CN221226246U

CN221226246U - Gap film and photovoltaic module

Info

Publication number: CN221226246U
Application number: CN202322858225.8U
Authority: CN
Inventors: 蒋忠伟; 帅莉芳; 王乐
Original assignee: Trina Solar Co Ltd
Current assignee: Trina Solar Co Ltd
Priority date: 2023-10-24
Filing date: 2023-10-24
Publication date: 2024-06-25
Anticipated expiration: 2033-10-24

Abstract

The application relates to a gap film and a photovoltaic module. The gap film is provided with a non-overlapping region and an overlapping region positioned on at least one side of the non-overlapping region, and the gap film and the solar cell can be overlapped in the overlapping region; the gap film comprises a bonding layer, a substrate layer and a reflecting structure; the substrate layer comprises at least one matrix arranged on one side of the bonding layer along the first direction, the matrix comprises an overlapped part positioned in the overlapped area, and the thickness of the overlapped part is gradually increased along the second direction; the second direction is a direction pointing from the overlapping area to the non-overlapping area and is perpendicular to the first direction; the reflecting structure covers one side of the substrate layer, which is away from the bonding layer, and is used for reflecting sunlight so that the sunlight can reach the solar cell. The application can reduce the probability of grid breakage of the solar cell and improve the output power and reliability of the photovoltaic module; the light utilization rate is improved, and the photoelectric conversion efficiency of the photovoltaic module is improved.

Description

Gap film and photovoltaic module

Technical Field

The application relates to the technical field of photovoltaic cells, in particular to a gap film and a photovoltaic module.

Background

A solar cell, also called a photovoltaic cell, is a semiconductor device that directly converts light energy of the sun into electrical energy. Because it is a green environment-friendly product, does not cause environmental pollution, and solar energy is renewable resource, therefore, the solar cell is a novel cell with wide development prospect.

In the photovoltaic module, a plurality of solar cells are arranged, gaps exist among the solar cells, when solar rays irradiate the gap area, the substrate surface of the gap area reflects part of sunlight, so that the part of sunlight cannot be utilized by the solar cells, the utilization rate of light energy is reduced, and the photoelectric conversion efficiency of the photovoltaic module is reduced.

In the related art, in order to improve the solar light utilization rate and the photoelectric conversion efficiency of the photovoltaic module, a reflective film is disposed on the back plate of the photovoltaic module and corresponds to the gap area between the solar cells, so that the light can reach the solar cells. However, when the photovoltaic module is obtained by lamination or subjected to stress aging test (such as thermal cycle test, mechanical load test, etc.), the grid line of the solar cell close to the gap area is easy to break, which affects the output power and reliability of the photovoltaic module.

Disclosure of Invention

Accordingly, it is necessary to provide a gap film and a photovoltaic module, which are aimed at the problem that the grid line of the solar cell close to the gap region is easy to break and the output power and the reliability of the photovoltaic module are affected.

An embodiment of the first aspect of the present application provides a gap film for a photovoltaic module, the photovoltaic module including a solar cell, the gap film having a non-overlapping region and an overlapping region located on at least one side of the non-overlapping region, the gap film and the solar cell being capable of overlapping in the overlapping region; the gap film comprises a bonding layer, a substrate layer and a reflecting structure; the substrate layer comprises at least one matrix arranged on one side of the bonding layer along a first direction, the matrix comprises an overlapped part positioned in the overlapped area, and the thickness of the overlapped part gradually increases along a second direction; the second direction is a direction pointing from the overlapping region to the non-overlapping region, and is perpendicular to the first direction; the reflecting structure covers one side of the substrate layer, which is away from the bonding layer, and is used for reflecting sunlight so that the sunlight can reach the solar cell.

In one embodiment, the base further comprises a main body portion, the main body portion being located in the non-overlapping region; the gap film comprises two overlapping areas positioned at two sides of the non-overlapping area; the two overlapping parts are positioned in the two overlapping areas in a one-to-one correspondence manner; both of the overlapping portions are connected with the main body portion.

In one embodiment, the number of the matrixes is a plurality, and the matrixes are distributed at intervals along the first direction and extend along a third direction; the third direction is perpendicular to the first direction and the second direction; the two overlapped parts are distributed on two sides of the substrate layer along the first direction and are respectively connected with the main body parts of the corresponding matrixes.

