JP6003490B2 - Easy-adhesive layer composition and white back surface protective sheet using the same - Google Patents

Description

  The present invention provides a white back surface protection sheet for a solar cell module, and can easily form a white easy adhesion layer having excellent adhesion and blocking resistance with a solar cell module sealing material. It is related with the white back surface protection sheet for solar cell modules which formed the layer composition and the white easily bonding layer using it.

  In recent years, solar cells as a clean energy source have attracted attention due to the growing awareness of environmental issues. Generally, a solar cell module constituting a solar cell has a structure in which each member of a transparent front substrate, a front surface side sealing material, a solar cell, a back surface side sealing material, and a back surface protection sheet is laminated in order from the light receiving surface side. And has a function of generating electric power when sunlight enters the solar battery cell.

  The back surface protection sheet has a role of preventing moisture (water vapor) from entering the back surface side sealing material. Therefore, high adhesion is provided between the laminated back surface protection sheet and the back surface side sealing material. It is required that the adhesive part and the bonded part have high durability.

  As a method for integrating the members including the back surface protective sheet in the manufacturing process of the solar cell module, a method of integrating by vacuum heat laminating can be mentioned. During integration by such a method, an easy-adhesion layer made of a mixture of an acrylic resin, a silane coupling agent, and a polyisocyanate curing agent is formed in order to enhance the adhesion between the back surface protection sheet and the sealing material. The back surface protection sheet (refer patent document 1) which improved adhesiveness by doing is disclosed.

  On the other hand, for further widespread use of solar cells, further improvement in the power generation rate of solar cell modules is strongly demanded. In order to improve the power generation efficiency, out of the incident light to the solar cell module, the light passing through the periphery of the solar cell element or the gap between the elements without contributing to power generation is made light reflective. It is conceivable that the light is reflected by the back surface protective sheet and is directed again to the solar cell element to contribute to power generation. As such a back surface protection sheet having light reflectivity, a back surface protection sheet in which a white resin film, a resin film coated with a metal oxide, and a hydrolysis resistant resin film are sequentially laminated has been proposed (Patent Document). 2).

JP 2006-320991 A Japanese Patent Laid-Open No. 2002-100788

  However, the back surface protective sheet described in Patent Document 1 is premised on the use of EVA as a sealing material, and does not have sufficient adhesion to a sealing material made of a polyethylene resin such as LLDPE. Further, since the easy-adhesion layer is exposed on the outermost surface as a product before lamination, blocking resistance that is not required for a normal adhesive layer is required. However, the back surface protection sheet described in Patent Document 1 has high adhesion and resistance. The point of achieving both blocking properties was insufficient.

  On the other hand, the back surface protective sheet described in Patent Document 2 reflects the passing light by the white resin film. However, in the white resin film, a part of the passing light is absorbed and the reflectance, particularly the power generation efficiency. The diffuse reflectance, which is said to have a large correlation with the improvement of the light intensity, is insufficient, and in order to improve the diffuse reflectance, a special light diffusing means such as micro beads or a micro lens array is required. There is a problem that an extremely high coating technique is required and the manufacturing cost increases.

  In order to solve this problem, in the back surface protection sheet, it is considered that the white pigment that has been conventionally contained in the resin layer or the like is included in the adhesive layer or the primer layer in order to improve the diffuse reflectance. However, in general, the addition of a pigment to an adhesive layer or the like causes a decrease in adhesiveness to a base layer resin such as an adhesive layer.

  The present invention has been made in view of the above situation, and has extremely high adhesiveness with the back surface side sealing material for solar cell modules, so that it can be used in harsh environments for a long time. An object of the present invention is to provide a white back surface protective sheet for a solar cell module that can withstand, is further excellent in blocking resistance, and contributes to an improvement in power generation efficiency of the solar cell module.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have determined that an easy-adhesion layer composition, which is a material for forming a white easy-adhesion layer on the back surface protection sheet, has a crosslinkable main resin as a polyisocyanate compound By containing a cross-linked resin cross-linked under a predetermined NCO / OH ratio, a predetermined amount of colloidal silica, a white pigment, a silane coupling agent, and an organometallic coordination compound. The present inventors have found that a white back surface protective sheet having both high adhesion and blocking resistance can be obtained, and have completed the present invention. More specifically, the present invention provides the following.

  (1) An easy-adhesion layer composition for forming a white easy-adhesion layer on the surface of a white back surface protective sheet for a solar cell module, wherein a) a crosslinkable main component resin is crosslinked by b) a polyisocyanate compound A resin, c) an aggregation inhibitor, d) a white pigment, e) a silane coupling agent, and f) an organometallic coordination compound, and c) the aggregation inhibitor is colloidal silica, Content ratio with respect to the total amount of said a) crosslinkable main ingredient resin, said b) polyisocyanate compound, and said d) white pigment is 0.1 to 25.0 mass%, said b) The easily bonding layer composition whose ratio of the NCO value of a polyisocyanate compound and the OH value of said a) crosslinkable main ingredient resin is 1.0 or more and 4.7 or less.

  (2) The c) anti-aggregation agent has a content ratio with respect to the total amount of the a) crosslinkable main resin, b) polyisocyanate compound, and d) white pigment of 0.1% by mass or more and 10%. The easily bonding layer composition as described in (1) which is 0.0 mass% or less.

  (3) The easy-adhesion layer composition according to (1) or (2), wherein the colloidal silica has been subjected to a hydrophobic treatment and has an average particle diameter of 1 nm to 500 nm.

  (4) The easily bonding layer composition as described in (3) whose average particle diameter of the said colloidal silica is 3 nm or more and 30 nm or less.

  (5) The easy adhesion layer composition according to any one of (1) to (4), wherein the d) white pigment is titanium oxide having an average particle size of 0.1 μm or more and 0.5 μm or less.

  (6) The e) silane coupling agent is e1) a mercapto group-containing silane coupling agent, or e2) an epoxy group-containing silane coupling agent, or a mixture of these two silane coupling agents (1 ) To (5), the easy-adhesion layer composition.

  (7) The a) crosslinkable main component resin is a crosslinkable substituent-containing acrylic resin, and the glass transition point (Tg) thereof is 25 ° C. or higher and 70 ° C. or lower, according to any one of (1) to (6) Easy adhesion layer composition.

  (8) It is a white back surface protection sheet for solar cell modules in which the white easily bonding layer is formed in one surface, The said white easily bonding layer is easy in any one of (1) to (7) A white back surface protective sheet in which a coating liquid containing an adhesive layer composition is formed on one side of a back surface protective sheet for a solar cell module.

  (9) A method for producing a white back surface protective sheet for a solar cell module in which a white easy adhesion layer is formed on one surface, wherein the easy adhesion layer composition according to any one of (1) to (7) Of a white backside protective sheet comprising: a coating liquid coating process for coating a coating liquid containing a coating on one surface of a resin substrate; and a film forming process for forming a white easy-adhesion layer by forming a film on the coating liquid. Production method.

