KR101381715B1 - Hot melt film for Solar cell module - Google Patents

Abstract

The present invention is a polyester film layer formed with a polyurethane hot melt adhesive layer on one surface by in-line coating; A fluorine film layer laminated on the opposite surface on which the polyurethane hot melt adhesive layer of the polyester film layer is formed; It relates to a solar module back sheet having excellent thermal adhesiveness.
The solar cell backsheet according to the present invention is excellent in adhesiveness with the encapsulant while the manufacturing process is simple and the cost can be reduced.

Description

Solar adhesive back sheet with excellent heat adhesiveness and manufacturing method thereof {Hot melt film for Solar cell module}

The present invention relates to a back sheet for a photovoltaic module, and has a new laminated structure in which a structure laminated with a conventional PVF (Tedlar) film, PET film, and PVF (TVDF) film has a new laminated structure, and has excellent thermal adhesiveness. It is about.

Solar cells for solar power generation can start from silicon and various compounds, and become electricity when they become solar cells. However, since one cell does not have sufficient output, each cell must be connected in series or parallel. This state of connection is called a "solar module".

The photovoltaic module is laminated with glass, EVA, solar cell, EVA, and back sheet. The back sheet is a material that is laid at the bottom of the module, and TPT (Tedlar / PET / Tedlar) type is used a lot, and the ribbon is used as a passage through which current flows, so 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.

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

Eva (EVA) was jointly developed in 1970 by NASA and DuPont for 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.

Polyethylene telephthalate (PET) film uses a flat plastic film with constant thickness and physical properties and has excellent strength to form the basic structure of the 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.

BACKGROUND ART Conventionally, a TPT (Tedlar / PET / Tedlar) type backsheet requires a process of laminating a Tedlar film and a PET film through an adhesive agent, respectively. In addition, a back sheet and a sealing material, EVA A step of bonding with 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 price increase according to the conventional adhesive coating process of the various steps as described above, the present invention can reduce the process and cost by forming the adhesive layer through the in-line coating on the polyester film It was found that the adhesiveness with the polyester film is improved to complete the present invention.

That is, the present invention can shorten the process by lowering the Tedlar film layer from the Tedlar film / PET film / Tedlar film lamination structure, which is used for the back sheet for the solar module, and can lower the product price, and it is an EVA film which is an encapsulant. An object of the present invention is to provide a film for back sheet having excellent adhesiveness with.

In order to solve the above object, the present invention is an invention for further removing the Tedlar film adhered to the encapsulant in the structure that was conventionally laminated with a Tedlar film / PET film / Tedlar film, the adhesiveness of the encapsulant EVA instead of the Tedlar film It is characteristic to form a polyurethane adhesive layer so as to be excellent.

However, when the polyurethane adhesive layer is applied offline on the PET film, there is a problem in that the cost increases because the process is further increased, and the coating thickness becomes thick, which has the disadvantage of increasing the cost. Therefore, the present inventors have found that the coating thickness is thin and the adhesion to the PET film is improved by applying an aqueous dispersion composition (emulsion) to form a polyurethane hot melt adhesive layer in the stretching process during the manufacturing process of the PET film by the inline coating method. The present invention was completed.

In addition, as a composition for forming a polyurethane adhesive layer, in the process of assembling the photovoltaic module, the EVA film and the back sheet are heat-bonded under high temperature conditions, so that a water dispersion composition (emulsion) is developed to express sufficient adhesive force when heat-bonded under high temperature conditions. It is characterized by controlling the diisocyanate and polyol content of the polyurethane resin forming.

In addition, in order to be used in the in-line process to be prepared as a water dispersion composition (emulsion), it is characterized by the addition of a specific wetting agent and dispersion stabilizer to the polyurethane resin to produce a composition having excellent water dispersibility.

More specifically, the present invention relates to

A polyester film layer having a polyurethane hot melt adhesive layer formed on one surface by an inline coating;

A fluorine film layer laminated on the opposite surface on which the polyurethane hot melt adhesive layer of the polyester film layer is formed;

It relates to a solar module back sheet having excellent thermal adhesiveness.

