating, spray coating, and air knife coating.

Hereinafter, an aspect of the back sheet for a solar module according to the present invention will be described in detail with reference to the drawings.

As shown in FIGS. 1 to 6, in one aspect of the present invention, a printed layer 20 is formed on a polyester base film 10, and the printed layer 20 is the polyester base film 10 Formed only on a part of the surface. More specifically, i) a printed layer formed by being spaced apart on only a portion of the surface of the polyester base film, ii) a printed layer formed on only a portion of the surface of the polyester base film and having a continuous pattern, iii) a border of the solar cell. Accordingly, it may be selected from a printed layer formed on only a portion of the surface of the polyester base film and iv) a printed layer formed on only a portion of the surface of the polyester base film in the form of a sea island.

In the sea island form, the part where the printed layer is not formed forms an island, the part where the printed layer is formed forms a sea, and the island part forms a solar cell of a solar module ( 30) may be located. In addition, the sea portion and the solar cell may partially overlap. That is, in one aspect of the present invention, the printed layer may partially overlap the solar cell of the solar module. Some overlap here This means that the solar cell can partially overlap the printed layer of the sea part beyond the boundary of the island part.

More specifically, the printing layer may be formed in an area other than the portion where the solar cell (solar cell) is located in the photovoltaic module, and the size of the island portion is equal to or smaller than the size of the solar cell. All gaps between solar cells can be made to look black.

Specifically, the printed layer 20 may be formed in a portion corresponding to the circumference of the solar cell in the portion where one or more solar cells are located, as shown in FIG. 1, and as shown in FIGS. 2 and 3, the shape of the solar cell. And it is also possible that the sea portion and the island portion are not completely divided according to the layout, and a part of the printed layer is discontinuously formed. In addition, FIG. 4 is an aspect showing a cross section of the back sheet of the present invention, in which a printed layer 20 is formed on one side of a base film 10, and solar between the printed layer 20 and the printed layer 20 It shows where the cell 30 is located. FIG. 5 shows an aspect of a printed pattern to which the aspect of FIG. 2 is applied, and shows the entire printed pattern. FIG. 6 shows an aspect of a printed pattern to which the aspect of FIG. 3 is applied, and shows the entire printed pattern.

When applied to a solar cell module using the back sheet of the present invention, the solar cell can be positioned on the portion of the base film 10 corresponding to the portion where the printed layer 20 is not formed, and if necessary, the printed layer and Solar cells may partially overlap. 1 to 6 are only for helping understanding of the present invention, but are not limited thereto, and the shape of the printed layer may vary depending on the structure or shape of the solar cell, and is formed on one or both sides of the polyester base film. it could be

[Polyester base film]

In one aspect of the present invention, the polyester base film may be a single layer film made of a transparent film or a white film.

In one aspect of the present invention, when the polyester base film is a transparent film, it is preferable to prevent aging and deterioration by blocking ultraviolet rays reaching the ground surface, and for this purpose, a polyester resin and a light stabilizer may be included. . The light stabilizer is a benzophenone compound, a benzotriazole compound, a benzoxazinone compound, a benzoate compound, a phenyl salicylate compound, and a hindered It may include any one or two or more selected from the group consisting of amine-based compounds (Hindered Amine), but is not limited thereto. By including the light stabilizer, it can be applied not only to the front light receiving type solar module but also to the double side light receiving type solar module.

The light stabilizer is preferably used in an amount to block ultraviolet rays of 280 to 360 nm, which is an ultraviolet wavelength range, and to express physical properties with an ultraviolet transmittance of 5% or less, but is not limited to, 0.15 to 1.5 of the total weight of the polyester base film It may be to use weight percent. More preferably, it may be to use 0.3 to 1.0% by weight.

When the UV transmittance is 5% or less, more specifically, in the range of 0.1 to 5%, aging of the base film can be prevented, and durability and weather resistance are excellent, so it is preferable.

The light stabilizer is preferably added at the time of manufacturing the polyester base film, and more preferably, the dispersibility of the light stabilizer is improved by preparing a compounding chip containing the light stabilizer, mixing it with the polyester chip, and preparing a film by melting and extruding the light stabilizer. can make it even better.

In addition, when the polyester base film of the present invention is a transparent film, UV transmittance is 5% or less at 360 nm, intrinsic viscosity is 0.60 to 0.85 dl / g, after 30 minutes at 150 ° C., machine direction heat shrinkage is 2.0% or less, It is preferable that the elongation retention rate in the machine direction after 50 hours at 121° C. and 100% RH is 40% or more.

When the UV transmittance is 5% or less at 360 nm, photostability against ultraviolet rays can be secured, and when the transmittance is greater than 5%, physical properties and decomposition of the backsheet may be caused due to long-term use.

It is preferable that the intrinsic viscosity is 0.60 to 0.85 dl/g, and since durability and weather resistance are excellent in the above range, long-term use may be possible when applied to a solar module.

It is preferable that the machine direction heat shrinkage is 2.0% or less, preferably 0.5 to 1.5%, and more preferably 0.5 to 1.0%. there is.

In addition, after 50 hours at 121 ℃, RH100%, it is preferable that the elongation retention rate in the machine direction is 40 to 99%, preferably 70 to 99%. this may fall

In the present invention, by using a substrate film that simultaneously satisfies the UV transmittance, intrinsic viscosity, heat shrinkage rate, and elongation retention rate, weather resistance is greatly improved, compared to using a general polyester film when applied as a back sheet of a solar module. This can be improved by 10% or more.

In addition, the polyester base film may have a thickness of 150 to 350 μm, and is suitable for use as a back sheet for a solar module at this thickness, but is not limited thereto.

In addition, in one aspect of the present invention, the polyester base film may be a single layer film made of a white film. In the case of a white film, it can be suitably used for a front light-receiving type, and it can serve to return light that does not reach the solar cell among the light absorbed through the front substrate and reaches the back sheet back to the solar cell.

