JP5614360B2 - Back protection sheet for solar cell module - Google Patents

Description

  The present invention relates to a back surface protection sheet for a solar cell module.

  In recent years, solar cells as a clean energy source have attracted attention due to the growing awareness of environmental issues. In general, a solar cell module that constitutes a solar cell has a configuration in which a transparent front substrate, a sealing material, a solar cell element, a sealing material, and a back surface protection sheet are laminated in order from the light receiving surface side. It has a function of generating electricity by being incident on the battery element.

  In the said solar cell module, the said back surface protection sheet is normally made into the white back surface protection sheet formed using the material containing a white pigment. By doing in this way, among the light incident from the transparent front substrate, the light that has been transmitted without being absorbed by the solar cell element is reflected, and the solar cell element absorbs the light again, thereby generating the power generation efficiency of the solar cell module. Can be improved (Patent Document 1).

  However, the request | requirement with respect to the power generation efficiency improvement of a solar cell module is still getting stronger, and the back surface protection sheet which contributes to power generation efficiency improvement more is calculated | required.

  Moreover, in a solar cell module, what made the external appearance of the back surface protection sheet black may be calculated | required from a design viewpoint. As a method for making the appearance black, a method of providing a black resin layer containing carbon black in the outermost layer is common.

  However, since carbon black absorbs near infrared rays contained in sunlight, the temperature of the solar cell module is raised during use, and as a result, the power generation efficiency of the solar cell module is reduced.

  On the other hand, solar cell modules are generally installed outdoors for a long period of time, and are always exposed to harsh environments such as strong ultraviolet rays, heat rays, and wind and rain. For this reason, extremely high weather resistance and durability are calculated | required by the back surface protection sheet for solar cell modules.

  Therefore, in order to suppress heat storage in the black layer and to further improve the power generation efficiency by making reflected light incident on the solar cell element, a black resin layer kneaded into the resin with an infrared transmitting pigment and infrared reflection A back surface protection sheet for a solar cell module has been developed, which includes a white resin layer having heat resistance, a back surface protection layer having weather resistance, and the like, and is manufactured by bonding these layers with an adhesive or the like. (Patent Document 2).

  In such a back surface protection sheet for a solar cell module, since it is necessary to manufacture by laminating a plurality of layers having different characteristics, further improvement is required for the adhesion and adhesion durability between the respective layers. It was. Moreover, there existed room for the further improvement also about cost becoming higher than the conventional back surface protection sheet by many essential processes and an essential member.

Japanese Patent Laid-Open No. 2002-100788 JP 2010-199555 A

  The present invention has been made in order to solve the above-described problems, and its purpose is to provide a back surface protection sheet for a solar cell module having a black appearance in order to satisfy the demands of a customer related to design. An object of the present invention is to provide a solar cell module back surface protection sheet that has sufficient weather resistance and durability and can sufficiently contribute to improvement of power generation efficiency of the solar cell module at a low cost.

  The inventors of the present invention have made extensive studies to solve the above problems. As a result, in the back surface protection sheet for solar cell modules, by laminating a plurality of layers including a reflective layer via a black adhesive layer made of a black adhesive containing a specific resin and a dark organic pigment, etc. The present inventors have found that the above problems can be solved and have completed the present invention. More specifically, the present invention provides the following.

(1) A plurality of layers including at least a transparent adhesion layer that is disposed on the outermost layer in the back surface protective sheet for solar cell module and transmits all rays and a reflection layer that reflects near infrared rays of 750 nm to 1500 nm is laminated. A back surface protection sheet for solar cell modules,
At least one of the adhesive layers formed between the plurality of layers is a black adhesive layer, and the black adhesive layer is made of a black adhesive containing a main resin and a dark organic pigment. A back protective sheet for a solar cell module, which transmits near infrared rays having a wavelength of 750 nm to 1500 nm.

  (2) The back surface protection sheet for solar cell modules according to (1), wherein the black adhesive layer is disposed on the inner surface of the back surface protection sheet for solar cells of the transparent adhesion layer.

  (3) The back surface protection sheet for solar cell modules as described in (1) or (2) whose said organic pigment is an oxazine pigment.

  (4) The back surface protective sheet for a solar cell module according to any one of (1) to (3), wherein the reflective layer is a white resin layer made of a resin containing a white pigment.

  (5) The back surface for a solar cell module according to any one of (1) to (3), wherein the reflective layer is a metal reflective layer formed by laminating a metal vapor deposition layer on a resin base material or a metal foil. Protective sheet.

  (6) A solar cell module obtained by laminating the back surface protective sheet for solar cell module according to any one of (1) to (5).

  (7) The solar cell module according to claim 6, wherein thin-film solar cell elements are laminated.

  According to the present invention, since the black adhesive layer 60 for meeting the design requirement is a black adhesive layer that transmits near-infrared rays, the solar cell module is prevented from being heated to high temperature, thereby improving the power generation efficiency. At the same time, a solar cell module back protection sheet having high durability can be manufactured at a lower cost than the conventional one while making a sufficient contribution.

It is a schematic diagram of the cross section which illustrates an example of the layer structure about a solar cell module. It is a figure which shows typically the cross section of 1st Embodiment of the back surface protection sheet. It is a figure which shows typically the cross section of 2nd Embodiment of the back surface protection sheet. It is a figure which shows the reflectance (%) of the light with a wavelength of 500 nm to 1800 nm of the back surface protection sheet of an Example, a comparative example, and a reference example.

  Hereinafter, the back surface protection sheet for solar cell modules of the present invention (in the present specification, simply referred to as “back surface protection sheet”) will be described in detail. The present invention is not limited to the embodiments described below.