In one embodiment, the substrate layer further includes a connector connected between adjacent substrates, all of the connectors are located in the non-overlapping region, the thickness of each of the connectors is equal, and the thickness of the connector is smaller than the maximum thickness of the overlapping portion.

In one embodiment, the thickness is equal throughout the body portion; the buffer layer covers the overlapping part and one side of the connector, which is away from the bonding layer, and the surface of one side of the buffer layer, which is away from the bonding layer, is flush with the surface of one side of the main body part; the reflecting structure covers one side of the substrate layer and one side of the buffer layer, which are away from the bonding layer.

In one embodiment, the material of the buffer layer includes one or more of ultraviolet curing glue, ethylene-vinyl acetate copolymer and ethylene-octene copolymer.

In one embodiment, the reflective structure comprises a microstructure layer and a reflective layer, wherein the microstructure layer covers one side of the substrate layer, which is away from the bonding layer, and comprises a plurality of microstructures which are arranged on one side surface of the substrate layer, which is away from the bonding layer, and are arranged in parallel, and the microstructures are configured as prisms; the reflective layer covers a side of the microstructured layer facing away from the adhesive layer.

In one embodiment, the material of the microstructure layer includes ultraviolet curing glue, the thickness of the reflecting layer is 1-100nm, and the material of the reflecting layer is aluminum.

In one embodiment, the material of the bonding layer comprises at least one of ethylene-vinyl acetate copolymer and ethylene-octene copolymer, and the thickness of the bonding layer is 10-100 um; the material of the substrate layer comprises thermoplastic polyester, the maximum thickness of the substrate layer is 60-100 um, and the minimum thickness of the substrate layer is 10-60 um.

Embodiments of the second aspect of the present application provide a photovoltaic module comprising a solar cell and a gap film as described in any one of the first aspects; and the solar cell and the gap film are overlapped in the overlapping area.

The gap film can be used for a photovoltaic module. The gap film comprises a bonding layer, a substrate layer and a reflecting structure, and the gap film can be conveniently fixed on the photovoltaic module through the bonding layer; the gap film is provided with a non-overlapping area and an overlapping area, the gap film and the solar cell sheet can be overlapped in the overlapping area, the substrate of the substrate layer comprises an overlapping part positioned in the overlapping area, the thickness of the overlapping part is gradually increased along a second direction, and the second direction is the direction from the overlapping area to the non-overlapping area, so that the thickness of the gap film in the overlapping area can be reduced, the thickness of an overlapping part between the solar cell sheet and the gap film can be reduced, the stress born by the edge of the solar cell sheet during lamination operation and stress test can be reduced, the probability of grid breakage of grid lines of the solar cell sheet, particularly fine grid lines is reduced, and the output power and reliability of the photovoltaic module are improved; the reflecting structure covers one side of the substrate layer, which is away from the bonding layer, and can reflect sunlight so that the sunlight can reach the solar cell, thereby improving the light utilization rate and the photoelectric conversion efficiency of the photovoltaic module.

Drawings

Fig. 1 is a schematic structural view of a spacer film according to some embodiments of the present application.

Fig. 2 is a schematic view of another structure of a spacer film according to some embodiments of the application.

Fig. 3 is another schematic structure of a spacer according to some embodiments of the application.

Fig. 4 is another schematic structural view of a spacer according to some embodiments of the present application.

Fig. 5 is a schematic structural diagram of a photovoltaic module according to some embodiments of the present application.

Fig. 6 is a schematic plan view of a photovoltaic module in some embodiments of the present application.

Reference numerals illustrate:

10. A gap film; 10a, overlap region; 10b, non-overlapping regions; 20. a photovoltaic module; 210. a solar cell; 110. a bonding layer; 120. a substrate layer; 121. a base; 1211. an overlapping portion; 1212. a main body portion; 122. a connecting body; 130. a reflective structure; 131. a microstructure layer; 132. a reflective layer; 140. a buffer layer; x, a first direction; y, second direction; z, third direction.

