JP2019117906A - Protective sheet for solar cell and solar cell module - Google Patents

Abstract

To provide a protective sheet for solar cell or a solar cell module having the same, capable of achieving excellent heat resistance and high generation efficiency obtained of a solar cell.SOLUTION: The protective sheet for solar cell includes: a composite base material 10 including a fibrous material having a refractive index within a range of 1.50-1.62 at 25°C and a wavelength of 550 nm and resin with refractive index within a range of 1.50-1.62 at 25°C and a wavelength of 550 nm and having a content of a fibrous material to a total mass of the resin and the fibrous material of 10 mass%-80 mass%; a surface base material 11 with a refractive index within a range of 1.47-1.55 at 25°C and a wavelength of 550 nm, which are laminated.SELECTED DRAWING: Figure 1

Description

  The present disclosure relates to a solar cell protective sheet and a solar cell module.

DESCRIPTION OF RELATED ART Conventionally, the technique regarding the solar cell module containing a solar cell element and the protective sheet for solar cells which is one member of a solar cell module is known.
For example, Patent Document 1 describes a resin-based composite film material obtained by applying a mixture of a resin and a curing agent to a fibrous material and curing the mixture.

International Publication No. 2017/140002

In patent document 1, when the reinforced glass is used for protection of a solar cell by laminating | stacking the resin type composite film material containing the above-mentioned fibrous material, and a fluororesin film and using it as a protective sheet for solar cells, In comparison, it is described that the weight reduction of the solar cell module can be achieved.
As a result of intensive investigations, the present inventors have excellent heat resistance when using a solar cell protective sheet in which the resin-based composite film material described in Patent Document 1 and a fluororesin film are laminated. The inventors have found that there is a problem that the light transmission is low and the power generation efficiency of the solar cell is low.

  The problem to be solved by the embodiment according to the present disclosure is to provide a solar cell protective sheet having excellent heat resistance and high power generation efficiency of a solar cell to be obtained, or a solar cell module including the above solar cell protective sheet. It is.

Specific means for solving the problems include the following aspects.
<1> Fibrous material whose refractive index at a wavelength of 550 nm is in the range of 1.50 to 1.62, and refractive index at 25 ° C. at a wavelength of 550 nm within the range of 1.50 to 1.62 A composite substrate containing a certain resin, wherein the content of the fibrous material is 10% by mass to 80% by mass with respect to the total mass of the resin and the fibrous material;
A surface substrate having a refractive index at 25 ° C. and a wavelength of 550 nm within the range of 1.47 to 1.55;
Protective sheet for solar cells.
The solar cell protective sheet as described in said <1> whose transmittance | permeability of the light of <2> 25 degreeC and wavelength 550 nm is 80% or more.
The protective sheet for solar cells as described in said <1> or <2> whose <3> above-mentioned fibrous material is glass fiber.
<4> The sun according to any one of <1> to <3>, wherein the resin is at least one resin selected from the group consisting of polyester resin, epoxy resin, acrylic resin, and urethane resin. Battery protection sheet.
The protective sheet for solar cells as described in any one of said <1>-<4> further equipped with a hard-coat layer on the surface on the opposite side to the composite base material of <5> said surface base material.
The solar cell protective sheet as described in any one of <1>-<5> further equipped with an adhesive layer between <6> the said surface base material and the said composite base material.
<7> A device structure including a solar cell device and a sealing material for sealing the solar cell device,
The solar cell protective sheet according to any one of the above <1> to <6>, which is disposed on the side where sunlight is incident on the element structure part,
A solar cell back sheet disposed on the side opposite to the side where sunlight is incident on the element structure portion;
Solar cell module.

  According to an embodiment of the present disclosure, there is provided a solar cell protective sheet having excellent heat resistance and high power generation efficiency of a solar cell to be obtained, or a solar cell module including the solar cell protective sheet. it can.

It is a schematic sectional drawing which shows an example of a solar cell module provided with the protective sheet for solar cells concerning this indication. It is a schematic sectional drawing which shows an example of the composite base material used in this indication. It is a schematic sectional drawing which shows the structure of the solar cell module manufactured in the Example.

In the present disclosure, a numerical range represented using “to” means a range including numerical values described before and after “to” as the lower limit value and the upper limit value.
In the present disclosure, the amount of each component in the composition means the total amount of the plurality of substances present in the composition unless a plurality of substances corresponding to each component are present in the composition. Do.
In the present disclosure, the term "step" is included in the term if the intended purpose of the step is achieved, even if it can not be clearly distinguished from other steps, as well as independent steps.
In the present disclosure, “(meth) acrylic” means at least one of acrylic and methacrylic, and “(meth) acrylate” means at least one of acrylate and methacrylate.
In the present disclosure, "solid content" refers to all components except the solvent.
In the present disclosure, the “front sheet for solar cell” refers to a sheet disposed on the side where sunlight is incident as viewed from the solar cell element in the solar cell module.
In the present disclosure, the “solar cell back sheet” refers to a sheet disposed on the side opposite to the side on which sunlight is incident, as viewed from the solar cell element, in the solar cell module.
In the present disclosure, “a protective sheet for solar cells” refers to a concept including both the front sheet for solar cells and the back sheet for solar cells in a solar cell module.
In the present disclosure, a combination of preferred embodiments is a more preferred embodiment.

(Protective sheet for solar cells)
The protective sheet for a solar cell according to the present disclosure is a fibrous material having a refractive index of 1.50 to 1.62 at 25 ° C. and a wavelength of 550 nm, and a refractive index of 1.50 at 25 ° C. and a wavelength of 550 nm. A composite base material containing a resin in the range of ̃1.62 and containing 10% by mass to 80% by mass of the fibrous material relative to the total mass of the resin and the fibrous material at 25 ° C., a wavelength It is a protective sheet for solar cells in which the surface base material whose refractive index in 550 nm is within the range of 1.47 to 1.55 is laminated.
Hereinafter, in the present disclosure, when the refractive index is simply described, it refers to the refractive index at a wavelength of 550 nm at 25 ° C. unless otherwise specified.
As a result of intensive studies, the present inventors have found that the protective sheet for a solar cell according to the present disclosure is excellent in heat resistance, and the power generation efficiency of the obtained solar cell is high.
The mechanism by which the above effect is obtained is unknown, but is presumed as follows.
In the composite substrate, the refractive index of the fibrous material in the composite substrate is in the range of 1.50 to 1.62, and the refractive index of the resin is in the range of 1.50 to 1.62. It is considered that scattering of light at the interface between the resin and the fibrous material is suppressed, and a solar cell protective sheet having high light transmittance can be obtained. Therefore, when the solar cell protective sheet containing such a composite base material is used for a solar cell, it is estimated that it is excellent in power generation efficiency.
Furthermore, when the refractive index of the surface substrate is in the range of 1.47 to 1.55, reflection of light at the interface between the composite substrate and the surface substrate is reduced, and the power generation efficiency of the solar cell is excellent. Conceivable.
In addition, since the deformation due to heat and the like is suppressed by containing the fibrous material in the composite substrate, it is considered that the heat resistance is also excellent.

FIG. 1 is a schematic cross-sectional view showing an example of a solar cell module provided with a solar cell protective sheet according to the present disclosure.
The solar cell module illustrated in FIG. 1 is also an example of a solar cell module according to the present disclosure described later.

  As shown in FIG. 1, the solar cell module 100 according to this example includes a sealing material 34 (for example, ethylene-vinyl acetate copolymer (EVA) that seals the solar cell element 32 and the solar cell element 32. Element structure portion 36 including a sealing material, a solar cell front sheet 20 disposed on the side where the sunlight 50 is incident to the element structure portion 36, and the sunlight 50 to the element structure portion 36. And a solar cell back sheet 40 disposed on the side opposite to the incident side.

The solar cell front sheet 20 is an example of a solar cell protective sheet according to the present disclosure.
The front sheet 20 for solar cells is a composite substrate 10 and a surface substrate 11 (first layer) laminated on one surface of the composite substrate 10 (specifically, the surface on the side on which the sunlight 50 is incident). And a hard coat layer 12 (second layer) disposed on the surface of the first layer.
The hard coat layer 12 may be omitted.
On the surface of the hard coat layer 12 opposite to the surface substrate 11 (if the hard coat layer 12 is omitted, on the surface of the surface substrate 11 opposite to the composite substrate 10) , And may further have other layers such as an antireflective layer.
Further, between the hard coat layer 12 and the surface base 11 (in the case where the hard coat layer 12 is omitted, the surface base 11 on the surface opposite to the composite base 10) is irradiated with ultraviolet light. You may further have other layers, such as a well-known gas barrier layer etc., such as an absorption layer.
Furthermore, an adhesive layer may be further included between the composite substrate 10 and the surface substrate 11.

The solar cell front sheet 20 further has the third layer 13 and the fourth layer 14 in this order as a back surface layer on the side opposite to the surface substrate 11 and the hard coat layer 12 side as viewed from the composite substrate 10. Prepare. The third layer 13 and the fourth layer 14 have the function of an easy adhesion layer to facilitate adhesion to the element structure 36.
However, the third layer 13 and the fourth layer 14 are not essential, and at least one of the third layer 13 and the fourth layer 14 may be omitted.
In addition, an undercoat layer may be provided on at least one of the surface on the surface substrate 11 side of the composite substrate 10 and the surface on the third layer 13 side. That is, the composite substrate 10 may be a substrate film with an undercoat layer.