Also,

a) melt extruding a polyester resin to prepare a polyester sheet;

b) stretching the polyester sheet in the machine direction;

c) 0.5 to 5% by weight of an aqueous dispersion of one-component polyurethane containing 5 to 25% by weight of diisocyanate and 40 to 70% by weight of polyisocyanate as solid content on one surface of the polyester film drawn in the machine direction, and an emulsifier 0.01 to 1 A polyurethane hot melt adhesive layer was formed by applying a polyurethane emulsion containing water so as to satisfy the weight%, the wetting agent 0.01 to 0.5 wt%, the dispersion stabilizer 0.1 to 5 wt%, and the balance 100 wt%, and then stretch in the transverse direction. Making;

d) heat setting the biaxially stretched polyester film;

e) laminating a fluorine film using a polyurethane-based adhesive on the opposite side to which the polyurethane emulsion is applied;

It relates to a manufacturing method of a solar module back sheet having excellent thermal adhesiveness comprising a.

Hereinafter, the present invention will be described more specifically.

In the present invention, the polyester film may be polyethylene terephthalate, polyethylene naphthalate and the like. More preferably, polyethylene terephthalate having an intrinsic viscosity of 0.6 to 0.7 is preferable because of excellent weather resistance and hydrolysis resistance. In addition, the polyester film has a thickness of 12 ~ 250㎛ advantageous production, it is preferable because it can implement a variety of laminated structure.

The present invention forms a polyurethane hot melt adhesive layer by in-line coating on one surface in the process of producing such a polyester film.

The polyurethane hot melt adhesive layer is preferably a dry coating thickness of 50 ~ 300nm, the adhesive strength of 1 ~ 10kg / inch. If the dry coating thickness is less than 50nm, the adhesive strength may be weak, if it exceeds 300nm, the cost is increased, the adhesiveness may increase and the processability may be lowered. In addition, the adhesive force is preferable because the adhesive strength is excellent in the range of 1kg / inch ~ 10kg / inch.

The water dispersion composition (emulsion) to form the polyurethane hot melt adhesive layer is 0.5 to 5% by weight of the water dispersion one-component polyurethane containing 5 to 25% by weight of diisocyanate, 40 to 70% by weight of the polyol, and emulsifier 0.01 ~ by solid content It is preferable to use a polyurethane emulsion comprising water so as to satisfy 1% by weight, 0.01 to 0.5% by weight of the wetting agent, 0.1 to 5% by weight of the dispersion stabilizer and the remaining 100% by weight.

The water dispersion one-component polyurethane is used in the above range because it contains the isocyanate and polyol, water and additives and the like in the range of 5 to 25% by weight of diisocyanate, 40 to 70% by weight of polyol It is preferable. The polyol may be used any one or more selected from polyethylene glycol, polycaprolactam.

In addition, the emulsifier is used to disperse the polyurethane resin may be used a nonionic, anionic and cationic surfactant, etc., the content is preferably 0.01 to 1% by weight (confirmation). .

The wetting agent is used to uniformly apply the polyester film and the emulsion, it is preferable to use the one selected from polyethylene glycol, polyethylene ester, etc., since the coating property is greatly improved, for example, FO-28 Etc. The content is preferably 0.01 to 0.5% by weight because it is excellent in adhesion.

The dispersion stabilizer is used for the dispersion stability of the emulsion, it may be used a nonionic surfactant, and the like, specifically, for example, polyoxyethylene octylphenyl ether (Han concentration, OP series) and the like can be used.

In addition, if necessary, particles may be added to improve slip properties of the coating layer using the polyurethane emulsion, and inorganic particles and organic particles may be added. The content is preferably used 0.01 to 5% by weight.

In addition, additives such as crosslinking agents, UV stabilizers, antistatic agents, and the like, which are commonly used in the art, may be further added as necessary.

