JP2015032751A - Rear surface protective sheet for solar cell module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a module for solar cell combining superior weatherability and superior design based on the sense of mat of appearance.SOLUTION: A rear surface protective sheet 6 for solar cell module has a coating layer 61 formed on the surface of a base material layer 60. The coating layer 61 contains a plurality of resins capable of phase separation, and an inorganic filler. The inorganic filler exists, while aggregating, in at least one of the plurality of resins capable of phase separation, and protrusions and recesses are formed on the surface of the coating layer 61 by presence and absence of aggregation.

Description

  The present invention relates to a back surface protection sheet for a solar cell module. More specifically, the present invention relates to a back surface protective sheet for a solar cell module that has preferable physical properties as a back surface protective sheet for a solar cell module and excellent design properties based on a matte appearance of the surface appearance.

  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 constituting a solar cell has a configuration in which a transparent front substrate, a front sealing material, a solar cell element, a back sealing material, and a back surface protection sheet are laminated in order from the light receiving surface side. It has a function of generating power by entering the solar cell element.

  The solar cell module is used outdoors for a long period of time. Therefore, each member constituting the solar cell module is required to have durability that can withstand a severe outdoor environment for a long period of time. Among them, the back surface protection sheet is particularly required to have high adhesion and adhesion durability with the back surface side sealing material sheet.

  Conventionally, fluorine-based films have been widely used as such back surface protective sheets. However, as a response to the demand for manufacturing cost reduction and weight reduction, on the surface of the base sheet that can be obtained at a relatively low cost, such as polyethylene terephthalate (PET) or ethylene-vinyl acetate copolymer (EVA), There has been proposed a back surface protection sheet with improved weather resistance by coating a resin composition that becomes a coating layer having weather resistance (Patent Document 1).

  On the other hand, for the purpose of improving the design properties of the solar cell module, there is a demand for a back surface protective sheet having a matte appearance on the surface. As a means for providing the matte feeling on the surface of the back surface protection sheet, generally, a production method for giving a matte feeling to the surface appearance by adding a large amount of silica as a filler to the coating layer is widely known. ing.

Special table 2010-519742 gazette

  When the coating layer for improving the weather resistance is formed on the outermost layer side like the back surface protective sheet described in Patent Document 1, it is difficult to give a mat feeling while keeping the weather resistance. This is because the addition of the silica described above may cause the precipitation and hydrolysis to lead to a decrease in weather resistance. Therefore, it is a back surface protection sheet having a coating layer for enhancing weather resistance on the outermost layer, and has a sufficient weather resistance and an excellent design based on a matte appearance for a solar cell module. The protective sheet did not exist yet.

  This invention is made in view of the above situations, and provides the back surface protection sheet for modules for solar cells which has the outstanding weather resistance and the outstanding designability based on the mat | matte feeling of an external appearance. Objective.

  As a result of intensive studies to solve the above problems, the present inventors have developed a coating layer formed on the surface of the back protection sheet for solar cell modules in order to provide the back protection sheet with weather resistance. As the material to be used, in addition to the inorganic particles, two types of resins that are hardly compatible with each other and can be phase-separated are used, so that the inorganic particles are unevenly distributed and aggregated only in a part of the specific resin side. While maintaining the weather resistance of the coating layer, the present inventors have found that the surface appearance of the coating layer can be given a matte feeling that is extremely favorable in terms of design, and the present invention has been completed. More specifically, the present invention provides the following.

  (1) A back surface protection sheet for a solar cell module in which a coating layer is formed on the surface of a base material layer, wherein the coating layer contains a plurality of phase-separable resins and an inorganic filler. The inorganic filler is aggregated and present in at least one of the plurality of phase-separable resins, and irregularities are formed on the surface of the coating layer depending on the presence or absence of the aggregation. Features a protective sheet for the back surface.

  (2) The back surface protective sheet according to (1), wherein the gloss value (60 °) according to JIS Z8741-1997 on the surface of the coating layer is 5 or more and 10 or less.

  (3) The difference between the SP value of at least one resin among the plurality of phase-separable resins and the SP value of the other resin is 1.0 or more and less than 9.0 (1) or (2 ) The back surface protection sheet described in the above.

  (4) The back surface protective sheet according to any one of (1) to (3), wherein the plurality of phase-separable resins are an acrylic resin and a urethane resin.

  (5) The back surface protective sheet according to any one of (1) to (4), wherein the coating layer further includes a curing agent.

  (6) The back surface protective sheet according to (5), wherein the curing agent is a polyisocyanate compound.

  (7) The back surface protective sheet according to any one of (1) to (6), wherein the average arithmetic roughness (Ra) of the uneven shape is 0.24 μm or more and 3.0 μm.

