JP5459596B2 - Solar cell back surface protection sheet and solar cell module - Google Patents

Description

The present invention relates to a back protective sheet and a solar cell module for solar cells.

  Solar cells are attracting attention as a new energy source that is pollution-free and friendly to the global environment. The structure of a general solar cell module is to cover the surface that is exposed to sunlight with glass, seal the solar cells with a sealing resin made of thermoplastics, and back protection sheet such as heat-resistant and weather-resistant plastic material on the back It is the structure which stuck together. Several solar cells are connected in series or in parallel to one solar cell module.

Since the solar cell module is used outdoors, sufficient durability and weather resistance are required. In particular, the back protective sheet is required to have water vapor barrier properties in addition to weather resistance. This is because when moisture permeates into the solar cell module, the sealing resin is deteriorated (peeling or discolored) or the wiring is corroded, and the output of the module is finally reduced.
As a back surface protection sheet for solar cells, it has a laminated structure in which an adhesive is formed on both sides of a polyester-based sheet substrate to form an adhesive layer, and a weather-resistant resin film such as a film made of polyvinyl fluoride is bonded. Moreover, the back surface protection sheet for solar cells which improved the barrier property and the weather resistance is known (for example, patent documents 1-3).

  As the adhesive, an adhesive mainly composed of urethane resin or polyester resin is used. However, the adhesive layer formed by these adhesives may be peeled off due to deterioration after long-term use over 10 years. That is, an adhesive mainly composed of a urethane resin or a polyester resin is susceptible to hydrolysis due to moisture absorption, and the resin itself has low heat resistance. For this reason, it deteriorates due to the influence of heat, humidity and ultraviolet rays over a long period of use. As a result, the mechanical strength is lowered and peeling is likely to occur at the adhesive layer interface.

  As a method for solving this problem, a method in which a fluororesin is directly extruded and laminated on a polyester sheet substrate such as a polyethylene terephthalate (PET) substrate is shown. However, this method has a problem that the polyester-based sheet base material shrinks due to the melting temperature of the fluororesin and the sheet base material is wrinkled. In order to suppress the thermal shrinkage of the sheet base material, it is conceivable to use a heat-resistant PET sheet or a polyethylene naphthalate (PEN) sheet, but this method is very expensive.

  On the other hand, in recent years, a solar cell called a back contact type in which all of the charge extraction structure such as wiring materials and electrodes that cause a loss of the light receiving area is formed on the back surface of the solar cell as the efficiency of the solar cell module increases. Has been developed. The solar cells are connected by a back surface protection sheet (hereinafter, also referred to as “back contact circuit material”) having a circuit formed on the surface. That is, a terminal part is formed in the back surface of a photovoltaic cell, and this photovoltaic cell is connected via the circuit material for back contacts. In the circuit material for back contact, the circuit other than the connection portion with the terminal portion of the solar battery cell is covered with an insulating resin layer, thereby ensuring the corrosion resistance of the circuit and the insulation between the circuits.

In the circuit material for back contact, an adhesive mainly composed of urethane resin and polyester resin is applied to both sides of the polyester sheet base material, metal foil is applied to one side, and weather resistance such as fluororesin is applied to the other side. A functional resin film is laminated. However, the circuit material for back contact has the following problems.
(I) As described above, when the adhesive is used, there arises a problem that the metal foil and the weather-resistant resin film are peeled off during long-term use. Further, since the insulating property of the adhesive is not sufficiently high, the insulating property between the circuits cannot be ensured sufficiently.
(Ii) Since the heat resistance of the polyester film substrate is low, the drying temperature when forming the adhesive layer, the laminating temperature when laminating the metal foil and the weather resistant resin film, when forming the insulating resin layer The curing temperature or the like cannot be set to a high temperature, and the production conditions are limited. Therefore, not only the materials that can be used are limited, but also the productivity is lowered.
(Iii) Since the polyester film base material has a large dimensional change at a high temperature, stress tends to concentrate on the junction between the circuit material for back contact and the solar battery cell. As a result, the connection reliability may not be ensured, for example, the terminal joint may peel off or cracks may occur.
(Iv) Due to the difference in thermal expansion between the metal foil and the polyester film base material, the circuit material for back contact after the lamination tends to warp.
(V) When a solar cell module is manufactured industrially by laminating a circuit material for back contact using a soldering iron or the like, it is difficult to position a member to be laminated with high accuracy, and productivity is insufficient. is there. Considering the rapid demand in the future, it is desired to improve productivity with a view to connecting circuits and automating the lamination process.

JP 2001-68701 A JP 2001-68695 A Japanese Patent Laid-Open No. 61-251176

The present invention provides a back contact circuit that can laminate a metal foil and an insulating resin layer forming a circuit with high accuracy, has excellent durability such as weather resistance, heat resistance, and moisture resistance, and also has excellent insulation reliability. It aims at provision of the base material for back surface protection sheets for solar cells which gives the back surface protection sheet for solar cells which can be applied as a material.
In addition, the present invention provides a solar cell back surface that can be stacked with high accuracy in the production of solar cell modules, has excellent durability such as weather resistance, heat resistance, moisture resistance, and insulation reliability. The purpose is to provide a protective sheet.