In the present invention, the fluorine film uses a film made of polyvinyl fluoride (PVF), PVDF, or the like, and may typically use trade names such as Tedlar and Kynar. The fluorine film may be laminated by an adhesive such as polyurethane or polyester based on one surface of a polyester on which a polyurethane hot melt adhesive layer is formed by an inline coating method.

Next, the method of manufacturing the backsheet of the present invention will be described in detail.

The present invention comprises the steps of melt-extrusion of the polyester resin to make a sheet, uniaxially stretch it, apply a polyurethane emulsion and biaxially stretch in the transverse direction to produce a polyester film; Stacking a fluorine film on the polyester film using an adhesive; .

More specifically, the present invention relates to

a) melt extruding a polyester resin to prepare a polyester sheet;

b) stretching the polyester sheet in the machine direction;

c) 0.5 to 5% by weight of an aqueous dispersion of one-component polyurethane containing 5 to 25% by weight of diisocyanate and 40 to 70% by weight of polyisocyanate as solid content on one surface of the polyester film drawn in the machine direction, and an emulsifier 0.01 to 1 A polyurethane hot melt adhesive layer was formed by applying a polyurethane emulsion containing water so as to satisfy the weight%, the wetting agent 0.01 to 0.5 wt%, the dispersion stabilizer 0.1 to 5 wt%, and the balance 100 wt%, and then stretch in the transverse direction. Making;

d) heat setting the biaxially stretched polyester film;

e) laminating a fluorine film using a polyurethane-based adhesive on the opposite side to which the polyurethane emulsion is applied;

.

Step a) is a process of melting the resin in a cylinder to produce a polyester film into a sheet through a T-die in order to produce a polyester film.

Step b) is a process for producing a polyester film by biaxially stretching the polyester sheet, it is preferable that the stretching in the machine direction using one or more rollers.

Next, the polyurethane adhesive layer is formed by the inline coating method in step c), and it is preferable to use a water-dispersed emulsion to be used for the inline coating.

At this time, the composition of the emulsion for forming the polyurethane hot melt adhesive layer is as described above, it is preferable to apply so that the dry coating thickness after stretching at 50 ~ 300nm.

The polyurethane emulsion is applied to form a polyurethane hot melt adhesive layer, and then stretched in the transverse direction. At this time, it is preferable to use a tenter for lateral stretch.

Next, to remove the moisture used in the hot melt adhesive layer, the adhesive layer is cured, and dried and heat-set to prevent the film from shrinking.

In addition, if necessary, the corona treatment may be performed on the surface of the polyester film before applying the polyurethane emulsion or before applying the polyurethane-based adhesive to bond the fluorine film.

The solar cell backsheet according to the present invention can simplify the manufacturing process, the manufacturing cost can be reduced by removing one fluorine film layer, and the adhesion between the encapsulant EVA and the backsheet is excellent.

1 is a cross-sectional view showing a back sheet for a photovoltaic module according to the present invention.
Figure 2 is a cross-sectional view showing a laminated structure of the solar module to which the solar module back sheet according to the present invention.

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.

The following physical property measuring method is demonstrated concretely.

1. Adhesion

The adhesion between the encapsulant EVA film and the polyurethane adhesive layer was evaluated. Bonding method is to laminate the encapsulant EVA film and the polyurethane adhesive layer in contact with each other, and then bonded under conditions of 70g / ㎠ for 10 minutes at 150 ℃, then peeled off at a peel angle of 180 degrees, peeling speed 300mm / min at room temperature Evaluated.

2. Hydrolysis resistance

The prepared backsheet film was placed in an autoclave, maintained at 120 ° C. and 100% humidity for 30 hours, and then adhered and peeled off in the same manner as in the adhesion test to evaluate the adhesion strength retention relative to the initial adhesion.

Adhesion Retention Rate = (Adhesion / Initial Adhesion After Evaluation) * 100

Example 1

Preparation of Polyurethane Emulsions

Polyurethane-based resin (20% by weight of diisocyanate, 60% by weight of polyol) (2% by weight of Superflex 500M), 0.1% by weight of emulsifier (polyoxyethylene nonyl phenyl ether), wetting agent (FO of Japan Holdings) -28) A polyurethane emulsion was prepared by mixing 0.1% by weight, 0.5% by weight of a dispersion stabilizer (OP-concentrate, OP-40) and 97.3% by weight of water.

