JP5556878B2 - Laminated cover substrate for solar cell, solar cell, and method for producing laminated cover substrate for solar cell - Google Patents

Description

  The present invention relates to a laminated cover substrate for solar cells, a solar cell using the laminated cover substrate for solar cells, and a method for producing the laminated cover substrate for solar cells.

In recent years, the spread of solar cells that can be used by converting solar energy into electrical energy has attracted attention as a measure for preventing global warming. In such a solar cell, high efficiency of power generation is required. High efficiency is deeply related to low cost and light weight.
Factors relating to the efficiency of the solar cell include the quantum efficiency in the semiconductor portion in the solar cell, the surface reflectance of the cover substrate (light receiving surface) of the solar cell, and the like. In particular, reducing the surface reflection of the cover substrate leads to efficient conversion of energy by taking solar energy into the solar cell, and improving the efficiency of the solar cell regardless of the type and characteristics of the semiconductor part. This is significant because it is possible. Further, for example, the surface reflection of the cover substrate of the solar cell applied to the roof or the wall surface may cause reflected light pollution.

Here, Patent Document 1 reports a method for improving the antiglare property of a film by controlling the arithmetic average surface roughness of the surface. However, the above method does not suppress the surface reflection of the film itself, and even if this method is used, it is difficult to improve the power generation efficiency of the solar cell.
Further, Patent Document 2 proposes a cover substrate that combines an antiglare layer having a fine unevenness on the surface with a layer having a low refractive index in order to impart antiglare properties at the same time as preventing reflection of light. Yes. However, the above-mentioned document does not mention the optimum conditions for the unevenness of the antiglare layer. Furthermore, since the refractive index of the low refractive index layer is estimated to be about 1.4, it is difficult to obtain a cover substrate that can sufficiently take in solar energy. Therefore, it cannot be said that a sufficient antireflection effect is obtained simultaneously with the antiglare property.

Patent Document 3 proposes to form an uneven pattern on a solar cell by using a co-hydrolyzed / polycondensate of a specific alkoxysilane, and to improve the utilization efficiency of solar energy by reflection and scattering effects. However, a layer having a refractive index of 1.4 or more is actually formed, and it cannot be said that a sufficient antireflection effect is obtained as described above.
Patent Document 4 proposes an antireflection layer having an uneven surface with a step of 0.01 μm to 1 μm. However, as far as the examples are concerned, it is estimated that the refractive index of the antireflection layer itself is about 1.3, and it cannot be said that a sufficient antireflection effect is obtained as described above.

  Furthermore, Patent Document 5 proposes an antireflection layer having a refractive index of 1.22 to 1.44 on a glass substrate. However, the antiglare property is not mentioned, and further improvements such as improvement of the antiglare property are required for use in solar cells constructed on an actual roof or wall surface.

JP 11-298030 A JP 7-333404 A JP 2000-216417 A Japanese Patent Laid-Open No. 2002-270866 Japanese translation of PCT publication No. 2002-543028

Based on the above, solar cell modules having high antireflection performance and maintaining sufficient antiglare properties and laminated cover substrates for solar cells used in solar cell modules have not been obtained yet, and the provision thereof is hoped for. It is rare.
The present invention was devised in view of the above problems, and an object of the present invention is to obtain a solar cell laminated cover substrate and a solar cell having high antireflection performance and excellent antiglare properties. To do.

As a result of intensive studies to solve the above problems, the present inventors have a laminated film having a constant refractive index on the light-transmitting substrate, and the center line average surface roughness of the light receiving surface, and the surface roughness The present inventors have found that a laminated cover substrate for a solar cell that is excellent in anti-glare property and has a significantly improved sunlight transmittance can be obtained by being in a certain region having a maximum height, and has led to the present invention.
The first gist of the present invention is a laminated cover substrate for a solar cell in which a laminated film having a refractive index of 1.05 to 1.3 is laminated on one side and / or both sides of a translucent base material. center line average surface roughness Ra of the surface side is 0.3 μm~10μm, and the maximum height Rmax of the surface roughness is the 0.1Myuemu～50myuemu, the surface roughness of the light-receiving surface side of the ToruHikarimoto material The maximum height Rmax is 11.73 to 50 μm, and the laminated film is provided at least on the light receiving surface side of the light-transmitting base material. ).

In the laminated cover substrate for a solar cell, it is preferable that the maximum film thickness of the laminated film is 50 nm to 10 μm (Claim 2), and it is preferable that the translucent substrate is tempered glass (Claim 3). Furthermore, it is preferable that the area of the laminated cover substrate for solar cells is 0.1 m ² or more.
Further, the total light transmittance of D65 light in the laminated cover substrate for solar cells is preferably 80% or more (Claim 5), and the laminated cover substrate for solar cells preferably has a heat ray blocking layer ( Claim 6).

According to a second aspect of the present invention, there is provided a solar cell module comprising the above-described laminated cover substrate for solar cells.
The third gist of the present invention is a method for producing the above-described laminated cover substrate for solar cells, wherein the laminated film is formed using a silica-based precursor having a viscosity of 0.05 Pas · sec or less. It exists in the manufacturing method of the laminated cover board | substrate for solar cells characterized by having (Claim 8).

In the method for producing a laminated cover substrate for a solar cell, the silica precursor preferably has a pH of 2 or less (claim 9).
Moreover, in the manufacturing method of the said laminated cover board | substrate for solar cells, it is preferable to pass through the heating process of 100 to 800 degreeC in the formation process of the said laminated film (Claim 10).

  According to the laminated cover substrate for a solar cell of the present invention, the centerline average surface roughness on the light-receiving surface side and the maximum height of the surface roughness are within a predetermined range, so that the antiglare property is high. It is possible to prevent reflection light pollution and the like from occurring. In addition, a combination with a laminated film having a predetermined refractive index can provide a laminated cover substrate for a solar cell that can take solar energy into the solar cell side extremely efficiently.

Moreover, according to the solar cell module of the present invention, since the solar cell laminated cover substrate is used, solar energy can be taken in very efficiently and converted into electric energy.
Furthermore, according to the method for manufacturing a laminated cover substrate for a solar cell of the present invention, a laminated film is formed using a silica-based precursor having a predetermined viscosity, so that a laminated cover substrate for a solar cell is manufactured with high productivity. Is possible.

It is a schematic sectional drawing which shows an example of the laminated cover board | substrate for solar cells of this invention. It is a schematic sectional drawing which shows the other example of the laminated cover board | substrate for solar cells of this invention.

Hereinafter, the present invention will be described in detail with reference to embodiments, examples, etc., but the present invention is not limited to the following embodiments, examples, etc., and may be arbitrarily selected without departing from the gist of the present invention. You can change it to
The manufacturing method of the laminated cover substrate for solar cells, the solar cell, and the laminated cover substrate for solar cells of the present invention will be described below.

A. First, the laminated cover substrate for solar cells of the present invention will be described. The laminated cover substrate for a solar cell of the present invention is obtained by laminating a laminated film having a predetermined refractive index on one side and / or both sides of a translucent base material, and the center line average surface roughness Ra on the light receiving surface side. In addition, the maximum height Rmax of the surface roughness is within a predetermined range. In addition, when the light-receiving surface side as used in the field of this invention is used for a solar cell module, the solar cell laminated cover board | substrate shall mean the side into which sunlight enters.

  According to the present invention, since the center line average surface roughness Ra on the light receiving surface side and the maximum height Rmax of the surface roughness are within a predetermined range, the reflection of sunlight energy is made diffuse reflection. The antiglare property can be increased. Therefore, when the laminated cover substrate for a solar cell of the present invention is applied to a solar cell module used for a roof or a wall surface, reflected light pollution is less likely to occur.

Furthermore, since the laminated film is formed, it is possible to reduce the reflection of solar energy of the laminated cover substrate for solar cells, and to take solar energy into the solar cell side very efficiently, A solar cell module with high power generation efficiency can be realized.
Hereinafter, the characteristic of the laminated cover substrate for solar cells of this invention is demonstrated, and each member which comprises the laminated cover substrate for solar cells is demonstrated after that.

[1. Characteristics of laminated cover substrates for solar cells]
1-1. Structure The structure of the laminated cover substrate for a solar cell of the present invention is not particularly limited as long as it has a light-transmitting substrate and a laminated film. For example, as shown in FIG. 1, a structure in which a laminated film 2 is laminated on the unevenness of a translucent substrate 1 having unevenness with a predetermined surface roughness, or a translucent light having no unevenness as shown in FIG. 2. A configuration in which a laminated film 2 having irregularities with a predetermined roughness is laminated on the substrate 1 can be employed. 1 and 2 are used for convenience in explaining the solar cell laminated cover substrate of the present invention, and the configuration of the solar cell laminated cover substrate is not limited to the above configuration. Any changes can be made without departing from the spirit of the present invention.

In the laminated cover substrate for a solar cell of the present invention, the laminated film may be laminated only on one side of the light-transmitting substrate, or may be laminated on both sides, but at least from the viewpoint of preventing reflection of solar energy. It is preferable to laminate on the light receiving surface side of the translucent substrate.
In addition, conventionally, the heat generated by the solar cell laminated cover substrate, the solar cell, or both due to sunlight propagates or stays in the solar cell, which may reduce the power generation efficiency of the solar cell. It was. Therefore, by laminating the laminated film on the side opposite to the light receiving surface (cell side) of the translucent base material, it becomes possible to suppress the propagation of heat from the above-described laminated cover substrate for solar cells. The effect which reduces the power generation efficiency fall of the photovoltaic cell by propagation of can also be expected. Therefore, you may have a laminated film on both surfaces of a translucent base material.

  Here, the laminated cover substrate for a solar cell of the present invention may have necessary layers as appropriate in addition to the light-transmitting substrate and the laminated film. For example, between a laminated film and a translucent substrate, on a laminated film, or on a translucent substrate, a heat ray blocking layer, an antifouling layer, an ultraviolet degradation preventing layer, a hydrophilic layer, a hydrophobic layer, an antifogging layer A layer, an adhesive layer, an adhesive layer, a hard layer, a conductive layer, a reflective layer, an antiglare layer, a diffusion layer, and the like may be included. In this invention, since it becomes possible to reduce the power generation efficiency fall of the solar cell module especially by propagation of the heat | fever from the laminated cover board | substrate for solar cells, it is preferable to have a heat ray blocking layer.

