Encapsulant for PV module, method of manufacturing the same and PV module comprising the same

Abstract

The present application relates to an encapsulant for a PV module, a method of manufacturing the same and a PV module. The encapsulant according to an embodiment of the present application has excellent heat resistance or the like and improved creep physical properties, and thus even when the encapsulant is used under conditions of a high temperature and/or high humidity for a long time, deformation is small and the encapsulant can exhibit excellent adhesive strength. Accordingly, when the encapsulant is applied to a PV module, durability or the like may be improved.

Claims

1. An encapsulant for a photovoltaic (PV) module, comprising: an ethylene/α-olefin-based copolymer; a silane modified ethylene/α-olefin-based copolymer; and a heat resistant polymer resin having a melting point (Tm) higher than the ethylene/α-olefin-based polymer, wherein the silane modified ethylene/α-olefin-based copolymer is the ethylene/α-olefin-based copolymer graft polymerized with a silane compound, and wherein the silane compound comprises a compound represented by Formula 1:
DSiR.sup.1.sub.pR.sup.2.sub.(3-p)  [Formula 1] wherein D is an alkenyl group, R.sup.1 is an alkoxy group, an alkylthio group, an aryloxy group, an acyloxy group, a hydroxy group, a halogen group, an amine group or —R.sup.3R.sup.4, R.sup.3 is an oxygen (O) or sulfur (S) atom, R.sup.4 is an alkyl group, an aryl group, or an acyl group, R.sup.2 is hydrogen, an alkyl group, an aryl group, or an aralkyl group, and p is an integer in a range of 1 to 3.

2. The encapsulant of claim 1, wherein the heat resistant polymer resin has a melting point (Tm) of 100° C. or more.

3. The encapsulant of claim 1, wherein the heat resistant polymer resin has a melting point (Tm) in a range of 100 to 150° C.

4. The encapsulant of claim 1, wherein the heat resistant polymer resin has a melt index (MI) lower than the ethylene/α-olefin-based copolymer.

5. The encapsulant of claim 1, wherein the heat resistant polymer resin has a melt index (MI) in a range of 0.1 g/10 min to 40 g/10 min at a temperature of 190° C. and a load of 2.16 kg.

6. The encapsulant of claim 1, wherein the heat resistant polymer resin is included in a range of 0.1 to 10 parts by weight with respect to 100 parts by weight of a mixture of the ethylene/α-olefin-based copolymer and the silane modified ethylene/α-olefin-based copolymer.

7. The encapsulant of claim 1, wherein the heat resistant polymer resin is included in a range of 1 to 5 parts by weight with respect to 100 parts by weight of a mixture of the ethylene/α-olefin-based copolymer and the silane modified ethylene/α-olefin-based copolymer.

8. The encapsulant of claim 1, wherein the heat resistant polymer resin is a polyethylene-based resin and/or a polypropylene-based resin.

9. The encapsulant of claim 1, wherein the heat resistant polymer resin comprises a low density polyethylene.

10. The encapsulant of claim 1, satisfying the following Expression 1:
ΔX≦3 mm  [Expression 1] in the Expression 1, after two layers of encapsulants having a size of 20 cm×25 cm (width×length) are overlapped and interposed between a first glass plate having a thickness of 3.2 and having a size of 20 cm×30 cm (width×length) and a second glass plate having a thickness of 3.2 and having a size of 20 cm×30 cm (width×length) and laminated to prepare a sample having a size of 20 cm×35 cm (width×length), the sample was vertically (90°) erected, the first glass plate was fixedly suspended, the sample was maintained at 100° C. for 10 hours, and here, an average value of vertically creeping distances of a left side, a center, and a right side of the second glass plate is represented by ΔX.