  (10) In the solar cell module in which the white back surface protective sheet according to (8), the sealing material, and the solar cell element are integrated at least, the white back surface protective sheet via the white easy-adhesive layer. And a solar cell module in which the sealing material containing a polyethylene resin is integrated.

(11) The sealing material is copolymerized using at least a low density polyethylene (LDPE) having a density of 0.900 g / cm ³ or less and / or a linear low density polyethylene (LLDPE) and an ethylenically unsaturated silane compound as a comonomer. (10) The solar cell module according to (10), which is a sealing material containing a polyethylene-based resin containing a silane copolymer.

  According to the present invention, by forming a white easy-adhesion layer using an easy-adhesion layer composition having a specific composition, it is possible to prevent blocking of the white back-side protective sheet with the easy-adhesion layer-formed back surface, and a polyethylene-based seal. A white back surface protective sheet having high adhesion to a sealing material including a stopper can be provided.

It is sectional drawing which shows an example of the laminated constitution of the solar cell module of this invention.

  A specific embodiment of the present invention will be described. This embodiment is an easy-adhesion layer composition for forming a white easy-adhesion layer on a white back-protection sheet for solar cells, a white back-protection sheet using the white easy-adhesion layer and a method for producing the same, and It is a solar cell module using a white back surface protection sheet.

<Easily adhesive layer composition>
First, the easy-adhesion layer composition of the present invention will be described. The easy-adhesion layer composition of the present embodiment is used for forming a white easy-adhesion layer on the surface of the back surface protective sheet base material layer, and the white easy-adhesion layer has a white back surface protection sheet for solar cell modules. As such, preferable adhesiveness and blocking resistance can be imparted.

[Composition of easy adhesion layer composition]
The easy-adhesion layer composition comprises a) a crosslinkable main component resin, b) a polyisocyanate compound, c) colloidal silica, d) a white pigment, e) a silane coupling agent, and f) an organometallic coordination compound. The composition containing. This is characterized in that colloidal silica is used as the anti-agglomeration agent added to prevent sedimentation of the white pigment in the easy-adhesion layer ink and a decrease in adhesion of the white easy-adhesion layer due to aggregation.

[A) Crosslinkable main resin
As what can be used as the crosslinkable main resin, for example, a crosslinkable substituent-containing acrylic resin, or a polyol compound, a crosslinkable substituent-containing urethane resin, a crosslinkable substitution-containing fluororesin, a crosslinkable substituent-containing vinyl resin, Examples thereof include crosslinkable substituent-containing olefin resins. In the case where the cross-linked resin is a cross-linked acrylic resin, for example, the main resin is a cross-linkable substituent-containing acrylic resin, and the cross-linked acrylic resin is obtained by reacting this with a polyisocyanate compound. When the cross-linked resin is a cross-linked urethane resin, for example, the main resin is a polyol, and a cross-linked urethane resin is obtained by a reaction between this and a polyisocyanate compound (conceptually including a urethane prepolymer terminated with an isocyanate group). In the present specification, the resin compound before being cured by being crosslinked with a polyisocyanate compound is referred to as “crosslinkable main resin (or simply“ main resin ”)”, and is a resin contained in the white easy-adhesion layer, Distinguish from resins that have cured to form a white easy-adhesion layer. Hereinafter, each constituent material will be described.

(Crosslinkable substituent-containing acrylic resin)
A crosslinkable substituent-containing acrylic resin (hereinafter also simply referred to as “acrylic resin”) as an example of the main resin will be described. The acrylic resin used as the main resin has a plurality of crosslinkable substituents for reacting with the polyisocyanate compound, and is cured by reacting with the polyisocyanate compound to form a firm film. Here, examples of the crosslinkable substituent include a hydroxyl group, an amino group, and a carboxyl group. The main resin is selected from a solvent-soluble resin or a resin dispersible in a solvent. From the viewpoint of availability and crosslinking reactivity, the crosslinkable substituent is preferably a hydroxyl group. A preferred hydroxyl value range is from 5 to 100.

  As the acrylic resin, one or two or more kinds of acrylic acid compound and a monomer having a crosslinkable substituent, one or two or more kinds of acrylic acid compound and a monomer having a crosslinkable substituent, Those obtained by copolymerizing one or more ethylenic monomers are used. Here, in addition to the above monomer, a monomer having a substituent for imparting weather resistance to the acrylic resin may be used as a monomer used for obtaining the acrylic resin.

  Such acrylic resins include (meth) acrylic acid-2-hydroxyethyl, (meth) acrylic acid-2-hydroxypropyl, (meth) acrylic acid-2-hydroxy-3-phenoxypropyl, ethylene glycol mono (meth) ) (Meth) acrylic compounds having hydroxyl groups such as acrylate and propylene glycol mono (meth) acrylate, and (meth) acrylic acid or alkyl groups as methyl, ethyl, n-propyl, i-propyl, n- Examples include those obtained by copolymerizing an alkyl (meth) acrylate monomer having a butyl group, i-butyl group, t-butyl group, 2-ethylhexyl group, cyclohexyl group, or the like. Further, as a monomer used for copolymerization, (meth) acrylamide, N-alkyl (meth) acrylamide, N, N-dialkyl (meth) acrylamide (alkyl groups include methyl group, ethyl group, n -Propyl group, i-propyl group, n-butyl group, i-butyl group, t-butyl group, 2-ethylhexyl group, cyclohexyl group and the like), N-alkoxy (meth) acrylamide, N, N-di Alkoxy (meth) acrylamide (alkoxy groups include methoxy group, ethoxy group, butoxy group, isobutoxy group, etc.), amide group-containing monomers such as N-methylol (meth) acrylamide, N-phenyl (meth) acrylamide, Contains glycidyl groups such as glycidyl (meth) acrylate and allyl glycidyl ether Monomer, styrene, α-methylstyrene, vinyl methyl ether, vinyl ethyl ether, maleic acid, alkyl maleic acid monoester, fumaric acid, alkyl fumaric acid monoester, itaconic acid, alkyl itaconic acid monoester, (meth) acrylonitrile, chloride Various compounds having an ethylenically unsaturated bond such as vinylidene, ethylene, propylene, vinyl chloride, vinyl acetate, and butadiene may be used. Among these, a copolymer of methyl (meth) acrylate and 2-ethylhexyl acrylate, a copolymer of at least methyl (meth) acrylate, 2-ethylhexyl acrylate, and a hydroxyl group-containing (meth) acrylate is preferably used. Is done. Moreover, 1000-300,000 is mentioned as a preferable mass mean molecular weight of such resin.

