JPWO2012050190A1 - Back surface protection sheet for solar cell module and solar cell module - Google Patents

Abstract

It is an object of the present invention to provide a back surface protection sheet that can form a predetermined uneven structure on the surface with good transfer and reproducibility and increase electric conversion efficiency, and a solar cell module using the same. In a back surface protection sheet for a solar cell module provided with a single-sided light incident type solar cell element, at least one surface of the back surface protection sheet has an endothermic peak temperature at the time of DSC measurement and a heat generation peak at the time of temperature decrease. A back surface protective sheet for a solar cell module, which is made of polybutylene terephthalate or a polybutylene terephthalate copolymer having a temperature difference of 40 ° C. or less, and has a concavo-convex structure whose surface is formed by a slope.

Description

  The present invention relates to a solar cell module back surface protective sheet and a solar cell module in which a plurality of single-sided light incident type solar cell elements are enclosed, and more specifically, to a solar cell back surface protective sheet and a solar cell with improved power conversion efficiency. The present invention relates to a battery module.

  2. Description of the Related Art In recent years, a solar cell power generation system including a solar cell module has become widespread as one of power generation means using clean energy due to an increase in environmental awareness. The solar cell module has a plurality of plate-like solar cell elements arranged. These solar cell elements are sandwiched between ethylene-vinyl acetate copolymers called sealing materials, and a front plate such as glass is placed on the side where the sunlight strikes. However, the back surface protection sheet for solar cell modules (hereinafter abbreviated as back surface protection sheet) having weather resistance and moisture resistance is superimposed on the opposite side in this order. And it is integrally molded by a vacuum heating lamination method or the like.

  This back surface protection sheet protects the solar cell element and the sealing material, protects the solar cell element from external mechanical shock and pressure, prevents moisture penetration, and prevents deterioration of the solar cell element. Functions such as are required. Therefore, the adhesiveness with the sealing material is important for the back surface protection sheet, and it is necessary to have an adhesive force that does not peel even if left for a long time in high temperature and high humidity.

  Under such circumstances, in the development of solar cell modules, how to increase the so-called power conversion efficiency of efficiently converting the solar energy incident on the solar cell module into electric energy has become a major issue. Various devices have been proposed for not only the elements but also the back surface protection sheet.

  In Patent Document 1, in a solar cell module having a light-transmitting front plate, a solar cell element, a sealing material, and a back surface protection sheet, an uneven structure having a light scattering reflection function is formed on the front plate side of the back surface protection sheet. A back protection sheet has been proposed. The uneven structure of the back surface protective sheet is obtained by applying or injecting a thermosetting resin or an ultraviolet curable resin to an uneven surface such as a flat stamper, and placing a base material such as polyethylene terephthalate on the surface. By separating the polyethylene terephthalate sheet from the stamper, it is formed by a process, and more preferably by applying a scattering element of white pigment, metal particles, highly refractive particles and hollow particles dispersed in the resin to the surface of the concavo-convex structure can get. Thus, it had the subject that many processes were required in order to manufacture the back surface protection sheet which has a light-scattering reflection function.

  In order to form a concavo-convex structure on the surface of the polyethylene terephthalate sheet, there is a means for placing and bonding the concavo-convex structure made of a thermosetting resin or an ultraviolet curable resin formed with a stamper as described above on the surface of the polyethylene terephthalate sheet. It is necessary to select because the concavo-convex structure is relaxed in the cooling process even if shaping is performed on the surface of the polyethylene terephthalate sheet heated and melted with an embossing roll or the like in which the desired concavo-convex structure is formed. This is because a phenomenon that the top of the convex portion becomes smooth occurs and a desired surface shape cannot be obtained. Moreover, even if a polyethylene terephthalate sheet having a desired concavo-convex structure formed by any method is obtained, in order to bond the polyethylene terephthalate sheet to an ethylene-vinyl acetate copolymer that is a sealing material, both are used under reduced pressure. When heated at 150 ° C. for 30 minutes while in close contact, the uneven structure formed on the surface of the polyethylene terephthalate sheet is flattened and the initial purpose cannot be achieved.