11. An encapsulant for a photovoltaic (PV) module, comprising: an ethylene/α-olefin-based copolymer; a silane modified ethylene/α-olefin-based copolymer; and a heat resistant polymer resin having a melting point (Tm) higher than the ethylene/α-olefin-based polymer, wherein the silane modified ethylene/α-olefin-based copolymer is the ethylene/α-olefin-based copolymer graft polymerized with a silane compound, and wherein the silane compound comprises a compound represented by Formula 2:
SiR.sup.5.sub.qR.sup.6.sub.(4-q)  [Formula 2] wherein R.sup.5 is —(CH.sub.2).sub.vNR.sup.7R.sup.8, R.sup.7 and R.sup.8 are each independently hydrogen or R.sup.9NH.sub.2 bound to nitrogen atoms, R.sup.9 is an alkylene group having 1 to 6 carbon atoms, R.sup.6 is halogen, an amine group, —R.sup.10R.sup.11 or —R.sup.11, R.sup.10 is an oxygen (O) or sulfur (S) atom, R.sup.11 is hydrogen, an alkyl group, an aryl group, an aralkyl group, or an acyl group, v is an integer of 1 or more, and q is an integer in a range of 1 to 4.

12. An encapsulant for a photovoltaic (PV) module, comprising: an ethylene/α-olefin-based copolymer; a silane modified ethylene/α-olefin-based copolymer; and a heat resistant polymer resin having a melting point (Tm) higher than the ethylene/α-olefin-based polymer, wherein the silane modified ethylene/α-olefin-based copolymer comprises a main chain including a polymerization unit of an olefin-based monomer and a branched chain bound to the main chain, and the branched chain includes a compound represented by Formula 3 or Formula 4:
—SiR.sup.12R.sup.13R.sup.14  [Formula 3] wherein, in Formula 3, R.sup.12 and R.sup.13 are each independently halogen, an amine group, —R.sup.15R.sup.16 or —R.sup.16, R.sup.15 is an oxygen (O) or sulfur (S) atom, R.sup.16 is hydrogen, an alkyl group, an aryl group, an aralkyl group, or an acyl group, R.sup.14 is —OSiR.sup.17.sub.mR.sup.18.sub.(2-m)R.sup.19, R.sup.17 and R.sup.18 are each independently halogen, an amine group, —R.sup.20R.sup.21 or —R.sup.21, R.sup.20 is an oxygen (O) or sulfur (S) atom, R.sup.21 is hydrogen, an alkyl group, an aryl group, an aralkyl group, or an acyl group, R.sup.19 is —(CH.sub.2).sub.nNR.sup.22R.sup.23, R.sup.22 and R.sup.23 are each independently hydrogen bound to nitrogen atoms or R.sup.24NH.sub.2, R.sup.24 is an alkylene group, m is an integer of 1 or 2, and n is an integer of 1 or more,
—SiR.sup.25.sub.rR.sup.26.sub.(3-r)  [Formula 4] wherein, in Formula 4, R.sup.25 and R.sup.26 are each independently halogen, an amine group, —R.sup.27R.sup.28 or —R.sup.28, R.sup.27 is an oxygen (O) or sulfur (S) atom, R.sup.28 is hydrogen, an alkyl group, an aryl group, an aralkyl group, or an acyl group, and r is an integer in a range of 1 to 3.

13. A method of manufacturing the encapsulant for a photovoltaic (PV) module of claim 1, comprising manufacturing a sheet-shaped resin composition which includes the ethylene/α-olefin-based copolymer, the silane modified ethylene/α-olefin-based copolymer and the heat resistant polymer resin having a melting point higher than the ethylene/α-olefin-based polymer.

14. A PV module comprising an encapsulant layer including the encapsulant according to claim 1.

15. The PV module of claim 14, comprising: a front substrate; the encapsulant layer formed on the front substrate; a solar cell encapsulated by the encapsulant layer; and a back sheet formed on the encapsulant layer.

Description

DESCRIPTION OF DRAWINGS

(1) FIG. 1 is a cross sectional view of a solar cell module, as a conventional PV module.

(2) FIG. 2 is a view for describing a method of measuring creep physical properties for the encapsulant according to an embodiment of the present application as an example.

(3) FIG. 3 is a view exemplarily illustrating the structure of a PV module according to an embodiment of the present application.

(4) FIG. 4 shows pictures illustrating an evaluation result of encapsulant samples according to Example 1 and Comparative Example 1 of the present application.

MODES OF THE INVENTION

(5) Hereinafter, the present application will be described in detail in conjunction with examples according to the present application and comparative examples not according to the present application, but the scope of the present application is not limited the following examples.