1-2. Centerline average surface roughness Ra on the light-receiving surface side, maximum height Rmax, and average interval between the irregularities The centerline average surface roughness Ra on the light-receiving surface side of the laminated cover substrate for solar cells of the present invention is usually 0.1 μm or more. , Preferably 0.2 μm or more, more preferably 0.3 μm or more. Moreover, it is 10 micrometers or less normally, Preferably it is 7 micrometers or less, More preferably, it is 5 micrometers or less, Most preferably, it is 4 micrometers or less.

  At this time, the maximum height Rmax of the surface roughness is usually 0.1 μm or more, preferably 0.2 μm or more, more preferably 0.4 μm or more, and particularly preferably 0.6 μm or more. Moreover, it is 50 micrometers or less normally, Preferably it is 40 micrometers or less, More preferably, it is 35 micrometers or less, Most preferably, it is 30 micrometers or less. By making the centerline average surface roughness and the maximum height of the surface roughness within the above ranges, the reflection of light from the laminated cover substrate for solar cells is made diffuse reflection, and the laminated cover substrate for solar cells has anti-glare properties. It becomes possible to have.

Furthermore, the average spacing Sm of the irregularities is not particularly limited, but is usually 0.005 mm or more, preferably 0.01 mm or more, more preferably 0.05 mm from the viewpoint of antifouling properties and antiglare properties. That's it. Moreover, it is 20 mm or less normally, Preferably it is 15 mm or less, More preferably, it is 12 mm or less. Below this range, the surface may be easily soiled, and when it exceeds this range, sufficient antiglare properties may not be obtained.
The center line average surface roughness Ra, the maximum height Rmax of the surface roughness, and the average interval Sm of the irregularities are obtained by measuring with a general-purpose surface roughness meter according to JIS-B0601.

1-3. Size The area of the laminated cover substrate for a solar cell of the present invention is preferably 0.1 m ² or more, more preferably 0.25 m ² or more, and further preferably 1 m ² or more. When the size is smaller than this size, the amount of power generation when the solar cell module is made is low, and the antireflection effect by the laminated film may not be sufficiently exhibited.

  Further, the thickness of the entire solar cell cover substrate is preferably 0.05 mm or more, more preferably 0.1 mm or more from the viewpoint of mechanical strength and gas barrier properties. Moreover, 80 mm or less is preferable from a lightweight viewpoint and a light-transmissive viewpoint, More preferably, it is 30 mm or less, More preferably, it is 10 mm or less.

1-4. Transmittance and haze The total light transmittance of D65 light of the laminated cover substrate for solar cells of the present invention is usually 80% or more, preferably 85% or more, more preferably 90% or more. Thereby, the power generation efficiency of the solar cell module can be improved.

  Moreover, the haze of the laminated cover substrate for solar cells is usually 5% or more, preferably 10% or more, more preferably 15% or more. Moreover, it is 95% or less normally, Preferably it is 92% or less, More preferably, it is 90% or less. Having a haze equal to or greater than the lower limit means that diffuse transmitted light is present, and the diffuse transmitted light has a long optical path length in the solar battery cell, and thus can contribute to an improvement in the efficiency of the solar battery. However, when the haze is larger than the upper limit, the amount of diffuse transmitted light may be too large, and the total light transmittance may be reduced.

  The total light transmittance and haze value can be obtained by measuring with a haze meter according to JIS-K7105. In this invention, it shall be the value measured by Suga Test Instruments Co., Ltd. product haze meter HZ-2. In addition, when there is an uneven | corrugated structure also in the cell part side of the laminated cover board | substrate for solar cells, this structure influences a total light transmittance and a haze. However, since the cell portion side of the cover substrate for solar cells is normally filled with a resin layer such as EVA (ethylene-vinyl acetate copolymer) when used in a solar cell module, it is derived from the irregularities on the cell portion side. The total light transmittance and haze to be used actually have little effect on the antiglare property and efficiency of the solar cell. Therefore, the solar cell stacking cover substrate having irregularities on the cell part side fills the irregularities on the cell part side with a resin or solvent such as EVA having a refractive index close to the transparent base material, and only the light rays on the light receiving surface contribute. It is preferable to measure transmittance and haze.

[2. Translucent substrate]
Next, the material and various characteristics of the translucent base material used for the laminated cover substrate for solar cells of the present invention will be described.

2-1. Materials The light-transmitting substrate used in the present invention is not particularly limited, and those generally used for a general laminated cover substrate for a solar cell can be used, and specifically, glass, resin, etc. can be mentioned, Glass is preferably used from the viewpoints of dimensional stability and gas barrier properties.
Any kind of glass can be used as the glass used for the translucent substrate. For example, silicate glass such as silicate glass, high silicate glass, alkali silicate glass, lead alkali glass, soda lime glass, potash lime glass, barium glass, borosilicate glass, alumina silicate glass, phosphate glass, etc. Tempered glass. Among them, soda lime glass is preferable in terms of price. Furthermore, it is also preferable to use tempered glass from the viewpoint of impact resistance. In addition, the cover glass used for solar cells capable of photoelectric conversion even in the near-infrared light, such as single crystal solar cells and other crystal solar cells, is near red due to the divalent iron ions contained in ordinary soda-lime glass. Since it has absorption in the outer region, it is more preferable to use white plate tempered glass having improved light transmittance by reducing the iron ion content and having excellent impact strength. The total iron oxide content in the glass composition of the white plate tempered glass is preferably 0.06% by weight or less in terms of Fe ₂ O ₃ . More preferably, it is 0.04 weight% or less, More preferably, it is 0.02 weight% or less. When it is larger than this range, the absorption of near-infrared light by iron ions may become remarkable as described above. Further, from the viewpoint of adhesion to the laminated film, it is preferable that the ratio of potassium, calcium, and zinc is small. The ratio of the potassium, calcium, and zinc can be measured by XPS, and the total content of potassium, calcium, and zinc is preferably 0.1 or less, more preferably 0.08 or less in terms of element ratio with silicon. 05 or less is more preferable.
Any tempering method can be applied to the tempered glass. For example, the glass strengthening method includes physical strengthening, chemical strengthening, and lamination strengthening. In particular, physical strengthening is a strengthening method by heat treatment, and when the heat treatment is used for forming the laminated film of the present invention, it is preferable from the viewpoint that both the strengthening step and the film forming step can be achieved.

The resin used for the translucent substrate is not particularly limited as long as it has translucency, but from the viewpoint of dimensional stability, a resin having a high glass transition point and high heat resistance temperature is preferable. Specifically, polyethylene terephthalate, polyethylene naphthalate; homopolymers such as trifluoroethylene chloride resin, polyvinylidene fluoride, polyvinyl fluoride, tetrafluoroethylene-perfluorovinylether copolymer, tetrafluoroethylene- Fluorine films such as copolymers such as hexafluoropropylene copolymer, tetrafluoroethylene-ethylene copolymer; polyacrylate films such as aromatic dicarboxylic acid-bisphenol copolymer aromatic polyester; polysulfone, polyethersulfone, etc. Sulfur-containing polymer film; polycarbonate film; amorphous polyolefin resin, cycloolefin resin; norbornene resin; polymethacrylate resin; olefin-maleimide copolymer, para-aramid, fluorinated polyimide Polystyrene, polyvinyl chloride, cellulose triacetate and the like.
The said glass and resin may be used individually by 1 type, and may use 2 or more types by arbitrary combinations.

2-2. Centerline average surface roughness, maximum height of surface roughness, and average interval of unevenness As described above, in the laminated cover substrate for solar cells of the present invention, the centerline average surface roughness within a predetermined range on the light receiving surface side It has a thickness. The light-transmitting substrate surface may have irregularities so that the surface on the light-receiving surface side of the laminated cover substrate for solar cells has the centerline average surface roughness, but for example, a laminated film formed on the light-receiving surface side In the case where it has irregularities and realizes the above-mentioned centerline average surface roughness and the maximum height of the surface roughness, the centerline average surface roughness and the maximum height of the surface roughness of the translucent substrate, etc. Is not particularly limited. Moreover, it is not specifically limited about the centerline average surface roughness etc. of the surface on the opposite side to the light-receiving surface side of a translucent base material.

  When the above-mentioned center line average surface roughness on the light receiving surface side of the laminated cover substrate for solar cells is realized by the unevenness of the surface of the light transmissive substrate, that is, the unevenness is formed on the surface of the light transmissive substrate, and the laminated film is formed thereon. The centerline average surface roughness Ra on the light-receiving surface side of the translucent substrate in the case where the above-mentioned centerline average surface roughness is realized by forming is usually 0.2 μm or more, preferably 0.3 μm or more. Moreover, it is 20 micrometers or less normally, Preferably it is 15 micrometers or less, More preferably, it is 10 micrometers or less, Most preferably, it is 8 micrometers or less. If it is smaller than this range, it becomes difficult to set the center line average surface roughness of the surface of the laminated cover substrate for solar cells within the above-mentioned range after the laminated film is formed. Moreover, if it exceeds such a range, the power generation efficiency of the solar cell module may be reduced by reducing the adhesion with the laminated film or the transmittance.

  The maximum height Rmax of the surface roughness is usually 0.2 μm or more, preferably 0.3 μm or more, more preferably 0.5 μm or more, and particularly preferably 0.8 μm or more. Moreover, it is 60 micrometers or less normally, Preferably it is 50 micrometers or less, More preferably, it is 40 micrometers or less, Most preferably, it is 35 micrometers or less. Below this range, it becomes difficult to make the maximum height of the surface roughness of the surface of the laminated cover substrate for solar cells within the above-mentioned range after the laminated film is formed. Moreover, when it exceeds this range, the adhesiveness with the laminated film may be lowered, or the antifouling property may be impaired.

  Further, the average interval Sm of the irregularities is not particularly limited, but is usually 0.005 mm or more, preferably 0.01 mm or more, more preferably 0.05 mm or more from the viewpoint of antifouling properties and antiglare properties. . Moreover, it is 20 mm or less normally, Preferably it is 15 mm or less, More preferably, it is 12 mm or less. Below this range, the surface may be easily soiled, and when it exceeds this range, sufficient antiglare properties may not be obtained.