The solar cell module 100 may include other members in addition to the above-described members.
Other members include an adhesive layer disposed between the members, a terminal box disposed on the opposite side to the element structure portion 36 with respect to the solar cell back sheet 40, and the like.

The solar cell front sheet 20 is a member to which sunlight 50 is directly incident.
For this reason, the higher the light transmittance of the solar cell front sheet 20, the higher the power generation efficiency of the solar cell.
In this regard, in the solar cell front sheet 20, when the respective refractive indices of the resin and the fibrous material contained in the composite substrate 10 and the surface substrate 11 take specific values, the light transmittance is excellent and excellent. It is considered that the power generation efficiency is high.
Moreover, when using a solar cell especially in places, such as a roof top, it may be required that the deformation | transformation by heat does not occur easily with respect to the solar cell front sheet 20, ie, it is required that it is excellent in heat resistance. is there.
Also in this regard, in the solar cell front sheet 20, the composite substrate 10 is considered to have excellent heat resistance because it contains a fibrous material.

  In the present disclosure, of the two surfaces of the composite substrate in the protective sheet for a solar cell, the surface on which the surface substrate and, if necessary, the hard coat layer (second layer) are formed is referred to as “front side”. In some cases, the surface opposite to the front surface (the surface on which the third layer and the fourth layer are formed if necessary) may be referred to as the "back surface".

  Hereinafter, each element of the protective sheet for solar cells which concerns on this indication is demonstrated.

<Composite substrate>
The protective sheet for a solar cell according to the present disclosure includes a fibrous material having a refractive index in the range of 1.50 to 1.62, and a resin having a refractive index in the range of 1.50 to 1.62. The composite base material which is 10 mass%-80 mass% of content of the said fibrous material with respect to the total mass of the said resin and the said fibrous material is provided.
In the composite substrate, an embodiment in which a resin is contained between fibers of fibrous material is preferable.
The composite substrate may contain at least a part of a fibrous material, and at least a portion of the surface direction of the composite substrate corresponding to the upper part of the solar battery cell. Preferably, it is further preferable that the fibrous material is included in the entire area in the surface direction.
In addition, in the thickness direction of the composite substrate, there may be a place where the fibrous material is not contained.

FIG. 2 is a schematic cross-sectional view showing an example of a composite substrate 10 according to the present disclosure.
The composite substrate 10 comprises a resin 18 and a fibrous material 16. In addition, the inside of the fibrous material 16 is filled with a resin 18.
In FIG. 2, the fibrous material 16 is included in a part of the composite substrate 10 in the thickness direction, and is included in all of the surface directions.

[Fibrous material]
The fibrous material contained in the composite substrate in the present disclosure may be in the form of a single fiber, may be in the form of a woven fabric in which fibers are woven, or may be in the form of a non-woven fabric in which fibers are intertwined. . From the viewpoint of heat resistance and power generation efficiency of the solar cell, it is preferable to be in the form of fiber cloth.
The shape of the woven fabric in the case where the fibrous material is on a woven fabric is not particularly limited, and it may be formed by plain weave, twill weave, rib weave or satin weave or a composite of these weaves.
The basis weight of the case fibrous material is a woven or nonwoven fabric (mass per square ^meter), it is preferably ^{5g / m 2 ~50g / m 2} , a 10g / ^{m 2} ~30g / m 2 Is more preferred.
The diameter of the fibers in the fibrous material is not particularly limited, but is preferably 1 μm to 100 μm.

-Refractive index-
The refractive index of the fibrous material is in the range of 1.50 to 1.62, and from the viewpoint of further improving the power generation efficiency of the obtained solar cell, it is preferably 1.51 to 1.60, and 1 More preferably, it is .52 to 1.58.
In the present disclosure, the refractive index can be determined using an ellipsometer

-Material-
The material of the fibrous material is not particularly limited as long as it satisfies the range of the refractive index, and may be an inorganic material, an organic material, or an organic-inorganic composite material, but from the viewpoint of light resistance And inorganic materials are preferable.
The inorganic material is not particularly limited, but is preferably glass fiber.
The organic material is not particularly limited, but is preferably an aramid fiber.

The composite substrate may contain a fibrous material singly or in combination of two or more.
The content of the fibrous material in the composite substrate relative to the total mass of the resin and the fibrous material is 10% by mass to 80% by mass, preferably 15% by mass to 65% by mass, and 20% by mass It is more preferable that it is 50 mass%.
The content of the fibrous material relative to the total mass of the composite resin is preferably 5% by mass to 80% by mass, and more preferably 10% by mass to 50% by mass.
Moreover, it is preferable that it is 50 mass%-100 mass%, and, as for sum total content of the said resin with respect to the total mass of composite resin, and the said fibrous material, it is more preferable that it is 80 mass%-100 mass%.
The thickness of the fibrous material in the composite substrate is preferably 5 μm to 100 μm, and more preferably 10 μm to 50 μm.
The thermal decomposition temperature of the fibrous material is preferably 300 ° C. or more, more preferably 400 ° C. or more, and still more preferably 500 ° C. or more.
The thermal decomposition temperature is calculated by measuring the temperature at which the mass reduction rate can be maintained at 80% or more when the substance is heated in the air at a temperature rising rate of 10 ° C./min. As a measuring apparatus, it is possible to use TG-DTA apparatus, STA7000 manufactured by Hitachi High-Technologies Corporation, or the like.

-Specific example-
A commercially available product may be used as the fibrous material. Commercially available products include E01Z SK, E02Z SK, E02B SK, E03A, E03E SK, E03C SK, E06B, E06E SK, E06C SK, E09B SK, E10D, E10T, E10A, E10B, E15R, E15A, E18A (all of which are incorporated herein by reference). Preferably manufactured by Co., Ltd.

〔resin〕
The resin contained in the composite substrate in the present disclosure is not particularly limited as long as the range of the refractive index described later is satisfied, but at least one resin selected from the group consisting of polyester resin, epoxy resin, acrylic resin and urethane resin Is preferred.

-Polyester resin-
The polyester resin is not particularly limited, and examples thereof include linear saturated polyesters synthesized from an aliphatic dibasic acid or an ester-forming derivative thereof and a diol or an ester-forming derivative thereof. Specific examples of the linear saturated polyester include condensation products of ethylene glycol and 1, 4-butanedicarboxylic acid, and condensation products of ethylene glycol and cyclohexanecarboxylic acid.

-Epoxy resin-
The epoxy resin is not particularly limited, but novolak epoxy resin, bisphenol epoxy resin, glycidyl amine epoxy resin, glycidyl ether epoxy resin, triphenolmethane epoxy resin, triphenolpropane epoxy resin, alkyl-modified triphenol Methane type epoxy resin, triazine nucleus containing epoxy resin, dicyclopentadiene modified phenol type epoxy resin, naphthol type epoxy resin, naphthalene type epoxy resin, phenol aralkyl type epoxy resin having at least one of phenylene skeleton and biphenylene skeleton, phenylene skeleton and Aralkyl type epoxy resin such as naphthol aralkyl type epoxy resin having at least one of biphenylene skeleton, and aliphatic epoxy resin Etc. The.

-Acrylic resin-
The acrylic resin is not particularly limited as long as it is a resin containing a structural unit having a structural unit derived from acrylic acid, methacrylic acid, an acrylic acid ester compound or a methacrylic acid ester compound, and 50 mass% or more of the above structural units It is preferable that it is resin containing.

-Urethane resin-
Although it does not specifically limit as a polyurethane, For example, polycarbonate-type polyurethane, polyether-type polyurethane, polyester-type polyurethane, these modified products, etc. are mentioned.

-Refractive index-
The refractive index of the resin is in the range of 1.50 to 1.62, and from the viewpoint of further improving the power generation efficiency of the obtained solar cell, it is preferably 1.51 to 1.60, and 1.52 to More preferably, it is 1.58.
Further, from the viewpoint of further improving the power generation efficiency of the solar cell to be obtained, the absolute value of the difference between the refractive index of the fibrous material contained in the composite substrate and the refractive index of the resin contained in the composite substrate is It is preferably 0 to 0.10, and more preferably 0 to 0.05.

-Glass transition temperature-
The glass transition temperature (Tg) of the above-mentioned resin is preferably 70 ° C. to 160 ° C., more preferably 80 ° C. to 140 ° C., from the viewpoint of facilitating the production of a composite substrate by lamination described later. .
In the present disclosure, Tg can be a value measured under a normal measurement condition using a differential scanning calorimeter (DSC) EXSTAR 6220 manufactured by SII Nano Technology Inc.
However, when measurement is difficult due to decomposition of the polymer, etc., the calculated Tg calculated by the following formula is applied. The calculated Tg is calculated by the following equation T.
1 / Tg = Σ (Xi / Tgi) (T)
Here, in the polymer to be calculated, n kinds of monomer components from i = 1 to n are copolymerized. Xi is the mass fraction of the ith monomer (ΣXi = 1), and Tgi is the glass transition temperature (absolute temperature) of the homopolymer of the ith monomer. Is the sum of i = 1 to n. The value of the homopolymer glass transition temperature (Tgi) of each monomer is the value of Polymer Handbook (3rd Edition) (J. Brandrup, EHImmergut (Wiley-Interscience, 1989)).