The present invention employs the following configuration in order to solve the above problems.
[1] A solar cell back surface protection sheet comprising a solar cell back surface protection sheet substrate, a plurality of metal foils, and an insulating resin layer that insulates between the metal foils, the solar cell back surface protection The base material for sheet is formed by impregnating a fiber base material with a thermosetting resin and laminating on one surface of the dried prepreg, a position control mark for positioning a member laminated on the prepreg, and the prepreg surface. Conductive wire portions that electrically connect a plurality of metal foils are formed by a printing method , and a plurality of layers are formed on the composite material layer on which the prepreg of the substrate for a back surface protection sheet for a solar cell is cured. The metal foil is positioned and laminated by the position control mark, the metal foils are connected to each other by the conducting wire part, and further, the position along the position control mark so as to cover the metal foil Resin for control The insulating resin layer are laminated, the back protective sheet for a solar cell as indicia are formed.
[ 2 ] The back surface protective sheet for solar cell according to [ 1 ], wherein a protective layer is laminated on a surface opposite to the laminated surface of the metal foil and the insulating resin layer in the composite material layer.
[3] A solar cell module having the solar cell back surface protective sheet according to [1] or [2].

By using the substrate for the back surface protection sheet for solar cells of the present invention, the metal foil forming the circuit and the insulating resin layer can be laminated with high accuracy, and are excellent in durability such as weather resistance, heat resistance, moisture resistance, Moreover, the back surface protection sheet for solar cells applicable as a circuit material for back contacts which was excellent also in insulation reliability can be manufactured.
Moreover, the back surface protection sheet for solar cells of this invention is applicable as a circuit material for back contacts, is excellent in durability, such as a weather resistance, heat resistance, and moisture resistance, and is excellent also in insulation reliability. Moreover, if the back surface protection sheet for solar cells of this invention is used, in the manufacture of a solar cell module, a photovoltaic cell etc. can be laminated | stacked with high precision.

It is the top view which showed an example of embodiment of the base material for back surface protection sheets for solar cells of this invention. It is the top view which showed an example of embodiment of the back surface protection sheet for solar cells of this invention. It is sectional drawing which cut | disconnected the back surface protection sheet for solar cells of FIG. 2 by the straight line I-I '. It is the top view which showed 1 process of the manufacturing method of the back surface protection sheet for solar cells of this invention. It is sectional drawing which showed one Example of the solar cell module provided with the back surface protection sheet for solar cells of this invention. It is sectional drawing which showed 1 process of the manufacturing method of the solar cell module of FIG.

[Substrate for back surface protection sheet for solar cells]
The substrate for back surface protection sheet for solar cells of the present invention (hereinafter simply referred to as “substrate for protection sheet”) is a back surface protection sheet for solar cells that protects the back surface of a solar cell module, particularly as a circuit material for back contact. It is a base material used for the back surface protection sheet for solar cells to apply. Hereafter, an example of embodiment of the base material for protective sheets of this invention is shown and demonstrated in detail.
The substrate for protective sheet 1 of the present embodiment is a position control mark for positioning a member laminated on the prepreg 2A on one surface of the prepreg 2A which is impregnated with a thermosetting resin in a fiber substrate. 3 and a conductive wire portion 4 for electrically connecting a plurality of metal foils laminated on the surface of the prepreg 2A.

Examples of the fiber base material of the prepreg 2A include glass fiber, aramid fiber, fluorine fiber, polyester fiber, polyarylate fiber, and the like. Among these, glass fiber is preferable from the viewpoints of affinity with thermosetting resin, insulation reliability, and material cost.
The fiber shape of the fiber base material is preferably a woven fabric using long fibers, such as a plain weave, a twill weave, a satin weave, a plain plain weave, or an open calami weave. Since the short fiber-like material tends to protrude the fiber end on the surface of the prepreg, there is a possibility that bubbles are generated at the interface with the metal foil or the insulating resin layer.

As the thermosetting resin, an addition polymerization type thermosetting resin that cures without generating a by-product is preferable.
Addition polymerization type thermosetting resins include epoxy resin, unsaturated polyester resin, phenol resin, diallyl phthalate resin, acrylic resin, cyanate resin, cyanate ester-epoxy resin, cyanate ester-maleimide resin, cyanate ester- Examples thereof include maleimide-epoxy resins, maleimide resins, maleimide-vinyl resins, bisallylnadiimide resins, and mixed resins obtained by blending two or more of these.
The thickness of the prepreg 2A is preferably 50 μm or more from the viewpoint of dielectric breakdown resistance and puncture resistance, and particularly preferably 100 to 300 μm from the viewpoint of handling properties (bending rigidity) during production.

