JP2014072435A - Protective sheet and solar cell module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a protective sheet capable of suppressing an occurrence of blocking and enhancing adhesion between a fluororesin layer and a substrate, and to provide a solar cell module.SOLUTION: A protective sheet 1 includes a substrate 10 and a fluororesin layer 11 coated and formed on the substrate 10. The fluororesin layer 11 contains fine particles. The glass-transition temperature of the fluororesin layer 11 is 40°C or lower. The average particle size of the fine particles is larger than the thickness T of the fluororesin layer 11 and less than two times of the thickness of the fluororesin layer. The content of the fine particles in the fluororesin layer in reference to the fluororesin layer is 3 weight % or higher and 20 weight % or lower.

Description

  The technology of the present disclosure relates to a protective sheet and a solar cell module including the protective sheet.

  2. Description of the Related Art In recent years, solar power generation that obtains an electromotive force with a photoelectric conversion element has attracted attention as a power generation method with a small environmental load. A solar cell module used for photovoltaic power generation mainly includes a plurality of electrically connected photoelectric conversion elements, a sealing material that seals the photoelectric conversion elements, a surface protection sheet that protects the surface of the module, and a module It is comprised from the back surface protection sheet which protects a back surface. Further, in the surface protection sheet, a fluororesin layer is formed on a resin base material in order to increase transparency, chemical stability, and mechanical strength.

  As a method for forming a fluororesin layer, there are known a method of attaching a fluororesin film to a substrate using an adhesive, and a method of applying a coating liquid containing a fluororesin to a substrate (for example, Patent Document 1). reference). The method of applying and forming the fluororesin layer has a simpler manufacturing process and a higher degree of freedom when imparting a function to the fluororesin layer than the method of adhesively forming the fluororesin layer.

International Publication No. 2007/063698

  By the way, in the method of applying and forming the fluororesin layer, when the formed protective sheet is wound around the roll, the surface of the fluororesin layer wound inside contacts the back surface of the substrate wound outside. . And the blocking which the surface of the surface protection sheet wound inside and the back surface of the surface protection sheet wound outside may adhere may occur. Also, the method of applying and forming the fluororesin layer is different from the method of forming the fluororesin layer by adhesion, and the base material and the fluororesin layer are not adhered by the adhesive layer. Therefore, in the surface protective sheet on which the fluororesin layer is applied and formed, it is desired that both the above-described blocking is suppressed and the adhesion between the fluororesin layer and the substrate is enhanced.

  An object of the technology of the present disclosure is to provide a protective sheet and a solar cell module that are capable of suppressing the occurrence of blocking and enhancing the adhesion between the fluororesin layer and the substrate. To do.

  The protective sheet which solves the said subject is equipped with a base material and the fluororesin layer apply | coated and formed on the surface of the said base material. And the said fluororesin layer contains microparticles | fine-particles, the glass transition temperature of the said fluororesin layer is 40 degrees C or less, the average particle diameter of the said microparticles is larger than the thickness of the said fluororesin layer, and the said fluororesin The content of the fine particles in the fluororesin layer is 3 wt% or more and 20 wt% or less with respect to the fluororesin layer.

  The solar cell module which solves the said subject is a solar cell module provided with a protection sheet on the surface, Comprising: The said protection sheet is provided with the base material and the fluororesin layer apply | coated and formed on the surface of the said base material. And the said fluororesin layer contains microparticles | fine-particles, the glass transition temperature of the said fluororesin layer is 40 degrees C or less, the average particle diameter of the said microparticles is larger than the thickness of the said fluororesin layer, and the said fluororesin The content of the fine particles in the fluororesin layer is 3 wt% or more and 20 wt% or less with respect to the fluororesin layer.

According to the said structure, coexistence with suppression of generation | occurrence | production of blocking and improving the adhesiveness between a fluororesin layer and a base material is attained.
In the protective sheet, the base material is preferably made of a resin. According to this configuration, the flexibility as the protective sheet is enhanced and the protective sheet can be reduced in weight.

  In the protective sheet, the base material preferably has a thermal shrinkage rate of 5% or less at 150 ° C. for 30 minutes. According to this configuration, for example, even when the protective sheet is placed under high heat conditions such as a solar cell sealing step, the base material can be prevented from being deformed.