JP 2010-123720 A

  The present invention has been made in view of the above problems, and provides a back surface protective sheet that can form a predetermined uneven structure on the surface, can be formed with good reproducibility, and can increase electrical conversion efficiency, and a solar cell module using the same. With the goal.

  The inventors of the present invention measured the temperature difference between the endothermic peak temperature at the time of temperature rise and the exothermic peak temperature at the time of temperature drop (hereinafter abbreviated as ΔTmc) in the measurement with a differential scanning calorimeter (hereinafter abbreviated as DSC measurement). Is a polybutylene terephthalate (hereinafter abbreviated as PBT) or a polybutylene terephthalate copolymer (hereinafter abbreviated as PBT copolymer) having a small embossing roll formed with a predetermined concavo-convex structure on the molten sheet surface. It has been found that by pressing, a predetermined concavo-convex structure can be transferred to the sheet surface, and the reproducibility can be shaped well, and the present invention has been completed.

That is, according to the present invention,
(1) In a back surface protection sheet for a solar cell module provided with a single-sided light incident type solar cell element, at least one side surface layer of the back surface protection sheet has an endothermic peak temperature at the time of temperature rise in DSC measurement and an exothermic peak temperature at the time of temperature drop. A back surface protective sheet for a solar cell module comprising a polybutylene terephthalate having a temperature difference of 40 ° C. or less, or a polybutylene terephthalate copolymer, and having a concavo-convex structure in which the surface is formed as a slope,
(2) A single-sided light-incident solar cell module using the back surface protective sheet according to (1) is provided,
(3) The solar cell module according to (2), wherein the back surface protection sheet satisfies the formula (1),

1 / n ≦ sin 2θ ≦ x / (x ² + y ² ) ^1/2 equation (1)
(However, 0 <θ <45)

θ: Angle (degrees) between the front plate surface and the extended surface of the slope of the back surface protection sheet uneven structure
x: Spacing between adjacent solar cell elements (mm)
y: Distance (mm) between the front plate side surface of the solar cell element and the valley portion of the back surface protection sheet
n: Refractive index of the front plate

(4) The angle formed by the direction of the line connecting the convex portions at the shortest distance of the concavo-convex structure on the surface of the back surface protective sheet and the direction in which the solar cell elements are arranged is 10 to 80 degrees (2) or (3) The described solar cell module is provided.

  Since the back surface protection sheet of the present invention uses PBT or PBT copolymer having a ΔTmc of 40 ° C. or less, a predetermined uneven structure can be transferred to the sheet surface and formed with good reproducibility. Has the effect of improving the power conversion efficiency by effectively using the sunlight that has been lost. In addition, the rugged structure on the surface has an effect that the dynamic friction coefficient is small and handling when assembling a solar cell module is easy.

It is a typical perspective view which shows one Embodiment of the back surface protection sheet of this invention. It is a typical perspective view which shows other embodiment of the back surface protection sheet of this invention. FIG. 3 is a cross-sectional view taken along III-III ′ of the back surface protection sheet shown in FIG. 1. It is a typical fragmentary sectional view of the solar cell module using the back surface protection sheet of this invention. It is a typical top view which shows one Embodiment of the solar cell module of this invention. It is a typical top view of the solar cell module using the back surface protection sheet shown in FIG. 3 is a cross-sectional view of the vicinity of the surface of the back surface protective sheet obtained in Example 1 using a laser scope. FIG. 4 is a cross-sectional view of the vicinity of the surface of the back surface protective sheet obtained in Example 2 using a laser scope. FIG.

  Hereinafter, the back surface protection sheet for solar cell modules and solar cell module of this invention are demonstrated in detail.