In the production of the solar cell back surface protective sheet, the position control mark 3 in the present invention is a layer position of a member laminated on the prepreg 2A (metal foil forming a circuit, insulating resin layer ensuring insulation between circuits). It is a mark for positioning, and is formed by a printing method using conductive ink.
The shape, forming position, and number of the position control marks 3 are not particularly limited, and may be appropriately selected so that the stacking position of the members stacked on the prepreg 2A surface becomes clear. In the present embodiment, four cross-shaped position control marks 3 are formed on the upper, lower, left and right edges of the prepreg 2A surface, respectively. Thus, for example, as shown in FIG. 4, when stacking a total of six metal foils 5 in two rows of three in the vertical direction, the three metal foils 5 in the vertical direction are placed in the center of the metal foil 5. The foil 5 is arranged so as to be positioned at the two position control marks 3 in the left-right direction, and the two metal foils 5 in the left-right direction are arranged so as to sandwich the two position control marks 3 in the up-down direction. By doing so, the stacking position can be controlled with high accuracy. Further, the position where the curable resin for forming the insulating resin layer is applied can be controlled with high accuracy by using the position control mark 3 as a reference.

  The ink for forming the position control mark 3 may be an ink that can form a desired mark by printing and drying by a printing method. For example, non-conductive ink such as process ink, silver ink, copper ink, Examples thereof include mixed inks of silver and copper and conductive inks such as black carbon. Further, a conductive paste may be used. Especially, it is preferable that it is the same ink as the ink which forms the conducting wire part 4 from the point of productivity, and a conductive ink and a conductive paste are preferable.

  The film thickness of the printing of the position control mark 3 is not particularly limited as long as the lamination position of the laminated member can be clearly determined, and is preferably 2 to 40 μm.

  The conducting wire part 4 is a part which forms a circuit by electrically connecting a plurality of metal foils laminated on the protective sheet base material in the solar cell back surface protective sheet. That is, a circuit of a back contact circuit material (solar cell back surface protection sheet) is formed by the plurality of metal foils laminated on the protective sheet base material and the conductor portion 4 connecting the metal foils.

  The conducting wire portion 4 is formed by a printing method using conductive ink. The conductive ink for forming the conductive wire portion 4 may be any conductive ink that can form a desired conductive wire by printing and drying by a printing method, and the same conductive ink as the position control mark 3 can be used. Ink, copper ink, and mixed ink of silver and copper are preferred. Further, other conductive ink such as black carbon or conductive paste may be used.

  The printed film thickness of the conductive wire portion 4 is not particularly limited as long as it can be formed with a good circuit by being connected to a metal foil, and is preferably 20 to 40 μm.

Examples of the printing method for forming the position control mark 3 and the conductor portion 4 include a gravure printing method, a gravure offset printing method, and a stencil printing method. The formation of the position control mark 3 and the conductor portion 4 is preferably performed in an environment having a cleanliness class of 10,000 or less by these printing methods.
The drying temperature after printing is preferably 100 to 130 ° C. If drying temperature is 100 degreeC or more, productivity of the base material 1 for protective sheets will improve.

  The position control mark 3 and the conductor portion 4 may be formed separately using the same or different conductive ink, or may be formed simultaneously using the same conductive ink, but the same from the point of productivity. It is preferable to form the conductive ink at the same time.

[Back side protection sheet for solar cells]
Next, the back surface protection sheet for solar cells of this invention is demonstrated. The back surface protection sheet for solar cells of this invention is a protection sheet which has the base material for protection sheets of this invention mentioned above, and is a protection sheet applied especially as a circuit material for back contacts. Hereinafter, as an example of the back surface protection sheet for solar cells of the present invention, an embodiment using the substrate 1 for protection sheet will be described in detail.
As shown in FIGS. 2 and 3, the back surface protective sheet 10 for solar cells of the present embodiment has formed the protective sheet substrate 1, the position control mark 3 and the conductive wire portion 4 of the protective sheet substrate 1. A plurality of metal foils 5 (six in this embodiment) laminated on the surface, an insulating resin layer 6 formed on the metal foil 5, and a protective layer laminated on the remaining surface of the protective sheet substrate 1 7. In the insulating resin layer 6, openings 6 a corresponding to the respective metal foils 5 are formed. Moreover, the conducting wire part 4 and the metal foil 5 of the base material 1 for protective sheets are electrically connected.

  The base material 1 for protective sheets in the back surface protective sheet 10 for solar cells has the composite material layer 2 by which the thermosetting resin of prepreg 2A was hardened. The prepreg 2A is cured when the metal foil 5 is laminated.

The metal foil 5 plays a role of forming a circuit having a desired shape and size by being electrically connected to the conductor portion 4.
The metal foil 5 may be any metal foil having electrical conductivity, and examples thereof include gold foil, aluminum foil, copper foil, zinc foil, and stainless steel foil. Among these, copper foil is particularly preferable from the viewpoint of electrical characteristics and material cost.
The thickness of the metal foil 5 is preferably 10 μm or more and more preferably 12 to 50 μm from the viewpoint of electrical characteristics.

The shape and size of the metal foil 5 can be selected as appropriate in order to form a desired circuit pattern. Examples of the shape of the metal foil 5 include a comb shape and a square shape.
The metal foil 5 may be processed into a desired circuit pattern after being laminated on the protective sheet substrate 1 or may be laminated in advance to have a desired circuit shape.