  In the protective sheet, it is preferable that a water vapor barrier layer is further provided on the surface of the substrate opposite to the surface on which the fluororesin layer is formed. According to this configuration, the passage of water vapor to the protective sheet is suppressed.

  According to the technique of the present disclosure, it is possible to achieve both the suppression of the occurrence of blocking and the enhancement of the adhesion between the fluororesin layer and the substrate.

It is sectional drawing which shows the cross-section of the protection sheet in one Embodiment in the technique of this indication. It is sectional drawing which shows the cross-section of the solar cell module in one Embodiment in the technique of this indication.

  With reference to FIG.1 and FIG.2, one Embodiment of a protection sheet and a solar cell module is described. The protective sheet of this embodiment is used as a surface protective sheet that protects the surface of the solar cell module.

[Configuration of protective sheet]
The configuration of the protective sheet 1 will be described with reference to FIG.
As shown in FIG. 1, a fluororesin layer 11 including a filler 12 is applied and formed on a base material 10. A water vapor barrier layer 14 is bonded to the surface of the substrate 10 opposite to the surface on which the fluororesin layer 11 is formed via an adhesive layer 13. By providing the barrier layer 14, when the protective sheet 1 is used as a surface member of the solar cell module, water vapor is prevented from entering the element region. The protective sheet 1 is formed by laminating a barrier layer 14 on the other surface of the substrate 10 after the fluororesin layer 11 is formed on one surface of the substrate 10.

  The material of the base material 10 is not particularly limited as long as it is a material having transparency and weather resistance. For example, polyester resins such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), and polycarbonate resins have high transparency and weather resistance, and are suitable for the material of the substrate 10. Other material systems can be appropriately selected from the viewpoints of heat resistance, strength properties, electrical insulation, and the like.

  The thickness of the base material 10 is not specifically limited, For example, it selects in consideration of performance required for the protection sheet for solar cells, such as electrical insulation and water vapor | steam barrier property. In consideration of workability in the coating process of the fluororesin layer 11 and the laminating process of the barrier layer 14, the thickness of the substrate 10 is preferably 25 μm or more and 300 μm or less, and more preferably 50 μm or more and 250 μm or less.

  The thermal contraction rate of the substrate 10 is preferably 5% or less at 150 ° C. for 30 minutes. The conditions of 150 ° C. and 30 minutes are general sealing conditions for solar cells. If the thermal shrinkage rate is 5% or less under these conditions, it is possible to suppress wrinkling of the base material 10 and changes in the dimensions of the base material 10 in the solar cell sealing step. In order to suppress the heat shrinkage rate, an annealing process is performed.

The fluororesin layer 11 includes a fluororesin crosslinked with polyisocyanate and a filler as fine particles.
The formation process of the fluororesin layer 11 includes an application process, a drying process, and an aging process. In the coating step, a coating solution that is a solution containing a main fluororesin and a curing agent polyisocyanate is applied to the substrate 10. A filler is added to the coating solution. In the drying step, the solvent is removed from the coating solution by heat drying, and the main agent and the curing agent are polymerized. As a result, the hydroxyl group of the fluororesin and the isocyanate group of the polyisocyanate are bonded to form a urethane bond, so that the fluororesin is cross-linked and the fluororesin layer 11 is cured. Usually, since the bonding between the hydroxyl group of the fluororesin and the isocyanate group of the curing agent does not proceed sufficiently in a short time, an aging step is performed to promote curing.

  As the fluororesin, a fluororesin that contains a hydroxyl group in the resin skeleton and is soluble in a general-purpose solvent is used. For example, a homopolymer of tetrafluoroethylene (TFE), a copolymer of chlorotrifluoroethylene (CTFE) or TFE and hexafluoropropylene (HFP) or perfluoro (alkyl vinyl ether) (PAVE), etc. A copolymer with another copolymerizable monomer may be used.

  The hydroxyl value of the fluororesin is preferably 20 [mgKOH / g] or more and 200 [mgKOH / g] or less, and more preferably 40 [mgKOH / g] or more and 120 [mgKOH / g] or less. When the hydroxyl value is 20 [mgKOH / g] or more, an appropriate crosslinking density can be obtained, so that the mechanical strength of the fluororesin layer 11 and the adhesion with the substrate 10 are improved. When the hydroxyl value is 200 [mgKOH / g] or less, the relative fluorine content in the fluororesin layer is maintained within an appropriate range, so that the weather resistance of the fluororesin layer 11 is improved.