  (8) The back surface protective sheet according to any one of (1) to (7), wherein a weather resistant layer made of a transparent resin is laminated on the surface of the coating layer.

  (9) The method for producing a back surface protective sheet according to any one of (1) to (8), comprising a base resin material, an inorganic filler, and a solvent on the surface of the base material layer. A step of applying a coating liquid, wherein the base resin material includes a plurality of phase-separable resins, and among the plurality of phase-separable resins by phase separation of the base resin material The manufacturing method of a back surface protection sheet, wherein the inorganic filler aggregates in at least one resin.

  (10) The back surface protection sheet according to any one of (1) to (8), a sealing material, and a solar cell element are laminated, and the coating layer or the weathering layer of the back surface protection sheet is A solar cell module disposed on one outermost layer of the solar cell module.

  (11) The solar cell module according to (10), wherein the sealing material is an ethylene-vinyl acetate copolymer resin or a polyethylene resin.

  According to the present invention, it is a back surface protection sheet for a solar cell module in which a coating layer is formed on the surface of a base material layer, and has excellent weather resistance and excellent design based on a matte appearance. The back surface protection sheet for modules for solar cells can be provided.

It is sectional drawing which shows an example of the laminated constitution of the solar cell module using the back surface protection sheet for solar cell modules of this invention. It is sectional drawing which shows an example of the laminated constitution of the back surface protection sheet for solar cell modules of this invention. It is a cross-sectional SEM photograph of the back surface protection sheet (Example) for solar cell modules of this invention, and the aspect by which the unevenness | corrugation is formed in the sheet | seat surface because the inorganic filler aggregates and exists in one resin. It is shown. It is a cross-sectional SEM photograph of the back surface protection sheet for a conventional inorganic filler solar cell module (Comparative Example 3), which contains an inorganic filler but does not contain a plurality of phase-separable resins. It indicates that it is not formed on the surface. It is the surface SEM photograph of the back surface protection sheet (Example) for solar cell modules of this invention, and the aspect by which the unevenness | corrugation is formed in the sheet | seat surface is shown. It is the surface SEM photograph of the back surface protection sheet (comparative example 3) for the conventional inorganic filler solar cell module which contains an inorganic filler, but does not contain a plurality of phase-separable resins. It shows that there is.

  Hereinafter, the back surface protection sheet for solar cell modules of this invention is demonstrated in detail. The present invention is not limited to the embodiments described below.

<Basic configuration of solar cell module>
First, the basic structure of the solar cell module in which the back surface protective sheet of the present invention is used will be described. FIG. 1: is a cross-sectional schematic diagram which shows an example of the laminated constitution about the solar cell module 1 which is one Embodiment of this invention. As shown in FIG. 1, the solar cell module 1 has a transparent front substrate 2, a front sealing material layer 3, a solar cell element 4, a back sealing material layer 5, and a back surface protection sheet 6 laminated in this order from the light receiving surface side. It is a configuration. Since the back surface protection sheet for solar cell modules is used by being arranged in the outermost layer in the solar cell module in this way, it is essential to have high weather resistance. The back surface protective sheet 6 of the present invention has such weather resistance and further has excellent design properties based on the matte appearance. By disposing the back surface protective sheet 6 of the present invention on the outermost layer constituting the appearance of the solar cell module 1, the design of the solar cell module 1 can be remarkably improved.

<Back protection sheet>
The back surface protection sheet 6 which is embodiment of this invention is demonstrated using FIG. The back surface protective sheet 6 is a laminate including a base material layer 60 and a coating layer 61. The coating layer 61 is formed on the surface of the base layer 60 that is the outermost layer when integrated as the solar cell module 1.

[Base material layer]
The base material layer 60 is made of polyethylene terephthalate (PET), ethylene-vinyl acetate copolymer (EVA), modified polyphenylene ether, polycarbonate, etc., having heat resistance, dimensional stability, impact resistance, transparency, weather resistance, Various resin sheets provided can be used. Among them, PET that is excellent in processability and is available at a relatively low price can be preferably used. A coating layer 61 is laminated on one surface of the base material layer 60 to form the back surface protection sheet 6. The thickness of the base material layer 60 is not particularly limited. However, if the thickness of the base material layer 60 is 15 μm or more, it is preferable in terms of mechanical strength, and if it is 300 μm or less, it is preferable in terms of workability.

  The base material layer 60 may contain components other than the above resin as long as the effects of the present invention are not impaired. Also, for example, workability, heat resistance, light resistance, weather resistance, mechanical properties, dimensional stability, antioxidant properties, slipperiness, mold release properties, flame retardancy, antifungal properties, electrical properties, etc. Various plastic compounding agents and additives, other resins, and the like can be added for the purpose of improvement and modification. The addition amount of these additives and the like is not particularly limited, and can be arbitrarily added according to the purpose. Common additives include, for example, lubricants, crosslinking agents, antioxidants, UV absorbers, light stabilizers, fillers, lubricants, reinforcing fibers, reinforcing agents, antistatic agents, flame retardants, flame retardants, foaming Agents, fungicides, coloring additives, pigments, modifying resins and the like.