Detailed Description

In order that the above objects, features and advantages of the application will be readily understood, a more particular description of the application will be rendered by reference to the appended drawings. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present application. The present application may be embodied in many other forms than described herein and similarly modified by those skilled in the art without departing from the spirit of the application, whereby the application is not limited to the specific embodiments disclosed below.

In the description of the present application, it should be understood that, if any, these terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., are used herein with respect to the orientation or positional relationship shown in the drawings, these terms refer to the orientation or positional relationship for convenience of description and simplicity of description only, and do not indicate or imply that the apparatus or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore should not be construed as limiting the application.

Furthermore, the terms "first," "second," and the like, if any, are used for descriptive purposes only and are not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include at least one such feature. In the description of the present application, the terms "plurality" and "a plurality" if any, mean at least two, such as two, three, etc., unless specifically defined otherwise.

In the present application, unless explicitly stated and limited otherwise, the terms "mounted," "connected," "secured," and the like are to be construed broadly. For example, the two parts can be fixedly connected, detachably connected or integrated; can be mechanically or electrically connected; either directly or indirectly, through intermediaries, or both, may be in communication with each other or in interaction with each other, unless expressly defined otherwise. The specific meaning of the above terms in the present application can be understood by those of ordinary skill in the art according to the specific circumstances.

In the present application, unless expressly stated or limited otherwise, the meaning of a first feature being "on" or "off" a second feature, and the like, is that the first and second features are either in direct contact or in indirect contact through an intervening medium. Moreover, a first feature being "above," "over" and "on" a second feature may be a first feature being directly above or obliquely above the second feature, or simply indicating that the first feature is level higher than the second feature. The first feature being "under", "below" and "beneath" the second feature may be the first feature being directly under or obliquely below the second feature, or simply indicating that the first feature is less level than the second feature.

It will be understood that if an element is referred to as being "fixed" or "disposed" on another element, it can be directly on the other element or intervening elements may also be present. If an element is referred to as being "connected" to another element, it can be directly connected to the other element or intervening elements may also be present. The terms "vertical," "horizontal," "upper," "lower," "left," "right," and the like as used herein, if any, are for descriptive purposes only and do not represent a unique embodiment.

In the related art, in order to improve the utilization rate of sunlight and the photoelectric conversion efficiency of a photovoltaic module, a reflecting film is arranged on a back plate of the photovoltaic module and corresponds to a gap area between solar cells, the reflecting film reflects sunlight and changes the angle at which the sunlight is reflected out, so that the sunlight can reach the solar cells after being reflected for multiple times. However, when the photovoltaic module is obtained by lamination or subjected to stress aging test (such as thermal cycle test, mechanical load test, etc.), the grid line of the solar cell close to the gap area is easy to break, which affects the output power and reliability of the photovoltaic module.

Based on the problems, the application provides a gap film and a photovoltaic module, which are used for reducing the probability of grid breakage of grid lines of a solar cell and improving the output power and reliability of the photovoltaic module.

Referring to fig. 1, 2 and 5, an embodiment of the first aspect of the present application provides a gap film 10 for a photovoltaic module 20, where the photovoltaic module 20 includes a solar cell 210, the gap film 10 has a non-overlapping region 10b and an overlapping region 10a located on at least one side of the non-overlapping region 10b, and the gap film 10 and the solar cell 210 can overlap in the overlapping region 10 a; the gap film 10 includes an adhesive layer 110, a substrate layer 120, and a reflective structure 130; the base material layer 120 includes at least one base body 121 disposed on one side of the adhesive layer 110 in the first direction X, the base body 121 including an overlap portion 1211 located at the overlap region 10a, the thickness of the overlap portion 1211 gradually increasing in the second direction Y; the second direction Y is a direction pointing from the overlapping region 10a to the non-overlapping region 10b, and is perpendicular to the first direction X; the reflective structure 130 covers a side of the substrate layer 120 facing away from the adhesive layer 110, and the reflective structure 130 is configured to reflect sunlight, so that the sunlight can reach the solar cell 210.