  As polyisocyanate, modified materials of various materials such as hexamethylene diisocyanate, isophorone diisocyanate, tolylene diisocyanate, xylylene diisocyanate, hydrogenated xylylene diisocyanate, or other prepolymers can be used. As a form of polyisocyanate, modified bodies such as simple substances (monomers), trimers (trimers) and other multimers, various alcohol adducts (adducts), and allophanate group-containing multimers can be used.

  The substance amount ratio of the isocyanate group to the hydroxyl group (hereinafter referred to as (NCO / OH) ratio) is preferably 0.3 or more and 2.0 or less, and more preferably 0.4 or more and 1.5 or less. When the (NCO / OH) ratio is 0.4 or more, an appropriate crosslinking density can be obtained, so that the mechanical strength of the fluororesin layer 11 is improved. Moreover, the adhesiveness between the base material 10 of the fluororesin layer 11 improves that (NCO / OH) ratio is 1.5 or less.

  When the glass transition temperature after the aging process of the fluororesin layer 11 is 40 ° C. or less, the adhesion between the fluororesin layer 11 and the substrate 10 becomes good. In order to satisfy this condition, the polyisocyanate is preferably an adduct-modified product or an allophanate group-containing multimer. The prepolymer is preferably hexamethylene diisocyanate, and is preferably an adduct-modified product of hexamethylene diisocyanate or an allophanate group-containing multimer.

  As the filler, transparent particles made of an inorganic substance or a resin are used. As the transparent particles made of an inorganic substance, for example, particles made of an oxide such as silica, alumina, titania, or particles such as calcium carbonate or barium sulfate can be used. Transparent particles made of resin include acrylic resin, styrene resin, acrylic styrene resin, or a cross-linked product thereof, melamine formaldehyde resin, polytetrafluoroethylene, perfluoroalkoxy resin, tetrafluoroethylene-hexafluoropropylene copolymer, poly Particles made of fluororesin such as fluorovinylidene and ethylene-tetrafluoroethylene copolymer, and silicone resin can be used.

  The average particle diameter of the filler is a size exposed from the surface 11 a of the fluororesin layer 11, is larger than the thickness T of the fluororesin layer 11, and does not exceed twice the thickness of the fluororesin layer 11. It is a range. Occurrence of blocking is suppressed when the average particle diameter is larger than the thickness of the fluororesin layer 11. Moreover, the adhesiveness between the fluororesin layer 11 and the base material 10 is improved when the average particle diameter is not more than twice the thickness of the fluororesin layer 11.

  In addition, the thickness of the fluororesin layer 11 is a thickness at a location where the filler is not included in the cross section of the fluororesin layer 11. The thickness of the fluororesin layer 11 is determined by observing a cross section of the fluororesin layer 11 with a scanning electron microscope (SEM). Moreover, the average particle diameter of a filler is calculated | required by the laser diffraction method (JIS Z 8825) prescribed | regulated to JIS specification. The average particle diameter of the filler may be an average value of the particle diameters of the arbitrary 100 particles in the cross section of the fluororesin layer 11 when the maximum diameter of each particle is defined as the particle diameter.

  It is preferable that the addition amount of a filler is 3 mass% or more and 20 mass% or less with respect to resin solid content. Generation | occurrence | production of blocking is suppressed because the addition amount of a filler is 3 mass% or more. Moreover, the adhesiveness between the fluororesin layer 11 and the base material 10 is improved by the addition amount of a filler being 20 mass% or less.

  The fluororesin layer 11 may contain various additives as necessary within a range that does not impair transparency and adhesion. Additives for the fluororesin layer 11 include urethane reaction catalysts such as tin and titanium compounds, UV absorbers, light stabilizers, antistatic agents, coupling agents, antifoaming agents, thickeners, leveling agents, and anti-gelling agents. And fillers. Among these additives, an ultraviolet absorber is preferably added in order to improve light resistance.