  Conventionally, in the formation of a white easy-adhesion layer using an acrylic resin, from the viewpoint of blocking resistance, the glass transition point (Tg) of the acrylic resin is preferably 50 ° C. or higher, and the Tg is less than 50 ° C. Even if it has the property, the blocking resistance is lowered, which is not preferable. However, in the easy-adhesion layer composition of the present invention in which colloidal silica is selected as an anti-aggregation agent for preventing aggregation of the white pigment and the silane coupling agent and the organometallic coordination compound are used in combination, formation of the white easy-adhesion layer Even if it is a case where acrylic resin whose Tg is lower than conventional, for example, Tg is less than 50 degreeC, is used as a main ingredient resin, a white back surface protection sheet provided with sufficient blocking resistance can be manufactured. In the present invention, the Tg of the acrylic resin is preferably 25 ° C. or higher and 70 ° C. or lower, and more preferably 30 ° C. or higher and 70 ° C. or lower. When Tg is less than 25 ° C., even when colloidal silica, a silane coupling agent, and an organometallic coordination compound are used in combination, blocking resistance is lowered, which is not preferable. On the other hand, when Tg exceeds 70 ° C., the adhesiveness is lowered, which is not preferable.

[B] Polyisocyanate compound]
Next, the polyisocyanate compound will be described. A polyisocyanate compound is a compound having two or more isocyanate groups in one molecule. As described above, the polyisocyanate compound crosslinks the main resin and cures (high molecular weight) to form a resin contained in the white easy-adhesion layer. At this time, a polyisocyanate compound becomes a part of resin contained in a white easily bonding layer with main ingredient resin. Examples of the polyisocyanate compound include aliphatic, alicyclic, aromatic, and aromatic-aliphatic compounds. The white easy-adhesion layer is exposed to the external environment for a long period of time. From the standpoint of suppressing the coloration associated with, aliphatic and alicyclic polyisocyanate compounds are preferably used.

  Specific examples of the polyisocyanate compound include aliphatic isocyanates having 3 to 12 carbon atoms such as hexamethylene diisocyanate (HDI), 2,2,4-trimethylhexane diisocyanate, and lysine diisocyanate; 1,4-cyclohexane diisocyanate, isophorone diisocyanate ( Alicyclic diisocyanates having 5 to 18 carbon atoms such as IPDI); modified products of these diisocyanates (burettes, isocyanurate modified products, etc.). These can be used alone or in combination of two or more.

  The polyisocyanate compound is prepared such that the ratio of the NCO value to the OH value of the crosslinkable main resin (hereinafter also simply referred to as “NCO / OH ratio”) is 1.0 or more and 4.7 or less. To do. By setting the NCO / OH ratio in the above range, in the back protective sheet, in general, it is possible to achieve the improvement in adhesion and the improvement in blocking resistance, which are also contradictory requests, in a preferable range in a balanced manner. Can do. When the NCO / OH ratio is less than 1.0, the adhesion is insufficient, while when the NCO / OH ratio exceeds 4.7, the blocking resistance is insufficient.

[C) Colloidal silica
The easy-adhesion layer composition of the present invention uses colloidal silica as an anti-agglomeration agent for preventing a decrease in adhesion of the white easy-adhesion layer due to precipitation and aggregation of the white pigment. Colloidal silica is a colloid composed of fine particles having a particle size of about several hundred nm or less of an inorganic oxide containing silicon containing silicon dioxide (including hydrates thereof) as a main component.

  Generally, colloidal silica has a spherical shape and an irregular shape, but the colloidal silica used in the easy-adhesion layer composition of the present invention is an irregular shape, and more specifically, spherical particles. It has a structure in which a plurality of (primary particles) are connected.

  The average particle diameter of the primary particles contained in the colloidal silica is not particularly limited, but colloidal silica having an average particle diameter of 1 nm to 500 nm can be used. The average particle system is preferably in the range of 3 nm to 30 nm, and more preferably in the range of 5 nm to 20 nm. Colloidal silica having an average particle diameter of 1 nm or more and 500 nm or less can be uniformly and stably dispersed in the organic dispersion medium, and thus can sufficiently prevent precipitation and aggregation of the white pigment. Moreover, it is further more preferable to set it as the range of 3 nm or more and 30 nm or less in the point which can prevent sedimentation and aggregation of a white pigment, without reducing the concealment property by a white pigment. When the average particle diameter of colloidal silica is smaller than 1 nm, the stability as colloidal silica is lacking, and the storage stability of the easily adhesive composition becomes poor. On the other hand, if the average particle diameter is larger than 500 nm, the effect of preventing the precipitation and aggregation of the white pigment cannot be obtained sufficiently.

  Here, the average particle diameter of colloidal silica in the present invention refers to an average particle diameter when an amorphous colloidal silica in which a plurality of primary particles are combined is regarded as a sphere. The particle diameter of the irregular colloidal silica in which a plurality of primary particles are combined is a value measured by a light scattering method using a laser analysis / scattering particle size distribution measuring apparatus LA950 (manufactured by Horiba, Ltd.). It is.

  In addition, the colloidal silica is preferably subjected to a hydrophobic treatment in particular, so that the colloidal silica can be dispersed without agglomerating with each other, thereby preventing aggregation of the white pigment and dispersing the easily adhesive composition. Can do. For example, when general silica particles having a particle size of about 3 μm containing silicon dioxide as a main component are added as in the case of colloidal silica, sufficient adhesion is imparted to the white easy-adhesive layer made of the easy-adhesive composition. I can't.

  The colloidal silica may contain inorganic salts such as sodium hydroxide, potassium hydroxide, lithium hydroxide and ammonium hydroxide, and organic salts such as tetramethylammonium hydroxide. These inorganic salts and organic salts act, for example, as colloid stabilizers.

  As colloidal silica satisfying the above-mentioned requirements, for example, “Snow Tech O” and “Snow Tech C” (both manufactured by Nissan Chemical Industries, Ltd.) can be used in the easily adhesive composition of the present invention. Yes, easily available from the market. Moreover, colloidal silica can also be used individually by 1 type or in combination of 2 or more types.

  The content ratio of colloidal silica in the easy-adhesion layer composition is 0.05% by mass or more and 5.0% with respect to the total amount of a) crosslinkable main resin, b) polyisocyanate compound, and d) white pigment. It is preferably at most 0.1 mass% and preferably at least 0.1 mass% but no greater than 2.0 mass%. If the content ratio of the colloidal silica is less than 0.05% by mass, precipitation and aggregation of the white pigment may not be sufficiently prevented. If the content ratio exceeds 5.0 mass%, the adhesiveness with the sealing material may be reduced.