Moreover, when a composite base material contains 2 or more types of resin as resin, it is preferable that Tg of the resin component in a composite base material is 50 degreeC-180 degreeC, and it is more preferable that it is 60 degreeC-160 degreeC.
The Tg of the resin component is determined as follows.
The Tg of the first resin is Tg 1 (K), the mass fraction of the first resin to the total mass of the resin components is W 1, and the Tg of the second resin is Tg 2 (K), the total of resin components When the mass fraction of the second resin to the mass is W2, the Tg0 (K) of the resin component can be estimated according to the following FOX equation.
FOX formula: 1 / Tg0 = (W1 / Tg1) + (W2 / Tg2)
When the resin component contains three or more resins, the Tg of the resin component is Tgn (K) for the Tg of the nth resin, and the mass fraction of the nth resin to the total mass of the resin component is Wn , And in the same manner as above, it is possible to estimate according to the following equation.
FOX formula: 1 / Tg0 = (W1 / Tg1) + (W2 / Tg2) + (W3 / Tg3)... + (Wn / Tgn)

The composite substrate may contain one kind of resin alone, or may contain two or more kinds.
The content of the resin relative to the total mass of the composite resin is preferably 1% by mass to 30% by mass, and more preferably 5% by mass to 20% by mass.

[Other ingredients]
The composite substrate may further contain other components.
As other components, stabilizers, processing aids, coloring inhibitors, coloring agents, UV absorbers, plasticizers, modifiers, fillers and the like can be mentioned.

[Characteristics of Composite Substrate]
The thickness of the composite substrate is preferably 40 μm to 600 μm, and more preferably 60 μm to 400 μm from the viewpoint of the power generation efficiency of the solar cell obtained and impact resistance.

[Method of producing composite substrate]
Although the manufacturing method of the composite substrate used in the present disclosure is not particularly limited, for example, a method of introducing a resin into a fibrous material by laminating a resin film and a fibrous material at a high temperature, a resin, and According to the method, a composition containing a crosslinking agent is applied to or impregnated in a fibrous material, and the composition is reacted by heating or the like to introduce a resin into the fibrous material.
In the above-mentioned lamination, the surface substrate, the resin film, and the fibrous material may be stacked in this order and simultaneously laminated. In that case, the surface substrate may have an adhesive layer, a hard coat layer, an antireflective layer, an ultraviolet ray absorbing layer, etc. described later.

<Surface base material>
The protective sheet for a solar cell according to the present disclosure contains a surface base material having a refractive index in the range of 1.47 to 1.55.
The surface substrate is not particularly limited as long as the refractive index is in the above range, and a known resin sheet can be used.
Examples of the surface substrate include polyesters such as polyethylene terephthalate as a resin material; polycarbonates; polyolefins such as polypropylene and polyethylene; for example, a substrate containing an acrylic resin such as polymethyl methacrylate, and the surface substrate and the composite substrate It is preferable that it is a base material containing polyolefin or an acrylic resin from the viewpoint of the adhesiveness of the above.

Moreover, as a surface base material, it is preferable that it is a base material containing resin different from the above-mentioned composite base material.
The refractive index of the resin is preferably in the range of 1.47 to 1.55, and preferably 1.48 to 1.53, from the viewpoint of further improving the power generation efficiency of the solar cell obtained. More preferably, it is 1.49 to 1.52.

[Refractive index]
The refractive index of the surface base material is in the range of 1.47 to 1.55, and preferably 1.48 to 1.53 from the viewpoint of further improving the power generation efficiency of the obtained solar cell. More preferably, it is 49 to 1.52.

[Characteristics of surface substrate]
The thickness of the surface substrate is preferably 25 μm to 400 μm, and more preferably 40 μm to 300 μm from the viewpoint of the power generation efficiency of the solar cell obtained and impact resistance.
90% to 93.0% is preferable, 91.0% to 92.8% is more preferable, and 91.8% to 92.5% is further preferable.

<Adhesive layer>
The protective sheet for a solar cell according to the present disclosure preferably includes an adhesive layer between the surface substrate and the composite substrate.
By providing the adhesive layer, the adhesion between the surface substrate and the composite substrate is improved, and a solar cell protective sheet having excellent durability can be obtained.

The adhesive layer includes a layer containing a known pressure-sensitive adhesive or a known adhesive, or a layer containing a cured product of these.
The adhesive layer is preferably a layer obtained by applying a coating solution for forming an adhesive layer containing a resin and a crosslinking agent, and drying or curing the coating solution.
The resin is not particularly limited, but polyolefin resin, urethane resin, polyester resin, acrylic resin, polyvinyl alcohol, polyamide resin, silicone resin and the like can be mentioned, and from the viewpoint of adhesion, polyolefin resin is preferable.
It does not specifically limit as a crosslinking agent, An oxazoline type crosslinking agent, an epoxy-type crosslinking agent, a block isocyanate type crosslinking agent etc. are mentioned, An oxazoline type crosslinking agent is preferable.

  The coating liquid for forming an adhesive layer may further contain known components such as a surfactant and a solvent.

  The thickness of the adhesive layer is preferably 0.2 μm to 10 μm, and more preferably 0.5 μm to 5 μm from the viewpoint of improving the power generation efficiency of the solar cell.

  The adhesive layer is formed, for example, by applying a coating solution for forming an adhesive layer to a surface substrate or a composite substrate and drying it.

<Hard coat layer>
The protective sheet for a solar cell according to the present disclosure preferably further comprises a hard coat layer on the side of the surface substrate opposite to the composite substrate.
By providing the hard coat layer, a solar cell protective sheet having further excellent heat resistance can be obtained. This is considered to be because the permeation of oxygen into the inside of the solar cell protective sheet is suppressed by the hard coat layer, and therefore the deterioration of the surface base material due to oxygen is suppressed.
The hard coat layer is not particularly limited, and examples thereof include known hard coat layers in the field of solar cells. For example, JP-A-2013-45045, JP-A-2013-43352, and JP-A-2012-232459 JP 2012-128157, JP 2011-131409, JP 2011-131404, JP 2011-126162, JP 2011-75705, JP 2009-286981, and the like JP 2009-263567, JP 2009-75248, JP 2007-164206, JP 2006-96811, JP 2004-75970, JP 2002-156505, JP 2001 No.-272 503, WO 12/018087, When Publication No. 12/098967, WO 12/086659, may be made of a hard coat layer as described in WO 11/105594.

Further, the pencil hardness of the surface of the hard coat layer is preferably B or more from the viewpoint of the scratch resistance of the protective sheet for solar cells, and the pencil hardness of the surface of the hard coat layer is more preferably HB or more , F or more is more preferable.
The upper limit of the pencil hardness of the surface of the hard coat layer is not particularly limited, but the upper limit of the pencil hardness of the surface of the hard coat layer is preferably 3H or less, more preferably 2H or less.
In addition, the pencil hardness of the surface of a hard-coat layer means the value measured based on JISK5600-5-4: 1999. As a pencil, Hiyuni manufactured by Mitsubishi Pencil Co., Ltd. is used.

Hereinafter, preferred embodiments of the hard coat layer will be described.
The hard coat layer preferably contains at least one siloxane resin containing a constitutional unit represented by the following formula S1 and a constitutional unit represented by the following formula S2.
[* -SiO _3/2 ] Formula S1
[SiO _4/2 ] Formula S2
In formula S1, * represents a binding site to another structure. However, at the aforementioned bonding site, the Si atom in the formula S1 is not directly bonded to the O atom.
When the hard coat layer contains at least one siloxane resin, the scratch resistance (for example, the scratch resistance against external force such as scratching and abrasion) of the hard coat layer can be secured. In addition, when the hard coat layer contains a siloxane resin, the transparency of the hard coat layer can also be secured.

[Siloxane resin]
The siloxane resin contained in the hard coat layer is not particularly limited as long as it is a compound including the structural unit represented by Formula S1 and the structural unit represented by Formula S2. The siloxane resin in the present disclosure does not include silica particles which are inorganic particles described later.
The siloxane resin contained in the hard coat layer may be only one type or two or more types.

It is preferable that the structural unit represented by Formula S1 is a structural unit derived from the trifunctional alkoxysilane contained in the trifunctional or less alkoxysilane mentioned later. That is, the structure included in * is preferably a structure derived from R ^s3 described later.
It is preferable that the structural unit represented by Formula S2 is a structural unit derived from the tetrafunctional alkoxysilane mentioned later.

From the viewpoint that the pencil hardness of the hard coat layer is easily improved, the Si atom molar amount in the constitutional unit represented by the formula S1 in the above-mentioned siloxane resin is the molar amount of Si atom in the constitutional unit represented by the formula S2. On the other hand, it is preferably 1.0 to 7.5 times, more preferably 1.5 to 4.5 times.
When two or more structural units represented by the formula S1 are contained, “the Si atom molar amount of the structural unit represented by the formula S1” is a total Si atom of two or more structural units represented by the formula S1 Means molar amount.
When two or more structural units represented by the formula S2 are contained, "the Si atom molar amount of the structural unit represented by the formula S2" is the total Si atom of the structural units represented by two or more types S2. Means molar amount.
A siloxane resin, wherein the Si atom molar amount in the structural unit represented by the formula S1 in the above-mentioned siloxane resin is 1.0 or more times the molar amount of Si atom in the structural unit represented by the formula S2 Toughness is improved, and the occurrence of cracking of the hard coat layer is suppressed.
Siloxane resin, when the Si atom molar amount in the structural unit represented by the formula S1 in the above-mentioned siloxane resin is 7.5 or less times the molar amount of Si atom in the structural unit represented by the formula S2 The hardness of the hard coat layer is improved, and the pencil hardness of the hard coat layer is improved.
The total value of the Si atom molar amount of the constituent unit represented by the formula S1 and the Si atom molar amount of the constituent unit represented by the formula S2 is 80 mol%, relative to the total Si atom molar amount contained in the siloxane resin It is preferable that it is the above, 90 mol% or more is more preferable, and 100 mol% is especially preferable.
The Si atom molar amount of the structural unit represented by the formula S1 in the above-mentioned siloxane resin and the Si atom molar amount of the structural unit represented by the formula S2 are in the range of up to 50% in the film thickness direction from the surface of the hard coat layer Part of the siloxane resin is scraped off, 10 mg sampled therefrom, and analyzed by solid ²⁹ Si-NMR, which can be measured by the peak intensity of Si atoms in trifunctional and tetrafunctional siloxanes.

