KR20120119295A - Olefin film for solar cell module - Google Patents

Abstract

PURPOSE: An olefin based film for photovoltaic module back sheets is provided to enhance adhesive properties with ethylene vinyl acetate(EVA) and with polyester films. CONSTITUTION: An olefin based film for photovoltaic module back sheets comprises a core layer and a skin layer. The core layer is composed of polyolefin based film. The skin layer is laminated on both sides of the core layer. The skin layer includes a mixture of ethylene vinyl acetate and maleic anhydride graft-copolymer. The polyolefin based film contains low density polyethylene, linear low density polyethylene, high density polyethylene, one or more blended materials selected from polymethylpentene, a based resin selected from a copolymer thereof, inorganic particles, and UV absorbent.

Description

Olefin film for solar module back sheet {Olefin film for Solar Cell Module}

The present invention relates to an olefin-based film for a solar module back sheet, and to a film having a new laminated structure replacing a fluorine film in contact with an encapsulant in a structure that is conventionally laminated with a fluorine film / PET film / fluorine film.

Solar cells for photovoltaic power generation start from silicon or various compounds and become electricity when they form a solar cell. However, one cell does not get enough output, so each cell must be connected in series or in parallel. This connection is called a solar module.

The solar module is formed by laminating glass, EVA (ethylene vinyl acetate, EVA), solar cell, EVA (ethylene vinyl acetate, EVA), and back sheet. The back sheet is laminated at the bottom of the module to protect the solar cell by blocking dust, shock, and moisture. TPT (Tedlar / PET / Tedlar) type is widely used, and ribbon is used as a passage for transmitting current. Therefore, a material coated with silver or tin lead on copper is used.

The solar cell backsheet is the core material that protects the cell by attaching it to the back of the solar cell module. Durability, weather resistance, insulation, moisture permeability, etc. are required. Generally, fluorine film and PET film are laminated.

As the fluorine film, a fluorine film having excellent weatherability and durability is used. Currently, Tedlar film made of PVF resin developed by DuPont in 1961 is mainly used. However, due to the high price and short supply, some companies may replace it with other films such as PET.

EVA co-developed NASA and DuPont in 1970 as materials for solar cells used in satellites. It is currently used as a standard for sealing materials for solar cells. Japanese firms (Mitsui Chemical, Bridgestone) dominate over 70% of the world market. Inside the solar cell serves to seal and fill the cell. It is excellent in strength, transparency and insulation.

Polyester telephthalate (PET) film uses a planar plastic film with a certain thickness and physical properties, and has excellent strength to form a backbone of a back sheet. Due to its excellent physical, chemical, mechanical and optical properties, it is widely used in food packaging materials and office supplies to advanced electric and electronic products such as semiconductors and displays. In recent years, the use of the solar cell back sheet is increasing due to its excellent durability and weather resistance.

Glass uses less iron to prevent light reflection.

Conventionally, a TPT (Tedlar / PET / Tedlar) type backsheet requires a process of laminating through an adhesive in order to stack a Tedlar film and a PET film. In order to adhere using a polyurethane adhesive or the like was further required. Tedlar films used in existing backsheets are expensive, accounting for more than 80% of the manufacturing cost of backsheets, which contributes to higher backsheet costs.

Therefore, a study was attempted to remove the Tedlar film adhered to the encapsulant (EVA film) in order to reduce the manufacturing cost, but the adhesive of the PET film and the EVA film is difficult to adhere, so the researchers of the present invention have tried to improve this. .

As a result of the study to solve the process problems and the increase in price according to the conventional adhesive coating process of the various steps as described above, the present invention, when using an olefin-based film laminated in a specific structure, the adhesiveness with the encapsulant (EVA film) And the adhesiveness with the polyester film is excellent, the reflectance is excellent, the light is sent back to the solar cell to increase the light efficiency, and found that the weather resistance is improved to complete the present invention.

That is, the present invention is excellent in the adhesiveness with the encapsulant (EVA film) and the polyester film, and has a high reflectance to return the light to the solar cell to increase the light efficiency, improve the weather resistance of the solar module To provide a polyolefin-based film for the sealing material.

The present invention relates to an olefin-based film for a solar module backsheet, and is an invention for replacing a Tedlar film adhered to an encapsulant in a structure that was conventionally laminated with a Tedlar film / PET film / Tedlar film, PET film and an encapsulant EVA The polyolefin coefficient which can expect the effect of increasing the efficiency of the solar cell by blocking phototransmission of the polyester film by blocking the light transmitted through the skin layer and the polyester film with excellent adhesiveness and returning the transmitted light to the solar cell The present invention relates to an olefin-based film for a solar module backsheet composed of a core layer using paper.