[D) White pigment]
As the white pigment added to the easy-adhesion layer composition, titanium oxide, or calcium carbonate, zinc sulfide, barium hydroxide, or the like can be used. Among these, titanium oxide can be preferably used because it is excellent in weather resistance, is easy to paint, and is easy to obtain including the price. Among them, the average particle size is 0.1 μm or more and 0.5 μm or less. The titanium oxide can be particularly preferably used. Titanium oxide having an average particle size of less than 0.1 μm transmits light and is not preferable for a white pigment. On the other hand, if the average particle diameter exceeds 0.5 μm, it is difficult to form a uniform easy-adhesion layer. Further, in the easy-adhesion layer composition of the present invention, by using the colloidal silica, it is possible to disperse titanium oxide with little light transmission, and thus such an average particle diameter of 0.1 μm or more and 0.5 μm. Hereinafter, titanium oxide can be particularly preferably used as a white pigment.

  The amount of the white pigment added to the easy-adhesion layer composition is preferably a solid content ratio (P / V ratio) other than the pigment / pigment in the easy-adhesion layer composition, and is preferably 0.3 to 5.0, More preferably, it is 0.5-3.0. In particular, in the case of titanium oxide, it is preferably 1.0 to 2.0. A higher solid content ratio (P / V ratio) is preferable because the concealability can be maintained even if the coating film thickness is reduced. If the pigment content is less than 0.3, the weather resistance may not be maintained, and if it exceeds 5.0, adhesion may be reduced, and the coating film may become brittle. is there.

  Conventionally, in the case where a white pigment is essential, it has been difficult to form a white easy-adhesion layer that achieves a high level of adhesion and blocking resistance on the surface of the base material layer of the white back protection sheet. According to the easy-adhesion layer composition of the invention, it is possible to form a white easy-adhesion layer having a white appearance and having both excellent adhesion and blocking resistance at a high level.

[E) Silane coupling agent
In the easily bonding layer composition of this invention, in order to provide preferable adhesiveness and blocking resistance to a white easily bonding layer, the silane coupling agent added to an easily bonding layer composition is added. The silane coupling agent is e1) a mercapto group-containing silane coupling agent (hereinafter also referred to as a mercapto-based silane coupling agent) or e2) an epoxy group-containing silane coupling agent (hereinafter also referred to as an epoxy-based silane coupling agent). Or a mixture of these two silane coupling agents. By using these silane coupling agents, it is possible to reduce variation in the improvement effect such as adhesiveness due to the aging of the coupling agent.

[E1) Mercapto group-containing silane coupling agent]
The mercapto-based silane coupling agent is represented by the general formula [R1-Si (OR2) ³ ] (R1 represents a mercaptoalkyl group and R2 represents an alkyl group, respectively). Examples include mercaptopropylmethyldimethoxysilane, 3-mercaptopropyltrimethoxysilane, and 6-mercaptohexatrimethoxysilane. The mercapto-based silane coupling agent is not particularly limited, and a known silane coupling agent can be suitably used. For example, “KBM802” and “KBM803” (both manufactured by Shin-Etsu Silicone Co., Ltd.) are available and can be easily obtained from the market.

[E2) Epoxy group-containing silane coupling agent]
The epoxy-based silane coupling agent, the general formula ^{[R3-Si-R4 (3} -m) R5 m] (m represents an integer of 1 to 3, R3 represents an epoxy group, R4 represents an alkyl group, R5 represents an alkoxy group), and examples include 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, and 3-glycidoxypropyl. And methyldiethoxysilane. These may be used alone or in combination of two or more. In addition, an epoxy-type silane coupling agent is not specifically limited, A well-known silane coupling agent can be used suitably. For example, there are “KBM303”, “KBM402”, “KBM403”, “KBE402”, and “KBE403” (all manufactured by “Shin-Etsu Silicone Co., Ltd.”), which are easily available from the market.

  About the silane coupling agent to be added to the easy-adhesion layer composition of the present invention, even if any of the mercapto silane coupling agent and the epoxy silane coupling agent is added, The blocking resistance can be improved at the same time. In order to achieve these objects, any silane coupling agent can be suitably used. However, when a mercapto silane coupling agent is used, the improvement in blocking resistance is particularly remarkable, and an epoxy silane When a coupling agent is used, the improvement of the adhesiveness with respect to EVA and a polyethylene-type sealing material is especially remarkable.

  In the easy-adhesion layer composition of the present invention, the silane coupling agent to be added is more preferably a mixture of two silane coupling agents, a mercapto-based silane coupling agent and an epoxy-based silane coupling agent. It can be set as an easily bonding layer composition.

[F) Organometallic coordination compound]
In the easy-adhesion layer composition of the present invention, an organometallic coordination compound is added to the easy-adhesion layer composition. The organometallic coordination compound is also called a chelating agent and is presumed to contribute to curing as a crosslinking agent. In particular, when used in combination with the silane coupling agent, the adhesive strength is remarkably improved. In addition, it is possible to improve the blocking resistance of the white easy adhesion layer.

  Examples of organometallic coordination compounds include titanium acetylacetonate, titanium octyl glycolate, titanium triethanolamate, tetra-n-butyl titanate, aluminum acetylacetonate, aluminum bisethylacetoacetate monoacetylacetonate, aluminum isopropylate. Examples thereof include rate monosecondary butyrate, aluminum alkyl acetoacetate diisopropylate, aluminum trisacetylacetonate, zirconium acetylacetonate, and acetylacetone zirconium butyrate. Among these, aluminum triacetylacetonate can be preferably used in terms of blocking resistance and adhesiveness with the sealing material.

  Here, the white easy adhesion layer formed on one surface of the white back surface protection sheet by the easy adhesion layer composition of the present invention is in contact with the back surface side sealing material layer of the back surface protection sheet base material layer in the solar cell module. Located on the outermost surface of the side. Moreover, the white back surface protection sheet of this invention provided with the said white easily bonding layer is also a product distribute | circulated independently, before integrating as a solar cell module. Therefore, for smooth distribution and storage, the white easy-adhesion layer is required to have blocking resistance when completed as a white back protective sheet after crosslinking. The easy-adhesion layer composition of the present invention generally has a white back surface protective sheet that requires the addition of a white pigment that is likely to lead to a decrease in adhesiveness, and the adhesion of the white easy-adhesion layer by the addition of a predetermined colloidal silica or the like. While preventing reduction, it is also possible to realize an improvement in blocking resistance of the white easy adhesion layer by using an organometallic coordination compound and a silane coupling agent in combination as an additive to the easy adhesion layer composition. it can.

[Other additives]
In the easy-adhesion layer composition of the present invention, other additives for imparting weather resistance, light resistance, heat resistance, moisture resistance, flame resistance, etc. to the white easy-adhesion layer are added as necessary. . In addition, the easy-adhesion layer composition is usually added to the sulfur agent as a coating liquid and used to form a white easy-adhesion layer, but other additives are used for the stability of the coating liquid containing the easy-adhesion layer composition, It is added as necessary in order to improve coating properties, drying properties, blocking resistance and the like.