  When an ultraviolet absorber is added to the fluororesin layer 11, the ultraviolet absorber absorbs the ultraviolet rays of sunlight, so that the base material 10, the fluororesin layer 11, and other components are prevented from being deteriorated by the ultraviolet rays. It is done. The kind of the ultraviolet absorber is not particularly limited, and is appropriately selected and used in consideration of compatibility with the fluororesin and necessary ultraviolet cut ability. For example, ultraviolet absorbers such as benzophenone, benzotriazole, oxalic anilide, and hydroxytriazine can be used. The addition amount of the ultraviolet absorber is preferably from 0.1% by mass to 50% by mass and more preferably from 0.5% by mass to 10% by mass with respect to the fluororesin.

  The thickness of the fluororesin layer 11 is preferably 3 μm or more and 50 μm or less, and more preferably 5 μm or more and 40 μm or less. Weather resistance improves that thickness is 3 micrometers or more. Further, when the thickness is 50 μm or less, the manufacturing cost does not become too high. The thickness of the fluororesin layer 11 can be measured by using a transmission electron microscope, a scanning electron microscope, a micrometer, or the like.

[Operation of protective sheet]
In the manufacturing process of the protective sheet 1, in order to increase productivity, the coating step in the step of forming the fluororesin layer 11 is usually performed by a roll-to-roll method. And an aging process is performed in the state by which the base material 10 in which the fluororesin layer 11 was formed was wound up.

  At this time, if a fluororesin layer having a low glass transition temperature is used, the fluororesin layer is kept at a temperature equal to or higher than the glass transition temperature during aging, so that the film becomes rubbery and has fluidity. Thus, in order to suppress the occurrence of blocking due to the fluidity of the film in the aging process, the fine particles are added to the fluororesin layer, and the surface roughness and the dynamic friction coefficient between the front surface and the back surface are simply specified. Is not enough.

  The present inventor has found that blocking is suppressed when the glass transition temperature of the fluororesin layer before the aging step is equal to or higher than the temperature of the aging step. On the other hand, when the glass transition temperature is excessively high, it has also been found that there is a problem that the adhesion between the fluororesin layer and the substrate deteriorates. This suggests that the fluororesin layer having a high glass transition temperature exceeding 80 ° C. is brittle because it is in a glass state at room temperature, the shrinkage is large and the residual stress is high, and this is the cause. .

Based on these findings, the present inventor has found that both the resistance to blocking and good adhesion can be obtained by satisfying the following conditions.
-The glass transition temperature of the fluororesin layer 11 is 40 degrees C or less.
-The average particle diameter of a filler is larger than the thickness T of a fluororesin layer.
-The average particle diameter of the filler does not exceed twice the thickness of the fluororesin layer.
The filler content is 3% by weight or more and 20% by weight or less with respect to the fluororesin layer.

  That is, according to the protective sheet 1 of the present embodiment, blocking caused by the aging process being performed is suppressed, and the adhesion between the fluororesin layer 11 and the substrate 10 is enhanced. Therefore, the protective sheet 1 is preferably used as a surface member of a solar cell module particularly for outdoor use.

[Configuration of solar cell module]
With reference to FIG. 2, the structure of a solar cell module provided with the protection sheet 1 is demonstrated.
As shown in FIG. 2, the solar cell module 20 includes the above-described protective sheet 1, a plurality of solar cells 2, a sealing material 3 that seals the solar cells 2, and a back surface protective sheet 4. . The protective sheet 1 is provided as a surface protective sheet on the surface on the solar light incident side of the sealing material 3 in which the solar battery cells 2 are sealed. Moreover, the back surface protection sheet 4 is provided in the surface on the opposite side to the incident side of the sunlight in the sealing material 3, ie, the side on which the protection sheet 1 is provided. In such a configuration, the solar cell module 20 is used by providing appropriate wiring between the solar cells 2, the sealing material 3, and the back surface protection sheet.

  According to the said structure, while the generation | occurrence | production of blocking is suppressed, the performance of the solar cell module 20 is improved by using the protective sheet 1 with which adhesiveness is improved.