The center line average surface roughness Ra, the maximum height Rmax of the surface roughness, and the average interval Sm can be the same as the measurement method in the laminated cover substrate for solar cells.
Here, the method for forming the irregularities on the surface of the translucent substrate is not particularly limited. For example, blasting, embossing, etching, sputtering, CVD, surface coating, etc. Obtained by applying the method.

2-3. Transmittance and haze The total light transmittance of D65 light of the light-transmitting substrate is preferably 80% or more, more preferably 83% or more, and more preferably 85% or more in terms of power generation efficiency of the solar cell module. To preferred.
The haze is usually 5% or more, preferably 10% or more, more preferably 15% or more. Moreover, it is 97% or less normally, Preferably it is 95% or less, More preferably, it is 93% or less. Having a haze equal to or greater than the lower limit means that diffuse transmitted light is present, and the diffuse transmitted light has a long optical path length in the solar battery cell, and thus can contribute to an improvement in the efficiency of the solar battery. However, when the haze is larger than the upper limit, the amount of diffuse transmitted light may be too large, and the total light transmittance may be reduced.

  The said light transmittance and the said haze can be made to be the same as that of the measuring method of each value in the laminated cover board | substrate for solar cells mentioned above.

2-4. Refractive index Moreover, the refractive index of the said translucent base material is 1.40 or more normally, Preferably it is 1.43 or more. Moreover, it is 1.7 or less normally, Preferably it is 1.65 or less, More preferably, it is 1.53 or less. By having the refractive index of the translucent substrate in such a range, a laminated film having a predetermined refractive index described later can exhibit a higher antireflection effect regardless of the type of the translucent substrate. Moreover, when a translucent base material is glass, the glass exceeding this range has many optical uses and may be expensive. When the translucent base material is a resin, the resin exceeding the above range is limited, and thus may be restricted as a laminated cover substrate for a solar cell. Examples of the refractive index measurement method include spectroscopic ellipsometry and prism coupler.

2-5. Size Furthermore, the area of the translucent substrate is appropriately selected according to the area of the laminated cover substrate for solar cells of the present invention. Moreover, the thickness of the said translucent base material is 0.05 mm or more normally from a viewpoint of mechanical strength and gas barrier property, Preferably it is 0.1 mm or more. Further, from the viewpoint of weight reduction and light transmittance, it is usually 80 mm or less, preferably 30 mm or less, more preferably 10 mm or less.

[3. Laminated film]
Next, the material and various characteristics of the laminated film used for the laminated cover substrate for solar cells of the present invention will be described.

3-1. Material The material of the laminated film is not particularly limited as long as it can form a film having a refractive index to be described later, and examples thereof include an organic layer such as a resin, an inorganic layer, and a composite layer of an organic material and an inorganic material. However, from the viewpoint of dimensional stability and heat resistance, an inorganic layer or a composite layer of an organic material and an inorganic material is preferable, and an inorganic layer is more preferable. Moreover, when a laminated film is formed on both surfaces of a translucent substrate, they may be films made of different materials or may be films made of the same material.

  Each laminated film may be composed of a single layer, or may be composed of a plurality of layers in which two or more layers are laminated. The number of stacked layers is not particularly limited, but is preferably 5 layers or less, more preferably 3 layers or less, and particularly preferably 1 layer from the viewpoint of film stability (reduction of internal strain). If the number of layers exceeds five, phenomena such as peeling are likely to occur at the interface between the layers, and film stability (reliability) may be reduced. When a plurality of layers are stacked, each layer may be the same layer or different layers.

Examples of the inorganic material used for forming the laminated film include metal oxides such as silicon oxide and aluminum oxide, and silicon nitride. These may be used alone or in combination of two or more in any ratio and combination. Among these, it is more preferable to use silicon oxide from the viewpoint of film stability.
Furthermore, a material having an arbitrary chemical composition containing a positive element may be contained. For example, yttrium oxide, lanthanum oxide, cerium oxide, praseodymium oxide, samarium oxide, europium oxide, gadolinium oxide, terbium oxide, dysprosium oxide, holmium oxide, erbium oxide, thulium oxide, titanium oxide, zirconium oxide, chromium oxide, manganese oxide, Transition metal oxide compositions such as iron oxide, cobalt oxide, nickel oxide, copper oxide, zinc oxide, cadmium oxide, gallium oxide, indium oxide, germanium oxide, tin oxide, lead oxide; lithium oxide, sodium oxide, potassium oxide, oxide Alkali metal oxide compositions such as rubidium and cesium oxide; alkaline earth metal compositions such as magnesium oxide, calcium oxide, strontium oxide and barium oxide; boron oxide composition; aluminum oxide composition; It can be. In addition, known inorganic glass compositions such as a chalcogenide glass composition and a fluoride glass composition, and metal nanoparticles such as gold, silver, and copper can also be exemplified. You may use these individually by 1 type or 2 or more types by arbitrary ratios and combinations.

  The organic material used for forming the laminated film is not particularly limited as long as it has excellent light resistance and durability, but specifically, polyimide resin, polymethyl methacrylate resin, polycarbonate resin, silicone resin. , Polyurethane resin, epoxy resin, polyethersulfone resin and the like. One of these may be used alone, or two or more of these may be mixed or laminated.

3-2. Refractive index From the viewpoint of antireflection, the refractive index of the laminated film is usually 1.05 or more, but from the viewpoint of mechanical strength and antifouling property (reliability of antireflection performance due to dirt) of the laminated film, 1.08 or more. Preferably, it is 1.1 or more, particularly preferably 1.13 or more. Moreover, it is 1.3 or less normally, Preferably it is 1.28 or less, More preferably, it is 1.26 or less.

  Generally, when the refractive index of the laminated film is small, the laminated film contains “air” or “fluorine” having a low refractive index. For example, when approaching the refractive index of air (1.0), the laminated film often has pores, and if it is smaller than the above lower limit, the antifouling property may be remarkably lowered or the mechanical strength may be lowered. There is sex. On the other hand, when the above upper limit is exceeded, there is a possibility that the antireflection effect due to dirt is remarkably lowered and the efficiency of the solar cell cannot be increased. Examples of the refractive index measurement method include spectroscopic ellipsometry, prism coupler, and reflective spectral film thickness meter.

Here, in order to make the refractive index of the laminated film in the above-described range, it is effective to make the laminated film have a porous structure, and the structure of the pores is not particularly limited. Examples of the structure include a tunnel shape, independent holes, or a connecting hole connecting them. However, continuous pores are preferred as the structure of the pores, and such continuous pores can be confirmed by an electron microscope. For example, as a method for forming a laminated film having a porous structure, the following methods may be mentioned.
(1) A method of forming a laminate having a porous structure by forming voids between particles by forming a laminate comprising fine particles.
(2) A method of forming a laminate having a porous structure by performing an etching process on the laminate.
(3) A method of forming a laminate having a porous structure by forming a laminate containing a porogen (a source of pores) and adding a treatment to make the porogen pores. In addition, as a process which makes a porogen a void | hole, a supercritical carbon dioxide process, a solvent process, heat processing, a freeze-dry process, etc. are mentioned. (4) A method of combining the above methods into a porous structure.

  For example, in “B. Manufacturing method of laminated cover substrate for solar cell” described later, a method of forming a laminated film using a predetermined silica-based precursor containing a templating agent as a porogen will be described.

3-3. Centerline average surface roughness, maximum height of surface roughness, and average interval between irregularities As described above, in the laminated cover substrate for a solar cell of the present invention, the surface on the light receiving surface side is a centerline within a predetermined range. It has an average surface roughness. When the laminated film is located on the outermost layer on the light-receiving surface side of the laminated cover substrate for solar cells, the laminated film surface has the centerline average surface roughness and the maximum height. At this time, the laminated film itself may have unevenness, and the centerline average surface roughness or the maximum height of the surface roughness may be realized, and along the unevenness formed on the surface of the translucent substrate. A laminated film may be formed to realize the centerline average surface roughness and the maximum height of the surface roughness.

The center line average surface roughness Ra of the laminated film, the maximum height Rmax of the surface roughness, and the average interval Sm of the irregularities when the laminated film is formed on the outermost layer on the light receiving surface side of the laminated cover substrate for solar cells. Is the same as the above values on the light receiving surface side of the above-described laminated cover substrate for solar cells.
In addition, there is no restriction | limiting in particular about the surface roughness of the laminated film formed in the surface on the opposite side to the light-receiving surface side.

3-4. Maximum film thickness The maximum film thickness of the laminated film is usually 50 nm or more, preferably 60 nm or more, more preferably 70 nm or more, and particularly preferably 80 nm or more, from the viewpoints of antireflection performance and antiglare properties. Further, it is usually 10 μm or less, preferably 5 μm or less, more preferably 1 μm or less, and particularly preferably 500 nm or less. If the thickness is less than 50 nm, it may be difficult to form a film having a uniform thickness. If the thickness exceeds 10 μm, it may be difficult to obtain a uniform film when laminated on the uneven surface. When the laminated film is composed of a plurality of layers, the total thickness of each layer is within the above range.

  Further, for example, in the case of a laminated film having an uneven surface as shown in FIG. 2, the maximum film thickness of the laminated film is the distance between the surface of the laminated film opposite to the light transmissive substrate and the light transmissive substrate. Is the largest value. Examples of the method for measuring the maximum film thickness include spectroscopic ellipsometry, interference film thickness meter, reflection spectral film thickness meter, contact step meter, prism coupler, and electron microscope observation of the cross section of the laminated cover substrate for solar cells.

[4. Heat ray blocking layer]
Examples of the material for forming the heat ray blocking layer include transparent dielectric multilayers, materials having absorption in the infrared region, metals, and the like. These are used alone or in combination of two or more in any ratio and combination. be able to. Of these, a multilayer body of transparent dielectric and a material having absorption in the infrared region are particularly preferable.

The film thickness of the heat ray blocking layer is usually 5 nm or more, preferably 15 nm or more, more preferably 100 nm or more. Moreover, it is 100 micrometers or less normally, Preferably it is 50 micrometers or less, More preferably, it is 5 micrometers or less.
Further, the infrared transmittance at a wavelength of 1300 nm to 2500 nm is usually 5% or more, preferably 10% or more, more preferably 15% or more, and usually 95% or less, preferably 85% or less, more preferably 70% or less. is there. If the lower limit is not reached, the total light transmittance may be reduced, and if the upper limit is exceeded, the power generation efficiency in the solar cell may be reduced. The infrared transmittance is defined as an average value of transmittances every 50 nm at wavelengths of 1300 nm to 2500 nm measured with a spectrophotometer.