Preparation of Polyester Film for Back Sheet

A polyethylene terephthalate chip having a moisture content of 100 ppm or less was injected into a melt extruder, melted, and then extruded through a T-die, followed by quenching and solidifying with a casting drum having a surface temperature of 20 ° C. to prepare a polyethylene terephthalate sheet having a thickness of 2000 μm. .

The prepared polyethylene terephthalate sheet was stretched 3.5 times in the machine direction (MD) at 110 ° C. and then cooled to room temperature. Thereafter, the polyurethane emulsion was coated on one surface by a bar coating method, and then stretched 3.5 times in a transverse direction (TD) through preheating and drying at 140 ° C. Thereafter, heat treatment was performed at 235 ° C. in a 5-stage tenter, followed by heat setting by relaxing 10% in the machine direction and the transverse direction at 200 ° C. to prepare a 250 μm biaxially oriented film having an adhesive layer formed on one surface thereof. The dry coating thickness after extending | stretching the said contact bonding layer was 100 nm.

Manufacture of Back Sheet for Solar Module

On the opposite side on which the adhesive layer of the biaxially stretched polyester film with the adhesive layer prepared was formed, a Tedlar film was laminated using a polyurethane adhesive.

The physical properties of the backsheet thus obtained are shown in Table 1 below.

[Comparative Example 1]

Preparation of Polyester Film for Back Sheet

A polyethylene terephthalate chip having a moisture content of 100 ppm or less was injected into a melt extruder, melted, and then extruded through a T-die, followed by quenching and solidifying with a casting drum having a surface temperature of 20 ° C. to prepare a polyethylene terephthalate sheet having a thickness of 2000 μm. .

The prepared polyethylene terephthalate sheet was stretched 3.5 times in the machine direction (MD) at 110 ° C. and then cooled to room temperature. Then, the film was stretched 3.5 times in the transverse direction (TD) through preheating and drying at 140 ° C. Thereafter, heat treatment was performed at 235 ° C. in a 5-stage tenter, 10% relaxation at 200 ° C. in the machine direction and in the transverse direction, heat setting, and a corona treatment on one surface to prepare a 250 μm biaxially oriented film. .

Manufacture of Back Sheet for Solar Module

On the opposite side on which the adhesive layer of the biaxially stretched polyester film with the adhesive layer prepared was formed, a Tedlar film was laminated using a polyurethane adhesive.

The physical properties of the backsheet thus obtained are shown in Table 1 below.

[Comparative Example 2]

Preparation of Polyester Emulsions

Polyester resin (Takamatsu, based on solid content of KLX-017) 2% by weight, 0.1% by weight emulsifier (polyoxyethylene nonyl phenyl ether), 0.25% by weight of wetting agent (FO-28 from Japan Oil & Fat), dispersion stabilizer Polyurethane emulsions were prepared by mixing 0.5% by weight (hypertensive, OP-40) and 97.15% by weight of water.

Preparation of Polyester Film for Back Sheet

A polyethylene terephthalate chip having a moisture content of 100 ppm or less was injected into a melt extruder, melted, and then extruded through a T-die, followed by quenching and solidifying with a casting drum having a surface temperature of 20 ° C. to prepare a polyethylene terephthalate sheet having a thickness of 2000 μm. .

The prepared polyethylene terephthalate sheet was stretched 3.5 times in the machine direction (MD) at 110 ° C. and then cooled to room temperature. Thereafter, the polyester emulsion was coated on one surface by a bar coating method, and then stretched 3.5 times in a transverse direction (TD) through preheating and drying at 140 ° C. Thereafter, heat treatment was performed at 235 ° C. in a 5-stage tenter, followed by heat setting by relaxing 10% in the machine direction and the transverse direction at 200 ° C. to prepare a 250 μm biaxially oriented film having an adhesive layer formed on one surface thereof.