  The siloxane resin contained in the hard coat layer preferably contains a hydrolytic condensate of a trifunctional alkoxysilane and a tetrafunctional alkoxysilane from the viewpoint of easier adjustment of the degree of crosslinking of the siloxane resin.

At least one kind of siloxane resin contained in the hard coat layer is a tetrafunctional alkoxysilane, and 1.4 times to 10 times the mass of trifunctional alkoxysilane or less with respect to the mass of the tetrafunctional alkoxysilane Of a tetrafunctional alkoxysilane and a tetrafunctional alkoxysilane having a mass of 2.0 times to 6.0 times the mass of the tetrafunctional alkoxysilane It is more preferable to include the hydrolysis condensate of
In this aspect, the tetrafunctional alkoxysilane and the trifunctional or less alkoxysilane may each be only one type or two or more types.
In the case where two or more tetrafunctional alkoxysilanes are used, the “amount of tetrafunctional alkoxysilane” means the total amount of two or more tetrafunctional alkoxysilanes.
When the trifunctional or less alkoxysilane is two or more types, "an amount of the trifunctional or less alkoxysilane" means a total amount of two or more trifunctional or less trifunctional alkoxysilanes.

  Hereinafter, tetrafunctional alkoxysilane and trifunctional alkoxysilane with an amount of X mass times to Y mass times (for example, 1.4 mass times to 10 mass times) the amount of the tetrafunctional alkoxysilane and "A siloxane resin having a mass ratio [three or less functional / four functional] X to Y" (for example, a mass ratio [three or less functional / four functional]) is 1.4 to It is also referred to as siloxane resin (10).

When at least one of the siloxane resins contained in the hard coat layer is a siloxane resin having a mass ratio [trifunctional or less / four functional] of 1.4 to 10, generation of cracks in the hard coat layer is easily suppressed , Pencil hardness is easy to improve.
Specifically, the toughness of the siloxane resin is improved and the occurrence of cracking of the hard coat layer is suppressed when the mass ratio [trifunctional or less / 4 functional] is 1.4 or more.
The hardness of a siloxane resin improves that mass ratio [3 or less function / 4 functions] is 10 or less, and the pencil hardness of a hard-coat layer improves.
The proportion of the siloxane resin having a mass ratio of [three or less functional / 4 functional] occupying 1.4 to 10 in all the siloxane resins contained in the hard coat layer is preferably 80% by mass or more, 90% by mass It is more preferable that it is the above, and it is especially preferable that it is 100 mass%.

The mass ratio [trifunctional or less / 4 functional] in the siloxane resin whose mass ratio [trifunctional or less / 4 functional] is 1.4 to 10 is from the viewpoint of suppression of cracking of the hard coat layer and improvement of pencil hardness And 2.0 to 6.0 are preferable.
In other words, at least one of the siloxane resins contained in the hard coat layer is a tetrafunctional alkoxysilane and this tetrafunctional alkoxysilane, from the viewpoint of further suppressing the occurrence of cracks in the hard coat layer and further improving the pencil hardness. A hydrolysis condensation product of 2.0 to 6.0 times the mass of trifunctional or less alkoxysilane with respect to the total mass of the alkoxysilane (that is, the mass ratio [trifunctional or less or 4 functional] is 2.0 It is preferable that it is siloxane resin which is -6.0.
In this case, the ratio of the siloxane resin having a mass ratio [3 or less functional / 4 functional] occupied 2.0 to 6.0 in all the siloxane resins contained in the hard coat layer is 80% by mass or more. Preferably, it is 90% by mass or more, and particularly preferably 100% by mass.

In the present specification, tetrafunctional alkoxysilane means an alkoxysilane in which the number of alkoxy groups directly bonded to a silicon atom in one molecule is four.
In the present specification, a trifunctional or less alkoxysilane means an alkoxysilane in which the number of alkoxy groups directly bonded to a silicon atom in one molecule is 1 or more and 3 or less.

-Functionalized alkoxysilane-
The tetrafunctional alkoxysilane is not particularly limited, but an alkoxysilane represented by the following general formula (a) is preferable.

Si (OR ^S1 ) ₄ ... general formula (a)

In General Formula (a), four R ^S1s each independently represent an alkyl group having 1 to 6 carbon atoms.
The four R ^{1 s} are each independently preferably an alkyl group having 1 to 4 carbon atoms (more preferably 1 to 3, particularly preferably 1 or 2).

Specific examples of tetrafunctional alkoxysilanes include tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, tetrabutoxysilane, methoxytriethoxysilane, ethoxytrimethoxysilane, methoxytripropoxysilane, ethoxytripropoxysilane, propoxytrimethoxysilane , Propoxy triethoxy silane, dimethoxy diethoxy silane and the like.
Among them, tetramethoxysilane or tetraethoxysilane is preferable.

Alkoxysilanes of -3 or less functionality
Although there is no restriction | limiting in particular as a trifunctional or less functional alkoxysilane, The alkoxysilane represented by the following general formula (b) is preferable.

R ^S3 _4-n Si (OR ^S2 ) _n ... general formula (b)

In general formula (b), n represents an integer of 1 to 3.
R ^S2 represents an alkyl group having 1 to 6 carbon atoms.
When n is 2 or 3, a plurality of R ^S2 may be the same or different.
R ^S3 represents a C 1-15 organic group.
When 4-n is 2 or 3, multiple ^RSs may be the same or different.

Preferred embodiments of R ^{S2 in} the general formula (b) are the same as the preferred embodiments of R ^{S1 in} the general formula (a).

  N in the general formula (b) is preferably 2 or 3, and particularly preferably 3.

R ^S3 in the general formula (b) represents an organic group having 1 to 15 carbon atoms.
When the carbon number of R ^S3 is 1 to 15, the hardness of the hard coat layer and the adhesion between the hard coat layer and the surface substrate are improved.
The organic group represented by R ^S3 may have a heteroatom such as oxygen, nitrogen or sulfur. When the organic group represented by R ^S3 has a hetero atom, the adhesion between the hard coat layer and the surface substrate can be further improved.
As an organic group represented by R ^S3 ,
Preferred is a substituted or unsubstituted hydrocarbon group,
A substituted or unsubstituted alkyl group, a substituted or unsubstituted alkenyl group, or a substituted or unsubstituted aryl group is more preferable.

The organic group represented by R ^S3 preferably contains an epoxy group.
The organic group represented by R ^S3 is more preferably a hydrocarbon group substituted by an epoxy group-containing substituent, and still more preferably an alkyl group substituted by an epoxy group-containing substituent.
As a substituent containing an epoxy group, an epoxy group, glycidyl group, glycidoxy group, 3,4- epoxycyclohexyl group etc. are mentioned.

The organic group represented by R ^S3 may contain an alkyl group, an alkenyl group, an aryl group, an amido group, a urethane group, a urea group, an ester group, a hydroxy group, a carboxy group, a (meth) acryloyl group and the like.

The organic group represented by R ^S3 preferably contains no amino group.
The reason is that, since the organic group represented by R ^S3 does not contain an amino group, when a mixture of tetrafunctional alkoxysilane and trifunctional or lower alkoxysilane is mixed and hydrolyzed, dehydration condensation occurs between silanols generated. It is because it is hard to accelerate and the reaction liquid becomes stable.

The trifunctional or less alkoxysilane preferably contains an epoxy group, as described above.
Specific examples of trifunctional or lower alkoxysilane containing an epoxy group include 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, 2- (3,4-epoxycyclohexyl) ethyltriethoxysilane, 2- (3) , 4-Epoxycyclohexyl) ethyltriethoxysilane, 2- (3,4-epoxycyclohexyl) ethylmethyldimethoxysilane, 2- (3,4-epoxycyclohexyl) ethylmethyldiethoxysilane, 3-glycidoxypropyltrimethoxy Silane, 3-glycidoxypropyl triethoxysilane, etc. are mentioned.
Examples of commercial products of trifunctional or lower alkoxysilane containing an epoxy group include KBE-403 (manufactured by Shin-Etsu Chemical Co., Ltd.).