  Examples of other additives include a dispersant, an antifoaming agent, a light stabilizer, an ultraviolet absorber, a heat stabilizer, and an antioxidant. These can use a well-known thing without a restriction | limiting in particular, According to the performance calculated | required by a coating liquid and a white easily bonding layer, it selects suitably.

<White back protection sheet>
The white back surface protection sheet will be described. The white back surface protection sheet of this embodiment includes a back surface protection sheet base material layer and a white back surface protection for solar cell modules formed including a white easy-adhesion layer formed on the surface of the back surface protection sheet base material layer. It is a sheet.

[Back protection sheet base material layer]
The back surface protective sheet base material layer constituting the white back surface protective sheet becomes a white back surface protective sheet by forming a white easy adhesive layer on the surface with the easy adhesive layer composition described above.

  As the back protective sheet base material layer, a resin sheet obtained by molding a resin into a sheet shape is used. Examples of such resin sheets include polyethylene resins, polypropylene resins, cyclic polyolefin resins, polystyrene resins, acrylonitrile-styrene copolymers, acrylonitrile-butadiene-styrene copolymers, polyvinyl chloride resins, fluorine Resins, poly (meth) acrylic resins, polycarbonate resins, polyester resins such as polyethylene terephthalate (PET), polyethylene naphthalate, polyamide resins such as various nylons, polyimide resins, polyamideimide resins, polyaryls Various resin sheets such as phthalate resin, silicone resin, polysulfone resin, polyphenylene sulfide resin, polyethersulfone resin, polyurethane resin, acetal resin, cellulose resin, etc. It is possible to use. Among these resin sheets, polyethylene resin, polypropylene resin, polyethylene terephthalate resin, polycarbonate resin, and polyethylene naphthalate are particularly preferably used. Among them, for example, a biaxially stretched polyethylene terephthalate or a biaxially stretched polypropylene resin film or sheet is particularly preferable. In this specification, the term “resin sheet” is used as the name of a product obtained by processing these resins into a sheet shape, but this term is used as a concept including a resin film. These may be a single layer or a laminate composed of a plurality of layers laminated with a conventionally known adhesive or the like.

  A light shielding layer can be provided as a layer disposed on the outermost side or the entire outer side in the solar cell module among the surfaces of the back surface protective sheet base material layer. By providing this light-shielding layer, it becomes possible to use a resin sheet having somewhat low light resistance as a substrate from the viewpoint of cost. Examples of such a sheet include aluminum foil, aluminum vapor deposition film, polyethylene terephthalate resin colored in black or white, polypropylene resin, polyethylene resin, and the like.

  Moreover, you may provide the weathering layer which consists of a fluorine film etc. in the outermost layer of a white back surface protection sheet. As a specific example, a weather resistant layer by dry laminating a fluorine film or a polyester film on the surface opposite to the surface of the back surface protective sheet base material layer on which the white easy-adhesive layer is provided using a urethane-based adhesive. Can be provided.

  What is necessary is just to determine the thickness of a back surface protection sheet base material layer suitably in consideration of the thickness requested | required of a white back surface protection sheet. As an example, the thickness of the back surface protective sheet base material layer may be in the range of 10 μm to 500 μm, but is not particularly limited.

[Configuration of white easy-adhesion layer]
The white easy-adhesion layer is a so-called primer layer, and is formed as a crosslinked resin of a polyisocyanate compound on at least one outermost surface of the white back surface protective sheet. The white easy-adhesion layer is formed by applying a coating liquid containing the easy-adhesion layer composition described above to the surface of the back surface protective sheet base material layer and forming a film from the applied coating liquid.

  A coating liquid contains the easily bonding layer composition of this invention, and contains a solvent and other various additives as needed. Here, the main resin is cross-linked and polymerized by reacting with the polyisocyanate compound. About a main ingredient and a hardening | curing agent, it is preferable that they are a 2 liquid type which mixes these just before use. The polyisocyanate compound is a compound containing a plurality of isocyanate groups in one molecule.

  The white easy-adhesion layer having the above-described structure has a well-balanced improvement in adhesion and blocking resistance, which are essential for the so-called primer layer of the back surface protection sheet, and particularly diffusion of light at a wavelength of 750 to 1500 nm. The reflectance is sufficiently increased to a preferable range.

  Here, the diffuse reflectance of the back surface protective sheet in the present specification is a value measured with a spectrophotometer (manufactured by Shimadzu Corporation, UV-3100), and is a white plate obtained by solidifying a fine powder of barium sulfate. The relative value of the diffuse reflectance with a diffuse reflectance of 100% shall be said.

<Method for producing white back surface protection sheet>
[Formation of coating solution and white adhesive layer]
The white easy-adhesion layer is formed by drying the solvent from the coating liquid applied on the above-mentioned back surface protective sheet base material layer and crosslinking the main resin contained in the coating liquid with the polyisocyanate compound. The coating liquid contains an organic solvent for dissolving or dispersing the main resin.

  The content of the main resin in the coating liquid is preferably 10 to 60% by mass. When the content of the resin in the coating liquid is 10% by mass or more, the pigment contained in the coating liquid can be favorably dispersed. Further, when the content of the resin in the coating liquid is 60% by mass or less, the coating property of the coating liquid is improved.

  The amount of the polyisocyanate compound used is adjusted so that the NCO / OH ratio (ratio of NCO number of curing agent / OH number of main resin) is 1.0 or more and 4.7 or less. It is preferable that they are 1 mass part or more and 75 mass parts or less with respect to 100 mass parts of main ingredient resin. When the NCO / OH ratio exceeds the above amount, side reaction products due to the reaction between the remaining isocyanate groups and the moisture in the air increase, and the adhesiveness, heat resistance and durability decrease, but the NCO / OH ratio is If it is the range of this, favorable adhesiveness, heat resistance, and durability can be obtained. In addition, when using the solution containing a polyisocyanate compound as a hardening | curing agent and making it a 2 liquid type coating liquid, a well-known organic solvent is suitably selected and used for a hardening | curing agent. Such a solvent will be described later.

  The content of the silane coupling agent is preferably from 0.1% by weight to 10% by weight, more preferably from 0.5% by weight to 8% by weight, based on the total amount of the main resin and the polyisocyanate compound. Preferably they are 1.0 mass% or more and 8 mass% or less. Adhesiveness required as a white back surface protection sheet for solar cell modules does not express that content of a silane coupling agent is less than 0.1 mass%. Moreover, even if the content of the silane coupling agent exceeds 10% by mass, there is no further improvement in adhesion and the film becomes brittle, which is not preferable.

