MULTILAYER FILMS CONTAINING A FLUORINATED COPOLYMER RESIN LAYER AND A CROSS-LINKABLE IONOMERIC ENCAPSULANT LAYER

• US 20120152323A1
• Filed: 12/21/2010
• Published: 06/21/2012
• Est. Priority Date: 12/21/2010
• Status: Active Grant

• Current Assignee: E. I. du Pont de Nemours and Company (Corteva, Inc.)
• Original Assignee: E. I. du Pont de Nemours and Company (Corteva, Inc.)
• Inventors: PREJEAN, GEORGE WYATT, SAMUELS, SAM LOUIS, PERRY, PENNY L.
• Granted Patent: US 8,507,097 B2
• Time in Patent Office: Days
• US Class Current: 136/251
• CPC Class Codes: B32B 17/10743 containing acrylate (co)polymers or salts thereof
• CPC Class Codes: B32B 2250/02 2 layers
• CPC Class Codes: B32B 2250/246 All polymers belonging to those covered by groups B32B27/32 and B32B27/30
• CPC Class Codes: B32B 2270/00 Resin or rubber layer containing a blend of at least two different polymers
• CPC Class Codes: B32B 2307/412 Transparent
• CPC Class Codes: B32B 2309/105 Thickness
• CPC Class Codes: B32B 2310/0825 using IR radiation
• CPC Class Codes: B32B 2327/12 containing fluorine
• CPC Class Codes: B32B 2457/12 Photovoltaic modules
• CPC Class Codes: B32B 27/08 of synthetic resin
• CPC Class Codes: B32B 27/16 specially treated, e.g. irradiated
• CPC Class Codes: B32B 27/304 comprising vinyl halide (co)polymers, e.g. PVC, PVDC, PVF, PVDF
• CPC Class Codes: B32B 27/308 comprising acrylic (co)polymers
• CPC Class Codes: B32B 27/322 comprising halogenated polyolefins, e.g. PTFE
• CPC Class Codes: B32B 37/12 characterised by using adhesives
• CPC Class Codes: H01L 31/0481 characterised by the composition of the encapsulation material
• CPC Class Codes: Y02E 10/50 Photovoltaic [PV] energy
• CPC Class Codes: Y10T 156/10 Methods of surface bonding and/or assembly therefor
• CPC Class Codes: Y10T 156/1054 and simultaneously bonding [e.g., cut-seaming]
• CPC Class Codes: Y10T 428/3154 Of fluorinated addition polymer from unsaturated monomers
• CPC Class Codes: Y10T 428/31544 : Addition polymer is perhalogenated

Abstract

A multilayer film comprises a layer consisting essentially of a fluorinated copolymer resin and a layer consisting essentially of an ethylene copolymer ionomer blend. The ethylene copolymer ionomer blend, or the product of crosslinking the blend, can be used as an encapsulant layer for solar cells, and the multilayer film is useful as a component of photovoltaic modules. Methods for preparing the multilayer films and the photovoltaic modules are also described.

Claims

1. A transparent multilayer film comprising:

A. a first film layer comprising a fluorinated copolymer resin composition wherein i) the fluorinated copolymer comprises copolymerized units of tetrafluoroethylene and copolymerized units of comonomers selected from the group consisting of ethylene, perfluorinated comonomer, and combinations thereof, and ii) at least one surface of the first film layer has been modified by a surface treatment; and

B. a second film layer consisting essentially of a blend composition, said blend composition comprising about 10 to about 90 wt % of an Ethylene Copolymer 1 and about 90 to about 10 wt % of an Ethylene Copolymer 2, based on the total weight of the blend composition, and said blend composition consisting essentially of an Ethylene Copolymer 1 and an Ethylene Copolymer 2;

said Ethylene Copolymer 1 consists essentially of copolymerized units of ethylene, optionally about 10 to about 40 wt % of copolymerized units of a first olefin having a formula of CH₂═

C(R¹)CO₂R², and about 2 to about 30 wt % of copolymerized units of a second olefin having a formula of CH₂═