  FIG. 4 is a schematic partial cross-sectional view of the solar cell module 1 using the back surface protective sheet of the present invention. The solar cell module 1 of the present invention includes a back surface protection sheet 11, a sealing material 12, a solar cell element 13, and a front plate 14. The sunlight L1 enters from the front plate, and most of the sunlight L2 enters the surface of the solar cell element. On the other hand, in the case of the solar cell module using the back surface protection sheet of the present invention, the sunlight L3 that has passed between the solar cell elements is reflected by the back surface protection sheet having a surface composed of a plurality of irregularities formed by slopes, and sunlight. It becomes L4, is further reflected by the front plate, becomes sunlight L5 and enters the solar cell element, solar energy is converted into electric energy, and power generation conversion efficiency can be increased. On the other hand, in the solar cell module using the conventional back surface protection sheet, the sunlight L3 that has passed between the solar cell elements is scattered by the back surface protection sheet and is not incident on the solar cell elements efficiently and is a loss of solar energy. It has become.

  In this way, by using the back surface protective sheet having a predetermined concavo-convex structure, it is possible to obtain a solar cell module that can effectively use sunlight passing between solar cell elements that has conventionally been a loss, As described above, conventionally, many steps are required to obtain a back surface protective sheet having a predetermined uneven structure.

  For the back surface protective sheet for solar cell module of the present invention, PBT or PBT copolymer having ΔTmc of 40 ° C. or lower can be suitably used. Moreover, what mixed a small amount of thermoplastic resins, such as a polycarbonate and a polyethylene terephthalate, to PBT or a PBT copolymer can also be used. Here, ΔTmc is an endothermic peak temperature (Tm) at the time of temperature increase (temperature increase rate 10 ° C./min) and heat generation at the time of temperature decrease (temperature decrease rate 10 ° C./min) in DSC measurement of PBT or PBT copolymer. It means the temperature difference (ΔTmc = Tm−Tc) from the peak temperature (Tc).

  As PBT, there are a method of polycondensation of 1,4-butanediol and terephthalic acid, a method of polycondensation of 1,4-butanediol and a lower alkyl ester of terephthalic acid, and the like. PBT can also be used. The intrinsic viscosity of the PBT used in the present invention is preferably 0.6 to 1.5, and more preferably 0.8 to 1.4.

  On the other hand, as a PBT copolymer, a part of butylene glycol is replaced with ethylene glycol, propylene glycol, or cyclohexanedimethanol, or a part of terephthalic acid is isophthalic acid, 2,6-naphthalenedicarboxylic acid, or adipine. The thing replaced with the acid can be mentioned.

  The solar cell module is required to stably convert solar energy into electric energy over a long period of time, and the characteristics of the back surface protection sheet for the solar cell module of the present invention are greatly deteriorated over a long period of time. It is required not to let it. The PBT and PBT copolymer suitable for the present invention contain an ester bond, cause hydrolysis due to moisture, reduce the molecular weight, and may deteriorate physical properties when used over a long period of time. Therefore, the PBT or PBT copolymer used in the present invention preferably has a small number of terminal carboxyl groups in order to prevent hydrolysis under high temperature and high humidity. Specifically, PBT or a PBT copolymer having a carboxyl group equivalent of 40 meq / kg or less, more preferably 30 meq / kg or less is preferable.

  In the back surface protective sheet of the present invention, the carbodiimide compound is added to the PBT or PBT copolymer in order to suppress hydrolysis, and the phenolic, phosphorus, or sulfur type is used to prevent thermal degradation when melted into a sheet. In order to prevent deterioration due to ultraviolet rays contained in sunlight, an antioxidant such as an ultraviolet absorber or a light stabilizer, and an anti-blocking agent or a flame retardant as necessary can be added.