  As the multilayer body of the transparent dielectric, for example, a high refractive index layer and a low refractive index layer can be alternately laminated. The interface between the high refractive index layer and the low refractive index layer may be completely separated, or the high refractive index layer and the low refractive index layer may be mixed at the interface. The number of layers of the high refractive index layer and the low refractive index layer may be usually 1 or more, usually 5 or less, preferably 3 or less. One high refractive index layer may be used. When the number of stacked layers is increased, production may be difficult, and when a solar cell is used, the power generation cost may increase.

Examples of the transparent dielectric material include thermoplastic resins, thermosetting resins, photocurable resins, inorganic oxides, and composites thereof. Examples of the metal include aluminum, gold, silver, and copper. Furthermore, examples of the material having absorption in the infrared region include metal compounds such as In ₂ O ₃ , dyes, and the like. These may be used alone or in combination of two or more in any ratio and combination. As a method for forming a heat ray blocking layer using a metal or an inorganic oxide, any method such as a vacuum deposition method, a sputtering method, a vapor phase growth method, a plasma CVD method, a coating method, or the like may be used.

B. Next, the manufacturing method of the laminated cover board | substrate for solar cells in this invention is demonstrated. The manufacturing method of the laminated cover substrate for solar cells of this invention is related with the manufacturing method of "A. laminated cover substrate for solar cells" mentioned above, and forms formation of a laminated film from the silica type precursor which has a predetermined | prescribed viscosity. It has a process.

According to the present invention, since the laminated film is formed using the silica-based precursor, a laminated cover substrate for a solar cell can be formed by using a wet coating method, and a conventionally known dry coating method. Compared to the above, it can be advantageous in terms of cost, productivity, equipment, and the like. Further, since the laminated film is formed using the silica-based precursor, it is possible to form a laminated film having a low refractive index. Therefore, by using the laminated cover substrate for a solar cell manufactured according to the present invention, it becomes possible to take in more solar energy to the solar cell side, and an efficient solar cell module can be realized.
Hereinafter, the silica-based precursor used in the present invention will be described, and then the formation process for forming the laminated film and other processes will be described.

[1. Silica-based precursor]
The silica-based precursor referred to in the present invention refers to a composition used for forming a laminated film containing at least silica, and the type thereof is not particularly limited. For example, tetraalkoxysilanes, hydrolysates thereof, And at least one selected from the group consisting of partial condensates (hereinafter referred to as “tetraalkoxysilane group” as appropriate), and alkoxysilanes other than the tetraalkoxysilane (hereinafter referred to as “other alkoxysilanes” as appropriate), At least one selected from the group consisting of the hydrolyzate and partial condensate (hereinafter referred to as “other alkoxysilane group” as appropriate) and / or at least one selected from the tetraalkoxysilane group and the other At least one partial condensate selected from the alkoxysilane group (hereinafter referred to as “specific” And that Bunchijimigobutsu "), and water, and an organic solvent, and the catalyst preferably contains a templating agent to form the pores.

1-1. Tetraalkoxysilane Group There is no limitation on the type of the tetraalkoxysilane, and for example, tetramethoxysilane, tetraethoxysilane, tetra (n-propoxy) silane, tetraisopropoxysilane, tetra (n-butoxy) silane and the like are preferable. Can be mentioned. Examples of the tetraalkoxysilane group include hydrolysates and partial condensates (such as oligomers) of the above tetraalkoxysilanes.

  However, since tetraalkoxysilanes tend to undergo hydrolysis and partial condensation over time, even when only tetraalkoxysilanes are prepared, the hydrolysates and partial condensates of tetraalkoxysilanes are usually tetraalkoxysilanes. Often co-exists with other species. In addition, the compound which belongs to the tetraalkoxysilane group may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and a ratio.

1-2. Other Alkoxysilane Groups As the other alkoxysilanes, any alkoxysilanes that do not belong to the tetraalkoxysilanes described above can be used. Suitable examples include trialkoxysilanes such as trimethoxysilane, triethoxysilane, methyltrimethoxysilane, methyltriethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane; dimethyldimethoxysilane, dimethyldiethoxysilane, diphenyl Dialkoxysilanes such as dimethoxysilane and diphenyldiethoxysilane; bis (trimethoxysilyl) methane, bis (triethoxysilyl) methane, 1,2-bis (trimethoxysilyl) ethane, 1,2-bis (triethoxy 2 or more organic residues such as silyl) ethane, 1,4-bis (trimethoxysilyl) benzene, 1,4-bis (triethoxysilyl) benzene, 1,3,5-tris (trimethoxysilyl) benzene The trialkoxysilyl group of 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-glycidyloxypropyltrimethoxysilane, 3-glycidyloxypropyltriethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-acryloyl Examples include alkyl groups substituted with silicon atoms such as loxypropyltrimethoxysilane and 3-carboxypropyltrimethoxysilane having a reactive functional group. Examples of other alkoxysilane groups include hydrolysates and partial condensates (such as oligomers) of the other alkoxysilanes.

Among these, monoalkylalkoxysilanes and dialkylalkoxysilanes having an aromatic hydrocarbon group or an aliphatic hydrocarbon group are preferable. Specific examples include methyltrimethoxysilane, methyltriethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, dimethyldimethoxysilane, and dimethyldiethylsilane.
However, since other alkoxysilanes tend to undergo hydrolysis and partial condensation over time, even when only other alkoxysilanes are prepared, other alkoxysilane hydrolysates and partial condensates are usually other. Often coexists with other alkoxysilanes.
In addition, the compound which belongs to other alkoxysilanes may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and ratios.

1-3. Specific partial condensate Any specific condensate may be used as long as it is a partial condensate obtained by partial condensation of at least one selected from the above-described tetraalkoxysilane group and at least one selected from another alkoxysilane group. be able to. Preferable examples include partial condensates obtained by partial condensation of those exemplified as preferred examples of tetraalkoxysilanes and those exemplified as preferred examples of other alkoxysilanes.

  In addition, the specific partial condensate may use only 1 type and may use 2 or more types together by arbitrary combinations and a ratio. Furthermore, although the specific partial condensate may be used only as the specific partial condensate, it may be used in combination with one or both of the tetraalkoxysilanes and other alkoxysilanes described above.

1-4. Preferred combinations Among the combinations of tetraalkoxysilanes and other tetraalkoxysilanes described above, particularly preferred combinations include tetraethoxysilane as a tetraalkoxysilane and an aromatic hydrocarbon group as another alkoxysilane. The combination with the monoalkyl alkoxysilane or dialkyl alkoxysilane which has an aliphatic hydrocarbon group is mentioned. According to this combination, a laminated film having homogeneity and durability can be obtained.

1-5. Content ratio of alkoxysilanes The content ratio of the alkoxysilanes described above in the silica-based precursor satisfies the following condition (1). That is, the ratio of silicon atoms derived from tetraalkoxysilanes to silicon atoms derived from all alkoxysilanes is usually 0.3 (mol / mol) or more, preferably 0.35 (mol / mol) or more, more preferably 0. .4 (mol / mol) or more, and usually 0.7 (mol / mol) or less, preferably 0.65 (mol / mol) or less, more preferably 0.6 (mol / mol) or less. (Condition (1)). When the ratio is too small, the hydrophobicity of the obtained laminated film becomes high, but the bond strength of -O-Si-O- is reduced, so that the mechanical strength of the laminated film is weak and the water resistance is similarly reduced. there's a possibility that. On the other hand, when the ratio is too large, the residual silanol groups in the laminated film increase, and the water resistance may also decrease.

Here, the silicon atoms derived from all alkoxysilanes refer to the total number of silicon atoms contained in the tetraalkoxysilane group, other alkoxysilane groups, and the specific partial condensate contained in the silica-based precursor. The silicon atom derived from tetraalkoxysilane corresponds to the number of silicon atoms contained in the tetraalkoxysilane group contained in the silica-based precursor and the tetraalkoxysilane group among silicon atoms contained in the specific partial condensate. Total with the number of silicon atoms belonging to the partial structure. Therefore, even if the silica-based precursor contains a compound having a silicon atom in addition to the alkoxysilanes, the silicon atom that the compound has does not participate in the calculation of the ratio.
In addition, the ratio of the silicon atom derived from tetraalkoxysilane to the silicon atom derived from all the alkoxysilanes can be measured by Si-NMR.

1-6. Water The silica-based precursor used in the present invention preferably contains water, and the purity of water is preferably high. Usually, water subjected to either or both of ion exchange and distillation is used. However, when forming a laminated film with higher purity, it is preferable to use distilled water, and it is preferable to use ultrapure water ion-exchanged after distillation. Specifically, for example, water that has passed through a filter having a pore size of 0.01 μm to 0.5 μm may be used.

The amount of water used in the silica-based precursor is set to satisfy the following condition (2). That is, the ratio of water to silicon atoms derived from all alkoxysilanes is usually 10 (mol / mol) or more, preferably 11 (mol / mol) or more, more preferably 12 (mol / mol) or more (conditions ( 2)). If the ratio of water to silicon atoms derived from all alkoxysilanes is smaller than the above range, it is difficult to control the sol-gel reaction, the pot life is short, and there is a possibility that a laminated film having an extremely hydrophobic surface can be obtained. is there. For this reason, the water resistance of the laminated film is lowered, and the surface may be roughened.
The amount of water can be calculated by the Karl Fischer method (coulometric titration method).

1-7. Solvent The silica-based precursor preferably contains an organic solvent, and the type of the organic solvent is not limited. Among these, as the organic solvent, it is preferable to use one or more organic silanes having the ability to mix the alkoxysilanes and water described above. Examples of suitable organic solvents include C1-C4 monohydric alcohols such as methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, t-butanol, 1-pentanol, Alcohols such as polyhydric alcohols such as dihydric alcohols having 1 to 4 carbon atoms, glycerin and pentaerythritol; diethylene glycol, ethylene glycol monomethyl ether, ethylene glycol dimethyl ether, 2-ethoxyethanol, propylene glycol monomethyl ether, propylene glycol methyl ether acetate Ethers or esterified products of the above alcohols; ketones such as acetone and methyl ethyl ketone; formamide, N-methylformamide, N-ethylformamide, N, N-dimethylphenol Muamide, N, N-diethylformamide, N-methylacetamide, N-ethylacetamide, N, N-dimethylacetamide, N, N-diethylacetamide, N-methylpyrrolidone, N-formylmorpholine, N-acetylmorpholine, N- Amides such as formylpiperidine, N-acetylpiperidine, N-formylpyrrolidine, N-acetylpyrrolidine, N, N′-diformylpiperazine, N, N′-diformylpiperazine, N, N′-diacetylpiperazine; Examples include lactones such as butyrolactone; ureas such as tetramethylurea and N, N′-dimethylimidazolidine; dimethyl sulfoxide and the like. Among these, alcohols are preferable and monohydric alcohols are more preferable for the contained alkoxysilanes to perform hydrolysis under more stable conditions.