The function of the constituent material of the protective sheet described above will be described with reference to the following specific examples and comparative examples.
[Example 1]
(Coating material)
The coating liquid used for formation of the fluororesin layer of Example 1 was prepared using the following fluororesin solution, curing agent, filler, and ultraviolet absorber.
・ Fluorine resin solution: TFE copolymer (manufactured by Daikin Industries, trade name: Zeffle GK570, resin hydroxyl value: 63, solvent: butyl acetate)
Curing agent: hexamethylene diisocyanate allophanate (Mitsui Chemicals, trade name: D178NL)
Filler: Acrylic filler (manufactured by Sekisui Plastics, trade name: Sekisui Tech Polymer, average particle size: 15 μm)
・ Ultraviolet absorber: hydroxyphenyltriazine ultraviolet absorber (manufactured by BASF, trade name: TINUVIN477)
(How to create a protective sheet)
It mix | blended so that the equivalent ratio of the reaction part of the hardening | curing agent with respect to the curable reactive group of a TFE-type copolymer might be set to 1.0. The ultraviolet absorber was added so that it might become 8 weight% with respect to the solid content weight of a coating liquid. The filler was added so that it might become 3 weight% with respect to the solid content weight of a coating liquid. Butyl acetate was added so that the total solid concentration after mixing was 56%. In this way, a coating solution for the fluororesin layer was prepared.

  A PET base material (trade name: VN (Teijin DuPont), thickness 125 μm) was prepared as the base material of Example 1, and the base material was subjected to corona treatment. The coating liquid of Example 1 was apply | coated to the surface of the PET base material to which the corona treatment was performed using the wire bar (counter 30). The PET substrate after the coating step was put into a circulation oven EYELA WINDY OVEN WFO-1000ND (manufactured by Tokyo Rika Kikai Co., Ltd.) set at 170 ° C. and dried for 1 minute. It has been confirmed that the temperature of the PET base material is increased to 140 ° C. by the thermocouple. The PET base material on which the coating film after the drying step was formed was allowed to stand in an environment of 40 ° C. for 96 hours as an aging step, whereby the fluororesin layer of Example 1 was obtained. In addition, the thickness T of the fluororesin layer at a portion where no filler was included was 14 μm.

Subsequently, a transparent barrier film (trade name: GL-AEH (letter printing), thickness 12 μm) was adhered to the substrate on which the fluororesin layer was formed with a urethane curable adhesive, and the protective sheet of Example 1 was attached. Obtained.
[Example 2]
A protective sheet of Example 2 was obtained in the same manner as Example 1 except that the amount of filler added was changed to 20% by weight with respect to the solid content weight of the coating solution.
[Example 3]
The type of filler is changed to an acrylic filler (manufactured by Sekisui Chemicals Co., Ltd., trade name: Sekisui Tech Polymer, average particle size: 26 μm), and other conditions are the same as in Example 1, and the protective sheet of Example 3 is used. Got.
[Example 4]
The type of filler was changed to an acrylic filler (Sekisui Chemicals, product name: Sekisui Tech Polymer, average particle size: 26 μm), and the amount of filler added was 20% by weight with respect to the solid content weight of the coating solution. The protective sheet of Example 4 was obtained in the same manner as in Example 1 except for the above.
[Comparative Example 1]
The type of filler was changed to an acrylic filler (manufactured by Sekisui Plastics Co., Ltd., trade name: Sekisui Tech Polymer, average particle size: 12 μm), and other conditions were the same as in Example 1, and the protective sheet of Comparative Example 1 Got.
[Comparative Example 2]
The type of filler was changed to an acrylic filler (Sekisui Plastics Industries, trade name: Sekisui Tech Polymer, average particle size: 12 μm), and the amount of filler added was 20% by weight with respect to the solid weight of the coating solution. The protective sheet of Comparative Example 2 was obtained in the same manner as in Example 1 except for the above.
[Comparative Example 3]
The type of filler was changed to an acrylic filler (manufactured by Sekisui Chemicals Co., Ltd., trade name: Sekisui Tech Polymer, average particle size: 30 μm), and other conditions were the same as in Example 1, and the protective sheet of Comparative Example 3 Got.
[Comparative Example 4]
The filler type was changed to an acrylic filler (manufactured by Sekisui Plastics Co., Ltd., trade name: Sekisui Tech Polymer, average particle size: 30 μm), and the amount of filler added was 20% by weight with respect to the solid content weight of the coating solution. The protective sheet of Comparative Example 4 was obtained in the same manner as in Example 1 except for the above.
[Comparative Example 5]
The filler type was changed to an acrylic filler (manufactured by Sekisui Plastics Co., Ltd., trade name: Sekisui Tech Polymer, average particle size: 15 μm), and the amount of filler added was 1% by weight with respect to the solid weight of the coating solution. The protective sheet of Comparative Example 5 was obtained in the same manner as in Example 1 except for the above.
[Comparative Example 6]
The type of filler was changed to an acrylic filler (manufactured by Sekisui Plastics Co., Ltd., trade name: Sekisui Tech Polymer, average particle size: 15 μm), and the amount of filler added was 22% by weight with respect to the solid content weight of the coating solution. The protective sheet of Comparative Example 6 was obtained in the same manner as in Example 1 except for the above.
[Comparative Example 7]
The type of filler was changed to acrylic filler (Sekisui Chemicals, product name: Sekisui Tech Polymer, average particle size: 30 μm), and the amount of filler added was 1% by weight with respect to the solid content weight of the coating solution. The protective sheet of Comparative Example 7 was obtained in the same manner as in Example 1 except for the above.
[Comparative Example 8]
The type of filler was changed to an acrylic filler (Sekisui Chemical Co., Ltd., trade name: Sekisui Tech Polymer, average particle size: 30 μm), and the added amount of the filler was 22% by weight based on the solid content weight of the coating solution. The protective sheet of Comparative Example 8 was obtained in the same manner as in Example 1 except for the above.
[Comparative Example 9]
A protective sheet of Comparative Example 9 was obtained in the same manner as in Example 1 except that no filler was added.
[Comparative Example 10]
The curing agent was changed to an xylylene diisocyanate adduct (trade name: D110N, manufactured by Mitsui Chemicals), the filler was not added, and the other conditions were the same as in Example 1 except that the protective sheet of Comparative Example 10 was used. Got.
[Evaluation method]
The following items were evaluated with respect to Examples and Comparative Examples.