  The content of the organometallic coordination compound is preferably 0.1% by mass or more and 7% by mass or less, more preferably 0.5% by mass or more and 5% by mass or less based on the total amount of the main resin and the polyisocyanate compound. is there. When the content of the organometallic coordination compound is less than 0.1% by mass, blocking resistance preferable as a white back surface protective sheet for a solar cell module cannot be obtained. Further, even if the content of the organometallic coordination compound exceeds 7% by mass, there is no further improvement in blocking resistance and adhesion, which is not preferable. In addition, it is preferable that ratio of content of an organometallic coordination compound and a silane coupling agent is the range of 25: 75-75: 25.

  Next, the solvent used for the coating liquid will be described. A solvent is added in order to provide the coating liquid with the applicability | paintability with respect to a back surface protection sheet base material layer. After the coating liquid is applied to the back surface protective sheet base material layer, the solvent contained in the applied coating liquid is volatilized, and a white easy adhesion layer is formed on the surface of the back surface protective sheet base material layer by the subsequent curing reaction. The

  The solvent is not particularly limited as long as it can dissolve or disperse components such as the main resin and the polyisocyanate compound and does not react with the polyisocyanate compound contained in the coating liquid. Examples of such solvents include water-insoluble solvents such as toluene, xylene, butyl acetate, and ethyl acetate, and water-soluble solvents such as acetone, methyl ethyl ketone, and methyl isobutyl ketone. A solvent is suitably selected according to the resin component used for a coating liquid, and is used individually or in combination of 2 or more types. Further, in order to adjust the drying speed during coating, a high boiling point solvent such as tripropylene glycol dimethyl ether may be added.

  The coating liquid is prepared by mixing a main resin, a solvent, and necessary additives. Of the components contained in the coating liquid, the silane coupling agent, organometallic coordination compound, and polyisocyanate compound, as already mentioned, in order to avoid reacting with the main resin component during storage, Is preferably used as an additive or curing agent which is a separate solution. In this case, the main agent, the additive, and the curing agent are mixed immediately before use to form a coating liquid.

  What is necessary is just to set the viscosity of a coating liquid suitably according to the coating method of a coating liquid. An example of the viscosity of the coating solution is preferably 10 to 100 cPs, more preferably 50 to 80 cPs. The viscosity of the coating solution may be adjusted by adjusting the amount of solvent added to the coating solution.

  Next, a method for forming the white easy-adhesion layer by applying the coating liquid on the surface of the back surface protective sheet base material layer will be described. The white easy-adhesion layer is formed by applying the coating liquid on the surface of the back surface protective sheet base material layer to form a coating film, and after evaporating the solvent contained in the coating film, the main resin and polyisocyanate compound contained in the coating film Are cured by crosslinking reaction.

  As a method for applying the coating liquid to the surface of the back surface protective sheet base material layer, a conventionally known method can be used without any particular limitation. Examples of such a coating method include a printing method, a coating method using a gravure coater, a roll coating method, a spray coating method, a dip coating method, a solid coating method, and a brush coating method.

  As a method for evaporating the solvent contained in the coating film, a conventionally known method can be used without particular limitation. Examples of such an evaporation method include a heating method, a reduced pressure drying method, a hot air drying method, and a natural drying method, but are not particularly limited. The conditions for evaporating the solvent contained in the coating film may be appropriately set according to the solvent to be used, but the heating time and heating temperature are 15 seconds to 5 minutes, 60 to 60 when using a gear oven. It is preferably in the range of 200 ° C, more preferably in the range of 30 ° C to 2 minutes, and 70 ° C to 120 ° C. By heating in this way, preferable blocking resistance and adhesiveness are exhibited. The coating film obtained by evaporating the solvent is subjected to curing for sufficiently carrying out the crosslinking reaction. Curing conditions may be set as appropriate according to the types of the main resin and polyisocyanate compound used. Examples of the curing conditions include leaving at 40 to 60 ° C. for 3 to 7 days.

  When the solvent is removed from the coating film by evaporation, the base resin, the polyisocyanate compound and the additive added to the coating solution remain on the surface of the back surface protective sheet base material layer to form a film. This film is cured to form a white easy adhesion layer. The thickness of a white easily bonding layer is not specifically limited, What is necessary is just to determine suitably according to the conditions to which a white back surface protection sheet is applied. As thickness of a white easily bonding layer, 0.1-30 micrometers is preferable and 0.5-5 micrometers is more preferable. If the thickness of the white easy-adhesion layer is 0.1 μm or more, sufficient adhesion can be imparted. If the thickness of the white easy-adhesion layer is 30 μm or less, it is possible to impart workability with good blocking resistance and to reduce the cost.

  In the production of the back surface protection sheet provided with the white easy-adhesion layer by the conventional general method, while preventing the decrease in the adhesion due to the aggregation of the white pigment, it was not possible to sufficiently improve the blocking resistance at the same time. According to the production method using the easy-adhesion layer composition of the present invention, it is possible to stably produce a white back surface protective sheet having both favorable adhesiveness and blocking resistance and having a sufficiently high diffuse reflectance. Can do.

<Solar cell module>
FIG. 1 is a cross-sectional view showing an example of the layer structure of the solar cell module of the present invention. In the solar cell module 1 of the present invention, the transparent front substrate 2, the front side sealing material layer 3, the solar cell element 4, the back side sealing material layer 5, and the white back surface protection sheet 6 are arranged from the incident light receiving surface side. They are stacked in order. The solar cell module 1 of the present invention uses the above white back surface protective sheet as the white back surface protective sheet 6.

  For example, the solar cell module 1 is formed by sequentially laminating the members including the transparent front substrate 2, the front side sealing material layer 3, the solar cell element 4, the back side sealing material layer 5, and the white back surface protective sheet 6. Then, it is integrated by vacuum suction or the like, and thereafter, the above-mentioned member can be manufactured by thermocompression molding as an integral molded body by a molding method such as a lamination method.

  Further, the solar cell module 1 is formed on the front side sealing material layer 3 on each of the front side and the back side of the solar cell element 4 by a molding method usually used in ordinary thermoplastic resins, for example, T-die extrusion molding. And the back surface side sealing material layer 5 are melt-laminated to sandwich the solar cell element 4 with the front surface side sealing material layer 3 and the back surface side sealing material layer 5, and then the transparent front substrate 2 and the white back surface protection sheet 6. May be laminated sequentially, and then these may be integrated by vacuum suction or the like and heat-pressed.

  In the present invention, a white easy-adhesion layer is formed on the bonding surface side with the back surface side sealing material layer 5 in the white back surface protection sheet 6 described above, whereby the adhesiveness with the back surface side sealing material. In particular, the adhesion with the back side sealing material made of polyethylene resin is significantly improved. For this reason, not only EVA but polyethylene resin can be suitably used as the back surface side sealing material. That is, the white back surface protective sheet of the present invention is particularly preferable for a back surface sealing material made of polyethylene resin, and is characterized in that it has both adhesion to the back surface sealing material made of polyethylene resin and weather resistance. Moreover, since this white back surface protection sheet is excellent in blocking resistance, it is excellent also in the handling property as a white back surface protection sheet before modularization.