  The insulating resin layer 6 is a layer that plays a role of preventing corrosion of the position control mark 3, the conductive wire portion 4, and the metal foil 5 and ensuring insulation between circuits. The insulating resin layer 6 is laminated so as to cover the metal foil 5 and to form a position control resin mark 6 b along the position control mark 3 of the protective sheet substrate 1. The resin mark 6b for position control is used for controlling and overlapping each position with high accuracy when the solar cell back surface protection sheet 10 is overlapped with the solar cell in the manufacture of the solar cell module.

  The material for forming the insulating resin layer 6 is not particularly limited as long as it is a resin capable of imparting the above-mentioned corrosion prevention function and insulating properties. For example, epoxy resin, cyanate resins, bismaleimides, bismaleimides and diamines are used. Thermosetting resins such as addition polymerization products, phenol resins, resol resins, isocyanates, triallyl isocyanurates, triallyl cyanurates, and vinyl group-containing polyolefin compounds can be mentioned. Among these, an epoxy resin is particularly preferable from the viewpoint of balance of performance such as heat resistance and insulation.

  10-60 micrometers is preferable and, as for the thickness of the insulating resin layer 6, 20-40 micrometers is more preferable. If the thickness of the insulating resin layer 6 is 10 μm or more, it is easy to obtain a sufficient anti-corrosion function and insulation. If the thickness of the insulating resin layer 6 exceeds 60 μm, cracks are likely to occur when the protective sheet substrate 1 is bent, and a drying failure may occur, resulting in a decrease in insulation resistance.

In the insulating resin layer 6, openings 6 a corresponding to the respective metal foils 5 are formed. A conductive material is formed by filling the opening 6a with a conductive material, and the metal foil 5 and the solar battery cell are electrically connected by connecting the conductive part to the metal foil 5 and the terminal part of the solar battery cell. Connected to.
The planar shape of the opening 6a (planar shape of the conductive portion to be filled) is not particularly limited, and various shapes such as a perfect circle and an ellipse can be applied according to the terminal shape of the connected solar cells.
What is necessary is just to select the magnitude | size (size of the electroconductive part with which it fills) of the opening part 6a in consideration of the connection strength with a photovoltaic cell. For example, when the planar shape of the opening 6a is a perfect circle, the diameter thereof is preferably 5 mm or more. Particularly, when the solar cell back surface protective sheet 10 is manufactured, the diameter is blocked by the thermosetting resin oozing out from the prepreg 2A. Considering 10 mm or more is more preferable. Further, the diameter of the opening 6a is preferably 15 mm or less for the purpose of minimizing the depression of the metal foil 5 during pressure lamination in the production of the solar cell module.

The protective layer 7 has weather resistance and is a layer that protects the composite material layer 2 and a circuit composed of the conductor portion 4 and the metal foil 5. Moreover, it is preferable that the protective layer 7 is excellent in heat resistance, moisture resistance, and chemical resistance.
As the protective layer 7, a layer containing a fluorine-containing resin is preferable because cracks and pinholes are hardly formed at low cost.
Examples of the fluorine-containing resin include polyvinyl fluoride resin (PVF), polyvinylidene fluoride resin (PVDF), polytetrafluoroethylene resin (PTFE), ethylene-tetrafluoroethylene copolymer resin (ETFE), and ethylene-chlorotrifluoro. Examples thereof include an ethylene copolymer resin (ECTFE), a terpolymer resin of tetrafluoroethylene (TFE), hexafluoropropylene (HFP), and vinylidene fluoride (VDF).
In addition, when the protective layer 7 contains a fluorine-containing resin, in order to improve the adhesion with the composite material layer 2, the surface thereof is subjected to easy adhesion treatment such as corona discharge treatment or plasma discharge treatment. Is preferred.

  Moreover, as the protective layer 7, you may use the vapor deposition film etc. with which the metal compound or the inorganic compound was vapor-deposited on the ultra-thin glass of the thickness of 50 micrometers or less which can be obtained also with a roll, and a polyester-type film. These have excellent water vapor barrier properties. However, ultra-thin glass and vapor-deposited film are expensive to produce and tend to cause cracks and pinholes.

  The thickness of the protective layer 7 is preferably 5 to 200 μm. In particular, when the protective layer 7 contains a fluorine-containing resin, it is preferably 25 to 100 μm from the viewpoint of water vapor barrier properties.

(Production method)
Hereinafter, the manufacturing method of the back surface protection sheet 10 for solar cells is demonstrated. However, the manufacturing method of the back surface protection sheet for solar cells of this invention is not limited to the method shown below.
As a manufacturing method of the back surface protection sheet 10 for solar cells, the method which has the following process (I) and (II) is mentioned, for example.
(I) As shown in FIG. 4, the prepreg 2A is arranged on the resin film forming the protective layer 7, and the metal foil 5 is arranged on the prepreg 2A by positioning using the position control mark 3, and the prepreg 2A is cured to obtain a laminated sheet of the protective layer 7, the composite material layer 2, and the metal foil 5.
(II) As shown in FIG. 2, the opening is formed so that the position control resin mark 6b covering the metal foil 5 and along the position control mark 3 is formed on the basis of the position control mark 3. The insulating resin layer 6 having 6a is laminated.