More specifically, the present invention

A core layer made of a polyolefin-based film;

A skin layer laminated on both sides of the core layer and comprising a mixture of maleic anhydride graft copolymer and ethylene vinyl acetate;

It relates to an olefin-based film for a solar module backsheet comprising a.

The present invention also relates to a solar module back sheet having at least one layer of the olefin-based film of the present invention comprising a skin layer on both the core layer and the core layer.

One aspect of the solar module back sheet of the present invention is a laminate of the olefin-based film and the polyester film.

Another embodiment of the solar module back sheet of the present invention is a lamination of the coating layer or film consisting of the olefin-based film, the polyester film and the fluorine resin.

The olefin-based film for a solar module backsheet according to the present invention is preferably used in a portion in contact with the encapsulant in the configuration of the backsheet, but is not limited thereto.

Hereinafter, the present invention will be described more specifically.

The olefin-based film of the present invention is a film used for a solar module backsheet, and is preferably suitable for replacing a fluorine film in contact with an encapsulant. Therefore, the adhesion with the encapsulant is very important, the adhesion with the PET film is also important, and it should satisfy the excellent physical properties.

In order to satisfy all of these properties, the present invention is a structure in which a core layer made of a polyolefin-based film and a skin layer made of a mixture of maleic anhydride graft copolymer and ethylene vinyl acetate are laminated on both sides thereof.

First, the core layer of the present invention will be described.

The core layer of the present invention is characterized by being made of a polyolefin-based film. The polyolefin-based film is preferable because of its high affinity with ethylene vinyl acetate (EVA), which is a sealing agent, and moderate strength and flexibility.

In addition, the polyolefin-based film is excellent in durability by containing the inorganic particles and the UV absorber, excellent UV blocking effect can increase the light efficiency.

In the present invention, the polyolefin-based film includes a polyolefin-based resin and additives, and specifically, the polyolefin-based resin is any one or more blends selected from low density polyethylene, linear low density polyethylene, high density polyethylene, and polymethylpentene, or these It can be selected from the copolymer of. More preferably, it is preferable to use low density polyethylene and linear low density polyethylene because it is excellent in strength and flexibility.

The additive preferably contains inorganic particles and UV absorbers.

The inorganic particles reflect the light passing through the solar cell and return it to the cell to increase the light efficiency, and serves to inhibit the photolysis of PET by blocking the UV transmitted through the PET film forming the backsheet. Specifically, for example, it is preferable to use one or a mixture of two or more selected from titanium dioxide, barium sulfate, calcium carbonate and zinc oxide, more preferably titanium dioxide, and more preferably rutile type. It is preferable to use titanium dioxide because it is excellent in light blocking properties and reflection efficiency. The content is preferably 10 to 20% by weight of the polyolefin-based film content. When used in less than 10% by weight, the effect is insignificant, and when used in excess of 20% by weight causes a decrease in the physical properties of the film.

The UV absorber is used to suppress photolysis of the olefin resin constituting the core layer, it is preferable to use 0.1 to 5% by weight because it is suitable for expressing the durability required by the product.

Next, the skin layer of this invention is demonstrated concretely.

In the present invention, the skin layer using the mixture of the maleic anhydride graft copolymer and ethylene vinyl acetate can be very improved adhesion when the EVA resin and the PET film of the lower film forming the back sheet is further filled. .

The maleic anhydride graft copolymer is maleic anhydride graft low density polyethylene (MAH-g-LDPE), maleic anhydride graft linear low density polyethylene (MAH-g-LLDPE), maleic anhydride graft high density polyethylene (MAH-g-HDPE) One or a mixture of two or more selected from maleic anhydride graft ethylene vinyl acetate (MAH-g-EVA) may be used.

The skin layer has a vinyl acetate content of 3 to 20% by weight, a maleic anhydride content of 1000 to 7000 ppm, the melt index (MI) of 0.7 to 4.5g / 10 minutes (190 ℃, 2.16kg) to use desirable. The content is excellent in the adhesive strength with the EVA as well as the sealing material in the above range, and if it exceeds the above range, the sticky property of the surface is increased may cause problems in the process.