(6) Physical properties in the examples and the comparative examples were evaluated according to the following method as below.

(7) 1. Measurement and Evaluation of Creep Physical Properties

(8) 1) Glass plate and encapsulant sheet: two low iron tempered glass plates (weight: 475 g) having a thickness of 3.2 mm, and a size of 20 cm×30 cm (width×length) were prepared. Further, encapsulant sheets (thickness: about 500 μm) according to each of the examples and comparative examples were cut to a size of 20 cm×25 cm (width×length).

(9) 2) Thermal lamination: two encapsulant sheets were stacked between two glass plates in the sequence of a first glass plate (lower plate), (two) encapsulants, and a second glass plate (upper plate). The first glass plate and the second glass plate were stacked to extend above and below the two encapsulants, respectively, with gaps of about 5 cm (refer to FIG. 2). Then, a thermal lamination was performed in a vacuum laminator at a temperature of 150° C. for 17 minutes (vacuuming for 6 minutes.fwdarw.compressing for 1 minute.fwdarw.maintaining for 10 minutes), and thereby a sample having a size of 20 cm×35 cm (width×length) was prepared.

(10) 3) Measurement of creeping distance: the sample was vertically erected in a chamber, the first glass plate was suspended through a clamp, the sample was stored vertically held in the chamber maintaining the temperature of 100° C. and the humidity of 60% for 10 hours (refer to FIG. 2), each creeping distance (sliding distance) of the left side, center, and right side of the second glass plate from a base line each was measured, the average value (ΔX) thereof was calculated and evaluated according to the following standard, and then was shown in Table 1.

(11) <Evaluation Standard>

(12) O: when the average value (ΔX) of the creeping distances measured at each of the left side, center, and right side was 3 mm or less.

(13) X: when the average value (ΔX) of the creeping distances measured at each of the left side, center, and right side was more than 3 mm.

Example 1

(14) <Preparation of Silane Modified Ethylene/α-Olefin Copolymer>

(15) After vinyltrimethoxy silane (VTMS) and Luperox®101 (2,5-bis(tert-butylperoxy)-2,5-dimethylhexane) were mixed in the weight ratio of 50:1, the mixture was included in the ethylene/1-octene copolymer (LC670; LG Chem.) having a density of 0.870 g/cm.sup.3 and a melt index (MI) of 5 g/10 min at a temperature of 190° C. and a load of 2.16 kg at 5 parts by weight with respect to 100 parts by weight of the ethylene/1-octene copolymer, was put into a twin-screw extruder together with the ethylene/1-octene copolymer, was extruded (heated, melted and stirred) at a temperature of 220° C. to perform a grafting reaction, and thereby the master batch of a silane modified ethylene/α-olefin copolymer (hereinafter, referred to as “Si M/B”) was prepared.

(16) <Preparation of Encapsulant Sheet>

(17) A certain amount of a UV absorbent, a UV stabilizer and an antioxidant was mixed with the ethylene/1-octene copolymer (LC670; LG Chem., hereinafter, referred to as a “base resin”) having a density of 0.870 g/cm.sup.3, a melting point (Tm) of 58° C., and a melt index (MI) of 5 g/10 min at a temperature of 190° C. and a load of 2.16 kg, and then extruded to prepare a UV master batch (hereinafter, referred to as a “UV M/B”).

(18) Thereafter, a base resin, Si M/B and UV M/B prepared as above, and a low density polyethylene (BC500; LG Chem., hereinafter, referred to as a “LDPE”) having a melting point (Tm) of about 105° C. and a melt index (MI) of 3 g/10 min at a temperature of 190° C. and a load of 2.16 kg as a heat resistant polymer resin were mixed in the weight ratio of 65:35:3:2, and thereby a mixture was prepared.

(19) The mixture was introduced into the hopper of an extruding machine having a twin-screw extruder (φ19 mm) and a T die (width: 200 mm), extruded at a temperature of 180° C. and the extracting speed of 3 m/min, and thereby an encapsulant sheet having a thickness of about 500 μm was prepared.