When the polyester base film of the present invention is a white film, it includes inorganic particles in the base film, and inorganic particles commonly used in the art may be used without limitation, and specifically, for example, titanium dioxide, barium sulfate , any one selected from calcium carbonate, magnesium carbonate, zinc carbonate, zinc oxide, magnesium oxide, calcium phosphate, silica, alumina, talc, and kaolin, or a mixture of two or more may be used. More preferably, it is preferable to use rutile titanium dioxide because the light absorption region shifts toward a long wavelength and photolysis by UV is suppressed, thereby improving durability. It is preferable to use 3 to 20% by weight of the total content of the polyester base film. When used at less than 3% by weight, it is difficult to apply to the back sheet as a single layer film due to low whiteness and reflectance. When used at more than 20% by weight, the sheet is brittle and brittle due to the high crystallization progress of the casting sheet, making it difficult to stretch. It is difficult, and film forming stability may be greatly reduced. In addition, even if the film has sufficient reflectance, it is difficult to use it as a back sheet because long-term durability, that is, PCT property, which is a characteristic required when used for a solar cell back sheet, is reduced.

It is preferable to use inorganic particles having an average particle diameter of 0.1 to 0.5 μm, particularly preferably 0.15 to 0.30 μm. If it is less than 0.1㎛, it causes poor dispersibility due to the re-agglomeration of fine particles, and the filter in the film forming process is often clogged, which can significantly reduce workability. Therefore, operability such as breakage is poor due to poor elongation, and even if the same content is applied, the reflectance is low, and if the particle content is increased to achieve the required reflectance, the economic feasibility may be reduced due to an increase in manufacturing cost and a decrease in fairness.

In addition, in the case of a white film, an optical brightener may be included to improve the reflectance and whiteness of the film as needed, and preferably, a benzoxazol optical brightener is contained in an amount of 100 to 500 ppm in the total content of the film. can In the above range, the whiteness is excellent, the light reflection efficiency is good, and the UV stability is excellent, so that yellowing can be reduced when exposed to the outside for a long time.

Specific examples of the benzoxazol-based optical brightener include 2,5-thiophene diylbis (5-tert-butyl-1,3-benzoxazole), 4,4'-bis (2-methoxysti) Lyl) -1,1'-biphenyl, 2,2'-(1,2-ethenediyldi-4,1-phenylene) bisbenzoxazole and the like can be used. As commercialized examples thereof, Eastman's OB-1 and the like may be used, but are not limited thereto.

In one aspect of the present invention, even in the case of a white film, it may further include a light stabilizer like the transparent film, which is the same as described above.

In one aspect of the present invention, when the polyester base film is a white film, the whiteness is 80 or more, the intrinsic viscosity is 0.60 to 0.85 dl / g, and the machine direction heat shrinkage is 2.0% or less after 30 minutes at 150 ° C., 121 ° C. , It is preferable that the elongation retention rate in the machine direction after 50 hours at 100% RH is 40% or more.

The whiteness is 80 or more, preferably 90 to 110, more preferably 100 to 105, and if less than 80, the effect of increasing the target light reflection efficiency is small, and the light reflection efficiency rises in the whiteness range Accordingly, the power generation efficiency by light conversion in the solar module can be increased by 0.2 to 0.5%.

The intrinsic viscosity is preferably 0.60 to 0.85 dl/g, and since durability and weather resistance are excellent in the above range, long-term use may be possible when applied to a solar module.

It is preferable that the machine direction heat shrinkage is 2.0% or less, preferably 0.5 to 1.5%, and more preferably 0.5 to 1.0%. there is.

In addition, after 50 hours at 121 ℃, RH100%, it is preferable that the elongation retention in the machine direction is 40% or more, specifically 40 to 99%, preferably 70 to 99%, and if less than 40%, the physical properties deteriorate over time may occur rapidly and may reduce long-term durability.

In the present invention, by using a substrate film that simultaneously satisfies the above whiteness, intrinsic viscosity, heat shrinkage rate, and elongation retention rate, weather resistance is greatly improved, and when applied as a back sheet of a solar module, weather resistance is improved compared to using a general polyester film. It can be improved by 10% or more.

In addition, the polyester base film may have a thickness of 150 to 350 μm, and is suitable for use as a back sheet for a solar module at this thickness, but is not limited thereto.

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

The polyester resin is a general term for polymers in which the main bond in the main chain is a monomer residue and the covalent bond binding the monomer residue is an ester bond. Usually, a dicarboxylic acid compound and a dihydroxy compound or a dicarboxylic acid ester derivative and a dihydroxy compound It can be obtained by subjecting a hydroxy compound to condensation polymerization.

Here, as a dicarboxylic acid compound, 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 cyclohexanedicarboxylic acid, Oxycarboxylic acids, such as para-oxybenzoic acid, etc. are mentioned. Further, as dicarboxylic acid ester derivatives, esters of the above dicarboxylic acid compounds, such as dimethyl terephthalate, diethyl terephthalate, 2-hydroxyethyl methyl terephthalate, dimethyl 2,6-naphthalenedicarboxylic acid, isophthalic acid Dimethyl, dimethyl adipate, dimethyl maleate, dimethyl dimer acid, etc. are mentioned.

Examples of the hydroxy compound 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 dimethacrylates such as 1,4-cyclohexanedimethanol. Aromatic dihydroxy compounds, such as a hydroxy compound, bisphenol A, and bisphenol S, etc. are mentioned.

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

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

In one aspect of the present invention, the polyester-based base film may use a film having excellent hydrolysis resistance, 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 having excellent hydrolysis resistance may use a low content of oligomers generated during condensation polymerization. In addition, the hydrolysis resistance may be further improved by further applying heat treatment to improve the known hydrolysis resistance to the polyester film to reduce the moisture content of the polyester and reduce the shrinkage rate.