Step (I):
As shown in FIG. 4, the prepreg 2A is arranged on the resin film forming the protective layer 7, and the metal foil 5 is arranged on the prepreg 2A using the position control mark 3, and the prepreg 2A is arranged. By curing, the protective layer 7 and the metal foil 5 are laminated to obtain a laminated sheet having a circuit having a pattern of a predetermined shape and dimensions, in a laminated structure of the protective layer 7 / composite material layer 2 / metal foil 5.
The circuit pattern of the metal foil 5 may be formed by a photolithography / etching method using a dry film resist or a liquid resist after the metal foil 5 is laminated, and is laminated by a punching process using a Thomson blade whose edge is processed into a circuit shape. It may be formed in advance.

As a method for laminating the metal foil 5 and the protective layer 7, a pressure laminating method in a vacuum state is preferable. The metal foil 5 can be laminated by a method using a roll laminator under normal pressure. However, in the case of a pressure lamination method in a vacuum state, the composite material layer 2 obtained by curing the prepreg 2A and the metal foil 5 are used. It is easy to prevent the adhesive strength from being reduced due to the generation of air bubbles between them, and the metal foil 5 is difficult to peel off even when used outdoors for a long time.
The degree of vacuum at the time of lamination in the pressure lamination method is preferably 20 Torr or less, and more preferably 10 Torr or less.

The lamination conditions of the metal foil 5 and the protective layer 7 vary depending on the prepreg 2A used, but the temperature is preferably 150 to 200 ° C. The lamination temperature is preferably within a range of ± 30 ° C. from the melting temperature of the thermosetting resin impregnated in the prepreg 2A. If the lamination temperature is too low, the thermosetting resin is not sufficiently melted and is difficult to spread on the surface of the prepreg 2A, and the adhesive strength between the resulting composite material layer 2 and the metal foil 5 may be lowered. On the other hand, if the lamination temperature is too high, the solvent in the thermosetting resin may rapidly evaporate and bubbles may be generated. Further, the viscosity of the thermosetting resin is excessively lowered, and the thermosetting resin flows out to the outer peripheral portion of the fiber base material, so that the composite material layer 2 may become thinner than a predetermined thickness.
The lamination pressure of the metal foil 5 is preferably 0.5 to 3.0 MPa.
The lamination time of the metal foil 5 is preferably 10 to 40 minutes.

  The position control of the metal foil 5 using the position control mark 3 may be performed by visual observation, or an image recognition system such as a CCD camera may be used.

Process (II):
As shown in FIG. 2, the position control mark 3 is used as a reference, and the opening 6 a is provided so as to cover the metal foil 5 and to form the position control resin mark 6 b along the position control mark 3. The insulating resin layer 6 is laminated.
The form of the thermosetting resin that forms the insulating protective layer 6 is not particularly limited, such as varnish, two-component ink, and dry film. As a method for forming the opening 6a, a dry film having a shape corresponding to the shape of the metal foil 5 and the position control mark 3 is obtained by applying a thermosetting resin having photosensitivity on a film base material and semi-curing it. It is preferable to form the insulating protective layer 6 using, and form the opening 6a by photolithography. At this time, by arranging the dry film with reference to the position control mark 3, the position of the insulating resin layer 6 can be controlled with high accuracy.
In addition, when the position of the opening 6a does not require high accuracy and the dimension is sufficiently large, such as several millimeters or more, an insulating protective layer having the opening 6a directly by screen printing from the viewpoint of material cost and productivity. The method of forming 6 is particularly preferred. In the formation of the insulating protective layer 6, the insulating protective layer is formed on the basis of the position control mark 3 by using a screen plate having plate holes having shapes corresponding to the shapes of all the metal foils 5 and the position control mark 3. The stacking position of 6 can be highly controlled.

  Control of the lamination position of the insulating resin layer 6 using the position control mark 3 may be performed by visual observation, or an image recognition system such as a CCD camera may be used.

  In addition, the manufacturing method of the solar cell protection sheet of this invention is not limited to the method mentioned above. For example, even in the method of laminating only the metal foil in the step (I), and then laminating the protective layer by applying and curing a resin for forming the protective layer on the remaining surface of the composite material layer 2. Good. In this case, the protective layer may be laminated before the insulating resin layer is laminated or after the insulating resin layer is laminated.

The solar cell back surface protective sheet of the present invention described above does not use an easily hydrolyzed adhesive mainly composed of a urethane-based resin or a polyester-based resin, and the metal foil is directly applied to the composite material layer in which the prepreg is cured. Laminated. Moreover, the metal foil etc. are laminated | stacked with high precision by using the mark for position control of the base material for protective sheets. Therefore, the adhesive strength is high, the durability such as weather resistance, heat resistance, and moisture resistance is excellent, and the insulation reliability is also excellent. Moreover, if the back surface protection sheet for solar cells of this invention is used, lamination | stacking of a photovoltaic cell etc. can be implemented with high precision in manufacture of a solar cell module.
In addition, the base material for protective sheet and the back surface protective sheet for solar cell of the present invention can more easily manufacture a high-quality product in which each layer is laminated with high accuracy by automation of manufacturing using a position control mark. Be expected.