  First, the solar cell module in which the back surface protection sheet for solar cell modules of this invention is used is demonstrated. FIG. 1 is a schematic cross-sectional view illustrating an example of the layer structure of a solar cell module. As shown in FIG. 1, the solar cell module 1 constituting the solar cell includes a transparent front substrate 2, a front sealing material layer 3, a solar cell element 4, a back sealing material layer 5, from the light receiving surface side of the incident light 7. It is the structure by which the back surface protection sheet 6 was laminated | stacked in order. These are sequentially laminated and integrated by, for example, vacuum heat laminating. In this case, the laminating temperature is preferably in the range of 130 ° C to 190 ° C. The laminating time is preferably in the range of 5 to 60 minutes, particularly preferably in the range of 8 to 40 minutes. In this manner, the solar cell module 1 can be manufactured by thermocompression-bonding each of the above layers as an integrally molded body.

[Overall structure of back protection sheet for solar cell module]
The back surface protection sheet which concerns on 1st Embodiment of this invention is demonstrated using FIG. The back surface protective sheet 6 has a black adhesive layer 60, a reflective layer 61, and a transparent adhesion layer 62. The reflective layer 61 and the transparent adhesive layer 62 are bonded via the black adhesive layer 60. In the solar cell module 1, the reflective layer 61 is disposed on the outermost layer side of the module, and the transparent adhesion layer 62 is disposed on the inner layer side of the module, that is, on the back sealing material layer 5 side.

  Here, since most of the sealing materials for solar cell modules are generally transparent or translucent, when the solar cell module 1 is viewed from the transparent front substrate 2 side, the gap where the solar cell elements 4 are not disposed. With respect to the portion, the color of the black adhesive layer 60 can be seen through the transparent adhesion layer 62. In addition, the solar cell element 4 often has a black surface or a dark color close thereto. In particular, for thin-film solar cell elements, for which demand is increasing in recent years, the surface of most products is black or a dark color close thereto. Since the back surface protective sheet 6 has a black adhesive layer 60 of black or a dark color close thereto, the appearance of many solar cell modules, particularly thin film solar cell modules equipped with thin film solar cell elements, is black or close to that. It can be unified in dark color and can be preferable in terms of design.

  In the back surface protective sheet 6, sunlight that has not been absorbed by the solar cell element 4 enters from the transparent adhesion layer 62 side. Most of the near infrared rays contained in the incident light passes through the black adhesive layer 60 without being absorbed, and therefore reaches the reflective layer 61. Since the reflective layer 61 reflects near infrared rays, most of the near infrared rays that reach the reflective layer 61 are reflected back to the black adhesive layer 60. The reflected near-infrared light passes through the black adhesive layer 60 and is further reflected and absorbed by the solar cell element 4. Since the black adhesive layer 60 does not absorb near infrared rays, the temperature rise of the solar cell module 1 due to near infrared absorption in the black adhesive layer 60 is suppressed. As a result, it is possible to prevent a decrease in power generation efficiency due to a temperature increase of the solar cell module 1.

  Moreover, in the back surface protection sheet 6, as above-mentioned, the near-infrared amount absorbed by a solar cell element increases. As a result, the power generation efficiency of the solar cell module can be improved.

  In a thin film solar cell module, suppressing the temperature of all the components in the module to a low level does not necessarily contribute to the improvement of power generation efficiency. Depending on the relationship with the annealing effect, the solar cell that is black or dark About the surface temperature of a battery element, it is preferable to raise to about 50 to 70 degreeC. The back surface protection sheet 6 of the present invention stores near infrared rays reflected by the reflective layer 61 in the back surface protection sheet 6 while limiting the appearance to black or a dark color close to it in order to satisfy the design requirements. Without being lost to the solar cell element 4 without loss, the surface temperature of the thin-film solar cell element that is black or dark can be efficiently increased to the above temperature. Also from such a point, the back surface protection sheet 6 of this invention can be used suitably especially for a thin film type solar cell module.

<Black adhesive layer>
The black adhesive layer 60 is an adhesive layer provided mainly for joining the reflective layer 61 and the transparent adhesion layer 62. In the present embodiment, the black adhesive layer 60 is formed by curing a black adhesive applied to the upper surface of the reflective layer 61 or the lower surface of the transparent adhesion layer 62 facing the upper surface after lamination. As will be described later, the arrangement of the black adhesive layer 60 is not limited to this in the back surface protective sheet according to the present invention, but the back surface protective sheet is designed by forming the black adhesive layer 60 at this position. There is an advantage that it is easy to make it preferable in terms of sex.

  The black adhesive layer 60 is required to have sufficient adhesion and adhesion durability. In addition to such characteristics, the back surface protection sheet 6 of the present invention has an appearance of black or a dark color close thereto. That is, it is important to have a property of absorbing visible light and transmitting near infrared rays.

  Here, the near infrared ray is a region closest to the visible region in the infrared region, but the detailed wavelength region has various values depending on the literature. The near infrared ray in the present invention refers to an electromagnetic wave having a wavelength range of 750 nm to 2200 nm. Among them, the wavelength that promotes heat storage is 1000 nm or more and 1500 nm or less.

  As the black adhesive forming the black adhesive layer 60, an adhesive having a property of transmitting light having a wavelength of 750 nm to 1500 nm in a cured state is used. “Transmitting light with a wavelength of 750 nm to 1500 nm” means that the black adhesive layer 60 transmits light with a wavelength of 750 nm to 1500 nm of 15% or more, preferably 50% or more, and more preferably 80% or more. It means to do. Further, the transmittance of visible light and ultraviolet light is not particularly defined as long as it is in the category colored black.

  The black adhesive composition used for the black adhesive layer 60 is preferably a two-component type composed of a main agent and a curing agent, and further contains an organic pigment. From the viewpoint of applicability and handling properties, a suitable solvent is used as the composition. included.

[Main agent]
The main component is preferably a polyurethane / polycarbonate diol system comprising a mixture of polyurethane diol and aliphatic polycarbonate diol. Both the polyurethane diol and the aliphatic polycarbonate diol constituting the main agent are polyols having a hydroxyl group, and react with a curing agent having an isocyanate group to constitute an adhesive layer. In the present invention, the adhesive property and the weather resistance of the adhesive layer are improved by making the main agent a mixture containing a specific amount of a specific polyurethane diol and an aliphatic polycarbonate diol.