The polyethylene resin is not particularly limited as long as the main component is polyethylene, but is preferably low density polyethylene (LDPE), more preferably linear low density polyethylene (LLDPE), and particularly preferably metallocene linear low density. Polyethylene. Linear low density polyethylene is a copolymer of ethylene and α-olefin. The density of the polyethylene resin used in the present invention is preferably 0.900 g / cm ³ or less, and more preferably in the range of 0.870 to 0.890 g / cm ³ . If it is this range, favorable transparency and heat resistance can be provided, maintaining sheet workability.

  The polyethylene resin in the present invention includes not only ordinary polyethylene obtained by polymerizing ethylene, but also a resin obtained by polymerizing a compound having an ethylenically unsaturated bond such as α-olefin, ethylenic resin, etc. Resins obtained by copolymerizing a plurality of different compounds having an unsaturated bond, modified resins obtained by grafting different chemical species to these resins, and the like are included. Especially, the polyethylene-type resin containing the silane copolymer formed by copolymerizing at least (alpha) -olefin and an ethylenically unsaturated silane compound as a comonomer can be used preferably. By using such a resin, adhesion between a sealing material and a member such as a transparent front substrate or a solar cell element can be obtained. Examples of the silane copolymer include those described in JP-A-2003-46105.

  The polyethylene resin composition contains a small amount of a polymerization initiator such as t-butylperoxy 2-ethylhexyl carbonate, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane. Specifically, it is 0.02 mass% or more and less than 0.5 mass%. Thereby, heat resistance can be imparted without the film forming property being reduced due to the generation of gel during molding, and the transparency being lowered.

  Furthermore, the white back surface protective sheet 6 of the present invention has passed through the white back surface protective sheet 6 without contributing to power generation out of incident light to the solar cell module 1 by forming the white easy adhesion layer. The light can be reflected to reach the light receiving surface of the solar cell element 4 at a high rate.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. However, the present invention is not limited to the following examples.

  The coating liquid which forms a white easily bonding layer in the white back surface protection sheet of each Example and a comparative example was adjusted using the following easily bonding layer composition and a solvent. The composition ratios of the coating liquids of the examples and comparative examples were as shown below.

  Crosslinkable main resin (acrylic polyol resin): Tg 40 ° C., acid value 6, hydroxyl value 19, weight average molecular weight 17000. The compounding ratio in the coating solution was 16 parts by mass.

  Polyisocyanate compound (HDI curing agent): (product name “FG700”, manufactured by DNP Fine Chemical Co., Ltd.). The compounding ratio in the coating solution was as shown in Table 1. Further, the NCO value of the polyisocyanate compound and the OH value ratio of the crosslinkable main resin (NCO / OH ratio) were blended so as to have the ratio shown in Table 1.

  Organometallic coordination compound (aluminum trisacetylacetonate): (product name “aluminum chelate A (W)”, manufactured by Kawaken Fine Chemical Co., Ltd.): The compounding ratio in the coating solution was 1 part by mass. In addition, content ratio (mass%) with respect to the total amount of crosslinkable main ingredient resin and a polyisocyanate compound is 5.6 mass%.

Aggregation inhibitor 1 (colloidal silica): particle size 16 nm. (Product name “Snow Tech O”, manufactured by Nissan Chemical Industries, Ltd.)
Aggregation inhibitor 2 (silica particles): particle size 3 μm. (Product name “sicastar”, manufactured by Core Front Co., Ltd.)
The mixing ratio of the aggregation inhibitor in the coating solution was as shown in Table 1. In addition, about the aggregation inhibitor, content ratio (mass%) with respect to the total amount of crosslinkable main ingredient resin, a polyisocyanate compound, and the following white pigment was also written together as "content ratio" in Table 1.

White pigment (titanium oxide): particle size 250 nm. (Product name "Tai Pure R-105" manufactured by DuPont)
The compounding ratio in the coating solution was 24 parts by mass.

Silane coupling agent 1 (3-glycidoxypropyltriethoxysilane): (product name “KBE-403”): manufactured by Shin-Etsu Silicone Co., Ltd.
The compounding ratio in the coating solution was 0.75 parts by mass.
Silane coupling agent 2 (3-mercaptopropyltrimethoxysilane): (Product name “KBM803”, manufactured by Shin-Etsu Silicone Co., Ltd.).
The compounding ratio in the coating solution was 0.75 parts by mass. Moreover, as for the total addition amount of the silane coupling agent 1 and 2, content ratio (mass%) with respect to the total amount of a crosslinkable main ingredient resin and a polyisocyanate compound has become all 8.4 mass%. .

Solvent: ethyl acetate: toluene = 1: 1 mixed solution.
The compounding ratio in the coating solution was 160 parts by mass.

  The easy-adhesion layer composition was prepared for each of the Examples and Comparative Examples by blending as shown in Table 1, and the solvent was further added to adjust each Example and Comparative Example.

A sheet made of biaxially stretched polyethylene terephthalate (PET) having a thickness of 188 μm was used as a white back protective sheet base material layer. Each coating solution prepared as described above was applied to the surface of this white backside protective sheet base material layer with a bar coater, and the coated coating solution was dried at 120 ° C. for 2 minutes, and then at 3 ° C. at 3 ° C. A white easy-adhesion layer was formed by curing for days and used as back surface protection sheet samples of Examples 1 to 4 and Comparative Examples 1 to 5. The coating amount of each coating solution was 3 g / m ² .

About each sample of produced Examples 1-4 and Comparative Examples 1-5, the following sealing material sheet 1 or 2 was applied to the surface which applied the said coating liquid at 150 degreeC for 15 minutes of the solar cell module. Lamination was performed using a production vacuum laminator, and the following adhesive evaluation samples were obtained.
Sealing material sheet 1: ethylene-vinyl acetate copolymer resin (EVA) sheet. (Product name "S-11" manufactured by Bridgestone)
Sealing material sheet 2: Low-density polyethylene resin (LLDPE) sheet Extruding temperature of resin blended so that the mass ratio of the following silane-modified transparent resin, weatherproof masterbatch, and polymerization initiator compound resin is 20: 5: 80 A weakly crosslinkable LLDPE resin formed to a thickness of 200 μm at 210 ° C.
Silane modified transparent resin: vinyl trimethoxy with respect to 98 parts by mass of metallocene linear low density polyethylene (M-LLDPE) having a density of 0.881 g / cm ³ and an MFR at 190 ° C. of 2 g / 10 min. 2 parts by mass of silane and 0.1 part by mass of dicumyl peroxide as a radical generator (reaction catalyst) are mixed, melted and kneaded at 200 ° C., density 0.884 g / cm ³ , MFR at 190 ° C. A silane-modified transparent resin having a weight of 1.8 g / 10 min.
Weatherproof masterbatch: 3.8 parts by mass of benzophenol UV absorber and hindered amine light stabilizer 5 with respect to 100 parts by mass of powder obtained by pulverizing Ziegler linear low density polyethylene having a density of 0.880 g / cm ³ A master batch in which parts by mass and 0.5 parts by mass of a phosphorous heat stabilizer are mixed, melted, processed, and pelletized.
Polymerization initiator compound resin: t-amyl-peroxy-2-ethylhexyl carbonate with respect to 100 parts by mass of M-LLDPE pellets with a density of 0.880 g / cm ³ and MFR at 190 ° C. of 3.1 g / 10 min. Resin impregnated with 1 part by mass and compounded with compound pellets.