  In addition, the back surface protection sheet for solar cells of this invention is not limited to the said back surface protection sheet 10 for solar cells. For example, the back surface protection sheet for solar cells which does not have a protective layer may be sufficient as the other side of the surface in which the circuit of the composite material layer was formed.

[Solar cell module]
Hereinafter, an example of embodiment of the solar cell module which has the back surface protection sheet for solar cells mentioned above is demonstrated. However, the solar cell module having the solar cell back surface protective sheet of the present invention is not limited to the solar cell module described below.
As shown in FIG. 5, the solar cell module 100 of the present embodiment includes a solar cell 20, a sealing layer 30 that seals the solar cell 20, and a light receiving surface side of the solar cell 20 in the sealing layer 30. The solar cell back surface protective sheet 10 disposed so that the protective layer 7 is the outermost layer on the rear surface side of the translucent substrate 40 and the sealing layer 30, the solar cell 20, and the solar cell surface And a conductive portion 50 that electrically connects the metal foil 5 of the back surface protective sheet 10. The upper end portion of the conductive portion 50 of the solar cell back surface protective sheet 10 is electrically connected to the terminal portion 20 a on the back surface side of the solar cell 20.
The solar cell module 100 is obtained by unitizing the solar cell back surface protective sheet 10 that is a circuit material for back contact so that the protective layer 7 is the outermost surface.

The solar battery cell 20 is a cell having a function of converting sunlight incident on the light receiving surface by electricity into electricity.
As the solar cell 20, a solar cell normally used for a solar cell module can be used. For example, the solar cell 20 is made of a single crystal silicon substrate, a polycrystalline silicon substrate, etc. 20a), and a cell in which an antireflection film is further provided on the light receiving surface.

Examples of the sealing resin that forms the sealing layer 30 include ethylene-vinyl acetate copolymer resin, polyurethane resin, vinyl chloride resin, silicone resin, and polyvinyl butyral resin.
The sealing layer 30 is usually formed by embedding and sealing the solar cells 20 by using two films made of the sealing resin, sandwiching the solar cells 20 and applying heat and pressure. .

Examples of the translucent substrate 40 include a glass substrate and a transparent resin substrate.
Examples of the glass substrate include white plate glass, tempered glass, double tempered glass and heat ray reflective glass, and white plate tempered glass is preferable.
Examples of the transparent resin constituting the transparent resin substrate include acrylic resin, polycarbonate, and polyethylene terephthalate.

The conductive portion 50 is a portion formed by filling the opening 6 a of the insulating resin layer 6 in the solar cell back surface protective sheet 10 with a conductive material, and one end thereof is electrically connected to the metal foil 5. . The other end is electrically connected to the terminal portion 20 a of the solar battery cell 20.
The conductive material forming the conductive portion 50 is preferably a material having a volume resistivity of 10 ⁻⁴ Ω · cm or less from the viewpoint of preventing heat generation during current application, such as a conductive paste, a conductive nano-ink of fine metal particles, etc. Can be used.
The conductive material forming the conductive portion 50 is more preferably a solder paste in consideration of connection strength and material cost. The solder paste is also preferable in that it can be filled by screen printing using a normal metal mask. Moreover, the solder paste after filling can be electrically connected to the metal foil 5 by melting by a reflow process.

(Production method)
As a manufacturing method of the solar cell module 100, the method shown below is mentioned, for example. However, the manufacturing method of the solar cell module of the present invention is not limited to the method shown below.
As shown in FIG. 6, the solar cell back surface protective sheet 10 in which the conductive part 50 is formed by filling the opening 6a of the insulating resin layer 6 with a conductive material is placed with the insulating resin layer 6 facing upward. And the sealing resin film 30A in which the opening part 30a with a larger diameter than the terminal part 20a of the photovoltaic cell 20 was formed on the back surface protection sheet 10 for the photovoltaic cell, and the photovoltaic cell 20 (in this embodiment). 2), the sealing resin film 30B, and the translucent substrate 40 are sequentially overlapped in a positioned state. At this time, the stacking position of each member is controlled by using a position control resin mark 6 b covering the position control mark 3.
For example, a position control mark similar to the position control mark 3 is formed on the sealing resin film 30A, the sealing resin film 30B, and the translucent substrate 40, and the position control mark and the position control resin mark are formed. By stacking so that 6b matches, the stacking position can be controlled with high accuracy. The solar battery cell 20 has the terminal portion 20a as an upper surface (the light receiving surface faces the translucent substrate 40 side), and the terminal portion 20a is overlapped with the position control resin mark 6b as a reference, whereby the terminal portion 20a is sealed with the sealing resin film 30A. Is laminated so as to correspond to the opening 30a.
The control of the stacking position may be performed visually or using an image recognition system such as a CCD camera.

  Next, the solar cell 20 is sealed with the sealing resin film 30 </ b> A and the sealing resin film 30 </ b> B by performing a vacuum laminating process in this state, and the sealing layer 30 is formed. By the vacuum laminating process, the gap around the connection portion between the conductive portion 50 and the solar battery cell 20 is sealed with a sealing resin without bubbles.