[Coating layer]
The coating layer 61 is obtained by applying a coating liquid for forming the coating layer 61 to one surface of the base material layer 60 and forming a film from the applied coating liquid. As the coating liquid, a mixed resin of a first main resin and a second main resin that can be phase separated is used as a main resin, and an inorganic filler is added thereto. The coating layer 61 is preferably formed as a cross-linked resin in which the main resin is cross-linked with a curing agent such as a polyisocyanate compound. In the following description of the present specification, the resin compound before being cured by being crosslinked by a curing agent is referred to as “crosslinkable main resin (or simply“ main resin ”)”, and a resin contained in the coating layer, That is, it is distinguished from a crosslinked resin that is cured to form a coating layer.

  FIG. 3 is a cross-sectional SEM photograph of the back surface protective sheet (Example described in paragraph 0075 and below) of the present invention. FIG. 5 is a surface SEM photograph of the back protection sheet. The coating layer 61 is composed of a first main resin and a second main resin that are phase-separable. As can be seen from FIG. 3, in the coating layer 61, the first main resin and the second main resin are phase-separated, the first main resin forms the first region 611, and the second main resin forms the second region 612. Forming. And the inorganic filler is unevenly distributed in the 1st area | region 611, these inorganic fillers aggregate, and the coarse particle part 7 is formed. Further, as can be seen from FIG. 5, the surface of the coating layer has an uneven shape that gives a matte feeling to the surface of the back protective sheet.

  In this specification, “phase separable” means that two or more component solutions and solid solutions are stable as ink before printing and can be applied without separation, but after coating and drying. It shall be said that the phases are separated. The first main resin and the second main resin that can be phase-separated can be phase-separated without being mixed with each other when the first main resin and the second main resin are printed at room temperature. Say that.

  As can be seen from FIGS. 3 and 5, in the coating layer 61 of the back surface protective sheet 6, only the surface on the portion where the coarse particle portion 7 formed in the first region 611 is raised in a convex shape, Unevenness is formed on the surface of the coating layer 61.

  The average arithmetic roughness (Ra) of the above irregularities formed on the surface of the coating layer 61 of the back surface protective sheet 6 is 0.24 μm or more and 3.0 μm. When the average arithmetic roughness (Ra) of the uneven shape on the surface of the coating layer 61 is in the above range, the surface of the back surface protective sheet 6 on the side of the coating layer 61 has a mat feeling that exhibits excellent design. Is granted.

  The uneven shape on the surface of the coating layer 61 cannot be formed simply by mixing an arbitrary inorganic filler in a coating layer for enhancing general weather resistance. It can be formed only by a configuration unique to the present application having a plurality of phase-separable resins and an inorganic filler as essential constituent requirements. Due to the unevenness, the surface of the back surface protective sheet 6 on the side of the coating layer 61 is given a matte feeling that exhibits excellent design properties.

  In addition, the surface roughness of the coating layer 61 is set to such a rugged shape as defined in JIS Z8741-1997, and the gloss value (60 °) is an extremely preferable range from the viewpoint of improving the design. It can be 10 or less.

  Next, the details of the coating liquid for forming the coating layer 61 having the preferable mat feeling as described above will be described.

(First main resin and second main resin)
As the main resin of the coating liquid for forming the coating layer 61, a first main resin and a second main resin that are phase-separable from each other are used.

  Specific criteria for determining whether or not the resins are phase-separable from each other are not necessarily uniquely limited. However, as a representative index, the difference between the SP value of one resin and the SP value of another resin (hereinafter, this difference is also simply referred to as “SP value difference”) is an index. It can be. More specifically, the first and second main ingredients of the coating liquid according to the present invention are obtained by using a plurality of resins having an SP value difference of 1.0 or more and less than 9.0 as a plurality of resins that can be phase-separated from each other. It can be preferably used as a resin. In a plurality of resins, when the difference in SP value is less than 1.0, the gloss value exceeds 10 and the coating layer does not exhibit a sufficient matte feeling. The ink becomes unstable and is separated before printing. End up.

  As the first main resin and the second main resin that are the main resin of the coating liquid according to the present invention, as a typical combination that satisfies the above requirements, an acrylic resin is used as the first main resin, Combinations using urethane resins can be mentioned. As an example, the SP value of polymethyl methacrylate, which is an acrylic resin, is 9.1, and the SP value of polypolyurethane, which is a urethane resin, is 10.3. Therefore, the SP value difference of these resins is approximately 1.2, and a resin obtained by mixing these resins can be preferably used as the main resin of the coating liquid according to the present invention.