Manufacture of Back Sheet for Solar Module

On the opposite side on which the adhesive layer of the biaxially stretched polyester film with the adhesive layer prepared was formed, a Tedlar film was laminated using a polyurethane adhesive.

The physical properties of the backsheet thus obtained are shown in Table 1 below.

[Table 1]

100: encapsulant for solar modules
200: solar module back sheet
11: solar cell 12: EVA encapsulant
21: polyester film
22: polyurethane hot melt adhesive layer
23: fluorine film
24: adhesive layer

Claims (11)

Polyurethane emulsion containing water dispersion one-component polyurethane containing 5 to 25% by weight of diisocyanate and 40 to 70% by weight of polyol, emulsifier, wetting agent, dispersion stabilizer and water in solid content in the stretching process of polyester film A polyester film layer having a polyurethane hot melt adhesive layer formed on one surface by inline coating;
A fluorine film layer laminated by an adhesive on the opposite surface on which the polyurethane hot melt adhesive layer of the polyester film layer is formed;
Solar module back sheet excellent thermal adhesiveness comprising a. The method of claim 1,
The fluorine film layer is a solar module back sheet having excellent thermal adhesiveness laminated by an adhesive selected from a polyurethane-based, polyester-based. The method of claim 1,
The polyurethane hot melt adhesive layer has a dry coating thickness of 50 ~ 300nm, the adhesive force of 1 ~ 10kg / inch solar module back sheet having excellent thermal adhesiveness. The method of claim 3,
The polyurethane hot melt adhesive layer is 0.5 to 5% by weight of a one-component polyurethane dispersion of water containing 5 to 25% by weight of diisocyanate, 40 to 70% by weight of polyol, emulsifier 0.01 to 1% by weight, wetting agent 0.01 to 0.5 A solar cell back sheet having excellent thermal adhesiveness applied in a stretching process of a polyester film by using a polyurethane emulsion containing water to satisfy the weight%, the dispersion stabilizer 0.1 to 5% by weight and the rest 100% by weight. 5. The method of claim 4,
The polyurethane emulsion is a solar module back sheet having excellent thermal adhesiveness further comprises 0.01 to 5% by weight of inorganic particles or organic particles. 5. The method of claim 4,
The stretching step is a biaxial stretching step, and applied to the polyurethane emulsion after stretching in the machine direction, and then stretched in the transverse direction excellent solar adhesive back sheet. The method of claim 1,
The polyester film is a solar module back sheet having excellent heat adhesiveness of 12 ~ 250㎛ thickness. a) melt extruding a polyester resin to prepare a polyester sheet;
b) stretching the polyester sheet in the machine direction;
c) 0.5 to 5% by weight of an aqueous dispersion of one-component polyurethane containing 5 to 25% by weight of diisocyanate and 40 to 70% by weight of polyisocyanate as solid content on one surface of the polyester film drawn in the machine direction, and an emulsifier 0.01 to 1 A polyurethane hot melt adhesive layer was formed by applying a polyurethane emulsion containing water so as to satisfy the weight%, the wetting agent 0.01 to 0.5 wt%, the dispersion stabilizer 0.1 to 5 wt%, and the balance 100 wt%, and then stretch in the transverse direction. Doing;
d) heat setting the biaxially stretched polyester film;
e) laminating a fluorine film using an adhesive selected from polyurethane and polyester based on the opposite side of the polyurethane emulsion;
Manufacturing method of a solar module back sheet having excellent thermal adhesiveness comprising a. The method of claim 8,
The polyurethane emulsion is a method of manufacturing a solar module back sheet having excellent thermal adhesiveness to apply so that the coating thickness after drying to 50 ~ 300nm. The method of claim 8,
The polyurethane emulsion is a method of manufacturing a solar module back sheet having excellent thermal adhesiveness of 1 ~ 10kg / inch after drying the adhesive force. The method of claim 8,
The polyester film is a manufacturing method of a solar module back sheet having excellent heat adhesiveness of 12 ~ 250㎛ thickness.

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