  Further, the back surface protection sheet is colored white, so that the reflectance is increased, the electric conversion efficiency of the solar cell module from solar energy to electrical energy is increased, and the weather resistance of the back surface protection sheet is improved. . In order to color the back surface protective sheet in white, it is preferable to add a white pigment (metal oxide) such as titanium oxide, zinc oxide, or aluminum oxide to the back surface protective sheet. Of these, titanium oxide is particularly preferable because it has a high refractive index and is easily dispersed in PBT or PBT copolymer. Moreover, these addition amounts are preferably 5 to 30 parts by weight with respect to 100 parts by weight of PBT or PBT copolymer.

  The back surface protective sheet of the present invention is embossed by a stamper such as an embossing roll in order to give a specific uneven structure to the sheet surface. The PBT or PBT copolymer having the ΔTmc of 40 ° C. or less is uneven. It is preferable because the surface shape of the stamper that imparts the structure can be transferred and reproduced more faithfully, and a desired uneven structure can be easily obtained. On the other hand, when a thermoplastic resin having a ΔTmc exceeding 40 ° C., such as polyethylene terephthalate, is used, the uneven structure transferred while the polyethylene terephthalate sheet is cooled and solidified is eased even if the stamper is embossed on the sheet surface. The surface shape cannot be faithfully transferred or reproduced, and the shape of the obtained polyethylene terephthalate sheet surface, particularly in the vicinity of the top of the concavo-convex structure, becomes gentle, and sunlight cannot be used effectively.

  As described above, it is assumed that the PBT or PBT copolymer having ΔTmc of 40 ° C. or less can more faithfully transfer and reproduce the surface shape of a stamper such as an emboss roll. That is, when the molten thermoplastic resin is cooled after shaping with an embossing roll or the like, the volume shrinks with cooling, but the PBT or PBT copolymer having a small ΔTmc is crystallized immediately after cooling and solidification. This is considered to be because the volume shrinkage due to cooling is smaller than that of a thermoplastic resin that is slow to crystallize. As described above, the PBT or PBT copolymer having a small ΔTmc begins to crystallize immediately after solidification and the whole solidifies rapidly, so that the volume shrinkage is small, and the uneven structure on the surface of the embossing roll is transferred to the back protective sheet surface. Presumably one that can be faithfully transferred and reproduced.

  The uneven structure of the back surface protective sheet may have a periodic structure or an irregular shape. The pitch of the concavo-convex structure is preferably 500 μm or less, and more preferably 400 μm or less. When the pitch of the concavo-convex structure is larger than 500 μm, it is not preferable because a resin is hardly filled in the tip portion of the concavo-convex structure when the concavo-convex structure is formed, and transferability is deteriorated. On the other hand, if the pitch of the concavo-convex structure is too small, it becomes difficult to produce a stamper such as an embossing roll. Therefore, the pitch of the concavo-convex structure is preferably 25 μm or more. Further, the height of the projections of the concavo-convex structure is preferably 50 μm or less, more preferably 40 μm or less. When this height exceeds 50 μm, transfer and reproduction when transferring the concavo-convex structure on the stamper surface to the back surface protection sheet The tip of the convex part is easily chipped. On the other hand, the height of the convex part of the concavo-convex structure is preferably 5 μm or more, more preferably 10 μm or more, and when this height is less than 5 μm, sunlight cannot be used effectively. Here, “the pitch of the concavo-convex structure” means the distance between the apexes of the peak portions 15 (see FIG. 3) of two adjacent convex portions. Further, the “height of the convex portion of the concavo-convex structure” means a distance in a direction perpendicular to the back surface protection sheet plane between the peak portion 15 and the valley portion 16 of the convex portion.

  Furthermore, the concavo-convex structure is preferably formed by a slope, and more preferably, the slope has a shape close to a plane. When the concavo-convex structure is formed with an inclined surface close to a flat surface, it is possible to reflect sunlight incident between the solar cell elements in an arbitrary direction, and further by appropriately selecting the angle of the inclined surface, Is more preferable because it can be incident on the front plate at a critical angle or more and the reflected light from the back surface protection sheet can be confined in the solar cell module.