C(R³)COOH, wherein the weight percentages of the copolymerized units of the first olefin and of the second olefin are based on the total weight of said Ethylene Copolymer 1;

wherein about 10 to about 90 wt % of the carboxylic acid groups are neutralized to form carboxylate salts;

wherein R¹ represents hydrogen or an alkyl group, R² represents an alkyl group, and R³ represents hydrogen or an alkyl group; and

wherein said Ethylene Copolymer 2 consists essentially of copolymerized units of ethylene, optionally about 20 to about 40 wt % of copolymerized units of the first olefin, and about 3 to about 15 wt % of copolymerized units of a third olefin having a formula of CH₂═

C(R⁴)-D, wherein the weight percentages of the copolymerized units of the first olefin and of the third olefin are based on the total weight of said Ethylene Copolymer 2;

wherein R⁴ represents hydrogen or an alkyl group;

wherein -D represents a moiety selected from the group consisting of —

CO₂R⁵, —

CO₂R⁶—

R⁵, —

R⁶—

R⁵, —

O—

R⁵, and —

R⁵;

wherein R⁵ represents a moiety containing an epoxy group and R⁶ represents an alkylene group;

with the proviso that none of said first, second or third olefins is a dicarboxylic acid or a di-ester, mono-ester or anhydride of the dicarboxylic acid; and

wherein a surface of the second film layer is adhered to the modified surface of the first film layer.

2. The transparent multilayer film of claim 1, wherein at least a portion of the carboxylate groups or the carboxylic acid groups of Ethylene Copolymer 1 are reacted with at least a portion of the epoxy groups of Ethylene Copolymer 2 to form cross-links between Ethylene Copolymer 1 and Ethylene Copolymer 2.

3. The transparent multilayer film of claim 1, wherein R¹ represents hydrogen or a methyl group, R² represents a butyl group, R³ represents hydrogen or a methyl group, R⁴ represents hydrogen or a methyl group, and -D is —

R⁵, wherein R⁵ represents a moiety containing a glycidyl group.

4. The transparent multilayer film of claim 1, wherein the first olefin is n-butyl acrylate and the second olefin is acrylic acid or methacrylic acid.

5. The transparent multilayer film of claim 1, wherein the third olefin is glycidyl methacrylate.

6. A method for preparing the transparent multilayer film of claim 1, said method comprising the steps of:

A. providing the first film layer;

B. providing the second film layer;

C. contacting a surface of the second film layer with the modified surface of the first film layer; and

D. adhering the first film layer to the second film layer by the application of heat and optionally pressure or vacuum.

7. The method of claim 6 wherein the at least one surface of the first film layer is modified with an aminosilane.

8. A method for preparing a photovoltaic module, the method comprising the steps:

A. providing a solar cell layer;

B. providing a multilayer film laminate according to claim 1 that is larger in area than the solar cell layer;

C. overlaying the solar cell layer with the multilayer film laminate such that

1. the surface of the second layer of the multilayer film laminate contacts the solar cell layer;

2. a portion of the second layer of the multilayer film laminate extends beyond the perimeter of the solar cell layer; and

3. the portion of the second layer of the multilayer film laminate that extends beyond the perimeter of the solar cell layer contacts another layer that is an encapsulant layer; and

D. adhering the second layer of the multilayer film laminate to the encapsulant layer by the application of heat and optionally pressure or vacuum to provide a photovoltaic module.

9. The method of claim 8 wherein the encapsulant layer comprises a polymeric material selected from the group consisting of ethylene acid copolymers, ionomers of ethylene acid copolymers, ethylene vinyl acetate copolymers, poly(vinyl acetals), polyurethanes, polyvinylchlorides, polyethylenes, polyolefin block copolymer elastomers, copolymers of α

-olefins and α

,β

-ethylenically unsaturated carboxylic acid esters, silicone elastomers, epoxy resins, and combinations of two or more thereof.

10. The method of claim 8 wherein an additional layer is adhered to the surface of the encapsulant layer opposite the surface that contacts portions of the surface of the second layer.

11. The method of claim 8 wherein the surface of the first film layer that is in contact with the second film layer is modified with an aminosilane.

12. A photovoltaic module comprising the transparent multilayer film of claim 1.

13. A photovoltaic module of claim 12, wherein the blend composition is at least partially crosslinked.