More preferably, the intrinsic viscosity of the polyester resin used in the manufacture of a compounding chip of a polyester resin and a light stabilizer or inorganic particles is 0.80 to 1.40 dl/g, and in the manufacture of a base film, the compounding chip and The intrinsic viscosity of the polyester resin used together is preferably 0.63 to 0.90 dl/g. When the intrinsic viscosity of the polyester resin used in manufacturing the compounding chip is less than 0.80 dl/g, processability and durability may be weakened due to the decrease in the viscosity of the compounding chip during film manufacturing, and in the manufacture of the base film When 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 processability improves, but durability and weather resistance cannot be improved, and 0.90 dl/g If it is exceeded, productivity may be deteriorated due to high discharge pressure during manufacturing using the existing polyethylene terephthalate resin production expectation and breakage during stretching.

[Primer coating layer]

In one aspect of the present invention, the polyester base film may include a polyester film and a primer coating layer selected from acrylic resins, polyester resins, and polyurethane resins on one or both surfaces of the polyester film.

At this time, the polyester film is the same as described in the polyester base film.

In one aspect of the present invention, the primer layer may be applied in-line in a uniaxial or biaxial stretching process when manufacturing a polyester base film, and then cured and dried in a heat treatment process after stretching to form a coating film. More specifically, it may be formed by including a process of applying a primer coating composition to one or both surfaces before or after the stretching.

In addition, by forming the primer layer, the adhesive force between the printed layer and the polyester base film may be further improved.

In addition, when manufacturing the solar module, the primer layer in the portion where the printing layer is not formed may improve the stability of the solar module due to high adhesive strength with ethylene vinyl acetate (EVA) as an encapsulant.

In the primer coating layer of the present invention, the acrylic resin is an acrylic resin such as methyl methacrylate, ethyl methacrylate, isobutyl methacrylate, normal butyl methyl methacrylate, copolymer or terpolymer of acrylic acid and methacrylic acid can be used.

More specifically, one aspect of the primer coating layer of the present invention is to prepare 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 balance of water After coating on the base film, it is preferable to have a dry coating thickness of 30 to 120 nm through stretching and heat treatment processes. The application method is not limited as long as it is a known application method such as a Mayer bar method or a gravure method.

As the polyester-based resin, a dicarboxylic acid component containing an alkali metal sulfonic acid compound and a glycol component containing diethylene glycol may be copolymerized.

As the dicarboxylic acid component, an aromatic dicarboxylic acid and an alkali metal sulfonic acid salt compound may 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 biphenyl dicarboxylic acid. Aliphatic dicarboxylic acids such as acid, adipic acid and sebacic acid, and alicyclic dicarboxylic acids such as cyclohexane dicarboxylic acid may 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-sulfo isophthalic acid, 4-sulfo isophthalic acid, 4-sulfonaphthalenic acid-2,7-dicarboxylic acid, and the like, preferably. may be included in 6 to 20 mol% of the total acid component. When used at less than 6 mol%, the dispersion time of the resin in water is prolonged and dispersibility is low, and when used at more than 20 mol%, water resistance may be lowered.

As the glycol component, diethylene glycol and aliphatic glycol having 2 to 8 carbon atoms or alicyclic glycol having 6 to 12 carbon atoms may be used. 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, and the like may 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, one embodiment of the primer coating layer of the present invention is an aqueous dispersion composition containing 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 balance of water. After manufacturing and applying on a base film, it is preferable to have a dry coating thickness of 30 to 120 nm through stretching and heat treatment processes. The application method is not limited as long as it is a known application method such as a Mayer bar method or a gravure method.

The polyurethane-based resin may be prepared 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 group to enable water dispersion. The branched glycol refers to glycol having three or more functional groups.

The polyurethane-based primer coating layer includes 10 to 75% by weight of a linear prepolymer having two isocyanate end groups partially or entirely blocked by inorganic acid groups and 25 to 75 wt % of a branched prepolymer having three or more isocyanate end groups partially or entirely blocked by inorganic acid groups. A polyurethane coating composition containing 90% by weight of a water-dispersible polyurethane resin and water may be applied and formed. When the content of the branched prepolymer satisfies the above range, it is possible to form a coating film having excellent adhesion to the encapsulant. In addition, when the content of the branched prepolymer exceeds 90% by weight, the viscosity rapidly rises due to excessive gelation, making it difficult to prepare an aqueous dispersion composition, and defects in the surface appearance such as cracking when coating the film surface. this can happen

In the method for preparing the water-dispersible polyurethane resin, for example, 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 are reacted to prepare a prepolymer having isocyanate as an end group, , It can be prepared by reacting 3 to 4% by weight of an inorganic acid salt to block an ionic group of a sulfate at an isocyanate terminal, but is not limited thereto.

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

The trimethylol propane is used to prepare a prepolymer having a trifunctional group, and is preferably used in an amount of 0.3 to 1.2% by weight. If less than 0.3% by weight is used, the crosslinking density may decrease and anti-blocking properties may deteriorate, and if it is used in excess of 1.2% by weight, the crosslinking density becomes excessively high and the elongation property deteriorates, resulting in poor coating appearance. This is not excellent, and the adhesive strength may be deteriorated.

The isocyanate compound is not limited, but it is preferable to use hexamethylene diisocyanate. It is possible to prepare a prepolymer having a trifunctional group in the range of using 50 to 57% by weight.

It is preferable to use sodium hydrogen sulfate (Sodium Hydrogen Sulfate) as the inorganic acid salt, and it is preferable to use 3 to 4% by weight.

More specifically, one aspect of the primer coating layer of the present invention includes 2 to 20% by weight of the polyurethane-based 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 balance of water. After preparing the aqueous dispersion composition and applying it on the base film, it is preferable to have a dry coating thickness of 30 to 120 nm through stretching and heat treatment processes. The application method is not limited as long as it is a known application method such as a Mayer bar method or a gravure method.