Examples of the vacuum laminating process include the following processes.
First, preheat at 120 to 150 ° C. for 3 to 5 minutes while evacuating, and then heat at 120 to 150 ° C. for 3 to 10 minutes while reducing the pressure from both sides of the laminate on which the above-described members are laminated. Laminate. By this lamination, the sealing resin becomes a molten state, and is bonded and integrated with the solar battery cell 20 and the solar battery back surface protective sheet 10. In addition, the conductive part 50 is thermally cured and bonded to the terminal part 20 a of the solar battery cell 20. Further, the sealing layer 30 is formed by heating at 140 to 160 ° C. for 20 to 40 minutes to thermally cure the sealing resin.
The solar cell module 100 is preferably sealed with butyl rubber at the end and fixed with an aluminum frame.

  In the solar cell module, the edge portion where the position control mark on the protective sheet base material is formed may be cut off, or the edge portion may be sealed with a sealing resin.

Hereinafter, the present invention will be described in detail with reference to Examples and Comparative Examples. However, the present invention is not limited by the following description.
[Example 1]
As shown in FIG. 1, the thickness of the prepreg 2A (Mitsubishi Gas Chemical Co., Ltd., CCL-EL190, 150 μm thick) is thickened by screen printing using a conductive paste (manufactured by Asahi Chemical Laboratory, PLS-4300). 10 μm of the position control mark 3 and the conductive part 4 were printed to obtain the protective sheet substrate 1.
Thereafter, as shown in FIG. 4, a plurality of copper foils divided into comb shapes having a predetermined size as metal foil 5 while being positioned on the prepreg 2 </ b> A of the base material 1 for the protective sheet by the position control mark 3 ( A polyvinyl fluoride film (manufactured by DuPont, manufactured by DuPont, which has a 1 mm thick Teflon (registered trademark) plate) and a protective layer 7 is formed on the remaining surface. A dollar film (thickness 25 μm) was overlaid, and a stainless steel plate and a cushioning material were placed on the outside, and these were placed between the hot plates of a test press machine (made by Kitagawa Seiki, 500 mm × 500 mm type). Vacuuming was started in this state, and pressurization was started when the degree of vacuum reached 1.5 kPa. The lamination conditions were a lamination temperature of 180 ° C., a lamination time of 30 minutes, and a lamination pressure of 2.0 MPa. The obtained laminated sheet had a good finish with no warping or bubbles.

  Next, a circuit was formed using a screen printing machine provided with a screen plate having a plate hole having a shape corresponding to the shape of all the metal foils 5 and the position control marks 3, and the circuit was formed on the basis of the position control marks 3. A solder resist ink (manufactured by Taiyo Ink Manufacturing Co., Ltd., PSR-4000 EG30) was applied on the laminated sheet so as to have a resin thickness of 35 μm. Thereafter, preliminary drying is performed at 80 ° C. for 30 minutes, and single-sided exposure is performed at 500 mJ using a film mask, followed by spray development with a 1.0% sodium carbonate solution for 120 seconds to form the opening 6a. It was heat-cured at 30 ° C. for 30 minutes to obtain a back protective sheet 10 for a solar cell having the insulating resin layer 6 illustrated in FIG.

[Example 2]
A Teflon (registered trademark) plate having a thickness of 10 mm was fixed on the stage of a flat plate press, and a piece of copper foil (manufactured by Nippon Electrolytic Co., Ltd., PBN-10, 18 μm) was placed on the upper surface, and the cutting edge was processed into a circuit shape. Punching was performed with a Thomson blade to obtain a plurality of metal foils 5 having a comb-shaped circuit pattern of a predetermined dimension. The punching process is performed for fine shapes such as gaps in circuit patterns and pin holes for positioning, and then has a dimension corresponding to the minimum unit of the solar battery cell (the same outer dimension as the copper foil of Example 1). The outline of the entire circuit was performed. The metal foil 5 on which the circuit pattern was formed was collected from the stage with an air suction disk.

  A protective sheet substrate 1 was obtained in the same manner as in Example 1 except that ELC-4765 (manufactured by Sumitomo Bakelite, thickness: 200 μm) was used as the prepreg 2A. Thereafter, the protective sheet substrate 1 was overlaid on a polyvinyl fluoride film (manufactured by DuPont, Tedlar film, thickness 25 μm) forming the protective layer 7, and a circuit pattern was formed on the prepreg 2A. A plurality of the metal foils 5 are arranged on the basis of the position control mark 3, and a stainless steel plate and a cushioning material are appropriately arranged on the outside thereof. The heat of a test press machine (Kitakawa Seiki, 500 mm × 500 mm type) Installed between the panels. Vacuuming was started in this state, and pressurization was started when the degree of vacuum reached 1.5 kPa. The lamination conditions were a lamination temperature of 170 ° C., a lamination time of 30 minutes, and a lamination pressure of 2.0 MPa. The resulting laminated sheet had a good finish with no warping or bubbles.