The gap film 10 provided by the embodiment of the application can be used for a photovoltaic module 20. The gap film 10 includes an adhesive layer 110, a substrate layer 120, and a reflective structure 130, and the gap film 10 can be conveniently fixed to the photovoltaic module 20 by the adhesive layer 110; the gap film 10 has a non-overlapping region 10b and an overlapping region 10a, the gap film 10 and the solar cell 210 can overlap in the overlapping region 10a, the base 121 of the substrate layer 120 includes an overlapping portion 1211 located in the overlapping region 10a, the thickness of the gap film 10 in the overlapping region 10a can be reduced by gradually increasing the thickness of the overlapping portion 1211 along a second direction Y, which is a direction from the overlapping region 10a to the non-overlapping region 10b, so that the thickness of the gap film 10 in the overlapping region 10a can be reduced, the stress born by the edge of the solar cell 210 during lamination operation and stress test can be reduced, the probability of breakage of the grid line, particularly the thin grid line, of the solar cell 210 can be reduced, and the output power and reliability of the photovoltaic module 20 can be improved; by making the reflective structure 130 cover the side of the substrate layer 120 facing away from the adhesive layer 110, the reflective structure 130 can reflect sunlight, so that the sunlight can reach the solar cell 210, thereby improving the light utilization rate and the photoelectric conversion efficiency of the photovoltaic module 20.

In one embodiment, the base 121 further comprises a main body portion 1212, the main body portion 1212 being located in the non-overlap region 10b; the gap film 10 includes two overlapped regions 10a located at both sides of the non-overlapped region 10b; the two overlapping portions 1211 are located in the two overlapping areas 10a in one-to-one correspondence; both overlapping portions 1211 are connected to the main body portion 1212. In this way, the gap film 10 and the solar cells 210 located at two sides thereof can be correspondingly overlapped in the two overlapped areas 10a, so that the sunlight irradiated to the gap area between the solar cells 210 can be reflected by the gap film 10 and reach the solar cells 210, the light utilization rate is further improved, and the photoelectric conversion efficiency of the photovoltaic module 20 is improved.

In one embodiment, the number of the substrates 121 is plural, and the plural substrates 121 are spaced apart along the first direction X and extend along the third direction Z; the third direction Z is perpendicular to the first direction X and the second direction Y; the two overlapping portions 1211 are distributed on both sides of the substrate layer 120 along the first direction X, and are respectively connected to the main portions 1212 of the corresponding base 121. In this way, the local structural strength of the gap film 10 can be reduced, the flexibility of the gap film 10 can be improved, the concentrated stress borne by the edge of the solar cell during lamination operation and stress test can be reduced, the probability of grid breakage of the grid line of the solar cell 210, especially the thin grid line, can be reduced, and the output power and reliability of the photovoltaic module 20 can be improved.

In one embodiment, the substrate layer 120 further includes connectors 122, wherein the connectors 122 are connected between adjacent substrates 121, all the connectors 122 are located in the non-overlapping region 10b, the thickness of each of the connectors 122 is equal, and the thickness of the connectors 122 is smaller than the maximum thickness of the overlapping portion 1211. The multiple substrates 121 can be connected into a whole through the connecting bodies 122, the reflecting structure 130 can cover all the connecting bodies 122 and one sides of all the substrates 121, which are away from the bonding layer 110, so that the area of the reflecting structure 130 is increased, the light utilization rate is further improved, and the photoelectric conversion efficiency of the photovoltaic module 20 is improved; by making the thickness of the connection body 122 smaller than the maximum thickness of the overlap portion 1211, the thickness of the local portion of the base material layer 120 can be reduced, the structural strength of the local portion of the gap film 10 can be reduced, and the flexibility of the gap film 10 can be improved.

In one embodiment, the thickness of the main body 1212 is equal throughout, and the gap film 10 further includes a buffer layer 140, where the buffer layer 140 covers the overlapping portion 1211 and a side of the connecting body 122 facing away from the adhesive layer 110, and a surface of the buffer layer 140 facing away from the adhesive layer 110 is flush with a surface of the main body 1212; the reflective structure 130 covers the substrate layer 120 and a side of the buffer layer 140 facing away from the adhesive layer 110. By making the buffer layer 140 cover the overlapping portion 1211 and the side of the connecting body 122 facing away from the adhesive layer 110, a side surface of the buffer layer 140 facing away from the adhesive layer 110 is flush with a side surface of the main body portion 1212, so that the reflective structure 130 can be conveniently manufactured.