Specific examples of the epoxy group-free trifunctional or lower alkoxysilane include vinyltrimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-acryloxypropyltrimethoxysilane, 3-chloropropyltrimethoxysilane, and 3-chloropropyltrimethoxysilane. Ureidopropyltrimethoxysilane, propyltrimethoxysilane, phenyltrimethoxysilane, vinyltriethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-acryloxypropyltriethoxysilane, 3-chloropropyltriethoxysilane, 3-ureido Propyltriethoxysilane, methyltriethoxysilane, methyltrimethoxysilane, ethyltriethoxysilane, ethyltrimethoxysilane, propyltriethoxysilane, propyltrimethoxysila , Phenyltriethoxysilane, phenyltrimethoxysilane, and the like.
As a commercial item of the trifunctional or less alkoxysilane which does not contain an epoxy group, KBE-13 (made by Shin-Etsu Chemical Co., Ltd.) etc. are mentioned.

  70 mass% or more is preferable with respect to solid content of a hard-coat layer, as for content of the siloxane resin contained in a hard-coat layer, 80 mass% or more is more preferable, and 90 mass% or more is especially preferable. The upper limit is not particularly limited, and may be 100% by mass.

[Inorganic particles]
The hard coat layer preferably contains at least one inorganic particle from the viewpoint of further improving the hardness of the hard coat layer.
The inorganic particles are preferably at least one inorganic particle selected from the group consisting of metal oxide particles and inorganic nitride particles, from the viewpoint of further improving the hardness of the hard coat layer.

Examples of metal oxide particles include silica particles, alumina particles, zirconia particles, and titania particles.
Examples of the inorganic nitride particles include boron nitride particles and the like.

  The hard coat layer preferably contains silica particles from the viewpoint of crosslinking with the siloxane resin in the hard coat layer.

Examples of the silica particles include dry powdery silica produced by combustion of silicon tetrachloride; colloidal silica in which silicon dioxide or a hydrate thereof is dispersed in water;
When using dry powdery silica, it can be used by dispersing it in water using an ultrasonic dispersion machine or the like.
The silica particles are not particularly limited. Specifically, the Sea Hoster series such as Sea Hoster KE-P10 (manufactured by Nippon Shokubai Co., Ltd.), and the Snowtex (registered trademark) series such as Snowtex (registered trademark) OZL-35 Nissan Chemical Industries, Ltd.) and the like.

The number average particle size of the inorganic particles is preferably 300 nm or less, more preferably 200 nm or less, and particularly preferably 100 nm or less.
When the number average particle size of the inorganic particles is 300 nm or less, a hard coat layer having a smooth surface can be obtained.
On the other hand, the number average particle size of the inorganic particles is preferably 5 nm or more, and more preferably 10 nm or more.
When the number average particle size of the inorganic particles is 5 nm or more, the hardness of the hard coat layer can be further improved.

The number average particle diameter of the inorganic particles is determined by observing the cross section of the hard coat layer with a scanning electron microscope (SEM), selecting 100 particles contained in the range corresponding to an actual area of 1 mm ^2, and measuring the particle diameter of each particle It refers to the value determined by measuring and simply averaging the measured values (the particle size of each particle).

The content of the inorganic particles is preferably 5% by mass to 60% by mass, more preferably 10% by mass to 50% by mass, and more preferably 20% by mass to 50% by mass with respect to the solid content of the hard coat layer. Is particularly preferred.
The total amount of the siloxane resin and the inorganic particles is preferably 80% by mass or more, more preferably 90% by mass or more, and particularly preferably 100% by mass, with respect to the solid content of the hard coat layer.

[Metal complex]
The hard coat layer preferably contains a metal complex as a curing agent.
The metal complex is preferably a metal complex containing at least one metal element selected from the group consisting of aluminum, magnesium, manganese, titanium, copper, cobalt, zinc, hafnium and zirconium.

Metal complexes can be easily obtained by reacting a metal alkoxide with a chelating agent.
As examples of chelating agents, β-diketones such as acetylacetone, benzoylacetone and dibenzoylmethane; β-keto acid esters such as ethyl acetoacetate and ethyl benzoylacetate can be used.
As a metal complex, an aluminum chelate complex is preferable.

Examples of metal complexes include ethyl acetoacetate aluminum diisopropylate, aluminum tris (ethyl acetoacetate), alkyl acetoacetate aluminum diisopropylate, aluminum monoacetylacetonate bis (ethylacetoacetate), aluminum tris (acetylacetonate) Aluminum chelate complexes, etc .;
Magnesium chelate complexes such as ethyl acetoacetate magnesium monoisopropylate, magnesium bis (ethylacetoacetate), alkyl acetoacetate magnesium monoisopropylate, magnesium bis (acetylacetonate);
Zirconium chelate complexes such as zirconium tetraacetylacetonate, zirconium tributoxyacetylacetonate, zirconium acetylacetonate bis (ethylacetoacetate);
Manganese chelate complexes such as manganese acetylacetonate;
Cobalt chelate complexes such as cobalt acetylacetonate;
Copper chelate complexes such as copper acetylacetonate;
Titanium chelate complexes such as titanium acetylacetonate and titanium oxyacetylacetonate;
Etc.
Among these, aluminum tris (acetylacetonate), aluminum tris (ethylacetoacetate), magnesium bis (acetylacetonate), magnesium bis (ethylacetoacetate), or zirconium tetraacetylacetonate is preferable. Aluminum tris (acetylacetonate), aluminum tris (ethylacetoacetate), or aluminum monoacetylacetonate bis (ethylacetoacetate) is particularly preferable in consideration of storage stability and availability.

  As a commercial item of the solution of a metal complex, aluminum chelate A (W), aluminum chelate D, aluminum chelate M (Kawaken Fine Chemical Co., Ltd. product) etc. are mentioned.

The content of the metal complex in the hard coat layer is preferably 5% by mass to 50% by mass, more preferably 5% by mass to 40% by mass, and still more preferably 10% by mass to 30% by mass, with respect to the total amount of siloxane.
By using the metal complex at the lower limit value or more, the reaction rate of dehydration condensation of silanol can be made an appropriate rate, and a hard coat layer having excellent uniformity of thickness and high alkali resistance can be obtained.

[Other ingredients]
The hard coat layer may contain other components in addition to the components described above.
For example, the hard coat layer may contain at least one surfactant.
Thereby, the slipperiness of the surface of the hard coat layer is improved, and the friction on the surface of the hard coat layer is reduced.
As the surfactant, various surfactants such as a fluorine-based surfactant, a nonionic surfactant, a cationic surfactant, an anionic surfactant, a silicone surfactant and the like can be used.

Only one surfactant may be used, or two or more surfactants may be combined.
The content of the surfactant is preferably 0.001% by mass to 10% by mass, more preferably 0.01% by mass to 5% by mass, based on the solid content of the hard coat layer, and still more preferably It is 0.1 mass% to 1 mass%.

The hard coat layer (or the coating liquid for forming a hard coat layer) may contain a pH adjuster.
Examples of pH adjusters include acids such as nitric acid, oxalic acid, acetic acid, formic acid and hydrochloric acid, and alkalis such as ammonia, triethylamine, ethylenediamine, sodium hydroxide and potassium hydroxide.

The hard coat layer may contain an ultraviolet absorber.
As an ultraviolet absorber, the compound similar to the ultraviolet absorber contained in the ultraviolet absorption layer mentioned later is mentioned, A metal oxide particle is mentioned especially preferably.

The thickness of the hard coat layer is preferably 0.1 μm to 5 μm, more preferably 0.2 μm to 4 μm, and still more preferably 0.3 μm to 3 μm.
When the thickness of the hard coat is 0.1 μm or more, it is advantageous in terms of the hardness of the surface of the hard coat layer.
When the thickness of the hard coat layer is 5 μm or less, the transparency and the handleability of the solar cell protective sheet are further improved.

[Method of forming hard coat layer]
The method of forming the hard coat layer is not particularly limited.
As a method of forming a hard coat layer, for example, a coating solution for forming a hard coat layer containing a solvent and a hydrolyzate of alkoxysilane is applied onto a surface substrate and dried to allow hydrolysis and condensation of the alkoxysilane. The method of forming the hard-coat layer containing the siloxane resin which is a substance is mentioned.

As a method of preparing a coating solution for forming a hard coat layer, a hydrolyzate of the trifunctional alkoxysilane obtained by hydrolyzing an alkoxysilane (for example, a tetrafunctional alkoxysilane and a trifunctional alkoxysilane or less) and 4 The method of obtaining the coating liquid for hard-coat layer formation containing the hydrolyzate of a functional alkoxysilane is preferable.
Preparation of coating solution for hard coat layer formation including components other than hydrolyzate of alkoxysilane (for example, inorganic particles, metal complexes, surfactants, silicone particles (for example, silicone powder manufactured by Shin-Etsu Chemical Co., Ltd.), etc.) In the above preparation method, before hydrolysis of alkoxysilane, during hydrolysis of alkoxysilane, and at least one step after hydrolysis of alkoxysilane (preferably after hydrolysis of alkoxysilane) And components other than the above alkoxysilane hydrolyzate are added.
In the example of the method for forming a hard coat layer, the obtained coating liquid for forming a hard coat layer is applied and dried to form a siloxane resin which is a hydrolytic condensate of an alkoxysilane (and, if necessary, other components) To form a hard coat layer containing