  The main component polyurethane diol is a polyurethane having a urethane structure as its repeating unit and having hydroxyl groups at both ends. The number average molecular weight of the polyurethane diol is preferably 7000 to 13000. When it is 7000 or more, it is preferable because the reactivity with the curing agent is good, and when it is 13000 or less, dissolution in a solvent is improved.

  The hydroxyl value of the polyurethane diol is preferably in the range of 10 to 50 mgKOH / g. When the hydroxyl value of the polyurethane diol is 10 mg KOH / g or more, most of the added curing agent component reacts with the hydroxyl group contained in the main component, and when it is 50 mg KOH / g or less, the reaction with the curing agent is more likely. This is preferable because it proceeds.

  The polyurethane diol is characterized in that it is obtained by reacting an aliphatic polycarbonate diol, 1,6 hexanediol and isophorone diisocyanate as a main component of the adhesive in order to improve its adhesion and weather resistance. Hereinafter, the aliphatic polycarbonate diol, 1,6 hexanediol and isophorone diisocyanate, which are components of the polyurethane diol, will be described.

  Aliphatic polycarbonate diol is a component of polyurethane diol that can react with the following isophorone diisocyanate. The aliphatic polycarbonate diol has a carbonate structure as a repeating unit and has hydroxyl groups at both ends. The hydroxyl groups at both ends can be cured with an isocyanate group.

  The aliphatic polycarbonate diol can be produced by a method using an alkylene carbonate and a diol as raw materials, a method using a dialkyl carbonate or a diaryl carbonate and a diol, and the like. The aliphatic polycarbonate diol used in the present invention can be produced by appropriately selecting the above production method according to the performance required for the main component.

  Examples of the alkylene carbonate that can be used for the production of the aliphatic polycarbonate diol include ethylene carbonate, trimethylene carbonate, 1,2-propylene carbonate, 1,2-butylene carbonate, 1,3-butylene carbonate, 1,2-pentylene carbonate, and the like. Is mentioned. Examples of the dialkyl carbonate include dimethyl carbonate, diethyl carbonate, and dipropyl carbonate. Examples of the diaryl carbonate include diphenyl carbonate.

  Diols having no side chain such as ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, Diols having side chains such as 2-methyl-1,8-octanediol, neopentyl glycol, 2-ethyl-1,6-hexanediol, and cyclic diols such as 1,3-cyclohexanediol and 1,4-cyclohexanediol Can be mentioned. One type of diol may be used, or a copolymerized polycarbonate diol using two or more types of diol as raw materials may be used.

  The number average molecular weight of the aliphatic polycarbonate diol is preferably 1000 to 2000. When it is 1000 or more, it is preferable because a curing reaction with diisocyanate easily occurs, and when it is 2000 or less, solubility in a solvent as an adhesive component is improved. In the production of polycarbonate diol, the reactivity of the monomer is high and the molecular weight is easily increased. Therefore, in order to obtain a polycarbonate diol having a predetermined number average molecular weight, it is necessary to control the reaction rate and the like.

  Commercially available aliphatic polycarbonate diols can also be used. In order to obtain an adhesive having excellent durability, weather resistance, heat resistance, and hydrolysis resistance, for example, an aliphatic polycarbonate diol having a number average molecular weight of 1000 (manufactured by Asahi Kasei Chemicals, trade name “Duranol T5651”), number average molecular weight 2000 aliphatic polycarbonate diol (manufactured by Asahi Kasei Chemicals Corporation, trade name “Duranol T5662”) can be preferably used.

  1,6 hexanediol is an aliphatic diol and can react with the following isophorone diisocyanate to form a polyurethane diol. 1,6 hexanediol is liquid at room temperature and can be dissolved in a solvent as an adhesive component.

  Polyester diols can be used with 1,6 hexanediol. The polyester diol is a polyol having two or more hydroxyl groups as in 1,6 hexanediol, but can also be an ester with a carboxylic acid having a bulky aromatic ring in its basic skeleton, so that isophorone diisocyanate and An excellent curing speed and cohesive force can be imparted to the polyurethane diol obtained by the reaction. Examples of polyester diols include aromatic polyester diols produced using isophthalic acid. In the present invention, the polyester diol can be produced by adopting a predetermined combination of a carboxylic acid compound and a diol according to a conventional method.

  The number average molecular weight of the polyester diol is preferably 3000 to 4000. When the number average molecular weight of the polyester diol is 3000 or more, the reactivity with the curing agent is improved, and when the number average molecular weight of the polyester diol is 4000 or less, the solubility in a solvent is improved.

  Isophorone diisocyanate is a constituent component of polyurethane diol and is an alicyclic polyisocyanate. Isophorone diisocyanate reacts with the hydroxyl group of the aliphatic polycarbonate diol, 1,6 hexanediol or polyester diol to form a polyurethane diol which is a main component.

  The above-described aliphatic polycarbonate diol, aliphatic diol and isophorone diisocyanate are dissolved in a solvent, mixed, and reacted by heating under reflux to obtain a solution of a polyurethane diol as a main component. In the above reaction, the hydroxyl groups at both ends of each of the aliphatic polycarbonate diol and the aliphatic diol react with the isocyanate group of isophorone diisocyanate to form a urethane bond and cure.

  The compounding amount of 1,6 hexanediol in the reaction system for producing the main component polyurethane diol is 5 to 15 parts by mass, preferably 2 to 8 parts by mass with respect to 100 parts by mass of the aliphatic polycarbonate diol. preferable. When the blending amount of 1,6 hexanediol is 5 parts by mass or more, a durable adhesive component can be obtained, and when it is 15 parts by mass or less, solubility in a solvent is improved, which is preferable. .

  Moreover, it is preferable that the compounding quantity of the polyester diol in the reaction system which manufactures polyurethane diol is 50-100 mass parts with respect to 100 mass parts of aliphatic polycarbonate diol. When the blending amount of the polyester diol is 50 parts by mass or more, a durable adhesive component can be obtained, and when it is 100 parts by mass or less, the solubility in a solvent is improved.