In addition, only 1 type may be used for an organic solvent and it may use 2 or more types together by arbitrary combinations and a ratio. In particular, when a laminated film is used, two or more kinds of organic solvents are used in combination from the viewpoint that the refractive index is low and the adhesiveness with the light-transmitting substrate can be improved. Is preferably used as the organic solvent.
However, in order to form a uniform laminated film by heat treatment after applying the silica-based precursor, a certain degree of curing (condensation reaction of alkoxysilanes) and removal of water are simultaneously performed during the heat treatment. It is preferable. Therefore, it is preferable to use an organic solvent in which the organic solvent in the silica-based precursor is volatilized in a temperature range in which moisture existing near or inside the surface can be removed to some extent.

  Therefore, it is preferable that the silica-based precursor contains an organic solvent having a boiling point in a predetermined range as an organic solvent at a predetermined high ratio. Specifically, it is preferable to satisfy the following condition (3). That is, an organic solvent having a boiling point of usually 55 ° C. or higher, preferably 60 ° C. or higher, more preferably 65 ° C. or higher, and usually 140 ° C. or lower, preferably 135 ° C. or lower, more preferably 130 ° C. or lower. (Referred to as “boiling point solvent”), and the ratio of the predetermined boiling point solvent in the total organic solvent is usually 80% by weight or more, preferably 83% by weight or more, more preferably 85% by weight or more (conditions) (3)). In addition, the upper limit of the said ratio is 100 weight% normally. If the boiling point is too low, the silica-based precursor is cured with insufficient sol-gel reaction, and the laminated film of the present invention may be extremely inferior in water resistance. On the other hand, if the boiling point is too high, the sol-gel reaction proceeds locally, so that the laminated film of the present invention becomes heterogeneous, which may lead to a decrease in surface properties and a decrease in water resistance. Furthermore, when the ratio of the predetermined boiling point solvent is low, the above advantages may not be obtained. From this point of view, examples of the predetermined boiling point solvent include ethanol, 1-propanol, t-butanol, 2-propanol, 1-butanol, 1-pentanol, and ethyl acetate. Therefore, it is preferable to use at least one selected from these as the organic solvent.

  Moreover, the usage-amount of the whole organic solvent is arbitrary unless the effect of this invention is impaired remarkably. However, with respect to the silicon atoms derived from all alkoxysilanes, usually 0.01 mol / mol or more, particularly 0.1 mol / mol or more, particularly 1 mol / mol or more is preferable, and usually 100 mol / mol or less, particularly 70 mol / mol. It is preferably not more than mol, particularly not more than 20 mol / mol. If the amount of the organic solvent used is too small, the surface properties of the laminated film may be degraded. If it is too large, the film quality may be affected by the surface energy of the substrate when the laminated film is formed on the substrate. There is.

1-8. Catalyst The silica-based precursor preferably contains a catalyst. As the catalyst, a substance that promotes the hydrolysis and dehydration condensation reaction of the above-mentioned alkoxysilanes can be arbitrarily used.
Examples include acids such as hydrochloric acid, nitric acid, sulfuric acid, formic acid, acetic acid, oxalic acid and maleic acid; amines such as ammonia, butylamine, dibutylamine and triethylamine; bases such as pyridine; acetylacetone complexes of aluminum, etc. Lewis acids; and the like.

Moreover, a metal chelate compound is also mentioned as an example of a catalyst. Examples of the metal species of the metal chelate compound include titanium, aluminum, zirconium, tin, and antimony. Specific examples of the metal chelate compound include the following.
Examples of the aluminum complex include di-ethoxy mono (acetylacetonato) aluminum, di-n-propoxy mono (acetylacetonato) aluminum, di-isopropoxy mono (acetylacetonato) aluminum, di-n- Butoxy mono (acetylacetonato) aluminum, di-sec-butoxy mono (acetylacetonato) aluminum, di-tert-butoxy mono (acetylacetonato) aluminum, monoethoxy bis (acetylacetonato) aluminum, mono -N-propoxy bis (acetylacetonato) aluminum, monoisopropoxy bis (acetylacetonato) aluminum, mono-n-butoxy bis (acetylacetonato) aluminum, mono-sec-but Si-bis (acetylacetonato) aluminum, mono-tert-butoxy bis (acetylacetonato) aluminum, tris (acetylacetonato) aluminum, diethoxy mono (ethylacetoacetate) aluminum, di-n-propoxy mono ( Ethyl acetoacetate) aluminum, diisopropoxy mono (ethyl acetoacetate) aluminum, di-n-butoxy mono (ethyl acetoacetate) aluminum, di-sec-butoxy mono (ethyl acetoacetate) aluminum, di-tert- Butoxy mono (ethyl acetoacetate) aluminum, monoethoxy bis (ethyl acetoacetate) aluminum, mono-n-propoxy bis (ethyl acetoacetate) aluminum, mono Sopropoxy bis (ethyl acetoacetate) aluminum, mono-n-butoxy bis (ethyl acetoacetate) aluminum, mono-sec-butoxy bis (ethyl acetoacetate) aluminum, mono-tert-butoxy bis (ethyl acetoacetate) Examples thereof include aluminum chelate compounds such as aluminum and tris (ethylacetoacetate) aluminum.

  Titanium complexes include triethoxy mono (acetylacetonato) titanium, tri-n-propoxy mono (acetylacetonato) titanium, triisopropoxy mono (acetylacetonato) titanium, tri-n-butoxy mono (acetyl). Acetonato) titanium, tri-sec-butoxy mono (acetylacetonato) titanium, tri-tert-butoxy mono (acetylacetonato) titanium, diethoxy bis (acetylacetonato) titanium, di-n-propoxy bis (Acetylacetonato) titanium, diisopropoxy bis (acetylacetonato) titanium, di-n-butoxy bis (acetylacetonato) titanium, di-sec-butoxy bis (acetylacetonato) titanium, di-tert -Butoxy bis (ace Ruacetonate) titanium, monoethoxy tris (acetylacetonato) titanium, mono-n-propoxy tris (acetylacetonato) titanium, monoisopropoxy tris (acetylacetonato) titanium, mono-n-butoxy tris (acetyl) Acetonato) titanium, mono-sec-butoxy-tris (acetylacetonato) titanium, mono-tert-butoxy-tris (acetylacetonato) titanium, tetrakis (acetylacetonato) titanium, triethoxy mono (ethylacetoacetate) titanium , Tri-n-propoxy mono (ethyl acetoacetate) titanium, triisopropoxy mono (ethyl acetoacetate) titanium, tri-n-butoxy mono (ethyl acetoacetate) titanium, tri-sec-butyl Xy mono (ethyl acetoacetate) titanium, tri-tert-butoxy mono (ethyl acetoacetate) titanium, diethoxy bis (ethyl acetoacetate) titanium, di-n-propoxy bis (ethyl acetoacetate) titanium, diiso Propoxy bis (ethyl acetoacetate) titanium, di-n-butoxy bis (ethyl acetoacetate) titanium, di-sec-butoxy bis (ethyl acetoacetate) titanium, di-tert-butoxy bis (ethyl acetoacetate) Titanium, monoethoxy tris (ethyl acetoacetate) titanium, mono-n-propoxy tris (ethyl acetoacetate) titanium, monoisopropoxy tris (ethyl acetoacetate) titanium, mono-n-butoxy tris (ethyl acetoacetate) Acetate) titanium, mono-sec-butoxy tris (ethyl acetoacetate) titanium, mono-tert-butoxy tris (ethyl acetoacetate) titanium, tetrakis (ethyl acetoacetate) titanium, mono (acetylacetonate) tris (ethyl aceto) Acetate) titanium, bis (acetylacetonato) bis (ethylacetoacetate) titanium, tris (acetylacetonato) mono (ethylacetoacetate) titanium and the like.

Among those described above, acids or metal chelate compounds are preferable and acids are more preferable in order to more easily control the hydrolysis and dehydration condensation reaction of alkoxysilanes. In addition, a catalyst may use only 1 type and may use 2 or more types together by arbitrary combinations and a ratio.
Among these, from the viewpoints of film-forming properties on uneven surfaces and crack resistance, it is preferable that the pH of the silica-based precursor is 2 or less. Specifically, hydrochloric acid, nitric acid, sulfuric acid, formic acid, acetic acid, oxalic acid, malein Acids such as acids are preferred.

  The amount of the catalyst used is arbitrary as long as the effects of the present invention are not significantly impaired. However, it is usually 0.001 mol times or more, especially 0.003 mol times or more, particularly preferably 0.005 mol times or more, and usually 0.8 mol times or less, especially 0.5 mol times or less, especially with respect to alkoxysilanes. Is preferably 0.1 mol times or less. If the amount of the catalyst used is too small, the hydrolysis reaction does not proceed properly, and active groups such as silanol groups are likely to remain in the laminated film after production, which may reduce the water resistance of the laminated film. It becomes difficult to control the reaction, and the surface concentration of the laminated film may be deteriorated by further increasing the catalyst concentration during production.

1-9. Template Agent It is effective to mix a template agent in order to form pores in the laminated film formed according to the present invention and to control the amount of pores. The templating agent is not particularly limited as long as it is a compound having a decomposition temperature other than the solvent of 130 ° C. or higher, but from the viewpoint of refractive index control, a surfactant such as cetyltrimethylammonium chloride, and a polymer species such as polyethylene glycol are used. Preferably, a nonionic polymer is more preferable from the viewpoint of the stability of the silica-based precursor. Furthermore, a compound having an ethylene oxide moiety is preferable from the viewpoint of compatibility with alkoxysilanes. The main chain skeleton structure is not particularly limited.