In addition, the primer coating layer may be formed using a mixture of the polyester-based resin and the polyurethane-based resin, and in this case, the mixing ratio of the polyester-based resin and the polyurethane-based resin may be in a weight ratio of 9:1 to 6:4. An aqueous dispersion composition is 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 After applying to, it is preferable to have a dry coating thickness of 30 ~ 120nm through stretching and heat treatment processes. The application method is not limited as long as it is a known application method such as a Mayer bar method or a gravure method.

[printing layer]

In one aspect of the present invention, the printing layer containing the black pigment may be formed by applying a black ink composition containing a binder resin, an organic solvent, and a black pigment.

The binder resin may be made of a thermosetting resin alone or a mixed resin of a thermosetting resin and a thermoplastic resin. As the thermosetting resin, a polyurethane-based resin is preferable, and the thermosetting polyurethane includes polycarbonate polyurethane, polyester polyurethane, polyurethane, and the like. It is preferable to use a polyurethane resin having a glass transition temperature (Tg) of 10° C. or higher, and more specifically, it is preferable to use a polyurethane resin having a glass transition temperature of 10 to 50° C. When the glass transition temperature (Tg) is less than 10 ℃, the transfer of the printed layer occurs easily, and when the glass transition temperature (Tg) exceeds 50 ℃, it is too brittle and can easily break when the printed layer is bent. can fall

The thermoplastic resin is preferably a polyvinyl chloride-based resin, and the thermoplastic polyvinyl chloride may be a polyvinyl chloride polyvinyl acetate copolymer, a polyvinyl chloride homopolymer, or the like. It is preferable to use a polyvinyl chloride resin having a glass transition temperature (Tg) of 40° C. or more, and if it is less than 40° C., blocking of the printed layer may occur. When used as a mixed resin with the polyurethane resin, the polyvinyl chloride resin and the polyurethane resin may be mixed and used in a weight ratio of 20:80 to 80:20, and by using in this range, the uniform dispersibility of the black pigment It is possible to secure durability as well as adhesion by securing the flexibility of the printed layer.

The organic solvent is not limited as long as it can dissolve the binder resin, and specifically, for example, solvent naphtha, dimethylformamide, methyl ethyl ketone, acetone, ethyl acetate, tetrahydrofuran, dioxane, cyclohexanone, n-hexane, toluene, xylene, methanol, ethanol, n-propanol, isopropanol, etc. may be used alone or in combination of two or more, but is not limited thereto.

The black pigment may use carbon black, and it is preferable to use carbon black having an average particle diameter of 15 to 58 nm to flatten the surface of the printed layer, and the content may be 5 to 60% by weight in the printed layer. . Since it is possible to impart a desired aesthetic within the above range, it is suitable but not limited thereto.

The application method may be to use a screen printing method, an offset method, a digital printing method, roll coating, gravure coating, reverse coating, spray coating, air knife coating, and the like, but is not limited thereto.

In addition, if necessary, the black pigment composition may further include a dispersant for improving the dispersibility of the black pigment.

In one aspect of the present invention, the printed layer preferably has a thickness of 1 to 35 μm because it has a small level difference with the base film and contains a sufficient amount of black pigment, but is not limited thereto.

[Manufacturing method]

For a more specific example of the method for manufacturing the back sheet for a solar module of the present invention, a) a first compounding chip containing a polyester resin having an intrinsic viscosity of 0.80 to 1.40 dl/g and a light stabilizer; A polyester resin having a viscosity of 0.80 to 1.40 dl/g and a second compounding chip containing inorganic particles or a mixture thereof and a polyester resin having an intrinsic viscosity of 0.63 to 0.90 dl/g are melt-extruded and manufacturing an unstretched sheet;

b) preparing a film by uniaxially stretching the unstretched sheet in the longitudinal direction and then biaxially stretching in the width direction; and

c) forming a printed layer by applying a composition for a printed layer including a binder resin, an organic solvent and a black pigment to only a portion of the surface of the base film;

includes

In one aspect of the present invention, step a) may be mixing a polyester resin having an intrinsic viscosity of 0.63 to 0.90 dl/g with any one or a mixture thereof selected from the first compounding chip and the second compounding chip. there is.

More specifically, in one aspect of the present invention, step a) is a polyester resin having an intrinsic viscosity of 0.63 to 0.90 dl / g, a polyester resin having an intrinsic viscosity of 0.8 to 1.4 dl / g, and a benzophenone-based compound (Benzophenone ), a group consisting of benzotriazole, benzoxazinone, benzoate, phenyl salicylates, and hindered amines In this case, the polyester base film is made into a transparent film.

In another embodiment of the present invention, in step a), a polyester resin having an intrinsic viscosity of 0.63 to 0.90 dl/g, a polyester resin having an intrinsic viscosity of 0.8 to 1.4 dl/g, and inorganic particles are kneaded. It may be used by mixing the pounding chips, and in this case, the polyester base film may be made into a white film.

Another aspect of the present invention, in step a), a polyester resin having an intrinsic viscosity of 0.63 to 0.90 dl/g, a polyester resin having an intrinsic viscosity of 0.8 to 1.4 dl/g, and a benzophenone-based compound (Benzophenone), Selected from the group consisting of Benzotriazole, Benzoxazinone, Benzoate, Phenyl Salicylates and Hindered Amine A first compounding chip in which any one or two or more light stabilizers are kneaded and a second compounding chip in which inorganic particles are kneaded with a polyester resin having an intrinsic viscosity of 0.8 to 1.4 dl/g may be mixed and used, In this case, the polyester base film may be made into a white film.

Step b) is a process of manufacturing a film, and the stretching ratio of the film in the longitudinal direction and the width direction is not limited, but may be 2 to 6 times, respectively, and after stretching, relaxation and heat setting may be added. Specifically, after stretching the unstretched sheet in the longitudinal and width directions, the film may be prepared by heat treatment, and may be stretched and heat treated by a method commonly used in the art. More specifically, although not limited to, the film is stretched 2 to 6 times between rolls heated at 80° C. to 110° C. using the difference in circumferential speed between the rolls in the longitudinal direction of the film, and the film is stretched in the width direction at 95° C. to 160° C. It may be stretched 2 to 6 times at ° C, and relaxation and heat treatment may be performed at 200 ° C to 240 ° C. The base film may have a thickness of 150 to 350 μm, but is not limited thereto.