  As said acrylic resin, the crosslinkable substituent containing acrylic resin which has a hydroxyl group for reacting with a polyisocyanate compound can be used especially preferable. Moreover, as said urethane type resin, a crosslinkable substituent containing urethane resin can be used especially preferable.

  The crosslinkable substituent-containing acrylic resin and the crosslinkable substituent-containing urethane resin have a plurality of hydroxyl groups for reacting with the polyisocyanate compound, and are cured and cured by reacting with the polyisocyanate compound to crosslink. Form. Further, the acrylic resin and the urethane resin can ensure the solvent resistance of the coating layer 61 from the viewpoint of good weather resistance and chemical resistance.

  The crosslinkable substituent-containing acrylic resin and the crosslinkable substituent-containing urethane resin have a plurality of crosslinkable substituents for reacting with the polyisocyanate compound, and are cured by being cross-linked by reacting with the polyisocyanate compound. Forms a strong 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 dispersed in a solvent. From the viewpoint of availability and crosslinking reactivity, the crosslinkable substituent is preferably a hydroxyl group. A preferable range of the hydroxyl value is 18 or more and 100 or less.

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

  As the crosslinkable substituent-containing urethane resin, one or two or more urethane compounds and a monomer having a crosslinkable substituent are copolymerized, or one or two or more urethane compounds and a crosslinkable substituent are included. What copolymerized the monomer and 1 type, or 2 or more types of ethylenic monomers is used.

  Examples of the crosslinkable substituent-containing urethane resin include polyester polyurethane resin, polyether polyurethane resin, polycarbonate polyurethane resin, and the like obtained by copolymerizing one or more urethane compounds and a monomer having a crosslinkable substituent. One or two or more urethane compounds, a monomer having a crosslinkable substituent, and one or two or more ethylenic monomers are copolymerized.

  As described above, the hydroxyl values of the exemplified first and second main resin are 18 or more and 100 or less, and preferably 20 or more and 90 or less. When the hydroxyl value of the first main resin and the second main resin is 18 or more, the crosslinking proceeds sufficiently and the coating layer 61 can be provided with preferable solvent resistance. When the hydroxyl value of the second main resin exceeds 100, the first main resin and the second main resin remain unreacted in the coating layer 61 and the weather resistance of the back surface protective sheet 6 decreases, which is not preferable. .

  The content ratio of the first main resin and the second main resin in the coating liquid is preferably 30:70 to 70:30, and the total content thereof is preferably 10 to 60% by mass. When the content ratio of the first and second main resin in the coating liquid is within the above range and the total content is 10% by mass or more, a desired film thickness can be obtained using a gravure coater. it can. Moreover, when the content of the main resin in the coating liquid is 60% by mass or less, the coating property of the coating liquid is improved.

  The thickness of the coating layer 61 is not specifically limited, What is necessary is just to determine suitably according to the conditions to which the back surface protection sheet 6 is applied. The thickness of the coating layer 61 is preferably 0.1 μm or more and 30 μm or less, and more preferably 0.5 μm or more and 7 μm or less. If the thickness of the coating layer 61 is less than 0.1 μm, sufficient weather resistance cannot be imparted, and even if the thickness of the coating layer 61 exceeds 30 μm, the amount of coating liquid to be applied is large. This is not desirable because it is necessary and increases costs.

(Inorganic filler)
In order to form the coarse particle portion 7 in the coating layer 61, an inorganic filler is added to the coating liquid containing the first main resin and the second main resin as main components. As the inorganic filler, the following inorganic pigments can be preferably used. For example, titanium oxide, calcium carbonate, carbon black, titanium black, Cu-Mn composite oxide, Cu-Cr-Mn composite oxide, or zinc oxide, aluminum oxide, iron oxide, silicon oxide, barium sulfate, carbonic acid Calcium, titanium yellow, chrome green, ultramarine, aluminum powder, mica, barium carbonate, talc and the like can be used. Among these, titanium oxide is preferably used as the white pigment, and carbon black is preferably used as the black pigment because it is excellent in weather resistance, easy to paint, and easy to obtain including price. . Incidentally, these inorganic fillers usually also have an effect as an ultraviolet blocking material, so they are often added even when there is no special improvement in design properties. Only by adding, it does not stably develop a sufficient matte feeling equivalent to the present application. These inorganic fillers can contribute to the improvement of the design properties equivalent to the present application only by the combination with the main resin composition of the coating liquid unique to the present application.