Next, the curable resin piece of the prepreg that had oozed out on the circuit was removed by buffing (JP Buff, manufactured by Jablo Industries). Further, in order to connect another circuit independent of the circuit composed of the conductive wire portion 4 and the metal foil 5, silver ink (REXALPHA / RA FS 005, manufactured by Toyo Ink Manufacturing Co., Ltd.) is formed in a predetermined position with a screen printer. And baked at 180 ° C. for 60 minutes.
The laminated sheet in which a circuit is formed on the basis of the position control mark 3 using a screen printing machine provided with a screen plate having a plate hole having a shape corresponding to the shape of all the metal foils 5 and the position control mark 3 A solder resist ink (manufactured by Yamaei Chemical Co., SSR-671W-9) was applied thereon so that the resin thickness was 35 μm. At this time, an opening serving as the opening 6a was directly formed in the coating film with a screen printing plate. Then, after preliminary drying at 80 ° C. for 15 minutes, heat curing was performed at 150 ° C. for 60 minutes to form the insulating resin layer 6 having the opening 6a, and the solar cell back surface protective sheet 10 illustrated in FIG. 2 was obtained. .

[Evaluation method]
About the back surface protection sheet for solar cells obtained in the Example, it evaluated by the method shown below.
(1) Initial adhesive strength (n = 5)
Pretreatment: None Equipment: Tensilon RTC-1250 (Orientec)
Distance between chucks: 60mm
Crosshead speed: 5.0 mm / min Sample: 10 mm × 100 mm × about 0.4 mm
(2) Adhesive strength after dump heat (n = 5)
Pretreatment conditions: 85 ° C./85%/3000 hours The apparatus and measurement conditions are the same as (1).
(3) Adhesive strength after cold heat treatment (n = 5)
Pretreatment conditions: −40 ° C./20 minutes, 80 ° C./20 minutes of cold heat treatment 200 times The apparatus and measurement conditions are the same as (1).
(4) Insulation reliability (n = 5)
Comb dimensions: L / S = 550/100, 550/400, 550/600 (line width L was fixed and gap S was changed)
Measurement conditions: 135 ° C./85%/192 hours Applied voltage: 1.0 V
The judgment criteria were “◯” when the insulation resistance value was 1 × 10 ⁻⁶ Ω or more, and “X” when the insulation resistance value was less than 1 × 10 ⁻⁶ Ω.
(5) Initial resistance value The resistance value of the circuit (L / S = 100/100) in the solar cell back surface protective sheet before carrying out the dump heat of (2) was measured under the same conditions as in (4) above. .
(6) Resistance value after dump heat The resistance value of the circuit (L / S = 100/100) in the back protective sheet for solar cell after the dump heat of (2) is performed under the same conditions as in (4) above. It was measured.
Table 1 shows the evaluation results of the back protective sheets for solar cells of Example 1 and Example 2. The adhesive strength of (1) to (3) in Table 1 is an average value measured 5 times, and the inside of () is a peeled layer.

  As shown in Table 1, in Examples 1 and 2 which are the back surface protective sheets for solar cells of the present invention, they have excellent adhesive strength and are also bonded after dump heat (85 ° C./85%/3000 hours). The decrease in strength was suppressed. Moreover, the back surface protection sheet for solar cells of Examples 1 and 2 was excellent in insulation reliability, and there was not much change in resistance value due to dump heat. Thus, the back surface protection sheet for solar cells of this invention was excellent in durability compared with the circuit material for back contacts of the past. These results are because bubbles are not generated at the interface between the circuit and the composite material layer by pressure lamination in vacuum without using an adhesive, and the lamination position is highly controlled. Conceivable.

  Since the back surface protection sheet for solar cells of the present invention is excellent in durability such as weather resistance, heat resistance, moisture resistance and the like and excellent in insulation reliability, it can be suitably used as a circuit material for back contact.

  DESCRIPTION OF SYMBOLS 1 Base material for back surface protection sheets for solar cells 2A Prepreg 2 Composite material layer 3 Position control mark 4 Conductor part 5 Metal foil 6 Insulating resin layer 6a Opening 6b Position control resin mark 10 Solar cell back surface protection sheet 20 Solar cell Cell 30 Sealing layer 40 Translucent substrate 50 Conductive part

Claims (3)

A solar cell back surface protective sheet having a base material for a back surface protective sheet for solar cells, a plurality of metal foils, and an insulating resin layer that insulates between the metal foils,
The solar cell back protective sheet for a base material, the fibrous base material is impregnated with a thermosetting resin on one surface of the prepreg drying, and marks for position control of the positioning of the member to be laminated onto the prepreg The conductive wire portion that electrically connects a plurality of metal foils laminated on the prepreg surface is formed by a printing method ,
On the composite material layer on which the prepreg of the base material for the back surface protective sheet for solar cells is cured, a plurality of metal foils are positioned and laminated by the position control mark, and the metal foils are connected to each other by the conductor portion. Has been
Furthermore, the said back surface protection sheet for solar cells by which the said insulating resin layer is laminated | stacked so that the resin mark for position control along the said mark for position control may be formed so that the said metal foil may be covered . Wherein the stacking surface opposite to the surface of the metal foil and the insulating resin layer in the composite material layer, the protective layer is laminated, the back protective sheet for a solar cell according to claim 1. The solar cell module which has a back surface protection sheet for solar cells of Claim 1 or 2.

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