In the step b), the timing of applying the primer coating composition to the film varies according to the film stretching process. In the case of sequential biaxial stretching, the primer coating composition is applied after stretching the film in the longitudinal direction and then stretching the film in the width direction. In the case of simultaneous biaxial stretching, the film may be stretched in the longitudinal direction and the width direction after applying the primer coating composition to the unstretched sheet.

The step c) is for forming a print layer, and the composition for the print layer is printed by a method selected from screen printing method, offset method, digital printing method, roll coating, gravure coating, reverse coating, spray coating, and air knife coating. It may be formed, and the thickness may be 1 to 35 μm, but is not limited thereto. The composition for the printing layer is the same as described above.

The present invention will be described in more detail based on the following Examples and Comparative Examples. However, the following Examples and Comparative Examples are only one example for explaining 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 of base film

After melting the film with ortho chlorophenol at 160 ± 2 ° C, the viscosity of the sample in the viscometer was measured using an automatic viscosity meter (Skyvis-4000) at 25 ° C, and the sample was calculated according to the following formula 1 The intrinsic viscosity (I.V.) of was obtained. The unit of intrinsic viscosity is dl/g.

[Calculation 1]

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

2) UV transmittance

Using a spectrophotometer (Varian, UV-Vis Spectrophotometer Cary 5000), transmittance was measured at a wavelength of 200 nm to 800 nm, and transmittance at 360 nm was confirmed.

The transmittance at 360 nm was specified as UV transmittance.

3) Whiteness Index

After taking 10 measurement samples within 1m from the entire width of the film roll in the longitudinal direction (MD), using a spectrophotometer (Datacolor, Datacolor 600) to measure the whiteness index of each film sample, The average value of 8 samples excluding the value and the minimum value was obtained, and this was used as the Whiteness Index.

4) Elongation retention rate in MD direction after PCT (Pressure Cooker Test)

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

Within the length range of less than 5 m in the length direction of the film roll, the longitudinal direction is the MD direction of the film and the horizontal direction is the TD direction, and two samples are taken for measurement with a size of 300 mm × 200 mm. First, a sample for measuring physical properties is made with the length of the MD and TD directions of 300 mm × 15 mm for one sample taken, and then the measurement sample width is 15 mm, the sample length is 50 mm, and the tensile speed (Cross head -up speed) at 500mm/min, after measuring the cutting elongation in the machine direction (MD) of the film before PCT treatment using a universal tensile tester (Instron Tensile Test Machine) 10 times, excluding the maximum and minimum values Average values were obtained.

For another sample of 300 mm in the MD direction and 200 mm in the TD direction, cut the sample with a knife to be 200 mm long in the MD direction at intervals of 15 mm continuously in the TD direction based on one corner, and repeat this 10 times. After making a cut film with a sample size (MD×TD) of 200mm×15mm hanging on one sample, punching a hole at a position of 270mm from the starting point of cutting in the TD direction, and making it a sample hanger in the autoclave After putting it in an autoclave by hanging it 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 × 2 bar pressure. When the aging is completed, take it out of the autoclave and leave it at room temperature for 24 hours. Then, take a small sample of 200mm × 15mm that has been cut in advance with a knife before aging, and measure the sample width 15mm in the same way as above. , Cutting elongation in the machine direction (MD) of the film after PCT treatment using a universal tensile tester (Instron Tensile Test Machine) with a gauge length of 50 mm and a cross head-up speed of 500 mm/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 MD direction elongation retention after PCT was obtained according to the following formula 2.

[Calculation 2]

5) Heat shrinkage rate (150℃×30 minutes)

After measuring the length of the film in the machine direction and width direction by cutting it in the normal direction of 200mm × 200mm with respect to the machine direction (MD) and width direction (TD) of the film, After heat shrinking for 30 minutes, the machine direction (MD) and width direction (TD) lengths of the heat-shrinked film were measured, and the heat shrinkage rates in the machine direction (MD) and width direction (TD) of the film were calculated according to Equation 3 below. .

[Calculation 3]

6) Adhesion evaluation

For the printed layer formed on the base film according to Examples and Comparative Examples of the present invention, a Cross Hatch Cutter (YCC-230/1) was used to form 100 compartments in a size of 1 cm × 1 cm, and then the adhesive force evaluation tape, Adhesion was evaluated using Nichban No.405.

After attaching the adhesiveness evaluation tape firmly on 100 grids, after 3 minutes, removing the adhesiveness evaluation tape was repeated three times, and then the number of grids remaining on the base film was counted to calculate adhesion according to Equation 4 Rescued.

[Calculation 4]

7) Module manufacturing and efficiency evaluation

After manufacturing a module using the film according to Examples and Comparative Examples of the present invention, its efficiency was compared and evaluated.

A 2.5 mm thick low iron tempered glass, a 500 μm thick EVA encapsulant, a 6-inch monocrystalline silicon wafer solar cell, a 500 μm thick EVA encapsulant, and a film having a printed layer of the above example or a comparative example were sequentially laminated and vacuum laminator was applied. 5 minutes in vacuum and 10 minutes at 150 ° C. to produce a solar cell module with an expected output of 200 W.

Open circuit voltage (Voc), short circuit current (Isc), rated voltage (Vpm), and rated current (Ipm) of the module were measured using Spire's SPI-SUNSIMULATOR 4600i product.

In order to evaluate the power change efficiency of the manufactured module, first, the power (Pmax) of the module was obtained according to Equation 5, and the efficiency of the example was compared and evaluated based on the power value of the comparative example according to Equation 6.