The used amount of alkoxysilane (for example, the total amount used of tetrafunctional alkoxysilane and trifunctional alkoxysilane or less) in preparation of the coating solution for forming a hard coat layer is the solid content of the coating solution for forming a hard coat layer. In contrast, 20% by mass to 80% by mass is preferable, 20% by mass to 70% by mass is more preferable, and 30% by mass to 70% by mass is particularly preferable.
The preferable range of the usage ratio (mass ratio) of the tetrafunctional alkoxysilane and the trifunctional alkoxysilane or less in the preparation of the coating solution for forming a hard coat layer is the above-mentioned siloxane (that is, the hydrolytic condensate of the alkoxysilane) It is the same as the preferable range of the mass ratio of [3 or less functional / 4 functional].
In the case of forming a hard coat layer containing the above-mentioned inorganic particles, the content of the inorganic particles in the hard coat layer forming coating solution is 5% by mass to 60% by mass with respect to the solid content of the hard coat layer forming coating solution Is preferably 10% by mass to 50% by mass, and particularly preferably 20% by mass to 50% by mass.
When the hard coat layer containing the above-mentioned metal complex is formed, the content of the metal complex in the hard coat layer forming coating solution is 5% by mass to 50% with respect to the total amount of alkoxysilane in the hard coat layer forming coating solution. % By mass is preferable, 5% by mass to 40% by mass is more preferable, and 10% by mass to 30% by mass is more preferable. By using the metal complex at the lower limit or more, the reaction rate of dehydration condensation of silanol can be made an appropriate rate, and a hard coat layer with uniform thickness and high alkali resistance can be formed.
In the case of forming a hard coat layer containing the above-mentioned surfactant, the content of the surfactant in the hard coat layer forming coating solution is preferably 0.001% by mass to 10% of the solid content of the hard coat. It is mass%, More preferably, it is 0.01 mass%-5 mass%, More preferably, it is 0.1 mass%-1 mass%.

<Antireflection layer>
The protective sheet for a solar cell according to the present disclosure is formed on the surface of the hard coat layer opposite to the surface substrate (when the hard coat layer is omitted, the surface substrate opposite to the composite substrate) On the surface of the optical disk) may have an antireflective layer (AR layer).
The antireflective layer includes a layer having a refractive index lower than that of the surface substrate.
The refractive index of the antireflective layer is preferably 1.15 to 1.35, and more preferably 1.20 to 1.32.
Examples of the antireflection layer include a coating film having a void, and JP-A-2017-500384, JP-A-2014-203006, JP-A-H01-312501, JP-A-H07-140303, and the like can be used. JP-Hei 03-199043, JP-A 11-035313, JP-A 2001-188104, JP-A 11-061043, JP-A 11-292568, JP-A 2005-10470, International Publication No. It is possible to use the antireflective film etc. which are described in 2007/0695996 grade | etc.,.
The antireflective layer is formed by applying a coating solution for forming an antireflective layer containing each component contained in the above-mentioned antireflective layer and, if necessary, a solvent on a surface substrate, and drying it as necessary. Be done. Moreover, you may perform processes, such as a heating for forming a space | gap, after the said application as needed.

<UV ray absorbing layer>
The protective sheet for a solar cell according to the present disclosure is between the surface substrate and the hard coat layer (when the hard coat layer is omitted, on the surface of the surface substrate opposite to the composite substrate) May have an ultraviolet absorbing layer.
The UV absorbing layer is preferably a layer containing a UV absorber, and is preferably a layer containing a UV absorber and a cured sol-gel, or a layer containing a UV absorber and a binder polymer.
As a ultraviolet absorber, a well-known ultraviolet absorber can be used without a restriction | limiting in particular, It may be an organic compound or an inorganic compound.
As an ultraviolet absorber, a triazine compound, a benzotriazole compound, a benzophenone compound, a salicylic acid compound, metal oxide particle etc. are mentioned, for example. The UV absorber may be a polymer containing a UV absorbing structure, and the polymer containing a UV absorbing structure includes at least a part of the structure of a triazine compound, a benzotriazole compound, a benzophenone compound, a salicylic acid compound, etc. The acrylic resin etc. which contain the monomer unit derived from an acrylic acid ester compound are mentioned.
The sol-gel cured product includes a cured product obtained by hydrolysis and polycondensation of an alkoxide compound of at least one element selected from the group consisting of Si, Ti, Zr and Al.
As the binder polymer, polyolefin, acrylic resin, polyester, polyurethane and the like can be mentioned.
The ultraviolet absorbing layer is formed by applying a coating solution for forming an ultraviolet absorbing layer, which contains each of the components contained in the ultraviolet absorbing layer and, if necessary, a solvent, on the surface substrate, and drying it as necessary. Ru.

<Back layer>
The protective sheet for a solar cell according to the present disclosure has a back layer on the side opposite to the surface substrate side of the composite substrate (ie, the front surface side of the composite substrate) (ie, the back surface side of the composite substrate). You may have.
The back surface layer functions as, for example, a layer for close contact with a sealing material (for example, a sealing material containing ethylene-vinyl acetate copolymer (EVA)) in a solar cell module.
The back layer preferably contains a binder polymer.
The back layer may be only one layer or two or more layers.

For example, the protective sheet for a solar cell has a third layer (for example, the above-mentioned third layer 13) and a fourth layer (for example, the above-mentioned fourth layer 14) as a back surface layer on the back surface side of the composite substrate. It can be provided in this order.
Hereinafter, the third layer and the fourth layer provided on the solar cell protective sheet as needed will be described.

[Third layer]
The third layer preferably contains a binder polymer.
As a binder polymer which may be contained in the third layer, for example, an acrylic resin or an acrylic resin containing a styrene skeleton is more preferable from the viewpoint of adhesion to a sealing material when applied to a solar cell module, for example.

As an acrylic resin containing a styrene skeleton, a structural unit derived from at least one compound selected from the group consisting of acrylic acid, methacrylic acid, acrylic esters, and methacrylic esters, and a monomer having a styrene skeleton (for example, And a structural unit derived from styrene, α-methylstyrene, divinylbenzene, vinyltoluene and the like).
As a commercial item of the dispersion liquid of the acrylic resin containing styrene frame | skeleton, AS-563A (made by Daicel Finechem Co., Ltd. product) etc. are mentioned, for example.

The third layer may contain a known ultraviolet absorber.
Examples of the ultraviolet ray absorbing compound which may be contained in the third layer include the same as the ultraviolet ray absorbing compound of the ultraviolet ray absorbing layer.

The thickness of the third layer is preferably thicker than the thickness of the fourth layer which is an easy adhesion layer described later, from the viewpoint of improving the adhesion to the sealing material. That is, when the thickness of the third layer is (b) and the thickness of the fourth layer is (c), it is preferable that (b)> (c), (b): (c) The range of 2: 1 to 15: 1 is more preferable.
Moreover, 0.5 micrometer or more is preferable and, as for the thickness of a 3rd layer, 0.7 micrometer or more is more preferable. The thickness of the third layer is preferably 7.0 μm or less.

  Within the above range, the third layer thickness and the ratio of the third layer thickness to the fourth layer thickness exhibit well the film characteristics of the third layer, and the solar cell protective sheet and the sealing material And the durability of the solar cell module are more excellent.

The method of forming the third layer is not particularly limited.
As a method of forming the third layer, for example, a method of applying a coating solution for forming the third layer containing a solvent and the component (solid content) of the third layer described above on the back surface of the composite substrate and drying Can be mentioned.

[Fourth layer]
The solar cell protective sheet of the present disclosure may include a fourth layer (for example, the fourth layer 14 described above) on the third layer.
The fourth layer is a layer which is in direct contact with the sealing material of the solar cell module, that is, a layer which functions as an easy adhesion layer to the sealing material of the solar cell module.

The fourth layer preferably contains a binder polymer.
The binder polymer in the fourth layer is preferably at least one polymer selected from the group consisting of polyolefins, acrylic resins, polyesters, and polyurethanes from the viewpoint of adhesion to the sealing material.
The binder polymer in the fourth layer preferably contains at least a polyolefin, and more preferably a polyolefin, from the viewpoint of the adhesion to the sealing material.

As polyolefin, for example, modified polyolefin is preferable.
When forming the 4th layer containing polyolefin, you may use the commercial item of the dispersion of polyolefin.
As a commercial item of the dispersion of polyolefin, for example, Arrow Base (registered trademark) SE-1013N, SD-1010, TC-4010, TD-4010 (both are manufactured by Unitika Co., Ltd.), Hitec S3148, S3121, S8512 (both Toho Chemical Co., Ltd. product, Chemipearl (registered trademark) S-120, S-75N, V100, EV210H (all are Mitsui Chemical Co., Ltd. product) etc. are mentioned.
Among them, using an arrow base (registered trademark) SE-1013N, which is a terpolymer of low density polyethylene, an acrylic ester, and maleic anhydride, made by UNITICA CO., LTD., Improves adhesion. preferable.

The fourth layer may contain an antistatic agent, a preservative, and the like.
Examples of the antistatic agent include surfactants such as nonionic surfactants, organic conductive materials, and the like.
As surfactant used for the antistatic agent which the 4th layer may contain, nonionic surfactant, anionic surfactant, etc. are preferable, and nonionic surfactant is preferable among them, ethylene glycol chain (polyoxyethylene chain (polyoxyethylene chain) Nonionic surfactants having — (CH ₂ —CH ₂ —O) _n —) and having no carbon-carbon triple bond (alkyne bond) are preferred. Furthermore, those having an ethylene glycol chain of 7 to 30 are particularly preferred.
More specifically, hexaethylene glycol monododecyl ether, 3,6,9,12,15-pentaoxahexadecane-1-ol, polyoxyethylene phenyl ether, polyoxyethylene methyl phenyl ether, polyoxyethylene naphthyl ether, Although polyoxyethylene methyl naphthyl ether etc. are mentioned, it is not limited to these.
The content of the surfactant as the antistatic agent is preferably 2.5% by mass to 40% by mass, and more preferably 5.0% by mass to 35% by mass, with respect to the solid content of the fourth layer. It is more preferably 10% by mass to 30% by mass.
The fall of a partial discharge voltage is suppressed as it is the range of this content, and adhesiveness with a sealing material is maintained favorable.