Next, the method of manufacturing the olefinic film for solar module backsheet of this invention is demonstrated concretely.

Although the structure of lamination | stacking using an adhesive agent is also possible for the olefin type film of this invention, lamination | stacking by coextrusion is more preferable because it can shorten a process and is excellent in the adhesive force between layers.

More specifically, the present invention

a) 75 to 89% by weight of base resin selected from one or more blends or two or more copolymers selected from low density polyethylene, linear low density polyethylene, high density polyethylene, polymethylpentene, 10 to 20% by weight inorganic particles and UV Compounding 0.1-5% by weight of absorbent to prepare a masterbatch;

b) Injecting the mixture (B) of the master batch (A), maleic anhydride graft copolymer and ethylene vinyl acetate prepared in step a) to the extruder, and then co-extruded to form a B / A / B three-layer structure Extruding the sheet;

c) stretching the sheet in the longitudinal and transverse directions; And

d) heat setting and relaxing;

It includes.

In the present invention, the inorganic particles and the UV absorber in the step a) are preferably prepared in a masterbatch because they have excellent dispersibility and miscibility.

In the present invention, the core layer is preferably 40 to 70% of the total film thickness. If it is less than 40%, it is difficult to express the required properties, and if it is more than 70%, it is difficult to uniformly adjust the thickness of the skin layer.

Moreover, it is preferable that total film thickness is 50-150 micrometers. If the thickness is less than 50 µm, the properties of the adhesive force and the light transmittance are lowered. If the thickness is greater than 150 µm, the ratio of the total thickness of the back sheet becomes too large to express the physical properties of the entire back sheet.

The solar module backsheet provided with one or more layers of the olefinic film which concerns on this invention is also included in the scope of the present invention.

By replacing the fluorine film used in the existing back sheet through the present invention can solve the difficulty of supplying fluorine, it is possible to secure a price competitiveness. In addition, the process can be simplified by not using an adhesive necessary for bonding the fluorine film and the EVA film.

Hereinafter, the present invention will be described in detail with reference to the following examples. However, the present invention is not limited to the following examples.

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

1) Adhesive

The adhesion between the skin layer and the PET film and the adhesion between the skin layer and the encapsulant (EVA film) were measured. At this time, PET film was used PET film (Kolon, CI900), EVA film was used as the EVA film for the encapsulant having a VA content of 33%.

The adhesive method is laminated so that the skin layer and PET film or EVA film is in contact with each other, and then bonded under conditions of 70g / cm 2 at 150 ° C. for 10 minutes, and then peeled at a peel angle of 180 degrees and a peel rate of 300 mm / min at room temperature. Evaluated.

2) UV transmittance

The coextruded film was measured for transmittance at 380 nm using a VARIAN Cary 5000 UV-Vis-NIR Spectrophotometer.

3) reflectance

The relative reflectance of a 100% barium sulfate standard white plate on a spectrophotometer (Varian UV Spectrophotometers Cary 5000), measured at 550 nm visible light. In this case, the measurement angle is 3 ° 20 ", the average time of detecting the signal in the detector is 0.1s, the interval of the analysis data is 1nm, and the scan speed is 600nm / min.

Example 1

Titanium Dioxide Masterbatch

Titanium dioxide masterbatches were prepared by compounding 15 wt% linear low density polyethylene (Mw 101,900, Mn 29,500, SK Chem. FT810) and 85 wt% TiO ₂ .

UV absorber masterbatch

A UV absorber masterbatch was prepared by compounding 80% by weight of linear low density polyethylene (Mw 101,900, Mn 29,500, SK Chem. FT810) and 20% by weight of UV absorber (Chimassorb 944).

Preparation of Masterbatch for Skin Layer

Maleic anhydride graft linear low density polyethylene and ethylene vinyl acetate mixture (Hyundai Engineering Plastics, GV630L / 1002) with a melt index (MI) of 0.9 g / 10 min (190 ° C, 2.16 kg) are used as the masterbatch (B) for the skin layer. It was.

Coextrusion

10 wt% of the titanium dioxide masterbatch, 5 wt% of the UV absorber masterbatch and 85 wt% of the linear low density polyethylene (Mw 101,900, Mn 29,500, SKChem.FT810) were mixed in a melt extruder to 8.5 wt% of titanium dioxide and the UV absorber 1 The core layer composition (A) and the skin layer masterbatch (B) were added to a melt extruder, each melt-extruded, and then co-extruded to a three layer B / A / B through a T-die at a surface temperature of 20%. A three-layer coextrusion film having a thickness of 50 µm was prepared by quenching and solidifying with a casting drum at ℃. At this time, the thickness of the core layer was 20 µm.