[Calculation 5]

[Calculation 6]

[Manufacture Example 1] Manufacture of the first compounding chip

After mixing 90% by weight of polyethylene terephthalate chips with an intrinsic viscosity of 0.95dl/g and 10% by weight of a benzoxazinone-based light stabilizer, knead them in a ribbon mixer at 30rpm for 10 minutes. A first compounding chip was prepared by melt extrusion at 270° C. using a co-rotating twin screw extruder.

[Production Example 2] Production of a second compounding chip

After mixing 50% by weight of polyethylene terephthalate chips with an intrinsic viscosity of 0.95dl/g and 50% by weight of rutile titanium dioxide with an average particle diameter of 0.22㎛, knead them in a ribbon mixer at 30rpm for 10 minutes, , A second compounding chip was prepared by melt extrusion at 270° C. using a co-rotating twin screw extruder having one vent.

[Example 1]

1) Manufacture of base film

15% by weight of the first compounding chips and 85% by weight of polyethylene terephthalate chips having an intrinsic viscosity of 0.80 dl/g were put into an extruder and melted at 280°C. Thereafter, an unstretched sheet was prepared from a casting roll at 20° C. while extruding through a T-die. Then, after stretching it 3.4 times in the longitudinal direction, it was continuously stretched 3.8 times in the width direction, and heat treatment was performed at 230° C. to prepare a base film having a thickness of 160 μm.

The physical properties of the prepared film were measured and shown in Table 1 below.

2) Formation of printed layer

A composition for a printing layer was prepared by mixing 20% by weight of carbon black having an average particle diameter of 27 nm as a black pigment, 20% by weight of a mixed resin, and 60% by weight of a mixed solvent.

The mixed resin was used by mixing a polyvinyl chloride resin having a glass transition temperature of 74° C. and a weight average molecular weight of 27,000 g/mol, and a polyurethane resin having a glass transition temperature of 23° C., Shore Hardness 54D, and specific gravity of 1.21 at a weight ratio of 50:50. .

The mixed solvent was used by mixing toluene, methyl ethyl ketone and cyclohexanone at a weight ratio of 1:1:1.

The composition for the print layer was applied to a base film by screen printing, and a print layer having a thickness of 3 μm was printed at a drying temperature of 80° C. at a process speed of 10 M per minute.

At this time, as shown in FIG. 5, the printing layer was formed in most areas except for the portion where the solar cell is located when assembling the solar module.

The efficiency of the module obtained from the physical properties of the film on which the printed layer is formed and the power (Pmax) of the module manufactured using the same are shown in Table 1 below.

[Example 2]

1) Manufacture of base film

After stretching 3.4 times in the longitudinal direction in Example 1, the coating composition for forming a primer coating layer prepared by the following method was applied to the film by a bar coating method, and then stretched 3.8 times in the width direction continuously, A film was prepared in the same manner, except that a substrate film having a thickness of 160 μm was formed by performing heat treatment at 230° C. and having a primer coating layer having a thickness of 80 nm.

The physical properties of the prepared film were measured and shown in Table 1 below.

2) Preparation of coating composition for forming a primer coating layer

(1) Preparation of polyester binder

40 mol (26 mol%) of 2,6-naphtalene dicarboxly acid, 5 mol (3.3 mol%) of sodium 2,5-dicarboxybenzene sulfonate ), dimethyl terephthalic acid 5 mol (3.3 mol%) and bis [4 (2-hydroxyethoxy) phenyl] fluorene (Bis [4 (2-hydroxyethoxy) phenyl] fluorene) 20 mol (13.3 mol%), triglyceride (Triglyceride, a product of KAO CORPORATION (trade name 85P)) Mix 10 moles (6.6 mole%) and 70 moles (46.6 mole%) of ethylene glycol in a solventless state, put them in a reactor, and raise the temperature by 1℃ per minute from 170℃ to 250℃. While reacting, the esterification reaction proceeded, and at the same time, the temperature was raised to 260 ° C. and the pressure in the reactor was reduced to 1 mmHg, and polycondensation reaction was performed while recovering diol as a by-product, thereby preparing a polyester resin having an intrinsic viscosity of 1.0. At this time, the intrinsic viscosity of the polyester resin was measured using a mixed solvent of tetrachloroethane:phenol weight ratio = 1:1 and using a viscometer at 35°C.

80% by weight of water was added to 20% by weight of the prepared polyester resin and dispersed to prepare a polyester binder for a primer coating layer having a solid content of 20% by weight.

(2) Manufacture of polyurethane binder

40% by weight of polyethyleneadipate diol, 0.6% by weight of trimethylol propane, and 55.9% by weight of hexamethylene diisocyanate are reacted to prepare a prepolymer having an isocyanate functional group as a terminal group After that, 3.5% by weight of sodium hydrogen sulfate as an ionic group is reacted with isocyanate, which is a terminal functional group of the prepolymer, to prepare polyurethane having an ionic group and having a weight average molecular weight of 14,400 g/mol. did

20% by weight of the prepared polyurethane was dispersed in 80% by weight of water to prepare a polyurethane binder for a primer coating layer having a solid content of 20% by weight.

(3) Preparation of coating composition

5% by weight of a mixed solution of the polyester binder and polyurethane binder in a weight ratio of 85:15, 0.3% by weight of a silicone-based wetting agent, and 0.3% by weight of colloidal silica particles having an average particle diameter of 140 nm were added to distilled water, and 2% by weight at room temperature. A coating composition for forming a primer coating layer was prepared by stirring for a period of time.

3) Formation of printed layer

A printed layer was formed in the same manner as in Example 1.

The efficiency of the module obtained from the physical properties of the film on which the printed layer is formed and the power (Pmax) of the module manufactured using the same are shown in Table 1 below.