  The aliphatic polycarbonate diol, and the solvent that can be used when the aliphatic diol and isophorone diisocyanate are reacted are not particularly limited as long as they can dissolve these compounds and do not react with the solvent. Although not intended, examples thereof include carboxylic acid ester solvents such as ethyl acetate from the viewpoint of compatibility with solvents and the like and processability during lamination.

  The aliphatic polycarbonate diol as the main component reacts with the curing agent component having an isocyanate group. As the aliphatic polycarbonate diol, the same aliphatic polycarbonate diol as used in the production of the polyurethane diol can be used.

  The main ingredient component is a mixture of the above-described polyurethane diol and aliphatic polycarbonate diol. The mass ratio of the polyurethane diol and the aliphatic polycarbonate diol in the mixture is preferably 10 to 20 parts by mass with respect to 100 parts by mass of the polyurethane diol. When the amount of the aliphatic polycarbonate diol is 10 parts by mass or more, the adhesion is suitably reduced, and when it is 20 parts by mass or less, the reaction between the polyurethane diol and the curing agent is likely to occur.

  In addition to the main component polyurethane diol and aliphatic polycarbonate diol, if necessary, a tackifier, a stabilizer, a filler, a plasticizer, a softening point improver, a catalyst, etc. are added to the main agent. Can be mixed as. Examples of tackifiers include rosin resins and terpene resins. Examples of the stabilizer include an antioxidant and an ultraviolet ray inhibitor. Examples of the filler include inorganic fillers.

[Curing agent]
The curing agent for the black adhesive is mainly composed of a polyisocyanate compound. The polyisocyanate compound is a compound having two or more isocyanate groups in one molecule, and the isocyanate group reacts with a hydroxyl group in the polyurethane diol compound as the main agent to crosslink the polyurethane diol compound. Such a polyisocyanate compound is not particularly limited as long as it can crosslink the main polyurethane diol compound. For example, polyurethane diisocyanate, hexamethylene diisocyanate (hereinafter, “HDI”), Examples thereof include isocyanurate-modified isophorone diisocyanate (hereinafter, “nurate-modified IPDI”). Among these polyisocyanate compounds, a mixture of HDI and nurate-modified IPDI is preferable from the viewpoint of improving the reactivity with respect to hydroxyl groups. When the curing agent is a mixture of HDI and nurate-modified IPDI, it is preferable to use HDI and nurate-modified IPDI in the range of 70:30 to 50:50 (mass ratio).

[Combination of main agent and curing agent]
The adhesive component is mainly composed of a main agent and a curing agent, but the mixing ratio of the main agent and the curing agent is such that the ratio of (isocyanate group derived from polyisocyanate compound) / (hydroxyl group derived from polyurethane diol compound) is 1. It is preferably in the range of 0.0 to 3.5, and more preferably in the range of 1.2 to 3.0. It is preferable that the blending ratio of the polyurethane diol compound as the main component and the polyisocyanate compound as the curing agent component is in the above range because an adhesive capable of firmly bonding the respective substrates can be obtained.

[Organic pigments]
A dark organic pigment is used as a coloring material for making the adhesive black in order to provide design properties. In general, inorganic pigments such as carbon black are widely used as coloring pigments for synthetic resins. In the present invention, black pigments can be bonded by using dark organic pigments. The agent layer 60 can be a layer that transmits near infrared rays. Specific examples of dark organic pigments added to the adhesive include oxazine, pyrrole, quinacridone, azo, perylene, dioxane, isoindolinone, indanthrene, quinophthalone, perinone, phthalocyanine And the like. Oxazine-based organic pigments can be particularly preferably used from the viewpoint of UV resistance. In addition, by adding a dark organic pigment, the polyurethane / polycarbonate diol adhesive improves the durability of adhesion such as thermal durability and UV resistance. Also from the viewpoint of improving the adhesion durability, an oxazine-based organic pigment can be particularly preferably used.

  As the oxazine-based organic pigment, for example, a dioxazine-based compound as described in JP-A-2003-105217 can be preferably used and is not particularly limited. The preferred content is about 10% to 30% in terms of solid mass ratio.

  An inorganic black pigment can be supplementarily added to the black adhesive layer at a ratio within a predetermined range to adjust the black color to a preferable color. A typical example of the inorganic black pigment is carbon black. The inorganic black pigment may be added in a range of 3 to 50% by mass with respect to the main resin. If the addition amount is within this range, the appearance of the black adhesive layer 60 can be appropriately adjusted to an optimum color while maintaining other preferable physical properties of the black adhesive layer 60 in the present invention.

[Additives such as silane coupling agents]
In addition to the above, if necessary, a silane coupling agent, a tackifier, a stabilizer, a filler, a plasticizer, a softening point improver, a catalyst, and the like can be mixed as additives. Examples of the silane coupling agent include silane monomers such as methyltrimethoxysilane and methyltriethoxysilane, vinylsilanes such as vinyltriethoxysilane and vinyltrimethoxysilane, 3-methacryloxypropylethoxysilane, and 3-methacryloxypropylmethoxy. Mention may be made of epoxysilanes such as methacrylic silanes such as silane, 3-glycidoxypropyltrimethoxysilane and 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane. Examples of tackifiers include rosin resins and terpene resins. Examples of the stabilizer include an antioxidant and an ultraviolet ray inhibitor. Examples of the filler include inorganic fillers.

  In addition, it is preferable that the addition amount of the said silane coupling agent is 1 to 3 mass% silane coupling agent with respect to a total of 100 mass parts of the adhesive main agent and a hardening | curing agent, Addition of a silane coupling agent When the amount is 1% by mass or more, the adhesion is good, and when it is 3% by mass or less, the durability is improved.

[solvent]
As the above black adhesive composition, it is preferable to add a solvent component in order to obtain good coating properties and handling suitability. Examples of such a solvent component include, but are not limited to, carboxylic acid esters such as ethyl acetate, methyl acetate, and methyl propionate. As described above, the adhesive is configured as a two-component agent consisting of a main agent and a curing agent, but the solvent component used in the main agent and the solvent component used in the curing agent are each independently selected and may be the same. May be different.