  The amount of the inorganic filler contained in the coating layer 61 is preferably a solid content ratio (P / V ratio) other than the inorganic filler / inorganic filler in the coating solution, and is preferably 0.3 or more and 3.0 or less. More preferably, it is 5 or more and 2.0 or less. In particular, in the case of a titanium oxide pigment generally used as a white pigment, it is preferably 1.0 or more and 2.0 or less. 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 3.0, the adhesion may be lowered, and the coating film may become brittle. is there.

(Curing agent)
A polyisocyanate compound can be used as the curing agent for causing the crosslinking reaction of the first main resin and the second main resin to proceed. A polyisocyanate compound is a compound having two or more isocyanate groups in one molecule.

  The polyisocyanate compound crosslinks and cures (high molecular weight) the first main resin and the second main resin to form a resin contained in the coating layer 61. At this time, a polyisocyanate compound becomes a part of resin contained in the coating layer 61 with main ingredient resin. Examples of the polyisocyanate compound include aliphatic, alicyclic, aromatic, and aromatic-aliphatic compounds, but the coating layer is associated with being exposed to the external environment for a long period of time. From the viewpoint of suppressing coloring, an aliphatic or alicyclic polyisocyanate compound is 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.

  Regarding the amount of these polyisocyanate compounds added to the coating liquid, the mass of the NCO group of the polyisocyanate compound relative to the total of 100 parts by mass of the first and second main resin is 0 to 16.0 parts by mass, preferably Is appropriately adjusted to be 2.1 parts by mass or more and 14.3 parts by mass or less. Moreover, it is preferable to adjust appropriately so that NCO / OH ratio of a coating liquid may be 0.5 or more and 3.0 or less. Thereby, preferable solvent resistance can be imparted to the coating layer 61. When the NCO / OH ratio is less than 0.5, the solvent resistance becomes insufficient. On the other hand, when the NCO / OH ratio exceeds 3.0, the adhesion to the base material layer 60 becomes insufficient.

(solvent)
The solvent used in the coating liquid is added to impart applicability to the base material layer 60 to the coating liquid. After the coating liquid is applied to the base material layer 60, the solvent contained in the applied coating liquid is volatilized, and the coating layer 61 is formed on the surface of the base material layer 60 by the subsequent curing reaction. Therefore, the solvent can dissolve or disperse components such as the first and second main resin and the curing agent constituting the coating layer 61, and does not react with the curing agent contained in the coating liquid. If it is.

  Further, the solvent in the present invention may be a single main solvent which is a single kind of organic solvent, or an auxiliary solvent which is an organic solvent other than the main solvent is added to the main solvent. It may be a mixture.

  The main solvent is not particularly limited. However, when polycarbonate is used as the base material layer 60, a solvent having an SP value of 19.3 or more and 20.3 or less can be preferably used. In this case, the content of the main solvent with respect to 100 parts by mass of the solvent is preferably 50 parts by mass or more and 100 parts by mass or less. A specific example of such a main solvent is methyl isobutyl ketone (MIBK). Another example that can be used is cyclohexanone.

  The auxiliary solvent is not particularly limited, but as described above, when polycarbonate is used as the base material layer 60, a solvent having an SP value of 22.0 or more can be preferably used. And 0 mass part may be sufficient as content of the auxiliary solvent with respect to 100 mass parts of solvents, and is 0 mass part or more and 100 mass parts or less. A preferred specific example of such an auxiliary solvent is isopropyl alcohol (IPA).

  The solvent having the above composition is presumed to have a property of dissolving a part of polycarbonate generally having an SP value of about 18 within an appropriate range. When such a solvent is applied to the polycarbonate resin, for example, by appropriately dissolving a portion in the range of about 0.1 μm to 5 μm from the resin surface, adhesion between the base material layer 60 and the coating layer 61 is achieved. It is thought that it can contribute to the improvement of performance.

(Other additives)
In the coating layer 61, for example, sheet processability, heat resistance, weather resistance, mechanical properties, dimensional stability, antioxidant properties, slipperiness, mold release properties, flame retardancy, antifungal properties, electricity Various plastic compounding agents, additives, and the like can be added as necessary for the purpose of improving and modifying the physical characteristics, strength, and the like. Examples of other additives include a dispersant, an antifoaming agent, a light stabilizer, a heat stabilizer, and an antioxidant. Any known one can be used without particular limitation, and is appropriately selected depending on the performance required for the coating liquid and the coating layer 61.

[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, on the surface of the coating layer 61 of the base material layer 60, a transparent weathering layer made of, for example, a fluororesin or an EB curable resin that does not adversely affect the design properties may be provided. Thereby, the weather resistance of the back surface protection sheet 6 can be improved further. Further, on the surface on which the coating layer 61 is not formed, an adhesion reinforcing layer made of a polyolefin resin such as polyethylene resin or polypropylene resin, polyethylene terephthalate (PET), or a silane coupling agent, if necessary. You may provide the primer layer which consists of a resin mixture containing adhesiveness improvement agents, such as. Or you may provide the other reinforcement layer for increasing the intensity | strength of the back surface protection sheet 6 between the base material layer 60, the adhesion reinforcement layer, etc., for example.