  Specific examples of the main chain skeleton structure include polyether, polyester, polyurethane, polyolefin, polycarbonate, polydiene, polyvinyl ether, polystyrene, and derivatives thereof. Among these, a polymer containing a polyether as a constituent component is preferable. Specific examples thereof include polyethylene glycol (hereinafter referred to as “PEG” as appropriate), polypropylene glycol, polyisobutylene glycol, and the like. Among these, polyethylene oxide-polypropylene oxide-polyethylene oxide triblock polymer and / or polyethylene glycol are particularly preferable. In addition, the said template agent may use only 1 type and may use 2 or more types together by arbitrary combinations and a ratio.

  The amount of the templating agent used is arbitrary as long as the effects of the present invention are not significantly impaired. However, the ratio of the templating agent according to the present invention to silicon atoms derived from all alkoxysilanes is usually 0.001 (mol / mol) or more, preferably 0.002 (mol / mol) or more, more preferably 0.003. (Mol / mol) or more, usually 0.05 (mol / mol) or less, preferably 0.04 (mol / mol) or less, more preferably 0.03 (mol / mol) or less. When the ratio is too small, the formed laminated film cannot form a sufficient porous structure, and a low refractive index may not be realized. On the other hand, when the said ratio is too large, when the laminated | multilayer film | membrane is shape | molded, the said template agent will precipitate excessively on the surface and there exists a possibility of roughening the surface.

  Further, from the viewpoint of reducing impurities, the templating agent preferably does not contain a cation. Moreover, even if it contains a cation, the amount of the cation is preferably small. Specifically, the amount of the templating agent in the silica-based precursor is preferably 10% by weight or less, more preferably 5% by weight or less, and particularly preferably 1% by weight or less. If the cation component remains, there is a possibility that the light-transmitting substrate is deteriorated or the formed laminated film is colored.

1-10. Other Substances As long as it is possible to produce the laminated film of the present invention, the silica-based precursor may contain components other than the alkoxysilanes, water, organic solvent, catalyst, and templating agent described above. . Moreover, the said component may use only 1 type and may use 2 or more types together by arbitrary combinations and a ratio.

1-11. Physical Properties of Silica-Based Precursor The pH of the above-mentioned silica-based precursor is usually 2 or less, preferably 1.8 or less, from the viewpoint of film-forming properties on the surface of a light-transmitting substrate having irregularities and crack resistance, for example. More preferably, it is 1.5 or less.
The viscosity of the silica-based precursor is usually 0.05 Pas · sec or less, preferably 0.03 Pas · sec or less, more preferably 0.02 Pas · sec or less, from the viewpoint of film forming properties. The viscosity is measured with a rotational viscometer.

[2. Formation process to form laminated film]
In the present invention, the method for forming the laminated film is not particularly limited as long as it is a method using the above silica-based precursor. Usually, it can obtain in order of a silica type precursor preparation process, a coating process, a baking process, and a cooling process. In addition to the above steps, a surface treatment step of the light-transmitting substrate, a silylation treatment step of the laminated film, and the like may be performed.

2-1. Silica-based precursor preparation step In the silica-based precursor preparation step, the above-described components constituting the silica-based precursor are mixed to prepare a silica-based precursor. At this time, there is no limitation on the order of mixing the components. In addition, each component may be mixed all at once, or may be mixed continuously or intermittently in two or more times.
However, in order to control the sol-gel reaction, which has heretofore been difficult to control, and to prepare the silica precursor more industrially, it is preferable to mix in the following manner. That is, alkoxysilanes, water, a catalyst and a solvent are mixed, and the mixture is aged to hydrolyze and dehydrate and condense alkoxysilanes to some extent. Thereafter, a templating agent is mixed with the above mixture to prepare a silica-based precursor. Thereby, the affinity of alkoxysilanes and a templating agent can be maintained under sol-gel reaction conditions. The aging may be performed after mixing the mixture and the templating agent.

  During the ripening, heating is preferably performed in order to advance hydrolysis / dehydration condensation reaction of alkoxysilanes. The heating condition is not particularly limited as long as it does not exceed the boiling point of the solvent to be used, but it is usually 40 ° C. or higher, preferably 50 ° C. or higher, and particularly preferably 60 ° C. or higher. If the heating temperature is too low, the reaction time becomes extremely long, and the productivity may decrease. On the other hand, the upper limit of the heating temperature is preferably 100 ° C. or less, and more preferably 95 ° C. or less. If it exceeds 100 ° C., the water in the silica-based precursor will boil, and the decomposition / dehydration condensation reaction may not be controlled.

  The aging time is not limited, but is usually 10 minutes or more, preferably 20 minutes or more, more preferably 30 minutes or more, and usually 10 hours or less, preferably 8 hours or less, more preferably 5 hours or less. If the aging time is too short, it may be difficult to proceed with the aging reaction uniformly.If the aging time is too long, the volatilization of the solvent cannot be ignored, the composition ratio changes, and the stability of the silica precursor decreases, There is a possibility that the water resistance of the obtained laminated film is lowered.

Furthermore, although there is no restriction | limiting in the pressure conditions at the time of ageing | curing | ripening, Usually, it matures by a normal pressure. When the pressure changes, the boiling point of the solvent also changes, and the solvent during aging volatilizes (evaporates), the composition ratio changes, the stability of the silica-based precursor becomes low, and the laminated film has high water resistance. May not be obtained.
Further, it is preferable that the silica-based precursor is further mixed with an organic solvent and diluted after the aging and before the film forming step. Thereby, the sol-gel reaction rate in a silica type precursor can be reduced, and it becomes possible to maintain the pot life of a silica type precursor long.

2-2. Step of surface-treating translucent substrate It is preferable to wash the translucent substrate surface before applying the silica-based precursor. In addition to cleaning the surface of the light-transmitting substrate, surface treatment may be applied to the area where the silica-based precursor is applied on the surface of the light-transmitting substrate, if necessary.
As a method for cleaning the light-transmitting substrate, for example, as a chemical method, acids such as hydrofluoric acid, sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid, alkanes such as aqueous sodium hydroxide, hydrogen peroxide and concentrated sulfuric acid, hydrochloric acid, ammonia Examples of the physical method include immersion in a mixed liquid such as heat treatment in vacuum, ion sputtering, UV ozone treatment, corona treatment, and plasma treatment. In the surface treatment, heating and immersion in strong acids such as concentrated sulfuric acid, hydrochloric acid and nitric acid can be mentioned.

  Furthermore, there is a method of forming an adsorbing layer such as a surfactant or a polymer electrolyte for a light-transmitting substrate having poor adhesion to the laminated film. These methods can be performed alone or in any combination of two or more.

2-3. Silica-based precursor coating step The silica-based precursor coating method can be a wet method, and is not particularly limited. For example, spin coating, spray coating, dip coating, curtain coating, inkjet, and the like. Methods such as a method, a roll coating method, a blade coating method, a screen printing method, and a die coating method are used.

Among these, from the viewpoint of film homogeneity, spin coating, spray coating, dip coating, curtain coating, roll coating, and die coating are preferable, and spin coating, dip coating, spray coating, and die coating are particularly preferable. preferable.
For example, when the silica-based precursor is formed into a film by a casting method such as die coating, the casting speed is not limited, but is usually 0.1 m / min or more, preferably 0.5 m / min or more, more preferably 1 m / min. Min. Or more, and usually 1000 m / min or less, preferably 700 m / min or less, more preferably 500 m / min or less. If the casting speed is too slow, the film thickness may be uneven. If it is too fast, it may be difficult to control the wettability between the light-transmitting substrate and the silica-based precursor.

  In the dip coating method, the translucent substrate may be dipped in the coating solution and pulled up at an arbitrary speed. The pulling speed at this time is not limited, but is usually 0.01 mm / second or more, preferably 0.05 mm / second or more, more preferably 0.1 mm / second or more, and usually 50 mm / second or less, preferably 30 mm / second. Second or less, more preferably 20 mm / second or less. If the pulling speed is too slow or too fast, the film thickness of the laminated film may be uneven. On the other hand, although there is no restriction | limiting in the speed | rate which immerses a translucent base material in a coating liquid, Usually, it is preferable to immerse a translucent base material in a coating liquid at a speed | rate comparable as a raising speed. Further, the immersion may be continued for an appropriate period of time after the translucent substrate is immersed in the coating solution and then pulled up. There is no limitation on the duration of this immersion, but it is usually 1 second or more, preferably 3 seconds or more, more preferably 5 seconds or more, and usually 48 hours or less, preferably 24 hours or less, more preferably 12 hours or less. is there. If this time is too short, the adhesiveness to the light-transmitting substrate may be inferior, and if it is too long, a film may be formed during immersion and the smoothness may be inferior.

  Furthermore, when the silica-based precursor is applied and formed by spin coating, the rotation speed is usually 10 revolutions / minute or more, preferably 50 revolutions / minute or more, more preferably 100 revolutions / minute or more, and usually 100,000 revolutions / minute. Min or less, preferably 50000 revolutions / minute or less, more preferably 10,000 revolutions / minute or less. If the rotational speed is too slow, there may be unevenness in the film thickness of the laminated film to be formed.If it is too fast, the vaporization of the solvent will easily proceed, and the reaction such as hydrolysis of alkoxysilanes will not proceed sufficiently, resulting in water resistance. May be inferior.

However, in the silica precursor coating step in the production method of the present invention, the relative humidity is usually 20% or more, preferably 25% or more, more preferably 30% or more, and usually 85% or less, preferably 80% or less, More preferably, the coating is performed in an environment of 75% or less. By setting the relative humidity in the coating process within the above range, a film having high surface smoothness can be obtained.
There is no restriction | limiting in the atmosphere in an application | coating process. For example, the film may be formed in an air atmosphere, or may be applied in an inert atmosphere such as argon.

  Moreover, although there is no restriction | limiting in the temperature at the time of performing an application | coating process, Usually, 0 degreeC or more, Preferably it is 10 degreeC or more, More preferably, it is 20 degreeC or more, Usually, 100 degreeC or less, Preferably it is 80 degreeC or less, More preferably, it is 70 degreeC. Hereinafter, it is more preferably 60 ° C. or less, particularly preferably 50 ° C. or less, particularly preferably 40 ° C. or less. If the temperature at the time of application is too low, the solvent is difficult to evaporate and the surface smoothness of the film may be lowered. If it is too high, the curing of the alkoxysilanes proceeds rapidly and the film distortion may increase.