[Example 3]

1) Manufacture of film

30% by weight of the second compounding chips and 70% by weight of polyethylene terephthalate chips having an intrinsic viscosity of 0.80 dl/g were put into an extruder and melted at 280°C. Thereafter, an unstretched sheet was prepared from a casting roll at 20° C. while extruding through a T-die. Then, after stretching it 3.0 times in the longitudinal direction, it was continuously stretched 3.4 times in the width direction, and heat treatment was performed at 225° C. to prepare a base film having a thickness of 310 μm.

The physical properties of the prepared film were measured and shown in Table 1 below.

2) Formation of printed layer

As a black pigment, 10% by weight of carbon black with an average particle diameter of 27 nm, a polyvinyl chloride resin with a glass transition temperature of 74 ° C and a weight average molecular weight of 27,000 g / mol, and a polyurethane resin with a glass transition temperature of 23 ° C, Shore Hardness 54D, and specific gravity of 1.21 were used. A composition for a printing layer was prepared by mixing 30% by weight of a mixed resin in a 40:60 weight ratio and 60% by weight of a mixed solvent in which toluene, methylethylketone, and cyclohexanone were mixed in a weight ratio of 1:1:1 as solvents. .

The composition for the print layer was applied to one surface of a base film by screen printing, and a print layer having a thickness of 15 μm was printed at a drying temperature of 80° C. at a process speed of 5M per minute.

At this time, as shown in FIG. 6, when assembling the solar module, the printing layer was formed in most areas except for the portion where the solar cell is located.

The efficiency of the module obtained from the physical properties of the film on which the printed layer is formed and the power (Pmax) of the module manufactured using the same are shown in Table 1 below.

[Example 4]

1) Manufacture of film

After stretching 3.0 times in the longitudinal direction in Example 3, the same coating composition for forming a primer coating layer as in Example 2 was applied to the film by a bar coating method, and then stretched 3.4 times in the width direction continuously, A film was prepared in the same manner, except that a substrate film having a thickness of 310 μm on which a primer coating layer was formed was prepared by performing heat treatment at 225 ° C.

The physical properties of the prepared film were measured and shown in Table 1 below.

2) Formation of printed layer

A printed layer was formed in the same manner as in Example 3.

The efficiency of the module obtained from the physical properties of the film on which the printed layer is formed and the power (Pmax) of the module manufactured using the same are shown in Table 1 below.

[Example 5]

1) Manufacture of film

10% by weight of the first compounding chip, 10% by weight of the second compounding chip, and 80% by weight of a polyethylene terephthalate chip having an intrinsic viscosity of 0.80 dl/g were put into an extruder and melted at 280°C. Thereafter, an unstretched sheet was prepared from a casting roll at 20° C. while extruding through a T-die. Then, after stretching it 3.2 times in the longitudinal direction, it was continuously stretched 3.6 times in the width direction, and heat treatment was performed at 225° C. to prepare a base film having a thickness of 200 μm.

The physical properties of the prepared film were measured and shown in Table 1 below.

2) Formation of printed layer

As a black pigment, 10% by weight of carbon black with an average particle diameter of 27 nm, a polyvinyl chloride resin with a glass transition temperature of 74 ° C and a weight average molecular weight of 27,000 g / mol, and a polyurethane resin with a glass transition temperature of 23 ° C, Shore Hardness 54D, and specific gravity of 1.21 were used. A composition for a printing layer was prepared by mixing 35% by weight of a mixed resin mixed at a weight ratio of 60:40 and 55% by weight of a mixed solvent obtained by mixing toluene, methylethylketone, and cyclohexanone at a weight ratio of 1:1:1 as solvents. .

The composition for the print layer was applied to a base film by screen printing, and a print layer having a thickness of 30 μm was printed at a drying temperature of 80° C. at a process speed of 4M per minute.

At this time, as shown in FIG. 6, when assembling the solar module, the printing layer was formed in most areas except for the portion where the solar cell is located.

The efficiency of the module obtained from the physical properties of the film on which the printed layer is formed and the power (Pmax) of the module manufactured using the same are shown in Table 1 below.

[Example 6]

1) Manufacture of film

After stretching 3.2 times in the longitudinal direction in Example 5, the same coating composition for forming a primer coating layer as in Example 2 was applied to the film by a bar coating method, and then stretched 3.6 times in the width direction continuously, A film was prepared in the same manner except that a base film having a thickness of 200 μm on which a primer coating layer was formed was prepared by performing heat treatment at 225 ° C.

The physical properties of the prepared film were measured and shown in Table 1 below.

2) Formation of printed layer

A printed layer was formed in the same manner as in Example 5.

The efficiency of the module obtained from the physical properties of the film on which the printed layer is formed and the power (Pmax) of the module manufactured using the same are shown in Table 1 below.

[Comparative Example 1]

After mixing 90% by weight of polyethylene terephthalate chips with an intrinsic viscosity of 0.95 dl/g and 10% by weight of carbon black with an average particle diameter of 27 nm, knead them in a ribbon mixer at 30 rpm for 10 minutes. Compounding chips were prepared by melt-extruding at 270° C. using a co-rotating twin-screw extruder.

10% by weight of the compounding chip and 90% by weight of a polyethylene terephthalate chip having an intrinsic viscosity of 0.80 dl/g were put into an extruder and melted at 280° C. to prepare a film in the same manner as in Example 6, with a separate primer layer and printing. It did not form a layer.

The efficiency of the module obtained from the physical properties of the manufactured film and the power (Pmax) of the module manufactured using the same is shown in Table 1 below.

division write
originality of the film
viscosity
(dl/g) UV
permeability
(%) whiteness MD Shindo
retention rate
(%) MD heat shrinkage rate
(%) Adhesion (%) module
efficiency
(%) Example 1 0.71 1.32 73.5 67.2 1.1 8 105 Example 2 0.70 1.35 72.7 62.5 1.0 100 106 Example 3 0.64 0.08 96.3 50.2 1.0 6 108 Example 4 0.65 0.09 95.8 43.1 0.9 100 109 Example 5 0.66 0.32 87.8 51.3 1.2 5 107 Example 6 0.67 0.33 86.9 44.2 1.1 100 108 Comparative Example 1 0.64 0.00 7.8 21.4 1.2 0 100

As shown in Table 1, the backsheets for solar modules of Examples 1 to 6 of the present invention give aesthetic beauty in appearance by applying black pigment only to areas where solar cells are not located, and at the same time Compared to Comparative Example 1 using the black film, it was found that the temperature rise in the module due to the absorption of solar heat was small, and the power change efficiency of the module was greatly improved by 5% or more.