  As the organic conductive material, for example, a cationic conductive compound having a cationic substituent such as an ammonium group, an amine base, or a quaternary ammonium group in the molecule; a sulfonate group, a phosphate group, a carboxylate group, etc. Anionic conductive compounds having the anionic property; ionic conductive materials such as amphoteric conductive compounds having both an anionic substituent and a cationic substituent; polyacetylene derived from conjugated polyene skeleton, poly Conductive polymer compounds such as paraphenylene, polyaniline, polythiophene, polyparaphenylene vinylene, polypyrrole and the like can be mentioned.

The method for forming the fourth layer is not particularly limited.
As a method of forming the fourth layer, for example, a method of applying a coating solution for forming a fourth layer containing a solvent and the component (solid content) of the fourth layer described above on the third layer and drying it may be mentioned. .

<Subbing layer>
As mentioned above, a subbing layer may be provided on at least one surface of the surface substrate or the composite substrate.

The subbing layer preferably contains a binder polymer.
The binder polymer which may be contained in the undercoat layer is not particularly limited.
As a binder polymer which may be contained in undercoat, an acrylic resin, polyester, polyolefin, silicone resin etc. are mentioned, for example.
The undercoat layer preferably contains an acrylic resin.
As an acrylic resin, the thing similar to the acrylic resin which may be contained in the 3rd layer mentioned above is mentioned.
It is more preferable that the acrylic resin content ratio in the binder polymer contained in the undercoat layer is 50% by mass or more.
When 50% by mass or more of the binder polymer is an acrylic resin, the modulus of elasticity of the undercoat layer is easily adjusted to 0.7 GPa or more, and the cohesive failure resistance in the case of using the front sheet for a solar cell is further improved.

  The subbing layer may contain a surfactant, an antioxidant, a preservative, and the like.

The thickness of the undercoat layer is preferably 0.01 μm or more, more preferably 0.03 μm or more, and still more preferably 0.05 μm or more.
The thickness of the undercoat layer is preferably 1 μm or less, more preferably 0.8 μm or less, and still more preferably 0.7 μm or less.

The subbing layer can be formed by applying a coating liquid for forming a subbing layer containing the solvent and the solid content of the subbing layer on a surface substrate or a composite substrate and drying it.
The undercoat layer may be formed by in-line coating using the above-described undercoat layer-forming coating solution.
An in-line coating method is a method of applying a coating solution for forming an undercoat layer at a stage before winding the produced substrate, and an off-line coating method in which the produced substrate is wound and then separately applied. It is distinguished.
As an embodiment of forming the undercoat layer by the in-line coating method, a film obtained by applying the undercoat layer-forming coating solution to one surface of the film stretched in the first direction and applying the undercoat layer-forming coating solution is a film An aspect in which a substrate with a subbing layer is produced by stretching in the second direction orthogonal to the first direction along the surface is preferable.

The solar cell protective sheet according to the present disclosure may include other layers other than the above-described layers.
The solar cell protective sheet according to the present disclosure preferably has a light transmittance at 25 ° C. and a wavelength of 550 nm of 80% or more, more preferably 83% or more, and 85% or more. Is more preferred. The transmittance is measured using a spectrophotometer V670 (manufactured by JASCO Corporation).

(Manufacturing method of protective sheet for solar cells)
The preferable manufacturing method of the protection sheet for solar cells which concerns on this indication is:
Applying a resin in the fibrous material to form a composite substrate (composite substrate forming step);
And (d) laminating the composite base material and the surface base material.

<Composite substrate forming process>
Here, the preferable formation method of the composite base material in a composite base material formation process is as above-mentioned.

<Lamination process>
The laminating step is preferably performed by laminating the produced composite substrate and the surface substrate. The conditions of the lamination may be appropriately set according to the physical properties of the surface base material and the material of the composite base material, and the resin or crosslinking agent contained in the coating solution for forming an adhesive layer.
When formation of a composite substrate is performed by the above-mentioned lamination, you may carry out by laminating | stacking simultaneously a surface base material, a resin film, and a fibrous material in this order, and laminating them. That is, the composite substrate formation step and the lamination step may be performed simultaneously.

  A coating liquid for forming an adhesive layer such that an adhesive layer is formed between the composite substrate and the surface substrate on the surface of the composite substrate or the surface substrate when laminating the composite substrate and the surface substrate May be given. The application method is not particularly limited, and for example, a known application method or the like may be used.

<Step of Forming Hard Coat Layer>
In addition, the method for producing a solar cell protective sheet may further include the step of applying a hard coat layer forming coating solution on the surface substrate to form a hard coat layer.
In the step of forming the hard coat layer, the applied hard coat layer forming coating solution may be dried.
The step of forming the hard coat layer may be performed before laminating the composite substrate and the surface substrate, or may be performed after laminating.
The method for applying the hard coat layer-forming coating solution is not particularly limited, and for example, a known coating method may be used.

<Step of Forming Antireflection Layer>
Moreover, the manufacturing method of the protective sheet for solar cells may further include the process of providing the coating liquid for anti-reflective layer formation on a surface base material, and forming an anti-reflective layer.
In the step of forming the antireflective layer, the applied antireflective layer forming coating solution may be dried. In addition, a void may be formed in the antireflective layer by heating the applied coating solution for forming an antireflective layer.
When the method for producing a protective sheet for a solar cell includes the step of forming a hard coat layer, the step of forming the antireflective layer is preferably performed after the step of forming the hard coat layer. That is, the antireflective layer is preferably formed on the side opposite to the side having the surface base of the hard coat layer.
The step of forming the antireflective layer may be performed before laminating the composite substrate and the surface substrate, or may be performed after laminating.
The application method of the coating liquid for forming an antireflective layer is not particularly limited, and for example, a known coating method may be used.

<Step of Forming Ultraviolet Absorbing Layer>
Moreover, the manufacturing method of the protective sheet for solar cells may further include the process of providing the coating liquid for ultraviolet absorption layer formation on a surface base material, and forming an ultraviolet absorption layer.
In the step of forming the ultraviolet absorbing layer, the applied coating solution for forming an ultraviolet absorbing layer may be dried.
The step of forming the ultraviolet absorbing layer is preferably performed prior to the step of forming the hard coat layer. That is, the UV absorbing layer is preferably formed between the hard coat layer and the surface substrate.
The step of forming the ultraviolet absorbing layer may be performed before laminating the composite substrate and the surface substrate, or may be performed after laminating.
The application method of the coating liquid for forming the ultraviolet absorbing layer is not particularly limited, and for example, a known coating method may be used.

<Step of Forming Back Layer>
Moreover, the manufacturing method of the protection sheet for solar cells is the process of preparing the coating liquid for back surface layer formation for forming the above-mentioned back surface layer (for example, at least one of 3rd layer and 4th layer), and a composite base material, The method may include the step of applying a coating solution for forming a back surface layer on the back surface of the substrate and drying to form the back surface layer.

(Solar cell module)
The solar cell module according to the present disclosure (for example, the above-described solar cell module 100) is
An element structure (for example, the above-described element structure 36) including a solar cell element (for example, the above-described solar cell element 32) and a sealing material (for example, the above-described sealing material 34) ,
The protective sheet for a solar cell according to the above-mentioned present disclosure (for example, the above-mentioned front sheet for a solar cell 20) according to the above-mentioned present disclosure, which is disposed on the side where sunlight (for example, the above-mentioned sunlight 50) is incident When,
A solar cell back sheet (for example, the above-described solar cell back sheet 40) disposed on the side opposite to the side where sunlight is incident on the element structure portion;
Equipped with

  About an example (solar cell module 100) of a solar cell module concerning this indication, it is as having already explained with reference to FIG.

  About a solar cell backsheet, publicly known documents, such as JP, 2012-195583, A, JP 2015-186861, A, JP 2015-185687, A, JP 2015-146360, etc. can be referred to suitably, for example.

  For each component of the solar cell module, for example, “PV building system constituent material” (edited by Eiichi Sugimoto, Industrial Research Association, Inc., published in 2008) can be referred to.

  As a solar cell element, a silicon solar cell element containing single crystal silicon, polycrystalline silicon, amorphous silicon, etc .; Compound semiconductors such as copper-indium-gallium-selenium, copper-indium-selenium, cadmium-tellurium, gallium-arsenic and the like Various well-known solar cell elements, such as a compound semiconductor solar cell element containing; It is applicable.

Hereinafter, the present invention will be more specifically described by way of examples. However, the present invention is not limited to the following examples as long as the gist thereof is not exceeded.
Hereinafter, “parts” is based on mass unless otherwise specified.

Example 1
<Formation of Surface Substrate A>
Coating solution A for forming a hard coat layer described below is applied to a polypropylene substrate (refractive index = 1.52, Trefan BO60-2500, Toray Industries, Inc., substrate thickness 60 μm), and dried at 170 ° C. for 2 minutes As a result, a hard coat layer having a thickness of 1 μm was formed.
In detail, the hydrolyzate of alkoxysilane (KBE-403 and KBE-04) was condensed by the said drying, and the hard-coat layer containing the siloxane resin which is a hydrolysis condensation product of the said alkoxysilane was formed.
Thereafter, a coating solution B for forming an adhesive layer described below was applied to the surface opposite to the hard coat layer, and dried at 170 ° C. for 2 minutes to form an adhesive layer having a thickness of 2 μm.
Surface base material A was obtained by the above.