Example 2

(20) The encapsulant sheet was prepared in the same manner as in Example 1 except that the LDPE was included at 1 part by weight with respect to 100 parts by weight of the mixture of the base resin and Si M/B.

Example 3

(21) The encapsulant sheet was prepared in the same manner as in Example 1 except that the LDPE was included at 3 parts by weight with respect to 100 parts by weight of the mixture of the base resin and Si M/B.

Example 4

(22) The encapsulant sheet was prepared in the same manner as in Example 1 except that the LDPE was included at 5 parts by weight with respect to 100 parts by weight of the mixture of the base resin and Si M/B.

Example 5

(23) The encapsulant sheet was prepared in the same manner as in Example 1 except that a LDPE (BF0300; LG Chem.) having a melting point (Tm) of about 105° C., the melt index (MI) of 0.3 g/10 min at 190° C. and a load of 2.16 kg was included as a heat resistant polymer resin.

Example 6

(24) The encapsulant sheet was prepared in the same manner as in Example 1 except that a LDPE (LB8500; LG Chem.) having a melting point (Tm) of about 105° C., a melt index (MI) of 8.5 g/10 min at 190° C. and a load of 2.16 kg was included as a heat resistant polymer resin.

Example 7

(25) The encapsulant sheet was prepared in the same manner as in Example 1 except that a LDPE (MB9205; LG Chem.) having a melting point (Tm) of about 105° C., a melt index (MI) of 24 g/10 min at 190° C. and a load of 2.16 kg was included as a heat resistant polymer resin.

Comparative Example 1

(26) The encapsulant sheet was prepared in the same manner as in Example 1 except that the LDPE was not introduced into the hopper of the extruding machine, and a mixture in which the base resin, Si M/B and UV M/B were mixed in the weight ratio of 63.1:34:2.9 was used.

Comparative Example 2

(27) The encapsulant sheet was prepared in the same manner as in Example 1 except that a LDPE (MB9500; LG Chem.) having a melting point (Tm) of about 105° C., a melt index (MI) of 50 g/10 min at 190° C. and a load of 2.16 kg was included as a heat resistant polymer resin.

(28) The anti-creep properties of each of the encapsulant sheets according to Examples 1 to 4 and Comparative Example 1 were shown in the following Table 1.

(29) TABLE-US-00001 TABLE 1 Comparative Example Example Classification 1 2 3 4 1 Left 0 1.5 0 0 4.0 Center 0 1.5 0 0 4.0 Right 0 1.5 0 0 3.5 Average values 0 1.5 0 0 3.8 Creep evaluation ∘ ∘ ∘ ∘ x Unit: mm

(30) Further, FIG. 4 shows the pictures of the encapsulant sheets according to Example 1 and Comparative Example 1 right after the test for anti-creep properties.

(31) As shown in Table 1 and FIG. 4, when the heat resistant polymer resin (LDPE) was included, creep properties were improved, the creeping distance was minimal or there was no creeping, and thus the encapsulant sheet could be determined to be useful for an encapsulant.

(32) Further, creep properties of encapsulant sheets according to Examples 5 to 7 and Comparative Example 2 were shown in the following Table 2.

(33) TABLE-US-00002 TABLE 2 Comparative Example Example Classification 5 6 7 2 Left 0 0.8 2.5 4.0 Center 0 0.8 2.5 4.0 Right 0 0.8 2.5 4.0 Average values 0 0.8 2.5 4.0 Creep evaluation ∘ ∘ ∘ x Unit: mm

(34) As shown in Table 2, it was determined that creep physical properties could differ according to the melt index (MI) of a LDPE, and when the melt index (MI) was about 40 g/10 min or less, creep physical properties were excellent enough for the encapsulant sheet to be applied to the encapsulant.

DESCRIPTION OF NUMERAL

(35) 1, 100: BACK SHEET 2a, 221: FRONT ENCAPSULANT LAYER 2B, 222: BACK ENCAPSULANT LAYER 3: TEMPERED GLASS 10: BASE 20, 30: SURFACE LAYER 210: FRONT SUBSTRATE 220: ENCAPSULANT LAYER C: SOLAR CELL