<Production method of back surface protection sheet>
The back surface protection sheet 6 can be manufactured by performing a coating process for forming a coating layer 61 on one surface of the base material layer 60 using the coating liquid described above.

(Manufacturing method of coating liquid)
Although the manufacturing method of a coating liquid is not specifically limited, The manufacturing method demonstrated below can be used suitably.

  By mixing the main resin and other additives as required, a main liquid can be obtained. Examples of the mixing method include a production method including a step of uniformly dispersing the main resin and other additives. Further, a dispersant may be used in the step of dispersing the inorganic filler. Various dispersing machines can be used for this dispersion step. Examples thereof include a roll mill machine, a bead mill machine, a high-speed stirring and dispersing machine, a twin screw extruder, a Banbury mixer, and a pressure kneader. The coating solution is preferably of a two-component type in which the prepared main agent solution and a solution containing a polyisocyanate compound are mixed as a curing agent immediately before use.

  The resin concentration of the coating liquid is usually 10 to 100%, more preferably 20 to 80%, based on weight. Moreover, it is preferable that a viscosity is 50-50,000 cP / 25 degreeC normally, and it is still more preferable that it is 100-100,000 cP / 25 degreeC.

  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.

  As a coating process, first, a coating liquid is applied on one surface of the base material layer 60. As a coating method, a conventionally known method can be used without 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.

The coating amount of the coating liquid, weathering resistance, coating properties, from the viewpoint of cost, preferably 0.1 to 10 g / ^{m 2} (dry weight), 0.1 to 8 g / ^{m 2} (dry mass) and more preferably .

  Next, the solvent in the coating liquid is volatilized by heat treatment. As the volatilization method, a conventionally known method can be used without particular limitation. Examples of such a 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 volatilizing the solvent contained in the coating solution 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 solvent resistance and adhesiveness are developed. In the process of volatilization of the solvent, the coating layer 61 is formed into a film by crosslinking the main resin contained in the coating liquid with a curing agent such as a polyisocyanate compound.

  When the solvent is volatilized and removed from the coating liquid, the first main resin, the second main resin, the inorganic filler, the curing agent, and other additives added to the coating liquid remain on the surface of the base material layer 60 to form a film. . This film is cured to form the coating layer 61.

  After volatilizing the solvent, it is preferable to subject the back surface protective sheet 6 to curing in order to further advance the crosslinking reaction. Curing conditions may be set as appropriate according to the types of the main resin and the curing agent used. Examples of the curing conditions include leaving at 40 to 60 ° C. for 3 to 7 days.

  In the film formation process, the first main resin and the second main resin are phase-separated. And since the inorganic filler is dispersed in the resin, a resin having a low Tg flows and either one of the main resin (in this embodiment, a copolymer of a polyurethane urethane and an acrylic which is the second main resin). It is unevenly distributed only on the resin side) and aggregates. The aggregated inorganic filler forms massive coarse particle portions 7. The coarse particle portion 7 acts as a single solid upon curing shrinkage (polymerization shrinkage) of a plurality of phase-separable resins that become the coating layer 61. For this reason, on the surface on the part where the coarse particle part 7 exists, a part of the coating layer 61 protrudes in a convex shape, whereby irregularities are formed, and a favorable matte feeling is imparted to the appearance of the coating layer 61.

<Method for manufacturing solar cell module>
The solar cell module 1 is, for example, vacuum suction after sequentially laminating members composed of the transparent front substrate 2, the front sealing material layer 3, the solar cell element 4, the back sealing material layer 5, and the back surface protection sheet 6. Then, the above-mentioned members can be manufactured by thermocompression molding as an integrally molded body by a molding method such as a lamination method. For example, in the case of vacuum heat laminating, 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. Thus, the solar cell module 1 can be manufactured by thermocompression-bonding each of the above layers as an integrally molded body.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further more concretely, this invention is not limited to a following example at all.

<Manufacture of coating liquid>
First, the coating liquid used for the back surface protection sheet of this invention was manufactured. The coating liquid was produced by blending a predetermined amount of a main resin and a curing agent described below. A specific manufacturing method will be described below.