Preparation of Coating Solution A for Forming Hard Coat Layer
-Composition-
Trifunctional alkoxysilane (KBE-403 (3-glycidoxypropyltriethoxysilane), Shin-Etsu Chemical Co., Ltd. product) ... 8.5 parts Tetrafunctional alkoxysilane (KBE-04 (tetraethoxysilane), Shin-Etsu Chemical Industry Co., Ltd .: 2.6 parts Acetic acid aqueous solution (manufactured by Daicel Co., Ltd., industrial acetic acid): 0.2 parts Metal complex solution (Aluminum chelate D, manufactured by Kawaken Fine Chemical Co., Ltd., 76 mass) % Isopropyl alcohol (IPA) solution ··· 2.5 parts of an aqueous dispersion of inorganic particles (Snowtex (registered trademark) OZL-35, average particle size 400 nm, Nissan Chemical Industries, Ltd., solid content 35.5 mass) %) ... 24.5 parts of a surfactant solution diluted with water (Lapisol (registered trademark) A-90, manufactured by NOF Corporation, 1 mass% solid content, anionic surfactant) ... 3.3 parts Surface activity Dilution solution (Naroacty (registered trademark) CL-95, Sanyo Chemical Industries, Ltd., solid content 1% by mass, nonionic surfactant) ... 2.3 parts · water · · · 100 parts in total Remaining Amount The Si atom molar amount in the constituent unit represented by the formula S1 was 2.4 times the molar amount of Si atom in the constituent unit represented by the formula S2.

The preparation of the hard coat layer forming coating solution A was carried out in detail in the following procedure.
After KBE-403 is added to an aqueous solution of acetic acid and hydrolyzed sufficiently, KBE-04 is added and hydrolyzed sufficiently, and a mixture containing hydrolysates of these alkoxysilanes (KBE-403 and KBE-04) is added. I got a liquid. Then, to this mixture, aluminum chelate D, Snowtex (registered trademark) OZL-35, surfactant (Lapisol (registered trademark) A-90), surfactant (Naroacty (registered trademark) CL-95), And the coating liquid A for hard-coat layer formation was obtained by adding water.

[Preparation of Coating Solution B for Forming Adhesive Layer]
· Polyolefin resin water dispersion (Arrow Base (registered trademark) SE-1013 N, manufactured by Unitika Co., Ltd., solid content: 20% by mass) ... 17.5 parts-Water diluted solution of oxazoline crosslinking agent (Epocross (registered trademark) WS -700, manufactured by Nippon Shokubai Co., Ltd., solid content 25% by mass,... 3.5 parts water-diluted liquid of nonionic surfactant (EMALEX (registered trademark) 110, manufactured by Nippon Emulsion Co., Ltd., solid content 10 mass %) ... ... 4.3 parts, water ... 100 parts in total

<Preparation of glass fiber composite resin sheet C>
Glass fiber sheet (refractive index = 1.56, E02B SK, 19 g / m ² , thickness 20 μm, manufactured by Unitika Co., Ltd.) which is a fibrous material, and acrylic resin sheet (refractive index = 1.52, Acryprene HBS 006, thickness 50 μm, 58 g / m ² , manufactured by Mitsubishi Chemical Corporation, and the above-mentioned surface substrate A, which is a polypropylene substrate on which a hard coat is formed, in this order, the hard coat layer is opposite to the acrylic resin sheet A glass fiber composite resin sheet C, which is a protective sheet for a solar cell according to the present disclosure, was formed by performing heat lamination at 145 ° C. for 30 minutes under 1 atm.
The glass fiber composite resin sheet in which the composite base material in which a part of acrylic resin sheet was contained in the inside of a glass fiber sheet, the adhesion layer, and the polypropylene base material which is a surface base material were laminated in this order by the said heating lamination. C was obtained.
Content of the glass fiber with respect to the total mass of the glass fiber and acrylic resin in the composite sheet B was 25 mass%.
The thickness of the portion containing the glass fiber sheet in the composite substrate is 20 μm, the thickness of the entire composite substrate is 50 μm, and the thickness of the polypropylene substrate as the surface substrate is 60 μm. .

<Evaluation of transmittance and heat resistance of protective sheet for solar cells>
It was 88% when the transmittance | permeability in 25 degreeC and 550 nm was measured using UV3100PC and Shimadzu Corp. make about the produced glass fiber composite resin sheet C.
Moreover, although heat processing was carried out with the oven of 200 degreeC, the produced glass fiber composite resin sheet C did not cause a fire spread and extreme deformation, but high heat resistance was confirmed.

Hereinafter, the solar cell module described in FIG. 3 is manufactured. FIG. 3 is a schematic cross-sectional view showing the configuration of the solar cell module.
In FIG. 3, the solar cell module 100 includes a solar cell front sheet 20, an adhesive filling layer 72 which is a sealing material, a crystalline Si cell 76, an adhesive filling layer 72 which is a sealing material, and a back for solar cells And the sheet 40 in this order,
The solar cell front sheet 20 includes the hard coat layer 12 formed by the above-described hard coat layer forming coating solution A, the surface base material 11 which is a polypropylene base material included in the above-described glass fiber composite resin sheet C, and And the composite substrate 10 contained in the above-described glass fiber composite resin sheet C.
As the solar cell back sheet 40, HF-32 (250 μm thick, manufactured by Fujifilm Corporation) was used, and as the adhesive filling layer 72, EVA (F-806P, manufactured by Hangzhou DG Technology, 400 μm) was used. .
Specifically, the prepared glass fiber composite resin sheet C, the adhesive filling layer 72, the crystalline Si cell 76, the adhesive filling layer 72, and the solar cell back sheet 40 are laminated in the order of FIG. The solar cell module was produced by performing heat lamination for 30 minutes and 1 atmosphere pressure.

<Evaluation of power generation efficiency>
Conversion efficiency is 16% or more when I-V characteristics (current-voltage characteristics) are measured by irradiating AM 1.5, that is, light of 100 mW / cm 2 with a solar simulator (SUN 2000, manufactured by ABET Technologies). It was confirmed.

(Example 2)
In the formation of the surface substrate A, in the same manner as in Example 1 except that the polypropylene substrate was changed to an acrylic sheet (n = 1.52, Technoloy S001, thickness 50 μm, Sumika Acrylic Co., Ltd.). , A glass fiber composite resin sheet C, and the solar cell module described in FIG. 3 were produced.

<Evaluation of transmittance and heat resistance of protective sheet for solar cells>
The transmittance of the glass fiber composite resin sheet C prepared in Example 2 at 25 ° C. and 550 nm was 88% when measured using UV 3100 PC, manufactured by Shimadzu Corporation.
Moreover, although the glass fiber composite resin sheet C produced in Example 2 was heat-processed by the oven of 200 degreeC, spreading fire and extreme deformation did not arise but high heat resistance was confirmed.

<Evaluation of power generation efficiency>
When the solar cell module manufactured in Example 2 is irradiated with light of AM 1.5, ie, 100 mW / cm ^{2 by} a solar simulator to measure the IV characteristics, the conversion efficiency is 16% or more It was confirmed.

10 composite substrate 11 surface substrate (first layer)
12 Hard coat layer (second layer)
13 Third Layer 14 Fourth Layer 16 Fibrous Material 18 Resin 20 Front Sheet for Solar Cell 32 Solar Cell Element 34 Sealing Material 36 Element Structure 40 Solar Cell Back Sheet 50 Sunlight 72 Adhesive Filled Layer 74 Adhesive Layer 76 Crystal Layer Si cell 100 solar cell module

Claims (7)

A fibrous material having a refractive index of 1.50 to 1.62 at 25 ° C. and a wavelength of 550 nm, and a resin having a refractive index of 1.50 to 1.62 at 25 ° C. and a wavelength of 550 nm A composite substrate containing 10% by mass to 80% by mass of the fibrous material with respect to the total mass of the resin and the fibrous material,
A surface substrate having a refractive index at 25 ° C. and a wavelength of 550 nm within the range of 1.47 to 1.55;
Protective sheet for solar cells.   The solar cell protective sheet according to claim 1, wherein the transmittance of light having a wavelength of 550 nm at 25 ° C is 80% or more.   The solar cell protective sheet according to claim 1, wherein the fibrous material is glass fiber.   The solar cell protective sheet according to any one of claims 1 to 3, wherein the resin is at least one resin selected from the group consisting of polyester resin, epoxy resin, acrylic resin and urethane resin. .   The solar cell protective sheet according to any one of claims 1 to 4, further comprising a hard coat layer on the surface of the surface substrate opposite to the composite substrate.   The solar cell protective sheet according to any one of claims 1 to 5, further comprising an adhesive layer between the surface substrate and the composite substrate. An element structure portion including a solar cell element and a sealing material for sealing the solar cell element;
The solar cell protective sheet according to any one of claims 1 to 6, which is disposed on the side where sunlight is incident to the element structure portion;
A solar cell back sheet disposed on the side opposite to the side where sunlight is incident on the element structure portion;
Solar cell module.