  When the regular concavo-convex structure on the surface of the back surface protective sheet has a periodic structure as shown in FIG. 1 or FIG. 2, a line (D1 or D2) connecting the convex portions at the shortest distance and the figure It is particularly preferable that the solar cell element and the back surface protective sheet are laminated so that an angle α (see FIG. 6) formed with the alignment direction (D3) of the solar cell elements shown in FIG. When the angle α formed by the line (D1 or D2) connecting the convex portions at the shortest distance of the concavo-convex structure and the alignment direction (D3) of the solar cell elements is close to 90 degrees, it was reflected by the back surface protection sheet. Even if sunlight is incident on the front plate at an angle greater than the critical angle, the reflected light is reciprocally attenuated between the solar cell elements only by repeated reflection between the front plate and the back surface protective sheet between the solar cell elements, Since the sunlight hitting the surface of the solar cell element is reduced, the effect is reduced.

As described above, in order to confine the reflected light from the back surface protection sheet in the solar cell module, the angle θ formed by the front plate surface and the extended surface of the inclined surface of the back surface protection sheet uneven structure satisfies the formula (1). Is preferred.

1 / n ≦ sin 2θ ≦ x / (x ² + y ² ) ^1/2 equation (1)
(However, 0 <θ <45)

θ: Angle (degrees) between the front plate surface and the extended surface of the slope of the back surface protection sheet uneven structure
x: Spacing between adjacent solar cell elements (mm)
y: Distance (mm) between the front plate side surface of the solar cell element and the valley portion of the back surface protection sheet
n: Refractive index of the front plate

  If the angle θ between the front plate surface and the extended surface of the slope of the back surface protection sheet concavo-convex structure satisfies Equation (1), the angle at which sunlight reflected by the back surface protection sheet is incident on the front plate is greater than the critical angle It is more preferable because it is totally reflected by the front plate and sunlight can be confined in the solar cell module.

  The back surface protective sheet of the present invention is obtained by forming a PBT or PBT copolymer having a ΔTmc of 40 ° C. or lower into a sheet shape and shaping a predetermined surface shape, at least one side surface. It may be a single layer, or may be a back surface protective sheet having a multilayer structure in which layers having other purposes are laminated by coextrusion. Furthermore, in order to provide gas barrier properties, a gas barrier film or the like on which an inorganic oxide is deposited may be bonded to form a multilayer back surface protective sheet. In that case, it is preferable to bond on at least one surface so that the uneven structure formed on the layer of PBT or PBT copolymer having a TMC of 40 ° C. or lower is located on the outermost surface of the back surface protective sheet.

  In order to obtain such a back surface protective sheet, for example, PBT or PBT copolymer having ΔTmc of 40 ° C. or lower is supplied to an extruder equipped with a flat die, and PBT extruded from the flat die of the extruder or By pulling the PBT copolymer sheet between the embossing rolls having a predetermined concavo-convex structure formed thereon, the predetermined concavo-convex structure can be transferred to the surface of the PBT or PBT copolymer sheet with good reproducibility. The obtained back surface protective sheet can be used in an unstretched state. In particular, PBT or PBT copolymer has a higher crystallization rate than other polyesters, and has an effect that a film having mechanical properties that can be used practically without stretching is obtained. In addition, in order to obtain the back surface protection sheet of the said multilayer structure, it can co-extrude from the flat die equipped with the several extruder, and can obtain it by a normal method.

  In order to form a concavo-convex structure on the surface of the back surface protection sheet, the sheet obtained by extruding PBT or PBT copolymer is shaped by a stamper having a predetermined concavo-convex structure under heating in the next step. However, immediately after the PBT or PBT copolymer is extruded from the flat die by extrusion molding, the method of sandwiching it with an embossing roll having a predetermined concavo-convex structure and taking it out is the same as in ordinary extrusion molding. Since the back surface protection sheet which has an uneven structure is obtained, it is preferable.