  Although there is no restriction | limiting in the pressure at the time of performing an application | coating process, Usually 0.05 Mpa or more, Preferably it is 0.08 Mpa or more, More preferably, it is 0.1 Mpa or more, Usually, 0.3 Mpa or less, Preferably it is 0.2 Mpa or less. Preferably it is 0.15 MPa or less. If the pressure is too low, the solvent tends to evaporate and the leveling effect after film formation cannot be obtained, and the smoothness of the film may decrease.If it is too high, the solvent is difficult to evaporate and the surface property of the film may decrease. There is sex.

  Incidentally, there is a difference in drying speed between the dip coating method and the spin coating method, and a slight difference may occur in the stable structure of the film immediately after coating. This can be adjusted by changing the atmosphere during film formation. In addition, the slight difference in the stable structure of the film can be dealt with by the surface treatment of the translucent substrate.

2-4. Firing step The method for heat-treating the silica-based precursor is not particularly limited. For example, an in-furnace baking method in which a translucent base material is disposed in a heating furnace (baking furnace) to heat the silica-based precursor film, a plate (Hot plate) A hot plate system in which a translucent substrate is mounted and the silica-based precursor film is heated via the plate, a heater is disposed on the upper surface side and / or the lower surface side of the translucent substrate, Examples include a method of heating a silica-based precursor film by irradiating electromagnetic waves (for example, infrared rays) from a heater.

  There is no restriction on the heating temperature, and it is optional as long as the silica-based precursor can be cured, but it is usually 100 ° C or higher, preferably 230 ° C or higher, more preferably 300 ° C or higher, further preferably 320 ° C or higher, particularly preferably 350 ° C or higher. Also, it is usually 800 ° C. or lower, more preferably 550 ° C. or lower, and further preferably 450 ° C. or lower. If the heating temperature is too low, the refractive index of the resulting film (that is, the laminated film) may not decrease or may be colored. On the other hand, if the heating temperature is too high, the linear expansion of the translucent base material and the laminated film is different, and peeling or the like may occur. In the heating step, the heating may be performed continuously at the heating temperature, but the heating may be performed intermittently.

  When heating, the rate of temperature increase is arbitrary as long as the effect of the present invention is not significantly impaired, but is usually 1 ° C./min or more, preferably 10 ° C./min or more, and usually 500 ° C./min or less, preferably 300. The temperature is raised at a temperature of ℃ / min or less. If the rate of temperature increase is too slow, the film may become dense, resulting in increased film strain and reduced water resistance, and if the rate of temperature increase is too high, the film strain may be increased and water resistance may be decreased. .

  The heating time is arbitrary as long as the effect of the present invention is not significantly impaired, but is usually 30 seconds or more, preferably 1 minute or more, more preferably 2 minutes or more, and usually 5 hours or less, preferably 2 hours or less, More preferably, it is 1 hour or less. If the heating time is too short, the templating agent may not be sufficiently removed, and if it is too long, the reaction of the alkoxysilane proceeds and the adhesion to the light-transmitting substrate may be reduced.

The pressure at the time of heating is arbitrary as long as the effect of the present invention is not significantly impaired, but a reduced pressure environment is preferable. This is because the vaporization of the solvent proceeds more than the reaction of alkoxysilane, which may result in a film having poor water resistance. From this viewpoint, in the heating step, the pressure is usually 0.2 MPa or less, preferably 0.15 MPa or less, more preferably 0.1 MPa or less. On the other hand, the lower limit of the pressure is not limited, but is usually 10 ⁻⁴ MPa or more, preferably 10 ⁻³ MPa or more, more preferably 10 ⁻² MPa or more. If the pressure is too low, the vaporization of the solvent proceeds more than the reaction of alkoxysilane, which may result in a film with poor water resistance.

  The atmosphere during heating is arbitrary as long as the effects of the present invention are not significantly impaired. Among them, an environment in which drying unevenness is unlikely to occur is preferable. Among these, it is preferable to perform heating in an air atmosphere. It is also possible to perform an inert gas treatment and dry in an inert atmosphere.

2-5. Cooling Step In the cooling step, the laminated film that has reached a high temperature in the heating step is cooled. At this time, the cooling rate is not particularly limited, but is usually 0.1 ° C./min or more, preferably 0.5 ° C./min or more, more preferably 0.8 ° C./min or more, further preferably 1 ° C./min or more. Also, it is usually 50 ° C./min or less, preferably 30 ° C. or less, more preferably 20 ° C./min or less, and further preferably 10 ° C./min or less. If the cooling rate is too slow, the production cost may increase, and if it is too fast, the film quality is expected to deteriorate due to the difference in linear expansion between the translucent substrate and the laminated film.

  The atmosphere in the cooling step is arbitrary as long as the effects of the present invention are not significantly impaired, and may be, for example, a vacuum environment or an inert gas environment. Furthermore, although there is no restriction | limiting in temperature and humidity, normally it cools at normal temperature and normal humidity.

2-6. Silylation treatment By treating the obtained laminated film with a silylating agent, the surface can be made more excellent in functionality. By treating with a silylating agent, hydrophobicity is imparted to the laminated film, and contamination of the pores due to contamination can be prevented.

  Examples of the silylating agent include trimethylmethoxysilane, trimethylethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, methyltrimethoxysilane, methyltriethoxysilane, dimethylethoxysilane, methyldiethoxysilane, dimethylvinylmethoxysilane, and dimethyl. Alkoxysilanes such as vinylethoxysilane, diphenyldimethoxysilane, diphenyldiethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, trimethylchlorosilane, dimethyldichlorosilane, methyltrichlorosilane, methyldichlorosilane, dimethylchlorosilane, dimethylvinylchlorosilane, Methyl vinyl dichlorosilane, methyl chloro disilane, triphenyl chloro silane, methyl diphenyl chloro Chlorosilanes such as silane, diphenyldichlorosilane, hexamethyldisilazane, N, N′-bis (trimethylsilyl) urea, N-trimethylsilylacetamide, dimethyltrimethylsilylamine, diethyltriethylsilylamine, trimethylsilylimidazole and other silazanes, (3, 3,3-trifluoropropyl) trimethoxysilane, (3,3,3-trifluoropropyl) triethoxysilane, pentafluorophenyltrimethoxysilane, pentafluorophenyltriethoxysilane, etc. And alkoxysilanes having a group. These can be used alone or in combination of two or more in any ratio and combination.

  Silylation can be performed by applying a silylating agent to the laminated film, immersing the laminated film in the silylating agent, or exposing the laminated film to the vapor of the silylating agent.

3. Other Steps In the production method of the present invention, unless the effects of the present invention are significantly impaired, an arbitrary step is performed at any stage before, during and after each step in the formation process of the laminated film described above. May be. In addition to the process of forming the laminated film, an arbitrary process can be performed at an arbitrary stage as necessary.

  In the production method of the present invention, the laminated film of the present invention is formed into a film shape. However, if the film is formed into a shape other than the film shape, a forming step of forming into a predetermined shape may be performed instead of the coating step. .

C. Next, the solar cell module of the present invention will be described. The solar cell as used in the present invention is an element or device capable of converting light energy into electric power using the photovoltaic effect, and the solar cell module is one or more solar cells. The structure provided with a protective member.

The solar cell module of the present invention has the above-mentioned “A. Laminated cover substrate for solar cells”.
According to this invention, since it has the said laminated | stacked cover substrate for solar cells, there is little reflection of solar energy, and it becomes possible to take in solar energy very efficiently in a photovoltaic cell. Therefore, a solar cell module with high power generation efficiency can be obtained. Moreover, since the said laminated | stacked cover substrate for solar cells is high in glare-proof property, when the solar cell module of this invention is used for a roof or a wall surface, it also has the advantage that a reflected light pollution cannot be made.

  Examples of solar cells that can be used in the solar cell module of the present invention include silicon solar cells such as single crystal silicon solar cells, polycrystalline silicon solar cells, and amorphous silicon solar cells, CIS solar cells, CIGS solar cells, GaAs A compound solar cell such as a solar cell, a dye-sensitized solar cell, an organic thin film solar cell, a multi-junction solar cell, and a HIT solar cell are exemplified, but not limited thereto.

  Various types of structures of the solar cell module have been studied, but the structure of the solar cell module of the present invention is not particularly limited. A typical example is a super straight type. As a specific structure of the super straight type solar cell module, a plurality of solar cells connected in series or in parallel are arranged, and the laminated cover substrate for solar cells of the present invention is arranged on the light receiving surface side as a surface protection member. A weather resistant film is disposed as a back surface protection member on the non-light receiving surface side. A transparent filler is sealed between the solar cells.

  As the weather resistant film, for example, a multilayer film in which aluminum or the like is sandwiched between fluororesins is used. Examples of the transparent filler include EVA (ethylene-vinyl acetate copolymer) and polyvinyl butyral. Moreover, as a structure of a photovoltaic cell, it can be set as the structure which pinched | interposed the semiconductor layer between a pair of electrode layers, for example. The kind of solar cell is not particularly limited, and a widely used solar cell can be arbitrarily used.

  Another representative example is a substrate integrated solar cell module. As a structure of the substrate integrated solar cell module, for example, a transparent electrode layer, a thin film semiconductor layer, and a back electrode layer are sequentially laminated on the laminated cover substrate for solar cells of the present invention and patterned. As the transparent electrode layer, for example, an oxide such as ITO or IZO (indium zinc oxide) or a metal thin film is used. As the thin film semiconductor layer, for example, amorphous silicon, thin film crystalline silicon, a composite thereof, or the like is used. Furthermore, as the back electrode layer, for example, a conductive thin film such as aluminum or silver is used.

  In the solar cell module of the present invention, regardless of the module structure, the laminated cover substrate for solar cells is a protective member on the light receiving surface side, and the surface having the above-described surface roughness faces the light receiving surface side (module outside) Used in The solar cell module may be configured such that the solar cell laminated cover substrate is the outermost layer. For example, a functional layer such as an antifouling layer may be provided on the outer side of the solar cell laminated cover substrate. Good.