(Glass transition temperature measurement)
Each of the coating liquid of the example and the coating liquid of the comparative example is coated on the Teflon sheet, and similarly to the above-described protective sheet creation method, the drying process and the aging process are sequentially performed after the coating process, and from the top of the Teflon sheet. The coating film was carefully peeled off so as not to be deformed, and a fluororesin film for testing was prepared. And the temperature dependence of the dynamic viscoelasticity of the produced fluororesin film | membrane was evaluated. Dynamic viscoelasticity was measured using DMS6200 manufactured by SII Nanotechnology. The measurement conditions are a tensile measurement mode, a temperature range of 0 to 100 ° C., a temperature increase rate of 2 ° C./min, a measurement frequency of 1 Hz, and a sample shape having a length of 20 mm and a width of 10 mm. The peak temperature of the loss elastic modulus E "in the data measured with vapor DMS was taken as the glass transition temperature of the fluororesin film.

(Adhesion evaluation)
Each of the protective sheet of the example and the protective sheet of the comparative example was put into a wet heat acceleration tester and subjected to a pressure cooker test (PCT) treatment. The acceleration tester used is Palamount HAST CHAMBER PM 222 manufactured by ETAC. The treatment conditions are 144 h under the conditions of 105 ° C. and 100% RH. The adhesion of the fluororesin layer was evaluated on the PCT-treated test piece.

For the evaluation of adhesion, a cross-cut test was performed according to the following procedure. This is the same as the test described in the old JIS K5400: 1990.
1. After making 11 cuts with a width of 1 mm, change the direction by 90 ° and make another 11 cuts. (Make 100 1mm square grids)
2. Adhere cellophane tape to the cut fluororesin surface and rub it with an eraser to attach the tape to the fluororesin film.
3. 1 minute after attaching the tape, hold the end of the tape at a right angle to the fluororesin surface and peel it off instantaneously.

(Blocking evaluation)
The prepared protective sheets were laminated so that the fluororesin surfaces did not overlap each other, a weight of ² kg / cm ² was applied, and the sample after being held at 40 ° C. for 96 hours was observed and classified as follows. The case where the protective sheets easily peeled off and no change was observed in the appearance of the protective sheet was indicated as “◯”. On the other hand, the case where peeling between the protective sheets was not easy and a change was observed in the appearance of the protective sheet was defined as “X”.