In one embodiment, the material of the buffer layer 140 includes one or more of ultraviolet curing glue, ethylene-vinyl acetate copolymer (abbreviated as EVA), and ethylene-octene copolymer (abbreviated as POE). The buffer layer 140 may be fabricated by coating, compounding, etc.

In one embodiment, the reflective structure 130 includes a microstructure layer 131 and a reflective layer 132, where the microstructure layer 131 covers a side of the substrate layer 120 facing away from the adhesive layer 110, and the microstructure layer 131 includes a plurality of microstructures disposed on a surface of the side of the substrate layer 120 facing away from the adhesive layer 110 and arranged in parallel, and the microstructures are configured as prisms; the reflective layer 132 covers the side of the microstructured layer 131 facing away from the adhesive layer 110. The angle of sunlight reflected out can be changed by matching the microstructure layer 131 and the reflecting layer 132, so that the sunlight reaches the solar cell 210 through multiple reflections, thereby improving the light utilization rate and the photoelectric conversion efficiency of the photovoltaic module 20.

Further, the cross section of the prism can be an isosceles triangle, and the vertex angle of the isosceles triangle is 90-150 degrees.

In one embodiment, the material of the microstructure layer 131 includes ultraviolet curing glue, the thickness of the reflective layer 132 is 1-100nm, and the material of the reflective layer 132 is aluminum.

In one embodiment, the material of the adhesive layer 110 includes at least one of ethylene-vinyl acetate copolymer and ethylene-octene copolymer, and the thickness of the adhesive layer 110 is 10-100 um; the material of the substrate layer 120 includes thermoplastic polyester, the maximum thickness of the substrate layer 120 is 60-100 um, and the minimum thickness of the substrate layer 120 is 10-60 um. A microstructure layer 131 can be arranged on the substrate layer 120 by adopting a coating die imprinting mode, a screen printing mode and the like, and an aluminum reflecting layer 132 is deposited on the surface of the microstructure layer 131 by adopting a vacuum coating mode, a magnetron sputtering mode and the like, so that the substrate layer 120 with the reflecting structure 130 is obtained; and then the adhesive layer 110 and the substrate layer 120 with the reflecting structure 130 are compounded by adopting the modes of tape casting, film pasting, gluing and the like, so as to obtain the gap film 10.

Embodiments of the second aspect of the present application provide a photovoltaic module 20, including a solar cell 210 and a spacer film 10 according to any one of the first aspect, where the solar cell 210 and the spacer film 10 overlap in an overlapping region 10 a.

In particular, the photovoltaic module 20 may include glass, a backsheet, a solar cell 210, and an encapsulation film. The back plate may be glass and the gap film 10 is provided on the back plate. The packaging adhesive film is made of one of ethylene-vinyl acetate copolymer (EVA), ethylene-octene copolymer (POE), polyvinyl butyral (PVB), silicone adhesive and ethylene-butyl acrylate copolymer (EBA). The solar cell may be an interdigitated back contact cell (INTERDIGITATED BACK CONTACT, IBC), HJT cell (Heterojunction WITH INTRINSIC THIN FILM, heterojunction cell), TOPCon cell (Tunnel Oxide Passivated Contact, tunnel oxide passivation contact cell), MWT cell (Metallization wrapthrough, metal wrap through cell) or PERC cell (PASSIVATED EMITTER AND REAR CELL, passivation emitter back solar cell).

According to the photovoltaic module 20 provided by the embodiment of the application, the solar cell 210 and the gap film 10 are overlapped in the overlapped area 10a, the substrate layer 120 of the gap film 10 comprises the overlapped part 1211 positioned in the overlapped area 10a, the thickness of the overlapped part 1211 is gradually increased along the second direction Y, and the second direction Y is the direction from the overlapped area 10a to the non-overlapped area 10b, so that the thickness of the gap film 10 in the overlapped area 10a can be reduced, the thickness of the overlapped part between the solar cell 210 and the gap film 10 can be reduced, the stress born by the edge of the solar cell 210 during lamination operation and stress test can be reduced, the probability of grid breakage of grid lines of the solar cell 210, particularly thin grid lines, is reduced, and the output power and reliability of the photovoltaic module 20 are improved; by making the reflective structure 130 cover the side of the substrate layer 120 facing away from the adhesive layer 110, the reflective structure 130 can reflect sunlight, so that the sunlight can reach the solar cell 210, thereby improving the light utilization rate and the photoelectric conversion efficiency of the photovoltaic module 20.