  Examples of the functional layer include a heat ray blocking layer, an ultraviolet deterioration preventing layer, a hydrophilic layer, an antifouling layer, an antifogging layer, a moisture proof layer, an adhesive layer, a hard layer, a conductive layer, a reflective layer, an antiglare layer, and a diffusion layer. A layer etc. are mentioned, These can be used by laminating | stacking 1 layer independent or 2 layers or more in arbitrary combinations. In particular, the solar cell module of the present invention preferably has a heat ray blocking layer in order to reduce a decrease in power generation efficiency of the solar cell due to heat generated by sunlight irradiation.

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the description of the following examples unless departing from the gist thereof.
In the following, the centerline average surface roughness Ra and the maximum height Rmax of the surface roughness are 3 with a surface roughness profile measuring machine (Surfcom 570A manufactured by Tokyo Seimitsu Co., Ltd.) under the condition of one scanning distance of 30 mm. The average value measured once was calculated.

The refractive index is J. A. The value at a wavelength of 550 nm measured with a spectroscopic ellipsometer manufactured by Woollam Co., Ltd. is used.
The film thickness was estimated by observing the fracture surface of the laminated cover substrate with an electron microscope.
The total light transmittance Tt of D65 light was measured with a haze meter (HZ-2 manufactured by Suga Test Instruments Co., Ltd.). In addition, the total light transmittance of the translucent base material before forming a laminated body was set to Tt_sub, and the total light transmittance of the laminated cover board | substrate for solar cells was set to Tt_ar.

The reflectance R was measured with a spectrophotometer (U-4000 manufactured by Hitachi, Ltd.) equipped with a 5 ° specular reflection accessory (P / N132-0462). The maximum value of the measured value in the wavelength range of 400 to 800 nm is R-max.
The viscosity was determined by measuring the viscosity at a shear rate of 100 sec ⁻¹ using ARES-FRT100 manufactured by Rheometrics.

Example 1
[Preparation of silica-based precursor]
1.70 g of tetraethoxysilane, 1.73 g of methyltriethoxysilane, and 0.58 g of ethanol (boiling point: 78.3 ° C.) are mixed. Further, 1.39 g of water and 3.26 g of 0.3 wt% hydrochloric acid aqueous solution as a catalyst. And a mixture (A) was prepared by stirring in a water bath at 60 ° C. for 30 minutes and further at room temperature for 30 minutes.

  Next, 0.61 g of polyethylene oxide-polypropylene oxide-polyethylene oxide triblock polymer (weight average molecular weight 5,800, ratio of ethylene oxide moiety 30 wt%) manufactured by ALDRICH as a templating agent was mixed with ethanol 0.8 g. It was set as the mixture (B). The said mixture (A) was mixed with the mixture (B), and it stirred at room temperature for 60 minutes, and prepared the mixture (C).

10 ml of this mixture (C) and 10 ml of 1-butanol (boiling point 117.3 ° C.) as a dilution solvent were mixed and stirred at room temperature for 30 minutes, and then with a 0.20 μm filter (manufactured by Whatman Japan Co., Ltd.). The composition (D) (silica-based precursor) was obtained by filtering.
In this composition (D), the ratio of silicon atoms derived from tetraethoxysilane, water, and templating agent to silicon atoms derived from all alkoxysilanes (tetraethoxysilane and methyltriethoxysilane) was 0.46. 14.4 and 0.0059 (mol / mol).
The obtained silica precursor had a pH of 1 and a viscosity of 0.005 Pas · sec.

[Manufacture of laminated cover substrates for solar cells]
On a smooth glass (centerline average surface roughness Ra = 0.01 μm, maximum height of surface roughness Rmax = 0.13 μm), the silica-based precursor was spin-coated at 500 rpm for 2 minutes (Mikasa ( The substrate for spin-refractive index measurement of the laminated film was obtained by spin-coating with a hot plate at 450 ° C. for 2 minutes and cooling at room temperature for 5 minutes. The refractive index of the obtained laminated film was 1.25.

  Next, 1 ml of the silica-based precursor was uniformly dropped on the blasted glass (average surface roughness Ra = 0.47 μm, maximum height Rmax = 4.76 μm, size 76 mm × 52 mm). Then, spin coat with a spin coater (manufactured by Mikasa Co., Ltd.) under conditions of 500 rpm for 2 minutes, bake on a 450 ° C. hot plate (manufactured by ASONE Co., Ltd.) for 2 minutes, and cool at room temperature for 5 minutes. Thus, a laminated cover substrate for a solar cell including a laminated body having a refractive index of 1.25 was obtained. The center line average surface roughness Ra of the obtained laminated cover substrate for solar cells was 0.49 μm, and the maximum height Rmax of the surface roughness was 5.77 μm. The maximum film thickness of the laminated film was 1.2 μm. The results of the total light transmittance Tt and the reflectance of the obtained laminated cover substrate for solar cells are shown in Table 1.

(Example 2)
A silica-based precursor was prepared in the same manner as in Example 1. Thereafter, 0.5 ml of the silica-based precursor was uniformly dropped on the blasted glass (center line average surface roughness Ra = 1.11 μm, maximum height of surface roughness Rmax = 11.73 μm), 500 rpm, Spin coating was performed in the same manner as in Example 1 under conditions of 2 minutes, baking was performed on a hot plate at 450 ° C. for 2 minutes, and cooling was performed at room temperature for 5 minutes to obtain a laminated cover substrate for a solar cell.

  When the refractive index of the laminated film was measured in the same manner as in Example 1, the refractive index of the obtained laminated film was 1.25. Moreover, the center line average surface roughness Ra of the laminated cover substrate for solar cells was 1.09 μm, and the maximum height Rmax of the surface roughness was 10.60 μm. The maximum film thickness of the laminated film was 400 nm. The results of the total light transmittance Tt and the reflectance of the obtained laminated cover substrate for solar cells are shown in Table 1.

(Example 3)
A silica-based precursor was prepared in the same manner as in Example 1. Thereafter, 1 ml of the silica-based precursor is uniformly dropped on glass (center line average surface roughness Ra = 2.55 μm, maximum height of surface roughness Rmax = 22.89 μm), under conditions of 500 rpm for 2 minutes. Spin coating was performed in the same manner as in Example 1, baking was performed on a hot plate at 450 ° C. for 2 minutes, and cooling was performed at room temperature for 5 minutes to obtain a laminated cover substrate for a solar cell.

When the refractive index of the laminated film was measured in the same manner as in Example 1, the refractive index of the obtained laminated film was 1.25. Moreover, the center line average surface roughness Ra of the laminated cover substrate for solar cells was 2.51 μm, and the maximum height Rmax of the surface roughness was 24.45 μm. The maximum film thickness of the laminated film was 600 nm. Table 1 shows the results of the total light transmittance Tt and the reflectance of the obtained laminated cover substrate for solar cells.
(Comparative Example 1)
In the same manner as in Example 1, the composition (D) of Example 1 was obtained. A silica-based precursor was prepared by mixing 4 ml of this composition (D) and 6 ml of 1-butanol as a diluent solvent.

  The resulting silica-based precursor had a pH of 1 and a viscosity of 0.003 Pas · sec. Thereafter, 1 ml of the silica-based precursor was uniformly dropped onto glass without treatment (center line average surface roughness Ra = 0.01 μm, maximum height of surface roughness Rmax = 0.13 μm), and 500 rpm for 2 minutes. The film was spin-coated in the same manner as in Example 1, baked on a hot plate at 450 ° C. for 2 minutes, and cooled at room temperature for 5 minutes to obtain a laminated cover substrate for a solar cell.

  The obtained laminated film had a refractive index of 1.25, the center line average surface roughness Ra of the laminated cover substrate was 0 μm, and the maximum height Rmax of the surface roughness was 0.16 μm. The maximum film thickness of the laminated film was 160 nm. Table 1 shows the results of the total light transmittance Tt and the reflectance of the obtained laminated cover substrate for solar cells.

  As shown in Table 1, in Examples 1 to 3, the specular reflection R-max in the visible light wavelength region (400 to 800 nm) is sufficiently small, so that it has excellent antiglare properties and the total light transmittance Tt is also remarkably high. It is greatly improved, and it can be seen that it has excellent performance that achieves both antiglare and antireflection properties.

  The present invention can be used for any industrial solar cell. In particular, according to the present invention, since it has an antiglare property and an antireflection function, it can be used for, for example, a roof or a wall surface. Suitable for batteries.

DESCRIPTION OF SYMBOLS 1 Translucent base material 2 Laminated film

Claims (10)

A laminated cover substrate for a solar cell in which a laminated film having a refractive index of 1.05 to 1.3 is laminated on one side and / or both sides of a translucent substrate,
The center line average surface roughness Ra on the light receiving surface side is 0.3 μm to 10 μm, and the maximum height Rmax of the surface roughness is 0.1 μm to 50 μm,
The maximum height Rmax of the surface roughness on the light receiving surface side of the translucent substrate is 11.73 to 50 μm,
The laminated film, that Yusuke on the light-receiving surface side of at least the above ToruHikarimoto material
Laminated cover substrate for a solar cell, wherein a call. The laminated cover substrate for a solar cell according to claim 1, wherein the laminated film has a maximum film thickness of 50 nm to 10 μm. The laminated cover substrate for a solar cell according to claim 1 or 2, wherein the translucent substrate is tempered glass. 4. The laminated cover substrate for a solar cell according to claim 1, wherein the area is 0.1 m ² or more. The laminated cover substrate for a solar cell according to any one of claims 1 to 4, wherein the total light transmittance of D65 light is 80% or more. It has a heat ray blocking layer, The laminated cover board for solar cells of any one of Claims 1-5 characterized by the above-mentioned. It has a laminated cover board | substrate for solar cells of any one of Claims 1-6, The solar cell module characterized by the above-mentioned. It is a manufacturing method of the lamination | stacking cover board | substrate for solar cells of any one of Claims 1-6, Comprising: The said laminated film is formed using the silica type precursor of the viscosity of 0.05 Pas * sec or less containing a templating agent. The manufacturing method of the laminated cover board | substrate for solar cells characterized by having the formation process to do. The method for producing a laminated cover substrate for a solar cell according to claim 8, wherein the silica-based precursor has a pH of 2 or less. 10. The method for manufacturing a laminated cover substrate for a solar cell according to claim 8, wherein a heating step of 100 ° C. to 800 ° C. is performed in the process of forming the laminated film.

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