(Formation of black adhesive layer)
The black adhesive layer 60 can be formed by applying or laminating the black adhesive composition described above on the reflective layer 61 and / or the transparent adhesive layer 62 and drying and curing it. As a coating method, it can be applied by a coating method such as a roll coating method, a gravure roll coating method, a kiss coating method, or the like, or a printing method. The coating amount is 3 g / m ² or more and 7 g / m ² or less, and the thickness of the black adhesive layer 60 is preferably in the range of 2.0 to 8.0 μm. If it is within this range, it may be appropriately changed depending on the adhesive strength necessary for the sheet laminated member for solar cell modules, and since it is within this range, the near infrared can be sufficiently transmitted. Can penetrate well.

  The black adhesive composition is not limited to this, and may be any composition form such as an aqueous type, a solution type, an emulsion type, and a dispersion type, and the properties are film / sheet type, powder type, solid type, etc. Any form such as a shape may be used, and the bonding mechanism may be any form such as a chemical reaction type, a solvent volatilization type, a heat melting type, and a hot pressure type. When a solution-type adhesive is used, the solid matter mixed so that the dark organic pigment is 20 to 60% by mass and the main resin is 20 to 60% by mass in the mass ratio in the total solids is a solvent. And the composition may be adjusted so that the mass ratio of the solid matter in the total composition is 10% or more and 60% or less.

<Reflective layer>
The reflective layer 61 is made of a resin sheet containing a white pigment or a resin sheet on which a coat layer (a coating film or a printed film) containing a white pigment is formed, and is a white resin layer that reflects near infrared rays. The reflective layer 61 contributes to improving the power generation efficiency of the solar cell module 1 by reflecting the near infrared light transmitted through the black adhesive layer 60. In this specification, the term “resin sheet” is used as the name of the resin processed into a sheet shape, but this term is used as a concept including a resin film.

  Examples of the resin sheet constituting the reflective layer 61 include fluorine resins such as PTFE (polytetrafluoroethylene) and ETFE (tetrafluoroethylene / ethylene copolymer), poly (meth) acrylic resins, and PET (polyethylene terephthalate). A resin sheet such as polyester resin can be preferably used. Here, in this embodiment, since the reflective layer 61 is arrange | positioned in the outermost layer in the solar cell module 1, high weather resistance, barrier property, and hydrolysis resistance are calculated | required. From such a viewpoint, among these, it is particularly preferable to use a fluorine-based resin typified by ETFE or a polyester-based resin typified by PET.

  The reflective layer 61 needs to have a function of reflecting near infrared rays. Therefore, it is preferable to use a white resin layer containing a white pigment having a particle size of 0.5 μm or more and 1.5 μm or less, and more preferably a particle size of 0.8 μm or more and 1.2 μm or less. Further, in the reflective layer 61, the white pigment particles having a particle size of 0.8 μm or more and 1.2 μm or less are preferably 80% by mass or more of the particles of the all white pigment. By setting the particle size and distribution ratio of the white pigment in the above range, the white resin layer efficiently reflects near-infrared rays. Therefore, the white pigment contributes to the improvement in power generation efficiency of the solar cell module. Reflecting near-infrared means, for example, a function in which the integrated reflectance is 85% or more in a wavelength region of approximately 750 nm to 2200 nm.

  A typical example of a white pigment having a particle size of 0.5 μm or more and 1.5 μm or less is titanium oxide. In the present invention, titanium oxide is preferably used as the white pigment. Here, the titanium oxide includes surface-treated titanium oxide. For example, in the case of titanium oxide, its production can be performed as follows.

  A hydrous titanium oxide is used as a raw material, and 0.1 mass% or more and 0.5 mass% or less of an aluminum compound in terms of aluminum oxide and 0.1 mass% or more and 0.5 mass% or less in terms of potassium carbonate based on the titanium oxide content. It can manufacture by adding the following potassium compounds and 0.2 mass% or more and 1.0 mass% or less zinc compounds in conversion of zinc oxide, and drying and baking.

  Examples of the method for producing the reflective layer 61 include a method of forming a coat layer containing a white pigment on a resin sheet, and a method of kneading a white pigment in the resin sheet. Any of them can be produced by a conventionally known method without any limitation.

  When forming a coating layer (coating film or printing film) containing a white pigment on a resin sheet, the main component is an ordinary vehicle for paint or ink, and a white pigment is added to this, and if necessary, , UV absorbers, cross-linking agents, and other additives are optionally added to prepare paints or ink compositions, and are applied or printed on the surface of the substrate film using a normal coating method or printing method. Then, the coating film or the printing film can be formed.

  When the white pigment is kneaded into the resin sheet, the resin constituting the resin sheet is a main component, and a white pigment is added to the resin, and if necessary, other additives are optionally added to the resin sheet. By adjusting the composition, for example, a film or sheet can be produced by a film forming method such as an extrusion method or a T-die method, and a sheet formed by kneading a white pigment can be produced.

<Transparent adhesion layer>
The transparent adhesion layer 62 has a function of improving the adhesion between the back surface sealing material layer 5 using a polyolefin such as ethylene-vinyl acetate alcohol copolymer resin (EVA resin) or polyethylene, and the back surface protection sheet 6. . Further, the transparent adhesive layer 62 is required to transmit near infrared light reflected by the reflective layer 61, and to be transparent or translucent from the request for design. From such a viewpoint, it is preferable to use a polyethylene resin, a polyolefin resin such as a polypropylene resin, or polyethylene terephthalate (PET) for the transparent adhesion layer 62. Among these resins, it is particularly preferable to use PET that is highly transparent and less turbid in appearance and excellent in design. “Transmitting all light” means that the total light transmittance is 80% or more.

<Other layers>
The back surface protective sheet 6 of the present invention may be provided with other layers as long as the effects of the present invention are not impaired. For example, a weathering layer (not shown) made of a fluorine-based resin, polyethylene terephthalate (PET), or the like may be further provided on the outer side of the reflective layer 61. In this case, the weather resistant layer may be black for improving the design. Or you may provide the other transparent reinforcement layer (not shown) for increasing the intensity | strength of the back surface protection sheet 6 between the reflection layer 61 and the transparent contact | adherence layer 62, for example.