The technical features of the above-described embodiments may be arbitrarily combined, and all possible combinations of the technical features in the above-described embodiments are not described for brevity of description, however, as long as there is no contradiction between the combinations of the technical features, they should be considered as the scope of the description.

The above examples illustrate only a few embodiments of the application, which are described in detail and are not to be construed as limiting the scope of the claims. It should be noted that it will be apparent to those skilled in the art that several variations and modifications can be made without departing from the spirit of the application, which are all within the scope of the application. Accordingly, the scope of protection of the present application is to be determined by the appended claims.

Claims

1. A gap film for a photovoltaic module comprising a solar cell, wherein the gap film has a non-overlapping region and an overlapping region on at least one side of the non-overlapping region, the gap film and the solar cell being capable of overlapping in the overlapping region;

The gap film comprises a bonding layer, a substrate layer and a reflecting structure;

The substrate layer comprises at least one matrix arranged on one side of the bonding layer along a first direction, the matrix comprises an overlapped part positioned in the overlapped area, and the thickness of the overlapped part gradually increases along a second direction; the second direction is a direction pointing from the overlapping region to the non-overlapping region, and is perpendicular to the first direction;

And the reflecting structure is covered on one side of the substrate layer, which is away from the bonding layer, and is used for reflecting sunlight so that the sunlight can reach the solar cell.

2. The gap film of claim 1 wherein the substrate further comprises a body portion, the body portion being located in the non-overlapping region;

The gap film comprises two overlapping areas positioned at two sides of the non-overlapping area; the two overlapping parts are positioned in the two overlapping areas in a one-to-one correspondence manner; both of the overlapping portions are connected with the main body portion.

3. The gap film according to claim 2, wherein the number of the substrates is plural, the plural substrates being spaced apart along the first direction and extending along a third direction; the third direction is perpendicular to the first direction and the second direction; the two overlapped parts are distributed on two sides of the substrate layer along the first direction and are respectively connected with the main body parts of the corresponding matrixes.

4. A gap film according to claim 3 wherein the substrate layer further comprises connectors connected between adjacent ones of the substrates, all of the connectors being located in the non-overlapping regions, the connectors being of equal thickness throughout and the connectors being of a thickness less than the maximum thickness of the overlapping portions.

5. The gap film of claim 4, wherein the thickness is equal throughout the body portion;

The buffer layer covers the overlapping part and one side of the connector, which is away from the bonding layer, and the surface of one side of the buffer layer, which is away from the bonding layer, is flush with the surface of one side of the main body part, which is away from the bonding layer; the reflecting structure covers one side of the substrate layer and one side of the buffer layer, which are away from the bonding layer.

6. The gap film according to claim 5, wherein,

The material of the buffer layer comprises one or more of ultraviolet curing glue, ethylene-vinyl acetate copolymer and ethylene-octene copolymer.

7. The gap film of claim 1, wherein the reflective structure comprises:

A microstructure layer covering one side of the substrate layer, which is far away from the bonding layer, wherein the microstructure layer comprises a plurality of microstructures which are arranged on one side surface of the substrate layer, which is far away from the bonding layer, and the microstructures are configured as prisms;

And the reflecting layer is covered on one side of the microstructure layer, which is away from the bonding layer.

8. The spacer film of claim 7, wherein the microstructure layer comprises an ultraviolet curable adhesive, the reflective layer has a thickness of 1-100nm, and the reflective layer is made of aluminum.

9. The gap film according to claim 1, wherein the material of the adhesive layer comprises at least one of ethylene-vinyl acetate copolymer and ethylene-octene copolymer, and the thickness of the adhesive layer is 10-100 um; the material of the substrate layer comprises thermoplastic polyester, the maximum thickness of the substrate layer is 60-100 um, and the minimum thickness of the substrate layer is 10-60 um.

10. A photovoltaic module comprising a solar cell sheet and the gap film of any one of claims 1 to 9; and the solar cell and the gap film are overlapped in the overlapping area.