  Table 1 shows the evaluation results for the above items.

As shown in Table 1, in Examples 1, 2, 3, and 4 that satisfy all the following conditions (a), (b), and (c), occurrence of blocking is suppressed and good adhesion is obtained. It was.
(A) The glass transition temperature of the fluororesin layer is 40 ° C. or lower.
(B) The fluororesin layer contains a filler, the average particle diameter of the filler is larger than the thickness of the fluororesin layer, and does not exceed twice the thickness of the fluororesin layer.
(C) The filler content in the fluororesin layer is 3% by weight or more and 20% by weight or less with respect to the fluororesin layer.

  On the other hand, Comparative Examples 1, 2, 3, 4, 5, 6, 7, 8, 9, and 10 that do not satisfy at least one of the above conditions (a), (b), and (c) At least one of the blocking inhibition results was low.

According to the above embodiment, the effects listed below can be obtained.
(1) The glass transition temperature of the fluororesin layer 11 is 40 ° C. or less, the average particle diameter of the filler is larger than the thickness of the fluororesin layer 11, and does not exceed twice the thickness of the fluororesin layer 11. Since the content of the filler in the fluororesin layer 11 is 3 wt% or more and 20 wt% or less, the occurrence of blocking is suppressed and the adhesion between the fluororesin layer 11 and the substrate 10 is enhanced. It becomes possible to achieve both. In addition, according to the said structure, it is not restricted to the blocking which generate | occur | produces due to performing an aging process, For example, a blocking occurs mainly due to a temperature change, such as a temperature rise during conveyance of a protection sheet. Can be suppressed.

(2) Since the base material 10 is resin, the flexibility as a protective sheet is enhanced and the protective sheet can be reduced in weight.
(3) Since the base material 10 has a thermal contraction rate of 5% or less at 150 ° C. for 30 minutes, the base material 10 can be prevented from being deformed in the solar cell sealing step.

(4) Since the barrier layer 14 is provided on the surface of the substrate 10 opposite to the surface on which the fluororesin layer 11 is formed, water vapor can be prevented from entering the element region.
The above embodiment can be modified as follows.

-Two or more kinds of fillers may be added to the fluororesin layer 11.
-The material of the base material 10 is not limited to resin, and glass may be used.
-The protective sheet 1 may omit the barrier layer 14. In addition, a transparent substrate may be further laminated on the barrier layer 14 via an adhesive layer.

  -The use of a protection sheet is not restricted to the surface member of a solar cell module. In particular, the protective sheet can be suitably used as a protective sheet for devices and parts installed outdoors.

  DESCRIPTION OF SYMBOLS 1 ... Protective sheet, 2 ... Solar cell, 3 ... Sealing material, 4 ... Back surface protection sheet, 10 ... Base material, 11 ... Fluororesin layer, 12 ... Filler, 14 ... Barrier layer, 20 ... Solar cell module.

Claims (5)

A substrate;
A fluororesin layer formed on the surface of the substrate,
The fluororesin layer includes fine particles,
The glass transition temperature of the fluororesin layer is 40 ° C. or less,
The average particle diameter of the fine particles is larger than the thickness of the fluororesin layer and in a range not exceeding twice the thickness of the fluororesin layer,
The protective sheet, wherein the content of the fine particles in the fluororesin layer is 3% by weight or more and 20% by weight or less with respect to the fluororesin layer. The protective sheet according to claim 1, wherein the base material is made of a resin. The protective sheet according to claim 1 or 2, wherein the base material has a thermal shrinkage rate of 5% or less at 150 ° C for 30 minutes. The protective sheet according to any one of claims 1 to 3, further comprising a water vapor barrier layer on a surface of the substrate opposite to the surface on which the fluororesin layer is formed. A solar cell module having a protective sheet on the surface,
The protective sheet is
A substrate;
A fluororesin layer formed on the surface of the substrate,
The fluororesin layer includes fine particles,
The glass transition temperature of the fluororesin layer is 40 ° C. or less,
The average particle diameter of the fine particles is larger than the thickness of the fluororesin layer and in a range not exceeding twice the thickness of the fluororesin layer,
The solar cell module, wherein the content of the fine particles in the fluororesin layer is 3% by weight or more and 20% by weight or less with respect to the fluororesin layer.

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