[Example]
Example coating solutions were prepared as follows.
(First base resin)
Polyurethane urethane and acrylic copolymer resin. Hydroxyl value 0.
(Second main resin)
An acrylic resin in which an acrylic resin A having a hydroxyl value of 81 and Tg of 91 ° C. and an acrylic resin B having a hydroxyl value of 283 and Tg of 25 ° C. are mixed at 50/50. It consists of the following components in [].
[Methyl methacrylate, butyl acrylate, butyl methacrylate, 2-hydroxyethyl methacrylate, vinyl methacrylate (trace detection), (methacrylic acid), (ethylene glycol dimethacrylate), azobisisobutyronitrile]
What mixed the said 1st main ingredient resin and 2nd main ingredient resin in the ratio of 1: 1 was made into main ingredient resin of an Example.
(Inorganic filler)
Titanium oxide ("Ti-Pure (registered trademark) R-105" (manufactured by DuPont)). It added in the coating liquid in the ratio of 100 mass parts with respect to 100 mass parts of main ingredient resin.
(Curing agent)
A hexamethylene diisocyanate (HDI) -based polyisocyanate compound was used. The ratio (mass%) of the NCO group in each polyisocyanate compound was 23.0%. It added in the coating liquid in the ratio of 6.8 mass parts with respect to 100 mass parts of main ingredient resin.

(solvent)
Solvent: A mixture of MEK, MIBK, and IPA (mixing ratio 5: 3: 2) was used. The resin concentration of the coating solution was adjusted to 13.7% (solid content concentration 31.5%) on a weight basis.

  The coating liquid of the manufacture example which contains the main ingredient resin, inorganic filler, and hardening | curing agent of said Example by the said compounding ratio (mass part) was adjusted. In addition, it was 6.8 when the mass of the NCO group of the polyisocyanate compound with respect to 100 mass parts of main ingredient resin was measured about the coating liquid of the Example. The P / V ratio of the coating liquid of the example was 1.0.

[Comparative Example 1]
The coating liquid of the comparative example was prepared as follows. For Comparative Example 1, the second main resin (acrylic resin) used in the above examples was used as the main resin. Other inorganic fillers, curing agents, and solvent blending ratios and adjustment methods were the same as in Examples, and the coating liquid of Comparative Example 1 was prepared.

[Comparative Example 2]
For Comparative Example 2, a resin obtained by copolymerizing an acrylic polyol resin with an ultraviolet absorber (UVA) and a hindered amine light stabilizer (HALS) (“Hals Hybrid Polymer” manufactured by Nippon Shokubai Co., Ltd.) is the main resin (main resin 3 ). Other inorganic fillers, curing agents, and solvent blending ratios and adjustment methods were the same as in Examples, and the coating liquid of Comparative Example 1 was prepared.

[Comparative Example 3]
For Comparative Example 3, the main resin 3 used in Comparative Example 2 was used as the main resin, and the amount of inorganic filler added was increased by about + 20%.

  In addition, about the coating liquid of Comparative Examples 1-3, when the mass of the NCO group of the polyisocyanate compound with respect to 100 mass parts of main ingredient resin was measured, 5.1 (Comparative Example 1) and 8.0 (Comparative Example 2), respectively, It was 8.0 (Comparative Example 3). In addition, P / V ratio of each coating liquid of Comparative Examples 1-3 was 2.0.

<Manufacture of backside protection sheet>
By applying the coating liquids of Examples and Comparative Examples 1 to 3 manufactured as described above to one side of the base material for the back surface protection sheet shown below, and subsequently evaporating the solvent component from the applied coating liquid. The coating layer was formed, and the back surface protection sheets of Examples and Comparative Examples 1 to 3 were manufactured. The coating amount of the coating liquid was 9 g / m ^{2 in} all cases, the coating was performed by the Miyabar method, the solvent was evaporated by drying in an oven at 100 ° C. for 2 minutes, and the mixture was further left standing at 40 ° C. for 7 days for curing.
Back surface protective sheet substrate: Polyethylene terephthalate (PET) substrate: Thickness 188 μm (trade name “Lumirror S10”, manufactured by Toray Industries, Inc.)

<Evaluation of adhesion of backside protection sheet>
[Adhesion test]
The back surface protective sheets of Examples and Comparative Examples 1 to 3 prepared as described above were subjected to an adhesion test according to ASTM D3359 and JIS 5400, and the adhesion between each layer was evaluated according to the following criteria. The evaluation results are shown in Table 1 below as “adhesiveness”.
A: 0% coating peeling B: Less than 5% coating peeling C: 5% or more and less than 50% coating peeling D: 50 to 100% coating peeling

<Solvent resistance evaluation of back surface protection sheet>
[Solvent resistance test]
About the back surface protection sheet of an Example and Comparative Examples 1-3, the following solvent resistance test was done and solvent resistance was evaluated. A solvent resistance test according to ASTM D5402-06 was performed on the surface of each back protection sheet on the coating layer side. A cotton soaked with acetone was used as the solvent, and the surface was rubbed 25 times with a force of 1500 g at a rate of about once per second, and the surface was observed and evaluated according to the following evaluation criteria. The evaluation results are shown in Table 1 below as “solvent resistance”.
A: No peeling of coating layer, no change in appearance B: No peeling of coating layer, change in appearance C: Peeling of coating layer by 15 reciprocating rubs D: Peeling of coating layer by 5 reciprocating rubs

<Designability evaluation 1 of back surface protection sheet>
Based on JISZ8741-1997, the gloss value (60 degree) of the surface of the back surface protection sheet of an Example and Comparative Examples 1-3 was measured using GM-26PRO by Murakami Color Research Laboratory. The results are shown in Table 1 as “gross values”.