  When other layers are provided on the back surface protective sheet, an adhesive layer for adhering each layer may be formed at a plurality of positions. At this time, if each of the layers disposed between the transparent adhesive layer 62 and the black adhesive layer 60 is transparent, any adhesive layer on the transparent adhesive layer side of the reflective layer 61 among the plurality of adhesive layers is black bonded. By setting it as the agent layer 60, it can be set as the back surface protection sheet which has sufficient weather resistance and durability, and can fully contribute to the improvement of the power generation efficiency of a solar cell module, while making the external appearance black. Such a back surface protection sheet is also within the scope of the present invention.

  Also, for example, in a back surface protection sheet formed by laminating a reflective layer that reflects near infrared rays and a black layer made of a resin containing a black pigment, the black layer and other layers can be bonded together with an adhesive. It is necessary and an adhesive layer is often provided. Such a back surface protective sheet also has an advantage that the color tone of the black layer can be easily adjusted by imparting a coloring function to the adhesive layer. As long as the constituent requirements of the present invention are satisfied, such a back surface protection sheet is also within the scope of the present invention.

<Method for manufacturing back surface protection sheet for solar cell module>
The back surface protective sheet 6 can be manufactured by providing a black adhesive layer 60 between the reflective layer 61 and the transparent adhesion layer 62 and performing dry lamination. In addition, even when an adhesive bond layer becomes a several layer by providing another layer, each layer can be stuck and laminated | stacked by the same method.

[Other Embodiments of Back Surface Protection Sheet for Solar Cell Module]
The back surface protection sheet 6a which concerns on 2nd Embodiment of this invention is demonstrated using FIG. The back surface protection sheet 6a has the same configuration as the back surface protection sheet 6 according to the first embodiment in that it includes a black adhesive layer 60 and a transparent adhesion layer 62. However, the back surface protective sheet 6a according to the second embodiment differs from the back surface protective sheet 6 in that the reflective layer is a metal reflective layer 61a formed by forming a metal vapor deposition film 611 on the reflective layer base 612.

  In the back surface protection sheet 6a, the reflection layer 61 in the first embodiment is the metal reflection layer 61a, thereby further improving the near-infrared reflectance and contributing to the improvement of the power generation efficiency of the solar cell module 1. I can do it. Moreover, since the metal reflective layer 61a has high durability and is excellent in moisture resistance that prevents moisture, oxygen, and the like from entering the solar cell module 1, long-term performance deterioration of the solar cell module 1 is achieved. Can be minimized.

  The method for forming the metal vapor deposition film 611 on the surface of the reflective layer base 612 is not particularly limited, and a known vapor deposition method can be used. Such deposition methods include physical vapor deposition methods such as vacuum deposition methods, sputtering methods, ion plating methods, and ion cluster beam methods, and chemical methods such as plasma chemical vapor deposition methods, thermal chemical vapor deposition methods, and photochemical vapor deposition methods. The vapor phase growth method is mentioned.

  The metal vapor deposition film 611 is not particularly limited as long as it is a thin film formed by vapor deposition of a metal oxide. Examples of the metal oxide include silicon (Si), aluminum (Al), magnesium (Mg), calcium (Ca), potassium (K), tin (Sn), sodium (Na), boron (B), titanium ( Examples include Ti), lead (Pb), zirconium (Zr), yttrium (Y), and the like. Among these, metals such as silicon and aluminum are particularly preferable. A particularly preferred metal oxide is silica alumina.

  The thickness of the metal vapor deposition film 611 is not particularly limited, but is preferably 5 to 100 nm, and preferably 10 to 60 nm. When the thickness of the metal vapor deposition film 611 is 5 nm or more, sufficient moisture resistance and weather resistance can be imparted. When the thickness of the metal vapor deposition film 611 is 100 nm or less, the metal vapor deposition film 611 itself Since generation | occurrence | production of a crack and cracking can be suppressed, it is preferable.

  The metal reflective layer 61a may be a metal foil. When a metal foil is used as the metal reflection layer 61a, an aluminum foil can be suitably used. When using an aluminum foil, the thickness is preferably about 20 to 40 μm. If the thickness is less than the above range, it is not preferable because it may cause inconvenience such as wrinkles at the time of lamination. On the other hand, if the thickness exceeds the above range, the reflection performance and moisture resistance are not improved, and the cost is increased. Absent. In addition, when using the metal reflective layer 61a as a metal foil in this way, the back surface protective sheet 6a is further provided with a weather resistant layer (not shown) made of, for example, weather resistant PET on the outer layer side of the metal reflective layer 61a. More preferable weather resistance can be imparted.

  In the back surface protection sheet 6a, it is preferable to laminate | stack the intermediate | middle layer 64 between the metal reflective layer 61a and the transparent contact | adherence layer 62 via the black adhesive layer 60 and the contact bonding layer 60a. The intermediate layer 64 is a layer arranged mainly for the purpose of ensuring strength and reducing the burden on the coating portion.

  As a material that can be used for the intermediate layer 64, any material may be used as long as it has appropriate strength and high adhesion to both layers between the metal reflective layer 61a and the transparent adhesion layer 62, polyethylene terephthalate, Examples of the resin include polyethylene naphthalate and polybutylene terephthalate. The intermediate layer 64 can be manufactured by using a conventionally known film forming method. The thickness of the intermediate layer 64 is not particularly limited, but is preferably 12 to 250 μm. When the thickness is 12 μm or more, it is preferable because necessary mechanical strength can be obtained.

  The back surface protective sheet according to the second embodiment of the present invention has a power generation efficiency of the solar cell module due to a synergistic effect of the high near infrared reflectance of the metal reflective layer and the high near infrared transmittance of the black adhesive layer 60. Is further improved.

  Moreover, since the back surface protective sheet 6a according to the second embodiment in which the reflective layer is the metal reflective layer 61a is excellent in gas, particularly oxygen and water vapor barrier properties, the thin-film solar cell element such as amorphous silicon or CIGS compound type is particularly preferable. It can use suitably for a thin film type solar cell module provided with.