The physical properties of the co-extruded film was measured and shown in Table 1 below.

[Example 2]

It was prepared in the same manner as in Example 1, wherein a three-layer coextrusion film having a total thickness of the prepared film was 100 μm. At this time, the thickness of the core layer was 70 µm.

The physical properties of the co-extruded film was measured and shown in Table 1 below.

[Example 3]

It was prepared in the same manner as in Example 1, wherein a three-layer coextrusion film having a total thickness of the prepared film was 100 μm. At this time, the thickness of the core layer was 60 µm.

The physical properties of the co-extruded film was measured and shown in Table 1 below.

Example 4

It was prepared in the same manner as in Example 1, wherein a three-layer coextrusion film having a total thickness of the prepared film was 100 μm. At this time, the thickness of the core layer was 40 µm.

The physical properties of the co-extruded film was measured and shown in Table 1 below.

[Example 5]

It was prepared in the same manner as in Example 1, wherein a three-layer coextrusion film having a total thickness of the prepared film was 150 μm. At this time, the thickness of the core layer was 90 µm.

The physical properties of the co-extruded film was measured and shown in Table 1 below.

[Example 6]

Except for adding the titanium dioxide masterbatch content in Example 1 to 5% by weight (4.25% by weight of the total film weight) was prepared in the same manner as in Example 1.

The physical properties of the co-extruded film was measured and shown in Table 1 below.

[Example 7]

Except for adding the content of the titanium dioxide masterbatch in Example 1 to 1% by weight (0.85% by weight of the total film weight) was prepared in the same manner as in Example 1.

The physical properties of the co-extruded film was measured and shown in Table 1 below.

[Example 8]

It was prepared in the same manner as in Example 1, wherein a three-layer coextrusion film having a total thickness of the prepared film was 50 μm. At this time, the thickness of the core layer was 10 μm.

The physical properties of the co-extruded film was measured and shown in Table 1 below.

[Table 1]

As shown in the above table, the olefin-based film according to the present invention has excellent adhesion with PET film and EVA film, low transmittance at 380nm, and reflectance at 550nm is 64% or more, so it is not applicable to solar module backsheet. It was possible to find out.

Claims (11)

A core layer made of a polyolefin-based film;
A skin layer laminated on both sides of the core layer and comprising a mixture of maleic anhydride graft copolymer and ethylene vinyl acetate;
Olefin-based film comprising a. The method of claim 1,
The polyolefin-based film is any one selected from low-density polyethylene, linear low-density polyethylene, high-density polyethylene, polymethylpentene, two or more blends or a copolymer thereof, an olefin-based containing inorganic particles and UV absorbers film. The method of claim 2,
The inorganic particles are any one or a mixture of two or more selected from titanium dioxide, barium sulfate, calcium carbonate, zinc oxide. The method of claim 2,
The polyolefin-based film is an olefin-based film containing 75 to 89% by weight of the base resin, 3 to 15% by weight of inorganic particles and 0.1 to 5% by weight of the UV absorber. The method of claim 1,
The maleic anhydride graft copolymer is maleic anhydride graft low density polyethylene (MAH-g-LDPE), maleic anhydride graft linear low density polyethylene (MAH-g-LLDPE), maleic anhydride graft high density polyethylene (MAH-g-HDPE) , An olefin-based film which is any one or a mixture of two or more selected from maleic anhydride graft ethylene vinyl acetate (MAH-g-EVA). The method of claim 1,
The skin layer has an vinyl acetate content of 3 to 20 wt%, maleic anhydride content of 1000 to 7000 ppm, and melt index (MI) of 0.7 to 4.5 g / 10 min (190 ° C., 2.16 kg). The method of claim 1,
The olefin-based film to be laminated by the co-extrusion method during the lamination. The method of claim 1,
The core layer is 40 to 70% of the total film thickness, the total film thickness is 50 to 150㎛ olefin-based film. A solar module back sheet comprising at least one layer of the olefin-based film of any one of claims 1 to 8. The method of claim 9,
The solar module back sheet is a solar module back sheet of any one of the olefin-based film and the polyester film of any one selected from claim 1 to 8. The method of claim 10,
The solar module back sheet is a solar module back sheet further comprises a coating layer or a film made of fluorine resin.