  In order to form the concavo-convex structure on the surface of the back surface protection sheet of the present invention, there is a method using an embossing roll. To form the concavo-convex structure on the surface of the embossing roll, for example, a diamond stylus used when manufacturing a gravure cylinder plate The engraving plate making method and the mill pressing method are enumerated.

  Thus, since PBT or a PBT copolymer can be used without stretching after film formation, the concavo-convex structure of the sheet imparted during film formation can be maintained as it is. In contrast, other polyesters such as polyethylene terephthalate require a stretching process after film formation, and the uneven structure on the sheet surface provided in the film forming process is stretched in the stretching process to maintain a predetermined uneven structure. The problem that it is not possible arises. Also from such a point, it is necessary to manufacture a back surface protection sheet having a predetermined uneven structure using PBT or a PBT copolymer.

  The back protective sheet of the present invention preferably has a thickness of 100 μm to 600 μm so as not to allow moisture to penetrate into the solar cell module. When the thickness of the back surface protection sheet is less than 100 μm, moisture easily penetrates into the solar cell module, and the back surface protection sheet is thin, so that the stiffness is weak and wrinkles are likely to occur during handling. Since it becomes difficult to handle, it is not preferable, and when the thickness exceeds 600 μm, it is not preferable because it is difficult to wind the obtained back surface protective sheet into a roll.

  Thus, the obtained back surface protection sheet is a front plate, a sealing material, a solar cell element, a sealing material, a back surface protection sheet so that the surface which formed the uneven structure of the back surface protection sheet may turn into a sealing material side. Are integrated in this order to form a solar cell module.

  The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples. The characteristics were evaluated by the following method.

(1) DSC measurement Using a differential scanning calorimeter (DSC), measured at a rate of temperature increase of 10 ° C / min and a rate of temperature decrease of 10 ° C / min. The endothermic peak temperature at the time of temperature increase and the exothermic peak temperature at the time of temperature decrease Was measured.

(2) Measurement of solution viscosity Intrinsic viscosity was calculated | required by melt | dissolving PBT in a phenol-tetrachloroethane mixed solvent (1: 1 by weight ratio), and measuring at 25 degreeC using an Ubbelohde viscometer.

(3) Evaluation of electrical conversion efficiency The space | interval y of the front plate side surface of the solar cell element shown in FIG. 4 and the trough part of a back surface protection sheet is 0.6 mm, and the space | interval of the solar cell element shown in FIG. The front plate, the sealing material, the solar cell elements (four are arranged in a square shape), the sealing material, and the back surface protection sheet are integrated in this order so that the thickness becomes 0.5 mm and b: 2.5 mm. Got a module. The electrical conversion efficiency of the solar cell module was measured using a solar simulator (manufactured by Nisshinbo Industries, Inc., measurement conditions: irradiation of light adjusted with a solar radiation standard sunlight with a filter, air mass 1.5).
[Reference example]

  DSC measurement was performed on PBT and polyethylene terephthalate, and ΔTmc was determined from the endothermic peak temperature and the exothermic peak temperature, and is shown in Table 1.

［実施例１］

[Example 1]

Using a single-layer film forming apparatus equipped with a flat die, a mixture containing 10 parts by weight of titanium oxide per 100 parts by weight of PBT (inherent viscosity: 1.1, carboxyl group equivalent: 7 meq / kg) was extruded, and a side of 78 μm, It was taken up while being shaped with an embossing roll having a regular quadrangular pyramid recess having a height of 27 μm and a slope angle (θ) of 35 degrees to obtain a back protective sheet having a thickness of 188 μm having a convex structure of a regular quadrangular pyramid on the surface. The cross-sectional measurement result of the uneven structure part of the obtained back surface protection sheet surface is shown in FIG. Table 2 shows the characteristics of the solar cell module assembled by setting the angle (α) between the direction of the line connecting the convex portions at the shortest distance of the concavo-convex structure of the back surface protection sheet and the direction of arrangement of the solar cell elements to 45 degrees. Shown in
[Example 2]

  A back protective sheet having a semi-matte surface was obtained in the same manner as in Example 1 except that a rubber roll having a semi-matte surface was used. The cross-sectional measurement result of the uneven structure portion of the obtained back surface protection sheet is shown in FIG. 8, and the characteristics of the solar cell module assembled using the obtained back surface protection sheet are shown in Table 2.