  EXAMPLES Hereinafter, although an Example, a reference example, and a comparative example demonstrate this invention further more concretely, this invention is not limited to a following example etc.

<Test Example 1>
In order to evaluate the adhesiveness and adhesion durability of the back surface protective sheet according to the present invention, two types of adhesives were produced by the method shown below, and samples for measuring adhesiveness using the adhesives were prepared.

[Black adhesive (Adhesive 1)]
[Main agent]
In a nitrogen atmosphere, a flask equipped with a stirrer and a nitrogen inlet tube was charged with ethylene glycol (32.3 parts by mass), 2,2-dimethyl-1,3-propanediol (270.8 parts by mass), and 1,6-hexane. Diol (122.9 parts by mass), adipic acid (228.1 parts by mass), and isophthalic acid (664 parts by mass) were added, bubbled with nitrogen at 180 ° C. to 220 ° C., and reacted to an acid value of 2 mg KOH / g. Ethyl acetate (860 parts by mass) was added to obtain a 50% solution of polyester diol H. The obtained resin had a hydroxyl value of 32 mgKOH / g and a number average molecular weight of about 3500.
In a flask equipped with a stirrer in a nitrogen atmosphere, 100 parts by mass of an aliphatic polycarbonate diol having a number average molecular weight of 1000 (manufactured by Asahi Kasei Chemicals Co., Ltd., trade names “Duranol T5651” and below, abbreviated as “PDC1000”), the above polyester diol H ( 50 mass parts), 1,6-hexanediol (2 mass parts), isophorone diisocyanate (23.8 mass parts), ethyl acetate (175.8 mass parts), and 2270 cm ⁻¹ isocyanate in infrared absorption spectrum. The mixture was heated to reflux until absorption of water disappeared to obtain a 50% solution of polyurethane diol. The obtained resin had a hydroxyl value of 14 mg KOH / g and a number average molecular weight of about 8,000.
The main agent was prepared by mixing 100 parts by mass of the above polyurethane diol and 15 parts by mass of the aliphatic polycarbonate diol (B) (PDC1000).

[Curing agent]
A mixture of hexamethylene diisocyanate (HDI adduct: bifunctional) and isocyanurate-modified isophorone diisocyanate (nurate-modified IPDI) was used. The mixing ratio of the adduct-modified HDI and the nurate-modified IPDI (HDI adduct) / (nurate-modified IPDI) was 6: 4 (mass ratio).
Organic pigment: Dioxazine compound Solvent: Ethyl acetate The main agent (solid content: 50% by mass), the curing agent (solid content: 10% by mass), and the organic pigment (solid content: 20% by mass) are dissolved in the solvent. The solid content was adjusted to be ^{2 to} 15 g / m ² (the film thickness after curing was ^{2 to} 15 μm), and was manufactured, applied, dried and cured.
[Adhesive containing no organic pigment (Adhesive 2)]
It was prepared in the same manner as in Adhesive 1 except that it did not contain an organic pigment.
[Adhesion measurement samples (Examples 1 to 3, Reference Examples 1 to 3)]
The following types of resin sheets were bonded with the adhesive 1 and the adhesive 2 according to the combinations shown in Table 1 below, to prepare samples for adhesion measurement of Examples 1 to 3 and Reference Examples 1 to 3. For sample preparation, the adhesive 1 or 2 is gravure-coated on the resin sheet 1 shown in Table 1 (the coating amount is 7 g / m ² ) to form an adhesive layer having a thickness of 3 μm (dry state). The resin sheet 2 shown was laminated | stacked, 45-55 degreeC, the aging process of 168 hours was performed, and it was carried out by making it heat-harden.
For the resin sheets 1 and 2, the following resins were used.
ETFE: 25 μm, trade name: 25 PW, manufactured by Asahi Glass Co., Ltd. PET: 50-250 μm, trade name: Lumirror S10, manufactured by Toray Industries, Inc. PE: 50-100 μm, trade name: manufactured by Mitsubishi Plastics

<Evaluation 1>
Tests on adhesiveness were performed on the samples of Examples 1 to 3 and Reference Examples 1 to 3 by the following method, and the adhesiveness was evaluated based on the measurement results. All specimens are 15 mm wide.
(Adhesion test)
In accordance with JIS K6854-3, the peel strength (N) of each sample of Examples 1 to 3 and Reference Examples 1 to 3 was determined by the T-type peel adhesion strength test method. This was done by measuring the value. For each sample measurement, measurement was performed at 23 ° C. under a peeling condition of 50 mm / min using a peeling test apparatus (trade name “TENSILON RTA-1150-H” manufactured by A & D Co., Ltd.). The average value of three measurements was adopted.
(Pressure cooker (PCT) test)
According to JIS C60068-2-66, a durability test was performed for 96 hours at a temperature of 120 ° C., a humidity of 85%, and a pressure of 1.6 atm. The adhesion test was performed in a state where the sample after the test was placed in an environment at a temperature of 120 ° C. for 5 minutes using a constant temperature and high humidity bath.
(Dump heat (DH) test)
In accordance with JIS C8917, each sample was subjected to a durability test for 1000 hours under the conditions of a test chamber temperature of 85 ° C. and a humidity of 85%. The adhesion test was performed in a state where the sample after the test was placed in an environment at a temperature of 120 ° C. for 5 minutes using a constant temperature and high humidity bath.
(High intensity xenon irradiation test)
In accordance with JIS C8917, each sample was subjected to a durability test for 500 hours under conditions of a black panel temperature (BPT) of 63 ° C. and a humidity of 50%. The adhesion test was performed in a state where the sample after the test was placed in an environment at a temperature of 120 ° C. for 5 minutes using a constant temperature and high humidity bath.

  From Table 1, although the back surface protection sheet of the present invention is a back surface protection sheet for solar cell modules having a black appearance, it is practical even when compared with a back surface protection sheet having the same configuration and not having a black appearance. It can be seen that it has sufficiently high weather resistance and durability that can be said to be inferior. In particular, regarding the heat durability, it can be seen that the adhesion durability of the adhesive layer can be improved to a more preferable value by adding a black organic pigment to the adhesive constituting the adhesive layer.