<Designability evaluation 2 of back surface protection sheet>
The average arithmetic roughness (Ra) of the unevenness | corrugation shape of the surface of the back surface protection sheet of an Example and Comparative Examples 1-3 was measured by the following method.
(Measurement method) According to JIS B0601-1994, measurement was performed with a cut-off value λc = 0.8 mm and an evaluation length 1n = 4 mm. The results are shown in Table 1 as “Ra”.

<Designability evaluation 3 of back surface protection sheet>
The presence or absence of the matte feeling of the surface of the back surface protection sheet of an Example and Comparative Examples 1-3 was observed, and the following evaluation criteria evaluated. The evaluation results are shown in Table 1 as “mat feeling”.
A: Clear mat feeling B: Unclear but mat feeling C: No mat feeling

<Designability evaluation 4 of back surface protection sheet>
About the back surface protection sheet of the comparative example 3, the SEM photograph (FIG. 4, FIG. 6) of a cross section and the surface was image | photographed on the same conditions as the Example, and it compared with the same photograph (FIG. 3, FIG. 5) of the example. From the cross-sectional view of FIG. 4, the back surface protective sheet of Comparative Example 3 contains an inorganic filler but does not contain a plurality of phase-separable resins. Is not forming. Moreover, from the sectional view of FIG. 4 and the front view of FIG. 6, it can be seen that the back surface protective sheet of Comparative Example 3 is not formed with unevenness that gives a matte feeling to the sheet surface. Moreover, the expression of a matte feeling preferable in the design properties in Examples and the non-expression of such a matte feeling in Comparative Examples 1 to 3 have been confirmed by visual observation.

  From Table 1, the back surface protection sheet of this invention is excellent in adhesiveness and solvent resistance, and can provide preferable designability (mat feeling) to the back surface protection sheet for solar cell modules. I understand that there is.

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 Base material layer 61 Coating layer 611 1st area | region 612 2nd area | region 7 Coarse particle part

Claims (11)

A back surface protection sheet for a solar cell module in which a coating layer is formed on the surface of a base material layer,
The coating layer comprises a plurality of phase-separable resins and an inorganic filler,
The inorganic filler is aggregated and present in at least one of the plurality of phase-separable resins, and irregularities are formed on the surface of the coating layer depending on the presence or absence of the aggregation. Back protection sheet.   The back surface protection sheet according to claim 1, wherein the surface of the coating layer has a gloss value (60 °) according to JIS Z8741-1997 of 5 or more and 10 or less.   The back surface according to claim 1 or 2, wherein a difference between an SP value of at least one resin among the plurality of resins capable of phase separation and an SP value of another resin is 1.0 or more and less than 9.0. Protective sheet.   The back surface protective sheet according to any one of claims 1 to 3, wherein the plurality of phase-separable resins are an acrylic resin and a urethane resin.   The back surface protective sheet according to any one of claims 1 to 4, wherein the coating layer further contains a curing agent.   The back surface protective sheet according to claim 5, wherein the curing agent is a polyisocyanate compound.   The back protective sheet according to any one of claims 1 to 6, wherein an average arithmetic roughness (Ra) of the uneven shape is 0.24 µm or more and 3.0 µm.   The back surface protection sheet according to any one of claims 1 to 7, wherein a weather resistant layer made of a transparent resin is laminated on the surface of the coating layer. It is a manufacturing method of the back protection sheet according to any one of claims 1 to 8,
A step of applying a coating liquid containing a base resin material, an inorganic filler, and a solvent to the surface of the base material layer,
The base resin material contains a plurality of phase separable resins,
The method for producing a back surface protection sheet, wherein the inorganic filler aggregates in at least one of the plurality of resins that can be phase separated by phase separation of the base resin material. The back surface protective sheet according to any one of claims 1 to 8, a sealing material, and a solar cell element are laminated,
The solar cell module in which the coating layer or the weatherproof layer of the back surface protection sheet is disposed in one outermost layer of the solar cell module.   The solar cell module according to claim 10, wherein the sealing material is an ethylene-vinyl acetate copolymer resin or a polyethylene resin.