  The solar cell module using the back surface protection sheet having unevenness using the PBTs of Example 1 and Example 2 has improved electrical conversion efficiency than the conventional solar cell module using the back surface protection sheet having no unevenness. Further, the surface of the back surface protection sheet using the PBT of Example 1 has a convex portion having a slope close to a flat surface, and the uneven structure on the surface of the embossing roll is transferred with good reproducibility. Compared with the solar cell module using the back surface protection sheet having the random irregularities of Example 2, the solar cell module that was obtained was able to improve the electrical conversion efficiency by 0.2%.

Since the back surface protective sheet of the present invention has a predetermined concavo-convex structure on its surface, it has the effect that the electrical conversion efficiency can be increased by effectively using sunlight that was originally lost, Due to the uneven structure on the surface, the coefficient of dynamic friction is small, and there is also an effect that it is easy to handle when assembled into a solar cell module. In addition, it has excellent mechanical properties, heat and moisture resistance, good adhesion to the sealing material, and low water vapor transmission rate, which are the features of PBT and PBT copolymer. In addition, the deterioration of the solar cell element can be suppressed, and the solar cell module back surface protective sheet can be suitably used for a long period of time.

DESCRIPTION OF SYMBOLS 1: Solar cell module 11: Back surface protection sheet 12: Sealing material 13: Solar cell element 14: Front plate 15: Peak part of uneven structure 16: Valley part of uneven structure D1: Between convex parts in shortest distance of uneven structure D2: Direction of a line connecting convex portions at the shortest distance of the concavo-convex structure D3: Direction of arrangement of solar cell elements L1: Sunlight incident on solar cell module L2: Sun incident on solar cell element Light L3: Sunlight straightly traveling between solar cell elements L4: Sunlight reflected by the back surface protection sheet L5: Sunlight reflected by the front surface plate θ: Extension surface of the slope of the front surface and the back surface protection sheet uneven structure X: Interval between adjacent solar cell elements y: Interval between front plate side surface of solar cell element and valley portion of back surface protection sheet a: Interval between adjacent solar cell elements b: Adjacent Spacing of solar cell elements α: Angle formed by D2 and D3

Claims (4)

In the back surface protection sheet for a solar cell module provided with a single-sided light incident type solar cell element, at least one side surface layer of the back surface protection sheet has a temperature between an endothermic peak temperature at the time of DSC measurement and an exothermic peak temperature at the time of temperature decrease. A back surface protective sheet for a solar cell module, comprising a polybutylene terephthalate or a polybutylene terephthalate copolymer having a difference of 40 ° C. or less and having a concavo-convex structure having a surface formed by a slope.
A single-sided light incident type solar cell module using the back surface protective sheet according to claim 1.
The solar cell module according to claim 2, wherein the back surface protection sheet satisfies the formula (1).

1 / n ≦ sin 2θ ≦ x / (x ² + y ² ) ^1/2 equation (1)
(However, 0 <θ <45)

θ: Angle (degrees) between the front plate surface and the extended surface of the slope of the back surface protection sheet uneven structure
x: Spacing between adjacent solar cell elements (mm)
y: Distance (mm) between the front plate side surface of the solar cell element and the valley portion of the back surface protection sheet
n: Refractive index of the front plate
The angle α between the direction of the line connecting the convex portions at the shortest distance of the regular concavo-convex structure on the surface of the back surface protective sheet and the direction in which the solar cell elements are arranged is 10 to 80 degrees. The solar cell module according to claim 2 or 3.

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