<Test Example 2>
In order to evaluate the near-infrared reflectivity (transmittance) of the back surface protective sheet according to the present invention, as a comparative example of Examples and a reference example, materials for reflectivity measurement were prepared by the following methods.
[Reflective measurement sample (Example 4, Comparative Example 1, Reference Example 4)]
The following resin was used as a resin base material used as a reflection layer.
Reflective layer 1: silica-deposited PET: 12 μm, trade name: Tech Barrier LX, manufactured by Mitsubishi Plastics Co., Ltd. The following adhesive was used as an adhesive constituting the black adhesive layer.
Black adhesive (adhesive 1): The same adhesive as that used in Test Example 1 was used.
Black adhesive containing an inorganic pigment (adhesive 3): the same main agent as the adhesive 1, (50% by mass in mass ratio with respect to the total blended adhesive), the same curing agent as the adhesive 1 (10% by mass in the same ratio) Carbon black (40% by mass in the same ratio) is dissolved in the same solvent as the adhesive 1 and adjusted so that the solid content is ^{2 to} 15 g / m ² (the film thickness after curing is ^{2 to} 15 μm). did. In addition, about carbon black, said amount was added as a required amount in order to set it as the black color of the same grade as the adhesive agent 1. FIG.
[Example 4]: On the sheet made of the reflective layer 1, the adhesive 1 is gravure-coated (coating amount is 7 g / m ² ) to form an adhesive layer having a thickness of 3 μm (dry state). A sample was prepared by performing an aging treatment at 55 ° C. for 168 hours and curing by overheating.
[Reference Example 4] A single layer sheet composed of the reflective layer 1 was used as a sample.
[Comparative Example 1]: The adhesive 3 is gravure coated on the sheet made of the reflective layer 1 (the coating amount is 7 g / m ² ) to form an adhesive layer having a thickness of 3 μm (dry state). A sample was prepared by aging treatment at 55 ° C. for 168 hours and heat curing.
[Adhesion measurement samples (Examples 1 to 3, Reference Examples 1 to 3)]
The following types of resin sheets cut to a width of 15 mm were bonded with the adhesive 1 and the adhesive 2 according to the combinations shown in Table 1 below, and the adhesiveness measurement samples of Examples 1 to 3 and Reference Examples 1 to 3 were used. Created. For sample preparation, the adhesive 1 or 2 is gravure-coated on the resin sheet 1 shown in Table 1 (the coating amount is 7 g / m ² ) to form an adhesive layer having a thickness of 3 μm (dry state). The resin sheet 2 shown was laminated | stacked, 45-55 degreeC, the aging process of 168 hours was performed, and it was carried out by making it heat-harden.

<Evaluation 2>
Reflection of light having a wavelength of 500 nm to 1750 nm when light is incident on the samples of Example 4, Reference Example 4 and Comparative Example 1 using a spectrophotometer (manufactured by Hitachi High-Technologies Corporation, “U-4100”). Rate (%) was evaluated. In Example 4 and Comparative Example 1, light was incident from the black layer side (side where the adhesive was applied). The evaluation results are shown in FIG.

  The back protective sheet of the present invention from FIG. 4 is provided with a black adhesive layer containing a dark organic pigment, thereby improving the near infrared transmittance in the black layer, and thus having a black appearance, Compared with the case where a conventional inorganic black pigment is added, the reflectance of near infrared rays is remarkably high, and even when compared with a back surface protection sheet having a similar configuration having no black appearance, particularly in the near infrared region. It can be seen that it has a sufficiently high reflectivity so that there is no practical difference.

  From the above, the back surface protective sheet of the present invention has sufficient weather resistance and durability while being a back surface protective sheet having a black appearance in order to satisfy the demands of consumers concerning design properties. It can be seen that it can sufficiently contribute to the improvement of power generation efficiency, and because of its configuration, the members and processes can be saved, so that the productivity is high.

DESCRIPTION OF SYMBOLS 1 Solar cell module 2 Transparent front substrate 3 Front sealing material layer 4 Solar cell element 5 Back surface sealing material layer 6 Back surface protection sheet 60 Black adhesive layer 61 Reflective layer 62 Transparent adhesion layer

Claims (8)

A transparent adhesion layer that is disposed in the outermost layer in the back surface protection sheet for the solar cell module and transmits all rays,
A back surface protection sheet for a solar cell module formed by laminating a plurality of layers including at least a reflective layer that reflects near infrared rays of 750 nm to 1500 nm,
At least one of the adhesive layers formed between the plurality of layers is a black adhesive layer;
The black adhesive layer is composed of a black adhesive containing a main resin and a dark organic pigment,
The organic pigment is an oxazine pigment;
A back protective sheet for a solar cell module, which transmits near infrared rays having a wavelength of 750 nm to 1500 nm. The back surface protective sheet for a solar cell module according to claim 1, wherein a main component constituting the main resin is a polyurethane / polycarbonate diol system. The solar cell module according to claim 1 or 2, wherein the mass ratio of the polyurethane diol and the aliphatic carbonate diol in the mixture of the main component is 10 to 20 parts by mass of the aliphatic carbonate diol with respect to 100 parts by mass of the polyurethane diol. Back surface protection sheet. The back surface protection sheet for solar cell modules in any one of Claim 1 to 3 with which the said black adhesive bond layer is arrange | positioned in the inner surface in the back surface protection sheet for solar cells of the said transparent adhesion layer. The back protective sheet for a solar cell module according to any one of claims 1 to 4 , wherein the reflective layer is a white resin layer made of a resin containing a white pigment. The back protective sheet for a solar cell module according to any one of claims 1 to 5 , wherein the reflective layer is a metal reflective layer formed by laminating a metal vapor-deposited layer on a resin base material or a metal foil. The solar cell module formed by laminating | stacking the back surface protection sheet for solar cell modules in any one of Claim 1 to 6 . The solar cell module of Claim 7 formed by laminating | stacking a thin film type solar cell element.

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