In addition, compared to Comparative Example 1 to which the black film was applied, the films of Examples 1 to 6 had a high MD elongation retention rate after PCT treatment and excellent hydrolysis resistance, and through this, it was found that the weather resistance to the external environment was also excellent.

In order to improve the adhesion and durability of the printed layer formed by applying the black pigment, it was found that it is preferable to form a primer coating layer during the film manufacturing process as in Examples 2 and 4 to 6.

At 360nm, UV transmittance of 5% or less or whiteness of 80 or more, intrinsic viscosity of 0.60 to 0.85dl/g, after 30 minutes at 150℃, shrinkage rate in the machine direction is less than 2%, elongation retention in the machine direction after 50 hours at 121℃ RH100% is 40 A printed layer having a continuous pattern in the shape of a sea-island shape is formed to show the same color as the solar cell applied to the solar module using a film having a film having a film having a density of at least %, and heat is absorbed by placing the solar cell in an area where the printed layer is not formed. As a result, it was found that the power conversion efficiency of the module can be improved by preventing the temperature of the solar cell from rising, and aesthetics are excellent by applying a backsheet having a printed layer of the same color as the solar cell.

10: base film
20: printing layer
30: solar cell

Claims (15)

A polyester base film;
It is formed on one side or both sides of the polyester base film and includes a printed layer formed on only a portion of the surface of the polyester base film,
The printed layer includes a mixed resin of a polyurethane-based resin having a glass transition temperature of 10 to 50° C. and a polyvinyl chloride-based resin having a glass transition temperature of 40° C. or more and a black pigment,
The mixed resin is a back sheet for a solar module in which a polyvinyl chloride-based resin and a polyurethane-based resin are mixed in a weight ratio of 20:80 to 80:20.
According to claim 1,
The polyester base film comprises a polyester film and one or both sides thereof selected from a polyurethane-based resin and a polyester-based resin, or a mixture thereof. A back sheet for a solar module having a primer coating layer formed thereon.
According to claim 1,
The polyester base film has a whiteness of 80 or more, an intrinsic viscosity of 0.60 to 0.85 dl/g, a machine direction heat shrinkage of 2.0% or less after 30 minutes at 150 ° C, and elongation in the machine direction after 50 hours at 121 ° C and RH 100%. A white film (A) having a retention rate of 40% or more; or
UV transmittance less than 5% at 360nm, intrinsic viscosity 0.60 ~ 0.85 dl/g, machine direction heat shrinkage less than 2.0% after 30 minutes at 150℃, elongation retention rate in machine direction after 50 hours at 121℃, RH 100% A back sheet for a solar module that is a transparent film (B) of 40% or more.
According to claim 1,
The polyester base film is a back sheet for a solar module comprising any one or a mixture of two or more selected from a light stabilizer and inorganic particles.
According to claim 4,
The light stabilizer content is 0.15 to 1.5% by weight of the total weight of the polyester base film back sheet for a solar module.
According to claim 4,
The content of the inorganic particles is 3 to 20% by weight of the total weight of the polyester base film back sheet for a solar module.
According to claim 1,
The polyester base film has a thickness of 150 to 350 μm, and the printed layer has a thickness of 1 to 35 μm.
According to claim 1,
The black pigment is a back sheet for a solar module that is carbon black.
delete According to claim 1,
The black pigment is a back sheet for a solar module comprising 5 to 60% by weight in the printed layer.
According to claim 1,
The printed layer includes: i) a printed layer formed by being spaced apart on only a portion of the surface of the polyester base film, ii) a printed layer formed on only a portion of the surface of the polyester base film and having a continuous pattern, iii) forming an edge of the solar cell. A back sheet for a solar module selected from a printed layer formed on only a portion of the surface of the polyester base film and iv) a printed layer formed on only a portion of the surface of the polyester base film in the form of a sea island.
According to claim 1,
The printed layer is a back sheet for a solar module that partially overlaps the solar cell of the solar module.
a) 1st compounding chip containing a polyester resin with an intrinsic viscosity of 0.80 to 1.40 dl/g and a light stabilizer, and 2nd compounding with a polyester resin with an intrinsic viscosity of 0.80 to 1.40 dl/g and inorganic particles preparing an unstretched sheet by melt-extruding any one selected from chips or a mixture thereof and a polyester resin having an intrinsic viscosity of 0.63 to 0.90 dl/g;
b) preparing a base film by uniaxially stretching the unstretched sheet in the longitudinal direction and then biaxially stretching in the width direction; and
c) forming a printed layer by applying a composition for a printed layer including a binder resin, an organic solvent and a black pigment to only a portion of the surface of the base film;
The binder resin is a mixed resin of a polyurethane-based resin having a glass transition temperature of 10 to 50 ° C and a polyvinyl chloride-based resin having a glass transition temperature of 40 ° C or more,
The mixed resin is a method of manufacturing a back sheet for a solar module in which a polyvinyl chloride-based resin and a polyurethane-based resin are mixed in a weight ratio of 20:80 to 80:20.
According to claim 13,
In the step b), the method of manufacturing a back sheet for a solar module further comprising the step of applying a primer coating composition to one or both surfaces before the stretching or after the uniaxial stretching.
According to claim 13,
In step c), the coating method is selected from screen printing method, offset method, digital printing method, roll coating, gravure coating, reverse coating, spray coating, and air knife coating.

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