<Evaluation of ink stability>
Examples 1-5, base resin (40 parts by mass), white pigment (60 parts by mass), aggregation inhibitor (each condition), toluene (50 parts by mass) and ethyl acetate (100 parts by mass) of Comparative Examples 1 to 3 ) Was stored at 40 ° C. for 1 month, and then the ink stability was observed by checking the presence or absence of sedimentation and aggregation in the mixture, and evaluated according to the following criteria.
[Evaluation criteria]
A: It can be used as it is without sedimentation.
B: Although sedimented, it can be used when redispersed.
C: Since it has aggregated, it cannot be used.

<Evaluation of blocking resistance>
About the sample of Examples 1-5 and Comparative Examples 1-3, blocking resistance was measured with the following method.
(Blocking resistance test)
Each coating solution having the composition shown in Table 1 is applied to the surface of a 50 μm thick biaxially oriented polyethylene terephthalate (PET) film with a bar coater, and the applied coating solution is dried at 120 ° C. for 2 minutes. Thus, a white easy-adhesion layer was formed on the substrate surface. And what was cured at 50 degreeC for 3 days in the state which piled up and contacted the same PET film on the surface of the white easily bonding layer immediately after drying was made into the sample for blocking resistance evaluation. The blocking resistance test was performed by the method of evaluating the blocking state by peeling off the overlapped portions of the respective samples for evaluation of blocking resistance, and evaluated according to the following criteria.
[Evaluation criteria]
A: Sheets peel off naturally without transition of white easy-adhesion layer B: There is no transfer of white easy-adhesion layer, and there is some adhesion when peeling between substrates C: Transfer of white easy-adhesion layer, and / Or there is a close response when peeling between substrates

<Evaluation of adhesiveness>
About the sample for adhesive evaluation of Examples 1-4 and Comparative Examples 1-5, the adhesiveness with respect to said sealing material sheets 1 and 2 and each was measured with the following method.
(Adhesion test)
About each sample for evaluation, peel strength (N) was measured and evaluated about adhesiveness in 180-degree peel of 15 mm width. For the measurement, using a peeling test apparatus (manufactured by “A & D Co., Ltd., trade name“ TENSILON RTG-1210 ”), measurement is performed at 25 ° C. under a peeling condition of 50 mm / min at 180 ° peel. The average value of four measurements was adopted and evaluated according to the following criteria. The results are shown in Table 2.
[Evaluation criteria]
A: 30N / 15mm or more B: 15N / 15mm or more, less than 30N / 15mm C: Less than 15N / 15mm

  It turns out that Examples 1-5 are what has preferable processability aptitude, blocking resistance, adhesiveness, and a diffuse reflectance as a back surface protection sheet for solar cell modules. In particular, it can be seen that by limiting the aggregation inhibitor to an appropriate amount of colloidal silica, the adhesiveness can be improved to the required range and the diffuse reflectance can be improved to the more preferable range. From this, the easily bonding layer composition of this invention manufactures the white back surface protection sheet which has favorable adhesiveness with respect to the sealing material sheet which consists of EVA and a polyethylene-type resin, and has favorable blocking resistance. It is understood that this is preferable.

DESCRIPTION OF SYMBOLS 1 Solar cell module 2 Transparent front substrate 3 Front side sealing material layer 4 Solar cell element 5 Back side sealing material layer 6 White back surface protection sheet

Claims (9)

An easy-adhesion layer composition for forming a white easy-adhesion layer on the surface of a white back surface protective sheet for a solar cell module,
a) a crosslinkable main resin, b) a crosslinked resin crosslinked with a polyisocyanate compound;
c) an anti-agglomeration agent;
d) a white pigment;
e) a silane coupling agent;
f) an organometallic coordination compound,
The c) aggregation inhibitor is colloidal silica, and the content ratio with respect to the total amount of the a) crosslinkable main component resin, the b) polyisocyanate compound, and the d) white pigment is 0.1% by mass. More than 10.0 % by mass,
The easy-adhesion layer composition in which the ratio of the NCO value of the b) polyisocyanate compound and the OH value of the a) crosslinkable main resin is 1.0 or more and 4.7 or less. The easy-adhesion layer composition according to claim 1 , wherein the colloidal silica has an average particle size of 3 nm or more and 30 nm or less. The easy-adhesion layer composition according to claim 1 or 2, wherein the d) white pigment is titanium oxide having an average particle size of 0.1 µm to 0.5 µm. Wherein e) a silane coupling agent, e1) a mercapto group-containing silane coupling agent, or, e2) an epoxy group-containing silane coupling agent, or claims 1-3 which is a mixture of these two kinds of silane coupling agent The easily bonding layer composition in any one of. The easy-adhesion layer composition according to any one of claims 1 to 4 , wherein the a) crosslinkable main component resin is a crosslinkable substituent-containing acrylic resin, and its glass transition point (Tg) is 25 ° C or higher and 70 ° C or lower. . A white back surface protective sheet for a solar cell module in which a white easy adhesion layer is formed on one surface,
The white easy-adhesion layer is formed by coating the coating liquid containing the easy-adhesion layer composition according to any one of claims 1 to 5 on one side of the white back surface protective sheet for the solar cell module. White back protection sheet. A method for producing a white back surface protective sheet for a solar cell module in which a white easy adhesion layer is formed on one side,
A coating liquid application step of applying a coating liquid containing the easy-adhesion layer composition according to any one of claims 1 to 5 to one surface of a resin substrate;
A film forming step of forming a white easy-adhesion layer by forming a film of the coating liquid. In the solar cell module in which the white back surface protective sheet according to claim 6 , the sealing material, and the solar cell element are integrated at least.
The solar cell module in which the white back surface protective sheet and the sealing material containing a polyethylene-based resin are integrated via the white easy-adhesion layer. The sealing material is formed by copolymerizing at least a low density polyethylene (LDPE) having a density of 0.900 g / cm ³ or less and / or a linear low density polyethylene (LLDPE) and an ethylenically unsaturated silane compound as a comonomer. The solar cell module according to claim 8 , wherein the solar cell module is a sealing material containing a polyethylene-based resin containing a silane copolymer.

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